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SDMS DocID 251749 Response to EPA-DEP Comments Dated March 31, 2005 On the Draft Technical Impracticability Evaluation Hows Corner Superfund Site, Plymouth, Maine A WOODARD&CURRAN Engineering Science Operations 41 Hutchins Drive Portland, ME 04102 (207)774-2112 www.woodardcurran.com

SDMS DocID 251749 - Records Collections · 2020-06-13 · CORPORATE OFFICES: Maine, Massachusetts, New Hampshire, Connecticut New, York, Florida Engineering • Science • Operations

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Page 1: SDMS DocID 251749 - Records Collections · 2020-06-13 · CORPORATE OFFICES: Maine, Massachusetts, New Hampshire, Connecticut New, York, Florida Engineering • Science • Operations

SDMS DocID 251749

Response to EPA-DEP Comments Dated March 31 2005

On the Draft Technical Impracticability Evaluation Hows Corner Superfund Site Plymouth Maine

A WOODARDampCURRAN Engineering bull Science bull Operations

41 Hutchins Drive Portland ME 04102

(207)774-2112

wwwwoodardcurrancom

CORPORATE OFFICES Maine Massachusetts New Hampshire Connecticut New York Florida

Engineering bull Sc ience bull Operat ions Operational offices throughout the US

May 3 2005 Via FedEx

Mr Terry Connolly Remedial Project Manager USEPA - New England Region 1 Congress Street Suite 1100 (HBT) Boston MA 02114-2023

Subject Hows Corner Superfund Site Plymouth Maine (Site) Transmittal of Responses to Comments Dated March 31 2005 on Draft Technical Impracticability (IT) Report

Dear Mr Connolly

As requested in your letter dated March 31 2005 two copies of written responses to the agencies comments on the Draft Technical Impracticability Report are enclosed for your review Three copies of the responses have been sent to Rebecca Hewert at MEDEP and one copy has been sent to Michael Healey at TetraTechNUS

The PRP Technical Committee would be pleased to speak with you or meet with you after you have had an opportunity to review the enclosed material Please call Mark Beliveau or me to discuss a schedule for continuing our progress toward completion of the TI Evaluation Report for the Hows Corner Site

In the meantime if you have questions on the enclosed responses please contact me at 2077742112

Sincerely

WOODARD amp CURRAN INC

Thomas R Eschner Senior Project Manager

Enclosures

cc Rebecca Hewett MEDEP (3 copies) Michael Helaey TetraTechNUS (1 copy) Mark Beliveau Pierce Atwood (1 copy)

41 Hutchins Drive bull Portland Maine 04102 bull (207)774-2112- (800)426-4262 bull (207) 774-6635 (Fax) wwwwoodardcurrancom

VVOODAFDampCURRAN Engineering bull Science bull Operations

bcc Jim Rawson General Electric (1 copy) Don Frost JrKristin Larson Skadded Arps Slate Meather amp Flom (1 copy) Philip Buckley Rudman amp Winchell (1 copy) Andrew HamiltonHeather Parent Eaton Peabody (1 copy) Joanna Brown Pierce Atwood (1 copy) Philip Buckley Virginia Putnam Rudman amp Winchell (1 copy) Andrew Hamilton Heather Parent Eaton Peabody (1 copy) Kenneth Farber Central Maine Power (1 copy) Robert Fitzgerald Goodwin Proctor (1 copy) Jack Guswa JG Environmental (1 copy)

21194102 TConnelly 050305 2 May 32005

Response to EPA-DEP Comment 1 Dated March 312005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

lib

IIMJ

Ufa

M

EPA-DEP Comment 1

Comment 1 Institutional Controls It is recognized by all parties that institutional controls are and will continue to be an integral part of the remedy for the site Having said that the agencies need to have a presentation of the institutional controls including a copy of the town ordinance regarding the ICZ a figure showing the ICZ and the properties with restrictive covenants a table of the 57 properties identified within the ICZ by tax lot number and owners name location of all private wells whether for drinking water residential or agricultural purpose the status of any well abandonment efforts as well as a discussion as how these controls will be monitored

As this information may change over time such as through sale of property or sub-division of a property or well abandonment the agencies believe that presentation of the institutional controls information can best be accomplished with a stand-alone document that can be periodically updated rather than incorporated into the TI report Then as with other documentation such as the RIFS relevant information from the Institutional Control report can be summarized in the TI report

Response The Hows Corner PRP Group will prepare a document that describes the institutional controls for the Site The following items will comprise the document

bull a map of the Site vicinity showing the Institutional Control Zone (ICZ) boundary and properties with restrictive covenants

bull a tabulation of properties located within the ICZ organized by tax lot number and owners name and listing for each property

o the number of connections provided or to be provided to the property o the presence of private wells o the status of well abandonment for the property

bull a copy of the town ordinance regarding the ICZ bull an example of the restrictive covenant for the properties located within the ICZ and bull a discussion of the monitoring program for the institutional controls

The PRPs agree that a stand-alone document is appropriate for the reporting purposes requested by the comment The document can then be updated at periodic intervals mutually agreed upon by the PRPs and the EPA and DEP The status of the PRPs efforts regarding institutional controls and upgrades to the Plymouth water system is summarized in Section 123 of the Draft Technical Impracticability (TI) Evaluation Report Figure 1-2 of the TI Report is a map showing improvements to the Plymouth water system as well as properties that are connected to the system The information in the TI Report will be updated prior to submittal of the final report

Response to EPA Comment 1 050205doc 1 of 1 Woodard amp Curran (211941)

m

Response to EPA-DEP Comment 2 Dated March 312005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

EPA-DEP Comment 2

Comment 2 As discussed in our January meeting the results of the TI field work and their interpretation need to be presented in the TI report Listed below are some specific comments on this with the goal being a discussion of how the site conceptual model and site modeling were revised as a result of the 2004 field work

a analysis of the aquifer test to include a figure presenting the drawdown observed in each monitoring well at the end of the aquifer test The horizontal hydraulic gradient should not be included since this method tends to accentuate the anisotropy Two figures may be needed one for shallow bedrock and one for deep bedrock an evaluation of the appropriateness of the Cooper-Jacob (CJ) method for analyzing the aquifer test data including a comparison of the pattern of observed drawdown to the pattern of fracture orientations determined from the borehole geophysics confirmation that u lt 001 and that calculated values for T and S are similar for several observation wells an interpretation of the change in slope on the CJ plots near the end of the aquifer test the recovery data should be evaluated since it may provide insight as to why the slopes changed the marked increase in slope near the end of the test strongly suggests that a barrier (ie no flow) boundary was encountered and if a boundary was encountered T and S need to be calculated from the pre-boundary portions of the CJ plots It may be appropriate to analyse the aquifer test data using Theis as well as the Moench dual porosity model (both analysis methods are available in Aqtesolv pumping test modeling software) so that all parties have confidence in the transmissivity and storativity numbers derived from the CJ analysis b numerous bedrock borings (including angled holes) were drilled during the most recent field investigation yet no summary of the findings or the geophysical logging or packer test and sampling results have been provided c have any input parameters been changed in the flow transport and batch-flushing models as a result of the 2004 fieldwork If so which ones and why were the changes made (ie justify the changes)

Response The objective of the pumping test conducted at the Hows Corner Site during September 2004 was to observe the response of the groundwater system to pumping for use in refining the site conceptual model The refined site conceptual model would in turn be used to recalibrate the flow model and aid in the design of the hydraulic containment system being constructed under the authority of the AOC for the RD

The results of the pumping test are illustrated by plots of the drawdown at the end of the test The enclosed three drawdown plots (shallow bedrock deep bedrock and combined) represent the change in water level at the end of the test from the initial pre-test water level The shallow bedrock figure shows a northeast-southwest trending ellipsoidal area of drawdown that extends approximately 2000 feet along the major axis and approximately 800 feet along the minor axis The northeast-southwest orientation of the drawdown ellipse is consistent with the orientation of likely water-bearing fractures as identified from geophysical logging during the TI investigation The deep bedrock figure and combined figure also show ellipsoidal areas of drawdown with similar orientation A secondary axis with a more northerly orientation is evident on the figures showing drawdown in deep bedrock and in combined shallow and deep bedrock The maximum drawdown measured in shallow bedrock was 29 feet at MW-2EB The maximum drawdown measured in deep bedrock was 54 feet at the pumping well (PW-207) The drawdown ellipse is

Response to EPA Comment 2 050205doc 1 of 24 Woodard amp Curran (211941)

approximately coincident with the location of the modeled capture zone as presented on Figure 3shy1 of the TI Evaluation report

The enclosed three potentiometric surface maps (shallow bedrock deep bedrock and combined) represent the water surface elevations measured at the end of the test which was 72 hours or three days after it began All three maps show the presence of the groundwater high located in the southeast portion of the 17-acre property This high area shows relatively little relief but with the exception of the measurements at MW-2DDB which shows anomalously high water levels the central area of the high is at lower elevation than the perimeter The measurements at MWshy2DDB are hypothesized to result from water that is unable to drain rapidly enough to equilibrate with the rest of the formation

The pumping test data initially were analyzed using the Cooper-Jacob method for the late test data The results of this analysis are summarized in the table entitled Pumping Test Analytical Results It was recognized that because the aquifer is not uniform isotropic and infinite in areal extent the assumptions on which the underlying Theis equation is based were not met and because of the length of the test the criteria for use of the Cooper-Jacob of analysis were not explicitly met We recognize that the complexity of the hydrogeologic characteristics of the formation would be a significant limitation if the calculated values from the pumping test analysis were to be used as absolute representations of the hydraulic parameters of the formation However the range of values from this pumping test analysis were used as guidelines or bounding values for recalibration of the flow model

Woodard amp Curran also analyzed the pumping test data using the Theis and Moench methods The enclosed table entitled Pumping Test Analytical Results also summarizes the results of analysis of the data using these analytical methods Again although none of the methods may be strictly applicable they provide values that are guidelines for parametric ranges used in model calibration Hydraulic conductivity values calculated from the different analytical methods were as follow

Minimum Maximum Mean (ftday) (ftday) (ftda

bull Cooper-Jacob 020 067 038 bull Theis 035 1476 392 bull Moench (Fissure) 027 210 099

Storage coefficients calculated from the different analytical methods were as follow

Minimum Maximum Mean bull Cooper-Jacob 830E-04 392E-02 651E-03 bull Theis 547E-05 359E-03 473E-04 bull Moench (Block) 803E-05 402E-02 489E-03

Storage coefficients calculated using the Theis method were one to two orders of magnitude lower than values calculated using the Cooper Jacob or Moench (Block) methods Although the fissure system values are thought to be appropriate for evaluating hydraulic conductivity because the majority of flow is through fractures the block system values are appropriate for evaluation of storage because the limited fractures account for only a small part of the total storage in the bedrock

Response to EPA Comment 2 050205doc 2 of 24 Woodard amp Curran (211941)

Woodard amp Cunran used the values estimated from the pumping test analysis as an initial data set for transient benchmarking by running a 3-day simulated pumping test Calibration of the model was accomplished by comparing measured drawdowns obtained during the pumping test to calculated drawdowns from the flow model The hydraulic parameter values in the model were varied from the initial values but within the range calculated from the pumping test analysis The additional model calibration was considered to be completed when the calculated drawdowns were sufficiently close to measured drawdowns The resulting values of the hydraulic parameters of the calibrated model were then considered acceptable to provide satisfactory prediction of the response of the flow system to other hydraulic stresses

Regional water-level data were reviewed prior to data analysis A plot of water levels in the closest USGS regional background well (provided in the TI Data Package and attached) indicates that throughout the period of the test and subsequent recovery water levels were declining on a regional scale Although the decline in water levels is gradual the change in slope observed on the Cooper-Jacob plots is thought to represent the point at which the drawdown at a given location caused by pumping becomes less significant compared to the regional drawdown This occurs at about a day after start of pumping The effect of the regional decline in water levels can also be seen in the initial rapid rise in water levels in response to pump shut off followed by a decline in water levels after about a day after the pump is shut off

Additional information obtained during the TI field work was reviewed and evaluated in updating the conceptual model for the site In general the additional information corroborated the understanding of the Site presented in the RI report In particular the northeast-southwest fracture orientation was confirmed as the predominant orientation Geophysical logging during the TI investigation however showed the dip direction of fractures to be more variable and the dip angles to be shallower than was understood based on the RI data (see enclosed figure Packer Testing Results in Vicinity of Source Area) The additional borings installed within the fenced area and to the east of the fenced area showed that the area in which concentrations of total VOCs in groundwater exceeded 10000 pgL was more limited than portrayed in the RI and FS reports Packer testing of the intervals identified by geophysical logging as likely or possibly transmissive (see enclosed borehole geophysical logs) showed VOC concentrations within the packered intervals at a given borehole to be either essentially constant (eg MW-203 MW-204 MW-205) or increasing with depth (eg PW-207) Information on hydraulic conductivity and VOC concentrations in packered intervals is summarized on two separate tables for the 1999 RI wells and 2004 TI wells (Packer Permeability and Packer Sampling Results for Potential Fracture Intervals - enclosed) The orientation hydraulic conductivity and VOC concentrations of features identified as likely or possibly transmissive is summarized in a separate table (Orientation Permeability and Groundwater Sampling Results for Transmissive Features shyenclosed)

Table 4-1 of the TI Evaluation report summarizes the variation of input parameters to the flow and batch-flushing models as the project progressed from RI to FS to TI As described above for calculations in the TI Evaluation report hydraulic conductivity values were adjusted during the model calibration to pumping test drawdown data Measured fraction of organic carbon values and VOC concentrations were used in the Batch-Flushing model along with recharge calculated from the ModFlow model For calculation of pore flush volumes using the Batch-Flushing model the ratio of density to porosity was constrained to a range of 4 to 10 which is the typical range of such ratios in porous media (Freeze amp Cherry 1979) The basis for this change was stated in Appendix C of the TI Waiver Evaluation Report and is described in the response to Comment 3

Response to EPA Comment 2 050205doc 3 of 24 Woodard amp Curran (211941)

REFERENCE

Freeze RA and Cherry JA 1979 Groundwater Prentice-Hall Inc Englewood Cliffs NJ 07632 p 410-412

Response to EPA Comment 2 050205doc 4 of 24 Woodard amp Curran (211941)

LIST OF ATTACHMENTS (Response to Comment 2)

Figure - Drawdown at 72 Hours Shallow Wells

Figure - Drawdown at 72 Hours Deep Wells

Figure - Drawdown at 72 Hours

Figure - Potentiometric Surface at 72 Hours Shallow Wells

Figure - Potentiometric Surface at 72 Hours Deep Wells

Figure - End of Pumping Test Bedrock Potentiometric Surface at 72 Hours

Table - Pumping Test Analytical Results

Figure - USGS Background Groundwater Level

Figure - Packer Testing Results in Vicinity of Source Area

Figure - Borehole Geophysical Log MW-203

Figure - Borehole Geophysical Log MW-204

Figure - Borehole Geophysical Log MW-205

Figure - Borehole Geophysical Log MW-206

Figure - Borehole Geophysical Log PW-207

Table - Packer Permeability and Packer Sampling Results for Potential Fracture Intervals 1999 Drilling Program (2 pages)

Table - Packer Permeability and Packer Sampling Results for Potential Fracture Intervals 2004 Drilling Program

Table - Orientation Permeability and Groundwater Sampling Results for Transmissive Features 2004 Drilling Program (2 pages)

Response to EPA Comment 2 050205doc 5 of 24 Woodard amp Curran (211941)

(MEDEP Pond 1) Farm Pond

0 150 300

FEET

Monitoring Well

Figure X Pumping Well Drawdown at 72 Hours

_ - 17-Acre Property Boundary Shallow Wells Hows Corner Superfund Site Drawdown Contour (ft) Plymouth Maine

151 | Drawdown (ft) WOODARD ampCURRAN

^Stk Engineering bull Science bull Operations bull 211941 Hows CornlaquorwipDrawingsTI EVALDrawdown-72hrs_shallowdwg04-19-05

MW-3B

413951 W-6DB JMW-6SB

(MEDEP Pond 1) Farm Pond

Monitoring Well

Pumping Well

17-Acre Property Boundary

Groundwater Elevation Contour (ft)

211941 Hows CornerwipDrowngsTI EVALpo-tent-aU-72-hrsdwg

Figure X End of Pumping Test

Bedrock Potentiometric Surface at 72 Hours Hows Corner Superfund Site

Plymouth Maine ^ WOODARD amp CURRAN

Englnesring bull Science bull Ope

(MEDEP Pond 1) Farm Pond

Monitoring Well

Pumping Well Drawdown atFigure X

72 Hours _bullbull_ 17-Acre Property Boundary Deep Wells

Drawdown Contour (ft) Hows Corner Superfund Site

Plymouth Maine 151 | Drawdown (ft)

= WOODARD ampCURRAN 211941 Hows CornerwipDrawingsTI EVALDrawdown-72hrs_deepdwg04-19-05

Engineering bull Science bull Operations

(MEDEP Pond 1) Farm Pond

028 MW-12DB

MW-125B 040

l - _ ^ I 016 I N

050 MW-15SB

MW-15DB 048

A J s

- A - Monitoring Well

-$poundbull Pumping Well

_bullmdash 17-Acre Property Boundary

^ Drawdown Contour (ft)

151 I Drawdown (ft)

211941 Hows CornerwgtpDrawinQsT EVAI_Drawdown-72brsdwg04mdash19-05

Figure X Drawdown at 72 Hours

Hows Corner Superfund Site Plymouth Maine

^ WOODARD ampCURRAN Engineering bull Science bull Operations i

(MEDEP Pond 1) Farm Pond

Monitoring Well

Pumping Well

_bullbull_ 17-Acre Property Boundary

f Groundwater Elevation Contour (ft)

|419Q0| Groundwater Elevation

211941 Hows CornerwipDrawinqsTI EVALPotSurf-72hrs_shallowdwg04-19-05

150 300

FEET

Figure X Potentiometric Surface at 72 Hours

Shallow Wells Hows Corner Superfund Site

Plymouth Maine

WOODARD ampCURRAN Engineering bull Science bull Operations

29212 MW-108D

(MEDEP Pond 1) Farm Pond

Monitoring Well

Pumping Well

mdashbullbulllaquo 1 7-Acre Property Boundary

bull Groundwater Elevation Contour (ft)

1419001 Groundwater Elevation

211941 Hows CornerwipDrawingsTI EVALPotSurf-72hrs_deepdwg04-19-05

150 300 =5fc= FEET

Figure X Potentiometric Surface at 72 Hours

Deep Wells Hows Corner Superfund Site

Plymouth Maine

WOODARDampCURRAN Engineering bull Science bull Operations bull

--

Pumping Test Analytical Results Hows Corner Superfund Site

Plymouth Maine

Well ID oper Jaccb Analyses 2 Theis Analyses Fissure

Well Id Rd (ft)

Saturated Thickness

Transmissivity

(ft2day) K

(ft2day) K

(cmsec) Storage

Coefficient Transmissivity

(ft2day) K

(ft2day)

K (cmsec)

Storage Coefficient

System K

(ftday) PW-207OB 8 85 481 057 200E-04 392E-02 36 042 150E-04 809E-04 027 MW-103S 50 85 451 053 187E-04 720E-03 92 108 382E-04 283E-04 083 MW-103D 54 185 455 025 868E-05 210E-02 65 035 123E-04 237E-04 044 MW-2IB 59 85 352 041 146E-04 699E-03 104 123 433E-04 512E-04 052 MW-2DB 63 85 334 039 139E-04 845E-03 148 080 283E-04 239E-04 046 MW-104D 95 185 489 02 6 932E-05 654E-03 98 053 186E-04 547E-05 037 MW-104I 97 85 33 03 9 137E-04 362E-03 117 137 484E-04 962E-05 048 MW-101I 107 85 364 043 151E-04 490E-03 511 601 212E-03 223E-04 136 MW-102D 134 185 435 024 829E-05 248E-03 108 058 206E-04 850E-05 065 MW-101D 138 185 492 027 938E-05 511E-03 671 362 128E-03 700E-04 172 MW-205 219 85 57 067 237E-04 255E-03 447 526 186E-03 359E-03 -shyMW-204D 221 185 367 020 700E-05 170E-03 790 427 151E-O3 155E-04 147 MW-204S 225 85 379 045 157E-04 156E-03 1031 1213 428E-03 313E-04 199 MW-1B 228 85 325 038 135E-04 977E-04 340 400 141E-03 739E-05 054 MW-203S 273 85 489 058 203E-04 117E-03 1255 14 76 521 E-03 216E-04 210 MW-106D 278 185 51 028 972E-05 141E-03 1065 576 203E-03 360E-04 104 MW-203D 278 185 478 026 911E-05 152E-O3 765 414 146E-03 364E-04 138 MW-105D 364 185 44 024 839E-05 830E-04 769 415 147E-03 200E-04 127

1 Analyses conducted using Cooper and Jakob method on late drawdown data collected during constant

discharge pumping test conducted at the Hows Comer Site from September 20 - 30 2004

2 Analyses conducted using Theis solution for unconfmed approximation (1935)

J Analyses conducted using Moench method for dual porosity estimation (1984)

Fissure System Storage

Coefficient 402E-04 117E-06 264E-04 300E-04 932E-05 235E-07 502E-05 326E-06 801E-05 542E-04

-

803E-05 762E-05 134E-05 498E-05 115E-04

47E-04 838E-05

3 ysesh Analysis

Block System K (ft2day)

251E-02 207E-03 564E-04 163E-04 585E-04 465E-02 153E-04 498E-03 855E-04 356E-03

-

292E-03 394E-03 720E-04 526E-03 160E-01 35OE-O1 287E-03

Block System Storage

Coefficient

402E-02 164E-04 183E-02 330E-03 158E-03 847E-03 286E-03 326E-04 803E-05 272E-03

723E-04 686E-04 148E-04 349E-04 115E-03 47E-04 838E-04

Theis - Moench - CJ - AnalyticalResults_4-19-O5xls

DRAFT

242

24

238

236

bulla

c

i

a Q

234

232

228

226

Hows Corner Constant Discharge Testing USGS Background Groundwater Level USGS 445319068560101 ME-PEW456 Kenduskeag Maine

End of Monitored Recovery Period 09302004

Regional Background Location i 226 miles from Pumping Locatio

lt

697

NOTES

1 Groundwater samples collected in 1999 were screened for five volatile organic compounds (VOCs) only N

tetrachloroethene (PCE) exceeded reporting limits MW-2030 082304 082304 082304 082304 u

2 Strike and Dip of likely or possible transmissive 30 45 55 85 feature within the packer interval from which the indicated sample was collected

MW-204D

PCE TOTAL VOCs

081904 30

220 2636

A

081904 46-50 540 6436by

081904 IT

260 3073

x

MW-105D

PCE TOTAL VOCs

111199 50-60 2100 2100

MW-106D

PCE TOTAL VOCs

111199 76-86

400 400

111199 137-147

1400 1400

111299 1355-1455

350 350

PCE TOTAL VOCs

44 84

64

MW-6SB

bulli

lt

gt-

170 234

35

I I i

140 192

^^52

^^52

130 183

52 - lt

S A 34

PW-207 082404 082404 082404 20 37

PCE 1300 TOTAL VOCs

17-Acre George West Property Boundary

MW-113D

PCE TOTAL VOCs

112299 46-56

350 350

112299 70-80 190 190

150

112299 105-115

129 129

112399 138-148

230 230

L e g e n d ( J New Monitoring Well-Summer

Site Property Boundary ^ P u m p i n g Well-Summer 2004

-xmdashxshy Source Area

bull0shy Monitoring Well shy Pre 2004 Angled Boring-Summer 2004

211941laquoipdwgTI-ELV21ig41paltker-data2

2004 PCE of Total

bull lt70 VOCs

M W - 1 14D ^ ^

Figure xx Packer Testing Results in

Vicinity of Source Area Hows Corner Superfund Site

Plymouth Maine ^ WOODARD ampCURRAN

^^^^^^^^^^m ampKm Engineering - Science bull Operations

c Northeast Geophysical Services Borehole Geophysical Log

MW-203 Date logged 081704 Plymouth Maine

I Flowmeter Measurements Tomporaturo(C) Acoustic Televiewer

7 5 8 8 5 9 95 Caliper (Inches) Resistance (Ohms) Spontaneous Potential (mVj Dip In Degrees PCE Total VOCs

3 0 2 0 8 0 laquodeg 4S 1000 1400 1800 2200 MO HO 1000 1200 MOO 0 laquo deg ugL ugL n 1 1 1 1 1 1 1 1 1 i 1 1 1 1 n 1 1 1 1 1 1 1 1 1 1 1 n I l l l l l l l n

Ambient Flowneter pumping Rowmeter 11 gpm 6

H

bull

magnetic 10 bull 10 bull - 10 - north - 1 0I

-

_

bullbullbull - bull

20 bull bull20 bull ^ ltr~mdash 01

I

4 ^

LOS7

^

44 84 I I

Xr - 2

lt ^ bull30 -_ _^O1J- 1 _ 050 30 - 3 0

0r - - 3

C -j [ bull bull bull | shy

-O8 H ~ 1 045 7

1 4040 - 40 - -40 r - 14gt 13

V1s -- -023 f 1022 1V 170 234 I

T lt bull B gtf 50^ J50 - - 5 0 - - 5 0

I eet be

lo

i 1

1 1

1

140 192 - - - -t shy

-mdashj bullpound 60 - $o - - 60 - -60

H i I c

bull024

ampbull

3 - T lt ftft rgt He

70 bull j 70 - - 70 - 7 0 -

in -j bullbull shy

-021 1 T 022

- Ton _ Ov

26

130 183 NF NF

90 -_ 90 - 7 90 - -90

-

ifi Jf

3J

^gt _ N F NF bull bull shy

| H100 - j 100 bullbull 100 - -100

1 1 1 1 1 1 1 ) | 1 f I 1 1 1 ) 0 20 40 60 80

flft mdash ftn - mdash rVt

30 4 g 0 20 40 60 Dip in Degrees bullbull

Likely or poss bleFluid Resistivity (ohmmeters) The dip direction-- indicated

^ t h e l i n e extending from t h

I Iransmissive zone circle The strike of the feature is 90 degrees from this

The acoustic televiewer graph displays the mostprominent features selectedffom the acoustic televiewer

R n r a h n l c D O t t n O I B

f i o n n h w c i r a l U K U p i i y SI Ud l

1 rn l_Og Packered Interval August 2004

E tog The location dip angle and dip direction of the sleeted M W - 2 0 3 Groundwater samples were collected by Woodard S Curran on H23120M features are approximate Refer to the televiewer og of His _ well for more precise detail Plymouth Maine Date logged 081704

I

1

Northeast Geophysical Services Borehole Geophysical Log MW-204 D a t e l o gge d 072604

Plymouth Maine

n 3

Flowrneter Measurements(in gpm)

Caliper (Inches)0 3 5 4 0

1 1 1 1 1 1 1 t 1 1 1 1 1 1Ambient Rowmeler pumping Flowmetsr 05gpm

Templaquorature (C) bull bull bull bull i

7 75 8 8S 9 Resistance (Ohms) Spontaneous Potential (mV)

4000 SOW 600 4M 0

Acoustic Televiewer (interpreted)

Dip in Degrees 0 20 4060 SO

at N

PCEugL

Total VOCs ugL

- -_ a

10-

shy 10 bull - 10 shymagnetic

north - 10

o o

bull 1

11

11

1 1

1 1

11 1

1 1

1 1

1 1

1 1

1 1

1 1

1 1

1 1 E 1

- L

3 7 2 0 2 0r bull 20 bull - shy

i S_ N F

bull30 bull 7 3 0 220 2636shy1^ J J 004

fI f V ^

40 shy 4 0 4 0 shy - 4 0rbull019 [_ 007 w8 - - shy5 c

bull

gt

Ia50i 540 6436

bull50 - - 50 - - 5 0

-QQ7 - bull - -t T

pound V gtk

B 6 0 - e o - 7 6 0 -60shyQ 1 1

Q -007 -004 bull1 mdash T - J ~

bull

- - shyT 70 -J c [TO- - 70 - 7 0-

V Y 1- -004 -003

mdash T -h - y - j i - - mdash 260 3073 - gt=7

80 -j NF bull80 - - 80 - - 8 0Jgt

bull i

i 1

i i

C- bull shy

90 shy

K

Jlt i90 90 shy - 9 0shy -

l

ii

I I I I

NF bull M J

I ^ ^ - ^ bull 1

mdash mdash - _

s -7 ^100shy

till

1 100 100- H - 1 0 0shy -1 x Likety or possible k ^ Iransmissive zonebull

1 i i i ii i i i | l l l l | l i l l 0 20 40 ED 80

1 -

3 0SOFluid Resistivity (ohmmeters)

Dip in Degrees The djp ^ ^ o n is indicated ty Ihe line extending from tha circle The strike of Ihe feature

19- 3U UIHJIW93 IolII l l l lraquo

bull

The acousfc televiewer graph displays the mostprominent features selected from the acoustic televiewer109 The location dip angle and dip direction of Ihe sleetedfeatures are approximate Refer to the televiewer log of thiswentormore precise detail

B o r e h o l e G e O D h V S I C a l LOO B W H U I B w c w p n y o i v a i w v yM W - 2 0 4

P l y m O U t n MaiDB

Packorod Interval August 2004Groundwater san-ples wampramp collected by Woodard a Curran on OMO23C4

Date logged 072604

C

I

E Northeast Geophysical Services Borehole Geophysical Log Date logged 072704

I MW-205

Plymouth Maine

Flowmeter Measurements Temperature (C) Acoustic Televiewer (In gpm) I ~l (Interpreted)

I 85 10 Caliper (inches) 95

Dip in D g r laquo Resistance (Ohms) Spo ontaneous Potential (mV PCE Total VOCs 3 0 16 4 0 4 5 ) 20 40 60 80 10 00 2000 30 00 4VJ 400 -3 laquo

i i i i 1 i i I i 11 4 0 D 1 I I ugL ugL

C h

iii Ambient Flowmetar pumping

Flowmeter 1 25 gprn

I bull$bull

i

I rmdash magnetic 1 north ^^^^ 1 VI f

10 ~ I C x 10 bull - 10 bullbull

4 5 6mdashmdash f 1000B 11448 noisy nodi a raquo ^

mdash 5rt mdashi mdash Oft pound) 1100B 12509

cjmdash1 007

-

i i i 1

en

8 B a B

30 mdash

-

40 shy

-mdash I -

50 -_

__NF lt005

- 30 - - 3 0 it 34V

MO P26 V S) 1300B 13776 _ N F NF

26

40 bull - 40 bull 7-40 gt J Vf1 cX

) -j -

_ N F NF 50 c bull - 50 ^ 7-50

i I

I

c

B pound 60 - 6 0 7 60 - 7-60 a i 1

_ N F NF i Si f f 70 -_ bull70 bull - 70 shyC I 9

-m bull - shyA

_ N F NF 80 80 -j bull80 bull - 80 - C- 33 34

bull

5-i r

i 1

J r

Ck

_ N F NF 9 0 90 - - 90 shy

i bullCshy

J rK bull

100 -j ^ Likely or possible bull100- - 100- I -100

transmissive zone bull - ^ bull shy] |

1 1 1 1 1 1 1 I 1 i i i 1 i i 1 1 0 20 40 SO SO 10 20 30 40 50 Dip in Degrees 30 4 0 Fluid Resistivity (ohmmeters) Thlaquo dip direction is indicated

by the line extern r g from the circle The strike of he feature is 90 degrees from ihis

The acoustic televiewer graph displays the most

I Borehole Geophysical Log Packered Interval August2004 prominent features selected from the acoustic televiewer

Groundwatcr samples were oollccled by Woodard amp Cufran orgt S172004 log The location dip angle and dip direction of ins slsctsd MW-205 features are approximate Refelt to the televiewer log of this wall for more precise detail Plymouth Maine Date logged 072704

I

C

I Northeast Geophysical Services Borehole Geophysical Log Date logged 072704

I MW-206

Plymouth Maine

Flowmetor Measurements Temperature (C) Acoustic Televiewer | I r T i i i i i i i i i i i i i i r I |(in gpm) (Interpreted)

I 75 8 flS 9 95

Caliper (inches) Resistance (Ohms) Spontaneous Potential (mV) Dip In Degress PCE Total VOCs 30 35 40 4 5 0 20 40 M 90 4500 5500 6500 ugL ugL I i i

I I

- 1 0

I - 2 0

I 2900B 32401

i i L

E 0

i 6300B 68901

i I 0 20 40 SO 80

20 30 40 50 Dip in Dlaquogralaquos

amp 4 a Fluid Resistivity (ohrnmeters) The dip dirertion is indicated Likely or possible by iho line extending from the transmissive zone circle The striKe of the feature

is 90 degrees from tNs

Borehole Geophysical Log Packered Interval August 2004

E amples were collected by Woodard amp Cunan oo SM82004 log Thraquo location 4p angle and dip direction of the sloeled MW-206 feature are approximate Refer to the televiewer 109 of this well for more precise detail Plymouth Maine Date logged 072704

C

I Northeast Geophysical Services Borehole Geophysical Log

Date logged 082304 PW-207

I Plymouth Maine

Fiowmeter Measurements Temperature (C) Acoustic Televiewer

I (in gpm) (interpreted)

75 8 85 9 95 Caliper (inches) Resistance f0tims) Spontaneous Potential (mV) Dip in Degrees PCE Total VOCs

55 60 0 20 40 SO 80 ugL ugL I I I I I I I

Ambienl Fiowmeter pumping Flewmater

magnetic - 10 - - 1 0

north

i - 20 - - 2 0

1300 1410

i - 30 - - 3 0

i tf

5400 5802 - 40 - - 4 0

B - 50 - - 5 0

I 18000 19234

- 60 - - 6 0

I 12000 13085

- 70 - - 7 0

- 8 0

i - 9 0 19000 20354

G - 100- -100

I 110 110 bull110

0 20 40 60 SO 10 20 30 Dip m Degrees

Fluid Resistivity (ohmmeters) I 50

The dip direction is indicated by ihe line extending from the circle The strike of the fealure is 90 degrees from this

Borehole Geophysical Log

G Packorod Interval August 20(M log The location dip angle and dip dirlaquocton or the sleeted Groundaier samplss were ooliecled by Woodard i Curran on ampt24f2ltXM PW-207 failures are approximate Reter to the televiewer log of this wlaquoll for more precise detail PlyPIOUth Maine Date logged 082304

I

Table XX Packer Permeability and Packer Sampling Results for Potential Fracture Intervals

1

WellID MW-101D MW-101D MW-101D MW-101D MW-101D MW-101D MW-101D MW-101D MW-101D MW-101D MW-I01D MW-101D MW-101D MW-102D MW-102D MW-I02D MW-102D MW102D MW-102D MW-102D MW-102D MW-102D MW-I02D MW-102D MW-102D MW-102D MW-103D MW-103D MW-103D MW-103D MW-I03D MW-103D MW-103D MW-103D MW-103D MW-103D MW-103D MW-103D MW-I03D MW-104D MW-104D MW-104D MW-104D MW-I04D MW-104D MW-104D MW-104D MW-104D MW-104D MW-104D MW-105D MW-105D MW106D MW-106D MW-106D MW-107D MW-107D

1999 Drilling Program

Hows Corner Superfund Site Plymouth Maine

Potential Fracture Top Of Bottom 6 Depth to lt Topof i Interval from Packer Packer Middle of Elevation Hydraulic bull PCE

GS ELEV 1 Rock Drilling Interval Interval Interval of Interval Conductivity Concentration (ft msl) (ft msl) TEST (ftbgs) (ftbgs) r(ftbgs) ( f t b (ft mil) (cmsec) (raquogL)

4339 4329 13 28-29 33-3537-39 271 376 324 4016 OOOE+00 4339 12 37-3444-46 380 485 433 3907 157E-04 4339 11 488 593 541 3799 132E-04 4339 10 60-61 578 683 631 3709 OOOE+00 4339 9 678 783 731 3609 I79E-05 4339 8 778 883 831 3509 106E-05 4339 7 880 985 933 3407 243E-05 4339 6 990 1095 1043 3297 339E-06 4339 5 1090 1195 1143 3197 OOOE+00 4339 4 1190 1295 1243 3097 OOOE+00 4339 3 1365-1375 1290 1395 1343 2997 OOOE+00 4339 2 147-157 1390 1495 1443 2897 580E-05 4339 1 147-157 1470 1575 1523 2817 741E-05 43161 43061 13 166 271 219 4098 333E-04 43161 12 30-3136-40 260 365 313 4004 I54E-05 43161 11 36-4041-43 362 467 415 3902 548E-05 43161 10 470 575 523 3794 598E-05 43161 9 570 675 623 3694 197FOS 43161 8 670 775 723 3594 OOOE+00 43161 7 770 875 823 3494 891 E-05 43161 6 83-94 870 975 923 3394 139E-05 43161 5 970 1075 1023 3294 123E-04 43161 4 1070 1175 1123 3194 526E-06 43161 3 1170 1275 1223 3094 138E-05 43161 2 1270 1375 1323 2994 671E-06 43161 1 1370 1475 1423 2894 OOOE+00 42997 42497 13 18-19 170 275 223 4077 OOOE+00 42997 12 260 365 313 3987 766E-05 42997 11 360 465 413 3887 727E-05 42997 10 460 565 513 3787 192E-05 42997 9 560 665 613 3687 752E-05 42997 8 660 765 713 3587 778E-05 42997 7 85-86 763 868 816 3484 260E-05 42997 6 860 965 913 3387 289E-05 42997 5 102-103 960 1065 1013 3287 102E-04 42997 4 1060 1165 1113 3187 522E-06 42997 3 1160 1265 1213 3087 520E-06 42997 2 129-130 1260 1365 1313 2987 960E-04 42997 1 1360 1465 1413 2887 OOOE+00 43372 42922 11 35-37 42-45 350 455 403 3935 684E-04 43372 10 460 565 513 3825 500E-05 43372 9 560 665 613 3725 106E-05 43372 8 72-74 660 765 713 3625 204E-05 43372 7 760 865 813 3525 872E-06 43372 6 860 965 913 3425 467E-06 43372 5 960 1065 1013 3325 200E-05 43372 4 1060 1165 1113 3225 354E-05 43372 3 125-130 1160 1265 1213 3125 157E-05 43372 2 125-130 1260 1365 1313 3025 337E-04 43372 1 1365 1465 1415 2922 689E-06 43052 43002 2 54-58 490 595 543 3763 124E-05 2100 43052 1 139-140 145-146 1367 1472 1420 2886 154E-04 1400 43291 4391 3 bullI133 260 365 313 4017 439F06 43291 2 77-78 760 865 813 3517 230E-03 400 43291 1 143-144 1355 1460 1408 2922 971E-06 350

29958 27258 4 450 555 503 2493 OOOE+00 (21)A 29958 3 103-105 1000 1105 1053 1943 752E-04 (063)A

Table XX Packer Permeability and Packer Sampling Results for Potential Fracture Intervals

1999 Drilling Program

Hows Corner Supcrfund Site Plymouth Maine

gtbull i Potential Fracture Top _OfBot Bottom of Depth to ltbull Top of Interval from f Packer Packer Middle Of

GS ELEV lt Hock Drilling interval Interval Interval WeD ID ft msl) (ft msl) TEST (ftbgs) ltft$gs) (ftbgs) (ftbgs)

MW-107D 29958 2 128-130 1200 1305 1253

MW-107D 29958 1 139-141 1350 1455 1403

MW-108D 31904 31104 6 35-36 300 405 353 MW-108D 31904 5 60-62 550 655 603

MW-108D 31904 4 80-83 750 855 803

MW-108D 31904 3 118-119 123-124 1150 1255 1203

MW-108D 31904 2 147-149 1440 1545 1493

MW-108D 31904 1 1700 1805 1753

MW-110D 40576 40426 2 21-31 210 315 263 MW-110D 40576 1 148-154 1460 1565 1513 MW-I11D 40519 4 70-71 650 755 703

MW-111D 40519 3 79-82 84-86 780 885 833 MW-I11D 40519 2 97-102 950 1055 1003 MW-111D 40519 1 1370 1475 1423

MW-112D 3027 2942 4 42-52 420 525 473 MW-112D 3027 3 850 955 903 MW112D 3027 2 1100 1205 1153 MW-112D 3027 1 135-136 140-141 1340 1445 1393

MW-113D 43085 43085 5 250 355 303 MW-I13D 43085 4 47-49 460 565 513 MW-113D 43085 3 73-74 700 805 753 MW-113D 43085 2 1050 1155 1103 MW-113D 43085 1 1380 1485 1433

MW-114D 42394 41594 4 48-49 450 555 503 MW-114D 42394 3 79-81 740 845 793 MW-114D 42394 2 121-129 1250 1355 1303 MW-114D 42394 1 134-142 1350 1455 1403

MW-115D 4035 4035 4 300 405 353 MW-1I5D 4035 3 70-71 650 755 703 MW-115D 4035 2 1150 1255 1203 MW-115D 4035 1 1400 1505 1453

LOT-28W 382 7 450 555 503 LOT28W 382 6 550 655 603 LOT-28W 382 5 650 755 703 LOT28W 382 4 750 855 803 LOT-28W 382 3 850 955 903 LOT-28W 382 2 950 1055 1003 LOT-28W 382 1 1055 1155 1105

NOTES cmsec = centimeters per second ft bgs = leet below ground surface It msl = feet below mean sea level lt = not detected at indicated reporting limil A = detected below laboratory PQL ( ) = detected below reporting limits

Elevation of Interval

(ft nisi) 174

159

283gt 2588

2388

1988

1698

1438

3795 2545 3349 3219 3049 2629

2555 2125 1875 1635

4006 3796 3556 3206 2876

3737 3447 2937 2837

3683 3333 2833 2583

3318 3218 3118 3018 2918 2818 2715

Hydraulic Conductivity

(cmsec)

323E-05

208E-05

471E-03

471E-03

624E-05

3I6E-05

264E-05

261 E-05

OOOE+00 200E-04 953E-05 OOOE+00 OOOE+00 212E-05

361 E-05 410E-06 2gQE06 292E-05

786E-05 124E-05 151 E-05 822E-06 82IE-06

858E-05 I69E-05 352E-03 866E-05

223E-05 394E-06 122E-05 525E-06

831 E-05 182F-05 L62E-05 129E-05 190E-05 890E-04 981 E-04

PCEraquo Concentration

(ugL)

lt5

(14A)

98 11

15

22

11

30

200 (62)A

110 210 300 240

(44)A (23)A

5

350 190 129 230

2200 1900 2600 2600

(17)A (16)A (19)A

96

Table XX Packer Permeability and Packer Sampling Results for Potential Fracture Intervals

2004 Drilling Program

Hows Corner Superfund Site Plymouth Maine

Top of Bottom of Depth to Midpoint

t K

ELEV (ft Potential Transmissive Zones Packer Interval

Packer Interval

Middle of Interval

Elevation of interval

Hydraulic Conductivity

PCE Concentration

Well ID msl) TESTr (ft bgs)- (ftbgs) (ftbgs) (ftbgs) (ft msl) (cmsec) (ogt) MW-203D 43227 4 277279 24 32 28 4043 667E-05 44

3 408415420 39 49 44 3883 593E-05 170 2 526 530 49 57 53 3793 101E-04 140 I 828830842 80 88 84 3483 701E-05 130

MW-204D 43262 5 295 300 26 34 30 4023 902E-05 220 4 463496513516 45 53 49 3833 119E-04 540 3 681685688 63 71 67 3653 OOOE+00 2 758 76 2 71 79 75 3573 309E-05 260 I 88 96 92 3403 OOOE+00

MW-205 42389 3 164 166 168 15 20 175 4148 OOOE+00 1000B 2 302305312 30 35 325 3998 107E-04 1300B 1 40 45 425 3898 OOOE+00

MW-206D 43007 5 17 72 195 4128 291E-05 4 296 302 307 29 34 315 4008 940E-05 2900B 3 522 52 57 545 3778 944E-07 2 656 64 69 665 3658 353E-06 1 92392793 4939 91 96 935 3388 614E-05 6300B

PW-207 43477 5 184622162819 18 29 235 4088 209E-05 1300 4 3508 32 43 375 3948 568E-06 5400 3 53325341542154325559 50 61 555 3768 821E-05 18000

6359 61 72 665 3658 866E-06 12000 1 8685 84 89 865 3458 213E-05 19000

NOTES cmsec = centimeters per second ft bgs = feet below ground surface ft msl = feet above mean sea level B = detected in lab blank

Table XX Orientation Permeability and Groundwater Sampling Results for Transmissive Features

2004 Drilling Program

Hows Corner Superfund Site Plymouth Maine

Borehole Geophisical Feature depth Dip True Dip True Transmissive Log Feature (Feet) Degrees Azimuth Strike bullvgt(Ltk|iy^

Number v Tosftble) v MW-203 5 277 64 337 67 Likely

6 279 59 11 281 Likely 8 352 14 177 87 Likely 11 381 46 96 6 Possible 12 408 35 271 1 Possible 14 415 57 250 340 Possible 15 420 58 202 292 Likely 18 526 52 75 345 Likely 19 530 52 82 352 Likely 28 828 48 75 345 Likely 29 830 52 17 287 Likely 30 830 56 233 323 Possible 31 842 50 130 40 Likely

MW-204 4 295 15 147 57 Likely 5 300 43 91 1 Likely 11 439 31 80 350 Possible 12 440 46 219 309 Possible 14 463 50 358 88 Likely 15 496 34 198 288 Likely 16 513 54 17 287 Likely 17 516 33 14 284 Likely 25 681 39 359 89 Possible 26 685 22 45 315 Possible 27 688 35 73 343 Possible 32 758 45 236 326 Likely 33 762 46 306 36 Likely

MW-205 5 164 69 106 16 Possible 6 166 78 165 75 Possible 7 168 82 115 25 Possible 8 168 68 116 26 Possible 12 215 46 222 312 Possible 13 217 75 62 332 Possible 14 219 29 32 302 Possible 16 237 69 250 340 Possible 17 256 73 353 83 Possible 18 272 44 202 292 Possible 21 299 37 196 286 Possible 22 302 31 206 296 Possible 23 305 59 48 318 Likely 24 312 63 42 312 Likely

MW-206 1 264 37 181 271 Likely 2 296 69 217 307 Likely 3 302 66 233 323 Likely 4 307 64 224 314 Likely 8 342 62 259 349 Likely

jjHydraulic GoiDanctilyity j(cmsecjw

667 E-05

593 E-05

101 P04

710 E-05

902 E-05

119 E-04

0

309 E-05

0

107 E-04

94 E-05

PCE (ugL)

44

170

140

130

220

540

260

IOOOB

1100B

1300B

2900B

STotal vVoCsv tig1)

84

234

192

183

2636

6436

3073

11448

12509

13776

32401

PCEyo dfCTotaf

52

73

73

7 1

83

84

85

87

88

94

90

Table XX Orientation Permeability and Groundwater Sampling Results for Transmissive Features

2004 Drilling Program

Hows Corner Superfund Site Plymouth Maine

Borehole Geophisical Feature deptt raquoip True pip True Transraissive Log Feature (Feet) shy Degrees Azimuth Strike (tikely

Number raquo Possible) 22 522 57 54 324 Possible 25 656 40 82 352 Possible 32 871 59 151 61 Possible 33 883 53 185 275 Possible 34 895 7 175 85 Likely 35 899 53 90 0 Likely 36 902 49 184 274 Likely 37 923 9 175 85 Likely 38 927 42 206 296 Likely 39 934 48 167 77 Likely 40 939 26 180 90 Likely

PW-207 1 1846 33 167 77 Likely 4 2216 49 289 19 Possible 7 2819 59 265 355 Possible 11 3508 55 189 279 Possible 18 5332 43 305 35 Likely 19 5341 51 30 300 Likely 20 5421 20 254 344 Likely 21 5432 39 301 31 Likely 23 5559 52 302 32 Likely 25 6359 24 182 272 Possible 29 8049 77 231 321 Possible 30 8685 78 38 308 Likely 32 9334 29 194 284 Likely

NOTES

B = detected in lab blank

Hydraulic Conductivity

(cmsee) 944 E-07 353 E-06

614 E-05

209 E-05

568 E-06

821 E-05

866 E-06

213 E-05

bulltCE (ugL)

6300B

1300

5400

18000

12000

19000

Total VOCs (ug1)

68901

1410

5802

19234

13085

20354

PCE of Total VOCs

9 1

92

93

94

92

93

Response to EPA-DEP Comment 3 Dated March 312005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

lit

EPA-DEP Comment 3

Comment 3 The reported f values and resultant Kd values There remains doubt that the values used in the flushing model accurately reflect the propensity for PCE to sorb to the bedrock The ^ values presented in Appendix B may be unrealistically high because the bedrock samples may have contained organic carbon that was unavailable for sorption The reported f values are only qualitative estimates of the organic carbon content of the bedrock samples The Walkley and Black organic carbon measurement method is quick and simple but the results obtained cannot be considered quantitative because it requires a correction factor which often results in erroneous values it assumes the organic carbon has an average valence of zero oxidizable and reducible constituents such as chloride ferrous iron and manganese oxides interfere with the results and the errors introduced by interference are potentially greater when the organic carbon content is low at low f values it is not clear that organic carbon is controlling PCE sorption (Schwarzenbach and Westall 1981 Mackay et al 1986 Fetter 1999)

In order to derive a Kd-based retardation factor that is reasonable given the reported f values and the rapid advance of the PCE plume described on pages 4-11 and 4-12 the flushing model requires a bulk density to porosity ratio that is roughly two orders of magnitude higher than the actual ratio for the Hows Corner bedrock (page 4-4) This apparent discrepancy needs to be addressed

Response This comment raises several concerns about the collection and analysis of samples for fraction of organic carbon (f^) the quality of the resulting data and the implications of the use of those data for estimation of the retardation of groundwater contaminant movement Results of bedrock analysis for f were proposed in the TI Evaluation Work Plan for use in conjunction with groundwater contaminant concentrations and aquifer information to estimate cleanup times using the Batch Flushing model It is important to use accurate f values from representative bedrock in the Batch Flushing model in order to obtain reasonable estimates of the remedial time frame Because of the importance of accurate and representative results the TI Investigation field program was designed and conducted both to collect samples representative of the rock volume most likely to be in contact with contaminated groundwater and to analyze them using an appropriate refereed analytical method Five potential methods for evaluating f were identified Of the five methods the Walkey-Black method was selected because it has minimal method interferences and a sufficiently low detection limit as well as a long history of use in agronomy and contamination studies The PRP Group is pleased with the quality of the data obtained from the bedrock samples as represented by their precision and reproducibility

The first part of this comment relates to the determination of fraction of organic carbon (f^) values The several subparts of the first paragraph are addressed individually in items 1 through 5 below The second part of the comment regarding the resultant distribution coefficient (Kd) values is addressed separately as item 6 below

1 There remains doubt that the values used in the flushing model accurately reflect the propensity for PCE to sorb to the bedrock

bull The rock core samples used for f (gocg) analysis were from core immediately adjacent to fractures These rock core samples included the fracture surfaces themselves and rock core extending back less than 1 cm from the fractures Therefore the foe data reported in the TI Evaluation represents the f of bedrock through which groundwater will travel and to which PCE will adsorb Based on the careful selection of sample locations and the

Response to EPA Comment 3 050205doc 1 of 11 Woodard amp Curran (211941)

number of samples collected we are confident that the measured f values are representative of the f at points of contact for PCE with the bedrock it is these f values that determine the propensity of PCE to sorb to the bedrock

bull The samples of rock core collected for analysis of f originated from 19 different locations varying in depth from 11 to 90 feet Therefore it is very unlikely that the rock core samples were contaminated with extraneous organic carbon from above ground

2 The foc values presented in Appendix B may be unrealistically high because the bedrock samples may have contained organic carbon that was unavailable for sorption

bull As noted in response 1 the f data reported in Appendix B represents organic carbon primarily associated with the surface of fractures in the bedrock through which groundwater is most likely to travel Therefore it is this organic carbon that the contaminants in the groundwater will come in contact with and adsorb to in the fractured rock at the site

bull The chemical oxidation agents used in the Walkey-Black method oxidize the easily oxidizable organic carbon in the medium and the foe is calculated from the quantity of the agent consumed Therefore it is unlikely that the analysis of the bedrock samples measured organic carbon that was unavailable for sorption

3 The reported foc values are only qualitative estimates of the organic carbon content of the bedrock samples

bull The reported f values are accurate quantitative results Schumachers review of Methods for the determination of total organic carbon (TOC) in soils and sediments (NCEA-C-1282 EMASC-001 April 2002) identifies the Walkley-Black method which was used to analyze the reported foc values as the reference method for comparison to other methods for analyzing total organic carbon

bull Schumacher also points out that if anything the WalkJey-Black method may underestimate the total organic carbon in a sample due to possible incomplete oxidation of organic carbon Usually the incomplete oxidation of total organic carbon in environmental samples is corrected for by multiplying the measured foe by 130 (Walkley amp Black 1934 Schulte 1995)

bull When the f data in the TI Evaluation Report (WampC 2005) Appendix B (attached) are analyzed statistically the standard deviation of the f for the 19 samples analyzed is 174 of the average f Given this standard deviation the 95 confidence interval for this data ranged from a low of 000123 gocg to a high of 000253 gocgm

The labs Method of Detection Limit (MDL) for the f measured using the Walkley-Black method is 00001 gocg Therefore the average (000188 gocg) the mean (000185 gocg) and geometric mean (000187 gocg) of the f values for the rock core at Hows Corner are all statistically significantly greater than the MDL of the Walkley-Black method

In addition to the aforementioned statistical analysis of the foe data triplicate samples (n = 3) from the same rock core (including one sample from the 19 rock core samples) were

Response to EPA Comment 3 050205doc 2 of Woodard amp Curran (211941)

analyzed for their f to determine the repeatability of the Walkley-Black method The average the mean and the geometric mean of the f values of these replicate samples was 000162 gocg 000150 gocg and 000159 gocgm respectively The standard deviation of these measurements was 000039 gocg

4 The Walkley and Black organic carbon measurement method is quick and simple but the results obtained cannot be considered quantitative because it requires a correction factor which often results in erroneous values it assumes the organic carbon has an average valence of zero oxidizable and reducible constituents such as chloride ferrous iron and manganese oxides interfere with the results and the errors introduced by interference are potentially greater when the organic carbon content is low at low foc values it is not clear that organic carbon is controlling PCE sorption (Schwarzenbach and Westall 1981 Mackay et al 1986 Fetter 1999)

bull Schumachers review (NCEA-C-1282 EMASC-001 April 2002) of the Walkley-Black method identifies several potential problems with this analytical method that could occur if the analytical lab is not familiar with the nuances of the chemistry associated with this method Interestingly Schumachers review neglected one of the more important analytical steps required to avoid errors in quantifying f in samples where there might beNAPL

It is absolutely critical to eliminate any NAPL from rock core samples prior to using the Walkley-Black method to measure foe in such samples This was done by the lab (PTS Laboratories) that measured the foe in the rock core samples from Hows Corner The lab used the Dean-Stark method (solvent extraction) to remove all hydrocarbons (including PCE and other NAPLs) from the sample (PTS Laboratories) This extraction method does not interfere with the subsequent analysis of the natural organic carbon associated with the rock core

Subsequently the samples were dried at 150degC to a constant weight (normally 16 hours) This latter step oxidizes all inorganic minerals including ferrous bearing minerals to ferric oxides and precludes their interference during the oxidation of the samples with chromic acid This procedure completely eliminates any positive bias in the reported foc

data that might have occurred due to the presence of ferrous ions and other reduced minerals

bull As noted in Response 3 the incomplete oxidation of total organic carbon results in an underestimate of the f and is corrected for by multiplying the f by a correction factor of 130 (Walkley amp Black 1934 Schulte 1995) The fx data reported in the TI Evaluation was corrected accordingly by using this correction factor

bull Excess chloride (Cl~) in percent weight quantities as found in saline soils may interfere with the quantitative titration of reduced chromium (Walkley 1947) However given that the primary rock type at the Hows Corner site is phyllite it is highly unlikely that there was sufficient chloride in the rock core samples for this to occur

bull Manganese oxides may also interfere with the analysis of f through competing with the dichromate ion for any oxidizable carbon (Walkley 1947) However in such cases the reported f would be an underestimate of the f present in the rock core Walkley (1947)

Response to EPA Comment 3 050205doc 3 of 11 Woodard amp Curran (211941)

4

reported that in the case where the ratio of MnO2 to carbon is 85 to 1 the error in the carbon determinations would only be 0 to 6 percent

It may also be useful to compare the analysis of total organic carbon in a geologic matrix that contains high levels of manganese using EPA method 9060 to the Walkley-Black method Table 1 summarizes data provided by one of the PRPs that compares the analysis of total organic carbon in a geologic matrix that contains approximately 02 wgt manganese (approximately 03 wgt manganese oxide)

Table 1 Comparison of total organic carbon measured using the EPA- 9060 method and the Walkley-Black method

Laboratory EPA-9060 Method Walkley-Black Method A Ave 00226 gocg Not analyzed

Stdev 000251 gocg n = 5

B Ave 002219 gocg Ave 002050 gocg Stdev = 000316 gocg Stdev =000971 gocg

n= 10 n = 10

The similarity in the total organic carbon concentrations measured by these two different methods provides further confidence that the Walkley-Black method is a viable method for analysis of total organic carbon in the presence of manganese equivalent to at least 10 by weight of the total organic carbon

5 The Walkley and Black organic carbon measurement at lowf^ values it is not clear that organic carbon is controlling PCE sorption (Schwarzenbach and Westall 1981 Mackay et al 1986 Fetter 1999)

bull Schwarzenbach and Westalls (1981) paper states that f values of less than 0001 gocg should not be used in combination with Kow (octanol-water partition coefficients) values to calculate K^ values (solid phase partition coefficients) values for a specific contaminant It should be noted that the TI Evaluation did not use the f data to calculate the KQC from the Kow Instead as requested by the EPA the measured KOC value for PCE was used to calculate the retardation factor for this contaminant

bull Schwarzenbach et al (2003) stated more recently that Even at very low f values (ie foe = 0001 kgoc - kg1 solid) sorption to the organic components of a natural sorbent may still be the dominant mechanism in defining the adsorption of organic compounds to geological matrices

bull In 1985 M Piwoni from the US EPA Robert S Kerr Environmental Research Laboratory published a paper (Banerjee et al 1985) that showed that for very hydrophobic molecules TOC content of the sorbent will control sorption down to levels of organic carbon that defy quantitation Contaminants such as the PCE found in the groundwater at Hows Corner are in this category of compounds

Given the aforementioned reasons the f values reported in the TI Evaluation are accurate within the noted statistical limitations and will have a predictable impact upon the retardation of PCE during groundwater transport

Response to EPA Comment 3 050205doc 4 of 11 Woodard amp Curran (211941)

6 In order to derive a Kd-based retardation factor that is reasonable given the reported foc

values and the rapid advance of the PCE plume described on pages 4-11 and 4-12 the flushing model requires a bulk density to porosity ratio that is roughly two orders of magnitude higher than the actual ratio for the Hows Comer bedrock (page 4-4) This apparent discrepancy needs to be addressed

The apparent discrepancy of bulk density to porosity ratios is most likely due to the fact that the Batch Flushing Model was originally developed for a porous medium and is not directly applicable to fractured bedrock As stated in Appendix C (page C-4) of the Draft Technical Impracticability Evaluation Report in order to use the Batch Flushing Model to describe the transport of contaminated groundwater in fractured bedrock where the matrix porosity is insignificant it is more appropriate to use a fracture surface area to void space ratio to calculate the retardation factor (R) than a bulk density to porosity ratio (Freeze amp Cherry 1979)

Since it is impractical to determine the actual surface area to which contaminants can adsorb the Batch Flushing Model was used with two simplifying assumptions bull The Kd was calculated from the f and the K^ bull The bulk density to porosity ratio term in the Batch Flushing Model was constrained to range

from 4 to 10 the typical range of such ratios in porous media (Freeze amp Cherry 1979)

If one uses site specific bedrock bulk density and porosity values the bulk density to porosity ratio is several orders of magnitude greater (specifically 273 gcc bullbull 000165 (dimensionless) = 1654 gcc) than the range of ratios of 4 to 10 used in the Batch Flushing Model in the Draft Technical Impracticability Evaluation Report Constraining the bulk density to porosity ratio within the range of ratios of 4 to 10 results in significantly lower R value than would be obtained using specific bedrock bulk density and porosity values

In summary in bedrock where fractures are the primary porosity the bulk density to porosity ratio can vary considerably and will be a function of the number of fractures and the fracture aperture The calculated bulk density to porosity ratio will be inversely proportional to the porosity This means that in fractured rock with limited fracturing and smaller porosity the calculated bulk density to porosity ratio is greater and will result in a greater calculated retardation factor than in bedrock with more extensive fracturing and greater porosity Consequently the calculated retardation factor will be greater for bedrock with less surface area available for sorption than bedrock with greater surface area for sorption This is contrary to what actually occurs

4 Response to EPA Comment 3 050205doc 5 of 11 Woodard amp Curran (211941)

m

REFERENCES

Banerjee P MD Piwoni K Ebeid (1985) Sorption of organic contaminants to a low carbon subsurface core Chemosphere _14 1057-1067

Freeze RA JA Cherry (1979) Groundwater Prentice Hall Englewood Cliffs NJ pg 604

PTS Laboratories wwwptsgeolabscompdf files3TOCnotepdf

Schulte EE (1995) Recommended soil organic matter tests in Recommended Soil Testing Procedures for the Northeastern United States Northeastern Regional Publication No 493 Chapter 8

Schwarzenbach RP J Westall (1981) Transport of nonpolar organic compounds from surface water to groundwater Laboratory sorption studies Environ Sci Tech 15 1360-1367

Schwarzenbach RP PM Gschwend DM Imboden (2003) Environmental Organic Chemistry Wiley-Interscience pg 292 408 amp 412

Walkley A LA Black (1934) An examination of the Degtjareff method for determining soil organic matter and a proposed modification of the chromic acid titration method Soil Science 37 29-38

Walkley A (1947) A critical examination of a rapid method for determining organic carbon in soils - effect of variations in digestion conditions and of inorganic soil constituents Soil Science 63251-264

Woodard amp Curran Inc (WampC) 2005 Draft Technical Impracticability Evaluation Hows Corner Superfund Site Plymouth Maine January 2005

Response to EPA Comment 3 050205doc 6 of Woodard amp Curran (211941)

LIST OF ATTACHMENTS (Response to Comment 3)

Appendix B to Draft Technical Impracticability Evaluation Measurement of foe at Hows Corner (4 pages)

m

Response to EPA Comment 3 050205doc 7 of 11 Woodard amp Curran (211941)

Appendix B Measurement of foe of Rock Core at Hows Corner

There are two general approaches to measure the fraction of organic carbon (foe) in rock cores

bull Measurement of weight loss by ignition of organic matter bull Chemical oxidization of organic carbon to carbon dioxide and either

subsequent quantification of the oxidant used for the reaction or quantification of the carbon dioxide produced during this oxidation process

The weight loss method is subject to errors caused by volatilization of substances other than organic materials such as water hydroxides and mineral carbonates Quantification of foe by the weight loss method is particularly sensitive to the presence of carbonates in rock cores There are however weight loss methods that are designed to differentiate between organic carbon and the aforementioned interfering materials but they require considerable care and are less accurate at low foe values Hence the weight loss method was not well suited for measuring the foe of the rock core from Hows Corner

The chemical oxidation of organic carbon is much better suited for quantifying organic carbon in rock cores such as those from Hows Corner This method uses a strong chemical oxidant to oxidize organic carbon to carbon dioxide and then measures either the chemical oxidant used to oxidize the organic carbon or the quantity of carbon dioxide produced In addition this general approach is not subject to interference by volatilization of other constituents of the rock core

There are at least two such chemical oxidation methods

bull The method of Baccini which was described by Schwarzenbach amp Westall (1981) first acidifies the sample to eliminate interference by carbonates Then a strong oxidant is used to chemically oxidize the organic carbon to carbon dioxide The resulting carbon dioxide is subsequently reduced to methane and quantified using a flame ionization detector Unfortunately this method has not been described in detail in a referred journal Hence it is would not have been appropriate to use to characterize the foe in the Hows Corner rock core

bull The more commonly used method to quantify foe in rock core is the Walkley-Black method (1934) This method is preferred for RBCA and DODDOE projects and by the oil industry

The Walkley-Black method uses an excess of chromic acid to oxidize (digest) organic matter to carbon dioxide The remaining chromic acid that was not consumed during the oxidation of the organic carbon is then quantified by titration with ferrous sulfate The difference in chromic acid prior to and after the oxidation of the organic carbon represents the total chromic acid used to oxidize

Hows Corner TI Evaluation Page 1 January 13 2005 Appendix B

the organic carbon in the sample The latter can be calculated using the chemical stoichiometry of the reaction

The Walkley-Black method is very accurate for samples that contain less than 2 organic carbon matter The minimum detection limit (MDL) for the Walkley-Black method is 100 mgkg or an foe of 0001

Given the rock core at Hows Corner was expected to contain less than 2 organic carbon the Walkley-Black method was used to measure the foe from 19 different rock core samples collected from varying depths ranging from 11 to 90 feet

Table 1 provides a statistical summary of the aforementioned data

Table 1 Statistical summary of foe data from rock cores collected at varying depths

Statistical Parameter Calculated Value foe Minimum Detection Limit (MDL) 00010 Number of samples analyzed (n) 19 Average foe 00019 Median foe 00019 Geometric Mean foe 00019 Standard deviation of foe measurements 000033 Relative standard deviation 174 -+ 95 Confidence intervals 00012 to 00025

The data in Table 1 shows the following

bull The foe from the Hows Corner rock cores are statistically greater than the MDL of the Walkley-Black analytical method

bull The average and median values for the foe of the Hows Corner rock cores from varying depths are nearly identical indicating that there is little variability in the foe values in the source zone at the site

bull The standard deviation of these measurements is 000033 which is 174 of the average foe

bull The 95 confidence intervals of the foe of the rock core at Hows Corner are 00012 to 00025

The foe was also analyzed from three separate samples taken from the same rock core at a depth of 55 feet (Only one of these samples was included in the data summarized in Table 1) Table 2 shows the statistical repeatability of this type of analysis

Hows Corner TI Evaluation Page 2 January 13 2005 Appendix B

Table 2 Repeatability of analysis of foe from one rock core at 55 feet in depth

Statistical Parameter Calculated Value Number of samples analyzed (n) 3 Average foe 00016 Median foe 00015 Geometric Mean foe 00016 Standard deviation of foe measurements 000039 Relative standard deviation 240 -+ 95 Confidence intervals 00008 to 00024

The data in Table 2 shows the following

bull The percent relative standard deviation of these three analyses of foe from the same rock core at Hows Corner is 24

bull The 95 confidence interval of the foes measured in this particular rock core at Hows Conrer is 00008 to 00024

These results show that there is good repeatability in using the Walkley-Black method for analysis of the foe in the rock core at Hows Corner

References Schwarzenbach amp Westall (1981) Transport of nonpolar organic compounds from surface water to groundwater Laboratory sorption studies Environ Sci Tech 15 1360-1367

Walkley A I A Black (1934) An examination of Degtjareff method for determining soil organic matter and a proposed modification of the chromic acid titration method Soil Sci 37 29-37

Hows Corner Tl Evaluation Page S January 13 2005 Appendix B

Woodard and Curran PTS Laboratories PTS File No 34618

ORGANIC CARBON DATA (METHODOLOGY WALKLEY-BLACK)

PROJECT NAME PROJECT NO

SAMPLE ID

203-chip-13 203-chip-23 203-chip-27 203-chip-38 203-chip-42 203-chip-47 203-chip-52 203-chip-58 203-chip-69 203-chip-82 207-chip-11 207-chip-19 207-chip-24 207-chip-29 207-chip-35 207-chip-45 207-chip-55 207-chip-87 207-chip-90

207-chip-55 55-MS

55-MSMSD

Hows Corner NA

DEPTH ft

13 23 27 38 42 47 52 58 69 82 11 19 24 29 35 45 55 87 90

55 NA NA

MATRIX

Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip

Average Median

Geometric Mean Standard Deviation Relative Std Dev

+- 95 Confidence Interval n

Rock Chip Rock Chip Rock Chip

Average Median

Geometric Mean Standard Deviation Relative Std Dev

+- 95 Confidence Interval n

FRACTION ORGANIC CARBON

(gg)

170E-03 185E-03 185E-03 170E-03 240E-03 190E-03 230E-03 180E-03 170E-03 115E-03 195E-03 220E-03 220E-03 235E-03 135E-03 190E-03 205E-03 175E-03 160E-03

188E-03 185E-03 185E-03 327E-04

1739 123E-03 to

19

205E-03 130E-03 150E-03

162E-03 150E-03 159E-03 388E-04

2402 840E-04 to

3

2532E-03

2393E-03

Hows Corner Tl Evaluation Appendix B January 13 2005

Response to EPA-DEP Comment 4 Dated March 31 2005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

EPA-DEP Comment 4

Comment 4 Distribution of contaminants First the TI report seems based on the assertion that there is DNAPL at the source area yet it also appears to represent that the source area is small and the bedrock below 85 is competent (or less fractured) and less impacted by the release of contaminants Some of the confusion may result from using most recent data when that data is from several different sampling events over several years and there is no discernible difference in concentrations between shallow and deep bedrock or as in Section 421 where generally decreased generally increase generally similar and similar concentrations in four consecutive sentences leads to a muddled picture of the contaminant distribution

Second the report asserts that the distribution of contaminants over the entire plume has not changed with time but fails to support this conclusion with data again relying on data that is from different sampling dates for one composite representation

Response The likely presence of dense non-aqueous phase liquid (DNAPL) at the Hows Corner Site and the determination that the source area is small are not mutually exclusive and both are conclusions drawn from information obtained during field investigations The presence of DNAPL in the source area is based on the elevated concentrations of volatile organic compounds (VOCs) detected in the groundwater (WampC 2001 WampC 2002) The conclusion that the source area is small is based on the area in which VOCs in groundwater have been detected at concentrations that are considered to be indicative of the presence of DNAPL nearby Similarly the conclusion that fracture frequency decreases at depths greater than approximately 50 to 85 feet below ground surface was based on field observation during the RI field work The fact that zones with observed fractures exhibited higher hydraulic conductivities than zones without fractures coupled with the decreasing frequency of observed fractures with depth led to the conclusion that the hydraulic conductivity of the bulk rock decreases with depth

The most recent data from all wells were used to provide the maximum VOC data set size During the RI all of the previously-existing and then newly-installed monitoring wells were sampled along with several residential wells The RI sampling included up to 48 monitoring wells Subsequent to the RI and prior to the TI three rounds of monitoring were conducted to verify that the plume was stable 15 monitoring wells were sampled during each of the three rounds During the TI field investigation 29 wells were sampled for VOCs The sampled wells included all of the newly-installed wells and a subset of wells installed during the RI for a total of 29 monitoring wells By using most recent data VOC results from 53 monitoring wells were included in the evaluation (see table labeled Sampling Events for listing of monitoring wells) This approach was selected because there generally was little variation in the data from a particular location between years This is borne out by the attached individual plots of VOCs detected in shallow bedrock and deep bedrock for the Pre-ROD (December 1999January 2000) and Supplemental (May 2000) sampling events and for June 2001 January 2002 and April 2003 sampling events The Pre-ROD and Supplemental plots are similar to the subsequent plots from the 2001 2002 and 2003 sampling events

In addition to maps showing the spatial distribution of VOC data at a given time trend plots of the data from a particular location through time (attached) indicate that since the RI concentrations generally have been stable or have decreased Together the maps and trend plots and the data from which they were developed indicate that the distribution of contaminants over the entire plume has not changed appreciably with time

Response to EPA Comment 4 050305doc 1 of 26 Woodard amp Curran (211941)

REFERENCES

Woodard amp Curran Inc (WampC) 2001 Final Remedial Investigation Report Hows Corner Superfund Plymouth Maine July 2001

Woodard amp Curran Inc (WampC) 2002 Final Feasibility Study Report - Non-Source Area Groundwater Hows Corner Superfund Site Plymouth Maine Hows Corner Superfund Plymouth Maine July 2002

Response to EPA Comment 4 050305doc 2 of 26 Woodard amp Curran (211941)

LIST OF ATTACHMENTS (Response to Comment 4)

Table - Sampling Events 1999 - 2004 (2 pages)

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater Pre-ROD Sampling Event

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater Pre-ROD Sampling Event

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater Supplemental Sampling Event

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater Supplemental Sampling Event

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater June 2001

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater June 2001

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater January 2002

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater January 2002

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater April 2003

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater April 2003

Figure - Concentration Trends - Non-Source Area Wells MW-1B and MW-3B

Figure - Concentration Trends - Non-Source Area Wells MW-13DB and MW-16DB

Figure - Concentration Trends - Non-Source Area Wells MW-16IB and MW- 108D

Figure - Concentration Trends - Non-Source Area Wells MW-108S and MW-112D

Figure - Concentration Trends - Non-Source Area Wells MW-112S and MW-114D

Figure - Concentration Trends - Non-Source Area Wells MW-114S and MW-115D

Figure - Concentration Trends -Source Area Wells MW-2DB and MW-2IB

Figure - Concentration Trends -Source Area Wells MW-102S and MW-103D

Figure - Concentration Trends -Source Area Wells MW-103S and MW-104D

Figure - Concentration Trends -Source Area Wells MW-104I and MW-106D

Figure - Concentration Trends -Source Area Wells MW-106S

Response to EPA Comment 4 050305doc 3 of 26 Woodard amp Curran (211941)

I I

El I

II I I 1 I

I

i

Event Baseline Case ID WC-01 WC-01

Well Date Aug-99 Oct-99 LOT10 1 LOT1-1 1 LOT11-4 LOT14 1 LOT15 1 LOT15-1 1 LOT16 1 LOT16-1 1 LOT17 1 LOT18 1 LOT19 1 LOT2 LOT20 1 LOT21-10 1 LOT21-11 1 LOT21-12 1 LOT21-13 1 LOT21-14 1 LOT21-2 1 LOT21-5 1 LOT21-7 LOT21 -8 1 LOT21-9 1 LOT23 1 LOT24 1 LOT28-1 1 LOT28-2 1 LOT28-3 1 LOT28-4 1 LOT28W 1 LOT30 1 LOT30-1 1 LOT30-2 1 LOT30-3 1 LOT30-4 1 LOT30-5 LOT31 LOT35 1 LOT41 1 LOT42-1 1 LOT43-1 1 LOT43-4 1 LOT6-1 1 LOT67 1 LOT6-7 1 LOT6-8A 1 LOT6-8B 1 LOT80-1 1 LOT82 1 MW-101D MW-1011 MW-101S MW-102D MW-102S MW-103D MW-103S MW-104D MW-1041 MW-104S MW-105D MW-106D

Groundwater Sampling Location Summary 1999 - 2004xls

Sampling Events 1999-2004

Hows Corner Superfund Site Plymouth Maine

Supplemental 2001 2002 2003 Pumping 2004 Pre-ROD Rl Sampling Sampling Sampling Test Sampling WC-03 WC-09 WC-25 WC-30 WC-42B WC-56 WC-58 Dec-99 May-00 Jun-01 Jan-02 Apr-03 Sep-04 Sep-04

1

1 1 1

1 1 1 1 1

1 1

1

1 1

1 1 1

1 1 1 1 1

1

1 1

1 1 1 1

1

1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

Sampling Events 1999-2004

Hows Corner Super-fund Site Plymouth Maine

Supplemental 2001 2002 2003 Pumping Event Baseline Pre-ROD Rl Sampling Sampling Sampling Test

Case ID WC-01 WC-01 WC-03 WC-09 WC-25 WC-30 WC-42B WC-56

ll

Well Date Aug-99 Oct-99 Dec-99 May-00 Jun-01 Jan-02 Apr-03 Sep-04 MW-106S 1 1 1 1 1 MW-107D 1 1 MW-108D 1 1 1 1 1 MW-108S 1 1 1 1 1 MW-110D 1 1 MW-111D 1 1 MW-112D 1 1 1 1 1 MW-112S 1 1 1 1 1 MW-113D 1 1 MW-114D 1 1 1 1 1 MW-114S 1 1 1 1 1 MW-115D 1 1 1 1 1 MW-12DB 1 1 1 MW-12SB 1 1 1 MW-13DB 1 1 1 1 1 1 MW-13SB 1 1 1 MW-14DB 1 1 MW-14SO 1 1 MW-15DB 1 1 1 MW-15SB 1 1 1 MW-16DB 1 1 1 1 1 1 MW-16IB 1 1 1 1 1 1 MW-16SO 1 1 MW-17DO 1 1 1 MW-17SO 1 1 1 MW-1B 1 1 1 1 1 1 MW-203D MW-203S MW-204D MW-204S MW-205 MW-206D

I MW-206S MW-2DB 1 1 MW-2DDB 1 1 MW-2IB 1 1 1 1 1 1 MW-3B 1 1 1 1 1 1

I MW-4O 1 1 1 MW-5B 1 1

II MW-6DB 1 1 1 MW-6SB 1 1 1 MW-8DB 1 1 1 MW-8SB 1 1 1

II PW-207 1 SEEP-1 1 SUBTOTAL - RESIDENTIAL 44 25 0 2 0 3 0 SUBTOTAL - MONITORING 22 48 41 15 15 15 1

Total 3 66 73 41 17 15 18 1

I Included in most recent data

I Notes 1 - Overburden well not included in most recent data for plotting

2 - Tetrahydrofuran and 2-Butanone were the only two compounds detected in this well and are thought to be the result of well repair not included in most recent data for plotting

3 - Not included in most recent data for plotting

2004 Sampling

WC-58 Sep-04

1

1 1

1 1

1 1 1

1

1 1

1 1 1 1 1 1 1 1 1

1 1

1

0 29

29

Groundwatef Sampling Location Summary 1999 - 2004xls

I

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

monitoring well Figure 4-14 total VOC contour (ugl) - December 1999January 2000 Distribution of Total VOCs in

Note SW-113 is located downstream of SEEP-1 Shallow Bedrock Groundwater total concentration of detected VOCs ND= not detected these two locations were sampled during the Pre-ROD Sampling Event

Baseline Sampling Event in OctoberNovember 1999 Hows Corner Superfund Site Surface Water Sampling Location A Plymouth Maine Seep Sampling Location laquo- WOODARD ampCURRAN

995037wipri reportepa ri interim final feb 2001cadd drawingsfinalfig 4-14

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

0 300 600 I

FEET

Q residential well Figure 4-16 monitoring well Distribution of Total VOCs in

Deep Bedrock Groundwater total VOCs contour (ugl) Pre-ROD Sampling Event

active residential wells with lot number Hows Corner Superfund Site 2deg42deg Plymouth Maine total concentration of detected VOCs ND= not detected WOODARD ampCURRAN Enyinaaring bull Science bull Operations bull

995037wipri reportepa ri interim final feb 2001cadd drawingsfinalfig4mdash16

PLYMOUTH POND

PLYMOUTH POND

1 628Tl7MW-2bB 12135

PLYMOUTH POND

monitoring well Figure 4-20

V total VOC contour (ugl) - June 2000 Distribution of Total VOCs in Shallow Bedrock Groundwater

| 34 | total concentration of detected VOCs ND= not detected NA = not analyzed Supplemental Sampling Event Note SW-113 is located downstream of SEEP-1 Hows Corner Superfund Site

Surface Water Sampling Location these two locations were sampled during the Plymouth Maine Baseline Sampling Event in OctoberNovember 1999 Seep Sampling Location WOODARD amp CURRAN

Engineering bull Science - Operations bull 995037wipri reportepa ri interim final feb 2001 cadd drawingsfinalfig 4-20

residential well Figure 4-22 Distribution of Total VOCs in

monitoring well Deep Bedrock Groundwater

total VOCs contour (ugl) Supplemental Sampling Event

Hows Corner Superfund Site

total concentration of detected VOCs ND= not detected NA = not analyzed Plymouth Maine

WOODARD amp CURRAN

995037wipri reportepa-ri interim final feb 2001cadd drawingsfinalfig 4-22 Engineering bull Science - Operations bull

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

FEET

Shallow Monitoring Well

Deep Monitoring Well

C Detected Concentration ND = Not Detected Figure 1-XS Distribution of Total VOCs in Shallow Bedrock Groundwater

Pumping Well

17-Acre Property Boundary Concentration Contour (ugl)

June 2001 Hows Corner Superfund Site

Plymouth Maine WOODARDampCURRAN

-i^rhvj bull Scbncn bull Operations bull 211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0601 dwg04-20-05

PLYMOUTH POND Hopkins Road V

O

PLYMOUTH POND

PLYMOUTH POND

o

0 300 600 mdashfa FEET

Shallow Monitoring Well bull bull - 17-Acre Property Boundary Figure 1-XD

Deep Monitoring Well 1 I Detected Concentration ND = Not Detected Distribution of Total VOCs in Deep Bedrock Groundwater

-mf- Pumping Well June 2001 Residential Well Hows Corner Superfund Site

Plymouth Maine i h Surface Water Sampling Point

g WOODARD ampCURRAN _ ^ _ ^ _ _ yen_ rj i|Hlaquorlny bull Science bull Opt

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0601 dwg04-20-05

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

Shallow Monitoring Well

Deep Monitoring Well

Detected Concentration ND = Not Detected Figure 1-YS Distribution of Total VOCs in Shallow Bedrock Groundwater

Pumping Well

17-Acre Property Boundary Concentration Contour (ugl)

January 2002 Hows Corner Superfund Site

Plymouth Maine WOODARD amp CURRAN Engineering Science- Operations bull

211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0102dwg04-20-05

PLYMOUTH POND

PLYMOUTH POND

Site Pand^ laquoum-laquoBTuitaraquo tLV

vVlf-(

PLYMOUTH POND

0 300 600 ^ = FEET

Shallow Monitoring Well mdashbullbullbull 17-Acre Property Boundary Figure 1-YD - A - Deep Monitoring Well FT Detected Concentration ND = Not Detected Distribution of Total VOCs in

Deep Bedrock Groundwater Pumping Well January 2002 Residential Well Hows Corner Superfund Site

Plymouth Maine Surface Water Sampling Point

WOODARD ampCURRAN Engineering Sciencs- Operations bulli Si

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0102dwg04-20-05

- m j

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND j A O-shy

Shallow Monitoring Well E Detected Concentration ND = Not Detected Figure 1-ZS Distribution of Total VOCs in

Deep Monitoring Well Shallow Bedrock Groundwater

Pumping Well Hows Corner

April 2003 Superfund Site

17-Acre Property Boundary Plymouth Maine Concentration Contour (ugl) r WOODARD ampCURRAN

Engineering bull Science bull Operations bull 211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0403dwg04-20-05

s S pound

PLYMOUTH POND

PLYMOUTH POND

- -

5 PLYMOUTH POND

Jo

FEET

ft Shallow Monitoring Well mdashbullbullmdash 17-Acre Property Boundary Figure 1-ZD Deep Monitoring Well I 1 I Detected Concentration ND = Not Detected Distribution of Total VOCs in

Deep Bedrock Groundwater Pumping Well April 2003

Q) Residential Well Hows Corner Superfund Site Plymouth Maine

(T) Surface Water Sampling Point WOODARD ampCURRAN poundKk EnginawtirKj bull Science - Operations bull

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0403dwg04-20-05

0 Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

B MW-1B

I 12000

PCE

B 10000 Total VOCs

I

i 2000

i 0 Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

c MW-3B

G 2000

1800

B PCE

1600 Total VOCs

1 I I E

il-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

G E

211941

El

I I z E

80

Concentration Trends shy Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-13DB

Total VOCs

c i i c o

Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

MW-16DB

30

c i c c I c o

Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99

PCE

Total VOCs

Jul-01 Jul-03

211941

O bi

c Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

I MW-16IB

i 35

3

c Total VOCs

lt- 2 5

0 | gt

o

1 sectI

c c 0 4

Jul-90 Jul-92 Jul-94 Jul-96 Jul-98 Jul-00 Jul-02 Jul-04

I I MW-108D

I 12

PCE 10

Total VOCs c oc 3

E E I 0

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

E 211941

c Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

fi MW-108S

I I 40

PCE 35

Total VOCs

30

I f 26

20 I o

I 15

10

c Dec-99 Dec-00 Dec-01 Dec-02 Dec-03 I 0

I MW-112D

c 35 - imdash

I A3 shyTotal VOCs

o c

E 1 2

I

ition

B 1 ^

-i c 3

0 Dec-99 Dec-OO Dec-01 Dec-02 Dec-03

211941

I

i

I

cII

Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-112S

08

PCE

Total VOCs 06

o 04

02

0 Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

MW-114D

o

12000

10000

8000

6000

PCE

Total VOCs

4000

2000

i

ccEIIc

i

i

E

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

211941

Con

cent

ratio

n (

ug

l)

E Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

I MW-114S

E A5000 -- Total VOCs

- 4000

0 3000

2000

i 1000

i n shy

Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

MW-115D

c PCE

Total VOCs

c E

o

C c

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03 I 0

211941

IepoundII

EIEIIGICCIccc

30000

25000

20000

o bullsect 15000 b

o 10000 U

5000

0 Aug-99

25000

20000

5000

0 Aug-99

211941

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-2DB

PCE

Total VOCs

Aug-01 Aug-03

MW-2IB

PCE

Total VOCs

Aug-01 Aug-03

IDIBI

ii EIDIISIBIG C

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-102S

6000

5000 PCE

Total VOCs

4000

O 3000

2000

1000

0 Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

MW-103D

16000

~ 14000 ugt 3- 12000 o

^ 10000

sect 8000

O 6000

4000

2000

PCE

Total VOCs

0Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

211941

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

G MW-103S

I I

ampo

12000

10000

E sectc

S

8000

6000

4000

2000

0Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

G I 6000

MW-104D

i 5000

PCE

Total VOCs

i i c

2000

1000

Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

E I

211941

cIccIG

IIBCccBcIc

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-1041

PCE Total VOCs

a 25000

0 20000

a 15000

10000

5000

0 Jan-OO Jan-01 Jan-02 Jan-03 Jan-04

MW-106D

3000

2500 PCE

Total VOCs

=sect 2000

o bullsect 1500

1000

500

0 Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

211941

c Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

c MW-106S

I PCE

Total VOCs

i

i Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

i

i i i E

C

211941 c

Response to EPA-DEP Comment 5 Dated March 312005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

iiw

EPA-DEP Comment 5

Comment 5 Matrix Diffusion The report as well as other proponents of matrix diffusion suggest that depletion of DNAPL (Section 5112 page 5-15) needs to be achieved While that might be the ideal the goal is to achieve performance standards and that goal may be attainable while there is residual contamination in the rock perhaps even DNAPL globules The low bedrock matrix porosity (page 1-15) the high permeability values (page 4-4) the relative flux of the groundwater (page 5-5) and the decrease in surface area and out of the mainstream pockets (appendix C-4) all suggest that the diffusion out of the rock matrix would be insubstantial relative to the regional flux of groundwater through the Site

Response The TI Evaluation Report does not explicitly consider or rely upon matrix diffusion as a basis for requesting a TI Waiver for a portion of the Hows Corner Site The technical literature provides documentation that matrix diffusion can be a significant process that affects chemical transport and groundwater remediation timeframes in unconsolidated and consolidated media including fractured rock (US EPA 1989 Freeze and Cherry 1979 Pankow and Cherry 1996 Fountain 1998) Back diffusion of contaminants from the matrix porosity of the fractured rock can prolong the time necessary to achieve groundwater cleanup goals particularly for compounds such as PCE for which the cleanup goal is a low concentration It is our expectation that matrix diffusion has occurred at the Hows Corner Site and that back diffusion of PCE from the rock matrix will also occur Although the extent to which matrix diffusion is occurring at the Hows Comer Site has not been determined and that lack of knowledge contributes to uncertainty regarding the cleanup times at the Site the effect of matrix diffusion is to lengthen rather than shorten the time required for remediation

REFERENCES

Fountain JC 1998 Technologies for Dense Nonaqueous Phase Liquid Source Zone Remediation Ground-Water Remediation Technologies Analysis Center Technology Evaluation Report TE-98-02 December

Freeze RA and Cherry JA 1979 Groundwater Prentice-Hall Inc Englewood Cliffs NJ 07632 p 410-412

Pankow J F and Cherry J A 1996 Dense Chlorinated Solvents Waterloo Press Portland OR 97291-1399 p 67-88

US EPA 1989 Transport and Fate of Contaminants in the Subsurface EPA6254-89019 p 17-18

Response to EPA Comment 5 050305doc 1 of 1 Woodard amp Curran (211941)

WOODARD amp CURRAN Maine Massachusetts New Hampshire Connecticut Florida Operational offices across the US 1-800-426-4262 www woodardcurran com

Page 2: SDMS DocID 251749 - Records Collections · 2020-06-13 · CORPORATE OFFICES: Maine, Massachusetts, New Hampshire, Connecticut New, York, Florida Engineering • Science • Operations

CORPORATE OFFICES Maine Massachusetts New Hampshire Connecticut New York Florida

Engineering bull Sc ience bull Operat ions Operational offices throughout the US

May 3 2005 Via FedEx

Mr Terry Connolly Remedial Project Manager USEPA - New England Region 1 Congress Street Suite 1100 (HBT) Boston MA 02114-2023

Subject Hows Corner Superfund Site Plymouth Maine (Site) Transmittal of Responses to Comments Dated March 31 2005 on Draft Technical Impracticability (IT) Report

Dear Mr Connolly

As requested in your letter dated March 31 2005 two copies of written responses to the agencies comments on the Draft Technical Impracticability Report are enclosed for your review Three copies of the responses have been sent to Rebecca Hewert at MEDEP and one copy has been sent to Michael Healey at TetraTechNUS

The PRP Technical Committee would be pleased to speak with you or meet with you after you have had an opportunity to review the enclosed material Please call Mark Beliveau or me to discuss a schedule for continuing our progress toward completion of the TI Evaluation Report for the Hows Corner Site

In the meantime if you have questions on the enclosed responses please contact me at 2077742112

Sincerely

WOODARD amp CURRAN INC

Thomas R Eschner Senior Project Manager

Enclosures

cc Rebecca Hewett MEDEP (3 copies) Michael Helaey TetraTechNUS (1 copy) Mark Beliveau Pierce Atwood (1 copy)

41 Hutchins Drive bull Portland Maine 04102 bull (207)774-2112- (800)426-4262 bull (207) 774-6635 (Fax) wwwwoodardcurrancom

VVOODAFDampCURRAN Engineering bull Science bull Operations

bcc Jim Rawson General Electric (1 copy) Don Frost JrKristin Larson Skadded Arps Slate Meather amp Flom (1 copy) Philip Buckley Rudman amp Winchell (1 copy) Andrew HamiltonHeather Parent Eaton Peabody (1 copy) Joanna Brown Pierce Atwood (1 copy) Philip Buckley Virginia Putnam Rudman amp Winchell (1 copy) Andrew Hamilton Heather Parent Eaton Peabody (1 copy) Kenneth Farber Central Maine Power (1 copy) Robert Fitzgerald Goodwin Proctor (1 copy) Jack Guswa JG Environmental (1 copy)

21194102 TConnelly 050305 2 May 32005

Response to EPA-DEP Comment 1 Dated March 312005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

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EPA-DEP Comment 1

Comment 1 Institutional Controls It is recognized by all parties that institutional controls are and will continue to be an integral part of the remedy for the site Having said that the agencies need to have a presentation of the institutional controls including a copy of the town ordinance regarding the ICZ a figure showing the ICZ and the properties with restrictive covenants a table of the 57 properties identified within the ICZ by tax lot number and owners name location of all private wells whether for drinking water residential or agricultural purpose the status of any well abandonment efforts as well as a discussion as how these controls will be monitored

As this information may change over time such as through sale of property or sub-division of a property or well abandonment the agencies believe that presentation of the institutional controls information can best be accomplished with a stand-alone document that can be periodically updated rather than incorporated into the TI report Then as with other documentation such as the RIFS relevant information from the Institutional Control report can be summarized in the TI report

Response The Hows Corner PRP Group will prepare a document that describes the institutional controls for the Site The following items will comprise the document

bull a map of the Site vicinity showing the Institutional Control Zone (ICZ) boundary and properties with restrictive covenants

bull a tabulation of properties located within the ICZ organized by tax lot number and owners name and listing for each property

o the number of connections provided or to be provided to the property o the presence of private wells o the status of well abandonment for the property

bull a copy of the town ordinance regarding the ICZ bull an example of the restrictive covenant for the properties located within the ICZ and bull a discussion of the monitoring program for the institutional controls

The PRPs agree that a stand-alone document is appropriate for the reporting purposes requested by the comment The document can then be updated at periodic intervals mutually agreed upon by the PRPs and the EPA and DEP The status of the PRPs efforts regarding institutional controls and upgrades to the Plymouth water system is summarized in Section 123 of the Draft Technical Impracticability (TI) Evaluation Report Figure 1-2 of the TI Report is a map showing improvements to the Plymouth water system as well as properties that are connected to the system The information in the TI Report will be updated prior to submittal of the final report

Response to EPA Comment 1 050205doc 1 of 1 Woodard amp Curran (211941)

m

Response to EPA-DEP Comment 2 Dated March 312005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

EPA-DEP Comment 2

Comment 2 As discussed in our January meeting the results of the TI field work and their interpretation need to be presented in the TI report Listed below are some specific comments on this with the goal being a discussion of how the site conceptual model and site modeling were revised as a result of the 2004 field work

a analysis of the aquifer test to include a figure presenting the drawdown observed in each monitoring well at the end of the aquifer test The horizontal hydraulic gradient should not be included since this method tends to accentuate the anisotropy Two figures may be needed one for shallow bedrock and one for deep bedrock an evaluation of the appropriateness of the Cooper-Jacob (CJ) method for analyzing the aquifer test data including a comparison of the pattern of observed drawdown to the pattern of fracture orientations determined from the borehole geophysics confirmation that u lt 001 and that calculated values for T and S are similar for several observation wells an interpretation of the change in slope on the CJ plots near the end of the aquifer test the recovery data should be evaluated since it may provide insight as to why the slopes changed the marked increase in slope near the end of the test strongly suggests that a barrier (ie no flow) boundary was encountered and if a boundary was encountered T and S need to be calculated from the pre-boundary portions of the CJ plots It may be appropriate to analyse the aquifer test data using Theis as well as the Moench dual porosity model (both analysis methods are available in Aqtesolv pumping test modeling software) so that all parties have confidence in the transmissivity and storativity numbers derived from the CJ analysis b numerous bedrock borings (including angled holes) were drilled during the most recent field investigation yet no summary of the findings or the geophysical logging or packer test and sampling results have been provided c have any input parameters been changed in the flow transport and batch-flushing models as a result of the 2004 fieldwork If so which ones and why were the changes made (ie justify the changes)

Response The objective of the pumping test conducted at the Hows Corner Site during September 2004 was to observe the response of the groundwater system to pumping for use in refining the site conceptual model The refined site conceptual model would in turn be used to recalibrate the flow model and aid in the design of the hydraulic containment system being constructed under the authority of the AOC for the RD

The results of the pumping test are illustrated by plots of the drawdown at the end of the test The enclosed three drawdown plots (shallow bedrock deep bedrock and combined) represent the change in water level at the end of the test from the initial pre-test water level The shallow bedrock figure shows a northeast-southwest trending ellipsoidal area of drawdown that extends approximately 2000 feet along the major axis and approximately 800 feet along the minor axis The northeast-southwest orientation of the drawdown ellipse is consistent with the orientation of likely water-bearing fractures as identified from geophysical logging during the TI investigation The deep bedrock figure and combined figure also show ellipsoidal areas of drawdown with similar orientation A secondary axis with a more northerly orientation is evident on the figures showing drawdown in deep bedrock and in combined shallow and deep bedrock The maximum drawdown measured in shallow bedrock was 29 feet at MW-2EB The maximum drawdown measured in deep bedrock was 54 feet at the pumping well (PW-207) The drawdown ellipse is

Response to EPA Comment 2 050205doc 1 of 24 Woodard amp Curran (211941)

approximately coincident with the location of the modeled capture zone as presented on Figure 3shy1 of the TI Evaluation report

The enclosed three potentiometric surface maps (shallow bedrock deep bedrock and combined) represent the water surface elevations measured at the end of the test which was 72 hours or three days after it began All three maps show the presence of the groundwater high located in the southeast portion of the 17-acre property This high area shows relatively little relief but with the exception of the measurements at MW-2DDB which shows anomalously high water levels the central area of the high is at lower elevation than the perimeter The measurements at MWshy2DDB are hypothesized to result from water that is unable to drain rapidly enough to equilibrate with the rest of the formation

The pumping test data initially were analyzed using the Cooper-Jacob method for the late test data The results of this analysis are summarized in the table entitled Pumping Test Analytical Results It was recognized that because the aquifer is not uniform isotropic and infinite in areal extent the assumptions on which the underlying Theis equation is based were not met and because of the length of the test the criteria for use of the Cooper-Jacob of analysis were not explicitly met We recognize that the complexity of the hydrogeologic characteristics of the formation would be a significant limitation if the calculated values from the pumping test analysis were to be used as absolute representations of the hydraulic parameters of the formation However the range of values from this pumping test analysis were used as guidelines or bounding values for recalibration of the flow model

Woodard amp Curran also analyzed the pumping test data using the Theis and Moench methods The enclosed table entitled Pumping Test Analytical Results also summarizes the results of analysis of the data using these analytical methods Again although none of the methods may be strictly applicable they provide values that are guidelines for parametric ranges used in model calibration Hydraulic conductivity values calculated from the different analytical methods were as follow

Minimum Maximum Mean (ftday) (ftday) (ftda

bull Cooper-Jacob 020 067 038 bull Theis 035 1476 392 bull Moench (Fissure) 027 210 099

Storage coefficients calculated from the different analytical methods were as follow

Minimum Maximum Mean bull Cooper-Jacob 830E-04 392E-02 651E-03 bull Theis 547E-05 359E-03 473E-04 bull Moench (Block) 803E-05 402E-02 489E-03

Storage coefficients calculated using the Theis method were one to two orders of magnitude lower than values calculated using the Cooper Jacob or Moench (Block) methods Although the fissure system values are thought to be appropriate for evaluating hydraulic conductivity because the majority of flow is through fractures the block system values are appropriate for evaluation of storage because the limited fractures account for only a small part of the total storage in the bedrock

Response to EPA Comment 2 050205doc 2 of 24 Woodard amp Curran (211941)

Woodard amp Cunran used the values estimated from the pumping test analysis as an initial data set for transient benchmarking by running a 3-day simulated pumping test Calibration of the model was accomplished by comparing measured drawdowns obtained during the pumping test to calculated drawdowns from the flow model The hydraulic parameter values in the model were varied from the initial values but within the range calculated from the pumping test analysis The additional model calibration was considered to be completed when the calculated drawdowns were sufficiently close to measured drawdowns The resulting values of the hydraulic parameters of the calibrated model were then considered acceptable to provide satisfactory prediction of the response of the flow system to other hydraulic stresses

Regional water-level data were reviewed prior to data analysis A plot of water levels in the closest USGS regional background well (provided in the TI Data Package and attached) indicates that throughout the period of the test and subsequent recovery water levels were declining on a regional scale Although the decline in water levels is gradual the change in slope observed on the Cooper-Jacob plots is thought to represent the point at which the drawdown at a given location caused by pumping becomes less significant compared to the regional drawdown This occurs at about a day after start of pumping The effect of the regional decline in water levels can also be seen in the initial rapid rise in water levels in response to pump shut off followed by a decline in water levels after about a day after the pump is shut off

Additional information obtained during the TI field work was reviewed and evaluated in updating the conceptual model for the site In general the additional information corroborated the understanding of the Site presented in the RI report In particular the northeast-southwest fracture orientation was confirmed as the predominant orientation Geophysical logging during the TI investigation however showed the dip direction of fractures to be more variable and the dip angles to be shallower than was understood based on the RI data (see enclosed figure Packer Testing Results in Vicinity of Source Area) The additional borings installed within the fenced area and to the east of the fenced area showed that the area in which concentrations of total VOCs in groundwater exceeded 10000 pgL was more limited than portrayed in the RI and FS reports Packer testing of the intervals identified by geophysical logging as likely or possibly transmissive (see enclosed borehole geophysical logs) showed VOC concentrations within the packered intervals at a given borehole to be either essentially constant (eg MW-203 MW-204 MW-205) or increasing with depth (eg PW-207) Information on hydraulic conductivity and VOC concentrations in packered intervals is summarized on two separate tables for the 1999 RI wells and 2004 TI wells (Packer Permeability and Packer Sampling Results for Potential Fracture Intervals - enclosed) The orientation hydraulic conductivity and VOC concentrations of features identified as likely or possibly transmissive is summarized in a separate table (Orientation Permeability and Groundwater Sampling Results for Transmissive Features shyenclosed)

Table 4-1 of the TI Evaluation report summarizes the variation of input parameters to the flow and batch-flushing models as the project progressed from RI to FS to TI As described above for calculations in the TI Evaluation report hydraulic conductivity values were adjusted during the model calibration to pumping test drawdown data Measured fraction of organic carbon values and VOC concentrations were used in the Batch-Flushing model along with recharge calculated from the ModFlow model For calculation of pore flush volumes using the Batch-Flushing model the ratio of density to porosity was constrained to a range of 4 to 10 which is the typical range of such ratios in porous media (Freeze amp Cherry 1979) The basis for this change was stated in Appendix C of the TI Waiver Evaluation Report and is described in the response to Comment 3

Response to EPA Comment 2 050205doc 3 of 24 Woodard amp Curran (211941)

REFERENCE

Freeze RA and Cherry JA 1979 Groundwater Prentice-Hall Inc Englewood Cliffs NJ 07632 p 410-412

Response to EPA Comment 2 050205doc 4 of 24 Woodard amp Curran (211941)

LIST OF ATTACHMENTS (Response to Comment 2)

Figure - Drawdown at 72 Hours Shallow Wells

Figure - Drawdown at 72 Hours Deep Wells

Figure - Drawdown at 72 Hours

Figure - Potentiometric Surface at 72 Hours Shallow Wells

Figure - Potentiometric Surface at 72 Hours Deep Wells

Figure - End of Pumping Test Bedrock Potentiometric Surface at 72 Hours

Table - Pumping Test Analytical Results

Figure - USGS Background Groundwater Level

Figure - Packer Testing Results in Vicinity of Source Area

Figure - Borehole Geophysical Log MW-203

Figure - Borehole Geophysical Log MW-204

Figure - Borehole Geophysical Log MW-205

Figure - Borehole Geophysical Log MW-206

Figure - Borehole Geophysical Log PW-207

Table - Packer Permeability and Packer Sampling Results for Potential Fracture Intervals 1999 Drilling Program (2 pages)

Table - Packer Permeability and Packer Sampling Results for Potential Fracture Intervals 2004 Drilling Program

Table - Orientation Permeability and Groundwater Sampling Results for Transmissive Features 2004 Drilling Program (2 pages)

Response to EPA Comment 2 050205doc 5 of 24 Woodard amp Curran (211941)

(MEDEP Pond 1) Farm Pond

0 150 300

FEET

Monitoring Well

Figure X Pumping Well Drawdown at 72 Hours

_ - 17-Acre Property Boundary Shallow Wells Hows Corner Superfund Site Drawdown Contour (ft) Plymouth Maine

151 | Drawdown (ft) WOODARD ampCURRAN

^Stk Engineering bull Science bull Operations bull 211941 Hows CornlaquorwipDrawingsTI EVALDrawdown-72hrs_shallowdwg04-19-05

MW-3B

413951 W-6DB JMW-6SB

(MEDEP Pond 1) Farm Pond

Monitoring Well

Pumping Well

17-Acre Property Boundary

Groundwater Elevation Contour (ft)

211941 Hows CornerwipDrowngsTI EVALpo-tent-aU-72-hrsdwg

Figure X End of Pumping Test

Bedrock Potentiometric Surface at 72 Hours Hows Corner Superfund Site

Plymouth Maine ^ WOODARD amp CURRAN

Englnesring bull Science bull Ope

(MEDEP Pond 1) Farm Pond

Monitoring Well

Pumping Well Drawdown atFigure X

72 Hours _bullbull_ 17-Acre Property Boundary Deep Wells

Drawdown Contour (ft) Hows Corner Superfund Site

Plymouth Maine 151 | Drawdown (ft)

= WOODARD ampCURRAN 211941 Hows CornerwipDrawingsTI EVALDrawdown-72hrs_deepdwg04-19-05

Engineering bull Science bull Operations

(MEDEP Pond 1) Farm Pond

028 MW-12DB

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_bullmdash 17-Acre Property Boundary

^ Drawdown Contour (ft)

151 I Drawdown (ft)

211941 Hows CornerwgtpDrawinQsT EVAI_Drawdown-72brsdwg04mdash19-05

Figure X Drawdown at 72 Hours

Hows Corner Superfund Site Plymouth Maine

^ WOODARD ampCURRAN Engineering bull Science bull Operations i

(MEDEP Pond 1) Farm Pond

Monitoring Well

Pumping Well

_bullbull_ 17-Acre Property Boundary

f Groundwater Elevation Contour (ft)

|419Q0| Groundwater Elevation

211941 Hows CornerwipDrawinqsTI EVALPotSurf-72hrs_shallowdwg04-19-05

150 300

FEET

Figure X Potentiometric Surface at 72 Hours

Shallow Wells Hows Corner Superfund Site

Plymouth Maine

WOODARD ampCURRAN Engineering bull Science bull Operations

29212 MW-108D

(MEDEP Pond 1) Farm Pond

Monitoring Well

Pumping Well

mdashbullbulllaquo 1 7-Acre Property Boundary

bull Groundwater Elevation Contour (ft)

1419001 Groundwater Elevation

211941 Hows CornerwipDrawingsTI EVALPotSurf-72hrs_deepdwg04-19-05

150 300 =5fc= FEET

Figure X Potentiometric Surface at 72 Hours

Deep Wells Hows Corner Superfund Site

Plymouth Maine

WOODARDampCURRAN Engineering bull Science bull Operations bull

--

Pumping Test Analytical Results Hows Corner Superfund Site

Plymouth Maine

Well ID oper Jaccb Analyses 2 Theis Analyses Fissure

Well Id Rd (ft)

Saturated Thickness

Transmissivity

(ft2day) K

(ft2day) K

(cmsec) Storage

Coefficient Transmissivity

(ft2day) K

(ft2day)

K (cmsec)

Storage Coefficient

System K

(ftday) PW-207OB 8 85 481 057 200E-04 392E-02 36 042 150E-04 809E-04 027 MW-103S 50 85 451 053 187E-04 720E-03 92 108 382E-04 283E-04 083 MW-103D 54 185 455 025 868E-05 210E-02 65 035 123E-04 237E-04 044 MW-2IB 59 85 352 041 146E-04 699E-03 104 123 433E-04 512E-04 052 MW-2DB 63 85 334 039 139E-04 845E-03 148 080 283E-04 239E-04 046 MW-104D 95 185 489 02 6 932E-05 654E-03 98 053 186E-04 547E-05 037 MW-104I 97 85 33 03 9 137E-04 362E-03 117 137 484E-04 962E-05 048 MW-101I 107 85 364 043 151E-04 490E-03 511 601 212E-03 223E-04 136 MW-102D 134 185 435 024 829E-05 248E-03 108 058 206E-04 850E-05 065 MW-101D 138 185 492 027 938E-05 511E-03 671 362 128E-03 700E-04 172 MW-205 219 85 57 067 237E-04 255E-03 447 526 186E-03 359E-03 -shyMW-204D 221 185 367 020 700E-05 170E-03 790 427 151E-O3 155E-04 147 MW-204S 225 85 379 045 157E-04 156E-03 1031 1213 428E-03 313E-04 199 MW-1B 228 85 325 038 135E-04 977E-04 340 400 141E-03 739E-05 054 MW-203S 273 85 489 058 203E-04 117E-03 1255 14 76 521 E-03 216E-04 210 MW-106D 278 185 51 028 972E-05 141E-03 1065 576 203E-03 360E-04 104 MW-203D 278 185 478 026 911E-05 152E-O3 765 414 146E-03 364E-04 138 MW-105D 364 185 44 024 839E-05 830E-04 769 415 147E-03 200E-04 127

1 Analyses conducted using Cooper and Jakob method on late drawdown data collected during constant

discharge pumping test conducted at the Hows Comer Site from September 20 - 30 2004

2 Analyses conducted using Theis solution for unconfmed approximation (1935)

J Analyses conducted using Moench method for dual porosity estimation (1984)

Fissure System Storage

Coefficient 402E-04 117E-06 264E-04 300E-04 932E-05 235E-07 502E-05 326E-06 801E-05 542E-04

-

803E-05 762E-05 134E-05 498E-05 115E-04

47E-04 838E-05

3 ysesh Analysis

Block System K (ft2day)

251E-02 207E-03 564E-04 163E-04 585E-04 465E-02 153E-04 498E-03 855E-04 356E-03

-

292E-03 394E-03 720E-04 526E-03 160E-01 35OE-O1 287E-03

Block System Storage

Coefficient

402E-02 164E-04 183E-02 330E-03 158E-03 847E-03 286E-03 326E-04 803E-05 272E-03

723E-04 686E-04 148E-04 349E-04 115E-03 47E-04 838E-04

Theis - Moench - CJ - AnalyticalResults_4-19-O5xls

DRAFT

242

24

238

236

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c

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234

232

228

226

Hows Corner Constant Discharge Testing USGS Background Groundwater Level USGS 445319068560101 ME-PEW456 Kenduskeag Maine

End of Monitored Recovery Period 09302004

Regional Background Location i 226 miles from Pumping Locatio

lt

697

NOTES

1 Groundwater samples collected in 1999 were screened for five volatile organic compounds (VOCs) only N

tetrachloroethene (PCE) exceeded reporting limits MW-2030 082304 082304 082304 082304 u

2 Strike and Dip of likely or possible transmissive 30 45 55 85 feature within the packer interval from which the indicated sample was collected

MW-204D

PCE TOTAL VOCs

081904 30

220 2636

A

081904 46-50 540 6436by

081904 IT

260 3073

x

MW-105D

PCE TOTAL VOCs

111199 50-60 2100 2100

MW-106D

PCE TOTAL VOCs

111199 76-86

400 400

111199 137-147

1400 1400

111299 1355-1455

350 350

PCE TOTAL VOCs

44 84

64

MW-6SB

bulli

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170 234

35

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140 192

^^52

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130 183

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S A 34

PW-207 082404 082404 082404 20 37

PCE 1300 TOTAL VOCs

17-Acre George West Property Boundary

MW-113D

PCE TOTAL VOCs

112299 46-56

350 350

112299 70-80 190 190

150

112299 105-115

129 129

112399 138-148

230 230

L e g e n d ( J New Monitoring Well-Summer

Site Property Boundary ^ P u m p i n g Well-Summer 2004

-xmdashxshy Source Area

bull0shy Monitoring Well shy Pre 2004 Angled Boring-Summer 2004

211941laquoipdwgTI-ELV21ig41paltker-data2

2004 PCE of Total

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M W - 1 14D ^ ^

Figure xx Packer Testing Results in

Vicinity of Source Area Hows Corner Superfund Site

Plymouth Maine ^ WOODARD ampCURRAN

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c Northeast Geophysical Services Borehole Geophysical Log

MW-203 Date logged 081704 Plymouth Maine

I Flowmeter Measurements Tomporaturo(C) Acoustic Televiewer

7 5 8 8 5 9 95 Caliper (Inches) Resistance (Ohms) Spontaneous Potential (mVj Dip In Degrees PCE Total VOCs

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The acoustic televiewer graph displays the mostprominent features selectedffom the acoustic televiewer

R n r a h n l c D O t t n O I B

f i o n n h w c i r a l U K U p i i y SI Ud l

1 rn l_Og Packered Interval August 2004

E tog The location dip angle and dip direction of the sleeted M W - 2 0 3 Groundwater samples were collected by Woodard S Curran on H23120M features are approximate Refer to the televiewer og of His _ well for more precise detail Plymouth Maine Date logged 081704

I

1

Northeast Geophysical Services Borehole Geophysical Log MW-204 D a t e l o gge d 072604

Plymouth Maine

n 3

Flowrneter Measurements(in gpm)

Caliper (Inches)0 3 5 4 0

1 1 1 1 1 1 1 t 1 1 1 1 1 1Ambient Rowmeler pumping Flowmetsr 05gpm

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7 75 8 8S 9 Resistance (Ohms) Spontaneous Potential (mV)

4000 SOW 600 4M 0

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- - shyT 70 -J c [TO- - 70 - 7 0-

V Y 1- -004 -003

mdash T -h - y - j i - - mdash 260 3073 - gt=7

80 -j NF bull80 - - 80 - - 8 0Jgt

bull i

i 1

i i

C- bull shy

90 shy

K

Jlt i90 90 shy - 9 0shy -

l

ii

I I I I

NF bull M J

I ^ ^ - ^ bull 1

mdash mdash - _

s -7 ^100shy

till

1 100 100- H - 1 0 0shy -1 x Likety or possible k ^ Iransmissive zonebull

1 i i i ii i i i | l l l l | l i l l 0 20 40 ED 80

1 -

3 0SOFluid Resistivity (ohmmeters)

Dip in Degrees The djp ^ ^ o n is indicated ty Ihe line extending from tha circle The strike of Ihe feature

19- 3U UIHJIW93 IolII l l l lraquo

bull

The acousfc televiewer graph displays the mostprominent features selected from the acoustic televiewer109 The location dip angle and dip direction of Ihe sleetedfeatures are approximate Refer to the televiewer log of thiswentormore precise detail

B o r e h o l e G e O D h V S I C a l LOO B W H U I B w c w p n y o i v a i w v yM W - 2 0 4

P l y m O U t n MaiDB

Packorod Interval August 2004Groundwater san-ples wampramp collected by Woodard a Curran on OMO23C4

Date logged 072604

C

I

E Northeast Geophysical Services Borehole Geophysical Log Date logged 072704

I MW-205

Plymouth Maine

Flowmeter Measurements Temperature (C) Acoustic Televiewer (In gpm) I ~l (Interpreted)

I 85 10 Caliper (inches) 95

Dip in D g r laquo Resistance (Ohms) Spo ontaneous Potential (mV PCE Total VOCs 3 0 16 4 0 4 5 ) 20 40 60 80 10 00 2000 30 00 4VJ 400 -3 laquo

i i i i 1 i i I i 11 4 0 D 1 I I ugL ugL

C h

iii Ambient Flowmetar pumping

Flowmeter 1 25 gprn

I bull$bull

i

I rmdash magnetic 1 north ^^^^ 1 VI f

10 ~ I C x 10 bull - 10 bullbull

4 5 6mdashmdash f 1000B 11448 noisy nodi a raquo ^

mdash 5rt mdashi mdash Oft pound) 1100B 12509

cjmdash1 007

-

i i i 1

en

8 B a B

30 mdash

-

40 shy

-mdash I -

50 -_

__NF lt005

- 30 - - 3 0 it 34V

MO P26 V S) 1300B 13776 _ N F NF

26

40 bull - 40 bull 7-40 gt J Vf1 cX

) -j -

_ N F NF 50 c bull - 50 ^ 7-50

i I

I

c

B pound 60 - 6 0 7 60 - 7-60 a i 1

_ N F NF i Si f f 70 -_ bull70 bull - 70 shyC I 9

-m bull - shyA

_ N F NF 80 80 -j bull80 bull - 80 - C- 33 34

bull

5-i r

i 1

J r

Ck

_ N F NF 9 0 90 - - 90 shy

i bullCshy

J rK bull

100 -j ^ Likely or possible bull100- - 100- I -100

transmissive zone bull - ^ bull shy] |

1 1 1 1 1 1 1 I 1 i i i 1 i i 1 1 0 20 40 SO SO 10 20 30 40 50 Dip in Degrees 30 4 0 Fluid Resistivity (ohmmeters) Thlaquo dip direction is indicated

by the line extern r g from the circle The strike of he feature is 90 degrees from ihis

The acoustic televiewer graph displays the most

I Borehole Geophysical Log Packered Interval August2004 prominent features selected from the acoustic televiewer

Groundwatcr samples were oollccled by Woodard amp Cufran orgt S172004 log The location dip angle and dip direction of ins slsctsd MW-205 features are approximate Refelt to the televiewer log of this wall for more precise detail Plymouth Maine Date logged 072704

I

C

I Northeast Geophysical Services Borehole Geophysical Log Date logged 072704

I MW-206

Plymouth Maine

Flowmetor Measurements Temperature (C) Acoustic Televiewer | I r T i i i i i i i i i i i i i i r I |(in gpm) (Interpreted)

I 75 8 flS 9 95

Caliper (inches) Resistance (Ohms) Spontaneous Potential (mV) Dip In Degress PCE Total VOCs 30 35 40 4 5 0 20 40 M 90 4500 5500 6500 ugL ugL I i i

I I

- 1 0

I - 2 0

I 2900B 32401

i i L

E 0

i 6300B 68901

i I 0 20 40 SO 80

20 30 40 50 Dip in Dlaquogralaquos

amp 4 a Fluid Resistivity (ohrnmeters) The dip dirertion is indicated Likely or possible by iho line extending from the transmissive zone circle The striKe of the feature

is 90 degrees from tNs

Borehole Geophysical Log Packered Interval August 2004

E amples were collected by Woodard amp Cunan oo SM82004 log Thraquo location 4p angle and dip direction of the sloeled MW-206 feature are approximate Refer to the televiewer 109 of this well for more precise detail Plymouth Maine Date logged 072704

C

I Northeast Geophysical Services Borehole Geophysical Log

Date logged 082304 PW-207

I Plymouth Maine

Fiowmeter Measurements Temperature (C) Acoustic Televiewer

I (in gpm) (interpreted)

75 8 85 9 95 Caliper (inches) Resistance f0tims) Spontaneous Potential (mV) Dip in Degrees PCE Total VOCs

55 60 0 20 40 SO 80 ugL ugL I I I I I I I

Ambienl Fiowmeter pumping Flewmater

magnetic - 10 - - 1 0

north

i - 20 - - 2 0

1300 1410

i - 30 - - 3 0

i tf

5400 5802 - 40 - - 4 0

B - 50 - - 5 0

I 18000 19234

- 60 - - 6 0

I 12000 13085

- 70 - - 7 0

- 8 0

i - 9 0 19000 20354

G - 100- -100

I 110 110 bull110

0 20 40 60 SO 10 20 30 Dip m Degrees

Fluid Resistivity (ohmmeters) I 50

The dip direction is indicated by ihe line extending from the circle The strike of the fealure is 90 degrees from this

Borehole Geophysical Log

G Packorod Interval August 20(M log The location dip angle and dip dirlaquocton or the sleeted Groundaier samplss were ooliecled by Woodard i Curran on ampt24f2ltXM PW-207 failures are approximate Reter to the televiewer log of this wlaquoll for more precise detail PlyPIOUth Maine Date logged 082304

I

Table XX Packer Permeability and Packer Sampling Results for Potential Fracture Intervals

1

WellID MW-101D MW-101D MW-101D MW-101D MW-101D MW-101D MW-101D MW-101D MW-101D MW-101D MW-I01D MW-101D MW-101D MW-102D MW-102D MW-I02D MW-102D MW102D MW-102D MW-102D MW-102D MW-102D MW-I02D MW-102D MW-102D MW-102D MW-103D MW-103D MW-103D MW-103D MW-I03D MW-103D MW-103D MW-103D MW-103D MW-103D MW-103D MW-103D MW-I03D MW-104D MW-104D MW-104D MW-104D MW-I04D MW-104D MW-104D MW-104D MW-104D MW-104D MW-104D MW-105D MW-105D MW106D MW-106D MW-106D MW-107D MW-107D

1999 Drilling Program

Hows Corner Superfund Site Plymouth Maine

Potential Fracture Top Of Bottom 6 Depth to lt Topof i Interval from Packer Packer Middle of Elevation Hydraulic bull PCE

GS ELEV 1 Rock Drilling Interval Interval Interval of Interval Conductivity Concentration (ft msl) (ft msl) TEST (ftbgs) (ftbgs) r(ftbgs) ( f t b (ft mil) (cmsec) (raquogL)

4339 4329 13 28-29 33-3537-39 271 376 324 4016 OOOE+00 4339 12 37-3444-46 380 485 433 3907 157E-04 4339 11 488 593 541 3799 132E-04 4339 10 60-61 578 683 631 3709 OOOE+00 4339 9 678 783 731 3609 I79E-05 4339 8 778 883 831 3509 106E-05 4339 7 880 985 933 3407 243E-05 4339 6 990 1095 1043 3297 339E-06 4339 5 1090 1195 1143 3197 OOOE+00 4339 4 1190 1295 1243 3097 OOOE+00 4339 3 1365-1375 1290 1395 1343 2997 OOOE+00 4339 2 147-157 1390 1495 1443 2897 580E-05 4339 1 147-157 1470 1575 1523 2817 741E-05 43161 43061 13 166 271 219 4098 333E-04 43161 12 30-3136-40 260 365 313 4004 I54E-05 43161 11 36-4041-43 362 467 415 3902 548E-05 43161 10 470 575 523 3794 598E-05 43161 9 570 675 623 3694 197FOS 43161 8 670 775 723 3594 OOOE+00 43161 7 770 875 823 3494 891 E-05 43161 6 83-94 870 975 923 3394 139E-05 43161 5 970 1075 1023 3294 123E-04 43161 4 1070 1175 1123 3194 526E-06 43161 3 1170 1275 1223 3094 138E-05 43161 2 1270 1375 1323 2994 671E-06 43161 1 1370 1475 1423 2894 OOOE+00 42997 42497 13 18-19 170 275 223 4077 OOOE+00 42997 12 260 365 313 3987 766E-05 42997 11 360 465 413 3887 727E-05 42997 10 460 565 513 3787 192E-05 42997 9 560 665 613 3687 752E-05 42997 8 660 765 713 3587 778E-05 42997 7 85-86 763 868 816 3484 260E-05 42997 6 860 965 913 3387 289E-05 42997 5 102-103 960 1065 1013 3287 102E-04 42997 4 1060 1165 1113 3187 522E-06 42997 3 1160 1265 1213 3087 520E-06 42997 2 129-130 1260 1365 1313 2987 960E-04 42997 1 1360 1465 1413 2887 OOOE+00 43372 42922 11 35-37 42-45 350 455 403 3935 684E-04 43372 10 460 565 513 3825 500E-05 43372 9 560 665 613 3725 106E-05 43372 8 72-74 660 765 713 3625 204E-05 43372 7 760 865 813 3525 872E-06 43372 6 860 965 913 3425 467E-06 43372 5 960 1065 1013 3325 200E-05 43372 4 1060 1165 1113 3225 354E-05 43372 3 125-130 1160 1265 1213 3125 157E-05 43372 2 125-130 1260 1365 1313 3025 337E-04 43372 1 1365 1465 1415 2922 689E-06 43052 43002 2 54-58 490 595 543 3763 124E-05 2100 43052 1 139-140 145-146 1367 1472 1420 2886 154E-04 1400 43291 4391 3 bullI133 260 365 313 4017 439F06 43291 2 77-78 760 865 813 3517 230E-03 400 43291 1 143-144 1355 1460 1408 2922 971E-06 350

29958 27258 4 450 555 503 2493 OOOE+00 (21)A 29958 3 103-105 1000 1105 1053 1943 752E-04 (063)A

Table XX Packer Permeability and Packer Sampling Results for Potential Fracture Intervals

1999 Drilling Program

Hows Corner Supcrfund Site Plymouth Maine

gtbull i Potential Fracture Top _OfBot Bottom of Depth to ltbull Top of Interval from f Packer Packer Middle Of

GS ELEV lt Hock Drilling interval Interval Interval WeD ID ft msl) (ft msl) TEST (ftbgs) ltft$gs) (ftbgs) (ftbgs)

MW-107D 29958 2 128-130 1200 1305 1253

MW-107D 29958 1 139-141 1350 1455 1403

MW-108D 31904 31104 6 35-36 300 405 353 MW-108D 31904 5 60-62 550 655 603

MW-108D 31904 4 80-83 750 855 803

MW-108D 31904 3 118-119 123-124 1150 1255 1203

MW-108D 31904 2 147-149 1440 1545 1493

MW-108D 31904 1 1700 1805 1753

MW-110D 40576 40426 2 21-31 210 315 263 MW-110D 40576 1 148-154 1460 1565 1513 MW-I11D 40519 4 70-71 650 755 703

MW-111D 40519 3 79-82 84-86 780 885 833 MW-I11D 40519 2 97-102 950 1055 1003 MW-111D 40519 1 1370 1475 1423

MW-112D 3027 2942 4 42-52 420 525 473 MW-112D 3027 3 850 955 903 MW112D 3027 2 1100 1205 1153 MW-112D 3027 1 135-136 140-141 1340 1445 1393

MW-113D 43085 43085 5 250 355 303 MW-I13D 43085 4 47-49 460 565 513 MW-113D 43085 3 73-74 700 805 753 MW-113D 43085 2 1050 1155 1103 MW-113D 43085 1 1380 1485 1433

MW-114D 42394 41594 4 48-49 450 555 503 MW-114D 42394 3 79-81 740 845 793 MW-114D 42394 2 121-129 1250 1355 1303 MW-114D 42394 1 134-142 1350 1455 1403

MW-115D 4035 4035 4 300 405 353 MW-1I5D 4035 3 70-71 650 755 703 MW-115D 4035 2 1150 1255 1203 MW-115D 4035 1 1400 1505 1453

LOT-28W 382 7 450 555 503 LOT28W 382 6 550 655 603 LOT-28W 382 5 650 755 703 LOT28W 382 4 750 855 803 LOT-28W 382 3 850 955 903 LOT-28W 382 2 950 1055 1003 LOT-28W 382 1 1055 1155 1105

NOTES cmsec = centimeters per second ft bgs = leet below ground surface It msl = feet below mean sea level lt = not detected at indicated reporting limil A = detected below laboratory PQL ( ) = detected below reporting limits

Elevation of Interval

(ft nisi) 174

159

283gt 2588

2388

1988

1698

1438

3795 2545 3349 3219 3049 2629

2555 2125 1875 1635

4006 3796 3556 3206 2876

3737 3447 2937 2837

3683 3333 2833 2583

3318 3218 3118 3018 2918 2818 2715

Hydraulic Conductivity

(cmsec)

323E-05

208E-05

471E-03

471E-03

624E-05

3I6E-05

264E-05

261 E-05

OOOE+00 200E-04 953E-05 OOOE+00 OOOE+00 212E-05

361 E-05 410E-06 2gQE06 292E-05

786E-05 124E-05 151 E-05 822E-06 82IE-06

858E-05 I69E-05 352E-03 866E-05

223E-05 394E-06 122E-05 525E-06

831 E-05 182F-05 L62E-05 129E-05 190E-05 890E-04 981 E-04

PCEraquo Concentration

(ugL)

lt5

(14A)

98 11

15

22

11

30

200 (62)A

110 210 300 240

(44)A (23)A

5

350 190 129 230

2200 1900 2600 2600

(17)A (16)A (19)A

96

Table XX Packer Permeability and Packer Sampling Results for Potential Fracture Intervals

2004 Drilling Program

Hows Corner Superfund Site Plymouth Maine

Top of Bottom of Depth to Midpoint

t K

ELEV (ft Potential Transmissive Zones Packer Interval

Packer Interval

Middle of Interval

Elevation of interval

Hydraulic Conductivity

PCE Concentration

Well ID msl) TESTr (ft bgs)- (ftbgs) (ftbgs) (ftbgs) (ft msl) (cmsec) (ogt) MW-203D 43227 4 277279 24 32 28 4043 667E-05 44

3 408415420 39 49 44 3883 593E-05 170 2 526 530 49 57 53 3793 101E-04 140 I 828830842 80 88 84 3483 701E-05 130

MW-204D 43262 5 295 300 26 34 30 4023 902E-05 220 4 463496513516 45 53 49 3833 119E-04 540 3 681685688 63 71 67 3653 OOOE+00 2 758 76 2 71 79 75 3573 309E-05 260 I 88 96 92 3403 OOOE+00

MW-205 42389 3 164 166 168 15 20 175 4148 OOOE+00 1000B 2 302305312 30 35 325 3998 107E-04 1300B 1 40 45 425 3898 OOOE+00

MW-206D 43007 5 17 72 195 4128 291E-05 4 296 302 307 29 34 315 4008 940E-05 2900B 3 522 52 57 545 3778 944E-07 2 656 64 69 665 3658 353E-06 1 92392793 4939 91 96 935 3388 614E-05 6300B

PW-207 43477 5 184622162819 18 29 235 4088 209E-05 1300 4 3508 32 43 375 3948 568E-06 5400 3 53325341542154325559 50 61 555 3768 821E-05 18000

6359 61 72 665 3658 866E-06 12000 1 8685 84 89 865 3458 213E-05 19000

NOTES cmsec = centimeters per second ft bgs = feet below ground surface ft msl = feet above mean sea level B = detected in lab blank

Table XX Orientation Permeability and Groundwater Sampling Results for Transmissive Features

2004 Drilling Program

Hows Corner Superfund Site Plymouth Maine

Borehole Geophisical Feature depth Dip True Dip True Transmissive Log Feature (Feet) Degrees Azimuth Strike bullvgt(Ltk|iy^

Number v Tosftble) v MW-203 5 277 64 337 67 Likely

6 279 59 11 281 Likely 8 352 14 177 87 Likely 11 381 46 96 6 Possible 12 408 35 271 1 Possible 14 415 57 250 340 Possible 15 420 58 202 292 Likely 18 526 52 75 345 Likely 19 530 52 82 352 Likely 28 828 48 75 345 Likely 29 830 52 17 287 Likely 30 830 56 233 323 Possible 31 842 50 130 40 Likely

MW-204 4 295 15 147 57 Likely 5 300 43 91 1 Likely 11 439 31 80 350 Possible 12 440 46 219 309 Possible 14 463 50 358 88 Likely 15 496 34 198 288 Likely 16 513 54 17 287 Likely 17 516 33 14 284 Likely 25 681 39 359 89 Possible 26 685 22 45 315 Possible 27 688 35 73 343 Possible 32 758 45 236 326 Likely 33 762 46 306 36 Likely

MW-205 5 164 69 106 16 Possible 6 166 78 165 75 Possible 7 168 82 115 25 Possible 8 168 68 116 26 Possible 12 215 46 222 312 Possible 13 217 75 62 332 Possible 14 219 29 32 302 Possible 16 237 69 250 340 Possible 17 256 73 353 83 Possible 18 272 44 202 292 Possible 21 299 37 196 286 Possible 22 302 31 206 296 Possible 23 305 59 48 318 Likely 24 312 63 42 312 Likely

MW-206 1 264 37 181 271 Likely 2 296 69 217 307 Likely 3 302 66 233 323 Likely 4 307 64 224 314 Likely 8 342 62 259 349 Likely

jjHydraulic GoiDanctilyity j(cmsecjw

667 E-05

593 E-05

101 P04

710 E-05

902 E-05

119 E-04

0

309 E-05

0

107 E-04

94 E-05

PCE (ugL)

44

170

140

130

220

540

260

IOOOB

1100B

1300B

2900B

STotal vVoCsv tig1)

84

234

192

183

2636

6436

3073

11448

12509

13776

32401

PCEyo dfCTotaf

52

73

73

7 1

83

84

85

87

88

94

90

Table XX Orientation Permeability and Groundwater Sampling Results for Transmissive Features

2004 Drilling Program

Hows Corner Superfund Site Plymouth Maine

Borehole Geophisical Feature deptt raquoip True pip True Transraissive Log Feature (Feet) shy Degrees Azimuth Strike (tikely

Number raquo Possible) 22 522 57 54 324 Possible 25 656 40 82 352 Possible 32 871 59 151 61 Possible 33 883 53 185 275 Possible 34 895 7 175 85 Likely 35 899 53 90 0 Likely 36 902 49 184 274 Likely 37 923 9 175 85 Likely 38 927 42 206 296 Likely 39 934 48 167 77 Likely 40 939 26 180 90 Likely

PW-207 1 1846 33 167 77 Likely 4 2216 49 289 19 Possible 7 2819 59 265 355 Possible 11 3508 55 189 279 Possible 18 5332 43 305 35 Likely 19 5341 51 30 300 Likely 20 5421 20 254 344 Likely 21 5432 39 301 31 Likely 23 5559 52 302 32 Likely 25 6359 24 182 272 Possible 29 8049 77 231 321 Possible 30 8685 78 38 308 Likely 32 9334 29 194 284 Likely

NOTES

B = detected in lab blank

Hydraulic Conductivity

(cmsee) 944 E-07 353 E-06

614 E-05

209 E-05

568 E-06

821 E-05

866 E-06

213 E-05

bulltCE (ugL)

6300B

1300

5400

18000

12000

19000

Total VOCs (ug1)

68901

1410

5802

19234

13085

20354

PCE of Total VOCs

9 1

92

93

94

92

93

Response to EPA-DEP Comment 3 Dated March 312005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

lit

EPA-DEP Comment 3

Comment 3 The reported f values and resultant Kd values There remains doubt that the values used in the flushing model accurately reflect the propensity for PCE to sorb to the bedrock The ^ values presented in Appendix B may be unrealistically high because the bedrock samples may have contained organic carbon that was unavailable for sorption The reported f values are only qualitative estimates of the organic carbon content of the bedrock samples The Walkley and Black organic carbon measurement method is quick and simple but the results obtained cannot be considered quantitative because it requires a correction factor which often results in erroneous values it assumes the organic carbon has an average valence of zero oxidizable and reducible constituents such as chloride ferrous iron and manganese oxides interfere with the results and the errors introduced by interference are potentially greater when the organic carbon content is low at low f values it is not clear that organic carbon is controlling PCE sorption (Schwarzenbach and Westall 1981 Mackay et al 1986 Fetter 1999)

In order to derive a Kd-based retardation factor that is reasonable given the reported f values and the rapid advance of the PCE plume described on pages 4-11 and 4-12 the flushing model requires a bulk density to porosity ratio that is roughly two orders of magnitude higher than the actual ratio for the Hows Corner bedrock (page 4-4) This apparent discrepancy needs to be addressed

Response This comment raises several concerns about the collection and analysis of samples for fraction of organic carbon (f^) the quality of the resulting data and the implications of the use of those data for estimation of the retardation of groundwater contaminant movement Results of bedrock analysis for f were proposed in the TI Evaluation Work Plan for use in conjunction with groundwater contaminant concentrations and aquifer information to estimate cleanup times using the Batch Flushing model It is important to use accurate f values from representative bedrock in the Batch Flushing model in order to obtain reasonable estimates of the remedial time frame Because of the importance of accurate and representative results the TI Investigation field program was designed and conducted both to collect samples representative of the rock volume most likely to be in contact with contaminated groundwater and to analyze them using an appropriate refereed analytical method Five potential methods for evaluating f were identified Of the five methods the Walkey-Black method was selected because it has minimal method interferences and a sufficiently low detection limit as well as a long history of use in agronomy and contamination studies The PRP Group is pleased with the quality of the data obtained from the bedrock samples as represented by their precision and reproducibility

The first part of this comment relates to the determination of fraction of organic carbon (f^) values The several subparts of the first paragraph are addressed individually in items 1 through 5 below The second part of the comment regarding the resultant distribution coefficient (Kd) values is addressed separately as item 6 below

1 There remains doubt that the values used in the flushing model accurately reflect the propensity for PCE to sorb to the bedrock

bull The rock core samples used for f (gocg) analysis were from core immediately adjacent to fractures These rock core samples included the fracture surfaces themselves and rock core extending back less than 1 cm from the fractures Therefore the foe data reported in the TI Evaluation represents the f of bedrock through which groundwater will travel and to which PCE will adsorb Based on the careful selection of sample locations and the

Response to EPA Comment 3 050205doc 1 of 11 Woodard amp Curran (211941)

number of samples collected we are confident that the measured f values are representative of the f at points of contact for PCE with the bedrock it is these f values that determine the propensity of PCE to sorb to the bedrock

bull The samples of rock core collected for analysis of f originated from 19 different locations varying in depth from 11 to 90 feet Therefore it is very unlikely that the rock core samples were contaminated with extraneous organic carbon from above ground

2 The foc values presented in Appendix B may be unrealistically high because the bedrock samples may have contained organic carbon that was unavailable for sorption

bull As noted in response 1 the f data reported in Appendix B represents organic carbon primarily associated with the surface of fractures in the bedrock through which groundwater is most likely to travel Therefore it is this organic carbon that the contaminants in the groundwater will come in contact with and adsorb to in the fractured rock at the site

bull The chemical oxidation agents used in the Walkey-Black method oxidize the easily oxidizable organic carbon in the medium and the foe is calculated from the quantity of the agent consumed Therefore it is unlikely that the analysis of the bedrock samples measured organic carbon that was unavailable for sorption

3 The reported foc values are only qualitative estimates of the organic carbon content of the bedrock samples

bull The reported f values are accurate quantitative results Schumachers review of Methods for the determination of total organic carbon (TOC) in soils and sediments (NCEA-C-1282 EMASC-001 April 2002) identifies the Walkley-Black method which was used to analyze the reported foc values as the reference method for comparison to other methods for analyzing total organic carbon

bull Schumacher also points out that if anything the WalkJey-Black method may underestimate the total organic carbon in a sample due to possible incomplete oxidation of organic carbon Usually the incomplete oxidation of total organic carbon in environmental samples is corrected for by multiplying the measured foe by 130 (Walkley amp Black 1934 Schulte 1995)

bull When the f data in the TI Evaluation Report (WampC 2005) Appendix B (attached) are analyzed statistically the standard deviation of the f for the 19 samples analyzed is 174 of the average f Given this standard deviation the 95 confidence interval for this data ranged from a low of 000123 gocg to a high of 000253 gocgm

The labs Method of Detection Limit (MDL) for the f measured using the Walkley-Black method is 00001 gocg Therefore the average (000188 gocg) the mean (000185 gocg) and geometric mean (000187 gocg) of the f values for the rock core at Hows Corner are all statistically significantly greater than the MDL of the Walkley-Black method

In addition to the aforementioned statistical analysis of the foe data triplicate samples (n = 3) from the same rock core (including one sample from the 19 rock core samples) were

Response to EPA Comment 3 050205doc 2 of Woodard amp Curran (211941)

analyzed for their f to determine the repeatability of the Walkley-Black method The average the mean and the geometric mean of the f values of these replicate samples was 000162 gocg 000150 gocg and 000159 gocgm respectively The standard deviation of these measurements was 000039 gocg

4 The Walkley and Black organic carbon measurement method is quick and simple but the results obtained cannot be considered quantitative because it requires a correction factor which often results in erroneous values it assumes the organic carbon has an average valence of zero oxidizable and reducible constituents such as chloride ferrous iron and manganese oxides interfere with the results and the errors introduced by interference are potentially greater when the organic carbon content is low at low foc values it is not clear that organic carbon is controlling PCE sorption (Schwarzenbach and Westall 1981 Mackay et al 1986 Fetter 1999)

bull Schumachers review (NCEA-C-1282 EMASC-001 April 2002) of the Walkley-Black method identifies several potential problems with this analytical method that could occur if the analytical lab is not familiar with the nuances of the chemistry associated with this method Interestingly Schumachers review neglected one of the more important analytical steps required to avoid errors in quantifying f in samples where there might beNAPL

It is absolutely critical to eliminate any NAPL from rock core samples prior to using the Walkley-Black method to measure foe in such samples This was done by the lab (PTS Laboratories) that measured the foe in the rock core samples from Hows Corner The lab used the Dean-Stark method (solvent extraction) to remove all hydrocarbons (including PCE and other NAPLs) from the sample (PTS Laboratories) This extraction method does not interfere with the subsequent analysis of the natural organic carbon associated with the rock core

Subsequently the samples were dried at 150degC to a constant weight (normally 16 hours) This latter step oxidizes all inorganic minerals including ferrous bearing minerals to ferric oxides and precludes their interference during the oxidation of the samples with chromic acid This procedure completely eliminates any positive bias in the reported foc

data that might have occurred due to the presence of ferrous ions and other reduced minerals

bull As noted in Response 3 the incomplete oxidation of total organic carbon results in an underestimate of the f and is corrected for by multiplying the f by a correction factor of 130 (Walkley amp Black 1934 Schulte 1995) The fx data reported in the TI Evaluation was corrected accordingly by using this correction factor

bull Excess chloride (Cl~) in percent weight quantities as found in saline soils may interfere with the quantitative titration of reduced chromium (Walkley 1947) However given that the primary rock type at the Hows Corner site is phyllite it is highly unlikely that there was sufficient chloride in the rock core samples for this to occur

bull Manganese oxides may also interfere with the analysis of f through competing with the dichromate ion for any oxidizable carbon (Walkley 1947) However in such cases the reported f would be an underestimate of the f present in the rock core Walkley (1947)

Response to EPA Comment 3 050205doc 3 of 11 Woodard amp Curran (211941)

4

reported that in the case where the ratio of MnO2 to carbon is 85 to 1 the error in the carbon determinations would only be 0 to 6 percent

It may also be useful to compare the analysis of total organic carbon in a geologic matrix that contains high levels of manganese using EPA method 9060 to the Walkley-Black method Table 1 summarizes data provided by one of the PRPs that compares the analysis of total organic carbon in a geologic matrix that contains approximately 02 wgt manganese (approximately 03 wgt manganese oxide)

Table 1 Comparison of total organic carbon measured using the EPA- 9060 method and the Walkley-Black method

Laboratory EPA-9060 Method Walkley-Black Method A Ave 00226 gocg Not analyzed

Stdev 000251 gocg n = 5

B Ave 002219 gocg Ave 002050 gocg Stdev = 000316 gocg Stdev =000971 gocg

n= 10 n = 10

The similarity in the total organic carbon concentrations measured by these two different methods provides further confidence that the Walkley-Black method is a viable method for analysis of total organic carbon in the presence of manganese equivalent to at least 10 by weight of the total organic carbon

5 The Walkley and Black organic carbon measurement at lowf^ values it is not clear that organic carbon is controlling PCE sorption (Schwarzenbach and Westall 1981 Mackay et al 1986 Fetter 1999)

bull Schwarzenbach and Westalls (1981) paper states that f values of less than 0001 gocg should not be used in combination with Kow (octanol-water partition coefficients) values to calculate K^ values (solid phase partition coefficients) values for a specific contaminant It should be noted that the TI Evaluation did not use the f data to calculate the KQC from the Kow Instead as requested by the EPA the measured KOC value for PCE was used to calculate the retardation factor for this contaminant

bull Schwarzenbach et al (2003) stated more recently that Even at very low f values (ie foe = 0001 kgoc - kg1 solid) sorption to the organic components of a natural sorbent may still be the dominant mechanism in defining the adsorption of organic compounds to geological matrices

bull In 1985 M Piwoni from the US EPA Robert S Kerr Environmental Research Laboratory published a paper (Banerjee et al 1985) that showed that for very hydrophobic molecules TOC content of the sorbent will control sorption down to levels of organic carbon that defy quantitation Contaminants such as the PCE found in the groundwater at Hows Corner are in this category of compounds

Given the aforementioned reasons the f values reported in the TI Evaluation are accurate within the noted statistical limitations and will have a predictable impact upon the retardation of PCE during groundwater transport

Response to EPA Comment 3 050205doc 4 of 11 Woodard amp Curran (211941)

6 In order to derive a Kd-based retardation factor that is reasonable given the reported foc

values and the rapid advance of the PCE plume described on pages 4-11 and 4-12 the flushing model requires a bulk density to porosity ratio that is roughly two orders of magnitude higher than the actual ratio for the Hows Comer bedrock (page 4-4) This apparent discrepancy needs to be addressed

The apparent discrepancy of bulk density to porosity ratios is most likely due to the fact that the Batch Flushing Model was originally developed for a porous medium and is not directly applicable to fractured bedrock As stated in Appendix C (page C-4) of the Draft Technical Impracticability Evaluation Report in order to use the Batch Flushing Model to describe the transport of contaminated groundwater in fractured bedrock where the matrix porosity is insignificant it is more appropriate to use a fracture surface area to void space ratio to calculate the retardation factor (R) than a bulk density to porosity ratio (Freeze amp Cherry 1979)

Since it is impractical to determine the actual surface area to which contaminants can adsorb the Batch Flushing Model was used with two simplifying assumptions bull The Kd was calculated from the f and the K^ bull The bulk density to porosity ratio term in the Batch Flushing Model was constrained to range

from 4 to 10 the typical range of such ratios in porous media (Freeze amp Cherry 1979)

If one uses site specific bedrock bulk density and porosity values the bulk density to porosity ratio is several orders of magnitude greater (specifically 273 gcc bullbull 000165 (dimensionless) = 1654 gcc) than the range of ratios of 4 to 10 used in the Batch Flushing Model in the Draft Technical Impracticability Evaluation Report Constraining the bulk density to porosity ratio within the range of ratios of 4 to 10 results in significantly lower R value than would be obtained using specific bedrock bulk density and porosity values

In summary in bedrock where fractures are the primary porosity the bulk density to porosity ratio can vary considerably and will be a function of the number of fractures and the fracture aperture The calculated bulk density to porosity ratio will be inversely proportional to the porosity This means that in fractured rock with limited fracturing and smaller porosity the calculated bulk density to porosity ratio is greater and will result in a greater calculated retardation factor than in bedrock with more extensive fracturing and greater porosity Consequently the calculated retardation factor will be greater for bedrock with less surface area available for sorption than bedrock with greater surface area for sorption This is contrary to what actually occurs

4 Response to EPA Comment 3 050205doc 5 of 11 Woodard amp Curran (211941)

m

REFERENCES

Banerjee P MD Piwoni K Ebeid (1985) Sorption of organic contaminants to a low carbon subsurface core Chemosphere _14 1057-1067

Freeze RA JA Cherry (1979) Groundwater Prentice Hall Englewood Cliffs NJ pg 604

PTS Laboratories wwwptsgeolabscompdf files3TOCnotepdf

Schulte EE (1995) Recommended soil organic matter tests in Recommended Soil Testing Procedures for the Northeastern United States Northeastern Regional Publication No 493 Chapter 8

Schwarzenbach RP J Westall (1981) Transport of nonpolar organic compounds from surface water to groundwater Laboratory sorption studies Environ Sci Tech 15 1360-1367

Schwarzenbach RP PM Gschwend DM Imboden (2003) Environmental Organic Chemistry Wiley-Interscience pg 292 408 amp 412

Walkley A LA Black (1934) An examination of the Degtjareff method for determining soil organic matter and a proposed modification of the chromic acid titration method Soil Science 37 29-38

Walkley A (1947) A critical examination of a rapid method for determining organic carbon in soils - effect of variations in digestion conditions and of inorganic soil constituents Soil Science 63251-264

Woodard amp Curran Inc (WampC) 2005 Draft Technical Impracticability Evaluation Hows Corner Superfund Site Plymouth Maine January 2005

Response to EPA Comment 3 050205doc 6 of Woodard amp Curran (211941)

LIST OF ATTACHMENTS (Response to Comment 3)

Appendix B to Draft Technical Impracticability Evaluation Measurement of foe at Hows Corner (4 pages)

m

Response to EPA Comment 3 050205doc 7 of 11 Woodard amp Curran (211941)

Appendix B Measurement of foe of Rock Core at Hows Corner

There are two general approaches to measure the fraction of organic carbon (foe) in rock cores

bull Measurement of weight loss by ignition of organic matter bull Chemical oxidization of organic carbon to carbon dioxide and either

subsequent quantification of the oxidant used for the reaction or quantification of the carbon dioxide produced during this oxidation process

The weight loss method is subject to errors caused by volatilization of substances other than organic materials such as water hydroxides and mineral carbonates Quantification of foe by the weight loss method is particularly sensitive to the presence of carbonates in rock cores There are however weight loss methods that are designed to differentiate between organic carbon and the aforementioned interfering materials but they require considerable care and are less accurate at low foe values Hence the weight loss method was not well suited for measuring the foe of the rock core from Hows Corner

The chemical oxidation of organic carbon is much better suited for quantifying organic carbon in rock cores such as those from Hows Corner This method uses a strong chemical oxidant to oxidize organic carbon to carbon dioxide and then measures either the chemical oxidant used to oxidize the organic carbon or the quantity of carbon dioxide produced In addition this general approach is not subject to interference by volatilization of other constituents of the rock core

There are at least two such chemical oxidation methods

bull The method of Baccini which was described by Schwarzenbach amp Westall (1981) first acidifies the sample to eliminate interference by carbonates Then a strong oxidant is used to chemically oxidize the organic carbon to carbon dioxide The resulting carbon dioxide is subsequently reduced to methane and quantified using a flame ionization detector Unfortunately this method has not been described in detail in a referred journal Hence it is would not have been appropriate to use to characterize the foe in the Hows Corner rock core

bull The more commonly used method to quantify foe in rock core is the Walkley-Black method (1934) This method is preferred for RBCA and DODDOE projects and by the oil industry

The Walkley-Black method uses an excess of chromic acid to oxidize (digest) organic matter to carbon dioxide The remaining chromic acid that was not consumed during the oxidation of the organic carbon is then quantified by titration with ferrous sulfate The difference in chromic acid prior to and after the oxidation of the organic carbon represents the total chromic acid used to oxidize

Hows Corner TI Evaluation Page 1 January 13 2005 Appendix B

the organic carbon in the sample The latter can be calculated using the chemical stoichiometry of the reaction

The Walkley-Black method is very accurate for samples that contain less than 2 organic carbon matter The minimum detection limit (MDL) for the Walkley-Black method is 100 mgkg or an foe of 0001

Given the rock core at Hows Corner was expected to contain less than 2 organic carbon the Walkley-Black method was used to measure the foe from 19 different rock core samples collected from varying depths ranging from 11 to 90 feet

Table 1 provides a statistical summary of the aforementioned data

Table 1 Statistical summary of foe data from rock cores collected at varying depths

Statistical Parameter Calculated Value foe Minimum Detection Limit (MDL) 00010 Number of samples analyzed (n) 19 Average foe 00019 Median foe 00019 Geometric Mean foe 00019 Standard deviation of foe measurements 000033 Relative standard deviation 174 -+ 95 Confidence intervals 00012 to 00025

The data in Table 1 shows the following

bull The foe from the Hows Corner rock cores are statistically greater than the MDL of the Walkley-Black analytical method

bull The average and median values for the foe of the Hows Corner rock cores from varying depths are nearly identical indicating that there is little variability in the foe values in the source zone at the site

bull The standard deviation of these measurements is 000033 which is 174 of the average foe

bull The 95 confidence intervals of the foe of the rock core at Hows Corner are 00012 to 00025

The foe was also analyzed from three separate samples taken from the same rock core at a depth of 55 feet (Only one of these samples was included in the data summarized in Table 1) Table 2 shows the statistical repeatability of this type of analysis

Hows Corner TI Evaluation Page 2 January 13 2005 Appendix B

Table 2 Repeatability of analysis of foe from one rock core at 55 feet in depth

Statistical Parameter Calculated Value Number of samples analyzed (n) 3 Average foe 00016 Median foe 00015 Geometric Mean foe 00016 Standard deviation of foe measurements 000039 Relative standard deviation 240 -+ 95 Confidence intervals 00008 to 00024

The data in Table 2 shows the following

bull The percent relative standard deviation of these three analyses of foe from the same rock core at Hows Corner is 24

bull The 95 confidence interval of the foes measured in this particular rock core at Hows Conrer is 00008 to 00024

These results show that there is good repeatability in using the Walkley-Black method for analysis of the foe in the rock core at Hows Corner

References Schwarzenbach amp Westall (1981) Transport of nonpolar organic compounds from surface water to groundwater Laboratory sorption studies Environ Sci Tech 15 1360-1367

Walkley A I A Black (1934) An examination of Degtjareff method for determining soil organic matter and a proposed modification of the chromic acid titration method Soil Sci 37 29-37

Hows Corner Tl Evaluation Page S January 13 2005 Appendix B

Woodard and Curran PTS Laboratories PTS File No 34618

ORGANIC CARBON DATA (METHODOLOGY WALKLEY-BLACK)

PROJECT NAME PROJECT NO

SAMPLE ID

203-chip-13 203-chip-23 203-chip-27 203-chip-38 203-chip-42 203-chip-47 203-chip-52 203-chip-58 203-chip-69 203-chip-82 207-chip-11 207-chip-19 207-chip-24 207-chip-29 207-chip-35 207-chip-45 207-chip-55 207-chip-87 207-chip-90

207-chip-55 55-MS

55-MSMSD

Hows Corner NA

DEPTH ft

13 23 27 38 42 47 52 58 69 82 11 19 24 29 35 45 55 87 90

55 NA NA

MATRIX

Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip

Average Median

Geometric Mean Standard Deviation Relative Std Dev

+- 95 Confidence Interval n

Rock Chip Rock Chip Rock Chip

Average Median

Geometric Mean Standard Deviation Relative Std Dev

+- 95 Confidence Interval n

FRACTION ORGANIC CARBON

(gg)

170E-03 185E-03 185E-03 170E-03 240E-03 190E-03 230E-03 180E-03 170E-03 115E-03 195E-03 220E-03 220E-03 235E-03 135E-03 190E-03 205E-03 175E-03 160E-03

188E-03 185E-03 185E-03 327E-04

1739 123E-03 to

19

205E-03 130E-03 150E-03

162E-03 150E-03 159E-03 388E-04

2402 840E-04 to

3

2532E-03

2393E-03

Hows Corner Tl Evaluation Appendix B January 13 2005

Response to EPA-DEP Comment 4 Dated March 31 2005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

EPA-DEP Comment 4

Comment 4 Distribution of contaminants First the TI report seems based on the assertion that there is DNAPL at the source area yet it also appears to represent that the source area is small and the bedrock below 85 is competent (or less fractured) and less impacted by the release of contaminants Some of the confusion may result from using most recent data when that data is from several different sampling events over several years and there is no discernible difference in concentrations between shallow and deep bedrock or as in Section 421 where generally decreased generally increase generally similar and similar concentrations in four consecutive sentences leads to a muddled picture of the contaminant distribution

Second the report asserts that the distribution of contaminants over the entire plume has not changed with time but fails to support this conclusion with data again relying on data that is from different sampling dates for one composite representation

Response The likely presence of dense non-aqueous phase liquid (DNAPL) at the Hows Corner Site and the determination that the source area is small are not mutually exclusive and both are conclusions drawn from information obtained during field investigations The presence of DNAPL in the source area is based on the elevated concentrations of volatile organic compounds (VOCs) detected in the groundwater (WampC 2001 WampC 2002) The conclusion that the source area is small is based on the area in which VOCs in groundwater have been detected at concentrations that are considered to be indicative of the presence of DNAPL nearby Similarly the conclusion that fracture frequency decreases at depths greater than approximately 50 to 85 feet below ground surface was based on field observation during the RI field work The fact that zones with observed fractures exhibited higher hydraulic conductivities than zones without fractures coupled with the decreasing frequency of observed fractures with depth led to the conclusion that the hydraulic conductivity of the bulk rock decreases with depth

The most recent data from all wells were used to provide the maximum VOC data set size During the RI all of the previously-existing and then newly-installed monitoring wells were sampled along with several residential wells The RI sampling included up to 48 monitoring wells Subsequent to the RI and prior to the TI three rounds of monitoring were conducted to verify that the plume was stable 15 monitoring wells were sampled during each of the three rounds During the TI field investigation 29 wells were sampled for VOCs The sampled wells included all of the newly-installed wells and a subset of wells installed during the RI for a total of 29 monitoring wells By using most recent data VOC results from 53 monitoring wells were included in the evaluation (see table labeled Sampling Events for listing of monitoring wells) This approach was selected because there generally was little variation in the data from a particular location between years This is borne out by the attached individual plots of VOCs detected in shallow bedrock and deep bedrock for the Pre-ROD (December 1999January 2000) and Supplemental (May 2000) sampling events and for June 2001 January 2002 and April 2003 sampling events The Pre-ROD and Supplemental plots are similar to the subsequent plots from the 2001 2002 and 2003 sampling events

In addition to maps showing the spatial distribution of VOC data at a given time trend plots of the data from a particular location through time (attached) indicate that since the RI concentrations generally have been stable or have decreased Together the maps and trend plots and the data from which they were developed indicate that the distribution of contaminants over the entire plume has not changed appreciably with time

Response to EPA Comment 4 050305doc 1 of 26 Woodard amp Curran (211941)

REFERENCES

Woodard amp Curran Inc (WampC) 2001 Final Remedial Investigation Report Hows Corner Superfund Plymouth Maine July 2001

Woodard amp Curran Inc (WampC) 2002 Final Feasibility Study Report - Non-Source Area Groundwater Hows Corner Superfund Site Plymouth Maine Hows Corner Superfund Plymouth Maine July 2002

Response to EPA Comment 4 050305doc 2 of 26 Woodard amp Curran (211941)

LIST OF ATTACHMENTS (Response to Comment 4)

Table - Sampling Events 1999 - 2004 (2 pages)

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater Pre-ROD Sampling Event

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater Pre-ROD Sampling Event

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater Supplemental Sampling Event

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater Supplemental Sampling Event

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater June 2001

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater June 2001

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater January 2002

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater January 2002

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater April 2003

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater April 2003

Figure - Concentration Trends - Non-Source Area Wells MW-1B and MW-3B

Figure - Concentration Trends - Non-Source Area Wells MW-13DB and MW-16DB

Figure - Concentration Trends - Non-Source Area Wells MW-16IB and MW- 108D

Figure - Concentration Trends - Non-Source Area Wells MW-108S and MW-112D

Figure - Concentration Trends - Non-Source Area Wells MW-112S and MW-114D

Figure - Concentration Trends - Non-Source Area Wells MW-114S and MW-115D

Figure - Concentration Trends -Source Area Wells MW-2DB and MW-2IB

Figure - Concentration Trends -Source Area Wells MW-102S and MW-103D

Figure - Concentration Trends -Source Area Wells MW-103S and MW-104D

Figure - Concentration Trends -Source Area Wells MW-104I and MW-106D

Figure - Concentration Trends -Source Area Wells MW-106S

Response to EPA Comment 4 050305doc 3 of 26 Woodard amp Curran (211941)

I I

El I

II I I 1 I

I

i

Event Baseline Case ID WC-01 WC-01

Well Date Aug-99 Oct-99 LOT10 1 LOT1-1 1 LOT11-4 LOT14 1 LOT15 1 LOT15-1 1 LOT16 1 LOT16-1 1 LOT17 1 LOT18 1 LOT19 1 LOT2 LOT20 1 LOT21-10 1 LOT21-11 1 LOT21-12 1 LOT21-13 1 LOT21-14 1 LOT21-2 1 LOT21-5 1 LOT21-7 LOT21 -8 1 LOT21-9 1 LOT23 1 LOT24 1 LOT28-1 1 LOT28-2 1 LOT28-3 1 LOT28-4 1 LOT28W 1 LOT30 1 LOT30-1 1 LOT30-2 1 LOT30-3 1 LOT30-4 1 LOT30-5 LOT31 LOT35 1 LOT41 1 LOT42-1 1 LOT43-1 1 LOT43-4 1 LOT6-1 1 LOT67 1 LOT6-7 1 LOT6-8A 1 LOT6-8B 1 LOT80-1 1 LOT82 1 MW-101D MW-1011 MW-101S MW-102D MW-102S MW-103D MW-103S MW-104D MW-1041 MW-104S MW-105D MW-106D

Groundwater Sampling Location Summary 1999 - 2004xls

Sampling Events 1999-2004

Hows Corner Superfund Site Plymouth Maine

Supplemental 2001 2002 2003 Pumping 2004 Pre-ROD Rl Sampling Sampling Sampling Test Sampling WC-03 WC-09 WC-25 WC-30 WC-42B WC-56 WC-58 Dec-99 May-00 Jun-01 Jan-02 Apr-03 Sep-04 Sep-04

1

1 1 1

1 1 1 1 1

1 1

1

1 1

1 1 1

1 1 1 1 1

1

1 1

1 1 1 1

1

1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

Sampling Events 1999-2004

Hows Corner Super-fund Site Plymouth Maine

Supplemental 2001 2002 2003 Pumping Event Baseline Pre-ROD Rl Sampling Sampling Sampling Test

Case ID WC-01 WC-01 WC-03 WC-09 WC-25 WC-30 WC-42B WC-56

ll

Well Date Aug-99 Oct-99 Dec-99 May-00 Jun-01 Jan-02 Apr-03 Sep-04 MW-106S 1 1 1 1 1 MW-107D 1 1 MW-108D 1 1 1 1 1 MW-108S 1 1 1 1 1 MW-110D 1 1 MW-111D 1 1 MW-112D 1 1 1 1 1 MW-112S 1 1 1 1 1 MW-113D 1 1 MW-114D 1 1 1 1 1 MW-114S 1 1 1 1 1 MW-115D 1 1 1 1 1 MW-12DB 1 1 1 MW-12SB 1 1 1 MW-13DB 1 1 1 1 1 1 MW-13SB 1 1 1 MW-14DB 1 1 MW-14SO 1 1 MW-15DB 1 1 1 MW-15SB 1 1 1 MW-16DB 1 1 1 1 1 1 MW-16IB 1 1 1 1 1 1 MW-16SO 1 1 MW-17DO 1 1 1 MW-17SO 1 1 1 MW-1B 1 1 1 1 1 1 MW-203D MW-203S MW-204D MW-204S MW-205 MW-206D

I MW-206S MW-2DB 1 1 MW-2DDB 1 1 MW-2IB 1 1 1 1 1 1 MW-3B 1 1 1 1 1 1

I MW-4O 1 1 1 MW-5B 1 1

II MW-6DB 1 1 1 MW-6SB 1 1 1 MW-8DB 1 1 1 MW-8SB 1 1 1

II PW-207 1 SEEP-1 1 SUBTOTAL - RESIDENTIAL 44 25 0 2 0 3 0 SUBTOTAL - MONITORING 22 48 41 15 15 15 1

Total 3 66 73 41 17 15 18 1

I Included in most recent data

I Notes 1 - Overburden well not included in most recent data for plotting

2 - Tetrahydrofuran and 2-Butanone were the only two compounds detected in this well and are thought to be the result of well repair not included in most recent data for plotting

3 - Not included in most recent data for plotting

2004 Sampling

WC-58 Sep-04

1

1 1

1 1

1 1 1

1

1 1

1 1 1 1 1 1 1 1 1

1 1

1

0 29

29

Groundwatef Sampling Location Summary 1999 - 2004xls

I

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

monitoring well Figure 4-14 total VOC contour (ugl) - December 1999January 2000 Distribution of Total VOCs in

Note SW-113 is located downstream of SEEP-1 Shallow Bedrock Groundwater total concentration of detected VOCs ND= not detected these two locations were sampled during the Pre-ROD Sampling Event

Baseline Sampling Event in OctoberNovember 1999 Hows Corner Superfund Site Surface Water Sampling Location A Plymouth Maine Seep Sampling Location laquo- WOODARD ampCURRAN

995037wipri reportepa ri interim final feb 2001cadd drawingsfinalfig 4-14

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

0 300 600 I

FEET

Q residential well Figure 4-16 monitoring well Distribution of Total VOCs in

Deep Bedrock Groundwater total VOCs contour (ugl) Pre-ROD Sampling Event

active residential wells with lot number Hows Corner Superfund Site 2deg42deg Plymouth Maine total concentration of detected VOCs ND= not detected WOODARD ampCURRAN Enyinaaring bull Science bull Operations bull

995037wipri reportepa ri interim final feb 2001cadd drawingsfinalfig4mdash16

PLYMOUTH POND

PLYMOUTH POND

1 628Tl7MW-2bB 12135

PLYMOUTH POND

monitoring well Figure 4-20

V total VOC contour (ugl) - June 2000 Distribution of Total VOCs in Shallow Bedrock Groundwater

| 34 | total concentration of detected VOCs ND= not detected NA = not analyzed Supplemental Sampling Event Note SW-113 is located downstream of SEEP-1 Hows Corner Superfund Site

Surface Water Sampling Location these two locations were sampled during the Plymouth Maine Baseline Sampling Event in OctoberNovember 1999 Seep Sampling Location WOODARD amp CURRAN

Engineering bull Science - Operations bull 995037wipri reportepa ri interim final feb 2001 cadd drawingsfinalfig 4-20

residential well Figure 4-22 Distribution of Total VOCs in

monitoring well Deep Bedrock Groundwater

total VOCs contour (ugl) Supplemental Sampling Event

Hows Corner Superfund Site

total concentration of detected VOCs ND= not detected NA = not analyzed Plymouth Maine

WOODARD amp CURRAN

995037wipri reportepa-ri interim final feb 2001cadd drawingsfinalfig 4-22 Engineering bull Science - Operations bull

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

FEET

Shallow Monitoring Well

Deep Monitoring Well

C Detected Concentration ND = Not Detected Figure 1-XS Distribution of Total VOCs in Shallow Bedrock Groundwater

Pumping Well

17-Acre Property Boundary Concentration Contour (ugl)

June 2001 Hows Corner Superfund Site

Plymouth Maine WOODARDampCURRAN

-i^rhvj bull Scbncn bull Operations bull 211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0601 dwg04-20-05

PLYMOUTH POND Hopkins Road V

O

PLYMOUTH POND

PLYMOUTH POND

o

0 300 600 mdashfa FEET

Shallow Monitoring Well bull bull - 17-Acre Property Boundary Figure 1-XD

Deep Monitoring Well 1 I Detected Concentration ND = Not Detected Distribution of Total VOCs in Deep Bedrock Groundwater

-mf- Pumping Well June 2001 Residential Well Hows Corner Superfund Site

Plymouth Maine i h Surface Water Sampling Point

g WOODARD ampCURRAN _ ^ _ ^ _ _ yen_ rj i|Hlaquorlny bull Science bull Opt

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0601 dwg04-20-05

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

Shallow Monitoring Well

Deep Monitoring Well

Detected Concentration ND = Not Detected Figure 1-YS Distribution of Total VOCs in Shallow Bedrock Groundwater

Pumping Well

17-Acre Property Boundary Concentration Contour (ugl)

January 2002 Hows Corner Superfund Site

Plymouth Maine WOODARD amp CURRAN Engineering Science- Operations bull

211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0102dwg04-20-05

PLYMOUTH POND

PLYMOUTH POND

Site Pand^ laquoum-laquoBTuitaraquo tLV

vVlf-(

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0 300 600 ^ = FEET

Shallow Monitoring Well mdashbullbullbull 17-Acre Property Boundary Figure 1-YD - A - Deep Monitoring Well FT Detected Concentration ND = Not Detected Distribution of Total VOCs in

Deep Bedrock Groundwater Pumping Well January 2002 Residential Well Hows Corner Superfund Site

Plymouth Maine Surface Water Sampling Point

WOODARD ampCURRAN Engineering Sciencs- Operations bulli Si

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0102dwg04-20-05

- m j

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PLYMOUTH POND

PLYMOUTH POND j A O-shy

Shallow Monitoring Well E Detected Concentration ND = Not Detected Figure 1-ZS Distribution of Total VOCs in

Deep Monitoring Well Shallow Bedrock Groundwater

Pumping Well Hows Corner

April 2003 Superfund Site

17-Acre Property Boundary Plymouth Maine Concentration Contour (ugl) r WOODARD ampCURRAN

Engineering bull Science bull Operations bull 211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0403dwg04-20-05

s S pound

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- -

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Jo

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ft Shallow Monitoring Well mdashbullbullmdash 17-Acre Property Boundary Figure 1-ZD Deep Monitoring Well I 1 I Detected Concentration ND = Not Detected Distribution of Total VOCs in

Deep Bedrock Groundwater Pumping Well April 2003

Q) Residential Well Hows Corner Superfund Site Plymouth Maine

(T) Surface Water Sampling Point WOODARD ampCURRAN poundKk EnginawtirKj bull Science - Operations bull

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0403dwg04-20-05

0 Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

B MW-1B

I 12000

PCE

B 10000 Total VOCs

I

i 2000

i 0 Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

c MW-3B

G 2000

1800

B PCE

1600 Total VOCs

1 I I E

il-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

G E

211941

El

I I z E

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Concentration Trends shy Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-13DB

Total VOCs

c i i c o

Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

MW-16DB

30

c i c c I c o

Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99

PCE

Total VOCs

Jul-01 Jul-03

211941

O bi

c Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

I MW-16IB

i 35

3

c Total VOCs

lt- 2 5

0 | gt

o

1 sectI

c c 0 4

Jul-90 Jul-92 Jul-94 Jul-96 Jul-98 Jul-00 Jul-02 Jul-04

I I MW-108D

I 12

PCE 10

Total VOCs c oc 3

E E I 0

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

E 211941

c Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

fi MW-108S

I I 40

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Total VOCs

30

I f 26

20 I o

I 15

10

c Dec-99 Dec-00 Dec-01 Dec-02 Dec-03 I 0

I MW-112D

c 35 - imdash

I A3 shyTotal VOCs

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I

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0 Dec-99 Dec-OO Dec-01 Dec-02 Dec-03

211941

I

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Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-112S

08

PCE

Total VOCs 06

o 04

02

0 Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

MW-114D

o

12000

10000

8000

6000

PCE

Total VOCs

4000

2000

i

ccEIIc

i

i

E

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

211941

Con

cent

ratio

n (

ug

l)

E Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

I MW-114S

E A5000 -- Total VOCs

- 4000

0 3000

2000

i 1000

i n shy

Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

MW-115D

c PCE

Total VOCs

c E

o

C c

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03 I 0

211941

IepoundII

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30000

25000

20000

o bullsect 15000 b

o 10000 U

5000

0 Aug-99

25000

20000

5000

0 Aug-99

211941

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-2DB

PCE

Total VOCs

Aug-01 Aug-03

MW-2IB

PCE

Total VOCs

Aug-01 Aug-03

IDIBI

ii EIDIISIBIG C

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-102S

6000

5000 PCE

Total VOCs

4000

O 3000

2000

1000

0 Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

MW-103D

16000

~ 14000 ugt 3- 12000 o

^ 10000

sect 8000

O 6000

4000

2000

PCE

Total VOCs

0Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

211941

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

G MW-103S

I I

ampo

12000

10000

E sectc

S

8000

6000

4000

2000

0Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

G I 6000

MW-104D

i 5000

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Total VOCs

i i c

2000

1000

Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

E I

211941

cIccIG

IIBCccBcIc

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-1041

PCE Total VOCs

a 25000

0 20000

a 15000

10000

5000

0 Jan-OO Jan-01 Jan-02 Jan-03 Jan-04

MW-106D

3000

2500 PCE

Total VOCs

=sect 2000

o bullsect 1500

1000

500

0 Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

211941

c Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

c MW-106S

I PCE

Total VOCs

i

i Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

i

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211941 c

Response to EPA-DEP Comment 5 Dated March 312005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

iiw

EPA-DEP Comment 5

Comment 5 Matrix Diffusion The report as well as other proponents of matrix diffusion suggest that depletion of DNAPL (Section 5112 page 5-15) needs to be achieved While that might be the ideal the goal is to achieve performance standards and that goal may be attainable while there is residual contamination in the rock perhaps even DNAPL globules The low bedrock matrix porosity (page 1-15) the high permeability values (page 4-4) the relative flux of the groundwater (page 5-5) and the decrease in surface area and out of the mainstream pockets (appendix C-4) all suggest that the diffusion out of the rock matrix would be insubstantial relative to the regional flux of groundwater through the Site

Response The TI Evaluation Report does not explicitly consider or rely upon matrix diffusion as a basis for requesting a TI Waiver for a portion of the Hows Corner Site The technical literature provides documentation that matrix diffusion can be a significant process that affects chemical transport and groundwater remediation timeframes in unconsolidated and consolidated media including fractured rock (US EPA 1989 Freeze and Cherry 1979 Pankow and Cherry 1996 Fountain 1998) Back diffusion of contaminants from the matrix porosity of the fractured rock can prolong the time necessary to achieve groundwater cleanup goals particularly for compounds such as PCE for which the cleanup goal is a low concentration It is our expectation that matrix diffusion has occurred at the Hows Corner Site and that back diffusion of PCE from the rock matrix will also occur Although the extent to which matrix diffusion is occurring at the Hows Comer Site has not been determined and that lack of knowledge contributes to uncertainty regarding the cleanup times at the Site the effect of matrix diffusion is to lengthen rather than shorten the time required for remediation

REFERENCES

Fountain JC 1998 Technologies for Dense Nonaqueous Phase Liquid Source Zone Remediation Ground-Water Remediation Technologies Analysis Center Technology Evaluation Report TE-98-02 December

Freeze RA and Cherry JA 1979 Groundwater Prentice-Hall Inc Englewood Cliffs NJ 07632 p 410-412

Pankow J F and Cherry J A 1996 Dense Chlorinated Solvents Waterloo Press Portland OR 97291-1399 p 67-88

US EPA 1989 Transport and Fate of Contaminants in the Subsurface EPA6254-89019 p 17-18

Response to EPA Comment 5 050305doc 1 of 1 Woodard amp Curran (211941)

WOODARD amp CURRAN Maine Massachusetts New Hampshire Connecticut Florida Operational offices across the US 1-800-426-4262 www woodardcurran com

Page 3: SDMS DocID 251749 - Records Collections · 2020-06-13 · CORPORATE OFFICES: Maine, Massachusetts, New Hampshire, Connecticut New, York, Florida Engineering • Science • Operations

VVOODAFDampCURRAN Engineering bull Science bull Operations

bcc Jim Rawson General Electric (1 copy) Don Frost JrKristin Larson Skadded Arps Slate Meather amp Flom (1 copy) Philip Buckley Rudman amp Winchell (1 copy) Andrew HamiltonHeather Parent Eaton Peabody (1 copy) Joanna Brown Pierce Atwood (1 copy) Philip Buckley Virginia Putnam Rudman amp Winchell (1 copy) Andrew Hamilton Heather Parent Eaton Peabody (1 copy) Kenneth Farber Central Maine Power (1 copy) Robert Fitzgerald Goodwin Proctor (1 copy) Jack Guswa JG Environmental (1 copy)

21194102 TConnelly 050305 2 May 32005

Response to EPA-DEP Comment 1 Dated March 312005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

lib

IIMJ

Ufa

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EPA-DEP Comment 1

Comment 1 Institutional Controls It is recognized by all parties that institutional controls are and will continue to be an integral part of the remedy for the site Having said that the agencies need to have a presentation of the institutional controls including a copy of the town ordinance regarding the ICZ a figure showing the ICZ and the properties with restrictive covenants a table of the 57 properties identified within the ICZ by tax lot number and owners name location of all private wells whether for drinking water residential or agricultural purpose the status of any well abandonment efforts as well as a discussion as how these controls will be monitored

As this information may change over time such as through sale of property or sub-division of a property or well abandonment the agencies believe that presentation of the institutional controls information can best be accomplished with a stand-alone document that can be periodically updated rather than incorporated into the TI report Then as with other documentation such as the RIFS relevant information from the Institutional Control report can be summarized in the TI report

Response The Hows Corner PRP Group will prepare a document that describes the institutional controls for the Site The following items will comprise the document

bull a map of the Site vicinity showing the Institutional Control Zone (ICZ) boundary and properties with restrictive covenants

bull a tabulation of properties located within the ICZ organized by tax lot number and owners name and listing for each property

o the number of connections provided or to be provided to the property o the presence of private wells o the status of well abandonment for the property

bull a copy of the town ordinance regarding the ICZ bull an example of the restrictive covenant for the properties located within the ICZ and bull a discussion of the monitoring program for the institutional controls

The PRPs agree that a stand-alone document is appropriate for the reporting purposes requested by the comment The document can then be updated at periodic intervals mutually agreed upon by the PRPs and the EPA and DEP The status of the PRPs efforts regarding institutional controls and upgrades to the Plymouth water system is summarized in Section 123 of the Draft Technical Impracticability (TI) Evaluation Report Figure 1-2 of the TI Report is a map showing improvements to the Plymouth water system as well as properties that are connected to the system The information in the TI Report will be updated prior to submittal of the final report

Response to EPA Comment 1 050205doc 1 of 1 Woodard amp Curran (211941)

m

Response to EPA-DEP Comment 2 Dated March 312005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

EPA-DEP Comment 2

Comment 2 As discussed in our January meeting the results of the TI field work and their interpretation need to be presented in the TI report Listed below are some specific comments on this with the goal being a discussion of how the site conceptual model and site modeling were revised as a result of the 2004 field work

a analysis of the aquifer test to include a figure presenting the drawdown observed in each monitoring well at the end of the aquifer test The horizontal hydraulic gradient should not be included since this method tends to accentuate the anisotropy Two figures may be needed one for shallow bedrock and one for deep bedrock an evaluation of the appropriateness of the Cooper-Jacob (CJ) method for analyzing the aquifer test data including a comparison of the pattern of observed drawdown to the pattern of fracture orientations determined from the borehole geophysics confirmation that u lt 001 and that calculated values for T and S are similar for several observation wells an interpretation of the change in slope on the CJ plots near the end of the aquifer test the recovery data should be evaluated since it may provide insight as to why the slopes changed the marked increase in slope near the end of the test strongly suggests that a barrier (ie no flow) boundary was encountered and if a boundary was encountered T and S need to be calculated from the pre-boundary portions of the CJ plots It may be appropriate to analyse the aquifer test data using Theis as well as the Moench dual porosity model (both analysis methods are available in Aqtesolv pumping test modeling software) so that all parties have confidence in the transmissivity and storativity numbers derived from the CJ analysis b numerous bedrock borings (including angled holes) were drilled during the most recent field investigation yet no summary of the findings or the geophysical logging or packer test and sampling results have been provided c have any input parameters been changed in the flow transport and batch-flushing models as a result of the 2004 fieldwork If so which ones and why were the changes made (ie justify the changes)

Response The objective of the pumping test conducted at the Hows Corner Site during September 2004 was to observe the response of the groundwater system to pumping for use in refining the site conceptual model The refined site conceptual model would in turn be used to recalibrate the flow model and aid in the design of the hydraulic containment system being constructed under the authority of the AOC for the RD

The results of the pumping test are illustrated by plots of the drawdown at the end of the test The enclosed three drawdown plots (shallow bedrock deep bedrock and combined) represent the change in water level at the end of the test from the initial pre-test water level The shallow bedrock figure shows a northeast-southwest trending ellipsoidal area of drawdown that extends approximately 2000 feet along the major axis and approximately 800 feet along the minor axis The northeast-southwest orientation of the drawdown ellipse is consistent with the orientation of likely water-bearing fractures as identified from geophysical logging during the TI investigation The deep bedrock figure and combined figure also show ellipsoidal areas of drawdown with similar orientation A secondary axis with a more northerly orientation is evident on the figures showing drawdown in deep bedrock and in combined shallow and deep bedrock The maximum drawdown measured in shallow bedrock was 29 feet at MW-2EB The maximum drawdown measured in deep bedrock was 54 feet at the pumping well (PW-207) The drawdown ellipse is

Response to EPA Comment 2 050205doc 1 of 24 Woodard amp Curran (211941)

approximately coincident with the location of the modeled capture zone as presented on Figure 3shy1 of the TI Evaluation report

The enclosed three potentiometric surface maps (shallow bedrock deep bedrock and combined) represent the water surface elevations measured at the end of the test which was 72 hours or three days after it began All three maps show the presence of the groundwater high located in the southeast portion of the 17-acre property This high area shows relatively little relief but with the exception of the measurements at MW-2DDB which shows anomalously high water levels the central area of the high is at lower elevation than the perimeter The measurements at MWshy2DDB are hypothesized to result from water that is unable to drain rapidly enough to equilibrate with the rest of the formation

The pumping test data initially were analyzed using the Cooper-Jacob method for the late test data The results of this analysis are summarized in the table entitled Pumping Test Analytical Results It was recognized that because the aquifer is not uniform isotropic and infinite in areal extent the assumptions on which the underlying Theis equation is based were not met and because of the length of the test the criteria for use of the Cooper-Jacob of analysis were not explicitly met We recognize that the complexity of the hydrogeologic characteristics of the formation would be a significant limitation if the calculated values from the pumping test analysis were to be used as absolute representations of the hydraulic parameters of the formation However the range of values from this pumping test analysis were used as guidelines or bounding values for recalibration of the flow model

Woodard amp Curran also analyzed the pumping test data using the Theis and Moench methods The enclosed table entitled Pumping Test Analytical Results also summarizes the results of analysis of the data using these analytical methods Again although none of the methods may be strictly applicable they provide values that are guidelines for parametric ranges used in model calibration Hydraulic conductivity values calculated from the different analytical methods were as follow

Minimum Maximum Mean (ftday) (ftday) (ftda

bull Cooper-Jacob 020 067 038 bull Theis 035 1476 392 bull Moench (Fissure) 027 210 099

Storage coefficients calculated from the different analytical methods were as follow

Minimum Maximum Mean bull Cooper-Jacob 830E-04 392E-02 651E-03 bull Theis 547E-05 359E-03 473E-04 bull Moench (Block) 803E-05 402E-02 489E-03

Storage coefficients calculated using the Theis method were one to two orders of magnitude lower than values calculated using the Cooper Jacob or Moench (Block) methods Although the fissure system values are thought to be appropriate for evaluating hydraulic conductivity because the majority of flow is through fractures the block system values are appropriate for evaluation of storage because the limited fractures account for only a small part of the total storage in the bedrock

Response to EPA Comment 2 050205doc 2 of 24 Woodard amp Curran (211941)

Woodard amp Cunran used the values estimated from the pumping test analysis as an initial data set for transient benchmarking by running a 3-day simulated pumping test Calibration of the model was accomplished by comparing measured drawdowns obtained during the pumping test to calculated drawdowns from the flow model The hydraulic parameter values in the model were varied from the initial values but within the range calculated from the pumping test analysis The additional model calibration was considered to be completed when the calculated drawdowns were sufficiently close to measured drawdowns The resulting values of the hydraulic parameters of the calibrated model were then considered acceptable to provide satisfactory prediction of the response of the flow system to other hydraulic stresses

Regional water-level data were reviewed prior to data analysis A plot of water levels in the closest USGS regional background well (provided in the TI Data Package and attached) indicates that throughout the period of the test and subsequent recovery water levels were declining on a regional scale Although the decline in water levels is gradual the change in slope observed on the Cooper-Jacob plots is thought to represent the point at which the drawdown at a given location caused by pumping becomes less significant compared to the regional drawdown This occurs at about a day after start of pumping The effect of the regional decline in water levels can also be seen in the initial rapid rise in water levels in response to pump shut off followed by a decline in water levels after about a day after the pump is shut off

Additional information obtained during the TI field work was reviewed and evaluated in updating the conceptual model for the site In general the additional information corroborated the understanding of the Site presented in the RI report In particular the northeast-southwest fracture orientation was confirmed as the predominant orientation Geophysical logging during the TI investigation however showed the dip direction of fractures to be more variable and the dip angles to be shallower than was understood based on the RI data (see enclosed figure Packer Testing Results in Vicinity of Source Area) The additional borings installed within the fenced area and to the east of the fenced area showed that the area in which concentrations of total VOCs in groundwater exceeded 10000 pgL was more limited than portrayed in the RI and FS reports Packer testing of the intervals identified by geophysical logging as likely or possibly transmissive (see enclosed borehole geophysical logs) showed VOC concentrations within the packered intervals at a given borehole to be either essentially constant (eg MW-203 MW-204 MW-205) or increasing with depth (eg PW-207) Information on hydraulic conductivity and VOC concentrations in packered intervals is summarized on two separate tables for the 1999 RI wells and 2004 TI wells (Packer Permeability and Packer Sampling Results for Potential Fracture Intervals - enclosed) The orientation hydraulic conductivity and VOC concentrations of features identified as likely or possibly transmissive is summarized in a separate table (Orientation Permeability and Groundwater Sampling Results for Transmissive Features shyenclosed)

Table 4-1 of the TI Evaluation report summarizes the variation of input parameters to the flow and batch-flushing models as the project progressed from RI to FS to TI As described above for calculations in the TI Evaluation report hydraulic conductivity values were adjusted during the model calibration to pumping test drawdown data Measured fraction of organic carbon values and VOC concentrations were used in the Batch-Flushing model along with recharge calculated from the ModFlow model For calculation of pore flush volumes using the Batch-Flushing model the ratio of density to porosity was constrained to a range of 4 to 10 which is the typical range of such ratios in porous media (Freeze amp Cherry 1979) The basis for this change was stated in Appendix C of the TI Waiver Evaluation Report and is described in the response to Comment 3

Response to EPA Comment 2 050205doc 3 of 24 Woodard amp Curran (211941)

REFERENCE

Freeze RA and Cherry JA 1979 Groundwater Prentice-Hall Inc Englewood Cliffs NJ 07632 p 410-412

Response to EPA Comment 2 050205doc 4 of 24 Woodard amp Curran (211941)

LIST OF ATTACHMENTS (Response to Comment 2)

Figure - Drawdown at 72 Hours Shallow Wells

Figure - Drawdown at 72 Hours Deep Wells

Figure - Drawdown at 72 Hours

Figure - Potentiometric Surface at 72 Hours Shallow Wells

Figure - Potentiometric Surface at 72 Hours Deep Wells

Figure - End of Pumping Test Bedrock Potentiometric Surface at 72 Hours

Table - Pumping Test Analytical Results

Figure - USGS Background Groundwater Level

Figure - Packer Testing Results in Vicinity of Source Area

Figure - Borehole Geophysical Log MW-203

Figure - Borehole Geophysical Log MW-204

Figure - Borehole Geophysical Log MW-205

Figure - Borehole Geophysical Log MW-206

Figure - Borehole Geophysical Log PW-207

Table - Packer Permeability and Packer Sampling Results for Potential Fracture Intervals 1999 Drilling Program (2 pages)

Table - Packer Permeability and Packer Sampling Results for Potential Fracture Intervals 2004 Drilling Program

Table - Orientation Permeability and Groundwater Sampling Results for Transmissive Features 2004 Drilling Program (2 pages)

Response to EPA Comment 2 050205doc 5 of 24 Woodard amp Curran (211941)

(MEDEP Pond 1) Farm Pond

0 150 300

FEET

Monitoring Well

Figure X Pumping Well Drawdown at 72 Hours

_ - 17-Acre Property Boundary Shallow Wells Hows Corner Superfund Site Drawdown Contour (ft) Plymouth Maine

151 | Drawdown (ft) WOODARD ampCURRAN

^Stk Engineering bull Science bull Operations bull 211941 Hows CornlaquorwipDrawingsTI EVALDrawdown-72hrs_shallowdwg04-19-05

MW-3B

413951 W-6DB JMW-6SB

(MEDEP Pond 1) Farm Pond

Monitoring Well

Pumping Well

17-Acre Property Boundary

Groundwater Elevation Contour (ft)

211941 Hows CornerwipDrowngsTI EVALpo-tent-aU-72-hrsdwg

Figure X End of Pumping Test

Bedrock Potentiometric Surface at 72 Hours Hows Corner Superfund Site

Plymouth Maine ^ WOODARD amp CURRAN

Englnesring bull Science bull Ope

(MEDEP Pond 1) Farm Pond

Monitoring Well

Pumping Well Drawdown atFigure X

72 Hours _bullbull_ 17-Acre Property Boundary Deep Wells

Drawdown Contour (ft) Hows Corner Superfund Site

Plymouth Maine 151 | Drawdown (ft)

= WOODARD ampCURRAN 211941 Hows CornerwipDrawingsTI EVALDrawdown-72hrs_deepdwg04-19-05

Engineering bull Science bull Operations

(MEDEP Pond 1) Farm Pond

028 MW-12DB

MW-125B 040

l - _ ^ I 016 I N

050 MW-15SB

MW-15DB 048

A J s

- A - Monitoring Well

-$poundbull Pumping Well

_bullmdash 17-Acre Property Boundary

^ Drawdown Contour (ft)

151 I Drawdown (ft)

211941 Hows CornerwgtpDrawinQsT EVAI_Drawdown-72brsdwg04mdash19-05

Figure X Drawdown at 72 Hours

Hows Corner Superfund Site Plymouth Maine

^ WOODARD ampCURRAN Engineering bull Science bull Operations i

(MEDEP Pond 1) Farm Pond

Monitoring Well

Pumping Well

_bullbull_ 17-Acre Property Boundary

f Groundwater Elevation Contour (ft)

|419Q0| Groundwater Elevation

211941 Hows CornerwipDrawinqsTI EVALPotSurf-72hrs_shallowdwg04-19-05

150 300

FEET

Figure X Potentiometric Surface at 72 Hours

Shallow Wells Hows Corner Superfund Site

Plymouth Maine

WOODARD ampCURRAN Engineering bull Science bull Operations

29212 MW-108D

(MEDEP Pond 1) Farm Pond

Monitoring Well

Pumping Well

mdashbullbulllaquo 1 7-Acre Property Boundary

bull Groundwater Elevation Contour (ft)

1419001 Groundwater Elevation

211941 Hows CornerwipDrawingsTI EVALPotSurf-72hrs_deepdwg04-19-05

150 300 =5fc= FEET

Figure X Potentiometric Surface at 72 Hours

Deep Wells Hows Corner Superfund Site

Plymouth Maine

WOODARDampCURRAN Engineering bull Science bull Operations bull

--

Pumping Test Analytical Results Hows Corner Superfund Site

Plymouth Maine

Well ID oper Jaccb Analyses 2 Theis Analyses Fissure

Well Id Rd (ft)

Saturated Thickness

Transmissivity

(ft2day) K

(ft2day) K

(cmsec) Storage

Coefficient Transmissivity

(ft2day) K

(ft2day)

K (cmsec)

Storage Coefficient

System K

(ftday) PW-207OB 8 85 481 057 200E-04 392E-02 36 042 150E-04 809E-04 027 MW-103S 50 85 451 053 187E-04 720E-03 92 108 382E-04 283E-04 083 MW-103D 54 185 455 025 868E-05 210E-02 65 035 123E-04 237E-04 044 MW-2IB 59 85 352 041 146E-04 699E-03 104 123 433E-04 512E-04 052 MW-2DB 63 85 334 039 139E-04 845E-03 148 080 283E-04 239E-04 046 MW-104D 95 185 489 02 6 932E-05 654E-03 98 053 186E-04 547E-05 037 MW-104I 97 85 33 03 9 137E-04 362E-03 117 137 484E-04 962E-05 048 MW-101I 107 85 364 043 151E-04 490E-03 511 601 212E-03 223E-04 136 MW-102D 134 185 435 024 829E-05 248E-03 108 058 206E-04 850E-05 065 MW-101D 138 185 492 027 938E-05 511E-03 671 362 128E-03 700E-04 172 MW-205 219 85 57 067 237E-04 255E-03 447 526 186E-03 359E-03 -shyMW-204D 221 185 367 020 700E-05 170E-03 790 427 151E-O3 155E-04 147 MW-204S 225 85 379 045 157E-04 156E-03 1031 1213 428E-03 313E-04 199 MW-1B 228 85 325 038 135E-04 977E-04 340 400 141E-03 739E-05 054 MW-203S 273 85 489 058 203E-04 117E-03 1255 14 76 521 E-03 216E-04 210 MW-106D 278 185 51 028 972E-05 141E-03 1065 576 203E-03 360E-04 104 MW-203D 278 185 478 026 911E-05 152E-O3 765 414 146E-03 364E-04 138 MW-105D 364 185 44 024 839E-05 830E-04 769 415 147E-03 200E-04 127

1 Analyses conducted using Cooper and Jakob method on late drawdown data collected during constant

discharge pumping test conducted at the Hows Comer Site from September 20 - 30 2004

2 Analyses conducted using Theis solution for unconfmed approximation (1935)

J Analyses conducted using Moench method for dual porosity estimation (1984)

Fissure System Storage

Coefficient 402E-04 117E-06 264E-04 300E-04 932E-05 235E-07 502E-05 326E-06 801E-05 542E-04

-

803E-05 762E-05 134E-05 498E-05 115E-04

47E-04 838E-05

3 ysesh Analysis

Block System K (ft2day)

251E-02 207E-03 564E-04 163E-04 585E-04 465E-02 153E-04 498E-03 855E-04 356E-03

-

292E-03 394E-03 720E-04 526E-03 160E-01 35OE-O1 287E-03

Block System Storage

Coefficient

402E-02 164E-04 183E-02 330E-03 158E-03 847E-03 286E-03 326E-04 803E-05 272E-03

723E-04 686E-04 148E-04 349E-04 115E-03 47E-04 838E-04

Theis - Moench - CJ - AnalyticalResults_4-19-O5xls

DRAFT

242

24

238

236

bulla

c

i

a Q

234

232

228

226

Hows Corner Constant Discharge Testing USGS Background Groundwater Level USGS 445319068560101 ME-PEW456 Kenduskeag Maine

End of Monitored Recovery Period 09302004

Regional Background Location i 226 miles from Pumping Locatio

lt

697

NOTES

1 Groundwater samples collected in 1999 were screened for five volatile organic compounds (VOCs) only N

tetrachloroethene (PCE) exceeded reporting limits MW-2030 082304 082304 082304 082304 u

2 Strike and Dip of likely or possible transmissive 30 45 55 85 feature within the packer interval from which the indicated sample was collected

MW-204D

PCE TOTAL VOCs

081904 30

220 2636

A

081904 46-50 540 6436by

081904 IT

260 3073

x

MW-105D

PCE TOTAL VOCs

111199 50-60 2100 2100

MW-106D

PCE TOTAL VOCs

111199 76-86

400 400

111199 137-147

1400 1400

111299 1355-1455

350 350

PCE TOTAL VOCs

44 84

64

MW-6SB

bulli

lt

gt-

170 234

35

I I i

140 192

^^52

^^52

130 183

52 - lt

S A 34

PW-207 082404 082404 082404 20 37

PCE 1300 TOTAL VOCs

17-Acre George West Property Boundary

MW-113D

PCE TOTAL VOCs

112299 46-56

350 350

112299 70-80 190 190

150

112299 105-115

129 129

112399 138-148

230 230

L e g e n d ( J New Monitoring Well-Summer

Site Property Boundary ^ P u m p i n g Well-Summer 2004

-xmdashxshy Source Area

bull0shy Monitoring Well shy Pre 2004 Angled Boring-Summer 2004

211941laquoipdwgTI-ELV21ig41paltker-data2

2004 PCE of Total

bull lt70 VOCs

M W - 1 14D ^ ^

Figure xx Packer Testing Results in

Vicinity of Source Area Hows Corner Superfund Site

Plymouth Maine ^ WOODARD ampCURRAN

^^^^^^^^^^m ampKm Engineering - Science bull Operations

c Northeast Geophysical Services Borehole Geophysical Log

MW-203 Date logged 081704 Plymouth Maine

I Flowmeter Measurements Tomporaturo(C) Acoustic Televiewer

7 5 8 8 5 9 95 Caliper (Inches) Resistance (Ohms) Spontaneous Potential (mVj Dip In Degrees PCE Total VOCs

3 0 2 0 8 0 laquodeg 4S 1000 1400 1800 2200 MO HO 1000 1200 MOO 0 laquo deg ugL ugL n 1 1 1 1 1 1 1 1 1 i 1 1 1 1 n 1 1 1 1 1 1 1 1 1 1 1 n I l l l l l l l n

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30 4 g 0 20 40 60 Dip in Degrees bullbull

Likely or poss bleFluid Resistivity (ohmmeters) The dip direction-- indicated

^ t h e l i n e extending from t h

I Iransmissive zone circle The strike of the feature is 90 degrees from this

The acoustic televiewer graph displays the mostprominent features selectedffom the acoustic televiewer

R n r a h n l c D O t t n O I B

f i o n n h w c i r a l U K U p i i y SI Ud l

1 rn l_Og Packered Interval August 2004

E tog The location dip angle and dip direction of the sleeted M W - 2 0 3 Groundwater samples were collected by Woodard S Curran on H23120M features are approximate Refer to the televiewer og of His _ well for more precise detail Plymouth Maine Date logged 081704

I

1

Northeast Geophysical Services Borehole Geophysical Log MW-204 D a t e l o gge d 072604

Plymouth Maine

n 3

Flowrneter Measurements(in gpm)

Caliper (Inches)0 3 5 4 0

1 1 1 1 1 1 1 t 1 1 1 1 1 1Ambient Rowmeler pumping Flowmetsr 05gpm

Templaquorature (C) bull bull bull bull i

7 75 8 8S 9 Resistance (Ohms) Spontaneous Potential (mV)

4000 SOW 600 4M 0

Acoustic Televiewer (interpreted)

Dip in Degrees 0 20 4060 SO

at N

PCEugL

Total VOCs ugL

- -_ a

10-

shy 10 bull - 10 shymagnetic

north - 10

o o

bull 1

11

11

1 1

1 1

11 1

1 1

1 1

1 1

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1 1

1 1

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1 1 E 1

- L

3 7 2 0 2 0r bull 20 bull - shy

i S_ N F

bull30 bull 7 3 0 220 2636shy1^ J J 004

fI f V ^

40 shy 4 0 4 0 shy - 4 0rbull019 [_ 007 w8 - - shy5 c

bull

gt

Ia50i 540 6436

bull50 - - 50 - - 5 0

-QQ7 - bull - -t T

pound V gtk

B 6 0 - e o - 7 6 0 -60shyQ 1 1

Q -007 -004 bull1 mdash T - J ~

bull

- - shyT 70 -J c [TO- - 70 - 7 0-

V Y 1- -004 -003

mdash T -h - y - j i - - mdash 260 3073 - gt=7

80 -j NF bull80 - - 80 - - 8 0Jgt

bull i

i 1

i i

C- bull shy

90 shy

K

Jlt i90 90 shy - 9 0shy -

l

ii

I I I I

NF bull M J

I ^ ^ - ^ bull 1

mdash mdash - _

s -7 ^100shy

till

1 100 100- H - 1 0 0shy -1 x Likety or possible k ^ Iransmissive zonebull

1 i i i ii i i i | l l l l | l i l l 0 20 40 ED 80

1 -

3 0SOFluid Resistivity (ohmmeters)

Dip in Degrees The djp ^ ^ o n is indicated ty Ihe line extending from tha circle The strike of Ihe feature

19- 3U UIHJIW93 IolII l l l lraquo

bull

The acousfc televiewer graph displays the mostprominent features selected from the acoustic televiewer109 The location dip angle and dip direction of Ihe sleetedfeatures are approximate Refer to the televiewer log of thiswentormore precise detail

B o r e h o l e G e O D h V S I C a l LOO B W H U I B w c w p n y o i v a i w v yM W - 2 0 4

P l y m O U t n MaiDB

Packorod Interval August 2004Groundwater san-ples wampramp collected by Woodard a Curran on OMO23C4

Date logged 072604

C

I

E Northeast Geophysical Services Borehole Geophysical Log Date logged 072704

I MW-205

Plymouth Maine

Flowmeter Measurements Temperature (C) Acoustic Televiewer (In gpm) I ~l (Interpreted)

I 85 10 Caliper (inches) 95

Dip in D g r laquo Resistance (Ohms) Spo ontaneous Potential (mV PCE Total VOCs 3 0 16 4 0 4 5 ) 20 40 60 80 10 00 2000 30 00 4VJ 400 -3 laquo

i i i i 1 i i I i 11 4 0 D 1 I I ugL ugL

C h

iii Ambient Flowmetar pumping

Flowmeter 1 25 gprn

I bull$bull

i

I rmdash magnetic 1 north ^^^^ 1 VI f

10 ~ I C x 10 bull - 10 bullbull

4 5 6mdashmdash f 1000B 11448 noisy nodi a raquo ^

mdash 5rt mdashi mdash Oft pound) 1100B 12509

cjmdash1 007

-

i i i 1

en

8 B a B

30 mdash

-

40 shy

-mdash I -

50 -_

__NF lt005

- 30 - - 3 0 it 34V

MO P26 V S) 1300B 13776 _ N F NF

26

40 bull - 40 bull 7-40 gt J Vf1 cX

) -j -

_ N F NF 50 c bull - 50 ^ 7-50

i I

I

c

B pound 60 - 6 0 7 60 - 7-60 a i 1

_ N F NF i Si f f 70 -_ bull70 bull - 70 shyC I 9

-m bull - shyA

_ N F NF 80 80 -j bull80 bull - 80 - C- 33 34

bull

5-i r

i 1

J r

Ck

_ N F NF 9 0 90 - - 90 shy

i bullCshy

J rK bull

100 -j ^ Likely or possible bull100- - 100- I -100

transmissive zone bull - ^ bull shy] |

1 1 1 1 1 1 1 I 1 i i i 1 i i 1 1 0 20 40 SO SO 10 20 30 40 50 Dip in Degrees 30 4 0 Fluid Resistivity (ohmmeters) Thlaquo dip direction is indicated

by the line extern r g from the circle The strike of he feature is 90 degrees from ihis

The acoustic televiewer graph displays the most

I Borehole Geophysical Log Packered Interval August2004 prominent features selected from the acoustic televiewer

Groundwatcr samples were oollccled by Woodard amp Cufran orgt S172004 log The location dip angle and dip direction of ins slsctsd MW-205 features are approximate Refelt to the televiewer log of this wall for more precise detail Plymouth Maine Date logged 072704

I

C

I Northeast Geophysical Services Borehole Geophysical Log Date logged 072704

I MW-206

Plymouth Maine

Flowmetor Measurements Temperature (C) Acoustic Televiewer | I r T i i i i i i i i i i i i i i r I |(in gpm) (Interpreted)

I 75 8 flS 9 95

Caliper (inches) Resistance (Ohms) Spontaneous Potential (mV) Dip In Degress PCE Total VOCs 30 35 40 4 5 0 20 40 M 90 4500 5500 6500 ugL ugL I i i

I I

- 1 0

I - 2 0

I 2900B 32401

i i L

E 0

i 6300B 68901

i I 0 20 40 SO 80

20 30 40 50 Dip in Dlaquogralaquos

amp 4 a Fluid Resistivity (ohrnmeters) The dip dirertion is indicated Likely or possible by iho line extending from the transmissive zone circle The striKe of the feature

is 90 degrees from tNs

Borehole Geophysical Log Packered Interval August 2004

E amples were collected by Woodard amp Cunan oo SM82004 log Thraquo location 4p angle and dip direction of the sloeled MW-206 feature are approximate Refer to the televiewer 109 of this well for more precise detail Plymouth Maine Date logged 072704

C

I Northeast Geophysical Services Borehole Geophysical Log

Date logged 082304 PW-207

I Plymouth Maine

Fiowmeter Measurements Temperature (C) Acoustic Televiewer

I (in gpm) (interpreted)

75 8 85 9 95 Caliper (inches) Resistance f0tims) Spontaneous Potential (mV) Dip in Degrees PCE Total VOCs

55 60 0 20 40 SO 80 ugL ugL I I I I I I I

Ambienl Fiowmeter pumping Flewmater

magnetic - 10 - - 1 0

north

i - 20 - - 2 0

1300 1410

i - 30 - - 3 0

i tf

5400 5802 - 40 - - 4 0

B - 50 - - 5 0

I 18000 19234

- 60 - - 6 0

I 12000 13085

- 70 - - 7 0

- 8 0

i - 9 0 19000 20354

G - 100- -100

I 110 110 bull110

0 20 40 60 SO 10 20 30 Dip m Degrees

Fluid Resistivity (ohmmeters) I 50

The dip direction is indicated by ihe line extending from the circle The strike of the fealure is 90 degrees from this

Borehole Geophysical Log

G Packorod Interval August 20(M log The location dip angle and dip dirlaquocton or the sleeted Groundaier samplss were ooliecled by Woodard i Curran on ampt24f2ltXM PW-207 failures are approximate Reter to the televiewer log of this wlaquoll for more precise detail PlyPIOUth Maine Date logged 082304

I

Table XX Packer Permeability and Packer Sampling Results for Potential Fracture Intervals

1

WellID MW-101D MW-101D MW-101D MW-101D MW-101D MW-101D MW-101D MW-101D MW-101D MW-101D MW-I01D MW-101D MW-101D MW-102D MW-102D MW-I02D MW-102D MW102D MW-102D MW-102D MW-102D MW-102D MW-I02D MW-102D MW-102D MW-102D MW-103D MW-103D MW-103D MW-103D MW-I03D MW-103D MW-103D MW-103D MW-103D MW-103D MW-103D MW-103D MW-I03D MW-104D MW-104D MW-104D MW-104D MW-I04D MW-104D MW-104D MW-104D MW-104D MW-104D MW-104D MW-105D MW-105D MW106D MW-106D MW-106D MW-107D MW-107D

1999 Drilling Program

Hows Corner Superfund Site Plymouth Maine

Potential Fracture Top Of Bottom 6 Depth to lt Topof i Interval from Packer Packer Middle of Elevation Hydraulic bull PCE

GS ELEV 1 Rock Drilling Interval Interval Interval of Interval Conductivity Concentration (ft msl) (ft msl) TEST (ftbgs) (ftbgs) r(ftbgs) ( f t b (ft mil) (cmsec) (raquogL)

4339 4329 13 28-29 33-3537-39 271 376 324 4016 OOOE+00 4339 12 37-3444-46 380 485 433 3907 157E-04 4339 11 488 593 541 3799 132E-04 4339 10 60-61 578 683 631 3709 OOOE+00 4339 9 678 783 731 3609 I79E-05 4339 8 778 883 831 3509 106E-05 4339 7 880 985 933 3407 243E-05 4339 6 990 1095 1043 3297 339E-06 4339 5 1090 1195 1143 3197 OOOE+00 4339 4 1190 1295 1243 3097 OOOE+00 4339 3 1365-1375 1290 1395 1343 2997 OOOE+00 4339 2 147-157 1390 1495 1443 2897 580E-05 4339 1 147-157 1470 1575 1523 2817 741E-05 43161 43061 13 166 271 219 4098 333E-04 43161 12 30-3136-40 260 365 313 4004 I54E-05 43161 11 36-4041-43 362 467 415 3902 548E-05 43161 10 470 575 523 3794 598E-05 43161 9 570 675 623 3694 197FOS 43161 8 670 775 723 3594 OOOE+00 43161 7 770 875 823 3494 891 E-05 43161 6 83-94 870 975 923 3394 139E-05 43161 5 970 1075 1023 3294 123E-04 43161 4 1070 1175 1123 3194 526E-06 43161 3 1170 1275 1223 3094 138E-05 43161 2 1270 1375 1323 2994 671E-06 43161 1 1370 1475 1423 2894 OOOE+00 42997 42497 13 18-19 170 275 223 4077 OOOE+00 42997 12 260 365 313 3987 766E-05 42997 11 360 465 413 3887 727E-05 42997 10 460 565 513 3787 192E-05 42997 9 560 665 613 3687 752E-05 42997 8 660 765 713 3587 778E-05 42997 7 85-86 763 868 816 3484 260E-05 42997 6 860 965 913 3387 289E-05 42997 5 102-103 960 1065 1013 3287 102E-04 42997 4 1060 1165 1113 3187 522E-06 42997 3 1160 1265 1213 3087 520E-06 42997 2 129-130 1260 1365 1313 2987 960E-04 42997 1 1360 1465 1413 2887 OOOE+00 43372 42922 11 35-37 42-45 350 455 403 3935 684E-04 43372 10 460 565 513 3825 500E-05 43372 9 560 665 613 3725 106E-05 43372 8 72-74 660 765 713 3625 204E-05 43372 7 760 865 813 3525 872E-06 43372 6 860 965 913 3425 467E-06 43372 5 960 1065 1013 3325 200E-05 43372 4 1060 1165 1113 3225 354E-05 43372 3 125-130 1160 1265 1213 3125 157E-05 43372 2 125-130 1260 1365 1313 3025 337E-04 43372 1 1365 1465 1415 2922 689E-06 43052 43002 2 54-58 490 595 543 3763 124E-05 2100 43052 1 139-140 145-146 1367 1472 1420 2886 154E-04 1400 43291 4391 3 bullI133 260 365 313 4017 439F06 43291 2 77-78 760 865 813 3517 230E-03 400 43291 1 143-144 1355 1460 1408 2922 971E-06 350

29958 27258 4 450 555 503 2493 OOOE+00 (21)A 29958 3 103-105 1000 1105 1053 1943 752E-04 (063)A

Table XX Packer Permeability and Packer Sampling Results for Potential Fracture Intervals

1999 Drilling Program

Hows Corner Supcrfund Site Plymouth Maine

gtbull i Potential Fracture Top _OfBot Bottom of Depth to ltbull Top of Interval from f Packer Packer Middle Of

GS ELEV lt Hock Drilling interval Interval Interval WeD ID ft msl) (ft msl) TEST (ftbgs) ltft$gs) (ftbgs) (ftbgs)

MW-107D 29958 2 128-130 1200 1305 1253

MW-107D 29958 1 139-141 1350 1455 1403

MW-108D 31904 31104 6 35-36 300 405 353 MW-108D 31904 5 60-62 550 655 603

MW-108D 31904 4 80-83 750 855 803

MW-108D 31904 3 118-119 123-124 1150 1255 1203

MW-108D 31904 2 147-149 1440 1545 1493

MW-108D 31904 1 1700 1805 1753

MW-110D 40576 40426 2 21-31 210 315 263 MW-110D 40576 1 148-154 1460 1565 1513 MW-I11D 40519 4 70-71 650 755 703

MW-111D 40519 3 79-82 84-86 780 885 833 MW-I11D 40519 2 97-102 950 1055 1003 MW-111D 40519 1 1370 1475 1423

MW-112D 3027 2942 4 42-52 420 525 473 MW-112D 3027 3 850 955 903 MW112D 3027 2 1100 1205 1153 MW-112D 3027 1 135-136 140-141 1340 1445 1393

MW-113D 43085 43085 5 250 355 303 MW-I13D 43085 4 47-49 460 565 513 MW-113D 43085 3 73-74 700 805 753 MW-113D 43085 2 1050 1155 1103 MW-113D 43085 1 1380 1485 1433

MW-114D 42394 41594 4 48-49 450 555 503 MW-114D 42394 3 79-81 740 845 793 MW-114D 42394 2 121-129 1250 1355 1303 MW-114D 42394 1 134-142 1350 1455 1403

MW-115D 4035 4035 4 300 405 353 MW-1I5D 4035 3 70-71 650 755 703 MW-115D 4035 2 1150 1255 1203 MW-115D 4035 1 1400 1505 1453

LOT-28W 382 7 450 555 503 LOT28W 382 6 550 655 603 LOT-28W 382 5 650 755 703 LOT28W 382 4 750 855 803 LOT-28W 382 3 850 955 903 LOT-28W 382 2 950 1055 1003 LOT-28W 382 1 1055 1155 1105

NOTES cmsec = centimeters per second ft bgs = leet below ground surface It msl = feet below mean sea level lt = not detected at indicated reporting limil A = detected below laboratory PQL ( ) = detected below reporting limits

Elevation of Interval

(ft nisi) 174

159

283gt 2588

2388

1988

1698

1438

3795 2545 3349 3219 3049 2629

2555 2125 1875 1635

4006 3796 3556 3206 2876

3737 3447 2937 2837

3683 3333 2833 2583

3318 3218 3118 3018 2918 2818 2715

Hydraulic Conductivity

(cmsec)

323E-05

208E-05

471E-03

471E-03

624E-05

3I6E-05

264E-05

261 E-05

OOOE+00 200E-04 953E-05 OOOE+00 OOOE+00 212E-05

361 E-05 410E-06 2gQE06 292E-05

786E-05 124E-05 151 E-05 822E-06 82IE-06

858E-05 I69E-05 352E-03 866E-05

223E-05 394E-06 122E-05 525E-06

831 E-05 182F-05 L62E-05 129E-05 190E-05 890E-04 981 E-04

PCEraquo Concentration

(ugL)

lt5

(14A)

98 11

15

22

11

30

200 (62)A

110 210 300 240

(44)A (23)A

5

350 190 129 230

2200 1900 2600 2600

(17)A (16)A (19)A

96

Table XX Packer Permeability and Packer Sampling Results for Potential Fracture Intervals

2004 Drilling Program

Hows Corner Superfund Site Plymouth Maine

Top of Bottom of Depth to Midpoint

t K

ELEV (ft Potential Transmissive Zones Packer Interval

Packer Interval

Middle of Interval

Elevation of interval

Hydraulic Conductivity

PCE Concentration

Well ID msl) TESTr (ft bgs)- (ftbgs) (ftbgs) (ftbgs) (ft msl) (cmsec) (ogt) MW-203D 43227 4 277279 24 32 28 4043 667E-05 44

3 408415420 39 49 44 3883 593E-05 170 2 526 530 49 57 53 3793 101E-04 140 I 828830842 80 88 84 3483 701E-05 130

MW-204D 43262 5 295 300 26 34 30 4023 902E-05 220 4 463496513516 45 53 49 3833 119E-04 540 3 681685688 63 71 67 3653 OOOE+00 2 758 76 2 71 79 75 3573 309E-05 260 I 88 96 92 3403 OOOE+00

MW-205 42389 3 164 166 168 15 20 175 4148 OOOE+00 1000B 2 302305312 30 35 325 3998 107E-04 1300B 1 40 45 425 3898 OOOE+00

MW-206D 43007 5 17 72 195 4128 291E-05 4 296 302 307 29 34 315 4008 940E-05 2900B 3 522 52 57 545 3778 944E-07 2 656 64 69 665 3658 353E-06 1 92392793 4939 91 96 935 3388 614E-05 6300B

PW-207 43477 5 184622162819 18 29 235 4088 209E-05 1300 4 3508 32 43 375 3948 568E-06 5400 3 53325341542154325559 50 61 555 3768 821E-05 18000

6359 61 72 665 3658 866E-06 12000 1 8685 84 89 865 3458 213E-05 19000

NOTES cmsec = centimeters per second ft bgs = feet below ground surface ft msl = feet above mean sea level B = detected in lab blank

Table XX Orientation Permeability and Groundwater Sampling Results for Transmissive Features

2004 Drilling Program

Hows Corner Superfund Site Plymouth Maine

Borehole Geophisical Feature depth Dip True Dip True Transmissive Log Feature (Feet) Degrees Azimuth Strike bullvgt(Ltk|iy^

Number v Tosftble) v MW-203 5 277 64 337 67 Likely

6 279 59 11 281 Likely 8 352 14 177 87 Likely 11 381 46 96 6 Possible 12 408 35 271 1 Possible 14 415 57 250 340 Possible 15 420 58 202 292 Likely 18 526 52 75 345 Likely 19 530 52 82 352 Likely 28 828 48 75 345 Likely 29 830 52 17 287 Likely 30 830 56 233 323 Possible 31 842 50 130 40 Likely

MW-204 4 295 15 147 57 Likely 5 300 43 91 1 Likely 11 439 31 80 350 Possible 12 440 46 219 309 Possible 14 463 50 358 88 Likely 15 496 34 198 288 Likely 16 513 54 17 287 Likely 17 516 33 14 284 Likely 25 681 39 359 89 Possible 26 685 22 45 315 Possible 27 688 35 73 343 Possible 32 758 45 236 326 Likely 33 762 46 306 36 Likely

MW-205 5 164 69 106 16 Possible 6 166 78 165 75 Possible 7 168 82 115 25 Possible 8 168 68 116 26 Possible 12 215 46 222 312 Possible 13 217 75 62 332 Possible 14 219 29 32 302 Possible 16 237 69 250 340 Possible 17 256 73 353 83 Possible 18 272 44 202 292 Possible 21 299 37 196 286 Possible 22 302 31 206 296 Possible 23 305 59 48 318 Likely 24 312 63 42 312 Likely

MW-206 1 264 37 181 271 Likely 2 296 69 217 307 Likely 3 302 66 233 323 Likely 4 307 64 224 314 Likely 8 342 62 259 349 Likely

jjHydraulic GoiDanctilyity j(cmsecjw

667 E-05

593 E-05

101 P04

710 E-05

902 E-05

119 E-04

0

309 E-05

0

107 E-04

94 E-05

PCE (ugL)

44

170

140

130

220

540

260

IOOOB

1100B

1300B

2900B

STotal vVoCsv tig1)

84

234

192

183

2636

6436

3073

11448

12509

13776

32401

PCEyo dfCTotaf

52

73

73

7 1

83

84

85

87

88

94

90

Table XX Orientation Permeability and Groundwater Sampling Results for Transmissive Features

2004 Drilling Program

Hows Corner Superfund Site Plymouth Maine

Borehole Geophisical Feature deptt raquoip True pip True Transraissive Log Feature (Feet) shy Degrees Azimuth Strike (tikely

Number raquo Possible) 22 522 57 54 324 Possible 25 656 40 82 352 Possible 32 871 59 151 61 Possible 33 883 53 185 275 Possible 34 895 7 175 85 Likely 35 899 53 90 0 Likely 36 902 49 184 274 Likely 37 923 9 175 85 Likely 38 927 42 206 296 Likely 39 934 48 167 77 Likely 40 939 26 180 90 Likely

PW-207 1 1846 33 167 77 Likely 4 2216 49 289 19 Possible 7 2819 59 265 355 Possible 11 3508 55 189 279 Possible 18 5332 43 305 35 Likely 19 5341 51 30 300 Likely 20 5421 20 254 344 Likely 21 5432 39 301 31 Likely 23 5559 52 302 32 Likely 25 6359 24 182 272 Possible 29 8049 77 231 321 Possible 30 8685 78 38 308 Likely 32 9334 29 194 284 Likely

NOTES

B = detected in lab blank

Hydraulic Conductivity

(cmsee) 944 E-07 353 E-06

614 E-05

209 E-05

568 E-06

821 E-05

866 E-06

213 E-05

bulltCE (ugL)

6300B

1300

5400

18000

12000

19000

Total VOCs (ug1)

68901

1410

5802

19234

13085

20354

PCE of Total VOCs

9 1

92

93

94

92

93

Response to EPA-DEP Comment 3 Dated March 312005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

lit

EPA-DEP Comment 3

Comment 3 The reported f values and resultant Kd values There remains doubt that the values used in the flushing model accurately reflect the propensity for PCE to sorb to the bedrock The ^ values presented in Appendix B may be unrealistically high because the bedrock samples may have contained organic carbon that was unavailable for sorption The reported f values are only qualitative estimates of the organic carbon content of the bedrock samples The Walkley and Black organic carbon measurement method is quick and simple but the results obtained cannot be considered quantitative because it requires a correction factor which often results in erroneous values it assumes the organic carbon has an average valence of zero oxidizable and reducible constituents such as chloride ferrous iron and manganese oxides interfere with the results and the errors introduced by interference are potentially greater when the organic carbon content is low at low f values it is not clear that organic carbon is controlling PCE sorption (Schwarzenbach and Westall 1981 Mackay et al 1986 Fetter 1999)

In order to derive a Kd-based retardation factor that is reasonable given the reported f values and the rapid advance of the PCE plume described on pages 4-11 and 4-12 the flushing model requires a bulk density to porosity ratio that is roughly two orders of magnitude higher than the actual ratio for the Hows Corner bedrock (page 4-4) This apparent discrepancy needs to be addressed

Response This comment raises several concerns about the collection and analysis of samples for fraction of organic carbon (f^) the quality of the resulting data and the implications of the use of those data for estimation of the retardation of groundwater contaminant movement Results of bedrock analysis for f were proposed in the TI Evaluation Work Plan for use in conjunction with groundwater contaminant concentrations and aquifer information to estimate cleanup times using the Batch Flushing model It is important to use accurate f values from representative bedrock in the Batch Flushing model in order to obtain reasonable estimates of the remedial time frame Because of the importance of accurate and representative results the TI Investigation field program was designed and conducted both to collect samples representative of the rock volume most likely to be in contact with contaminated groundwater and to analyze them using an appropriate refereed analytical method Five potential methods for evaluating f were identified Of the five methods the Walkey-Black method was selected because it has minimal method interferences and a sufficiently low detection limit as well as a long history of use in agronomy and contamination studies The PRP Group is pleased with the quality of the data obtained from the bedrock samples as represented by their precision and reproducibility

The first part of this comment relates to the determination of fraction of organic carbon (f^) values The several subparts of the first paragraph are addressed individually in items 1 through 5 below The second part of the comment regarding the resultant distribution coefficient (Kd) values is addressed separately as item 6 below

1 There remains doubt that the values used in the flushing model accurately reflect the propensity for PCE to sorb to the bedrock

bull The rock core samples used for f (gocg) analysis were from core immediately adjacent to fractures These rock core samples included the fracture surfaces themselves and rock core extending back less than 1 cm from the fractures Therefore the foe data reported in the TI Evaluation represents the f of bedrock through which groundwater will travel and to which PCE will adsorb Based on the careful selection of sample locations and the

Response to EPA Comment 3 050205doc 1 of 11 Woodard amp Curran (211941)

number of samples collected we are confident that the measured f values are representative of the f at points of contact for PCE with the bedrock it is these f values that determine the propensity of PCE to sorb to the bedrock

bull The samples of rock core collected for analysis of f originated from 19 different locations varying in depth from 11 to 90 feet Therefore it is very unlikely that the rock core samples were contaminated with extraneous organic carbon from above ground

2 The foc values presented in Appendix B may be unrealistically high because the bedrock samples may have contained organic carbon that was unavailable for sorption

bull As noted in response 1 the f data reported in Appendix B represents organic carbon primarily associated with the surface of fractures in the bedrock through which groundwater is most likely to travel Therefore it is this organic carbon that the contaminants in the groundwater will come in contact with and adsorb to in the fractured rock at the site

bull The chemical oxidation agents used in the Walkey-Black method oxidize the easily oxidizable organic carbon in the medium and the foe is calculated from the quantity of the agent consumed Therefore it is unlikely that the analysis of the bedrock samples measured organic carbon that was unavailable for sorption

3 The reported foc values are only qualitative estimates of the organic carbon content of the bedrock samples

bull The reported f values are accurate quantitative results Schumachers review of Methods for the determination of total organic carbon (TOC) in soils and sediments (NCEA-C-1282 EMASC-001 April 2002) identifies the Walkley-Black method which was used to analyze the reported foc values as the reference method for comparison to other methods for analyzing total organic carbon

bull Schumacher also points out that if anything the WalkJey-Black method may underestimate the total organic carbon in a sample due to possible incomplete oxidation of organic carbon Usually the incomplete oxidation of total organic carbon in environmental samples is corrected for by multiplying the measured foe by 130 (Walkley amp Black 1934 Schulte 1995)

bull When the f data in the TI Evaluation Report (WampC 2005) Appendix B (attached) are analyzed statistically the standard deviation of the f for the 19 samples analyzed is 174 of the average f Given this standard deviation the 95 confidence interval for this data ranged from a low of 000123 gocg to a high of 000253 gocgm

The labs Method of Detection Limit (MDL) for the f measured using the Walkley-Black method is 00001 gocg Therefore the average (000188 gocg) the mean (000185 gocg) and geometric mean (000187 gocg) of the f values for the rock core at Hows Corner are all statistically significantly greater than the MDL of the Walkley-Black method

In addition to the aforementioned statistical analysis of the foe data triplicate samples (n = 3) from the same rock core (including one sample from the 19 rock core samples) were

Response to EPA Comment 3 050205doc 2 of Woodard amp Curran (211941)

analyzed for their f to determine the repeatability of the Walkley-Black method The average the mean and the geometric mean of the f values of these replicate samples was 000162 gocg 000150 gocg and 000159 gocgm respectively The standard deviation of these measurements was 000039 gocg

4 The Walkley and Black organic carbon measurement method is quick and simple but the results obtained cannot be considered quantitative because it requires a correction factor which often results in erroneous values it assumes the organic carbon has an average valence of zero oxidizable and reducible constituents such as chloride ferrous iron and manganese oxides interfere with the results and the errors introduced by interference are potentially greater when the organic carbon content is low at low foc values it is not clear that organic carbon is controlling PCE sorption (Schwarzenbach and Westall 1981 Mackay et al 1986 Fetter 1999)

bull Schumachers review (NCEA-C-1282 EMASC-001 April 2002) of the Walkley-Black method identifies several potential problems with this analytical method that could occur if the analytical lab is not familiar with the nuances of the chemistry associated with this method Interestingly Schumachers review neglected one of the more important analytical steps required to avoid errors in quantifying f in samples where there might beNAPL

It is absolutely critical to eliminate any NAPL from rock core samples prior to using the Walkley-Black method to measure foe in such samples This was done by the lab (PTS Laboratories) that measured the foe in the rock core samples from Hows Corner The lab used the Dean-Stark method (solvent extraction) to remove all hydrocarbons (including PCE and other NAPLs) from the sample (PTS Laboratories) This extraction method does not interfere with the subsequent analysis of the natural organic carbon associated with the rock core

Subsequently the samples were dried at 150degC to a constant weight (normally 16 hours) This latter step oxidizes all inorganic minerals including ferrous bearing minerals to ferric oxides and precludes their interference during the oxidation of the samples with chromic acid This procedure completely eliminates any positive bias in the reported foc

data that might have occurred due to the presence of ferrous ions and other reduced minerals

bull As noted in Response 3 the incomplete oxidation of total organic carbon results in an underestimate of the f and is corrected for by multiplying the f by a correction factor of 130 (Walkley amp Black 1934 Schulte 1995) The fx data reported in the TI Evaluation was corrected accordingly by using this correction factor

bull Excess chloride (Cl~) in percent weight quantities as found in saline soils may interfere with the quantitative titration of reduced chromium (Walkley 1947) However given that the primary rock type at the Hows Corner site is phyllite it is highly unlikely that there was sufficient chloride in the rock core samples for this to occur

bull Manganese oxides may also interfere with the analysis of f through competing with the dichromate ion for any oxidizable carbon (Walkley 1947) However in such cases the reported f would be an underestimate of the f present in the rock core Walkley (1947)

Response to EPA Comment 3 050205doc 3 of 11 Woodard amp Curran (211941)

4

reported that in the case where the ratio of MnO2 to carbon is 85 to 1 the error in the carbon determinations would only be 0 to 6 percent

It may also be useful to compare the analysis of total organic carbon in a geologic matrix that contains high levels of manganese using EPA method 9060 to the Walkley-Black method Table 1 summarizes data provided by one of the PRPs that compares the analysis of total organic carbon in a geologic matrix that contains approximately 02 wgt manganese (approximately 03 wgt manganese oxide)

Table 1 Comparison of total organic carbon measured using the EPA- 9060 method and the Walkley-Black method

Laboratory EPA-9060 Method Walkley-Black Method A Ave 00226 gocg Not analyzed

Stdev 000251 gocg n = 5

B Ave 002219 gocg Ave 002050 gocg Stdev = 000316 gocg Stdev =000971 gocg

n= 10 n = 10

The similarity in the total organic carbon concentrations measured by these two different methods provides further confidence that the Walkley-Black method is a viable method for analysis of total organic carbon in the presence of manganese equivalent to at least 10 by weight of the total organic carbon

5 The Walkley and Black organic carbon measurement at lowf^ values it is not clear that organic carbon is controlling PCE sorption (Schwarzenbach and Westall 1981 Mackay et al 1986 Fetter 1999)

bull Schwarzenbach and Westalls (1981) paper states that f values of less than 0001 gocg should not be used in combination with Kow (octanol-water partition coefficients) values to calculate K^ values (solid phase partition coefficients) values for a specific contaminant It should be noted that the TI Evaluation did not use the f data to calculate the KQC from the Kow Instead as requested by the EPA the measured KOC value for PCE was used to calculate the retardation factor for this contaminant

bull Schwarzenbach et al (2003) stated more recently that Even at very low f values (ie foe = 0001 kgoc - kg1 solid) sorption to the organic components of a natural sorbent may still be the dominant mechanism in defining the adsorption of organic compounds to geological matrices

bull In 1985 M Piwoni from the US EPA Robert S Kerr Environmental Research Laboratory published a paper (Banerjee et al 1985) that showed that for very hydrophobic molecules TOC content of the sorbent will control sorption down to levels of organic carbon that defy quantitation Contaminants such as the PCE found in the groundwater at Hows Corner are in this category of compounds

Given the aforementioned reasons the f values reported in the TI Evaluation are accurate within the noted statistical limitations and will have a predictable impact upon the retardation of PCE during groundwater transport

Response to EPA Comment 3 050205doc 4 of 11 Woodard amp Curran (211941)

6 In order to derive a Kd-based retardation factor that is reasonable given the reported foc

values and the rapid advance of the PCE plume described on pages 4-11 and 4-12 the flushing model requires a bulk density to porosity ratio that is roughly two orders of magnitude higher than the actual ratio for the Hows Comer bedrock (page 4-4) This apparent discrepancy needs to be addressed

The apparent discrepancy of bulk density to porosity ratios is most likely due to the fact that the Batch Flushing Model was originally developed for a porous medium and is not directly applicable to fractured bedrock As stated in Appendix C (page C-4) of the Draft Technical Impracticability Evaluation Report in order to use the Batch Flushing Model to describe the transport of contaminated groundwater in fractured bedrock where the matrix porosity is insignificant it is more appropriate to use a fracture surface area to void space ratio to calculate the retardation factor (R) than a bulk density to porosity ratio (Freeze amp Cherry 1979)

Since it is impractical to determine the actual surface area to which contaminants can adsorb the Batch Flushing Model was used with two simplifying assumptions bull The Kd was calculated from the f and the K^ bull The bulk density to porosity ratio term in the Batch Flushing Model was constrained to range

from 4 to 10 the typical range of such ratios in porous media (Freeze amp Cherry 1979)

If one uses site specific bedrock bulk density and porosity values the bulk density to porosity ratio is several orders of magnitude greater (specifically 273 gcc bullbull 000165 (dimensionless) = 1654 gcc) than the range of ratios of 4 to 10 used in the Batch Flushing Model in the Draft Technical Impracticability Evaluation Report Constraining the bulk density to porosity ratio within the range of ratios of 4 to 10 results in significantly lower R value than would be obtained using specific bedrock bulk density and porosity values

In summary in bedrock where fractures are the primary porosity the bulk density to porosity ratio can vary considerably and will be a function of the number of fractures and the fracture aperture The calculated bulk density to porosity ratio will be inversely proportional to the porosity This means that in fractured rock with limited fracturing and smaller porosity the calculated bulk density to porosity ratio is greater and will result in a greater calculated retardation factor than in bedrock with more extensive fracturing and greater porosity Consequently the calculated retardation factor will be greater for bedrock with less surface area available for sorption than bedrock with greater surface area for sorption This is contrary to what actually occurs

4 Response to EPA Comment 3 050205doc 5 of 11 Woodard amp Curran (211941)

m

REFERENCES

Banerjee P MD Piwoni K Ebeid (1985) Sorption of organic contaminants to a low carbon subsurface core Chemosphere _14 1057-1067

Freeze RA JA Cherry (1979) Groundwater Prentice Hall Englewood Cliffs NJ pg 604

PTS Laboratories wwwptsgeolabscompdf files3TOCnotepdf

Schulte EE (1995) Recommended soil organic matter tests in Recommended Soil Testing Procedures for the Northeastern United States Northeastern Regional Publication No 493 Chapter 8

Schwarzenbach RP J Westall (1981) Transport of nonpolar organic compounds from surface water to groundwater Laboratory sorption studies Environ Sci Tech 15 1360-1367

Schwarzenbach RP PM Gschwend DM Imboden (2003) Environmental Organic Chemistry Wiley-Interscience pg 292 408 amp 412

Walkley A LA Black (1934) An examination of the Degtjareff method for determining soil organic matter and a proposed modification of the chromic acid titration method Soil Science 37 29-38

Walkley A (1947) A critical examination of a rapid method for determining organic carbon in soils - effect of variations in digestion conditions and of inorganic soil constituents Soil Science 63251-264

Woodard amp Curran Inc (WampC) 2005 Draft Technical Impracticability Evaluation Hows Corner Superfund Site Plymouth Maine January 2005

Response to EPA Comment 3 050205doc 6 of Woodard amp Curran (211941)

LIST OF ATTACHMENTS (Response to Comment 3)

Appendix B to Draft Technical Impracticability Evaluation Measurement of foe at Hows Corner (4 pages)

m

Response to EPA Comment 3 050205doc 7 of 11 Woodard amp Curran (211941)

Appendix B Measurement of foe of Rock Core at Hows Corner

There are two general approaches to measure the fraction of organic carbon (foe) in rock cores

bull Measurement of weight loss by ignition of organic matter bull Chemical oxidization of organic carbon to carbon dioxide and either

subsequent quantification of the oxidant used for the reaction or quantification of the carbon dioxide produced during this oxidation process

The weight loss method is subject to errors caused by volatilization of substances other than organic materials such as water hydroxides and mineral carbonates Quantification of foe by the weight loss method is particularly sensitive to the presence of carbonates in rock cores There are however weight loss methods that are designed to differentiate between organic carbon and the aforementioned interfering materials but they require considerable care and are less accurate at low foe values Hence the weight loss method was not well suited for measuring the foe of the rock core from Hows Corner

The chemical oxidation of organic carbon is much better suited for quantifying organic carbon in rock cores such as those from Hows Corner This method uses a strong chemical oxidant to oxidize organic carbon to carbon dioxide and then measures either the chemical oxidant used to oxidize the organic carbon or the quantity of carbon dioxide produced In addition this general approach is not subject to interference by volatilization of other constituents of the rock core

There are at least two such chemical oxidation methods

bull The method of Baccini which was described by Schwarzenbach amp Westall (1981) first acidifies the sample to eliminate interference by carbonates Then a strong oxidant is used to chemically oxidize the organic carbon to carbon dioxide The resulting carbon dioxide is subsequently reduced to methane and quantified using a flame ionization detector Unfortunately this method has not been described in detail in a referred journal Hence it is would not have been appropriate to use to characterize the foe in the Hows Corner rock core

bull The more commonly used method to quantify foe in rock core is the Walkley-Black method (1934) This method is preferred for RBCA and DODDOE projects and by the oil industry

The Walkley-Black method uses an excess of chromic acid to oxidize (digest) organic matter to carbon dioxide The remaining chromic acid that was not consumed during the oxidation of the organic carbon is then quantified by titration with ferrous sulfate The difference in chromic acid prior to and after the oxidation of the organic carbon represents the total chromic acid used to oxidize

Hows Corner TI Evaluation Page 1 January 13 2005 Appendix B

the organic carbon in the sample The latter can be calculated using the chemical stoichiometry of the reaction

The Walkley-Black method is very accurate for samples that contain less than 2 organic carbon matter The minimum detection limit (MDL) for the Walkley-Black method is 100 mgkg or an foe of 0001

Given the rock core at Hows Corner was expected to contain less than 2 organic carbon the Walkley-Black method was used to measure the foe from 19 different rock core samples collected from varying depths ranging from 11 to 90 feet

Table 1 provides a statistical summary of the aforementioned data

Table 1 Statistical summary of foe data from rock cores collected at varying depths

Statistical Parameter Calculated Value foe Minimum Detection Limit (MDL) 00010 Number of samples analyzed (n) 19 Average foe 00019 Median foe 00019 Geometric Mean foe 00019 Standard deviation of foe measurements 000033 Relative standard deviation 174 -+ 95 Confidence intervals 00012 to 00025

The data in Table 1 shows the following

bull The foe from the Hows Corner rock cores are statistically greater than the MDL of the Walkley-Black analytical method

bull The average and median values for the foe of the Hows Corner rock cores from varying depths are nearly identical indicating that there is little variability in the foe values in the source zone at the site

bull The standard deviation of these measurements is 000033 which is 174 of the average foe

bull The 95 confidence intervals of the foe of the rock core at Hows Corner are 00012 to 00025

The foe was also analyzed from three separate samples taken from the same rock core at a depth of 55 feet (Only one of these samples was included in the data summarized in Table 1) Table 2 shows the statistical repeatability of this type of analysis

Hows Corner TI Evaluation Page 2 January 13 2005 Appendix B

Table 2 Repeatability of analysis of foe from one rock core at 55 feet in depth

Statistical Parameter Calculated Value Number of samples analyzed (n) 3 Average foe 00016 Median foe 00015 Geometric Mean foe 00016 Standard deviation of foe measurements 000039 Relative standard deviation 240 -+ 95 Confidence intervals 00008 to 00024

The data in Table 2 shows the following

bull The percent relative standard deviation of these three analyses of foe from the same rock core at Hows Corner is 24

bull The 95 confidence interval of the foes measured in this particular rock core at Hows Conrer is 00008 to 00024

These results show that there is good repeatability in using the Walkley-Black method for analysis of the foe in the rock core at Hows Corner

References Schwarzenbach amp Westall (1981) Transport of nonpolar organic compounds from surface water to groundwater Laboratory sorption studies Environ Sci Tech 15 1360-1367

Walkley A I A Black (1934) An examination of Degtjareff method for determining soil organic matter and a proposed modification of the chromic acid titration method Soil Sci 37 29-37

Hows Corner Tl Evaluation Page S January 13 2005 Appendix B

Woodard and Curran PTS Laboratories PTS File No 34618

ORGANIC CARBON DATA (METHODOLOGY WALKLEY-BLACK)

PROJECT NAME PROJECT NO

SAMPLE ID

203-chip-13 203-chip-23 203-chip-27 203-chip-38 203-chip-42 203-chip-47 203-chip-52 203-chip-58 203-chip-69 203-chip-82 207-chip-11 207-chip-19 207-chip-24 207-chip-29 207-chip-35 207-chip-45 207-chip-55 207-chip-87 207-chip-90

207-chip-55 55-MS

55-MSMSD

Hows Corner NA

DEPTH ft

13 23 27 38 42 47 52 58 69 82 11 19 24 29 35 45 55 87 90

55 NA NA

MATRIX

Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip

Average Median

Geometric Mean Standard Deviation Relative Std Dev

+- 95 Confidence Interval n

Rock Chip Rock Chip Rock Chip

Average Median

Geometric Mean Standard Deviation Relative Std Dev

+- 95 Confidence Interval n

FRACTION ORGANIC CARBON

(gg)

170E-03 185E-03 185E-03 170E-03 240E-03 190E-03 230E-03 180E-03 170E-03 115E-03 195E-03 220E-03 220E-03 235E-03 135E-03 190E-03 205E-03 175E-03 160E-03

188E-03 185E-03 185E-03 327E-04

1739 123E-03 to

19

205E-03 130E-03 150E-03

162E-03 150E-03 159E-03 388E-04

2402 840E-04 to

3

2532E-03

2393E-03

Hows Corner Tl Evaluation Appendix B January 13 2005

Response to EPA-DEP Comment 4 Dated March 31 2005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

EPA-DEP Comment 4

Comment 4 Distribution of contaminants First the TI report seems based on the assertion that there is DNAPL at the source area yet it also appears to represent that the source area is small and the bedrock below 85 is competent (or less fractured) and less impacted by the release of contaminants Some of the confusion may result from using most recent data when that data is from several different sampling events over several years and there is no discernible difference in concentrations between shallow and deep bedrock or as in Section 421 where generally decreased generally increase generally similar and similar concentrations in four consecutive sentences leads to a muddled picture of the contaminant distribution

Second the report asserts that the distribution of contaminants over the entire plume has not changed with time but fails to support this conclusion with data again relying on data that is from different sampling dates for one composite representation

Response The likely presence of dense non-aqueous phase liquid (DNAPL) at the Hows Corner Site and the determination that the source area is small are not mutually exclusive and both are conclusions drawn from information obtained during field investigations The presence of DNAPL in the source area is based on the elevated concentrations of volatile organic compounds (VOCs) detected in the groundwater (WampC 2001 WampC 2002) The conclusion that the source area is small is based on the area in which VOCs in groundwater have been detected at concentrations that are considered to be indicative of the presence of DNAPL nearby Similarly the conclusion that fracture frequency decreases at depths greater than approximately 50 to 85 feet below ground surface was based on field observation during the RI field work The fact that zones with observed fractures exhibited higher hydraulic conductivities than zones without fractures coupled with the decreasing frequency of observed fractures with depth led to the conclusion that the hydraulic conductivity of the bulk rock decreases with depth

The most recent data from all wells were used to provide the maximum VOC data set size During the RI all of the previously-existing and then newly-installed monitoring wells were sampled along with several residential wells The RI sampling included up to 48 monitoring wells Subsequent to the RI and prior to the TI three rounds of monitoring were conducted to verify that the plume was stable 15 monitoring wells were sampled during each of the three rounds During the TI field investigation 29 wells were sampled for VOCs The sampled wells included all of the newly-installed wells and a subset of wells installed during the RI for a total of 29 monitoring wells By using most recent data VOC results from 53 monitoring wells were included in the evaluation (see table labeled Sampling Events for listing of monitoring wells) This approach was selected because there generally was little variation in the data from a particular location between years This is borne out by the attached individual plots of VOCs detected in shallow bedrock and deep bedrock for the Pre-ROD (December 1999January 2000) and Supplemental (May 2000) sampling events and for June 2001 January 2002 and April 2003 sampling events The Pre-ROD and Supplemental plots are similar to the subsequent plots from the 2001 2002 and 2003 sampling events

In addition to maps showing the spatial distribution of VOC data at a given time trend plots of the data from a particular location through time (attached) indicate that since the RI concentrations generally have been stable or have decreased Together the maps and trend plots and the data from which they were developed indicate that the distribution of contaminants over the entire plume has not changed appreciably with time

Response to EPA Comment 4 050305doc 1 of 26 Woodard amp Curran (211941)

REFERENCES

Woodard amp Curran Inc (WampC) 2001 Final Remedial Investigation Report Hows Corner Superfund Plymouth Maine July 2001

Woodard amp Curran Inc (WampC) 2002 Final Feasibility Study Report - Non-Source Area Groundwater Hows Corner Superfund Site Plymouth Maine Hows Corner Superfund Plymouth Maine July 2002

Response to EPA Comment 4 050305doc 2 of 26 Woodard amp Curran (211941)

LIST OF ATTACHMENTS (Response to Comment 4)

Table - Sampling Events 1999 - 2004 (2 pages)

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater Pre-ROD Sampling Event

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater Pre-ROD Sampling Event

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater Supplemental Sampling Event

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater Supplemental Sampling Event

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater June 2001

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater June 2001

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater January 2002

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater January 2002

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater April 2003

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater April 2003

Figure - Concentration Trends - Non-Source Area Wells MW-1B and MW-3B

Figure - Concentration Trends - Non-Source Area Wells MW-13DB and MW-16DB

Figure - Concentration Trends - Non-Source Area Wells MW-16IB and MW- 108D

Figure - Concentration Trends - Non-Source Area Wells MW-108S and MW-112D

Figure - Concentration Trends - Non-Source Area Wells MW-112S and MW-114D

Figure - Concentration Trends - Non-Source Area Wells MW-114S and MW-115D

Figure - Concentration Trends -Source Area Wells MW-2DB and MW-2IB

Figure - Concentration Trends -Source Area Wells MW-102S and MW-103D

Figure - Concentration Trends -Source Area Wells MW-103S and MW-104D

Figure - Concentration Trends -Source Area Wells MW-104I and MW-106D

Figure - Concentration Trends -Source Area Wells MW-106S

Response to EPA Comment 4 050305doc 3 of 26 Woodard amp Curran (211941)

I I

El I

II I I 1 I

I

i

Event Baseline Case ID WC-01 WC-01

Well Date Aug-99 Oct-99 LOT10 1 LOT1-1 1 LOT11-4 LOT14 1 LOT15 1 LOT15-1 1 LOT16 1 LOT16-1 1 LOT17 1 LOT18 1 LOT19 1 LOT2 LOT20 1 LOT21-10 1 LOT21-11 1 LOT21-12 1 LOT21-13 1 LOT21-14 1 LOT21-2 1 LOT21-5 1 LOT21-7 LOT21 -8 1 LOT21-9 1 LOT23 1 LOT24 1 LOT28-1 1 LOT28-2 1 LOT28-3 1 LOT28-4 1 LOT28W 1 LOT30 1 LOT30-1 1 LOT30-2 1 LOT30-3 1 LOT30-4 1 LOT30-5 LOT31 LOT35 1 LOT41 1 LOT42-1 1 LOT43-1 1 LOT43-4 1 LOT6-1 1 LOT67 1 LOT6-7 1 LOT6-8A 1 LOT6-8B 1 LOT80-1 1 LOT82 1 MW-101D MW-1011 MW-101S MW-102D MW-102S MW-103D MW-103S MW-104D MW-1041 MW-104S MW-105D MW-106D

Groundwater Sampling Location Summary 1999 - 2004xls

Sampling Events 1999-2004

Hows Corner Superfund Site Plymouth Maine

Supplemental 2001 2002 2003 Pumping 2004 Pre-ROD Rl Sampling Sampling Sampling Test Sampling WC-03 WC-09 WC-25 WC-30 WC-42B WC-56 WC-58 Dec-99 May-00 Jun-01 Jan-02 Apr-03 Sep-04 Sep-04

1

1 1 1

1 1 1 1 1

1 1

1

1 1

1 1 1

1 1 1 1 1

1

1 1

1 1 1 1

1

1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

Sampling Events 1999-2004

Hows Corner Super-fund Site Plymouth Maine

Supplemental 2001 2002 2003 Pumping Event Baseline Pre-ROD Rl Sampling Sampling Sampling Test

Case ID WC-01 WC-01 WC-03 WC-09 WC-25 WC-30 WC-42B WC-56

ll

Well Date Aug-99 Oct-99 Dec-99 May-00 Jun-01 Jan-02 Apr-03 Sep-04 MW-106S 1 1 1 1 1 MW-107D 1 1 MW-108D 1 1 1 1 1 MW-108S 1 1 1 1 1 MW-110D 1 1 MW-111D 1 1 MW-112D 1 1 1 1 1 MW-112S 1 1 1 1 1 MW-113D 1 1 MW-114D 1 1 1 1 1 MW-114S 1 1 1 1 1 MW-115D 1 1 1 1 1 MW-12DB 1 1 1 MW-12SB 1 1 1 MW-13DB 1 1 1 1 1 1 MW-13SB 1 1 1 MW-14DB 1 1 MW-14SO 1 1 MW-15DB 1 1 1 MW-15SB 1 1 1 MW-16DB 1 1 1 1 1 1 MW-16IB 1 1 1 1 1 1 MW-16SO 1 1 MW-17DO 1 1 1 MW-17SO 1 1 1 MW-1B 1 1 1 1 1 1 MW-203D MW-203S MW-204D MW-204S MW-205 MW-206D

I MW-206S MW-2DB 1 1 MW-2DDB 1 1 MW-2IB 1 1 1 1 1 1 MW-3B 1 1 1 1 1 1

I MW-4O 1 1 1 MW-5B 1 1

II MW-6DB 1 1 1 MW-6SB 1 1 1 MW-8DB 1 1 1 MW-8SB 1 1 1

II PW-207 1 SEEP-1 1 SUBTOTAL - RESIDENTIAL 44 25 0 2 0 3 0 SUBTOTAL - MONITORING 22 48 41 15 15 15 1

Total 3 66 73 41 17 15 18 1

I Included in most recent data

I Notes 1 - Overburden well not included in most recent data for plotting

2 - Tetrahydrofuran and 2-Butanone were the only two compounds detected in this well and are thought to be the result of well repair not included in most recent data for plotting

3 - Not included in most recent data for plotting

2004 Sampling

WC-58 Sep-04

1

1 1

1 1

1 1 1

1

1 1

1 1 1 1 1 1 1 1 1

1 1

1

0 29

29

Groundwatef Sampling Location Summary 1999 - 2004xls

I

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

monitoring well Figure 4-14 total VOC contour (ugl) - December 1999January 2000 Distribution of Total VOCs in

Note SW-113 is located downstream of SEEP-1 Shallow Bedrock Groundwater total concentration of detected VOCs ND= not detected these two locations were sampled during the Pre-ROD Sampling Event

Baseline Sampling Event in OctoberNovember 1999 Hows Corner Superfund Site Surface Water Sampling Location A Plymouth Maine Seep Sampling Location laquo- WOODARD ampCURRAN

995037wipri reportepa ri interim final feb 2001cadd drawingsfinalfig 4-14

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

0 300 600 I

FEET

Q residential well Figure 4-16 monitoring well Distribution of Total VOCs in

Deep Bedrock Groundwater total VOCs contour (ugl) Pre-ROD Sampling Event

active residential wells with lot number Hows Corner Superfund Site 2deg42deg Plymouth Maine total concentration of detected VOCs ND= not detected WOODARD ampCURRAN Enyinaaring bull Science bull Operations bull

995037wipri reportepa ri interim final feb 2001cadd drawingsfinalfig4mdash16

PLYMOUTH POND

PLYMOUTH POND

1 628Tl7MW-2bB 12135

PLYMOUTH POND

monitoring well Figure 4-20

V total VOC contour (ugl) - June 2000 Distribution of Total VOCs in Shallow Bedrock Groundwater

| 34 | total concentration of detected VOCs ND= not detected NA = not analyzed Supplemental Sampling Event Note SW-113 is located downstream of SEEP-1 Hows Corner Superfund Site

Surface Water Sampling Location these two locations were sampled during the Plymouth Maine Baseline Sampling Event in OctoberNovember 1999 Seep Sampling Location WOODARD amp CURRAN

Engineering bull Science - Operations bull 995037wipri reportepa ri interim final feb 2001 cadd drawingsfinalfig 4-20

residential well Figure 4-22 Distribution of Total VOCs in

monitoring well Deep Bedrock Groundwater

total VOCs contour (ugl) Supplemental Sampling Event

Hows Corner Superfund Site

total concentration of detected VOCs ND= not detected NA = not analyzed Plymouth Maine

WOODARD amp CURRAN

995037wipri reportepa-ri interim final feb 2001cadd drawingsfinalfig 4-22 Engineering bull Science - Operations bull

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

FEET

Shallow Monitoring Well

Deep Monitoring Well

C Detected Concentration ND = Not Detected Figure 1-XS Distribution of Total VOCs in Shallow Bedrock Groundwater

Pumping Well

17-Acre Property Boundary Concentration Contour (ugl)

June 2001 Hows Corner Superfund Site

Plymouth Maine WOODARDampCURRAN

-i^rhvj bull Scbncn bull Operations bull 211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0601 dwg04-20-05

PLYMOUTH POND Hopkins Road V

O

PLYMOUTH POND

PLYMOUTH POND

o

0 300 600 mdashfa FEET

Shallow Monitoring Well bull bull - 17-Acre Property Boundary Figure 1-XD

Deep Monitoring Well 1 I Detected Concentration ND = Not Detected Distribution of Total VOCs in Deep Bedrock Groundwater

-mf- Pumping Well June 2001 Residential Well Hows Corner Superfund Site

Plymouth Maine i h Surface Water Sampling Point

g WOODARD ampCURRAN _ ^ _ ^ _ _ yen_ rj i|Hlaquorlny bull Science bull Opt

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0601 dwg04-20-05

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PLYMOUTH POND

PLYMOUTH POND

Shallow Monitoring Well

Deep Monitoring Well

Detected Concentration ND = Not Detected Figure 1-YS Distribution of Total VOCs in Shallow Bedrock Groundwater

Pumping Well

17-Acre Property Boundary Concentration Contour (ugl)

January 2002 Hows Corner Superfund Site

Plymouth Maine WOODARD amp CURRAN Engineering Science- Operations bull

211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0102dwg04-20-05

PLYMOUTH POND

PLYMOUTH POND

Site Pand^ laquoum-laquoBTuitaraquo tLV

vVlf-(

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Shallow Monitoring Well mdashbullbullbull 17-Acre Property Boundary Figure 1-YD - A - Deep Monitoring Well FT Detected Concentration ND = Not Detected Distribution of Total VOCs in

Deep Bedrock Groundwater Pumping Well January 2002 Residential Well Hows Corner Superfund Site

Plymouth Maine Surface Water Sampling Point

WOODARD ampCURRAN Engineering Sciencs- Operations bulli Si

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0102dwg04-20-05

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PLYMOUTH POND

PLYMOUTH POND j A O-shy

Shallow Monitoring Well E Detected Concentration ND = Not Detected Figure 1-ZS Distribution of Total VOCs in

Deep Monitoring Well Shallow Bedrock Groundwater

Pumping Well Hows Corner

April 2003 Superfund Site

17-Acre Property Boundary Plymouth Maine Concentration Contour (ugl) r WOODARD ampCURRAN

Engineering bull Science bull Operations bull 211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0403dwg04-20-05

s S pound

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- -

5 PLYMOUTH POND

Jo

FEET

ft Shallow Monitoring Well mdashbullbullmdash 17-Acre Property Boundary Figure 1-ZD Deep Monitoring Well I 1 I Detected Concentration ND = Not Detected Distribution of Total VOCs in

Deep Bedrock Groundwater Pumping Well April 2003

Q) Residential Well Hows Corner Superfund Site Plymouth Maine

(T) Surface Water Sampling Point WOODARD ampCURRAN poundKk EnginawtirKj bull Science - Operations bull

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0403dwg04-20-05

0 Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

B MW-1B

I 12000

PCE

B 10000 Total VOCs

I

i 2000

i 0 Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

c MW-3B

G 2000

1800

B PCE

1600 Total VOCs

1 I I E

il-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

G E

211941

El

I I z E

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Concentration Trends shy Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-13DB

Total VOCs

c i i c o

Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

MW-16DB

30

c i c c I c o

Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99

PCE

Total VOCs

Jul-01 Jul-03

211941

O bi

c Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

I MW-16IB

i 35

3

c Total VOCs

lt- 2 5

0 | gt

o

1 sectI

c c 0 4

Jul-90 Jul-92 Jul-94 Jul-96 Jul-98 Jul-00 Jul-02 Jul-04

I I MW-108D

I 12

PCE 10

Total VOCs c oc 3

E E I 0

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

E 211941

c Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

fi MW-108S

I I 40

PCE 35

Total VOCs

30

I f 26

20 I o

I 15

10

c Dec-99 Dec-00 Dec-01 Dec-02 Dec-03 I 0

I MW-112D

c 35 - imdash

I A3 shyTotal VOCs

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E 1 2

I

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B 1 ^

-i c 3

0 Dec-99 Dec-OO Dec-01 Dec-02 Dec-03

211941

I

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Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-112S

08

PCE

Total VOCs 06

o 04

02

0 Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

MW-114D

o

12000

10000

8000

6000

PCE

Total VOCs

4000

2000

i

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Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

211941

Con

cent

ratio

n (

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l)

E Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

I MW-114S

E A5000 -- Total VOCs

- 4000

0 3000

2000

i 1000

i n shy

Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

MW-115D

c PCE

Total VOCs

c E

o

C c

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03 I 0

211941

IepoundII

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30000

25000

20000

o bullsect 15000 b

o 10000 U

5000

0 Aug-99

25000

20000

5000

0 Aug-99

211941

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-2DB

PCE

Total VOCs

Aug-01 Aug-03

MW-2IB

PCE

Total VOCs

Aug-01 Aug-03

IDIBI

ii EIDIISIBIG C

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-102S

6000

5000 PCE

Total VOCs

4000

O 3000

2000

1000

0 Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

MW-103D

16000

~ 14000 ugt 3- 12000 o

^ 10000

sect 8000

O 6000

4000

2000

PCE

Total VOCs

0Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

211941

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

G MW-103S

I I

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12000

10000

E sectc

S

8000

6000

4000

2000

0Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

G I 6000

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Total VOCs

i i c

2000

1000

Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

E I

211941

cIccIG

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Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-1041

PCE Total VOCs

a 25000

0 20000

a 15000

10000

5000

0 Jan-OO Jan-01 Jan-02 Jan-03 Jan-04

MW-106D

3000

2500 PCE

Total VOCs

=sect 2000

o bullsect 1500

1000

500

0 Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

211941

c Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

c MW-106S

I PCE

Total VOCs

i

i Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

i

i i i E

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211941 c

Response to EPA-DEP Comment 5 Dated March 312005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

iiw

EPA-DEP Comment 5

Comment 5 Matrix Diffusion The report as well as other proponents of matrix diffusion suggest that depletion of DNAPL (Section 5112 page 5-15) needs to be achieved While that might be the ideal the goal is to achieve performance standards and that goal may be attainable while there is residual contamination in the rock perhaps even DNAPL globules The low bedrock matrix porosity (page 1-15) the high permeability values (page 4-4) the relative flux of the groundwater (page 5-5) and the decrease in surface area and out of the mainstream pockets (appendix C-4) all suggest that the diffusion out of the rock matrix would be insubstantial relative to the regional flux of groundwater through the Site

Response The TI Evaluation Report does not explicitly consider or rely upon matrix diffusion as a basis for requesting a TI Waiver for a portion of the Hows Corner Site The technical literature provides documentation that matrix diffusion can be a significant process that affects chemical transport and groundwater remediation timeframes in unconsolidated and consolidated media including fractured rock (US EPA 1989 Freeze and Cherry 1979 Pankow and Cherry 1996 Fountain 1998) Back diffusion of contaminants from the matrix porosity of the fractured rock can prolong the time necessary to achieve groundwater cleanup goals particularly for compounds such as PCE for which the cleanup goal is a low concentration It is our expectation that matrix diffusion has occurred at the Hows Corner Site and that back diffusion of PCE from the rock matrix will also occur Although the extent to which matrix diffusion is occurring at the Hows Comer Site has not been determined and that lack of knowledge contributes to uncertainty regarding the cleanup times at the Site the effect of matrix diffusion is to lengthen rather than shorten the time required for remediation

REFERENCES

Fountain JC 1998 Technologies for Dense Nonaqueous Phase Liquid Source Zone Remediation Ground-Water Remediation Technologies Analysis Center Technology Evaluation Report TE-98-02 December

Freeze RA and Cherry JA 1979 Groundwater Prentice-Hall Inc Englewood Cliffs NJ 07632 p 410-412

Pankow J F and Cherry J A 1996 Dense Chlorinated Solvents Waterloo Press Portland OR 97291-1399 p 67-88

US EPA 1989 Transport and Fate of Contaminants in the Subsurface EPA6254-89019 p 17-18

Response to EPA Comment 5 050305doc 1 of 1 Woodard amp Curran (211941)

WOODARD amp CURRAN Maine Massachusetts New Hampshire Connecticut Florida Operational offices across the US 1-800-426-4262 www woodardcurran com

Page 4: SDMS DocID 251749 - Records Collections · 2020-06-13 · CORPORATE OFFICES: Maine, Massachusetts, New Hampshire, Connecticut New, York, Florida Engineering • Science • Operations

Response to EPA-DEP Comment 1 Dated March 312005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

lib

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EPA-DEP Comment 1

Comment 1 Institutional Controls It is recognized by all parties that institutional controls are and will continue to be an integral part of the remedy for the site Having said that the agencies need to have a presentation of the institutional controls including a copy of the town ordinance regarding the ICZ a figure showing the ICZ and the properties with restrictive covenants a table of the 57 properties identified within the ICZ by tax lot number and owners name location of all private wells whether for drinking water residential or agricultural purpose the status of any well abandonment efforts as well as a discussion as how these controls will be monitored

As this information may change over time such as through sale of property or sub-division of a property or well abandonment the agencies believe that presentation of the institutional controls information can best be accomplished with a stand-alone document that can be periodically updated rather than incorporated into the TI report Then as with other documentation such as the RIFS relevant information from the Institutional Control report can be summarized in the TI report

Response The Hows Corner PRP Group will prepare a document that describes the institutional controls for the Site The following items will comprise the document

bull a map of the Site vicinity showing the Institutional Control Zone (ICZ) boundary and properties with restrictive covenants

bull a tabulation of properties located within the ICZ organized by tax lot number and owners name and listing for each property

o the number of connections provided or to be provided to the property o the presence of private wells o the status of well abandonment for the property

bull a copy of the town ordinance regarding the ICZ bull an example of the restrictive covenant for the properties located within the ICZ and bull a discussion of the monitoring program for the institutional controls

The PRPs agree that a stand-alone document is appropriate for the reporting purposes requested by the comment The document can then be updated at periodic intervals mutually agreed upon by the PRPs and the EPA and DEP The status of the PRPs efforts regarding institutional controls and upgrades to the Plymouth water system is summarized in Section 123 of the Draft Technical Impracticability (TI) Evaluation Report Figure 1-2 of the TI Report is a map showing improvements to the Plymouth water system as well as properties that are connected to the system The information in the TI Report will be updated prior to submittal of the final report

Response to EPA Comment 1 050205doc 1 of 1 Woodard amp Curran (211941)

m

Response to EPA-DEP Comment 2 Dated March 312005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

EPA-DEP Comment 2

Comment 2 As discussed in our January meeting the results of the TI field work and their interpretation need to be presented in the TI report Listed below are some specific comments on this with the goal being a discussion of how the site conceptual model and site modeling were revised as a result of the 2004 field work

a analysis of the aquifer test to include a figure presenting the drawdown observed in each monitoring well at the end of the aquifer test The horizontal hydraulic gradient should not be included since this method tends to accentuate the anisotropy Two figures may be needed one for shallow bedrock and one for deep bedrock an evaluation of the appropriateness of the Cooper-Jacob (CJ) method for analyzing the aquifer test data including a comparison of the pattern of observed drawdown to the pattern of fracture orientations determined from the borehole geophysics confirmation that u lt 001 and that calculated values for T and S are similar for several observation wells an interpretation of the change in slope on the CJ plots near the end of the aquifer test the recovery data should be evaluated since it may provide insight as to why the slopes changed the marked increase in slope near the end of the test strongly suggests that a barrier (ie no flow) boundary was encountered and if a boundary was encountered T and S need to be calculated from the pre-boundary portions of the CJ plots It may be appropriate to analyse the aquifer test data using Theis as well as the Moench dual porosity model (both analysis methods are available in Aqtesolv pumping test modeling software) so that all parties have confidence in the transmissivity and storativity numbers derived from the CJ analysis b numerous bedrock borings (including angled holes) were drilled during the most recent field investigation yet no summary of the findings or the geophysical logging or packer test and sampling results have been provided c have any input parameters been changed in the flow transport and batch-flushing models as a result of the 2004 fieldwork If so which ones and why were the changes made (ie justify the changes)

Response The objective of the pumping test conducted at the Hows Corner Site during September 2004 was to observe the response of the groundwater system to pumping for use in refining the site conceptual model The refined site conceptual model would in turn be used to recalibrate the flow model and aid in the design of the hydraulic containment system being constructed under the authority of the AOC for the RD

The results of the pumping test are illustrated by plots of the drawdown at the end of the test The enclosed three drawdown plots (shallow bedrock deep bedrock and combined) represent the change in water level at the end of the test from the initial pre-test water level The shallow bedrock figure shows a northeast-southwest trending ellipsoidal area of drawdown that extends approximately 2000 feet along the major axis and approximately 800 feet along the minor axis The northeast-southwest orientation of the drawdown ellipse is consistent with the orientation of likely water-bearing fractures as identified from geophysical logging during the TI investigation The deep bedrock figure and combined figure also show ellipsoidal areas of drawdown with similar orientation A secondary axis with a more northerly orientation is evident on the figures showing drawdown in deep bedrock and in combined shallow and deep bedrock The maximum drawdown measured in shallow bedrock was 29 feet at MW-2EB The maximum drawdown measured in deep bedrock was 54 feet at the pumping well (PW-207) The drawdown ellipse is

Response to EPA Comment 2 050205doc 1 of 24 Woodard amp Curran (211941)

approximately coincident with the location of the modeled capture zone as presented on Figure 3shy1 of the TI Evaluation report

The enclosed three potentiometric surface maps (shallow bedrock deep bedrock and combined) represent the water surface elevations measured at the end of the test which was 72 hours or three days after it began All three maps show the presence of the groundwater high located in the southeast portion of the 17-acre property This high area shows relatively little relief but with the exception of the measurements at MW-2DDB which shows anomalously high water levels the central area of the high is at lower elevation than the perimeter The measurements at MWshy2DDB are hypothesized to result from water that is unable to drain rapidly enough to equilibrate with the rest of the formation

The pumping test data initially were analyzed using the Cooper-Jacob method for the late test data The results of this analysis are summarized in the table entitled Pumping Test Analytical Results It was recognized that because the aquifer is not uniform isotropic and infinite in areal extent the assumptions on which the underlying Theis equation is based were not met and because of the length of the test the criteria for use of the Cooper-Jacob of analysis were not explicitly met We recognize that the complexity of the hydrogeologic characteristics of the formation would be a significant limitation if the calculated values from the pumping test analysis were to be used as absolute representations of the hydraulic parameters of the formation However the range of values from this pumping test analysis were used as guidelines or bounding values for recalibration of the flow model

Woodard amp Curran also analyzed the pumping test data using the Theis and Moench methods The enclosed table entitled Pumping Test Analytical Results also summarizes the results of analysis of the data using these analytical methods Again although none of the methods may be strictly applicable they provide values that are guidelines for parametric ranges used in model calibration Hydraulic conductivity values calculated from the different analytical methods were as follow

Minimum Maximum Mean (ftday) (ftday) (ftda

bull Cooper-Jacob 020 067 038 bull Theis 035 1476 392 bull Moench (Fissure) 027 210 099

Storage coefficients calculated from the different analytical methods were as follow

Minimum Maximum Mean bull Cooper-Jacob 830E-04 392E-02 651E-03 bull Theis 547E-05 359E-03 473E-04 bull Moench (Block) 803E-05 402E-02 489E-03

Storage coefficients calculated using the Theis method were one to two orders of magnitude lower than values calculated using the Cooper Jacob or Moench (Block) methods Although the fissure system values are thought to be appropriate for evaluating hydraulic conductivity because the majority of flow is through fractures the block system values are appropriate for evaluation of storage because the limited fractures account for only a small part of the total storage in the bedrock

Response to EPA Comment 2 050205doc 2 of 24 Woodard amp Curran (211941)

Woodard amp Cunran used the values estimated from the pumping test analysis as an initial data set for transient benchmarking by running a 3-day simulated pumping test Calibration of the model was accomplished by comparing measured drawdowns obtained during the pumping test to calculated drawdowns from the flow model The hydraulic parameter values in the model were varied from the initial values but within the range calculated from the pumping test analysis The additional model calibration was considered to be completed when the calculated drawdowns were sufficiently close to measured drawdowns The resulting values of the hydraulic parameters of the calibrated model were then considered acceptable to provide satisfactory prediction of the response of the flow system to other hydraulic stresses

Regional water-level data were reviewed prior to data analysis A plot of water levels in the closest USGS regional background well (provided in the TI Data Package and attached) indicates that throughout the period of the test and subsequent recovery water levels were declining on a regional scale Although the decline in water levels is gradual the change in slope observed on the Cooper-Jacob plots is thought to represent the point at which the drawdown at a given location caused by pumping becomes less significant compared to the regional drawdown This occurs at about a day after start of pumping The effect of the regional decline in water levels can also be seen in the initial rapid rise in water levels in response to pump shut off followed by a decline in water levels after about a day after the pump is shut off

Additional information obtained during the TI field work was reviewed and evaluated in updating the conceptual model for the site In general the additional information corroborated the understanding of the Site presented in the RI report In particular the northeast-southwest fracture orientation was confirmed as the predominant orientation Geophysical logging during the TI investigation however showed the dip direction of fractures to be more variable and the dip angles to be shallower than was understood based on the RI data (see enclosed figure Packer Testing Results in Vicinity of Source Area) The additional borings installed within the fenced area and to the east of the fenced area showed that the area in which concentrations of total VOCs in groundwater exceeded 10000 pgL was more limited than portrayed in the RI and FS reports Packer testing of the intervals identified by geophysical logging as likely or possibly transmissive (see enclosed borehole geophysical logs) showed VOC concentrations within the packered intervals at a given borehole to be either essentially constant (eg MW-203 MW-204 MW-205) or increasing with depth (eg PW-207) Information on hydraulic conductivity and VOC concentrations in packered intervals is summarized on two separate tables for the 1999 RI wells and 2004 TI wells (Packer Permeability and Packer Sampling Results for Potential Fracture Intervals - enclosed) The orientation hydraulic conductivity and VOC concentrations of features identified as likely or possibly transmissive is summarized in a separate table (Orientation Permeability and Groundwater Sampling Results for Transmissive Features shyenclosed)

Table 4-1 of the TI Evaluation report summarizes the variation of input parameters to the flow and batch-flushing models as the project progressed from RI to FS to TI As described above for calculations in the TI Evaluation report hydraulic conductivity values were adjusted during the model calibration to pumping test drawdown data Measured fraction of organic carbon values and VOC concentrations were used in the Batch-Flushing model along with recharge calculated from the ModFlow model For calculation of pore flush volumes using the Batch-Flushing model the ratio of density to porosity was constrained to a range of 4 to 10 which is the typical range of such ratios in porous media (Freeze amp Cherry 1979) The basis for this change was stated in Appendix C of the TI Waiver Evaluation Report and is described in the response to Comment 3

Response to EPA Comment 2 050205doc 3 of 24 Woodard amp Curran (211941)

REFERENCE

Freeze RA and Cherry JA 1979 Groundwater Prentice-Hall Inc Englewood Cliffs NJ 07632 p 410-412

Response to EPA Comment 2 050205doc 4 of 24 Woodard amp Curran (211941)

LIST OF ATTACHMENTS (Response to Comment 2)

Figure - Drawdown at 72 Hours Shallow Wells

Figure - Drawdown at 72 Hours Deep Wells

Figure - Drawdown at 72 Hours

Figure - Potentiometric Surface at 72 Hours Shallow Wells

Figure - Potentiometric Surface at 72 Hours Deep Wells

Figure - End of Pumping Test Bedrock Potentiometric Surface at 72 Hours

Table - Pumping Test Analytical Results

Figure - USGS Background Groundwater Level

Figure - Packer Testing Results in Vicinity of Source Area

Figure - Borehole Geophysical Log MW-203

Figure - Borehole Geophysical Log MW-204

Figure - Borehole Geophysical Log MW-205

Figure - Borehole Geophysical Log MW-206

Figure - Borehole Geophysical Log PW-207

Table - Packer Permeability and Packer Sampling Results for Potential Fracture Intervals 1999 Drilling Program (2 pages)

Table - Packer Permeability and Packer Sampling Results for Potential Fracture Intervals 2004 Drilling Program

Table - Orientation Permeability and Groundwater Sampling Results for Transmissive Features 2004 Drilling Program (2 pages)

Response to EPA Comment 2 050205doc 5 of 24 Woodard amp Curran (211941)

(MEDEP Pond 1) Farm Pond

0 150 300

FEET

Monitoring Well

Figure X Pumping Well Drawdown at 72 Hours

_ - 17-Acre Property Boundary Shallow Wells Hows Corner Superfund Site Drawdown Contour (ft) Plymouth Maine

151 | Drawdown (ft) WOODARD ampCURRAN

^Stk Engineering bull Science bull Operations bull 211941 Hows CornlaquorwipDrawingsTI EVALDrawdown-72hrs_shallowdwg04-19-05

MW-3B

413951 W-6DB JMW-6SB

(MEDEP Pond 1) Farm Pond

Monitoring Well

Pumping Well

17-Acre Property Boundary

Groundwater Elevation Contour (ft)

211941 Hows CornerwipDrowngsTI EVALpo-tent-aU-72-hrsdwg

Figure X End of Pumping Test

Bedrock Potentiometric Surface at 72 Hours Hows Corner Superfund Site

Plymouth Maine ^ WOODARD amp CURRAN

Englnesring bull Science bull Ope

(MEDEP Pond 1) Farm Pond

Monitoring Well

Pumping Well Drawdown atFigure X

72 Hours _bullbull_ 17-Acre Property Boundary Deep Wells

Drawdown Contour (ft) Hows Corner Superfund Site

Plymouth Maine 151 | Drawdown (ft)

= WOODARD ampCURRAN 211941 Hows CornerwipDrawingsTI EVALDrawdown-72hrs_deepdwg04-19-05

Engineering bull Science bull Operations

(MEDEP Pond 1) Farm Pond

028 MW-12DB

MW-125B 040

l - _ ^ I 016 I N

050 MW-15SB

MW-15DB 048

A J s

- A - Monitoring Well

-$poundbull Pumping Well

_bullmdash 17-Acre Property Boundary

^ Drawdown Contour (ft)

151 I Drawdown (ft)

211941 Hows CornerwgtpDrawinQsT EVAI_Drawdown-72brsdwg04mdash19-05

Figure X Drawdown at 72 Hours

Hows Corner Superfund Site Plymouth Maine

^ WOODARD ampCURRAN Engineering bull Science bull Operations i

(MEDEP Pond 1) Farm Pond

Monitoring Well

Pumping Well

_bullbull_ 17-Acre Property Boundary

f Groundwater Elevation Contour (ft)

|419Q0| Groundwater Elevation

211941 Hows CornerwipDrawinqsTI EVALPotSurf-72hrs_shallowdwg04-19-05

150 300

FEET

Figure X Potentiometric Surface at 72 Hours

Shallow Wells Hows Corner Superfund Site

Plymouth Maine

WOODARD ampCURRAN Engineering bull Science bull Operations

29212 MW-108D

(MEDEP Pond 1) Farm Pond

Monitoring Well

Pumping Well

mdashbullbulllaquo 1 7-Acre Property Boundary

bull Groundwater Elevation Contour (ft)

1419001 Groundwater Elevation

211941 Hows CornerwipDrawingsTI EVALPotSurf-72hrs_deepdwg04-19-05

150 300 =5fc= FEET

Figure X Potentiometric Surface at 72 Hours

Deep Wells Hows Corner Superfund Site

Plymouth Maine

WOODARDampCURRAN Engineering bull Science bull Operations bull

--

Pumping Test Analytical Results Hows Corner Superfund Site

Plymouth Maine

Well ID oper Jaccb Analyses 2 Theis Analyses Fissure

Well Id Rd (ft)

Saturated Thickness

Transmissivity

(ft2day) K

(ft2day) K

(cmsec) Storage

Coefficient Transmissivity

(ft2day) K

(ft2day)

K (cmsec)

Storage Coefficient

System K

(ftday) PW-207OB 8 85 481 057 200E-04 392E-02 36 042 150E-04 809E-04 027 MW-103S 50 85 451 053 187E-04 720E-03 92 108 382E-04 283E-04 083 MW-103D 54 185 455 025 868E-05 210E-02 65 035 123E-04 237E-04 044 MW-2IB 59 85 352 041 146E-04 699E-03 104 123 433E-04 512E-04 052 MW-2DB 63 85 334 039 139E-04 845E-03 148 080 283E-04 239E-04 046 MW-104D 95 185 489 02 6 932E-05 654E-03 98 053 186E-04 547E-05 037 MW-104I 97 85 33 03 9 137E-04 362E-03 117 137 484E-04 962E-05 048 MW-101I 107 85 364 043 151E-04 490E-03 511 601 212E-03 223E-04 136 MW-102D 134 185 435 024 829E-05 248E-03 108 058 206E-04 850E-05 065 MW-101D 138 185 492 027 938E-05 511E-03 671 362 128E-03 700E-04 172 MW-205 219 85 57 067 237E-04 255E-03 447 526 186E-03 359E-03 -shyMW-204D 221 185 367 020 700E-05 170E-03 790 427 151E-O3 155E-04 147 MW-204S 225 85 379 045 157E-04 156E-03 1031 1213 428E-03 313E-04 199 MW-1B 228 85 325 038 135E-04 977E-04 340 400 141E-03 739E-05 054 MW-203S 273 85 489 058 203E-04 117E-03 1255 14 76 521 E-03 216E-04 210 MW-106D 278 185 51 028 972E-05 141E-03 1065 576 203E-03 360E-04 104 MW-203D 278 185 478 026 911E-05 152E-O3 765 414 146E-03 364E-04 138 MW-105D 364 185 44 024 839E-05 830E-04 769 415 147E-03 200E-04 127

1 Analyses conducted using Cooper and Jakob method on late drawdown data collected during constant

discharge pumping test conducted at the Hows Comer Site from September 20 - 30 2004

2 Analyses conducted using Theis solution for unconfmed approximation (1935)

J Analyses conducted using Moench method for dual porosity estimation (1984)

Fissure System Storage

Coefficient 402E-04 117E-06 264E-04 300E-04 932E-05 235E-07 502E-05 326E-06 801E-05 542E-04

-

803E-05 762E-05 134E-05 498E-05 115E-04

47E-04 838E-05

3 ysesh Analysis

Block System K (ft2day)

251E-02 207E-03 564E-04 163E-04 585E-04 465E-02 153E-04 498E-03 855E-04 356E-03

-

292E-03 394E-03 720E-04 526E-03 160E-01 35OE-O1 287E-03

Block System Storage

Coefficient

402E-02 164E-04 183E-02 330E-03 158E-03 847E-03 286E-03 326E-04 803E-05 272E-03

723E-04 686E-04 148E-04 349E-04 115E-03 47E-04 838E-04

Theis - Moench - CJ - AnalyticalResults_4-19-O5xls

DRAFT

242

24

238

236

bulla

c

i

a Q

234

232

228

226

Hows Corner Constant Discharge Testing USGS Background Groundwater Level USGS 445319068560101 ME-PEW456 Kenduskeag Maine

End of Monitored Recovery Period 09302004

Regional Background Location i 226 miles from Pumping Locatio

lt

697

NOTES

1 Groundwater samples collected in 1999 were screened for five volatile organic compounds (VOCs) only N

tetrachloroethene (PCE) exceeded reporting limits MW-2030 082304 082304 082304 082304 u

2 Strike and Dip of likely or possible transmissive 30 45 55 85 feature within the packer interval from which the indicated sample was collected

MW-204D

PCE TOTAL VOCs

081904 30

220 2636

A

081904 46-50 540 6436by

081904 IT

260 3073

x

MW-105D

PCE TOTAL VOCs

111199 50-60 2100 2100

MW-106D

PCE TOTAL VOCs

111199 76-86

400 400

111199 137-147

1400 1400

111299 1355-1455

350 350

PCE TOTAL VOCs

44 84

64

MW-6SB

bulli

lt

gt-

170 234

35

I I i

140 192

^^52

^^52

130 183

52 - lt

S A 34

PW-207 082404 082404 082404 20 37

PCE 1300 TOTAL VOCs

17-Acre George West Property Boundary

MW-113D

PCE TOTAL VOCs

112299 46-56

350 350

112299 70-80 190 190

150

112299 105-115

129 129

112399 138-148

230 230

L e g e n d ( J New Monitoring Well-Summer

Site Property Boundary ^ P u m p i n g Well-Summer 2004

-xmdashxshy Source Area

bull0shy Monitoring Well shy Pre 2004 Angled Boring-Summer 2004

211941laquoipdwgTI-ELV21ig41paltker-data2

2004 PCE of Total

bull lt70 VOCs

M W - 1 14D ^ ^

Figure xx Packer Testing Results in

Vicinity of Source Area Hows Corner Superfund Site

Plymouth Maine ^ WOODARD ampCURRAN

^^^^^^^^^^m ampKm Engineering - Science bull Operations

c Northeast Geophysical Services Borehole Geophysical Log

MW-203 Date logged 081704 Plymouth Maine

I Flowmeter Measurements Tomporaturo(C) Acoustic Televiewer

7 5 8 8 5 9 95 Caliper (Inches) Resistance (Ohms) Spontaneous Potential (mVj Dip In Degrees PCE Total VOCs

3 0 2 0 8 0 laquodeg 4S 1000 1400 1800 2200 MO HO 1000 1200 MOO 0 laquo deg ugL ugL n 1 1 1 1 1 1 1 1 1 i 1 1 1 1 n 1 1 1 1 1 1 1 1 1 1 1 n I l l l l l l l n

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| H100 - j 100 bullbull 100 - -100

1 1 1 1 1 1 1 ) | 1 f I 1 1 1 ) 0 20 40 60 80

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30 4 g 0 20 40 60 Dip in Degrees bullbull

Likely or poss bleFluid Resistivity (ohmmeters) The dip direction-- indicated

^ t h e l i n e extending from t h

I Iransmissive zone circle The strike of the feature is 90 degrees from this

The acoustic televiewer graph displays the mostprominent features selectedffom the acoustic televiewer

R n r a h n l c D O t t n O I B

f i o n n h w c i r a l U K U p i i y SI Ud l

1 rn l_Og Packered Interval August 2004

E tog The location dip angle and dip direction of the sleeted M W - 2 0 3 Groundwater samples were collected by Woodard S Curran on H23120M features are approximate Refer to the televiewer og of His _ well for more precise detail Plymouth Maine Date logged 081704

I

1

Northeast Geophysical Services Borehole Geophysical Log MW-204 D a t e l o gge d 072604

Plymouth Maine

n 3

Flowrneter Measurements(in gpm)

Caliper (Inches)0 3 5 4 0

1 1 1 1 1 1 1 t 1 1 1 1 1 1Ambient Rowmeler pumping Flowmetsr 05gpm

Templaquorature (C) bull bull bull bull i

7 75 8 8S 9 Resistance (Ohms) Spontaneous Potential (mV)

4000 SOW 600 4M 0

Acoustic Televiewer (interpreted)

Dip in Degrees 0 20 4060 SO

at N

PCEugL

Total VOCs ugL

- -_ a

10-

shy 10 bull - 10 shymagnetic

north - 10

o o

bull 1

11

11

1 1

1 1

11 1

1 1

1 1

1 1

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1 1

1 1

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1 1 E 1

- L

3 7 2 0 2 0r bull 20 bull - shy

i S_ N F

bull30 bull 7 3 0 220 2636shy1^ J J 004

fI f V ^

40 shy 4 0 4 0 shy - 4 0rbull019 [_ 007 w8 - - shy5 c

bull

gt

Ia50i 540 6436

bull50 - - 50 - - 5 0

-QQ7 - bull - -t T

pound V gtk

B 6 0 - e o - 7 6 0 -60shyQ 1 1

Q -007 -004 bull1 mdash T - J ~

bull

- - shyT 70 -J c [TO- - 70 - 7 0-

V Y 1- -004 -003

mdash T -h - y - j i - - mdash 260 3073 - gt=7

80 -j NF bull80 - - 80 - - 8 0Jgt

bull i

i 1

i i

C- bull shy

90 shy

K

Jlt i90 90 shy - 9 0shy -

l

ii

I I I I

NF bull M J

I ^ ^ - ^ bull 1

mdash mdash - _

s -7 ^100shy

till

1 100 100- H - 1 0 0shy -1 x Likety or possible k ^ Iransmissive zonebull

1 i i i ii i i i | l l l l | l i l l 0 20 40 ED 80

1 -

3 0SOFluid Resistivity (ohmmeters)

Dip in Degrees The djp ^ ^ o n is indicated ty Ihe line extending from tha circle The strike of Ihe feature

19- 3U UIHJIW93 IolII l l l lraquo

bull

The acousfc televiewer graph displays the mostprominent features selected from the acoustic televiewer109 The location dip angle and dip direction of Ihe sleetedfeatures are approximate Refer to the televiewer log of thiswentormore precise detail

B o r e h o l e G e O D h V S I C a l LOO B W H U I B w c w p n y o i v a i w v yM W - 2 0 4

P l y m O U t n MaiDB

Packorod Interval August 2004Groundwater san-ples wampramp collected by Woodard a Curran on OMO23C4

Date logged 072604

C

I

E Northeast Geophysical Services Borehole Geophysical Log Date logged 072704

I MW-205

Plymouth Maine

Flowmeter Measurements Temperature (C) Acoustic Televiewer (In gpm) I ~l (Interpreted)

I 85 10 Caliper (inches) 95

Dip in D g r laquo Resistance (Ohms) Spo ontaneous Potential (mV PCE Total VOCs 3 0 16 4 0 4 5 ) 20 40 60 80 10 00 2000 30 00 4VJ 400 -3 laquo

i i i i 1 i i I i 11 4 0 D 1 I I ugL ugL

C h

iii Ambient Flowmetar pumping

Flowmeter 1 25 gprn

I bull$bull

i

I rmdash magnetic 1 north ^^^^ 1 VI f

10 ~ I C x 10 bull - 10 bullbull

4 5 6mdashmdash f 1000B 11448 noisy nodi a raquo ^

mdash 5rt mdashi mdash Oft pound) 1100B 12509

cjmdash1 007

-

i i i 1

en

8 B a B

30 mdash

-

40 shy

-mdash I -

50 -_

__NF lt005

- 30 - - 3 0 it 34V

MO P26 V S) 1300B 13776 _ N F NF

26

40 bull - 40 bull 7-40 gt J Vf1 cX

) -j -

_ N F NF 50 c bull - 50 ^ 7-50

i I

I

c

B pound 60 - 6 0 7 60 - 7-60 a i 1

_ N F NF i Si f f 70 -_ bull70 bull - 70 shyC I 9

-m bull - shyA

_ N F NF 80 80 -j bull80 bull - 80 - C- 33 34

bull

5-i r

i 1

J r

Ck

_ N F NF 9 0 90 - - 90 shy

i bullCshy

J rK bull

100 -j ^ Likely or possible bull100- - 100- I -100

transmissive zone bull - ^ bull shy] |

1 1 1 1 1 1 1 I 1 i i i 1 i i 1 1 0 20 40 SO SO 10 20 30 40 50 Dip in Degrees 30 4 0 Fluid Resistivity (ohmmeters) Thlaquo dip direction is indicated

by the line extern r g from the circle The strike of he feature is 90 degrees from ihis

The acoustic televiewer graph displays the most

I Borehole Geophysical Log Packered Interval August2004 prominent features selected from the acoustic televiewer

Groundwatcr samples were oollccled by Woodard amp Cufran orgt S172004 log The location dip angle and dip direction of ins slsctsd MW-205 features are approximate Refelt to the televiewer log of this wall for more precise detail Plymouth Maine Date logged 072704

I

C

I Northeast Geophysical Services Borehole Geophysical Log Date logged 072704

I MW-206

Plymouth Maine

Flowmetor Measurements Temperature (C) Acoustic Televiewer | I r T i i i i i i i i i i i i i i r I |(in gpm) (Interpreted)

I 75 8 flS 9 95

Caliper (inches) Resistance (Ohms) Spontaneous Potential (mV) Dip In Degress PCE Total VOCs 30 35 40 4 5 0 20 40 M 90 4500 5500 6500 ugL ugL I i i

I I

- 1 0

I - 2 0

I 2900B 32401

i i L

E 0

i 6300B 68901

i I 0 20 40 SO 80

20 30 40 50 Dip in Dlaquogralaquos

amp 4 a Fluid Resistivity (ohrnmeters) The dip dirertion is indicated Likely or possible by iho line extending from the transmissive zone circle The striKe of the feature

is 90 degrees from tNs

Borehole Geophysical Log Packered Interval August 2004

E amples were collected by Woodard amp Cunan oo SM82004 log Thraquo location 4p angle and dip direction of the sloeled MW-206 feature are approximate Refer to the televiewer 109 of this well for more precise detail Plymouth Maine Date logged 072704

C

I Northeast Geophysical Services Borehole Geophysical Log

Date logged 082304 PW-207

I Plymouth Maine

Fiowmeter Measurements Temperature (C) Acoustic Televiewer

I (in gpm) (interpreted)

75 8 85 9 95 Caliper (inches) Resistance f0tims) Spontaneous Potential (mV) Dip in Degrees PCE Total VOCs

55 60 0 20 40 SO 80 ugL ugL I I I I I I I

Ambienl Fiowmeter pumping Flewmater

magnetic - 10 - - 1 0

north

i - 20 - - 2 0

1300 1410

i - 30 - - 3 0

i tf

5400 5802 - 40 - - 4 0

B - 50 - - 5 0

I 18000 19234

- 60 - - 6 0

I 12000 13085

- 70 - - 7 0

- 8 0

i - 9 0 19000 20354

G - 100- -100

I 110 110 bull110

0 20 40 60 SO 10 20 30 Dip m Degrees

Fluid Resistivity (ohmmeters) I 50

The dip direction is indicated by ihe line extending from the circle The strike of the fealure is 90 degrees from this

Borehole Geophysical Log

G Packorod Interval August 20(M log The location dip angle and dip dirlaquocton or the sleeted Groundaier samplss were ooliecled by Woodard i Curran on ampt24f2ltXM PW-207 failures are approximate Reter to the televiewer log of this wlaquoll for more precise detail PlyPIOUth Maine Date logged 082304

I

Table XX Packer Permeability and Packer Sampling Results for Potential Fracture Intervals

1

WellID MW-101D MW-101D MW-101D MW-101D MW-101D MW-101D MW-101D MW-101D MW-101D MW-101D MW-I01D MW-101D MW-101D MW-102D MW-102D MW-I02D MW-102D MW102D MW-102D MW-102D MW-102D MW-102D MW-I02D MW-102D MW-102D MW-102D MW-103D MW-103D MW-103D MW-103D MW-I03D MW-103D MW-103D MW-103D MW-103D MW-103D MW-103D MW-103D MW-I03D MW-104D MW-104D MW-104D MW-104D MW-I04D MW-104D MW-104D MW-104D MW-104D MW-104D MW-104D MW-105D MW-105D MW106D MW-106D MW-106D MW-107D MW-107D

1999 Drilling Program

Hows Corner Superfund Site Plymouth Maine

Potential Fracture Top Of Bottom 6 Depth to lt Topof i Interval from Packer Packer Middle of Elevation Hydraulic bull PCE

GS ELEV 1 Rock Drilling Interval Interval Interval of Interval Conductivity Concentration (ft msl) (ft msl) TEST (ftbgs) (ftbgs) r(ftbgs) ( f t b (ft mil) (cmsec) (raquogL)

4339 4329 13 28-29 33-3537-39 271 376 324 4016 OOOE+00 4339 12 37-3444-46 380 485 433 3907 157E-04 4339 11 488 593 541 3799 132E-04 4339 10 60-61 578 683 631 3709 OOOE+00 4339 9 678 783 731 3609 I79E-05 4339 8 778 883 831 3509 106E-05 4339 7 880 985 933 3407 243E-05 4339 6 990 1095 1043 3297 339E-06 4339 5 1090 1195 1143 3197 OOOE+00 4339 4 1190 1295 1243 3097 OOOE+00 4339 3 1365-1375 1290 1395 1343 2997 OOOE+00 4339 2 147-157 1390 1495 1443 2897 580E-05 4339 1 147-157 1470 1575 1523 2817 741E-05 43161 43061 13 166 271 219 4098 333E-04 43161 12 30-3136-40 260 365 313 4004 I54E-05 43161 11 36-4041-43 362 467 415 3902 548E-05 43161 10 470 575 523 3794 598E-05 43161 9 570 675 623 3694 197FOS 43161 8 670 775 723 3594 OOOE+00 43161 7 770 875 823 3494 891 E-05 43161 6 83-94 870 975 923 3394 139E-05 43161 5 970 1075 1023 3294 123E-04 43161 4 1070 1175 1123 3194 526E-06 43161 3 1170 1275 1223 3094 138E-05 43161 2 1270 1375 1323 2994 671E-06 43161 1 1370 1475 1423 2894 OOOE+00 42997 42497 13 18-19 170 275 223 4077 OOOE+00 42997 12 260 365 313 3987 766E-05 42997 11 360 465 413 3887 727E-05 42997 10 460 565 513 3787 192E-05 42997 9 560 665 613 3687 752E-05 42997 8 660 765 713 3587 778E-05 42997 7 85-86 763 868 816 3484 260E-05 42997 6 860 965 913 3387 289E-05 42997 5 102-103 960 1065 1013 3287 102E-04 42997 4 1060 1165 1113 3187 522E-06 42997 3 1160 1265 1213 3087 520E-06 42997 2 129-130 1260 1365 1313 2987 960E-04 42997 1 1360 1465 1413 2887 OOOE+00 43372 42922 11 35-37 42-45 350 455 403 3935 684E-04 43372 10 460 565 513 3825 500E-05 43372 9 560 665 613 3725 106E-05 43372 8 72-74 660 765 713 3625 204E-05 43372 7 760 865 813 3525 872E-06 43372 6 860 965 913 3425 467E-06 43372 5 960 1065 1013 3325 200E-05 43372 4 1060 1165 1113 3225 354E-05 43372 3 125-130 1160 1265 1213 3125 157E-05 43372 2 125-130 1260 1365 1313 3025 337E-04 43372 1 1365 1465 1415 2922 689E-06 43052 43002 2 54-58 490 595 543 3763 124E-05 2100 43052 1 139-140 145-146 1367 1472 1420 2886 154E-04 1400 43291 4391 3 bullI133 260 365 313 4017 439F06 43291 2 77-78 760 865 813 3517 230E-03 400 43291 1 143-144 1355 1460 1408 2922 971E-06 350

29958 27258 4 450 555 503 2493 OOOE+00 (21)A 29958 3 103-105 1000 1105 1053 1943 752E-04 (063)A

Table XX Packer Permeability and Packer Sampling Results for Potential Fracture Intervals

1999 Drilling Program

Hows Corner Supcrfund Site Plymouth Maine

gtbull i Potential Fracture Top _OfBot Bottom of Depth to ltbull Top of Interval from f Packer Packer Middle Of

GS ELEV lt Hock Drilling interval Interval Interval WeD ID ft msl) (ft msl) TEST (ftbgs) ltft$gs) (ftbgs) (ftbgs)

MW-107D 29958 2 128-130 1200 1305 1253

MW-107D 29958 1 139-141 1350 1455 1403

MW-108D 31904 31104 6 35-36 300 405 353 MW-108D 31904 5 60-62 550 655 603

MW-108D 31904 4 80-83 750 855 803

MW-108D 31904 3 118-119 123-124 1150 1255 1203

MW-108D 31904 2 147-149 1440 1545 1493

MW-108D 31904 1 1700 1805 1753

MW-110D 40576 40426 2 21-31 210 315 263 MW-110D 40576 1 148-154 1460 1565 1513 MW-I11D 40519 4 70-71 650 755 703

MW-111D 40519 3 79-82 84-86 780 885 833 MW-I11D 40519 2 97-102 950 1055 1003 MW-111D 40519 1 1370 1475 1423

MW-112D 3027 2942 4 42-52 420 525 473 MW-112D 3027 3 850 955 903 MW112D 3027 2 1100 1205 1153 MW-112D 3027 1 135-136 140-141 1340 1445 1393

MW-113D 43085 43085 5 250 355 303 MW-I13D 43085 4 47-49 460 565 513 MW-113D 43085 3 73-74 700 805 753 MW-113D 43085 2 1050 1155 1103 MW-113D 43085 1 1380 1485 1433

MW-114D 42394 41594 4 48-49 450 555 503 MW-114D 42394 3 79-81 740 845 793 MW-114D 42394 2 121-129 1250 1355 1303 MW-114D 42394 1 134-142 1350 1455 1403

MW-115D 4035 4035 4 300 405 353 MW-1I5D 4035 3 70-71 650 755 703 MW-115D 4035 2 1150 1255 1203 MW-115D 4035 1 1400 1505 1453

LOT-28W 382 7 450 555 503 LOT28W 382 6 550 655 603 LOT-28W 382 5 650 755 703 LOT28W 382 4 750 855 803 LOT-28W 382 3 850 955 903 LOT-28W 382 2 950 1055 1003 LOT-28W 382 1 1055 1155 1105

NOTES cmsec = centimeters per second ft bgs = leet below ground surface It msl = feet below mean sea level lt = not detected at indicated reporting limil A = detected below laboratory PQL ( ) = detected below reporting limits

Elevation of Interval

(ft nisi) 174

159

283gt 2588

2388

1988

1698

1438

3795 2545 3349 3219 3049 2629

2555 2125 1875 1635

4006 3796 3556 3206 2876

3737 3447 2937 2837

3683 3333 2833 2583

3318 3218 3118 3018 2918 2818 2715

Hydraulic Conductivity

(cmsec)

323E-05

208E-05

471E-03

471E-03

624E-05

3I6E-05

264E-05

261 E-05

OOOE+00 200E-04 953E-05 OOOE+00 OOOE+00 212E-05

361 E-05 410E-06 2gQE06 292E-05

786E-05 124E-05 151 E-05 822E-06 82IE-06

858E-05 I69E-05 352E-03 866E-05

223E-05 394E-06 122E-05 525E-06

831 E-05 182F-05 L62E-05 129E-05 190E-05 890E-04 981 E-04

PCEraquo Concentration

(ugL)

lt5

(14A)

98 11

15

22

11

30

200 (62)A

110 210 300 240

(44)A (23)A

5

350 190 129 230

2200 1900 2600 2600

(17)A (16)A (19)A

96

Table XX Packer Permeability and Packer Sampling Results for Potential Fracture Intervals

2004 Drilling Program

Hows Corner Superfund Site Plymouth Maine

Top of Bottom of Depth to Midpoint

t K

ELEV (ft Potential Transmissive Zones Packer Interval

Packer Interval

Middle of Interval

Elevation of interval

Hydraulic Conductivity

PCE Concentration

Well ID msl) TESTr (ft bgs)- (ftbgs) (ftbgs) (ftbgs) (ft msl) (cmsec) (ogt) MW-203D 43227 4 277279 24 32 28 4043 667E-05 44

3 408415420 39 49 44 3883 593E-05 170 2 526 530 49 57 53 3793 101E-04 140 I 828830842 80 88 84 3483 701E-05 130

MW-204D 43262 5 295 300 26 34 30 4023 902E-05 220 4 463496513516 45 53 49 3833 119E-04 540 3 681685688 63 71 67 3653 OOOE+00 2 758 76 2 71 79 75 3573 309E-05 260 I 88 96 92 3403 OOOE+00

MW-205 42389 3 164 166 168 15 20 175 4148 OOOE+00 1000B 2 302305312 30 35 325 3998 107E-04 1300B 1 40 45 425 3898 OOOE+00

MW-206D 43007 5 17 72 195 4128 291E-05 4 296 302 307 29 34 315 4008 940E-05 2900B 3 522 52 57 545 3778 944E-07 2 656 64 69 665 3658 353E-06 1 92392793 4939 91 96 935 3388 614E-05 6300B

PW-207 43477 5 184622162819 18 29 235 4088 209E-05 1300 4 3508 32 43 375 3948 568E-06 5400 3 53325341542154325559 50 61 555 3768 821E-05 18000

6359 61 72 665 3658 866E-06 12000 1 8685 84 89 865 3458 213E-05 19000

NOTES cmsec = centimeters per second ft bgs = feet below ground surface ft msl = feet above mean sea level B = detected in lab blank

Table XX Orientation Permeability and Groundwater Sampling Results for Transmissive Features

2004 Drilling Program

Hows Corner Superfund Site Plymouth Maine

Borehole Geophisical Feature depth Dip True Dip True Transmissive Log Feature (Feet) Degrees Azimuth Strike bullvgt(Ltk|iy^

Number v Tosftble) v MW-203 5 277 64 337 67 Likely

6 279 59 11 281 Likely 8 352 14 177 87 Likely 11 381 46 96 6 Possible 12 408 35 271 1 Possible 14 415 57 250 340 Possible 15 420 58 202 292 Likely 18 526 52 75 345 Likely 19 530 52 82 352 Likely 28 828 48 75 345 Likely 29 830 52 17 287 Likely 30 830 56 233 323 Possible 31 842 50 130 40 Likely

MW-204 4 295 15 147 57 Likely 5 300 43 91 1 Likely 11 439 31 80 350 Possible 12 440 46 219 309 Possible 14 463 50 358 88 Likely 15 496 34 198 288 Likely 16 513 54 17 287 Likely 17 516 33 14 284 Likely 25 681 39 359 89 Possible 26 685 22 45 315 Possible 27 688 35 73 343 Possible 32 758 45 236 326 Likely 33 762 46 306 36 Likely

MW-205 5 164 69 106 16 Possible 6 166 78 165 75 Possible 7 168 82 115 25 Possible 8 168 68 116 26 Possible 12 215 46 222 312 Possible 13 217 75 62 332 Possible 14 219 29 32 302 Possible 16 237 69 250 340 Possible 17 256 73 353 83 Possible 18 272 44 202 292 Possible 21 299 37 196 286 Possible 22 302 31 206 296 Possible 23 305 59 48 318 Likely 24 312 63 42 312 Likely

MW-206 1 264 37 181 271 Likely 2 296 69 217 307 Likely 3 302 66 233 323 Likely 4 307 64 224 314 Likely 8 342 62 259 349 Likely

jjHydraulic GoiDanctilyity j(cmsecjw

667 E-05

593 E-05

101 P04

710 E-05

902 E-05

119 E-04

0

309 E-05

0

107 E-04

94 E-05

PCE (ugL)

44

170

140

130

220

540

260

IOOOB

1100B

1300B

2900B

STotal vVoCsv tig1)

84

234

192

183

2636

6436

3073

11448

12509

13776

32401

PCEyo dfCTotaf

52

73

73

7 1

83

84

85

87

88

94

90

Table XX Orientation Permeability and Groundwater Sampling Results for Transmissive Features

2004 Drilling Program

Hows Corner Superfund Site Plymouth Maine

Borehole Geophisical Feature deptt raquoip True pip True Transraissive Log Feature (Feet) shy Degrees Azimuth Strike (tikely

Number raquo Possible) 22 522 57 54 324 Possible 25 656 40 82 352 Possible 32 871 59 151 61 Possible 33 883 53 185 275 Possible 34 895 7 175 85 Likely 35 899 53 90 0 Likely 36 902 49 184 274 Likely 37 923 9 175 85 Likely 38 927 42 206 296 Likely 39 934 48 167 77 Likely 40 939 26 180 90 Likely

PW-207 1 1846 33 167 77 Likely 4 2216 49 289 19 Possible 7 2819 59 265 355 Possible 11 3508 55 189 279 Possible 18 5332 43 305 35 Likely 19 5341 51 30 300 Likely 20 5421 20 254 344 Likely 21 5432 39 301 31 Likely 23 5559 52 302 32 Likely 25 6359 24 182 272 Possible 29 8049 77 231 321 Possible 30 8685 78 38 308 Likely 32 9334 29 194 284 Likely

NOTES

B = detected in lab blank

Hydraulic Conductivity

(cmsee) 944 E-07 353 E-06

614 E-05

209 E-05

568 E-06

821 E-05

866 E-06

213 E-05

bulltCE (ugL)

6300B

1300

5400

18000

12000

19000

Total VOCs (ug1)

68901

1410

5802

19234

13085

20354

PCE of Total VOCs

9 1

92

93

94

92

93

Response to EPA-DEP Comment 3 Dated March 312005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

lit

EPA-DEP Comment 3

Comment 3 The reported f values and resultant Kd values There remains doubt that the values used in the flushing model accurately reflect the propensity for PCE to sorb to the bedrock The ^ values presented in Appendix B may be unrealistically high because the bedrock samples may have contained organic carbon that was unavailable for sorption The reported f values are only qualitative estimates of the organic carbon content of the bedrock samples The Walkley and Black organic carbon measurement method is quick and simple but the results obtained cannot be considered quantitative because it requires a correction factor which often results in erroneous values it assumes the organic carbon has an average valence of zero oxidizable and reducible constituents such as chloride ferrous iron and manganese oxides interfere with the results and the errors introduced by interference are potentially greater when the organic carbon content is low at low f values it is not clear that organic carbon is controlling PCE sorption (Schwarzenbach and Westall 1981 Mackay et al 1986 Fetter 1999)

In order to derive a Kd-based retardation factor that is reasonable given the reported f values and the rapid advance of the PCE plume described on pages 4-11 and 4-12 the flushing model requires a bulk density to porosity ratio that is roughly two orders of magnitude higher than the actual ratio for the Hows Corner bedrock (page 4-4) This apparent discrepancy needs to be addressed

Response This comment raises several concerns about the collection and analysis of samples for fraction of organic carbon (f^) the quality of the resulting data and the implications of the use of those data for estimation of the retardation of groundwater contaminant movement Results of bedrock analysis for f were proposed in the TI Evaluation Work Plan for use in conjunction with groundwater contaminant concentrations and aquifer information to estimate cleanup times using the Batch Flushing model It is important to use accurate f values from representative bedrock in the Batch Flushing model in order to obtain reasonable estimates of the remedial time frame Because of the importance of accurate and representative results the TI Investigation field program was designed and conducted both to collect samples representative of the rock volume most likely to be in contact with contaminated groundwater and to analyze them using an appropriate refereed analytical method Five potential methods for evaluating f were identified Of the five methods the Walkey-Black method was selected because it has minimal method interferences and a sufficiently low detection limit as well as a long history of use in agronomy and contamination studies The PRP Group is pleased with the quality of the data obtained from the bedrock samples as represented by their precision and reproducibility

The first part of this comment relates to the determination of fraction of organic carbon (f^) values The several subparts of the first paragraph are addressed individually in items 1 through 5 below The second part of the comment regarding the resultant distribution coefficient (Kd) values is addressed separately as item 6 below

1 There remains doubt that the values used in the flushing model accurately reflect the propensity for PCE to sorb to the bedrock

bull The rock core samples used for f (gocg) analysis were from core immediately adjacent to fractures These rock core samples included the fracture surfaces themselves and rock core extending back less than 1 cm from the fractures Therefore the foe data reported in the TI Evaluation represents the f of bedrock through which groundwater will travel and to which PCE will adsorb Based on the careful selection of sample locations and the

Response to EPA Comment 3 050205doc 1 of 11 Woodard amp Curran (211941)

number of samples collected we are confident that the measured f values are representative of the f at points of contact for PCE with the bedrock it is these f values that determine the propensity of PCE to sorb to the bedrock

bull The samples of rock core collected for analysis of f originated from 19 different locations varying in depth from 11 to 90 feet Therefore it is very unlikely that the rock core samples were contaminated with extraneous organic carbon from above ground

2 The foc values presented in Appendix B may be unrealistically high because the bedrock samples may have contained organic carbon that was unavailable for sorption

bull As noted in response 1 the f data reported in Appendix B represents organic carbon primarily associated with the surface of fractures in the bedrock through which groundwater is most likely to travel Therefore it is this organic carbon that the contaminants in the groundwater will come in contact with and adsorb to in the fractured rock at the site

bull The chemical oxidation agents used in the Walkey-Black method oxidize the easily oxidizable organic carbon in the medium and the foe is calculated from the quantity of the agent consumed Therefore it is unlikely that the analysis of the bedrock samples measured organic carbon that was unavailable for sorption

3 The reported foc values are only qualitative estimates of the organic carbon content of the bedrock samples

bull The reported f values are accurate quantitative results Schumachers review of Methods for the determination of total organic carbon (TOC) in soils and sediments (NCEA-C-1282 EMASC-001 April 2002) identifies the Walkley-Black method which was used to analyze the reported foc values as the reference method for comparison to other methods for analyzing total organic carbon

bull Schumacher also points out that if anything the WalkJey-Black method may underestimate the total organic carbon in a sample due to possible incomplete oxidation of organic carbon Usually the incomplete oxidation of total organic carbon in environmental samples is corrected for by multiplying the measured foe by 130 (Walkley amp Black 1934 Schulte 1995)

bull When the f data in the TI Evaluation Report (WampC 2005) Appendix B (attached) are analyzed statistically the standard deviation of the f for the 19 samples analyzed is 174 of the average f Given this standard deviation the 95 confidence interval for this data ranged from a low of 000123 gocg to a high of 000253 gocgm

The labs Method of Detection Limit (MDL) for the f measured using the Walkley-Black method is 00001 gocg Therefore the average (000188 gocg) the mean (000185 gocg) and geometric mean (000187 gocg) of the f values for the rock core at Hows Corner are all statistically significantly greater than the MDL of the Walkley-Black method

In addition to the aforementioned statistical analysis of the foe data triplicate samples (n = 3) from the same rock core (including one sample from the 19 rock core samples) were

Response to EPA Comment 3 050205doc 2 of Woodard amp Curran (211941)

analyzed for their f to determine the repeatability of the Walkley-Black method The average the mean and the geometric mean of the f values of these replicate samples was 000162 gocg 000150 gocg and 000159 gocgm respectively The standard deviation of these measurements was 000039 gocg

4 The Walkley and Black organic carbon measurement method is quick and simple but the results obtained cannot be considered quantitative because it requires a correction factor which often results in erroneous values it assumes the organic carbon has an average valence of zero oxidizable and reducible constituents such as chloride ferrous iron and manganese oxides interfere with the results and the errors introduced by interference are potentially greater when the organic carbon content is low at low foc values it is not clear that organic carbon is controlling PCE sorption (Schwarzenbach and Westall 1981 Mackay et al 1986 Fetter 1999)

bull Schumachers review (NCEA-C-1282 EMASC-001 April 2002) of the Walkley-Black method identifies several potential problems with this analytical method that could occur if the analytical lab is not familiar with the nuances of the chemistry associated with this method Interestingly Schumachers review neglected one of the more important analytical steps required to avoid errors in quantifying f in samples where there might beNAPL

It is absolutely critical to eliminate any NAPL from rock core samples prior to using the Walkley-Black method to measure foe in such samples This was done by the lab (PTS Laboratories) that measured the foe in the rock core samples from Hows Corner The lab used the Dean-Stark method (solvent extraction) to remove all hydrocarbons (including PCE and other NAPLs) from the sample (PTS Laboratories) This extraction method does not interfere with the subsequent analysis of the natural organic carbon associated with the rock core

Subsequently the samples were dried at 150degC to a constant weight (normally 16 hours) This latter step oxidizes all inorganic minerals including ferrous bearing minerals to ferric oxides and precludes their interference during the oxidation of the samples with chromic acid This procedure completely eliminates any positive bias in the reported foc

data that might have occurred due to the presence of ferrous ions and other reduced minerals

bull As noted in Response 3 the incomplete oxidation of total organic carbon results in an underestimate of the f and is corrected for by multiplying the f by a correction factor of 130 (Walkley amp Black 1934 Schulte 1995) The fx data reported in the TI Evaluation was corrected accordingly by using this correction factor

bull Excess chloride (Cl~) in percent weight quantities as found in saline soils may interfere with the quantitative titration of reduced chromium (Walkley 1947) However given that the primary rock type at the Hows Corner site is phyllite it is highly unlikely that there was sufficient chloride in the rock core samples for this to occur

bull Manganese oxides may also interfere with the analysis of f through competing with the dichromate ion for any oxidizable carbon (Walkley 1947) However in such cases the reported f would be an underestimate of the f present in the rock core Walkley (1947)

Response to EPA Comment 3 050205doc 3 of 11 Woodard amp Curran (211941)

4

reported that in the case where the ratio of MnO2 to carbon is 85 to 1 the error in the carbon determinations would only be 0 to 6 percent

It may also be useful to compare the analysis of total organic carbon in a geologic matrix that contains high levels of manganese using EPA method 9060 to the Walkley-Black method Table 1 summarizes data provided by one of the PRPs that compares the analysis of total organic carbon in a geologic matrix that contains approximately 02 wgt manganese (approximately 03 wgt manganese oxide)

Table 1 Comparison of total organic carbon measured using the EPA- 9060 method and the Walkley-Black method

Laboratory EPA-9060 Method Walkley-Black Method A Ave 00226 gocg Not analyzed

Stdev 000251 gocg n = 5

B Ave 002219 gocg Ave 002050 gocg Stdev = 000316 gocg Stdev =000971 gocg

n= 10 n = 10

The similarity in the total organic carbon concentrations measured by these two different methods provides further confidence that the Walkley-Black method is a viable method for analysis of total organic carbon in the presence of manganese equivalent to at least 10 by weight of the total organic carbon

5 The Walkley and Black organic carbon measurement at lowf^ values it is not clear that organic carbon is controlling PCE sorption (Schwarzenbach and Westall 1981 Mackay et al 1986 Fetter 1999)

bull Schwarzenbach and Westalls (1981) paper states that f values of less than 0001 gocg should not be used in combination with Kow (octanol-water partition coefficients) values to calculate K^ values (solid phase partition coefficients) values for a specific contaminant It should be noted that the TI Evaluation did not use the f data to calculate the KQC from the Kow Instead as requested by the EPA the measured KOC value for PCE was used to calculate the retardation factor for this contaminant

bull Schwarzenbach et al (2003) stated more recently that Even at very low f values (ie foe = 0001 kgoc - kg1 solid) sorption to the organic components of a natural sorbent may still be the dominant mechanism in defining the adsorption of organic compounds to geological matrices

bull In 1985 M Piwoni from the US EPA Robert S Kerr Environmental Research Laboratory published a paper (Banerjee et al 1985) that showed that for very hydrophobic molecules TOC content of the sorbent will control sorption down to levels of organic carbon that defy quantitation Contaminants such as the PCE found in the groundwater at Hows Corner are in this category of compounds

Given the aforementioned reasons the f values reported in the TI Evaluation are accurate within the noted statistical limitations and will have a predictable impact upon the retardation of PCE during groundwater transport

Response to EPA Comment 3 050205doc 4 of 11 Woodard amp Curran (211941)

6 In order to derive a Kd-based retardation factor that is reasonable given the reported foc

values and the rapid advance of the PCE plume described on pages 4-11 and 4-12 the flushing model requires a bulk density to porosity ratio that is roughly two orders of magnitude higher than the actual ratio for the Hows Comer bedrock (page 4-4) This apparent discrepancy needs to be addressed

The apparent discrepancy of bulk density to porosity ratios is most likely due to the fact that the Batch Flushing Model was originally developed for a porous medium and is not directly applicable to fractured bedrock As stated in Appendix C (page C-4) of the Draft Technical Impracticability Evaluation Report in order to use the Batch Flushing Model to describe the transport of contaminated groundwater in fractured bedrock where the matrix porosity is insignificant it is more appropriate to use a fracture surface area to void space ratio to calculate the retardation factor (R) than a bulk density to porosity ratio (Freeze amp Cherry 1979)

Since it is impractical to determine the actual surface area to which contaminants can adsorb the Batch Flushing Model was used with two simplifying assumptions bull The Kd was calculated from the f and the K^ bull The bulk density to porosity ratio term in the Batch Flushing Model was constrained to range

from 4 to 10 the typical range of such ratios in porous media (Freeze amp Cherry 1979)

If one uses site specific bedrock bulk density and porosity values the bulk density to porosity ratio is several orders of magnitude greater (specifically 273 gcc bullbull 000165 (dimensionless) = 1654 gcc) than the range of ratios of 4 to 10 used in the Batch Flushing Model in the Draft Technical Impracticability Evaluation Report Constraining the bulk density to porosity ratio within the range of ratios of 4 to 10 results in significantly lower R value than would be obtained using specific bedrock bulk density and porosity values

In summary in bedrock where fractures are the primary porosity the bulk density to porosity ratio can vary considerably and will be a function of the number of fractures and the fracture aperture The calculated bulk density to porosity ratio will be inversely proportional to the porosity This means that in fractured rock with limited fracturing and smaller porosity the calculated bulk density to porosity ratio is greater and will result in a greater calculated retardation factor than in bedrock with more extensive fracturing and greater porosity Consequently the calculated retardation factor will be greater for bedrock with less surface area available for sorption than bedrock with greater surface area for sorption This is contrary to what actually occurs

4 Response to EPA Comment 3 050205doc 5 of 11 Woodard amp Curran (211941)

m

REFERENCES

Banerjee P MD Piwoni K Ebeid (1985) Sorption of organic contaminants to a low carbon subsurface core Chemosphere _14 1057-1067

Freeze RA JA Cherry (1979) Groundwater Prentice Hall Englewood Cliffs NJ pg 604

PTS Laboratories wwwptsgeolabscompdf files3TOCnotepdf

Schulte EE (1995) Recommended soil organic matter tests in Recommended Soil Testing Procedures for the Northeastern United States Northeastern Regional Publication No 493 Chapter 8

Schwarzenbach RP J Westall (1981) Transport of nonpolar organic compounds from surface water to groundwater Laboratory sorption studies Environ Sci Tech 15 1360-1367

Schwarzenbach RP PM Gschwend DM Imboden (2003) Environmental Organic Chemistry Wiley-Interscience pg 292 408 amp 412

Walkley A LA Black (1934) An examination of the Degtjareff method for determining soil organic matter and a proposed modification of the chromic acid titration method Soil Science 37 29-38

Walkley A (1947) A critical examination of a rapid method for determining organic carbon in soils - effect of variations in digestion conditions and of inorganic soil constituents Soil Science 63251-264

Woodard amp Curran Inc (WampC) 2005 Draft Technical Impracticability Evaluation Hows Corner Superfund Site Plymouth Maine January 2005

Response to EPA Comment 3 050205doc 6 of Woodard amp Curran (211941)

LIST OF ATTACHMENTS (Response to Comment 3)

Appendix B to Draft Technical Impracticability Evaluation Measurement of foe at Hows Corner (4 pages)

m

Response to EPA Comment 3 050205doc 7 of 11 Woodard amp Curran (211941)

Appendix B Measurement of foe of Rock Core at Hows Corner

There are two general approaches to measure the fraction of organic carbon (foe) in rock cores

bull Measurement of weight loss by ignition of organic matter bull Chemical oxidization of organic carbon to carbon dioxide and either

subsequent quantification of the oxidant used for the reaction or quantification of the carbon dioxide produced during this oxidation process

The weight loss method is subject to errors caused by volatilization of substances other than organic materials such as water hydroxides and mineral carbonates Quantification of foe by the weight loss method is particularly sensitive to the presence of carbonates in rock cores There are however weight loss methods that are designed to differentiate between organic carbon and the aforementioned interfering materials but they require considerable care and are less accurate at low foe values Hence the weight loss method was not well suited for measuring the foe of the rock core from Hows Corner

The chemical oxidation of organic carbon is much better suited for quantifying organic carbon in rock cores such as those from Hows Corner This method uses a strong chemical oxidant to oxidize organic carbon to carbon dioxide and then measures either the chemical oxidant used to oxidize the organic carbon or the quantity of carbon dioxide produced In addition this general approach is not subject to interference by volatilization of other constituents of the rock core

There are at least two such chemical oxidation methods

bull The method of Baccini which was described by Schwarzenbach amp Westall (1981) first acidifies the sample to eliminate interference by carbonates Then a strong oxidant is used to chemically oxidize the organic carbon to carbon dioxide The resulting carbon dioxide is subsequently reduced to methane and quantified using a flame ionization detector Unfortunately this method has not been described in detail in a referred journal Hence it is would not have been appropriate to use to characterize the foe in the Hows Corner rock core

bull The more commonly used method to quantify foe in rock core is the Walkley-Black method (1934) This method is preferred for RBCA and DODDOE projects and by the oil industry

The Walkley-Black method uses an excess of chromic acid to oxidize (digest) organic matter to carbon dioxide The remaining chromic acid that was not consumed during the oxidation of the organic carbon is then quantified by titration with ferrous sulfate The difference in chromic acid prior to and after the oxidation of the organic carbon represents the total chromic acid used to oxidize

Hows Corner TI Evaluation Page 1 January 13 2005 Appendix B

the organic carbon in the sample The latter can be calculated using the chemical stoichiometry of the reaction

The Walkley-Black method is very accurate for samples that contain less than 2 organic carbon matter The minimum detection limit (MDL) for the Walkley-Black method is 100 mgkg or an foe of 0001

Given the rock core at Hows Corner was expected to contain less than 2 organic carbon the Walkley-Black method was used to measure the foe from 19 different rock core samples collected from varying depths ranging from 11 to 90 feet

Table 1 provides a statistical summary of the aforementioned data

Table 1 Statistical summary of foe data from rock cores collected at varying depths

Statistical Parameter Calculated Value foe Minimum Detection Limit (MDL) 00010 Number of samples analyzed (n) 19 Average foe 00019 Median foe 00019 Geometric Mean foe 00019 Standard deviation of foe measurements 000033 Relative standard deviation 174 -+ 95 Confidence intervals 00012 to 00025

The data in Table 1 shows the following

bull The foe from the Hows Corner rock cores are statistically greater than the MDL of the Walkley-Black analytical method

bull The average and median values for the foe of the Hows Corner rock cores from varying depths are nearly identical indicating that there is little variability in the foe values in the source zone at the site

bull The standard deviation of these measurements is 000033 which is 174 of the average foe

bull The 95 confidence intervals of the foe of the rock core at Hows Corner are 00012 to 00025

The foe was also analyzed from three separate samples taken from the same rock core at a depth of 55 feet (Only one of these samples was included in the data summarized in Table 1) Table 2 shows the statistical repeatability of this type of analysis

Hows Corner TI Evaluation Page 2 January 13 2005 Appendix B

Table 2 Repeatability of analysis of foe from one rock core at 55 feet in depth

Statistical Parameter Calculated Value Number of samples analyzed (n) 3 Average foe 00016 Median foe 00015 Geometric Mean foe 00016 Standard deviation of foe measurements 000039 Relative standard deviation 240 -+ 95 Confidence intervals 00008 to 00024

The data in Table 2 shows the following

bull The percent relative standard deviation of these three analyses of foe from the same rock core at Hows Corner is 24

bull The 95 confidence interval of the foes measured in this particular rock core at Hows Conrer is 00008 to 00024

These results show that there is good repeatability in using the Walkley-Black method for analysis of the foe in the rock core at Hows Corner

References Schwarzenbach amp Westall (1981) Transport of nonpolar organic compounds from surface water to groundwater Laboratory sorption studies Environ Sci Tech 15 1360-1367

Walkley A I A Black (1934) An examination of Degtjareff method for determining soil organic matter and a proposed modification of the chromic acid titration method Soil Sci 37 29-37

Hows Corner Tl Evaluation Page S January 13 2005 Appendix B

Woodard and Curran PTS Laboratories PTS File No 34618

ORGANIC CARBON DATA (METHODOLOGY WALKLEY-BLACK)

PROJECT NAME PROJECT NO

SAMPLE ID

203-chip-13 203-chip-23 203-chip-27 203-chip-38 203-chip-42 203-chip-47 203-chip-52 203-chip-58 203-chip-69 203-chip-82 207-chip-11 207-chip-19 207-chip-24 207-chip-29 207-chip-35 207-chip-45 207-chip-55 207-chip-87 207-chip-90

207-chip-55 55-MS

55-MSMSD

Hows Corner NA

DEPTH ft

13 23 27 38 42 47 52 58 69 82 11 19 24 29 35 45 55 87 90

55 NA NA

MATRIX

Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip

Average Median

Geometric Mean Standard Deviation Relative Std Dev

+- 95 Confidence Interval n

Rock Chip Rock Chip Rock Chip

Average Median

Geometric Mean Standard Deviation Relative Std Dev

+- 95 Confidence Interval n

FRACTION ORGANIC CARBON

(gg)

170E-03 185E-03 185E-03 170E-03 240E-03 190E-03 230E-03 180E-03 170E-03 115E-03 195E-03 220E-03 220E-03 235E-03 135E-03 190E-03 205E-03 175E-03 160E-03

188E-03 185E-03 185E-03 327E-04

1739 123E-03 to

19

205E-03 130E-03 150E-03

162E-03 150E-03 159E-03 388E-04

2402 840E-04 to

3

2532E-03

2393E-03

Hows Corner Tl Evaluation Appendix B January 13 2005

Response to EPA-DEP Comment 4 Dated March 31 2005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

EPA-DEP Comment 4

Comment 4 Distribution of contaminants First the TI report seems based on the assertion that there is DNAPL at the source area yet it also appears to represent that the source area is small and the bedrock below 85 is competent (or less fractured) and less impacted by the release of contaminants Some of the confusion may result from using most recent data when that data is from several different sampling events over several years and there is no discernible difference in concentrations between shallow and deep bedrock or as in Section 421 where generally decreased generally increase generally similar and similar concentrations in four consecutive sentences leads to a muddled picture of the contaminant distribution

Second the report asserts that the distribution of contaminants over the entire plume has not changed with time but fails to support this conclusion with data again relying on data that is from different sampling dates for one composite representation

Response The likely presence of dense non-aqueous phase liquid (DNAPL) at the Hows Corner Site and the determination that the source area is small are not mutually exclusive and both are conclusions drawn from information obtained during field investigations The presence of DNAPL in the source area is based on the elevated concentrations of volatile organic compounds (VOCs) detected in the groundwater (WampC 2001 WampC 2002) The conclusion that the source area is small is based on the area in which VOCs in groundwater have been detected at concentrations that are considered to be indicative of the presence of DNAPL nearby Similarly the conclusion that fracture frequency decreases at depths greater than approximately 50 to 85 feet below ground surface was based on field observation during the RI field work The fact that zones with observed fractures exhibited higher hydraulic conductivities than zones without fractures coupled with the decreasing frequency of observed fractures with depth led to the conclusion that the hydraulic conductivity of the bulk rock decreases with depth

The most recent data from all wells were used to provide the maximum VOC data set size During the RI all of the previously-existing and then newly-installed monitoring wells were sampled along with several residential wells The RI sampling included up to 48 monitoring wells Subsequent to the RI and prior to the TI three rounds of monitoring were conducted to verify that the plume was stable 15 monitoring wells were sampled during each of the three rounds During the TI field investigation 29 wells were sampled for VOCs The sampled wells included all of the newly-installed wells and a subset of wells installed during the RI for a total of 29 monitoring wells By using most recent data VOC results from 53 monitoring wells were included in the evaluation (see table labeled Sampling Events for listing of monitoring wells) This approach was selected because there generally was little variation in the data from a particular location between years This is borne out by the attached individual plots of VOCs detected in shallow bedrock and deep bedrock for the Pre-ROD (December 1999January 2000) and Supplemental (May 2000) sampling events and for June 2001 January 2002 and April 2003 sampling events The Pre-ROD and Supplemental plots are similar to the subsequent plots from the 2001 2002 and 2003 sampling events

In addition to maps showing the spatial distribution of VOC data at a given time trend plots of the data from a particular location through time (attached) indicate that since the RI concentrations generally have been stable or have decreased Together the maps and trend plots and the data from which they were developed indicate that the distribution of contaminants over the entire plume has not changed appreciably with time

Response to EPA Comment 4 050305doc 1 of 26 Woodard amp Curran (211941)

REFERENCES

Woodard amp Curran Inc (WampC) 2001 Final Remedial Investigation Report Hows Corner Superfund Plymouth Maine July 2001

Woodard amp Curran Inc (WampC) 2002 Final Feasibility Study Report - Non-Source Area Groundwater Hows Corner Superfund Site Plymouth Maine Hows Corner Superfund Plymouth Maine July 2002

Response to EPA Comment 4 050305doc 2 of 26 Woodard amp Curran (211941)

LIST OF ATTACHMENTS (Response to Comment 4)

Table - Sampling Events 1999 - 2004 (2 pages)

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater Pre-ROD Sampling Event

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater Pre-ROD Sampling Event

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater Supplemental Sampling Event

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater Supplemental Sampling Event

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater June 2001

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater June 2001

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater January 2002

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater January 2002

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater April 2003

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater April 2003

Figure - Concentration Trends - Non-Source Area Wells MW-1B and MW-3B

Figure - Concentration Trends - Non-Source Area Wells MW-13DB and MW-16DB

Figure - Concentration Trends - Non-Source Area Wells MW-16IB and MW- 108D

Figure - Concentration Trends - Non-Source Area Wells MW-108S and MW-112D

Figure - Concentration Trends - Non-Source Area Wells MW-112S and MW-114D

Figure - Concentration Trends - Non-Source Area Wells MW-114S and MW-115D

Figure - Concentration Trends -Source Area Wells MW-2DB and MW-2IB

Figure - Concentration Trends -Source Area Wells MW-102S and MW-103D

Figure - Concentration Trends -Source Area Wells MW-103S and MW-104D

Figure - Concentration Trends -Source Area Wells MW-104I and MW-106D

Figure - Concentration Trends -Source Area Wells MW-106S

Response to EPA Comment 4 050305doc 3 of 26 Woodard amp Curran (211941)

I I

El I

II I I 1 I

I

i

Event Baseline Case ID WC-01 WC-01

Well Date Aug-99 Oct-99 LOT10 1 LOT1-1 1 LOT11-4 LOT14 1 LOT15 1 LOT15-1 1 LOT16 1 LOT16-1 1 LOT17 1 LOT18 1 LOT19 1 LOT2 LOT20 1 LOT21-10 1 LOT21-11 1 LOT21-12 1 LOT21-13 1 LOT21-14 1 LOT21-2 1 LOT21-5 1 LOT21-7 LOT21 -8 1 LOT21-9 1 LOT23 1 LOT24 1 LOT28-1 1 LOT28-2 1 LOT28-3 1 LOT28-4 1 LOT28W 1 LOT30 1 LOT30-1 1 LOT30-2 1 LOT30-3 1 LOT30-4 1 LOT30-5 LOT31 LOT35 1 LOT41 1 LOT42-1 1 LOT43-1 1 LOT43-4 1 LOT6-1 1 LOT67 1 LOT6-7 1 LOT6-8A 1 LOT6-8B 1 LOT80-1 1 LOT82 1 MW-101D MW-1011 MW-101S MW-102D MW-102S MW-103D MW-103S MW-104D MW-1041 MW-104S MW-105D MW-106D

Groundwater Sampling Location Summary 1999 - 2004xls

Sampling Events 1999-2004

Hows Corner Superfund Site Plymouth Maine

Supplemental 2001 2002 2003 Pumping 2004 Pre-ROD Rl Sampling Sampling Sampling Test Sampling WC-03 WC-09 WC-25 WC-30 WC-42B WC-56 WC-58 Dec-99 May-00 Jun-01 Jan-02 Apr-03 Sep-04 Sep-04

1

1 1 1

1 1 1 1 1

1 1

1

1 1

1 1 1

1 1 1 1 1

1

1 1

1 1 1 1

1

1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

Sampling Events 1999-2004

Hows Corner Super-fund Site Plymouth Maine

Supplemental 2001 2002 2003 Pumping Event Baseline Pre-ROD Rl Sampling Sampling Sampling Test

Case ID WC-01 WC-01 WC-03 WC-09 WC-25 WC-30 WC-42B WC-56

ll

Well Date Aug-99 Oct-99 Dec-99 May-00 Jun-01 Jan-02 Apr-03 Sep-04 MW-106S 1 1 1 1 1 MW-107D 1 1 MW-108D 1 1 1 1 1 MW-108S 1 1 1 1 1 MW-110D 1 1 MW-111D 1 1 MW-112D 1 1 1 1 1 MW-112S 1 1 1 1 1 MW-113D 1 1 MW-114D 1 1 1 1 1 MW-114S 1 1 1 1 1 MW-115D 1 1 1 1 1 MW-12DB 1 1 1 MW-12SB 1 1 1 MW-13DB 1 1 1 1 1 1 MW-13SB 1 1 1 MW-14DB 1 1 MW-14SO 1 1 MW-15DB 1 1 1 MW-15SB 1 1 1 MW-16DB 1 1 1 1 1 1 MW-16IB 1 1 1 1 1 1 MW-16SO 1 1 MW-17DO 1 1 1 MW-17SO 1 1 1 MW-1B 1 1 1 1 1 1 MW-203D MW-203S MW-204D MW-204S MW-205 MW-206D

I MW-206S MW-2DB 1 1 MW-2DDB 1 1 MW-2IB 1 1 1 1 1 1 MW-3B 1 1 1 1 1 1

I MW-4O 1 1 1 MW-5B 1 1

II MW-6DB 1 1 1 MW-6SB 1 1 1 MW-8DB 1 1 1 MW-8SB 1 1 1

II PW-207 1 SEEP-1 1 SUBTOTAL - RESIDENTIAL 44 25 0 2 0 3 0 SUBTOTAL - MONITORING 22 48 41 15 15 15 1

Total 3 66 73 41 17 15 18 1

I Included in most recent data

I Notes 1 - Overburden well not included in most recent data for plotting

2 - Tetrahydrofuran and 2-Butanone were the only two compounds detected in this well and are thought to be the result of well repair not included in most recent data for plotting

3 - Not included in most recent data for plotting

2004 Sampling

WC-58 Sep-04

1

1 1

1 1

1 1 1

1

1 1

1 1 1 1 1 1 1 1 1

1 1

1

0 29

29

Groundwatef Sampling Location Summary 1999 - 2004xls

I

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

monitoring well Figure 4-14 total VOC contour (ugl) - December 1999January 2000 Distribution of Total VOCs in

Note SW-113 is located downstream of SEEP-1 Shallow Bedrock Groundwater total concentration of detected VOCs ND= not detected these two locations were sampled during the Pre-ROD Sampling Event

Baseline Sampling Event in OctoberNovember 1999 Hows Corner Superfund Site Surface Water Sampling Location A Plymouth Maine Seep Sampling Location laquo- WOODARD ampCURRAN

995037wipri reportepa ri interim final feb 2001cadd drawingsfinalfig 4-14

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

0 300 600 I

FEET

Q residential well Figure 4-16 monitoring well Distribution of Total VOCs in

Deep Bedrock Groundwater total VOCs contour (ugl) Pre-ROD Sampling Event

active residential wells with lot number Hows Corner Superfund Site 2deg42deg Plymouth Maine total concentration of detected VOCs ND= not detected WOODARD ampCURRAN Enyinaaring bull Science bull Operations bull

995037wipri reportepa ri interim final feb 2001cadd drawingsfinalfig4mdash16

PLYMOUTH POND

PLYMOUTH POND

1 628Tl7MW-2bB 12135

PLYMOUTH POND

monitoring well Figure 4-20

V total VOC contour (ugl) - June 2000 Distribution of Total VOCs in Shallow Bedrock Groundwater

| 34 | total concentration of detected VOCs ND= not detected NA = not analyzed Supplemental Sampling Event Note SW-113 is located downstream of SEEP-1 Hows Corner Superfund Site

Surface Water Sampling Location these two locations were sampled during the Plymouth Maine Baseline Sampling Event in OctoberNovember 1999 Seep Sampling Location WOODARD amp CURRAN

Engineering bull Science - Operations bull 995037wipri reportepa ri interim final feb 2001 cadd drawingsfinalfig 4-20

residential well Figure 4-22 Distribution of Total VOCs in

monitoring well Deep Bedrock Groundwater

total VOCs contour (ugl) Supplemental Sampling Event

Hows Corner Superfund Site

total concentration of detected VOCs ND= not detected NA = not analyzed Plymouth Maine

WOODARD amp CURRAN

995037wipri reportepa-ri interim final feb 2001cadd drawingsfinalfig 4-22 Engineering bull Science - Operations bull

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

FEET

Shallow Monitoring Well

Deep Monitoring Well

C Detected Concentration ND = Not Detected Figure 1-XS Distribution of Total VOCs in Shallow Bedrock Groundwater

Pumping Well

17-Acre Property Boundary Concentration Contour (ugl)

June 2001 Hows Corner Superfund Site

Plymouth Maine WOODARDampCURRAN

-i^rhvj bull Scbncn bull Operations bull 211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0601 dwg04-20-05

PLYMOUTH POND Hopkins Road V

O

PLYMOUTH POND

PLYMOUTH POND

o

0 300 600 mdashfa FEET

Shallow Monitoring Well bull bull - 17-Acre Property Boundary Figure 1-XD

Deep Monitoring Well 1 I Detected Concentration ND = Not Detected Distribution of Total VOCs in Deep Bedrock Groundwater

-mf- Pumping Well June 2001 Residential Well Hows Corner Superfund Site

Plymouth Maine i h Surface Water Sampling Point

g WOODARD ampCURRAN _ ^ _ ^ _ _ yen_ rj i|Hlaquorlny bull Science bull Opt

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0601 dwg04-20-05

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PLYMOUTH POND

PLYMOUTH POND

Shallow Monitoring Well

Deep Monitoring Well

Detected Concentration ND = Not Detected Figure 1-YS Distribution of Total VOCs in Shallow Bedrock Groundwater

Pumping Well

17-Acre Property Boundary Concentration Contour (ugl)

January 2002 Hows Corner Superfund Site

Plymouth Maine WOODARD amp CURRAN Engineering Science- Operations bull

211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0102dwg04-20-05

PLYMOUTH POND

PLYMOUTH POND

Site Pand^ laquoum-laquoBTuitaraquo tLV

vVlf-(

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Shallow Monitoring Well mdashbullbullbull 17-Acre Property Boundary Figure 1-YD - A - Deep Monitoring Well FT Detected Concentration ND = Not Detected Distribution of Total VOCs in

Deep Bedrock Groundwater Pumping Well January 2002 Residential Well Hows Corner Superfund Site

Plymouth Maine Surface Water Sampling Point

WOODARD ampCURRAN Engineering Sciencs- Operations bulli Si

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0102dwg04-20-05

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PLYMOUTH POND

PLYMOUTH POND j A O-shy

Shallow Monitoring Well E Detected Concentration ND = Not Detected Figure 1-ZS Distribution of Total VOCs in

Deep Monitoring Well Shallow Bedrock Groundwater

Pumping Well Hows Corner

April 2003 Superfund Site

17-Acre Property Boundary Plymouth Maine Concentration Contour (ugl) r WOODARD ampCURRAN

Engineering bull Science bull Operations bull 211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0403dwg04-20-05

s S pound

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- -

5 PLYMOUTH POND

Jo

FEET

ft Shallow Monitoring Well mdashbullbullmdash 17-Acre Property Boundary Figure 1-ZD Deep Monitoring Well I 1 I Detected Concentration ND = Not Detected Distribution of Total VOCs in

Deep Bedrock Groundwater Pumping Well April 2003

Q) Residential Well Hows Corner Superfund Site Plymouth Maine

(T) Surface Water Sampling Point WOODARD ampCURRAN poundKk EnginawtirKj bull Science - Operations bull

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0403dwg04-20-05

0 Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

B MW-1B

I 12000

PCE

B 10000 Total VOCs

I

i 2000

i 0 Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

c MW-3B

G 2000

1800

B PCE

1600 Total VOCs

1 I I E

il-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

G E

211941

El

I I z E

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Concentration Trends shy Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-13DB

Total VOCs

c i i c o

Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

MW-16DB

30

c i c c I c o

Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99

PCE

Total VOCs

Jul-01 Jul-03

211941

O bi

c Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

I MW-16IB

i 35

3

c Total VOCs

lt- 2 5

0 | gt

o

1 sectI

c c 0 4

Jul-90 Jul-92 Jul-94 Jul-96 Jul-98 Jul-00 Jul-02 Jul-04

I I MW-108D

I 12

PCE 10

Total VOCs c oc 3

E E I 0

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

E 211941

c Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

fi MW-108S

I I 40

PCE 35

Total VOCs

30

I f 26

20 I o

I 15

10

c Dec-99 Dec-00 Dec-01 Dec-02 Dec-03 I 0

I MW-112D

c 35 - imdash

I A3 shyTotal VOCs

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E 1 2

I

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B 1 ^

-i c 3

0 Dec-99 Dec-OO Dec-01 Dec-02 Dec-03

211941

I

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Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-112S

08

PCE

Total VOCs 06

o 04

02

0 Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

MW-114D

o

12000

10000

8000

6000

PCE

Total VOCs

4000

2000

i

ccEIIc

i

i

E

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

211941

Con

cent

ratio

n (

ug

l)

E Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

I MW-114S

E A5000 -- Total VOCs

- 4000

0 3000

2000

i 1000

i n shy

Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

MW-115D

c PCE

Total VOCs

c E

o

C c

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03 I 0

211941

IepoundII

EIEIIGICCIccc

30000

25000

20000

o bullsect 15000 b

o 10000 U

5000

0 Aug-99

25000

20000

5000

0 Aug-99

211941

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-2DB

PCE

Total VOCs

Aug-01 Aug-03

MW-2IB

PCE

Total VOCs

Aug-01 Aug-03

IDIBI

ii EIDIISIBIG C

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-102S

6000

5000 PCE

Total VOCs

4000

O 3000

2000

1000

0 Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

MW-103D

16000

~ 14000 ugt 3- 12000 o

^ 10000

sect 8000

O 6000

4000

2000

PCE

Total VOCs

0Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

211941

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

G MW-103S

I I

ampo

12000

10000

E sectc

S

8000

6000

4000

2000

0Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

G I 6000

MW-104D

i 5000

PCE

Total VOCs

i i c

2000

1000

Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

E I

211941

cIccIG

IIBCccBcIc

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-1041

PCE Total VOCs

a 25000

0 20000

a 15000

10000

5000

0 Jan-OO Jan-01 Jan-02 Jan-03 Jan-04

MW-106D

3000

2500 PCE

Total VOCs

=sect 2000

o bullsect 1500

1000

500

0 Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

211941

c Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

c MW-106S

I PCE

Total VOCs

i

i Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

i

i i i E

C

211941 c

Response to EPA-DEP Comment 5 Dated March 312005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

iiw

EPA-DEP Comment 5

Comment 5 Matrix Diffusion The report as well as other proponents of matrix diffusion suggest that depletion of DNAPL (Section 5112 page 5-15) needs to be achieved While that might be the ideal the goal is to achieve performance standards and that goal may be attainable while there is residual contamination in the rock perhaps even DNAPL globules The low bedrock matrix porosity (page 1-15) the high permeability values (page 4-4) the relative flux of the groundwater (page 5-5) and the decrease in surface area and out of the mainstream pockets (appendix C-4) all suggest that the diffusion out of the rock matrix would be insubstantial relative to the regional flux of groundwater through the Site

Response The TI Evaluation Report does not explicitly consider or rely upon matrix diffusion as a basis for requesting a TI Waiver for a portion of the Hows Corner Site The technical literature provides documentation that matrix diffusion can be a significant process that affects chemical transport and groundwater remediation timeframes in unconsolidated and consolidated media including fractured rock (US EPA 1989 Freeze and Cherry 1979 Pankow and Cherry 1996 Fountain 1998) Back diffusion of contaminants from the matrix porosity of the fractured rock can prolong the time necessary to achieve groundwater cleanup goals particularly for compounds such as PCE for which the cleanup goal is a low concentration It is our expectation that matrix diffusion has occurred at the Hows Corner Site and that back diffusion of PCE from the rock matrix will also occur Although the extent to which matrix diffusion is occurring at the Hows Comer Site has not been determined and that lack of knowledge contributes to uncertainty regarding the cleanup times at the Site the effect of matrix diffusion is to lengthen rather than shorten the time required for remediation

REFERENCES

Fountain JC 1998 Technologies for Dense Nonaqueous Phase Liquid Source Zone Remediation Ground-Water Remediation Technologies Analysis Center Technology Evaluation Report TE-98-02 December

Freeze RA and Cherry JA 1979 Groundwater Prentice-Hall Inc Englewood Cliffs NJ 07632 p 410-412

Pankow J F and Cherry J A 1996 Dense Chlorinated Solvents Waterloo Press Portland OR 97291-1399 p 67-88

US EPA 1989 Transport and Fate of Contaminants in the Subsurface EPA6254-89019 p 17-18

Response to EPA Comment 5 050305doc 1 of 1 Woodard amp Curran (211941)

WOODARD amp CURRAN Maine Massachusetts New Hampshire Connecticut Florida Operational offices across the US 1-800-426-4262 www woodardcurran com

Page 5: SDMS DocID 251749 - Records Collections · 2020-06-13 · CORPORATE OFFICES: Maine, Massachusetts, New Hampshire, Connecticut New, York, Florida Engineering • Science • Operations

EPA-DEP Comment 1

Comment 1 Institutional Controls It is recognized by all parties that institutional controls are and will continue to be an integral part of the remedy for the site Having said that the agencies need to have a presentation of the institutional controls including a copy of the town ordinance regarding the ICZ a figure showing the ICZ and the properties with restrictive covenants a table of the 57 properties identified within the ICZ by tax lot number and owners name location of all private wells whether for drinking water residential or agricultural purpose the status of any well abandonment efforts as well as a discussion as how these controls will be monitored

As this information may change over time such as through sale of property or sub-division of a property or well abandonment the agencies believe that presentation of the institutional controls information can best be accomplished with a stand-alone document that can be periodically updated rather than incorporated into the TI report Then as with other documentation such as the RIFS relevant information from the Institutional Control report can be summarized in the TI report

Response The Hows Corner PRP Group will prepare a document that describes the institutional controls for the Site The following items will comprise the document

bull a map of the Site vicinity showing the Institutional Control Zone (ICZ) boundary and properties with restrictive covenants

bull a tabulation of properties located within the ICZ organized by tax lot number and owners name and listing for each property

o the number of connections provided or to be provided to the property o the presence of private wells o the status of well abandonment for the property

bull a copy of the town ordinance regarding the ICZ bull an example of the restrictive covenant for the properties located within the ICZ and bull a discussion of the monitoring program for the institutional controls

The PRPs agree that a stand-alone document is appropriate for the reporting purposes requested by the comment The document can then be updated at periodic intervals mutually agreed upon by the PRPs and the EPA and DEP The status of the PRPs efforts regarding institutional controls and upgrades to the Plymouth water system is summarized in Section 123 of the Draft Technical Impracticability (TI) Evaluation Report Figure 1-2 of the TI Report is a map showing improvements to the Plymouth water system as well as properties that are connected to the system The information in the TI Report will be updated prior to submittal of the final report

Response to EPA Comment 1 050205doc 1 of 1 Woodard amp Curran (211941)

m

Response to EPA-DEP Comment 2 Dated March 312005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

EPA-DEP Comment 2

Comment 2 As discussed in our January meeting the results of the TI field work and their interpretation need to be presented in the TI report Listed below are some specific comments on this with the goal being a discussion of how the site conceptual model and site modeling were revised as a result of the 2004 field work

a analysis of the aquifer test to include a figure presenting the drawdown observed in each monitoring well at the end of the aquifer test The horizontal hydraulic gradient should not be included since this method tends to accentuate the anisotropy Two figures may be needed one for shallow bedrock and one for deep bedrock an evaluation of the appropriateness of the Cooper-Jacob (CJ) method for analyzing the aquifer test data including a comparison of the pattern of observed drawdown to the pattern of fracture orientations determined from the borehole geophysics confirmation that u lt 001 and that calculated values for T and S are similar for several observation wells an interpretation of the change in slope on the CJ plots near the end of the aquifer test the recovery data should be evaluated since it may provide insight as to why the slopes changed the marked increase in slope near the end of the test strongly suggests that a barrier (ie no flow) boundary was encountered and if a boundary was encountered T and S need to be calculated from the pre-boundary portions of the CJ plots It may be appropriate to analyse the aquifer test data using Theis as well as the Moench dual porosity model (both analysis methods are available in Aqtesolv pumping test modeling software) so that all parties have confidence in the transmissivity and storativity numbers derived from the CJ analysis b numerous bedrock borings (including angled holes) were drilled during the most recent field investigation yet no summary of the findings or the geophysical logging or packer test and sampling results have been provided c have any input parameters been changed in the flow transport and batch-flushing models as a result of the 2004 fieldwork If so which ones and why were the changes made (ie justify the changes)

Response The objective of the pumping test conducted at the Hows Corner Site during September 2004 was to observe the response of the groundwater system to pumping for use in refining the site conceptual model The refined site conceptual model would in turn be used to recalibrate the flow model and aid in the design of the hydraulic containment system being constructed under the authority of the AOC for the RD

The results of the pumping test are illustrated by plots of the drawdown at the end of the test The enclosed three drawdown plots (shallow bedrock deep bedrock and combined) represent the change in water level at the end of the test from the initial pre-test water level The shallow bedrock figure shows a northeast-southwest trending ellipsoidal area of drawdown that extends approximately 2000 feet along the major axis and approximately 800 feet along the minor axis The northeast-southwest orientation of the drawdown ellipse is consistent with the orientation of likely water-bearing fractures as identified from geophysical logging during the TI investigation The deep bedrock figure and combined figure also show ellipsoidal areas of drawdown with similar orientation A secondary axis with a more northerly orientation is evident on the figures showing drawdown in deep bedrock and in combined shallow and deep bedrock The maximum drawdown measured in shallow bedrock was 29 feet at MW-2EB The maximum drawdown measured in deep bedrock was 54 feet at the pumping well (PW-207) The drawdown ellipse is

Response to EPA Comment 2 050205doc 1 of 24 Woodard amp Curran (211941)

approximately coincident with the location of the modeled capture zone as presented on Figure 3shy1 of the TI Evaluation report

The enclosed three potentiometric surface maps (shallow bedrock deep bedrock and combined) represent the water surface elevations measured at the end of the test which was 72 hours or three days after it began All three maps show the presence of the groundwater high located in the southeast portion of the 17-acre property This high area shows relatively little relief but with the exception of the measurements at MW-2DDB which shows anomalously high water levels the central area of the high is at lower elevation than the perimeter The measurements at MWshy2DDB are hypothesized to result from water that is unable to drain rapidly enough to equilibrate with the rest of the formation

The pumping test data initially were analyzed using the Cooper-Jacob method for the late test data The results of this analysis are summarized in the table entitled Pumping Test Analytical Results It was recognized that because the aquifer is not uniform isotropic and infinite in areal extent the assumptions on which the underlying Theis equation is based were not met and because of the length of the test the criteria for use of the Cooper-Jacob of analysis were not explicitly met We recognize that the complexity of the hydrogeologic characteristics of the formation would be a significant limitation if the calculated values from the pumping test analysis were to be used as absolute representations of the hydraulic parameters of the formation However the range of values from this pumping test analysis were used as guidelines or bounding values for recalibration of the flow model

Woodard amp Curran also analyzed the pumping test data using the Theis and Moench methods The enclosed table entitled Pumping Test Analytical Results also summarizes the results of analysis of the data using these analytical methods Again although none of the methods may be strictly applicable they provide values that are guidelines for parametric ranges used in model calibration Hydraulic conductivity values calculated from the different analytical methods were as follow

Minimum Maximum Mean (ftday) (ftday) (ftda

bull Cooper-Jacob 020 067 038 bull Theis 035 1476 392 bull Moench (Fissure) 027 210 099

Storage coefficients calculated from the different analytical methods were as follow

Minimum Maximum Mean bull Cooper-Jacob 830E-04 392E-02 651E-03 bull Theis 547E-05 359E-03 473E-04 bull Moench (Block) 803E-05 402E-02 489E-03

Storage coefficients calculated using the Theis method were one to two orders of magnitude lower than values calculated using the Cooper Jacob or Moench (Block) methods Although the fissure system values are thought to be appropriate for evaluating hydraulic conductivity because the majority of flow is through fractures the block system values are appropriate for evaluation of storage because the limited fractures account for only a small part of the total storage in the bedrock

Response to EPA Comment 2 050205doc 2 of 24 Woodard amp Curran (211941)

Woodard amp Cunran used the values estimated from the pumping test analysis as an initial data set for transient benchmarking by running a 3-day simulated pumping test Calibration of the model was accomplished by comparing measured drawdowns obtained during the pumping test to calculated drawdowns from the flow model The hydraulic parameter values in the model were varied from the initial values but within the range calculated from the pumping test analysis The additional model calibration was considered to be completed when the calculated drawdowns were sufficiently close to measured drawdowns The resulting values of the hydraulic parameters of the calibrated model were then considered acceptable to provide satisfactory prediction of the response of the flow system to other hydraulic stresses

Regional water-level data were reviewed prior to data analysis A plot of water levels in the closest USGS regional background well (provided in the TI Data Package and attached) indicates that throughout the period of the test and subsequent recovery water levels were declining on a regional scale Although the decline in water levels is gradual the change in slope observed on the Cooper-Jacob plots is thought to represent the point at which the drawdown at a given location caused by pumping becomes less significant compared to the regional drawdown This occurs at about a day after start of pumping The effect of the regional decline in water levels can also be seen in the initial rapid rise in water levels in response to pump shut off followed by a decline in water levels after about a day after the pump is shut off

Additional information obtained during the TI field work was reviewed and evaluated in updating the conceptual model for the site In general the additional information corroborated the understanding of the Site presented in the RI report In particular the northeast-southwest fracture orientation was confirmed as the predominant orientation Geophysical logging during the TI investigation however showed the dip direction of fractures to be more variable and the dip angles to be shallower than was understood based on the RI data (see enclosed figure Packer Testing Results in Vicinity of Source Area) The additional borings installed within the fenced area and to the east of the fenced area showed that the area in which concentrations of total VOCs in groundwater exceeded 10000 pgL was more limited than portrayed in the RI and FS reports Packer testing of the intervals identified by geophysical logging as likely or possibly transmissive (see enclosed borehole geophysical logs) showed VOC concentrations within the packered intervals at a given borehole to be either essentially constant (eg MW-203 MW-204 MW-205) or increasing with depth (eg PW-207) Information on hydraulic conductivity and VOC concentrations in packered intervals is summarized on two separate tables for the 1999 RI wells and 2004 TI wells (Packer Permeability and Packer Sampling Results for Potential Fracture Intervals - enclosed) The orientation hydraulic conductivity and VOC concentrations of features identified as likely or possibly transmissive is summarized in a separate table (Orientation Permeability and Groundwater Sampling Results for Transmissive Features shyenclosed)

Table 4-1 of the TI Evaluation report summarizes the variation of input parameters to the flow and batch-flushing models as the project progressed from RI to FS to TI As described above for calculations in the TI Evaluation report hydraulic conductivity values were adjusted during the model calibration to pumping test drawdown data Measured fraction of organic carbon values and VOC concentrations were used in the Batch-Flushing model along with recharge calculated from the ModFlow model For calculation of pore flush volumes using the Batch-Flushing model the ratio of density to porosity was constrained to a range of 4 to 10 which is the typical range of such ratios in porous media (Freeze amp Cherry 1979) The basis for this change was stated in Appendix C of the TI Waiver Evaluation Report and is described in the response to Comment 3

Response to EPA Comment 2 050205doc 3 of 24 Woodard amp Curran (211941)

REFERENCE

Freeze RA and Cherry JA 1979 Groundwater Prentice-Hall Inc Englewood Cliffs NJ 07632 p 410-412

Response to EPA Comment 2 050205doc 4 of 24 Woodard amp Curran (211941)

LIST OF ATTACHMENTS (Response to Comment 2)

Figure - Drawdown at 72 Hours Shallow Wells

Figure - Drawdown at 72 Hours Deep Wells

Figure - Drawdown at 72 Hours

Figure - Potentiometric Surface at 72 Hours Shallow Wells

Figure - Potentiometric Surface at 72 Hours Deep Wells

Figure - End of Pumping Test Bedrock Potentiometric Surface at 72 Hours

Table - Pumping Test Analytical Results

Figure - USGS Background Groundwater Level

Figure - Packer Testing Results in Vicinity of Source Area

Figure - Borehole Geophysical Log MW-203

Figure - Borehole Geophysical Log MW-204

Figure - Borehole Geophysical Log MW-205

Figure - Borehole Geophysical Log MW-206

Figure - Borehole Geophysical Log PW-207

Table - Packer Permeability and Packer Sampling Results for Potential Fracture Intervals 1999 Drilling Program (2 pages)

Table - Packer Permeability and Packer Sampling Results for Potential Fracture Intervals 2004 Drilling Program

Table - Orientation Permeability and Groundwater Sampling Results for Transmissive Features 2004 Drilling Program (2 pages)

Response to EPA Comment 2 050205doc 5 of 24 Woodard amp Curran (211941)

(MEDEP Pond 1) Farm Pond

0 150 300

FEET

Monitoring Well

Figure X Pumping Well Drawdown at 72 Hours

_ - 17-Acre Property Boundary Shallow Wells Hows Corner Superfund Site Drawdown Contour (ft) Plymouth Maine

151 | Drawdown (ft) WOODARD ampCURRAN

^Stk Engineering bull Science bull Operations bull 211941 Hows CornlaquorwipDrawingsTI EVALDrawdown-72hrs_shallowdwg04-19-05

MW-3B

413951 W-6DB JMW-6SB

(MEDEP Pond 1) Farm Pond

Monitoring Well

Pumping Well

17-Acre Property Boundary

Groundwater Elevation Contour (ft)

211941 Hows CornerwipDrowngsTI EVALpo-tent-aU-72-hrsdwg

Figure X End of Pumping Test

Bedrock Potentiometric Surface at 72 Hours Hows Corner Superfund Site

Plymouth Maine ^ WOODARD amp CURRAN

Englnesring bull Science bull Ope

(MEDEP Pond 1) Farm Pond

Monitoring Well

Pumping Well Drawdown atFigure X

72 Hours _bullbull_ 17-Acre Property Boundary Deep Wells

Drawdown Contour (ft) Hows Corner Superfund Site

Plymouth Maine 151 | Drawdown (ft)

= WOODARD ampCURRAN 211941 Hows CornerwipDrawingsTI EVALDrawdown-72hrs_deepdwg04-19-05

Engineering bull Science bull Operations

(MEDEP Pond 1) Farm Pond

028 MW-12DB

MW-125B 040

l - _ ^ I 016 I N

050 MW-15SB

MW-15DB 048

A J s

- A - Monitoring Well

-$poundbull Pumping Well

_bullmdash 17-Acre Property Boundary

^ Drawdown Contour (ft)

151 I Drawdown (ft)

211941 Hows CornerwgtpDrawinQsT EVAI_Drawdown-72brsdwg04mdash19-05

Figure X Drawdown at 72 Hours

Hows Corner Superfund Site Plymouth Maine

^ WOODARD ampCURRAN Engineering bull Science bull Operations i

(MEDEP Pond 1) Farm Pond

Monitoring Well

Pumping Well

_bullbull_ 17-Acre Property Boundary

f Groundwater Elevation Contour (ft)

|419Q0| Groundwater Elevation

211941 Hows CornerwipDrawinqsTI EVALPotSurf-72hrs_shallowdwg04-19-05

150 300

FEET

Figure X Potentiometric Surface at 72 Hours

Shallow Wells Hows Corner Superfund Site

Plymouth Maine

WOODARD ampCURRAN Engineering bull Science bull Operations

29212 MW-108D

(MEDEP Pond 1) Farm Pond

Monitoring Well

Pumping Well

mdashbullbulllaquo 1 7-Acre Property Boundary

bull Groundwater Elevation Contour (ft)

1419001 Groundwater Elevation

211941 Hows CornerwipDrawingsTI EVALPotSurf-72hrs_deepdwg04-19-05

150 300 =5fc= FEET

Figure X Potentiometric Surface at 72 Hours

Deep Wells Hows Corner Superfund Site

Plymouth Maine

WOODARDampCURRAN Engineering bull Science bull Operations bull

--

Pumping Test Analytical Results Hows Corner Superfund Site

Plymouth Maine

Well ID oper Jaccb Analyses 2 Theis Analyses Fissure

Well Id Rd (ft)

Saturated Thickness

Transmissivity

(ft2day) K

(ft2day) K

(cmsec) Storage

Coefficient Transmissivity

(ft2day) K

(ft2day)

K (cmsec)

Storage Coefficient

System K

(ftday) PW-207OB 8 85 481 057 200E-04 392E-02 36 042 150E-04 809E-04 027 MW-103S 50 85 451 053 187E-04 720E-03 92 108 382E-04 283E-04 083 MW-103D 54 185 455 025 868E-05 210E-02 65 035 123E-04 237E-04 044 MW-2IB 59 85 352 041 146E-04 699E-03 104 123 433E-04 512E-04 052 MW-2DB 63 85 334 039 139E-04 845E-03 148 080 283E-04 239E-04 046 MW-104D 95 185 489 02 6 932E-05 654E-03 98 053 186E-04 547E-05 037 MW-104I 97 85 33 03 9 137E-04 362E-03 117 137 484E-04 962E-05 048 MW-101I 107 85 364 043 151E-04 490E-03 511 601 212E-03 223E-04 136 MW-102D 134 185 435 024 829E-05 248E-03 108 058 206E-04 850E-05 065 MW-101D 138 185 492 027 938E-05 511E-03 671 362 128E-03 700E-04 172 MW-205 219 85 57 067 237E-04 255E-03 447 526 186E-03 359E-03 -shyMW-204D 221 185 367 020 700E-05 170E-03 790 427 151E-O3 155E-04 147 MW-204S 225 85 379 045 157E-04 156E-03 1031 1213 428E-03 313E-04 199 MW-1B 228 85 325 038 135E-04 977E-04 340 400 141E-03 739E-05 054 MW-203S 273 85 489 058 203E-04 117E-03 1255 14 76 521 E-03 216E-04 210 MW-106D 278 185 51 028 972E-05 141E-03 1065 576 203E-03 360E-04 104 MW-203D 278 185 478 026 911E-05 152E-O3 765 414 146E-03 364E-04 138 MW-105D 364 185 44 024 839E-05 830E-04 769 415 147E-03 200E-04 127

1 Analyses conducted using Cooper and Jakob method on late drawdown data collected during constant

discharge pumping test conducted at the Hows Comer Site from September 20 - 30 2004

2 Analyses conducted using Theis solution for unconfmed approximation (1935)

J Analyses conducted using Moench method for dual porosity estimation (1984)

Fissure System Storage

Coefficient 402E-04 117E-06 264E-04 300E-04 932E-05 235E-07 502E-05 326E-06 801E-05 542E-04

-

803E-05 762E-05 134E-05 498E-05 115E-04

47E-04 838E-05

3 ysesh Analysis

Block System K (ft2day)

251E-02 207E-03 564E-04 163E-04 585E-04 465E-02 153E-04 498E-03 855E-04 356E-03

-

292E-03 394E-03 720E-04 526E-03 160E-01 35OE-O1 287E-03

Block System Storage

Coefficient

402E-02 164E-04 183E-02 330E-03 158E-03 847E-03 286E-03 326E-04 803E-05 272E-03

723E-04 686E-04 148E-04 349E-04 115E-03 47E-04 838E-04

Theis - Moench - CJ - AnalyticalResults_4-19-O5xls

DRAFT

242

24

238

236

bulla

c

i

a Q

234

232

228

226

Hows Corner Constant Discharge Testing USGS Background Groundwater Level USGS 445319068560101 ME-PEW456 Kenduskeag Maine

End of Monitored Recovery Period 09302004

Regional Background Location i 226 miles from Pumping Locatio

lt

697

NOTES

1 Groundwater samples collected in 1999 were screened for five volatile organic compounds (VOCs) only N

tetrachloroethene (PCE) exceeded reporting limits MW-2030 082304 082304 082304 082304 u

2 Strike and Dip of likely or possible transmissive 30 45 55 85 feature within the packer interval from which the indicated sample was collected

MW-204D

PCE TOTAL VOCs

081904 30

220 2636

A

081904 46-50 540 6436by

081904 IT

260 3073

x

MW-105D

PCE TOTAL VOCs

111199 50-60 2100 2100

MW-106D

PCE TOTAL VOCs

111199 76-86

400 400

111199 137-147

1400 1400

111299 1355-1455

350 350

PCE TOTAL VOCs

44 84

64

MW-6SB

bulli

lt

gt-

170 234

35

I I i

140 192

^^52

^^52

130 183

52 - lt

S A 34

PW-207 082404 082404 082404 20 37

PCE 1300 TOTAL VOCs

17-Acre George West Property Boundary

MW-113D

PCE TOTAL VOCs

112299 46-56

350 350

112299 70-80 190 190

150

112299 105-115

129 129

112399 138-148

230 230

L e g e n d ( J New Monitoring Well-Summer

Site Property Boundary ^ P u m p i n g Well-Summer 2004

-xmdashxshy Source Area

bull0shy Monitoring Well shy Pre 2004 Angled Boring-Summer 2004

211941laquoipdwgTI-ELV21ig41paltker-data2

2004 PCE of Total

bull lt70 VOCs

M W - 1 14D ^ ^

Figure xx Packer Testing Results in

Vicinity of Source Area Hows Corner Superfund Site

Plymouth Maine ^ WOODARD ampCURRAN

^^^^^^^^^^m ampKm Engineering - Science bull Operations

c Northeast Geophysical Services Borehole Geophysical Log

MW-203 Date logged 081704 Plymouth Maine

I Flowmeter Measurements Tomporaturo(C) Acoustic Televiewer

7 5 8 8 5 9 95 Caliper (Inches) Resistance (Ohms) Spontaneous Potential (mVj Dip In Degrees PCE Total VOCs

3 0 2 0 8 0 laquodeg 4S 1000 1400 1800 2200 MO HO 1000 1200 MOO 0 laquo deg ugL ugL n 1 1 1 1 1 1 1 1 1 i 1 1 1 1 n 1 1 1 1 1 1 1 1 1 1 1 n I l l l l l l l n

Ambient Flowneter pumping Rowmeter 11 gpm 6

H

bull

magnetic 10 bull 10 bull - 10 - north - 1 0I

-

_

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20 bull bull20 bull ^ ltr~mdash 01

I

4 ^

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-O8 H ~ 1 045 7

1 4040 - 40 - -40 r - 14gt 13

V1s -- -023 f 1022 1V 170 234 I

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I eet be

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i 1

1 1

1

140 192 - - - -t shy

-mdashj bullpound 60 - $o - - 60 - -60

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bull024

ampbull

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70 bull j 70 - - 70 - 7 0 -

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-021 1 T 022

- Ton _ Ov

26

130 183 NF NF

90 -_ 90 - 7 90 - -90

-

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3J

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| H100 - j 100 bullbull 100 - -100

1 1 1 1 1 1 1 ) | 1 f I 1 1 1 ) 0 20 40 60 80

flft mdash ftn - mdash rVt

30 4 g 0 20 40 60 Dip in Degrees bullbull

Likely or poss bleFluid Resistivity (ohmmeters) The dip direction-- indicated

^ t h e l i n e extending from t h

I Iransmissive zone circle The strike of the feature is 90 degrees from this

The acoustic televiewer graph displays the mostprominent features selectedffom the acoustic televiewer

R n r a h n l c D O t t n O I B

f i o n n h w c i r a l U K U p i i y SI Ud l

1 rn l_Og Packered Interval August 2004

E tog The location dip angle and dip direction of the sleeted M W - 2 0 3 Groundwater samples were collected by Woodard S Curran on H23120M features are approximate Refer to the televiewer og of His _ well for more precise detail Plymouth Maine Date logged 081704

I

1

Northeast Geophysical Services Borehole Geophysical Log MW-204 D a t e l o gge d 072604

Plymouth Maine

n 3

Flowrneter Measurements(in gpm)

Caliper (Inches)0 3 5 4 0

1 1 1 1 1 1 1 t 1 1 1 1 1 1Ambient Rowmeler pumping Flowmetsr 05gpm

Templaquorature (C) bull bull bull bull i

7 75 8 8S 9 Resistance (Ohms) Spontaneous Potential (mV)

4000 SOW 600 4M 0

Acoustic Televiewer (interpreted)

Dip in Degrees 0 20 4060 SO

at N

PCEugL

Total VOCs ugL

- -_ a

10-

shy 10 bull - 10 shymagnetic

north - 10

o o

bull 1

11

11

1 1

1 1

11 1

1 1

1 1

1 1

1 1

1 1

1 1

1 1

1 1 E 1

- L

3 7 2 0 2 0r bull 20 bull - shy

i S_ N F

bull30 bull 7 3 0 220 2636shy1^ J J 004

fI f V ^

40 shy 4 0 4 0 shy - 4 0rbull019 [_ 007 w8 - - shy5 c

bull

gt

Ia50i 540 6436

bull50 - - 50 - - 5 0

-QQ7 - bull - -t T

pound V gtk

B 6 0 - e o - 7 6 0 -60shyQ 1 1

Q -007 -004 bull1 mdash T - J ~

bull

- - shyT 70 -J c [TO- - 70 - 7 0-

V Y 1- -004 -003

mdash T -h - y - j i - - mdash 260 3073 - gt=7

80 -j NF bull80 - - 80 - - 8 0Jgt

bull i

i 1

i i

C- bull shy

90 shy

K

Jlt i90 90 shy - 9 0shy -

l

ii

I I I I

NF bull M J

I ^ ^ - ^ bull 1

mdash mdash - _

s -7 ^100shy

till

1 100 100- H - 1 0 0shy -1 x Likety or possible k ^ Iransmissive zonebull

1 i i i ii i i i | l l l l | l i l l 0 20 40 ED 80

1 -

3 0SOFluid Resistivity (ohmmeters)

Dip in Degrees The djp ^ ^ o n is indicated ty Ihe line extending from tha circle The strike of Ihe feature

19- 3U UIHJIW93 IolII l l l lraquo

bull

The acousfc televiewer graph displays the mostprominent features selected from the acoustic televiewer109 The location dip angle and dip direction of Ihe sleetedfeatures are approximate Refer to the televiewer log of thiswentormore precise detail

B o r e h o l e G e O D h V S I C a l LOO B W H U I B w c w p n y o i v a i w v yM W - 2 0 4

P l y m O U t n MaiDB

Packorod Interval August 2004Groundwater san-ples wampramp collected by Woodard a Curran on OMO23C4

Date logged 072604

C

I

E Northeast Geophysical Services Borehole Geophysical Log Date logged 072704

I MW-205

Plymouth Maine

Flowmeter Measurements Temperature (C) Acoustic Televiewer (In gpm) I ~l (Interpreted)

I 85 10 Caliper (inches) 95

Dip in D g r laquo Resistance (Ohms) Spo ontaneous Potential (mV PCE Total VOCs 3 0 16 4 0 4 5 ) 20 40 60 80 10 00 2000 30 00 4VJ 400 -3 laquo

i i i i 1 i i I i 11 4 0 D 1 I I ugL ugL

C h

iii Ambient Flowmetar pumping

Flowmeter 1 25 gprn

I bull$bull

i

I rmdash magnetic 1 north ^^^^ 1 VI f

10 ~ I C x 10 bull - 10 bullbull

4 5 6mdashmdash f 1000B 11448 noisy nodi a raquo ^

mdash 5rt mdashi mdash Oft pound) 1100B 12509

cjmdash1 007

-

i i i 1

en

8 B a B

30 mdash

-

40 shy

-mdash I -

50 -_

__NF lt005

- 30 - - 3 0 it 34V

MO P26 V S) 1300B 13776 _ N F NF

26

40 bull - 40 bull 7-40 gt J Vf1 cX

) -j -

_ N F NF 50 c bull - 50 ^ 7-50

i I

I

c

B pound 60 - 6 0 7 60 - 7-60 a i 1

_ N F NF i Si f f 70 -_ bull70 bull - 70 shyC I 9

-m bull - shyA

_ N F NF 80 80 -j bull80 bull - 80 - C- 33 34

bull

5-i r

i 1

J r

Ck

_ N F NF 9 0 90 - - 90 shy

i bullCshy

J rK bull

100 -j ^ Likely or possible bull100- - 100- I -100

transmissive zone bull - ^ bull shy] |

1 1 1 1 1 1 1 I 1 i i i 1 i i 1 1 0 20 40 SO SO 10 20 30 40 50 Dip in Degrees 30 4 0 Fluid Resistivity (ohmmeters) Thlaquo dip direction is indicated

by the line extern r g from the circle The strike of he feature is 90 degrees from ihis

The acoustic televiewer graph displays the most

I Borehole Geophysical Log Packered Interval August2004 prominent features selected from the acoustic televiewer

Groundwatcr samples were oollccled by Woodard amp Cufran orgt S172004 log The location dip angle and dip direction of ins slsctsd MW-205 features are approximate Refelt to the televiewer log of this wall for more precise detail Plymouth Maine Date logged 072704

I

C

I Northeast Geophysical Services Borehole Geophysical Log Date logged 072704

I MW-206

Plymouth Maine

Flowmetor Measurements Temperature (C) Acoustic Televiewer | I r T i i i i i i i i i i i i i i r I |(in gpm) (Interpreted)

I 75 8 flS 9 95

Caliper (inches) Resistance (Ohms) Spontaneous Potential (mV) Dip In Degress PCE Total VOCs 30 35 40 4 5 0 20 40 M 90 4500 5500 6500 ugL ugL I i i

I I

- 1 0

I - 2 0

I 2900B 32401

i i L

E 0

i 6300B 68901

i I 0 20 40 SO 80

20 30 40 50 Dip in Dlaquogralaquos

amp 4 a Fluid Resistivity (ohrnmeters) The dip dirertion is indicated Likely or possible by iho line extending from the transmissive zone circle The striKe of the feature

is 90 degrees from tNs

Borehole Geophysical Log Packered Interval August 2004

E amples were collected by Woodard amp Cunan oo SM82004 log Thraquo location 4p angle and dip direction of the sloeled MW-206 feature are approximate Refer to the televiewer 109 of this well for more precise detail Plymouth Maine Date logged 072704

C

I Northeast Geophysical Services Borehole Geophysical Log

Date logged 082304 PW-207

I Plymouth Maine

Fiowmeter Measurements Temperature (C) Acoustic Televiewer

I (in gpm) (interpreted)

75 8 85 9 95 Caliper (inches) Resistance f0tims) Spontaneous Potential (mV) Dip in Degrees PCE Total VOCs

55 60 0 20 40 SO 80 ugL ugL I I I I I I I

Ambienl Fiowmeter pumping Flewmater

magnetic - 10 - - 1 0

north

i - 20 - - 2 0

1300 1410

i - 30 - - 3 0

i tf

5400 5802 - 40 - - 4 0

B - 50 - - 5 0

I 18000 19234

- 60 - - 6 0

I 12000 13085

- 70 - - 7 0

- 8 0

i - 9 0 19000 20354

G - 100- -100

I 110 110 bull110

0 20 40 60 SO 10 20 30 Dip m Degrees

Fluid Resistivity (ohmmeters) I 50

The dip direction is indicated by ihe line extending from the circle The strike of the fealure is 90 degrees from this

Borehole Geophysical Log

G Packorod Interval August 20(M log The location dip angle and dip dirlaquocton or the sleeted Groundaier samplss were ooliecled by Woodard i Curran on ampt24f2ltXM PW-207 failures are approximate Reter to the televiewer log of this wlaquoll for more precise detail PlyPIOUth Maine Date logged 082304

I

Table XX Packer Permeability and Packer Sampling Results for Potential Fracture Intervals

1

WellID MW-101D MW-101D MW-101D MW-101D MW-101D MW-101D MW-101D MW-101D MW-101D MW-101D MW-I01D MW-101D MW-101D MW-102D MW-102D MW-I02D MW-102D MW102D MW-102D MW-102D MW-102D MW-102D MW-I02D MW-102D MW-102D MW-102D MW-103D MW-103D MW-103D MW-103D MW-I03D MW-103D MW-103D MW-103D MW-103D MW-103D MW-103D MW-103D MW-I03D MW-104D MW-104D MW-104D MW-104D MW-I04D MW-104D MW-104D MW-104D MW-104D MW-104D MW-104D MW-105D MW-105D MW106D MW-106D MW-106D MW-107D MW-107D

1999 Drilling Program

Hows Corner Superfund Site Plymouth Maine

Potential Fracture Top Of Bottom 6 Depth to lt Topof i Interval from Packer Packer Middle of Elevation Hydraulic bull PCE

GS ELEV 1 Rock Drilling Interval Interval Interval of Interval Conductivity Concentration (ft msl) (ft msl) TEST (ftbgs) (ftbgs) r(ftbgs) ( f t b (ft mil) (cmsec) (raquogL)

4339 4329 13 28-29 33-3537-39 271 376 324 4016 OOOE+00 4339 12 37-3444-46 380 485 433 3907 157E-04 4339 11 488 593 541 3799 132E-04 4339 10 60-61 578 683 631 3709 OOOE+00 4339 9 678 783 731 3609 I79E-05 4339 8 778 883 831 3509 106E-05 4339 7 880 985 933 3407 243E-05 4339 6 990 1095 1043 3297 339E-06 4339 5 1090 1195 1143 3197 OOOE+00 4339 4 1190 1295 1243 3097 OOOE+00 4339 3 1365-1375 1290 1395 1343 2997 OOOE+00 4339 2 147-157 1390 1495 1443 2897 580E-05 4339 1 147-157 1470 1575 1523 2817 741E-05 43161 43061 13 166 271 219 4098 333E-04 43161 12 30-3136-40 260 365 313 4004 I54E-05 43161 11 36-4041-43 362 467 415 3902 548E-05 43161 10 470 575 523 3794 598E-05 43161 9 570 675 623 3694 197FOS 43161 8 670 775 723 3594 OOOE+00 43161 7 770 875 823 3494 891 E-05 43161 6 83-94 870 975 923 3394 139E-05 43161 5 970 1075 1023 3294 123E-04 43161 4 1070 1175 1123 3194 526E-06 43161 3 1170 1275 1223 3094 138E-05 43161 2 1270 1375 1323 2994 671E-06 43161 1 1370 1475 1423 2894 OOOE+00 42997 42497 13 18-19 170 275 223 4077 OOOE+00 42997 12 260 365 313 3987 766E-05 42997 11 360 465 413 3887 727E-05 42997 10 460 565 513 3787 192E-05 42997 9 560 665 613 3687 752E-05 42997 8 660 765 713 3587 778E-05 42997 7 85-86 763 868 816 3484 260E-05 42997 6 860 965 913 3387 289E-05 42997 5 102-103 960 1065 1013 3287 102E-04 42997 4 1060 1165 1113 3187 522E-06 42997 3 1160 1265 1213 3087 520E-06 42997 2 129-130 1260 1365 1313 2987 960E-04 42997 1 1360 1465 1413 2887 OOOE+00 43372 42922 11 35-37 42-45 350 455 403 3935 684E-04 43372 10 460 565 513 3825 500E-05 43372 9 560 665 613 3725 106E-05 43372 8 72-74 660 765 713 3625 204E-05 43372 7 760 865 813 3525 872E-06 43372 6 860 965 913 3425 467E-06 43372 5 960 1065 1013 3325 200E-05 43372 4 1060 1165 1113 3225 354E-05 43372 3 125-130 1160 1265 1213 3125 157E-05 43372 2 125-130 1260 1365 1313 3025 337E-04 43372 1 1365 1465 1415 2922 689E-06 43052 43002 2 54-58 490 595 543 3763 124E-05 2100 43052 1 139-140 145-146 1367 1472 1420 2886 154E-04 1400 43291 4391 3 bullI133 260 365 313 4017 439F06 43291 2 77-78 760 865 813 3517 230E-03 400 43291 1 143-144 1355 1460 1408 2922 971E-06 350

29958 27258 4 450 555 503 2493 OOOE+00 (21)A 29958 3 103-105 1000 1105 1053 1943 752E-04 (063)A

Table XX Packer Permeability and Packer Sampling Results for Potential Fracture Intervals

1999 Drilling Program

Hows Corner Supcrfund Site Plymouth Maine

gtbull i Potential Fracture Top _OfBot Bottom of Depth to ltbull Top of Interval from f Packer Packer Middle Of

GS ELEV lt Hock Drilling interval Interval Interval WeD ID ft msl) (ft msl) TEST (ftbgs) ltft$gs) (ftbgs) (ftbgs)

MW-107D 29958 2 128-130 1200 1305 1253

MW-107D 29958 1 139-141 1350 1455 1403

MW-108D 31904 31104 6 35-36 300 405 353 MW-108D 31904 5 60-62 550 655 603

MW-108D 31904 4 80-83 750 855 803

MW-108D 31904 3 118-119 123-124 1150 1255 1203

MW-108D 31904 2 147-149 1440 1545 1493

MW-108D 31904 1 1700 1805 1753

MW-110D 40576 40426 2 21-31 210 315 263 MW-110D 40576 1 148-154 1460 1565 1513 MW-I11D 40519 4 70-71 650 755 703

MW-111D 40519 3 79-82 84-86 780 885 833 MW-I11D 40519 2 97-102 950 1055 1003 MW-111D 40519 1 1370 1475 1423

MW-112D 3027 2942 4 42-52 420 525 473 MW-112D 3027 3 850 955 903 MW112D 3027 2 1100 1205 1153 MW-112D 3027 1 135-136 140-141 1340 1445 1393

MW-113D 43085 43085 5 250 355 303 MW-I13D 43085 4 47-49 460 565 513 MW-113D 43085 3 73-74 700 805 753 MW-113D 43085 2 1050 1155 1103 MW-113D 43085 1 1380 1485 1433

MW-114D 42394 41594 4 48-49 450 555 503 MW-114D 42394 3 79-81 740 845 793 MW-114D 42394 2 121-129 1250 1355 1303 MW-114D 42394 1 134-142 1350 1455 1403

MW-115D 4035 4035 4 300 405 353 MW-1I5D 4035 3 70-71 650 755 703 MW-115D 4035 2 1150 1255 1203 MW-115D 4035 1 1400 1505 1453

LOT-28W 382 7 450 555 503 LOT28W 382 6 550 655 603 LOT-28W 382 5 650 755 703 LOT28W 382 4 750 855 803 LOT-28W 382 3 850 955 903 LOT-28W 382 2 950 1055 1003 LOT-28W 382 1 1055 1155 1105

NOTES cmsec = centimeters per second ft bgs = leet below ground surface It msl = feet below mean sea level lt = not detected at indicated reporting limil A = detected below laboratory PQL ( ) = detected below reporting limits

Elevation of Interval

(ft nisi) 174

159

283gt 2588

2388

1988

1698

1438

3795 2545 3349 3219 3049 2629

2555 2125 1875 1635

4006 3796 3556 3206 2876

3737 3447 2937 2837

3683 3333 2833 2583

3318 3218 3118 3018 2918 2818 2715

Hydraulic Conductivity

(cmsec)

323E-05

208E-05

471E-03

471E-03

624E-05

3I6E-05

264E-05

261 E-05

OOOE+00 200E-04 953E-05 OOOE+00 OOOE+00 212E-05

361 E-05 410E-06 2gQE06 292E-05

786E-05 124E-05 151 E-05 822E-06 82IE-06

858E-05 I69E-05 352E-03 866E-05

223E-05 394E-06 122E-05 525E-06

831 E-05 182F-05 L62E-05 129E-05 190E-05 890E-04 981 E-04

PCEraquo Concentration

(ugL)

lt5

(14A)

98 11

15

22

11

30

200 (62)A

110 210 300 240

(44)A (23)A

5

350 190 129 230

2200 1900 2600 2600

(17)A (16)A (19)A

96

Table XX Packer Permeability and Packer Sampling Results for Potential Fracture Intervals

2004 Drilling Program

Hows Corner Superfund Site Plymouth Maine

Top of Bottom of Depth to Midpoint

t K

ELEV (ft Potential Transmissive Zones Packer Interval

Packer Interval

Middle of Interval

Elevation of interval

Hydraulic Conductivity

PCE Concentration

Well ID msl) TESTr (ft bgs)- (ftbgs) (ftbgs) (ftbgs) (ft msl) (cmsec) (ogt) MW-203D 43227 4 277279 24 32 28 4043 667E-05 44

3 408415420 39 49 44 3883 593E-05 170 2 526 530 49 57 53 3793 101E-04 140 I 828830842 80 88 84 3483 701E-05 130

MW-204D 43262 5 295 300 26 34 30 4023 902E-05 220 4 463496513516 45 53 49 3833 119E-04 540 3 681685688 63 71 67 3653 OOOE+00 2 758 76 2 71 79 75 3573 309E-05 260 I 88 96 92 3403 OOOE+00

MW-205 42389 3 164 166 168 15 20 175 4148 OOOE+00 1000B 2 302305312 30 35 325 3998 107E-04 1300B 1 40 45 425 3898 OOOE+00

MW-206D 43007 5 17 72 195 4128 291E-05 4 296 302 307 29 34 315 4008 940E-05 2900B 3 522 52 57 545 3778 944E-07 2 656 64 69 665 3658 353E-06 1 92392793 4939 91 96 935 3388 614E-05 6300B

PW-207 43477 5 184622162819 18 29 235 4088 209E-05 1300 4 3508 32 43 375 3948 568E-06 5400 3 53325341542154325559 50 61 555 3768 821E-05 18000

6359 61 72 665 3658 866E-06 12000 1 8685 84 89 865 3458 213E-05 19000

NOTES cmsec = centimeters per second ft bgs = feet below ground surface ft msl = feet above mean sea level B = detected in lab blank

Table XX Orientation Permeability and Groundwater Sampling Results for Transmissive Features

2004 Drilling Program

Hows Corner Superfund Site Plymouth Maine

Borehole Geophisical Feature depth Dip True Dip True Transmissive Log Feature (Feet) Degrees Azimuth Strike bullvgt(Ltk|iy^

Number v Tosftble) v MW-203 5 277 64 337 67 Likely

6 279 59 11 281 Likely 8 352 14 177 87 Likely 11 381 46 96 6 Possible 12 408 35 271 1 Possible 14 415 57 250 340 Possible 15 420 58 202 292 Likely 18 526 52 75 345 Likely 19 530 52 82 352 Likely 28 828 48 75 345 Likely 29 830 52 17 287 Likely 30 830 56 233 323 Possible 31 842 50 130 40 Likely

MW-204 4 295 15 147 57 Likely 5 300 43 91 1 Likely 11 439 31 80 350 Possible 12 440 46 219 309 Possible 14 463 50 358 88 Likely 15 496 34 198 288 Likely 16 513 54 17 287 Likely 17 516 33 14 284 Likely 25 681 39 359 89 Possible 26 685 22 45 315 Possible 27 688 35 73 343 Possible 32 758 45 236 326 Likely 33 762 46 306 36 Likely

MW-205 5 164 69 106 16 Possible 6 166 78 165 75 Possible 7 168 82 115 25 Possible 8 168 68 116 26 Possible 12 215 46 222 312 Possible 13 217 75 62 332 Possible 14 219 29 32 302 Possible 16 237 69 250 340 Possible 17 256 73 353 83 Possible 18 272 44 202 292 Possible 21 299 37 196 286 Possible 22 302 31 206 296 Possible 23 305 59 48 318 Likely 24 312 63 42 312 Likely

MW-206 1 264 37 181 271 Likely 2 296 69 217 307 Likely 3 302 66 233 323 Likely 4 307 64 224 314 Likely 8 342 62 259 349 Likely

jjHydraulic GoiDanctilyity j(cmsecjw

667 E-05

593 E-05

101 P04

710 E-05

902 E-05

119 E-04

0

309 E-05

0

107 E-04

94 E-05

PCE (ugL)

44

170

140

130

220

540

260

IOOOB

1100B

1300B

2900B

STotal vVoCsv tig1)

84

234

192

183

2636

6436

3073

11448

12509

13776

32401

PCEyo dfCTotaf

52

73

73

7 1

83

84

85

87

88

94

90

Table XX Orientation Permeability and Groundwater Sampling Results for Transmissive Features

2004 Drilling Program

Hows Corner Superfund Site Plymouth Maine

Borehole Geophisical Feature deptt raquoip True pip True Transraissive Log Feature (Feet) shy Degrees Azimuth Strike (tikely

Number raquo Possible) 22 522 57 54 324 Possible 25 656 40 82 352 Possible 32 871 59 151 61 Possible 33 883 53 185 275 Possible 34 895 7 175 85 Likely 35 899 53 90 0 Likely 36 902 49 184 274 Likely 37 923 9 175 85 Likely 38 927 42 206 296 Likely 39 934 48 167 77 Likely 40 939 26 180 90 Likely

PW-207 1 1846 33 167 77 Likely 4 2216 49 289 19 Possible 7 2819 59 265 355 Possible 11 3508 55 189 279 Possible 18 5332 43 305 35 Likely 19 5341 51 30 300 Likely 20 5421 20 254 344 Likely 21 5432 39 301 31 Likely 23 5559 52 302 32 Likely 25 6359 24 182 272 Possible 29 8049 77 231 321 Possible 30 8685 78 38 308 Likely 32 9334 29 194 284 Likely

NOTES

B = detected in lab blank

Hydraulic Conductivity

(cmsee) 944 E-07 353 E-06

614 E-05

209 E-05

568 E-06

821 E-05

866 E-06

213 E-05

bulltCE (ugL)

6300B

1300

5400

18000

12000

19000

Total VOCs (ug1)

68901

1410

5802

19234

13085

20354

PCE of Total VOCs

9 1

92

93

94

92

93

Response to EPA-DEP Comment 3 Dated March 312005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

lit

EPA-DEP Comment 3

Comment 3 The reported f values and resultant Kd values There remains doubt that the values used in the flushing model accurately reflect the propensity for PCE to sorb to the bedrock The ^ values presented in Appendix B may be unrealistically high because the bedrock samples may have contained organic carbon that was unavailable for sorption The reported f values are only qualitative estimates of the organic carbon content of the bedrock samples The Walkley and Black organic carbon measurement method is quick and simple but the results obtained cannot be considered quantitative because it requires a correction factor which often results in erroneous values it assumes the organic carbon has an average valence of zero oxidizable and reducible constituents such as chloride ferrous iron and manganese oxides interfere with the results and the errors introduced by interference are potentially greater when the organic carbon content is low at low f values it is not clear that organic carbon is controlling PCE sorption (Schwarzenbach and Westall 1981 Mackay et al 1986 Fetter 1999)

In order to derive a Kd-based retardation factor that is reasonable given the reported f values and the rapid advance of the PCE plume described on pages 4-11 and 4-12 the flushing model requires a bulk density to porosity ratio that is roughly two orders of magnitude higher than the actual ratio for the Hows Corner bedrock (page 4-4) This apparent discrepancy needs to be addressed

Response This comment raises several concerns about the collection and analysis of samples for fraction of organic carbon (f^) the quality of the resulting data and the implications of the use of those data for estimation of the retardation of groundwater contaminant movement Results of bedrock analysis for f were proposed in the TI Evaluation Work Plan for use in conjunction with groundwater contaminant concentrations and aquifer information to estimate cleanup times using the Batch Flushing model It is important to use accurate f values from representative bedrock in the Batch Flushing model in order to obtain reasonable estimates of the remedial time frame Because of the importance of accurate and representative results the TI Investigation field program was designed and conducted both to collect samples representative of the rock volume most likely to be in contact with contaminated groundwater and to analyze them using an appropriate refereed analytical method Five potential methods for evaluating f were identified Of the five methods the Walkey-Black method was selected because it has minimal method interferences and a sufficiently low detection limit as well as a long history of use in agronomy and contamination studies The PRP Group is pleased with the quality of the data obtained from the bedrock samples as represented by their precision and reproducibility

The first part of this comment relates to the determination of fraction of organic carbon (f^) values The several subparts of the first paragraph are addressed individually in items 1 through 5 below The second part of the comment regarding the resultant distribution coefficient (Kd) values is addressed separately as item 6 below

1 There remains doubt that the values used in the flushing model accurately reflect the propensity for PCE to sorb to the bedrock

bull The rock core samples used for f (gocg) analysis were from core immediately adjacent to fractures These rock core samples included the fracture surfaces themselves and rock core extending back less than 1 cm from the fractures Therefore the foe data reported in the TI Evaluation represents the f of bedrock through which groundwater will travel and to which PCE will adsorb Based on the careful selection of sample locations and the

Response to EPA Comment 3 050205doc 1 of 11 Woodard amp Curran (211941)

number of samples collected we are confident that the measured f values are representative of the f at points of contact for PCE with the bedrock it is these f values that determine the propensity of PCE to sorb to the bedrock

bull The samples of rock core collected for analysis of f originated from 19 different locations varying in depth from 11 to 90 feet Therefore it is very unlikely that the rock core samples were contaminated with extraneous organic carbon from above ground

2 The foc values presented in Appendix B may be unrealistically high because the bedrock samples may have contained organic carbon that was unavailable for sorption

bull As noted in response 1 the f data reported in Appendix B represents organic carbon primarily associated with the surface of fractures in the bedrock through which groundwater is most likely to travel Therefore it is this organic carbon that the contaminants in the groundwater will come in contact with and adsorb to in the fractured rock at the site

bull The chemical oxidation agents used in the Walkey-Black method oxidize the easily oxidizable organic carbon in the medium and the foe is calculated from the quantity of the agent consumed Therefore it is unlikely that the analysis of the bedrock samples measured organic carbon that was unavailable for sorption

3 The reported foc values are only qualitative estimates of the organic carbon content of the bedrock samples

bull The reported f values are accurate quantitative results Schumachers review of Methods for the determination of total organic carbon (TOC) in soils and sediments (NCEA-C-1282 EMASC-001 April 2002) identifies the Walkley-Black method which was used to analyze the reported foc values as the reference method for comparison to other methods for analyzing total organic carbon

bull Schumacher also points out that if anything the WalkJey-Black method may underestimate the total organic carbon in a sample due to possible incomplete oxidation of organic carbon Usually the incomplete oxidation of total organic carbon in environmental samples is corrected for by multiplying the measured foe by 130 (Walkley amp Black 1934 Schulte 1995)

bull When the f data in the TI Evaluation Report (WampC 2005) Appendix B (attached) are analyzed statistically the standard deviation of the f for the 19 samples analyzed is 174 of the average f Given this standard deviation the 95 confidence interval for this data ranged from a low of 000123 gocg to a high of 000253 gocgm

The labs Method of Detection Limit (MDL) for the f measured using the Walkley-Black method is 00001 gocg Therefore the average (000188 gocg) the mean (000185 gocg) and geometric mean (000187 gocg) of the f values for the rock core at Hows Corner are all statistically significantly greater than the MDL of the Walkley-Black method

In addition to the aforementioned statistical analysis of the foe data triplicate samples (n = 3) from the same rock core (including one sample from the 19 rock core samples) were

Response to EPA Comment 3 050205doc 2 of Woodard amp Curran (211941)

analyzed for their f to determine the repeatability of the Walkley-Black method The average the mean and the geometric mean of the f values of these replicate samples was 000162 gocg 000150 gocg and 000159 gocgm respectively The standard deviation of these measurements was 000039 gocg

4 The Walkley and Black organic carbon measurement method is quick and simple but the results obtained cannot be considered quantitative because it requires a correction factor which often results in erroneous values it assumes the organic carbon has an average valence of zero oxidizable and reducible constituents such as chloride ferrous iron and manganese oxides interfere with the results and the errors introduced by interference are potentially greater when the organic carbon content is low at low foc values it is not clear that organic carbon is controlling PCE sorption (Schwarzenbach and Westall 1981 Mackay et al 1986 Fetter 1999)

bull Schumachers review (NCEA-C-1282 EMASC-001 April 2002) of the Walkley-Black method identifies several potential problems with this analytical method that could occur if the analytical lab is not familiar with the nuances of the chemistry associated with this method Interestingly Schumachers review neglected one of the more important analytical steps required to avoid errors in quantifying f in samples where there might beNAPL

It is absolutely critical to eliminate any NAPL from rock core samples prior to using the Walkley-Black method to measure foe in such samples This was done by the lab (PTS Laboratories) that measured the foe in the rock core samples from Hows Corner The lab used the Dean-Stark method (solvent extraction) to remove all hydrocarbons (including PCE and other NAPLs) from the sample (PTS Laboratories) This extraction method does not interfere with the subsequent analysis of the natural organic carbon associated with the rock core

Subsequently the samples were dried at 150degC to a constant weight (normally 16 hours) This latter step oxidizes all inorganic minerals including ferrous bearing minerals to ferric oxides and precludes their interference during the oxidation of the samples with chromic acid This procedure completely eliminates any positive bias in the reported foc

data that might have occurred due to the presence of ferrous ions and other reduced minerals

bull As noted in Response 3 the incomplete oxidation of total organic carbon results in an underestimate of the f and is corrected for by multiplying the f by a correction factor of 130 (Walkley amp Black 1934 Schulte 1995) The fx data reported in the TI Evaluation was corrected accordingly by using this correction factor

bull Excess chloride (Cl~) in percent weight quantities as found in saline soils may interfere with the quantitative titration of reduced chromium (Walkley 1947) However given that the primary rock type at the Hows Corner site is phyllite it is highly unlikely that there was sufficient chloride in the rock core samples for this to occur

bull Manganese oxides may also interfere with the analysis of f through competing with the dichromate ion for any oxidizable carbon (Walkley 1947) However in such cases the reported f would be an underestimate of the f present in the rock core Walkley (1947)

Response to EPA Comment 3 050205doc 3 of 11 Woodard amp Curran (211941)

4

reported that in the case where the ratio of MnO2 to carbon is 85 to 1 the error in the carbon determinations would only be 0 to 6 percent

It may also be useful to compare the analysis of total organic carbon in a geologic matrix that contains high levels of manganese using EPA method 9060 to the Walkley-Black method Table 1 summarizes data provided by one of the PRPs that compares the analysis of total organic carbon in a geologic matrix that contains approximately 02 wgt manganese (approximately 03 wgt manganese oxide)

Table 1 Comparison of total organic carbon measured using the EPA- 9060 method and the Walkley-Black method

Laboratory EPA-9060 Method Walkley-Black Method A Ave 00226 gocg Not analyzed

Stdev 000251 gocg n = 5

B Ave 002219 gocg Ave 002050 gocg Stdev = 000316 gocg Stdev =000971 gocg

n= 10 n = 10

The similarity in the total organic carbon concentrations measured by these two different methods provides further confidence that the Walkley-Black method is a viable method for analysis of total organic carbon in the presence of manganese equivalent to at least 10 by weight of the total organic carbon

5 The Walkley and Black organic carbon measurement at lowf^ values it is not clear that organic carbon is controlling PCE sorption (Schwarzenbach and Westall 1981 Mackay et al 1986 Fetter 1999)

bull Schwarzenbach and Westalls (1981) paper states that f values of less than 0001 gocg should not be used in combination with Kow (octanol-water partition coefficients) values to calculate K^ values (solid phase partition coefficients) values for a specific contaminant It should be noted that the TI Evaluation did not use the f data to calculate the KQC from the Kow Instead as requested by the EPA the measured KOC value for PCE was used to calculate the retardation factor for this contaminant

bull Schwarzenbach et al (2003) stated more recently that Even at very low f values (ie foe = 0001 kgoc - kg1 solid) sorption to the organic components of a natural sorbent may still be the dominant mechanism in defining the adsorption of organic compounds to geological matrices

bull In 1985 M Piwoni from the US EPA Robert S Kerr Environmental Research Laboratory published a paper (Banerjee et al 1985) that showed that for very hydrophobic molecules TOC content of the sorbent will control sorption down to levels of organic carbon that defy quantitation Contaminants such as the PCE found in the groundwater at Hows Corner are in this category of compounds

Given the aforementioned reasons the f values reported in the TI Evaluation are accurate within the noted statistical limitations and will have a predictable impact upon the retardation of PCE during groundwater transport

Response to EPA Comment 3 050205doc 4 of 11 Woodard amp Curran (211941)

6 In order to derive a Kd-based retardation factor that is reasonable given the reported foc

values and the rapid advance of the PCE plume described on pages 4-11 and 4-12 the flushing model requires a bulk density to porosity ratio that is roughly two orders of magnitude higher than the actual ratio for the Hows Comer bedrock (page 4-4) This apparent discrepancy needs to be addressed

The apparent discrepancy of bulk density to porosity ratios is most likely due to the fact that the Batch Flushing Model was originally developed for a porous medium and is not directly applicable to fractured bedrock As stated in Appendix C (page C-4) of the Draft Technical Impracticability Evaluation Report in order to use the Batch Flushing Model to describe the transport of contaminated groundwater in fractured bedrock where the matrix porosity is insignificant it is more appropriate to use a fracture surface area to void space ratio to calculate the retardation factor (R) than a bulk density to porosity ratio (Freeze amp Cherry 1979)

Since it is impractical to determine the actual surface area to which contaminants can adsorb the Batch Flushing Model was used with two simplifying assumptions bull The Kd was calculated from the f and the K^ bull The bulk density to porosity ratio term in the Batch Flushing Model was constrained to range

from 4 to 10 the typical range of such ratios in porous media (Freeze amp Cherry 1979)

If one uses site specific bedrock bulk density and porosity values the bulk density to porosity ratio is several orders of magnitude greater (specifically 273 gcc bullbull 000165 (dimensionless) = 1654 gcc) than the range of ratios of 4 to 10 used in the Batch Flushing Model in the Draft Technical Impracticability Evaluation Report Constraining the bulk density to porosity ratio within the range of ratios of 4 to 10 results in significantly lower R value than would be obtained using specific bedrock bulk density and porosity values

In summary in bedrock where fractures are the primary porosity the bulk density to porosity ratio can vary considerably and will be a function of the number of fractures and the fracture aperture The calculated bulk density to porosity ratio will be inversely proportional to the porosity This means that in fractured rock with limited fracturing and smaller porosity the calculated bulk density to porosity ratio is greater and will result in a greater calculated retardation factor than in bedrock with more extensive fracturing and greater porosity Consequently the calculated retardation factor will be greater for bedrock with less surface area available for sorption than bedrock with greater surface area for sorption This is contrary to what actually occurs

4 Response to EPA Comment 3 050205doc 5 of 11 Woodard amp Curran (211941)

m

REFERENCES

Banerjee P MD Piwoni K Ebeid (1985) Sorption of organic contaminants to a low carbon subsurface core Chemosphere _14 1057-1067

Freeze RA JA Cherry (1979) Groundwater Prentice Hall Englewood Cliffs NJ pg 604

PTS Laboratories wwwptsgeolabscompdf files3TOCnotepdf

Schulte EE (1995) Recommended soil organic matter tests in Recommended Soil Testing Procedures for the Northeastern United States Northeastern Regional Publication No 493 Chapter 8

Schwarzenbach RP J Westall (1981) Transport of nonpolar organic compounds from surface water to groundwater Laboratory sorption studies Environ Sci Tech 15 1360-1367

Schwarzenbach RP PM Gschwend DM Imboden (2003) Environmental Organic Chemistry Wiley-Interscience pg 292 408 amp 412

Walkley A LA Black (1934) An examination of the Degtjareff method for determining soil organic matter and a proposed modification of the chromic acid titration method Soil Science 37 29-38

Walkley A (1947) A critical examination of a rapid method for determining organic carbon in soils - effect of variations in digestion conditions and of inorganic soil constituents Soil Science 63251-264

Woodard amp Curran Inc (WampC) 2005 Draft Technical Impracticability Evaluation Hows Corner Superfund Site Plymouth Maine January 2005

Response to EPA Comment 3 050205doc 6 of Woodard amp Curran (211941)

LIST OF ATTACHMENTS (Response to Comment 3)

Appendix B to Draft Technical Impracticability Evaluation Measurement of foe at Hows Corner (4 pages)

m

Response to EPA Comment 3 050205doc 7 of 11 Woodard amp Curran (211941)

Appendix B Measurement of foe of Rock Core at Hows Corner

There are two general approaches to measure the fraction of organic carbon (foe) in rock cores

bull Measurement of weight loss by ignition of organic matter bull Chemical oxidization of organic carbon to carbon dioxide and either

subsequent quantification of the oxidant used for the reaction or quantification of the carbon dioxide produced during this oxidation process

The weight loss method is subject to errors caused by volatilization of substances other than organic materials such as water hydroxides and mineral carbonates Quantification of foe by the weight loss method is particularly sensitive to the presence of carbonates in rock cores There are however weight loss methods that are designed to differentiate between organic carbon and the aforementioned interfering materials but they require considerable care and are less accurate at low foe values Hence the weight loss method was not well suited for measuring the foe of the rock core from Hows Corner

The chemical oxidation of organic carbon is much better suited for quantifying organic carbon in rock cores such as those from Hows Corner This method uses a strong chemical oxidant to oxidize organic carbon to carbon dioxide and then measures either the chemical oxidant used to oxidize the organic carbon or the quantity of carbon dioxide produced In addition this general approach is not subject to interference by volatilization of other constituents of the rock core

There are at least two such chemical oxidation methods

bull The method of Baccini which was described by Schwarzenbach amp Westall (1981) first acidifies the sample to eliminate interference by carbonates Then a strong oxidant is used to chemically oxidize the organic carbon to carbon dioxide The resulting carbon dioxide is subsequently reduced to methane and quantified using a flame ionization detector Unfortunately this method has not been described in detail in a referred journal Hence it is would not have been appropriate to use to characterize the foe in the Hows Corner rock core

bull The more commonly used method to quantify foe in rock core is the Walkley-Black method (1934) This method is preferred for RBCA and DODDOE projects and by the oil industry

The Walkley-Black method uses an excess of chromic acid to oxidize (digest) organic matter to carbon dioxide The remaining chromic acid that was not consumed during the oxidation of the organic carbon is then quantified by titration with ferrous sulfate The difference in chromic acid prior to and after the oxidation of the organic carbon represents the total chromic acid used to oxidize

Hows Corner TI Evaluation Page 1 January 13 2005 Appendix B

the organic carbon in the sample The latter can be calculated using the chemical stoichiometry of the reaction

The Walkley-Black method is very accurate for samples that contain less than 2 organic carbon matter The minimum detection limit (MDL) for the Walkley-Black method is 100 mgkg or an foe of 0001

Given the rock core at Hows Corner was expected to contain less than 2 organic carbon the Walkley-Black method was used to measure the foe from 19 different rock core samples collected from varying depths ranging from 11 to 90 feet

Table 1 provides a statistical summary of the aforementioned data

Table 1 Statistical summary of foe data from rock cores collected at varying depths

Statistical Parameter Calculated Value foe Minimum Detection Limit (MDL) 00010 Number of samples analyzed (n) 19 Average foe 00019 Median foe 00019 Geometric Mean foe 00019 Standard deviation of foe measurements 000033 Relative standard deviation 174 -+ 95 Confidence intervals 00012 to 00025

The data in Table 1 shows the following

bull The foe from the Hows Corner rock cores are statistically greater than the MDL of the Walkley-Black analytical method

bull The average and median values for the foe of the Hows Corner rock cores from varying depths are nearly identical indicating that there is little variability in the foe values in the source zone at the site

bull The standard deviation of these measurements is 000033 which is 174 of the average foe

bull The 95 confidence intervals of the foe of the rock core at Hows Corner are 00012 to 00025

The foe was also analyzed from three separate samples taken from the same rock core at a depth of 55 feet (Only one of these samples was included in the data summarized in Table 1) Table 2 shows the statistical repeatability of this type of analysis

Hows Corner TI Evaluation Page 2 January 13 2005 Appendix B

Table 2 Repeatability of analysis of foe from one rock core at 55 feet in depth

Statistical Parameter Calculated Value Number of samples analyzed (n) 3 Average foe 00016 Median foe 00015 Geometric Mean foe 00016 Standard deviation of foe measurements 000039 Relative standard deviation 240 -+ 95 Confidence intervals 00008 to 00024

The data in Table 2 shows the following

bull The percent relative standard deviation of these three analyses of foe from the same rock core at Hows Corner is 24

bull The 95 confidence interval of the foes measured in this particular rock core at Hows Conrer is 00008 to 00024

These results show that there is good repeatability in using the Walkley-Black method for analysis of the foe in the rock core at Hows Corner

References Schwarzenbach amp Westall (1981) Transport of nonpolar organic compounds from surface water to groundwater Laboratory sorption studies Environ Sci Tech 15 1360-1367

Walkley A I A Black (1934) An examination of Degtjareff method for determining soil organic matter and a proposed modification of the chromic acid titration method Soil Sci 37 29-37

Hows Corner Tl Evaluation Page S January 13 2005 Appendix B

Woodard and Curran PTS Laboratories PTS File No 34618

ORGANIC CARBON DATA (METHODOLOGY WALKLEY-BLACK)

PROJECT NAME PROJECT NO

SAMPLE ID

203-chip-13 203-chip-23 203-chip-27 203-chip-38 203-chip-42 203-chip-47 203-chip-52 203-chip-58 203-chip-69 203-chip-82 207-chip-11 207-chip-19 207-chip-24 207-chip-29 207-chip-35 207-chip-45 207-chip-55 207-chip-87 207-chip-90

207-chip-55 55-MS

55-MSMSD

Hows Corner NA

DEPTH ft

13 23 27 38 42 47 52 58 69 82 11 19 24 29 35 45 55 87 90

55 NA NA

MATRIX

Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip

Average Median

Geometric Mean Standard Deviation Relative Std Dev

+- 95 Confidence Interval n

Rock Chip Rock Chip Rock Chip

Average Median

Geometric Mean Standard Deviation Relative Std Dev

+- 95 Confidence Interval n

FRACTION ORGANIC CARBON

(gg)

170E-03 185E-03 185E-03 170E-03 240E-03 190E-03 230E-03 180E-03 170E-03 115E-03 195E-03 220E-03 220E-03 235E-03 135E-03 190E-03 205E-03 175E-03 160E-03

188E-03 185E-03 185E-03 327E-04

1739 123E-03 to

19

205E-03 130E-03 150E-03

162E-03 150E-03 159E-03 388E-04

2402 840E-04 to

3

2532E-03

2393E-03

Hows Corner Tl Evaluation Appendix B January 13 2005

Response to EPA-DEP Comment 4 Dated March 31 2005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

EPA-DEP Comment 4

Comment 4 Distribution of contaminants First the TI report seems based on the assertion that there is DNAPL at the source area yet it also appears to represent that the source area is small and the bedrock below 85 is competent (or less fractured) and less impacted by the release of contaminants Some of the confusion may result from using most recent data when that data is from several different sampling events over several years and there is no discernible difference in concentrations between shallow and deep bedrock or as in Section 421 where generally decreased generally increase generally similar and similar concentrations in four consecutive sentences leads to a muddled picture of the contaminant distribution

Second the report asserts that the distribution of contaminants over the entire plume has not changed with time but fails to support this conclusion with data again relying on data that is from different sampling dates for one composite representation

Response The likely presence of dense non-aqueous phase liquid (DNAPL) at the Hows Corner Site and the determination that the source area is small are not mutually exclusive and both are conclusions drawn from information obtained during field investigations The presence of DNAPL in the source area is based on the elevated concentrations of volatile organic compounds (VOCs) detected in the groundwater (WampC 2001 WampC 2002) The conclusion that the source area is small is based on the area in which VOCs in groundwater have been detected at concentrations that are considered to be indicative of the presence of DNAPL nearby Similarly the conclusion that fracture frequency decreases at depths greater than approximately 50 to 85 feet below ground surface was based on field observation during the RI field work The fact that zones with observed fractures exhibited higher hydraulic conductivities than zones without fractures coupled with the decreasing frequency of observed fractures with depth led to the conclusion that the hydraulic conductivity of the bulk rock decreases with depth

The most recent data from all wells were used to provide the maximum VOC data set size During the RI all of the previously-existing and then newly-installed monitoring wells were sampled along with several residential wells The RI sampling included up to 48 monitoring wells Subsequent to the RI and prior to the TI three rounds of monitoring were conducted to verify that the plume was stable 15 monitoring wells were sampled during each of the three rounds During the TI field investigation 29 wells were sampled for VOCs The sampled wells included all of the newly-installed wells and a subset of wells installed during the RI for a total of 29 monitoring wells By using most recent data VOC results from 53 monitoring wells were included in the evaluation (see table labeled Sampling Events for listing of monitoring wells) This approach was selected because there generally was little variation in the data from a particular location between years This is borne out by the attached individual plots of VOCs detected in shallow bedrock and deep bedrock for the Pre-ROD (December 1999January 2000) and Supplemental (May 2000) sampling events and for June 2001 January 2002 and April 2003 sampling events The Pre-ROD and Supplemental plots are similar to the subsequent plots from the 2001 2002 and 2003 sampling events

In addition to maps showing the spatial distribution of VOC data at a given time trend plots of the data from a particular location through time (attached) indicate that since the RI concentrations generally have been stable or have decreased Together the maps and trend plots and the data from which they were developed indicate that the distribution of contaminants over the entire plume has not changed appreciably with time

Response to EPA Comment 4 050305doc 1 of 26 Woodard amp Curran (211941)

REFERENCES

Woodard amp Curran Inc (WampC) 2001 Final Remedial Investigation Report Hows Corner Superfund Plymouth Maine July 2001

Woodard amp Curran Inc (WampC) 2002 Final Feasibility Study Report - Non-Source Area Groundwater Hows Corner Superfund Site Plymouth Maine Hows Corner Superfund Plymouth Maine July 2002

Response to EPA Comment 4 050305doc 2 of 26 Woodard amp Curran (211941)

LIST OF ATTACHMENTS (Response to Comment 4)

Table - Sampling Events 1999 - 2004 (2 pages)

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater Pre-ROD Sampling Event

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater Pre-ROD Sampling Event

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater Supplemental Sampling Event

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater Supplemental Sampling Event

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater June 2001

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater June 2001

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater January 2002

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater January 2002

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater April 2003

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater April 2003

Figure - Concentration Trends - Non-Source Area Wells MW-1B and MW-3B

Figure - Concentration Trends - Non-Source Area Wells MW-13DB and MW-16DB

Figure - Concentration Trends - Non-Source Area Wells MW-16IB and MW- 108D

Figure - Concentration Trends - Non-Source Area Wells MW-108S and MW-112D

Figure - Concentration Trends - Non-Source Area Wells MW-112S and MW-114D

Figure - Concentration Trends - Non-Source Area Wells MW-114S and MW-115D

Figure - Concentration Trends -Source Area Wells MW-2DB and MW-2IB

Figure - Concentration Trends -Source Area Wells MW-102S and MW-103D

Figure - Concentration Trends -Source Area Wells MW-103S and MW-104D

Figure - Concentration Trends -Source Area Wells MW-104I and MW-106D

Figure - Concentration Trends -Source Area Wells MW-106S

Response to EPA Comment 4 050305doc 3 of 26 Woodard amp Curran (211941)

I I

El I

II I I 1 I

I

i

Event Baseline Case ID WC-01 WC-01

Well Date Aug-99 Oct-99 LOT10 1 LOT1-1 1 LOT11-4 LOT14 1 LOT15 1 LOT15-1 1 LOT16 1 LOT16-1 1 LOT17 1 LOT18 1 LOT19 1 LOT2 LOT20 1 LOT21-10 1 LOT21-11 1 LOT21-12 1 LOT21-13 1 LOT21-14 1 LOT21-2 1 LOT21-5 1 LOT21-7 LOT21 -8 1 LOT21-9 1 LOT23 1 LOT24 1 LOT28-1 1 LOT28-2 1 LOT28-3 1 LOT28-4 1 LOT28W 1 LOT30 1 LOT30-1 1 LOT30-2 1 LOT30-3 1 LOT30-4 1 LOT30-5 LOT31 LOT35 1 LOT41 1 LOT42-1 1 LOT43-1 1 LOT43-4 1 LOT6-1 1 LOT67 1 LOT6-7 1 LOT6-8A 1 LOT6-8B 1 LOT80-1 1 LOT82 1 MW-101D MW-1011 MW-101S MW-102D MW-102S MW-103D MW-103S MW-104D MW-1041 MW-104S MW-105D MW-106D

Groundwater Sampling Location Summary 1999 - 2004xls

Sampling Events 1999-2004

Hows Corner Superfund Site Plymouth Maine

Supplemental 2001 2002 2003 Pumping 2004 Pre-ROD Rl Sampling Sampling Sampling Test Sampling WC-03 WC-09 WC-25 WC-30 WC-42B WC-56 WC-58 Dec-99 May-00 Jun-01 Jan-02 Apr-03 Sep-04 Sep-04

1

1 1 1

1 1 1 1 1

1 1

1

1 1

1 1 1

1 1 1 1 1

1

1 1

1 1 1 1

1

1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

Sampling Events 1999-2004

Hows Corner Super-fund Site Plymouth Maine

Supplemental 2001 2002 2003 Pumping Event Baseline Pre-ROD Rl Sampling Sampling Sampling Test

Case ID WC-01 WC-01 WC-03 WC-09 WC-25 WC-30 WC-42B WC-56

ll

Well Date Aug-99 Oct-99 Dec-99 May-00 Jun-01 Jan-02 Apr-03 Sep-04 MW-106S 1 1 1 1 1 MW-107D 1 1 MW-108D 1 1 1 1 1 MW-108S 1 1 1 1 1 MW-110D 1 1 MW-111D 1 1 MW-112D 1 1 1 1 1 MW-112S 1 1 1 1 1 MW-113D 1 1 MW-114D 1 1 1 1 1 MW-114S 1 1 1 1 1 MW-115D 1 1 1 1 1 MW-12DB 1 1 1 MW-12SB 1 1 1 MW-13DB 1 1 1 1 1 1 MW-13SB 1 1 1 MW-14DB 1 1 MW-14SO 1 1 MW-15DB 1 1 1 MW-15SB 1 1 1 MW-16DB 1 1 1 1 1 1 MW-16IB 1 1 1 1 1 1 MW-16SO 1 1 MW-17DO 1 1 1 MW-17SO 1 1 1 MW-1B 1 1 1 1 1 1 MW-203D MW-203S MW-204D MW-204S MW-205 MW-206D

I MW-206S MW-2DB 1 1 MW-2DDB 1 1 MW-2IB 1 1 1 1 1 1 MW-3B 1 1 1 1 1 1

I MW-4O 1 1 1 MW-5B 1 1

II MW-6DB 1 1 1 MW-6SB 1 1 1 MW-8DB 1 1 1 MW-8SB 1 1 1

II PW-207 1 SEEP-1 1 SUBTOTAL - RESIDENTIAL 44 25 0 2 0 3 0 SUBTOTAL - MONITORING 22 48 41 15 15 15 1

Total 3 66 73 41 17 15 18 1

I Included in most recent data

I Notes 1 - Overburden well not included in most recent data for plotting

2 - Tetrahydrofuran and 2-Butanone were the only two compounds detected in this well and are thought to be the result of well repair not included in most recent data for plotting

3 - Not included in most recent data for plotting

2004 Sampling

WC-58 Sep-04

1

1 1

1 1

1 1 1

1

1 1

1 1 1 1 1 1 1 1 1

1 1

1

0 29

29

Groundwatef Sampling Location Summary 1999 - 2004xls

I

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

monitoring well Figure 4-14 total VOC contour (ugl) - December 1999January 2000 Distribution of Total VOCs in

Note SW-113 is located downstream of SEEP-1 Shallow Bedrock Groundwater total concentration of detected VOCs ND= not detected these two locations were sampled during the Pre-ROD Sampling Event

Baseline Sampling Event in OctoberNovember 1999 Hows Corner Superfund Site Surface Water Sampling Location A Plymouth Maine Seep Sampling Location laquo- WOODARD ampCURRAN

995037wipri reportepa ri interim final feb 2001cadd drawingsfinalfig 4-14

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

0 300 600 I

FEET

Q residential well Figure 4-16 monitoring well Distribution of Total VOCs in

Deep Bedrock Groundwater total VOCs contour (ugl) Pre-ROD Sampling Event

active residential wells with lot number Hows Corner Superfund Site 2deg42deg Plymouth Maine total concentration of detected VOCs ND= not detected WOODARD ampCURRAN Enyinaaring bull Science bull Operations bull

995037wipri reportepa ri interim final feb 2001cadd drawingsfinalfig4mdash16

PLYMOUTH POND

PLYMOUTH POND

1 628Tl7MW-2bB 12135

PLYMOUTH POND

monitoring well Figure 4-20

V total VOC contour (ugl) - June 2000 Distribution of Total VOCs in Shallow Bedrock Groundwater

| 34 | total concentration of detected VOCs ND= not detected NA = not analyzed Supplemental Sampling Event Note SW-113 is located downstream of SEEP-1 Hows Corner Superfund Site

Surface Water Sampling Location these two locations were sampled during the Plymouth Maine Baseline Sampling Event in OctoberNovember 1999 Seep Sampling Location WOODARD amp CURRAN

Engineering bull Science - Operations bull 995037wipri reportepa ri interim final feb 2001 cadd drawingsfinalfig 4-20

residential well Figure 4-22 Distribution of Total VOCs in

monitoring well Deep Bedrock Groundwater

total VOCs contour (ugl) Supplemental Sampling Event

Hows Corner Superfund Site

total concentration of detected VOCs ND= not detected NA = not analyzed Plymouth Maine

WOODARD amp CURRAN

995037wipri reportepa-ri interim final feb 2001cadd drawingsfinalfig 4-22 Engineering bull Science - Operations bull

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

FEET

Shallow Monitoring Well

Deep Monitoring Well

C Detected Concentration ND = Not Detected Figure 1-XS Distribution of Total VOCs in Shallow Bedrock Groundwater

Pumping Well

17-Acre Property Boundary Concentration Contour (ugl)

June 2001 Hows Corner Superfund Site

Plymouth Maine WOODARDampCURRAN

-i^rhvj bull Scbncn bull Operations bull 211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0601 dwg04-20-05

PLYMOUTH POND Hopkins Road V

O

PLYMOUTH POND

PLYMOUTH POND

o

0 300 600 mdashfa FEET

Shallow Monitoring Well bull bull - 17-Acre Property Boundary Figure 1-XD

Deep Monitoring Well 1 I Detected Concentration ND = Not Detected Distribution of Total VOCs in Deep Bedrock Groundwater

-mf- Pumping Well June 2001 Residential Well Hows Corner Superfund Site

Plymouth Maine i h Surface Water Sampling Point

g WOODARD ampCURRAN _ ^ _ ^ _ _ yen_ rj i|Hlaquorlny bull Science bull Opt

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0601 dwg04-20-05

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

Shallow Monitoring Well

Deep Monitoring Well

Detected Concentration ND = Not Detected Figure 1-YS Distribution of Total VOCs in Shallow Bedrock Groundwater

Pumping Well

17-Acre Property Boundary Concentration Contour (ugl)

January 2002 Hows Corner Superfund Site

Plymouth Maine WOODARD amp CURRAN Engineering Science- Operations bull

211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0102dwg04-20-05

PLYMOUTH POND

PLYMOUTH POND

Site Pand^ laquoum-laquoBTuitaraquo tLV

vVlf-(

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0 300 600 ^ = FEET

Shallow Monitoring Well mdashbullbullbull 17-Acre Property Boundary Figure 1-YD - A - Deep Monitoring Well FT Detected Concentration ND = Not Detected Distribution of Total VOCs in

Deep Bedrock Groundwater Pumping Well January 2002 Residential Well Hows Corner Superfund Site

Plymouth Maine Surface Water Sampling Point

WOODARD ampCURRAN Engineering Sciencs- Operations bulli Si

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0102dwg04-20-05

- m j

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PLYMOUTH POND

PLYMOUTH POND j A O-shy

Shallow Monitoring Well E Detected Concentration ND = Not Detected Figure 1-ZS Distribution of Total VOCs in

Deep Monitoring Well Shallow Bedrock Groundwater

Pumping Well Hows Corner

April 2003 Superfund Site

17-Acre Property Boundary Plymouth Maine Concentration Contour (ugl) r WOODARD ampCURRAN

Engineering bull Science bull Operations bull 211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0403dwg04-20-05

s S pound

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- -

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Jo

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ft Shallow Monitoring Well mdashbullbullmdash 17-Acre Property Boundary Figure 1-ZD Deep Monitoring Well I 1 I Detected Concentration ND = Not Detected Distribution of Total VOCs in

Deep Bedrock Groundwater Pumping Well April 2003

Q) Residential Well Hows Corner Superfund Site Plymouth Maine

(T) Surface Water Sampling Point WOODARD ampCURRAN poundKk EnginawtirKj bull Science - Operations bull

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0403dwg04-20-05

0 Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

B MW-1B

I 12000

PCE

B 10000 Total VOCs

I

i 2000

i 0 Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

c MW-3B

G 2000

1800

B PCE

1600 Total VOCs

1 I I E

il-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

G E

211941

El

I I z E

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Concentration Trends shy Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-13DB

Total VOCs

c i i c o

Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

MW-16DB

30

c i c c I c o

Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99

PCE

Total VOCs

Jul-01 Jul-03

211941

O bi

c Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

I MW-16IB

i 35

3

c Total VOCs

lt- 2 5

0 | gt

o

1 sectI

c c 0 4

Jul-90 Jul-92 Jul-94 Jul-96 Jul-98 Jul-00 Jul-02 Jul-04

I I MW-108D

I 12

PCE 10

Total VOCs c oc 3

E E I 0

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

E 211941

c Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

fi MW-108S

I I 40

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Total VOCs

30

I f 26

20 I o

I 15

10

c Dec-99 Dec-00 Dec-01 Dec-02 Dec-03 I 0

I MW-112D

c 35 - imdash

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I

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211941

I

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Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-112S

08

PCE

Total VOCs 06

o 04

02

0 Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

MW-114D

o

12000

10000

8000

6000

PCE

Total VOCs

4000

2000

i

ccEIIc

i

i

E

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

211941

Con

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ratio

n (

ug

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E Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

I MW-114S

E A5000 -- Total VOCs

- 4000

0 3000

2000

i 1000

i n shy

Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

MW-115D

c PCE

Total VOCs

c E

o

C c

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03 I 0

211941

IepoundII

EIEIIGICCIccc

30000

25000

20000

o bullsect 15000 b

o 10000 U

5000

0 Aug-99

25000

20000

5000

0 Aug-99

211941

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-2DB

PCE

Total VOCs

Aug-01 Aug-03

MW-2IB

PCE

Total VOCs

Aug-01 Aug-03

IDIBI

ii EIDIISIBIG C

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-102S

6000

5000 PCE

Total VOCs

4000

O 3000

2000

1000

0 Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

MW-103D

16000

~ 14000 ugt 3- 12000 o

^ 10000

sect 8000

O 6000

4000

2000

PCE

Total VOCs

0Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

211941

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

G MW-103S

I I

ampo

12000

10000

E sectc

S

8000

6000

4000

2000

0Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

G I 6000

MW-104D

i 5000

PCE

Total VOCs

i i c

2000

1000

Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

E I

211941

cIccIG

IIBCccBcIc

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-1041

PCE Total VOCs

a 25000

0 20000

a 15000

10000

5000

0 Jan-OO Jan-01 Jan-02 Jan-03 Jan-04

MW-106D

3000

2500 PCE

Total VOCs

=sect 2000

o bullsect 1500

1000

500

0 Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

211941

c Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

c MW-106S

I PCE

Total VOCs

i

i Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

i

i i i E

C

211941 c

Response to EPA-DEP Comment 5 Dated March 312005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

iiw

EPA-DEP Comment 5

Comment 5 Matrix Diffusion The report as well as other proponents of matrix diffusion suggest that depletion of DNAPL (Section 5112 page 5-15) needs to be achieved While that might be the ideal the goal is to achieve performance standards and that goal may be attainable while there is residual contamination in the rock perhaps even DNAPL globules The low bedrock matrix porosity (page 1-15) the high permeability values (page 4-4) the relative flux of the groundwater (page 5-5) and the decrease in surface area and out of the mainstream pockets (appendix C-4) all suggest that the diffusion out of the rock matrix would be insubstantial relative to the regional flux of groundwater through the Site

Response The TI Evaluation Report does not explicitly consider or rely upon matrix diffusion as a basis for requesting a TI Waiver for a portion of the Hows Corner Site The technical literature provides documentation that matrix diffusion can be a significant process that affects chemical transport and groundwater remediation timeframes in unconsolidated and consolidated media including fractured rock (US EPA 1989 Freeze and Cherry 1979 Pankow and Cherry 1996 Fountain 1998) Back diffusion of contaminants from the matrix porosity of the fractured rock can prolong the time necessary to achieve groundwater cleanup goals particularly for compounds such as PCE for which the cleanup goal is a low concentration It is our expectation that matrix diffusion has occurred at the Hows Corner Site and that back diffusion of PCE from the rock matrix will also occur Although the extent to which matrix diffusion is occurring at the Hows Comer Site has not been determined and that lack of knowledge contributes to uncertainty regarding the cleanup times at the Site the effect of matrix diffusion is to lengthen rather than shorten the time required for remediation

REFERENCES

Fountain JC 1998 Technologies for Dense Nonaqueous Phase Liquid Source Zone Remediation Ground-Water Remediation Technologies Analysis Center Technology Evaluation Report TE-98-02 December

Freeze RA and Cherry JA 1979 Groundwater Prentice-Hall Inc Englewood Cliffs NJ 07632 p 410-412

Pankow J F and Cherry J A 1996 Dense Chlorinated Solvents Waterloo Press Portland OR 97291-1399 p 67-88

US EPA 1989 Transport and Fate of Contaminants in the Subsurface EPA6254-89019 p 17-18

Response to EPA Comment 5 050305doc 1 of 1 Woodard amp Curran (211941)

WOODARD amp CURRAN Maine Massachusetts New Hampshire Connecticut Florida Operational offices across the US 1-800-426-4262 www woodardcurran com

Page 6: SDMS DocID 251749 - Records Collections · 2020-06-13 · CORPORATE OFFICES: Maine, Massachusetts, New Hampshire, Connecticut New, York, Florida Engineering • Science • Operations

m

Response to EPA-DEP Comment 2 Dated March 312005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

EPA-DEP Comment 2

Comment 2 As discussed in our January meeting the results of the TI field work and their interpretation need to be presented in the TI report Listed below are some specific comments on this with the goal being a discussion of how the site conceptual model and site modeling were revised as a result of the 2004 field work

a analysis of the aquifer test to include a figure presenting the drawdown observed in each monitoring well at the end of the aquifer test The horizontal hydraulic gradient should not be included since this method tends to accentuate the anisotropy Two figures may be needed one for shallow bedrock and one for deep bedrock an evaluation of the appropriateness of the Cooper-Jacob (CJ) method for analyzing the aquifer test data including a comparison of the pattern of observed drawdown to the pattern of fracture orientations determined from the borehole geophysics confirmation that u lt 001 and that calculated values for T and S are similar for several observation wells an interpretation of the change in slope on the CJ plots near the end of the aquifer test the recovery data should be evaluated since it may provide insight as to why the slopes changed the marked increase in slope near the end of the test strongly suggests that a barrier (ie no flow) boundary was encountered and if a boundary was encountered T and S need to be calculated from the pre-boundary portions of the CJ plots It may be appropriate to analyse the aquifer test data using Theis as well as the Moench dual porosity model (both analysis methods are available in Aqtesolv pumping test modeling software) so that all parties have confidence in the transmissivity and storativity numbers derived from the CJ analysis b numerous bedrock borings (including angled holes) were drilled during the most recent field investigation yet no summary of the findings or the geophysical logging or packer test and sampling results have been provided c have any input parameters been changed in the flow transport and batch-flushing models as a result of the 2004 fieldwork If so which ones and why were the changes made (ie justify the changes)

Response The objective of the pumping test conducted at the Hows Corner Site during September 2004 was to observe the response of the groundwater system to pumping for use in refining the site conceptual model The refined site conceptual model would in turn be used to recalibrate the flow model and aid in the design of the hydraulic containment system being constructed under the authority of the AOC for the RD

The results of the pumping test are illustrated by plots of the drawdown at the end of the test The enclosed three drawdown plots (shallow bedrock deep bedrock and combined) represent the change in water level at the end of the test from the initial pre-test water level The shallow bedrock figure shows a northeast-southwest trending ellipsoidal area of drawdown that extends approximately 2000 feet along the major axis and approximately 800 feet along the minor axis The northeast-southwest orientation of the drawdown ellipse is consistent with the orientation of likely water-bearing fractures as identified from geophysical logging during the TI investigation The deep bedrock figure and combined figure also show ellipsoidal areas of drawdown with similar orientation A secondary axis with a more northerly orientation is evident on the figures showing drawdown in deep bedrock and in combined shallow and deep bedrock The maximum drawdown measured in shallow bedrock was 29 feet at MW-2EB The maximum drawdown measured in deep bedrock was 54 feet at the pumping well (PW-207) The drawdown ellipse is

Response to EPA Comment 2 050205doc 1 of 24 Woodard amp Curran (211941)

approximately coincident with the location of the modeled capture zone as presented on Figure 3shy1 of the TI Evaluation report

The enclosed three potentiometric surface maps (shallow bedrock deep bedrock and combined) represent the water surface elevations measured at the end of the test which was 72 hours or three days after it began All three maps show the presence of the groundwater high located in the southeast portion of the 17-acre property This high area shows relatively little relief but with the exception of the measurements at MW-2DDB which shows anomalously high water levels the central area of the high is at lower elevation than the perimeter The measurements at MWshy2DDB are hypothesized to result from water that is unable to drain rapidly enough to equilibrate with the rest of the formation

The pumping test data initially were analyzed using the Cooper-Jacob method for the late test data The results of this analysis are summarized in the table entitled Pumping Test Analytical Results It was recognized that because the aquifer is not uniform isotropic and infinite in areal extent the assumptions on which the underlying Theis equation is based were not met and because of the length of the test the criteria for use of the Cooper-Jacob of analysis were not explicitly met We recognize that the complexity of the hydrogeologic characteristics of the formation would be a significant limitation if the calculated values from the pumping test analysis were to be used as absolute representations of the hydraulic parameters of the formation However the range of values from this pumping test analysis were used as guidelines or bounding values for recalibration of the flow model

Woodard amp Curran also analyzed the pumping test data using the Theis and Moench methods The enclosed table entitled Pumping Test Analytical Results also summarizes the results of analysis of the data using these analytical methods Again although none of the methods may be strictly applicable they provide values that are guidelines for parametric ranges used in model calibration Hydraulic conductivity values calculated from the different analytical methods were as follow

Minimum Maximum Mean (ftday) (ftday) (ftda

bull Cooper-Jacob 020 067 038 bull Theis 035 1476 392 bull Moench (Fissure) 027 210 099

Storage coefficients calculated from the different analytical methods were as follow

Minimum Maximum Mean bull Cooper-Jacob 830E-04 392E-02 651E-03 bull Theis 547E-05 359E-03 473E-04 bull Moench (Block) 803E-05 402E-02 489E-03

Storage coefficients calculated using the Theis method were one to two orders of magnitude lower than values calculated using the Cooper Jacob or Moench (Block) methods Although the fissure system values are thought to be appropriate for evaluating hydraulic conductivity because the majority of flow is through fractures the block system values are appropriate for evaluation of storage because the limited fractures account for only a small part of the total storage in the bedrock

Response to EPA Comment 2 050205doc 2 of 24 Woodard amp Curran (211941)

Woodard amp Cunran used the values estimated from the pumping test analysis as an initial data set for transient benchmarking by running a 3-day simulated pumping test Calibration of the model was accomplished by comparing measured drawdowns obtained during the pumping test to calculated drawdowns from the flow model The hydraulic parameter values in the model were varied from the initial values but within the range calculated from the pumping test analysis The additional model calibration was considered to be completed when the calculated drawdowns were sufficiently close to measured drawdowns The resulting values of the hydraulic parameters of the calibrated model were then considered acceptable to provide satisfactory prediction of the response of the flow system to other hydraulic stresses

Regional water-level data were reviewed prior to data analysis A plot of water levels in the closest USGS regional background well (provided in the TI Data Package and attached) indicates that throughout the period of the test and subsequent recovery water levels were declining on a regional scale Although the decline in water levels is gradual the change in slope observed on the Cooper-Jacob plots is thought to represent the point at which the drawdown at a given location caused by pumping becomes less significant compared to the regional drawdown This occurs at about a day after start of pumping The effect of the regional decline in water levels can also be seen in the initial rapid rise in water levels in response to pump shut off followed by a decline in water levels after about a day after the pump is shut off

Additional information obtained during the TI field work was reviewed and evaluated in updating the conceptual model for the site In general the additional information corroborated the understanding of the Site presented in the RI report In particular the northeast-southwest fracture orientation was confirmed as the predominant orientation Geophysical logging during the TI investigation however showed the dip direction of fractures to be more variable and the dip angles to be shallower than was understood based on the RI data (see enclosed figure Packer Testing Results in Vicinity of Source Area) The additional borings installed within the fenced area and to the east of the fenced area showed that the area in which concentrations of total VOCs in groundwater exceeded 10000 pgL was more limited than portrayed in the RI and FS reports Packer testing of the intervals identified by geophysical logging as likely or possibly transmissive (see enclosed borehole geophysical logs) showed VOC concentrations within the packered intervals at a given borehole to be either essentially constant (eg MW-203 MW-204 MW-205) or increasing with depth (eg PW-207) Information on hydraulic conductivity and VOC concentrations in packered intervals is summarized on two separate tables for the 1999 RI wells and 2004 TI wells (Packer Permeability and Packer Sampling Results for Potential Fracture Intervals - enclosed) The orientation hydraulic conductivity and VOC concentrations of features identified as likely or possibly transmissive is summarized in a separate table (Orientation Permeability and Groundwater Sampling Results for Transmissive Features shyenclosed)

Table 4-1 of the TI Evaluation report summarizes the variation of input parameters to the flow and batch-flushing models as the project progressed from RI to FS to TI As described above for calculations in the TI Evaluation report hydraulic conductivity values were adjusted during the model calibration to pumping test drawdown data Measured fraction of organic carbon values and VOC concentrations were used in the Batch-Flushing model along with recharge calculated from the ModFlow model For calculation of pore flush volumes using the Batch-Flushing model the ratio of density to porosity was constrained to a range of 4 to 10 which is the typical range of such ratios in porous media (Freeze amp Cherry 1979) The basis for this change was stated in Appendix C of the TI Waiver Evaluation Report and is described in the response to Comment 3

Response to EPA Comment 2 050205doc 3 of 24 Woodard amp Curran (211941)

REFERENCE

Freeze RA and Cherry JA 1979 Groundwater Prentice-Hall Inc Englewood Cliffs NJ 07632 p 410-412

Response to EPA Comment 2 050205doc 4 of 24 Woodard amp Curran (211941)

LIST OF ATTACHMENTS (Response to Comment 2)

Figure - Drawdown at 72 Hours Shallow Wells

Figure - Drawdown at 72 Hours Deep Wells

Figure - Drawdown at 72 Hours

Figure - Potentiometric Surface at 72 Hours Shallow Wells

Figure - Potentiometric Surface at 72 Hours Deep Wells

Figure - End of Pumping Test Bedrock Potentiometric Surface at 72 Hours

Table - Pumping Test Analytical Results

Figure - USGS Background Groundwater Level

Figure - Packer Testing Results in Vicinity of Source Area

Figure - Borehole Geophysical Log MW-203

Figure - Borehole Geophysical Log MW-204

Figure - Borehole Geophysical Log MW-205

Figure - Borehole Geophysical Log MW-206

Figure - Borehole Geophysical Log PW-207

Table - Packer Permeability and Packer Sampling Results for Potential Fracture Intervals 1999 Drilling Program (2 pages)

Table - Packer Permeability and Packer Sampling Results for Potential Fracture Intervals 2004 Drilling Program

Table - Orientation Permeability and Groundwater Sampling Results for Transmissive Features 2004 Drilling Program (2 pages)

Response to EPA Comment 2 050205doc 5 of 24 Woodard amp Curran (211941)

(MEDEP Pond 1) Farm Pond

0 150 300

FEET

Monitoring Well

Figure X Pumping Well Drawdown at 72 Hours

_ - 17-Acre Property Boundary Shallow Wells Hows Corner Superfund Site Drawdown Contour (ft) Plymouth Maine

151 | Drawdown (ft) WOODARD ampCURRAN

^Stk Engineering bull Science bull Operations bull 211941 Hows CornlaquorwipDrawingsTI EVALDrawdown-72hrs_shallowdwg04-19-05

MW-3B

413951 W-6DB JMW-6SB

(MEDEP Pond 1) Farm Pond

Monitoring Well

Pumping Well

17-Acre Property Boundary

Groundwater Elevation Contour (ft)

211941 Hows CornerwipDrowngsTI EVALpo-tent-aU-72-hrsdwg

Figure X End of Pumping Test

Bedrock Potentiometric Surface at 72 Hours Hows Corner Superfund Site

Plymouth Maine ^ WOODARD amp CURRAN

Englnesring bull Science bull Ope

(MEDEP Pond 1) Farm Pond

Monitoring Well

Pumping Well Drawdown atFigure X

72 Hours _bullbull_ 17-Acre Property Boundary Deep Wells

Drawdown Contour (ft) Hows Corner Superfund Site

Plymouth Maine 151 | Drawdown (ft)

= WOODARD ampCURRAN 211941 Hows CornerwipDrawingsTI EVALDrawdown-72hrs_deepdwg04-19-05

Engineering bull Science bull Operations

(MEDEP Pond 1) Farm Pond

028 MW-12DB

MW-125B 040

l - _ ^ I 016 I N

050 MW-15SB

MW-15DB 048

A J s

- A - Monitoring Well

-$poundbull Pumping Well

_bullmdash 17-Acre Property Boundary

^ Drawdown Contour (ft)

151 I Drawdown (ft)

211941 Hows CornerwgtpDrawinQsT EVAI_Drawdown-72brsdwg04mdash19-05

Figure X Drawdown at 72 Hours

Hows Corner Superfund Site Plymouth Maine

^ WOODARD ampCURRAN Engineering bull Science bull Operations i

(MEDEP Pond 1) Farm Pond

Monitoring Well

Pumping Well

_bullbull_ 17-Acre Property Boundary

f Groundwater Elevation Contour (ft)

|419Q0| Groundwater Elevation

211941 Hows CornerwipDrawinqsTI EVALPotSurf-72hrs_shallowdwg04-19-05

150 300

FEET

Figure X Potentiometric Surface at 72 Hours

Shallow Wells Hows Corner Superfund Site

Plymouth Maine

WOODARD ampCURRAN Engineering bull Science bull Operations

29212 MW-108D

(MEDEP Pond 1) Farm Pond

Monitoring Well

Pumping Well

mdashbullbulllaquo 1 7-Acre Property Boundary

bull Groundwater Elevation Contour (ft)

1419001 Groundwater Elevation

211941 Hows CornerwipDrawingsTI EVALPotSurf-72hrs_deepdwg04-19-05

150 300 =5fc= FEET

Figure X Potentiometric Surface at 72 Hours

Deep Wells Hows Corner Superfund Site

Plymouth Maine

WOODARDampCURRAN Engineering bull Science bull Operations bull

--

Pumping Test Analytical Results Hows Corner Superfund Site

Plymouth Maine

Well ID oper Jaccb Analyses 2 Theis Analyses Fissure

Well Id Rd (ft)

Saturated Thickness

Transmissivity

(ft2day) K

(ft2day) K

(cmsec) Storage

Coefficient Transmissivity

(ft2day) K

(ft2day)

K (cmsec)

Storage Coefficient

System K

(ftday) PW-207OB 8 85 481 057 200E-04 392E-02 36 042 150E-04 809E-04 027 MW-103S 50 85 451 053 187E-04 720E-03 92 108 382E-04 283E-04 083 MW-103D 54 185 455 025 868E-05 210E-02 65 035 123E-04 237E-04 044 MW-2IB 59 85 352 041 146E-04 699E-03 104 123 433E-04 512E-04 052 MW-2DB 63 85 334 039 139E-04 845E-03 148 080 283E-04 239E-04 046 MW-104D 95 185 489 02 6 932E-05 654E-03 98 053 186E-04 547E-05 037 MW-104I 97 85 33 03 9 137E-04 362E-03 117 137 484E-04 962E-05 048 MW-101I 107 85 364 043 151E-04 490E-03 511 601 212E-03 223E-04 136 MW-102D 134 185 435 024 829E-05 248E-03 108 058 206E-04 850E-05 065 MW-101D 138 185 492 027 938E-05 511E-03 671 362 128E-03 700E-04 172 MW-205 219 85 57 067 237E-04 255E-03 447 526 186E-03 359E-03 -shyMW-204D 221 185 367 020 700E-05 170E-03 790 427 151E-O3 155E-04 147 MW-204S 225 85 379 045 157E-04 156E-03 1031 1213 428E-03 313E-04 199 MW-1B 228 85 325 038 135E-04 977E-04 340 400 141E-03 739E-05 054 MW-203S 273 85 489 058 203E-04 117E-03 1255 14 76 521 E-03 216E-04 210 MW-106D 278 185 51 028 972E-05 141E-03 1065 576 203E-03 360E-04 104 MW-203D 278 185 478 026 911E-05 152E-O3 765 414 146E-03 364E-04 138 MW-105D 364 185 44 024 839E-05 830E-04 769 415 147E-03 200E-04 127

1 Analyses conducted using Cooper and Jakob method on late drawdown data collected during constant

discharge pumping test conducted at the Hows Comer Site from September 20 - 30 2004

2 Analyses conducted using Theis solution for unconfmed approximation (1935)

J Analyses conducted using Moench method for dual porosity estimation (1984)

Fissure System Storage

Coefficient 402E-04 117E-06 264E-04 300E-04 932E-05 235E-07 502E-05 326E-06 801E-05 542E-04

-

803E-05 762E-05 134E-05 498E-05 115E-04

47E-04 838E-05

3 ysesh Analysis

Block System K (ft2day)

251E-02 207E-03 564E-04 163E-04 585E-04 465E-02 153E-04 498E-03 855E-04 356E-03

-

292E-03 394E-03 720E-04 526E-03 160E-01 35OE-O1 287E-03

Block System Storage

Coefficient

402E-02 164E-04 183E-02 330E-03 158E-03 847E-03 286E-03 326E-04 803E-05 272E-03

723E-04 686E-04 148E-04 349E-04 115E-03 47E-04 838E-04

Theis - Moench - CJ - AnalyticalResults_4-19-O5xls

DRAFT

242

24

238

236

bulla

c

i

a Q

234

232

228

226

Hows Corner Constant Discharge Testing USGS Background Groundwater Level USGS 445319068560101 ME-PEW456 Kenduskeag Maine

End of Monitored Recovery Period 09302004

Regional Background Location i 226 miles from Pumping Locatio

lt

697

NOTES

1 Groundwater samples collected in 1999 were screened for five volatile organic compounds (VOCs) only N

tetrachloroethene (PCE) exceeded reporting limits MW-2030 082304 082304 082304 082304 u

2 Strike and Dip of likely or possible transmissive 30 45 55 85 feature within the packer interval from which the indicated sample was collected

MW-204D

PCE TOTAL VOCs

081904 30

220 2636

A

081904 46-50 540 6436by

081904 IT

260 3073

x

MW-105D

PCE TOTAL VOCs

111199 50-60 2100 2100

MW-106D

PCE TOTAL VOCs

111199 76-86

400 400

111199 137-147

1400 1400

111299 1355-1455

350 350

PCE TOTAL VOCs

44 84

64

MW-6SB

bulli

lt

gt-

170 234

35

I I i

140 192

^^52

^^52

130 183

52 - lt

S A 34

PW-207 082404 082404 082404 20 37

PCE 1300 TOTAL VOCs

17-Acre George West Property Boundary

MW-113D

PCE TOTAL VOCs

112299 46-56

350 350

112299 70-80 190 190

150

112299 105-115

129 129

112399 138-148

230 230

L e g e n d ( J New Monitoring Well-Summer

Site Property Boundary ^ P u m p i n g Well-Summer 2004

-xmdashxshy Source Area

bull0shy Monitoring Well shy Pre 2004 Angled Boring-Summer 2004

211941laquoipdwgTI-ELV21ig41paltker-data2

2004 PCE of Total

bull lt70 VOCs

M W - 1 14D ^ ^

Figure xx Packer Testing Results in

Vicinity of Source Area Hows Corner Superfund Site

Plymouth Maine ^ WOODARD ampCURRAN

^^^^^^^^^^m ampKm Engineering - Science bull Operations

c Northeast Geophysical Services Borehole Geophysical Log

MW-203 Date logged 081704 Plymouth Maine

I Flowmeter Measurements Tomporaturo(C) Acoustic Televiewer

7 5 8 8 5 9 95 Caliper (Inches) Resistance (Ohms) Spontaneous Potential (mVj Dip In Degrees PCE Total VOCs

3 0 2 0 8 0 laquodeg 4S 1000 1400 1800 2200 MO HO 1000 1200 MOO 0 laquo deg ugL ugL n 1 1 1 1 1 1 1 1 1 i 1 1 1 1 n 1 1 1 1 1 1 1 1 1 1 1 n I l l l l l l l n

Ambient Flowneter pumping Rowmeter 11 gpm 6

H

bull

magnetic 10 bull 10 bull - 10 - north - 1 0I

-

_

bullbullbull - bull

20 bull bull20 bull ^ ltr~mdash 01

I

4 ^

LOS7

^

44 84 I I

Xr - 2

lt ^ bull30 -_ _^O1J- 1 _ 050 30 - 3 0

0r - - 3

C -j [ bull bull bull | shy

-O8 H ~ 1 045 7

1 4040 - 40 - -40 r - 14gt 13

V1s -- -023 f 1022 1V 170 234 I

T lt bull B gtf 50^ J50 - - 5 0 - - 5 0

I eet be

lo

i 1

1 1

1

140 192 - - - -t shy

-mdashj bullpound 60 - $o - - 60 - -60

H i I c

bull024

ampbull

3 - T lt ftft rgt He

70 bull j 70 - - 70 - 7 0 -

in -j bullbull shy

-021 1 T 022

- Ton _ Ov

26

130 183 NF NF

90 -_ 90 - 7 90 - -90

-

ifi Jf

3J

^gt _ N F NF bull bull shy

| H100 - j 100 bullbull 100 - -100

1 1 1 1 1 1 1 ) | 1 f I 1 1 1 ) 0 20 40 60 80

flft mdash ftn - mdash rVt

30 4 g 0 20 40 60 Dip in Degrees bullbull

Likely or poss bleFluid Resistivity (ohmmeters) The dip direction-- indicated

^ t h e l i n e extending from t h

I Iransmissive zone circle The strike of the feature is 90 degrees from this

The acoustic televiewer graph displays the mostprominent features selectedffom the acoustic televiewer

R n r a h n l c D O t t n O I B

f i o n n h w c i r a l U K U p i i y SI Ud l

1 rn l_Og Packered Interval August 2004

E tog The location dip angle and dip direction of the sleeted M W - 2 0 3 Groundwater samples were collected by Woodard S Curran on H23120M features are approximate Refer to the televiewer og of His _ well for more precise detail Plymouth Maine Date logged 081704

I

1

Northeast Geophysical Services Borehole Geophysical Log MW-204 D a t e l o gge d 072604

Plymouth Maine

n 3

Flowrneter Measurements(in gpm)

Caliper (Inches)0 3 5 4 0

1 1 1 1 1 1 1 t 1 1 1 1 1 1Ambient Rowmeler pumping Flowmetsr 05gpm

Templaquorature (C) bull bull bull bull i

7 75 8 8S 9 Resistance (Ohms) Spontaneous Potential (mV)

4000 SOW 600 4M 0

Acoustic Televiewer (interpreted)

Dip in Degrees 0 20 4060 SO

at N

PCEugL

Total VOCs ugL

- -_ a

10-

shy 10 bull - 10 shymagnetic

north - 10

o o

bull 1

11

11

1 1

1 1

11 1

1 1

1 1

1 1

1 1

1 1

1 1

1 1

1 1 E 1

- L

3 7 2 0 2 0r bull 20 bull - shy

i S_ N F

bull30 bull 7 3 0 220 2636shy1^ J J 004

fI f V ^

40 shy 4 0 4 0 shy - 4 0rbull019 [_ 007 w8 - - shy5 c

bull

gt

Ia50i 540 6436

bull50 - - 50 - - 5 0

-QQ7 - bull - -t T

pound V gtk

B 6 0 - e o - 7 6 0 -60shyQ 1 1

Q -007 -004 bull1 mdash T - J ~

bull

- - shyT 70 -J c [TO- - 70 - 7 0-

V Y 1- -004 -003

mdash T -h - y - j i - - mdash 260 3073 - gt=7

80 -j NF bull80 - - 80 - - 8 0Jgt

bull i

i 1

i i

C- bull shy

90 shy

K

Jlt i90 90 shy - 9 0shy -

l

ii

I I I I

NF bull M J

I ^ ^ - ^ bull 1

mdash mdash - _

s -7 ^100shy

till

1 100 100- H - 1 0 0shy -1 x Likety or possible k ^ Iransmissive zonebull

1 i i i ii i i i | l l l l | l i l l 0 20 40 ED 80

1 -

3 0SOFluid Resistivity (ohmmeters)

Dip in Degrees The djp ^ ^ o n is indicated ty Ihe line extending from tha circle The strike of Ihe feature

19- 3U UIHJIW93 IolII l l l lraquo

bull

The acousfc televiewer graph displays the mostprominent features selected from the acoustic televiewer109 The location dip angle and dip direction of Ihe sleetedfeatures are approximate Refer to the televiewer log of thiswentormore precise detail

B o r e h o l e G e O D h V S I C a l LOO B W H U I B w c w p n y o i v a i w v yM W - 2 0 4

P l y m O U t n MaiDB

Packorod Interval August 2004Groundwater san-ples wampramp collected by Woodard a Curran on OMO23C4

Date logged 072604

C

I

E Northeast Geophysical Services Borehole Geophysical Log Date logged 072704

I MW-205

Plymouth Maine

Flowmeter Measurements Temperature (C) Acoustic Televiewer (In gpm) I ~l (Interpreted)

I 85 10 Caliper (inches) 95

Dip in D g r laquo Resistance (Ohms) Spo ontaneous Potential (mV PCE Total VOCs 3 0 16 4 0 4 5 ) 20 40 60 80 10 00 2000 30 00 4VJ 400 -3 laquo

i i i i 1 i i I i 11 4 0 D 1 I I ugL ugL

C h

iii Ambient Flowmetar pumping

Flowmeter 1 25 gprn

I bull$bull

i

I rmdash magnetic 1 north ^^^^ 1 VI f

10 ~ I C x 10 bull - 10 bullbull

4 5 6mdashmdash f 1000B 11448 noisy nodi a raquo ^

mdash 5rt mdashi mdash Oft pound) 1100B 12509

cjmdash1 007

-

i i i 1

en

8 B a B

30 mdash

-

40 shy

-mdash I -

50 -_

__NF lt005

- 30 - - 3 0 it 34V

MO P26 V S) 1300B 13776 _ N F NF

26

40 bull - 40 bull 7-40 gt J Vf1 cX

) -j -

_ N F NF 50 c bull - 50 ^ 7-50

i I

I

c

B pound 60 - 6 0 7 60 - 7-60 a i 1

_ N F NF i Si f f 70 -_ bull70 bull - 70 shyC I 9

-m bull - shyA

_ N F NF 80 80 -j bull80 bull - 80 - C- 33 34

bull

5-i r

i 1

J r

Ck

_ N F NF 9 0 90 - - 90 shy

i bullCshy

J rK bull

100 -j ^ Likely or possible bull100- - 100- I -100

transmissive zone bull - ^ bull shy] |

1 1 1 1 1 1 1 I 1 i i i 1 i i 1 1 0 20 40 SO SO 10 20 30 40 50 Dip in Degrees 30 4 0 Fluid Resistivity (ohmmeters) Thlaquo dip direction is indicated

by the line extern r g from the circle The strike of he feature is 90 degrees from ihis

The acoustic televiewer graph displays the most

I Borehole Geophysical Log Packered Interval August2004 prominent features selected from the acoustic televiewer

Groundwatcr samples were oollccled by Woodard amp Cufran orgt S172004 log The location dip angle and dip direction of ins slsctsd MW-205 features are approximate Refelt to the televiewer log of this wall for more precise detail Plymouth Maine Date logged 072704

I

C

I Northeast Geophysical Services Borehole Geophysical Log Date logged 072704

I MW-206

Plymouth Maine

Flowmetor Measurements Temperature (C) Acoustic Televiewer | I r T i i i i i i i i i i i i i i r I |(in gpm) (Interpreted)

I 75 8 flS 9 95

Caliper (inches) Resistance (Ohms) Spontaneous Potential (mV) Dip In Degress PCE Total VOCs 30 35 40 4 5 0 20 40 M 90 4500 5500 6500 ugL ugL I i i

I I

- 1 0

I - 2 0

I 2900B 32401

i i L

E 0

i 6300B 68901

i I 0 20 40 SO 80

20 30 40 50 Dip in Dlaquogralaquos

amp 4 a Fluid Resistivity (ohrnmeters) The dip dirertion is indicated Likely or possible by iho line extending from the transmissive zone circle The striKe of the feature

is 90 degrees from tNs

Borehole Geophysical Log Packered Interval August 2004

E amples were collected by Woodard amp Cunan oo SM82004 log Thraquo location 4p angle and dip direction of the sloeled MW-206 feature are approximate Refer to the televiewer 109 of this well for more precise detail Plymouth Maine Date logged 072704

C

I Northeast Geophysical Services Borehole Geophysical Log

Date logged 082304 PW-207

I Plymouth Maine

Fiowmeter Measurements Temperature (C) Acoustic Televiewer

I (in gpm) (interpreted)

75 8 85 9 95 Caliper (inches) Resistance f0tims) Spontaneous Potential (mV) Dip in Degrees PCE Total VOCs

55 60 0 20 40 SO 80 ugL ugL I I I I I I I

Ambienl Fiowmeter pumping Flewmater

magnetic - 10 - - 1 0

north

i - 20 - - 2 0

1300 1410

i - 30 - - 3 0

i tf

5400 5802 - 40 - - 4 0

B - 50 - - 5 0

I 18000 19234

- 60 - - 6 0

I 12000 13085

- 70 - - 7 0

- 8 0

i - 9 0 19000 20354

G - 100- -100

I 110 110 bull110

0 20 40 60 SO 10 20 30 Dip m Degrees

Fluid Resistivity (ohmmeters) I 50

The dip direction is indicated by ihe line extending from the circle The strike of the fealure is 90 degrees from this

Borehole Geophysical Log

G Packorod Interval August 20(M log The location dip angle and dip dirlaquocton or the sleeted Groundaier samplss were ooliecled by Woodard i Curran on ampt24f2ltXM PW-207 failures are approximate Reter to the televiewer log of this wlaquoll for more precise detail PlyPIOUth Maine Date logged 082304

I

Table XX Packer Permeability and Packer Sampling Results for Potential Fracture Intervals

1

WellID MW-101D MW-101D MW-101D MW-101D MW-101D MW-101D MW-101D MW-101D MW-101D MW-101D MW-I01D MW-101D MW-101D MW-102D MW-102D MW-I02D MW-102D MW102D MW-102D MW-102D MW-102D MW-102D MW-I02D MW-102D MW-102D MW-102D MW-103D MW-103D MW-103D MW-103D MW-I03D MW-103D MW-103D MW-103D MW-103D MW-103D MW-103D MW-103D MW-I03D MW-104D MW-104D MW-104D MW-104D MW-I04D MW-104D MW-104D MW-104D MW-104D MW-104D MW-104D MW-105D MW-105D MW106D MW-106D MW-106D MW-107D MW-107D

1999 Drilling Program

Hows Corner Superfund Site Plymouth Maine

Potential Fracture Top Of Bottom 6 Depth to lt Topof i Interval from Packer Packer Middle of Elevation Hydraulic bull PCE

GS ELEV 1 Rock Drilling Interval Interval Interval of Interval Conductivity Concentration (ft msl) (ft msl) TEST (ftbgs) (ftbgs) r(ftbgs) ( f t b (ft mil) (cmsec) (raquogL)

4339 4329 13 28-29 33-3537-39 271 376 324 4016 OOOE+00 4339 12 37-3444-46 380 485 433 3907 157E-04 4339 11 488 593 541 3799 132E-04 4339 10 60-61 578 683 631 3709 OOOE+00 4339 9 678 783 731 3609 I79E-05 4339 8 778 883 831 3509 106E-05 4339 7 880 985 933 3407 243E-05 4339 6 990 1095 1043 3297 339E-06 4339 5 1090 1195 1143 3197 OOOE+00 4339 4 1190 1295 1243 3097 OOOE+00 4339 3 1365-1375 1290 1395 1343 2997 OOOE+00 4339 2 147-157 1390 1495 1443 2897 580E-05 4339 1 147-157 1470 1575 1523 2817 741E-05 43161 43061 13 166 271 219 4098 333E-04 43161 12 30-3136-40 260 365 313 4004 I54E-05 43161 11 36-4041-43 362 467 415 3902 548E-05 43161 10 470 575 523 3794 598E-05 43161 9 570 675 623 3694 197FOS 43161 8 670 775 723 3594 OOOE+00 43161 7 770 875 823 3494 891 E-05 43161 6 83-94 870 975 923 3394 139E-05 43161 5 970 1075 1023 3294 123E-04 43161 4 1070 1175 1123 3194 526E-06 43161 3 1170 1275 1223 3094 138E-05 43161 2 1270 1375 1323 2994 671E-06 43161 1 1370 1475 1423 2894 OOOE+00 42997 42497 13 18-19 170 275 223 4077 OOOE+00 42997 12 260 365 313 3987 766E-05 42997 11 360 465 413 3887 727E-05 42997 10 460 565 513 3787 192E-05 42997 9 560 665 613 3687 752E-05 42997 8 660 765 713 3587 778E-05 42997 7 85-86 763 868 816 3484 260E-05 42997 6 860 965 913 3387 289E-05 42997 5 102-103 960 1065 1013 3287 102E-04 42997 4 1060 1165 1113 3187 522E-06 42997 3 1160 1265 1213 3087 520E-06 42997 2 129-130 1260 1365 1313 2987 960E-04 42997 1 1360 1465 1413 2887 OOOE+00 43372 42922 11 35-37 42-45 350 455 403 3935 684E-04 43372 10 460 565 513 3825 500E-05 43372 9 560 665 613 3725 106E-05 43372 8 72-74 660 765 713 3625 204E-05 43372 7 760 865 813 3525 872E-06 43372 6 860 965 913 3425 467E-06 43372 5 960 1065 1013 3325 200E-05 43372 4 1060 1165 1113 3225 354E-05 43372 3 125-130 1160 1265 1213 3125 157E-05 43372 2 125-130 1260 1365 1313 3025 337E-04 43372 1 1365 1465 1415 2922 689E-06 43052 43002 2 54-58 490 595 543 3763 124E-05 2100 43052 1 139-140 145-146 1367 1472 1420 2886 154E-04 1400 43291 4391 3 bullI133 260 365 313 4017 439F06 43291 2 77-78 760 865 813 3517 230E-03 400 43291 1 143-144 1355 1460 1408 2922 971E-06 350

29958 27258 4 450 555 503 2493 OOOE+00 (21)A 29958 3 103-105 1000 1105 1053 1943 752E-04 (063)A

Table XX Packer Permeability and Packer Sampling Results for Potential Fracture Intervals

1999 Drilling Program

Hows Corner Supcrfund Site Plymouth Maine

gtbull i Potential Fracture Top _OfBot Bottom of Depth to ltbull Top of Interval from f Packer Packer Middle Of

GS ELEV lt Hock Drilling interval Interval Interval WeD ID ft msl) (ft msl) TEST (ftbgs) ltft$gs) (ftbgs) (ftbgs)

MW-107D 29958 2 128-130 1200 1305 1253

MW-107D 29958 1 139-141 1350 1455 1403

MW-108D 31904 31104 6 35-36 300 405 353 MW-108D 31904 5 60-62 550 655 603

MW-108D 31904 4 80-83 750 855 803

MW-108D 31904 3 118-119 123-124 1150 1255 1203

MW-108D 31904 2 147-149 1440 1545 1493

MW-108D 31904 1 1700 1805 1753

MW-110D 40576 40426 2 21-31 210 315 263 MW-110D 40576 1 148-154 1460 1565 1513 MW-I11D 40519 4 70-71 650 755 703

MW-111D 40519 3 79-82 84-86 780 885 833 MW-I11D 40519 2 97-102 950 1055 1003 MW-111D 40519 1 1370 1475 1423

MW-112D 3027 2942 4 42-52 420 525 473 MW-112D 3027 3 850 955 903 MW112D 3027 2 1100 1205 1153 MW-112D 3027 1 135-136 140-141 1340 1445 1393

MW-113D 43085 43085 5 250 355 303 MW-I13D 43085 4 47-49 460 565 513 MW-113D 43085 3 73-74 700 805 753 MW-113D 43085 2 1050 1155 1103 MW-113D 43085 1 1380 1485 1433

MW-114D 42394 41594 4 48-49 450 555 503 MW-114D 42394 3 79-81 740 845 793 MW-114D 42394 2 121-129 1250 1355 1303 MW-114D 42394 1 134-142 1350 1455 1403

MW-115D 4035 4035 4 300 405 353 MW-1I5D 4035 3 70-71 650 755 703 MW-115D 4035 2 1150 1255 1203 MW-115D 4035 1 1400 1505 1453

LOT-28W 382 7 450 555 503 LOT28W 382 6 550 655 603 LOT-28W 382 5 650 755 703 LOT28W 382 4 750 855 803 LOT-28W 382 3 850 955 903 LOT-28W 382 2 950 1055 1003 LOT-28W 382 1 1055 1155 1105

NOTES cmsec = centimeters per second ft bgs = leet below ground surface It msl = feet below mean sea level lt = not detected at indicated reporting limil A = detected below laboratory PQL ( ) = detected below reporting limits

Elevation of Interval

(ft nisi) 174

159

283gt 2588

2388

1988

1698

1438

3795 2545 3349 3219 3049 2629

2555 2125 1875 1635

4006 3796 3556 3206 2876

3737 3447 2937 2837

3683 3333 2833 2583

3318 3218 3118 3018 2918 2818 2715

Hydraulic Conductivity

(cmsec)

323E-05

208E-05

471E-03

471E-03

624E-05

3I6E-05

264E-05

261 E-05

OOOE+00 200E-04 953E-05 OOOE+00 OOOE+00 212E-05

361 E-05 410E-06 2gQE06 292E-05

786E-05 124E-05 151 E-05 822E-06 82IE-06

858E-05 I69E-05 352E-03 866E-05

223E-05 394E-06 122E-05 525E-06

831 E-05 182F-05 L62E-05 129E-05 190E-05 890E-04 981 E-04

PCEraquo Concentration

(ugL)

lt5

(14A)

98 11

15

22

11

30

200 (62)A

110 210 300 240

(44)A (23)A

5

350 190 129 230

2200 1900 2600 2600

(17)A (16)A (19)A

96

Table XX Packer Permeability and Packer Sampling Results for Potential Fracture Intervals

2004 Drilling Program

Hows Corner Superfund Site Plymouth Maine

Top of Bottom of Depth to Midpoint

t K

ELEV (ft Potential Transmissive Zones Packer Interval

Packer Interval

Middle of Interval

Elevation of interval

Hydraulic Conductivity

PCE Concentration

Well ID msl) TESTr (ft bgs)- (ftbgs) (ftbgs) (ftbgs) (ft msl) (cmsec) (ogt) MW-203D 43227 4 277279 24 32 28 4043 667E-05 44

3 408415420 39 49 44 3883 593E-05 170 2 526 530 49 57 53 3793 101E-04 140 I 828830842 80 88 84 3483 701E-05 130

MW-204D 43262 5 295 300 26 34 30 4023 902E-05 220 4 463496513516 45 53 49 3833 119E-04 540 3 681685688 63 71 67 3653 OOOE+00 2 758 76 2 71 79 75 3573 309E-05 260 I 88 96 92 3403 OOOE+00

MW-205 42389 3 164 166 168 15 20 175 4148 OOOE+00 1000B 2 302305312 30 35 325 3998 107E-04 1300B 1 40 45 425 3898 OOOE+00

MW-206D 43007 5 17 72 195 4128 291E-05 4 296 302 307 29 34 315 4008 940E-05 2900B 3 522 52 57 545 3778 944E-07 2 656 64 69 665 3658 353E-06 1 92392793 4939 91 96 935 3388 614E-05 6300B

PW-207 43477 5 184622162819 18 29 235 4088 209E-05 1300 4 3508 32 43 375 3948 568E-06 5400 3 53325341542154325559 50 61 555 3768 821E-05 18000

6359 61 72 665 3658 866E-06 12000 1 8685 84 89 865 3458 213E-05 19000

NOTES cmsec = centimeters per second ft bgs = feet below ground surface ft msl = feet above mean sea level B = detected in lab blank

Table XX Orientation Permeability and Groundwater Sampling Results for Transmissive Features

2004 Drilling Program

Hows Corner Superfund Site Plymouth Maine

Borehole Geophisical Feature depth Dip True Dip True Transmissive Log Feature (Feet) Degrees Azimuth Strike bullvgt(Ltk|iy^

Number v Tosftble) v MW-203 5 277 64 337 67 Likely

6 279 59 11 281 Likely 8 352 14 177 87 Likely 11 381 46 96 6 Possible 12 408 35 271 1 Possible 14 415 57 250 340 Possible 15 420 58 202 292 Likely 18 526 52 75 345 Likely 19 530 52 82 352 Likely 28 828 48 75 345 Likely 29 830 52 17 287 Likely 30 830 56 233 323 Possible 31 842 50 130 40 Likely

MW-204 4 295 15 147 57 Likely 5 300 43 91 1 Likely 11 439 31 80 350 Possible 12 440 46 219 309 Possible 14 463 50 358 88 Likely 15 496 34 198 288 Likely 16 513 54 17 287 Likely 17 516 33 14 284 Likely 25 681 39 359 89 Possible 26 685 22 45 315 Possible 27 688 35 73 343 Possible 32 758 45 236 326 Likely 33 762 46 306 36 Likely

MW-205 5 164 69 106 16 Possible 6 166 78 165 75 Possible 7 168 82 115 25 Possible 8 168 68 116 26 Possible 12 215 46 222 312 Possible 13 217 75 62 332 Possible 14 219 29 32 302 Possible 16 237 69 250 340 Possible 17 256 73 353 83 Possible 18 272 44 202 292 Possible 21 299 37 196 286 Possible 22 302 31 206 296 Possible 23 305 59 48 318 Likely 24 312 63 42 312 Likely

MW-206 1 264 37 181 271 Likely 2 296 69 217 307 Likely 3 302 66 233 323 Likely 4 307 64 224 314 Likely 8 342 62 259 349 Likely

jjHydraulic GoiDanctilyity j(cmsecjw

667 E-05

593 E-05

101 P04

710 E-05

902 E-05

119 E-04

0

309 E-05

0

107 E-04

94 E-05

PCE (ugL)

44

170

140

130

220

540

260

IOOOB

1100B

1300B

2900B

STotal vVoCsv tig1)

84

234

192

183

2636

6436

3073

11448

12509

13776

32401

PCEyo dfCTotaf

52

73

73

7 1

83

84

85

87

88

94

90

Table XX Orientation Permeability and Groundwater Sampling Results for Transmissive Features

2004 Drilling Program

Hows Corner Superfund Site Plymouth Maine

Borehole Geophisical Feature deptt raquoip True pip True Transraissive Log Feature (Feet) shy Degrees Azimuth Strike (tikely

Number raquo Possible) 22 522 57 54 324 Possible 25 656 40 82 352 Possible 32 871 59 151 61 Possible 33 883 53 185 275 Possible 34 895 7 175 85 Likely 35 899 53 90 0 Likely 36 902 49 184 274 Likely 37 923 9 175 85 Likely 38 927 42 206 296 Likely 39 934 48 167 77 Likely 40 939 26 180 90 Likely

PW-207 1 1846 33 167 77 Likely 4 2216 49 289 19 Possible 7 2819 59 265 355 Possible 11 3508 55 189 279 Possible 18 5332 43 305 35 Likely 19 5341 51 30 300 Likely 20 5421 20 254 344 Likely 21 5432 39 301 31 Likely 23 5559 52 302 32 Likely 25 6359 24 182 272 Possible 29 8049 77 231 321 Possible 30 8685 78 38 308 Likely 32 9334 29 194 284 Likely

NOTES

B = detected in lab blank

Hydraulic Conductivity

(cmsee) 944 E-07 353 E-06

614 E-05

209 E-05

568 E-06

821 E-05

866 E-06

213 E-05

bulltCE (ugL)

6300B

1300

5400

18000

12000

19000

Total VOCs (ug1)

68901

1410

5802

19234

13085

20354

PCE of Total VOCs

9 1

92

93

94

92

93

Response to EPA-DEP Comment 3 Dated March 312005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

lit

EPA-DEP Comment 3

Comment 3 The reported f values and resultant Kd values There remains doubt that the values used in the flushing model accurately reflect the propensity for PCE to sorb to the bedrock The ^ values presented in Appendix B may be unrealistically high because the bedrock samples may have contained organic carbon that was unavailable for sorption The reported f values are only qualitative estimates of the organic carbon content of the bedrock samples The Walkley and Black organic carbon measurement method is quick and simple but the results obtained cannot be considered quantitative because it requires a correction factor which often results in erroneous values it assumes the organic carbon has an average valence of zero oxidizable and reducible constituents such as chloride ferrous iron and manganese oxides interfere with the results and the errors introduced by interference are potentially greater when the organic carbon content is low at low f values it is not clear that organic carbon is controlling PCE sorption (Schwarzenbach and Westall 1981 Mackay et al 1986 Fetter 1999)

In order to derive a Kd-based retardation factor that is reasonable given the reported f values and the rapid advance of the PCE plume described on pages 4-11 and 4-12 the flushing model requires a bulk density to porosity ratio that is roughly two orders of magnitude higher than the actual ratio for the Hows Corner bedrock (page 4-4) This apparent discrepancy needs to be addressed

Response This comment raises several concerns about the collection and analysis of samples for fraction of organic carbon (f^) the quality of the resulting data and the implications of the use of those data for estimation of the retardation of groundwater contaminant movement Results of bedrock analysis for f were proposed in the TI Evaluation Work Plan for use in conjunction with groundwater contaminant concentrations and aquifer information to estimate cleanup times using the Batch Flushing model It is important to use accurate f values from representative bedrock in the Batch Flushing model in order to obtain reasonable estimates of the remedial time frame Because of the importance of accurate and representative results the TI Investigation field program was designed and conducted both to collect samples representative of the rock volume most likely to be in contact with contaminated groundwater and to analyze them using an appropriate refereed analytical method Five potential methods for evaluating f were identified Of the five methods the Walkey-Black method was selected because it has minimal method interferences and a sufficiently low detection limit as well as a long history of use in agronomy and contamination studies The PRP Group is pleased with the quality of the data obtained from the bedrock samples as represented by their precision and reproducibility

The first part of this comment relates to the determination of fraction of organic carbon (f^) values The several subparts of the first paragraph are addressed individually in items 1 through 5 below The second part of the comment regarding the resultant distribution coefficient (Kd) values is addressed separately as item 6 below

1 There remains doubt that the values used in the flushing model accurately reflect the propensity for PCE to sorb to the bedrock

bull The rock core samples used for f (gocg) analysis were from core immediately adjacent to fractures These rock core samples included the fracture surfaces themselves and rock core extending back less than 1 cm from the fractures Therefore the foe data reported in the TI Evaluation represents the f of bedrock through which groundwater will travel and to which PCE will adsorb Based on the careful selection of sample locations and the

Response to EPA Comment 3 050205doc 1 of 11 Woodard amp Curran (211941)

number of samples collected we are confident that the measured f values are representative of the f at points of contact for PCE with the bedrock it is these f values that determine the propensity of PCE to sorb to the bedrock

bull The samples of rock core collected for analysis of f originated from 19 different locations varying in depth from 11 to 90 feet Therefore it is very unlikely that the rock core samples were contaminated with extraneous organic carbon from above ground

2 The foc values presented in Appendix B may be unrealistically high because the bedrock samples may have contained organic carbon that was unavailable for sorption

bull As noted in response 1 the f data reported in Appendix B represents organic carbon primarily associated with the surface of fractures in the bedrock through which groundwater is most likely to travel Therefore it is this organic carbon that the contaminants in the groundwater will come in contact with and adsorb to in the fractured rock at the site

bull The chemical oxidation agents used in the Walkey-Black method oxidize the easily oxidizable organic carbon in the medium and the foe is calculated from the quantity of the agent consumed Therefore it is unlikely that the analysis of the bedrock samples measured organic carbon that was unavailable for sorption

3 The reported foc values are only qualitative estimates of the organic carbon content of the bedrock samples

bull The reported f values are accurate quantitative results Schumachers review of Methods for the determination of total organic carbon (TOC) in soils and sediments (NCEA-C-1282 EMASC-001 April 2002) identifies the Walkley-Black method which was used to analyze the reported foc values as the reference method for comparison to other methods for analyzing total organic carbon

bull Schumacher also points out that if anything the WalkJey-Black method may underestimate the total organic carbon in a sample due to possible incomplete oxidation of organic carbon Usually the incomplete oxidation of total organic carbon in environmental samples is corrected for by multiplying the measured foe by 130 (Walkley amp Black 1934 Schulte 1995)

bull When the f data in the TI Evaluation Report (WampC 2005) Appendix B (attached) are analyzed statistically the standard deviation of the f for the 19 samples analyzed is 174 of the average f Given this standard deviation the 95 confidence interval for this data ranged from a low of 000123 gocg to a high of 000253 gocgm

The labs Method of Detection Limit (MDL) for the f measured using the Walkley-Black method is 00001 gocg Therefore the average (000188 gocg) the mean (000185 gocg) and geometric mean (000187 gocg) of the f values for the rock core at Hows Corner are all statistically significantly greater than the MDL of the Walkley-Black method

In addition to the aforementioned statistical analysis of the foe data triplicate samples (n = 3) from the same rock core (including one sample from the 19 rock core samples) were

Response to EPA Comment 3 050205doc 2 of Woodard amp Curran (211941)

analyzed for their f to determine the repeatability of the Walkley-Black method The average the mean and the geometric mean of the f values of these replicate samples was 000162 gocg 000150 gocg and 000159 gocgm respectively The standard deviation of these measurements was 000039 gocg

4 The Walkley and Black organic carbon measurement method is quick and simple but the results obtained cannot be considered quantitative because it requires a correction factor which often results in erroneous values it assumes the organic carbon has an average valence of zero oxidizable and reducible constituents such as chloride ferrous iron and manganese oxides interfere with the results and the errors introduced by interference are potentially greater when the organic carbon content is low at low foc values it is not clear that organic carbon is controlling PCE sorption (Schwarzenbach and Westall 1981 Mackay et al 1986 Fetter 1999)

bull Schumachers review (NCEA-C-1282 EMASC-001 April 2002) of the Walkley-Black method identifies several potential problems with this analytical method that could occur if the analytical lab is not familiar with the nuances of the chemistry associated with this method Interestingly Schumachers review neglected one of the more important analytical steps required to avoid errors in quantifying f in samples where there might beNAPL

It is absolutely critical to eliminate any NAPL from rock core samples prior to using the Walkley-Black method to measure foe in such samples This was done by the lab (PTS Laboratories) that measured the foe in the rock core samples from Hows Corner The lab used the Dean-Stark method (solvent extraction) to remove all hydrocarbons (including PCE and other NAPLs) from the sample (PTS Laboratories) This extraction method does not interfere with the subsequent analysis of the natural organic carbon associated with the rock core

Subsequently the samples were dried at 150degC to a constant weight (normally 16 hours) This latter step oxidizes all inorganic minerals including ferrous bearing minerals to ferric oxides and precludes their interference during the oxidation of the samples with chromic acid This procedure completely eliminates any positive bias in the reported foc

data that might have occurred due to the presence of ferrous ions and other reduced minerals

bull As noted in Response 3 the incomplete oxidation of total organic carbon results in an underestimate of the f and is corrected for by multiplying the f by a correction factor of 130 (Walkley amp Black 1934 Schulte 1995) The fx data reported in the TI Evaluation was corrected accordingly by using this correction factor

bull Excess chloride (Cl~) in percent weight quantities as found in saline soils may interfere with the quantitative titration of reduced chromium (Walkley 1947) However given that the primary rock type at the Hows Corner site is phyllite it is highly unlikely that there was sufficient chloride in the rock core samples for this to occur

bull Manganese oxides may also interfere with the analysis of f through competing with the dichromate ion for any oxidizable carbon (Walkley 1947) However in such cases the reported f would be an underestimate of the f present in the rock core Walkley (1947)

Response to EPA Comment 3 050205doc 3 of 11 Woodard amp Curran (211941)

4

reported that in the case where the ratio of MnO2 to carbon is 85 to 1 the error in the carbon determinations would only be 0 to 6 percent

It may also be useful to compare the analysis of total organic carbon in a geologic matrix that contains high levels of manganese using EPA method 9060 to the Walkley-Black method Table 1 summarizes data provided by one of the PRPs that compares the analysis of total organic carbon in a geologic matrix that contains approximately 02 wgt manganese (approximately 03 wgt manganese oxide)

Table 1 Comparison of total organic carbon measured using the EPA- 9060 method and the Walkley-Black method

Laboratory EPA-9060 Method Walkley-Black Method A Ave 00226 gocg Not analyzed

Stdev 000251 gocg n = 5

B Ave 002219 gocg Ave 002050 gocg Stdev = 000316 gocg Stdev =000971 gocg

n= 10 n = 10

The similarity in the total organic carbon concentrations measured by these two different methods provides further confidence that the Walkley-Black method is a viable method for analysis of total organic carbon in the presence of manganese equivalent to at least 10 by weight of the total organic carbon

5 The Walkley and Black organic carbon measurement at lowf^ values it is not clear that organic carbon is controlling PCE sorption (Schwarzenbach and Westall 1981 Mackay et al 1986 Fetter 1999)

bull Schwarzenbach and Westalls (1981) paper states that f values of less than 0001 gocg should not be used in combination with Kow (octanol-water partition coefficients) values to calculate K^ values (solid phase partition coefficients) values for a specific contaminant It should be noted that the TI Evaluation did not use the f data to calculate the KQC from the Kow Instead as requested by the EPA the measured KOC value for PCE was used to calculate the retardation factor for this contaminant

bull Schwarzenbach et al (2003) stated more recently that Even at very low f values (ie foe = 0001 kgoc - kg1 solid) sorption to the organic components of a natural sorbent may still be the dominant mechanism in defining the adsorption of organic compounds to geological matrices

bull In 1985 M Piwoni from the US EPA Robert S Kerr Environmental Research Laboratory published a paper (Banerjee et al 1985) that showed that for very hydrophobic molecules TOC content of the sorbent will control sorption down to levels of organic carbon that defy quantitation Contaminants such as the PCE found in the groundwater at Hows Corner are in this category of compounds

Given the aforementioned reasons the f values reported in the TI Evaluation are accurate within the noted statistical limitations and will have a predictable impact upon the retardation of PCE during groundwater transport

Response to EPA Comment 3 050205doc 4 of 11 Woodard amp Curran (211941)

6 In order to derive a Kd-based retardation factor that is reasonable given the reported foc

values and the rapid advance of the PCE plume described on pages 4-11 and 4-12 the flushing model requires a bulk density to porosity ratio that is roughly two orders of magnitude higher than the actual ratio for the Hows Comer bedrock (page 4-4) This apparent discrepancy needs to be addressed

The apparent discrepancy of bulk density to porosity ratios is most likely due to the fact that the Batch Flushing Model was originally developed for a porous medium and is not directly applicable to fractured bedrock As stated in Appendix C (page C-4) of the Draft Technical Impracticability Evaluation Report in order to use the Batch Flushing Model to describe the transport of contaminated groundwater in fractured bedrock where the matrix porosity is insignificant it is more appropriate to use a fracture surface area to void space ratio to calculate the retardation factor (R) than a bulk density to porosity ratio (Freeze amp Cherry 1979)

Since it is impractical to determine the actual surface area to which contaminants can adsorb the Batch Flushing Model was used with two simplifying assumptions bull The Kd was calculated from the f and the K^ bull The bulk density to porosity ratio term in the Batch Flushing Model was constrained to range

from 4 to 10 the typical range of such ratios in porous media (Freeze amp Cherry 1979)

If one uses site specific bedrock bulk density and porosity values the bulk density to porosity ratio is several orders of magnitude greater (specifically 273 gcc bullbull 000165 (dimensionless) = 1654 gcc) than the range of ratios of 4 to 10 used in the Batch Flushing Model in the Draft Technical Impracticability Evaluation Report Constraining the bulk density to porosity ratio within the range of ratios of 4 to 10 results in significantly lower R value than would be obtained using specific bedrock bulk density and porosity values

In summary in bedrock where fractures are the primary porosity the bulk density to porosity ratio can vary considerably and will be a function of the number of fractures and the fracture aperture The calculated bulk density to porosity ratio will be inversely proportional to the porosity This means that in fractured rock with limited fracturing and smaller porosity the calculated bulk density to porosity ratio is greater and will result in a greater calculated retardation factor than in bedrock with more extensive fracturing and greater porosity Consequently the calculated retardation factor will be greater for bedrock with less surface area available for sorption than bedrock with greater surface area for sorption This is contrary to what actually occurs

4 Response to EPA Comment 3 050205doc 5 of 11 Woodard amp Curran (211941)

m

REFERENCES

Banerjee P MD Piwoni K Ebeid (1985) Sorption of organic contaminants to a low carbon subsurface core Chemosphere _14 1057-1067

Freeze RA JA Cherry (1979) Groundwater Prentice Hall Englewood Cliffs NJ pg 604

PTS Laboratories wwwptsgeolabscompdf files3TOCnotepdf

Schulte EE (1995) Recommended soil organic matter tests in Recommended Soil Testing Procedures for the Northeastern United States Northeastern Regional Publication No 493 Chapter 8

Schwarzenbach RP J Westall (1981) Transport of nonpolar organic compounds from surface water to groundwater Laboratory sorption studies Environ Sci Tech 15 1360-1367

Schwarzenbach RP PM Gschwend DM Imboden (2003) Environmental Organic Chemistry Wiley-Interscience pg 292 408 amp 412

Walkley A LA Black (1934) An examination of the Degtjareff method for determining soil organic matter and a proposed modification of the chromic acid titration method Soil Science 37 29-38

Walkley A (1947) A critical examination of a rapid method for determining organic carbon in soils - effect of variations in digestion conditions and of inorganic soil constituents Soil Science 63251-264

Woodard amp Curran Inc (WampC) 2005 Draft Technical Impracticability Evaluation Hows Corner Superfund Site Plymouth Maine January 2005

Response to EPA Comment 3 050205doc 6 of Woodard amp Curran (211941)

LIST OF ATTACHMENTS (Response to Comment 3)

Appendix B to Draft Technical Impracticability Evaluation Measurement of foe at Hows Corner (4 pages)

m

Response to EPA Comment 3 050205doc 7 of 11 Woodard amp Curran (211941)

Appendix B Measurement of foe of Rock Core at Hows Corner

There are two general approaches to measure the fraction of organic carbon (foe) in rock cores

bull Measurement of weight loss by ignition of organic matter bull Chemical oxidization of organic carbon to carbon dioxide and either

subsequent quantification of the oxidant used for the reaction or quantification of the carbon dioxide produced during this oxidation process

The weight loss method is subject to errors caused by volatilization of substances other than organic materials such as water hydroxides and mineral carbonates Quantification of foe by the weight loss method is particularly sensitive to the presence of carbonates in rock cores There are however weight loss methods that are designed to differentiate between organic carbon and the aforementioned interfering materials but they require considerable care and are less accurate at low foe values Hence the weight loss method was not well suited for measuring the foe of the rock core from Hows Corner

The chemical oxidation of organic carbon is much better suited for quantifying organic carbon in rock cores such as those from Hows Corner This method uses a strong chemical oxidant to oxidize organic carbon to carbon dioxide and then measures either the chemical oxidant used to oxidize the organic carbon or the quantity of carbon dioxide produced In addition this general approach is not subject to interference by volatilization of other constituents of the rock core

There are at least two such chemical oxidation methods

bull The method of Baccini which was described by Schwarzenbach amp Westall (1981) first acidifies the sample to eliminate interference by carbonates Then a strong oxidant is used to chemically oxidize the organic carbon to carbon dioxide The resulting carbon dioxide is subsequently reduced to methane and quantified using a flame ionization detector Unfortunately this method has not been described in detail in a referred journal Hence it is would not have been appropriate to use to characterize the foe in the Hows Corner rock core

bull The more commonly used method to quantify foe in rock core is the Walkley-Black method (1934) This method is preferred for RBCA and DODDOE projects and by the oil industry

The Walkley-Black method uses an excess of chromic acid to oxidize (digest) organic matter to carbon dioxide The remaining chromic acid that was not consumed during the oxidation of the organic carbon is then quantified by titration with ferrous sulfate The difference in chromic acid prior to and after the oxidation of the organic carbon represents the total chromic acid used to oxidize

Hows Corner TI Evaluation Page 1 January 13 2005 Appendix B

the organic carbon in the sample The latter can be calculated using the chemical stoichiometry of the reaction

The Walkley-Black method is very accurate for samples that contain less than 2 organic carbon matter The minimum detection limit (MDL) for the Walkley-Black method is 100 mgkg or an foe of 0001

Given the rock core at Hows Corner was expected to contain less than 2 organic carbon the Walkley-Black method was used to measure the foe from 19 different rock core samples collected from varying depths ranging from 11 to 90 feet

Table 1 provides a statistical summary of the aforementioned data

Table 1 Statistical summary of foe data from rock cores collected at varying depths

Statistical Parameter Calculated Value foe Minimum Detection Limit (MDL) 00010 Number of samples analyzed (n) 19 Average foe 00019 Median foe 00019 Geometric Mean foe 00019 Standard deviation of foe measurements 000033 Relative standard deviation 174 -+ 95 Confidence intervals 00012 to 00025

The data in Table 1 shows the following

bull The foe from the Hows Corner rock cores are statistically greater than the MDL of the Walkley-Black analytical method

bull The average and median values for the foe of the Hows Corner rock cores from varying depths are nearly identical indicating that there is little variability in the foe values in the source zone at the site

bull The standard deviation of these measurements is 000033 which is 174 of the average foe

bull The 95 confidence intervals of the foe of the rock core at Hows Corner are 00012 to 00025

The foe was also analyzed from three separate samples taken from the same rock core at a depth of 55 feet (Only one of these samples was included in the data summarized in Table 1) Table 2 shows the statistical repeatability of this type of analysis

Hows Corner TI Evaluation Page 2 January 13 2005 Appendix B

Table 2 Repeatability of analysis of foe from one rock core at 55 feet in depth

Statistical Parameter Calculated Value Number of samples analyzed (n) 3 Average foe 00016 Median foe 00015 Geometric Mean foe 00016 Standard deviation of foe measurements 000039 Relative standard deviation 240 -+ 95 Confidence intervals 00008 to 00024

The data in Table 2 shows the following

bull The percent relative standard deviation of these three analyses of foe from the same rock core at Hows Corner is 24

bull The 95 confidence interval of the foes measured in this particular rock core at Hows Conrer is 00008 to 00024

These results show that there is good repeatability in using the Walkley-Black method for analysis of the foe in the rock core at Hows Corner

References Schwarzenbach amp Westall (1981) Transport of nonpolar organic compounds from surface water to groundwater Laboratory sorption studies Environ Sci Tech 15 1360-1367

Walkley A I A Black (1934) An examination of Degtjareff method for determining soil organic matter and a proposed modification of the chromic acid titration method Soil Sci 37 29-37

Hows Corner Tl Evaluation Page S January 13 2005 Appendix B

Woodard and Curran PTS Laboratories PTS File No 34618

ORGANIC CARBON DATA (METHODOLOGY WALKLEY-BLACK)

PROJECT NAME PROJECT NO

SAMPLE ID

203-chip-13 203-chip-23 203-chip-27 203-chip-38 203-chip-42 203-chip-47 203-chip-52 203-chip-58 203-chip-69 203-chip-82 207-chip-11 207-chip-19 207-chip-24 207-chip-29 207-chip-35 207-chip-45 207-chip-55 207-chip-87 207-chip-90

207-chip-55 55-MS

55-MSMSD

Hows Corner NA

DEPTH ft

13 23 27 38 42 47 52 58 69 82 11 19 24 29 35 45 55 87 90

55 NA NA

MATRIX

Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip

Average Median

Geometric Mean Standard Deviation Relative Std Dev

+- 95 Confidence Interval n

Rock Chip Rock Chip Rock Chip

Average Median

Geometric Mean Standard Deviation Relative Std Dev

+- 95 Confidence Interval n

FRACTION ORGANIC CARBON

(gg)

170E-03 185E-03 185E-03 170E-03 240E-03 190E-03 230E-03 180E-03 170E-03 115E-03 195E-03 220E-03 220E-03 235E-03 135E-03 190E-03 205E-03 175E-03 160E-03

188E-03 185E-03 185E-03 327E-04

1739 123E-03 to

19

205E-03 130E-03 150E-03

162E-03 150E-03 159E-03 388E-04

2402 840E-04 to

3

2532E-03

2393E-03

Hows Corner Tl Evaluation Appendix B January 13 2005

Response to EPA-DEP Comment 4 Dated March 31 2005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

EPA-DEP Comment 4

Comment 4 Distribution of contaminants First the TI report seems based on the assertion that there is DNAPL at the source area yet it also appears to represent that the source area is small and the bedrock below 85 is competent (or less fractured) and less impacted by the release of contaminants Some of the confusion may result from using most recent data when that data is from several different sampling events over several years and there is no discernible difference in concentrations between shallow and deep bedrock or as in Section 421 where generally decreased generally increase generally similar and similar concentrations in four consecutive sentences leads to a muddled picture of the contaminant distribution

Second the report asserts that the distribution of contaminants over the entire plume has not changed with time but fails to support this conclusion with data again relying on data that is from different sampling dates for one composite representation

Response The likely presence of dense non-aqueous phase liquid (DNAPL) at the Hows Corner Site and the determination that the source area is small are not mutually exclusive and both are conclusions drawn from information obtained during field investigations The presence of DNAPL in the source area is based on the elevated concentrations of volatile organic compounds (VOCs) detected in the groundwater (WampC 2001 WampC 2002) The conclusion that the source area is small is based on the area in which VOCs in groundwater have been detected at concentrations that are considered to be indicative of the presence of DNAPL nearby Similarly the conclusion that fracture frequency decreases at depths greater than approximately 50 to 85 feet below ground surface was based on field observation during the RI field work The fact that zones with observed fractures exhibited higher hydraulic conductivities than zones without fractures coupled with the decreasing frequency of observed fractures with depth led to the conclusion that the hydraulic conductivity of the bulk rock decreases with depth

The most recent data from all wells were used to provide the maximum VOC data set size During the RI all of the previously-existing and then newly-installed monitoring wells were sampled along with several residential wells The RI sampling included up to 48 monitoring wells Subsequent to the RI and prior to the TI three rounds of monitoring were conducted to verify that the plume was stable 15 monitoring wells were sampled during each of the three rounds During the TI field investigation 29 wells were sampled for VOCs The sampled wells included all of the newly-installed wells and a subset of wells installed during the RI for a total of 29 monitoring wells By using most recent data VOC results from 53 monitoring wells were included in the evaluation (see table labeled Sampling Events for listing of monitoring wells) This approach was selected because there generally was little variation in the data from a particular location between years This is borne out by the attached individual plots of VOCs detected in shallow bedrock and deep bedrock for the Pre-ROD (December 1999January 2000) and Supplemental (May 2000) sampling events and for June 2001 January 2002 and April 2003 sampling events The Pre-ROD and Supplemental plots are similar to the subsequent plots from the 2001 2002 and 2003 sampling events

In addition to maps showing the spatial distribution of VOC data at a given time trend plots of the data from a particular location through time (attached) indicate that since the RI concentrations generally have been stable or have decreased Together the maps and trend plots and the data from which they were developed indicate that the distribution of contaminants over the entire plume has not changed appreciably with time

Response to EPA Comment 4 050305doc 1 of 26 Woodard amp Curran (211941)

REFERENCES

Woodard amp Curran Inc (WampC) 2001 Final Remedial Investigation Report Hows Corner Superfund Plymouth Maine July 2001

Woodard amp Curran Inc (WampC) 2002 Final Feasibility Study Report - Non-Source Area Groundwater Hows Corner Superfund Site Plymouth Maine Hows Corner Superfund Plymouth Maine July 2002

Response to EPA Comment 4 050305doc 2 of 26 Woodard amp Curran (211941)

LIST OF ATTACHMENTS (Response to Comment 4)

Table - Sampling Events 1999 - 2004 (2 pages)

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater Pre-ROD Sampling Event

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater Pre-ROD Sampling Event

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater Supplemental Sampling Event

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater Supplemental Sampling Event

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater June 2001

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater June 2001

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater January 2002

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater January 2002

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater April 2003

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater April 2003

Figure - Concentration Trends - Non-Source Area Wells MW-1B and MW-3B

Figure - Concentration Trends - Non-Source Area Wells MW-13DB and MW-16DB

Figure - Concentration Trends - Non-Source Area Wells MW-16IB and MW- 108D

Figure - Concentration Trends - Non-Source Area Wells MW-108S and MW-112D

Figure - Concentration Trends - Non-Source Area Wells MW-112S and MW-114D

Figure - Concentration Trends - Non-Source Area Wells MW-114S and MW-115D

Figure - Concentration Trends -Source Area Wells MW-2DB and MW-2IB

Figure - Concentration Trends -Source Area Wells MW-102S and MW-103D

Figure - Concentration Trends -Source Area Wells MW-103S and MW-104D

Figure - Concentration Trends -Source Area Wells MW-104I and MW-106D

Figure - Concentration Trends -Source Area Wells MW-106S

Response to EPA Comment 4 050305doc 3 of 26 Woodard amp Curran (211941)

I I

El I

II I I 1 I

I

i

Event Baseline Case ID WC-01 WC-01

Well Date Aug-99 Oct-99 LOT10 1 LOT1-1 1 LOT11-4 LOT14 1 LOT15 1 LOT15-1 1 LOT16 1 LOT16-1 1 LOT17 1 LOT18 1 LOT19 1 LOT2 LOT20 1 LOT21-10 1 LOT21-11 1 LOT21-12 1 LOT21-13 1 LOT21-14 1 LOT21-2 1 LOT21-5 1 LOT21-7 LOT21 -8 1 LOT21-9 1 LOT23 1 LOT24 1 LOT28-1 1 LOT28-2 1 LOT28-3 1 LOT28-4 1 LOT28W 1 LOT30 1 LOT30-1 1 LOT30-2 1 LOT30-3 1 LOT30-4 1 LOT30-5 LOT31 LOT35 1 LOT41 1 LOT42-1 1 LOT43-1 1 LOT43-4 1 LOT6-1 1 LOT67 1 LOT6-7 1 LOT6-8A 1 LOT6-8B 1 LOT80-1 1 LOT82 1 MW-101D MW-1011 MW-101S MW-102D MW-102S MW-103D MW-103S MW-104D MW-1041 MW-104S MW-105D MW-106D

Groundwater Sampling Location Summary 1999 - 2004xls

Sampling Events 1999-2004

Hows Corner Superfund Site Plymouth Maine

Supplemental 2001 2002 2003 Pumping 2004 Pre-ROD Rl Sampling Sampling Sampling Test Sampling WC-03 WC-09 WC-25 WC-30 WC-42B WC-56 WC-58 Dec-99 May-00 Jun-01 Jan-02 Apr-03 Sep-04 Sep-04

1

1 1 1

1 1 1 1 1

1 1

1

1 1

1 1 1

1 1 1 1 1

1

1 1

1 1 1 1

1

1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

Sampling Events 1999-2004

Hows Corner Super-fund Site Plymouth Maine

Supplemental 2001 2002 2003 Pumping Event Baseline Pre-ROD Rl Sampling Sampling Sampling Test

Case ID WC-01 WC-01 WC-03 WC-09 WC-25 WC-30 WC-42B WC-56

ll

Well Date Aug-99 Oct-99 Dec-99 May-00 Jun-01 Jan-02 Apr-03 Sep-04 MW-106S 1 1 1 1 1 MW-107D 1 1 MW-108D 1 1 1 1 1 MW-108S 1 1 1 1 1 MW-110D 1 1 MW-111D 1 1 MW-112D 1 1 1 1 1 MW-112S 1 1 1 1 1 MW-113D 1 1 MW-114D 1 1 1 1 1 MW-114S 1 1 1 1 1 MW-115D 1 1 1 1 1 MW-12DB 1 1 1 MW-12SB 1 1 1 MW-13DB 1 1 1 1 1 1 MW-13SB 1 1 1 MW-14DB 1 1 MW-14SO 1 1 MW-15DB 1 1 1 MW-15SB 1 1 1 MW-16DB 1 1 1 1 1 1 MW-16IB 1 1 1 1 1 1 MW-16SO 1 1 MW-17DO 1 1 1 MW-17SO 1 1 1 MW-1B 1 1 1 1 1 1 MW-203D MW-203S MW-204D MW-204S MW-205 MW-206D

I MW-206S MW-2DB 1 1 MW-2DDB 1 1 MW-2IB 1 1 1 1 1 1 MW-3B 1 1 1 1 1 1

I MW-4O 1 1 1 MW-5B 1 1

II MW-6DB 1 1 1 MW-6SB 1 1 1 MW-8DB 1 1 1 MW-8SB 1 1 1

II PW-207 1 SEEP-1 1 SUBTOTAL - RESIDENTIAL 44 25 0 2 0 3 0 SUBTOTAL - MONITORING 22 48 41 15 15 15 1

Total 3 66 73 41 17 15 18 1

I Included in most recent data

I Notes 1 - Overburden well not included in most recent data for plotting

2 - Tetrahydrofuran and 2-Butanone were the only two compounds detected in this well and are thought to be the result of well repair not included in most recent data for plotting

3 - Not included in most recent data for plotting

2004 Sampling

WC-58 Sep-04

1

1 1

1 1

1 1 1

1

1 1

1 1 1 1 1 1 1 1 1

1 1

1

0 29

29

Groundwatef Sampling Location Summary 1999 - 2004xls

I

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

monitoring well Figure 4-14 total VOC contour (ugl) - December 1999January 2000 Distribution of Total VOCs in

Note SW-113 is located downstream of SEEP-1 Shallow Bedrock Groundwater total concentration of detected VOCs ND= not detected these two locations were sampled during the Pre-ROD Sampling Event

Baseline Sampling Event in OctoberNovember 1999 Hows Corner Superfund Site Surface Water Sampling Location A Plymouth Maine Seep Sampling Location laquo- WOODARD ampCURRAN

995037wipri reportepa ri interim final feb 2001cadd drawingsfinalfig 4-14

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

0 300 600 I

FEET

Q residential well Figure 4-16 monitoring well Distribution of Total VOCs in

Deep Bedrock Groundwater total VOCs contour (ugl) Pre-ROD Sampling Event

active residential wells with lot number Hows Corner Superfund Site 2deg42deg Plymouth Maine total concentration of detected VOCs ND= not detected WOODARD ampCURRAN Enyinaaring bull Science bull Operations bull

995037wipri reportepa ri interim final feb 2001cadd drawingsfinalfig4mdash16

PLYMOUTH POND

PLYMOUTH POND

1 628Tl7MW-2bB 12135

PLYMOUTH POND

monitoring well Figure 4-20

V total VOC contour (ugl) - June 2000 Distribution of Total VOCs in Shallow Bedrock Groundwater

| 34 | total concentration of detected VOCs ND= not detected NA = not analyzed Supplemental Sampling Event Note SW-113 is located downstream of SEEP-1 Hows Corner Superfund Site

Surface Water Sampling Location these two locations were sampled during the Plymouth Maine Baseline Sampling Event in OctoberNovember 1999 Seep Sampling Location WOODARD amp CURRAN

Engineering bull Science - Operations bull 995037wipri reportepa ri interim final feb 2001 cadd drawingsfinalfig 4-20

residential well Figure 4-22 Distribution of Total VOCs in

monitoring well Deep Bedrock Groundwater

total VOCs contour (ugl) Supplemental Sampling Event

Hows Corner Superfund Site

total concentration of detected VOCs ND= not detected NA = not analyzed Plymouth Maine

WOODARD amp CURRAN

995037wipri reportepa-ri interim final feb 2001cadd drawingsfinalfig 4-22 Engineering bull Science - Operations bull

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

FEET

Shallow Monitoring Well

Deep Monitoring Well

C Detected Concentration ND = Not Detected Figure 1-XS Distribution of Total VOCs in Shallow Bedrock Groundwater

Pumping Well

17-Acre Property Boundary Concentration Contour (ugl)

June 2001 Hows Corner Superfund Site

Plymouth Maine WOODARDampCURRAN

-i^rhvj bull Scbncn bull Operations bull 211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0601 dwg04-20-05

PLYMOUTH POND Hopkins Road V

O

PLYMOUTH POND

PLYMOUTH POND

o

0 300 600 mdashfa FEET

Shallow Monitoring Well bull bull - 17-Acre Property Boundary Figure 1-XD

Deep Monitoring Well 1 I Detected Concentration ND = Not Detected Distribution of Total VOCs in Deep Bedrock Groundwater

-mf- Pumping Well June 2001 Residential Well Hows Corner Superfund Site

Plymouth Maine i h Surface Water Sampling Point

g WOODARD ampCURRAN _ ^ _ ^ _ _ yen_ rj i|Hlaquorlny bull Science bull Opt

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0601 dwg04-20-05

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

Shallow Monitoring Well

Deep Monitoring Well

Detected Concentration ND = Not Detected Figure 1-YS Distribution of Total VOCs in Shallow Bedrock Groundwater

Pumping Well

17-Acre Property Boundary Concentration Contour (ugl)

January 2002 Hows Corner Superfund Site

Plymouth Maine WOODARD amp CURRAN Engineering Science- Operations bull

211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0102dwg04-20-05

PLYMOUTH POND

PLYMOUTH POND

Site Pand^ laquoum-laquoBTuitaraquo tLV

vVlf-(

PLYMOUTH POND

0 300 600 ^ = FEET

Shallow Monitoring Well mdashbullbullbull 17-Acre Property Boundary Figure 1-YD - A - Deep Monitoring Well FT Detected Concentration ND = Not Detected Distribution of Total VOCs in

Deep Bedrock Groundwater Pumping Well January 2002 Residential Well Hows Corner Superfund Site

Plymouth Maine Surface Water Sampling Point

WOODARD ampCURRAN Engineering Sciencs- Operations bulli Si

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0102dwg04-20-05

- m j

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND j A O-shy

Shallow Monitoring Well E Detected Concentration ND = Not Detected Figure 1-ZS Distribution of Total VOCs in

Deep Monitoring Well Shallow Bedrock Groundwater

Pumping Well Hows Corner

April 2003 Superfund Site

17-Acre Property Boundary Plymouth Maine Concentration Contour (ugl) r WOODARD ampCURRAN

Engineering bull Science bull Operations bull 211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0403dwg04-20-05

s S pound

PLYMOUTH POND

PLYMOUTH POND

- -

5 PLYMOUTH POND

Jo

FEET

ft Shallow Monitoring Well mdashbullbullmdash 17-Acre Property Boundary Figure 1-ZD Deep Monitoring Well I 1 I Detected Concentration ND = Not Detected Distribution of Total VOCs in

Deep Bedrock Groundwater Pumping Well April 2003

Q) Residential Well Hows Corner Superfund Site Plymouth Maine

(T) Surface Water Sampling Point WOODARD ampCURRAN poundKk EnginawtirKj bull Science - Operations bull

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0403dwg04-20-05

0 Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

B MW-1B

I 12000

PCE

B 10000 Total VOCs

I

i 2000

i 0 Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

c MW-3B

G 2000

1800

B PCE

1600 Total VOCs

1 I I E

il-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

G E

211941

El

I I z E

80

Concentration Trends shy Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-13DB

Total VOCs

c i i c o

Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

MW-16DB

30

c i c c I c o

Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99

PCE

Total VOCs

Jul-01 Jul-03

211941

O bi

c Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

I MW-16IB

i 35

3

c Total VOCs

lt- 2 5

0 | gt

o

1 sectI

c c 0 4

Jul-90 Jul-92 Jul-94 Jul-96 Jul-98 Jul-00 Jul-02 Jul-04

I I MW-108D

I 12

PCE 10

Total VOCs c oc 3

E E I 0

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

E 211941

c Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

fi MW-108S

I I 40

PCE 35

Total VOCs

30

I f 26

20 I o

I 15

10

c Dec-99 Dec-00 Dec-01 Dec-02 Dec-03 I 0

I MW-112D

c 35 - imdash

I A3 shyTotal VOCs

o c

E 1 2

I

ition

B 1 ^

-i c 3

0 Dec-99 Dec-OO Dec-01 Dec-02 Dec-03

211941

I

i

I

cII

Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-112S

08

PCE

Total VOCs 06

o 04

02

0 Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

MW-114D

o

12000

10000

8000

6000

PCE

Total VOCs

4000

2000

i

ccEIIc

i

i

E

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

211941

Con

cent

ratio

n (

ug

l)

E Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

I MW-114S

E A5000 -- Total VOCs

- 4000

0 3000

2000

i 1000

i n shy

Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

MW-115D

c PCE

Total VOCs

c E

o

C c

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03 I 0

211941

IepoundII

EIEIIGICCIccc

30000

25000

20000

o bullsect 15000 b

o 10000 U

5000

0 Aug-99

25000

20000

5000

0 Aug-99

211941

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-2DB

PCE

Total VOCs

Aug-01 Aug-03

MW-2IB

PCE

Total VOCs

Aug-01 Aug-03

IDIBI

ii EIDIISIBIG C

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-102S

6000

5000 PCE

Total VOCs

4000

O 3000

2000

1000

0 Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

MW-103D

16000

~ 14000 ugt 3- 12000 o

^ 10000

sect 8000

O 6000

4000

2000

PCE

Total VOCs

0Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

211941

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

G MW-103S

I I

ampo

12000

10000

E sectc

S

8000

6000

4000

2000

0Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

G I 6000

MW-104D

i 5000

PCE

Total VOCs

i i c

2000

1000

Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

E I

211941

cIccIG

IIBCccBcIc

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-1041

PCE Total VOCs

a 25000

0 20000

a 15000

10000

5000

0 Jan-OO Jan-01 Jan-02 Jan-03 Jan-04

MW-106D

3000

2500 PCE

Total VOCs

=sect 2000

o bullsect 1500

1000

500

0 Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

211941

c Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

c MW-106S

I PCE

Total VOCs

i

i Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

i

i i i E

C

211941 c

Response to EPA-DEP Comment 5 Dated March 312005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

iiw

EPA-DEP Comment 5

Comment 5 Matrix Diffusion The report as well as other proponents of matrix diffusion suggest that depletion of DNAPL (Section 5112 page 5-15) needs to be achieved While that might be the ideal the goal is to achieve performance standards and that goal may be attainable while there is residual contamination in the rock perhaps even DNAPL globules The low bedrock matrix porosity (page 1-15) the high permeability values (page 4-4) the relative flux of the groundwater (page 5-5) and the decrease in surface area and out of the mainstream pockets (appendix C-4) all suggest that the diffusion out of the rock matrix would be insubstantial relative to the regional flux of groundwater through the Site

Response The TI Evaluation Report does not explicitly consider or rely upon matrix diffusion as a basis for requesting a TI Waiver for a portion of the Hows Corner Site The technical literature provides documentation that matrix diffusion can be a significant process that affects chemical transport and groundwater remediation timeframes in unconsolidated and consolidated media including fractured rock (US EPA 1989 Freeze and Cherry 1979 Pankow and Cherry 1996 Fountain 1998) Back diffusion of contaminants from the matrix porosity of the fractured rock can prolong the time necessary to achieve groundwater cleanup goals particularly for compounds such as PCE for which the cleanup goal is a low concentration It is our expectation that matrix diffusion has occurred at the Hows Corner Site and that back diffusion of PCE from the rock matrix will also occur Although the extent to which matrix diffusion is occurring at the Hows Comer Site has not been determined and that lack of knowledge contributes to uncertainty regarding the cleanup times at the Site the effect of matrix diffusion is to lengthen rather than shorten the time required for remediation

REFERENCES

Fountain JC 1998 Technologies for Dense Nonaqueous Phase Liquid Source Zone Remediation Ground-Water Remediation Technologies Analysis Center Technology Evaluation Report TE-98-02 December

Freeze RA and Cherry JA 1979 Groundwater Prentice-Hall Inc Englewood Cliffs NJ 07632 p 410-412

Pankow J F and Cherry J A 1996 Dense Chlorinated Solvents Waterloo Press Portland OR 97291-1399 p 67-88

US EPA 1989 Transport and Fate of Contaminants in the Subsurface EPA6254-89019 p 17-18

Response to EPA Comment 5 050305doc 1 of 1 Woodard amp Curran (211941)

WOODARD amp CURRAN Maine Massachusetts New Hampshire Connecticut Florida Operational offices across the US 1-800-426-4262 www woodardcurran com

Page 7: SDMS DocID 251749 - Records Collections · 2020-06-13 · CORPORATE OFFICES: Maine, Massachusetts, New Hampshire, Connecticut New, York, Florida Engineering • Science • Operations

EPA-DEP Comment 2

Comment 2 As discussed in our January meeting the results of the TI field work and their interpretation need to be presented in the TI report Listed below are some specific comments on this with the goal being a discussion of how the site conceptual model and site modeling were revised as a result of the 2004 field work

a analysis of the aquifer test to include a figure presenting the drawdown observed in each monitoring well at the end of the aquifer test The horizontal hydraulic gradient should not be included since this method tends to accentuate the anisotropy Two figures may be needed one for shallow bedrock and one for deep bedrock an evaluation of the appropriateness of the Cooper-Jacob (CJ) method for analyzing the aquifer test data including a comparison of the pattern of observed drawdown to the pattern of fracture orientations determined from the borehole geophysics confirmation that u lt 001 and that calculated values for T and S are similar for several observation wells an interpretation of the change in slope on the CJ plots near the end of the aquifer test the recovery data should be evaluated since it may provide insight as to why the slopes changed the marked increase in slope near the end of the test strongly suggests that a barrier (ie no flow) boundary was encountered and if a boundary was encountered T and S need to be calculated from the pre-boundary portions of the CJ plots It may be appropriate to analyse the aquifer test data using Theis as well as the Moench dual porosity model (both analysis methods are available in Aqtesolv pumping test modeling software) so that all parties have confidence in the transmissivity and storativity numbers derived from the CJ analysis b numerous bedrock borings (including angled holes) were drilled during the most recent field investigation yet no summary of the findings or the geophysical logging or packer test and sampling results have been provided c have any input parameters been changed in the flow transport and batch-flushing models as a result of the 2004 fieldwork If so which ones and why were the changes made (ie justify the changes)

Response The objective of the pumping test conducted at the Hows Corner Site during September 2004 was to observe the response of the groundwater system to pumping for use in refining the site conceptual model The refined site conceptual model would in turn be used to recalibrate the flow model and aid in the design of the hydraulic containment system being constructed under the authority of the AOC for the RD

The results of the pumping test are illustrated by plots of the drawdown at the end of the test The enclosed three drawdown plots (shallow bedrock deep bedrock and combined) represent the change in water level at the end of the test from the initial pre-test water level The shallow bedrock figure shows a northeast-southwest trending ellipsoidal area of drawdown that extends approximately 2000 feet along the major axis and approximately 800 feet along the minor axis The northeast-southwest orientation of the drawdown ellipse is consistent with the orientation of likely water-bearing fractures as identified from geophysical logging during the TI investigation The deep bedrock figure and combined figure also show ellipsoidal areas of drawdown with similar orientation A secondary axis with a more northerly orientation is evident on the figures showing drawdown in deep bedrock and in combined shallow and deep bedrock The maximum drawdown measured in shallow bedrock was 29 feet at MW-2EB The maximum drawdown measured in deep bedrock was 54 feet at the pumping well (PW-207) The drawdown ellipse is

Response to EPA Comment 2 050205doc 1 of 24 Woodard amp Curran (211941)

approximately coincident with the location of the modeled capture zone as presented on Figure 3shy1 of the TI Evaluation report

The enclosed three potentiometric surface maps (shallow bedrock deep bedrock and combined) represent the water surface elevations measured at the end of the test which was 72 hours or three days after it began All three maps show the presence of the groundwater high located in the southeast portion of the 17-acre property This high area shows relatively little relief but with the exception of the measurements at MW-2DDB which shows anomalously high water levels the central area of the high is at lower elevation than the perimeter The measurements at MWshy2DDB are hypothesized to result from water that is unable to drain rapidly enough to equilibrate with the rest of the formation

The pumping test data initially were analyzed using the Cooper-Jacob method for the late test data The results of this analysis are summarized in the table entitled Pumping Test Analytical Results It was recognized that because the aquifer is not uniform isotropic and infinite in areal extent the assumptions on which the underlying Theis equation is based were not met and because of the length of the test the criteria for use of the Cooper-Jacob of analysis were not explicitly met We recognize that the complexity of the hydrogeologic characteristics of the formation would be a significant limitation if the calculated values from the pumping test analysis were to be used as absolute representations of the hydraulic parameters of the formation However the range of values from this pumping test analysis were used as guidelines or bounding values for recalibration of the flow model

Woodard amp Curran also analyzed the pumping test data using the Theis and Moench methods The enclosed table entitled Pumping Test Analytical Results also summarizes the results of analysis of the data using these analytical methods Again although none of the methods may be strictly applicable they provide values that are guidelines for parametric ranges used in model calibration Hydraulic conductivity values calculated from the different analytical methods were as follow

Minimum Maximum Mean (ftday) (ftday) (ftda

bull Cooper-Jacob 020 067 038 bull Theis 035 1476 392 bull Moench (Fissure) 027 210 099

Storage coefficients calculated from the different analytical methods were as follow

Minimum Maximum Mean bull Cooper-Jacob 830E-04 392E-02 651E-03 bull Theis 547E-05 359E-03 473E-04 bull Moench (Block) 803E-05 402E-02 489E-03

Storage coefficients calculated using the Theis method were one to two orders of magnitude lower than values calculated using the Cooper Jacob or Moench (Block) methods Although the fissure system values are thought to be appropriate for evaluating hydraulic conductivity because the majority of flow is through fractures the block system values are appropriate for evaluation of storage because the limited fractures account for only a small part of the total storage in the bedrock

Response to EPA Comment 2 050205doc 2 of 24 Woodard amp Curran (211941)

Woodard amp Cunran used the values estimated from the pumping test analysis as an initial data set for transient benchmarking by running a 3-day simulated pumping test Calibration of the model was accomplished by comparing measured drawdowns obtained during the pumping test to calculated drawdowns from the flow model The hydraulic parameter values in the model were varied from the initial values but within the range calculated from the pumping test analysis The additional model calibration was considered to be completed when the calculated drawdowns were sufficiently close to measured drawdowns The resulting values of the hydraulic parameters of the calibrated model were then considered acceptable to provide satisfactory prediction of the response of the flow system to other hydraulic stresses

Regional water-level data were reviewed prior to data analysis A plot of water levels in the closest USGS regional background well (provided in the TI Data Package and attached) indicates that throughout the period of the test and subsequent recovery water levels were declining on a regional scale Although the decline in water levels is gradual the change in slope observed on the Cooper-Jacob plots is thought to represent the point at which the drawdown at a given location caused by pumping becomes less significant compared to the regional drawdown This occurs at about a day after start of pumping The effect of the regional decline in water levels can also be seen in the initial rapid rise in water levels in response to pump shut off followed by a decline in water levels after about a day after the pump is shut off

Additional information obtained during the TI field work was reviewed and evaluated in updating the conceptual model for the site In general the additional information corroborated the understanding of the Site presented in the RI report In particular the northeast-southwest fracture orientation was confirmed as the predominant orientation Geophysical logging during the TI investigation however showed the dip direction of fractures to be more variable and the dip angles to be shallower than was understood based on the RI data (see enclosed figure Packer Testing Results in Vicinity of Source Area) The additional borings installed within the fenced area and to the east of the fenced area showed that the area in which concentrations of total VOCs in groundwater exceeded 10000 pgL was more limited than portrayed in the RI and FS reports Packer testing of the intervals identified by geophysical logging as likely or possibly transmissive (see enclosed borehole geophysical logs) showed VOC concentrations within the packered intervals at a given borehole to be either essentially constant (eg MW-203 MW-204 MW-205) or increasing with depth (eg PW-207) Information on hydraulic conductivity and VOC concentrations in packered intervals is summarized on two separate tables for the 1999 RI wells and 2004 TI wells (Packer Permeability and Packer Sampling Results for Potential Fracture Intervals - enclosed) The orientation hydraulic conductivity and VOC concentrations of features identified as likely or possibly transmissive is summarized in a separate table (Orientation Permeability and Groundwater Sampling Results for Transmissive Features shyenclosed)

Table 4-1 of the TI Evaluation report summarizes the variation of input parameters to the flow and batch-flushing models as the project progressed from RI to FS to TI As described above for calculations in the TI Evaluation report hydraulic conductivity values were adjusted during the model calibration to pumping test drawdown data Measured fraction of organic carbon values and VOC concentrations were used in the Batch-Flushing model along with recharge calculated from the ModFlow model For calculation of pore flush volumes using the Batch-Flushing model the ratio of density to porosity was constrained to a range of 4 to 10 which is the typical range of such ratios in porous media (Freeze amp Cherry 1979) The basis for this change was stated in Appendix C of the TI Waiver Evaluation Report and is described in the response to Comment 3

Response to EPA Comment 2 050205doc 3 of 24 Woodard amp Curran (211941)

REFERENCE

Freeze RA and Cherry JA 1979 Groundwater Prentice-Hall Inc Englewood Cliffs NJ 07632 p 410-412

Response to EPA Comment 2 050205doc 4 of 24 Woodard amp Curran (211941)

LIST OF ATTACHMENTS (Response to Comment 2)

Figure - Drawdown at 72 Hours Shallow Wells

Figure - Drawdown at 72 Hours Deep Wells

Figure - Drawdown at 72 Hours

Figure - Potentiometric Surface at 72 Hours Shallow Wells

Figure - Potentiometric Surface at 72 Hours Deep Wells

Figure - End of Pumping Test Bedrock Potentiometric Surface at 72 Hours

Table - Pumping Test Analytical Results

Figure - USGS Background Groundwater Level

Figure - Packer Testing Results in Vicinity of Source Area

Figure - Borehole Geophysical Log MW-203

Figure - Borehole Geophysical Log MW-204

Figure - Borehole Geophysical Log MW-205

Figure - Borehole Geophysical Log MW-206

Figure - Borehole Geophysical Log PW-207

Table - Packer Permeability and Packer Sampling Results for Potential Fracture Intervals 1999 Drilling Program (2 pages)

Table - Packer Permeability and Packer Sampling Results for Potential Fracture Intervals 2004 Drilling Program

Table - Orientation Permeability and Groundwater Sampling Results for Transmissive Features 2004 Drilling Program (2 pages)

Response to EPA Comment 2 050205doc 5 of 24 Woodard amp Curran (211941)

(MEDEP Pond 1) Farm Pond

0 150 300

FEET

Monitoring Well

Figure X Pumping Well Drawdown at 72 Hours

_ - 17-Acre Property Boundary Shallow Wells Hows Corner Superfund Site Drawdown Contour (ft) Plymouth Maine

151 | Drawdown (ft) WOODARD ampCURRAN

^Stk Engineering bull Science bull Operations bull 211941 Hows CornlaquorwipDrawingsTI EVALDrawdown-72hrs_shallowdwg04-19-05

MW-3B

413951 W-6DB JMW-6SB

(MEDEP Pond 1) Farm Pond

Monitoring Well

Pumping Well

17-Acre Property Boundary

Groundwater Elevation Contour (ft)

211941 Hows CornerwipDrowngsTI EVALpo-tent-aU-72-hrsdwg

Figure X End of Pumping Test

Bedrock Potentiometric Surface at 72 Hours Hows Corner Superfund Site

Plymouth Maine ^ WOODARD amp CURRAN

Englnesring bull Science bull Ope

(MEDEP Pond 1) Farm Pond

Monitoring Well

Pumping Well Drawdown atFigure X

72 Hours _bullbull_ 17-Acre Property Boundary Deep Wells

Drawdown Contour (ft) Hows Corner Superfund Site

Plymouth Maine 151 | Drawdown (ft)

= WOODARD ampCURRAN 211941 Hows CornerwipDrawingsTI EVALDrawdown-72hrs_deepdwg04-19-05

Engineering bull Science bull Operations

(MEDEP Pond 1) Farm Pond

028 MW-12DB

MW-125B 040

l - _ ^ I 016 I N

050 MW-15SB

MW-15DB 048

A J s

- A - Monitoring Well

-$poundbull Pumping Well

_bullmdash 17-Acre Property Boundary

^ Drawdown Contour (ft)

151 I Drawdown (ft)

211941 Hows CornerwgtpDrawinQsT EVAI_Drawdown-72brsdwg04mdash19-05

Figure X Drawdown at 72 Hours

Hows Corner Superfund Site Plymouth Maine

^ WOODARD ampCURRAN Engineering bull Science bull Operations i

(MEDEP Pond 1) Farm Pond

Monitoring Well

Pumping Well

_bullbull_ 17-Acre Property Boundary

f Groundwater Elevation Contour (ft)

|419Q0| Groundwater Elevation

211941 Hows CornerwipDrawinqsTI EVALPotSurf-72hrs_shallowdwg04-19-05

150 300

FEET

Figure X Potentiometric Surface at 72 Hours

Shallow Wells Hows Corner Superfund Site

Plymouth Maine

WOODARD ampCURRAN Engineering bull Science bull Operations

29212 MW-108D

(MEDEP Pond 1) Farm Pond

Monitoring Well

Pumping Well

mdashbullbulllaquo 1 7-Acre Property Boundary

bull Groundwater Elevation Contour (ft)

1419001 Groundwater Elevation

211941 Hows CornerwipDrawingsTI EVALPotSurf-72hrs_deepdwg04-19-05

150 300 =5fc= FEET

Figure X Potentiometric Surface at 72 Hours

Deep Wells Hows Corner Superfund Site

Plymouth Maine

WOODARDampCURRAN Engineering bull Science bull Operations bull

--

Pumping Test Analytical Results Hows Corner Superfund Site

Plymouth Maine

Well ID oper Jaccb Analyses 2 Theis Analyses Fissure

Well Id Rd (ft)

Saturated Thickness

Transmissivity

(ft2day) K

(ft2day) K

(cmsec) Storage

Coefficient Transmissivity

(ft2day) K

(ft2day)

K (cmsec)

Storage Coefficient

System K

(ftday) PW-207OB 8 85 481 057 200E-04 392E-02 36 042 150E-04 809E-04 027 MW-103S 50 85 451 053 187E-04 720E-03 92 108 382E-04 283E-04 083 MW-103D 54 185 455 025 868E-05 210E-02 65 035 123E-04 237E-04 044 MW-2IB 59 85 352 041 146E-04 699E-03 104 123 433E-04 512E-04 052 MW-2DB 63 85 334 039 139E-04 845E-03 148 080 283E-04 239E-04 046 MW-104D 95 185 489 02 6 932E-05 654E-03 98 053 186E-04 547E-05 037 MW-104I 97 85 33 03 9 137E-04 362E-03 117 137 484E-04 962E-05 048 MW-101I 107 85 364 043 151E-04 490E-03 511 601 212E-03 223E-04 136 MW-102D 134 185 435 024 829E-05 248E-03 108 058 206E-04 850E-05 065 MW-101D 138 185 492 027 938E-05 511E-03 671 362 128E-03 700E-04 172 MW-205 219 85 57 067 237E-04 255E-03 447 526 186E-03 359E-03 -shyMW-204D 221 185 367 020 700E-05 170E-03 790 427 151E-O3 155E-04 147 MW-204S 225 85 379 045 157E-04 156E-03 1031 1213 428E-03 313E-04 199 MW-1B 228 85 325 038 135E-04 977E-04 340 400 141E-03 739E-05 054 MW-203S 273 85 489 058 203E-04 117E-03 1255 14 76 521 E-03 216E-04 210 MW-106D 278 185 51 028 972E-05 141E-03 1065 576 203E-03 360E-04 104 MW-203D 278 185 478 026 911E-05 152E-O3 765 414 146E-03 364E-04 138 MW-105D 364 185 44 024 839E-05 830E-04 769 415 147E-03 200E-04 127

1 Analyses conducted using Cooper and Jakob method on late drawdown data collected during constant

discharge pumping test conducted at the Hows Comer Site from September 20 - 30 2004

2 Analyses conducted using Theis solution for unconfmed approximation (1935)

J Analyses conducted using Moench method for dual porosity estimation (1984)

Fissure System Storage

Coefficient 402E-04 117E-06 264E-04 300E-04 932E-05 235E-07 502E-05 326E-06 801E-05 542E-04

-

803E-05 762E-05 134E-05 498E-05 115E-04

47E-04 838E-05

3 ysesh Analysis

Block System K (ft2day)

251E-02 207E-03 564E-04 163E-04 585E-04 465E-02 153E-04 498E-03 855E-04 356E-03

-

292E-03 394E-03 720E-04 526E-03 160E-01 35OE-O1 287E-03

Block System Storage

Coefficient

402E-02 164E-04 183E-02 330E-03 158E-03 847E-03 286E-03 326E-04 803E-05 272E-03

723E-04 686E-04 148E-04 349E-04 115E-03 47E-04 838E-04

Theis - Moench - CJ - AnalyticalResults_4-19-O5xls

DRAFT

242

24

238

236

bulla

c

i

a Q

234

232

228

226

Hows Corner Constant Discharge Testing USGS Background Groundwater Level USGS 445319068560101 ME-PEW456 Kenduskeag Maine

End of Monitored Recovery Period 09302004

Regional Background Location i 226 miles from Pumping Locatio

lt

697

NOTES

1 Groundwater samples collected in 1999 were screened for five volatile organic compounds (VOCs) only N

tetrachloroethene (PCE) exceeded reporting limits MW-2030 082304 082304 082304 082304 u

2 Strike and Dip of likely or possible transmissive 30 45 55 85 feature within the packer interval from which the indicated sample was collected

MW-204D

PCE TOTAL VOCs

081904 30

220 2636

A

081904 46-50 540 6436by

081904 IT

260 3073

x

MW-105D

PCE TOTAL VOCs

111199 50-60 2100 2100

MW-106D

PCE TOTAL VOCs

111199 76-86

400 400

111199 137-147

1400 1400

111299 1355-1455

350 350

PCE TOTAL VOCs

44 84

64

MW-6SB

bulli

lt

gt-

170 234

35

I I i

140 192

^^52

^^52

130 183

52 - lt

S A 34

PW-207 082404 082404 082404 20 37

PCE 1300 TOTAL VOCs

17-Acre George West Property Boundary

MW-113D

PCE TOTAL VOCs

112299 46-56

350 350

112299 70-80 190 190

150

112299 105-115

129 129

112399 138-148

230 230

L e g e n d ( J New Monitoring Well-Summer

Site Property Boundary ^ P u m p i n g Well-Summer 2004

-xmdashxshy Source Area

bull0shy Monitoring Well shy Pre 2004 Angled Boring-Summer 2004

211941laquoipdwgTI-ELV21ig41paltker-data2

2004 PCE of Total

bull lt70 VOCs

M W - 1 14D ^ ^

Figure xx Packer Testing Results in

Vicinity of Source Area Hows Corner Superfund Site

Plymouth Maine ^ WOODARD ampCURRAN

^^^^^^^^^^m ampKm Engineering - Science bull Operations

c Northeast Geophysical Services Borehole Geophysical Log

MW-203 Date logged 081704 Plymouth Maine

I Flowmeter Measurements Tomporaturo(C) Acoustic Televiewer

7 5 8 8 5 9 95 Caliper (Inches) Resistance (Ohms) Spontaneous Potential (mVj Dip In Degrees PCE Total VOCs

3 0 2 0 8 0 laquodeg 4S 1000 1400 1800 2200 MO HO 1000 1200 MOO 0 laquo deg ugL ugL n 1 1 1 1 1 1 1 1 1 i 1 1 1 1 n 1 1 1 1 1 1 1 1 1 1 1 n I l l l l l l l n

Ambient Flowneter pumping Rowmeter 11 gpm 6

H

bull

magnetic 10 bull 10 bull - 10 - north - 1 0I

-

_

bullbullbull - bull

20 bull bull20 bull ^ ltr~mdash 01

I

4 ^

LOS7

^

44 84 I I

Xr - 2

lt ^ bull30 -_ _^O1J- 1 _ 050 30 - 3 0

0r - - 3

C -j [ bull bull bull | shy

-O8 H ~ 1 045 7

1 4040 - 40 - -40 r - 14gt 13

V1s -- -023 f 1022 1V 170 234 I

T lt bull B gtf 50^ J50 - - 5 0 - - 5 0

I eet be

lo

i 1

1 1

1

140 192 - - - -t shy

-mdashj bullpound 60 - $o - - 60 - -60

H i I c

bull024

ampbull

3 - T lt ftft rgt He

70 bull j 70 - - 70 - 7 0 -

in -j bullbull shy

-021 1 T 022

- Ton _ Ov

26

130 183 NF NF

90 -_ 90 - 7 90 - -90

-

ifi Jf

3J

^gt _ N F NF bull bull shy

| H100 - j 100 bullbull 100 - -100

1 1 1 1 1 1 1 ) | 1 f I 1 1 1 ) 0 20 40 60 80

flft mdash ftn - mdash rVt

30 4 g 0 20 40 60 Dip in Degrees bullbull

Likely or poss bleFluid Resistivity (ohmmeters) The dip direction-- indicated

^ t h e l i n e extending from t h

I Iransmissive zone circle The strike of the feature is 90 degrees from this

The acoustic televiewer graph displays the mostprominent features selectedffom the acoustic televiewer

R n r a h n l c D O t t n O I B

f i o n n h w c i r a l U K U p i i y SI Ud l

1 rn l_Og Packered Interval August 2004

E tog The location dip angle and dip direction of the sleeted M W - 2 0 3 Groundwater samples were collected by Woodard S Curran on H23120M features are approximate Refer to the televiewer og of His _ well for more precise detail Plymouth Maine Date logged 081704

I

1

Northeast Geophysical Services Borehole Geophysical Log MW-204 D a t e l o gge d 072604

Plymouth Maine

n 3

Flowrneter Measurements(in gpm)

Caliper (Inches)0 3 5 4 0

1 1 1 1 1 1 1 t 1 1 1 1 1 1Ambient Rowmeler pumping Flowmetsr 05gpm

Templaquorature (C) bull bull bull bull i

7 75 8 8S 9 Resistance (Ohms) Spontaneous Potential (mV)

4000 SOW 600 4M 0

Acoustic Televiewer (interpreted)

Dip in Degrees 0 20 4060 SO

at N

PCEugL

Total VOCs ugL

- -_ a

10-

shy 10 bull - 10 shymagnetic

north - 10

o o

bull 1

11

11

1 1

1 1

11 1

1 1

1 1

1 1

1 1

1 1

1 1

1 1

1 1 E 1

- L

3 7 2 0 2 0r bull 20 bull - shy

i S_ N F

bull30 bull 7 3 0 220 2636shy1^ J J 004

fI f V ^

40 shy 4 0 4 0 shy - 4 0rbull019 [_ 007 w8 - - shy5 c

bull

gt

Ia50i 540 6436

bull50 - - 50 - - 5 0

-QQ7 - bull - -t T

pound V gtk

B 6 0 - e o - 7 6 0 -60shyQ 1 1

Q -007 -004 bull1 mdash T - J ~

bull

- - shyT 70 -J c [TO- - 70 - 7 0-

V Y 1- -004 -003

mdash T -h - y - j i - - mdash 260 3073 - gt=7

80 -j NF bull80 - - 80 - - 8 0Jgt

bull i

i 1

i i

C- bull shy

90 shy

K

Jlt i90 90 shy - 9 0shy -

l

ii

I I I I

NF bull M J

I ^ ^ - ^ bull 1

mdash mdash - _

s -7 ^100shy

till

1 100 100- H - 1 0 0shy -1 x Likety or possible k ^ Iransmissive zonebull

1 i i i ii i i i | l l l l | l i l l 0 20 40 ED 80

1 -

3 0SOFluid Resistivity (ohmmeters)

Dip in Degrees The djp ^ ^ o n is indicated ty Ihe line extending from tha circle The strike of Ihe feature

19- 3U UIHJIW93 IolII l l l lraquo

bull

The acousfc televiewer graph displays the mostprominent features selected from the acoustic televiewer109 The location dip angle and dip direction of Ihe sleetedfeatures are approximate Refer to the televiewer log of thiswentormore precise detail

B o r e h o l e G e O D h V S I C a l LOO B W H U I B w c w p n y o i v a i w v yM W - 2 0 4

P l y m O U t n MaiDB

Packorod Interval August 2004Groundwater san-ples wampramp collected by Woodard a Curran on OMO23C4

Date logged 072604

C

I

E Northeast Geophysical Services Borehole Geophysical Log Date logged 072704

I MW-205

Plymouth Maine

Flowmeter Measurements Temperature (C) Acoustic Televiewer (In gpm) I ~l (Interpreted)

I 85 10 Caliper (inches) 95

Dip in D g r laquo Resistance (Ohms) Spo ontaneous Potential (mV PCE Total VOCs 3 0 16 4 0 4 5 ) 20 40 60 80 10 00 2000 30 00 4VJ 400 -3 laquo

i i i i 1 i i I i 11 4 0 D 1 I I ugL ugL

C h

iii Ambient Flowmetar pumping

Flowmeter 1 25 gprn

I bull$bull

i

I rmdash magnetic 1 north ^^^^ 1 VI f

10 ~ I C x 10 bull - 10 bullbull

4 5 6mdashmdash f 1000B 11448 noisy nodi a raquo ^

mdash 5rt mdashi mdash Oft pound) 1100B 12509

cjmdash1 007

-

i i i 1

en

8 B a B

30 mdash

-

40 shy

-mdash I -

50 -_

__NF lt005

- 30 - - 3 0 it 34V

MO P26 V S) 1300B 13776 _ N F NF

26

40 bull - 40 bull 7-40 gt J Vf1 cX

) -j -

_ N F NF 50 c bull - 50 ^ 7-50

i I

I

c

B pound 60 - 6 0 7 60 - 7-60 a i 1

_ N F NF i Si f f 70 -_ bull70 bull - 70 shyC I 9

-m bull - shyA

_ N F NF 80 80 -j bull80 bull - 80 - C- 33 34

bull

5-i r

i 1

J r

Ck

_ N F NF 9 0 90 - - 90 shy

i bullCshy

J rK bull

100 -j ^ Likely or possible bull100- - 100- I -100

transmissive zone bull - ^ bull shy] |

1 1 1 1 1 1 1 I 1 i i i 1 i i 1 1 0 20 40 SO SO 10 20 30 40 50 Dip in Degrees 30 4 0 Fluid Resistivity (ohmmeters) Thlaquo dip direction is indicated

by the line extern r g from the circle The strike of he feature is 90 degrees from ihis

The acoustic televiewer graph displays the most

I Borehole Geophysical Log Packered Interval August2004 prominent features selected from the acoustic televiewer

Groundwatcr samples were oollccled by Woodard amp Cufran orgt S172004 log The location dip angle and dip direction of ins slsctsd MW-205 features are approximate Refelt to the televiewer log of this wall for more precise detail Plymouth Maine Date logged 072704

I

C

I Northeast Geophysical Services Borehole Geophysical Log Date logged 072704

I MW-206

Plymouth Maine

Flowmetor Measurements Temperature (C) Acoustic Televiewer | I r T i i i i i i i i i i i i i i r I |(in gpm) (Interpreted)

I 75 8 flS 9 95

Caliper (inches) Resistance (Ohms) Spontaneous Potential (mV) Dip In Degress PCE Total VOCs 30 35 40 4 5 0 20 40 M 90 4500 5500 6500 ugL ugL I i i

I I

- 1 0

I - 2 0

I 2900B 32401

i i L

E 0

i 6300B 68901

i I 0 20 40 SO 80

20 30 40 50 Dip in Dlaquogralaquos

amp 4 a Fluid Resistivity (ohrnmeters) The dip dirertion is indicated Likely or possible by iho line extending from the transmissive zone circle The striKe of the feature

is 90 degrees from tNs

Borehole Geophysical Log Packered Interval August 2004

E amples were collected by Woodard amp Cunan oo SM82004 log Thraquo location 4p angle and dip direction of the sloeled MW-206 feature are approximate Refer to the televiewer 109 of this well for more precise detail Plymouth Maine Date logged 072704

C

I Northeast Geophysical Services Borehole Geophysical Log

Date logged 082304 PW-207

I Plymouth Maine

Fiowmeter Measurements Temperature (C) Acoustic Televiewer

I (in gpm) (interpreted)

75 8 85 9 95 Caliper (inches) Resistance f0tims) Spontaneous Potential (mV) Dip in Degrees PCE Total VOCs

55 60 0 20 40 SO 80 ugL ugL I I I I I I I

Ambienl Fiowmeter pumping Flewmater

magnetic - 10 - - 1 0

north

i - 20 - - 2 0

1300 1410

i - 30 - - 3 0

i tf

5400 5802 - 40 - - 4 0

B - 50 - - 5 0

I 18000 19234

- 60 - - 6 0

I 12000 13085

- 70 - - 7 0

- 8 0

i - 9 0 19000 20354

G - 100- -100

I 110 110 bull110

0 20 40 60 SO 10 20 30 Dip m Degrees

Fluid Resistivity (ohmmeters) I 50

The dip direction is indicated by ihe line extending from the circle The strike of the fealure is 90 degrees from this

Borehole Geophysical Log

G Packorod Interval August 20(M log The location dip angle and dip dirlaquocton or the sleeted Groundaier samplss were ooliecled by Woodard i Curran on ampt24f2ltXM PW-207 failures are approximate Reter to the televiewer log of this wlaquoll for more precise detail PlyPIOUth Maine Date logged 082304

I

Table XX Packer Permeability and Packer Sampling Results for Potential Fracture Intervals

1

WellID MW-101D MW-101D MW-101D MW-101D MW-101D MW-101D MW-101D MW-101D MW-101D MW-101D MW-I01D MW-101D MW-101D MW-102D MW-102D MW-I02D MW-102D MW102D MW-102D MW-102D MW-102D MW-102D MW-I02D MW-102D MW-102D MW-102D MW-103D MW-103D MW-103D MW-103D MW-I03D MW-103D MW-103D MW-103D MW-103D MW-103D MW-103D MW-103D MW-I03D MW-104D MW-104D MW-104D MW-104D MW-I04D MW-104D MW-104D MW-104D MW-104D MW-104D MW-104D MW-105D MW-105D MW106D MW-106D MW-106D MW-107D MW-107D

1999 Drilling Program

Hows Corner Superfund Site Plymouth Maine

Potential Fracture Top Of Bottom 6 Depth to lt Topof i Interval from Packer Packer Middle of Elevation Hydraulic bull PCE

GS ELEV 1 Rock Drilling Interval Interval Interval of Interval Conductivity Concentration (ft msl) (ft msl) TEST (ftbgs) (ftbgs) r(ftbgs) ( f t b (ft mil) (cmsec) (raquogL)

4339 4329 13 28-29 33-3537-39 271 376 324 4016 OOOE+00 4339 12 37-3444-46 380 485 433 3907 157E-04 4339 11 488 593 541 3799 132E-04 4339 10 60-61 578 683 631 3709 OOOE+00 4339 9 678 783 731 3609 I79E-05 4339 8 778 883 831 3509 106E-05 4339 7 880 985 933 3407 243E-05 4339 6 990 1095 1043 3297 339E-06 4339 5 1090 1195 1143 3197 OOOE+00 4339 4 1190 1295 1243 3097 OOOE+00 4339 3 1365-1375 1290 1395 1343 2997 OOOE+00 4339 2 147-157 1390 1495 1443 2897 580E-05 4339 1 147-157 1470 1575 1523 2817 741E-05 43161 43061 13 166 271 219 4098 333E-04 43161 12 30-3136-40 260 365 313 4004 I54E-05 43161 11 36-4041-43 362 467 415 3902 548E-05 43161 10 470 575 523 3794 598E-05 43161 9 570 675 623 3694 197FOS 43161 8 670 775 723 3594 OOOE+00 43161 7 770 875 823 3494 891 E-05 43161 6 83-94 870 975 923 3394 139E-05 43161 5 970 1075 1023 3294 123E-04 43161 4 1070 1175 1123 3194 526E-06 43161 3 1170 1275 1223 3094 138E-05 43161 2 1270 1375 1323 2994 671E-06 43161 1 1370 1475 1423 2894 OOOE+00 42997 42497 13 18-19 170 275 223 4077 OOOE+00 42997 12 260 365 313 3987 766E-05 42997 11 360 465 413 3887 727E-05 42997 10 460 565 513 3787 192E-05 42997 9 560 665 613 3687 752E-05 42997 8 660 765 713 3587 778E-05 42997 7 85-86 763 868 816 3484 260E-05 42997 6 860 965 913 3387 289E-05 42997 5 102-103 960 1065 1013 3287 102E-04 42997 4 1060 1165 1113 3187 522E-06 42997 3 1160 1265 1213 3087 520E-06 42997 2 129-130 1260 1365 1313 2987 960E-04 42997 1 1360 1465 1413 2887 OOOE+00 43372 42922 11 35-37 42-45 350 455 403 3935 684E-04 43372 10 460 565 513 3825 500E-05 43372 9 560 665 613 3725 106E-05 43372 8 72-74 660 765 713 3625 204E-05 43372 7 760 865 813 3525 872E-06 43372 6 860 965 913 3425 467E-06 43372 5 960 1065 1013 3325 200E-05 43372 4 1060 1165 1113 3225 354E-05 43372 3 125-130 1160 1265 1213 3125 157E-05 43372 2 125-130 1260 1365 1313 3025 337E-04 43372 1 1365 1465 1415 2922 689E-06 43052 43002 2 54-58 490 595 543 3763 124E-05 2100 43052 1 139-140 145-146 1367 1472 1420 2886 154E-04 1400 43291 4391 3 bullI133 260 365 313 4017 439F06 43291 2 77-78 760 865 813 3517 230E-03 400 43291 1 143-144 1355 1460 1408 2922 971E-06 350

29958 27258 4 450 555 503 2493 OOOE+00 (21)A 29958 3 103-105 1000 1105 1053 1943 752E-04 (063)A

Table XX Packer Permeability and Packer Sampling Results for Potential Fracture Intervals

1999 Drilling Program

Hows Corner Supcrfund Site Plymouth Maine

gtbull i Potential Fracture Top _OfBot Bottom of Depth to ltbull Top of Interval from f Packer Packer Middle Of

GS ELEV lt Hock Drilling interval Interval Interval WeD ID ft msl) (ft msl) TEST (ftbgs) ltft$gs) (ftbgs) (ftbgs)

MW-107D 29958 2 128-130 1200 1305 1253

MW-107D 29958 1 139-141 1350 1455 1403

MW-108D 31904 31104 6 35-36 300 405 353 MW-108D 31904 5 60-62 550 655 603

MW-108D 31904 4 80-83 750 855 803

MW-108D 31904 3 118-119 123-124 1150 1255 1203

MW-108D 31904 2 147-149 1440 1545 1493

MW-108D 31904 1 1700 1805 1753

MW-110D 40576 40426 2 21-31 210 315 263 MW-110D 40576 1 148-154 1460 1565 1513 MW-I11D 40519 4 70-71 650 755 703

MW-111D 40519 3 79-82 84-86 780 885 833 MW-I11D 40519 2 97-102 950 1055 1003 MW-111D 40519 1 1370 1475 1423

MW-112D 3027 2942 4 42-52 420 525 473 MW-112D 3027 3 850 955 903 MW112D 3027 2 1100 1205 1153 MW-112D 3027 1 135-136 140-141 1340 1445 1393

MW-113D 43085 43085 5 250 355 303 MW-I13D 43085 4 47-49 460 565 513 MW-113D 43085 3 73-74 700 805 753 MW-113D 43085 2 1050 1155 1103 MW-113D 43085 1 1380 1485 1433

MW-114D 42394 41594 4 48-49 450 555 503 MW-114D 42394 3 79-81 740 845 793 MW-114D 42394 2 121-129 1250 1355 1303 MW-114D 42394 1 134-142 1350 1455 1403

MW-115D 4035 4035 4 300 405 353 MW-1I5D 4035 3 70-71 650 755 703 MW-115D 4035 2 1150 1255 1203 MW-115D 4035 1 1400 1505 1453

LOT-28W 382 7 450 555 503 LOT28W 382 6 550 655 603 LOT-28W 382 5 650 755 703 LOT28W 382 4 750 855 803 LOT-28W 382 3 850 955 903 LOT-28W 382 2 950 1055 1003 LOT-28W 382 1 1055 1155 1105

NOTES cmsec = centimeters per second ft bgs = leet below ground surface It msl = feet below mean sea level lt = not detected at indicated reporting limil A = detected below laboratory PQL ( ) = detected below reporting limits

Elevation of Interval

(ft nisi) 174

159

283gt 2588

2388

1988

1698

1438

3795 2545 3349 3219 3049 2629

2555 2125 1875 1635

4006 3796 3556 3206 2876

3737 3447 2937 2837

3683 3333 2833 2583

3318 3218 3118 3018 2918 2818 2715

Hydraulic Conductivity

(cmsec)

323E-05

208E-05

471E-03

471E-03

624E-05

3I6E-05

264E-05

261 E-05

OOOE+00 200E-04 953E-05 OOOE+00 OOOE+00 212E-05

361 E-05 410E-06 2gQE06 292E-05

786E-05 124E-05 151 E-05 822E-06 82IE-06

858E-05 I69E-05 352E-03 866E-05

223E-05 394E-06 122E-05 525E-06

831 E-05 182F-05 L62E-05 129E-05 190E-05 890E-04 981 E-04

PCEraquo Concentration

(ugL)

lt5

(14A)

98 11

15

22

11

30

200 (62)A

110 210 300 240

(44)A (23)A

5

350 190 129 230

2200 1900 2600 2600

(17)A (16)A (19)A

96

Table XX Packer Permeability and Packer Sampling Results for Potential Fracture Intervals

2004 Drilling Program

Hows Corner Superfund Site Plymouth Maine

Top of Bottom of Depth to Midpoint

t K

ELEV (ft Potential Transmissive Zones Packer Interval

Packer Interval

Middle of Interval

Elevation of interval

Hydraulic Conductivity

PCE Concentration

Well ID msl) TESTr (ft bgs)- (ftbgs) (ftbgs) (ftbgs) (ft msl) (cmsec) (ogt) MW-203D 43227 4 277279 24 32 28 4043 667E-05 44

3 408415420 39 49 44 3883 593E-05 170 2 526 530 49 57 53 3793 101E-04 140 I 828830842 80 88 84 3483 701E-05 130

MW-204D 43262 5 295 300 26 34 30 4023 902E-05 220 4 463496513516 45 53 49 3833 119E-04 540 3 681685688 63 71 67 3653 OOOE+00 2 758 76 2 71 79 75 3573 309E-05 260 I 88 96 92 3403 OOOE+00

MW-205 42389 3 164 166 168 15 20 175 4148 OOOE+00 1000B 2 302305312 30 35 325 3998 107E-04 1300B 1 40 45 425 3898 OOOE+00

MW-206D 43007 5 17 72 195 4128 291E-05 4 296 302 307 29 34 315 4008 940E-05 2900B 3 522 52 57 545 3778 944E-07 2 656 64 69 665 3658 353E-06 1 92392793 4939 91 96 935 3388 614E-05 6300B

PW-207 43477 5 184622162819 18 29 235 4088 209E-05 1300 4 3508 32 43 375 3948 568E-06 5400 3 53325341542154325559 50 61 555 3768 821E-05 18000

6359 61 72 665 3658 866E-06 12000 1 8685 84 89 865 3458 213E-05 19000

NOTES cmsec = centimeters per second ft bgs = feet below ground surface ft msl = feet above mean sea level B = detected in lab blank

Table XX Orientation Permeability and Groundwater Sampling Results for Transmissive Features

2004 Drilling Program

Hows Corner Superfund Site Plymouth Maine

Borehole Geophisical Feature depth Dip True Dip True Transmissive Log Feature (Feet) Degrees Azimuth Strike bullvgt(Ltk|iy^

Number v Tosftble) v MW-203 5 277 64 337 67 Likely

6 279 59 11 281 Likely 8 352 14 177 87 Likely 11 381 46 96 6 Possible 12 408 35 271 1 Possible 14 415 57 250 340 Possible 15 420 58 202 292 Likely 18 526 52 75 345 Likely 19 530 52 82 352 Likely 28 828 48 75 345 Likely 29 830 52 17 287 Likely 30 830 56 233 323 Possible 31 842 50 130 40 Likely

MW-204 4 295 15 147 57 Likely 5 300 43 91 1 Likely 11 439 31 80 350 Possible 12 440 46 219 309 Possible 14 463 50 358 88 Likely 15 496 34 198 288 Likely 16 513 54 17 287 Likely 17 516 33 14 284 Likely 25 681 39 359 89 Possible 26 685 22 45 315 Possible 27 688 35 73 343 Possible 32 758 45 236 326 Likely 33 762 46 306 36 Likely

MW-205 5 164 69 106 16 Possible 6 166 78 165 75 Possible 7 168 82 115 25 Possible 8 168 68 116 26 Possible 12 215 46 222 312 Possible 13 217 75 62 332 Possible 14 219 29 32 302 Possible 16 237 69 250 340 Possible 17 256 73 353 83 Possible 18 272 44 202 292 Possible 21 299 37 196 286 Possible 22 302 31 206 296 Possible 23 305 59 48 318 Likely 24 312 63 42 312 Likely

MW-206 1 264 37 181 271 Likely 2 296 69 217 307 Likely 3 302 66 233 323 Likely 4 307 64 224 314 Likely 8 342 62 259 349 Likely

jjHydraulic GoiDanctilyity j(cmsecjw

667 E-05

593 E-05

101 P04

710 E-05

902 E-05

119 E-04

0

309 E-05

0

107 E-04

94 E-05

PCE (ugL)

44

170

140

130

220

540

260

IOOOB

1100B

1300B

2900B

STotal vVoCsv tig1)

84

234

192

183

2636

6436

3073

11448

12509

13776

32401

PCEyo dfCTotaf

52

73

73

7 1

83

84

85

87

88

94

90

Table XX Orientation Permeability and Groundwater Sampling Results for Transmissive Features

2004 Drilling Program

Hows Corner Superfund Site Plymouth Maine

Borehole Geophisical Feature deptt raquoip True pip True Transraissive Log Feature (Feet) shy Degrees Azimuth Strike (tikely

Number raquo Possible) 22 522 57 54 324 Possible 25 656 40 82 352 Possible 32 871 59 151 61 Possible 33 883 53 185 275 Possible 34 895 7 175 85 Likely 35 899 53 90 0 Likely 36 902 49 184 274 Likely 37 923 9 175 85 Likely 38 927 42 206 296 Likely 39 934 48 167 77 Likely 40 939 26 180 90 Likely

PW-207 1 1846 33 167 77 Likely 4 2216 49 289 19 Possible 7 2819 59 265 355 Possible 11 3508 55 189 279 Possible 18 5332 43 305 35 Likely 19 5341 51 30 300 Likely 20 5421 20 254 344 Likely 21 5432 39 301 31 Likely 23 5559 52 302 32 Likely 25 6359 24 182 272 Possible 29 8049 77 231 321 Possible 30 8685 78 38 308 Likely 32 9334 29 194 284 Likely

NOTES

B = detected in lab blank

Hydraulic Conductivity

(cmsee) 944 E-07 353 E-06

614 E-05

209 E-05

568 E-06

821 E-05

866 E-06

213 E-05

bulltCE (ugL)

6300B

1300

5400

18000

12000

19000

Total VOCs (ug1)

68901

1410

5802

19234

13085

20354

PCE of Total VOCs

9 1

92

93

94

92

93

Response to EPA-DEP Comment 3 Dated March 312005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

lit

EPA-DEP Comment 3

Comment 3 The reported f values and resultant Kd values There remains doubt that the values used in the flushing model accurately reflect the propensity for PCE to sorb to the bedrock The ^ values presented in Appendix B may be unrealistically high because the bedrock samples may have contained organic carbon that was unavailable for sorption The reported f values are only qualitative estimates of the organic carbon content of the bedrock samples The Walkley and Black organic carbon measurement method is quick and simple but the results obtained cannot be considered quantitative because it requires a correction factor which often results in erroneous values it assumes the organic carbon has an average valence of zero oxidizable and reducible constituents such as chloride ferrous iron and manganese oxides interfere with the results and the errors introduced by interference are potentially greater when the organic carbon content is low at low f values it is not clear that organic carbon is controlling PCE sorption (Schwarzenbach and Westall 1981 Mackay et al 1986 Fetter 1999)

In order to derive a Kd-based retardation factor that is reasonable given the reported f values and the rapid advance of the PCE plume described on pages 4-11 and 4-12 the flushing model requires a bulk density to porosity ratio that is roughly two orders of magnitude higher than the actual ratio for the Hows Corner bedrock (page 4-4) This apparent discrepancy needs to be addressed

Response This comment raises several concerns about the collection and analysis of samples for fraction of organic carbon (f^) the quality of the resulting data and the implications of the use of those data for estimation of the retardation of groundwater contaminant movement Results of bedrock analysis for f were proposed in the TI Evaluation Work Plan for use in conjunction with groundwater contaminant concentrations and aquifer information to estimate cleanup times using the Batch Flushing model It is important to use accurate f values from representative bedrock in the Batch Flushing model in order to obtain reasonable estimates of the remedial time frame Because of the importance of accurate and representative results the TI Investigation field program was designed and conducted both to collect samples representative of the rock volume most likely to be in contact with contaminated groundwater and to analyze them using an appropriate refereed analytical method Five potential methods for evaluating f were identified Of the five methods the Walkey-Black method was selected because it has minimal method interferences and a sufficiently low detection limit as well as a long history of use in agronomy and contamination studies The PRP Group is pleased with the quality of the data obtained from the bedrock samples as represented by their precision and reproducibility

The first part of this comment relates to the determination of fraction of organic carbon (f^) values The several subparts of the first paragraph are addressed individually in items 1 through 5 below The second part of the comment regarding the resultant distribution coefficient (Kd) values is addressed separately as item 6 below

1 There remains doubt that the values used in the flushing model accurately reflect the propensity for PCE to sorb to the bedrock

bull The rock core samples used for f (gocg) analysis were from core immediately adjacent to fractures These rock core samples included the fracture surfaces themselves and rock core extending back less than 1 cm from the fractures Therefore the foe data reported in the TI Evaluation represents the f of bedrock through which groundwater will travel and to which PCE will adsorb Based on the careful selection of sample locations and the

Response to EPA Comment 3 050205doc 1 of 11 Woodard amp Curran (211941)

number of samples collected we are confident that the measured f values are representative of the f at points of contact for PCE with the bedrock it is these f values that determine the propensity of PCE to sorb to the bedrock

bull The samples of rock core collected for analysis of f originated from 19 different locations varying in depth from 11 to 90 feet Therefore it is very unlikely that the rock core samples were contaminated with extraneous organic carbon from above ground

2 The foc values presented in Appendix B may be unrealistically high because the bedrock samples may have contained organic carbon that was unavailable for sorption

bull As noted in response 1 the f data reported in Appendix B represents organic carbon primarily associated with the surface of fractures in the bedrock through which groundwater is most likely to travel Therefore it is this organic carbon that the contaminants in the groundwater will come in contact with and adsorb to in the fractured rock at the site

bull The chemical oxidation agents used in the Walkey-Black method oxidize the easily oxidizable organic carbon in the medium and the foe is calculated from the quantity of the agent consumed Therefore it is unlikely that the analysis of the bedrock samples measured organic carbon that was unavailable for sorption

3 The reported foc values are only qualitative estimates of the organic carbon content of the bedrock samples

bull The reported f values are accurate quantitative results Schumachers review of Methods for the determination of total organic carbon (TOC) in soils and sediments (NCEA-C-1282 EMASC-001 April 2002) identifies the Walkley-Black method which was used to analyze the reported foc values as the reference method for comparison to other methods for analyzing total organic carbon

bull Schumacher also points out that if anything the WalkJey-Black method may underestimate the total organic carbon in a sample due to possible incomplete oxidation of organic carbon Usually the incomplete oxidation of total organic carbon in environmental samples is corrected for by multiplying the measured foe by 130 (Walkley amp Black 1934 Schulte 1995)

bull When the f data in the TI Evaluation Report (WampC 2005) Appendix B (attached) are analyzed statistically the standard deviation of the f for the 19 samples analyzed is 174 of the average f Given this standard deviation the 95 confidence interval for this data ranged from a low of 000123 gocg to a high of 000253 gocgm

The labs Method of Detection Limit (MDL) for the f measured using the Walkley-Black method is 00001 gocg Therefore the average (000188 gocg) the mean (000185 gocg) and geometric mean (000187 gocg) of the f values for the rock core at Hows Corner are all statistically significantly greater than the MDL of the Walkley-Black method

In addition to the aforementioned statistical analysis of the foe data triplicate samples (n = 3) from the same rock core (including one sample from the 19 rock core samples) were

Response to EPA Comment 3 050205doc 2 of Woodard amp Curran (211941)

analyzed for their f to determine the repeatability of the Walkley-Black method The average the mean and the geometric mean of the f values of these replicate samples was 000162 gocg 000150 gocg and 000159 gocgm respectively The standard deviation of these measurements was 000039 gocg

4 The Walkley and Black organic carbon measurement method is quick and simple but the results obtained cannot be considered quantitative because it requires a correction factor which often results in erroneous values it assumes the organic carbon has an average valence of zero oxidizable and reducible constituents such as chloride ferrous iron and manganese oxides interfere with the results and the errors introduced by interference are potentially greater when the organic carbon content is low at low foc values it is not clear that organic carbon is controlling PCE sorption (Schwarzenbach and Westall 1981 Mackay et al 1986 Fetter 1999)

bull Schumachers review (NCEA-C-1282 EMASC-001 April 2002) of the Walkley-Black method identifies several potential problems with this analytical method that could occur if the analytical lab is not familiar with the nuances of the chemistry associated with this method Interestingly Schumachers review neglected one of the more important analytical steps required to avoid errors in quantifying f in samples where there might beNAPL

It is absolutely critical to eliminate any NAPL from rock core samples prior to using the Walkley-Black method to measure foe in such samples This was done by the lab (PTS Laboratories) that measured the foe in the rock core samples from Hows Corner The lab used the Dean-Stark method (solvent extraction) to remove all hydrocarbons (including PCE and other NAPLs) from the sample (PTS Laboratories) This extraction method does not interfere with the subsequent analysis of the natural organic carbon associated with the rock core

Subsequently the samples were dried at 150degC to a constant weight (normally 16 hours) This latter step oxidizes all inorganic minerals including ferrous bearing minerals to ferric oxides and precludes their interference during the oxidation of the samples with chromic acid This procedure completely eliminates any positive bias in the reported foc

data that might have occurred due to the presence of ferrous ions and other reduced minerals

bull As noted in Response 3 the incomplete oxidation of total organic carbon results in an underestimate of the f and is corrected for by multiplying the f by a correction factor of 130 (Walkley amp Black 1934 Schulte 1995) The fx data reported in the TI Evaluation was corrected accordingly by using this correction factor

bull Excess chloride (Cl~) in percent weight quantities as found in saline soils may interfere with the quantitative titration of reduced chromium (Walkley 1947) However given that the primary rock type at the Hows Corner site is phyllite it is highly unlikely that there was sufficient chloride in the rock core samples for this to occur

bull Manganese oxides may also interfere with the analysis of f through competing with the dichromate ion for any oxidizable carbon (Walkley 1947) However in such cases the reported f would be an underestimate of the f present in the rock core Walkley (1947)

Response to EPA Comment 3 050205doc 3 of 11 Woodard amp Curran (211941)

4

reported that in the case where the ratio of MnO2 to carbon is 85 to 1 the error in the carbon determinations would only be 0 to 6 percent

It may also be useful to compare the analysis of total organic carbon in a geologic matrix that contains high levels of manganese using EPA method 9060 to the Walkley-Black method Table 1 summarizes data provided by one of the PRPs that compares the analysis of total organic carbon in a geologic matrix that contains approximately 02 wgt manganese (approximately 03 wgt manganese oxide)

Table 1 Comparison of total organic carbon measured using the EPA- 9060 method and the Walkley-Black method

Laboratory EPA-9060 Method Walkley-Black Method A Ave 00226 gocg Not analyzed

Stdev 000251 gocg n = 5

B Ave 002219 gocg Ave 002050 gocg Stdev = 000316 gocg Stdev =000971 gocg

n= 10 n = 10

The similarity in the total organic carbon concentrations measured by these two different methods provides further confidence that the Walkley-Black method is a viable method for analysis of total organic carbon in the presence of manganese equivalent to at least 10 by weight of the total organic carbon

5 The Walkley and Black organic carbon measurement at lowf^ values it is not clear that organic carbon is controlling PCE sorption (Schwarzenbach and Westall 1981 Mackay et al 1986 Fetter 1999)

bull Schwarzenbach and Westalls (1981) paper states that f values of less than 0001 gocg should not be used in combination with Kow (octanol-water partition coefficients) values to calculate K^ values (solid phase partition coefficients) values for a specific contaminant It should be noted that the TI Evaluation did not use the f data to calculate the KQC from the Kow Instead as requested by the EPA the measured KOC value for PCE was used to calculate the retardation factor for this contaminant

bull Schwarzenbach et al (2003) stated more recently that Even at very low f values (ie foe = 0001 kgoc - kg1 solid) sorption to the organic components of a natural sorbent may still be the dominant mechanism in defining the adsorption of organic compounds to geological matrices

bull In 1985 M Piwoni from the US EPA Robert S Kerr Environmental Research Laboratory published a paper (Banerjee et al 1985) that showed that for very hydrophobic molecules TOC content of the sorbent will control sorption down to levels of organic carbon that defy quantitation Contaminants such as the PCE found in the groundwater at Hows Corner are in this category of compounds

Given the aforementioned reasons the f values reported in the TI Evaluation are accurate within the noted statistical limitations and will have a predictable impact upon the retardation of PCE during groundwater transport

Response to EPA Comment 3 050205doc 4 of 11 Woodard amp Curran (211941)

6 In order to derive a Kd-based retardation factor that is reasonable given the reported foc

values and the rapid advance of the PCE plume described on pages 4-11 and 4-12 the flushing model requires a bulk density to porosity ratio that is roughly two orders of magnitude higher than the actual ratio for the Hows Comer bedrock (page 4-4) This apparent discrepancy needs to be addressed

The apparent discrepancy of bulk density to porosity ratios is most likely due to the fact that the Batch Flushing Model was originally developed for a porous medium and is not directly applicable to fractured bedrock As stated in Appendix C (page C-4) of the Draft Technical Impracticability Evaluation Report in order to use the Batch Flushing Model to describe the transport of contaminated groundwater in fractured bedrock where the matrix porosity is insignificant it is more appropriate to use a fracture surface area to void space ratio to calculate the retardation factor (R) than a bulk density to porosity ratio (Freeze amp Cherry 1979)

Since it is impractical to determine the actual surface area to which contaminants can adsorb the Batch Flushing Model was used with two simplifying assumptions bull The Kd was calculated from the f and the K^ bull The bulk density to porosity ratio term in the Batch Flushing Model was constrained to range

from 4 to 10 the typical range of such ratios in porous media (Freeze amp Cherry 1979)

If one uses site specific bedrock bulk density and porosity values the bulk density to porosity ratio is several orders of magnitude greater (specifically 273 gcc bullbull 000165 (dimensionless) = 1654 gcc) than the range of ratios of 4 to 10 used in the Batch Flushing Model in the Draft Technical Impracticability Evaluation Report Constraining the bulk density to porosity ratio within the range of ratios of 4 to 10 results in significantly lower R value than would be obtained using specific bedrock bulk density and porosity values

In summary in bedrock where fractures are the primary porosity the bulk density to porosity ratio can vary considerably and will be a function of the number of fractures and the fracture aperture The calculated bulk density to porosity ratio will be inversely proportional to the porosity This means that in fractured rock with limited fracturing and smaller porosity the calculated bulk density to porosity ratio is greater and will result in a greater calculated retardation factor than in bedrock with more extensive fracturing and greater porosity Consequently the calculated retardation factor will be greater for bedrock with less surface area available for sorption than bedrock with greater surface area for sorption This is contrary to what actually occurs

4 Response to EPA Comment 3 050205doc 5 of 11 Woodard amp Curran (211941)

m

REFERENCES

Banerjee P MD Piwoni K Ebeid (1985) Sorption of organic contaminants to a low carbon subsurface core Chemosphere _14 1057-1067

Freeze RA JA Cherry (1979) Groundwater Prentice Hall Englewood Cliffs NJ pg 604

PTS Laboratories wwwptsgeolabscompdf files3TOCnotepdf

Schulte EE (1995) Recommended soil organic matter tests in Recommended Soil Testing Procedures for the Northeastern United States Northeastern Regional Publication No 493 Chapter 8

Schwarzenbach RP J Westall (1981) Transport of nonpolar organic compounds from surface water to groundwater Laboratory sorption studies Environ Sci Tech 15 1360-1367

Schwarzenbach RP PM Gschwend DM Imboden (2003) Environmental Organic Chemistry Wiley-Interscience pg 292 408 amp 412

Walkley A LA Black (1934) An examination of the Degtjareff method for determining soil organic matter and a proposed modification of the chromic acid titration method Soil Science 37 29-38

Walkley A (1947) A critical examination of a rapid method for determining organic carbon in soils - effect of variations in digestion conditions and of inorganic soil constituents Soil Science 63251-264

Woodard amp Curran Inc (WampC) 2005 Draft Technical Impracticability Evaluation Hows Corner Superfund Site Plymouth Maine January 2005

Response to EPA Comment 3 050205doc 6 of Woodard amp Curran (211941)

LIST OF ATTACHMENTS (Response to Comment 3)

Appendix B to Draft Technical Impracticability Evaluation Measurement of foe at Hows Corner (4 pages)

m

Response to EPA Comment 3 050205doc 7 of 11 Woodard amp Curran (211941)

Appendix B Measurement of foe of Rock Core at Hows Corner

There are two general approaches to measure the fraction of organic carbon (foe) in rock cores

bull Measurement of weight loss by ignition of organic matter bull Chemical oxidization of organic carbon to carbon dioxide and either

subsequent quantification of the oxidant used for the reaction or quantification of the carbon dioxide produced during this oxidation process

The weight loss method is subject to errors caused by volatilization of substances other than organic materials such as water hydroxides and mineral carbonates Quantification of foe by the weight loss method is particularly sensitive to the presence of carbonates in rock cores There are however weight loss methods that are designed to differentiate between organic carbon and the aforementioned interfering materials but they require considerable care and are less accurate at low foe values Hence the weight loss method was not well suited for measuring the foe of the rock core from Hows Corner

The chemical oxidation of organic carbon is much better suited for quantifying organic carbon in rock cores such as those from Hows Corner This method uses a strong chemical oxidant to oxidize organic carbon to carbon dioxide and then measures either the chemical oxidant used to oxidize the organic carbon or the quantity of carbon dioxide produced In addition this general approach is not subject to interference by volatilization of other constituents of the rock core

There are at least two such chemical oxidation methods

bull The method of Baccini which was described by Schwarzenbach amp Westall (1981) first acidifies the sample to eliminate interference by carbonates Then a strong oxidant is used to chemically oxidize the organic carbon to carbon dioxide The resulting carbon dioxide is subsequently reduced to methane and quantified using a flame ionization detector Unfortunately this method has not been described in detail in a referred journal Hence it is would not have been appropriate to use to characterize the foe in the Hows Corner rock core

bull The more commonly used method to quantify foe in rock core is the Walkley-Black method (1934) This method is preferred for RBCA and DODDOE projects and by the oil industry

The Walkley-Black method uses an excess of chromic acid to oxidize (digest) organic matter to carbon dioxide The remaining chromic acid that was not consumed during the oxidation of the organic carbon is then quantified by titration with ferrous sulfate The difference in chromic acid prior to and after the oxidation of the organic carbon represents the total chromic acid used to oxidize

Hows Corner TI Evaluation Page 1 January 13 2005 Appendix B

the organic carbon in the sample The latter can be calculated using the chemical stoichiometry of the reaction

The Walkley-Black method is very accurate for samples that contain less than 2 organic carbon matter The minimum detection limit (MDL) for the Walkley-Black method is 100 mgkg or an foe of 0001

Given the rock core at Hows Corner was expected to contain less than 2 organic carbon the Walkley-Black method was used to measure the foe from 19 different rock core samples collected from varying depths ranging from 11 to 90 feet

Table 1 provides a statistical summary of the aforementioned data

Table 1 Statistical summary of foe data from rock cores collected at varying depths

Statistical Parameter Calculated Value foe Minimum Detection Limit (MDL) 00010 Number of samples analyzed (n) 19 Average foe 00019 Median foe 00019 Geometric Mean foe 00019 Standard deviation of foe measurements 000033 Relative standard deviation 174 -+ 95 Confidence intervals 00012 to 00025

The data in Table 1 shows the following

bull The foe from the Hows Corner rock cores are statistically greater than the MDL of the Walkley-Black analytical method

bull The average and median values for the foe of the Hows Corner rock cores from varying depths are nearly identical indicating that there is little variability in the foe values in the source zone at the site

bull The standard deviation of these measurements is 000033 which is 174 of the average foe

bull The 95 confidence intervals of the foe of the rock core at Hows Corner are 00012 to 00025

The foe was also analyzed from three separate samples taken from the same rock core at a depth of 55 feet (Only one of these samples was included in the data summarized in Table 1) Table 2 shows the statistical repeatability of this type of analysis

Hows Corner TI Evaluation Page 2 January 13 2005 Appendix B

Table 2 Repeatability of analysis of foe from one rock core at 55 feet in depth

Statistical Parameter Calculated Value Number of samples analyzed (n) 3 Average foe 00016 Median foe 00015 Geometric Mean foe 00016 Standard deviation of foe measurements 000039 Relative standard deviation 240 -+ 95 Confidence intervals 00008 to 00024

The data in Table 2 shows the following

bull The percent relative standard deviation of these three analyses of foe from the same rock core at Hows Corner is 24

bull The 95 confidence interval of the foes measured in this particular rock core at Hows Conrer is 00008 to 00024

These results show that there is good repeatability in using the Walkley-Black method for analysis of the foe in the rock core at Hows Corner

References Schwarzenbach amp Westall (1981) Transport of nonpolar organic compounds from surface water to groundwater Laboratory sorption studies Environ Sci Tech 15 1360-1367

Walkley A I A Black (1934) An examination of Degtjareff method for determining soil organic matter and a proposed modification of the chromic acid titration method Soil Sci 37 29-37

Hows Corner Tl Evaluation Page S January 13 2005 Appendix B

Woodard and Curran PTS Laboratories PTS File No 34618

ORGANIC CARBON DATA (METHODOLOGY WALKLEY-BLACK)

PROJECT NAME PROJECT NO

SAMPLE ID

203-chip-13 203-chip-23 203-chip-27 203-chip-38 203-chip-42 203-chip-47 203-chip-52 203-chip-58 203-chip-69 203-chip-82 207-chip-11 207-chip-19 207-chip-24 207-chip-29 207-chip-35 207-chip-45 207-chip-55 207-chip-87 207-chip-90

207-chip-55 55-MS

55-MSMSD

Hows Corner NA

DEPTH ft

13 23 27 38 42 47 52 58 69 82 11 19 24 29 35 45 55 87 90

55 NA NA

MATRIX

Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip

Average Median

Geometric Mean Standard Deviation Relative Std Dev

+- 95 Confidence Interval n

Rock Chip Rock Chip Rock Chip

Average Median

Geometric Mean Standard Deviation Relative Std Dev

+- 95 Confidence Interval n

FRACTION ORGANIC CARBON

(gg)

170E-03 185E-03 185E-03 170E-03 240E-03 190E-03 230E-03 180E-03 170E-03 115E-03 195E-03 220E-03 220E-03 235E-03 135E-03 190E-03 205E-03 175E-03 160E-03

188E-03 185E-03 185E-03 327E-04

1739 123E-03 to

19

205E-03 130E-03 150E-03

162E-03 150E-03 159E-03 388E-04

2402 840E-04 to

3

2532E-03

2393E-03

Hows Corner Tl Evaluation Appendix B January 13 2005

Response to EPA-DEP Comment 4 Dated March 31 2005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

EPA-DEP Comment 4

Comment 4 Distribution of contaminants First the TI report seems based on the assertion that there is DNAPL at the source area yet it also appears to represent that the source area is small and the bedrock below 85 is competent (or less fractured) and less impacted by the release of contaminants Some of the confusion may result from using most recent data when that data is from several different sampling events over several years and there is no discernible difference in concentrations between shallow and deep bedrock or as in Section 421 where generally decreased generally increase generally similar and similar concentrations in four consecutive sentences leads to a muddled picture of the contaminant distribution

Second the report asserts that the distribution of contaminants over the entire plume has not changed with time but fails to support this conclusion with data again relying on data that is from different sampling dates for one composite representation

Response The likely presence of dense non-aqueous phase liquid (DNAPL) at the Hows Corner Site and the determination that the source area is small are not mutually exclusive and both are conclusions drawn from information obtained during field investigations The presence of DNAPL in the source area is based on the elevated concentrations of volatile organic compounds (VOCs) detected in the groundwater (WampC 2001 WampC 2002) The conclusion that the source area is small is based on the area in which VOCs in groundwater have been detected at concentrations that are considered to be indicative of the presence of DNAPL nearby Similarly the conclusion that fracture frequency decreases at depths greater than approximately 50 to 85 feet below ground surface was based on field observation during the RI field work The fact that zones with observed fractures exhibited higher hydraulic conductivities than zones without fractures coupled with the decreasing frequency of observed fractures with depth led to the conclusion that the hydraulic conductivity of the bulk rock decreases with depth

The most recent data from all wells were used to provide the maximum VOC data set size During the RI all of the previously-existing and then newly-installed monitoring wells were sampled along with several residential wells The RI sampling included up to 48 monitoring wells Subsequent to the RI and prior to the TI three rounds of monitoring were conducted to verify that the plume was stable 15 monitoring wells were sampled during each of the three rounds During the TI field investigation 29 wells were sampled for VOCs The sampled wells included all of the newly-installed wells and a subset of wells installed during the RI for a total of 29 monitoring wells By using most recent data VOC results from 53 monitoring wells were included in the evaluation (see table labeled Sampling Events for listing of monitoring wells) This approach was selected because there generally was little variation in the data from a particular location between years This is borne out by the attached individual plots of VOCs detected in shallow bedrock and deep bedrock for the Pre-ROD (December 1999January 2000) and Supplemental (May 2000) sampling events and for June 2001 January 2002 and April 2003 sampling events The Pre-ROD and Supplemental plots are similar to the subsequent plots from the 2001 2002 and 2003 sampling events

In addition to maps showing the spatial distribution of VOC data at a given time trend plots of the data from a particular location through time (attached) indicate that since the RI concentrations generally have been stable or have decreased Together the maps and trend plots and the data from which they were developed indicate that the distribution of contaminants over the entire plume has not changed appreciably with time

Response to EPA Comment 4 050305doc 1 of 26 Woodard amp Curran (211941)

REFERENCES

Woodard amp Curran Inc (WampC) 2001 Final Remedial Investigation Report Hows Corner Superfund Plymouth Maine July 2001

Woodard amp Curran Inc (WampC) 2002 Final Feasibility Study Report - Non-Source Area Groundwater Hows Corner Superfund Site Plymouth Maine Hows Corner Superfund Plymouth Maine July 2002

Response to EPA Comment 4 050305doc 2 of 26 Woodard amp Curran (211941)

LIST OF ATTACHMENTS (Response to Comment 4)

Table - Sampling Events 1999 - 2004 (2 pages)

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater Pre-ROD Sampling Event

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater Pre-ROD Sampling Event

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater Supplemental Sampling Event

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater Supplemental Sampling Event

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater June 2001

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater June 2001

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater January 2002

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater January 2002

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater April 2003

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater April 2003

Figure - Concentration Trends - Non-Source Area Wells MW-1B and MW-3B

Figure - Concentration Trends - Non-Source Area Wells MW-13DB and MW-16DB

Figure - Concentration Trends - Non-Source Area Wells MW-16IB and MW- 108D

Figure - Concentration Trends - Non-Source Area Wells MW-108S and MW-112D

Figure - Concentration Trends - Non-Source Area Wells MW-112S and MW-114D

Figure - Concentration Trends - Non-Source Area Wells MW-114S and MW-115D

Figure - Concentration Trends -Source Area Wells MW-2DB and MW-2IB

Figure - Concentration Trends -Source Area Wells MW-102S and MW-103D

Figure - Concentration Trends -Source Area Wells MW-103S and MW-104D

Figure - Concentration Trends -Source Area Wells MW-104I and MW-106D

Figure - Concentration Trends -Source Area Wells MW-106S

Response to EPA Comment 4 050305doc 3 of 26 Woodard amp Curran (211941)

I I

El I

II I I 1 I

I

i

Event Baseline Case ID WC-01 WC-01

Well Date Aug-99 Oct-99 LOT10 1 LOT1-1 1 LOT11-4 LOT14 1 LOT15 1 LOT15-1 1 LOT16 1 LOT16-1 1 LOT17 1 LOT18 1 LOT19 1 LOT2 LOT20 1 LOT21-10 1 LOT21-11 1 LOT21-12 1 LOT21-13 1 LOT21-14 1 LOT21-2 1 LOT21-5 1 LOT21-7 LOT21 -8 1 LOT21-9 1 LOT23 1 LOT24 1 LOT28-1 1 LOT28-2 1 LOT28-3 1 LOT28-4 1 LOT28W 1 LOT30 1 LOT30-1 1 LOT30-2 1 LOT30-3 1 LOT30-4 1 LOT30-5 LOT31 LOT35 1 LOT41 1 LOT42-1 1 LOT43-1 1 LOT43-4 1 LOT6-1 1 LOT67 1 LOT6-7 1 LOT6-8A 1 LOT6-8B 1 LOT80-1 1 LOT82 1 MW-101D MW-1011 MW-101S MW-102D MW-102S MW-103D MW-103S MW-104D MW-1041 MW-104S MW-105D MW-106D

Groundwater Sampling Location Summary 1999 - 2004xls

Sampling Events 1999-2004

Hows Corner Superfund Site Plymouth Maine

Supplemental 2001 2002 2003 Pumping 2004 Pre-ROD Rl Sampling Sampling Sampling Test Sampling WC-03 WC-09 WC-25 WC-30 WC-42B WC-56 WC-58 Dec-99 May-00 Jun-01 Jan-02 Apr-03 Sep-04 Sep-04

1

1 1 1

1 1 1 1 1

1 1

1

1 1

1 1 1

1 1 1 1 1

1

1 1

1 1 1 1

1

1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

Sampling Events 1999-2004

Hows Corner Super-fund Site Plymouth Maine

Supplemental 2001 2002 2003 Pumping Event Baseline Pre-ROD Rl Sampling Sampling Sampling Test

Case ID WC-01 WC-01 WC-03 WC-09 WC-25 WC-30 WC-42B WC-56

ll

Well Date Aug-99 Oct-99 Dec-99 May-00 Jun-01 Jan-02 Apr-03 Sep-04 MW-106S 1 1 1 1 1 MW-107D 1 1 MW-108D 1 1 1 1 1 MW-108S 1 1 1 1 1 MW-110D 1 1 MW-111D 1 1 MW-112D 1 1 1 1 1 MW-112S 1 1 1 1 1 MW-113D 1 1 MW-114D 1 1 1 1 1 MW-114S 1 1 1 1 1 MW-115D 1 1 1 1 1 MW-12DB 1 1 1 MW-12SB 1 1 1 MW-13DB 1 1 1 1 1 1 MW-13SB 1 1 1 MW-14DB 1 1 MW-14SO 1 1 MW-15DB 1 1 1 MW-15SB 1 1 1 MW-16DB 1 1 1 1 1 1 MW-16IB 1 1 1 1 1 1 MW-16SO 1 1 MW-17DO 1 1 1 MW-17SO 1 1 1 MW-1B 1 1 1 1 1 1 MW-203D MW-203S MW-204D MW-204S MW-205 MW-206D

I MW-206S MW-2DB 1 1 MW-2DDB 1 1 MW-2IB 1 1 1 1 1 1 MW-3B 1 1 1 1 1 1

I MW-4O 1 1 1 MW-5B 1 1

II MW-6DB 1 1 1 MW-6SB 1 1 1 MW-8DB 1 1 1 MW-8SB 1 1 1

II PW-207 1 SEEP-1 1 SUBTOTAL - RESIDENTIAL 44 25 0 2 0 3 0 SUBTOTAL - MONITORING 22 48 41 15 15 15 1

Total 3 66 73 41 17 15 18 1

I Included in most recent data

I Notes 1 - Overburden well not included in most recent data for plotting

2 - Tetrahydrofuran and 2-Butanone were the only two compounds detected in this well and are thought to be the result of well repair not included in most recent data for plotting

3 - Not included in most recent data for plotting

2004 Sampling

WC-58 Sep-04

1

1 1

1 1

1 1 1

1

1 1

1 1 1 1 1 1 1 1 1

1 1

1

0 29

29

Groundwatef Sampling Location Summary 1999 - 2004xls

I

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

monitoring well Figure 4-14 total VOC contour (ugl) - December 1999January 2000 Distribution of Total VOCs in

Note SW-113 is located downstream of SEEP-1 Shallow Bedrock Groundwater total concentration of detected VOCs ND= not detected these two locations were sampled during the Pre-ROD Sampling Event

Baseline Sampling Event in OctoberNovember 1999 Hows Corner Superfund Site Surface Water Sampling Location A Plymouth Maine Seep Sampling Location laquo- WOODARD ampCURRAN

995037wipri reportepa ri interim final feb 2001cadd drawingsfinalfig 4-14

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

0 300 600 I

FEET

Q residential well Figure 4-16 monitoring well Distribution of Total VOCs in

Deep Bedrock Groundwater total VOCs contour (ugl) Pre-ROD Sampling Event

active residential wells with lot number Hows Corner Superfund Site 2deg42deg Plymouth Maine total concentration of detected VOCs ND= not detected WOODARD ampCURRAN Enyinaaring bull Science bull Operations bull

995037wipri reportepa ri interim final feb 2001cadd drawingsfinalfig4mdash16

PLYMOUTH POND

PLYMOUTH POND

1 628Tl7MW-2bB 12135

PLYMOUTH POND

monitoring well Figure 4-20

V total VOC contour (ugl) - June 2000 Distribution of Total VOCs in Shallow Bedrock Groundwater

| 34 | total concentration of detected VOCs ND= not detected NA = not analyzed Supplemental Sampling Event Note SW-113 is located downstream of SEEP-1 Hows Corner Superfund Site

Surface Water Sampling Location these two locations were sampled during the Plymouth Maine Baseline Sampling Event in OctoberNovember 1999 Seep Sampling Location WOODARD amp CURRAN

Engineering bull Science - Operations bull 995037wipri reportepa ri interim final feb 2001 cadd drawingsfinalfig 4-20

residential well Figure 4-22 Distribution of Total VOCs in

monitoring well Deep Bedrock Groundwater

total VOCs contour (ugl) Supplemental Sampling Event

Hows Corner Superfund Site

total concentration of detected VOCs ND= not detected NA = not analyzed Plymouth Maine

WOODARD amp CURRAN

995037wipri reportepa-ri interim final feb 2001cadd drawingsfinalfig 4-22 Engineering bull Science - Operations bull

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

FEET

Shallow Monitoring Well

Deep Monitoring Well

C Detected Concentration ND = Not Detected Figure 1-XS Distribution of Total VOCs in Shallow Bedrock Groundwater

Pumping Well

17-Acre Property Boundary Concentration Contour (ugl)

June 2001 Hows Corner Superfund Site

Plymouth Maine WOODARDampCURRAN

-i^rhvj bull Scbncn bull Operations bull 211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0601 dwg04-20-05

PLYMOUTH POND Hopkins Road V

O

PLYMOUTH POND

PLYMOUTH POND

o

0 300 600 mdashfa FEET

Shallow Monitoring Well bull bull - 17-Acre Property Boundary Figure 1-XD

Deep Monitoring Well 1 I Detected Concentration ND = Not Detected Distribution of Total VOCs in Deep Bedrock Groundwater

-mf- Pumping Well June 2001 Residential Well Hows Corner Superfund Site

Plymouth Maine i h Surface Water Sampling Point

g WOODARD ampCURRAN _ ^ _ ^ _ _ yen_ rj i|Hlaquorlny bull Science bull Opt

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0601 dwg04-20-05

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

Shallow Monitoring Well

Deep Monitoring Well

Detected Concentration ND = Not Detected Figure 1-YS Distribution of Total VOCs in Shallow Bedrock Groundwater

Pumping Well

17-Acre Property Boundary Concentration Contour (ugl)

January 2002 Hows Corner Superfund Site

Plymouth Maine WOODARD amp CURRAN Engineering Science- Operations bull

211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0102dwg04-20-05

PLYMOUTH POND

PLYMOUTH POND

Site Pand^ laquoum-laquoBTuitaraquo tLV

vVlf-(

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0 300 600 ^ = FEET

Shallow Monitoring Well mdashbullbullbull 17-Acre Property Boundary Figure 1-YD - A - Deep Monitoring Well FT Detected Concentration ND = Not Detected Distribution of Total VOCs in

Deep Bedrock Groundwater Pumping Well January 2002 Residential Well Hows Corner Superfund Site

Plymouth Maine Surface Water Sampling Point

WOODARD ampCURRAN Engineering Sciencs- Operations bulli Si

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0102dwg04-20-05

- m j

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND j A O-shy

Shallow Monitoring Well E Detected Concentration ND = Not Detected Figure 1-ZS Distribution of Total VOCs in

Deep Monitoring Well Shallow Bedrock Groundwater

Pumping Well Hows Corner

April 2003 Superfund Site

17-Acre Property Boundary Plymouth Maine Concentration Contour (ugl) r WOODARD ampCURRAN

Engineering bull Science bull Operations bull 211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0403dwg04-20-05

s S pound

PLYMOUTH POND

PLYMOUTH POND

- -

5 PLYMOUTH POND

Jo

FEET

ft Shallow Monitoring Well mdashbullbullmdash 17-Acre Property Boundary Figure 1-ZD Deep Monitoring Well I 1 I Detected Concentration ND = Not Detected Distribution of Total VOCs in

Deep Bedrock Groundwater Pumping Well April 2003

Q) Residential Well Hows Corner Superfund Site Plymouth Maine

(T) Surface Water Sampling Point WOODARD ampCURRAN poundKk EnginawtirKj bull Science - Operations bull

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0403dwg04-20-05

0 Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

B MW-1B

I 12000

PCE

B 10000 Total VOCs

I

i 2000

i 0 Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

c MW-3B

G 2000

1800

B PCE

1600 Total VOCs

1 I I E

il-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

G E

211941

El

I I z E

80

Concentration Trends shy Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-13DB

Total VOCs

c i i c o

Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

MW-16DB

30

c i c c I c o

Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99

PCE

Total VOCs

Jul-01 Jul-03

211941

O bi

c Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

I MW-16IB

i 35

3

c Total VOCs

lt- 2 5

0 | gt

o

1 sectI

c c 0 4

Jul-90 Jul-92 Jul-94 Jul-96 Jul-98 Jul-00 Jul-02 Jul-04

I I MW-108D

I 12

PCE 10

Total VOCs c oc 3

E E I 0

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

E 211941

c Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

fi MW-108S

I I 40

PCE 35

Total VOCs

30

I f 26

20 I o

I 15

10

c Dec-99 Dec-00 Dec-01 Dec-02 Dec-03 I 0

I MW-112D

c 35 - imdash

I A3 shyTotal VOCs

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E 1 2

I

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B 1 ^

-i c 3

0 Dec-99 Dec-OO Dec-01 Dec-02 Dec-03

211941

I

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Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-112S

08

PCE

Total VOCs 06

o 04

02

0 Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

MW-114D

o

12000

10000

8000

6000

PCE

Total VOCs

4000

2000

i

ccEIIc

i

i

E

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

211941

Con

cent

ratio

n (

ug

l)

E Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

I MW-114S

E A5000 -- Total VOCs

- 4000

0 3000

2000

i 1000

i n shy

Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

MW-115D

c PCE

Total VOCs

c E

o

C c

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03 I 0

211941

IepoundII

EIEIIGICCIccc

30000

25000

20000

o bullsect 15000 b

o 10000 U

5000

0 Aug-99

25000

20000

5000

0 Aug-99

211941

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-2DB

PCE

Total VOCs

Aug-01 Aug-03

MW-2IB

PCE

Total VOCs

Aug-01 Aug-03

IDIBI

ii EIDIISIBIG C

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-102S

6000

5000 PCE

Total VOCs

4000

O 3000

2000

1000

0 Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

MW-103D

16000

~ 14000 ugt 3- 12000 o

^ 10000

sect 8000

O 6000

4000

2000

PCE

Total VOCs

0Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

211941

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

G MW-103S

I I

ampo

12000

10000

E sectc

S

8000

6000

4000

2000

0Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

G I 6000

MW-104D

i 5000

PCE

Total VOCs

i i c

2000

1000

Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

E I

211941

cIccIG

IIBCccBcIc

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-1041

PCE Total VOCs

a 25000

0 20000

a 15000

10000

5000

0 Jan-OO Jan-01 Jan-02 Jan-03 Jan-04

MW-106D

3000

2500 PCE

Total VOCs

=sect 2000

o bullsect 1500

1000

500

0 Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

211941

c Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

c MW-106S

I PCE

Total VOCs

i

i Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

i

i i i E

C

211941 c

Response to EPA-DEP Comment 5 Dated March 312005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

iiw

EPA-DEP Comment 5

Comment 5 Matrix Diffusion The report as well as other proponents of matrix diffusion suggest that depletion of DNAPL (Section 5112 page 5-15) needs to be achieved While that might be the ideal the goal is to achieve performance standards and that goal may be attainable while there is residual contamination in the rock perhaps even DNAPL globules The low bedrock matrix porosity (page 1-15) the high permeability values (page 4-4) the relative flux of the groundwater (page 5-5) and the decrease in surface area and out of the mainstream pockets (appendix C-4) all suggest that the diffusion out of the rock matrix would be insubstantial relative to the regional flux of groundwater through the Site

Response The TI Evaluation Report does not explicitly consider or rely upon matrix diffusion as a basis for requesting a TI Waiver for a portion of the Hows Corner Site The technical literature provides documentation that matrix diffusion can be a significant process that affects chemical transport and groundwater remediation timeframes in unconsolidated and consolidated media including fractured rock (US EPA 1989 Freeze and Cherry 1979 Pankow and Cherry 1996 Fountain 1998) Back diffusion of contaminants from the matrix porosity of the fractured rock can prolong the time necessary to achieve groundwater cleanup goals particularly for compounds such as PCE for which the cleanup goal is a low concentration It is our expectation that matrix diffusion has occurred at the Hows Corner Site and that back diffusion of PCE from the rock matrix will also occur Although the extent to which matrix diffusion is occurring at the Hows Comer Site has not been determined and that lack of knowledge contributes to uncertainty regarding the cleanup times at the Site the effect of matrix diffusion is to lengthen rather than shorten the time required for remediation

REFERENCES

Fountain JC 1998 Technologies for Dense Nonaqueous Phase Liquid Source Zone Remediation Ground-Water Remediation Technologies Analysis Center Technology Evaluation Report TE-98-02 December

Freeze RA and Cherry JA 1979 Groundwater Prentice-Hall Inc Englewood Cliffs NJ 07632 p 410-412

Pankow J F and Cherry J A 1996 Dense Chlorinated Solvents Waterloo Press Portland OR 97291-1399 p 67-88

US EPA 1989 Transport and Fate of Contaminants in the Subsurface EPA6254-89019 p 17-18

Response to EPA Comment 5 050305doc 1 of 1 Woodard amp Curran (211941)

WOODARD amp CURRAN Maine Massachusetts New Hampshire Connecticut Florida Operational offices across the US 1-800-426-4262 www woodardcurran com

Page 8: SDMS DocID 251749 - Records Collections · 2020-06-13 · CORPORATE OFFICES: Maine, Massachusetts, New Hampshire, Connecticut New, York, Florida Engineering • Science • Operations

approximately coincident with the location of the modeled capture zone as presented on Figure 3shy1 of the TI Evaluation report

The enclosed three potentiometric surface maps (shallow bedrock deep bedrock and combined) represent the water surface elevations measured at the end of the test which was 72 hours or three days after it began All three maps show the presence of the groundwater high located in the southeast portion of the 17-acre property This high area shows relatively little relief but with the exception of the measurements at MW-2DDB which shows anomalously high water levels the central area of the high is at lower elevation than the perimeter The measurements at MWshy2DDB are hypothesized to result from water that is unable to drain rapidly enough to equilibrate with the rest of the formation

The pumping test data initially were analyzed using the Cooper-Jacob method for the late test data The results of this analysis are summarized in the table entitled Pumping Test Analytical Results It was recognized that because the aquifer is not uniform isotropic and infinite in areal extent the assumptions on which the underlying Theis equation is based were not met and because of the length of the test the criteria for use of the Cooper-Jacob of analysis were not explicitly met We recognize that the complexity of the hydrogeologic characteristics of the formation would be a significant limitation if the calculated values from the pumping test analysis were to be used as absolute representations of the hydraulic parameters of the formation However the range of values from this pumping test analysis were used as guidelines or bounding values for recalibration of the flow model

Woodard amp Curran also analyzed the pumping test data using the Theis and Moench methods The enclosed table entitled Pumping Test Analytical Results also summarizes the results of analysis of the data using these analytical methods Again although none of the methods may be strictly applicable they provide values that are guidelines for parametric ranges used in model calibration Hydraulic conductivity values calculated from the different analytical methods were as follow

Minimum Maximum Mean (ftday) (ftday) (ftda

bull Cooper-Jacob 020 067 038 bull Theis 035 1476 392 bull Moench (Fissure) 027 210 099

Storage coefficients calculated from the different analytical methods were as follow

Minimum Maximum Mean bull Cooper-Jacob 830E-04 392E-02 651E-03 bull Theis 547E-05 359E-03 473E-04 bull Moench (Block) 803E-05 402E-02 489E-03

Storage coefficients calculated using the Theis method were one to two orders of magnitude lower than values calculated using the Cooper Jacob or Moench (Block) methods Although the fissure system values are thought to be appropriate for evaluating hydraulic conductivity because the majority of flow is through fractures the block system values are appropriate for evaluation of storage because the limited fractures account for only a small part of the total storage in the bedrock

Response to EPA Comment 2 050205doc 2 of 24 Woodard amp Curran (211941)

Woodard amp Cunran used the values estimated from the pumping test analysis as an initial data set for transient benchmarking by running a 3-day simulated pumping test Calibration of the model was accomplished by comparing measured drawdowns obtained during the pumping test to calculated drawdowns from the flow model The hydraulic parameter values in the model were varied from the initial values but within the range calculated from the pumping test analysis The additional model calibration was considered to be completed when the calculated drawdowns were sufficiently close to measured drawdowns The resulting values of the hydraulic parameters of the calibrated model were then considered acceptable to provide satisfactory prediction of the response of the flow system to other hydraulic stresses

Regional water-level data were reviewed prior to data analysis A plot of water levels in the closest USGS regional background well (provided in the TI Data Package and attached) indicates that throughout the period of the test and subsequent recovery water levels were declining on a regional scale Although the decline in water levels is gradual the change in slope observed on the Cooper-Jacob plots is thought to represent the point at which the drawdown at a given location caused by pumping becomes less significant compared to the regional drawdown This occurs at about a day after start of pumping The effect of the regional decline in water levels can also be seen in the initial rapid rise in water levels in response to pump shut off followed by a decline in water levels after about a day after the pump is shut off

Additional information obtained during the TI field work was reviewed and evaluated in updating the conceptual model for the site In general the additional information corroborated the understanding of the Site presented in the RI report In particular the northeast-southwest fracture orientation was confirmed as the predominant orientation Geophysical logging during the TI investigation however showed the dip direction of fractures to be more variable and the dip angles to be shallower than was understood based on the RI data (see enclosed figure Packer Testing Results in Vicinity of Source Area) The additional borings installed within the fenced area and to the east of the fenced area showed that the area in which concentrations of total VOCs in groundwater exceeded 10000 pgL was more limited than portrayed in the RI and FS reports Packer testing of the intervals identified by geophysical logging as likely or possibly transmissive (see enclosed borehole geophysical logs) showed VOC concentrations within the packered intervals at a given borehole to be either essentially constant (eg MW-203 MW-204 MW-205) or increasing with depth (eg PW-207) Information on hydraulic conductivity and VOC concentrations in packered intervals is summarized on two separate tables for the 1999 RI wells and 2004 TI wells (Packer Permeability and Packer Sampling Results for Potential Fracture Intervals - enclosed) The orientation hydraulic conductivity and VOC concentrations of features identified as likely or possibly transmissive is summarized in a separate table (Orientation Permeability and Groundwater Sampling Results for Transmissive Features shyenclosed)

Table 4-1 of the TI Evaluation report summarizes the variation of input parameters to the flow and batch-flushing models as the project progressed from RI to FS to TI As described above for calculations in the TI Evaluation report hydraulic conductivity values were adjusted during the model calibration to pumping test drawdown data Measured fraction of organic carbon values and VOC concentrations were used in the Batch-Flushing model along with recharge calculated from the ModFlow model For calculation of pore flush volumes using the Batch-Flushing model the ratio of density to porosity was constrained to a range of 4 to 10 which is the typical range of such ratios in porous media (Freeze amp Cherry 1979) The basis for this change was stated in Appendix C of the TI Waiver Evaluation Report and is described in the response to Comment 3

Response to EPA Comment 2 050205doc 3 of 24 Woodard amp Curran (211941)

REFERENCE

Freeze RA and Cherry JA 1979 Groundwater Prentice-Hall Inc Englewood Cliffs NJ 07632 p 410-412

Response to EPA Comment 2 050205doc 4 of 24 Woodard amp Curran (211941)

LIST OF ATTACHMENTS (Response to Comment 2)

Figure - Drawdown at 72 Hours Shallow Wells

Figure - Drawdown at 72 Hours Deep Wells

Figure - Drawdown at 72 Hours

Figure - Potentiometric Surface at 72 Hours Shallow Wells

Figure - Potentiometric Surface at 72 Hours Deep Wells

Figure - End of Pumping Test Bedrock Potentiometric Surface at 72 Hours

Table - Pumping Test Analytical Results

Figure - USGS Background Groundwater Level

Figure - Packer Testing Results in Vicinity of Source Area

Figure - Borehole Geophysical Log MW-203

Figure - Borehole Geophysical Log MW-204

Figure - Borehole Geophysical Log MW-205

Figure - Borehole Geophysical Log MW-206

Figure - Borehole Geophysical Log PW-207

Table - Packer Permeability and Packer Sampling Results for Potential Fracture Intervals 1999 Drilling Program (2 pages)

Table - Packer Permeability and Packer Sampling Results for Potential Fracture Intervals 2004 Drilling Program

Table - Orientation Permeability and Groundwater Sampling Results for Transmissive Features 2004 Drilling Program (2 pages)

Response to EPA Comment 2 050205doc 5 of 24 Woodard amp Curran (211941)

(MEDEP Pond 1) Farm Pond

0 150 300

FEET

Monitoring Well

Figure X Pumping Well Drawdown at 72 Hours

_ - 17-Acre Property Boundary Shallow Wells Hows Corner Superfund Site Drawdown Contour (ft) Plymouth Maine

151 | Drawdown (ft) WOODARD ampCURRAN

^Stk Engineering bull Science bull Operations bull 211941 Hows CornlaquorwipDrawingsTI EVALDrawdown-72hrs_shallowdwg04-19-05

MW-3B

413951 W-6DB JMW-6SB

(MEDEP Pond 1) Farm Pond

Monitoring Well

Pumping Well

17-Acre Property Boundary

Groundwater Elevation Contour (ft)

211941 Hows CornerwipDrowngsTI EVALpo-tent-aU-72-hrsdwg

Figure X End of Pumping Test

Bedrock Potentiometric Surface at 72 Hours Hows Corner Superfund Site

Plymouth Maine ^ WOODARD amp CURRAN

Englnesring bull Science bull Ope

(MEDEP Pond 1) Farm Pond

Monitoring Well

Pumping Well Drawdown atFigure X

72 Hours _bullbull_ 17-Acre Property Boundary Deep Wells

Drawdown Contour (ft) Hows Corner Superfund Site

Plymouth Maine 151 | Drawdown (ft)

= WOODARD ampCURRAN 211941 Hows CornerwipDrawingsTI EVALDrawdown-72hrs_deepdwg04-19-05

Engineering bull Science bull Operations

(MEDEP Pond 1) Farm Pond

028 MW-12DB

MW-125B 040

l - _ ^ I 016 I N

050 MW-15SB

MW-15DB 048

A J s

- A - Monitoring Well

-$poundbull Pumping Well

_bullmdash 17-Acre Property Boundary

^ Drawdown Contour (ft)

151 I Drawdown (ft)

211941 Hows CornerwgtpDrawinQsT EVAI_Drawdown-72brsdwg04mdash19-05

Figure X Drawdown at 72 Hours

Hows Corner Superfund Site Plymouth Maine

^ WOODARD ampCURRAN Engineering bull Science bull Operations i

(MEDEP Pond 1) Farm Pond

Monitoring Well

Pumping Well

_bullbull_ 17-Acre Property Boundary

f Groundwater Elevation Contour (ft)

|419Q0| Groundwater Elevation

211941 Hows CornerwipDrawinqsTI EVALPotSurf-72hrs_shallowdwg04-19-05

150 300

FEET

Figure X Potentiometric Surface at 72 Hours

Shallow Wells Hows Corner Superfund Site

Plymouth Maine

WOODARD ampCURRAN Engineering bull Science bull Operations

29212 MW-108D

(MEDEP Pond 1) Farm Pond

Monitoring Well

Pumping Well

mdashbullbulllaquo 1 7-Acre Property Boundary

bull Groundwater Elevation Contour (ft)

1419001 Groundwater Elevation

211941 Hows CornerwipDrawingsTI EVALPotSurf-72hrs_deepdwg04-19-05

150 300 =5fc= FEET

Figure X Potentiometric Surface at 72 Hours

Deep Wells Hows Corner Superfund Site

Plymouth Maine

WOODARDampCURRAN Engineering bull Science bull Operations bull

--

Pumping Test Analytical Results Hows Corner Superfund Site

Plymouth Maine

Well ID oper Jaccb Analyses 2 Theis Analyses Fissure

Well Id Rd (ft)

Saturated Thickness

Transmissivity

(ft2day) K

(ft2day) K

(cmsec) Storage

Coefficient Transmissivity

(ft2day) K

(ft2day)

K (cmsec)

Storage Coefficient

System K

(ftday) PW-207OB 8 85 481 057 200E-04 392E-02 36 042 150E-04 809E-04 027 MW-103S 50 85 451 053 187E-04 720E-03 92 108 382E-04 283E-04 083 MW-103D 54 185 455 025 868E-05 210E-02 65 035 123E-04 237E-04 044 MW-2IB 59 85 352 041 146E-04 699E-03 104 123 433E-04 512E-04 052 MW-2DB 63 85 334 039 139E-04 845E-03 148 080 283E-04 239E-04 046 MW-104D 95 185 489 02 6 932E-05 654E-03 98 053 186E-04 547E-05 037 MW-104I 97 85 33 03 9 137E-04 362E-03 117 137 484E-04 962E-05 048 MW-101I 107 85 364 043 151E-04 490E-03 511 601 212E-03 223E-04 136 MW-102D 134 185 435 024 829E-05 248E-03 108 058 206E-04 850E-05 065 MW-101D 138 185 492 027 938E-05 511E-03 671 362 128E-03 700E-04 172 MW-205 219 85 57 067 237E-04 255E-03 447 526 186E-03 359E-03 -shyMW-204D 221 185 367 020 700E-05 170E-03 790 427 151E-O3 155E-04 147 MW-204S 225 85 379 045 157E-04 156E-03 1031 1213 428E-03 313E-04 199 MW-1B 228 85 325 038 135E-04 977E-04 340 400 141E-03 739E-05 054 MW-203S 273 85 489 058 203E-04 117E-03 1255 14 76 521 E-03 216E-04 210 MW-106D 278 185 51 028 972E-05 141E-03 1065 576 203E-03 360E-04 104 MW-203D 278 185 478 026 911E-05 152E-O3 765 414 146E-03 364E-04 138 MW-105D 364 185 44 024 839E-05 830E-04 769 415 147E-03 200E-04 127

1 Analyses conducted using Cooper and Jakob method on late drawdown data collected during constant

discharge pumping test conducted at the Hows Comer Site from September 20 - 30 2004

2 Analyses conducted using Theis solution for unconfmed approximation (1935)

J Analyses conducted using Moench method for dual porosity estimation (1984)

Fissure System Storage

Coefficient 402E-04 117E-06 264E-04 300E-04 932E-05 235E-07 502E-05 326E-06 801E-05 542E-04

-

803E-05 762E-05 134E-05 498E-05 115E-04

47E-04 838E-05

3 ysesh Analysis

Block System K (ft2day)

251E-02 207E-03 564E-04 163E-04 585E-04 465E-02 153E-04 498E-03 855E-04 356E-03

-

292E-03 394E-03 720E-04 526E-03 160E-01 35OE-O1 287E-03

Block System Storage

Coefficient

402E-02 164E-04 183E-02 330E-03 158E-03 847E-03 286E-03 326E-04 803E-05 272E-03

723E-04 686E-04 148E-04 349E-04 115E-03 47E-04 838E-04

Theis - Moench - CJ - AnalyticalResults_4-19-O5xls

DRAFT

242

24

238

236

bulla

c

i

a Q

234

232

228

226

Hows Corner Constant Discharge Testing USGS Background Groundwater Level USGS 445319068560101 ME-PEW456 Kenduskeag Maine

End of Monitored Recovery Period 09302004

Regional Background Location i 226 miles from Pumping Locatio

lt

697

NOTES

1 Groundwater samples collected in 1999 were screened for five volatile organic compounds (VOCs) only N

tetrachloroethene (PCE) exceeded reporting limits MW-2030 082304 082304 082304 082304 u

2 Strike and Dip of likely or possible transmissive 30 45 55 85 feature within the packer interval from which the indicated sample was collected

MW-204D

PCE TOTAL VOCs

081904 30

220 2636

A

081904 46-50 540 6436by

081904 IT

260 3073

x

MW-105D

PCE TOTAL VOCs

111199 50-60 2100 2100

MW-106D

PCE TOTAL VOCs

111199 76-86

400 400

111199 137-147

1400 1400

111299 1355-1455

350 350

PCE TOTAL VOCs

44 84

64

MW-6SB

bulli

lt

gt-

170 234

35

I I i

140 192

^^52

^^52

130 183

52 - lt

S A 34

PW-207 082404 082404 082404 20 37

PCE 1300 TOTAL VOCs

17-Acre George West Property Boundary

MW-113D

PCE TOTAL VOCs

112299 46-56

350 350

112299 70-80 190 190

150

112299 105-115

129 129

112399 138-148

230 230

L e g e n d ( J New Monitoring Well-Summer

Site Property Boundary ^ P u m p i n g Well-Summer 2004

-xmdashxshy Source Area

bull0shy Monitoring Well shy Pre 2004 Angled Boring-Summer 2004

211941laquoipdwgTI-ELV21ig41paltker-data2

2004 PCE of Total

bull lt70 VOCs

M W - 1 14D ^ ^

Figure xx Packer Testing Results in

Vicinity of Source Area Hows Corner Superfund Site

Plymouth Maine ^ WOODARD ampCURRAN

^^^^^^^^^^m ampKm Engineering - Science bull Operations

c Northeast Geophysical Services Borehole Geophysical Log

MW-203 Date logged 081704 Plymouth Maine

I Flowmeter Measurements Tomporaturo(C) Acoustic Televiewer

7 5 8 8 5 9 95 Caliper (Inches) Resistance (Ohms) Spontaneous Potential (mVj Dip In Degrees PCE Total VOCs

3 0 2 0 8 0 laquodeg 4S 1000 1400 1800 2200 MO HO 1000 1200 MOO 0 laquo deg ugL ugL n 1 1 1 1 1 1 1 1 1 i 1 1 1 1 n 1 1 1 1 1 1 1 1 1 1 1 n I l l l l l l l n

Ambient Flowneter pumping Rowmeter 11 gpm 6

H

bull

magnetic 10 bull 10 bull - 10 - north - 1 0I

-

_

bullbullbull - bull

20 bull bull20 bull ^ ltr~mdash 01

I

4 ^

LOS7

^

44 84 I I

Xr - 2

lt ^ bull30 -_ _^O1J- 1 _ 050 30 - 3 0

0r - - 3

C -j [ bull bull bull | shy

-O8 H ~ 1 045 7

1 4040 - 40 - -40 r - 14gt 13

V1s -- -023 f 1022 1V 170 234 I

T lt bull B gtf 50^ J50 - - 5 0 - - 5 0

I eet be

lo

i 1

1 1

1

140 192 - - - -t shy

-mdashj bullpound 60 - $o - - 60 - -60

H i I c

bull024

ampbull

3 - T lt ftft rgt He

70 bull j 70 - - 70 - 7 0 -

in -j bullbull shy

-021 1 T 022

- Ton _ Ov

26

130 183 NF NF

90 -_ 90 - 7 90 - -90

-

ifi Jf

3J

^gt _ N F NF bull bull shy

| H100 - j 100 bullbull 100 - -100

1 1 1 1 1 1 1 ) | 1 f I 1 1 1 ) 0 20 40 60 80

flft mdash ftn - mdash rVt

30 4 g 0 20 40 60 Dip in Degrees bullbull

Likely or poss bleFluid Resistivity (ohmmeters) The dip direction-- indicated

^ t h e l i n e extending from t h

I Iransmissive zone circle The strike of the feature is 90 degrees from this

The acoustic televiewer graph displays the mostprominent features selectedffom the acoustic televiewer

R n r a h n l c D O t t n O I B

f i o n n h w c i r a l U K U p i i y SI Ud l

1 rn l_Og Packered Interval August 2004

E tog The location dip angle and dip direction of the sleeted M W - 2 0 3 Groundwater samples were collected by Woodard S Curran on H23120M features are approximate Refer to the televiewer og of His _ well for more precise detail Plymouth Maine Date logged 081704

I

1

Northeast Geophysical Services Borehole Geophysical Log MW-204 D a t e l o gge d 072604

Plymouth Maine

n 3

Flowrneter Measurements(in gpm)

Caliper (Inches)0 3 5 4 0

1 1 1 1 1 1 1 t 1 1 1 1 1 1Ambient Rowmeler pumping Flowmetsr 05gpm

Templaquorature (C) bull bull bull bull i

7 75 8 8S 9 Resistance (Ohms) Spontaneous Potential (mV)

4000 SOW 600 4M 0

Acoustic Televiewer (interpreted)

Dip in Degrees 0 20 4060 SO

at N

PCEugL

Total VOCs ugL

- -_ a

10-

shy 10 bull - 10 shymagnetic

north - 10

o o

bull 1

11

11

1 1

1 1

11 1

1 1

1 1

1 1

1 1

1 1

1 1

1 1

1 1 E 1

- L

3 7 2 0 2 0r bull 20 bull - shy

i S_ N F

bull30 bull 7 3 0 220 2636shy1^ J J 004

fI f V ^

40 shy 4 0 4 0 shy - 4 0rbull019 [_ 007 w8 - - shy5 c

bull

gt

Ia50i 540 6436

bull50 - - 50 - - 5 0

-QQ7 - bull - -t T

pound V gtk

B 6 0 - e o - 7 6 0 -60shyQ 1 1

Q -007 -004 bull1 mdash T - J ~

bull

- - shyT 70 -J c [TO- - 70 - 7 0-

V Y 1- -004 -003

mdash T -h - y - j i - - mdash 260 3073 - gt=7

80 -j NF bull80 - - 80 - - 8 0Jgt

bull i

i 1

i i

C- bull shy

90 shy

K

Jlt i90 90 shy - 9 0shy -

l

ii

I I I I

NF bull M J

I ^ ^ - ^ bull 1

mdash mdash - _

s -7 ^100shy

till

1 100 100- H - 1 0 0shy -1 x Likety or possible k ^ Iransmissive zonebull

1 i i i ii i i i | l l l l | l i l l 0 20 40 ED 80

1 -

3 0SOFluid Resistivity (ohmmeters)

Dip in Degrees The djp ^ ^ o n is indicated ty Ihe line extending from tha circle The strike of Ihe feature

19- 3U UIHJIW93 IolII l l l lraquo

bull

The acousfc televiewer graph displays the mostprominent features selected from the acoustic televiewer109 The location dip angle and dip direction of Ihe sleetedfeatures are approximate Refer to the televiewer log of thiswentormore precise detail

B o r e h o l e G e O D h V S I C a l LOO B W H U I B w c w p n y o i v a i w v yM W - 2 0 4

P l y m O U t n MaiDB

Packorod Interval August 2004Groundwater san-ples wampramp collected by Woodard a Curran on OMO23C4

Date logged 072604

C

I

E Northeast Geophysical Services Borehole Geophysical Log Date logged 072704

I MW-205

Plymouth Maine

Flowmeter Measurements Temperature (C) Acoustic Televiewer (In gpm) I ~l (Interpreted)

I 85 10 Caliper (inches) 95

Dip in D g r laquo Resistance (Ohms) Spo ontaneous Potential (mV PCE Total VOCs 3 0 16 4 0 4 5 ) 20 40 60 80 10 00 2000 30 00 4VJ 400 -3 laquo

i i i i 1 i i I i 11 4 0 D 1 I I ugL ugL

C h

iii Ambient Flowmetar pumping

Flowmeter 1 25 gprn

I bull$bull

i

I rmdash magnetic 1 north ^^^^ 1 VI f

10 ~ I C x 10 bull - 10 bullbull

4 5 6mdashmdash f 1000B 11448 noisy nodi a raquo ^

mdash 5rt mdashi mdash Oft pound) 1100B 12509

cjmdash1 007

-

i i i 1

en

8 B a B

30 mdash

-

40 shy

-mdash I -

50 -_

__NF lt005

- 30 - - 3 0 it 34V

MO P26 V S) 1300B 13776 _ N F NF

26

40 bull - 40 bull 7-40 gt J Vf1 cX

) -j -

_ N F NF 50 c bull - 50 ^ 7-50

i I

I

c

B pound 60 - 6 0 7 60 - 7-60 a i 1

_ N F NF i Si f f 70 -_ bull70 bull - 70 shyC I 9

-m bull - shyA

_ N F NF 80 80 -j bull80 bull - 80 - C- 33 34

bull

5-i r

i 1

J r

Ck

_ N F NF 9 0 90 - - 90 shy

i bullCshy

J rK bull

100 -j ^ Likely or possible bull100- - 100- I -100

transmissive zone bull - ^ bull shy] |

1 1 1 1 1 1 1 I 1 i i i 1 i i 1 1 0 20 40 SO SO 10 20 30 40 50 Dip in Degrees 30 4 0 Fluid Resistivity (ohmmeters) Thlaquo dip direction is indicated

by the line extern r g from the circle The strike of he feature is 90 degrees from ihis

The acoustic televiewer graph displays the most

I Borehole Geophysical Log Packered Interval August2004 prominent features selected from the acoustic televiewer

Groundwatcr samples were oollccled by Woodard amp Cufran orgt S172004 log The location dip angle and dip direction of ins slsctsd MW-205 features are approximate Refelt to the televiewer log of this wall for more precise detail Plymouth Maine Date logged 072704

I

C

I Northeast Geophysical Services Borehole Geophysical Log Date logged 072704

I MW-206

Plymouth Maine

Flowmetor Measurements Temperature (C) Acoustic Televiewer | I r T i i i i i i i i i i i i i i r I |(in gpm) (Interpreted)

I 75 8 flS 9 95

Caliper (inches) Resistance (Ohms) Spontaneous Potential (mV) Dip In Degress PCE Total VOCs 30 35 40 4 5 0 20 40 M 90 4500 5500 6500 ugL ugL I i i

I I

- 1 0

I - 2 0

I 2900B 32401

i i L

E 0

i 6300B 68901

i I 0 20 40 SO 80

20 30 40 50 Dip in Dlaquogralaquos

amp 4 a Fluid Resistivity (ohrnmeters) The dip dirertion is indicated Likely or possible by iho line extending from the transmissive zone circle The striKe of the feature

is 90 degrees from tNs

Borehole Geophysical Log Packered Interval August 2004

E amples were collected by Woodard amp Cunan oo SM82004 log Thraquo location 4p angle and dip direction of the sloeled MW-206 feature are approximate Refer to the televiewer 109 of this well for more precise detail Plymouth Maine Date logged 072704

C

I Northeast Geophysical Services Borehole Geophysical Log

Date logged 082304 PW-207

I Plymouth Maine

Fiowmeter Measurements Temperature (C) Acoustic Televiewer

I (in gpm) (interpreted)

75 8 85 9 95 Caliper (inches) Resistance f0tims) Spontaneous Potential (mV) Dip in Degrees PCE Total VOCs

55 60 0 20 40 SO 80 ugL ugL I I I I I I I

Ambienl Fiowmeter pumping Flewmater

magnetic - 10 - - 1 0

north

i - 20 - - 2 0

1300 1410

i - 30 - - 3 0

i tf

5400 5802 - 40 - - 4 0

B - 50 - - 5 0

I 18000 19234

- 60 - - 6 0

I 12000 13085

- 70 - - 7 0

- 8 0

i - 9 0 19000 20354

G - 100- -100

I 110 110 bull110

0 20 40 60 SO 10 20 30 Dip m Degrees

Fluid Resistivity (ohmmeters) I 50

The dip direction is indicated by ihe line extending from the circle The strike of the fealure is 90 degrees from this

Borehole Geophysical Log

G Packorod Interval August 20(M log The location dip angle and dip dirlaquocton or the sleeted Groundaier samplss were ooliecled by Woodard i Curran on ampt24f2ltXM PW-207 failures are approximate Reter to the televiewer log of this wlaquoll for more precise detail PlyPIOUth Maine Date logged 082304

I

Table XX Packer Permeability and Packer Sampling Results for Potential Fracture Intervals

1

WellID MW-101D MW-101D MW-101D MW-101D MW-101D MW-101D MW-101D MW-101D MW-101D MW-101D MW-I01D MW-101D MW-101D MW-102D MW-102D MW-I02D MW-102D MW102D MW-102D MW-102D MW-102D MW-102D MW-I02D MW-102D MW-102D MW-102D MW-103D MW-103D MW-103D MW-103D MW-I03D MW-103D MW-103D MW-103D MW-103D MW-103D MW-103D MW-103D MW-I03D MW-104D MW-104D MW-104D MW-104D MW-I04D MW-104D MW-104D MW-104D MW-104D MW-104D MW-104D MW-105D MW-105D MW106D MW-106D MW-106D MW-107D MW-107D

1999 Drilling Program

Hows Corner Superfund Site Plymouth Maine

Potential Fracture Top Of Bottom 6 Depth to lt Topof i Interval from Packer Packer Middle of Elevation Hydraulic bull PCE

GS ELEV 1 Rock Drilling Interval Interval Interval of Interval Conductivity Concentration (ft msl) (ft msl) TEST (ftbgs) (ftbgs) r(ftbgs) ( f t b (ft mil) (cmsec) (raquogL)

4339 4329 13 28-29 33-3537-39 271 376 324 4016 OOOE+00 4339 12 37-3444-46 380 485 433 3907 157E-04 4339 11 488 593 541 3799 132E-04 4339 10 60-61 578 683 631 3709 OOOE+00 4339 9 678 783 731 3609 I79E-05 4339 8 778 883 831 3509 106E-05 4339 7 880 985 933 3407 243E-05 4339 6 990 1095 1043 3297 339E-06 4339 5 1090 1195 1143 3197 OOOE+00 4339 4 1190 1295 1243 3097 OOOE+00 4339 3 1365-1375 1290 1395 1343 2997 OOOE+00 4339 2 147-157 1390 1495 1443 2897 580E-05 4339 1 147-157 1470 1575 1523 2817 741E-05 43161 43061 13 166 271 219 4098 333E-04 43161 12 30-3136-40 260 365 313 4004 I54E-05 43161 11 36-4041-43 362 467 415 3902 548E-05 43161 10 470 575 523 3794 598E-05 43161 9 570 675 623 3694 197FOS 43161 8 670 775 723 3594 OOOE+00 43161 7 770 875 823 3494 891 E-05 43161 6 83-94 870 975 923 3394 139E-05 43161 5 970 1075 1023 3294 123E-04 43161 4 1070 1175 1123 3194 526E-06 43161 3 1170 1275 1223 3094 138E-05 43161 2 1270 1375 1323 2994 671E-06 43161 1 1370 1475 1423 2894 OOOE+00 42997 42497 13 18-19 170 275 223 4077 OOOE+00 42997 12 260 365 313 3987 766E-05 42997 11 360 465 413 3887 727E-05 42997 10 460 565 513 3787 192E-05 42997 9 560 665 613 3687 752E-05 42997 8 660 765 713 3587 778E-05 42997 7 85-86 763 868 816 3484 260E-05 42997 6 860 965 913 3387 289E-05 42997 5 102-103 960 1065 1013 3287 102E-04 42997 4 1060 1165 1113 3187 522E-06 42997 3 1160 1265 1213 3087 520E-06 42997 2 129-130 1260 1365 1313 2987 960E-04 42997 1 1360 1465 1413 2887 OOOE+00 43372 42922 11 35-37 42-45 350 455 403 3935 684E-04 43372 10 460 565 513 3825 500E-05 43372 9 560 665 613 3725 106E-05 43372 8 72-74 660 765 713 3625 204E-05 43372 7 760 865 813 3525 872E-06 43372 6 860 965 913 3425 467E-06 43372 5 960 1065 1013 3325 200E-05 43372 4 1060 1165 1113 3225 354E-05 43372 3 125-130 1160 1265 1213 3125 157E-05 43372 2 125-130 1260 1365 1313 3025 337E-04 43372 1 1365 1465 1415 2922 689E-06 43052 43002 2 54-58 490 595 543 3763 124E-05 2100 43052 1 139-140 145-146 1367 1472 1420 2886 154E-04 1400 43291 4391 3 bullI133 260 365 313 4017 439F06 43291 2 77-78 760 865 813 3517 230E-03 400 43291 1 143-144 1355 1460 1408 2922 971E-06 350

29958 27258 4 450 555 503 2493 OOOE+00 (21)A 29958 3 103-105 1000 1105 1053 1943 752E-04 (063)A

Table XX Packer Permeability and Packer Sampling Results for Potential Fracture Intervals

1999 Drilling Program

Hows Corner Supcrfund Site Plymouth Maine

gtbull i Potential Fracture Top _OfBot Bottom of Depth to ltbull Top of Interval from f Packer Packer Middle Of

GS ELEV lt Hock Drilling interval Interval Interval WeD ID ft msl) (ft msl) TEST (ftbgs) ltft$gs) (ftbgs) (ftbgs)

MW-107D 29958 2 128-130 1200 1305 1253

MW-107D 29958 1 139-141 1350 1455 1403

MW-108D 31904 31104 6 35-36 300 405 353 MW-108D 31904 5 60-62 550 655 603

MW-108D 31904 4 80-83 750 855 803

MW-108D 31904 3 118-119 123-124 1150 1255 1203

MW-108D 31904 2 147-149 1440 1545 1493

MW-108D 31904 1 1700 1805 1753

MW-110D 40576 40426 2 21-31 210 315 263 MW-110D 40576 1 148-154 1460 1565 1513 MW-I11D 40519 4 70-71 650 755 703

MW-111D 40519 3 79-82 84-86 780 885 833 MW-I11D 40519 2 97-102 950 1055 1003 MW-111D 40519 1 1370 1475 1423

MW-112D 3027 2942 4 42-52 420 525 473 MW-112D 3027 3 850 955 903 MW112D 3027 2 1100 1205 1153 MW-112D 3027 1 135-136 140-141 1340 1445 1393

MW-113D 43085 43085 5 250 355 303 MW-I13D 43085 4 47-49 460 565 513 MW-113D 43085 3 73-74 700 805 753 MW-113D 43085 2 1050 1155 1103 MW-113D 43085 1 1380 1485 1433

MW-114D 42394 41594 4 48-49 450 555 503 MW-114D 42394 3 79-81 740 845 793 MW-114D 42394 2 121-129 1250 1355 1303 MW-114D 42394 1 134-142 1350 1455 1403

MW-115D 4035 4035 4 300 405 353 MW-1I5D 4035 3 70-71 650 755 703 MW-115D 4035 2 1150 1255 1203 MW-115D 4035 1 1400 1505 1453

LOT-28W 382 7 450 555 503 LOT28W 382 6 550 655 603 LOT-28W 382 5 650 755 703 LOT28W 382 4 750 855 803 LOT-28W 382 3 850 955 903 LOT-28W 382 2 950 1055 1003 LOT-28W 382 1 1055 1155 1105

NOTES cmsec = centimeters per second ft bgs = leet below ground surface It msl = feet below mean sea level lt = not detected at indicated reporting limil A = detected below laboratory PQL ( ) = detected below reporting limits

Elevation of Interval

(ft nisi) 174

159

283gt 2588

2388

1988

1698

1438

3795 2545 3349 3219 3049 2629

2555 2125 1875 1635

4006 3796 3556 3206 2876

3737 3447 2937 2837

3683 3333 2833 2583

3318 3218 3118 3018 2918 2818 2715

Hydraulic Conductivity

(cmsec)

323E-05

208E-05

471E-03

471E-03

624E-05

3I6E-05

264E-05

261 E-05

OOOE+00 200E-04 953E-05 OOOE+00 OOOE+00 212E-05

361 E-05 410E-06 2gQE06 292E-05

786E-05 124E-05 151 E-05 822E-06 82IE-06

858E-05 I69E-05 352E-03 866E-05

223E-05 394E-06 122E-05 525E-06

831 E-05 182F-05 L62E-05 129E-05 190E-05 890E-04 981 E-04

PCEraquo Concentration

(ugL)

lt5

(14A)

98 11

15

22

11

30

200 (62)A

110 210 300 240

(44)A (23)A

5

350 190 129 230

2200 1900 2600 2600

(17)A (16)A (19)A

96

Table XX Packer Permeability and Packer Sampling Results for Potential Fracture Intervals

2004 Drilling Program

Hows Corner Superfund Site Plymouth Maine

Top of Bottom of Depth to Midpoint

t K

ELEV (ft Potential Transmissive Zones Packer Interval

Packer Interval

Middle of Interval

Elevation of interval

Hydraulic Conductivity

PCE Concentration

Well ID msl) TESTr (ft bgs)- (ftbgs) (ftbgs) (ftbgs) (ft msl) (cmsec) (ogt) MW-203D 43227 4 277279 24 32 28 4043 667E-05 44

3 408415420 39 49 44 3883 593E-05 170 2 526 530 49 57 53 3793 101E-04 140 I 828830842 80 88 84 3483 701E-05 130

MW-204D 43262 5 295 300 26 34 30 4023 902E-05 220 4 463496513516 45 53 49 3833 119E-04 540 3 681685688 63 71 67 3653 OOOE+00 2 758 76 2 71 79 75 3573 309E-05 260 I 88 96 92 3403 OOOE+00

MW-205 42389 3 164 166 168 15 20 175 4148 OOOE+00 1000B 2 302305312 30 35 325 3998 107E-04 1300B 1 40 45 425 3898 OOOE+00

MW-206D 43007 5 17 72 195 4128 291E-05 4 296 302 307 29 34 315 4008 940E-05 2900B 3 522 52 57 545 3778 944E-07 2 656 64 69 665 3658 353E-06 1 92392793 4939 91 96 935 3388 614E-05 6300B

PW-207 43477 5 184622162819 18 29 235 4088 209E-05 1300 4 3508 32 43 375 3948 568E-06 5400 3 53325341542154325559 50 61 555 3768 821E-05 18000

6359 61 72 665 3658 866E-06 12000 1 8685 84 89 865 3458 213E-05 19000

NOTES cmsec = centimeters per second ft bgs = feet below ground surface ft msl = feet above mean sea level B = detected in lab blank

Table XX Orientation Permeability and Groundwater Sampling Results for Transmissive Features

2004 Drilling Program

Hows Corner Superfund Site Plymouth Maine

Borehole Geophisical Feature depth Dip True Dip True Transmissive Log Feature (Feet) Degrees Azimuth Strike bullvgt(Ltk|iy^

Number v Tosftble) v MW-203 5 277 64 337 67 Likely

6 279 59 11 281 Likely 8 352 14 177 87 Likely 11 381 46 96 6 Possible 12 408 35 271 1 Possible 14 415 57 250 340 Possible 15 420 58 202 292 Likely 18 526 52 75 345 Likely 19 530 52 82 352 Likely 28 828 48 75 345 Likely 29 830 52 17 287 Likely 30 830 56 233 323 Possible 31 842 50 130 40 Likely

MW-204 4 295 15 147 57 Likely 5 300 43 91 1 Likely 11 439 31 80 350 Possible 12 440 46 219 309 Possible 14 463 50 358 88 Likely 15 496 34 198 288 Likely 16 513 54 17 287 Likely 17 516 33 14 284 Likely 25 681 39 359 89 Possible 26 685 22 45 315 Possible 27 688 35 73 343 Possible 32 758 45 236 326 Likely 33 762 46 306 36 Likely

MW-205 5 164 69 106 16 Possible 6 166 78 165 75 Possible 7 168 82 115 25 Possible 8 168 68 116 26 Possible 12 215 46 222 312 Possible 13 217 75 62 332 Possible 14 219 29 32 302 Possible 16 237 69 250 340 Possible 17 256 73 353 83 Possible 18 272 44 202 292 Possible 21 299 37 196 286 Possible 22 302 31 206 296 Possible 23 305 59 48 318 Likely 24 312 63 42 312 Likely

MW-206 1 264 37 181 271 Likely 2 296 69 217 307 Likely 3 302 66 233 323 Likely 4 307 64 224 314 Likely 8 342 62 259 349 Likely

jjHydraulic GoiDanctilyity j(cmsecjw

667 E-05

593 E-05

101 P04

710 E-05

902 E-05

119 E-04

0

309 E-05

0

107 E-04

94 E-05

PCE (ugL)

44

170

140

130

220

540

260

IOOOB

1100B

1300B

2900B

STotal vVoCsv tig1)

84

234

192

183

2636

6436

3073

11448

12509

13776

32401

PCEyo dfCTotaf

52

73

73

7 1

83

84

85

87

88

94

90

Table XX Orientation Permeability and Groundwater Sampling Results for Transmissive Features

2004 Drilling Program

Hows Corner Superfund Site Plymouth Maine

Borehole Geophisical Feature deptt raquoip True pip True Transraissive Log Feature (Feet) shy Degrees Azimuth Strike (tikely

Number raquo Possible) 22 522 57 54 324 Possible 25 656 40 82 352 Possible 32 871 59 151 61 Possible 33 883 53 185 275 Possible 34 895 7 175 85 Likely 35 899 53 90 0 Likely 36 902 49 184 274 Likely 37 923 9 175 85 Likely 38 927 42 206 296 Likely 39 934 48 167 77 Likely 40 939 26 180 90 Likely

PW-207 1 1846 33 167 77 Likely 4 2216 49 289 19 Possible 7 2819 59 265 355 Possible 11 3508 55 189 279 Possible 18 5332 43 305 35 Likely 19 5341 51 30 300 Likely 20 5421 20 254 344 Likely 21 5432 39 301 31 Likely 23 5559 52 302 32 Likely 25 6359 24 182 272 Possible 29 8049 77 231 321 Possible 30 8685 78 38 308 Likely 32 9334 29 194 284 Likely

NOTES

B = detected in lab blank

Hydraulic Conductivity

(cmsee) 944 E-07 353 E-06

614 E-05

209 E-05

568 E-06

821 E-05

866 E-06

213 E-05

bulltCE (ugL)

6300B

1300

5400

18000

12000

19000

Total VOCs (ug1)

68901

1410

5802

19234

13085

20354

PCE of Total VOCs

9 1

92

93

94

92

93

Response to EPA-DEP Comment 3 Dated March 312005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

lit

EPA-DEP Comment 3

Comment 3 The reported f values and resultant Kd values There remains doubt that the values used in the flushing model accurately reflect the propensity for PCE to sorb to the bedrock The ^ values presented in Appendix B may be unrealistically high because the bedrock samples may have contained organic carbon that was unavailable for sorption The reported f values are only qualitative estimates of the organic carbon content of the bedrock samples The Walkley and Black organic carbon measurement method is quick and simple but the results obtained cannot be considered quantitative because it requires a correction factor which often results in erroneous values it assumes the organic carbon has an average valence of zero oxidizable and reducible constituents such as chloride ferrous iron and manganese oxides interfere with the results and the errors introduced by interference are potentially greater when the organic carbon content is low at low f values it is not clear that organic carbon is controlling PCE sorption (Schwarzenbach and Westall 1981 Mackay et al 1986 Fetter 1999)

In order to derive a Kd-based retardation factor that is reasonable given the reported f values and the rapid advance of the PCE plume described on pages 4-11 and 4-12 the flushing model requires a bulk density to porosity ratio that is roughly two orders of magnitude higher than the actual ratio for the Hows Corner bedrock (page 4-4) This apparent discrepancy needs to be addressed

Response This comment raises several concerns about the collection and analysis of samples for fraction of organic carbon (f^) the quality of the resulting data and the implications of the use of those data for estimation of the retardation of groundwater contaminant movement Results of bedrock analysis for f were proposed in the TI Evaluation Work Plan for use in conjunction with groundwater contaminant concentrations and aquifer information to estimate cleanup times using the Batch Flushing model It is important to use accurate f values from representative bedrock in the Batch Flushing model in order to obtain reasonable estimates of the remedial time frame Because of the importance of accurate and representative results the TI Investigation field program was designed and conducted both to collect samples representative of the rock volume most likely to be in contact with contaminated groundwater and to analyze them using an appropriate refereed analytical method Five potential methods for evaluating f were identified Of the five methods the Walkey-Black method was selected because it has minimal method interferences and a sufficiently low detection limit as well as a long history of use in agronomy and contamination studies The PRP Group is pleased with the quality of the data obtained from the bedrock samples as represented by their precision and reproducibility

The first part of this comment relates to the determination of fraction of organic carbon (f^) values The several subparts of the first paragraph are addressed individually in items 1 through 5 below The second part of the comment regarding the resultant distribution coefficient (Kd) values is addressed separately as item 6 below

1 There remains doubt that the values used in the flushing model accurately reflect the propensity for PCE to sorb to the bedrock

bull The rock core samples used for f (gocg) analysis were from core immediately adjacent to fractures These rock core samples included the fracture surfaces themselves and rock core extending back less than 1 cm from the fractures Therefore the foe data reported in the TI Evaluation represents the f of bedrock through which groundwater will travel and to which PCE will adsorb Based on the careful selection of sample locations and the

Response to EPA Comment 3 050205doc 1 of 11 Woodard amp Curran (211941)

number of samples collected we are confident that the measured f values are representative of the f at points of contact for PCE with the bedrock it is these f values that determine the propensity of PCE to sorb to the bedrock

bull The samples of rock core collected for analysis of f originated from 19 different locations varying in depth from 11 to 90 feet Therefore it is very unlikely that the rock core samples were contaminated with extraneous organic carbon from above ground

2 The foc values presented in Appendix B may be unrealistically high because the bedrock samples may have contained organic carbon that was unavailable for sorption

bull As noted in response 1 the f data reported in Appendix B represents organic carbon primarily associated with the surface of fractures in the bedrock through which groundwater is most likely to travel Therefore it is this organic carbon that the contaminants in the groundwater will come in contact with and adsorb to in the fractured rock at the site

bull The chemical oxidation agents used in the Walkey-Black method oxidize the easily oxidizable organic carbon in the medium and the foe is calculated from the quantity of the agent consumed Therefore it is unlikely that the analysis of the bedrock samples measured organic carbon that was unavailable for sorption

3 The reported foc values are only qualitative estimates of the organic carbon content of the bedrock samples

bull The reported f values are accurate quantitative results Schumachers review of Methods for the determination of total organic carbon (TOC) in soils and sediments (NCEA-C-1282 EMASC-001 April 2002) identifies the Walkley-Black method which was used to analyze the reported foc values as the reference method for comparison to other methods for analyzing total organic carbon

bull Schumacher also points out that if anything the WalkJey-Black method may underestimate the total organic carbon in a sample due to possible incomplete oxidation of organic carbon Usually the incomplete oxidation of total organic carbon in environmental samples is corrected for by multiplying the measured foe by 130 (Walkley amp Black 1934 Schulte 1995)

bull When the f data in the TI Evaluation Report (WampC 2005) Appendix B (attached) are analyzed statistically the standard deviation of the f for the 19 samples analyzed is 174 of the average f Given this standard deviation the 95 confidence interval for this data ranged from a low of 000123 gocg to a high of 000253 gocgm

The labs Method of Detection Limit (MDL) for the f measured using the Walkley-Black method is 00001 gocg Therefore the average (000188 gocg) the mean (000185 gocg) and geometric mean (000187 gocg) of the f values for the rock core at Hows Corner are all statistically significantly greater than the MDL of the Walkley-Black method

In addition to the aforementioned statistical analysis of the foe data triplicate samples (n = 3) from the same rock core (including one sample from the 19 rock core samples) were

Response to EPA Comment 3 050205doc 2 of Woodard amp Curran (211941)

analyzed for their f to determine the repeatability of the Walkley-Black method The average the mean and the geometric mean of the f values of these replicate samples was 000162 gocg 000150 gocg and 000159 gocgm respectively The standard deviation of these measurements was 000039 gocg

4 The Walkley and Black organic carbon measurement method is quick and simple but the results obtained cannot be considered quantitative because it requires a correction factor which often results in erroneous values it assumes the organic carbon has an average valence of zero oxidizable and reducible constituents such as chloride ferrous iron and manganese oxides interfere with the results and the errors introduced by interference are potentially greater when the organic carbon content is low at low foc values it is not clear that organic carbon is controlling PCE sorption (Schwarzenbach and Westall 1981 Mackay et al 1986 Fetter 1999)

bull Schumachers review (NCEA-C-1282 EMASC-001 April 2002) of the Walkley-Black method identifies several potential problems with this analytical method that could occur if the analytical lab is not familiar with the nuances of the chemistry associated with this method Interestingly Schumachers review neglected one of the more important analytical steps required to avoid errors in quantifying f in samples where there might beNAPL

It is absolutely critical to eliminate any NAPL from rock core samples prior to using the Walkley-Black method to measure foe in such samples This was done by the lab (PTS Laboratories) that measured the foe in the rock core samples from Hows Corner The lab used the Dean-Stark method (solvent extraction) to remove all hydrocarbons (including PCE and other NAPLs) from the sample (PTS Laboratories) This extraction method does not interfere with the subsequent analysis of the natural organic carbon associated with the rock core

Subsequently the samples were dried at 150degC to a constant weight (normally 16 hours) This latter step oxidizes all inorganic minerals including ferrous bearing minerals to ferric oxides and precludes their interference during the oxidation of the samples with chromic acid This procedure completely eliminates any positive bias in the reported foc

data that might have occurred due to the presence of ferrous ions and other reduced minerals

bull As noted in Response 3 the incomplete oxidation of total organic carbon results in an underestimate of the f and is corrected for by multiplying the f by a correction factor of 130 (Walkley amp Black 1934 Schulte 1995) The fx data reported in the TI Evaluation was corrected accordingly by using this correction factor

bull Excess chloride (Cl~) in percent weight quantities as found in saline soils may interfere with the quantitative titration of reduced chromium (Walkley 1947) However given that the primary rock type at the Hows Corner site is phyllite it is highly unlikely that there was sufficient chloride in the rock core samples for this to occur

bull Manganese oxides may also interfere with the analysis of f through competing with the dichromate ion for any oxidizable carbon (Walkley 1947) However in such cases the reported f would be an underestimate of the f present in the rock core Walkley (1947)

Response to EPA Comment 3 050205doc 3 of 11 Woodard amp Curran (211941)

4

reported that in the case where the ratio of MnO2 to carbon is 85 to 1 the error in the carbon determinations would only be 0 to 6 percent

It may also be useful to compare the analysis of total organic carbon in a geologic matrix that contains high levels of manganese using EPA method 9060 to the Walkley-Black method Table 1 summarizes data provided by one of the PRPs that compares the analysis of total organic carbon in a geologic matrix that contains approximately 02 wgt manganese (approximately 03 wgt manganese oxide)

Table 1 Comparison of total organic carbon measured using the EPA- 9060 method and the Walkley-Black method

Laboratory EPA-9060 Method Walkley-Black Method A Ave 00226 gocg Not analyzed

Stdev 000251 gocg n = 5

B Ave 002219 gocg Ave 002050 gocg Stdev = 000316 gocg Stdev =000971 gocg

n= 10 n = 10

The similarity in the total organic carbon concentrations measured by these two different methods provides further confidence that the Walkley-Black method is a viable method for analysis of total organic carbon in the presence of manganese equivalent to at least 10 by weight of the total organic carbon

5 The Walkley and Black organic carbon measurement at lowf^ values it is not clear that organic carbon is controlling PCE sorption (Schwarzenbach and Westall 1981 Mackay et al 1986 Fetter 1999)

bull Schwarzenbach and Westalls (1981) paper states that f values of less than 0001 gocg should not be used in combination with Kow (octanol-water partition coefficients) values to calculate K^ values (solid phase partition coefficients) values for a specific contaminant It should be noted that the TI Evaluation did not use the f data to calculate the KQC from the Kow Instead as requested by the EPA the measured KOC value for PCE was used to calculate the retardation factor for this contaminant

bull Schwarzenbach et al (2003) stated more recently that Even at very low f values (ie foe = 0001 kgoc - kg1 solid) sorption to the organic components of a natural sorbent may still be the dominant mechanism in defining the adsorption of organic compounds to geological matrices

bull In 1985 M Piwoni from the US EPA Robert S Kerr Environmental Research Laboratory published a paper (Banerjee et al 1985) that showed that for very hydrophobic molecules TOC content of the sorbent will control sorption down to levels of organic carbon that defy quantitation Contaminants such as the PCE found in the groundwater at Hows Corner are in this category of compounds

Given the aforementioned reasons the f values reported in the TI Evaluation are accurate within the noted statistical limitations and will have a predictable impact upon the retardation of PCE during groundwater transport

Response to EPA Comment 3 050205doc 4 of 11 Woodard amp Curran (211941)

6 In order to derive a Kd-based retardation factor that is reasonable given the reported foc

values and the rapid advance of the PCE plume described on pages 4-11 and 4-12 the flushing model requires a bulk density to porosity ratio that is roughly two orders of magnitude higher than the actual ratio for the Hows Comer bedrock (page 4-4) This apparent discrepancy needs to be addressed

The apparent discrepancy of bulk density to porosity ratios is most likely due to the fact that the Batch Flushing Model was originally developed for a porous medium and is not directly applicable to fractured bedrock As stated in Appendix C (page C-4) of the Draft Technical Impracticability Evaluation Report in order to use the Batch Flushing Model to describe the transport of contaminated groundwater in fractured bedrock where the matrix porosity is insignificant it is more appropriate to use a fracture surface area to void space ratio to calculate the retardation factor (R) than a bulk density to porosity ratio (Freeze amp Cherry 1979)

Since it is impractical to determine the actual surface area to which contaminants can adsorb the Batch Flushing Model was used with two simplifying assumptions bull The Kd was calculated from the f and the K^ bull The bulk density to porosity ratio term in the Batch Flushing Model was constrained to range

from 4 to 10 the typical range of such ratios in porous media (Freeze amp Cherry 1979)

If one uses site specific bedrock bulk density and porosity values the bulk density to porosity ratio is several orders of magnitude greater (specifically 273 gcc bullbull 000165 (dimensionless) = 1654 gcc) than the range of ratios of 4 to 10 used in the Batch Flushing Model in the Draft Technical Impracticability Evaluation Report Constraining the bulk density to porosity ratio within the range of ratios of 4 to 10 results in significantly lower R value than would be obtained using specific bedrock bulk density and porosity values

In summary in bedrock where fractures are the primary porosity the bulk density to porosity ratio can vary considerably and will be a function of the number of fractures and the fracture aperture The calculated bulk density to porosity ratio will be inversely proportional to the porosity This means that in fractured rock with limited fracturing and smaller porosity the calculated bulk density to porosity ratio is greater and will result in a greater calculated retardation factor than in bedrock with more extensive fracturing and greater porosity Consequently the calculated retardation factor will be greater for bedrock with less surface area available for sorption than bedrock with greater surface area for sorption This is contrary to what actually occurs

4 Response to EPA Comment 3 050205doc 5 of 11 Woodard amp Curran (211941)

m

REFERENCES

Banerjee P MD Piwoni K Ebeid (1985) Sorption of organic contaminants to a low carbon subsurface core Chemosphere _14 1057-1067

Freeze RA JA Cherry (1979) Groundwater Prentice Hall Englewood Cliffs NJ pg 604

PTS Laboratories wwwptsgeolabscompdf files3TOCnotepdf

Schulte EE (1995) Recommended soil organic matter tests in Recommended Soil Testing Procedures for the Northeastern United States Northeastern Regional Publication No 493 Chapter 8

Schwarzenbach RP J Westall (1981) Transport of nonpolar organic compounds from surface water to groundwater Laboratory sorption studies Environ Sci Tech 15 1360-1367

Schwarzenbach RP PM Gschwend DM Imboden (2003) Environmental Organic Chemistry Wiley-Interscience pg 292 408 amp 412

Walkley A LA Black (1934) An examination of the Degtjareff method for determining soil organic matter and a proposed modification of the chromic acid titration method Soil Science 37 29-38

Walkley A (1947) A critical examination of a rapid method for determining organic carbon in soils - effect of variations in digestion conditions and of inorganic soil constituents Soil Science 63251-264

Woodard amp Curran Inc (WampC) 2005 Draft Technical Impracticability Evaluation Hows Corner Superfund Site Plymouth Maine January 2005

Response to EPA Comment 3 050205doc 6 of Woodard amp Curran (211941)

LIST OF ATTACHMENTS (Response to Comment 3)

Appendix B to Draft Technical Impracticability Evaluation Measurement of foe at Hows Corner (4 pages)

m

Response to EPA Comment 3 050205doc 7 of 11 Woodard amp Curran (211941)

Appendix B Measurement of foe of Rock Core at Hows Corner

There are two general approaches to measure the fraction of organic carbon (foe) in rock cores

bull Measurement of weight loss by ignition of organic matter bull Chemical oxidization of organic carbon to carbon dioxide and either

subsequent quantification of the oxidant used for the reaction or quantification of the carbon dioxide produced during this oxidation process

The weight loss method is subject to errors caused by volatilization of substances other than organic materials such as water hydroxides and mineral carbonates Quantification of foe by the weight loss method is particularly sensitive to the presence of carbonates in rock cores There are however weight loss methods that are designed to differentiate between organic carbon and the aforementioned interfering materials but they require considerable care and are less accurate at low foe values Hence the weight loss method was not well suited for measuring the foe of the rock core from Hows Corner

The chemical oxidation of organic carbon is much better suited for quantifying organic carbon in rock cores such as those from Hows Corner This method uses a strong chemical oxidant to oxidize organic carbon to carbon dioxide and then measures either the chemical oxidant used to oxidize the organic carbon or the quantity of carbon dioxide produced In addition this general approach is not subject to interference by volatilization of other constituents of the rock core

There are at least two such chemical oxidation methods

bull The method of Baccini which was described by Schwarzenbach amp Westall (1981) first acidifies the sample to eliminate interference by carbonates Then a strong oxidant is used to chemically oxidize the organic carbon to carbon dioxide The resulting carbon dioxide is subsequently reduced to methane and quantified using a flame ionization detector Unfortunately this method has not been described in detail in a referred journal Hence it is would not have been appropriate to use to characterize the foe in the Hows Corner rock core

bull The more commonly used method to quantify foe in rock core is the Walkley-Black method (1934) This method is preferred for RBCA and DODDOE projects and by the oil industry

The Walkley-Black method uses an excess of chromic acid to oxidize (digest) organic matter to carbon dioxide The remaining chromic acid that was not consumed during the oxidation of the organic carbon is then quantified by titration with ferrous sulfate The difference in chromic acid prior to and after the oxidation of the organic carbon represents the total chromic acid used to oxidize

Hows Corner TI Evaluation Page 1 January 13 2005 Appendix B

the organic carbon in the sample The latter can be calculated using the chemical stoichiometry of the reaction

The Walkley-Black method is very accurate for samples that contain less than 2 organic carbon matter The minimum detection limit (MDL) for the Walkley-Black method is 100 mgkg or an foe of 0001

Given the rock core at Hows Corner was expected to contain less than 2 organic carbon the Walkley-Black method was used to measure the foe from 19 different rock core samples collected from varying depths ranging from 11 to 90 feet

Table 1 provides a statistical summary of the aforementioned data

Table 1 Statistical summary of foe data from rock cores collected at varying depths

Statistical Parameter Calculated Value foe Minimum Detection Limit (MDL) 00010 Number of samples analyzed (n) 19 Average foe 00019 Median foe 00019 Geometric Mean foe 00019 Standard deviation of foe measurements 000033 Relative standard deviation 174 -+ 95 Confidence intervals 00012 to 00025

The data in Table 1 shows the following

bull The foe from the Hows Corner rock cores are statistically greater than the MDL of the Walkley-Black analytical method

bull The average and median values for the foe of the Hows Corner rock cores from varying depths are nearly identical indicating that there is little variability in the foe values in the source zone at the site

bull The standard deviation of these measurements is 000033 which is 174 of the average foe

bull The 95 confidence intervals of the foe of the rock core at Hows Corner are 00012 to 00025

The foe was also analyzed from three separate samples taken from the same rock core at a depth of 55 feet (Only one of these samples was included in the data summarized in Table 1) Table 2 shows the statistical repeatability of this type of analysis

Hows Corner TI Evaluation Page 2 January 13 2005 Appendix B

Table 2 Repeatability of analysis of foe from one rock core at 55 feet in depth

Statistical Parameter Calculated Value Number of samples analyzed (n) 3 Average foe 00016 Median foe 00015 Geometric Mean foe 00016 Standard deviation of foe measurements 000039 Relative standard deviation 240 -+ 95 Confidence intervals 00008 to 00024

The data in Table 2 shows the following

bull The percent relative standard deviation of these three analyses of foe from the same rock core at Hows Corner is 24

bull The 95 confidence interval of the foes measured in this particular rock core at Hows Conrer is 00008 to 00024

These results show that there is good repeatability in using the Walkley-Black method for analysis of the foe in the rock core at Hows Corner

References Schwarzenbach amp Westall (1981) Transport of nonpolar organic compounds from surface water to groundwater Laboratory sorption studies Environ Sci Tech 15 1360-1367

Walkley A I A Black (1934) An examination of Degtjareff method for determining soil organic matter and a proposed modification of the chromic acid titration method Soil Sci 37 29-37

Hows Corner Tl Evaluation Page S January 13 2005 Appendix B

Woodard and Curran PTS Laboratories PTS File No 34618

ORGANIC CARBON DATA (METHODOLOGY WALKLEY-BLACK)

PROJECT NAME PROJECT NO

SAMPLE ID

203-chip-13 203-chip-23 203-chip-27 203-chip-38 203-chip-42 203-chip-47 203-chip-52 203-chip-58 203-chip-69 203-chip-82 207-chip-11 207-chip-19 207-chip-24 207-chip-29 207-chip-35 207-chip-45 207-chip-55 207-chip-87 207-chip-90

207-chip-55 55-MS

55-MSMSD

Hows Corner NA

DEPTH ft

13 23 27 38 42 47 52 58 69 82 11 19 24 29 35 45 55 87 90

55 NA NA

MATRIX

Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip

Average Median

Geometric Mean Standard Deviation Relative Std Dev

+- 95 Confidence Interval n

Rock Chip Rock Chip Rock Chip

Average Median

Geometric Mean Standard Deviation Relative Std Dev

+- 95 Confidence Interval n

FRACTION ORGANIC CARBON

(gg)

170E-03 185E-03 185E-03 170E-03 240E-03 190E-03 230E-03 180E-03 170E-03 115E-03 195E-03 220E-03 220E-03 235E-03 135E-03 190E-03 205E-03 175E-03 160E-03

188E-03 185E-03 185E-03 327E-04

1739 123E-03 to

19

205E-03 130E-03 150E-03

162E-03 150E-03 159E-03 388E-04

2402 840E-04 to

3

2532E-03

2393E-03

Hows Corner Tl Evaluation Appendix B January 13 2005

Response to EPA-DEP Comment 4 Dated March 31 2005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

EPA-DEP Comment 4

Comment 4 Distribution of contaminants First the TI report seems based on the assertion that there is DNAPL at the source area yet it also appears to represent that the source area is small and the bedrock below 85 is competent (or less fractured) and less impacted by the release of contaminants Some of the confusion may result from using most recent data when that data is from several different sampling events over several years and there is no discernible difference in concentrations between shallow and deep bedrock or as in Section 421 where generally decreased generally increase generally similar and similar concentrations in four consecutive sentences leads to a muddled picture of the contaminant distribution

Second the report asserts that the distribution of contaminants over the entire plume has not changed with time but fails to support this conclusion with data again relying on data that is from different sampling dates for one composite representation

Response The likely presence of dense non-aqueous phase liquid (DNAPL) at the Hows Corner Site and the determination that the source area is small are not mutually exclusive and both are conclusions drawn from information obtained during field investigations The presence of DNAPL in the source area is based on the elevated concentrations of volatile organic compounds (VOCs) detected in the groundwater (WampC 2001 WampC 2002) The conclusion that the source area is small is based on the area in which VOCs in groundwater have been detected at concentrations that are considered to be indicative of the presence of DNAPL nearby Similarly the conclusion that fracture frequency decreases at depths greater than approximately 50 to 85 feet below ground surface was based on field observation during the RI field work The fact that zones with observed fractures exhibited higher hydraulic conductivities than zones without fractures coupled with the decreasing frequency of observed fractures with depth led to the conclusion that the hydraulic conductivity of the bulk rock decreases with depth

The most recent data from all wells were used to provide the maximum VOC data set size During the RI all of the previously-existing and then newly-installed monitoring wells were sampled along with several residential wells The RI sampling included up to 48 monitoring wells Subsequent to the RI and prior to the TI three rounds of monitoring were conducted to verify that the plume was stable 15 monitoring wells were sampled during each of the three rounds During the TI field investigation 29 wells were sampled for VOCs The sampled wells included all of the newly-installed wells and a subset of wells installed during the RI for a total of 29 monitoring wells By using most recent data VOC results from 53 monitoring wells were included in the evaluation (see table labeled Sampling Events for listing of monitoring wells) This approach was selected because there generally was little variation in the data from a particular location between years This is borne out by the attached individual plots of VOCs detected in shallow bedrock and deep bedrock for the Pre-ROD (December 1999January 2000) and Supplemental (May 2000) sampling events and for June 2001 January 2002 and April 2003 sampling events The Pre-ROD and Supplemental plots are similar to the subsequent plots from the 2001 2002 and 2003 sampling events

In addition to maps showing the spatial distribution of VOC data at a given time trend plots of the data from a particular location through time (attached) indicate that since the RI concentrations generally have been stable or have decreased Together the maps and trend plots and the data from which they were developed indicate that the distribution of contaminants over the entire plume has not changed appreciably with time

Response to EPA Comment 4 050305doc 1 of 26 Woodard amp Curran (211941)

REFERENCES

Woodard amp Curran Inc (WampC) 2001 Final Remedial Investigation Report Hows Corner Superfund Plymouth Maine July 2001

Woodard amp Curran Inc (WampC) 2002 Final Feasibility Study Report - Non-Source Area Groundwater Hows Corner Superfund Site Plymouth Maine Hows Corner Superfund Plymouth Maine July 2002

Response to EPA Comment 4 050305doc 2 of 26 Woodard amp Curran (211941)

LIST OF ATTACHMENTS (Response to Comment 4)

Table - Sampling Events 1999 - 2004 (2 pages)

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater Pre-ROD Sampling Event

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater Pre-ROD Sampling Event

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater Supplemental Sampling Event

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater Supplemental Sampling Event

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater June 2001

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater June 2001

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater January 2002

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater January 2002

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater April 2003

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater April 2003

Figure - Concentration Trends - Non-Source Area Wells MW-1B and MW-3B

Figure - Concentration Trends - Non-Source Area Wells MW-13DB and MW-16DB

Figure - Concentration Trends - Non-Source Area Wells MW-16IB and MW- 108D

Figure - Concentration Trends - Non-Source Area Wells MW-108S and MW-112D

Figure - Concentration Trends - Non-Source Area Wells MW-112S and MW-114D

Figure - Concentration Trends - Non-Source Area Wells MW-114S and MW-115D

Figure - Concentration Trends -Source Area Wells MW-2DB and MW-2IB

Figure - Concentration Trends -Source Area Wells MW-102S and MW-103D

Figure - Concentration Trends -Source Area Wells MW-103S and MW-104D

Figure - Concentration Trends -Source Area Wells MW-104I and MW-106D

Figure - Concentration Trends -Source Area Wells MW-106S

Response to EPA Comment 4 050305doc 3 of 26 Woodard amp Curran (211941)

I I

El I

II I I 1 I

I

i

Event Baseline Case ID WC-01 WC-01

Well Date Aug-99 Oct-99 LOT10 1 LOT1-1 1 LOT11-4 LOT14 1 LOT15 1 LOT15-1 1 LOT16 1 LOT16-1 1 LOT17 1 LOT18 1 LOT19 1 LOT2 LOT20 1 LOT21-10 1 LOT21-11 1 LOT21-12 1 LOT21-13 1 LOT21-14 1 LOT21-2 1 LOT21-5 1 LOT21-7 LOT21 -8 1 LOT21-9 1 LOT23 1 LOT24 1 LOT28-1 1 LOT28-2 1 LOT28-3 1 LOT28-4 1 LOT28W 1 LOT30 1 LOT30-1 1 LOT30-2 1 LOT30-3 1 LOT30-4 1 LOT30-5 LOT31 LOT35 1 LOT41 1 LOT42-1 1 LOT43-1 1 LOT43-4 1 LOT6-1 1 LOT67 1 LOT6-7 1 LOT6-8A 1 LOT6-8B 1 LOT80-1 1 LOT82 1 MW-101D MW-1011 MW-101S MW-102D MW-102S MW-103D MW-103S MW-104D MW-1041 MW-104S MW-105D MW-106D

Groundwater Sampling Location Summary 1999 - 2004xls

Sampling Events 1999-2004

Hows Corner Superfund Site Plymouth Maine

Supplemental 2001 2002 2003 Pumping 2004 Pre-ROD Rl Sampling Sampling Sampling Test Sampling WC-03 WC-09 WC-25 WC-30 WC-42B WC-56 WC-58 Dec-99 May-00 Jun-01 Jan-02 Apr-03 Sep-04 Sep-04

1

1 1 1

1 1 1 1 1

1 1

1

1 1

1 1 1

1 1 1 1 1

1

1 1

1 1 1 1

1

1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

Sampling Events 1999-2004

Hows Corner Super-fund Site Plymouth Maine

Supplemental 2001 2002 2003 Pumping Event Baseline Pre-ROD Rl Sampling Sampling Sampling Test

Case ID WC-01 WC-01 WC-03 WC-09 WC-25 WC-30 WC-42B WC-56

ll

Well Date Aug-99 Oct-99 Dec-99 May-00 Jun-01 Jan-02 Apr-03 Sep-04 MW-106S 1 1 1 1 1 MW-107D 1 1 MW-108D 1 1 1 1 1 MW-108S 1 1 1 1 1 MW-110D 1 1 MW-111D 1 1 MW-112D 1 1 1 1 1 MW-112S 1 1 1 1 1 MW-113D 1 1 MW-114D 1 1 1 1 1 MW-114S 1 1 1 1 1 MW-115D 1 1 1 1 1 MW-12DB 1 1 1 MW-12SB 1 1 1 MW-13DB 1 1 1 1 1 1 MW-13SB 1 1 1 MW-14DB 1 1 MW-14SO 1 1 MW-15DB 1 1 1 MW-15SB 1 1 1 MW-16DB 1 1 1 1 1 1 MW-16IB 1 1 1 1 1 1 MW-16SO 1 1 MW-17DO 1 1 1 MW-17SO 1 1 1 MW-1B 1 1 1 1 1 1 MW-203D MW-203S MW-204D MW-204S MW-205 MW-206D

I MW-206S MW-2DB 1 1 MW-2DDB 1 1 MW-2IB 1 1 1 1 1 1 MW-3B 1 1 1 1 1 1

I MW-4O 1 1 1 MW-5B 1 1

II MW-6DB 1 1 1 MW-6SB 1 1 1 MW-8DB 1 1 1 MW-8SB 1 1 1

II PW-207 1 SEEP-1 1 SUBTOTAL - RESIDENTIAL 44 25 0 2 0 3 0 SUBTOTAL - MONITORING 22 48 41 15 15 15 1

Total 3 66 73 41 17 15 18 1

I Included in most recent data

I Notes 1 - Overburden well not included in most recent data for plotting

2 - Tetrahydrofuran and 2-Butanone were the only two compounds detected in this well and are thought to be the result of well repair not included in most recent data for plotting

3 - Not included in most recent data for plotting

2004 Sampling

WC-58 Sep-04

1

1 1

1 1

1 1 1

1

1 1

1 1 1 1 1 1 1 1 1

1 1

1

0 29

29

Groundwatef Sampling Location Summary 1999 - 2004xls

I

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

monitoring well Figure 4-14 total VOC contour (ugl) - December 1999January 2000 Distribution of Total VOCs in

Note SW-113 is located downstream of SEEP-1 Shallow Bedrock Groundwater total concentration of detected VOCs ND= not detected these two locations were sampled during the Pre-ROD Sampling Event

Baseline Sampling Event in OctoberNovember 1999 Hows Corner Superfund Site Surface Water Sampling Location A Plymouth Maine Seep Sampling Location laquo- WOODARD ampCURRAN

995037wipri reportepa ri interim final feb 2001cadd drawingsfinalfig 4-14

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

0 300 600 I

FEET

Q residential well Figure 4-16 monitoring well Distribution of Total VOCs in

Deep Bedrock Groundwater total VOCs contour (ugl) Pre-ROD Sampling Event

active residential wells with lot number Hows Corner Superfund Site 2deg42deg Plymouth Maine total concentration of detected VOCs ND= not detected WOODARD ampCURRAN Enyinaaring bull Science bull Operations bull

995037wipri reportepa ri interim final feb 2001cadd drawingsfinalfig4mdash16

PLYMOUTH POND

PLYMOUTH POND

1 628Tl7MW-2bB 12135

PLYMOUTH POND

monitoring well Figure 4-20

V total VOC contour (ugl) - June 2000 Distribution of Total VOCs in Shallow Bedrock Groundwater

| 34 | total concentration of detected VOCs ND= not detected NA = not analyzed Supplemental Sampling Event Note SW-113 is located downstream of SEEP-1 Hows Corner Superfund Site

Surface Water Sampling Location these two locations were sampled during the Plymouth Maine Baseline Sampling Event in OctoberNovember 1999 Seep Sampling Location WOODARD amp CURRAN

Engineering bull Science - Operations bull 995037wipri reportepa ri interim final feb 2001 cadd drawingsfinalfig 4-20

residential well Figure 4-22 Distribution of Total VOCs in

monitoring well Deep Bedrock Groundwater

total VOCs contour (ugl) Supplemental Sampling Event

Hows Corner Superfund Site

total concentration of detected VOCs ND= not detected NA = not analyzed Plymouth Maine

WOODARD amp CURRAN

995037wipri reportepa-ri interim final feb 2001cadd drawingsfinalfig 4-22 Engineering bull Science - Operations bull

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

FEET

Shallow Monitoring Well

Deep Monitoring Well

C Detected Concentration ND = Not Detected Figure 1-XS Distribution of Total VOCs in Shallow Bedrock Groundwater

Pumping Well

17-Acre Property Boundary Concentration Contour (ugl)

June 2001 Hows Corner Superfund Site

Plymouth Maine WOODARDampCURRAN

-i^rhvj bull Scbncn bull Operations bull 211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0601 dwg04-20-05

PLYMOUTH POND Hopkins Road V

O

PLYMOUTH POND

PLYMOUTH POND

o

0 300 600 mdashfa FEET

Shallow Monitoring Well bull bull - 17-Acre Property Boundary Figure 1-XD

Deep Monitoring Well 1 I Detected Concentration ND = Not Detected Distribution of Total VOCs in Deep Bedrock Groundwater

-mf- Pumping Well June 2001 Residential Well Hows Corner Superfund Site

Plymouth Maine i h Surface Water Sampling Point

g WOODARD ampCURRAN _ ^ _ ^ _ _ yen_ rj i|Hlaquorlny bull Science bull Opt

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0601 dwg04-20-05

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

Shallow Monitoring Well

Deep Monitoring Well

Detected Concentration ND = Not Detected Figure 1-YS Distribution of Total VOCs in Shallow Bedrock Groundwater

Pumping Well

17-Acre Property Boundary Concentration Contour (ugl)

January 2002 Hows Corner Superfund Site

Plymouth Maine WOODARD amp CURRAN Engineering Science- Operations bull

211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0102dwg04-20-05

PLYMOUTH POND

PLYMOUTH POND

Site Pand^ laquoum-laquoBTuitaraquo tLV

vVlf-(

PLYMOUTH POND

0 300 600 ^ = FEET

Shallow Monitoring Well mdashbullbullbull 17-Acre Property Boundary Figure 1-YD - A - Deep Monitoring Well FT Detected Concentration ND = Not Detected Distribution of Total VOCs in

Deep Bedrock Groundwater Pumping Well January 2002 Residential Well Hows Corner Superfund Site

Plymouth Maine Surface Water Sampling Point

WOODARD ampCURRAN Engineering Sciencs- Operations bulli Si

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0102dwg04-20-05

- m j

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND j A O-shy

Shallow Monitoring Well E Detected Concentration ND = Not Detected Figure 1-ZS Distribution of Total VOCs in

Deep Monitoring Well Shallow Bedrock Groundwater

Pumping Well Hows Corner

April 2003 Superfund Site

17-Acre Property Boundary Plymouth Maine Concentration Contour (ugl) r WOODARD ampCURRAN

Engineering bull Science bull Operations bull 211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0403dwg04-20-05

s S pound

PLYMOUTH POND

PLYMOUTH POND

- -

5 PLYMOUTH POND

Jo

FEET

ft Shallow Monitoring Well mdashbullbullmdash 17-Acre Property Boundary Figure 1-ZD Deep Monitoring Well I 1 I Detected Concentration ND = Not Detected Distribution of Total VOCs in

Deep Bedrock Groundwater Pumping Well April 2003

Q) Residential Well Hows Corner Superfund Site Plymouth Maine

(T) Surface Water Sampling Point WOODARD ampCURRAN poundKk EnginawtirKj bull Science - Operations bull

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0403dwg04-20-05

0 Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

B MW-1B

I 12000

PCE

B 10000 Total VOCs

I

i 2000

i 0 Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

c MW-3B

G 2000

1800

B PCE

1600 Total VOCs

1 I I E

il-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

G E

211941

El

I I z E

80

Concentration Trends shy Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-13DB

Total VOCs

c i i c o

Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

MW-16DB

30

c i c c I c o

Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99

PCE

Total VOCs

Jul-01 Jul-03

211941

O bi

c Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

I MW-16IB

i 35

3

c Total VOCs

lt- 2 5

0 | gt

o

1 sectI

c c 0 4

Jul-90 Jul-92 Jul-94 Jul-96 Jul-98 Jul-00 Jul-02 Jul-04

I I MW-108D

I 12

PCE 10

Total VOCs c oc 3

E E I 0

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

E 211941

c Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

fi MW-108S

I I 40

PCE 35

Total VOCs

30

I f 26

20 I o

I 15

10

c Dec-99 Dec-00 Dec-01 Dec-02 Dec-03 I 0

I MW-112D

c 35 - imdash

I A3 shyTotal VOCs

o c

E 1 2

I

ition

B 1 ^

-i c 3

0 Dec-99 Dec-OO Dec-01 Dec-02 Dec-03

211941

I

i

I

cII

Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-112S

08

PCE

Total VOCs 06

o 04

02

0 Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

MW-114D

o

12000

10000

8000

6000

PCE

Total VOCs

4000

2000

i

ccEIIc

i

i

E

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

211941

Con

cent

ratio

n (

ug

l)

E Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

I MW-114S

E A5000 -- Total VOCs

- 4000

0 3000

2000

i 1000

i n shy

Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

MW-115D

c PCE

Total VOCs

c E

o

C c

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03 I 0

211941

IepoundII

EIEIIGICCIccc

30000

25000

20000

o bullsect 15000 b

o 10000 U

5000

0 Aug-99

25000

20000

5000

0 Aug-99

211941

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-2DB

PCE

Total VOCs

Aug-01 Aug-03

MW-2IB

PCE

Total VOCs

Aug-01 Aug-03

IDIBI

ii EIDIISIBIG C

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-102S

6000

5000 PCE

Total VOCs

4000

O 3000

2000

1000

0 Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

MW-103D

16000

~ 14000 ugt 3- 12000 o

^ 10000

sect 8000

O 6000

4000

2000

PCE

Total VOCs

0Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

211941

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

G MW-103S

I I

ampo

12000

10000

E sectc

S

8000

6000

4000

2000

0Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

G I 6000

MW-104D

i 5000

PCE

Total VOCs

i i c

2000

1000

Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

E I

211941

cIccIG

IIBCccBcIc

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-1041

PCE Total VOCs

a 25000

0 20000

a 15000

10000

5000

0 Jan-OO Jan-01 Jan-02 Jan-03 Jan-04

MW-106D

3000

2500 PCE

Total VOCs

=sect 2000

o bullsect 1500

1000

500

0 Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

211941

c Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

c MW-106S

I PCE

Total VOCs

i

i Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

i

i i i E

C

211941 c

Response to EPA-DEP Comment 5 Dated March 312005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

iiw

EPA-DEP Comment 5

Comment 5 Matrix Diffusion The report as well as other proponents of matrix diffusion suggest that depletion of DNAPL (Section 5112 page 5-15) needs to be achieved While that might be the ideal the goal is to achieve performance standards and that goal may be attainable while there is residual contamination in the rock perhaps even DNAPL globules The low bedrock matrix porosity (page 1-15) the high permeability values (page 4-4) the relative flux of the groundwater (page 5-5) and the decrease in surface area and out of the mainstream pockets (appendix C-4) all suggest that the diffusion out of the rock matrix would be insubstantial relative to the regional flux of groundwater through the Site

Response The TI Evaluation Report does not explicitly consider or rely upon matrix diffusion as a basis for requesting a TI Waiver for a portion of the Hows Corner Site The technical literature provides documentation that matrix diffusion can be a significant process that affects chemical transport and groundwater remediation timeframes in unconsolidated and consolidated media including fractured rock (US EPA 1989 Freeze and Cherry 1979 Pankow and Cherry 1996 Fountain 1998) Back diffusion of contaminants from the matrix porosity of the fractured rock can prolong the time necessary to achieve groundwater cleanup goals particularly for compounds such as PCE for which the cleanup goal is a low concentration It is our expectation that matrix diffusion has occurred at the Hows Corner Site and that back diffusion of PCE from the rock matrix will also occur Although the extent to which matrix diffusion is occurring at the Hows Comer Site has not been determined and that lack of knowledge contributes to uncertainty regarding the cleanup times at the Site the effect of matrix diffusion is to lengthen rather than shorten the time required for remediation

REFERENCES

Fountain JC 1998 Technologies for Dense Nonaqueous Phase Liquid Source Zone Remediation Ground-Water Remediation Technologies Analysis Center Technology Evaluation Report TE-98-02 December

Freeze RA and Cherry JA 1979 Groundwater Prentice-Hall Inc Englewood Cliffs NJ 07632 p 410-412

Pankow J F and Cherry J A 1996 Dense Chlorinated Solvents Waterloo Press Portland OR 97291-1399 p 67-88

US EPA 1989 Transport and Fate of Contaminants in the Subsurface EPA6254-89019 p 17-18

Response to EPA Comment 5 050305doc 1 of 1 Woodard amp Curran (211941)

WOODARD amp CURRAN Maine Massachusetts New Hampshire Connecticut Florida Operational offices across the US 1-800-426-4262 www woodardcurran com

Page 9: SDMS DocID 251749 - Records Collections · 2020-06-13 · CORPORATE OFFICES: Maine, Massachusetts, New Hampshire, Connecticut New, York, Florida Engineering • Science • Operations

Woodard amp Cunran used the values estimated from the pumping test analysis as an initial data set for transient benchmarking by running a 3-day simulated pumping test Calibration of the model was accomplished by comparing measured drawdowns obtained during the pumping test to calculated drawdowns from the flow model The hydraulic parameter values in the model were varied from the initial values but within the range calculated from the pumping test analysis The additional model calibration was considered to be completed when the calculated drawdowns were sufficiently close to measured drawdowns The resulting values of the hydraulic parameters of the calibrated model were then considered acceptable to provide satisfactory prediction of the response of the flow system to other hydraulic stresses

Regional water-level data were reviewed prior to data analysis A plot of water levels in the closest USGS regional background well (provided in the TI Data Package and attached) indicates that throughout the period of the test and subsequent recovery water levels were declining on a regional scale Although the decline in water levels is gradual the change in slope observed on the Cooper-Jacob plots is thought to represent the point at which the drawdown at a given location caused by pumping becomes less significant compared to the regional drawdown This occurs at about a day after start of pumping The effect of the regional decline in water levels can also be seen in the initial rapid rise in water levels in response to pump shut off followed by a decline in water levels after about a day after the pump is shut off

Additional information obtained during the TI field work was reviewed and evaluated in updating the conceptual model for the site In general the additional information corroborated the understanding of the Site presented in the RI report In particular the northeast-southwest fracture orientation was confirmed as the predominant orientation Geophysical logging during the TI investigation however showed the dip direction of fractures to be more variable and the dip angles to be shallower than was understood based on the RI data (see enclosed figure Packer Testing Results in Vicinity of Source Area) The additional borings installed within the fenced area and to the east of the fenced area showed that the area in which concentrations of total VOCs in groundwater exceeded 10000 pgL was more limited than portrayed in the RI and FS reports Packer testing of the intervals identified by geophysical logging as likely or possibly transmissive (see enclosed borehole geophysical logs) showed VOC concentrations within the packered intervals at a given borehole to be either essentially constant (eg MW-203 MW-204 MW-205) or increasing with depth (eg PW-207) Information on hydraulic conductivity and VOC concentrations in packered intervals is summarized on two separate tables for the 1999 RI wells and 2004 TI wells (Packer Permeability and Packer Sampling Results for Potential Fracture Intervals - enclosed) The orientation hydraulic conductivity and VOC concentrations of features identified as likely or possibly transmissive is summarized in a separate table (Orientation Permeability and Groundwater Sampling Results for Transmissive Features shyenclosed)

Table 4-1 of the TI Evaluation report summarizes the variation of input parameters to the flow and batch-flushing models as the project progressed from RI to FS to TI As described above for calculations in the TI Evaluation report hydraulic conductivity values were adjusted during the model calibration to pumping test drawdown data Measured fraction of organic carbon values and VOC concentrations were used in the Batch-Flushing model along with recharge calculated from the ModFlow model For calculation of pore flush volumes using the Batch-Flushing model the ratio of density to porosity was constrained to a range of 4 to 10 which is the typical range of such ratios in porous media (Freeze amp Cherry 1979) The basis for this change was stated in Appendix C of the TI Waiver Evaluation Report and is described in the response to Comment 3

Response to EPA Comment 2 050205doc 3 of 24 Woodard amp Curran (211941)

REFERENCE

Freeze RA and Cherry JA 1979 Groundwater Prentice-Hall Inc Englewood Cliffs NJ 07632 p 410-412

Response to EPA Comment 2 050205doc 4 of 24 Woodard amp Curran (211941)

LIST OF ATTACHMENTS (Response to Comment 2)

Figure - Drawdown at 72 Hours Shallow Wells

Figure - Drawdown at 72 Hours Deep Wells

Figure - Drawdown at 72 Hours

Figure - Potentiometric Surface at 72 Hours Shallow Wells

Figure - Potentiometric Surface at 72 Hours Deep Wells

Figure - End of Pumping Test Bedrock Potentiometric Surface at 72 Hours

Table - Pumping Test Analytical Results

Figure - USGS Background Groundwater Level

Figure - Packer Testing Results in Vicinity of Source Area

Figure - Borehole Geophysical Log MW-203

Figure - Borehole Geophysical Log MW-204

Figure - Borehole Geophysical Log MW-205

Figure - Borehole Geophysical Log MW-206

Figure - Borehole Geophysical Log PW-207

Table - Packer Permeability and Packer Sampling Results for Potential Fracture Intervals 1999 Drilling Program (2 pages)

Table - Packer Permeability and Packer Sampling Results for Potential Fracture Intervals 2004 Drilling Program

Table - Orientation Permeability and Groundwater Sampling Results for Transmissive Features 2004 Drilling Program (2 pages)

Response to EPA Comment 2 050205doc 5 of 24 Woodard amp Curran (211941)

(MEDEP Pond 1) Farm Pond

0 150 300

FEET

Monitoring Well

Figure X Pumping Well Drawdown at 72 Hours

_ - 17-Acre Property Boundary Shallow Wells Hows Corner Superfund Site Drawdown Contour (ft) Plymouth Maine

151 | Drawdown (ft) WOODARD ampCURRAN

^Stk Engineering bull Science bull Operations bull 211941 Hows CornlaquorwipDrawingsTI EVALDrawdown-72hrs_shallowdwg04-19-05

MW-3B

413951 W-6DB JMW-6SB

(MEDEP Pond 1) Farm Pond

Monitoring Well

Pumping Well

17-Acre Property Boundary

Groundwater Elevation Contour (ft)

211941 Hows CornerwipDrowngsTI EVALpo-tent-aU-72-hrsdwg

Figure X End of Pumping Test

Bedrock Potentiometric Surface at 72 Hours Hows Corner Superfund Site

Plymouth Maine ^ WOODARD amp CURRAN

Englnesring bull Science bull Ope

(MEDEP Pond 1) Farm Pond

Monitoring Well

Pumping Well Drawdown atFigure X

72 Hours _bullbull_ 17-Acre Property Boundary Deep Wells

Drawdown Contour (ft) Hows Corner Superfund Site

Plymouth Maine 151 | Drawdown (ft)

= WOODARD ampCURRAN 211941 Hows CornerwipDrawingsTI EVALDrawdown-72hrs_deepdwg04-19-05

Engineering bull Science bull Operations

(MEDEP Pond 1) Farm Pond

028 MW-12DB

MW-125B 040

l - _ ^ I 016 I N

050 MW-15SB

MW-15DB 048

A J s

- A - Monitoring Well

-$poundbull Pumping Well

_bullmdash 17-Acre Property Boundary

^ Drawdown Contour (ft)

151 I Drawdown (ft)

211941 Hows CornerwgtpDrawinQsT EVAI_Drawdown-72brsdwg04mdash19-05

Figure X Drawdown at 72 Hours

Hows Corner Superfund Site Plymouth Maine

^ WOODARD ampCURRAN Engineering bull Science bull Operations i

(MEDEP Pond 1) Farm Pond

Monitoring Well

Pumping Well

_bullbull_ 17-Acre Property Boundary

f Groundwater Elevation Contour (ft)

|419Q0| Groundwater Elevation

211941 Hows CornerwipDrawinqsTI EVALPotSurf-72hrs_shallowdwg04-19-05

150 300

FEET

Figure X Potentiometric Surface at 72 Hours

Shallow Wells Hows Corner Superfund Site

Plymouth Maine

WOODARD ampCURRAN Engineering bull Science bull Operations

29212 MW-108D

(MEDEP Pond 1) Farm Pond

Monitoring Well

Pumping Well

mdashbullbulllaquo 1 7-Acre Property Boundary

bull Groundwater Elevation Contour (ft)

1419001 Groundwater Elevation

211941 Hows CornerwipDrawingsTI EVALPotSurf-72hrs_deepdwg04-19-05

150 300 =5fc= FEET

Figure X Potentiometric Surface at 72 Hours

Deep Wells Hows Corner Superfund Site

Plymouth Maine

WOODARDampCURRAN Engineering bull Science bull Operations bull

--

Pumping Test Analytical Results Hows Corner Superfund Site

Plymouth Maine

Well ID oper Jaccb Analyses 2 Theis Analyses Fissure

Well Id Rd (ft)

Saturated Thickness

Transmissivity

(ft2day) K

(ft2day) K

(cmsec) Storage

Coefficient Transmissivity

(ft2day) K

(ft2day)

K (cmsec)

Storage Coefficient

System K

(ftday) PW-207OB 8 85 481 057 200E-04 392E-02 36 042 150E-04 809E-04 027 MW-103S 50 85 451 053 187E-04 720E-03 92 108 382E-04 283E-04 083 MW-103D 54 185 455 025 868E-05 210E-02 65 035 123E-04 237E-04 044 MW-2IB 59 85 352 041 146E-04 699E-03 104 123 433E-04 512E-04 052 MW-2DB 63 85 334 039 139E-04 845E-03 148 080 283E-04 239E-04 046 MW-104D 95 185 489 02 6 932E-05 654E-03 98 053 186E-04 547E-05 037 MW-104I 97 85 33 03 9 137E-04 362E-03 117 137 484E-04 962E-05 048 MW-101I 107 85 364 043 151E-04 490E-03 511 601 212E-03 223E-04 136 MW-102D 134 185 435 024 829E-05 248E-03 108 058 206E-04 850E-05 065 MW-101D 138 185 492 027 938E-05 511E-03 671 362 128E-03 700E-04 172 MW-205 219 85 57 067 237E-04 255E-03 447 526 186E-03 359E-03 -shyMW-204D 221 185 367 020 700E-05 170E-03 790 427 151E-O3 155E-04 147 MW-204S 225 85 379 045 157E-04 156E-03 1031 1213 428E-03 313E-04 199 MW-1B 228 85 325 038 135E-04 977E-04 340 400 141E-03 739E-05 054 MW-203S 273 85 489 058 203E-04 117E-03 1255 14 76 521 E-03 216E-04 210 MW-106D 278 185 51 028 972E-05 141E-03 1065 576 203E-03 360E-04 104 MW-203D 278 185 478 026 911E-05 152E-O3 765 414 146E-03 364E-04 138 MW-105D 364 185 44 024 839E-05 830E-04 769 415 147E-03 200E-04 127

1 Analyses conducted using Cooper and Jakob method on late drawdown data collected during constant

discharge pumping test conducted at the Hows Comer Site from September 20 - 30 2004

2 Analyses conducted using Theis solution for unconfmed approximation (1935)

J Analyses conducted using Moench method for dual porosity estimation (1984)

Fissure System Storage

Coefficient 402E-04 117E-06 264E-04 300E-04 932E-05 235E-07 502E-05 326E-06 801E-05 542E-04

-

803E-05 762E-05 134E-05 498E-05 115E-04

47E-04 838E-05

3 ysesh Analysis

Block System K (ft2day)

251E-02 207E-03 564E-04 163E-04 585E-04 465E-02 153E-04 498E-03 855E-04 356E-03

-

292E-03 394E-03 720E-04 526E-03 160E-01 35OE-O1 287E-03

Block System Storage

Coefficient

402E-02 164E-04 183E-02 330E-03 158E-03 847E-03 286E-03 326E-04 803E-05 272E-03

723E-04 686E-04 148E-04 349E-04 115E-03 47E-04 838E-04

Theis - Moench - CJ - AnalyticalResults_4-19-O5xls

DRAFT

242

24

238

236

bulla

c

i

a Q

234

232

228

226

Hows Corner Constant Discharge Testing USGS Background Groundwater Level USGS 445319068560101 ME-PEW456 Kenduskeag Maine

End of Monitored Recovery Period 09302004

Regional Background Location i 226 miles from Pumping Locatio

lt

697

NOTES

1 Groundwater samples collected in 1999 were screened for five volatile organic compounds (VOCs) only N

tetrachloroethene (PCE) exceeded reporting limits MW-2030 082304 082304 082304 082304 u

2 Strike and Dip of likely or possible transmissive 30 45 55 85 feature within the packer interval from which the indicated sample was collected

MW-204D

PCE TOTAL VOCs

081904 30

220 2636

A

081904 46-50 540 6436by

081904 IT

260 3073

x

MW-105D

PCE TOTAL VOCs

111199 50-60 2100 2100

MW-106D

PCE TOTAL VOCs

111199 76-86

400 400

111199 137-147

1400 1400

111299 1355-1455

350 350

PCE TOTAL VOCs

44 84

64

MW-6SB

bulli

lt

gt-

170 234

35

I I i

140 192

^^52

^^52

130 183

52 - lt

S A 34

PW-207 082404 082404 082404 20 37

PCE 1300 TOTAL VOCs

17-Acre George West Property Boundary

MW-113D

PCE TOTAL VOCs

112299 46-56

350 350

112299 70-80 190 190

150

112299 105-115

129 129

112399 138-148

230 230

L e g e n d ( J New Monitoring Well-Summer

Site Property Boundary ^ P u m p i n g Well-Summer 2004

-xmdashxshy Source Area

bull0shy Monitoring Well shy Pre 2004 Angled Boring-Summer 2004

211941laquoipdwgTI-ELV21ig41paltker-data2

2004 PCE of Total

bull lt70 VOCs

M W - 1 14D ^ ^

Figure xx Packer Testing Results in

Vicinity of Source Area Hows Corner Superfund Site

Plymouth Maine ^ WOODARD ampCURRAN

^^^^^^^^^^m ampKm Engineering - Science bull Operations

c Northeast Geophysical Services Borehole Geophysical Log

MW-203 Date logged 081704 Plymouth Maine

I Flowmeter Measurements Tomporaturo(C) Acoustic Televiewer

7 5 8 8 5 9 95 Caliper (Inches) Resistance (Ohms) Spontaneous Potential (mVj Dip In Degrees PCE Total VOCs

3 0 2 0 8 0 laquodeg 4S 1000 1400 1800 2200 MO HO 1000 1200 MOO 0 laquo deg ugL ugL n 1 1 1 1 1 1 1 1 1 i 1 1 1 1 n 1 1 1 1 1 1 1 1 1 1 1 n I l l l l l l l n

Ambient Flowneter pumping Rowmeter 11 gpm 6

H

bull

magnetic 10 bull 10 bull - 10 - north - 1 0I

-

_

bullbullbull - bull

20 bull bull20 bull ^ ltr~mdash 01

I

4 ^

LOS7

^

44 84 I I

Xr - 2

lt ^ bull30 -_ _^O1J- 1 _ 050 30 - 3 0

0r - - 3

C -j [ bull bull bull | shy

-O8 H ~ 1 045 7

1 4040 - 40 - -40 r - 14gt 13

V1s -- -023 f 1022 1V 170 234 I

T lt bull B gtf 50^ J50 - - 5 0 - - 5 0

I eet be

lo

i 1

1 1

1

140 192 - - - -t shy

-mdashj bullpound 60 - $o - - 60 - -60

H i I c

bull024

ampbull

3 - T lt ftft rgt He

70 bull j 70 - - 70 - 7 0 -

in -j bullbull shy

-021 1 T 022

- Ton _ Ov

26

130 183 NF NF

90 -_ 90 - 7 90 - -90

-

ifi Jf

3J

^gt _ N F NF bull bull shy

| H100 - j 100 bullbull 100 - -100

1 1 1 1 1 1 1 ) | 1 f I 1 1 1 ) 0 20 40 60 80

flft mdash ftn - mdash rVt

30 4 g 0 20 40 60 Dip in Degrees bullbull

Likely or poss bleFluid Resistivity (ohmmeters) The dip direction-- indicated

^ t h e l i n e extending from t h

I Iransmissive zone circle The strike of the feature is 90 degrees from this

The acoustic televiewer graph displays the mostprominent features selectedffom the acoustic televiewer

R n r a h n l c D O t t n O I B

f i o n n h w c i r a l U K U p i i y SI Ud l

1 rn l_Og Packered Interval August 2004

E tog The location dip angle and dip direction of the sleeted M W - 2 0 3 Groundwater samples were collected by Woodard S Curran on H23120M features are approximate Refer to the televiewer og of His _ well for more precise detail Plymouth Maine Date logged 081704

I

1

Northeast Geophysical Services Borehole Geophysical Log MW-204 D a t e l o gge d 072604

Plymouth Maine

n 3

Flowrneter Measurements(in gpm)

Caliper (Inches)0 3 5 4 0

1 1 1 1 1 1 1 t 1 1 1 1 1 1Ambient Rowmeler pumping Flowmetsr 05gpm

Templaquorature (C) bull bull bull bull i

7 75 8 8S 9 Resistance (Ohms) Spontaneous Potential (mV)

4000 SOW 600 4M 0

Acoustic Televiewer (interpreted)

Dip in Degrees 0 20 4060 SO

at N

PCEugL

Total VOCs ugL

- -_ a

10-

shy 10 bull - 10 shymagnetic

north - 10

o o

bull 1

11

11

1 1

1 1

11 1

1 1

1 1

1 1

1 1

1 1

1 1

1 1

1 1 E 1

- L

3 7 2 0 2 0r bull 20 bull - shy

i S_ N F

bull30 bull 7 3 0 220 2636shy1^ J J 004

fI f V ^

40 shy 4 0 4 0 shy - 4 0rbull019 [_ 007 w8 - - shy5 c

bull

gt

Ia50i 540 6436

bull50 - - 50 - - 5 0

-QQ7 - bull - -t T

pound V gtk

B 6 0 - e o - 7 6 0 -60shyQ 1 1

Q -007 -004 bull1 mdash T - J ~

bull

- - shyT 70 -J c [TO- - 70 - 7 0-

V Y 1- -004 -003

mdash T -h - y - j i - - mdash 260 3073 - gt=7

80 -j NF bull80 - - 80 - - 8 0Jgt

bull i

i 1

i i

C- bull shy

90 shy

K

Jlt i90 90 shy - 9 0shy -

l

ii

I I I I

NF bull M J

I ^ ^ - ^ bull 1

mdash mdash - _

s -7 ^100shy

till

1 100 100- H - 1 0 0shy -1 x Likety or possible k ^ Iransmissive zonebull

1 i i i ii i i i | l l l l | l i l l 0 20 40 ED 80

1 -

3 0SOFluid Resistivity (ohmmeters)

Dip in Degrees The djp ^ ^ o n is indicated ty Ihe line extending from tha circle The strike of Ihe feature

19- 3U UIHJIW93 IolII l l l lraquo

bull

The acousfc televiewer graph displays the mostprominent features selected from the acoustic televiewer109 The location dip angle and dip direction of Ihe sleetedfeatures are approximate Refer to the televiewer log of thiswentormore precise detail

B o r e h o l e G e O D h V S I C a l LOO B W H U I B w c w p n y o i v a i w v yM W - 2 0 4

P l y m O U t n MaiDB

Packorod Interval August 2004Groundwater san-ples wampramp collected by Woodard a Curran on OMO23C4

Date logged 072604

C

I

E Northeast Geophysical Services Borehole Geophysical Log Date logged 072704

I MW-205

Plymouth Maine

Flowmeter Measurements Temperature (C) Acoustic Televiewer (In gpm) I ~l (Interpreted)

I 85 10 Caliper (inches) 95

Dip in D g r laquo Resistance (Ohms) Spo ontaneous Potential (mV PCE Total VOCs 3 0 16 4 0 4 5 ) 20 40 60 80 10 00 2000 30 00 4VJ 400 -3 laquo

i i i i 1 i i I i 11 4 0 D 1 I I ugL ugL

C h

iii Ambient Flowmetar pumping

Flowmeter 1 25 gprn

I bull$bull

i

I rmdash magnetic 1 north ^^^^ 1 VI f

10 ~ I C x 10 bull - 10 bullbull

4 5 6mdashmdash f 1000B 11448 noisy nodi a raquo ^

mdash 5rt mdashi mdash Oft pound) 1100B 12509

cjmdash1 007

-

i i i 1

en

8 B a B

30 mdash

-

40 shy

-mdash I -

50 -_

__NF lt005

- 30 - - 3 0 it 34V

MO P26 V S) 1300B 13776 _ N F NF

26

40 bull - 40 bull 7-40 gt J Vf1 cX

) -j -

_ N F NF 50 c bull - 50 ^ 7-50

i I

I

c

B pound 60 - 6 0 7 60 - 7-60 a i 1

_ N F NF i Si f f 70 -_ bull70 bull - 70 shyC I 9

-m bull - shyA

_ N F NF 80 80 -j bull80 bull - 80 - C- 33 34

bull

5-i r

i 1

J r

Ck

_ N F NF 9 0 90 - - 90 shy

i bullCshy

J rK bull

100 -j ^ Likely or possible bull100- - 100- I -100

transmissive zone bull - ^ bull shy] |

1 1 1 1 1 1 1 I 1 i i i 1 i i 1 1 0 20 40 SO SO 10 20 30 40 50 Dip in Degrees 30 4 0 Fluid Resistivity (ohmmeters) Thlaquo dip direction is indicated

by the line extern r g from the circle The strike of he feature is 90 degrees from ihis

The acoustic televiewer graph displays the most

I Borehole Geophysical Log Packered Interval August2004 prominent features selected from the acoustic televiewer

Groundwatcr samples were oollccled by Woodard amp Cufran orgt S172004 log The location dip angle and dip direction of ins slsctsd MW-205 features are approximate Refelt to the televiewer log of this wall for more precise detail Plymouth Maine Date logged 072704

I

C

I Northeast Geophysical Services Borehole Geophysical Log Date logged 072704

I MW-206

Plymouth Maine

Flowmetor Measurements Temperature (C) Acoustic Televiewer | I r T i i i i i i i i i i i i i i r I |(in gpm) (Interpreted)

I 75 8 flS 9 95

Caliper (inches) Resistance (Ohms) Spontaneous Potential (mV) Dip In Degress PCE Total VOCs 30 35 40 4 5 0 20 40 M 90 4500 5500 6500 ugL ugL I i i

I I

- 1 0

I - 2 0

I 2900B 32401

i i L

E 0

i 6300B 68901

i I 0 20 40 SO 80

20 30 40 50 Dip in Dlaquogralaquos

amp 4 a Fluid Resistivity (ohrnmeters) The dip dirertion is indicated Likely or possible by iho line extending from the transmissive zone circle The striKe of the feature

is 90 degrees from tNs

Borehole Geophysical Log Packered Interval August 2004

E amples were collected by Woodard amp Cunan oo SM82004 log Thraquo location 4p angle and dip direction of the sloeled MW-206 feature are approximate Refer to the televiewer 109 of this well for more precise detail Plymouth Maine Date logged 072704

C

I Northeast Geophysical Services Borehole Geophysical Log

Date logged 082304 PW-207

I Plymouth Maine

Fiowmeter Measurements Temperature (C) Acoustic Televiewer

I (in gpm) (interpreted)

75 8 85 9 95 Caliper (inches) Resistance f0tims) Spontaneous Potential (mV) Dip in Degrees PCE Total VOCs

55 60 0 20 40 SO 80 ugL ugL I I I I I I I

Ambienl Fiowmeter pumping Flewmater

magnetic - 10 - - 1 0

north

i - 20 - - 2 0

1300 1410

i - 30 - - 3 0

i tf

5400 5802 - 40 - - 4 0

B - 50 - - 5 0

I 18000 19234

- 60 - - 6 0

I 12000 13085

- 70 - - 7 0

- 8 0

i - 9 0 19000 20354

G - 100- -100

I 110 110 bull110

0 20 40 60 SO 10 20 30 Dip m Degrees

Fluid Resistivity (ohmmeters) I 50

The dip direction is indicated by ihe line extending from the circle The strike of the fealure is 90 degrees from this

Borehole Geophysical Log

G Packorod Interval August 20(M log The location dip angle and dip dirlaquocton or the sleeted Groundaier samplss were ooliecled by Woodard i Curran on ampt24f2ltXM PW-207 failures are approximate Reter to the televiewer log of this wlaquoll for more precise detail PlyPIOUth Maine Date logged 082304

I

Table XX Packer Permeability and Packer Sampling Results for Potential Fracture Intervals

1

WellID MW-101D MW-101D MW-101D MW-101D MW-101D MW-101D MW-101D MW-101D MW-101D MW-101D MW-I01D MW-101D MW-101D MW-102D MW-102D MW-I02D MW-102D MW102D MW-102D MW-102D MW-102D MW-102D MW-I02D MW-102D MW-102D MW-102D MW-103D MW-103D MW-103D MW-103D MW-I03D MW-103D MW-103D MW-103D MW-103D MW-103D MW-103D MW-103D MW-I03D MW-104D MW-104D MW-104D MW-104D MW-I04D MW-104D MW-104D MW-104D MW-104D MW-104D MW-104D MW-105D MW-105D MW106D MW-106D MW-106D MW-107D MW-107D

1999 Drilling Program

Hows Corner Superfund Site Plymouth Maine

Potential Fracture Top Of Bottom 6 Depth to lt Topof i Interval from Packer Packer Middle of Elevation Hydraulic bull PCE

GS ELEV 1 Rock Drilling Interval Interval Interval of Interval Conductivity Concentration (ft msl) (ft msl) TEST (ftbgs) (ftbgs) r(ftbgs) ( f t b (ft mil) (cmsec) (raquogL)

4339 4329 13 28-29 33-3537-39 271 376 324 4016 OOOE+00 4339 12 37-3444-46 380 485 433 3907 157E-04 4339 11 488 593 541 3799 132E-04 4339 10 60-61 578 683 631 3709 OOOE+00 4339 9 678 783 731 3609 I79E-05 4339 8 778 883 831 3509 106E-05 4339 7 880 985 933 3407 243E-05 4339 6 990 1095 1043 3297 339E-06 4339 5 1090 1195 1143 3197 OOOE+00 4339 4 1190 1295 1243 3097 OOOE+00 4339 3 1365-1375 1290 1395 1343 2997 OOOE+00 4339 2 147-157 1390 1495 1443 2897 580E-05 4339 1 147-157 1470 1575 1523 2817 741E-05 43161 43061 13 166 271 219 4098 333E-04 43161 12 30-3136-40 260 365 313 4004 I54E-05 43161 11 36-4041-43 362 467 415 3902 548E-05 43161 10 470 575 523 3794 598E-05 43161 9 570 675 623 3694 197FOS 43161 8 670 775 723 3594 OOOE+00 43161 7 770 875 823 3494 891 E-05 43161 6 83-94 870 975 923 3394 139E-05 43161 5 970 1075 1023 3294 123E-04 43161 4 1070 1175 1123 3194 526E-06 43161 3 1170 1275 1223 3094 138E-05 43161 2 1270 1375 1323 2994 671E-06 43161 1 1370 1475 1423 2894 OOOE+00 42997 42497 13 18-19 170 275 223 4077 OOOE+00 42997 12 260 365 313 3987 766E-05 42997 11 360 465 413 3887 727E-05 42997 10 460 565 513 3787 192E-05 42997 9 560 665 613 3687 752E-05 42997 8 660 765 713 3587 778E-05 42997 7 85-86 763 868 816 3484 260E-05 42997 6 860 965 913 3387 289E-05 42997 5 102-103 960 1065 1013 3287 102E-04 42997 4 1060 1165 1113 3187 522E-06 42997 3 1160 1265 1213 3087 520E-06 42997 2 129-130 1260 1365 1313 2987 960E-04 42997 1 1360 1465 1413 2887 OOOE+00 43372 42922 11 35-37 42-45 350 455 403 3935 684E-04 43372 10 460 565 513 3825 500E-05 43372 9 560 665 613 3725 106E-05 43372 8 72-74 660 765 713 3625 204E-05 43372 7 760 865 813 3525 872E-06 43372 6 860 965 913 3425 467E-06 43372 5 960 1065 1013 3325 200E-05 43372 4 1060 1165 1113 3225 354E-05 43372 3 125-130 1160 1265 1213 3125 157E-05 43372 2 125-130 1260 1365 1313 3025 337E-04 43372 1 1365 1465 1415 2922 689E-06 43052 43002 2 54-58 490 595 543 3763 124E-05 2100 43052 1 139-140 145-146 1367 1472 1420 2886 154E-04 1400 43291 4391 3 bullI133 260 365 313 4017 439F06 43291 2 77-78 760 865 813 3517 230E-03 400 43291 1 143-144 1355 1460 1408 2922 971E-06 350

29958 27258 4 450 555 503 2493 OOOE+00 (21)A 29958 3 103-105 1000 1105 1053 1943 752E-04 (063)A

Table XX Packer Permeability and Packer Sampling Results for Potential Fracture Intervals

1999 Drilling Program

Hows Corner Supcrfund Site Plymouth Maine

gtbull i Potential Fracture Top _OfBot Bottom of Depth to ltbull Top of Interval from f Packer Packer Middle Of

GS ELEV lt Hock Drilling interval Interval Interval WeD ID ft msl) (ft msl) TEST (ftbgs) ltft$gs) (ftbgs) (ftbgs)

MW-107D 29958 2 128-130 1200 1305 1253

MW-107D 29958 1 139-141 1350 1455 1403

MW-108D 31904 31104 6 35-36 300 405 353 MW-108D 31904 5 60-62 550 655 603

MW-108D 31904 4 80-83 750 855 803

MW-108D 31904 3 118-119 123-124 1150 1255 1203

MW-108D 31904 2 147-149 1440 1545 1493

MW-108D 31904 1 1700 1805 1753

MW-110D 40576 40426 2 21-31 210 315 263 MW-110D 40576 1 148-154 1460 1565 1513 MW-I11D 40519 4 70-71 650 755 703

MW-111D 40519 3 79-82 84-86 780 885 833 MW-I11D 40519 2 97-102 950 1055 1003 MW-111D 40519 1 1370 1475 1423

MW-112D 3027 2942 4 42-52 420 525 473 MW-112D 3027 3 850 955 903 MW112D 3027 2 1100 1205 1153 MW-112D 3027 1 135-136 140-141 1340 1445 1393

MW-113D 43085 43085 5 250 355 303 MW-I13D 43085 4 47-49 460 565 513 MW-113D 43085 3 73-74 700 805 753 MW-113D 43085 2 1050 1155 1103 MW-113D 43085 1 1380 1485 1433

MW-114D 42394 41594 4 48-49 450 555 503 MW-114D 42394 3 79-81 740 845 793 MW-114D 42394 2 121-129 1250 1355 1303 MW-114D 42394 1 134-142 1350 1455 1403

MW-115D 4035 4035 4 300 405 353 MW-1I5D 4035 3 70-71 650 755 703 MW-115D 4035 2 1150 1255 1203 MW-115D 4035 1 1400 1505 1453

LOT-28W 382 7 450 555 503 LOT28W 382 6 550 655 603 LOT-28W 382 5 650 755 703 LOT28W 382 4 750 855 803 LOT-28W 382 3 850 955 903 LOT-28W 382 2 950 1055 1003 LOT-28W 382 1 1055 1155 1105

NOTES cmsec = centimeters per second ft bgs = leet below ground surface It msl = feet below mean sea level lt = not detected at indicated reporting limil A = detected below laboratory PQL ( ) = detected below reporting limits

Elevation of Interval

(ft nisi) 174

159

283gt 2588

2388

1988

1698

1438

3795 2545 3349 3219 3049 2629

2555 2125 1875 1635

4006 3796 3556 3206 2876

3737 3447 2937 2837

3683 3333 2833 2583

3318 3218 3118 3018 2918 2818 2715

Hydraulic Conductivity

(cmsec)

323E-05

208E-05

471E-03

471E-03

624E-05

3I6E-05

264E-05

261 E-05

OOOE+00 200E-04 953E-05 OOOE+00 OOOE+00 212E-05

361 E-05 410E-06 2gQE06 292E-05

786E-05 124E-05 151 E-05 822E-06 82IE-06

858E-05 I69E-05 352E-03 866E-05

223E-05 394E-06 122E-05 525E-06

831 E-05 182F-05 L62E-05 129E-05 190E-05 890E-04 981 E-04

PCEraquo Concentration

(ugL)

lt5

(14A)

98 11

15

22

11

30

200 (62)A

110 210 300 240

(44)A (23)A

5

350 190 129 230

2200 1900 2600 2600

(17)A (16)A (19)A

96

Table XX Packer Permeability and Packer Sampling Results for Potential Fracture Intervals

2004 Drilling Program

Hows Corner Superfund Site Plymouth Maine

Top of Bottom of Depth to Midpoint

t K

ELEV (ft Potential Transmissive Zones Packer Interval

Packer Interval

Middle of Interval

Elevation of interval

Hydraulic Conductivity

PCE Concentration

Well ID msl) TESTr (ft bgs)- (ftbgs) (ftbgs) (ftbgs) (ft msl) (cmsec) (ogt) MW-203D 43227 4 277279 24 32 28 4043 667E-05 44

3 408415420 39 49 44 3883 593E-05 170 2 526 530 49 57 53 3793 101E-04 140 I 828830842 80 88 84 3483 701E-05 130

MW-204D 43262 5 295 300 26 34 30 4023 902E-05 220 4 463496513516 45 53 49 3833 119E-04 540 3 681685688 63 71 67 3653 OOOE+00 2 758 76 2 71 79 75 3573 309E-05 260 I 88 96 92 3403 OOOE+00

MW-205 42389 3 164 166 168 15 20 175 4148 OOOE+00 1000B 2 302305312 30 35 325 3998 107E-04 1300B 1 40 45 425 3898 OOOE+00

MW-206D 43007 5 17 72 195 4128 291E-05 4 296 302 307 29 34 315 4008 940E-05 2900B 3 522 52 57 545 3778 944E-07 2 656 64 69 665 3658 353E-06 1 92392793 4939 91 96 935 3388 614E-05 6300B

PW-207 43477 5 184622162819 18 29 235 4088 209E-05 1300 4 3508 32 43 375 3948 568E-06 5400 3 53325341542154325559 50 61 555 3768 821E-05 18000

6359 61 72 665 3658 866E-06 12000 1 8685 84 89 865 3458 213E-05 19000

NOTES cmsec = centimeters per second ft bgs = feet below ground surface ft msl = feet above mean sea level B = detected in lab blank

Table XX Orientation Permeability and Groundwater Sampling Results for Transmissive Features

2004 Drilling Program

Hows Corner Superfund Site Plymouth Maine

Borehole Geophisical Feature depth Dip True Dip True Transmissive Log Feature (Feet) Degrees Azimuth Strike bullvgt(Ltk|iy^

Number v Tosftble) v MW-203 5 277 64 337 67 Likely

6 279 59 11 281 Likely 8 352 14 177 87 Likely 11 381 46 96 6 Possible 12 408 35 271 1 Possible 14 415 57 250 340 Possible 15 420 58 202 292 Likely 18 526 52 75 345 Likely 19 530 52 82 352 Likely 28 828 48 75 345 Likely 29 830 52 17 287 Likely 30 830 56 233 323 Possible 31 842 50 130 40 Likely

MW-204 4 295 15 147 57 Likely 5 300 43 91 1 Likely 11 439 31 80 350 Possible 12 440 46 219 309 Possible 14 463 50 358 88 Likely 15 496 34 198 288 Likely 16 513 54 17 287 Likely 17 516 33 14 284 Likely 25 681 39 359 89 Possible 26 685 22 45 315 Possible 27 688 35 73 343 Possible 32 758 45 236 326 Likely 33 762 46 306 36 Likely

MW-205 5 164 69 106 16 Possible 6 166 78 165 75 Possible 7 168 82 115 25 Possible 8 168 68 116 26 Possible 12 215 46 222 312 Possible 13 217 75 62 332 Possible 14 219 29 32 302 Possible 16 237 69 250 340 Possible 17 256 73 353 83 Possible 18 272 44 202 292 Possible 21 299 37 196 286 Possible 22 302 31 206 296 Possible 23 305 59 48 318 Likely 24 312 63 42 312 Likely

MW-206 1 264 37 181 271 Likely 2 296 69 217 307 Likely 3 302 66 233 323 Likely 4 307 64 224 314 Likely 8 342 62 259 349 Likely

jjHydraulic GoiDanctilyity j(cmsecjw

667 E-05

593 E-05

101 P04

710 E-05

902 E-05

119 E-04

0

309 E-05

0

107 E-04

94 E-05

PCE (ugL)

44

170

140

130

220

540

260

IOOOB

1100B

1300B

2900B

STotal vVoCsv tig1)

84

234

192

183

2636

6436

3073

11448

12509

13776

32401

PCEyo dfCTotaf

52

73

73

7 1

83

84

85

87

88

94

90

Table XX Orientation Permeability and Groundwater Sampling Results for Transmissive Features

2004 Drilling Program

Hows Corner Superfund Site Plymouth Maine

Borehole Geophisical Feature deptt raquoip True pip True Transraissive Log Feature (Feet) shy Degrees Azimuth Strike (tikely

Number raquo Possible) 22 522 57 54 324 Possible 25 656 40 82 352 Possible 32 871 59 151 61 Possible 33 883 53 185 275 Possible 34 895 7 175 85 Likely 35 899 53 90 0 Likely 36 902 49 184 274 Likely 37 923 9 175 85 Likely 38 927 42 206 296 Likely 39 934 48 167 77 Likely 40 939 26 180 90 Likely

PW-207 1 1846 33 167 77 Likely 4 2216 49 289 19 Possible 7 2819 59 265 355 Possible 11 3508 55 189 279 Possible 18 5332 43 305 35 Likely 19 5341 51 30 300 Likely 20 5421 20 254 344 Likely 21 5432 39 301 31 Likely 23 5559 52 302 32 Likely 25 6359 24 182 272 Possible 29 8049 77 231 321 Possible 30 8685 78 38 308 Likely 32 9334 29 194 284 Likely

NOTES

B = detected in lab blank

Hydraulic Conductivity

(cmsee) 944 E-07 353 E-06

614 E-05

209 E-05

568 E-06

821 E-05

866 E-06

213 E-05

bulltCE (ugL)

6300B

1300

5400

18000

12000

19000

Total VOCs (ug1)

68901

1410

5802

19234

13085

20354

PCE of Total VOCs

9 1

92

93

94

92

93

Response to EPA-DEP Comment 3 Dated March 312005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

lit

EPA-DEP Comment 3

Comment 3 The reported f values and resultant Kd values There remains doubt that the values used in the flushing model accurately reflect the propensity for PCE to sorb to the bedrock The ^ values presented in Appendix B may be unrealistically high because the bedrock samples may have contained organic carbon that was unavailable for sorption The reported f values are only qualitative estimates of the organic carbon content of the bedrock samples The Walkley and Black organic carbon measurement method is quick and simple but the results obtained cannot be considered quantitative because it requires a correction factor which often results in erroneous values it assumes the organic carbon has an average valence of zero oxidizable and reducible constituents such as chloride ferrous iron and manganese oxides interfere with the results and the errors introduced by interference are potentially greater when the organic carbon content is low at low f values it is not clear that organic carbon is controlling PCE sorption (Schwarzenbach and Westall 1981 Mackay et al 1986 Fetter 1999)

In order to derive a Kd-based retardation factor that is reasonable given the reported f values and the rapid advance of the PCE plume described on pages 4-11 and 4-12 the flushing model requires a bulk density to porosity ratio that is roughly two orders of magnitude higher than the actual ratio for the Hows Corner bedrock (page 4-4) This apparent discrepancy needs to be addressed

Response This comment raises several concerns about the collection and analysis of samples for fraction of organic carbon (f^) the quality of the resulting data and the implications of the use of those data for estimation of the retardation of groundwater contaminant movement Results of bedrock analysis for f were proposed in the TI Evaluation Work Plan for use in conjunction with groundwater contaminant concentrations and aquifer information to estimate cleanup times using the Batch Flushing model It is important to use accurate f values from representative bedrock in the Batch Flushing model in order to obtain reasonable estimates of the remedial time frame Because of the importance of accurate and representative results the TI Investigation field program was designed and conducted both to collect samples representative of the rock volume most likely to be in contact with contaminated groundwater and to analyze them using an appropriate refereed analytical method Five potential methods for evaluating f were identified Of the five methods the Walkey-Black method was selected because it has minimal method interferences and a sufficiently low detection limit as well as a long history of use in agronomy and contamination studies The PRP Group is pleased with the quality of the data obtained from the bedrock samples as represented by their precision and reproducibility

The first part of this comment relates to the determination of fraction of organic carbon (f^) values The several subparts of the first paragraph are addressed individually in items 1 through 5 below The second part of the comment regarding the resultant distribution coefficient (Kd) values is addressed separately as item 6 below

1 There remains doubt that the values used in the flushing model accurately reflect the propensity for PCE to sorb to the bedrock

bull The rock core samples used for f (gocg) analysis were from core immediately adjacent to fractures These rock core samples included the fracture surfaces themselves and rock core extending back less than 1 cm from the fractures Therefore the foe data reported in the TI Evaluation represents the f of bedrock through which groundwater will travel and to which PCE will adsorb Based on the careful selection of sample locations and the

Response to EPA Comment 3 050205doc 1 of 11 Woodard amp Curran (211941)

number of samples collected we are confident that the measured f values are representative of the f at points of contact for PCE with the bedrock it is these f values that determine the propensity of PCE to sorb to the bedrock

bull The samples of rock core collected for analysis of f originated from 19 different locations varying in depth from 11 to 90 feet Therefore it is very unlikely that the rock core samples were contaminated with extraneous organic carbon from above ground

2 The foc values presented in Appendix B may be unrealistically high because the bedrock samples may have contained organic carbon that was unavailable for sorption

bull As noted in response 1 the f data reported in Appendix B represents organic carbon primarily associated with the surface of fractures in the bedrock through which groundwater is most likely to travel Therefore it is this organic carbon that the contaminants in the groundwater will come in contact with and adsorb to in the fractured rock at the site

bull The chemical oxidation agents used in the Walkey-Black method oxidize the easily oxidizable organic carbon in the medium and the foe is calculated from the quantity of the agent consumed Therefore it is unlikely that the analysis of the bedrock samples measured organic carbon that was unavailable for sorption

3 The reported foc values are only qualitative estimates of the organic carbon content of the bedrock samples

bull The reported f values are accurate quantitative results Schumachers review of Methods for the determination of total organic carbon (TOC) in soils and sediments (NCEA-C-1282 EMASC-001 April 2002) identifies the Walkley-Black method which was used to analyze the reported foc values as the reference method for comparison to other methods for analyzing total organic carbon

bull Schumacher also points out that if anything the WalkJey-Black method may underestimate the total organic carbon in a sample due to possible incomplete oxidation of organic carbon Usually the incomplete oxidation of total organic carbon in environmental samples is corrected for by multiplying the measured foe by 130 (Walkley amp Black 1934 Schulte 1995)

bull When the f data in the TI Evaluation Report (WampC 2005) Appendix B (attached) are analyzed statistically the standard deviation of the f for the 19 samples analyzed is 174 of the average f Given this standard deviation the 95 confidence interval for this data ranged from a low of 000123 gocg to a high of 000253 gocgm

The labs Method of Detection Limit (MDL) for the f measured using the Walkley-Black method is 00001 gocg Therefore the average (000188 gocg) the mean (000185 gocg) and geometric mean (000187 gocg) of the f values for the rock core at Hows Corner are all statistically significantly greater than the MDL of the Walkley-Black method

In addition to the aforementioned statistical analysis of the foe data triplicate samples (n = 3) from the same rock core (including one sample from the 19 rock core samples) were

Response to EPA Comment 3 050205doc 2 of Woodard amp Curran (211941)

analyzed for their f to determine the repeatability of the Walkley-Black method The average the mean and the geometric mean of the f values of these replicate samples was 000162 gocg 000150 gocg and 000159 gocgm respectively The standard deviation of these measurements was 000039 gocg

4 The Walkley and Black organic carbon measurement method is quick and simple but the results obtained cannot be considered quantitative because it requires a correction factor which often results in erroneous values it assumes the organic carbon has an average valence of zero oxidizable and reducible constituents such as chloride ferrous iron and manganese oxides interfere with the results and the errors introduced by interference are potentially greater when the organic carbon content is low at low foc values it is not clear that organic carbon is controlling PCE sorption (Schwarzenbach and Westall 1981 Mackay et al 1986 Fetter 1999)

bull Schumachers review (NCEA-C-1282 EMASC-001 April 2002) of the Walkley-Black method identifies several potential problems with this analytical method that could occur if the analytical lab is not familiar with the nuances of the chemistry associated with this method Interestingly Schumachers review neglected one of the more important analytical steps required to avoid errors in quantifying f in samples where there might beNAPL

It is absolutely critical to eliminate any NAPL from rock core samples prior to using the Walkley-Black method to measure foe in such samples This was done by the lab (PTS Laboratories) that measured the foe in the rock core samples from Hows Corner The lab used the Dean-Stark method (solvent extraction) to remove all hydrocarbons (including PCE and other NAPLs) from the sample (PTS Laboratories) This extraction method does not interfere with the subsequent analysis of the natural organic carbon associated with the rock core

Subsequently the samples were dried at 150degC to a constant weight (normally 16 hours) This latter step oxidizes all inorganic minerals including ferrous bearing minerals to ferric oxides and precludes their interference during the oxidation of the samples with chromic acid This procedure completely eliminates any positive bias in the reported foc

data that might have occurred due to the presence of ferrous ions and other reduced minerals

bull As noted in Response 3 the incomplete oxidation of total organic carbon results in an underestimate of the f and is corrected for by multiplying the f by a correction factor of 130 (Walkley amp Black 1934 Schulte 1995) The fx data reported in the TI Evaluation was corrected accordingly by using this correction factor

bull Excess chloride (Cl~) in percent weight quantities as found in saline soils may interfere with the quantitative titration of reduced chromium (Walkley 1947) However given that the primary rock type at the Hows Corner site is phyllite it is highly unlikely that there was sufficient chloride in the rock core samples for this to occur

bull Manganese oxides may also interfere with the analysis of f through competing with the dichromate ion for any oxidizable carbon (Walkley 1947) However in such cases the reported f would be an underestimate of the f present in the rock core Walkley (1947)

Response to EPA Comment 3 050205doc 3 of 11 Woodard amp Curran (211941)

4

reported that in the case where the ratio of MnO2 to carbon is 85 to 1 the error in the carbon determinations would only be 0 to 6 percent

It may also be useful to compare the analysis of total organic carbon in a geologic matrix that contains high levels of manganese using EPA method 9060 to the Walkley-Black method Table 1 summarizes data provided by one of the PRPs that compares the analysis of total organic carbon in a geologic matrix that contains approximately 02 wgt manganese (approximately 03 wgt manganese oxide)

Table 1 Comparison of total organic carbon measured using the EPA- 9060 method and the Walkley-Black method

Laboratory EPA-9060 Method Walkley-Black Method A Ave 00226 gocg Not analyzed

Stdev 000251 gocg n = 5

B Ave 002219 gocg Ave 002050 gocg Stdev = 000316 gocg Stdev =000971 gocg

n= 10 n = 10

The similarity in the total organic carbon concentrations measured by these two different methods provides further confidence that the Walkley-Black method is a viable method for analysis of total organic carbon in the presence of manganese equivalent to at least 10 by weight of the total organic carbon

5 The Walkley and Black organic carbon measurement at lowf^ values it is not clear that organic carbon is controlling PCE sorption (Schwarzenbach and Westall 1981 Mackay et al 1986 Fetter 1999)

bull Schwarzenbach and Westalls (1981) paper states that f values of less than 0001 gocg should not be used in combination with Kow (octanol-water partition coefficients) values to calculate K^ values (solid phase partition coefficients) values for a specific contaminant It should be noted that the TI Evaluation did not use the f data to calculate the KQC from the Kow Instead as requested by the EPA the measured KOC value for PCE was used to calculate the retardation factor for this contaminant

bull Schwarzenbach et al (2003) stated more recently that Even at very low f values (ie foe = 0001 kgoc - kg1 solid) sorption to the organic components of a natural sorbent may still be the dominant mechanism in defining the adsorption of organic compounds to geological matrices

bull In 1985 M Piwoni from the US EPA Robert S Kerr Environmental Research Laboratory published a paper (Banerjee et al 1985) that showed that for very hydrophobic molecules TOC content of the sorbent will control sorption down to levels of organic carbon that defy quantitation Contaminants such as the PCE found in the groundwater at Hows Corner are in this category of compounds

Given the aforementioned reasons the f values reported in the TI Evaluation are accurate within the noted statistical limitations and will have a predictable impact upon the retardation of PCE during groundwater transport

Response to EPA Comment 3 050205doc 4 of 11 Woodard amp Curran (211941)

6 In order to derive a Kd-based retardation factor that is reasonable given the reported foc

values and the rapid advance of the PCE plume described on pages 4-11 and 4-12 the flushing model requires a bulk density to porosity ratio that is roughly two orders of magnitude higher than the actual ratio for the Hows Comer bedrock (page 4-4) This apparent discrepancy needs to be addressed

The apparent discrepancy of bulk density to porosity ratios is most likely due to the fact that the Batch Flushing Model was originally developed for a porous medium and is not directly applicable to fractured bedrock As stated in Appendix C (page C-4) of the Draft Technical Impracticability Evaluation Report in order to use the Batch Flushing Model to describe the transport of contaminated groundwater in fractured bedrock where the matrix porosity is insignificant it is more appropriate to use a fracture surface area to void space ratio to calculate the retardation factor (R) than a bulk density to porosity ratio (Freeze amp Cherry 1979)

Since it is impractical to determine the actual surface area to which contaminants can adsorb the Batch Flushing Model was used with two simplifying assumptions bull The Kd was calculated from the f and the K^ bull The bulk density to porosity ratio term in the Batch Flushing Model was constrained to range

from 4 to 10 the typical range of such ratios in porous media (Freeze amp Cherry 1979)

If one uses site specific bedrock bulk density and porosity values the bulk density to porosity ratio is several orders of magnitude greater (specifically 273 gcc bullbull 000165 (dimensionless) = 1654 gcc) than the range of ratios of 4 to 10 used in the Batch Flushing Model in the Draft Technical Impracticability Evaluation Report Constraining the bulk density to porosity ratio within the range of ratios of 4 to 10 results in significantly lower R value than would be obtained using specific bedrock bulk density and porosity values

In summary in bedrock where fractures are the primary porosity the bulk density to porosity ratio can vary considerably and will be a function of the number of fractures and the fracture aperture The calculated bulk density to porosity ratio will be inversely proportional to the porosity This means that in fractured rock with limited fracturing and smaller porosity the calculated bulk density to porosity ratio is greater and will result in a greater calculated retardation factor than in bedrock with more extensive fracturing and greater porosity Consequently the calculated retardation factor will be greater for bedrock with less surface area available for sorption than bedrock with greater surface area for sorption This is contrary to what actually occurs

4 Response to EPA Comment 3 050205doc 5 of 11 Woodard amp Curran (211941)

m

REFERENCES

Banerjee P MD Piwoni K Ebeid (1985) Sorption of organic contaminants to a low carbon subsurface core Chemosphere _14 1057-1067

Freeze RA JA Cherry (1979) Groundwater Prentice Hall Englewood Cliffs NJ pg 604

PTS Laboratories wwwptsgeolabscompdf files3TOCnotepdf

Schulte EE (1995) Recommended soil organic matter tests in Recommended Soil Testing Procedures for the Northeastern United States Northeastern Regional Publication No 493 Chapter 8

Schwarzenbach RP J Westall (1981) Transport of nonpolar organic compounds from surface water to groundwater Laboratory sorption studies Environ Sci Tech 15 1360-1367

Schwarzenbach RP PM Gschwend DM Imboden (2003) Environmental Organic Chemistry Wiley-Interscience pg 292 408 amp 412

Walkley A LA Black (1934) An examination of the Degtjareff method for determining soil organic matter and a proposed modification of the chromic acid titration method Soil Science 37 29-38

Walkley A (1947) A critical examination of a rapid method for determining organic carbon in soils - effect of variations in digestion conditions and of inorganic soil constituents Soil Science 63251-264

Woodard amp Curran Inc (WampC) 2005 Draft Technical Impracticability Evaluation Hows Corner Superfund Site Plymouth Maine January 2005

Response to EPA Comment 3 050205doc 6 of Woodard amp Curran (211941)

LIST OF ATTACHMENTS (Response to Comment 3)

Appendix B to Draft Technical Impracticability Evaluation Measurement of foe at Hows Corner (4 pages)

m

Response to EPA Comment 3 050205doc 7 of 11 Woodard amp Curran (211941)

Appendix B Measurement of foe of Rock Core at Hows Corner

There are two general approaches to measure the fraction of organic carbon (foe) in rock cores

bull Measurement of weight loss by ignition of organic matter bull Chemical oxidization of organic carbon to carbon dioxide and either

subsequent quantification of the oxidant used for the reaction or quantification of the carbon dioxide produced during this oxidation process

The weight loss method is subject to errors caused by volatilization of substances other than organic materials such as water hydroxides and mineral carbonates Quantification of foe by the weight loss method is particularly sensitive to the presence of carbonates in rock cores There are however weight loss methods that are designed to differentiate between organic carbon and the aforementioned interfering materials but they require considerable care and are less accurate at low foe values Hence the weight loss method was not well suited for measuring the foe of the rock core from Hows Corner

The chemical oxidation of organic carbon is much better suited for quantifying organic carbon in rock cores such as those from Hows Corner This method uses a strong chemical oxidant to oxidize organic carbon to carbon dioxide and then measures either the chemical oxidant used to oxidize the organic carbon or the quantity of carbon dioxide produced In addition this general approach is not subject to interference by volatilization of other constituents of the rock core

There are at least two such chemical oxidation methods

bull The method of Baccini which was described by Schwarzenbach amp Westall (1981) first acidifies the sample to eliminate interference by carbonates Then a strong oxidant is used to chemically oxidize the organic carbon to carbon dioxide The resulting carbon dioxide is subsequently reduced to methane and quantified using a flame ionization detector Unfortunately this method has not been described in detail in a referred journal Hence it is would not have been appropriate to use to characterize the foe in the Hows Corner rock core

bull The more commonly used method to quantify foe in rock core is the Walkley-Black method (1934) This method is preferred for RBCA and DODDOE projects and by the oil industry

The Walkley-Black method uses an excess of chromic acid to oxidize (digest) organic matter to carbon dioxide The remaining chromic acid that was not consumed during the oxidation of the organic carbon is then quantified by titration with ferrous sulfate The difference in chromic acid prior to and after the oxidation of the organic carbon represents the total chromic acid used to oxidize

Hows Corner TI Evaluation Page 1 January 13 2005 Appendix B

the organic carbon in the sample The latter can be calculated using the chemical stoichiometry of the reaction

The Walkley-Black method is very accurate for samples that contain less than 2 organic carbon matter The minimum detection limit (MDL) for the Walkley-Black method is 100 mgkg or an foe of 0001

Given the rock core at Hows Corner was expected to contain less than 2 organic carbon the Walkley-Black method was used to measure the foe from 19 different rock core samples collected from varying depths ranging from 11 to 90 feet

Table 1 provides a statistical summary of the aforementioned data

Table 1 Statistical summary of foe data from rock cores collected at varying depths

Statistical Parameter Calculated Value foe Minimum Detection Limit (MDL) 00010 Number of samples analyzed (n) 19 Average foe 00019 Median foe 00019 Geometric Mean foe 00019 Standard deviation of foe measurements 000033 Relative standard deviation 174 -+ 95 Confidence intervals 00012 to 00025

The data in Table 1 shows the following

bull The foe from the Hows Corner rock cores are statistically greater than the MDL of the Walkley-Black analytical method

bull The average and median values for the foe of the Hows Corner rock cores from varying depths are nearly identical indicating that there is little variability in the foe values in the source zone at the site

bull The standard deviation of these measurements is 000033 which is 174 of the average foe

bull The 95 confidence intervals of the foe of the rock core at Hows Corner are 00012 to 00025

The foe was also analyzed from three separate samples taken from the same rock core at a depth of 55 feet (Only one of these samples was included in the data summarized in Table 1) Table 2 shows the statistical repeatability of this type of analysis

Hows Corner TI Evaluation Page 2 January 13 2005 Appendix B

Table 2 Repeatability of analysis of foe from one rock core at 55 feet in depth

Statistical Parameter Calculated Value Number of samples analyzed (n) 3 Average foe 00016 Median foe 00015 Geometric Mean foe 00016 Standard deviation of foe measurements 000039 Relative standard deviation 240 -+ 95 Confidence intervals 00008 to 00024

The data in Table 2 shows the following

bull The percent relative standard deviation of these three analyses of foe from the same rock core at Hows Corner is 24

bull The 95 confidence interval of the foes measured in this particular rock core at Hows Conrer is 00008 to 00024

These results show that there is good repeatability in using the Walkley-Black method for analysis of the foe in the rock core at Hows Corner

References Schwarzenbach amp Westall (1981) Transport of nonpolar organic compounds from surface water to groundwater Laboratory sorption studies Environ Sci Tech 15 1360-1367

Walkley A I A Black (1934) An examination of Degtjareff method for determining soil organic matter and a proposed modification of the chromic acid titration method Soil Sci 37 29-37

Hows Corner Tl Evaluation Page S January 13 2005 Appendix B

Woodard and Curran PTS Laboratories PTS File No 34618

ORGANIC CARBON DATA (METHODOLOGY WALKLEY-BLACK)

PROJECT NAME PROJECT NO

SAMPLE ID

203-chip-13 203-chip-23 203-chip-27 203-chip-38 203-chip-42 203-chip-47 203-chip-52 203-chip-58 203-chip-69 203-chip-82 207-chip-11 207-chip-19 207-chip-24 207-chip-29 207-chip-35 207-chip-45 207-chip-55 207-chip-87 207-chip-90

207-chip-55 55-MS

55-MSMSD

Hows Corner NA

DEPTH ft

13 23 27 38 42 47 52 58 69 82 11 19 24 29 35 45 55 87 90

55 NA NA

MATRIX

Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip

Average Median

Geometric Mean Standard Deviation Relative Std Dev

+- 95 Confidence Interval n

Rock Chip Rock Chip Rock Chip

Average Median

Geometric Mean Standard Deviation Relative Std Dev

+- 95 Confidence Interval n

FRACTION ORGANIC CARBON

(gg)

170E-03 185E-03 185E-03 170E-03 240E-03 190E-03 230E-03 180E-03 170E-03 115E-03 195E-03 220E-03 220E-03 235E-03 135E-03 190E-03 205E-03 175E-03 160E-03

188E-03 185E-03 185E-03 327E-04

1739 123E-03 to

19

205E-03 130E-03 150E-03

162E-03 150E-03 159E-03 388E-04

2402 840E-04 to

3

2532E-03

2393E-03

Hows Corner Tl Evaluation Appendix B January 13 2005

Response to EPA-DEP Comment 4 Dated March 31 2005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

EPA-DEP Comment 4

Comment 4 Distribution of contaminants First the TI report seems based on the assertion that there is DNAPL at the source area yet it also appears to represent that the source area is small and the bedrock below 85 is competent (or less fractured) and less impacted by the release of contaminants Some of the confusion may result from using most recent data when that data is from several different sampling events over several years and there is no discernible difference in concentrations between shallow and deep bedrock or as in Section 421 where generally decreased generally increase generally similar and similar concentrations in four consecutive sentences leads to a muddled picture of the contaminant distribution

Second the report asserts that the distribution of contaminants over the entire plume has not changed with time but fails to support this conclusion with data again relying on data that is from different sampling dates for one composite representation

Response The likely presence of dense non-aqueous phase liquid (DNAPL) at the Hows Corner Site and the determination that the source area is small are not mutually exclusive and both are conclusions drawn from information obtained during field investigations The presence of DNAPL in the source area is based on the elevated concentrations of volatile organic compounds (VOCs) detected in the groundwater (WampC 2001 WampC 2002) The conclusion that the source area is small is based on the area in which VOCs in groundwater have been detected at concentrations that are considered to be indicative of the presence of DNAPL nearby Similarly the conclusion that fracture frequency decreases at depths greater than approximately 50 to 85 feet below ground surface was based on field observation during the RI field work The fact that zones with observed fractures exhibited higher hydraulic conductivities than zones without fractures coupled with the decreasing frequency of observed fractures with depth led to the conclusion that the hydraulic conductivity of the bulk rock decreases with depth

The most recent data from all wells were used to provide the maximum VOC data set size During the RI all of the previously-existing and then newly-installed monitoring wells were sampled along with several residential wells The RI sampling included up to 48 monitoring wells Subsequent to the RI and prior to the TI three rounds of monitoring were conducted to verify that the plume was stable 15 monitoring wells were sampled during each of the three rounds During the TI field investigation 29 wells were sampled for VOCs The sampled wells included all of the newly-installed wells and a subset of wells installed during the RI for a total of 29 monitoring wells By using most recent data VOC results from 53 monitoring wells were included in the evaluation (see table labeled Sampling Events for listing of monitoring wells) This approach was selected because there generally was little variation in the data from a particular location between years This is borne out by the attached individual plots of VOCs detected in shallow bedrock and deep bedrock for the Pre-ROD (December 1999January 2000) and Supplemental (May 2000) sampling events and for June 2001 January 2002 and April 2003 sampling events The Pre-ROD and Supplemental plots are similar to the subsequent plots from the 2001 2002 and 2003 sampling events

In addition to maps showing the spatial distribution of VOC data at a given time trend plots of the data from a particular location through time (attached) indicate that since the RI concentrations generally have been stable or have decreased Together the maps and trend plots and the data from which they were developed indicate that the distribution of contaminants over the entire plume has not changed appreciably with time

Response to EPA Comment 4 050305doc 1 of 26 Woodard amp Curran (211941)

REFERENCES

Woodard amp Curran Inc (WampC) 2001 Final Remedial Investigation Report Hows Corner Superfund Plymouth Maine July 2001

Woodard amp Curran Inc (WampC) 2002 Final Feasibility Study Report - Non-Source Area Groundwater Hows Corner Superfund Site Plymouth Maine Hows Corner Superfund Plymouth Maine July 2002

Response to EPA Comment 4 050305doc 2 of 26 Woodard amp Curran (211941)

LIST OF ATTACHMENTS (Response to Comment 4)

Table - Sampling Events 1999 - 2004 (2 pages)

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater Pre-ROD Sampling Event

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater Pre-ROD Sampling Event

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater Supplemental Sampling Event

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater Supplemental Sampling Event

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater June 2001

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater June 2001

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater January 2002

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater January 2002

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater April 2003

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater April 2003

Figure - Concentration Trends - Non-Source Area Wells MW-1B and MW-3B

Figure - Concentration Trends - Non-Source Area Wells MW-13DB and MW-16DB

Figure - Concentration Trends - Non-Source Area Wells MW-16IB and MW- 108D

Figure - Concentration Trends - Non-Source Area Wells MW-108S and MW-112D

Figure - Concentration Trends - Non-Source Area Wells MW-112S and MW-114D

Figure - Concentration Trends - Non-Source Area Wells MW-114S and MW-115D

Figure - Concentration Trends -Source Area Wells MW-2DB and MW-2IB

Figure - Concentration Trends -Source Area Wells MW-102S and MW-103D

Figure - Concentration Trends -Source Area Wells MW-103S and MW-104D

Figure - Concentration Trends -Source Area Wells MW-104I and MW-106D

Figure - Concentration Trends -Source Area Wells MW-106S

Response to EPA Comment 4 050305doc 3 of 26 Woodard amp Curran (211941)

I I

El I

II I I 1 I

I

i

Event Baseline Case ID WC-01 WC-01

Well Date Aug-99 Oct-99 LOT10 1 LOT1-1 1 LOT11-4 LOT14 1 LOT15 1 LOT15-1 1 LOT16 1 LOT16-1 1 LOT17 1 LOT18 1 LOT19 1 LOT2 LOT20 1 LOT21-10 1 LOT21-11 1 LOT21-12 1 LOT21-13 1 LOT21-14 1 LOT21-2 1 LOT21-5 1 LOT21-7 LOT21 -8 1 LOT21-9 1 LOT23 1 LOT24 1 LOT28-1 1 LOT28-2 1 LOT28-3 1 LOT28-4 1 LOT28W 1 LOT30 1 LOT30-1 1 LOT30-2 1 LOT30-3 1 LOT30-4 1 LOT30-5 LOT31 LOT35 1 LOT41 1 LOT42-1 1 LOT43-1 1 LOT43-4 1 LOT6-1 1 LOT67 1 LOT6-7 1 LOT6-8A 1 LOT6-8B 1 LOT80-1 1 LOT82 1 MW-101D MW-1011 MW-101S MW-102D MW-102S MW-103D MW-103S MW-104D MW-1041 MW-104S MW-105D MW-106D

Groundwater Sampling Location Summary 1999 - 2004xls

Sampling Events 1999-2004

Hows Corner Superfund Site Plymouth Maine

Supplemental 2001 2002 2003 Pumping 2004 Pre-ROD Rl Sampling Sampling Sampling Test Sampling WC-03 WC-09 WC-25 WC-30 WC-42B WC-56 WC-58 Dec-99 May-00 Jun-01 Jan-02 Apr-03 Sep-04 Sep-04

1

1 1 1

1 1 1 1 1

1 1

1

1 1

1 1 1

1 1 1 1 1

1

1 1

1 1 1 1

1

1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

Sampling Events 1999-2004

Hows Corner Super-fund Site Plymouth Maine

Supplemental 2001 2002 2003 Pumping Event Baseline Pre-ROD Rl Sampling Sampling Sampling Test

Case ID WC-01 WC-01 WC-03 WC-09 WC-25 WC-30 WC-42B WC-56

ll

Well Date Aug-99 Oct-99 Dec-99 May-00 Jun-01 Jan-02 Apr-03 Sep-04 MW-106S 1 1 1 1 1 MW-107D 1 1 MW-108D 1 1 1 1 1 MW-108S 1 1 1 1 1 MW-110D 1 1 MW-111D 1 1 MW-112D 1 1 1 1 1 MW-112S 1 1 1 1 1 MW-113D 1 1 MW-114D 1 1 1 1 1 MW-114S 1 1 1 1 1 MW-115D 1 1 1 1 1 MW-12DB 1 1 1 MW-12SB 1 1 1 MW-13DB 1 1 1 1 1 1 MW-13SB 1 1 1 MW-14DB 1 1 MW-14SO 1 1 MW-15DB 1 1 1 MW-15SB 1 1 1 MW-16DB 1 1 1 1 1 1 MW-16IB 1 1 1 1 1 1 MW-16SO 1 1 MW-17DO 1 1 1 MW-17SO 1 1 1 MW-1B 1 1 1 1 1 1 MW-203D MW-203S MW-204D MW-204S MW-205 MW-206D

I MW-206S MW-2DB 1 1 MW-2DDB 1 1 MW-2IB 1 1 1 1 1 1 MW-3B 1 1 1 1 1 1

I MW-4O 1 1 1 MW-5B 1 1

II MW-6DB 1 1 1 MW-6SB 1 1 1 MW-8DB 1 1 1 MW-8SB 1 1 1

II PW-207 1 SEEP-1 1 SUBTOTAL - RESIDENTIAL 44 25 0 2 0 3 0 SUBTOTAL - MONITORING 22 48 41 15 15 15 1

Total 3 66 73 41 17 15 18 1

I Included in most recent data

I Notes 1 - Overburden well not included in most recent data for plotting

2 - Tetrahydrofuran and 2-Butanone were the only two compounds detected in this well and are thought to be the result of well repair not included in most recent data for plotting

3 - Not included in most recent data for plotting

2004 Sampling

WC-58 Sep-04

1

1 1

1 1

1 1 1

1

1 1

1 1 1 1 1 1 1 1 1

1 1

1

0 29

29

Groundwatef Sampling Location Summary 1999 - 2004xls

I

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

monitoring well Figure 4-14 total VOC contour (ugl) - December 1999January 2000 Distribution of Total VOCs in

Note SW-113 is located downstream of SEEP-1 Shallow Bedrock Groundwater total concentration of detected VOCs ND= not detected these two locations were sampled during the Pre-ROD Sampling Event

Baseline Sampling Event in OctoberNovember 1999 Hows Corner Superfund Site Surface Water Sampling Location A Plymouth Maine Seep Sampling Location laquo- WOODARD ampCURRAN

995037wipri reportepa ri interim final feb 2001cadd drawingsfinalfig 4-14

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

0 300 600 I

FEET

Q residential well Figure 4-16 monitoring well Distribution of Total VOCs in

Deep Bedrock Groundwater total VOCs contour (ugl) Pre-ROD Sampling Event

active residential wells with lot number Hows Corner Superfund Site 2deg42deg Plymouth Maine total concentration of detected VOCs ND= not detected WOODARD ampCURRAN Enyinaaring bull Science bull Operations bull

995037wipri reportepa ri interim final feb 2001cadd drawingsfinalfig4mdash16

PLYMOUTH POND

PLYMOUTH POND

1 628Tl7MW-2bB 12135

PLYMOUTH POND

monitoring well Figure 4-20

V total VOC contour (ugl) - June 2000 Distribution of Total VOCs in Shallow Bedrock Groundwater

| 34 | total concentration of detected VOCs ND= not detected NA = not analyzed Supplemental Sampling Event Note SW-113 is located downstream of SEEP-1 Hows Corner Superfund Site

Surface Water Sampling Location these two locations were sampled during the Plymouth Maine Baseline Sampling Event in OctoberNovember 1999 Seep Sampling Location WOODARD amp CURRAN

Engineering bull Science - Operations bull 995037wipri reportepa ri interim final feb 2001 cadd drawingsfinalfig 4-20

residential well Figure 4-22 Distribution of Total VOCs in

monitoring well Deep Bedrock Groundwater

total VOCs contour (ugl) Supplemental Sampling Event

Hows Corner Superfund Site

total concentration of detected VOCs ND= not detected NA = not analyzed Plymouth Maine

WOODARD amp CURRAN

995037wipri reportepa-ri interim final feb 2001cadd drawingsfinalfig 4-22 Engineering bull Science - Operations bull

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

FEET

Shallow Monitoring Well

Deep Monitoring Well

C Detected Concentration ND = Not Detected Figure 1-XS Distribution of Total VOCs in Shallow Bedrock Groundwater

Pumping Well

17-Acre Property Boundary Concentration Contour (ugl)

June 2001 Hows Corner Superfund Site

Plymouth Maine WOODARDampCURRAN

-i^rhvj bull Scbncn bull Operations bull 211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0601 dwg04-20-05

PLYMOUTH POND Hopkins Road V

O

PLYMOUTH POND

PLYMOUTH POND

o

0 300 600 mdashfa FEET

Shallow Monitoring Well bull bull - 17-Acre Property Boundary Figure 1-XD

Deep Monitoring Well 1 I Detected Concentration ND = Not Detected Distribution of Total VOCs in Deep Bedrock Groundwater

-mf- Pumping Well June 2001 Residential Well Hows Corner Superfund Site

Plymouth Maine i h Surface Water Sampling Point

g WOODARD ampCURRAN _ ^ _ ^ _ _ yen_ rj i|Hlaquorlny bull Science bull Opt

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0601 dwg04-20-05

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

Shallow Monitoring Well

Deep Monitoring Well

Detected Concentration ND = Not Detected Figure 1-YS Distribution of Total VOCs in Shallow Bedrock Groundwater

Pumping Well

17-Acre Property Boundary Concentration Contour (ugl)

January 2002 Hows Corner Superfund Site

Plymouth Maine WOODARD amp CURRAN Engineering Science- Operations bull

211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0102dwg04-20-05

PLYMOUTH POND

PLYMOUTH POND

Site Pand^ laquoum-laquoBTuitaraquo tLV

vVlf-(

PLYMOUTH POND

0 300 600 ^ = FEET

Shallow Monitoring Well mdashbullbullbull 17-Acre Property Boundary Figure 1-YD - A - Deep Monitoring Well FT Detected Concentration ND = Not Detected Distribution of Total VOCs in

Deep Bedrock Groundwater Pumping Well January 2002 Residential Well Hows Corner Superfund Site

Plymouth Maine Surface Water Sampling Point

WOODARD ampCURRAN Engineering Sciencs- Operations bulli Si

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0102dwg04-20-05

- m j

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND j A O-shy

Shallow Monitoring Well E Detected Concentration ND = Not Detected Figure 1-ZS Distribution of Total VOCs in

Deep Monitoring Well Shallow Bedrock Groundwater

Pumping Well Hows Corner

April 2003 Superfund Site

17-Acre Property Boundary Plymouth Maine Concentration Contour (ugl) r WOODARD ampCURRAN

Engineering bull Science bull Operations bull 211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0403dwg04-20-05

s S pound

PLYMOUTH POND

PLYMOUTH POND

- -

5 PLYMOUTH POND

Jo

FEET

ft Shallow Monitoring Well mdashbullbullmdash 17-Acre Property Boundary Figure 1-ZD Deep Monitoring Well I 1 I Detected Concentration ND = Not Detected Distribution of Total VOCs in

Deep Bedrock Groundwater Pumping Well April 2003

Q) Residential Well Hows Corner Superfund Site Plymouth Maine

(T) Surface Water Sampling Point WOODARD ampCURRAN poundKk EnginawtirKj bull Science - Operations bull

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0403dwg04-20-05

0 Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

B MW-1B

I 12000

PCE

B 10000 Total VOCs

I

i 2000

i 0 Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

c MW-3B

G 2000

1800

B PCE

1600 Total VOCs

1 I I E

il-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

G E

211941

El

I I z E

80

Concentration Trends shy Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-13DB

Total VOCs

c i i c o

Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

MW-16DB

30

c i c c I c o

Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99

PCE

Total VOCs

Jul-01 Jul-03

211941

O bi

c Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

I MW-16IB

i 35

3

c Total VOCs

lt- 2 5

0 | gt

o

1 sectI

c c 0 4

Jul-90 Jul-92 Jul-94 Jul-96 Jul-98 Jul-00 Jul-02 Jul-04

I I MW-108D

I 12

PCE 10

Total VOCs c oc 3

E E I 0

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

E 211941

c Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

fi MW-108S

I I 40

PCE 35

Total VOCs

30

I f 26

20 I o

I 15

10

c Dec-99 Dec-00 Dec-01 Dec-02 Dec-03 I 0

I MW-112D

c 35 - imdash

I A3 shyTotal VOCs

o c

E 1 2

I

ition

B 1 ^

-i c 3

0 Dec-99 Dec-OO Dec-01 Dec-02 Dec-03

211941

I

i

I

cII

Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-112S

08

PCE

Total VOCs 06

o 04

02

0 Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

MW-114D

o

12000

10000

8000

6000

PCE

Total VOCs

4000

2000

i

ccEIIc

i

i

E

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

211941

Con

cent

ratio

n (

ug

l)

E Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

I MW-114S

E A5000 -- Total VOCs

- 4000

0 3000

2000

i 1000

i n shy

Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

MW-115D

c PCE

Total VOCs

c E

o

C c

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03 I 0

211941

IepoundII

EIEIIGICCIccc

30000

25000

20000

o bullsect 15000 b

o 10000 U

5000

0 Aug-99

25000

20000

5000

0 Aug-99

211941

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-2DB

PCE

Total VOCs

Aug-01 Aug-03

MW-2IB

PCE

Total VOCs

Aug-01 Aug-03

IDIBI

ii EIDIISIBIG C

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-102S

6000

5000 PCE

Total VOCs

4000

O 3000

2000

1000

0 Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

MW-103D

16000

~ 14000 ugt 3- 12000 o

^ 10000

sect 8000

O 6000

4000

2000

PCE

Total VOCs

0Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

211941

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

G MW-103S

I I

ampo

12000

10000

E sectc

S

8000

6000

4000

2000

0Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

G I 6000

MW-104D

i 5000

PCE

Total VOCs

i i c

2000

1000

Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

E I

211941

cIccIG

IIBCccBcIc

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-1041

PCE Total VOCs

a 25000

0 20000

a 15000

10000

5000

0 Jan-OO Jan-01 Jan-02 Jan-03 Jan-04

MW-106D

3000

2500 PCE

Total VOCs

=sect 2000

o bullsect 1500

1000

500

0 Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

211941

c Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

c MW-106S

I PCE

Total VOCs

i

i Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

i

i i i E

C

211941 c

Response to EPA-DEP Comment 5 Dated March 312005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

iiw

EPA-DEP Comment 5

Comment 5 Matrix Diffusion The report as well as other proponents of matrix diffusion suggest that depletion of DNAPL (Section 5112 page 5-15) needs to be achieved While that might be the ideal the goal is to achieve performance standards and that goal may be attainable while there is residual contamination in the rock perhaps even DNAPL globules The low bedrock matrix porosity (page 1-15) the high permeability values (page 4-4) the relative flux of the groundwater (page 5-5) and the decrease in surface area and out of the mainstream pockets (appendix C-4) all suggest that the diffusion out of the rock matrix would be insubstantial relative to the regional flux of groundwater through the Site

Response The TI Evaluation Report does not explicitly consider or rely upon matrix diffusion as a basis for requesting a TI Waiver for a portion of the Hows Corner Site The technical literature provides documentation that matrix diffusion can be a significant process that affects chemical transport and groundwater remediation timeframes in unconsolidated and consolidated media including fractured rock (US EPA 1989 Freeze and Cherry 1979 Pankow and Cherry 1996 Fountain 1998) Back diffusion of contaminants from the matrix porosity of the fractured rock can prolong the time necessary to achieve groundwater cleanup goals particularly for compounds such as PCE for which the cleanup goal is a low concentration It is our expectation that matrix diffusion has occurred at the Hows Corner Site and that back diffusion of PCE from the rock matrix will also occur Although the extent to which matrix diffusion is occurring at the Hows Comer Site has not been determined and that lack of knowledge contributes to uncertainty regarding the cleanup times at the Site the effect of matrix diffusion is to lengthen rather than shorten the time required for remediation

REFERENCES

Fountain JC 1998 Technologies for Dense Nonaqueous Phase Liquid Source Zone Remediation Ground-Water Remediation Technologies Analysis Center Technology Evaluation Report TE-98-02 December

Freeze RA and Cherry JA 1979 Groundwater Prentice-Hall Inc Englewood Cliffs NJ 07632 p 410-412

Pankow J F and Cherry J A 1996 Dense Chlorinated Solvents Waterloo Press Portland OR 97291-1399 p 67-88

US EPA 1989 Transport and Fate of Contaminants in the Subsurface EPA6254-89019 p 17-18

Response to EPA Comment 5 050305doc 1 of 1 Woodard amp Curran (211941)

WOODARD amp CURRAN Maine Massachusetts New Hampshire Connecticut Florida Operational offices across the US 1-800-426-4262 www woodardcurran com

Page 10: SDMS DocID 251749 - Records Collections · 2020-06-13 · CORPORATE OFFICES: Maine, Massachusetts, New Hampshire, Connecticut New, York, Florida Engineering • Science • Operations

REFERENCE

Freeze RA and Cherry JA 1979 Groundwater Prentice-Hall Inc Englewood Cliffs NJ 07632 p 410-412

Response to EPA Comment 2 050205doc 4 of 24 Woodard amp Curran (211941)

LIST OF ATTACHMENTS (Response to Comment 2)

Figure - Drawdown at 72 Hours Shallow Wells

Figure - Drawdown at 72 Hours Deep Wells

Figure - Drawdown at 72 Hours

Figure - Potentiometric Surface at 72 Hours Shallow Wells

Figure - Potentiometric Surface at 72 Hours Deep Wells

Figure - End of Pumping Test Bedrock Potentiometric Surface at 72 Hours

Table - Pumping Test Analytical Results

Figure - USGS Background Groundwater Level

Figure - Packer Testing Results in Vicinity of Source Area

Figure - Borehole Geophysical Log MW-203

Figure - Borehole Geophysical Log MW-204

Figure - Borehole Geophysical Log MW-205

Figure - Borehole Geophysical Log MW-206

Figure - Borehole Geophysical Log PW-207

Table - Packer Permeability and Packer Sampling Results for Potential Fracture Intervals 1999 Drilling Program (2 pages)

Table - Packer Permeability and Packer Sampling Results for Potential Fracture Intervals 2004 Drilling Program

Table - Orientation Permeability and Groundwater Sampling Results for Transmissive Features 2004 Drilling Program (2 pages)

Response to EPA Comment 2 050205doc 5 of 24 Woodard amp Curran (211941)

(MEDEP Pond 1) Farm Pond

0 150 300

FEET

Monitoring Well

Figure X Pumping Well Drawdown at 72 Hours

_ - 17-Acre Property Boundary Shallow Wells Hows Corner Superfund Site Drawdown Contour (ft) Plymouth Maine

151 | Drawdown (ft) WOODARD ampCURRAN

^Stk Engineering bull Science bull Operations bull 211941 Hows CornlaquorwipDrawingsTI EVALDrawdown-72hrs_shallowdwg04-19-05

MW-3B

413951 W-6DB JMW-6SB

(MEDEP Pond 1) Farm Pond

Monitoring Well

Pumping Well

17-Acre Property Boundary

Groundwater Elevation Contour (ft)

211941 Hows CornerwipDrowngsTI EVALpo-tent-aU-72-hrsdwg

Figure X End of Pumping Test

Bedrock Potentiometric Surface at 72 Hours Hows Corner Superfund Site

Plymouth Maine ^ WOODARD amp CURRAN

Englnesring bull Science bull Ope

(MEDEP Pond 1) Farm Pond

Monitoring Well

Pumping Well Drawdown atFigure X

72 Hours _bullbull_ 17-Acre Property Boundary Deep Wells

Drawdown Contour (ft) Hows Corner Superfund Site

Plymouth Maine 151 | Drawdown (ft)

= WOODARD ampCURRAN 211941 Hows CornerwipDrawingsTI EVALDrawdown-72hrs_deepdwg04-19-05

Engineering bull Science bull Operations

(MEDEP Pond 1) Farm Pond

028 MW-12DB

MW-125B 040

l - _ ^ I 016 I N

050 MW-15SB

MW-15DB 048

A J s

- A - Monitoring Well

-$poundbull Pumping Well

_bullmdash 17-Acre Property Boundary

^ Drawdown Contour (ft)

151 I Drawdown (ft)

211941 Hows CornerwgtpDrawinQsT EVAI_Drawdown-72brsdwg04mdash19-05

Figure X Drawdown at 72 Hours

Hows Corner Superfund Site Plymouth Maine

^ WOODARD ampCURRAN Engineering bull Science bull Operations i

(MEDEP Pond 1) Farm Pond

Monitoring Well

Pumping Well

_bullbull_ 17-Acre Property Boundary

f Groundwater Elevation Contour (ft)

|419Q0| Groundwater Elevation

211941 Hows CornerwipDrawinqsTI EVALPotSurf-72hrs_shallowdwg04-19-05

150 300

FEET

Figure X Potentiometric Surface at 72 Hours

Shallow Wells Hows Corner Superfund Site

Plymouth Maine

WOODARD ampCURRAN Engineering bull Science bull Operations

29212 MW-108D

(MEDEP Pond 1) Farm Pond

Monitoring Well

Pumping Well

mdashbullbulllaquo 1 7-Acre Property Boundary

bull Groundwater Elevation Contour (ft)

1419001 Groundwater Elevation

211941 Hows CornerwipDrawingsTI EVALPotSurf-72hrs_deepdwg04-19-05

150 300 =5fc= FEET

Figure X Potentiometric Surface at 72 Hours

Deep Wells Hows Corner Superfund Site

Plymouth Maine

WOODARDampCURRAN Engineering bull Science bull Operations bull

--

Pumping Test Analytical Results Hows Corner Superfund Site

Plymouth Maine

Well ID oper Jaccb Analyses 2 Theis Analyses Fissure

Well Id Rd (ft)

Saturated Thickness

Transmissivity

(ft2day) K

(ft2day) K

(cmsec) Storage

Coefficient Transmissivity

(ft2day) K

(ft2day)

K (cmsec)

Storage Coefficient

System K

(ftday) PW-207OB 8 85 481 057 200E-04 392E-02 36 042 150E-04 809E-04 027 MW-103S 50 85 451 053 187E-04 720E-03 92 108 382E-04 283E-04 083 MW-103D 54 185 455 025 868E-05 210E-02 65 035 123E-04 237E-04 044 MW-2IB 59 85 352 041 146E-04 699E-03 104 123 433E-04 512E-04 052 MW-2DB 63 85 334 039 139E-04 845E-03 148 080 283E-04 239E-04 046 MW-104D 95 185 489 02 6 932E-05 654E-03 98 053 186E-04 547E-05 037 MW-104I 97 85 33 03 9 137E-04 362E-03 117 137 484E-04 962E-05 048 MW-101I 107 85 364 043 151E-04 490E-03 511 601 212E-03 223E-04 136 MW-102D 134 185 435 024 829E-05 248E-03 108 058 206E-04 850E-05 065 MW-101D 138 185 492 027 938E-05 511E-03 671 362 128E-03 700E-04 172 MW-205 219 85 57 067 237E-04 255E-03 447 526 186E-03 359E-03 -shyMW-204D 221 185 367 020 700E-05 170E-03 790 427 151E-O3 155E-04 147 MW-204S 225 85 379 045 157E-04 156E-03 1031 1213 428E-03 313E-04 199 MW-1B 228 85 325 038 135E-04 977E-04 340 400 141E-03 739E-05 054 MW-203S 273 85 489 058 203E-04 117E-03 1255 14 76 521 E-03 216E-04 210 MW-106D 278 185 51 028 972E-05 141E-03 1065 576 203E-03 360E-04 104 MW-203D 278 185 478 026 911E-05 152E-O3 765 414 146E-03 364E-04 138 MW-105D 364 185 44 024 839E-05 830E-04 769 415 147E-03 200E-04 127

1 Analyses conducted using Cooper and Jakob method on late drawdown data collected during constant

discharge pumping test conducted at the Hows Comer Site from September 20 - 30 2004

2 Analyses conducted using Theis solution for unconfmed approximation (1935)

J Analyses conducted using Moench method for dual porosity estimation (1984)

Fissure System Storage

Coefficient 402E-04 117E-06 264E-04 300E-04 932E-05 235E-07 502E-05 326E-06 801E-05 542E-04

-

803E-05 762E-05 134E-05 498E-05 115E-04

47E-04 838E-05

3 ysesh Analysis

Block System K (ft2day)

251E-02 207E-03 564E-04 163E-04 585E-04 465E-02 153E-04 498E-03 855E-04 356E-03

-

292E-03 394E-03 720E-04 526E-03 160E-01 35OE-O1 287E-03

Block System Storage

Coefficient

402E-02 164E-04 183E-02 330E-03 158E-03 847E-03 286E-03 326E-04 803E-05 272E-03

723E-04 686E-04 148E-04 349E-04 115E-03 47E-04 838E-04

Theis - Moench - CJ - AnalyticalResults_4-19-O5xls

DRAFT

242

24

238

236

bulla

c

i

a Q

234

232

228

226

Hows Corner Constant Discharge Testing USGS Background Groundwater Level USGS 445319068560101 ME-PEW456 Kenduskeag Maine

End of Monitored Recovery Period 09302004

Regional Background Location i 226 miles from Pumping Locatio

lt

697

NOTES

1 Groundwater samples collected in 1999 were screened for five volatile organic compounds (VOCs) only N

tetrachloroethene (PCE) exceeded reporting limits MW-2030 082304 082304 082304 082304 u

2 Strike and Dip of likely or possible transmissive 30 45 55 85 feature within the packer interval from which the indicated sample was collected

MW-204D

PCE TOTAL VOCs

081904 30

220 2636

A

081904 46-50 540 6436by

081904 IT

260 3073

x

MW-105D

PCE TOTAL VOCs

111199 50-60 2100 2100

MW-106D

PCE TOTAL VOCs

111199 76-86

400 400

111199 137-147

1400 1400

111299 1355-1455

350 350

PCE TOTAL VOCs

44 84

64

MW-6SB

bulli

lt

gt-

170 234

35

I I i

140 192

^^52

^^52

130 183

52 - lt

S A 34

PW-207 082404 082404 082404 20 37

PCE 1300 TOTAL VOCs

17-Acre George West Property Boundary

MW-113D

PCE TOTAL VOCs

112299 46-56

350 350

112299 70-80 190 190

150

112299 105-115

129 129

112399 138-148

230 230

L e g e n d ( J New Monitoring Well-Summer

Site Property Boundary ^ P u m p i n g Well-Summer 2004

-xmdashxshy Source Area

bull0shy Monitoring Well shy Pre 2004 Angled Boring-Summer 2004

211941laquoipdwgTI-ELV21ig41paltker-data2

2004 PCE of Total

bull lt70 VOCs

M W - 1 14D ^ ^

Figure xx Packer Testing Results in

Vicinity of Source Area Hows Corner Superfund Site

Plymouth Maine ^ WOODARD ampCURRAN

^^^^^^^^^^m ampKm Engineering - Science bull Operations

c Northeast Geophysical Services Borehole Geophysical Log

MW-203 Date logged 081704 Plymouth Maine

I Flowmeter Measurements Tomporaturo(C) Acoustic Televiewer

7 5 8 8 5 9 95 Caliper (Inches) Resistance (Ohms) Spontaneous Potential (mVj Dip In Degrees PCE Total VOCs

3 0 2 0 8 0 laquodeg 4S 1000 1400 1800 2200 MO HO 1000 1200 MOO 0 laquo deg ugL ugL n 1 1 1 1 1 1 1 1 1 i 1 1 1 1 n 1 1 1 1 1 1 1 1 1 1 1 n I l l l l l l l n

Ambient Flowneter pumping Rowmeter 11 gpm 6

H

bull

magnetic 10 bull 10 bull - 10 - north - 1 0I

-

_

bullbullbull - bull

20 bull bull20 bull ^ ltr~mdash 01

I

4 ^

LOS7

^

44 84 I I

Xr - 2

lt ^ bull30 -_ _^O1J- 1 _ 050 30 - 3 0

0r - - 3

C -j [ bull bull bull | shy

-O8 H ~ 1 045 7

1 4040 - 40 - -40 r - 14gt 13

V1s -- -023 f 1022 1V 170 234 I

T lt bull B gtf 50^ J50 - - 5 0 - - 5 0

I eet be

lo

i 1

1 1

1

140 192 - - - -t shy

-mdashj bullpound 60 - $o - - 60 - -60

H i I c

bull024

ampbull

3 - T lt ftft rgt He

70 bull j 70 - - 70 - 7 0 -

in -j bullbull shy

-021 1 T 022

- Ton _ Ov

26

130 183 NF NF

90 -_ 90 - 7 90 - -90

-

ifi Jf

3J

^gt _ N F NF bull bull shy

| H100 - j 100 bullbull 100 - -100

1 1 1 1 1 1 1 ) | 1 f I 1 1 1 ) 0 20 40 60 80

flft mdash ftn - mdash rVt

30 4 g 0 20 40 60 Dip in Degrees bullbull

Likely or poss bleFluid Resistivity (ohmmeters) The dip direction-- indicated

^ t h e l i n e extending from t h

I Iransmissive zone circle The strike of the feature is 90 degrees from this

The acoustic televiewer graph displays the mostprominent features selectedffom the acoustic televiewer

R n r a h n l c D O t t n O I B

f i o n n h w c i r a l U K U p i i y SI Ud l

1 rn l_Og Packered Interval August 2004

E tog The location dip angle and dip direction of the sleeted M W - 2 0 3 Groundwater samples were collected by Woodard S Curran on H23120M features are approximate Refer to the televiewer og of His _ well for more precise detail Plymouth Maine Date logged 081704

I

1

Northeast Geophysical Services Borehole Geophysical Log MW-204 D a t e l o gge d 072604

Plymouth Maine

n 3

Flowrneter Measurements(in gpm)

Caliper (Inches)0 3 5 4 0

1 1 1 1 1 1 1 t 1 1 1 1 1 1Ambient Rowmeler pumping Flowmetsr 05gpm

Templaquorature (C) bull bull bull bull i

7 75 8 8S 9 Resistance (Ohms) Spontaneous Potential (mV)

4000 SOW 600 4M 0

Acoustic Televiewer (interpreted)

Dip in Degrees 0 20 4060 SO

at N

PCEugL

Total VOCs ugL

- -_ a

10-

shy 10 bull - 10 shymagnetic

north - 10

o o

bull 1

11

11

1 1

1 1

11 1

1 1

1 1

1 1

1 1

1 1

1 1

1 1

1 1 E 1

- L

3 7 2 0 2 0r bull 20 bull - shy

i S_ N F

bull30 bull 7 3 0 220 2636shy1^ J J 004

fI f V ^

40 shy 4 0 4 0 shy - 4 0rbull019 [_ 007 w8 - - shy5 c

bull

gt

Ia50i 540 6436

bull50 - - 50 - - 5 0

-QQ7 - bull - -t T

pound V gtk

B 6 0 - e o - 7 6 0 -60shyQ 1 1

Q -007 -004 bull1 mdash T - J ~

bull

- - shyT 70 -J c [TO- - 70 - 7 0-

V Y 1- -004 -003

mdash T -h - y - j i - - mdash 260 3073 - gt=7

80 -j NF bull80 - - 80 - - 8 0Jgt

bull i

i 1

i i

C- bull shy

90 shy

K

Jlt i90 90 shy - 9 0shy -

l

ii

I I I I

NF bull M J

I ^ ^ - ^ bull 1

mdash mdash - _

s -7 ^100shy

till

1 100 100- H - 1 0 0shy -1 x Likety or possible k ^ Iransmissive zonebull

1 i i i ii i i i | l l l l | l i l l 0 20 40 ED 80

1 -

3 0SOFluid Resistivity (ohmmeters)

Dip in Degrees The djp ^ ^ o n is indicated ty Ihe line extending from tha circle The strike of Ihe feature

19- 3U UIHJIW93 IolII l l l lraquo

bull

The acousfc televiewer graph displays the mostprominent features selected from the acoustic televiewer109 The location dip angle and dip direction of Ihe sleetedfeatures are approximate Refer to the televiewer log of thiswentormore precise detail

B o r e h o l e G e O D h V S I C a l LOO B W H U I B w c w p n y o i v a i w v yM W - 2 0 4

P l y m O U t n MaiDB

Packorod Interval August 2004Groundwater san-ples wampramp collected by Woodard a Curran on OMO23C4

Date logged 072604

C

I

E Northeast Geophysical Services Borehole Geophysical Log Date logged 072704

I MW-205

Plymouth Maine

Flowmeter Measurements Temperature (C) Acoustic Televiewer (In gpm) I ~l (Interpreted)

I 85 10 Caliper (inches) 95

Dip in D g r laquo Resistance (Ohms) Spo ontaneous Potential (mV PCE Total VOCs 3 0 16 4 0 4 5 ) 20 40 60 80 10 00 2000 30 00 4VJ 400 -3 laquo

i i i i 1 i i I i 11 4 0 D 1 I I ugL ugL

C h

iii Ambient Flowmetar pumping

Flowmeter 1 25 gprn

I bull$bull

i

I rmdash magnetic 1 north ^^^^ 1 VI f

10 ~ I C x 10 bull - 10 bullbull

4 5 6mdashmdash f 1000B 11448 noisy nodi a raquo ^

mdash 5rt mdashi mdash Oft pound) 1100B 12509

cjmdash1 007

-

i i i 1

en

8 B a B

30 mdash

-

40 shy

-mdash I -

50 -_

__NF lt005

- 30 - - 3 0 it 34V

MO P26 V S) 1300B 13776 _ N F NF

26

40 bull - 40 bull 7-40 gt J Vf1 cX

) -j -

_ N F NF 50 c bull - 50 ^ 7-50

i I

I

c

B pound 60 - 6 0 7 60 - 7-60 a i 1

_ N F NF i Si f f 70 -_ bull70 bull - 70 shyC I 9

-m bull - shyA

_ N F NF 80 80 -j bull80 bull - 80 - C- 33 34

bull

5-i r

i 1

J r

Ck

_ N F NF 9 0 90 - - 90 shy

i bullCshy

J rK bull

100 -j ^ Likely or possible bull100- - 100- I -100

transmissive zone bull - ^ bull shy] |

1 1 1 1 1 1 1 I 1 i i i 1 i i 1 1 0 20 40 SO SO 10 20 30 40 50 Dip in Degrees 30 4 0 Fluid Resistivity (ohmmeters) Thlaquo dip direction is indicated

by the line extern r g from the circle The strike of he feature is 90 degrees from ihis

The acoustic televiewer graph displays the most

I Borehole Geophysical Log Packered Interval August2004 prominent features selected from the acoustic televiewer

Groundwatcr samples were oollccled by Woodard amp Cufran orgt S172004 log The location dip angle and dip direction of ins slsctsd MW-205 features are approximate Refelt to the televiewer log of this wall for more precise detail Plymouth Maine Date logged 072704

I

C

I Northeast Geophysical Services Borehole Geophysical Log Date logged 072704

I MW-206

Plymouth Maine

Flowmetor Measurements Temperature (C) Acoustic Televiewer | I r T i i i i i i i i i i i i i i r I |(in gpm) (Interpreted)

I 75 8 flS 9 95

Caliper (inches) Resistance (Ohms) Spontaneous Potential (mV) Dip In Degress PCE Total VOCs 30 35 40 4 5 0 20 40 M 90 4500 5500 6500 ugL ugL I i i

I I

- 1 0

I - 2 0

I 2900B 32401

i i L

E 0

i 6300B 68901

i I 0 20 40 SO 80

20 30 40 50 Dip in Dlaquogralaquos

amp 4 a Fluid Resistivity (ohrnmeters) The dip dirertion is indicated Likely or possible by iho line extending from the transmissive zone circle The striKe of the feature

is 90 degrees from tNs

Borehole Geophysical Log Packered Interval August 2004

E amples were collected by Woodard amp Cunan oo SM82004 log Thraquo location 4p angle and dip direction of the sloeled MW-206 feature are approximate Refer to the televiewer 109 of this well for more precise detail Plymouth Maine Date logged 072704

C

I Northeast Geophysical Services Borehole Geophysical Log

Date logged 082304 PW-207

I Plymouth Maine

Fiowmeter Measurements Temperature (C) Acoustic Televiewer

I (in gpm) (interpreted)

75 8 85 9 95 Caliper (inches) Resistance f0tims) Spontaneous Potential (mV) Dip in Degrees PCE Total VOCs

55 60 0 20 40 SO 80 ugL ugL I I I I I I I

Ambienl Fiowmeter pumping Flewmater

magnetic - 10 - - 1 0

north

i - 20 - - 2 0

1300 1410

i - 30 - - 3 0

i tf

5400 5802 - 40 - - 4 0

B - 50 - - 5 0

I 18000 19234

- 60 - - 6 0

I 12000 13085

- 70 - - 7 0

- 8 0

i - 9 0 19000 20354

G - 100- -100

I 110 110 bull110

0 20 40 60 SO 10 20 30 Dip m Degrees

Fluid Resistivity (ohmmeters) I 50

The dip direction is indicated by ihe line extending from the circle The strike of the fealure is 90 degrees from this

Borehole Geophysical Log

G Packorod Interval August 20(M log The location dip angle and dip dirlaquocton or the sleeted Groundaier samplss were ooliecled by Woodard i Curran on ampt24f2ltXM PW-207 failures are approximate Reter to the televiewer log of this wlaquoll for more precise detail PlyPIOUth Maine Date logged 082304

I

Table XX Packer Permeability and Packer Sampling Results for Potential Fracture Intervals

1

WellID MW-101D MW-101D MW-101D MW-101D MW-101D MW-101D MW-101D MW-101D MW-101D MW-101D MW-I01D MW-101D MW-101D MW-102D MW-102D MW-I02D MW-102D MW102D MW-102D MW-102D MW-102D MW-102D MW-I02D MW-102D MW-102D MW-102D MW-103D MW-103D MW-103D MW-103D MW-I03D MW-103D MW-103D MW-103D MW-103D MW-103D MW-103D MW-103D MW-I03D MW-104D MW-104D MW-104D MW-104D MW-I04D MW-104D MW-104D MW-104D MW-104D MW-104D MW-104D MW-105D MW-105D MW106D MW-106D MW-106D MW-107D MW-107D

1999 Drilling Program

Hows Corner Superfund Site Plymouth Maine

Potential Fracture Top Of Bottom 6 Depth to lt Topof i Interval from Packer Packer Middle of Elevation Hydraulic bull PCE

GS ELEV 1 Rock Drilling Interval Interval Interval of Interval Conductivity Concentration (ft msl) (ft msl) TEST (ftbgs) (ftbgs) r(ftbgs) ( f t b (ft mil) (cmsec) (raquogL)

4339 4329 13 28-29 33-3537-39 271 376 324 4016 OOOE+00 4339 12 37-3444-46 380 485 433 3907 157E-04 4339 11 488 593 541 3799 132E-04 4339 10 60-61 578 683 631 3709 OOOE+00 4339 9 678 783 731 3609 I79E-05 4339 8 778 883 831 3509 106E-05 4339 7 880 985 933 3407 243E-05 4339 6 990 1095 1043 3297 339E-06 4339 5 1090 1195 1143 3197 OOOE+00 4339 4 1190 1295 1243 3097 OOOE+00 4339 3 1365-1375 1290 1395 1343 2997 OOOE+00 4339 2 147-157 1390 1495 1443 2897 580E-05 4339 1 147-157 1470 1575 1523 2817 741E-05 43161 43061 13 166 271 219 4098 333E-04 43161 12 30-3136-40 260 365 313 4004 I54E-05 43161 11 36-4041-43 362 467 415 3902 548E-05 43161 10 470 575 523 3794 598E-05 43161 9 570 675 623 3694 197FOS 43161 8 670 775 723 3594 OOOE+00 43161 7 770 875 823 3494 891 E-05 43161 6 83-94 870 975 923 3394 139E-05 43161 5 970 1075 1023 3294 123E-04 43161 4 1070 1175 1123 3194 526E-06 43161 3 1170 1275 1223 3094 138E-05 43161 2 1270 1375 1323 2994 671E-06 43161 1 1370 1475 1423 2894 OOOE+00 42997 42497 13 18-19 170 275 223 4077 OOOE+00 42997 12 260 365 313 3987 766E-05 42997 11 360 465 413 3887 727E-05 42997 10 460 565 513 3787 192E-05 42997 9 560 665 613 3687 752E-05 42997 8 660 765 713 3587 778E-05 42997 7 85-86 763 868 816 3484 260E-05 42997 6 860 965 913 3387 289E-05 42997 5 102-103 960 1065 1013 3287 102E-04 42997 4 1060 1165 1113 3187 522E-06 42997 3 1160 1265 1213 3087 520E-06 42997 2 129-130 1260 1365 1313 2987 960E-04 42997 1 1360 1465 1413 2887 OOOE+00 43372 42922 11 35-37 42-45 350 455 403 3935 684E-04 43372 10 460 565 513 3825 500E-05 43372 9 560 665 613 3725 106E-05 43372 8 72-74 660 765 713 3625 204E-05 43372 7 760 865 813 3525 872E-06 43372 6 860 965 913 3425 467E-06 43372 5 960 1065 1013 3325 200E-05 43372 4 1060 1165 1113 3225 354E-05 43372 3 125-130 1160 1265 1213 3125 157E-05 43372 2 125-130 1260 1365 1313 3025 337E-04 43372 1 1365 1465 1415 2922 689E-06 43052 43002 2 54-58 490 595 543 3763 124E-05 2100 43052 1 139-140 145-146 1367 1472 1420 2886 154E-04 1400 43291 4391 3 bullI133 260 365 313 4017 439F06 43291 2 77-78 760 865 813 3517 230E-03 400 43291 1 143-144 1355 1460 1408 2922 971E-06 350

29958 27258 4 450 555 503 2493 OOOE+00 (21)A 29958 3 103-105 1000 1105 1053 1943 752E-04 (063)A

Table XX Packer Permeability and Packer Sampling Results for Potential Fracture Intervals

1999 Drilling Program

Hows Corner Supcrfund Site Plymouth Maine

gtbull i Potential Fracture Top _OfBot Bottom of Depth to ltbull Top of Interval from f Packer Packer Middle Of

GS ELEV lt Hock Drilling interval Interval Interval WeD ID ft msl) (ft msl) TEST (ftbgs) ltft$gs) (ftbgs) (ftbgs)

MW-107D 29958 2 128-130 1200 1305 1253

MW-107D 29958 1 139-141 1350 1455 1403

MW-108D 31904 31104 6 35-36 300 405 353 MW-108D 31904 5 60-62 550 655 603

MW-108D 31904 4 80-83 750 855 803

MW-108D 31904 3 118-119 123-124 1150 1255 1203

MW-108D 31904 2 147-149 1440 1545 1493

MW-108D 31904 1 1700 1805 1753

MW-110D 40576 40426 2 21-31 210 315 263 MW-110D 40576 1 148-154 1460 1565 1513 MW-I11D 40519 4 70-71 650 755 703

MW-111D 40519 3 79-82 84-86 780 885 833 MW-I11D 40519 2 97-102 950 1055 1003 MW-111D 40519 1 1370 1475 1423

MW-112D 3027 2942 4 42-52 420 525 473 MW-112D 3027 3 850 955 903 MW112D 3027 2 1100 1205 1153 MW-112D 3027 1 135-136 140-141 1340 1445 1393

MW-113D 43085 43085 5 250 355 303 MW-I13D 43085 4 47-49 460 565 513 MW-113D 43085 3 73-74 700 805 753 MW-113D 43085 2 1050 1155 1103 MW-113D 43085 1 1380 1485 1433

MW-114D 42394 41594 4 48-49 450 555 503 MW-114D 42394 3 79-81 740 845 793 MW-114D 42394 2 121-129 1250 1355 1303 MW-114D 42394 1 134-142 1350 1455 1403

MW-115D 4035 4035 4 300 405 353 MW-1I5D 4035 3 70-71 650 755 703 MW-115D 4035 2 1150 1255 1203 MW-115D 4035 1 1400 1505 1453

LOT-28W 382 7 450 555 503 LOT28W 382 6 550 655 603 LOT-28W 382 5 650 755 703 LOT28W 382 4 750 855 803 LOT-28W 382 3 850 955 903 LOT-28W 382 2 950 1055 1003 LOT-28W 382 1 1055 1155 1105

NOTES cmsec = centimeters per second ft bgs = leet below ground surface It msl = feet below mean sea level lt = not detected at indicated reporting limil A = detected below laboratory PQL ( ) = detected below reporting limits

Elevation of Interval

(ft nisi) 174

159

283gt 2588

2388

1988

1698

1438

3795 2545 3349 3219 3049 2629

2555 2125 1875 1635

4006 3796 3556 3206 2876

3737 3447 2937 2837

3683 3333 2833 2583

3318 3218 3118 3018 2918 2818 2715

Hydraulic Conductivity

(cmsec)

323E-05

208E-05

471E-03

471E-03

624E-05

3I6E-05

264E-05

261 E-05

OOOE+00 200E-04 953E-05 OOOE+00 OOOE+00 212E-05

361 E-05 410E-06 2gQE06 292E-05

786E-05 124E-05 151 E-05 822E-06 82IE-06

858E-05 I69E-05 352E-03 866E-05

223E-05 394E-06 122E-05 525E-06

831 E-05 182F-05 L62E-05 129E-05 190E-05 890E-04 981 E-04

PCEraquo Concentration

(ugL)

lt5

(14A)

98 11

15

22

11

30

200 (62)A

110 210 300 240

(44)A (23)A

5

350 190 129 230

2200 1900 2600 2600

(17)A (16)A (19)A

96

Table XX Packer Permeability and Packer Sampling Results for Potential Fracture Intervals

2004 Drilling Program

Hows Corner Superfund Site Plymouth Maine

Top of Bottom of Depth to Midpoint

t K

ELEV (ft Potential Transmissive Zones Packer Interval

Packer Interval

Middle of Interval

Elevation of interval

Hydraulic Conductivity

PCE Concentration

Well ID msl) TESTr (ft bgs)- (ftbgs) (ftbgs) (ftbgs) (ft msl) (cmsec) (ogt) MW-203D 43227 4 277279 24 32 28 4043 667E-05 44

3 408415420 39 49 44 3883 593E-05 170 2 526 530 49 57 53 3793 101E-04 140 I 828830842 80 88 84 3483 701E-05 130

MW-204D 43262 5 295 300 26 34 30 4023 902E-05 220 4 463496513516 45 53 49 3833 119E-04 540 3 681685688 63 71 67 3653 OOOE+00 2 758 76 2 71 79 75 3573 309E-05 260 I 88 96 92 3403 OOOE+00

MW-205 42389 3 164 166 168 15 20 175 4148 OOOE+00 1000B 2 302305312 30 35 325 3998 107E-04 1300B 1 40 45 425 3898 OOOE+00

MW-206D 43007 5 17 72 195 4128 291E-05 4 296 302 307 29 34 315 4008 940E-05 2900B 3 522 52 57 545 3778 944E-07 2 656 64 69 665 3658 353E-06 1 92392793 4939 91 96 935 3388 614E-05 6300B

PW-207 43477 5 184622162819 18 29 235 4088 209E-05 1300 4 3508 32 43 375 3948 568E-06 5400 3 53325341542154325559 50 61 555 3768 821E-05 18000

6359 61 72 665 3658 866E-06 12000 1 8685 84 89 865 3458 213E-05 19000

NOTES cmsec = centimeters per second ft bgs = feet below ground surface ft msl = feet above mean sea level B = detected in lab blank

Table XX Orientation Permeability and Groundwater Sampling Results for Transmissive Features

2004 Drilling Program

Hows Corner Superfund Site Plymouth Maine

Borehole Geophisical Feature depth Dip True Dip True Transmissive Log Feature (Feet) Degrees Azimuth Strike bullvgt(Ltk|iy^

Number v Tosftble) v MW-203 5 277 64 337 67 Likely

6 279 59 11 281 Likely 8 352 14 177 87 Likely 11 381 46 96 6 Possible 12 408 35 271 1 Possible 14 415 57 250 340 Possible 15 420 58 202 292 Likely 18 526 52 75 345 Likely 19 530 52 82 352 Likely 28 828 48 75 345 Likely 29 830 52 17 287 Likely 30 830 56 233 323 Possible 31 842 50 130 40 Likely

MW-204 4 295 15 147 57 Likely 5 300 43 91 1 Likely 11 439 31 80 350 Possible 12 440 46 219 309 Possible 14 463 50 358 88 Likely 15 496 34 198 288 Likely 16 513 54 17 287 Likely 17 516 33 14 284 Likely 25 681 39 359 89 Possible 26 685 22 45 315 Possible 27 688 35 73 343 Possible 32 758 45 236 326 Likely 33 762 46 306 36 Likely

MW-205 5 164 69 106 16 Possible 6 166 78 165 75 Possible 7 168 82 115 25 Possible 8 168 68 116 26 Possible 12 215 46 222 312 Possible 13 217 75 62 332 Possible 14 219 29 32 302 Possible 16 237 69 250 340 Possible 17 256 73 353 83 Possible 18 272 44 202 292 Possible 21 299 37 196 286 Possible 22 302 31 206 296 Possible 23 305 59 48 318 Likely 24 312 63 42 312 Likely

MW-206 1 264 37 181 271 Likely 2 296 69 217 307 Likely 3 302 66 233 323 Likely 4 307 64 224 314 Likely 8 342 62 259 349 Likely

jjHydraulic GoiDanctilyity j(cmsecjw

667 E-05

593 E-05

101 P04

710 E-05

902 E-05

119 E-04

0

309 E-05

0

107 E-04

94 E-05

PCE (ugL)

44

170

140

130

220

540

260

IOOOB

1100B

1300B

2900B

STotal vVoCsv tig1)

84

234

192

183

2636

6436

3073

11448

12509

13776

32401

PCEyo dfCTotaf

52

73

73

7 1

83

84

85

87

88

94

90

Table XX Orientation Permeability and Groundwater Sampling Results for Transmissive Features

2004 Drilling Program

Hows Corner Superfund Site Plymouth Maine

Borehole Geophisical Feature deptt raquoip True pip True Transraissive Log Feature (Feet) shy Degrees Azimuth Strike (tikely

Number raquo Possible) 22 522 57 54 324 Possible 25 656 40 82 352 Possible 32 871 59 151 61 Possible 33 883 53 185 275 Possible 34 895 7 175 85 Likely 35 899 53 90 0 Likely 36 902 49 184 274 Likely 37 923 9 175 85 Likely 38 927 42 206 296 Likely 39 934 48 167 77 Likely 40 939 26 180 90 Likely

PW-207 1 1846 33 167 77 Likely 4 2216 49 289 19 Possible 7 2819 59 265 355 Possible 11 3508 55 189 279 Possible 18 5332 43 305 35 Likely 19 5341 51 30 300 Likely 20 5421 20 254 344 Likely 21 5432 39 301 31 Likely 23 5559 52 302 32 Likely 25 6359 24 182 272 Possible 29 8049 77 231 321 Possible 30 8685 78 38 308 Likely 32 9334 29 194 284 Likely

NOTES

B = detected in lab blank

Hydraulic Conductivity

(cmsee) 944 E-07 353 E-06

614 E-05

209 E-05

568 E-06

821 E-05

866 E-06

213 E-05

bulltCE (ugL)

6300B

1300

5400

18000

12000

19000

Total VOCs (ug1)

68901

1410

5802

19234

13085

20354

PCE of Total VOCs

9 1

92

93

94

92

93

Response to EPA-DEP Comment 3 Dated March 312005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

lit

EPA-DEP Comment 3

Comment 3 The reported f values and resultant Kd values There remains doubt that the values used in the flushing model accurately reflect the propensity for PCE to sorb to the bedrock The ^ values presented in Appendix B may be unrealistically high because the bedrock samples may have contained organic carbon that was unavailable for sorption The reported f values are only qualitative estimates of the organic carbon content of the bedrock samples The Walkley and Black organic carbon measurement method is quick and simple but the results obtained cannot be considered quantitative because it requires a correction factor which often results in erroneous values it assumes the organic carbon has an average valence of zero oxidizable and reducible constituents such as chloride ferrous iron and manganese oxides interfere with the results and the errors introduced by interference are potentially greater when the organic carbon content is low at low f values it is not clear that organic carbon is controlling PCE sorption (Schwarzenbach and Westall 1981 Mackay et al 1986 Fetter 1999)

In order to derive a Kd-based retardation factor that is reasonable given the reported f values and the rapid advance of the PCE plume described on pages 4-11 and 4-12 the flushing model requires a bulk density to porosity ratio that is roughly two orders of magnitude higher than the actual ratio for the Hows Corner bedrock (page 4-4) This apparent discrepancy needs to be addressed

Response This comment raises several concerns about the collection and analysis of samples for fraction of organic carbon (f^) the quality of the resulting data and the implications of the use of those data for estimation of the retardation of groundwater contaminant movement Results of bedrock analysis for f were proposed in the TI Evaluation Work Plan for use in conjunction with groundwater contaminant concentrations and aquifer information to estimate cleanup times using the Batch Flushing model It is important to use accurate f values from representative bedrock in the Batch Flushing model in order to obtain reasonable estimates of the remedial time frame Because of the importance of accurate and representative results the TI Investigation field program was designed and conducted both to collect samples representative of the rock volume most likely to be in contact with contaminated groundwater and to analyze them using an appropriate refereed analytical method Five potential methods for evaluating f were identified Of the five methods the Walkey-Black method was selected because it has minimal method interferences and a sufficiently low detection limit as well as a long history of use in agronomy and contamination studies The PRP Group is pleased with the quality of the data obtained from the bedrock samples as represented by their precision and reproducibility

The first part of this comment relates to the determination of fraction of organic carbon (f^) values The several subparts of the first paragraph are addressed individually in items 1 through 5 below The second part of the comment regarding the resultant distribution coefficient (Kd) values is addressed separately as item 6 below

1 There remains doubt that the values used in the flushing model accurately reflect the propensity for PCE to sorb to the bedrock

bull The rock core samples used for f (gocg) analysis were from core immediately adjacent to fractures These rock core samples included the fracture surfaces themselves and rock core extending back less than 1 cm from the fractures Therefore the foe data reported in the TI Evaluation represents the f of bedrock through which groundwater will travel and to which PCE will adsorb Based on the careful selection of sample locations and the

Response to EPA Comment 3 050205doc 1 of 11 Woodard amp Curran (211941)

number of samples collected we are confident that the measured f values are representative of the f at points of contact for PCE with the bedrock it is these f values that determine the propensity of PCE to sorb to the bedrock

bull The samples of rock core collected for analysis of f originated from 19 different locations varying in depth from 11 to 90 feet Therefore it is very unlikely that the rock core samples were contaminated with extraneous organic carbon from above ground

2 The foc values presented in Appendix B may be unrealistically high because the bedrock samples may have contained organic carbon that was unavailable for sorption

bull As noted in response 1 the f data reported in Appendix B represents organic carbon primarily associated with the surface of fractures in the bedrock through which groundwater is most likely to travel Therefore it is this organic carbon that the contaminants in the groundwater will come in contact with and adsorb to in the fractured rock at the site

bull The chemical oxidation agents used in the Walkey-Black method oxidize the easily oxidizable organic carbon in the medium and the foe is calculated from the quantity of the agent consumed Therefore it is unlikely that the analysis of the bedrock samples measured organic carbon that was unavailable for sorption

3 The reported foc values are only qualitative estimates of the organic carbon content of the bedrock samples

bull The reported f values are accurate quantitative results Schumachers review of Methods for the determination of total organic carbon (TOC) in soils and sediments (NCEA-C-1282 EMASC-001 April 2002) identifies the Walkley-Black method which was used to analyze the reported foc values as the reference method for comparison to other methods for analyzing total organic carbon

bull Schumacher also points out that if anything the WalkJey-Black method may underestimate the total organic carbon in a sample due to possible incomplete oxidation of organic carbon Usually the incomplete oxidation of total organic carbon in environmental samples is corrected for by multiplying the measured foe by 130 (Walkley amp Black 1934 Schulte 1995)

bull When the f data in the TI Evaluation Report (WampC 2005) Appendix B (attached) are analyzed statistically the standard deviation of the f for the 19 samples analyzed is 174 of the average f Given this standard deviation the 95 confidence interval for this data ranged from a low of 000123 gocg to a high of 000253 gocgm

The labs Method of Detection Limit (MDL) for the f measured using the Walkley-Black method is 00001 gocg Therefore the average (000188 gocg) the mean (000185 gocg) and geometric mean (000187 gocg) of the f values for the rock core at Hows Corner are all statistically significantly greater than the MDL of the Walkley-Black method

In addition to the aforementioned statistical analysis of the foe data triplicate samples (n = 3) from the same rock core (including one sample from the 19 rock core samples) were

Response to EPA Comment 3 050205doc 2 of Woodard amp Curran (211941)

analyzed for their f to determine the repeatability of the Walkley-Black method The average the mean and the geometric mean of the f values of these replicate samples was 000162 gocg 000150 gocg and 000159 gocgm respectively The standard deviation of these measurements was 000039 gocg

4 The Walkley and Black organic carbon measurement method is quick and simple but the results obtained cannot be considered quantitative because it requires a correction factor which often results in erroneous values it assumes the organic carbon has an average valence of zero oxidizable and reducible constituents such as chloride ferrous iron and manganese oxides interfere with the results and the errors introduced by interference are potentially greater when the organic carbon content is low at low foc values it is not clear that organic carbon is controlling PCE sorption (Schwarzenbach and Westall 1981 Mackay et al 1986 Fetter 1999)

bull Schumachers review (NCEA-C-1282 EMASC-001 April 2002) of the Walkley-Black method identifies several potential problems with this analytical method that could occur if the analytical lab is not familiar with the nuances of the chemistry associated with this method Interestingly Schumachers review neglected one of the more important analytical steps required to avoid errors in quantifying f in samples where there might beNAPL

It is absolutely critical to eliminate any NAPL from rock core samples prior to using the Walkley-Black method to measure foe in such samples This was done by the lab (PTS Laboratories) that measured the foe in the rock core samples from Hows Corner The lab used the Dean-Stark method (solvent extraction) to remove all hydrocarbons (including PCE and other NAPLs) from the sample (PTS Laboratories) This extraction method does not interfere with the subsequent analysis of the natural organic carbon associated with the rock core

Subsequently the samples were dried at 150degC to a constant weight (normally 16 hours) This latter step oxidizes all inorganic minerals including ferrous bearing minerals to ferric oxides and precludes their interference during the oxidation of the samples with chromic acid This procedure completely eliminates any positive bias in the reported foc

data that might have occurred due to the presence of ferrous ions and other reduced minerals

bull As noted in Response 3 the incomplete oxidation of total organic carbon results in an underestimate of the f and is corrected for by multiplying the f by a correction factor of 130 (Walkley amp Black 1934 Schulte 1995) The fx data reported in the TI Evaluation was corrected accordingly by using this correction factor

bull Excess chloride (Cl~) in percent weight quantities as found in saline soils may interfere with the quantitative titration of reduced chromium (Walkley 1947) However given that the primary rock type at the Hows Corner site is phyllite it is highly unlikely that there was sufficient chloride in the rock core samples for this to occur

bull Manganese oxides may also interfere with the analysis of f through competing with the dichromate ion for any oxidizable carbon (Walkley 1947) However in such cases the reported f would be an underestimate of the f present in the rock core Walkley (1947)

Response to EPA Comment 3 050205doc 3 of 11 Woodard amp Curran (211941)

4

reported that in the case where the ratio of MnO2 to carbon is 85 to 1 the error in the carbon determinations would only be 0 to 6 percent

It may also be useful to compare the analysis of total organic carbon in a geologic matrix that contains high levels of manganese using EPA method 9060 to the Walkley-Black method Table 1 summarizes data provided by one of the PRPs that compares the analysis of total organic carbon in a geologic matrix that contains approximately 02 wgt manganese (approximately 03 wgt manganese oxide)

Table 1 Comparison of total organic carbon measured using the EPA- 9060 method and the Walkley-Black method

Laboratory EPA-9060 Method Walkley-Black Method A Ave 00226 gocg Not analyzed

Stdev 000251 gocg n = 5

B Ave 002219 gocg Ave 002050 gocg Stdev = 000316 gocg Stdev =000971 gocg

n= 10 n = 10

The similarity in the total organic carbon concentrations measured by these two different methods provides further confidence that the Walkley-Black method is a viable method for analysis of total organic carbon in the presence of manganese equivalent to at least 10 by weight of the total organic carbon

5 The Walkley and Black organic carbon measurement at lowf^ values it is not clear that organic carbon is controlling PCE sorption (Schwarzenbach and Westall 1981 Mackay et al 1986 Fetter 1999)

bull Schwarzenbach and Westalls (1981) paper states that f values of less than 0001 gocg should not be used in combination with Kow (octanol-water partition coefficients) values to calculate K^ values (solid phase partition coefficients) values for a specific contaminant It should be noted that the TI Evaluation did not use the f data to calculate the KQC from the Kow Instead as requested by the EPA the measured KOC value for PCE was used to calculate the retardation factor for this contaminant

bull Schwarzenbach et al (2003) stated more recently that Even at very low f values (ie foe = 0001 kgoc - kg1 solid) sorption to the organic components of a natural sorbent may still be the dominant mechanism in defining the adsorption of organic compounds to geological matrices

bull In 1985 M Piwoni from the US EPA Robert S Kerr Environmental Research Laboratory published a paper (Banerjee et al 1985) that showed that for very hydrophobic molecules TOC content of the sorbent will control sorption down to levels of organic carbon that defy quantitation Contaminants such as the PCE found in the groundwater at Hows Corner are in this category of compounds

Given the aforementioned reasons the f values reported in the TI Evaluation are accurate within the noted statistical limitations and will have a predictable impact upon the retardation of PCE during groundwater transport

Response to EPA Comment 3 050205doc 4 of 11 Woodard amp Curran (211941)

6 In order to derive a Kd-based retardation factor that is reasonable given the reported foc

values and the rapid advance of the PCE plume described on pages 4-11 and 4-12 the flushing model requires a bulk density to porosity ratio that is roughly two orders of magnitude higher than the actual ratio for the Hows Comer bedrock (page 4-4) This apparent discrepancy needs to be addressed

The apparent discrepancy of bulk density to porosity ratios is most likely due to the fact that the Batch Flushing Model was originally developed for a porous medium and is not directly applicable to fractured bedrock As stated in Appendix C (page C-4) of the Draft Technical Impracticability Evaluation Report in order to use the Batch Flushing Model to describe the transport of contaminated groundwater in fractured bedrock where the matrix porosity is insignificant it is more appropriate to use a fracture surface area to void space ratio to calculate the retardation factor (R) than a bulk density to porosity ratio (Freeze amp Cherry 1979)

Since it is impractical to determine the actual surface area to which contaminants can adsorb the Batch Flushing Model was used with two simplifying assumptions bull The Kd was calculated from the f and the K^ bull The bulk density to porosity ratio term in the Batch Flushing Model was constrained to range

from 4 to 10 the typical range of such ratios in porous media (Freeze amp Cherry 1979)

If one uses site specific bedrock bulk density and porosity values the bulk density to porosity ratio is several orders of magnitude greater (specifically 273 gcc bullbull 000165 (dimensionless) = 1654 gcc) than the range of ratios of 4 to 10 used in the Batch Flushing Model in the Draft Technical Impracticability Evaluation Report Constraining the bulk density to porosity ratio within the range of ratios of 4 to 10 results in significantly lower R value than would be obtained using specific bedrock bulk density and porosity values

In summary in bedrock where fractures are the primary porosity the bulk density to porosity ratio can vary considerably and will be a function of the number of fractures and the fracture aperture The calculated bulk density to porosity ratio will be inversely proportional to the porosity This means that in fractured rock with limited fracturing and smaller porosity the calculated bulk density to porosity ratio is greater and will result in a greater calculated retardation factor than in bedrock with more extensive fracturing and greater porosity Consequently the calculated retardation factor will be greater for bedrock with less surface area available for sorption than bedrock with greater surface area for sorption This is contrary to what actually occurs

4 Response to EPA Comment 3 050205doc 5 of 11 Woodard amp Curran (211941)

m

REFERENCES

Banerjee P MD Piwoni K Ebeid (1985) Sorption of organic contaminants to a low carbon subsurface core Chemosphere _14 1057-1067

Freeze RA JA Cherry (1979) Groundwater Prentice Hall Englewood Cliffs NJ pg 604

PTS Laboratories wwwptsgeolabscompdf files3TOCnotepdf

Schulte EE (1995) Recommended soil organic matter tests in Recommended Soil Testing Procedures for the Northeastern United States Northeastern Regional Publication No 493 Chapter 8

Schwarzenbach RP J Westall (1981) Transport of nonpolar organic compounds from surface water to groundwater Laboratory sorption studies Environ Sci Tech 15 1360-1367

Schwarzenbach RP PM Gschwend DM Imboden (2003) Environmental Organic Chemistry Wiley-Interscience pg 292 408 amp 412

Walkley A LA Black (1934) An examination of the Degtjareff method for determining soil organic matter and a proposed modification of the chromic acid titration method Soil Science 37 29-38

Walkley A (1947) A critical examination of a rapid method for determining organic carbon in soils - effect of variations in digestion conditions and of inorganic soil constituents Soil Science 63251-264

Woodard amp Curran Inc (WampC) 2005 Draft Technical Impracticability Evaluation Hows Corner Superfund Site Plymouth Maine January 2005

Response to EPA Comment 3 050205doc 6 of Woodard amp Curran (211941)

LIST OF ATTACHMENTS (Response to Comment 3)

Appendix B to Draft Technical Impracticability Evaluation Measurement of foe at Hows Corner (4 pages)

m

Response to EPA Comment 3 050205doc 7 of 11 Woodard amp Curran (211941)

Appendix B Measurement of foe of Rock Core at Hows Corner

There are two general approaches to measure the fraction of organic carbon (foe) in rock cores

bull Measurement of weight loss by ignition of organic matter bull Chemical oxidization of organic carbon to carbon dioxide and either

subsequent quantification of the oxidant used for the reaction or quantification of the carbon dioxide produced during this oxidation process

The weight loss method is subject to errors caused by volatilization of substances other than organic materials such as water hydroxides and mineral carbonates Quantification of foe by the weight loss method is particularly sensitive to the presence of carbonates in rock cores There are however weight loss methods that are designed to differentiate between organic carbon and the aforementioned interfering materials but they require considerable care and are less accurate at low foe values Hence the weight loss method was not well suited for measuring the foe of the rock core from Hows Corner

The chemical oxidation of organic carbon is much better suited for quantifying organic carbon in rock cores such as those from Hows Corner This method uses a strong chemical oxidant to oxidize organic carbon to carbon dioxide and then measures either the chemical oxidant used to oxidize the organic carbon or the quantity of carbon dioxide produced In addition this general approach is not subject to interference by volatilization of other constituents of the rock core

There are at least two such chemical oxidation methods

bull The method of Baccini which was described by Schwarzenbach amp Westall (1981) first acidifies the sample to eliminate interference by carbonates Then a strong oxidant is used to chemically oxidize the organic carbon to carbon dioxide The resulting carbon dioxide is subsequently reduced to methane and quantified using a flame ionization detector Unfortunately this method has not been described in detail in a referred journal Hence it is would not have been appropriate to use to characterize the foe in the Hows Corner rock core

bull The more commonly used method to quantify foe in rock core is the Walkley-Black method (1934) This method is preferred for RBCA and DODDOE projects and by the oil industry

The Walkley-Black method uses an excess of chromic acid to oxidize (digest) organic matter to carbon dioxide The remaining chromic acid that was not consumed during the oxidation of the organic carbon is then quantified by titration with ferrous sulfate The difference in chromic acid prior to and after the oxidation of the organic carbon represents the total chromic acid used to oxidize

Hows Corner TI Evaluation Page 1 January 13 2005 Appendix B

the organic carbon in the sample The latter can be calculated using the chemical stoichiometry of the reaction

The Walkley-Black method is very accurate for samples that contain less than 2 organic carbon matter The minimum detection limit (MDL) for the Walkley-Black method is 100 mgkg or an foe of 0001

Given the rock core at Hows Corner was expected to contain less than 2 organic carbon the Walkley-Black method was used to measure the foe from 19 different rock core samples collected from varying depths ranging from 11 to 90 feet

Table 1 provides a statistical summary of the aforementioned data

Table 1 Statistical summary of foe data from rock cores collected at varying depths

Statistical Parameter Calculated Value foe Minimum Detection Limit (MDL) 00010 Number of samples analyzed (n) 19 Average foe 00019 Median foe 00019 Geometric Mean foe 00019 Standard deviation of foe measurements 000033 Relative standard deviation 174 -+ 95 Confidence intervals 00012 to 00025

The data in Table 1 shows the following

bull The foe from the Hows Corner rock cores are statistically greater than the MDL of the Walkley-Black analytical method

bull The average and median values for the foe of the Hows Corner rock cores from varying depths are nearly identical indicating that there is little variability in the foe values in the source zone at the site

bull The standard deviation of these measurements is 000033 which is 174 of the average foe

bull The 95 confidence intervals of the foe of the rock core at Hows Corner are 00012 to 00025

The foe was also analyzed from three separate samples taken from the same rock core at a depth of 55 feet (Only one of these samples was included in the data summarized in Table 1) Table 2 shows the statistical repeatability of this type of analysis

Hows Corner TI Evaluation Page 2 January 13 2005 Appendix B

Table 2 Repeatability of analysis of foe from one rock core at 55 feet in depth

Statistical Parameter Calculated Value Number of samples analyzed (n) 3 Average foe 00016 Median foe 00015 Geometric Mean foe 00016 Standard deviation of foe measurements 000039 Relative standard deviation 240 -+ 95 Confidence intervals 00008 to 00024

The data in Table 2 shows the following

bull The percent relative standard deviation of these three analyses of foe from the same rock core at Hows Corner is 24

bull The 95 confidence interval of the foes measured in this particular rock core at Hows Conrer is 00008 to 00024

These results show that there is good repeatability in using the Walkley-Black method for analysis of the foe in the rock core at Hows Corner

References Schwarzenbach amp Westall (1981) Transport of nonpolar organic compounds from surface water to groundwater Laboratory sorption studies Environ Sci Tech 15 1360-1367

Walkley A I A Black (1934) An examination of Degtjareff method for determining soil organic matter and a proposed modification of the chromic acid titration method Soil Sci 37 29-37

Hows Corner Tl Evaluation Page S January 13 2005 Appendix B

Woodard and Curran PTS Laboratories PTS File No 34618

ORGANIC CARBON DATA (METHODOLOGY WALKLEY-BLACK)

PROJECT NAME PROJECT NO

SAMPLE ID

203-chip-13 203-chip-23 203-chip-27 203-chip-38 203-chip-42 203-chip-47 203-chip-52 203-chip-58 203-chip-69 203-chip-82 207-chip-11 207-chip-19 207-chip-24 207-chip-29 207-chip-35 207-chip-45 207-chip-55 207-chip-87 207-chip-90

207-chip-55 55-MS

55-MSMSD

Hows Corner NA

DEPTH ft

13 23 27 38 42 47 52 58 69 82 11 19 24 29 35 45 55 87 90

55 NA NA

MATRIX

Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip

Average Median

Geometric Mean Standard Deviation Relative Std Dev

+- 95 Confidence Interval n

Rock Chip Rock Chip Rock Chip

Average Median

Geometric Mean Standard Deviation Relative Std Dev

+- 95 Confidence Interval n

FRACTION ORGANIC CARBON

(gg)

170E-03 185E-03 185E-03 170E-03 240E-03 190E-03 230E-03 180E-03 170E-03 115E-03 195E-03 220E-03 220E-03 235E-03 135E-03 190E-03 205E-03 175E-03 160E-03

188E-03 185E-03 185E-03 327E-04

1739 123E-03 to

19

205E-03 130E-03 150E-03

162E-03 150E-03 159E-03 388E-04

2402 840E-04 to

3

2532E-03

2393E-03

Hows Corner Tl Evaluation Appendix B January 13 2005

Response to EPA-DEP Comment 4 Dated March 31 2005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

EPA-DEP Comment 4

Comment 4 Distribution of contaminants First the TI report seems based on the assertion that there is DNAPL at the source area yet it also appears to represent that the source area is small and the bedrock below 85 is competent (or less fractured) and less impacted by the release of contaminants Some of the confusion may result from using most recent data when that data is from several different sampling events over several years and there is no discernible difference in concentrations between shallow and deep bedrock or as in Section 421 where generally decreased generally increase generally similar and similar concentrations in four consecutive sentences leads to a muddled picture of the contaminant distribution

Second the report asserts that the distribution of contaminants over the entire plume has not changed with time but fails to support this conclusion with data again relying on data that is from different sampling dates for one composite representation

Response The likely presence of dense non-aqueous phase liquid (DNAPL) at the Hows Corner Site and the determination that the source area is small are not mutually exclusive and both are conclusions drawn from information obtained during field investigations The presence of DNAPL in the source area is based on the elevated concentrations of volatile organic compounds (VOCs) detected in the groundwater (WampC 2001 WampC 2002) The conclusion that the source area is small is based on the area in which VOCs in groundwater have been detected at concentrations that are considered to be indicative of the presence of DNAPL nearby Similarly the conclusion that fracture frequency decreases at depths greater than approximately 50 to 85 feet below ground surface was based on field observation during the RI field work The fact that zones with observed fractures exhibited higher hydraulic conductivities than zones without fractures coupled with the decreasing frequency of observed fractures with depth led to the conclusion that the hydraulic conductivity of the bulk rock decreases with depth

The most recent data from all wells were used to provide the maximum VOC data set size During the RI all of the previously-existing and then newly-installed monitoring wells were sampled along with several residential wells The RI sampling included up to 48 monitoring wells Subsequent to the RI and prior to the TI three rounds of monitoring were conducted to verify that the plume was stable 15 monitoring wells were sampled during each of the three rounds During the TI field investigation 29 wells were sampled for VOCs The sampled wells included all of the newly-installed wells and a subset of wells installed during the RI for a total of 29 monitoring wells By using most recent data VOC results from 53 monitoring wells were included in the evaluation (see table labeled Sampling Events for listing of monitoring wells) This approach was selected because there generally was little variation in the data from a particular location between years This is borne out by the attached individual plots of VOCs detected in shallow bedrock and deep bedrock for the Pre-ROD (December 1999January 2000) and Supplemental (May 2000) sampling events and for June 2001 January 2002 and April 2003 sampling events The Pre-ROD and Supplemental plots are similar to the subsequent plots from the 2001 2002 and 2003 sampling events

In addition to maps showing the spatial distribution of VOC data at a given time trend plots of the data from a particular location through time (attached) indicate that since the RI concentrations generally have been stable or have decreased Together the maps and trend plots and the data from which they were developed indicate that the distribution of contaminants over the entire plume has not changed appreciably with time

Response to EPA Comment 4 050305doc 1 of 26 Woodard amp Curran (211941)

REFERENCES

Woodard amp Curran Inc (WampC) 2001 Final Remedial Investigation Report Hows Corner Superfund Plymouth Maine July 2001

Woodard amp Curran Inc (WampC) 2002 Final Feasibility Study Report - Non-Source Area Groundwater Hows Corner Superfund Site Plymouth Maine Hows Corner Superfund Plymouth Maine July 2002

Response to EPA Comment 4 050305doc 2 of 26 Woodard amp Curran (211941)

LIST OF ATTACHMENTS (Response to Comment 4)

Table - Sampling Events 1999 - 2004 (2 pages)

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater Pre-ROD Sampling Event

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater Pre-ROD Sampling Event

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater Supplemental Sampling Event

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater Supplemental Sampling Event

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater June 2001

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater June 2001

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater January 2002

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater January 2002

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater April 2003

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater April 2003

Figure - Concentration Trends - Non-Source Area Wells MW-1B and MW-3B

Figure - Concentration Trends - Non-Source Area Wells MW-13DB and MW-16DB

Figure - Concentration Trends - Non-Source Area Wells MW-16IB and MW- 108D

Figure - Concentration Trends - Non-Source Area Wells MW-108S and MW-112D

Figure - Concentration Trends - Non-Source Area Wells MW-112S and MW-114D

Figure - Concentration Trends - Non-Source Area Wells MW-114S and MW-115D

Figure - Concentration Trends -Source Area Wells MW-2DB and MW-2IB

Figure - Concentration Trends -Source Area Wells MW-102S and MW-103D

Figure - Concentration Trends -Source Area Wells MW-103S and MW-104D

Figure - Concentration Trends -Source Area Wells MW-104I and MW-106D

Figure - Concentration Trends -Source Area Wells MW-106S

Response to EPA Comment 4 050305doc 3 of 26 Woodard amp Curran (211941)

I I

El I

II I I 1 I

I

i

Event Baseline Case ID WC-01 WC-01

Well Date Aug-99 Oct-99 LOT10 1 LOT1-1 1 LOT11-4 LOT14 1 LOT15 1 LOT15-1 1 LOT16 1 LOT16-1 1 LOT17 1 LOT18 1 LOT19 1 LOT2 LOT20 1 LOT21-10 1 LOT21-11 1 LOT21-12 1 LOT21-13 1 LOT21-14 1 LOT21-2 1 LOT21-5 1 LOT21-7 LOT21 -8 1 LOT21-9 1 LOT23 1 LOT24 1 LOT28-1 1 LOT28-2 1 LOT28-3 1 LOT28-4 1 LOT28W 1 LOT30 1 LOT30-1 1 LOT30-2 1 LOT30-3 1 LOT30-4 1 LOT30-5 LOT31 LOT35 1 LOT41 1 LOT42-1 1 LOT43-1 1 LOT43-4 1 LOT6-1 1 LOT67 1 LOT6-7 1 LOT6-8A 1 LOT6-8B 1 LOT80-1 1 LOT82 1 MW-101D MW-1011 MW-101S MW-102D MW-102S MW-103D MW-103S MW-104D MW-1041 MW-104S MW-105D MW-106D

Groundwater Sampling Location Summary 1999 - 2004xls

Sampling Events 1999-2004

Hows Corner Superfund Site Plymouth Maine

Supplemental 2001 2002 2003 Pumping 2004 Pre-ROD Rl Sampling Sampling Sampling Test Sampling WC-03 WC-09 WC-25 WC-30 WC-42B WC-56 WC-58 Dec-99 May-00 Jun-01 Jan-02 Apr-03 Sep-04 Sep-04

1

1 1 1

1 1 1 1 1

1 1

1

1 1

1 1 1

1 1 1 1 1

1

1 1

1 1 1 1

1

1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

Sampling Events 1999-2004

Hows Corner Super-fund Site Plymouth Maine

Supplemental 2001 2002 2003 Pumping Event Baseline Pre-ROD Rl Sampling Sampling Sampling Test

Case ID WC-01 WC-01 WC-03 WC-09 WC-25 WC-30 WC-42B WC-56

ll

Well Date Aug-99 Oct-99 Dec-99 May-00 Jun-01 Jan-02 Apr-03 Sep-04 MW-106S 1 1 1 1 1 MW-107D 1 1 MW-108D 1 1 1 1 1 MW-108S 1 1 1 1 1 MW-110D 1 1 MW-111D 1 1 MW-112D 1 1 1 1 1 MW-112S 1 1 1 1 1 MW-113D 1 1 MW-114D 1 1 1 1 1 MW-114S 1 1 1 1 1 MW-115D 1 1 1 1 1 MW-12DB 1 1 1 MW-12SB 1 1 1 MW-13DB 1 1 1 1 1 1 MW-13SB 1 1 1 MW-14DB 1 1 MW-14SO 1 1 MW-15DB 1 1 1 MW-15SB 1 1 1 MW-16DB 1 1 1 1 1 1 MW-16IB 1 1 1 1 1 1 MW-16SO 1 1 MW-17DO 1 1 1 MW-17SO 1 1 1 MW-1B 1 1 1 1 1 1 MW-203D MW-203S MW-204D MW-204S MW-205 MW-206D

I MW-206S MW-2DB 1 1 MW-2DDB 1 1 MW-2IB 1 1 1 1 1 1 MW-3B 1 1 1 1 1 1

I MW-4O 1 1 1 MW-5B 1 1

II MW-6DB 1 1 1 MW-6SB 1 1 1 MW-8DB 1 1 1 MW-8SB 1 1 1

II PW-207 1 SEEP-1 1 SUBTOTAL - RESIDENTIAL 44 25 0 2 0 3 0 SUBTOTAL - MONITORING 22 48 41 15 15 15 1

Total 3 66 73 41 17 15 18 1

I Included in most recent data

I Notes 1 - Overburden well not included in most recent data for plotting

2 - Tetrahydrofuran and 2-Butanone were the only two compounds detected in this well and are thought to be the result of well repair not included in most recent data for plotting

3 - Not included in most recent data for plotting

2004 Sampling

WC-58 Sep-04

1

1 1

1 1

1 1 1

1

1 1

1 1 1 1 1 1 1 1 1

1 1

1

0 29

29

Groundwatef Sampling Location Summary 1999 - 2004xls

I

PLYMOUTH POND

PLYMOUTH POND

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monitoring well Figure 4-14 total VOC contour (ugl) - December 1999January 2000 Distribution of Total VOCs in

Note SW-113 is located downstream of SEEP-1 Shallow Bedrock Groundwater total concentration of detected VOCs ND= not detected these two locations were sampled during the Pre-ROD Sampling Event

Baseline Sampling Event in OctoberNovember 1999 Hows Corner Superfund Site Surface Water Sampling Location A Plymouth Maine Seep Sampling Location laquo- WOODARD ampCURRAN

995037wipri reportepa ri interim final feb 2001cadd drawingsfinalfig 4-14

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

0 300 600 I

FEET

Q residential well Figure 4-16 monitoring well Distribution of Total VOCs in

Deep Bedrock Groundwater total VOCs contour (ugl) Pre-ROD Sampling Event

active residential wells with lot number Hows Corner Superfund Site 2deg42deg Plymouth Maine total concentration of detected VOCs ND= not detected WOODARD ampCURRAN Enyinaaring bull Science bull Operations bull

995037wipri reportepa ri interim final feb 2001cadd drawingsfinalfig4mdash16

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monitoring well Figure 4-20

V total VOC contour (ugl) - June 2000 Distribution of Total VOCs in Shallow Bedrock Groundwater

| 34 | total concentration of detected VOCs ND= not detected NA = not analyzed Supplemental Sampling Event Note SW-113 is located downstream of SEEP-1 Hows Corner Superfund Site

Surface Water Sampling Location these two locations were sampled during the Plymouth Maine Baseline Sampling Event in OctoberNovember 1999 Seep Sampling Location WOODARD amp CURRAN

Engineering bull Science - Operations bull 995037wipri reportepa ri interim final feb 2001 cadd drawingsfinalfig 4-20

residential well Figure 4-22 Distribution of Total VOCs in

monitoring well Deep Bedrock Groundwater

total VOCs contour (ugl) Supplemental Sampling Event

Hows Corner Superfund Site

total concentration of detected VOCs ND= not detected NA = not analyzed Plymouth Maine

WOODARD amp CURRAN

995037wipri reportepa-ri interim final feb 2001cadd drawingsfinalfig 4-22 Engineering bull Science - Operations bull

PLYMOUTH POND

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Shallow Monitoring Well

Deep Monitoring Well

C Detected Concentration ND = Not Detected Figure 1-XS Distribution of Total VOCs in Shallow Bedrock Groundwater

Pumping Well

17-Acre Property Boundary Concentration Contour (ugl)

June 2001 Hows Corner Superfund Site

Plymouth Maine WOODARDampCURRAN

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Shallow Monitoring Well bull bull - 17-Acre Property Boundary Figure 1-XD

Deep Monitoring Well 1 I Detected Concentration ND = Not Detected Distribution of Total VOCs in Deep Bedrock Groundwater

-mf- Pumping Well June 2001 Residential Well Hows Corner Superfund Site

Plymouth Maine i h Surface Water Sampling Point

g WOODARD ampCURRAN _ ^ _ ^ _ _ yen_ rj i|Hlaquorlny bull Science bull Opt

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Detected Concentration ND = Not Detected Figure 1-YS Distribution of Total VOCs in Shallow Bedrock Groundwater

Pumping Well

17-Acre Property Boundary Concentration Contour (ugl)

January 2002 Hows Corner Superfund Site

Plymouth Maine WOODARD amp CURRAN Engineering Science- Operations bull

211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0102dwg04-20-05

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Deep Bedrock Groundwater Pumping Well January 2002 Residential Well Hows Corner Superfund Site

Plymouth Maine Surface Water Sampling Point

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PLYMOUTH POND

PLYMOUTH POND j A O-shy

Shallow Monitoring Well E Detected Concentration ND = Not Detected Figure 1-ZS Distribution of Total VOCs in

Deep Monitoring Well Shallow Bedrock Groundwater

Pumping Well Hows Corner

April 2003 Superfund Site

17-Acre Property Boundary Plymouth Maine Concentration Contour (ugl) r WOODARD ampCURRAN

Engineering bull Science bull Operations bull 211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0403dwg04-20-05

s S pound

PLYMOUTH POND

PLYMOUTH POND

- -

5 PLYMOUTH POND

Jo

FEET

ft Shallow Monitoring Well mdashbullbullmdash 17-Acre Property Boundary Figure 1-ZD Deep Monitoring Well I 1 I Detected Concentration ND = Not Detected Distribution of Total VOCs in

Deep Bedrock Groundwater Pumping Well April 2003

Q) Residential Well Hows Corner Superfund Site Plymouth Maine

(T) Surface Water Sampling Point WOODARD ampCURRAN poundKk EnginawtirKj bull Science - Operations bull

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0403dwg04-20-05

0 Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

B MW-1B

I 12000

PCE

B 10000 Total VOCs

I

i 2000

i 0 Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

c MW-3B

G 2000

1800

B PCE

1600 Total VOCs

1 I I E

il-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

G E

211941

El

I I z E

80

Concentration Trends shy Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-13DB

Total VOCs

c i i c o

Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

MW-16DB

30

c i c c I c o

Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99

PCE

Total VOCs

Jul-01 Jul-03

211941

O bi

c Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

I MW-16IB

i 35

3

c Total VOCs

lt- 2 5

0 | gt

o

1 sectI

c c 0 4

Jul-90 Jul-92 Jul-94 Jul-96 Jul-98 Jul-00 Jul-02 Jul-04

I I MW-108D

I 12

PCE 10

Total VOCs c oc 3

E E I 0

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

E 211941

c Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

fi MW-108S

I I 40

PCE 35

Total VOCs

30

I f 26

20 I o

I 15

10

c Dec-99 Dec-00 Dec-01 Dec-02 Dec-03 I 0

I MW-112D

c 35 - imdash

I A3 shyTotal VOCs

o c

E 1 2

I

ition

B 1 ^

-i c 3

0 Dec-99 Dec-OO Dec-01 Dec-02 Dec-03

211941

I

i

I

cII

Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-112S

08

PCE

Total VOCs 06

o 04

02

0 Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

MW-114D

o

12000

10000

8000

6000

PCE

Total VOCs

4000

2000

i

ccEIIc

i

i

E

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

211941

Con

cent

ratio

n (

ug

l)

E Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

I MW-114S

E A5000 -- Total VOCs

- 4000

0 3000

2000

i 1000

i n shy

Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

MW-115D

c PCE

Total VOCs

c E

o

C c

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03 I 0

211941

IepoundII

EIEIIGICCIccc

30000

25000

20000

o bullsect 15000 b

o 10000 U

5000

0 Aug-99

25000

20000

5000

0 Aug-99

211941

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-2DB

PCE

Total VOCs

Aug-01 Aug-03

MW-2IB

PCE

Total VOCs

Aug-01 Aug-03

IDIBI

ii EIDIISIBIG C

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-102S

6000

5000 PCE

Total VOCs

4000

O 3000

2000

1000

0 Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

MW-103D

16000

~ 14000 ugt 3- 12000 o

^ 10000

sect 8000

O 6000

4000

2000

PCE

Total VOCs

0Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

211941

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

G MW-103S

I I

ampo

12000

10000

E sectc

S

8000

6000

4000

2000

0Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

G I 6000

MW-104D

i 5000

PCE

Total VOCs

i i c

2000

1000

Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

E I

211941

cIccIG

IIBCccBcIc

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-1041

PCE Total VOCs

a 25000

0 20000

a 15000

10000

5000

0 Jan-OO Jan-01 Jan-02 Jan-03 Jan-04

MW-106D

3000

2500 PCE

Total VOCs

=sect 2000

o bullsect 1500

1000

500

0 Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

211941

c Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

c MW-106S

I PCE

Total VOCs

i

i Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

i

i i i E

C

211941 c

Response to EPA-DEP Comment 5 Dated March 312005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

iiw

EPA-DEP Comment 5

Comment 5 Matrix Diffusion The report as well as other proponents of matrix diffusion suggest that depletion of DNAPL (Section 5112 page 5-15) needs to be achieved While that might be the ideal the goal is to achieve performance standards and that goal may be attainable while there is residual contamination in the rock perhaps even DNAPL globules The low bedrock matrix porosity (page 1-15) the high permeability values (page 4-4) the relative flux of the groundwater (page 5-5) and the decrease in surface area and out of the mainstream pockets (appendix C-4) all suggest that the diffusion out of the rock matrix would be insubstantial relative to the regional flux of groundwater through the Site

Response The TI Evaluation Report does not explicitly consider or rely upon matrix diffusion as a basis for requesting a TI Waiver for a portion of the Hows Corner Site The technical literature provides documentation that matrix diffusion can be a significant process that affects chemical transport and groundwater remediation timeframes in unconsolidated and consolidated media including fractured rock (US EPA 1989 Freeze and Cherry 1979 Pankow and Cherry 1996 Fountain 1998) Back diffusion of contaminants from the matrix porosity of the fractured rock can prolong the time necessary to achieve groundwater cleanup goals particularly for compounds such as PCE for which the cleanup goal is a low concentration It is our expectation that matrix diffusion has occurred at the Hows Corner Site and that back diffusion of PCE from the rock matrix will also occur Although the extent to which matrix diffusion is occurring at the Hows Comer Site has not been determined and that lack of knowledge contributes to uncertainty regarding the cleanup times at the Site the effect of matrix diffusion is to lengthen rather than shorten the time required for remediation

REFERENCES

Fountain JC 1998 Technologies for Dense Nonaqueous Phase Liquid Source Zone Remediation Ground-Water Remediation Technologies Analysis Center Technology Evaluation Report TE-98-02 December

Freeze RA and Cherry JA 1979 Groundwater Prentice-Hall Inc Englewood Cliffs NJ 07632 p 410-412

Pankow J F and Cherry J A 1996 Dense Chlorinated Solvents Waterloo Press Portland OR 97291-1399 p 67-88

US EPA 1989 Transport and Fate of Contaminants in the Subsurface EPA6254-89019 p 17-18

Response to EPA Comment 5 050305doc 1 of 1 Woodard amp Curran (211941)

WOODARD amp CURRAN Maine Massachusetts New Hampshire Connecticut Florida Operational offices across the US 1-800-426-4262 www woodardcurran com

Page 11: SDMS DocID 251749 - Records Collections · 2020-06-13 · CORPORATE OFFICES: Maine, Massachusetts, New Hampshire, Connecticut New, York, Florida Engineering • Science • Operations

LIST OF ATTACHMENTS (Response to Comment 2)

Figure - Drawdown at 72 Hours Shallow Wells

Figure - Drawdown at 72 Hours Deep Wells

Figure - Drawdown at 72 Hours

Figure - Potentiometric Surface at 72 Hours Shallow Wells

Figure - Potentiometric Surface at 72 Hours Deep Wells

Figure - End of Pumping Test Bedrock Potentiometric Surface at 72 Hours

Table - Pumping Test Analytical Results

Figure - USGS Background Groundwater Level

Figure - Packer Testing Results in Vicinity of Source Area

Figure - Borehole Geophysical Log MW-203

Figure - Borehole Geophysical Log MW-204

Figure - Borehole Geophysical Log MW-205

Figure - Borehole Geophysical Log MW-206

Figure - Borehole Geophysical Log PW-207

Table - Packer Permeability and Packer Sampling Results for Potential Fracture Intervals 1999 Drilling Program (2 pages)

Table - Packer Permeability and Packer Sampling Results for Potential Fracture Intervals 2004 Drilling Program

Table - Orientation Permeability and Groundwater Sampling Results for Transmissive Features 2004 Drilling Program (2 pages)

Response to EPA Comment 2 050205doc 5 of 24 Woodard amp Curran (211941)

(MEDEP Pond 1) Farm Pond

0 150 300

FEET

Monitoring Well

Figure X Pumping Well Drawdown at 72 Hours

_ - 17-Acre Property Boundary Shallow Wells Hows Corner Superfund Site Drawdown Contour (ft) Plymouth Maine

151 | Drawdown (ft) WOODARD ampCURRAN

^Stk Engineering bull Science bull Operations bull 211941 Hows CornlaquorwipDrawingsTI EVALDrawdown-72hrs_shallowdwg04-19-05

MW-3B

413951 W-6DB JMW-6SB

(MEDEP Pond 1) Farm Pond

Monitoring Well

Pumping Well

17-Acre Property Boundary

Groundwater Elevation Contour (ft)

211941 Hows CornerwipDrowngsTI EVALpo-tent-aU-72-hrsdwg

Figure X End of Pumping Test

Bedrock Potentiometric Surface at 72 Hours Hows Corner Superfund Site

Plymouth Maine ^ WOODARD amp CURRAN

Englnesring bull Science bull Ope

(MEDEP Pond 1) Farm Pond

Monitoring Well

Pumping Well Drawdown atFigure X

72 Hours _bullbull_ 17-Acre Property Boundary Deep Wells

Drawdown Contour (ft) Hows Corner Superfund Site

Plymouth Maine 151 | Drawdown (ft)

= WOODARD ampCURRAN 211941 Hows CornerwipDrawingsTI EVALDrawdown-72hrs_deepdwg04-19-05

Engineering bull Science bull Operations

(MEDEP Pond 1) Farm Pond

028 MW-12DB

MW-125B 040

l - _ ^ I 016 I N

050 MW-15SB

MW-15DB 048

A J s

- A - Monitoring Well

-$poundbull Pumping Well

_bullmdash 17-Acre Property Boundary

^ Drawdown Contour (ft)

151 I Drawdown (ft)

211941 Hows CornerwgtpDrawinQsT EVAI_Drawdown-72brsdwg04mdash19-05

Figure X Drawdown at 72 Hours

Hows Corner Superfund Site Plymouth Maine

^ WOODARD ampCURRAN Engineering bull Science bull Operations i

(MEDEP Pond 1) Farm Pond

Monitoring Well

Pumping Well

_bullbull_ 17-Acre Property Boundary

f Groundwater Elevation Contour (ft)

|419Q0| Groundwater Elevation

211941 Hows CornerwipDrawinqsTI EVALPotSurf-72hrs_shallowdwg04-19-05

150 300

FEET

Figure X Potentiometric Surface at 72 Hours

Shallow Wells Hows Corner Superfund Site

Plymouth Maine

WOODARD ampCURRAN Engineering bull Science bull Operations

29212 MW-108D

(MEDEP Pond 1) Farm Pond

Monitoring Well

Pumping Well

mdashbullbulllaquo 1 7-Acre Property Boundary

bull Groundwater Elevation Contour (ft)

1419001 Groundwater Elevation

211941 Hows CornerwipDrawingsTI EVALPotSurf-72hrs_deepdwg04-19-05

150 300 =5fc= FEET

Figure X Potentiometric Surface at 72 Hours

Deep Wells Hows Corner Superfund Site

Plymouth Maine

WOODARDampCURRAN Engineering bull Science bull Operations bull

--

Pumping Test Analytical Results Hows Corner Superfund Site

Plymouth Maine

Well ID oper Jaccb Analyses 2 Theis Analyses Fissure

Well Id Rd (ft)

Saturated Thickness

Transmissivity

(ft2day) K

(ft2day) K

(cmsec) Storage

Coefficient Transmissivity

(ft2day) K

(ft2day)

K (cmsec)

Storage Coefficient

System K

(ftday) PW-207OB 8 85 481 057 200E-04 392E-02 36 042 150E-04 809E-04 027 MW-103S 50 85 451 053 187E-04 720E-03 92 108 382E-04 283E-04 083 MW-103D 54 185 455 025 868E-05 210E-02 65 035 123E-04 237E-04 044 MW-2IB 59 85 352 041 146E-04 699E-03 104 123 433E-04 512E-04 052 MW-2DB 63 85 334 039 139E-04 845E-03 148 080 283E-04 239E-04 046 MW-104D 95 185 489 02 6 932E-05 654E-03 98 053 186E-04 547E-05 037 MW-104I 97 85 33 03 9 137E-04 362E-03 117 137 484E-04 962E-05 048 MW-101I 107 85 364 043 151E-04 490E-03 511 601 212E-03 223E-04 136 MW-102D 134 185 435 024 829E-05 248E-03 108 058 206E-04 850E-05 065 MW-101D 138 185 492 027 938E-05 511E-03 671 362 128E-03 700E-04 172 MW-205 219 85 57 067 237E-04 255E-03 447 526 186E-03 359E-03 -shyMW-204D 221 185 367 020 700E-05 170E-03 790 427 151E-O3 155E-04 147 MW-204S 225 85 379 045 157E-04 156E-03 1031 1213 428E-03 313E-04 199 MW-1B 228 85 325 038 135E-04 977E-04 340 400 141E-03 739E-05 054 MW-203S 273 85 489 058 203E-04 117E-03 1255 14 76 521 E-03 216E-04 210 MW-106D 278 185 51 028 972E-05 141E-03 1065 576 203E-03 360E-04 104 MW-203D 278 185 478 026 911E-05 152E-O3 765 414 146E-03 364E-04 138 MW-105D 364 185 44 024 839E-05 830E-04 769 415 147E-03 200E-04 127

1 Analyses conducted using Cooper and Jakob method on late drawdown data collected during constant

discharge pumping test conducted at the Hows Comer Site from September 20 - 30 2004

2 Analyses conducted using Theis solution for unconfmed approximation (1935)

J Analyses conducted using Moench method for dual porosity estimation (1984)

Fissure System Storage

Coefficient 402E-04 117E-06 264E-04 300E-04 932E-05 235E-07 502E-05 326E-06 801E-05 542E-04

-

803E-05 762E-05 134E-05 498E-05 115E-04

47E-04 838E-05

3 ysesh Analysis

Block System K (ft2day)

251E-02 207E-03 564E-04 163E-04 585E-04 465E-02 153E-04 498E-03 855E-04 356E-03

-

292E-03 394E-03 720E-04 526E-03 160E-01 35OE-O1 287E-03

Block System Storage

Coefficient

402E-02 164E-04 183E-02 330E-03 158E-03 847E-03 286E-03 326E-04 803E-05 272E-03

723E-04 686E-04 148E-04 349E-04 115E-03 47E-04 838E-04

Theis - Moench - CJ - AnalyticalResults_4-19-O5xls

DRAFT

242

24

238

236

bulla

c

i

a Q

234

232

228

226

Hows Corner Constant Discharge Testing USGS Background Groundwater Level USGS 445319068560101 ME-PEW456 Kenduskeag Maine

End of Monitored Recovery Period 09302004

Regional Background Location i 226 miles from Pumping Locatio

lt

697

NOTES

1 Groundwater samples collected in 1999 were screened for five volatile organic compounds (VOCs) only N

tetrachloroethene (PCE) exceeded reporting limits MW-2030 082304 082304 082304 082304 u

2 Strike and Dip of likely or possible transmissive 30 45 55 85 feature within the packer interval from which the indicated sample was collected

MW-204D

PCE TOTAL VOCs

081904 30

220 2636

A

081904 46-50 540 6436by

081904 IT

260 3073

x

MW-105D

PCE TOTAL VOCs

111199 50-60 2100 2100

MW-106D

PCE TOTAL VOCs

111199 76-86

400 400

111199 137-147

1400 1400

111299 1355-1455

350 350

PCE TOTAL VOCs

44 84

64

MW-6SB

bulli

lt

gt-

170 234

35

I I i

140 192

^^52

^^52

130 183

52 - lt

S A 34

PW-207 082404 082404 082404 20 37

PCE 1300 TOTAL VOCs

17-Acre George West Property Boundary

MW-113D

PCE TOTAL VOCs

112299 46-56

350 350

112299 70-80 190 190

150

112299 105-115

129 129

112399 138-148

230 230

L e g e n d ( J New Monitoring Well-Summer

Site Property Boundary ^ P u m p i n g Well-Summer 2004

-xmdashxshy Source Area

bull0shy Monitoring Well shy Pre 2004 Angled Boring-Summer 2004

211941laquoipdwgTI-ELV21ig41paltker-data2

2004 PCE of Total

bull lt70 VOCs

M W - 1 14D ^ ^

Figure xx Packer Testing Results in

Vicinity of Source Area Hows Corner Superfund Site

Plymouth Maine ^ WOODARD ampCURRAN

^^^^^^^^^^m ampKm Engineering - Science bull Operations

c Northeast Geophysical Services Borehole Geophysical Log

MW-203 Date logged 081704 Plymouth Maine

I Flowmeter Measurements Tomporaturo(C) Acoustic Televiewer

7 5 8 8 5 9 95 Caliper (Inches) Resistance (Ohms) Spontaneous Potential (mVj Dip In Degrees PCE Total VOCs

3 0 2 0 8 0 laquodeg 4S 1000 1400 1800 2200 MO HO 1000 1200 MOO 0 laquo deg ugL ugL n 1 1 1 1 1 1 1 1 1 i 1 1 1 1 n 1 1 1 1 1 1 1 1 1 1 1 n I l l l l l l l n

Ambient Flowneter pumping Rowmeter 11 gpm 6

H

bull

magnetic 10 bull 10 bull - 10 - north - 1 0I

-

_

bullbullbull - bull

20 bull bull20 bull ^ ltr~mdash 01

I

4 ^

LOS7

^

44 84 I I

Xr - 2

lt ^ bull30 -_ _^O1J- 1 _ 050 30 - 3 0

0r - - 3

C -j [ bull bull bull | shy

-O8 H ~ 1 045 7

1 4040 - 40 - -40 r - 14gt 13

V1s -- -023 f 1022 1V 170 234 I

T lt bull B gtf 50^ J50 - - 5 0 - - 5 0

I eet be

lo

i 1

1 1

1

140 192 - - - -t shy

-mdashj bullpound 60 - $o - - 60 - -60

H i I c

bull024

ampbull

3 - T lt ftft rgt He

70 bull j 70 - - 70 - 7 0 -

in -j bullbull shy

-021 1 T 022

- Ton _ Ov

26

130 183 NF NF

90 -_ 90 - 7 90 - -90

-

ifi Jf

3J

^gt _ N F NF bull bull shy

| H100 - j 100 bullbull 100 - -100

1 1 1 1 1 1 1 ) | 1 f I 1 1 1 ) 0 20 40 60 80

flft mdash ftn - mdash rVt

30 4 g 0 20 40 60 Dip in Degrees bullbull

Likely or poss bleFluid Resistivity (ohmmeters) The dip direction-- indicated

^ t h e l i n e extending from t h

I Iransmissive zone circle The strike of the feature is 90 degrees from this

The acoustic televiewer graph displays the mostprominent features selectedffom the acoustic televiewer

R n r a h n l c D O t t n O I B

f i o n n h w c i r a l U K U p i i y SI Ud l

1 rn l_Og Packered Interval August 2004

E tog The location dip angle and dip direction of the sleeted M W - 2 0 3 Groundwater samples were collected by Woodard S Curran on H23120M features are approximate Refer to the televiewer og of His _ well for more precise detail Plymouth Maine Date logged 081704

I

1

Northeast Geophysical Services Borehole Geophysical Log MW-204 D a t e l o gge d 072604

Plymouth Maine

n 3

Flowrneter Measurements(in gpm)

Caliper (Inches)0 3 5 4 0

1 1 1 1 1 1 1 t 1 1 1 1 1 1Ambient Rowmeler pumping Flowmetsr 05gpm

Templaquorature (C) bull bull bull bull i

7 75 8 8S 9 Resistance (Ohms) Spontaneous Potential (mV)

4000 SOW 600 4M 0

Acoustic Televiewer (interpreted)

Dip in Degrees 0 20 4060 SO

at N

PCEugL

Total VOCs ugL

- -_ a

10-

shy 10 bull - 10 shymagnetic

north - 10

o o

bull 1

11

11

1 1

1 1

11 1

1 1

1 1

1 1

1 1

1 1

1 1

1 1

1 1 E 1

- L

3 7 2 0 2 0r bull 20 bull - shy

i S_ N F

bull30 bull 7 3 0 220 2636shy1^ J J 004

fI f V ^

40 shy 4 0 4 0 shy - 4 0rbull019 [_ 007 w8 - - shy5 c

bull

gt

Ia50i 540 6436

bull50 - - 50 - - 5 0

-QQ7 - bull - -t T

pound V gtk

B 6 0 - e o - 7 6 0 -60shyQ 1 1

Q -007 -004 bull1 mdash T - J ~

bull

- - shyT 70 -J c [TO- - 70 - 7 0-

V Y 1- -004 -003

mdash T -h - y - j i - - mdash 260 3073 - gt=7

80 -j NF bull80 - - 80 - - 8 0Jgt

bull i

i 1

i i

C- bull shy

90 shy

K

Jlt i90 90 shy - 9 0shy -

l

ii

I I I I

NF bull M J

I ^ ^ - ^ bull 1

mdash mdash - _

s -7 ^100shy

till

1 100 100- H - 1 0 0shy -1 x Likety or possible k ^ Iransmissive zonebull

1 i i i ii i i i | l l l l | l i l l 0 20 40 ED 80

1 -

3 0SOFluid Resistivity (ohmmeters)

Dip in Degrees The djp ^ ^ o n is indicated ty Ihe line extending from tha circle The strike of Ihe feature

19- 3U UIHJIW93 IolII l l l lraquo

bull

The acousfc televiewer graph displays the mostprominent features selected from the acoustic televiewer109 The location dip angle and dip direction of Ihe sleetedfeatures are approximate Refer to the televiewer log of thiswentormore precise detail

B o r e h o l e G e O D h V S I C a l LOO B W H U I B w c w p n y o i v a i w v yM W - 2 0 4

P l y m O U t n MaiDB

Packorod Interval August 2004Groundwater san-ples wampramp collected by Woodard a Curran on OMO23C4

Date logged 072604

C

I

E Northeast Geophysical Services Borehole Geophysical Log Date logged 072704

I MW-205

Plymouth Maine

Flowmeter Measurements Temperature (C) Acoustic Televiewer (In gpm) I ~l (Interpreted)

I 85 10 Caliper (inches) 95

Dip in D g r laquo Resistance (Ohms) Spo ontaneous Potential (mV PCE Total VOCs 3 0 16 4 0 4 5 ) 20 40 60 80 10 00 2000 30 00 4VJ 400 -3 laquo

i i i i 1 i i I i 11 4 0 D 1 I I ugL ugL

C h

iii Ambient Flowmetar pumping

Flowmeter 1 25 gprn

I bull$bull

i

I rmdash magnetic 1 north ^^^^ 1 VI f

10 ~ I C x 10 bull - 10 bullbull

4 5 6mdashmdash f 1000B 11448 noisy nodi a raquo ^

mdash 5rt mdashi mdash Oft pound) 1100B 12509

cjmdash1 007

-

i i i 1

en

8 B a B

30 mdash

-

40 shy

-mdash I -

50 -_

__NF lt005

- 30 - - 3 0 it 34V

MO P26 V S) 1300B 13776 _ N F NF

26

40 bull - 40 bull 7-40 gt J Vf1 cX

) -j -

_ N F NF 50 c bull - 50 ^ 7-50

i I

I

c

B pound 60 - 6 0 7 60 - 7-60 a i 1

_ N F NF i Si f f 70 -_ bull70 bull - 70 shyC I 9

-m bull - shyA

_ N F NF 80 80 -j bull80 bull - 80 - C- 33 34

bull

5-i r

i 1

J r

Ck

_ N F NF 9 0 90 - - 90 shy

i bullCshy

J rK bull

100 -j ^ Likely or possible bull100- - 100- I -100

transmissive zone bull - ^ bull shy] |

1 1 1 1 1 1 1 I 1 i i i 1 i i 1 1 0 20 40 SO SO 10 20 30 40 50 Dip in Degrees 30 4 0 Fluid Resistivity (ohmmeters) Thlaquo dip direction is indicated

by the line extern r g from the circle The strike of he feature is 90 degrees from ihis

The acoustic televiewer graph displays the most

I Borehole Geophysical Log Packered Interval August2004 prominent features selected from the acoustic televiewer

Groundwatcr samples were oollccled by Woodard amp Cufran orgt S172004 log The location dip angle and dip direction of ins slsctsd MW-205 features are approximate Refelt to the televiewer log of this wall for more precise detail Plymouth Maine Date logged 072704

I

C

I Northeast Geophysical Services Borehole Geophysical Log Date logged 072704

I MW-206

Plymouth Maine

Flowmetor Measurements Temperature (C) Acoustic Televiewer | I r T i i i i i i i i i i i i i i r I |(in gpm) (Interpreted)

I 75 8 flS 9 95

Caliper (inches) Resistance (Ohms) Spontaneous Potential (mV) Dip In Degress PCE Total VOCs 30 35 40 4 5 0 20 40 M 90 4500 5500 6500 ugL ugL I i i

I I

- 1 0

I - 2 0

I 2900B 32401

i i L

E 0

i 6300B 68901

i I 0 20 40 SO 80

20 30 40 50 Dip in Dlaquogralaquos

amp 4 a Fluid Resistivity (ohrnmeters) The dip dirertion is indicated Likely or possible by iho line extending from the transmissive zone circle The striKe of the feature

is 90 degrees from tNs

Borehole Geophysical Log Packered Interval August 2004

E amples were collected by Woodard amp Cunan oo SM82004 log Thraquo location 4p angle and dip direction of the sloeled MW-206 feature are approximate Refer to the televiewer 109 of this well for more precise detail Plymouth Maine Date logged 072704

C

I Northeast Geophysical Services Borehole Geophysical Log

Date logged 082304 PW-207

I Plymouth Maine

Fiowmeter Measurements Temperature (C) Acoustic Televiewer

I (in gpm) (interpreted)

75 8 85 9 95 Caliper (inches) Resistance f0tims) Spontaneous Potential (mV) Dip in Degrees PCE Total VOCs

55 60 0 20 40 SO 80 ugL ugL I I I I I I I

Ambienl Fiowmeter pumping Flewmater

magnetic - 10 - - 1 0

north

i - 20 - - 2 0

1300 1410

i - 30 - - 3 0

i tf

5400 5802 - 40 - - 4 0

B - 50 - - 5 0

I 18000 19234

- 60 - - 6 0

I 12000 13085

- 70 - - 7 0

- 8 0

i - 9 0 19000 20354

G - 100- -100

I 110 110 bull110

0 20 40 60 SO 10 20 30 Dip m Degrees

Fluid Resistivity (ohmmeters) I 50

The dip direction is indicated by ihe line extending from the circle The strike of the fealure is 90 degrees from this

Borehole Geophysical Log

G Packorod Interval August 20(M log The location dip angle and dip dirlaquocton or the sleeted Groundaier samplss were ooliecled by Woodard i Curran on ampt24f2ltXM PW-207 failures are approximate Reter to the televiewer log of this wlaquoll for more precise detail PlyPIOUth Maine Date logged 082304

I

Table XX Packer Permeability and Packer Sampling Results for Potential Fracture Intervals

1

WellID MW-101D MW-101D MW-101D MW-101D MW-101D MW-101D MW-101D MW-101D MW-101D MW-101D MW-I01D MW-101D MW-101D MW-102D MW-102D MW-I02D MW-102D MW102D MW-102D MW-102D MW-102D MW-102D MW-I02D MW-102D MW-102D MW-102D MW-103D MW-103D MW-103D MW-103D MW-I03D MW-103D MW-103D MW-103D MW-103D MW-103D MW-103D MW-103D MW-I03D MW-104D MW-104D MW-104D MW-104D MW-I04D MW-104D MW-104D MW-104D MW-104D MW-104D MW-104D MW-105D MW-105D MW106D MW-106D MW-106D MW-107D MW-107D

1999 Drilling Program

Hows Corner Superfund Site Plymouth Maine

Potential Fracture Top Of Bottom 6 Depth to lt Topof i Interval from Packer Packer Middle of Elevation Hydraulic bull PCE

GS ELEV 1 Rock Drilling Interval Interval Interval of Interval Conductivity Concentration (ft msl) (ft msl) TEST (ftbgs) (ftbgs) r(ftbgs) ( f t b (ft mil) (cmsec) (raquogL)

4339 4329 13 28-29 33-3537-39 271 376 324 4016 OOOE+00 4339 12 37-3444-46 380 485 433 3907 157E-04 4339 11 488 593 541 3799 132E-04 4339 10 60-61 578 683 631 3709 OOOE+00 4339 9 678 783 731 3609 I79E-05 4339 8 778 883 831 3509 106E-05 4339 7 880 985 933 3407 243E-05 4339 6 990 1095 1043 3297 339E-06 4339 5 1090 1195 1143 3197 OOOE+00 4339 4 1190 1295 1243 3097 OOOE+00 4339 3 1365-1375 1290 1395 1343 2997 OOOE+00 4339 2 147-157 1390 1495 1443 2897 580E-05 4339 1 147-157 1470 1575 1523 2817 741E-05 43161 43061 13 166 271 219 4098 333E-04 43161 12 30-3136-40 260 365 313 4004 I54E-05 43161 11 36-4041-43 362 467 415 3902 548E-05 43161 10 470 575 523 3794 598E-05 43161 9 570 675 623 3694 197FOS 43161 8 670 775 723 3594 OOOE+00 43161 7 770 875 823 3494 891 E-05 43161 6 83-94 870 975 923 3394 139E-05 43161 5 970 1075 1023 3294 123E-04 43161 4 1070 1175 1123 3194 526E-06 43161 3 1170 1275 1223 3094 138E-05 43161 2 1270 1375 1323 2994 671E-06 43161 1 1370 1475 1423 2894 OOOE+00 42997 42497 13 18-19 170 275 223 4077 OOOE+00 42997 12 260 365 313 3987 766E-05 42997 11 360 465 413 3887 727E-05 42997 10 460 565 513 3787 192E-05 42997 9 560 665 613 3687 752E-05 42997 8 660 765 713 3587 778E-05 42997 7 85-86 763 868 816 3484 260E-05 42997 6 860 965 913 3387 289E-05 42997 5 102-103 960 1065 1013 3287 102E-04 42997 4 1060 1165 1113 3187 522E-06 42997 3 1160 1265 1213 3087 520E-06 42997 2 129-130 1260 1365 1313 2987 960E-04 42997 1 1360 1465 1413 2887 OOOE+00 43372 42922 11 35-37 42-45 350 455 403 3935 684E-04 43372 10 460 565 513 3825 500E-05 43372 9 560 665 613 3725 106E-05 43372 8 72-74 660 765 713 3625 204E-05 43372 7 760 865 813 3525 872E-06 43372 6 860 965 913 3425 467E-06 43372 5 960 1065 1013 3325 200E-05 43372 4 1060 1165 1113 3225 354E-05 43372 3 125-130 1160 1265 1213 3125 157E-05 43372 2 125-130 1260 1365 1313 3025 337E-04 43372 1 1365 1465 1415 2922 689E-06 43052 43002 2 54-58 490 595 543 3763 124E-05 2100 43052 1 139-140 145-146 1367 1472 1420 2886 154E-04 1400 43291 4391 3 bullI133 260 365 313 4017 439F06 43291 2 77-78 760 865 813 3517 230E-03 400 43291 1 143-144 1355 1460 1408 2922 971E-06 350

29958 27258 4 450 555 503 2493 OOOE+00 (21)A 29958 3 103-105 1000 1105 1053 1943 752E-04 (063)A

Table XX Packer Permeability and Packer Sampling Results for Potential Fracture Intervals

1999 Drilling Program

Hows Corner Supcrfund Site Plymouth Maine

gtbull i Potential Fracture Top _OfBot Bottom of Depth to ltbull Top of Interval from f Packer Packer Middle Of

GS ELEV lt Hock Drilling interval Interval Interval WeD ID ft msl) (ft msl) TEST (ftbgs) ltft$gs) (ftbgs) (ftbgs)

MW-107D 29958 2 128-130 1200 1305 1253

MW-107D 29958 1 139-141 1350 1455 1403

MW-108D 31904 31104 6 35-36 300 405 353 MW-108D 31904 5 60-62 550 655 603

MW-108D 31904 4 80-83 750 855 803

MW-108D 31904 3 118-119 123-124 1150 1255 1203

MW-108D 31904 2 147-149 1440 1545 1493

MW-108D 31904 1 1700 1805 1753

MW-110D 40576 40426 2 21-31 210 315 263 MW-110D 40576 1 148-154 1460 1565 1513 MW-I11D 40519 4 70-71 650 755 703

MW-111D 40519 3 79-82 84-86 780 885 833 MW-I11D 40519 2 97-102 950 1055 1003 MW-111D 40519 1 1370 1475 1423

MW-112D 3027 2942 4 42-52 420 525 473 MW-112D 3027 3 850 955 903 MW112D 3027 2 1100 1205 1153 MW-112D 3027 1 135-136 140-141 1340 1445 1393

MW-113D 43085 43085 5 250 355 303 MW-I13D 43085 4 47-49 460 565 513 MW-113D 43085 3 73-74 700 805 753 MW-113D 43085 2 1050 1155 1103 MW-113D 43085 1 1380 1485 1433

MW-114D 42394 41594 4 48-49 450 555 503 MW-114D 42394 3 79-81 740 845 793 MW-114D 42394 2 121-129 1250 1355 1303 MW-114D 42394 1 134-142 1350 1455 1403

MW-115D 4035 4035 4 300 405 353 MW-1I5D 4035 3 70-71 650 755 703 MW-115D 4035 2 1150 1255 1203 MW-115D 4035 1 1400 1505 1453

LOT-28W 382 7 450 555 503 LOT28W 382 6 550 655 603 LOT-28W 382 5 650 755 703 LOT28W 382 4 750 855 803 LOT-28W 382 3 850 955 903 LOT-28W 382 2 950 1055 1003 LOT-28W 382 1 1055 1155 1105

NOTES cmsec = centimeters per second ft bgs = leet below ground surface It msl = feet below mean sea level lt = not detected at indicated reporting limil A = detected below laboratory PQL ( ) = detected below reporting limits

Elevation of Interval

(ft nisi) 174

159

283gt 2588

2388

1988

1698

1438

3795 2545 3349 3219 3049 2629

2555 2125 1875 1635

4006 3796 3556 3206 2876

3737 3447 2937 2837

3683 3333 2833 2583

3318 3218 3118 3018 2918 2818 2715

Hydraulic Conductivity

(cmsec)

323E-05

208E-05

471E-03

471E-03

624E-05

3I6E-05

264E-05

261 E-05

OOOE+00 200E-04 953E-05 OOOE+00 OOOE+00 212E-05

361 E-05 410E-06 2gQE06 292E-05

786E-05 124E-05 151 E-05 822E-06 82IE-06

858E-05 I69E-05 352E-03 866E-05

223E-05 394E-06 122E-05 525E-06

831 E-05 182F-05 L62E-05 129E-05 190E-05 890E-04 981 E-04

PCEraquo Concentration

(ugL)

lt5

(14A)

98 11

15

22

11

30

200 (62)A

110 210 300 240

(44)A (23)A

5

350 190 129 230

2200 1900 2600 2600

(17)A (16)A (19)A

96

Table XX Packer Permeability and Packer Sampling Results for Potential Fracture Intervals

2004 Drilling Program

Hows Corner Superfund Site Plymouth Maine

Top of Bottom of Depth to Midpoint

t K

ELEV (ft Potential Transmissive Zones Packer Interval

Packer Interval

Middle of Interval

Elevation of interval

Hydraulic Conductivity

PCE Concentration

Well ID msl) TESTr (ft bgs)- (ftbgs) (ftbgs) (ftbgs) (ft msl) (cmsec) (ogt) MW-203D 43227 4 277279 24 32 28 4043 667E-05 44

3 408415420 39 49 44 3883 593E-05 170 2 526 530 49 57 53 3793 101E-04 140 I 828830842 80 88 84 3483 701E-05 130

MW-204D 43262 5 295 300 26 34 30 4023 902E-05 220 4 463496513516 45 53 49 3833 119E-04 540 3 681685688 63 71 67 3653 OOOE+00 2 758 76 2 71 79 75 3573 309E-05 260 I 88 96 92 3403 OOOE+00

MW-205 42389 3 164 166 168 15 20 175 4148 OOOE+00 1000B 2 302305312 30 35 325 3998 107E-04 1300B 1 40 45 425 3898 OOOE+00

MW-206D 43007 5 17 72 195 4128 291E-05 4 296 302 307 29 34 315 4008 940E-05 2900B 3 522 52 57 545 3778 944E-07 2 656 64 69 665 3658 353E-06 1 92392793 4939 91 96 935 3388 614E-05 6300B

PW-207 43477 5 184622162819 18 29 235 4088 209E-05 1300 4 3508 32 43 375 3948 568E-06 5400 3 53325341542154325559 50 61 555 3768 821E-05 18000

6359 61 72 665 3658 866E-06 12000 1 8685 84 89 865 3458 213E-05 19000

NOTES cmsec = centimeters per second ft bgs = feet below ground surface ft msl = feet above mean sea level B = detected in lab blank

Table XX Orientation Permeability and Groundwater Sampling Results for Transmissive Features

2004 Drilling Program

Hows Corner Superfund Site Plymouth Maine

Borehole Geophisical Feature depth Dip True Dip True Transmissive Log Feature (Feet) Degrees Azimuth Strike bullvgt(Ltk|iy^

Number v Tosftble) v MW-203 5 277 64 337 67 Likely

6 279 59 11 281 Likely 8 352 14 177 87 Likely 11 381 46 96 6 Possible 12 408 35 271 1 Possible 14 415 57 250 340 Possible 15 420 58 202 292 Likely 18 526 52 75 345 Likely 19 530 52 82 352 Likely 28 828 48 75 345 Likely 29 830 52 17 287 Likely 30 830 56 233 323 Possible 31 842 50 130 40 Likely

MW-204 4 295 15 147 57 Likely 5 300 43 91 1 Likely 11 439 31 80 350 Possible 12 440 46 219 309 Possible 14 463 50 358 88 Likely 15 496 34 198 288 Likely 16 513 54 17 287 Likely 17 516 33 14 284 Likely 25 681 39 359 89 Possible 26 685 22 45 315 Possible 27 688 35 73 343 Possible 32 758 45 236 326 Likely 33 762 46 306 36 Likely

MW-205 5 164 69 106 16 Possible 6 166 78 165 75 Possible 7 168 82 115 25 Possible 8 168 68 116 26 Possible 12 215 46 222 312 Possible 13 217 75 62 332 Possible 14 219 29 32 302 Possible 16 237 69 250 340 Possible 17 256 73 353 83 Possible 18 272 44 202 292 Possible 21 299 37 196 286 Possible 22 302 31 206 296 Possible 23 305 59 48 318 Likely 24 312 63 42 312 Likely

MW-206 1 264 37 181 271 Likely 2 296 69 217 307 Likely 3 302 66 233 323 Likely 4 307 64 224 314 Likely 8 342 62 259 349 Likely

jjHydraulic GoiDanctilyity j(cmsecjw

667 E-05

593 E-05

101 P04

710 E-05

902 E-05

119 E-04

0

309 E-05

0

107 E-04

94 E-05

PCE (ugL)

44

170

140

130

220

540

260

IOOOB

1100B

1300B

2900B

STotal vVoCsv tig1)

84

234

192

183

2636

6436

3073

11448

12509

13776

32401

PCEyo dfCTotaf

52

73

73

7 1

83

84

85

87

88

94

90

Table XX Orientation Permeability and Groundwater Sampling Results for Transmissive Features

2004 Drilling Program

Hows Corner Superfund Site Plymouth Maine

Borehole Geophisical Feature deptt raquoip True pip True Transraissive Log Feature (Feet) shy Degrees Azimuth Strike (tikely

Number raquo Possible) 22 522 57 54 324 Possible 25 656 40 82 352 Possible 32 871 59 151 61 Possible 33 883 53 185 275 Possible 34 895 7 175 85 Likely 35 899 53 90 0 Likely 36 902 49 184 274 Likely 37 923 9 175 85 Likely 38 927 42 206 296 Likely 39 934 48 167 77 Likely 40 939 26 180 90 Likely

PW-207 1 1846 33 167 77 Likely 4 2216 49 289 19 Possible 7 2819 59 265 355 Possible 11 3508 55 189 279 Possible 18 5332 43 305 35 Likely 19 5341 51 30 300 Likely 20 5421 20 254 344 Likely 21 5432 39 301 31 Likely 23 5559 52 302 32 Likely 25 6359 24 182 272 Possible 29 8049 77 231 321 Possible 30 8685 78 38 308 Likely 32 9334 29 194 284 Likely

NOTES

B = detected in lab blank

Hydraulic Conductivity

(cmsee) 944 E-07 353 E-06

614 E-05

209 E-05

568 E-06

821 E-05

866 E-06

213 E-05

bulltCE (ugL)

6300B

1300

5400

18000

12000

19000

Total VOCs (ug1)

68901

1410

5802

19234

13085

20354

PCE of Total VOCs

9 1

92

93

94

92

93

Response to EPA-DEP Comment 3 Dated March 312005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

lit

EPA-DEP Comment 3

Comment 3 The reported f values and resultant Kd values There remains doubt that the values used in the flushing model accurately reflect the propensity for PCE to sorb to the bedrock The ^ values presented in Appendix B may be unrealistically high because the bedrock samples may have contained organic carbon that was unavailable for sorption The reported f values are only qualitative estimates of the organic carbon content of the bedrock samples The Walkley and Black organic carbon measurement method is quick and simple but the results obtained cannot be considered quantitative because it requires a correction factor which often results in erroneous values it assumes the organic carbon has an average valence of zero oxidizable and reducible constituents such as chloride ferrous iron and manganese oxides interfere with the results and the errors introduced by interference are potentially greater when the organic carbon content is low at low f values it is not clear that organic carbon is controlling PCE sorption (Schwarzenbach and Westall 1981 Mackay et al 1986 Fetter 1999)

In order to derive a Kd-based retardation factor that is reasonable given the reported f values and the rapid advance of the PCE plume described on pages 4-11 and 4-12 the flushing model requires a bulk density to porosity ratio that is roughly two orders of magnitude higher than the actual ratio for the Hows Corner bedrock (page 4-4) This apparent discrepancy needs to be addressed

Response This comment raises several concerns about the collection and analysis of samples for fraction of organic carbon (f^) the quality of the resulting data and the implications of the use of those data for estimation of the retardation of groundwater contaminant movement Results of bedrock analysis for f were proposed in the TI Evaluation Work Plan for use in conjunction with groundwater contaminant concentrations and aquifer information to estimate cleanup times using the Batch Flushing model It is important to use accurate f values from representative bedrock in the Batch Flushing model in order to obtain reasonable estimates of the remedial time frame Because of the importance of accurate and representative results the TI Investigation field program was designed and conducted both to collect samples representative of the rock volume most likely to be in contact with contaminated groundwater and to analyze them using an appropriate refereed analytical method Five potential methods for evaluating f were identified Of the five methods the Walkey-Black method was selected because it has minimal method interferences and a sufficiently low detection limit as well as a long history of use in agronomy and contamination studies The PRP Group is pleased with the quality of the data obtained from the bedrock samples as represented by their precision and reproducibility

The first part of this comment relates to the determination of fraction of organic carbon (f^) values The several subparts of the first paragraph are addressed individually in items 1 through 5 below The second part of the comment regarding the resultant distribution coefficient (Kd) values is addressed separately as item 6 below

1 There remains doubt that the values used in the flushing model accurately reflect the propensity for PCE to sorb to the bedrock

bull The rock core samples used for f (gocg) analysis were from core immediately adjacent to fractures These rock core samples included the fracture surfaces themselves and rock core extending back less than 1 cm from the fractures Therefore the foe data reported in the TI Evaluation represents the f of bedrock through which groundwater will travel and to which PCE will adsorb Based on the careful selection of sample locations and the

Response to EPA Comment 3 050205doc 1 of 11 Woodard amp Curran (211941)

number of samples collected we are confident that the measured f values are representative of the f at points of contact for PCE with the bedrock it is these f values that determine the propensity of PCE to sorb to the bedrock

bull The samples of rock core collected for analysis of f originated from 19 different locations varying in depth from 11 to 90 feet Therefore it is very unlikely that the rock core samples were contaminated with extraneous organic carbon from above ground

2 The foc values presented in Appendix B may be unrealistically high because the bedrock samples may have contained organic carbon that was unavailable for sorption

bull As noted in response 1 the f data reported in Appendix B represents organic carbon primarily associated with the surface of fractures in the bedrock through which groundwater is most likely to travel Therefore it is this organic carbon that the contaminants in the groundwater will come in contact with and adsorb to in the fractured rock at the site

bull The chemical oxidation agents used in the Walkey-Black method oxidize the easily oxidizable organic carbon in the medium and the foe is calculated from the quantity of the agent consumed Therefore it is unlikely that the analysis of the bedrock samples measured organic carbon that was unavailable for sorption

3 The reported foc values are only qualitative estimates of the organic carbon content of the bedrock samples

bull The reported f values are accurate quantitative results Schumachers review of Methods for the determination of total organic carbon (TOC) in soils and sediments (NCEA-C-1282 EMASC-001 April 2002) identifies the Walkley-Black method which was used to analyze the reported foc values as the reference method for comparison to other methods for analyzing total organic carbon

bull Schumacher also points out that if anything the WalkJey-Black method may underestimate the total organic carbon in a sample due to possible incomplete oxidation of organic carbon Usually the incomplete oxidation of total organic carbon in environmental samples is corrected for by multiplying the measured foe by 130 (Walkley amp Black 1934 Schulte 1995)

bull When the f data in the TI Evaluation Report (WampC 2005) Appendix B (attached) are analyzed statistically the standard deviation of the f for the 19 samples analyzed is 174 of the average f Given this standard deviation the 95 confidence interval for this data ranged from a low of 000123 gocg to a high of 000253 gocgm

The labs Method of Detection Limit (MDL) for the f measured using the Walkley-Black method is 00001 gocg Therefore the average (000188 gocg) the mean (000185 gocg) and geometric mean (000187 gocg) of the f values for the rock core at Hows Corner are all statistically significantly greater than the MDL of the Walkley-Black method

In addition to the aforementioned statistical analysis of the foe data triplicate samples (n = 3) from the same rock core (including one sample from the 19 rock core samples) were

Response to EPA Comment 3 050205doc 2 of Woodard amp Curran (211941)

analyzed for their f to determine the repeatability of the Walkley-Black method The average the mean and the geometric mean of the f values of these replicate samples was 000162 gocg 000150 gocg and 000159 gocgm respectively The standard deviation of these measurements was 000039 gocg

4 The Walkley and Black organic carbon measurement method is quick and simple but the results obtained cannot be considered quantitative because it requires a correction factor which often results in erroneous values it assumes the organic carbon has an average valence of zero oxidizable and reducible constituents such as chloride ferrous iron and manganese oxides interfere with the results and the errors introduced by interference are potentially greater when the organic carbon content is low at low foc values it is not clear that organic carbon is controlling PCE sorption (Schwarzenbach and Westall 1981 Mackay et al 1986 Fetter 1999)

bull Schumachers review (NCEA-C-1282 EMASC-001 April 2002) of the Walkley-Black method identifies several potential problems with this analytical method that could occur if the analytical lab is not familiar with the nuances of the chemistry associated with this method Interestingly Schumachers review neglected one of the more important analytical steps required to avoid errors in quantifying f in samples where there might beNAPL

It is absolutely critical to eliminate any NAPL from rock core samples prior to using the Walkley-Black method to measure foe in such samples This was done by the lab (PTS Laboratories) that measured the foe in the rock core samples from Hows Corner The lab used the Dean-Stark method (solvent extraction) to remove all hydrocarbons (including PCE and other NAPLs) from the sample (PTS Laboratories) This extraction method does not interfere with the subsequent analysis of the natural organic carbon associated with the rock core

Subsequently the samples were dried at 150degC to a constant weight (normally 16 hours) This latter step oxidizes all inorganic minerals including ferrous bearing minerals to ferric oxides and precludes their interference during the oxidation of the samples with chromic acid This procedure completely eliminates any positive bias in the reported foc

data that might have occurred due to the presence of ferrous ions and other reduced minerals

bull As noted in Response 3 the incomplete oxidation of total organic carbon results in an underestimate of the f and is corrected for by multiplying the f by a correction factor of 130 (Walkley amp Black 1934 Schulte 1995) The fx data reported in the TI Evaluation was corrected accordingly by using this correction factor

bull Excess chloride (Cl~) in percent weight quantities as found in saline soils may interfere with the quantitative titration of reduced chromium (Walkley 1947) However given that the primary rock type at the Hows Corner site is phyllite it is highly unlikely that there was sufficient chloride in the rock core samples for this to occur

bull Manganese oxides may also interfere with the analysis of f through competing with the dichromate ion for any oxidizable carbon (Walkley 1947) However in such cases the reported f would be an underestimate of the f present in the rock core Walkley (1947)

Response to EPA Comment 3 050205doc 3 of 11 Woodard amp Curran (211941)

4

reported that in the case where the ratio of MnO2 to carbon is 85 to 1 the error in the carbon determinations would only be 0 to 6 percent

It may also be useful to compare the analysis of total organic carbon in a geologic matrix that contains high levels of manganese using EPA method 9060 to the Walkley-Black method Table 1 summarizes data provided by one of the PRPs that compares the analysis of total organic carbon in a geologic matrix that contains approximately 02 wgt manganese (approximately 03 wgt manganese oxide)

Table 1 Comparison of total organic carbon measured using the EPA- 9060 method and the Walkley-Black method

Laboratory EPA-9060 Method Walkley-Black Method A Ave 00226 gocg Not analyzed

Stdev 000251 gocg n = 5

B Ave 002219 gocg Ave 002050 gocg Stdev = 000316 gocg Stdev =000971 gocg

n= 10 n = 10

The similarity in the total organic carbon concentrations measured by these two different methods provides further confidence that the Walkley-Black method is a viable method for analysis of total organic carbon in the presence of manganese equivalent to at least 10 by weight of the total organic carbon

5 The Walkley and Black organic carbon measurement at lowf^ values it is not clear that organic carbon is controlling PCE sorption (Schwarzenbach and Westall 1981 Mackay et al 1986 Fetter 1999)

bull Schwarzenbach and Westalls (1981) paper states that f values of less than 0001 gocg should not be used in combination with Kow (octanol-water partition coefficients) values to calculate K^ values (solid phase partition coefficients) values for a specific contaminant It should be noted that the TI Evaluation did not use the f data to calculate the KQC from the Kow Instead as requested by the EPA the measured KOC value for PCE was used to calculate the retardation factor for this contaminant

bull Schwarzenbach et al (2003) stated more recently that Even at very low f values (ie foe = 0001 kgoc - kg1 solid) sorption to the organic components of a natural sorbent may still be the dominant mechanism in defining the adsorption of organic compounds to geological matrices

bull In 1985 M Piwoni from the US EPA Robert S Kerr Environmental Research Laboratory published a paper (Banerjee et al 1985) that showed that for very hydrophobic molecules TOC content of the sorbent will control sorption down to levels of organic carbon that defy quantitation Contaminants such as the PCE found in the groundwater at Hows Corner are in this category of compounds

Given the aforementioned reasons the f values reported in the TI Evaluation are accurate within the noted statistical limitations and will have a predictable impact upon the retardation of PCE during groundwater transport

Response to EPA Comment 3 050205doc 4 of 11 Woodard amp Curran (211941)

6 In order to derive a Kd-based retardation factor that is reasonable given the reported foc

values and the rapid advance of the PCE plume described on pages 4-11 and 4-12 the flushing model requires a bulk density to porosity ratio that is roughly two orders of magnitude higher than the actual ratio for the Hows Comer bedrock (page 4-4) This apparent discrepancy needs to be addressed

The apparent discrepancy of bulk density to porosity ratios is most likely due to the fact that the Batch Flushing Model was originally developed for a porous medium and is not directly applicable to fractured bedrock As stated in Appendix C (page C-4) of the Draft Technical Impracticability Evaluation Report in order to use the Batch Flushing Model to describe the transport of contaminated groundwater in fractured bedrock where the matrix porosity is insignificant it is more appropriate to use a fracture surface area to void space ratio to calculate the retardation factor (R) than a bulk density to porosity ratio (Freeze amp Cherry 1979)

Since it is impractical to determine the actual surface area to which contaminants can adsorb the Batch Flushing Model was used with two simplifying assumptions bull The Kd was calculated from the f and the K^ bull The bulk density to porosity ratio term in the Batch Flushing Model was constrained to range

from 4 to 10 the typical range of such ratios in porous media (Freeze amp Cherry 1979)

If one uses site specific bedrock bulk density and porosity values the bulk density to porosity ratio is several orders of magnitude greater (specifically 273 gcc bullbull 000165 (dimensionless) = 1654 gcc) than the range of ratios of 4 to 10 used in the Batch Flushing Model in the Draft Technical Impracticability Evaluation Report Constraining the bulk density to porosity ratio within the range of ratios of 4 to 10 results in significantly lower R value than would be obtained using specific bedrock bulk density and porosity values

In summary in bedrock where fractures are the primary porosity the bulk density to porosity ratio can vary considerably and will be a function of the number of fractures and the fracture aperture The calculated bulk density to porosity ratio will be inversely proportional to the porosity This means that in fractured rock with limited fracturing and smaller porosity the calculated bulk density to porosity ratio is greater and will result in a greater calculated retardation factor than in bedrock with more extensive fracturing and greater porosity Consequently the calculated retardation factor will be greater for bedrock with less surface area available for sorption than bedrock with greater surface area for sorption This is contrary to what actually occurs

4 Response to EPA Comment 3 050205doc 5 of 11 Woodard amp Curran (211941)

m

REFERENCES

Banerjee P MD Piwoni K Ebeid (1985) Sorption of organic contaminants to a low carbon subsurface core Chemosphere _14 1057-1067

Freeze RA JA Cherry (1979) Groundwater Prentice Hall Englewood Cliffs NJ pg 604

PTS Laboratories wwwptsgeolabscompdf files3TOCnotepdf

Schulte EE (1995) Recommended soil organic matter tests in Recommended Soil Testing Procedures for the Northeastern United States Northeastern Regional Publication No 493 Chapter 8

Schwarzenbach RP J Westall (1981) Transport of nonpolar organic compounds from surface water to groundwater Laboratory sorption studies Environ Sci Tech 15 1360-1367

Schwarzenbach RP PM Gschwend DM Imboden (2003) Environmental Organic Chemistry Wiley-Interscience pg 292 408 amp 412

Walkley A LA Black (1934) An examination of the Degtjareff method for determining soil organic matter and a proposed modification of the chromic acid titration method Soil Science 37 29-38

Walkley A (1947) A critical examination of a rapid method for determining organic carbon in soils - effect of variations in digestion conditions and of inorganic soil constituents Soil Science 63251-264

Woodard amp Curran Inc (WampC) 2005 Draft Technical Impracticability Evaluation Hows Corner Superfund Site Plymouth Maine January 2005

Response to EPA Comment 3 050205doc 6 of Woodard amp Curran (211941)

LIST OF ATTACHMENTS (Response to Comment 3)

Appendix B to Draft Technical Impracticability Evaluation Measurement of foe at Hows Corner (4 pages)

m

Response to EPA Comment 3 050205doc 7 of 11 Woodard amp Curran (211941)

Appendix B Measurement of foe of Rock Core at Hows Corner

There are two general approaches to measure the fraction of organic carbon (foe) in rock cores

bull Measurement of weight loss by ignition of organic matter bull Chemical oxidization of organic carbon to carbon dioxide and either

subsequent quantification of the oxidant used for the reaction or quantification of the carbon dioxide produced during this oxidation process

The weight loss method is subject to errors caused by volatilization of substances other than organic materials such as water hydroxides and mineral carbonates Quantification of foe by the weight loss method is particularly sensitive to the presence of carbonates in rock cores There are however weight loss methods that are designed to differentiate between organic carbon and the aforementioned interfering materials but they require considerable care and are less accurate at low foe values Hence the weight loss method was not well suited for measuring the foe of the rock core from Hows Corner

The chemical oxidation of organic carbon is much better suited for quantifying organic carbon in rock cores such as those from Hows Corner This method uses a strong chemical oxidant to oxidize organic carbon to carbon dioxide and then measures either the chemical oxidant used to oxidize the organic carbon or the quantity of carbon dioxide produced In addition this general approach is not subject to interference by volatilization of other constituents of the rock core

There are at least two such chemical oxidation methods

bull The method of Baccini which was described by Schwarzenbach amp Westall (1981) first acidifies the sample to eliminate interference by carbonates Then a strong oxidant is used to chemically oxidize the organic carbon to carbon dioxide The resulting carbon dioxide is subsequently reduced to methane and quantified using a flame ionization detector Unfortunately this method has not been described in detail in a referred journal Hence it is would not have been appropriate to use to characterize the foe in the Hows Corner rock core

bull The more commonly used method to quantify foe in rock core is the Walkley-Black method (1934) This method is preferred for RBCA and DODDOE projects and by the oil industry

The Walkley-Black method uses an excess of chromic acid to oxidize (digest) organic matter to carbon dioxide The remaining chromic acid that was not consumed during the oxidation of the organic carbon is then quantified by titration with ferrous sulfate The difference in chromic acid prior to and after the oxidation of the organic carbon represents the total chromic acid used to oxidize

Hows Corner TI Evaluation Page 1 January 13 2005 Appendix B

the organic carbon in the sample The latter can be calculated using the chemical stoichiometry of the reaction

The Walkley-Black method is very accurate for samples that contain less than 2 organic carbon matter The minimum detection limit (MDL) for the Walkley-Black method is 100 mgkg or an foe of 0001

Given the rock core at Hows Corner was expected to contain less than 2 organic carbon the Walkley-Black method was used to measure the foe from 19 different rock core samples collected from varying depths ranging from 11 to 90 feet

Table 1 provides a statistical summary of the aforementioned data

Table 1 Statistical summary of foe data from rock cores collected at varying depths

Statistical Parameter Calculated Value foe Minimum Detection Limit (MDL) 00010 Number of samples analyzed (n) 19 Average foe 00019 Median foe 00019 Geometric Mean foe 00019 Standard deviation of foe measurements 000033 Relative standard deviation 174 -+ 95 Confidence intervals 00012 to 00025

The data in Table 1 shows the following

bull The foe from the Hows Corner rock cores are statistically greater than the MDL of the Walkley-Black analytical method

bull The average and median values for the foe of the Hows Corner rock cores from varying depths are nearly identical indicating that there is little variability in the foe values in the source zone at the site

bull The standard deviation of these measurements is 000033 which is 174 of the average foe

bull The 95 confidence intervals of the foe of the rock core at Hows Corner are 00012 to 00025

The foe was also analyzed from three separate samples taken from the same rock core at a depth of 55 feet (Only one of these samples was included in the data summarized in Table 1) Table 2 shows the statistical repeatability of this type of analysis

Hows Corner TI Evaluation Page 2 January 13 2005 Appendix B

Table 2 Repeatability of analysis of foe from one rock core at 55 feet in depth

Statistical Parameter Calculated Value Number of samples analyzed (n) 3 Average foe 00016 Median foe 00015 Geometric Mean foe 00016 Standard deviation of foe measurements 000039 Relative standard deviation 240 -+ 95 Confidence intervals 00008 to 00024

The data in Table 2 shows the following

bull The percent relative standard deviation of these three analyses of foe from the same rock core at Hows Corner is 24

bull The 95 confidence interval of the foes measured in this particular rock core at Hows Conrer is 00008 to 00024

These results show that there is good repeatability in using the Walkley-Black method for analysis of the foe in the rock core at Hows Corner

References Schwarzenbach amp Westall (1981) Transport of nonpolar organic compounds from surface water to groundwater Laboratory sorption studies Environ Sci Tech 15 1360-1367

Walkley A I A Black (1934) An examination of Degtjareff method for determining soil organic matter and a proposed modification of the chromic acid titration method Soil Sci 37 29-37

Hows Corner Tl Evaluation Page S January 13 2005 Appendix B

Woodard and Curran PTS Laboratories PTS File No 34618

ORGANIC CARBON DATA (METHODOLOGY WALKLEY-BLACK)

PROJECT NAME PROJECT NO

SAMPLE ID

203-chip-13 203-chip-23 203-chip-27 203-chip-38 203-chip-42 203-chip-47 203-chip-52 203-chip-58 203-chip-69 203-chip-82 207-chip-11 207-chip-19 207-chip-24 207-chip-29 207-chip-35 207-chip-45 207-chip-55 207-chip-87 207-chip-90

207-chip-55 55-MS

55-MSMSD

Hows Corner NA

DEPTH ft

13 23 27 38 42 47 52 58 69 82 11 19 24 29 35 45 55 87 90

55 NA NA

MATRIX

Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip

Average Median

Geometric Mean Standard Deviation Relative Std Dev

+- 95 Confidence Interval n

Rock Chip Rock Chip Rock Chip

Average Median

Geometric Mean Standard Deviation Relative Std Dev

+- 95 Confidence Interval n

FRACTION ORGANIC CARBON

(gg)

170E-03 185E-03 185E-03 170E-03 240E-03 190E-03 230E-03 180E-03 170E-03 115E-03 195E-03 220E-03 220E-03 235E-03 135E-03 190E-03 205E-03 175E-03 160E-03

188E-03 185E-03 185E-03 327E-04

1739 123E-03 to

19

205E-03 130E-03 150E-03

162E-03 150E-03 159E-03 388E-04

2402 840E-04 to

3

2532E-03

2393E-03

Hows Corner Tl Evaluation Appendix B January 13 2005

Response to EPA-DEP Comment 4 Dated March 31 2005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

EPA-DEP Comment 4

Comment 4 Distribution of contaminants First the TI report seems based on the assertion that there is DNAPL at the source area yet it also appears to represent that the source area is small and the bedrock below 85 is competent (or less fractured) and less impacted by the release of contaminants Some of the confusion may result from using most recent data when that data is from several different sampling events over several years and there is no discernible difference in concentrations between shallow and deep bedrock or as in Section 421 where generally decreased generally increase generally similar and similar concentrations in four consecutive sentences leads to a muddled picture of the contaminant distribution

Second the report asserts that the distribution of contaminants over the entire plume has not changed with time but fails to support this conclusion with data again relying on data that is from different sampling dates for one composite representation

Response The likely presence of dense non-aqueous phase liquid (DNAPL) at the Hows Corner Site and the determination that the source area is small are not mutually exclusive and both are conclusions drawn from information obtained during field investigations The presence of DNAPL in the source area is based on the elevated concentrations of volatile organic compounds (VOCs) detected in the groundwater (WampC 2001 WampC 2002) The conclusion that the source area is small is based on the area in which VOCs in groundwater have been detected at concentrations that are considered to be indicative of the presence of DNAPL nearby Similarly the conclusion that fracture frequency decreases at depths greater than approximately 50 to 85 feet below ground surface was based on field observation during the RI field work The fact that zones with observed fractures exhibited higher hydraulic conductivities than zones without fractures coupled with the decreasing frequency of observed fractures with depth led to the conclusion that the hydraulic conductivity of the bulk rock decreases with depth

The most recent data from all wells were used to provide the maximum VOC data set size During the RI all of the previously-existing and then newly-installed monitoring wells were sampled along with several residential wells The RI sampling included up to 48 monitoring wells Subsequent to the RI and prior to the TI three rounds of monitoring were conducted to verify that the plume was stable 15 monitoring wells were sampled during each of the three rounds During the TI field investigation 29 wells were sampled for VOCs The sampled wells included all of the newly-installed wells and a subset of wells installed during the RI for a total of 29 monitoring wells By using most recent data VOC results from 53 monitoring wells were included in the evaluation (see table labeled Sampling Events for listing of monitoring wells) This approach was selected because there generally was little variation in the data from a particular location between years This is borne out by the attached individual plots of VOCs detected in shallow bedrock and deep bedrock for the Pre-ROD (December 1999January 2000) and Supplemental (May 2000) sampling events and for June 2001 January 2002 and April 2003 sampling events The Pre-ROD and Supplemental plots are similar to the subsequent plots from the 2001 2002 and 2003 sampling events

In addition to maps showing the spatial distribution of VOC data at a given time trend plots of the data from a particular location through time (attached) indicate that since the RI concentrations generally have been stable or have decreased Together the maps and trend plots and the data from which they were developed indicate that the distribution of contaminants over the entire plume has not changed appreciably with time

Response to EPA Comment 4 050305doc 1 of 26 Woodard amp Curran (211941)

REFERENCES

Woodard amp Curran Inc (WampC) 2001 Final Remedial Investigation Report Hows Corner Superfund Plymouth Maine July 2001

Woodard amp Curran Inc (WampC) 2002 Final Feasibility Study Report - Non-Source Area Groundwater Hows Corner Superfund Site Plymouth Maine Hows Corner Superfund Plymouth Maine July 2002

Response to EPA Comment 4 050305doc 2 of 26 Woodard amp Curran (211941)

LIST OF ATTACHMENTS (Response to Comment 4)

Table - Sampling Events 1999 - 2004 (2 pages)

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater Pre-ROD Sampling Event

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater Pre-ROD Sampling Event

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater Supplemental Sampling Event

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater Supplemental Sampling Event

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater June 2001

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater June 2001

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater January 2002

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater January 2002

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater April 2003

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater April 2003

Figure - Concentration Trends - Non-Source Area Wells MW-1B and MW-3B

Figure - Concentration Trends - Non-Source Area Wells MW-13DB and MW-16DB

Figure - Concentration Trends - Non-Source Area Wells MW-16IB and MW- 108D

Figure - Concentration Trends - Non-Source Area Wells MW-108S and MW-112D

Figure - Concentration Trends - Non-Source Area Wells MW-112S and MW-114D

Figure - Concentration Trends - Non-Source Area Wells MW-114S and MW-115D

Figure - Concentration Trends -Source Area Wells MW-2DB and MW-2IB

Figure - Concentration Trends -Source Area Wells MW-102S and MW-103D

Figure - Concentration Trends -Source Area Wells MW-103S and MW-104D

Figure - Concentration Trends -Source Area Wells MW-104I and MW-106D

Figure - Concentration Trends -Source Area Wells MW-106S

Response to EPA Comment 4 050305doc 3 of 26 Woodard amp Curran (211941)

I I

El I

II I I 1 I

I

i

Event Baseline Case ID WC-01 WC-01

Well Date Aug-99 Oct-99 LOT10 1 LOT1-1 1 LOT11-4 LOT14 1 LOT15 1 LOT15-1 1 LOT16 1 LOT16-1 1 LOT17 1 LOT18 1 LOT19 1 LOT2 LOT20 1 LOT21-10 1 LOT21-11 1 LOT21-12 1 LOT21-13 1 LOT21-14 1 LOT21-2 1 LOT21-5 1 LOT21-7 LOT21 -8 1 LOT21-9 1 LOT23 1 LOT24 1 LOT28-1 1 LOT28-2 1 LOT28-3 1 LOT28-4 1 LOT28W 1 LOT30 1 LOT30-1 1 LOT30-2 1 LOT30-3 1 LOT30-4 1 LOT30-5 LOT31 LOT35 1 LOT41 1 LOT42-1 1 LOT43-1 1 LOT43-4 1 LOT6-1 1 LOT67 1 LOT6-7 1 LOT6-8A 1 LOT6-8B 1 LOT80-1 1 LOT82 1 MW-101D MW-1011 MW-101S MW-102D MW-102S MW-103D MW-103S MW-104D MW-1041 MW-104S MW-105D MW-106D

Groundwater Sampling Location Summary 1999 - 2004xls

Sampling Events 1999-2004

Hows Corner Superfund Site Plymouth Maine

Supplemental 2001 2002 2003 Pumping 2004 Pre-ROD Rl Sampling Sampling Sampling Test Sampling WC-03 WC-09 WC-25 WC-30 WC-42B WC-56 WC-58 Dec-99 May-00 Jun-01 Jan-02 Apr-03 Sep-04 Sep-04

1

1 1 1

1 1 1 1 1

1 1

1

1 1

1 1 1

1 1 1 1 1

1

1 1

1 1 1 1

1

1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

Sampling Events 1999-2004

Hows Corner Super-fund Site Plymouth Maine

Supplemental 2001 2002 2003 Pumping Event Baseline Pre-ROD Rl Sampling Sampling Sampling Test

Case ID WC-01 WC-01 WC-03 WC-09 WC-25 WC-30 WC-42B WC-56

ll

Well Date Aug-99 Oct-99 Dec-99 May-00 Jun-01 Jan-02 Apr-03 Sep-04 MW-106S 1 1 1 1 1 MW-107D 1 1 MW-108D 1 1 1 1 1 MW-108S 1 1 1 1 1 MW-110D 1 1 MW-111D 1 1 MW-112D 1 1 1 1 1 MW-112S 1 1 1 1 1 MW-113D 1 1 MW-114D 1 1 1 1 1 MW-114S 1 1 1 1 1 MW-115D 1 1 1 1 1 MW-12DB 1 1 1 MW-12SB 1 1 1 MW-13DB 1 1 1 1 1 1 MW-13SB 1 1 1 MW-14DB 1 1 MW-14SO 1 1 MW-15DB 1 1 1 MW-15SB 1 1 1 MW-16DB 1 1 1 1 1 1 MW-16IB 1 1 1 1 1 1 MW-16SO 1 1 MW-17DO 1 1 1 MW-17SO 1 1 1 MW-1B 1 1 1 1 1 1 MW-203D MW-203S MW-204D MW-204S MW-205 MW-206D

I MW-206S MW-2DB 1 1 MW-2DDB 1 1 MW-2IB 1 1 1 1 1 1 MW-3B 1 1 1 1 1 1

I MW-4O 1 1 1 MW-5B 1 1

II MW-6DB 1 1 1 MW-6SB 1 1 1 MW-8DB 1 1 1 MW-8SB 1 1 1

II PW-207 1 SEEP-1 1 SUBTOTAL - RESIDENTIAL 44 25 0 2 0 3 0 SUBTOTAL - MONITORING 22 48 41 15 15 15 1

Total 3 66 73 41 17 15 18 1

I Included in most recent data

I Notes 1 - Overburden well not included in most recent data for plotting

2 - Tetrahydrofuran and 2-Butanone were the only two compounds detected in this well and are thought to be the result of well repair not included in most recent data for plotting

3 - Not included in most recent data for plotting

2004 Sampling

WC-58 Sep-04

1

1 1

1 1

1 1 1

1

1 1

1 1 1 1 1 1 1 1 1

1 1

1

0 29

29

Groundwatef Sampling Location Summary 1999 - 2004xls

I

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

monitoring well Figure 4-14 total VOC contour (ugl) - December 1999January 2000 Distribution of Total VOCs in

Note SW-113 is located downstream of SEEP-1 Shallow Bedrock Groundwater total concentration of detected VOCs ND= not detected these two locations were sampled during the Pre-ROD Sampling Event

Baseline Sampling Event in OctoberNovember 1999 Hows Corner Superfund Site Surface Water Sampling Location A Plymouth Maine Seep Sampling Location laquo- WOODARD ampCURRAN

995037wipri reportepa ri interim final feb 2001cadd drawingsfinalfig 4-14

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

0 300 600 I

FEET

Q residential well Figure 4-16 monitoring well Distribution of Total VOCs in

Deep Bedrock Groundwater total VOCs contour (ugl) Pre-ROD Sampling Event

active residential wells with lot number Hows Corner Superfund Site 2deg42deg Plymouth Maine total concentration of detected VOCs ND= not detected WOODARD ampCURRAN Enyinaaring bull Science bull Operations bull

995037wipri reportepa ri interim final feb 2001cadd drawingsfinalfig4mdash16

PLYMOUTH POND

PLYMOUTH POND

1 628Tl7MW-2bB 12135

PLYMOUTH POND

monitoring well Figure 4-20

V total VOC contour (ugl) - June 2000 Distribution of Total VOCs in Shallow Bedrock Groundwater

| 34 | total concentration of detected VOCs ND= not detected NA = not analyzed Supplemental Sampling Event Note SW-113 is located downstream of SEEP-1 Hows Corner Superfund Site

Surface Water Sampling Location these two locations were sampled during the Plymouth Maine Baseline Sampling Event in OctoberNovember 1999 Seep Sampling Location WOODARD amp CURRAN

Engineering bull Science - Operations bull 995037wipri reportepa ri interim final feb 2001 cadd drawingsfinalfig 4-20

residential well Figure 4-22 Distribution of Total VOCs in

monitoring well Deep Bedrock Groundwater

total VOCs contour (ugl) Supplemental Sampling Event

Hows Corner Superfund Site

total concentration of detected VOCs ND= not detected NA = not analyzed Plymouth Maine

WOODARD amp CURRAN

995037wipri reportepa-ri interim final feb 2001cadd drawingsfinalfig 4-22 Engineering bull Science - Operations bull

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

FEET

Shallow Monitoring Well

Deep Monitoring Well

C Detected Concentration ND = Not Detected Figure 1-XS Distribution of Total VOCs in Shallow Bedrock Groundwater

Pumping Well

17-Acre Property Boundary Concentration Contour (ugl)

June 2001 Hows Corner Superfund Site

Plymouth Maine WOODARDampCURRAN

-i^rhvj bull Scbncn bull Operations bull 211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0601 dwg04-20-05

PLYMOUTH POND Hopkins Road V

O

PLYMOUTH POND

PLYMOUTH POND

o

0 300 600 mdashfa FEET

Shallow Monitoring Well bull bull - 17-Acre Property Boundary Figure 1-XD

Deep Monitoring Well 1 I Detected Concentration ND = Not Detected Distribution of Total VOCs in Deep Bedrock Groundwater

-mf- Pumping Well June 2001 Residential Well Hows Corner Superfund Site

Plymouth Maine i h Surface Water Sampling Point

g WOODARD ampCURRAN _ ^ _ ^ _ _ yen_ rj i|Hlaquorlny bull Science bull Opt

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0601 dwg04-20-05

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

Shallow Monitoring Well

Deep Monitoring Well

Detected Concentration ND = Not Detected Figure 1-YS Distribution of Total VOCs in Shallow Bedrock Groundwater

Pumping Well

17-Acre Property Boundary Concentration Contour (ugl)

January 2002 Hows Corner Superfund Site

Plymouth Maine WOODARD amp CURRAN Engineering Science- Operations bull

211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0102dwg04-20-05

PLYMOUTH POND

PLYMOUTH POND

Site Pand^ laquoum-laquoBTuitaraquo tLV

vVlf-(

PLYMOUTH POND

0 300 600 ^ = FEET

Shallow Monitoring Well mdashbullbullbull 17-Acre Property Boundary Figure 1-YD - A - Deep Monitoring Well FT Detected Concentration ND = Not Detected Distribution of Total VOCs in

Deep Bedrock Groundwater Pumping Well January 2002 Residential Well Hows Corner Superfund Site

Plymouth Maine Surface Water Sampling Point

WOODARD ampCURRAN Engineering Sciencs- Operations bulli Si

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0102dwg04-20-05

- m j

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND j A O-shy

Shallow Monitoring Well E Detected Concentration ND = Not Detected Figure 1-ZS Distribution of Total VOCs in

Deep Monitoring Well Shallow Bedrock Groundwater

Pumping Well Hows Corner

April 2003 Superfund Site

17-Acre Property Boundary Plymouth Maine Concentration Contour (ugl) r WOODARD ampCURRAN

Engineering bull Science bull Operations bull 211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0403dwg04-20-05

s S pound

PLYMOUTH POND

PLYMOUTH POND

- -

5 PLYMOUTH POND

Jo

FEET

ft Shallow Monitoring Well mdashbullbullmdash 17-Acre Property Boundary Figure 1-ZD Deep Monitoring Well I 1 I Detected Concentration ND = Not Detected Distribution of Total VOCs in

Deep Bedrock Groundwater Pumping Well April 2003

Q) Residential Well Hows Corner Superfund Site Plymouth Maine

(T) Surface Water Sampling Point WOODARD ampCURRAN poundKk EnginawtirKj bull Science - Operations bull

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0403dwg04-20-05

0 Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

B MW-1B

I 12000

PCE

B 10000 Total VOCs

I

i 2000

i 0 Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

c MW-3B

G 2000

1800

B PCE

1600 Total VOCs

1 I I E

il-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

G E

211941

El

I I z E

80

Concentration Trends shy Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-13DB

Total VOCs

c i i c o

Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

MW-16DB

30

c i c c I c o

Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99

PCE

Total VOCs

Jul-01 Jul-03

211941

O bi

c Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

I MW-16IB

i 35

3

c Total VOCs

lt- 2 5

0 | gt

o

1 sectI

c c 0 4

Jul-90 Jul-92 Jul-94 Jul-96 Jul-98 Jul-00 Jul-02 Jul-04

I I MW-108D

I 12

PCE 10

Total VOCs c oc 3

E E I 0

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

E 211941

c Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

fi MW-108S

I I 40

PCE 35

Total VOCs

30

I f 26

20 I o

I 15

10

c Dec-99 Dec-00 Dec-01 Dec-02 Dec-03 I 0

I MW-112D

c 35 - imdash

I A3 shyTotal VOCs

o c

E 1 2

I

ition

B 1 ^

-i c 3

0 Dec-99 Dec-OO Dec-01 Dec-02 Dec-03

211941

I

i

I

cII

Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-112S

08

PCE

Total VOCs 06

o 04

02

0 Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

MW-114D

o

12000

10000

8000

6000

PCE

Total VOCs

4000

2000

i

ccEIIc

i

i

E

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

211941

Con

cent

ratio

n (

ug

l)

E Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

I MW-114S

E A5000 -- Total VOCs

- 4000

0 3000

2000

i 1000

i n shy

Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

MW-115D

c PCE

Total VOCs

c E

o

C c

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03 I 0

211941

IepoundII

EIEIIGICCIccc

30000

25000

20000

o bullsect 15000 b

o 10000 U

5000

0 Aug-99

25000

20000

5000

0 Aug-99

211941

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-2DB

PCE

Total VOCs

Aug-01 Aug-03

MW-2IB

PCE

Total VOCs

Aug-01 Aug-03

IDIBI

ii EIDIISIBIG C

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-102S

6000

5000 PCE

Total VOCs

4000

O 3000

2000

1000

0 Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

MW-103D

16000

~ 14000 ugt 3- 12000 o

^ 10000

sect 8000

O 6000

4000

2000

PCE

Total VOCs

0Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

211941

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

G MW-103S

I I

ampo

12000

10000

E sectc

S

8000

6000

4000

2000

0Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

G I 6000

MW-104D

i 5000

PCE

Total VOCs

i i c

2000

1000

Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

E I

211941

cIccIG

IIBCccBcIc

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-1041

PCE Total VOCs

a 25000

0 20000

a 15000

10000

5000

0 Jan-OO Jan-01 Jan-02 Jan-03 Jan-04

MW-106D

3000

2500 PCE

Total VOCs

=sect 2000

o bullsect 1500

1000

500

0 Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

211941

c Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

c MW-106S

I PCE

Total VOCs

i

i Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

i

i i i E

C

211941 c

Response to EPA-DEP Comment 5 Dated March 312005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

iiw

EPA-DEP Comment 5

Comment 5 Matrix Diffusion The report as well as other proponents of matrix diffusion suggest that depletion of DNAPL (Section 5112 page 5-15) needs to be achieved While that might be the ideal the goal is to achieve performance standards and that goal may be attainable while there is residual contamination in the rock perhaps even DNAPL globules The low bedrock matrix porosity (page 1-15) the high permeability values (page 4-4) the relative flux of the groundwater (page 5-5) and the decrease in surface area and out of the mainstream pockets (appendix C-4) all suggest that the diffusion out of the rock matrix would be insubstantial relative to the regional flux of groundwater through the Site

Response The TI Evaluation Report does not explicitly consider or rely upon matrix diffusion as a basis for requesting a TI Waiver for a portion of the Hows Corner Site The technical literature provides documentation that matrix diffusion can be a significant process that affects chemical transport and groundwater remediation timeframes in unconsolidated and consolidated media including fractured rock (US EPA 1989 Freeze and Cherry 1979 Pankow and Cherry 1996 Fountain 1998) Back diffusion of contaminants from the matrix porosity of the fractured rock can prolong the time necessary to achieve groundwater cleanup goals particularly for compounds such as PCE for which the cleanup goal is a low concentration It is our expectation that matrix diffusion has occurred at the Hows Corner Site and that back diffusion of PCE from the rock matrix will also occur Although the extent to which matrix diffusion is occurring at the Hows Comer Site has not been determined and that lack of knowledge contributes to uncertainty regarding the cleanup times at the Site the effect of matrix diffusion is to lengthen rather than shorten the time required for remediation

REFERENCES

Fountain JC 1998 Technologies for Dense Nonaqueous Phase Liquid Source Zone Remediation Ground-Water Remediation Technologies Analysis Center Technology Evaluation Report TE-98-02 December

Freeze RA and Cherry JA 1979 Groundwater Prentice-Hall Inc Englewood Cliffs NJ 07632 p 410-412

Pankow J F and Cherry J A 1996 Dense Chlorinated Solvents Waterloo Press Portland OR 97291-1399 p 67-88

US EPA 1989 Transport and Fate of Contaminants in the Subsurface EPA6254-89019 p 17-18

Response to EPA Comment 5 050305doc 1 of 1 Woodard amp Curran (211941)

WOODARD amp CURRAN Maine Massachusetts New Hampshire Connecticut Florida Operational offices across the US 1-800-426-4262 www woodardcurran com

Page 12: SDMS DocID 251749 - Records Collections · 2020-06-13 · CORPORATE OFFICES: Maine, Massachusetts, New Hampshire, Connecticut New, York, Florida Engineering • Science • Operations

(MEDEP Pond 1) Farm Pond

0 150 300

FEET

Monitoring Well

Figure X Pumping Well Drawdown at 72 Hours

_ - 17-Acre Property Boundary Shallow Wells Hows Corner Superfund Site Drawdown Contour (ft) Plymouth Maine

151 | Drawdown (ft) WOODARD ampCURRAN

^Stk Engineering bull Science bull Operations bull 211941 Hows CornlaquorwipDrawingsTI EVALDrawdown-72hrs_shallowdwg04-19-05

MW-3B

413951 W-6DB JMW-6SB

(MEDEP Pond 1) Farm Pond

Monitoring Well

Pumping Well

17-Acre Property Boundary

Groundwater Elevation Contour (ft)

211941 Hows CornerwipDrowngsTI EVALpo-tent-aU-72-hrsdwg

Figure X End of Pumping Test

Bedrock Potentiometric Surface at 72 Hours Hows Corner Superfund Site

Plymouth Maine ^ WOODARD amp CURRAN

Englnesring bull Science bull Ope

(MEDEP Pond 1) Farm Pond

Monitoring Well

Pumping Well Drawdown atFigure X

72 Hours _bullbull_ 17-Acre Property Boundary Deep Wells

Drawdown Contour (ft) Hows Corner Superfund Site

Plymouth Maine 151 | Drawdown (ft)

= WOODARD ampCURRAN 211941 Hows CornerwipDrawingsTI EVALDrawdown-72hrs_deepdwg04-19-05

Engineering bull Science bull Operations

(MEDEP Pond 1) Farm Pond

028 MW-12DB

MW-125B 040

l - _ ^ I 016 I N

050 MW-15SB

MW-15DB 048

A J s

- A - Monitoring Well

-$poundbull Pumping Well

_bullmdash 17-Acre Property Boundary

^ Drawdown Contour (ft)

151 I Drawdown (ft)

211941 Hows CornerwgtpDrawinQsT EVAI_Drawdown-72brsdwg04mdash19-05

Figure X Drawdown at 72 Hours

Hows Corner Superfund Site Plymouth Maine

^ WOODARD ampCURRAN Engineering bull Science bull Operations i

(MEDEP Pond 1) Farm Pond

Monitoring Well

Pumping Well

_bullbull_ 17-Acre Property Boundary

f Groundwater Elevation Contour (ft)

|419Q0| Groundwater Elevation

211941 Hows CornerwipDrawinqsTI EVALPotSurf-72hrs_shallowdwg04-19-05

150 300

FEET

Figure X Potentiometric Surface at 72 Hours

Shallow Wells Hows Corner Superfund Site

Plymouth Maine

WOODARD ampCURRAN Engineering bull Science bull Operations

29212 MW-108D

(MEDEP Pond 1) Farm Pond

Monitoring Well

Pumping Well

mdashbullbulllaquo 1 7-Acre Property Boundary

bull Groundwater Elevation Contour (ft)

1419001 Groundwater Elevation

211941 Hows CornerwipDrawingsTI EVALPotSurf-72hrs_deepdwg04-19-05

150 300 =5fc= FEET

Figure X Potentiometric Surface at 72 Hours

Deep Wells Hows Corner Superfund Site

Plymouth Maine

WOODARDampCURRAN Engineering bull Science bull Operations bull

--

Pumping Test Analytical Results Hows Corner Superfund Site

Plymouth Maine

Well ID oper Jaccb Analyses 2 Theis Analyses Fissure

Well Id Rd (ft)

Saturated Thickness

Transmissivity

(ft2day) K

(ft2day) K

(cmsec) Storage

Coefficient Transmissivity

(ft2day) K

(ft2day)

K (cmsec)

Storage Coefficient

System K

(ftday) PW-207OB 8 85 481 057 200E-04 392E-02 36 042 150E-04 809E-04 027 MW-103S 50 85 451 053 187E-04 720E-03 92 108 382E-04 283E-04 083 MW-103D 54 185 455 025 868E-05 210E-02 65 035 123E-04 237E-04 044 MW-2IB 59 85 352 041 146E-04 699E-03 104 123 433E-04 512E-04 052 MW-2DB 63 85 334 039 139E-04 845E-03 148 080 283E-04 239E-04 046 MW-104D 95 185 489 02 6 932E-05 654E-03 98 053 186E-04 547E-05 037 MW-104I 97 85 33 03 9 137E-04 362E-03 117 137 484E-04 962E-05 048 MW-101I 107 85 364 043 151E-04 490E-03 511 601 212E-03 223E-04 136 MW-102D 134 185 435 024 829E-05 248E-03 108 058 206E-04 850E-05 065 MW-101D 138 185 492 027 938E-05 511E-03 671 362 128E-03 700E-04 172 MW-205 219 85 57 067 237E-04 255E-03 447 526 186E-03 359E-03 -shyMW-204D 221 185 367 020 700E-05 170E-03 790 427 151E-O3 155E-04 147 MW-204S 225 85 379 045 157E-04 156E-03 1031 1213 428E-03 313E-04 199 MW-1B 228 85 325 038 135E-04 977E-04 340 400 141E-03 739E-05 054 MW-203S 273 85 489 058 203E-04 117E-03 1255 14 76 521 E-03 216E-04 210 MW-106D 278 185 51 028 972E-05 141E-03 1065 576 203E-03 360E-04 104 MW-203D 278 185 478 026 911E-05 152E-O3 765 414 146E-03 364E-04 138 MW-105D 364 185 44 024 839E-05 830E-04 769 415 147E-03 200E-04 127

1 Analyses conducted using Cooper and Jakob method on late drawdown data collected during constant

discharge pumping test conducted at the Hows Comer Site from September 20 - 30 2004

2 Analyses conducted using Theis solution for unconfmed approximation (1935)

J Analyses conducted using Moench method for dual porosity estimation (1984)

Fissure System Storage

Coefficient 402E-04 117E-06 264E-04 300E-04 932E-05 235E-07 502E-05 326E-06 801E-05 542E-04

-

803E-05 762E-05 134E-05 498E-05 115E-04

47E-04 838E-05

3 ysesh Analysis

Block System K (ft2day)

251E-02 207E-03 564E-04 163E-04 585E-04 465E-02 153E-04 498E-03 855E-04 356E-03

-

292E-03 394E-03 720E-04 526E-03 160E-01 35OE-O1 287E-03

Block System Storage

Coefficient

402E-02 164E-04 183E-02 330E-03 158E-03 847E-03 286E-03 326E-04 803E-05 272E-03

723E-04 686E-04 148E-04 349E-04 115E-03 47E-04 838E-04

Theis - Moench - CJ - AnalyticalResults_4-19-O5xls

DRAFT

242

24

238

236

bulla

c

i

a Q

234

232

228

226

Hows Corner Constant Discharge Testing USGS Background Groundwater Level USGS 445319068560101 ME-PEW456 Kenduskeag Maine

End of Monitored Recovery Period 09302004

Regional Background Location i 226 miles from Pumping Locatio

lt

697

NOTES

1 Groundwater samples collected in 1999 were screened for five volatile organic compounds (VOCs) only N

tetrachloroethene (PCE) exceeded reporting limits MW-2030 082304 082304 082304 082304 u

2 Strike and Dip of likely or possible transmissive 30 45 55 85 feature within the packer interval from which the indicated sample was collected

MW-204D

PCE TOTAL VOCs

081904 30

220 2636

A

081904 46-50 540 6436by

081904 IT

260 3073

x

MW-105D

PCE TOTAL VOCs

111199 50-60 2100 2100

MW-106D

PCE TOTAL VOCs

111199 76-86

400 400

111199 137-147

1400 1400

111299 1355-1455

350 350

PCE TOTAL VOCs

44 84

64

MW-6SB

bulli

lt

gt-

170 234

35

I I i

140 192

^^52

^^52

130 183

52 - lt

S A 34

PW-207 082404 082404 082404 20 37

PCE 1300 TOTAL VOCs

17-Acre George West Property Boundary

MW-113D

PCE TOTAL VOCs

112299 46-56

350 350

112299 70-80 190 190

150

112299 105-115

129 129

112399 138-148

230 230

L e g e n d ( J New Monitoring Well-Summer

Site Property Boundary ^ P u m p i n g Well-Summer 2004

-xmdashxshy Source Area

bull0shy Monitoring Well shy Pre 2004 Angled Boring-Summer 2004

211941laquoipdwgTI-ELV21ig41paltker-data2

2004 PCE of Total

bull lt70 VOCs

M W - 1 14D ^ ^

Figure xx Packer Testing Results in

Vicinity of Source Area Hows Corner Superfund Site

Plymouth Maine ^ WOODARD ampCURRAN

^^^^^^^^^^m ampKm Engineering - Science bull Operations

c Northeast Geophysical Services Borehole Geophysical Log

MW-203 Date logged 081704 Plymouth Maine

I Flowmeter Measurements Tomporaturo(C) Acoustic Televiewer

7 5 8 8 5 9 95 Caliper (Inches) Resistance (Ohms) Spontaneous Potential (mVj Dip In Degrees PCE Total VOCs

3 0 2 0 8 0 laquodeg 4S 1000 1400 1800 2200 MO HO 1000 1200 MOO 0 laquo deg ugL ugL n 1 1 1 1 1 1 1 1 1 i 1 1 1 1 n 1 1 1 1 1 1 1 1 1 1 1 n I l l l l l l l n

Ambient Flowneter pumping Rowmeter 11 gpm 6

H

bull

magnetic 10 bull 10 bull - 10 - north - 1 0I

-

_

bullbullbull - bull

20 bull bull20 bull ^ ltr~mdash 01

I

4 ^

LOS7

^

44 84 I I

Xr - 2

lt ^ bull30 -_ _^O1J- 1 _ 050 30 - 3 0

0r - - 3

C -j [ bull bull bull | shy

-O8 H ~ 1 045 7

1 4040 - 40 - -40 r - 14gt 13

V1s -- -023 f 1022 1V 170 234 I

T lt bull B gtf 50^ J50 - - 5 0 - - 5 0

I eet be

lo

i 1

1 1

1

140 192 - - - -t shy

-mdashj bullpound 60 - $o - - 60 - -60

H i I c

bull024

ampbull

3 - T lt ftft rgt He

70 bull j 70 - - 70 - 7 0 -

in -j bullbull shy

-021 1 T 022

- Ton _ Ov

26

130 183 NF NF

90 -_ 90 - 7 90 - -90

-

ifi Jf

3J

^gt _ N F NF bull bull shy

| H100 - j 100 bullbull 100 - -100

1 1 1 1 1 1 1 ) | 1 f I 1 1 1 ) 0 20 40 60 80

flft mdash ftn - mdash rVt

30 4 g 0 20 40 60 Dip in Degrees bullbull

Likely or poss bleFluid Resistivity (ohmmeters) The dip direction-- indicated

^ t h e l i n e extending from t h

I Iransmissive zone circle The strike of the feature is 90 degrees from this

The acoustic televiewer graph displays the mostprominent features selectedffom the acoustic televiewer

R n r a h n l c D O t t n O I B

f i o n n h w c i r a l U K U p i i y SI Ud l

1 rn l_Og Packered Interval August 2004

E tog The location dip angle and dip direction of the sleeted M W - 2 0 3 Groundwater samples were collected by Woodard S Curran on H23120M features are approximate Refer to the televiewer og of His _ well for more precise detail Plymouth Maine Date logged 081704

I

1

Northeast Geophysical Services Borehole Geophysical Log MW-204 D a t e l o gge d 072604

Plymouth Maine

n 3

Flowrneter Measurements(in gpm)

Caliper (Inches)0 3 5 4 0

1 1 1 1 1 1 1 t 1 1 1 1 1 1Ambient Rowmeler pumping Flowmetsr 05gpm

Templaquorature (C) bull bull bull bull i

7 75 8 8S 9 Resistance (Ohms) Spontaneous Potential (mV)

4000 SOW 600 4M 0

Acoustic Televiewer (interpreted)

Dip in Degrees 0 20 4060 SO

at N

PCEugL

Total VOCs ugL

- -_ a

10-

shy 10 bull - 10 shymagnetic

north - 10

o o

bull 1

11

11

1 1

1 1

11 1

1 1

1 1

1 1

1 1

1 1

1 1

1 1

1 1 E 1

- L

3 7 2 0 2 0r bull 20 bull - shy

i S_ N F

bull30 bull 7 3 0 220 2636shy1^ J J 004

fI f V ^

40 shy 4 0 4 0 shy - 4 0rbull019 [_ 007 w8 - - shy5 c

bull

gt

Ia50i 540 6436

bull50 - - 50 - - 5 0

-QQ7 - bull - -t T

pound V gtk

B 6 0 - e o - 7 6 0 -60shyQ 1 1

Q -007 -004 bull1 mdash T - J ~

bull

- - shyT 70 -J c [TO- - 70 - 7 0-

V Y 1- -004 -003

mdash T -h - y - j i - - mdash 260 3073 - gt=7

80 -j NF bull80 - - 80 - - 8 0Jgt

bull i

i 1

i i

C- bull shy

90 shy

K

Jlt i90 90 shy - 9 0shy -

l

ii

I I I I

NF bull M J

I ^ ^ - ^ bull 1

mdash mdash - _

s -7 ^100shy

till

1 100 100- H - 1 0 0shy -1 x Likety or possible k ^ Iransmissive zonebull

1 i i i ii i i i | l l l l | l i l l 0 20 40 ED 80

1 -

3 0SOFluid Resistivity (ohmmeters)

Dip in Degrees The djp ^ ^ o n is indicated ty Ihe line extending from tha circle The strike of Ihe feature

19- 3U UIHJIW93 IolII l l l lraquo

bull

The acousfc televiewer graph displays the mostprominent features selected from the acoustic televiewer109 The location dip angle and dip direction of Ihe sleetedfeatures are approximate Refer to the televiewer log of thiswentormore precise detail

B o r e h o l e G e O D h V S I C a l LOO B W H U I B w c w p n y o i v a i w v yM W - 2 0 4

P l y m O U t n MaiDB

Packorod Interval August 2004Groundwater san-ples wampramp collected by Woodard a Curran on OMO23C4

Date logged 072604

C

I

E Northeast Geophysical Services Borehole Geophysical Log Date logged 072704

I MW-205

Plymouth Maine

Flowmeter Measurements Temperature (C) Acoustic Televiewer (In gpm) I ~l (Interpreted)

I 85 10 Caliper (inches) 95

Dip in D g r laquo Resistance (Ohms) Spo ontaneous Potential (mV PCE Total VOCs 3 0 16 4 0 4 5 ) 20 40 60 80 10 00 2000 30 00 4VJ 400 -3 laquo

i i i i 1 i i I i 11 4 0 D 1 I I ugL ugL

C h

iii Ambient Flowmetar pumping

Flowmeter 1 25 gprn

I bull$bull

i

I rmdash magnetic 1 north ^^^^ 1 VI f

10 ~ I C x 10 bull - 10 bullbull

4 5 6mdashmdash f 1000B 11448 noisy nodi a raquo ^

mdash 5rt mdashi mdash Oft pound) 1100B 12509

cjmdash1 007

-

i i i 1

en

8 B a B

30 mdash

-

40 shy

-mdash I -

50 -_

__NF lt005

- 30 - - 3 0 it 34V

MO P26 V S) 1300B 13776 _ N F NF

26

40 bull - 40 bull 7-40 gt J Vf1 cX

) -j -

_ N F NF 50 c bull - 50 ^ 7-50

i I

I

c

B pound 60 - 6 0 7 60 - 7-60 a i 1

_ N F NF i Si f f 70 -_ bull70 bull - 70 shyC I 9

-m bull - shyA

_ N F NF 80 80 -j bull80 bull - 80 - C- 33 34

bull

5-i r

i 1

J r

Ck

_ N F NF 9 0 90 - - 90 shy

i bullCshy

J rK bull

100 -j ^ Likely or possible bull100- - 100- I -100

transmissive zone bull - ^ bull shy] |

1 1 1 1 1 1 1 I 1 i i i 1 i i 1 1 0 20 40 SO SO 10 20 30 40 50 Dip in Degrees 30 4 0 Fluid Resistivity (ohmmeters) Thlaquo dip direction is indicated

by the line extern r g from the circle The strike of he feature is 90 degrees from ihis

The acoustic televiewer graph displays the most

I Borehole Geophysical Log Packered Interval August2004 prominent features selected from the acoustic televiewer

Groundwatcr samples were oollccled by Woodard amp Cufran orgt S172004 log The location dip angle and dip direction of ins slsctsd MW-205 features are approximate Refelt to the televiewer log of this wall for more precise detail Plymouth Maine Date logged 072704

I

C

I Northeast Geophysical Services Borehole Geophysical Log Date logged 072704

I MW-206

Plymouth Maine

Flowmetor Measurements Temperature (C) Acoustic Televiewer | I r T i i i i i i i i i i i i i i r I |(in gpm) (Interpreted)

I 75 8 flS 9 95

Caliper (inches) Resistance (Ohms) Spontaneous Potential (mV) Dip In Degress PCE Total VOCs 30 35 40 4 5 0 20 40 M 90 4500 5500 6500 ugL ugL I i i

I I

- 1 0

I - 2 0

I 2900B 32401

i i L

E 0

i 6300B 68901

i I 0 20 40 SO 80

20 30 40 50 Dip in Dlaquogralaquos

amp 4 a Fluid Resistivity (ohrnmeters) The dip dirertion is indicated Likely or possible by iho line extending from the transmissive zone circle The striKe of the feature

is 90 degrees from tNs

Borehole Geophysical Log Packered Interval August 2004

E amples were collected by Woodard amp Cunan oo SM82004 log Thraquo location 4p angle and dip direction of the sloeled MW-206 feature are approximate Refer to the televiewer 109 of this well for more precise detail Plymouth Maine Date logged 072704

C

I Northeast Geophysical Services Borehole Geophysical Log

Date logged 082304 PW-207

I Plymouth Maine

Fiowmeter Measurements Temperature (C) Acoustic Televiewer

I (in gpm) (interpreted)

75 8 85 9 95 Caliper (inches) Resistance f0tims) Spontaneous Potential (mV) Dip in Degrees PCE Total VOCs

55 60 0 20 40 SO 80 ugL ugL I I I I I I I

Ambienl Fiowmeter pumping Flewmater

magnetic - 10 - - 1 0

north

i - 20 - - 2 0

1300 1410

i - 30 - - 3 0

i tf

5400 5802 - 40 - - 4 0

B - 50 - - 5 0

I 18000 19234

- 60 - - 6 0

I 12000 13085

- 70 - - 7 0

- 8 0

i - 9 0 19000 20354

G - 100- -100

I 110 110 bull110

0 20 40 60 SO 10 20 30 Dip m Degrees

Fluid Resistivity (ohmmeters) I 50

The dip direction is indicated by ihe line extending from the circle The strike of the fealure is 90 degrees from this

Borehole Geophysical Log

G Packorod Interval August 20(M log The location dip angle and dip dirlaquocton or the sleeted Groundaier samplss were ooliecled by Woodard i Curran on ampt24f2ltXM PW-207 failures are approximate Reter to the televiewer log of this wlaquoll for more precise detail PlyPIOUth Maine Date logged 082304

I

Table XX Packer Permeability and Packer Sampling Results for Potential Fracture Intervals

1

WellID MW-101D MW-101D MW-101D MW-101D MW-101D MW-101D MW-101D MW-101D MW-101D MW-101D MW-I01D MW-101D MW-101D MW-102D MW-102D MW-I02D MW-102D MW102D MW-102D MW-102D MW-102D MW-102D MW-I02D MW-102D MW-102D MW-102D MW-103D MW-103D MW-103D MW-103D MW-I03D MW-103D MW-103D MW-103D MW-103D MW-103D MW-103D MW-103D MW-I03D MW-104D MW-104D MW-104D MW-104D MW-I04D MW-104D MW-104D MW-104D MW-104D MW-104D MW-104D MW-105D MW-105D MW106D MW-106D MW-106D MW-107D MW-107D

1999 Drilling Program

Hows Corner Superfund Site Plymouth Maine

Potential Fracture Top Of Bottom 6 Depth to lt Topof i Interval from Packer Packer Middle of Elevation Hydraulic bull PCE

GS ELEV 1 Rock Drilling Interval Interval Interval of Interval Conductivity Concentration (ft msl) (ft msl) TEST (ftbgs) (ftbgs) r(ftbgs) ( f t b (ft mil) (cmsec) (raquogL)

4339 4329 13 28-29 33-3537-39 271 376 324 4016 OOOE+00 4339 12 37-3444-46 380 485 433 3907 157E-04 4339 11 488 593 541 3799 132E-04 4339 10 60-61 578 683 631 3709 OOOE+00 4339 9 678 783 731 3609 I79E-05 4339 8 778 883 831 3509 106E-05 4339 7 880 985 933 3407 243E-05 4339 6 990 1095 1043 3297 339E-06 4339 5 1090 1195 1143 3197 OOOE+00 4339 4 1190 1295 1243 3097 OOOE+00 4339 3 1365-1375 1290 1395 1343 2997 OOOE+00 4339 2 147-157 1390 1495 1443 2897 580E-05 4339 1 147-157 1470 1575 1523 2817 741E-05 43161 43061 13 166 271 219 4098 333E-04 43161 12 30-3136-40 260 365 313 4004 I54E-05 43161 11 36-4041-43 362 467 415 3902 548E-05 43161 10 470 575 523 3794 598E-05 43161 9 570 675 623 3694 197FOS 43161 8 670 775 723 3594 OOOE+00 43161 7 770 875 823 3494 891 E-05 43161 6 83-94 870 975 923 3394 139E-05 43161 5 970 1075 1023 3294 123E-04 43161 4 1070 1175 1123 3194 526E-06 43161 3 1170 1275 1223 3094 138E-05 43161 2 1270 1375 1323 2994 671E-06 43161 1 1370 1475 1423 2894 OOOE+00 42997 42497 13 18-19 170 275 223 4077 OOOE+00 42997 12 260 365 313 3987 766E-05 42997 11 360 465 413 3887 727E-05 42997 10 460 565 513 3787 192E-05 42997 9 560 665 613 3687 752E-05 42997 8 660 765 713 3587 778E-05 42997 7 85-86 763 868 816 3484 260E-05 42997 6 860 965 913 3387 289E-05 42997 5 102-103 960 1065 1013 3287 102E-04 42997 4 1060 1165 1113 3187 522E-06 42997 3 1160 1265 1213 3087 520E-06 42997 2 129-130 1260 1365 1313 2987 960E-04 42997 1 1360 1465 1413 2887 OOOE+00 43372 42922 11 35-37 42-45 350 455 403 3935 684E-04 43372 10 460 565 513 3825 500E-05 43372 9 560 665 613 3725 106E-05 43372 8 72-74 660 765 713 3625 204E-05 43372 7 760 865 813 3525 872E-06 43372 6 860 965 913 3425 467E-06 43372 5 960 1065 1013 3325 200E-05 43372 4 1060 1165 1113 3225 354E-05 43372 3 125-130 1160 1265 1213 3125 157E-05 43372 2 125-130 1260 1365 1313 3025 337E-04 43372 1 1365 1465 1415 2922 689E-06 43052 43002 2 54-58 490 595 543 3763 124E-05 2100 43052 1 139-140 145-146 1367 1472 1420 2886 154E-04 1400 43291 4391 3 bullI133 260 365 313 4017 439F06 43291 2 77-78 760 865 813 3517 230E-03 400 43291 1 143-144 1355 1460 1408 2922 971E-06 350

29958 27258 4 450 555 503 2493 OOOE+00 (21)A 29958 3 103-105 1000 1105 1053 1943 752E-04 (063)A

Table XX Packer Permeability and Packer Sampling Results for Potential Fracture Intervals

1999 Drilling Program

Hows Corner Supcrfund Site Plymouth Maine

gtbull i Potential Fracture Top _OfBot Bottom of Depth to ltbull Top of Interval from f Packer Packer Middle Of

GS ELEV lt Hock Drilling interval Interval Interval WeD ID ft msl) (ft msl) TEST (ftbgs) ltft$gs) (ftbgs) (ftbgs)

MW-107D 29958 2 128-130 1200 1305 1253

MW-107D 29958 1 139-141 1350 1455 1403

MW-108D 31904 31104 6 35-36 300 405 353 MW-108D 31904 5 60-62 550 655 603

MW-108D 31904 4 80-83 750 855 803

MW-108D 31904 3 118-119 123-124 1150 1255 1203

MW-108D 31904 2 147-149 1440 1545 1493

MW-108D 31904 1 1700 1805 1753

MW-110D 40576 40426 2 21-31 210 315 263 MW-110D 40576 1 148-154 1460 1565 1513 MW-I11D 40519 4 70-71 650 755 703

MW-111D 40519 3 79-82 84-86 780 885 833 MW-I11D 40519 2 97-102 950 1055 1003 MW-111D 40519 1 1370 1475 1423

MW-112D 3027 2942 4 42-52 420 525 473 MW-112D 3027 3 850 955 903 MW112D 3027 2 1100 1205 1153 MW-112D 3027 1 135-136 140-141 1340 1445 1393

MW-113D 43085 43085 5 250 355 303 MW-I13D 43085 4 47-49 460 565 513 MW-113D 43085 3 73-74 700 805 753 MW-113D 43085 2 1050 1155 1103 MW-113D 43085 1 1380 1485 1433

MW-114D 42394 41594 4 48-49 450 555 503 MW-114D 42394 3 79-81 740 845 793 MW-114D 42394 2 121-129 1250 1355 1303 MW-114D 42394 1 134-142 1350 1455 1403

MW-115D 4035 4035 4 300 405 353 MW-1I5D 4035 3 70-71 650 755 703 MW-115D 4035 2 1150 1255 1203 MW-115D 4035 1 1400 1505 1453

LOT-28W 382 7 450 555 503 LOT28W 382 6 550 655 603 LOT-28W 382 5 650 755 703 LOT28W 382 4 750 855 803 LOT-28W 382 3 850 955 903 LOT-28W 382 2 950 1055 1003 LOT-28W 382 1 1055 1155 1105

NOTES cmsec = centimeters per second ft bgs = leet below ground surface It msl = feet below mean sea level lt = not detected at indicated reporting limil A = detected below laboratory PQL ( ) = detected below reporting limits

Elevation of Interval

(ft nisi) 174

159

283gt 2588

2388

1988

1698

1438

3795 2545 3349 3219 3049 2629

2555 2125 1875 1635

4006 3796 3556 3206 2876

3737 3447 2937 2837

3683 3333 2833 2583

3318 3218 3118 3018 2918 2818 2715

Hydraulic Conductivity

(cmsec)

323E-05

208E-05

471E-03

471E-03

624E-05

3I6E-05

264E-05

261 E-05

OOOE+00 200E-04 953E-05 OOOE+00 OOOE+00 212E-05

361 E-05 410E-06 2gQE06 292E-05

786E-05 124E-05 151 E-05 822E-06 82IE-06

858E-05 I69E-05 352E-03 866E-05

223E-05 394E-06 122E-05 525E-06

831 E-05 182F-05 L62E-05 129E-05 190E-05 890E-04 981 E-04

PCEraquo Concentration

(ugL)

lt5

(14A)

98 11

15

22

11

30

200 (62)A

110 210 300 240

(44)A (23)A

5

350 190 129 230

2200 1900 2600 2600

(17)A (16)A (19)A

96

Table XX Packer Permeability and Packer Sampling Results for Potential Fracture Intervals

2004 Drilling Program

Hows Corner Superfund Site Plymouth Maine

Top of Bottom of Depth to Midpoint

t K

ELEV (ft Potential Transmissive Zones Packer Interval

Packer Interval

Middle of Interval

Elevation of interval

Hydraulic Conductivity

PCE Concentration

Well ID msl) TESTr (ft bgs)- (ftbgs) (ftbgs) (ftbgs) (ft msl) (cmsec) (ogt) MW-203D 43227 4 277279 24 32 28 4043 667E-05 44

3 408415420 39 49 44 3883 593E-05 170 2 526 530 49 57 53 3793 101E-04 140 I 828830842 80 88 84 3483 701E-05 130

MW-204D 43262 5 295 300 26 34 30 4023 902E-05 220 4 463496513516 45 53 49 3833 119E-04 540 3 681685688 63 71 67 3653 OOOE+00 2 758 76 2 71 79 75 3573 309E-05 260 I 88 96 92 3403 OOOE+00

MW-205 42389 3 164 166 168 15 20 175 4148 OOOE+00 1000B 2 302305312 30 35 325 3998 107E-04 1300B 1 40 45 425 3898 OOOE+00

MW-206D 43007 5 17 72 195 4128 291E-05 4 296 302 307 29 34 315 4008 940E-05 2900B 3 522 52 57 545 3778 944E-07 2 656 64 69 665 3658 353E-06 1 92392793 4939 91 96 935 3388 614E-05 6300B

PW-207 43477 5 184622162819 18 29 235 4088 209E-05 1300 4 3508 32 43 375 3948 568E-06 5400 3 53325341542154325559 50 61 555 3768 821E-05 18000

6359 61 72 665 3658 866E-06 12000 1 8685 84 89 865 3458 213E-05 19000

NOTES cmsec = centimeters per second ft bgs = feet below ground surface ft msl = feet above mean sea level B = detected in lab blank

Table XX Orientation Permeability and Groundwater Sampling Results for Transmissive Features

2004 Drilling Program

Hows Corner Superfund Site Plymouth Maine

Borehole Geophisical Feature depth Dip True Dip True Transmissive Log Feature (Feet) Degrees Azimuth Strike bullvgt(Ltk|iy^

Number v Tosftble) v MW-203 5 277 64 337 67 Likely

6 279 59 11 281 Likely 8 352 14 177 87 Likely 11 381 46 96 6 Possible 12 408 35 271 1 Possible 14 415 57 250 340 Possible 15 420 58 202 292 Likely 18 526 52 75 345 Likely 19 530 52 82 352 Likely 28 828 48 75 345 Likely 29 830 52 17 287 Likely 30 830 56 233 323 Possible 31 842 50 130 40 Likely

MW-204 4 295 15 147 57 Likely 5 300 43 91 1 Likely 11 439 31 80 350 Possible 12 440 46 219 309 Possible 14 463 50 358 88 Likely 15 496 34 198 288 Likely 16 513 54 17 287 Likely 17 516 33 14 284 Likely 25 681 39 359 89 Possible 26 685 22 45 315 Possible 27 688 35 73 343 Possible 32 758 45 236 326 Likely 33 762 46 306 36 Likely

MW-205 5 164 69 106 16 Possible 6 166 78 165 75 Possible 7 168 82 115 25 Possible 8 168 68 116 26 Possible 12 215 46 222 312 Possible 13 217 75 62 332 Possible 14 219 29 32 302 Possible 16 237 69 250 340 Possible 17 256 73 353 83 Possible 18 272 44 202 292 Possible 21 299 37 196 286 Possible 22 302 31 206 296 Possible 23 305 59 48 318 Likely 24 312 63 42 312 Likely

MW-206 1 264 37 181 271 Likely 2 296 69 217 307 Likely 3 302 66 233 323 Likely 4 307 64 224 314 Likely 8 342 62 259 349 Likely

jjHydraulic GoiDanctilyity j(cmsecjw

667 E-05

593 E-05

101 P04

710 E-05

902 E-05

119 E-04

0

309 E-05

0

107 E-04

94 E-05

PCE (ugL)

44

170

140

130

220

540

260

IOOOB

1100B

1300B

2900B

STotal vVoCsv tig1)

84

234

192

183

2636

6436

3073

11448

12509

13776

32401

PCEyo dfCTotaf

52

73

73

7 1

83

84

85

87

88

94

90

Table XX Orientation Permeability and Groundwater Sampling Results for Transmissive Features

2004 Drilling Program

Hows Corner Superfund Site Plymouth Maine

Borehole Geophisical Feature deptt raquoip True pip True Transraissive Log Feature (Feet) shy Degrees Azimuth Strike (tikely

Number raquo Possible) 22 522 57 54 324 Possible 25 656 40 82 352 Possible 32 871 59 151 61 Possible 33 883 53 185 275 Possible 34 895 7 175 85 Likely 35 899 53 90 0 Likely 36 902 49 184 274 Likely 37 923 9 175 85 Likely 38 927 42 206 296 Likely 39 934 48 167 77 Likely 40 939 26 180 90 Likely

PW-207 1 1846 33 167 77 Likely 4 2216 49 289 19 Possible 7 2819 59 265 355 Possible 11 3508 55 189 279 Possible 18 5332 43 305 35 Likely 19 5341 51 30 300 Likely 20 5421 20 254 344 Likely 21 5432 39 301 31 Likely 23 5559 52 302 32 Likely 25 6359 24 182 272 Possible 29 8049 77 231 321 Possible 30 8685 78 38 308 Likely 32 9334 29 194 284 Likely

NOTES

B = detected in lab blank

Hydraulic Conductivity

(cmsee) 944 E-07 353 E-06

614 E-05

209 E-05

568 E-06

821 E-05

866 E-06

213 E-05

bulltCE (ugL)

6300B

1300

5400

18000

12000

19000

Total VOCs (ug1)

68901

1410

5802

19234

13085

20354

PCE of Total VOCs

9 1

92

93

94

92

93

Response to EPA-DEP Comment 3 Dated March 312005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

lit

EPA-DEP Comment 3

Comment 3 The reported f values and resultant Kd values There remains doubt that the values used in the flushing model accurately reflect the propensity for PCE to sorb to the bedrock The ^ values presented in Appendix B may be unrealistically high because the bedrock samples may have contained organic carbon that was unavailable for sorption The reported f values are only qualitative estimates of the organic carbon content of the bedrock samples The Walkley and Black organic carbon measurement method is quick and simple but the results obtained cannot be considered quantitative because it requires a correction factor which often results in erroneous values it assumes the organic carbon has an average valence of zero oxidizable and reducible constituents such as chloride ferrous iron and manganese oxides interfere with the results and the errors introduced by interference are potentially greater when the organic carbon content is low at low f values it is not clear that organic carbon is controlling PCE sorption (Schwarzenbach and Westall 1981 Mackay et al 1986 Fetter 1999)

In order to derive a Kd-based retardation factor that is reasonable given the reported f values and the rapid advance of the PCE plume described on pages 4-11 and 4-12 the flushing model requires a bulk density to porosity ratio that is roughly two orders of magnitude higher than the actual ratio for the Hows Corner bedrock (page 4-4) This apparent discrepancy needs to be addressed

Response This comment raises several concerns about the collection and analysis of samples for fraction of organic carbon (f^) the quality of the resulting data and the implications of the use of those data for estimation of the retardation of groundwater contaminant movement Results of bedrock analysis for f were proposed in the TI Evaluation Work Plan for use in conjunction with groundwater contaminant concentrations and aquifer information to estimate cleanup times using the Batch Flushing model It is important to use accurate f values from representative bedrock in the Batch Flushing model in order to obtain reasonable estimates of the remedial time frame Because of the importance of accurate and representative results the TI Investigation field program was designed and conducted both to collect samples representative of the rock volume most likely to be in contact with contaminated groundwater and to analyze them using an appropriate refereed analytical method Five potential methods for evaluating f were identified Of the five methods the Walkey-Black method was selected because it has minimal method interferences and a sufficiently low detection limit as well as a long history of use in agronomy and contamination studies The PRP Group is pleased with the quality of the data obtained from the bedrock samples as represented by their precision and reproducibility

The first part of this comment relates to the determination of fraction of organic carbon (f^) values The several subparts of the first paragraph are addressed individually in items 1 through 5 below The second part of the comment regarding the resultant distribution coefficient (Kd) values is addressed separately as item 6 below

1 There remains doubt that the values used in the flushing model accurately reflect the propensity for PCE to sorb to the bedrock

bull The rock core samples used for f (gocg) analysis were from core immediately adjacent to fractures These rock core samples included the fracture surfaces themselves and rock core extending back less than 1 cm from the fractures Therefore the foe data reported in the TI Evaluation represents the f of bedrock through which groundwater will travel and to which PCE will adsorb Based on the careful selection of sample locations and the

Response to EPA Comment 3 050205doc 1 of 11 Woodard amp Curran (211941)

number of samples collected we are confident that the measured f values are representative of the f at points of contact for PCE with the bedrock it is these f values that determine the propensity of PCE to sorb to the bedrock

bull The samples of rock core collected for analysis of f originated from 19 different locations varying in depth from 11 to 90 feet Therefore it is very unlikely that the rock core samples were contaminated with extraneous organic carbon from above ground

2 The foc values presented in Appendix B may be unrealistically high because the bedrock samples may have contained organic carbon that was unavailable for sorption

bull As noted in response 1 the f data reported in Appendix B represents organic carbon primarily associated with the surface of fractures in the bedrock through which groundwater is most likely to travel Therefore it is this organic carbon that the contaminants in the groundwater will come in contact with and adsorb to in the fractured rock at the site

bull The chemical oxidation agents used in the Walkey-Black method oxidize the easily oxidizable organic carbon in the medium and the foe is calculated from the quantity of the agent consumed Therefore it is unlikely that the analysis of the bedrock samples measured organic carbon that was unavailable for sorption

3 The reported foc values are only qualitative estimates of the organic carbon content of the bedrock samples

bull The reported f values are accurate quantitative results Schumachers review of Methods for the determination of total organic carbon (TOC) in soils and sediments (NCEA-C-1282 EMASC-001 April 2002) identifies the Walkley-Black method which was used to analyze the reported foc values as the reference method for comparison to other methods for analyzing total organic carbon

bull Schumacher also points out that if anything the WalkJey-Black method may underestimate the total organic carbon in a sample due to possible incomplete oxidation of organic carbon Usually the incomplete oxidation of total organic carbon in environmental samples is corrected for by multiplying the measured foe by 130 (Walkley amp Black 1934 Schulte 1995)

bull When the f data in the TI Evaluation Report (WampC 2005) Appendix B (attached) are analyzed statistically the standard deviation of the f for the 19 samples analyzed is 174 of the average f Given this standard deviation the 95 confidence interval for this data ranged from a low of 000123 gocg to a high of 000253 gocgm

The labs Method of Detection Limit (MDL) for the f measured using the Walkley-Black method is 00001 gocg Therefore the average (000188 gocg) the mean (000185 gocg) and geometric mean (000187 gocg) of the f values for the rock core at Hows Corner are all statistically significantly greater than the MDL of the Walkley-Black method

In addition to the aforementioned statistical analysis of the foe data triplicate samples (n = 3) from the same rock core (including one sample from the 19 rock core samples) were

Response to EPA Comment 3 050205doc 2 of Woodard amp Curran (211941)

analyzed for their f to determine the repeatability of the Walkley-Black method The average the mean and the geometric mean of the f values of these replicate samples was 000162 gocg 000150 gocg and 000159 gocgm respectively The standard deviation of these measurements was 000039 gocg

4 The Walkley and Black organic carbon measurement method is quick and simple but the results obtained cannot be considered quantitative because it requires a correction factor which often results in erroneous values it assumes the organic carbon has an average valence of zero oxidizable and reducible constituents such as chloride ferrous iron and manganese oxides interfere with the results and the errors introduced by interference are potentially greater when the organic carbon content is low at low foc values it is not clear that organic carbon is controlling PCE sorption (Schwarzenbach and Westall 1981 Mackay et al 1986 Fetter 1999)

bull Schumachers review (NCEA-C-1282 EMASC-001 April 2002) of the Walkley-Black method identifies several potential problems with this analytical method that could occur if the analytical lab is not familiar with the nuances of the chemistry associated with this method Interestingly Schumachers review neglected one of the more important analytical steps required to avoid errors in quantifying f in samples where there might beNAPL

It is absolutely critical to eliminate any NAPL from rock core samples prior to using the Walkley-Black method to measure foe in such samples This was done by the lab (PTS Laboratories) that measured the foe in the rock core samples from Hows Corner The lab used the Dean-Stark method (solvent extraction) to remove all hydrocarbons (including PCE and other NAPLs) from the sample (PTS Laboratories) This extraction method does not interfere with the subsequent analysis of the natural organic carbon associated with the rock core

Subsequently the samples were dried at 150degC to a constant weight (normally 16 hours) This latter step oxidizes all inorganic minerals including ferrous bearing minerals to ferric oxides and precludes their interference during the oxidation of the samples with chromic acid This procedure completely eliminates any positive bias in the reported foc

data that might have occurred due to the presence of ferrous ions and other reduced minerals

bull As noted in Response 3 the incomplete oxidation of total organic carbon results in an underestimate of the f and is corrected for by multiplying the f by a correction factor of 130 (Walkley amp Black 1934 Schulte 1995) The fx data reported in the TI Evaluation was corrected accordingly by using this correction factor

bull Excess chloride (Cl~) in percent weight quantities as found in saline soils may interfere with the quantitative titration of reduced chromium (Walkley 1947) However given that the primary rock type at the Hows Corner site is phyllite it is highly unlikely that there was sufficient chloride in the rock core samples for this to occur

bull Manganese oxides may also interfere with the analysis of f through competing with the dichromate ion for any oxidizable carbon (Walkley 1947) However in such cases the reported f would be an underestimate of the f present in the rock core Walkley (1947)

Response to EPA Comment 3 050205doc 3 of 11 Woodard amp Curran (211941)

4

reported that in the case where the ratio of MnO2 to carbon is 85 to 1 the error in the carbon determinations would only be 0 to 6 percent

It may also be useful to compare the analysis of total organic carbon in a geologic matrix that contains high levels of manganese using EPA method 9060 to the Walkley-Black method Table 1 summarizes data provided by one of the PRPs that compares the analysis of total organic carbon in a geologic matrix that contains approximately 02 wgt manganese (approximately 03 wgt manganese oxide)

Table 1 Comparison of total organic carbon measured using the EPA- 9060 method and the Walkley-Black method

Laboratory EPA-9060 Method Walkley-Black Method A Ave 00226 gocg Not analyzed

Stdev 000251 gocg n = 5

B Ave 002219 gocg Ave 002050 gocg Stdev = 000316 gocg Stdev =000971 gocg

n= 10 n = 10

The similarity in the total organic carbon concentrations measured by these two different methods provides further confidence that the Walkley-Black method is a viable method for analysis of total organic carbon in the presence of manganese equivalent to at least 10 by weight of the total organic carbon

5 The Walkley and Black organic carbon measurement at lowf^ values it is not clear that organic carbon is controlling PCE sorption (Schwarzenbach and Westall 1981 Mackay et al 1986 Fetter 1999)

bull Schwarzenbach and Westalls (1981) paper states that f values of less than 0001 gocg should not be used in combination with Kow (octanol-water partition coefficients) values to calculate K^ values (solid phase partition coefficients) values for a specific contaminant It should be noted that the TI Evaluation did not use the f data to calculate the KQC from the Kow Instead as requested by the EPA the measured KOC value for PCE was used to calculate the retardation factor for this contaminant

bull Schwarzenbach et al (2003) stated more recently that Even at very low f values (ie foe = 0001 kgoc - kg1 solid) sorption to the organic components of a natural sorbent may still be the dominant mechanism in defining the adsorption of organic compounds to geological matrices

bull In 1985 M Piwoni from the US EPA Robert S Kerr Environmental Research Laboratory published a paper (Banerjee et al 1985) that showed that for very hydrophobic molecules TOC content of the sorbent will control sorption down to levels of organic carbon that defy quantitation Contaminants such as the PCE found in the groundwater at Hows Corner are in this category of compounds

Given the aforementioned reasons the f values reported in the TI Evaluation are accurate within the noted statistical limitations and will have a predictable impact upon the retardation of PCE during groundwater transport

Response to EPA Comment 3 050205doc 4 of 11 Woodard amp Curran (211941)

6 In order to derive a Kd-based retardation factor that is reasonable given the reported foc

values and the rapid advance of the PCE plume described on pages 4-11 and 4-12 the flushing model requires a bulk density to porosity ratio that is roughly two orders of magnitude higher than the actual ratio for the Hows Comer bedrock (page 4-4) This apparent discrepancy needs to be addressed

The apparent discrepancy of bulk density to porosity ratios is most likely due to the fact that the Batch Flushing Model was originally developed for a porous medium and is not directly applicable to fractured bedrock As stated in Appendix C (page C-4) of the Draft Technical Impracticability Evaluation Report in order to use the Batch Flushing Model to describe the transport of contaminated groundwater in fractured bedrock where the matrix porosity is insignificant it is more appropriate to use a fracture surface area to void space ratio to calculate the retardation factor (R) than a bulk density to porosity ratio (Freeze amp Cherry 1979)

Since it is impractical to determine the actual surface area to which contaminants can adsorb the Batch Flushing Model was used with two simplifying assumptions bull The Kd was calculated from the f and the K^ bull The bulk density to porosity ratio term in the Batch Flushing Model was constrained to range

from 4 to 10 the typical range of such ratios in porous media (Freeze amp Cherry 1979)

If one uses site specific bedrock bulk density and porosity values the bulk density to porosity ratio is several orders of magnitude greater (specifically 273 gcc bullbull 000165 (dimensionless) = 1654 gcc) than the range of ratios of 4 to 10 used in the Batch Flushing Model in the Draft Technical Impracticability Evaluation Report Constraining the bulk density to porosity ratio within the range of ratios of 4 to 10 results in significantly lower R value than would be obtained using specific bedrock bulk density and porosity values

In summary in bedrock where fractures are the primary porosity the bulk density to porosity ratio can vary considerably and will be a function of the number of fractures and the fracture aperture The calculated bulk density to porosity ratio will be inversely proportional to the porosity This means that in fractured rock with limited fracturing and smaller porosity the calculated bulk density to porosity ratio is greater and will result in a greater calculated retardation factor than in bedrock with more extensive fracturing and greater porosity Consequently the calculated retardation factor will be greater for bedrock with less surface area available for sorption than bedrock with greater surface area for sorption This is contrary to what actually occurs

4 Response to EPA Comment 3 050205doc 5 of 11 Woodard amp Curran (211941)

m

REFERENCES

Banerjee P MD Piwoni K Ebeid (1985) Sorption of organic contaminants to a low carbon subsurface core Chemosphere _14 1057-1067

Freeze RA JA Cherry (1979) Groundwater Prentice Hall Englewood Cliffs NJ pg 604

PTS Laboratories wwwptsgeolabscompdf files3TOCnotepdf

Schulte EE (1995) Recommended soil organic matter tests in Recommended Soil Testing Procedures for the Northeastern United States Northeastern Regional Publication No 493 Chapter 8

Schwarzenbach RP J Westall (1981) Transport of nonpolar organic compounds from surface water to groundwater Laboratory sorption studies Environ Sci Tech 15 1360-1367

Schwarzenbach RP PM Gschwend DM Imboden (2003) Environmental Organic Chemistry Wiley-Interscience pg 292 408 amp 412

Walkley A LA Black (1934) An examination of the Degtjareff method for determining soil organic matter and a proposed modification of the chromic acid titration method Soil Science 37 29-38

Walkley A (1947) A critical examination of a rapid method for determining organic carbon in soils - effect of variations in digestion conditions and of inorganic soil constituents Soil Science 63251-264

Woodard amp Curran Inc (WampC) 2005 Draft Technical Impracticability Evaluation Hows Corner Superfund Site Plymouth Maine January 2005

Response to EPA Comment 3 050205doc 6 of Woodard amp Curran (211941)

LIST OF ATTACHMENTS (Response to Comment 3)

Appendix B to Draft Technical Impracticability Evaluation Measurement of foe at Hows Corner (4 pages)

m

Response to EPA Comment 3 050205doc 7 of 11 Woodard amp Curran (211941)

Appendix B Measurement of foe of Rock Core at Hows Corner

There are two general approaches to measure the fraction of organic carbon (foe) in rock cores

bull Measurement of weight loss by ignition of organic matter bull Chemical oxidization of organic carbon to carbon dioxide and either

subsequent quantification of the oxidant used for the reaction or quantification of the carbon dioxide produced during this oxidation process

The weight loss method is subject to errors caused by volatilization of substances other than organic materials such as water hydroxides and mineral carbonates Quantification of foe by the weight loss method is particularly sensitive to the presence of carbonates in rock cores There are however weight loss methods that are designed to differentiate between organic carbon and the aforementioned interfering materials but they require considerable care and are less accurate at low foe values Hence the weight loss method was not well suited for measuring the foe of the rock core from Hows Corner

The chemical oxidation of organic carbon is much better suited for quantifying organic carbon in rock cores such as those from Hows Corner This method uses a strong chemical oxidant to oxidize organic carbon to carbon dioxide and then measures either the chemical oxidant used to oxidize the organic carbon or the quantity of carbon dioxide produced In addition this general approach is not subject to interference by volatilization of other constituents of the rock core

There are at least two such chemical oxidation methods

bull The method of Baccini which was described by Schwarzenbach amp Westall (1981) first acidifies the sample to eliminate interference by carbonates Then a strong oxidant is used to chemically oxidize the organic carbon to carbon dioxide The resulting carbon dioxide is subsequently reduced to methane and quantified using a flame ionization detector Unfortunately this method has not been described in detail in a referred journal Hence it is would not have been appropriate to use to characterize the foe in the Hows Corner rock core

bull The more commonly used method to quantify foe in rock core is the Walkley-Black method (1934) This method is preferred for RBCA and DODDOE projects and by the oil industry

The Walkley-Black method uses an excess of chromic acid to oxidize (digest) organic matter to carbon dioxide The remaining chromic acid that was not consumed during the oxidation of the organic carbon is then quantified by titration with ferrous sulfate The difference in chromic acid prior to and after the oxidation of the organic carbon represents the total chromic acid used to oxidize

Hows Corner TI Evaluation Page 1 January 13 2005 Appendix B

the organic carbon in the sample The latter can be calculated using the chemical stoichiometry of the reaction

The Walkley-Black method is very accurate for samples that contain less than 2 organic carbon matter The minimum detection limit (MDL) for the Walkley-Black method is 100 mgkg or an foe of 0001

Given the rock core at Hows Corner was expected to contain less than 2 organic carbon the Walkley-Black method was used to measure the foe from 19 different rock core samples collected from varying depths ranging from 11 to 90 feet

Table 1 provides a statistical summary of the aforementioned data

Table 1 Statistical summary of foe data from rock cores collected at varying depths

Statistical Parameter Calculated Value foe Minimum Detection Limit (MDL) 00010 Number of samples analyzed (n) 19 Average foe 00019 Median foe 00019 Geometric Mean foe 00019 Standard deviation of foe measurements 000033 Relative standard deviation 174 -+ 95 Confidence intervals 00012 to 00025

The data in Table 1 shows the following

bull The foe from the Hows Corner rock cores are statistically greater than the MDL of the Walkley-Black analytical method

bull The average and median values for the foe of the Hows Corner rock cores from varying depths are nearly identical indicating that there is little variability in the foe values in the source zone at the site

bull The standard deviation of these measurements is 000033 which is 174 of the average foe

bull The 95 confidence intervals of the foe of the rock core at Hows Corner are 00012 to 00025

The foe was also analyzed from three separate samples taken from the same rock core at a depth of 55 feet (Only one of these samples was included in the data summarized in Table 1) Table 2 shows the statistical repeatability of this type of analysis

Hows Corner TI Evaluation Page 2 January 13 2005 Appendix B

Table 2 Repeatability of analysis of foe from one rock core at 55 feet in depth

Statistical Parameter Calculated Value Number of samples analyzed (n) 3 Average foe 00016 Median foe 00015 Geometric Mean foe 00016 Standard deviation of foe measurements 000039 Relative standard deviation 240 -+ 95 Confidence intervals 00008 to 00024

The data in Table 2 shows the following

bull The percent relative standard deviation of these three analyses of foe from the same rock core at Hows Corner is 24

bull The 95 confidence interval of the foes measured in this particular rock core at Hows Conrer is 00008 to 00024

These results show that there is good repeatability in using the Walkley-Black method for analysis of the foe in the rock core at Hows Corner

References Schwarzenbach amp Westall (1981) Transport of nonpolar organic compounds from surface water to groundwater Laboratory sorption studies Environ Sci Tech 15 1360-1367

Walkley A I A Black (1934) An examination of Degtjareff method for determining soil organic matter and a proposed modification of the chromic acid titration method Soil Sci 37 29-37

Hows Corner Tl Evaluation Page S January 13 2005 Appendix B

Woodard and Curran PTS Laboratories PTS File No 34618

ORGANIC CARBON DATA (METHODOLOGY WALKLEY-BLACK)

PROJECT NAME PROJECT NO

SAMPLE ID

203-chip-13 203-chip-23 203-chip-27 203-chip-38 203-chip-42 203-chip-47 203-chip-52 203-chip-58 203-chip-69 203-chip-82 207-chip-11 207-chip-19 207-chip-24 207-chip-29 207-chip-35 207-chip-45 207-chip-55 207-chip-87 207-chip-90

207-chip-55 55-MS

55-MSMSD

Hows Corner NA

DEPTH ft

13 23 27 38 42 47 52 58 69 82 11 19 24 29 35 45 55 87 90

55 NA NA

MATRIX

Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip

Average Median

Geometric Mean Standard Deviation Relative Std Dev

+- 95 Confidence Interval n

Rock Chip Rock Chip Rock Chip

Average Median

Geometric Mean Standard Deviation Relative Std Dev

+- 95 Confidence Interval n

FRACTION ORGANIC CARBON

(gg)

170E-03 185E-03 185E-03 170E-03 240E-03 190E-03 230E-03 180E-03 170E-03 115E-03 195E-03 220E-03 220E-03 235E-03 135E-03 190E-03 205E-03 175E-03 160E-03

188E-03 185E-03 185E-03 327E-04

1739 123E-03 to

19

205E-03 130E-03 150E-03

162E-03 150E-03 159E-03 388E-04

2402 840E-04 to

3

2532E-03

2393E-03

Hows Corner Tl Evaluation Appendix B January 13 2005

Response to EPA-DEP Comment 4 Dated March 31 2005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

EPA-DEP Comment 4

Comment 4 Distribution of contaminants First the TI report seems based on the assertion that there is DNAPL at the source area yet it also appears to represent that the source area is small and the bedrock below 85 is competent (or less fractured) and less impacted by the release of contaminants Some of the confusion may result from using most recent data when that data is from several different sampling events over several years and there is no discernible difference in concentrations between shallow and deep bedrock or as in Section 421 where generally decreased generally increase generally similar and similar concentrations in four consecutive sentences leads to a muddled picture of the contaminant distribution

Second the report asserts that the distribution of contaminants over the entire plume has not changed with time but fails to support this conclusion with data again relying on data that is from different sampling dates for one composite representation

Response The likely presence of dense non-aqueous phase liquid (DNAPL) at the Hows Corner Site and the determination that the source area is small are not mutually exclusive and both are conclusions drawn from information obtained during field investigations The presence of DNAPL in the source area is based on the elevated concentrations of volatile organic compounds (VOCs) detected in the groundwater (WampC 2001 WampC 2002) The conclusion that the source area is small is based on the area in which VOCs in groundwater have been detected at concentrations that are considered to be indicative of the presence of DNAPL nearby Similarly the conclusion that fracture frequency decreases at depths greater than approximately 50 to 85 feet below ground surface was based on field observation during the RI field work The fact that zones with observed fractures exhibited higher hydraulic conductivities than zones without fractures coupled with the decreasing frequency of observed fractures with depth led to the conclusion that the hydraulic conductivity of the bulk rock decreases with depth

The most recent data from all wells were used to provide the maximum VOC data set size During the RI all of the previously-existing and then newly-installed monitoring wells were sampled along with several residential wells The RI sampling included up to 48 monitoring wells Subsequent to the RI and prior to the TI three rounds of monitoring were conducted to verify that the plume was stable 15 monitoring wells were sampled during each of the three rounds During the TI field investigation 29 wells were sampled for VOCs The sampled wells included all of the newly-installed wells and a subset of wells installed during the RI for a total of 29 monitoring wells By using most recent data VOC results from 53 monitoring wells were included in the evaluation (see table labeled Sampling Events for listing of monitoring wells) This approach was selected because there generally was little variation in the data from a particular location between years This is borne out by the attached individual plots of VOCs detected in shallow bedrock and deep bedrock for the Pre-ROD (December 1999January 2000) and Supplemental (May 2000) sampling events and for June 2001 January 2002 and April 2003 sampling events The Pre-ROD and Supplemental plots are similar to the subsequent plots from the 2001 2002 and 2003 sampling events

In addition to maps showing the spatial distribution of VOC data at a given time trend plots of the data from a particular location through time (attached) indicate that since the RI concentrations generally have been stable or have decreased Together the maps and trend plots and the data from which they were developed indicate that the distribution of contaminants over the entire plume has not changed appreciably with time

Response to EPA Comment 4 050305doc 1 of 26 Woodard amp Curran (211941)

REFERENCES

Woodard amp Curran Inc (WampC) 2001 Final Remedial Investigation Report Hows Corner Superfund Plymouth Maine July 2001

Woodard amp Curran Inc (WampC) 2002 Final Feasibility Study Report - Non-Source Area Groundwater Hows Corner Superfund Site Plymouth Maine Hows Corner Superfund Plymouth Maine July 2002

Response to EPA Comment 4 050305doc 2 of 26 Woodard amp Curran (211941)

LIST OF ATTACHMENTS (Response to Comment 4)

Table - Sampling Events 1999 - 2004 (2 pages)

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater Pre-ROD Sampling Event

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater Pre-ROD Sampling Event

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater Supplemental Sampling Event

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater Supplemental Sampling Event

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater June 2001

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater June 2001

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater January 2002

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater January 2002

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater April 2003

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater April 2003

Figure - Concentration Trends - Non-Source Area Wells MW-1B and MW-3B

Figure - Concentration Trends - Non-Source Area Wells MW-13DB and MW-16DB

Figure - Concentration Trends - Non-Source Area Wells MW-16IB and MW- 108D

Figure - Concentration Trends - Non-Source Area Wells MW-108S and MW-112D

Figure - Concentration Trends - Non-Source Area Wells MW-112S and MW-114D

Figure - Concentration Trends - Non-Source Area Wells MW-114S and MW-115D

Figure - Concentration Trends -Source Area Wells MW-2DB and MW-2IB

Figure - Concentration Trends -Source Area Wells MW-102S and MW-103D

Figure - Concentration Trends -Source Area Wells MW-103S and MW-104D

Figure - Concentration Trends -Source Area Wells MW-104I and MW-106D

Figure - Concentration Trends -Source Area Wells MW-106S

Response to EPA Comment 4 050305doc 3 of 26 Woodard amp Curran (211941)

I I

El I

II I I 1 I

I

i

Event Baseline Case ID WC-01 WC-01

Well Date Aug-99 Oct-99 LOT10 1 LOT1-1 1 LOT11-4 LOT14 1 LOT15 1 LOT15-1 1 LOT16 1 LOT16-1 1 LOT17 1 LOT18 1 LOT19 1 LOT2 LOT20 1 LOT21-10 1 LOT21-11 1 LOT21-12 1 LOT21-13 1 LOT21-14 1 LOT21-2 1 LOT21-5 1 LOT21-7 LOT21 -8 1 LOT21-9 1 LOT23 1 LOT24 1 LOT28-1 1 LOT28-2 1 LOT28-3 1 LOT28-4 1 LOT28W 1 LOT30 1 LOT30-1 1 LOT30-2 1 LOT30-3 1 LOT30-4 1 LOT30-5 LOT31 LOT35 1 LOT41 1 LOT42-1 1 LOT43-1 1 LOT43-4 1 LOT6-1 1 LOT67 1 LOT6-7 1 LOT6-8A 1 LOT6-8B 1 LOT80-1 1 LOT82 1 MW-101D MW-1011 MW-101S MW-102D MW-102S MW-103D MW-103S MW-104D MW-1041 MW-104S MW-105D MW-106D

Groundwater Sampling Location Summary 1999 - 2004xls

Sampling Events 1999-2004

Hows Corner Superfund Site Plymouth Maine

Supplemental 2001 2002 2003 Pumping 2004 Pre-ROD Rl Sampling Sampling Sampling Test Sampling WC-03 WC-09 WC-25 WC-30 WC-42B WC-56 WC-58 Dec-99 May-00 Jun-01 Jan-02 Apr-03 Sep-04 Sep-04

1

1 1 1

1 1 1 1 1

1 1

1

1 1

1 1 1

1 1 1 1 1

1

1 1

1 1 1 1

1

1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

Sampling Events 1999-2004

Hows Corner Super-fund Site Plymouth Maine

Supplemental 2001 2002 2003 Pumping Event Baseline Pre-ROD Rl Sampling Sampling Sampling Test

Case ID WC-01 WC-01 WC-03 WC-09 WC-25 WC-30 WC-42B WC-56

ll

Well Date Aug-99 Oct-99 Dec-99 May-00 Jun-01 Jan-02 Apr-03 Sep-04 MW-106S 1 1 1 1 1 MW-107D 1 1 MW-108D 1 1 1 1 1 MW-108S 1 1 1 1 1 MW-110D 1 1 MW-111D 1 1 MW-112D 1 1 1 1 1 MW-112S 1 1 1 1 1 MW-113D 1 1 MW-114D 1 1 1 1 1 MW-114S 1 1 1 1 1 MW-115D 1 1 1 1 1 MW-12DB 1 1 1 MW-12SB 1 1 1 MW-13DB 1 1 1 1 1 1 MW-13SB 1 1 1 MW-14DB 1 1 MW-14SO 1 1 MW-15DB 1 1 1 MW-15SB 1 1 1 MW-16DB 1 1 1 1 1 1 MW-16IB 1 1 1 1 1 1 MW-16SO 1 1 MW-17DO 1 1 1 MW-17SO 1 1 1 MW-1B 1 1 1 1 1 1 MW-203D MW-203S MW-204D MW-204S MW-205 MW-206D

I MW-206S MW-2DB 1 1 MW-2DDB 1 1 MW-2IB 1 1 1 1 1 1 MW-3B 1 1 1 1 1 1

I MW-4O 1 1 1 MW-5B 1 1

II MW-6DB 1 1 1 MW-6SB 1 1 1 MW-8DB 1 1 1 MW-8SB 1 1 1

II PW-207 1 SEEP-1 1 SUBTOTAL - RESIDENTIAL 44 25 0 2 0 3 0 SUBTOTAL - MONITORING 22 48 41 15 15 15 1

Total 3 66 73 41 17 15 18 1

I Included in most recent data

I Notes 1 - Overburden well not included in most recent data for plotting

2 - Tetrahydrofuran and 2-Butanone were the only two compounds detected in this well and are thought to be the result of well repair not included in most recent data for plotting

3 - Not included in most recent data for plotting

2004 Sampling

WC-58 Sep-04

1

1 1

1 1

1 1 1

1

1 1

1 1 1 1 1 1 1 1 1

1 1

1

0 29

29

Groundwatef Sampling Location Summary 1999 - 2004xls

I

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

monitoring well Figure 4-14 total VOC contour (ugl) - December 1999January 2000 Distribution of Total VOCs in

Note SW-113 is located downstream of SEEP-1 Shallow Bedrock Groundwater total concentration of detected VOCs ND= not detected these two locations were sampled during the Pre-ROD Sampling Event

Baseline Sampling Event in OctoberNovember 1999 Hows Corner Superfund Site Surface Water Sampling Location A Plymouth Maine Seep Sampling Location laquo- WOODARD ampCURRAN

995037wipri reportepa ri interim final feb 2001cadd drawingsfinalfig 4-14

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

0 300 600 I

FEET

Q residential well Figure 4-16 monitoring well Distribution of Total VOCs in

Deep Bedrock Groundwater total VOCs contour (ugl) Pre-ROD Sampling Event

active residential wells with lot number Hows Corner Superfund Site 2deg42deg Plymouth Maine total concentration of detected VOCs ND= not detected WOODARD ampCURRAN Enyinaaring bull Science bull Operations bull

995037wipri reportepa ri interim final feb 2001cadd drawingsfinalfig4mdash16

PLYMOUTH POND

PLYMOUTH POND

1 628Tl7MW-2bB 12135

PLYMOUTH POND

monitoring well Figure 4-20

V total VOC contour (ugl) - June 2000 Distribution of Total VOCs in Shallow Bedrock Groundwater

| 34 | total concentration of detected VOCs ND= not detected NA = not analyzed Supplemental Sampling Event Note SW-113 is located downstream of SEEP-1 Hows Corner Superfund Site

Surface Water Sampling Location these two locations were sampled during the Plymouth Maine Baseline Sampling Event in OctoberNovember 1999 Seep Sampling Location WOODARD amp CURRAN

Engineering bull Science - Operations bull 995037wipri reportepa ri interim final feb 2001 cadd drawingsfinalfig 4-20

residential well Figure 4-22 Distribution of Total VOCs in

monitoring well Deep Bedrock Groundwater

total VOCs contour (ugl) Supplemental Sampling Event

Hows Corner Superfund Site

total concentration of detected VOCs ND= not detected NA = not analyzed Plymouth Maine

WOODARD amp CURRAN

995037wipri reportepa-ri interim final feb 2001cadd drawingsfinalfig 4-22 Engineering bull Science - Operations bull

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

FEET

Shallow Monitoring Well

Deep Monitoring Well

C Detected Concentration ND = Not Detected Figure 1-XS Distribution of Total VOCs in Shallow Bedrock Groundwater

Pumping Well

17-Acre Property Boundary Concentration Contour (ugl)

June 2001 Hows Corner Superfund Site

Plymouth Maine WOODARDampCURRAN

-i^rhvj bull Scbncn bull Operations bull 211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0601 dwg04-20-05

PLYMOUTH POND Hopkins Road V

O

PLYMOUTH POND

PLYMOUTH POND

o

0 300 600 mdashfa FEET

Shallow Monitoring Well bull bull - 17-Acre Property Boundary Figure 1-XD

Deep Monitoring Well 1 I Detected Concentration ND = Not Detected Distribution of Total VOCs in Deep Bedrock Groundwater

-mf- Pumping Well June 2001 Residential Well Hows Corner Superfund Site

Plymouth Maine i h Surface Water Sampling Point

g WOODARD ampCURRAN _ ^ _ ^ _ _ yen_ rj i|Hlaquorlny bull Science bull Opt

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0601 dwg04-20-05

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

Shallow Monitoring Well

Deep Monitoring Well

Detected Concentration ND = Not Detected Figure 1-YS Distribution of Total VOCs in Shallow Bedrock Groundwater

Pumping Well

17-Acre Property Boundary Concentration Contour (ugl)

January 2002 Hows Corner Superfund Site

Plymouth Maine WOODARD amp CURRAN Engineering Science- Operations bull

211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0102dwg04-20-05

PLYMOUTH POND

PLYMOUTH POND

Site Pand^ laquoum-laquoBTuitaraquo tLV

vVlf-(

PLYMOUTH POND

0 300 600 ^ = FEET

Shallow Monitoring Well mdashbullbullbull 17-Acre Property Boundary Figure 1-YD - A - Deep Monitoring Well FT Detected Concentration ND = Not Detected Distribution of Total VOCs in

Deep Bedrock Groundwater Pumping Well January 2002 Residential Well Hows Corner Superfund Site

Plymouth Maine Surface Water Sampling Point

WOODARD ampCURRAN Engineering Sciencs- Operations bulli Si

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0102dwg04-20-05

- m j

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND j A O-shy

Shallow Monitoring Well E Detected Concentration ND = Not Detected Figure 1-ZS Distribution of Total VOCs in

Deep Monitoring Well Shallow Bedrock Groundwater

Pumping Well Hows Corner

April 2003 Superfund Site

17-Acre Property Boundary Plymouth Maine Concentration Contour (ugl) r WOODARD ampCURRAN

Engineering bull Science bull Operations bull 211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0403dwg04-20-05

s S pound

PLYMOUTH POND

PLYMOUTH POND

- -

5 PLYMOUTH POND

Jo

FEET

ft Shallow Monitoring Well mdashbullbullmdash 17-Acre Property Boundary Figure 1-ZD Deep Monitoring Well I 1 I Detected Concentration ND = Not Detected Distribution of Total VOCs in

Deep Bedrock Groundwater Pumping Well April 2003

Q) Residential Well Hows Corner Superfund Site Plymouth Maine

(T) Surface Water Sampling Point WOODARD ampCURRAN poundKk EnginawtirKj bull Science - Operations bull

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0403dwg04-20-05

0 Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

B MW-1B

I 12000

PCE

B 10000 Total VOCs

I

i 2000

i 0 Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

c MW-3B

G 2000

1800

B PCE

1600 Total VOCs

1 I I E

il-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

G E

211941

El

I I z E

80

Concentration Trends shy Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-13DB

Total VOCs

c i i c o

Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

MW-16DB

30

c i c c I c o

Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99

PCE

Total VOCs

Jul-01 Jul-03

211941

O bi

c Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

I MW-16IB

i 35

3

c Total VOCs

lt- 2 5

0 | gt

o

1 sectI

c c 0 4

Jul-90 Jul-92 Jul-94 Jul-96 Jul-98 Jul-00 Jul-02 Jul-04

I I MW-108D

I 12

PCE 10

Total VOCs c oc 3

E E I 0

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

E 211941

c Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

fi MW-108S

I I 40

PCE 35

Total VOCs

30

I f 26

20 I o

I 15

10

c Dec-99 Dec-00 Dec-01 Dec-02 Dec-03 I 0

I MW-112D

c 35 - imdash

I A3 shyTotal VOCs

o c

E 1 2

I

ition

B 1 ^

-i c 3

0 Dec-99 Dec-OO Dec-01 Dec-02 Dec-03

211941

I

i

I

cII

Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-112S

08

PCE

Total VOCs 06

o 04

02

0 Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

MW-114D

o

12000

10000

8000

6000

PCE

Total VOCs

4000

2000

i

ccEIIc

i

i

E

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

211941

Con

cent

ratio

n (

ug

l)

E Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

I MW-114S

E A5000 -- Total VOCs

- 4000

0 3000

2000

i 1000

i n shy

Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

MW-115D

c PCE

Total VOCs

c E

o

C c

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03 I 0

211941

IepoundII

EIEIIGICCIccc

30000

25000

20000

o bullsect 15000 b

o 10000 U

5000

0 Aug-99

25000

20000

5000

0 Aug-99

211941

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-2DB

PCE

Total VOCs

Aug-01 Aug-03

MW-2IB

PCE

Total VOCs

Aug-01 Aug-03

IDIBI

ii EIDIISIBIG C

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-102S

6000

5000 PCE

Total VOCs

4000

O 3000

2000

1000

0 Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

MW-103D

16000

~ 14000 ugt 3- 12000 o

^ 10000

sect 8000

O 6000

4000

2000

PCE

Total VOCs

0Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

211941

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

G MW-103S

I I

ampo

12000

10000

E sectc

S

8000

6000

4000

2000

0Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

G I 6000

MW-104D

i 5000

PCE

Total VOCs

i i c

2000

1000

Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

E I

211941

cIccIG

IIBCccBcIc

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-1041

PCE Total VOCs

a 25000

0 20000

a 15000

10000

5000

0 Jan-OO Jan-01 Jan-02 Jan-03 Jan-04

MW-106D

3000

2500 PCE

Total VOCs

=sect 2000

o bullsect 1500

1000

500

0 Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

211941

c Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

c MW-106S

I PCE

Total VOCs

i

i Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

i

i i i E

C

211941 c

Response to EPA-DEP Comment 5 Dated March 312005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

iiw

EPA-DEP Comment 5

Comment 5 Matrix Diffusion The report as well as other proponents of matrix diffusion suggest that depletion of DNAPL (Section 5112 page 5-15) needs to be achieved While that might be the ideal the goal is to achieve performance standards and that goal may be attainable while there is residual contamination in the rock perhaps even DNAPL globules The low bedrock matrix porosity (page 1-15) the high permeability values (page 4-4) the relative flux of the groundwater (page 5-5) and the decrease in surface area and out of the mainstream pockets (appendix C-4) all suggest that the diffusion out of the rock matrix would be insubstantial relative to the regional flux of groundwater through the Site

Response The TI Evaluation Report does not explicitly consider or rely upon matrix diffusion as a basis for requesting a TI Waiver for a portion of the Hows Corner Site The technical literature provides documentation that matrix diffusion can be a significant process that affects chemical transport and groundwater remediation timeframes in unconsolidated and consolidated media including fractured rock (US EPA 1989 Freeze and Cherry 1979 Pankow and Cherry 1996 Fountain 1998) Back diffusion of contaminants from the matrix porosity of the fractured rock can prolong the time necessary to achieve groundwater cleanup goals particularly for compounds such as PCE for which the cleanup goal is a low concentration It is our expectation that matrix diffusion has occurred at the Hows Corner Site and that back diffusion of PCE from the rock matrix will also occur Although the extent to which matrix diffusion is occurring at the Hows Comer Site has not been determined and that lack of knowledge contributes to uncertainty regarding the cleanup times at the Site the effect of matrix diffusion is to lengthen rather than shorten the time required for remediation

REFERENCES

Fountain JC 1998 Technologies for Dense Nonaqueous Phase Liquid Source Zone Remediation Ground-Water Remediation Technologies Analysis Center Technology Evaluation Report TE-98-02 December

Freeze RA and Cherry JA 1979 Groundwater Prentice-Hall Inc Englewood Cliffs NJ 07632 p 410-412

Pankow J F and Cherry J A 1996 Dense Chlorinated Solvents Waterloo Press Portland OR 97291-1399 p 67-88

US EPA 1989 Transport and Fate of Contaminants in the Subsurface EPA6254-89019 p 17-18

Response to EPA Comment 5 050305doc 1 of 1 Woodard amp Curran (211941)

WOODARD amp CURRAN Maine Massachusetts New Hampshire Connecticut Florida Operational offices across the US 1-800-426-4262 www woodardcurran com

Page 13: SDMS DocID 251749 - Records Collections · 2020-06-13 · CORPORATE OFFICES: Maine, Massachusetts, New Hampshire, Connecticut New, York, Florida Engineering • Science • Operations

MW-3B

413951 W-6DB JMW-6SB

(MEDEP Pond 1) Farm Pond

Monitoring Well

Pumping Well

17-Acre Property Boundary

Groundwater Elevation Contour (ft)

211941 Hows CornerwipDrowngsTI EVALpo-tent-aU-72-hrsdwg

Figure X End of Pumping Test

Bedrock Potentiometric Surface at 72 Hours Hows Corner Superfund Site

Plymouth Maine ^ WOODARD amp CURRAN

Englnesring bull Science bull Ope

(MEDEP Pond 1) Farm Pond

Monitoring Well

Pumping Well Drawdown atFigure X

72 Hours _bullbull_ 17-Acre Property Boundary Deep Wells

Drawdown Contour (ft) Hows Corner Superfund Site

Plymouth Maine 151 | Drawdown (ft)

= WOODARD ampCURRAN 211941 Hows CornerwipDrawingsTI EVALDrawdown-72hrs_deepdwg04-19-05

Engineering bull Science bull Operations

(MEDEP Pond 1) Farm Pond

028 MW-12DB

MW-125B 040

l - _ ^ I 016 I N

050 MW-15SB

MW-15DB 048

A J s

- A - Monitoring Well

-$poundbull Pumping Well

_bullmdash 17-Acre Property Boundary

^ Drawdown Contour (ft)

151 I Drawdown (ft)

211941 Hows CornerwgtpDrawinQsT EVAI_Drawdown-72brsdwg04mdash19-05

Figure X Drawdown at 72 Hours

Hows Corner Superfund Site Plymouth Maine

^ WOODARD ampCURRAN Engineering bull Science bull Operations i

(MEDEP Pond 1) Farm Pond

Monitoring Well

Pumping Well

_bullbull_ 17-Acre Property Boundary

f Groundwater Elevation Contour (ft)

|419Q0| Groundwater Elevation

211941 Hows CornerwipDrawinqsTI EVALPotSurf-72hrs_shallowdwg04-19-05

150 300

FEET

Figure X Potentiometric Surface at 72 Hours

Shallow Wells Hows Corner Superfund Site

Plymouth Maine

WOODARD ampCURRAN Engineering bull Science bull Operations

29212 MW-108D

(MEDEP Pond 1) Farm Pond

Monitoring Well

Pumping Well

mdashbullbulllaquo 1 7-Acre Property Boundary

bull Groundwater Elevation Contour (ft)

1419001 Groundwater Elevation

211941 Hows CornerwipDrawingsTI EVALPotSurf-72hrs_deepdwg04-19-05

150 300 =5fc= FEET

Figure X Potentiometric Surface at 72 Hours

Deep Wells Hows Corner Superfund Site

Plymouth Maine

WOODARDampCURRAN Engineering bull Science bull Operations bull

--

Pumping Test Analytical Results Hows Corner Superfund Site

Plymouth Maine

Well ID oper Jaccb Analyses 2 Theis Analyses Fissure

Well Id Rd (ft)

Saturated Thickness

Transmissivity

(ft2day) K

(ft2day) K

(cmsec) Storage

Coefficient Transmissivity

(ft2day) K

(ft2day)

K (cmsec)

Storage Coefficient

System K

(ftday) PW-207OB 8 85 481 057 200E-04 392E-02 36 042 150E-04 809E-04 027 MW-103S 50 85 451 053 187E-04 720E-03 92 108 382E-04 283E-04 083 MW-103D 54 185 455 025 868E-05 210E-02 65 035 123E-04 237E-04 044 MW-2IB 59 85 352 041 146E-04 699E-03 104 123 433E-04 512E-04 052 MW-2DB 63 85 334 039 139E-04 845E-03 148 080 283E-04 239E-04 046 MW-104D 95 185 489 02 6 932E-05 654E-03 98 053 186E-04 547E-05 037 MW-104I 97 85 33 03 9 137E-04 362E-03 117 137 484E-04 962E-05 048 MW-101I 107 85 364 043 151E-04 490E-03 511 601 212E-03 223E-04 136 MW-102D 134 185 435 024 829E-05 248E-03 108 058 206E-04 850E-05 065 MW-101D 138 185 492 027 938E-05 511E-03 671 362 128E-03 700E-04 172 MW-205 219 85 57 067 237E-04 255E-03 447 526 186E-03 359E-03 -shyMW-204D 221 185 367 020 700E-05 170E-03 790 427 151E-O3 155E-04 147 MW-204S 225 85 379 045 157E-04 156E-03 1031 1213 428E-03 313E-04 199 MW-1B 228 85 325 038 135E-04 977E-04 340 400 141E-03 739E-05 054 MW-203S 273 85 489 058 203E-04 117E-03 1255 14 76 521 E-03 216E-04 210 MW-106D 278 185 51 028 972E-05 141E-03 1065 576 203E-03 360E-04 104 MW-203D 278 185 478 026 911E-05 152E-O3 765 414 146E-03 364E-04 138 MW-105D 364 185 44 024 839E-05 830E-04 769 415 147E-03 200E-04 127

1 Analyses conducted using Cooper and Jakob method on late drawdown data collected during constant

discharge pumping test conducted at the Hows Comer Site from September 20 - 30 2004

2 Analyses conducted using Theis solution for unconfmed approximation (1935)

J Analyses conducted using Moench method for dual porosity estimation (1984)

Fissure System Storage

Coefficient 402E-04 117E-06 264E-04 300E-04 932E-05 235E-07 502E-05 326E-06 801E-05 542E-04

-

803E-05 762E-05 134E-05 498E-05 115E-04

47E-04 838E-05

3 ysesh Analysis

Block System K (ft2day)

251E-02 207E-03 564E-04 163E-04 585E-04 465E-02 153E-04 498E-03 855E-04 356E-03

-

292E-03 394E-03 720E-04 526E-03 160E-01 35OE-O1 287E-03

Block System Storage

Coefficient

402E-02 164E-04 183E-02 330E-03 158E-03 847E-03 286E-03 326E-04 803E-05 272E-03

723E-04 686E-04 148E-04 349E-04 115E-03 47E-04 838E-04

Theis - Moench - CJ - AnalyticalResults_4-19-O5xls

DRAFT

242

24

238

236

bulla

c

i

a Q

234

232

228

226

Hows Corner Constant Discharge Testing USGS Background Groundwater Level USGS 445319068560101 ME-PEW456 Kenduskeag Maine

End of Monitored Recovery Period 09302004

Regional Background Location i 226 miles from Pumping Locatio

lt

697

NOTES

1 Groundwater samples collected in 1999 were screened for five volatile organic compounds (VOCs) only N

tetrachloroethene (PCE) exceeded reporting limits MW-2030 082304 082304 082304 082304 u

2 Strike and Dip of likely or possible transmissive 30 45 55 85 feature within the packer interval from which the indicated sample was collected

MW-204D

PCE TOTAL VOCs

081904 30

220 2636

A

081904 46-50 540 6436by

081904 IT

260 3073

x

MW-105D

PCE TOTAL VOCs

111199 50-60 2100 2100

MW-106D

PCE TOTAL VOCs

111199 76-86

400 400

111199 137-147

1400 1400

111299 1355-1455

350 350

PCE TOTAL VOCs

44 84

64

MW-6SB

bulli

lt

gt-

170 234

35

I I i

140 192

^^52

^^52

130 183

52 - lt

S A 34

PW-207 082404 082404 082404 20 37

PCE 1300 TOTAL VOCs

17-Acre George West Property Boundary

MW-113D

PCE TOTAL VOCs

112299 46-56

350 350

112299 70-80 190 190

150

112299 105-115

129 129

112399 138-148

230 230

L e g e n d ( J New Monitoring Well-Summer

Site Property Boundary ^ P u m p i n g Well-Summer 2004

-xmdashxshy Source Area

bull0shy Monitoring Well shy Pre 2004 Angled Boring-Summer 2004

211941laquoipdwgTI-ELV21ig41paltker-data2

2004 PCE of Total

bull lt70 VOCs

M W - 1 14D ^ ^

Figure xx Packer Testing Results in

Vicinity of Source Area Hows Corner Superfund Site

Plymouth Maine ^ WOODARD ampCURRAN

^^^^^^^^^^m ampKm Engineering - Science bull Operations

c Northeast Geophysical Services Borehole Geophysical Log

MW-203 Date logged 081704 Plymouth Maine

I Flowmeter Measurements Tomporaturo(C) Acoustic Televiewer

7 5 8 8 5 9 95 Caliper (Inches) Resistance (Ohms) Spontaneous Potential (mVj Dip In Degrees PCE Total VOCs

3 0 2 0 8 0 laquodeg 4S 1000 1400 1800 2200 MO HO 1000 1200 MOO 0 laquo deg ugL ugL n 1 1 1 1 1 1 1 1 1 i 1 1 1 1 n 1 1 1 1 1 1 1 1 1 1 1 n I l l l l l l l n

Ambient Flowneter pumping Rowmeter 11 gpm 6

H

bull

magnetic 10 bull 10 bull - 10 - north - 1 0I

-

_

bullbullbull - bull

20 bull bull20 bull ^ ltr~mdash 01

I

4 ^

LOS7

^

44 84 I I

Xr - 2

lt ^ bull30 -_ _^O1J- 1 _ 050 30 - 3 0

0r - - 3

C -j [ bull bull bull | shy

-O8 H ~ 1 045 7

1 4040 - 40 - -40 r - 14gt 13

V1s -- -023 f 1022 1V 170 234 I

T lt bull B gtf 50^ J50 - - 5 0 - - 5 0

I eet be

lo

i 1

1 1

1

140 192 - - - -t shy

-mdashj bullpound 60 - $o - - 60 - -60

H i I c

bull024

ampbull

3 - T lt ftft rgt He

70 bull j 70 - - 70 - 7 0 -

in -j bullbull shy

-021 1 T 022

- Ton _ Ov

26

130 183 NF NF

90 -_ 90 - 7 90 - -90

-

ifi Jf

3J

^gt _ N F NF bull bull shy

| H100 - j 100 bullbull 100 - -100

1 1 1 1 1 1 1 ) | 1 f I 1 1 1 ) 0 20 40 60 80

flft mdash ftn - mdash rVt

30 4 g 0 20 40 60 Dip in Degrees bullbull

Likely or poss bleFluid Resistivity (ohmmeters) The dip direction-- indicated

^ t h e l i n e extending from t h

I Iransmissive zone circle The strike of the feature is 90 degrees from this

The acoustic televiewer graph displays the mostprominent features selectedffom the acoustic televiewer

R n r a h n l c D O t t n O I B

f i o n n h w c i r a l U K U p i i y SI Ud l

1 rn l_Og Packered Interval August 2004

E tog The location dip angle and dip direction of the sleeted M W - 2 0 3 Groundwater samples were collected by Woodard S Curran on H23120M features are approximate Refer to the televiewer og of His _ well for more precise detail Plymouth Maine Date logged 081704

I

1

Northeast Geophysical Services Borehole Geophysical Log MW-204 D a t e l o gge d 072604

Plymouth Maine

n 3

Flowrneter Measurements(in gpm)

Caliper (Inches)0 3 5 4 0

1 1 1 1 1 1 1 t 1 1 1 1 1 1Ambient Rowmeler pumping Flowmetsr 05gpm

Templaquorature (C) bull bull bull bull i

7 75 8 8S 9 Resistance (Ohms) Spontaneous Potential (mV)

4000 SOW 600 4M 0

Acoustic Televiewer (interpreted)

Dip in Degrees 0 20 4060 SO

at N

PCEugL

Total VOCs ugL

- -_ a

10-

shy 10 bull - 10 shymagnetic

north - 10

o o

bull 1

11

11

1 1

1 1

11 1

1 1

1 1

1 1

1 1

1 1

1 1

1 1

1 1 E 1

- L

3 7 2 0 2 0r bull 20 bull - shy

i S_ N F

bull30 bull 7 3 0 220 2636shy1^ J J 004

fI f V ^

40 shy 4 0 4 0 shy - 4 0rbull019 [_ 007 w8 - - shy5 c

bull

gt

Ia50i 540 6436

bull50 - - 50 - - 5 0

-QQ7 - bull - -t T

pound V gtk

B 6 0 - e o - 7 6 0 -60shyQ 1 1

Q -007 -004 bull1 mdash T - J ~

bull

- - shyT 70 -J c [TO- - 70 - 7 0-

V Y 1- -004 -003

mdash T -h - y - j i - - mdash 260 3073 - gt=7

80 -j NF bull80 - - 80 - - 8 0Jgt

bull i

i 1

i i

C- bull shy

90 shy

K

Jlt i90 90 shy - 9 0shy -

l

ii

I I I I

NF bull M J

I ^ ^ - ^ bull 1

mdash mdash - _

s -7 ^100shy

till

1 100 100- H - 1 0 0shy -1 x Likety or possible k ^ Iransmissive zonebull

1 i i i ii i i i | l l l l | l i l l 0 20 40 ED 80

1 -

3 0SOFluid Resistivity (ohmmeters)

Dip in Degrees The djp ^ ^ o n is indicated ty Ihe line extending from tha circle The strike of Ihe feature

19- 3U UIHJIW93 IolII l l l lraquo

bull

The acousfc televiewer graph displays the mostprominent features selected from the acoustic televiewer109 The location dip angle and dip direction of Ihe sleetedfeatures are approximate Refer to the televiewer log of thiswentormore precise detail

B o r e h o l e G e O D h V S I C a l LOO B W H U I B w c w p n y o i v a i w v yM W - 2 0 4

P l y m O U t n MaiDB

Packorod Interval August 2004Groundwater san-ples wampramp collected by Woodard a Curran on OMO23C4

Date logged 072604

C

I

E Northeast Geophysical Services Borehole Geophysical Log Date logged 072704

I MW-205

Plymouth Maine

Flowmeter Measurements Temperature (C) Acoustic Televiewer (In gpm) I ~l (Interpreted)

I 85 10 Caliper (inches) 95

Dip in D g r laquo Resistance (Ohms) Spo ontaneous Potential (mV PCE Total VOCs 3 0 16 4 0 4 5 ) 20 40 60 80 10 00 2000 30 00 4VJ 400 -3 laquo

i i i i 1 i i I i 11 4 0 D 1 I I ugL ugL

C h

iii Ambient Flowmetar pumping

Flowmeter 1 25 gprn

I bull$bull

i

I rmdash magnetic 1 north ^^^^ 1 VI f

10 ~ I C x 10 bull - 10 bullbull

4 5 6mdashmdash f 1000B 11448 noisy nodi a raquo ^

mdash 5rt mdashi mdash Oft pound) 1100B 12509

cjmdash1 007

-

i i i 1

en

8 B a B

30 mdash

-

40 shy

-mdash I -

50 -_

__NF lt005

- 30 - - 3 0 it 34V

MO P26 V S) 1300B 13776 _ N F NF

26

40 bull - 40 bull 7-40 gt J Vf1 cX

) -j -

_ N F NF 50 c bull - 50 ^ 7-50

i I

I

c

B pound 60 - 6 0 7 60 - 7-60 a i 1

_ N F NF i Si f f 70 -_ bull70 bull - 70 shyC I 9

-m bull - shyA

_ N F NF 80 80 -j bull80 bull - 80 - C- 33 34

bull

5-i r

i 1

J r

Ck

_ N F NF 9 0 90 - - 90 shy

i bullCshy

J rK bull

100 -j ^ Likely or possible bull100- - 100- I -100

transmissive zone bull - ^ bull shy] |

1 1 1 1 1 1 1 I 1 i i i 1 i i 1 1 0 20 40 SO SO 10 20 30 40 50 Dip in Degrees 30 4 0 Fluid Resistivity (ohmmeters) Thlaquo dip direction is indicated

by the line extern r g from the circle The strike of he feature is 90 degrees from ihis

The acoustic televiewer graph displays the most

I Borehole Geophysical Log Packered Interval August2004 prominent features selected from the acoustic televiewer

Groundwatcr samples were oollccled by Woodard amp Cufran orgt S172004 log The location dip angle and dip direction of ins slsctsd MW-205 features are approximate Refelt to the televiewer log of this wall for more precise detail Plymouth Maine Date logged 072704

I

C

I Northeast Geophysical Services Borehole Geophysical Log Date logged 072704

I MW-206

Plymouth Maine

Flowmetor Measurements Temperature (C) Acoustic Televiewer | I r T i i i i i i i i i i i i i i r I |(in gpm) (Interpreted)

I 75 8 flS 9 95

Caliper (inches) Resistance (Ohms) Spontaneous Potential (mV) Dip In Degress PCE Total VOCs 30 35 40 4 5 0 20 40 M 90 4500 5500 6500 ugL ugL I i i

I I

- 1 0

I - 2 0

I 2900B 32401

i i L

E 0

i 6300B 68901

i I 0 20 40 SO 80

20 30 40 50 Dip in Dlaquogralaquos

amp 4 a Fluid Resistivity (ohrnmeters) The dip dirertion is indicated Likely or possible by iho line extending from the transmissive zone circle The striKe of the feature

is 90 degrees from tNs

Borehole Geophysical Log Packered Interval August 2004

E amples were collected by Woodard amp Cunan oo SM82004 log Thraquo location 4p angle and dip direction of the sloeled MW-206 feature are approximate Refer to the televiewer 109 of this well for more precise detail Plymouth Maine Date logged 072704

C

I Northeast Geophysical Services Borehole Geophysical Log

Date logged 082304 PW-207

I Plymouth Maine

Fiowmeter Measurements Temperature (C) Acoustic Televiewer

I (in gpm) (interpreted)

75 8 85 9 95 Caliper (inches) Resistance f0tims) Spontaneous Potential (mV) Dip in Degrees PCE Total VOCs

55 60 0 20 40 SO 80 ugL ugL I I I I I I I

Ambienl Fiowmeter pumping Flewmater

magnetic - 10 - - 1 0

north

i - 20 - - 2 0

1300 1410

i - 30 - - 3 0

i tf

5400 5802 - 40 - - 4 0

B - 50 - - 5 0

I 18000 19234

- 60 - - 6 0

I 12000 13085

- 70 - - 7 0

- 8 0

i - 9 0 19000 20354

G - 100- -100

I 110 110 bull110

0 20 40 60 SO 10 20 30 Dip m Degrees

Fluid Resistivity (ohmmeters) I 50

The dip direction is indicated by ihe line extending from the circle The strike of the fealure is 90 degrees from this

Borehole Geophysical Log

G Packorod Interval August 20(M log The location dip angle and dip dirlaquocton or the sleeted Groundaier samplss were ooliecled by Woodard i Curran on ampt24f2ltXM PW-207 failures are approximate Reter to the televiewer log of this wlaquoll for more precise detail PlyPIOUth Maine Date logged 082304

I

Table XX Packer Permeability and Packer Sampling Results for Potential Fracture Intervals

1

WellID MW-101D MW-101D MW-101D MW-101D MW-101D MW-101D MW-101D MW-101D MW-101D MW-101D MW-I01D MW-101D MW-101D MW-102D MW-102D MW-I02D MW-102D MW102D MW-102D MW-102D MW-102D MW-102D MW-I02D MW-102D MW-102D MW-102D MW-103D MW-103D MW-103D MW-103D MW-I03D MW-103D MW-103D MW-103D MW-103D MW-103D MW-103D MW-103D MW-I03D MW-104D MW-104D MW-104D MW-104D MW-I04D MW-104D MW-104D MW-104D MW-104D MW-104D MW-104D MW-105D MW-105D MW106D MW-106D MW-106D MW-107D MW-107D

1999 Drilling Program

Hows Corner Superfund Site Plymouth Maine

Potential Fracture Top Of Bottom 6 Depth to lt Topof i Interval from Packer Packer Middle of Elevation Hydraulic bull PCE

GS ELEV 1 Rock Drilling Interval Interval Interval of Interval Conductivity Concentration (ft msl) (ft msl) TEST (ftbgs) (ftbgs) r(ftbgs) ( f t b (ft mil) (cmsec) (raquogL)

4339 4329 13 28-29 33-3537-39 271 376 324 4016 OOOE+00 4339 12 37-3444-46 380 485 433 3907 157E-04 4339 11 488 593 541 3799 132E-04 4339 10 60-61 578 683 631 3709 OOOE+00 4339 9 678 783 731 3609 I79E-05 4339 8 778 883 831 3509 106E-05 4339 7 880 985 933 3407 243E-05 4339 6 990 1095 1043 3297 339E-06 4339 5 1090 1195 1143 3197 OOOE+00 4339 4 1190 1295 1243 3097 OOOE+00 4339 3 1365-1375 1290 1395 1343 2997 OOOE+00 4339 2 147-157 1390 1495 1443 2897 580E-05 4339 1 147-157 1470 1575 1523 2817 741E-05 43161 43061 13 166 271 219 4098 333E-04 43161 12 30-3136-40 260 365 313 4004 I54E-05 43161 11 36-4041-43 362 467 415 3902 548E-05 43161 10 470 575 523 3794 598E-05 43161 9 570 675 623 3694 197FOS 43161 8 670 775 723 3594 OOOE+00 43161 7 770 875 823 3494 891 E-05 43161 6 83-94 870 975 923 3394 139E-05 43161 5 970 1075 1023 3294 123E-04 43161 4 1070 1175 1123 3194 526E-06 43161 3 1170 1275 1223 3094 138E-05 43161 2 1270 1375 1323 2994 671E-06 43161 1 1370 1475 1423 2894 OOOE+00 42997 42497 13 18-19 170 275 223 4077 OOOE+00 42997 12 260 365 313 3987 766E-05 42997 11 360 465 413 3887 727E-05 42997 10 460 565 513 3787 192E-05 42997 9 560 665 613 3687 752E-05 42997 8 660 765 713 3587 778E-05 42997 7 85-86 763 868 816 3484 260E-05 42997 6 860 965 913 3387 289E-05 42997 5 102-103 960 1065 1013 3287 102E-04 42997 4 1060 1165 1113 3187 522E-06 42997 3 1160 1265 1213 3087 520E-06 42997 2 129-130 1260 1365 1313 2987 960E-04 42997 1 1360 1465 1413 2887 OOOE+00 43372 42922 11 35-37 42-45 350 455 403 3935 684E-04 43372 10 460 565 513 3825 500E-05 43372 9 560 665 613 3725 106E-05 43372 8 72-74 660 765 713 3625 204E-05 43372 7 760 865 813 3525 872E-06 43372 6 860 965 913 3425 467E-06 43372 5 960 1065 1013 3325 200E-05 43372 4 1060 1165 1113 3225 354E-05 43372 3 125-130 1160 1265 1213 3125 157E-05 43372 2 125-130 1260 1365 1313 3025 337E-04 43372 1 1365 1465 1415 2922 689E-06 43052 43002 2 54-58 490 595 543 3763 124E-05 2100 43052 1 139-140 145-146 1367 1472 1420 2886 154E-04 1400 43291 4391 3 bullI133 260 365 313 4017 439F06 43291 2 77-78 760 865 813 3517 230E-03 400 43291 1 143-144 1355 1460 1408 2922 971E-06 350

29958 27258 4 450 555 503 2493 OOOE+00 (21)A 29958 3 103-105 1000 1105 1053 1943 752E-04 (063)A

Table XX Packer Permeability and Packer Sampling Results for Potential Fracture Intervals

1999 Drilling Program

Hows Corner Supcrfund Site Plymouth Maine

gtbull i Potential Fracture Top _OfBot Bottom of Depth to ltbull Top of Interval from f Packer Packer Middle Of

GS ELEV lt Hock Drilling interval Interval Interval WeD ID ft msl) (ft msl) TEST (ftbgs) ltft$gs) (ftbgs) (ftbgs)

MW-107D 29958 2 128-130 1200 1305 1253

MW-107D 29958 1 139-141 1350 1455 1403

MW-108D 31904 31104 6 35-36 300 405 353 MW-108D 31904 5 60-62 550 655 603

MW-108D 31904 4 80-83 750 855 803

MW-108D 31904 3 118-119 123-124 1150 1255 1203

MW-108D 31904 2 147-149 1440 1545 1493

MW-108D 31904 1 1700 1805 1753

MW-110D 40576 40426 2 21-31 210 315 263 MW-110D 40576 1 148-154 1460 1565 1513 MW-I11D 40519 4 70-71 650 755 703

MW-111D 40519 3 79-82 84-86 780 885 833 MW-I11D 40519 2 97-102 950 1055 1003 MW-111D 40519 1 1370 1475 1423

MW-112D 3027 2942 4 42-52 420 525 473 MW-112D 3027 3 850 955 903 MW112D 3027 2 1100 1205 1153 MW-112D 3027 1 135-136 140-141 1340 1445 1393

MW-113D 43085 43085 5 250 355 303 MW-I13D 43085 4 47-49 460 565 513 MW-113D 43085 3 73-74 700 805 753 MW-113D 43085 2 1050 1155 1103 MW-113D 43085 1 1380 1485 1433

MW-114D 42394 41594 4 48-49 450 555 503 MW-114D 42394 3 79-81 740 845 793 MW-114D 42394 2 121-129 1250 1355 1303 MW-114D 42394 1 134-142 1350 1455 1403

MW-115D 4035 4035 4 300 405 353 MW-1I5D 4035 3 70-71 650 755 703 MW-115D 4035 2 1150 1255 1203 MW-115D 4035 1 1400 1505 1453

LOT-28W 382 7 450 555 503 LOT28W 382 6 550 655 603 LOT-28W 382 5 650 755 703 LOT28W 382 4 750 855 803 LOT-28W 382 3 850 955 903 LOT-28W 382 2 950 1055 1003 LOT-28W 382 1 1055 1155 1105

NOTES cmsec = centimeters per second ft bgs = leet below ground surface It msl = feet below mean sea level lt = not detected at indicated reporting limil A = detected below laboratory PQL ( ) = detected below reporting limits

Elevation of Interval

(ft nisi) 174

159

283gt 2588

2388

1988

1698

1438

3795 2545 3349 3219 3049 2629

2555 2125 1875 1635

4006 3796 3556 3206 2876

3737 3447 2937 2837

3683 3333 2833 2583

3318 3218 3118 3018 2918 2818 2715

Hydraulic Conductivity

(cmsec)

323E-05

208E-05

471E-03

471E-03

624E-05

3I6E-05

264E-05

261 E-05

OOOE+00 200E-04 953E-05 OOOE+00 OOOE+00 212E-05

361 E-05 410E-06 2gQE06 292E-05

786E-05 124E-05 151 E-05 822E-06 82IE-06

858E-05 I69E-05 352E-03 866E-05

223E-05 394E-06 122E-05 525E-06

831 E-05 182F-05 L62E-05 129E-05 190E-05 890E-04 981 E-04

PCEraquo Concentration

(ugL)

lt5

(14A)

98 11

15

22

11

30

200 (62)A

110 210 300 240

(44)A (23)A

5

350 190 129 230

2200 1900 2600 2600

(17)A (16)A (19)A

96

Table XX Packer Permeability and Packer Sampling Results for Potential Fracture Intervals

2004 Drilling Program

Hows Corner Superfund Site Plymouth Maine

Top of Bottom of Depth to Midpoint

t K

ELEV (ft Potential Transmissive Zones Packer Interval

Packer Interval

Middle of Interval

Elevation of interval

Hydraulic Conductivity

PCE Concentration

Well ID msl) TESTr (ft bgs)- (ftbgs) (ftbgs) (ftbgs) (ft msl) (cmsec) (ogt) MW-203D 43227 4 277279 24 32 28 4043 667E-05 44

3 408415420 39 49 44 3883 593E-05 170 2 526 530 49 57 53 3793 101E-04 140 I 828830842 80 88 84 3483 701E-05 130

MW-204D 43262 5 295 300 26 34 30 4023 902E-05 220 4 463496513516 45 53 49 3833 119E-04 540 3 681685688 63 71 67 3653 OOOE+00 2 758 76 2 71 79 75 3573 309E-05 260 I 88 96 92 3403 OOOE+00

MW-205 42389 3 164 166 168 15 20 175 4148 OOOE+00 1000B 2 302305312 30 35 325 3998 107E-04 1300B 1 40 45 425 3898 OOOE+00

MW-206D 43007 5 17 72 195 4128 291E-05 4 296 302 307 29 34 315 4008 940E-05 2900B 3 522 52 57 545 3778 944E-07 2 656 64 69 665 3658 353E-06 1 92392793 4939 91 96 935 3388 614E-05 6300B

PW-207 43477 5 184622162819 18 29 235 4088 209E-05 1300 4 3508 32 43 375 3948 568E-06 5400 3 53325341542154325559 50 61 555 3768 821E-05 18000

6359 61 72 665 3658 866E-06 12000 1 8685 84 89 865 3458 213E-05 19000

NOTES cmsec = centimeters per second ft bgs = feet below ground surface ft msl = feet above mean sea level B = detected in lab blank

Table XX Orientation Permeability and Groundwater Sampling Results for Transmissive Features

2004 Drilling Program

Hows Corner Superfund Site Plymouth Maine

Borehole Geophisical Feature depth Dip True Dip True Transmissive Log Feature (Feet) Degrees Azimuth Strike bullvgt(Ltk|iy^

Number v Tosftble) v MW-203 5 277 64 337 67 Likely

6 279 59 11 281 Likely 8 352 14 177 87 Likely 11 381 46 96 6 Possible 12 408 35 271 1 Possible 14 415 57 250 340 Possible 15 420 58 202 292 Likely 18 526 52 75 345 Likely 19 530 52 82 352 Likely 28 828 48 75 345 Likely 29 830 52 17 287 Likely 30 830 56 233 323 Possible 31 842 50 130 40 Likely

MW-204 4 295 15 147 57 Likely 5 300 43 91 1 Likely 11 439 31 80 350 Possible 12 440 46 219 309 Possible 14 463 50 358 88 Likely 15 496 34 198 288 Likely 16 513 54 17 287 Likely 17 516 33 14 284 Likely 25 681 39 359 89 Possible 26 685 22 45 315 Possible 27 688 35 73 343 Possible 32 758 45 236 326 Likely 33 762 46 306 36 Likely

MW-205 5 164 69 106 16 Possible 6 166 78 165 75 Possible 7 168 82 115 25 Possible 8 168 68 116 26 Possible 12 215 46 222 312 Possible 13 217 75 62 332 Possible 14 219 29 32 302 Possible 16 237 69 250 340 Possible 17 256 73 353 83 Possible 18 272 44 202 292 Possible 21 299 37 196 286 Possible 22 302 31 206 296 Possible 23 305 59 48 318 Likely 24 312 63 42 312 Likely

MW-206 1 264 37 181 271 Likely 2 296 69 217 307 Likely 3 302 66 233 323 Likely 4 307 64 224 314 Likely 8 342 62 259 349 Likely

jjHydraulic GoiDanctilyity j(cmsecjw

667 E-05

593 E-05

101 P04

710 E-05

902 E-05

119 E-04

0

309 E-05

0

107 E-04

94 E-05

PCE (ugL)

44

170

140

130

220

540

260

IOOOB

1100B

1300B

2900B

STotal vVoCsv tig1)

84

234

192

183

2636

6436

3073

11448

12509

13776

32401

PCEyo dfCTotaf

52

73

73

7 1

83

84

85

87

88

94

90

Table XX Orientation Permeability and Groundwater Sampling Results for Transmissive Features

2004 Drilling Program

Hows Corner Superfund Site Plymouth Maine

Borehole Geophisical Feature deptt raquoip True pip True Transraissive Log Feature (Feet) shy Degrees Azimuth Strike (tikely

Number raquo Possible) 22 522 57 54 324 Possible 25 656 40 82 352 Possible 32 871 59 151 61 Possible 33 883 53 185 275 Possible 34 895 7 175 85 Likely 35 899 53 90 0 Likely 36 902 49 184 274 Likely 37 923 9 175 85 Likely 38 927 42 206 296 Likely 39 934 48 167 77 Likely 40 939 26 180 90 Likely

PW-207 1 1846 33 167 77 Likely 4 2216 49 289 19 Possible 7 2819 59 265 355 Possible 11 3508 55 189 279 Possible 18 5332 43 305 35 Likely 19 5341 51 30 300 Likely 20 5421 20 254 344 Likely 21 5432 39 301 31 Likely 23 5559 52 302 32 Likely 25 6359 24 182 272 Possible 29 8049 77 231 321 Possible 30 8685 78 38 308 Likely 32 9334 29 194 284 Likely

NOTES

B = detected in lab blank

Hydraulic Conductivity

(cmsee) 944 E-07 353 E-06

614 E-05

209 E-05

568 E-06

821 E-05

866 E-06

213 E-05

bulltCE (ugL)

6300B

1300

5400

18000

12000

19000

Total VOCs (ug1)

68901

1410

5802

19234

13085

20354

PCE of Total VOCs

9 1

92

93

94

92

93

Response to EPA-DEP Comment 3 Dated March 312005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

lit

EPA-DEP Comment 3

Comment 3 The reported f values and resultant Kd values There remains doubt that the values used in the flushing model accurately reflect the propensity for PCE to sorb to the bedrock The ^ values presented in Appendix B may be unrealistically high because the bedrock samples may have contained organic carbon that was unavailable for sorption The reported f values are only qualitative estimates of the organic carbon content of the bedrock samples The Walkley and Black organic carbon measurement method is quick and simple but the results obtained cannot be considered quantitative because it requires a correction factor which often results in erroneous values it assumes the organic carbon has an average valence of zero oxidizable and reducible constituents such as chloride ferrous iron and manganese oxides interfere with the results and the errors introduced by interference are potentially greater when the organic carbon content is low at low f values it is not clear that organic carbon is controlling PCE sorption (Schwarzenbach and Westall 1981 Mackay et al 1986 Fetter 1999)

In order to derive a Kd-based retardation factor that is reasonable given the reported f values and the rapid advance of the PCE plume described on pages 4-11 and 4-12 the flushing model requires a bulk density to porosity ratio that is roughly two orders of magnitude higher than the actual ratio for the Hows Corner bedrock (page 4-4) This apparent discrepancy needs to be addressed

Response This comment raises several concerns about the collection and analysis of samples for fraction of organic carbon (f^) the quality of the resulting data and the implications of the use of those data for estimation of the retardation of groundwater contaminant movement Results of bedrock analysis for f were proposed in the TI Evaluation Work Plan for use in conjunction with groundwater contaminant concentrations and aquifer information to estimate cleanup times using the Batch Flushing model It is important to use accurate f values from representative bedrock in the Batch Flushing model in order to obtain reasonable estimates of the remedial time frame Because of the importance of accurate and representative results the TI Investigation field program was designed and conducted both to collect samples representative of the rock volume most likely to be in contact with contaminated groundwater and to analyze them using an appropriate refereed analytical method Five potential methods for evaluating f were identified Of the five methods the Walkey-Black method was selected because it has minimal method interferences and a sufficiently low detection limit as well as a long history of use in agronomy and contamination studies The PRP Group is pleased with the quality of the data obtained from the bedrock samples as represented by their precision and reproducibility

The first part of this comment relates to the determination of fraction of organic carbon (f^) values The several subparts of the first paragraph are addressed individually in items 1 through 5 below The second part of the comment regarding the resultant distribution coefficient (Kd) values is addressed separately as item 6 below

1 There remains doubt that the values used in the flushing model accurately reflect the propensity for PCE to sorb to the bedrock

bull The rock core samples used for f (gocg) analysis were from core immediately adjacent to fractures These rock core samples included the fracture surfaces themselves and rock core extending back less than 1 cm from the fractures Therefore the foe data reported in the TI Evaluation represents the f of bedrock through which groundwater will travel and to which PCE will adsorb Based on the careful selection of sample locations and the

Response to EPA Comment 3 050205doc 1 of 11 Woodard amp Curran (211941)

number of samples collected we are confident that the measured f values are representative of the f at points of contact for PCE with the bedrock it is these f values that determine the propensity of PCE to sorb to the bedrock

bull The samples of rock core collected for analysis of f originated from 19 different locations varying in depth from 11 to 90 feet Therefore it is very unlikely that the rock core samples were contaminated with extraneous organic carbon from above ground

2 The foc values presented in Appendix B may be unrealistically high because the bedrock samples may have contained organic carbon that was unavailable for sorption

bull As noted in response 1 the f data reported in Appendix B represents organic carbon primarily associated with the surface of fractures in the bedrock through which groundwater is most likely to travel Therefore it is this organic carbon that the contaminants in the groundwater will come in contact with and adsorb to in the fractured rock at the site

bull The chemical oxidation agents used in the Walkey-Black method oxidize the easily oxidizable organic carbon in the medium and the foe is calculated from the quantity of the agent consumed Therefore it is unlikely that the analysis of the bedrock samples measured organic carbon that was unavailable for sorption

3 The reported foc values are only qualitative estimates of the organic carbon content of the bedrock samples

bull The reported f values are accurate quantitative results Schumachers review of Methods for the determination of total organic carbon (TOC) in soils and sediments (NCEA-C-1282 EMASC-001 April 2002) identifies the Walkley-Black method which was used to analyze the reported foc values as the reference method for comparison to other methods for analyzing total organic carbon

bull Schumacher also points out that if anything the WalkJey-Black method may underestimate the total organic carbon in a sample due to possible incomplete oxidation of organic carbon Usually the incomplete oxidation of total organic carbon in environmental samples is corrected for by multiplying the measured foe by 130 (Walkley amp Black 1934 Schulte 1995)

bull When the f data in the TI Evaluation Report (WampC 2005) Appendix B (attached) are analyzed statistically the standard deviation of the f for the 19 samples analyzed is 174 of the average f Given this standard deviation the 95 confidence interval for this data ranged from a low of 000123 gocg to a high of 000253 gocgm

The labs Method of Detection Limit (MDL) for the f measured using the Walkley-Black method is 00001 gocg Therefore the average (000188 gocg) the mean (000185 gocg) and geometric mean (000187 gocg) of the f values for the rock core at Hows Corner are all statistically significantly greater than the MDL of the Walkley-Black method

In addition to the aforementioned statistical analysis of the foe data triplicate samples (n = 3) from the same rock core (including one sample from the 19 rock core samples) were

Response to EPA Comment 3 050205doc 2 of Woodard amp Curran (211941)

analyzed for their f to determine the repeatability of the Walkley-Black method The average the mean and the geometric mean of the f values of these replicate samples was 000162 gocg 000150 gocg and 000159 gocgm respectively The standard deviation of these measurements was 000039 gocg

4 The Walkley and Black organic carbon measurement method is quick and simple but the results obtained cannot be considered quantitative because it requires a correction factor which often results in erroneous values it assumes the organic carbon has an average valence of zero oxidizable and reducible constituents such as chloride ferrous iron and manganese oxides interfere with the results and the errors introduced by interference are potentially greater when the organic carbon content is low at low foc values it is not clear that organic carbon is controlling PCE sorption (Schwarzenbach and Westall 1981 Mackay et al 1986 Fetter 1999)

bull Schumachers review (NCEA-C-1282 EMASC-001 April 2002) of the Walkley-Black method identifies several potential problems with this analytical method that could occur if the analytical lab is not familiar with the nuances of the chemistry associated with this method Interestingly Schumachers review neglected one of the more important analytical steps required to avoid errors in quantifying f in samples where there might beNAPL

It is absolutely critical to eliminate any NAPL from rock core samples prior to using the Walkley-Black method to measure foe in such samples This was done by the lab (PTS Laboratories) that measured the foe in the rock core samples from Hows Corner The lab used the Dean-Stark method (solvent extraction) to remove all hydrocarbons (including PCE and other NAPLs) from the sample (PTS Laboratories) This extraction method does not interfere with the subsequent analysis of the natural organic carbon associated with the rock core

Subsequently the samples were dried at 150degC to a constant weight (normally 16 hours) This latter step oxidizes all inorganic minerals including ferrous bearing minerals to ferric oxides and precludes their interference during the oxidation of the samples with chromic acid This procedure completely eliminates any positive bias in the reported foc

data that might have occurred due to the presence of ferrous ions and other reduced minerals

bull As noted in Response 3 the incomplete oxidation of total organic carbon results in an underestimate of the f and is corrected for by multiplying the f by a correction factor of 130 (Walkley amp Black 1934 Schulte 1995) The fx data reported in the TI Evaluation was corrected accordingly by using this correction factor

bull Excess chloride (Cl~) in percent weight quantities as found in saline soils may interfere with the quantitative titration of reduced chromium (Walkley 1947) However given that the primary rock type at the Hows Corner site is phyllite it is highly unlikely that there was sufficient chloride in the rock core samples for this to occur

bull Manganese oxides may also interfere with the analysis of f through competing with the dichromate ion for any oxidizable carbon (Walkley 1947) However in such cases the reported f would be an underestimate of the f present in the rock core Walkley (1947)

Response to EPA Comment 3 050205doc 3 of 11 Woodard amp Curran (211941)

4

reported that in the case where the ratio of MnO2 to carbon is 85 to 1 the error in the carbon determinations would only be 0 to 6 percent

It may also be useful to compare the analysis of total organic carbon in a geologic matrix that contains high levels of manganese using EPA method 9060 to the Walkley-Black method Table 1 summarizes data provided by one of the PRPs that compares the analysis of total organic carbon in a geologic matrix that contains approximately 02 wgt manganese (approximately 03 wgt manganese oxide)

Table 1 Comparison of total organic carbon measured using the EPA- 9060 method and the Walkley-Black method

Laboratory EPA-9060 Method Walkley-Black Method A Ave 00226 gocg Not analyzed

Stdev 000251 gocg n = 5

B Ave 002219 gocg Ave 002050 gocg Stdev = 000316 gocg Stdev =000971 gocg

n= 10 n = 10

The similarity in the total organic carbon concentrations measured by these two different methods provides further confidence that the Walkley-Black method is a viable method for analysis of total organic carbon in the presence of manganese equivalent to at least 10 by weight of the total organic carbon

5 The Walkley and Black organic carbon measurement at lowf^ values it is not clear that organic carbon is controlling PCE sorption (Schwarzenbach and Westall 1981 Mackay et al 1986 Fetter 1999)

bull Schwarzenbach and Westalls (1981) paper states that f values of less than 0001 gocg should not be used in combination with Kow (octanol-water partition coefficients) values to calculate K^ values (solid phase partition coefficients) values for a specific contaminant It should be noted that the TI Evaluation did not use the f data to calculate the KQC from the Kow Instead as requested by the EPA the measured KOC value for PCE was used to calculate the retardation factor for this contaminant

bull Schwarzenbach et al (2003) stated more recently that Even at very low f values (ie foe = 0001 kgoc - kg1 solid) sorption to the organic components of a natural sorbent may still be the dominant mechanism in defining the adsorption of organic compounds to geological matrices

bull In 1985 M Piwoni from the US EPA Robert S Kerr Environmental Research Laboratory published a paper (Banerjee et al 1985) that showed that for very hydrophobic molecules TOC content of the sorbent will control sorption down to levels of organic carbon that defy quantitation Contaminants such as the PCE found in the groundwater at Hows Corner are in this category of compounds

Given the aforementioned reasons the f values reported in the TI Evaluation are accurate within the noted statistical limitations and will have a predictable impact upon the retardation of PCE during groundwater transport

Response to EPA Comment 3 050205doc 4 of 11 Woodard amp Curran (211941)

6 In order to derive a Kd-based retardation factor that is reasonable given the reported foc

values and the rapid advance of the PCE plume described on pages 4-11 and 4-12 the flushing model requires a bulk density to porosity ratio that is roughly two orders of magnitude higher than the actual ratio for the Hows Comer bedrock (page 4-4) This apparent discrepancy needs to be addressed

The apparent discrepancy of bulk density to porosity ratios is most likely due to the fact that the Batch Flushing Model was originally developed for a porous medium and is not directly applicable to fractured bedrock As stated in Appendix C (page C-4) of the Draft Technical Impracticability Evaluation Report in order to use the Batch Flushing Model to describe the transport of contaminated groundwater in fractured bedrock where the matrix porosity is insignificant it is more appropriate to use a fracture surface area to void space ratio to calculate the retardation factor (R) than a bulk density to porosity ratio (Freeze amp Cherry 1979)

Since it is impractical to determine the actual surface area to which contaminants can adsorb the Batch Flushing Model was used with two simplifying assumptions bull The Kd was calculated from the f and the K^ bull The bulk density to porosity ratio term in the Batch Flushing Model was constrained to range

from 4 to 10 the typical range of such ratios in porous media (Freeze amp Cherry 1979)

If one uses site specific bedrock bulk density and porosity values the bulk density to porosity ratio is several orders of magnitude greater (specifically 273 gcc bullbull 000165 (dimensionless) = 1654 gcc) than the range of ratios of 4 to 10 used in the Batch Flushing Model in the Draft Technical Impracticability Evaluation Report Constraining the bulk density to porosity ratio within the range of ratios of 4 to 10 results in significantly lower R value than would be obtained using specific bedrock bulk density and porosity values

In summary in bedrock where fractures are the primary porosity the bulk density to porosity ratio can vary considerably and will be a function of the number of fractures and the fracture aperture The calculated bulk density to porosity ratio will be inversely proportional to the porosity This means that in fractured rock with limited fracturing and smaller porosity the calculated bulk density to porosity ratio is greater and will result in a greater calculated retardation factor than in bedrock with more extensive fracturing and greater porosity Consequently the calculated retardation factor will be greater for bedrock with less surface area available for sorption than bedrock with greater surface area for sorption This is contrary to what actually occurs

4 Response to EPA Comment 3 050205doc 5 of 11 Woodard amp Curran (211941)

m

REFERENCES

Banerjee P MD Piwoni K Ebeid (1985) Sorption of organic contaminants to a low carbon subsurface core Chemosphere _14 1057-1067

Freeze RA JA Cherry (1979) Groundwater Prentice Hall Englewood Cliffs NJ pg 604

PTS Laboratories wwwptsgeolabscompdf files3TOCnotepdf

Schulte EE (1995) Recommended soil organic matter tests in Recommended Soil Testing Procedures for the Northeastern United States Northeastern Regional Publication No 493 Chapter 8

Schwarzenbach RP J Westall (1981) Transport of nonpolar organic compounds from surface water to groundwater Laboratory sorption studies Environ Sci Tech 15 1360-1367

Schwarzenbach RP PM Gschwend DM Imboden (2003) Environmental Organic Chemistry Wiley-Interscience pg 292 408 amp 412

Walkley A LA Black (1934) An examination of the Degtjareff method for determining soil organic matter and a proposed modification of the chromic acid titration method Soil Science 37 29-38

Walkley A (1947) A critical examination of a rapid method for determining organic carbon in soils - effect of variations in digestion conditions and of inorganic soil constituents Soil Science 63251-264

Woodard amp Curran Inc (WampC) 2005 Draft Technical Impracticability Evaluation Hows Corner Superfund Site Plymouth Maine January 2005

Response to EPA Comment 3 050205doc 6 of Woodard amp Curran (211941)

LIST OF ATTACHMENTS (Response to Comment 3)

Appendix B to Draft Technical Impracticability Evaluation Measurement of foe at Hows Corner (4 pages)

m

Response to EPA Comment 3 050205doc 7 of 11 Woodard amp Curran (211941)

Appendix B Measurement of foe of Rock Core at Hows Corner

There are two general approaches to measure the fraction of organic carbon (foe) in rock cores

bull Measurement of weight loss by ignition of organic matter bull Chemical oxidization of organic carbon to carbon dioxide and either

subsequent quantification of the oxidant used for the reaction or quantification of the carbon dioxide produced during this oxidation process

The weight loss method is subject to errors caused by volatilization of substances other than organic materials such as water hydroxides and mineral carbonates Quantification of foe by the weight loss method is particularly sensitive to the presence of carbonates in rock cores There are however weight loss methods that are designed to differentiate between organic carbon and the aforementioned interfering materials but they require considerable care and are less accurate at low foe values Hence the weight loss method was not well suited for measuring the foe of the rock core from Hows Corner

The chemical oxidation of organic carbon is much better suited for quantifying organic carbon in rock cores such as those from Hows Corner This method uses a strong chemical oxidant to oxidize organic carbon to carbon dioxide and then measures either the chemical oxidant used to oxidize the organic carbon or the quantity of carbon dioxide produced In addition this general approach is not subject to interference by volatilization of other constituents of the rock core

There are at least two such chemical oxidation methods

bull The method of Baccini which was described by Schwarzenbach amp Westall (1981) first acidifies the sample to eliminate interference by carbonates Then a strong oxidant is used to chemically oxidize the organic carbon to carbon dioxide The resulting carbon dioxide is subsequently reduced to methane and quantified using a flame ionization detector Unfortunately this method has not been described in detail in a referred journal Hence it is would not have been appropriate to use to characterize the foe in the Hows Corner rock core

bull The more commonly used method to quantify foe in rock core is the Walkley-Black method (1934) This method is preferred for RBCA and DODDOE projects and by the oil industry

The Walkley-Black method uses an excess of chromic acid to oxidize (digest) organic matter to carbon dioxide The remaining chromic acid that was not consumed during the oxidation of the organic carbon is then quantified by titration with ferrous sulfate The difference in chromic acid prior to and after the oxidation of the organic carbon represents the total chromic acid used to oxidize

Hows Corner TI Evaluation Page 1 January 13 2005 Appendix B

the organic carbon in the sample The latter can be calculated using the chemical stoichiometry of the reaction

The Walkley-Black method is very accurate for samples that contain less than 2 organic carbon matter The minimum detection limit (MDL) for the Walkley-Black method is 100 mgkg or an foe of 0001

Given the rock core at Hows Corner was expected to contain less than 2 organic carbon the Walkley-Black method was used to measure the foe from 19 different rock core samples collected from varying depths ranging from 11 to 90 feet

Table 1 provides a statistical summary of the aforementioned data

Table 1 Statistical summary of foe data from rock cores collected at varying depths

Statistical Parameter Calculated Value foe Minimum Detection Limit (MDL) 00010 Number of samples analyzed (n) 19 Average foe 00019 Median foe 00019 Geometric Mean foe 00019 Standard deviation of foe measurements 000033 Relative standard deviation 174 -+ 95 Confidence intervals 00012 to 00025

The data in Table 1 shows the following

bull The foe from the Hows Corner rock cores are statistically greater than the MDL of the Walkley-Black analytical method

bull The average and median values for the foe of the Hows Corner rock cores from varying depths are nearly identical indicating that there is little variability in the foe values in the source zone at the site

bull The standard deviation of these measurements is 000033 which is 174 of the average foe

bull The 95 confidence intervals of the foe of the rock core at Hows Corner are 00012 to 00025

The foe was also analyzed from three separate samples taken from the same rock core at a depth of 55 feet (Only one of these samples was included in the data summarized in Table 1) Table 2 shows the statistical repeatability of this type of analysis

Hows Corner TI Evaluation Page 2 January 13 2005 Appendix B

Table 2 Repeatability of analysis of foe from one rock core at 55 feet in depth

Statistical Parameter Calculated Value Number of samples analyzed (n) 3 Average foe 00016 Median foe 00015 Geometric Mean foe 00016 Standard deviation of foe measurements 000039 Relative standard deviation 240 -+ 95 Confidence intervals 00008 to 00024

The data in Table 2 shows the following

bull The percent relative standard deviation of these three analyses of foe from the same rock core at Hows Corner is 24

bull The 95 confidence interval of the foes measured in this particular rock core at Hows Conrer is 00008 to 00024

These results show that there is good repeatability in using the Walkley-Black method for analysis of the foe in the rock core at Hows Corner

References Schwarzenbach amp Westall (1981) Transport of nonpolar organic compounds from surface water to groundwater Laboratory sorption studies Environ Sci Tech 15 1360-1367

Walkley A I A Black (1934) An examination of Degtjareff method for determining soil organic matter and a proposed modification of the chromic acid titration method Soil Sci 37 29-37

Hows Corner Tl Evaluation Page S January 13 2005 Appendix B

Woodard and Curran PTS Laboratories PTS File No 34618

ORGANIC CARBON DATA (METHODOLOGY WALKLEY-BLACK)

PROJECT NAME PROJECT NO

SAMPLE ID

203-chip-13 203-chip-23 203-chip-27 203-chip-38 203-chip-42 203-chip-47 203-chip-52 203-chip-58 203-chip-69 203-chip-82 207-chip-11 207-chip-19 207-chip-24 207-chip-29 207-chip-35 207-chip-45 207-chip-55 207-chip-87 207-chip-90

207-chip-55 55-MS

55-MSMSD

Hows Corner NA

DEPTH ft

13 23 27 38 42 47 52 58 69 82 11 19 24 29 35 45 55 87 90

55 NA NA

MATRIX

Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip

Average Median

Geometric Mean Standard Deviation Relative Std Dev

+- 95 Confidence Interval n

Rock Chip Rock Chip Rock Chip

Average Median

Geometric Mean Standard Deviation Relative Std Dev

+- 95 Confidence Interval n

FRACTION ORGANIC CARBON

(gg)

170E-03 185E-03 185E-03 170E-03 240E-03 190E-03 230E-03 180E-03 170E-03 115E-03 195E-03 220E-03 220E-03 235E-03 135E-03 190E-03 205E-03 175E-03 160E-03

188E-03 185E-03 185E-03 327E-04

1739 123E-03 to

19

205E-03 130E-03 150E-03

162E-03 150E-03 159E-03 388E-04

2402 840E-04 to

3

2532E-03

2393E-03

Hows Corner Tl Evaluation Appendix B January 13 2005

Response to EPA-DEP Comment 4 Dated March 31 2005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

EPA-DEP Comment 4

Comment 4 Distribution of contaminants First the TI report seems based on the assertion that there is DNAPL at the source area yet it also appears to represent that the source area is small and the bedrock below 85 is competent (or less fractured) and less impacted by the release of contaminants Some of the confusion may result from using most recent data when that data is from several different sampling events over several years and there is no discernible difference in concentrations between shallow and deep bedrock or as in Section 421 where generally decreased generally increase generally similar and similar concentrations in four consecutive sentences leads to a muddled picture of the contaminant distribution

Second the report asserts that the distribution of contaminants over the entire plume has not changed with time but fails to support this conclusion with data again relying on data that is from different sampling dates for one composite representation

Response The likely presence of dense non-aqueous phase liquid (DNAPL) at the Hows Corner Site and the determination that the source area is small are not mutually exclusive and both are conclusions drawn from information obtained during field investigations The presence of DNAPL in the source area is based on the elevated concentrations of volatile organic compounds (VOCs) detected in the groundwater (WampC 2001 WampC 2002) The conclusion that the source area is small is based on the area in which VOCs in groundwater have been detected at concentrations that are considered to be indicative of the presence of DNAPL nearby Similarly the conclusion that fracture frequency decreases at depths greater than approximately 50 to 85 feet below ground surface was based on field observation during the RI field work The fact that zones with observed fractures exhibited higher hydraulic conductivities than zones without fractures coupled with the decreasing frequency of observed fractures with depth led to the conclusion that the hydraulic conductivity of the bulk rock decreases with depth

The most recent data from all wells were used to provide the maximum VOC data set size During the RI all of the previously-existing and then newly-installed monitoring wells were sampled along with several residential wells The RI sampling included up to 48 monitoring wells Subsequent to the RI and prior to the TI three rounds of monitoring were conducted to verify that the plume was stable 15 monitoring wells were sampled during each of the three rounds During the TI field investigation 29 wells were sampled for VOCs The sampled wells included all of the newly-installed wells and a subset of wells installed during the RI for a total of 29 monitoring wells By using most recent data VOC results from 53 monitoring wells were included in the evaluation (see table labeled Sampling Events for listing of monitoring wells) This approach was selected because there generally was little variation in the data from a particular location between years This is borne out by the attached individual plots of VOCs detected in shallow bedrock and deep bedrock for the Pre-ROD (December 1999January 2000) and Supplemental (May 2000) sampling events and for June 2001 January 2002 and April 2003 sampling events The Pre-ROD and Supplemental plots are similar to the subsequent plots from the 2001 2002 and 2003 sampling events

In addition to maps showing the spatial distribution of VOC data at a given time trend plots of the data from a particular location through time (attached) indicate that since the RI concentrations generally have been stable or have decreased Together the maps and trend plots and the data from which they were developed indicate that the distribution of contaminants over the entire plume has not changed appreciably with time

Response to EPA Comment 4 050305doc 1 of 26 Woodard amp Curran (211941)

REFERENCES

Woodard amp Curran Inc (WampC) 2001 Final Remedial Investigation Report Hows Corner Superfund Plymouth Maine July 2001

Woodard amp Curran Inc (WampC) 2002 Final Feasibility Study Report - Non-Source Area Groundwater Hows Corner Superfund Site Plymouth Maine Hows Corner Superfund Plymouth Maine July 2002

Response to EPA Comment 4 050305doc 2 of 26 Woodard amp Curran (211941)

LIST OF ATTACHMENTS (Response to Comment 4)

Table - Sampling Events 1999 - 2004 (2 pages)

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater Pre-ROD Sampling Event

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater Pre-ROD Sampling Event

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater Supplemental Sampling Event

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater Supplemental Sampling Event

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater June 2001

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater June 2001

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater January 2002

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater January 2002

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater April 2003

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater April 2003

Figure - Concentration Trends - Non-Source Area Wells MW-1B and MW-3B

Figure - Concentration Trends - Non-Source Area Wells MW-13DB and MW-16DB

Figure - Concentration Trends - Non-Source Area Wells MW-16IB and MW- 108D

Figure - Concentration Trends - Non-Source Area Wells MW-108S and MW-112D

Figure - Concentration Trends - Non-Source Area Wells MW-112S and MW-114D

Figure - Concentration Trends - Non-Source Area Wells MW-114S and MW-115D

Figure - Concentration Trends -Source Area Wells MW-2DB and MW-2IB

Figure - Concentration Trends -Source Area Wells MW-102S and MW-103D

Figure - Concentration Trends -Source Area Wells MW-103S and MW-104D

Figure - Concentration Trends -Source Area Wells MW-104I and MW-106D

Figure - Concentration Trends -Source Area Wells MW-106S

Response to EPA Comment 4 050305doc 3 of 26 Woodard amp Curran (211941)

I I

El I

II I I 1 I

I

i

Event Baseline Case ID WC-01 WC-01

Well Date Aug-99 Oct-99 LOT10 1 LOT1-1 1 LOT11-4 LOT14 1 LOT15 1 LOT15-1 1 LOT16 1 LOT16-1 1 LOT17 1 LOT18 1 LOT19 1 LOT2 LOT20 1 LOT21-10 1 LOT21-11 1 LOT21-12 1 LOT21-13 1 LOT21-14 1 LOT21-2 1 LOT21-5 1 LOT21-7 LOT21 -8 1 LOT21-9 1 LOT23 1 LOT24 1 LOT28-1 1 LOT28-2 1 LOT28-3 1 LOT28-4 1 LOT28W 1 LOT30 1 LOT30-1 1 LOT30-2 1 LOT30-3 1 LOT30-4 1 LOT30-5 LOT31 LOT35 1 LOT41 1 LOT42-1 1 LOT43-1 1 LOT43-4 1 LOT6-1 1 LOT67 1 LOT6-7 1 LOT6-8A 1 LOT6-8B 1 LOT80-1 1 LOT82 1 MW-101D MW-1011 MW-101S MW-102D MW-102S MW-103D MW-103S MW-104D MW-1041 MW-104S MW-105D MW-106D

Groundwater Sampling Location Summary 1999 - 2004xls

Sampling Events 1999-2004

Hows Corner Superfund Site Plymouth Maine

Supplemental 2001 2002 2003 Pumping 2004 Pre-ROD Rl Sampling Sampling Sampling Test Sampling WC-03 WC-09 WC-25 WC-30 WC-42B WC-56 WC-58 Dec-99 May-00 Jun-01 Jan-02 Apr-03 Sep-04 Sep-04

1

1 1 1

1 1 1 1 1

1 1

1

1 1

1 1 1

1 1 1 1 1

1

1 1

1 1 1 1

1

1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

Sampling Events 1999-2004

Hows Corner Super-fund Site Plymouth Maine

Supplemental 2001 2002 2003 Pumping Event Baseline Pre-ROD Rl Sampling Sampling Sampling Test

Case ID WC-01 WC-01 WC-03 WC-09 WC-25 WC-30 WC-42B WC-56

ll

Well Date Aug-99 Oct-99 Dec-99 May-00 Jun-01 Jan-02 Apr-03 Sep-04 MW-106S 1 1 1 1 1 MW-107D 1 1 MW-108D 1 1 1 1 1 MW-108S 1 1 1 1 1 MW-110D 1 1 MW-111D 1 1 MW-112D 1 1 1 1 1 MW-112S 1 1 1 1 1 MW-113D 1 1 MW-114D 1 1 1 1 1 MW-114S 1 1 1 1 1 MW-115D 1 1 1 1 1 MW-12DB 1 1 1 MW-12SB 1 1 1 MW-13DB 1 1 1 1 1 1 MW-13SB 1 1 1 MW-14DB 1 1 MW-14SO 1 1 MW-15DB 1 1 1 MW-15SB 1 1 1 MW-16DB 1 1 1 1 1 1 MW-16IB 1 1 1 1 1 1 MW-16SO 1 1 MW-17DO 1 1 1 MW-17SO 1 1 1 MW-1B 1 1 1 1 1 1 MW-203D MW-203S MW-204D MW-204S MW-205 MW-206D

I MW-206S MW-2DB 1 1 MW-2DDB 1 1 MW-2IB 1 1 1 1 1 1 MW-3B 1 1 1 1 1 1

I MW-4O 1 1 1 MW-5B 1 1

II MW-6DB 1 1 1 MW-6SB 1 1 1 MW-8DB 1 1 1 MW-8SB 1 1 1

II PW-207 1 SEEP-1 1 SUBTOTAL - RESIDENTIAL 44 25 0 2 0 3 0 SUBTOTAL - MONITORING 22 48 41 15 15 15 1

Total 3 66 73 41 17 15 18 1

I Included in most recent data

I Notes 1 - Overburden well not included in most recent data for plotting

2 - Tetrahydrofuran and 2-Butanone were the only two compounds detected in this well and are thought to be the result of well repair not included in most recent data for plotting

3 - Not included in most recent data for plotting

2004 Sampling

WC-58 Sep-04

1

1 1

1 1

1 1 1

1

1 1

1 1 1 1 1 1 1 1 1

1 1

1

0 29

29

Groundwatef Sampling Location Summary 1999 - 2004xls

I

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

monitoring well Figure 4-14 total VOC contour (ugl) - December 1999January 2000 Distribution of Total VOCs in

Note SW-113 is located downstream of SEEP-1 Shallow Bedrock Groundwater total concentration of detected VOCs ND= not detected these two locations were sampled during the Pre-ROD Sampling Event

Baseline Sampling Event in OctoberNovember 1999 Hows Corner Superfund Site Surface Water Sampling Location A Plymouth Maine Seep Sampling Location laquo- WOODARD ampCURRAN

995037wipri reportepa ri interim final feb 2001cadd drawingsfinalfig 4-14

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

0 300 600 I

FEET

Q residential well Figure 4-16 monitoring well Distribution of Total VOCs in

Deep Bedrock Groundwater total VOCs contour (ugl) Pre-ROD Sampling Event

active residential wells with lot number Hows Corner Superfund Site 2deg42deg Plymouth Maine total concentration of detected VOCs ND= not detected WOODARD ampCURRAN Enyinaaring bull Science bull Operations bull

995037wipri reportepa ri interim final feb 2001cadd drawingsfinalfig4mdash16

PLYMOUTH POND

PLYMOUTH POND

1 628Tl7MW-2bB 12135

PLYMOUTH POND

monitoring well Figure 4-20

V total VOC contour (ugl) - June 2000 Distribution of Total VOCs in Shallow Bedrock Groundwater

| 34 | total concentration of detected VOCs ND= not detected NA = not analyzed Supplemental Sampling Event Note SW-113 is located downstream of SEEP-1 Hows Corner Superfund Site

Surface Water Sampling Location these two locations were sampled during the Plymouth Maine Baseline Sampling Event in OctoberNovember 1999 Seep Sampling Location WOODARD amp CURRAN

Engineering bull Science - Operations bull 995037wipri reportepa ri interim final feb 2001 cadd drawingsfinalfig 4-20

residential well Figure 4-22 Distribution of Total VOCs in

monitoring well Deep Bedrock Groundwater

total VOCs contour (ugl) Supplemental Sampling Event

Hows Corner Superfund Site

total concentration of detected VOCs ND= not detected NA = not analyzed Plymouth Maine

WOODARD amp CURRAN

995037wipri reportepa-ri interim final feb 2001cadd drawingsfinalfig 4-22 Engineering bull Science - Operations bull

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

FEET

Shallow Monitoring Well

Deep Monitoring Well

C Detected Concentration ND = Not Detected Figure 1-XS Distribution of Total VOCs in Shallow Bedrock Groundwater

Pumping Well

17-Acre Property Boundary Concentration Contour (ugl)

June 2001 Hows Corner Superfund Site

Plymouth Maine WOODARDampCURRAN

-i^rhvj bull Scbncn bull Operations bull 211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0601 dwg04-20-05

PLYMOUTH POND Hopkins Road V

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PLYMOUTH POND

PLYMOUTH POND

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0 300 600 mdashfa FEET

Shallow Monitoring Well bull bull - 17-Acre Property Boundary Figure 1-XD

Deep Monitoring Well 1 I Detected Concentration ND = Not Detected Distribution of Total VOCs in Deep Bedrock Groundwater

-mf- Pumping Well June 2001 Residential Well Hows Corner Superfund Site

Plymouth Maine i h Surface Water Sampling Point

g WOODARD ampCURRAN _ ^ _ ^ _ _ yen_ rj i|Hlaquorlny bull Science bull Opt

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0601 dwg04-20-05

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PLYMOUTH POND

PLYMOUTH POND

Shallow Monitoring Well

Deep Monitoring Well

Detected Concentration ND = Not Detected Figure 1-YS Distribution of Total VOCs in Shallow Bedrock Groundwater

Pumping Well

17-Acre Property Boundary Concentration Contour (ugl)

January 2002 Hows Corner Superfund Site

Plymouth Maine WOODARD amp CURRAN Engineering Science- Operations bull

211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0102dwg04-20-05

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Site Pand^ laquoum-laquoBTuitaraquo tLV

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Shallow Monitoring Well mdashbullbullbull 17-Acre Property Boundary Figure 1-YD - A - Deep Monitoring Well FT Detected Concentration ND = Not Detected Distribution of Total VOCs in

Deep Bedrock Groundwater Pumping Well January 2002 Residential Well Hows Corner Superfund Site

Plymouth Maine Surface Water Sampling Point

WOODARD ampCURRAN Engineering Sciencs- Operations bulli Si

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0102dwg04-20-05

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Shallow Monitoring Well E Detected Concentration ND = Not Detected Figure 1-ZS Distribution of Total VOCs in

Deep Monitoring Well Shallow Bedrock Groundwater

Pumping Well Hows Corner

April 2003 Superfund Site

17-Acre Property Boundary Plymouth Maine Concentration Contour (ugl) r WOODARD ampCURRAN

Engineering bull Science bull Operations bull 211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0403dwg04-20-05

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ft Shallow Monitoring Well mdashbullbullmdash 17-Acre Property Boundary Figure 1-ZD Deep Monitoring Well I 1 I Detected Concentration ND = Not Detected Distribution of Total VOCs in

Deep Bedrock Groundwater Pumping Well April 2003

Q) Residential Well Hows Corner Superfund Site Plymouth Maine

(T) Surface Water Sampling Point WOODARD ampCURRAN poundKk EnginawtirKj bull Science - Operations bull

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0 Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

B MW-1B

I 12000

PCE

B 10000 Total VOCs

I

i 2000

i 0 Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

c MW-3B

G 2000

1800

B PCE

1600 Total VOCs

1 I I E

il-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

G E

211941

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I I z E

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Concentration Trends shy Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-13DB

Total VOCs

c i i c o

Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

MW-16DB

30

c i c c I c o

Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99

PCE

Total VOCs

Jul-01 Jul-03

211941

O bi

c Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

I MW-16IB

i 35

3

c Total VOCs

lt- 2 5

0 | gt

o

1 sectI

c c 0 4

Jul-90 Jul-92 Jul-94 Jul-96 Jul-98 Jul-00 Jul-02 Jul-04

I I MW-108D

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PCE 10

Total VOCs c oc 3

E E I 0

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

E 211941

c Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

fi MW-108S

I I 40

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Total VOCs

30

I f 26

20 I o

I 15

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c Dec-99 Dec-00 Dec-01 Dec-02 Dec-03 I 0

I MW-112D

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I

ition

B 1 ^

-i c 3

0 Dec-99 Dec-OO Dec-01 Dec-02 Dec-03

211941

I

i

I

cII

Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-112S

08

PCE

Total VOCs 06

o 04

02

0 Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

MW-114D

o

12000

10000

8000

6000

PCE

Total VOCs

4000

2000

i

ccEIIc

i

i

E

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

211941

Con

cent

ratio

n (

ug

l)

E Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

I MW-114S

E A5000 -- Total VOCs

- 4000

0 3000

2000

i 1000

i n shy

Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

MW-115D

c PCE

Total VOCs

c E

o

C c

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03 I 0

211941

IepoundII

EIEIIGICCIccc

30000

25000

20000

o bullsect 15000 b

o 10000 U

5000

0 Aug-99

25000

20000

5000

0 Aug-99

211941

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-2DB

PCE

Total VOCs

Aug-01 Aug-03

MW-2IB

PCE

Total VOCs

Aug-01 Aug-03

IDIBI

ii EIDIISIBIG C

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-102S

6000

5000 PCE

Total VOCs

4000

O 3000

2000

1000

0 Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

MW-103D

16000

~ 14000 ugt 3- 12000 o

^ 10000

sect 8000

O 6000

4000

2000

PCE

Total VOCs

0Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

211941

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

G MW-103S

I I

ampo

12000

10000

E sectc

S

8000

6000

4000

2000

0Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

G I 6000

MW-104D

i 5000

PCE

Total VOCs

i i c

2000

1000

Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

E I

211941

cIccIG

IIBCccBcIc

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-1041

PCE Total VOCs

a 25000

0 20000

a 15000

10000

5000

0 Jan-OO Jan-01 Jan-02 Jan-03 Jan-04

MW-106D

3000

2500 PCE

Total VOCs

=sect 2000

o bullsect 1500

1000

500

0 Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

211941

c Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

c MW-106S

I PCE

Total VOCs

i

i Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

i

i i i E

C

211941 c

Response to EPA-DEP Comment 5 Dated March 312005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

iiw

EPA-DEP Comment 5

Comment 5 Matrix Diffusion The report as well as other proponents of matrix diffusion suggest that depletion of DNAPL (Section 5112 page 5-15) needs to be achieved While that might be the ideal the goal is to achieve performance standards and that goal may be attainable while there is residual contamination in the rock perhaps even DNAPL globules The low bedrock matrix porosity (page 1-15) the high permeability values (page 4-4) the relative flux of the groundwater (page 5-5) and the decrease in surface area and out of the mainstream pockets (appendix C-4) all suggest that the diffusion out of the rock matrix would be insubstantial relative to the regional flux of groundwater through the Site

Response The TI Evaluation Report does not explicitly consider or rely upon matrix diffusion as a basis for requesting a TI Waiver for a portion of the Hows Corner Site The technical literature provides documentation that matrix diffusion can be a significant process that affects chemical transport and groundwater remediation timeframes in unconsolidated and consolidated media including fractured rock (US EPA 1989 Freeze and Cherry 1979 Pankow and Cherry 1996 Fountain 1998) Back diffusion of contaminants from the matrix porosity of the fractured rock can prolong the time necessary to achieve groundwater cleanup goals particularly for compounds such as PCE for which the cleanup goal is a low concentration It is our expectation that matrix diffusion has occurred at the Hows Corner Site and that back diffusion of PCE from the rock matrix will also occur Although the extent to which matrix diffusion is occurring at the Hows Comer Site has not been determined and that lack of knowledge contributes to uncertainty regarding the cleanup times at the Site the effect of matrix diffusion is to lengthen rather than shorten the time required for remediation

REFERENCES

Fountain JC 1998 Technologies for Dense Nonaqueous Phase Liquid Source Zone Remediation Ground-Water Remediation Technologies Analysis Center Technology Evaluation Report TE-98-02 December

Freeze RA and Cherry JA 1979 Groundwater Prentice-Hall Inc Englewood Cliffs NJ 07632 p 410-412

Pankow J F and Cherry J A 1996 Dense Chlorinated Solvents Waterloo Press Portland OR 97291-1399 p 67-88

US EPA 1989 Transport and Fate of Contaminants in the Subsurface EPA6254-89019 p 17-18

Response to EPA Comment 5 050305doc 1 of 1 Woodard amp Curran (211941)

WOODARD amp CURRAN Maine Massachusetts New Hampshire Connecticut Florida Operational offices across the US 1-800-426-4262 www woodardcurran com

Page 14: SDMS DocID 251749 - Records Collections · 2020-06-13 · CORPORATE OFFICES: Maine, Massachusetts, New Hampshire, Connecticut New, York, Florida Engineering • Science • Operations

(MEDEP Pond 1) Farm Pond

Monitoring Well

Pumping Well Drawdown atFigure X

72 Hours _bullbull_ 17-Acre Property Boundary Deep Wells

Drawdown Contour (ft) Hows Corner Superfund Site

Plymouth Maine 151 | Drawdown (ft)

= WOODARD ampCURRAN 211941 Hows CornerwipDrawingsTI EVALDrawdown-72hrs_deepdwg04-19-05

Engineering bull Science bull Operations

(MEDEP Pond 1) Farm Pond

028 MW-12DB

MW-125B 040

l - _ ^ I 016 I N

050 MW-15SB

MW-15DB 048

A J s

- A - Monitoring Well

-$poundbull Pumping Well

_bullmdash 17-Acre Property Boundary

^ Drawdown Contour (ft)

151 I Drawdown (ft)

211941 Hows CornerwgtpDrawinQsT EVAI_Drawdown-72brsdwg04mdash19-05

Figure X Drawdown at 72 Hours

Hows Corner Superfund Site Plymouth Maine

^ WOODARD ampCURRAN Engineering bull Science bull Operations i

(MEDEP Pond 1) Farm Pond

Monitoring Well

Pumping Well

_bullbull_ 17-Acre Property Boundary

f Groundwater Elevation Contour (ft)

|419Q0| Groundwater Elevation

211941 Hows CornerwipDrawinqsTI EVALPotSurf-72hrs_shallowdwg04-19-05

150 300

FEET

Figure X Potentiometric Surface at 72 Hours

Shallow Wells Hows Corner Superfund Site

Plymouth Maine

WOODARD ampCURRAN Engineering bull Science bull Operations

29212 MW-108D

(MEDEP Pond 1) Farm Pond

Monitoring Well

Pumping Well

mdashbullbulllaquo 1 7-Acre Property Boundary

bull Groundwater Elevation Contour (ft)

1419001 Groundwater Elevation

211941 Hows CornerwipDrawingsTI EVALPotSurf-72hrs_deepdwg04-19-05

150 300 =5fc= FEET

Figure X Potentiometric Surface at 72 Hours

Deep Wells Hows Corner Superfund Site

Plymouth Maine

WOODARDampCURRAN Engineering bull Science bull Operations bull

--

Pumping Test Analytical Results Hows Corner Superfund Site

Plymouth Maine

Well ID oper Jaccb Analyses 2 Theis Analyses Fissure

Well Id Rd (ft)

Saturated Thickness

Transmissivity

(ft2day) K

(ft2day) K

(cmsec) Storage

Coefficient Transmissivity

(ft2day) K

(ft2day)

K (cmsec)

Storage Coefficient

System K

(ftday) PW-207OB 8 85 481 057 200E-04 392E-02 36 042 150E-04 809E-04 027 MW-103S 50 85 451 053 187E-04 720E-03 92 108 382E-04 283E-04 083 MW-103D 54 185 455 025 868E-05 210E-02 65 035 123E-04 237E-04 044 MW-2IB 59 85 352 041 146E-04 699E-03 104 123 433E-04 512E-04 052 MW-2DB 63 85 334 039 139E-04 845E-03 148 080 283E-04 239E-04 046 MW-104D 95 185 489 02 6 932E-05 654E-03 98 053 186E-04 547E-05 037 MW-104I 97 85 33 03 9 137E-04 362E-03 117 137 484E-04 962E-05 048 MW-101I 107 85 364 043 151E-04 490E-03 511 601 212E-03 223E-04 136 MW-102D 134 185 435 024 829E-05 248E-03 108 058 206E-04 850E-05 065 MW-101D 138 185 492 027 938E-05 511E-03 671 362 128E-03 700E-04 172 MW-205 219 85 57 067 237E-04 255E-03 447 526 186E-03 359E-03 -shyMW-204D 221 185 367 020 700E-05 170E-03 790 427 151E-O3 155E-04 147 MW-204S 225 85 379 045 157E-04 156E-03 1031 1213 428E-03 313E-04 199 MW-1B 228 85 325 038 135E-04 977E-04 340 400 141E-03 739E-05 054 MW-203S 273 85 489 058 203E-04 117E-03 1255 14 76 521 E-03 216E-04 210 MW-106D 278 185 51 028 972E-05 141E-03 1065 576 203E-03 360E-04 104 MW-203D 278 185 478 026 911E-05 152E-O3 765 414 146E-03 364E-04 138 MW-105D 364 185 44 024 839E-05 830E-04 769 415 147E-03 200E-04 127

1 Analyses conducted using Cooper and Jakob method on late drawdown data collected during constant

discharge pumping test conducted at the Hows Comer Site from September 20 - 30 2004

2 Analyses conducted using Theis solution for unconfmed approximation (1935)

J Analyses conducted using Moench method for dual porosity estimation (1984)

Fissure System Storage

Coefficient 402E-04 117E-06 264E-04 300E-04 932E-05 235E-07 502E-05 326E-06 801E-05 542E-04

-

803E-05 762E-05 134E-05 498E-05 115E-04

47E-04 838E-05

3 ysesh Analysis

Block System K (ft2day)

251E-02 207E-03 564E-04 163E-04 585E-04 465E-02 153E-04 498E-03 855E-04 356E-03

-

292E-03 394E-03 720E-04 526E-03 160E-01 35OE-O1 287E-03

Block System Storage

Coefficient

402E-02 164E-04 183E-02 330E-03 158E-03 847E-03 286E-03 326E-04 803E-05 272E-03

723E-04 686E-04 148E-04 349E-04 115E-03 47E-04 838E-04

Theis - Moench - CJ - AnalyticalResults_4-19-O5xls

DRAFT

242

24

238

236

bulla

c

i

a Q

234

232

228

226

Hows Corner Constant Discharge Testing USGS Background Groundwater Level USGS 445319068560101 ME-PEW456 Kenduskeag Maine

End of Monitored Recovery Period 09302004

Regional Background Location i 226 miles from Pumping Locatio

lt

697

NOTES

1 Groundwater samples collected in 1999 were screened for five volatile organic compounds (VOCs) only N

tetrachloroethene (PCE) exceeded reporting limits MW-2030 082304 082304 082304 082304 u

2 Strike and Dip of likely or possible transmissive 30 45 55 85 feature within the packer interval from which the indicated sample was collected

MW-204D

PCE TOTAL VOCs

081904 30

220 2636

A

081904 46-50 540 6436by

081904 IT

260 3073

x

MW-105D

PCE TOTAL VOCs

111199 50-60 2100 2100

MW-106D

PCE TOTAL VOCs

111199 76-86

400 400

111199 137-147

1400 1400

111299 1355-1455

350 350

PCE TOTAL VOCs

44 84

64

MW-6SB

bulli

lt

gt-

170 234

35

I I i

140 192

^^52

^^52

130 183

52 - lt

S A 34

PW-207 082404 082404 082404 20 37

PCE 1300 TOTAL VOCs

17-Acre George West Property Boundary

MW-113D

PCE TOTAL VOCs

112299 46-56

350 350

112299 70-80 190 190

150

112299 105-115

129 129

112399 138-148

230 230

L e g e n d ( J New Monitoring Well-Summer

Site Property Boundary ^ P u m p i n g Well-Summer 2004

-xmdashxshy Source Area

bull0shy Monitoring Well shy Pre 2004 Angled Boring-Summer 2004

211941laquoipdwgTI-ELV21ig41paltker-data2

2004 PCE of Total

bull lt70 VOCs

M W - 1 14D ^ ^

Figure xx Packer Testing Results in

Vicinity of Source Area Hows Corner Superfund Site

Plymouth Maine ^ WOODARD ampCURRAN

^^^^^^^^^^m ampKm Engineering - Science bull Operations

c Northeast Geophysical Services Borehole Geophysical Log

MW-203 Date logged 081704 Plymouth Maine

I Flowmeter Measurements Tomporaturo(C) Acoustic Televiewer

7 5 8 8 5 9 95 Caliper (Inches) Resistance (Ohms) Spontaneous Potential (mVj Dip In Degrees PCE Total VOCs

3 0 2 0 8 0 laquodeg 4S 1000 1400 1800 2200 MO HO 1000 1200 MOO 0 laquo deg ugL ugL n 1 1 1 1 1 1 1 1 1 i 1 1 1 1 n 1 1 1 1 1 1 1 1 1 1 1 n I l l l l l l l n

Ambient Flowneter pumping Rowmeter 11 gpm 6

H

bull

magnetic 10 bull 10 bull - 10 - north - 1 0I

-

_

bullbullbull - bull

20 bull bull20 bull ^ ltr~mdash 01

I

4 ^

LOS7

^

44 84 I I

Xr - 2

lt ^ bull30 -_ _^O1J- 1 _ 050 30 - 3 0

0r - - 3

C -j [ bull bull bull | shy

-O8 H ~ 1 045 7

1 4040 - 40 - -40 r - 14gt 13

V1s -- -023 f 1022 1V 170 234 I

T lt bull B gtf 50^ J50 - - 5 0 - - 5 0

I eet be

lo

i 1

1 1

1

140 192 - - - -t shy

-mdashj bullpound 60 - $o - - 60 - -60

H i I c

bull024

ampbull

3 - T lt ftft rgt He

70 bull j 70 - - 70 - 7 0 -

in -j bullbull shy

-021 1 T 022

- Ton _ Ov

26

130 183 NF NF

90 -_ 90 - 7 90 - -90

-

ifi Jf

3J

^gt _ N F NF bull bull shy

| H100 - j 100 bullbull 100 - -100

1 1 1 1 1 1 1 ) | 1 f I 1 1 1 ) 0 20 40 60 80

flft mdash ftn - mdash rVt

30 4 g 0 20 40 60 Dip in Degrees bullbull

Likely or poss bleFluid Resistivity (ohmmeters) The dip direction-- indicated

^ t h e l i n e extending from t h

I Iransmissive zone circle The strike of the feature is 90 degrees from this

The acoustic televiewer graph displays the mostprominent features selectedffom the acoustic televiewer

R n r a h n l c D O t t n O I B

f i o n n h w c i r a l U K U p i i y SI Ud l

1 rn l_Og Packered Interval August 2004

E tog The location dip angle and dip direction of the sleeted M W - 2 0 3 Groundwater samples were collected by Woodard S Curran on H23120M features are approximate Refer to the televiewer og of His _ well for more precise detail Plymouth Maine Date logged 081704

I

1

Northeast Geophysical Services Borehole Geophysical Log MW-204 D a t e l o gge d 072604

Plymouth Maine

n 3

Flowrneter Measurements(in gpm)

Caliper (Inches)0 3 5 4 0

1 1 1 1 1 1 1 t 1 1 1 1 1 1Ambient Rowmeler pumping Flowmetsr 05gpm

Templaquorature (C) bull bull bull bull i

7 75 8 8S 9 Resistance (Ohms) Spontaneous Potential (mV)

4000 SOW 600 4M 0

Acoustic Televiewer (interpreted)

Dip in Degrees 0 20 4060 SO

at N

PCEugL

Total VOCs ugL

- -_ a

10-

shy 10 bull - 10 shymagnetic

north - 10

o o

bull 1

11

11

1 1

1 1

11 1

1 1

1 1

1 1

1 1

1 1

1 1

1 1

1 1 E 1

- L

3 7 2 0 2 0r bull 20 bull - shy

i S_ N F

bull30 bull 7 3 0 220 2636shy1^ J J 004

fI f V ^

40 shy 4 0 4 0 shy - 4 0rbull019 [_ 007 w8 - - shy5 c

bull

gt

Ia50i 540 6436

bull50 - - 50 - - 5 0

-QQ7 - bull - -t T

pound V gtk

B 6 0 - e o - 7 6 0 -60shyQ 1 1

Q -007 -004 bull1 mdash T - J ~

bull

- - shyT 70 -J c [TO- - 70 - 7 0-

V Y 1- -004 -003

mdash T -h - y - j i - - mdash 260 3073 - gt=7

80 -j NF bull80 - - 80 - - 8 0Jgt

bull i

i 1

i i

C- bull shy

90 shy

K

Jlt i90 90 shy - 9 0shy -

l

ii

I I I I

NF bull M J

I ^ ^ - ^ bull 1

mdash mdash - _

s -7 ^100shy

till

1 100 100- H - 1 0 0shy -1 x Likety or possible k ^ Iransmissive zonebull

1 i i i ii i i i | l l l l | l i l l 0 20 40 ED 80

1 -

3 0SOFluid Resistivity (ohmmeters)

Dip in Degrees The djp ^ ^ o n is indicated ty Ihe line extending from tha circle The strike of Ihe feature

19- 3U UIHJIW93 IolII l l l lraquo

bull

The acousfc televiewer graph displays the mostprominent features selected from the acoustic televiewer109 The location dip angle and dip direction of Ihe sleetedfeatures are approximate Refer to the televiewer log of thiswentormore precise detail

B o r e h o l e G e O D h V S I C a l LOO B W H U I B w c w p n y o i v a i w v yM W - 2 0 4

P l y m O U t n MaiDB

Packorod Interval August 2004Groundwater san-ples wampramp collected by Woodard a Curran on OMO23C4

Date logged 072604

C

I

E Northeast Geophysical Services Borehole Geophysical Log Date logged 072704

I MW-205

Plymouth Maine

Flowmeter Measurements Temperature (C) Acoustic Televiewer (In gpm) I ~l (Interpreted)

I 85 10 Caliper (inches) 95

Dip in D g r laquo Resistance (Ohms) Spo ontaneous Potential (mV PCE Total VOCs 3 0 16 4 0 4 5 ) 20 40 60 80 10 00 2000 30 00 4VJ 400 -3 laquo

i i i i 1 i i I i 11 4 0 D 1 I I ugL ugL

C h

iii Ambient Flowmetar pumping

Flowmeter 1 25 gprn

I bull$bull

i

I rmdash magnetic 1 north ^^^^ 1 VI f

10 ~ I C x 10 bull - 10 bullbull

4 5 6mdashmdash f 1000B 11448 noisy nodi a raquo ^

mdash 5rt mdashi mdash Oft pound) 1100B 12509

cjmdash1 007

-

i i i 1

en

8 B a B

30 mdash

-

40 shy

-mdash I -

50 -_

__NF lt005

- 30 - - 3 0 it 34V

MO P26 V S) 1300B 13776 _ N F NF

26

40 bull - 40 bull 7-40 gt J Vf1 cX

) -j -

_ N F NF 50 c bull - 50 ^ 7-50

i I

I

c

B pound 60 - 6 0 7 60 - 7-60 a i 1

_ N F NF i Si f f 70 -_ bull70 bull - 70 shyC I 9

-m bull - shyA

_ N F NF 80 80 -j bull80 bull - 80 - C- 33 34

bull

5-i r

i 1

J r

Ck

_ N F NF 9 0 90 - - 90 shy

i bullCshy

J rK bull

100 -j ^ Likely or possible bull100- - 100- I -100

transmissive zone bull - ^ bull shy] |

1 1 1 1 1 1 1 I 1 i i i 1 i i 1 1 0 20 40 SO SO 10 20 30 40 50 Dip in Degrees 30 4 0 Fluid Resistivity (ohmmeters) Thlaquo dip direction is indicated

by the line extern r g from the circle The strike of he feature is 90 degrees from ihis

The acoustic televiewer graph displays the most

I Borehole Geophysical Log Packered Interval August2004 prominent features selected from the acoustic televiewer

Groundwatcr samples were oollccled by Woodard amp Cufran orgt S172004 log The location dip angle and dip direction of ins slsctsd MW-205 features are approximate Refelt to the televiewer log of this wall for more precise detail Plymouth Maine Date logged 072704

I

C

I Northeast Geophysical Services Borehole Geophysical Log Date logged 072704

I MW-206

Plymouth Maine

Flowmetor Measurements Temperature (C) Acoustic Televiewer | I r T i i i i i i i i i i i i i i r I |(in gpm) (Interpreted)

I 75 8 flS 9 95

Caliper (inches) Resistance (Ohms) Spontaneous Potential (mV) Dip In Degress PCE Total VOCs 30 35 40 4 5 0 20 40 M 90 4500 5500 6500 ugL ugL I i i

I I

- 1 0

I - 2 0

I 2900B 32401

i i L

E 0

i 6300B 68901

i I 0 20 40 SO 80

20 30 40 50 Dip in Dlaquogralaquos

amp 4 a Fluid Resistivity (ohrnmeters) The dip dirertion is indicated Likely or possible by iho line extending from the transmissive zone circle The striKe of the feature

is 90 degrees from tNs

Borehole Geophysical Log Packered Interval August 2004

E amples were collected by Woodard amp Cunan oo SM82004 log Thraquo location 4p angle and dip direction of the sloeled MW-206 feature are approximate Refer to the televiewer 109 of this well for more precise detail Plymouth Maine Date logged 072704

C

I Northeast Geophysical Services Borehole Geophysical Log

Date logged 082304 PW-207

I Plymouth Maine

Fiowmeter Measurements Temperature (C) Acoustic Televiewer

I (in gpm) (interpreted)

75 8 85 9 95 Caliper (inches) Resistance f0tims) Spontaneous Potential (mV) Dip in Degrees PCE Total VOCs

55 60 0 20 40 SO 80 ugL ugL I I I I I I I

Ambienl Fiowmeter pumping Flewmater

magnetic - 10 - - 1 0

north

i - 20 - - 2 0

1300 1410

i - 30 - - 3 0

i tf

5400 5802 - 40 - - 4 0

B - 50 - - 5 0

I 18000 19234

- 60 - - 6 0

I 12000 13085

- 70 - - 7 0

- 8 0

i - 9 0 19000 20354

G - 100- -100

I 110 110 bull110

0 20 40 60 SO 10 20 30 Dip m Degrees

Fluid Resistivity (ohmmeters) I 50

The dip direction is indicated by ihe line extending from the circle The strike of the fealure is 90 degrees from this

Borehole Geophysical Log

G Packorod Interval August 20(M log The location dip angle and dip dirlaquocton or the sleeted Groundaier samplss were ooliecled by Woodard i Curran on ampt24f2ltXM PW-207 failures are approximate Reter to the televiewer log of this wlaquoll for more precise detail PlyPIOUth Maine Date logged 082304

I

Table XX Packer Permeability and Packer Sampling Results for Potential Fracture Intervals

1

WellID MW-101D MW-101D MW-101D MW-101D MW-101D MW-101D MW-101D MW-101D MW-101D MW-101D MW-I01D MW-101D MW-101D MW-102D MW-102D MW-I02D MW-102D MW102D MW-102D MW-102D MW-102D MW-102D MW-I02D MW-102D MW-102D MW-102D MW-103D MW-103D MW-103D MW-103D MW-I03D MW-103D MW-103D MW-103D MW-103D MW-103D MW-103D MW-103D MW-I03D MW-104D MW-104D MW-104D MW-104D MW-I04D MW-104D MW-104D MW-104D MW-104D MW-104D MW-104D MW-105D MW-105D MW106D MW-106D MW-106D MW-107D MW-107D

1999 Drilling Program

Hows Corner Superfund Site Plymouth Maine

Potential Fracture Top Of Bottom 6 Depth to lt Topof i Interval from Packer Packer Middle of Elevation Hydraulic bull PCE

GS ELEV 1 Rock Drilling Interval Interval Interval of Interval Conductivity Concentration (ft msl) (ft msl) TEST (ftbgs) (ftbgs) r(ftbgs) ( f t b (ft mil) (cmsec) (raquogL)

4339 4329 13 28-29 33-3537-39 271 376 324 4016 OOOE+00 4339 12 37-3444-46 380 485 433 3907 157E-04 4339 11 488 593 541 3799 132E-04 4339 10 60-61 578 683 631 3709 OOOE+00 4339 9 678 783 731 3609 I79E-05 4339 8 778 883 831 3509 106E-05 4339 7 880 985 933 3407 243E-05 4339 6 990 1095 1043 3297 339E-06 4339 5 1090 1195 1143 3197 OOOE+00 4339 4 1190 1295 1243 3097 OOOE+00 4339 3 1365-1375 1290 1395 1343 2997 OOOE+00 4339 2 147-157 1390 1495 1443 2897 580E-05 4339 1 147-157 1470 1575 1523 2817 741E-05 43161 43061 13 166 271 219 4098 333E-04 43161 12 30-3136-40 260 365 313 4004 I54E-05 43161 11 36-4041-43 362 467 415 3902 548E-05 43161 10 470 575 523 3794 598E-05 43161 9 570 675 623 3694 197FOS 43161 8 670 775 723 3594 OOOE+00 43161 7 770 875 823 3494 891 E-05 43161 6 83-94 870 975 923 3394 139E-05 43161 5 970 1075 1023 3294 123E-04 43161 4 1070 1175 1123 3194 526E-06 43161 3 1170 1275 1223 3094 138E-05 43161 2 1270 1375 1323 2994 671E-06 43161 1 1370 1475 1423 2894 OOOE+00 42997 42497 13 18-19 170 275 223 4077 OOOE+00 42997 12 260 365 313 3987 766E-05 42997 11 360 465 413 3887 727E-05 42997 10 460 565 513 3787 192E-05 42997 9 560 665 613 3687 752E-05 42997 8 660 765 713 3587 778E-05 42997 7 85-86 763 868 816 3484 260E-05 42997 6 860 965 913 3387 289E-05 42997 5 102-103 960 1065 1013 3287 102E-04 42997 4 1060 1165 1113 3187 522E-06 42997 3 1160 1265 1213 3087 520E-06 42997 2 129-130 1260 1365 1313 2987 960E-04 42997 1 1360 1465 1413 2887 OOOE+00 43372 42922 11 35-37 42-45 350 455 403 3935 684E-04 43372 10 460 565 513 3825 500E-05 43372 9 560 665 613 3725 106E-05 43372 8 72-74 660 765 713 3625 204E-05 43372 7 760 865 813 3525 872E-06 43372 6 860 965 913 3425 467E-06 43372 5 960 1065 1013 3325 200E-05 43372 4 1060 1165 1113 3225 354E-05 43372 3 125-130 1160 1265 1213 3125 157E-05 43372 2 125-130 1260 1365 1313 3025 337E-04 43372 1 1365 1465 1415 2922 689E-06 43052 43002 2 54-58 490 595 543 3763 124E-05 2100 43052 1 139-140 145-146 1367 1472 1420 2886 154E-04 1400 43291 4391 3 bullI133 260 365 313 4017 439F06 43291 2 77-78 760 865 813 3517 230E-03 400 43291 1 143-144 1355 1460 1408 2922 971E-06 350

29958 27258 4 450 555 503 2493 OOOE+00 (21)A 29958 3 103-105 1000 1105 1053 1943 752E-04 (063)A

Table XX Packer Permeability and Packer Sampling Results for Potential Fracture Intervals

1999 Drilling Program

Hows Corner Supcrfund Site Plymouth Maine

gtbull i Potential Fracture Top _OfBot Bottom of Depth to ltbull Top of Interval from f Packer Packer Middle Of

GS ELEV lt Hock Drilling interval Interval Interval WeD ID ft msl) (ft msl) TEST (ftbgs) ltft$gs) (ftbgs) (ftbgs)

MW-107D 29958 2 128-130 1200 1305 1253

MW-107D 29958 1 139-141 1350 1455 1403

MW-108D 31904 31104 6 35-36 300 405 353 MW-108D 31904 5 60-62 550 655 603

MW-108D 31904 4 80-83 750 855 803

MW-108D 31904 3 118-119 123-124 1150 1255 1203

MW-108D 31904 2 147-149 1440 1545 1493

MW-108D 31904 1 1700 1805 1753

MW-110D 40576 40426 2 21-31 210 315 263 MW-110D 40576 1 148-154 1460 1565 1513 MW-I11D 40519 4 70-71 650 755 703

MW-111D 40519 3 79-82 84-86 780 885 833 MW-I11D 40519 2 97-102 950 1055 1003 MW-111D 40519 1 1370 1475 1423

MW-112D 3027 2942 4 42-52 420 525 473 MW-112D 3027 3 850 955 903 MW112D 3027 2 1100 1205 1153 MW-112D 3027 1 135-136 140-141 1340 1445 1393

MW-113D 43085 43085 5 250 355 303 MW-I13D 43085 4 47-49 460 565 513 MW-113D 43085 3 73-74 700 805 753 MW-113D 43085 2 1050 1155 1103 MW-113D 43085 1 1380 1485 1433

MW-114D 42394 41594 4 48-49 450 555 503 MW-114D 42394 3 79-81 740 845 793 MW-114D 42394 2 121-129 1250 1355 1303 MW-114D 42394 1 134-142 1350 1455 1403

MW-115D 4035 4035 4 300 405 353 MW-1I5D 4035 3 70-71 650 755 703 MW-115D 4035 2 1150 1255 1203 MW-115D 4035 1 1400 1505 1453

LOT-28W 382 7 450 555 503 LOT28W 382 6 550 655 603 LOT-28W 382 5 650 755 703 LOT28W 382 4 750 855 803 LOT-28W 382 3 850 955 903 LOT-28W 382 2 950 1055 1003 LOT-28W 382 1 1055 1155 1105

NOTES cmsec = centimeters per second ft bgs = leet below ground surface It msl = feet below mean sea level lt = not detected at indicated reporting limil A = detected below laboratory PQL ( ) = detected below reporting limits

Elevation of Interval

(ft nisi) 174

159

283gt 2588

2388

1988

1698

1438

3795 2545 3349 3219 3049 2629

2555 2125 1875 1635

4006 3796 3556 3206 2876

3737 3447 2937 2837

3683 3333 2833 2583

3318 3218 3118 3018 2918 2818 2715

Hydraulic Conductivity

(cmsec)

323E-05

208E-05

471E-03

471E-03

624E-05

3I6E-05

264E-05

261 E-05

OOOE+00 200E-04 953E-05 OOOE+00 OOOE+00 212E-05

361 E-05 410E-06 2gQE06 292E-05

786E-05 124E-05 151 E-05 822E-06 82IE-06

858E-05 I69E-05 352E-03 866E-05

223E-05 394E-06 122E-05 525E-06

831 E-05 182F-05 L62E-05 129E-05 190E-05 890E-04 981 E-04

PCEraquo Concentration

(ugL)

lt5

(14A)

98 11

15

22

11

30

200 (62)A

110 210 300 240

(44)A (23)A

5

350 190 129 230

2200 1900 2600 2600

(17)A (16)A (19)A

96

Table XX Packer Permeability and Packer Sampling Results for Potential Fracture Intervals

2004 Drilling Program

Hows Corner Superfund Site Plymouth Maine

Top of Bottom of Depth to Midpoint

t K

ELEV (ft Potential Transmissive Zones Packer Interval

Packer Interval

Middle of Interval

Elevation of interval

Hydraulic Conductivity

PCE Concentration

Well ID msl) TESTr (ft bgs)- (ftbgs) (ftbgs) (ftbgs) (ft msl) (cmsec) (ogt) MW-203D 43227 4 277279 24 32 28 4043 667E-05 44

3 408415420 39 49 44 3883 593E-05 170 2 526 530 49 57 53 3793 101E-04 140 I 828830842 80 88 84 3483 701E-05 130

MW-204D 43262 5 295 300 26 34 30 4023 902E-05 220 4 463496513516 45 53 49 3833 119E-04 540 3 681685688 63 71 67 3653 OOOE+00 2 758 76 2 71 79 75 3573 309E-05 260 I 88 96 92 3403 OOOE+00

MW-205 42389 3 164 166 168 15 20 175 4148 OOOE+00 1000B 2 302305312 30 35 325 3998 107E-04 1300B 1 40 45 425 3898 OOOE+00

MW-206D 43007 5 17 72 195 4128 291E-05 4 296 302 307 29 34 315 4008 940E-05 2900B 3 522 52 57 545 3778 944E-07 2 656 64 69 665 3658 353E-06 1 92392793 4939 91 96 935 3388 614E-05 6300B

PW-207 43477 5 184622162819 18 29 235 4088 209E-05 1300 4 3508 32 43 375 3948 568E-06 5400 3 53325341542154325559 50 61 555 3768 821E-05 18000

6359 61 72 665 3658 866E-06 12000 1 8685 84 89 865 3458 213E-05 19000

NOTES cmsec = centimeters per second ft bgs = feet below ground surface ft msl = feet above mean sea level B = detected in lab blank

Table XX Orientation Permeability and Groundwater Sampling Results for Transmissive Features

2004 Drilling Program

Hows Corner Superfund Site Plymouth Maine

Borehole Geophisical Feature depth Dip True Dip True Transmissive Log Feature (Feet) Degrees Azimuth Strike bullvgt(Ltk|iy^

Number v Tosftble) v MW-203 5 277 64 337 67 Likely

6 279 59 11 281 Likely 8 352 14 177 87 Likely 11 381 46 96 6 Possible 12 408 35 271 1 Possible 14 415 57 250 340 Possible 15 420 58 202 292 Likely 18 526 52 75 345 Likely 19 530 52 82 352 Likely 28 828 48 75 345 Likely 29 830 52 17 287 Likely 30 830 56 233 323 Possible 31 842 50 130 40 Likely

MW-204 4 295 15 147 57 Likely 5 300 43 91 1 Likely 11 439 31 80 350 Possible 12 440 46 219 309 Possible 14 463 50 358 88 Likely 15 496 34 198 288 Likely 16 513 54 17 287 Likely 17 516 33 14 284 Likely 25 681 39 359 89 Possible 26 685 22 45 315 Possible 27 688 35 73 343 Possible 32 758 45 236 326 Likely 33 762 46 306 36 Likely

MW-205 5 164 69 106 16 Possible 6 166 78 165 75 Possible 7 168 82 115 25 Possible 8 168 68 116 26 Possible 12 215 46 222 312 Possible 13 217 75 62 332 Possible 14 219 29 32 302 Possible 16 237 69 250 340 Possible 17 256 73 353 83 Possible 18 272 44 202 292 Possible 21 299 37 196 286 Possible 22 302 31 206 296 Possible 23 305 59 48 318 Likely 24 312 63 42 312 Likely

MW-206 1 264 37 181 271 Likely 2 296 69 217 307 Likely 3 302 66 233 323 Likely 4 307 64 224 314 Likely 8 342 62 259 349 Likely

jjHydraulic GoiDanctilyity j(cmsecjw

667 E-05

593 E-05

101 P04

710 E-05

902 E-05

119 E-04

0

309 E-05

0

107 E-04

94 E-05

PCE (ugL)

44

170

140

130

220

540

260

IOOOB

1100B

1300B

2900B

STotal vVoCsv tig1)

84

234

192

183

2636

6436

3073

11448

12509

13776

32401

PCEyo dfCTotaf

52

73

73

7 1

83

84

85

87

88

94

90

Table XX Orientation Permeability and Groundwater Sampling Results for Transmissive Features

2004 Drilling Program

Hows Corner Superfund Site Plymouth Maine

Borehole Geophisical Feature deptt raquoip True pip True Transraissive Log Feature (Feet) shy Degrees Azimuth Strike (tikely

Number raquo Possible) 22 522 57 54 324 Possible 25 656 40 82 352 Possible 32 871 59 151 61 Possible 33 883 53 185 275 Possible 34 895 7 175 85 Likely 35 899 53 90 0 Likely 36 902 49 184 274 Likely 37 923 9 175 85 Likely 38 927 42 206 296 Likely 39 934 48 167 77 Likely 40 939 26 180 90 Likely

PW-207 1 1846 33 167 77 Likely 4 2216 49 289 19 Possible 7 2819 59 265 355 Possible 11 3508 55 189 279 Possible 18 5332 43 305 35 Likely 19 5341 51 30 300 Likely 20 5421 20 254 344 Likely 21 5432 39 301 31 Likely 23 5559 52 302 32 Likely 25 6359 24 182 272 Possible 29 8049 77 231 321 Possible 30 8685 78 38 308 Likely 32 9334 29 194 284 Likely

NOTES

B = detected in lab blank

Hydraulic Conductivity

(cmsee) 944 E-07 353 E-06

614 E-05

209 E-05

568 E-06

821 E-05

866 E-06

213 E-05

bulltCE (ugL)

6300B

1300

5400

18000

12000

19000

Total VOCs (ug1)

68901

1410

5802

19234

13085

20354

PCE of Total VOCs

9 1

92

93

94

92

93

Response to EPA-DEP Comment 3 Dated March 312005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

lit

EPA-DEP Comment 3

Comment 3 The reported f values and resultant Kd values There remains doubt that the values used in the flushing model accurately reflect the propensity for PCE to sorb to the bedrock The ^ values presented in Appendix B may be unrealistically high because the bedrock samples may have contained organic carbon that was unavailable for sorption The reported f values are only qualitative estimates of the organic carbon content of the bedrock samples The Walkley and Black organic carbon measurement method is quick and simple but the results obtained cannot be considered quantitative because it requires a correction factor which often results in erroneous values it assumes the organic carbon has an average valence of zero oxidizable and reducible constituents such as chloride ferrous iron and manganese oxides interfere with the results and the errors introduced by interference are potentially greater when the organic carbon content is low at low f values it is not clear that organic carbon is controlling PCE sorption (Schwarzenbach and Westall 1981 Mackay et al 1986 Fetter 1999)

In order to derive a Kd-based retardation factor that is reasonable given the reported f values and the rapid advance of the PCE plume described on pages 4-11 and 4-12 the flushing model requires a bulk density to porosity ratio that is roughly two orders of magnitude higher than the actual ratio for the Hows Corner bedrock (page 4-4) This apparent discrepancy needs to be addressed

Response This comment raises several concerns about the collection and analysis of samples for fraction of organic carbon (f^) the quality of the resulting data and the implications of the use of those data for estimation of the retardation of groundwater contaminant movement Results of bedrock analysis for f were proposed in the TI Evaluation Work Plan for use in conjunction with groundwater contaminant concentrations and aquifer information to estimate cleanup times using the Batch Flushing model It is important to use accurate f values from representative bedrock in the Batch Flushing model in order to obtain reasonable estimates of the remedial time frame Because of the importance of accurate and representative results the TI Investigation field program was designed and conducted both to collect samples representative of the rock volume most likely to be in contact with contaminated groundwater and to analyze them using an appropriate refereed analytical method Five potential methods for evaluating f were identified Of the five methods the Walkey-Black method was selected because it has minimal method interferences and a sufficiently low detection limit as well as a long history of use in agronomy and contamination studies The PRP Group is pleased with the quality of the data obtained from the bedrock samples as represented by their precision and reproducibility

The first part of this comment relates to the determination of fraction of organic carbon (f^) values The several subparts of the first paragraph are addressed individually in items 1 through 5 below The second part of the comment regarding the resultant distribution coefficient (Kd) values is addressed separately as item 6 below

1 There remains doubt that the values used in the flushing model accurately reflect the propensity for PCE to sorb to the bedrock

bull The rock core samples used for f (gocg) analysis were from core immediately adjacent to fractures These rock core samples included the fracture surfaces themselves and rock core extending back less than 1 cm from the fractures Therefore the foe data reported in the TI Evaluation represents the f of bedrock through which groundwater will travel and to which PCE will adsorb Based on the careful selection of sample locations and the

Response to EPA Comment 3 050205doc 1 of 11 Woodard amp Curran (211941)

number of samples collected we are confident that the measured f values are representative of the f at points of contact for PCE with the bedrock it is these f values that determine the propensity of PCE to sorb to the bedrock

bull The samples of rock core collected for analysis of f originated from 19 different locations varying in depth from 11 to 90 feet Therefore it is very unlikely that the rock core samples were contaminated with extraneous organic carbon from above ground

2 The foc values presented in Appendix B may be unrealistically high because the bedrock samples may have contained organic carbon that was unavailable for sorption

bull As noted in response 1 the f data reported in Appendix B represents organic carbon primarily associated with the surface of fractures in the bedrock through which groundwater is most likely to travel Therefore it is this organic carbon that the contaminants in the groundwater will come in contact with and adsorb to in the fractured rock at the site

bull The chemical oxidation agents used in the Walkey-Black method oxidize the easily oxidizable organic carbon in the medium and the foe is calculated from the quantity of the agent consumed Therefore it is unlikely that the analysis of the bedrock samples measured organic carbon that was unavailable for sorption

3 The reported foc values are only qualitative estimates of the organic carbon content of the bedrock samples

bull The reported f values are accurate quantitative results Schumachers review of Methods for the determination of total organic carbon (TOC) in soils and sediments (NCEA-C-1282 EMASC-001 April 2002) identifies the Walkley-Black method which was used to analyze the reported foc values as the reference method for comparison to other methods for analyzing total organic carbon

bull Schumacher also points out that if anything the WalkJey-Black method may underestimate the total organic carbon in a sample due to possible incomplete oxidation of organic carbon Usually the incomplete oxidation of total organic carbon in environmental samples is corrected for by multiplying the measured foe by 130 (Walkley amp Black 1934 Schulte 1995)

bull When the f data in the TI Evaluation Report (WampC 2005) Appendix B (attached) are analyzed statistically the standard deviation of the f for the 19 samples analyzed is 174 of the average f Given this standard deviation the 95 confidence interval for this data ranged from a low of 000123 gocg to a high of 000253 gocgm

The labs Method of Detection Limit (MDL) for the f measured using the Walkley-Black method is 00001 gocg Therefore the average (000188 gocg) the mean (000185 gocg) and geometric mean (000187 gocg) of the f values for the rock core at Hows Corner are all statistically significantly greater than the MDL of the Walkley-Black method

In addition to the aforementioned statistical analysis of the foe data triplicate samples (n = 3) from the same rock core (including one sample from the 19 rock core samples) were

Response to EPA Comment 3 050205doc 2 of Woodard amp Curran (211941)

analyzed for their f to determine the repeatability of the Walkley-Black method The average the mean and the geometric mean of the f values of these replicate samples was 000162 gocg 000150 gocg and 000159 gocgm respectively The standard deviation of these measurements was 000039 gocg

4 The Walkley and Black organic carbon measurement method is quick and simple but the results obtained cannot be considered quantitative because it requires a correction factor which often results in erroneous values it assumes the organic carbon has an average valence of zero oxidizable and reducible constituents such as chloride ferrous iron and manganese oxides interfere with the results and the errors introduced by interference are potentially greater when the organic carbon content is low at low foc values it is not clear that organic carbon is controlling PCE sorption (Schwarzenbach and Westall 1981 Mackay et al 1986 Fetter 1999)

bull Schumachers review (NCEA-C-1282 EMASC-001 April 2002) of the Walkley-Black method identifies several potential problems with this analytical method that could occur if the analytical lab is not familiar with the nuances of the chemistry associated with this method Interestingly Schumachers review neglected one of the more important analytical steps required to avoid errors in quantifying f in samples where there might beNAPL

It is absolutely critical to eliminate any NAPL from rock core samples prior to using the Walkley-Black method to measure foe in such samples This was done by the lab (PTS Laboratories) that measured the foe in the rock core samples from Hows Corner The lab used the Dean-Stark method (solvent extraction) to remove all hydrocarbons (including PCE and other NAPLs) from the sample (PTS Laboratories) This extraction method does not interfere with the subsequent analysis of the natural organic carbon associated with the rock core

Subsequently the samples were dried at 150degC to a constant weight (normally 16 hours) This latter step oxidizes all inorganic minerals including ferrous bearing minerals to ferric oxides and precludes their interference during the oxidation of the samples with chromic acid This procedure completely eliminates any positive bias in the reported foc

data that might have occurred due to the presence of ferrous ions and other reduced minerals

bull As noted in Response 3 the incomplete oxidation of total organic carbon results in an underestimate of the f and is corrected for by multiplying the f by a correction factor of 130 (Walkley amp Black 1934 Schulte 1995) The fx data reported in the TI Evaluation was corrected accordingly by using this correction factor

bull Excess chloride (Cl~) in percent weight quantities as found in saline soils may interfere with the quantitative titration of reduced chromium (Walkley 1947) However given that the primary rock type at the Hows Corner site is phyllite it is highly unlikely that there was sufficient chloride in the rock core samples for this to occur

bull Manganese oxides may also interfere with the analysis of f through competing with the dichromate ion for any oxidizable carbon (Walkley 1947) However in such cases the reported f would be an underestimate of the f present in the rock core Walkley (1947)

Response to EPA Comment 3 050205doc 3 of 11 Woodard amp Curran (211941)

4

reported that in the case where the ratio of MnO2 to carbon is 85 to 1 the error in the carbon determinations would only be 0 to 6 percent

It may also be useful to compare the analysis of total organic carbon in a geologic matrix that contains high levels of manganese using EPA method 9060 to the Walkley-Black method Table 1 summarizes data provided by one of the PRPs that compares the analysis of total organic carbon in a geologic matrix that contains approximately 02 wgt manganese (approximately 03 wgt manganese oxide)

Table 1 Comparison of total organic carbon measured using the EPA- 9060 method and the Walkley-Black method

Laboratory EPA-9060 Method Walkley-Black Method A Ave 00226 gocg Not analyzed

Stdev 000251 gocg n = 5

B Ave 002219 gocg Ave 002050 gocg Stdev = 000316 gocg Stdev =000971 gocg

n= 10 n = 10

The similarity in the total organic carbon concentrations measured by these two different methods provides further confidence that the Walkley-Black method is a viable method for analysis of total organic carbon in the presence of manganese equivalent to at least 10 by weight of the total organic carbon

5 The Walkley and Black organic carbon measurement at lowf^ values it is not clear that organic carbon is controlling PCE sorption (Schwarzenbach and Westall 1981 Mackay et al 1986 Fetter 1999)

bull Schwarzenbach and Westalls (1981) paper states that f values of less than 0001 gocg should not be used in combination with Kow (octanol-water partition coefficients) values to calculate K^ values (solid phase partition coefficients) values for a specific contaminant It should be noted that the TI Evaluation did not use the f data to calculate the KQC from the Kow Instead as requested by the EPA the measured KOC value for PCE was used to calculate the retardation factor for this contaminant

bull Schwarzenbach et al (2003) stated more recently that Even at very low f values (ie foe = 0001 kgoc - kg1 solid) sorption to the organic components of a natural sorbent may still be the dominant mechanism in defining the adsorption of organic compounds to geological matrices

bull In 1985 M Piwoni from the US EPA Robert S Kerr Environmental Research Laboratory published a paper (Banerjee et al 1985) that showed that for very hydrophobic molecules TOC content of the sorbent will control sorption down to levels of organic carbon that defy quantitation Contaminants such as the PCE found in the groundwater at Hows Corner are in this category of compounds

Given the aforementioned reasons the f values reported in the TI Evaluation are accurate within the noted statistical limitations and will have a predictable impact upon the retardation of PCE during groundwater transport

Response to EPA Comment 3 050205doc 4 of 11 Woodard amp Curran (211941)

6 In order to derive a Kd-based retardation factor that is reasonable given the reported foc

values and the rapid advance of the PCE plume described on pages 4-11 and 4-12 the flushing model requires a bulk density to porosity ratio that is roughly two orders of magnitude higher than the actual ratio for the Hows Comer bedrock (page 4-4) This apparent discrepancy needs to be addressed

The apparent discrepancy of bulk density to porosity ratios is most likely due to the fact that the Batch Flushing Model was originally developed for a porous medium and is not directly applicable to fractured bedrock As stated in Appendix C (page C-4) of the Draft Technical Impracticability Evaluation Report in order to use the Batch Flushing Model to describe the transport of contaminated groundwater in fractured bedrock where the matrix porosity is insignificant it is more appropriate to use a fracture surface area to void space ratio to calculate the retardation factor (R) than a bulk density to porosity ratio (Freeze amp Cherry 1979)

Since it is impractical to determine the actual surface area to which contaminants can adsorb the Batch Flushing Model was used with two simplifying assumptions bull The Kd was calculated from the f and the K^ bull The bulk density to porosity ratio term in the Batch Flushing Model was constrained to range

from 4 to 10 the typical range of such ratios in porous media (Freeze amp Cherry 1979)

If one uses site specific bedrock bulk density and porosity values the bulk density to porosity ratio is several orders of magnitude greater (specifically 273 gcc bullbull 000165 (dimensionless) = 1654 gcc) than the range of ratios of 4 to 10 used in the Batch Flushing Model in the Draft Technical Impracticability Evaluation Report Constraining the bulk density to porosity ratio within the range of ratios of 4 to 10 results in significantly lower R value than would be obtained using specific bedrock bulk density and porosity values

In summary in bedrock where fractures are the primary porosity the bulk density to porosity ratio can vary considerably and will be a function of the number of fractures and the fracture aperture The calculated bulk density to porosity ratio will be inversely proportional to the porosity This means that in fractured rock with limited fracturing and smaller porosity the calculated bulk density to porosity ratio is greater and will result in a greater calculated retardation factor than in bedrock with more extensive fracturing and greater porosity Consequently the calculated retardation factor will be greater for bedrock with less surface area available for sorption than bedrock with greater surface area for sorption This is contrary to what actually occurs

4 Response to EPA Comment 3 050205doc 5 of 11 Woodard amp Curran (211941)

m

REFERENCES

Banerjee P MD Piwoni K Ebeid (1985) Sorption of organic contaminants to a low carbon subsurface core Chemosphere _14 1057-1067

Freeze RA JA Cherry (1979) Groundwater Prentice Hall Englewood Cliffs NJ pg 604

PTS Laboratories wwwptsgeolabscompdf files3TOCnotepdf

Schulte EE (1995) Recommended soil organic matter tests in Recommended Soil Testing Procedures for the Northeastern United States Northeastern Regional Publication No 493 Chapter 8

Schwarzenbach RP J Westall (1981) Transport of nonpolar organic compounds from surface water to groundwater Laboratory sorption studies Environ Sci Tech 15 1360-1367

Schwarzenbach RP PM Gschwend DM Imboden (2003) Environmental Organic Chemistry Wiley-Interscience pg 292 408 amp 412

Walkley A LA Black (1934) An examination of the Degtjareff method for determining soil organic matter and a proposed modification of the chromic acid titration method Soil Science 37 29-38

Walkley A (1947) A critical examination of a rapid method for determining organic carbon in soils - effect of variations in digestion conditions and of inorganic soil constituents Soil Science 63251-264

Woodard amp Curran Inc (WampC) 2005 Draft Technical Impracticability Evaluation Hows Corner Superfund Site Plymouth Maine January 2005

Response to EPA Comment 3 050205doc 6 of Woodard amp Curran (211941)

LIST OF ATTACHMENTS (Response to Comment 3)

Appendix B to Draft Technical Impracticability Evaluation Measurement of foe at Hows Corner (4 pages)

m

Response to EPA Comment 3 050205doc 7 of 11 Woodard amp Curran (211941)

Appendix B Measurement of foe of Rock Core at Hows Corner

There are two general approaches to measure the fraction of organic carbon (foe) in rock cores

bull Measurement of weight loss by ignition of organic matter bull Chemical oxidization of organic carbon to carbon dioxide and either

subsequent quantification of the oxidant used for the reaction or quantification of the carbon dioxide produced during this oxidation process

The weight loss method is subject to errors caused by volatilization of substances other than organic materials such as water hydroxides and mineral carbonates Quantification of foe by the weight loss method is particularly sensitive to the presence of carbonates in rock cores There are however weight loss methods that are designed to differentiate between organic carbon and the aforementioned interfering materials but they require considerable care and are less accurate at low foe values Hence the weight loss method was not well suited for measuring the foe of the rock core from Hows Corner

The chemical oxidation of organic carbon is much better suited for quantifying organic carbon in rock cores such as those from Hows Corner This method uses a strong chemical oxidant to oxidize organic carbon to carbon dioxide and then measures either the chemical oxidant used to oxidize the organic carbon or the quantity of carbon dioxide produced In addition this general approach is not subject to interference by volatilization of other constituents of the rock core

There are at least two such chemical oxidation methods

bull The method of Baccini which was described by Schwarzenbach amp Westall (1981) first acidifies the sample to eliminate interference by carbonates Then a strong oxidant is used to chemically oxidize the organic carbon to carbon dioxide The resulting carbon dioxide is subsequently reduced to methane and quantified using a flame ionization detector Unfortunately this method has not been described in detail in a referred journal Hence it is would not have been appropriate to use to characterize the foe in the Hows Corner rock core

bull The more commonly used method to quantify foe in rock core is the Walkley-Black method (1934) This method is preferred for RBCA and DODDOE projects and by the oil industry

The Walkley-Black method uses an excess of chromic acid to oxidize (digest) organic matter to carbon dioxide The remaining chromic acid that was not consumed during the oxidation of the organic carbon is then quantified by titration with ferrous sulfate The difference in chromic acid prior to and after the oxidation of the organic carbon represents the total chromic acid used to oxidize

Hows Corner TI Evaluation Page 1 January 13 2005 Appendix B

the organic carbon in the sample The latter can be calculated using the chemical stoichiometry of the reaction

The Walkley-Black method is very accurate for samples that contain less than 2 organic carbon matter The minimum detection limit (MDL) for the Walkley-Black method is 100 mgkg or an foe of 0001

Given the rock core at Hows Corner was expected to contain less than 2 organic carbon the Walkley-Black method was used to measure the foe from 19 different rock core samples collected from varying depths ranging from 11 to 90 feet

Table 1 provides a statistical summary of the aforementioned data

Table 1 Statistical summary of foe data from rock cores collected at varying depths

Statistical Parameter Calculated Value foe Minimum Detection Limit (MDL) 00010 Number of samples analyzed (n) 19 Average foe 00019 Median foe 00019 Geometric Mean foe 00019 Standard deviation of foe measurements 000033 Relative standard deviation 174 -+ 95 Confidence intervals 00012 to 00025

The data in Table 1 shows the following

bull The foe from the Hows Corner rock cores are statistically greater than the MDL of the Walkley-Black analytical method

bull The average and median values for the foe of the Hows Corner rock cores from varying depths are nearly identical indicating that there is little variability in the foe values in the source zone at the site

bull The standard deviation of these measurements is 000033 which is 174 of the average foe

bull The 95 confidence intervals of the foe of the rock core at Hows Corner are 00012 to 00025

The foe was also analyzed from three separate samples taken from the same rock core at a depth of 55 feet (Only one of these samples was included in the data summarized in Table 1) Table 2 shows the statistical repeatability of this type of analysis

Hows Corner TI Evaluation Page 2 January 13 2005 Appendix B

Table 2 Repeatability of analysis of foe from one rock core at 55 feet in depth

Statistical Parameter Calculated Value Number of samples analyzed (n) 3 Average foe 00016 Median foe 00015 Geometric Mean foe 00016 Standard deviation of foe measurements 000039 Relative standard deviation 240 -+ 95 Confidence intervals 00008 to 00024

The data in Table 2 shows the following

bull The percent relative standard deviation of these three analyses of foe from the same rock core at Hows Corner is 24

bull The 95 confidence interval of the foes measured in this particular rock core at Hows Conrer is 00008 to 00024

These results show that there is good repeatability in using the Walkley-Black method for analysis of the foe in the rock core at Hows Corner

References Schwarzenbach amp Westall (1981) Transport of nonpolar organic compounds from surface water to groundwater Laboratory sorption studies Environ Sci Tech 15 1360-1367

Walkley A I A Black (1934) An examination of Degtjareff method for determining soil organic matter and a proposed modification of the chromic acid titration method Soil Sci 37 29-37

Hows Corner Tl Evaluation Page S January 13 2005 Appendix B

Woodard and Curran PTS Laboratories PTS File No 34618

ORGANIC CARBON DATA (METHODOLOGY WALKLEY-BLACK)

PROJECT NAME PROJECT NO

SAMPLE ID

203-chip-13 203-chip-23 203-chip-27 203-chip-38 203-chip-42 203-chip-47 203-chip-52 203-chip-58 203-chip-69 203-chip-82 207-chip-11 207-chip-19 207-chip-24 207-chip-29 207-chip-35 207-chip-45 207-chip-55 207-chip-87 207-chip-90

207-chip-55 55-MS

55-MSMSD

Hows Corner NA

DEPTH ft

13 23 27 38 42 47 52 58 69 82 11 19 24 29 35 45 55 87 90

55 NA NA

MATRIX

Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip

Average Median

Geometric Mean Standard Deviation Relative Std Dev

+- 95 Confidence Interval n

Rock Chip Rock Chip Rock Chip

Average Median

Geometric Mean Standard Deviation Relative Std Dev

+- 95 Confidence Interval n

FRACTION ORGANIC CARBON

(gg)

170E-03 185E-03 185E-03 170E-03 240E-03 190E-03 230E-03 180E-03 170E-03 115E-03 195E-03 220E-03 220E-03 235E-03 135E-03 190E-03 205E-03 175E-03 160E-03

188E-03 185E-03 185E-03 327E-04

1739 123E-03 to

19

205E-03 130E-03 150E-03

162E-03 150E-03 159E-03 388E-04

2402 840E-04 to

3

2532E-03

2393E-03

Hows Corner Tl Evaluation Appendix B January 13 2005

Response to EPA-DEP Comment 4 Dated March 31 2005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

EPA-DEP Comment 4

Comment 4 Distribution of contaminants First the TI report seems based on the assertion that there is DNAPL at the source area yet it also appears to represent that the source area is small and the bedrock below 85 is competent (or less fractured) and less impacted by the release of contaminants Some of the confusion may result from using most recent data when that data is from several different sampling events over several years and there is no discernible difference in concentrations between shallow and deep bedrock or as in Section 421 where generally decreased generally increase generally similar and similar concentrations in four consecutive sentences leads to a muddled picture of the contaminant distribution

Second the report asserts that the distribution of contaminants over the entire plume has not changed with time but fails to support this conclusion with data again relying on data that is from different sampling dates for one composite representation

Response The likely presence of dense non-aqueous phase liquid (DNAPL) at the Hows Corner Site and the determination that the source area is small are not mutually exclusive and both are conclusions drawn from information obtained during field investigations The presence of DNAPL in the source area is based on the elevated concentrations of volatile organic compounds (VOCs) detected in the groundwater (WampC 2001 WampC 2002) The conclusion that the source area is small is based on the area in which VOCs in groundwater have been detected at concentrations that are considered to be indicative of the presence of DNAPL nearby Similarly the conclusion that fracture frequency decreases at depths greater than approximately 50 to 85 feet below ground surface was based on field observation during the RI field work The fact that zones with observed fractures exhibited higher hydraulic conductivities than zones without fractures coupled with the decreasing frequency of observed fractures with depth led to the conclusion that the hydraulic conductivity of the bulk rock decreases with depth

The most recent data from all wells were used to provide the maximum VOC data set size During the RI all of the previously-existing and then newly-installed monitoring wells were sampled along with several residential wells The RI sampling included up to 48 monitoring wells Subsequent to the RI and prior to the TI three rounds of monitoring were conducted to verify that the plume was stable 15 monitoring wells were sampled during each of the three rounds During the TI field investigation 29 wells were sampled for VOCs The sampled wells included all of the newly-installed wells and a subset of wells installed during the RI for a total of 29 monitoring wells By using most recent data VOC results from 53 monitoring wells were included in the evaluation (see table labeled Sampling Events for listing of monitoring wells) This approach was selected because there generally was little variation in the data from a particular location between years This is borne out by the attached individual plots of VOCs detected in shallow bedrock and deep bedrock for the Pre-ROD (December 1999January 2000) and Supplemental (May 2000) sampling events and for June 2001 January 2002 and April 2003 sampling events The Pre-ROD and Supplemental plots are similar to the subsequent plots from the 2001 2002 and 2003 sampling events

In addition to maps showing the spatial distribution of VOC data at a given time trend plots of the data from a particular location through time (attached) indicate that since the RI concentrations generally have been stable or have decreased Together the maps and trend plots and the data from which they were developed indicate that the distribution of contaminants over the entire plume has not changed appreciably with time

Response to EPA Comment 4 050305doc 1 of 26 Woodard amp Curran (211941)

REFERENCES

Woodard amp Curran Inc (WampC) 2001 Final Remedial Investigation Report Hows Corner Superfund Plymouth Maine July 2001

Woodard amp Curran Inc (WampC) 2002 Final Feasibility Study Report - Non-Source Area Groundwater Hows Corner Superfund Site Plymouth Maine Hows Corner Superfund Plymouth Maine July 2002

Response to EPA Comment 4 050305doc 2 of 26 Woodard amp Curran (211941)

LIST OF ATTACHMENTS (Response to Comment 4)

Table - Sampling Events 1999 - 2004 (2 pages)

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater Pre-ROD Sampling Event

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater Pre-ROD Sampling Event

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater Supplemental Sampling Event

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater Supplemental Sampling Event

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater June 2001

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater June 2001

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater January 2002

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater January 2002

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater April 2003

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater April 2003

Figure - Concentration Trends - Non-Source Area Wells MW-1B and MW-3B

Figure - Concentration Trends - Non-Source Area Wells MW-13DB and MW-16DB

Figure - Concentration Trends - Non-Source Area Wells MW-16IB and MW- 108D

Figure - Concentration Trends - Non-Source Area Wells MW-108S and MW-112D

Figure - Concentration Trends - Non-Source Area Wells MW-112S and MW-114D

Figure - Concentration Trends - Non-Source Area Wells MW-114S and MW-115D

Figure - Concentration Trends -Source Area Wells MW-2DB and MW-2IB

Figure - Concentration Trends -Source Area Wells MW-102S and MW-103D

Figure - Concentration Trends -Source Area Wells MW-103S and MW-104D

Figure - Concentration Trends -Source Area Wells MW-104I and MW-106D

Figure - Concentration Trends -Source Area Wells MW-106S

Response to EPA Comment 4 050305doc 3 of 26 Woodard amp Curran (211941)

I I

El I

II I I 1 I

I

i

Event Baseline Case ID WC-01 WC-01

Well Date Aug-99 Oct-99 LOT10 1 LOT1-1 1 LOT11-4 LOT14 1 LOT15 1 LOT15-1 1 LOT16 1 LOT16-1 1 LOT17 1 LOT18 1 LOT19 1 LOT2 LOT20 1 LOT21-10 1 LOT21-11 1 LOT21-12 1 LOT21-13 1 LOT21-14 1 LOT21-2 1 LOT21-5 1 LOT21-7 LOT21 -8 1 LOT21-9 1 LOT23 1 LOT24 1 LOT28-1 1 LOT28-2 1 LOT28-3 1 LOT28-4 1 LOT28W 1 LOT30 1 LOT30-1 1 LOT30-2 1 LOT30-3 1 LOT30-4 1 LOT30-5 LOT31 LOT35 1 LOT41 1 LOT42-1 1 LOT43-1 1 LOT43-4 1 LOT6-1 1 LOT67 1 LOT6-7 1 LOT6-8A 1 LOT6-8B 1 LOT80-1 1 LOT82 1 MW-101D MW-1011 MW-101S MW-102D MW-102S MW-103D MW-103S MW-104D MW-1041 MW-104S MW-105D MW-106D

Groundwater Sampling Location Summary 1999 - 2004xls

Sampling Events 1999-2004

Hows Corner Superfund Site Plymouth Maine

Supplemental 2001 2002 2003 Pumping 2004 Pre-ROD Rl Sampling Sampling Sampling Test Sampling WC-03 WC-09 WC-25 WC-30 WC-42B WC-56 WC-58 Dec-99 May-00 Jun-01 Jan-02 Apr-03 Sep-04 Sep-04

1

1 1 1

1 1 1 1 1

1 1

1

1 1

1 1 1

1 1 1 1 1

1

1 1

1 1 1 1

1

1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

Sampling Events 1999-2004

Hows Corner Super-fund Site Plymouth Maine

Supplemental 2001 2002 2003 Pumping Event Baseline Pre-ROD Rl Sampling Sampling Sampling Test

Case ID WC-01 WC-01 WC-03 WC-09 WC-25 WC-30 WC-42B WC-56

ll

Well Date Aug-99 Oct-99 Dec-99 May-00 Jun-01 Jan-02 Apr-03 Sep-04 MW-106S 1 1 1 1 1 MW-107D 1 1 MW-108D 1 1 1 1 1 MW-108S 1 1 1 1 1 MW-110D 1 1 MW-111D 1 1 MW-112D 1 1 1 1 1 MW-112S 1 1 1 1 1 MW-113D 1 1 MW-114D 1 1 1 1 1 MW-114S 1 1 1 1 1 MW-115D 1 1 1 1 1 MW-12DB 1 1 1 MW-12SB 1 1 1 MW-13DB 1 1 1 1 1 1 MW-13SB 1 1 1 MW-14DB 1 1 MW-14SO 1 1 MW-15DB 1 1 1 MW-15SB 1 1 1 MW-16DB 1 1 1 1 1 1 MW-16IB 1 1 1 1 1 1 MW-16SO 1 1 MW-17DO 1 1 1 MW-17SO 1 1 1 MW-1B 1 1 1 1 1 1 MW-203D MW-203S MW-204D MW-204S MW-205 MW-206D

I MW-206S MW-2DB 1 1 MW-2DDB 1 1 MW-2IB 1 1 1 1 1 1 MW-3B 1 1 1 1 1 1

I MW-4O 1 1 1 MW-5B 1 1

II MW-6DB 1 1 1 MW-6SB 1 1 1 MW-8DB 1 1 1 MW-8SB 1 1 1

II PW-207 1 SEEP-1 1 SUBTOTAL - RESIDENTIAL 44 25 0 2 0 3 0 SUBTOTAL - MONITORING 22 48 41 15 15 15 1

Total 3 66 73 41 17 15 18 1

I Included in most recent data

I Notes 1 - Overburden well not included in most recent data for plotting

2 - Tetrahydrofuran and 2-Butanone were the only two compounds detected in this well and are thought to be the result of well repair not included in most recent data for plotting

3 - Not included in most recent data for plotting

2004 Sampling

WC-58 Sep-04

1

1 1

1 1

1 1 1

1

1 1

1 1 1 1 1 1 1 1 1

1 1

1

0 29

29

Groundwatef Sampling Location Summary 1999 - 2004xls

I

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

monitoring well Figure 4-14 total VOC contour (ugl) - December 1999January 2000 Distribution of Total VOCs in

Note SW-113 is located downstream of SEEP-1 Shallow Bedrock Groundwater total concentration of detected VOCs ND= not detected these two locations were sampled during the Pre-ROD Sampling Event

Baseline Sampling Event in OctoberNovember 1999 Hows Corner Superfund Site Surface Water Sampling Location A Plymouth Maine Seep Sampling Location laquo- WOODARD ampCURRAN

995037wipri reportepa ri interim final feb 2001cadd drawingsfinalfig 4-14

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

0 300 600 I

FEET

Q residential well Figure 4-16 monitoring well Distribution of Total VOCs in

Deep Bedrock Groundwater total VOCs contour (ugl) Pre-ROD Sampling Event

active residential wells with lot number Hows Corner Superfund Site 2deg42deg Plymouth Maine total concentration of detected VOCs ND= not detected WOODARD ampCURRAN Enyinaaring bull Science bull Operations bull

995037wipri reportepa ri interim final feb 2001cadd drawingsfinalfig4mdash16

PLYMOUTH POND

PLYMOUTH POND

1 628Tl7MW-2bB 12135

PLYMOUTH POND

monitoring well Figure 4-20

V total VOC contour (ugl) - June 2000 Distribution of Total VOCs in Shallow Bedrock Groundwater

| 34 | total concentration of detected VOCs ND= not detected NA = not analyzed Supplemental Sampling Event Note SW-113 is located downstream of SEEP-1 Hows Corner Superfund Site

Surface Water Sampling Location these two locations were sampled during the Plymouth Maine Baseline Sampling Event in OctoberNovember 1999 Seep Sampling Location WOODARD amp CURRAN

Engineering bull Science - Operations bull 995037wipri reportepa ri interim final feb 2001 cadd drawingsfinalfig 4-20

residential well Figure 4-22 Distribution of Total VOCs in

monitoring well Deep Bedrock Groundwater

total VOCs contour (ugl) Supplemental Sampling Event

Hows Corner Superfund Site

total concentration of detected VOCs ND= not detected NA = not analyzed Plymouth Maine

WOODARD amp CURRAN

995037wipri reportepa-ri interim final feb 2001cadd drawingsfinalfig 4-22 Engineering bull Science - Operations bull

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

FEET

Shallow Monitoring Well

Deep Monitoring Well

C Detected Concentration ND = Not Detected Figure 1-XS Distribution of Total VOCs in Shallow Bedrock Groundwater

Pumping Well

17-Acre Property Boundary Concentration Contour (ugl)

June 2001 Hows Corner Superfund Site

Plymouth Maine WOODARDampCURRAN

-i^rhvj bull Scbncn bull Operations bull 211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0601 dwg04-20-05

PLYMOUTH POND Hopkins Road V

O

PLYMOUTH POND

PLYMOUTH POND

o

0 300 600 mdashfa FEET

Shallow Monitoring Well bull bull - 17-Acre Property Boundary Figure 1-XD

Deep Monitoring Well 1 I Detected Concentration ND = Not Detected Distribution of Total VOCs in Deep Bedrock Groundwater

-mf- Pumping Well June 2001 Residential Well Hows Corner Superfund Site

Plymouth Maine i h Surface Water Sampling Point

g WOODARD ampCURRAN _ ^ _ ^ _ _ yen_ rj i|Hlaquorlny bull Science bull Opt

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0601 dwg04-20-05

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

Shallow Monitoring Well

Deep Monitoring Well

Detected Concentration ND = Not Detected Figure 1-YS Distribution of Total VOCs in Shallow Bedrock Groundwater

Pumping Well

17-Acre Property Boundary Concentration Contour (ugl)

January 2002 Hows Corner Superfund Site

Plymouth Maine WOODARD amp CURRAN Engineering Science- Operations bull

211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0102dwg04-20-05

PLYMOUTH POND

PLYMOUTH POND

Site Pand^ laquoum-laquoBTuitaraquo tLV

vVlf-(

PLYMOUTH POND

0 300 600 ^ = FEET

Shallow Monitoring Well mdashbullbullbull 17-Acre Property Boundary Figure 1-YD - A - Deep Monitoring Well FT Detected Concentration ND = Not Detected Distribution of Total VOCs in

Deep Bedrock Groundwater Pumping Well January 2002 Residential Well Hows Corner Superfund Site

Plymouth Maine Surface Water Sampling Point

WOODARD ampCURRAN Engineering Sciencs- Operations bulli Si

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0102dwg04-20-05

- m j

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND j A O-shy

Shallow Monitoring Well E Detected Concentration ND = Not Detected Figure 1-ZS Distribution of Total VOCs in

Deep Monitoring Well Shallow Bedrock Groundwater

Pumping Well Hows Corner

April 2003 Superfund Site

17-Acre Property Boundary Plymouth Maine Concentration Contour (ugl) r WOODARD ampCURRAN

Engineering bull Science bull Operations bull 211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0403dwg04-20-05

s S pound

PLYMOUTH POND

PLYMOUTH POND

- -

5 PLYMOUTH POND

Jo

FEET

ft Shallow Monitoring Well mdashbullbullmdash 17-Acre Property Boundary Figure 1-ZD Deep Monitoring Well I 1 I Detected Concentration ND = Not Detected Distribution of Total VOCs in

Deep Bedrock Groundwater Pumping Well April 2003

Q) Residential Well Hows Corner Superfund Site Plymouth Maine

(T) Surface Water Sampling Point WOODARD ampCURRAN poundKk EnginawtirKj bull Science - Operations bull

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0403dwg04-20-05

0 Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

B MW-1B

I 12000

PCE

B 10000 Total VOCs

I

i 2000

i 0 Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

c MW-3B

G 2000

1800

B PCE

1600 Total VOCs

1 I I E

il-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

G E

211941

El

I I z E

80

Concentration Trends shy Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-13DB

Total VOCs

c i i c o

Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

MW-16DB

30

c i c c I c o

Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99

PCE

Total VOCs

Jul-01 Jul-03

211941

O bi

c Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

I MW-16IB

i 35

3

c Total VOCs

lt- 2 5

0 | gt

o

1 sectI

c c 0 4

Jul-90 Jul-92 Jul-94 Jul-96 Jul-98 Jul-00 Jul-02 Jul-04

I I MW-108D

I 12

PCE 10

Total VOCs c oc 3

E E I 0

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

E 211941

c Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

fi MW-108S

I I 40

PCE 35

Total VOCs

30

I f 26

20 I o

I 15

10

c Dec-99 Dec-00 Dec-01 Dec-02 Dec-03 I 0

I MW-112D

c 35 - imdash

I A3 shyTotal VOCs

o c

E 1 2

I

ition

B 1 ^

-i c 3

0 Dec-99 Dec-OO Dec-01 Dec-02 Dec-03

211941

I

i

I

cII

Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-112S

08

PCE

Total VOCs 06

o 04

02

0 Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

MW-114D

o

12000

10000

8000

6000

PCE

Total VOCs

4000

2000

i

ccEIIc

i

i

E

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

211941

Con

cent

ratio

n (

ug

l)

E Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

I MW-114S

E A5000 -- Total VOCs

- 4000

0 3000

2000

i 1000

i n shy

Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

MW-115D

c PCE

Total VOCs

c E

o

C c

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03 I 0

211941

IepoundII

EIEIIGICCIccc

30000

25000

20000

o bullsect 15000 b

o 10000 U

5000

0 Aug-99

25000

20000

5000

0 Aug-99

211941

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-2DB

PCE

Total VOCs

Aug-01 Aug-03

MW-2IB

PCE

Total VOCs

Aug-01 Aug-03

IDIBI

ii EIDIISIBIG C

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-102S

6000

5000 PCE

Total VOCs

4000

O 3000

2000

1000

0 Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

MW-103D

16000

~ 14000 ugt 3- 12000 o

^ 10000

sect 8000

O 6000

4000

2000

PCE

Total VOCs

0Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

211941

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

G MW-103S

I I

ampo

12000

10000

E sectc

S

8000

6000

4000

2000

0Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

G I 6000

MW-104D

i 5000

PCE

Total VOCs

i i c

2000

1000

Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

E I

211941

cIccIG

IIBCccBcIc

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-1041

PCE Total VOCs

a 25000

0 20000

a 15000

10000

5000

0 Jan-OO Jan-01 Jan-02 Jan-03 Jan-04

MW-106D

3000

2500 PCE

Total VOCs

=sect 2000

o bullsect 1500

1000

500

0 Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

211941

c Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

c MW-106S

I PCE

Total VOCs

i

i Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

i

i i i E

C

211941 c

Response to EPA-DEP Comment 5 Dated March 312005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

iiw

EPA-DEP Comment 5

Comment 5 Matrix Diffusion The report as well as other proponents of matrix diffusion suggest that depletion of DNAPL (Section 5112 page 5-15) needs to be achieved While that might be the ideal the goal is to achieve performance standards and that goal may be attainable while there is residual contamination in the rock perhaps even DNAPL globules The low bedrock matrix porosity (page 1-15) the high permeability values (page 4-4) the relative flux of the groundwater (page 5-5) and the decrease in surface area and out of the mainstream pockets (appendix C-4) all suggest that the diffusion out of the rock matrix would be insubstantial relative to the regional flux of groundwater through the Site

Response The TI Evaluation Report does not explicitly consider or rely upon matrix diffusion as a basis for requesting a TI Waiver for a portion of the Hows Corner Site The technical literature provides documentation that matrix diffusion can be a significant process that affects chemical transport and groundwater remediation timeframes in unconsolidated and consolidated media including fractured rock (US EPA 1989 Freeze and Cherry 1979 Pankow and Cherry 1996 Fountain 1998) Back diffusion of contaminants from the matrix porosity of the fractured rock can prolong the time necessary to achieve groundwater cleanup goals particularly for compounds such as PCE for which the cleanup goal is a low concentration It is our expectation that matrix diffusion has occurred at the Hows Corner Site and that back diffusion of PCE from the rock matrix will also occur Although the extent to which matrix diffusion is occurring at the Hows Comer Site has not been determined and that lack of knowledge contributes to uncertainty regarding the cleanup times at the Site the effect of matrix diffusion is to lengthen rather than shorten the time required for remediation

REFERENCES

Fountain JC 1998 Technologies for Dense Nonaqueous Phase Liquid Source Zone Remediation Ground-Water Remediation Technologies Analysis Center Technology Evaluation Report TE-98-02 December

Freeze RA and Cherry JA 1979 Groundwater Prentice-Hall Inc Englewood Cliffs NJ 07632 p 410-412

Pankow J F and Cherry J A 1996 Dense Chlorinated Solvents Waterloo Press Portland OR 97291-1399 p 67-88

US EPA 1989 Transport and Fate of Contaminants in the Subsurface EPA6254-89019 p 17-18

Response to EPA Comment 5 050305doc 1 of 1 Woodard amp Curran (211941)

WOODARD amp CURRAN Maine Massachusetts New Hampshire Connecticut Florida Operational offices across the US 1-800-426-4262 www woodardcurran com

Page 15: SDMS DocID 251749 - Records Collections · 2020-06-13 · CORPORATE OFFICES: Maine, Massachusetts, New Hampshire, Connecticut New, York, Florida Engineering • Science • Operations

(MEDEP Pond 1) Farm Pond

028 MW-12DB

MW-125B 040

l - _ ^ I 016 I N

050 MW-15SB

MW-15DB 048

A J s

- A - Monitoring Well

-$poundbull Pumping Well

_bullmdash 17-Acre Property Boundary

^ Drawdown Contour (ft)

151 I Drawdown (ft)

211941 Hows CornerwgtpDrawinQsT EVAI_Drawdown-72brsdwg04mdash19-05

Figure X Drawdown at 72 Hours

Hows Corner Superfund Site Plymouth Maine

^ WOODARD ampCURRAN Engineering bull Science bull Operations i

(MEDEP Pond 1) Farm Pond

Monitoring Well

Pumping Well

_bullbull_ 17-Acre Property Boundary

f Groundwater Elevation Contour (ft)

|419Q0| Groundwater Elevation

211941 Hows CornerwipDrawinqsTI EVALPotSurf-72hrs_shallowdwg04-19-05

150 300

FEET

Figure X Potentiometric Surface at 72 Hours

Shallow Wells Hows Corner Superfund Site

Plymouth Maine

WOODARD ampCURRAN Engineering bull Science bull Operations

29212 MW-108D

(MEDEP Pond 1) Farm Pond

Monitoring Well

Pumping Well

mdashbullbulllaquo 1 7-Acre Property Boundary

bull Groundwater Elevation Contour (ft)

1419001 Groundwater Elevation

211941 Hows CornerwipDrawingsTI EVALPotSurf-72hrs_deepdwg04-19-05

150 300 =5fc= FEET

Figure X Potentiometric Surface at 72 Hours

Deep Wells Hows Corner Superfund Site

Plymouth Maine

WOODARDampCURRAN Engineering bull Science bull Operations bull

--

Pumping Test Analytical Results Hows Corner Superfund Site

Plymouth Maine

Well ID oper Jaccb Analyses 2 Theis Analyses Fissure

Well Id Rd (ft)

Saturated Thickness

Transmissivity

(ft2day) K

(ft2day) K

(cmsec) Storage

Coefficient Transmissivity

(ft2day) K

(ft2day)

K (cmsec)

Storage Coefficient

System K

(ftday) PW-207OB 8 85 481 057 200E-04 392E-02 36 042 150E-04 809E-04 027 MW-103S 50 85 451 053 187E-04 720E-03 92 108 382E-04 283E-04 083 MW-103D 54 185 455 025 868E-05 210E-02 65 035 123E-04 237E-04 044 MW-2IB 59 85 352 041 146E-04 699E-03 104 123 433E-04 512E-04 052 MW-2DB 63 85 334 039 139E-04 845E-03 148 080 283E-04 239E-04 046 MW-104D 95 185 489 02 6 932E-05 654E-03 98 053 186E-04 547E-05 037 MW-104I 97 85 33 03 9 137E-04 362E-03 117 137 484E-04 962E-05 048 MW-101I 107 85 364 043 151E-04 490E-03 511 601 212E-03 223E-04 136 MW-102D 134 185 435 024 829E-05 248E-03 108 058 206E-04 850E-05 065 MW-101D 138 185 492 027 938E-05 511E-03 671 362 128E-03 700E-04 172 MW-205 219 85 57 067 237E-04 255E-03 447 526 186E-03 359E-03 -shyMW-204D 221 185 367 020 700E-05 170E-03 790 427 151E-O3 155E-04 147 MW-204S 225 85 379 045 157E-04 156E-03 1031 1213 428E-03 313E-04 199 MW-1B 228 85 325 038 135E-04 977E-04 340 400 141E-03 739E-05 054 MW-203S 273 85 489 058 203E-04 117E-03 1255 14 76 521 E-03 216E-04 210 MW-106D 278 185 51 028 972E-05 141E-03 1065 576 203E-03 360E-04 104 MW-203D 278 185 478 026 911E-05 152E-O3 765 414 146E-03 364E-04 138 MW-105D 364 185 44 024 839E-05 830E-04 769 415 147E-03 200E-04 127

1 Analyses conducted using Cooper and Jakob method on late drawdown data collected during constant

discharge pumping test conducted at the Hows Comer Site from September 20 - 30 2004

2 Analyses conducted using Theis solution for unconfmed approximation (1935)

J Analyses conducted using Moench method for dual porosity estimation (1984)

Fissure System Storage

Coefficient 402E-04 117E-06 264E-04 300E-04 932E-05 235E-07 502E-05 326E-06 801E-05 542E-04

-

803E-05 762E-05 134E-05 498E-05 115E-04

47E-04 838E-05

3 ysesh Analysis

Block System K (ft2day)

251E-02 207E-03 564E-04 163E-04 585E-04 465E-02 153E-04 498E-03 855E-04 356E-03

-

292E-03 394E-03 720E-04 526E-03 160E-01 35OE-O1 287E-03

Block System Storage

Coefficient

402E-02 164E-04 183E-02 330E-03 158E-03 847E-03 286E-03 326E-04 803E-05 272E-03

723E-04 686E-04 148E-04 349E-04 115E-03 47E-04 838E-04

Theis - Moench - CJ - AnalyticalResults_4-19-O5xls

DRAFT

242

24

238

236

bulla

c

i

a Q

234

232

228

226

Hows Corner Constant Discharge Testing USGS Background Groundwater Level USGS 445319068560101 ME-PEW456 Kenduskeag Maine

End of Monitored Recovery Period 09302004

Regional Background Location i 226 miles from Pumping Locatio

lt

697

NOTES

1 Groundwater samples collected in 1999 were screened for five volatile organic compounds (VOCs) only N

tetrachloroethene (PCE) exceeded reporting limits MW-2030 082304 082304 082304 082304 u

2 Strike and Dip of likely or possible transmissive 30 45 55 85 feature within the packer interval from which the indicated sample was collected

MW-204D

PCE TOTAL VOCs

081904 30

220 2636

A

081904 46-50 540 6436by

081904 IT

260 3073

x

MW-105D

PCE TOTAL VOCs

111199 50-60 2100 2100

MW-106D

PCE TOTAL VOCs

111199 76-86

400 400

111199 137-147

1400 1400

111299 1355-1455

350 350

PCE TOTAL VOCs

44 84

64

MW-6SB

bulli

lt

gt-

170 234

35

I I i

140 192

^^52

^^52

130 183

52 - lt

S A 34

PW-207 082404 082404 082404 20 37

PCE 1300 TOTAL VOCs

17-Acre George West Property Boundary

MW-113D

PCE TOTAL VOCs

112299 46-56

350 350

112299 70-80 190 190

150

112299 105-115

129 129

112399 138-148

230 230

L e g e n d ( J New Monitoring Well-Summer

Site Property Boundary ^ P u m p i n g Well-Summer 2004

-xmdashxshy Source Area

bull0shy Monitoring Well shy Pre 2004 Angled Boring-Summer 2004

211941laquoipdwgTI-ELV21ig41paltker-data2

2004 PCE of Total

bull lt70 VOCs

M W - 1 14D ^ ^

Figure xx Packer Testing Results in

Vicinity of Source Area Hows Corner Superfund Site

Plymouth Maine ^ WOODARD ampCURRAN

^^^^^^^^^^m ampKm Engineering - Science bull Operations

c Northeast Geophysical Services Borehole Geophysical Log

MW-203 Date logged 081704 Plymouth Maine

I Flowmeter Measurements Tomporaturo(C) Acoustic Televiewer

7 5 8 8 5 9 95 Caliper (Inches) Resistance (Ohms) Spontaneous Potential (mVj Dip In Degrees PCE Total VOCs

3 0 2 0 8 0 laquodeg 4S 1000 1400 1800 2200 MO HO 1000 1200 MOO 0 laquo deg ugL ugL n 1 1 1 1 1 1 1 1 1 i 1 1 1 1 n 1 1 1 1 1 1 1 1 1 1 1 n I l l l l l l l n

Ambient Flowneter pumping Rowmeter 11 gpm 6

H

bull

magnetic 10 bull 10 bull - 10 - north - 1 0I

-

_

bullbullbull - bull

20 bull bull20 bull ^ ltr~mdash 01

I

4 ^

LOS7

^

44 84 I I

Xr - 2

lt ^ bull30 -_ _^O1J- 1 _ 050 30 - 3 0

0r - - 3

C -j [ bull bull bull | shy

-O8 H ~ 1 045 7

1 4040 - 40 - -40 r - 14gt 13

V1s -- -023 f 1022 1V 170 234 I

T lt bull B gtf 50^ J50 - - 5 0 - - 5 0

I eet be

lo

i 1

1 1

1

140 192 - - - -t shy

-mdashj bullpound 60 - $o - - 60 - -60

H i I c

bull024

ampbull

3 - T lt ftft rgt He

70 bull j 70 - - 70 - 7 0 -

in -j bullbull shy

-021 1 T 022

- Ton _ Ov

26

130 183 NF NF

90 -_ 90 - 7 90 - -90

-

ifi Jf

3J

^gt _ N F NF bull bull shy

| H100 - j 100 bullbull 100 - -100

1 1 1 1 1 1 1 ) | 1 f I 1 1 1 ) 0 20 40 60 80

flft mdash ftn - mdash rVt

30 4 g 0 20 40 60 Dip in Degrees bullbull

Likely or poss bleFluid Resistivity (ohmmeters) The dip direction-- indicated

^ t h e l i n e extending from t h

I Iransmissive zone circle The strike of the feature is 90 degrees from this

The acoustic televiewer graph displays the mostprominent features selectedffom the acoustic televiewer

R n r a h n l c D O t t n O I B

f i o n n h w c i r a l U K U p i i y SI Ud l

1 rn l_Og Packered Interval August 2004

E tog The location dip angle and dip direction of the sleeted M W - 2 0 3 Groundwater samples were collected by Woodard S Curran on H23120M features are approximate Refer to the televiewer og of His _ well for more precise detail Plymouth Maine Date logged 081704

I

1

Northeast Geophysical Services Borehole Geophysical Log MW-204 D a t e l o gge d 072604

Plymouth Maine

n 3

Flowrneter Measurements(in gpm)

Caliper (Inches)0 3 5 4 0

1 1 1 1 1 1 1 t 1 1 1 1 1 1Ambient Rowmeler pumping Flowmetsr 05gpm

Templaquorature (C) bull bull bull bull i

7 75 8 8S 9 Resistance (Ohms) Spontaneous Potential (mV)

4000 SOW 600 4M 0

Acoustic Televiewer (interpreted)

Dip in Degrees 0 20 4060 SO

at N

PCEugL

Total VOCs ugL

- -_ a

10-

shy 10 bull - 10 shymagnetic

north - 10

o o

bull 1

11

11

1 1

1 1

11 1

1 1

1 1

1 1

1 1

1 1

1 1

1 1

1 1 E 1

- L

3 7 2 0 2 0r bull 20 bull - shy

i S_ N F

bull30 bull 7 3 0 220 2636shy1^ J J 004

fI f V ^

40 shy 4 0 4 0 shy - 4 0rbull019 [_ 007 w8 - - shy5 c

bull

gt

Ia50i 540 6436

bull50 - - 50 - - 5 0

-QQ7 - bull - -t T

pound V gtk

B 6 0 - e o - 7 6 0 -60shyQ 1 1

Q -007 -004 bull1 mdash T - J ~

bull

- - shyT 70 -J c [TO- - 70 - 7 0-

V Y 1- -004 -003

mdash T -h - y - j i - - mdash 260 3073 - gt=7

80 -j NF bull80 - - 80 - - 8 0Jgt

bull i

i 1

i i

C- bull shy

90 shy

K

Jlt i90 90 shy - 9 0shy -

l

ii

I I I I

NF bull M J

I ^ ^ - ^ bull 1

mdash mdash - _

s -7 ^100shy

till

1 100 100- H - 1 0 0shy -1 x Likety or possible k ^ Iransmissive zonebull

1 i i i ii i i i | l l l l | l i l l 0 20 40 ED 80

1 -

3 0SOFluid Resistivity (ohmmeters)

Dip in Degrees The djp ^ ^ o n is indicated ty Ihe line extending from tha circle The strike of Ihe feature

19- 3U UIHJIW93 IolII l l l lraquo

bull

The acousfc televiewer graph displays the mostprominent features selected from the acoustic televiewer109 The location dip angle and dip direction of Ihe sleetedfeatures are approximate Refer to the televiewer log of thiswentormore precise detail

B o r e h o l e G e O D h V S I C a l LOO B W H U I B w c w p n y o i v a i w v yM W - 2 0 4

P l y m O U t n MaiDB

Packorod Interval August 2004Groundwater san-ples wampramp collected by Woodard a Curran on OMO23C4

Date logged 072604

C

I

E Northeast Geophysical Services Borehole Geophysical Log Date logged 072704

I MW-205

Plymouth Maine

Flowmeter Measurements Temperature (C) Acoustic Televiewer (In gpm) I ~l (Interpreted)

I 85 10 Caliper (inches) 95

Dip in D g r laquo Resistance (Ohms) Spo ontaneous Potential (mV PCE Total VOCs 3 0 16 4 0 4 5 ) 20 40 60 80 10 00 2000 30 00 4VJ 400 -3 laquo

i i i i 1 i i I i 11 4 0 D 1 I I ugL ugL

C h

iii Ambient Flowmetar pumping

Flowmeter 1 25 gprn

I bull$bull

i

I rmdash magnetic 1 north ^^^^ 1 VI f

10 ~ I C x 10 bull - 10 bullbull

4 5 6mdashmdash f 1000B 11448 noisy nodi a raquo ^

mdash 5rt mdashi mdash Oft pound) 1100B 12509

cjmdash1 007

-

i i i 1

en

8 B a B

30 mdash

-

40 shy

-mdash I -

50 -_

__NF lt005

- 30 - - 3 0 it 34V

MO P26 V S) 1300B 13776 _ N F NF

26

40 bull - 40 bull 7-40 gt J Vf1 cX

) -j -

_ N F NF 50 c bull - 50 ^ 7-50

i I

I

c

B pound 60 - 6 0 7 60 - 7-60 a i 1

_ N F NF i Si f f 70 -_ bull70 bull - 70 shyC I 9

-m bull - shyA

_ N F NF 80 80 -j bull80 bull - 80 - C- 33 34

bull

5-i r

i 1

J r

Ck

_ N F NF 9 0 90 - - 90 shy

i bullCshy

J rK bull

100 -j ^ Likely or possible bull100- - 100- I -100

transmissive zone bull - ^ bull shy] |

1 1 1 1 1 1 1 I 1 i i i 1 i i 1 1 0 20 40 SO SO 10 20 30 40 50 Dip in Degrees 30 4 0 Fluid Resistivity (ohmmeters) Thlaquo dip direction is indicated

by the line extern r g from the circle The strike of he feature is 90 degrees from ihis

The acoustic televiewer graph displays the most

I Borehole Geophysical Log Packered Interval August2004 prominent features selected from the acoustic televiewer

Groundwatcr samples were oollccled by Woodard amp Cufran orgt S172004 log The location dip angle and dip direction of ins slsctsd MW-205 features are approximate Refelt to the televiewer log of this wall for more precise detail Plymouth Maine Date logged 072704

I

C

I Northeast Geophysical Services Borehole Geophysical Log Date logged 072704

I MW-206

Plymouth Maine

Flowmetor Measurements Temperature (C) Acoustic Televiewer | I r T i i i i i i i i i i i i i i r I |(in gpm) (Interpreted)

I 75 8 flS 9 95

Caliper (inches) Resistance (Ohms) Spontaneous Potential (mV) Dip In Degress PCE Total VOCs 30 35 40 4 5 0 20 40 M 90 4500 5500 6500 ugL ugL I i i

I I

- 1 0

I - 2 0

I 2900B 32401

i i L

E 0

i 6300B 68901

i I 0 20 40 SO 80

20 30 40 50 Dip in Dlaquogralaquos

amp 4 a Fluid Resistivity (ohrnmeters) The dip dirertion is indicated Likely or possible by iho line extending from the transmissive zone circle The striKe of the feature

is 90 degrees from tNs

Borehole Geophysical Log Packered Interval August 2004

E amples were collected by Woodard amp Cunan oo SM82004 log Thraquo location 4p angle and dip direction of the sloeled MW-206 feature are approximate Refer to the televiewer 109 of this well for more precise detail Plymouth Maine Date logged 072704

C

I Northeast Geophysical Services Borehole Geophysical Log

Date logged 082304 PW-207

I Plymouth Maine

Fiowmeter Measurements Temperature (C) Acoustic Televiewer

I (in gpm) (interpreted)

75 8 85 9 95 Caliper (inches) Resistance f0tims) Spontaneous Potential (mV) Dip in Degrees PCE Total VOCs

55 60 0 20 40 SO 80 ugL ugL I I I I I I I

Ambienl Fiowmeter pumping Flewmater

magnetic - 10 - - 1 0

north

i - 20 - - 2 0

1300 1410

i - 30 - - 3 0

i tf

5400 5802 - 40 - - 4 0

B - 50 - - 5 0

I 18000 19234

- 60 - - 6 0

I 12000 13085

- 70 - - 7 0

- 8 0

i - 9 0 19000 20354

G - 100- -100

I 110 110 bull110

0 20 40 60 SO 10 20 30 Dip m Degrees

Fluid Resistivity (ohmmeters) I 50

The dip direction is indicated by ihe line extending from the circle The strike of the fealure is 90 degrees from this

Borehole Geophysical Log

G Packorod Interval August 20(M log The location dip angle and dip dirlaquocton or the sleeted Groundaier samplss were ooliecled by Woodard i Curran on ampt24f2ltXM PW-207 failures are approximate Reter to the televiewer log of this wlaquoll for more precise detail PlyPIOUth Maine Date logged 082304

I

Table XX Packer Permeability and Packer Sampling Results for Potential Fracture Intervals

1

WellID MW-101D MW-101D MW-101D MW-101D MW-101D MW-101D MW-101D MW-101D MW-101D MW-101D MW-I01D MW-101D MW-101D MW-102D MW-102D MW-I02D MW-102D MW102D MW-102D MW-102D MW-102D MW-102D MW-I02D MW-102D MW-102D MW-102D MW-103D MW-103D MW-103D MW-103D MW-I03D MW-103D MW-103D MW-103D MW-103D MW-103D MW-103D MW-103D MW-I03D MW-104D MW-104D MW-104D MW-104D MW-I04D MW-104D MW-104D MW-104D MW-104D MW-104D MW-104D MW-105D MW-105D MW106D MW-106D MW-106D MW-107D MW-107D

1999 Drilling Program

Hows Corner Superfund Site Plymouth Maine

Potential Fracture Top Of Bottom 6 Depth to lt Topof i Interval from Packer Packer Middle of Elevation Hydraulic bull PCE

GS ELEV 1 Rock Drilling Interval Interval Interval of Interval Conductivity Concentration (ft msl) (ft msl) TEST (ftbgs) (ftbgs) r(ftbgs) ( f t b (ft mil) (cmsec) (raquogL)

4339 4329 13 28-29 33-3537-39 271 376 324 4016 OOOE+00 4339 12 37-3444-46 380 485 433 3907 157E-04 4339 11 488 593 541 3799 132E-04 4339 10 60-61 578 683 631 3709 OOOE+00 4339 9 678 783 731 3609 I79E-05 4339 8 778 883 831 3509 106E-05 4339 7 880 985 933 3407 243E-05 4339 6 990 1095 1043 3297 339E-06 4339 5 1090 1195 1143 3197 OOOE+00 4339 4 1190 1295 1243 3097 OOOE+00 4339 3 1365-1375 1290 1395 1343 2997 OOOE+00 4339 2 147-157 1390 1495 1443 2897 580E-05 4339 1 147-157 1470 1575 1523 2817 741E-05 43161 43061 13 166 271 219 4098 333E-04 43161 12 30-3136-40 260 365 313 4004 I54E-05 43161 11 36-4041-43 362 467 415 3902 548E-05 43161 10 470 575 523 3794 598E-05 43161 9 570 675 623 3694 197FOS 43161 8 670 775 723 3594 OOOE+00 43161 7 770 875 823 3494 891 E-05 43161 6 83-94 870 975 923 3394 139E-05 43161 5 970 1075 1023 3294 123E-04 43161 4 1070 1175 1123 3194 526E-06 43161 3 1170 1275 1223 3094 138E-05 43161 2 1270 1375 1323 2994 671E-06 43161 1 1370 1475 1423 2894 OOOE+00 42997 42497 13 18-19 170 275 223 4077 OOOE+00 42997 12 260 365 313 3987 766E-05 42997 11 360 465 413 3887 727E-05 42997 10 460 565 513 3787 192E-05 42997 9 560 665 613 3687 752E-05 42997 8 660 765 713 3587 778E-05 42997 7 85-86 763 868 816 3484 260E-05 42997 6 860 965 913 3387 289E-05 42997 5 102-103 960 1065 1013 3287 102E-04 42997 4 1060 1165 1113 3187 522E-06 42997 3 1160 1265 1213 3087 520E-06 42997 2 129-130 1260 1365 1313 2987 960E-04 42997 1 1360 1465 1413 2887 OOOE+00 43372 42922 11 35-37 42-45 350 455 403 3935 684E-04 43372 10 460 565 513 3825 500E-05 43372 9 560 665 613 3725 106E-05 43372 8 72-74 660 765 713 3625 204E-05 43372 7 760 865 813 3525 872E-06 43372 6 860 965 913 3425 467E-06 43372 5 960 1065 1013 3325 200E-05 43372 4 1060 1165 1113 3225 354E-05 43372 3 125-130 1160 1265 1213 3125 157E-05 43372 2 125-130 1260 1365 1313 3025 337E-04 43372 1 1365 1465 1415 2922 689E-06 43052 43002 2 54-58 490 595 543 3763 124E-05 2100 43052 1 139-140 145-146 1367 1472 1420 2886 154E-04 1400 43291 4391 3 bullI133 260 365 313 4017 439F06 43291 2 77-78 760 865 813 3517 230E-03 400 43291 1 143-144 1355 1460 1408 2922 971E-06 350

29958 27258 4 450 555 503 2493 OOOE+00 (21)A 29958 3 103-105 1000 1105 1053 1943 752E-04 (063)A

Table XX Packer Permeability and Packer Sampling Results for Potential Fracture Intervals

1999 Drilling Program

Hows Corner Supcrfund Site Plymouth Maine

gtbull i Potential Fracture Top _OfBot Bottom of Depth to ltbull Top of Interval from f Packer Packer Middle Of

GS ELEV lt Hock Drilling interval Interval Interval WeD ID ft msl) (ft msl) TEST (ftbgs) ltft$gs) (ftbgs) (ftbgs)

MW-107D 29958 2 128-130 1200 1305 1253

MW-107D 29958 1 139-141 1350 1455 1403

MW-108D 31904 31104 6 35-36 300 405 353 MW-108D 31904 5 60-62 550 655 603

MW-108D 31904 4 80-83 750 855 803

MW-108D 31904 3 118-119 123-124 1150 1255 1203

MW-108D 31904 2 147-149 1440 1545 1493

MW-108D 31904 1 1700 1805 1753

MW-110D 40576 40426 2 21-31 210 315 263 MW-110D 40576 1 148-154 1460 1565 1513 MW-I11D 40519 4 70-71 650 755 703

MW-111D 40519 3 79-82 84-86 780 885 833 MW-I11D 40519 2 97-102 950 1055 1003 MW-111D 40519 1 1370 1475 1423

MW-112D 3027 2942 4 42-52 420 525 473 MW-112D 3027 3 850 955 903 MW112D 3027 2 1100 1205 1153 MW-112D 3027 1 135-136 140-141 1340 1445 1393

MW-113D 43085 43085 5 250 355 303 MW-I13D 43085 4 47-49 460 565 513 MW-113D 43085 3 73-74 700 805 753 MW-113D 43085 2 1050 1155 1103 MW-113D 43085 1 1380 1485 1433

MW-114D 42394 41594 4 48-49 450 555 503 MW-114D 42394 3 79-81 740 845 793 MW-114D 42394 2 121-129 1250 1355 1303 MW-114D 42394 1 134-142 1350 1455 1403

MW-115D 4035 4035 4 300 405 353 MW-1I5D 4035 3 70-71 650 755 703 MW-115D 4035 2 1150 1255 1203 MW-115D 4035 1 1400 1505 1453

LOT-28W 382 7 450 555 503 LOT28W 382 6 550 655 603 LOT-28W 382 5 650 755 703 LOT28W 382 4 750 855 803 LOT-28W 382 3 850 955 903 LOT-28W 382 2 950 1055 1003 LOT-28W 382 1 1055 1155 1105

NOTES cmsec = centimeters per second ft bgs = leet below ground surface It msl = feet below mean sea level lt = not detected at indicated reporting limil A = detected below laboratory PQL ( ) = detected below reporting limits

Elevation of Interval

(ft nisi) 174

159

283gt 2588

2388

1988

1698

1438

3795 2545 3349 3219 3049 2629

2555 2125 1875 1635

4006 3796 3556 3206 2876

3737 3447 2937 2837

3683 3333 2833 2583

3318 3218 3118 3018 2918 2818 2715

Hydraulic Conductivity

(cmsec)

323E-05

208E-05

471E-03

471E-03

624E-05

3I6E-05

264E-05

261 E-05

OOOE+00 200E-04 953E-05 OOOE+00 OOOE+00 212E-05

361 E-05 410E-06 2gQE06 292E-05

786E-05 124E-05 151 E-05 822E-06 82IE-06

858E-05 I69E-05 352E-03 866E-05

223E-05 394E-06 122E-05 525E-06

831 E-05 182F-05 L62E-05 129E-05 190E-05 890E-04 981 E-04

PCEraquo Concentration

(ugL)

lt5

(14A)

98 11

15

22

11

30

200 (62)A

110 210 300 240

(44)A (23)A

5

350 190 129 230

2200 1900 2600 2600

(17)A (16)A (19)A

96

Table XX Packer Permeability and Packer Sampling Results for Potential Fracture Intervals

2004 Drilling Program

Hows Corner Superfund Site Plymouth Maine

Top of Bottom of Depth to Midpoint

t K

ELEV (ft Potential Transmissive Zones Packer Interval

Packer Interval

Middle of Interval

Elevation of interval

Hydraulic Conductivity

PCE Concentration

Well ID msl) TESTr (ft bgs)- (ftbgs) (ftbgs) (ftbgs) (ft msl) (cmsec) (ogt) MW-203D 43227 4 277279 24 32 28 4043 667E-05 44

3 408415420 39 49 44 3883 593E-05 170 2 526 530 49 57 53 3793 101E-04 140 I 828830842 80 88 84 3483 701E-05 130

MW-204D 43262 5 295 300 26 34 30 4023 902E-05 220 4 463496513516 45 53 49 3833 119E-04 540 3 681685688 63 71 67 3653 OOOE+00 2 758 76 2 71 79 75 3573 309E-05 260 I 88 96 92 3403 OOOE+00

MW-205 42389 3 164 166 168 15 20 175 4148 OOOE+00 1000B 2 302305312 30 35 325 3998 107E-04 1300B 1 40 45 425 3898 OOOE+00

MW-206D 43007 5 17 72 195 4128 291E-05 4 296 302 307 29 34 315 4008 940E-05 2900B 3 522 52 57 545 3778 944E-07 2 656 64 69 665 3658 353E-06 1 92392793 4939 91 96 935 3388 614E-05 6300B

PW-207 43477 5 184622162819 18 29 235 4088 209E-05 1300 4 3508 32 43 375 3948 568E-06 5400 3 53325341542154325559 50 61 555 3768 821E-05 18000

6359 61 72 665 3658 866E-06 12000 1 8685 84 89 865 3458 213E-05 19000

NOTES cmsec = centimeters per second ft bgs = feet below ground surface ft msl = feet above mean sea level B = detected in lab blank

Table XX Orientation Permeability and Groundwater Sampling Results for Transmissive Features

2004 Drilling Program

Hows Corner Superfund Site Plymouth Maine

Borehole Geophisical Feature depth Dip True Dip True Transmissive Log Feature (Feet) Degrees Azimuth Strike bullvgt(Ltk|iy^

Number v Tosftble) v MW-203 5 277 64 337 67 Likely

6 279 59 11 281 Likely 8 352 14 177 87 Likely 11 381 46 96 6 Possible 12 408 35 271 1 Possible 14 415 57 250 340 Possible 15 420 58 202 292 Likely 18 526 52 75 345 Likely 19 530 52 82 352 Likely 28 828 48 75 345 Likely 29 830 52 17 287 Likely 30 830 56 233 323 Possible 31 842 50 130 40 Likely

MW-204 4 295 15 147 57 Likely 5 300 43 91 1 Likely 11 439 31 80 350 Possible 12 440 46 219 309 Possible 14 463 50 358 88 Likely 15 496 34 198 288 Likely 16 513 54 17 287 Likely 17 516 33 14 284 Likely 25 681 39 359 89 Possible 26 685 22 45 315 Possible 27 688 35 73 343 Possible 32 758 45 236 326 Likely 33 762 46 306 36 Likely

MW-205 5 164 69 106 16 Possible 6 166 78 165 75 Possible 7 168 82 115 25 Possible 8 168 68 116 26 Possible 12 215 46 222 312 Possible 13 217 75 62 332 Possible 14 219 29 32 302 Possible 16 237 69 250 340 Possible 17 256 73 353 83 Possible 18 272 44 202 292 Possible 21 299 37 196 286 Possible 22 302 31 206 296 Possible 23 305 59 48 318 Likely 24 312 63 42 312 Likely

MW-206 1 264 37 181 271 Likely 2 296 69 217 307 Likely 3 302 66 233 323 Likely 4 307 64 224 314 Likely 8 342 62 259 349 Likely

jjHydraulic GoiDanctilyity j(cmsecjw

667 E-05

593 E-05

101 P04

710 E-05

902 E-05

119 E-04

0

309 E-05

0

107 E-04

94 E-05

PCE (ugL)

44

170

140

130

220

540

260

IOOOB

1100B

1300B

2900B

STotal vVoCsv tig1)

84

234

192

183

2636

6436

3073

11448

12509

13776

32401

PCEyo dfCTotaf

52

73

73

7 1

83

84

85

87

88

94

90

Table XX Orientation Permeability and Groundwater Sampling Results for Transmissive Features

2004 Drilling Program

Hows Corner Superfund Site Plymouth Maine

Borehole Geophisical Feature deptt raquoip True pip True Transraissive Log Feature (Feet) shy Degrees Azimuth Strike (tikely

Number raquo Possible) 22 522 57 54 324 Possible 25 656 40 82 352 Possible 32 871 59 151 61 Possible 33 883 53 185 275 Possible 34 895 7 175 85 Likely 35 899 53 90 0 Likely 36 902 49 184 274 Likely 37 923 9 175 85 Likely 38 927 42 206 296 Likely 39 934 48 167 77 Likely 40 939 26 180 90 Likely

PW-207 1 1846 33 167 77 Likely 4 2216 49 289 19 Possible 7 2819 59 265 355 Possible 11 3508 55 189 279 Possible 18 5332 43 305 35 Likely 19 5341 51 30 300 Likely 20 5421 20 254 344 Likely 21 5432 39 301 31 Likely 23 5559 52 302 32 Likely 25 6359 24 182 272 Possible 29 8049 77 231 321 Possible 30 8685 78 38 308 Likely 32 9334 29 194 284 Likely

NOTES

B = detected in lab blank

Hydraulic Conductivity

(cmsee) 944 E-07 353 E-06

614 E-05

209 E-05

568 E-06

821 E-05

866 E-06

213 E-05

bulltCE (ugL)

6300B

1300

5400

18000

12000

19000

Total VOCs (ug1)

68901

1410

5802

19234

13085

20354

PCE of Total VOCs

9 1

92

93

94

92

93

Response to EPA-DEP Comment 3 Dated March 312005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

lit

EPA-DEP Comment 3

Comment 3 The reported f values and resultant Kd values There remains doubt that the values used in the flushing model accurately reflect the propensity for PCE to sorb to the bedrock The ^ values presented in Appendix B may be unrealistically high because the bedrock samples may have contained organic carbon that was unavailable for sorption The reported f values are only qualitative estimates of the organic carbon content of the bedrock samples The Walkley and Black organic carbon measurement method is quick and simple but the results obtained cannot be considered quantitative because it requires a correction factor which often results in erroneous values it assumes the organic carbon has an average valence of zero oxidizable and reducible constituents such as chloride ferrous iron and manganese oxides interfere with the results and the errors introduced by interference are potentially greater when the organic carbon content is low at low f values it is not clear that organic carbon is controlling PCE sorption (Schwarzenbach and Westall 1981 Mackay et al 1986 Fetter 1999)

In order to derive a Kd-based retardation factor that is reasonable given the reported f values and the rapid advance of the PCE plume described on pages 4-11 and 4-12 the flushing model requires a bulk density to porosity ratio that is roughly two orders of magnitude higher than the actual ratio for the Hows Corner bedrock (page 4-4) This apparent discrepancy needs to be addressed

Response This comment raises several concerns about the collection and analysis of samples for fraction of organic carbon (f^) the quality of the resulting data and the implications of the use of those data for estimation of the retardation of groundwater contaminant movement Results of bedrock analysis for f were proposed in the TI Evaluation Work Plan for use in conjunction with groundwater contaminant concentrations and aquifer information to estimate cleanup times using the Batch Flushing model It is important to use accurate f values from representative bedrock in the Batch Flushing model in order to obtain reasonable estimates of the remedial time frame Because of the importance of accurate and representative results the TI Investigation field program was designed and conducted both to collect samples representative of the rock volume most likely to be in contact with contaminated groundwater and to analyze them using an appropriate refereed analytical method Five potential methods for evaluating f were identified Of the five methods the Walkey-Black method was selected because it has minimal method interferences and a sufficiently low detection limit as well as a long history of use in agronomy and contamination studies The PRP Group is pleased with the quality of the data obtained from the bedrock samples as represented by their precision and reproducibility

The first part of this comment relates to the determination of fraction of organic carbon (f^) values The several subparts of the first paragraph are addressed individually in items 1 through 5 below The second part of the comment regarding the resultant distribution coefficient (Kd) values is addressed separately as item 6 below

1 There remains doubt that the values used in the flushing model accurately reflect the propensity for PCE to sorb to the bedrock

bull The rock core samples used for f (gocg) analysis were from core immediately adjacent to fractures These rock core samples included the fracture surfaces themselves and rock core extending back less than 1 cm from the fractures Therefore the foe data reported in the TI Evaluation represents the f of bedrock through which groundwater will travel and to which PCE will adsorb Based on the careful selection of sample locations and the

Response to EPA Comment 3 050205doc 1 of 11 Woodard amp Curran (211941)

number of samples collected we are confident that the measured f values are representative of the f at points of contact for PCE with the bedrock it is these f values that determine the propensity of PCE to sorb to the bedrock

bull The samples of rock core collected for analysis of f originated from 19 different locations varying in depth from 11 to 90 feet Therefore it is very unlikely that the rock core samples were contaminated with extraneous organic carbon from above ground

2 The foc values presented in Appendix B may be unrealistically high because the bedrock samples may have contained organic carbon that was unavailable for sorption

bull As noted in response 1 the f data reported in Appendix B represents organic carbon primarily associated with the surface of fractures in the bedrock through which groundwater is most likely to travel Therefore it is this organic carbon that the contaminants in the groundwater will come in contact with and adsorb to in the fractured rock at the site

bull The chemical oxidation agents used in the Walkey-Black method oxidize the easily oxidizable organic carbon in the medium and the foe is calculated from the quantity of the agent consumed Therefore it is unlikely that the analysis of the bedrock samples measured organic carbon that was unavailable for sorption

3 The reported foc values are only qualitative estimates of the organic carbon content of the bedrock samples

bull The reported f values are accurate quantitative results Schumachers review of Methods for the determination of total organic carbon (TOC) in soils and sediments (NCEA-C-1282 EMASC-001 April 2002) identifies the Walkley-Black method which was used to analyze the reported foc values as the reference method for comparison to other methods for analyzing total organic carbon

bull Schumacher also points out that if anything the WalkJey-Black method may underestimate the total organic carbon in a sample due to possible incomplete oxidation of organic carbon Usually the incomplete oxidation of total organic carbon in environmental samples is corrected for by multiplying the measured foe by 130 (Walkley amp Black 1934 Schulte 1995)

bull When the f data in the TI Evaluation Report (WampC 2005) Appendix B (attached) are analyzed statistically the standard deviation of the f for the 19 samples analyzed is 174 of the average f Given this standard deviation the 95 confidence interval for this data ranged from a low of 000123 gocg to a high of 000253 gocgm

The labs Method of Detection Limit (MDL) for the f measured using the Walkley-Black method is 00001 gocg Therefore the average (000188 gocg) the mean (000185 gocg) and geometric mean (000187 gocg) of the f values for the rock core at Hows Corner are all statistically significantly greater than the MDL of the Walkley-Black method

In addition to the aforementioned statistical analysis of the foe data triplicate samples (n = 3) from the same rock core (including one sample from the 19 rock core samples) were

Response to EPA Comment 3 050205doc 2 of Woodard amp Curran (211941)

analyzed for their f to determine the repeatability of the Walkley-Black method The average the mean and the geometric mean of the f values of these replicate samples was 000162 gocg 000150 gocg and 000159 gocgm respectively The standard deviation of these measurements was 000039 gocg

4 The Walkley and Black organic carbon measurement method is quick and simple but the results obtained cannot be considered quantitative because it requires a correction factor which often results in erroneous values it assumes the organic carbon has an average valence of zero oxidizable and reducible constituents such as chloride ferrous iron and manganese oxides interfere with the results and the errors introduced by interference are potentially greater when the organic carbon content is low at low foc values it is not clear that organic carbon is controlling PCE sorption (Schwarzenbach and Westall 1981 Mackay et al 1986 Fetter 1999)

bull Schumachers review (NCEA-C-1282 EMASC-001 April 2002) of the Walkley-Black method identifies several potential problems with this analytical method that could occur if the analytical lab is not familiar with the nuances of the chemistry associated with this method Interestingly Schumachers review neglected one of the more important analytical steps required to avoid errors in quantifying f in samples where there might beNAPL

It is absolutely critical to eliminate any NAPL from rock core samples prior to using the Walkley-Black method to measure foe in such samples This was done by the lab (PTS Laboratories) that measured the foe in the rock core samples from Hows Corner The lab used the Dean-Stark method (solvent extraction) to remove all hydrocarbons (including PCE and other NAPLs) from the sample (PTS Laboratories) This extraction method does not interfere with the subsequent analysis of the natural organic carbon associated with the rock core

Subsequently the samples were dried at 150degC to a constant weight (normally 16 hours) This latter step oxidizes all inorganic minerals including ferrous bearing minerals to ferric oxides and precludes their interference during the oxidation of the samples with chromic acid This procedure completely eliminates any positive bias in the reported foc

data that might have occurred due to the presence of ferrous ions and other reduced minerals

bull As noted in Response 3 the incomplete oxidation of total organic carbon results in an underestimate of the f and is corrected for by multiplying the f by a correction factor of 130 (Walkley amp Black 1934 Schulte 1995) The fx data reported in the TI Evaluation was corrected accordingly by using this correction factor

bull Excess chloride (Cl~) in percent weight quantities as found in saline soils may interfere with the quantitative titration of reduced chromium (Walkley 1947) However given that the primary rock type at the Hows Corner site is phyllite it is highly unlikely that there was sufficient chloride in the rock core samples for this to occur

bull Manganese oxides may also interfere with the analysis of f through competing with the dichromate ion for any oxidizable carbon (Walkley 1947) However in such cases the reported f would be an underestimate of the f present in the rock core Walkley (1947)

Response to EPA Comment 3 050205doc 3 of 11 Woodard amp Curran (211941)

4

reported that in the case where the ratio of MnO2 to carbon is 85 to 1 the error in the carbon determinations would only be 0 to 6 percent

It may also be useful to compare the analysis of total organic carbon in a geologic matrix that contains high levels of manganese using EPA method 9060 to the Walkley-Black method Table 1 summarizes data provided by one of the PRPs that compares the analysis of total organic carbon in a geologic matrix that contains approximately 02 wgt manganese (approximately 03 wgt manganese oxide)

Table 1 Comparison of total organic carbon measured using the EPA- 9060 method and the Walkley-Black method

Laboratory EPA-9060 Method Walkley-Black Method A Ave 00226 gocg Not analyzed

Stdev 000251 gocg n = 5

B Ave 002219 gocg Ave 002050 gocg Stdev = 000316 gocg Stdev =000971 gocg

n= 10 n = 10

The similarity in the total organic carbon concentrations measured by these two different methods provides further confidence that the Walkley-Black method is a viable method for analysis of total organic carbon in the presence of manganese equivalent to at least 10 by weight of the total organic carbon

5 The Walkley and Black organic carbon measurement at lowf^ values it is not clear that organic carbon is controlling PCE sorption (Schwarzenbach and Westall 1981 Mackay et al 1986 Fetter 1999)

bull Schwarzenbach and Westalls (1981) paper states that f values of less than 0001 gocg should not be used in combination with Kow (octanol-water partition coefficients) values to calculate K^ values (solid phase partition coefficients) values for a specific contaminant It should be noted that the TI Evaluation did not use the f data to calculate the KQC from the Kow Instead as requested by the EPA the measured KOC value for PCE was used to calculate the retardation factor for this contaminant

bull Schwarzenbach et al (2003) stated more recently that Even at very low f values (ie foe = 0001 kgoc - kg1 solid) sorption to the organic components of a natural sorbent may still be the dominant mechanism in defining the adsorption of organic compounds to geological matrices

bull In 1985 M Piwoni from the US EPA Robert S Kerr Environmental Research Laboratory published a paper (Banerjee et al 1985) that showed that for very hydrophobic molecules TOC content of the sorbent will control sorption down to levels of organic carbon that defy quantitation Contaminants such as the PCE found in the groundwater at Hows Corner are in this category of compounds

Given the aforementioned reasons the f values reported in the TI Evaluation are accurate within the noted statistical limitations and will have a predictable impact upon the retardation of PCE during groundwater transport

Response to EPA Comment 3 050205doc 4 of 11 Woodard amp Curran (211941)

6 In order to derive a Kd-based retardation factor that is reasonable given the reported foc

values and the rapid advance of the PCE plume described on pages 4-11 and 4-12 the flushing model requires a bulk density to porosity ratio that is roughly two orders of magnitude higher than the actual ratio for the Hows Comer bedrock (page 4-4) This apparent discrepancy needs to be addressed

The apparent discrepancy of bulk density to porosity ratios is most likely due to the fact that the Batch Flushing Model was originally developed for a porous medium and is not directly applicable to fractured bedrock As stated in Appendix C (page C-4) of the Draft Technical Impracticability Evaluation Report in order to use the Batch Flushing Model to describe the transport of contaminated groundwater in fractured bedrock where the matrix porosity is insignificant it is more appropriate to use a fracture surface area to void space ratio to calculate the retardation factor (R) than a bulk density to porosity ratio (Freeze amp Cherry 1979)

Since it is impractical to determine the actual surface area to which contaminants can adsorb the Batch Flushing Model was used with two simplifying assumptions bull The Kd was calculated from the f and the K^ bull The bulk density to porosity ratio term in the Batch Flushing Model was constrained to range

from 4 to 10 the typical range of such ratios in porous media (Freeze amp Cherry 1979)

If one uses site specific bedrock bulk density and porosity values the bulk density to porosity ratio is several orders of magnitude greater (specifically 273 gcc bullbull 000165 (dimensionless) = 1654 gcc) than the range of ratios of 4 to 10 used in the Batch Flushing Model in the Draft Technical Impracticability Evaluation Report Constraining the bulk density to porosity ratio within the range of ratios of 4 to 10 results in significantly lower R value than would be obtained using specific bedrock bulk density and porosity values

In summary in bedrock where fractures are the primary porosity the bulk density to porosity ratio can vary considerably and will be a function of the number of fractures and the fracture aperture The calculated bulk density to porosity ratio will be inversely proportional to the porosity This means that in fractured rock with limited fracturing and smaller porosity the calculated bulk density to porosity ratio is greater and will result in a greater calculated retardation factor than in bedrock with more extensive fracturing and greater porosity Consequently the calculated retardation factor will be greater for bedrock with less surface area available for sorption than bedrock with greater surface area for sorption This is contrary to what actually occurs

4 Response to EPA Comment 3 050205doc 5 of 11 Woodard amp Curran (211941)

m

REFERENCES

Banerjee P MD Piwoni K Ebeid (1985) Sorption of organic contaminants to a low carbon subsurface core Chemosphere _14 1057-1067

Freeze RA JA Cherry (1979) Groundwater Prentice Hall Englewood Cliffs NJ pg 604

PTS Laboratories wwwptsgeolabscompdf files3TOCnotepdf

Schulte EE (1995) Recommended soil organic matter tests in Recommended Soil Testing Procedures for the Northeastern United States Northeastern Regional Publication No 493 Chapter 8

Schwarzenbach RP J Westall (1981) Transport of nonpolar organic compounds from surface water to groundwater Laboratory sorption studies Environ Sci Tech 15 1360-1367

Schwarzenbach RP PM Gschwend DM Imboden (2003) Environmental Organic Chemistry Wiley-Interscience pg 292 408 amp 412

Walkley A LA Black (1934) An examination of the Degtjareff method for determining soil organic matter and a proposed modification of the chromic acid titration method Soil Science 37 29-38

Walkley A (1947) A critical examination of a rapid method for determining organic carbon in soils - effect of variations in digestion conditions and of inorganic soil constituents Soil Science 63251-264

Woodard amp Curran Inc (WampC) 2005 Draft Technical Impracticability Evaluation Hows Corner Superfund Site Plymouth Maine January 2005

Response to EPA Comment 3 050205doc 6 of Woodard amp Curran (211941)

LIST OF ATTACHMENTS (Response to Comment 3)

Appendix B to Draft Technical Impracticability Evaluation Measurement of foe at Hows Corner (4 pages)

m

Response to EPA Comment 3 050205doc 7 of 11 Woodard amp Curran (211941)

Appendix B Measurement of foe of Rock Core at Hows Corner

There are two general approaches to measure the fraction of organic carbon (foe) in rock cores

bull Measurement of weight loss by ignition of organic matter bull Chemical oxidization of organic carbon to carbon dioxide and either

subsequent quantification of the oxidant used for the reaction or quantification of the carbon dioxide produced during this oxidation process

The weight loss method is subject to errors caused by volatilization of substances other than organic materials such as water hydroxides and mineral carbonates Quantification of foe by the weight loss method is particularly sensitive to the presence of carbonates in rock cores There are however weight loss methods that are designed to differentiate between organic carbon and the aforementioned interfering materials but they require considerable care and are less accurate at low foe values Hence the weight loss method was not well suited for measuring the foe of the rock core from Hows Corner

The chemical oxidation of organic carbon is much better suited for quantifying organic carbon in rock cores such as those from Hows Corner This method uses a strong chemical oxidant to oxidize organic carbon to carbon dioxide and then measures either the chemical oxidant used to oxidize the organic carbon or the quantity of carbon dioxide produced In addition this general approach is not subject to interference by volatilization of other constituents of the rock core

There are at least two such chemical oxidation methods

bull The method of Baccini which was described by Schwarzenbach amp Westall (1981) first acidifies the sample to eliminate interference by carbonates Then a strong oxidant is used to chemically oxidize the organic carbon to carbon dioxide The resulting carbon dioxide is subsequently reduced to methane and quantified using a flame ionization detector Unfortunately this method has not been described in detail in a referred journal Hence it is would not have been appropriate to use to characterize the foe in the Hows Corner rock core

bull The more commonly used method to quantify foe in rock core is the Walkley-Black method (1934) This method is preferred for RBCA and DODDOE projects and by the oil industry

The Walkley-Black method uses an excess of chromic acid to oxidize (digest) organic matter to carbon dioxide The remaining chromic acid that was not consumed during the oxidation of the organic carbon is then quantified by titration with ferrous sulfate The difference in chromic acid prior to and after the oxidation of the organic carbon represents the total chromic acid used to oxidize

Hows Corner TI Evaluation Page 1 January 13 2005 Appendix B

the organic carbon in the sample The latter can be calculated using the chemical stoichiometry of the reaction

The Walkley-Black method is very accurate for samples that contain less than 2 organic carbon matter The minimum detection limit (MDL) for the Walkley-Black method is 100 mgkg or an foe of 0001

Given the rock core at Hows Corner was expected to contain less than 2 organic carbon the Walkley-Black method was used to measure the foe from 19 different rock core samples collected from varying depths ranging from 11 to 90 feet

Table 1 provides a statistical summary of the aforementioned data

Table 1 Statistical summary of foe data from rock cores collected at varying depths

Statistical Parameter Calculated Value foe Minimum Detection Limit (MDL) 00010 Number of samples analyzed (n) 19 Average foe 00019 Median foe 00019 Geometric Mean foe 00019 Standard deviation of foe measurements 000033 Relative standard deviation 174 -+ 95 Confidence intervals 00012 to 00025

The data in Table 1 shows the following

bull The foe from the Hows Corner rock cores are statistically greater than the MDL of the Walkley-Black analytical method

bull The average and median values for the foe of the Hows Corner rock cores from varying depths are nearly identical indicating that there is little variability in the foe values in the source zone at the site

bull The standard deviation of these measurements is 000033 which is 174 of the average foe

bull The 95 confidence intervals of the foe of the rock core at Hows Corner are 00012 to 00025

The foe was also analyzed from three separate samples taken from the same rock core at a depth of 55 feet (Only one of these samples was included in the data summarized in Table 1) Table 2 shows the statistical repeatability of this type of analysis

Hows Corner TI Evaluation Page 2 January 13 2005 Appendix B

Table 2 Repeatability of analysis of foe from one rock core at 55 feet in depth

Statistical Parameter Calculated Value Number of samples analyzed (n) 3 Average foe 00016 Median foe 00015 Geometric Mean foe 00016 Standard deviation of foe measurements 000039 Relative standard deviation 240 -+ 95 Confidence intervals 00008 to 00024

The data in Table 2 shows the following

bull The percent relative standard deviation of these three analyses of foe from the same rock core at Hows Corner is 24

bull The 95 confidence interval of the foes measured in this particular rock core at Hows Conrer is 00008 to 00024

These results show that there is good repeatability in using the Walkley-Black method for analysis of the foe in the rock core at Hows Corner

References Schwarzenbach amp Westall (1981) Transport of nonpolar organic compounds from surface water to groundwater Laboratory sorption studies Environ Sci Tech 15 1360-1367

Walkley A I A Black (1934) An examination of Degtjareff method for determining soil organic matter and a proposed modification of the chromic acid titration method Soil Sci 37 29-37

Hows Corner Tl Evaluation Page S January 13 2005 Appendix B

Woodard and Curran PTS Laboratories PTS File No 34618

ORGANIC CARBON DATA (METHODOLOGY WALKLEY-BLACK)

PROJECT NAME PROJECT NO

SAMPLE ID

203-chip-13 203-chip-23 203-chip-27 203-chip-38 203-chip-42 203-chip-47 203-chip-52 203-chip-58 203-chip-69 203-chip-82 207-chip-11 207-chip-19 207-chip-24 207-chip-29 207-chip-35 207-chip-45 207-chip-55 207-chip-87 207-chip-90

207-chip-55 55-MS

55-MSMSD

Hows Corner NA

DEPTH ft

13 23 27 38 42 47 52 58 69 82 11 19 24 29 35 45 55 87 90

55 NA NA

MATRIX

Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip

Average Median

Geometric Mean Standard Deviation Relative Std Dev

+- 95 Confidence Interval n

Rock Chip Rock Chip Rock Chip

Average Median

Geometric Mean Standard Deviation Relative Std Dev

+- 95 Confidence Interval n

FRACTION ORGANIC CARBON

(gg)

170E-03 185E-03 185E-03 170E-03 240E-03 190E-03 230E-03 180E-03 170E-03 115E-03 195E-03 220E-03 220E-03 235E-03 135E-03 190E-03 205E-03 175E-03 160E-03

188E-03 185E-03 185E-03 327E-04

1739 123E-03 to

19

205E-03 130E-03 150E-03

162E-03 150E-03 159E-03 388E-04

2402 840E-04 to

3

2532E-03

2393E-03

Hows Corner Tl Evaluation Appendix B January 13 2005

Response to EPA-DEP Comment 4 Dated March 31 2005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

EPA-DEP Comment 4

Comment 4 Distribution of contaminants First the TI report seems based on the assertion that there is DNAPL at the source area yet it also appears to represent that the source area is small and the bedrock below 85 is competent (or less fractured) and less impacted by the release of contaminants Some of the confusion may result from using most recent data when that data is from several different sampling events over several years and there is no discernible difference in concentrations between shallow and deep bedrock or as in Section 421 where generally decreased generally increase generally similar and similar concentrations in four consecutive sentences leads to a muddled picture of the contaminant distribution

Second the report asserts that the distribution of contaminants over the entire plume has not changed with time but fails to support this conclusion with data again relying on data that is from different sampling dates for one composite representation

Response The likely presence of dense non-aqueous phase liquid (DNAPL) at the Hows Corner Site and the determination that the source area is small are not mutually exclusive and both are conclusions drawn from information obtained during field investigations The presence of DNAPL in the source area is based on the elevated concentrations of volatile organic compounds (VOCs) detected in the groundwater (WampC 2001 WampC 2002) The conclusion that the source area is small is based on the area in which VOCs in groundwater have been detected at concentrations that are considered to be indicative of the presence of DNAPL nearby Similarly the conclusion that fracture frequency decreases at depths greater than approximately 50 to 85 feet below ground surface was based on field observation during the RI field work The fact that zones with observed fractures exhibited higher hydraulic conductivities than zones without fractures coupled with the decreasing frequency of observed fractures with depth led to the conclusion that the hydraulic conductivity of the bulk rock decreases with depth

The most recent data from all wells were used to provide the maximum VOC data set size During the RI all of the previously-existing and then newly-installed monitoring wells were sampled along with several residential wells The RI sampling included up to 48 monitoring wells Subsequent to the RI and prior to the TI three rounds of monitoring were conducted to verify that the plume was stable 15 monitoring wells were sampled during each of the three rounds During the TI field investigation 29 wells were sampled for VOCs The sampled wells included all of the newly-installed wells and a subset of wells installed during the RI for a total of 29 monitoring wells By using most recent data VOC results from 53 monitoring wells were included in the evaluation (see table labeled Sampling Events for listing of monitoring wells) This approach was selected because there generally was little variation in the data from a particular location between years This is borne out by the attached individual plots of VOCs detected in shallow bedrock and deep bedrock for the Pre-ROD (December 1999January 2000) and Supplemental (May 2000) sampling events and for June 2001 January 2002 and April 2003 sampling events The Pre-ROD and Supplemental plots are similar to the subsequent plots from the 2001 2002 and 2003 sampling events

In addition to maps showing the spatial distribution of VOC data at a given time trend plots of the data from a particular location through time (attached) indicate that since the RI concentrations generally have been stable or have decreased Together the maps and trend plots and the data from which they were developed indicate that the distribution of contaminants over the entire plume has not changed appreciably with time

Response to EPA Comment 4 050305doc 1 of 26 Woodard amp Curran (211941)

REFERENCES

Woodard amp Curran Inc (WampC) 2001 Final Remedial Investigation Report Hows Corner Superfund Plymouth Maine July 2001

Woodard amp Curran Inc (WampC) 2002 Final Feasibility Study Report - Non-Source Area Groundwater Hows Corner Superfund Site Plymouth Maine Hows Corner Superfund Plymouth Maine July 2002

Response to EPA Comment 4 050305doc 2 of 26 Woodard amp Curran (211941)

LIST OF ATTACHMENTS (Response to Comment 4)

Table - Sampling Events 1999 - 2004 (2 pages)

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater Pre-ROD Sampling Event

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater Pre-ROD Sampling Event

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater Supplemental Sampling Event

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater Supplemental Sampling Event

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater June 2001

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater June 2001

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater January 2002

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater January 2002

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater April 2003

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater April 2003

Figure - Concentration Trends - Non-Source Area Wells MW-1B and MW-3B

Figure - Concentration Trends - Non-Source Area Wells MW-13DB and MW-16DB

Figure - Concentration Trends - Non-Source Area Wells MW-16IB and MW- 108D

Figure - Concentration Trends - Non-Source Area Wells MW-108S and MW-112D

Figure - Concentration Trends - Non-Source Area Wells MW-112S and MW-114D

Figure - Concentration Trends - Non-Source Area Wells MW-114S and MW-115D

Figure - Concentration Trends -Source Area Wells MW-2DB and MW-2IB

Figure - Concentration Trends -Source Area Wells MW-102S and MW-103D

Figure - Concentration Trends -Source Area Wells MW-103S and MW-104D

Figure - Concentration Trends -Source Area Wells MW-104I and MW-106D

Figure - Concentration Trends -Source Area Wells MW-106S

Response to EPA Comment 4 050305doc 3 of 26 Woodard amp Curran (211941)

I I

El I

II I I 1 I

I

i

Event Baseline Case ID WC-01 WC-01

Well Date Aug-99 Oct-99 LOT10 1 LOT1-1 1 LOT11-4 LOT14 1 LOT15 1 LOT15-1 1 LOT16 1 LOT16-1 1 LOT17 1 LOT18 1 LOT19 1 LOT2 LOT20 1 LOT21-10 1 LOT21-11 1 LOT21-12 1 LOT21-13 1 LOT21-14 1 LOT21-2 1 LOT21-5 1 LOT21-7 LOT21 -8 1 LOT21-9 1 LOT23 1 LOT24 1 LOT28-1 1 LOT28-2 1 LOT28-3 1 LOT28-4 1 LOT28W 1 LOT30 1 LOT30-1 1 LOT30-2 1 LOT30-3 1 LOT30-4 1 LOT30-5 LOT31 LOT35 1 LOT41 1 LOT42-1 1 LOT43-1 1 LOT43-4 1 LOT6-1 1 LOT67 1 LOT6-7 1 LOT6-8A 1 LOT6-8B 1 LOT80-1 1 LOT82 1 MW-101D MW-1011 MW-101S MW-102D MW-102S MW-103D MW-103S MW-104D MW-1041 MW-104S MW-105D MW-106D

Groundwater Sampling Location Summary 1999 - 2004xls

Sampling Events 1999-2004

Hows Corner Superfund Site Plymouth Maine

Supplemental 2001 2002 2003 Pumping 2004 Pre-ROD Rl Sampling Sampling Sampling Test Sampling WC-03 WC-09 WC-25 WC-30 WC-42B WC-56 WC-58 Dec-99 May-00 Jun-01 Jan-02 Apr-03 Sep-04 Sep-04

1

1 1 1

1 1 1 1 1

1 1

1

1 1

1 1 1

1 1 1 1 1

1

1 1

1 1 1 1

1

1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

Sampling Events 1999-2004

Hows Corner Super-fund Site Plymouth Maine

Supplemental 2001 2002 2003 Pumping Event Baseline Pre-ROD Rl Sampling Sampling Sampling Test

Case ID WC-01 WC-01 WC-03 WC-09 WC-25 WC-30 WC-42B WC-56

ll

Well Date Aug-99 Oct-99 Dec-99 May-00 Jun-01 Jan-02 Apr-03 Sep-04 MW-106S 1 1 1 1 1 MW-107D 1 1 MW-108D 1 1 1 1 1 MW-108S 1 1 1 1 1 MW-110D 1 1 MW-111D 1 1 MW-112D 1 1 1 1 1 MW-112S 1 1 1 1 1 MW-113D 1 1 MW-114D 1 1 1 1 1 MW-114S 1 1 1 1 1 MW-115D 1 1 1 1 1 MW-12DB 1 1 1 MW-12SB 1 1 1 MW-13DB 1 1 1 1 1 1 MW-13SB 1 1 1 MW-14DB 1 1 MW-14SO 1 1 MW-15DB 1 1 1 MW-15SB 1 1 1 MW-16DB 1 1 1 1 1 1 MW-16IB 1 1 1 1 1 1 MW-16SO 1 1 MW-17DO 1 1 1 MW-17SO 1 1 1 MW-1B 1 1 1 1 1 1 MW-203D MW-203S MW-204D MW-204S MW-205 MW-206D

I MW-206S MW-2DB 1 1 MW-2DDB 1 1 MW-2IB 1 1 1 1 1 1 MW-3B 1 1 1 1 1 1

I MW-4O 1 1 1 MW-5B 1 1

II MW-6DB 1 1 1 MW-6SB 1 1 1 MW-8DB 1 1 1 MW-8SB 1 1 1

II PW-207 1 SEEP-1 1 SUBTOTAL - RESIDENTIAL 44 25 0 2 0 3 0 SUBTOTAL - MONITORING 22 48 41 15 15 15 1

Total 3 66 73 41 17 15 18 1

I Included in most recent data

I Notes 1 - Overburden well not included in most recent data for plotting

2 - Tetrahydrofuran and 2-Butanone were the only two compounds detected in this well and are thought to be the result of well repair not included in most recent data for plotting

3 - Not included in most recent data for plotting

2004 Sampling

WC-58 Sep-04

1

1 1

1 1

1 1 1

1

1 1

1 1 1 1 1 1 1 1 1

1 1

1

0 29

29

Groundwatef Sampling Location Summary 1999 - 2004xls

I

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

monitoring well Figure 4-14 total VOC contour (ugl) - December 1999January 2000 Distribution of Total VOCs in

Note SW-113 is located downstream of SEEP-1 Shallow Bedrock Groundwater total concentration of detected VOCs ND= not detected these two locations were sampled during the Pre-ROD Sampling Event

Baseline Sampling Event in OctoberNovember 1999 Hows Corner Superfund Site Surface Water Sampling Location A Plymouth Maine Seep Sampling Location laquo- WOODARD ampCURRAN

995037wipri reportepa ri interim final feb 2001cadd drawingsfinalfig 4-14

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

0 300 600 I

FEET

Q residential well Figure 4-16 monitoring well Distribution of Total VOCs in

Deep Bedrock Groundwater total VOCs contour (ugl) Pre-ROD Sampling Event

active residential wells with lot number Hows Corner Superfund Site 2deg42deg Plymouth Maine total concentration of detected VOCs ND= not detected WOODARD ampCURRAN Enyinaaring bull Science bull Operations bull

995037wipri reportepa ri interim final feb 2001cadd drawingsfinalfig4mdash16

PLYMOUTH POND

PLYMOUTH POND

1 628Tl7MW-2bB 12135

PLYMOUTH POND

monitoring well Figure 4-20

V total VOC contour (ugl) - June 2000 Distribution of Total VOCs in Shallow Bedrock Groundwater

| 34 | total concentration of detected VOCs ND= not detected NA = not analyzed Supplemental Sampling Event Note SW-113 is located downstream of SEEP-1 Hows Corner Superfund Site

Surface Water Sampling Location these two locations were sampled during the Plymouth Maine Baseline Sampling Event in OctoberNovember 1999 Seep Sampling Location WOODARD amp CURRAN

Engineering bull Science - Operations bull 995037wipri reportepa ri interim final feb 2001 cadd drawingsfinalfig 4-20

residential well Figure 4-22 Distribution of Total VOCs in

monitoring well Deep Bedrock Groundwater

total VOCs contour (ugl) Supplemental Sampling Event

Hows Corner Superfund Site

total concentration of detected VOCs ND= not detected NA = not analyzed Plymouth Maine

WOODARD amp CURRAN

995037wipri reportepa-ri interim final feb 2001cadd drawingsfinalfig 4-22 Engineering bull Science - Operations bull

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

FEET

Shallow Monitoring Well

Deep Monitoring Well

C Detected Concentration ND = Not Detected Figure 1-XS Distribution of Total VOCs in Shallow Bedrock Groundwater

Pumping Well

17-Acre Property Boundary Concentration Contour (ugl)

June 2001 Hows Corner Superfund Site

Plymouth Maine WOODARDampCURRAN

-i^rhvj bull Scbncn bull Operations bull 211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0601 dwg04-20-05

PLYMOUTH POND Hopkins Road V

O

PLYMOUTH POND

PLYMOUTH POND

o

0 300 600 mdashfa FEET

Shallow Monitoring Well bull bull - 17-Acre Property Boundary Figure 1-XD

Deep Monitoring Well 1 I Detected Concentration ND = Not Detected Distribution of Total VOCs in Deep Bedrock Groundwater

-mf- Pumping Well June 2001 Residential Well Hows Corner Superfund Site

Plymouth Maine i h Surface Water Sampling Point

g WOODARD ampCURRAN _ ^ _ ^ _ _ yen_ rj i|Hlaquorlny bull Science bull Opt

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0601 dwg04-20-05

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

Shallow Monitoring Well

Deep Monitoring Well

Detected Concentration ND = Not Detected Figure 1-YS Distribution of Total VOCs in Shallow Bedrock Groundwater

Pumping Well

17-Acre Property Boundary Concentration Contour (ugl)

January 2002 Hows Corner Superfund Site

Plymouth Maine WOODARD amp CURRAN Engineering Science- Operations bull

211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0102dwg04-20-05

PLYMOUTH POND

PLYMOUTH POND

Site Pand^ laquoum-laquoBTuitaraquo tLV

vVlf-(

PLYMOUTH POND

0 300 600 ^ = FEET

Shallow Monitoring Well mdashbullbullbull 17-Acre Property Boundary Figure 1-YD - A - Deep Monitoring Well FT Detected Concentration ND = Not Detected Distribution of Total VOCs in

Deep Bedrock Groundwater Pumping Well January 2002 Residential Well Hows Corner Superfund Site

Plymouth Maine Surface Water Sampling Point

WOODARD ampCURRAN Engineering Sciencs- Operations bulli Si

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0102dwg04-20-05

- m j

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND j A O-shy

Shallow Monitoring Well E Detected Concentration ND = Not Detected Figure 1-ZS Distribution of Total VOCs in

Deep Monitoring Well Shallow Bedrock Groundwater

Pumping Well Hows Corner

April 2003 Superfund Site

17-Acre Property Boundary Plymouth Maine Concentration Contour (ugl) r WOODARD ampCURRAN

Engineering bull Science bull Operations bull 211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0403dwg04-20-05

s S pound

PLYMOUTH POND

PLYMOUTH POND

- -

5 PLYMOUTH POND

Jo

FEET

ft Shallow Monitoring Well mdashbullbullmdash 17-Acre Property Boundary Figure 1-ZD Deep Monitoring Well I 1 I Detected Concentration ND = Not Detected Distribution of Total VOCs in

Deep Bedrock Groundwater Pumping Well April 2003

Q) Residential Well Hows Corner Superfund Site Plymouth Maine

(T) Surface Water Sampling Point WOODARD ampCURRAN poundKk EnginawtirKj bull Science - Operations bull

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0403dwg04-20-05

0 Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

B MW-1B

I 12000

PCE

B 10000 Total VOCs

I

i 2000

i 0 Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

c MW-3B

G 2000

1800

B PCE

1600 Total VOCs

1 I I E

il-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

G E

211941

El

I I z E

80

Concentration Trends shy Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-13DB

Total VOCs

c i i c o

Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

MW-16DB

30

c i c c I c o

Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99

PCE

Total VOCs

Jul-01 Jul-03

211941

O bi

c Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

I MW-16IB

i 35

3

c Total VOCs

lt- 2 5

0 | gt

o

1 sectI

c c 0 4

Jul-90 Jul-92 Jul-94 Jul-96 Jul-98 Jul-00 Jul-02 Jul-04

I I MW-108D

I 12

PCE 10

Total VOCs c oc 3

E E I 0

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

E 211941

c Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

fi MW-108S

I I 40

PCE 35

Total VOCs

30

I f 26

20 I o

I 15

10

c Dec-99 Dec-00 Dec-01 Dec-02 Dec-03 I 0

I MW-112D

c 35 - imdash

I A3 shyTotal VOCs

o c

E 1 2

I

ition

B 1 ^

-i c 3

0 Dec-99 Dec-OO Dec-01 Dec-02 Dec-03

211941

I

i

I

cII

Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-112S

08

PCE

Total VOCs 06

o 04

02

0 Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

MW-114D

o

12000

10000

8000

6000

PCE

Total VOCs

4000

2000

i

ccEIIc

i

i

E

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

211941

Con

cent

ratio

n (

ug

l)

E Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

I MW-114S

E A5000 -- Total VOCs

- 4000

0 3000

2000

i 1000

i n shy

Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

MW-115D

c PCE

Total VOCs

c E

o

C c

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03 I 0

211941

IepoundII

EIEIIGICCIccc

30000

25000

20000

o bullsect 15000 b

o 10000 U

5000

0 Aug-99

25000

20000

5000

0 Aug-99

211941

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-2DB

PCE

Total VOCs

Aug-01 Aug-03

MW-2IB

PCE

Total VOCs

Aug-01 Aug-03

IDIBI

ii EIDIISIBIG C

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-102S

6000

5000 PCE

Total VOCs

4000

O 3000

2000

1000

0 Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

MW-103D

16000

~ 14000 ugt 3- 12000 o

^ 10000

sect 8000

O 6000

4000

2000

PCE

Total VOCs

0Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

211941

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

G MW-103S

I I

ampo

12000

10000

E sectc

S

8000

6000

4000

2000

0Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

G I 6000

MW-104D

i 5000

PCE

Total VOCs

i i c

2000

1000

Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

E I

211941

cIccIG

IIBCccBcIc

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-1041

PCE Total VOCs

a 25000

0 20000

a 15000

10000

5000

0 Jan-OO Jan-01 Jan-02 Jan-03 Jan-04

MW-106D

3000

2500 PCE

Total VOCs

=sect 2000

o bullsect 1500

1000

500

0 Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

211941

c Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

c MW-106S

I PCE

Total VOCs

i

i Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

i

i i i E

C

211941 c

Response to EPA-DEP Comment 5 Dated March 312005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

iiw

EPA-DEP Comment 5

Comment 5 Matrix Diffusion The report as well as other proponents of matrix diffusion suggest that depletion of DNAPL (Section 5112 page 5-15) needs to be achieved While that might be the ideal the goal is to achieve performance standards and that goal may be attainable while there is residual contamination in the rock perhaps even DNAPL globules The low bedrock matrix porosity (page 1-15) the high permeability values (page 4-4) the relative flux of the groundwater (page 5-5) and the decrease in surface area and out of the mainstream pockets (appendix C-4) all suggest that the diffusion out of the rock matrix would be insubstantial relative to the regional flux of groundwater through the Site

Response The TI Evaluation Report does not explicitly consider or rely upon matrix diffusion as a basis for requesting a TI Waiver for a portion of the Hows Corner Site The technical literature provides documentation that matrix diffusion can be a significant process that affects chemical transport and groundwater remediation timeframes in unconsolidated and consolidated media including fractured rock (US EPA 1989 Freeze and Cherry 1979 Pankow and Cherry 1996 Fountain 1998) Back diffusion of contaminants from the matrix porosity of the fractured rock can prolong the time necessary to achieve groundwater cleanup goals particularly for compounds such as PCE for which the cleanup goal is a low concentration It is our expectation that matrix diffusion has occurred at the Hows Corner Site and that back diffusion of PCE from the rock matrix will also occur Although the extent to which matrix diffusion is occurring at the Hows Comer Site has not been determined and that lack of knowledge contributes to uncertainty regarding the cleanup times at the Site the effect of matrix diffusion is to lengthen rather than shorten the time required for remediation

REFERENCES

Fountain JC 1998 Technologies for Dense Nonaqueous Phase Liquid Source Zone Remediation Ground-Water Remediation Technologies Analysis Center Technology Evaluation Report TE-98-02 December

Freeze RA and Cherry JA 1979 Groundwater Prentice-Hall Inc Englewood Cliffs NJ 07632 p 410-412

Pankow J F and Cherry J A 1996 Dense Chlorinated Solvents Waterloo Press Portland OR 97291-1399 p 67-88

US EPA 1989 Transport and Fate of Contaminants in the Subsurface EPA6254-89019 p 17-18

Response to EPA Comment 5 050305doc 1 of 1 Woodard amp Curran (211941)

WOODARD amp CURRAN Maine Massachusetts New Hampshire Connecticut Florida Operational offices across the US 1-800-426-4262 www woodardcurran com

Page 16: SDMS DocID 251749 - Records Collections · 2020-06-13 · CORPORATE OFFICES: Maine, Massachusetts, New Hampshire, Connecticut New, York, Florida Engineering • Science • Operations

(MEDEP Pond 1) Farm Pond

Monitoring Well

Pumping Well

_bullbull_ 17-Acre Property Boundary

f Groundwater Elevation Contour (ft)

|419Q0| Groundwater Elevation

211941 Hows CornerwipDrawinqsTI EVALPotSurf-72hrs_shallowdwg04-19-05

150 300

FEET

Figure X Potentiometric Surface at 72 Hours

Shallow Wells Hows Corner Superfund Site

Plymouth Maine

WOODARD ampCURRAN Engineering bull Science bull Operations

29212 MW-108D

(MEDEP Pond 1) Farm Pond

Monitoring Well

Pumping Well

mdashbullbulllaquo 1 7-Acre Property Boundary

bull Groundwater Elevation Contour (ft)

1419001 Groundwater Elevation

211941 Hows CornerwipDrawingsTI EVALPotSurf-72hrs_deepdwg04-19-05

150 300 =5fc= FEET

Figure X Potentiometric Surface at 72 Hours

Deep Wells Hows Corner Superfund Site

Plymouth Maine

WOODARDampCURRAN Engineering bull Science bull Operations bull

--

Pumping Test Analytical Results Hows Corner Superfund Site

Plymouth Maine

Well ID oper Jaccb Analyses 2 Theis Analyses Fissure

Well Id Rd (ft)

Saturated Thickness

Transmissivity

(ft2day) K

(ft2day) K

(cmsec) Storage

Coefficient Transmissivity

(ft2day) K

(ft2day)

K (cmsec)

Storage Coefficient

System K

(ftday) PW-207OB 8 85 481 057 200E-04 392E-02 36 042 150E-04 809E-04 027 MW-103S 50 85 451 053 187E-04 720E-03 92 108 382E-04 283E-04 083 MW-103D 54 185 455 025 868E-05 210E-02 65 035 123E-04 237E-04 044 MW-2IB 59 85 352 041 146E-04 699E-03 104 123 433E-04 512E-04 052 MW-2DB 63 85 334 039 139E-04 845E-03 148 080 283E-04 239E-04 046 MW-104D 95 185 489 02 6 932E-05 654E-03 98 053 186E-04 547E-05 037 MW-104I 97 85 33 03 9 137E-04 362E-03 117 137 484E-04 962E-05 048 MW-101I 107 85 364 043 151E-04 490E-03 511 601 212E-03 223E-04 136 MW-102D 134 185 435 024 829E-05 248E-03 108 058 206E-04 850E-05 065 MW-101D 138 185 492 027 938E-05 511E-03 671 362 128E-03 700E-04 172 MW-205 219 85 57 067 237E-04 255E-03 447 526 186E-03 359E-03 -shyMW-204D 221 185 367 020 700E-05 170E-03 790 427 151E-O3 155E-04 147 MW-204S 225 85 379 045 157E-04 156E-03 1031 1213 428E-03 313E-04 199 MW-1B 228 85 325 038 135E-04 977E-04 340 400 141E-03 739E-05 054 MW-203S 273 85 489 058 203E-04 117E-03 1255 14 76 521 E-03 216E-04 210 MW-106D 278 185 51 028 972E-05 141E-03 1065 576 203E-03 360E-04 104 MW-203D 278 185 478 026 911E-05 152E-O3 765 414 146E-03 364E-04 138 MW-105D 364 185 44 024 839E-05 830E-04 769 415 147E-03 200E-04 127

1 Analyses conducted using Cooper and Jakob method on late drawdown data collected during constant

discharge pumping test conducted at the Hows Comer Site from September 20 - 30 2004

2 Analyses conducted using Theis solution for unconfmed approximation (1935)

J Analyses conducted using Moench method for dual porosity estimation (1984)

Fissure System Storage

Coefficient 402E-04 117E-06 264E-04 300E-04 932E-05 235E-07 502E-05 326E-06 801E-05 542E-04

-

803E-05 762E-05 134E-05 498E-05 115E-04

47E-04 838E-05

3 ysesh Analysis

Block System K (ft2day)

251E-02 207E-03 564E-04 163E-04 585E-04 465E-02 153E-04 498E-03 855E-04 356E-03

-

292E-03 394E-03 720E-04 526E-03 160E-01 35OE-O1 287E-03

Block System Storage

Coefficient

402E-02 164E-04 183E-02 330E-03 158E-03 847E-03 286E-03 326E-04 803E-05 272E-03

723E-04 686E-04 148E-04 349E-04 115E-03 47E-04 838E-04

Theis - Moench - CJ - AnalyticalResults_4-19-O5xls

DRAFT

242

24

238

236

bulla

c

i

a Q

234

232

228

226

Hows Corner Constant Discharge Testing USGS Background Groundwater Level USGS 445319068560101 ME-PEW456 Kenduskeag Maine

End of Monitored Recovery Period 09302004

Regional Background Location i 226 miles from Pumping Locatio

lt

697

NOTES

1 Groundwater samples collected in 1999 were screened for five volatile organic compounds (VOCs) only N

tetrachloroethene (PCE) exceeded reporting limits MW-2030 082304 082304 082304 082304 u

2 Strike and Dip of likely or possible transmissive 30 45 55 85 feature within the packer interval from which the indicated sample was collected

MW-204D

PCE TOTAL VOCs

081904 30

220 2636

A

081904 46-50 540 6436by

081904 IT

260 3073

x

MW-105D

PCE TOTAL VOCs

111199 50-60 2100 2100

MW-106D

PCE TOTAL VOCs

111199 76-86

400 400

111199 137-147

1400 1400

111299 1355-1455

350 350

PCE TOTAL VOCs

44 84

64

MW-6SB

bulli

lt

gt-

170 234

35

I I i

140 192

^^52

^^52

130 183

52 - lt

S A 34

PW-207 082404 082404 082404 20 37

PCE 1300 TOTAL VOCs

17-Acre George West Property Boundary

MW-113D

PCE TOTAL VOCs

112299 46-56

350 350

112299 70-80 190 190

150

112299 105-115

129 129

112399 138-148

230 230

L e g e n d ( J New Monitoring Well-Summer

Site Property Boundary ^ P u m p i n g Well-Summer 2004

-xmdashxshy Source Area

bull0shy Monitoring Well shy Pre 2004 Angled Boring-Summer 2004

211941laquoipdwgTI-ELV21ig41paltker-data2

2004 PCE of Total

bull lt70 VOCs

M W - 1 14D ^ ^

Figure xx Packer Testing Results in

Vicinity of Source Area Hows Corner Superfund Site

Plymouth Maine ^ WOODARD ampCURRAN

^^^^^^^^^^m ampKm Engineering - Science bull Operations

c Northeast Geophysical Services Borehole Geophysical Log

MW-203 Date logged 081704 Plymouth Maine

I Flowmeter Measurements Tomporaturo(C) Acoustic Televiewer

7 5 8 8 5 9 95 Caliper (Inches) Resistance (Ohms) Spontaneous Potential (mVj Dip In Degrees PCE Total VOCs

3 0 2 0 8 0 laquodeg 4S 1000 1400 1800 2200 MO HO 1000 1200 MOO 0 laquo deg ugL ugL n 1 1 1 1 1 1 1 1 1 i 1 1 1 1 n 1 1 1 1 1 1 1 1 1 1 1 n I l l l l l l l n

Ambient Flowneter pumping Rowmeter 11 gpm 6

H

bull

magnetic 10 bull 10 bull - 10 - north - 1 0I

-

_

bullbullbull - bull

20 bull bull20 bull ^ ltr~mdash 01

I

4 ^

LOS7

^

44 84 I I

Xr - 2

lt ^ bull30 -_ _^O1J- 1 _ 050 30 - 3 0

0r - - 3

C -j [ bull bull bull | shy

-O8 H ~ 1 045 7

1 4040 - 40 - -40 r - 14gt 13

V1s -- -023 f 1022 1V 170 234 I

T lt bull B gtf 50^ J50 - - 5 0 - - 5 0

I eet be

lo

i 1

1 1

1

140 192 - - - -t shy

-mdashj bullpound 60 - $o - - 60 - -60

H i I c

bull024

ampbull

3 - T lt ftft rgt He

70 bull j 70 - - 70 - 7 0 -

in -j bullbull shy

-021 1 T 022

- Ton _ Ov

26

130 183 NF NF

90 -_ 90 - 7 90 - -90

-

ifi Jf

3J

^gt _ N F NF bull bull shy

| H100 - j 100 bullbull 100 - -100

1 1 1 1 1 1 1 ) | 1 f I 1 1 1 ) 0 20 40 60 80

flft mdash ftn - mdash rVt

30 4 g 0 20 40 60 Dip in Degrees bullbull

Likely or poss bleFluid Resistivity (ohmmeters) The dip direction-- indicated

^ t h e l i n e extending from t h

I Iransmissive zone circle The strike of the feature is 90 degrees from this

The acoustic televiewer graph displays the mostprominent features selectedffom the acoustic televiewer

R n r a h n l c D O t t n O I B

f i o n n h w c i r a l U K U p i i y SI Ud l

1 rn l_Og Packered Interval August 2004

E tog The location dip angle and dip direction of the sleeted M W - 2 0 3 Groundwater samples were collected by Woodard S Curran on H23120M features are approximate Refer to the televiewer og of His _ well for more precise detail Plymouth Maine Date logged 081704

I

1

Northeast Geophysical Services Borehole Geophysical Log MW-204 D a t e l o gge d 072604

Plymouth Maine

n 3

Flowrneter Measurements(in gpm)

Caliper (Inches)0 3 5 4 0

1 1 1 1 1 1 1 t 1 1 1 1 1 1Ambient Rowmeler pumping Flowmetsr 05gpm

Templaquorature (C) bull bull bull bull i

7 75 8 8S 9 Resistance (Ohms) Spontaneous Potential (mV)

4000 SOW 600 4M 0

Acoustic Televiewer (interpreted)

Dip in Degrees 0 20 4060 SO

at N

PCEugL

Total VOCs ugL

- -_ a

10-

shy 10 bull - 10 shymagnetic

north - 10

o o

bull 1

11

11

1 1

1 1

11 1

1 1

1 1

1 1

1 1

1 1

1 1

1 1

1 1 E 1

- L

3 7 2 0 2 0r bull 20 bull - shy

i S_ N F

bull30 bull 7 3 0 220 2636shy1^ J J 004

fI f V ^

40 shy 4 0 4 0 shy - 4 0rbull019 [_ 007 w8 - - shy5 c

bull

gt

Ia50i 540 6436

bull50 - - 50 - - 5 0

-QQ7 - bull - -t T

pound V gtk

B 6 0 - e o - 7 6 0 -60shyQ 1 1

Q -007 -004 bull1 mdash T - J ~

bull

- - shyT 70 -J c [TO- - 70 - 7 0-

V Y 1- -004 -003

mdash T -h - y - j i - - mdash 260 3073 - gt=7

80 -j NF bull80 - - 80 - - 8 0Jgt

bull i

i 1

i i

C- bull shy

90 shy

K

Jlt i90 90 shy - 9 0shy -

l

ii

I I I I

NF bull M J

I ^ ^ - ^ bull 1

mdash mdash - _

s -7 ^100shy

till

1 100 100- H - 1 0 0shy -1 x Likety or possible k ^ Iransmissive zonebull

1 i i i ii i i i | l l l l | l i l l 0 20 40 ED 80

1 -

3 0SOFluid Resistivity (ohmmeters)

Dip in Degrees The djp ^ ^ o n is indicated ty Ihe line extending from tha circle The strike of Ihe feature

19- 3U UIHJIW93 IolII l l l lraquo

bull

The acousfc televiewer graph displays the mostprominent features selected from the acoustic televiewer109 The location dip angle and dip direction of Ihe sleetedfeatures are approximate Refer to the televiewer log of thiswentormore precise detail

B o r e h o l e G e O D h V S I C a l LOO B W H U I B w c w p n y o i v a i w v yM W - 2 0 4

P l y m O U t n MaiDB

Packorod Interval August 2004Groundwater san-ples wampramp collected by Woodard a Curran on OMO23C4

Date logged 072604

C

I

E Northeast Geophysical Services Borehole Geophysical Log Date logged 072704

I MW-205

Plymouth Maine

Flowmeter Measurements Temperature (C) Acoustic Televiewer (In gpm) I ~l (Interpreted)

I 85 10 Caliper (inches) 95

Dip in D g r laquo Resistance (Ohms) Spo ontaneous Potential (mV PCE Total VOCs 3 0 16 4 0 4 5 ) 20 40 60 80 10 00 2000 30 00 4VJ 400 -3 laquo

i i i i 1 i i I i 11 4 0 D 1 I I ugL ugL

C h

iii Ambient Flowmetar pumping

Flowmeter 1 25 gprn

I bull$bull

i

I rmdash magnetic 1 north ^^^^ 1 VI f

10 ~ I C x 10 bull - 10 bullbull

4 5 6mdashmdash f 1000B 11448 noisy nodi a raquo ^

mdash 5rt mdashi mdash Oft pound) 1100B 12509

cjmdash1 007

-

i i i 1

en

8 B a B

30 mdash

-

40 shy

-mdash I -

50 -_

__NF lt005

- 30 - - 3 0 it 34V

MO P26 V S) 1300B 13776 _ N F NF

26

40 bull - 40 bull 7-40 gt J Vf1 cX

) -j -

_ N F NF 50 c bull - 50 ^ 7-50

i I

I

c

B pound 60 - 6 0 7 60 - 7-60 a i 1

_ N F NF i Si f f 70 -_ bull70 bull - 70 shyC I 9

-m bull - shyA

_ N F NF 80 80 -j bull80 bull - 80 - C- 33 34

bull

5-i r

i 1

J r

Ck

_ N F NF 9 0 90 - - 90 shy

i bullCshy

J rK bull

100 -j ^ Likely or possible bull100- - 100- I -100

transmissive zone bull - ^ bull shy] |

1 1 1 1 1 1 1 I 1 i i i 1 i i 1 1 0 20 40 SO SO 10 20 30 40 50 Dip in Degrees 30 4 0 Fluid Resistivity (ohmmeters) Thlaquo dip direction is indicated

by the line extern r g from the circle The strike of he feature is 90 degrees from ihis

The acoustic televiewer graph displays the most

I Borehole Geophysical Log Packered Interval August2004 prominent features selected from the acoustic televiewer

Groundwatcr samples were oollccled by Woodard amp Cufran orgt S172004 log The location dip angle and dip direction of ins slsctsd MW-205 features are approximate Refelt to the televiewer log of this wall for more precise detail Plymouth Maine Date logged 072704

I

C

I Northeast Geophysical Services Borehole Geophysical Log Date logged 072704

I MW-206

Plymouth Maine

Flowmetor Measurements Temperature (C) Acoustic Televiewer | I r T i i i i i i i i i i i i i i r I |(in gpm) (Interpreted)

I 75 8 flS 9 95

Caliper (inches) Resistance (Ohms) Spontaneous Potential (mV) Dip In Degress PCE Total VOCs 30 35 40 4 5 0 20 40 M 90 4500 5500 6500 ugL ugL I i i

I I

- 1 0

I - 2 0

I 2900B 32401

i i L

E 0

i 6300B 68901

i I 0 20 40 SO 80

20 30 40 50 Dip in Dlaquogralaquos

amp 4 a Fluid Resistivity (ohrnmeters) The dip dirertion is indicated Likely or possible by iho line extending from the transmissive zone circle The striKe of the feature

is 90 degrees from tNs

Borehole Geophysical Log Packered Interval August 2004

E amples were collected by Woodard amp Cunan oo SM82004 log Thraquo location 4p angle and dip direction of the sloeled MW-206 feature are approximate Refer to the televiewer 109 of this well for more precise detail Plymouth Maine Date logged 072704

C

I Northeast Geophysical Services Borehole Geophysical Log

Date logged 082304 PW-207

I Plymouth Maine

Fiowmeter Measurements Temperature (C) Acoustic Televiewer

I (in gpm) (interpreted)

75 8 85 9 95 Caliper (inches) Resistance f0tims) Spontaneous Potential (mV) Dip in Degrees PCE Total VOCs

55 60 0 20 40 SO 80 ugL ugL I I I I I I I

Ambienl Fiowmeter pumping Flewmater

magnetic - 10 - - 1 0

north

i - 20 - - 2 0

1300 1410

i - 30 - - 3 0

i tf

5400 5802 - 40 - - 4 0

B - 50 - - 5 0

I 18000 19234

- 60 - - 6 0

I 12000 13085

- 70 - - 7 0

- 8 0

i - 9 0 19000 20354

G - 100- -100

I 110 110 bull110

0 20 40 60 SO 10 20 30 Dip m Degrees

Fluid Resistivity (ohmmeters) I 50

The dip direction is indicated by ihe line extending from the circle The strike of the fealure is 90 degrees from this

Borehole Geophysical Log

G Packorod Interval August 20(M log The location dip angle and dip dirlaquocton or the sleeted Groundaier samplss were ooliecled by Woodard i Curran on ampt24f2ltXM PW-207 failures are approximate Reter to the televiewer log of this wlaquoll for more precise detail PlyPIOUth Maine Date logged 082304

I

Table XX Packer Permeability and Packer Sampling Results for Potential Fracture Intervals

1

WellID MW-101D MW-101D MW-101D MW-101D MW-101D MW-101D MW-101D MW-101D MW-101D MW-101D MW-I01D MW-101D MW-101D MW-102D MW-102D MW-I02D MW-102D MW102D MW-102D MW-102D MW-102D MW-102D MW-I02D MW-102D MW-102D MW-102D MW-103D MW-103D MW-103D MW-103D MW-I03D MW-103D MW-103D MW-103D MW-103D MW-103D MW-103D MW-103D MW-I03D MW-104D MW-104D MW-104D MW-104D MW-I04D MW-104D MW-104D MW-104D MW-104D MW-104D MW-104D MW-105D MW-105D MW106D MW-106D MW-106D MW-107D MW-107D

1999 Drilling Program

Hows Corner Superfund Site Plymouth Maine

Potential Fracture Top Of Bottom 6 Depth to lt Topof i Interval from Packer Packer Middle of Elevation Hydraulic bull PCE

GS ELEV 1 Rock Drilling Interval Interval Interval of Interval Conductivity Concentration (ft msl) (ft msl) TEST (ftbgs) (ftbgs) r(ftbgs) ( f t b (ft mil) (cmsec) (raquogL)

4339 4329 13 28-29 33-3537-39 271 376 324 4016 OOOE+00 4339 12 37-3444-46 380 485 433 3907 157E-04 4339 11 488 593 541 3799 132E-04 4339 10 60-61 578 683 631 3709 OOOE+00 4339 9 678 783 731 3609 I79E-05 4339 8 778 883 831 3509 106E-05 4339 7 880 985 933 3407 243E-05 4339 6 990 1095 1043 3297 339E-06 4339 5 1090 1195 1143 3197 OOOE+00 4339 4 1190 1295 1243 3097 OOOE+00 4339 3 1365-1375 1290 1395 1343 2997 OOOE+00 4339 2 147-157 1390 1495 1443 2897 580E-05 4339 1 147-157 1470 1575 1523 2817 741E-05 43161 43061 13 166 271 219 4098 333E-04 43161 12 30-3136-40 260 365 313 4004 I54E-05 43161 11 36-4041-43 362 467 415 3902 548E-05 43161 10 470 575 523 3794 598E-05 43161 9 570 675 623 3694 197FOS 43161 8 670 775 723 3594 OOOE+00 43161 7 770 875 823 3494 891 E-05 43161 6 83-94 870 975 923 3394 139E-05 43161 5 970 1075 1023 3294 123E-04 43161 4 1070 1175 1123 3194 526E-06 43161 3 1170 1275 1223 3094 138E-05 43161 2 1270 1375 1323 2994 671E-06 43161 1 1370 1475 1423 2894 OOOE+00 42997 42497 13 18-19 170 275 223 4077 OOOE+00 42997 12 260 365 313 3987 766E-05 42997 11 360 465 413 3887 727E-05 42997 10 460 565 513 3787 192E-05 42997 9 560 665 613 3687 752E-05 42997 8 660 765 713 3587 778E-05 42997 7 85-86 763 868 816 3484 260E-05 42997 6 860 965 913 3387 289E-05 42997 5 102-103 960 1065 1013 3287 102E-04 42997 4 1060 1165 1113 3187 522E-06 42997 3 1160 1265 1213 3087 520E-06 42997 2 129-130 1260 1365 1313 2987 960E-04 42997 1 1360 1465 1413 2887 OOOE+00 43372 42922 11 35-37 42-45 350 455 403 3935 684E-04 43372 10 460 565 513 3825 500E-05 43372 9 560 665 613 3725 106E-05 43372 8 72-74 660 765 713 3625 204E-05 43372 7 760 865 813 3525 872E-06 43372 6 860 965 913 3425 467E-06 43372 5 960 1065 1013 3325 200E-05 43372 4 1060 1165 1113 3225 354E-05 43372 3 125-130 1160 1265 1213 3125 157E-05 43372 2 125-130 1260 1365 1313 3025 337E-04 43372 1 1365 1465 1415 2922 689E-06 43052 43002 2 54-58 490 595 543 3763 124E-05 2100 43052 1 139-140 145-146 1367 1472 1420 2886 154E-04 1400 43291 4391 3 bullI133 260 365 313 4017 439F06 43291 2 77-78 760 865 813 3517 230E-03 400 43291 1 143-144 1355 1460 1408 2922 971E-06 350

29958 27258 4 450 555 503 2493 OOOE+00 (21)A 29958 3 103-105 1000 1105 1053 1943 752E-04 (063)A

Table XX Packer Permeability and Packer Sampling Results for Potential Fracture Intervals

1999 Drilling Program

Hows Corner Supcrfund Site Plymouth Maine

gtbull i Potential Fracture Top _OfBot Bottom of Depth to ltbull Top of Interval from f Packer Packer Middle Of

GS ELEV lt Hock Drilling interval Interval Interval WeD ID ft msl) (ft msl) TEST (ftbgs) ltft$gs) (ftbgs) (ftbgs)

MW-107D 29958 2 128-130 1200 1305 1253

MW-107D 29958 1 139-141 1350 1455 1403

MW-108D 31904 31104 6 35-36 300 405 353 MW-108D 31904 5 60-62 550 655 603

MW-108D 31904 4 80-83 750 855 803

MW-108D 31904 3 118-119 123-124 1150 1255 1203

MW-108D 31904 2 147-149 1440 1545 1493

MW-108D 31904 1 1700 1805 1753

MW-110D 40576 40426 2 21-31 210 315 263 MW-110D 40576 1 148-154 1460 1565 1513 MW-I11D 40519 4 70-71 650 755 703

MW-111D 40519 3 79-82 84-86 780 885 833 MW-I11D 40519 2 97-102 950 1055 1003 MW-111D 40519 1 1370 1475 1423

MW-112D 3027 2942 4 42-52 420 525 473 MW-112D 3027 3 850 955 903 MW112D 3027 2 1100 1205 1153 MW-112D 3027 1 135-136 140-141 1340 1445 1393

MW-113D 43085 43085 5 250 355 303 MW-I13D 43085 4 47-49 460 565 513 MW-113D 43085 3 73-74 700 805 753 MW-113D 43085 2 1050 1155 1103 MW-113D 43085 1 1380 1485 1433

MW-114D 42394 41594 4 48-49 450 555 503 MW-114D 42394 3 79-81 740 845 793 MW-114D 42394 2 121-129 1250 1355 1303 MW-114D 42394 1 134-142 1350 1455 1403

MW-115D 4035 4035 4 300 405 353 MW-1I5D 4035 3 70-71 650 755 703 MW-115D 4035 2 1150 1255 1203 MW-115D 4035 1 1400 1505 1453

LOT-28W 382 7 450 555 503 LOT28W 382 6 550 655 603 LOT-28W 382 5 650 755 703 LOT28W 382 4 750 855 803 LOT-28W 382 3 850 955 903 LOT-28W 382 2 950 1055 1003 LOT-28W 382 1 1055 1155 1105

NOTES cmsec = centimeters per second ft bgs = leet below ground surface It msl = feet below mean sea level lt = not detected at indicated reporting limil A = detected below laboratory PQL ( ) = detected below reporting limits

Elevation of Interval

(ft nisi) 174

159

283gt 2588

2388

1988

1698

1438

3795 2545 3349 3219 3049 2629

2555 2125 1875 1635

4006 3796 3556 3206 2876

3737 3447 2937 2837

3683 3333 2833 2583

3318 3218 3118 3018 2918 2818 2715

Hydraulic Conductivity

(cmsec)

323E-05

208E-05

471E-03

471E-03

624E-05

3I6E-05

264E-05

261 E-05

OOOE+00 200E-04 953E-05 OOOE+00 OOOE+00 212E-05

361 E-05 410E-06 2gQE06 292E-05

786E-05 124E-05 151 E-05 822E-06 82IE-06

858E-05 I69E-05 352E-03 866E-05

223E-05 394E-06 122E-05 525E-06

831 E-05 182F-05 L62E-05 129E-05 190E-05 890E-04 981 E-04

PCEraquo Concentration

(ugL)

lt5

(14A)

98 11

15

22

11

30

200 (62)A

110 210 300 240

(44)A (23)A

5

350 190 129 230

2200 1900 2600 2600

(17)A (16)A (19)A

96

Table XX Packer Permeability and Packer Sampling Results for Potential Fracture Intervals

2004 Drilling Program

Hows Corner Superfund Site Plymouth Maine

Top of Bottom of Depth to Midpoint

t K

ELEV (ft Potential Transmissive Zones Packer Interval

Packer Interval

Middle of Interval

Elevation of interval

Hydraulic Conductivity

PCE Concentration

Well ID msl) TESTr (ft bgs)- (ftbgs) (ftbgs) (ftbgs) (ft msl) (cmsec) (ogt) MW-203D 43227 4 277279 24 32 28 4043 667E-05 44

3 408415420 39 49 44 3883 593E-05 170 2 526 530 49 57 53 3793 101E-04 140 I 828830842 80 88 84 3483 701E-05 130

MW-204D 43262 5 295 300 26 34 30 4023 902E-05 220 4 463496513516 45 53 49 3833 119E-04 540 3 681685688 63 71 67 3653 OOOE+00 2 758 76 2 71 79 75 3573 309E-05 260 I 88 96 92 3403 OOOE+00

MW-205 42389 3 164 166 168 15 20 175 4148 OOOE+00 1000B 2 302305312 30 35 325 3998 107E-04 1300B 1 40 45 425 3898 OOOE+00

MW-206D 43007 5 17 72 195 4128 291E-05 4 296 302 307 29 34 315 4008 940E-05 2900B 3 522 52 57 545 3778 944E-07 2 656 64 69 665 3658 353E-06 1 92392793 4939 91 96 935 3388 614E-05 6300B

PW-207 43477 5 184622162819 18 29 235 4088 209E-05 1300 4 3508 32 43 375 3948 568E-06 5400 3 53325341542154325559 50 61 555 3768 821E-05 18000

6359 61 72 665 3658 866E-06 12000 1 8685 84 89 865 3458 213E-05 19000

NOTES cmsec = centimeters per second ft bgs = feet below ground surface ft msl = feet above mean sea level B = detected in lab blank

Table XX Orientation Permeability and Groundwater Sampling Results for Transmissive Features

2004 Drilling Program

Hows Corner Superfund Site Plymouth Maine

Borehole Geophisical Feature depth Dip True Dip True Transmissive Log Feature (Feet) Degrees Azimuth Strike bullvgt(Ltk|iy^

Number v Tosftble) v MW-203 5 277 64 337 67 Likely

6 279 59 11 281 Likely 8 352 14 177 87 Likely 11 381 46 96 6 Possible 12 408 35 271 1 Possible 14 415 57 250 340 Possible 15 420 58 202 292 Likely 18 526 52 75 345 Likely 19 530 52 82 352 Likely 28 828 48 75 345 Likely 29 830 52 17 287 Likely 30 830 56 233 323 Possible 31 842 50 130 40 Likely

MW-204 4 295 15 147 57 Likely 5 300 43 91 1 Likely 11 439 31 80 350 Possible 12 440 46 219 309 Possible 14 463 50 358 88 Likely 15 496 34 198 288 Likely 16 513 54 17 287 Likely 17 516 33 14 284 Likely 25 681 39 359 89 Possible 26 685 22 45 315 Possible 27 688 35 73 343 Possible 32 758 45 236 326 Likely 33 762 46 306 36 Likely

MW-205 5 164 69 106 16 Possible 6 166 78 165 75 Possible 7 168 82 115 25 Possible 8 168 68 116 26 Possible 12 215 46 222 312 Possible 13 217 75 62 332 Possible 14 219 29 32 302 Possible 16 237 69 250 340 Possible 17 256 73 353 83 Possible 18 272 44 202 292 Possible 21 299 37 196 286 Possible 22 302 31 206 296 Possible 23 305 59 48 318 Likely 24 312 63 42 312 Likely

MW-206 1 264 37 181 271 Likely 2 296 69 217 307 Likely 3 302 66 233 323 Likely 4 307 64 224 314 Likely 8 342 62 259 349 Likely

jjHydraulic GoiDanctilyity j(cmsecjw

667 E-05

593 E-05

101 P04

710 E-05

902 E-05

119 E-04

0

309 E-05

0

107 E-04

94 E-05

PCE (ugL)

44

170

140

130

220

540

260

IOOOB

1100B

1300B

2900B

STotal vVoCsv tig1)

84

234

192

183

2636

6436

3073

11448

12509

13776

32401

PCEyo dfCTotaf

52

73

73

7 1

83

84

85

87

88

94

90

Table XX Orientation Permeability and Groundwater Sampling Results for Transmissive Features

2004 Drilling Program

Hows Corner Superfund Site Plymouth Maine

Borehole Geophisical Feature deptt raquoip True pip True Transraissive Log Feature (Feet) shy Degrees Azimuth Strike (tikely

Number raquo Possible) 22 522 57 54 324 Possible 25 656 40 82 352 Possible 32 871 59 151 61 Possible 33 883 53 185 275 Possible 34 895 7 175 85 Likely 35 899 53 90 0 Likely 36 902 49 184 274 Likely 37 923 9 175 85 Likely 38 927 42 206 296 Likely 39 934 48 167 77 Likely 40 939 26 180 90 Likely

PW-207 1 1846 33 167 77 Likely 4 2216 49 289 19 Possible 7 2819 59 265 355 Possible 11 3508 55 189 279 Possible 18 5332 43 305 35 Likely 19 5341 51 30 300 Likely 20 5421 20 254 344 Likely 21 5432 39 301 31 Likely 23 5559 52 302 32 Likely 25 6359 24 182 272 Possible 29 8049 77 231 321 Possible 30 8685 78 38 308 Likely 32 9334 29 194 284 Likely

NOTES

B = detected in lab blank

Hydraulic Conductivity

(cmsee) 944 E-07 353 E-06

614 E-05

209 E-05

568 E-06

821 E-05

866 E-06

213 E-05

bulltCE (ugL)

6300B

1300

5400

18000

12000

19000

Total VOCs (ug1)

68901

1410

5802

19234

13085

20354

PCE of Total VOCs

9 1

92

93

94

92

93

Response to EPA-DEP Comment 3 Dated March 312005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

lit

EPA-DEP Comment 3

Comment 3 The reported f values and resultant Kd values There remains doubt that the values used in the flushing model accurately reflect the propensity for PCE to sorb to the bedrock The ^ values presented in Appendix B may be unrealistically high because the bedrock samples may have contained organic carbon that was unavailable for sorption The reported f values are only qualitative estimates of the organic carbon content of the bedrock samples The Walkley and Black organic carbon measurement method is quick and simple but the results obtained cannot be considered quantitative because it requires a correction factor which often results in erroneous values it assumes the organic carbon has an average valence of zero oxidizable and reducible constituents such as chloride ferrous iron and manganese oxides interfere with the results and the errors introduced by interference are potentially greater when the organic carbon content is low at low f values it is not clear that organic carbon is controlling PCE sorption (Schwarzenbach and Westall 1981 Mackay et al 1986 Fetter 1999)

In order to derive a Kd-based retardation factor that is reasonable given the reported f values and the rapid advance of the PCE plume described on pages 4-11 and 4-12 the flushing model requires a bulk density to porosity ratio that is roughly two orders of magnitude higher than the actual ratio for the Hows Corner bedrock (page 4-4) This apparent discrepancy needs to be addressed

Response This comment raises several concerns about the collection and analysis of samples for fraction of organic carbon (f^) the quality of the resulting data and the implications of the use of those data for estimation of the retardation of groundwater contaminant movement Results of bedrock analysis for f were proposed in the TI Evaluation Work Plan for use in conjunction with groundwater contaminant concentrations and aquifer information to estimate cleanup times using the Batch Flushing model It is important to use accurate f values from representative bedrock in the Batch Flushing model in order to obtain reasonable estimates of the remedial time frame Because of the importance of accurate and representative results the TI Investigation field program was designed and conducted both to collect samples representative of the rock volume most likely to be in contact with contaminated groundwater and to analyze them using an appropriate refereed analytical method Five potential methods for evaluating f were identified Of the five methods the Walkey-Black method was selected because it has minimal method interferences and a sufficiently low detection limit as well as a long history of use in agronomy and contamination studies The PRP Group is pleased with the quality of the data obtained from the bedrock samples as represented by their precision and reproducibility

The first part of this comment relates to the determination of fraction of organic carbon (f^) values The several subparts of the first paragraph are addressed individually in items 1 through 5 below The second part of the comment regarding the resultant distribution coefficient (Kd) values is addressed separately as item 6 below

1 There remains doubt that the values used in the flushing model accurately reflect the propensity for PCE to sorb to the bedrock

bull The rock core samples used for f (gocg) analysis were from core immediately adjacent to fractures These rock core samples included the fracture surfaces themselves and rock core extending back less than 1 cm from the fractures Therefore the foe data reported in the TI Evaluation represents the f of bedrock through which groundwater will travel and to which PCE will adsorb Based on the careful selection of sample locations and the

Response to EPA Comment 3 050205doc 1 of 11 Woodard amp Curran (211941)

number of samples collected we are confident that the measured f values are representative of the f at points of contact for PCE with the bedrock it is these f values that determine the propensity of PCE to sorb to the bedrock

bull The samples of rock core collected for analysis of f originated from 19 different locations varying in depth from 11 to 90 feet Therefore it is very unlikely that the rock core samples were contaminated with extraneous organic carbon from above ground

2 The foc values presented in Appendix B may be unrealistically high because the bedrock samples may have contained organic carbon that was unavailable for sorption

bull As noted in response 1 the f data reported in Appendix B represents organic carbon primarily associated with the surface of fractures in the bedrock through which groundwater is most likely to travel Therefore it is this organic carbon that the contaminants in the groundwater will come in contact with and adsorb to in the fractured rock at the site

bull The chemical oxidation agents used in the Walkey-Black method oxidize the easily oxidizable organic carbon in the medium and the foe is calculated from the quantity of the agent consumed Therefore it is unlikely that the analysis of the bedrock samples measured organic carbon that was unavailable for sorption

3 The reported foc values are only qualitative estimates of the organic carbon content of the bedrock samples

bull The reported f values are accurate quantitative results Schumachers review of Methods for the determination of total organic carbon (TOC) in soils and sediments (NCEA-C-1282 EMASC-001 April 2002) identifies the Walkley-Black method which was used to analyze the reported foc values as the reference method for comparison to other methods for analyzing total organic carbon

bull Schumacher also points out that if anything the WalkJey-Black method may underestimate the total organic carbon in a sample due to possible incomplete oxidation of organic carbon Usually the incomplete oxidation of total organic carbon in environmental samples is corrected for by multiplying the measured foe by 130 (Walkley amp Black 1934 Schulte 1995)

bull When the f data in the TI Evaluation Report (WampC 2005) Appendix B (attached) are analyzed statistically the standard deviation of the f for the 19 samples analyzed is 174 of the average f Given this standard deviation the 95 confidence interval for this data ranged from a low of 000123 gocg to a high of 000253 gocgm

The labs Method of Detection Limit (MDL) for the f measured using the Walkley-Black method is 00001 gocg Therefore the average (000188 gocg) the mean (000185 gocg) and geometric mean (000187 gocg) of the f values for the rock core at Hows Corner are all statistically significantly greater than the MDL of the Walkley-Black method

In addition to the aforementioned statistical analysis of the foe data triplicate samples (n = 3) from the same rock core (including one sample from the 19 rock core samples) were

Response to EPA Comment 3 050205doc 2 of Woodard amp Curran (211941)

analyzed for their f to determine the repeatability of the Walkley-Black method The average the mean and the geometric mean of the f values of these replicate samples was 000162 gocg 000150 gocg and 000159 gocgm respectively The standard deviation of these measurements was 000039 gocg

4 The Walkley and Black organic carbon measurement method is quick and simple but the results obtained cannot be considered quantitative because it requires a correction factor which often results in erroneous values it assumes the organic carbon has an average valence of zero oxidizable and reducible constituents such as chloride ferrous iron and manganese oxides interfere with the results and the errors introduced by interference are potentially greater when the organic carbon content is low at low foc values it is not clear that organic carbon is controlling PCE sorption (Schwarzenbach and Westall 1981 Mackay et al 1986 Fetter 1999)

bull Schumachers review (NCEA-C-1282 EMASC-001 April 2002) of the Walkley-Black method identifies several potential problems with this analytical method that could occur if the analytical lab is not familiar with the nuances of the chemistry associated with this method Interestingly Schumachers review neglected one of the more important analytical steps required to avoid errors in quantifying f in samples where there might beNAPL

It is absolutely critical to eliminate any NAPL from rock core samples prior to using the Walkley-Black method to measure foe in such samples This was done by the lab (PTS Laboratories) that measured the foe in the rock core samples from Hows Corner The lab used the Dean-Stark method (solvent extraction) to remove all hydrocarbons (including PCE and other NAPLs) from the sample (PTS Laboratories) This extraction method does not interfere with the subsequent analysis of the natural organic carbon associated with the rock core

Subsequently the samples were dried at 150degC to a constant weight (normally 16 hours) This latter step oxidizes all inorganic minerals including ferrous bearing minerals to ferric oxides and precludes their interference during the oxidation of the samples with chromic acid This procedure completely eliminates any positive bias in the reported foc

data that might have occurred due to the presence of ferrous ions and other reduced minerals

bull As noted in Response 3 the incomplete oxidation of total organic carbon results in an underestimate of the f and is corrected for by multiplying the f by a correction factor of 130 (Walkley amp Black 1934 Schulte 1995) The fx data reported in the TI Evaluation was corrected accordingly by using this correction factor

bull Excess chloride (Cl~) in percent weight quantities as found in saline soils may interfere with the quantitative titration of reduced chromium (Walkley 1947) However given that the primary rock type at the Hows Corner site is phyllite it is highly unlikely that there was sufficient chloride in the rock core samples for this to occur

bull Manganese oxides may also interfere with the analysis of f through competing with the dichromate ion for any oxidizable carbon (Walkley 1947) However in such cases the reported f would be an underestimate of the f present in the rock core Walkley (1947)

Response to EPA Comment 3 050205doc 3 of 11 Woodard amp Curran (211941)

4

reported that in the case where the ratio of MnO2 to carbon is 85 to 1 the error in the carbon determinations would only be 0 to 6 percent

It may also be useful to compare the analysis of total organic carbon in a geologic matrix that contains high levels of manganese using EPA method 9060 to the Walkley-Black method Table 1 summarizes data provided by one of the PRPs that compares the analysis of total organic carbon in a geologic matrix that contains approximately 02 wgt manganese (approximately 03 wgt manganese oxide)

Table 1 Comparison of total organic carbon measured using the EPA- 9060 method and the Walkley-Black method

Laboratory EPA-9060 Method Walkley-Black Method A Ave 00226 gocg Not analyzed

Stdev 000251 gocg n = 5

B Ave 002219 gocg Ave 002050 gocg Stdev = 000316 gocg Stdev =000971 gocg

n= 10 n = 10

The similarity in the total organic carbon concentrations measured by these two different methods provides further confidence that the Walkley-Black method is a viable method for analysis of total organic carbon in the presence of manganese equivalent to at least 10 by weight of the total organic carbon

5 The Walkley and Black organic carbon measurement at lowf^ values it is not clear that organic carbon is controlling PCE sorption (Schwarzenbach and Westall 1981 Mackay et al 1986 Fetter 1999)

bull Schwarzenbach and Westalls (1981) paper states that f values of less than 0001 gocg should not be used in combination with Kow (octanol-water partition coefficients) values to calculate K^ values (solid phase partition coefficients) values for a specific contaminant It should be noted that the TI Evaluation did not use the f data to calculate the KQC from the Kow Instead as requested by the EPA the measured KOC value for PCE was used to calculate the retardation factor for this contaminant

bull Schwarzenbach et al (2003) stated more recently that Even at very low f values (ie foe = 0001 kgoc - kg1 solid) sorption to the organic components of a natural sorbent may still be the dominant mechanism in defining the adsorption of organic compounds to geological matrices

bull In 1985 M Piwoni from the US EPA Robert S Kerr Environmental Research Laboratory published a paper (Banerjee et al 1985) that showed that for very hydrophobic molecules TOC content of the sorbent will control sorption down to levels of organic carbon that defy quantitation Contaminants such as the PCE found in the groundwater at Hows Corner are in this category of compounds

Given the aforementioned reasons the f values reported in the TI Evaluation are accurate within the noted statistical limitations and will have a predictable impact upon the retardation of PCE during groundwater transport

Response to EPA Comment 3 050205doc 4 of 11 Woodard amp Curran (211941)

6 In order to derive a Kd-based retardation factor that is reasonable given the reported foc

values and the rapid advance of the PCE plume described on pages 4-11 and 4-12 the flushing model requires a bulk density to porosity ratio that is roughly two orders of magnitude higher than the actual ratio for the Hows Comer bedrock (page 4-4) This apparent discrepancy needs to be addressed

The apparent discrepancy of bulk density to porosity ratios is most likely due to the fact that the Batch Flushing Model was originally developed for a porous medium and is not directly applicable to fractured bedrock As stated in Appendix C (page C-4) of the Draft Technical Impracticability Evaluation Report in order to use the Batch Flushing Model to describe the transport of contaminated groundwater in fractured bedrock where the matrix porosity is insignificant it is more appropriate to use a fracture surface area to void space ratio to calculate the retardation factor (R) than a bulk density to porosity ratio (Freeze amp Cherry 1979)

Since it is impractical to determine the actual surface area to which contaminants can adsorb the Batch Flushing Model was used with two simplifying assumptions bull The Kd was calculated from the f and the K^ bull The bulk density to porosity ratio term in the Batch Flushing Model was constrained to range

from 4 to 10 the typical range of such ratios in porous media (Freeze amp Cherry 1979)

If one uses site specific bedrock bulk density and porosity values the bulk density to porosity ratio is several orders of magnitude greater (specifically 273 gcc bullbull 000165 (dimensionless) = 1654 gcc) than the range of ratios of 4 to 10 used in the Batch Flushing Model in the Draft Technical Impracticability Evaluation Report Constraining the bulk density to porosity ratio within the range of ratios of 4 to 10 results in significantly lower R value than would be obtained using specific bedrock bulk density and porosity values

In summary in bedrock where fractures are the primary porosity the bulk density to porosity ratio can vary considerably and will be a function of the number of fractures and the fracture aperture The calculated bulk density to porosity ratio will be inversely proportional to the porosity This means that in fractured rock with limited fracturing and smaller porosity the calculated bulk density to porosity ratio is greater and will result in a greater calculated retardation factor than in bedrock with more extensive fracturing and greater porosity Consequently the calculated retardation factor will be greater for bedrock with less surface area available for sorption than bedrock with greater surface area for sorption This is contrary to what actually occurs

4 Response to EPA Comment 3 050205doc 5 of 11 Woodard amp Curran (211941)

m

REFERENCES

Banerjee P MD Piwoni K Ebeid (1985) Sorption of organic contaminants to a low carbon subsurface core Chemosphere _14 1057-1067

Freeze RA JA Cherry (1979) Groundwater Prentice Hall Englewood Cliffs NJ pg 604

PTS Laboratories wwwptsgeolabscompdf files3TOCnotepdf

Schulte EE (1995) Recommended soil organic matter tests in Recommended Soil Testing Procedures for the Northeastern United States Northeastern Regional Publication No 493 Chapter 8

Schwarzenbach RP J Westall (1981) Transport of nonpolar organic compounds from surface water to groundwater Laboratory sorption studies Environ Sci Tech 15 1360-1367

Schwarzenbach RP PM Gschwend DM Imboden (2003) Environmental Organic Chemistry Wiley-Interscience pg 292 408 amp 412

Walkley A LA Black (1934) An examination of the Degtjareff method for determining soil organic matter and a proposed modification of the chromic acid titration method Soil Science 37 29-38

Walkley A (1947) A critical examination of a rapid method for determining organic carbon in soils - effect of variations in digestion conditions and of inorganic soil constituents Soil Science 63251-264

Woodard amp Curran Inc (WampC) 2005 Draft Technical Impracticability Evaluation Hows Corner Superfund Site Plymouth Maine January 2005

Response to EPA Comment 3 050205doc 6 of Woodard amp Curran (211941)

LIST OF ATTACHMENTS (Response to Comment 3)

Appendix B to Draft Technical Impracticability Evaluation Measurement of foe at Hows Corner (4 pages)

m

Response to EPA Comment 3 050205doc 7 of 11 Woodard amp Curran (211941)

Appendix B Measurement of foe of Rock Core at Hows Corner

There are two general approaches to measure the fraction of organic carbon (foe) in rock cores

bull Measurement of weight loss by ignition of organic matter bull Chemical oxidization of organic carbon to carbon dioxide and either

subsequent quantification of the oxidant used for the reaction or quantification of the carbon dioxide produced during this oxidation process

The weight loss method is subject to errors caused by volatilization of substances other than organic materials such as water hydroxides and mineral carbonates Quantification of foe by the weight loss method is particularly sensitive to the presence of carbonates in rock cores There are however weight loss methods that are designed to differentiate between organic carbon and the aforementioned interfering materials but they require considerable care and are less accurate at low foe values Hence the weight loss method was not well suited for measuring the foe of the rock core from Hows Corner

The chemical oxidation of organic carbon is much better suited for quantifying organic carbon in rock cores such as those from Hows Corner This method uses a strong chemical oxidant to oxidize organic carbon to carbon dioxide and then measures either the chemical oxidant used to oxidize the organic carbon or the quantity of carbon dioxide produced In addition this general approach is not subject to interference by volatilization of other constituents of the rock core

There are at least two such chemical oxidation methods

bull The method of Baccini which was described by Schwarzenbach amp Westall (1981) first acidifies the sample to eliminate interference by carbonates Then a strong oxidant is used to chemically oxidize the organic carbon to carbon dioxide The resulting carbon dioxide is subsequently reduced to methane and quantified using a flame ionization detector Unfortunately this method has not been described in detail in a referred journal Hence it is would not have been appropriate to use to characterize the foe in the Hows Corner rock core

bull The more commonly used method to quantify foe in rock core is the Walkley-Black method (1934) This method is preferred for RBCA and DODDOE projects and by the oil industry

The Walkley-Black method uses an excess of chromic acid to oxidize (digest) organic matter to carbon dioxide The remaining chromic acid that was not consumed during the oxidation of the organic carbon is then quantified by titration with ferrous sulfate The difference in chromic acid prior to and after the oxidation of the organic carbon represents the total chromic acid used to oxidize

Hows Corner TI Evaluation Page 1 January 13 2005 Appendix B

the organic carbon in the sample The latter can be calculated using the chemical stoichiometry of the reaction

The Walkley-Black method is very accurate for samples that contain less than 2 organic carbon matter The minimum detection limit (MDL) for the Walkley-Black method is 100 mgkg or an foe of 0001

Given the rock core at Hows Corner was expected to contain less than 2 organic carbon the Walkley-Black method was used to measure the foe from 19 different rock core samples collected from varying depths ranging from 11 to 90 feet

Table 1 provides a statistical summary of the aforementioned data

Table 1 Statistical summary of foe data from rock cores collected at varying depths

Statistical Parameter Calculated Value foe Minimum Detection Limit (MDL) 00010 Number of samples analyzed (n) 19 Average foe 00019 Median foe 00019 Geometric Mean foe 00019 Standard deviation of foe measurements 000033 Relative standard deviation 174 -+ 95 Confidence intervals 00012 to 00025

The data in Table 1 shows the following

bull The foe from the Hows Corner rock cores are statistically greater than the MDL of the Walkley-Black analytical method

bull The average and median values for the foe of the Hows Corner rock cores from varying depths are nearly identical indicating that there is little variability in the foe values in the source zone at the site

bull The standard deviation of these measurements is 000033 which is 174 of the average foe

bull The 95 confidence intervals of the foe of the rock core at Hows Corner are 00012 to 00025

The foe was also analyzed from three separate samples taken from the same rock core at a depth of 55 feet (Only one of these samples was included in the data summarized in Table 1) Table 2 shows the statistical repeatability of this type of analysis

Hows Corner TI Evaluation Page 2 January 13 2005 Appendix B

Table 2 Repeatability of analysis of foe from one rock core at 55 feet in depth

Statistical Parameter Calculated Value Number of samples analyzed (n) 3 Average foe 00016 Median foe 00015 Geometric Mean foe 00016 Standard deviation of foe measurements 000039 Relative standard deviation 240 -+ 95 Confidence intervals 00008 to 00024

The data in Table 2 shows the following

bull The percent relative standard deviation of these three analyses of foe from the same rock core at Hows Corner is 24

bull The 95 confidence interval of the foes measured in this particular rock core at Hows Conrer is 00008 to 00024

These results show that there is good repeatability in using the Walkley-Black method for analysis of the foe in the rock core at Hows Corner

References Schwarzenbach amp Westall (1981) Transport of nonpolar organic compounds from surface water to groundwater Laboratory sorption studies Environ Sci Tech 15 1360-1367

Walkley A I A Black (1934) An examination of Degtjareff method for determining soil organic matter and a proposed modification of the chromic acid titration method Soil Sci 37 29-37

Hows Corner Tl Evaluation Page S January 13 2005 Appendix B

Woodard and Curran PTS Laboratories PTS File No 34618

ORGANIC CARBON DATA (METHODOLOGY WALKLEY-BLACK)

PROJECT NAME PROJECT NO

SAMPLE ID

203-chip-13 203-chip-23 203-chip-27 203-chip-38 203-chip-42 203-chip-47 203-chip-52 203-chip-58 203-chip-69 203-chip-82 207-chip-11 207-chip-19 207-chip-24 207-chip-29 207-chip-35 207-chip-45 207-chip-55 207-chip-87 207-chip-90

207-chip-55 55-MS

55-MSMSD

Hows Corner NA

DEPTH ft

13 23 27 38 42 47 52 58 69 82 11 19 24 29 35 45 55 87 90

55 NA NA

MATRIX

Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip

Average Median

Geometric Mean Standard Deviation Relative Std Dev

+- 95 Confidence Interval n

Rock Chip Rock Chip Rock Chip

Average Median

Geometric Mean Standard Deviation Relative Std Dev

+- 95 Confidence Interval n

FRACTION ORGANIC CARBON

(gg)

170E-03 185E-03 185E-03 170E-03 240E-03 190E-03 230E-03 180E-03 170E-03 115E-03 195E-03 220E-03 220E-03 235E-03 135E-03 190E-03 205E-03 175E-03 160E-03

188E-03 185E-03 185E-03 327E-04

1739 123E-03 to

19

205E-03 130E-03 150E-03

162E-03 150E-03 159E-03 388E-04

2402 840E-04 to

3

2532E-03

2393E-03

Hows Corner Tl Evaluation Appendix B January 13 2005

Response to EPA-DEP Comment 4 Dated March 31 2005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

EPA-DEP Comment 4

Comment 4 Distribution of contaminants First the TI report seems based on the assertion that there is DNAPL at the source area yet it also appears to represent that the source area is small and the bedrock below 85 is competent (or less fractured) and less impacted by the release of contaminants Some of the confusion may result from using most recent data when that data is from several different sampling events over several years and there is no discernible difference in concentrations between shallow and deep bedrock or as in Section 421 where generally decreased generally increase generally similar and similar concentrations in four consecutive sentences leads to a muddled picture of the contaminant distribution

Second the report asserts that the distribution of contaminants over the entire plume has not changed with time but fails to support this conclusion with data again relying on data that is from different sampling dates for one composite representation

Response The likely presence of dense non-aqueous phase liquid (DNAPL) at the Hows Corner Site and the determination that the source area is small are not mutually exclusive and both are conclusions drawn from information obtained during field investigations The presence of DNAPL in the source area is based on the elevated concentrations of volatile organic compounds (VOCs) detected in the groundwater (WampC 2001 WampC 2002) The conclusion that the source area is small is based on the area in which VOCs in groundwater have been detected at concentrations that are considered to be indicative of the presence of DNAPL nearby Similarly the conclusion that fracture frequency decreases at depths greater than approximately 50 to 85 feet below ground surface was based on field observation during the RI field work The fact that zones with observed fractures exhibited higher hydraulic conductivities than zones without fractures coupled with the decreasing frequency of observed fractures with depth led to the conclusion that the hydraulic conductivity of the bulk rock decreases with depth

The most recent data from all wells were used to provide the maximum VOC data set size During the RI all of the previously-existing and then newly-installed monitoring wells were sampled along with several residential wells The RI sampling included up to 48 monitoring wells Subsequent to the RI and prior to the TI three rounds of monitoring were conducted to verify that the plume was stable 15 monitoring wells were sampled during each of the three rounds During the TI field investigation 29 wells were sampled for VOCs The sampled wells included all of the newly-installed wells and a subset of wells installed during the RI for a total of 29 monitoring wells By using most recent data VOC results from 53 monitoring wells were included in the evaluation (see table labeled Sampling Events for listing of monitoring wells) This approach was selected because there generally was little variation in the data from a particular location between years This is borne out by the attached individual plots of VOCs detected in shallow bedrock and deep bedrock for the Pre-ROD (December 1999January 2000) and Supplemental (May 2000) sampling events and for June 2001 January 2002 and April 2003 sampling events The Pre-ROD and Supplemental plots are similar to the subsequent plots from the 2001 2002 and 2003 sampling events

In addition to maps showing the spatial distribution of VOC data at a given time trend plots of the data from a particular location through time (attached) indicate that since the RI concentrations generally have been stable or have decreased Together the maps and trend plots and the data from which they were developed indicate that the distribution of contaminants over the entire plume has not changed appreciably with time

Response to EPA Comment 4 050305doc 1 of 26 Woodard amp Curran (211941)

REFERENCES

Woodard amp Curran Inc (WampC) 2001 Final Remedial Investigation Report Hows Corner Superfund Plymouth Maine July 2001

Woodard amp Curran Inc (WampC) 2002 Final Feasibility Study Report - Non-Source Area Groundwater Hows Corner Superfund Site Plymouth Maine Hows Corner Superfund Plymouth Maine July 2002

Response to EPA Comment 4 050305doc 2 of 26 Woodard amp Curran (211941)

LIST OF ATTACHMENTS (Response to Comment 4)

Table - Sampling Events 1999 - 2004 (2 pages)

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater Pre-ROD Sampling Event

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater Pre-ROD Sampling Event

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater Supplemental Sampling Event

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater Supplemental Sampling Event

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater June 2001

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater June 2001

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater January 2002

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater January 2002

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater April 2003

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater April 2003

Figure - Concentration Trends - Non-Source Area Wells MW-1B and MW-3B

Figure - Concentration Trends - Non-Source Area Wells MW-13DB and MW-16DB

Figure - Concentration Trends - Non-Source Area Wells MW-16IB and MW- 108D

Figure - Concentration Trends - Non-Source Area Wells MW-108S and MW-112D

Figure - Concentration Trends - Non-Source Area Wells MW-112S and MW-114D

Figure - Concentration Trends - Non-Source Area Wells MW-114S and MW-115D

Figure - Concentration Trends -Source Area Wells MW-2DB and MW-2IB

Figure - Concentration Trends -Source Area Wells MW-102S and MW-103D

Figure - Concentration Trends -Source Area Wells MW-103S and MW-104D

Figure - Concentration Trends -Source Area Wells MW-104I and MW-106D

Figure - Concentration Trends -Source Area Wells MW-106S

Response to EPA Comment 4 050305doc 3 of 26 Woodard amp Curran (211941)

I I

El I

II I I 1 I

I

i

Event Baseline Case ID WC-01 WC-01

Well Date Aug-99 Oct-99 LOT10 1 LOT1-1 1 LOT11-4 LOT14 1 LOT15 1 LOT15-1 1 LOT16 1 LOT16-1 1 LOT17 1 LOT18 1 LOT19 1 LOT2 LOT20 1 LOT21-10 1 LOT21-11 1 LOT21-12 1 LOT21-13 1 LOT21-14 1 LOT21-2 1 LOT21-5 1 LOT21-7 LOT21 -8 1 LOT21-9 1 LOT23 1 LOT24 1 LOT28-1 1 LOT28-2 1 LOT28-3 1 LOT28-4 1 LOT28W 1 LOT30 1 LOT30-1 1 LOT30-2 1 LOT30-3 1 LOT30-4 1 LOT30-5 LOT31 LOT35 1 LOT41 1 LOT42-1 1 LOT43-1 1 LOT43-4 1 LOT6-1 1 LOT67 1 LOT6-7 1 LOT6-8A 1 LOT6-8B 1 LOT80-1 1 LOT82 1 MW-101D MW-1011 MW-101S MW-102D MW-102S MW-103D MW-103S MW-104D MW-1041 MW-104S MW-105D MW-106D

Groundwater Sampling Location Summary 1999 - 2004xls

Sampling Events 1999-2004

Hows Corner Superfund Site Plymouth Maine

Supplemental 2001 2002 2003 Pumping 2004 Pre-ROD Rl Sampling Sampling Sampling Test Sampling WC-03 WC-09 WC-25 WC-30 WC-42B WC-56 WC-58 Dec-99 May-00 Jun-01 Jan-02 Apr-03 Sep-04 Sep-04

1

1 1 1

1 1 1 1 1

1 1

1

1 1

1 1 1

1 1 1 1 1

1

1 1

1 1 1 1

1

1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

Sampling Events 1999-2004

Hows Corner Super-fund Site Plymouth Maine

Supplemental 2001 2002 2003 Pumping Event Baseline Pre-ROD Rl Sampling Sampling Sampling Test

Case ID WC-01 WC-01 WC-03 WC-09 WC-25 WC-30 WC-42B WC-56

ll

Well Date Aug-99 Oct-99 Dec-99 May-00 Jun-01 Jan-02 Apr-03 Sep-04 MW-106S 1 1 1 1 1 MW-107D 1 1 MW-108D 1 1 1 1 1 MW-108S 1 1 1 1 1 MW-110D 1 1 MW-111D 1 1 MW-112D 1 1 1 1 1 MW-112S 1 1 1 1 1 MW-113D 1 1 MW-114D 1 1 1 1 1 MW-114S 1 1 1 1 1 MW-115D 1 1 1 1 1 MW-12DB 1 1 1 MW-12SB 1 1 1 MW-13DB 1 1 1 1 1 1 MW-13SB 1 1 1 MW-14DB 1 1 MW-14SO 1 1 MW-15DB 1 1 1 MW-15SB 1 1 1 MW-16DB 1 1 1 1 1 1 MW-16IB 1 1 1 1 1 1 MW-16SO 1 1 MW-17DO 1 1 1 MW-17SO 1 1 1 MW-1B 1 1 1 1 1 1 MW-203D MW-203S MW-204D MW-204S MW-205 MW-206D

I MW-206S MW-2DB 1 1 MW-2DDB 1 1 MW-2IB 1 1 1 1 1 1 MW-3B 1 1 1 1 1 1

I MW-4O 1 1 1 MW-5B 1 1

II MW-6DB 1 1 1 MW-6SB 1 1 1 MW-8DB 1 1 1 MW-8SB 1 1 1

II PW-207 1 SEEP-1 1 SUBTOTAL - RESIDENTIAL 44 25 0 2 0 3 0 SUBTOTAL - MONITORING 22 48 41 15 15 15 1

Total 3 66 73 41 17 15 18 1

I Included in most recent data

I Notes 1 - Overburden well not included in most recent data for plotting

2 - Tetrahydrofuran and 2-Butanone were the only two compounds detected in this well and are thought to be the result of well repair not included in most recent data for plotting

3 - Not included in most recent data for plotting

2004 Sampling

WC-58 Sep-04

1

1 1

1 1

1 1 1

1

1 1

1 1 1 1 1 1 1 1 1

1 1

1

0 29

29

Groundwatef Sampling Location Summary 1999 - 2004xls

I

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

monitoring well Figure 4-14 total VOC contour (ugl) - December 1999January 2000 Distribution of Total VOCs in

Note SW-113 is located downstream of SEEP-1 Shallow Bedrock Groundwater total concentration of detected VOCs ND= not detected these two locations were sampled during the Pre-ROD Sampling Event

Baseline Sampling Event in OctoberNovember 1999 Hows Corner Superfund Site Surface Water Sampling Location A Plymouth Maine Seep Sampling Location laquo- WOODARD ampCURRAN

995037wipri reportepa ri interim final feb 2001cadd drawingsfinalfig 4-14

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

0 300 600 I

FEET

Q residential well Figure 4-16 monitoring well Distribution of Total VOCs in

Deep Bedrock Groundwater total VOCs contour (ugl) Pre-ROD Sampling Event

active residential wells with lot number Hows Corner Superfund Site 2deg42deg Plymouth Maine total concentration of detected VOCs ND= not detected WOODARD ampCURRAN Enyinaaring bull Science bull Operations bull

995037wipri reportepa ri interim final feb 2001cadd drawingsfinalfig4mdash16

PLYMOUTH POND

PLYMOUTH POND

1 628Tl7MW-2bB 12135

PLYMOUTH POND

monitoring well Figure 4-20

V total VOC contour (ugl) - June 2000 Distribution of Total VOCs in Shallow Bedrock Groundwater

| 34 | total concentration of detected VOCs ND= not detected NA = not analyzed Supplemental Sampling Event Note SW-113 is located downstream of SEEP-1 Hows Corner Superfund Site

Surface Water Sampling Location these two locations were sampled during the Plymouth Maine Baseline Sampling Event in OctoberNovember 1999 Seep Sampling Location WOODARD amp CURRAN

Engineering bull Science - Operations bull 995037wipri reportepa ri interim final feb 2001 cadd drawingsfinalfig 4-20

residential well Figure 4-22 Distribution of Total VOCs in

monitoring well Deep Bedrock Groundwater

total VOCs contour (ugl) Supplemental Sampling Event

Hows Corner Superfund Site

total concentration of detected VOCs ND= not detected NA = not analyzed Plymouth Maine

WOODARD amp CURRAN

995037wipri reportepa-ri interim final feb 2001cadd drawingsfinalfig 4-22 Engineering bull Science - Operations bull

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

FEET

Shallow Monitoring Well

Deep Monitoring Well

C Detected Concentration ND = Not Detected Figure 1-XS Distribution of Total VOCs in Shallow Bedrock Groundwater

Pumping Well

17-Acre Property Boundary Concentration Contour (ugl)

June 2001 Hows Corner Superfund Site

Plymouth Maine WOODARDampCURRAN

-i^rhvj bull Scbncn bull Operations bull 211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0601 dwg04-20-05

PLYMOUTH POND Hopkins Road V

O

PLYMOUTH POND

PLYMOUTH POND

o

0 300 600 mdashfa FEET

Shallow Monitoring Well bull bull - 17-Acre Property Boundary Figure 1-XD

Deep Monitoring Well 1 I Detected Concentration ND = Not Detected Distribution of Total VOCs in Deep Bedrock Groundwater

-mf- Pumping Well June 2001 Residential Well Hows Corner Superfund Site

Plymouth Maine i h Surface Water Sampling Point

g WOODARD ampCURRAN _ ^ _ ^ _ _ yen_ rj i|Hlaquorlny bull Science bull Opt

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0601 dwg04-20-05

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

Shallow Monitoring Well

Deep Monitoring Well

Detected Concentration ND = Not Detected Figure 1-YS Distribution of Total VOCs in Shallow Bedrock Groundwater

Pumping Well

17-Acre Property Boundary Concentration Contour (ugl)

January 2002 Hows Corner Superfund Site

Plymouth Maine WOODARD amp CURRAN Engineering Science- Operations bull

211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0102dwg04-20-05

PLYMOUTH POND

PLYMOUTH POND

Site Pand^ laquoum-laquoBTuitaraquo tLV

vVlf-(

PLYMOUTH POND

0 300 600 ^ = FEET

Shallow Monitoring Well mdashbullbullbull 17-Acre Property Boundary Figure 1-YD - A - Deep Monitoring Well FT Detected Concentration ND = Not Detected Distribution of Total VOCs in

Deep Bedrock Groundwater Pumping Well January 2002 Residential Well Hows Corner Superfund Site

Plymouth Maine Surface Water Sampling Point

WOODARD ampCURRAN Engineering Sciencs- Operations bulli Si

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0102dwg04-20-05

- m j

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND j A O-shy

Shallow Monitoring Well E Detected Concentration ND = Not Detected Figure 1-ZS Distribution of Total VOCs in

Deep Monitoring Well Shallow Bedrock Groundwater

Pumping Well Hows Corner

April 2003 Superfund Site

17-Acre Property Boundary Plymouth Maine Concentration Contour (ugl) r WOODARD ampCURRAN

Engineering bull Science bull Operations bull 211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0403dwg04-20-05

s S pound

PLYMOUTH POND

PLYMOUTH POND

- -

5 PLYMOUTH POND

Jo

FEET

ft Shallow Monitoring Well mdashbullbullmdash 17-Acre Property Boundary Figure 1-ZD Deep Monitoring Well I 1 I Detected Concentration ND = Not Detected Distribution of Total VOCs in

Deep Bedrock Groundwater Pumping Well April 2003

Q) Residential Well Hows Corner Superfund Site Plymouth Maine

(T) Surface Water Sampling Point WOODARD ampCURRAN poundKk EnginawtirKj bull Science - Operations bull

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0403dwg04-20-05

0 Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

B MW-1B

I 12000

PCE

B 10000 Total VOCs

I

i 2000

i 0 Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

c MW-3B

G 2000

1800

B PCE

1600 Total VOCs

1 I I E

il-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

G E

211941

El

I I z E

80

Concentration Trends shy Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-13DB

Total VOCs

c i i c o

Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

MW-16DB

30

c i c c I c o

Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99

PCE

Total VOCs

Jul-01 Jul-03

211941

O bi

c Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

I MW-16IB

i 35

3

c Total VOCs

lt- 2 5

0 | gt

o

1 sectI

c c 0 4

Jul-90 Jul-92 Jul-94 Jul-96 Jul-98 Jul-00 Jul-02 Jul-04

I I MW-108D

I 12

PCE 10

Total VOCs c oc 3

E E I 0

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

E 211941

c Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

fi MW-108S

I I 40

PCE 35

Total VOCs

30

I f 26

20 I o

I 15

10

c Dec-99 Dec-00 Dec-01 Dec-02 Dec-03 I 0

I MW-112D

c 35 - imdash

I A3 shyTotal VOCs

o c

E 1 2

I

ition

B 1 ^

-i c 3

0 Dec-99 Dec-OO Dec-01 Dec-02 Dec-03

211941

I

i

I

cII

Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-112S

08

PCE

Total VOCs 06

o 04

02

0 Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

MW-114D

o

12000

10000

8000

6000

PCE

Total VOCs

4000

2000

i

ccEIIc

i

i

E

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

211941

Con

cent

ratio

n (

ug

l)

E Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

I MW-114S

E A5000 -- Total VOCs

- 4000

0 3000

2000

i 1000

i n shy

Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

MW-115D

c PCE

Total VOCs

c E

o

C c

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03 I 0

211941

IepoundII

EIEIIGICCIccc

30000

25000

20000

o bullsect 15000 b

o 10000 U

5000

0 Aug-99

25000

20000

5000

0 Aug-99

211941

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-2DB

PCE

Total VOCs

Aug-01 Aug-03

MW-2IB

PCE

Total VOCs

Aug-01 Aug-03

IDIBI

ii EIDIISIBIG C

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-102S

6000

5000 PCE

Total VOCs

4000

O 3000

2000

1000

0 Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

MW-103D

16000

~ 14000 ugt 3- 12000 o

^ 10000

sect 8000

O 6000

4000

2000

PCE

Total VOCs

0Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

211941

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

G MW-103S

I I

ampo

12000

10000

E sectc

S

8000

6000

4000

2000

0Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

G I 6000

MW-104D

i 5000

PCE

Total VOCs

i i c

2000

1000

Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

E I

211941

cIccIG

IIBCccBcIc

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-1041

PCE Total VOCs

a 25000

0 20000

a 15000

10000

5000

0 Jan-OO Jan-01 Jan-02 Jan-03 Jan-04

MW-106D

3000

2500 PCE

Total VOCs

=sect 2000

o bullsect 1500

1000

500

0 Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

211941

c Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

c MW-106S

I PCE

Total VOCs

i

i Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

i

i i i E

C

211941 c

Response to EPA-DEP Comment 5 Dated March 312005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

iiw

EPA-DEP Comment 5

Comment 5 Matrix Diffusion The report as well as other proponents of matrix diffusion suggest that depletion of DNAPL (Section 5112 page 5-15) needs to be achieved While that might be the ideal the goal is to achieve performance standards and that goal may be attainable while there is residual contamination in the rock perhaps even DNAPL globules The low bedrock matrix porosity (page 1-15) the high permeability values (page 4-4) the relative flux of the groundwater (page 5-5) and the decrease in surface area and out of the mainstream pockets (appendix C-4) all suggest that the diffusion out of the rock matrix would be insubstantial relative to the regional flux of groundwater through the Site

Response The TI Evaluation Report does not explicitly consider or rely upon matrix diffusion as a basis for requesting a TI Waiver for a portion of the Hows Corner Site The technical literature provides documentation that matrix diffusion can be a significant process that affects chemical transport and groundwater remediation timeframes in unconsolidated and consolidated media including fractured rock (US EPA 1989 Freeze and Cherry 1979 Pankow and Cherry 1996 Fountain 1998) Back diffusion of contaminants from the matrix porosity of the fractured rock can prolong the time necessary to achieve groundwater cleanup goals particularly for compounds such as PCE for which the cleanup goal is a low concentration It is our expectation that matrix diffusion has occurred at the Hows Corner Site and that back diffusion of PCE from the rock matrix will also occur Although the extent to which matrix diffusion is occurring at the Hows Comer Site has not been determined and that lack of knowledge contributes to uncertainty regarding the cleanup times at the Site the effect of matrix diffusion is to lengthen rather than shorten the time required for remediation

REFERENCES

Fountain JC 1998 Technologies for Dense Nonaqueous Phase Liquid Source Zone Remediation Ground-Water Remediation Technologies Analysis Center Technology Evaluation Report TE-98-02 December

Freeze RA and Cherry JA 1979 Groundwater Prentice-Hall Inc Englewood Cliffs NJ 07632 p 410-412

Pankow J F and Cherry J A 1996 Dense Chlorinated Solvents Waterloo Press Portland OR 97291-1399 p 67-88

US EPA 1989 Transport and Fate of Contaminants in the Subsurface EPA6254-89019 p 17-18

Response to EPA Comment 5 050305doc 1 of 1 Woodard amp Curran (211941)

WOODARD amp CURRAN Maine Massachusetts New Hampshire Connecticut Florida Operational offices across the US 1-800-426-4262 www woodardcurran com

Page 17: SDMS DocID 251749 - Records Collections · 2020-06-13 · CORPORATE OFFICES: Maine, Massachusetts, New Hampshire, Connecticut New, York, Florida Engineering • Science • Operations

29212 MW-108D

(MEDEP Pond 1) Farm Pond

Monitoring Well

Pumping Well

mdashbullbulllaquo 1 7-Acre Property Boundary

bull Groundwater Elevation Contour (ft)

1419001 Groundwater Elevation

211941 Hows CornerwipDrawingsTI EVALPotSurf-72hrs_deepdwg04-19-05

150 300 =5fc= FEET

Figure X Potentiometric Surface at 72 Hours

Deep Wells Hows Corner Superfund Site

Plymouth Maine

WOODARDampCURRAN Engineering bull Science bull Operations bull

--

Pumping Test Analytical Results Hows Corner Superfund Site

Plymouth Maine

Well ID oper Jaccb Analyses 2 Theis Analyses Fissure

Well Id Rd (ft)

Saturated Thickness

Transmissivity

(ft2day) K

(ft2day) K

(cmsec) Storage

Coefficient Transmissivity

(ft2day) K

(ft2day)

K (cmsec)

Storage Coefficient

System K

(ftday) PW-207OB 8 85 481 057 200E-04 392E-02 36 042 150E-04 809E-04 027 MW-103S 50 85 451 053 187E-04 720E-03 92 108 382E-04 283E-04 083 MW-103D 54 185 455 025 868E-05 210E-02 65 035 123E-04 237E-04 044 MW-2IB 59 85 352 041 146E-04 699E-03 104 123 433E-04 512E-04 052 MW-2DB 63 85 334 039 139E-04 845E-03 148 080 283E-04 239E-04 046 MW-104D 95 185 489 02 6 932E-05 654E-03 98 053 186E-04 547E-05 037 MW-104I 97 85 33 03 9 137E-04 362E-03 117 137 484E-04 962E-05 048 MW-101I 107 85 364 043 151E-04 490E-03 511 601 212E-03 223E-04 136 MW-102D 134 185 435 024 829E-05 248E-03 108 058 206E-04 850E-05 065 MW-101D 138 185 492 027 938E-05 511E-03 671 362 128E-03 700E-04 172 MW-205 219 85 57 067 237E-04 255E-03 447 526 186E-03 359E-03 -shyMW-204D 221 185 367 020 700E-05 170E-03 790 427 151E-O3 155E-04 147 MW-204S 225 85 379 045 157E-04 156E-03 1031 1213 428E-03 313E-04 199 MW-1B 228 85 325 038 135E-04 977E-04 340 400 141E-03 739E-05 054 MW-203S 273 85 489 058 203E-04 117E-03 1255 14 76 521 E-03 216E-04 210 MW-106D 278 185 51 028 972E-05 141E-03 1065 576 203E-03 360E-04 104 MW-203D 278 185 478 026 911E-05 152E-O3 765 414 146E-03 364E-04 138 MW-105D 364 185 44 024 839E-05 830E-04 769 415 147E-03 200E-04 127

1 Analyses conducted using Cooper and Jakob method on late drawdown data collected during constant

discharge pumping test conducted at the Hows Comer Site from September 20 - 30 2004

2 Analyses conducted using Theis solution for unconfmed approximation (1935)

J Analyses conducted using Moench method for dual porosity estimation (1984)

Fissure System Storage

Coefficient 402E-04 117E-06 264E-04 300E-04 932E-05 235E-07 502E-05 326E-06 801E-05 542E-04

-

803E-05 762E-05 134E-05 498E-05 115E-04

47E-04 838E-05

3 ysesh Analysis

Block System K (ft2day)

251E-02 207E-03 564E-04 163E-04 585E-04 465E-02 153E-04 498E-03 855E-04 356E-03

-

292E-03 394E-03 720E-04 526E-03 160E-01 35OE-O1 287E-03

Block System Storage

Coefficient

402E-02 164E-04 183E-02 330E-03 158E-03 847E-03 286E-03 326E-04 803E-05 272E-03

723E-04 686E-04 148E-04 349E-04 115E-03 47E-04 838E-04

Theis - Moench - CJ - AnalyticalResults_4-19-O5xls

DRAFT

242

24

238

236

bulla

c

i

a Q

234

232

228

226

Hows Corner Constant Discharge Testing USGS Background Groundwater Level USGS 445319068560101 ME-PEW456 Kenduskeag Maine

End of Monitored Recovery Period 09302004

Regional Background Location i 226 miles from Pumping Locatio

lt

697

NOTES

1 Groundwater samples collected in 1999 were screened for five volatile organic compounds (VOCs) only N

tetrachloroethene (PCE) exceeded reporting limits MW-2030 082304 082304 082304 082304 u

2 Strike and Dip of likely or possible transmissive 30 45 55 85 feature within the packer interval from which the indicated sample was collected

MW-204D

PCE TOTAL VOCs

081904 30

220 2636

A

081904 46-50 540 6436by

081904 IT

260 3073

x

MW-105D

PCE TOTAL VOCs

111199 50-60 2100 2100

MW-106D

PCE TOTAL VOCs

111199 76-86

400 400

111199 137-147

1400 1400

111299 1355-1455

350 350

PCE TOTAL VOCs

44 84

64

MW-6SB

bulli

lt

gt-

170 234

35

I I i

140 192

^^52

^^52

130 183

52 - lt

S A 34

PW-207 082404 082404 082404 20 37

PCE 1300 TOTAL VOCs

17-Acre George West Property Boundary

MW-113D

PCE TOTAL VOCs

112299 46-56

350 350

112299 70-80 190 190

150

112299 105-115

129 129

112399 138-148

230 230

L e g e n d ( J New Monitoring Well-Summer

Site Property Boundary ^ P u m p i n g Well-Summer 2004

-xmdashxshy Source Area

bull0shy Monitoring Well shy Pre 2004 Angled Boring-Summer 2004

211941laquoipdwgTI-ELV21ig41paltker-data2

2004 PCE of Total

bull lt70 VOCs

M W - 1 14D ^ ^

Figure xx Packer Testing Results in

Vicinity of Source Area Hows Corner Superfund Site

Plymouth Maine ^ WOODARD ampCURRAN

^^^^^^^^^^m ampKm Engineering - Science bull Operations

c Northeast Geophysical Services Borehole Geophysical Log

MW-203 Date logged 081704 Plymouth Maine

I Flowmeter Measurements Tomporaturo(C) Acoustic Televiewer

7 5 8 8 5 9 95 Caliper (Inches) Resistance (Ohms) Spontaneous Potential (mVj Dip In Degrees PCE Total VOCs

3 0 2 0 8 0 laquodeg 4S 1000 1400 1800 2200 MO HO 1000 1200 MOO 0 laquo deg ugL ugL n 1 1 1 1 1 1 1 1 1 i 1 1 1 1 n 1 1 1 1 1 1 1 1 1 1 1 n I l l l l l l l n

Ambient Flowneter pumping Rowmeter 11 gpm 6

H

bull

magnetic 10 bull 10 bull - 10 - north - 1 0I

-

_

bullbullbull - bull

20 bull bull20 bull ^ ltr~mdash 01

I

4 ^

LOS7

^

44 84 I I

Xr - 2

lt ^ bull30 -_ _^O1J- 1 _ 050 30 - 3 0

0r - - 3

C -j [ bull bull bull | shy

-O8 H ~ 1 045 7

1 4040 - 40 - -40 r - 14gt 13

V1s -- -023 f 1022 1V 170 234 I

T lt bull B gtf 50^ J50 - - 5 0 - - 5 0

I eet be

lo

i 1

1 1

1

140 192 - - - -t shy

-mdashj bullpound 60 - $o - - 60 - -60

H i I c

bull024

ampbull

3 - T lt ftft rgt He

70 bull j 70 - - 70 - 7 0 -

in -j bullbull shy

-021 1 T 022

- Ton _ Ov

26

130 183 NF NF

90 -_ 90 - 7 90 - -90

-

ifi Jf

3J

^gt _ N F NF bull bull shy

| H100 - j 100 bullbull 100 - -100

1 1 1 1 1 1 1 ) | 1 f I 1 1 1 ) 0 20 40 60 80

flft mdash ftn - mdash rVt

30 4 g 0 20 40 60 Dip in Degrees bullbull

Likely or poss bleFluid Resistivity (ohmmeters) The dip direction-- indicated

^ t h e l i n e extending from t h

I Iransmissive zone circle The strike of the feature is 90 degrees from this

The acoustic televiewer graph displays the mostprominent features selectedffom the acoustic televiewer

R n r a h n l c D O t t n O I B

f i o n n h w c i r a l U K U p i i y SI Ud l

1 rn l_Og Packered Interval August 2004

E tog The location dip angle and dip direction of the sleeted M W - 2 0 3 Groundwater samples were collected by Woodard S Curran on H23120M features are approximate Refer to the televiewer og of His _ well for more precise detail Plymouth Maine Date logged 081704

I

1

Northeast Geophysical Services Borehole Geophysical Log MW-204 D a t e l o gge d 072604

Plymouth Maine

n 3

Flowrneter Measurements(in gpm)

Caliper (Inches)0 3 5 4 0

1 1 1 1 1 1 1 t 1 1 1 1 1 1Ambient Rowmeler pumping Flowmetsr 05gpm

Templaquorature (C) bull bull bull bull i

7 75 8 8S 9 Resistance (Ohms) Spontaneous Potential (mV)

4000 SOW 600 4M 0

Acoustic Televiewer (interpreted)

Dip in Degrees 0 20 4060 SO

at N

PCEugL

Total VOCs ugL

- -_ a

10-

shy 10 bull - 10 shymagnetic

north - 10

o o

bull 1

11

11

1 1

1 1

11 1

1 1

1 1

1 1

1 1

1 1

1 1

1 1

1 1 E 1

- L

3 7 2 0 2 0r bull 20 bull - shy

i S_ N F

bull30 bull 7 3 0 220 2636shy1^ J J 004

fI f V ^

40 shy 4 0 4 0 shy - 4 0rbull019 [_ 007 w8 - - shy5 c

bull

gt

Ia50i 540 6436

bull50 - - 50 - - 5 0

-QQ7 - bull - -t T

pound V gtk

B 6 0 - e o - 7 6 0 -60shyQ 1 1

Q -007 -004 bull1 mdash T - J ~

bull

- - shyT 70 -J c [TO- - 70 - 7 0-

V Y 1- -004 -003

mdash T -h - y - j i - - mdash 260 3073 - gt=7

80 -j NF bull80 - - 80 - - 8 0Jgt

bull i

i 1

i i

C- bull shy

90 shy

K

Jlt i90 90 shy - 9 0shy -

l

ii

I I I I

NF bull M J

I ^ ^ - ^ bull 1

mdash mdash - _

s -7 ^100shy

till

1 100 100- H - 1 0 0shy -1 x Likety or possible k ^ Iransmissive zonebull

1 i i i ii i i i | l l l l | l i l l 0 20 40 ED 80

1 -

3 0SOFluid Resistivity (ohmmeters)

Dip in Degrees The djp ^ ^ o n is indicated ty Ihe line extending from tha circle The strike of Ihe feature

19- 3U UIHJIW93 IolII l l l lraquo

bull

The acousfc televiewer graph displays the mostprominent features selected from the acoustic televiewer109 The location dip angle and dip direction of Ihe sleetedfeatures are approximate Refer to the televiewer log of thiswentormore precise detail

B o r e h o l e G e O D h V S I C a l LOO B W H U I B w c w p n y o i v a i w v yM W - 2 0 4

P l y m O U t n MaiDB

Packorod Interval August 2004Groundwater san-ples wampramp collected by Woodard a Curran on OMO23C4

Date logged 072604

C

I

E Northeast Geophysical Services Borehole Geophysical Log Date logged 072704

I MW-205

Plymouth Maine

Flowmeter Measurements Temperature (C) Acoustic Televiewer (In gpm) I ~l (Interpreted)

I 85 10 Caliper (inches) 95

Dip in D g r laquo Resistance (Ohms) Spo ontaneous Potential (mV PCE Total VOCs 3 0 16 4 0 4 5 ) 20 40 60 80 10 00 2000 30 00 4VJ 400 -3 laquo

i i i i 1 i i I i 11 4 0 D 1 I I ugL ugL

C h

iii Ambient Flowmetar pumping

Flowmeter 1 25 gprn

I bull$bull

i

I rmdash magnetic 1 north ^^^^ 1 VI f

10 ~ I C x 10 bull - 10 bullbull

4 5 6mdashmdash f 1000B 11448 noisy nodi a raquo ^

mdash 5rt mdashi mdash Oft pound) 1100B 12509

cjmdash1 007

-

i i i 1

en

8 B a B

30 mdash

-

40 shy

-mdash I -

50 -_

__NF lt005

- 30 - - 3 0 it 34V

MO P26 V S) 1300B 13776 _ N F NF

26

40 bull - 40 bull 7-40 gt J Vf1 cX

) -j -

_ N F NF 50 c bull - 50 ^ 7-50

i I

I

c

B pound 60 - 6 0 7 60 - 7-60 a i 1

_ N F NF i Si f f 70 -_ bull70 bull - 70 shyC I 9

-m bull - shyA

_ N F NF 80 80 -j bull80 bull - 80 - C- 33 34

bull

5-i r

i 1

J r

Ck

_ N F NF 9 0 90 - - 90 shy

i bullCshy

J rK bull

100 -j ^ Likely or possible bull100- - 100- I -100

transmissive zone bull - ^ bull shy] |

1 1 1 1 1 1 1 I 1 i i i 1 i i 1 1 0 20 40 SO SO 10 20 30 40 50 Dip in Degrees 30 4 0 Fluid Resistivity (ohmmeters) Thlaquo dip direction is indicated

by the line extern r g from the circle The strike of he feature is 90 degrees from ihis

The acoustic televiewer graph displays the most

I Borehole Geophysical Log Packered Interval August2004 prominent features selected from the acoustic televiewer

Groundwatcr samples were oollccled by Woodard amp Cufran orgt S172004 log The location dip angle and dip direction of ins slsctsd MW-205 features are approximate Refelt to the televiewer log of this wall for more precise detail Plymouth Maine Date logged 072704

I

C

I Northeast Geophysical Services Borehole Geophysical Log Date logged 072704

I MW-206

Plymouth Maine

Flowmetor Measurements Temperature (C) Acoustic Televiewer | I r T i i i i i i i i i i i i i i r I |(in gpm) (Interpreted)

I 75 8 flS 9 95

Caliper (inches) Resistance (Ohms) Spontaneous Potential (mV) Dip In Degress PCE Total VOCs 30 35 40 4 5 0 20 40 M 90 4500 5500 6500 ugL ugL I i i

I I

- 1 0

I - 2 0

I 2900B 32401

i i L

E 0

i 6300B 68901

i I 0 20 40 SO 80

20 30 40 50 Dip in Dlaquogralaquos

amp 4 a Fluid Resistivity (ohrnmeters) The dip dirertion is indicated Likely or possible by iho line extending from the transmissive zone circle The striKe of the feature

is 90 degrees from tNs

Borehole Geophysical Log Packered Interval August 2004

E amples were collected by Woodard amp Cunan oo SM82004 log Thraquo location 4p angle and dip direction of the sloeled MW-206 feature are approximate Refer to the televiewer 109 of this well for more precise detail Plymouth Maine Date logged 072704

C

I Northeast Geophysical Services Borehole Geophysical Log

Date logged 082304 PW-207

I Plymouth Maine

Fiowmeter Measurements Temperature (C) Acoustic Televiewer

I (in gpm) (interpreted)

75 8 85 9 95 Caliper (inches) Resistance f0tims) Spontaneous Potential (mV) Dip in Degrees PCE Total VOCs

55 60 0 20 40 SO 80 ugL ugL I I I I I I I

Ambienl Fiowmeter pumping Flewmater

magnetic - 10 - - 1 0

north

i - 20 - - 2 0

1300 1410

i - 30 - - 3 0

i tf

5400 5802 - 40 - - 4 0

B - 50 - - 5 0

I 18000 19234

- 60 - - 6 0

I 12000 13085

- 70 - - 7 0

- 8 0

i - 9 0 19000 20354

G - 100- -100

I 110 110 bull110

0 20 40 60 SO 10 20 30 Dip m Degrees

Fluid Resistivity (ohmmeters) I 50

The dip direction is indicated by ihe line extending from the circle The strike of the fealure is 90 degrees from this

Borehole Geophysical Log

G Packorod Interval August 20(M log The location dip angle and dip dirlaquocton or the sleeted Groundaier samplss were ooliecled by Woodard i Curran on ampt24f2ltXM PW-207 failures are approximate Reter to the televiewer log of this wlaquoll for more precise detail PlyPIOUth Maine Date logged 082304

I

Table XX Packer Permeability and Packer Sampling Results for Potential Fracture Intervals

1

WellID MW-101D MW-101D MW-101D MW-101D MW-101D MW-101D MW-101D MW-101D MW-101D MW-101D MW-I01D MW-101D MW-101D MW-102D MW-102D MW-I02D MW-102D MW102D MW-102D MW-102D MW-102D MW-102D MW-I02D MW-102D MW-102D MW-102D MW-103D MW-103D MW-103D MW-103D MW-I03D MW-103D MW-103D MW-103D MW-103D MW-103D MW-103D MW-103D MW-I03D MW-104D MW-104D MW-104D MW-104D MW-I04D MW-104D MW-104D MW-104D MW-104D MW-104D MW-104D MW-105D MW-105D MW106D MW-106D MW-106D MW-107D MW-107D

1999 Drilling Program

Hows Corner Superfund Site Plymouth Maine

Potential Fracture Top Of Bottom 6 Depth to lt Topof i Interval from Packer Packer Middle of Elevation Hydraulic bull PCE

GS ELEV 1 Rock Drilling Interval Interval Interval of Interval Conductivity Concentration (ft msl) (ft msl) TEST (ftbgs) (ftbgs) r(ftbgs) ( f t b (ft mil) (cmsec) (raquogL)

4339 4329 13 28-29 33-3537-39 271 376 324 4016 OOOE+00 4339 12 37-3444-46 380 485 433 3907 157E-04 4339 11 488 593 541 3799 132E-04 4339 10 60-61 578 683 631 3709 OOOE+00 4339 9 678 783 731 3609 I79E-05 4339 8 778 883 831 3509 106E-05 4339 7 880 985 933 3407 243E-05 4339 6 990 1095 1043 3297 339E-06 4339 5 1090 1195 1143 3197 OOOE+00 4339 4 1190 1295 1243 3097 OOOE+00 4339 3 1365-1375 1290 1395 1343 2997 OOOE+00 4339 2 147-157 1390 1495 1443 2897 580E-05 4339 1 147-157 1470 1575 1523 2817 741E-05 43161 43061 13 166 271 219 4098 333E-04 43161 12 30-3136-40 260 365 313 4004 I54E-05 43161 11 36-4041-43 362 467 415 3902 548E-05 43161 10 470 575 523 3794 598E-05 43161 9 570 675 623 3694 197FOS 43161 8 670 775 723 3594 OOOE+00 43161 7 770 875 823 3494 891 E-05 43161 6 83-94 870 975 923 3394 139E-05 43161 5 970 1075 1023 3294 123E-04 43161 4 1070 1175 1123 3194 526E-06 43161 3 1170 1275 1223 3094 138E-05 43161 2 1270 1375 1323 2994 671E-06 43161 1 1370 1475 1423 2894 OOOE+00 42997 42497 13 18-19 170 275 223 4077 OOOE+00 42997 12 260 365 313 3987 766E-05 42997 11 360 465 413 3887 727E-05 42997 10 460 565 513 3787 192E-05 42997 9 560 665 613 3687 752E-05 42997 8 660 765 713 3587 778E-05 42997 7 85-86 763 868 816 3484 260E-05 42997 6 860 965 913 3387 289E-05 42997 5 102-103 960 1065 1013 3287 102E-04 42997 4 1060 1165 1113 3187 522E-06 42997 3 1160 1265 1213 3087 520E-06 42997 2 129-130 1260 1365 1313 2987 960E-04 42997 1 1360 1465 1413 2887 OOOE+00 43372 42922 11 35-37 42-45 350 455 403 3935 684E-04 43372 10 460 565 513 3825 500E-05 43372 9 560 665 613 3725 106E-05 43372 8 72-74 660 765 713 3625 204E-05 43372 7 760 865 813 3525 872E-06 43372 6 860 965 913 3425 467E-06 43372 5 960 1065 1013 3325 200E-05 43372 4 1060 1165 1113 3225 354E-05 43372 3 125-130 1160 1265 1213 3125 157E-05 43372 2 125-130 1260 1365 1313 3025 337E-04 43372 1 1365 1465 1415 2922 689E-06 43052 43002 2 54-58 490 595 543 3763 124E-05 2100 43052 1 139-140 145-146 1367 1472 1420 2886 154E-04 1400 43291 4391 3 bullI133 260 365 313 4017 439F06 43291 2 77-78 760 865 813 3517 230E-03 400 43291 1 143-144 1355 1460 1408 2922 971E-06 350

29958 27258 4 450 555 503 2493 OOOE+00 (21)A 29958 3 103-105 1000 1105 1053 1943 752E-04 (063)A

Table XX Packer Permeability and Packer Sampling Results for Potential Fracture Intervals

1999 Drilling Program

Hows Corner Supcrfund Site Plymouth Maine

gtbull i Potential Fracture Top _OfBot Bottom of Depth to ltbull Top of Interval from f Packer Packer Middle Of

GS ELEV lt Hock Drilling interval Interval Interval WeD ID ft msl) (ft msl) TEST (ftbgs) ltft$gs) (ftbgs) (ftbgs)

MW-107D 29958 2 128-130 1200 1305 1253

MW-107D 29958 1 139-141 1350 1455 1403

MW-108D 31904 31104 6 35-36 300 405 353 MW-108D 31904 5 60-62 550 655 603

MW-108D 31904 4 80-83 750 855 803

MW-108D 31904 3 118-119 123-124 1150 1255 1203

MW-108D 31904 2 147-149 1440 1545 1493

MW-108D 31904 1 1700 1805 1753

MW-110D 40576 40426 2 21-31 210 315 263 MW-110D 40576 1 148-154 1460 1565 1513 MW-I11D 40519 4 70-71 650 755 703

MW-111D 40519 3 79-82 84-86 780 885 833 MW-I11D 40519 2 97-102 950 1055 1003 MW-111D 40519 1 1370 1475 1423

MW-112D 3027 2942 4 42-52 420 525 473 MW-112D 3027 3 850 955 903 MW112D 3027 2 1100 1205 1153 MW-112D 3027 1 135-136 140-141 1340 1445 1393

MW-113D 43085 43085 5 250 355 303 MW-I13D 43085 4 47-49 460 565 513 MW-113D 43085 3 73-74 700 805 753 MW-113D 43085 2 1050 1155 1103 MW-113D 43085 1 1380 1485 1433

MW-114D 42394 41594 4 48-49 450 555 503 MW-114D 42394 3 79-81 740 845 793 MW-114D 42394 2 121-129 1250 1355 1303 MW-114D 42394 1 134-142 1350 1455 1403

MW-115D 4035 4035 4 300 405 353 MW-1I5D 4035 3 70-71 650 755 703 MW-115D 4035 2 1150 1255 1203 MW-115D 4035 1 1400 1505 1453

LOT-28W 382 7 450 555 503 LOT28W 382 6 550 655 603 LOT-28W 382 5 650 755 703 LOT28W 382 4 750 855 803 LOT-28W 382 3 850 955 903 LOT-28W 382 2 950 1055 1003 LOT-28W 382 1 1055 1155 1105

NOTES cmsec = centimeters per second ft bgs = leet below ground surface It msl = feet below mean sea level lt = not detected at indicated reporting limil A = detected below laboratory PQL ( ) = detected below reporting limits

Elevation of Interval

(ft nisi) 174

159

283gt 2588

2388

1988

1698

1438

3795 2545 3349 3219 3049 2629

2555 2125 1875 1635

4006 3796 3556 3206 2876

3737 3447 2937 2837

3683 3333 2833 2583

3318 3218 3118 3018 2918 2818 2715

Hydraulic Conductivity

(cmsec)

323E-05

208E-05

471E-03

471E-03

624E-05

3I6E-05

264E-05

261 E-05

OOOE+00 200E-04 953E-05 OOOE+00 OOOE+00 212E-05

361 E-05 410E-06 2gQE06 292E-05

786E-05 124E-05 151 E-05 822E-06 82IE-06

858E-05 I69E-05 352E-03 866E-05

223E-05 394E-06 122E-05 525E-06

831 E-05 182F-05 L62E-05 129E-05 190E-05 890E-04 981 E-04

PCEraquo Concentration

(ugL)

lt5

(14A)

98 11

15

22

11

30

200 (62)A

110 210 300 240

(44)A (23)A

5

350 190 129 230

2200 1900 2600 2600

(17)A (16)A (19)A

96

Table XX Packer Permeability and Packer Sampling Results for Potential Fracture Intervals

2004 Drilling Program

Hows Corner Superfund Site Plymouth Maine

Top of Bottom of Depth to Midpoint

t K

ELEV (ft Potential Transmissive Zones Packer Interval

Packer Interval

Middle of Interval

Elevation of interval

Hydraulic Conductivity

PCE Concentration

Well ID msl) TESTr (ft bgs)- (ftbgs) (ftbgs) (ftbgs) (ft msl) (cmsec) (ogt) MW-203D 43227 4 277279 24 32 28 4043 667E-05 44

3 408415420 39 49 44 3883 593E-05 170 2 526 530 49 57 53 3793 101E-04 140 I 828830842 80 88 84 3483 701E-05 130

MW-204D 43262 5 295 300 26 34 30 4023 902E-05 220 4 463496513516 45 53 49 3833 119E-04 540 3 681685688 63 71 67 3653 OOOE+00 2 758 76 2 71 79 75 3573 309E-05 260 I 88 96 92 3403 OOOE+00

MW-205 42389 3 164 166 168 15 20 175 4148 OOOE+00 1000B 2 302305312 30 35 325 3998 107E-04 1300B 1 40 45 425 3898 OOOE+00

MW-206D 43007 5 17 72 195 4128 291E-05 4 296 302 307 29 34 315 4008 940E-05 2900B 3 522 52 57 545 3778 944E-07 2 656 64 69 665 3658 353E-06 1 92392793 4939 91 96 935 3388 614E-05 6300B

PW-207 43477 5 184622162819 18 29 235 4088 209E-05 1300 4 3508 32 43 375 3948 568E-06 5400 3 53325341542154325559 50 61 555 3768 821E-05 18000

6359 61 72 665 3658 866E-06 12000 1 8685 84 89 865 3458 213E-05 19000

NOTES cmsec = centimeters per second ft bgs = feet below ground surface ft msl = feet above mean sea level B = detected in lab blank

Table XX Orientation Permeability and Groundwater Sampling Results for Transmissive Features

2004 Drilling Program

Hows Corner Superfund Site Plymouth Maine

Borehole Geophisical Feature depth Dip True Dip True Transmissive Log Feature (Feet) Degrees Azimuth Strike bullvgt(Ltk|iy^

Number v Tosftble) v MW-203 5 277 64 337 67 Likely

6 279 59 11 281 Likely 8 352 14 177 87 Likely 11 381 46 96 6 Possible 12 408 35 271 1 Possible 14 415 57 250 340 Possible 15 420 58 202 292 Likely 18 526 52 75 345 Likely 19 530 52 82 352 Likely 28 828 48 75 345 Likely 29 830 52 17 287 Likely 30 830 56 233 323 Possible 31 842 50 130 40 Likely

MW-204 4 295 15 147 57 Likely 5 300 43 91 1 Likely 11 439 31 80 350 Possible 12 440 46 219 309 Possible 14 463 50 358 88 Likely 15 496 34 198 288 Likely 16 513 54 17 287 Likely 17 516 33 14 284 Likely 25 681 39 359 89 Possible 26 685 22 45 315 Possible 27 688 35 73 343 Possible 32 758 45 236 326 Likely 33 762 46 306 36 Likely

MW-205 5 164 69 106 16 Possible 6 166 78 165 75 Possible 7 168 82 115 25 Possible 8 168 68 116 26 Possible 12 215 46 222 312 Possible 13 217 75 62 332 Possible 14 219 29 32 302 Possible 16 237 69 250 340 Possible 17 256 73 353 83 Possible 18 272 44 202 292 Possible 21 299 37 196 286 Possible 22 302 31 206 296 Possible 23 305 59 48 318 Likely 24 312 63 42 312 Likely

MW-206 1 264 37 181 271 Likely 2 296 69 217 307 Likely 3 302 66 233 323 Likely 4 307 64 224 314 Likely 8 342 62 259 349 Likely

jjHydraulic GoiDanctilyity j(cmsecjw

667 E-05

593 E-05

101 P04

710 E-05

902 E-05

119 E-04

0

309 E-05

0

107 E-04

94 E-05

PCE (ugL)

44

170

140

130

220

540

260

IOOOB

1100B

1300B

2900B

STotal vVoCsv tig1)

84

234

192

183

2636

6436

3073

11448

12509

13776

32401

PCEyo dfCTotaf

52

73

73

7 1

83

84

85

87

88

94

90

Table XX Orientation Permeability and Groundwater Sampling Results for Transmissive Features

2004 Drilling Program

Hows Corner Superfund Site Plymouth Maine

Borehole Geophisical Feature deptt raquoip True pip True Transraissive Log Feature (Feet) shy Degrees Azimuth Strike (tikely

Number raquo Possible) 22 522 57 54 324 Possible 25 656 40 82 352 Possible 32 871 59 151 61 Possible 33 883 53 185 275 Possible 34 895 7 175 85 Likely 35 899 53 90 0 Likely 36 902 49 184 274 Likely 37 923 9 175 85 Likely 38 927 42 206 296 Likely 39 934 48 167 77 Likely 40 939 26 180 90 Likely

PW-207 1 1846 33 167 77 Likely 4 2216 49 289 19 Possible 7 2819 59 265 355 Possible 11 3508 55 189 279 Possible 18 5332 43 305 35 Likely 19 5341 51 30 300 Likely 20 5421 20 254 344 Likely 21 5432 39 301 31 Likely 23 5559 52 302 32 Likely 25 6359 24 182 272 Possible 29 8049 77 231 321 Possible 30 8685 78 38 308 Likely 32 9334 29 194 284 Likely

NOTES

B = detected in lab blank

Hydraulic Conductivity

(cmsee) 944 E-07 353 E-06

614 E-05

209 E-05

568 E-06

821 E-05

866 E-06

213 E-05

bulltCE (ugL)

6300B

1300

5400

18000

12000

19000

Total VOCs (ug1)

68901

1410

5802

19234

13085

20354

PCE of Total VOCs

9 1

92

93

94

92

93

Response to EPA-DEP Comment 3 Dated March 312005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

lit

EPA-DEP Comment 3

Comment 3 The reported f values and resultant Kd values There remains doubt that the values used in the flushing model accurately reflect the propensity for PCE to sorb to the bedrock The ^ values presented in Appendix B may be unrealistically high because the bedrock samples may have contained organic carbon that was unavailable for sorption The reported f values are only qualitative estimates of the organic carbon content of the bedrock samples The Walkley and Black organic carbon measurement method is quick and simple but the results obtained cannot be considered quantitative because it requires a correction factor which often results in erroneous values it assumes the organic carbon has an average valence of zero oxidizable and reducible constituents such as chloride ferrous iron and manganese oxides interfere with the results and the errors introduced by interference are potentially greater when the organic carbon content is low at low f values it is not clear that organic carbon is controlling PCE sorption (Schwarzenbach and Westall 1981 Mackay et al 1986 Fetter 1999)

In order to derive a Kd-based retardation factor that is reasonable given the reported f values and the rapid advance of the PCE plume described on pages 4-11 and 4-12 the flushing model requires a bulk density to porosity ratio that is roughly two orders of magnitude higher than the actual ratio for the Hows Corner bedrock (page 4-4) This apparent discrepancy needs to be addressed

Response This comment raises several concerns about the collection and analysis of samples for fraction of organic carbon (f^) the quality of the resulting data and the implications of the use of those data for estimation of the retardation of groundwater contaminant movement Results of bedrock analysis for f were proposed in the TI Evaluation Work Plan for use in conjunction with groundwater contaminant concentrations and aquifer information to estimate cleanup times using the Batch Flushing model It is important to use accurate f values from representative bedrock in the Batch Flushing model in order to obtain reasonable estimates of the remedial time frame Because of the importance of accurate and representative results the TI Investigation field program was designed and conducted both to collect samples representative of the rock volume most likely to be in contact with contaminated groundwater and to analyze them using an appropriate refereed analytical method Five potential methods for evaluating f were identified Of the five methods the Walkey-Black method was selected because it has minimal method interferences and a sufficiently low detection limit as well as a long history of use in agronomy and contamination studies The PRP Group is pleased with the quality of the data obtained from the bedrock samples as represented by their precision and reproducibility

The first part of this comment relates to the determination of fraction of organic carbon (f^) values The several subparts of the first paragraph are addressed individually in items 1 through 5 below The second part of the comment regarding the resultant distribution coefficient (Kd) values is addressed separately as item 6 below

1 There remains doubt that the values used in the flushing model accurately reflect the propensity for PCE to sorb to the bedrock

bull The rock core samples used for f (gocg) analysis were from core immediately adjacent to fractures These rock core samples included the fracture surfaces themselves and rock core extending back less than 1 cm from the fractures Therefore the foe data reported in the TI Evaluation represents the f of bedrock through which groundwater will travel and to which PCE will adsorb Based on the careful selection of sample locations and the

Response to EPA Comment 3 050205doc 1 of 11 Woodard amp Curran (211941)

number of samples collected we are confident that the measured f values are representative of the f at points of contact for PCE with the bedrock it is these f values that determine the propensity of PCE to sorb to the bedrock

bull The samples of rock core collected for analysis of f originated from 19 different locations varying in depth from 11 to 90 feet Therefore it is very unlikely that the rock core samples were contaminated with extraneous organic carbon from above ground

2 The foc values presented in Appendix B may be unrealistically high because the bedrock samples may have contained organic carbon that was unavailable for sorption

bull As noted in response 1 the f data reported in Appendix B represents organic carbon primarily associated with the surface of fractures in the bedrock through which groundwater is most likely to travel Therefore it is this organic carbon that the contaminants in the groundwater will come in contact with and adsorb to in the fractured rock at the site

bull The chemical oxidation agents used in the Walkey-Black method oxidize the easily oxidizable organic carbon in the medium and the foe is calculated from the quantity of the agent consumed Therefore it is unlikely that the analysis of the bedrock samples measured organic carbon that was unavailable for sorption

3 The reported foc values are only qualitative estimates of the organic carbon content of the bedrock samples

bull The reported f values are accurate quantitative results Schumachers review of Methods for the determination of total organic carbon (TOC) in soils and sediments (NCEA-C-1282 EMASC-001 April 2002) identifies the Walkley-Black method which was used to analyze the reported foc values as the reference method for comparison to other methods for analyzing total organic carbon

bull Schumacher also points out that if anything the WalkJey-Black method may underestimate the total organic carbon in a sample due to possible incomplete oxidation of organic carbon Usually the incomplete oxidation of total organic carbon in environmental samples is corrected for by multiplying the measured foe by 130 (Walkley amp Black 1934 Schulte 1995)

bull When the f data in the TI Evaluation Report (WampC 2005) Appendix B (attached) are analyzed statistically the standard deviation of the f for the 19 samples analyzed is 174 of the average f Given this standard deviation the 95 confidence interval for this data ranged from a low of 000123 gocg to a high of 000253 gocgm

The labs Method of Detection Limit (MDL) for the f measured using the Walkley-Black method is 00001 gocg Therefore the average (000188 gocg) the mean (000185 gocg) and geometric mean (000187 gocg) of the f values for the rock core at Hows Corner are all statistically significantly greater than the MDL of the Walkley-Black method

In addition to the aforementioned statistical analysis of the foe data triplicate samples (n = 3) from the same rock core (including one sample from the 19 rock core samples) were

Response to EPA Comment 3 050205doc 2 of Woodard amp Curran (211941)

analyzed for their f to determine the repeatability of the Walkley-Black method The average the mean and the geometric mean of the f values of these replicate samples was 000162 gocg 000150 gocg and 000159 gocgm respectively The standard deviation of these measurements was 000039 gocg

4 The Walkley and Black organic carbon measurement method is quick and simple but the results obtained cannot be considered quantitative because it requires a correction factor which often results in erroneous values it assumes the organic carbon has an average valence of zero oxidizable and reducible constituents such as chloride ferrous iron and manganese oxides interfere with the results and the errors introduced by interference are potentially greater when the organic carbon content is low at low foc values it is not clear that organic carbon is controlling PCE sorption (Schwarzenbach and Westall 1981 Mackay et al 1986 Fetter 1999)

bull Schumachers review (NCEA-C-1282 EMASC-001 April 2002) of the Walkley-Black method identifies several potential problems with this analytical method that could occur if the analytical lab is not familiar with the nuances of the chemistry associated with this method Interestingly Schumachers review neglected one of the more important analytical steps required to avoid errors in quantifying f in samples where there might beNAPL

It is absolutely critical to eliminate any NAPL from rock core samples prior to using the Walkley-Black method to measure foe in such samples This was done by the lab (PTS Laboratories) that measured the foe in the rock core samples from Hows Corner The lab used the Dean-Stark method (solvent extraction) to remove all hydrocarbons (including PCE and other NAPLs) from the sample (PTS Laboratories) This extraction method does not interfere with the subsequent analysis of the natural organic carbon associated with the rock core

Subsequently the samples were dried at 150degC to a constant weight (normally 16 hours) This latter step oxidizes all inorganic minerals including ferrous bearing minerals to ferric oxides and precludes their interference during the oxidation of the samples with chromic acid This procedure completely eliminates any positive bias in the reported foc

data that might have occurred due to the presence of ferrous ions and other reduced minerals

bull As noted in Response 3 the incomplete oxidation of total organic carbon results in an underestimate of the f and is corrected for by multiplying the f by a correction factor of 130 (Walkley amp Black 1934 Schulte 1995) The fx data reported in the TI Evaluation was corrected accordingly by using this correction factor

bull Excess chloride (Cl~) in percent weight quantities as found in saline soils may interfere with the quantitative titration of reduced chromium (Walkley 1947) However given that the primary rock type at the Hows Corner site is phyllite it is highly unlikely that there was sufficient chloride in the rock core samples for this to occur

bull Manganese oxides may also interfere with the analysis of f through competing with the dichromate ion for any oxidizable carbon (Walkley 1947) However in such cases the reported f would be an underestimate of the f present in the rock core Walkley (1947)

Response to EPA Comment 3 050205doc 3 of 11 Woodard amp Curran (211941)

4

reported that in the case where the ratio of MnO2 to carbon is 85 to 1 the error in the carbon determinations would only be 0 to 6 percent

It may also be useful to compare the analysis of total organic carbon in a geologic matrix that contains high levels of manganese using EPA method 9060 to the Walkley-Black method Table 1 summarizes data provided by one of the PRPs that compares the analysis of total organic carbon in a geologic matrix that contains approximately 02 wgt manganese (approximately 03 wgt manganese oxide)

Table 1 Comparison of total organic carbon measured using the EPA- 9060 method and the Walkley-Black method

Laboratory EPA-9060 Method Walkley-Black Method A Ave 00226 gocg Not analyzed

Stdev 000251 gocg n = 5

B Ave 002219 gocg Ave 002050 gocg Stdev = 000316 gocg Stdev =000971 gocg

n= 10 n = 10

The similarity in the total organic carbon concentrations measured by these two different methods provides further confidence that the Walkley-Black method is a viable method for analysis of total organic carbon in the presence of manganese equivalent to at least 10 by weight of the total organic carbon

5 The Walkley and Black organic carbon measurement at lowf^ values it is not clear that organic carbon is controlling PCE sorption (Schwarzenbach and Westall 1981 Mackay et al 1986 Fetter 1999)

bull Schwarzenbach and Westalls (1981) paper states that f values of less than 0001 gocg should not be used in combination with Kow (octanol-water partition coefficients) values to calculate K^ values (solid phase partition coefficients) values for a specific contaminant It should be noted that the TI Evaluation did not use the f data to calculate the KQC from the Kow Instead as requested by the EPA the measured KOC value for PCE was used to calculate the retardation factor for this contaminant

bull Schwarzenbach et al (2003) stated more recently that Even at very low f values (ie foe = 0001 kgoc - kg1 solid) sorption to the organic components of a natural sorbent may still be the dominant mechanism in defining the adsorption of organic compounds to geological matrices

bull In 1985 M Piwoni from the US EPA Robert S Kerr Environmental Research Laboratory published a paper (Banerjee et al 1985) that showed that for very hydrophobic molecules TOC content of the sorbent will control sorption down to levels of organic carbon that defy quantitation Contaminants such as the PCE found in the groundwater at Hows Corner are in this category of compounds

Given the aforementioned reasons the f values reported in the TI Evaluation are accurate within the noted statistical limitations and will have a predictable impact upon the retardation of PCE during groundwater transport

Response to EPA Comment 3 050205doc 4 of 11 Woodard amp Curran (211941)

6 In order to derive a Kd-based retardation factor that is reasonable given the reported foc

values and the rapid advance of the PCE plume described on pages 4-11 and 4-12 the flushing model requires a bulk density to porosity ratio that is roughly two orders of magnitude higher than the actual ratio for the Hows Comer bedrock (page 4-4) This apparent discrepancy needs to be addressed

The apparent discrepancy of bulk density to porosity ratios is most likely due to the fact that the Batch Flushing Model was originally developed for a porous medium and is not directly applicable to fractured bedrock As stated in Appendix C (page C-4) of the Draft Technical Impracticability Evaluation Report in order to use the Batch Flushing Model to describe the transport of contaminated groundwater in fractured bedrock where the matrix porosity is insignificant it is more appropriate to use a fracture surface area to void space ratio to calculate the retardation factor (R) than a bulk density to porosity ratio (Freeze amp Cherry 1979)

Since it is impractical to determine the actual surface area to which contaminants can adsorb the Batch Flushing Model was used with two simplifying assumptions bull The Kd was calculated from the f and the K^ bull The bulk density to porosity ratio term in the Batch Flushing Model was constrained to range

from 4 to 10 the typical range of such ratios in porous media (Freeze amp Cherry 1979)

If one uses site specific bedrock bulk density and porosity values the bulk density to porosity ratio is several orders of magnitude greater (specifically 273 gcc bullbull 000165 (dimensionless) = 1654 gcc) than the range of ratios of 4 to 10 used in the Batch Flushing Model in the Draft Technical Impracticability Evaluation Report Constraining the bulk density to porosity ratio within the range of ratios of 4 to 10 results in significantly lower R value than would be obtained using specific bedrock bulk density and porosity values

In summary in bedrock where fractures are the primary porosity the bulk density to porosity ratio can vary considerably and will be a function of the number of fractures and the fracture aperture The calculated bulk density to porosity ratio will be inversely proportional to the porosity This means that in fractured rock with limited fracturing and smaller porosity the calculated bulk density to porosity ratio is greater and will result in a greater calculated retardation factor than in bedrock with more extensive fracturing and greater porosity Consequently the calculated retardation factor will be greater for bedrock with less surface area available for sorption than bedrock with greater surface area for sorption This is contrary to what actually occurs

4 Response to EPA Comment 3 050205doc 5 of 11 Woodard amp Curran (211941)

m

REFERENCES

Banerjee P MD Piwoni K Ebeid (1985) Sorption of organic contaminants to a low carbon subsurface core Chemosphere _14 1057-1067

Freeze RA JA Cherry (1979) Groundwater Prentice Hall Englewood Cliffs NJ pg 604

PTS Laboratories wwwptsgeolabscompdf files3TOCnotepdf

Schulte EE (1995) Recommended soil organic matter tests in Recommended Soil Testing Procedures for the Northeastern United States Northeastern Regional Publication No 493 Chapter 8

Schwarzenbach RP J Westall (1981) Transport of nonpolar organic compounds from surface water to groundwater Laboratory sorption studies Environ Sci Tech 15 1360-1367

Schwarzenbach RP PM Gschwend DM Imboden (2003) Environmental Organic Chemistry Wiley-Interscience pg 292 408 amp 412

Walkley A LA Black (1934) An examination of the Degtjareff method for determining soil organic matter and a proposed modification of the chromic acid titration method Soil Science 37 29-38

Walkley A (1947) A critical examination of a rapid method for determining organic carbon in soils - effect of variations in digestion conditions and of inorganic soil constituents Soil Science 63251-264

Woodard amp Curran Inc (WampC) 2005 Draft Technical Impracticability Evaluation Hows Corner Superfund Site Plymouth Maine January 2005

Response to EPA Comment 3 050205doc 6 of Woodard amp Curran (211941)

LIST OF ATTACHMENTS (Response to Comment 3)

Appendix B to Draft Technical Impracticability Evaluation Measurement of foe at Hows Corner (4 pages)

m

Response to EPA Comment 3 050205doc 7 of 11 Woodard amp Curran (211941)

Appendix B Measurement of foe of Rock Core at Hows Corner

There are two general approaches to measure the fraction of organic carbon (foe) in rock cores

bull Measurement of weight loss by ignition of organic matter bull Chemical oxidization of organic carbon to carbon dioxide and either

subsequent quantification of the oxidant used for the reaction or quantification of the carbon dioxide produced during this oxidation process

The weight loss method is subject to errors caused by volatilization of substances other than organic materials such as water hydroxides and mineral carbonates Quantification of foe by the weight loss method is particularly sensitive to the presence of carbonates in rock cores There are however weight loss methods that are designed to differentiate between organic carbon and the aforementioned interfering materials but they require considerable care and are less accurate at low foe values Hence the weight loss method was not well suited for measuring the foe of the rock core from Hows Corner

The chemical oxidation of organic carbon is much better suited for quantifying organic carbon in rock cores such as those from Hows Corner This method uses a strong chemical oxidant to oxidize organic carbon to carbon dioxide and then measures either the chemical oxidant used to oxidize the organic carbon or the quantity of carbon dioxide produced In addition this general approach is not subject to interference by volatilization of other constituents of the rock core

There are at least two such chemical oxidation methods

bull The method of Baccini which was described by Schwarzenbach amp Westall (1981) first acidifies the sample to eliminate interference by carbonates Then a strong oxidant is used to chemically oxidize the organic carbon to carbon dioxide The resulting carbon dioxide is subsequently reduced to methane and quantified using a flame ionization detector Unfortunately this method has not been described in detail in a referred journal Hence it is would not have been appropriate to use to characterize the foe in the Hows Corner rock core

bull The more commonly used method to quantify foe in rock core is the Walkley-Black method (1934) This method is preferred for RBCA and DODDOE projects and by the oil industry

The Walkley-Black method uses an excess of chromic acid to oxidize (digest) organic matter to carbon dioxide The remaining chromic acid that was not consumed during the oxidation of the organic carbon is then quantified by titration with ferrous sulfate The difference in chromic acid prior to and after the oxidation of the organic carbon represents the total chromic acid used to oxidize

Hows Corner TI Evaluation Page 1 January 13 2005 Appendix B

the organic carbon in the sample The latter can be calculated using the chemical stoichiometry of the reaction

The Walkley-Black method is very accurate for samples that contain less than 2 organic carbon matter The minimum detection limit (MDL) for the Walkley-Black method is 100 mgkg or an foe of 0001

Given the rock core at Hows Corner was expected to contain less than 2 organic carbon the Walkley-Black method was used to measure the foe from 19 different rock core samples collected from varying depths ranging from 11 to 90 feet

Table 1 provides a statistical summary of the aforementioned data

Table 1 Statistical summary of foe data from rock cores collected at varying depths

Statistical Parameter Calculated Value foe Minimum Detection Limit (MDL) 00010 Number of samples analyzed (n) 19 Average foe 00019 Median foe 00019 Geometric Mean foe 00019 Standard deviation of foe measurements 000033 Relative standard deviation 174 -+ 95 Confidence intervals 00012 to 00025

The data in Table 1 shows the following

bull The foe from the Hows Corner rock cores are statistically greater than the MDL of the Walkley-Black analytical method

bull The average and median values for the foe of the Hows Corner rock cores from varying depths are nearly identical indicating that there is little variability in the foe values in the source zone at the site

bull The standard deviation of these measurements is 000033 which is 174 of the average foe

bull The 95 confidence intervals of the foe of the rock core at Hows Corner are 00012 to 00025

The foe was also analyzed from three separate samples taken from the same rock core at a depth of 55 feet (Only one of these samples was included in the data summarized in Table 1) Table 2 shows the statistical repeatability of this type of analysis

Hows Corner TI Evaluation Page 2 January 13 2005 Appendix B

Table 2 Repeatability of analysis of foe from one rock core at 55 feet in depth

Statistical Parameter Calculated Value Number of samples analyzed (n) 3 Average foe 00016 Median foe 00015 Geometric Mean foe 00016 Standard deviation of foe measurements 000039 Relative standard deviation 240 -+ 95 Confidence intervals 00008 to 00024

The data in Table 2 shows the following

bull The percent relative standard deviation of these three analyses of foe from the same rock core at Hows Corner is 24

bull The 95 confidence interval of the foes measured in this particular rock core at Hows Conrer is 00008 to 00024

These results show that there is good repeatability in using the Walkley-Black method for analysis of the foe in the rock core at Hows Corner

References Schwarzenbach amp Westall (1981) Transport of nonpolar organic compounds from surface water to groundwater Laboratory sorption studies Environ Sci Tech 15 1360-1367

Walkley A I A Black (1934) An examination of Degtjareff method for determining soil organic matter and a proposed modification of the chromic acid titration method Soil Sci 37 29-37

Hows Corner Tl Evaluation Page S January 13 2005 Appendix B

Woodard and Curran PTS Laboratories PTS File No 34618

ORGANIC CARBON DATA (METHODOLOGY WALKLEY-BLACK)

PROJECT NAME PROJECT NO

SAMPLE ID

203-chip-13 203-chip-23 203-chip-27 203-chip-38 203-chip-42 203-chip-47 203-chip-52 203-chip-58 203-chip-69 203-chip-82 207-chip-11 207-chip-19 207-chip-24 207-chip-29 207-chip-35 207-chip-45 207-chip-55 207-chip-87 207-chip-90

207-chip-55 55-MS

55-MSMSD

Hows Corner NA

DEPTH ft

13 23 27 38 42 47 52 58 69 82 11 19 24 29 35 45 55 87 90

55 NA NA

MATRIX

Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip

Average Median

Geometric Mean Standard Deviation Relative Std Dev

+- 95 Confidence Interval n

Rock Chip Rock Chip Rock Chip

Average Median

Geometric Mean Standard Deviation Relative Std Dev

+- 95 Confidence Interval n

FRACTION ORGANIC CARBON

(gg)

170E-03 185E-03 185E-03 170E-03 240E-03 190E-03 230E-03 180E-03 170E-03 115E-03 195E-03 220E-03 220E-03 235E-03 135E-03 190E-03 205E-03 175E-03 160E-03

188E-03 185E-03 185E-03 327E-04

1739 123E-03 to

19

205E-03 130E-03 150E-03

162E-03 150E-03 159E-03 388E-04

2402 840E-04 to

3

2532E-03

2393E-03

Hows Corner Tl Evaluation Appendix B January 13 2005

Response to EPA-DEP Comment 4 Dated March 31 2005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

EPA-DEP Comment 4

Comment 4 Distribution of contaminants First the TI report seems based on the assertion that there is DNAPL at the source area yet it also appears to represent that the source area is small and the bedrock below 85 is competent (or less fractured) and less impacted by the release of contaminants Some of the confusion may result from using most recent data when that data is from several different sampling events over several years and there is no discernible difference in concentrations between shallow and deep bedrock or as in Section 421 where generally decreased generally increase generally similar and similar concentrations in four consecutive sentences leads to a muddled picture of the contaminant distribution

Second the report asserts that the distribution of contaminants over the entire plume has not changed with time but fails to support this conclusion with data again relying on data that is from different sampling dates for one composite representation

Response The likely presence of dense non-aqueous phase liquid (DNAPL) at the Hows Corner Site and the determination that the source area is small are not mutually exclusive and both are conclusions drawn from information obtained during field investigations The presence of DNAPL in the source area is based on the elevated concentrations of volatile organic compounds (VOCs) detected in the groundwater (WampC 2001 WampC 2002) The conclusion that the source area is small is based on the area in which VOCs in groundwater have been detected at concentrations that are considered to be indicative of the presence of DNAPL nearby Similarly the conclusion that fracture frequency decreases at depths greater than approximately 50 to 85 feet below ground surface was based on field observation during the RI field work The fact that zones with observed fractures exhibited higher hydraulic conductivities than zones without fractures coupled with the decreasing frequency of observed fractures with depth led to the conclusion that the hydraulic conductivity of the bulk rock decreases with depth

The most recent data from all wells were used to provide the maximum VOC data set size During the RI all of the previously-existing and then newly-installed monitoring wells were sampled along with several residential wells The RI sampling included up to 48 monitoring wells Subsequent to the RI and prior to the TI three rounds of monitoring were conducted to verify that the plume was stable 15 monitoring wells were sampled during each of the three rounds During the TI field investigation 29 wells were sampled for VOCs The sampled wells included all of the newly-installed wells and a subset of wells installed during the RI for a total of 29 monitoring wells By using most recent data VOC results from 53 monitoring wells were included in the evaluation (see table labeled Sampling Events for listing of monitoring wells) This approach was selected because there generally was little variation in the data from a particular location between years This is borne out by the attached individual plots of VOCs detected in shallow bedrock and deep bedrock for the Pre-ROD (December 1999January 2000) and Supplemental (May 2000) sampling events and for June 2001 January 2002 and April 2003 sampling events The Pre-ROD and Supplemental plots are similar to the subsequent plots from the 2001 2002 and 2003 sampling events

In addition to maps showing the spatial distribution of VOC data at a given time trend plots of the data from a particular location through time (attached) indicate that since the RI concentrations generally have been stable or have decreased Together the maps and trend plots and the data from which they were developed indicate that the distribution of contaminants over the entire plume has not changed appreciably with time

Response to EPA Comment 4 050305doc 1 of 26 Woodard amp Curran (211941)

REFERENCES

Woodard amp Curran Inc (WampC) 2001 Final Remedial Investigation Report Hows Corner Superfund Plymouth Maine July 2001

Woodard amp Curran Inc (WampC) 2002 Final Feasibility Study Report - Non-Source Area Groundwater Hows Corner Superfund Site Plymouth Maine Hows Corner Superfund Plymouth Maine July 2002

Response to EPA Comment 4 050305doc 2 of 26 Woodard amp Curran (211941)

LIST OF ATTACHMENTS (Response to Comment 4)

Table - Sampling Events 1999 - 2004 (2 pages)

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater Pre-ROD Sampling Event

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater Pre-ROD Sampling Event

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater Supplemental Sampling Event

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater Supplemental Sampling Event

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater June 2001

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater June 2001

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater January 2002

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater January 2002

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater April 2003

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater April 2003

Figure - Concentration Trends - Non-Source Area Wells MW-1B and MW-3B

Figure - Concentration Trends - Non-Source Area Wells MW-13DB and MW-16DB

Figure - Concentration Trends - Non-Source Area Wells MW-16IB and MW- 108D

Figure - Concentration Trends - Non-Source Area Wells MW-108S and MW-112D

Figure - Concentration Trends - Non-Source Area Wells MW-112S and MW-114D

Figure - Concentration Trends - Non-Source Area Wells MW-114S and MW-115D

Figure - Concentration Trends -Source Area Wells MW-2DB and MW-2IB

Figure - Concentration Trends -Source Area Wells MW-102S and MW-103D

Figure - Concentration Trends -Source Area Wells MW-103S and MW-104D

Figure - Concentration Trends -Source Area Wells MW-104I and MW-106D

Figure - Concentration Trends -Source Area Wells MW-106S

Response to EPA Comment 4 050305doc 3 of 26 Woodard amp Curran (211941)

I I

El I

II I I 1 I

I

i

Event Baseline Case ID WC-01 WC-01

Well Date Aug-99 Oct-99 LOT10 1 LOT1-1 1 LOT11-4 LOT14 1 LOT15 1 LOT15-1 1 LOT16 1 LOT16-1 1 LOT17 1 LOT18 1 LOT19 1 LOT2 LOT20 1 LOT21-10 1 LOT21-11 1 LOT21-12 1 LOT21-13 1 LOT21-14 1 LOT21-2 1 LOT21-5 1 LOT21-7 LOT21 -8 1 LOT21-9 1 LOT23 1 LOT24 1 LOT28-1 1 LOT28-2 1 LOT28-3 1 LOT28-4 1 LOT28W 1 LOT30 1 LOT30-1 1 LOT30-2 1 LOT30-3 1 LOT30-4 1 LOT30-5 LOT31 LOT35 1 LOT41 1 LOT42-1 1 LOT43-1 1 LOT43-4 1 LOT6-1 1 LOT67 1 LOT6-7 1 LOT6-8A 1 LOT6-8B 1 LOT80-1 1 LOT82 1 MW-101D MW-1011 MW-101S MW-102D MW-102S MW-103D MW-103S MW-104D MW-1041 MW-104S MW-105D MW-106D

Groundwater Sampling Location Summary 1999 - 2004xls

Sampling Events 1999-2004

Hows Corner Superfund Site Plymouth Maine

Supplemental 2001 2002 2003 Pumping 2004 Pre-ROD Rl Sampling Sampling Sampling Test Sampling WC-03 WC-09 WC-25 WC-30 WC-42B WC-56 WC-58 Dec-99 May-00 Jun-01 Jan-02 Apr-03 Sep-04 Sep-04

1

1 1 1

1 1 1 1 1

1 1

1

1 1

1 1 1

1 1 1 1 1

1

1 1

1 1 1 1

1

1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

Sampling Events 1999-2004

Hows Corner Super-fund Site Plymouth Maine

Supplemental 2001 2002 2003 Pumping Event Baseline Pre-ROD Rl Sampling Sampling Sampling Test

Case ID WC-01 WC-01 WC-03 WC-09 WC-25 WC-30 WC-42B WC-56

ll

Well Date Aug-99 Oct-99 Dec-99 May-00 Jun-01 Jan-02 Apr-03 Sep-04 MW-106S 1 1 1 1 1 MW-107D 1 1 MW-108D 1 1 1 1 1 MW-108S 1 1 1 1 1 MW-110D 1 1 MW-111D 1 1 MW-112D 1 1 1 1 1 MW-112S 1 1 1 1 1 MW-113D 1 1 MW-114D 1 1 1 1 1 MW-114S 1 1 1 1 1 MW-115D 1 1 1 1 1 MW-12DB 1 1 1 MW-12SB 1 1 1 MW-13DB 1 1 1 1 1 1 MW-13SB 1 1 1 MW-14DB 1 1 MW-14SO 1 1 MW-15DB 1 1 1 MW-15SB 1 1 1 MW-16DB 1 1 1 1 1 1 MW-16IB 1 1 1 1 1 1 MW-16SO 1 1 MW-17DO 1 1 1 MW-17SO 1 1 1 MW-1B 1 1 1 1 1 1 MW-203D MW-203S MW-204D MW-204S MW-205 MW-206D

I MW-206S MW-2DB 1 1 MW-2DDB 1 1 MW-2IB 1 1 1 1 1 1 MW-3B 1 1 1 1 1 1

I MW-4O 1 1 1 MW-5B 1 1

II MW-6DB 1 1 1 MW-6SB 1 1 1 MW-8DB 1 1 1 MW-8SB 1 1 1

II PW-207 1 SEEP-1 1 SUBTOTAL - RESIDENTIAL 44 25 0 2 0 3 0 SUBTOTAL - MONITORING 22 48 41 15 15 15 1

Total 3 66 73 41 17 15 18 1

I Included in most recent data

I Notes 1 - Overburden well not included in most recent data for plotting

2 - Tetrahydrofuran and 2-Butanone were the only two compounds detected in this well and are thought to be the result of well repair not included in most recent data for plotting

3 - Not included in most recent data for plotting

2004 Sampling

WC-58 Sep-04

1

1 1

1 1

1 1 1

1

1 1

1 1 1 1 1 1 1 1 1

1 1

1

0 29

29

Groundwatef Sampling Location Summary 1999 - 2004xls

I

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

monitoring well Figure 4-14 total VOC contour (ugl) - December 1999January 2000 Distribution of Total VOCs in

Note SW-113 is located downstream of SEEP-1 Shallow Bedrock Groundwater total concentration of detected VOCs ND= not detected these two locations were sampled during the Pre-ROD Sampling Event

Baseline Sampling Event in OctoberNovember 1999 Hows Corner Superfund Site Surface Water Sampling Location A Plymouth Maine Seep Sampling Location laquo- WOODARD ampCURRAN

995037wipri reportepa ri interim final feb 2001cadd drawingsfinalfig 4-14

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

0 300 600 I

FEET

Q residential well Figure 4-16 monitoring well Distribution of Total VOCs in

Deep Bedrock Groundwater total VOCs contour (ugl) Pre-ROD Sampling Event

active residential wells with lot number Hows Corner Superfund Site 2deg42deg Plymouth Maine total concentration of detected VOCs ND= not detected WOODARD ampCURRAN Enyinaaring bull Science bull Operations bull

995037wipri reportepa ri interim final feb 2001cadd drawingsfinalfig4mdash16

PLYMOUTH POND

PLYMOUTH POND

1 628Tl7MW-2bB 12135

PLYMOUTH POND

monitoring well Figure 4-20

V total VOC contour (ugl) - June 2000 Distribution of Total VOCs in Shallow Bedrock Groundwater

| 34 | total concentration of detected VOCs ND= not detected NA = not analyzed Supplemental Sampling Event Note SW-113 is located downstream of SEEP-1 Hows Corner Superfund Site

Surface Water Sampling Location these two locations were sampled during the Plymouth Maine Baseline Sampling Event in OctoberNovember 1999 Seep Sampling Location WOODARD amp CURRAN

Engineering bull Science - Operations bull 995037wipri reportepa ri interim final feb 2001 cadd drawingsfinalfig 4-20

residential well Figure 4-22 Distribution of Total VOCs in

monitoring well Deep Bedrock Groundwater

total VOCs contour (ugl) Supplemental Sampling Event

Hows Corner Superfund Site

total concentration of detected VOCs ND= not detected NA = not analyzed Plymouth Maine

WOODARD amp CURRAN

995037wipri reportepa-ri interim final feb 2001cadd drawingsfinalfig 4-22 Engineering bull Science - Operations bull

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

FEET

Shallow Monitoring Well

Deep Monitoring Well

C Detected Concentration ND = Not Detected Figure 1-XS Distribution of Total VOCs in Shallow Bedrock Groundwater

Pumping Well

17-Acre Property Boundary Concentration Contour (ugl)

June 2001 Hows Corner Superfund Site

Plymouth Maine WOODARDampCURRAN

-i^rhvj bull Scbncn bull Operations bull 211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0601 dwg04-20-05

PLYMOUTH POND Hopkins Road V

O

PLYMOUTH POND

PLYMOUTH POND

o

0 300 600 mdashfa FEET

Shallow Monitoring Well bull bull - 17-Acre Property Boundary Figure 1-XD

Deep Monitoring Well 1 I Detected Concentration ND = Not Detected Distribution of Total VOCs in Deep Bedrock Groundwater

-mf- Pumping Well June 2001 Residential Well Hows Corner Superfund Site

Plymouth Maine i h Surface Water Sampling Point

g WOODARD ampCURRAN _ ^ _ ^ _ _ yen_ rj i|Hlaquorlny bull Science bull Opt

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0601 dwg04-20-05

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

Shallow Monitoring Well

Deep Monitoring Well

Detected Concentration ND = Not Detected Figure 1-YS Distribution of Total VOCs in Shallow Bedrock Groundwater

Pumping Well

17-Acre Property Boundary Concentration Contour (ugl)

January 2002 Hows Corner Superfund Site

Plymouth Maine WOODARD amp CURRAN Engineering Science- Operations bull

211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0102dwg04-20-05

PLYMOUTH POND

PLYMOUTH POND

Site Pand^ laquoum-laquoBTuitaraquo tLV

vVlf-(

PLYMOUTH POND

0 300 600 ^ = FEET

Shallow Monitoring Well mdashbullbullbull 17-Acre Property Boundary Figure 1-YD - A - Deep Monitoring Well FT Detected Concentration ND = Not Detected Distribution of Total VOCs in

Deep Bedrock Groundwater Pumping Well January 2002 Residential Well Hows Corner Superfund Site

Plymouth Maine Surface Water Sampling Point

WOODARD ampCURRAN Engineering Sciencs- Operations bulli Si

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0102dwg04-20-05

- m j

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND j A O-shy

Shallow Monitoring Well E Detected Concentration ND = Not Detected Figure 1-ZS Distribution of Total VOCs in

Deep Monitoring Well Shallow Bedrock Groundwater

Pumping Well Hows Corner

April 2003 Superfund Site

17-Acre Property Boundary Plymouth Maine Concentration Contour (ugl) r WOODARD ampCURRAN

Engineering bull Science bull Operations bull 211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0403dwg04-20-05

s S pound

PLYMOUTH POND

PLYMOUTH POND

- -

5 PLYMOUTH POND

Jo

FEET

ft Shallow Monitoring Well mdashbullbullmdash 17-Acre Property Boundary Figure 1-ZD Deep Monitoring Well I 1 I Detected Concentration ND = Not Detected Distribution of Total VOCs in

Deep Bedrock Groundwater Pumping Well April 2003

Q) Residential Well Hows Corner Superfund Site Plymouth Maine

(T) Surface Water Sampling Point WOODARD ampCURRAN poundKk EnginawtirKj bull Science - Operations bull

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0403dwg04-20-05

0 Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

B MW-1B

I 12000

PCE

B 10000 Total VOCs

I

i 2000

i 0 Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

c MW-3B

G 2000

1800

B PCE

1600 Total VOCs

1 I I E

il-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

G E

211941

El

I I z E

80

Concentration Trends shy Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-13DB

Total VOCs

c i i c o

Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

MW-16DB

30

c i c c I c o

Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99

PCE

Total VOCs

Jul-01 Jul-03

211941

O bi

c Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

I MW-16IB

i 35

3

c Total VOCs

lt- 2 5

0 | gt

o

1 sectI

c c 0 4

Jul-90 Jul-92 Jul-94 Jul-96 Jul-98 Jul-00 Jul-02 Jul-04

I I MW-108D

I 12

PCE 10

Total VOCs c oc 3

E E I 0

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

E 211941

c Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

fi MW-108S

I I 40

PCE 35

Total VOCs

30

I f 26

20 I o

I 15

10

c Dec-99 Dec-00 Dec-01 Dec-02 Dec-03 I 0

I MW-112D

c 35 - imdash

I A3 shyTotal VOCs

o c

E 1 2

I

ition

B 1 ^

-i c 3

0 Dec-99 Dec-OO Dec-01 Dec-02 Dec-03

211941

I

i

I

cII

Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-112S

08

PCE

Total VOCs 06

o 04

02

0 Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

MW-114D

o

12000

10000

8000

6000

PCE

Total VOCs

4000

2000

i

ccEIIc

i

i

E

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

211941

Con

cent

ratio

n (

ug

l)

E Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

I MW-114S

E A5000 -- Total VOCs

- 4000

0 3000

2000

i 1000

i n shy

Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

MW-115D

c PCE

Total VOCs

c E

o

C c

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03 I 0

211941

IepoundII

EIEIIGICCIccc

30000

25000

20000

o bullsect 15000 b

o 10000 U

5000

0 Aug-99

25000

20000

5000

0 Aug-99

211941

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-2DB

PCE

Total VOCs

Aug-01 Aug-03

MW-2IB

PCE

Total VOCs

Aug-01 Aug-03

IDIBI

ii EIDIISIBIG C

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-102S

6000

5000 PCE

Total VOCs

4000

O 3000

2000

1000

0 Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

MW-103D

16000

~ 14000 ugt 3- 12000 o

^ 10000

sect 8000

O 6000

4000

2000

PCE

Total VOCs

0Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

211941

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

G MW-103S

I I

ampo

12000

10000

E sectc

S

8000

6000

4000

2000

0Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

G I 6000

MW-104D

i 5000

PCE

Total VOCs

i i c

2000

1000

Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

E I

211941

cIccIG

IIBCccBcIc

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-1041

PCE Total VOCs

a 25000

0 20000

a 15000

10000

5000

0 Jan-OO Jan-01 Jan-02 Jan-03 Jan-04

MW-106D

3000

2500 PCE

Total VOCs

=sect 2000

o bullsect 1500

1000

500

0 Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

211941

c Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

c MW-106S

I PCE

Total VOCs

i

i Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

i

i i i E

C

211941 c

Response to EPA-DEP Comment 5 Dated March 312005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

iiw

EPA-DEP Comment 5

Comment 5 Matrix Diffusion The report as well as other proponents of matrix diffusion suggest that depletion of DNAPL (Section 5112 page 5-15) needs to be achieved While that might be the ideal the goal is to achieve performance standards and that goal may be attainable while there is residual contamination in the rock perhaps even DNAPL globules The low bedrock matrix porosity (page 1-15) the high permeability values (page 4-4) the relative flux of the groundwater (page 5-5) and the decrease in surface area and out of the mainstream pockets (appendix C-4) all suggest that the diffusion out of the rock matrix would be insubstantial relative to the regional flux of groundwater through the Site

Response The TI Evaluation Report does not explicitly consider or rely upon matrix diffusion as a basis for requesting a TI Waiver for a portion of the Hows Corner Site The technical literature provides documentation that matrix diffusion can be a significant process that affects chemical transport and groundwater remediation timeframes in unconsolidated and consolidated media including fractured rock (US EPA 1989 Freeze and Cherry 1979 Pankow and Cherry 1996 Fountain 1998) Back diffusion of contaminants from the matrix porosity of the fractured rock can prolong the time necessary to achieve groundwater cleanup goals particularly for compounds such as PCE for which the cleanup goal is a low concentration It is our expectation that matrix diffusion has occurred at the Hows Corner Site and that back diffusion of PCE from the rock matrix will also occur Although the extent to which matrix diffusion is occurring at the Hows Comer Site has not been determined and that lack of knowledge contributes to uncertainty regarding the cleanup times at the Site the effect of matrix diffusion is to lengthen rather than shorten the time required for remediation

REFERENCES

Fountain JC 1998 Technologies for Dense Nonaqueous Phase Liquid Source Zone Remediation Ground-Water Remediation Technologies Analysis Center Technology Evaluation Report TE-98-02 December

Freeze RA and Cherry JA 1979 Groundwater Prentice-Hall Inc Englewood Cliffs NJ 07632 p 410-412

Pankow J F and Cherry J A 1996 Dense Chlorinated Solvents Waterloo Press Portland OR 97291-1399 p 67-88

US EPA 1989 Transport and Fate of Contaminants in the Subsurface EPA6254-89019 p 17-18

Response to EPA Comment 5 050305doc 1 of 1 Woodard amp Curran (211941)

WOODARD amp CURRAN Maine Massachusetts New Hampshire Connecticut Florida Operational offices across the US 1-800-426-4262 www woodardcurran com

Page 18: SDMS DocID 251749 - Records Collections · 2020-06-13 · CORPORATE OFFICES: Maine, Massachusetts, New Hampshire, Connecticut New, York, Florida Engineering • Science • Operations

--

Pumping Test Analytical Results Hows Corner Superfund Site

Plymouth Maine

Well ID oper Jaccb Analyses 2 Theis Analyses Fissure

Well Id Rd (ft)

Saturated Thickness

Transmissivity

(ft2day) K

(ft2day) K

(cmsec) Storage

Coefficient Transmissivity

(ft2day) K

(ft2day)

K (cmsec)

Storage Coefficient

System K

(ftday) PW-207OB 8 85 481 057 200E-04 392E-02 36 042 150E-04 809E-04 027 MW-103S 50 85 451 053 187E-04 720E-03 92 108 382E-04 283E-04 083 MW-103D 54 185 455 025 868E-05 210E-02 65 035 123E-04 237E-04 044 MW-2IB 59 85 352 041 146E-04 699E-03 104 123 433E-04 512E-04 052 MW-2DB 63 85 334 039 139E-04 845E-03 148 080 283E-04 239E-04 046 MW-104D 95 185 489 02 6 932E-05 654E-03 98 053 186E-04 547E-05 037 MW-104I 97 85 33 03 9 137E-04 362E-03 117 137 484E-04 962E-05 048 MW-101I 107 85 364 043 151E-04 490E-03 511 601 212E-03 223E-04 136 MW-102D 134 185 435 024 829E-05 248E-03 108 058 206E-04 850E-05 065 MW-101D 138 185 492 027 938E-05 511E-03 671 362 128E-03 700E-04 172 MW-205 219 85 57 067 237E-04 255E-03 447 526 186E-03 359E-03 -shyMW-204D 221 185 367 020 700E-05 170E-03 790 427 151E-O3 155E-04 147 MW-204S 225 85 379 045 157E-04 156E-03 1031 1213 428E-03 313E-04 199 MW-1B 228 85 325 038 135E-04 977E-04 340 400 141E-03 739E-05 054 MW-203S 273 85 489 058 203E-04 117E-03 1255 14 76 521 E-03 216E-04 210 MW-106D 278 185 51 028 972E-05 141E-03 1065 576 203E-03 360E-04 104 MW-203D 278 185 478 026 911E-05 152E-O3 765 414 146E-03 364E-04 138 MW-105D 364 185 44 024 839E-05 830E-04 769 415 147E-03 200E-04 127

1 Analyses conducted using Cooper and Jakob method on late drawdown data collected during constant

discharge pumping test conducted at the Hows Comer Site from September 20 - 30 2004

2 Analyses conducted using Theis solution for unconfmed approximation (1935)

J Analyses conducted using Moench method for dual porosity estimation (1984)

Fissure System Storage

Coefficient 402E-04 117E-06 264E-04 300E-04 932E-05 235E-07 502E-05 326E-06 801E-05 542E-04

-

803E-05 762E-05 134E-05 498E-05 115E-04

47E-04 838E-05

3 ysesh Analysis

Block System K (ft2day)

251E-02 207E-03 564E-04 163E-04 585E-04 465E-02 153E-04 498E-03 855E-04 356E-03

-

292E-03 394E-03 720E-04 526E-03 160E-01 35OE-O1 287E-03

Block System Storage

Coefficient

402E-02 164E-04 183E-02 330E-03 158E-03 847E-03 286E-03 326E-04 803E-05 272E-03

723E-04 686E-04 148E-04 349E-04 115E-03 47E-04 838E-04

Theis - Moench - CJ - AnalyticalResults_4-19-O5xls

DRAFT

242

24

238

236

bulla

c

i

a Q

234

232

228

226

Hows Corner Constant Discharge Testing USGS Background Groundwater Level USGS 445319068560101 ME-PEW456 Kenduskeag Maine

End of Monitored Recovery Period 09302004

Regional Background Location i 226 miles from Pumping Locatio

lt

697

NOTES

1 Groundwater samples collected in 1999 were screened for five volatile organic compounds (VOCs) only N

tetrachloroethene (PCE) exceeded reporting limits MW-2030 082304 082304 082304 082304 u

2 Strike and Dip of likely or possible transmissive 30 45 55 85 feature within the packer interval from which the indicated sample was collected

MW-204D

PCE TOTAL VOCs

081904 30

220 2636

A

081904 46-50 540 6436by

081904 IT

260 3073

x

MW-105D

PCE TOTAL VOCs

111199 50-60 2100 2100

MW-106D

PCE TOTAL VOCs

111199 76-86

400 400

111199 137-147

1400 1400

111299 1355-1455

350 350

PCE TOTAL VOCs

44 84

64

MW-6SB

bulli

lt

gt-

170 234

35

I I i

140 192

^^52

^^52

130 183

52 - lt

S A 34

PW-207 082404 082404 082404 20 37

PCE 1300 TOTAL VOCs

17-Acre George West Property Boundary

MW-113D

PCE TOTAL VOCs

112299 46-56

350 350

112299 70-80 190 190

150

112299 105-115

129 129

112399 138-148

230 230

L e g e n d ( J New Monitoring Well-Summer

Site Property Boundary ^ P u m p i n g Well-Summer 2004

-xmdashxshy Source Area

bull0shy Monitoring Well shy Pre 2004 Angled Boring-Summer 2004

211941laquoipdwgTI-ELV21ig41paltker-data2

2004 PCE of Total

bull lt70 VOCs

M W - 1 14D ^ ^

Figure xx Packer Testing Results in

Vicinity of Source Area Hows Corner Superfund Site

Plymouth Maine ^ WOODARD ampCURRAN

^^^^^^^^^^m ampKm Engineering - Science bull Operations

c Northeast Geophysical Services Borehole Geophysical Log

MW-203 Date logged 081704 Plymouth Maine

I Flowmeter Measurements Tomporaturo(C) Acoustic Televiewer

7 5 8 8 5 9 95 Caliper (Inches) Resistance (Ohms) Spontaneous Potential (mVj Dip In Degrees PCE Total VOCs

3 0 2 0 8 0 laquodeg 4S 1000 1400 1800 2200 MO HO 1000 1200 MOO 0 laquo deg ugL ugL n 1 1 1 1 1 1 1 1 1 i 1 1 1 1 n 1 1 1 1 1 1 1 1 1 1 1 n I l l l l l l l n

Ambient Flowneter pumping Rowmeter 11 gpm 6

H

bull

magnetic 10 bull 10 bull - 10 - north - 1 0I

-

_

bullbullbull - bull

20 bull bull20 bull ^ ltr~mdash 01

I

4 ^

LOS7

^

44 84 I I

Xr - 2

lt ^ bull30 -_ _^O1J- 1 _ 050 30 - 3 0

0r - - 3

C -j [ bull bull bull | shy

-O8 H ~ 1 045 7

1 4040 - 40 - -40 r - 14gt 13

V1s -- -023 f 1022 1V 170 234 I

T lt bull B gtf 50^ J50 - - 5 0 - - 5 0

I eet be

lo

i 1

1 1

1

140 192 - - - -t shy

-mdashj bullpound 60 - $o - - 60 - -60

H i I c

bull024

ampbull

3 - T lt ftft rgt He

70 bull j 70 - - 70 - 7 0 -

in -j bullbull shy

-021 1 T 022

- Ton _ Ov

26

130 183 NF NF

90 -_ 90 - 7 90 - -90

-

ifi Jf

3J

^gt _ N F NF bull bull shy

| H100 - j 100 bullbull 100 - -100

1 1 1 1 1 1 1 ) | 1 f I 1 1 1 ) 0 20 40 60 80

flft mdash ftn - mdash rVt

30 4 g 0 20 40 60 Dip in Degrees bullbull

Likely or poss bleFluid Resistivity (ohmmeters) The dip direction-- indicated

^ t h e l i n e extending from t h

I Iransmissive zone circle The strike of the feature is 90 degrees from this

The acoustic televiewer graph displays the mostprominent features selectedffom the acoustic televiewer

R n r a h n l c D O t t n O I B

f i o n n h w c i r a l U K U p i i y SI Ud l

1 rn l_Og Packered Interval August 2004

E tog The location dip angle and dip direction of the sleeted M W - 2 0 3 Groundwater samples were collected by Woodard S Curran on H23120M features are approximate Refer to the televiewer og of His _ well for more precise detail Plymouth Maine Date logged 081704

I

1

Northeast Geophysical Services Borehole Geophysical Log MW-204 D a t e l o gge d 072604

Plymouth Maine

n 3

Flowrneter Measurements(in gpm)

Caliper (Inches)0 3 5 4 0

1 1 1 1 1 1 1 t 1 1 1 1 1 1Ambient Rowmeler pumping Flowmetsr 05gpm

Templaquorature (C) bull bull bull bull i

7 75 8 8S 9 Resistance (Ohms) Spontaneous Potential (mV)

4000 SOW 600 4M 0

Acoustic Televiewer (interpreted)

Dip in Degrees 0 20 4060 SO

at N

PCEugL

Total VOCs ugL

- -_ a

10-

shy 10 bull - 10 shymagnetic

north - 10

o o

bull 1

11

11

1 1

1 1

11 1

1 1

1 1

1 1

1 1

1 1

1 1

1 1

1 1 E 1

- L

3 7 2 0 2 0r bull 20 bull - shy

i S_ N F

bull30 bull 7 3 0 220 2636shy1^ J J 004

fI f V ^

40 shy 4 0 4 0 shy - 4 0rbull019 [_ 007 w8 - - shy5 c

bull

gt

Ia50i 540 6436

bull50 - - 50 - - 5 0

-QQ7 - bull - -t T

pound V gtk

B 6 0 - e o - 7 6 0 -60shyQ 1 1

Q -007 -004 bull1 mdash T - J ~

bull

- - shyT 70 -J c [TO- - 70 - 7 0-

V Y 1- -004 -003

mdash T -h - y - j i - - mdash 260 3073 - gt=7

80 -j NF bull80 - - 80 - - 8 0Jgt

bull i

i 1

i i

C- bull shy

90 shy

K

Jlt i90 90 shy - 9 0shy -

l

ii

I I I I

NF bull M J

I ^ ^ - ^ bull 1

mdash mdash - _

s -7 ^100shy

till

1 100 100- H - 1 0 0shy -1 x Likety or possible k ^ Iransmissive zonebull

1 i i i ii i i i | l l l l | l i l l 0 20 40 ED 80

1 -

3 0SOFluid Resistivity (ohmmeters)

Dip in Degrees The djp ^ ^ o n is indicated ty Ihe line extending from tha circle The strike of Ihe feature

19- 3U UIHJIW93 IolII l l l lraquo

bull

The acousfc televiewer graph displays the mostprominent features selected from the acoustic televiewer109 The location dip angle and dip direction of Ihe sleetedfeatures are approximate Refer to the televiewer log of thiswentormore precise detail

B o r e h o l e G e O D h V S I C a l LOO B W H U I B w c w p n y o i v a i w v yM W - 2 0 4

P l y m O U t n MaiDB

Packorod Interval August 2004Groundwater san-ples wampramp collected by Woodard a Curran on OMO23C4

Date logged 072604

C

I

E Northeast Geophysical Services Borehole Geophysical Log Date logged 072704

I MW-205

Plymouth Maine

Flowmeter Measurements Temperature (C) Acoustic Televiewer (In gpm) I ~l (Interpreted)

I 85 10 Caliper (inches) 95

Dip in D g r laquo Resistance (Ohms) Spo ontaneous Potential (mV PCE Total VOCs 3 0 16 4 0 4 5 ) 20 40 60 80 10 00 2000 30 00 4VJ 400 -3 laquo

i i i i 1 i i I i 11 4 0 D 1 I I ugL ugL

C h

iii Ambient Flowmetar pumping

Flowmeter 1 25 gprn

I bull$bull

i

I rmdash magnetic 1 north ^^^^ 1 VI f

10 ~ I C x 10 bull - 10 bullbull

4 5 6mdashmdash f 1000B 11448 noisy nodi a raquo ^

mdash 5rt mdashi mdash Oft pound) 1100B 12509

cjmdash1 007

-

i i i 1

en

8 B a B

30 mdash

-

40 shy

-mdash I -

50 -_

__NF lt005

- 30 - - 3 0 it 34V

MO P26 V S) 1300B 13776 _ N F NF

26

40 bull - 40 bull 7-40 gt J Vf1 cX

) -j -

_ N F NF 50 c bull - 50 ^ 7-50

i I

I

c

B pound 60 - 6 0 7 60 - 7-60 a i 1

_ N F NF i Si f f 70 -_ bull70 bull - 70 shyC I 9

-m bull - shyA

_ N F NF 80 80 -j bull80 bull - 80 - C- 33 34

bull

5-i r

i 1

J r

Ck

_ N F NF 9 0 90 - - 90 shy

i bullCshy

J rK bull

100 -j ^ Likely or possible bull100- - 100- I -100

transmissive zone bull - ^ bull shy] |

1 1 1 1 1 1 1 I 1 i i i 1 i i 1 1 0 20 40 SO SO 10 20 30 40 50 Dip in Degrees 30 4 0 Fluid Resistivity (ohmmeters) Thlaquo dip direction is indicated

by the line extern r g from the circle The strike of he feature is 90 degrees from ihis

The acoustic televiewer graph displays the most

I Borehole Geophysical Log Packered Interval August2004 prominent features selected from the acoustic televiewer

Groundwatcr samples were oollccled by Woodard amp Cufran orgt S172004 log The location dip angle and dip direction of ins slsctsd MW-205 features are approximate Refelt to the televiewer log of this wall for more precise detail Plymouth Maine Date logged 072704

I

C

I Northeast Geophysical Services Borehole Geophysical Log Date logged 072704

I MW-206

Plymouth Maine

Flowmetor Measurements Temperature (C) Acoustic Televiewer | I r T i i i i i i i i i i i i i i r I |(in gpm) (Interpreted)

I 75 8 flS 9 95

Caliper (inches) Resistance (Ohms) Spontaneous Potential (mV) Dip In Degress PCE Total VOCs 30 35 40 4 5 0 20 40 M 90 4500 5500 6500 ugL ugL I i i

I I

- 1 0

I - 2 0

I 2900B 32401

i i L

E 0

i 6300B 68901

i I 0 20 40 SO 80

20 30 40 50 Dip in Dlaquogralaquos

amp 4 a Fluid Resistivity (ohrnmeters) The dip dirertion is indicated Likely or possible by iho line extending from the transmissive zone circle The striKe of the feature

is 90 degrees from tNs

Borehole Geophysical Log Packered Interval August 2004

E amples were collected by Woodard amp Cunan oo SM82004 log Thraquo location 4p angle and dip direction of the sloeled MW-206 feature are approximate Refer to the televiewer 109 of this well for more precise detail Plymouth Maine Date logged 072704

C

I Northeast Geophysical Services Borehole Geophysical Log

Date logged 082304 PW-207

I Plymouth Maine

Fiowmeter Measurements Temperature (C) Acoustic Televiewer

I (in gpm) (interpreted)

75 8 85 9 95 Caliper (inches) Resistance f0tims) Spontaneous Potential (mV) Dip in Degrees PCE Total VOCs

55 60 0 20 40 SO 80 ugL ugL I I I I I I I

Ambienl Fiowmeter pumping Flewmater

magnetic - 10 - - 1 0

north

i - 20 - - 2 0

1300 1410

i - 30 - - 3 0

i tf

5400 5802 - 40 - - 4 0

B - 50 - - 5 0

I 18000 19234

- 60 - - 6 0

I 12000 13085

- 70 - - 7 0

- 8 0

i - 9 0 19000 20354

G - 100- -100

I 110 110 bull110

0 20 40 60 SO 10 20 30 Dip m Degrees

Fluid Resistivity (ohmmeters) I 50

The dip direction is indicated by ihe line extending from the circle The strike of the fealure is 90 degrees from this

Borehole Geophysical Log

G Packorod Interval August 20(M log The location dip angle and dip dirlaquocton or the sleeted Groundaier samplss were ooliecled by Woodard i Curran on ampt24f2ltXM PW-207 failures are approximate Reter to the televiewer log of this wlaquoll for more precise detail PlyPIOUth Maine Date logged 082304

I

Table XX Packer Permeability and Packer Sampling Results for Potential Fracture Intervals

1

WellID MW-101D MW-101D MW-101D MW-101D MW-101D MW-101D MW-101D MW-101D MW-101D MW-101D MW-I01D MW-101D MW-101D MW-102D MW-102D MW-I02D MW-102D MW102D MW-102D MW-102D MW-102D MW-102D MW-I02D MW-102D MW-102D MW-102D MW-103D MW-103D MW-103D MW-103D MW-I03D MW-103D MW-103D MW-103D MW-103D MW-103D MW-103D MW-103D MW-I03D MW-104D MW-104D MW-104D MW-104D MW-I04D MW-104D MW-104D MW-104D MW-104D MW-104D MW-104D MW-105D MW-105D MW106D MW-106D MW-106D MW-107D MW-107D

1999 Drilling Program

Hows Corner Superfund Site Plymouth Maine

Potential Fracture Top Of Bottom 6 Depth to lt Topof i Interval from Packer Packer Middle of Elevation Hydraulic bull PCE

GS ELEV 1 Rock Drilling Interval Interval Interval of Interval Conductivity Concentration (ft msl) (ft msl) TEST (ftbgs) (ftbgs) r(ftbgs) ( f t b (ft mil) (cmsec) (raquogL)

4339 4329 13 28-29 33-3537-39 271 376 324 4016 OOOE+00 4339 12 37-3444-46 380 485 433 3907 157E-04 4339 11 488 593 541 3799 132E-04 4339 10 60-61 578 683 631 3709 OOOE+00 4339 9 678 783 731 3609 I79E-05 4339 8 778 883 831 3509 106E-05 4339 7 880 985 933 3407 243E-05 4339 6 990 1095 1043 3297 339E-06 4339 5 1090 1195 1143 3197 OOOE+00 4339 4 1190 1295 1243 3097 OOOE+00 4339 3 1365-1375 1290 1395 1343 2997 OOOE+00 4339 2 147-157 1390 1495 1443 2897 580E-05 4339 1 147-157 1470 1575 1523 2817 741E-05 43161 43061 13 166 271 219 4098 333E-04 43161 12 30-3136-40 260 365 313 4004 I54E-05 43161 11 36-4041-43 362 467 415 3902 548E-05 43161 10 470 575 523 3794 598E-05 43161 9 570 675 623 3694 197FOS 43161 8 670 775 723 3594 OOOE+00 43161 7 770 875 823 3494 891 E-05 43161 6 83-94 870 975 923 3394 139E-05 43161 5 970 1075 1023 3294 123E-04 43161 4 1070 1175 1123 3194 526E-06 43161 3 1170 1275 1223 3094 138E-05 43161 2 1270 1375 1323 2994 671E-06 43161 1 1370 1475 1423 2894 OOOE+00 42997 42497 13 18-19 170 275 223 4077 OOOE+00 42997 12 260 365 313 3987 766E-05 42997 11 360 465 413 3887 727E-05 42997 10 460 565 513 3787 192E-05 42997 9 560 665 613 3687 752E-05 42997 8 660 765 713 3587 778E-05 42997 7 85-86 763 868 816 3484 260E-05 42997 6 860 965 913 3387 289E-05 42997 5 102-103 960 1065 1013 3287 102E-04 42997 4 1060 1165 1113 3187 522E-06 42997 3 1160 1265 1213 3087 520E-06 42997 2 129-130 1260 1365 1313 2987 960E-04 42997 1 1360 1465 1413 2887 OOOE+00 43372 42922 11 35-37 42-45 350 455 403 3935 684E-04 43372 10 460 565 513 3825 500E-05 43372 9 560 665 613 3725 106E-05 43372 8 72-74 660 765 713 3625 204E-05 43372 7 760 865 813 3525 872E-06 43372 6 860 965 913 3425 467E-06 43372 5 960 1065 1013 3325 200E-05 43372 4 1060 1165 1113 3225 354E-05 43372 3 125-130 1160 1265 1213 3125 157E-05 43372 2 125-130 1260 1365 1313 3025 337E-04 43372 1 1365 1465 1415 2922 689E-06 43052 43002 2 54-58 490 595 543 3763 124E-05 2100 43052 1 139-140 145-146 1367 1472 1420 2886 154E-04 1400 43291 4391 3 bullI133 260 365 313 4017 439F06 43291 2 77-78 760 865 813 3517 230E-03 400 43291 1 143-144 1355 1460 1408 2922 971E-06 350

29958 27258 4 450 555 503 2493 OOOE+00 (21)A 29958 3 103-105 1000 1105 1053 1943 752E-04 (063)A

Table XX Packer Permeability and Packer Sampling Results for Potential Fracture Intervals

1999 Drilling Program

Hows Corner Supcrfund Site Plymouth Maine

gtbull i Potential Fracture Top _OfBot Bottom of Depth to ltbull Top of Interval from f Packer Packer Middle Of

GS ELEV lt Hock Drilling interval Interval Interval WeD ID ft msl) (ft msl) TEST (ftbgs) ltft$gs) (ftbgs) (ftbgs)

MW-107D 29958 2 128-130 1200 1305 1253

MW-107D 29958 1 139-141 1350 1455 1403

MW-108D 31904 31104 6 35-36 300 405 353 MW-108D 31904 5 60-62 550 655 603

MW-108D 31904 4 80-83 750 855 803

MW-108D 31904 3 118-119 123-124 1150 1255 1203

MW-108D 31904 2 147-149 1440 1545 1493

MW-108D 31904 1 1700 1805 1753

MW-110D 40576 40426 2 21-31 210 315 263 MW-110D 40576 1 148-154 1460 1565 1513 MW-I11D 40519 4 70-71 650 755 703

MW-111D 40519 3 79-82 84-86 780 885 833 MW-I11D 40519 2 97-102 950 1055 1003 MW-111D 40519 1 1370 1475 1423

MW-112D 3027 2942 4 42-52 420 525 473 MW-112D 3027 3 850 955 903 MW112D 3027 2 1100 1205 1153 MW-112D 3027 1 135-136 140-141 1340 1445 1393

MW-113D 43085 43085 5 250 355 303 MW-I13D 43085 4 47-49 460 565 513 MW-113D 43085 3 73-74 700 805 753 MW-113D 43085 2 1050 1155 1103 MW-113D 43085 1 1380 1485 1433

MW-114D 42394 41594 4 48-49 450 555 503 MW-114D 42394 3 79-81 740 845 793 MW-114D 42394 2 121-129 1250 1355 1303 MW-114D 42394 1 134-142 1350 1455 1403

MW-115D 4035 4035 4 300 405 353 MW-1I5D 4035 3 70-71 650 755 703 MW-115D 4035 2 1150 1255 1203 MW-115D 4035 1 1400 1505 1453

LOT-28W 382 7 450 555 503 LOT28W 382 6 550 655 603 LOT-28W 382 5 650 755 703 LOT28W 382 4 750 855 803 LOT-28W 382 3 850 955 903 LOT-28W 382 2 950 1055 1003 LOT-28W 382 1 1055 1155 1105

NOTES cmsec = centimeters per second ft bgs = leet below ground surface It msl = feet below mean sea level lt = not detected at indicated reporting limil A = detected below laboratory PQL ( ) = detected below reporting limits

Elevation of Interval

(ft nisi) 174

159

283gt 2588

2388

1988

1698

1438

3795 2545 3349 3219 3049 2629

2555 2125 1875 1635

4006 3796 3556 3206 2876

3737 3447 2937 2837

3683 3333 2833 2583

3318 3218 3118 3018 2918 2818 2715

Hydraulic Conductivity

(cmsec)

323E-05

208E-05

471E-03

471E-03

624E-05

3I6E-05

264E-05

261 E-05

OOOE+00 200E-04 953E-05 OOOE+00 OOOE+00 212E-05

361 E-05 410E-06 2gQE06 292E-05

786E-05 124E-05 151 E-05 822E-06 82IE-06

858E-05 I69E-05 352E-03 866E-05

223E-05 394E-06 122E-05 525E-06

831 E-05 182F-05 L62E-05 129E-05 190E-05 890E-04 981 E-04

PCEraquo Concentration

(ugL)

lt5

(14A)

98 11

15

22

11

30

200 (62)A

110 210 300 240

(44)A (23)A

5

350 190 129 230

2200 1900 2600 2600

(17)A (16)A (19)A

96

Table XX Packer Permeability and Packer Sampling Results for Potential Fracture Intervals

2004 Drilling Program

Hows Corner Superfund Site Plymouth Maine

Top of Bottom of Depth to Midpoint

t K

ELEV (ft Potential Transmissive Zones Packer Interval

Packer Interval

Middle of Interval

Elevation of interval

Hydraulic Conductivity

PCE Concentration

Well ID msl) TESTr (ft bgs)- (ftbgs) (ftbgs) (ftbgs) (ft msl) (cmsec) (ogt) MW-203D 43227 4 277279 24 32 28 4043 667E-05 44

3 408415420 39 49 44 3883 593E-05 170 2 526 530 49 57 53 3793 101E-04 140 I 828830842 80 88 84 3483 701E-05 130

MW-204D 43262 5 295 300 26 34 30 4023 902E-05 220 4 463496513516 45 53 49 3833 119E-04 540 3 681685688 63 71 67 3653 OOOE+00 2 758 76 2 71 79 75 3573 309E-05 260 I 88 96 92 3403 OOOE+00

MW-205 42389 3 164 166 168 15 20 175 4148 OOOE+00 1000B 2 302305312 30 35 325 3998 107E-04 1300B 1 40 45 425 3898 OOOE+00

MW-206D 43007 5 17 72 195 4128 291E-05 4 296 302 307 29 34 315 4008 940E-05 2900B 3 522 52 57 545 3778 944E-07 2 656 64 69 665 3658 353E-06 1 92392793 4939 91 96 935 3388 614E-05 6300B

PW-207 43477 5 184622162819 18 29 235 4088 209E-05 1300 4 3508 32 43 375 3948 568E-06 5400 3 53325341542154325559 50 61 555 3768 821E-05 18000

6359 61 72 665 3658 866E-06 12000 1 8685 84 89 865 3458 213E-05 19000

NOTES cmsec = centimeters per second ft bgs = feet below ground surface ft msl = feet above mean sea level B = detected in lab blank

Table XX Orientation Permeability and Groundwater Sampling Results for Transmissive Features

2004 Drilling Program

Hows Corner Superfund Site Plymouth Maine

Borehole Geophisical Feature depth Dip True Dip True Transmissive Log Feature (Feet) Degrees Azimuth Strike bullvgt(Ltk|iy^

Number v Tosftble) v MW-203 5 277 64 337 67 Likely

6 279 59 11 281 Likely 8 352 14 177 87 Likely 11 381 46 96 6 Possible 12 408 35 271 1 Possible 14 415 57 250 340 Possible 15 420 58 202 292 Likely 18 526 52 75 345 Likely 19 530 52 82 352 Likely 28 828 48 75 345 Likely 29 830 52 17 287 Likely 30 830 56 233 323 Possible 31 842 50 130 40 Likely

MW-204 4 295 15 147 57 Likely 5 300 43 91 1 Likely 11 439 31 80 350 Possible 12 440 46 219 309 Possible 14 463 50 358 88 Likely 15 496 34 198 288 Likely 16 513 54 17 287 Likely 17 516 33 14 284 Likely 25 681 39 359 89 Possible 26 685 22 45 315 Possible 27 688 35 73 343 Possible 32 758 45 236 326 Likely 33 762 46 306 36 Likely

MW-205 5 164 69 106 16 Possible 6 166 78 165 75 Possible 7 168 82 115 25 Possible 8 168 68 116 26 Possible 12 215 46 222 312 Possible 13 217 75 62 332 Possible 14 219 29 32 302 Possible 16 237 69 250 340 Possible 17 256 73 353 83 Possible 18 272 44 202 292 Possible 21 299 37 196 286 Possible 22 302 31 206 296 Possible 23 305 59 48 318 Likely 24 312 63 42 312 Likely

MW-206 1 264 37 181 271 Likely 2 296 69 217 307 Likely 3 302 66 233 323 Likely 4 307 64 224 314 Likely 8 342 62 259 349 Likely

jjHydraulic GoiDanctilyity j(cmsecjw

667 E-05

593 E-05

101 P04

710 E-05

902 E-05

119 E-04

0

309 E-05

0

107 E-04

94 E-05

PCE (ugL)

44

170

140

130

220

540

260

IOOOB

1100B

1300B

2900B

STotal vVoCsv tig1)

84

234

192

183

2636

6436

3073

11448

12509

13776

32401

PCEyo dfCTotaf

52

73

73

7 1

83

84

85

87

88

94

90

Table XX Orientation Permeability and Groundwater Sampling Results for Transmissive Features

2004 Drilling Program

Hows Corner Superfund Site Plymouth Maine

Borehole Geophisical Feature deptt raquoip True pip True Transraissive Log Feature (Feet) shy Degrees Azimuth Strike (tikely

Number raquo Possible) 22 522 57 54 324 Possible 25 656 40 82 352 Possible 32 871 59 151 61 Possible 33 883 53 185 275 Possible 34 895 7 175 85 Likely 35 899 53 90 0 Likely 36 902 49 184 274 Likely 37 923 9 175 85 Likely 38 927 42 206 296 Likely 39 934 48 167 77 Likely 40 939 26 180 90 Likely

PW-207 1 1846 33 167 77 Likely 4 2216 49 289 19 Possible 7 2819 59 265 355 Possible 11 3508 55 189 279 Possible 18 5332 43 305 35 Likely 19 5341 51 30 300 Likely 20 5421 20 254 344 Likely 21 5432 39 301 31 Likely 23 5559 52 302 32 Likely 25 6359 24 182 272 Possible 29 8049 77 231 321 Possible 30 8685 78 38 308 Likely 32 9334 29 194 284 Likely

NOTES

B = detected in lab blank

Hydraulic Conductivity

(cmsee) 944 E-07 353 E-06

614 E-05

209 E-05

568 E-06

821 E-05

866 E-06

213 E-05

bulltCE (ugL)

6300B

1300

5400

18000

12000

19000

Total VOCs (ug1)

68901

1410

5802

19234

13085

20354

PCE of Total VOCs

9 1

92

93

94

92

93

Response to EPA-DEP Comment 3 Dated March 312005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

lit

EPA-DEP Comment 3

Comment 3 The reported f values and resultant Kd values There remains doubt that the values used in the flushing model accurately reflect the propensity for PCE to sorb to the bedrock The ^ values presented in Appendix B may be unrealistically high because the bedrock samples may have contained organic carbon that was unavailable for sorption The reported f values are only qualitative estimates of the organic carbon content of the bedrock samples The Walkley and Black organic carbon measurement method is quick and simple but the results obtained cannot be considered quantitative because it requires a correction factor which often results in erroneous values it assumes the organic carbon has an average valence of zero oxidizable and reducible constituents such as chloride ferrous iron and manganese oxides interfere with the results and the errors introduced by interference are potentially greater when the organic carbon content is low at low f values it is not clear that organic carbon is controlling PCE sorption (Schwarzenbach and Westall 1981 Mackay et al 1986 Fetter 1999)

In order to derive a Kd-based retardation factor that is reasonable given the reported f values and the rapid advance of the PCE plume described on pages 4-11 and 4-12 the flushing model requires a bulk density to porosity ratio that is roughly two orders of magnitude higher than the actual ratio for the Hows Corner bedrock (page 4-4) This apparent discrepancy needs to be addressed

Response This comment raises several concerns about the collection and analysis of samples for fraction of organic carbon (f^) the quality of the resulting data and the implications of the use of those data for estimation of the retardation of groundwater contaminant movement Results of bedrock analysis for f were proposed in the TI Evaluation Work Plan for use in conjunction with groundwater contaminant concentrations and aquifer information to estimate cleanup times using the Batch Flushing model It is important to use accurate f values from representative bedrock in the Batch Flushing model in order to obtain reasonable estimates of the remedial time frame Because of the importance of accurate and representative results the TI Investigation field program was designed and conducted both to collect samples representative of the rock volume most likely to be in contact with contaminated groundwater and to analyze them using an appropriate refereed analytical method Five potential methods for evaluating f were identified Of the five methods the Walkey-Black method was selected because it has minimal method interferences and a sufficiently low detection limit as well as a long history of use in agronomy and contamination studies The PRP Group is pleased with the quality of the data obtained from the bedrock samples as represented by their precision and reproducibility

The first part of this comment relates to the determination of fraction of organic carbon (f^) values The several subparts of the first paragraph are addressed individually in items 1 through 5 below The second part of the comment regarding the resultant distribution coefficient (Kd) values is addressed separately as item 6 below

1 There remains doubt that the values used in the flushing model accurately reflect the propensity for PCE to sorb to the bedrock

bull The rock core samples used for f (gocg) analysis were from core immediately adjacent to fractures These rock core samples included the fracture surfaces themselves and rock core extending back less than 1 cm from the fractures Therefore the foe data reported in the TI Evaluation represents the f of bedrock through which groundwater will travel and to which PCE will adsorb Based on the careful selection of sample locations and the

Response to EPA Comment 3 050205doc 1 of 11 Woodard amp Curran (211941)

number of samples collected we are confident that the measured f values are representative of the f at points of contact for PCE with the bedrock it is these f values that determine the propensity of PCE to sorb to the bedrock

bull The samples of rock core collected for analysis of f originated from 19 different locations varying in depth from 11 to 90 feet Therefore it is very unlikely that the rock core samples were contaminated with extraneous organic carbon from above ground

2 The foc values presented in Appendix B may be unrealistically high because the bedrock samples may have contained organic carbon that was unavailable for sorption

bull As noted in response 1 the f data reported in Appendix B represents organic carbon primarily associated with the surface of fractures in the bedrock through which groundwater is most likely to travel Therefore it is this organic carbon that the contaminants in the groundwater will come in contact with and adsorb to in the fractured rock at the site

bull The chemical oxidation agents used in the Walkey-Black method oxidize the easily oxidizable organic carbon in the medium and the foe is calculated from the quantity of the agent consumed Therefore it is unlikely that the analysis of the bedrock samples measured organic carbon that was unavailable for sorption

3 The reported foc values are only qualitative estimates of the organic carbon content of the bedrock samples

bull The reported f values are accurate quantitative results Schumachers review of Methods for the determination of total organic carbon (TOC) in soils and sediments (NCEA-C-1282 EMASC-001 April 2002) identifies the Walkley-Black method which was used to analyze the reported foc values as the reference method for comparison to other methods for analyzing total organic carbon

bull Schumacher also points out that if anything the WalkJey-Black method may underestimate the total organic carbon in a sample due to possible incomplete oxidation of organic carbon Usually the incomplete oxidation of total organic carbon in environmental samples is corrected for by multiplying the measured foe by 130 (Walkley amp Black 1934 Schulte 1995)

bull When the f data in the TI Evaluation Report (WampC 2005) Appendix B (attached) are analyzed statistically the standard deviation of the f for the 19 samples analyzed is 174 of the average f Given this standard deviation the 95 confidence interval for this data ranged from a low of 000123 gocg to a high of 000253 gocgm

The labs Method of Detection Limit (MDL) for the f measured using the Walkley-Black method is 00001 gocg Therefore the average (000188 gocg) the mean (000185 gocg) and geometric mean (000187 gocg) of the f values for the rock core at Hows Corner are all statistically significantly greater than the MDL of the Walkley-Black method

In addition to the aforementioned statistical analysis of the foe data triplicate samples (n = 3) from the same rock core (including one sample from the 19 rock core samples) were

Response to EPA Comment 3 050205doc 2 of Woodard amp Curran (211941)

analyzed for their f to determine the repeatability of the Walkley-Black method The average the mean and the geometric mean of the f values of these replicate samples was 000162 gocg 000150 gocg and 000159 gocgm respectively The standard deviation of these measurements was 000039 gocg

4 The Walkley and Black organic carbon measurement method is quick and simple but the results obtained cannot be considered quantitative because it requires a correction factor which often results in erroneous values it assumes the organic carbon has an average valence of zero oxidizable and reducible constituents such as chloride ferrous iron and manganese oxides interfere with the results and the errors introduced by interference are potentially greater when the organic carbon content is low at low foc values it is not clear that organic carbon is controlling PCE sorption (Schwarzenbach and Westall 1981 Mackay et al 1986 Fetter 1999)

bull Schumachers review (NCEA-C-1282 EMASC-001 April 2002) of the Walkley-Black method identifies several potential problems with this analytical method that could occur if the analytical lab is not familiar with the nuances of the chemistry associated with this method Interestingly Schumachers review neglected one of the more important analytical steps required to avoid errors in quantifying f in samples where there might beNAPL

It is absolutely critical to eliminate any NAPL from rock core samples prior to using the Walkley-Black method to measure foe in such samples This was done by the lab (PTS Laboratories) that measured the foe in the rock core samples from Hows Corner The lab used the Dean-Stark method (solvent extraction) to remove all hydrocarbons (including PCE and other NAPLs) from the sample (PTS Laboratories) This extraction method does not interfere with the subsequent analysis of the natural organic carbon associated with the rock core

Subsequently the samples were dried at 150degC to a constant weight (normally 16 hours) This latter step oxidizes all inorganic minerals including ferrous bearing minerals to ferric oxides and precludes their interference during the oxidation of the samples with chromic acid This procedure completely eliminates any positive bias in the reported foc

data that might have occurred due to the presence of ferrous ions and other reduced minerals

bull As noted in Response 3 the incomplete oxidation of total organic carbon results in an underestimate of the f and is corrected for by multiplying the f by a correction factor of 130 (Walkley amp Black 1934 Schulte 1995) The fx data reported in the TI Evaluation was corrected accordingly by using this correction factor

bull Excess chloride (Cl~) in percent weight quantities as found in saline soils may interfere with the quantitative titration of reduced chromium (Walkley 1947) However given that the primary rock type at the Hows Corner site is phyllite it is highly unlikely that there was sufficient chloride in the rock core samples for this to occur

bull Manganese oxides may also interfere with the analysis of f through competing with the dichromate ion for any oxidizable carbon (Walkley 1947) However in such cases the reported f would be an underestimate of the f present in the rock core Walkley (1947)

Response to EPA Comment 3 050205doc 3 of 11 Woodard amp Curran (211941)

4

reported that in the case where the ratio of MnO2 to carbon is 85 to 1 the error in the carbon determinations would only be 0 to 6 percent

It may also be useful to compare the analysis of total organic carbon in a geologic matrix that contains high levels of manganese using EPA method 9060 to the Walkley-Black method Table 1 summarizes data provided by one of the PRPs that compares the analysis of total organic carbon in a geologic matrix that contains approximately 02 wgt manganese (approximately 03 wgt manganese oxide)

Table 1 Comparison of total organic carbon measured using the EPA- 9060 method and the Walkley-Black method

Laboratory EPA-9060 Method Walkley-Black Method A Ave 00226 gocg Not analyzed

Stdev 000251 gocg n = 5

B Ave 002219 gocg Ave 002050 gocg Stdev = 000316 gocg Stdev =000971 gocg

n= 10 n = 10

The similarity in the total organic carbon concentrations measured by these two different methods provides further confidence that the Walkley-Black method is a viable method for analysis of total organic carbon in the presence of manganese equivalent to at least 10 by weight of the total organic carbon

5 The Walkley and Black organic carbon measurement at lowf^ values it is not clear that organic carbon is controlling PCE sorption (Schwarzenbach and Westall 1981 Mackay et al 1986 Fetter 1999)

bull Schwarzenbach and Westalls (1981) paper states that f values of less than 0001 gocg should not be used in combination with Kow (octanol-water partition coefficients) values to calculate K^ values (solid phase partition coefficients) values for a specific contaminant It should be noted that the TI Evaluation did not use the f data to calculate the KQC from the Kow Instead as requested by the EPA the measured KOC value for PCE was used to calculate the retardation factor for this contaminant

bull Schwarzenbach et al (2003) stated more recently that Even at very low f values (ie foe = 0001 kgoc - kg1 solid) sorption to the organic components of a natural sorbent may still be the dominant mechanism in defining the adsorption of organic compounds to geological matrices

bull In 1985 M Piwoni from the US EPA Robert S Kerr Environmental Research Laboratory published a paper (Banerjee et al 1985) that showed that for very hydrophobic molecules TOC content of the sorbent will control sorption down to levels of organic carbon that defy quantitation Contaminants such as the PCE found in the groundwater at Hows Corner are in this category of compounds

Given the aforementioned reasons the f values reported in the TI Evaluation are accurate within the noted statistical limitations and will have a predictable impact upon the retardation of PCE during groundwater transport

Response to EPA Comment 3 050205doc 4 of 11 Woodard amp Curran (211941)

6 In order to derive a Kd-based retardation factor that is reasonable given the reported foc

values and the rapid advance of the PCE plume described on pages 4-11 and 4-12 the flushing model requires a bulk density to porosity ratio that is roughly two orders of magnitude higher than the actual ratio for the Hows Comer bedrock (page 4-4) This apparent discrepancy needs to be addressed

The apparent discrepancy of bulk density to porosity ratios is most likely due to the fact that the Batch Flushing Model was originally developed for a porous medium and is not directly applicable to fractured bedrock As stated in Appendix C (page C-4) of the Draft Technical Impracticability Evaluation Report in order to use the Batch Flushing Model to describe the transport of contaminated groundwater in fractured bedrock where the matrix porosity is insignificant it is more appropriate to use a fracture surface area to void space ratio to calculate the retardation factor (R) than a bulk density to porosity ratio (Freeze amp Cherry 1979)

Since it is impractical to determine the actual surface area to which contaminants can adsorb the Batch Flushing Model was used with two simplifying assumptions bull The Kd was calculated from the f and the K^ bull The bulk density to porosity ratio term in the Batch Flushing Model was constrained to range

from 4 to 10 the typical range of such ratios in porous media (Freeze amp Cherry 1979)

If one uses site specific bedrock bulk density and porosity values the bulk density to porosity ratio is several orders of magnitude greater (specifically 273 gcc bullbull 000165 (dimensionless) = 1654 gcc) than the range of ratios of 4 to 10 used in the Batch Flushing Model in the Draft Technical Impracticability Evaluation Report Constraining the bulk density to porosity ratio within the range of ratios of 4 to 10 results in significantly lower R value than would be obtained using specific bedrock bulk density and porosity values

In summary in bedrock where fractures are the primary porosity the bulk density to porosity ratio can vary considerably and will be a function of the number of fractures and the fracture aperture The calculated bulk density to porosity ratio will be inversely proportional to the porosity This means that in fractured rock with limited fracturing and smaller porosity the calculated bulk density to porosity ratio is greater and will result in a greater calculated retardation factor than in bedrock with more extensive fracturing and greater porosity Consequently the calculated retardation factor will be greater for bedrock with less surface area available for sorption than bedrock with greater surface area for sorption This is contrary to what actually occurs

4 Response to EPA Comment 3 050205doc 5 of 11 Woodard amp Curran (211941)

m

REFERENCES

Banerjee P MD Piwoni K Ebeid (1985) Sorption of organic contaminants to a low carbon subsurface core Chemosphere _14 1057-1067

Freeze RA JA Cherry (1979) Groundwater Prentice Hall Englewood Cliffs NJ pg 604

PTS Laboratories wwwptsgeolabscompdf files3TOCnotepdf

Schulte EE (1995) Recommended soil organic matter tests in Recommended Soil Testing Procedures for the Northeastern United States Northeastern Regional Publication No 493 Chapter 8

Schwarzenbach RP J Westall (1981) Transport of nonpolar organic compounds from surface water to groundwater Laboratory sorption studies Environ Sci Tech 15 1360-1367

Schwarzenbach RP PM Gschwend DM Imboden (2003) Environmental Organic Chemistry Wiley-Interscience pg 292 408 amp 412

Walkley A LA Black (1934) An examination of the Degtjareff method for determining soil organic matter and a proposed modification of the chromic acid titration method Soil Science 37 29-38

Walkley A (1947) A critical examination of a rapid method for determining organic carbon in soils - effect of variations in digestion conditions and of inorganic soil constituents Soil Science 63251-264

Woodard amp Curran Inc (WampC) 2005 Draft Technical Impracticability Evaluation Hows Corner Superfund Site Plymouth Maine January 2005

Response to EPA Comment 3 050205doc 6 of Woodard amp Curran (211941)

LIST OF ATTACHMENTS (Response to Comment 3)

Appendix B to Draft Technical Impracticability Evaluation Measurement of foe at Hows Corner (4 pages)

m

Response to EPA Comment 3 050205doc 7 of 11 Woodard amp Curran (211941)

Appendix B Measurement of foe of Rock Core at Hows Corner

There are two general approaches to measure the fraction of organic carbon (foe) in rock cores

bull Measurement of weight loss by ignition of organic matter bull Chemical oxidization of organic carbon to carbon dioxide and either

subsequent quantification of the oxidant used for the reaction or quantification of the carbon dioxide produced during this oxidation process

The weight loss method is subject to errors caused by volatilization of substances other than organic materials such as water hydroxides and mineral carbonates Quantification of foe by the weight loss method is particularly sensitive to the presence of carbonates in rock cores There are however weight loss methods that are designed to differentiate between organic carbon and the aforementioned interfering materials but they require considerable care and are less accurate at low foe values Hence the weight loss method was not well suited for measuring the foe of the rock core from Hows Corner

The chemical oxidation of organic carbon is much better suited for quantifying organic carbon in rock cores such as those from Hows Corner This method uses a strong chemical oxidant to oxidize organic carbon to carbon dioxide and then measures either the chemical oxidant used to oxidize the organic carbon or the quantity of carbon dioxide produced In addition this general approach is not subject to interference by volatilization of other constituents of the rock core

There are at least two such chemical oxidation methods

bull The method of Baccini which was described by Schwarzenbach amp Westall (1981) first acidifies the sample to eliminate interference by carbonates Then a strong oxidant is used to chemically oxidize the organic carbon to carbon dioxide The resulting carbon dioxide is subsequently reduced to methane and quantified using a flame ionization detector Unfortunately this method has not been described in detail in a referred journal Hence it is would not have been appropriate to use to characterize the foe in the Hows Corner rock core

bull The more commonly used method to quantify foe in rock core is the Walkley-Black method (1934) This method is preferred for RBCA and DODDOE projects and by the oil industry

The Walkley-Black method uses an excess of chromic acid to oxidize (digest) organic matter to carbon dioxide The remaining chromic acid that was not consumed during the oxidation of the organic carbon is then quantified by titration with ferrous sulfate The difference in chromic acid prior to and after the oxidation of the organic carbon represents the total chromic acid used to oxidize

Hows Corner TI Evaluation Page 1 January 13 2005 Appendix B

the organic carbon in the sample The latter can be calculated using the chemical stoichiometry of the reaction

The Walkley-Black method is very accurate for samples that contain less than 2 organic carbon matter The minimum detection limit (MDL) for the Walkley-Black method is 100 mgkg or an foe of 0001

Given the rock core at Hows Corner was expected to contain less than 2 organic carbon the Walkley-Black method was used to measure the foe from 19 different rock core samples collected from varying depths ranging from 11 to 90 feet

Table 1 provides a statistical summary of the aforementioned data

Table 1 Statistical summary of foe data from rock cores collected at varying depths

Statistical Parameter Calculated Value foe Minimum Detection Limit (MDL) 00010 Number of samples analyzed (n) 19 Average foe 00019 Median foe 00019 Geometric Mean foe 00019 Standard deviation of foe measurements 000033 Relative standard deviation 174 -+ 95 Confidence intervals 00012 to 00025

The data in Table 1 shows the following

bull The foe from the Hows Corner rock cores are statistically greater than the MDL of the Walkley-Black analytical method

bull The average and median values for the foe of the Hows Corner rock cores from varying depths are nearly identical indicating that there is little variability in the foe values in the source zone at the site

bull The standard deviation of these measurements is 000033 which is 174 of the average foe

bull The 95 confidence intervals of the foe of the rock core at Hows Corner are 00012 to 00025

The foe was also analyzed from three separate samples taken from the same rock core at a depth of 55 feet (Only one of these samples was included in the data summarized in Table 1) Table 2 shows the statistical repeatability of this type of analysis

Hows Corner TI Evaluation Page 2 January 13 2005 Appendix B

Table 2 Repeatability of analysis of foe from one rock core at 55 feet in depth

Statistical Parameter Calculated Value Number of samples analyzed (n) 3 Average foe 00016 Median foe 00015 Geometric Mean foe 00016 Standard deviation of foe measurements 000039 Relative standard deviation 240 -+ 95 Confidence intervals 00008 to 00024

The data in Table 2 shows the following

bull The percent relative standard deviation of these three analyses of foe from the same rock core at Hows Corner is 24

bull The 95 confidence interval of the foes measured in this particular rock core at Hows Conrer is 00008 to 00024

These results show that there is good repeatability in using the Walkley-Black method for analysis of the foe in the rock core at Hows Corner

References Schwarzenbach amp Westall (1981) Transport of nonpolar organic compounds from surface water to groundwater Laboratory sorption studies Environ Sci Tech 15 1360-1367

Walkley A I A Black (1934) An examination of Degtjareff method for determining soil organic matter and a proposed modification of the chromic acid titration method Soil Sci 37 29-37

Hows Corner Tl Evaluation Page S January 13 2005 Appendix B

Woodard and Curran PTS Laboratories PTS File No 34618

ORGANIC CARBON DATA (METHODOLOGY WALKLEY-BLACK)

PROJECT NAME PROJECT NO

SAMPLE ID

203-chip-13 203-chip-23 203-chip-27 203-chip-38 203-chip-42 203-chip-47 203-chip-52 203-chip-58 203-chip-69 203-chip-82 207-chip-11 207-chip-19 207-chip-24 207-chip-29 207-chip-35 207-chip-45 207-chip-55 207-chip-87 207-chip-90

207-chip-55 55-MS

55-MSMSD

Hows Corner NA

DEPTH ft

13 23 27 38 42 47 52 58 69 82 11 19 24 29 35 45 55 87 90

55 NA NA

MATRIX

Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip

Average Median

Geometric Mean Standard Deviation Relative Std Dev

+- 95 Confidence Interval n

Rock Chip Rock Chip Rock Chip

Average Median

Geometric Mean Standard Deviation Relative Std Dev

+- 95 Confidence Interval n

FRACTION ORGANIC CARBON

(gg)

170E-03 185E-03 185E-03 170E-03 240E-03 190E-03 230E-03 180E-03 170E-03 115E-03 195E-03 220E-03 220E-03 235E-03 135E-03 190E-03 205E-03 175E-03 160E-03

188E-03 185E-03 185E-03 327E-04

1739 123E-03 to

19

205E-03 130E-03 150E-03

162E-03 150E-03 159E-03 388E-04

2402 840E-04 to

3

2532E-03

2393E-03

Hows Corner Tl Evaluation Appendix B January 13 2005

Response to EPA-DEP Comment 4 Dated March 31 2005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

EPA-DEP Comment 4

Comment 4 Distribution of contaminants First the TI report seems based on the assertion that there is DNAPL at the source area yet it also appears to represent that the source area is small and the bedrock below 85 is competent (or less fractured) and less impacted by the release of contaminants Some of the confusion may result from using most recent data when that data is from several different sampling events over several years and there is no discernible difference in concentrations between shallow and deep bedrock or as in Section 421 where generally decreased generally increase generally similar and similar concentrations in four consecutive sentences leads to a muddled picture of the contaminant distribution

Second the report asserts that the distribution of contaminants over the entire plume has not changed with time but fails to support this conclusion with data again relying on data that is from different sampling dates for one composite representation

Response The likely presence of dense non-aqueous phase liquid (DNAPL) at the Hows Corner Site and the determination that the source area is small are not mutually exclusive and both are conclusions drawn from information obtained during field investigations The presence of DNAPL in the source area is based on the elevated concentrations of volatile organic compounds (VOCs) detected in the groundwater (WampC 2001 WampC 2002) The conclusion that the source area is small is based on the area in which VOCs in groundwater have been detected at concentrations that are considered to be indicative of the presence of DNAPL nearby Similarly the conclusion that fracture frequency decreases at depths greater than approximately 50 to 85 feet below ground surface was based on field observation during the RI field work The fact that zones with observed fractures exhibited higher hydraulic conductivities than zones without fractures coupled with the decreasing frequency of observed fractures with depth led to the conclusion that the hydraulic conductivity of the bulk rock decreases with depth

The most recent data from all wells were used to provide the maximum VOC data set size During the RI all of the previously-existing and then newly-installed monitoring wells were sampled along with several residential wells The RI sampling included up to 48 monitoring wells Subsequent to the RI and prior to the TI three rounds of monitoring were conducted to verify that the plume was stable 15 monitoring wells were sampled during each of the three rounds During the TI field investigation 29 wells were sampled for VOCs The sampled wells included all of the newly-installed wells and a subset of wells installed during the RI for a total of 29 monitoring wells By using most recent data VOC results from 53 monitoring wells were included in the evaluation (see table labeled Sampling Events for listing of monitoring wells) This approach was selected because there generally was little variation in the data from a particular location between years This is borne out by the attached individual plots of VOCs detected in shallow bedrock and deep bedrock for the Pre-ROD (December 1999January 2000) and Supplemental (May 2000) sampling events and for June 2001 January 2002 and April 2003 sampling events The Pre-ROD and Supplemental plots are similar to the subsequent plots from the 2001 2002 and 2003 sampling events

In addition to maps showing the spatial distribution of VOC data at a given time trend plots of the data from a particular location through time (attached) indicate that since the RI concentrations generally have been stable or have decreased Together the maps and trend plots and the data from which they were developed indicate that the distribution of contaminants over the entire plume has not changed appreciably with time

Response to EPA Comment 4 050305doc 1 of 26 Woodard amp Curran (211941)

REFERENCES

Woodard amp Curran Inc (WampC) 2001 Final Remedial Investigation Report Hows Corner Superfund Plymouth Maine July 2001

Woodard amp Curran Inc (WampC) 2002 Final Feasibility Study Report - Non-Source Area Groundwater Hows Corner Superfund Site Plymouth Maine Hows Corner Superfund Plymouth Maine July 2002

Response to EPA Comment 4 050305doc 2 of 26 Woodard amp Curran (211941)

LIST OF ATTACHMENTS (Response to Comment 4)

Table - Sampling Events 1999 - 2004 (2 pages)

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater Pre-ROD Sampling Event

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater Pre-ROD Sampling Event

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater Supplemental Sampling Event

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater Supplemental Sampling Event

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater June 2001

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater June 2001

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater January 2002

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater January 2002

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater April 2003

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater April 2003

Figure - Concentration Trends - Non-Source Area Wells MW-1B and MW-3B

Figure - Concentration Trends - Non-Source Area Wells MW-13DB and MW-16DB

Figure - Concentration Trends - Non-Source Area Wells MW-16IB and MW- 108D

Figure - Concentration Trends - Non-Source Area Wells MW-108S and MW-112D

Figure - Concentration Trends - Non-Source Area Wells MW-112S and MW-114D

Figure - Concentration Trends - Non-Source Area Wells MW-114S and MW-115D

Figure - Concentration Trends -Source Area Wells MW-2DB and MW-2IB

Figure - Concentration Trends -Source Area Wells MW-102S and MW-103D

Figure - Concentration Trends -Source Area Wells MW-103S and MW-104D

Figure - Concentration Trends -Source Area Wells MW-104I and MW-106D

Figure - Concentration Trends -Source Area Wells MW-106S

Response to EPA Comment 4 050305doc 3 of 26 Woodard amp Curran (211941)

I I

El I

II I I 1 I

I

i

Event Baseline Case ID WC-01 WC-01

Well Date Aug-99 Oct-99 LOT10 1 LOT1-1 1 LOT11-4 LOT14 1 LOT15 1 LOT15-1 1 LOT16 1 LOT16-1 1 LOT17 1 LOT18 1 LOT19 1 LOT2 LOT20 1 LOT21-10 1 LOT21-11 1 LOT21-12 1 LOT21-13 1 LOT21-14 1 LOT21-2 1 LOT21-5 1 LOT21-7 LOT21 -8 1 LOT21-9 1 LOT23 1 LOT24 1 LOT28-1 1 LOT28-2 1 LOT28-3 1 LOT28-4 1 LOT28W 1 LOT30 1 LOT30-1 1 LOT30-2 1 LOT30-3 1 LOT30-4 1 LOT30-5 LOT31 LOT35 1 LOT41 1 LOT42-1 1 LOT43-1 1 LOT43-4 1 LOT6-1 1 LOT67 1 LOT6-7 1 LOT6-8A 1 LOT6-8B 1 LOT80-1 1 LOT82 1 MW-101D MW-1011 MW-101S MW-102D MW-102S MW-103D MW-103S MW-104D MW-1041 MW-104S MW-105D MW-106D

Groundwater Sampling Location Summary 1999 - 2004xls

Sampling Events 1999-2004

Hows Corner Superfund Site Plymouth Maine

Supplemental 2001 2002 2003 Pumping 2004 Pre-ROD Rl Sampling Sampling Sampling Test Sampling WC-03 WC-09 WC-25 WC-30 WC-42B WC-56 WC-58 Dec-99 May-00 Jun-01 Jan-02 Apr-03 Sep-04 Sep-04

1

1 1 1

1 1 1 1 1

1 1

1

1 1

1 1 1

1 1 1 1 1

1

1 1

1 1 1 1

1

1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

Sampling Events 1999-2004

Hows Corner Super-fund Site Plymouth Maine

Supplemental 2001 2002 2003 Pumping Event Baseline Pre-ROD Rl Sampling Sampling Sampling Test

Case ID WC-01 WC-01 WC-03 WC-09 WC-25 WC-30 WC-42B WC-56

ll

Well Date Aug-99 Oct-99 Dec-99 May-00 Jun-01 Jan-02 Apr-03 Sep-04 MW-106S 1 1 1 1 1 MW-107D 1 1 MW-108D 1 1 1 1 1 MW-108S 1 1 1 1 1 MW-110D 1 1 MW-111D 1 1 MW-112D 1 1 1 1 1 MW-112S 1 1 1 1 1 MW-113D 1 1 MW-114D 1 1 1 1 1 MW-114S 1 1 1 1 1 MW-115D 1 1 1 1 1 MW-12DB 1 1 1 MW-12SB 1 1 1 MW-13DB 1 1 1 1 1 1 MW-13SB 1 1 1 MW-14DB 1 1 MW-14SO 1 1 MW-15DB 1 1 1 MW-15SB 1 1 1 MW-16DB 1 1 1 1 1 1 MW-16IB 1 1 1 1 1 1 MW-16SO 1 1 MW-17DO 1 1 1 MW-17SO 1 1 1 MW-1B 1 1 1 1 1 1 MW-203D MW-203S MW-204D MW-204S MW-205 MW-206D

I MW-206S MW-2DB 1 1 MW-2DDB 1 1 MW-2IB 1 1 1 1 1 1 MW-3B 1 1 1 1 1 1

I MW-4O 1 1 1 MW-5B 1 1

II MW-6DB 1 1 1 MW-6SB 1 1 1 MW-8DB 1 1 1 MW-8SB 1 1 1

II PW-207 1 SEEP-1 1 SUBTOTAL - RESIDENTIAL 44 25 0 2 0 3 0 SUBTOTAL - MONITORING 22 48 41 15 15 15 1

Total 3 66 73 41 17 15 18 1

I Included in most recent data

I Notes 1 - Overburden well not included in most recent data for plotting

2 - Tetrahydrofuran and 2-Butanone were the only two compounds detected in this well and are thought to be the result of well repair not included in most recent data for plotting

3 - Not included in most recent data for plotting

2004 Sampling

WC-58 Sep-04

1

1 1

1 1

1 1 1

1

1 1

1 1 1 1 1 1 1 1 1

1 1

1

0 29

29

Groundwatef Sampling Location Summary 1999 - 2004xls

I

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

monitoring well Figure 4-14 total VOC contour (ugl) - December 1999January 2000 Distribution of Total VOCs in

Note SW-113 is located downstream of SEEP-1 Shallow Bedrock Groundwater total concentration of detected VOCs ND= not detected these two locations were sampled during the Pre-ROD Sampling Event

Baseline Sampling Event in OctoberNovember 1999 Hows Corner Superfund Site Surface Water Sampling Location A Plymouth Maine Seep Sampling Location laquo- WOODARD ampCURRAN

995037wipri reportepa ri interim final feb 2001cadd drawingsfinalfig 4-14

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

0 300 600 I

FEET

Q residential well Figure 4-16 monitoring well Distribution of Total VOCs in

Deep Bedrock Groundwater total VOCs contour (ugl) Pre-ROD Sampling Event

active residential wells with lot number Hows Corner Superfund Site 2deg42deg Plymouth Maine total concentration of detected VOCs ND= not detected WOODARD ampCURRAN Enyinaaring bull Science bull Operations bull

995037wipri reportepa ri interim final feb 2001cadd drawingsfinalfig4mdash16

PLYMOUTH POND

PLYMOUTH POND

1 628Tl7MW-2bB 12135

PLYMOUTH POND

monitoring well Figure 4-20

V total VOC contour (ugl) - June 2000 Distribution of Total VOCs in Shallow Bedrock Groundwater

| 34 | total concentration of detected VOCs ND= not detected NA = not analyzed Supplemental Sampling Event Note SW-113 is located downstream of SEEP-1 Hows Corner Superfund Site

Surface Water Sampling Location these two locations were sampled during the Plymouth Maine Baseline Sampling Event in OctoberNovember 1999 Seep Sampling Location WOODARD amp CURRAN

Engineering bull Science - Operations bull 995037wipri reportepa ri interim final feb 2001 cadd drawingsfinalfig 4-20

residential well Figure 4-22 Distribution of Total VOCs in

monitoring well Deep Bedrock Groundwater

total VOCs contour (ugl) Supplemental Sampling Event

Hows Corner Superfund Site

total concentration of detected VOCs ND= not detected NA = not analyzed Plymouth Maine

WOODARD amp CURRAN

995037wipri reportepa-ri interim final feb 2001cadd drawingsfinalfig 4-22 Engineering bull Science - Operations bull

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

FEET

Shallow Monitoring Well

Deep Monitoring Well

C Detected Concentration ND = Not Detected Figure 1-XS Distribution of Total VOCs in Shallow Bedrock Groundwater

Pumping Well

17-Acre Property Boundary Concentration Contour (ugl)

June 2001 Hows Corner Superfund Site

Plymouth Maine WOODARDampCURRAN

-i^rhvj bull Scbncn bull Operations bull 211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0601 dwg04-20-05

PLYMOUTH POND Hopkins Road V

O

PLYMOUTH POND

PLYMOUTH POND

o

0 300 600 mdashfa FEET

Shallow Monitoring Well bull bull - 17-Acre Property Boundary Figure 1-XD

Deep Monitoring Well 1 I Detected Concentration ND = Not Detected Distribution of Total VOCs in Deep Bedrock Groundwater

-mf- Pumping Well June 2001 Residential Well Hows Corner Superfund Site

Plymouth Maine i h Surface Water Sampling Point

g WOODARD ampCURRAN _ ^ _ ^ _ _ yen_ rj i|Hlaquorlny bull Science bull Opt

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0601 dwg04-20-05

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

Shallow Monitoring Well

Deep Monitoring Well

Detected Concentration ND = Not Detected Figure 1-YS Distribution of Total VOCs in Shallow Bedrock Groundwater

Pumping Well

17-Acre Property Boundary Concentration Contour (ugl)

January 2002 Hows Corner Superfund Site

Plymouth Maine WOODARD amp CURRAN Engineering Science- Operations bull

211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0102dwg04-20-05

PLYMOUTH POND

PLYMOUTH POND

Site Pand^ laquoum-laquoBTuitaraquo tLV

vVlf-(

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0 300 600 ^ = FEET

Shallow Monitoring Well mdashbullbullbull 17-Acre Property Boundary Figure 1-YD - A - Deep Monitoring Well FT Detected Concentration ND = Not Detected Distribution of Total VOCs in

Deep Bedrock Groundwater Pumping Well January 2002 Residential Well Hows Corner Superfund Site

Plymouth Maine Surface Water Sampling Point

WOODARD ampCURRAN Engineering Sciencs- Operations bulli Si

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0102dwg04-20-05

- m j

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND j A O-shy

Shallow Monitoring Well E Detected Concentration ND = Not Detected Figure 1-ZS Distribution of Total VOCs in

Deep Monitoring Well Shallow Bedrock Groundwater

Pumping Well Hows Corner

April 2003 Superfund Site

17-Acre Property Boundary Plymouth Maine Concentration Contour (ugl) r WOODARD ampCURRAN

Engineering bull Science bull Operations bull 211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0403dwg04-20-05

s S pound

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PLYMOUTH POND

- -

5 PLYMOUTH POND

Jo

FEET

ft Shallow Monitoring Well mdashbullbullmdash 17-Acre Property Boundary Figure 1-ZD Deep Monitoring Well I 1 I Detected Concentration ND = Not Detected Distribution of Total VOCs in

Deep Bedrock Groundwater Pumping Well April 2003

Q) Residential Well Hows Corner Superfund Site Plymouth Maine

(T) Surface Water Sampling Point WOODARD ampCURRAN poundKk EnginawtirKj bull Science - Operations bull

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0403dwg04-20-05

0 Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

B MW-1B

I 12000

PCE

B 10000 Total VOCs

I

i 2000

i 0 Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

c MW-3B

G 2000

1800

B PCE

1600 Total VOCs

1 I I E

il-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

G E

211941

El

I I z E

80

Concentration Trends shy Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-13DB

Total VOCs

c i i c o

Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

MW-16DB

30

c i c c I c o

Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99

PCE

Total VOCs

Jul-01 Jul-03

211941

O bi

c Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

I MW-16IB

i 35

3

c Total VOCs

lt- 2 5

0 | gt

o

1 sectI

c c 0 4

Jul-90 Jul-92 Jul-94 Jul-96 Jul-98 Jul-00 Jul-02 Jul-04

I I MW-108D

I 12

PCE 10

Total VOCs c oc 3

E E I 0

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

E 211941

c Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

fi MW-108S

I I 40

PCE 35

Total VOCs

30

I f 26

20 I o

I 15

10

c Dec-99 Dec-00 Dec-01 Dec-02 Dec-03 I 0

I MW-112D

c 35 - imdash

I A3 shyTotal VOCs

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E 1 2

I

ition

B 1 ^

-i c 3

0 Dec-99 Dec-OO Dec-01 Dec-02 Dec-03

211941

I

i

I

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Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-112S

08

PCE

Total VOCs 06

o 04

02

0 Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

MW-114D

o

12000

10000

8000

6000

PCE

Total VOCs

4000

2000

i

ccEIIc

i

i

E

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

211941

Con

cent

ratio

n (

ug

l)

E Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

I MW-114S

E A5000 -- Total VOCs

- 4000

0 3000

2000

i 1000

i n shy

Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

MW-115D

c PCE

Total VOCs

c E

o

C c

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03 I 0

211941

IepoundII

EIEIIGICCIccc

30000

25000

20000

o bullsect 15000 b

o 10000 U

5000

0 Aug-99

25000

20000

5000

0 Aug-99

211941

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-2DB

PCE

Total VOCs

Aug-01 Aug-03

MW-2IB

PCE

Total VOCs

Aug-01 Aug-03

IDIBI

ii EIDIISIBIG C

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-102S

6000

5000 PCE

Total VOCs

4000

O 3000

2000

1000

0 Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

MW-103D

16000

~ 14000 ugt 3- 12000 o

^ 10000

sect 8000

O 6000

4000

2000

PCE

Total VOCs

0Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

211941

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

G MW-103S

I I

ampo

12000

10000

E sectc

S

8000

6000

4000

2000

0Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

G I 6000

MW-104D

i 5000

PCE

Total VOCs

i i c

2000

1000

Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

E I

211941

cIccIG

IIBCccBcIc

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-1041

PCE Total VOCs

a 25000

0 20000

a 15000

10000

5000

0 Jan-OO Jan-01 Jan-02 Jan-03 Jan-04

MW-106D

3000

2500 PCE

Total VOCs

=sect 2000

o bullsect 1500

1000

500

0 Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

211941

c Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

c MW-106S

I PCE

Total VOCs

i

i Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

i

i i i E

C

211941 c

Response to EPA-DEP Comment 5 Dated March 312005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

iiw

EPA-DEP Comment 5

Comment 5 Matrix Diffusion The report as well as other proponents of matrix diffusion suggest that depletion of DNAPL (Section 5112 page 5-15) needs to be achieved While that might be the ideal the goal is to achieve performance standards and that goal may be attainable while there is residual contamination in the rock perhaps even DNAPL globules The low bedrock matrix porosity (page 1-15) the high permeability values (page 4-4) the relative flux of the groundwater (page 5-5) and the decrease in surface area and out of the mainstream pockets (appendix C-4) all suggest that the diffusion out of the rock matrix would be insubstantial relative to the regional flux of groundwater through the Site

Response The TI Evaluation Report does not explicitly consider or rely upon matrix diffusion as a basis for requesting a TI Waiver for a portion of the Hows Corner Site The technical literature provides documentation that matrix diffusion can be a significant process that affects chemical transport and groundwater remediation timeframes in unconsolidated and consolidated media including fractured rock (US EPA 1989 Freeze and Cherry 1979 Pankow and Cherry 1996 Fountain 1998) Back diffusion of contaminants from the matrix porosity of the fractured rock can prolong the time necessary to achieve groundwater cleanup goals particularly for compounds such as PCE for which the cleanup goal is a low concentration It is our expectation that matrix diffusion has occurred at the Hows Corner Site and that back diffusion of PCE from the rock matrix will also occur Although the extent to which matrix diffusion is occurring at the Hows Comer Site has not been determined and that lack of knowledge contributes to uncertainty regarding the cleanup times at the Site the effect of matrix diffusion is to lengthen rather than shorten the time required for remediation

REFERENCES

Fountain JC 1998 Technologies for Dense Nonaqueous Phase Liquid Source Zone Remediation Ground-Water Remediation Technologies Analysis Center Technology Evaluation Report TE-98-02 December

Freeze RA and Cherry JA 1979 Groundwater Prentice-Hall Inc Englewood Cliffs NJ 07632 p 410-412

Pankow J F and Cherry J A 1996 Dense Chlorinated Solvents Waterloo Press Portland OR 97291-1399 p 67-88

US EPA 1989 Transport and Fate of Contaminants in the Subsurface EPA6254-89019 p 17-18

Response to EPA Comment 5 050305doc 1 of 1 Woodard amp Curran (211941)

WOODARD amp CURRAN Maine Massachusetts New Hampshire Connecticut Florida Operational offices across the US 1-800-426-4262 www woodardcurran com

Page 19: SDMS DocID 251749 - Records Collections · 2020-06-13 · CORPORATE OFFICES: Maine, Massachusetts, New Hampshire, Connecticut New, York, Florida Engineering • Science • Operations

DRAFT

242

24

238

236

bulla

c

i

a Q

234

232

228

226

Hows Corner Constant Discharge Testing USGS Background Groundwater Level USGS 445319068560101 ME-PEW456 Kenduskeag Maine

End of Monitored Recovery Period 09302004

Regional Background Location i 226 miles from Pumping Locatio

lt

697

NOTES

1 Groundwater samples collected in 1999 were screened for five volatile organic compounds (VOCs) only N

tetrachloroethene (PCE) exceeded reporting limits MW-2030 082304 082304 082304 082304 u

2 Strike and Dip of likely or possible transmissive 30 45 55 85 feature within the packer interval from which the indicated sample was collected

MW-204D

PCE TOTAL VOCs

081904 30

220 2636

A

081904 46-50 540 6436by

081904 IT

260 3073

x

MW-105D

PCE TOTAL VOCs

111199 50-60 2100 2100

MW-106D

PCE TOTAL VOCs

111199 76-86

400 400

111199 137-147

1400 1400

111299 1355-1455

350 350

PCE TOTAL VOCs

44 84

64

MW-6SB

bulli

lt

gt-

170 234

35

I I i

140 192

^^52

^^52

130 183

52 - lt

S A 34

PW-207 082404 082404 082404 20 37

PCE 1300 TOTAL VOCs

17-Acre George West Property Boundary

MW-113D

PCE TOTAL VOCs

112299 46-56

350 350

112299 70-80 190 190

150

112299 105-115

129 129

112399 138-148

230 230

L e g e n d ( J New Monitoring Well-Summer

Site Property Boundary ^ P u m p i n g Well-Summer 2004

-xmdashxshy Source Area

bull0shy Monitoring Well shy Pre 2004 Angled Boring-Summer 2004

211941laquoipdwgTI-ELV21ig41paltker-data2

2004 PCE of Total

bull lt70 VOCs

M W - 1 14D ^ ^

Figure xx Packer Testing Results in

Vicinity of Source Area Hows Corner Superfund Site

Plymouth Maine ^ WOODARD ampCURRAN

^^^^^^^^^^m ampKm Engineering - Science bull Operations

c Northeast Geophysical Services Borehole Geophysical Log

MW-203 Date logged 081704 Plymouth Maine

I Flowmeter Measurements Tomporaturo(C) Acoustic Televiewer

7 5 8 8 5 9 95 Caliper (Inches) Resistance (Ohms) Spontaneous Potential (mVj Dip In Degrees PCE Total VOCs

3 0 2 0 8 0 laquodeg 4S 1000 1400 1800 2200 MO HO 1000 1200 MOO 0 laquo deg ugL ugL n 1 1 1 1 1 1 1 1 1 i 1 1 1 1 n 1 1 1 1 1 1 1 1 1 1 1 n I l l l l l l l n

Ambient Flowneter pumping Rowmeter 11 gpm 6

H

bull

magnetic 10 bull 10 bull - 10 - north - 1 0I

-

_

bullbullbull - bull

20 bull bull20 bull ^ ltr~mdash 01

I

4 ^

LOS7

^

44 84 I I

Xr - 2

lt ^ bull30 -_ _^O1J- 1 _ 050 30 - 3 0

0r - - 3

C -j [ bull bull bull | shy

-O8 H ~ 1 045 7

1 4040 - 40 - -40 r - 14gt 13

V1s -- -023 f 1022 1V 170 234 I

T lt bull B gtf 50^ J50 - - 5 0 - - 5 0

I eet be

lo

i 1

1 1

1

140 192 - - - -t shy

-mdashj bullpound 60 - $o - - 60 - -60

H i I c

bull024

ampbull

3 - T lt ftft rgt He

70 bull j 70 - - 70 - 7 0 -

in -j bullbull shy

-021 1 T 022

- Ton _ Ov

26

130 183 NF NF

90 -_ 90 - 7 90 - -90

-

ifi Jf

3J

^gt _ N F NF bull bull shy

| H100 - j 100 bullbull 100 - -100

1 1 1 1 1 1 1 ) | 1 f I 1 1 1 ) 0 20 40 60 80

flft mdash ftn - mdash rVt

30 4 g 0 20 40 60 Dip in Degrees bullbull

Likely or poss bleFluid Resistivity (ohmmeters) The dip direction-- indicated

^ t h e l i n e extending from t h

I Iransmissive zone circle The strike of the feature is 90 degrees from this

The acoustic televiewer graph displays the mostprominent features selectedffom the acoustic televiewer

R n r a h n l c D O t t n O I B

f i o n n h w c i r a l U K U p i i y SI Ud l

1 rn l_Og Packered Interval August 2004

E tog The location dip angle and dip direction of the sleeted M W - 2 0 3 Groundwater samples were collected by Woodard S Curran on H23120M features are approximate Refer to the televiewer og of His _ well for more precise detail Plymouth Maine Date logged 081704

I

1

Northeast Geophysical Services Borehole Geophysical Log MW-204 D a t e l o gge d 072604

Plymouth Maine

n 3

Flowrneter Measurements(in gpm)

Caliper (Inches)0 3 5 4 0

1 1 1 1 1 1 1 t 1 1 1 1 1 1Ambient Rowmeler pumping Flowmetsr 05gpm

Templaquorature (C) bull bull bull bull i

7 75 8 8S 9 Resistance (Ohms) Spontaneous Potential (mV)

4000 SOW 600 4M 0

Acoustic Televiewer (interpreted)

Dip in Degrees 0 20 4060 SO

at N

PCEugL

Total VOCs ugL

- -_ a

10-

shy 10 bull - 10 shymagnetic

north - 10

o o

bull 1

11

11

1 1

1 1

11 1

1 1

1 1

1 1

1 1

1 1

1 1

1 1

1 1 E 1

- L

3 7 2 0 2 0r bull 20 bull - shy

i S_ N F

bull30 bull 7 3 0 220 2636shy1^ J J 004

fI f V ^

40 shy 4 0 4 0 shy - 4 0rbull019 [_ 007 w8 - - shy5 c

bull

gt

Ia50i 540 6436

bull50 - - 50 - - 5 0

-QQ7 - bull - -t T

pound V gtk

B 6 0 - e o - 7 6 0 -60shyQ 1 1

Q -007 -004 bull1 mdash T - J ~

bull

- - shyT 70 -J c [TO- - 70 - 7 0-

V Y 1- -004 -003

mdash T -h - y - j i - - mdash 260 3073 - gt=7

80 -j NF bull80 - - 80 - - 8 0Jgt

bull i

i 1

i i

C- bull shy

90 shy

K

Jlt i90 90 shy - 9 0shy -

l

ii

I I I I

NF bull M J

I ^ ^ - ^ bull 1

mdash mdash - _

s -7 ^100shy

till

1 100 100- H - 1 0 0shy -1 x Likety or possible k ^ Iransmissive zonebull

1 i i i ii i i i | l l l l | l i l l 0 20 40 ED 80

1 -

3 0SOFluid Resistivity (ohmmeters)

Dip in Degrees The djp ^ ^ o n is indicated ty Ihe line extending from tha circle The strike of Ihe feature

19- 3U UIHJIW93 IolII l l l lraquo

bull

The acousfc televiewer graph displays the mostprominent features selected from the acoustic televiewer109 The location dip angle and dip direction of Ihe sleetedfeatures are approximate Refer to the televiewer log of thiswentormore precise detail

B o r e h o l e G e O D h V S I C a l LOO B W H U I B w c w p n y o i v a i w v yM W - 2 0 4

P l y m O U t n MaiDB

Packorod Interval August 2004Groundwater san-ples wampramp collected by Woodard a Curran on OMO23C4

Date logged 072604

C

I

E Northeast Geophysical Services Borehole Geophysical Log Date logged 072704

I MW-205

Plymouth Maine

Flowmeter Measurements Temperature (C) Acoustic Televiewer (In gpm) I ~l (Interpreted)

I 85 10 Caliper (inches) 95

Dip in D g r laquo Resistance (Ohms) Spo ontaneous Potential (mV PCE Total VOCs 3 0 16 4 0 4 5 ) 20 40 60 80 10 00 2000 30 00 4VJ 400 -3 laquo

i i i i 1 i i I i 11 4 0 D 1 I I ugL ugL

C h

iii Ambient Flowmetar pumping

Flowmeter 1 25 gprn

I bull$bull

i

I rmdash magnetic 1 north ^^^^ 1 VI f

10 ~ I C x 10 bull - 10 bullbull

4 5 6mdashmdash f 1000B 11448 noisy nodi a raquo ^

mdash 5rt mdashi mdash Oft pound) 1100B 12509

cjmdash1 007

-

i i i 1

en

8 B a B

30 mdash

-

40 shy

-mdash I -

50 -_

__NF lt005

- 30 - - 3 0 it 34V

MO P26 V S) 1300B 13776 _ N F NF

26

40 bull - 40 bull 7-40 gt J Vf1 cX

) -j -

_ N F NF 50 c bull - 50 ^ 7-50

i I

I

c

B pound 60 - 6 0 7 60 - 7-60 a i 1

_ N F NF i Si f f 70 -_ bull70 bull - 70 shyC I 9

-m bull - shyA

_ N F NF 80 80 -j bull80 bull - 80 - C- 33 34

bull

5-i r

i 1

J r

Ck

_ N F NF 9 0 90 - - 90 shy

i bullCshy

J rK bull

100 -j ^ Likely or possible bull100- - 100- I -100

transmissive zone bull - ^ bull shy] |

1 1 1 1 1 1 1 I 1 i i i 1 i i 1 1 0 20 40 SO SO 10 20 30 40 50 Dip in Degrees 30 4 0 Fluid Resistivity (ohmmeters) Thlaquo dip direction is indicated

by the line extern r g from the circle The strike of he feature is 90 degrees from ihis

The acoustic televiewer graph displays the most

I Borehole Geophysical Log Packered Interval August2004 prominent features selected from the acoustic televiewer

Groundwatcr samples were oollccled by Woodard amp Cufran orgt S172004 log The location dip angle and dip direction of ins slsctsd MW-205 features are approximate Refelt to the televiewer log of this wall for more precise detail Plymouth Maine Date logged 072704

I

C

I Northeast Geophysical Services Borehole Geophysical Log Date logged 072704

I MW-206

Plymouth Maine

Flowmetor Measurements Temperature (C) Acoustic Televiewer | I r T i i i i i i i i i i i i i i r I |(in gpm) (Interpreted)

I 75 8 flS 9 95

Caliper (inches) Resistance (Ohms) Spontaneous Potential (mV) Dip In Degress PCE Total VOCs 30 35 40 4 5 0 20 40 M 90 4500 5500 6500 ugL ugL I i i

I I

- 1 0

I - 2 0

I 2900B 32401

i i L

E 0

i 6300B 68901

i I 0 20 40 SO 80

20 30 40 50 Dip in Dlaquogralaquos

amp 4 a Fluid Resistivity (ohrnmeters) The dip dirertion is indicated Likely or possible by iho line extending from the transmissive zone circle The striKe of the feature

is 90 degrees from tNs

Borehole Geophysical Log Packered Interval August 2004

E amples were collected by Woodard amp Cunan oo SM82004 log Thraquo location 4p angle and dip direction of the sloeled MW-206 feature are approximate Refer to the televiewer 109 of this well for more precise detail Plymouth Maine Date logged 072704

C

I Northeast Geophysical Services Borehole Geophysical Log

Date logged 082304 PW-207

I Plymouth Maine

Fiowmeter Measurements Temperature (C) Acoustic Televiewer

I (in gpm) (interpreted)

75 8 85 9 95 Caliper (inches) Resistance f0tims) Spontaneous Potential (mV) Dip in Degrees PCE Total VOCs

55 60 0 20 40 SO 80 ugL ugL I I I I I I I

Ambienl Fiowmeter pumping Flewmater

magnetic - 10 - - 1 0

north

i - 20 - - 2 0

1300 1410

i - 30 - - 3 0

i tf

5400 5802 - 40 - - 4 0

B - 50 - - 5 0

I 18000 19234

- 60 - - 6 0

I 12000 13085

- 70 - - 7 0

- 8 0

i - 9 0 19000 20354

G - 100- -100

I 110 110 bull110

0 20 40 60 SO 10 20 30 Dip m Degrees

Fluid Resistivity (ohmmeters) I 50

The dip direction is indicated by ihe line extending from the circle The strike of the fealure is 90 degrees from this

Borehole Geophysical Log

G Packorod Interval August 20(M log The location dip angle and dip dirlaquocton or the sleeted Groundaier samplss were ooliecled by Woodard i Curran on ampt24f2ltXM PW-207 failures are approximate Reter to the televiewer log of this wlaquoll for more precise detail PlyPIOUth Maine Date logged 082304

I

Table XX Packer Permeability and Packer Sampling Results for Potential Fracture Intervals

1

WellID MW-101D MW-101D MW-101D MW-101D MW-101D MW-101D MW-101D MW-101D MW-101D MW-101D MW-I01D MW-101D MW-101D MW-102D MW-102D MW-I02D MW-102D MW102D MW-102D MW-102D MW-102D MW-102D MW-I02D MW-102D MW-102D MW-102D MW-103D MW-103D MW-103D MW-103D MW-I03D MW-103D MW-103D MW-103D MW-103D MW-103D MW-103D MW-103D MW-I03D MW-104D MW-104D MW-104D MW-104D MW-I04D MW-104D MW-104D MW-104D MW-104D MW-104D MW-104D MW-105D MW-105D MW106D MW-106D MW-106D MW-107D MW-107D

1999 Drilling Program

Hows Corner Superfund Site Plymouth Maine

Potential Fracture Top Of Bottom 6 Depth to lt Topof i Interval from Packer Packer Middle of Elevation Hydraulic bull PCE

GS ELEV 1 Rock Drilling Interval Interval Interval of Interval Conductivity Concentration (ft msl) (ft msl) TEST (ftbgs) (ftbgs) r(ftbgs) ( f t b (ft mil) (cmsec) (raquogL)

4339 4329 13 28-29 33-3537-39 271 376 324 4016 OOOE+00 4339 12 37-3444-46 380 485 433 3907 157E-04 4339 11 488 593 541 3799 132E-04 4339 10 60-61 578 683 631 3709 OOOE+00 4339 9 678 783 731 3609 I79E-05 4339 8 778 883 831 3509 106E-05 4339 7 880 985 933 3407 243E-05 4339 6 990 1095 1043 3297 339E-06 4339 5 1090 1195 1143 3197 OOOE+00 4339 4 1190 1295 1243 3097 OOOE+00 4339 3 1365-1375 1290 1395 1343 2997 OOOE+00 4339 2 147-157 1390 1495 1443 2897 580E-05 4339 1 147-157 1470 1575 1523 2817 741E-05 43161 43061 13 166 271 219 4098 333E-04 43161 12 30-3136-40 260 365 313 4004 I54E-05 43161 11 36-4041-43 362 467 415 3902 548E-05 43161 10 470 575 523 3794 598E-05 43161 9 570 675 623 3694 197FOS 43161 8 670 775 723 3594 OOOE+00 43161 7 770 875 823 3494 891 E-05 43161 6 83-94 870 975 923 3394 139E-05 43161 5 970 1075 1023 3294 123E-04 43161 4 1070 1175 1123 3194 526E-06 43161 3 1170 1275 1223 3094 138E-05 43161 2 1270 1375 1323 2994 671E-06 43161 1 1370 1475 1423 2894 OOOE+00 42997 42497 13 18-19 170 275 223 4077 OOOE+00 42997 12 260 365 313 3987 766E-05 42997 11 360 465 413 3887 727E-05 42997 10 460 565 513 3787 192E-05 42997 9 560 665 613 3687 752E-05 42997 8 660 765 713 3587 778E-05 42997 7 85-86 763 868 816 3484 260E-05 42997 6 860 965 913 3387 289E-05 42997 5 102-103 960 1065 1013 3287 102E-04 42997 4 1060 1165 1113 3187 522E-06 42997 3 1160 1265 1213 3087 520E-06 42997 2 129-130 1260 1365 1313 2987 960E-04 42997 1 1360 1465 1413 2887 OOOE+00 43372 42922 11 35-37 42-45 350 455 403 3935 684E-04 43372 10 460 565 513 3825 500E-05 43372 9 560 665 613 3725 106E-05 43372 8 72-74 660 765 713 3625 204E-05 43372 7 760 865 813 3525 872E-06 43372 6 860 965 913 3425 467E-06 43372 5 960 1065 1013 3325 200E-05 43372 4 1060 1165 1113 3225 354E-05 43372 3 125-130 1160 1265 1213 3125 157E-05 43372 2 125-130 1260 1365 1313 3025 337E-04 43372 1 1365 1465 1415 2922 689E-06 43052 43002 2 54-58 490 595 543 3763 124E-05 2100 43052 1 139-140 145-146 1367 1472 1420 2886 154E-04 1400 43291 4391 3 bullI133 260 365 313 4017 439F06 43291 2 77-78 760 865 813 3517 230E-03 400 43291 1 143-144 1355 1460 1408 2922 971E-06 350

29958 27258 4 450 555 503 2493 OOOE+00 (21)A 29958 3 103-105 1000 1105 1053 1943 752E-04 (063)A

Table XX Packer Permeability and Packer Sampling Results for Potential Fracture Intervals

1999 Drilling Program

Hows Corner Supcrfund Site Plymouth Maine

gtbull i Potential Fracture Top _OfBot Bottom of Depth to ltbull Top of Interval from f Packer Packer Middle Of

GS ELEV lt Hock Drilling interval Interval Interval WeD ID ft msl) (ft msl) TEST (ftbgs) ltft$gs) (ftbgs) (ftbgs)

MW-107D 29958 2 128-130 1200 1305 1253

MW-107D 29958 1 139-141 1350 1455 1403

MW-108D 31904 31104 6 35-36 300 405 353 MW-108D 31904 5 60-62 550 655 603

MW-108D 31904 4 80-83 750 855 803

MW-108D 31904 3 118-119 123-124 1150 1255 1203

MW-108D 31904 2 147-149 1440 1545 1493

MW-108D 31904 1 1700 1805 1753

MW-110D 40576 40426 2 21-31 210 315 263 MW-110D 40576 1 148-154 1460 1565 1513 MW-I11D 40519 4 70-71 650 755 703

MW-111D 40519 3 79-82 84-86 780 885 833 MW-I11D 40519 2 97-102 950 1055 1003 MW-111D 40519 1 1370 1475 1423

MW-112D 3027 2942 4 42-52 420 525 473 MW-112D 3027 3 850 955 903 MW112D 3027 2 1100 1205 1153 MW-112D 3027 1 135-136 140-141 1340 1445 1393

MW-113D 43085 43085 5 250 355 303 MW-I13D 43085 4 47-49 460 565 513 MW-113D 43085 3 73-74 700 805 753 MW-113D 43085 2 1050 1155 1103 MW-113D 43085 1 1380 1485 1433

MW-114D 42394 41594 4 48-49 450 555 503 MW-114D 42394 3 79-81 740 845 793 MW-114D 42394 2 121-129 1250 1355 1303 MW-114D 42394 1 134-142 1350 1455 1403

MW-115D 4035 4035 4 300 405 353 MW-1I5D 4035 3 70-71 650 755 703 MW-115D 4035 2 1150 1255 1203 MW-115D 4035 1 1400 1505 1453

LOT-28W 382 7 450 555 503 LOT28W 382 6 550 655 603 LOT-28W 382 5 650 755 703 LOT28W 382 4 750 855 803 LOT-28W 382 3 850 955 903 LOT-28W 382 2 950 1055 1003 LOT-28W 382 1 1055 1155 1105

NOTES cmsec = centimeters per second ft bgs = leet below ground surface It msl = feet below mean sea level lt = not detected at indicated reporting limil A = detected below laboratory PQL ( ) = detected below reporting limits

Elevation of Interval

(ft nisi) 174

159

283gt 2588

2388

1988

1698

1438

3795 2545 3349 3219 3049 2629

2555 2125 1875 1635

4006 3796 3556 3206 2876

3737 3447 2937 2837

3683 3333 2833 2583

3318 3218 3118 3018 2918 2818 2715

Hydraulic Conductivity

(cmsec)

323E-05

208E-05

471E-03

471E-03

624E-05

3I6E-05

264E-05

261 E-05

OOOE+00 200E-04 953E-05 OOOE+00 OOOE+00 212E-05

361 E-05 410E-06 2gQE06 292E-05

786E-05 124E-05 151 E-05 822E-06 82IE-06

858E-05 I69E-05 352E-03 866E-05

223E-05 394E-06 122E-05 525E-06

831 E-05 182F-05 L62E-05 129E-05 190E-05 890E-04 981 E-04

PCEraquo Concentration

(ugL)

lt5

(14A)

98 11

15

22

11

30

200 (62)A

110 210 300 240

(44)A (23)A

5

350 190 129 230

2200 1900 2600 2600

(17)A (16)A (19)A

96

Table XX Packer Permeability and Packer Sampling Results for Potential Fracture Intervals

2004 Drilling Program

Hows Corner Superfund Site Plymouth Maine

Top of Bottom of Depth to Midpoint

t K

ELEV (ft Potential Transmissive Zones Packer Interval

Packer Interval

Middle of Interval

Elevation of interval

Hydraulic Conductivity

PCE Concentration

Well ID msl) TESTr (ft bgs)- (ftbgs) (ftbgs) (ftbgs) (ft msl) (cmsec) (ogt) MW-203D 43227 4 277279 24 32 28 4043 667E-05 44

3 408415420 39 49 44 3883 593E-05 170 2 526 530 49 57 53 3793 101E-04 140 I 828830842 80 88 84 3483 701E-05 130

MW-204D 43262 5 295 300 26 34 30 4023 902E-05 220 4 463496513516 45 53 49 3833 119E-04 540 3 681685688 63 71 67 3653 OOOE+00 2 758 76 2 71 79 75 3573 309E-05 260 I 88 96 92 3403 OOOE+00

MW-205 42389 3 164 166 168 15 20 175 4148 OOOE+00 1000B 2 302305312 30 35 325 3998 107E-04 1300B 1 40 45 425 3898 OOOE+00

MW-206D 43007 5 17 72 195 4128 291E-05 4 296 302 307 29 34 315 4008 940E-05 2900B 3 522 52 57 545 3778 944E-07 2 656 64 69 665 3658 353E-06 1 92392793 4939 91 96 935 3388 614E-05 6300B

PW-207 43477 5 184622162819 18 29 235 4088 209E-05 1300 4 3508 32 43 375 3948 568E-06 5400 3 53325341542154325559 50 61 555 3768 821E-05 18000

6359 61 72 665 3658 866E-06 12000 1 8685 84 89 865 3458 213E-05 19000

NOTES cmsec = centimeters per second ft bgs = feet below ground surface ft msl = feet above mean sea level B = detected in lab blank

Table XX Orientation Permeability and Groundwater Sampling Results for Transmissive Features

2004 Drilling Program

Hows Corner Superfund Site Plymouth Maine

Borehole Geophisical Feature depth Dip True Dip True Transmissive Log Feature (Feet) Degrees Azimuth Strike bullvgt(Ltk|iy^

Number v Tosftble) v MW-203 5 277 64 337 67 Likely

6 279 59 11 281 Likely 8 352 14 177 87 Likely 11 381 46 96 6 Possible 12 408 35 271 1 Possible 14 415 57 250 340 Possible 15 420 58 202 292 Likely 18 526 52 75 345 Likely 19 530 52 82 352 Likely 28 828 48 75 345 Likely 29 830 52 17 287 Likely 30 830 56 233 323 Possible 31 842 50 130 40 Likely

MW-204 4 295 15 147 57 Likely 5 300 43 91 1 Likely 11 439 31 80 350 Possible 12 440 46 219 309 Possible 14 463 50 358 88 Likely 15 496 34 198 288 Likely 16 513 54 17 287 Likely 17 516 33 14 284 Likely 25 681 39 359 89 Possible 26 685 22 45 315 Possible 27 688 35 73 343 Possible 32 758 45 236 326 Likely 33 762 46 306 36 Likely

MW-205 5 164 69 106 16 Possible 6 166 78 165 75 Possible 7 168 82 115 25 Possible 8 168 68 116 26 Possible 12 215 46 222 312 Possible 13 217 75 62 332 Possible 14 219 29 32 302 Possible 16 237 69 250 340 Possible 17 256 73 353 83 Possible 18 272 44 202 292 Possible 21 299 37 196 286 Possible 22 302 31 206 296 Possible 23 305 59 48 318 Likely 24 312 63 42 312 Likely

MW-206 1 264 37 181 271 Likely 2 296 69 217 307 Likely 3 302 66 233 323 Likely 4 307 64 224 314 Likely 8 342 62 259 349 Likely

jjHydraulic GoiDanctilyity j(cmsecjw

667 E-05

593 E-05

101 P04

710 E-05

902 E-05

119 E-04

0

309 E-05

0

107 E-04

94 E-05

PCE (ugL)

44

170

140

130

220

540

260

IOOOB

1100B

1300B

2900B

STotal vVoCsv tig1)

84

234

192

183

2636

6436

3073

11448

12509

13776

32401

PCEyo dfCTotaf

52

73

73

7 1

83

84

85

87

88

94

90

Table XX Orientation Permeability and Groundwater Sampling Results for Transmissive Features

2004 Drilling Program

Hows Corner Superfund Site Plymouth Maine

Borehole Geophisical Feature deptt raquoip True pip True Transraissive Log Feature (Feet) shy Degrees Azimuth Strike (tikely

Number raquo Possible) 22 522 57 54 324 Possible 25 656 40 82 352 Possible 32 871 59 151 61 Possible 33 883 53 185 275 Possible 34 895 7 175 85 Likely 35 899 53 90 0 Likely 36 902 49 184 274 Likely 37 923 9 175 85 Likely 38 927 42 206 296 Likely 39 934 48 167 77 Likely 40 939 26 180 90 Likely

PW-207 1 1846 33 167 77 Likely 4 2216 49 289 19 Possible 7 2819 59 265 355 Possible 11 3508 55 189 279 Possible 18 5332 43 305 35 Likely 19 5341 51 30 300 Likely 20 5421 20 254 344 Likely 21 5432 39 301 31 Likely 23 5559 52 302 32 Likely 25 6359 24 182 272 Possible 29 8049 77 231 321 Possible 30 8685 78 38 308 Likely 32 9334 29 194 284 Likely

NOTES

B = detected in lab blank

Hydraulic Conductivity

(cmsee) 944 E-07 353 E-06

614 E-05

209 E-05

568 E-06

821 E-05

866 E-06

213 E-05

bulltCE (ugL)

6300B

1300

5400

18000

12000

19000

Total VOCs (ug1)

68901

1410

5802

19234

13085

20354

PCE of Total VOCs

9 1

92

93

94

92

93

Response to EPA-DEP Comment 3 Dated March 312005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

lit

EPA-DEP Comment 3

Comment 3 The reported f values and resultant Kd values There remains doubt that the values used in the flushing model accurately reflect the propensity for PCE to sorb to the bedrock The ^ values presented in Appendix B may be unrealistically high because the bedrock samples may have contained organic carbon that was unavailable for sorption The reported f values are only qualitative estimates of the organic carbon content of the bedrock samples The Walkley and Black organic carbon measurement method is quick and simple but the results obtained cannot be considered quantitative because it requires a correction factor which often results in erroneous values it assumes the organic carbon has an average valence of zero oxidizable and reducible constituents such as chloride ferrous iron and manganese oxides interfere with the results and the errors introduced by interference are potentially greater when the organic carbon content is low at low f values it is not clear that organic carbon is controlling PCE sorption (Schwarzenbach and Westall 1981 Mackay et al 1986 Fetter 1999)

In order to derive a Kd-based retardation factor that is reasonable given the reported f values and the rapid advance of the PCE plume described on pages 4-11 and 4-12 the flushing model requires a bulk density to porosity ratio that is roughly two orders of magnitude higher than the actual ratio for the Hows Corner bedrock (page 4-4) This apparent discrepancy needs to be addressed

Response This comment raises several concerns about the collection and analysis of samples for fraction of organic carbon (f^) the quality of the resulting data and the implications of the use of those data for estimation of the retardation of groundwater contaminant movement Results of bedrock analysis for f were proposed in the TI Evaluation Work Plan for use in conjunction with groundwater contaminant concentrations and aquifer information to estimate cleanup times using the Batch Flushing model It is important to use accurate f values from representative bedrock in the Batch Flushing model in order to obtain reasonable estimates of the remedial time frame Because of the importance of accurate and representative results the TI Investigation field program was designed and conducted both to collect samples representative of the rock volume most likely to be in contact with contaminated groundwater and to analyze them using an appropriate refereed analytical method Five potential methods for evaluating f were identified Of the five methods the Walkey-Black method was selected because it has minimal method interferences and a sufficiently low detection limit as well as a long history of use in agronomy and contamination studies The PRP Group is pleased with the quality of the data obtained from the bedrock samples as represented by their precision and reproducibility

The first part of this comment relates to the determination of fraction of organic carbon (f^) values The several subparts of the first paragraph are addressed individually in items 1 through 5 below The second part of the comment regarding the resultant distribution coefficient (Kd) values is addressed separately as item 6 below

1 There remains doubt that the values used in the flushing model accurately reflect the propensity for PCE to sorb to the bedrock

bull The rock core samples used for f (gocg) analysis were from core immediately adjacent to fractures These rock core samples included the fracture surfaces themselves and rock core extending back less than 1 cm from the fractures Therefore the foe data reported in the TI Evaluation represents the f of bedrock through which groundwater will travel and to which PCE will adsorb Based on the careful selection of sample locations and the

Response to EPA Comment 3 050205doc 1 of 11 Woodard amp Curran (211941)

number of samples collected we are confident that the measured f values are representative of the f at points of contact for PCE with the bedrock it is these f values that determine the propensity of PCE to sorb to the bedrock

bull The samples of rock core collected for analysis of f originated from 19 different locations varying in depth from 11 to 90 feet Therefore it is very unlikely that the rock core samples were contaminated with extraneous organic carbon from above ground

2 The foc values presented in Appendix B may be unrealistically high because the bedrock samples may have contained organic carbon that was unavailable for sorption

bull As noted in response 1 the f data reported in Appendix B represents organic carbon primarily associated with the surface of fractures in the bedrock through which groundwater is most likely to travel Therefore it is this organic carbon that the contaminants in the groundwater will come in contact with and adsorb to in the fractured rock at the site

bull The chemical oxidation agents used in the Walkey-Black method oxidize the easily oxidizable organic carbon in the medium and the foe is calculated from the quantity of the agent consumed Therefore it is unlikely that the analysis of the bedrock samples measured organic carbon that was unavailable for sorption

3 The reported foc values are only qualitative estimates of the organic carbon content of the bedrock samples

bull The reported f values are accurate quantitative results Schumachers review of Methods for the determination of total organic carbon (TOC) in soils and sediments (NCEA-C-1282 EMASC-001 April 2002) identifies the Walkley-Black method which was used to analyze the reported foc values as the reference method for comparison to other methods for analyzing total organic carbon

bull Schumacher also points out that if anything the WalkJey-Black method may underestimate the total organic carbon in a sample due to possible incomplete oxidation of organic carbon Usually the incomplete oxidation of total organic carbon in environmental samples is corrected for by multiplying the measured foe by 130 (Walkley amp Black 1934 Schulte 1995)

bull When the f data in the TI Evaluation Report (WampC 2005) Appendix B (attached) are analyzed statistically the standard deviation of the f for the 19 samples analyzed is 174 of the average f Given this standard deviation the 95 confidence interval for this data ranged from a low of 000123 gocg to a high of 000253 gocgm

The labs Method of Detection Limit (MDL) for the f measured using the Walkley-Black method is 00001 gocg Therefore the average (000188 gocg) the mean (000185 gocg) and geometric mean (000187 gocg) of the f values for the rock core at Hows Corner are all statistically significantly greater than the MDL of the Walkley-Black method

In addition to the aforementioned statistical analysis of the foe data triplicate samples (n = 3) from the same rock core (including one sample from the 19 rock core samples) were

Response to EPA Comment 3 050205doc 2 of Woodard amp Curran (211941)

analyzed for their f to determine the repeatability of the Walkley-Black method The average the mean and the geometric mean of the f values of these replicate samples was 000162 gocg 000150 gocg and 000159 gocgm respectively The standard deviation of these measurements was 000039 gocg

4 The Walkley and Black organic carbon measurement method is quick and simple but the results obtained cannot be considered quantitative because it requires a correction factor which often results in erroneous values it assumes the organic carbon has an average valence of zero oxidizable and reducible constituents such as chloride ferrous iron and manganese oxides interfere with the results and the errors introduced by interference are potentially greater when the organic carbon content is low at low foc values it is not clear that organic carbon is controlling PCE sorption (Schwarzenbach and Westall 1981 Mackay et al 1986 Fetter 1999)

bull Schumachers review (NCEA-C-1282 EMASC-001 April 2002) of the Walkley-Black method identifies several potential problems with this analytical method that could occur if the analytical lab is not familiar with the nuances of the chemistry associated with this method Interestingly Schumachers review neglected one of the more important analytical steps required to avoid errors in quantifying f in samples where there might beNAPL

It is absolutely critical to eliminate any NAPL from rock core samples prior to using the Walkley-Black method to measure foe in such samples This was done by the lab (PTS Laboratories) that measured the foe in the rock core samples from Hows Corner The lab used the Dean-Stark method (solvent extraction) to remove all hydrocarbons (including PCE and other NAPLs) from the sample (PTS Laboratories) This extraction method does not interfere with the subsequent analysis of the natural organic carbon associated with the rock core

Subsequently the samples were dried at 150degC to a constant weight (normally 16 hours) This latter step oxidizes all inorganic minerals including ferrous bearing minerals to ferric oxides and precludes their interference during the oxidation of the samples with chromic acid This procedure completely eliminates any positive bias in the reported foc

data that might have occurred due to the presence of ferrous ions and other reduced minerals

bull As noted in Response 3 the incomplete oxidation of total organic carbon results in an underestimate of the f and is corrected for by multiplying the f by a correction factor of 130 (Walkley amp Black 1934 Schulte 1995) The fx data reported in the TI Evaluation was corrected accordingly by using this correction factor

bull Excess chloride (Cl~) in percent weight quantities as found in saline soils may interfere with the quantitative titration of reduced chromium (Walkley 1947) However given that the primary rock type at the Hows Corner site is phyllite it is highly unlikely that there was sufficient chloride in the rock core samples for this to occur

bull Manganese oxides may also interfere with the analysis of f through competing with the dichromate ion for any oxidizable carbon (Walkley 1947) However in such cases the reported f would be an underestimate of the f present in the rock core Walkley (1947)

Response to EPA Comment 3 050205doc 3 of 11 Woodard amp Curran (211941)

4

reported that in the case where the ratio of MnO2 to carbon is 85 to 1 the error in the carbon determinations would only be 0 to 6 percent

It may also be useful to compare the analysis of total organic carbon in a geologic matrix that contains high levels of manganese using EPA method 9060 to the Walkley-Black method Table 1 summarizes data provided by one of the PRPs that compares the analysis of total organic carbon in a geologic matrix that contains approximately 02 wgt manganese (approximately 03 wgt manganese oxide)

Table 1 Comparison of total organic carbon measured using the EPA- 9060 method and the Walkley-Black method

Laboratory EPA-9060 Method Walkley-Black Method A Ave 00226 gocg Not analyzed

Stdev 000251 gocg n = 5

B Ave 002219 gocg Ave 002050 gocg Stdev = 000316 gocg Stdev =000971 gocg

n= 10 n = 10

The similarity in the total organic carbon concentrations measured by these two different methods provides further confidence that the Walkley-Black method is a viable method for analysis of total organic carbon in the presence of manganese equivalent to at least 10 by weight of the total organic carbon

5 The Walkley and Black organic carbon measurement at lowf^ values it is not clear that organic carbon is controlling PCE sorption (Schwarzenbach and Westall 1981 Mackay et al 1986 Fetter 1999)

bull Schwarzenbach and Westalls (1981) paper states that f values of less than 0001 gocg should not be used in combination with Kow (octanol-water partition coefficients) values to calculate K^ values (solid phase partition coefficients) values for a specific contaminant It should be noted that the TI Evaluation did not use the f data to calculate the KQC from the Kow Instead as requested by the EPA the measured KOC value for PCE was used to calculate the retardation factor for this contaminant

bull Schwarzenbach et al (2003) stated more recently that Even at very low f values (ie foe = 0001 kgoc - kg1 solid) sorption to the organic components of a natural sorbent may still be the dominant mechanism in defining the adsorption of organic compounds to geological matrices

bull In 1985 M Piwoni from the US EPA Robert S Kerr Environmental Research Laboratory published a paper (Banerjee et al 1985) that showed that for very hydrophobic molecules TOC content of the sorbent will control sorption down to levels of organic carbon that defy quantitation Contaminants such as the PCE found in the groundwater at Hows Corner are in this category of compounds

Given the aforementioned reasons the f values reported in the TI Evaluation are accurate within the noted statistical limitations and will have a predictable impact upon the retardation of PCE during groundwater transport

Response to EPA Comment 3 050205doc 4 of 11 Woodard amp Curran (211941)

6 In order to derive a Kd-based retardation factor that is reasonable given the reported foc

values and the rapid advance of the PCE plume described on pages 4-11 and 4-12 the flushing model requires a bulk density to porosity ratio that is roughly two orders of magnitude higher than the actual ratio for the Hows Comer bedrock (page 4-4) This apparent discrepancy needs to be addressed

The apparent discrepancy of bulk density to porosity ratios is most likely due to the fact that the Batch Flushing Model was originally developed for a porous medium and is not directly applicable to fractured bedrock As stated in Appendix C (page C-4) of the Draft Technical Impracticability Evaluation Report in order to use the Batch Flushing Model to describe the transport of contaminated groundwater in fractured bedrock where the matrix porosity is insignificant it is more appropriate to use a fracture surface area to void space ratio to calculate the retardation factor (R) than a bulk density to porosity ratio (Freeze amp Cherry 1979)

Since it is impractical to determine the actual surface area to which contaminants can adsorb the Batch Flushing Model was used with two simplifying assumptions bull The Kd was calculated from the f and the K^ bull The bulk density to porosity ratio term in the Batch Flushing Model was constrained to range

from 4 to 10 the typical range of such ratios in porous media (Freeze amp Cherry 1979)

If one uses site specific bedrock bulk density and porosity values the bulk density to porosity ratio is several orders of magnitude greater (specifically 273 gcc bullbull 000165 (dimensionless) = 1654 gcc) than the range of ratios of 4 to 10 used in the Batch Flushing Model in the Draft Technical Impracticability Evaluation Report Constraining the bulk density to porosity ratio within the range of ratios of 4 to 10 results in significantly lower R value than would be obtained using specific bedrock bulk density and porosity values

In summary in bedrock where fractures are the primary porosity the bulk density to porosity ratio can vary considerably and will be a function of the number of fractures and the fracture aperture The calculated bulk density to porosity ratio will be inversely proportional to the porosity This means that in fractured rock with limited fracturing and smaller porosity the calculated bulk density to porosity ratio is greater and will result in a greater calculated retardation factor than in bedrock with more extensive fracturing and greater porosity Consequently the calculated retardation factor will be greater for bedrock with less surface area available for sorption than bedrock with greater surface area for sorption This is contrary to what actually occurs

4 Response to EPA Comment 3 050205doc 5 of 11 Woodard amp Curran (211941)

m

REFERENCES

Banerjee P MD Piwoni K Ebeid (1985) Sorption of organic contaminants to a low carbon subsurface core Chemosphere _14 1057-1067

Freeze RA JA Cherry (1979) Groundwater Prentice Hall Englewood Cliffs NJ pg 604

PTS Laboratories wwwptsgeolabscompdf files3TOCnotepdf

Schulte EE (1995) Recommended soil organic matter tests in Recommended Soil Testing Procedures for the Northeastern United States Northeastern Regional Publication No 493 Chapter 8

Schwarzenbach RP J Westall (1981) Transport of nonpolar organic compounds from surface water to groundwater Laboratory sorption studies Environ Sci Tech 15 1360-1367

Schwarzenbach RP PM Gschwend DM Imboden (2003) Environmental Organic Chemistry Wiley-Interscience pg 292 408 amp 412

Walkley A LA Black (1934) An examination of the Degtjareff method for determining soil organic matter and a proposed modification of the chromic acid titration method Soil Science 37 29-38

Walkley A (1947) A critical examination of a rapid method for determining organic carbon in soils - effect of variations in digestion conditions and of inorganic soil constituents Soil Science 63251-264

Woodard amp Curran Inc (WampC) 2005 Draft Technical Impracticability Evaluation Hows Corner Superfund Site Plymouth Maine January 2005

Response to EPA Comment 3 050205doc 6 of Woodard amp Curran (211941)

LIST OF ATTACHMENTS (Response to Comment 3)

Appendix B to Draft Technical Impracticability Evaluation Measurement of foe at Hows Corner (4 pages)

m

Response to EPA Comment 3 050205doc 7 of 11 Woodard amp Curran (211941)

Appendix B Measurement of foe of Rock Core at Hows Corner

There are two general approaches to measure the fraction of organic carbon (foe) in rock cores

bull Measurement of weight loss by ignition of organic matter bull Chemical oxidization of organic carbon to carbon dioxide and either

subsequent quantification of the oxidant used for the reaction or quantification of the carbon dioxide produced during this oxidation process

The weight loss method is subject to errors caused by volatilization of substances other than organic materials such as water hydroxides and mineral carbonates Quantification of foe by the weight loss method is particularly sensitive to the presence of carbonates in rock cores There are however weight loss methods that are designed to differentiate between organic carbon and the aforementioned interfering materials but they require considerable care and are less accurate at low foe values Hence the weight loss method was not well suited for measuring the foe of the rock core from Hows Corner

The chemical oxidation of organic carbon is much better suited for quantifying organic carbon in rock cores such as those from Hows Corner This method uses a strong chemical oxidant to oxidize organic carbon to carbon dioxide and then measures either the chemical oxidant used to oxidize the organic carbon or the quantity of carbon dioxide produced In addition this general approach is not subject to interference by volatilization of other constituents of the rock core

There are at least two such chemical oxidation methods

bull The method of Baccini which was described by Schwarzenbach amp Westall (1981) first acidifies the sample to eliminate interference by carbonates Then a strong oxidant is used to chemically oxidize the organic carbon to carbon dioxide The resulting carbon dioxide is subsequently reduced to methane and quantified using a flame ionization detector Unfortunately this method has not been described in detail in a referred journal Hence it is would not have been appropriate to use to characterize the foe in the Hows Corner rock core

bull The more commonly used method to quantify foe in rock core is the Walkley-Black method (1934) This method is preferred for RBCA and DODDOE projects and by the oil industry

The Walkley-Black method uses an excess of chromic acid to oxidize (digest) organic matter to carbon dioxide The remaining chromic acid that was not consumed during the oxidation of the organic carbon is then quantified by titration with ferrous sulfate The difference in chromic acid prior to and after the oxidation of the organic carbon represents the total chromic acid used to oxidize

Hows Corner TI Evaluation Page 1 January 13 2005 Appendix B

the organic carbon in the sample The latter can be calculated using the chemical stoichiometry of the reaction

The Walkley-Black method is very accurate for samples that contain less than 2 organic carbon matter The minimum detection limit (MDL) for the Walkley-Black method is 100 mgkg or an foe of 0001

Given the rock core at Hows Corner was expected to contain less than 2 organic carbon the Walkley-Black method was used to measure the foe from 19 different rock core samples collected from varying depths ranging from 11 to 90 feet

Table 1 provides a statistical summary of the aforementioned data

Table 1 Statistical summary of foe data from rock cores collected at varying depths

Statistical Parameter Calculated Value foe Minimum Detection Limit (MDL) 00010 Number of samples analyzed (n) 19 Average foe 00019 Median foe 00019 Geometric Mean foe 00019 Standard deviation of foe measurements 000033 Relative standard deviation 174 -+ 95 Confidence intervals 00012 to 00025

The data in Table 1 shows the following

bull The foe from the Hows Corner rock cores are statistically greater than the MDL of the Walkley-Black analytical method

bull The average and median values for the foe of the Hows Corner rock cores from varying depths are nearly identical indicating that there is little variability in the foe values in the source zone at the site

bull The standard deviation of these measurements is 000033 which is 174 of the average foe

bull The 95 confidence intervals of the foe of the rock core at Hows Corner are 00012 to 00025

The foe was also analyzed from three separate samples taken from the same rock core at a depth of 55 feet (Only one of these samples was included in the data summarized in Table 1) Table 2 shows the statistical repeatability of this type of analysis

Hows Corner TI Evaluation Page 2 January 13 2005 Appendix B

Table 2 Repeatability of analysis of foe from one rock core at 55 feet in depth

Statistical Parameter Calculated Value Number of samples analyzed (n) 3 Average foe 00016 Median foe 00015 Geometric Mean foe 00016 Standard deviation of foe measurements 000039 Relative standard deviation 240 -+ 95 Confidence intervals 00008 to 00024

The data in Table 2 shows the following

bull The percent relative standard deviation of these three analyses of foe from the same rock core at Hows Corner is 24

bull The 95 confidence interval of the foes measured in this particular rock core at Hows Conrer is 00008 to 00024

These results show that there is good repeatability in using the Walkley-Black method for analysis of the foe in the rock core at Hows Corner

References Schwarzenbach amp Westall (1981) Transport of nonpolar organic compounds from surface water to groundwater Laboratory sorption studies Environ Sci Tech 15 1360-1367

Walkley A I A Black (1934) An examination of Degtjareff method for determining soil organic matter and a proposed modification of the chromic acid titration method Soil Sci 37 29-37

Hows Corner Tl Evaluation Page S January 13 2005 Appendix B

Woodard and Curran PTS Laboratories PTS File No 34618

ORGANIC CARBON DATA (METHODOLOGY WALKLEY-BLACK)

PROJECT NAME PROJECT NO

SAMPLE ID

203-chip-13 203-chip-23 203-chip-27 203-chip-38 203-chip-42 203-chip-47 203-chip-52 203-chip-58 203-chip-69 203-chip-82 207-chip-11 207-chip-19 207-chip-24 207-chip-29 207-chip-35 207-chip-45 207-chip-55 207-chip-87 207-chip-90

207-chip-55 55-MS

55-MSMSD

Hows Corner NA

DEPTH ft

13 23 27 38 42 47 52 58 69 82 11 19 24 29 35 45 55 87 90

55 NA NA

MATRIX

Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip

Average Median

Geometric Mean Standard Deviation Relative Std Dev

+- 95 Confidence Interval n

Rock Chip Rock Chip Rock Chip

Average Median

Geometric Mean Standard Deviation Relative Std Dev

+- 95 Confidence Interval n

FRACTION ORGANIC CARBON

(gg)

170E-03 185E-03 185E-03 170E-03 240E-03 190E-03 230E-03 180E-03 170E-03 115E-03 195E-03 220E-03 220E-03 235E-03 135E-03 190E-03 205E-03 175E-03 160E-03

188E-03 185E-03 185E-03 327E-04

1739 123E-03 to

19

205E-03 130E-03 150E-03

162E-03 150E-03 159E-03 388E-04

2402 840E-04 to

3

2532E-03

2393E-03

Hows Corner Tl Evaluation Appendix B January 13 2005

Response to EPA-DEP Comment 4 Dated March 31 2005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

EPA-DEP Comment 4

Comment 4 Distribution of contaminants First the TI report seems based on the assertion that there is DNAPL at the source area yet it also appears to represent that the source area is small and the bedrock below 85 is competent (or less fractured) and less impacted by the release of contaminants Some of the confusion may result from using most recent data when that data is from several different sampling events over several years and there is no discernible difference in concentrations between shallow and deep bedrock or as in Section 421 where generally decreased generally increase generally similar and similar concentrations in four consecutive sentences leads to a muddled picture of the contaminant distribution

Second the report asserts that the distribution of contaminants over the entire plume has not changed with time but fails to support this conclusion with data again relying on data that is from different sampling dates for one composite representation

Response The likely presence of dense non-aqueous phase liquid (DNAPL) at the Hows Corner Site and the determination that the source area is small are not mutually exclusive and both are conclusions drawn from information obtained during field investigations The presence of DNAPL in the source area is based on the elevated concentrations of volatile organic compounds (VOCs) detected in the groundwater (WampC 2001 WampC 2002) The conclusion that the source area is small is based on the area in which VOCs in groundwater have been detected at concentrations that are considered to be indicative of the presence of DNAPL nearby Similarly the conclusion that fracture frequency decreases at depths greater than approximately 50 to 85 feet below ground surface was based on field observation during the RI field work The fact that zones with observed fractures exhibited higher hydraulic conductivities than zones without fractures coupled with the decreasing frequency of observed fractures with depth led to the conclusion that the hydraulic conductivity of the bulk rock decreases with depth

The most recent data from all wells were used to provide the maximum VOC data set size During the RI all of the previously-existing and then newly-installed monitoring wells were sampled along with several residential wells The RI sampling included up to 48 monitoring wells Subsequent to the RI and prior to the TI three rounds of monitoring were conducted to verify that the plume was stable 15 monitoring wells were sampled during each of the three rounds During the TI field investigation 29 wells were sampled for VOCs The sampled wells included all of the newly-installed wells and a subset of wells installed during the RI for a total of 29 monitoring wells By using most recent data VOC results from 53 monitoring wells were included in the evaluation (see table labeled Sampling Events for listing of monitoring wells) This approach was selected because there generally was little variation in the data from a particular location between years This is borne out by the attached individual plots of VOCs detected in shallow bedrock and deep bedrock for the Pre-ROD (December 1999January 2000) and Supplemental (May 2000) sampling events and for June 2001 January 2002 and April 2003 sampling events The Pre-ROD and Supplemental plots are similar to the subsequent plots from the 2001 2002 and 2003 sampling events

In addition to maps showing the spatial distribution of VOC data at a given time trend plots of the data from a particular location through time (attached) indicate that since the RI concentrations generally have been stable or have decreased Together the maps and trend plots and the data from which they were developed indicate that the distribution of contaminants over the entire plume has not changed appreciably with time

Response to EPA Comment 4 050305doc 1 of 26 Woodard amp Curran (211941)

REFERENCES

Woodard amp Curran Inc (WampC) 2001 Final Remedial Investigation Report Hows Corner Superfund Plymouth Maine July 2001

Woodard amp Curran Inc (WampC) 2002 Final Feasibility Study Report - Non-Source Area Groundwater Hows Corner Superfund Site Plymouth Maine Hows Corner Superfund Plymouth Maine July 2002

Response to EPA Comment 4 050305doc 2 of 26 Woodard amp Curran (211941)

LIST OF ATTACHMENTS (Response to Comment 4)

Table - Sampling Events 1999 - 2004 (2 pages)

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater Pre-ROD Sampling Event

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater Pre-ROD Sampling Event

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater Supplemental Sampling Event

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater Supplemental Sampling Event

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater June 2001

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater June 2001

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater January 2002

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater January 2002

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater April 2003

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater April 2003

Figure - Concentration Trends - Non-Source Area Wells MW-1B and MW-3B

Figure - Concentration Trends - Non-Source Area Wells MW-13DB and MW-16DB

Figure - Concentration Trends - Non-Source Area Wells MW-16IB and MW- 108D

Figure - Concentration Trends - Non-Source Area Wells MW-108S and MW-112D

Figure - Concentration Trends - Non-Source Area Wells MW-112S and MW-114D

Figure - Concentration Trends - Non-Source Area Wells MW-114S and MW-115D

Figure - Concentration Trends -Source Area Wells MW-2DB and MW-2IB

Figure - Concentration Trends -Source Area Wells MW-102S and MW-103D

Figure - Concentration Trends -Source Area Wells MW-103S and MW-104D

Figure - Concentration Trends -Source Area Wells MW-104I and MW-106D

Figure - Concentration Trends -Source Area Wells MW-106S

Response to EPA Comment 4 050305doc 3 of 26 Woodard amp Curran (211941)

I I

El I

II I I 1 I

I

i

Event Baseline Case ID WC-01 WC-01

Well Date Aug-99 Oct-99 LOT10 1 LOT1-1 1 LOT11-4 LOT14 1 LOT15 1 LOT15-1 1 LOT16 1 LOT16-1 1 LOT17 1 LOT18 1 LOT19 1 LOT2 LOT20 1 LOT21-10 1 LOT21-11 1 LOT21-12 1 LOT21-13 1 LOT21-14 1 LOT21-2 1 LOT21-5 1 LOT21-7 LOT21 -8 1 LOT21-9 1 LOT23 1 LOT24 1 LOT28-1 1 LOT28-2 1 LOT28-3 1 LOT28-4 1 LOT28W 1 LOT30 1 LOT30-1 1 LOT30-2 1 LOT30-3 1 LOT30-4 1 LOT30-5 LOT31 LOT35 1 LOT41 1 LOT42-1 1 LOT43-1 1 LOT43-4 1 LOT6-1 1 LOT67 1 LOT6-7 1 LOT6-8A 1 LOT6-8B 1 LOT80-1 1 LOT82 1 MW-101D MW-1011 MW-101S MW-102D MW-102S MW-103D MW-103S MW-104D MW-1041 MW-104S MW-105D MW-106D

Groundwater Sampling Location Summary 1999 - 2004xls

Sampling Events 1999-2004

Hows Corner Superfund Site Plymouth Maine

Supplemental 2001 2002 2003 Pumping 2004 Pre-ROD Rl Sampling Sampling Sampling Test Sampling WC-03 WC-09 WC-25 WC-30 WC-42B WC-56 WC-58 Dec-99 May-00 Jun-01 Jan-02 Apr-03 Sep-04 Sep-04

1

1 1 1

1 1 1 1 1

1 1

1

1 1

1 1 1

1 1 1 1 1

1

1 1

1 1 1 1

1

1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

Sampling Events 1999-2004

Hows Corner Super-fund Site Plymouth Maine

Supplemental 2001 2002 2003 Pumping Event Baseline Pre-ROD Rl Sampling Sampling Sampling Test

Case ID WC-01 WC-01 WC-03 WC-09 WC-25 WC-30 WC-42B WC-56

ll

Well Date Aug-99 Oct-99 Dec-99 May-00 Jun-01 Jan-02 Apr-03 Sep-04 MW-106S 1 1 1 1 1 MW-107D 1 1 MW-108D 1 1 1 1 1 MW-108S 1 1 1 1 1 MW-110D 1 1 MW-111D 1 1 MW-112D 1 1 1 1 1 MW-112S 1 1 1 1 1 MW-113D 1 1 MW-114D 1 1 1 1 1 MW-114S 1 1 1 1 1 MW-115D 1 1 1 1 1 MW-12DB 1 1 1 MW-12SB 1 1 1 MW-13DB 1 1 1 1 1 1 MW-13SB 1 1 1 MW-14DB 1 1 MW-14SO 1 1 MW-15DB 1 1 1 MW-15SB 1 1 1 MW-16DB 1 1 1 1 1 1 MW-16IB 1 1 1 1 1 1 MW-16SO 1 1 MW-17DO 1 1 1 MW-17SO 1 1 1 MW-1B 1 1 1 1 1 1 MW-203D MW-203S MW-204D MW-204S MW-205 MW-206D

I MW-206S MW-2DB 1 1 MW-2DDB 1 1 MW-2IB 1 1 1 1 1 1 MW-3B 1 1 1 1 1 1

I MW-4O 1 1 1 MW-5B 1 1

II MW-6DB 1 1 1 MW-6SB 1 1 1 MW-8DB 1 1 1 MW-8SB 1 1 1

II PW-207 1 SEEP-1 1 SUBTOTAL - RESIDENTIAL 44 25 0 2 0 3 0 SUBTOTAL - MONITORING 22 48 41 15 15 15 1

Total 3 66 73 41 17 15 18 1

I Included in most recent data

I Notes 1 - Overburden well not included in most recent data for plotting

2 - Tetrahydrofuran and 2-Butanone were the only two compounds detected in this well and are thought to be the result of well repair not included in most recent data for plotting

3 - Not included in most recent data for plotting

2004 Sampling

WC-58 Sep-04

1

1 1

1 1

1 1 1

1

1 1

1 1 1 1 1 1 1 1 1

1 1

1

0 29

29

Groundwatef Sampling Location Summary 1999 - 2004xls

I

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

monitoring well Figure 4-14 total VOC contour (ugl) - December 1999January 2000 Distribution of Total VOCs in

Note SW-113 is located downstream of SEEP-1 Shallow Bedrock Groundwater total concentration of detected VOCs ND= not detected these two locations were sampled during the Pre-ROD Sampling Event

Baseline Sampling Event in OctoberNovember 1999 Hows Corner Superfund Site Surface Water Sampling Location A Plymouth Maine Seep Sampling Location laquo- WOODARD ampCURRAN

995037wipri reportepa ri interim final feb 2001cadd drawingsfinalfig 4-14

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

0 300 600 I

FEET

Q residential well Figure 4-16 monitoring well Distribution of Total VOCs in

Deep Bedrock Groundwater total VOCs contour (ugl) Pre-ROD Sampling Event

active residential wells with lot number Hows Corner Superfund Site 2deg42deg Plymouth Maine total concentration of detected VOCs ND= not detected WOODARD ampCURRAN Enyinaaring bull Science bull Operations bull

995037wipri reportepa ri interim final feb 2001cadd drawingsfinalfig4mdash16

PLYMOUTH POND

PLYMOUTH POND

1 628Tl7MW-2bB 12135

PLYMOUTH POND

monitoring well Figure 4-20

V total VOC contour (ugl) - June 2000 Distribution of Total VOCs in Shallow Bedrock Groundwater

| 34 | total concentration of detected VOCs ND= not detected NA = not analyzed Supplemental Sampling Event Note SW-113 is located downstream of SEEP-1 Hows Corner Superfund Site

Surface Water Sampling Location these two locations were sampled during the Plymouth Maine Baseline Sampling Event in OctoberNovember 1999 Seep Sampling Location WOODARD amp CURRAN

Engineering bull Science - Operations bull 995037wipri reportepa ri interim final feb 2001 cadd drawingsfinalfig 4-20

residential well Figure 4-22 Distribution of Total VOCs in

monitoring well Deep Bedrock Groundwater

total VOCs contour (ugl) Supplemental Sampling Event

Hows Corner Superfund Site

total concentration of detected VOCs ND= not detected NA = not analyzed Plymouth Maine

WOODARD amp CURRAN

995037wipri reportepa-ri interim final feb 2001cadd drawingsfinalfig 4-22 Engineering bull Science - Operations bull

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

FEET

Shallow Monitoring Well

Deep Monitoring Well

C Detected Concentration ND = Not Detected Figure 1-XS Distribution of Total VOCs in Shallow Bedrock Groundwater

Pumping Well

17-Acre Property Boundary Concentration Contour (ugl)

June 2001 Hows Corner Superfund Site

Plymouth Maine WOODARDampCURRAN

-i^rhvj bull Scbncn bull Operations bull 211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0601 dwg04-20-05

PLYMOUTH POND Hopkins Road V

O

PLYMOUTH POND

PLYMOUTH POND

o

0 300 600 mdashfa FEET

Shallow Monitoring Well bull bull - 17-Acre Property Boundary Figure 1-XD

Deep Monitoring Well 1 I Detected Concentration ND = Not Detected Distribution of Total VOCs in Deep Bedrock Groundwater

-mf- Pumping Well June 2001 Residential Well Hows Corner Superfund Site

Plymouth Maine i h Surface Water Sampling Point

g WOODARD ampCURRAN _ ^ _ ^ _ _ yen_ rj i|Hlaquorlny bull Science bull Opt

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0601 dwg04-20-05

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

Shallow Monitoring Well

Deep Monitoring Well

Detected Concentration ND = Not Detected Figure 1-YS Distribution of Total VOCs in Shallow Bedrock Groundwater

Pumping Well

17-Acre Property Boundary Concentration Contour (ugl)

January 2002 Hows Corner Superfund Site

Plymouth Maine WOODARD amp CURRAN Engineering Science- Operations bull

211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0102dwg04-20-05

PLYMOUTH POND

PLYMOUTH POND

Site Pand^ laquoum-laquoBTuitaraquo tLV

vVlf-(

PLYMOUTH POND

0 300 600 ^ = FEET

Shallow Monitoring Well mdashbullbullbull 17-Acre Property Boundary Figure 1-YD - A - Deep Monitoring Well FT Detected Concentration ND = Not Detected Distribution of Total VOCs in

Deep Bedrock Groundwater Pumping Well January 2002 Residential Well Hows Corner Superfund Site

Plymouth Maine Surface Water Sampling Point

WOODARD ampCURRAN Engineering Sciencs- Operations bulli Si

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0102dwg04-20-05

- m j

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND j A O-shy

Shallow Monitoring Well E Detected Concentration ND = Not Detected Figure 1-ZS Distribution of Total VOCs in

Deep Monitoring Well Shallow Bedrock Groundwater

Pumping Well Hows Corner

April 2003 Superfund Site

17-Acre Property Boundary Plymouth Maine Concentration Contour (ugl) r WOODARD ampCURRAN

Engineering bull Science bull Operations bull 211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0403dwg04-20-05

s S pound

PLYMOUTH POND

PLYMOUTH POND

- -

5 PLYMOUTH POND

Jo

FEET

ft Shallow Monitoring Well mdashbullbullmdash 17-Acre Property Boundary Figure 1-ZD Deep Monitoring Well I 1 I Detected Concentration ND = Not Detected Distribution of Total VOCs in

Deep Bedrock Groundwater Pumping Well April 2003

Q) Residential Well Hows Corner Superfund Site Plymouth Maine

(T) Surface Water Sampling Point WOODARD ampCURRAN poundKk EnginawtirKj bull Science - Operations bull

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0403dwg04-20-05

0 Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

B MW-1B

I 12000

PCE

B 10000 Total VOCs

I

i 2000

i 0 Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

c MW-3B

G 2000

1800

B PCE

1600 Total VOCs

1 I I E

il-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

G E

211941

El

I I z E

80

Concentration Trends shy Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-13DB

Total VOCs

c i i c o

Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

MW-16DB

30

c i c c I c o

Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99

PCE

Total VOCs

Jul-01 Jul-03

211941

O bi

c Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

I MW-16IB

i 35

3

c Total VOCs

lt- 2 5

0 | gt

o

1 sectI

c c 0 4

Jul-90 Jul-92 Jul-94 Jul-96 Jul-98 Jul-00 Jul-02 Jul-04

I I MW-108D

I 12

PCE 10

Total VOCs c oc 3

E E I 0

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

E 211941

c Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

fi MW-108S

I I 40

PCE 35

Total VOCs

30

I f 26

20 I o

I 15

10

c Dec-99 Dec-00 Dec-01 Dec-02 Dec-03 I 0

I MW-112D

c 35 - imdash

I A3 shyTotal VOCs

o c

E 1 2

I

ition

B 1 ^

-i c 3

0 Dec-99 Dec-OO Dec-01 Dec-02 Dec-03

211941

I

i

I

cII

Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-112S

08

PCE

Total VOCs 06

o 04

02

0 Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

MW-114D

o

12000

10000

8000

6000

PCE

Total VOCs

4000

2000

i

ccEIIc

i

i

E

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

211941

Con

cent

ratio

n (

ug

l)

E Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

I MW-114S

E A5000 -- Total VOCs

- 4000

0 3000

2000

i 1000

i n shy

Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

MW-115D

c PCE

Total VOCs

c E

o

C c

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03 I 0

211941

IepoundII

EIEIIGICCIccc

30000

25000

20000

o bullsect 15000 b

o 10000 U

5000

0 Aug-99

25000

20000

5000

0 Aug-99

211941

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-2DB

PCE

Total VOCs

Aug-01 Aug-03

MW-2IB

PCE

Total VOCs

Aug-01 Aug-03

IDIBI

ii EIDIISIBIG C

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-102S

6000

5000 PCE

Total VOCs

4000

O 3000

2000

1000

0 Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

MW-103D

16000

~ 14000 ugt 3- 12000 o

^ 10000

sect 8000

O 6000

4000

2000

PCE

Total VOCs

0Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

211941

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

G MW-103S

I I

ampo

12000

10000

E sectc

S

8000

6000

4000

2000

0Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

G I 6000

MW-104D

i 5000

PCE

Total VOCs

i i c

2000

1000

Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

E I

211941

cIccIG

IIBCccBcIc

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-1041

PCE Total VOCs

a 25000

0 20000

a 15000

10000

5000

0 Jan-OO Jan-01 Jan-02 Jan-03 Jan-04

MW-106D

3000

2500 PCE

Total VOCs

=sect 2000

o bullsect 1500

1000

500

0 Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

211941

c Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

c MW-106S

I PCE

Total VOCs

i

i Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

i

i i i E

C

211941 c

Response to EPA-DEP Comment 5 Dated March 312005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

iiw

EPA-DEP Comment 5

Comment 5 Matrix Diffusion The report as well as other proponents of matrix diffusion suggest that depletion of DNAPL (Section 5112 page 5-15) needs to be achieved While that might be the ideal the goal is to achieve performance standards and that goal may be attainable while there is residual contamination in the rock perhaps even DNAPL globules The low bedrock matrix porosity (page 1-15) the high permeability values (page 4-4) the relative flux of the groundwater (page 5-5) and the decrease in surface area and out of the mainstream pockets (appendix C-4) all suggest that the diffusion out of the rock matrix would be insubstantial relative to the regional flux of groundwater through the Site

Response The TI Evaluation Report does not explicitly consider or rely upon matrix diffusion as a basis for requesting a TI Waiver for a portion of the Hows Corner Site The technical literature provides documentation that matrix diffusion can be a significant process that affects chemical transport and groundwater remediation timeframes in unconsolidated and consolidated media including fractured rock (US EPA 1989 Freeze and Cherry 1979 Pankow and Cherry 1996 Fountain 1998) Back diffusion of contaminants from the matrix porosity of the fractured rock can prolong the time necessary to achieve groundwater cleanup goals particularly for compounds such as PCE for which the cleanup goal is a low concentration It is our expectation that matrix diffusion has occurred at the Hows Corner Site and that back diffusion of PCE from the rock matrix will also occur Although the extent to which matrix diffusion is occurring at the Hows Comer Site has not been determined and that lack of knowledge contributes to uncertainty regarding the cleanup times at the Site the effect of matrix diffusion is to lengthen rather than shorten the time required for remediation

REFERENCES

Fountain JC 1998 Technologies for Dense Nonaqueous Phase Liquid Source Zone Remediation Ground-Water Remediation Technologies Analysis Center Technology Evaluation Report TE-98-02 December

Freeze RA and Cherry JA 1979 Groundwater Prentice-Hall Inc Englewood Cliffs NJ 07632 p 410-412

Pankow J F and Cherry J A 1996 Dense Chlorinated Solvents Waterloo Press Portland OR 97291-1399 p 67-88

US EPA 1989 Transport and Fate of Contaminants in the Subsurface EPA6254-89019 p 17-18

Response to EPA Comment 5 050305doc 1 of 1 Woodard amp Curran (211941)

WOODARD amp CURRAN Maine Massachusetts New Hampshire Connecticut Florida Operational offices across the US 1-800-426-4262 www woodardcurran com

Page 20: SDMS DocID 251749 - Records Collections · 2020-06-13 · CORPORATE OFFICES: Maine, Massachusetts, New Hampshire, Connecticut New, York, Florida Engineering • Science • Operations

697

NOTES

1 Groundwater samples collected in 1999 were screened for five volatile organic compounds (VOCs) only N

tetrachloroethene (PCE) exceeded reporting limits MW-2030 082304 082304 082304 082304 u

2 Strike and Dip of likely or possible transmissive 30 45 55 85 feature within the packer interval from which the indicated sample was collected

MW-204D

PCE TOTAL VOCs

081904 30

220 2636

A

081904 46-50 540 6436by

081904 IT

260 3073

x

MW-105D

PCE TOTAL VOCs

111199 50-60 2100 2100

MW-106D

PCE TOTAL VOCs

111199 76-86

400 400

111199 137-147

1400 1400

111299 1355-1455

350 350

PCE TOTAL VOCs

44 84

64

MW-6SB

bulli

lt

gt-

170 234

35

I I i

140 192

^^52

^^52

130 183

52 - lt

S A 34

PW-207 082404 082404 082404 20 37

PCE 1300 TOTAL VOCs

17-Acre George West Property Boundary

MW-113D

PCE TOTAL VOCs

112299 46-56

350 350

112299 70-80 190 190

150

112299 105-115

129 129

112399 138-148

230 230

L e g e n d ( J New Monitoring Well-Summer

Site Property Boundary ^ P u m p i n g Well-Summer 2004

-xmdashxshy Source Area

bull0shy Monitoring Well shy Pre 2004 Angled Boring-Summer 2004

211941laquoipdwgTI-ELV21ig41paltker-data2

2004 PCE of Total

bull lt70 VOCs

M W - 1 14D ^ ^

Figure xx Packer Testing Results in

Vicinity of Source Area Hows Corner Superfund Site

Plymouth Maine ^ WOODARD ampCURRAN

^^^^^^^^^^m ampKm Engineering - Science bull Operations

c Northeast Geophysical Services Borehole Geophysical Log

MW-203 Date logged 081704 Plymouth Maine

I Flowmeter Measurements Tomporaturo(C) Acoustic Televiewer

7 5 8 8 5 9 95 Caliper (Inches) Resistance (Ohms) Spontaneous Potential (mVj Dip In Degrees PCE Total VOCs

3 0 2 0 8 0 laquodeg 4S 1000 1400 1800 2200 MO HO 1000 1200 MOO 0 laquo deg ugL ugL n 1 1 1 1 1 1 1 1 1 i 1 1 1 1 n 1 1 1 1 1 1 1 1 1 1 1 n I l l l l l l l n

Ambient Flowneter pumping Rowmeter 11 gpm 6

H

bull

magnetic 10 bull 10 bull - 10 - north - 1 0I

-

_

bullbullbull - bull

20 bull bull20 bull ^ ltr~mdash 01

I

4 ^

LOS7

^

44 84 I I

Xr - 2

lt ^ bull30 -_ _^O1J- 1 _ 050 30 - 3 0

0r - - 3

C -j [ bull bull bull | shy

-O8 H ~ 1 045 7

1 4040 - 40 - -40 r - 14gt 13

V1s -- -023 f 1022 1V 170 234 I

T lt bull B gtf 50^ J50 - - 5 0 - - 5 0

I eet be

lo

i 1

1 1

1

140 192 - - - -t shy

-mdashj bullpound 60 - $o - - 60 - -60

H i I c

bull024

ampbull

3 - T lt ftft rgt He

70 bull j 70 - - 70 - 7 0 -

in -j bullbull shy

-021 1 T 022

- Ton _ Ov

26

130 183 NF NF

90 -_ 90 - 7 90 - -90

-

ifi Jf

3J

^gt _ N F NF bull bull shy

| H100 - j 100 bullbull 100 - -100

1 1 1 1 1 1 1 ) | 1 f I 1 1 1 ) 0 20 40 60 80

flft mdash ftn - mdash rVt

30 4 g 0 20 40 60 Dip in Degrees bullbull

Likely or poss bleFluid Resistivity (ohmmeters) The dip direction-- indicated

^ t h e l i n e extending from t h

I Iransmissive zone circle The strike of the feature is 90 degrees from this

The acoustic televiewer graph displays the mostprominent features selectedffom the acoustic televiewer

R n r a h n l c D O t t n O I B

f i o n n h w c i r a l U K U p i i y SI Ud l

1 rn l_Og Packered Interval August 2004

E tog The location dip angle and dip direction of the sleeted M W - 2 0 3 Groundwater samples were collected by Woodard S Curran on H23120M features are approximate Refer to the televiewer og of His _ well for more precise detail Plymouth Maine Date logged 081704

I

1

Northeast Geophysical Services Borehole Geophysical Log MW-204 D a t e l o gge d 072604

Plymouth Maine

n 3

Flowrneter Measurements(in gpm)

Caliper (Inches)0 3 5 4 0

1 1 1 1 1 1 1 t 1 1 1 1 1 1Ambient Rowmeler pumping Flowmetsr 05gpm

Templaquorature (C) bull bull bull bull i

7 75 8 8S 9 Resistance (Ohms) Spontaneous Potential (mV)

4000 SOW 600 4M 0

Acoustic Televiewer (interpreted)

Dip in Degrees 0 20 4060 SO

at N

PCEugL

Total VOCs ugL

- -_ a

10-

shy 10 bull - 10 shymagnetic

north - 10

o o

bull 1

11

11

1 1

1 1

11 1

1 1

1 1

1 1

1 1

1 1

1 1

1 1

1 1 E 1

- L

3 7 2 0 2 0r bull 20 bull - shy

i S_ N F

bull30 bull 7 3 0 220 2636shy1^ J J 004

fI f V ^

40 shy 4 0 4 0 shy - 4 0rbull019 [_ 007 w8 - - shy5 c

bull

gt

Ia50i 540 6436

bull50 - - 50 - - 5 0

-QQ7 - bull - -t T

pound V gtk

B 6 0 - e o - 7 6 0 -60shyQ 1 1

Q -007 -004 bull1 mdash T - J ~

bull

- - shyT 70 -J c [TO- - 70 - 7 0-

V Y 1- -004 -003

mdash T -h - y - j i - - mdash 260 3073 - gt=7

80 -j NF bull80 - - 80 - - 8 0Jgt

bull i

i 1

i i

C- bull shy

90 shy

K

Jlt i90 90 shy - 9 0shy -

l

ii

I I I I

NF bull M J

I ^ ^ - ^ bull 1

mdash mdash - _

s -7 ^100shy

till

1 100 100- H - 1 0 0shy -1 x Likety or possible k ^ Iransmissive zonebull

1 i i i ii i i i | l l l l | l i l l 0 20 40 ED 80

1 -

3 0SOFluid Resistivity (ohmmeters)

Dip in Degrees The djp ^ ^ o n is indicated ty Ihe line extending from tha circle The strike of Ihe feature

19- 3U UIHJIW93 IolII l l l lraquo

bull

The acousfc televiewer graph displays the mostprominent features selected from the acoustic televiewer109 The location dip angle and dip direction of Ihe sleetedfeatures are approximate Refer to the televiewer log of thiswentormore precise detail

B o r e h o l e G e O D h V S I C a l LOO B W H U I B w c w p n y o i v a i w v yM W - 2 0 4

P l y m O U t n MaiDB

Packorod Interval August 2004Groundwater san-ples wampramp collected by Woodard a Curran on OMO23C4

Date logged 072604

C

I

E Northeast Geophysical Services Borehole Geophysical Log Date logged 072704

I MW-205

Plymouth Maine

Flowmeter Measurements Temperature (C) Acoustic Televiewer (In gpm) I ~l (Interpreted)

I 85 10 Caliper (inches) 95

Dip in D g r laquo Resistance (Ohms) Spo ontaneous Potential (mV PCE Total VOCs 3 0 16 4 0 4 5 ) 20 40 60 80 10 00 2000 30 00 4VJ 400 -3 laquo

i i i i 1 i i I i 11 4 0 D 1 I I ugL ugL

C h

iii Ambient Flowmetar pumping

Flowmeter 1 25 gprn

I bull$bull

i

I rmdash magnetic 1 north ^^^^ 1 VI f

10 ~ I C x 10 bull - 10 bullbull

4 5 6mdashmdash f 1000B 11448 noisy nodi a raquo ^

mdash 5rt mdashi mdash Oft pound) 1100B 12509

cjmdash1 007

-

i i i 1

en

8 B a B

30 mdash

-

40 shy

-mdash I -

50 -_

__NF lt005

- 30 - - 3 0 it 34V

MO P26 V S) 1300B 13776 _ N F NF

26

40 bull - 40 bull 7-40 gt J Vf1 cX

) -j -

_ N F NF 50 c bull - 50 ^ 7-50

i I

I

c

B pound 60 - 6 0 7 60 - 7-60 a i 1

_ N F NF i Si f f 70 -_ bull70 bull - 70 shyC I 9

-m bull - shyA

_ N F NF 80 80 -j bull80 bull - 80 - C- 33 34

bull

5-i r

i 1

J r

Ck

_ N F NF 9 0 90 - - 90 shy

i bullCshy

J rK bull

100 -j ^ Likely or possible bull100- - 100- I -100

transmissive zone bull - ^ bull shy] |

1 1 1 1 1 1 1 I 1 i i i 1 i i 1 1 0 20 40 SO SO 10 20 30 40 50 Dip in Degrees 30 4 0 Fluid Resistivity (ohmmeters) Thlaquo dip direction is indicated

by the line extern r g from the circle The strike of he feature is 90 degrees from ihis

The acoustic televiewer graph displays the most

I Borehole Geophysical Log Packered Interval August2004 prominent features selected from the acoustic televiewer

Groundwatcr samples were oollccled by Woodard amp Cufran orgt S172004 log The location dip angle and dip direction of ins slsctsd MW-205 features are approximate Refelt to the televiewer log of this wall for more precise detail Plymouth Maine Date logged 072704

I

C

I Northeast Geophysical Services Borehole Geophysical Log Date logged 072704

I MW-206

Plymouth Maine

Flowmetor Measurements Temperature (C) Acoustic Televiewer | I r T i i i i i i i i i i i i i i r I |(in gpm) (Interpreted)

I 75 8 flS 9 95

Caliper (inches) Resistance (Ohms) Spontaneous Potential (mV) Dip In Degress PCE Total VOCs 30 35 40 4 5 0 20 40 M 90 4500 5500 6500 ugL ugL I i i

I I

- 1 0

I - 2 0

I 2900B 32401

i i L

E 0

i 6300B 68901

i I 0 20 40 SO 80

20 30 40 50 Dip in Dlaquogralaquos

amp 4 a Fluid Resistivity (ohrnmeters) The dip dirertion is indicated Likely or possible by iho line extending from the transmissive zone circle The striKe of the feature

is 90 degrees from tNs

Borehole Geophysical Log Packered Interval August 2004

E amples were collected by Woodard amp Cunan oo SM82004 log Thraquo location 4p angle and dip direction of the sloeled MW-206 feature are approximate Refer to the televiewer 109 of this well for more precise detail Plymouth Maine Date logged 072704

C

I Northeast Geophysical Services Borehole Geophysical Log

Date logged 082304 PW-207

I Plymouth Maine

Fiowmeter Measurements Temperature (C) Acoustic Televiewer

I (in gpm) (interpreted)

75 8 85 9 95 Caliper (inches) Resistance f0tims) Spontaneous Potential (mV) Dip in Degrees PCE Total VOCs

55 60 0 20 40 SO 80 ugL ugL I I I I I I I

Ambienl Fiowmeter pumping Flewmater

magnetic - 10 - - 1 0

north

i - 20 - - 2 0

1300 1410

i - 30 - - 3 0

i tf

5400 5802 - 40 - - 4 0

B - 50 - - 5 0

I 18000 19234

- 60 - - 6 0

I 12000 13085

- 70 - - 7 0

- 8 0

i - 9 0 19000 20354

G - 100- -100

I 110 110 bull110

0 20 40 60 SO 10 20 30 Dip m Degrees

Fluid Resistivity (ohmmeters) I 50

The dip direction is indicated by ihe line extending from the circle The strike of the fealure is 90 degrees from this

Borehole Geophysical Log

G Packorod Interval August 20(M log The location dip angle and dip dirlaquocton or the sleeted Groundaier samplss were ooliecled by Woodard i Curran on ampt24f2ltXM PW-207 failures are approximate Reter to the televiewer log of this wlaquoll for more precise detail PlyPIOUth Maine Date logged 082304

I

Table XX Packer Permeability and Packer Sampling Results for Potential Fracture Intervals

1

WellID MW-101D MW-101D MW-101D MW-101D MW-101D MW-101D MW-101D MW-101D MW-101D MW-101D MW-I01D MW-101D MW-101D MW-102D MW-102D MW-I02D MW-102D MW102D MW-102D MW-102D MW-102D MW-102D MW-I02D MW-102D MW-102D MW-102D MW-103D MW-103D MW-103D MW-103D MW-I03D MW-103D MW-103D MW-103D MW-103D MW-103D MW-103D MW-103D MW-I03D MW-104D MW-104D MW-104D MW-104D MW-I04D MW-104D MW-104D MW-104D MW-104D MW-104D MW-104D MW-105D MW-105D MW106D MW-106D MW-106D MW-107D MW-107D

1999 Drilling Program

Hows Corner Superfund Site Plymouth Maine

Potential Fracture Top Of Bottom 6 Depth to lt Topof i Interval from Packer Packer Middle of Elevation Hydraulic bull PCE

GS ELEV 1 Rock Drilling Interval Interval Interval of Interval Conductivity Concentration (ft msl) (ft msl) TEST (ftbgs) (ftbgs) r(ftbgs) ( f t b (ft mil) (cmsec) (raquogL)

4339 4329 13 28-29 33-3537-39 271 376 324 4016 OOOE+00 4339 12 37-3444-46 380 485 433 3907 157E-04 4339 11 488 593 541 3799 132E-04 4339 10 60-61 578 683 631 3709 OOOE+00 4339 9 678 783 731 3609 I79E-05 4339 8 778 883 831 3509 106E-05 4339 7 880 985 933 3407 243E-05 4339 6 990 1095 1043 3297 339E-06 4339 5 1090 1195 1143 3197 OOOE+00 4339 4 1190 1295 1243 3097 OOOE+00 4339 3 1365-1375 1290 1395 1343 2997 OOOE+00 4339 2 147-157 1390 1495 1443 2897 580E-05 4339 1 147-157 1470 1575 1523 2817 741E-05 43161 43061 13 166 271 219 4098 333E-04 43161 12 30-3136-40 260 365 313 4004 I54E-05 43161 11 36-4041-43 362 467 415 3902 548E-05 43161 10 470 575 523 3794 598E-05 43161 9 570 675 623 3694 197FOS 43161 8 670 775 723 3594 OOOE+00 43161 7 770 875 823 3494 891 E-05 43161 6 83-94 870 975 923 3394 139E-05 43161 5 970 1075 1023 3294 123E-04 43161 4 1070 1175 1123 3194 526E-06 43161 3 1170 1275 1223 3094 138E-05 43161 2 1270 1375 1323 2994 671E-06 43161 1 1370 1475 1423 2894 OOOE+00 42997 42497 13 18-19 170 275 223 4077 OOOE+00 42997 12 260 365 313 3987 766E-05 42997 11 360 465 413 3887 727E-05 42997 10 460 565 513 3787 192E-05 42997 9 560 665 613 3687 752E-05 42997 8 660 765 713 3587 778E-05 42997 7 85-86 763 868 816 3484 260E-05 42997 6 860 965 913 3387 289E-05 42997 5 102-103 960 1065 1013 3287 102E-04 42997 4 1060 1165 1113 3187 522E-06 42997 3 1160 1265 1213 3087 520E-06 42997 2 129-130 1260 1365 1313 2987 960E-04 42997 1 1360 1465 1413 2887 OOOE+00 43372 42922 11 35-37 42-45 350 455 403 3935 684E-04 43372 10 460 565 513 3825 500E-05 43372 9 560 665 613 3725 106E-05 43372 8 72-74 660 765 713 3625 204E-05 43372 7 760 865 813 3525 872E-06 43372 6 860 965 913 3425 467E-06 43372 5 960 1065 1013 3325 200E-05 43372 4 1060 1165 1113 3225 354E-05 43372 3 125-130 1160 1265 1213 3125 157E-05 43372 2 125-130 1260 1365 1313 3025 337E-04 43372 1 1365 1465 1415 2922 689E-06 43052 43002 2 54-58 490 595 543 3763 124E-05 2100 43052 1 139-140 145-146 1367 1472 1420 2886 154E-04 1400 43291 4391 3 bullI133 260 365 313 4017 439F06 43291 2 77-78 760 865 813 3517 230E-03 400 43291 1 143-144 1355 1460 1408 2922 971E-06 350

29958 27258 4 450 555 503 2493 OOOE+00 (21)A 29958 3 103-105 1000 1105 1053 1943 752E-04 (063)A

Table XX Packer Permeability and Packer Sampling Results for Potential Fracture Intervals

1999 Drilling Program

Hows Corner Supcrfund Site Plymouth Maine

gtbull i Potential Fracture Top _OfBot Bottom of Depth to ltbull Top of Interval from f Packer Packer Middle Of

GS ELEV lt Hock Drilling interval Interval Interval WeD ID ft msl) (ft msl) TEST (ftbgs) ltft$gs) (ftbgs) (ftbgs)

MW-107D 29958 2 128-130 1200 1305 1253

MW-107D 29958 1 139-141 1350 1455 1403

MW-108D 31904 31104 6 35-36 300 405 353 MW-108D 31904 5 60-62 550 655 603

MW-108D 31904 4 80-83 750 855 803

MW-108D 31904 3 118-119 123-124 1150 1255 1203

MW-108D 31904 2 147-149 1440 1545 1493

MW-108D 31904 1 1700 1805 1753

MW-110D 40576 40426 2 21-31 210 315 263 MW-110D 40576 1 148-154 1460 1565 1513 MW-I11D 40519 4 70-71 650 755 703

MW-111D 40519 3 79-82 84-86 780 885 833 MW-I11D 40519 2 97-102 950 1055 1003 MW-111D 40519 1 1370 1475 1423

MW-112D 3027 2942 4 42-52 420 525 473 MW-112D 3027 3 850 955 903 MW112D 3027 2 1100 1205 1153 MW-112D 3027 1 135-136 140-141 1340 1445 1393

MW-113D 43085 43085 5 250 355 303 MW-I13D 43085 4 47-49 460 565 513 MW-113D 43085 3 73-74 700 805 753 MW-113D 43085 2 1050 1155 1103 MW-113D 43085 1 1380 1485 1433

MW-114D 42394 41594 4 48-49 450 555 503 MW-114D 42394 3 79-81 740 845 793 MW-114D 42394 2 121-129 1250 1355 1303 MW-114D 42394 1 134-142 1350 1455 1403

MW-115D 4035 4035 4 300 405 353 MW-1I5D 4035 3 70-71 650 755 703 MW-115D 4035 2 1150 1255 1203 MW-115D 4035 1 1400 1505 1453

LOT-28W 382 7 450 555 503 LOT28W 382 6 550 655 603 LOT-28W 382 5 650 755 703 LOT28W 382 4 750 855 803 LOT-28W 382 3 850 955 903 LOT-28W 382 2 950 1055 1003 LOT-28W 382 1 1055 1155 1105

NOTES cmsec = centimeters per second ft bgs = leet below ground surface It msl = feet below mean sea level lt = not detected at indicated reporting limil A = detected below laboratory PQL ( ) = detected below reporting limits

Elevation of Interval

(ft nisi) 174

159

283gt 2588

2388

1988

1698

1438

3795 2545 3349 3219 3049 2629

2555 2125 1875 1635

4006 3796 3556 3206 2876

3737 3447 2937 2837

3683 3333 2833 2583

3318 3218 3118 3018 2918 2818 2715

Hydraulic Conductivity

(cmsec)

323E-05

208E-05

471E-03

471E-03

624E-05

3I6E-05

264E-05

261 E-05

OOOE+00 200E-04 953E-05 OOOE+00 OOOE+00 212E-05

361 E-05 410E-06 2gQE06 292E-05

786E-05 124E-05 151 E-05 822E-06 82IE-06

858E-05 I69E-05 352E-03 866E-05

223E-05 394E-06 122E-05 525E-06

831 E-05 182F-05 L62E-05 129E-05 190E-05 890E-04 981 E-04

PCEraquo Concentration

(ugL)

lt5

(14A)

98 11

15

22

11

30

200 (62)A

110 210 300 240

(44)A (23)A

5

350 190 129 230

2200 1900 2600 2600

(17)A (16)A (19)A

96

Table XX Packer Permeability and Packer Sampling Results for Potential Fracture Intervals

2004 Drilling Program

Hows Corner Superfund Site Plymouth Maine

Top of Bottom of Depth to Midpoint

t K

ELEV (ft Potential Transmissive Zones Packer Interval

Packer Interval

Middle of Interval

Elevation of interval

Hydraulic Conductivity

PCE Concentration

Well ID msl) TESTr (ft bgs)- (ftbgs) (ftbgs) (ftbgs) (ft msl) (cmsec) (ogt) MW-203D 43227 4 277279 24 32 28 4043 667E-05 44

3 408415420 39 49 44 3883 593E-05 170 2 526 530 49 57 53 3793 101E-04 140 I 828830842 80 88 84 3483 701E-05 130

MW-204D 43262 5 295 300 26 34 30 4023 902E-05 220 4 463496513516 45 53 49 3833 119E-04 540 3 681685688 63 71 67 3653 OOOE+00 2 758 76 2 71 79 75 3573 309E-05 260 I 88 96 92 3403 OOOE+00

MW-205 42389 3 164 166 168 15 20 175 4148 OOOE+00 1000B 2 302305312 30 35 325 3998 107E-04 1300B 1 40 45 425 3898 OOOE+00

MW-206D 43007 5 17 72 195 4128 291E-05 4 296 302 307 29 34 315 4008 940E-05 2900B 3 522 52 57 545 3778 944E-07 2 656 64 69 665 3658 353E-06 1 92392793 4939 91 96 935 3388 614E-05 6300B

PW-207 43477 5 184622162819 18 29 235 4088 209E-05 1300 4 3508 32 43 375 3948 568E-06 5400 3 53325341542154325559 50 61 555 3768 821E-05 18000

6359 61 72 665 3658 866E-06 12000 1 8685 84 89 865 3458 213E-05 19000

NOTES cmsec = centimeters per second ft bgs = feet below ground surface ft msl = feet above mean sea level B = detected in lab blank

Table XX Orientation Permeability and Groundwater Sampling Results for Transmissive Features

2004 Drilling Program

Hows Corner Superfund Site Plymouth Maine

Borehole Geophisical Feature depth Dip True Dip True Transmissive Log Feature (Feet) Degrees Azimuth Strike bullvgt(Ltk|iy^

Number v Tosftble) v MW-203 5 277 64 337 67 Likely

6 279 59 11 281 Likely 8 352 14 177 87 Likely 11 381 46 96 6 Possible 12 408 35 271 1 Possible 14 415 57 250 340 Possible 15 420 58 202 292 Likely 18 526 52 75 345 Likely 19 530 52 82 352 Likely 28 828 48 75 345 Likely 29 830 52 17 287 Likely 30 830 56 233 323 Possible 31 842 50 130 40 Likely

MW-204 4 295 15 147 57 Likely 5 300 43 91 1 Likely 11 439 31 80 350 Possible 12 440 46 219 309 Possible 14 463 50 358 88 Likely 15 496 34 198 288 Likely 16 513 54 17 287 Likely 17 516 33 14 284 Likely 25 681 39 359 89 Possible 26 685 22 45 315 Possible 27 688 35 73 343 Possible 32 758 45 236 326 Likely 33 762 46 306 36 Likely

MW-205 5 164 69 106 16 Possible 6 166 78 165 75 Possible 7 168 82 115 25 Possible 8 168 68 116 26 Possible 12 215 46 222 312 Possible 13 217 75 62 332 Possible 14 219 29 32 302 Possible 16 237 69 250 340 Possible 17 256 73 353 83 Possible 18 272 44 202 292 Possible 21 299 37 196 286 Possible 22 302 31 206 296 Possible 23 305 59 48 318 Likely 24 312 63 42 312 Likely

MW-206 1 264 37 181 271 Likely 2 296 69 217 307 Likely 3 302 66 233 323 Likely 4 307 64 224 314 Likely 8 342 62 259 349 Likely

jjHydraulic GoiDanctilyity j(cmsecjw

667 E-05

593 E-05

101 P04

710 E-05

902 E-05

119 E-04

0

309 E-05

0

107 E-04

94 E-05

PCE (ugL)

44

170

140

130

220

540

260

IOOOB

1100B

1300B

2900B

STotal vVoCsv tig1)

84

234

192

183

2636

6436

3073

11448

12509

13776

32401

PCEyo dfCTotaf

52

73

73

7 1

83

84

85

87

88

94

90

Table XX Orientation Permeability and Groundwater Sampling Results for Transmissive Features

2004 Drilling Program

Hows Corner Superfund Site Plymouth Maine

Borehole Geophisical Feature deptt raquoip True pip True Transraissive Log Feature (Feet) shy Degrees Azimuth Strike (tikely

Number raquo Possible) 22 522 57 54 324 Possible 25 656 40 82 352 Possible 32 871 59 151 61 Possible 33 883 53 185 275 Possible 34 895 7 175 85 Likely 35 899 53 90 0 Likely 36 902 49 184 274 Likely 37 923 9 175 85 Likely 38 927 42 206 296 Likely 39 934 48 167 77 Likely 40 939 26 180 90 Likely

PW-207 1 1846 33 167 77 Likely 4 2216 49 289 19 Possible 7 2819 59 265 355 Possible 11 3508 55 189 279 Possible 18 5332 43 305 35 Likely 19 5341 51 30 300 Likely 20 5421 20 254 344 Likely 21 5432 39 301 31 Likely 23 5559 52 302 32 Likely 25 6359 24 182 272 Possible 29 8049 77 231 321 Possible 30 8685 78 38 308 Likely 32 9334 29 194 284 Likely

NOTES

B = detected in lab blank

Hydraulic Conductivity

(cmsee) 944 E-07 353 E-06

614 E-05

209 E-05

568 E-06

821 E-05

866 E-06

213 E-05

bulltCE (ugL)

6300B

1300

5400

18000

12000

19000

Total VOCs (ug1)

68901

1410

5802

19234

13085

20354

PCE of Total VOCs

9 1

92

93

94

92

93

Response to EPA-DEP Comment 3 Dated March 312005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

lit

EPA-DEP Comment 3

Comment 3 The reported f values and resultant Kd values There remains doubt that the values used in the flushing model accurately reflect the propensity for PCE to sorb to the bedrock The ^ values presented in Appendix B may be unrealistically high because the bedrock samples may have contained organic carbon that was unavailable for sorption The reported f values are only qualitative estimates of the organic carbon content of the bedrock samples The Walkley and Black organic carbon measurement method is quick and simple but the results obtained cannot be considered quantitative because it requires a correction factor which often results in erroneous values it assumes the organic carbon has an average valence of zero oxidizable and reducible constituents such as chloride ferrous iron and manganese oxides interfere with the results and the errors introduced by interference are potentially greater when the organic carbon content is low at low f values it is not clear that organic carbon is controlling PCE sorption (Schwarzenbach and Westall 1981 Mackay et al 1986 Fetter 1999)

In order to derive a Kd-based retardation factor that is reasonable given the reported f values and the rapid advance of the PCE plume described on pages 4-11 and 4-12 the flushing model requires a bulk density to porosity ratio that is roughly two orders of magnitude higher than the actual ratio for the Hows Corner bedrock (page 4-4) This apparent discrepancy needs to be addressed

Response This comment raises several concerns about the collection and analysis of samples for fraction of organic carbon (f^) the quality of the resulting data and the implications of the use of those data for estimation of the retardation of groundwater contaminant movement Results of bedrock analysis for f were proposed in the TI Evaluation Work Plan for use in conjunction with groundwater contaminant concentrations and aquifer information to estimate cleanup times using the Batch Flushing model It is important to use accurate f values from representative bedrock in the Batch Flushing model in order to obtain reasonable estimates of the remedial time frame Because of the importance of accurate and representative results the TI Investigation field program was designed and conducted both to collect samples representative of the rock volume most likely to be in contact with contaminated groundwater and to analyze them using an appropriate refereed analytical method Five potential methods for evaluating f were identified Of the five methods the Walkey-Black method was selected because it has minimal method interferences and a sufficiently low detection limit as well as a long history of use in agronomy and contamination studies The PRP Group is pleased with the quality of the data obtained from the bedrock samples as represented by their precision and reproducibility

The first part of this comment relates to the determination of fraction of organic carbon (f^) values The several subparts of the first paragraph are addressed individually in items 1 through 5 below The second part of the comment regarding the resultant distribution coefficient (Kd) values is addressed separately as item 6 below

1 There remains doubt that the values used in the flushing model accurately reflect the propensity for PCE to sorb to the bedrock

bull The rock core samples used for f (gocg) analysis were from core immediately adjacent to fractures These rock core samples included the fracture surfaces themselves and rock core extending back less than 1 cm from the fractures Therefore the foe data reported in the TI Evaluation represents the f of bedrock through which groundwater will travel and to which PCE will adsorb Based on the careful selection of sample locations and the

Response to EPA Comment 3 050205doc 1 of 11 Woodard amp Curran (211941)

number of samples collected we are confident that the measured f values are representative of the f at points of contact for PCE with the bedrock it is these f values that determine the propensity of PCE to sorb to the bedrock

bull The samples of rock core collected for analysis of f originated from 19 different locations varying in depth from 11 to 90 feet Therefore it is very unlikely that the rock core samples were contaminated with extraneous organic carbon from above ground

2 The foc values presented in Appendix B may be unrealistically high because the bedrock samples may have contained organic carbon that was unavailable for sorption

bull As noted in response 1 the f data reported in Appendix B represents organic carbon primarily associated with the surface of fractures in the bedrock through which groundwater is most likely to travel Therefore it is this organic carbon that the contaminants in the groundwater will come in contact with and adsorb to in the fractured rock at the site

bull The chemical oxidation agents used in the Walkey-Black method oxidize the easily oxidizable organic carbon in the medium and the foe is calculated from the quantity of the agent consumed Therefore it is unlikely that the analysis of the bedrock samples measured organic carbon that was unavailable for sorption

3 The reported foc values are only qualitative estimates of the organic carbon content of the bedrock samples

bull The reported f values are accurate quantitative results Schumachers review of Methods for the determination of total organic carbon (TOC) in soils and sediments (NCEA-C-1282 EMASC-001 April 2002) identifies the Walkley-Black method which was used to analyze the reported foc values as the reference method for comparison to other methods for analyzing total organic carbon

bull Schumacher also points out that if anything the WalkJey-Black method may underestimate the total organic carbon in a sample due to possible incomplete oxidation of organic carbon Usually the incomplete oxidation of total organic carbon in environmental samples is corrected for by multiplying the measured foe by 130 (Walkley amp Black 1934 Schulte 1995)

bull When the f data in the TI Evaluation Report (WampC 2005) Appendix B (attached) are analyzed statistically the standard deviation of the f for the 19 samples analyzed is 174 of the average f Given this standard deviation the 95 confidence interval for this data ranged from a low of 000123 gocg to a high of 000253 gocgm

The labs Method of Detection Limit (MDL) for the f measured using the Walkley-Black method is 00001 gocg Therefore the average (000188 gocg) the mean (000185 gocg) and geometric mean (000187 gocg) of the f values for the rock core at Hows Corner are all statistically significantly greater than the MDL of the Walkley-Black method

In addition to the aforementioned statistical analysis of the foe data triplicate samples (n = 3) from the same rock core (including one sample from the 19 rock core samples) were

Response to EPA Comment 3 050205doc 2 of Woodard amp Curran (211941)

analyzed for their f to determine the repeatability of the Walkley-Black method The average the mean and the geometric mean of the f values of these replicate samples was 000162 gocg 000150 gocg and 000159 gocgm respectively The standard deviation of these measurements was 000039 gocg

4 The Walkley and Black organic carbon measurement method is quick and simple but the results obtained cannot be considered quantitative because it requires a correction factor which often results in erroneous values it assumes the organic carbon has an average valence of zero oxidizable and reducible constituents such as chloride ferrous iron and manganese oxides interfere with the results and the errors introduced by interference are potentially greater when the organic carbon content is low at low foc values it is not clear that organic carbon is controlling PCE sorption (Schwarzenbach and Westall 1981 Mackay et al 1986 Fetter 1999)

bull Schumachers review (NCEA-C-1282 EMASC-001 April 2002) of the Walkley-Black method identifies several potential problems with this analytical method that could occur if the analytical lab is not familiar with the nuances of the chemistry associated with this method Interestingly Schumachers review neglected one of the more important analytical steps required to avoid errors in quantifying f in samples where there might beNAPL

It is absolutely critical to eliminate any NAPL from rock core samples prior to using the Walkley-Black method to measure foe in such samples This was done by the lab (PTS Laboratories) that measured the foe in the rock core samples from Hows Corner The lab used the Dean-Stark method (solvent extraction) to remove all hydrocarbons (including PCE and other NAPLs) from the sample (PTS Laboratories) This extraction method does not interfere with the subsequent analysis of the natural organic carbon associated with the rock core

Subsequently the samples were dried at 150degC to a constant weight (normally 16 hours) This latter step oxidizes all inorganic minerals including ferrous bearing minerals to ferric oxides and precludes their interference during the oxidation of the samples with chromic acid This procedure completely eliminates any positive bias in the reported foc

data that might have occurred due to the presence of ferrous ions and other reduced minerals

bull As noted in Response 3 the incomplete oxidation of total organic carbon results in an underestimate of the f and is corrected for by multiplying the f by a correction factor of 130 (Walkley amp Black 1934 Schulte 1995) The fx data reported in the TI Evaluation was corrected accordingly by using this correction factor

bull Excess chloride (Cl~) in percent weight quantities as found in saline soils may interfere with the quantitative titration of reduced chromium (Walkley 1947) However given that the primary rock type at the Hows Corner site is phyllite it is highly unlikely that there was sufficient chloride in the rock core samples for this to occur

bull Manganese oxides may also interfere with the analysis of f through competing with the dichromate ion for any oxidizable carbon (Walkley 1947) However in such cases the reported f would be an underestimate of the f present in the rock core Walkley (1947)

Response to EPA Comment 3 050205doc 3 of 11 Woodard amp Curran (211941)

4

reported that in the case where the ratio of MnO2 to carbon is 85 to 1 the error in the carbon determinations would only be 0 to 6 percent

It may also be useful to compare the analysis of total organic carbon in a geologic matrix that contains high levels of manganese using EPA method 9060 to the Walkley-Black method Table 1 summarizes data provided by one of the PRPs that compares the analysis of total organic carbon in a geologic matrix that contains approximately 02 wgt manganese (approximately 03 wgt manganese oxide)

Table 1 Comparison of total organic carbon measured using the EPA- 9060 method and the Walkley-Black method

Laboratory EPA-9060 Method Walkley-Black Method A Ave 00226 gocg Not analyzed

Stdev 000251 gocg n = 5

B Ave 002219 gocg Ave 002050 gocg Stdev = 000316 gocg Stdev =000971 gocg

n= 10 n = 10

The similarity in the total organic carbon concentrations measured by these two different methods provides further confidence that the Walkley-Black method is a viable method for analysis of total organic carbon in the presence of manganese equivalent to at least 10 by weight of the total organic carbon

5 The Walkley and Black organic carbon measurement at lowf^ values it is not clear that organic carbon is controlling PCE sorption (Schwarzenbach and Westall 1981 Mackay et al 1986 Fetter 1999)

bull Schwarzenbach and Westalls (1981) paper states that f values of less than 0001 gocg should not be used in combination with Kow (octanol-water partition coefficients) values to calculate K^ values (solid phase partition coefficients) values for a specific contaminant It should be noted that the TI Evaluation did not use the f data to calculate the KQC from the Kow Instead as requested by the EPA the measured KOC value for PCE was used to calculate the retardation factor for this contaminant

bull Schwarzenbach et al (2003) stated more recently that Even at very low f values (ie foe = 0001 kgoc - kg1 solid) sorption to the organic components of a natural sorbent may still be the dominant mechanism in defining the adsorption of organic compounds to geological matrices

bull In 1985 M Piwoni from the US EPA Robert S Kerr Environmental Research Laboratory published a paper (Banerjee et al 1985) that showed that for very hydrophobic molecules TOC content of the sorbent will control sorption down to levels of organic carbon that defy quantitation Contaminants such as the PCE found in the groundwater at Hows Corner are in this category of compounds

Given the aforementioned reasons the f values reported in the TI Evaluation are accurate within the noted statistical limitations and will have a predictable impact upon the retardation of PCE during groundwater transport

Response to EPA Comment 3 050205doc 4 of 11 Woodard amp Curran (211941)

6 In order to derive a Kd-based retardation factor that is reasonable given the reported foc

values and the rapid advance of the PCE plume described on pages 4-11 and 4-12 the flushing model requires a bulk density to porosity ratio that is roughly two orders of magnitude higher than the actual ratio for the Hows Comer bedrock (page 4-4) This apparent discrepancy needs to be addressed

The apparent discrepancy of bulk density to porosity ratios is most likely due to the fact that the Batch Flushing Model was originally developed for a porous medium and is not directly applicable to fractured bedrock As stated in Appendix C (page C-4) of the Draft Technical Impracticability Evaluation Report in order to use the Batch Flushing Model to describe the transport of contaminated groundwater in fractured bedrock where the matrix porosity is insignificant it is more appropriate to use a fracture surface area to void space ratio to calculate the retardation factor (R) than a bulk density to porosity ratio (Freeze amp Cherry 1979)

Since it is impractical to determine the actual surface area to which contaminants can adsorb the Batch Flushing Model was used with two simplifying assumptions bull The Kd was calculated from the f and the K^ bull The bulk density to porosity ratio term in the Batch Flushing Model was constrained to range

from 4 to 10 the typical range of such ratios in porous media (Freeze amp Cherry 1979)

If one uses site specific bedrock bulk density and porosity values the bulk density to porosity ratio is several orders of magnitude greater (specifically 273 gcc bullbull 000165 (dimensionless) = 1654 gcc) than the range of ratios of 4 to 10 used in the Batch Flushing Model in the Draft Technical Impracticability Evaluation Report Constraining the bulk density to porosity ratio within the range of ratios of 4 to 10 results in significantly lower R value than would be obtained using specific bedrock bulk density and porosity values

In summary in bedrock where fractures are the primary porosity the bulk density to porosity ratio can vary considerably and will be a function of the number of fractures and the fracture aperture The calculated bulk density to porosity ratio will be inversely proportional to the porosity This means that in fractured rock with limited fracturing and smaller porosity the calculated bulk density to porosity ratio is greater and will result in a greater calculated retardation factor than in bedrock with more extensive fracturing and greater porosity Consequently the calculated retardation factor will be greater for bedrock with less surface area available for sorption than bedrock with greater surface area for sorption This is contrary to what actually occurs

4 Response to EPA Comment 3 050205doc 5 of 11 Woodard amp Curran (211941)

m

REFERENCES

Banerjee P MD Piwoni K Ebeid (1985) Sorption of organic contaminants to a low carbon subsurface core Chemosphere _14 1057-1067

Freeze RA JA Cherry (1979) Groundwater Prentice Hall Englewood Cliffs NJ pg 604

PTS Laboratories wwwptsgeolabscompdf files3TOCnotepdf

Schulte EE (1995) Recommended soil organic matter tests in Recommended Soil Testing Procedures for the Northeastern United States Northeastern Regional Publication No 493 Chapter 8

Schwarzenbach RP J Westall (1981) Transport of nonpolar organic compounds from surface water to groundwater Laboratory sorption studies Environ Sci Tech 15 1360-1367

Schwarzenbach RP PM Gschwend DM Imboden (2003) Environmental Organic Chemistry Wiley-Interscience pg 292 408 amp 412

Walkley A LA Black (1934) An examination of the Degtjareff method for determining soil organic matter and a proposed modification of the chromic acid titration method Soil Science 37 29-38

Walkley A (1947) A critical examination of a rapid method for determining organic carbon in soils - effect of variations in digestion conditions and of inorganic soil constituents Soil Science 63251-264

Woodard amp Curran Inc (WampC) 2005 Draft Technical Impracticability Evaluation Hows Corner Superfund Site Plymouth Maine January 2005

Response to EPA Comment 3 050205doc 6 of Woodard amp Curran (211941)

LIST OF ATTACHMENTS (Response to Comment 3)

Appendix B to Draft Technical Impracticability Evaluation Measurement of foe at Hows Corner (4 pages)

m

Response to EPA Comment 3 050205doc 7 of 11 Woodard amp Curran (211941)

Appendix B Measurement of foe of Rock Core at Hows Corner

There are two general approaches to measure the fraction of organic carbon (foe) in rock cores

bull Measurement of weight loss by ignition of organic matter bull Chemical oxidization of organic carbon to carbon dioxide and either

subsequent quantification of the oxidant used for the reaction or quantification of the carbon dioxide produced during this oxidation process

The weight loss method is subject to errors caused by volatilization of substances other than organic materials such as water hydroxides and mineral carbonates Quantification of foe by the weight loss method is particularly sensitive to the presence of carbonates in rock cores There are however weight loss methods that are designed to differentiate between organic carbon and the aforementioned interfering materials but they require considerable care and are less accurate at low foe values Hence the weight loss method was not well suited for measuring the foe of the rock core from Hows Corner

The chemical oxidation of organic carbon is much better suited for quantifying organic carbon in rock cores such as those from Hows Corner This method uses a strong chemical oxidant to oxidize organic carbon to carbon dioxide and then measures either the chemical oxidant used to oxidize the organic carbon or the quantity of carbon dioxide produced In addition this general approach is not subject to interference by volatilization of other constituents of the rock core

There are at least two such chemical oxidation methods

bull The method of Baccini which was described by Schwarzenbach amp Westall (1981) first acidifies the sample to eliminate interference by carbonates Then a strong oxidant is used to chemically oxidize the organic carbon to carbon dioxide The resulting carbon dioxide is subsequently reduced to methane and quantified using a flame ionization detector Unfortunately this method has not been described in detail in a referred journal Hence it is would not have been appropriate to use to characterize the foe in the Hows Corner rock core

bull The more commonly used method to quantify foe in rock core is the Walkley-Black method (1934) This method is preferred for RBCA and DODDOE projects and by the oil industry

The Walkley-Black method uses an excess of chromic acid to oxidize (digest) organic matter to carbon dioxide The remaining chromic acid that was not consumed during the oxidation of the organic carbon is then quantified by titration with ferrous sulfate The difference in chromic acid prior to and after the oxidation of the organic carbon represents the total chromic acid used to oxidize

Hows Corner TI Evaluation Page 1 January 13 2005 Appendix B

the organic carbon in the sample The latter can be calculated using the chemical stoichiometry of the reaction

The Walkley-Black method is very accurate for samples that contain less than 2 organic carbon matter The minimum detection limit (MDL) for the Walkley-Black method is 100 mgkg or an foe of 0001

Given the rock core at Hows Corner was expected to contain less than 2 organic carbon the Walkley-Black method was used to measure the foe from 19 different rock core samples collected from varying depths ranging from 11 to 90 feet

Table 1 provides a statistical summary of the aforementioned data

Table 1 Statistical summary of foe data from rock cores collected at varying depths

Statistical Parameter Calculated Value foe Minimum Detection Limit (MDL) 00010 Number of samples analyzed (n) 19 Average foe 00019 Median foe 00019 Geometric Mean foe 00019 Standard deviation of foe measurements 000033 Relative standard deviation 174 -+ 95 Confidence intervals 00012 to 00025

The data in Table 1 shows the following

bull The foe from the Hows Corner rock cores are statistically greater than the MDL of the Walkley-Black analytical method

bull The average and median values for the foe of the Hows Corner rock cores from varying depths are nearly identical indicating that there is little variability in the foe values in the source zone at the site

bull The standard deviation of these measurements is 000033 which is 174 of the average foe

bull The 95 confidence intervals of the foe of the rock core at Hows Corner are 00012 to 00025

The foe was also analyzed from three separate samples taken from the same rock core at a depth of 55 feet (Only one of these samples was included in the data summarized in Table 1) Table 2 shows the statistical repeatability of this type of analysis

Hows Corner TI Evaluation Page 2 January 13 2005 Appendix B

Table 2 Repeatability of analysis of foe from one rock core at 55 feet in depth

Statistical Parameter Calculated Value Number of samples analyzed (n) 3 Average foe 00016 Median foe 00015 Geometric Mean foe 00016 Standard deviation of foe measurements 000039 Relative standard deviation 240 -+ 95 Confidence intervals 00008 to 00024

The data in Table 2 shows the following

bull The percent relative standard deviation of these three analyses of foe from the same rock core at Hows Corner is 24

bull The 95 confidence interval of the foes measured in this particular rock core at Hows Conrer is 00008 to 00024

These results show that there is good repeatability in using the Walkley-Black method for analysis of the foe in the rock core at Hows Corner

References Schwarzenbach amp Westall (1981) Transport of nonpolar organic compounds from surface water to groundwater Laboratory sorption studies Environ Sci Tech 15 1360-1367

Walkley A I A Black (1934) An examination of Degtjareff method for determining soil organic matter and a proposed modification of the chromic acid titration method Soil Sci 37 29-37

Hows Corner Tl Evaluation Page S January 13 2005 Appendix B

Woodard and Curran PTS Laboratories PTS File No 34618

ORGANIC CARBON DATA (METHODOLOGY WALKLEY-BLACK)

PROJECT NAME PROJECT NO

SAMPLE ID

203-chip-13 203-chip-23 203-chip-27 203-chip-38 203-chip-42 203-chip-47 203-chip-52 203-chip-58 203-chip-69 203-chip-82 207-chip-11 207-chip-19 207-chip-24 207-chip-29 207-chip-35 207-chip-45 207-chip-55 207-chip-87 207-chip-90

207-chip-55 55-MS

55-MSMSD

Hows Corner NA

DEPTH ft

13 23 27 38 42 47 52 58 69 82 11 19 24 29 35 45 55 87 90

55 NA NA

MATRIX

Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip

Average Median

Geometric Mean Standard Deviation Relative Std Dev

+- 95 Confidence Interval n

Rock Chip Rock Chip Rock Chip

Average Median

Geometric Mean Standard Deviation Relative Std Dev

+- 95 Confidence Interval n

FRACTION ORGANIC CARBON

(gg)

170E-03 185E-03 185E-03 170E-03 240E-03 190E-03 230E-03 180E-03 170E-03 115E-03 195E-03 220E-03 220E-03 235E-03 135E-03 190E-03 205E-03 175E-03 160E-03

188E-03 185E-03 185E-03 327E-04

1739 123E-03 to

19

205E-03 130E-03 150E-03

162E-03 150E-03 159E-03 388E-04

2402 840E-04 to

3

2532E-03

2393E-03

Hows Corner Tl Evaluation Appendix B January 13 2005

Response to EPA-DEP Comment 4 Dated March 31 2005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

EPA-DEP Comment 4

Comment 4 Distribution of contaminants First the TI report seems based on the assertion that there is DNAPL at the source area yet it also appears to represent that the source area is small and the bedrock below 85 is competent (or less fractured) and less impacted by the release of contaminants Some of the confusion may result from using most recent data when that data is from several different sampling events over several years and there is no discernible difference in concentrations between shallow and deep bedrock or as in Section 421 where generally decreased generally increase generally similar and similar concentrations in four consecutive sentences leads to a muddled picture of the contaminant distribution

Second the report asserts that the distribution of contaminants over the entire plume has not changed with time but fails to support this conclusion with data again relying on data that is from different sampling dates for one composite representation

Response The likely presence of dense non-aqueous phase liquid (DNAPL) at the Hows Corner Site and the determination that the source area is small are not mutually exclusive and both are conclusions drawn from information obtained during field investigations The presence of DNAPL in the source area is based on the elevated concentrations of volatile organic compounds (VOCs) detected in the groundwater (WampC 2001 WampC 2002) The conclusion that the source area is small is based on the area in which VOCs in groundwater have been detected at concentrations that are considered to be indicative of the presence of DNAPL nearby Similarly the conclusion that fracture frequency decreases at depths greater than approximately 50 to 85 feet below ground surface was based on field observation during the RI field work The fact that zones with observed fractures exhibited higher hydraulic conductivities than zones without fractures coupled with the decreasing frequency of observed fractures with depth led to the conclusion that the hydraulic conductivity of the bulk rock decreases with depth

The most recent data from all wells were used to provide the maximum VOC data set size During the RI all of the previously-existing and then newly-installed monitoring wells were sampled along with several residential wells The RI sampling included up to 48 monitoring wells Subsequent to the RI and prior to the TI three rounds of monitoring were conducted to verify that the plume was stable 15 monitoring wells were sampled during each of the three rounds During the TI field investigation 29 wells were sampled for VOCs The sampled wells included all of the newly-installed wells and a subset of wells installed during the RI for a total of 29 monitoring wells By using most recent data VOC results from 53 monitoring wells were included in the evaluation (see table labeled Sampling Events for listing of monitoring wells) This approach was selected because there generally was little variation in the data from a particular location between years This is borne out by the attached individual plots of VOCs detected in shallow bedrock and deep bedrock for the Pre-ROD (December 1999January 2000) and Supplemental (May 2000) sampling events and for June 2001 January 2002 and April 2003 sampling events The Pre-ROD and Supplemental plots are similar to the subsequent plots from the 2001 2002 and 2003 sampling events

In addition to maps showing the spatial distribution of VOC data at a given time trend plots of the data from a particular location through time (attached) indicate that since the RI concentrations generally have been stable or have decreased Together the maps and trend plots and the data from which they were developed indicate that the distribution of contaminants over the entire plume has not changed appreciably with time

Response to EPA Comment 4 050305doc 1 of 26 Woodard amp Curran (211941)

REFERENCES

Woodard amp Curran Inc (WampC) 2001 Final Remedial Investigation Report Hows Corner Superfund Plymouth Maine July 2001

Woodard amp Curran Inc (WampC) 2002 Final Feasibility Study Report - Non-Source Area Groundwater Hows Corner Superfund Site Plymouth Maine Hows Corner Superfund Plymouth Maine July 2002

Response to EPA Comment 4 050305doc 2 of 26 Woodard amp Curran (211941)

LIST OF ATTACHMENTS (Response to Comment 4)

Table - Sampling Events 1999 - 2004 (2 pages)

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater Pre-ROD Sampling Event

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater Pre-ROD Sampling Event

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater Supplemental Sampling Event

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater Supplemental Sampling Event

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater June 2001

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater June 2001

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater January 2002

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater January 2002

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater April 2003

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater April 2003

Figure - Concentration Trends - Non-Source Area Wells MW-1B and MW-3B

Figure - Concentration Trends - Non-Source Area Wells MW-13DB and MW-16DB

Figure - Concentration Trends - Non-Source Area Wells MW-16IB and MW- 108D

Figure - Concentration Trends - Non-Source Area Wells MW-108S and MW-112D

Figure - Concentration Trends - Non-Source Area Wells MW-112S and MW-114D

Figure - Concentration Trends - Non-Source Area Wells MW-114S and MW-115D

Figure - Concentration Trends -Source Area Wells MW-2DB and MW-2IB

Figure - Concentration Trends -Source Area Wells MW-102S and MW-103D

Figure - Concentration Trends -Source Area Wells MW-103S and MW-104D

Figure - Concentration Trends -Source Area Wells MW-104I and MW-106D

Figure - Concentration Trends -Source Area Wells MW-106S

Response to EPA Comment 4 050305doc 3 of 26 Woodard amp Curran (211941)

I I

El I

II I I 1 I

I

i

Event Baseline Case ID WC-01 WC-01

Well Date Aug-99 Oct-99 LOT10 1 LOT1-1 1 LOT11-4 LOT14 1 LOT15 1 LOT15-1 1 LOT16 1 LOT16-1 1 LOT17 1 LOT18 1 LOT19 1 LOT2 LOT20 1 LOT21-10 1 LOT21-11 1 LOT21-12 1 LOT21-13 1 LOT21-14 1 LOT21-2 1 LOT21-5 1 LOT21-7 LOT21 -8 1 LOT21-9 1 LOT23 1 LOT24 1 LOT28-1 1 LOT28-2 1 LOT28-3 1 LOT28-4 1 LOT28W 1 LOT30 1 LOT30-1 1 LOT30-2 1 LOT30-3 1 LOT30-4 1 LOT30-5 LOT31 LOT35 1 LOT41 1 LOT42-1 1 LOT43-1 1 LOT43-4 1 LOT6-1 1 LOT67 1 LOT6-7 1 LOT6-8A 1 LOT6-8B 1 LOT80-1 1 LOT82 1 MW-101D MW-1011 MW-101S MW-102D MW-102S MW-103D MW-103S MW-104D MW-1041 MW-104S MW-105D MW-106D

Groundwater Sampling Location Summary 1999 - 2004xls

Sampling Events 1999-2004

Hows Corner Superfund Site Plymouth Maine

Supplemental 2001 2002 2003 Pumping 2004 Pre-ROD Rl Sampling Sampling Sampling Test Sampling WC-03 WC-09 WC-25 WC-30 WC-42B WC-56 WC-58 Dec-99 May-00 Jun-01 Jan-02 Apr-03 Sep-04 Sep-04

1

1 1 1

1 1 1 1 1

1 1

1

1 1

1 1 1

1 1 1 1 1

1

1 1

1 1 1 1

1

1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

Sampling Events 1999-2004

Hows Corner Super-fund Site Plymouth Maine

Supplemental 2001 2002 2003 Pumping Event Baseline Pre-ROD Rl Sampling Sampling Sampling Test

Case ID WC-01 WC-01 WC-03 WC-09 WC-25 WC-30 WC-42B WC-56

ll

Well Date Aug-99 Oct-99 Dec-99 May-00 Jun-01 Jan-02 Apr-03 Sep-04 MW-106S 1 1 1 1 1 MW-107D 1 1 MW-108D 1 1 1 1 1 MW-108S 1 1 1 1 1 MW-110D 1 1 MW-111D 1 1 MW-112D 1 1 1 1 1 MW-112S 1 1 1 1 1 MW-113D 1 1 MW-114D 1 1 1 1 1 MW-114S 1 1 1 1 1 MW-115D 1 1 1 1 1 MW-12DB 1 1 1 MW-12SB 1 1 1 MW-13DB 1 1 1 1 1 1 MW-13SB 1 1 1 MW-14DB 1 1 MW-14SO 1 1 MW-15DB 1 1 1 MW-15SB 1 1 1 MW-16DB 1 1 1 1 1 1 MW-16IB 1 1 1 1 1 1 MW-16SO 1 1 MW-17DO 1 1 1 MW-17SO 1 1 1 MW-1B 1 1 1 1 1 1 MW-203D MW-203S MW-204D MW-204S MW-205 MW-206D

I MW-206S MW-2DB 1 1 MW-2DDB 1 1 MW-2IB 1 1 1 1 1 1 MW-3B 1 1 1 1 1 1

I MW-4O 1 1 1 MW-5B 1 1

II MW-6DB 1 1 1 MW-6SB 1 1 1 MW-8DB 1 1 1 MW-8SB 1 1 1

II PW-207 1 SEEP-1 1 SUBTOTAL - RESIDENTIAL 44 25 0 2 0 3 0 SUBTOTAL - MONITORING 22 48 41 15 15 15 1

Total 3 66 73 41 17 15 18 1

I Included in most recent data

I Notes 1 - Overburden well not included in most recent data for plotting

2 - Tetrahydrofuran and 2-Butanone were the only two compounds detected in this well and are thought to be the result of well repair not included in most recent data for plotting

3 - Not included in most recent data for plotting

2004 Sampling

WC-58 Sep-04

1

1 1

1 1

1 1 1

1

1 1

1 1 1 1 1 1 1 1 1

1 1

1

0 29

29

Groundwatef Sampling Location Summary 1999 - 2004xls

I

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

monitoring well Figure 4-14 total VOC contour (ugl) - December 1999January 2000 Distribution of Total VOCs in

Note SW-113 is located downstream of SEEP-1 Shallow Bedrock Groundwater total concentration of detected VOCs ND= not detected these two locations were sampled during the Pre-ROD Sampling Event

Baseline Sampling Event in OctoberNovember 1999 Hows Corner Superfund Site Surface Water Sampling Location A Plymouth Maine Seep Sampling Location laquo- WOODARD ampCURRAN

995037wipri reportepa ri interim final feb 2001cadd drawingsfinalfig 4-14

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

0 300 600 I

FEET

Q residential well Figure 4-16 monitoring well Distribution of Total VOCs in

Deep Bedrock Groundwater total VOCs contour (ugl) Pre-ROD Sampling Event

active residential wells with lot number Hows Corner Superfund Site 2deg42deg Plymouth Maine total concentration of detected VOCs ND= not detected WOODARD ampCURRAN Enyinaaring bull Science bull Operations bull

995037wipri reportepa ri interim final feb 2001cadd drawingsfinalfig4mdash16

PLYMOUTH POND

PLYMOUTH POND

1 628Tl7MW-2bB 12135

PLYMOUTH POND

monitoring well Figure 4-20

V total VOC contour (ugl) - June 2000 Distribution of Total VOCs in Shallow Bedrock Groundwater

| 34 | total concentration of detected VOCs ND= not detected NA = not analyzed Supplemental Sampling Event Note SW-113 is located downstream of SEEP-1 Hows Corner Superfund Site

Surface Water Sampling Location these two locations were sampled during the Plymouth Maine Baseline Sampling Event in OctoberNovember 1999 Seep Sampling Location WOODARD amp CURRAN

Engineering bull Science - Operations bull 995037wipri reportepa ri interim final feb 2001 cadd drawingsfinalfig 4-20

residential well Figure 4-22 Distribution of Total VOCs in

monitoring well Deep Bedrock Groundwater

total VOCs contour (ugl) Supplemental Sampling Event

Hows Corner Superfund Site

total concentration of detected VOCs ND= not detected NA = not analyzed Plymouth Maine

WOODARD amp CURRAN

995037wipri reportepa-ri interim final feb 2001cadd drawingsfinalfig 4-22 Engineering bull Science - Operations bull

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

FEET

Shallow Monitoring Well

Deep Monitoring Well

C Detected Concentration ND = Not Detected Figure 1-XS Distribution of Total VOCs in Shallow Bedrock Groundwater

Pumping Well

17-Acre Property Boundary Concentration Contour (ugl)

June 2001 Hows Corner Superfund Site

Plymouth Maine WOODARDampCURRAN

-i^rhvj bull Scbncn bull Operations bull 211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0601 dwg04-20-05

PLYMOUTH POND Hopkins Road V

O

PLYMOUTH POND

PLYMOUTH POND

o

0 300 600 mdashfa FEET

Shallow Monitoring Well bull bull - 17-Acre Property Boundary Figure 1-XD

Deep Monitoring Well 1 I Detected Concentration ND = Not Detected Distribution of Total VOCs in Deep Bedrock Groundwater

-mf- Pumping Well June 2001 Residential Well Hows Corner Superfund Site

Plymouth Maine i h Surface Water Sampling Point

g WOODARD ampCURRAN _ ^ _ ^ _ _ yen_ rj i|Hlaquorlny bull Science bull Opt

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0601 dwg04-20-05

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

Shallow Monitoring Well

Deep Monitoring Well

Detected Concentration ND = Not Detected Figure 1-YS Distribution of Total VOCs in Shallow Bedrock Groundwater

Pumping Well

17-Acre Property Boundary Concentration Contour (ugl)

January 2002 Hows Corner Superfund Site

Plymouth Maine WOODARD amp CURRAN Engineering Science- Operations bull

211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0102dwg04-20-05

PLYMOUTH POND

PLYMOUTH POND

Site Pand^ laquoum-laquoBTuitaraquo tLV

vVlf-(

PLYMOUTH POND

0 300 600 ^ = FEET

Shallow Monitoring Well mdashbullbullbull 17-Acre Property Boundary Figure 1-YD - A - Deep Monitoring Well FT Detected Concentration ND = Not Detected Distribution of Total VOCs in

Deep Bedrock Groundwater Pumping Well January 2002 Residential Well Hows Corner Superfund Site

Plymouth Maine Surface Water Sampling Point

WOODARD ampCURRAN Engineering Sciencs- Operations bulli Si

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0102dwg04-20-05

- m j

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND j A O-shy

Shallow Monitoring Well E Detected Concentration ND = Not Detected Figure 1-ZS Distribution of Total VOCs in

Deep Monitoring Well Shallow Bedrock Groundwater

Pumping Well Hows Corner

April 2003 Superfund Site

17-Acre Property Boundary Plymouth Maine Concentration Contour (ugl) r WOODARD ampCURRAN

Engineering bull Science bull Operations bull 211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0403dwg04-20-05

s S pound

PLYMOUTH POND

PLYMOUTH POND

- -

5 PLYMOUTH POND

Jo

FEET

ft Shallow Monitoring Well mdashbullbullmdash 17-Acre Property Boundary Figure 1-ZD Deep Monitoring Well I 1 I Detected Concentration ND = Not Detected Distribution of Total VOCs in

Deep Bedrock Groundwater Pumping Well April 2003

Q) Residential Well Hows Corner Superfund Site Plymouth Maine

(T) Surface Water Sampling Point WOODARD ampCURRAN poundKk EnginawtirKj bull Science - Operations bull

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0403dwg04-20-05

0 Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

B MW-1B

I 12000

PCE

B 10000 Total VOCs

I

i 2000

i 0 Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

c MW-3B

G 2000

1800

B PCE

1600 Total VOCs

1 I I E

il-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

G E

211941

El

I I z E

80

Concentration Trends shy Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-13DB

Total VOCs

c i i c o

Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

MW-16DB

30

c i c c I c o

Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99

PCE

Total VOCs

Jul-01 Jul-03

211941

O bi

c Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

I MW-16IB

i 35

3

c Total VOCs

lt- 2 5

0 | gt

o

1 sectI

c c 0 4

Jul-90 Jul-92 Jul-94 Jul-96 Jul-98 Jul-00 Jul-02 Jul-04

I I MW-108D

I 12

PCE 10

Total VOCs c oc 3

E E I 0

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

E 211941

c Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

fi MW-108S

I I 40

PCE 35

Total VOCs

30

I f 26

20 I o

I 15

10

c Dec-99 Dec-00 Dec-01 Dec-02 Dec-03 I 0

I MW-112D

c 35 - imdash

I A3 shyTotal VOCs

o c

E 1 2

I

ition

B 1 ^

-i c 3

0 Dec-99 Dec-OO Dec-01 Dec-02 Dec-03

211941

I

i

I

cII

Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-112S

08

PCE

Total VOCs 06

o 04

02

0 Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

MW-114D

o

12000

10000

8000

6000

PCE

Total VOCs

4000

2000

i

ccEIIc

i

i

E

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

211941

Con

cent

ratio

n (

ug

l)

E Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

I MW-114S

E A5000 -- Total VOCs

- 4000

0 3000

2000

i 1000

i n shy

Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

MW-115D

c PCE

Total VOCs

c E

o

C c

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03 I 0

211941

IepoundII

EIEIIGICCIccc

30000

25000

20000

o bullsect 15000 b

o 10000 U

5000

0 Aug-99

25000

20000

5000

0 Aug-99

211941

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-2DB

PCE

Total VOCs

Aug-01 Aug-03

MW-2IB

PCE

Total VOCs

Aug-01 Aug-03

IDIBI

ii EIDIISIBIG C

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-102S

6000

5000 PCE

Total VOCs

4000

O 3000

2000

1000

0 Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

MW-103D

16000

~ 14000 ugt 3- 12000 o

^ 10000

sect 8000

O 6000

4000

2000

PCE

Total VOCs

0Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

211941

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

G MW-103S

I I

ampo

12000

10000

E sectc

S

8000

6000

4000

2000

0Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

G I 6000

MW-104D

i 5000

PCE

Total VOCs

i i c

2000

1000

Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

E I

211941

cIccIG

IIBCccBcIc

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-1041

PCE Total VOCs

a 25000

0 20000

a 15000

10000

5000

0 Jan-OO Jan-01 Jan-02 Jan-03 Jan-04

MW-106D

3000

2500 PCE

Total VOCs

=sect 2000

o bullsect 1500

1000

500

0 Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

211941

c Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

c MW-106S

I PCE

Total VOCs

i

i Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

i

i i i E

C

211941 c

Response to EPA-DEP Comment 5 Dated March 312005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

iiw

EPA-DEP Comment 5

Comment 5 Matrix Diffusion The report as well as other proponents of matrix diffusion suggest that depletion of DNAPL (Section 5112 page 5-15) needs to be achieved While that might be the ideal the goal is to achieve performance standards and that goal may be attainable while there is residual contamination in the rock perhaps even DNAPL globules The low bedrock matrix porosity (page 1-15) the high permeability values (page 4-4) the relative flux of the groundwater (page 5-5) and the decrease in surface area and out of the mainstream pockets (appendix C-4) all suggest that the diffusion out of the rock matrix would be insubstantial relative to the regional flux of groundwater through the Site

Response The TI Evaluation Report does not explicitly consider or rely upon matrix diffusion as a basis for requesting a TI Waiver for a portion of the Hows Corner Site The technical literature provides documentation that matrix diffusion can be a significant process that affects chemical transport and groundwater remediation timeframes in unconsolidated and consolidated media including fractured rock (US EPA 1989 Freeze and Cherry 1979 Pankow and Cherry 1996 Fountain 1998) Back diffusion of contaminants from the matrix porosity of the fractured rock can prolong the time necessary to achieve groundwater cleanup goals particularly for compounds such as PCE for which the cleanup goal is a low concentration It is our expectation that matrix diffusion has occurred at the Hows Corner Site and that back diffusion of PCE from the rock matrix will also occur Although the extent to which matrix diffusion is occurring at the Hows Comer Site has not been determined and that lack of knowledge contributes to uncertainty regarding the cleanup times at the Site the effect of matrix diffusion is to lengthen rather than shorten the time required for remediation

REFERENCES

Fountain JC 1998 Technologies for Dense Nonaqueous Phase Liquid Source Zone Remediation Ground-Water Remediation Technologies Analysis Center Technology Evaluation Report TE-98-02 December

Freeze RA and Cherry JA 1979 Groundwater Prentice-Hall Inc Englewood Cliffs NJ 07632 p 410-412

Pankow J F and Cherry J A 1996 Dense Chlorinated Solvents Waterloo Press Portland OR 97291-1399 p 67-88

US EPA 1989 Transport and Fate of Contaminants in the Subsurface EPA6254-89019 p 17-18

Response to EPA Comment 5 050305doc 1 of 1 Woodard amp Curran (211941)

WOODARD amp CURRAN Maine Massachusetts New Hampshire Connecticut Florida Operational offices across the US 1-800-426-4262 www woodardcurran com

Page 21: SDMS DocID 251749 - Records Collections · 2020-06-13 · CORPORATE OFFICES: Maine, Massachusetts, New Hampshire, Connecticut New, York, Florida Engineering • Science • Operations

c Northeast Geophysical Services Borehole Geophysical Log

MW-203 Date logged 081704 Plymouth Maine

I Flowmeter Measurements Tomporaturo(C) Acoustic Televiewer

7 5 8 8 5 9 95 Caliper (Inches) Resistance (Ohms) Spontaneous Potential (mVj Dip In Degrees PCE Total VOCs

3 0 2 0 8 0 laquodeg 4S 1000 1400 1800 2200 MO HO 1000 1200 MOO 0 laquo deg ugL ugL n 1 1 1 1 1 1 1 1 1 i 1 1 1 1 n 1 1 1 1 1 1 1 1 1 1 1 n I l l l l l l l n

Ambient Flowneter pumping Rowmeter 11 gpm 6

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magnetic 10 bull 10 bull - 10 - north - 1 0I

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20 bull bull20 bull ^ ltr~mdash 01

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I eet be

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70 bull j 70 - - 70 - 7 0 -

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1 1 1 1 1 1 1 ) | 1 f I 1 1 1 ) 0 20 40 60 80

flft mdash ftn - mdash rVt

30 4 g 0 20 40 60 Dip in Degrees bullbull

Likely or poss bleFluid Resistivity (ohmmeters) The dip direction-- indicated

^ t h e l i n e extending from t h

I Iransmissive zone circle The strike of the feature is 90 degrees from this

The acoustic televiewer graph displays the mostprominent features selectedffom the acoustic televiewer

R n r a h n l c D O t t n O I B

f i o n n h w c i r a l U K U p i i y SI Ud l

1 rn l_Og Packered Interval August 2004

E tog The location dip angle and dip direction of the sleeted M W - 2 0 3 Groundwater samples were collected by Woodard S Curran on H23120M features are approximate Refer to the televiewer og of His _ well for more precise detail Plymouth Maine Date logged 081704

I

1

Northeast Geophysical Services Borehole Geophysical Log MW-204 D a t e l o gge d 072604

Plymouth Maine

n 3

Flowrneter Measurements(in gpm)

Caliper (Inches)0 3 5 4 0

1 1 1 1 1 1 1 t 1 1 1 1 1 1Ambient Rowmeler pumping Flowmetsr 05gpm

Templaquorature (C) bull bull bull bull i

7 75 8 8S 9 Resistance (Ohms) Spontaneous Potential (mV)

4000 SOW 600 4M 0

Acoustic Televiewer (interpreted)

Dip in Degrees 0 20 4060 SO

at N

PCEugL

Total VOCs ugL

- -_ a

10-

shy 10 bull - 10 shymagnetic

north - 10

o o

bull 1

11

11

1 1

1 1

11 1

1 1

1 1

1 1

1 1

1 1

1 1

1 1

1 1 E 1

- L

3 7 2 0 2 0r bull 20 bull - shy

i S_ N F

bull30 bull 7 3 0 220 2636shy1^ J J 004

fI f V ^

40 shy 4 0 4 0 shy - 4 0rbull019 [_ 007 w8 - - shy5 c

bull

gt

Ia50i 540 6436

bull50 - - 50 - - 5 0

-QQ7 - bull - -t T

pound V gtk

B 6 0 - e o - 7 6 0 -60shyQ 1 1

Q -007 -004 bull1 mdash T - J ~

bull

- - shyT 70 -J c [TO- - 70 - 7 0-

V Y 1- -004 -003

mdash T -h - y - j i - - mdash 260 3073 - gt=7

80 -j NF bull80 - - 80 - - 8 0Jgt

bull i

i 1

i i

C- bull shy

90 shy

K

Jlt i90 90 shy - 9 0shy -

l

ii

I I I I

NF bull M J

I ^ ^ - ^ bull 1

mdash mdash - _

s -7 ^100shy

till

1 100 100- H - 1 0 0shy -1 x Likety or possible k ^ Iransmissive zonebull

1 i i i ii i i i | l l l l | l i l l 0 20 40 ED 80

1 -

3 0SOFluid Resistivity (ohmmeters)

Dip in Degrees The djp ^ ^ o n is indicated ty Ihe line extending from tha circle The strike of Ihe feature

19- 3U UIHJIW93 IolII l l l lraquo

bull

The acousfc televiewer graph displays the mostprominent features selected from the acoustic televiewer109 The location dip angle and dip direction of Ihe sleetedfeatures are approximate Refer to the televiewer log of thiswentormore precise detail

B o r e h o l e G e O D h V S I C a l LOO B W H U I B w c w p n y o i v a i w v yM W - 2 0 4

P l y m O U t n MaiDB

Packorod Interval August 2004Groundwater san-ples wampramp collected by Woodard a Curran on OMO23C4

Date logged 072604

C

I

E Northeast Geophysical Services Borehole Geophysical Log Date logged 072704

I MW-205

Plymouth Maine

Flowmeter Measurements Temperature (C) Acoustic Televiewer (In gpm) I ~l (Interpreted)

I 85 10 Caliper (inches) 95

Dip in D g r laquo Resistance (Ohms) Spo ontaneous Potential (mV PCE Total VOCs 3 0 16 4 0 4 5 ) 20 40 60 80 10 00 2000 30 00 4VJ 400 -3 laquo

i i i i 1 i i I i 11 4 0 D 1 I I ugL ugL

C h

iii Ambient Flowmetar pumping

Flowmeter 1 25 gprn

I bull$bull

i

I rmdash magnetic 1 north ^^^^ 1 VI f

10 ~ I C x 10 bull - 10 bullbull

4 5 6mdashmdash f 1000B 11448 noisy nodi a raquo ^

mdash 5rt mdashi mdash Oft pound) 1100B 12509

cjmdash1 007

-

i i i 1

en

8 B a B

30 mdash

-

40 shy

-mdash I -

50 -_

__NF lt005

- 30 - - 3 0 it 34V

MO P26 V S) 1300B 13776 _ N F NF

26

40 bull - 40 bull 7-40 gt J Vf1 cX

) -j -

_ N F NF 50 c bull - 50 ^ 7-50

i I

I

c

B pound 60 - 6 0 7 60 - 7-60 a i 1

_ N F NF i Si f f 70 -_ bull70 bull - 70 shyC I 9

-m bull - shyA

_ N F NF 80 80 -j bull80 bull - 80 - C- 33 34

bull

5-i r

i 1

J r

Ck

_ N F NF 9 0 90 - - 90 shy

i bullCshy

J rK bull

100 -j ^ Likely or possible bull100- - 100- I -100

transmissive zone bull - ^ bull shy] |

1 1 1 1 1 1 1 I 1 i i i 1 i i 1 1 0 20 40 SO SO 10 20 30 40 50 Dip in Degrees 30 4 0 Fluid Resistivity (ohmmeters) Thlaquo dip direction is indicated

by the line extern r g from the circle The strike of he feature is 90 degrees from ihis

The acoustic televiewer graph displays the most

I Borehole Geophysical Log Packered Interval August2004 prominent features selected from the acoustic televiewer

Groundwatcr samples were oollccled by Woodard amp Cufran orgt S172004 log The location dip angle and dip direction of ins slsctsd MW-205 features are approximate Refelt to the televiewer log of this wall for more precise detail Plymouth Maine Date logged 072704

I

C

I Northeast Geophysical Services Borehole Geophysical Log Date logged 072704

I MW-206

Plymouth Maine

Flowmetor Measurements Temperature (C) Acoustic Televiewer | I r T i i i i i i i i i i i i i i r I |(in gpm) (Interpreted)

I 75 8 flS 9 95

Caliper (inches) Resistance (Ohms) Spontaneous Potential (mV) Dip In Degress PCE Total VOCs 30 35 40 4 5 0 20 40 M 90 4500 5500 6500 ugL ugL I i i

I I

- 1 0

I - 2 0

I 2900B 32401

i i L

E 0

i 6300B 68901

i I 0 20 40 SO 80

20 30 40 50 Dip in Dlaquogralaquos

amp 4 a Fluid Resistivity (ohrnmeters) The dip dirertion is indicated Likely or possible by iho line extending from the transmissive zone circle The striKe of the feature

is 90 degrees from tNs

Borehole Geophysical Log Packered Interval August 2004

E amples were collected by Woodard amp Cunan oo SM82004 log Thraquo location 4p angle and dip direction of the sloeled MW-206 feature are approximate Refer to the televiewer 109 of this well for more precise detail Plymouth Maine Date logged 072704

C

I Northeast Geophysical Services Borehole Geophysical Log

Date logged 082304 PW-207

I Plymouth Maine

Fiowmeter Measurements Temperature (C) Acoustic Televiewer

I (in gpm) (interpreted)

75 8 85 9 95 Caliper (inches) Resistance f0tims) Spontaneous Potential (mV) Dip in Degrees PCE Total VOCs

55 60 0 20 40 SO 80 ugL ugL I I I I I I I

Ambienl Fiowmeter pumping Flewmater

magnetic - 10 - - 1 0

north

i - 20 - - 2 0

1300 1410

i - 30 - - 3 0

i tf

5400 5802 - 40 - - 4 0

B - 50 - - 5 0

I 18000 19234

- 60 - - 6 0

I 12000 13085

- 70 - - 7 0

- 8 0

i - 9 0 19000 20354

G - 100- -100

I 110 110 bull110

0 20 40 60 SO 10 20 30 Dip m Degrees

Fluid Resistivity (ohmmeters) I 50

The dip direction is indicated by ihe line extending from the circle The strike of the fealure is 90 degrees from this

Borehole Geophysical Log

G Packorod Interval August 20(M log The location dip angle and dip dirlaquocton or the sleeted Groundaier samplss were ooliecled by Woodard i Curran on ampt24f2ltXM PW-207 failures are approximate Reter to the televiewer log of this wlaquoll for more precise detail PlyPIOUth Maine Date logged 082304

I

Table XX Packer Permeability and Packer Sampling Results for Potential Fracture Intervals

1

WellID MW-101D MW-101D MW-101D MW-101D MW-101D MW-101D MW-101D MW-101D MW-101D MW-101D MW-I01D MW-101D MW-101D MW-102D MW-102D MW-I02D MW-102D MW102D MW-102D MW-102D MW-102D MW-102D MW-I02D MW-102D MW-102D MW-102D MW-103D MW-103D MW-103D MW-103D MW-I03D MW-103D MW-103D MW-103D MW-103D MW-103D MW-103D MW-103D MW-I03D MW-104D MW-104D MW-104D MW-104D MW-I04D MW-104D MW-104D MW-104D MW-104D MW-104D MW-104D MW-105D MW-105D MW106D MW-106D MW-106D MW-107D MW-107D

1999 Drilling Program

Hows Corner Superfund Site Plymouth Maine

Potential Fracture Top Of Bottom 6 Depth to lt Topof i Interval from Packer Packer Middle of Elevation Hydraulic bull PCE

GS ELEV 1 Rock Drilling Interval Interval Interval of Interval Conductivity Concentration (ft msl) (ft msl) TEST (ftbgs) (ftbgs) r(ftbgs) ( f t b (ft mil) (cmsec) (raquogL)

4339 4329 13 28-29 33-3537-39 271 376 324 4016 OOOE+00 4339 12 37-3444-46 380 485 433 3907 157E-04 4339 11 488 593 541 3799 132E-04 4339 10 60-61 578 683 631 3709 OOOE+00 4339 9 678 783 731 3609 I79E-05 4339 8 778 883 831 3509 106E-05 4339 7 880 985 933 3407 243E-05 4339 6 990 1095 1043 3297 339E-06 4339 5 1090 1195 1143 3197 OOOE+00 4339 4 1190 1295 1243 3097 OOOE+00 4339 3 1365-1375 1290 1395 1343 2997 OOOE+00 4339 2 147-157 1390 1495 1443 2897 580E-05 4339 1 147-157 1470 1575 1523 2817 741E-05 43161 43061 13 166 271 219 4098 333E-04 43161 12 30-3136-40 260 365 313 4004 I54E-05 43161 11 36-4041-43 362 467 415 3902 548E-05 43161 10 470 575 523 3794 598E-05 43161 9 570 675 623 3694 197FOS 43161 8 670 775 723 3594 OOOE+00 43161 7 770 875 823 3494 891 E-05 43161 6 83-94 870 975 923 3394 139E-05 43161 5 970 1075 1023 3294 123E-04 43161 4 1070 1175 1123 3194 526E-06 43161 3 1170 1275 1223 3094 138E-05 43161 2 1270 1375 1323 2994 671E-06 43161 1 1370 1475 1423 2894 OOOE+00 42997 42497 13 18-19 170 275 223 4077 OOOE+00 42997 12 260 365 313 3987 766E-05 42997 11 360 465 413 3887 727E-05 42997 10 460 565 513 3787 192E-05 42997 9 560 665 613 3687 752E-05 42997 8 660 765 713 3587 778E-05 42997 7 85-86 763 868 816 3484 260E-05 42997 6 860 965 913 3387 289E-05 42997 5 102-103 960 1065 1013 3287 102E-04 42997 4 1060 1165 1113 3187 522E-06 42997 3 1160 1265 1213 3087 520E-06 42997 2 129-130 1260 1365 1313 2987 960E-04 42997 1 1360 1465 1413 2887 OOOE+00 43372 42922 11 35-37 42-45 350 455 403 3935 684E-04 43372 10 460 565 513 3825 500E-05 43372 9 560 665 613 3725 106E-05 43372 8 72-74 660 765 713 3625 204E-05 43372 7 760 865 813 3525 872E-06 43372 6 860 965 913 3425 467E-06 43372 5 960 1065 1013 3325 200E-05 43372 4 1060 1165 1113 3225 354E-05 43372 3 125-130 1160 1265 1213 3125 157E-05 43372 2 125-130 1260 1365 1313 3025 337E-04 43372 1 1365 1465 1415 2922 689E-06 43052 43002 2 54-58 490 595 543 3763 124E-05 2100 43052 1 139-140 145-146 1367 1472 1420 2886 154E-04 1400 43291 4391 3 bullI133 260 365 313 4017 439F06 43291 2 77-78 760 865 813 3517 230E-03 400 43291 1 143-144 1355 1460 1408 2922 971E-06 350

29958 27258 4 450 555 503 2493 OOOE+00 (21)A 29958 3 103-105 1000 1105 1053 1943 752E-04 (063)A

Table XX Packer Permeability and Packer Sampling Results for Potential Fracture Intervals

1999 Drilling Program

Hows Corner Supcrfund Site Plymouth Maine

gtbull i Potential Fracture Top _OfBot Bottom of Depth to ltbull Top of Interval from f Packer Packer Middle Of

GS ELEV lt Hock Drilling interval Interval Interval WeD ID ft msl) (ft msl) TEST (ftbgs) ltft$gs) (ftbgs) (ftbgs)

MW-107D 29958 2 128-130 1200 1305 1253

MW-107D 29958 1 139-141 1350 1455 1403

MW-108D 31904 31104 6 35-36 300 405 353 MW-108D 31904 5 60-62 550 655 603

MW-108D 31904 4 80-83 750 855 803

MW-108D 31904 3 118-119 123-124 1150 1255 1203

MW-108D 31904 2 147-149 1440 1545 1493

MW-108D 31904 1 1700 1805 1753

MW-110D 40576 40426 2 21-31 210 315 263 MW-110D 40576 1 148-154 1460 1565 1513 MW-I11D 40519 4 70-71 650 755 703

MW-111D 40519 3 79-82 84-86 780 885 833 MW-I11D 40519 2 97-102 950 1055 1003 MW-111D 40519 1 1370 1475 1423

MW-112D 3027 2942 4 42-52 420 525 473 MW-112D 3027 3 850 955 903 MW112D 3027 2 1100 1205 1153 MW-112D 3027 1 135-136 140-141 1340 1445 1393

MW-113D 43085 43085 5 250 355 303 MW-I13D 43085 4 47-49 460 565 513 MW-113D 43085 3 73-74 700 805 753 MW-113D 43085 2 1050 1155 1103 MW-113D 43085 1 1380 1485 1433

MW-114D 42394 41594 4 48-49 450 555 503 MW-114D 42394 3 79-81 740 845 793 MW-114D 42394 2 121-129 1250 1355 1303 MW-114D 42394 1 134-142 1350 1455 1403

MW-115D 4035 4035 4 300 405 353 MW-1I5D 4035 3 70-71 650 755 703 MW-115D 4035 2 1150 1255 1203 MW-115D 4035 1 1400 1505 1453

LOT-28W 382 7 450 555 503 LOT28W 382 6 550 655 603 LOT-28W 382 5 650 755 703 LOT28W 382 4 750 855 803 LOT-28W 382 3 850 955 903 LOT-28W 382 2 950 1055 1003 LOT-28W 382 1 1055 1155 1105

NOTES cmsec = centimeters per second ft bgs = leet below ground surface It msl = feet below mean sea level lt = not detected at indicated reporting limil A = detected below laboratory PQL ( ) = detected below reporting limits

Elevation of Interval

(ft nisi) 174

159

283gt 2588

2388

1988

1698

1438

3795 2545 3349 3219 3049 2629

2555 2125 1875 1635

4006 3796 3556 3206 2876

3737 3447 2937 2837

3683 3333 2833 2583

3318 3218 3118 3018 2918 2818 2715

Hydraulic Conductivity

(cmsec)

323E-05

208E-05

471E-03

471E-03

624E-05

3I6E-05

264E-05

261 E-05

OOOE+00 200E-04 953E-05 OOOE+00 OOOE+00 212E-05

361 E-05 410E-06 2gQE06 292E-05

786E-05 124E-05 151 E-05 822E-06 82IE-06

858E-05 I69E-05 352E-03 866E-05

223E-05 394E-06 122E-05 525E-06

831 E-05 182F-05 L62E-05 129E-05 190E-05 890E-04 981 E-04

PCEraquo Concentration

(ugL)

lt5

(14A)

98 11

15

22

11

30

200 (62)A

110 210 300 240

(44)A (23)A

5

350 190 129 230

2200 1900 2600 2600

(17)A (16)A (19)A

96

Table XX Packer Permeability and Packer Sampling Results for Potential Fracture Intervals

2004 Drilling Program

Hows Corner Superfund Site Plymouth Maine

Top of Bottom of Depth to Midpoint

t K

ELEV (ft Potential Transmissive Zones Packer Interval

Packer Interval

Middle of Interval

Elevation of interval

Hydraulic Conductivity

PCE Concentration

Well ID msl) TESTr (ft bgs)- (ftbgs) (ftbgs) (ftbgs) (ft msl) (cmsec) (ogt) MW-203D 43227 4 277279 24 32 28 4043 667E-05 44

3 408415420 39 49 44 3883 593E-05 170 2 526 530 49 57 53 3793 101E-04 140 I 828830842 80 88 84 3483 701E-05 130

MW-204D 43262 5 295 300 26 34 30 4023 902E-05 220 4 463496513516 45 53 49 3833 119E-04 540 3 681685688 63 71 67 3653 OOOE+00 2 758 76 2 71 79 75 3573 309E-05 260 I 88 96 92 3403 OOOE+00

MW-205 42389 3 164 166 168 15 20 175 4148 OOOE+00 1000B 2 302305312 30 35 325 3998 107E-04 1300B 1 40 45 425 3898 OOOE+00

MW-206D 43007 5 17 72 195 4128 291E-05 4 296 302 307 29 34 315 4008 940E-05 2900B 3 522 52 57 545 3778 944E-07 2 656 64 69 665 3658 353E-06 1 92392793 4939 91 96 935 3388 614E-05 6300B

PW-207 43477 5 184622162819 18 29 235 4088 209E-05 1300 4 3508 32 43 375 3948 568E-06 5400 3 53325341542154325559 50 61 555 3768 821E-05 18000

6359 61 72 665 3658 866E-06 12000 1 8685 84 89 865 3458 213E-05 19000

NOTES cmsec = centimeters per second ft bgs = feet below ground surface ft msl = feet above mean sea level B = detected in lab blank

Table XX Orientation Permeability and Groundwater Sampling Results for Transmissive Features

2004 Drilling Program

Hows Corner Superfund Site Plymouth Maine

Borehole Geophisical Feature depth Dip True Dip True Transmissive Log Feature (Feet) Degrees Azimuth Strike bullvgt(Ltk|iy^

Number v Tosftble) v MW-203 5 277 64 337 67 Likely

6 279 59 11 281 Likely 8 352 14 177 87 Likely 11 381 46 96 6 Possible 12 408 35 271 1 Possible 14 415 57 250 340 Possible 15 420 58 202 292 Likely 18 526 52 75 345 Likely 19 530 52 82 352 Likely 28 828 48 75 345 Likely 29 830 52 17 287 Likely 30 830 56 233 323 Possible 31 842 50 130 40 Likely

MW-204 4 295 15 147 57 Likely 5 300 43 91 1 Likely 11 439 31 80 350 Possible 12 440 46 219 309 Possible 14 463 50 358 88 Likely 15 496 34 198 288 Likely 16 513 54 17 287 Likely 17 516 33 14 284 Likely 25 681 39 359 89 Possible 26 685 22 45 315 Possible 27 688 35 73 343 Possible 32 758 45 236 326 Likely 33 762 46 306 36 Likely

MW-205 5 164 69 106 16 Possible 6 166 78 165 75 Possible 7 168 82 115 25 Possible 8 168 68 116 26 Possible 12 215 46 222 312 Possible 13 217 75 62 332 Possible 14 219 29 32 302 Possible 16 237 69 250 340 Possible 17 256 73 353 83 Possible 18 272 44 202 292 Possible 21 299 37 196 286 Possible 22 302 31 206 296 Possible 23 305 59 48 318 Likely 24 312 63 42 312 Likely

MW-206 1 264 37 181 271 Likely 2 296 69 217 307 Likely 3 302 66 233 323 Likely 4 307 64 224 314 Likely 8 342 62 259 349 Likely

jjHydraulic GoiDanctilyity j(cmsecjw

667 E-05

593 E-05

101 P04

710 E-05

902 E-05

119 E-04

0

309 E-05

0

107 E-04

94 E-05

PCE (ugL)

44

170

140

130

220

540

260

IOOOB

1100B

1300B

2900B

STotal vVoCsv tig1)

84

234

192

183

2636

6436

3073

11448

12509

13776

32401

PCEyo dfCTotaf

52

73

73

7 1

83

84

85

87

88

94

90

Table XX Orientation Permeability and Groundwater Sampling Results for Transmissive Features

2004 Drilling Program

Hows Corner Superfund Site Plymouth Maine

Borehole Geophisical Feature deptt raquoip True pip True Transraissive Log Feature (Feet) shy Degrees Azimuth Strike (tikely

Number raquo Possible) 22 522 57 54 324 Possible 25 656 40 82 352 Possible 32 871 59 151 61 Possible 33 883 53 185 275 Possible 34 895 7 175 85 Likely 35 899 53 90 0 Likely 36 902 49 184 274 Likely 37 923 9 175 85 Likely 38 927 42 206 296 Likely 39 934 48 167 77 Likely 40 939 26 180 90 Likely

PW-207 1 1846 33 167 77 Likely 4 2216 49 289 19 Possible 7 2819 59 265 355 Possible 11 3508 55 189 279 Possible 18 5332 43 305 35 Likely 19 5341 51 30 300 Likely 20 5421 20 254 344 Likely 21 5432 39 301 31 Likely 23 5559 52 302 32 Likely 25 6359 24 182 272 Possible 29 8049 77 231 321 Possible 30 8685 78 38 308 Likely 32 9334 29 194 284 Likely

NOTES

B = detected in lab blank

Hydraulic Conductivity

(cmsee) 944 E-07 353 E-06

614 E-05

209 E-05

568 E-06

821 E-05

866 E-06

213 E-05

bulltCE (ugL)

6300B

1300

5400

18000

12000

19000

Total VOCs (ug1)

68901

1410

5802

19234

13085

20354

PCE of Total VOCs

9 1

92

93

94

92

93

Response to EPA-DEP Comment 3 Dated March 312005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

lit

EPA-DEP Comment 3

Comment 3 The reported f values and resultant Kd values There remains doubt that the values used in the flushing model accurately reflect the propensity for PCE to sorb to the bedrock The ^ values presented in Appendix B may be unrealistically high because the bedrock samples may have contained organic carbon that was unavailable for sorption The reported f values are only qualitative estimates of the organic carbon content of the bedrock samples The Walkley and Black organic carbon measurement method is quick and simple but the results obtained cannot be considered quantitative because it requires a correction factor which often results in erroneous values it assumes the organic carbon has an average valence of zero oxidizable and reducible constituents such as chloride ferrous iron and manganese oxides interfere with the results and the errors introduced by interference are potentially greater when the organic carbon content is low at low f values it is not clear that organic carbon is controlling PCE sorption (Schwarzenbach and Westall 1981 Mackay et al 1986 Fetter 1999)

In order to derive a Kd-based retardation factor that is reasonable given the reported f values and the rapid advance of the PCE plume described on pages 4-11 and 4-12 the flushing model requires a bulk density to porosity ratio that is roughly two orders of magnitude higher than the actual ratio for the Hows Corner bedrock (page 4-4) This apparent discrepancy needs to be addressed

Response This comment raises several concerns about the collection and analysis of samples for fraction of organic carbon (f^) the quality of the resulting data and the implications of the use of those data for estimation of the retardation of groundwater contaminant movement Results of bedrock analysis for f were proposed in the TI Evaluation Work Plan for use in conjunction with groundwater contaminant concentrations and aquifer information to estimate cleanup times using the Batch Flushing model It is important to use accurate f values from representative bedrock in the Batch Flushing model in order to obtain reasonable estimates of the remedial time frame Because of the importance of accurate and representative results the TI Investigation field program was designed and conducted both to collect samples representative of the rock volume most likely to be in contact with contaminated groundwater and to analyze them using an appropriate refereed analytical method Five potential methods for evaluating f were identified Of the five methods the Walkey-Black method was selected because it has minimal method interferences and a sufficiently low detection limit as well as a long history of use in agronomy and contamination studies The PRP Group is pleased with the quality of the data obtained from the bedrock samples as represented by their precision and reproducibility

The first part of this comment relates to the determination of fraction of organic carbon (f^) values The several subparts of the first paragraph are addressed individually in items 1 through 5 below The second part of the comment regarding the resultant distribution coefficient (Kd) values is addressed separately as item 6 below

1 There remains doubt that the values used in the flushing model accurately reflect the propensity for PCE to sorb to the bedrock

bull The rock core samples used for f (gocg) analysis were from core immediately adjacent to fractures These rock core samples included the fracture surfaces themselves and rock core extending back less than 1 cm from the fractures Therefore the foe data reported in the TI Evaluation represents the f of bedrock through which groundwater will travel and to which PCE will adsorb Based on the careful selection of sample locations and the

Response to EPA Comment 3 050205doc 1 of 11 Woodard amp Curran (211941)

number of samples collected we are confident that the measured f values are representative of the f at points of contact for PCE with the bedrock it is these f values that determine the propensity of PCE to sorb to the bedrock

bull The samples of rock core collected for analysis of f originated from 19 different locations varying in depth from 11 to 90 feet Therefore it is very unlikely that the rock core samples were contaminated with extraneous organic carbon from above ground

2 The foc values presented in Appendix B may be unrealistically high because the bedrock samples may have contained organic carbon that was unavailable for sorption

bull As noted in response 1 the f data reported in Appendix B represents organic carbon primarily associated with the surface of fractures in the bedrock through which groundwater is most likely to travel Therefore it is this organic carbon that the contaminants in the groundwater will come in contact with and adsorb to in the fractured rock at the site

bull The chemical oxidation agents used in the Walkey-Black method oxidize the easily oxidizable organic carbon in the medium and the foe is calculated from the quantity of the agent consumed Therefore it is unlikely that the analysis of the bedrock samples measured organic carbon that was unavailable for sorption

3 The reported foc values are only qualitative estimates of the organic carbon content of the bedrock samples

bull The reported f values are accurate quantitative results Schumachers review of Methods for the determination of total organic carbon (TOC) in soils and sediments (NCEA-C-1282 EMASC-001 April 2002) identifies the Walkley-Black method which was used to analyze the reported foc values as the reference method for comparison to other methods for analyzing total organic carbon

bull Schumacher also points out that if anything the WalkJey-Black method may underestimate the total organic carbon in a sample due to possible incomplete oxidation of organic carbon Usually the incomplete oxidation of total organic carbon in environmental samples is corrected for by multiplying the measured foe by 130 (Walkley amp Black 1934 Schulte 1995)

bull When the f data in the TI Evaluation Report (WampC 2005) Appendix B (attached) are analyzed statistically the standard deviation of the f for the 19 samples analyzed is 174 of the average f Given this standard deviation the 95 confidence interval for this data ranged from a low of 000123 gocg to a high of 000253 gocgm

The labs Method of Detection Limit (MDL) for the f measured using the Walkley-Black method is 00001 gocg Therefore the average (000188 gocg) the mean (000185 gocg) and geometric mean (000187 gocg) of the f values for the rock core at Hows Corner are all statistically significantly greater than the MDL of the Walkley-Black method

In addition to the aforementioned statistical analysis of the foe data triplicate samples (n = 3) from the same rock core (including one sample from the 19 rock core samples) were

Response to EPA Comment 3 050205doc 2 of Woodard amp Curran (211941)

analyzed for their f to determine the repeatability of the Walkley-Black method The average the mean and the geometric mean of the f values of these replicate samples was 000162 gocg 000150 gocg and 000159 gocgm respectively The standard deviation of these measurements was 000039 gocg

4 The Walkley and Black organic carbon measurement method is quick and simple but the results obtained cannot be considered quantitative because it requires a correction factor which often results in erroneous values it assumes the organic carbon has an average valence of zero oxidizable and reducible constituents such as chloride ferrous iron and manganese oxides interfere with the results and the errors introduced by interference are potentially greater when the organic carbon content is low at low foc values it is not clear that organic carbon is controlling PCE sorption (Schwarzenbach and Westall 1981 Mackay et al 1986 Fetter 1999)

bull Schumachers review (NCEA-C-1282 EMASC-001 April 2002) of the Walkley-Black method identifies several potential problems with this analytical method that could occur if the analytical lab is not familiar with the nuances of the chemistry associated with this method Interestingly Schumachers review neglected one of the more important analytical steps required to avoid errors in quantifying f in samples where there might beNAPL

It is absolutely critical to eliminate any NAPL from rock core samples prior to using the Walkley-Black method to measure foe in such samples This was done by the lab (PTS Laboratories) that measured the foe in the rock core samples from Hows Corner The lab used the Dean-Stark method (solvent extraction) to remove all hydrocarbons (including PCE and other NAPLs) from the sample (PTS Laboratories) This extraction method does not interfere with the subsequent analysis of the natural organic carbon associated with the rock core

Subsequently the samples were dried at 150degC to a constant weight (normally 16 hours) This latter step oxidizes all inorganic minerals including ferrous bearing minerals to ferric oxides and precludes their interference during the oxidation of the samples with chromic acid This procedure completely eliminates any positive bias in the reported foc

data that might have occurred due to the presence of ferrous ions and other reduced minerals

bull As noted in Response 3 the incomplete oxidation of total organic carbon results in an underestimate of the f and is corrected for by multiplying the f by a correction factor of 130 (Walkley amp Black 1934 Schulte 1995) The fx data reported in the TI Evaluation was corrected accordingly by using this correction factor

bull Excess chloride (Cl~) in percent weight quantities as found in saline soils may interfere with the quantitative titration of reduced chromium (Walkley 1947) However given that the primary rock type at the Hows Corner site is phyllite it is highly unlikely that there was sufficient chloride in the rock core samples for this to occur

bull Manganese oxides may also interfere with the analysis of f through competing with the dichromate ion for any oxidizable carbon (Walkley 1947) However in such cases the reported f would be an underestimate of the f present in the rock core Walkley (1947)

Response to EPA Comment 3 050205doc 3 of 11 Woodard amp Curran (211941)

4

reported that in the case where the ratio of MnO2 to carbon is 85 to 1 the error in the carbon determinations would only be 0 to 6 percent

It may also be useful to compare the analysis of total organic carbon in a geologic matrix that contains high levels of manganese using EPA method 9060 to the Walkley-Black method Table 1 summarizes data provided by one of the PRPs that compares the analysis of total organic carbon in a geologic matrix that contains approximately 02 wgt manganese (approximately 03 wgt manganese oxide)

Table 1 Comparison of total organic carbon measured using the EPA- 9060 method and the Walkley-Black method

Laboratory EPA-9060 Method Walkley-Black Method A Ave 00226 gocg Not analyzed

Stdev 000251 gocg n = 5

B Ave 002219 gocg Ave 002050 gocg Stdev = 000316 gocg Stdev =000971 gocg

n= 10 n = 10

The similarity in the total organic carbon concentrations measured by these two different methods provides further confidence that the Walkley-Black method is a viable method for analysis of total organic carbon in the presence of manganese equivalent to at least 10 by weight of the total organic carbon

5 The Walkley and Black organic carbon measurement at lowf^ values it is not clear that organic carbon is controlling PCE sorption (Schwarzenbach and Westall 1981 Mackay et al 1986 Fetter 1999)

bull Schwarzenbach and Westalls (1981) paper states that f values of less than 0001 gocg should not be used in combination with Kow (octanol-water partition coefficients) values to calculate K^ values (solid phase partition coefficients) values for a specific contaminant It should be noted that the TI Evaluation did not use the f data to calculate the KQC from the Kow Instead as requested by the EPA the measured KOC value for PCE was used to calculate the retardation factor for this contaminant

bull Schwarzenbach et al (2003) stated more recently that Even at very low f values (ie foe = 0001 kgoc - kg1 solid) sorption to the organic components of a natural sorbent may still be the dominant mechanism in defining the adsorption of organic compounds to geological matrices

bull In 1985 M Piwoni from the US EPA Robert S Kerr Environmental Research Laboratory published a paper (Banerjee et al 1985) that showed that for very hydrophobic molecules TOC content of the sorbent will control sorption down to levels of organic carbon that defy quantitation Contaminants such as the PCE found in the groundwater at Hows Corner are in this category of compounds

Given the aforementioned reasons the f values reported in the TI Evaluation are accurate within the noted statistical limitations and will have a predictable impact upon the retardation of PCE during groundwater transport

Response to EPA Comment 3 050205doc 4 of 11 Woodard amp Curran (211941)

6 In order to derive a Kd-based retardation factor that is reasonable given the reported foc

values and the rapid advance of the PCE plume described on pages 4-11 and 4-12 the flushing model requires a bulk density to porosity ratio that is roughly two orders of magnitude higher than the actual ratio for the Hows Comer bedrock (page 4-4) This apparent discrepancy needs to be addressed

The apparent discrepancy of bulk density to porosity ratios is most likely due to the fact that the Batch Flushing Model was originally developed for a porous medium and is not directly applicable to fractured bedrock As stated in Appendix C (page C-4) of the Draft Technical Impracticability Evaluation Report in order to use the Batch Flushing Model to describe the transport of contaminated groundwater in fractured bedrock where the matrix porosity is insignificant it is more appropriate to use a fracture surface area to void space ratio to calculate the retardation factor (R) than a bulk density to porosity ratio (Freeze amp Cherry 1979)

Since it is impractical to determine the actual surface area to which contaminants can adsorb the Batch Flushing Model was used with two simplifying assumptions bull The Kd was calculated from the f and the K^ bull The bulk density to porosity ratio term in the Batch Flushing Model was constrained to range

from 4 to 10 the typical range of such ratios in porous media (Freeze amp Cherry 1979)

If one uses site specific bedrock bulk density and porosity values the bulk density to porosity ratio is several orders of magnitude greater (specifically 273 gcc bullbull 000165 (dimensionless) = 1654 gcc) than the range of ratios of 4 to 10 used in the Batch Flushing Model in the Draft Technical Impracticability Evaluation Report Constraining the bulk density to porosity ratio within the range of ratios of 4 to 10 results in significantly lower R value than would be obtained using specific bedrock bulk density and porosity values

In summary in bedrock where fractures are the primary porosity the bulk density to porosity ratio can vary considerably and will be a function of the number of fractures and the fracture aperture The calculated bulk density to porosity ratio will be inversely proportional to the porosity This means that in fractured rock with limited fracturing and smaller porosity the calculated bulk density to porosity ratio is greater and will result in a greater calculated retardation factor than in bedrock with more extensive fracturing and greater porosity Consequently the calculated retardation factor will be greater for bedrock with less surface area available for sorption than bedrock with greater surface area for sorption This is contrary to what actually occurs

4 Response to EPA Comment 3 050205doc 5 of 11 Woodard amp Curran (211941)

m

REFERENCES

Banerjee P MD Piwoni K Ebeid (1985) Sorption of organic contaminants to a low carbon subsurface core Chemosphere _14 1057-1067

Freeze RA JA Cherry (1979) Groundwater Prentice Hall Englewood Cliffs NJ pg 604

PTS Laboratories wwwptsgeolabscompdf files3TOCnotepdf

Schulte EE (1995) Recommended soil organic matter tests in Recommended Soil Testing Procedures for the Northeastern United States Northeastern Regional Publication No 493 Chapter 8

Schwarzenbach RP J Westall (1981) Transport of nonpolar organic compounds from surface water to groundwater Laboratory sorption studies Environ Sci Tech 15 1360-1367

Schwarzenbach RP PM Gschwend DM Imboden (2003) Environmental Organic Chemistry Wiley-Interscience pg 292 408 amp 412

Walkley A LA Black (1934) An examination of the Degtjareff method for determining soil organic matter and a proposed modification of the chromic acid titration method Soil Science 37 29-38

Walkley A (1947) A critical examination of a rapid method for determining organic carbon in soils - effect of variations in digestion conditions and of inorganic soil constituents Soil Science 63251-264

Woodard amp Curran Inc (WampC) 2005 Draft Technical Impracticability Evaluation Hows Corner Superfund Site Plymouth Maine January 2005

Response to EPA Comment 3 050205doc 6 of Woodard amp Curran (211941)

LIST OF ATTACHMENTS (Response to Comment 3)

Appendix B to Draft Technical Impracticability Evaluation Measurement of foe at Hows Corner (4 pages)

m

Response to EPA Comment 3 050205doc 7 of 11 Woodard amp Curran (211941)

Appendix B Measurement of foe of Rock Core at Hows Corner

There are two general approaches to measure the fraction of organic carbon (foe) in rock cores

bull Measurement of weight loss by ignition of organic matter bull Chemical oxidization of organic carbon to carbon dioxide and either

subsequent quantification of the oxidant used for the reaction or quantification of the carbon dioxide produced during this oxidation process

The weight loss method is subject to errors caused by volatilization of substances other than organic materials such as water hydroxides and mineral carbonates Quantification of foe by the weight loss method is particularly sensitive to the presence of carbonates in rock cores There are however weight loss methods that are designed to differentiate between organic carbon and the aforementioned interfering materials but they require considerable care and are less accurate at low foe values Hence the weight loss method was not well suited for measuring the foe of the rock core from Hows Corner

The chemical oxidation of organic carbon is much better suited for quantifying organic carbon in rock cores such as those from Hows Corner This method uses a strong chemical oxidant to oxidize organic carbon to carbon dioxide and then measures either the chemical oxidant used to oxidize the organic carbon or the quantity of carbon dioxide produced In addition this general approach is not subject to interference by volatilization of other constituents of the rock core

There are at least two such chemical oxidation methods

bull The method of Baccini which was described by Schwarzenbach amp Westall (1981) first acidifies the sample to eliminate interference by carbonates Then a strong oxidant is used to chemically oxidize the organic carbon to carbon dioxide The resulting carbon dioxide is subsequently reduced to methane and quantified using a flame ionization detector Unfortunately this method has not been described in detail in a referred journal Hence it is would not have been appropriate to use to characterize the foe in the Hows Corner rock core

bull The more commonly used method to quantify foe in rock core is the Walkley-Black method (1934) This method is preferred for RBCA and DODDOE projects and by the oil industry

The Walkley-Black method uses an excess of chromic acid to oxidize (digest) organic matter to carbon dioxide The remaining chromic acid that was not consumed during the oxidation of the organic carbon is then quantified by titration with ferrous sulfate The difference in chromic acid prior to and after the oxidation of the organic carbon represents the total chromic acid used to oxidize

Hows Corner TI Evaluation Page 1 January 13 2005 Appendix B

the organic carbon in the sample The latter can be calculated using the chemical stoichiometry of the reaction

The Walkley-Black method is very accurate for samples that contain less than 2 organic carbon matter The minimum detection limit (MDL) for the Walkley-Black method is 100 mgkg or an foe of 0001

Given the rock core at Hows Corner was expected to contain less than 2 organic carbon the Walkley-Black method was used to measure the foe from 19 different rock core samples collected from varying depths ranging from 11 to 90 feet

Table 1 provides a statistical summary of the aforementioned data

Table 1 Statistical summary of foe data from rock cores collected at varying depths

Statistical Parameter Calculated Value foe Minimum Detection Limit (MDL) 00010 Number of samples analyzed (n) 19 Average foe 00019 Median foe 00019 Geometric Mean foe 00019 Standard deviation of foe measurements 000033 Relative standard deviation 174 -+ 95 Confidence intervals 00012 to 00025

The data in Table 1 shows the following

bull The foe from the Hows Corner rock cores are statistically greater than the MDL of the Walkley-Black analytical method

bull The average and median values for the foe of the Hows Corner rock cores from varying depths are nearly identical indicating that there is little variability in the foe values in the source zone at the site

bull The standard deviation of these measurements is 000033 which is 174 of the average foe

bull The 95 confidence intervals of the foe of the rock core at Hows Corner are 00012 to 00025

The foe was also analyzed from three separate samples taken from the same rock core at a depth of 55 feet (Only one of these samples was included in the data summarized in Table 1) Table 2 shows the statistical repeatability of this type of analysis

Hows Corner TI Evaluation Page 2 January 13 2005 Appendix B

Table 2 Repeatability of analysis of foe from one rock core at 55 feet in depth

Statistical Parameter Calculated Value Number of samples analyzed (n) 3 Average foe 00016 Median foe 00015 Geometric Mean foe 00016 Standard deviation of foe measurements 000039 Relative standard deviation 240 -+ 95 Confidence intervals 00008 to 00024

The data in Table 2 shows the following

bull The percent relative standard deviation of these three analyses of foe from the same rock core at Hows Corner is 24

bull The 95 confidence interval of the foes measured in this particular rock core at Hows Conrer is 00008 to 00024

These results show that there is good repeatability in using the Walkley-Black method for analysis of the foe in the rock core at Hows Corner

References Schwarzenbach amp Westall (1981) Transport of nonpolar organic compounds from surface water to groundwater Laboratory sorption studies Environ Sci Tech 15 1360-1367

Walkley A I A Black (1934) An examination of Degtjareff method for determining soil organic matter and a proposed modification of the chromic acid titration method Soil Sci 37 29-37

Hows Corner Tl Evaluation Page S January 13 2005 Appendix B

Woodard and Curran PTS Laboratories PTS File No 34618

ORGANIC CARBON DATA (METHODOLOGY WALKLEY-BLACK)

PROJECT NAME PROJECT NO

SAMPLE ID

203-chip-13 203-chip-23 203-chip-27 203-chip-38 203-chip-42 203-chip-47 203-chip-52 203-chip-58 203-chip-69 203-chip-82 207-chip-11 207-chip-19 207-chip-24 207-chip-29 207-chip-35 207-chip-45 207-chip-55 207-chip-87 207-chip-90

207-chip-55 55-MS

55-MSMSD

Hows Corner NA

DEPTH ft

13 23 27 38 42 47 52 58 69 82 11 19 24 29 35 45 55 87 90

55 NA NA

MATRIX

Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip

Average Median

Geometric Mean Standard Deviation Relative Std Dev

+- 95 Confidence Interval n

Rock Chip Rock Chip Rock Chip

Average Median

Geometric Mean Standard Deviation Relative Std Dev

+- 95 Confidence Interval n

FRACTION ORGANIC CARBON

(gg)

170E-03 185E-03 185E-03 170E-03 240E-03 190E-03 230E-03 180E-03 170E-03 115E-03 195E-03 220E-03 220E-03 235E-03 135E-03 190E-03 205E-03 175E-03 160E-03

188E-03 185E-03 185E-03 327E-04

1739 123E-03 to

19

205E-03 130E-03 150E-03

162E-03 150E-03 159E-03 388E-04

2402 840E-04 to

3

2532E-03

2393E-03

Hows Corner Tl Evaluation Appendix B January 13 2005

Response to EPA-DEP Comment 4 Dated March 31 2005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

EPA-DEP Comment 4

Comment 4 Distribution of contaminants First the TI report seems based on the assertion that there is DNAPL at the source area yet it also appears to represent that the source area is small and the bedrock below 85 is competent (or less fractured) and less impacted by the release of contaminants Some of the confusion may result from using most recent data when that data is from several different sampling events over several years and there is no discernible difference in concentrations between shallow and deep bedrock or as in Section 421 where generally decreased generally increase generally similar and similar concentrations in four consecutive sentences leads to a muddled picture of the contaminant distribution

Second the report asserts that the distribution of contaminants over the entire plume has not changed with time but fails to support this conclusion with data again relying on data that is from different sampling dates for one composite representation

Response The likely presence of dense non-aqueous phase liquid (DNAPL) at the Hows Corner Site and the determination that the source area is small are not mutually exclusive and both are conclusions drawn from information obtained during field investigations The presence of DNAPL in the source area is based on the elevated concentrations of volatile organic compounds (VOCs) detected in the groundwater (WampC 2001 WampC 2002) The conclusion that the source area is small is based on the area in which VOCs in groundwater have been detected at concentrations that are considered to be indicative of the presence of DNAPL nearby Similarly the conclusion that fracture frequency decreases at depths greater than approximately 50 to 85 feet below ground surface was based on field observation during the RI field work The fact that zones with observed fractures exhibited higher hydraulic conductivities than zones without fractures coupled with the decreasing frequency of observed fractures with depth led to the conclusion that the hydraulic conductivity of the bulk rock decreases with depth

The most recent data from all wells were used to provide the maximum VOC data set size During the RI all of the previously-existing and then newly-installed monitoring wells were sampled along with several residential wells The RI sampling included up to 48 monitoring wells Subsequent to the RI and prior to the TI three rounds of monitoring were conducted to verify that the plume was stable 15 monitoring wells were sampled during each of the three rounds During the TI field investigation 29 wells were sampled for VOCs The sampled wells included all of the newly-installed wells and a subset of wells installed during the RI for a total of 29 monitoring wells By using most recent data VOC results from 53 monitoring wells were included in the evaluation (see table labeled Sampling Events for listing of monitoring wells) This approach was selected because there generally was little variation in the data from a particular location between years This is borne out by the attached individual plots of VOCs detected in shallow bedrock and deep bedrock for the Pre-ROD (December 1999January 2000) and Supplemental (May 2000) sampling events and for June 2001 January 2002 and April 2003 sampling events The Pre-ROD and Supplemental plots are similar to the subsequent plots from the 2001 2002 and 2003 sampling events

In addition to maps showing the spatial distribution of VOC data at a given time trend plots of the data from a particular location through time (attached) indicate that since the RI concentrations generally have been stable or have decreased Together the maps and trend plots and the data from which they were developed indicate that the distribution of contaminants over the entire plume has not changed appreciably with time

Response to EPA Comment 4 050305doc 1 of 26 Woodard amp Curran (211941)

REFERENCES

Woodard amp Curran Inc (WampC) 2001 Final Remedial Investigation Report Hows Corner Superfund Plymouth Maine July 2001

Woodard amp Curran Inc (WampC) 2002 Final Feasibility Study Report - Non-Source Area Groundwater Hows Corner Superfund Site Plymouth Maine Hows Corner Superfund Plymouth Maine July 2002

Response to EPA Comment 4 050305doc 2 of 26 Woodard amp Curran (211941)

LIST OF ATTACHMENTS (Response to Comment 4)

Table - Sampling Events 1999 - 2004 (2 pages)

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater Pre-ROD Sampling Event

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater Pre-ROD Sampling Event

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater Supplemental Sampling Event

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater Supplemental Sampling Event

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater June 2001

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater June 2001

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater January 2002

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater January 2002

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater April 2003

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater April 2003

Figure - Concentration Trends - Non-Source Area Wells MW-1B and MW-3B

Figure - Concentration Trends - Non-Source Area Wells MW-13DB and MW-16DB

Figure - Concentration Trends - Non-Source Area Wells MW-16IB and MW- 108D

Figure - Concentration Trends - Non-Source Area Wells MW-108S and MW-112D

Figure - Concentration Trends - Non-Source Area Wells MW-112S and MW-114D

Figure - Concentration Trends - Non-Source Area Wells MW-114S and MW-115D

Figure - Concentration Trends -Source Area Wells MW-2DB and MW-2IB

Figure - Concentration Trends -Source Area Wells MW-102S and MW-103D

Figure - Concentration Trends -Source Area Wells MW-103S and MW-104D

Figure - Concentration Trends -Source Area Wells MW-104I and MW-106D

Figure - Concentration Trends -Source Area Wells MW-106S

Response to EPA Comment 4 050305doc 3 of 26 Woodard amp Curran (211941)

I I

El I

II I I 1 I

I

i

Event Baseline Case ID WC-01 WC-01

Well Date Aug-99 Oct-99 LOT10 1 LOT1-1 1 LOT11-4 LOT14 1 LOT15 1 LOT15-1 1 LOT16 1 LOT16-1 1 LOT17 1 LOT18 1 LOT19 1 LOT2 LOT20 1 LOT21-10 1 LOT21-11 1 LOT21-12 1 LOT21-13 1 LOT21-14 1 LOT21-2 1 LOT21-5 1 LOT21-7 LOT21 -8 1 LOT21-9 1 LOT23 1 LOT24 1 LOT28-1 1 LOT28-2 1 LOT28-3 1 LOT28-4 1 LOT28W 1 LOT30 1 LOT30-1 1 LOT30-2 1 LOT30-3 1 LOT30-4 1 LOT30-5 LOT31 LOT35 1 LOT41 1 LOT42-1 1 LOT43-1 1 LOT43-4 1 LOT6-1 1 LOT67 1 LOT6-7 1 LOT6-8A 1 LOT6-8B 1 LOT80-1 1 LOT82 1 MW-101D MW-1011 MW-101S MW-102D MW-102S MW-103D MW-103S MW-104D MW-1041 MW-104S MW-105D MW-106D

Groundwater Sampling Location Summary 1999 - 2004xls

Sampling Events 1999-2004

Hows Corner Superfund Site Plymouth Maine

Supplemental 2001 2002 2003 Pumping 2004 Pre-ROD Rl Sampling Sampling Sampling Test Sampling WC-03 WC-09 WC-25 WC-30 WC-42B WC-56 WC-58 Dec-99 May-00 Jun-01 Jan-02 Apr-03 Sep-04 Sep-04

1

1 1 1

1 1 1 1 1

1 1

1

1 1

1 1 1

1 1 1 1 1

1

1 1

1 1 1 1

1

1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

Sampling Events 1999-2004

Hows Corner Super-fund Site Plymouth Maine

Supplemental 2001 2002 2003 Pumping Event Baseline Pre-ROD Rl Sampling Sampling Sampling Test

Case ID WC-01 WC-01 WC-03 WC-09 WC-25 WC-30 WC-42B WC-56

ll

Well Date Aug-99 Oct-99 Dec-99 May-00 Jun-01 Jan-02 Apr-03 Sep-04 MW-106S 1 1 1 1 1 MW-107D 1 1 MW-108D 1 1 1 1 1 MW-108S 1 1 1 1 1 MW-110D 1 1 MW-111D 1 1 MW-112D 1 1 1 1 1 MW-112S 1 1 1 1 1 MW-113D 1 1 MW-114D 1 1 1 1 1 MW-114S 1 1 1 1 1 MW-115D 1 1 1 1 1 MW-12DB 1 1 1 MW-12SB 1 1 1 MW-13DB 1 1 1 1 1 1 MW-13SB 1 1 1 MW-14DB 1 1 MW-14SO 1 1 MW-15DB 1 1 1 MW-15SB 1 1 1 MW-16DB 1 1 1 1 1 1 MW-16IB 1 1 1 1 1 1 MW-16SO 1 1 MW-17DO 1 1 1 MW-17SO 1 1 1 MW-1B 1 1 1 1 1 1 MW-203D MW-203S MW-204D MW-204S MW-205 MW-206D

I MW-206S MW-2DB 1 1 MW-2DDB 1 1 MW-2IB 1 1 1 1 1 1 MW-3B 1 1 1 1 1 1

I MW-4O 1 1 1 MW-5B 1 1

II MW-6DB 1 1 1 MW-6SB 1 1 1 MW-8DB 1 1 1 MW-8SB 1 1 1

II PW-207 1 SEEP-1 1 SUBTOTAL - RESIDENTIAL 44 25 0 2 0 3 0 SUBTOTAL - MONITORING 22 48 41 15 15 15 1

Total 3 66 73 41 17 15 18 1

I Included in most recent data

I Notes 1 - Overburden well not included in most recent data for plotting

2 - Tetrahydrofuran and 2-Butanone were the only two compounds detected in this well and are thought to be the result of well repair not included in most recent data for plotting

3 - Not included in most recent data for plotting

2004 Sampling

WC-58 Sep-04

1

1 1

1 1

1 1 1

1

1 1

1 1 1 1 1 1 1 1 1

1 1

1

0 29

29

Groundwatef Sampling Location Summary 1999 - 2004xls

I

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

monitoring well Figure 4-14 total VOC contour (ugl) - December 1999January 2000 Distribution of Total VOCs in

Note SW-113 is located downstream of SEEP-1 Shallow Bedrock Groundwater total concentration of detected VOCs ND= not detected these two locations were sampled during the Pre-ROD Sampling Event

Baseline Sampling Event in OctoberNovember 1999 Hows Corner Superfund Site Surface Water Sampling Location A Plymouth Maine Seep Sampling Location laquo- WOODARD ampCURRAN

995037wipri reportepa ri interim final feb 2001cadd drawingsfinalfig 4-14

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

0 300 600 I

FEET

Q residential well Figure 4-16 monitoring well Distribution of Total VOCs in

Deep Bedrock Groundwater total VOCs contour (ugl) Pre-ROD Sampling Event

active residential wells with lot number Hows Corner Superfund Site 2deg42deg Plymouth Maine total concentration of detected VOCs ND= not detected WOODARD ampCURRAN Enyinaaring bull Science bull Operations bull

995037wipri reportepa ri interim final feb 2001cadd drawingsfinalfig4mdash16

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PLYMOUTH POND

1 628Tl7MW-2bB 12135

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monitoring well Figure 4-20

V total VOC contour (ugl) - June 2000 Distribution of Total VOCs in Shallow Bedrock Groundwater

| 34 | total concentration of detected VOCs ND= not detected NA = not analyzed Supplemental Sampling Event Note SW-113 is located downstream of SEEP-1 Hows Corner Superfund Site

Surface Water Sampling Location these two locations were sampled during the Plymouth Maine Baseline Sampling Event in OctoberNovember 1999 Seep Sampling Location WOODARD amp CURRAN

Engineering bull Science - Operations bull 995037wipri reportepa ri interim final feb 2001 cadd drawingsfinalfig 4-20

residential well Figure 4-22 Distribution of Total VOCs in

monitoring well Deep Bedrock Groundwater

total VOCs contour (ugl) Supplemental Sampling Event

Hows Corner Superfund Site

total concentration of detected VOCs ND= not detected NA = not analyzed Plymouth Maine

WOODARD amp CURRAN

995037wipri reportepa-ri interim final feb 2001cadd drawingsfinalfig 4-22 Engineering bull Science - Operations bull

PLYMOUTH POND

PLYMOUTH POND

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Shallow Monitoring Well

Deep Monitoring Well

C Detected Concentration ND = Not Detected Figure 1-XS Distribution of Total VOCs in Shallow Bedrock Groundwater

Pumping Well

17-Acre Property Boundary Concentration Contour (ugl)

June 2001 Hows Corner Superfund Site

Plymouth Maine WOODARDampCURRAN

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Deep Monitoring Well 1 I Detected Concentration ND = Not Detected Distribution of Total VOCs in Deep Bedrock Groundwater

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Plymouth Maine i h Surface Water Sampling Point

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Detected Concentration ND = Not Detected Figure 1-YS Distribution of Total VOCs in Shallow Bedrock Groundwater

Pumping Well

17-Acre Property Boundary Concentration Contour (ugl)

January 2002 Hows Corner Superfund Site

Plymouth Maine WOODARD amp CURRAN Engineering Science- Operations bull

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Deep Bedrock Groundwater Pumping Well January 2002 Residential Well Hows Corner Superfund Site

Plymouth Maine Surface Water Sampling Point

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Shallow Monitoring Well E Detected Concentration ND = Not Detected Figure 1-ZS Distribution of Total VOCs in

Deep Monitoring Well Shallow Bedrock Groundwater

Pumping Well Hows Corner

April 2003 Superfund Site

17-Acre Property Boundary Plymouth Maine Concentration Contour (ugl) r WOODARD ampCURRAN

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0 Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

B MW-1B

I 12000

PCE

B 10000 Total VOCs

I

i 2000

i 0 Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

c MW-3B

G 2000

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B PCE

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211941

El

I I z E

80

Concentration Trends shy Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-13DB

Total VOCs

c i i c o

Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

MW-16DB

30

c i c c I c o

Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99

PCE

Total VOCs

Jul-01 Jul-03

211941

O bi

c Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

I MW-16IB

i 35

3

c Total VOCs

lt- 2 5

0 | gt

o

1 sectI

c c 0 4

Jul-90 Jul-92 Jul-94 Jul-96 Jul-98 Jul-00 Jul-02 Jul-04

I I MW-108D

I 12

PCE 10

Total VOCs c oc 3

E E I 0

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

E 211941

c Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

fi MW-108S

I I 40

PCE 35

Total VOCs

30

I f 26

20 I o

I 15

10

c Dec-99 Dec-00 Dec-01 Dec-02 Dec-03 I 0

I MW-112D

c 35 - imdash

I A3 shyTotal VOCs

o c

E 1 2

I

ition

B 1 ^

-i c 3

0 Dec-99 Dec-OO Dec-01 Dec-02 Dec-03

211941

I

i

I

cII

Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-112S

08

PCE

Total VOCs 06

o 04

02

0 Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

MW-114D

o

12000

10000

8000

6000

PCE

Total VOCs

4000

2000

i

ccEIIc

i

i

E

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

211941

Con

cent

ratio

n (

ug

l)

E Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

I MW-114S

E A5000 -- Total VOCs

- 4000

0 3000

2000

i 1000

i n shy

Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

MW-115D

c PCE

Total VOCs

c E

o

C c

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03 I 0

211941

IepoundII

EIEIIGICCIccc

30000

25000

20000

o bullsect 15000 b

o 10000 U

5000

0 Aug-99

25000

20000

5000

0 Aug-99

211941

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-2DB

PCE

Total VOCs

Aug-01 Aug-03

MW-2IB

PCE

Total VOCs

Aug-01 Aug-03

IDIBI

ii EIDIISIBIG C

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-102S

6000

5000 PCE

Total VOCs

4000

O 3000

2000

1000

0 Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

MW-103D

16000

~ 14000 ugt 3- 12000 o

^ 10000

sect 8000

O 6000

4000

2000

PCE

Total VOCs

0Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

211941

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

G MW-103S

I I

ampo

12000

10000

E sectc

S

8000

6000

4000

2000

0Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

G I 6000

MW-104D

i 5000

PCE

Total VOCs

i i c

2000

1000

Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

E I

211941

cIccIG

IIBCccBcIc

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-1041

PCE Total VOCs

a 25000

0 20000

a 15000

10000

5000

0 Jan-OO Jan-01 Jan-02 Jan-03 Jan-04

MW-106D

3000

2500 PCE

Total VOCs

=sect 2000

o bullsect 1500

1000

500

0 Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

211941

c Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

c MW-106S

I PCE

Total VOCs

i

i Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

i

i i i E

C

211941 c

Response to EPA-DEP Comment 5 Dated March 312005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

iiw

EPA-DEP Comment 5

Comment 5 Matrix Diffusion The report as well as other proponents of matrix diffusion suggest that depletion of DNAPL (Section 5112 page 5-15) needs to be achieved While that might be the ideal the goal is to achieve performance standards and that goal may be attainable while there is residual contamination in the rock perhaps even DNAPL globules The low bedrock matrix porosity (page 1-15) the high permeability values (page 4-4) the relative flux of the groundwater (page 5-5) and the decrease in surface area and out of the mainstream pockets (appendix C-4) all suggest that the diffusion out of the rock matrix would be insubstantial relative to the regional flux of groundwater through the Site

Response The TI Evaluation Report does not explicitly consider or rely upon matrix diffusion as a basis for requesting a TI Waiver for a portion of the Hows Corner Site The technical literature provides documentation that matrix diffusion can be a significant process that affects chemical transport and groundwater remediation timeframes in unconsolidated and consolidated media including fractured rock (US EPA 1989 Freeze and Cherry 1979 Pankow and Cherry 1996 Fountain 1998) Back diffusion of contaminants from the matrix porosity of the fractured rock can prolong the time necessary to achieve groundwater cleanup goals particularly for compounds such as PCE for which the cleanup goal is a low concentration It is our expectation that matrix diffusion has occurred at the Hows Corner Site and that back diffusion of PCE from the rock matrix will also occur Although the extent to which matrix diffusion is occurring at the Hows Comer Site has not been determined and that lack of knowledge contributes to uncertainty regarding the cleanup times at the Site the effect of matrix diffusion is to lengthen rather than shorten the time required for remediation

REFERENCES

Fountain JC 1998 Technologies for Dense Nonaqueous Phase Liquid Source Zone Remediation Ground-Water Remediation Technologies Analysis Center Technology Evaluation Report TE-98-02 December

Freeze RA and Cherry JA 1979 Groundwater Prentice-Hall Inc Englewood Cliffs NJ 07632 p 410-412

Pankow J F and Cherry J A 1996 Dense Chlorinated Solvents Waterloo Press Portland OR 97291-1399 p 67-88

US EPA 1989 Transport and Fate of Contaminants in the Subsurface EPA6254-89019 p 17-18

Response to EPA Comment 5 050305doc 1 of 1 Woodard amp Curran (211941)

WOODARD amp CURRAN Maine Massachusetts New Hampshire Connecticut Florida Operational offices across the US 1-800-426-4262 www woodardcurran com

Page 22: SDMS DocID 251749 - Records Collections · 2020-06-13 · CORPORATE OFFICES: Maine, Massachusetts, New Hampshire, Connecticut New, York, Florida Engineering • Science • Operations

1

Northeast Geophysical Services Borehole Geophysical Log MW-204 D a t e l o gge d 072604

Plymouth Maine

n 3

Flowrneter Measurements(in gpm)

Caliper (Inches)0 3 5 4 0

1 1 1 1 1 1 1 t 1 1 1 1 1 1Ambient Rowmeler pumping Flowmetsr 05gpm

Templaquorature (C) bull bull bull bull i

7 75 8 8S 9 Resistance (Ohms) Spontaneous Potential (mV)

4000 SOW 600 4M 0

Acoustic Televiewer (interpreted)

Dip in Degrees 0 20 4060 SO

at N

PCEugL

Total VOCs ugL

- -_ a

10-

shy 10 bull - 10 shymagnetic

north - 10

o o

bull 1

11

11

1 1

1 1

11 1

1 1

1 1

1 1

1 1

1 1

1 1

1 1

1 1 E 1

- L

3 7 2 0 2 0r bull 20 bull - shy

i S_ N F

bull30 bull 7 3 0 220 2636shy1^ J J 004

fI f V ^

40 shy 4 0 4 0 shy - 4 0rbull019 [_ 007 w8 - - shy5 c

bull

gt

Ia50i 540 6436

bull50 - - 50 - - 5 0

-QQ7 - bull - -t T

pound V gtk

B 6 0 - e o - 7 6 0 -60shyQ 1 1

Q -007 -004 bull1 mdash T - J ~

bull

- - shyT 70 -J c [TO- - 70 - 7 0-

V Y 1- -004 -003

mdash T -h - y - j i - - mdash 260 3073 - gt=7

80 -j NF bull80 - - 80 - - 8 0Jgt

bull i

i 1

i i

C- bull shy

90 shy

K

Jlt i90 90 shy - 9 0shy -

l

ii

I I I I

NF bull M J

I ^ ^ - ^ bull 1

mdash mdash - _

s -7 ^100shy

till

1 100 100- H - 1 0 0shy -1 x Likety or possible k ^ Iransmissive zonebull

1 i i i ii i i i | l l l l | l i l l 0 20 40 ED 80

1 -

3 0SOFluid Resistivity (ohmmeters)

Dip in Degrees The djp ^ ^ o n is indicated ty Ihe line extending from tha circle The strike of Ihe feature

19- 3U UIHJIW93 IolII l l l lraquo

bull

The acousfc televiewer graph displays the mostprominent features selected from the acoustic televiewer109 The location dip angle and dip direction of Ihe sleetedfeatures are approximate Refer to the televiewer log of thiswentormore precise detail

B o r e h o l e G e O D h V S I C a l LOO B W H U I B w c w p n y o i v a i w v yM W - 2 0 4

P l y m O U t n MaiDB

Packorod Interval August 2004Groundwater san-ples wampramp collected by Woodard a Curran on OMO23C4

Date logged 072604

C

I

E Northeast Geophysical Services Borehole Geophysical Log Date logged 072704

I MW-205

Plymouth Maine

Flowmeter Measurements Temperature (C) Acoustic Televiewer (In gpm) I ~l (Interpreted)

I 85 10 Caliper (inches) 95

Dip in D g r laquo Resistance (Ohms) Spo ontaneous Potential (mV PCE Total VOCs 3 0 16 4 0 4 5 ) 20 40 60 80 10 00 2000 30 00 4VJ 400 -3 laquo

i i i i 1 i i I i 11 4 0 D 1 I I ugL ugL

C h

iii Ambient Flowmetar pumping

Flowmeter 1 25 gprn

I bull$bull

i

I rmdash magnetic 1 north ^^^^ 1 VI f

10 ~ I C x 10 bull - 10 bullbull

4 5 6mdashmdash f 1000B 11448 noisy nodi a raquo ^

mdash 5rt mdashi mdash Oft pound) 1100B 12509

cjmdash1 007

-

i i i 1

en

8 B a B

30 mdash

-

40 shy

-mdash I -

50 -_

__NF lt005

- 30 - - 3 0 it 34V

MO P26 V S) 1300B 13776 _ N F NF

26

40 bull - 40 bull 7-40 gt J Vf1 cX

) -j -

_ N F NF 50 c bull - 50 ^ 7-50

i I

I

c

B pound 60 - 6 0 7 60 - 7-60 a i 1

_ N F NF i Si f f 70 -_ bull70 bull - 70 shyC I 9

-m bull - shyA

_ N F NF 80 80 -j bull80 bull - 80 - C- 33 34

bull

5-i r

i 1

J r

Ck

_ N F NF 9 0 90 - - 90 shy

i bullCshy

J rK bull

100 -j ^ Likely or possible bull100- - 100- I -100

transmissive zone bull - ^ bull shy] |

1 1 1 1 1 1 1 I 1 i i i 1 i i 1 1 0 20 40 SO SO 10 20 30 40 50 Dip in Degrees 30 4 0 Fluid Resistivity (ohmmeters) Thlaquo dip direction is indicated

by the line extern r g from the circle The strike of he feature is 90 degrees from ihis

The acoustic televiewer graph displays the most

I Borehole Geophysical Log Packered Interval August2004 prominent features selected from the acoustic televiewer

Groundwatcr samples were oollccled by Woodard amp Cufran orgt S172004 log The location dip angle and dip direction of ins slsctsd MW-205 features are approximate Refelt to the televiewer log of this wall for more precise detail Plymouth Maine Date logged 072704

I

C

I Northeast Geophysical Services Borehole Geophysical Log Date logged 072704

I MW-206

Plymouth Maine

Flowmetor Measurements Temperature (C) Acoustic Televiewer | I r T i i i i i i i i i i i i i i r I |(in gpm) (Interpreted)

I 75 8 flS 9 95

Caliper (inches) Resistance (Ohms) Spontaneous Potential (mV) Dip In Degress PCE Total VOCs 30 35 40 4 5 0 20 40 M 90 4500 5500 6500 ugL ugL I i i

I I

- 1 0

I - 2 0

I 2900B 32401

i i L

E 0

i 6300B 68901

i I 0 20 40 SO 80

20 30 40 50 Dip in Dlaquogralaquos

amp 4 a Fluid Resistivity (ohrnmeters) The dip dirertion is indicated Likely or possible by iho line extending from the transmissive zone circle The striKe of the feature

is 90 degrees from tNs

Borehole Geophysical Log Packered Interval August 2004

E amples were collected by Woodard amp Cunan oo SM82004 log Thraquo location 4p angle and dip direction of the sloeled MW-206 feature are approximate Refer to the televiewer 109 of this well for more precise detail Plymouth Maine Date logged 072704

C

I Northeast Geophysical Services Borehole Geophysical Log

Date logged 082304 PW-207

I Plymouth Maine

Fiowmeter Measurements Temperature (C) Acoustic Televiewer

I (in gpm) (interpreted)

75 8 85 9 95 Caliper (inches) Resistance f0tims) Spontaneous Potential (mV) Dip in Degrees PCE Total VOCs

55 60 0 20 40 SO 80 ugL ugL I I I I I I I

Ambienl Fiowmeter pumping Flewmater

magnetic - 10 - - 1 0

north

i - 20 - - 2 0

1300 1410

i - 30 - - 3 0

i tf

5400 5802 - 40 - - 4 0

B - 50 - - 5 0

I 18000 19234

- 60 - - 6 0

I 12000 13085

- 70 - - 7 0

- 8 0

i - 9 0 19000 20354

G - 100- -100

I 110 110 bull110

0 20 40 60 SO 10 20 30 Dip m Degrees

Fluid Resistivity (ohmmeters) I 50

The dip direction is indicated by ihe line extending from the circle The strike of the fealure is 90 degrees from this

Borehole Geophysical Log

G Packorod Interval August 20(M log The location dip angle and dip dirlaquocton or the sleeted Groundaier samplss were ooliecled by Woodard i Curran on ampt24f2ltXM PW-207 failures are approximate Reter to the televiewer log of this wlaquoll for more precise detail PlyPIOUth Maine Date logged 082304

I

Table XX Packer Permeability and Packer Sampling Results for Potential Fracture Intervals

1

WellID MW-101D MW-101D MW-101D MW-101D MW-101D MW-101D MW-101D MW-101D MW-101D MW-101D MW-I01D MW-101D MW-101D MW-102D MW-102D MW-I02D MW-102D MW102D MW-102D MW-102D MW-102D MW-102D MW-I02D MW-102D MW-102D MW-102D MW-103D MW-103D MW-103D MW-103D MW-I03D MW-103D MW-103D MW-103D MW-103D MW-103D MW-103D MW-103D MW-I03D MW-104D MW-104D MW-104D MW-104D MW-I04D MW-104D MW-104D MW-104D MW-104D MW-104D MW-104D MW-105D MW-105D MW106D MW-106D MW-106D MW-107D MW-107D

1999 Drilling Program

Hows Corner Superfund Site Plymouth Maine

Potential Fracture Top Of Bottom 6 Depth to lt Topof i Interval from Packer Packer Middle of Elevation Hydraulic bull PCE

GS ELEV 1 Rock Drilling Interval Interval Interval of Interval Conductivity Concentration (ft msl) (ft msl) TEST (ftbgs) (ftbgs) r(ftbgs) ( f t b (ft mil) (cmsec) (raquogL)

4339 4329 13 28-29 33-3537-39 271 376 324 4016 OOOE+00 4339 12 37-3444-46 380 485 433 3907 157E-04 4339 11 488 593 541 3799 132E-04 4339 10 60-61 578 683 631 3709 OOOE+00 4339 9 678 783 731 3609 I79E-05 4339 8 778 883 831 3509 106E-05 4339 7 880 985 933 3407 243E-05 4339 6 990 1095 1043 3297 339E-06 4339 5 1090 1195 1143 3197 OOOE+00 4339 4 1190 1295 1243 3097 OOOE+00 4339 3 1365-1375 1290 1395 1343 2997 OOOE+00 4339 2 147-157 1390 1495 1443 2897 580E-05 4339 1 147-157 1470 1575 1523 2817 741E-05 43161 43061 13 166 271 219 4098 333E-04 43161 12 30-3136-40 260 365 313 4004 I54E-05 43161 11 36-4041-43 362 467 415 3902 548E-05 43161 10 470 575 523 3794 598E-05 43161 9 570 675 623 3694 197FOS 43161 8 670 775 723 3594 OOOE+00 43161 7 770 875 823 3494 891 E-05 43161 6 83-94 870 975 923 3394 139E-05 43161 5 970 1075 1023 3294 123E-04 43161 4 1070 1175 1123 3194 526E-06 43161 3 1170 1275 1223 3094 138E-05 43161 2 1270 1375 1323 2994 671E-06 43161 1 1370 1475 1423 2894 OOOE+00 42997 42497 13 18-19 170 275 223 4077 OOOE+00 42997 12 260 365 313 3987 766E-05 42997 11 360 465 413 3887 727E-05 42997 10 460 565 513 3787 192E-05 42997 9 560 665 613 3687 752E-05 42997 8 660 765 713 3587 778E-05 42997 7 85-86 763 868 816 3484 260E-05 42997 6 860 965 913 3387 289E-05 42997 5 102-103 960 1065 1013 3287 102E-04 42997 4 1060 1165 1113 3187 522E-06 42997 3 1160 1265 1213 3087 520E-06 42997 2 129-130 1260 1365 1313 2987 960E-04 42997 1 1360 1465 1413 2887 OOOE+00 43372 42922 11 35-37 42-45 350 455 403 3935 684E-04 43372 10 460 565 513 3825 500E-05 43372 9 560 665 613 3725 106E-05 43372 8 72-74 660 765 713 3625 204E-05 43372 7 760 865 813 3525 872E-06 43372 6 860 965 913 3425 467E-06 43372 5 960 1065 1013 3325 200E-05 43372 4 1060 1165 1113 3225 354E-05 43372 3 125-130 1160 1265 1213 3125 157E-05 43372 2 125-130 1260 1365 1313 3025 337E-04 43372 1 1365 1465 1415 2922 689E-06 43052 43002 2 54-58 490 595 543 3763 124E-05 2100 43052 1 139-140 145-146 1367 1472 1420 2886 154E-04 1400 43291 4391 3 bullI133 260 365 313 4017 439F06 43291 2 77-78 760 865 813 3517 230E-03 400 43291 1 143-144 1355 1460 1408 2922 971E-06 350

29958 27258 4 450 555 503 2493 OOOE+00 (21)A 29958 3 103-105 1000 1105 1053 1943 752E-04 (063)A

Table XX Packer Permeability and Packer Sampling Results for Potential Fracture Intervals

1999 Drilling Program

Hows Corner Supcrfund Site Plymouth Maine

gtbull i Potential Fracture Top _OfBot Bottom of Depth to ltbull Top of Interval from f Packer Packer Middle Of

GS ELEV lt Hock Drilling interval Interval Interval WeD ID ft msl) (ft msl) TEST (ftbgs) ltft$gs) (ftbgs) (ftbgs)

MW-107D 29958 2 128-130 1200 1305 1253

MW-107D 29958 1 139-141 1350 1455 1403

MW-108D 31904 31104 6 35-36 300 405 353 MW-108D 31904 5 60-62 550 655 603

MW-108D 31904 4 80-83 750 855 803

MW-108D 31904 3 118-119 123-124 1150 1255 1203

MW-108D 31904 2 147-149 1440 1545 1493

MW-108D 31904 1 1700 1805 1753

MW-110D 40576 40426 2 21-31 210 315 263 MW-110D 40576 1 148-154 1460 1565 1513 MW-I11D 40519 4 70-71 650 755 703

MW-111D 40519 3 79-82 84-86 780 885 833 MW-I11D 40519 2 97-102 950 1055 1003 MW-111D 40519 1 1370 1475 1423

MW-112D 3027 2942 4 42-52 420 525 473 MW-112D 3027 3 850 955 903 MW112D 3027 2 1100 1205 1153 MW-112D 3027 1 135-136 140-141 1340 1445 1393

MW-113D 43085 43085 5 250 355 303 MW-I13D 43085 4 47-49 460 565 513 MW-113D 43085 3 73-74 700 805 753 MW-113D 43085 2 1050 1155 1103 MW-113D 43085 1 1380 1485 1433

MW-114D 42394 41594 4 48-49 450 555 503 MW-114D 42394 3 79-81 740 845 793 MW-114D 42394 2 121-129 1250 1355 1303 MW-114D 42394 1 134-142 1350 1455 1403

MW-115D 4035 4035 4 300 405 353 MW-1I5D 4035 3 70-71 650 755 703 MW-115D 4035 2 1150 1255 1203 MW-115D 4035 1 1400 1505 1453

LOT-28W 382 7 450 555 503 LOT28W 382 6 550 655 603 LOT-28W 382 5 650 755 703 LOT28W 382 4 750 855 803 LOT-28W 382 3 850 955 903 LOT-28W 382 2 950 1055 1003 LOT-28W 382 1 1055 1155 1105

NOTES cmsec = centimeters per second ft bgs = leet below ground surface It msl = feet below mean sea level lt = not detected at indicated reporting limil A = detected below laboratory PQL ( ) = detected below reporting limits

Elevation of Interval

(ft nisi) 174

159

283gt 2588

2388

1988

1698

1438

3795 2545 3349 3219 3049 2629

2555 2125 1875 1635

4006 3796 3556 3206 2876

3737 3447 2937 2837

3683 3333 2833 2583

3318 3218 3118 3018 2918 2818 2715

Hydraulic Conductivity

(cmsec)

323E-05

208E-05

471E-03

471E-03

624E-05

3I6E-05

264E-05

261 E-05

OOOE+00 200E-04 953E-05 OOOE+00 OOOE+00 212E-05

361 E-05 410E-06 2gQE06 292E-05

786E-05 124E-05 151 E-05 822E-06 82IE-06

858E-05 I69E-05 352E-03 866E-05

223E-05 394E-06 122E-05 525E-06

831 E-05 182F-05 L62E-05 129E-05 190E-05 890E-04 981 E-04

PCEraquo Concentration

(ugL)

lt5

(14A)

98 11

15

22

11

30

200 (62)A

110 210 300 240

(44)A (23)A

5

350 190 129 230

2200 1900 2600 2600

(17)A (16)A (19)A

96

Table XX Packer Permeability and Packer Sampling Results for Potential Fracture Intervals

2004 Drilling Program

Hows Corner Superfund Site Plymouth Maine

Top of Bottom of Depth to Midpoint

t K

ELEV (ft Potential Transmissive Zones Packer Interval

Packer Interval

Middle of Interval

Elevation of interval

Hydraulic Conductivity

PCE Concentration

Well ID msl) TESTr (ft bgs)- (ftbgs) (ftbgs) (ftbgs) (ft msl) (cmsec) (ogt) MW-203D 43227 4 277279 24 32 28 4043 667E-05 44

3 408415420 39 49 44 3883 593E-05 170 2 526 530 49 57 53 3793 101E-04 140 I 828830842 80 88 84 3483 701E-05 130

MW-204D 43262 5 295 300 26 34 30 4023 902E-05 220 4 463496513516 45 53 49 3833 119E-04 540 3 681685688 63 71 67 3653 OOOE+00 2 758 76 2 71 79 75 3573 309E-05 260 I 88 96 92 3403 OOOE+00

MW-205 42389 3 164 166 168 15 20 175 4148 OOOE+00 1000B 2 302305312 30 35 325 3998 107E-04 1300B 1 40 45 425 3898 OOOE+00

MW-206D 43007 5 17 72 195 4128 291E-05 4 296 302 307 29 34 315 4008 940E-05 2900B 3 522 52 57 545 3778 944E-07 2 656 64 69 665 3658 353E-06 1 92392793 4939 91 96 935 3388 614E-05 6300B

PW-207 43477 5 184622162819 18 29 235 4088 209E-05 1300 4 3508 32 43 375 3948 568E-06 5400 3 53325341542154325559 50 61 555 3768 821E-05 18000

6359 61 72 665 3658 866E-06 12000 1 8685 84 89 865 3458 213E-05 19000

NOTES cmsec = centimeters per second ft bgs = feet below ground surface ft msl = feet above mean sea level B = detected in lab blank

Table XX Orientation Permeability and Groundwater Sampling Results for Transmissive Features

2004 Drilling Program

Hows Corner Superfund Site Plymouth Maine

Borehole Geophisical Feature depth Dip True Dip True Transmissive Log Feature (Feet) Degrees Azimuth Strike bullvgt(Ltk|iy^

Number v Tosftble) v MW-203 5 277 64 337 67 Likely

6 279 59 11 281 Likely 8 352 14 177 87 Likely 11 381 46 96 6 Possible 12 408 35 271 1 Possible 14 415 57 250 340 Possible 15 420 58 202 292 Likely 18 526 52 75 345 Likely 19 530 52 82 352 Likely 28 828 48 75 345 Likely 29 830 52 17 287 Likely 30 830 56 233 323 Possible 31 842 50 130 40 Likely

MW-204 4 295 15 147 57 Likely 5 300 43 91 1 Likely 11 439 31 80 350 Possible 12 440 46 219 309 Possible 14 463 50 358 88 Likely 15 496 34 198 288 Likely 16 513 54 17 287 Likely 17 516 33 14 284 Likely 25 681 39 359 89 Possible 26 685 22 45 315 Possible 27 688 35 73 343 Possible 32 758 45 236 326 Likely 33 762 46 306 36 Likely

MW-205 5 164 69 106 16 Possible 6 166 78 165 75 Possible 7 168 82 115 25 Possible 8 168 68 116 26 Possible 12 215 46 222 312 Possible 13 217 75 62 332 Possible 14 219 29 32 302 Possible 16 237 69 250 340 Possible 17 256 73 353 83 Possible 18 272 44 202 292 Possible 21 299 37 196 286 Possible 22 302 31 206 296 Possible 23 305 59 48 318 Likely 24 312 63 42 312 Likely

MW-206 1 264 37 181 271 Likely 2 296 69 217 307 Likely 3 302 66 233 323 Likely 4 307 64 224 314 Likely 8 342 62 259 349 Likely

jjHydraulic GoiDanctilyity j(cmsecjw

667 E-05

593 E-05

101 P04

710 E-05

902 E-05

119 E-04

0

309 E-05

0

107 E-04

94 E-05

PCE (ugL)

44

170

140

130

220

540

260

IOOOB

1100B

1300B

2900B

STotal vVoCsv tig1)

84

234

192

183

2636

6436

3073

11448

12509

13776

32401

PCEyo dfCTotaf

52

73

73

7 1

83

84

85

87

88

94

90

Table XX Orientation Permeability and Groundwater Sampling Results for Transmissive Features

2004 Drilling Program

Hows Corner Superfund Site Plymouth Maine

Borehole Geophisical Feature deptt raquoip True pip True Transraissive Log Feature (Feet) shy Degrees Azimuth Strike (tikely

Number raquo Possible) 22 522 57 54 324 Possible 25 656 40 82 352 Possible 32 871 59 151 61 Possible 33 883 53 185 275 Possible 34 895 7 175 85 Likely 35 899 53 90 0 Likely 36 902 49 184 274 Likely 37 923 9 175 85 Likely 38 927 42 206 296 Likely 39 934 48 167 77 Likely 40 939 26 180 90 Likely

PW-207 1 1846 33 167 77 Likely 4 2216 49 289 19 Possible 7 2819 59 265 355 Possible 11 3508 55 189 279 Possible 18 5332 43 305 35 Likely 19 5341 51 30 300 Likely 20 5421 20 254 344 Likely 21 5432 39 301 31 Likely 23 5559 52 302 32 Likely 25 6359 24 182 272 Possible 29 8049 77 231 321 Possible 30 8685 78 38 308 Likely 32 9334 29 194 284 Likely

NOTES

B = detected in lab blank

Hydraulic Conductivity

(cmsee) 944 E-07 353 E-06

614 E-05

209 E-05

568 E-06

821 E-05

866 E-06

213 E-05

bulltCE (ugL)

6300B

1300

5400

18000

12000

19000

Total VOCs (ug1)

68901

1410

5802

19234

13085

20354

PCE of Total VOCs

9 1

92

93

94

92

93

Response to EPA-DEP Comment 3 Dated March 312005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

lit

EPA-DEP Comment 3

Comment 3 The reported f values and resultant Kd values There remains doubt that the values used in the flushing model accurately reflect the propensity for PCE to sorb to the bedrock The ^ values presented in Appendix B may be unrealistically high because the bedrock samples may have contained organic carbon that was unavailable for sorption The reported f values are only qualitative estimates of the organic carbon content of the bedrock samples The Walkley and Black organic carbon measurement method is quick and simple but the results obtained cannot be considered quantitative because it requires a correction factor which often results in erroneous values it assumes the organic carbon has an average valence of zero oxidizable and reducible constituents such as chloride ferrous iron and manganese oxides interfere with the results and the errors introduced by interference are potentially greater when the organic carbon content is low at low f values it is not clear that organic carbon is controlling PCE sorption (Schwarzenbach and Westall 1981 Mackay et al 1986 Fetter 1999)

In order to derive a Kd-based retardation factor that is reasonable given the reported f values and the rapid advance of the PCE plume described on pages 4-11 and 4-12 the flushing model requires a bulk density to porosity ratio that is roughly two orders of magnitude higher than the actual ratio for the Hows Corner bedrock (page 4-4) This apparent discrepancy needs to be addressed

Response This comment raises several concerns about the collection and analysis of samples for fraction of organic carbon (f^) the quality of the resulting data and the implications of the use of those data for estimation of the retardation of groundwater contaminant movement Results of bedrock analysis for f were proposed in the TI Evaluation Work Plan for use in conjunction with groundwater contaminant concentrations and aquifer information to estimate cleanup times using the Batch Flushing model It is important to use accurate f values from representative bedrock in the Batch Flushing model in order to obtain reasonable estimates of the remedial time frame Because of the importance of accurate and representative results the TI Investigation field program was designed and conducted both to collect samples representative of the rock volume most likely to be in contact with contaminated groundwater and to analyze them using an appropriate refereed analytical method Five potential methods for evaluating f were identified Of the five methods the Walkey-Black method was selected because it has minimal method interferences and a sufficiently low detection limit as well as a long history of use in agronomy and contamination studies The PRP Group is pleased with the quality of the data obtained from the bedrock samples as represented by their precision and reproducibility

The first part of this comment relates to the determination of fraction of organic carbon (f^) values The several subparts of the first paragraph are addressed individually in items 1 through 5 below The second part of the comment regarding the resultant distribution coefficient (Kd) values is addressed separately as item 6 below

1 There remains doubt that the values used in the flushing model accurately reflect the propensity for PCE to sorb to the bedrock

bull The rock core samples used for f (gocg) analysis were from core immediately adjacent to fractures These rock core samples included the fracture surfaces themselves and rock core extending back less than 1 cm from the fractures Therefore the foe data reported in the TI Evaluation represents the f of bedrock through which groundwater will travel and to which PCE will adsorb Based on the careful selection of sample locations and the

Response to EPA Comment 3 050205doc 1 of 11 Woodard amp Curran (211941)

number of samples collected we are confident that the measured f values are representative of the f at points of contact for PCE with the bedrock it is these f values that determine the propensity of PCE to sorb to the bedrock

bull The samples of rock core collected for analysis of f originated from 19 different locations varying in depth from 11 to 90 feet Therefore it is very unlikely that the rock core samples were contaminated with extraneous organic carbon from above ground

2 The foc values presented in Appendix B may be unrealistically high because the bedrock samples may have contained organic carbon that was unavailable for sorption

bull As noted in response 1 the f data reported in Appendix B represents organic carbon primarily associated with the surface of fractures in the bedrock through which groundwater is most likely to travel Therefore it is this organic carbon that the contaminants in the groundwater will come in contact with and adsorb to in the fractured rock at the site

bull The chemical oxidation agents used in the Walkey-Black method oxidize the easily oxidizable organic carbon in the medium and the foe is calculated from the quantity of the agent consumed Therefore it is unlikely that the analysis of the bedrock samples measured organic carbon that was unavailable for sorption

3 The reported foc values are only qualitative estimates of the organic carbon content of the bedrock samples

bull The reported f values are accurate quantitative results Schumachers review of Methods for the determination of total organic carbon (TOC) in soils and sediments (NCEA-C-1282 EMASC-001 April 2002) identifies the Walkley-Black method which was used to analyze the reported foc values as the reference method for comparison to other methods for analyzing total organic carbon

bull Schumacher also points out that if anything the WalkJey-Black method may underestimate the total organic carbon in a sample due to possible incomplete oxidation of organic carbon Usually the incomplete oxidation of total organic carbon in environmental samples is corrected for by multiplying the measured foe by 130 (Walkley amp Black 1934 Schulte 1995)

bull When the f data in the TI Evaluation Report (WampC 2005) Appendix B (attached) are analyzed statistically the standard deviation of the f for the 19 samples analyzed is 174 of the average f Given this standard deviation the 95 confidence interval for this data ranged from a low of 000123 gocg to a high of 000253 gocgm

The labs Method of Detection Limit (MDL) for the f measured using the Walkley-Black method is 00001 gocg Therefore the average (000188 gocg) the mean (000185 gocg) and geometric mean (000187 gocg) of the f values for the rock core at Hows Corner are all statistically significantly greater than the MDL of the Walkley-Black method

In addition to the aforementioned statistical analysis of the foe data triplicate samples (n = 3) from the same rock core (including one sample from the 19 rock core samples) were

Response to EPA Comment 3 050205doc 2 of Woodard amp Curran (211941)

analyzed for their f to determine the repeatability of the Walkley-Black method The average the mean and the geometric mean of the f values of these replicate samples was 000162 gocg 000150 gocg and 000159 gocgm respectively The standard deviation of these measurements was 000039 gocg

4 The Walkley and Black organic carbon measurement method is quick and simple but the results obtained cannot be considered quantitative because it requires a correction factor which often results in erroneous values it assumes the organic carbon has an average valence of zero oxidizable and reducible constituents such as chloride ferrous iron and manganese oxides interfere with the results and the errors introduced by interference are potentially greater when the organic carbon content is low at low foc values it is not clear that organic carbon is controlling PCE sorption (Schwarzenbach and Westall 1981 Mackay et al 1986 Fetter 1999)

bull Schumachers review (NCEA-C-1282 EMASC-001 April 2002) of the Walkley-Black method identifies several potential problems with this analytical method that could occur if the analytical lab is not familiar with the nuances of the chemistry associated with this method Interestingly Schumachers review neglected one of the more important analytical steps required to avoid errors in quantifying f in samples where there might beNAPL

It is absolutely critical to eliminate any NAPL from rock core samples prior to using the Walkley-Black method to measure foe in such samples This was done by the lab (PTS Laboratories) that measured the foe in the rock core samples from Hows Corner The lab used the Dean-Stark method (solvent extraction) to remove all hydrocarbons (including PCE and other NAPLs) from the sample (PTS Laboratories) This extraction method does not interfere with the subsequent analysis of the natural organic carbon associated with the rock core

Subsequently the samples were dried at 150degC to a constant weight (normally 16 hours) This latter step oxidizes all inorganic minerals including ferrous bearing minerals to ferric oxides and precludes their interference during the oxidation of the samples with chromic acid This procedure completely eliminates any positive bias in the reported foc

data that might have occurred due to the presence of ferrous ions and other reduced minerals

bull As noted in Response 3 the incomplete oxidation of total organic carbon results in an underestimate of the f and is corrected for by multiplying the f by a correction factor of 130 (Walkley amp Black 1934 Schulte 1995) The fx data reported in the TI Evaluation was corrected accordingly by using this correction factor

bull Excess chloride (Cl~) in percent weight quantities as found in saline soils may interfere with the quantitative titration of reduced chromium (Walkley 1947) However given that the primary rock type at the Hows Corner site is phyllite it is highly unlikely that there was sufficient chloride in the rock core samples for this to occur

bull Manganese oxides may also interfere with the analysis of f through competing with the dichromate ion for any oxidizable carbon (Walkley 1947) However in such cases the reported f would be an underestimate of the f present in the rock core Walkley (1947)

Response to EPA Comment 3 050205doc 3 of 11 Woodard amp Curran (211941)

4

reported that in the case where the ratio of MnO2 to carbon is 85 to 1 the error in the carbon determinations would only be 0 to 6 percent

It may also be useful to compare the analysis of total organic carbon in a geologic matrix that contains high levels of manganese using EPA method 9060 to the Walkley-Black method Table 1 summarizes data provided by one of the PRPs that compares the analysis of total organic carbon in a geologic matrix that contains approximately 02 wgt manganese (approximately 03 wgt manganese oxide)

Table 1 Comparison of total organic carbon measured using the EPA- 9060 method and the Walkley-Black method

Laboratory EPA-9060 Method Walkley-Black Method A Ave 00226 gocg Not analyzed

Stdev 000251 gocg n = 5

B Ave 002219 gocg Ave 002050 gocg Stdev = 000316 gocg Stdev =000971 gocg

n= 10 n = 10

The similarity in the total organic carbon concentrations measured by these two different methods provides further confidence that the Walkley-Black method is a viable method for analysis of total organic carbon in the presence of manganese equivalent to at least 10 by weight of the total organic carbon

5 The Walkley and Black organic carbon measurement at lowf^ values it is not clear that organic carbon is controlling PCE sorption (Schwarzenbach and Westall 1981 Mackay et al 1986 Fetter 1999)

bull Schwarzenbach and Westalls (1981) paper states that f values of less than 0001 gocg should not be used in combination with Kow (octanol-water partition coefficients) values to calculate K^ values (solid phase partition coefficients) values for a specific contaminant It should be noted that the TI Evaluation did not use the f data to calculate the KQC from the Kow Instead as requested by the EPA the measured KOC value for PCE was used to calculate the retardation factor for this contaminant

bull Schwarzenbach et al (2003) stated more recently that Even at very low f values (ie foe = 0001 kgoc - kg1 solid) sorption to the organic components of a natural sorbent may still be the dominant mechanism in defining the adsorption of organic compounds to geological matrices

bull In 1985 M Piwoni from the US EPA Robert S Kerr Environmental Research Laboratory published a paper (Banerjee et al 1985) that showed that for very hydrophobic molecules TOC content of the sorbent will control sorption down to levels of organic carbon that defy quantitation Contaminants such as the PCE found in the groundwater at Hows Corner are in this category of compounds

Given the aforementioned reasons the f values reported in the TI Evaluation are accurate within the noted statistical limitations and will have a predictable impact upon the retardation of PCE during groundwater transport

Response to EPA Comment 3 050205doc 4 of 11 Woodard amp Curran (211941)

6 In order to derive a Kd-based retardation factor that is reasonable given the reported foc

values and the rapid advance of the PCE plume described on pages 4-11 and 4-12 the flushing model requires a bulk density to porosity ratio that is roughly two orders of magnitude higher than the actual ratio for the Hows Comer bedrock (page 4-4) This apparent discrepancy needs to be addressed

The apparent discrepancy of bulk density to porosity ratios is most likely due to the fact that the Batch Flushing Model was originally developed for a porous medium and is not directly applicable to fractured bedrock As stated in Appendix C (page C-4) of the Draft Technical Impracticability Evaluation Report in order to use the Batch Flushing Model to describe the transport of contaminated groundwater in fractured bedrock where the matrix porosity is insignificant it is more appropriate to use a fracture surface area to void space ratio to calculate the retardation factor (R) than a bulk density to porosity ratio (Freeze amp Cherry 1979)

Since it is impractical to determine the actual surface area to which contaminants can adsorb the Batch Flushing Model was used with two simplifying assumptions bull The Kd was calculated from the f and the K^ bull The bulk density to porosity ratio term in the Batch Flushing Model was constrained to range

from 4 to 10 the typical range of such ratios in porous media (Freeze amp Cherry 1979)

If one uses site specific bedrock bulk density and porosity values the bulk density to porosity ratio is several orders of magnitude greater (specifically 273 gcc bullbull 000165 (dimensionless) = 1654 gcc) than the range of ratios of 4 to 10 used in the Batch Flushing Model in the Draft Technical Impracticability Evaluation Report Constraining the bulk density to porosity ratio within the range of ratios of 4 to 10 results in significantly lower R value than would be obtained using specific bedrock bulk density and porosity values

In summary in bedrock where fractures are the primary porosity the bulk density to porosity ratio can vary considerably and will be a function of the number of fractures and the fracture aperture The calculated bulk density to porosity ratio will be inversely proportional to the porosity This means that in fractured rock with limited fracturing and smaller porosity the calculated bulk density to porosity ratio is greater and will result in a greater calculated retardation factor than in bedrock with more extensive fracturing and greater porosity Consequently the calculated retardation factor will be greater for bedrock with less surface area available for sorption than bedrock with greater surface area for sorption This is contrary to what actually occurs

4 Response to EPA Comment 3 050205doc 5 of 11 Woodard amp Curran (211941)

m

REFERENCES

Banerjee P MD Piwoni K Ebeid (1985) Sorption of organic contaminants to a low carbon subsurface core Chemosphere _14 1057-1067

Freeze RA JA Cherry (1979) Groundwater Prentice Hall Englewood Cliffs NJ pg 604

PTS Laboratories wwwptsgeolabscompdf files3TOCnotepdf

Schulte EE (1995) Recommended soil organic matter tests in Recommended Soil Testing Procedures for the Northeastern United States Northeastern Regional Publication No 493 Chapter 8

Schwarzenbach RP J Westall (1981) Transport of nonpolar organic compounds from surface water to groundwater Laboratory sorption studies Environ Sci Tech 15 1360-1367

Schwarzenbach RP PM Gschwend DM Imboden (2003) Environmental Organic Chemistry Wiley-Interscience pg 292 408 amp 412

Walkley A LA Black (1934) An examination of the Degtjareff method for determining soil organic matter and a proposed modification of the chromic acid titration method Soil Science 37 29-38

Walkley A (1947) A critical examination of a rapid method for determining organic carbon in soils - effect of variations in digestion conditions and of inorganic soil constituents Soil Science 63251-264

Woodard amp Curran Inc (WampC) 2005 Draft Technical Impracticability Evaluation Hows Corner Superfund Site Plymouth Maine January 2005

Response to EPA Comment 3 050205doc 6 of Woodard amp Curran (211941)

LIST OF ATTACHMENTS (Response to Comment 3)

Appendix B to Draft Technical Impracticability Evaluation Measurement of foe at Hows Corner (4 pages)

m

Response to EPA Comment 3 050205doc 7 of 11 Woodard amp Curran (211941)

Appendix B Measurement of foe of Rock Core at Hows Corner

There are two general approaches to measure the fraction of organic carbon (foe) in rock cores

bull Measurement of weight loss by ignition of organic matter bull Chemical oxidization of organic carbon to carbon dioxide and either

subsequent quantification of the oxidant used for the reaction or quantification of the carbon dioxide produced during this oxidation process

The weight loss method is subject to errors caused by volatilization of substances other than organic materials such as water hydroxides and mineral carbonates Quantification of foe by the weight loss method is particularly sensitive to the presence of carbonates in rock cores There are however weight loss methods that are designed to differentiate between organic carbon and the aforementioned interfering materials but they require considerable care and are less accurate at low foe values Hence the weight loss method was not well suited for measuring the foe of the rock core from Hows Corner

The chemical oxidation of organic carbon is much better suited for quantifying organic carbon in rock cores such as those from Hows Corner This method uses a strong chemical oxidant to oxidize organic carbon to carbon dioxide and then measures either the chemical oxidant used to oxidize the organic carbon or the quantity of carbon dioxide produced In addition this general approach is not subject to interference by volatilization of other constituents of the rock core

There are at least two such chemical oxidation methods

bull The method of Baccini which was described by Schwarzenbach amp Westall (1981) first acidifies the sample to eliminate interference by carbonates Then a strong oxidant is used to chemically oxidize the organic carbon to carbon dioxide The resulting carbon dioxide is subsequently reduced to methane and quantified using a flame ionization detector Unfortunately this method has not been described in detail in a referred journal Hence it is would not have been appropriate to use to characterize the foe in the Hows Corner rock core

bull The more commonly used method to quantify foe in rock core is the Walkley-Black method (1934) This method is preferred for RBCA and DODDOE projects and by the oil industry

The Walkley-Black method uses an excess of chromic acid to oxidize (digest) organic matter to carbon dioxide The remaining chromic acid that was not consumed during the oxidation of the organic carbon is then quantified by titration with ferrous sulfate The difference in chromic acid prior to and after the oxidation of the organic carbon represents the total chromic acid used to oxidize

Hows Corner TI Evaluation Page 1 January 13 2005 Appendix B

the organic carbon in the sample The latter can be calculated using the chemical stoichiometry of the reaction

The Walkley-Black method is very accurate for samples that contain less than 2 organic carbon matter The minimum detection limit (MDL) for the Walkley-Black method is 100 mgkg or an foe of 0001

Given the rock core at Hows Corner was expected to contain less than 2 organic carbon the Walkley-Black method was used to measure the foe from 19 different rock core samples collected from varying depths ranging from 11 to 90 feet

Table 1 provides a statistical summary of the aforementioned data

Table 1 Statistical summary of foe data from rock cores collected at varying depths

Statistical Parameter Calculated Value foe Minimum Detection Limit (MDL) 00010 Number of samples analyzed (n) 19 Average foe 00019 Median foe 00019 Geometric Mean foe 00019 Standard deviation of foe measurements 000033 Relative standard deviation 174 -+ 95 Confidence intervals 00012 to 00025

The data in Table 1 shows the following

bull The foe from the Hows Corner rock cores are statistically greater than the MDL of the Walkley-Black analytical method

bull The average and median values for the foe of the Hows Corner rock cores from varying depths are nearly identical indicating that there is little variability in the foe values in the source zone at the site

bull The standard deviation of these measurements is 000033 which is 174 of the average foe

bull The 95 confidence intervals of the foe of the rock core at Hows Corner are 00012 to 00025

The foe was also analyzed from three separate samples taken from the same rock core at a depth of 55 feet (Only one of these samples was included in the data summarized in Table 1) Table 2 shows the statistical repeatability of this type of analysis

Hows Corner TI Evaluation Page 2 January 13 2005 Appendix B

Table 2 Repeatability of analysis of foe from one rock core at 55 feet in depth

Statistical Parameter Calculated Value Number of samples analyzed (n) 3 Average foe 00016 Median foe 00015 Geometric Mean foe 00016 Standard deviation of foe measurements 000039 Relative standard deviation 240 -+ 95 Confidence intervals 00008 to 00024

The data in Table 2 shows the following

bull The percent relative standard deviation of these three analyses of foe from the same rock core at Hows Corner is 24

bull The 95 confidence interval of the foes measured in this particular rock core at Hows Conrer is 00008 to 00024

These results show that there is good repeatability in using the Walkley-Black method for analysis of the foe in the rock core at Hows Corner

References Schwarzenbach amp Westall (1981) Transport of nonpolar organic compounds from surface water to groundwater Laboratory sorption studies Environ Sci Tech 15 1360-1367

Walkley A I A Black (1934) An examination of Degtjareff method for determining soil organic matter and a proposed modification of the chromic acid titration method Soil Sci 37 29-37

Hows Corner Tl Evaluation Page S January 13 2005 Appendix B

Woodard and Curran PTS Laboratories PTS File No 34618

ORGANIC CARBON DATA (METHODOLOGY WALKLEY-BLACK)

PROJECT NAME PROJECT NO

SAMPLE ID

203-chip-13 203-chip-23 203-chip-27 203-chip-38 203-chip-42 203-chip-47 203-chip-52 203-chip-58 203-chip-69 203-chip-82 207-chip-11 207-chip-19 207-chip-24 207-chip-29 207-chip-35 207-chip-45 207-chip-55 207-chip-87 207-chip-90

207-chip-55 55-MS

55-MSMSD

Hows Corner NA

DEPTH ft

13 23 27 38 42 47 52 58 69 82 11 19 24 29 35 45 55 87 90

55 NA NA

MATRIX

Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip

Average Median

Geometric Mean Standard Deviation Relative Std Dev

+- 95 Confidence Interval n

Rock Chip Rock Chip Rock Chip

Average Median

Geometric Mean Standard Deviation Relative Std Dev

+- 95 Confidence Interval n

FRACTION ORGANIC CARBON

(gg)

170E-03 185E-03 185E-03 170E-03 240E-03 190E-03 230E-03 180E-03 170E-03 115E-03 195E-03 220E-03 220E-03 235E-03 135E-03 190E-03 205E-03 175E-03 160E-03

188E-03 185E-03 185E-03 327E-04

1739 123E-03 to

19

205E-03 130E-03 150E-03

162E-03 150E-03 159E-03 388E-04

2402 840E-04 to

3

2532E-03

2393E-03

Hows Corner Tl Evaluation Appendix B January 13 2005

Response to EPA-DEP Comment 4 Dated March 31 2005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

EPA-DEP Comment 4

Comment 4 Distribution of contaminants First the TI report seems based on the assertion that there is DNAPL at the source area yet it also appears to represent that the source area is small and the bedrock below 85 is competent (or less fractured) and less impacted by the release of contaminants Some of the confusion may result from using most recent data when that data is from several different sampling events over several years and there is no discernible difference in concentrations between shallow and deep bedrock or as in Section 421 where generally decreased generally increase generally similar and similar concentrations in four consecutive sentences leads to a muddled picture of the contaminant distribution

Second the report asserts that the distribution of contaminants over the entire plume has not changed with time but fails to support this conclusion with data again relying on data that is from different sampling dates for one composite representation

Response The likely presence of dense non-aqueous phase liquid (DNAPL) at the Hows Corner Site and the determination that the source area is small are not mutually exclusive and both are conclusions drawn from information obtained during field investigations The presence of DNAPL in the source area is based on the elevated concentrations of volatile organic compounds (VOCs) detected in the groundwater (WampC 2001 WampC 2002) The conclusion that the source area is small is based on the area in which VOCs in groundwater have been detected at concentrations that are considered to be indicative of the presence of DNAPL nearby Similarly the conclusion that fracture frequency decreases at depths greater than approximately 50 to 85 feet below ground surface was based on field observation during the RI field work The fact that zones with observed fractures exhibited higher hydraulic conductivities than zones without fractures coupled with the decreasing frequency of observed fractures with depth led to the conclusion that the hydraulic conductivity of the bulk rock decreases with depth

The most recent data from all wells were used to provide the maximum VOC data set size During the RI all of the previously-existing and then newly-installed monitoring wells were sampled along with several residential wells The RI sampling included up to 48 monitoring wells Subsequent to the RI and prior to the TI three rounds of monitoring were conducted to verify that the plume was stable 15 monitoring wells were sampled during each of the three rounds During the TI field investigation 29 wells were sampled for VOCs The sampled wells included all of the newly-installed wells and a subset of wells installed during the RI for a total of 29 monitoring wells By using most recent data VOC results from 53 monitoring wells were included in the evaluation (see table labeled Sampling Events for listing of monitoring wells) This approach was selected because there generally was little variation in the data from a particular location between years This is borne out by the attached individual plots of VOCs detected in shallow bedrock and deep bedrock for the Pre-ROD (December 1999January 2000) and Supplemental (May 2000) sampling events and for June 2001 January 2002 and April 2003 sampling events The Pre-ROD and Supplemental plots are similar to the subsequent plots from the 2001 2002 and 2003 sampling events

In addition to maps showing the spatial distribution of VOC data at a given time trend plots of the data from a particular location through time (attached) indicate that since the RI concentrations generally have been stable or have decreased Together the maps and trend plots and the data from which they were developed indicate that the distribution of contaminants over the entire plume has not changed appreciably with time

Response to EPA Comment 4 050305doc 1 of 26 Woodard amp Curran (211941)

REFERENCES

Woodard amp Curran Inc (WampC) 2001 Final Remedial Investigation Report Hows Corner Superfund Plymouth Maine July 2001

Woodard amp Curran Inc (WampC) 2002 Final Feasibility Study Report - Non-Source Area Groundwater Hows Corner Superfund Site Plymouth Maine Hows Corner Superfund Plymouth Maine July 2002

Response to EPA Comment 4 050305doc 2 of 26 Woodard amp Curran (211941)

LIST OF ATTACHMENTS (Response to Comment 4)

Table - Sampling Events 1999 - 2004 (2 pages)

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater Pre-ROD Sampling Event

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater Pre-ROD Sampling Event

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater Supplemental Sampling Event

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater Supplemental Sampling Event

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater June 2001

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater June 2001

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater January 2002

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater January 2002

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater April 2003

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater April 2003

Figure - Concentration Trends - Non-Source Area Wells MW-1B and MW-3B

Figure - Concentration Trends - Non-Source Area Wells MW-13DB and MW-16DB

Figure - Concentration Trends - Non-Source Area Wells MW-16IB and MW- 108D

Figure - Concentration Trends - Non-Source Area Wells MW-108S and MW-112D

Figure - Concentration Trends - Non-Source Area Wells MW-112S and MW-114D

Figure - Concentration Trends - Non-Source Area Wells MW-114S and MW-115D

Figure - Concentration Trends -Source Area Wells MW-2DB and MW-2IB

Figure - Concentration Trends -Source Area Wells MW-102S and MW-103D

Figure - Concentration Trends -Source Area Wells MW-103S and MW-104D

Figure - Concentration Trends -Source Area Wells MW-104I and MW-106D

Figure - Concentration Trends -Source Area Wells MW-106S

Response to EPA Comment 4 050305doc 3 of 26 Woodard amp Curran (211941)

I I

El I

II I I 1 I

I

i

Event Baseline Case ID WC-01 WC-01

Well Date Aug-99 Oct-99 LOT10 1 LOT1-1 1 LOT11-4 LOT14 1 LOT15 1 LOT15-1 1 LOT16 1 LOT16-1 1 LOT17 1 LOT18 1 LOT19 1 LOT2 LOT20 1 LOT21-10 1 LOT21-11 1 LOT21-12 1 LOT21-13 1 LOT21-14 1 LOT21-2 1 LOT21-5 1 LOT21-7 LOT21 -8 1 LOT21-9 1 LOT23 1 LOT24 1 LOT28-1 1 LOT28-2 1 LOT28-3 1 LOT28-4 1 LOT28W 1 LOT30 1 LOT30-1 1 LOT30-2 1 LOT30-3 1 LOT30-4 1 LOT30-5 LOT31 LOT35 1 LOT41 1 LOT42-1 1 LOT43-1 1 LOT43-4 1 LOT6-1 1 LOT67 1 LOT6-7 1 LOT6-8A 1 LOT6-8B 1 LOT80-1 1 LOT82 1 MW-101D MW-1011 MW-101S MW-102D MW-102S MW-103D MW-103S MW-104D MW-1041 MW-104S MW-105D MW-106D

Groundwater Sampling Location Summary 1999 - 2004xls

Sampling Events 1999-2004

Hows Corner Superfund Site Plymouth Maine

Supplemental 2001 2002 2003 Pumping 2004 Pre-ROD Rl Sampling Sampling Sampling Test Sampling WC-03 WC-09 WC-25 WC-30 WC-42B WC-56 WC-58 Dec-99 May-00 Jun-01 Jan-02 Apr-03 Sep-04 Sep-04

1

1 1 1

1 1 1 1 1

1 1

1

1 1

1 1 1

1 1 1 1 1

1

1 1

1 1 1 1

1

1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

Sampling Events 1999-2004

Hows Corner Super-fund Site Plymouth Maine

Supplemental 2001 2002 2003 Pumping Event Baseline Pre-ROD Rl Sampling Sampling Sampling Test

Case ID WC-01 WC-01 WC-03 WC-09 WC-25 WC-30 WC-42B WC-56

ll

Well Date Aug-99 Oct-99 Dec-99 May-00 Jun-01 Jan-02 Apr-03 Sep-04 MW-106S 1 1 1 1 1 MW-107D 1 1 MW-108D 1 1 1 1 1 MW-108S 1 1 1 1 1 MW-110D 1 1 MW-111D 1 1 MW-112D 1 1 1 1 1 MW-112S 1 1 1 1 1 MW-113D 1 1 MW-114D 1 1 1 1 1 MW-114S 1 1 1 1 1 MW-115D 1 1 1 1 1 MW-12DB 1 1 1 MW-12SB 1 1 1 MW-13DB 1 1 1 1 1 1 MW-13SB 1 1 1 MW-14DB 1 1 MW-14SO 1 1 MW-15DB 1 1 1 MW-15SB 1 1 1 MW-16DB 1 1 1 1 1 1 MW-16IB 1 1 1 1 1 1 MW-16SO 1 1 MW-17DO 1 1 1 MW-17SO 1 1 1 MW-1B 1 1 1 1 1 1 MW-203D MW-203S MW-204D MW-204S MW-205 MW-206D

I MW-206S MW-2DB 1 1 MW-2DDB 1 1 MW-2IB 1 1 1 1 1 1 MW-3B 1 1 1 1 1 1

I MW-4O 1 1 1 MW-5B 1 1

II MW-6DB 1 1 1 MW-6SB 1 1 1 MW-8DB 1 1 1 MW-8SB 1 1 1

II PW-207 1 SEEP-1 1 SUBTOTAL - RESIDENTIAL 44 25 0 2 0 3 0 SUBTOTAL - MONITORING 22 48 41 15 15 15 1

Total 3 66 73 41 17 15 18 1

I Included in most recent data

I Notes 1 - Overburden well not included in most recent data for plotting

2 - Tetrahydrofuran and 2-Butanone were the only two compounds detected in this well and are thought to be the result of well repair not included in most recent data for plotting

3 - Not included in most recent data for plotting

2004 Sampling

WC-58 Sep-04

1

1 1

1 1

1 1 1

1

1 1

1 1 1 1 1 1 1 1 1

1 1

1

0 29

29

Groundwatef Sampling Location Summary 1999 - 2004xls

I

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

monitoring well Figure 4-14 total VOC contour (ugl) - December 1999January 2000 Distribution of Total VOCs in

Note SW-113 is located downstream of SEEP-1 Shallow Bedrock Groundwater total concentration of detected VOCs ND= not detected these two locations were sampled during the Pre-ROD Sampling Event

Baseline Sampling Event in OctoberNovember 1999 Hows Corner Superfund Site Surface Water Sampling Location A Plymouth Maine Seep Sampling Location laquo- WOODARD ampCURRAN

995037wipri reportepa ri interim final feb 2001cadd drawingsfinalfig 4-14

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

0 300 600 I

FEET

Q residential well Figure 4-16 monitoring well Distribution of Total VOCs in

Deep Bedrock Groundwater total VOCs contour (ugl) Pre-ROD Sampling Event

active residential wells with lot number Hows Corner Superfund Site 2deg42deg Plymouth Maine total concentration of detected VOCs ND= not detected WOODARD ampCURRAN Enyinaaring bull Science bull Operations bull

995037wipri reportepa ri interim final feb 2001cadd drawingsfinalfig4mdash16

PLYMOUTH POND

PLYMOUTH POND

1 628Tl7MW-2bB 12135

PLYMOUTH POND

monitoring well Figure 4-20

V total VOC contour (ugl) - June 2000 Distribution of Total VOCs in Shallow Bedrock Groundwater

| 34 | total concentration of detected VOCs ND= not detected NA = not analyzed Supplemental Sampling Event Note SW-113 is located downstream of SEEP-1 Hows Corner Superfund Site

Surface Water Sampling Location these two locations were sampled during the Plymouth Maine Baseline Sampling Event in OctoberNovember 1999 Seep Sampling Location WOODARD amp CURRAN

Engineering bull Science - Operations bull 995037wipri reportepa ri interim final feb 2001 cadd drawingsfinalfig 4-20

residential well Figure 4-22 Distribution of Total VOCs in

monitoring well Deep Bedrock Groundwater

total VOCs contour (ugl) Supplemental Sampling Event

Hows Corner Superfund Site

total concentration of detected VOCs ND= not detected NA = not analyzed Plymouth Maine

WOODARD amp CURRAN

995037wipri reportepa-ri interim final feb 2001cadd drawingsfinalfig 4-22 Engineering bull Science - Operations bull

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

FEET

Shallow Monitoring Well

Deep Monitoring Well

C Detected Concentration ND = Not Detected Figure 1-XS Distribution of Total VOCs in Shallow Bedrock Groundwater

Pumping Well

17-Acre Property Boundary Concentration Contour (ugl)

June 2001 Hows Corner Superfund Site

Plymouth Maine WOODARDampCURRAN

-i^rhvj bull Scbncn bull Operations bull 211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0601 dwg04-20-05

PLYMOUTH POND Hopkins Road V

O

PLYMOUTH POND

PLYMOUTH POND

o

0 300 600 mdashfa FEET

Shallow Monitoring Well bull bull - 17-Acre Property Boundary Figure 1-XD

Deep Monitoring Well 1 I Detected Concentration ND = Not Detected Distribution of Total VOCs in Deep Bedrock Groundwater

-mf- Pumping Well June 2001 Residential Well Hows Corner Superfund Site

Plymouth Maine i h Surface Water Sampling Point

g WOODARD ampCURRAN _ ^ _ ^ _ _ yen_ rj i|Hlaquorlny bull Science bull Opt

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0601 dwg04-20-05

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

Shallow Monitoring Well

Deep Monitoring Well

Detected Concentration ND = Not Detected Figure 1-YS Distribution of Total VOCs in Shallow Bedrock Groundwater

Pumping Well

17-Acre Property Boundary Concentration Contour (ugl)

January 2002 Hows Corner Superfund Site

Plymouth Maine WOODARD amp CURRAN Engineering Science- Operations bull

211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0102dwg04-20-05

PLYMOUTH POND

PLYMOUTH POND

Site Pand^ laquoum-laquoBTuitaraquo tLV

vVlf-(

PLYMOUTH POND

0 300 600 ^ = FEET

Shallow Monitoring Well mdashbullbullbull 17-Acre Property Boundary Figure 1-YD - A - Deep Monitoring Well FT Detected Concentration ND = Not Detected Distribution of Total VOCs in

Deep Bedrock Groundwater Pumping Well January 2002 Residential Well Hows Corner Superfund Site

Plymouth Maine Surface Water Sampling Point

WOODARD ampCURRAN Engineering Sciencs- Operations bulli Si

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0102dwg04-20-05

- m j

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND j A O-shy

Shallow Monitoring Well E Detected Concentration ND = Not Detected Figure 1-ZS Distribution of Total VOCs in

Deep Monitoring Well Shallow Bedrock Groundwater

Pumping Well Hows Corner

April 2003 Superfund Site

17-Acre Property Boundary Plymouth Maine Concentration Contour (ugl) r WOODARD ampCURRAN

Engineering bull Science bull Operations bull 211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0403dwg04-20-05

s S pound

PLYMOUTH POND

PLYMOUTH POND

- -

5 PLYMOUTH POND

Jo

FEET

ft Shallow Monitoring Well mdashbullbullmdash 17-Acre Property Boundary Figure 1-ZD Deep Monitoring Well I 1 I Detected Concentration ND = Not Detected Distribution of Total VOCs in

Deep Bedrock Groundwater Pumping Well April 2003

Q) Residential Well Hows Corner Superfund Site Plymouth Maine

(T) Surface Water Sampling Point WOODARD ampCURRAN poundKk EnginawtirKj bull Science - Operations bull

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0403dwg04-20-05

0 Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

B MW-1B

I 12000

PCE

B 10000 Total VOCs

I

i 2000

i 0 Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

c MW-3B

G 2000

1800

B PCE

1600 Total VOCs

1 I I E

il-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

G E

211941

El

I I z E

80

Concentration Trends shy Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-13DB

Total VOCs

c i i c o

Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

MW-16DB

30

c i c c I c o

Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99

PCE

Total VOCs

Jul-01 Jul-03

211941

O bi

c Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

I MW-16IB

i 35

3

c Total VOCs

lt- 2 5

0 | gt

o

1 sectI

c c 0 4

Jul-90 Jul-92 Jul-94 Jul-96 Jul-98 Jul-00 Jul-02 Jul-04

I I MW-108D

I 12

PCE 10

Total VOCs c oc 3

E E I 0

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

E 211941

c Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

fi MW-108S

I I 40

PCE 35

Total VOCs

30

I f 26

20 I o

I 15

10

c Dec-99 Dec-00 Dec-01 Dec-02 Dec-03 I 0

I MW-112D

c 35 - imdash

I A3 shyTotal VOCs

o c

E 1 2

I

ition

B 1 ^

-i c 3

0 Dec-99 Dec-OO Dec-01 Dec-02 Dec-03

211941

I

i

I

cII

Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-112S

08

PCE

Total VOCs 06

o 04

02

0 Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

MW-114D

o

12000

10000

8000

6000

PCE

Total VOCs

4000

2000

i

ccEIIc

i

i

E

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

211941

Con

cent

ratio

n (

ug

l)

E Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

I MW-114S

E A5000 -- Total VOCs

- 4000

0 3000

2000

i 1000

i n shy

Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

MW-115D

c PCE

Total VOCs

c E

o

C c

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03 I 0

211941

IepoundII

EIEIIGICCIccc

30000

25000

20000

o bullsect 15000 b

o 10000 U

5000

0 Aug-99

25000

20000

5000

0 Aug-99

211941

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-2DB

PCE

Total VOCs

Aug-01 Aug-03

MW-2IB

PCE

Total VOCs

Aug-01 Aug-03

IDIBI

ii EIDIISIBIG C

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-102S

6000

5000 PCE

Total VOCs

4000

O 3000

2000

1000

0 Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

MW-103D

16000

~ 14000 ugt 3- 12000 o

^ 10000

sect 8000

O 6000

4000

2000

PCE

Total VOCs

0Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

211941

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

G MW-103S

I I

ampo

12000

10000

E sectc

S

8000

6000

4000

2000

0Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

G I 6000

MW-104D

i 5000

PCE

Total VOCs

i i c

2000

1000

Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

E I

211941

cIccIG

IIBCccBcIc

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-1041

PCE Total VOCs

a 25000

0 20000

a 15000

10000

5000

0 Jan-OO Jan-01 Jan-02 Jan-03 Jan-04

MW-106D

3000

2500 PCE

Total VOCs

=sect 2000

o bullsect 1500

1000

500

0 Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

211941

c Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

c MW-106S

I PCE

Total VOCs

i

i Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

i

i i i E

C

211941 c

Response to EPA-DEP Comment 5 Dated March 312005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

iiw

EPA-DEP Comment 5

Comment 5 Matrix Diffusion The report as well as other proponents of matrix diffusion suggest that depletion of DNAPL (Section 5112 page 5-15) needs to be achieved While that might be the ideal the goal is to achieve performance standards and that goal may be attainable while there is residual contamination in the rock perhaps even DNAPL globules The low bedrock matrix porosity (page 1-15) the high permeability values (page 4-4) the relative flux of the groundwater (page 5-5) and the decrease in surface area and out of the mainstream pockets (appendix C-4) all suggest that the diffusion out of the rock matrix would be insubstantial relative to the regional flux of groundwater through the Site

Response The TI Evaluation Report does not explicitly consider or rely upon matrix diffusion as a basis for requesting a TI Waiver for a portion of the Hows Corner Site The technical literature provides documentation that matrix diffusion can be a significant process that affects chemical transport and groundwater remediation timeframes in unconsolidated and consolidated media including fractured rock (US EPA 1989 Freeze and Cherry 1979 Pankow and Cherry 1996 Fountain 1998) Back diffusion of contaminants from the matrix porosity of the fractured rock can prolong the time necessary to achieve groundwater cleanup goals particularly for compounds such as PCE for which the cleanup goal is a low concentration It is our expectation that matrix diffusion has occurred at the Hows Corner Site and that back diffusion of PCE from the rock matrix will also occur Although the extent to which matrix diffusion is occurring at the Hows Comer Site has not been determined and that lack of knowledge contributes to uncertainty regarding the cleanup times at the Site the effect of matrix diffusion is to lengthen rather than shorten the time required for remediation

REFERENCES

Fountain JC 1998 Technologies for Dense Nonaqueous Phase Liquid Source Zone Remediation Ground-Water Remediation Technologies Analysis Center Technology Evaluation Report TE-98-02 December

Freeze RA and Cherry JA 1979 Groundwater Prentice-Hall Inc Englewood Cliffs NJ 07632 p 410-412

Pankow J F and Cherry J A 1996 Dense Chlorinated Solvents Waterloo Press Portland OR 97291-1399 p 67-88

US EPA 1989 Transport and Fate of Contaminants in the Subsurface EPA6254-89019 p 17-18

Response to EPA Comment 5 050305doc 1 of 1 Woodard amp Curran (211941)

WOODARD amp CURRAN Maine Massachusetts New Hampshire Connecticut Florida Operational offices across the US 1-800-426-4262 www woodardcurran com

Page 23: SDMS DocID 251749 - Records Collections · 2020-06-13 · CORPORATE OFFICES: Maine, Massachusetts, New Hampshire, Connecticut New, York, Florida Engineering • Science • Operations

I

E Northeast Geophysical Services Borehole Geophysical Log Date logged 072704

I MW-205

Plymouth Maine

Flowmeter Measurements Temperature (C) Acoustic Televiewer (In gpm) I ~l (Interpreted)

I 85 10 Caliper (inches) 95

Dip in D g r laquo Resistance (Ohms) Spo ontaneous Potential (mV PCE Total VOCs 3 0 16 4 0 4 5 ) 20 40 60 80 10 00 2000 30 00 4VJ 400 -3 laquo

i i i i 1 i i I i 11 4 0 D 1 I I ugL ugL

C h

iii Ambient Flowmetar pumping

Flowmeter 1 25 gprn

I bull$bull

i

I rmdash magnetic 1 north ^^^^ 1 VI f

10 ~ I C x 10 bull - 10 bullbull

4 5 6mdashmdash f 1000B 11448 noisy nodi a raquo ^

mdash 5rt mdashi mdash Oft pound) 1100B 12509

cjmdash1 007

-

i i i 1

en

8 B a B

30 mdash

-

40 shy

-mdash I -

50 -_

__NF lt005

- 30 - - 3 0 it 34V

MO P26 V S) 1300B 13776 _ N F NF

26

40 bull - 40 bull 7-40 gt J Vf1 cX

) -j -

_ N F NF 50 c bull - 50 ^ 7-50

i I

I

c

B pound 60 - 6 0 7 60 - 7-60 a i 1

_ N F NF i Si f f 70 -_ bull70 bull - 70 shyC I 9

-m bull - shyA

_ N F NF 80 80 -j bull80 bull - 80 - C- 33 34

bull

5-i r

i 1

J r

Ck

_ N F NF 9 0 90 - - 90 shy

i bullCshy

J rK bull

100 -j ^ Likely or possible bull100- - 100- I -100

transmissive zone bull - ^ bull shy] |

1 1 1 1 1 1 1 I 1 i i i 1 i i 1 1 0 20 40 SO SO 10 20 30 40 50 Dip in Degrees 30 4 0 Fluid Resistivity (ohmmeters) Thlaquo dip direction is indicated

by the line extern r g from the circle The strike of he feature is 90 degrees from ihis

The acoustic televiewer graph displays the most

I Borehole Geophysical Log Packered Interval August2004 prominent features selected from the acoustic televiewer

Groundwatcr samples were oollccled by Woodard amp Cufran orgt S172004 log The location dip angle and dip direction of ins slsctsd MW-205 features are approximate Refelt to the televiewer log of this wall for more precise detail Plymouth Maine Date logged 072704

I

C

I Northeast Geophysical Services Borehole Geophysical Log Date logged 072704

I MW-206

Plymouth Maine

Flowmetor Measurements Temperature (C) Acoustic Televiewer | I r T i i i i i i i i i i i i i i r I |(in gpm) (Interpreted)

I 75 8 flS 9 95

Caliper (inches) Resistance (Ohms) Spontaneous Potential (mV) Dip In Degress PCE Total VOCs 30 35 40 4 5 0 20 40 M 90 4500 5500 6500 ugL ugL I i i

I I

- 1 0

I - 2 0

I 2900B 32401

i i L

E 0

i 6300B 68901

i I 0 20 40 SO 80

20 30 40 50 Dip in Dlaquogralaquos

amp 4 a Fluid Resistivity (ohrnmeters) The dip dirertion is indicated Likely or possible by iho line extending from the transmissive zone circle The striKe of the feature

is 90 degrees from tNs

Borehole Geophysical Log Packered Interval August 2004

E amples were collected by Woodard amp Cunan oo SM82004 log Thraquo location 4p angle and dip direction of the sloeled MW-206 feature are approximate Refer to the televiewer 109 of this well for more precise detail Plymouth Maine Date logged 072704

C

I Northeast Geophysical Services Borehole Geophysical Log

Date logged 082304 PW-207

I Plymouth Maine

Fiowmeter Measurements Temperature (C) Acoustic Televiewer

I (in gpm) (interpreted)

75 8 85 9 95 Caliper (inches) Resistance f0tims) Spontaneous Potential (mV) Dip in Degrees PCE Total VOCs

55 60 0 20 40 SO 80 ugL ugL I I I I I I I

Ambienl Fiowmeter pumping Flewmater

magnetic - 10 - - 1 0

north

i - 20 - - 2 0

1300 1410

i - 30 - - 3 0

i tf

5400 5802 - 40 - - 4 0

B - 50 - - 5 0

I 18000 19234

- 60 - - 6 0

I 12000 13085

- 70 - - 7 0

- 8 0

i - 9 0 19000 20354

G - 100- -100

I 110 110 bull110

0 20 40 60 SO 10 20 30 Dip m Degrees

Fluid Resistivity (ohmmeters) I 50

The dip direction is indicated by ihe line extending from the circle The strike of the fealure is 90 degrees from this

Borehole Geophysical Log

G Packorod Interval August 20(M log The location dip angle and dip dirlaquocton or the sleeted Groundaier samplss were ooliecled by Woodard i Curran on ampt24f2ltXM PW-207 failures are approximate Reter to the televiewer log of this wlaquoll for more precise detail PlyPIOUth Maine Date logged 082304

I

Table XX Packer Permeability and Packer Sampling Results for Potential Fracture Intervals

1

WellID MW-101D MW-101D MW-101D MW-101D MW-101D MW-101D MW-101D MW-101D MW-101D MW-101D MW-I01D MW-101D MW-101D MW-102D MW-102D MW-I02D MW-102D MW102D MW-102D MW-102D MW-102D MW-102D MW-I02D MW-102D MW-102D MW-102D MW-103D MW-103D MW-103D MW-103D MW-I03D MW-103D MW-103D MW-103D MW-103D MW-103D MW-103D MW-103D MW-I03D MW-104D MW-104D MW-104D MW-104D MW-I04D MW-104D MW-104D MW-104D MW-104D MW-104D MW-104D MW-105D MW-105D MW106D MW-106D MW-106D MW-107D MW-107D

1999 Drilling Program

Hows Corner Superfund Site Plymouth Maine

Potential Fracture Top Of Bottom 6 Depth to lt Topof i Interval from Packer Packer Middle of Elevation Hydraulic bull PCE

GS ELEV 1 Rock Drilling Interval Interval Interval of Interval Conductivity Concentration (ft msl) (ft msl) TEST (ftbgs) (ftbgs) r(ftbgs) ( f t b (ft mil) (cmsec) (raquogL)

4339 4329 13 28-29 33-3537-39 271 376 324 4016 OOOE+00 4339 12 37-3444-46 380 485 433 3907 157E-04 4339 11 488 593 541 3799 132E-04 4339 10 60-61 578 683 631 3709 OOOE+00 4339 9 678 783 731 3609 I79E-05 4339 8 778 883 831 3509 106E-05 4339 7 880 985 933 3407 243E-05 4339 6 990 1095 1043 3297 339E-06 4339 5 1090 1195 1143 3197 OOOE+00 4339 4 1190 1295 1243 3097 OOOE+00 4339 3 1365-1375 1290 1395 1343 2997 OOOE+00 4339 2 147-157 1390 1495 1443 2897 580E-05 4339 1 147-157 1470 1575 1523 2817 741E-05 43161 43061 13 166 271 219 4098 333E-04 43161 12 30-3136-40 260 365 313 4004 I54E-05 43161 11 36-4041-43 362 467 415 3902 548E-05 43161 10 470 575 523 3794 598E-05 43161 9 570 675 623 3694 197FOS 43161 8 670 775 723 3594 OOOE+00 43161 7 770 875 823 3494 891 E-05 43161 6 83-94 870 975 923 3394 139E-05 43161 5 970 1075 1023 3294 123E-04 43161 4 1070 1175 1123 3194 526E-06 43161 3 1170 1275 1223 3094 138E-05 43161 2 1270 1375 1323 2994 671E-06 43161 1 1370 1475 1423 2894 OOOE+00 42997 42497 13 18-19 170 275 223 4077 OOOE+00 42997 12 260 365 313 3987 766E-05 42997 11 360 465 413 3887 727E-05 42997 10 460 565 513 3787 192E-05 42997 9 560 665 613 3687 752E-05 42997 8 660 765 713 3587 778E-05 42997 7 85-86 763 868 816 3484 260E-05 42997 6 860 965 913 3387 289E-05 42997 5 102-103 960 1065 1013 3287 102E-04 42997 4 1060 1165 1113 3187 522E-06 42997 3 1160 1265 1213 3087 520E-06 42997 2 129-130 1260 1365 1313 2987 960E-04 42997 1 1360 1465 1413 2887 OOOE+00 43372 42922 11 35-37 42-45 350 455 403 3935 684E-04 43372 10 460 565 513 3825 500E-05 43372 9 560 665 613 3725 106E-05 43372 8 72-74 660 765 713 3625 204E-05 43372 7 760 865 813 3525 872E-06 43372 6 860 965 913 3425 467E-06 43372 5 960 1065 1013 3325 200E-05 43372 4 1060 1165 1113 3225 354E-05 43372 3 125-130 1160 1265 1213 3125 157E-05 43372 2 125-130 1260 1365 1313 3025 337E-04 43372 1 1365 1465 1415 2922 689E-06 43052 43002 2 54-58 490 595 543 3763 124E-05 2100 43052 1 139-140 145-146 1367 1472 1420 2886 154E-04 1400 43291 4391 3 bullI133 260 365 313 4017 439F06 43291 2 77-78 760 865 813 3517 230E-03 400 43291 1 143-144 1355 1460 1408 2922 971E-06 350

29958 27258 4 450 555 503 2493 OOOE+00 (21)A 29958 3 103-105 1000 1105 1053 1943 752E-04 (063)A

Table XX Packer Permeability and Packer Sampling Results for Potential Fracture Intervals

1999 Drilling Program

Hows Corner Supcrfund Site Plymouth Maine

gtbull i Potential Fracture Top _OfBot Bottom of Depth to ltbull Top of Interval from f Packer Packer Middle Of

GS ELEV lt Hock Drilling interval Interval Interval WeD ID ft msl) (ft msl) TEST (ftbgs) ltft$gs) (ftbgs) (ftbgs)

MW-107D 29958 2 128-130 1200 1305 1253

MW-107D 29958 1 139-141 1350 1455 1403

MW-108D 31904 31104 6 35-36 300 405 353 MW-108D 31904 5 60-62 550 655 603

MW-108D 31904 4 80-83 750 855 803

MW-108D 31904 3 118-119 123-124 1150 1255 1203

MW-108D 31904 2 147-149 1440 1545 1493

MW-108D 31904 1 1700 1805 1753

MW-110D 40576 40426 2 21-31 210 315 263 MW-110D 40576 1 148-154 1460 1565 1513 MW-I11D 40519 4 70-71 650 755 703

MW-111D 40519 3 79-82 84-86 780 885 833 MW-I11D 40519 2 97-102 950 1055 1003 MW-111D 40519 1 1370 1475 1423

MW-112D 3027 2942 4 42-52 420 525 473 MW-112D 3027 3 850 955 903 MW112D 3027 2 1100 1205 1153 MW-112D 3027 1 135-136 140-141 1340 1445 1393

MW-113D 43085 43085 5 250 355 303 MW-I13D 43085 4 47-49 460 565 513 MW-113D 43085 3 73-74 700 805 753 MW-113D 43085 2 1050 1155 1103 MW-113D 43085 1 1380 1485 1433

MW-114D 42394 41594 4 48-49 450 555 503 MW-114D 42394 3 79-81 740 845 793 MW-114D 42394 2 121-129 1250 1355 1303 MW-114D 42394 1 134-142 1350 1455 1403

MW-115D 4035 4035 4 300 405 353 MW-1I5D 4035 3 70-71 650 755 703 MW-115D 4035 2 1150 1255 1203 MW-115D 4035 1 1400 1505 1453

LOT-28W 382 7 450 555 503 LOT28W 382 6 550 655 603 LOT-28W 382 5 650 755 703 LOT28W 382 4 750 855 803 LOT-28W 382 3 850 955 903 LOT-28W 382 2 950 1055 1003 LOT-28W 382 1 1055 1155 1105

NOTES cmsec = centimeters per second ft bgs = leet below ground surface It msl = feet below mean sea level lt = not detected at indicated reporting limil A = detected below laboratory PQL ( ) = detected below reporting limits

Elevation of Interval

(ft nisi) 174

159

283gt 2588

2388

1988

1698

1438

3795 2545 3349 3219 3049 2629

2555 2125 1875 1635

4006 3796 3556 3206 2876

3737 3447 2937 2837

3683 3333 2833 2583

3318 3218 3118 3018 2918 2818 2715

Hydraulic Conductivity

(cmsec)

323E-05

208E-05

471E-03

471E-03

624E-05

3I6E-05

264E-05

261 E-05

OOOE+00 200E-04 953E-05 OOOE+00 OOOE+00 212E-05

361 E-05 410E-06 2gQE06 292E-05

786E-05 124E-05 151 E-05 822E-06 82IE-06

858E-05 I69E-05 352E-03 866E-05

223E-05 394E-06 122E-05 525E-06

831 E-05 182F-05 L62E-05 129E-05 190E-05 890E-04 981 E-04

PCEraquo Concentration

(ugL)

lt5

(14A)

98 11

15

22

11

30

200 (62)A

110 210 300 240

(44)A (23)A

5

350 190 129 230

2200 1900 2600 2600

(17)A (16)A (19)A

96

Table XX Packer Permeability and Packer Sampling Results for Potential Fracture Intervals

2004 Drilling Program

Hows Corner Superfund Site Plymouth Maine

Top of Bottom of Depth to Midpoint

t K

ELEV (ft Potential Transmissive Zones Packer Interval

Packer Interval

Middle of Interval

Elevation of interval

Hydraulic Conductivity

PCE Concentration

Well ID msl) TESTr (ft bgs)- (ftbgs) (ftbgs) (ftbgs) (ft msl) (cmsec) (ogt) MW-203D 43227 4 277279 24 32 28 4043 667E-05 44

3 408415420 39 49 44 3883 593E-05 170 2 526 530 49 57 53 3793 101E-04 140 I 828830842 80 88 84 3483 701E-05 130

MW-204D 43262 5 295 300 26 34 30 4023 902E-05 220 4 463496513516 45 53 49 3833 119E-04 540 3 681685688 63 71 67 3653 OOOE+00 2 758 76 2 71 79 75 3573 309E-05 260 I 88 96 92 3403 OOOE+00

MW-205 42389 3 164 166 168 15 20 175 4148 OOOE+00 1000B 2 302305312 30 35 325 3998 107E-04 1300B 1 40 45 425 3898 OOOE+00

MW-206D 43007 5 17 72 195 4128 291E-05 4 296 302 307 29 34 315 4008 940E-05 2900B 3 522 52 57 545 3778 944E-07 2 656 64 69 665 3658 353E-06 1 92392793 4939 91 96 935 3388 614E-05 6300B

PW-207 43477 5 184622162819 18 29 235 4088 209E-05 1300 4 3508 32 43 375 3948 568E-06 5400 3 53325341542154325559 50 61 555 3768 821E-05 18000

6359 61 72 665 3658 866E-06 12000 1 8685 84 89 865 3458 213E-05 19000

NOTES cmsec = centimeters per second ft bgs = feet below ground surface ft msl = feet above mean sea level B = detected in lab blank

Table XX Orientation Permeability and Groundwater Sampling Results for Transmissive Features

2004 Drilling Program

Hows Corner Superfund Site Plymouth Maine

Borehole Geophisical Feature depth Dip True Dip True Transmissive Log Feature (Feet) Degrees Azimuth Strike bullvgt(Ltk|iy^

Number v Tosftble) v MW-203 5 277 64 337 67 Likely

6 279 59 11 281 Likely 8 352 14 177 87 Likely 11 381 46 96 6 Possible 12 408 35 271 1 Possible 14 415 57 250 340 Possible 15 420 58 202 292 Likely 18 526 52 75 345 Likely 19 530 52 82 352 Likely 28 828 48 75 345 Likely 29 830 52 17 287 Likely 30 830 56 233 323 Possible 31 842 50 130 40 Likely

MW-204 4 295 15 147 57 Likely 5 300 43 91 1 Likely 11 439 31 80 350 Possible 12 440 46 219 309 Possible 14 463 50 358 88 Likely 15 496 34 198 288 Likely 16 513 54 17 287 Likely 17 516 33 14 284 Likely 25 681 39 359 89 Possible 26 685 22 45 315 Possible 27 688 35 73 343 Possible 32 758 45 236 326 Likely 33 762 46 306 36 Likely

MW-205 5 164 69 106 16 Possible 6 166 78 165 75 Possible 7 168 82 115 25 Possible 8 168 68 116 26 Possible 12 215 46 222 312 Possible 13 217 75 62 332 Possible 14 219 29 32 302 Possible 16 237 69 250 340 Possible 17 256 73 353 83 Possible 18 272 44 202 292 Possible 21 299 37 196 286 Possible 22 302 31 206 296 Possible 23 305 59 48 318 Likely 24 312 63 42 312 Likely

MW-206 1 264 37 181 271 Likely 2 296 69 217 307 Likely 3 302 66 233 323 Likely 4 307 64 224 314 Likely 8 342 62 259 349 Likely

jjHydraulic GoiDanctilyity j(cmsecjw

667 E-05

593 E-05

101 P04

710 E-05

902 E-05

119 E-04

0

309 E-05

0

107 E-04

94 E-05

PCE (ugL)

44

170

140

130

220

540

260

IOOOB

1100B

1300B

2900B

STotal vVoCsv tig1)

84

234

192

183

2636

6436

3073

11448

12509

13776

32401

PCEyo dfCTotaf

52

73

73

7 1

83

84

85

87

88

94

90

Table XX Orientation Permeability and Groundwater Sampling Results for Transmissive Features

2004 Drilling Program

Hows Corner Superfund Site Plymouth Maine

Borehole Geophisical Feature deptt raquoip True pip True Transraissive Log Feature (Feet) shy Degrees Azimuth Strike (tikely

Number raquo Possible) 22 522 57 54 324 Possible 25 656 40 82 352 Possible 32 871 59 151 61 Possible 33 883 53 185 275 Possible 34 895 7 175 85 Likely 35 899 53 90 0 Likely 36 902 49 184 274 Likely 37 923 9 175 85 Likely 38 927 42 206 296 Likely 39 934 48 167 77 Likely 40 939 26 180 90 Likely

PW-207 1 1846 33 167 77 Likely 4 2216 49 289 19 Possible 7 2819 59 265 355 Possible 11 3508 55 189 279 Possible 18 5332 43 305 35 Likely 19 5341 51 30 300 Likely 20 5421 20 254 344 Likely 21 5432 39 301 31 Likely 23 5559 52 302 32 Likely 25 6359 24 182 272 Possible 29 8049 77 231 321 Possible 30 8685 78 38 308 Likely 32 9334 29 194 284 Likely

NOTES

B = detected in lab blank

Hydraulic Conductivity

(cmsee) 944 E-07 353 E-06

614 E-05

209 E-05

568 E-06

821 E-05

866 E-06

213 E-05

bulltCE (ugL)

6300B

1300

5400

18000

12000

19000

Total VOCs (ug1)

68901

1410

5802

19234

13085

20354

PCE of Total VOCs

9 1

92

93

94

92

93

Response to EPA-DEP Comment 3 Dated March 312005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

lit

EPA-DEP Comment 3

Comment 3 The reported f values and resultant Kd values There remains doubt that the values used in the flushing model accurately reflect the propensity for PCE to sorb to the bedrock The ^ values presented in Appendix B may be unrealistically high because the bedrock samples may have contained organic carbon that was unavailable for sorption The reported f values are only qualitative estimates of the organic carbon content of the bedrock samples The Walkley and Black organic carbon measurement method is quick and simple but the results obtained cannot be considered quantitative because it requires a correction factor which often results in erroneous values it assumes the organic carbon has an average valence of zero oxidizable and reducible constituents such as chloride ferrous iron and manganese oxides interfere with the results and the errors introduced by interference are potentially greater when the organic carbon content is low at low f values it is not clear that organic carbon is controlling PCE sorption (Schwarzenbach and Westall 1981 Mackay et al 1986 Fetter 1999)

In order to derive a Kd-based retardation factor that is reasonable given the reported f values and the rapid advance of the PCE plume described on pages 4-11 and 4-12 the flushing model requires a bulk density to porosity ratio that is roughly two orders of magnitude higher than the actual ratio for the Hows Corner bedrock (page 4-4) This apparent discrepancy needs to be addressed

Response This comment raises several concerns about the collection and analysis of samples for fraction of organic carbon (f^) the quality of the resulting data and the implications of the use of those data for estimation of the retardation of groundwater contaminant movement Results of bedrock analysis for f were proposed in the TI Evaluation Work Plan for use in conjunction with groundwater contaminant concentrations and aquifer information to estimate cleanup times using the Batch Flushing model It is important to use accurate f values from representative bedrock in the Batch Flushing model in order to obtain reasonable estimates of the remedial time frame Because of the importance of accurate and representative results the TI Investigation field program was designed and conducted both to collect samples representative of the rock volume most likely to be in contact with contaminated groundwater and to analyze them using an appropriate refereed analytical method Five potential methods for evaluating f were identified Of the five methods the Walkey-Black method was selected because it has minimal method interferences and a sufficiently low detection limit as well as a long history of use in agronomy and contamination studies The PRP Group is pleased with the quality of the data obtained from the bedrock samples as represented by their precision and reproducibility

The first part of this comment relates to the determination of fraction of organic carbon (f^) values The several subparts of the first paragraph are addressed individually in items 1 through 5 below The second part of the comment regarding the resultant distribution coefficient (Kd) values is addressed separately as item 6 below

1 There remains doubt that the values used in the flushing model accurately reflect the propensity for PCE to sorb to the bedrock

bull The rock core samples used for f (gocg) analysis were from core immediately adjacent to fractures These rock core samples included the fracture surfaces themselves and rock core extending back less than 1 cm from the fractures Therefore the foe data reported in the TI Evaluation represents the f of bedrock through which groundwater will travel and to which PCE will adsorb Based on the careful selection of sample locations and the

Response to EPA Comment 3 050205doc 1 of 11 Woodard amp Curran (211941)

number of samples collected we are confident that the measured f values are representative of the f at points of contact for PCE with the bedrock it is these f values that determine the propensity of PCE to sorb to the bedrock

bull The samples of rock core collected for analysis of f originated from 19 different locations varying in depth from 11 to 90 feet Therefore it is very unlikely that the rock core samples were contaminated with extraneous organic carbon from above ground

2 The foc values presented in Appendix B may be unrealistically high because the bedrock samples may have contained organic carbon that was unavailable for sorption

bull As noted in response 1 the f data reported in Appendix B represents organic carbon primarily associated with the surface of fractures in the bedrock through which groundwater is most likely to travel Therefore it is this organic carbon that the contaminants in the groundwater will come in contact with and adsorb to in the fractured rock at the site

bull The chemical oxidation agents used in the Walkey-Black method oxidize the easily oxidizable organic carbon in the medium and the foe is calculated from the quantity of the agent consumed Therefore it is unlikely that the analysis of the bedrock samples measured organic carbon that was unavailable for sorption

3 The reported foc values are only qualitative estimates of the organic carbon content of the bedrock samples

bull The reported f values are accurate quantitative results Schumachers review of Methods for the determination of total organic carbon (TOC) in soils and sediments (NCEA-C-1282 EMASC-001 April 2002) identifies the Walkley-Black method which was used to analyze the reported foc values as the reference method for comparison to other methods for analyzing total organic carbon

bull Schumacher also points out that if anything the WalkJey-Black method may underestimate the total organic carbon in a sample due to possible incomplete oxidation of organic carbon Usually the incomplete oxidation of total organic carbon in environmental samples is corrected for by multiplying the measured foe by 130 (Walkley amp Black 1934 Schulte 1995)

bull When the f data in the TI Evaluation Report (WampC 2005) Appendix B (attached) are analyzed statistically the standard deviation of the f for the 19 samples analyzed is 174 of the average f Given this standard deviation the 95 confidence interval for this data ranged from a low of 000123 gocg to a high of 000253 gocgm

The labs Method of Detection Limit (MDL) for the f measured using the Walkley-Black method is 00001 gocg Therefore the average (000188 gocg) the mean (000185 gocg) and geometric mean (000187 gocg) of the f values for the rock core at Hows Corner are all statistically significantly greater than the MDL of the Walkley-Black method

In addition to the aforementioned statistical analysis of the foe data triplicate samples (n = 3) from the same rock core (including one sample from the 19 rock core samples) were

Response to EPA Comment 3 050205doc 2 of Woodard amp Curran (211941)

analyzed for their f to determine the repeatability of the Walkley-Black method The average the mean and the geometric mean of the f values of these replicate samples was 000162 gocg 000150 gocg and 000159 gocgm respectively The standard deviation of these measurements was 000039 gocg

4 The Walkley and Black organic carbon measurement method is quick and simple but the results obtained cannot be considered quantitative because it requires a correction factor which often results in erroneous values it assumes the organic carbon has an average valence of zero oxidizable and reducible constituents such as chloride ferrous iron and manganese oxides interfere with the results and the errors introduced by interference are potentially greater when the organic carbon content is low at low foc values it is not clear that organic carbon is controlling PCE sorption (Schwarzenbach and Westall 1981 Mackay et al 1986 Fetter 1999)

bull Schumachers review (NCEA-C-1282 EMASC-001 April 2002) of the Walkley-Black method identifies several potential problems with this analytical method that could occur if the analytical lab is not familiar with the nuances of the chemistry associated with this method Interestingly Schumachers review neglected one of the more important analytical steps required to avoid errors in quantifying f in samples where there might beNAPL

It is absolutely critical to eliminate any NAPL from rock core samples prior to using the Walkley-Black method to measure foe in such samples This was done by the lab (PTS Laboratories) that measured the foe in the rock core samples from Hows Corner The lab used the Dean-Stark method (solvent extraction) to remove all hydrocarbons (including PCE and other NAPLs) from the sample (PTS Laboratories) This extraction method does not interfere with the subsequent analysis of the natural organic carbon associated with the rock core

Subsequently the samples were dried at 150degC to a constant weight (normally 16 hours) This latter step oxidizes all inorganic minerals including ferrous bearing minerals to ferric oxides and precludes their interference during the oxidation of the samples with chromic acid This procedure completely eliminates any positive bias in the reported foc

data that might have occurred due to the presence of ferrous ions and other reduced minerals

bull As noted in Response 3 the incomplete oxidation of total organic carbon results in an underestimate of the f and is corrected for by multiplying the f by a correction factor of 130 (Walkley amp Black 1934 Schulte 1995) The fx data reported in the TI Evaluation was corrected accordingly by using this correction factor

bull Excess chloride (Cl~) in percent weight quantities as found in saline soils may interfere with the quantitative titration of reduced chromium (Walkley 1947) However given that the primary rock type at the Hows Corner site is phyllite it is highly unlikely that there was sufficient chloride in the rock core samples for this to occur

bull Manganese oxides may also interfere with the analysis of f through competing with the dichromate ion for any oxidizable carbon (Walkley 1947) However in such cases the reported f would be an underestimate of the f present in the rock core Walkley (1947)

Response to EPA Comment 3 050205doc 3 of 11 Woodard amp Curran (211941)

4

reported that in the case where the ratio of MnO2 to carbon is 85 to 1 the error in the carbon determinations would only be 0 to 6 percent

It may also be useful to compare the analysis of total organic carbon in a geologic matrix that contains high levels of manganese using EPA method 9060 to the Walkley-Black method Table 1 summarizes data provided by one of the PRPs that compares the analysis of total organic carbon in a geologic matrix that contains approximately 02 wgt manganese (approximately 03 wgt manganese oxide)

Table 1 Comparison of total organic carbon measured using the EPA- 9060 method and the Walkley-Black method

Laboratory EPA-9060 Method Walkley-Black Method A Ave 00226 gocg Not analyzed

Stdev 000251 gocg n = 5

B Ave 002219 gocg Ave 002050 gocg Stdev = 000316 gocg Stdev =000971 gocg

n= 10 n = 10

The similarity in the total organic carbon concentrations measured by these two different methods provides further confidence that the Walkley-Black method is a viable method for analysis of total organic carbon in the presence of manganese equivalent to at least 10 by weight of the total organic carbon

5 The Walkley and Black organic carbon measurement at lowf^ values it is not clear that organic carbon is controlling PCE sorption (Schwarzenbach and Westall 1981 Mackay et al 1986 Fetter 1999)

bull Schwarzenbach and Westalls (1981) paper states that f values of less than 0001 gocg should not be used in combination with Kow (octanol-water partition coefficients) values to calculate K^ values (solid phase partition coefficients) values for a specific contaminant It should be noted that the TI Evaluation did not use the f data to calculate the KQC from the Kow Instead as requested by the EPA the measured KOC value for PCE was used to calculate the retardation factor for this contaminant

bull Schwarzenbach et al (2003) stated more recently that Even at very low f values (ie foe = 0001 kgoc - kg1 solid) sorption to the organic components of a natural sorbent may still be the dominant mechanism in defining the adsorption of organic compounds to geological matrices

bull In 1985 M Piwoni from the US EPA Robert S Kerr Environmental Research Laboratory published a paper (Banerjee et al 1985) that showed that for very hydrophobic molecules TOC content of the sorbent will control sorption down to levels of organic carbon that defy quantitation Contaminants such as the PCE found in the groundwater at Hows Corner are in this category of compounds

Given the aforementioned reasons the f values reported in the TI Evaluation are accurate within the noted statistical limitations and will have a predictable impact upon the retardation of PCE during groundwater transport

Response to EPA Comment 3 050205doc 4 of 11 Woodard amp Curran (211941)

6 In order to derive a Kd-based retardation factor that is reasonable given the reported foc

values and the rapid advance of the PCE plume described on pages 4-11 and 4-12 the flushing model requires a bulk density to porosity ratio that is roughly two orders of magnitude higher than the actual ratio for the Hows Comer bedrock (page 4-4) This apparent discrepancy needs to be addressed

The apparent discrepancy of bulk density to porosity ratios is most likely due to the fact that the Batch Flushing Model was originally developed for a porous medium and is not directly applicable to fractured bedrock As stated in Appendix C (page C-4) of the Draft Technical Impracticability Evaluation Report in order to use the Batch Flushing Model to describe the transport of contaminated groundwater in fractured bedrock where the matrix porosity is insignificant it is more appropriate to use a fracture surface area to void space ratio to calculate the retardation factor (R) than a bulk density to porosity ratio (Freeze amp Cherry 1979)

Since it is impractical to determine the actual surface area to which contaminants can adsorb the Batch Flushing Model was used with two simplifying assumptions bull The Kd was calculated from the f and the K^ bull The bulk density to porosity ratio term in the Batch Flushing Model was constrained to range

from 4 to 10 the typical range of such ratios in porous media (Freeze amp Cherry 1979)

If one uses site specific bedrock bulk density and porosity values the bulk density to porosity ratio is several orders of magnitude greater (specifically 273 gcc bullbull 000165 (dimensionless) = 1654 gcc) than the range of ratios of 4 to 10 used in the Batch Flushing Model in the Draft Technical Impracticability Evaluation Report Constraining the bulk density to porosity ratio within the range of ratios of 4 to 10 results in significantly lower R value than would be obtained using specific bedrock bulk density and porosity values

In summary in bedrock where fractures are the primary porosity the bulk density to porosity ratio can vary considerably and will be a function of the number of fractures and the fracture aperture The calculated bulk density to porosity ratio will be inversely proportional to the porosity This means that in fractured rock with limited fracturing and smaller porosity the calculated bulk density to porosity ratio is greater and will result in a greater calculated retardation factor than in bedrock with more extensive fracturing and greater porosity Consequently the calculated retardation factor will be greater for bedrock with less surface area available for sorption than bedrock with greater surface area for sorption This is contrary to what actually occurs

4 Response to EPA Comment 3 050205doc 5 of 11 Woodard amp Curran (211941)

m

REFERENCES

Banerjee P MD Piwoni K Ebeid (1985) Sorption of organic contaminants to a low carbon subsurface core Chemosphere _14 1057-1067

Freeze RA JA Cherry (1979) Groundwater Prentice Hall Englewood Cliffs NJ pg 604

PTS Laboratories wwwptsgeolabscompdf files3TOCnotepdf

Schulte EE (1995) Recommended soil organic matter tests in Recommended Soil Testing Procedures for the Northeastern United States Northeastern Regional Publication No 493 Chapter 8

Schwarzenbach RP J Westall (1981) Transport of nonpolar organic compounds from surface water to groundwater Laboratory sorption studies Environ Sci Tech 15 1360-1367

Schwarzenbach RP PM Gschwend DM Imboden (2003) Environmental Organic Chemistry Wiley-Interscience pg 292 408 amp 412

Walkley A LA Black (1934) An examination of the Degtjareff method for determining soil organic matter and a proposed modification of the chromic acid titration method Soil Science 37 29-38

Walkley A (1947) A critical examination of a rapid method for determining organic carbon in soils - effect of variations in digestion conditions and of inorganic soil constituents Soil Science 63251-264

Woodard amp Curran Inc (WampC) 2005 Draft Technical Impracticability Evaluation Hows Corner Superfund Site Plymouth Maine January 2005

Response to EPA Comment 3 050205doc 6 of Woodard amp Curran (211941)

LIST OF ATTACHMENTS (Response to Comment 3)

Appendix B to Draft Technical Impracticability Evaluation Measurement of foe at Hows Corner (4 pages)

m

Response to EPA Comment 3 050205doc 7 of 11 Woodard amp Curran (211941)

Appendix B Measurement of foe of Rock Core at Hows Corner

There are two general approaches to measure the fraction of organic carbon (foe) in rock cores

bull Measurement of weight loss by ignition of organic matter bull Chemical oxidization of organic carbon to carbon dioxide and either

subsequent quantification of the oxidant used for the reaction or quantification of the carbon dioxide produced during this oxidation process

The weight loss method is subject to errors caused by volatilization of substances other than organic materials such as water hydroxides and mineral carbonates Quantification of foe by the weight loss method is particularly sensitive to the presence of carbonates in rock cores There are however weight loss methods that are designed to differentiate between organic carbon and the aforementioned interfering materials but they require considerable care and are less accurate at low foe values Hence the weight loss method was not well suited for measuring the foe of the rock core from Hows Corner

The chemical oxidation of organic carbon is much better suited for quantifying organic carbon in rock cores such as those from Hows Corner This method uses a strong chemical oxidant to oxidize organic carbon to carbon dioxide and then measures either the chemical oxidant used to oxidize the organic carbon or the quantity of carbon dioxide produced In addition this general approach is not subject to interference by volatilization of other constituents of the rock core

There are at least two such chemical oxidation methods

bull The method of Baccini which was described by Schwarzenbach amp Westall (1981) first acidifies the sample to eliminate interference by carbonates Then a strong oxidant is used to chemically oxidize the organic carbon to carbon dioxide The resulting carbon dioxide is subsequently reduced to methane and quantified using a flame ionization detector Unfortunately this method has not been described in detail in a referred journal Hence it is would not have been appropriate to use to characterize the foe in the Hows Corner rock core

bull The more commonly used method to quantify foe in rock core is the Walkley-Black method (1934) This method is preferred for RBCA and DODDOE projects and by the oil industry

The Walkley-Black method uses an excess of chromic acid to oxidize (digest) organic matter to carbon dioxide The remaining chromic acid that was not consumed during the oxidation of the organic carbon is then quantified by titration with ferrous sulfate The difference in chromic acid prior to and after the oxidation of the organic carbon represents the total chromic acid used to oxidize

Hows Corner TI Evaluation Page 1 January 13 2005 Appendix B

the organic carbon in the sample The latter can be calculated using the chemical stoichiometry of the reaction

The Walkley-Black method is very accurate for samples that contain less than 2 organic carbon matter The minimum detection limit (MDL) for the Walkley-Black method is 100 mgkg or an foe of 0001

Given the rock core at Hows Corner was expected to contain less than 2 organic carbon the Walkley-Black method was used to measure the foe from 19 different rock core samples collected from varying depths ranging from 11 to 90 feet

Table 1 provides a statistical summary of the aforementioned data

Table 1 Statistical summary of foe data from rock cores collected at varying depths

Statistical Parameter Calculated Value foe Minimum Detection Limit (MDL) 00010 Number of samples analyzed (n) 19 Average foe 00019 Median foe 00019 Geometric Mean foe 00019 Standard deviation of foe measurements 000033 Relative standard deviation 174 -+ 95 Confidence intervals 00012 to 00025

The data in Table 1 shows the following

bull The foe from the Hows Corner rock cores are statistically greater than the MDL of the Walkley-Black analytical method

bull The average and median values for the foe of the Hows Corner rock cores from varying depths are nearly identical indicating that there is little variability in the foe values in the source zone at the site

bull The standard deviation of these measurements is 000033 which is 174 of the average foe

bull The 95 confidence intervals of the foe of the rock core at Hows Corner are 00012 to 00025

The foe was also analyzed from three separate samples taken from the same rock core at a depth of 55 feet (Only one of these samples was included in the data summarized in Table 1) Table 2 shows the statistical repeatability of this type of analysis

Hows Corner TI Evaluation Page 2 January 13 2005 Appendix B

Table 2 Repeatability of analysis of foe from one rock core at 55 feet in depth

Statistical Parameter Calculated Value Number of samples analyzed (n) 3 Average foe 00016 Median foe 00015 Geometric Mean foe 00016 Standard deviation of foe measurements 000039 Relative standard deviation 240 -+ 95 Confidence intervals 00008 to 00024

The data in Table 2 shows the following

bull The percent relative standard deviation of these three analyses of foe from the same rock core at Hows Corner is 24

bull The 95 confidence interval of the foes measured in this particular rock core at Hows Conrer is 00008 to 00024

These results show that there is good repeatability in using the Walkley-Black method for analysis of the foe in the rock core at Hows Corner

References Schwarzenbach amp Westall (1981) Transport of nonpolar organic compounds from surface water to groundwater Laboratory sorption studies Environ Sci Tech 15 1360-1367

Walkley A I A Black (1934) An examination of Degtjareff method for determining soil organic matter and a proposed modification of the chromic acid titration method Soil Sci 37 29-37

Hows Corner Tl Evaluation Page S January 13 2005 Appendix B

Woodard and Curran PTS Laboratories PTS File No 34618

ORGANIC CARBON DATA (METHODOLOGY WALKLEY-BLACK)

PROJECT NAME PROJECT NO

SAMPLE ID

203-chip-13 203-chip-23 203-chip-27 203-chip-38 203-chip-42 203-chip-47 203-chip-52 203-chip-58 203-chip-69 203-chip-82 207-chip-11 207-chip-19 207-chip-24 207-chip-29 207-chip-35 207-chip-45 207-chip-55 207-chip-87 207-chip-90

207-chip-55 55-MS

55-MSMSD

Hows Corner NA

DEPTH ft

13 23 27 38 42 47 52 58 69 82 11 19 24 29 35 45 55 87 90

55 NA NA

MATRIX

Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip

Average Median

Geometric Mean Standard Deviation Relative Std Dev

+- 95 Confidence Interval n

Rock Chip Rock Chip Rock Chip

Average Median

Geometric Mean Standard Deviation Relative Std Dev

+- 95 Confidence Interval n

FRACTION ORGANIC CARBON

(gg)

170E-03 185E-03 185E-03 170E-03 240E-03 190E-03 230E-03 180E-03 170E-03 115E-03 195E-03 220E-03 220E-03 235E-03 135E-03 190E-03 205E-03 175E-03 160E-03

188E-03 185E-03 185E-03 327E-04

1739 123E-03 to

19

205E-03 130E-03 150E-03

162E-03 150E-03 159E-03 388E-04

2402 840E-04 to

3

2532E-03

2393E-03

Hows Corner Tl Evaluation Appendix B January 13 2005

Response to EPA-DEP Comment 4 Dated March 31 2005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

EPA-DEP Comment 4

Comment 4 Distribution of contaminants First the TI report seems based on the assertion that there is DNAPL at the source area yet it also appears to represent that the source area is small and the bedrock below 85 is competent (or less fractured) and less impacted by the release of contaminants Some of the confusion may result from using most recent data when that data is from several different sampling events over several years and there is no discernible difference in concentrations between shallow and deep bedrock or as in Section 421 where generally decreased generally increase generally similar and similar concentrations in four consecutive sentences leads to a muddled picture of the contaminant distribution

Second the report asserts that the distribution of contaminants over the entire plume has not changed with time but fails to support this conclusion with data again relying on data that is from different sampling dates for one composite representation

Response The likely presence of dense non-aqueous phase liquid (DNAPL) at the Hows Corner Site and the determination that the source area is small are not mutually exclusive and both are conclusions drawn from information obtained during field investigations The presence of DNAPL in the source area is based on the elevated concentrations of volatile organic compounds (VOCs) detected in the groundwater (WampC 2001 WampC 2002) The conclusion that the source area is small is based on the area in which VOCs in groundwater have been detected at concentrations that are considered to be indicative of the presence of DNAPL nearby Similarly the conclusion that fracture frequency decreases at depths greater than approximately 50 to 85 feet below ground surface was based on field observation during the RI field work The fact that zones with observed fractures exhibited higher hydraulic conductivities than zones without fractures coupled with the decreasing frequency of observed fractures with depth led to the conclusion that the hydraulic conductivity of the bulk rock decreases with depth

The most recent data from all wells were used to provide the maximum VOC data set size During the RI all of the previously-existing and then newly-installed monitoring wells were sampled along with several residential wells The RI sampling included up to 48 monitoring wells Subsequent to the RI and prior to the TI three rounds of monitoring were conducted to verify that the plume was stable 15 monitoring wells were sampled during each of the three rounds During the TI field investigation 29 wells were sampled for VOCs The sampled wells included all of the newly-installed wells and a subset of wells installed during the RI for a total of 29 monitoring wells By using most recent data VOC results from 53 monitoring wells were included in the evaluation (see table labeled Sampling Events for listing of monitoring wells) This approach was selected because there generally was little variation in the data from a particular location between years This is borne out by the attached individual plots of VOCs detected in shallow bedrock and deep bedrock for the Pre-ROD (December 1999January 2000) and Supplemental (May 2000) sampling events and for June 2001 January 2002 and April 2003 sampling events The Pre-ROD and Supplemental plots are similar to the subsequent plots from the 2001 2002 and 2003 sampling events

In addition to maps showing the spatial distribution of VOC data at a given time trend plots of the data from a particular location through time (attached) indicate that since the RI concentrations generally have been stable or have decreased Together the maps and trend plots and the data from which they were developed indicate that the distribution of contaminants over the entire plume has not changed appreciably with time

Response to EPA Comment 4 050305doc 1 of 26 Woodard amp Curran (211941)

REFERENCES

Woodard amp Curran Inc (WampC) 2001 Final Remedial Investigation Report Hows Corner Superfund Plymouth Maine July 2001

Woodard amp Curran Inc (WampC) 2002 Final Feasibility Study Report - Non-Source Area Groundwater Hows Corner Superfund Site Plymouth Maine Hows Corner Superfund Plymouth Maine July 2002

Response to EPA Comment 4 050305doc 2 of 26 Woodard amp Curran (211941)

LIST OF ATTACHMENTS (Response to Comment 4)

Table - Sampling Events 1999 - 2004 (2 pages)

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater Pre-ROD Sampling Event

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater Pre-ROD Sampling Event

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater Supplemental Sampling Event

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater Supplemental Sampling Event

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater June 2001

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater June 2001

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater January 2002

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater January 2002

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater April 2003

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater April 2003

Figure - Concentration Trends - Non-Source Area Wells MW-1B and MW-3B

Figure - Concentration Trends - Non-Source Area Wells MW-13DB and MW-16DB

Figure - Concentration Trends - Non-Source Area Wells MW-16IB and MW- 108D

Figure - Concentration Trends - Non-Source Area Wells MW-108S and MW-112D

Figure - Concentration Trends - Non-Source Area Wells MW-112S and MW-114D

Figure - Concentration Trends - Non-Source Area Wells MW-114S and MW-115D

Figure - Concentration Trends -Source Area Wells MW-2DB and MW-2IB

Figure - Concentration Trends -Source Area Wells MW-102S and MW-103D

Figure - Concentration Trends -Source Area Wells MW-103S and MW-104D

Figure - Concentration Trends -Source Area Wells MW-104I and MW-106D

Figure - Concentration Trends -Source Area Wells MW-106S

Response to EPA Comment 4 050305doc 3 of 26 Woodard amp Curran (211941)

I I

El I

II I I 1 I

I

i

Event Baseline Case ID WC-01 WC-01

Well Date Aug-99 Oct-99 LOT10 1 LOT1-1 1 LOT11-4 LOT14 1 LOT15 1 LOT15-1 1 LOT16 1 LOT16-1 1 LOT17 1 LOT18 1 LOT19 1 LOT2 LOT20 1 LOT21-10 1 LOT21-11 1 LOT21-12 1 LOT21-13 1 LOT21-14 1 LOT21-2 1 LOT21-5 1 LOT21-7 LOT21 -8 1 LOT21-9 1 LOT23 1 LOT24 1 LOT28-1 1 LOT28-2 1 LOT28-3 1 LOT28-4 1 LOT28W 1 LOT30 1 LOT30-1 1 LOT30-2 1 LOT30-3 1 LOT30-4 1 LOT30-5 LOT31 LOT35 1 LOT41 1 LOT42-1 1 LOT43-1 1 LOT43-4 1 LOT6-1 1 LOT67 1 LOT6-7 1 LOT6-8A 1 LOT6-8B 1 LOT80-1 1 LOT82 1 MW-101D MW-1011 MW-101S MW-102D MW-102S MW-103D MW-103S MW-104D MW-1041 MW-104S MW-105D MW-106D

Groundwater Sampling Location Summary 1999 - 2004xls

Sampling Events 1999-2004

Hows Corner Superfund Site Plymouth Maine

Supplemental 2001 2002 2003 Pumping 2004 Pre-ROD Rl Sampling Sampling Sampling Test Sampling WC-03 WC-09 WC-25 WC-30 WC-42B WC-56 WC-58 Dec-99 May-00 Jun-01 Jan-02 Apr-03 Sep-04 Sep-04

1

1 1 1

1 1 1 1 1

1 1

1

1 1

1 1 1

1 1 1 1 1

1

1 1

1 1 1 1

1

1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

Sampling Events 1999-2004

Hows Corner Super-fund Site Plymouth Maine

Supplemental 2001 2002 2003 Pumping Event Baseline Pre-ROD Rl Sampling Sampling Sampling Test

Case ID WC-01 WC-01 WC-03 WC-09 WC-25 WC-30 WC-42B WC-56

ll

Well Date Aug-99 Oct-99 Dec-99 May-00 Jun-01 Jan-02 Apr-03 Sep-04 MW-106S 1 1 1 1 1 MW-107D 1 1 MW-108D 1 1 1 1 1 MW-108S 1 1 1 1 1 MW-110D 1 1 MW-111D 1 1 MW-112D 1 1 1 1 1 MW-112S 1 1 1 1 1 MW-113D 1 1 MW-114D 1 1 1 1 1 MW-114S 1 1 1 1 1 MW-115D 1 1 1 1 1 MW-12DB 1 1 1 MW-12SB 1 1 1 MW-13DB 1 1 1 1 1 1 MW-13SB 1 1 1 MW-14DB 1 1 MW-14SO 1 1 MW-15DB 1 1 1 MW-15SB 1 1 1 MW-16DB 1 1 1 1 1 1 MW-16IB 1 1 1 1 1 1 MW-16SO 1 1 MW-17DO 1 1 1 MW-17SO 1 1 1 MW-1B 1 1 1 1 1 1 MW-203D MW-203S MW-204D MW-204S MW-205 MW-206D

I MW-206S MW-2DB 1 1 MW-2DDB 1 1 MW-2IB 1 1 1 1 1 1 MW-3B 1 1 1 1 1 1

I MW-4O 1 1 1 MW-5B 1 1

II MW-6DB 1 1 1 MW-6SB 1 1 1 MW-8DB 1 1 1 MW-8SB 1 1 1

II PW-207 1 SEEP-1 1 SUBTOTAL - RESIDENTIAL 44 25 0 2 0 3 0 SUBTOTAL - MONITORING 22 48 41 15 15 15 1

Total 3 66 73 41 17 15 18 1

I Included in most recent data

I Notes 1 - Overburden well not included in most recent data for plotting

2 - Tetrahydrofuran and 2-Butanone were the only two compounds detected in this well and are thought to be the result of well repair not included in most recent data for plotting

3 - Not included in most recent data for plotting

2004 Sampling

WC-58 Sep-04

1

1 1

1 1

1 1 1

1

1 1

1 1 1 1 1 1 1 1 1

1 1

1

0 29

29

Groundwatef Sampling Location Summary 1999 - 2004xls

I

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

monitoring well Figure 4-14 total VOC contour (ugl) - December 1999January 2000 Distribution of Total VOCs in

Note SW-113 is located downstream of SEEP-1 Shallow Bedrock Groundwater total concentration of detected VOCs ND= not detected these two locations were sampled during the Pre-ROD Sampling Event

Baseline Sampling Event in OctoberNovember 1999 Hows Corner Superfund Site Surface Water Sampling Location A Plymouth Maine Seep Sampling Location laquo- WOODARD ampCURRAN

995037wipri reportepa ri interim final feb 2001cadd drawingsfinalfig 4-14

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

0 300 600 I

FEET

Q residential well Figure 4-16 monitoring well Distribution of Total VOCs in

Deep Bedrock Groundwater total VOCs contour (ugl) Pre-ROD Sampling Event

active residential wells with lot number Hows Corner Superfund Site 2deg42deg Plymouth Maine total concentration of detected VOCs ND= not detected WOODARD ampCURRAN Enyinaaring bull Science bull Operations bull

995037wipri reportepa ri interim final feb 2001cadd drawingsfinalfig4mdash16

PLYMOUTH POND

PLYMOUTH POND

1 628Tl7MW-2bB 12135

PLYMOUTH POND

monitoring well Figure 4-20

V total VOC contour (ugl) - June 2000 Distribution of Total VOCs in Shallow Bedrock Groundwater

| 34 | total concentration of detected VOCs ND= not detected NA = not analyzed Supplemental Sampling Event Note SW-113 is located downstream of SEEP-1 Hows Corner Superfund Site

Surface Water Sampling Location these two locations were sampled during the Plymouth Maine Baseline Sampling Event in OctoberNovember 1999 Seep Sampling Location WOODARD amp CURRAN

Engineering bull Science - Operations bull 995037wipri reportepa ri interim final feb 2001 cadd drawingsfinalfig 4-20

residential well Figure 4-22 Distribution of Total VOCs in

monitoring well Deep Bedrock Groundwater

total VOCs contour (ugl) Supplemental Sampling Event

Hows Corner Superfund Site

total concentration of detected VOCs ND= not detected NA = not analyzed Plymouth Maine

WOODARD amp CURRAN

995037wipri reportepa-ri interim final feb 2001cadd drawingsfinalfig 4-22 Engineering bull Science - Operations bull

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

FEET

Shallow Monitoring Well

Deep Monitoring Well

C Detected Concentration ND = Not Detected Figure 1-XS Distribution of Total VOCs in Shallow Bedrock Groundwater

Pumping Well

17-Acre Property Boundary Concentration Contour (ugl)

June 2001 Hows Corner Superfund Site

Plymouth Maine WOODARDampCURRAN

-i^rhvj bull Scbncn bull Operations bull 211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0601 dwg04-20-05

PLYMOUTH POND Hopkins Road V

O

PLYMOUTH POND

PLYMOUTH POND

o

0 300 600 mdashfa FEET

Shallow Monitoring Well bull bull - 17-Acre Property Boundary Figure 1-XD

Deep Monitoring Well 1 I Detected Concentration ND = Not Detected Distribution of Total VOCs in Deep Bedrock Groundwater

-mf- Pumping Well June 2001 Residential Well Hows Corner Superfund Site

Plymouth Maine i h Surface Water Sampling Point

g WOODARD ampCURRAN _ ^ _ ^ _ _ yen_ rj i|Hlaquorlny bull Science bull Opt

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0601 dwg04-20-05

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

Shallow Monitoring Well

Deep Monitoring Well

Detected Concentration ND = Not Detected Figure 1-YS Distribution of Total VOCs in Shallow Bedrock Groundwater

Pumping Well

17-Acre Property Boundary Concentration Contour (ugl)

January 2002 Hows Corner Superfund Site

Plymouth Maine WOODARD amp CURRAN Engineering Science- Operations bull

211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0102dwg04-20-05

PLYMOUTH POND

PLYMOUTH POND

Site Pand^ laquoum-laquoBTuitaraquo tLV

vVlf-(

PLYMOUTH POND

0 300 600 ^ = FEET

Shallow Monitoring Well mdashbullbullbull 17-Acre Property Boundary Figure 1-YD - A - Deep Monitoring Well FT Detected Concentration ND = Not Detected Distribution of Total VOCs in

Deep Bedrock Groundwater Pumping Well January 2002 Residential Well Hows Corner Superfund Site

Plymouth Maine Surface Water Sampling Point

WOODARD ampCURRAN Engineering Sciencs- Operations bulli Si

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0102dwg04-20-05

- m j

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND j A O-shy

Shallow Monitoring Well E Detected Concentration ND = Not Detected Figure 1-ZS Distribution of Total VOCs in

Deep Monitoring Well Shallow Bedrock Groundwater

Pumping Well Hows Corner

April 2003 Superfund Site

17-Acre Property Boundary Plymouth Maine Concentration Contour (ugl) r WOODARD ampCURRAN

Engineering bull Science bull Operations bull 211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0403dwg04-20-05

s S pound

PLYMOUTH POND

PLYMOUTH POND

- -

5 PLYMOUTH POND

Jo

FEET

ft Shallow Monitoring Well mdashbullbullmdash 17-Acre Property Boundary Figure 1-ZD Deep Monitoring Well I 1 I Detected Concentration ND = Not Detected Distribution of Total VOCs in

Deep Bedrock Groundwater Pumping Well April 2003

Q) Residential Well Hows Corner Superfund Site Plymouth Maine

(T) Surface Water Sampling Point WOODARD ampCURRAN poundKk EnginawtirKj bull Science - Operations bull

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0403dwg04-20-05

0 Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

B MW-1B

I 12000

PCE

B 10000 Total VOCs

I

i 2000

i 0 Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

c MW-3B

G 2000

1800

B PCE

1600 Total VOCs

1 I I E

il-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

G E

211941

El

I I z E

80

Concentration Trends shy Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-13DB

Total VOCs

c i i c o

Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

MW-16DB

30

c i c c I c o

Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99

PCE

Total VOCs

Jul-01 Jul-03

211941

O bi

c Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

I MW-16IB

i 35

3

c Total VOCs

lt- 2 5

0 | gt

o

1 sectI

c c 0 4

Jul-90 Jul-92 Jul-94 Jul-96 Jul-98 Jul-00 Jul-02 Jul-04

I I MW-108D

I 12

PCE 10

Total VOCs c oc 3

E E I 0

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

E 211941

c Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

fi MW-108S

I I 40

PCE 35

Total VOCs

30

I f 26

20 I o

I 15

10

c Dec-99 Dec-00 Dec-01 Dec-02 Dec-03 I 0

I MW-112D

c 35 - imdash

I A3 shyTotal VOCs

o c

E 1 2

I

ition

B 1 ^

-i c 3

0 Dec-99 Dec-OO Dec-01 Dec-02 Dec-03

211941

I

i

I

cII

Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-112S

08

PCE

Total VOCs 06

o 04

02

0 Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

MW-114D

o

12000

10000

8000

6000

PCE

Total VOCs

4000

2000

i

ccEIIc

i

i

E

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

211941

Con

cent

ratio

n (

ug

l)

E Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

I MW-114S

E A5000 -- Total VOCs

- 4000

0 3000

2000

i 1000

i n shy

Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

MW-115D

c PCE

Total VOCs

c E

o

C c

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03 I 0

211941

IepoundII

EIEIIGICCIccc

30000

25000

20000

o bullsect 15000 b

o 10000 U

5000

0 Aug-99

25000

20000

5000

0 Aug-99

211941

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-2DB

PCE

Total VOCs

Aug-01 Aug-03

MW-2IB

PCE

Total VOCs

Aug-01 Aug-03

IDIBI

ii EIDIISIBIG C

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-102S

6000

5000 PCE

Total VOCs

4000

O 3000

2000

1000

0 Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

MW-103D

16000

~ 14000 ugt 3- 12000 o

^ 10000

sect 8000

O 6000

4000

2000

PCE

Total VOCs

0Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

211941

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

G MW-103S

I I

ampo

12000

10000

E sectc

S

8000

6000

4000

2000

0Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

G I 6000

MW-104D

i 5000

PCE

Total VOCs

i i c

2000

1000

Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

E I

211941

cIccIG

IIBCccBcIc

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-1041

PCE Total VOCs

a 25000

0 20000

a 15000

10000

5000

0 Jan-OO Jan-01 Jan-02 Jan-03 Jan-04

MW-106D

3000

2500 PCE

Total VOCs

=sect 2000

o bullsect 1500

1000

500

0 Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

211941

c Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

c MW-106S

I PCE

Total VOCs

i

i Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

i

i i i E

C

211941 c

Response to EPA-DEP Comment 5 Dated March 312005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

iiw

EPA-DEP Comment 5

Comment 5 Matrix Diffusion The report as well as other proponents of matrix diffusion suggest that depletion of DNAPL (Section 5112 page 5-15) needs to be achieved While that might be the ideal the goal is to achieve performance standards and that goal may be attainable while there is residual contamination in the rock perhaps even DNAPL globules The low bedrock matrix porosity (page 1-15) the high permeability values (page 4-4) the relative flux of the groundwater (page 5-5) and the decrease in surface area and out of the mainstream pockets (appendix C-4) all suggest that the diffusion out of the rock matrix would be insubstantial relative to the regional flux of groundwater through the Site

Response The TI Evaluation Report does not explicitly consider or rely upon matrix diffusion as a basis for requesting a TI Waiver for a portion of the Hows Corner Site The technical literature provides documentation that matrix diffusion can be a significant process that affects chemical transport and groundwater remediation timeframes in unconsolidated and consolidated media including fractured rock (US EPA 1989 Freeze and Cherry 1979 Pankow and Cherry 1996 Fountain 1998) Back diffusion of contaminants from the matrix porosity of the fractured rock can prolong the time necessary to achieve groundwater cleanup goals particularly for compounds such as PCE for which the cleanup goal is a low concentration It is our expectation that matrix diffusion has occurred at the Hows Corner Site and that back diffusion of PCE from the rock matrix will also occur Although the extent to which matrix diffusion is occurring at the Hows Comer Site has not been determined and that lack of knowledge contributes to uncertainty regarding the cleanup times at the Site the effect of matrix diffusion is to lengthen rather than shorten the time required for remediation

REFERENCES

Fountain JC 1998 Technologies for Dense Nonaqueous Phase Liquid Source Zone Remediation Ground-Water Remediation Technologies Analysis Center Technology Evaluation Report TE-98-02 December

Freeze RA and Cherry JA 1979 Groundwater Prentice-Hall Inc Englewood Cliffs NJ 07632 p 410-412

Pankow J F and Cherry J A 1996 Dense Chlorinated Solvents Waterloo Press Portland OR 97291-1399 p 67-88

US EPA 1989 Transport and Fate of Contaminants in the Subsurface EPA6254-89019 p 17-18

Response to EPA Comment 5 050305doc 1 of 1 Woodard amp Curran (211941)

WOODARD amp CURRAN Maine Massachusetts New Hampshire Connecticut Florida Operational offices across the US 1-800-426-4262 www woodardcurran com

Page 24: SDMS DocID 251749 - Records Collections · 2020-06-13 · CORPORATE OFFICES: Maine, Massachusetts, New Hampshire, Connecticut New, York, Florida Engineering • Science • Operations

I Northeast Geophysical Services Borehole Geophysical Log Date logged 072704

I MW-206

Plymouth Maine

Flowmetor Measurements Temperature (C) Acoustic Televiewer | I r T i i i i i i i i i i i i i i r I |(in gpm) (Interpreted)

I 75 8 flS 9 95

Caliper (inches) Resistance (Ohms) Spontaneous Potential (mV) Dip In Degress PCE Total VOCs 30 35 40 4 5 0 20 40 M 90 4500 5500 6500 ugL ugL I i i

I I

- 1 0

I - 2 0

I 2900B 32401

i i L

E 0

i 6300B 68901

i I 0 20 40 SO 80

20 30 40 50 Dip in Dlaquogralaquos

amp 4 a Fluid Resistivity (ohrnmeters) The dip dirertion is indicated Likely or possible by iho line extending from the transmissive zone circle The striKe of the feature

is 90 degrees from tNs

Borehole Geophysical Log Packered Interval August 2004

E amples were collected by Woodard amp Cunan oo SM82004 log Thraquo location 4p angle and dip direction of the sloeled MW-206 feature are approximate Refer to the televiewer 109 of this well for more precise detail Plymouth Maine Date logged 072704

C

I Northeast Geophysical Services Borehole Geophysical Log

Date logged 082304 PW-207

I Plymouth Maine

Fiowmeter Measurements Temperature (C) Acoustic Televiewer

I (in gpm) (interpreted)

75 8 85 9 95 Caliper (inches) Resistance f0tims) Spontaneous Potential (mV) Dip in Degrees PCE Total VOCs

55 60 0 20 40 SO 80 ugL ugL I I I I I I I

Ambienl Fiowmeter pumping Flewmater

magnetic - 10 - - 1 0

north

i - 20 - - 2 0

1300 1410

i - 30 - - 3 0

i tf

5400 5802 - 40 - - 4 0

B - 50 - - 5 0

I 18000 19234

- 60 - - 6 0

I 12000 13085

- 70 - - 7 0

- 8 0

i - 9 0 19000 20354

G - 100- -100

I 110 110 bull110

0 20 40 60 SO 10 20 30 Dip m Degrees

Fluid Resistivity (ohmmeters) I 50

The dip direction is indicated by ihe line extending from the circle The strike of the fealure is 90 degrees from this

Borehole Geophysical Log

G Packorod Interval August 20(M log The location dip angle and dip dirlaquocton or the sleeted Groundaier samplss were ooliecled by Woodard i Curran on ampt24f2ltXM PW-207 failures are approximate Reter to the televiewer log of this wlaquoll for more precise detail PlyPIOUth Maine Date logged 082304

I

Table XX Packer Permeability and Packer Sampling Results for Potential Fracture Intervals

1

WellID MW-101D MW-101D MW-101D MW-101D MW-101D MW-101D MW-101D MW-101D MW-101D MW-101D MW-I01D MW-101D MW-101D MW-102D MW-102D MW-I02D MW-102D MW102D MW-102D MW-102D MW-102D MW-102D MW-I02D MW-102D MW-102D MW-102D MW-103D MW-103D MW-103D MW-103D MW-I03D MW-103D MW-103D MW-103D MW-103D MW-103D MW-103D MW-103D MW-I03D MW-104D MW-104D MW-104D MW-104D MW-I04D MW-104D MW-104D MW-104D MW-104D MW-104D MW-104D MW-105D MW-105D MW106D MW-106D MW-106D MW-107D MW-107D

1999 Drilling Program

Hows Corner Superfund Site Plymouth Maine

Potential Fracture Top Of Bottom 6 Depth to lt Topof i Interval from Packer Packer Middle of Elevation Hydraulic bull PCE

GS ELEV 1 Rock Drilling Interval Interval Interval of Interval Conductivity Concentration (ft msl) (ft msl) TEST (ftbgs) (ftbgs) r(ftbgs) ( f t b (ft mil) (cmsec) (raquogL)

4339 4329 13 28-29 33-3537-39 271 376 324 4016 OOOE+00 4339 12 37-3444-46 380 485 433 3907 157E-04 4339 11 488 593 541 3799 132E-04 4339 10 60-61 578 683 631 3709 OOOE+00 4339 9 678 783 731 3609 I79E-05 4339 8 778 883 831 3509 106E-05 4339 7 880 985 933 3407 243E-05 4339 6 990 1095 1043 3297 339E-06 4339 5 1090 1195 1143 3197 OOOE+00 4339 4 1190 1295 1243 3097 OOOE+00 4339 3 1365-1375 1290 1395 1343 2997 OOOE+00 4339 2 147-157 1390 1495 1443 2897 580E-05 4339 1 147-157 1470 1575 1523 2817 741E-05 43161 43061 13 166 271 219 4098 333E-04 43161 12 30-3136-40 260 365 313 4004 I54E-05 43161 11 36-4041-43 362 467 415 3902 548E-05 43161 10 470 575 523 3794 598E-05 43161 9 570 675 623 3694 197FOS 43161 8 670 775 723 3594 OOOE+00 43161 7 770 875 823 3494 891 E-05 43161 6 83-94 870 975 923 3394 139E-05 43161 5 970 1075 1023 3294 123E-04 43161 4 1070 1175 1123 3194 526E-06 43161 3 1170 1275 1223 3094 138E-05 43161 2 1270 1375 1323 2994 671E-06 43161 1 1370 1475 1423 2894 OOOE+00 42997 42497 13 18-19 170 275 223 4077 OOOE+00 42997 12 260 365 313 3987 766E-05 42997 11 360 465 413 3887 727E-05 42997 10 460 565 513 3787 192E-05 42997 9 560 665 613 3687 752E-05 42997 8 660 765 713 3587 778E-05 42997 7 85-86 763 868 816 3484 260E-05 42997 6 860 965 913 3387 289E-05 42997 5 102-103 960 1065 1013 3287 102E-04 42997 4 1060 1165 1113 3187 522E-06 42997 3 1160 1265 1213 3087 520E-06 42997 2 129-130 1260 1365 1313 2987 960E-04 42997 1 1360 1465 1413 2887 OOOE+00 43372 42922 11 35-37 42-45 350 455 403 3935 684E-04 43372 10 460 565 513 3825 500E-05 43372 9 560 665 613 3725 106E-05 43372 8 72-74 660 765 713 3625 204E-05 43372 7 760 865 813 3525 872E-06 43372 6 860 965 913 3425 467E-06 43372 5 960 1065 1013 3325 200E-05 43372 4 1060 1165 1113 3225 354E-05 43372 3 125-130 1160 1265 1213 3125 157E-05 43372 2 125-130 1260 1365 1313 3025 337E-04 43372 1 1365 1465 1415 2922 689E-06 43052 43002 2 54-58 490 595 543 3763 124E-05 2100 43052 1 139-140 145-146 1367 1472 1420 2886 154E-04 1400 43291 4391 3 bullI133 260 365 313 4017 439F06 43291 2 77-78 760 865 813 3517 230E-03 400 43291 1 143-144 1355 1460 1408 2922 971E-06 350

29958 27258 4 450 555 503 2493 OOOE+00 (21)A 29958 3 103-105 1000 1105 1053 1943 752E-04 (063)A

Table XX Packer Permeability and Packer Sampling Results for Potential Fracture Intervals

1999 Drilling Program

Hows Corner Supcrfund Site Plymouth Maine

gtbull i Potential Fracture Top _OfBot Bottom of Depth to ltbull Top of Interval from f Packer Packer Middle Of

GS ELEV lt Hock Drilling interval Interval Interval WeD ID ft msl) (ft msl) TEST (ftbgs) ltft$gs) (ftbgs) (ftbgs)

MW-107D 29958 2 128-130 1200 1305 1253

MW-107D 29958 1 139-141 1350 1455 1403

MW-108D 31904 31104 6 35-36 300 405 353 MW-108D 31904 5 60-62 550 655 603

MW-108D 31904 4 80-83 750 855 803

MW-108D 31904 3 118-119 123-124 1150 1255 1203

MW-108D 31904 2 147-149 1440 1545 1493

MW-108D 31904 1 1700 1805 1753

MW-110D 40576 40426 2 21-31 210 315 263 MW-110D 40576 1 148-154 1460 1565 1513 MW-I11D 40519 4 70-71 650 755 703

MW-111D 40519 3 79-82 84-86 780 885 833 MW-I11D 40519 2 97-102 950 1055 1003 MW-111D 40519 1 1370 1475 1423

MW-112D 3027 2942 4 42-52 420 525 473 MW-112D 3027 3 850 955 903 MW112D 3027 2 1100 1205 1153 MW-112D 3027 1 135-136 140-141 1340 1445 1393

MW-113D 43085 43085 5 250 355 303 MW-I13D 43085 4 47-49 460 565 513 MW-113D 43085 3 73-74 700 805 753 MW-113D 43085 2 1050 1155 1103 MW-113D 43085 1 1380 1485 1433

MW-114D 42394 41594 4 48-49 450 555 503 MW-114D 42394 3 79-81 740 845 793 MW-114D 42394 2 121-129 1250 1355 1303 MW-114D 42394 1 134-142 1350 1455 1403

MW-115D 4035 4035 4 300 405 353 MW-1I5D 4035 3 70-71 650 755 703 MW-115D 4035 2 1150 1255 1203 MW-115D 4035 1 1400 1505 1453

LOT-28W 382 7 450 555 503 LOT28W 382 6 550 655 603 LOT-28W 382 5 650 755 703 LOT28W 382 4 750 855 803 LOT-28W 382 3 850 955 903 LOT-28W 382 2 950 1055 1003 LOT-28W 382 1 1055 1155 1105

NOTES cmsec = centimeters per second ft bgs = leet below ground surface It msl = feet below mean sea level lt = not detected at indicated reporting limil A = detected below laboratory PQL ( ) = detected below reporting limits

Elevation of Interval

(ft nisi) 174

159

283gt 2588

2388

1988

1698

1438

3795 2545 3349 3219 3049 2629

2555 2125 1875 1635

4006 3796 3556 3206 2876

3737 3447 2937 2837

3683 3333 2833 2583

3318 3218 3118 3018 2918 2818 2715

Hydraulic Conductivity

(cmsec)

323E-05

208E-05

471E-03

471E-03

624E-05

3I6E-05

264E-05

261 E-05

OOOE+00 200E-04 953E-05 OOOE+00 OOOE+00 212E-05

361 E-05 410E-06 2gQE06 292E-05

786E-05 124E-05 151 E-05 822E-06 82IE-06

858E-05 I69E-05 352E-03 866E-05

223E-05 394E-06 122E-05 525E-06

831 E-05 182F-05 L62E-05 129E-05 190E-05 890E-04 981 E-04

PCEraquo Concentration

(ugL)

lt5

(14A)

98 11

15

22

11

30

200 (62)A

110 210 300 240

(44)A (23)A

5

350 190 129 230

2200 1900 2600 2600

(17)A (16)A (19)A

96

Table XX Packer Permeability and Packer Sampling Results for Potential Fracture Intervals

2004 Drilling Program

Hows Corner Superfund Site Plymouth Maine

Top of Bottom of Depth to Midpoint

t K

ELEV (ft Potential Transmissive Zones Packer Interval

Packer Interval

Middle of Interval

Elevation of interval

Hydraulic Conductivity

PCE Concentration

Well ID msl) TESTr (ft bgs)- (ftbgs) (ftbgs) (ftbgs) (ft msl) (cmsec) (ogt) MW-203D 43227 4 277279 24 32 28 4043 667E-05 44

3 408415420 39 49 44 3883 593E-05 170 2 526 530 49 57 53 3793 101E-04 140 I 828830842 80 88 84 3483 701E-05 130

MW-204D 43262 5 295 300 26 34 30 4023 902E-05 220 4 463496513516 45 53 49 3833 119E-04 540 3 681685688 63 71 67 3653 OOOE+00 2 758 76 2 71 79 75 3573 309E-05 260 I 88 96 92 3403 OOOE+00

MW-205 42389 3 164 166 168 15 20 175 4148 OOOE+00 1000B 2 302305312 30 35 325 3998 107E-04 1300B 1 40 45 425 3898 OOOE+00

MW-206D 43007 5 17 72 195 4128 291E-05 4 296 302 307 29 34 315 4008 940E-05 2900B 3 522 52 57 545 3778 944E-07 2 656 64 69 665 3658 353E-06 1 92392793 4939 91 96 935 3388 614E-05 6300B

PW-207 43477 5 184622162819 18 29 235 4088 209E-05 1300 4 3508 32 43 375 3948 568E-06 5400 3 53325341542154325559 50 61 555 3768 821E-05 18000

6359 61 72 665 3658 866E-06 12000 1 8685 84 89 865 3458 213E-05 19000

NOTES cmsec = centimeters per second ft bgs = feet below ground surface ft msl = feet above mean sea level B = detected in lab blank

Table XX Orientation Permeability and Groundwater Sampling Results for Transmissive Features

2004 Drilling Program

Hows Corner Superfund Site Plymouth Maine

Borehole Geophisical Feature depth Dip True Dip True Transmissive Log Feature (Feet) Degrees Azimuth Strike bullvgt(Ltk|iy^

Number v Tosftble) v MW-203 5 277 64 337 67 Likely

6 279 59 11 281 Likely 8 352 14 177 87 Likely 11 381 46 96 6 Possible 12 408 35 271 1 Possible 14 415 57 250 340 Possible 15 420 58 202 292 Likely 18 526 52 75 345 Likely 19 530 52 82 352 Likely 28 828 48 75 345 Likely 29 830 52 17 287 Likely 30 830 56 233 323 Possible 31 842 50 130 40 Likely

MW-204 4 295 15 147 57 Likely 5 300 43 91 1 Likely 11 439 31 80 350 Possible 12 440 46 219 309 Possible 14 463 50 358 88 Likely 15 496 34 198 288 Likely 16 513 54 17 287 Likely 17 516 33 14 284 Likely 25 681 39 359 89 Possible 26 685 22 45 315 Possible 27 688 35 73 343 Possible 32 758 45 236 326 Likely 33 762 46 306 36 Likely

MW-205 5 164 69 106 16 Possible 6 166 78 165 75 Possible 7 168 82 115 25 Possible 8 168 68 116 26 Possible 12 215 46 222 312 Possible 13 217 75 62 332 Possible 14 219 29 32 302 Possible 16 237 69 250 340 Possible 17 256 73 353 83 Possible 18 272 44 202 292 Possible 21 299 37 196 286 Possible 22 302 31 206 296 Possible 23 305 59 48 318 Likely 24 312 63 42 312 Likely

MW-206 1 264 37 181 271 Likely 2 296 69 217 307 Likely 3 302 66 233 323 Likely 4 307 64 224 314 Likely 8 342 62 259 349 Likely

jjHydraulic GoiDanctilyity j(cmsecjw

667 E-05

593 E-05

101 P04

710 E-05

902 E-05

119 E-04

0

309 E-05

0

107 E-04

94 E-05

PCE (ugL)

44

170

140

130

220

540

260

IOOOB

1100B

1300B

2900B

STotal vVoCsv tig1)

84

234

192

183

2636

6436

3073

11448

12509

13776

32401

PCEyo dfCTotaf

52

73

73

7 1

83

84

85

87

88

94

90

Table XX Orientation Permeability and Groundwater Sampling Results for Transmissive Features

2004 Drilling Program

Hows Corner Superfund Site Plymouth Maine

Borehole Geophisical Feature deptt raquoip True pip True Transraissive Log Feature (Feet) shy Degrees Azimuth Strike (tikely

Number raquo Possible) 22 522 57 54 324 Possible 25 656 40 82 352 Possible 32 871 59 151 61 Possible 33 883 53 185 275 Possible 34 895 7 175 85 Likely 35 899 53 90 0 Likely 36 902 49 184 274 Likely 37 923 9 175 85 Likely 38 927 42 206 296 Likely 39 934 48 167 77 Likely 40 939 26 180 90 Likely

PW-207 1 1846 33 167 77 Likely 4 2216 49 289 19 Possible 7 2819 59 265 355 Possible 11 3508 55 189 279 Possible 18 5332 43 305 35 Likely 19 5341 51 30 300 Likely 20 5421 20 254 344 Likely 21 5432 39 301 31 Likely 23 5559 52 302 32 Likely 25 6359 24 182 272 Possible 29 8049 77 231 321 Possible 30 8685 78 38 308 Likely 32 9334 29 194 284 Likely

NOTES

B = detected in lab blank

Hydraulic Conductivity

(cmsee) 944 E-07 353 E-06

614 E-05

209 E-05

568 E-06

821 E-05

866 E-06

213 E-05

bulltCE (ugL)

6300B

1300

5400

18000

12000

19000

Total VOCs (ug1)

68901

1410

5802

19234

13085

20354

PCE of Total VOCs

9 1

92

93

94

92

93

Response to EPA-DEP Comment 3 Dated March 312005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

lit

EPA-DEP Comment 3

Comment 3 The reported f values and resultant Kd values There remains doubt that the values used in the flushing model accurately reflect the propensity for PCE to sorb to the bedrock The ^ values presented in Appendix B may be unrealistically high because the bedrock samples may have contained organic carbon that was unavailable for sorption The reported f values are only qualitative estimates of the organic carbon content of the bedrock samples The Walkley and Black organic carbon measurement method is quick and simple but the results obtained cannot be considered quantitative because it requires a correction factor which often results in erroneous values it assumes the organic carbon has an average valence of zero oxidizable and reducible constituents such as chloride ferrous iron and manganese oxides interfere with the results and the errors introduced by interference are potentially greater when the organic carbon content is low at low f values it is not clear that organic carbon is controlling PCE sorption (Schwarzenbach and Westall 1981 Mackay et al 1986 Fetter 1999)

In order to derive a Kd-based retardation factor that is reasonable given the reported f values and the rapid advance of the PCE plume described on pages 4-11 and 4-12 the flushing model requires a bulk density to porosity ratio that is roughly two orders of magnitude higher than the actual ratio for the Hows Corner bedrock (page 4-4) This apparent discrepancy needs to be addressed

Response This comment raises several concerns about the collection and analysis of samples for fraction of organic carbon (f^) the quality of the resulting data and the implications of the use of those data for estimation of the retardation of groundwater contaminant movement Results of bedrock analysis for f were proposed in the TI Evaluation Work Plan for use in conjunction with groundwater contaminant concentrations and aquifer information to estimate cleanup times using the Batch Flushing model It is important to use accurate f values from representative bedrock in the Batch Flushing model in order to obtain reasonable estimates of the remedial time frame Because of the importance of accurate and representative results the TI Investigation field program was designed and conducted both to collect samples representative of the rock volume most likely to be in contact with contaminated groundwater and to analyze them using an appropriate refereed analytical method Five potential methods for evaluating f were identified Of the five methods the Walkey-Black method was selected because it has minimal method interferences and a sufficiently low detection limit as well as a long history of use in agronomy and contamination studies The PRP Group is pleased with the quality of the data obtained from the bedrock samples as represented by their precision and reproducibility

The first part of this comment relates to the determination of fraction of organic carbon (f^) values The several subparts of the first paragraph are addressed individually in items 1 through 5 below The second part of the comment regarding the resultant distribution coefficient (Kd) values is addressed separately as item 6 below

1 There remains doubt that the values used in the flushing model accurately reflect the propensity for PCE to sorb to the bedrock

bull The rock core samples used for f (gocg) analysis were from core immediately adjacent to fractures These rock core samples included the fracture surfaces themselves and rock core extending back less than 1 cm from the fractures Therefore the foe data reported in the TI Evaluation represents the f of bedrock through which groundwater will travel and to which PCE will adsorb Based on the careful selection of sample locations and the

Response to EPA Comment 3 050205doc 1 of 11 Woodard amp Curran (211941)

number of samples collected we are confident that the measured f values are representative of the f at points of contact for PCE with the bedrock it is these f values that determine the propensity of PCE to sorb to the bedrock

bull The samples of rock core collected for analysis of f originated from 19 different locations varying in depth from 11 to 90 feet Therefore it is very unlikely that the rock core samples were contaminated with extraneous organic carbon from above ground

2 The foc values presented in Appendix B may be unrealistically high because the bedrock samples may have contained organic carbon that was unavailable for sorption

bull As noted in response 1 the f data reported in Appendix B represents organic carbon primarily associated with the surface of fractures in the bedrock through which groundwater is most likely to travel Therefore it is this organic carbon that the contaminants in the groundwater will come in contact with and adsorb to in the fractured rock at the site

bull The chemical oxidation agents used in the Walkey-Black method oxidize the easily oxidizable organic carbon in the medium and the foe is calculated from the quantity of the agent consumed Therefore it is unlikely that the analysis of the bedrock samples measured organic carbon that was unavailable for sorption

3 The reported foc values are only qualitative estimates of the organic carbon content of the bedrock samples

bull The reported f values are accurate quantitative results Schumachers review of Methods for the determination of total organic carbon (TOC) in soils and sediments (NCEA-C-1282 EMASC-001 April 2002) identifies the Walkley-Black method which was used to analyze the reported foc values as the reference method for comparison to other methods for analyzing total organic carbon

bull Schumacher also points out that if anything the WalkJey-Black method may underestimate the total organic carbon in a sample due to possible incomplete oxidation of organic carbon Usually the incomplete oxidation of total organic carbon in environmental samples is corrected for by multiplying the measured foe by 130 (Walkley amp Black 1934 Schulte 1995)

bull When the f data in the TI Evaluation Report (WampC 2005) Appendix B (attached) are analyzed statistically the standard deviation of the f for the 19 samples analyzed is 174 of the average f Given this standard deviation the 95 confidence interval for this data ranged from a low of 000123 gocg to a high of 000253 gocgm

The labs Method of Detection Limit (MDL) for the f measured using the Walkley-Black method is 00001 gocg Therefore the average (000188 gocg) the mean (000185 gocg) and geometric mean (000187 gocg) of the f values for the rock core at Hows Corner are all statistically significantly greater than the MDL of the Walkley-Black method

In addition to the aforementioned statistical analysis of the foe data triplicate samples (n = 3) from the same rock core (including one sample from the 19 rock core samples) were

Response to EPA Comment 3 050205doc 2 of Woodard amp Curran (211941)

analyzed for their f to determine the repeatability of the Walkley-Black method The average the mean and the geometric mean of the f values of these replicate samples was 000162 gocg 000150 gocg and 000159 gocgm respectively The standard deviation of these measurements was 000039 gocg

4 The Walkley and Black organic carbon measurement method is quick and simple but the results obtained cannot be considered quantitative because it requires a correction factor which often results in erroneous values it assumes the organic carbon has an average valence of zero oxidizable and reducible constituents such as chloride ferrous iron and manganese oxides interfere with the results and the errors introduced by interference are potentially greater when the organic carbon content is low at low foc values it is not clear that organic carbon is controlling PCE sorption (Schwarzenbach and Westall 1981 Mackay et al 1986 Fetter 1999)

bull Schumachers review (NCEA-C-1282 EMASC-001 April 2002) of the Walkley-Black method identifies several potential problems with this analytical method that could occur if the analytical lab is not familiar with the nuances of the chemistry associated with this method Interestingly Schumachers review neglected one of the more important analytical steps required to avoid errors in quantifying f in samples where there might beNAPL

It is absolutely critical to eliminate any NAPL from rock core samples prior to using the Walkley-Black method to measure foe in such samples This was done by the lab (PTS Laboratories) that measured the foe in the rock core samples from Hows Corner The lab used the Dean-Stark method (solvent extraction) to remove all hydrocarbons (including PCE and other NAPLs) from the sample (PTS Laboratories) This extraction method does not interfere with the subsequent analysis of the natural organic carbon associated with the rock core

Subsequently the samples were dried at 150degC to a constant weight (normally 16 hours) This latter step oxidizes all inorganic minerals including ferrous bearing minerals to ferric oxides and precludes their interference during the oxidation of the samples with chromic acid This procedure completely eliminates any positive bias in the reported foc

data that might have occurred due to the presence of ferrous ions and other reduced minerals

bull As noted in Response 3 the incomplete oxidation of total organic carbon results in an underestimate of the f and is corrected for by multiplying the f by a correction factor of 130 (Walkley amp Black 1934 Schulte 1995) The fx data reported in the TI Evaluation was corrected accordingly by using this correction factor

bull Excess chloride (Cl~) in percent weight quantities as found in saline soils may interfere with the quantitative titration of reduced chromium (Walkley 1947) However given that the primary rock type at the Hows Corner site is phyllite it is highly unlikely that there was sufficient chloride in the rock core samples for this to occur

bull Manganese oxides may also interfere with the analysis of f through competing with the dichromate ion for any oxidizable carbon (Walkley 1947) However in such cases the reported f would be an underestimate of the f present in the rock core Walkley (1947)

Response to EPA Comment 3 050205doc 3 of 11 Woodard amp Curran (211941)

4

reported that in the case where the ratio of MnO2 to carbon is 85 to 1 the error in the carbon determinations would only be 0 to 6 percent

It may also be useful to compare the analysis of total organic carbon in a geologic matrix that contains high levels of manganese using EPA method 9060 to the Walkley-Black method Table 1 summarizes data provided by one of the PRPs that compares the analysis of total organic carbon in a geologic matrix that contains approximately 02 wgt manganese (approximately 03 wgt manganese oxide)

Table 1 Comparison of total organic carbon measured using the EPA- 9060 method and the Walkley-Black method

Laboratory EPA-9060 Method Walkley-Black Method A Ave 00226 gocg Not analyzed

Stdev 000251 gocg n = 5

B Ave 002219 gocg Ave 002050 gocg Stdev = 000316 gocg Stdev =000971 gocg

n= 10 n = 10

The similarity in the total organic carbon concentrations measured by these two different methods provides further confidence that the Walkley-Black method is a viable method for analysis of total organic carbon in the presence of manganese equivalent to at least 10 by weight of the total organic carbon

5 The Walkley and Black organic carbon measurement at lowf^ values it is not clear that organic carbon is controlling PCE sorption (Schwarzenbach and Westall 1981 Mackay et al 1986 Fetter 1999)

bull Schwarzenbach and Westalls (1981) paper states that f values of less than 0001 gocg should not be used in combination with Kow (octanol-water partition coefficients) values to calculate K^ values (solid phase partition coefficients) values for a specific contaminant It should be noted that the TI Evaluation did not use the f data to calculate the KQC from the Kow Instead as requested by the EPA the measured KOC value for PCE was used to calculate the retardation factor for this contaminant

bull Schwarzenbach et al (2003) stated more recently that Even at very low f values (ie foe = 0001 kgoc - kg1 solid) sorption to the organic components of a natural sorbent may still be the dominant mechanism in defining the adsorption of organic compounds to geological matrices

bull In 1985 M Piwoni from the US EPA Robert S Kerr Environmental Research Laboratory published a paper (Banerjee et al 1985) that showed that for very hydrophobic molecules TOC content of the sorbent will control sorption down to levels of organic carbon that defy quantitation Contaminants such as the PCE found in the groundwater at Hows Corner are in this category of compounds

Given the aforementioned reasons the f values reported in the TI Evaluation are accurate within the noted statistical limitations and will have a predictable impact upon the retardation of PCE during groundwater transport

Response to EPA Comment 3 050205doc 4 of 11 Woodard amp Curran (211941)

6 In order to derive a Kd-based retardation factor that is reasonable given the reported foc

values and the rapid advance of the PCE plume described on pages 4-11 and 4-12 the flushing model requires a bulk density to porosity ratio that is roughly two orders of magnitude higher than the actual ratio for the Hows Comer bedrock (page 4-4) This apparent discrepancy needs to be addressed

The apparent discrepancy of bulk density to porosity ratios is most likely due to the fact that the Batch Flushing Model was originally developed for a porous medium and is not directly applicable to fractured bedrock As stated in Appendix C (page C-4) of the Draft Technical Impracticability Evaluation Report in order to use the Batch Flushing Model to describe the transport of contaminated groundwater in fractured bedrock where the matrix porosity is insignificant it is more appropriate to use a fracture surface area to void space ratio to calculate the retardation factor (R) than a bulk density to porosity ratio (Freeze amp Cherry 1979)

Since it is impractical to determine the actual surface area to which contaminants can adsorb the Batch Flushing Model was used with two simplifying assumptions bull The Kd was calculated from the f and the K^ bull The bulk density to porosity ratio term in the Batch Flushing Model was constrained to range

from 4 to 10 the typical range of such ratios in porous media (Freeze amp Cherry 1979)

If one uses site specific bedrock bulk density and porosity values the bulk density to porosity ratio is several orders of magnitude greater (specifically 273 gcc bullbull 000165 (dimensionless) = 1654 gcc) than the range of ratios of 4 to 10 used in the Batch Flushing Model in the Draft Technical Impracticability Evaluation Report Constraining the bulk density to porosity ratio within the range of ratios of 4 to 10 results in significantly lower R value than would be obtained using specific bedrock bulk density and porosity values

In summary in bedrock where fractures are the primary porosity the bulk density to porosity ratio can vary considerably and will be a function of the number of fractures and the fracture aperture The calculated bulk density to porosity ratio will be inversely proportional to the porosity This means that in fractured rock with limited fracturing and smaller porosity the calculated bulk density to porosity ratio is greater and will result in a greater calculated retardation factor than in bedrock with more extensive fracturing and greater porosity Consequently the calculated retardation factor will be greater for bedrock with less surface area available for sorption than bedrock with greater surface area for sorption This is contrary to what actually occurs

4 Response to EPA Comment 3 050205doc 5 of 11 Woodard amp Curran (211941)

m

REFERENCES

Banerjee P MD Piwoni K Ebeid (1985) Sorption of organic contaminants to a low carbon subsurface core Chemosphere _14 1057-1067

Freeze RA JA Cherry (1979) Groundwater Prentice Hall Englewood Cliffs NJ pg 604

PTS Laboratories wwwptsgeolabscompdf files3TOCnotepdf

Schulte EE (1995) Recommended soil organic matter tests in Recommended Soil Testing Procedures for the Northeastern United States Northeastern Regional Publication No 493 Chapter 8

Schwarzenbach RP J Westall (1981) Transport of nonpolar organic compounds from surface water to groundwater Laboratory sorption studies Environ Sci Tech 15 1360-1367

Schwarzenbach RP PM Gschwend DM Imboden (2003) Environmental Organic Chemistry Wiley-Interscience pg 292 408 amp 412

Walkley A LA Black (1934) An examination of the Degtjareff method for determining soil organic matter and a proposed modification of the chromic acid titration method Soil Science 37 29-38

Walkley A (1947) A critical examination of a rapid method for determining organic carbon in soils - effect of variations in digestion conditions and of inorganic soil constituents Soil Science 63251-264

Woodard amp Curran Inc (WampC) 2005 Draft Technical Impracticability Evaluation Hows Corner Superfund Site Plymouth Maine January 2005

Response to EPA Comment 3 050205doc 6 of Woodard amp Curran (211941)

LIST OF ATTACHMENTS (Response to Comment 3)

Appendix B to Draft Technical Impracticability Evaluation Measurement of foe at Hows Corner (4 pages)

m

Response to EPA Comment 3 050205doc 7 of 11 Woodard amp Curran (211941)

Appendix B Measurement of foe of Rock Core at Hows Corner

There are two general approaches to measure the fraction of organic carbon (foe) in rock cores

bull Measurement of weight loss by ignition of organic matter bull Chemical oxidization of organic carbon to carbon dioxide and either

subsequent quantification of the oxidant used for the reaction or quantification of the carbon dioxide produced during this oxidation process

The weight loss method is subject to errors caused by volatilization of substances other than organic materials such as water hydroxides and mineral carbonates Quantification of foe by the weight loss method is particularly sensitive to the presence of carbonates in rock cores There are however weight loss methods that are designed to differentiate between organic carbon and the aforementioned interfering materials but they require considerable care and are less accurate at low foe values Hence the weight loss method was not well suited for measuring the foe of the rock core from Hows Corner

The chemical oxidation of organic carbon is much better suited for quantifying organic carbon in rock cores such as those from Hows Corner This method uses a strong chemical oxidant to oxidize organic carbon to carbon dioxide and then measures either the chemical oxidant used to oxidize the organic carbon or the quantity of carbon dioxide produced In addition this general approach is not subject to interference by volatilization of other constituents of the rock core

There are at least two such chemical oxidation methods

bull The method of Baccini which was described by Schwarzenbach amp Westall (1981) first acidifies the sample to eliminate interference by carbonates Then a strong oxidant is used to chemically oxidize the organic carbon to carbon dioxide The resulting carbon dioxide is subsequently reduced to methane and quantified using a flame ionization detector Unfortunately this method has not been described in detail in a referred journal Hence it is would not have been appropriate to use to characterize the foe in the Hows Corner rock core

bull The more commonly used method to quantify foe in rock core is the Walkley-Black method (1934) This method is preferred for RBCA and DODDOE projects and by the oil industry

The Walkley-Black method uses an excess of chromic acid to oxidize (digest) organic matter to carbon dioxide The remaining chromic acid that was not consumed during the oxidation of the organic carbon is then quantified by titration with ferrous sulfate The difference in chromic acid prior to and after the oxidation of the organic carbon represents the total chromic acid used to oxidize

Hows Corner TI Evaluation Page 1 January 13 2005 Appendix B

the organic carbon in the sample The latter can be calculated using the chemical stoichiometry of the reaction

The Walkley-Black method is very accurate for samples that contain less than 2 organic carbon matter The minimum detection limit (MDL) for the Walkley-Black method is 100 mgkg or an foe of 0001

Given the rock core at Hows Corner was expected to contain less than 2 organic carbon the Walkley-Black method was used to measure the foe from 19 different rock core samples collected from varying depths ranging from 11 to 90 feet

Table 1 provides a statistical summary of the aforementioned data

Table 1 Statistical summary of foe data from rock cores collected at varying depths

Statistical Parameter Calculated Value foe Minimum Detection Limit (MDL) 00010 Number of samples analyzed (n) 19 Average foe 00019 Median foe 00019 Geometric Mean foe 00019 Standard deviation of foe measurements 000033 Relative standard deviation 174 -+ 95 Confidence intervals 00012 to 00025

The data in Table 1 shows the following

bull The foe from the Hows Corner rock cores are statistically greater than the MDL of the Walkley-Black analytical method

bull The average and median values for the foe of the Hows Corner rock cores from varying depths are nearly identical indicating that there is little variability in the foe values in the source zone at the site

bull The standard deviation of these measurements is 000033 which is 174 of the average foe

bull The 95 confidence intervals of the foe of the rock core at Hows Corner are 00012 to 00025

The foe was also analyzed from three separate samples taken from the same rock core at a depth of 55 feet (Only one of these samples was included in the data summarized in Table 1) Table 2 shows the statistical repeatability of this type of analysis

Hows Corner TI Evaluation Page 2 January 13 2005 Appendix B

Table 2 Repeatability of analysis of foe from one rock core at 55 feet in depth

Statistical Parameter Calculated Value Number of samples analyzed (n) 3 Average foe 00016 Median foe 00015 Geometric Mean foe 00016 Standard deviation of foe measurements 000039 Relative standard deviation 240 -+ 95 Confidence intervals 00008 to 00024

The data in Table 2 shows the following

bull The percent relative standard deviation of these three analyses of foe from the same rock core at Hows Corner is 24

bull The 95 confidence interval of the foes measured in this particular rock core at Hows Conrer is 00008 to 00024

These results show that there is good repeatability in using the Walkley-Black method for analysis of the foe in the rock core at Hows Corner

References Schwarzenbach amp Westall (1981) Transport of nonpolar organic compounds from surface water to groundwater Laboratory sorption studies Environ Sci Tech 15 1360-1367

Walkley A I A Black (1934) An examination of Degtjareff method for determining soil organic matter and a proposed modification of the chromic acid titration method Soil Sci 37 29-37

Hows Corner Tl Evaluation Page S January 13 2005 Appendix B

Woodard and Curran PTS Laboratories PTS File No 34618

ORGANIC CARBON DATA (METHODOLOGY WALKLEY-BLACK)

PROJECT NAME PROJECT NO

SAMPLE ID

203-chip-13 203-chip-23 203-chip-27 203-chip-38 203-chip-42 203-chip-47 203-chip-52 203-chip-58 203-chip-69 203-chip-82 207-chip-11 207-chip-19 207-chip-24 207-chip-29 207-chip-35 207-chip-45 207-chip-55 207-chip-87 207-chip-90

207-chip-55 55-MS

55-MSMSD

Hows Corner NA

DEPTH ft

13 23 27 38 42 47 52 58 69 82 11 19 24 29 35 45 55 87 90

55 NA NA

MATRIX

Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip

Average Median

Geometric Mean Standard Deviation Relative Std Dev

+- 95 Confidence Interval n

Rock Chip Rock Chip Rock Chip

Average Median

Geometric Mean Standard Deviation Relative Std Dev

+- 95 Confidence Interval n

FRACTION ORGANIC CARBON

(gg)

170E-03 185E-03 185E-03 170E-03 240E-03 190E-03 230E-03 180E-03 170E-03 115E-03 195E-03 220E-03 220E-03 235E-03 135E-03 190E-03 205E-03 175E-03 160E-03

188E-03 185E-03 185E-03 327E-04

1739 123E-03 to

19

205E-03 130E-03 150E-03

162E-03 150E-03 159E-03 388E-04

2402 840E-04 to

3

2532E-03

2393E-03

Hows Corner Tl Evaluation Appendix B January 13 2005

Response to EPA-DEP Comment 4 Dated March 31 2005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

EPA-DEP Comment 4

Comment 4 Distribution of contaminants First the TI report seems based on the assertion that there is DNAPL at the source area yet it also appears to represent that the source area is small and the bedrock below 85 is competent (or less fractured) and less impacted by the release of contaminants Some of the confusion may result from using most recent data when that data is from several different sampling events over several years and there is no discernible difference in concentrations between shallow and deep bedrock or as in Section 421 where generally decreased generally increase generally similar and similar concentrations in four consecutive sentences leads to a muddled picture of the contaminant distribution

Second the report asserts that the distribution of contaminants over the entire plume has not changed with time but fails to support this conclusion with data again relying on data that is from different sampling dates for one composite representation

Response The likely presence of dense non-aqueous phase liquid (DNAPL) at the Hows Corner Site and the determination that the source area is small are not mutually exclusive and both are conclusions drawn from information obtained during field investigations The presence of DNAPL in the source area is based on the elevated concentrations of volatile organic compounds (VOCs) detected in the groundwater (WampC 2001 WampC 2002) The conclusion that the source area is small is based on the area in which VOCs in groundwater have been detected at concentrations that are considered to be indicative of the presence of DNAPL nearby Similarly the conclusion that fracture frequency decreases at depths greater than approximately 50 to 85 feet below ground surface was based on field observation during the RI field work The fact that zones with observed fractures exhibited higher hydraulic conductivities than zones without fractures coupled with the decreasing frequency of observed fractures with depth led to the conclusion that the hydraulic conductivity of the bulk rock decreases with depth

The most recent data from all wells were used to provide the maximum VOC data set size During the RI all of the previously-existing and then newly-installed monitoring wells were sampled along with several residential wells The RI sampling included up to 48 monitoring wells Subsequent to the RI and prior to the TI three rounds of monitoring were conducted to verify that the plume was stable 15 monitoring wells were sampled during each of the three rounds During the TI field investigation 29 wells were sampled for VOCs The sampled wells included all of the newly-installed wells and a subset of wells installed during the RI for a total of 29 monitoring wells By using most recent data VOC results from 53 monitoring wells were included in the evaluation (see table labeled Sampling Events for listing of monitoring wells) This approach was selected because there generally was little variation in the data from a particular location between years This is borne out by the attached individual plots of VOCs detected in shallow bedrock and deep bedrock for the Pre-ROD (December 1999January 2000) and Supplemental (May 2000) sampling events and for June 2001 January 2002 and April 2003 sampling events The Pre-ROD and Supplemental plots are similar to the subsequent plots from the 2001 2002 and 2003 sampling events

In addition to maps showing the spatial distribution of VOC data at a given time trend plots of the data from a particular location through time (attached) indicate that since the RI concentrations generally have been stable or have decreased Together the maps and trend plots and the data from which they were developed indicate that the distribution of contaminants over the entire plume has not changed appreciably with time

Response to EPA Comment 4 050305doc 1 of 26 Woodard amp Curran (211941)

REFERENCES

Woodard amp Curran Inc (WampC) 2001 Final Remedial Investigation Report Hows Corner Superfund Plymouth Maine July 2001

Woodard amp Curran Inc (WampC) 2002 Final Feasibility Study Report - Non-Source Area Groundwater Hows Corner Superfund Site Plymouth Maine Hows Corner Superfund Plymouth Maine July 2002

Response to EPA Comment 4 050305doc 2 of 26 Woodard amp Curran (211941)

LIST OF ATTACHMENTS (Response to Comment 4)

Table - Sampling Events 1999 - 2004 (2 pages)

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater Pre-ROD Sampling Event

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater Pre-ROD Sampling Event

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater Supplemental Sampling Event

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater Supplemental Sampling Event

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater June 2001

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater June 2001

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater January 2002

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater January 2002

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater April 2003

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater April 2003

Figure - Concentration Trends - Non-Source Area Wells MW-1B and MW-3B

Figure - Concentration Trends - Non-Source Area Wells MW-13DB and MW-16DB

Figure - Concentration Trends - Non-Source Area Wells MW-16IB and MW- 108D

Figure - Concentration Trends - Non-Source Area Wells MW-108S and MW-112D

Figure - Concentration Trends - Non-Source Area Wells MW-112S and MW-114D

Figure - Concentration Trends - Non-Source Area Wells MW-114S and MW-115D

Figure - Concentration Trends -Source Area Wells MW-2DB and MW-2IB

Figure - Concentration Trends -Source Area Wells MW-102S and MW-103D

Figure - Concentration Trends -Source Area Wells MW-103S and MW-104D

Figure - Concentration Trends -Source Area Wells MW-104I and MW-106D

Figure - Concentration Trends -Source Area Wells MW-106S

Response to EPA Comment 4 050305doc 3 of 26 Woodard amp Curran (211941)

I I

El I

II I I 1 I

I

i

Event Baseline Case ID WC-01 WC-01

Well Date Aug-99 Oct-99 LOT10 1 LOT1-1 1 LOT11-4 LOT14 1 LOT15 1 LOT15-1 1 LOT16 1 LOT16-1 1 LOT17 1 LOT18 1 LOT19 1 LOT2 LOT20 1 LOT21-10 1 LOT21-11 1 LOT21-12 1 LOT21-13 1 LOT21-14 1 LOT21-2 1 LOT21-5 1 LOT21-7 LOT21 -8 1 LOT21-9 1 LOT23 1 LOT24 1 LOT28-1 1 LOT28-2 1 LOT28-3 1 LOT28-4 1 LOT28W 1 LOT30 1 LOT30-1 1 LOT30-2 1 LOT30-3 1 LOT30-4 1 LOT30-5 LOT31 LOT35 1 LOT41 1 LOT42-1 1 LOT43-1 1 LOT43-4 1 LOT6-1 1 LOT67 1 LOT6-7 1 LOT6-8A 1 LOT6-8B 1 LOT80-1 1 LOT82 1 MW-101D MW-1011 MW-101S MW-102D MW-102S MW-103D MW-103S MW-104D MW-1041 MW-104S MW-105D MW-106D

Groundwater Sampling Location Summary 1999 - 2004xls

Sampling Events 1999-2004

Hows Corner Superfund Site Plymouth Maine

Supplemental 2001 2002 2003 Pumping 2004 Pre-ROD Rl Sampling Sampling Sampling Test Sampling WC-03 WC-09 WC-25 WC-30 WC-42B WC-56 WC-58 Dec-99 May-00 Jun-01 Jan-02 Apr-03 Sep-04 Sep-04

1

1 1 1

1 1 1 1 1

1 1

1

1 1

1 1 1

1 1 1 1 1

1

1 1

1 1 1 1

1

1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

Sampling Events 1999-2004

Hows Corner Super-fund Site Plymouth Maine

Supplemental 2001 2002 2003 Pumping Event Baseline Pre-ROD Rl Sampling Sampling Sampling Test

Case ID WC-01 WC-01 WC-03 WC-09 WC-25 WC-30 WC-42B WC-56

ll

Well Date Aug-99 Oct-99 Dec-99 May-00 Jun-01 Jan-02 Apr-03 Sep-04 MW-106S 1 1 1 1 1 MW-107D 1 1 MW-108D 1 1 1 1 1 MW-108S 1 1 1 1 1 MW-110D 1 1 MW-111D 1 1 MW-112D 1 1 1 1 1 MW-112S 1 1 1 1 1 MW-113D 1 1 MW-114D 1 1 1 1 1 MW-114S 1 1 1 1 1 MW-115D 1 1 1 1 1 MW-12DB 1 1 1 MW-12SB 1 1 1 MW-13DB 1 1 1 1 1 1 MW-13SB 1 1 1 MW-14DB 1 1 MW-14SO 1 1 MW-15DB 1 1 1 MW-15SB 1 1 1 MW-16DB 1 1 1 1 1 1 MW-16IB 1 1 1 1 1 1 MW-16SO 1 1 MW-17DO 1 1 1 MW-17SO 1 1 1 MW-1B 1 1 1 1 1 1 MW-203D MW-203S MW-204D MW-204S MW-205 MW-206D

I MW-206S MW-2DB 1 1 MW-2DDB 1 1 MW-2IB 1 1 1 1 1 1 MW-3B 1 1 1 1 1 1

I MW-4O 1 1 1 MW-5B 1 1

II MW-6DB 1 1 1 MW-6SB 1 1 1 MW-8DB 1 1 1 MW-8SB 1 1 1

II PW-207 1 SEEP-1 1 SUBTOTAL - RESIDENTIAL 44 25 0 2 0 3 0 SUBTOTAL - MONITORING 22 48 41 15 15 15 1

Total 3 66 73 41 17 15 18 1

I Included in most recent data

I Notes 1 - Overburden well not included in most recent data for plotting

2 - Tetrahydrofuran and 2-Butanone were the only two compounds detected in this well and are thought to be the result of well repair not included in most recent data for plotting

3 - Not included in most recent data for plotting

2004 Sampling

WC-58 Sep-04

1

1 1

1 1

1 1 1

1

1 1

1 1 1 1 1 1 1 1 1

1 1

1

0 29

29

Groundwatef Sampling Location Summary 1999 - 2004xls

I

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

monitoring well Figure 4-14 total VOC contour (ugl) - December 1999January 2000 Distribution of Total VOCs in

Note SW-113 is located downstream of SEEP-1 Shallow Bedrock Groundwater total concentration of detected VOCs ND= not detected these two locations were sampled during the Pre-ROD Sampling Event

Baseline Sampling Event in OctoberNovember 1999 Hows Corner Superfund Site Surface Water Sampling Location A Plymouth Maine Seep Sampling Location laquo- WOODARD ampCURRAN

995037wipri reportepa ri interim final feb 2001cadd drawingsfinalfig 4-14

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

0 300 600 I

FEET

Q residential well Figure 4-16 monitoring well Distribution of Total VOCs in

Deep Bedrock Groundwater total VOCs contour (ugl) Pre-ROD Sampling Event

active residential wells with lot number Hows Corner Superfund Site 2deg42deg Plymouth Maine total concentration of detected VOCs ND= not detected WOODARD ampCURRAN Enyinaaring bull Science bull Operations bull

995037wipri reportepa ri interim final feb 2001cadd drawingsfinalfig4mdash16

PLYMOUTH POND

PLYMOUTH POND

1 628Tl7MW-2bB 12135

PLYMOUTH POND

monitoring well Figure 4-20

V total VOC contour (ugl) - June 2000 Distribution of Total VOCs in Shallow Bedrock Groundwater

| 34 | total concentration of detected VOCs ND= not detected NA = not analyzed Supplemental Sampling Event Note SW-113 is located downstream of SEEP-1 Hows Corner Superfund Site

Surface Water Sampling Location these two locations were sampled during the Plymouth Maine Baseline Sampling Event in OctoberNovember 1999 Seep Sampling Location WOODARD amp CURRAN

Engineering bull Science - Operations bull 995037wipri reportepa ri interim final feb 2001 cadd drawingsfinalfig 4-20

residential well Figure 4-22 Distribution of Total VOCs in

monitoring well Deep Bedrock Groundwater

total VOCs contour (ugl) Supplemental Sampling Event

Hows Corner Superfund Site

total concentration of detected VOCs ND= not detected NA = not analyzed Plymouth Maine

WOODARD amp CURRAN

995037wipri reportepa-ri interim final feb 2001cadd drawingsfinalfig 4-22 Engineering bull Science - Operations bull

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

FEET

Shallow Monitoring Well

Deep Monitoring Well

C Detected Concentration ND = Not Detected Figure 1-XS Distribution of Total VOCs in Shallow Bedrock Groundwater

Pumping Well

17-Acre Property Boundary Concentration Contour (ugl)

June 2001 Hows Corner Superfund Site

Plymouth Maine WOODARDampCURRAN

-i^rhvj bull Scbncn bull Operations bull 211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0601 dwg04-20-05

PLYMOUTH POND Hopkins Road V

O

PLYMOUTH POND

PLYMOUTH POND

o

0 300 600 mdashfa FEET

Shallow Monitoring Well bull bull - 17-Acre Property Boundary Figure 1-XD

Deep Monitoring Well 1 I Detected Concentration ND = Not Detected Distribution of Total VOCs in Deep Bedrock Groundwater

-mf- Pumping Well June 2001 Residential Well Hows Corner Superfund Site

Plymouth Maine i h Surface Water Sampling Point

g WOODARD ampCURRAN _ ^ _ ^ _ _ yen_ rj i|Hlaquorlny bull Science bull Opt

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0601 dwg04-20-05

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

Shallow Monitoring Well

Deep Monitoring Well

Detected Concentration ND = Not Detected Figure 1-YS Distribution of Total VOCs in Shallow Bedrock Groundwater

Pumping Well

17-Acre Property Boundary Concentration Contour (ugl)

January 2002 Hows Corner Superfund Site

Plymouth Maine WOODARD amp CURRAN Engineering Science- Operations bull

211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0102dwg04-20-05

PLYMOUTH POND

PLYMOUTH POND

Site Pand^ laquoum-laquoBTuitaraquo tLV

vVlf-(

PLYMOUTH POND

0 300 600 ^ = FEET

Shallow Monitoring Well mdashbullbullbull 17-Acre Property Boundary Figure 1-YD - A - Deep Monitoring Well FT Detected Concentration ND = Not Detected Distribution of Total VOCs in

Deep Bedrock Groundwater Pumping Well January 2002 Residential Well Hows Corner Superfund Site

Plymouth Maine Surface Water Sampling Point

WOODARD ampCURRAN Engineering Sciencs- Operations bulli Si

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0102dwg04-20-05

- m j

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND j A O-shy

Shallow Monitoring Well E Detected Concentration ND = Not Detected Figure 1-ZS Distribution of Total VOCs in

Deep Monitoring Well Shallow Bedrock Groundwater

Pumping Well Hows Corner

April 2003 Superfund Site

17-Acre Property Boundary Plymouth Maine Concentration Contour (ugl) r WOODARD ampCURRAN

Engineering bull Science bull Operations bull 211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0403dwg04-20-05

s S pound

PLYMOUTH POND

PLYMOUTH POND

- -

5 PLYMOUTH POND

Jo

FEET

ft Shallow Monitoring Well mdashbullbullmdash 17-Acre Property Boundary Figure 1-ZD Deep Monitoring Well I 1 I Detected Concentration ND = Not Detected Distribution of Total VOCs in

Deep Bedrock Groundwater Pumping Well April 2003

Q) Residential Well Hows Corner Superfund Site Plymouth Maine

(T) Surface Water Sampling Point WOODARD ampCURRAN poundKk EnginawtirKj bull Science - Operations bull

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0403dwg04-20-05

0 Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

B MW-1B

I 12000

PCE

B 10000 Total VOCs

I

i 2000

i 0 Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

c MW-3B

G 2000

1800

B PCE

1600 Total VOCs

1 I I E

il-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

G E

211941

El

I I z E

80

Concentration Trends shy Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-13DB

Total VOCs

c i i c o

Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

MW-16DB

30

c i c c I c o

Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99

PCE

Total VOCs

Jul-01 Jul-03

211941

O bi

c Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

I MW-16IB

i 35

3

c Total VOCs

lt- 2 5

0 | gt

o

1 sectI

c c 0 4

Jul-90 Jul-92 Jul-94 Jul-96 Jul-98 Jul-00 Jul-02 Jul-04

I I MW-108D

I 12

PCE 10

Total VOCs c oc 3

E E I 0

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

E 211941

c Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

fi MW-108S

I I 40

PCE 35

Total VOCs

30

I f 26

20 I o

I 15

10

c Dec-99 Dec-00 Dec-01 Dec-02 Dec-03 I 0

I MW-112D

c 35 - imdash

I A3 shyTotal VOCs

o c

E 1 2

I

ition

B 1 ^

-i c 3

0 Dec-99 Dec-OO Dec-01 Dec-02 Dec-03

211941

I

i

I

cII

Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-112S

08

PCE

Total VOCs 06

o 04

02

0 Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

MW-114D

o

12000

10000

8000

6000

PCE

Total VOCs

4000

2000

i

ccEIIc

i

i

E

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

211941

Con

cent

ratio

n (

ug

l)

E Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

I MW-114S

E A5000 -- Total VOCs

- 4000

0 3000

2000

i 1000

i n shy

Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

MW-115D

c PCE

Total VOCs

c E

o

C c

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03 I 0

211941

IepoundII

EIEIIGICCIccc

30000

25000

20000

o bullsect 15000 b

o 10000 U

5000

0 Aug-99

25000

20000

5000

0 Aug-99

211941

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-2DB

PCE

Total VOCs

Aug-01 Aug-03

MW-2IB

PCE

Total VOCs

Aug-01 Aug-03

IDIBI

ii EIDIISIBIG C

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-102S

6000

5000 PCE

Total VOCs

4000

O 3000

2000

1000

0 Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

MW-103D

16000

~ 14000 ugt 3- 12000 o

^ 10000

sect 8000

O 6000

4000

2000

PCE

Total VOCs

0Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

211941

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

G MW-103S

I I

ampo

12000

10000

E sectc

S

8000

6000

4000

2000

0Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

G I 6000

MW-104D

i 5000

PCE

Total VOCs

i i c

2000

1000

Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

E I

211941

cIccIG

IIBCccBcIc

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-1041

PCE Total VOCs

a 25000

0 20000

a 15000

10000

5000

0 Jan-OO Jan-01 Jan-02 Jan-03 Jan-04

MW-106D

3000

2500 PCE

Total VOCs

=sect 2000

o bullsect 1500

1000

500

0 Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

211941

c Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

c MW-106S

I PCE

Total VOCs

i

i Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

i

i i i E

C

211941 c

Response to EPA-DEP Comment 5 Dated March 312005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

iiw

EPA-DEP Comment 5

Comment 5 Matrix Diffusion The report as well as other proponents of matrix diffusion suggest that depletion of DNAPL (Section 5112 page 5-15) needs to be achieved While that might be the ideal the goal is to achieve performance standards and that goal may be attainable while there is residual contamination in the rock perhaps even DNAPL globules The low bedrock matrix porosity (page 1-15) the high permeability values (page 4-4) the relative flux of the groundwater (page 5-5) and the decrease in surface area and out of the mainstream pockets (appendix C-4) all suggest that the diffusion out of the rock matrix would be insubstantial relative to the regional flux of groundwater through the Site

Response The TI Evaluation Report does not explicitly consider or rely upon matrix diffusion as a basis for requesting a TI Waiver for a portion of the Hows Corner Site The technical literature provides documentation that matrix diffusion can be a significant process that affects chemical transport and groundwater remediation timeframes in unconsolidated and consolidated media including fractured rock (US EPA 1989 Freeze and Cherry 1979 Pankow and Cherry 1996 Fountain 1998) Back diffusion of contaminants from the matrix porosity of the fractured rock can prolong the time necessary to achieve groundwater cleanup goals particularly for compounds such as PCE for which the cleanup goal is a low concentration It is our expectation that matrix diffusion has occurred at the Hows Corner Site and that back diffusion of PCE from the rock matrix will also occur Although the extent to which matrix diffusion is occurring at the Hows Comer Site has not been determined and that lack of knowledge contributes to uncertainty regarding the cleanup times at the Site the effect of matrix diffusion is to lengthen rather than shorten the time required for remediation

REFERENCES

Fountain JC 1998 Technologies for Dense Nonaqueous Phase Liquid Source Zone Remediation Ground-Water Remediation Technologies Analysis Center Technology Evaluation Report TE-98-02 December

Freeze RA and Cherry JA 1979 Groundwater Prentice-Hall Inc Englewood Cliffs NJ 07632 p 410-412

Pankow J F and Cherry J A 1996 Dense Chlorinated Solvents Waterloo Press Portland OR 97291-1399 p 67-88

US EPA 1989 Transport and Fate of Contaminants in the Subsurface EPA6254-89019 p 17-18

Response to EPA Comment 5 050305doc 1 of 1 Woodard amp Curran (211941)

WOODARD amp CURRAN Maine Massachusetts New Hampshire Connecticut Florida Operational offices across the US 1-800-426-4262 www woodardcurran com

Page 25: SDMS DocID 251749 - Records Collections · 2020-06-13 · CORPORATE OFFICES: Maine, Massachusetts, New Hampshire, Connecticut New, York, Florida Engineering • Science • Operations

I Northeast Geophysical Services Borehole Geophysical Log

Date logged 082304 PW-207

I Plymouth Maine

Fiowmeter Measurements Temperature (C) Acoustic Televiewer

I (in gpm) (interpreted)

75 8 85 9 95 Caliper (inches) Resistance f0tims) Spontaneous Potential (mV) Dip in Degrees PCE Total VOCs

55 60 0 20 40 SO 80 ugL ugL I I I I I I I

Ambienl Fiowmeter pumping Flewmater

magnetic - 10 - - 1 0

north

i - 20 - - 2 0

1300 1410

i - 30 - - 3 0

i tf

5400 5802 - 40 - - 4 0

B - 50 - - 5 0

I 18000 19234

- 60 - - 6 0

I 12000 13085

- 70 - - 7 0

- 8 0

i - 9 0 19000 20354

G - 100- -100

I 110 110 bull110

0 20 40 60 SO 10 20 30 Dip m Degrees

Fluid Resistivity (ohmmeters) I 50

The dip direction is indicated by ihe line extending from the circle The strike of the fealure is 90 degrees from this

Borehole Geophysical Log

G Packorod Interval August 20(M log The location dip angle and dip dirlaquocton or the sleeted Groundaier samplss were ooliecled by Woodard i Curran on ampt24f2ltXM PW-207 failures are approximate Reter to the televiewer log of this wlaquoll for more precise detail PlyPIOUth Maine Date logged 082304

I

Table XX Packer Permeability and Packer Sampling Results for Potential Fracture Intervals

1

WellID MW-101D MW-101D MW-101D MW-101D MW-101D MW-101D MW-101D MW-101D MW-101D MW-101D MW-I01D MW-101D MW-101D MW-102D MW-102D MW-I02D MW-102D MW102D MW-102D MW-102D MW-102D MW-102D MW-I02D MW-102D MW-102D MW-102D MW-103D MW-103D MW-103D MW-103D MW-I03D MW-103D MW-103D MW-103D MW-103D MW-103D MW-103D MW-103D MW-I03D MW-104D MW-104D MW-104D MW-104D MW-I04D MW-104D MW-104D MW-104D MW-104D MW-104D MW-104D MW-105D MW-105D MW106D MW-106D MW-106D MW-107D MW-107D

1999 Drilling Program

Hows Corner Superfund Site Plymouth Maine

Potential Fracture Top Of Bottom 6 Depth to lt Topof i Interval from Packer Packer Middle of Elevation Hydraulic bull PCE

GS ELEV 1 Rock Drilling Interval Interval Interval of Interval Conductivity Concentration (ft msl) (ft msl) TEST (ftbgs) (ftbgs) r(ftbgs) ( f t b (ft mil) (cmsec) (raquogL)

4339 4329 13 28-29 33-3537-39 271 376 324 4016 OOOE+00 4339 12 37-3444-46 380 485 433 3907 157E-04 4339 11 488 593 541 3799 132E-04 4339 10 60-61 578 683 631 3709 OOOE+00 4339 9 678 783 731 3609 I79E-05 4339 8 778 883 831 3509 106E-05 4339 7 880 985 933 3407 243E-05 4339 6 990 1095 1043 3297 339E-06 4339 5 1090 1195 1143 3197 OOOE+00 4339 4 1190 1295 1243 3097 OOOE+00 4339 3 1365-1375 1290 1395 1343 2997 OOOE+00 4339 2 147-157 1390 1495 1443 2897 580E-05 4339 1 147-157 1470 1575 1523 2817 741E-05 43161 43061 13 166 271 219 4098 333E-04 43161 12 30-3136-40 260 365 313 4004 I54E-05 43161 11 36-4041-43 362 467 415 3902 548E-05 43161 10 470 575 523 3794 598E-05 43161 9 570 675 623 3694 197FOS 43161 8 670 775 723 3594 OOOE+00 43161 7 770 875 823 3494 891 E-05 43161 6 83-94 870 975 923 3394 139E-05 43161 5 970 1075 1023 3294 123E-04 43161 4 1070 1175 1123 3194 526E-06 43161 3 1170 1275 1223 3094 138E-05 43161 2 1270 1375 1323 2994 671E-06 43161 1 1370 1475 1423 2894 OOOE+00 42997 42497 13 18-19 170 275 223 4077 OOOE+00 42997 12 260 365 313 3987 766E-05 42997 11 360 465 413 3887 727E-05 42997 10 460 565 513 3787 192E-05 42997 9 560 665 613 3687 752E-05 42997 8 660 765 713 3587 778E-05 42997 7 85-86 763 868 816 3484 260E-05 42997 6 860 965 913 3387 289E-05 42997 5 102-103 960 1065 1013 3287 102E-04 42997 4 1060 1165 1113 3187 522E-06 42997 3 1160 1265 1213 3087 520E-06 42997 2 129-130 1260 1365 1313 2987 960E-04 42997 1 1360 1465 1413 2887 OOOE+00 43372 42922 11 35-37 42-45 350 455 403 3935 684E-04 43372 10 460 565 513 3825 500E-05 43372 9 560 665 613 3725 106E-05 43372 8 72-74 660 765 713 3625 204E-05 43372 7 760 865 813 3525 872E-06 43372 6 860 965 913 3425 467E-06 43372 5 960 1065 1013 3325 200E-05 43372 4 1060 1165 1113 3225 354E-05 43372 3 125-130 1160 1265 1213 3125 157E-05 43372 2 125-130 1260 1365 1313 3025 337E-04 43372 1 1365 1465 1415 2922 689E-06 43052 43002 2 54-58 490 595 543 3763 124E-05 2100 43052 1 139-140 145-146 1367 1472 1420 2886 154E-04 1400 43291 4391 3 bullI133 260 365 313 4017 439F06 43291 2 77-78 760 865 813 3517 230E-03 400 43291 1 143-144 1355 1460 1408 2922 971E-06 350

29958 27258 4 450 555 503 2493 OOOE+00 (21)A 29958 3 103-105 1000 1105 1053 1943 752E-04 (063)A

Table XX Packer Permeability and Packer Sampling Results for Potential Fracture Intervals

1999 Drilling Program

Hows Corner Supcrfund Site Plymouth Maine

gtbull i Potential Fracture Top _OfBot Bottom of Depth to ltbull Top of Interval from f Packer Packer Middle Of

GS ELEV lt Hock Drilling interval Interval Interval WeD ID ft msl) (ft msl) TEST (ftbgs) ltft$gs) (ftbgs) (ftbgs)

MW-107D 29958 2 128-130 1200 1305 1253

MW-107D 29958 1 139-141 1350 1455 1403

MW-108D 31904 31104 6 35-36 300 405 353 MW-108D 31904 5 60-62 550 655 603

MW-108D 31904 4 80-83 750 855 803

MW-108D 31904 3 118-119 123-124 1150 1255 1203

MW-108D 31904 2 147-149 1440 1545 1493

MW-108D 31904 1 1700 1805 1753

MW-110D 40576 40426 2 21-31 210 315 263 MW-110D 40576 1 148-154 1460 1565 1513 MW-I11D 40519 4 70-71 650 755 703

MW-111D 40519 3 79-82 84-86 780 885 833 MW-I11D 40519 2 97-102 950 1055 1003 MW-111D 40519 1 1370 1475 1423

MW-112D 3027 2942 4 42-52 420 525 473 MW-112D 3027 3 850 955 903 MW112D 3027 2 1100 1205 1153 MW-112D 3027 1 135-136 140-141 1340 1445 1393

MW-113D 43085 43085 5 250 355 303 MW-I13D 43085 4 47-49 460 565 513 MW-113D 43085 3 73-74 700 805 753 MW-113D 43085 2 1050 1155 1103 MW-113D 43085 1 1380 1485 1433

MW-114D 42394 41594 4 48-49 450 555 503 MW-114D 42394 3 79-81 740 845 793 MW-114D 42394 2 121-129 1250 1355 1303 MW-114D 42394 1 134-142 1350 1455 1403

MW-115D 4035 4035 4 300 405 353 MW-1I5D 4035 3 70-71 650 755 703 MW-115D 4035 2 1150 1255 1203 MW-115D 4035 1 1400 1505 1453

LOT-28W 382 7 450 555 503 LOT28W 382 6 550 655 603 LOT-28W 382 5 650 755 703 LOT28W 382 4 750 855 803 LOT-28W 382 3 850 955 903 LOT-28W 382 2 950 1055 1003 LOT-28W 382 1 1055 1155 1105

NOTES cmsec = centimeters per second ft bgs = leet below ground surface It msl = feet below mean sea level lt = not detected at indicated reporting limil A = detected below laboratory PQL ( ) = detected below reporting limits

Elevation of Interval

(ft nisi) 174

159

283gt 2588

2388

1988

1698

1438

3795 2545 3349 3219 3049 2629

2555 2125 1875 1635

4006 3796 3556 3206 2876

3737 3447 2937 2837

3683 3333 2833 2583

3318 3218 3118 3018 2918 2818 2715

Hydraulic Conductivity

(cmsec)

323E-05

208E-05

471E-03

471E-03

624E-05

3I6E-05

264E-05

261 E-05

OOOE+00 200E-04 953E-05 OOOE+00 OOOE+00 212E-05

361 E-05 410E-06 2gQE06 292E-05

786E-05 124E-05 151 E-05 822E-06 82IE-06

858E-05 I69E-05 352E-03 866E-05

223E-05 394E-06 122E-05 525E-06

831 E-05 182F-05 L62E-05 129E-05 190E-05 890E-04 981 E-04

PCEraquo Concentration

(ugL)

lt5

(14A)

98 11

15

22

11

30

200 (62)A

110 210 300 240

(44)A (23)A

5

350 190 129 230

2200 1900 2600 2600

(17)A (16)A (19)A

96

Table XX Packer Permeability and Packer Sampling Results for Potential Fracture Intervals

2004 Drilling Program

Hows Corner Superfund Site Plymouth Maine

Top of Bottom of Depth to Midpoint

t K

ELEV (ft Potential Transmissive Zones Packer Interval

Packer Interval

Middle of Interval

Elevation of interval

Hydraulic Conductivity

PCE Concentration

Well ID msl) TESTr (ft bgs)- (ftbgs) (ftbgs) (ftbgs) (ft msl) (cmsec) (ogt) MW-203D 43227 4 277279 24 32 28 4043 667E-05 44

3 408415420 39 49 44 3883 593E-05 170 2 526 530 49 57 53 3793 101E-04 140 I 828830842 80 88 84 3483 701E-05 130

MW-204D 43262 5 295 300 26 34 30 4023 902E-05 220 4 463496513516 45 53 49 3833 119E-04 540 3 681685688 63 71 67 3653 OOOE+00 2 758 76 2 71 79 75 3573 309E-05 260 I 88 96 92 3403 OOOE+00

MW-205 42389 3 164 166 168 15 20 175 4148 OOOE+00 1000B 2 302305312 30 35 325 3998 107E-04 1300B 1 40 45 425 3898 OOOE+00

MW-206D 43007 5 17 72 195 4128 291E-05 4 296 302 307 29 34 315 4008 940E-05 2900B 3 522 52 57 545 3778 944E-07 2 656 64 69 665 3658 353E-06 1 92392793 4939 91 96 935 3388 614E-05 6300B

PW-207 43477 5 184622162819 18 29 235 4088 209E-05 1300 4 3508 32 43 375 3948 568E-06 5400 3 53325341542154325559 50 61 555 3768 821E-05 18000

6359 61 72 665 3658 866E-06 12000 1 8685 84 89 865 3458 213E-05 19000

NOTES cmsec = centimeters per second ft bgs = feet below ground surface ft msl = feet above mean sea level B = detected in lab blank

Table XX Orientation Permeability and Groundwater Sampling Results for Transmissive Features

2004 Drilling Program

Hows Corner Superfund Site Plymouth Maine

Borehole Geophisical Feature depth Dip True Dip True Transmissive Log Feature (Feet) Degrees Azimuth Strike bullvgt(Ltk|iy^

Number v Tosftble) v MW-203 5 277 64 337 67 Likely

6 279 59 11 281 Likely 8 352 14 177 87 Likely 11 381 46 96 6 Possible 12 408 35 271 1 Possible 14 415 57 250 340 Possible 15 420 58 202 292 Likely 18 526 52 75 345 Likely 19 530 52 82 352 Likely 28 828 48 75 345 Likely 29 830 52 17 287 Likely 30 830 56 233 323 Possible 31 842 50 130 40 Likely

MW-204 4 295 15 147 57 Likely 5 300 43 91 1 Likely 11 439 31 80 350 Possible 12 440 46 219 309 Possible 14 463 50 358 88 Likely 15 496 34 198 288 Likely 16 513 54 17 287 Likely 17 516 33 14 284 Likely 25 681 39 359 89 Possible 26 685 22 45 315 Possible 27 688 35 73 343 Possible 32 758 45 236 326 Likely 33 762 46 306 36 Likely

MW-205 5 164 69 106 16 Possible 6 166 78 165 75 Possible 7 168 82 115 25 Possible 8 168 68 116 26 Possible 12 215 46 222 312 Possible 13 217 75 62 332 Possible 14 219 29 32 302 Possible 16 237 69 250 340 Possible 17 256 73 353 83 Possible 18 272 44 202 292 Possible 21 299 37 196 286 Possible 22 302 31 206 296 Possible 23 305 59 48 318 Likely 24 312 63 42 312 Likely

MW-206 1 264 37 181 271 Likely 2 296 69 217 307 Likely 3 302 66 233 323 Likely 4 307 64 224 314 Likely 8 342 62 259 349 Likely

jjHydraulic GoiDanctilyity j(cmsecjw

667 E-05

593 E-05

101 P04

710 E-05

902 E-05

119 E-04

0

309 E-05

0

107 E-04

94 E-05

PCE (ugL)

44

170

140

130

220

540

260

IOOOB

1100B

1300B

2900B

STotal vVoCsv tig1)

84

234

192

183

2636

6436

3073

11448

12509

13776

32401

PCEyo dfCTotaf

52

73

73

7 1

83

84

85

87

88

94

90

Table XX Orientation Permeability and Groundwater Sampling Results for Transmissive Features

2004 Drilling Program

Hows Corner Superfund Site Plymouth Maine

Borehole Geophisical Feature deptt raquoip True pip True Transraissive Log Feature (Feet) shy Degrees Azimuth Strike (tikely

Number raquo Possible) 22 522 57 54 324 Possible 25 656 40 82 352 Possible 32 871 59 151 61 Possible 33 883 53 185 275 Possible 34 895 7 175 85 Likely 35 899 53 90 0 Likely 36 902 49 184 274 Likely 37 923 9 175 85 Likely 38 927 42 206 296 Likely 39 934 48 167 77 Likely 40 939 26 180 90 Likely

PW-207 1 1846 33 167 77 Likely 4 2216 49 289 19 Possible 7 2819 59 265 355 Possible 11 3508 55 189 279 Possible 18 5332 43 305 35 Likely 19 5341 51 30 300 Likely 20 5421 20 254 344 Likely 21 5432 39 301 31 Likely 23 5559 52 302 32 Likely 25 6359 24 182 272 Possible 29 8049 77 231 321 Possible 30 8685 78 38 308 Likely 32 9334 29 194 284 Likely

NOTES

B = detected in lab blank

Hydraulic Conductivity

(cmsee) 944 E-07 353 E-06

614 E-05

209 E-05

568 E-06

821 E-05

866 E-06

213 E-05

bulltCE (ugL)

6300B

1300

5400

18000

12000

19000

Total VOCs (ug1)

68901

1410

5802

19234

13085

20354

PCE of Total VOCs

9 1

92

93

94

92

93

Response to EPA-DEP Comment 3 Dated March 312005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

lit

EPA-DEP Comment 3

Comment 3 The reported f values and resultant Kd values There remains doubt that the values used in the flushing model accurately reflect the propensity for PCE to sorb to the bedrock The ^ values presented in Appendix B may be unrealistically high because the bedrock samples may have contained organic carbon that was unavailable for sorption The reported f values are only qualitative estimates of the organic carbon content of the bedrock samples The Walkley and Black organic carbon measurement method is quick and simple but the results obtained cannot be considered quantitative because it requires a correction factor which often results in erroneous values it assumes the organic carbon has an average valence of zero oxidizable and reducible constituents such as chloride ferrous iron and manganese oxides interfere with the results and the errors introduced by interference are potentially greater when the organic carbon content is low at low f values it is not clear that organic carbon is controlling PCE sorption (Schwarzenbach and Westall 1981 Mackay et al 1986 Fetter 1999)

In order to derive a Kd-based retardation factor that is reasonable given the reported f values and the rapid advance of the PCE plume described on pages 4-11 and 4-12 the flushing model requires a bulk density to porosity ratio that is roughly two orders of magnitude higher than the actual ratio for the Hows Corner bedrock (page 4-4) This apparent discrepancy needs to be addressed

Response This comment raises several concerns about the collection and analysis of samples for fraction of organic carbon (f^) the quality of the resulting data and the implications of the use of those data for estimation of the retardation of groundwater contaminant movement Results of bedrock analysis for f were proposed in the TI Evaluation Work Plan for use in conjunction with groundwater contaminant concentrations and aquifer information to estimate cleanup times using the Batch Flushing model It is important to use accurate f values from representative bedrock in the Batch Flushing model in order to obtain reasonable estimates of the remedial time frame Because of the importance of accurate and representative results the TI Investigation field program was designed and conducted both to collect samples representative of the rock volume most likely to be in contact with contaminated groundwater and to analyze them using an appropriate refereed analytical method Five potential methods for evaluating f were identified Of the five methods the Walkey-Black method was selected because it has minimal method interferences and a sufficiently low detection limit as well as a long history of use in agronomy and contamination studies The PRP Group is pleased with the quality of the data obtained from the bedrock samples as represented by their precision and reproducibility

The first part of this comment relates to the determination of fraction of organic carbon (f^) values The several subparts of the first paragraph are addressed individually in items 1 through 5 below The second part of the comment regarding the resultant distribution coefficient (Kd) values is addressed separately as item 6 below

1 There remains doubt that the values used in the flushing model accurately reflect the propensity for PCE to sorb to the bedrock

bull The rock core samples used for f (gocg) analysis were from core immediately adjacent to fractures These rock core samples included the fracture surfaces themselves and rock core extending back less than 1 cm from the fractures Therefore the foe data reported in the TI Evaluation represents the f of bedrock through which groundwater will travel and to which PCE will adsorb Based on the careful selection of sample locations and the

Response to EPA Comment 3 050205doc 1 of 11 Woodard amp Curran (211941)

number of samples collected we are confident that the measured f values are representative of the f at points of contact for PCE with the bedrock it is these f values that determine the propensity of PCE to sorb to the bedrock

bull The samples of rock core collected for analysis of f originated from 19 different locations varying in depth from 11 to 90 feet Therefore it is very unlikely that the rock core samples were contaminated with extraneous organic carbon from above ground

2 The foc values presented in Appendix B may be unrealistically high because the bedrock samples may have contained organic carbon that was unavailable for sorption

bull As noted in response 1 the f data reported in Appendix B represents organic carbon primarily associated with the surface of fractures in the bedrock through which groundwater is most likely to travel Therefore it is this organic carbon that the contaminants in the groundwater will come in contact with and adsorb to in the fractured rock at the site

bull The chemical oxidation agents used in the Walkey-Black method oxidize the easily oxidizable organic carbon in the medium and the foe is calculated from the quantity of the agent consumed Therefore it is unlikely that the analysis of the bedrock samples measured organic carbon that was unavailable for sorption

3 The reported foc values are only qualitative estimates of the organic carbon content of the bedrock samples

bull The reported f values are accurate quantitative results Schumachers review of Methods for the determination of total organic carbon (TOC) in soils and sediments (NCEA-C-1282 EMASC-001 April 2002) identifies the Walkley-Black method which was used to analyze the reported foc values as the reference method for comparison to other methods for analyzing total organic carbon

bull Schumacher also points out that if anything the WalkJey-Black method may underestimate the total organic carbon in a sample due to possible incomplete oxidation of organic carbon Usually the incomplete oxidation of total organic carbon in environmental samples is corrected for by multiplying the measured foe by 130 (Walkley amp Black 1934 Schulte 1995)

bull When the f data in the TI Evaluation Report (WampC 2005) Appendix B (attached) are analyzed statistically the standard deviation of the f for the 19 samples analyzed is 174 of the average f Given this standard deviation the 95 confidence interval for this data ranged from a low of 000123 gocg to a high of 000253 gocgm

The labs Method of Detection Limit (MDL) for the f measured using the Walkley-Black method is 00001 gocg Therefore the average (000188 gocg) the mean (000185 gocg) and geometric mean (000187 gocg) of the f values for the rock core at Hows Corner are all statistically significantly greater than the MDL of the Walkley-Black method

In addition to the aforementioned statistical analysis of the foe data triplicate samples (n = 3) from the same rock core (including one sample from the 19 rock core samples) were

Response to EPA Comment 3 050205doc 2 of Woodard amp Curran (211941)

analyzed for their f to determine the repeatability of the Walkley-Black method The average the mean and the geometric mean of the f values of these replicate samples was 000162 gocg 000150 gocg and 000159 gocgm respectively The standard deviation of these measurements was 000039 gocg

4 The Walkley and Black organic carbon measurement method is quick and simple but the results obtained cannot be considered quantitative because it requires a correction factor which often results in erroneous values it assumes the organic carbon has an average valence of zero oxidizable and reducible constituents such as chloride ferrous iron and manganese oxides interfere with the results and the errors introduced by interference are potentially greater when the organic carbon content is low at low foc values it is not clear that organic carbon is controlling PCE sorption (Schwarzenbach and Westall 1981 Mackay et al 1986 Fetter 1999)

bull Schumachers review (NCEA-C-1282 EMASC-001 April 2002) of the Walkley-Black method identifies several potential problems with this analytical method that could occur if the analytical lab is not familiar with the nuances of the chemistry associated with this method Interestingly Schumachers review neglected one of the more important analytical steps required to avoid errors in quantifying f in samples where there might beNAPL

It is absolutely critical to eliminate any NAPL from rock core samples prior to using the Walkley-Black method to measure foe in such samples This was done by the lab (PTS Laboratories) that measured the foe in the rock core samples from Hows Corner The lab used the Dean-Stark method (solvent extraction) to remove all hydrocarbons (including PCE and other NAPLs) from the sample (PTS Laboratories) This extraction method does not interfere with the subsequent analysis of the natural organic carbon associated with the rock core

Subsequently the samples were dried at 150degC to a constant weight (normally 16 hours) This latter step oxidizes all inorganic minerals including ferrous bearing minerals to ferric oxides and precludes their interference during the oxidation of the samples with chromic acid This procedure completely eliminates any positive bias in the reported foc

data that might have occurred due to the presence of ferrous ions and other reduced minerals

bull As noted in Response 3 the incomplete oxidation of total organic carbon results in an underestimate of the f and is corrected for by multiplying the f by a correction factor of 130 (Walkley amp Black 1934 Schulte 1995) The fx data reported in the TI Evaluation was corrected accordingly by using this correction factor

bull Excess chloride (Cl~) in percent weight quantities as found in saline soils may interfere with the quantitative titration of reduced chromium (Walkley 1947) However given that the primary rock type at the Hows Corner site is phyllite it is highly unlikely that there was sufficient chloride in the rock core samples for this to occur

bull Manganese oxides may also interfere with the analysis of f through competing with the dichromate ion for any oxidizable carbon (Walkley 1947) However in such cases the reported f would be an underestimate of the f present in the rock core Walkley (1947)

Response to EPA Comment 3 050205doc 3 of 11 Woodard amp Curran (211941)

4

reported that in the case where the ratio of MnO2 to carbon is 85 to 1 the error in the carbon determinations would only be 0 to 6 percent

It may also be useful to compare the analysis of total organic carbon in a geologic matrix that contains high levels of manganese using EPA method 9060 to the Walkley-Black method Table 1 summarizes data provided by one of the PRPs that compares the analysis of total organic carbon in a geologic matrix that contains approximately 02 wgt manganese (approximately 03 wgt manganese oxide)

Table 1 Comparison of total organic carbon measured using the EPA- 9060 method and the Walkley-Black method

Laboratory EPA-9060 Method Walkley-Black Method A Ave 00226 gocg Not analyzed

Stdev 000251 gocg n = 5

B Ave 002219 gocg Ave 002050 gocg Stdev = 000316 gocg Stdev =000971 gocg

n= 10 n = 10

The similarity in the total organic carbon concentrations measured by these two different methods provides further confidence that the Walkley-Black method is a viable method for analysis of total organic carbon in the presence of manganese equivalent to at least 10 by weight of the total organic carbon

5 The Walkley and Black organic carbon measurement at lowf^ values it is not clear that organic carbon is controlling PCE sorption (Schwarzenbach and Westall 1981 Mackay et al 1986 Fetter 1999)

bull Schwarzenbach and Westalls (1981) paper states that f values of less than 0001 gocg should not be used in combination with Kow (octanol-water partition coefficients) values to calculate K^ values (solid phase partition coefficients) values for a specific contaminant It should be noted that the TI Evaluation did not use the f data to calculate the KQC from the Kow Instead as requested by the EPA the measured KOC value for PCE was used to calculate the retardation factor for this contaminant

bull Schwarzenbach et al (2003) stated more recently that Even at very low f values (ie foe = 0001 kgoc - kg1 solid) sorption to the organic components of a natural sorbent may still be the dominant mechanism in defining the adsorption of organic compounds to geological matrices

bull In 1985 M Piwoni from the US EPA Robert S Kerr Environmental Research Laboratory published a paper (Banerjee et al 1985) that showed that for very hydrophobic molecules TOC content of the sorbent will control sorption down to levels of organic carbon that defy quantitation Contaminants such as the PCE found in the groundwater at Hows Corner are in this category of compounds

Given the aforementioned reasons the f values reported in the TI Evaluation are accurate within the noted statistical limitations and will have a predictable impact upon the retardation of PCE during groundwater transport

Response to EPA Comment 3 050205doc 4 of 11 Woodard amp Curran (211941)

6 In order to derive a Kd-based retardation factor that is reasonable given the reported foc

values and the rapid advance of the PCE plume described on pages 4-11 and 4-12 the flushing model requires a bulk density to porosity ratio that is roughly two orders of magnitude higher than the actual ratio for the Hows Comer bedrock (page 4-4) This apparent discrepancy needs to be addressed

The apparent discrepancy of bulk density to porosity ratios is most likely due to the fact that the Batch Flushing Model was originally developed for a porous medium and is not directly applicable to fractured bedrock As stated in Appendix C (page C-4) of the Draft Technical Impracticability Evaluation Report in order to use the Batch Flushing Model to describe the transport of contaminated groundwater in fractured bedrock where the matrix porosity is insignificant it is more appropriate to use a fracture surface area to void space ratio to calculate the retardation factor (R) than a bulk density to porosity ratio (Freeze amp Cherry 1979)

Since it is impractical to determine the actual surface area to which contaminants can adsorb the Batch Flushing Model was used with two simplifying assumptions bull The Kd was calculated from the f and the K^ bull The bulk density to porosity ratio term in the Batch Flushing Model was constrained to range

from 4 to 10 the typical range of such ratios in porous media (Freeze amp Cherry 1979)

If one uses site specific bedrock bulk density and porosity values the bulk density to porosity ratio is several orders of magnitude greater (specifically 273 gcc bullbull 000165 (dimensionless) = 1654 gcc) than the range of ratios of 4 to 10 used in the Batch Flushing Model in the Draft Technical Impracticability Evaluation Report Constraining the bulk density to porosity ratio within the range of ratios of 4 to 10 results in significantly lower R value than would be obtained using specific bedrock bulk density and porosity values

In summary in bedrock where fractures are the primary porosity the bulk density to porosity ratio can vary considerably and will be a function of the number of fractures and the fracture aperture The calculated bulk density to porosity ratio will be inversely proportional to the porosity This means that in fractured rock with limited fracturing and smaller porosity the calculated bulk density to porosity ratio is greater and will result in a greater calculated retardation factor than in bedrock with more extensive fracturing and greater porosity Consequently the calculated retardation factor will be greater for bedrock with less surface area available for sorption than bedrock with greater surface area for sorption This is contrary to what actually occurs

4 Response to EPA Comment 3 050205doc 5 of 11 Woodard amp Curran (211941)

m

REFERENCES

Banerjee P MD Piwoni K Ebeid (1985) Sorption of organic contaminants to a low carbon subsurface core Chemosphere _14 1057-1067

Freeze RA JA Cherry (1979) Groundwater Prentice Hall Englewood Cliffs NJ pg 604

PTS Laboratories wwwptsgeolabscompdf files3TOCnotepdf

Schulte EE (1995) Recommended soil organic matter tests in Recommended Soil Testing Procedures for the Northeastern United States Northeastern Regional Publication No 493 Chapter 8

Schwarzenbach RP J Westall (1981) Transport of nonpolar organic compounds from surface water to groundwater Laboratory sorption studies Environ Sci Tech 15 1360-1367

Schwarzenbach RP PM Gschwend DM Imboden (2003) Environmental Organic Chemistry Wiley-Interscience pg 292 408 amp 412

Walkley A LA Black (1934) An examination of the Degtjareff method for determining soil organic matter and a proposed modification of the chromic acid titration method Soil Science 37 29-38

Walkley A (1947) A critical examination of a rapid method for determining organic carbon in soils - effect of variations in digestion conditions and of inorganic soil constituents Soil Science 63251-264

Woodard amp Curran Inc (WampC) 2005 Draft Technical Impracticability Evaluation Hows Corner Superfund Site Plymouth Maine January 2005

Response to EPA Comment 3 050205doc 6 of Woodard amp Curran (211941)

LIST OF ATTACHMENTS (Response to Comment 3)

Appendix B to Draft Technical Impracticability Evaluation Measurement of foe at Hows Corner (4 pages)

m

Response to EPA Comment 3 050205doc 7 of 11 Woodard amp Curran (211941)

Appendix B Measurement of foe of Rock Core at Hows Corner

There are two general approaches to measure the fraction of organic carbon (foe) in rock cores

bull Measurement of weight loss by ignition of organic matter bull Chemical oxidization of organic carbon to carbon dioxide and either

subsequent quantification of the oxidant used for the reaction or quantification of the carbon dioxide produced during this oxidation process

The weight loss method is subject to errors caused by volatilization of substances other than organic materials such as water hydroxides and mineral carbonates Quantification of foe by the weight loss method is particularly sensitive to the presence of carbonates in rock cores There are however weight loss methods that are designed to differentiate between organic carbon and the aforementioned interfering materials but they require considerable care and are less accurate at low foe values Hence the weight loss method was not well suited for measuring the foe of the rock core from Hows Corner

The chemical oxidation of organic carbon is much better suited for quantifying organic carbon in rock cores such as those from Hows Corner This method uses a strong chemical oxidant to oxidize organic carbon to carbon dioxide and then measures either the chemical oxidant used to oxidize the organic carbon or the quantity of carbon dioxide produced In addition this general approach is not subject to interference by volatilization of other constituents of the rock core

There are at least two such chemical oxidation methods

bull The method of Baccini which was described by Schwarzenbach amp Westall (1981) first acidifies the sample to eliminate interference by carbonates Then a strong oxidant is used to chemically oxidize the organic carbon to carbon dioxide The resulting carbon dioxide is subsequently reduced to methane and quantified using a flame ionization detector Unfortunately this method has not been described in detail in a referred journal Hence it is would not have been appropriate to use to characterize the foe in the Hows Corner rock core

bull The more commonly used method to quantify foe in rock core is the Walkley-Black method (1934) This method is preferred for RBCA and DODDOE projects and by the oil industry

The Walkley-Black method uses an excess of chromic acid to oxidize (digest) organic matter to carbon dioxide The remaining chromic acid that was not consumed during the oxidation of the organic carbon is then quantified by titration with ferrous sulfate The difference in chromic acid prior to and after the oxidation of the organic carbon represents the total chromic acid used to oxidize

Hows Corner TI Evaluation Page 1 January 13 2005 Appendix B

the organic carbon in the sample The latter can be calculated using the chemical stoichiometry of the reaction

The Walkley-Black method is very accurate for samples that contain less than 2 organic carbon matter The minimum detection limit (MDL) for the Walkley-Black method is 100 mgkg or an foe of 0001

Given the rock core at Hows Corner was expected to contain less than 2 organic carbon the Walkley-Black method was used to measure the foe from 19 different rock core samples collected from varying depths ranging from 11 to 90 feet

Table 1 provides a statistical summary of the aforementioned data

Table 1 Statistical summary of foe data from rock cores collected at varying depths

Statistical Parameter Calculated Value foe Minimum Detection Limit (MDL) 00010 Number of samples analyzed (n) 19 Average foe 00019 Median foe 00019 Geometric Mean foe 00019 Standard deviation of foe measurements 000033 Relative standard deviation 174 -+ 95 Confidence intervals 00012 to 00025

The data in Table 1 shows the following

bull The foe from the Hows Corner rock cores are statistically greater than the MDL of the Walkley-Black analytical method

bull The average and median values for the foe of the Hows Corner rock cores from varying depths are nearly identical indicating that there is little variability in the foe values in the source zone at the site

bull The standard deviation of these measurements is 000033 which is 174 of the average foe

bull The 95 confidence intervals of the foe of the rock core at Hows Corner are 00012 to 00025

The foe was also analyzed from three separate samples taken from the same rock core at a depth of 55 feet (Only one of these samples was included in the data summarized in Table 1) Table 2 shows the statistical repeatability of this type of analysis

Hows Corner TI Evaluation Page 2 January 13 2005 Appendix B

Table 2 Repeatability of analysis of foe from one rock core at 55 feet in depth

Statistical Parameter Calculated Value Number of samples analyzed (n) 3 Average foe 00016 Median foe 00015 Geometric Mean foe 00016 Standard deviation of foe measurements 000039 Relative standard deviation 240 -+ 95 Confidence intervals 00008 to 00024

The data in Table 2 shows the following

bull The percent relative standard deviation of these three analyses of foe from the same rock core at Hows Corner is 24

bull The 95 confidence interval of the foes measured in this particular rock core at Hows Conrer is 00008 to 00024

These results show that there is good repeatability in using the Walkley-Black method for analysis of the foe in the rock core at Hows Corner

References Schwarzenbach amp Westall (1981) Transport of nonpolar organic compounds from surface water to groundwater Laboratory sorption studies Environ Sci Tech 15 1360-1367

Walkley A I A Black (1934) An examination of Degtjareff method for determining soil organic matter and a proposed modification of the chromic acid titration method Soil Sci 37 29-37

Hows Corner Tl Evaluation Page S January 13 2005 Appendix B

Woodard and Curran PTS Laboratories PTS File No 34618

ORGANIC CARBON DATA (METHODOLOGY WALKLEY-BLACK)

PROJECT NAME PROJECT NO

SAMPLE ID

203-chip-13 203-chip-23 203-chip-27 203-chip-38 203-chip-42 203-chip-47 203-chip-52 203-chip-58 203-chip-69 203-chip-82 207-chip-11 207-chip-19 207-chip-24 207-chip-29 207-chip-35 207-chip-45 207-chip-55 207-chip-87 207-chip-90

207-chip-55 55-MS

55-MSMSD

Hows Corner NA

DEPTH ft

13 23 27 38 42 47 52 58 69 82 11 19 24 29 35 45 55 87 90

55 NA NA

MATRIX

Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip

Average Median

Geometric Mean Standard Deviation Relative Std Dev

+- 95 Confidence Interval n

Rock Chip Rock Chip Rock Chip

Average Median

Geometric Mean Standard Deviation Relative Std Dev

+- 95 Confidence Interval n

FRACTION ORGANIC CARBON

(gg)

170E-03 185E-03 185E-03 170E-03 240E-03 190E-03 230E-03 180E-03 170E-03 115E-03 195E-03 220E-03 220E-03 235E-03 135E-03 190E-03 205E-03 175E-03 160E-03

188E-03 185E-03 185E-03 327E-04

1739 123E-03 to

19

205E-03 130E-03 150E-03

162E-03 150E-03 159E-03 388E-04

2402 840E-04 to

3

2532E-03

2393E-03

Hows Corner Tl Evaluation Appendix B January 13 2005

Response to EPA-DEP Comment 4 Dated March 31 2005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

EPA-DEP Comment 4

Comment 4 Distribution of contaminants First the TI report seems based on the assertion that there is DNAPL at the source area yet it also appears to represent that the source area is small and the bedrock below 85 is competent (or less fractured) and less impacted by the release of contaminants Some of the confusion may result from using most recent data when that data is from several different sampling events over several years and there is no discernible difference in concentrations between shallow and deep bedrock or as in Section 421 where generally decreased generally increase generally similar and similar concentrations in four consecutive sentences leads to a muddled picture of the contaminant distribution

Second the report asserts that the distribution of contaminants over the entire plume has not changed with time but fails to support this conclusion with data again relying on data that is from different sampling dates for one composite representation

Response The likely presence of dense non-aqueous phase liquid (DNAPL) at the Hows Corner Site and the determination that the source area is small are not mutually exclusive and both are conclusions drawn from information obtained during field investigations The presence of DNAPL in the source area is based on the elevated concentrations of volatile organic compounds (VOCs) detected in the groundwater (WampC 2001 WampC 2002) The conclusion that the source area is small is based on the area in which VOCs in groundwater have been detected at concentrations that are considered to be indicative of the presence of DNAPL nearby Similarly the conclusion that fracture frequency decreases at depths greater than approximately 50 to 85 feet below ground surface was based on field observation during the RI field work The fact that zones with observed fractures exhibited higher hydraulic conductivities than zones without fractures coupled with the decreasing frequency of observed fractures with depth led to the conclusion that the hydraulic conductivity of the bulk rock decreases with depth

The most recent data from all wells were used to provide the maximum VOC data set size During the RI all of the previously-existing and then newly-installed monitoring wells were sampled along with several residential wells The RI sampling included up to 48 monitoring wells Subsequent to the RI and prior to the TI three rounds of monitoring were conducted to verify that the plume was stable 15 monitoring wells were sampled during each of the three rounds During the TI field investigation 29 wells were sampled for VOCs The sampled wells included all of the newly-installed wells and a subset of wells installed during the RI for a total of 29 monitoring wells By using most recent data VOC results from 53 monitoring wells were included in the evaluation (see table labeled Sampling Events for listing of monitoring wells) This approach was selected because there generally was little variation in the data from a particular location between years This is borne out by the attached individual plots of VOCs detected in shallow bedrock and deep bedrock for the Pre-ROD (December 1999January 2000) and Supplemental (May 2000) sampling events and for June 2001 January 2002 and April 2003 sampling events The Pre-ROD and Supplemental plots are similar to the subsequent plots from the 2001 2002 and 2003 sampling events

In addition to maps showing the spatial distribution of VOC data at a given time trend plots of the data from a particular location through time (attached) indicate that since the RI concentrations generally have been stable or have decreased Together the maps and trend plots and the data from which they were developed indicate that the distribution of contaminants over the entire plume has not changed appreciably with time

Response to EPA Comment 4 050305doc 1 of 26 Woodard amp Curran (211941)

REFERENCES

Woodard amp Curran Inc (WampC) 2001 Final Remedial Investigation Report Hows Corner Superfund Plymouth Maine July 2001

Woodard amp Curran Inc (WampC) 2002 Final Feasibility Study Report - Non-Source Area Groundwater Hows Corner Superfund Site Plymouth Maine Hows Corner Superfund Plymouth Maine July 2002

Response to EPA Comment 4 050305doc 2 of 26 Woodard amp Curran (211941)

LIST OF ATTACHMENTS (Response to Comment 4)

Table - Sampling Events 1999 - 2004 (2 pages)

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater Pre-ROD Sampling Event

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater Pre-ROD Sampling Event

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater Supplemental Sampling Event

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater Supplemental Sampling Event

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater June 2001

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater June 2001

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater January 2002

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater January 2002

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater April 2003

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater April 2003

Figure - Concentration Trends - Non-Source Area Wells MW-1B and MW-3B

Figure - Concentration Trends - Non-Source Area Wells MW-13DB and MW-16DB

Figure - Concentration Trends - Non-Source Area Wells MW-16IB and MW- 108D

Figure - Concentration Trends - Non-Source Area Wells MW-108S and MW-112D

Figure - Concentration Trends - Non-Source Area Wells MW-112S and MW-114D

Figure - Concentration Trends - Non-Source Area Wells MW-114S and MW-115D

Figure - Concentration Trends -Source Area Wells MW-2DB and MW-2IB

Figure - Concentration Trends -Source Area Wells MW-102S and MW-103D

Figure - Concentration Trends -Source Area Wells MW-103S and MW-104D

Figure - Concentration Trends -Source Area Wells MW-104I and MW-106D

Figure - Concentration Trends -Source Area Wells MW-106S

Response to EPA Comment 4 050305doc 3 of 26 Woodard amp Curran (211941)

I I

El I

II I I 1 I

I

i

Event Baseline Case ID WC-01 WC-01

Well Date Aug-99 Oct-99 LOT10 1 LOT1-1 1 LOT11-4 LOT14 1 LOT15 1 LOT15-1 1 LOT16 1 LOT16-1 1 LOT17 1 LOT18 1 LOT19 1 LOT2 LOT20 1 LOT21-10 1 LOT21-11 1 LOT21-12 1 LOT21-13 1 LOT21-14 1 LOT21-2 1 LOT21-5 1 LOT21-7 LOT21 -8 1 LOT21-9 1 LOT23 1 LOT24 1 LOT28-1 1 LOT28-2 1 LOT28-3 1 LOT28-4 1 LOT28W 1 LOT30 1 LOT30-1 1 LOT30-2 1 LOT30-3 1 LOT30-4 1 LOT30-5 LOT31 LOT35 1 LOT41 1 LOT42-1 1 LOT43-1 1 LOT43-4 1 LOT6-1 1 LOT67 1 LOT6-7 1 LOT6-8A 1 LOT6-8B 1 LOT80-1 1 LOT82 1 MW-101D MW-1011 MW-101S MW-102D MW-102S MW-103D MW-103S MW-104D MW-1041 MW-104S MW-105D MW-106D

Groundwater Sampling Location Summary 1999 - 2004xls

Sampling Events 1999-2004

Hows Corner Superfund Site Plymouth Maine

Supplemental 2001 2002 2003 Pumping 2004 Pre-ROD Rl Sampling Sampling Sampling Test Sampling WC-03 WC-09 WC-25 WC-30 WC-42B WC-56 WC-58 Dec-99 May-00 Jun-01 Jan-02 Apr-03 Sep-04 Sep-04

1

1 1 1

1 1 1 1 1

1 1

1

1 1

1 1 1

1 1 1 1 1

1

1 1

1 1 1 1

1

1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

Sampling Events 1999-2004

Hows Corner Super-fund Site Plymouth Maine

Supplemental 2001 2002 2003 Pumping Event Baseline Pre-ROD Rl Sampling Sampling Sampling Test

Case ID WC-01 WC-01 WC-03 WC-09 WC-25 WC-30 WC-42B WC-56

ll

Well Date Aug-99 Oct-99 Dec-99 May-00 Jun-01 Jan-02 Apr-03 Sep-04 MW-106S 1 1 1 1 1 MW-107D 1 1 MW-108D 1 1 1 1 1 MW-108S 1 1 1 1 1 MW-110D 1 1 MW-111D 1 1 MW-112D 1 1 1 1 1 MW-112S 1 1 1 1 1 MW-113D 1 1 MW-114D 1 1 1 1 1 MW-114S 1 1 1 1 1 MW-115D 1 1 1 1 1 MW-12DB 1 1 1 MW-12SB 1 1 1 MW-13DB 1 1 1 1 1 1 MW-13SB 1 1 1 MW-14DB 1 1 MW-14SO 1 1 MW-15DB 1 1 1 MW-15SB 1 1 1 MW-16DB 1 1 1 1 1 1 MW-16IB 1 1 1 1 1 1 MW-16SO 1 1 MW-17DO 1 1 1 MW-17SO 1 1 1 MW-1B 1 1 1 1 1 1 MW-203D MW-203S MW-204D MW-204S MW-205 MW-206D

I MW-206S MW-2DB 1 1 MW-2DDB 1 1 MW-2IB 1 1 1 1 1 1 MW-3B 1 1 1 1 1 1

I MW-4O 1 1 1 MW-5B 1 1

II MW-6DB 1 1 1 MW-6SB 1 1 1 MW-8DB 1 1 1 MW-8SB 1 1 1

II PW-207 1 SEEP-1 1 SUBTOTAL - RESIDENTIAL 44 25 0 2 0 3 0 SUBTOTAL - MONITORING 22 48 41 15 15 15 1

Total 3 66 73 41 17 15 18 1

I Included in most recent data

I Notes 1 - Overburden well not included in most recent data for plotting

2 - Tetrahydrofuran and 2-Butanone were the only two compounds detected in this well and are thought to be the result of well repair not included in most recent data for plotting

3 - Not included in most recent data for plotting

2004 Sampling

WC-58 Sep-04

1

1 1

1 1

1 1 1

1

1 1

1 1 1 1 1 1 1 1 1

1 1

1

0 29

29

Groundwatef Sampling Location Summary 1999 - 2004xls

I

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

monitoring well Figure 4-14 total VOC contour (ugl) - December 1999January 2000 Distribution of Total VOCs in

Note SW-113 is located downstream of SEEP-1 Shallow Bedrock Groundwater total concentration of detected VOCs ND= not detected these two locations were sampled during the Pre-ROD Sampling Event

Baseline Sampling Event in OctoberNovember 1999 Hows Corner Superfund Site Surface Water Sampling Location A Plymouth Maine Seep Sampling Location laquo- WOODARD ampCURRAN

995037wipri reportepa ri interim final feb 2001cadd drawingsfinalfig 4-14

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

0 300 600 I

FEET

Q residential well Figure 4-16 monitoring well Distribution of Total VOCs in

Deep Bedrock Groundwater total VOCs contour (ugl) Pre-ROD Sampling Event

active residential wells with lot number Hows Corner Superfund Site 2deg42deg Plymouth Maine total concentration of detected VOCs ND= not detected WOODARD ampCURRAN Enyinaaring bull Science bull Operations bull

995037wipri reportepa ri interim final feb 2001cadd drawingsfinalfig4mdash16

PLYMOUTH POND

PLYMOUTH POND

1 628Tl7MW-2bB 12135

PLYMOUTH POND

monitoring well Figure 4-20

V total VOC contour (ugl) - June 2000 Distribution of Total VOCs in Shallow Bedrock Groundwater

| 34 | total concentration of detected VOCs ND= not detected NA = not analyzed Supplemental Sampling Event Note SW-113 is located downstream of SEEP-1 Hows Corner Superfund Site

Surface Water Sampling Location these two locations were sampled during the Plymouth Maine Baseline Sampling Event in OctoberNovember 1999 Seep Sampling Location WOODARD amp CURRAN

Engineering bull Science - Operations bull 995037wipri reportepa ri interim final feb 2001 cadd drawingsfinalfig 4-20

residential well Figure 4-22 Distribution of Total VOCs in

monitoring well Deep Bedrock Groundwater

total VOCs contour (ugl) Supplemental Sampling Event

Hows Corner Superfund Site

total concentration of detected VOCs ND= not detected NA = not analyzed Plymouth Maine

WOODARD amp CURRAN

995037wipri reportepa-ri interim final feb 2001cadd drawingsfinalfig 4-22 Engineering bull Science - Operations bull

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

FEET

Shallow Monitoring Well

Deep Monitoring Well

C Detected Concentration ND = Not Detected Figure 1-XS Distribution of Total VOCs in Shallow Bedrock Groundwater

Pumping Well

17-Acre Property Boundary Concentration Contour (ugl)

June 2001 Hows Corner Superfund Site

Plymouth Maine WOODARDampCURRAN

-i^rhvj bull Scbncn bull Operations bull 211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0601 dwg04-20-05

PLYMOUTH POND Hopkins Road V

O

PLYMOUTH POND

PLYMOUTH POND

o

0 300 600 mdashfa FEET

Shallow Monitoring Well bull bull - 17-Acre Property Boundary Figure 1-XD

Deep Monitoring Well 1 I Detected Concentration ND = Not Detected Distribution of Total VOCs in Deep Bedrock Groundwater

-mf- Pumping Well June 2001 Residential Well Hows Corner Superfund Site

Plymouth Maine i h Surface Water Sampling Point

g WOODARD ampCURRAN _ ^ _ ^ _ _ yen_ rj i|Hlaquorlny bull Science bull Opt

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0601 dwg04-20-05

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

Shallow Monitoring Well

Deep Monitoring Well

Detected Concentration ND = Not Detected Figure 1-YS Distribution of Total VOCs in Shallow Bedrock Groundwater

Pumping Well

17-Acre Property Boundary Concentration Contour (ugl)

January 2002 Hows Corner Superfund Site

Plymouth Maine WOODARD amp CURRAN Engineering Science- Operations bull

211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0102dwg04-20-05

PLYMOUTH POND

PLYMOUTH POND

Site Pand^ laquoum-laquoBTuitaraquo tLV

vVlf-(

PLYMOUTH POND

0 300 600 ^ = FEET

Shallow Monitoring Well mdashbullbullbull 17-Acre Property Boundary Figure 1-YD - A - Deep Monitoring Well FT Detected Concentration ND = Not Detected Distribution of Total VOCs in

Deep Bedrock Groundwater Pumping Well January 2002 Residential Well Hows Corner Superfund Site

Plymouth Maine Surface Water Sampling Point

WOODARD ampCURRAN Engineering Sciencs- Operations bulli Si

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0102dwg04-20-05

- m j

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND j A O-shy

Shallow Monitoring Well E Detected Concentration ND = Not Detected Figure 1-ZS Distribution of Total VOCs in

Deep Monitoring Well Shallow Bedrock Groundwater

Pumping Well Hows Corner

April 2003 Superfund Site

17-Acre Property Boundary Plymouth Maine Concentration Contour (ugl) r WOODARD ampCURRAN

Engineering bull Science bull Operations bull 211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0403dwg04-20-05

s S pound

PLYMOUTH POND

PLYMOUTH POND

- -

5 PLYMOUTH POND

Jo

FEET

ft Shallow Monitoring Well mdashbullbullmdash 17-Acre Property Boundary Figure 1-ZD Deep Monitoring Well I 1 I Detected Concentration ND = Not Detected Distribution of Total VOCs in

Deep Bedrock Groundwater Pumping Well April 2003

Q) Residential Well Hows Corner Superfund Site Plymouth Maine

(T) Surface Water Sampling Point WOODARD ampCURRAN poundKk EnginawtirKj bull Science - Operations bull

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0403dwg04-20-05

0 Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

B MW-1B

I 12000

PCE

B 10000 Total VOCs

I

i 2000

i 0 Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

c MW-3B

G 2000

1800

B PCE

1600 Total VOCs

1 I I E

il-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

G E

211941

El

I I z E

80

Concentration Trends shy Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-13DB

Total VOCs

c i i c o

Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

MW-16DB

30

c i c c I c o

Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99

PCE

Total VOCs

Jul-01 Jul-03

211941

O bi

c Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

I MW-16IB

i 35

3

c Total VOCs

lt- 2 5

0 | gt

o

1 sectI

c c 0 4

Jul-90 Jul-92 Jul-94 Jul-96 Jul-98 Jul-00 Jul-02 Jul-04

I I MW-108D

I 12

PCE 10

Total VOCs c oc 3

E E I 0

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

E 211941

c Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

fi MW-108S

I I 40

PCE 35

Total VOCs

30

I f 26

20 I o

I 15

10

c Dec-99 Dec-00 Dec-01 Dec-02 Dec-03 I 0

I MW-112D

c 35 - imdash

I A3 shyTotal VOCs

o c

E 1 2

I

ition

B 1 ^

-i c 3

0 Dec-99 Dec-OO Dec-01 Dec-02 Dec-03

211941

I

i

I

cII

Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-112S

08

PCE

Total VOCs 06

o 04

02

0 Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

MW-114D

o

12000

10000

8000

6000

PCE

Total VOCs

4000

2000

i

ccEIIc

i

i

E

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

211941

Con

cent

ratio

n (

ug

l)

E Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

I MW-114S

E A5000 -- Total VOCs

- 4000

0 3000

2000

i 1000

i n shy

Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

MW-115D

c PCE

Total VOCs

c E

o

C c

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03 I 0

211941

IepoundII

EIEIIGICCIccc

30000

25000

20000

o bullsect 15000 b

o 10000 U

5000

0 Aug-99

25000

20000

5000

0 Aug-99

211941

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-2DB

PCE

Total VOCs

Aug-01 Aug-03

MW-2IB

PCE

Total VOCs

Aug-01 Aug-03

IDIBI

ii EIDIISIBIG C

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-102S

6000

5000 PCE

Total VOCs

4000

O 3000

2000

1000

0 Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

MW-103D

16000

~ 14000 ugt 3- 12000 o

^ 10000

sect 8000

O 6000

4000

2000

PCE

Total VOCs

0Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

211941

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

G MW-103S

I I

ampo

12000

10000

E sectc

S

8000

6000

4000

2000

0Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

G I 6000

MW-104D

i 5000

PCE

Total VOCs

i i c

2000

1000

Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

E I

211941

cIccIG

IIBCccBcIc

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-1041

PCE Total VOCs

a 25000

0 20000

a 15000

10000

5000

0 Jan-OO Jan-01 Jan-02 Jan-03 Jan-04

MW-106D

3000

2500 PCE

Total VOCs

=sect 2000

o bullsect 1500

1000

500

0 Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

211941

c Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

c MW-106S

I PCE

Total VOCs

i

i Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

i

i i i E

C

211941 c

Response to EPA-DEP Comment 5 Dated March 312005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

iiw

EPA-DEP Comment 5

Comment 5 Matrix Diffusion The report as well as other proponents of matrix diffusion suggest that depletion of DNAPL (Section 5112 page 5-15) needs to be achieved While that might be the ideal the goal is to achieve performance standards and that goal may be attainable while there is residual contamination in the rock perhaps even DNAPL globules The low bedrock matrix porosity (page 1-15) the high permeability values (page 4-4) the relative flux of the groundwater (page 5-5) and the decrease in surface area and out of the mainstream pockets (appendix C-4) all suggest that the diffusion out of the rock matrix would be insubstantial relative to the regional flux of groundwater through the Site

Response The TI Evaluation Report does not explicitly consider or rely upon matrix diffusion as a basis for requesting a TI Waiver for a portion of the Hows Corner Site The technical literature provides documentation that matrix diffusion can be a significant process that affects chemical transport and groundwater remediation timeframes in unconsolidated and consolidated media including fractured rock (US EPA 1989 Freeze and Cherry 1979 Pankow and Cherry 1996 Fountain 1998) Back diffusion of contaminants from the matrix porosity of the fractured rock can prolong the time necessary to achieve groundwater cleanup goals particularly for compounds such as PCE for which the cleanup goal is a low concentration It is our expectation that matrix diffusion has occurred at the Hows Corner Site and that back diffusion of PCE from the rock matrix will also occur Although the extent to which matrix diffusion is occurring at the Hows Comer Site has not been determined and that lack of knowledge contributes to uncertainty regarding the cleanup times at the Site the effect of matrix diffusion is to lengthen rather than shorten the time required for remediation

REFERENCES

Fountain JC 1998 Technologies for Dense Nonaqueous Phase Liquid Source Zone Remediation Ground-Water Remediation Technologies Analysis Center Technology Evaluation Report TE-98-02 December

Freeze RA and Cherry JA 1979 Groundwater Prentice-Hall Inc Englewood Cliffs NJ 07632 p 410-412

Pankow J F and Cherry J A 1996 Dense Chlorinated Solvents Waterloo Press Portland OR 97291-1399 p 67-88

US EPA 1989 Transport and Fate of Contaminants in the Subsurface EPA6254-89019 p 17-18

Response to EPA Comment 5 050305doc 1 of 1 Woodard amp Curran (211941)

WOODARD amp CURRAN Maine Massachusetts New Hampshire Connecticut Florida Operational offices across the US 1-800-426-4262 www woodardcurran com

Page 26: SDMS DocID 251749 - Records Collections · 2020-06-13 · CORPORATE OFFICES: Maine, Massachusetts, New Hampshire, Connecticut New, York, Florida Engineering • Science • Operations

Table XX Packer Permeability and Packer Sampling Results for Potential Fracture Intervals

1

WellID MW-101D MW-101D MW-101D MW-101D MW-101D MW-101D MW-101D MW-101D MW-101D MW-101D MW-I01D MW-101D MW-101D MW-102D MW-102D MW-I02D MW-102D MW102D MW-102D MW-102D MW-102D MW-102D MW-I02D MW-102D MW-102D MW-102D MW-103D MW-103D MW-103D MW-103D MW-I03D MW-103D MW-103D MW-103D MW-103D MW-103D MW-103D MW-103D MW-I03D MW-104D MW-104D MW-104D MW-104D MW-I04D MW-104D MW-104D MW-104D MW-104D MW-104D MW-104D MW-105D MW-105D MW106D MW-106D MW-106D MW-107D MW-107D

1999 Drilling Program

Hows Corner Superfund Site Plymouth Maine

Potential Fracture Top Of Bottom 6 Depth to lt Topof i Interval from Packer Packer Middle of Elevation Hydraulic bull PCE

GS ELEV 1 Rock Drilling Interval Interval Interval of Interval Conductivity Concentration (ft msl) (ft msl) TEST (ftbgs) (ftbgs) r(ftbgs) ( f t b (ft mil) (cmsec) (raquogL)

4339 4329 13 28-29 33-3537-39 271 376 324 4016 OOOE+00 4339 12 37-3444-46 380 485 433 3907 157E-04 4339 11 488 593 541 3799 132E-04 4339 10 60-61 578 683 631 3709 OOOE+00 4339 9 678 783 731 3609 I79E-05 4339 8 778 883 831 3509 106E-05 4339 7 880 985 933 3407 243E-05 4339 6 990 1095 1043 3297 339E-06 4339 5 1090 1195 1143 3197 OOOE+00 4339 4 1190 1295 1243 3097 OOOE+00 4339 3 1365-1375 1290 1395 1343 2997 OOOE+00 4339 2 147-157 1390 1495 1443 2897 580E-05 4339 1 147-157 1470 1575 1523 2817 741E-05 43161 43061 13 166 271 219 4098 333E-04 43161 12 30-3136-40 260 365 313 4004 I54E-05 43161 11 36-4041-43 362 467 415 3902 548E-05 43161 10 470 575 523 3794 598E-05 43161 9 570 675 623 3694 197FOS 43161 8 670 775 723 3594 OOOE+00 43161 7 770 875 823 3494 891 E-05 43161 6 83-94 870 975 923 3394 139E-05 43161 5 970 1075 1023 3294 123E-04 43161 4 1070 1175 1123 3194 526E-06 43161 3 1170 1275 1223 3094 138E-05 43161 2 1270 1375 1323 2994 671E-06 43161 1 1370 1475 1423 2894 OOOE+00 42997 42497 13 18-19 170 275 223 4077 OOOE+00 42997 12 260 365 313 3987 766E-05 42997 11 360 465 413 3887 727E-05 42997 10 460 565 513 3787 192E-05 42997 9 560 665 613 3687 752E-05 42997 8 660 765 713 3587 778E-05 42997 7 85-86 763 868 816 3484 260E-05 42997 6 860 965 913 3387 289E-05 42997 5 102-103 960 1065 1013 3287 102E-04 42997 4 1060 1165 1113 3187 522E-06 42997 3 1160 1265 1213 3087 520E-06 42997 2 129-130 1260 1365 1313 2987 960E-04 42997 1 1360 1465 1413 2887 OOOE+00 43372 42922 11 35-37 42-45 350 455 403 3935 684E-04 43372 10 460 565 513 3825 500E-05 43372 9 560 665 613 3725 106E-05 43372 8 72-74 660 765 713 3625 204E-05 43372 7 760 865 813 3525 872E-06 43372 6 860 965 913 3425 467E-06 43372 5 960 1065 1013 3325 200E-05 43372 4 1060 1165 1113 3225 354E-05 43372 3 125-130 1160 1265 1213 3125 157E-05 43372 2 125-130 1260 1365 1313 3025 337E-04 43372 1 1365 1465 1415 2922 689E-06 43052 43002 2 54-58 490 595 543 3763 124E-05 2100 43052 1 139-140 145-146 1367 1472 1420 2886 154E-04 1400 43291 4391 3 bullI133 260 365 313 4017 439F06 43291 2 77-78 760 865 813 3517 230E-03 400 43291 1 143-144 1355 1460 1408 2922 971E-06 350

29958 27258 4 450 555 503 2493 OOOE+00 (21)A 29958 3 103-105 1000 1105 1053 1943 752E-04 (063)A

Table XX Packer Permeability and Packer Sampling Results for Potential Fracture Intervals

1999 Drilling Program

Hows Corner Supcrfund Site Plymouth Maine

gtbull i Potential Fracture Top _OfBot Bottom of Depth to ltbull Top of Interval from f Packer Packer Middle Of

GS ELEV lt Hock Drilling interval Interval Interval WeD ID ft msl) (ft msl) TEST (ftbgs) ltft$gs) (ftbgs) (ftbgs)

MW-107D 29958 2 128-130 1200 1305 1253

MW-107D 29958 1 139-141 1350 1455 1403

MW-108D 31904 31104 6 35-36 300 405 353 MW-108D 31904 5 60-62 550 655 603

MW-108D 31904 4 80-83 750 855 803

MW-108D 31904 3 118-119 123-124 1150 1255 1203

MW-108D 31904 2 147-149 1440 1545 1493

MW-108D 31904 1 1700 1805 1753

MW-110D 40576 40426 2 21-31 210 315 263 MW-110D 40576 1 148-154 1460 1565 1513 MW-I11D 40519 4 70-71 650 755 703

MW-111D 40519 3 79-82 84-86 780 885 833 MW-I11D 40519 2 97-102 950 1055 1003 MW-111D 40519 1 1370 1475 1423

MW-112D 3027 2942 4 42-52 420 525 473 MW-112D 3027 3 850 955 903 MW112D 3027 2 1100 1205 1153 MW-112D 3027 1 135-136 140-141 1340 1445 1393

MW-113D 43085 43085 5 250 355 303 MW-I13D 43085 4 47-49 460 565 513 MW-113D 43085 3 73-74 700 805 753 MW-113D 43085 2 1050 1155 1103 MW-113D 43085 1 1380 1485 1433

MW-114D 42394 41594 4 48-49 450 555 503 MW-114D 42394 3 79-81 740 845 793 MW-114D 42394 2 121-129 1250 1355 1303 MW-114D 42394 1 134-142 1350 1455 1403

MW-115D 4035 4035 4 300 405 353 MW-1I5D 4035 3 70-71 650 755 703 MW-115D 4035 2 1150 1255 1203 MW-115D 4035 1 1400 1505 1453

LOT-28W 382 7 450 555 503 LOT28W 382 6 550 655 603 LOT-28W 382 5 650 755 703 LOT28W 382 4 750 855 803 LOT-28W 382 3 850 955 903 LOT-28W 382 2 950 1055 1003 LOT-28W 382 1 1055 1155 1105

NOTES cmsec = centimeters per second ft bgs = leet below ground surface It msl = feet below mean sea level lt = not detected at indicated reporting limil A = detected below laboratory PQL ( ) = detected below reporting limits

Elevation of Interval

(ft nisi) 174

159

283gt 2588

2388

1988

1698

1438

3795 2545 3349 3219 3049 2629

2555 2125 1875 1635

4006 3796 3556 3206 2876

3737 3447 2937 2837

3683 3333 2833 2583

3318 3218 3118 3018 2918 2818 2715

Hydraulic Conductivity

(cmsec)

323E-05

208E-05

471E-03

471E-03

624E-05

3I6E-05

264E-05

261 E-05

OOOE+00 200E-04 953E-05 OOOE+00 OOOE+00 212E-05

361 E-05 410E-06 2gQE06 292E-05

786E-05 124E-05 151 E-05 822E-06 82IE-06

858E-05 I69E-05 352E-03 866E-05

223E-05 394E-06 122E-05 525E-06

831 E-05 182F-05 L62E-05 129E-05 190E-05 890E-04 981 E-04

PCEraquo Concentration

(ugL)

lt5

(14A)

98 11

15

22

11

30

200 (62)A

110 210 300 240

(44)A (23)A

5

350 190 129 230

2200 1900 2600 2600

(17)A (16)A (19)A

96

Table XX Packer Permeability and Packer Sampling Results for Potential Fracture Intervals

2004 Drilling Program

Hows Corner Superfund Site Plymouth Maine

Top of Bottom of Depth to Midpoint

t K

ELEV (ft Potential Transmissive Zones Packer Interval

Packer Interval

Middle of Interval

Elevation of interval

Hydraulic Conductivity

PCE Concentration

Well ID msl) TESTr (ft bgs)- (ftbgs) (ftbgs) (ftbgs) (ft msl) (cmsec) (ogt) MW-203D 43227 4 277279 24 32 28 4043 667E-05 44

3 408415420 39 49 44 3883 593E-05 170 2 526 530 49 57 53 3793 101E-04 140 I 828830842 80 88 84 3483 701E-05 130

MW-204D 43262 5 295 300 26 34 30 4023 902E-05 220 4 463496513516 45 53 49 3833 119E-04 540 3 681685688 63 71 67 3653 OOOE+00 2 758 76 2 71 79 75 3573 309E-05 260 I 88 96 92 3403 OOOE+00

MW-205 42389 3 164 166 168 15 20 175 4148 OOOE+00 1000B 2 302305312 30 35 325 3998 107E-04 1300B 1 40 45 425 3898 OOOE+00

MW-206D 43007 5 17 72 195 4128 291E-05 4 296 302 307 29 34 315 4008 940E-05 2900B 3 522 52 57 545 3778 944E-07 2 656 64 69 665 3658 353E-06 1 92392793 4939 91 96 935 3388 614E-05 6300B

PW-207 43477 5 184622162819 18 29 235 4088 209E-05 1300 4 3508 32 43 375 3948 568E-06 5400 3 53325341542154325559 50 61 555 3768 821E-05 18000

6359 61 72 665 3658 866E-06 12000 1 8685 84 89 865 3458 213E-05 19000

NOTES cmsec = centimeters per second ft bgs = feet below ground surface ft msl = feet above mean sea level B = detected in lab blank

Table XX Orientation Permeability and Groundwater Sampling Results for Transmissive Features

2004 Drilling Program

Hows Corner Superfund Site Plymouth Maine

Borehole Geophisical Feature depth Dip True Dip True Transmissive Log Feature (Feet) Degrees Azimuth Strike bullvgt(Ltk|iy^

Number v Tosftble) v MW-203 5 277 64 337 67 Likely

6 279 59 11 281 Likely 8 352 14 177 87 Likely 11 381 46 96 6 Possible 12 408 35 271 1 Possible 14 415 57 250 340 Possible 15 420 58 202 292 Likely 18 526 52 75 345 Likely 19 530 52 82 352 Likely 28 828 48 75 345 Likely 29 830 52 17 287 Likely 30 830 56 233 323 Possible 31 842 50 130 40 Likely

MW-204 4 295 15 147 57 Likely 5 300 43 91 1 Likely 11 439 31 80 350 Possible 12 440 46 219 309 Possible 14 463 50 358 88 Likely 15 496 34 198 288 Likely 16 513 54 17 287 Likely 17 516 33 14 284 Likely 25 681 39 359 89 Possible 26 685 22 45 315 Possible 27 688 35 73 343 Possible 32 758 45 236 326 Likely 33 762 46 306 36 Likely

MW-205 5 164 69 106 16 Possible 6 166 78 165 75 Possible 7 168 82 115 25 Possible 8 168 68 116 26 Possible 12 215 46 222 312 Possible 13 217 75 62 332 Possible 14 219 29 32 302 Possible 16 237 69 250 340 Possible 17 256 73 353 83 Possible 18 272 44 202 292 Possible 21 299 37 196 286 Possible 22 302 31 206 296 Possible 23 305 59 48 318 Likely 24 312 63 42 312 Likely

MW-206 1 264 37 181 271 Likely 2 296 69 217 307 Likely 3 302 66 233 323 Likely 4 307 64 224 314 Likely 8 342 62 259 349 Likely

jjHydraulic GoiDanctilyity j(cmsecjw

667 E-05

593 E-05

101 P04

710 E-05

902 E-05

119 E-04

0

309 E-05

0

107 E-04

94 E-05

PCE (ugL)

44

170

140

130

220

540

260

IOOOB

1100B

1300B

2900B

STotal vVoCsv tig1)

84

234

192

183

2636

6436

3073

11448

12509

13776

32401

PCEyo dfCTotaf

52

73

73

7 1

83

84

85

87

88

94

90

Table XX Orientation Permeability and Groundwater Sampling Results for Transmissive Features

2004 Drilling Program

Hows Corner Superfund Site Plymouth Maine

Borehole Geophisical Feature deptt raquoip True pip True Transraissive Log Feature (Feet) shy Degrees Azimuth Strike (tikely

Number raquo Possible) 22 522 57 54 324 Possible 25 656 40 82 352 Possible 32 871 59 151 61 Possible 33 883 53 185 275 Possible 34 895 7 175 85 Likely 35 899 53 90 0 Likely 36 902 49 184 274 Likely 37 923 9 175 85 Likely 38 927 42 206 296 Likely 39 934 48 167 77 Likely 40 939 26 180 90 Likely

PW-207 1 1846 33 167 77 Likely 4 2216 49 289 19 Possible 7 2819 59 265 355 Possible 11 3508 55 189 279 Possible 18 5332 43 305 35 Likely 19 5341 51 30 300 Likely 20 5421 20 254 344 Likely 21 5432 39 301 31 Likely 23 5559 52 302 32 Likely 25 6359 24 182 272 Possible 29 8049 77 231 321 Possible 30 8685 78 38 308 Likely 32 9334 29 194 284 Likely

NOTES

B = detected in lab blank

Hydraulic Conductivity

(cmsee) 944 E-07 353 E-06

614 E-05

209 E-05

568 E-06

821 E-05

866 E-06

213 E-05

bulltCE (ugL)

6300B

1300

5400

18000

12000

19000

Total VOCs (ug1)

68901

1410

5802

19234

13085

20354

PCE of Total VOCs

9 1

92

93

94

92

93

Response to EPA-DEP Comment 3 Dated March 312005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

lit

EPA-DEP Comment 3

Comment 3 The reported f values and resultant Kd values There remains doubt that the values used in the flushing model accurately reflect the propensity for PCE to sorb to the bedrock The ^ values presented in Appendix B may be unrealistically high because the bedrock samples may have contained organic carbon that was unavailable for sorption The reported f values are only qualitative estimates of the organic carbon content of the bedrock samples The Walkley and Black organic carbon measurement method is quick and simple but the results obtained cannot be considered quantitative because it requires a correction factor which often results in erroneous values it assumes the organic carbon has an average valence of zero oxidizable and reducible constituents such as chloride ferrous iron and manganese oxides interfere with the results and the errors introduced by interference are potentially greater when the organic carbon content is low at low f values it is not clear that organic carbon is controlling PCE sorption (Schwarzenbach and Westall 1981 Mackay et al 1986 Fetter 1999)

In order to derive a Kd-based retardation factor that is reasonable given the reported f values and the rapid advance of the PCE plume described on pages 4-11 and 4-12 the flushing model requires a bulk density to porosity ratio that is roughly two orders of magnitude higher than the actual ratio for the Hows Corner bedrock (page 4-4) This apparent discrepancy needs to be addressed

Response This comment raises several concerns about the collection and analysis of samples for fraction of organic carbon (f^) the quality of the resulting data and the implications of the use of those data for estimation of the retardation of groundwater contaminant movement Results of bedrock analysis for f were proposed in the TI Evaluation Work Plan for use in conjunction with groundwater contaminant concentrations and aquifer information to estimate cleanup times using the Batch Flushing model It is important to use accurate f values from representative bedrock in the Batch Flushing model in order to obtain reasonable estimates of the remedial time frame Because of the importance of accurate and representative results the TI Investigation field program was designed and conducted both to collect samples representative of the rock volume most likely to be in contact with contaminated groundwater and to analyze them using an appropriate refereed analytical method Five potential methods for evaluating f were identified Of the five methods the Walkey-Black method was selected because it has minimal method interferences and a sufficiently low detection limit as well as a long history of use in agronomy and contamination studies The PRP Group is pleased with the quality of the data obtained from the bedrock samples as represented by their precision and reproducibility

The first part of this comment relates to the determination of fraction of organic carbon (f^) values The several subparts of the first paragraph are addressed individually in items 1 through 5 below The second part of the comment regarding the resultant distribution coefficient (Kd) values is addressed separately as item 6 below

1 There remains doubt that the values used in the flushing model accurately reflect the propensity for PCE to sorb to the bedrock

bull The rock core samples used for f (gocg) analysis were from core immediately adjacent to fractures These rock core samples included the fracture surfaces themselves and rock core extending back less than 1 cm from the fractures Therefore the foe data reported in the TI Evaluation represents the f of bedrock through which groundwater will travel and to which PCE will adsorb Based on the careful selection of sample locations and the

Response to EPA Comment 3 050205doc 1 of 11 Woodard amp Curran (211941)

number of samples collected we are confident that the measured f values are representative of the f at points of contact for PCE with the bedrock it is these f values that determine the propensity of PCE to sorb to the bedrock

bull The samples of rock core collected for analysis of f originated from 19 different locations varying in depth from 11 to 90 feet Therefore it is very unlikely that the rock core samples were contaminated with extraneous organic carbon from above ground

2 The foc values presented in Appendix B may be unrealistically high because the bedrock samples may have contained organic carbon that was unavailable for sorption

bull As noted in response 1 the f data reported in Appendix B represents organic carbon primarily associated with the surface of fractures in the bedrock through which groundwater is most likely to travel Therefore it is this organic carbon that the contaminants in the groundwater will come in contact with and adsorb to in the fractured rock at the site

bull The chemical oxidation agents used in the Walkey-Black method oxidize the easily oxidizable organic carbon in the medium and the foe is calculated from the quantity of the agent consumed Therefore it is unlikely that the analysis of the bedrock samples measured organic carbon that was unavailable for sorption

3 The reported foc values are only qualitative estimates of the organic carbon content of the bedrock samples

bull The reported f values are accurate quantitative results Schumachers review of Methods for the determination of total organic carbon (TOC) in soils and sediments (NCEA-C-1282 EMASC-001 April 2002) identifies the Walkley-Black method which was used to analyze the reported foc values as the reference method for comparison to other methods for analyzing total organic carbon

bull Schumacher also points out that if anything the WalkJey-Black method may underestimate the total organic carbon in a sample due to possible incomplete oxidation of organic carbon Usually the incomplete oxidation of total organic carbon in environmental samples is corrected for by multiplying the measured foe by 130 (Walkley amp Black 1934 Schulte 1995)

bull When the f data in the TI Evaluation Report (WampC 2005) Appendix B (attached) are analyzed statistically the standard deviation of the f for the 19 samples analyzed is 174 of the average f Given this standard deviation the 95 confidence interval for this data ranged from a low of 000123 gocg to a high of 000253 gocgm

The labs Method of Detection Limit (MDL) for the f measured using the Walkley-Black method is 00001 gocg Therefore the average (000188 gocg) the mean (000185 gocg) and geometric mean (000187 gocg) of the f values for the rock core at Hows Corner are all statistically significantly greater than the MDL of the Walkley-Black method

In addition to the aforementioned statistical analysis of the foe data triplicate samples (n = 3) from the same rock core (including one sample from the 19 rock core samples) were

Response to EPA Comment 3 050205doc 2 of Woodard amp Curran (211941)

analyzed for their f to determine the repeatability of the Walkley-Black method The average the mean and the geometric mean of the f values of these replicate samples was 000162 gocg 000150 gocg and 000159 gocgm respectively The standard deviation of these measurements was 000039 gocg

4 The Walkley and Black organic carbon measurement method is quick and simple but the results obtained cannot be considered quantitative because it requires a correction factor which often results in erroneous values it assumes the organic carbon has an average valence of zero oxidizable and reducible constituents such as chloride ferrous iron and manganese oxides interfere with the results and the errors introduced by interference are potentially greater when the organic carbon content is low at low foc values it is not clear that organic carbon is controlling PCE sorption (Schwarzenbach and Westall 1981 Mackay et al 1986 Fetter 1999)

bull Schumachers review (NCEA-C-1282 EMASC-001 April 2002) of the Walkley-Black method identifies several potential problems with this analytical method that could occur if the analytical lab is not familiar with the nuances of the chemistry associated with this method Interestingly Schumachers review neglected one of the more important analytical steps required to avoid errors in quantifying f in samples where there might beNAPL

It is absolutely critical to eliminate any NAPL from rock core samples prior to using the Walkley-Black method to measure foe in such samples This was done by the lab (PTS Laboratories) that measured the foe in the rock core samples from Hows Corner The lab used the Dean-Stark method (solvent extraction) to remove all hydrocarbons (including PCE and other NAPLs) from the sample (PTS Laboratories) This extraction method does not interfere with the subsequent analysis of the natural organic carbon associated with the rock core

Subsequently the samples were dried at 150degC to a constant weight (normally 16 hours) This latter step oxidizes all inorganic minerals including ferrous bearing minerals to ferric oxides and precludes their interference during the oxidation of the samples with chromic acid This procedure completely eliminates any positive bias in the reported foc

data that might have occurred due to the presence of ferrous ions and other reduced minerals

bull As noted in Response 3 the incomplete oxidation of total organic carbon results in an underestimate of the f and is corrected for by multiplying the f by a correction factor of 130 (Walkley amp Black 1934 Schulte 1995) The fx data reported in the TI Evaluation was corrected accordingly by using this correction factor

bull Excess chloride (Cl~) in percent weight quantities as found in saline soils may interfere with the quantitative titration of reduced chromium (Walkley 1947) However given that the primary rock type at the Hows Corner site is phyllite it is highly unlikely that there was sufficient chloride in the rock core samples for this to occur

bull Manganese oxides may also interfere with the analysis of f through competing with the dichromate ion for any oxidizable carbon (Walkley 1947) However in such cases the reported f would be an underestimate of the f present in the rock core Walkley (1947)

Response to EPA Comment 3 050205doc 3 of 11 Woodard amp Curran (211941)

4

reported that in the case where the ratio of MnO2 to carbon is 85 to 1 the error in the carbon determinations would only be 0 to 6 percent

It may also be useful to compare the analysis of total organic carbon in a geologic matrix that contains high levels of manganese using EPA method 9060 to the Walkley-Black method Table 1 summarizes data provided by one of the PRPs that compares the analysis of total organic carbon in a geologic matrix that contains approximately 02 wgt manganese (approximately 03 wgt manganese oxide)

Table 1 Comparison of total organic carbon measured using the EPA- 9060 method and the Walkley-Black method

Laboratory EPA-9060 Method Walkley-Black Method A Ave 00226 gocg Not analyzed

Stdev 000251 gocg n = 5

B Ave 002219 gocg Ave 002050 gocg Stdev = 000316 gocg Stdev =000971 gocg

n= 10 n = 10

The similarity in the total organic carbon concentrations measured by these two different methods provides further confidence that the Walkley-Black method is a viable method for analysis of total organic carbon in the presence of manganese equivalent to at least 10 by weight of the total organic carbon

5 The Walkley and Black organic carbon measurement at lowf^ values it is not clear that organic carbon is controlling PCE sorption (Schwarzenbach and Westall 1981 Mackay et al 1986 Fetter 1999)

bull Schwarzenbach and Westalls (1981) paper states that f values of less than 0001 gocg should not be used in combination with Kow (octanol-water partition coefficients) values to calculate K^ values (solid phase partition coefficients) values for a specific contaminant It should be noted that the TI Evaluation did not use the f data to calculate the KQC from the Kow Instead as requested by the EPA the measured KOC value for PCE was used to calculate the retardation factor for this contaminant

bull Schwarzenbach et al (2003) stated more recently that Even at very low f values (ie foe = 0001 kgoc - kg1 solid) sorption to the organic components of a natural sorbent may still be the dominant mechanism in defining the adsorption of organic compounds to geological matrices

bull In 1985 M Piwoni from the US EPA Robert S Kerr Environmental Research Laboratory published a paper (Banerjee et al 1985) that showed that for very hydrophobic molecules TOC content of the sorbent will control sorption down to levels of organic carbon that defy quantitation Contaminants such as the PCE found in the groundwater at Hows Corner are in this category of compounds

Given the aforementioned reasons the f values reported in the TI Evaluation are accurate within the noted statistical limitations and will have a predictable impact upon the retardation of PCE during groundwater transport

Response to EPA Comment 3 050205doc 4 of 11 Woodard amp Curran (211941)

6 In order to derive a Kd-based retardation factor that is reasonable given the reported foc

values and the rapid advance of the PCE plume described on pages 4-11 and 4-12 the flushing model requires a bulk density to porosity ratio that is roughly two orders of magnitude higher than the actual ratio for the Hows Comer bedrock (page 4-4) This apparent discrepancy needs to be addressed

The apparent discrepancy of bulk density to porosity ratios is most likely due to the fact that the Batch Flushing Model was originally developed for a porous medium and is not directly applicable to fractured bedrock As stated in Appendix C (page C-4) of the Draft Technical Impracticability Evaluation Report in order to use the Batch Flushing Model to describe the transport of contaminated groundwater in fractured bedrock where the matrix porosity is insignificant it is more appropriate to use a fracture surface area to void space ratio to calculate the retardation factor (R) than a bulk density to porosity ratio (Freeze amp Cherry 1979)

Since it is impractical to determine the actual surface area to which contaminants can adsorb the Batch Flushing Model was used with two simplifying assumptions bull The Kd was calculated from the f and the K^ bull The bulk density to porosity ratio term in the Batch Flushing Model was constrained to range

from 4 to 10 the typical range of such ratios in porous media (Freeze amp Cherry 1979)

If one uses site specific bedrock bulk density and porosity values the bulk density to porosity ratio is several orders of magnitude greater (specifically 273 gcc bullbull 000165 (dimensionless) = 1654 gcc) than the range of ratios of 4 to 10 used in the Batch Flushing Model in the Draft Technical Impracticability Evaluation Report Constraining the bulk density to porosity ratio within the range of ratios of 4 to 10 results in significantly lower R value than would be obtained using specific bedrock bulk density and porosity values

In summary in bedrock where fractures are the primary porosity the bulk density to porosity ratio can vary considerably and will be a function of the number of fractures and the fracture aperture The calculated bulk density to porosity ratio will be inversely proportional to the porosity This means that in fractured rock with limited fracturing and smaller porosity the calculated bulk density to porosity ratio is greater and will result in a greater calculated retardation factor than in bedrock with more extensive fracturing and greater porosity Consequently the calculated retardation factor will be greater for bedrock with less surface area available for sorption than bedrock with greater surface area for sorption This is contrary to what actually occurs

4 Response to EPA Comment 3 050205doc 5 of 11 Woodard amp Curran (211941)

m

REFERENCES

Banerjee P MD Piwoni K Ebeid (1985) Sorption of organic contaminants to a low carbon subsurface core Chemosphere _14 1057-1067

Freeze RA JA Cherry (1979) Groundwater Prentice Hall Englewood Cliffs NJ pg 604

PTS Laboratories wwwptsgeolabscompdf files3TOCnotepdf

Schulte EE (1995) Recommended soil organic matter tests in Recommended Soil Testing Procedures for the Northeastern United States Northeastern Regional Publication No 493 Chapter 8

Schwarzenbach RP J Westall (1981) Transport of nonpolar organic compounds from surface water to groundwater Laboratory sorption studies Environ Sci Tech 15 1360-1367

Schwarzenbach RP PM Gschwend DM Imboden (2003) Environmental Organic Chemistry Wiley-Interscience pg 292 408 amp 412

Walkley A LA Black (1934) An examination of the Degtjareff method for determining soil organic matter and a proposed modification of the chromic acid titration method Soil Science 37 29-38

Walkley A (1947) A critical examination of a rapid method for determining organic carbon in soils - effect of variations in digestion conditions and of inorganic soil constituents Soil Science 63251-264

Woodard amp Curran Inc (WampC) 2005 Draft Technical Impracticability Evaluation Hows Corner Superfund Site Plymouth Maine January 2005

Response to EPA Comment 3 050205doc 6 of Woodard amp Curran (211941)

LIST OF ATTACHMENTS (Response to Comment 3)

Appendix B to Draft Technical Impracticability Evaluation Measurement of foe at Hows Corner (4 pages)

m

Response to EPA Comment 3 050205doc 7 of 11 Woodard amp Curran (211941)

Appendix B Measurement of foe of Rock Core at Hows Corner

There are two general approaches to measure the fraction of organic carbon (foe) in rock cores

bull Measurement of weight loss by ignition of organic matter bull Chemical oxidization of organic carbon to carbon dioxide and either

subsequent quantification of the oxidant used for the reaction or quantification of the carbon dioxide produced during this oxidation process

The weight loss method is subject to errors caused by volatilization of substances other than organic materials such as water hydroxides and mineral carbonates Quantification of foe by the weight loss method is particularly sensitive to the presence of carbonates in rock cores There are however weight loss methods that are designed to differentiate between organic carbon and the aforementioned interfering materials but they require considerable care and are less accurate at low foe values Hence the weight loss method was not well suited for measuring the foe of the rock core from Hows Corner

The chemical oxidation of organic carbon is much better suited for quantifying organic carbon in rock cores such as those from Hows Corner This method uses a strong chemical oxidant to oxidize organic carbon to carbon dioxide and then measures either the chemical oxidant used to oxidize the organic carbon or the quantity of carbon dioxide produced In addition this general approach is not subject to interference by volatilization of other constituents of the rock core

There are at least two such chemical oxidation methods

bull The method of Baccini which was described by Schwarzenbach amp Westall (1981) first acidifies the sample to eliminate interference by carbonates Then a strong oxidant is used to chemically oxidize the organic carbon to carbon dioxide The resulting carbon dioxide is subsequently reduced to methane and quantified using a flame ionization detector Unfortunately this method has not been described in detail in a referred journal Hence it is would not have been appropriate to use to characterize the foe in the Hows Corner rock core

bull The more commonly used method to quantify foe in rock core is the Walkley-Black method (1934) This method is preferred for RBCA and DODDOE projects and by the oil industry

The Walkley-Black method uses an excess of chromic acid to oxidize (digest) organic matter to carbon dioxide The remaining chromic acid that was not consumed during the oxidation of the organic carbon is then quantified by titration with ferrous sulfate The difference in chromic acid prior to and after the oxidation of the organic carbon represents the total chromic acid used to oxidize

Hows Corner TI Evaluation Page 1 January 13 2005 Appendix B

the organic carbon in the sample The latter can be calculated using the chemical stoichiometry of the reaction

The Walkley-Black method is very accurate for samples that contain less than 2 organic carbon matter The minimum detection limit (MDL) for the Walkley-Black method is 100 mgkg or an foe of 0001

Given the rock core at Hows Corner was expected to contain less than 2 organic carbon the Walkley-Black method was used to measure the foe from 19 different rock core samples collected from varying depths ranging from 11 to 90 feet

Table 1 provides a statistical summary of the aforementioned data

Table 1 Statistical summary of foe data from rock cores collected at varying depths

Statistical Parameter Calculated Value foe Minimum Detection Limit (MDL) 00010 Number of samples analyzed (n) 19 Average foe 00019 Median foe 00019 Geometric Mean foe 00019 Standard deviation of foe measurements 000033 Relative standard deviation 174 -+ 95 Confidence intervals 00012 to 00025

The data in Table 1 shows the following

bull The foe from the Hows Corner rock cores are statistically greater than the MDL of the Walkley-Black analytical method

bull The average and median values for the foe of the Hows Corner rock cores from varying depths are nearly identical indicating that there is little variability in the foe values in the source zone at the site

bull The standard deviation of these measurements is 000033 which is 174 of the average foe

bull The 95 confidence intervals of the foe of the rock core at Hows Corner are 00012 to 00025

The foe was also analyzed from three separate samples taken from the same rock core at a depth of 55 feet (Only one of these samples was included in the data summarized in Table 1) Table 2 shows the statistical repeatability of this type of analysis

Hows Corner TI Evaluation Page 2 January 13 2005 Appendix B

Table 2 Repeatability of analysis of foe from one rock core at 55 feet in depth

Statistical Parameter Calculated Value Number of samples analyzed (n) 3 Average foe 00016 Median foe 00015 Geometric Mean foe 00016 Standard deviation of foe measurements 000039 Relative standard deviation 240 -+ 95 Confidence intervals 00008 to 00024

The data in Table 2 shows the following

bull The percent relative standard deviation of these three analyses of foe from the same rock core at Hows Corner is 24

bull The 95 confidence interval of the foes measured in this particular rock core at Hows Conrer is 00008 to 00024

These results show that there is good repeatability in using the Walkley-Black method for analysis of the foe in the rock core at Hows Corner

References Schwarzenbach amp Westall (1981) Transport of nonpolar organic compounds from surface water to groundwater Laboratory sorption studies Environ Sci Tech 15 1360-1367

Walkley A I A Black (1934) An examination of Degtjareff method for determining soil organic matter and a proposed modification of the chromic acid titration method Soil Sci 37 29-37

Hows Corner Tl Evaluation Page S January 13 2005 Appendix B

Woodard and Curran PTS Laboratories PTS File No 34618

ORGANIC CARBON DATA (METHODOLOGY WALKLEY-BLACK)

PROJECT NAME PROJECT NO

SAMPLE ID

203-chip-13 203-chip-23 203-chip-27 203-chip-38 203-chip-42 203-chip-47 203-chip-52 203-chip-58 203-chip-69 203-chip-82 207-chip-11 207-chip-19 207-chip-24 207-chip-29 207-chip-35 207-chip-45 207-chip-55 207-chip-87 207-chip-90

207-chip-55 55-MS

55-MSMSD

Hows Corner NA

DEPTH ft

13 23 27 38 42 47 52 58 69 82 11 19 24 29 35 45 55 87 90

55 NA NA

MATRIX

Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip

Average Median

Geometric Mean Standard Deviation Relative Std Dev

+- 95 Confidence Interval n

Rock Chip Rock Chip Rock Chip

Average Median

Geometric Mean Standard Deviation Relative Std Dev

+- 95 Confidence Interval n

FRACTION ORGANIC CARBON

(gg)

170E-03 185E-03 185E-03 170E-03 240E-03 190E-03 230E-03 180E-03 170E-03 115E-03 195E-03 220E-03 220E-03 235E-03 135E-03 190E-03 205E-03 175E-03 160E-03

188E-03 185E-03 185E-03 327E-04

1739 123E-03 to

19

205E-03 130E-03 150E-03

162E-03 150E-03 159E-03 388E-04

2402 840E-04 to

3

2532E-03

2393E-03

Hows Corner Tl Evaluation Appendix B January 13 2005

Response to EPA-DEP Comment 4 Dated March 31 2005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

EPA-DEP Comment 4

Comment 4 Distribution of contaminants First the TI report seems based on the assertion that there is DNAPL at the source area yet it also appears to represent that the source area is small and the bedrock below 85 is competent (or less fractured) and less impacted by the release of contaminants Some of the confusion may result from using most recent data when that data is from several different sampling events over several years and there is no discernible difference in concentrations between shallow and deep bedrock or as in Section 421 where generally decreased generally increase generally similar and similar concentrations in four consecutive sentences leads to a muddled picture of the contaminant distribution

Second the report asserts that the distribution of contaminants over the entire plume has not changed with time but fails to support this conclusion with data again relying on data that is from different sampling dates for one composite representation

Response The likely presence of dense non-aqueous phase liquid (DNAPL) at the Hows Corner Site and the determination that the source area is small are not mutually exclusive and both are conclusions drawn from information obtained during field investigations The presence of DNAPL in the source area is based on the elevated concentrations of volatile organic compounds (VOCs) detected in the groundwater (WampC 2001 WampC 2002) The conclusion that the source area is small is based on the area in which VOCs in groundwater have been detected at concentrations that are considered to be indicative of the presence of DNAPL nearby Similarly the conclusion that fracture frequency decreases at depths greater than approximately 50 to 85 feet below ground surface was based on field observation during the RI field work The fact that zones with observed fractures exhibited higher hydraulic conductivities than zones without fractures coupled with the decreasing frequency of observed fractures with depth led to the conclusion that the hydraulic conductivity of the bulk rock decreases with depth

The most recent data from all wells were used to provide the maximum VOC data set size During the RI all of the previously-existing and then newly-installed monitoring wells were sampled along with several residential wells The RI sampling included up to 48 monitoring wells Subsequent to the RI and prior to the TI three rounds of monitoring were conducted to verify that the plume was stable 15 monitoring wells were sampled during each of the three rounds During the TI field investigation 29 wells were sampled for VOCs The sampled wells included all of the newly-installed wells and a subset of wells installed during the RI for a total of 29 monitoring wells By using most recent data VOC results from 53 monitoring wells were included in the evaluation (see table labeled Sampling Events for listing of monitoring wells) This approach was selected because there generally was little variation in the data from a particular location between years This is borne out by the attached individual plots of VOCs detected in shallow bedrock and deep bedrock for the Pre-ROD (December 1999January 2000) and Supplemental (May 2000) sampling events and for June 2001 January 2002 and April 2003 sampling events The Pre-ROD and Supplemental plots are similar to the subsequent plots from the 2001 2002 and 2003 sampling events

In addition to maps showing the spatial distribution of VOC data at a given time trend plots of the data from a particular location through time (attached) indicate that since the RI concentrations generally have been stable or have decreased Together the maps and trend plots and the data from which they were developed indicate that the distribution of contaminants over the entire plume has not changed appreciably with time

Response to EPA Comment 4 050305doc 1 of 26 Woodard amp Curran (211941)

REFERENCES

Woodard amp Curran Inc (WampC) 2001 Final Remedial Investigation Report Hows Corner Superfund Plymouth Maine July 2001

Woodard amp Curran Inc (WampC) 2002 Final Feasibility Study Report - Non-Source Area Groundwater Hows Corner Superfund Site Plymouth Maine Hows Corner Superfund Plymouth Maine July 2002

Response to EPA Comment 4 050305doc 2 of 26 Woodard amp Curran (211941)

LIST OF ATTACHMENTS (Response to Comment 4)

Table - Sampling Events 1999 - 2004 (2 pages)

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater Pre-ROD Sampling Event

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater Pre-ROD Sampling Event

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater Supplemental Sampling Event

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater Supplemental Sampling Event

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater June 2001

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater June 2001

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater January 2002

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater January 2002

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater April 2003

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater April 2003

Figure - Concentration Trends - Non-Source Area Wells MW-1B and MW-3B

Figure - Concentration Trends - Non-Source Area Wells MW-13DB and MW-16DB

Figure - Concentration Trends - Non-Source Area Wells MW-16IB and MW- 108D

Figure - Concentration Trends - Non-Source Area Wells MW-108S and MW-112D

Figure - Concentration Trends - Non-Source Area Wells MW-112S and MW-114D

Figure - Concentration Trends - Non-Source Area Wells MW-114S and MW-115D

Figure - Concentration Trends -Source Area Wells MW-2DB and MW-2IB

Figure - Concentration Trends -Source Area Wells MW-102S and MW-103D

Figure - Concentration Trends -Source Area Wells MW-103S and MW-104D

Figure - Concentration Trends -Source Area Wells MW-104I and MW-106D

Figure - Concentration Trends -Source Area Wells MW-106S

Response to EPA Comment 4 050305doc 3 of 26 Woodard amp Curran (211941)

I I

El I

II I I 1 I

I

i

Event Baseline Case ID WC-01 WC-01

Well Date Aug-99 Oct-99 LOT10 1 LOT1-1 1 LOT11-4 LOT14 1 LOT15 1 LOT15-1 1 LOT16 1 LOT16-1 1 LOT17 1 LOT18 1 LOT19 1 LOT2 LOT20 1 LOT21-10 1 LOT21-11 1 LOT21-12 1 LOT21-13 1 LOT21-14 1 LOT21-2 1 LOT21-5 1 LOT21-7 LOT21 -8 1 LOT21-9 1 LOT23 1 LOT24 1 LOT28-1 1 LOT28-2 1 LOT28-3 1 LOT28-4 1 LOT28W 1 LOT30 1 LOT30-1 1 LOT30-2 1 LOT30-3 1 LOT30-4 1 LOT30-5 LOT31 LOT35 1 LOT41 1 LOT42-1 1 LOT43-1 1 LOT43-4 1 LOT6-1 1 LOT67 1 LOT6-7 1 LOT6-8A 1 LOT6-8B 1 LOT80-1 1 LOT82 1 MW-101D MW-1011 MW-101S MW-102D MW-102S MW-103D MW-103S MW-104D MW-1041 MW-104S MW-105D MW-106D

Groundwater Sampling Location Summary 1999 - 2004xls

Sampling Events 1999-2004

Hows Corner Superfund Site Plymouth Maine

Supplemental 2001 2002 2003 Pumping 2004 Pre-ROD Rl Sampling Sampling Sampling Test Sampling WC-03 WC-09 WC-25 WC-30 WC-42B WC-56 WC-58 Dec-99 May-00 Jun-01 Jan-02 Apr-03 Sep-04 Sep-04

1

1 1 1

1 1 1 1 1

1 1

1

1 1

1 1 1

1 1 1 1 1

1

1 1

1 1 1 1

1

1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

Sampling Events 1999-2004

Hows Corner Super-fund Site Plymouth Maine

Supplemental 2001 2002 2003 Pumping Event Baseline Pre-ROD Rl Sampling Sampling Sampling Test

Case ID WC-01 WC-01 WC-03 WC-09 WC-25 WC-30 WC-42B WC-56

ll

Well Date Aug-99 Oct-99 Dec-99 May-00 Jun-01 Jan-02 Apr-03 Sep-04 MW-106S 1 1 1 1 1 MW-107D 1 1 MW-108D 1 1 1 1 1 MW-108S 1 1 1 1 1 MW-110D 1 1 MW-111D 1 1 MW-112D 1 1 1 1 1 MW-112S 1 1 1 1 1 MW-113D 1 1 MW-114D 1 1 1 1 1 MW-114S 1 1 1 1 1 MW-115D 1 1 1 1 1 MW-12DB 1 1 1 MW-12SB 1 1 1 MW-13DB 1 1 1 1 1 1 MW-13SB 1 1 1 MW-14DB 1 1 MW-14SO 1 1 MW-15DB 1 1 1 MW-15SB 1 1 1 MW-16DB 1 1 1 1 1 1 MW-16IB 1 1 1 1 1 1 MW-16SO 1 1 MW-17DO 1 1 1 MW-17SO 1 1 1 MW-1B 1 1 1 1 1 1 MW-203D MW-203S MW-204D MW-204S MW-205 MW-206D

I MW-206S MW-2DB 1 1 MW-2DDB 1 1 MW-2IB 1 1 1 1 1 1 MW-3B 1 1 1 1 1 1

I MW-4O 1 1 1 MW-5B 1 1

II MW-6DB 1 1 1 MW-6SB 1 1 1 MW-8DB 1 1 1 MW-8SB 1 1 1

II PW-207 1 SEEP-1 1 SUBTOTAL - RESIDENTIAL 44 25 0 2 0 3 0 SUBTOTAL - MONITORING 22 48 41 15 15 15 1

Total 3 66 73 41 17 15 18 1

I Included in most recent data

I Notes 1 - Overburden well not included in most recent data for plotting

2 - Tetrahydrofuran and 2-Butanone were the only two compounds detected in this well and are thought to be the result of well repair not included in most recent data for plotting

3 - Not included in most recent data for plotting

2004 Sampling

WC-58 Sep-04

1

1 1

1 1

1 1 1

1

1 1

1 1 1 1 1 1 1 1 1

1 1

1

0 29

29

Groundwatef Sampling Location Summary 1999 - 2004xls

I

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

monitoring well Figure 4-14 total VOC contour (ugl) - December 1999January 2000 Distribution of Total VOCs in

Note SW-113 is located downstream of SEEP-1 Shallow Bedrock Groundwater total concentration of detected VOCs ND= not detected these two locations were sampled during the Pre-ROD Sampling Event

Baseline Sampling Event in OctoberNovember 1999 Hows Corner Superfund Site Surface Water Sampling Location A Plymouth Maine Seep Sampling Location laquo- WOODARD ampCURRAN

995037wipri reportepa ri interim final feb 2001cadd drawingsfinalfig 4-14

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

0 300 600 I

FEET

Q residential well Figure 4-16 monitoring well Distribution of Total VOCs in

Deep Bedrock Groundwater total VOCs contour (ugl) Pre-ROD Sampling Event

active residential wells with lot number Hows Corner Superfund Site 2deg42deg Plymouth Maine total concentration of detected VOCs ND= not detected WOODARD ampCURRAN Enyinaaring bull Science bull Operations bull

995037wipri reportepa ri interim final feb 2001cadd drawingsfinalfig4mdash16

PLYMOUTH POND

PLYMOUTH POND

1 628Tl7MW-2bB 12135

PLYMOUTH POND

monitoring well Figure 4-20

V total VOC contour (ugl) - June 2000 Distribution of Total VOCs in Shallow Bedrock Groundwater

| 34 | total concentration of detected VOCs ND= not detected NA = not analyzed Supplemental Sampling Event Note SW-113 is located downstream of SEEP-1 Hows Corner Superfund Site

Surface Water Sampling Location these two locations were sampled during the Plymouth Maine Baseline Sampling Event in OctoberNovember 1999 Seep Sampling Location WOODARD amp CURRAN

Engineering bull Science - Operations bull 995037wipri reportepa ri interim final feb 2001 cadd drawingsfinalfig 4-20

residential well Figure 4-22 Distribution of Total VOCs in

monitoring well Deep Bedrock Groundwater

total VOCs contour (ugl) Supplemental Sampling Event

Hows Corner Superfund Site

total concentration of detected VOCs ND= not detected NA = not analyzed Plymouth Maine

WOODARD amp CURRAN

995037wipri reportepa-ri interim final feb 2001cadd drawingsfinalfig 4-22 Engineering bull Science - Operations bull

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

FEET

Shallow Monitoring Well

Deep Monitoring Well

C Detected Concentration ND = Not Detected Figure 1-XS Distribution of Total VOCs in Shallow Bedrock Groundwater

Pumping Well

17-Acre Property Boundary Concentration Contour (ugl)

June 2001 Hows Corner Superfund Site

Plymouth Maine WOODARDampCURRAN

-i^rhvj bull Scbncn bull Operations bull 211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0601 dwg04-20-05

PLYMOUTH POND Hopkins Road V

O

PLYMOUTH POND

PLYMOUTH POND

o

0 300 600 mdashfa FEET

Shallow Monitoring Well bull bull - 17-Acre Property Boundary Figure 1-XD

Deep Monitoring Well 1 I Detected Concentration ND = Not Detected Distribution of Total VOCs in Deep Bedrock Groundwater

-mf- Pumping Well June 2001 Residential Well Hows Corner Superfund Site

Plymouth Maine i h Surface Water Sampling Point

g WOODARD ampCURRAN _ ^ _ ^ _ _ yen_ rj i|Hlaquorlny bull Science bull Opt

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0601 dwg04-20-05

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

Shallow Monitoring Well

Deep Monitoring Well

Detected Concentration ND = Not Detected Figure 1-YS Distribution of Total VOCs in Shallow Bedrock Groundwater

Pumping Well

17-Acre Property Boundary Concentration Contour (ugl)

January 2002 Hows Corner Superfund Site

Plymouth Maine WOODARD amp CURRAN Engineering Science- Operations bull

211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0102dwg04-20-05

PLYMOUTH POND

PLYMOUTH POND

Site Pand^ laquoum-laquoBTuitaraquo tLV

vVlf-(

PLYMOUTH POND

0 300 600 ^ = FEET

Shallow Monitoring Well mdashbullbullbull 17-Acre Property Boundary Figure 1-YD - A - Deep Monitoring Well FT Detected Concentration ND = Not Detected Distribution of Total VOCs in

Deep Bedrock Groundwater Pumping Well January 2002 Residential Well Hows Corner Superfund Site

Plymouth Maine Surface Water Sampling Point

WOODARD ampCURRAN Engineering Sciencs- Operations bulli Si

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0102dwg04-20-05

- m j

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND j A O-shy

Shallow Monitoring Well E Detected Concentration ND = Not Detected Figure 1-ZS Distribution of Total VOCs in

Deep Monitoring Well Shallow Bedrock Groundwater

Pumping Well Hows Corner

April 2003 Superfund Site

17-Acre Property Boundary Plymouth Maine Concentration Contour (ugl) r WOODARD ampCURRAN

Engineering bull Science bull Operations bull 211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0403dwg04-20-05

s S pound

PLYMOUTH POND

PLYMOUTH POND

- -

5 PLYMOUTH POND

Jo

FEET

ft Shallow Monitoring Well mdashbullbullmdash 17-Acre Property Boundary Figure 1-ZD Deep Monitoring Well I 1 I Detected Concentration ND = Not Detected Distribution of Total VOCs in

Deep Bedrock Groundwater Pumping Well April 2003

Q) Residential Well Hows Corner Superfund Site Plymouth Maine

(T) Surface Water Sampling Point WOODARD ampCURRAN poundKk EnginawtirKj bull Science - Operations bull

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0403dwg04-20-05

0 Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

B MW-1B

I 12000

PCE

B 10000 Total VOCs

I

i 2000

i 0 Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

c MW-3B

G 2000

1800

B PCE

1600 Total VOCs

1 I I E

il-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

G E

211941

El

I I z E

80

Concentration Trends shy Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-13DB

Total VOCs

c i i c o

Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

MW-16DB

30

c i c c I c o

Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99

PCE

Total VOCs

Jul-01 Jul-03

211941

O bi

c Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

I MW-16IB

i 35

3

c Total VOCs

lt- 2 5

0 | gt

o

1 sectI

c c 0 4

Jul-90 Jul-92 Jul-94 Jul-96 Jul-98 Jul-00 Jul-02 Jul-04

I I MW-108D

I 12

PCE 10

Total VOCs c oc 3

E E I 0

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

E 211941

c Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

fi MW-108S

I I 40

PCE 35

Total VOCs

30

I f 26

20 I o

I 15

10

c Dec-99 Dec-00 Dec-01 Dec-02 Dec-03 I 0

I MW-112D

c 35 - imdash

I A3 shyTotal VOCs

o c

E 1 2

I

ition

B 1 ^

-i c 3

0 Dec-99 Dec-OO Dec-01 Dec-02 Dec-03

211941

I

i

I

cII

Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-112S

08

PCE

Total VOCs 06

o 04

02

0 Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

MW-114D

o

12000

10000

8000

6000

PCE

Total VOCs

4000

2000

i

ccEIIc

i

i

E

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

211941

Con

cent

ratio

n (

ug

l)

E Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

I MW-114S

E A5000 -- Total VOCs

- 4000

0 3000

2000

i 1000

i n shy

Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

MW-115D

c PCE

Total VOCs

c E

o

C c

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03 I 0

211941

IepoundII

EIEIIGICCIccc

30000

25000

20000

o bullsect 15000 b

o 10000 U

5000

0 Aug-99

25000

20000

5000

0 Aug-99

211941

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-2DB

PCE

Total VOCs

Aug-01 Aug-03

MW-2IB

PCE

Total VOCs

Aug-01 Aug-03

IDIBI

ii EIDIISIBIG C

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-102S

6000

5000 PCE

Total VOCs

4000

O 3000

2000

1000

0 Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

MW-103D

16000

~ 14000 ugt 3- 12000 o

^ 10000

sect 8000

O 6000

4000

2000

PCE

Total VOCs

0Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

211941

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

G MW-103S

I I

ampo

12000

10000

E sectc

S

8000

6000

4000

2000

0Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

G I 6000

MW-104D

i 5000

PCE

Total VOCs

i i c

2000

1000

Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

E I

211941

cIccIG

IIBCccBcIc

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-1041

PCE Total VOCs

a 25000

0 20000

a 15000

10000

5000

0 Jan-OO Jan-01 Jan-02 Jan-03 Jan-04

MW-106D

3000

2500 PCE

Total VOCs

=sect 2000

o bullsect 1500

1000

500

0 Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

211941

c Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

c MW-106S

I PCE

Total VOCs

i

i Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

i

i i i E

C

211941 c

Response to EPA-DEP Comment 5 Dated March 312005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

iiw

EPA-DEP Comment 5

Comment 5 Matrix Diffusion The report as well as other proponents of matrix diffusion suggest that depletion of DNAPL (Section 5112 page 5-15) needs to be achieved While that might be the ideal the goal is to achieve performance standards and that goal may be attainable while there is residual contamination in the rock perhaps even DNAPL globules The low bedrock matrix porosity (page 1-15) the high permeability values (page 4-4) the relative flux of the groundwater (page 5-5) and the decrease in surface area and out of the mainstream pockets (appendix C-4) all suggest that the diffusion out of the rock matrix would be insubstantial relative to the regional flux of groundwater through the Site

Response The TI Evaluation Report does not explicitly consider or rely upon matrix diffusion as a basis for requesting a TI Waiver for a portion of the Hows Corner Site The technical literature provides documentation that matrix diffusion can be a significant process that affects chemical transport and groundwater remediation timeframes in unconsolidated and consolidated media including fractured rock (US EPA 1989 Freeze and Cherry 1979 Pankow and Cherry 1996 Fountain 1998) Back diffusion of contaminants from the matrix porosity of the fractured rock can prolong the time necessary to achieve groundwater cleanup goals particularly for compounds such as PCE for which the cleanup goal is a low concentration It is our expectation that matrix diffusion has occurred at the Hows Corner Site and that back diffusion of PCE from the rock matrix will also occur Although the extent to which matrix diffusion is occurring at the Hows Comer Site has not been determined and that lack of knowledge contributes to uncertainty regarding the cleanup times at the Site the effect of matrix diffusion is to lengthen rather than shorten the time required for remediation

REFERENCES

Fountain JC 1998 Technologies for Dense Nonaqueous Phase Liquid Source Zone Remediation Ground-Water Remediation Technologies Analysis Center Technology Evaluation Report TE-98-02 December

Freeze RA and Cherry JA 1979 Groundwater Prentice-Hall Inc Englewood Cliffs NJ 07632 p 410-412

Pankow J F and Cherry J A 1996 Dense Chlorinated Solvents Waterloo Press Portland OR 97291-1399 p 67-88

US EPA 1989 Transport and Fate of Contaminants in the Subsurface EPA6254-89019 p 17-18

Response to EPA Comment 5 050305doc 1 of 1 Woodard amp Curran (211941)

WOODARD amp CURRAN Maine Massachusetts New Hampshire Connecticut Florida Operational offices across the US 1-800-426-4262 www woodardcurran com

Page 27: SDMS DocID 251749 - Records Collections · 2020-06-13 · CORPORATE OFFICES: Maine, Massachusetts, New Hampshire, Connecticut New, York, Florida Engineering • Science • Operations

Table XX Packer Permeability and Packer Sampling Results for Potential Fracture Intervals

1999 Drilling Program

Hows Corner Supcrfund Site Plymouth Maine

gtbull i Potential Fracture Top _OfBot Bottom of Depth to ltbull Top of Interval from f Packer Packer Middle Of

GS ELEV lt Hock Drilling interval Interval Interval WeD ID ft msl) (ft msl) TEST (ftbgs) ltft$gs) (ftbgs) (ftbgs)

MW-107D 29958 2 128-130 1200 1305 1253

MW-107D 29958 1 139-141 1350 1455 1403

MW-108D 31904 31104 6 35-36 300 405 353 MW-108D 31904 5 60-62 550 655 603

MW-108D 31904 4 80-83 750 855 803

MW-108D 31904 3 118-119 123-124 1150 1255 1203

MW-108D 31904 2 147-149 1440 1545 1493

MW-108D 31904 1 1700 1805 1753

MW-110D 40576 40426 2 21-31 210 315 263 MW-110D 40576 1 148-154 1460 1565 1513 MW-I11D 40519 4 70-71 650 755 703

MW-111D 40519 3 79-82 84-86 780 885 833 MW-I11D 40519 2 97-102 950 1055 1003 MW-111D 40519 1 1370 1475 1423

MW-112D 3027 2942 4 42-52 420 525 473 MW-112D 3027 3 850 955 903 MW112D 3027 2 1100 1205 1153 MW-112D 3027 1 135-136 140-141 1340 1445 1393

MW-113D 43085 43085 5 250 355 303 MW-I13D 43085 4 47-49 460 565 513 MW-113D 43085 3 73-74 700 805 753 MW-113D 43085 2 1050 1155 1103 MW-113D 43085 1 1380 1485 1433

MW-114D 42394 41594 4 48-49 450 555 503 MW-114D 42394 3 79-81 740 845 793 MW-114D 42394 2 121-129 1250 1355 1303 MW-114D 42394 1 134-142 1350 1455 1403

MW-115D 4035 4035 4 300 405 353 MW-1I5D 4035 3 70-71 650 755 703 MW-115D 4035 2 1150 1255 1203 MW-115D 4035 1 1400 1505 1453

LOT-28W 382 7 450 555 503 LOT28W 382 6 550 655 603 LOT-28W 382 5 650 755 703 LOT28W 382 4 750 855 803 LOT-28W 382 3 850 955 903 LOT-28W 382 2 950 1055 1003 LOT-28W 382 1 1055 1155 1105

NOTES cmsec = centimeters per second ft bgs = leet below ground surface It msl = feet below mean sea level lt = not detected at indicated reporting limil A = detected below laboratory PQL ( ) = detected below reporting limits

Elevation of Interval

(ft nisi) 174

159

283gt 2588

2388

1988

1698

1438

3795 2545 3349 3219 3049 2629

2555 2125 1875 1635

4006 3796 3556 3206 2876

3737 3447 2937 2837

3683 3333 2833 2583

3318 3218 3118 3018 2918 2818 2715

Hydraulic Conductivity

(cmsec)

323E-05

208E-05

471E-03

471E-03

624E-05

3I6E-05

264E-05

261 E-05

OOOE+00 200E-04 953E-05 OOOE+00 OOOE+00 212E-05

361 E-05 410E-06 2gQE06 292E-05

786E-05 124E-05 151 E-05 822E-06 82IE-06

858E-05 I69E-05 352E-03 866E-05

223E-05 394E-06 122E-05 525E-06

831 E-05 182F-05 L62E-05 129E-05 190E-05 890E-04 981 E-04

PCEraquo Concentration

(ugL)

lt5

(14A)

98 11

15

22

11

30

200 (62)A

110 210 300 240

(44)A (23)A

5

350 190 129 230

2200 1900 2600 2600

(17)A (16)A (19)A

96

Table XX Packer Permeability and Packer Sampling Results for Potential Fracture Intervals

2004 Drilling Program

Hows Corner Superfund Site Plymouth Maine

Top of Bottom of Depth to Midpoint

t K

ELEV (ft Potential Transmissive Zones Packer Interval

Packer Interval

Middle of Interval

Elevation of interval

Hydraulic Conductivity

PCE Concentration

Well ID msl) TESTr (ft bgs)- (ftbgs) (ftbgs) (ftbgs) (ft msl) (cmsec) (ogt) MW-203D 43227 4 277279 24 32 28 4043 667E-05 44

3 408415420 39 49 44 3883 593E-05 170 2 526 530 49 57 53 3793 101E-04 140 I 828830842 80 88 84 3483 701E-05 130

MW-204D 43262 5 295 300 26 34 30 4023 902E-05 220 4 463496513516 45 53 49 3833 119E-04 540 3 681685688 63 71 67 3653 OOOE+00 2 758 76 2 71 79 75 3573 309E-05 260 I 88 96 92 3403 OOOE+00

MW-205 42389 3 164 166 168 15 20 175 4148 OOOE+00 1000B 2 302305312 30 35 325 3998 107E-04 1300B 1 40 45 425 3898 OOOE+00

MW-206D 43007 5 17 72 195 4128 291E-05 4 296 302 307 29 34 315 4008 940E-05 2900B 3 522 52 57 545 3778 944E-07 2 656 64 69 665 3658 353E-06 1 92392793 4939 91 96 935 3388 614E-05 6300B

PW-207 43477 5 184622162819 18 29 235 4088 209E-05 1300 4 3508 32 43 375 3948 568E-06 5400 3 53325341542154325559 50 61 555 3768 821E-05 18000

6359 61 72 665 3658 866E-06 12000 1 8685 84 89 865 3458 213E-05 19000

NOTES cmsec = centimeters per second ft bgs = feet below ground surface ft msl = feet above mean sea level B = detected in lab blank

Table XX Orientation Permeability and Groundwater Sampling Results for Transmissive Features

2004 Drilling Program

Hows Corner Superfund Site Plymouth Maine

Borehole Geophisical Feature depth Dip True Dip True Transmissive Log Feature (Feet) Degrees Azimuth Strike bullvgt(Ltk|iy^

Number v Tosftble) v MW-203 5 277 64 337 67 Likely

6 279 59 11 281 Likely 8 352 14 177 87 Likely 11 381 46 96 6 Possible 12 408 35 271 1 Possible 14 415 57 250 340 Possible 15 420 58 202 292 Likely 18 526 52 75 345 Likely 19 530 52 82 352 Likely 28 828 48 75 345 Likely 29 830 52 17 287 Likely 30 830 56 233 323 Possible 31 842 50 130 40 Likely

MW-204 4 295 15 147 57 Likely 5 300 43 91 1 Likely 11 439 31 80 350 Possible 12 440 46 219 309 Possible 14 463 50 358 88 Likely 15 496 34 198 288 Likely 16 513 54 17 287 Likely 17 516 33 14 284 Likely 25 681 39 359 89 Possible 26 685 22 45 315 Possible 27 688 35 73 343 Possible 32 758 45 236 326 Likely 33 762 46 306 36 Likely

MW-205 5 164 69 106 16 Possible 6 166 78 165 75 Possible 7 168 82 115 25 Possible 8 168 68 116 26 Possible 12 215 46 222 312 Possible 13 217 75 62 332 Possible 14 219 29 32 302 Possible 16 237 69 250 340 Possible 17 256 73 353 83 Possible 18 272 44 202 292 Possible 21 299 37 196 286 Possible 22 302 31 206 296 Possible 23 305 59 48 318 Likely 24 312 63 42 312 Likely

MW-206 1 264 37 181 271 Likely 2 296 69 217 307 Likely 3 302 66 233 323 Likely 4 307 64 224 314 Likely 8 342 62 259 349 Likely

jjHydraulic GoiDanctilyity j(cmsecjw

667 E-05

593 E-05

101 P04

710 E-05

902 E-05

119 E-04

0

309 E-05

0

107 E-04

94 E-05

PCE (ugL)

44

170

140

130

220

540

260

IOOOB

1100B

1300B

2900B

STotal vVoCsv tig1)

84

234

192

183

2636

6436

3073

11448

12509

13776

32401

PCEyo dfCTotaf

52

73

73

7 1

83

84

85

87

88

94

90

Table XX Orientation Permeability and Groundwater Sampling Results for Transmissive Features

2004 Drilling Program

Hows Corner Superfund Site Plymouth Maine

Borehole Geophisical Feature deptt raquoip True pip True Transraissive Log Feature (Feet) shy Degrees Azimuth Strike (tikely

Number raquo Possible) 22 522 57 54 324 Possible 25 656 40 82 352 Possible 32 871 59 151 61 Possible 33 883 53 185 275 Possible 34 895 7 175 85 Likely 35 899 53 90 0 Likely 36 902 49 184 274 Likely 37 923 9 175 85 Likely 38 927 42 206 296 Likely 39 934 48 167 77 Likely 40 939 26 180 90 Likely

PW-207 1 1846 33 167 77 Likely 4 2216 49 289 19 Possible 7 2819 59 265 355 Possible 11 3508 55 189 279 Possible 18 5332 43 305 35 Likely 19 5341 51 30 300 Likely 20 5421 20 254 344 Likely 21 5432 39 301 31 Likely 23 5559 52 302 32 Likely 25 6359 24 182 272 Possible 29 8049 77 231 321 Possible 30 8685 78 38 308 Likely 32 9334 29 194 284 Likely

NOTES

B = detected in lab blank

Hydraulic Conductivity

(cmsee) 944 E-07 353 E-06

614 E-05

209 E-05

568 E-06

821 E-05

866 E-06

213 E-05

bulltCE (ugL)

6300B

1300

5400

18000

12000

19000

Total VOCs (ug1)

68901

1410

5802

19234

13085

20354

PCE of Total VOCs

9 1

92

93

94

92

93

Response to EPA-DEP Comment 3 Dated March 312005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

lit

EPA-DEP Comment 3

Comment 3 The reported f values and resultant Kd values There remains doubt that the values used in the flushing model accurately reflect the propensity for PCE to sorb to the bedrock The ^ values presented in Appendix B may be unrealistically high because the bedrock samples may have contained organic carbon that was unavailable for sorption The reported f values are only qualitative estimates of the organic carbon content of the bedrock samples The Walkley and Black organic carbon measurement method is quick and simple but the results obtained cannot be considered quantitative because it requires a correction factor which often results in erroneous values it assumes the organic carbon has an average valence of zero oxidizable and reducible constituents such as chloride ferrous iron and manganese oxides interfere with the results and the errors introduced by interference are potentially greater when the organic carbon content is low at low f values it is not clear that organic carbon is controlling PCE sorption (Schwarzenbach and Westall 1981 Mackay et al 1986 Fetter 1999)

In order to derive a Kd-based retardation factor that is reasonable given the reported f values and the rapid advance of the PCE plume described on pages 4-11 and 4-12 the flushing model requires a bulk density to porosity ratio that is roughly two orders of magnitude higher than the actual ratio for the Hows Corner bedrock (page 4-4) This apparent discrepancy needs to be addressed

Response This comment raises several concerns about the collection and analysis of samples for fraction of organic carbon (f^) the quality of the resulting data and the implications of the use of those data for estimation of the retardation of groundwater contaminant movement Results of bedrock analysis for f were proposed in the TI Evaluation Work Plan for use in conjunction with groundwater contaminant concentrations and aquifer information to estimate cleanup times using the Batch Flushing model It is important to use accurate f values from representative bedrock in the Batch Flushing model in order to obtain reasonable estimates of the remedial time frame Because of the importance of accurate and representative results the TI Investigation field program was designed and conducted both to collect samples representative of the rock volume most likely to be in contact with contaminated groundwater and to analyze them using an appropriate refereed analytical method Five potential methods for evaluating f were identified Of the five methods the Walkey-Black method was selected because it has minimal method interferences and a sufficiently low detection limit as well as a long history of use in agronomy and contamination studies The PRP Group is pleased with the quality of the data obtained from the bedrock samples as represented by their precision and reproducibility

The first part of this comment relates to the determination of fraction of organic carbon (f^) values The several subparts of the first paragraph are addressed individually in items 1 through 5 below The second part of the comment regarding the resultant distribution coefficient (Kd) values is addressed separately as item 6 below

1 There remains doubt that the values used in the flushing model accurately reflect the propensity for PCE to sorb to the bedrock

bull The rock core samples used for f (gocg) analysis were from core immediately adjacent to fractures These rock core samples included the fracture surfaces themselves and rock core extending back less than 1 cm from the fractures Therefore the foe data reported in the TI Evaluation represents the f of bedrock through which groundwater will travel and to which PCE will adsorb Based on the careful selection of sample locations and the

Response to EPA Comment 3 050205doc 1 of 11 Woodard amp Curran (211941)

number of samples collected we are confident that the measured f values are representative of the f at points of contact for PCE with the bedrock it is these f values that determine the propensity of PCE to sorb to the bedrock

bull The samples of rock core collected for analysis of f originated from 19 different locations varying in depth from 11 to 90 feet Therefore it is very unlikely that the rock core samples were contaminated with extraneous organic carbon from above ground

2 The foc values presented in Appendix B may be unrealistically high because the bedrock samples may have contained organic carbon that was unavailable for sorption

bull As noted in response 1 the f data reported in Appendix B represents organic carbon primarily associated with the surface of fractures in the bedrock through which groundwater is most likely to travel Therefore it is this organic carbon that the contaminants in the groundwater will come in contact with and adsorb to in the fractured rock at the site

bull The chemical oxidation agents used in the Walkey-Black method oxidize the easily oxidizable organic carbon in the medium and the foe is calculated from the quantity of the agent consumed Therefore it is unlikely that the analysis of the bedrock samples measured organic carbon that was unavailable for sorption

3 The reported foc values are only qualitative estimates of the organic carbon content of the bedrock samples

bull The reported f values are accurate quantitative results Schumachers review of Methods for the determination of total organic carbon (TOC) in soils and sediments (NCEA-C-1282 EMASC-001 April 2002) identifies the Walkley-Black method which was used to analyze the reported foc values as the reference method for comparison to other methods for analyzing total organic carbon

bull Schumacher also points out that if anything the WalkJey-Black method may underestimate the total organic carbon in a sample due to possible incomplete oxidation of organic carbon Usually the incomplete oxidation of total organic carbon in environmental samples is corrected for by multiplying the measured foe by 130 (Walkley amp Black 1934 Schulte 1995)

bull When the f data in the TI Evaluation Report (WampC 2005) Appendix B (attached) are analyzed statistically the standard deviation of the f for the 19 samples analyzed is 174 of the average f Given this standard deviation the 95 confidence interval for this data ranged from a low of 000123 gocg to a high of 000253 gocgm

The labs Method of Detection Limit (MDL) for the f measured using the Walkley-Black method is 00001 gocg Therefore the average (000188 gocg) the mean (000185 gocg) and geometric mean (000187 gocg) of the f values for the rock core at Hows Corner are all statistically significantly greater than the MDL of the Walkley-Black method

In addition to the aforementioned statistical analysis of the foe data triplicate samples (n = 3) from the same rock core (including one sample from the 19 rock core samples) were

Response to EPA Comment 3 050205doc 2 of Woodard amp Curran (211941)

analyzed for their f to determine the repeatability of the Walkley-Black method The average the mean and the geometric mean of the f values of these replicate samples was 000162 gocg 000150 gocg and 000159 gocgm respectively The standard deviation of these measurements was 000039 gocg

4 The Walkley and Black organic carbon measurement method is quick and simple but the results obtained cannot be considered quantitative because it requires a correction factor which often results in erroneous values it assumes the organic carbon has an average valence of zero oxidizable and reducible constituents such as chloride ferrous iron and manganese oxides interfere with the results and the errors introduced by interference are potentially greater when the organic carbon content is low at low foc values it is not clear that organic carbon is controlling PCE sorption (Schwarzenbach and Westall 1981 Mackay et al 1986 Fetter 1999)

bull Schumachers review (NCEA-C-1282 EMASC-001 April 2002) of the Walkley-Black method identifies several potential problems with this analytical method that could occur if the analytical lab is not familiar with the nuances of the chemistry associated with this method Interestingly Schumachers review neglected one of the more important analytical steps required to avoid errors in quantifying f in samples where there might beNAPL

It is absolutely critical to eliminate any NAPL from rock core samples prior to using the Walkley-Black method to measure foe in such samples This was done by the lab (PTS Laboratories) that measured the foe in the rock core samples from Hows Corner The lab used the Dean-Stark method (solvent extraction) to remove all hydrocarbons (including PCE and other NAPLs) from the sample (PTS Laboratories) This extraction method does not interfere with the subsequent analysis of the natural organic carbon associated with the rock core

Subsequently the samples were dried at 150degC to a constant weight (normally 16 hours) This latter step oxidizes all inorganic minerals including ferrous bearing minerals to ferric oxides and precludes their interference during the oxidation of the samples with chromic acid This procedure completely eliminates any positive bias in the reported foc

data that might have occurred due to the presence of ferrous ions and other reduced minerals

bull As noted in Response 3 the incomplete oxidation of total organic carbon results in an underestimate of the f and is corrected for by multiplying the f by a correction factor of 130 (Walkley amp Black 1934 Schulte 1995) The fx data reported in the TI Evaluation was corrected accordingly by using this correction factor

bull Excess chloride (Cl~) in percent weight quantities as found in saline soils may interfere with the quantitative titration of reduced chromium (Walkley 1947) However given that the primary rock type at the Hows Corner site is phyllite it is highly unlikely that there was sufficient chloride in the rock core samples for this to occur

bull Manganese oxides may also interfere with the analysis of f through competing with the dichromate ion for any oxidizable carbon (Walkley 1947) However in such cases the reported f would be an underestimate of the f present in the rock core Walkley (1947)

Response to EPA Comment 3 050205doc 3 of 11 Woodard amp Curran (211941)

4

reported that in the case where the ratio of MnO2 to carbon is 85 to 1 the error in the carbon determinations would only be 0 to 6 percent

It may also be useful to compare the analysis of total organic carbon in a geologic matrix that contains high levels of manganese using EPA method 9060 to the Walkley-Black method Table 1 summarizes data provided by one of the PRPs that compares the analysis of total organic carbon in a geologic matrix that contains approximately 02 wgt manganese (approximately 03 wgt manganese oxide)

Table 1 Comparison of total organic carbon measured using the EPA- 9060 method and the Walkley-Black method

Laboratory EPA-9060 Method Walkley-Black Method A Ave 00226 gocg Not analyzed

Stdev 000251 gocg n = 5

B Ave 002219 gocg Ave 002050 gocg Stdev = 000316 gocg Stdev =000971 gocg

n= 10 n = 10

The similarity in the total organic carbon concentrations measured by these two different methods provides further confidence that the Walkley-Black method is a viable method for analysis of total organic carbon in the presence of manganese equivalent to at least 10 by weight of the total organic carbon

5 The Walkley and Black organic carbon measurement at lowf^ values it is not clear that organic carbon is controlling PCE sorption (Schwarzenbach and Westall 1981 Mackay et al 1986 Fetter 1999)

bull Schwarzenbach and Westalls (1981) paper states that f values of less than 0001 gocg should not be used in combination with Kow (octanol-water partition coefficients) values to calculate K^ values (solid phase partition coefficients) values for a specific contaminant It should be noted that the TI Evaluation did not use the f data to calculate the KQC from the Kow Instead as requested by the EPA the measured KOC value for PCE was used to calculate the retardation factor for this contaminant

bull Schwarzenbach et al (2003) stated more recently that Even at very low f values (ie foe = 0001 kgoc - kg1 solid) sorption to the organic components of a natural sorbent may still be the dominant mechanism in defining the adsorption of organic compounds to geological matrices

bull In 1985 M Piwoni from the US EPA Robert S Kerr Environmental Research Laboratory published a paper (Banerjee et al 1985) that showed that for very hydrophobic molecules TOC content of the sorbent will control sorption down to levels of organic carbon that defy quantitation Contaminants such as the PCE found in the groundwater at Hows Corner are in this category of compounds

Given the aforementioned reasons the f values reported in the TI Evaluation are accurate within the noted statistical limitations and will have a predictable impact upon the retardation of PCE during groundwater transport

Response to EPA Comment 3 050205doc 4 of 11 Woodard amp Curran (211941)

6 In order to derive a Kd-based retardation factor that is reasonable given the reported foc

values and the rapid advance of the PCE plume described on pages 4-11 and 4-12 the flushing model requires a bulk density to porosity ratio that is roughly two orders of magnitude higher than the actual ratio for the Hows Comer bedrock (page 4-4) This apparent discrepancy needs to be addressed

The apparent discrepancy of bulk density to porosity ratios is most likely due to the fact that the Batch Flushing Model was originally developed for a porous medium and is not directly applicable to fractured bedrock As stated in Appendix C (page C-4) of the Draft Technical Impracticability Evaluation Report in order to use the Batch Flushing Model to describe the transport of contaminated groundwater in fractured bedrock where the matrix porosity is insignificant it is more appropriate to use a fracture surface area to void space ratio to calculate the retardation factor (R) than a bulk density to porosity ratio (Freeze amp Cherry 1979)

Since it is impractical to determine the actual surface area to which contaminants can adsorb the Batch Flushing Model was used with two simplifying assumptions bull The Kd was calculated from the f and the K^ bull The bulk density to porosity ratio term in the Batch Flushing Model was constrained to range

from 4 to 10 the typical range of such ratios in porous media (Freeze amp Cherry 1979)

If one uses site specific bedrock bulk density and porosity values the bulk density to porosity ratio is several orders of magnitude greater (specifically 273 gcc bullbull 000165 (dimensionless) = 1654 gcc) than the range of ratios of 4 to 10 used in the Batch Flushing Model in the Draft Technical Impracticability Evaluation Report Constraining the bulk density to porosity ratio within the range of ratios of 4 to 10 results in significantly lower R value than would be obtained using specific bedrock bulk density and porosity values

In summary in bedrock where fractures are the primary porosity the bulk density to porosity ratio can vary considerably and will be a function of the number of fractures and the fracture aperture The calculated bulk density to porosity ratio will be inversely proportional to the porosity This means that in fractured rock with limited fracturing and smaller porosity the calculated bulk density to porosity ratio is greater and will result in a greater calculated retardation factor than in bedrock with more extensive fracturing and greater porosity Consequently the calculated retardation factor will be greater for bedrock with less surface area available for sorption than bedrock with greater surface area for sorption This is contrary to what actually occurs

4 Response to EPA Comment 3 050205doc 5 of 11 Woodard amp Curran (211941)

m

REFERENCES

Banerjee P MD Piwoni K Ebeid (1985) Sorption of organic contaminants to a low carbon subsurface core Chemosphere _14 1057-1067

Freeze RA JA Cherry (1979) Groundwater Prentice Hall Englewood Cliffs NJ pg 604

PTS Laboratories wwwptsgeolabscompdf files3TOCnotepdf

Schulte EE (1995) Recommended soil organic matter tests in Recommended Soil Testing Procedures for the Northeastern United States Northeastern Regional Publication No 493 Chapter 8

Schwarzenbach RP J Westall (1981) Transport of nonpolar organic compounds from surface water to groundwater Laboratory sorption studies Environ Sci Tech 15 1360-1367

Schwarzenbach RP PM Gschwend DM Imboden (2003) Environmental Organic Chemistry Wiley-Interscience pg 292 408 amp 412

Walkley A LA Black (1934) An examination of the Degtjareff method for determining soil organic matter and a proposed modification of the chromic acid titration method Soil Science 37 29-38

Walkley A (1947) A critical examination of a rapid method for determining organic carbon in soils - effect of variations in digestion conditions and of inorganic soil constituents Soil Science 63251-264

Woodard amp Curran Inc (WampC) 2005 Draft Technical Impracticability Evaluation Hows Corner Superfund Site Plymouth Maine January 2005

Response to EPA Comment 3 050205doc 6 of Woodard amp Curran (211941)

LIST OF ATTACHMENTS (Response to Comment 3)

Appendix B to Draft Technical Impracticability Evaluation Measurement of foe at Hows Corner (4 pages)

m

Response to EPA Comment 3 050205doc 7 of 11 Woodard amp Curran (211941)

Appendix B Measurement of foe of Rock Core at Hows Corner

There are two general approaches to measure the fraction of organic carbon (foe) in rock cores

bull Measurement of weight loss by ignition of organic matter bull Chemical oxidization of organic carbon to carbon dioxide and either

subsequent quantification of the oxidant used for the reaction or quantification of the carbon dioxide produced during this oxidation process

The weight loss method is subject to errors caused by volatilization of substances other than organic materials such as water hydroxides and mineral carbonates Quantification of foe by the weight loss method is particularly sensitive to the presence of carbonates in rock cores There are however weight loss methods that are designed to differentiate between organic carbon and the aforementioned interfering materials but they require considerable care and are less accurate at low foe values Hence the weight loss method was not well suited for measuring the foe of the rock core from Hows Corner

The chemical oxidation of organic carbon is much better suited for quantifying organic carbon in rock cores such as those from Hows Corner This method uses a strong chemical oxidant to oxidize organic carbon to carbon dioxide and then measures either the chemical oxidant used to oxidize the organic carbon or the quantity of carbon dioxide produced In addition this general approach is not subject to interference by volatilization of other constituents of the rock core

There are at least two such chemical oxidation methods

bull The method of Baccini which was described by Schwarzenbach amp Westall (1981) first acidifies the sample to eliminate interference by carbonates Then a strong oxidant is used to chemically oxidize the organic carbon to carbon dioxide The resulting carbon dioxide is subsequently reduced to methane and quantified using a flame ionization detector Unfortunately this method has not been described in detail in a referred journal Hence it is would not have been appropriate to use to characterize the foe in the Hows Corner rock core

bull The more commonly used method to quantify foe in rock core is the Walkley-Black method (1934) This method is preferred for RBCA and DODDOE projects and by the oil industry

The Walkley-Black method uses an excess of chromic acid to oxidize (digest) organic matter to carbon dioxide The remaining chromic acid that was not consumed during the oxidation of the organic carbon is then quantified by titration with ferrous sulfate The difference in chromic acid prior to and after the oxidation of the organic carbon represents the total chromic acid used to oxidize

Hows Corner TI Evaluation Page 1 January 13 2005 Appendix B

the organic carbon in the sample The latter can be calculated using the chemical stoichiometry of the reaction

The Walkley-Black method is very accurate for samples that contain less than 2 organic carbon matter The minimum detection limit (MDL) for the Walkley-Black method is 100 mgkg or an foe of 0001

Given the rock core at Hows Corner was expected to contain less than 2 organic carbon the Walkley-Black method was used to measure the foe from 19 different rock core samples collected from varying depths ranging from 11 to 90 feet

Table 1 provides a statistical summary of the aforementioned data

Table 1 Statistical summary of foe data from rock cores collected at varying depths

Statistical Parameter Calculated Value foe Minimum Detection Limit (MDL) 00010 Number of samples analyzed (n) 19 Average foe 00019 Median foe 00019 Geometric Mean foe 00019 Standard deviation of foe measurements 000033 Relative standard deviation 174 -+ 95 Confidence intervals 00012 to 00025

The data in Table 1 shows the following

bull The foe from the Hows Corner rock cores are statistically greater than the MDL of the Walkley-Black analytical method

bull The average and median values for the foe of the Hows Corner rock cores from varying depths are nearly identical indicating that there is little variability in the foe values in the source zone at the site

bull The standard deviation of these measurements is 000033 which is 174 of the average foe

bull The 95 confidence intervals of the foe of the rock core at Hows Corner are 00012 to 00025

The foe was also analyzed from three separate samples taken from the same rock core at a depth of 55 feet (Only one of these samples was included in the data summarized in Table 1) Table 2 shows the statistical repeatability of this type of analysis

Hows Corner TI Evaluation Page 2 January 13 2005 Appendix B

Table 2 Repeatability of analysis of foe from one rock core at 55 feet in depth

Statistical Parameter Calculated Value Number of samples analyzed (n) 3 Average foe 00016 Median foe 00015 Geometric Mean foe 00016 Standard deviation of foe measurements 000039 Relative standard deviation 240 -+ 95 Confidence intervals 00008 to 00024

The data in Table 2 shows the following

bull The percent relative standard deviation of these three analyses of foe from the same rock core at Hows Corner is 24

bull The 95 confidence interval of the foes measured in this particular rock core at Hows Conrer is 00008 to 00024

These results show that there is good repeatability in using the Walkley-Black method for analysis of the foe in the rock core at Hows Corner

References Schwarzenbach amp Westall (1981) Transport of nonpolar organic compounds from surface water to groundwater Laboratory sorption studies Environ Sci Tech 15 1360-1367

Walkley A I A Black (1934) An examination of Degtjareff method for determining soil organic matter and a proposed modification of the chromic acid titration method Soil Sci 37 29-37

Hows Corner Tl Evaluation Page S January 13 2005 Appendix B

Woodard and Curran PTS Laboratories PTS File No 34618

ORGANIC CARBON DATA (METHODOLOGY WALKLEY-BLACK)

PROJECT NAME PROJECT NO

SAMPLE ID

203-chip-13 203-chip-23 203-chip-27 203-chip-38 203-chip-42 203-chip-47 203-chip-52 203-chip-58 203-chip-69 203-chip-82 207-chip-11 207-chip-19 207-chip-24 207-chip-29 207-chip-35 207-chip-45 207-chip-55 207-chip-87 207-chip-90

207-chip-55 55-MS

55-MSMSD

Hows Corner NA

DEPTH ft

13 23 27 38 42 47 52 58 69 82 11 19 24 29 35 45 55 87 90

55 NA NA

MATRIX

Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip

Average Median

Geometric Mean Standard Deviation Relative Std Dev

+- 95 Confidence Interval n

Rock Chip Rock Chip Rock Chip

Average Median

Geometric Mean Standard Deviation Relative Std Dev

+- 95 Confidence Interval n

FRACTION ORGANIC CARBON

(gg)

170E-03 185E-03 185E-03 170E-03 240E-03 190E-03 230E-03 180E-03 170E-03 115E-03 195E-03 220E-03 220E-03 235E-03 135E-03 190E-03 205E-03 175E-03 160E-03

188E-03 185E-03 185E-03 327E-04

1739 123E-03 to

19

205E-03 130E-03 150E-03

162E-03 150E-03 159E-03 388E-04

2402 840E-04 to

3

2532E-03

2393E-03

Hows Corner Tl Evaluation Appendix B January 13 2005

Response to EPA-DEP Comment 4 Dated March 31 2005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

EPA-DEP Comment 4

Comment 4 Distribution of contaminants First the TI report seems based on the assertion that there is DNAPL at the source area yet it also appears to represent that the source area is small and the bedrock below 85 is competent (or less fractured) and less impacted by the release of contaminants Some of the confusion may result from using most recent data when that data is from several different sampling events over several years and there is no discernible difference in concentrations between shallow and deep bedrock or as in Section 421 where generally decreased generally increase generally similar and similar concentrations in four consecutive sentences leads to a muddled picture of the contaminant distribution

Second the report asserts that the distribution of contaminants over the entire plume has not changed with time but fails to support this conclusion with data again relying on data that is from different sampling dates for one composite representation

Response The likely presence of dense non-aqueous phase liquid (DNAPL) at the Hows Corner Site and the determination that the source area is small are not mutually exclusive and both are conclusions drawn from information obtained during field investigations The presence of DNAPL in the source area is based on the elevated concentrations of volatile organic compounds (VOCs) detected in the groundwater (WampC 2001 WampC 2002) The conclusion that the source area is small is based on the area in which VOCs in groundwater have been detected at concentrations that are considered to be indicative of the presence of DNAPL nearby Similarly the conclusion that fracture frequency decreases at depths greater than approximately 50 to 85 feet below ground surface was based on field observation during the RI field work The fact that zones with observed fractures exhibited higher hydraulic conductivities than zones without fractures coupled with the decreasing frequency of observed fractures with depth led to the conclusion that the hydraulic conductivity of the bulk rock decreases with depth

The most recent data from all wells were used to provide the maximum VOC data set size During the RI all of the previously-existing and then newly-installed monitoring wells were sampled along with several residential wells The RI sampling included up to 48 monitoring wells Subsequent to the RI and prior to the TI three rounds of monitoring were conducted to verify that the plume was stable 15 monitoring wells were sampled during each of the three rounds During the TI field investigation 29 wells were sampled for VOCs The sampled wells included all of the newly-installed wells and a subset of wells installed during the RI for a total of 29 monitoring wells By using most recent data VOC results from 53 monitoring wells were included in the evaluation (see table labeled Sampling Events for listing of monitoring wells) This approach was selected because there generally was little variation in the data from a particular location between years This is borne out by the attached individual plots of VOCs detected in shallow bedrock and deep bedrock for the Pre-ROD (December 1999January 2000) and Supplemental (May 2000) sampling events and for June 2001 January 2002 and April 2003 sampling events The Pre-ROD and Supplemental plots are similar to the subsequent plots from the 2001 2002 and 2003 sampling events

In addition to maps showing the spatial distribution of VOC data at a given time trend plots of the data from a particular location through time (attached) indicate that since the RI concentrations generally have been stable or have decreased Together the maps and trend plots and the data from which they were developed indicate that the distribution of contaminants over the entire plume has not changed appreciably with time

Response to EPA Comment 4 050305doc 1 of 26 Woodard amp Curran (211941)

REFERENCES

Woodard amp Curran Inc (WampC) 2001 Final Remedial Investigation Report Hows Corner Superfund Plymouth Maine July 2001

Woodard amp Curran Inc (WampC) 2002 Final Feasibility Study Report - Non-Source Area Groundwater Hows Corner Superfund Site Plymouth Maine Hows Corner Superfund Plymouth Maine July 2002

Response to EPA Comment 4 050305doc 2 of 26 Woodard amp Curran (211941)

LIST OF ATTACHMENTS (Response to Comment 4)

Table - Sampling Events 1999 - 2004 (2 pages)

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater Pre-ROD Sampling Event

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater Pre-ROD Sampling Event

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater Supplemental Sampling Event

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater Supplemental Sampling Event

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater June 2001

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater June 2001

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater January 2002

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater January 2002

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater April 2003

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater April 2003

Figure - Concentration Trends - Non-Source Area Wells MW-1B and MW-3B

Figure - Concentration Trends - Non-Source Area Wells MW-13DB and MW-16DB

Figure - Concentration Trends - Non-Source Area Wells MW-16IB and MW- 108D

Figure - Concentration Trends - Non-Source Area Wells MW-108S and MW-112D

Figure - Concentration Trends - Non-Source Area Wells MW-112S and MW-114D

Figure - Concentration Trends - Non-Source Area Wells MW-114S and MW-115D

Figure - Concentration Trends -Source Area Wells MW-2DB and MW-2IB

Figure - Concentration Trends -Source Area Wells MW-102S and MW-103D

Figure - Concentration Trends -Source Area Wells MW-103S and MW-104D

Figure - Concentration Trends -Source Area Wells MW-104I and MW-106D

Figure - Concentration Trends -Source Area Wells MW-106S

Response to EPA Comment 4 050305doc 3 of 26 Woodard amp Curran (211941)

I I

El I

II I I 1 I

I

i

Event Baseline Case ID WC-01 WC-01

Well Date Aug-99 Oct-99 LOT10 1 LOT1-1 1 LOT11-4 LOT14 1 LOT15 1 LOT15-1 1 LOT16 1 LOT16-1 1 LOT17 1 LOT18 1 LOT19 1 LOT2 LOT20 1 LOT21-10 1 LOT21-11 1 LOT21-12 1 LOT21-13 1 LOT21-14 1 LOT21-2 1 LOT21-5 1 LOT21-7 LOT21 -8 1 LOT21-9 1 LOT23 1 LOT24 1 LOT28-1 1 LOT28-2 1 LOT28-3 1 LOT28-4 1 LOT28W 1 LOT30 1 LOT30-1 1 LOT30-2 1 LOT30-3 1 LOT30-4 1 LOT30-5 LOT31 LOT35 1 LOT41 1 LOT42-1 1 LOT43-1 1 LOT43-4 1 LOT6-1 1 LOT67 1 LOT6-7 1 LOT6-8A 1 LOT6-8B 1 LOT80-1 1 LOT82 1 MW-101D MW-1011 MW-101S MW-102D MW-102S MW-103D MW-103S MW-104D MW-1041 MW-104S MW-105D MW-106D

Groundwater Sampling Location Summary 1999 - 2004xls

Sampling Events 1999-2004

Hows Corner Superfund Site Plymouth Maine

Supplemental 2001 2002 2003 Pumping 2004 Pre-ROD Rl Sampling Sampling Sampling Test Sampling WC-03 WC-09 WC-25 WC-30 WC-42B WC-56 WC-58 Dec-99 May-00 Jun-01 Jan-02 Apr-03 Sep-04 Sep-04

1

1 1 1

1 1 1 1 1

1 1

1

1 1

1 1 1

1 1 1 1 1

1

1 1

1 1 1 1

1

1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

Sampling Events 1999-2004

Hows Corner Super-fund Site Plymouth Maine

Supplemental 2001 2002 2003 Pumping Event Baseline Pre-ROD Rl Sampling Sampling Sampling Test

Case ID WC-01 WC-01 WC-03 WC-09 WC-25 WC-30 WC-42B WC-56

ll

Well Date Aug-99 Oct-99 Dec-99 May-00 Jun-01 Jan-02 Apr-03 Sep-04 MW-106S 1 1 1 1 1 MW-107D 1 1 MW-108D 1 1 1 1 1 MW-108S 1 1 1 1 1 MW-110D 1 1 MW-111D 1 1 MW-112D 1 1 1 1 1 MW-112S 1 1 1 1 1 MW-113D 1 1 MW-114D 1 1 1 1 1 MW-114S 1 1 1 1 1 MW-115D 1 1 1 1 1 MW-12DB 1 1 1 MW-12SB 1 1 1 MW-13DB 1 1 1 1 1 1 MW-13SB 1 1 1 MW-14DB 1 1 MW-14SO 1 1 MW-15DB 1 1 1 MW-15SB 1 1 1 MW-16DB 1 1 1 1 1 1 MW-16IB 1 1 1 1 1 1 MW-16SO 1 1 MW-17DO 1 1 1 MW-17SO 1 1 1 MW-1B 1 1 1 1 1 1 MW-203D MW-203S MW-204D MW-204S MW-205 MW-206D

I MW-206S MW-2DB 1 1 MW-2DDB 1 1 MW-2IB 1 1 1 1 1 1 MW-3B 1 1 1 1 1 1

I MW-4O 1 1 1 MW-5B 1 1

II MW-6DB 1 1 1 MW-6SB 1 1 1 MW-8DB 1 1 1 MW-8SB 1 1 1

II PW-207 1 SEEP-1 1 SUBTOTAL - RESIDENTIAL 44 25 0 2 0 3 0 SUBTOTAL - MONITORING 22 48 41 15 15 15 1

Total 3 66 73 41 17 15 18 1

I Included in most recent data

I Notes 1 - Overburden well not included in most recent data for plotting

2 - Tetrahydrofuran and 2-Butanone were the only two compounds detected in this well and are thought to be the result of well repair not included in most recent data for plotting

3 - Not included in most recent data for plotting

2004 Sampling

WC-58 Sep-04

1

1 1

1 1

1 1 1

1

1 1

1 1 1 1 1 1 1 1 1

1 1

1

0 29

29

Groundwatef Sampling Location Summary 1999 - 2004xls

I

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

monitoring well Figure 4-14 total VOC contour (ugl) - December 1999January 2000 Distribution of Total VOCs in

Note SW-113 is located downstream of SEEP-1 Shallow Bedrock Groundwater total concentration of detected VOCs ND= not detected these two locations were sampled during the Pre-ROD Sampling Event

Baseline Sampling Event in OctoberNovember 1999 Hows Corner Superfund Site Surface Water Sampling Location A Plymouth Maine Seep Sampling Location laquo- WOODARD ampCURRAN

995037wipri reportepa ri interim final feb 2001cadd drawingsfinalfig 4-14

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

0 300 600 I

FEET

Q residential well Figure 4-16 monitoring well Distribution of Total VOCs in

Deep Bedrock Groundwater total VOCs contour (ugl) Pre-ROD Sampling Event

active residential wells with lot number Hows Corner Superfund Site 2deg42deg Plymouth Maine total concentration of detected VOCs ND= not detected WOODARD ampCURRAN Enyinaaring bull Science bull Operations bull

995037wipri reportepa ri interim final feb 2001cadd drawingsfinalfig4mdash16

PLYMOUTH POND

PLYMOUTH POND

1 628Tl7MW-2bB 12135

PLYMOUTH POND

monitoring well Figure 4-20

V total VOC contour (ugl) - June 2000 Distribution of Total VOCs in Shallow Bedrock Groundwater

| 34 | total concentration of detected VOCs ND= not detected NA = not analyzed Supplemental Sampling Event Note SW-113 is located downstream of SEEP-1 Hows Corner Superfund Site

Surface Water Sampling Location these two locations were sampled during the Plymouth Maine Baseline Sampling Event in OctoberNovember 1999 Seep Sampling Location WOODARD amp CURRAN

Engineering bull Science - Operations bull 995037wipri reportepa ri interim final feb 2001 cadd drawingsfinalfig 4-20

residential well Figure 4-22 Distribution of Total VOCs in

monitoring well Deep Bedrock Groundwater

total VOCs contour (ugl) Supplemental Sampling Event

Hows Corner Superfund Site

total concentration of detected VOCs ND= not detected NA = not analyzed Plymouth Maine

WOODARD amp CURRAN

995037wipri reportepa-ri interim final feb 2001cadd drawingsfinalfig 4-22 Engineering bull Science - Operations bull

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

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Shallow Monitoring Well

Deep Monitoring Well

C Detected Concentration ND = Not Detected Figure 1-XS Distribution of Total VOCs in Shallow Bedrock Groundwater

Pumping Well

17-Acre Property Boundary Concentration Contour (ugl)

June 2001 Hows Corner Superfund Site

Plymouth Maine WOODARDampCURRAN

-i^rhvj bull Scbncn bull Operations bull 211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0601 dwg04-20-05

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Shallow Monitoring Well bull bull - 17-Acre Property Boundary Figure 1-XD

Deep Monitoring Well 1 I Detected Concentration ND = Not Detected Distribution of Total VOCs in Deep Bedrock Groundwater

-mf- Pumping Well June 2001 Residential Well Hows Corner Superfund Site

Plymouth Maine i h Surface Water Sampling Point

g WOODARD ampCURRAN _ ^ _ ^ _ _ yen_ rj i|Hlaquorlny bull Science bull Opt

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Deep Monitoring Well

Detected Concentration ND = Not Detected Figure 1-YS Distribution of Total VOCs in Shallow Bedrock Groundwater

Pumping Well

17-Acre Property Boundary Concentration Contour (ugl)

January 2002 Hows Corner Superfund Site

Plymouth Maine WOODARD amp CURRAN Engineering Science- Operations bull

211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0102dwg04-20-05

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Shallow Monitoring Well mdashbullbullbull 17-Acre Property Boundary Figure 1-YD - A - Deep Monitoring Well FT Detected Concentration ND = Not Detected Distribution of Total VOCs in

Deep Bedrock Groundwater Pumping Well January 2002 Residential Well Hows Corner Superfund Site

Plymouth Maine Surface Water Sampling Point

WOODARD ampCURRAN Engineering Sciencs- Operations bulli Si

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0102dwg04-20-05

- m j

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND j A O-shy

Shallow Monitoring Well E Detected Concentration ND = Not Detected Figure 1-ZS Distribution of Total VOCs in

Deep Monitoring Well Shallow Bedrock Groundwater

Pumping Well Hows Corner

April 2003 Superfund Site

17-Acre Property Boundary Plymouth Maine Concentration Contour (ugl) r WOODARD ampCURRAN

Engineering bull Science bull Operations bull 211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0403dwg04-20-05

s S pound

PLYMOUTH POND

PLYMOUTH POND

- -

5 PLYMOUTH POND

Jo

FEET

ft Shallow Monitoring Well mdashbullbullmdash 17-Acre Property Boundary Figure 1-ZD Deep Monitoring Well I 1 I Detected Concentration ND = Not Detected Distribution of Total VOCs in

Deep Bedrock Groundwater Pumping Well April 2003

Q) Residential Well Hows Corner Superfund Site Plymouth Maine

(T) Surface Water Sampling Point WOODARD ampCURRAN poundKk EnginawtirKj bull Science - Operations bull

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0403dwg04-20-05

0 Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

B MW-1B

I 12000

PCE

B 10000 Total VOCs

I

i 2000

i 0 Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

c MW-3B

G 2000

1800

B PCE

1600 Total VOCs

1 I I E

il-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

G E

211941

El

I I z E

80

Concentration Trends shy Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-13DB

Total VOCs

c i i c o

Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

MW-16DB

30

c i c c I c o

Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99

PCE

Total VOCs

Jul-01 Jul-03

211941

O bi

c Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

I MW-16IB

i 35

3

c Total VOCs

lt- 2 5

0 | gt

o

1 sectI

c c 0 4

Jul-90 Jul-92 Jul-94 Jul-96 Jul-98 Jul-00 Jul-02 Jul-04

I I MW-108D

I 12

PCE 10

Total VOCs c oc 3

E E I 0

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

E 211941

c Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

fi MW-108S

I I 40

PCE 35

Total VOCs

30

I f 26

20 I o

I 15

10

c Dec-99 Dec-00 Dec-01 Dec-02 Dec-03 I 0

I MW-112D

c 35 - imdash

I A3 shyTotal VOCs

o c

E 1 2

I

ition

B 1 ^

-i c 3

0 Dec-99 Dec-OO Dec-01 Dec-02 Dec-03

211941

I

i

I

cII

Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-112S

08

PCE

Total VOCs 06

o 04

02

0 Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

MW-114D

o

12000

10000

8000

6000

PCE

Total VOCs

4000

2000

i

ccEIIc

i

i

E

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

211941

Con

cent

ratio

n (

ug

l)

E Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

I MW-114S

E A5000 -- Total VOCs

- 4000

0 3000

2000

i 1000

i n shy

Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

MW-115D

c PCE

Total VOCs

c E

o

C c

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03 I 0

211941

IepoundII

EIEIIGICCIccc

30000

25000

20000

o bullsect 15000 b

o 10000 U

5000

0 Aug-99

25000

20000

5000

0 Aug-99

211941

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-2DB

PCE

Total VOCs

Aug-01 Aug-03

MW-2IB

PCE

Total VOCs

Aug-01 Aug-03

IDIBI

ii EIDIISIBIG C

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-102S

6000

5000 PCE

Total VOCs

4000

O 3000

2000

1000

0 Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

MW-103D

16000

~ 14000 ugt 3- 12000 o

^ 10000

sect 8000

O 6000

4000

2000

PCE

Total VOCs

0Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

211941

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

G MW-103S

I I

ampo

12000

10000

E sectc

S

8000

6000

4000

2000

0Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

G I 6000

MW-104D

i 5000

PCE

Total VOCs

i i c

2000

1000

Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

E I

211941

cIccIG

IIBCccBcIc

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-1041

PCE Total VOCs

a 25000

0 20000

a 15000

10000

5000

0 Jan-OO Jan-01 Jan-02 Jan-03 Jan-04

MW-106D

3000

2500 PCE

Total VOCs

=sect 2000

o bullsect 1500

1000

500

0 Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

211941

c Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

c MW-106S

I PCE

Total VOCs

i

i Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

i

i i i E

C

211941 c

Response to EPA-DEP Comment 5 Dated March 312005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

iiw

EPA-DEP Comment 5

Comment 5 Matrix Diffusion The report as well as other proponents of matrix diffusion suggest that depletion of DNAPL (Section 5112 page 5-15) needs to be achieved While that might be the ideal the goal is to achieve performance standards and that goal may be attainable while there is residual contamination in the rock perhaps even DNAPL globules The low bedrock matrix porosity (page 1-15) the high permeability values (page 4-4) the relative flux of the groundwater (page 5-5) and the decrease in surface area and out of the mainstream pockets (appendix C-4) all suggest that the diffusion out of the rock matrix would be insubstantial relative to the regional flux of groundwater through the Site

Response The TI Evaluation Report does not explicitly consider or rely upon matrix diffusion as a basis for requesting a TI Waiver for a portion of the Hows Corner Site The technical literature provides documentation that matrix diffusion can be a significant process that affects chemical transport and groundwater remediation timeframes in unconsolidated and consolidated media including fractured rock (US EPA 1989 Freeze and Cherry 1979 Pankow and Cherry 1996 Fountain 1998) Back diffusion of contaminants from the matrix porosity of the fractured rock can prolong the time necessary to achieve groundwater cleanup goals particularly for compounds such as PCE for which the cleanup goal is a low concentration It is our expectation that matrix diffusion has occurred at the Hows Corner Site and that back diffusion of PCE from the rock matrix will also occur Although the extent to which matrix diffusion is occurring at the Hows Comer Site has not been determined and that lack of knowledge contributes to uncertainty regarding the cleanup times at the Site the effect of matrix diffusion is to lengthen rather than shorten the time required for remediation

REFERENCES

Fountain JC 1998 Technologies for Dense Nonaqueous Phase Liquid Source Zone Remediation Ground-Water Remediation Technologies Analysis Center Technology Evaluation Report TE-98-02 December

Freeze RA and Cherry JA 1979 Groundwater Prentice-Hall Inc Englewood Cliffs NJ 07632 p 410-412

Pankow J F and Cherry J A 1996 Dense Chlorinated Solvents Waterloo Press Portland OR 97291-1399 p 67-88

US EPA 1989 Transport and Fate of Contaminants in the Subsurface EPA6254-89019 p 17-18

Response to EPA Comment 5 050305doc 1 of 1 Woodard amp Curran (211941)

WOODARD amp CURRAN Maine Massachusetts New Hampshire Connecticut Florida Operational offices across the US 1-800-426-4262 www woodardcurran com

Page 28: SDMS DocID 251749 - Records Collections · 2020-06-13 · CORPORATE OFFICES: Maine, Massachusetts, New Hampshire, Connecticut New, York, Florida Engineering • Science • Operations

Table XX Packer Permeability and Packer Sampling Results for Potential Fracture Intervals

2004 Drilling Program

Hows Corner Superfund Site Plymouth Maine

Top of Bottom of Depth to Midpoint

t K

ELEV (ft Potential Transmissive Zones Packer Interval

Packer Interval

Middle of Interval

Elevation of interval

Hydraulic Conductivity

PCE Concentration

Well ID msl) TESTr (ft bgs)- (ftbgs) (ftbgs) (ftbgs) (ft msl) (cmsec) (ogt) MW-203D 43227 4 277279 24 32 28 4043 667E-05 44

3 408415420 39 49 44 3883 593E-05 170 2 526 530 49 57 53 3793 101E-04 140 I 828830842 80 88 84 3483 701E-05 130

MW-204D 43262 5 295 300 26 34 30 4023 902E-05 220 4 463496513516 45 53 49 3833 119E-04 540 3 681685688 63 71 67 3653 OOOE+00 2 758 76 2 71 79 75 3573 309E-05 260 I 88 96 92 3403 OOOE+00

MW-205 42389 3 164 166 168 15 20 175 4148 OOOE+00 1000B 2 302305312 30 35 325 3998 107E-04 1300B 1 40 45 425 3898 OOOE+00

MW-206D 43007 5 17 72 195 4128 291E-05 4 296 302 307 29 34 315 4008 940E-05 2900B 3 522 52 57 545 3778 944E-07 2 656 64 69 665 3658 353E-06 1 92392793 4939 91 96 935 3388 614E-05 6300B

PW-207 43477 5 184622162819 18 29 235 4088 209E-05 1300 4 3508 32 43 375 3948 568E-06 5400 3 53325341542154325559 50 61 555 3768 821E-05 18000

6359 61 72 665 3658 866E-06 12000 1 8685 84 89 865 3458 213E-05 19000

NOTES cmsec = centimeters per second ft bgs = feet below ground surface ft msl = feet above mean sea level B = detected in lab blank

Table XX Orientation Permeability and Groundwater Sampling Results for Transmissive Features

2004 Drilling Program

Hows Corner Superfund Site Plymouth Maine

Borehole Geophisical Feature depth Dip True Dip True Transmissive Log Feature (Feet) Degrees Azimuth Strike bullvgt(Ltk|iy^

Number v Tosftble) v MW-203 5 277 64 337 67 Likely

6 279 59 11 281 Likely 8 352 14 177 87 Likely 11 381 46 96 6 Possible 12 408 35 271 1 Possible 14 415 57 250 340 Possible 15 420 58 202 292 Likely 18 526 52 75 345 Likely 19 530 52 82 352 Likely 28 828 48 75 345 Likely 29 830 52 17 287 Likely 30 830 56 233 323 Possible 31 842 50 130 40 Likely

MW-204 4 295 15 147 57 Likely 5 300 43 91 1 Likely 11 439 31 80 350 Possible 12 440 46 219 309 Possible 14 463 50 358 88 Likely 15 496 34 198 288 Likely 16 513 54 17 287 Likely 17 516 33 14 284 Likely 25 681 39 359 89 Possible 26 685 22 45 315 Possible 27 688 35 73 343 Possible 32 758 45 236 326 Likely 33 762 46 306 36 Likely

MW-205 5 164 69 106 16 Possible 6 166 78 165 75 Possible 7 168 82 115 25 Possible 8 168 68 116 26 Possible 12 215 46 222 312 Possible 13 217 75 62 332 Possible 14 219 29 32 302 Possible 16 237 69 250 340 Possible 17 256 73 353 83 Possible 18 272 44 202 292 Possible 21 299 37 196 286 Possible 22 302 31 206 296 Possible 23 305 59 48 318 Likely 24 312 63 42 312 Likely

MW-206 1 264 37 181 271 Likely 2 296 69 217 307 Likely 3 302 66 233 323 Likely 4 307 64 224 314 Likely 8 342 62 259 349 Likely

jjHydraulic GoiDanctilyity j(cmsecjw

667 E-05

593 E-05

101 P04

710 E-05

902 E-05

119 E-04

0

309 E-05

0

107 E-04

94 E-05

PCE (ugL)

44

170

140

130

220

540

260

IOOOB

1100B

1300B

2900B

STotal vVoCsv tig1)

84

234

192

183

2636

6436

3073

11448

12509

13776

32401

PCEyo dfCTotaf

52

73

73

7 1

83

84

85

87

88

94

90

Table XX Orientation Permeability and Groundwater Sampling Results for Transmissive Features

2004 Drilling Program

Hows Corner Superfund Site Plymouth Maine

Borehole Geophisical Feature deptt raquoip True pip True Transraissive Log Feature (Feet) shy Degrees Azimuth Strike (tikely

Number raquo Possible) 22 522 57 54 324 Possible 25 656 40 82 352 Possible 32 871 59 151 61 Possible 33 883 53 185 275 Possible 34 895 7 175 85 Likely 35 899 53 90 0 Likely 36 902 49 184 274 Likely 37 923 9 175 85 Likely 38 927 42 206 296 Likely 39 934 48 167 77 Likely 40 939 26 180 90 Likely

PW-207 1 1846 33 167 77 Likely 4 2216 49 289 19 Possible 7 2819 59 265 355 Possible 11 3508 55 189 279 Possible 18 5332 43 305 35 Likely 19 5341 51 30 300 Likely 20 5421 20 254 344 Likely 21 5432 39 301 31 Likely 23 5559 52 302 32 Likely 25 6359 24 182 272 Possible 29 8049 77 231 321 Possible 30 8685 78 38 308 Likely 32 9334 29 194 284 Likely

NOTES

B = detected in lab blank

Hydraulic Conductivity

(cmsee) 944 E-07 353 E-06

614 E-05

209 E-05

568 E-06

821 E-05

866 E-06

213 E-05

bulltCE (ugL)

6300B

1300

5400

18000

12000

19000

Total VOCs (ug1)

68901

1410

5802

19234

13085

20354

PCE of Total VOCs

9 1

92

93

94

92

93

Response to EPA-DEP Comment 3 Dated March 312005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

lit

EPA-DEP Comment 3

Comment 3 The reported f values and resultant Kd values There remains doubt that the values used in the flushing model accurately reflect the propensity for PCE to sorb to the bedrock The ^ values presented in Appendix B may be unrealistically high because the bedrock samples may have contained organic carbon that was unavailable for sorption The reported f values are only qualitative estimates of the organic carbon content of the bedrock samples The Walkley and Black organic carbon measurement method is quick and simple but the results obtained cannot be considered quantitative because it requires a correction factor which often results in erroneous values it assumes the organic carbon has an average valence of zero oxidizable and reducible constituents such as chloride ferrous iron and manganese oxides interfere with the results and the errors introduced by interference are potentially greater when the organic carbon content is low at low f values it is not clear that organic carbon is controlling PCE sorption (Schwarzenbach and Westall 1981 Mackay et al 1986 Fetter 1999)

In order to derive a Kd-based retardation factor that is reasonable given the reported f values and the rapid advance of the PCE plume described on pages 4-11 and 4-12 the flushing model requires a bulk density to porosity ratio that is roughly two orders of magnitude higher than the actual ratio for the Hows Corner bedrock (page 4-4) This apparent discrepancy needs to be addressed

Response This comment raises several concerns about the collection and analysis of samples for fraction of organic carbon (f^) the quality of the resulting data and the implications of the use of those data for estimation of the retardation of groundwater contaminant movement Results of bedrock analysis for f were proposed in the TI Evaluation Work Plan for use in conjunction with groundwater contaminant concentrations and aquifer information to estimate cleanup times using the Batch Flushing model It is important to use accurate f values from representative bedrock in the Batch Flushing model in order to obtain reasonable estimates of the remedial time frame Because of the importance of accurate and representative results the TI Investigation field program was designed and conducted both to collect samples representative of the rock volume most likely to be in contact with contaminated groundwater and to analyze them using an appropriate refereed analytical method Five potential methods for evaluating f were identified Of the five methods the Walkey-Black method was selected because it has minimal method interferences and a sufficiently low detection limit as well as a long history of use in agronomy and contamination studies The PRP Group is pleased with the quality of the data obtained from the bedrock samples as represented by their precision and reproducibility

The first part of this comment relates to the determination of fraction of organic carbon (f^) values The several subparts of the first paragraph are addressed individually in items 1 through 5 below The second part of the comment regarding the resultant distribution coefficient (Kd) values is addressed separately as item 6 below

1 There remains doubt that the values used in the flushing model accurately reflect the propensity for PCE to sorb to the bedrock

bull The rock core samples used for f (gocg) analysis were from core immediately adjacent to fractures These rock core samples included the fracture surfaces themselves and rock core extending back less than 1 cm from the fractures Therefore the foe data reported in the TI Evaluation represents the f of bedrock through which groundwater will travel and to which PCE will adsorb Based on the careful selection of sample locations and the

Response to EPA Comment 3 050205doc 1 of 11 Woodard amp Curran (211941)

number of samples collected we are confident that the measured f values are representative of the f at points of contact for PCE with the bedrock it is these f values that determine the propensity of PCE to sorb to the bedrock

bull The samples of rock core collected for analysis of f originated from 19 different locations varying in depth from 11 to 90 feet Therefore it is very unlikely that the rock core samples were contaminated with extraneous organic carbon from above ground

2 The foc values presented in Appendix B may be unrealistically high because the bedrock samples may have contained organic carbon that was unavailable for sorption

bull As noted in response 1 the f data reported in Appendix B represents organic carbon primarily associated with the surface of fractures in the bedrock through which groundwater is most likely to travel Therefore it is this organic carbon that the contaminants in the groundwater will come in contact with and adsorb to in the fractured rock at the site

bull The chemical oxidation agents used in the Walkey-Black method oxidize the easily oxidizable organic carbon in the medium and the foe is calculated from the quantity of the agent consumed Therefore it is unlikely that the analysis of the bedrock samples measured organic carbon that was unavailable for sorption

3 The reported foc values are only qualitative estimates of the organic carbon content of the bedrock samples

bull The reported f values are accurate quantitative results Schumachers review of Methods for the determination of total organic carbon (TOC) in soils and sediments (NCEA-C-1282 EMASC-001 April 2002) identifies the Walkley-Black method which was used to analyze the reported foc values as the reference method for comparison to other methods for analyzing total organic carbon

bull Schumacher also points out that if anything the WalkJey-Black method may underestimate the total organic carbon in a sample due to possible incomplete oxidation of organic carbon Usually the incomplete oxidation of total organic carbon in environmental samples is corrected for by multiplying the measured foe by 130 (Walkley amp Black 1934 Schulte 1995)

bull When the f data in the TI Evaluation Report (WampC 2005) Appendix B (attached) are analyzed statistically the standard deviation of the f for the 19 samples analyzed is 174 of the average f Given this standard deviation the 95 confidence interval for this data ranged from a low of 000123 gocg to a high of 000253 gocgm

The labs Method of Detection Limit (MDL) for the f measured using the Walkley-Black method is 00001 gocg Therefore the average (000188 gocg) the mean (000185 gocg) and geometric mean (000187 gocg) of the f values for the rock core at Hows Corner are all statistically significantly greater than the MDL of the Walkley-Black method

In addition to the aforementioned statistical analysis of the foe data triplicate samples (n = 3) from the same rock core (including one sample from the 19 rock core samples) were

Response to EPA Comment 3 050205doc 2 of Woodard amp Curran (211941)

analyzed for their f to determine the repeatability of the Walkley-Black method The average the mean and the geometric mean of the f values of these replicate samples was 000162 gocg 000150 gocg and 000159 gocgm respectively The standard deviation of these measurements was 000039 gocg

4 The Walkley and Black organic carbon measurement method is quick and simple but the results obtained cannot be considered quantitative because it requires a correction factor which often results in erroneous values it assumes the organic carbon has an average valence of zero oxidizable and reducible constituents such as chloride ferrous iron and manganese oxides interfere with the results and the errors introduced by interference are potentially greater when the organic carbon content is low at low foc values it is not clear that organic carbon is controlling PCE sorption (Schwarzenbach and Westall 1981 Mackay et al 1986 Fetter 1999)

bull Schumachers review (NCEA-C-1282 EMASC-001 April 2002) of the Walkley-Black method identifies several potential problems with this analytical method that could occur if the analytical lab is not familiar with the nuances of the chemistry associated with this method Interestingly Schumachers review neglected one of the more important analytical steps required to avoid errors in quantifying f in samples where there might beNAPL

It is absolutely critical to eliminate any NAPL from rock core samples prior to using the Walkley-Black method to measure foe in such samples This was done by the lab (PTS Laboratories) that measured the foe in the rock core samples from Hows Corner The lab used the Dean-Stark method (solvent extraction) to remove all hydrocarbons (including PCE and other NAPLs) from the sample (PTS Laboratories) This extraction method does not interfere with the subsequent analysis of the natural organic carbon associated with the rock core

Subsequently the samples were dried at 150degC to a constant weight (normally 16 hours) This latter step oxidizes all inorganic minerals including ferrous bearing minerals to ferric oxides and precludes their interference during the oxidation of the samples with chromic acid This procedure completely eliminates any positive bias in the reported foc

data that might have occurred due to the presence of ferrous ions and other reduced minerals

bull As noted in Response 3 the incomplete oxidation of total organic carbon results in an underestimate of the f and is corrected for by multiplying the f by a correction factor of 130 (Walkley amp Black 1934 Schulte 1995) The fx data reported in the TI Evaluation was corrected accordingly by using this correction factor

bull Excess chloride (Cl~) in percent weight quantities as found in saline soils may interfere with the quantitative titration of reduced chromium (Walkley 1947) However given that the primary rock type at the Hows Corner site is phyllite it is highly unlikely that there was sufficient chloride in the rock core samples for this to occur

bull Manganese oxides may also interfere with the analysis of f through competing with the dichromate ion for any oxidizable carbon (Walkley 1947) However in such cases the reported f would be an underestimate of the f present in the rock core Walkley (1947)

Response to EPA Comment 3 050205doc 3 of 11 Woodard amp Curran (211941)

4

reported that in the case where the ratio of MnO2 to carbon is 85 to 1 the error in the carbon determinations would only be 0 to 6 percent

It may also be useful to compare the analysis of total organic carbon in a geologic matrix that contains high levels of manganese using EPA method 9060 to the Walkley-Black method Table 1 summarizes data provided by one of the PRPs that compares the analysis of total organic carbon in a geologic matrix that contains approximately 02 wgt manganese (approximately 03 wgt manganese oxide)

Table 1 Comparison of total organic carbon measured using the EPA- 9060 method and the Walkley-Black method

Laboratory EPA-9060 Method Walkley-Black Method A Ave 00226 gocg Not analyzed

Stdev 000251 gocg n = 5

B Ave 002219 gocg Ave 002050 gocg Stdev = 000316 gocg Stdev =000971 gocg

n= 10 n = 10

The similarity in the total organic carbon concentrations measured by these two different methods provides further confidence that the Walkley-Black method is a viable method for analysis of total organic carbon in the presence of manganese equivalent to at least 10 by weight of the total organic carbon

5 The Walkley and Black organic carbon measurement at lowf^ values it is not clear that organic carbon is controlling PCE sorption (Schwarzenbach and Westall 1981 Mackay et al 1986 Fetter 1999)

bull Schwarzenbach and Westalls (1981) paper states that f values of less than 0001 gocg should not be used in combination with Kow (octanol-water partition coefficients) values to calculate K^ values (solid phase partition coefficients) values for a specific contaminant It should be noted that the TI Evaluation did not use the f data to calculate the KQC from the Kow Instead as requested by the EPA the measured KOC value for PCE was used to calculate the retardation factor for this contaminant

bull Schwarzenbach et al (2003) stated more recently that Even at very low f values (ie foe = 0001 kgoc - kg1 solid) sorption to the organic components of a natural sorbent may still be the dominant mechanism in defining the adsorption of organic compounds to geological matrices

bull In 1985 M Piwoni from the US EPA Robert S Kerr Environmental Research Laboratory published a paper (Banerjee et al 1985) that showed that for very hydrophobic molecules TOC content of the sorbent will control sorption down to levels of organic carbon that defy quantitation Contaminants such as the PCE found in the groundwater at Hows Corner are in this category of compounds

Given the aforementioned reasons the f values reported in the TI Evaluation are accurate within the noted statistical limitations and will have a predictable impact upon the retardation of PCE during groundwater transport

Response to EPA Comment 3 050205doc 4 of 11 Woodard amp Curran (211941)

6 In order to derive a Kd-based retardation factor that is reasonable given the reported foc

values and the rapid advance of the PCE plume described on pages 4-11 and 4-12 the flushing model requires a bulk density to porosity ratio that is roughly two orders of magnitude higher than the actual ratio for the Hows Comer bedrock (page 4-4) This apparent discrepancy needs to be addressed

The apparent discrepancy of bulk density to porosity ratios is most likely due to the fact that the Batch Flushing Model was originally developed for a porous medium and is not directly applicable to fractured bedrock As stated in Appendix C (page C-4) of the Draft Technical Impracticability Evaluation Report in order to use the Batch Flushing Model to describe the transport of contaminated groundwater in fractured bedrock where the matrix porosity is insignificant it is more appropriate to use a fracture surface area to void space ratio to calculate the retardation factor (R) than a bulk density to porosity ratio (Freeze amp Cherry 1979)

Since it is impractical to determine the actual surface area to which contaminants can adsorb the Batch Flushing Model was used with two simplifying assumptions bull The Kd was calculated from the f and the K^ bull The bulk density to porosity ratio term in the Batch Flushing Model was constrained to range

from 4 to 10 the typical range of such ratios in porous media (Freeze amp Cherry 1979)

If one uses site specific bedrock bulk density and porosity values the bulk density to porosity ratio is several orders of magnitude greater (specifically 273 gcc bullbull 000165 (dimensionless) = 1654 gcc) than the range of ratios of 4 to 10 used in the Batch Flushing Model in the Draft Technical Impracticability Evaluation Report Constraining the bulk density to porosity ratio within the range of ratios of 4 to 10 results in significantly lower R value than would be obtained using specific bedrock bulk density and porosity values

In summary in bedrock where fractures are the primary porosity the bulk density to porosity ratio can vary considerably and will be a function of the number of fractures and the fracture aperture The calculated bulk density to porosity ratio will be inversely proportional to the porosity This means that in fractured rock with limited fracturing and smaller porosity the calculated bulk density to porosity ratio is greater and will result in a greater calculated retardation factor than in bedrock with more extensive fracturing and greater porosity Consequently the calculated retardation factor will be greater for bedrock with less surface area available for sorption than bedrock with greater surface area for sorption This is contrary to what actually occurs

4 Response to EPA Comment 3 050205doc 5 of 11 Woodard amp Curran (211941)

m

REFERENCES

Banerjee P MD Piwoni K Ebeid (1985) Sorption of organic contaminants to a low carbon subsurface core Chemosphere _14 1057-1067

Freeze RA JA Cherry (1979) Groundwater Prentice Hall Englewood Cliffs NJ pg 604

PTS Laboratories wwwptsgeolabscompdf files3TOCnotepdf

Schulte EE (1995) Recommended soil organic matter tests in Recommended Soil Testing Procedures for the Northeastern United States Northeastern Regional Publication No 493 Chapter 8

Schwarzenbach RP J Westall (1981) Transport of nonpolar organic compounds from surface water to groundwater Laboratory sorption studies Environ Sci Tech 15 1360-1367

Schwarzenbach RP PM Gschwend DM Imboden (2003) Environmental Organic Chemistry Wiley-Interscience pg 292 408 amp 412

Walkley A LA Black (1934) An examination of the Degtjareff method for determining soil organic matter and a proposed modification of the chromic acid titration method Soil Science 37 29-38

Walkley A (1947) A critical examination of a rapid method for determining organic carbon in soils - effect of variations in digestion conditions and of inorganic soil constituents Soil Science 63251-264

Woodard amp Curran Inc (WampC) 2005 Draft Technical Impracticability Evaluation Hows Corner Superfund Site Plymouth Maine January 2005

Response to EPA Comment 3 050205doc 6 of Woodard amp Curran (211941)

LIST OF ATTACHMENTS (Response to Comment 3)

Appendix B to Draft Technical Impracticability Evaluation Measurement of foe at Hows Corner (4 pages)

m

Response to EPA Comment 3 050205doc 7 of 11 Woodard amp Curran (211941)

Appendix B Measurement of foe of Rock Core at Hows Corner

There are two general approaches to measure the fraction of organic carbon (foe) in rock cores

bull Measurement of weight loss by ignition of organic matter bull Chemical oxidization of organic carbon to carbon dioxide and either

subsequent quantification of the oxidant used for the reaction or quantification of the carbon dioxide produced during this oxidation process

The weight loss method is subject to errors caused by volatilization of substances other than organic materials such as water hydroxides and mineral carbonates Quantification of foe by the weight loss method is particularly sensitive to the presence of carbonates in rock cores There are however weight loss methods that are designed to differentiate between organic carbon and the aforementioned interfering materials but they require considerable care and are less accurate at low foe values Hence the weight loss method was not well suited for measuring the foe of the rock core from Hows Corner

The chemical oxidation of organic carbon is much better suited for quantifying organic carbon in rock cores such as those from Hows Corner This method uses a strong chemical oxidant to oxidize organic carbon to carbon dioxide and then measures either the chemical oxidant used to oxidize the organic carbon or the quantity of carbon dioxide produced In addition this general approach is not subject to interference by volatilization of other constituents of the rock core

There are at least two such chemical oxidation methods

bull The method of Baccini which was described by Schwarzenbach amp Westall (1981) first acidifies the sample to eliminate interference by carbonates Then a strong oxidant is used to chemically oxidize the organic carbon to carbon dioxide The resulting carbon dioxide is subsequently reduced to methane and quantified using a flame ionization detector Unfortunately this method has not been described in detail in a referred journal Hence it is would not have been appropriate to use to characterize the foe in the Hows Corner rock core

bull The more commonly used method to quantify foe in rock core is the Walkley-Black method (1934) This method is preferred for RBCA and DODDOE projects and by the oil industry

The Walkley-Black method uses an excess of chromic acid to oxidize (digest) organic matter to carbon dioxide The remaining chromic acid that was not consumed during the oxidation of the organic carbon is then quantified by titration with ferrous sulfate The difference in chromic acid prior to and after the oxidation of the organic carbon represents the total chromic acid used to oxidize

Hows Corner TI Evaluation Page 1 January 13 2005 Appendix B

the organic carbon in the sample The latter can be calculated using the chemical stoichiometry of the reaction

The Walkley-Black method is very accurate for samples that contain less than 2 organic carbon matter The minimum detection limit (MDL) for the Walkley-Black method is 100 mgkg or an foe of 0001

Given the rock core at Hows Corner was expected to contain less than 2 organic carbon the Walkley-Black method was used to measure the foe from 19 different rock core samples collected from varying depths ranging from 11 to 90 feet

Table 1 provides a statistical summary of the aforementioned data

Table 1 Statistical summary of foe data from rock cores collected at varying depths

Statistical Parameter Calculated Value foe Minimum Detection Limit (MDL) 00010 Number of samples analyzed (n) 19 Average foe 00019 Median foe 00019 Geometric Mean foe 00019 Standard deviation of foe measurements 000033 Relative standard deviation 174 -+ 95 Confidence intervals 00012 to 00025

The data in Table 1 shows the following

bull The foe from the Hows Corner rock cores are statistically greater than the MDL of the Walkley-Black analytical method

bull The average and median values for the foe of the Hows Corner rock cores from varying depths are nearly identical indicating that there is little variability in the foe values in the source zone at the site

bull The standard deviation of these measurements is 000033 which is 174 of the average foe

bull The 95 confidence intervals of the foe of the rock core at Hows Corner are 00012 to 00025

The foe was also analyzed from three separate samples taken from the same rock core at a depth of 55 feet (Only one of these samples was included in the data summarized in Table 1) Table 2 shows the statistical repeatability of this type of analysis

Hows Corner TI Evaluation Page 2 January 13 2005 Appendix B

Table 2 Repeatability of analysis of foe from one rock core at 55 feet in depth

Statistical Parameter Calculated Value Number of samples analyzed (n) 3 Average foe 00016 Median foe 00015 Geometric Mean foe 00016 Standard deviation of foe measurements 000039 Relative standard deviation 240 -+ 95 Confidence intervals 00008 to 00024

The data in Table 2 shows the following

bull The percent relative standard deviation of these three analyses of foe from the same rock core at Hows Corner is 24

bull The 95 confidence interval of the foes measured in this particular rock core at Hows Conrer is 00008 to 00024

These results show that there is good repeatability in using the Walkley-Black method for analysis of the foe in the rock core at Hows Corner

References Schwarzenbach amp Westall (1981) Transport of nonpolar organic compounds from surface water to groundwater Laboratory sorption studies Environ Sci Tech 15 1360-1367

Walkley A I A Black (1934) An examination of Degtjareff method for determining soil organic matter and a proposed modification of the chromic acid titration method Soil Sci 37 29-37

Hows Corner Tl Evaluation Page S January 13 2005 Appendix B

Woodard and Curran PTS Laboratories PTS File No 34618

ORGANIC CARBON DATA (METHODOLOGY WALKLEY-BLACK)

PROJECT NAME PROJECT NO

SAMPLE ID

203-chip-13 203-chip-23 203-chip-27 203-chip-38 203-chip-42 203-chip-47 203-chip-52 203-chip-58 203-chip-69 203-chip-82 207-chip-11 207-chip-19 207-chip-24 207-chip-29 207-chip-35 207-chip-45 207-chip-55 207-chip-87 207-chip-90

207-chip-55 55-MS

55-MSMSD

Hows Corner NA

DEPTH ft

13 23 27 38 42 47 52 58 69 82 11 19 24 29 35 45 55 87 90

55 NA NA

MATRIX

Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip

Average Median

Geometric Mean Standard Deviation Relative Std Dev

+- 95 Confidence Interval n

Rock Chip Rock Chip Rock Chip

Average Median

Geometric Mean Standard Deviation Relative Std Dev

+- 95 Confidence Interval n

FRACTION ORGANIC CARBON

(gg)

170E-03 185E-03 185E-03 170E-03 240E-03 190E-03 230E-03 180E-03 170E-03 115E-03 195E-03 220E-03 220E-03 235E-03 135E-03 190E-03 205E-03 175E-03 160E-03

188E-03 185E-03 185E-03 327E-04

1739 123E-03 to

19

205E-03 130E-03 150E-03

162E-03 150E-03 159E-03 388E-04

2402 840E-04 to

3

2532E-03

2393E-03

Hows Corner Tl Evaluation Appendix B January 13 2005

Response to EPA-DEP Comment 4 Dated March 31 2005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

EPA-DEP Comment 4

Comment 4 Distribution of contaminants First the TI report seems based on the assertion that there is DNAPL at the source area yet it also appears to represent that the source area is small and the bedrock below 85 is competent (or less fractured) and less impacted by the release of contaminants Some of the confusion may result from using most recent data when that data is from several different sampling events over several years and there is no discernible difference in concentrations between shallow and deep bedrock or as in Section 421 where generally decreased generally increase generally similar and similar concentrations in four consecutive sentences leads to a muddled picture of the contaminant distribution

Second the report asserts that the distribution of contaminants over the entire plume has not changed with time but fails to support this conclusion with data again relying on data that is from different sampling dates for one composite representation

Response The likely presence of dense non-aqueous phase liquid (DNAPL) at the Hows Corner Site and the determination that the source area is small are not mutually exclusive and both are conclusions drawn from information obtained during field investigations The presence of DNAPL in the source area is based on the elevated concentrations of volatile organic compounds (VOCs) detected in the groundwater (WampC 2001 WampC 2002) The conclusion that the source area is small is based on the area in which VOCs in groundwater have been detected at concentrations that are considered to be indicative of the presence of DNAPL nearby Similarly the conclusion that fracture frequency decreases at depths greater than approximately 50 to 85 feet below ground surface was based on field observation during the RI field work The fact that zones with observed fractures exhibited higher hydraulic conductivities than zones without fractures coupled with the decreasing frequency of observed fractures with depth led to the conclusion that the hydraulic conductivity of the bulk rock decreases with depth

The most recent data from all wells were used to provide the maximum VOC data set size During the RI all of the previously-existing and then newly-installed monitoring wells were sampled along with several residential wells The RI sampling included up to 48 monitoring wells Subsequent to the RI and prior to the TI three rounds of monitoring were conducted to verify that the plume was stable 15 monitoring wells were sampled during each of the three rounds During the TI field investigation 29 wells were sampled for VOCs The sampled wells included all of the newly-installed wells and a subset of wells installed during the RI for a total of 29 monitoring wells By using most recent data VOC results from 53 monitoring wells were included in the evaluation (see table labeled Sampling Events for listing of monitoring wells) This approach was selected because there generally was little variation in the data from a particular location between years This is borne out by the attached individual plots of VOCs detected in shallow bedrock and deep bedrock for the Pre-ROD (December 1999January 2000) and Supplemental (May 2000) sampling events and for June 2001 January 2002 and April 2003 sampling events The Pre-ROD and Supplemental plots are similar to the subsequent plots from the 2001 2002 and 2003 sampling events

In addition to maps showing the spatial distribution of VOC data at a given time trend plots of the data from a particular location through time (attached) indicate that since the RI concentrations generally have been stable or have decreased Together the maps and trend plots and the data from which they were developed indicate that the distribution of contaminants over the entire plume has not changed appreciably with time

Response to EPA Comment 4 050305doc 1 of 26 Woodard amp Curran (211941)

REFERENCES

Woodard amp Curran Inc (WampC) 2001 Final Remedial Investigation Report Hows Corner Superfund Plymouth Maine July 2001

Woodard amp Curran Inc (WampC) 2002 Final Feasibility Study Report - Non-Source Area Groundwater Hows Corner Superfund Site Plymouth Maine Hows Corner Superfund Plymouth Maine July 2002

Response to EPA Comment 4 050305doc 2 of 26 Woodard amp Curran (211941)

LIST OF ATTACHMENTS (Response to Comment 4)

Table - Sampling Events 1999 - 2004 (2 pages)

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater Pre-ROD Sampling Event

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater Pre-ROD Sampling Event

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater Supplemental Sampling Event

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater Supplemental Sampling Event

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater June 2001

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater June 2001

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater January 2002

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater January 2002

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater April 2003

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater April 2003

Figure - Concentration Trends - Non-Source Area Wells MW-1B and MW-3B

Figure - Concentration Trends - Non-Source Area Wells MW-13DB and MW-16DB

Figure - Concentration Trends - Non-Source Area Wells MW-16IB and MW- 108D

Figure - Concentration Trends - Non-Source Area Wells MW-108S and MW-112D

Figure - Concentration Trends - Non-Source Area Wells MW-112S and MW-114D

Figure - Concentration Trends - Non-Source Area Wells MW-114S and MW-115D

Figure - Concentration Trends -Source Area Wells MW-2DB and MW-2IB

Figure - Concentration Trends -Source Area Wells MW-102S and MW-103D

Figure - Concentration Trends -Source Area Wells MW-103S and MW-104D

Figure - Concentration Trends -Source Area Wells MW-104I and MW-106D

Figure - Concentration Trends -Source Area Wells MW-106S

Response to EPA Comment 4 050305doc 3 of 26 Woodard amp Curran (211941)

I I

El I

II I I 1 I

I

i

Event Baseline Case ID WC-01 WC-01

Well Date Aug-99 Oct-99 LOT10 1 LOT1-1 1 LOT11-4 LOT14 1 LOT15 1 LOT15-1 1 LOT16 1 LOT16-1 1 LOT17 1 LOT18 1 LOT19 1 LOT2 LOT20 1 LOT21-10 1 LOT21-11 1 LOT21-12 1 LOT21-13 1 LOT21-14 1 LOT21-2 1 LOT21-5 1 LOT21-7 LOT21 -8 1 LOT21-9 1 LOT23 1 LOT24 1 LOT28-1 1 LOT28-2 1 LOT28-3 1 LOT28-4 1 LOT28W 1 LOT30 1 LOT30-1 1 LOT30-2 1 LOT30-3 1 LOT30-4 1 LOT30-5 LOT31 LOT35 1 LOT41 1 LOT42-1 1 LOT43-1 1 LOT43-4 1 LOT6-1 1 LOT67 1 LOT6-7 1 LOT6-8A 1 LOT6-8B 1 LOT80-1 1 LOT82 1 MW-101D MW-1011 MW-101S MW-102D MW-102S MW-103D MW-103S MW-104D MW-1041 MW-104S MW-105D MW-106D

Groundwater Sampling Location Summary 1999 - 2004xls

Sampling Events 1999-2004

Hows Corner Superfund Site Plymouth Maine

Supplemental 2001 2002 2003 Pumping 2004 Pre-ROD Rl Sampling Sampling Sampling Test Sampling WC-03 WC-09 WC-25 WC-30 WC-42B WC-56 WC-58 Dec-99 May-00 Jun-01 Jan-02 Apr-03 Sep-04 Sep-04

1

1 1 1

1 1 1 1 1

1 1

1

1 1

1 1 1

1 1 1 1 1

1

1 1

1 1 1 1

1

1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

Sampling Events 1999-2004

Hows Corner Super-fund Site Plymouth Maine

Supplemental 2001 2002 2003 Pumping Event Baseline Pre-ROD Rl Sampling Sampling Sampling Test

Case ID WC-01 WC-01 WC-03 WC-09 WC-25 WC-30 WC-42B WC-56

ll

Well Date Aug-99 Oct-99 Dec-99 May-00 Jun-01 Jan-02 Apr-03 Sep-04 MW-106S 1 1 1 1 1 MW-107D 1 1 MW-108D 1 1 1 1 1 MW-108S 1 1 1 1 1 MW-110D 1 1 MW-111D 1 1 MW-112D 1 1 1 1 1 MW-112S 1 1 1 1 1 MW-113D 1 1 MW-114D 1 1 1 1 1 MW-114S 1 1 1 1 1 MW-115D 1 1 1 1 1 MW-12DB 1 1 1 MW-12SB 1 1 1 MW-13DB 1 1 1 1 1 1 MW-13SB 1 1 1 MW-14DB 1 1 MW-14SO 1 1 MW-15DB 1 1 1 MW-15SB 1 1 1 MW-16DB 1 1 1 1 1 1 MW-16IB 1 1 1 1 1 1 MW-16SO 1 1 MW-17DO 1 1 1 MW-17SO 1 1 1 MW-1B 1 1 1 1 1 1 MW-203D MW-203S MW-204D MW-204S MW-205 MW-206D

I MW-206S MW-2DB 1 1 MW-2DDB 1 1 MW-2IB 1 1 1 1 1 1 MW-3B 1 1 1 1 1 1

I MW-4O 1 1 1 MW-5B 1 1

II MW-6DB 1 1 1 MW-6SB 1 1 1 MW-8DB 1 1 1 MW-8SB 1 1 1

II PW-207 1 SEEP-1 1 SUBTOTAL - RESIDENTIAL 44 25 0 2 0 3 0 SUBTOTAL - MONITORING 22 48 41 15 15 15 1

Total 3 66 73 41 17 15 18 1

I Included in most recent data

I Notes 1 - Overburden well not included in most recent data for plotting

2 - Tetrahydrofuran and 2-Butanone were the only two compounds detected in this well and are thought to be the result of well repair not included in most recent data for plotting

3 - Not included in most recent data for plotting

2004 Sampling

WC-58 Sep-04

1

1 1

1 1

1 1 1

1

1 1

1 1 1 1 1 1 1 1 1

1 1

1

0 29

29

Groundwatef Sampling Location Summary 1999 - 2004xls

I

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

monitoring well Figure 4-14 total VOC contour (ugl) - December 1999January 2000 Distribution of Total VOCs in

Note SW-113 is located downstream of SEEP-1 Shallow Bedrock Groundwater total concentration of detected VOCs ND= not detected these two locations were sampled during the Pre-ROD Sampling Event

Baseline Sampling Event in OctoberNovember 1999 Hows Corner Superfund Site Surface Water Sampling Location A Plymouth Maine Seep Sampling Location laquo- WOODARD ampCURRAN

995037wipri reportepa ri interim final feb 2001cadd drawingsfinalfig 4-14

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

0 300 600 I

FEET

Q residential well Figure 4-16 monitoring well Distribution of Total VOCs in

Deep Bedrock Groundwater total VOCs contour (ugl) Pre-ROD Sampling Event

active residential wells with lot number Hows Corner Superfund Site 2deg42deg Plymouth Maine total concentration of detected VOCs ND= not detected WOODARD ampCURRAN Enyinaaring bull Science bull Operations bull

995037wipri reportepa ri interim final feb 2001cadd drawingsfinalfig4mdash16

PLYMOUTH POND

PLYMOUTH POND

1 628Tl7MW-2bB 12135

PLYMOUTH POND

monitoring well Figure 4-20

V total VOC contour (ugl) - June 2000 Distribution of Total VOCs in Shallow Bedrock Groundwater

| 34 | total concentration of detected VOCs ND= not detected NA = not analyzed Supplemental Sampling Event Note SW-113 is located downstream of SEEP-1 Hows Corner Superfund Site

Surface Water Sampling Location these two locations were sampled during the Plymouth Maine Baseline Sampling Event in OctoberNovember 1999 Seep Sampling Location WOODARD amp CURRAN

Engineering bull Science - Operations bull 995037wipri reportepa ri interim final feb 2001 cadd drawingsfinalfig 4-20

residential well Figure 4-22 Distribution of Total VOCs in

monitoring well Deep Bedrock Groundwater

total VOCs contour (ugl) Supplemental Sampling Event

Hows Corner Superfund Site

total concentration of detected VOCs ND= not detected NA = not analyzed Plymouth Maine

WOODARD amp CURRAN

995037wipri reportepa-ri interim final feb 2001cadd drawingsfinalfig 4-22 Engineering bull Science - Operations bull

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

FEET

Shallow Monitoring Well

Deep Monitoring Well

C Detected Concentration ND = Not Detected Figure 1-XS Distribution of Total VOCs in Shallow Bedrock Groundwater

Pumping Well

17-Acre Property Boundary Concentration Contour (ugl)

June 2001 Hows Corner Superfund Site

Plymouth Maine WOODARDampCURRAN

-i^rhvj bull Scbncn bull Operations bull 211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0601 dwg04-20-05

PLYMOUTH POND Hopkins Road V

O

PLYMOUTH POND

PLYMOUTH POND

o

0 300 600 mdashfa FEET

Shallow Monitoring Well bull bull - 17-Acre Property Boundary Figure 1-XD

Deep Monitoring Well 1 I Detected Concentration ND = Not Detected Distribution of Total VOCs in Deep Bedrock Groundwater

-mf- Pumping Well June 2001 Residential Well Hows Corner Superfund Site

Plymouth Maine i h Surface Water Sampling Point

g WOODARD ampCURRAN _ ^ _ ^ _ _ yen_ rj i|Hlaquorlny bull Science bull Opt

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0601 dwg04-20-05

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

Shallow Monitoring Well

Deep Monitoring Well

Detected Concentration ND = Not Detected Figure 1-YS Distribution of Total VOCs in Shallow Bedrock Groundwater

Pumping Well

17-Acre Property Boundary Concentration Contour (ugl)

January 2002 Hows Corner Superfund Site

Plymouth Maine WOODARD amp CURRAN Engineering Science- Operations bull

211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0102dwg04-20-05

PLYMOUTH POND

PLYMOUTH POND

Site Pand^ laquoum-laquoBTuitaraquo tLV

vVlf-(

PLYMOUTH POND

0 300 600 ^ = FEET

Shallow Monitoring Well mdashbullbullbull 17-Acre Property Boundary Figure 1-YD - A - Deep Monitoring Well FT Detected Concentration ND = Not Detected Distribution of Total VOCs in

Deep Bedrock Groundwater Pumping Well January 2002 Residential Well Hows Corner Superfund Site

Plymouth Maine Surface Water Sampling Point

WOODARD ampCURRAN Engineering Sciencs- Operations bulli Si

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0102dwg04-20-05

- m j

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND j A O-shy

Shallow Monitoring Well E Detected Concentration ND = Not Detected Figure 1-ZS Distribution of Total VOCs in

Deep Monitoring Well Shallow Bedrock Groundwater

Pumping Well Hows Corner

April 2003 Superfund Site

17-Acre Property Boundary Plymouth Maine Concentration Contour (ugl) r WOODARD ampCURRAN

Engineering bull Science bull Operations bull 211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0403dwg04-20-05

s S pound

PLYMOUTH POND

PLYMOUTH POND

- -

5 PLYMOUTH POND

Jo

FEET

ft Shallow Monitoring Well mdashbullbullmdash 17-Acre Property Boundary Figure 1-ZD Deep Monitoring Well I 1 I Detected Concentration ND = Not Detected Distribution of Total VOCs in

Deep Bedrock Groundwater Pumping Well April 2003

Q) Residential Well Hows Corner Superfund Site Plymouth Maine

(T) Surface Water Sampling Point WOODARD ampCURRAN poundKk EnginawtirKj bull Science - Operations bull

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0403dwg04-20-05

0 Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

B MW-1B

I 12000

PCE

B 10000 Total VOCs

I

i 2000

i 0 Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

c MW-3B

G 2000

1800

B PCE

1600 Total VOCs

1 I I E

il-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

G E

211941

El

I I z E

80

Concentration Trends shy Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-13DB

Total VOCs

c i i c o

Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

MW-16DB

30

c i c c I c o

Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99

PCE

Total VOCs

Jul-01 Jul-03

211941

O bi

c Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

I MW-16IB

i 35

3

c Total VOCs

lt- 2 5

0 | gt

o

1 sectI

c c 0 4

Jul-90 Jul-92 Jul-94 Jul-96 Jul-98 Jul-00 Jul-02 Jul-04

I I MW-108D

I 12

PCE 10

Total VOCs c oc 3

E E I 0

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

E 211941

c Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

fi MW-108S

I I 40

PCE 35

Total VOCs

30

I f 26

20 I o

I 15

10

c Dec-99 Dec-00 Dec-01 Dec-02 Dec-03 I 0

I MW-112D

c 35 - imdash

I A3 shyTotal VOCs

o c

E 1 2

I

ition

B 1 ^

-i c 3

0 Dec-99 Dec-OO Dec-01 Dec-02 Dec-03

211941

I

i

I

cII

Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-112S

08

PCE

Total VOCs 06

o 04

02

0 Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

MW-114D

o

12000

10000

8000

6000

PCE

Total VOCs

4000

2000

i

ccEIIc

i

i

E

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

211941

Con

cent

ratio

n (

ug

l)

E Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

I MW-114S

E A5000 -- Total VOCs

- 4000

0 3000

2000

i 1000

i n shy

Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

MW-115D

c PCE

Total VOCs

c E

o

C c

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03 I 0

211941

IepoundII

EIEIIGICCIccc

30000

25000

20000

o bullsect 15000 b

o 10000 U

5000

0 Aug-99

25000

20000

5000

0 Aug-99

211941

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-2DB

PCE

Total VOCs

Aug-01 Aug-03

MW-2IB

PCE

Total VOCs

Aug-01 Aug-03

IDIBI

ii EIDIISIBIG C

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-102S

6000

5000 PCE

Total VOCs

4000

O 3000

2000

1000

0 Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

MW-103D

16000

~ 14000 ugt 3- 12000 o

^ 10000

sect 8000

O 6000

4000

2000

PCE

Total VOCs

0Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

211941

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

G MW-103S

I I

ampo

12000

10000

E sectc

S

8000

6000

4000

2000

0Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

G I 6000

MW-104D

i 5000

PCE

Total VOCs

i i c

2000

1000

Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

E I

211941

cIccIG

IIBCccBcIc

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-1041

PCE Total VOCs

a 25000

0 20000

a 15000

10000

5000

0 Jan-OO Jan-01 Jan-02 Jan-03 Jan-04

MW-106D

3000

2500 PCE

Total VOCs

=sect 2000

o bullsect 1500

1000

500

0 Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

211941

c Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

c MW-106S

I PCE

Total VOCs

i

i Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

i

i i i E

C

211941 c

Response to EPA-DEP Comment 5 Dated March 312005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

iiw

EPA-DEP Comment 5

Comment 5 Matrix Diffusion The report as well as other proponents of matrix diffusion suggest that depletion of DNAPL (Section 5112 page 5-15) needs to be achieved While that might be the ideal the goal is to achieve performance standards and that goal may be attainable while there is residual contamination in the rock perhaps even DNAPL globules The low bedrock matrix porosity (page 1-15) the high permeability values (page 4-4) the relative flux of the groundwater (page 5-5) and the decrease in surface area and out of the mainstream pockets (appendix C-4) all suggest that the diffusion out of the rock matrix would be insubstantial relative to the regional flux of groundwater through the Site

Response The TI Evaluation Report does not explicitly consider or rely upon matrix diffusion as a basis for requesting a TI Waiver for a portion of the Hows Corner Site The technical literature provides documentation that matrix diffusion can be a significant process that affects chemical transport and groundwater remediation timeframes in unconsolidated and consolidated media including fractured rock (US EPA 1989 Freeze and Cherry 1979 Pankow and Cherry 1996 Fountain 1998) Back diffusion of contaminants from the matrix porosity of the fractured rock can prolong the time necessary to achieve groundwater cleanup goals particularly for compounds such as PCE for which the cleanup goal is a low concentration It is our expectation that matrix diffusion has occurred at the Hows Corner Site and that back diffusion of PCE from the rock matrix will also occur Although the extent to which matrix diffusion is occurring at the Hows Comer Site has not been determined and that lack of knowledge contributes to uncertainty regarding the cleanup times at the Site the effect of matrix diffusion is to lengthen rather than shorten the time required for remediation

REFERENCES

Fountain JC 1998 Technologies for Dense Nonaqueous Phase Liquid Source Zone Remediation Ground-Water Remediation Technologies Analysis Center Technology Evaluation Report TE-98-02 December

Freeze RA and Cherry JA 1979 Groundwater Prentice-Hall Inc Englewood Cliffs NJ 07632 p 410-412

Pankow J F and Cherry J A 1996 Dense Chlorinated Solvents Waterloo Press Portland OR 97291-1399 p 67-88

US EPA 1989 Transport and Fate of Contaminants in the Subsurface EPA6254-89019 p 17-18

Response to EPA Comment 5 050305doc 1 of 1 Woodard amp Curran (211941)

WOODARD amp CURRAN Maine Massachusetts New Hampshire Connecticut Florida Operational offices across the US 1-800-426-4262 www woodardcurran com

Page 29: SDMS DocID 251749 - Records Collections · 2020-06-13 · CORPORATE OFFICES: Maine, Massachusetts, New Hampshire, Connecticut New, York, Florida Engineering • Science • Operations

Table XX Orientation Permeability and Groundwater Sampling Results for Transmissive Features

2004 Drilling Program

Hows Corner Superfund Site Plymouth Maine

Borehole Geophisical Feature depth Dip True Dip True Transmissive Log Feature (Feet) Degrees Azimuth Strike bullvgt(Ltk|iy^

Number v Tosftble) v MW-203 5 277 64 337 67 Likely

6 279 59 11 281 Likely 8 352 14 177 87 Likely 11 381 46 96 6 Possible 12 408 35 271 1 Possible 14 415 57 250 340 Possible 15 420 58 202 292 Likely 18 526 52 75 345 Likely 19 530 52 82 352 Likely 28 828 48 75 345 Likely 29 830 52 17 287 Likely 30 830 56 233 323 Possible 31 842 50 130 40 Likely

MW-204 4 295 15 147 57 Likely 5 300 43 91 1 Likely 11 439 31 80 350 Possible 12 440 46 219 309 Possible 14 463 50 358 88 Likely 15 496 34 198 288 Likely 16 513 54 17 287 Likely 17 516 33 14 284 Likely 25 681 39 359 89 Possible 26 685 22 45 315 Possible 27 688 35 73 343 Possible 32 758 45 236 326 Likely 33 762 46 306 36 Likely

MW-205 5 164 69 106 16 Possible 6 166 78 165 75 Possible 7 168 82 115 25 Possible 8 168 68 116 26 Possible 12 215 46 222 312 Possible 13 217 75 62 332 Possible 14 219 29 32 302 Possible 16 237 69 250 340 Possible 17 256 73 353 83 Possible 18 272 44 202 292 Possible 21 299 37 196 286 Possible 22 302 31 206 296 Possible 23 305 59 48 318 Likely 24 312 63 42 312 Likely

MW-206 1 264 37 181 271 Likely 2 296 69 217 307 Likely 3 302 66 233 323 Likely 4 307 64 224 314 Likely 8 342 62 259 349 Likely

jjHydraulic GoiDanctilyity j(cmsecjw

667 E-05

593 E-05

101 P04

710 E-05

902 E-05

119 E-04

0

309 E-05

0

107 E-04

94 E-05

PCE (ugL)

44

170

140

130

220

540

260

IOOOB

1100B

1300B

2900B

STotal vVoCsv tig1)

84

234

192

183

2636

6436

3073

11448

12509

13776

32401

PCEyo dfCTotaf

52

73

73

7 1

83

84

85

87

88

94

90

Table XX Orientation Permeability and Groundwater Sampling Results for Transmissive Features

2004 Drilling Program

Hows Corner Superfund Site Plymouth Maine

Borehole Geophisical Feature deptt raquoip True pip True Transraissive Log Feature (Feet) shy Degrees Azimuth Strike (tikely

Number raquo Possible) 22 522 57 54 324 Possible 25 656 40 82 352 Possible 32 871 59 151 61 Possible 33 883 53 185 275 Possible 34 895 7 175 85 Likely 35 899 53 90 0 Likely 36 902 49 184 274 Likely 37 923 9 175 85 Likely 38 927 42 206 296 Likely 39 934 48 167 77 Likely 40 939 26 180 90 Likely

PW-207 1 1846 33 167 77 Likely 4 2216 49 289 19 Possible 7 2819 59 265 355 Possible 11 3508 55 189 279 Possible 18 5332 43 305 35 Likely 19 5341 51 30 300 Likely 20 5421 20 254 344 Likely 21 5432 39 301 31 Likely 23 5559 52 302 32 Likely 25 6359 24 182 272 Possible 29 8049 77 231 321 Possible 30 8685 78 38 308 Likely 32 9334 29 194 284 Likely

NOTES

B = detected in lab blank

Hydraulic Conductivity

(cmsee) 944 E-07 353 E-06

614 E-05

209 E-05

568 E-06

821 E-05

866 E-06

213 E-05

bulltCE (ugL)

6300B

1300

5400

18000

12000

19000

Total VOCs (ug1)

68901

1410

5802

19234

13085

20354

PCE of Total VOCs

9 1

92

93

94

92

93

Response to EPA-DEP Comment 3 Dated March 312005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

lit

EPA-DEP Comment 3

Comment 3 The reported f values and resultant Kd values There remains doubt that the values used in the flushing model accurately reflect the propensity for PCE to sorb to the bedrock The ^ values presented in Appendix B may be unrealistically high because the bedrock samples may have contained organic carbon that was unavailable for sorption The reported f values are only qualitative estimates of the organic carbon content of the bedrock samples The Walkley and Black organic carbon measurement method is quick and simple but the results obtained cannot be considered quantitative because it requires a correction factor which often results in erroneous values it assumes the organic carbon has an average valence of zero oxidizable and reducible constituents such as chloride ferrous iron and manganese oxides interfere with the results and the errors introduced by interference are potentially greater when the organic carbon content is low at low f values it is not clear that organic carbon is controlling PCE sorption (Schwarzenbach and Westall 1981 Mackay et al 1986 Fetter 1999)

In order to derive a Kd-based retardation factor that is reasonable given the reported f values and the rapid advance of the PCE plume described on pages 4-11 and 4-12 the flushing model requires a bulk density to porosity ratio that is roughly two orders of magnitude higher than the actual ratio for the Hows Corner bedrock (page 4-4) This apparent discrepancy needs to be addressed

Response This comment raises several concerns about the collection and analysis of samples for fraction of organic carbon (f^) the quality of the resulting data and the implications of the use of those data for estimation of the retardation of groundwater contaminant movement Results of bedrock analysis for f were proposed in the TI Evaluation Work Plan for use in conjunction with groundwater contaminant concentrations and aquifer information to estimate cleanup times using the Batch Flushing model It is important to use accurate f values from representative bedrock in the Batch Flushing model in order to obtain reasonable estimates of the remedial time frame Because of the importance of accurate and representative results the TI Investigation field program was designed and conducted both to collect samples representative of the rock volume most likely to be in contact with contaminated groundwater and to analyze them using an appropriate refereed analytical method Five potential methods for evaluating f were identified Of the five methods the Walkey-Black method was selected because it has minimal method interferences and a sufficiently low detection limit as well as a long history of use in agronomy and contamination studies The PRP Group is pleased with the quality of the data obtained from the bedrock samples as represented by their precision and reproducibility

The first part of this comment relates to the determination of fraction of organic carbon (f^) values The several subparts of the first paragraph are addressed individually in items 1 through 5 below The second part of the comment regarding the resultant distribution coefficient (Kd) values is addressed separately as item 6 below

1 There remains doubt that the values used in the flushing model accurately reflect the propensity for PCE to sorb to the bedrock

bull The rock core samples used for f (gocg) analysis were from core immediately adjacent to fractures These rock core samples included the fracture surfaces themselves and rock core extending back less than 1 cm from the fractures Therefore the foe data reported in the TI Evaluation represents the f of bedrock through which groundwater will travel and to which PCE will adsorb Based on the careful selection of sample locations and the

Response to EPA Comment 3 050205doc 1 of 11 Woodard amp Curran (211941)

number of samples collected we are confident that the measured f values are representative of the f at points of contact for PCE with the bedrock it is these f values that determine the propensity of PCE to sorb to the bedrock

bull The samples of rock core collected for analysis of f originated from 19 different locations varying in depth from 11 to 90 feet Therefore it is very unlikely that the rock core samples were contaminated with extraneous organic carbon from above ground

2 The foc values presented in Appendix B may be unrealistically high because the bedrock samples may have contained organic carbon that was unavailable for sorption

bull As noted in response 1 the f data reported in Appendix B represents organic carbon primarily associated with the surface of fractures in the bedrock through which groundwater is most likely to travel Therefore it is this organic carbon that the contaminants in the groundwater will come in contact with and adsorb to in the fractured rock at the site

bull The chemical oxidation agents used in the Walkey-Black method oxidize the easily oxidizable organic carbon in the medium and the foe is calculated from the quantity of the agent consumed Therefore it is unlikely that the analysis of the bedrock samples measured organic carbon that was unavailable for sorption

3 The reported foc values are only qualitative estimates of the organic carbon content of the bedrock samples

bull The reported f values are accurate quantitative results Schumachers review of Methods for the determination of total organic carbon (TOC) in soils and sediments (NCEA-C-1282 EMASC-001 April 2002) identifies the Walkley-Black method which was used to analyze the reported foc values as the reference method for comparison to other methods for analyzing total organic carbon

bull Schumacher also points out that if anything the WalkJey-Black method may underestimate the total organic carbon in a sample due to possible incomplete oxidation of organic carbon Usually the incomplete oxidation of total organic carbon in environmental samples is corrected for by multiplying the measured foe by 130 (Walkley amp Black 1934 Schulte 1995)

bull When the f data in the TI Evaluation Report (WampC 2005) Appendix B (attached) are analyzed statistically the standard deviation of the f for the 19 samples analyzed is 174 of the average f Given this standard deviation the 95 confidence interval for this data ranged from a low of 000123 gocg to a high of 000253 gocgm

The labs Method of Detection Limit (MDL) for the f measured using the Walkley-Black method is 00001 gocg Therefore the average (000188 gocg) the mean (000185 gocg) and geometric mean (000187 gocg) of the f values for the rock core at Hows Corner are all statistically significantly greater than the MDL of the Walkley-Black method

In addition to the aforementioned statistical analysis of the foe data triplicate samples (n = 3) from the same rock core (including one sample from the 19 rock core samples) were

Response to EPA Comment 3 050205doc 2 of Woodard amp Curran (211941)

analyzed for their f to determine the repeatability of the Walkley-Black method The average the mean and the geometric mean of the f values of these replicate samples was 000162 gocg 000150 gocg and 000159 gocgm respectively The standard deviation of these measurements was 000039 gocg

4 The Walkley and Black organic carbon measurement method is quick and simple but the results obtained cannot be considered quantitative because it requires a correction factor which often results in erroneous values it assumes the organic carbon has an average valence of zero oxidizable and reducible constituents such as chloride ferrous iron and manganese oxides interfere with the results and the errors introduced by interference are potentially greater when the organic carbon content is low at low foc values it is not clear that organic carbon is controlling PCE sorption (Schwarzenbach and Westall 1981 Mackay et al 1986 Fetter 1999)

bull Schumachers review (NCEA-C-1282 EMASC-001 April 2002) of the Walkley-Black method identifies several potential problems with this analytical method that could occur if the analytical lab is not familiar with the nuances of the chemistry associated with this method Interestingly Schumachers review neglected one of the more important analytical steps required to avoid errors in quantifying f in samples where there might beNAPL

It is absolutely critical to eliminate any NAPL from rock core samples prior to using the Walkley-Black method to measure foe in such samples This was done by the lab (PTS Laboratories) that measured the foe in the rock core samples from Hows Corner The lab used the Dean-Stark method (solvent extraction) to remove all hydrocarbons (including PCE and other NAPLs) from the sample (PTS Laboratories) This extraction method does not interfere with the subsequent analysis of the natural organic carbon associated with the rock core

Subsequently the samples were dried at 150degC to a constant weight (normally 16 hours) This latter step oxidizes all inorganic minerals including ferrous bearing minerals to ferric oxides and precludes their interference during the oxidation of the samples with chromic acid This procedure completely eliminates any positive bias in the reported foc

data that might have occurred due to the presence of ferrous ions and other reduced minerals

bull As noted in Response 3 the incomplete oxidation of total organic carbon results in an underestimate of the f and is corrected for by multiplying the f by a correction factor of 130 (Walkley amp Black 1934 Schulte 1995) The fx data reported in the TI Evaluation was corrected accordingly by using this correction factor

bull Excess chloride (Cl~) in percent weight quantities as found in saline soils may interfere with the quantitative titration of reduced chromium (Walkley 1947) However given that the primary rock type at the Hows Corner site is phyllite it is highly unlikely that there was sufficient chloride in the rock core samples for this to occur

bull Manganese oxides may also interfere with the analysis of f through competing with the dichromate ion for any oxidizable carbon (Walkley 1947) However in such cases the reported f would be an underestimate of the f present in the rock core Walkley (1947)

Response to EPA Comment 3 050205doc 3 of 11 Woodard amp Curran (211941)

4

reported that in the case where the ratio of MnO2 to carbon is 85 to 1 the error in the carbon determinations would only be 0 to 6 percent

It may also be useful to compare the analysis of total organic carbon in a geologic matrix that contains high levels of manganese using EPA method 9060 to the Walkley-Black method Table 1 summarizes data provided by one of the PRPs that compares the analysis of total organic carbon in a geologic matrix that contains approximately 02 wgt manganese (approximately 03 wgt manganese oxide)

Table 1 Comparison of total organic carbon measured using the EPA- 9060 method and the Walkley-Black method

Laboratory EPA-9060 Method Walkley-Black Method A Ave 00226 gocg Not analyzed

Stdev 000251 gocg n = 5

B Ave 002219 gocg Ave 002050 gocg Stdev = 000316 gocg Stdev =000971 gocg

n= 10 n = 10

The similarity in the total organic carbon concentrations measured by these two different methods provides further confidence that the Walkley-Black method is a viable method for analysis of total organic carbon in the presence of manganese equivalent to at least 10 by weight of the total organic carbon

5 The Walkley and Black organic carbon measurement at lowf^ values it is not clear that organic carbon is controlling PCE sorption (Schwarzenbach and Westall 1981 Mackay et al 1986 Fetter 1999)

bull Schwarzenbach and Westalls (1981) paper states that f values of less than 0001 gocg should not be used in combination with Kow (octanol-water partition coefficients) values to calculate K^ values (solid phase partition coefficients) values for a specific contaminant It should be noted that the TI Evaluation did not use the f data to calculate the KQC from the Kow Instead as requested by the EPA the measured KOC value for PCE was used to calculate the retardation factor for this contaminant

bull Schwarzenbach et al (2003) stated more recently that Even at very low f values (ie foe = 0001 kgoc - kg1 solid) sorption to the organic components of a natural sorbent may still be the dominant mechanism in defining the adsorption of organic compounds to geological matrices

bull In 1985 M Piwoni from the US EPA Robert S Kerr Environmental Research Laboratory published a paper (Banerjee et al 1985) that showed that for very hydrophobic molecules TOC content of the sorbent will control sorption down to levels of organic carbon that defy quantitation Contaminants such as the PCE found in the groundwater at Hows Corner are in this category of compounds

Given the aforementioned reasons the f values reported in the TI Evaluation are accurate within the noted statistical limitations and will have a predictable impact upon the retardation of PCE during groundwater transport

Response to EPA Comment 3 050205doc 4 of 11 Woodard amp Curran (211941)

6 In order to derive a Kd-based retardation factor that is reasonable given the reported foc

values and the rapid advance of the PCE plume described on pages 4-11 and 4-12 the flushing model requires a bulk density to porosity ratio that is roughly two orders of magnitude higher than the actual ratio for the Hows Comer bedrock (page 4-4) This apparent discrepancy needs to be addressed

The apparent discrepancy of bulk density to porosity ratios is most likely due to the fact that the Batch Flushing Model was originally developed for a porous medium and is not directly applicable to fractured bedrock As stated in Appendix C (page C-4) of the Draft Technical Impracticability Evaluation Report in order to use the Batch Flushing Model to describe the transport of contaminated groundwater in fractured bedrock where the matrix porosity is insignificant it is more appropriate to use a fracture surface area to void space ratio to calculate the retardation factor (R) than a bulk density to porosity ratio (Freeze amp Cherry 1979)

Since it is impractical to determine the actual surface area to which contaminants can adsorb the Batch Flushing Model was used with two simplifying assumptions bull The Kd was calculated from the f and the K^ bull The bulk density to porosity ratio term in the Batch Flushing Model was constrained to range

from 4 to 10 the typical range of such ratios in porous media (Freeze amp Cherry 1979)

If one uses site specific bedrock bulk density and porosity values the bulk density to porosity ratio is several orders of magnitude greater (specifically 273 gcc bullbull 000165 (dimensionless) = 1654 gcc) than the range of ratios of 4 to 10 used in the Batch Flushing Model in the Draft Technical Impracticability Evaluation Report Constraining the bulk density to porosity ratio within the range of ratios of 4 to 10 results in significantly lower R value than would be obtained using specific bedrock bulk density and porosity values

In summary in bedrock where fractures are the primary porosity the bulk density to porosity ratio can vary considerably and will be a function of the number of fractures and the fracture aperture The calculated bulk density to porosity ratio will be inversely proportional to the porosity This means that in fractured rock with limited fracturing and smaller porosity the calculated bulk density to porosity ratio is greater and will result in a greater calculated retardation factor than in bedrock with more extensive fracturing and greater porosity Consequently the calculated retardation factor will be greater for bedrock with less surface area available for sorption than bedrock with greater surface area for sorption This is contrary to what actually occurs

4 Response to EPA Comment 3 050205doc 5 of 11 Woodard amp Curran (211941)

m

REFERENCES

Banerjee P MD Piwoni K Ebeid (1985) Sorption of organic contaminants to a low carbon subsurface core Chemosphere _14 1057-1067

Freeze RA JA Cherry (1979) Groundwater Prentice Hall Englewood Cliffs NJ pg 604

PTS Laboratories wwwptsgeolabscompdf files3TOCnotepdf

Schulte EE (1995) Recommended soil organic matter tests in Recommended Soil Testing Procedures for the Northeastern United States Northeastern Regional Publication No 493 Chapter 8

Schwarzenbach RP J Westall (1981) Transport of nonpolar organic compounds from surface water to groundwater Laboratory sorption studies Environ Sci Tech 15 1360-1367

Schwarzenbach RP PM Gschwend DM Imboden (2003) Environmental Organic Chemistry Wiley-Interscience pg 292 408 amp 412

Walkley A LA Black (1934) An examination of the Degtjareff method for determining soil organic matter and a proposed modification of the chromic acid titration method Soil Science 37 29-38

Walkley A (1947) A critical examination of a rapid method for determining organic carbon in soils - effect of variations in digestion conditions and of inorganic soil constituents Soil Science 63251-264

Woodard amp Curran Inc (WampC) 2005 Draft Technical Impracticability Evaluation Hows Corner Superfund Site Plymouth Maine January 2005

Response to EPA Comment 3 050205doc 6 of Woodard amp Curran (211941)

LIST OF ATTACHMENTS (Response to Comment 3)

Appendix B to Draft Technical Impracticability Evaluation Measurement of foe at Hows Corner (4 pages)

m

Response to EPA Comment 3 050205doc 7 of 11 Woodard amp Curran (211941)

Appendix B Measurement of foe of Rock Core at Hows Corner

There are two general approaches to measure the fraction of organic carbon (foe) in rock cores

bull Measurement of weight loss by ignition of organic matter bull Chemical oxidization of organic carbon to carbon dioxide and either

subsequent quantification of the oxidant used for the reaction or quantification of the carbon dioxide produced during this oxidation process

The weight loss method is subject to errors caused by volatilization of substances other than organic materials such as water hydroxides and mineral carbonates Quantification of foe by the weight loss method is particularly sensitive to the presence of carbonates in rock cores There are however weight loss methods that are designed to differentiate between organic carbon and the aforementioned interfering materials but they require considerable care and are less accurate at low foe values Hence the weight loss method was not well suited for measuring the foe of the rock core from Hows Corner

The chemical oxidation of organic carbon is much better suited for quantifying organic carbon in rock cores such as those from Hows Corner This method uses a strong chemical oxidant to oxidize organic carbon to carbon dioxide and then measures either the chemical oxidant used to oxidize the organic carbon or the quantity of carbon dioxide produced In addition this general approach is not subject to interference by volatilization of other constituents of the rock core

There are at least two such chemical oxidation methods

bull The method of Baccini which was described by Schwarzenbach amp Westall (1981) first acidifies the sample to eliminate interference by carbonates Then a strong oxidant is used to chemically oxidize the organic carbon to carbon dioxide The resulting carbon dioxide is subsequently reduced to methane and quantified using a flame ionization detector Unfortunately this method has not been described in detail in a referred journal Hence it is would not have been appropriate to use to characterize the foe in the Hows Corner rock core

bull The more commonly used method to quantify foe in rock core is the Walkley-Black method (1934) This method is preferred for RBCA and DODDOE projects and by the oil industry

The Walkley-Black method uses an excess of chromic acid to oxidize (digest) organic matter to carbon dioxide The remaining chromic acid that was not consumed during the oxidation of the organic carbon is then quantified by titration with ferrous sulfate The difference in chromic acid prior to and after the oxidation of the organic carbon represents the total chromic acid used to oxidize

Hows Corner TI Evaluation Page 1 January 13 2005 Appendix B

the organic carbon in the sample The latter can be calculated using the chemical stoichiometry of the reaction

The Walkley-Black method is very accurate for samples that contain less than 2 organic carbon matter The minimum detection limit (MDL) for the Walkley-Black method is 100 mgkg or an foe of 0001

Given the rock core at Hows Corner was expected to contain less than 2 organic carbon the Walkley-Black method was used to measure the foe from 19 different rock core samples collected from varying depths ranging from 11 to 90 feet

Table 1 provides a statistical summary of the aforementioned data

Table 1 Statistical summary of foe data from rock cores collected at varying depths

Statistical Parameter Calculated Value foe Minimum Detection Limit (MDL) 00010 Number of samples analyzed (n) 19 Average foe 00019 Median foe 00019 Geometric Mean foe 00019 Standard deviation of foe measurements 000033 Relative standard deviation 174 -+ 95 Confidence intervals 00012 to 00025

The data in Table 1 shows the following

bull The foe from the Hows Corner rock cores are statistically greater than the MDL of the Walkley-Black analytical method

bull The average and median values for the foe of the Hows Corner rock cores from varying depths are nearly identical indicating that there is little variability in the foe values in the source zone at the site

bull The standard deviation of these measurements is 000033 which is 174 of the average foe

bull The 95 confidence intervals of the foe of the rock core at Hows Corner are 00012 to 00025

The foe was also analyzed from three separate samples taken from the same rock core at a depth of 55 feet (Only one of these samples was included in the data summarized in Table 1) Table 2 shows the statistical repeatability of this type of analysis

Hows Corner TI Evaluation Page 2 January 13 2005 Appendix B

Table 2 Repeatability of analysis of foe from one rock core at 55 feet in depth

Statistical Parameter Calculated Value Number of samples analyzed (n) 3 Average foe 00016 Median foe 00015 Geometric Mean foe 00016 Standard deviation of foe measurements 000039 Relative standard deviation 240 -+ 95 Confidence intervals 00008 to 00024

The data in Table 2 shows the following

bull The percent relative standard deviation of these three analyses of foe from the same rock core at Hows Corner is 24

bull The 95 confidence interval of the foes measured in this particular rock core at Hows Conrer is 00008 to 00024

These results show that there is good repeatability in using the Walkley-Black method for analysis of the foe in the rock core at Hows Corner

References Schwarzenbach amp Westall (1981) Transport of nonpolar organic compounds from surface water to groundwater Laboratory sorption studies Environ Sci Tech 15 1360-1367

Walkley A I A Black (1934) An examination of Degtjareff method for determining soil organic matter and a proposed modification of the chromic acid titration method Soil Sci 37 29-37

Hows Corner Tl Evaluation Page S January 13 2005 Appendix B

Woodard and Curran PTS Laboratories PTS File No 34618

ORGANIC CARBON DATA (METHODOLOGY WALKLEY-BLACK)

PROJECT NAME PROJECT NO

SAMPLE ID

203-chip-13 203-chip-23 203-chip-27 203-chip-38 203-chip-42 203-chip-47 203-chip-52 203-chip-58 203-chip-69 203-chip-82 207-chip-11 207-chip-19 207-chip-24 207-chip-29 207-chip-35 207-chip-45 207-chip-55 207-chip-87 207-chip-90

207-chip-55 55-MS

55-MSMSD

Hows Corner NA

DEPTH ft

13 23 27 38 42 47 52 58 69 82 11 19 24 29 35 45 55 87 90

55 NA NA

MATRIX

Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip

Average Median

Geometric Mean Standard Deviation Relative Std Dev

+- 95 Confidence Interval n

Rock Chip Rock Chip Rock Chip

Average Median

Geometric Mean Standard Deviation Relative Std Dev

+- 95 Confidence Interval n

FRACTION ORGANIC CARBON

(gg)

170E-03 185E-03 185E-03 170E-03 240E-03 190E-03 230E-03 180E-03 170E-03 115E-03 195E-03 220E-03 220E-03 235E-03 135E-03 190E-03 205E-03 175E-03 160E-03

188E-03 185E-03 185E-03 327E-04

1739 123E-03 to

19

205E-03 130E-03 150E-03

162E-03 150E-03 159E-03 388E-04

2402 840E-04 to

3

2532E-03

2393E-03

Hows Corner Tl Evaluation Appendix B January 13 2005

Response to EPA-DEP Comment 4 Dated March 31 2005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

EPA-DEP Comment 4

Comment 4 Distribution of contaminants First the TI report seems based on the assertion that there is DNAPL at the source area yet it also appears to represent that the source area is small and the bedrock below 85 is competent (or less fractured) and less impacted by the release of contaminants Some of the confusion may result from using most recent data when that data is from several different sampling events over several years and there is no discernible difference in concentrations between shallow and deep bedrock or as in Section 421 where generally decreased generally increase generally similar and similar concentrations in four consecutive sentences leads to a muddled picture of the contaminant distribution

Second the report asserts that the distribution of contaminants over the entire plume has not changed with time but fails to support this conclusion with data again relying on data that is from different sampling dates for one composite representation

Response The likely presence of dense non-aqueous phase liquid (DNAPL) at the Hows Corner Site and the determination that the source area is small are not mutually exclusive and both are conclusions drawn from information obtained during field investigations The presence of DNAPL in the source area is based on the elevated concentrations of volatile organic compounds (VOCs) detected in the groundwater (WampC 2001 WampC 2002) The conclusion that the source area is small is based on the area in which VOCs in groundwater have been detected at concentrations that are considered to be indicative of the presence of DNAPL nearby Similarly the conclusion that fracture frequency decreases at depths greater than approximately 50 to 85 feet below ground surface was based on field observation during the RI field work The fact that zones with observed fractures exhibited higher hydraulic conductivities than zones without fractures coupled with the decreasing frequency of observed fractures with depth led to the conclusion that the hydraulic conductivity of the bulk rock decreases with depth

The most recent data from all wells were used to provide the maximum VOC data set size During the RI all of the previously-existing and then newly-installed monitoring wells were sampled along with several residential wells The RI sampling included up to 48 monitoring wells Subsequent to the RI and prior to the TI three rounds of monitoring were conducted to verify that the plume was stable 15 monitoring wells were sampled during each of the three rounds During the TI field investigation 29 wells were sampled for VOCs The sampled wells included all of the newly-installed wells and a subset of wells installed during the RI for a total of 29 monitoring wells By using most recent data VOC results from 53 monitoring wells were included in the evaluation (see table labeled Sampling Events for listing of monitoring wells) This approach was selected because there generally was little variation in the data from a particular location between years This is borne out by the attached individual plots of VOCs detected in shallow bedrock and deep bedrock for the Pre-ROD (December 1999January 2000) and Supplemental (May 2000) sampling events and for June 2001 January 2002 and April 2003 sampling events The Pre-ROD and Supplemental plots are similar to the subsequent plots from the 2001 2002 and 2003 sampling events

In addition to maps showing the spatial distribution of VOC data at a given time trend plots of the data from a particular location through time (attached) indicate that since the RI concentrations generally have been stable or have decreased Together the maps and trend plots and the data from which they were developed indicate that the distribution of contaminants over the entire plume has not changed appreciably with time

Response to EPA Comment 4 050305doc 1 of 26 Woodard amp Curran (211941)

REFERENCES

Woodard amp Curran Inc (WampC) 2001 Final Remedial Investigation Report Hows Corner Superfund Plymouth Maine July 2001

Woodard amp Curran Inc (WampC) 2002 Final Feasibility Study Report - Non-Source Area Groundwater Hows Corner Superfund Site Plymouth Maine Hows Corner Superfund Plymouth Maine July 2002

Response to EPA Comment 4 050305doc 2 of 26 Woodard amp Curran (211941)

LIST OF ATTACHMENTS (Response to Comment 4)

Table - Sampling Events 1999 - 2004 (2 pages)

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater Pre-ROD Sampling Event

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater Pre-ROD Sampling Event

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater Supplemental Sampling Event

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater Supplemental Sampling Event

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater June 2001

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater June 2001

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater January 2002

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater January 2002

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater April 2003

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater April 2003

Figure - Concentration Trends - Non-Source Area Wells MW-1B and MW-3B

Figure - Concentration Trends - Non-Source Area Wells MW-13DB and MW-16DB

Figure - Concentration Trends - Non-Source Area Wells MW-16IB and MW- 108D

Figure - Concentration Trends - Non-Source Area Wells MW-108S and MW-112D

Figure - Concentration Trends - Non-Source Area Wells MW-112S and MW-114D

Figure - Concentration Trends - Non-Source Area Wells MW-114S and MW-115D

Figure - Concentration Trends -Source Area Wells MW-2DB and MW-2IB

Figure - Concentration Trends -Source Area Wells MW-102S and MW-103D

Figure - Concentration Trends -Source Area Wells MW-103S and MW-104D

Figure - Concentration Trends -Source Area Wells MW-104I and MW-106D

Figure - Concentration Trends -Source Area Wells MW-106S

Response to EPA Comment 4 050305doc 3 of 26 Woodard amp Curran (211941)

I I

El I

II I I 1 I

I

i

Event Baseline Case ID WC-01 WC-01

Well Date Aug-99 Oct-99 LOT10 1 LOT1-1 1 LOT11-4 LOT14 1 LOT15 1 LOT15-1 1 LOT16 1 LOT16-1 1 LOT17 1 LOT18 1 LOT19 1 LOT2 LOT20 1 LOT21-10 1 LOT21-11 1 LOT21-12 1 LOT21-13 1 LOT21-14 1 LOT21-2 1 LOT21-5 1 LOT21-7 LOT21 -8 1 LOT21-9 1 LOT23 1 LOT24 1 LOT28-1 1 LOT28-2 1 LOT28-3 1 LOT28-4 1 LOT28W 1 LOT30 1 LOT30-1 1 LOT30-2 1 LOT30-3 1 LOT30-4 1 LOT30-5 LOT31 LOT35 1 LOT41 1 LOT42-1 1 LOT43-1 1 LOT43-4 1 LOT6-1 1 LOT67 1 LOT6-7 1 LOT6-8A 1 LOT6-8B 1 LOT80-1 1 LOT82 1 MW-101D MW-1011 MW-101S MW-102D MW-102S MW-103D MW-103S MW-104D MW-1041 MW-104S MW-105D MW-106D

Groundwater Sampling Location Summary 1999 - 2004xls

Sampling Events 1999-2004

Hows Corner Superfund Site Plymouth Maine

Supplemental 2001 2002 2003 Pumping 2004 Pre-ROD Rl Sampling Sampling Sampling Test Sampling WC-03 WC-09 WC-25 WC-30 WC-42B WC-56 WC-58 Dec-99 May-00 Jun-01 Jan-02 Apr-03 Sep-04 Sep-04

1

1 1 1

1 1 1 1 1

1 1

1

1 1

1 1 1

1 1 1 1 1

1

1 1

1 1 1 1

1

1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

Sampling Events 1999-2004

Hows Corner Super-fund Site Plymouth Maine

Supplemental 2001 2002 2003 Pumping Event Baseline Pre-ROD Rl Sampling Sampling Sampling Test

Case ID WC-01 WC-01 WC-03 WC-09 WC-25 WC-30 WC-42B WC-56

ll

Well Date Aug-99 Oct-99 Dec-99 May-00 Jun-01 Jan-02 Apr-03 Sep-04 MW-106S 1 1 1 1 1 MW-107D 1 1 MW-108D 1 1 1 1 1 MW-108S 1 1 1 1 1 MW-110D 1 1 MW-111D 1 1 MW-112D 1 1 1 1 1 MW-112S 1 1 1 1 1 MW-113D 1 1 MW-114D 1 1 1 1 1 MW-114S 1 1 1 1 1 MW-115D 1 1 1 1 1 MW-12DB 1 1 1 MW-12SB 1 1 1 MW-13DB 1 1 1 1 1 1 MW-13SB 1 1 1 MW-14DB 1 1 MW-14SO 1 1 MW-15DB 1 1 1 MW-15SB 1 1 1 MW-16DB 1 1 1 1 1 1 MW-16IB 1 1 1 1 1 1 MW-16SO 1 1 MW-17DO 1 1 1 MW-17SO 1 1 1 MW-1B 1 1 1 1 1 1 MW-203D MW-203S MW-204D MW-204S MW-205 MW-206D

I MW-206S MW-2DB 1 1 MW-2DDB 1 1 MW-2IB 1 1 1 1 1 1 MW-3B 1 1 1 1 1 1

I MW-4O 1 1 1 MW-5B 1 1

II MW-6DB 1 1 1 MW-6SB 1 1 1 MW-8DB 1 1 1 MW-8SB 1 1 1

II PW-207 1 SEEP-1 1 SUBTOTAL - RESIDENTIAL 44 25 0 2 0 3 0 SUBTOTAL - MONITORING 22 48 41 15 15 15 1

Total 3 66 73 41 17 15 18 1

I Included in most recent data

I Notes 1 - Overburden well not included in most recent data for plotting

2 - Tetrahydrofuran and 2-Butanone were the only two compounds detected in this well and are thought to be the result of well repair not included in most recent data for plotting

3 - Not included in most recent data for plotting

2004 Sampling

WC-58 Sep-04

1

1 1

1 1

1 1 1

1

1 1

1 1 1 1 1 1 1 1 1

1 1

1

0 29

29

Groundwatef Sampling Location Summary 1999 - 2004xls

I

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

monitoring well Figure 4-14 total VOC contour (ugl) - December 1999January 2000 Distribution of Total VOCs in

Note SW-113 is located downstream of SEEP-1 Shallow Bedrock Groundwater total concentration of detected VOCs ND= not detected these two locations were sampled during the Pre-ROD Sampling Event

Baseline Sampling Event in OctoberNovember 1999 Hows Corner Superfund Site Surface Water Sampling Location A Plymouth Maine Seep Sampling Location laquo- WOODARD ampCURRAN

995037wipri reportepa ri interim final feb 2001cadd drawingsfinalfig 4-14

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

0 300 600 I

FEET

Q residential well Figure 4-16 monitoring well Distribution of Total VOCs in

Deep Bedrock Groundwater total VOCs contour (ugl) Pre-ROD Sampling Event

active residential wells with lot number Hows Corner Superfund Site 2deg42deg Plymouth Maine total concentration of detected VOCs ND= not detected WOODARD ampCURRAN Enyinaaring bull Science bull Operations bull

995037wipri reportepa ri interim final feb 2001cadd drawingsfinalfig4mdash16

PLYMOUTH POND

PLYMOUTH POND

1 628Tl7MW-2bB 12135

PLYMOUTH POND

monitoring well Figure 4-20

V total VOC contour (ugl) - June 2000 Distribution of Total VOCs in Shallow Bedrock Groundwater

| 34 | total concentration of detected VOCs ND= not detected NA = not analyzed Supplemental Sampling Event Note SW-113 is located downstream of SEEP-1 Hows Corner Superfund Site

Surface Water Sampling Location these two locations were sampled during the Plymouth Maine Baseline Sampling Event in OctoberNovember 1999 Seep Sampling Location WOODARD amp CURRAN

Engineering bull Science - Operations bull 995037wipri reportepa ri interim final feb 2001 cadd drawingsfinalfig 4-20

residential well Figure 4-22 Distribution of Total VOCs in

monitoring well Deep Bedrock Groundwater

total VOCs contour (ugl) Supplemental Sampling Event

Hows Corner Superfund Site

total concentration of detected VOCs ND= not detected NA = not analyzed Plymouth Maine

WOODARD amp CURRAN

995037wipri reportepa-ri interim final feb 2001cadd drawingsfinalfig 4-22 Engineering bull Science - Operations bull

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

FEET

Shallow Monitoring Well

Deep Monitoring Well

C Detected Concentration ND = Not Detected Figure 1-XS Distribution of Total VOCs in Shallow Bedrock Groundwater

Pumping Well

17-Acre Property Boundary Concentration Contour (ugl)

June 2001 Hows Corner Superfund Site

Plymouth Maine WOODARDampCURRAN

-i^rhvj bull Scbncn bull Operations bull 211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0601 dwg04-20-05

PLYMOUTH POND Hopkins Road V

O

PLYMOUTH POND

PLYMOUTH POND

o

0 300 600 mdashfa FEET

Shallow Monitoring Well bull bull - 17-Acre Property Boundary Figure 1-XD

Deep Monitoring Well 1 I Detected Concentration ND = Not Detected Distribution of Total VOCs in Deep Bedrock Groundwater

-mf- Pumping Well June 2001 Residential Well Hows Corner Superfund Site

Plymouth Maine i h Surface Water Sampling Point

g WOODARD ampCURRAN _ ^ _ ^ _ _ yen_ rj i|Hlaquorlny bull Science bull Opt

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0601 dwg04-20-05

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

Shallow Monitoring Well

Deep Monitoring Well

Detected Concentration ND = Not Detected Figure 1-YS Distribution of Total VOCs in Shallow Bedrock Groundwater

Pumping Well

17-Acre Property Boundary Concentration Contour (ugl)

January 2002 Hows Corner Superfund Site

Plymouth Maine WOODARD amp CURRAN Engineering Science- Operations bull

211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0102dwg04-20-05

PLYMOUTH POND

PLYMOUTH POND

Site Pand^ laquoum-laquoBTuitaraquo tLV

vVlf-(

PLYMOUTH POND

0 300 600 ^ = FEET

Shallow Monitoring Well mdashbullbullbull 17-Acre Property Boundary Figure 1-YD - A - Deep Monitoring Well FT Detected Concentration ND = Not Detected Distribution of Total VOCs in

Deep Bedrock Groundwater Pumping Well January 2002 Residential Well Hows Corner Superfund Site

Plymouth Maine Surface Water Sampling Point

WOODARD ampCURRAN Engineering Sciencs- Operations bulli Si

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0102dwg04-20-05

- m j

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND j A O-shy

Shallow Monitoring Well E Detected Concentration ND = Not Detected Figure 1-ZS Distribution of Total VOCs in

Deep Monitoring Well Shallow Bedrock Groundwater

Pumping Well Hows Corner

April 2003 Superfund Site

17-Acre Property Boundary Plymouth Maine Concentration Contour (ugl) r WOODARD ampCURRAN

Engineering bull Science bull Operations bull 211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0403dwg04-20-05

s S pound

PLYMOUTH POND

PLYMOUTH POND

- -

5 PLYMOUTH POND

Jo

FEET

ft Shallow Monitoring Well mdashbullbullmdash 17-Acre Property Boundary Figure 1-ZD Deep Monitoring Well I 1 I Detected Concentration ND = Not Detected Distribution of Total VOCs in

Deep Bedrock Groundwater Pumping Well April 2003

Q) Residential Well Hows Corner Superfund Site Plymouth Maine

(T) Surface Water Sampling Point WOODARD ampCURRAN poundKk EnginawtirKj bull Science - Operations bull

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0403dwg04-20-05

0 Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

B MW-1B

I 12000

PCE

B 10000 Total VOCs

I

i 2000

i 0 Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

c MW-3B

G 2000

1800

B PCE

1600 Total VOCs

1 I I E

il-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

G E

211941

El

I I z E

80

Concentration Trends shy Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-13DB

Total VOCs

c i i c o

Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

MW-16DB

30

c i c c I c o

Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99

PCE

Total VOCs

Jul-01 Jul-03

211941

O bi

c Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

I MW-16IB

i 35

3

c Total VOCs

lt- 2 5

0 | gt

o

1 sectI

c c 0 4

Jul-90 Jul-92 Jul-94 Jul-96 Jul-98 Jul-00 Jul-02 Jul-04

I I MW-108D

I 12

PCE 10

Total VOCs c oc 3

E E I 0

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

E 211941

c Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

fi MW-108S

I I 40

PCE 35

Total VOCs

30

I f 26

20 I o

I 15

10

c Dec-99 Dec-00 Dec-01 Dec-02 Dec-03 I 0

I MW-112D

c 35 - imdash

I A3 shyTotal VOCs

o c

E 1 2

I

ition

B 1 ^

-i c 3

0 Dec-99 Dec-OO Dec-01 Dec-02 Dec-03

211941

I

i

I

cII

Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-112S

08

PCE

Total VOCs 06

o 04

02

0 Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

MW-114D

o

12000

10000

8000

6000

PCE

Total VOCs

4000

2000

i

ccEIIc

i

i

E

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

211941

Con

cent

ratio

n (

ug

l)

E Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

I MW-114S

E A5000 -- Total VOCs

- 4000

0 3000

2000

i 1000

i n shy

Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

MW-115D

c PCE

Total VOCs

c E

o

C c

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03 I 0

211941

IepoundII

EIEIIGICCIccc

30000

25000

20000

o bullsect 15000 b

o 10000 U

5000

0 Aug-99

25000

20000

5000

0 Aug-99

211941

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-2DB

PCE

Total VOCs

Aug-01 Aug-03

MW-2IB

PCE

Total VOCs

Aug-01 Aug-03

IDIBI

ii EIDIISIBIG C

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-102S

6000

5000 PCE

Total VOCs

4000

O 3000

2000

1000

0 Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

MW-103D

16000

~ 14000 ugt 3- 12000 o

^ 10000

sect 8000

O 6000

4000

2000

PCE

Total VOCs

0Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

211941

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

G MW-103S

I I

ampo

12000

10000

E sectc

S

8000

6000

4000

2000

0Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

G I 6000

MW-104D

i 5000

PCE

Total VOCs

i i c

2000

1000

Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

E I

211941

cIccIG

IIBCccBcIc

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-1041

PCE Total VOCs

a 25000

0 20000

a 15000

10000

5000

0 Jan-OO Jan-01 Jan-02 Jan-03 Jan-04

MW-106D

3000

2500 PCE

Total VOCs

=sect 2000

o bullsect 1500

1000

500

0 Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

211941

c Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

c MW-106S

I PCE

Total VOCs

i

i Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

i

i i i E

C

211941 c

Response to EPA-DEP Comment 5 Dated March 312005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

iiw

EPA-DEP Comment 5

Comment 5 Matrix Diffusion The report as well as other proponents of matrix diffusion suggest that depletion of DNAPL (Section 5112 page 5-15) needs to be achieved While that might be the ideal the goal is to achieve performance standards and that goal may be attainable while there is residual contamination in the rock perhaps even DNAPL globules The low bedrock matrix porosity (page 1-15) the high permeability values (page 4-4) the relative flux of the groundwater (page 5-5) and the decrease in surface area and out of the mainstream pockets (appendix C-4) all suggest that the diffusion out of the rock matrix would be insubstantial relative to the regional flux of groundwater through the Site

Response The TI Evaluation Report does not explicitly consider or rely upon matrix diffusion as a basis for requesting a TI Waiver for a portion of the Hows Corner Site The technical literature provides documentation that matrix diffusion can be a significant process that affects chemical transport and groundwater remediation timeframes in unconsolidated and consolidated media including fractured rock (US EPA 1989 Freeze and Cherry 1979 Pankow and Cherry 1996 Fountain 1998) Back diffusion of contaminants from the matrix porosity of the fractured rock can prolong the time necessary to achieve groundwater cleanup goals particularly for compounds such as PCE for which the cleanup goal is a low concentration It is our expectation that matrix diffusion has occurred at the Hows Corner Site and that back diffusion of PCE from the rock matrix will also occur Although the extent to which matrix diffusion is occurring at the Hows Comer Site has not been determined and that lack of knowledge contributes to uncertainty regarding the cleanup times at the Site the effect of matrix diffusion is to lengthen rather than shorten the time required for remediation

REFERENCES

Fountain JC 1998 Technologies for Dense Nonaqueous Phase Liquid Source Zone Remediation Ground-Water Remediation Technologies Analysis Center Technology Evaluation Report TE-98-02 December

Freeze RA and Cherry JA 1979 Groundwater Prentice-Hall Inc Englewood Cliffs NJ 07632 p 410-412

Pankow J F and Cherry J A 1996 Dense Chlorinated Solvents Waterloo Press Portland OR 97291-1399 p 67-88

US EPA 1989 Transport and Fate of Contaminants in the Subsurface EPA6254-89019 p 17-18

Response to EPA Comment 5 050305doc 1 of 1 Woodard amp Curran (211941)

WOODARD amp CURRAN Maine Massachusetts New Hampshire Connecticut Florida Operational offices across the US 1-800-426-4262 www woodardcurran com

Page 30: SDMS DocID 251749 - Records Collections · 2020-06-13 · CORPORATE OFFICES: Maine, Massachusetts, New Hampshire, Connecticut New, York, Florida Engineering • Science • Operations

Table XX Orientation Permeability and Groundwater Sampling Results for Transmissive Features

2004 Drilling Program

Hows Corner Superfund Site Plymouth Maine

Borehole Geophisical Feature deptt raquoip True pip True Transraissive Log Feature (Feet) shy Degrees Azimuth Strike (tikely

Number raquo Possible) 22 522 57 54 324 Possible 25 656 40 82 352 Possible 32 871 59 151 61 Possible 33 883 53 185 275 Possible 34 895 7 175 85 Likely 35 899 53 90 0 Likely 36 902 49 184 274 Likely 37 923 9 175 85 Likely 38 927 42 206 296 Likely 39 934 48 167 77 Likely 40 939 26 180 90 Likely

PW-207 1 1846 33 167 77 Likely 4 2216 49 289 19 Possible 7 2819 59 265 355 Possible 11 3508 55 189 279 Possible 18 5332 43 305 35 Likely 19 5341 51 30 300 Likely 20 5421 20 254 344 Likely 21 5432 39 301 31 Likely 23 5559 52 302 32 Likely 25 6359 24 182 272 Possible 29 8049 77 231 321 Possible 30 8685 78 38 308 Likely 32 9334 29 194 284 Likely

NOTES

B = detected in lab blank

Hydraulic Conductivity

(cmsee) 944 E-07 353 E-06

614 E-05

209 E-05

568 E-06

821 E-05

866 E-06

213 E-05

bulltCE (ugL)

6300B

1300

5400

18000

12000

19000

Total VOCs (ug1)

68901

1410

5802

19234

13085

20354

PCE of Total VOCs

9 1

92

93

94

92

93

Response to EPA-DEP Comment 3 Dated March 312005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

lit

EPA-DEP Comment 3

Comment 3 The reported f values and resultant Kd values There remains doubt that the values used in the flushing model accurately reflect the propensity for PCE to sorb to the bedrock The ^ values presented in Appendix B may be unrealistically high because the bedrock samples may have contained organic carbon that was unavailable for sorption The reported f values are only qualitative estimates of the organic carbon content of the bedrock samples The Walkley and Black organic carbon measurement method is quick and simple but the results obtained cannot be considered quantitative because it requires a correction factor which often results in erroneous values it assumes the organic carbon has an average valence of zero oxidizable and reducible constituents such as chloride ferrous iron and manganese oxides interfere with the results and the errors introduced by interference are potentially greater when the organic carbon content is low at low f values it is not clear that organic carbon is controlling PCE sorption (Schwarzenbach and Westall 1981 Mackay et al 1986 Fetter 1999)

In order to derive a Kd-based retardation factor that is reasonable given the reported f values and the rapid advance of the PCE plume described on pages 4-11 and 4-12 the flushing model requires a bulk density to porosity ratio that is roughly two orders of magnitude higher than the actual ratio for the Hows Corner bedrock (page 4-4) This apparent discrepancy needs to be addressed

Response This comment raises several concerns about the collection and analysis of samples for fraction of organic carbon (f^) the quality of the resulting data and the implications of the use of those data for estimation of the retardation of groundwater contaminant movement Results of bedrock analysis for f were proposed in the TI Evaluation Work Plan for use in conjunction with groundwater contaminant concentrations and aquifer information to estimate cleanup times using the Batch Flushing model It is important to use accurate f values from representative bedrock in the Batch Flushing model in order to obtain reasonable estimates of the remedial time frame Because of the importance of accurate and representative results the TI Investigation field program was designed and conducted both to collect samples representative of the rock volume most likely to be in contact with contaminated groundwater and to analyze them using an appropriate refereed analytical method Five potential methods for evaluating f were identified Of the five methods the Walkey-Black method was selected because it has minimal method interferences and a sufficiently low detection limit as well as a long history of use in agronomy and contamination studies The PRP Group is pleased with the quality of the data obtained from the bedrock samples as represented by their precision and reproducibility

The first part of this comment relates to the determination of fraction of organic carbon (f^) values The several subparts of the first paragraph are addressed individually in items 1 through 5 below The second part of the comment regarding the resultant distribution coefficient (Kd) values is addressed separately as item 6 below

1 There remains doubt that the values used in the flushing model accurately reflect the propensity for PCE to sorb to the bedrock

bull The rock core samples used for f (gocg) analysis were from core immediately adjacent to fractures These rock core samples included the fracture surfaces themselves and rock core extending back less than 1 cm from the fractures Therefore the foe data reported in the TI Evaluation represents the f of bedrock through which groundwater will travel and to which PCE will adsorb Based on the careful selection of sample locations and the

Response to EPA Comment 3 050205doc 1 of 11 Woodard amp Curran (211941)

number of samples collected we are confident that the measured f values are representative of the f at points of contact for PCE with the bedrock it is these f values that determine the propensity of PCE to sorb to the bedrock

bull The samples of rock core collected for analysis of f originated from 19 different locations varying in depth from 11 to 90 feet Therefore it is very unlikely that the rock core samples were contaminated with extraneous organic carbon from above ground

2 The foc values presented in Appendix B may be unrealistically high because the bedrock samples may have contained organic carbon that was unavailable for sorption

bull As noted in response 1 the f data reported in Appendix B represents organic carbon primarily associated with the surface of fractures in the bedrock through which groundwater is most likely to travel Therefore it is this organic carbon that the contaminants in the groundwater will come in contact with and adsorb to in the fractured rock at the site

bull The chemical oxidation agents used in the Walkey-Black method oxidize the easily oxidizable organic carbon in the medium and the foe is calculated from the quantity of the agent consumed Therefore it is unlikely that the analysis of the bedrock samples measured organic carbon that was unavailable for sorption

3 The reported foc values are only qualitative estimates of the organic carbon content of the bedrock samples

bull The reported f values are accurate quantitative results Schumachers review of Methods for the determination of total organic carbon (TOC) in soils and sediments (NCEA-C-1282 EMASC-001 April 2002) identifies the Walkley-Black method which was used to analyze the reported foc values as the reference method for comparison to other methods for analyzing total organic carbon

bull Schumacher also points out that if anything the WalkJey-Black method may underestimate the total organic carbon in a sample due to possible incomplete oxidation of organic carbon Usually the incomplete oxidation of total organic carbon in environmental samples is corrected for by multiplying the measured foe by 130 (Walkley amp Black 1934 Schulte 1995)

bull When the f data in the TI Evaluation Report (WampC 2005) Appendix B (attached) are analyzed statistically the standard deviation of the f for the 19 samples analyzed is 174 of the average f Given this standard deviation the 95 confidence interval for this data ranged from a low of 000123 gocg to a high of 000253 gocgm

The labs Method of Detection Limit (MDL) for the f measured using the Walkley-Black method is 00001 gocg Therefore the average (000188 gocg) the mean (000185 gocg) and geometric mean (000187 gocg) of the f values for the rock core at Hows Corner are all statistically significantly greater than the MDL of the Walkley-Black method

In addition to the aforementioned statistical analysis of the foe data triplicate samples (n = 3) from the same rock core (including one sample from the 19 rock core samples) were

Response to EPA Comment 3 050205doc 2 of Woodard amp Curran (211941)

analyzed for their f to determine the repeatability of the Walkley-Black method The average the mean and the geometric mean of the f values of these replicate samples was 000162 gocg 000150 gocg and 000159 gocgm respectively The standard deviation of these measurements was 000039 gocg

4 The Walkley and Black organic carbon measurement method is quick and simple but the results obtained cannot be considered quantitative because it requires a correction factor which often results in erroneous values it assumes the organic carbon has an average valence of zero oxidizable and reducible constituents such as chloride ferrous iron and manganese oxides interfere with the results and the errors introduced by interference are potentially greater when the organic carbon content is low at low foc values it is not clear that organic carbon is controlling PCE sorption (Schwarzenbach and Westall 1981 Mackay et al 1986 Fetter 1999)

bull Schumachers review (NCEA-C-1282 EMASC-001 April 2002) of the Walkley-Black method identifies several potential problems with this analytical method that could occur if the analytical lab is not familiar with the nuances of the chemistry associated with this method Interestingly Schumachers review neglected one of the more important analytical steps required to avoid errors in quantifying f in samples where there might beNAPL

It is absolutely critical to eliminate any NAPL from rock core samples prior to using the Walkley-Black method to measure foe in such samples This was done by the lab (PTS Laboratories) that measured the foe in the rock core samples from Hows Corner The lab used the Dean-Stark method (solvent extraction) to remove all hydrocarbons (including PCE and other NAPLs) from the sample (PTS Laboratories) This extraction method does not interfere with the subsequent analysis of the natural organic carbon associated with the rock core

Subsequently the samples were dried at 150degC to a constant weight (normally 16 hours) This latter step oxidizes all inorganic minerals including ferrous bearing minerals to ferric oxides and precludes their interference during the oxidation of the samples with chromic acid This procedure completely eliminates any positive bias in the reported foc

data that might have occurred due to the presence of ferrous ions and other reduced minerals

bull As noted in Response 3 the incomplete oxidation of total organic carbon results in an underestimate of the f and is corrected for by multiplying the f by a correction factor of 130 (Walkley amp Black 1934 Schulte 1995) The fx data reported in the TI Evaluation was corrected accordingly by using this correction factor

bull Excess chloride (Cl~) in percent weight quantities as found in saline soils may interfere with the quantitative titration of reduced chromium (Walkley 1947) However given that the primary rock type at the Hows Corner site is phyllite it is highly unlikely that there was sufficient chloride in the rock core samples for this to occur

bull Manganese oxides may also interfere with the analysis of f through competing with the dichromate ion for any oxidizable carbon (Walkley 1947) However in such cases the reported f would be an underestimate of the f present in the rock core Walkley (1947)

Response to EPA Comment 3 050205doc 3 of 11 Woodard amp Curran (211941)

4

reported that in the case where the ratio of MnO2 to carbon is 85 to 1 the error in the carbon determinations would only be 0 to 6 percent

It may also be useful to compare the analysis of total organic carbon in a geologic matrix that contains high levels of manganese using EPA method 9060 to the Walkley-Black method Table 1 summarizes data provided by one of the PRPs that compares the analysis of total organic carbon in a geologic matrix that contains approximately 02 wgt manganese (approximately 03 wgt manganese oxide)

Table 1 Comparison of total organic carbon measured using the EPA- 9060 method and the Walkley-Black method

Laboratory EPA-9060 Method Walkley-Black Method A Ave 00226 gocg Not analyzed

Stdev 000251 gocg n = 5

B Ave 002219 gocg Ave 002050 gocg Stdev = 000316 gocg Stdev =000971 gocg

n= 10 n = 10

The similarity in the total organic carbon concentrations measured by these two different methods provides further confidence that the Walkley-Black method is a viable method for analysis of total organic carbon in the presence of manganese equivalent to at least 10 by weight of the total organic carbon

5 The Walkley and Black organic carbon measurement at lowf^ values it is not clear that organic carbon is controlling PCE sorption (Schwarzenbach and Westall 1981 Mackay et al 1986 Fetter 1999)

bull Schwarzenbach and Westalls (1981) paper states that f values of less than 0001 gocg should not be used in combination with Kow (octanol-water partition coefficients) values to calculate K^ values (solid phase partition coefficients) values for a specific contaminant It should be noted that the TI Evaluation did not use the f data to calculate the KQC from the Kow Instead as requested by the EPA the measured KOC value for PCE was used to calculate the retardation factor for this contaminant

bull Schwarzenbach et al (2003) stated more recently that Even at very low f values (ie foe = 0001 kgoc - kg1 solid) sorption to the organic components of a natural sorbent may still be the dominant mechanism in defining the adsorption of organic compounds to geological matrices

bull In 1985 M Piwoni from the US EPA Robert S Kerr Environmental Research Laboratory published a paper (Banerjee et al 1985) that showed that for very hydrophobic molecules TOC content of the sorbent will control sorption down to levels of organic carbon that defy quantitation Contaminants such as the PCE found in the groundwater at Hows Corner are in this category of compounds

Given the aforementioned reasons the f values reported in the TI Evaluation are accurate within the noted statistical limitations and will have a predictable impact upon the retardation of PCE during groundwater transport

Response to EPA Comment 3 050205doc 4 of 11 Woodard amp Curran (211941)

6 In order to derive a Kd-based retardation factor that is reasonable given the reported foc

values and the rapid advance of the PCE plume described on pages 4-11 and 4-12 the flushing model requires a bulk density to porosity ratio that is roughly two orders of magnitude higher than the actual ratio for the Hows Comer bedrock (page 4-4) This apparent discrepancy needs to be addressed

The apparent discrepancy of bulk density to porosity ratios is most likely due to the fact that the Batch Flushing Model was originally developed for a porous medium and is not directly applicable to fractured bedrock As stated in Appendix C (page C-4) of the Draft Technical Impracticability Evaluation Report in order to use the Batch Flushing Model to describe the transport of contaminated groundwater in fractured bedrock where the matrix porosity is insignificant it is more appropriate to use a fracture surface area to void space ratio to calculate the retardation factor (R) than a bulk density to porosity ratio (Freeze amp Cherry 1979)

Since it is impractical to determine the actual surface area to which contaminants can adsorb the Batch Flushing Model was used with two simplifying assumptions bull The Kd was calculated from the f and the K^ bull The bulk density to porosity ratio term in the Batch Flushing Model was constrained to range

from 4 to 10 the typical range of such ratios in porous media (Freeze amp Cherry 1979)

If one uses site specific bedrock bulk density and porosity values the bulk density to porosity ratio is several orders of magnitude greater (specifically 273 gcc bullbull 000165 (dimensionless) = 1654 gcc) than the range of ratios of 4 to 10 used in the Batch Flushing Model in the Draft Technical Impracticability Evaluation Report Constraining the bulk density to porosity ratio within the range of ratios of 4 to 10 results in significantly lower R value than would be obtained using specific bedrock bulk density and porosity values

In summary in bedrock where fractures are the primary porosity the bulk density to porosity ratio can vary considerably and will be a function of the number of fractures and the fracture aperture The calculated bulk density to porosity ratio will be inversely proportional to the porosity This means that in fractured rock with limited fracturing and smaller porosity the calculated bulk density to porosity ratio is greater and will result in a greater calculated retardation factor than in bedrock with more extensive fracturing and greater porosity Consequently the calculated retardation factor will be greater for bedrock with less surface area available for sorption than bedrock with greater surface area for sorption This is contrary to what actually occurs

4 Response to EPA Comment 3 050205doc 5 of 11 Woodard amp Curran (211941)

m

REFERENCES

Banerjee P MD Piwoni K Ebeid (1985) Sorption of organic contaminants to a low carbon subsurface core Chemosphere _14 1057-1067

Freeze RA JA Cherry (1979) Groundwater Prentice Hall Englewood Cliffs NJ pg 604

PTS Laboratories wwwptsgeolabscompdf files3TOCnotepdf

Schulte EE (1995) Recommended soil organic matter tests in Recommended Soil Testing Procedures for the Northeastern United States Northeastern Regional Publication No 493 Chapter 8

Schwarzenbach RP J Westall (1981) Transport of nonpolar organic compounds from surface water to groundwater Laboratory sorption studies Environ Sci Tech 15 1360-1367

Schwarzenbach RP PM Gschwend DM Imboden (2003) Environmental Organic Chemistry Wiley-Interscience pg 292 408 amp 412

Walkley A LA Black (1934) An examination of the Degtjareff method for determining soil organic matter and a proposed modification of the chromic acid titration method Soil Science 37 29-38

Walkley A (1947) A critical examination of a rapid method for determining organic carbon in soils - effect of variations in digestion conditions and of inorganic soil constituents Soil Science 63251-264

Woodard amp Curran Inc (WampC) 2005 Draft Technical Impracticability Evaluation Hows Corner Superfund Site Plymouth Maine January 2005

Response to EPA Comment 3 050205doc 6 of Woodard amp Curran (211941)

LIST OF ATTACHMENTS (Response to Comment 3)

Appendix B to Draft Technical Impracticability Evaluation Measurement of foe at Hows Corner (4 pages)

m

Response to EPA Comment 3 050205doc 7 of 11 Woodard amp Curran (211941)

Appendix B Measurement of foe of Rock Core at Hows Corner

There are two general approaches to measure the fraction of organic carbon (foe) in rock cores

bull Measurement of weight loss by ignition of organic matter bull Chemical oxidization of organic carbon to carbon dioxide and either

subsequent quantification of the oxidant used for the reaction or quantification of the carbon dioxide produced during this oxidation process

The weight loss method is subject to errors caused by volatilization of substances other than organic materials such as water hydroxides and mineral carbonates Quantification of foe by the weight loss method is particularly sensitive to the presence of carbonates in rock cores There are however weight loss methods that are designed to differentiate between organic carbon and the aforementioned interfering materials but they require considerable care and are less accurate at low foe values Hence the weight loss method was not well suited for measuring the foe of the rock core from Hows Corner

The chemical oxidation of organic carbon is much better suited for quantifying organic carbon in rock cores such as those from Hows Corner This method uses a strong chemical oxidant to oxidize organic carbon to carbon dioxide and then measures either the chemical oxidant used to oxidize the organic carbon or the quantity of carbon dioxide produced In addition this general approach is not subject to interference by volatilization of other constituents of the rock core

There are at least two such chemical oxidation methods

bull The method of Baccini which was described by Schwarzenbach amp Westall (1981) first acidifies the sample to eliminate interference by carbonates Then a strong oxidant is used to chemically oxidize the organic carbon to carbon dioxide The resulting carbon dioxide is subsequently reduced to methane and quantified using a flame ionization detector Unfortunately this method has not been described in detail in a referred journal Hence it is would not have been appropriate to use to characterize the foe in the Hows Corner rock core

bull The more commonly used method to quantify foe in rock core is the Walkley-Black method (1934) This method is preferred for RBCA and DODDOE projects and by the oil industry

The Walkley-Black method uses an excess of chromic acid to oxidize (digest) organic matter to carbon dioxide The remaining chromic acid that was not consumed during the oxidation of the organic carbon is then quantified by titration with ferrous sulfate The difference in chromic acid prior to and after the oxidation of the organic carbon represents the total chromic acid used to oxidize

Hows Corner TI Evaluation Page 1 January 13 2005 Appendix B

the organic carbon in the sample The latter can be calculated using the chemical stoichiometry of the reaction

The Walkley-Black method is very accurate for samples that contain less than 2 organic carbon matter The minimum detection limit (MDL) for the Walkley-Black method is 100 mgkg or an foe of 0001

Given the rock core at Hows Corner was expected to contain less than 2 organic carbon the Walkley-Black method was used to measure the foe from 19 different rock core samples collected from varying depths ranging from 11 to 90 feet

Table 1 provides a statistical summary of the aforementioned data

Table 1 Statistical summary of foe data from rock cores collected at varying depths

Statistical Parameter Calculated Value foe Minimum Detection Limit (MDL) 00010 Number of samples analyzed (n) 19 Average foe 00019 Median foe 00019 Geometric Mean foe 00019 Standard deviation of foe measurements 000033 Relative standard deviation 174 -+ 95 Confidence intervals 00012 to 00025

The data in Table 1 shows the following

bull The foe from the Hows Corner rock cores are statistically greater than the MDL of the Walkley-Black analytical method

bull The average and median values for the foe of the Hows Corner rock cores from varying depths are nearly identical indicating that there is little variability in the foe values in the source zone at the site

bull The standard deviation of these measurements is 000033 which is 174 of the average foe

bull The 95 confidence intervals of the foe of the rock core at Hows Corner are 00012 to 00025

The foe was also analyzed from three separate samples taken from the same rock core at a depth of 55 feet (Only one of these samples was included in the data summarized in Table 1) Table 2 shows the statistical repeatability of this type of analysis

Hows Corner TI Evaluation Page 2 January 13 2005 Appendix B

Table 2 Repeatability of analysis of foe from one rock core at 55 feet in depth

Statistical Parameter Calculated Value Number of samples analyzed (n) 3 Average foe 00016 Median foe 00015 Geometric Mean foe 00016 Standard deviation of foe measurements 000039 Relative standard deviation 240 -+ 95 Confidence intervals 00008 to 00024

The data in Table 2 shows the following

bull The percent relative standard deviation of these three analyses of foe from the same rock core at Hows Corner is 24

bull The 95 confidence interval of the foes measured in this particular rock core at Hows Conrer is 00008 to 00024

These results show that there is good repeatability in using the Walkley-Black method for analysis of the foe in the rock core at Hows Corner

References Schwarzenbach amp Westall (1981) Transport of nonpolar organic compounds from surface water to groundwater Laboratory sorption studies Environ Sci Tech 15 1360-1367

Walkley A I A Black (1934) An examination of Degtjareff method for determining soil organic matter and a proposed modification of the chromic acid titration method Soil Sci 37 29-37

Hows Corner Tl Evaluation Page S January 13 2005 Appendix B

Woodard and Curran PTS Laboratories PTS File No 34618

ORGANIC CARBON DATA (METHODOLOGY WALKLEY-BLACK)

PROJECT NAME PROJECT NO

SAMPLE ID

203-chip-13 203-chip-23 203-chip-27 203-chip-38 203-chip-42 203-chip-47 203-chip-52 203-chip-58 203-chip-69 203-chip-82 207-chip-11 207-chip-19 207-chip-24 207-chip-29 207-chip-35 207-chip-45 207-chip-55 207-chip-87 207-chip-90

207-chip-55 55-MS

55-MSMSD

Hows Corner NA

DEPTH ft

13 23 27 38 42 47 52 58 69 82 11 19 24 29 35 45 55 87 90

55 NA NA

MATRIX

Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip

Average Median

Geometric Mean Standard Deviation Relative Std Dev

+- 95 Confidence Interval n

Rock Chip Rock Chip Rock Chip

Average Median

Geometric Mean Standard Deviation Relative Std Dev

+- 95 Confidence Interval n

FRACTION ORGANIC CARBON

(gg)

170E-03 185E-03 185E-03 170E-03 240E-03 190E-03 230E-03 180E-03 170E-03 115E-03 195E-03 220E-03 220E-03 235E-03 135E-03 190E-03 205E-03 175E-03 160E-03

188E-03 185E-03 185E-03 327E-04

1739 123E-03 to

19

205E-03 130E-03 150E-03

162E-03 150E-03 159E-03 388E-04

2402 840E-04 to

3

2532E-03

2393E-03

Hows Corner Tl Evaluation Appendix B January 13 2005

Response to EPA-DEP Comment 4 Dated March 31 2005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

EPA-DEP Comment 4

Comment 4 Distribution of contaminants First the TI report seems based on the assertion that there is DNAPL at the source area yet it also appears to represent that the source area is small and the bedrock below 85 is competent (or less fractured) and less impacted by the release of contaminants Some of the confusion may result from using most recent data when that data is from several different sampling events over several years and there is no discernible difference in concentrations between shallow and deep bedrock or as in Section 421 where generally decreased generally increase generally similar and similar concentrations in four consecutive sentences leads to a muddled picture of the contaminant distribution

Second the report asserts that the distribution of contaminants over the entire plume has not changed with time but fails to support this conclusion with data again relying on data that is from different sampling dates for one composite representation

Response The likely presence of dense non-aqueous phase liquid (DNAPL) at the Hows Corner Site and the determination that the source area is small are not mutually exclusive and both are conclusions drawn from information obtained during field investigations The presence of DNAPL in the source area is based on the elevated concentrations of volatile organic compounds (VOCs) detected in the groundwater (WampC 2001 WampC 2002) The conclusion that the source area is small is based on the area in which VOCs in groundwater have been detected at concentrations that are considered to be indicative of the presence of DNAPL nearby Similarly the conclusion that fracture frequency decreases at depths greater than approximately 50 to 85 feet below ground surface was based on field observation during the RI field work The fact that zones with observed fractures exhibited higher hydraulic conductivities than zones without fractures coupled with the decreasing frequency of observed fractures with depth led to the conclusion that the hydraulic conductivity of the bulk rock decreases with depth

The most recent data from all wells were used to provide the maximum VOC data set size During the RI all of the previously-existing and then newly-installed monitoring wells were sampled along with several residential wells The RI sampling included up to 48 monitoring wells Subsequent to the RI and prior to the TI three rounds of monitoring were conducted to verify that the plume was stable 15 monitoring wells were sampled during each of the three rounds During the TI field investigation 29 wells were sampled for VOCs The sampled wells included all of the newly-installed wells and a subset of wells installed during the RI for a total of 29 monitoring wells By using most recent data VOC results from 53 monitoring wells were included in the evaluation (see table labeled Sampling Events for listing of monitoring wells) This approach was selected because there generally was little variation in the data from a particular location between years This is borne out by the attached individual plots of VOCs detected in shallow bedrock and deep bedrock for the Pre-ROD (December 1999January 2000) and Supplemental (May 2000) sampling events and for June 2001 January 2002 and April 2003 sampling events The Pre-ROD and Supplemental plots are similar to the subsequent plots from the 2001 2002 and 2003 sampling events

In addition to maps showing the spatial distribution of VOC data at a given time trend plots of the data from a particular location through time (attached) indicate that since the RI concentrations generally have been stable or have decreased Together the maps and trend plots and the data from which they were developed indicate that the distribution of contaminants over the entire plume has not changed appreciably with time

Response to EPA Comment 4 050305doc 1 of 26 Woodard amp Curran (211941)

REFERENCES

Woodard amp Curran Inc (WampC) 2001 Final Remedial Investigation Report Hows Corner Superfund Plymouth Maine July 2001

Woodard amp Curran Inc (WampC) 2002 Final Feasibility Study Report - Non-Source Area Groundwater Hows Corner Superfund Site Plymouth Maine Hows Corner Superfund Plymouth Maine July 2002

Response to EPA Comment 4 050305doc 2 of 26 Woodard amp Curran (211941)

LIST OF ATTACHMENTS (Response to Comment 4)

Table - Sampling Events 1999 - 2004 (2 pages)

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater Pre-ROD Sampling Event

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater Pre-ROD Sampling Event

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater Supplemental Sampling Event

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater Supplemental Sampling Event

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater June 2001

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater June 2001

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater January 2002

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater January 2002

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater April 2003

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater April 2003

Figure - Concentration Trends - Non-Source Area Wells MW-1B and MW-3B

Figure - Concentration Trends - Non-Source Area Wells MW-13DB and MW-16DB

Figure - Concentration Trends - Non-Source Area Wells MW-16IB and MW- 108D

Figure - Concentration Trends - Non-Source Area Wells MW-108S and MW-112D

Figure - Concentration Trends - Non-Source Area Wells MW-112S and MW-114D

Figure - Concentration Trends - Non-Source Area Wells MW-114S and MW-115D

Figure - Concentration Trends -Source Area Wells MW-2DB and MW-2IB

Figure - Concentration Trends -Source Area Wells MW-102S and MW-103D

Figure - Concentration Trends -Source Area Wells MW-103S and MW-104D

Figure - Concentration Trends -Source Area Wells MW-104I and MW-106D

Figure - Concentration Trends -Source Area Wells MW-106S

Response to EPA Comment 4 050305doc 3 of 26 Woodard amp Curran (211941)

I I

El I

II I I 1 I

I

i

Event Baseline Case ID WC-01 WC-01

Well Date Aug-99 Oct-99 LOT10 1 LOT1-1 1 LOT11-4 LOT14 1 LOT15 1 LOT15-1 1 LOT16 1 LOT16-1 1 LOT17 1 LOT18 1 LOT19 1 LOT2 LOT20 1 LOT21-10 1 LOT21-11 1 LOT21-12 1 LOT21-13 1 LOT21-14 1 LOT21-2 1 LOT21-5 1 LOT21-7 LOT21 -8 1 LOT21-9 1 LOT23 1 LOT24 1 LOT28-1 1 LOT28-2 1 LOT28-3 1 LOT28-4 1 LOT28W 1 LOT30 1 LOT30-1 1 LOT30-2 1 LOT30-3 1 LOT30-4 1 LOT30-5 LOT31 LOT35 1 LOT41 1 LOT42-1 1 LOT43-1 1 LOT43-4 1 LOT6-1 1 LOT67 1 LOT6-7 1 LOT6-8A 1 LOT6-8B 1 LOT80-1 1 LOT82 1 MW-101D MW-1011 MW-101S MW-102D MW-102S MW-103D MW-103S MW-104D MW-1041 MW-104S MW-105D MW-106D

Groundwater Sampling Location Summary 1999 - 2004xls

Sampling Events 1999-2004

Hows Corner Superfund Site Plymouth Maine

Supplemental 2001 2002 2003 Pumping 2004 Pre-ROD Rl Sampling Sampling Sampling Test Sampling WC-03 WC-09 WC-25 WC-30 WC-42B WC-56 WC-58 Dec-99 May-00 Jun-01 Jan-02 Apr-03 Sep-04 Sep-04

1

1 1 1

1 1 1 1 1

1 1

1

1 1

1 1 1

1 1 1 1 1

1

1 1

1 1 1 1

1

1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

Sampling Events 1999-2004

Hows Corner Super-fund Site Plymouth Maine

Supplemental 2001 2002 2003 Pumping Event Baseline Pre-ROD Rl Sampling Sampling Sampling Test

Case ID WC-01 WC-01 WC-03 WC-09 WC-25 WC-30 WC-42B WC-56

ll

Well Date Aug-99 Oct-99 Dec-99 May-00 Jun-01 Jan-02 Apr-03 Sep-04 MW-106S 1 1 1 1 1 MW-107D 1 1 MW-108D 1 1 1 1 1 MW-108S 1 1 1 1 1 MW-110D 1 1 MW-111D 1 1 MW-112D 1 1 1 1 1 MW-112S 1 1 1 1 1 MW-113D 1 1 MW-114D 1 1 1 1 1 MW-114S 1 1 1 1 1 MW-115D 1 1 1 1 1 MW-12DB 1 1 1 MW-12SB 1 1 1 MW-13DB 1 1 1 1 1 1 MW-13SB 1 1 1 MW-14DB 1 1 MW-14SO 1 1 MW-15DB 1 1 1 MW-15SB 1 1 1 MW-16DB 1 1 1 1 1 1 MW-16IB 1 1 1 1 1 1 MW-16SO 1 1 MW-17DO 1 1 1 MW-17SO 1 1 1 MW-1B 1 1 1 1 1 1 MW-203D MW-203S MW-204D MW-204S MW-205 MW-206D

I MW-206S MW-2DB 1 1 MW-2DDB 1 1 MW-2IB 1 1 1 1 1 1 MW-3B 1 1 1 1 1 1

I MW-4O 1 1 1 MW-5B 1 1

II MW-6DB 1 1 1 MW-6SB 1 1 1 MW-8DB 1 1 1 MW-8SB 1 1 1

II PW-207 1 SEEP-1 1 SUBTOTAL - RESIDENTIAL 44 25 0 2 0 3 0 SUBTOTAL - MONITORING 22 48 41 15 15 15 1

Total 3 66 73 41 17 15 18 1

I Included in most recent data

I Notes 1 - Overburden well not included in most recent data for plotting

2 - Tetrahydrofuran and 2-Butanone were the only two compounds detected in this well and are thought to be the result of well repair not included in most recent data for plotting

3 - Not included in most recent data for plotting

2004 Sampling

WC-58 Sep-04

1

1 1

1 1

1 1 1

1

1 1

1 1 1 1 1 1 1 1 1

1 1

1

0 29

29

Groundwatef Sampling Location Summary 1999 - 2004xls

I

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

monitoring well Figure 4-14 total VOC contour (ugl) - December 1999January 2000 Distribution of Total VOCs in

Note SW-113 is located downstream of SEEP-1 Shallow Bedrock Groundwater total concentration of detected VOCs ND= not detected these two locations were sampled during the Pre-ROD Sampling Event

Baseline Sampling Event in OctoberNovember 1999 Hows Corner Superfund Site Surface Water Sampling Location A Plymouth Maine Seep Sampling Location laquo- WOODARD ampCURRAN

995037wipri reportepa ri interim final feb 2001cadd drawingsfinalfig 4-14

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

0 300 600 I

FEET

Q residential well Figure 4-16 monitoring well Distribution of Total VOCs in

Deep Bedrock Groundwater total VOCs contour (ugl) Pre-ROD Sampling Event

active residential wells with lot number Hows Corner Superfund Site 2deg42deg Plymouth Maine total concentration of detected VOCs ND= not detected WOODARD ampCURRAN Enyinaaring bull Science bull Operations bull

995037wipri reportepa ri interim final feb 2001cadd drawingsfinalfig4mdash16

PLYMOUTH POND

PLYMOUTH POND

1 628Tl7MW-2bB 12135

PLYMOUTH POND

monitoring well Figure 4-20

V total VOC contour (ugl) - June 2000 Distribution of Total VOCs in Shallow Bedrock Groundwater

| 34 | total concentration of detected VOCs ND= not detected NA = not analyzed Supplemental Sampling Event Note SW-113 is located downstream of SEEP-1 Hows Corner Superfund Site

Surface Water Sampling Location these two locations were sampled during the Plymouth Maine Baseline Sampling Event in OctoberNovember 1999 Seep Sampling Location WOODARD amp CURRAN

Engineering bull Science - Operations bull 995037wipri reportepa ri interim final feb 2001 cadd drawingsfinalfig 4-20

residential well Figure 4-22 Distribution of Total VOCs in

monitoring well Deep Bedrock Groundwater

total VOCs contour (ugl) Supplemental Sampling Event

Hows Corner Superfund Site

total concentration of detected VOCs ND= not detected NA = not analyzed Plymouth Maine

WOODARD amp CURRAN

995037wipri reportepa-ri interim final feb 2001cadd drawingsfinalfig 4-22 Engineering bull Science - Operations bull

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

FEET

Shallow Monitoring Well

Deep Monitoring Well

C Detected Concentration ND = Not Detected Figure 1-XS Distribution of Total VOCs in Shallow Bedrock Groundwater

Pumping Well

17-Acre Property Boundary Concentration Contour (ugl)

June 2001 Hows Corner Superfund Site

Plymouth Maine WOODARDampCURRAN

-i^rhvj bull Scbncn bull Operations bull 211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0601 dwg04-20-05

PLYMOUTH POND Hopkins Road V

O

PLYMOUTH POND

PLYMOUTH POND

o

0 300 600 mdashfa FEET

Shallow Monitoring Well bull bull - 17-Acre Property Boundary Figure 1-XD

Deep Monitoring Well 1 I Detected Concentration ND = Not Detected Distribution of Total VOCs in Deep Bedrock Groundwater

-mf- Pumping Well June 2001 Residential Well Hows Corner Superfund Site

Plymouth Maine i h Surface Water Sampling Point

g WOODARD ampCURRAN _ ^ _ ^ _ _ yen_ rj i|Hlaquorlny bull Science bull Opt

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0601 dwg04-20-05

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

Shallow Monitoring Well

Deep Monitoring Well

Detected Concentration ND = Not Detected Figure 1-YS Distribution of Total VOCs in Shallow Bedrock Groundwater

Pumping Well

17-Acre Property Boundary Concentration Contour (ugl)

January 2002 Hows Corner Superfund Site

Plymouth Maine WOODARD amp CURRAN Engineering Science- Operations bull

211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0102dwg04-20-05

PLYMOUTH POND

PLYMOUTH POND

Site Pand^ laquoum-laquoBTuitaraquo tLV

vVlf-(

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0 300 600 ^ = FEET

Shallow Monitoring Well mdashbullbullbull 17-Acre Property Boundary Figure 1-YD - A - Deep Monitoring Well FT Detected Concentration ND = Not Detected Distribution of Total VOCs in

Deep Bedrock Groundwater Pumping Well January 2002 Residential Well Hows Corner Superfund Site

Plymouth Maine Surface Water Sampling Point

WOODARD ampCURRAN Engineering Sciencs- Operations bulli Si

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0102dwg04-20-05

- m j

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND j A O-shy

Shallow Monitoring Well E Detected Concentration ND = Not Detected Figure 1-ZS Distribution of Total VOCs in

Deep Monitoring Well Shallow Bedrock Groundwater

Pumping Well Hows Corner

April 2003 Superfund Site

17-Acre Property Boundary Plymouth Maine Concentration Contour (ugl) r WOODARD ampCURRAN

Engineering bull Science bull Operations bull 211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0403dwg04-20-05

s S pound

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- -

5 PLYMOUTH POND

Jo

FEET

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Deep Bedrock Groundwater Pumping Well April 2003

Q) Residential Well Hows Corner Superfund Site Plymouth Maine

(T) Surface Water Sampling Point WOODARD ampCURRAN poundKk EnginawtirKj bull Science - Operations bull

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0403dwg04-20-05

0 Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

B MW-1B

I 12000

PCE

B 10000 Total VOCs

I

i 2000

i 0 Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

c MW-3B

G 2000

1800

B PCE

1600 Total VOCs

1 I I E

il-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

G E

211941

El

I I z E

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Concentration Trends shy Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-13DB

Total VOCs

c i i c o

Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

MW-16DB

30

c i c c I c o

Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99

PCE

Total VOCs

Jul-01 Jul-03

211941

O bi

c Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

I MW-16IB

i 35

3

c Total VOCs

lt- 2 5

0 | gt

o

1 sectI

c c 0 4

Jul-90 Jul-92 Jul-94 Jul-96 Jul-98 Jul-00 Jul-02 Jul-04

I I MW-108D

I 12

PCE 10

Total VOCs c oc 3

E E I 0

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

E 211941

c Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

fi MW-108S

I I 40

PCE 35

Total VOCs

30

I f 26

20 I o

I 15

10

c Dec-99 Dec-00 Dec-01 Dec-02 Dec-03 I 0

I MW-112D

c 35 - imdash

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I

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0 Dec-99 Dec-OO Dec-01 Dec-02 Dec-03

211941

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Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-112S

08

PCE

Total VOCs 06

o 04

02

0 Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

MW-114D

o

12000

10000

8000

6000

PCE

Total VOCs

4000

2000

i

ccEIIc

i

i

E

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

211941

Con

cent

ratio

n (

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E Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

I MW-114S

E A5000 -- Total VOCs

- 4000

0 3000

2000

i 1000

i n shy

Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

MW-115D

c PCE

Total VOCs

c E

o

C c

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03 I 0

211941

IepoundII

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30000

25000

20000

o bullsect 15000 b

o 10000 U

5000

0 Aug-99

25000

20000

5000

0 Aug-99

211941

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-2DB

PCE

Total VOCs

Aug-01 Aug-03

MW-2IB

PCE

Total VOCs

Aug-01 Aug-03

IDIBI

ii EIDIISIBIG C

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-102S

6000

5000 PCE

Total VOCs

4000

O 3000

2000

1000

0 Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

MW-103D

16000

~ 14000 ugt 3- 12000 o

^ 10000

sect 8000

O 6000

4000

2000

PCE

Total VOCs

0Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

211941

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

G MW-103S

I I

ampo

12000

10000

E sectc

S

8000

6000

4000

2000

0Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

G I 6000

MW-104D

i 5000

PCE

Total VOCs

i i c

2000

1000

Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

E I

211941

cIccIG

IIBCccBcIc

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-1041

PCE Total VOCs

a 25000

0 20000

a 15000

10000

5000

0 Jan-OO Jan-01 Jan-02 Jan-03 Jan-04

MW-106D

3000

2500 PCE

Total VOCs

=sect 2000

o bullsect 1500

1000

500

0 Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

211941

c Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

c MW-106S

I PCE

Total VOCs

i

i Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

i

i i i E

C

211941 c

Response to EPA-DEP Comment 5 Dated March 312005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

iiw

EPA-DEP Comment 5

Comment 5 Matrix Diffusion The report as well as other proponents of matrix diffusion suggest that depletion of DNAPL (Section 5112 page 5-15) needs to be achieved While that might be the ideal the goal is to achieve performance standards and that goal may be attainable while there is residual contamination in the rock perhaps even DNAPL globules The low bedrock matrix porosity (page 1-15) the high permeability values (page 4-4) the relative flux of the groundwater (page 5-5) and the decrease in surface area and out of the mainstream pockets (appendix C-4) all suggest that the diffusion out of the rock matrix would be insubstantial relative to the regional flux of groundwater through the Site

Response The TI Evaluation Report does not explicitly consider or rely upon matrix diffusion as a basis for requesting a TI Waiver for a portion of the Hows Corner Site The technical literature provides documentation that matrix diffusion can be a significant process that affects chemical transport and groundwater remediation timeframes in unconsolidated and consolidated media including fractured rock (US EPA 1989 Freeze and Cherry 1979 Pankow and Cherry 1996 Fountain 1998) Back diffusion of contaminants from the matrix porosity of the fractured rock can prolong the time necessary to achieve groundwater cleanup goals particularly for compounds such as PCE for which the cleanup goal is a low concentration It is our expectation that matrix diffusion has occurred at the Hows Corner Site and that back diffusion of PCE from the rock matrix will also occur Although the extent to which matrix diffusion is occurring at the Hows Comer Site has not been determined and that lack of knowledge contributes to uncertainty regarding the cleanup times at the Site the effect of matrix diffusion is to lengthen rather than shorten the time required for remediation

REFERENCES

Fountain JC 1998 Technologies for Dense Nonaqueous Phase Liquid Source Zone Remediation Ground-Water Remediation Technologies Analysis Center Technology Evaluation Report TE-98-02 December

Freeze RA and Cherry JA 1979 Groundwater Prentice-Hall Inc Englewood Cliffs NJ 07632 p 410-412

Pankow J F and Cherry J A 1996 Dense Chlorinated Solvents Waterloo Press Portland OR 97291-1399 p 67-88

US EPA 1989 Transport and Fate of Contaminants in the Subsurface EPA6254-89019 p 17-18

Response to EPA Comment 5 050305doc 1 of 1 Woodard amp Curran (211941)

WOODARD amp CURRAN Maine Massachusetts New Hampshire Connecticut Florida Operational offices across the US 1-800-426-4262 www woodardcurran com

Page 31: SDMS DocID 251749 - Records Collections · 2020-06-13 · CORPORATE OFFICES: Maine, Massachusetts, New Hampshire, Connecticut New, York, Florida Engineering • Science • Operations

Response to EPA-DEP Comment 3 Dated March 312005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

lit

EPA-DEP Comment 3

Comment 3 The reported f values and resultant Kd values There remains doubt that the values used in the flushing model accurately reflect the propensity for PCE to sorb to the bedrock The ^ values presented in Appendix B may be unrealistically high because the bedrock samples may have contained organic carbon that was unavailable for sorption The reported f values are only qualitative estimates of the organic carbon content of the bedrock samples The Walkley and Black organic carbon measurement method is quick and simple but the results obtained cannot be considered quantitative because it requires a correction factor which often results in erroneous values it assumes the organic carbon has an average valence of zero oxidizable and reducible constituents such as chloride ferrous iron and manganese oxides interfere with the results and the errors introduced by interference are potentially greater when the organic carbon content is low at low f values it is not clear that organic carbon is controlling PCE sorption (Schwarzenbach and Westall 1981 Mackay et al 1986 Fetter 1999)

In order to derive a Kd-based retardation factor that is reasonable given the reported f values and the rapid advance of the PCE plume described on pages 4-11 and 4-12 the flushing model requires a bulk density to porosity ratio that is roughly two orders of magnitude higher than the actual ratio for the Hows Corner bedrock (page 4-4) This apparent discrepancy needs to be addressed

Response This comment raises several concerns about the collection and analysis of samples for fraction of organic carbon (f^) the quality of the resulting data and the implications of the use of those data for estimation of the retardation of groundwater contaminant movement Results of bedrock analysis for f were proposed in the TI Evaluation Work Plan for use in conjunction with groundwater contaminant concentrations and aquifer information to estimate cleanup times using the Batch Flushing model It is important to use accurate f values from representative bedrock in the Batch Flushing model in order to obtain reasonable estimates of the remedial time frame Because of the importance of accurate and representative results the TI Investigation field program was designed and conducted both to collect samples representative of the rock volume most likely to be in contact with contaminated groundwater and to analyze them using an appropriate refereed analytical method Five potential methods for evaluating f were identified Of the five methods the Walkey-Black method was selected because it has minimal method interferences and a sufficiently low detection limit as well as a long history of use in agronomy and contamination studies The PRP Group is pleased with the quality of the data obtained from the bedrock samples as represented by their precision and reproducibility

The first part of this comment relates to the determination of fraction of organic carbon (f^) values The several subparts of the first paragraph are addressed individually in items 1 through 5 below The second part of the comment regarding the resultant distribution coefficient (Kd) values is addressed separately as item 6 below

1 There remains doubt that the values used in the flushing model accurately reflect the propensity for PCE to sorb to the bedrock

bull The rock core samples used for f (gocg) analysis were from core immediately adjacent to fractures These rock core samples included the fracture surfaces themselves and rock core extending back less than 1 cm from the fractures Therefore the foe data reported in the TI Evaluation represents the f of bedrock through which groundwater will travel and to which PCE will adsorb Based on the careful selection of sample locations and the

Response to EPA Comment 3 050205doc 1 of 11 Woodard amp Curran (211941)

number of samples collected we are confident that the measured f values are representative of the f at points of contact for PCE with the bedrock it is these f values that determine the propensity of PCE to sorb to the bedrock

bull The samples of rock core collected for analysis of f originated from 19 different locations varying in depth from 11 to 90 feet Therefore it is very unlikely that the rock core samples were contaminated with extraneous organic carbon from above ground

2 The foc values presented in Appendix B may be unrealistically high because the bedrock samples may have contained organic carbon that was unavailable for sorption

bull As noted in response 1 the f data reported in Appendix B represents organic carbon primarily associated with the surface of fractures in the bedrock through which groundwater is most likely to travel Therefore it is this organic carbon that the contaminants in the groundwater will come in contact with and adsorb to in the fractured rock at the site

bull The chemical oxidation agents used in the Walkey-Black method oxidize the easily oxidizable organic carbon in the medium and the foe is calculated from the quantity of the agent consumed Therefore it is unlikely that the analysis of the bedrock samples measured organic carbon that was unavailable for sorption

3 The reported foc values are only qualitative estimates of the organic carbon content of the bedrock samples

bull The reported f values are accurate quantitative results Schumachers review of Methods for the determination of total organic carbon (TOC) in soils and sediments (NCEA-C-1282 EMASC-001 April 2002) identifies the Walkley-Black method which was used to analyze the reported foc values as the reference method for comparison to other methods for analyzing total organic carbon

bull Schumacher also points out that if anything the WalkJey-Black method may underestimate the total organic carbon in a sample due to possible incomplete oxidation of organic carbon Usually the incomplete oxidation of total organic carbon in environmental samples is corrected for by multiplying the measured foe by 130 (Walkley amp Black 1934 Schulte 1995)

bull When the f data in the TI Evaluation Report (WampC 2005) Appendix B (attached) are analyzed statistically the standard deviation of the f for the 19 samples analyzed is 174 of the average f Given this standard deviation the 95 confidence interval for this data ranged from a low of 000123 gocg to a high of 000253 gocgm

The labs Method of Detection Limit (MDL) for the f measured using the Walkley-Black method is 00001 gocg Therefore the average (000188 gocg) the mean (000185 gocg) and geometric mean (000187 gocg) of the f values for the rock core at Hows Corner are all statistically significantly greater than the MDL of the Walkley-Black method

In addition to the aforementioned statistical analysis of the foe data triplicate samples (n = 3) from the same rock core (including one sample from the 19 rock core samples) were

Response to EPA Comment 3 050205doc 2 of Woodard amp Curran (211941)

analyzed for their f to determine the repeatability of the Walkley-Black method The average the mean and the geometric mean of the f values of these replicate samples was 000162 gocg 000150 gocg and 000159 gocgm respectively The standard deviation of these measurements was 000039 gocg

4 The Walkley and Black organic carbon measurement method is quick and simple but the results obtained cannot be considered quantitative because it requires a correction factor which often results in erroneous values it assumes the organic carbon has an average valence of zero oxidizable and reducible constituents such as chloride ferrous iron and manganese oxides interfere with the results and the errors introduced by interference are potentially greater when the organic carbon content is low at low foc values it is not clear that organic carbon is controlling PCE sorption (Schwarzenbach and Westall 1981 Mackay et al 1986 Fetter 1999)

bull Schumachers review (NCEA-C-1282 EMASC-001 April 2002) of the Walkley-Black method identifies several potential problems with this analytical method that could occur if the analytical lab is not familiar with the nuances of the chemistry associated with this method Interestingly Schumachers review neglected one of the more important analytical steps required to avoid errors in quantifying f in samples where there might beNAPL

It is absolutely critical to eliminate any NAPL from rock core samples prior to using the Walkley-Black method to measure foe in such samples This was done by the lab (PTS Laboratories) that measured the foe in the rock core samples from Hows Corner The lab used the Dean-Stark method (solvent extraction) to remove all hydrocarbons (including PCE and other NAPLs) from the sample (PTS Laboratories) This extraction method does not interfere with the subsequent analysis of the natural organic carbon associated with the rock core

Subsequently the samples were dried at 150degC to a constant weight (normally 16 hours) This latter step oxidizes all inorganic minerals including ferrous bearing minerals to ferric oxides and precludes their interference during the oxidation of the samples with chromic acid This procedure completely eliminates any positive bias in the reported foc

data that might have occurred due to the presence of ferrous ions and other reduced minerals

bull As noted in Response 3 the incomplete oxidation of total organic carbon results in an underestimate of the f and is corrected for by multiplying the f by a correction factor of 130 (Walkley amp Black 1934 Schulte 1995) The fx data reported in the TI Evaluation was corrected accordingly by using this correction factor

bull Excess chloride (Cl~) in percent weight quantities as found in saline soils may interfere with the quantitative titration of reduced chromium (Walkley 1947) However given that the primary rock type at the Hows Corner site is phyllite it is highly unlikely that there was sufficient chloride in the rock core samples for this to occur

bull Manganese oxides may also interfere with the analysis of f through competing with the dichromate ion for any oxidizable carbon (Walkley 1947) However in such cases the reported f would be an underestimate of the f present in the rock core Walkley (1947)

Response to EPA Comment 3 050205doc 3 of 11 Woodard amp Curran (211941)

4

reported that in the case where the ratio of MnO2 to carbon is 85 to 1 the error in the carbon determinations would only be 0 to 6 percent

It may also be useful to compare the analysis of total organic carbon in a geologic matrix that contains high levels of manganese using EPA method 9060 to the Walkley-Black method Table 1 summarizes data provided by one of the PRPs that compares the analysis of total organic carbon in a geologic matrix that contains approximately 02 wgt manganese (approximately 03 wgt manganese oxide)

Table 1 Comparison of total organic carbon measured using the EPA- 9060 method and the Walkley-Black method

Laboratory EPA-9060 Method Walkley-Black Method A Ave 00226 gocg Not analyzed

Stdev 000251 gocg n = 5

B Ave 002219 gocg Ave 002050 gocg Stdev = 000316 gocg Stdev =000971 gocg

n= 10 n = 10

The similarity in the total organic carbon concentrations measured by these two different methods provides further confidence that the Walkley-Black method is a viable method for analysis of total organic carbon in the presence of manganese equivalent to at least 10 by weight of the total organic carbon

5 The Walkley and Black organic carbon measurement at lowf^ values it is not clear that organic carbon is controlling PCE sorption (Schwarzenbach and Westall 1981 Mackay et al 1986 Fetter 1999)

bull Schwarzenbach and Westalls (1981) paper states that f values of less than 0001 gocg should not be used in combination with Kow (octanol-water partition coefficients) values to calculate K^ values (solid phase partition coefficients) values for a specific contaminant It should be noted that the TI Evaluation did not use the f data to calculate the KQC from the Kow Instead as requested by the EPA the measured KOC value for PCE was used to calculate the retardation factor for this contaminant

bull Schwarzenbach et al (2003) stated more recently that Even at very low f values (ie foe = 0001 kgoc - kg1 solid) sorption to the organic components of a natural sorbent may still be the dominant mechanism in defining the adsorption of organic compounds to geological matrices

bull In 1985 M Piwoni from the US EPA Robert S Kerr Environmental Research Laboratory published a paper (Banerjee et al 1985) that showed that for very hydrophobic molecules TOC content of the sorbent will control sorption down to levels of organic carbon that defy quantitation Contaminants such as the PCE found in the groundwater at Hows Corner are in this category of compounds

Given the aforementioned reasons the f values reported in the TI Evaluation are accurate within the noted statistical limitations and will have a predictable impact upon the retardation of PCE during groundwater transport

Response to EPA Comment 3 050205doc 4 of 11 Woodard amp Curran (211941)

6 In order to derive a Kd-based retardation factor that is reasonable given the reported foc

values and the rapid advance of the PCE plume described on pages 4-11 and 4-12 the flushing model requires a bulk density to porosity ratio that is roughly two orders of magnitude higher than the actual ratio for the Hows Comer bedrock (page 4-4) This apparent discrepancy needs to be addressed

The apparent discrepancy of bulk density to porosity ratios is most likely due to the fact that the Batch Flushing Model was originally developed for a porous medium and is not directly applicable to fractured bedrock As stated in Appendix C (page C-4) of the Draft Technical Impracticability Evaluation Report in order to use the Batch Flushing Model to describe the transport of contaminated groundwater in fractured bedrock where the matrix porosity is insignificant it is more appropriate to use a fracture surface area to void space ratio to calculate the retardation factor (R) than a bulk density to porosity ratio (Freeze amp Cherry 1979)

Since it is impractical to determine the actual surface area to which contaminants can adsorb the Batch Flushing Model was used with two simplifying assumptions bull The Kd was calculated from the f and the K^ bull The bulk density to porosity ratio term in the Batch Flushing Model was constrained to range

from 4 to 10 the typical range of such ratios in porous media (Freeze amp Cherry 1979)

If one uses site specific bedrock bulk density and porosity values the bulk density to porosity ratio is several orders of magnitude greater (specifically 273 gcc bullbull 000165 (dimensionless) = 1654 gcc) than the range of ratios of 4 to 10 used in the Batch Flushing Model in the Draft Technical Impracticability Evaluation Report Constraining the bulk density to porosity ratio within the range of ratios of 4 to 10 results in significantly lower R value than would be obtained using specific bedrock bulk density and porosity values

In summary in bedrock where fractures are the primary porosity the bulk density to porosity ratio can vary considerably and will be a function of the number of fractures and the fracture aperture The calculated bulk density to porosity ratio will be inversely proportional to the porosity This means that in fractured rock with limited fracturing and smaller porosity the calculated bulk density to porosity ratio is greater and will result in a greater calculated retardation factor than in bedrock with more extensive fracturing and greater porosity Consequently the calculated retardation factor will be greater for bedrock with less surface area available for sorption than bedrock with greater surface area for sorption This is contrary to what actually occurs

4 Response to EPA Comment 3 050205doc 5 of 11 Woodard amp Curran (211941)

m

REFERENCES

Banerjee P MD Piwoni K Ebeid (1985) Sorption of organic contaminants to a low carbon subsurface core Chemosphere _14 1057-1067

Freeze RA JA Cherry (1979) Groundwater Prentice Hall Englewood Cliffs NJ pg 604

PTS Laboratories wwwptsgeolabscompdf files3TOCnotepdf

Schulte EE (1995) Recommended soil organic matter tests in Recommended Soil Testing Procedures for the Northeastern United States Northeastern Regional Publication No 493 Chapter 8

Schwarzenbach RP J Westall (1981) Transport of nonpolar organic compounds from surface water to groundwater Laboratory sorption studies Environ Sci Tech 15 1360-1367

Schwarzenbach RP PM Gschwend DM Imboden (2003) Environmental Organic Chemistry Wiley-Interscience pg 292 408 amp 412

Walkley A LA Black (1934) An examination of the Degtjareff method for determining soil organic matter and a proposed modification of the chromic acid titration method Soil Science 37 29-38

Walkley A (1947) A critical examination of a rapid method for determining organic carbon in soils - effect of variations in digestion conditions and of inorganic soil constituents Soil Science 63251-264

Woodard amp Curran Inc (WampC) 2005 Draft Technical Impracticability Evaluation Hows Corner Superfund Site Plymouth Maine January 2005

Response to EPA Comment 3 050205doc 6 of Woodard amp Curran (211941)

LIST OF ATTACHMENTS (Response to Comment 3)

Appendix B to Draft Technical Impracticability Evaluation Measurement of foe at Hows Corner (4 pages)

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Response to EPA Comment 3 050205doc 7 of 11 Woodard amp Curran (211941)

Appendix B Measurement of foe of Rock Core at Hows Corner

There are two general approaches to measure the fraction of organic carbon (foe) in rock cores

bull Measurement of weight loss by ignition of organic matter bull Chemical oxidization of organic carbon to carbon dioxide and either

subsequent quantification of the oxidant used for the reaction or quantification of the carbon dioxide produced during this oxidation process

The weight loss method is subject to errors caused by volatilization of substances other than organic materials such as water hydroxides and mineral carbonates Quantification of foe by the weight loss method is particularly sensitive to the presence of carbonates in rock cores There are however weight loss methods that are designed to differentiate between organic carbon and the aforementioned interfering materials but they require considerable care and are less accurate at low foe values Hence the weight loss method was not well suited for measuring the foe of the rock core from Hows Corner

The chemical oxidation of organic carbon is much better suited for quantifying organic carbon in rock cores such as those from Hows Corner This method uses a strong chemical oxidant to oxidize organic carbon to carbon dioxide and then measures either the chemical oxidant used to oxidize the organic carbon or the quantity of carbon dioxide produced In addition this general approach is not subject to interference by volatilization of other constituents of the rock core

There are at least two such chemical oxidation methods

bull The method of Baccini which was described by Schwarzenbach amp Westall (1981) first acidifies the sample to eliminate interference by carbonates Then a strong oxidant is used to chemically oxidize the organic carbon to carbon dioxide The resulting carbon dioxide is subsequently reduced to methane and quantified using a flame ionization detector Unfortunately this method has not been described in detail in a referred journal Hence it is would not have been appropriate to use to characterize the foe in the Hows Corner rock core

bull The more commonly used method to quantify foe in rock core is the Walkley-Black method (1934) This method is preferred for RBCA and DODDOE projects and by the oil industry

The Walkley-Black method uses an excess of chromic acid to oxidize (digest) organic matter to carbon dioxide The remaining chromic acid that was not consumed during the oxidation of the organic carbon is then quantified by titration with ferrous sulfate The difference in chromic acid prior to and after the oxidation of the organic carbon represents the total chromic acid used to oxidize

Hows Corner TI Evaluation Page 1 January 13 2005 Appendix B

the organic carbon in the sample The latter can be calculated using the chemical stoichiometry of the reaction

The Walkley-Black method is very accurate for samples that contain less than 2 organic carbon matter The minimum detection limit (MDL) for the Walkley-Black method is 100 mgkg or an foe of 0001

Given the rock core at Hows Corner was expected to contain less than 2 organic carbon the Walkley-Black method was used to measure the foe from 19 different rock core samples collected from varying depths ranging from 11 to 90 feet

Table 1 provides a statistical summary of the aforementioned data

Table 1 Statistical summary of foe data from rock cores collected at varying depths

Statistical Parameter Calculated Value foe Minimum Detection Limit (MDL) 00010 Number of samples analyzed (n) 19 Average foe 00019 Median foe 00019 Geometric Mean foe 00019 Standard deviation of foe measurements 000033 Relative standard deviation 174 -+ 95 Confidence intervals 00012 to 00025

The data in Table 1 shows the following

bull The foe from the Hows Corner rock cores are statistically greater than the MDL of the Walkley-Black analytical method

bull The average and median values for the foe of the Hows Corner rock cores from varying depths are nearly identical indicating that there is little variability in the foe values in the source zone at the site

bull The standard deviation of these measurements is 000033 which is 174 of the average foe

bull The 95 confidence intervals of the foe of the rock core at Hows Corner are 00012 to 00025

The foe was also analyzed from three separate samples taken from the same rock core at a depth of 55 feet (Only one of these samples was included in the data summarized in Table 1) Table 2 shows the statistical repeatability of this type of analysis

Hows Corner TI Evaluation Page 2 January 13 2005 Appendix B

Table 2 Repeatability of analysis of foe from one rock core at 55 feet in depth

Statistical Parameter Calculated Value Number of samples analyzed (n) 3 Average foe 00016 Median foe 00015 Geometric Mean foe 00016 Standard deviation of foe measurements 000039 Relative standard deviation 240 -+ 95 Confidence intervals 00008 to 00024

The data in Table 2 shows the following

bull The percent relative standard deviation of these three analyses of foe from the same rock core at Hows Corner is 24

bull The 95 confidence interval of the foes measured in this particular rock core at Hows Conrer is 00008 to 00024

These results show that there is good repeatability in using the Walkley-Black method for analysis of the foe in the rock core at Hows Corner

References Schwarzenbach amp Westall (1981) Transport of nonpolar organic compounds from surface water to groundwater Laboratory sorption studies Environ Sci Tech 15 1360-1367

Walkley A I A Black (1934) An examination of Degtjareff method for determining soil organic matter and a proposed modification of the chromic acid titration method Soil Sci 37 29-37

Hows Corner Tl Evaluation Page S January 13 2005 Appendix B

Woodard and Curran PTS Laboratories PTS File No 34618

ORGANIC CARBON DATA (METHODOLOGY WALKLEY-BLACK)

PROJECT NAME PROJECT NO

SAMPLE ID

203-chip-13 203-chip-23 203-chip-27 203-chip-38 203-chip-42 203-chip-47 203-chip-52 203-chip-58 203-chip-69 203-chip-82 207-chip-11 207-chip-19 207-chip-24 207-chip-29 207-chip-35 207-chip-45 207-chip-55 207-chip-87 207-chip-90

207-chip-55 55-MS

55-MSMSD

Hows Corner NA

DEPTH ft

13 23 27 38 42 47 52 58 69 82 11 19 24 29 35 45 55 87 90

55 NA NA

MATRIX

Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip

Average Median

Geometric Mean Standard Deviation Relative Std Dev

+- 95 Confidence Interval n

Rock Chip Rock Chip Rock Chip

Average Median

Geometric Mean Standard Deviation Relative Std Dev

+- 95 Confidence Interval n

FRACTION ORGANIC CARBON

(gg)

170E-03 185E-03 185E-03 170E-03 240E-03 190E-03 230E-03 180E-03 170E-03 115E-03 195E-03 220E-03 220E-03 235E-03 135E-03 190E-03 205E-03 175E-03 160E-03

188E-03 185E-03 185E-03 327E-04

1739 123E-03 to

19

205E-03 130E-03 150E-03

162E-03 150E-03 159E-03 388E-04

2402 840E-04 to

3

2532E-03

2393E-03

Hows Corner Tl Evaluation Appendix B January 13 2005

Response to EPA-DEP Comment 4 Dated March 31 2005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

EPA-DEP Comment 4

Comment 4 Distribution of contaminants First the TI report seems based on the assertion that there is DNAPL at the source area yet it also appears to represent that the source area is small and the bedrock below 85 is competent (or less fractured) and less impacted by the release of contaminants Some of the confusion may result from using most recent data when that data is from several different sampling events over several years and there is no discernible difference in concentrations between shallow and deep bedrock or as in Section 421 where generally decreased generally increase generally similar and similar concentrations in four consecutive sentences leads to a muddled picture of the contaminant distribution

Second the report asserts that the distribution of contaminants over the entire plume has not changed with time but fails to support this conclusion with data again relying on data that is from different sampling dates for one composite representation

Response The likely presence of dense non-aqueous phase liquid (DNAPL) at the Hows Corner Site and the determination that the source area is small are not mutually exclusive and both are conclusions drawn from information obtained during field investigations The presence of DNAPL in the source area is based on the elevated concentrations of volatile organic compounds (VOCs) detected in the groundwater (WampC 2001 WampC 2002) The conclusion that the source area is small is based on the area in which VOCs in groundwater have been detected at concentrations that are considered to be indicative of the presence of DNAPL nearby Similarly the conclusion that fracture frequency decreases at depths greater than approximately 50 to 85 feet below ground surface was based on field observation during the RI field work The fact that zones with observed fractures exhibited higher hydraulic conductivities than zones without fractures coupled with the decreasing frequency of observed fractures with depth led to the conclusion that the hydraulic conductivity of the bulk rock decreases with depth

The most recent data from all wells were used to provide the maximum VOC data set size During the RI all of the previously-existing and then newly-installed monitoring wells were sampled along with several residential wells The RI sampling included up to 48 monitoring wells Subsequent to the RI and prior to the TI three rounds of monitoring were conducted to verify that the plume was stable 15 monitoring wells were sampled during each of the three rounds During the TI field investigation 29 wells were sampled for VOCs The sampled wells included all of the newly-installed wells and a subset of wells installed during the RI for a total of 29 monitoring wells By using most recent data VOC results from 53 monitoring wells were included in the evaluation (see table labeled Sampling Events for listing of monitoring wells) This approach was selected because there generally was little variation in the data from a particular location between years This is borne out by the attached individual plots of VOCs detected in shallow bedrock and deep bedrock for the Pre-ROD (December 1999January 2000) and Supplemental (May 2000) sampling events and for June 2001 January 2002 and April 2003 sampling events The Pre-ROD and Supplemental plots are similar to the subsequent plots from the 2001 2002 and 2003 sampling events

In addition to maps showing the spatial distribution of VOC data at a given time trend plots of the data from a particular location through time (attached) indicate that since the RI concentrations generally have been stable or have decreased Together the maps and trend plots and the data from which they were developed indicate that the distribution of contaminants over the entire plume has not changed appreciably with time

Response to EPA Comment 4 050305doc 1 of 26 Woodard amp Curran (211941)

REFERENCES

Woodard amp Curran Inc (WampC) 2001 Final Remedial Investigation Report Hows Corner Superfund Plymouth Maine July 2001

Woodard amp Curran Inc (WampC) 2002 Final Feasibility Study Report - Non-Source Area Groundwater Hows Corner Superfund Site Plymouth Maine Hows Corner Superfund Plymouth Maine July 2002

Response to EPA Comment 4 050305doc 2 of 26 Woodard amp Curran (211941)

LIST OF ATTACHMENTS (Response to Comment 4)

Table - Sampling Events 1999 - 2004 (2 pages)

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater Pre-ROD Sampling Event

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater Pre-ROD Sampling Event

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater Supplemental Sampling Event

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater Supplemental Sampling Event

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater June 2001

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater June 2001

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater January 2002

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater January 2002

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater April 2003

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater April 2003

Figure - Concentration Trends - Non-Source Area Wells MW-1B and MW-3B

Figure - Concentration Trends - Non-Source Area Wells MW-13DB and MW-16DB

Figure - Concentration Trends - Non-Source Area Wells MW-16IB and MW- 108D

Figure - Concentration Trends - Non-Source Area Wells MW-108S and MW-112D

Figure - Concentration Trends - Non-Source Area Wells MW-112S and MW-114D

Figure - Concentration Trends - Non-Source Area Wells MW-114S and MW-115D

Figure - Concentration Trends -Source Area Wells MW-2DB and MW-2IB

Figure - Concentration Trends -Source Area Wells MW-102S and MW-103D

Figure - Concentration Trends -Source Area Wells MW-103S and MW-104D

Figure - Concentration Trends -Source Area Wells MW-104I and MW-106D

Figure - Concentration Trends -Source Area Wells MW-106S

Response to EPA Comment 4 050305doc 3 of 26 Woodard amp Curran (211941)

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El I

II I I 1 I

I

i

Event Baseline Case ID WC-01 WC-01

Well Date Aug-99 Oct-99 LOT10 1 LOT1-1 1 LOT11-4 LOT14 1 LOT15 1 LOT15-1 1 LOT16 1 LOT16-1 1 LOT17 1 LOT18 1 LOT19 1 LOT2 LOT20 1 LOT21-10 1 LOT21-11 1 LOT21-12 1 LOT21-13 1 LOT21-14 1 LOT21-2 1 LOT21-5 1 LOT21-7 LOT21 -8 1 LOT21-9 1 LOT23 1 LOT24 1 LOT28-1 1 LOT28-2 1 LOT28-3 1 LOT28-4 1 LOT28W 1 LOT30 1 LOT30-1 1 LOT30-2 1 LOT30-3 1 LOT30-4 1 LOT30-5 LOT31 LOT35 1 LOT41 1 LOT42-1 1 LOT43-1 1 LOT43-4 1 LOT6-1 1 LOT67 1 LOT6-7 1 LOT6-8A 1 LOT6-8B 1 LOT80-1 1 LOT82 1 MW-101D MW-1011 MW-101S MW-102D MW-102S MW-103D MW-103S MW-104D MW-1041 MW-104S MW-105D MW-106D

Groundwater Sampling Location Summary 1999 - 2004xls

Sampling Events 1999-2004

Hows Corner Superfund Site Plymouth Maine

Supplemental 2001 2002 2003 Pumping 2004 Pre-ROD Rl Sampling Sampling Sampling Test Sampling WC-03 WC-09 WC-25 WC-30 WC-42B WC-56 WC-58 Dec-99 May-00 Jun-01 Jan-02 Apr-03 Sep-04 Sep-04

1

1 1 1

1 1 1 1 1

1 1

1

1 1

1 1 1

1 1 1 1 1

1

1 1

1 1 1 1

1

1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

Sampling Events 1999-2004

Hows Corner Super-fund Site Plymouth Maine

Supplemental 2001 2002 2003 Pumping Event Baseline Pre-ROD Rl Sampling Sampling Sampling Test

Case ID WC-01 WC-01 WC-03 WC-09 WC-25 WC-30 WC-42B WC-56

ll

Well Date Aug-99 Oct-99 Dec-99 May-00 Jun-01 Jan-02 Apr-03 Sep-04 MW-106S 1 1 1 1 1 MW-107D 1 1 MW-108D 1 1 1 1 1 MW-108S 1 1 1 1 1 MW-110D 1 1 MW-111D 1 1 MW-112D 1 1 1 1 1 MW-112S 1 1 1 1 1 MW-113D 1 1 MW-114D 1 1 1 1 1 MW-114S 1 1 1 1 1 MW-115D 1 1 1 1 1 MW-12DB 1 1 1 MW-12SB 1 1 1 MW-13DB 1 1 1 1 1 1 MW-13SB 1 1 1 MW-14DB 1 1 MW-14SO 1 1 MW-15DB 1 1 1 MW-15SB 1 1 1 MW-16DB 1 1 1 1 1 1 MW-16IB 1 1 1 1 1 1 MW-16SO 1 1 MW-17DO 1 1 1 MW-17SO 1 1 1 MW-1B 1 1 1 1 1 1 MW-203D MW-203S MW-204D MW-204S MW-205 MW-206D

I MW-206S MW-2DB 1 1 MW-2DDB 1 1 MW-2IB 1 1 1 1 1 1 MW-3B 1 1 1 1 1 1

I MW-4O 1 1 1 MW-5B 1 1

II MW-6DB 1 1 1 MW-6SB 1 1 1 MW-8DB 1 1 1 MW-8SB 1 1 1

II PW-207 1 SEEP-1 1 SUBTOTAL - RESIDENTIAL 44 25 0 2 0 3 0 SUBTOTAL - MONITORING 22 48 41 15 15 15 1

Total 3 66 73 41 17 15 18 1

I Included in most recent data

I Notes 1 - Overburden well not included in most recent data for plotting

2 - Tetrahydrofuran and 2-Butanone were the only two compounds detected in this well and are thought to be the result of well repair not included in most recent data for plotting

3 - Not included in most recent data for plotting

2004 Sampling

WC-58 Sep-04

1

1 1

1 1

1 1 1

1

1 1

1 1 1 1 1 1 1 1 1

1 1

1

0 29

29

Groundwatef Sampling Location Summary 1999 - 2004xls

I

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

monitoring well Figure 4-14 total VOC contour (ugl) - December 1999January 2000 Distribution of Total VOCs in

Note SW-113 is located downstream of SEEP-1 Shallow Bedrock Groundwater total concentration of detected VOCs ND= not detected these two locations were sampled during the Pre-ROD Sampling Event

Baseline Sampling Event in OctoberNovember 1999 Hows Corner Superfund Site Surface Water Sampling Location A Plymouth Maine Seep Sampling Location laquo- WOODARD ampCURRAN

995037wipri reportepa ri interim final feb 2001cadd drawingsfinalfig 4-14

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

0 300 600 I

FEET

Q residential well Figure 4-16 monitoring well Distribution of Total VOCs in

Deep Bedrock Groundwater total VOCs contour (ugl) Pre-ROD Sampling Event

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Response to EPA-DEP Comment 5 Dated March 312005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

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EPA-DEP Comment 5

Comment 5 Matrix Diffusion The report as well as other proponents of matrix diffusion suggest that depletion of DNAPL (Section 5112 page 5-15) needs to be achieved While that might be the ideal the goal is to achieve performance standards and that goal may be attainable while there is residual contamination in the rock perhaps even DNAPL globules The low bedrock matrix porosity (page 1-15) the high permeability values (page 4-4) the relative flux of the groundwater (page 5-5) and the decrease in surface area and out of the mainstream pockets (appendix C-4) all suggest that the diffusion out of the rock matrix would be insubstantial relative to the regional flux of groundwater through the Site

Response The TI Evaluation Report does not explicitly consider or rely upon matrix diffusion as a basis for requesting a TI Waiver for a portion of the Hows Corner Site The technical literature provides documentation that matrix diffusion can be a significant process that affects chemical transport and groundwater remediation timeframes in unconsolidated and consolidated media including fractured rock (US EPA 1989 Freeze and Cherry 1979 Pankow and Cherry 1996 Fountain 1998) Back diffusion of contaminants from the matrix porosity of the fractured rock can prolong the time necessary to achieve groundwater cleanup goals particularly for compounds such as PCE for which the cleanup goal is a low concentration It is our expectation that matrix diffusion has occurred at the Hows Corner Site and that back diffusion of PCE from the rock matrix will also occur Although the extent to which matrix diffusion is occurring at the Hows Comer Site has not been determined and that lack of knowledge contributes to uncertainty regarding the cleanup times at the Site the effect of matrix diffusion is to lengthen rather than shorten the time required for remediation

REFERENCES

Fountain JC 1998 Technologies for Dense Nonaqueous Phase Liquid Source Zone Remediation Ground-Water Remediation Technologies Analysis Center Technology Evaluation Report TE-98-02 December

Freeze RA and Cherry JA 1979 Groundwater Prentice-Hall Inc Englewood Cliffs NJ 07632 p 410-412

Pankow J F and Cherry J A 1996 Dense Chlorinated Solvents Waterloo Press Portland OR 97291-1399 p 67-88

US EPA 1989 Transport and Fate of Contaminants in the Subsurface EPA6254-89019 p 17-18

Response to EPA Comment 5 050305doc 1 of 1 Woodard amp Curran (211941)

WOODARD amp CURRAN Maine Massachusetts New Hampshire Connecticut Florida Operational offices across the US 1-800-426-4262 www woodardcurran com

Page 32: SDMS DocID 251749 - Records Collections · 2020-06-13 · CORPORATE OFFICES: Maine, Massachusetts, New Hampshire, Connecticut New, York, Florida Engineering • Science • Operations

EPA-DEP Comment 3

Comment 3 The reported f values and resultant Kd values There remains doubt that the values used in the flushing model accurately reflect the propensity for PCE to sorb to the bedrock The ^ values presented in Appendix B may be unrealistically high because the bedrock samples may have contained organic carbon that was unavailable for sorption The reported f values are only qualitative estimates of the organic carbon content of the bedrock samples The Walkley and Black organic carbon measurement method is quick and simple but the results obtained cannot be considered quantitative because it requires a correction factor which often results in erroneous values it assumes the organic carbon has an average valence of zero oxidizable and reducible constituents such as chloride ferrous iron and manganese oxides interfere with the results and the errors introduced by interference are potentially greater when the organic carbon content is low at low f values it is not clear that organic carbon is controlling PCE sorption (Schwarzenbach and Westall 1981 Mackay et al 1986 Fetter 1999)

In order to derive a Kd-based retardation factor that is reasonable given the reported f values and the rapid advance of the PCE plume described on pages 4-11 and 4-12 the flushing model requires a bulk density to porosity ratio that is roughly two orders of magnitude higher than the actual ratio for the Hows Corner bedrock (page 4-4) This apparent discrepancy needs to be addressed

Response This comment raises several concerns about the collection and analysis of samples for fraction of organic carbon (f^) the quality of the resulting data and the implications of the use of those data for estimation of the retardation of groundwater contaminant movement Results of bedrock analysis for f were proposed in the TI Evaluation Work Plan for use in conjunction with groundwater contaminant concentrations and aquifer information to estimate cleanup times using the Batch Flushing model It is important to use accurate f values from representative bedrock in the Batch Flushing model in order to obtain reasonable estimates of the remedial time frame Because of the importance of accurate and representative results the TI Investigation field program was designed and conducted both to collect samples representative of the rock volume most likely to be in contact with contaminated groundwater and to analyze them using an appropriate refereed analytical method Five potential methods for evaluating f were identified Of the five methods the Walkey-Black method was selected because it has minimal method interferences and a sufficiently low detection limit as well as a long history of use in agronomy and contamination studies The PRP Group is pleased with the quality of the data obtained from the bedrock samples as represented by their precision and reproducibility

The first part of this comment relates to the determination of fraction of organic carbon (f^) values The several subparts of the first paragraph are addressed individually in items 1 through 5 below The second part of the comment regarding the resultant distribution coefficient (Kd) values is addressed separately as item 6 below

1 There remains doubt that the values used in the flushing model accurately reflect the propensity for PCE to sorb to the bedrock

bull The rock core samples used for f (gocg) analysis were from core immediately adjacent to fractures These rock core samples included the fracture surfaces themselves and rock core extending back less than 1 cm from the fractures Therefore the foe data reported in the TI Evaluation represents the f of bedrock through which groundwater will travel and to which PCE will adsorb Based on the careful selection of sample locations and the

Response to EPA Comment 3 050205doc 1 of 11 Woodard amp Curran (211941)

number of samples collected we are confident that the measured f values are representative of the f at points of contact for PCE with the bedrock it is these f values that determine the propensity of PCE to sorb to the bedrock

bull The samples of rock core collected for analysis of f originated from 19 different locations varying in depth from 11 to 90 feet Therefore it is very unlikely that the rock core samples were contaminated with extraneous organic carbon from above ground

2 The foc values presented in Appendix B may be unrealistically high because the bedrock samples may have contained organic carbon that was unavailable for sorption

bull As noted in response 1 the f data reported in Appendix B represents organic carbon primarily associated with the surface of fractures in the bedrock through which groundwater is most likely to travel Therefore it is this organic carbon that the contaminants in the groundwater will come in contact with and adsorb to in the fractured rock at the site

bull The chemical oxidation agents used in the Walkey-Black method oxidize the easily oxidizable organic carbon in the medium and the foe is calculated from the quantity of the agent consumed Therefore it is unlikely that the analysis of the bedrock samples measured organic carbon that was unavailable for sorption

3 The reported foc values are only qualitative estimates of the organic carbon content of the bedrock samples

bull The reported f values are accurate quantitative results Schumachers review of Methods for the determination of total organic carbon (TOC) in soils and sediments (NCEA-C-1282 EMASC-001 April 2002) identifies the Walkley-Black method which was used to analyze the reported foc values as the reference method for comparison to other methods for analyzing total organic carbon

bull Schumacher also points out that if anything the WalkJey-Black method may underestimate the total organic carbon in a sample due to possible incomplete oxidation of organic carbon Usually the incomplete oxidation of total organic carbon in environmental samples is corrected for by multiplying the measured foe by 130 (Walkley amp Black 1934 Schulte 1995)

bull When the f data in the TI Evaluation Report (WampC 2005) Appendix B (attached) are analyzed statistically the standard deviation of the f for the 19 samples analyzed is 174 of the average f Given this standard deviation the 95 confidence interval for this data ranged from a low of 000123 gocg to a high of 000253 gocgm

The labs Method of Detection Limit (MDL) for the f measured using the Walkley-Black method is 00001 gocg Therefore the average (000188 gocg) the mean (000185 gocg) and geometric mean (000187 gocg) of the f values for the rock core at Hows Corner are all statistically significantly greater than the MDL of the Walkley-Black method

In addition to the aforementioned statistical analysis of the foe data triplicate samples (n = 3) from the same rock core (including one sample from the 19 rock core samples) were

Response to EPA Comment 3 050205doc 2 of Woodard amp Curran (211941)

analyzed for their f to determine the repeatability of the Walkley-Black method The average the mean and the geometric mean of the f values of these replicate samples was 000162 gocg 000150 gocg and 000159 gocgm respectively The standard deviation of these measurements was 000039 gocg

4 The Walkley and Black organic carbon measurement method is quick and simple but the results obtained cannot be considered quantitative because it requires a correction factor which often results in erroneous values it assumes the organic carbon has an average valence of zero oxidizable and reducible constituents such as chloride ferrous iron and manganese oxides interfere with the results and the errors introduced by interference are potentially greater when the organic carbon content is low at low foc values it is not clear that organic carbon is controlling PCE sorption (Schwarzenbach and Westall 1981 Mackay et al 1986 Fetter 1999)

bull Schumachers review (NCEA-C-1282 EMASC-001 April 2002) of the Walkley-Black method identifies several potential problems with this analytical method that could occur if the analytical lab is not familiar with the nuances of the chemistry associated with this method Interestingly Schumachers review neglected one of the more important analytical steps required to avoid errors in quantifying f in samples where there might beNAPL

It is absolutely critical to eliminate any NAPL from rock core samples prior to using the Walkley-Black method to measure foe in such samples This was done by the lab (PTS Laboratories) that measured the foe in the rock core samples from Hows Corner The lab used the Dean-Stark method (solvent extraction) to remove all hydrocarbons (including PCE and other NAPLs) from the sample (PTS Laboratories) This extraction method does not interfere with the subsequent analysis of the natural organic carbon associated with the rock core

Subsequently the samples were dried at 150degC to a constant weight (normally 16 hours) This latter step oxidizes all inorganic minerals including ferrous bearing minerals to ferric oxides and precludes their interference during the oxidation of the samples with chromic acid This procedure completely eliminates any positive bias in the reported foc

data that might have occurred due to the presence of ferrous ions and other reduced minerals

bull As noted in Response 3 the incomplete oxidation of total organic carbon results in an underestimate of the f and is corrected for by multiplying the f by a correction factor of 130 (Walkley amp Black 1934 Schulte 1995) The fx data reported in the TI Evaluation was corrected accordingly by using this correction factor

bull Excess chloride (Cl~) in percent weight quantities as found in saline soils may interfere with the quantitative titration of reduced chromium (Walkley 1947) However given that the primary rock type at the Hows Corner site is phyllite it is highly unlikely that there was sufficient chloride in the rock core samples for this to occur

bull Manganese oxides may also interfere with the analysis of f through competing with the dichromate ion for any oxidizable carbon (Walkley 1947) However in such cases the reported f would be an underestimate of the f present in the rock core Walkley (1947)

Response to EPA Comment 3 050205doc 3 of 11 Woodard amp Curran (211941)

4

reported that in the case where the ratio of MnO2 to carbon is 85 to 1 the error in the carbon determinations would only be 0 to 6 percent

It may also be useful to compare the analysis of total organic carbon in a geologic matrix that contains high levels of manganese using EPA method 9060 to the Walkley-Black method Table 1 summarizes data provided by one of the PRPs that compares the analysis of total organic carbon in a geologic matrix that contains approximately 02 wgt manganese (approximately 03 wgt manganese oxide)

Table 1 Comparison of total organic carbon measured using the EPA- 9060 method and the Walkley-Black method

Laboratory EPA-9060 Method Walkley-Black Method A Ave 00226 gocg Not analyzed

Stdev 000251 gocg n = 5

B Ave 002219 gocg Ave 002050 gocg Stdev = 000316 gocg Stdev =000971 gocg

n= 10 n = 10

The similarity in the total organic carbon concentrations measured by these two different methods provides further confidence that the Walkley-Black method is a viable method for analysis of total organic carbon in the presence of manganese equivalent to at least 10 by weight of the total organic carbon

5 The Walkley and Black organic carbon measurement at lowf^ values it is not clear that organic carbon is controlling PCE sorption (Schwarzenbach and Westall 1981 Mackay et al 1986 Fetter 1999)

bull Schwarzenbach and Westalls (1981) paper states that f values of less than 0001 gocg should not be used in combination with Kow (octanol-water partition coefficients) values to calculate K^ values (solid phase partition coefficients) values for a specific contaminant It should be noted that the TI Evaluation did not use the f data to calculate the KQC from the Kow Instead as requested by the EPA the measured KOC value for PCE was used to calculate the retardation factor for this contaminant

bull Schwarzenbach et al (2003) stated more recently that Even at very low f values (ie foe = 0001 kgoc - kg1 solid) sorption to the organic components of a natural sorbent may still be the dominant mechanism in defining the adsorption of organic compounds to geological matrices

bull In 1985 M Piwoni from the US EPA Robert S Kerr Environmental Research Laboratory published a paper (Banerjee et al 1985) that showed that for very hydrophobic molecules TOC content of the sorbent will control sorption down to levels of organic carbon that defy quantitation Contaminants such as the PCE found in the groundwater at Hows Corner are in this category of compounds

Given the aforementioned reasons the f values reported in the TI Evaluation are accurate within the noted statistical limitations and will have a predictable impact upon the retardation of PCE during groundwater transport

Response to EPA Comment 3 050205doc 4 of 11 Woodard amp Curran (211941)

6 In order to derive a Kd-based retardation factor that is reasonable given the reported foc

values and the rapid advance of the PCE plume described on pages 4-11 and 4-12 the flushing model requires a bulk density to porosity ratio that is roughly two orders of magnitude higher than the actual ratio for the Hows Comer bedrock (page 4-4) This apparent discrepancy needs to be addressed

The apparent discrepancy of bulk density to porosity ratios is most likely due to the fact that the Batch Flushing Model was originally developed for a porous medium and is not directly applicable to fractured bedrock As stated in Appendix C (page C-4) of the Draft Technical Impracticability Evaluation Report in order to use the Batch Flushing Model to describe the transport of contaminated groundwater in fractured bedrock where the matrix porosity is insignificant it is more appropriate to use a fracture surface area to void space ratio to calculate the retardation factor (R) than a bulk density to porosity ratio (Freeze amp Cherry 1979)

Since it is impractical to determine the actual surface area to which contaminants can adsorb the Batch Flushing Model was used with two simplifying assumptions bull The Kd was calculated from the f and the K^ bull The bulk density to porosity ratio term in the Batch Flushing Model was constrained to range

from 4 to 10 the typical range of such ratios in porous media (Freeze amp Cherry 1979)

If one uses site specific bedrock bulk density and porosity values the bulk density to porosity ratio is several orders of magnitude greater (specifically 273 gcc bullbull 000165 (dimensionless) = 1654 gcc) than the range of ratios of 4 to 10 used in the Batch Flushing Model in the Draft Technical Impracticability Evaluation Report Constraining the bulk density to porosity ratio within the range of ratios of 4 to 10 results in significantly lower R value than would be obtained using specific bedrock bulk density and porosity values

In summary in bedrock where fractures are the primary porosity the bulk density to porosity ratio can vary considerably and will be a function of the number of fractures and the fracture aperture The calculated bulk density to porosity ratio will be inversely proportional to the porosity This means that in fractured rock with limited fracturing and smaller porosity the calculated bulk density to porosity ratio is greater and will result in a greater calculated retardation factor than in bedrock with more extensive fracturing and greater porosity Consequently the calculated retardation factor will be greater for bedrock with less surface area available for sorption than bedrock with greater surface area for sorption This is contrary to what actually occurs

4 Response to EPA Comment 3 050205doc 5 of 11 Woodard amp Curran (211941)

m

REFERENCES

Banerjee P MD Piwoni K Ebeid (1985) Sorption of organic contaminants to a low carbon subsurface core Chemosphere _14 1057-1067

Freeze RA JA Cherry (1979) Groundwater Prentice Hall Englewood Cliffs NJ pg 604

PTS Laboratories wwwptsgeolabscompdf files3TOCnotepdf

Schulte EE (1995) Recommended soil organic matter tests in Recommended Soil Testing Procedures for the Northeastern United States Northeastern Regional Publication No 493 Chapter 8

Schwarzenbach RP J Westall (1981) Transport of nonpolar organic compounds from surface water to groundwater Laboratory sorption studies Environ Sci Tech 15 1360-1367

Schwarzenbach RP PM Gschwend DM Imboden (2003) Environmental Organic Chemistry Wiley-Interscience pg 292 408 amp 412

Walkley A LA Black (1934) An examination of the Degtjareff method for determining soil organic matter and a proposed modification of the chromic acid titration method Soil Science 37 29-38

Walkley A (1947) A critical examination of a rapid method for determining organic carbon in soils - effect of variations in digestion conditions and of inorganic soil constituents Soil Science 63251-264

Woodard amp Curran Inc (WampC) 2005 Draft Technical Impracticability Evaluation Hows Corner Superfund Site Plymouth Maine January 2005

Response to EPA Comment 3 050205doc 6 of Woodard amp Curran (211941)

LIST OF ATTACHMENTS (Response to Comment 3)

Appendix B to Draft Technical Impracticability Evaluation Measurement of foe at Hows Corner (4 pages)

m

Response to EPA Comment 3 050205doc 7 of 11 Woodard amp Curran (211941)

Appendix B Measurement of foe of Rock Core at Hows Corner

There are two general approaches to measure the fraction of organic carbon (foe) in rock cores

bull Measurement of weight loss by ignition of organic matter bull Chemical oxidization of organic carbon to carbon dioxide and either

subsequent quantification of the oxidant used for the reaction or quantification of the carbon dioxide produced during this oxidation process

The weight loss method is subject to errors caused by volatilization of substances other than organic materials such as water hydroxides and mineral carbonates Quantification of foe by the weight loss method is particularly sensitive to the presence of carbonates in rock cores There are however weight loss methods that are designed to differentiate between organic carbon and the aforementioned interfering materials but they require considerable care and are less accurate at low foe values Hence the weight loss method was not well suited for measuring the foe of the rock core from Hows Corner

The chemical oxidation of organic carbon is much better suited for quantifying organic carbon in rock cores such as those from Hows Corner This method uses a strong chemical oxidant to oxidize organic carbon to carbon dioxide and then measures either the chemical oxidant used to oxidize the organic carbon or the quantity of carbon dioxide produced In addition this general approach is not subject to interference by volatilization of other constituents of the rock core

There are at least two such chemical oxidation methods

bull The method of Baccini which was described by Schwarzenbach amp Westall (1981) first acidifies the sample to eliminate interference by carbonates Then a strong oxidant is used to chemically oxidize the organic carbon to carbon dioxide The resulting carbon dioxide is subsequently reduced to methane and quantified using a flame ionization detector Unfortunately this method has not been described in detail in a referred journal Hence it is would not have been appropriate to use to characterize the foe in the Hows Corner rock core

bull The more commonly used method to quantify foe in rock core is the Walkley-Black method (1934) This method is preferred for RBCA and DODDOE projects and by the oil industry

The Walkley-Black method uses an excess of chromic acid to oxidize (digest) organic matter to carbon dioxide The remaining chromic acid that was not consumed during the oxidation of the organic carbon is then quantified by titration with ferrous sulfate The difference in chromic acid prior to and after the oxidation of the organic carbon represents the total chromic acid used to oxidize

Hows Corner TI Evaluation Page 1 January 13 2005 Appendix B

the organic carbon in the sample The latter can be calculated using the chemical stoichiometry of the reaction

The Walkley-Black method is very accurate for samples that contain less than 2 organic carbon matter The minimum detection limit (MDL) for the Walkley-Black method is 100 mgkg or an foe of 0001

Given the rock core at Hows Corner was expected to contain less than 2 organic carbon the Walkley-Black method was used to measure the foe from 19 different rock core samples collected from varying depths ranging from 11 to 90 feet

Table 1 provides a statistical summary of the aforementioned data

Table 1 Statistical summary of foe data from rock cores collected at varying depths

Statistical Parameter Calculated Value foe Minimum Detection Limit (MDL) 00010 Number of samples analyzed (n) 19 Average foe 00019 Median foe 00019 Geometric Mean foe 00019 Standard deviation of foe measurements 000033 Relative standard deviation 174 -+ 95 Confidence intervals 00012 to 00025

The data in Table 1 shows the following

bull The foe from the Hows Corner rock cores are statistically greater than the MDL of the Walkley-Black analytical method

bull The average and median values for the foe of the Hows Corner rock cores from varying depths are nearly identical indicating that there is little variability in the foe values in the source zone at the site

bull The standard deviation of these measurements is 000033 which is 174 of the average foe

bull The 95 confidence intervals of the foe of the rock core at Hows Corner are 00012 to 00025

The foe was also analyzed from three separate samples taken from the same rock core at a depth of 55 feet (Only one of these samples was included in the data summarized in Table 1) Table 2 shows the statistical repeatability of this type of analysis

Hows Corner TI Evaluation Page 2 January 13 2005 Appendix B

Table 2 Repeatability of analysis of foe from one rock core at 55 feet in depth

Statistical Parameter Calculated Value Number of samples analyzed (n) 3 Average foe 00016 Median foe 00015 Geometric Mean foe 00016 Standard deviation of foe measurements 000039 Relative standard deviation 240 -+ 95 Confidence intervals 00008 to 00024

The data in Table 2 shows the following

bull The percent relative standard deviation of these three analyses of foe from the same rock core at Hows Corner is 24

bull The 95 confidence interval of the foes measured in this particular rock core at Hows Conrer is 00008 to 00024

These results show that there is good repeatability in using the Walkley-Black method for analysis of the foe in the rock core at Hows Corner

References Schwarzenbach amp Westall (1981) Transport of nonpolar organic compounds from surface water to groundwater Laboratory sorption studies Environ Sci Tech 15 1360-1367

Walkley A I A Black (1934) An examination of Degtjareff method for determining soil organic matter and a proposed modification of the chromic acid titration method Soil Sci 37 29-37

Hows Corner Tl Evaluation Page S January 13 2005 Appendix B

Woodard and Curran PTS Laboratories PTS File No 34618

ORGANIC CARBON DATA (METHODOLOGY WALKLEY-BLACK)

PROJECT NAME PROJECT NO

SAMPLE ID

203-chip-13 203-chip-23 203-chip-27 203-chip-38 203-chip-42 203-chip-47 203-chip-52 203-chip-58 203-chip-69 203-chip-82 207-chip-11 207-chip-19 207-chip-24 207-chip-29 207-chip-35 207-chip-45 207-chip-55 207-chip-87 207-chip-90

207-chip-55 55-MS

55-MSMSD

Hows Corner NA

DEPTH ft

13 23 27 38 42 47 52 58 69 82 11 19 24 29 35 45 55 87 90

55 NA NA

MATRIX

Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip

Average Median

Geometric Mean Standard Deviation Relative Std Dev

+- 95 Confidence Interval n

Rock Chip Rock Chip Rock Chip

Average Median

Geometric Mean Standard Deviation Relative Std Dev

+- 95 Confidence Interval n

FRACTION ORGANIC CARBON

(gg)

170E-03 185E-03 185E-03 170E-03 240E-03 190E-03 230E-03 180E-03 170E-03 115E-03 195E-03 220E-03 220E-03 235E-03 135E-03 190E-03 205E-03 175E-03 160E-03

188E-03 185E-03 185E-03 327E-04

1739 123E-03 to

19

205E-03 130E-03 150E-03

162E-03 150E-03 159E-03 388E-04

2402 840E-04 to

3

2532E-03

2393E-03

Hows Corner Tl Evaluation Appendix B January 13 2005

Response to EPA-DEP Comment 4 Dated March 31 2005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

EPA-DEP Comment 4

Comment 4 Distribution of contaminants First the TI report seems based on the assertion that there is DNAPL at the source area yet it also appears to represent that the source area is small and the bedrock below 85 is competent (or less fractured) and less impacted by the release of contaminants Some of the confusion may result from using most recent data when that data is from several different sampling events over several years and there is no discernible difference in concentrations between shallow and deep bedrock or as in Section 421 where generally decreased generally increase generally similar and similar concentrations in four consecutive sentences leads to a muddled picture of the contaminant distribution

Second the report asserts that the distribution of contaminants over the entire plume has not changed with time but fails to support this conclusion with data again relying on data that is from different sampling dates for one composite representation

Response The likely presence of dense non-aqueous phase liquid (DNAPL) at the Hows Corner Site and the determination that the source area is small are not mutually exclusive and both are conclusions drawn from information obtained during field investigations The presence of DNAPL in the source area is based on the elevated concentrations of volatile organic compounds (VOCs) detected in the groundwater (WampC 2001 WampC 2002) The conclusion that the source area is small is based on the area in which VOCs in groundwater have been detected at concentrations that are considered to be indicative of the presence of DNAPL nearby Similarly the conclusion that fracture frequency decreases at depths greater than approximately 50 to 85 feet below ground surface was based on field observation during the RI field work The fact that zones with observed fractures exhibited higher hydraulic conductivities than zones without fractures coupled with the decreasing frequency of observed fractures with depth led to the conclusion that the hydraulic conductivity of the bulk rock decreases with depth

The most recent data from all wells were used to provide the maximum VOC data set size During the RI all of the previously-existing and then newly-installed monitoring wells were sampled along with several residential wells The RI sampling included up to 48 monitoring wells Subsequent to the RI and prior to the TI three rounds of monitoring were conducted to verify that the plume was stable 15 monitoring wells were sampled during each of the three rounds During the TI field investigation 29 wells were sampled for VOCs The sampled wells included all of the newly-installed wells and a subset of wells installed during the RI for a total of 29 monitoring wells By using most recent data VOC results from 53 monitoring wells were included in the evaluation (see table labeled Sampling Events for listing of monitoring wells) This approach was selected because there generally was little variation in the data from a particular location between years This is borne out by the attached individual plots of VOCs detected in shallow bedrock and deep bedrock for the Pre-ROD (December 1999January 2000) and Supplemental (May 2000) sampling events and for June 2001 January 2002 and April 2003 sampling events The Pre-ROD and Supplemental plots are similar to the subsequent plots from the 2001 2002 and 2003 sampling events

In addition to maps showing the spatial distribution of VOC data at a given time trend plots of the data from a particular location through time (attached) indicate that since the RI concentrations generally have been stable or have decreased Together the maps and trend plots and the data from which they were developed indicate that the distribution of contaminants over the entire plume has not changed appreciably with time

Response to EPA Comment 4 050305doc 1 of 26 Woodard amp Curran (211941)

REFERENCES

Woodard amp Curran Inc (WampC) 2001 Final Remedial Investigation Report Hows Corner Superfund Plymouth Maine July 2001

Woodard amp Curran Inc (WampC) 2002 Final Feasibility Study Report - Non-Source Area Groundwater Hows Corner Superfund Site Plymouth Maine Hows Corner Superfund Plymouth Maine July 2002

Response to EPA Comment 4 050305doc 2 of 26 Woodard amp Curran (211941)

LIST OF ATTACHMENTS (Response to Comment 4)

Table - Sampling Events 1999 - 2004 (2 pages)

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater Pre-ROD Sampling Event

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater Pre-ROD Sampling Event

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater Supplemental Sampling Event

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater Supplemental Sampling Event

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater June 2001

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater June 2001

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater January 2002

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater January 2002

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater April 2003

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater April 2003

Figure - Concentration Trends - Non-Source Area Wells MW-1B and MW-3B

Figure - Concentration Trends - Non-Source Area Wells MW-13DB and MW-16DB

Figure - Concentration Trends - Non-Source Area Wells MW-16IB and MW- 108D

Figure - Concentration Trends - Non-Source Area Wells MW-108S and MW-112D

Figure - Concentration Trends - Non-Source Area Wells MW-112S and MW-114D

Figure - Concentration Trends - Non-Source Area Wells MW-114S and MW-115D

Figure - Concentration Trends -Source Area Wells MW-2DB and MW-2IB

Figure - Concentration Trends -Source Area Wells MW-102S and MW-103D

Figure - Concentration Trends -Source Area Wells MW-103S and MW-104D

Figure - Concentration Trends -Source Area Wells MW-104I and MW-106D

Figure - Concentration Trends -Source Area Wells MW-106S

Response to EPA Comment 4 050305doc 3 of 26 Woodard amp Curran (211941)

I I

El I

II I I 1 I

I

i

Event Baseline Case ID WC-01 WC-01

Well Date Aug-99 Oct-99 LOT10 1 LOT1-1 1 LOT11-4 LOT14 1 LOT15 1 LOT15-1 1 LOT16 1 LOT16-1 1 LOT17 1 LOT18 1 LOT19 1 LOT2 LOT20 1 LOT21-10 1 LOT21-11 1 LOT21-12 1 LOT21-13 1 LOT21-14 1 LOT21-2 1 LOT21-5 1 LOT21-7 LOT21 -8 1 LOT21-9 1 LOT23 1 LOT24 1 LOT28-1 1 LOT28-2 1 LOT28-3 1 LOT28-4 1 LOT28W 1 LOT30 1 LOT30-1 1 LOT30-2 1 LOT30-3 1 LOT30-4 1 LOT30-5 LOT31 LOT35 1 LOT41 1 LOT42-1 1 LOT43-1 1 LOT43-4 1 LOT6-1 1 LOT67 1 LOT6-7 1 LOT6-8A 1 LOT6-8B 1 LOT80-1 1 LOT82 1 MW-101D MW-1011 MW-101S MW-102D MW-102S MW-103D MW-103S MW-104D MW-1041 MW-104S MW-105D MW-106D

Groundwater Sampling Location Summary 1999 - 2004xls

Sampling Events 1999-2004

Hows Corner Superfund Site Plymouth Maine

Supplemental 2001 2002 2003 Pumping 2004 Pre-ROD Rl Sampling Sampling Sampling Test Sampling WC-03 WC-09 WC-25 WC-30 WC-42B WC-56 WC-58 Dec-99 May-00 Jun-01 Jan-02 Apr-03 Sep-04 Sep-04

1

1 1 1

1 1 1 1 1

1 1

1

1 1

1 1 1

1 1 1 1 1

1

1 1

1 1 1 1

1

1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

Sampling Events 1999-2004

Hows Corner Super-fund Site Plymouth Maine

Supplemental 2001 2002 2003 Pumping Event Baseline Pre-ROD Rl Sampling Sampling Sampling Test

Case ID WC-01 WC-01 WC-03 WC-09 WC-25 WC-30 WC-42B WC-56

ll

Well Date Aug-99 Oct-99 Dec-99 May-00 Jun-01 Jan-02 Apr-03 Sep-04 MW-106S 1 1 1 1 1 MW-107D 1 1 MW-108D 1 1 1 1 1 MW-108S 1 1 1 1 1 MW-110D 1 1 MW-111D 1 1 MW-112D 1 1 1 1 1 MW-112S 1 1 1 1 1 MW-113D 1 1 MW-114D 1 1 1 1 1 MW-114S 1 1 1 1 1 MW-115D 1 1 1 1 1 MW-12DB 1 1 1 MW-12SB 1 1 1 MW-13DB 1 1 1 1 1 1 MW-13SB 1 1 1 MW-14DB 1 1 MW-14SO 1 1 MW-15DB 1 1 1 MW-15SB 1 1 1 MW-16DB 1 1 1 1 1 1 MW-16IB 1 1 1 1 1 1 MW-16SO 1 1 MW-17DO 1 1 1 MW-17SO 1 1 1 MW-1B 1 1 1 1 1 1 MW-203D MW-203S MW-204D MW-204S MW-205 MW-206D

I MW-206S MW-2DB 1 1 MW-2DDB 1 1 MW-2IB 1 1 1 1 1 1 MW-3B 1 1 1 1 1 1

I MW-4O 1 1 1 MW-5B 1 1

II MW-6DB 1 1 1 MW-6SB 1 1 1 MW-8DB 1 1 1 MW-8SB 1 1 1

II PW-207 1 SEEP-1 1 SUBTOTAL - RESIDENTIAL 44 25 0 2 0 3 0 SUBTOTAL - MONITORING 22 48 41 15 15 15 1

Total 3 66 73 41 17 15 18 1

I Included in most recent data

I Notes 1 - Overburden well not included in most recent data for plotting

2 - Tetrahydrofuran and 2-Butanone were the only two compounds detected in this well and are thought to be the result of well repair not included in most recent data for plotting

3 - Not included in most recent data for plotting

2004 Sampling

WC-58 Sep-04

1

1 1

1 1

1 1 1

1

1 1

1 1 1 1 1 1 1 1 1

1 1

1

0 29

29

Groundwatef Sampling Location Summary 1999 - 2004xls

I

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

monitoring well Figure 4-14 total VOC contour (ugl) - December 1999January 2000 Distribution of Total VOCs in

Note SW-113 is located downstream of SEEP-1 Shallow Bedrock Groundwater total concentration of detected VOCs ND= not detected these two locations were sampled during the Pre-ROD Sampling Event

Baseline Sampling Event in OctoberNovember 1999 Hows Corner Superfund Site Surface Water Sampling Location A Plymouth Maine Seep Sampling Location laquo- WOODARD ampCURRAN

995037wipri reportepa ri interim final feb 2001cadd drawingsfinalfig 4-14

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

0 300 600 I

FEET

Q residential well Figure 4-16 monitoring well Distribution of Total VOCs in

Deep Bedrock Groundwater total VOCs contour (ugl) Pre-ROD Sampling Event

active residential wells with lot number Hows Corner Superfund Site 2deg42deg Plymouth Maine total concentration of detected VOCs ND= not detected WOODARD ampCURRAN Enyinaaring bull Science bull Operations bull

995037wipri reportepa ri interim final feb 2001cadd drawingsfinalfig4mdash16

PLYMOUTH POND

PLYMOUTH POND

1 628Tl7MW-2bB 12135

PLYMOUTH POND

monitoring well Figure 4-20

V total VOC contour (ugl) - June 2000 Distribution of Total VOCs in Shallow Bedrock Groundwater

| 34 | total concentration of detected VOCs ND= not detected NA = not analyzed Supplemental Sampling Event Note SW-113 is located downstream of SEEP-1 Hows Corner Superfund Site

Surface Water Sampling Location these two locations were sampled during the Plymouth Maine Baseline Sampling Event in OctoberNovember 1999 Seep Sampling Location WOODARD amp CURRAN

Engineering bull Science - Operations bull 995037wipri reportepa ri interim final feb 2001 cadd drawingsfinalfig 4-20

residential well Figure 4-22 Distribution of Total VOCs in

monitoring well Deep Bedrock Groundwater

total VOCs contour (ugl) Supplemental Sampling Event

Hows Corner Superfund Site

total concentration of detected VOCs ND= not detected NA = not analyzed Plymouth Maine

WOODARD amp CURRAN

995037wipri reportepa-ri interim final feb 2001cadd drawingsfinalfig 4-22 Engineering bull Science - Operations bull

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

FEET

Shallow Monitoring Well

Deep Monitoring Well

C Detected Concentration ND = Not Detected Figure 1-XS Distribution of Total VOCs in Shallow Bedrock Groundwater

Pumping Well

17-Acre Property Boundary Concentration Contour (ugl)

June 2001 Hows Corner Superfund Site

Plymouth Maine WOODARDampCURRAN

-i^rhvj bull Scbncn bull Operations bull 211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0601 dwg04-20-05

PLYMOUTH POND Hopkins Road V

O

PLYMOUTH POND

PLYMOUTH POND

o

0 300 600 mdashfa FEET

Shallow Monitoring Well bull bull - 17-Acre Property Boundary Figure 1-XD

Deep Monitoring Well 1 I Detected Concentration ND = Not Detected Distribution of Total VOCs in Deep Bedrock Groundwater

-mf- Pumping Well June 2001 Residential Well Hows Corner Superfund Site

Plymouth Maine i h Surface Water Sampling Point

g WOODARD ampCURRAN _ ^ _ ^ _ _ yen_ rj i|Hlaquorlny bull Science bull Opt

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0601 dwg04-20-05

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

Shallow Monitoring Well

Deep Monitoring Well

Detected Concentration ND = Not Detected Figure 1-YS Distribution of Total VOCs in Shallow Bedrock Groundwater

Pumping Well

17-Acre Property Boundary Concentration Contour (ugl)

January 2002 Hows Corner Superfund Site

Plymouth Maine WOODARD amp CURRAN Engineering Science- Operations bull

211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0102dwg04-20-05

PLYMOUTH POND

PLYMOUTH POND

Site Pand^ laquoum-laquoBTuitaraquo tLV

vVlf-(

PLYMOUTH POND

0 300 600 ^ = FEET

Shallow Monitoring Well mdashbullbullbull 17-Acre Property Boundary Figure 1-YD - A - Deep Monitoring Well FT Detected Concentration ND = Not Detected Distribution of Total VOCs in

Deep Bedrock Groundwater Pumping Well January 2002 Residential Well Hows Corner Superfund Site

Plymouth Maine Surface Water Sampling Point

WOODARD ampCURRAN Engineering Sciencs- Operations bulli Si

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0102dwg04-20-05

- m j

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND j A O-shy

Shallow Monitoring Well E Detected Concentration ND = Not Detected Figure 1-ZS Distribution of Total VOCs in

Deep Monitoring Well Shallow Bedrock Groundwater

Pumping Well Hows Corner

April 2003 Superfund Site

17-Acre Property Boundary Plymouth Maine Concentration Contour (ugl) r WOODARD ampCURRAN

Engineering bull Science bull Operations bull 211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0403dwg04-20-05

s S pound

PLYMOUTH POND

PLYMOUTH POND

- -

5 PLYMOUTH POND

Jo

FEET

ft Shallow Monitoring Well mdashbullbullmdash 17-Acre Property Boundary Figure 1-ZD Deep Monitoring Well I 1 I Detected Concentration ND = Not Detected Distribution of Total VOCs in

Deep Bedrock Groundwater Pumping Well April 2003

Q) Residential Well Hows Corner Superfund Site Plymouth Maine

(T) Surface Water Sampling Point WOODARD ampCURRAN poundKk EnginawtirKj bull Science - Operations bull

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0403dwg04-20-05

0 Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

B MW-1B

I 12000

PCE

B 10000 Total VOCs

I

i 2000

i 0 Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

c MW-3B

G 2000

1800

B PCE

1600 Total VOCs

1 I I E

il-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

G E

211941

El

I I z E

80

Concentration Trends shy Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-13DB

Total VOCs

c i i c o

Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

MW-16DB

30

c i c c I c o

Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99

PCE

Total VOCs

Jul-01 Jul-03

211941

O bi

c Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

I MW-16IB

i 35

3

c Total VOCs

lt- 2 5

0 | gt

o

1 sectI

c c 0 4

Jul-90 Jul-92 Jul-94 Jul-96 Jul-98 Jul-00 Jul-02 Jul-04

I I MW-108D

I 12

PCE 10

Total VOCs c oc 3

E E I 0

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

E 211941

c Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

fi MW-108S

I I 40

PCE 35

Total VOCs

30

I f 26

20 I o

I 15

10

c Dec-99 Dec-00 Dec-01 Dec-02 Dec-03 I 0

I MW-112D

c 35 - imdash

I A3 shyTotal VOCs

o c

E 1 2

I

ition

B 1 ^

-i c 3

0 Dec-99 Dec-OO Dec-01 Dec-02 Dec-03

211941

I

i

I

cII

Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-112S

08

PCE

Total VOCs 06

o 04

02

0 Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

MW-114D

o

12000

10000

8000

6000

PCE

Total VOCs

4000

2000

i

ccEIIc

i

i

E

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

211941

Con

cent

ratio

n (

ug

l)

E Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

I MW-114S

E A5000 -- Total VOCs

- 4000

0 3000

2000

i 1000

i n shy

Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

MW-115D

c PCE

Total VOCs

c E

o

C c

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03 I 0

211941

IepoundII

EIEIIGICCIccc

30000

25000

20000

o bullsect 15000 b

o 10000 U

5000

0 Aug-99

25000

20000

5000

0 Aug-99

211941

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-2DB

PCE

Total VOCs

Aug-01 Aug-03

MW-2IB

PCE

Total VOCs

Aug-01 Aug-03

IDIBI

ii EIDIISIBIG C

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-102S

6000

5000 PCE

Total VOCs

4000

O 3000

2000

1000

0 Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

MW-103D

16000

~ 14000 ugt 3- 12000 o

^ 10000

sect 8000

O 6000

4000

2000

PCE

Total VOCs

0Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

211941

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

G MW-103S

I I

ampo

12000

10000

E sectc

S

8000

6000

4000

2000

0Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

G I 6000

MW-104D

i 5000

PCE

Total VOCs

i i c

2000

1000

Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

E I

211941

cIccIG

IIBCccBcIc

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-1041

PCE Total VOCs

a 25000

0 20000

a 15000

10000

5000

0 Jan-OO Jan-01 Jan-02 Jan-03 Jan-04

MW-106D

3000

2500 PCE

Total VOCs

=sect 2000

o bullsect 1500

1000

500

0 Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

211941

c Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

c MW-106S

I PCE

Total VOCs

i

i Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

i

i i i E

C

211941 c

Response to EPA-DEP Comment 5 Dated March 312005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

iiw

EPA-DEP Comment 5

Comment 5 Matrix Diffusion The report as well as other proponents of matrix diffusion suggest that depletion of DNAPL (Section 5112 page 5-15) needs to be achieved While that might be the ideal the goal is to achieve performance standards and that goal may be attainable while there is residual contamination in the rock perhaps even DNAPL globules The low bedrock matrix porosity (page 1-15) the high permeability values (page 4-4) the relative flux of the groundwater (page 5-5) and the decrease in surface area and out of the mainstream pockets (appendix C-4) all suggest that the diffusion out of the rock matrix would be insubstantial relative to the regional flux of groundwater through the Site

Response The TI Evaluation Report does not explicitly consider or rely upon matrix diffusion as a basis for requesting a TI Waiver for a portion of the Hows Corner Site The technical literature provides documentation that matrix diffusion can be a significant process that affects chemical transport and groundwater remediation timeframes in unconsolidated and consolidated media including fractured rock (US EPA 1989 Freeze and Cherry 1979 Pankow and Cherry 1996 Fountain 1998) Back diffusion of contaminants from the matrix porosity of the fractured rock can prolong the time necessary to achieve groundwater cleanup goals particularly for compounds such as PCE for which the cleanup goal is a low concentration It is our expectation that matrix diffusion has occurred at the Hows Corner Site and that back diffusion of PCE from the rock matrix will also occur Although the extent to which matrix diffusion is occurring at the Hows Comer Site has not been determined and that lack of knowledge contributes to uncertainty regarding the cleanup times at the Site the effect of matrix diffusion is to lengthen rather than shorten the time required for remediation

REFERENCES

Fountain JC 1998 Technologies for Dense Nonaqueous Phase Liquid Source Zone Remediation Ground-Water Remediation Technologies Analysis Center Technology Evaluation Report TE-98-02 December

Freeze RA and Cherry JA 1979 Groundwater Prentice-Hall Inc Englewood Cliffs NJ 07632 p 410-412

Pankow J F and Cherry J A 1996 Dense Chlorinated Solvents Waterloo Press Portland OR 97291-1399 p 67-88

US EPA 1989 Transport and Fate of Contaminants in the Subsurface EPA6254-89019 p 17-18

Response to EPA Comment 5 050305doc 1 of 1 Woodard amp Curran (211941)

WOODARD amp CURRAN Maine Massachusetts New Hampshire Connecticut Florida Operational offices across the US 1-800-426-4262 www woodardcurran com

Page 33: SDMS DocID 251749 - Records Collections · 2020-06-13 · CORPORATE OFFICES: Maine, Massachusetts, New Hampshire, Connecticut New, York, Florida Engineering • Science • Operations

number of samples collected we are confident that the measured f values are representative of the f at points of contact for PCE with the bedrock it is these f values that determine the propensity of PCE to sorb to the bedrock

bull The samples of rock core collected for analysis of f originated from 19 different locations varying in depth from 11 to 90 feet Therefore it is very unlikely that the rock core samples were contaminated with extraneous organic carbon from above ground

2 The foc values presented in Appendix B may be unrealistically high because the bedrock samples may have contained organic carbon that was unavailable for sorption

bull As noted in response 1 the f data reported in Appendix B represents organic carbon primarily associated with the surface of fractures in the bedrock through which groundwater is most likely to travel Therefore it is this organic carbon that the contaminants in the groundwater will come in contact with and adsorb to in the fractured rock at the site

bull The chemical oxidation agents used in the Walkey-Black method oxidize the easily oxidizable organic carbon in the medium and the foe is calculated from the quantity of the agent consumed Therefore it is unlikely that the analysis of the bedrock samples measured organic carbon that was unavailable for sorption

3 The reported foc values are only qualitative estimates of the organic carbon content of the bedrock samples

bull The reported f values are accurate quantitative results Schumachers review of Methods for the determination of total organic carbon (TOC) in soils and sediments (NCEA-C-1282 EMASC-001 April 2002) identifies the Walkley-Black method which was used to analyze the reported foc values as the reference method for comparison to other methods for analyzing total organic carbon

bull Schumacher also points out that if anything the WalkJey-Black method may underestimate the total organic carbon in a sample due to possible incomplete oxidation of organic carbon Usually the incomplete oxidation of total organic carbon in environmental samples is corrected for by multiplying the measured foe by 130 (Walkley amp Black 1934 Schulte 1995)

bull When the f data in the TI Evaluation Report (WampC 2005) Appendix B (attached) are analyzed statistically the standard deviation of the f for the 19 samples analyzed is 174 of the average f Given this standard deviation the 95 confidence interval for this data ranged from a low of 000123 gocg to a high of 000253 gocgm

The labs Method of Detection Limit (MDL) for the f measured using the Walkley-Black method is 00001 gocg Therefore the average (000188 gocg) the mean (000185 gocg) and geometric mean (000187 gocg) of the f values for the rock core at Hows Corner are all statistically significantly greater than the MDL of the Walkley-Black method

In addition to the aforementioned statistical analysis of the foe data triplicate samples (n = 3) from the same rock core (including one sample from the 19 rock core samples) were

Response to EPA Comment 3 050205doc 2 of Woodard amp Curran (211941)

analyzed for their f to determine the repeatability of the Walkley-Black method The average the mean and the geometric mean of the f values of these replicate samples was 000162 gocg 000150 gocg and 000159 gocgm respectively The standard deviation of these measurements was 000039 gocg

4 The Walkley and Black organic carbon measurement method is quick and simple but the results obtained cannot be considered quantitative because it requires a correction factor which often results in erroneous values it assumes the organic carbon has an average valence of zero oxidizable and reducible constituents such as chloride ferrous iron and manganese oxides interfere with the results and the errors introduced by interference are potentially greater when the organic carbon content is low at low foc values it is not clear that organic carbon is controlling PCE sorption (Schwarzenbach and Westall 1981 Mackay et al 1986 Fetter 1999)

bull Schumachers review (NCEA-C-1282 EMASC-001 April 2002) of the Walkley-Black method identifies several potential problems with this analytical method that could occur if the analytical lab is not familiar with the nuances of the chemistry associated with this method Interestingly Schumachers review neglected one of the more important analytical steps required to avoid errors in quantifying f in samples where there might beNAPL

It is absolutely critical to eliminate any NAPL from rock core samples prior to using the Walkley-Black method to measure foe in such samples This was done by the lab (PTS Laboratories) that measured the foe in the rock core samples from Hows Corner The lab used the Dean-Stark method (solvent extraction) to remove all hydrocarbons (including PCE and other NAPLs) from the sample (PTS Laboratories) This extraction method does not interfere with the subsequent analysis of the natural organic carbon associated with the rock core

Subsequently the samples were dried at 150degC to a constant weight (normally 16 hours) This latter step oxidizes all inorganic minerals including ferrous bearing minerals to ferric oxides and precludes their interference during the oxidation of the samples with chromic acid This procedure completely eliminates any positive bias in the reported foc

data that might have occurred due to the presence of ferrous ions and other reduced minerals

bull As noted in Response 3 the incomplete oxidation of total organic carbon results in an underestimate of the f and is corrected for by multiplying the f by a correction factor of 130 (Walkley amp Black 1934 Schulte 1995) The fx data reported in the TI Evaluation was corrected accordingly by using this correction factor

bull Excess chloride (Cl~) in percent weight quantities as found in saline soils may interfere with the quantitative titration of reduced chromium (Walkley 1947) However given that the primary rock type at the Hows Corner site is phyllite it is highly unlikely that there was sufficient chloride in the rock core samples for this to occur

bull Manganese oxides may also interfere with the analysis of f through competing with the dichromate ion for any oxidizable carbon (Walkley 1947) However in such cases the reported f would be an underestimate of the f present in the rock core Walkley (1947)

Response to EPA Comment 3 050205doc 3 of 11 Woodard amp Curran (211941)

4

reported that in the case where the ratio of MnO2 to carbon is 85 to 1 the error in the carbon determinations would only be 0 to 6 percent

It may also be useful to compare the analysis of total organic carbon in a geologic matrix that contains high levels of manganese using EPA method 9060 to the Walkley-Black method Table 1 summarizes data provided by one of the PRPs that compares the analysis of total organic carbon in a geologic matrix that contains approximately 02 wgt manganese (approximately 03 wgt manganese oxide)

Table 1 Comparison of total organic carbon measured using the EPA- 9060 method and the Walkley-Black method

Laboratory EPA-9060 Method Walkley-Black Method A Ave 00226 gocg Not analyzed

Stdev 000251 gocg n = 5

B Ave 002219 gocg Ave 002050 gocg Stdev = 000316 gocg Stdev =000971 gocg

n= 10 n = 10

The similarity in the total organic carbon concentrations measured by these two different methods provides further confidence that the Walkley-Black method is a viable method for analysis of total organic carbon in the presence of manganese equivalent to at least 10 by weight of the total organic carbon

5 The Walkley and Black organic carbon measurement at lowf^ values it is not clear that organic carbon is controlling PCE sorption (Schwarzenbach and Westall 1981 Mackay et al 1986 Fetter 1999)

bull Schwarzenbach and Westalls (1981) paper states that f values of less than 0001 gocg should not be used in combination with Kow (octanol-water partition coefficients) values to calculate K^ values (solid phase partition coefficients) values for a specific contaminant It should be noted that the TI Evaluation did not use the f data to calculate the KQC from the Kow Instead as requested by the EPA the measured KOC value for PCE was used to calculate the retardation factor for this contaminant

bull Schwarzenbach et al (2003) stated more recently that Even at very low f values (ie foe = 0001 kgoc - kg1 solid) sorption to the organic components of a natural sorbent may still be the dominant mechanism in defining the adsorption of organic compounds to geological matrices

bull In 1985 M Piwoni from the US EPA Robert S Kerr Environmental Research Laboratory published a paper (Banerjee et al 1985) that showed that for very hydrophobic molecules TOC content of the sorbent will control sorption down to levels of organic carbon that defy quantitation Contaminants such as the PCE found in the groundwater at Hows Corner are in this category of compounds

Given the aforementioned reasons the f values reported in the TI Evaluation are accurate within the noted statistical limitations and will have a predictable impact upon the retardation of PCE during groundwater transport

Response to EPA Comment 3 050205doc 4 of 11 Woodard amp Curran (211941)

6 In order to derive a Kd-based retardation factor that is reasonable given the reported foc

values and the rapid advance of the PCE plume described on pages 4-11 and 4-12 the flushing model requires a bulk density to porosity ratio that is roughly two orders of magnitude higher than the actual ratio for the Hows Comer bedrock (page 4-4) This apparent discrepancy needs to be addressed

The apparent discrepancy of bulk density to porosity ratios is most likely due to the fact that the Batch Flushing Model was originally developed for a porous medium and is not directly applicable to fractured bedrock As stated in Appendix C (page C-4) of the Draft Technical Impracticability Evaluation Report in order to use the Batch Flushing Model to describe the transport of contaminated groundwater in fractured bedrock where the matrix porosity is insignificant it is more appropriate to use a fracture surface area to void space ratio to calculate the retardation factor (R) than a bulk density to porosity ratio (Freeze amp Cherry 1979)

Since it is impractical to determine the actual surface area to which contaminants can adsorb the Batch Flushing Model was used with two simplifying assumptions bull The Kd was calculated from the f and the K^ bull The bulk density to porosity ratio term in the Batch Flushing Model was constrained to range

from 4 to 10 the typical range of such ratios in porous media (Freeze amp Cherry 1979)

If one uses site specific bedrock bulk density and porosity values the bulk density to porosity ratio is several orders of magnitude greater (specifically 273 gcc bullbull 000165 (dimensionless) = 1654 gcc) than the range of ratios of 4 to 10 used in the Batch Flushing Model in the Draft Technical Impracticability Evaluation Report Constraining the bulk density to porosity ratio within the range of ratios of 4 to 10 results in significantly lower R value than would be obtained using specific bedrock bulk density and porosity values

In summary in bedrock where fractures are the primary porosity the bulk density to porosity ratio can vary considerably and will be a function of the number of fractures and the fracture aperture The calculated bulk density to porosity ratio will be inversely proportional to the porosity This means that in fractured rock with limited fracturing and smaller porosity the calculated bulk density to porosity ratio is greater and will result in a greater calculated retardation factor than in bedrock with more extensive fracturing and greater porosity Consequently the calculated retardation factor will be greater for bedrock with less surface area available for sorption than bedrock with greater surface area for sorption This is contrary to what actually occurs

4 Response to EPA Comment 3 050205doc 5 of 11 Woodard amp Curran (211941)

m

REFERENCES

Banerjee P MD Piwoni K Ebeid (1985) Sorption of organic contaminants to a low carbon subsurface core Chemosphere _14 1057-1067

Freeze RA JA Cherry (1979) Groundwater Prentice Hall Englewood Cliffs NJ pg 604

PTS Laboratories wwwptsgeolabscompdf files3TOCnotepdf

Schulte EE (1995) Recommended soil organic matter tests in Recommended Soil Testing Procedures for the Northeastern United States Northeastern Regional Publication No 493 Chapter 8

Schwarzenbach RP J Westall (1981) Transport of nonpolar organic compounds from surface water to groundwater Laboratory sorption studies Environ Sci Tech 15 1360-1367

Schwarzenbach RP PM Gschwend DM Imboden (2003) Environmental Organic Chemistry Wiley-Interscience pg 292 408 amp 412

Walkley A LA Black (1934) An examination of the Degtjareff method for determining soil organic matter and a proposed modification of the chromic acid titration method Soil Science 37 29-38

Walkley A (1947) A critical examination of a rapid method for determining organic carbon in soils - effect of variations in digestion conditions and of inorganic soil constituents Soil Science 63251-264

Woodard amp Curran Inc (WampC) 2005 Draft Technical Impracticability Evaluation Hows Corner Superfund Site Plymouth Maine January 2005

Response to EPA Comment 3 050205doc 6 of Woodard amp Curran (211941)

LIST OF ATTACHMENTS (Response to Comment 3)

Appendix B to Draft Technical Impracticability Evaluation Measurement of foe at Hows Corner (4 pages)

m

Response to EPA Comment 3 050205doc 7 of 11 Woodard amp Curran (211941)

Appendix B Measurement of foe of Rock Core at Hows Corner

There are two general approaches to measure the fraction of organic carbon (foe) in rock cores

bull Measurement of weight loss by ignition of organic matter bull Chemical oxidization of organic carbon to carbon dioxide and either

subsequent quantification of the oxidant used for the reaction or quantification of the carbon dioxide produced during this oxidation process

The weight loss method is subject to errors caused by volatilization of substances other than organic materials such as water hydroxides and mineral carbonates Quantification of foe by the weight loss method is particularly sensitive to the presence of carbonates in rock cores There are however weight loss methods that are designed to differentiate between organic carbon and the aforementioned interfering materials but they require considerable care and are less accurate at low foe values Hence the weight loss method was not well suited for measuring the foe of the rock core from Hows Corner

The chemical oxidation of organic carbon is much better suited for quantifying organic carbon in rock cores such as those from Hows Corner This method uses a strong chemical oxidant to oxidize organic carbon to carbon dioxide and then measures either the chemical oxidant used to oxidize the organic carbon or the quantity of carbon dioxide produced In addition this general approach is not subject to interference by volatilization of other constituents of the rock core

There are at least two such chemical oxidation methods

bull The method of Baccini which was described by Schwarzenbach amp Westall (1981) first acidifies the sample to eliminate interference by carbonates Then a strong oxidant is used to chemically oxidize the organic carbon to carbon dioxide The resulting carbon dioxide is subsequently reduced to methane and quantified using a flame ionization detector Unfortunately this method has not been described in detail in a referred journal Hence it is would not have been appropriate to use to characterize the foe in the Hows Corner rock core

bull The more commonly used method to quantify foe in rock core is the Walkley-Black method (1934) This method is preferred for RBCA and DODDOE projects and by the oil industry

The Walkley-Black method uses an excess of chromic acid to oxidize (digest) organic matter to carbon dioxide The remaining chromic acid that was not consumed during the oxidation of the organic carbon is then quantified by titration with ferrous sulfate The difference in chromic acid prior to and after the oxidation of the organic carbon represents the total chromic acid used to oxidize

Hows Corner TI Evaluation Page 1 January 13 2005 Appendix B

the organic carbon in the sample The latter can be calculated using the chemical stoichiometry of the reaction

The Walkley-Black method is very accurate for samples that contain less than 2 organic carbon matter The minimum detection limit (MDL) for the Walkley-Black method is 100 mgkg or an foe of 0001

Given the rock core at Hows Corner was expected to contain less than 2 organic carbon the Walkley-Black method was used to measure the foe from 19 different rock core samples collected from varying depths ranging from 11 to 90 feet

Table 1 provides a statistical summary of the aforementioned data

Table 1 Statistical summary of foe data from rock cores collected at varying depths

Statistical Parameter Calculated Value foe Minimum Detection Limit (MDL) 00010 Number of samples analyzed (n) 19 Average foe 00019 Median foe 00019 Geometric Mean foe 00019 Standard deviation of foe measurements 000033 Relative standard deviation 174 -+ 95 Confidence intervals 00012 to 00025

The data in Table 1 shows the following

bull The foe from the Hows Corner rock cores are statistically greater than the MDL of the Walkley-Black analytical method

bull The average and median values for the foe of the Hows Corner rock cores from varying depths are nearly identical indicating that there is little variability in the foe values in the source zone at the site

bull The standard deviation of these measurements is 000033 which is 174 of the average foe

bull The 95 confidence intervals of the foe of the rock core at Hows Corner are 00012 to 00025

The foe was also analyzed from three separate samples taken from the same rock core at a depth of 55 feet (Only one of these samples was included in the data summarized in Table 1) Table 2 shows the statistical repeatability of this type of analysis

Hows Corner TI Evaluation Page 2 January 13 2005 Appendix B

Table 2 Repeatability of analysis of foe from one rock core at 55 feet in depth

Statistical Parameter Calculated Value Number of samples analyzed (n) 3 Average foe 00016 Median foe 00015 Geometric Mean foe 00016 Standard deviation of foe measurements 000039 Relative standard deviation 240 -+ 95 Confidence intervals 00008 to 00024

The data in Table 2 shows the following

bull The percent relative standard deviation of these three analyses of foe from the same rock core at Hows Corner is 24

bull The 95 confidence interval of the foes measured in this particular rock core at Hows Conrer is 00008 to 00024

These results show that there is good repeatability in using the Walkley-Black method for analysis of the foe in the rock core at Hows Corner

References Schwarzenbach amp Westall (1981) Transport of nonpolar organic compounds from surface water to groundwater Laboratory sorption studies Environ Sci Tech 15 1360-1367

Walkley A I A Black (1934) An examination of Degtjareff method for determining soil organic matter and a proposed modification of the chromic acid titration method Soil Sci 37 29-37

Hows Corner Tl Evaluation Page S January 13 2005 Appendix B

Woodard and Curran PTS Laboratories PTS File No 34618

ORGANIC CARBON DATA (METHODOLOGY WALKLEY-BLACK)

PROJECT NAME PROJECT NO

SAMPLE ID

203-chip-13 203-chip-23 203-chip-27 203-chip-38 203-chip-42 203-chip-47 203-chip-52 203-chip-58 203-chip-69 203-chip-82 207-chip-11 207-chip-19 207-chip-24 207-chip-29 207-chip-35 207-chip-45 207-chip-55 207-chip-87 207-chip-90

207-chip-55 55-MS

55-MSMSD

Hows Corner NA

DEPTH ft

13 23 27 38 42 47 52 58 69 82 11 19 24 29 35 45 55 87 90

55 NA NA

MATRIX

Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip

Average Median

Geometric Mean Standard Deviation Relative Std Dev

+- 95 Confidence Interval n

Rock Chip Rock Chip Rock Chip

Average Median

Geometric Mean Standard Deviation Relative Std Dev

+- 95 Confidence Interval n

FRACTION ORGANIC CARBON

(gg)

170E-03 185E-03 185E-03 170E-03 240E-03 190E-03 230E-03 180E-03 170E-03 115E-03 195E-03 220E-03 220E-03 235E-03 135E-03 190E-03 205E-03 175E-03 160E-03

188E-03 185E-03 185E-03 327E-04

1739 123E-03 to

19

205E-03 130E-03 150E-03

162E-03 150E-03 159E-03 388E-04

2402 840E-04 to

3

2532E-03

2393E-03

Hows Corner Tl Evaluation Appendix B January 13 2005

Response to EPA-DEP Comment 4 Dated March 31 2005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

EPA-DEP Comment 4

Comment 4 Distribution of contaminants First the TI report seems based on the assertion that there is DNAPL at the source area yet it also appears to represent that the source area is small and the bedrock below 85 is competent (or less fractured) and less impacted by the release of contaminants Some of the confusion may result from using most recent data when that data is from several different sampling events over several years and there is no discernible difference in concentrations between shallow and deep bedrock or as in Section 421 where generally decreased generally increase generally similar and similar concentrations in four consecutive sentences leads to a muddled picture of the contaminant distribution

Second the report asserts that the distribution of contaminants over the entire plume has not changed with time but fails to support this conclusion with data again relying on data that is from different sampling dates for one composite representation

Response The likely presence of dense non-aqueous phase liquid (DNAPL) at the Hows Corner Site and the determination that the source area is small are not mutually exclusive and both are conclusions drawn from information obtained during field investigations The presence of DNAPL in the source area is based on the elevated concentrations of volatile organic compounds (VOCs) detected in the groundwater (WampC 2001 WampC 2002) The conclusion that the source area is small is based on the area in which VOCs in groundwater have been detected at concentrations that are considered to be indicative of the presence of DNAPL nearby Similarly the conclusion that fracture frequency decreases at depths greater than approximately 50 to 85 feet below ground surface was based on field observation during the RI field work The fact that zones with observed fractures exhibited higher hydraulic conductivities than zones without fractures coupled with the decreasing frequency of observed fractures with depth led to the conclusion that the hydraulic conductivity of the bulk rock decreases with depth

The most recent data from all wells were used to provide the maximum VOC data set size During the RI all of the previously-existing and then newly-installed monitoring wells were sampled along with several residential wells The RI sampling included up to 48 monitoring wells Subsequent to the RI and prior to the TI three rounds of monitoring were conducted to verify that the plume was stable 15 monitoring wells were sampled during each of the three rounds During the TI field investigation 29 wells were sampled for VOCs The sampled wells included all of the newly-installed wells and a subset of wells installed during the RI for a total of 29 monitoring wells By using most recent data VOC results from 53 monitoring wells were included in the evaluation (see table labeled Sampling Events for listing of monitoring wells) This approach was selected because there generally was little variation in the data from a particular location between years This is borne out by the attached individual plots of VOCs detected in shallow bedrock and deep bedrock for the Pre-ROD (December 1999January 2000) and Supplemental (May 2000) sampling events and for June 2001 January 2002 and April 2003 sampling events The Pre-ROD and Supplemental plots are similar to the subsequent plots from the 2001 2002 and 2003 sampling events

In addition to maps showing the spatial distribution of VOC data at a given time trend plots of the data from a particular location through time (attached) indicate that since the RI concentrations generally have been stable or have decreased Together the maps and trend plots and the data from which they were developed indicate that the distribution of contaminants over the entire plume has not changed appreciably with time

Response to EPA Comment 4 050305doc 1 of 26 Woodard amp Curran (211941)

REFERENCES

Woodard amp Curran Inc (WampC) 2001 Final Remedial Investigation Report Hows Corner Superfund Plymouth Maine July 2001

Woodard amp Curran Inc (WampC) 2002 Final Feasibility Study Report - Non-Source Area Groundwater Hows Corner Superfund Site Plymouth Maine Hows Corner Superfund Plymouth Maine July 2002

Response to EPA Comment 4 050305doc 2 of 26 Woodard amp Curran (211941)

LIST OF ATTACHMENTS (Response to Comment 4)

Table - Sampling Events 1999 - 2004 (2 pages)

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater Pre-ROD Sampling Event

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater Pre-ROD Sampling Event

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater Supplemental Sampling Event

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater Supplemental Sampling Event

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater June 2001

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater June 2001

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater January 2002

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater January 2002

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater April 2003

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater April 2003

Figure - Concentration Trends - Non-Source Area Wells MW-1B and MW-3B

Figure - Concentration Trends - Non-Source Area Wells MW-13DB and MW-16DB

Figure - Concentration Trends - Non-Source Area Wells MW-16IB and MW- 108D

Figure - Concentration Trends - Non-Source Area Wells MW-108S and MW-112D

Figure - Concentration Trends - Non-Source Area Wells MW-112S and MW-114D

Figure - Concentration Trends - Non-Source Area Wells MW-114S and MW-115D

Figure - Concentration Trends -Source Area Wells MW-2DB and MW-2IB

Figure - Concentration Trends -Source Area Wells MW-102S and MW-103D

Figure - Concentration Trends -Source Area Wells MW-103S and MW-104D

Figure - Concentration Trends -Source Area Wells MW-104I and MW-106D

Figure - Concentration Trends -Source Area Wells MW-106S

Response to EPA Comment 4 050305doc 3 of 26 Woodard amp Curran (211941)

I I

El I

II I I 1 I

I

i

Event Baseline Case ID WC-01 WC-01

Well Date Aug-99 Oct-99 LOT10 1 LOT1-1 1 LOT11-4 LOT14 1 LOT15 1 LOT15-1 1 LOT16 1 LOT16-1 1 LOT17 1 LOT18 1 LOT19 1 LOT2 LOT20 1 LOT21-10 1 LOT21-11 1 LOT21-12 1 LOT21-13 1 LOT21-14 1 LOT21-2 1 LOT21-5 1 LOT21-7 LOT21 -8 1 LOT21-9 1 LOT23 1 LOT24 1 LOT28-1 1 LOT28-2 1 LOT28-3 1 LOT28-4 1 LOT28W 1 LOT30 1 LOT30-1 1 LOT30-2 1 LOT30-3 1 LOT30-4 1 LOT30-5 LOT31 LOT35 1 LOT41 1 LOT42-1 1 LOT43-1 1 LOT43-4 1 LOT6-1 1 LOT67 1 LOT6-7 1 LOT6-8A 1 LOT6-8B 1 LOT80-1 1 LOT82 1 MW-101D MW-1011 MW-101S MW-102D MW-102S MW-103D MW-103S MW-104D MW-1041 MW-104S MW-105D MW-106D

Groundwater Sampling Location Summary 1999 - 2004xls

Sampling Events 1999-2004

Hows Corner Superfund Site Plymouth Maine

Supplemental 2001 2002 2003 Pumping 2004 Pre-ROD Rl Sampling Sampling Sampling Test Sampling WC-03 WC-09 WC-25 WC-30 WC-42B WC-56 WC-58 Dec-99 May-00 Jun-01 Jan-02 Apr-03 Sep-04 Sep-04

1

1 1 1

1 1 1 1 1

1 1

1

1 1

1 1 1

1 1 1 1 1

1

1 1

1 1 1 1

1

1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

Sampling Events 1999-2004

Hows Corner Super-fund Site Plymouth Maine

Supplemental 2001 2002 2003 Pumping Event Baseline Pre-ROD Rl Sampling Sampling Sampling Test

Case ID WC-01 WC-01 WC-03 WC-09 WC-25 WC-30 WC-42B WC-56

ll

Well Date Aug-99 Oct-99 Dec-99 May-00 Jun-01 Jan-02 Apr-03 Sep-04 MW-106S 1 1 1 1 1 MW-107D 1 1 MW-108D 1 1 1 1 1 MW-108S 1 1 1 1 1 MW-110D 1 1 MW-111D 1 1 MW-112D 1 1 1 1 1 MW-112S 1 1 1 1 1 MW-113D 1 1 MW-114D 1 1 1 1 1 MW-114S 1 1 1 1 1 MW-115D 1 1 1 1 1 MW-12DB 1 1 1 MW-12SB 1 1 1 MW-13DB 1 1 1 1 1 1 MW-13SB 1 1 1 MW-14DB 1 1 MW-14SO 1 1 MW-15DB 1 1 1 MW-15SB 1 1 1 MW-16DB 1 1 1 1 1 1 MW-16IB 1 1 1 1 1 1 MW-16SO 1 1 MW-17DO 1 1 1 MW-17SO 1 1 1 MW-1B 1 1 1 1 1 1 MW-203D MW-203S MW-204D MW-204S MW-205 MW-206D

I MW-206S MW-2DB 1 1 MW-2DDB 1 1 MW-2IB 1 1 1 1 1 1 MW-3B 1 1 1 1 1 1

I MW-4O 1 1 1 MW-5B 1 1

II MW-6DB 1 1 1 MW-6SB 1 1 1 MW-8DB 1 1 1 MW-8SB 1 1 1

II PW-207 1 SEEP-1 1 SUBTOTAL - RESIDENTIAL 44 25 0 2 0 3 0 SUBTOTAL - MONITORING 22 48 41 15 15 15 1

Total 3 66 73 41 17 15 18 1

I Included in most recent data

I Notes 1 - Overburden well not included in most recent data for plotting

2 - Tetrahydrofuran and 2-Butanone were the only two compounds detected in this well and are thought to be the result of well repair not included in most recent data for plotting

3 - Not included in most recent data for plotting

2004 Sampling

WC-58 Sep-04

1

1 1

1 1

1 1 1

1

1 1

1 1 1 1 1 1 1 1 1

1 1

1

0 29

29

Groundwatef Sampling Location Summary 1999 - 2004xls

I

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

monitoring well Figure 4-14 total VOC contour (ugl) - December 1999January 2000 Distribution of Total VOCs in

Note SW-113 is located downstream of SEEP-1 Shallow Bedrock Groundwater total concentration of detected VOCs ND= not detected these two locations were sampled during the Pre-ROD Sampling Event

Baseline Sampling Event in OctoberNovember 1999 Hows Corner Superfund Site Surface Water Sampling Location A Plymouth Maine Seep Sampling Location laquo- WOODARD ampCURRAN

995037wipri reportepa ri interim final feb 2001cadd drawingsfinalfig 4-14

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

0 300 600 I

FEET

Q residential well Figure 4-16 monitoring well Distribution of Total VOCs in

Deep Bedrock Groundwater total VOCs contour (ugl) Pre-ROD Sampling Event

active residential wells with lot number Hows Corner Superfund Site 2deg42deg Plymouth Maine total concentration of detected VOCs ND= not detected WOODARD ampCURRAN Enyinaaring bull Science bull Operations bull

995037wipri reportepa ri interim final feb 2001cadd drawingsfinalfig4mdash16

PLYMOUTH POND

PLYMOUTH POND

1 628Tl7MW-2bB 12135

PLYMOUTH POND

monitoring well Figure 4-20

V total VOC contour (ugl) - June 2000 Distribution of Total VOCs in Shallow Bedrock Groundwater

| 34 | total concentration of detected VOCs ND= not detected NA = not analyzed Supplemental Sampling Event Note SW-113 is located downstream of SEEP-1 Hows Corner Superfund Site

Surface Water Sampling Location these two locations were sampled during the Plymouth Maine Baseline Sampling Event in OctoberNovember 1999 Seep Sampling Location WOODARD amp CURRAN

Engineering bull Science - Operations bull 995037wipri reportepa ri interim final feb 2001 cadd drawingsfinalfig 4-20

residential well Figure 4-22 Distribution of Total VOCs in

monitoring well Deep Bedrock Groundwater

total VOCs contour (ugl) Supplemental Sampling Event

Hows Corner Superfund Site

total concentration of detected VOCs ND= not detected NA = not analyzed Plymouth Maine

WOODARD amp CURRAN

995037wipri reportepa-ri interim final feb 2001cadd drawingsfinalfig 4-22 Engineering bull Science - Operations bull

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

FEET

Shallow Monitoring Well

Deep Monitoring Well

C Detected Concentration ND = Not Detected Figure 1-XS Distribution of Total VOCs in Shallow Bedrock Groundwater

Pumping Well

17-Acre Property Boundary Concentration Contour (ugl)

June 2001 Hows Corner Superfund Site

Plymouth Maine WOODARDampCURRAN

-i^rhvj bull Scbncn bull Operations bull 211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0601 dwg04-20-05

PLYMOUTH POND Hopkins Road V

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PLYMOUTH POND

PLYMOUTH POND

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0 300 600 mdashfa FEET

Shallow Monitoring Well bull bull - 17-Acre Property Boundary Figure 1-XD

Deep Monitoring Well 1 I Detected Concentration ND = Not Detected Distribution of Total VOCs in Deep Bedrock Groundwater

-mf- Pumping Well June 2001 Residential Well Hows Corner Superfund Site

Plymouth Maine i h Surface Water Sampling Point

g WOODARD ampCURRAN _ ^ _ ^ _ _ yen_ rj i|Hlaquorlny bull Science bull Opt

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0601 dwg04-20-05

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PLYMOUTH POND

PLYMOUTH POND

Shallow Monitoring Well

Deep Monitoring Well

Detected Concentration ND = Not Detected Figure 1-YS Distribution of Total VOCs in Shallow Bedrock Groundwater

Pumping Well

17-Acre Property Boundary Concentration Contour (ugl)

January 2002 Hows Corner Superfund Site

Plymouth Maine WOODARD amp CURRAN Engineering Science- Operations bull

211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0102dwg04-20-05

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Site Pand^ laquoum-laquoBTuitaraquo tLV

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Shallow Monitoring Well mdashbullbullbull 17-Acre Property Boundary Figure 1-YD - A - Deep Monitoring Well FT Detected Concentration ND = Not Detected Distribution of Total VOCs in

Deep Bedrock Groundwater Pumping Well January 2002 Residential Well Hows Corner Superfund Site

Plymouth Maine Surface Water Sampling Point

WOODARD ampCURRAN Engineering Sciencs- Operations bulli Si

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0102dwg04-20-05

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Shallow Monitoring Well E Detected Concentration ND = Not Detected Figure 1-ZS Distribution of Total VOCs in

Deep Monitoring Well Shallow Bedrock Groundwater

Pumping Well Hows Corner

April 2003 Superfund Site

17-Acre Property Boundary Plymouth Maine Concentration Contour (ugl) r WOODARD ampCURRAN

Engineering bull Science bull Operations bull 211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0403dwg04-20-05

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ft Shallow Monitoring Well mdashbullbullmdash 17-Acre Property Boundary Figure 1-ZD Deep Monitoring Well I 1 I Detected Concentration ND = Not Detected Distribution of Total VOCs in

Deep Bedrock Groundwater Pumping Well April 2003

Q) Residential Well Hows Corner Superfund Site Plymouth Maine

(T) Surface Water Sampling Point WOODARD ampCURRAN poundKk EnginawtirKj bull Science - Operations bull

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0 Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

B MW-1B

I 12000

PCE

B 10000 Total VOCs

I

i 2000

i 0 Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

c MW-3B

G 2000

1800

B PCE

1600 Total VOCs

1 I I E

il-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

G E

211941

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I I z E

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Concentration Trends shy Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-13DB

Total VOCs

c i i c o

Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

MW-16DB

30

c i c c I c o

Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99

PCE

Total VOCs

Jul-01 Jul-03

211941

O bi

c Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

I MW-16IB

i 35

3

c Total VOCs

lt- 2 5

0 | gt

o

1 sectI

c c 0 4

Jul-90 Jul-92 Jul-94 Jul-96 Jul-98 Jul-00 Jul-02 Jul-04

I I MW-108D

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PCE 10

Total VOCs c oc 3

E E I 0

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

E 211941

c Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

fi MW-108S

I I 40

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Total VOCs

30

I f 26

20 I o

I 15

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c Dec-99 Dec-00 Dec-01 Dec-02 Dec-03 I 0

I MW-112D

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I

ition

B 1 ^

-i c 3

0 Dec-99 Dec-OO Dec-01 Dec-02 Dec-03

211941

I

i

I

cII

Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-112S

08

PCE

Total VOCs 06

o 04

02

0 Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

MW-114D

o

12000

10000

8000

6000

PCE

Total VOCs

4000

2000

i

ccEIIc

i

i

E

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

211941

Con

cent

ratio

n (

ug

l)

E Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

I MW-114S

E A5000 -- Total VOCs

- 4000

0 3000

2000

i 1000

i n shy

Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

MW-115D

c PCE

Total VOCs

c E

o

C c

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03 I 0

211941

IepoundII

EIEIIGICCIccc

30000

25000

20000

o bullsect 15000 b

o 10000 U

5000

0 Aug-99

25000

20000

5000

0 Aug-99

211941

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-2DB

PCE

Total VOCs

Aug-01 Aug-03

MW-2IB

PCE

Total VOCs

Aug-01 Aug-03

IDIBI

ii EIDIISIBIG C

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-102S

6000

5000 PCE

Total VOCs

4000

O 3000

2000

1000

0 Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

MW-103D

16000

~ 14000 ugt 3- 12000 o

^ 10000

sect 8000

O 6000

4000

2000

PCE

Total VOCs

0Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

211941

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

G MW-103S

I I

ampo

12000

10000

E sectc

S

8000

6000

4000

2000

0Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

G I 6000

MW-104D

i 5000

PCE

Total VOCs

i i c

2000

1000

Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

E I

211941

cIccIG

IIBCccBcIc

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-1041

PCE Total VOCs

a 25000

0 20000

a 15000

10000

5000

0 Jan-OO Jan-01 Jan-02 Jan-03 Jan-04

MW-106D

3000

2500 PCE

Total VOCs

=sect 2000

o bullsect 1500

1000

500

0 Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

211941

c Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

c MW-106S

I PCE

Total VOCs

i

i Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

i

i i i E

C

211941 c

Response to EPA-DEP Comment 5 Dated March 312005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

iiw

EPA-DEP Comment 5

Comment 5 Matrix Diffusion The report as well as other proponents of matrix diffusion suggest that depletion of DNAPL (Section 5112 page 5-15) needs to be achieved While that might be the ideal the goal is to achieve performance standards and that goal may be attainable while there is residual contamination in the rock perhaps even DNAPL globules The low bedrock matrix porosity (page 1-15) the high permeability values (page 4-4) the relative flux of the groundwater (page 5-5) and the decrease in surface area and out of the mainstream pockets (appendix C-4) all suggest that the diffusion out of the rock matrix would be insubstantial relative to the regional flux of groundwater through the Site

Response The TI Evaluation Report does not explicitly consider or rely upon matrix diffusion as a basis for requesting a TI Waiver for a portion of the Hows Corner Site The technical literature provides documentation that matrix diffusion can be a significant process that affects chemical transport and groundwater remediation timeframes in unconsolidated and consolidated media including fractured rock (US EPA 1989 Freeze and Cherry 1979 Pankow and Cherry 1996 Fountain 1998) Back diffusion of contaminants from the matrix porosity of the fractured rock can prolong the time necessary to achieve groundwater cleanup goals particularly for compounds such as PCE for which the cleanup goal is a low concentration It is our expectation that matrix diffusion has occurred at the Hows Corner Site and that back diffusion of PCE from the rock matrix will also occur Although the extent to which matrix diffusion is occurring at the Hows Comer Site has not been determined and that lack of knowledge contributes to uncertainty regarding the cleanup times at the Site the effect of matrix diffusion is to lengthen rather than shorten the time required for remediation

REFERENCES

Fountain JC 1998 Technologies for Dense Nonaqueous Phase Liquid Source Zone Remediation Ground-Water Remediation Technologies Analysis Center Technology Evaluation Report TE-98-02 December

Freeze RA and Cherry JA 1979 Groundwater Prentice-Hall Inc Englewood Cliffs NJ 07632 p 410-412

Pankow J F and Cherry J A 1996 Dense Chlorinated Solvents Waterloo Press Portland OR 97291-1399 p 67-88

US EPA 1989 Transport and Fate of Contaminants in the Subsurface EPA6254-89019 p 17-18

Response to EPA Comment 5 050305doc 1 of 1 Woodard amp Curran (211941)

WOODARD amp CURRAN Maine Massachusetts New Hampshire Connecticut Florida Operational offices across the US 1-800-426-4262 www woodardcurran com

Page 34: SDMS DocID 251749 - Records Collections · 2020-06-13 · CORPORATE OFFICES: Maine, Massachusetts, New Hampshire, Connecticut New, York, Florida Engineering • Science • Operations

analyzed for their f to determine the repeatability of the Walkley-Black method The average the mean and the geometric mean of the f values of these replicate samples was 000162 gocg 000150 gocg and 000159 gocgm respectively The standard deviation of these measurements was 000039 gocg

4 The Walkley and Black organic carbon measurement method is quick and simple but the results obtained cannot be considered quantitative because it requires a correction factor which often results in erroneous values it assumes the organic carbon has an average valence of zero oxidizable and reducible constituents such as chloride ferrous iron and manganese oxides interfere with the results and the errors introduced by interference are potentially greater when the organic carbon content is low at low foc values it is not clear that organic carbon is controlling PCE sorption (Schwarzenbach and Westall 1981 Mackay et al 1986 Fetter 1999)

bull Schumachers review (NCEA-C-1282 EMASC-001 April 2002) of the Walkley-Black method identifies several potential problems with this analytical method that could occur if the analytical lab is not familiar with the nuances of the chemistry associated with this method Interestingly Schumachers review neglected one of the more important analytical steps required to avoid errors in quantifying f in samples where there might beNAPL

It is absolutely critical to eliminate any NAPL from rock core samples prior to using the Walkley-Black method to measure foe in such samples This was done by the lab (PTS Laboratories) that measured the foe in the rock core samples from Hows Corner The lab used the Dean-Stark method (solvent extraction) to remove all hydrocarbons (including PCE and other NAPLs) from the sample (PTS Laboratories) This extraction method does not interfere with the subsequent analysis of the natural organic carbon associated with the rock core

Subsequently the samples were dried at 150degC to a constant weight (normally 16 hours) This latter step oxidizes all inorganic minerals including ferrous bearing minerals to ferric oxides and precludes their interference during the oxidation of the samples with chromic acid This procedure completely eliminates any positive bias in the reported foc

data that might have occurred due to the presence of ferrous ions and other reduced minerals

bull As noted in Response 3 the incomplete oxidation of total organic carbon results in an underestimate of the f and is corrected for by multiplying the f by a correction factor of 130 (Walkley amp Black 1934 Schulte 1995) The fx data reported in the TI Evaluation was corrected accordingly by using this correction factor

bull Excess chloride (Cl~) in percent weight quantities as found in saline soils may interfere with the quantitative titration of reduced chromium (Walkley 1947) However given that the primary rock type at the Hows Corner site is phyllite it is highly unlikely that there was sufficient chloride in the rock core samples for this to occur

bull Manganese oxides may also interfere with the analysis of f through competing with the dichromate ion for any oxidizable carbon (Walkley 1947) However in such cases the reported f would be an underestimate of the f present in the rock core Walkley (1947)

Response to EPA Comment 3 050205doc 3 of 11 Woodard amp Curran (211941)

4

reported that in the case where the ratio of MnO2 to carbon is 85 to 1 the error in the carbon determinations would only be 0 to 6 percent

It may also be useful to compare the analysis of total organic carbon in a geologic matrix that contains high levels of manganese using EPA method 9060 to the Walkley-Black method Table 1 summarizes data provided by one of the PRPs that compares the analysis of total organic carbon in a geologic matrix that contains approximately 02 wgt manganese (approximately 03 wgt manganese oxide)

Table 1 Comparison of total organic carbon measured using the EPA- 9060 method and the Walkley-Black method

Laboratory EPA-9060 Method Walkley-Black Method A Ave 00226 gocg Not analyzed

Stdev 000251 gocg n = 5

B Ave 002219 gocg Ave 002050 gocg Stdev = 000316 gocg Stdev =000971 gocg

n= 10 n = 10

The similarity in the total organic carbon concentrations measured by these two different methods provides further confidence that the Walkley-Black method is a viable method for analysis of total organic carbon in the presence of manganese equivalent to at least 10 by weight of the total organic carbon

5 The Walkley and Black organic carbon measurement at lowf^ values it is not clear that organic carbon is controlling PCE sorption (Schwarzenbach and Westall 1981 Mackay et al 1986 Fetter 1999)

bull Schwarzenbach and Westalls (1981) paper states that f values of less than 0001 gocg should not be used in combination with Kow (octanol-water partition coefficients) values to calculate K^ values (solid phase partition coefficients) values for a specific contaminant It should be noted that the TI Evaluation did not use the f data to calculate the KQC from the Kow Instead as requested by the EPA the measured KOC value for PCE was used to calculate the retardation factor for this contaminant

bull Schwarzenbach et al (2003) stated more recently that Even at very low f values (ie foe = 0001 kgoc - kg1 solid) sorption to the organic components of a natural sorbent may still be the dominant mechanism in defining the adsorption of organic compounds to geological matrices

bull In 1985 M Piwoni from the US EPA Robert S Kerr Environmental Research Laboratory published a paper (Banerjee et al 1985) that showed that for very hydrophobic molecules TOC content of the sorbent will control sorption down to levels of organic carbon that defy quantitation Contaminants such as the PCE found in the groundwater at Hows Corner are in this category of compounds

Given the aforementioned reasons the f values reported in the TI Evaluation are accurate within the noted statistical limitations and will have a predictable impact upon the retardation of PCE during groundwater transport

Response to EPA Comment 3 050205doc 4 of 11 Woodard amp Curran (211941)

6 In order to derive a Kd-based retardation factor that is reasonable given the reported foc

values and the rapid advance of the PCE plume described on pages 4-11 and 4-12 the flushing model requires a bulk density to porosity ratio that is roughly two orders of magnitude higher than the actual ratio for the Hows Comer bedrock (page 4-4) This apparent discrepancy needs to be addressed

The apparent discrepancy of bulk density to porosity ratios is most likely due to the fact that the Batch Flushing Model was originally developed for a porous medium and is not directly applicable to fractured bedrock As stated in Appendix C (page C-4) of the Draft Technical Impracticability Evaluation Report in order to use the Batch Flushing Model to describe the transport of contaminated groundwater in fractured bedrock where the matrix porosity is insignificant it is more appropriate to use a fracture surface area to void space ratio to calculate the retardation factor (R) than a bulk density to porosity ratio (Freeze amp Cherry 1979)

Since it is impractical to determine the actual surface area to which contaminants can adsorb the Batch Flushing Model was used with two simplifying assumptions bull The Kd was calculated from the f and the K^ bull The bulk density to porosity ratio term in the Batch Flushing Model was constrained to range

from 4 to 10 the typical range of such ratios in porous media (Freeze amp Cherry 1979)

If one uses site specific bedrock bulk density and porosity values the bulk density to porosity ratio is several orders of magnitude greater (specifically 273 gcc bullbull 000165 (dimensionless) = 1654 gcc) than the range of ratios of 4 to 10 used in the Batch Flushing Model in the Draft Technical Impracticability Evaluation Report Constraining the bulk density to porosity ratio within the range of ratios of 4 to 10 results in significantly lower R value than would be obtained using specific bedrock bulk density and porosity values

In summary in bedrock where fractures are the primary porosity the bulk density to porosity ratio can vary considerably and will be a function of the number of fractures and the fracture aperture The calculated bulk density to porosity ratio will be inversely proportional to the porosity This means that in fractured rock with limited fracturing and smaller porosity the calculated bulk density to porosity ratio is greater and will result in a greater calculated retardation factor than in bedrock with more extensive fracturing and greater porosity Consequently the calculated retardation factor will be greater for bedrock with less surface area available for sorption than bedrock with greater surface area for sorption This is contrary to what actually occurs

4 Response to EPA Comment 3 050205doc 5 of 11 Woodard amp Curran (211941)

m

REFERENCES

Banerjee P MD Piwoni K Ebeid (1985) Sorption of organic contaminants to a low carbon subsurface core Chemosphere _14 1057-1067

Freeze RA JA Cherry (1979) Groundwater Prentice Hall Englewood Cliffs NJ pg 604

PTS Laboratories wwwptsgeolabscompdf files3TOCnotepdf

Schulte EE (1995) Recommended soil organic matter tests in Recommended Soil Testing Procedures for the Northeastern United States Northeastern Regional Publication No 493 Chapter 8

Schwarzenbach RP J Westall (1981) Transport of nonpolar organic compounds from surface water to groundwater Laboratory sorption studies Environ Sci Tech 15 1360-1367

Schwarzenbach RP PM Gschwend DM Imboden (2003) Environmental Organic Chemistry Wiley-Interscience pg 292 408 amp 412

Walkley A LA Black (1934) An examination of the Degtjareff method for determining soil organic matter and a proposed modification of the chromic acid titration method Soil Science 37 29-38

Walkley A (1947) A critical examination of a rapid method for determining organic carbon in soils - effect of variations in digestion conditions and of inorganic soil constituents Soil Science 63251-264

Woodard amp Curran Inc (WampC) 2005 Draft Technical Impracticability Evaluation Hows Corner Superfund Site Plymouth Maine January 2005

Response to EPA Comment 3 050205doc 6 of Woodard amp Curran (211941)

LIST OF ATTACHMENTS (Response to Comment 3)

Appendix B to Draft Technical Impracticability Evaluation Measurement of foe at Hows Corner (4 pages)

m

Response to EPA Comment 3 050205doc 7 of 11 Woodard amp Curran (211941)

Appendix B Measurement of foe of Rock Core at Hows Corner

There are two general approaches to measure the fraction of organic carbon (foe) in rock cores

bull Measurement of weight loss by ignition of organic matter bull Chemical oxidization of organic carbon to carbon dioxide and either

subsequent quantification of the oxidant used for the reaction or quantification of the carbon dioxide produced during this oxidation process

The weight loss method is subject to errors caused by volatilization of substances other than organic materials such as water hydroxides and mineral carbonates Quantification of foe by the weight loss method is particularly sensitive to the presence of carbonates in rock cores There are however weight loss methods that are designed to differentiate between organic carbon and the aforementioned interfering materials but they require considerable care and are less accurate at low foe values Hence the weight loss method was not well suited for measuring the foe of the rock core from Hows Corner

The chemical oxidation of organic carbon is much better suited for quantifying organic carbon in rock cores such as those from Hows Corner This method uses a strong chemical oxidant to oxidize organic carbon to carbon dioxide and then measures either the chemical oxidant used to oxidize the organic carbon or the quantity of carbon dioxide produced In addition this general approach is not subject to interference by volatilization of other constituents of the rock core

There are at least two such chemical oxidation methods

bull The method of Baccini which was described by Schwarzenbach amp Westall (1981) first acidifies the sample to eliminate interference by carbonates Then a strong oxidant is used to chemically oxidize the organic carbon to carbon dioxide The resulting carbon dioxide is subsequently reduced to methane and quantified using a flame ionization detector Unfortunately this method has not been described in detail in a referred journal Hence it is would not have been appropriate to use to characterize the foe in the Hows Corner rock core

bull The more commonly used method to quantify foe in rock core is the Walkley-Black method (1934) This method is preferred for RBCA and DODDOE projects and by the oil industry

The Walkley-Black method uses an excess of chromic acid to oxidize (digest) organic matter to carbon dioxide The remaining chromic acid that was not consumed during the oxidation of the organic carbon is then quantified by titration with ferrous sulfate The difference in chromic acid prior to and after the oxidation of the organic carbon represents the total chromic acid used to oxidize

Hows Corner TI Evaluation Page 1 January 13 2005 Appendix B

the organic carbon in the sample The latter can be calculated using the chemical stoichiometry of the reaction

The Walkley-Black method is very accurate for samples that contain less than 2 organic carbon matter The minimum detection limit (MDL) for the Walkley-Black method is 100 mgkg or an foe of 0001

Given the rock core at Hows Corner was expected to contain less than 2 organic carbon the Walkley-Black method was used to measure the foe from 19 different rock core samples collected from varying depths ranging from 11 to 90 feet

Table 1 provides a statistical summary of the aforementioned data

Table 1 Statistical summary of foe data from rock cores collected at varying depths

Statistical Parameter Calculated Value foe Minimum Detection Limit (MDL) 00010 Number of samples analyzed (n) 19 Average foe 00019 Median foe 00019 Geometric Mean foe 00019 Standard deviation of foe measurements 000033 Relative standard deviation 174 -+ 95 Confidence intervals 00012 to 00025

The data in Table 1 shows the following

bull The foe from the Hows Corner rock cores are statistically greater than the MDL of the Walkley-Black analytical method

bull The average and median values for the foe of the Hows Corner rock cores from varying depths are nearly identical indicating that there is little variability in the foe values in the source zone at the site

bull The standard deviation of these measurements is 000033 which is 174 of the average foe

bull The 95 confidence intervals of the foe of the rock core at Hows Corner are 00012 to 00025

The foe was also analyzed from three separate samples taken from the same rock core at a depth of 55 feet (Only one of these samples was included in the data summarized in Table 1) Table 2 shows the statistical repeatability of this type of analysis

Hows Corner TI Evaluation Page 2 January 13 2005 Appendix B

Table 2 Repeatability of analysis of foe from one rock core at 55 feet in depth

Statistical Parameter Calculated Value Number of samples analyzed (n) 3 Average foe 00016 Median foe 00015 Geometric Mean foe 00016 Standard deviation of foe measurements 000039 Relative standard deviation 240 -+ 95 Confidence intervals 00008 to 00024

The data in Table 2 shows the following

bull The percent relative standard deviation of these three analyses of foe from the same rock core at Hows Corner is 24

bull The 95 confidence interval of the foes measured in this particular rock core at Hows Conrer is 00008 to 00024

These results show that there is good repeatability in using the Walkley-Black method for analysis of the foe in the rock core at Hows Corner

References Schwarzenbach amp Westall (1981) Transport of nonpolar organic compounds from surface water to groundwater Laboratory sorption studies Environ Sci Tech 15 1360-1367

Walkley A I A Black (1934) An examination of Degtjareff method for determining soil organic matter and a proposed modification of the chromic acid titration method Soil Sci 37 29-37

Hows Corner Tl Evaluation Page S January 13 2005 Appendix B

Woodard and Curran PTS Laboratories PTS File No 34618

ORGANIC CARBON DATA (METHODOLOGY WALKLEY-BLACK)

PROJECT NAME PROJECT NO

SAMPLE ID

203-chip-13 203-chip-23 203-chip-27 203-chip-38 203-chip-42 203-chip-47 203-chip-52 203-chip-58 203-chip-69 203-chip-82 207-chip-11 207-chip-19 207-chip-24 207-chip-29 207-chip-35 207-chip-45 207-chip-55 207-chip-87 207-chip-90

207-chip-55 55-MS

55-MSMSD

Hows Corner NA

DEPTH ft

13 23 27 38 42 47 52 58 69 82 11 19 24 29 35 45 55 87 90

55 NA NA

MATRIX

Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip

Average Median

Geometric Mean Standard Deviation Relative Std Dev

+- 95 Confidence Interval n

Rock Chip Rock Chip Rock Chip

Average Median

Geometric Mean Standard Deviation Relative Std Dev

+- 95 Confidence Interval n

FRACTION ORGANIC CARBON

(gg)

170E-03 185E-03 185E-03 170E-03 240E-03 190E-03 230E-03 180E-03 170E-03 115E-03 195E-03 220E-03 220E-03 235E-03 135E-03 190E-03 205E-03 175E-03 160E-03

188E-03 185E-03 185E-03 327E-04

1739 123E-03 to

19

205E-03 130E-03 150E-03

162E-03 150E-03 159E-03 388E-04

2402 840E-04 to

3

2532E-03

2393E-03

Hows Corner Tl Evaluation Appendix B January 13 2005

Response to EPA-DEP Comment 4 Dated March 31 2005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

EPA-DEP Comment 4

Comment 4 Distribution of contaminants First the TI report seems based on the assertion that there is DNAPL at the source area yet it also appears to represent that the source area is small and the bedrock below 85 is competent (or less fractured) and less impacted by the release of contaminants Some of the confusion may result from using most recent data when that data is from several different sampling events over several years and there is no discernible difference in concentrations between shallow and deep bedrock or as in Section 421 where generally decreased generally increase generally similar and similar concentrations in four consecutive sentences leads to a muddled picture of the contaminant distribution

Second the report asserts that the distribution of contaminants over the entire plume has not changed with time but fails to support this conclusion with data again relying on data that is from different sampling dates for one composite representation

Response The likely presence of dense non-aqueous phase liquid (DNAPL) at the Hows Corner Site and the determination that the source area is small are not mutually exclusive and both are conclusions drawn from information obtained during field investigations The presence of DNAPL in the source area is based on the elevated concentrations of volatile organic compounds (VOCs) detected in the groundwater (WampC 2001 WampC 2002) The conclusion that the source area is small is based on the area in which VOCs in groundwater have been detected at concentrations that are considered to be indicative of the presence of DNAPL nearby Similarly the conclusion that fracture frequency decreases at depths greater than approximately 50 to 85 feet below ground surface was based on field observation during the RI field work The fact that zones with observed fractures exhibited higher hydraulic conductivities than zones without fractures coupled with the decreasing frequency of observed fractures with depth led to the conclusion that the hydraulic conductivity of the bulk rock decreases with depth

The most recent data from all wells were used to provide the maximum VOC data set size During the RI all of the previously-existing and then newly-installed monitoring wells were sampled along with several residential wells The RI sampling included up to 48 monitoring wells Subsequent to the RI and prior to the TI three rounds of monitoring were conducted to verify that the plume was stable 15 monitoring wells were sampled during each of the three rounds During the TI field investigation 29 wells were sampled for VOCs The sampled wells included all of the newly-installed wells and a subset of wells installed during the RI for a total of 29 monitoring wells By using most recent data VOC results from 53 monitoring wells were included in the evaluation (see table labeled Sampling Events for listing of monitoring wells) This approach was selected because there generally was little variation in the data from a particular location between years This is borne out by the attached individual plots of VOCs detected in shallow bedrock and deep bedrock for the Pre-ROD (December 1999January 2000) and Supplemental (May 2000) sampling events and for June 2001 January 2002 and April 2003 sampling events The Pre-ROD and Supplemental plots are similar to the subsequent plots from the 2001 2002 and 2003 sampling events

In addition to maps showing the spatial distribution of VOC data at a given time trend plots of the data from a particular location through time (attached) indicate that since the RI concentrations generally have been stable or have decreased Together the maps and trend plots and the data from which they were developed indicate that the distribution of contaminants over the entire plume has not changed appreciably with time

Response to EPA Comment 4 050305doc 1 of 26 Woodard amp Curran (211941)

REFERENCES

Woodard amp Curran Inc (WampC) 2001 Final Remedial Investigation Report Hows Corner Superfund Plymouth Maine July 2001

Woodard amp Curran Inc (WampC) 2002 Final Feasibility Study Report - Non-Source Area Groundwater Hows Corner Superfund Site Plymouth Maine Hows Corner Superfund Plymouth Maine July 2002

Response to EPA Comment 4 050305doc 2 of 26 Woodard amp Curran (211941)

LIST OF ATTACHMENTS (Response to Comment 4)

Table - Sampling Events 1999 - 2004 (2 pages)

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater Pre-ROD Sampling Event

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater Pre-ROD Sampling Event

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater Supplemental Sampling Event

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater Supplemental Sampling Event

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater June 2001

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater June 2001

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater January 2002

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater January 2002

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater April 2003

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater April 2003

Figure - Concentration Trends - Non-Source Area Wells MW-1B and MW-3B

Figure - Concentration Trends - Non-Source Area Wells MW-13DB and MW-16DB

Figure - Concentration Trends - Non-Source Area Wells MW-16IB and MW- 108D

Figure - Concentration Trends - Non-Source Area Wells MW-108S and MW-112D

Figure - Concentration Trends - Non-Source Area Wells MW-112S and MW-114D

Figure - Concentration Trends - Non-Source Area Wells MW-114S and MW-115D

Figure - Concentration Trends -Source Area Wells MW-2DB and MW-2IB

Figure - Concentration Trends -Source Area Wells MW-102S and MW-103D

Figure - Concentration Trends -Source Area Wells MW-103S and MW-104D

Figure - Concentration Trends -Source Area Wells MW-104I and MW-106D

Figure - Concentration Trends -Source Area Wells MW-106S

Response to EPA Comment 4 050305doc 3 of 26 Woodard amp Curran (211941)

I I

El I

II I I 1 I

I

i

Event Baseline Case ID WC-01 WC-01

Well Date Aug-99 Oct-99 LOT10 1 LOT1-1 1 LOT11-4 LOT14 1 LOT15 1 LOT15-1 1 LOT16 1 LOT16-1 1 LOT17 1 LOT18 1 LOT19 1 LOT2 LOT20 1 LOT21-10 1 LOT21-11 1 LOT21-12 1 LOT21-13 1 LOT21-14 1 LOT21-2 1 LOT21-5 1 LOT21-7 LOT21 -8 1 LOT21-9 1 LOT23 1 LOT24 1 LOT28-1 1 LOT28-2 1 LOT28-3 1 LOT28-4 1 LOT28W 1 LOT30 1 LOT30-1 1 LOT30-2 1 LOT30-3 1 LOT30-4 1 LOT30-5 LOT31 LOT35 1 LOT41 1 LOT42-1 1 LOT43-1 1 LOT43-4 1 LOT6-1 1 LOT67 1 LOT6-7 1 LOT6-8A 1 LOT6-8B 1 LOT80-1 1 LOT82 1 MW-101D MW-1011 MW-101S MW-102D MW-102S MW-103D MW-103S MW-104D MW-1041 MW-104S MW-105D MW-106D

Groundwater Sampling Location Summary 1999 - 2004xls

Sampling Events 1999-2004

Hows Corner Superfund Site Plymouth Maine

Supplemental 2001 2002 2003 Pumping 2004 Pre-ROD Rl Sampling Sampling Sampling Test Sampling WC-03 WC-09 WC-25 WC-30 WC-42B WC-56 WC-58 Dec-99 May-00 Jun-01 Jan-02 Apr-03 Sep-04 Sep-04

1

1 1 1

1 1 1 1 1

1 1

1

1 1

1 1 1

1 1 1 1 1

1

1 1

1 1 1 1

1

1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

Sampling Events 1999-2004

Hows Corner Super-fund Site Plymouth Maine

Supplemental 2001 2002 2003 Pumping Event Baseline Pre-ROD Rl Sampling Sampling Sampling Test

Case ID WC-01 WC-01 WC-03 WC-09 WC-25 WC-30 WC-42B WC-56

ll

Well Date Aug-99 Oct-99 Dec-99 May-00 Jun-01 Jan-02 Apr-03 Sep-04 MW-106S 1 1 1 1 1 MW-107D 1 1 MW-108D 1 1 1 1 1 MW-108S 1 1 1 1 1 MW-110D 1 1 MW-111D 1 1 MW-112D 1 1 1 1 1 MW-112S 1 1 1 1 1 MW-113D 1 1 MW-114D 1 1 1 1 1 MW-114S 1 1 1 1 1 MW-115D 1 1 1 1 1 MW-12DB 1 1 1 MW-12SB 1 1 1 MW-13DB 1 1 1 1 1 1 MW-13SB 1 1 1 MW-14DB 1 1 MW-14SO 1 1 MW-15DB 1 1 1 MW-15SB 1 1 1 MW-16DB 1 1 1 1 1 1 MW-16IB 1 1 1 1 1 1 MW-16SO 1 1 MW-17DO 1 1 1 MW-17SO 1 1 1 MW-1B 1 1 1 1 1 1 MW-203D MW-203S MW-204D MW-204S MW-205 MW-206D

I MW-206S MW-2DB 1 1 MW-2DDB 1 1 MW-2IB 1 1 1 1 1 1 MW-3B 1 1 1 1 1 1

I MW-4O 1 1 1 MW-5B 1 1

II MW-6DB 1 1 1 MW-6SB 1 1 1 MW-8DB 1 1 1 MW-8SB 1 1 1

II PW-207 1 SEEP-1 1 SUBTOTAL - RESIDENTIAL 44 25 0 2 0 3 0 SUBTOTAL - MONITORING 22 48 41 15 15 15 1

Total 3 66 73 41 17 15 18 1

I Included in most recent data

I Notes 1 - Overburden well not included in most recent data for plotting

2 - Tetrahydrofuran and 2-Butanone were the only two compounds detected in this well and are thought to be the result of well repair not included in most recent data for plotting

3 - Not included in most recent data for plotting

2004 Sampling

WC-58 Sep-04

1

1 1

1 1

1 1 1

1

1 1

1 1 1 1 1 1 1 1 1

1 1

1

0 29

29

Groundwatef Sampling Location Summary 1999 - 2004xls

I

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

monitoring well Figure 4-14 total VOC contour (ugl) - December 1999January 2000 Distribution of Total VOCs in

Note SW-113 is located downstream of SEEP-1 Shallow Bedrock Groundwater total concentration of detected VOCs ND= not detected these two locations were sampled during the Pre-ROD Sampling Event

Baseline Sampling Event in OctoberNovember 1999 Hows Corner Superfund Site Surface Water Sampling Location A Plymouth Maine Seep Sampling Location laquo- WOODARD ampCURRAN

995037wipri reportepa ri interim final feb 2001cadd drawingsfinalfig 4-14

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

0 300 600 I

FEET

Q residential well Figure 4-16 monitoring well Distribution of Total VOCs in

Deep Bedrock Groundwater total VOCs contour (ugl) Pre-ROD Sampling Event

active residential wells with lot number Hows Corner Superfund Site 2deg42deg Plymouth Maine total concentration of detected VOCs ND= not detected WOODARD ampCURRAN Enyinaaring bull Science bull Operations bull

995037wipri reportepa ri interim final feb 2001cadd drawingsfinalfig4mdash16

PLYMOUTH POND

PLYMOUTH POND

1 628Tl7MW-2bB 12135

PLYMOUTH POND

monitoring well Figure 4-20

V total VOC contour (ugl) - June 2000 Distribution of Total VOCs in Shallow Bedrock Groundwater

| 34 | total concentration of detected VOCs ND= not detected NA = not analyzed Supplemental Sampling Event Note SW-113 is located downstream of SEEP-1 Hows Corner Superfund Site

Surface Water Sampling Location these two locations were sampled during the Plymouth Maine Baseline Sampling Event in OctoberNovember 1999 Seep Sampling Location WOODARD amp CURRAN

Engineering bull Science - Operations bull 995037wipri reportepa ri interim final feb 2001 cadd drawingsfinalfig 4-20

residential well Figure 4-22 Distribution of Total VOCs in

monitoring well Deep Bedrock Groundwater

total VOCs contour (ugl) Supplemental Sampling Event

Hows Corner Superfund Site

total concentration of detected VOCs ND= not detected NA = not analyzed Plymouth Maine

WOODARD amp CURRAN

995037wipri reportepa-ri interim final feb 2001cadd drawingsfinalfig 4-22 Engineering bull Science - Operations bull

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

FEET

Shallow Monitoring Well

Deep Monitoring Well

C Detected Concentration ND = Not Detected Figure 1-XS Distribution of Total VOCs in Shallow Bedrock Groundwater

Pumping Well

17-Acre Property Boundary Concentration Contour (ugl)

June 2001 Hows Corner Superfund Site

Plymouth Maine WOODARDampCURRAN

-i^rhvj bull Scbncn bull Operations bull 211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0601 dwg04-20-05

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PLYMOUTH POND

o

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Shallow Monitoring Well bull bull - 17-Acre Property Boundary Figure 1-XD

Deep Monitoring Well 1 I Detected Concentration ND = Not Detected Distribution of Total VOCs in Deep Bedrock Groundwater

-mf- Pumping Well June 2001 Residential Well Hows Corner Superfund Site

Plymouth Maine i h Surface Water Sampling Point

g WOODARD ampCURRAN _ ^ _ ^ _ _ yen_ rj i|Hlaquorlny bull Science bull Opt

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0601 dwg04-20-05

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PLYMOUTH POND

PLYMOUTH POND

Shallow Monitoring Well

Deep Monitoring Well

Detected Concentration ND = Not Detected Figure 1-YS Distribution of Total VOCs in Shallow Bedrock Groundwater

Pumping Well

17-Acre Property Boundary Concentration Contour (ugl)

January 2002 Hows Corner Superfund Site

Plymouth Maine WOODARD amp CURRAN Engineering Science- Operations bull

211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0102dwg04-20-05

PLYMOUTH POND

PLYMOUTH POND

Site Pand^ laquoum-laquoBTuitaraquo tLV

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0 300 600 ^ = FEET

Shallow Monitoring Well mdashbullbullbull 17-Acre Property Boundary Figure 1-YD - A - Deep Monitoring Well FT Detected Concentration ND = Not Detected Distribution of Total VOCs in

Deep Bedrock Groundwater Pumping Well January 2002 Residential Well Hows Corner Superfund Site

Plymouth Maine Surface Water Sampling Point

WOODARD ampCURRAN Engineering Sciencs- Operations bulli Si

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0102dwg04-20-05

- m j

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND j A O-shy

Shallow Monitoring Well E Detected Concentration ND = Not Detected Figure 1-ZS Distribution of Total VOCs in

Deep Monitoring Well Shallow Bedrock Groundwater

Pumping Well Hows Corner

April 2003 Superfund Site

17-Acre Property Boundary Plymouth Maine Concentration Contour (ugl) r WOODARD ampCURRAN

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- -

5 PLYMOUTH POND

Jo

FEET

ft Shallow Monitoring Well mdashbullbullmdash 17-Acre Property Boundary Figure 1-ZD Deep Monitoring Well I 1 I Detected Concentration ND = Not Detected Distribution of Total VOCs in

Deep Bedrock Groundwater Pumping Well April 2003

Q) Residential Well Hows Corner Superfund Site Plymouth Maine

(T) Surface Water Sampling Point WOODARD ampCURRAN poundKk EnginawtirKj bull Science - Operations bull

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0403dwg04-20-05

0 Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

B MW-1B

I 12000

PCE

B 10000 Total VOCs

I

i 2000

i 0 Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

c MW-3B

G 2000

1800

B PCE

1600 Total VOCs

1 I I E

il-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

G E

211941

El

I I z E

80

Concentration Trends shy Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-13DB

Total VOCs

c i i c o

Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

MW-16DB

30

c i c c I c o

Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99

PCE

Total VOCs

Jul-01 Jul-03

211941

O bi

c Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

I MW-16IB

i 35

3

c Total VOCs

lt- 2 5

0 | gt

o

1 sectI

c c 0 4

Jul-90 Jul-92 Jul-94 Jul-96 Jul-98 Jul-00 Jul-02 Jul-04

I I MW-108D

I 12

PCE 10

Total VOCs c oc 3

E E I 0

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

E 211941

c Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

fi MW-108S

I I 40

PCE 35

Total VOCs

30

I f 26

20 I o

I 15

10

c Dec-99 Dec-00 Dec-01 Dec-02 Dec-03 I 0

I MW-112D

c 35 - imdash

I A3 shyTotal VOCs

o c

E 1 2

I

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B 1 ^

-i c 3

0 Dec-99 Dec-OO Dec-01 Dec-02 Dec-03

211941

I

i

I

cII

Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-112S

08

PCE

Total VOCs 06

o 04

02

0 Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

MW-114D

o

12000

10000

8000

6000

PCE

Total VOCs

4000

2000

i

ccEIIc

i

i

E

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

211941

Con

cent

ratio

n (

ug

l)

E Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

I MW-114S

E A5000 -- Total VOCs

- 4000

0 3000

2000

i 1000

i n shy

Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

MW-115D

c PCE

Total VOCs

c E

o

C c

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03 I 0

211941

IepoundII

EIEIIGICCIccc

30000

25000

20000

o bullsect 15000 b

o 10000 U

5000

0 Aug-99

25000

20000

5000

0 Aug-99

211941

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-2DB

PCE

Total VOCs

Aug-01 Aug-03

MW-2IB

PCE

Total VOCs

Aug-01 Aug-03

IDIBI

ii EIDIISIBIG C

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-102S

6000

5000 PCE

Total VOCs

4000

O 3000

2000

1000

0 Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

MW-103D

16000

~ 14000 ugt 3- 12000 o

^ 10000

sect 8000

O 6000

4000

2000

PCE

Total VOCs

0Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

211941

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

G MW-103S

I I

ampo

12000

10000

E sectc

S

8000

6000

4000

2000

0Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

G I 6000

MW-104D

i 5000

PCE

Total VOCs

i i c

2000

1000

Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

E I

211941

cIccIG

IIBCccBcIc

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-1041

PCE Total VOCs

a 25000

0 20000

a 15000

10000

5000

0 Jan-OO Jan-01 Jan-02 Jan-03 Jan-04

MW-106D

3000

2500 PCE

Total VOCs

=sect 2000

o bullsect 1500

1000

500

0 Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

211941

c Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

c MW-106S

I PCE

Total VOCs

i

i Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

i

i i i E

C

211941 c

Response to EPA-DEP Comment 5 Dated March 312005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

iiw

EPA-DEP Comment 5

Comment 5 Matrix Diffusion The report as well as other proponents of matrix diffusion suggest that depletion of DNAPL (Section 5112 page 5-15) needs to be achieved While that might be the ideal the goal is to achieve performance standards and that goal may be attainable while there is residual contamination in the rock perhaps even DNAPL globules The low bedrock matrix porosity (page 1-15) the high permeability values (page 4-4) the relative flux of the groundwater (page 5-5) and the decrease in surface area and out of the mainstream pockets (appendix C-4) all suggest that the diffusion out of the rock matrix would be insubstantial relative to the regional flux of groundwater through the Site

Response The TI Evaluation Report does not explicitly consider or rely upon matrix diffusion as a basis for requesting a TI Waiver for a portion of the Hows Corner Site The technical literature provides documentation that matrix diffusion can be a significant process that affects chemical transport and groundwater remediation timeframes in unconsolidated and consolidated media including fractured rock (US EPA 1989 Freeze and Cherry 1979 Pankow and Cherry 1996 Fountain 1998) Back diffusion of contaminants from the matrix porosity of the fractured rock can prolong the time necessary to achieve groundwater cleanup goals particularly for compounds such as PCE for which the cleanup goal is a low concentration It is our expectation that matrix diffusion has occurred at the Hows Corner Site and that back diffusion of PCE from the rock matrix will also occur Although the extent to which matrix diffusion is occurring at the Hows Comer Site has not been determined and that lack of knowledge contributes to uncertainty regarding the cleanup times at the Site the effect of matrix diffusion is to lengthen rather than shorten the time required for remediation

REFERENCES

Fountain JC 1998 Technologies for Dense Nonaqueous Phase Liquid Source Zone Remediation Ground-Water Remediation Technologies Analysis Center Technology Evaluation Report TE-98-02 December

Freeze RA and Cherry JA 1979 Groundwater Prentice-Hall Inc Englewood Cliffs NJ 07632 p 410-412

Pankow J F and Cherry J A 1996 Dense Chlorinated Solvents Waterloo Press Portland OR 97291-1399 p 67-88

US EPA 1989 Transport and Fate of Contaminants in the Subsurface EPA6254-89019 p 17-18

Response to EPA Comment 5 050305doc 1 of 1 Woodard amp Curran (211941)

WOODARD amp CURRAN Maine Massachusetts New Hampshire Connecticut Florida Operational offices across the US 1-800-426-4262 www woodardcurran com

Page 35: SDMS DocID 251749 - Records Collections · 2020-06-13 · CORPORATE OFFICES: Maine, Massachusetts, New Hampshire, Connecticut New, York, Florida Engineering • Science • Operations

4

reported that in the case where the ratio of MnO2 to carbon is 85 to 1 the error in the carbon determinations would only be 0 to 6 percent

It may also be useful to compare the analysis of total organic carbon in a geologic matrix that contains high levels of manganese using EPA method 9060 to the Walkley-Black method Table 1 summarizes data provided by one of the PRPs that compares the analysis of total organic carbon in a geologic matrix that contains approximately 02 wgt manganese (approximately 03 wgt manganese oxide)

Table 1 Comparison of total organic carbon measured using the EPA- 9060 method and the Walkley-Black method

Laboratory EPA-9060 Method Walkley-Black Method A Ave 00226 gocg Not analyzed

Stdev 000251 gocg n = 5

B Ave 002219 gocg Ave 002050 gocg Stdev = 000316 gocg Stdev =000971 gocg

n= 10 n = 10

The similarity in the total organic carbon concentrations measured by these two different methods provides further confidence that the Walkley-Black method is a viable method for analysis of total organic carbon in the presence of manganese equivalent to at least 10 by weight of the total organic carbon

5 The Walkley and Black organic carbon measurement at lowf^ values it is not clear that organic carbon is controlling PCE sorption (Schwarzenbach and Westall 1981 Mackay et al 1986 Fetter 1999)

bull Schwarzenbach and Westalls (1981) paper states that f values of less than 0001 gocg should not be used in combination with Kow (octanol-water partition coefficients) values to calculate K^ values (solid phase partition coefficients) values for a specific contaminant It should be noted that the TI Evaluation did not use the f data to calculate the KQC from the Kow Instead as requested by the EPA the measured KOC value for PCE was used to calculate the retardation factor for this contaminant

bull Schwarzenbach et al (2003) stated more recently that Even at very low f values (ie foe = 0001 kgoc - kg1 solid) sorption to the organic components of a natural sorbent may still be the dominant mechanism in defining the adsorption of organic compounds to geological matrices

bull In 1985 M Piwoni from the US EPA Robert S Kerr Environmental Research Laboratory published a paper (Banerjee et al 1985) that showed that for very hydrophobic molecules TOC content of the sorbent will control sorption down to levels of organic carbon that defy quantitation Contaminants such as the PCE found in the groundwater at Hows Corner are in this category of compounds

Given the aforementioned reasons the f values reported in the TI Evaluation are accurate within the noted statistical limitations and will have a predictable impact upon the retardation of PCE during groundwater transport

Response to EPA Comment 3 050205doc 4 of 11 Woodard amp Curran (211941)

6 In order to derive a Kd-based retardation factor that is reasonable given the reported foc

values and the rapid advance of the PCE plume described on pages 4-11 and 4-12 the flushing model requires a bulk density to porosity ratio that is roughly two orders of magnitude higher than the actual ratio for the Hows Comer bedrock (page 4-4) This apparent discrepancy needs to be addressed

The apparent discrepancy of bulk density to porosity ratios is most likely due to the fact that the Batch Flushing Model was originally developed for a porous medium and is not directly applicable to fractured bedrock As stated in Appendix C (page C-4) of the Draft Technical Impracticability Evaluation Report in order to use the Batch Flushing Model to describe the transport of contaminated groundwater in fractured bedrock where the matrix porosity is insignificant it is more appropriate to use a fracture surface area to void space ratio to calculate the retardation factor (R) than a bulk density to porosity ratio (Freeze amp Cherry 1979)

Since it is impractical to determine the actual surface area to which contaminants can adsorb the Batch Flushing Model was used with two simplifying assumptions bull The Kd was calculated from the f and the K^ bull The bulk density to porosity ratio term in the Batch Flushing Model was constrained to range

from 4 to 10 the typical range of such ratios in porous media (Freeze amp Cherry 1979)

If one uses site specific bedrock bulk density and porosity values the bulk density to porosity ratio is several orders of magnitude greater (specifically 273 gcc bullbull 000165 (dimensionless) = 1654 gcc) than the range of ratios of 4 to 10 used in the Batch Flushing Model in the Draft Technical Impracticability Evaluation Report Constraining the bulk density to porosity ratio within the range of ratios of 4 to 10 results in significantly lower R value than would be obtained using specific bedrock bulk density and porosity values

In summary in bedrock where fractures are the primary porosity the bulk density to porosity ratio can vary considerably and will be a function of the number of fractures and the fracture aperture The calculated bulk density to porosity ratio will be inversely proportional to the porosity This means that in fractured rock with limited fracturing and smaller porosity the calculated bulk density to porosity ratio is greater and will result in a greater calculated retardation factor than in bedrock with more extensive fracturing and greater porosity Consequently the calculated retardation factor will be greater for bedrock with less surface area available for sorption than bedrock with greater surface area for sorption This is contrary to what actually occurs

4 Response to EPA Comment 3 050205doc 5 of 11 Woodard amp Curran (211941)

m

REFERENCES

Banerjee P MD Piwoni K Ebeid (1985) Sorption of organic contaminants to a low carbon subsurface core Chemosphere _14 1057-1067

Freeze RA JA Cherry (1979) Groundwater Prentice Hall Englewood Cliffs NJ pg 604

PTS Laboratories wwwptsgeolabscompdf files3TOCnotepdf

Schulte EE (1995) Recommended soil organic matter tests in Recommended Soil Testing Procedures for the Northeastern United States Northeastern Regional Publication No 493 Chapter 8

Schwarzenbach RP J Westall (1981) Transport of nonpolar organic compounds from surface water to groundwater Laboratory sorption studies Environ Sci Tech 15 1360-1367

Schwarzenbach RP PM Gschwend DM Imboden (2003) Environmental Organic Chemistry Wiley-Interscience pg 292 408 amp 412

Walkley A LA Black (1934) An examination of the Degtjareff method for determining soil organic matter and a proposed modification of the chromic acid titration method Soil Science 37 29-38

Walkley A (1947) A critical examination of a rapid method for determining organic carbon in soils - effect of variations in digestion conditions and of inorganic soil constituents Soil Science 63251-264

Woodard amp Curran Inc (WampC) 2005 Draft Technical Impracticability Evaluation Hows Corner Superfund Site Plymouth Maine January 2005

Response to EPA Comment 3 050205doc 6 of Woodard amp Curran (211941)

LIST OF ATTACHMENTS (Response to Comment 3)

Appendix B to Draft Technical Impracticability Evaluation Measurement of foe at Hows Corner (4 pages)

m

Response to EPA Comment 3 050205doc 7 of 11 Woodard amp Curran (211941)

Appendix B Measurement of foe of Rock Core at Hows Corner

There are two general approaches to measure the fraction of organic carbon (foe) in rock cores

bull Measurement of weight loss by ignition of organic matter bull Chemical oxidization of organic carbon to carbon dioxide and either

subsequent quantification of the oxidant used for the reaction or quantification of the carbon dioxide produced during this oxidation process

The weight loss method is subject to errors caused by volatilization of substances other than organic materials such as water hydroxides and mineral carbonates Quantification of foe by the weight loss method is particularly sensitive to the presence of carbonates in rock cores There are however weight loss methods that are designed to differentiate between organic carbon and the aforementioned interfering materials but they require considerable care and are less accurate at low foe values Hence the weight loss method was not well suited for measuring the foe of the rock core from Hows Corner

The chemical oxidation of organic carbon is much better suited for quantifying organic carbon in rock cores such as those from Hows Corner This method uses a strong chemical oxidant to oxidize organic carbon to carbon dioxide and then measures either the chemical oxidant used to oxidize the organic carbon or the quantity of carbon dioxide produced In addition this general approach is not subject to interference by volatilization of other constituents of the rock core

There are at least two such chemical oxidation methods

bull The method of Baccini which was described by Schwarzenbach amp Westall (1981) first acidifies the sample to eliminate interference by carbonates Then a strong oxidant is used to chemically oxidize the organic carbon to carbon dioxide The resulting carbon dioxide is subsequently reduced to methane and quantified using a flame ionization detector Unfortunately this method has not been described in detail in a referred journal Hence it is would not have been appropriate to use to characterize the foe in the Hows Corner rock core

bull The more commonly used method to quantify foe in rock core is the Walkley-Black method (1934) This method is preferred for RBCA and DODDOE projects and by the oil industry

The Walkley-Black method uses an excess of chromic acid to oxidize (digest) organic matter to carbon dioxide The remaining chromic acid that was not consumed during the oxidation of the organic carbon is then quantified by titration with ferrous sulfate The difference in chromic acid prior to and after the oxidation of the organic carbon represents the total chromic acid used to oxidize

Hows Corner TI Evaluation Page 1 January 13 2005 Appendix B

the organic carbon in the sample The latter can be calculated using the chemical stoichiometry of the reaction

The Walkley-Black method is very accurate for samples that contain less than 2 organic carbon matter The minimum detection limit (MDL) for the Walkley-Black method is 100 mgkg or an foe of 0001

Given the rock core at Hows Corner was expected to contain less than 2 organic carbon the Walkley-Black method was used to measure the foe from 19 different rock core samples collected from varying depths ranging from 11 to 90 feet

Table 1 provides a statistical summary of the aforementioned data

Table 1 Statistical summary of foe data from rock cores collected at varying depths

Statistical Parameter Calculated Value foe Minimum Detection Limit (MDL) 00010 Number of samples analyzed (n) 19 Average foe 00019 Median foe 00019 Geometric Mean foe 00019 Standard deviation of foe measurements 000033 Relative standard deviation 174 -+ 95 Confidence intervals 00012 to 00025

The data in Table 1 shows the following

bull The foe from the Hows Corner rock cores are statistically greater than the MDL of the Walkley-Black analytical method

bull The average and median values for the foe of the Hows Corner rock cores from varying depths are nearly identical indicating that there is little variability in the foe values in the source zone at the site

bull The standard deviation of these measurements is 000033 which is 174 of the average foe

bull The 95 confidence intervals of the foe of the rock core at Hows Corner are 00012 to 00025

The foe was also analyzed from three separate samples taken from the same rock core at a depth of 55 feet (Only one of these samples was included in the data summarized in Table 1) Table 2 shows the statistical repeatability of this type of analysis

Hows Corner TI Evaluation Page 2 January 13 2005 Appendix B

Table 2 Repeatability of analysis of foe from one rock core at 55 feet in depth

Statistical Parameter Calculated Value Number of samples analyzed (n) 3 Average foe 00016 Median foe 00015 Geometric Mean foe 00016 Standard deviation of foe measurements 000039 Relative standard deviation 240 -+ 95 Confidence intervals 00008 to 00024

The data in Table 2 shows the following

bull The percent relative standard deviation of these three analyses of foe from the same rock core at Hows Corner is 24

bull The 95 confidence interval of the foes measured in this particular rock core at Hows Conrer is 00008 to 00024

These results show that there is good repeatability in using the Walkley-Black method for analysis of the foe in the rock core at Hows Corner

References Schwarzenbach amp Westall (1981) Transport of nonpolar organic compounds from surface water to groundwater Laboratory sorption studies Environ Sci Tech 15 1360-1367

Walkley A I A Black (1934) An examination of Degtjareff method for determining soil organic matter and a proposed modification of the chromic acid titration method Soil Sci 37 29-37

Hows Corner Tl Evaluation Page S January 13 2005 Appendix B

Woodard and Curran PTS Laboratories PTS File No 34618

ORGANIC CARBON DATA (METHODOLOGY WALKLEY-BLACK)

PROJECT NAME PROJECT NO

SAMPLE ID

203-chip-13 203-chip-23 203-chip-27 203-chip-38 203-chip-42 203-chip-47 203-chip-52 203-chip-58 203-chip-69 203-chip-82 207-chip-11 207-chip-19 207-chip-24 207-chip-29 207-chip-35 207-chip-45 207-chip-55 207-chip-87 207-chip-90

207-chip-55 55-MS

55-MSMSD

Hows Corner NA

DEPTH ft

13 23 27 38 42 47 52 58 69 82 11 19 24 29 35 45 55 87 90

55 NA NA

MATRIX

Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip

Average Median

Geometric Mean Standard Deviation Relative Std Dev

+- 95 Confidence Interval n

Rock Chip Rock Chip Rock Chip

Average Median

Geometric Mean Standard Deviation Relative Std Dev

+- 95 Confidence Interval n

FRACTION ORGANIC CARBON

(gg)

170E-03 185E-03 185E-03 170E-03 240E-03 190E-03 230E-03 180E-03 170E-03 115E-03 195E-03 220E-03 220E-03 235E-03 135E-03 190E-03 205E-03 175E-03 160E-03

188E-03 185E-03 185E-03 327E-04

1739 123E-03 to

19

205E-03 130E-03 150E-03

162E-03 150E-03 159E-03 388E-04

2402 840E-04 to

3

2532E-03

2393E-03

Hows Corner Tl Evaluation Appendix B January 13 2005

Response to EPA-DEP Comment 4 Dated March 31 2005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

EPA-DEP Comment 4

Comment 4 Distribution of contaminants First the TI report seems based on the assertion that there is DNAPL at the source area yet it also appears to represent that the source area is small and the bedrock below 85 is competent (or less fractured) and less impacted by the release of contaminants Some of the confusion may result from using most recent data when that data is from several different sampling events over several years and there is no discernible difference in concentrations between shallow and deep bedrock or as in Section 421 where generally decreased generally increase generally similar and similar concentrations in four consecutive sentences leads to a muddled picture of the contaminant distribution

Second the report asserts that the distribution of contaminants over the entire plume has not changed with time but fails to support this conclusion with data again relying on data that is from different sampling dates for one composite representation

Response The likely presence of dense non-aqueous phase liquid (DNAPL) at the Hows Corner Site and the determination that the source area is small are not mutually exclusive and both are conclusions drawn from information obtained during field investigations The presence of DNAPL in the source area is based on the elevated concentrations of volatile organic compounds (VOCs) detected in the groundwater (WampC 2001 WampC 2002) The conclusion that the source area is small is based on the area in which VOCs in groundwater have been detected at concentrations that are considered to be indicative of the presence of DNAPL nearby Similarly the conclusion that fracture frequency decreases at depths greater than approximately 50 to 85 feet below ground surface was based on field observation during the RI field work The fact that zones with observed fractures exhibited higher hydraulic conductivities than zones without fractures coupled with the decreasing frequency of observed fractures with depth led to the conclusion that the hydraulic conductivity of the bulk rock decreases with depth

The most recent data from all wells were used to provide the maximum VOC data set size During the RI all of the previously-existing and then newly-installed monitoring wells were sampled along with several residential wells The RI sampling included up to 48 monitoring wells Subsequent to the RI and prior to the TI three rounds of monitoring were conducted to verify that the plume was stable 15 monitoring wells were sampled during each of the three rounds During the TI field investigation 29 wells were sampled for VOCs The sampled wells included all of the newly-installed wells and a subset of wells installed during the RI for a total of 29 monitoring wells By using most recent data VOC results from 53 monitoring wells were included in the evaluation (see table labeled Sampling Events for listing of monitoring wells) This approach was selected because there generally was little variation in the data from a particular location between years This is borne out by the attached individual plots of VOCs detected in shallow bedrock and deep bedrock for the Pre-ROD (December 1999January 2000) and Supplemental (May 2000) sampling events and for June 2001 January 2002 and April 2003 sampling events The Pre-ROD and Supplemental plots are similar to the subsequent plots from the 2001 2002 and 2003 sampling events

In addition to maps showing the spatial distribution of VOC data at a given time trend plots of the data from a particular location through time (attached) indicate that since the RI concentrations generally have been stable or have decreased Together the maps and trend plots and the data from which they were developed indicate that the distribution of contaminants over the entire plume has not changed appreciably with time

Response to EPA Comment 4 050305doc 1 of 26 Woodard amp Curran (211941)

REFERENCES

Woodard amp Curran Inc (WampC) 2001 Final Remedial Investigation Report Hows Corner Superfund Plymouth Maine July 2001

Woodard amp Curran Inc (WampC) 2002 Final Feasibility Study Report - Non-Source Area Groundwater Hows Corner Superfund Site Plymouth Maine Hows Corner Superfund Plymouth Maine July 2002

Response to EPA Comment 4 050305doc 2 of 26 Woodard amp Curran (211941)

LIST OF ATTACHMENTS (Response to Comment 4)

Table - Sampling Events 1999 - 2004 (2 pages)

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater Pre-ROD Sampling Event

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater Pre-ROD Sampling Event

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater Supplemental Sampling Event

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater Supplemental Sampling Event

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater June 2001

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater June 2001

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater January 2002

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater January 2002

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater April 2003

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater April 2003

Figure - Concentration Trends - Non-Source Area Wells MW-1B and MW-3B

Figure - Concentration Trends - Non-Source Area Wells MW-13DB and MW-16DB

Figure - Concentration Trends - Non-Source Area Wells MW-16IB and MW- 108D

Figure - Concentration Trends - Non-Source Area Wells MW-108S and MW-112D

Figure - Concentration Trends - Non-Source Area Wells MW-112S and MW-114D

Figure - Concentration Trends - Non-Source Area Wells MW-114S and MW-115D

Figure - Concentration Trends -Source Area Wells MW-2DB and MW-2IB

Figure - Concentration Trends -Source Area Wells MW-102S and MW-103D

Figure - Concentration Trends -Source Area Wells MW-103S and MW-104D

Figure - Concentration Trends -Source Area Wells MW-104I and MW-106D

Figure - Concentration Trends -Source Area Wells MW-106S

Response to EPA Comment 4 050305doc 3 of 26 Woodard amp Curran (211941)

I I

El I

II I I 1 I

I

i

Event Baseline Case ID WC-01 WC-01

Well Date Aug-99 Oct-99 LOT10 1 LOT1-1 1 LOT11-4 LOT14 1 LOT15 1 LOT15-1 1 LOT16 1 LOT16-1 1 LOT17 1 LOT18 1 LOT19 1 LOT2 LOT20 1 LOT21-10 1 LOT21-11 1 LOT21-12 1 LOT21-13 1 LOT21-14 1 LOT21-2 1 LOT21-5 1 LOT21-7 LOT21 -8 1 LOT21-9 1 LOT23 1 LOT24 1 LOT28-1 1 LOT28-2 1 LOT28-3 1 LOT28-4 1 LOT28W 1 LOT30 1 LOT30-1 1 LOT30-2 1 LOT30-3 1 LOT30-4 1 LOT30-5 LOT31 LOT35 1 LOT41 1 LOT42-1 1 LOT43-1 1 LOT43-4 1 LOT6-1 1 LOT67 1 LOT6-7 1 LOT6-8A 1 LOT6-8B 1 LOT80-1 1 LOT82 1 MW-101D MW-1011 MW-101S MW-102D MW-102S MW-103D MW-103S MW-104D MW-1041 MW-104S MW-105D MW-106D

Groundwater Sampling Location Summary 1999 - 2004xls

Sampling Events 1999-2004

Hows Corner Superfund Site Plymouth Maine

Supplemental 2001 2002 2003 Pumping 2004 Pre-ROD Rl Sampling Sampling Sampling Test Sampling WC-03 WC-09 WC-25 WC-30 WC-42B WC-56 WC-58 Dec-99 May-00 Jun-01 Jan-02 Apr-03 Sep-04 Sep-04

1

1 1 1

1 1 1 1 1

1 1

1

1 1

1 1 1

1 1 1 1 1

1

1 1

1 1 1 1

1

1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

Sampling Events 1999-2004

Hows Corner Super-fund Site Plymouth Maine

Supplemental 2001 2002 2003 Pumping Event Baseline Pre-ROD Rl Sampling Sampling Sampling Test

Case ID WC-01 WC-01 WC-03 WC-09 WC-25 WC-30 WC-42B WC-56

ll

Well Date Aug-99 Oct-99 Dec-99 May-00 Jun-01 Jan-02 Apr-03 Sep-04 MW-106S 1 1 1 1 1 MW-107D 1 1 MW-108D 1 1 1 1 1 MW-108S 1 1 1 1 1 MW-110D 1 1 MW-111D 1 1 MW-112D 1 1 1 1 1 MW-112S 1 1 1 1 1 MW-113D 1 1 MW-114D 1 1 1 1 1 MW-114S 1 1 1 1 1 MW-115D 1 1 1 1 1 MW-12DB 1 1 1 MW-12SB 1 1 1 MW-13DB 1 1 1 1 1 1 MW-13SB 1 1 1 MW-14DB 1 1 MW-14SO 1 1 MW-15DB 1 1 1 MW-15SB 1 1 1 MW-16DB 1 1 1 1 1 1 MW-16IB 1 1 1 1 1 1 MW-16SO 1 1 MW-17DO 1 1 1 MW-17SO 1 1 1 MW-1B 1 1 1 1 1 1 MW-203D MW-203S MW-204D MW-204S MW-205 MW-206D

I MW-206S MW-2DB 1 1 MW-2DDB 1 1 MW-2IB 1 1 1 1 1 1 MW-3B 1 1 1 1 1 1

I MW-4O 1 1 1 MW-5B 1 1

II MW-6DB 1 1 1 MW-6SB 1 1 1 MW-8DB 1 1 1 MW-8SB 1 1 1

II PW-207 1 SEEP-1 1 SUBTOTAL - RESIDENTIAL 44 25 0 2 0 3 0 SUBTOTAL - MONITORING 22 48 41 15 15 15 1

Total 3 66 73 41 17 15 18 1

I Included in most recent data

I Notes 1 - Overburden well not included in most recent data for plotting

2 - Tetrahydrofuran and 2-Butanone were the only two compounds detected in this well and are thought to be the result of well repair not included in most recent data for plotting

3 - Not included in most recent data for plotting

2004 Sampling

WC-58 Sep-04

1

1 1

1 1

1 1 1

1

1 1

1 1 1 1 1 1 1 1 1

1 1

1

0 29

29

Groundwatef Sampling Location Summary 1999 - 2004xls

I

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

monitoring well Figure 4-14 total VOC contour (ugl) - December 1999January 2000 Distribution of Total VOCs in

Note SW-113 is located downstream of SEEP-1 Shallow Bedrock Groundwater total concentration of detected VOCs ND= not detected these two locations were sampled during the Pre-ROD Sampling Event

Baseline Sampling Event in OctoberNovember 1999 Hows Corner Superfund Site Surface Water Sampling Location A Plymouth Maine Seep Sampling Location laquo- WOODARD ampCURRAN

995037wipri reportepa ri interim final feb 2001cadd drawingsfinalfig 4-14

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

0 300 600 I

FEET

Q residential well Figure 4-16 monitoring well Distribution of Total VOCs in

Deep Bedrock Groundwater total VOCs contour (ugl) Pre-ROD Sampling Event

active residential wells with lot number Hows Corner Superfund Site 2deg42deg Plymouth Maine total concentration of detected VOCs ND= not detected WOODARD ampCURRAN Enyinaaring bull Science bull Operations bull

995037wipri reportepa ri interim final feb 2001cadd drawingsfinalfig4mdash16

PLYMOUTH POND

PLYMOUTH POND

1 628Tl7MW-2bB 12135

PLYMOUTH POND

monitoring well Figure 4-20

V total VOC contour (ugl) - June 2000 Distribution of Total VOCs in Shallow Bedrock Groundwater

| 34 | total concentration of detected VOCs ND= not detected NA = not analyzed Supplemental Sampling Event Note SW-113 is located downstream of SEEP-1 Hows Corner Superfund Site

Surface Water Sampling Location these two locations were sampled during the Plymouth Maine Baseline Sampling Event in OctoberNovember 1999 Seep Sampling Location WOODARD amp CURRAN

Engineering bull Science - Operations bull 995037wipri reportepa ri interim final feb 2001 cadd drawingsfinalfig 4-20

residential well Figure 4-22 Distribution of Total VOCs in

monitoring well Deep Bedrock Groundwater

total VOCs contour (ugl) Supplemental Sampling Event

Hows Corner Superfund Site

total concentration of detected VOCs ND= not detected NA = not analyzed Plymouth Maine

WOODARD amp CURRAN

995037wipri reportepa-ri interim final feb 2001cadd drawingsfinalfig 4-22 Engineering bull Science - Operations bull

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

FEET

Shallow Monitoring Well

Deep Monitoring Well

C Detected Concentration ND = Not Detected Figure 1-XS Distribution of Total VOCs in Shallow Bedrock Groundwater

Pumping Well

17-Acre Property Boundary Concentration Contour (ugl)

June 2001 Hows Corner Superfund Site

Plymouth Maine WOODARDampCURRAN

-i^rhvj bull Scbncn bull Operations bull 211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0601 dwg04-20-05

PLYMOUTH POND Hopkins Road V

O

PLYMOUTH POND

PLYMOUTH POND

o

0 300 600 mdashfa FEET

Shallow Monitoring Well bull bull - 17-Acre Property Boundary Figure 1-XD

Deep Monitoring Well 1 I Detected Concentration ND = Not Detected Distribution of Total VOCs in Deep Bedrock Groundwater

-mf- Pumping Well June 2001 Residential Well Hows Corner Superfund Site

Plymouth Maine i h Surface Water Sampling Point

g WOODARD ampCURRAN _ ^ _ ^ _ _ yen_ rj i|Hlaquorlny bull Science bull Opt

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0601 dwg04-20-05

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

Shallow Monitoring Well

Deep Monitoring Well

Detected Concentration ND = Not Detected Figure 1-YS Distribution of Total VOCs in Shallow Bedrock Groundwater

Pumping Well

17-Acre Property Boundary Concentration Contour (ugl)

January 2002 Hows Corner Superfund Site

Plymouth Maine WOODARD amp CURRAN Engineering Science- Operations bull

211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0102dwg04-20-05

PLYMOUTH POND

PLYMOUTH POND

Site Pand^ laquoum-laquoBTuitaraquo tLV

vVlf-(

PLYMOUTH POND

0 300 600 ^ = FEET

Shallow Monitoring Well mdashbullbullbull 17-Acre Property Boundary Figure 1-YD - A - Deep Monitoring Well FT Detected Concentration ND = Not Detected Distribution of Total VOCs in

Deep Bedrock Groundwater Pumping Well January 2002 Residential Well Hows Corner Superfund Site

Plymouth Maine Surface Water Sampling Point

WOODARD ampCURRAN Engineering Sciencs- Operations bulli Si

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0102dwg04-20-05

- m j

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND j A O-shy

Shallow Monitoring Well E Detected Concentration ND = Not Detected Figure 1-ZS Distribution of Total VOCs in

Deep Monitoring Well Shallow Bedrock Groundwater

Pumping Well Hows Corner

April 2003 Superfund Site

17-Acre Property Boundary Plymouth Maine Concentration Contour (ugl) r WOODARD ampCURRAN

Engineering bull Science bull Operations bull 211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0403dwg04-20-05

s S pound

PLYMOUTH POND

PLYMOUTH POND

- -

5 PLYMOUTH POND

Jo

FEET

ft Shallow Monitoring Well mdashbullbullmdash 17-Acre Property Boundary Figure 1-ZD Deep Monitoring Well I 1 I Detected Concentration ND = Not Detected Distribution of Total VOCs in

Deep Bedrock Groundwater Pumping Well April 2003

Q) Residential Well Hows Corner Superfund Site Plymouth Maine

(T) Surface Water Sampling Point WOODARD ampCURRAN poundKk EnginawtirKj bull Science - Operations bull

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0403dwg04-20-05

0 Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

B MW-1B

I 12000

PCE

B 10000 Total VOCs

I

i 2000

i 0 Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

c MW-3B

G 2000

1800

B PCE

1600 Total VOCs

1 I I E

il-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

G E

211941

El

I I z E

80

Concentration Trends shy Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-13DB

Total VOCs

c i i c o

Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

MW-16DB

30

c i c c I c o

Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99

PCE

Total VOCs

Jul-01 Jul-03

211941

O bi

c Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

I MW-16IB

i 35

3

c Total VOCs

lt- 2 5

0 | gt

o

1 sectI

c c 0 4

Jul-90 Jul-92 Jul-94 Jul-96 Jul-98 Jul-00 Jul-02 Jul-04

I I MW-108D

I 12

PCE 10

Total VOCs c oc 3

E E I 0

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

E 211941

c Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

fi MW-108S

I I 40

PCE 35

Total VOCs

30

I f 26

20 I o

I 15

10

c Dec-99 Dec-00 Dec-01 Dec-02 Dec-03 I 0

I MW-112D

c 35 - imdash

I A3 shyTotal VOCs

o c

E 1 2

I

ition

B 1 ^

-i c 3

0 Dec-99 Dec-OO Dec-01 Dec-02 Dec-03

211941

I

i

I

cII

Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-112S

08

PCE

Total VOCs 06

o 04

02

0 Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

MW-114D

o

12000

10000

8000

6000

PCE

Total VOCs

4000

2000

i

ccEIIc

i

i

E

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

211941

Con

cent

ratio

n (

ug

l)

E Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

I MW-114S

E A5000 -- Total VOCs

- 4000

0 3000

2000

i 1000

i n shy

Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

MW-115D

c PCE

Total VOCs

c E

o

C c

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03 I 0

211941

IepoundII

EIEIIGICCIccc

30000

25000

20000

o bullsect 15000 b

o 10000 U

5000

0 Aug-99

25000

20000

5000

0 Aug-99

211941

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-2DB

PCE

Total VOCs

Aug-01 Aug-03

MW-2IB

PCE

Total VOCs

Aug-01 Aug-03

IDIBI

ii EIDIISIBIG C

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-102S

6000

5000 PCE

Total VOCs

4000

O 3000

2000

1000

0 Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

MW-103D

16000

~ 14000 ugt 3- 12000 o

^ 10000

sect 8000

O 6000

4000

2000

PCE

Total VOCs

0Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

211941

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

G MW-103S

I I

ampo

12000

10000

E sectc

S

8000

6000

4000

2000

0Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

G I 6000

MW-104D

i 5000

PCE

Total VOCs

i i c

2000

1000

Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

E I

211941

cIccIG

IIBCccBcIc

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-1041

PCE Total VOCs

a 25000

0 20000

a 15000

10000

5000

0 Jan-OO Jan-01 Jan-02 Jan-03 Jan-04

MW-106D

3000

2500 PCE

Total VOCs

=sect 2000

o bullsect 1500

1000

500

0 Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

211941

c Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

c MW-106S

I PCE

Total VOCs

i

i Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

i

i i i E

C

211941 c

Response to EPA-DEP Comment 5 Dated March 312005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

iiw

EPA-DEP Comment 5

Comment 5 Matrix Diffusion The report as well as other proponents of matrix diffusion suggest that depletion of DNAPL (Section 5112 page 5-15) needs to be achieved While that might be the ideal the goal is to achieve performance standards and that goal may be attainable while there is residual contamination in the rock perhaps even DNAPL globules The low bedrock matrix porosity (page 1-15) the high permeability values (page 4-4) the relative flux of the groundwater (page 5-5) and the decrease in surface area and out of the mainstream pockets (appendix C-4) all suggest that the diffusion out of the rock matrix would be insubstantial relative to the regional flux of groundwater through the Site

Response The TI Evaluation Report does not explicitly consider or rely upon matrix diffusion as a basis for requesting a TI Waiver for a portion of the Hows Corner Site The technical literature provides documentation that matrix diffusion can be a significant process that affects chemical transport and groundwater remediation timeframes in unconsolidated and consolidated media including fractured rock (US EPA 1989 Freeze and Cherry 1979 Pankow and Cherry 1996 Fountain 1998) Back diffusion of contaminants from the matrix porosity of the fractured rock can prolong the time necessary to achieve groundwater cleanup goals particularly for compounds such as PCE for which the cleanup goal is a low concentration It is our expectation that matrix diffusion has occurred at the Hows Corner Site and that back diffusion of PCE from the rock matrix will also occur Although the extent to which matrix diffusion is occurring at the Hows Comer Site has not been determined and that lack of knowledge contributes to uncertainty regarding the cleanup times at the Site the effect of matrix diffusion is to lengthen rather than shorten the time required for remediation

REFERENCES

Fountain JC 1998 Technologies for Dense Nonaqueous Phase Liquid Source Zone Remediation Ground-Water Remediation Technologies Analysis Center Technology Evaluation Report TE-98-02 December

Freeze RA and Cherry JA 1979 Groundwater Prentice-Hall Inc Englewood Cliffs NJ 07632 p 410-412

Pankow J F and Cherry J A 1996 Dense Chlorinated Solvents Waterloo Press Portland OR 97291-1399 p 67-88

US EPA 1989 Transport and Fate of Contaminants in the Subsurface EPA6254-89019 p 17-18

Response to EPA Comment 5 050305doc 1 of 1 Woodard amp Curran (211941)

WOODARD amp CURRAN Maine Massachusetts New Hampshire Connecticut Florida Operational offices across the US 1-800-426-4262 www woodardcurran com

Page 36: SDMS DocID 251749 - Records Collections · 2020-06-13 · CORPORATE OFFICES: Maine, Massachusetts, New Hampshire, Connecticut New, York, Florida Engineering • Science • Operations

6 In order to derive a Kd-based retardation factor that is reasonable given the reported foc

values and the rapid advance of the PCE plume described on pages 4-11 and 4-12 the flushing model requires a bulk density to porosity ratio that is roughly two orders of magnitude higher than the actual ratio for the Hows Comer bedrock (page 4-4) This apparent discrepancy needs to be addressed

The apparent discrepancy of bulk density to porosity ratios is most likely due to the fact that the Batch Flushing Model was originally developed for a porous medium and is not directly applicable to fractured bedrock As stated in Appendix C (page C-4) of the Draft Technical Impracticability Evaluation Report in order to use the Batch Flushing Model to describe the transport of contaminated groundwater in fractured bedrock where the matrix porosity is insignificant it is more appropriate to use a fracture surface area to void space ratio to calculate the retardation factor (R) than a bulk density to porosity ratio (Freeze amp Cherry 1979)

Since it is impractical to determine the actual surface area to which contaminants can adsorb the Batch Flushing Model was used with two simplifying assumptions bull The Kd was calculated from the f and the K^ bull The bulk density to porosity ratio term in the Batch Flushing Model was constrained to range

from 4 to 10 the typical range of such ratios in porous media (Freeze amp Cherry 1979)

If one uses site specific bedrock bulk density and porosity values the bulk density to porosity ratio is several orders of magnitude greater (specifically 273 gcc bullbull 000165 (dimensionless) = 1654 gcc) than the range of ratios of 4 to 10 used in the Batch Flushing Model in the Draft Technical Impracticability Evaluation Report Constraining the bulk density to porosity ratio within the range of ratios of 4 to 10 results in significantly lower R value than would be obtained using specific bedrock bulk density and porosity values

In summary in bedrock where fractures are the primary porosity the bulk density to porosity ratio can vary considerably and will be a function of the number of fractures and the fracture aperture The calculated bulk density to porosity ratio will be inversely proportional to the porosity This means that in fractured rock with limited fracturing and smaller porosity the calculated bulk density to porosity ratio is greater and will result in a greater calculated retardation factor than in bedrock with more extensive fracturing and greater porosity Consequently the calculated retardation factor will be greater for bedrock with less surface area available for sorption than bedrock with greater surface area for sorption This is contrary to what actually occurs

4 Response to EPA Comment 3 050205doc 5 of 11 Woodard amp Curran (211941)

m

REFERENCES

Banerjee P MD Piwoni K Ebeid (1985) Sorption of organic contaminants to a low carbon subsurface core Chemosphere _14 1057-1067

Freeze RA JA Cherry (1979) Groundwater Prentice Hall Englewood Cliffs NJ pg 604

PTS Laboratories wwwptsgeolabscompdf files3TOCnotepdf

Schulte EE (1995) Recommended soil organic matter tests in Recommended Soil Testing Procedures for the Northeastern United States Northeastern Regional Publication No 493 Chapter 8

Schwarzenbach RP J Westall (1981) Transport of nonpolar organic compounds from surface water to groundwater Laboratory sorption studies Environ Sci Tech 15 1360-1367

Schwarzenbach RP PM Gschwend DM Imboden (2003) Environmental Organic Chemistry Wiley-Interscience pg 292 408 amp 412

Walkley A LA Black (1934) An examination of the Degtjareff method for determining soil organic matter and a proposed modification of the chromic acid titration method Soil Science 37 29-38

Walkley A (1947) A critical examination of a rapid method for determining organic carbon in soils - effect of variations in digestion conditions and of inorganic soil constituents Soil Science 63251-264

Woodard amp Curran Inc (WampC) 2005 Draft Technical Impracticability Evaluation Hows Corner Superfund Site Plymouth Maine January 2005

Response to EPA Comment 3 050205doc 6 of Woodard amp Curran (211941)

LIST OF ATTACHMENTS (Response to Comment 3)

Appendix B to Draft Technical Impracticability Evaluation Measurement of foe at Hows Corner (4 pages)

m

Response to EPA Comment 3 050205doc 7 of 11 Woodard amp Curran (211941)

Appendix B Measurement of foe of Rock Core at Hows Corner

There are two general approaches to measure the fraction of organic carbon (foe) in rock cores

bull Measurement of weight loss by ignition of organic matter bull Chemical oxidization of organic carbon to carbon dioxide and either

subsequent quantification of the oxidant used for the reaction or quantification of the carbon dioxide produced during this oxidation process

The weight loss method is subject to errors caused by volatilization of substances other than organic materials such as water hydroxides and mineral carbonates Quantification of foe by the weight loss method is particularly sensitive to the presence of carbonates in rock cores There are however weight loss methods that are designed to differentiate between organic carbon and the aforementioned interfering materials but they require considerable care and are less accurate at low foe values Hence the weight loss method was not well suited for measuring the foe of the rock core from Hows Corner

The chemical oxidation of organic carbon is much better suited for quantifying organic carbon in rock cores such as those from Hows Corner This method uses a strong chemical oxidant to oxidize organic carbon to carbon dioxide and then measures either the chemical oxidant used to oxidize the organic carbon or the quantity of carbon dioxide produced In addition this general approach is not subject to interference by volatilization of other constituents of the rock core

There are at least two such chemical oxidation methods

bull The method of Baccini which was described by Schwarzenbach amp Westall (1981) first acidifies the sample to eliminate interference by carbonates Then a strong oxidant is used to chemically oxidize the organic carbon to carbon dioxide The resulting carbon dioxide is subsequently reduced to methane and quantified using a flame ionization detector Unfortunately this method has not been described in detail in a referred journal Hence it is would not have been appropriate to use to characterize the foe in the Hows Corner rock core

bull The more commonly used method to quantify foe in rock core is the Walkley-Black method (1934) This method is preferred for RBCA and DODDOE projects and by the oil industry

The Walkley-Black method uses an excess of chromic acid to oxidize (digest) organic matter to carbon dioxide The remaining chromic acid that was not consumed during the oxidation of the organic carbon is then quantified by titration with ferrous sulfate The difference in chromic acid prior to and after the oxidation of the organic carbon represents the total chromic acid used to oxidize

Hows Corner TI Evaluation Page 1 January 13 2005 Appendix B

the organic carbon in the sample The latter can be calculated using the chemical stoichiometry of the reaction

The Walkley-Black method is very accurate for samples that contain less than 2 organic carbon matter The minimum detection limit (MDL) for the Walkley-Black method is 100 mgkg or an foe of 0001

Given the rock core at Hows Corner was expected to contain less than 2 organic carbon the Walkley-Black method was used to measure the foe from 19 different rock core samples collected from varying depths ranging from 11 to 90 feet

Table 1 provides a statistical summary of the aforementioned data

Table 1 Statistical summary of foe data from rock cores collected at varying depths

Statistical Parameter Calculated Value foe Minimum Detection Limit (MDL) 00010 Number of samples analyzed (n) 19 Average foe 00019 Median foe 00019 Geometric Mean foe 00019 Standard deviation of foe measurements 000033 Relative standard deviation 174 -+ 95 Confidence intervals 00012 to 00025

The data in Table 1 shows the following

bull The foe from the Hows Corner rock cores are statistically greater than the MDL of the Walkley-Black analytical method

bull The average and median values for the foe of the Hows Corner rock cores from varying depths are nearly identical indicating that there is little variability in the foe values in the source zone at the site

bull The standard deviation of these measurements is 000033 which is 174 of the average foe

bull The 95 confidence intervals of the foe of the rock core at Hows Corner are 00012 to 00025

The foe was also analyzed from three separate samples taken from the same rock core at a depth of 55 feet (Only one of these samples was included in the data summarized in Table 1) Table 2 shows the statistical repeatability of this type of analysis

Hows Corner TI Evaluation Page 2 January 13 2005 Appendix B

Table 2 Repeatability of analysis of foe from one rock core at 55 feet in depth

Statistical Parameter Calculated Value Number of samples analyzed (n) 3 Average foe 00016 Median foe 00015 Geometric Mean foe 00016 Standard deviation of foe measurements 000039 Relative standard deviation 240 -+ 95 Confidence intervals 00008 to 00024

The data in Table 2 shows the following

bull The percent relative standard deviation of these three analyses of foe from the same rock core at Hows Corner is 24

bull The 95 confidence interval of the foes measured in this particular rock core at Hows Conrer is 00008 to 00024

These results show that there is good repeatability in using the Walkley-Black method for analysis of the foe in the rock core at Hows Corner

References Schwarzenbach amp Westall (1981) Transport of nonpolar organic compounds from surface water to groundwater Laboratory sorption studies Environ Sci Tech 15 1360-1367

Walkley A I A Black (1934) An examination of Degtjareff method for determining soil organic matter and a proposed modification of the chromic acid titration method Soil Sci 37 29-37

Hows Corner Tl Evaluation Page S January 13 2005 Appendix B

Woodard and Curran PTS Laboratories PTS File No 34618

ORGANIC CARBON DATA (METHODOLOGY WALKLEY-BLACK)

PROJECT NAME PROJECT NO

SAMPLE ID

203-chip-13 203-chip-23 203-chip-27 203-chip-38 203-chip-42 203-chip-47 203-chip-52 203-chip-58 203-chip-69 203-chip-82 207-chip-11 207-chip-19 207-chip-24 207-chip-29 207-chip-35 207-chip-45 207-chip-55 207-chip-87 207-chip-90

207-chip-55 55-MS

55-MSMSD

Hows Corner NA

DEPTH ft

13 23 27 38 42 47 52 58 69 82 11 19 24 29 35 45 55 87 90

55 NA NA

MATRIX

Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip

Average Median

Geometric Mean Standard Deviation Relative Std Dev

+- 95 Confidence Interval n

Rock Chip Rock Chip Rock Chip

Average Median

Geometric Mean Standard Deviation Relative Std Dev

+- 95 Confidence Interval n

FRACTION ORGANIC CARBON

(gg)

170E-03 185E-03 185E-03 170E-03 240E-03 190E-03 230E-03 180E-03 170E-03 115E-03 195E-03 220E-03 220E-03 235E-03 135E-03 190E-03 205E-03 175E-03 160E-03

188E-03 185E-03 185E-03 327E-04

1739 123E-03 to

19

205E-03 130E-03 150E-03

162E-03 150E-03 159E-03 388E-04

2402 840E-04 to

3

2532E-03

2393E-03

Hows Corner Tl Evaluation Appendix B January 13 2005

Response to EPA-DEP Comment 4 Dated March 31 2005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

EPA-DEP Comment 4

Comment 4 Distribution of contaminants First the TI report seems based on the assertion that there is DNAPL at the source area yet it also appears to represent that the source area is small and the bedrock below 85 is competent (or less fractured) and less impacted by the release of contaminants Some of the confusion may result from using most recent data when that data is from several different sampling events over several years and there is no discernible difference in concentrations between shallow and deep bedrock or as in Section 421 where generally decreased generally increase generally similar and similar concentrations in four consecutive sentences leads to a muddled picture of the contaminant distribution

Second the report asserts that the distribution of contaminants over the entire plume has not changed with time but fails to support this conclusion with data again relying on data that is from different sampling dates for one composite representation

Response The likely presence of dense non-aqueous phase liquid (DNAPL) at the Hows Corner Site and the determination that the source area is small are not mutually exclusive and both are conclusions drawn from information obtained during field investigations The presence of DNAPL in the source area is based on the elevated concentrations of volatile organic compounds (VOCs) detected in the groundwater (WampC 2001 WampC 2002) The conclusion that the source area is small is based on the area in which VOCs in groundwater have been detected at concentrations that are considered to be indicative of the presence of DNAPL nearby Similarly the conclusion that fracture frequency decreases at depths greater than approximately 50 to 85 feet below ground surface was based on field observation during the RI field work The fact that zones with observed fractures exhibited higher hydraulic conductivities than zones without fractures coupled with the decreasing frequency of observed fractures with depth led to the conclusion that the hydraulic conductivity of the bulk rock decreases with depth

The most recent data from all wells were used to provide the maximum VOC data set size During the RI all of the previously-existing and then newly-installed monitoring wells were sampled along with several residential wells The RI sampling included up to 48 monitoring wells Subsequent to the RI and prior to the TI three rounds of monitoring were conducted to verify that the plume was stable 15 monitoring wells were sampled during each of the three rounds During the TI field investigation 29 wells were sampled for VOCs The sampled wells included all of the newly-installed wells and a subset of wells installed during the RI for a total of 29 monitoring wells By using most recent data VOC results from 53 monitoring wells were included in the evaluation (see table labeled Sampling Events for listing of monitoring wells) This approach was selected because there generally was little variation in the data from a particular location between years This is borne out by the attached individual plots of VOCs detected in shallow bedrock and deep bedrock for the Pre-ROD (December 1999January 2000) and Supplemental (May 2000) sampling events and for June 2001 January 2002 and April 2003 sampling events The Pre-ROD and Supplemental plots are similar to the subsequent plots from the 2001 2002 and 2003 sampling events

In addition to maps showing the spatial distribution of VOC data at a given time trend plots of the data from a particular location through time (attached) indicate that since the RI concentrations generally have been stable or have decreased Together the maps and trend plots and the data from which they were developed indicate that the distribution of contaminants over the entire plume has not changed appreciably with time

Response to EPA Comment 4 050305doc 1 of 26 Woodard amp Curran (211941)

REFERENCES

Woodard amp Curran Inc (WampC) 2001 Final Remedial Investigation Report Hows Corner Superfund Plymouth Maine July 2001

Woodard amp Curran Inc (WampC) 2002 Final Feasibility Study Report - Non-Source Area Groundwater Hows Corner Superfund Site Plymouth Maine Hows Corner Superfund Plymouth Maine July 2002

Response to EPA Comment 4 050305doc 2 of 26 Woodard amp Curran (211941)

LIST OF ATTACHMENTS (Response to Comment 4)

Table - Sampling Events 1999 - 2004 (2 pages)

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater Pre-ROD Sampling Event

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater Pre-ROD Sampling Event

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater Supplemental Sampling Event

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater Supplemental Sampling Event

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater June 2001

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater June 2001

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater January 2002

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater January 2002

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater April 2003

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater April 2003

Figure - Concentration Trends - Non-Source Area Wells MW-1B and MW-3B

Figure - Concentration Trends - Non-Source Area Wells MW-13DB and MW-16DB

Figure - Concentration Trends - Non-Source Area Wells MW-16IB and MW- 108D

Figure - Concentration Trends - Non-Source Area Wells MW-108S and MW-112D

Figure - Concentration Trends - Non-Source Area Wells MW-112S and MW-114D

Figure - Concentration Trends - Non-Source Area Wells MW-114S and MW-115D

Figure - Concentration Trends -Source Area Wells MW-2DB and MW-2IB

Figure - Concentration Trends -Source Area Wells MW-102S and MW-103D

Figure - Concentration Trends -Source Area Wells MW-103S and MW-104D

Figure - Concentration Trends -Source Area Wells MW-104I and MW-106D

Figure - Concentration Trends -Source Area Wells MW-106S

Response to EPA Comment 4 050305doc 3 of 26 Woodard amp Curran (211941)

I I

El I

II I I 1 I

I

i

Event Baseline Case ID WC-01 WC-01

Well Date Aug-99 Oct-99 LOT10 1 LOT1-1 1 LOT11-4 LOT14 1 LOT15 1 LOT15-1 1 LOT16 1 LOT16-1 1 LOT17 1 LOT18 1 LOT19 1 LOT2 LOT20 1 LOT21-10 1 LOT21-11 1 LOT21-12 1 LOT21-13 1 LOT21-14 1 LOT21-2 1 LOT21-5 1 LOT21-7 LOT21 -8 1 LOT21-9 1 LOT23 1 LOT24 1 LOT28-1 1 LOT28-2 1 LOT28-3 1 LOT28-4 1 LOT28W 1 LOT30 1 LOT30-1 1 LOT30-2 1 LOT30-3 1 LOT30-4 1 LOT30-5 LOT31 LOT35 1 LOT41 1 LOT42-1 1 LOT43-1 1 LOT43-4 1 LOT6-1 1 LOT67 1 LOT6-7 1 LOT6-8A 1 LOT6-8B 1 LOT80-1 1 LOT82 1 MW-101D MW-1011 MW-101S MW-102D MW-102S MW-103D MW-103S MW-104D MW-1041 MW-104S MW-105D MW-106D

Groundwater Sampling Location Summary 1999 - 2004xls

Sampling Events 1999-2004

Hows Corner Superfund Site Plymouth Maine

Supplemental 2001 2002 2003 Pumping 2004 Pre-ROD Rl Sampling Sampling Sampling Test Sampling WC-03 WC-09 WC-25 WC-30 WC-42B WC-56 WC-58 Dec-99 May-00 Jun-01 Jan-02 Apr-03 Sep-04 Sep-04

1

1 1 1

1 1 1 1 1

1 1

1

1 1

1 1 1

1 1 1 1 1

1

1 1

1 1 1 1

1

1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

Sampling Events 1999-2004

Hows Corner Super-fund Site Plymouth Maine

Supplemental 2001 2002 2003 Pumping Event Baseline Pre-ROD Rl Sampling Sampling Sampling Test

Case ID WC-01 WC-01 WC-03 WC-09 WC-25 WC-30 WC-42B WC-56

ll

Well Date Aug-99 Oct-99 Dec-99 May-00 Jun-01 Jan-02 Apr-03 Sep-04 MW-106S 1 1 1 1 1 MW-107D 1 1 MW-108D 1 1 1 1 1 MW-108S 1 1 1 1 1 MW-110D 1 1 MW-111D 1 1 MW-112D 1 1 1 1 1 MW-112S 1 1 1 1 1 MW-113D 1 1 MW-114D 1 1 1 1 1 MW-114S 1 1 1 1 1 MW-115D 1 1 1 1 1 MW-12DB 1 1 1 MW-12SB 1 1 1 MW-13DB 1 1 1 1 1 1 MW-13SB 1 1 1 MW-14DB 1 1 MW-14SO 1 1 MW-15DB 1 1 1 MW-15SB 1 1 1 MW-16DB 1 1 1 1 1 1 MW-16IB 1 1 1 1 1 1 MW-16SO 1 1 MW-17DO 1 1 1 MW-17SO 1 1 1 MW-1B 1 1 1 1 1 1 MW-203D MW-203S MW-204D MW-204S MW-205 MW-206D

I MW-206S MW-2DB 1 1 MW-2DDB 1 1 MW-2IB 1 1 1 1 1 1 MW-3B 1 1 1 1 1 1

I MW-4O 1 1 1 MW-5B 1 1

II MW-6DB 1 1 1 MW-6SB 1 1 1 MW-8DB 1 1 1 MW-8SB 1 1 1

II PW-207 1 SEEP-1 1 SUBTOTAL - RESIDENTIAL 44 25 0 2 0 3 0 SUBTOTAL - MONITORING 22 48 41 15 15 15 1

Total 3 66 73 41 17 15 18 1

I Included in most recent data

I Notes 1 - Overburden well not included in most recent data for plotting

2 - Tetrahydrofuran and 2-Butanone were the only two compounds detected in this well and are thought to be the result of well repair not included in most recent data for plotting

3 - Not included in most recent data for plotting

2004 Sampling

WC-58 Sep-04

1

1 1

1 1

1 1 1

1

1 1

1 1 1 1 1 1 1 1 1

1 1

1

0 29

29

Groundwatef Sampling Location Summary 1999 - 2004xls

I

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

monitoring well Figure 4-14 total VOC contour (ugl) - December 1999January 2000 Distribution of Total VOCs in

Note SW-113 is located downstream of SEEP-1 Shallow Bedrock Groundwater total concentration of detected VOCs ND= not detected these two locations were sampled during the Pre-ROD Sampling Event

Baseline Sampling Event in OctoberNovember 1999 Hows Corner Superfund Site Surface Water Sampling Location A Plymouth Maine Seep Sampling Location laquo- WOODARD ampCURRAN

995037wipri reportepa ri interim final feb 2001cadd drawingsfinalfig 4-14

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

0 300 600 I

FEET

Q residential well Figure 4-16 monitoring well Distribution of Total VOCs in

Deep Bedrock Groundwater total VOCs contour (ugl) Pre-ROD Sampling Event

active residential wells with lot number Hows Corner Superfund Site 2deg42deg Plymouth Maine total concentration of detected VOCs ND= not detected WOODARD ampCURRAN Enyinaaring bull Science bull Operations bull

995037wipri reportepa ri interim final feb 2001cadd drawingsfinalfig4mdash16

PLYMOUTH POND

PLYMOUTH POND

1 628Tl7MW-2bB 12135

PLYMOUTH POND

monitoring well Figure 4-20

V total VOC contour (ugl) - June 2000 Distribution of Total VOCs in Shallow Bedrock Groundwater

| 34 | total concentration of detected VOCs ND= not detected NA = not analyzed Supplemental Sampling Event Note SW-113 is located downstream of SEEP-1 Hows Corner Superfund Site

Surface Water Sampling Location these two locations were sampled during the Plymouth Maine Baseline Sampling Event in OctoberNovember 1999 Seep Sampling Location WOODARD amp CURRAN

Engineering bull Science - Operations bull 995037wipri reportepa ri interim final feb 2001 cadd drawingsfinalfig 4-20

residential well Figure 4-22 Distribution of Total VOCs in

monitoring well Deep Bedrock Groundwater

total VOCs contour (ugl) Supplemental Sampling Event

Hows Corner Superfund Site

total concentration of detected VOCs ND= not detected NA = not analyzed Plymouth Maine

WOODARD amp CURRAN

995037wipri reportepa-ri interim final feb 2001cadd drawingsfinalfig 4-22 Engineering bull Science - Operations bull

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

FEET

Shallow Monitoring Well

Deep Monitoring Well

C Detected Concentration ND = Not Detected Figure 1-XS Distribution of Total VOCs in Shallow Bedrock Groundwater

Pumping Well

17-Acre Property Boundary Concentration Contour (ugl)

June 2001 Hows Corner Superfund Site

Plymouth Maine WOODARDampCURRAN

-i^rhvj bull Scbncn bull Operations bull 211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0601 dwg04-20-05

PLYMOUTH POND Hopkins Road V

O

PLYMOUTH POND

PLYMOUTH POND

o

0 300 600 mdashfa FEET

Shallow Monitoring Well bull bull - 17-Acre Property Boundary Figure 1-XD

Deep Monitoring Well 1 I Detected Concentration ND = Not Detected Distribution of Total VOCs in Deep Bedrock Groundwater

-mf- Pumping Well June 2001 Residential Well Hows Corner Superfund Site

Plymouth Maine i h Surface Water Sampling Point

g WOODARD ampCURRAN _ ^ _ ^ _ _ yen_ rj i|Hlaquorlny bull Science bull Opt

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0601 dwg04-20-05

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

Shallow Monitoring Well

Deep Monitoring Well

Detected Concentration ND = Not Detected Figure 1-YS Distribution of Total VOCs in Shallow Bedrock Groundwater

Pumping Well

17-Acre Property Boundary Concentration Contour (ugl)

January 2002 Hows Corner Superfund Site

Plymouth Maine WOODARD amp CURRAN Engineering Science- Operations bull

211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0102dwg04-20-05

PLYMOUTH POND

PLYMOUTH POND

Site Pand^ laquoum-laquoBTuitaraquo tLV

vVlf-(

PLYMOUTH POND

0 300 600 ^ = FEET

Shallow Monitoring Well mdashbullbullbull 17-Acre Property Boundary Figure 1-YD - A - Deep Monitoring Well FT Detected Concentration ND = Not Detected Distribution of Total VOCs in

Deep Bedrock Groundwater Pumping Well January 2002 Residential Well Hows Corner Superfund Site

Plymouth Maine Surface Water Sampling Point

WOODARD ampCURRAN Engineering Sciencs- Operations bulli Si

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0102dwg04-20-05

- m j

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND j A O-shy

Shallow Monitoring Well E Detected Concentration ND = Not Detected Figure 1-ZS Distribution of Total VOCs in

Deep Monitoring Well Shallow Bedrock Groundwater

Pumping Well Hows Corner

April 2003 Superfund Site

17-Acre Property Boundary Plymouth Maine Concentration Contour (ugl) r WOODARD ampCURRAN

Engineering bull Science bull Operations bull 211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0403dwg04-20-05

s S pound

PLYMOUTH POND

PLYMOUTH POND

- -

5 PLYMOUTH POND

Jo

FEET

ft Shallow Monitoring Well mdashbullbullmdash 17-Acre Property Boundary Figure 1-ZD Deep Monitoring Well I 1 I Detected Concentration ND = Not Detected Distribution of Total VOCs in

Deep Bedrock Groundwater Pumping Well April 2003

Q) Residential Well Hows Corner Superfund Site Plymouth Maine

(T) Surface Water Sampling Point WOODARD ampCURRAN poundKk EnginawtirKj bull Science - Operations bull

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0403dwg04-20-05

0 Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

B MW-1B

I 12000

PCE

B 10000 Total VOCs

I

i 2000

i 0 Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

c MW-3B

G 2000

1800

B PCE

1600 Total VOCs

1 I I E

il-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

G E

211941

El

I I z E

80

Concentration Trends shy Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-13DB

Total VOCs

c i i c o

Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

MW-16DB

30

c i c c I c o

Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99

PCE

Total VOCs

Jul-01 Jul-03

211941

O bi

c Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

I MW-16IB

i 35

3

c Total VOCs

lt- 2 5

0 | gt

o

1 sectI

c c 0 4

Jul-90 Jul-92 Jul-94 Jul-96 Jul-98 Jul-00 Jul-02 Jul-04

I I MW-108D

I 12

PCE 10

Total VOCs c oc 3

E E I 0

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

E 211941

c Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

fi MW-108S

I I 40

PCE 35

Total VOCs

30

I f 26

20 I o

I 15

10

c Dec-99 Dec-00 Dec-01 Dec-02 Dec-03 I 0

I MW-112D

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0 Dec-99 Dec-OO Dec-01 Dec-02 Dec-03

211941

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Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-112S

08

PCE

Total VOCs 06

o 04

02

0 Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

MW-114D

o

12000

10000

8000

6000

PCE

Total VOCs

4000

2000

i

ccEIIc

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i

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Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

211941

Con

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ratio

n (

ug

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E Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

I MW-114S

E A5000 -- Total VOCs

- 4000

0 3000

2000

i 1000

i n shy

Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

MW-115D

c PCE

Total VOCs

c E

o

C c

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03 I 0

211941

IepoundII

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30000

25000

20000

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5000

0 Aug-99

25000

20000

5000

0 Aug-99

211941

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-2DB

PCE

Total VOCs

Aug-01 Aug-03

MW-2IB

PCE

Total VOCs

Aug-01 Aug-03

IDIBI

ii EIDIISIBIG C

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-102S

6000

5000 PCE

Total VOCs

4000

O 3000

2000

1000

0 Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

MW-103D

16000

~ 14000 ugt 3- 12000 o

^ 10000

sect 8000

O 6000

4000

2000

PCE

Total VOCs

0Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

211941

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

G MW-103S

I I

ampo

12000

10000

E sectc

S

8000

6000

4000

2000

0Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

G I 6000

MW-104D

i 5000

PCE

Total VOCs

i i c

2000

1000

Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

E I

211941

cIccIG

IIBCccBcIc

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-1041

PCE Total VOCs

a 25000

0 20000

a 15000

10000

5000

0 Jan-OO Jan-01 Jan-02 Jan-03 Jan-04

MW-106D

3000

2500 PCE

Total VOCs

=sect 2000

o bullsect 1500

1000

500

0 Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

211941

c Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

c MW-106S

I PCE

Total VOCs

i

i Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

i

i i i E

C

211941 c

Response to EPA-DEP Comment 5 Dated March 312005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

iiw

EPA-DEP Comment 5

Comment 5 Matrix Diffusion The report as well as other proponents of matrix diffusion suggest that depletion of DNAPL (Section 5112 page 5-15) needs to be achieved While that might be the ideal the goal is to achieve performance standards and that goal may be attainable while there is residual contamination in the rock perhaps even DNAPL globules The low bedrock matrix porosity (page 1-15) the high permeability values (page 4-4) the relative flux of the groundwater (page 5-5) and the decrease in surface area and out of the mainstream pockets (appendix C-4) all suggest that the diffusion out of the rock matrix would be insubstantial relative to the regional flux of groundwater through the Site

Response The TI Evaluation Report does not explicitly consider or rely upon matrix diffusion as a basis for requesting a TI Waiver for a portion of the Hows Corner Site The technical literature provides documentation that matrix diffusion can be a significant process that affects chemical transport and groundwater remediation timeframes in unconsolidated and consolidated media including fractured rock (US EPA 1989 Freeze and Cherry 1979 Pankow and Cherry 1996 Fountain 1998) Back diffusion of contaminants from the matrix porosity of the fractured rock can prolong the time necessary to achieve groundwater cleanup goals particularly for compounds such as PCE for which the cleanup goal is a low concentration It is our expectation that matrix diffusion has occurred at the Hows Corner Site and that back diffusion of PCE from the rock matrix will also occur Although the extent to which matrix diffusion is occurring at the Hows Comer Site has not been determined and that lack of knowledge contributes to uncertainty regarding the cleanup times at the Site the effect of matrix diffusion is to lengthen rather than shorten the time required for remediation

REFERENCES

Fountain JC 1998 Technologies for Dense Nonaqueous Phase Liquid Source Zone Remediation Ground-Water Remediation Technologies Analysis Center Technology Evaluation Report TE-98-02 December

Freeze RA and Cherry JA 1979 Groundwater Prentice-Hall Inc Englewood Cliffs NJ 07632 p 410-412

Pankow J F and Cherry J A 1996 Dense Chlorinated Solvents Waterloo Press Portland OR 97291-1399 p 67-88

US EPA 1989 Transport and Fate of Contaminants in the Subsurface EPA6254-89019 p 17-18

Response to EPA Comment 5 050305doc 1 of 1 Woodard amp Curran (211941)

WOODARD amp CURRAN Maine Massachusetts New Hampshire Connecticut Florida Operational offices across the US 1-800-426-4262 www woodardcurran com

Page 37: SDMS DocID 251749 - Records Collections · 2020-06-13 · CORPORATE OFFICES: Maine, Massachusetts, New Hampshire, Connecticut New, York, Florida Engineering • Science • Operations

REFERENCES

Banerjee P MD Piwoni K Ebeid (1985) Sorption of organic contaminants to a low carbon subsurface core Chemosphere _14 1057-1067

Freeze RA JA Cherry (1979) Groundwater Prentice Hall Englewood Cliffs NJ pg 604

PTS Laboratories wwwptsgeolabscompdf files3TOCnotepdf

Schulte EE (1995) Recommended soil organic matter tests in Recommended Soil Testing Procedures for the Northeastern United States Northeastern Regional Publication No 493 Chapter 8

Schwarzenbach RP J Westall (1981) Transport of nonpolar organic compounds from surface water to groundwater Laboratory sorption studies Environ Sci Tech 15 1360-1367

Schwarzenbach RP PM Gschwend DM Imboden (2003) Environmental Organic Chemistry Wiley-Interscience pg 292 408 amp 412

Walkley A LA Black (1934) An examination of the Degtjareff method for determining soil organic matter and a proposed modification of the chromic acid titration method Soil Science 37 29-38

Walkley A (1947) A critical examination of a rapid method for determining organic carbon in soils - effect of variations in digestion conditions and of inorganic soil constituents Soil Science 63251-264

Woodard amp Curran Inc (WampC) 2005 Draft Technical Impracticability Evaluation Hows Corner Superfund Site Plymouth Maine January 2005

Response to EPA Comment 3 050205doc 6 of Woodard amp Curran (211941)

LIST OF ATTACHMENTS (Response to Comment 3)

Appendix B to Draft Technical Impracticability Evaluation Measurement of foe at Hows Corner (4 pages)

m

Response to EPA Comment 3 050205doc 7 of 11 Woodard amp Curran (211941)

Appendix B Measurement of foe of Rock Core at Hows Corner

There are two general approaches to measure the fraction of organic carbon (foe) in rock cores

bull Measurement of weight loss by ignition of organic matter bull Chemical oxidization of organic carbon to carbon dioxide and either

subsequent quantification of the oxidant used for the reaction or quantification of the carbon dioxide produced during this oxidation process

The weight loss method is subject to errors caused by volatilization of substances other than organic materials such as water hydroxides and mineral carbonates Quantification of foe by the weight loss method is particularly sensitive to the presence of carbonates in rock cores There are however weight loss methods that are designed to differentiate between organic carbon and the aforementioned interfering materials but they require considerable care and are less accurate at low foe values Hence the weight loss method was not well suited for measuring the foe of the rock core from Hows Corner

The chemical oxidation of organic carbon is much better suited for quantifying organic carbon in rock cores such as those from Hows Corner This method uses a strong chemical oxidant to oxidize organic carbon to carbon dioxide and then measures either the chemical oxidant used to oxidize the organic carbon or the quantity of carbon dioxide produced In addition this general approach is not subject to interference by volatilization of other constituents of the rock core

There are at least two such chemical oxidation methods

bull The method of Baccini which was described by Schwarzenbach amp Westall (1981) first acidifies the sample to eliminate interference by carbonates Then a strong oxidant is used to chemically oxidize the organic carbon to carbon dioxide The resulting carbon dioxide is subsequently reduced to methane and quantified using a flame ionization detector Unfortunately this method has not been described in detail in a referred journal Hence it is would not have been appropriate to use to characterize the foe in the Hows Corner rock core

bull The more commonly used method to quantify foe in rock core is the Walkley-Black method (1934) This method is preferred for RBCA and DODDOE projects and by the oil industry

The Walkley-Black method uses an excess of chromic acid to oxidize (digest) organic matter to carbon dioxide The remaining chromic acid that was not consumed during the oxidation of the organic carbon is then quantified by titration with ferrous sulfate The difference in chromic acid prior to and after the oxidation of the organic carbon represents the total chromic acid used to oxidize

Hows Corner TI Evaluation Page 1 January 13 2005 Appendix B

the organic carbon in the sample The latter can be calculated using the chemical stoichiometry of the reaction

The Walkley-Black method is very accurate for samples that contain less than 2 organic carbon matter The minimum detection limit (MDL) for the Walkley-Black method is 100 mgkg or an foe of 0001

Given the rock core at Hows Corner was expected to contain less than 2 organic carbon the Walkley-Black method was used to measure the foe from 19 different rock core samples collected from varying depths ranging from 11 to 90 feet

Table 1 provides a statistical summary of the aforementioned data

Table 1 Statistical summary of foe data from rock cores collected at varying depths

Statistical Parameter Calculated Value foe Minimum Detection Limit (MDL) 00010 Number of samples analyzed (n) 19 Average foe 00019 Median foe 00019 Geometric Mean foe 00019 Standard deviation of foe measurements 000033 Relative standard deviation 174 -+ 95 Confidence intervals 00012 to 00025

The data in Table 1 shows the following

bull The foe from the Hows Corner rock cores are statistically greater than the MDL of the Walkley-Black analytical method

bull The average and median values for the foe of the Hows Corner rock cores from varying depths are nearly identical indicating that there is little variability in the foe values in the source zone at the site

bull The standard deviation of these measurements is 000033 which is 174 of the average foe

bull The 95 confidence intervals of the foe of the rock core at Hows Corner are 00012 to 00025

The foe was also analyzed from three separate samples taken from the same rock core at a depth of 55 feet (Only one of these samples was included in the data summarized in Table 1) Table 2 shows the statistical repeatability of this type of analysis

Hows Corner TI Evaluation Page 2 January 13 2005 Appendix B

Table 2 Repeatability of analysis of foe from one rock core at 55 feet in depth

Statistical Parameter Calculated Value Number of samples analyzed (n) 3 Average foe 00016 Median foe 00015 Geometric Mean foe 00016 Standard deviation of foe measurements 000039 Relative standard deviation 240 -+ 95 Confidence intervals 00008 to 00024

The data in Table 2 shows the following

bull The percent relative standard deviation of these three analyses of foe from the same rock core at Hows Corner is 24

bull The 95 confidence interval of the foes measured in this particular rock core at Hows Conrer is 00008 to 00024

These results show that there is good repeatability in using the Walkley-Black method for analysis of the foe in the rock core at Hows Corner

References Schwarzenbach amp Westall (1981) Transport of nonpolar organic compounds from surface water to groundwater Laboratory sorption studies Environ Sci Tech 15 1360-1367

Walkley A I A Black (1934) An examination of Degtjareff method for determining soil organic matter and a proposed modification of the chromic acid titration method Soil Sci 37 29-37

Hows Corner Tl Evaluation Page S January 13 2005 Appendix B

Woodard and Curran PTS Laboratories PTS File No 34618

ORGANIC CARBON DATA (METHODOLOGY WALKLEY-BLACK)

PROJECT NAME PROJECT NO

SAMPLE ID

203-chip-13 203-chip-23 203-chip-27 203-chip-38 203-chip-42 203-chip-47 203-chip-52 203-chip-58 203-chip-69 203-chip-82 207-chip-11 207-chip-19 207-chip-24 207-chip-29 207-chip-35 207-chip-45 207-chip-55 207-chip-87 207-chip-90

207-chip-55 55-MS

55-MSMSD

Hows Corner NA

DEPTH ft

13 23 27 38 42 47 52 58 69 82 11 19 24 29 35 45 55 87 90

55 NA NA

MATRIX

Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip

Average Median

Geometric Mean Standard Deviation Relative Std Dev

+- 95 Confidence Interval n

Rock Chip Rock Chip Rock Chip

Average Median

Geometric Mean Standard Deviation Relative Std Dev

+- 95 Confidence Interval n

FRACTION ORGANIC CARBON

(gg)

170E-03 185E-03 185E-03 170E-03 240E-03 190E-03 230E-03 180E-03 170E-03 115E-03 195E-03 220E-03 220E-03 235E-03 135E-03 190E-03 205E-03 175E-03 160E-03

188E-03 185E-03 185E-03 327E-04

1739 123E-03 to

19

205E-03 130E-03 150E-03

162E-03 150E-03 159E-03 388E-04

2402 840E-04 to

3

2532E-03

2393E-03

Hows Corner Tl Evaluation Appendix B January 13 2005

Response to EPA-DEP Comment 4 Dated March 31 2005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

EPA-DEP Comment 4

Comment 4 Distribution of contaminants First the TI report seems based on the assertion that there is DNAPL at the source area yet it also appears to represent that the source area is small and the bedrock below 85 is competent (or less fractured) and less impacted by the release of contaminants Some of the confusion may result from using most recent data when that data is from several different sampling events over several years and there is no discernible difference in concentrations between shallow and deep bedrock or as in Section 421 where generally decreased generally increase generally similar and similar concentrations in four consecutive sentences leads to a muddled picture of the contaminant distribution

Second the report asserts that the distribution of contaminants over the entire plume has not changed with time but fails to support this conclusion with data again relying on data that is from different sampling dates for one composite representation

Response The likely presence of dense non-aqueous phase liquid (DNAPL) at the Hows Corner Site and the determination that the source area is small are not mutually exclusive and both are conclusions drawn from information obtained during field investigations The presence of DNAPL in the source area is based on the elevated concentrations of volatile organic compounds (VOCs) detected in the groundwater (WampC 2001 WampC 2002) The conclusion that the source area is small is based on the area in which VOCs in groundwater have been detected at concentrations that are considered to be indicative of the presence of DNAPL nearby Similarly the conclusion that fracture frequency decreases at depths greater than approximately 50 to 85 feet below ground surface was based on field observation during the RI field work The fact that zones with observed fractures exhibited higher hydraulic conductivities than zones without fractures coupled with the decreasing frequency of observed fractures with depth led to the conclusion that the hydraulic conductivity of the bulk rock decreases with depth

The most recent data from all wells were used to provide the maximum VOC data set size During the RI all of the previously-existing and then newly-installed monitoring wells were sampled along with several residential wells The RI sampling included up to 48 monitoring wells Subsequent to the RI and prior to the TI three rounds of monitoring were conducted to verify that the plume was stable 15 monitoring wells were sampled during each of the three rounds During the TI field investigation 29 wells were sampled for VOCs The sampled wells included all of the newly-installed wells and a subset of wells installed during the RI for a total of 29 monitoring wells By using most recent data VOC results from 53 monitoring wells were included in the evaluation (see table labeled Sampling Events for listing of monitoring wells) This approach was selected because there generally was little variation in the data from a particular location between years This is borne out by the attached individual plots of VOCs detected in shallow bedrock and deep bedrock for the Pre-ROD (December 1999January 2000) and Supplemental (May 2000) sampling events and for June 2001 January 2002 and April 2003 sampling events The Pre-ROD and Supplemental plots are similar to the subsequent plots from the 2001 2002 and 2003 sampling events

In addition to maps showing the spatial distribution of VOC data at a given time trend plots of the data from a particular location through time (attached) indicate that since the RI concentrations generally have been stable or have decreased Together the maps and trend plots and the data from which they were developed indicate that the distribution of contaminants over the entire plume has not changed appreciably with time

Response to EPA Comment 4 050305doc 1 of 26 Woodard amp Curran (211941)

REFERENCES

Woodard amp Curran Inc (WampC) 2001 Final Remedial Investigation Report Hows Corner Superfund Plymouth Maine July 2001

Woodard amp Curran Inc (WampC) 2002 Final Feasibility Study Report - Non-Source Area Groundwater Hows Corner Superfund Site Plymouth Maine Hows Corner Superfund Plymouth Maine July 2002

Response to EPA Comment 4 050305doc 2 of 26 Woodard amp Curran (211941)

LIST OF ATTACHMENTS (Response to Comment 4)

Table - Sampling Events 1999 - 2004 (2 pages)

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater Pre-ROD Sampling Event

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater Pre-ROD Sampling Event

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater Supplemental Sampling Event

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater Supplemental Sampling Event

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater June 2001

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater June 2001

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater January 2002

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater January 2002

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater April 2003

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater April 2003

Figure - Concentration Trends - Non-Source Area Wells MW-1B and MW-3B

Figure - Concentration Trends - Non-Source Area Wells MW-13DB and MW-16DB

Figure - Concentration Trends - Non-Source Area Wells MW-16IB and MW- 108D

Figure - Concentration Trends - Non-Source Area Wells MW-108S and MW-112D

Figure - Concentration Trends - Non-Source Area Wells MW-112S and MW-114D

Figure - Concentration Trends - Non-Source Area Wells MW-114S and MW-115D

Figure - Concentration Trends -Source Area Wells MW-2DB and MW-2IB

Figure - Concentration Trends -Source Area Wells MW-102S and MW-103D

Figure - Concentration Trends -Source Area Wells MW-103S and MW-104D

Figure - Concentration Trends -Source Area Wells MW-104I and MW-106D

Figure - Concentration Trends -Source Area Wells MW-106S

Response to EPA Comment 4 050305doc 3 of 26 Woodard amp Curran (211941)

I I

El I

II I I 1 I

I

i

Event Baseline Case ID WC-01 WC-01

Well Date Aug-99 Oct-99 LOT10 1 LOT1-1 1 LOT11-4 LOT14 1 LOT15 1 LOT15-1 1 LOT16 1 LOT16-1 1 LOT17 1 LOT18 1 LOT19 1 LOT2 LOT20 1 LOT21-10 1 LOT21-11 1 LOT21-12 1 LOT21-13 1 LOT21-14 1 LOT21-2 1 LOT21-5 1 LOT21-7 LOT21 -8 1 LOT21-9 1 LOT23 1 LOT24 1 LOT28-1 1 LOT28-2 1 LOT28-3 1 LOT28-4 1 LOT28W 1 LOT30 1 LOT30-1 1 LOT30-2 1 LOT30-3 1 LOT30-4 1 LOT30-5 LOT31 LOT35 1 LOT41 1 LOT42-1 1 LOT43-1 1 LOT43-4 1 LOT6-1 1 LOT67 1 LOT6-7 1 LOT6-8A 1 LOT6-8B 1 LOT80-1 1 LOT82 1 MW-101D MW-1011 MW-101S MW-102D MW-102S MW-103D MW-103S MW-104D MW-1041 MW-104S MW-105D MW-106D

Groundwater Sampling Location Summary 1999 - 2004xls

Sampling Events 1999-2004

Hows Corner Superfund Site Plymouth Maine

Supplemental 2001 2002 2003 Pumping 2004 Pre-ROD Rl Sampling Sampling Sampling Test Sampling WC-03 WC-09 WC-25 WC-30 WC-42B WC-56 WC-58 Dec-99 May-00 Jun-01 Jan-02 Apr-03 Sep-04 Sep-04

1

1 1 1

1 1 1 1 1

1 1

1

1 1

1 1 1

1 1 1 1 1

1

1 1

1 1 1 1

1

1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

Sampling Events 1999-2004

Hows Corner Super-fund Site Plymouth Maine

Supplemental 2001 2002 2003 Pumping Event Baseline Pre-ROD Rl Sampling Sampling Sampling Test

Case ID WC-01 WC-01 WC-03 WC-09 WC-25 WC-30 WC-42B WC-56

ll

Well Date Aug-99 Oct-99 Dec-99 May-00 Jun-01 Jan-02 Apr-03 Sep-04 MW-106S 1 1 1 1 1 MW-107D 1 1 MW-108D 1 1 1 1 1 MW-108S 1 1 1 1 1 MW-110D 1 1 MW-111D 1 1 MW-112D 1 1 1 1 1 MW-112S 1 1 1 1 1 MW-113D 1 1 MW-114D 1 1 1 1 1 MW-114S 1 1 1 1 1 MW-115D 1 1 1 1 1 MW-12DB 1 1 1 MW-12SB 1 1 1 MW-13DB 1 1 1 1 1 1 MW-13SB 1 1 1 MW-14DB 1 1 MW-14SO 1 1 MW-15DB 1 1 1 MW-15SB 1 1 1 MW-16DB 1 1 1 1 1 1 MW-16IB 1 1 1 1 1 1 MW-16SO 1 1 MW-17DO 1 1 1 MW-17SO 1 1 1 MW-1B 1 1 1 1 1 1 MW-203D MW-203S MW-204D MW-204S MW-205 MW-206D

I MW-206S MW-2DB 1 1 MW-2DDB 1 1 MW-2IB 1 1 1 1 1 1 MW-3B 1 1 1 1 1 1

I MW-4O 1 1 1 MW-5B 1 1

II MW-6DB 1 1 1 MW-6SB 1 1 1 MW-8DB 1 1 1 MW-8SB 1 1 1

II PW-207 1 SEEP-1 1 SUBTOTAL - RESIDENTIAL 44 25 0 2 0 3 0 SUBTOTAL - MONITORING 22 48 41 15 15 15 1

Total 3 66 73 41 17 15 18 1

I Included in most recent data

I Notes 1 - Overburden well not included in most recent data for plotting

2 - Tetrahydrofuran and 2-Butanone were the only two compounds detected in this well and are thought to be the result of well repair not included in most recent data for plotting

3 - Not included in most recent data for plotting

2004 Sampling

WC-58 Sep-04

1

1 1

1 1

1 1 1

1

1 1

1 1 1 1 1 1 1 1 1

1 1

1

0 29

29

Groundwatef Sampling Location Summary 1999 - 2004xls

I

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

monitoring well Figure 4-14 total VOC contour (ugl) - December 1999January 2000 Distribution of Total VOCs in

Note SW-113 is located downstream of SEEP-1 Shallow Bedrock Groundwater total concentration of detected VOCs ND= not detected these two locations were sampled during the Pre-ROD Sampling Event

Baseline Sampling Event in OctoberNovember 1999 Hows Corner Superfund Site Surface Water Sampling Location A Plymouth Maine Seep Sampling Location laquo- WOODARD ampCURRAN

995037wipri reportepa ri interim final feb 2001cadd drawingsfinalfig 4-14

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

0 300 600 I

FEET

Q residential well Figure 4-16 monitoring well Distribution of Total VOCs in

Deep Bedrock Groundwater total VOCs contour (ugl) Pre-ROD Sampling Event

active residential wells with lot number Hows Corner Superfund Site 2deg42deg Plymouth Maine total concentration of detected VOCs ND= not detected WOODARD ampCURRAN Enyinaaring bull Science bull Operations bull

995037wipri reportepa ri interim final feb 2001cadd drawingsfinalfig4mdash16

PLYMOUTH POND

PLYMOUTH POND

1 628Tl7MW-2bB 12135

PLYMOUTH POND

monitoring well Figure 4-20

V total VOC contour (ugl) - June 2000 Distribution of Total VOCs in Shallow Bedrock Groundwater

| 34 | total concentration of detected VOCs ND= not detected NA = not analyzed Supplemental Sampling Event Note SW-113 is located downstream of SEEP-1 Hows Corner Superfund Site

Surface Water Sampling Location these two locations were sampled during the Plymouth Maine Baseline Sampling Event in OctoberNovember 1999 Seep Sampling Location WOODARD amp CURRAN

Engineering bull Science - Operations bull 995037wipri reportepa ri interim final feb 2001 cadd drawingsfinalfig 4-20

residential well Figure 4-22 Distribution of Total VOCs in

monitoring well Deep Bedrock Groundwater

total VOCs contour (ugl) Supplemental Sampling Event

Hows Corner Superfund Site

total concentration of detected VOCs ND= not detected NA = not analyzed Plymouth Maine

WOODARD amp CURRAN

995037wipri reportepa-ri interim final feb 2001cadd drawingsfinalfig 4-22 Engineering bull Science - Operations bull

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

FEET

Shallow Monitoring Well

Deep Monitoring Well

C Detected Concentration ND = Not Detected Figure 1-XS Distribution of Total VOCs in Shallow Bedrock Groundwater

Pumping Well

17-Acre Property Boundary Concentration Contour (ugl)

June 2001 Hows Corner Superfund Site

Plymouth Maine WOODARDampCURRAN

-i^rhvj bull Scbncn bull Operations bull 211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0601 dwg04-20-05

PLYMOUTH POND Hopkins Road V

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PLYMOUTH POND

PLYMOUTH POND

o

0 300 600 mdashfa FEET

Shallow Monitoring Well bull bull - 17-Acre Property Boundary Figure 1-XD

Deep Monitoring Well 1 I Detected Concentration ND = Not Detected Distribution of Total VOCs in Deep Bedrock Groundwater

-mf- Pumping Well June 2001 Residential Well Hows Corner Superfund Site

Plymouth Maine i h Surface Water Sampling Point

g WOODARD ampCURRAN _ ^ _ ^ _ _ yen_ rj i|Hlaquorlny bull Science bull Opt

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0601 dwg04-20-05

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

Shallow Monitoring Well

Deep Monitoring Well

Detected Concentration ND = Not Detected Figure 1-YS Distribution of Total VOCs in Shallow Bedrock Groundwater

Pumping Well

17-Acre Property Boundary Concentration Contour (ugl)

January 2002 Hows Corner Superfund Site

Plymouth Maine WOODARD amp CURRAN Engineering Science- Operations bull

211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0102dwg04-20-05

PLYMOUTH POND

PLYMOUTH POND

Site Pand^ laquoum-laquoBTuitaraquo tLV

vVlf-(

PLYMOUTH POND

0 300 600 ^ = FEET

Shallow Monitoring Well mdashbullbullbull 17-Acre Property Boundary Figure 1-YD - A - Deep Monitoring Well FT Detected Concentration ND = Not Detected Distribution of Total VOCs in

Deep Bedrock Groundwater Pumping Well January 2002 Residential Well Hows Corner Superfund Site

Plymouth Maine Surface Water Sampling Point

WOODARD ampCURRAN Engineering Sciencs- Operations bulli Si

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0102dwg04-20-05

- m j

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND j A O-shy

Shallow Monitoring Well E Detected Concentration ND = Not Detected Figure 1-ZS Distribution of Total VOCs in

Deep Monitoring Well Shallow Bedrock Groundwater

Pumping Well Hows Corner

April 2003 Superfund Site

17-Acre Property Boundary Plymouth Maine Concentration Contour (ugl) r WOODARD ampCURRAN

Engineering bull Science bull Operations bull 211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0403dwg04-20-05

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PLYMOUTH POND

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Jo

FEET

ft Shallow Monitoring Well mdashbullbullmdash 17-Acre Property Boundary Figure 1-ZD Deep Monitoring Well I 1 I Detected Concentration ND = Not Detected Distribution of Total VOCs in

Deep Bedrock Groundwater Pumping Well April 2003

Q) Residential Well Hows Corner Superfund Site Plymouth Maine

(T) Surface Water Sampling Point WOODARD ampCURRAN poundKk EnginawtirKj bull Science - Operations bull

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0403dwg04-20-05

0 Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

B MW-1B

I 12000

PCE

B 10000 Total VOCs

I

i 2000

i 0 Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

c MW-3B

G 2000

1800

B PCE

1600 Total VOCs

1 I I E

il-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

G E

211941

El

I I z E

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Concentration Trends shy Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-13DB

Total VOCs

c i i c o

Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

MW-16DB

30

c i c c I c o

Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99

PCE

Total VOCs

Jul-01 Jul-03

211941

O bi

c Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

I MW-16IB

i 35

3

c Total VOCs

lt- 2 5

0 | gt

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Jul-90 Jul-92 Jul-94 Jul-96 Jul-98 Jul-00 Jul-02 Jul-04

I I MW-108D

I 12

PCE 10

Total VOCs c oc 3

E E I 0

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

E 211941

c Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

fi MW-108S

I I 40

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Total VOCs

30

I f 26

20 I o

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10

c Dec-99 Dec-00 Dec-01 Dec-02 Dec-03 I 0

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0 Dec-99 Dec-OO Dec-01 Dec-02 Dec-03

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Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-112S

08

PCE

Total VOCs 06

o 04

02

0 Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

MW-114D

o

12000

10000

8000

6000

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Total VOCs

4000

2000

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Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

211941

Con

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n (

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I MW-114S

E A5000 -- Total VOCs

- 4000

0 3000

2000

i 1000

i n shy

Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

MW-115D

c PCE

Total VOCs

c E

o

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Dec-99 Dec-00 Dec-01 Dec-02 Dec-03 I 0

211941

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30000

25000

20000

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5000

0 Aug-99

25000

20000

5000

0 Aug-99

211941

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-2DB

PCE

Total VOCs

Aug-01 Aug-03

MW-2IB

PCE

Total VOCs

Aug-01 Aug-03

IDIBI

ii EIDIISIBIG C

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-102S

6000

5000 PCE

Total VOCs

4000

O 3000

2000

1000

0 Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

MW-103D

16000

~ 14000 ugt 3- 12000 o

^ 10000

sect 8000

O 6000

4000

2000

PCE

Total VOCs

0Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

211941

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

G MW-103S

I I

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12000

10000

E sectc

S

8000

6000

4000

2000

0Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

G I 6000

MW-104D

i 5000

PCE

Total VOCs

i i c

2000

1000

Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

E I

211941

cIccIG

IIBCccBcIc

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-1041

PCE Total VOCs

a 25000

0 20000

a 15000

10000

5000

0 Jan-OO Jan-01 Jan-02 Jan-03 Jan-04

MW-106D

3000

2500 PCE

Total VOCs

=sect 2000

o bullsect 1500

1000

500

0 Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

211941

c Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

c MW-106S

I PCE

Total VOCs

i

i Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

i

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C

211941 c

Response to EPA-DEP Comment 5 Dated March 312005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

iiw

EPA-DEP Comment 5

Comment 5 Matrix Diffusion The report as well as other proponents of matrix diffusion suggest that depletion of DNAPL (Section 5112 page 5-15) needs to be achieved While that might be the ideal the goal is to achieve performance standards and that goal may be attainable while there is residual contamination in the rock perhaps even DNAPL globules The low bedrock matrix porosity (page 1-15) the high permeability values (page 4-4) the relative flux of the groundwater (page 5-5) and the decrease in surface area and out of the mainstream pockets (appendix C-4) all suggest that the diffusion out of the rock matrix would be insubstantial relative to the regional flux of groundwater through the Site

Response The TI Evaluation Report does not explicitly consider or rely upon matrix diffusion as a basis for requesting a TI Waiver for a portion of the Hows Corner Site The technical literature provides documentation that matrix diffusion can be a significant process that affects chemical transport and groundwater remediation timeframes in unconsolidated and consolidated media including fractured rock (US EPA 1989 Freeze and Cherry 1979 Pankow and Cherry 1996 Fountain 1998) Back diffusion of contaminants from the matrix porosity of the fractured rock can prolong the time necessary to achieve groundwater cleanup goals particularly for compounds such as PCE for which the cleanup goal is a low concentration It is our expectation that matrix diffusion has occurred at the Hows Corner Site and that back diffusion of PCE from the rock matrix will also occur Although the extent to which matrix diffusion is occurring at the Hows Comer Site has not been determined and that lack of knowledge contributes to uncertainty regarding the cleanup times at the Site the effect of matrix diffusion is to lengthen rather than shorten the time required for remediation

REFERENCES

Fountain JC 1998 Technologies for Dense Nonaqueous Phase Liquid Source Zone Remediation Ground-Water Remediation Technologies Analysis Center Technology Evaluation Report TE-98-02 December

Freeze RA and Cherry JA 1979 Groundwater Prentice-Hall Inc Englewood Cliffs NJ 07632 p 410-412

Pankow J F and Cherry J A 1996 Dense Chlorinated Solvents Waterloo Press Portland OR 97291-1399 p 67-88

US EPA 1989 Transport and Fate of Contaminants in the Subsurface EPA6254-89019 p 17-18

Response to EPA Comment 5 050305doc 1 of 1 Woodard amp Curran (211941)

WOODARD amp CURRAN Maine Massachusetts New Hampshire Connecticut Florida Operational offices across the US 1-800-426-4262 www woodardcurran com

Page 38: SDMS DocID 251749 - Records Collections · 2020-06-13 · CORPORATE OFFICES: Maine, Massachusetts, New Hampshire, Connecticut New, York, Florida Engineering • Science • Operations

LIST OF ATTACHMENTS (Response to Comment 3)

Appendix B to Draft Technical Impracticability Evaluation Measurement of foe at Hows Corner (4 pages)

m

Response to EPA Comment 3 050205doc 7 of 11 Woodard amp Curran (211941)

Appendix B Measurement of foe of Rock Core at Hows Corner

There are two general approaches to measure the fraction of organic carbon (foe) in rock cores

bull Measurement of weight loss by ignition of organic matter bull Chemical oxidization of organic carbon to carbon dioxide and either

subsequent quantification of the oxidant used for the reaction or quantification of the carbon dioxide produced during this oxidation process

The weight loss method is subject to errors caused by volatilization of substances other than organic materials such as water hydroxides and mineral carbonates Quantification of foe by the weight loss method is particularly sensitive to the presence of carbonates in rock cores There are however weight loss methods that are designed to differentiate between organic carbon and the aforementioned interfering materials but they require considerable care and are less accurate at low foe values Hence the weight loss method was not well suited for measuring the foe of the rock core from Hows Corner

The chemical oxidation of organic carbon is much better suited for quantifying organic carbon in rock cores such as those from Hows Corner This method uses a strong chemical oxidant to oxidize organic carbon to carbon dioxide and then measures either the chemical oxidant used to oxidize the organic carbon or the quantity of carbon dioxide produced In addition this general approach is not subject to interference by volatilization of other constituents of the rock core

There are at least two such chemical oxidation methods

bull The method of Baccini which was described by Schwarzenbach amp Westall (1981) first acidifies the sample to eliminate interference by carbonates Then a strong oxidant is used to chemically oxidize the organic carbon to carbon dioxide The resulting carbon dioxide is subsequently reduced to methane and quantified using a flame ionization detector Unfortunately this method has not been described in detail in a referred journal Hence it is would not have been appropriate to use to characterize the foe in the Hows Corner rock core

bull The more commonly used method to quantify foe in rock core is the Walkley-Black method (1934) This method is preferred for RBCA and DODDOE projects and by the oil industry

The Walkley-Black method uses an excess of chromic acid to oxidize (digest) organic matter to carbon dioxide The remaining chromic acid that was not consumed during the oxidation of the organic carbon is then quantified by titration with ferrous sulfate The difference in chromic acid prior to and after the oxidation of the organic carbon represents the total chromic acid used to oxidize

Hows Corner TI Evaluation Page 1 January 13 2005 Appendix B

the organic carbon in the sample The latter can be calculated using the chemical stoichiometry of the reaction

The Walkley-Black method is very accurate for samples that contain less than 2 organic carbon matter The minimum detection limit (MDL) for the Walkley-Black method is 100 mgkg or an foe of 0001

Given the rock core at Hows Corner was expected to contain less than 2 organic carbon the Walkley-Black method was used to measure the foe from 19 different rock core samples collected from varying depths ranging from 11 to 90 feet

Table 1 provides a statistical summary of the aforementioned data

Table 1 Statistical summary of foe data from rock cores collected at varying depths

Statistical Parameter Calculated Value foe Minimum Detection Limit (MDL) 00010 Number of samples analyzed (n) 19 Average foe 00019 Median foe 00019 Geometric Mean foe 00019 Standard deviation of foe measurements 000033 Relative standard deviation 174 -+ 95 Confidence intervals 00012 to 00025

The data in Table 1 shows the following

bull The foe from the Hows Corner rock cores are statistically greater than the MDL of the Walkley-Black analytical method

bull The average and median values for the foe of the Hows Corner rock cores from varying depths are nearly identical indicating that there is little variability in the foe values in the source zone at the site

bull The standard deviation of these measurements is 000033 which is 174 of the average foe

bull The 95 confidence intervals of the foe of the rock core at Hows Corner are 00012 to 00025

The foe was also analyzed from three separate samples taken from the same rock core at a depth of 55 feet (Only one of these samples was included in the data summarized in Table 1) Table 2 shows the statistical repeatability of this type of analysis

Hows Corner TI Evaluation Page 2 January 13 2005 Appendix B

Table 2 Repeatability of analysis of foe from one rock core at 55 feet in depth

Statistical Parameter Calculated Value Number of samples analyzed (n) 3 Average foe 00016 Median foe 00015 Geometric Mean foe 00016 Standard deviation of foe measurements 000039 Relative standard deviation 240 -+ 95 Confidence intervals 00008 to 00024

The data in Table 2 shows the following

bull The percent relative standard deviation of these three analyses of foe from the same rock core at Hows Corner is 24

bull The 95 confidence interval of the foes measured in this particular rock core at Hows Conrer is 00008 to 00024

These results show that there is good repeatability in using the Walkley-Black method for analysis of the foe in the rock core at Hows Corner

References Schwarzenbach amp Westall (1981) Transport of nonpolar organic compounds from surface water to groundwater Laboratory sorption studies Environ Sci Tech 15 1360-1367

Walkley A I A Black (1934) An examination of Degtjareff method for determining soil organic matter and a proposed modification of the chromic acid titration method Soil Sci 37 29-37

Hows Corner Tl Evaluation Page S January 13 2005 Appendix B

Woodard and Curran PTS Laboratories PTS File No 34618

ORGANIC CARBON DATA (METHODOLOGY WALKLEY-BLACK)

PROJECT NAME PROJECT NO

SAMPLE ID

203-chip-13 203-chip-23 203-chip-27 203-chip-38 203-chip-42 203-chip-47 203-chip-52 203-chip-58 203-chip-69 203-chip-82 207-chip-11 207-chip-19 207-chip-24 207-chip-29 207-chip-35 207-chip-45 207-chip-55 207-chip-87 207-chip-90

207-chip-55 55-MS

55-MSMSD

Hows Corner NA

DEPTH ft

13 23 27 38 42 47 52 58 69 82 11 19 24 29 35 45 55 87 90

55 NA NA

MATRIX

Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip

Average Median

Geometric Mean Standard Deviation Relative Std Dev

+- 95 Confidence Interval n

Rock Chip Rock Chip Rock Chip

Average Median

Geometric Mean Standard Deviation Relative Std Dev

+- 95 Confidence Interval n

FRACTION ORGANIC CARBON

(gg)

170E-03 185E-03 185E-03 170E-03 240E-03 190E-03 230E-03 180E-03 170E-03 115E-03 195E-03 220E-03 220E-03 235E-03 135E-03 190E-03 205E-03 175E-03 160E-03

188E-03 185E-03 185E-03 327E-04

1739 123E-03 to

19

205E-03 130E-03 150E-03

162E-03 150E-03 159E-03 388E-04

2402 840E-04 to

3

2532E-03

2393E-03

Hows Corner Tl Evaluation Appendix B January 13 2005

Response to EPA-DEP Comment 4 Dated March 31 2005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

EPA-DEP Comment 4

Comment 4 Distribution of contaminants First the TI report seems based on the assertion that there is DNAPL at the source area yet it also appears to represent that the source area is small and the bedrock below 85 is competent (or less fractured) and less impacted by the release of contaminants Some of the confusion may result from using most recent data when that data is from several different sampling events over several years and there is no discernible difference in concentrations between shallow and deep bedrock or as in Section 421 where generally decreased generally increase generally similar and similar concentrations in four consecutive sentences leads to a muddled picture of the contaminant distribution

Second the report asserts that the distribution of contaminants over the entire plume has not changed with time but fails to support this conclusion with data again relying on data that is from different sampling dates for one composite representation

Response The likely presence of dense non-aqueous phase liquid (DNAPL) at the Hows Corner Site and the determination that the source area is small are not mutually exclusive and both are conclusions drawn from information obtained during field investigations The presence of DNAPL in the source area is based on the elevated concentrations of volatile organic compounds (VOCs) detected in the groundwater (WampC 2001 WampC 2002) The conclusion that the source area is small is based on the area in which VOCs in groundwater have been detected at concentrations that are considered to be indicative of the presence of DNAPL nearby Similarly the conclusion that fracture frequency decreases at depths greater than approximately 50 to 85 feet below ground surface was based on field observation during the RI field work The fact that zones with observed fractures exhibited higher hydraulic conductivities than zones without fractures coupled with the decreasing frequency of observed fractures with depth led to the conclusion that the hydraulic conductivity of the bulk rock decreases with depth

The most recent data from all wells were used to provide the maximum VOC data set size During the RI all of the previously-existing and then newly-installed monitoring wells were sampled along with several residential wells The RI sampling included up to 48 monitoring wells Subsequent to the RI and prior to the TI three rounds of monitoring were conducted to verify that the plume was stable 15 monitoring wells were sampled during each of the three rounds During the TI field investigation 29 wells were sampled for VOCs The sampled wells included all of the newly-installed wells and a subset of wells installed during the RI for a total of 29 monitoring wells By using most recent data VOC results from 53 monitoring wells were included in the evaluation (see table labeled Sampling Events for listing of monitoring wells) This approach was selected because there generally was little variation in the data from a particular location between years This is borne out by the attached individual plots of VOCs detected in shallow bedrock and deep bedrock for the Pre-ROD (December 1999January 2000) and Supplemental (May 2000) sampling events and for June 2001 January 2002 and April 2003 sampling events The Pre-ROD and Supplemental plots are similar to the subsequent plots from the 2001 2002 and 2003 sampling events

In addition to maps showing the spatial distribution of VOC data at a given time trend plots of the data from a particular location through time (attached) indicate that since the RI concentrations generally have been stable or have decreased Together the maps and trend plots and the data from which they were developed indicate that the distribution of contaminants over the entire plume has not changed appreciably with time

Response to EPA Comment 4 050305doc 1 of 26 Woodard amp Curran (211941)

REFERENCES

Woodard amp Curran Inc (WampC) 2001 Final Remedial Investigation Report Hows Corner Superfund Plymouth Maine July 2001

Woodard amp Curran Inc (WampC) 2002 Final Feasibility Study Report - Non-Source Area Groundwater Hows Corner Superfund Site Plymouth Maine Hows Corner Superfund Plymouth Maine July 2002

Response to EPA Comment 4 050305doc 2 of 26 Woodard amp Curran (211941)

LIST OF ATTACHMENTS (Response to Comment 4)

Table - Sampling Events 1999 - 2004 (2 pages)

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater Pre-ROD Sampling Event

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater Pre-ROD Sampling Event

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater Supplemental Sampling Event

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater Supplemental Sampling Event

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater June 2001

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater June 2001

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater January 2002

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater January 2002

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater April 2003

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater April 2003

Figure - Concentration Trends - Non-Source Area Wells MW-1B and MW-3B

Figure - Concentration Trends - Non-Source Area Wells MW-13DB and MW-16DB

Figure - Concentration Trends - Non-Source Area Wells MW-16IB and MW- 108D

Figure - Concentration Trends - Non-Source Area Wells MW-108S and MW-112D

Figure - Concentration Trends - Non-Source Area Wells MW-112S and MW-114D

Figure - Concentration Trends - Non-Source Area Wells MW-114S and MW-115D

Figure - Concentration Trends -Source Area Wells MW-2DB and MW-2IB

Figure - Concentration Trends -Source Area Wells MW-102S and MW-103D

Figure - Concentration Trends -Source Area Wells MW-103S and MW-104D

Figure - Concentration Trends -Source Area Wells MW-104I and MW-106D

Figure - Concentration Trends -Source Area Wells MW-106S

Response to EPA Comment 4 050305doc 3 of 26 Woodard amp Curran (211941)

I I

El I

II I I 1 I

I

i

Event Baseline Case ID WC-01 WC-01

Well Date Aug-99 Oct-99 LOT10 1 LOT1-1 1 LOT11-4 LOT14 1 LOT15 1 LOT15-1 1 LOT16 1 LOT16-1 1 LOT17 1 LOT18 1 LOT19 1 LOT2 LOT20 1 LOT21-10 1 LOT21-11 1 LOT21-12 1 LOT21-13 1 LOT21-14 1 LOT21-2 1 LOT21-5 1 LOT21-7 LOT21 -8 1 LOT21-9 1 LOT23 1 LOT24 1 LOT28-1 1 LOT28-2 1 LOT28-3 1 LOT28-4 1 LOT28W 1 LOT30 1 LOT30-1 1 LOT30-2 1 LOT30-3 1 LOT30-4 1 LOT30-5 LOT31 LOT35 1 LOT41 1 LOT42-1 1 LOT43-1 1 LOT43-4 1 LOT6-1 1 LOT67 1 LOT6-7 1 LOT6-8A 1 LOT6-8B 1 LOT80-1 1 LOT82 1 MW-101D MW-1011 MW-101S MW-102D MW-102S MW-103D MW-103S MW-104D MW-1041 MW-104S MW-105D MW-106D

Groundwater Sampling Location Summary 1999 - 2004xls

Sampling Events 1999-2004

Hows Corner Superfund Site Plymouth Maine

Supplemental 2001 2002 2003 Pumping 2004 Pre-ROD Rl Sampling Sampling Sampling Test Sampling WC-03 WC-09 WC-25 WC-30 WC-42B WC-56 WC-58 Dec-99 May-00 Jun-01 Jan-02 Apr-03 Sep-04 Sep-04

1

1 1 1

1 1 1 1 1

1 1

1

1 1

1 1 1

1 1 1 1 1

1

1 1

1 1 1 1

1

1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

Sampling Events 1999-2004

Hows Corner Super-fund Site Plymouth Maine

Supplemental 2001 2002 2003 Pumping Event Baseline Pre-ROD Rl Sampling Sampling Sampling Test

Case ID WC-01 WC-01 WC-03 WC-09 WC-25 WC-30 WC-42B WC-56

ll

Well Date Aug-99 Oct-99 Dec-99 May-00 Jun-01 Jan-02 Apr-03 Sep-04 MW-106S 1 1 1 1 1 MW-107D 1 1 MW-108D 1 1 1 1 1 MW-108S 1 1 1 1 1 MW-110D 1 1 MW-111D 1 1 MW-112D 1 1 1 1 1 MW-112S 1 1 1 1 1 MW-113D 1 1 MW-114D 1 1 1 1 1 MW-114S 1 1 1 1 1 MW-115D 1 1 1 1 1 MW-12DB 1 1 1 MW-12SB 1 1 1 MW-13DB 1 1 1 1 1 1 MW-13SB 1 1 1 MW-14DB 1 1 MW-14SO 1 1 MW-15DB 1 1 1 MW-15SB 1 1 1 MW-16DB 1 1 1 1 1 1 MW-16IB 1 1 1 1 1 1 MW-16SO 1 1 MW-17DO 1 1 1 MW-17SO 1 1 1 MW-1B 1 1 1 1 1 1 MW-203D MW-203S MW-204D MW-204S MW-205 MW-206D

I MW-206S MW-2DB 1 1 MW-2DDB 1 1 MW-2IB 1 1 1 1 1 1 MW-3B 1 1 1 1 1 1

I MW-4O 1 1 1 MW-5B 1 1

II MW-6DB 1 1 1 MW-6SB 1 1 1 MW-8DB 1 1 1 MW-8SB 1 1 1

II PW-207 1 SEEP-1 1 SUBTOTAL - RESIDENTIAL 44 25 0 2 0 3 0 SUBTOTAL - MONITORING 22 48 41 15 15 15 1

Total 3 66 73 41 17 15 18 1

I Included in most recent data

I Notes 1 - Overburden well not included in most recent data for plotting

2 - Tetrahydrofuran and 2-Butanone were the only two compounds detected in this well and are thought to be the result of well repair not included in most recent data for plotting

3 - Not included in most recent data for plotting

2004 Sampling

WC-58 Sep-04

1

1 1

1 1

1 1 1

1

1 1

1 1 1 1 1 1 1 1 1

1 1

1

0 29

29

Groundwatef Sampling Location Summary 1999 - 2004xls

I

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

monitoring well Figure 4-14 total VOC contour (ugl) - December 1999January 2000 Distribution of Total VOCs in

Note SW-113 is located downstream of SEEP-1 Shallow Bedrock Groundwater total concentration of detected VOCs ND= not detected these two locations were sampled during the Pre-ROD Sampling Event

Baseline Sampling Event in OctoberNovember 1999 Hows Corner Superfund Site Surface Water Sampling Location A Plymouth Maine Seep Sampling Location laquo- WOODARD ampCURRAN

995037wipri reportepa ri interim final feb 2001cadd drawingsfinalfig 4-14

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

0 300 600 I

FEET

Q residential well Figure 4-16 monitoring well Distribution of Total VOCs in

Deep Bedrock Groundwater total VOCs contour (ugl) Pre-ROD Sampling Event

active residential wells with lot number Hows Corner Superfund Site 2deg42deg Plymouth Maine total concentration of detected VOCs ND= not detected WOODARD ampCURRAN Enyinaaring bull Science bull Operations bull

995037wipri reportepa ri interim final feb 2001cadd drawingsfinalfig4mdash16

PLYMOUTH POND

PLYMOUTH POND

1 628Tl7MW-2bB 12135

PLYMOUTH POND

monitoring well Figure 4-20

V total VOC contour (ugl) - June 2000 Distribution of Total VOCs in Shallow Bedrock Groundwater

| 34 | total concentration of detected VOCs ND= not detected NA = not analyzed Supplemental Sampling Event Note SW-113 is located downstream of SEEP-1 Hows Corner Superfund Site

Surface Water Sampling Location these two locations were sampled during the Plymouth Maine Baseline Sampling Event in OctoberNovember 1999 Seep Sampling Location WOODARD amp CURRAN

Engineering bull Science - Operations bull 995037wipri reportepa ri interim final feb 2001 cadd drawingsfinalfig 4-20

residential well Figure 4-22 Distribution of Total VOCs in

monitoring well Deep Bedrock Groundwater

total VOCs contour (ugl) Supplemental Sampling Event

Hows Corner Superfund Site

total concentration of detected VOCs ND= not detected NA = not analyzed Plymouth Maine

WOODARD amp CURRAN

995037wipri reportepa-ri interim final feb 2001cadd drawingsfinalfig 4-22 Engineering bull Science - Operations bull

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

FEET

Shallow Monitoring Well

Deep Monitoring Well

C Detected Concentration ND = Not Detected Figure 1-XS Distribution of Total VOCs in Shallow Bedrock Groundwater

Pumping Well

17-Acre Property Boundary Concentration Contour (ugl)

June 2001 Hows Corner Superfund Site

Plymouth Maine WOODARDampCURRAN

-i^rhvj bull Scbncn bull Operations bull 211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0601 dwg04-20-05

PLYMOUTH POND Hopkins Road V

O

PLYMOUTH POND

PLYMOUTH POND

o

0 300 600 mdashfa FEET

Shallow Monitoring Well bull bull - 17-Acre Property Boundary Figure 1-XD

Deep Monitoring Well 1 I Detected Concentration ND = Not Detected Distribution of Total VOCs in Deep Bedrock Groundwater

-mf- Pumping Well June 2001 Residential Well Hows Corner Superfund Site

Plymouth Maine i h Surface Water Sampling Point

g WOODARD ampCURRAN _ ^ _ ^ _ _ yen_ rj i|Hlaquorlny bull Science bull Opt

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0601 dwg04-20-05

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

Shallow Monitoring Well

Deep Monitoring Well

Detected Concentration ND = Not Detected Figure 1-YS Distribution of Total VOCs in Shallow Bedrock Groundwater

Pumping Well

17-Acre Property Boundary Concentration Contour (ugl)

January 2002 Hows Corner Superfund Site

Plymouth Maine WOODARD amp CURRAN Engineering Science- Operations bull

211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0102dwg04-20-05

PLYMOUTH POND

PLYMOUTH POND

Site Pand^ laquoum-laquoBTuitaraquo tLV

vVlf-(

PLYMOUTH POND

0 300 600 ^ = FEET

Shallow Monitoring Well mdashbullbullbull 17-Acre Property Boundary Figure 1-YD - A - Deep Monitoring Well FT Detected Concentration ND = Not Detected Distribution of Total VOCs in

Deep Bedrock Groundwater Pumping Well January 2002 Residential Well Hows Corner Superfund Site

Plymouth Maine Surface Water Sampling Point

WOODARD ampCURRAN Engineering Sciencs- Operations bulli Si

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0102dwg04-20-05

- m j

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND j A O-shy

Shallow Monitoring Well E Detected Concentration ND = Not Detected Figure 1-ZS Distribution of Total VOCs in

Deep Monitoring Well Shallow Bedrock Groundwater

Pumping Well Hows Corner

April 2003 Superfund Site

17-Acre Property Boundary Plymouth Maine Concentration Contour (ugl) r WOODARD ampCURRAN

Engineering bull Science bull Operations bull 211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0403dwg04-20-05

s S pound

PLYMOUTH POND

PLYMOUTH POND

- -

5 PLYMOUTH POND

Jo

FEET

ft Shallow Monitoring Well mdashbullbullmdash 17-Acre Property Boundary Figure 1-ZD Deep Monitoring Well I 1 I Detected Concentration ND = Not Detected Distribution of Total VOCs in

Deep Bedrock Groundwater Pumping Well April 2003

Q) Residential Well Hows Corner Superfund Site Plymouth Maine

(T) Surface Water Sampling Point WOODARD ampCURRAN poundKk EnginawtirKj bull Science - Operations bull

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0403dwg04-20-05

0 Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

B MW-1B

I 12000

PCE

B 10000 Total VOCs

I

i 2000

i 0 Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

c MW-3B

G 2000

1800

B PCE

1600 Total VOCs

1 I I E

il-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

G E

211941

El

I I z E

80

Concentration Trends shy Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-13DB

Total VOCs

c i i c o

Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

MW-16DB

30

c i c c I c o

Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99

PCE

Total VOCs

Jul-01 Jul-03

211941

O bi

c Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

I MW-16IB

i 35

3

c Total VOCs

lt- 2 5

0 | gt

o

1 sectI

c c 0 4

Jul-90 Jul-92 Jul-94 Jul-96 Jul-98 Jul-00 Jul-02 Jul-04

I I MW-108D

I 12

PCE 10

Total VOCs c oc 3

E E I 0

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

E 211941

c Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

fi MW-108S

I I 40

PCE 35

Total VOCs

30

I f 26

20 I o

I 15

10

c Dec-99 Dec-00 Dec-01 Dec-02 Dec-03 I 0

I MW-112D

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0 Dec-99 Dec-OO Dec-01 Dec-02 Dec-03

211941

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Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-112S

08

PCE

Total VOCs 06

o 04

02

0 Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

MW-114D

o

12000

10000

8000

6000

PCE

Total VOCs

4000

2000

i

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Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

211941

Con

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ratio

n (

ug

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E Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

I MW-114S

E A5000 -- Total VOCs

- 4000

0 3000

2000

i 1000

i n shy

Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

MW-115D

c PCE

Total VOCs

c E

o

C c

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03 I 0

211941

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30000

25000

20000

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5000

0 Aug-99

25000

20000

5000

0 Aug-99

211941

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-2DB

PCE

Total VOCs

Aug-01 Aug-03

MW-2IB

PCE

Total VOCs

Aug-01 Aug-03

IDIBI

ii EIDIISIBIG C

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-102S

6000

5000 PCE

Total VOCs

4000

O 3000

2000

1000

0 Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

MW-103D

16000

~ 14000 ugt 3- 12000 o

^ 10000

sect 8000

O 6000

4000

2000

PCE

Total VOCs

0Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

211941

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

G MW-103S

I I

ampo

12000

10000

E sectc

S

8000

6000

4000

2000

0Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

G I 6000

MW-104D

i 5000

PCE

Total VOCs

i i c

2000

1000

Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

E I

211941

cIccIG

IIBCccBcIc

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-1041

PCE Total VOCs

a 25000

0 20000

a 15000

10000

5000

0 Jan-OO Jan-01 Jan-02 Jan-03 Jan-04

MW-106D

3000

2500 PCE

Total VOCs

=sect 2000

o bullsect 1500

1000

500

0 Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

211941

c Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

c MW-106S

I PCE

Total VOCs

i

i Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

i

i i i E

C

211941 c

Response to EPA-DEP Comment 5 Dated March 312005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

iiw

EPA-DEP Comment 5

Comment 5 Matrix Diffusion The report as well as other proponents of matrix diffusion suggest that depletion of DNAPL (Section 5112 page 5-15) needs to be achieved While that might be the ideal the goal is to achieve performance standards and that goal may be attainable while there is residual contamination in the rock perhaps even DNAPL globules The low bedrock matrix porosity (page 1-15) the high permeability values (page 4-4) the relative flux of the groundwater (page 5-5) and the decrease in surface area and out of the mainstream pockets (appendix C-4) all suggest that the diffusion out of the rock matrix would be insubstantial relative to the regional flux of groundwater through the Site

Response The TI Evaluation Report does not explicitly consider or rely upon matrix diffusion as a basis for requesting a TI Waiver for a portion of the Hows Corner Site The technical literature provides documentation that matrix diffusion can be a significant process that affects chemical transport and groundwater remediation timeframes in unconsolidated and consolidated media including fractured rock (US EPA 1989 Freeze and Cherry 1979 Pankow and Cherry 1996 Fountain 1998) Back diffusion of contaminants from the matrix porosity of the fractured rock can prolong the time necessary to achieve groundwater cleanup goals particularly for compounds such as PCE for which the cleanup goal is a low concentration It is our expectation that matrix diffusion has occurred at the Hows Corner Site and that back diffusion of PCE from the rock matrix will also occur Although the extent to which matrix diffusion is occurring at the Hows Comer Site has not been determined and that lack of knowledge contributes to uncertainty regarding the cleanup times at the Site the effect of matrix diffusion is to lengthen rather than shorten the time required for remediation

REFERENCES

Fountain JC 1998 Technologies for Dense Nonaqueous Phase Liquid Source Zone Remediation Ground-Water Remediation Technologies Analysis Center Technology Evaluation Report TE-98-02 December

Freeze RA and Cherry JA 1979 Groundwater Prentice-Hall Inc Englewood Cliffs NJ 07632 p 410-412

Pankow J F and Cherry J A 1996 Dense Chlorinated Solvents Waterloo Press Portland OR 97291-1399 p 67-88

US EPA 1989 Transport and Fate of Contaminants in the Subsurface EPA6254-89019 p 17-18

Response to EPA Comment 5 050305doc 1 of 1 Woodard amp Curran (211941)

WOODARD amp CURRAN Maine Massachusetts New Hampshire Connecticut Florida Operational offices across the US 1-800-426-4262 www woodardcurran com

Page 39: SDMS DocID 251749 - Records Collections · 2020-06-13 · CORPORATE OFFICES: Maine, Massachusetts, New Hampshire, Connecticut New, York, Florida Engineering • Science • Operations

Appendix B Measurement of foe of Rock Core at Hows Corner

There are two general approaches to measure the fraction of organic carbon (foe) in rock cores

bull Measurement of weight loss by ignition of organic matter bull Chemical oxidization of organic carbon to carbon dioxide and either

subsequent quantification of the oxidant used for the reaction or quantification of the carbon dioxide produced during this oxidation process

The weight loss method is subject to errors caused by volatilization of substances other than organic materials such as water hydroxides and mineral carbonates Quantification of foe by the weight loss method is particularly sensitive to the presence of carbonates in rock cores There are however weight loss methods that are designed to differentiate between organic carbon and the aforementioned interfering materials but they require considerable care and are less accurate at low foe values Hence the weight loss method was not well suited for measuring the foe of the rock core from Hows Corner

The chemical oxidation of organic carbon is much better suited for quantifying organic carbon in rock cores such as those from Hows Corner This method uses a strong chemical oxidant to oxidize organic carbon to carbon dioxide and then measures either the chemical oxidant used to oxidize the organic carbon or the quantity of carbon dioxide produced In addition this general approach is not subject to interference by volatilization of other constituents of the rock core

There are at least two such chemical oxidation methods

bull The method of Baccini which was described by Schwarzenbach amp Westall (1981) first acidifies the sample to eliminate interference by carbonates Then a strong oxidant is used to chemically oxidize the organic carbon to carbon dioxide The resulting carbon dioxide is subsequently reduced to methane and quantified using a flame ionization detector Unfortunately this method has not been described in detail in a referred journal Hence it is would not have been appropriate to use to characterize the foe in the Hows Corner rock core

bull The more commonly used method to quantify foe in rock core is the Walkley-Black method (1934) This method is preferred for RBCA and DODDOE projects and by the oil industry

The Walkley-Black method uses an excess of chromic acid to oxidize (digest) organic matter to carbon dioxide The remaining chromic acid that was not consumed during the oxidation of the organic carbon is then quantified by titration with ferrous sulfate The difference in chromic acid prior to and after the oxidation of the organic carbon represents the total chromic acid used to oxidize

Hows Corner TI Evaluation Page 1 January 13 2005 Appendix B

the organic carbon in the sample The latter can be calculated using the chemical stoichiometry of the reaction

The Walkley-Black method is very accurate for samples that contain less than 2 organic carbon matter The minimum detection limit (MDL) for the Walkley-Black method is 100 mgkg or an foe of 0001

Given the rock core at Hows Corner was expected to contain less than 2 organic carbon the Walkley-Black method was used to measure the foe from 19 different rock core samples collected from varying depths ranging from 11 to 90 feet

Table 1 provides a statistical summary of the aforementioned data

Table 1 Statistical summary of foe data from rock cores collected at varying depths

Statistical Parameter Calculated Value foe Minimum Detection Limit (MDL) 00010 Number of samples analyzed (n) 19 Average foe 00019 Median foe 00019 Geometric Mean foe 00019 Standard deviation of foe measurements 000033 Relative standard deviation 174 -+ 95 Confidence intervals 00012 to 00025

The data in Table 1 shows the following

bull The foe from the Hows Corner rock cores are statistically greater than the MDL of the Walkley-Black analytical method

bull The average and median values for the foe of the Hows Corner rock cores from varying depths are nearly identical indicating that there is little variability in the foe values in the source zone at the site

bull The standard deviation of these measurements is 000033 which is 174 of the average foe

bull The 95 confidence intervals of the foe of the rock core at Hows Corner are 00012 to 00025

The foe was also analyzed from three separate samples taken from the same rock core at a depth of 55 feet (Only one of these samples was included in the data summarized in Table 1) Table 2 shows the statistical repeatability of this type of analysis

Hows Corner TI Evaluation Page 2 January 13 2005 Appendix B

Table 2 Repeatability of analysis of foe from one rock core at 55 feet in depth

Statistical Parameter Calculated Value Number of samples analyzed (n) 3 Average foe 00016 Median foe 00015 Geometric Mean foe 00016 Standard deviation of foe measurements 000039 Relative standard deviation 240 -+ 95 Confidence intervals 00008 to 00024

The data in Table 2 shows the following

bull The percent relative standard deviation of these three analyses of foe from the same rock core at Hows Corner is 24

bull The 95 confidence interval of the foes measured in this particular rock core at Hows Conrer is 00008 to 00024

These results show that there is good repeatability in using the Walkley-Black method for analysis of the foe in the rock core at Hows Corner

References Schwarzenbach amp Westall (1981) Transport of nonpolar organic compounds from surface water to groundwater Laboratory sorption studies Environ Sci Tech 15 1360-1367

Walkley A I A Black (1934) An examination of Degtjareff method for determining soil organic matter and a proposed modification of the chromic acid titration method Soil Sci 37 29-37

Hows Corner Tl Evaluation Page S January 13 2005 Appendix B

Woodard and Curran PTS Laboratories PTS File No 34618

ORGANIC CARBON DATA (METHODOLOGY WALKLEY-BLACK)

PROJECT NAME PROJECT NO

SAMPLE ID

203-chip-13 203-chip-23 203-chip-27 203-chip-38 203-chip-42 203-chip-47 203-chip-52 203-chip-58 203-chip-69 203-chip-82 207-chip-11 207-chip-19 207-chip-24 207-chip-29 207-chip-35 207-chip-45 207-chip-55 207-chip-87 207-chip-90

207-chip-55 55-MS

55-MSMSD

Hows Corner NA

DEPTH ft

13 23 27 38 42 47 52 58 69 82 11 19 24 29 35 45 55 87 90

55 NA NA

MATRIX

Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip

Average Median

Geometric Mean Standard Deviation Relative Std Dev

+- 95 Confidence Interval n

Rock Chip Rock Chip Rock Chip

Average Median

Geometric Mean Standard Deviation Relative Std Dev

+- 95 Confidence Interval n

FRACTION ORGANIC CARBON

(gg)

170E-03 185E-03 185E-03 170E-03 240E-03 190E-03 230E-03 180E-03 170E-03 115E-03 195E-03 220E-03 220E-03 235E-03 135E-03 190E-03 205E-03 175E-03 160E-03

188E-03 185E-03 185E-03 327E-04

1739 123E-03 to

19

205E-03 130E-03 150E-03

162E-03 150E-03 159E-03 388E-04

2402 840E-04 to

3

2532E-03

2393E-03

Hows Corner Tl Evaluation Appendix B January 13 2005

Response to EPA-DEP Comment 4 Dated March 31 2005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

EPA-DEP Comment 4

Comment 4 Distribution of contaminants First the TI report seems based on the assertion that there is DNAPL at the source area yet it also appears to represent that the source area is small and the bedrock below 85 is competent (or less fractured) and less impacted by the release of contaminants Some of the confusion may result from using most recent data when that data is from several different sampling events over several years and there is no discernible difference in concentrations between shallow and deep bedrock or as in Section 421 where generally decreased generally increase generally similar and similar concentrations in four consecutive sentences leads to a muddled picture of the contaminant distribution

Second the report asserts that the distribution of contaminants over the entire plume has not changed with time but fails to support this conclusion with data again relying on data that is from different sampling dates for one composite representation

Response The likely presence of dense non-aqueous phase liquid (DNAPL) at the Hows Corner Site and the determination that the source area is small are not mutually exclusive and both are conclusions drawn from information obtained during field investigations The presence of DNAPL in the source area is based on the elevated concentrations of volatile organic compounds (VOCs) detected in the groundwater (WampC 2001 WampC 2002) The conclusion that the source area is small is based on the area in which VOCs in groundwater have been detected at concentrations that are considered to be indicative of the presence of DNAPL nearby Similarly the conclusion that fracture frequency decreases at depths greater than approximately 50 to 85 feet below ground surface was based on field observation during the RI field work The fact that zones with observed fractures exhibited higher hydraulic conductivities than zones without fractures coupled with the decreasing frequency of observed fractures with depth led to the conclusion that the hydraulic conductivity of the bulk rock decreases with depth

The most recent data from all wells were used to provide the maximum VOC data set size During the RI all of the previously-existing and then newly-installed monitoring wells were sampled along with several residential wells The RI sampling included up to 48 monitoring wells Subsequent to the RI and prior to the TI three rounds of monitoring were conducted to verify that the plume was stable 15 monitoring wells were sampled during each of the three rounds During the TI field investigation 29 wells were sampled for VOCs The sampled wells included all of the newly-installed wells and a subset of wells installed during the RI for a total of 29 monitoring wells By using most recent data VOC results from 53 monitoring wells were included in the evaluation (see table labeled Sampling Events for listing of monitoring wells) This approach was selected because there generally was little variation in the data from a particular location between years This is borne out by the attached individual plots of VOCs detected in shallow bedrock and deep bedrock for the Pre-ROD (December 1999January 2000) and Supplemental (May 2000) sampling events and for June 2001 January 2002 and April 2003 sampling events The Pre-ROD and Supplemental plots are similar to the subsequent plots from the 2001 2002 and 2003 sampling events

In addition to maps showing the spatial distribution of VOC data at a given time trend plots of the data from a particular location through time (attached) indicate that since the RI concentrations generally have been stable or have decreased Together the maps and trend plots and the data from which they were developed indicate that the distribution of contaminants over the entire plume has not changed appreciably with time

Response to EPA Comment 4 050305doc 1 of 26 Woodard amp Curran (211941)

REFERENCES

Woodard amp Curran Inc (WampC) 2001 Final Remedial Investigation Report Hows Corner Superfund Plymouth Maine July 2001

Woodard amp Curran Inc (WampC) 2002 Final Feasibility Study Report - Non-Source Area Groundwater Hows Corner Superfund Site Plymouth Maine Hows Corner Superfund Plymouth Maine July 2002

Response to EPA Comment 4 050305doc 2 of 26 Woodard amp Curran (211941)

LIST OF ATTACHMENTS (Response to Comment 4)

Table - Sampling Events 1999 - 2004 (2 pages)

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater Pre-ROD Sampling Event

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater Pre-ROD Sampling Event

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater Supplemental Sampling Event

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater Supplemental Sampling Event

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater June 2001

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater June 2001

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater January 2002

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater January 2002

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater April 2003

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater April 2003

Figure - Concentration Trends - Non-Source Area Wells MW-1B and MW-3B

Figure - Concentration Trends - Non-Source Area Wells MW-13DB and MW-16DB

Figure - Concentration Trends - Non-Source Area Wells MW-16IB and MW- 108D

Figure - Concentration Trends - Non-Source Area Wells MW-108S and MW-112D

Figure - Concentration Trends - Non-Source Area Wells MW-112S and MW-114D

Figure - Concentration Trends - Non-Source Area Wells MW-114S and MW-115D

Figure - Concentration Trends -Source Area Wells MW-2DB and MW-2IB

Figure - Concentration Trends -Source Area Wells MW-102S and MW-103D

Figure - Concentration Trends -Source Area Wells MW-103S and MW-104D

Figure - Concentration Trends -Source Area Wells MW-104I and MW-106D

Figure - Concentration Trends -Source Area Wells MW-106S

Response to EPA Comment 4 050305doc 3 of 26 Woodard amp Curran (211941)

I I

El I

II I I 1 I

I

i

Event Baseline Case ID WC-01 WC-01

Well Date Aug-99 Oct-99 LOT10 1 LOT1-1 1 LOT11-4 LOT14 1 LOT15 1 LOT15-1 1 LOT16 1 LOT16-1 1 LOT17 1 LOT18 1 LOT19 1 LOT2 LOT20 1 LOT21-10 1 LOT21-11 1 LOT21-12 1 LOT21-13 1 LOT21-14 1 LOT21-2 1 LOT21-5 1 LOT21-7 LOT21 -8 1 LOT21-9 1 LOT23 1 LOT24 1 LOT28-1 1 LOT28-2 1 LOT28-3 1 LOT28-4 1 LOT28W 1 LOT30 1 LOT30-1 1 LOT30-2 1 LOT30-3 1 LOT30-4 1 LOT30-5 LOT31 LOT35 1 LOT41 1 LOT42-1 1 LOT43-1 1 LOT43-4 1 LOT6-1 1 LOT67 1 LOT6-7 1 LOT6-8A 1 LOT6-8B 1 LOT80-1 1 LOT82 1 MW-101D MW-1011 MW-101S MW-102D MW-102S MW-103D MW-103S MW-104D MW-1041 MW-104S MW-105D MW-106D

Groundwater Sampling Location Summary 1999 - 2004xls

Sampling Events 1999-2004

Hows Corner Superfund Site Plymouth Maine

Supplemental 2001 2002 2003 Pumping 2004 Pre-ROD Rl Sampling Sampling Sampling Test Sampling WC-03 WC-09 WC-25 WC-30 WC-42B WC-56 WC-58 Dec-99 May-00 Jun-01 Jan-02 Apr-03 Sep-04 Sep-04

1

1 1 1

1 1 1 1 1

1 1

1

1 1

1 1 1

1 1 1 1 1

1

1 1

1 1 1 1

1

1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

Sampling Events 1999-2004

Hows Corner Super-fund Site Plymouth Maine

Supplemental 2001 2002 2003 Pumping Event Baseline Pre-ROD Rl Sampling Sampling Sampling Test

Case ID WC-01 WC-01 WC-03 WC-09 WC-25 WC-30 WC-42B WC-56

ll

Well Date Aug-99 Oct-99 Dec-99 May-00 Jun-01 Jan-02 Apr-03 Sep-04 MW-106S 1 1 1 1 1 MW-107D 1 1 MW-108D 1 1 1 1 1 MW-108S 1 1 1 1 1 MW-110D 1 1 MW-111D 1 1 MW-112D 1 1 1 1 1 MW-112S 1 1 1 1 1 MW-113D 1 1 MW-114D 1 1 1 1 1 MW-114S 1 1 1 1 1 MW-115D 1 1 1 1 1 MW-12DB 1 1 1 MW-12SB 1 1 1 MW-13DB 1 1 1 1 1 1 MW-13SB 1 1 1 MW-14DB 1 1 MW-14SO 1 1 MW-15DB 1 1 1 MW-15SB 1 1 1 MW-16DB 1 1 1 1 1 1 MW-16IB 1 1 1 1 1 1 MW-16SO 1 1 MW-17DO 1 1 1 MW-17SO 1 1 1 MW-1B 1 1 1 1 1 1 MW-203D MW-203S MW-204D MW-204S MW-205 MW-206D

I MW-206S MW-2DB 1 1 MW-2DDB 1 1 MW-2IB 1 1 1 1 1 1 MW-3B 1 1 1 1 1 1

I MW-4O 1 1 1 MW-5B 1 1

II MW-6DB 1 1 1 MW-6SB 1 1 1 MW-8DB 1 1 1 MW-8SB 1 1 1

II PW-207 1 SEEP-1 1 SUBTOTAL - RESIDENTIAL 44 25 0 2 0 3 0 SUBTOTAL - MONITORING 22 48 41 15 15 15 1

Total 3 66 73 41 17 15 18 1

I Included in most recent data

I Notes 1 - Overburden well not included in most recent data for plotting

2 - Tetrahydrofuran and 2-Butanone were the only two compounds detected in this well and are thought to be the result of well repair not included in most recent data for plotting

3 - Not included in most recent data for plotting

2004 Sampling

WC-58 Sep-04

1

1 1

1 1

1 1 1

1

1 1

1 1 1 1 1 1 1 1 1

1 1

1

0 29

29

Groundwatef Sampling Location Summary 1999 - 2004xls

I

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

monitoring well Figure 4-14 total VOC contour (ugl) - December 1999January 2000 Distribution of Total VOCs in

Note SW-113 is located downstream of SEEP-1 Shallow Bedrock Groundwater total concentration of detected VOCs ND= not detected these two locations were sampled during the Pre-ROD Sampling Event

Baseline Sampling Event in OctoberNovember 1999 Hows Corner Superfund Site Surface Water Sampling Location A Plymouth Maine Seep Sampling Location laquo- WOODARD ampCURRAN

995037wipri reportepa ri interim final feb 2001cadd drawingsfinalfig 4-14

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

0 300 600 I

FEET

Q residential well Figure 4-16 monitoring well Distribution of Total VOCs in

Deep Bedrock Groundwater total VOCs contour (ugl) Pre-ROD Sampling Event

active residential wells with lot number Hows Corner Superfund Site 2deg42deg Plymouth Maine total concentration of detected VOCs ND= not detected WOODARD ampCURRAN Enyinaaring bull Science bull Operations bull

995037wipri reportepa ri interim final feb 2001cadd drawingsfinalfig4mdash16

PLYMOUTH POND

PLYMOUTH POND

1 628Tl7MW-2bB 12135

PLYMOUTH POND

monitoring well Figure 4-20

V total VOC contour (ugl) - June 2000 Distribution of Total VOCs in Shallow Bedrock Groundwater

| 34 | total concentration of detected VOCs ND= not detected NA = not analyzed Supplemental Sampling Event Note SW-113 is located downstream of SEEP-1 Hows Corner Superfund Site

Surface Water Sampling Location these two locations were sampled during the Plymouth Maine Baseline Sampling Event in OctoberNovember 1999 Seep Sampling Location WOODARD amp CURRAN

Engineering bull Science - Operations bull 995037wipri reportepa ri interim final feb 2001 cadd drawingsfinalfig 4-20

residential well Figure 4-22 Distribution of Total VOCs in

monitoring well Deep Bedrock Groundwater

total VOCs contour (ugl) Supplemental Sampling Event

Hows Corner Superfund Site

total concentration of detected VOCs ND= not detected NA = not analyzed Plymouth Maine

WOODARD amp CURRAN

995037wipri reportepa-ri interim final feb 2001cadd drawingsfinalfig 4-22 Engineering bull Science - Operations bull

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

FEET

Shallow Monitoring Well

Deep Monitoring Well

C Detected Concentration ND = Not Detected Figure 1-XS Distribution of Total VOCs in Shallow Bedrock Groundwater

Pumping Well

17-Acre Property Boundary Concentration Contour (ugl)

June 2001 Hows Corner Superfund Site

Plymouth Maine WOODARDampCURRAN

-i^rhvj bull Scbncn bull Operations bull 211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0601 dwg04-20-05

PLYMOUTH POND Hopkins Road V

O

PLYMOUTH POND

PLYMOUTH POND

o

0 300 600 mdashfa FEET

Shallow Monitoring Well bull bull - 17-Acre Property Boundary Figure 1-XD

Deep Monitoring Well 1 I Detected Concentration ND = Not Detected Distribution of Total VOCs in Deep Bedrock Groundwater

-mf- Pumping Well June 2001 Residential Well Hows Corner Superfund Site

Plymouth Maine i h Surface Water Sampling Point

g WOODARD ampCURRAN _ ^ _ ^ _ _ yen_ rj i|Hlaquorlny bull Science bull Opt

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0601 dwg04-20-05

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

Shallow Monitoring Well

Deep Monitoring Well

Detected Concentration ND = Not Detected Figure 1-YS Distribution of Total VOCs in Shallow Bedrock Groundwater

Pumping Well

17-Acre Property Boundary Concentration Contour (ugl)

January 2002 Hows Corner Superfund Site

Plymouth Maine WOODARD amp CURRAN Engineering Science- Operations bull

211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0102dwg04-20-05

PLYMOUTH POND

PLYMOUTH POND

Site Pand^ laquoum-laquoBTuitaraquo tLV

vVlf-(

PLYMOUTH POND

0 300 600 ^ = FEET

Shallow Monitoring Well mdashbullbullbull 17-Acre Property Boundary Figure 1-YD - A - Deep Monitoring Well FT Detected Concentration ND = Not Detected Distribution of Total VOCs in

Deep Bedrock Groundwater Pumping Well January 2002 Residential Well Hows Corner Superfund Site

Plymouth Maine Surface Water Sampling Point

WOODARD ampCURRAN Engineering Sciencs- Operations bulli Si

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0102dwg04-20-05

- m j

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND j A O-shy

Shallow Monitoring Well E Detected Concentration ND = Not Detected Figure 1-ZS Distribution of Total VOCs in

Deep Monitoring Well Shallow Bedrock Groundwater

Pumping Well Hows Corner

April 2003 Superfund Site

17-Acre Property Boundary Plymouth Maine Concentration Contour (ugl) r WOODARD ampCURRAN

Engineering bull Science bull Operations bull 211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0403dwg04-20-05

s S pound

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Jo

FEET

ft Shallow Monitoring Well mdashbullbullmdash 17-Acre Property Boundary Figure 1-ZD Deep Monitoring Well I 1 I Detected Concentration ND = Not Detected Distribution of Total VOCs in

Deep Bedrock Groundwater Pumping Well April 2003

Q) Residential Well Hows Corner Superfund Site Plymouth Maine

(T) Surface Water Sampling Point WOODARD ampCURRAN poundKk EnginawtirKj bull Science - Operations bull

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0403dwg04-20-05

0 Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

B MW-1B

I 12000

PCE

B 10000 Total VOCs

I

i 2000

i 0 Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

c MW-3B

G 2000

1800

B PCE

1600 Total VOCs

1 I I E

il-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

G E

211941

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I I z E

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Concentration Trends shy Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-13DB

Total VOCs

c i i c o

Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

MW-16DB

30

c i c c I c o

Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99

PCE

Total VOCs

Jul-01 Jul-03

211941

O bi

c Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

I MW-16IB

i 35

3

c Total VOCs

lt- 2 5

0 | gt

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1 sectI

c c 0 4

Jul-90 Jul-92 Jul-94 Jul-96 Jul-98 Jul-00 Jul-02 Jul-04

I I MW-108D

I 12

PCE 10

Total VOCs c oc 3

E E I 0

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

E 211941

c Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

fi MW-108S

I I 40

PCE 35

Total VOCs

30

I f 26

20 I o

I 15

10

c Dec-99 Dec-00 Dec-01 Dec-02 Dec-03 I 0

I MW-112D

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211941

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Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-112S

08

PCE

Total VOCs 06

o 04

02

0 Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

MW-114D

o

12000

10000

8000

6000

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Total VOCs

4000

2000

i

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Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

211941

Con

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n (

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I MW-114S

E A5000 -- Total VOCs

- 4000

0 3000

2000

i 1000

i n shy

Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

MW-115D

c PCE

Total VOCs

c E

o

C c

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03 I 0

211941

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30000

25000

20000

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5000

0 Aug-99

25000

20000

5000

0 Aug-99

211941

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-2DB

PCE

Total VOCs

Aug-01 Aug-03

MW-2IB

PCE

Total VOCs

Aug-01 Aug-03

IDIBI

ii EIDIISIBIG C

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-102S

6000

5000 PCE

Total VOCs

4000

O 3000

2000

1000

0 Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

MW-103D

16000

~ 14000 ugt 3- 12000 o

^ 10000

sect 8000

O 6000

4000

2000

PCE

Total VOCs

0Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

211941

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

G MW-103S

I I

ampo

12000

10000

E sectc

S

8000

6000

4000

2000

0Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

G I 6000

MW-104D

i 5000

PCE

Total VOCs

i i c

2000

1000

Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

E I

211941

cIccIG

IIBCccBcIc

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-1041

PCE Total VOCs

a 25000

0 20000

a 15000

10000

5000

0 Jan-OO Jan-01 Jan-02 Jan-03 Jan-04

MW-106D

3000

2500 PCE

Total VOCs

=sect 2000

o bullsect 1500

1000

500

0 Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

211941

c Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

c MW-106S

I PCE

Total VOCs

i

i Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

i

i i i E

C

211941 c

Response to EPA-DEP Comment 5 Dated March 312005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

iiw

EPA-DEP Comment 5

Comment 5 Matrix Diffusion The report as well as other proponents of matrix diffusion suggest that depletion of DNAPL (Section 5112 page 5-15) needs to be achieved While that might be the ideal the goal is to achieve performance standards and that goal may be attainable while there is residual contamination in the rock perhaps even DNAPL globules The low bedrock matrix porosity (page 1-15) the high permeability values (page 4-4) the relative flux of the groundwater (page 5-5) and the decrease in surface area and out of the mainstream pockets (appendix C-4) all suggest that the diffusion out of the rock matrix would be insubstantial relative to the regional flux of groundwater through the Site

Response The TI Evaluation Report does not explicitly consider or rely upon matrix diffusion as a basis for requesting a TI Waiver for a portion of the Hows Corner Site The technical literature provides documentation that matrix diffusion can be a significant process that affects chemical transport and groundwater remediation timeframes in unconsolidated and consolidated media including fractured rock (US EPA 1989 Freeze and Cherry 1979 Pankow and Cherry 1996 Fountain 1998) Back diffusion of contaminants from the matrix porosity of the fractured rock can prolong the time necessary to achieve groundwater cleanup goals particularly for compounds such as PCE for which the cleanup goal is a low concentration It is our expectation that matrix diffusion has occurred at the Hows Corner Site and that back diffusion of PCE from the rock matrix will also occur Although the extent to which matrix diffusion is occurring at the Hows Comer Site has not been determined and that lack of knowledge contributes to uncertainty regarding the cleanup times at the Site the effect of matrix diffusion is to lengthen rather than shorten the time required for remediation

REFERENCES

Fountain JC 1998 Technologies for Dense Nonaqueous Phase Liquid Source Zone Remediation Ground-Water Remediation Technologies Analysis Center Technology Evaluation Report TE-98-02 December

Freeze RA and Cherry JA 1979 Groundwater Prentice-Hall Inc Englewood Cliffs NJ 07632 p 410-412

Pankow J F and Cherry J A 1996 Dense Chlorinated Solvents Waterloo Press Portland OR 97291-1399 p 67-88

US EPA 1989 Transport and Fate of Contaminants in the Subsurface EPA6254-89019 p 17-18

Response to EPA Comment 5 050305doc 1 of 1 Woodard amp Curran (211941)

WOODARD amp CURRAN Maine Massachusetts New Hampshire Connecticut Florida Operational offices across the US 1-800-426-4262 www woodardcurran com

Page 40: SDMS DocID 251749 - Records Collections · 2020-06-13 · CORPORATE OFFICES: Maine, Massachusetts, New Hampshire, Connecticut New, York, Florida Engineering • Science • Operations

the organic carbon in the sample The latter can be calculated using the chemical stoichiometry of the reaction

The Walkley-Black method is very accurate for samples that contain less than 2 organic carbon matter The minimum detection limit (MDL) for the Walkley-Black method is 100 mgkg or an foe of 0001

Given the rock core at Hows Corner was expected to contain less than 2 organic carbon the Walkley-Black method was used to measure the foe from 19 different rock core samples collected from varying depths ranging from 11 to 90 feet

Table 1 provides a statistical summary of the aforementioned data

Table 1 Statistical summary of foe data from rock cores collected at varying depths

Statistical Parameter Calculated Value foe Minimum Detection Limit (MDL) 00010 Number of samples analyzed (n) 19 Average foe 00019 Median foe 00019 Geometric Mean foe 00019 Standard deviation of foe measurements 000033 Relative standard deviation 174 -+ 95 Confidence intervals 00012 to 00025

The data in Table 1 shows the following

bull The foe from the Hows Corner rock cores are statistically greater than the MDL of the Walkley-Black analytical method

bull The average and median values for the foe of the Hows Corner rock cores from varying depths are nearly identical indicating that there is little variability in the foe values in the source zone at the site

bull The standard deviation of these measurements is 000033 which is 174 of the average foe

bull The 95 confidence intervals of the foe of the rock core at Hows Corner are 00012 to 00025

The foe was also analyzed from three separate samples taken from the same rock core at a depth of 55 feet (Only one of these samples was included in the data summarized in Table 1) Table 2 shows the statistical repeatability of this type of analysis

Hows Corner TI Evaluation Page 2 January 13 2005 Appendix B

Table 2 Repeatability of analysis of foe from one rock core at 55 feet in depth

Statistical Parameter Calculated Value Number of samples analyzed (n) 3 Average foe 00016 Median foe 00015 Geometric Mean foe 00016 Standard deviation of foe measurements 000039 Relative standard deviation 240 -+ 95 Confidence intervals 00008 to 00024

The data in Table 2 shows the following

bull The percent relative standard deviation of these three analyses of foe from the same rock core at Hows Corner is 24

bull The 95 confidence interval of the foes measured in this particular rock core at Hows Conrer is 00008 to 00024

These results show that there is good repeatability in using the Walkley-Black method for analysis of the foe in the rock core at Hows Corner

References Schwarzenbach amp Westall (1981) Transport of nonpolar organic compounds from surface water to groundwater Laboratory sorption studies Environ Sci Tech 15 1360-1367

Walkley A I A Black (1934) An examination of Degtjareff method for determining soil organic matter and a proposed modification of the chromic acid titration method Soil Sci 37 29-37

Hows Corner Tl Evaluation Page S January 13 2005 Appendix B

Woodard and Curran PTS Laboratories PTS File No 34618

ORGANIC CARBON DATA (METHODOLOGY WALKLEY-BLACK)

PROJECT NAME PROJECT NO

SAMPLE ID

203-chip-13 203-chip-23 203-chip-27 203-chip-38 203-chip-42 203-chip-47 203-chip-52 203-chip-58 203-chip-69 203-chip-82 207-chip-11 207-chip-19 207-chip-24 207-chip-29 207-chip-35 207-chip-45 207-chip-55 207-chip-87 207-chip-90

207-chip-55 55-MS

55-MSMSD

Hows Corner NA

DEPTH ft

13 23 27 38 42 47 52 58 69 82 11 19 24 29 35 45 55 87 90

55 NA NA

MATRIX

Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip

Average Median

Geometric Mean Standard Deviation Relative Std Dev

+- 95 Confidence Interval n

Rock Chip Rock Chip Rock Chip

Average Median

Geometric Mean Standard Deviation Relative Std Dev

+- 95 Confidence Interval n

FRACTION ORGANIC CARBON

(gg)

170E-03 185E-03 185E-03 170E-03 240E-03 190E-03 230E-03 180E-03 170E-03 115E-03 195E-03 220E-03 220E-03 235E-03 135E-03 190E-03 205E-03 175E-03 160E-03

188E-03 185E-03 185E-03 327E-04

1739 123E-03 to

19

205E-03 130E-03 150E-03

162E-03 150E-03 159E-03 388E-04

2402 840E-04 to

3

2532E-03

2393E-03

Hows Corner Tl Evaluation Appendix B January 13 2005

Response to EPA-DEP Comment 4 Dated March 31 2005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

EPA-DEP Comment 4

Comment 4 Distribution of contaminants First the TI report seems based on the assertion that there is DNAPL at the source area yet it also appears to represent that the source area is small and the bedrock below 85 is competent (or less fractured) and less impacted by the release of contaminants Some of the confusion may result from using most recent data when that data is from several different sampling events over several years and there is no discernible difference in concentrations between shallow and deep bedrock or as in Section 421 where generally decreased generally increase generally similar and similar concentrations in four consecutive sentences leads to a muddled picture of the contaminant distribution

Second the report asserts that the distribution of contaminants over the entire plume has not changed with time but fails to support this conclusion with data again relying on data that is from different sampling dates for one composite representation

Response The likely presence of dense non-aqueous phase liquid (DNAPL) at the Hows Corner Site and the determination that the source area is small are not mutually exclusive and both are conclusions drawn from information obtained during field investigations The presence of DNAPL in the source area is based on the elevated concentrations of volatile organic compounds (VOCs) detected in the groundwater (WampC 2001 WampC 2002) The conclusion that the source area is small is based on the area in which VOCs in groundwater have been detected at concentrations that are considered to be indicative of the presence of DNAPL nearby Similarly the conclusion that fracture frequency decreases at depths greater than approximately 50 to 85 feet below ground surface was based on field observation during the RI field work The fact that zones with observed fractures exhibited higher hydraulic conductivities than zones without fractures coupled with the decreasing frequency of observed fractures with depth led to the conclusion that the hydraulic conductivity of the bulk rock decreases with depth

The most recent data from all wells were used to provide the maximum VOC data set size During the RI all of the previously-existing and then newly-installed monitoring wells were sampled along with several residential wells The RI sampling included up to 48 monitoring wells Subsequent to the RI and prior to the TI three rounds of monitoring were conducted to verify that the plume was stable 15 monitoring wells were sampled during each of the three rounds During the TI field investigation 29 wells were sampled for VOCs The sampled wells included all of the newly-installed wells and a subset of wells installed during the RI for a total of 29 monitoring wells By using most recent data VOC results from 53 monitoring wells were included in the evaluation (see table labeled Sampling Events for listing of monitoring wells) This approach was selected because there generally was little variation in the data from a particular location between years This is borne out by the attached individual plots of VOCs detected in shallow bedrock and deep bedrock for the Pre-ROD (December 1999January 2000) and Supplemental (May 2000) sampling events and for June 2001 January 2002 and April 2003 sampling events The Pre-ROD and Supplemental plots are similar to the subsequent plots from the 2001 2002 and 2003 sampling events

In addition to maps showing the spatial distribution of VOC data at a given time trend plots of the data from a particular location through time (attached) indicate that since the RI concentrations generally have been stable or have decreased Together the maps and trend plots and the data from which they were developed indicate that the distribution of contaminants over the entire plume has not changed appreciably with time

Response to EPA Comment 4 050305doc 1 of 26 Woodard amp Curran (211941)

REFERENCES

Woodard amp Curran Inc (WampC) 2001 Final Remedial Investigation Report Hows Corner Superfund Plymouth Maine July 2001

Woodard amp Curran Inc (WampC) 2002 Final Feasibility Study Report - Non-Source Area Groundwater Hows Corner Superfund Site Plymouth Maine Hows Corner Superfund Plymouth Maine July 2002

Response to EPA Comment 4 050305doc 2 of 26 Woodard amp Curran (211941)

LIST OF ATTACHMENTS (Response to Comment 4)

Table - Sampling Events 1999 - 2004 (2 pages)

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater Pre-ROD Sampling Event

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater Pre-ROD Sampling Event

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater Supplemental Sampling Event

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater Supplemental Sampling Event

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater June 2001

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater June 2001

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater January 2002

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater January 2002

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater April 2003

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater April 2003

Figure - Concentration Trends - Non-Source Area Wells MW-1B and MW-3B

Figure - Concentration Trends - Non-Source Area Wells MW-13DB and MW-16DB

Figure - Concentration Trends - Non-Source Area Wells MW-16IB and MW- 108D

Figure - Concentration Trends - Non-Source Area Wells MW-108S and MW-112D

Figure - Concentration Trends - Non-Source Area Wells MW-112S and MW-114D

Figure - Concentration Trends - Non-Source Area Wells MW-114S and MW-115D

Figure - Concentration Trends -Source Area Wells MW-2DB and MW-2IB

Figure - Concentration Trends -Source Area Wells MW-102S and MW-103D

Figure - Concentration Trends -Source Area Wells MW-103S and MW-104D

Figure - Concentration Trends -Source Area Wells MW-104I and MW-106D

Figure - Concentration Trends -Source Area Wells MW-106S

Response to EPA Comment 4 050305doc 3 of 26 Woodard amp Curran (211941)

I I

El I

II I I 1 I

I

i

Event Baseline Case ID WC-01 WC-01

Well Date Aug-99 Oct-99 LOT10 1 LOT1-1 1 LOT11-4 LOT14 1 LOT15 1 LOT15-1 1 LOT16 1 LOT16-1 1 LOT17 1 LOT18 1 LOT19 1 LOT2 LOT20 1 LOT21-10 1 LOT21-11 1 LOT21-12 1 LOT21-13 1 LOT21-14 1 LOT21-2 1 LOT21-5 1 LOT21-7 LOT21 -8 1 LOT21-9 1 LOT23 1 LOT24 1 LOT28-1 1 LOT28-2 1 LOT28-3 1 LOT28-4 1 LOT28W 1 LOT30 1 LOT30-1 1 LOT30-2 1 LOT30-3 1 LOT30-4 1 LOT30-5 LOT31 LOT35 1 LOT41 1 LOT42-1 1 LOT43-1 1 LOT43-4 1 LOT6-1 1 LOT67 1 LOT6-7 1 LOT6-8A 1 LOT6-8B 1 LOT80-1 1 LOT82 1 MW-101D MW-1011 MW-101S MW-102D MW-102S MW-103D MW-103S MW-104D MW-1041 MW-104S MW-105D MW-106D

Groundwater Sampling Location Summary 1999 - 2004xls

Sampling Events 1999-2004

Hows Corner Superfund Site Plymouth Maine

Supplemental 2001 2002 2003 Pumping 2004 Pre-ROD Rl Sampling Sampling Sampling Test Sampling WC-03 WC-09 WC-25 WC-30 WC-42B WC-56 WC-58 Dec-99 May-00 Jun-01 Jan-02 Apr-03 Sep-04 Sep-04

1

1 1 1

1 1 1 1 1

1 1

1

1 1

1 1 1

1 1 1 1 1

1

1 1

1 1 1 1

1

1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

Sampling Events 1999-2004

Hows Corner Super-fund Site Plymouth Maine

Supplemental 2001 2002 2003 Pumping Event Baseline Pre-ROD Rl Sampling Sampling Sampling Test

Case ID WC-01 WC-01 WC-03 WC-09 WC-25 WC-30 WC-42B WC-56

ll

Well Date Aug-99 Oct-99 Dec-99 May-00 Jun-01 Jan-02 Apr-03 Sep-04 MW-106S 1 1 1 1 1 MW-107D 1 1 MW-108D 1 1 1 1 1 MW-108S 1 1 1 1 1 MW-110D 1 1 MW-111D 1 1 MW-112D 1 1 1 1 1 MW-112S 1 1 1 1 1 MW-113D 1 1 MW-114D 1 1 1 1 1 MW-114S 1 1 1 1 1 MW-115D 1 1 1 1 1 MW-12DB 1 1 1 MW-12SB 1 1 1 MW-13DB 1 1 1 1 1 1 MW-13SB 1 1 1 MW-14DB 1 1 MW-14SO 1 1 MW-15DB 1 1 1 MW-15SB 1 1 1 MW-16DB 1 1 1 1 1 1 MW-16IB 1 1 1 1 1 1 MW-16SO 1 1 MW-17DO 1 1 1 MW-17SO 1 1 1 MW-1B 1 1 1 1 1 1 MW-203D MW-203S MW-204D MW-204S MW-205 MW-206D

I MW-206S MW-2DB 1 1 MW-2DDB 1 1 MW-2IB 1 1 1 1 1 1 MW-3B 1 1 1 1 1 1

I MW-4O 1 1 1 MW-5B 1 1

II MW-6DB 1 1 1 MW-6SB 1 1 1 MW-8DB 1 1 1 MW-8SB 1 1 1

II PW-207 1 SEEP-1 1 SUBTOTAL - RESIDENTIAL 44 25 0 2 0 3 0 SUBTOTAL - MONITORING 22 48 41 15 15 15 1

Total 3 66 73 41 17 15 18 1

I Included in most recent data

I Notes 1 - Overburden well not included in most recent data for plotting

2 - Tetrahydrofuran and 2-Butanone were the only two compounds detected in this well and are thought to be the result of well repair not included in most recent data for plotting

3 - Not included in most recent data for plotting

2004 Sampling

WC-58 Sep-04

1

1 1

1 1

1 1 1

1

1 1

1 1 1 1 1 1 1 1 1

1 1

1

0 29

29

Groundwatef Sampling Location Summary 1999 - 2004xls

I

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

monitoring well Figure 4-14 total VOC contour (ugl) - December 1999January 2000 Distribution of Total VOCs in

Note SW-113 is located downstream of SEEP-1 Shallow Bedrock Groundwater total concentration of detected VOCs ND= not detected these two locations were sampled during the Pre-ROD Sampling Event

Baseline Sampling Event in OctoberNovember 1999 Hows Corner Superfund Site Surface Water Sampling Location A Plymouth Maine Seep Sampling Location laquo- WOODARD ampCURRAN

995037wipri reportepa ri interim final feb 2001cadd drawingsfinalfig 4-14

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

0 300 600 I

FEET

Q residential well Figure 4-16 monitoring well Distribution of Total VOCs in

Deep Bedrock Groundwater total VOCs contour (ugl) Pre-ROD Sampling Event

active residential wells with lot number Hows Corner Superfund Site 2deg42deg Plymouth Maine total concentration of detected VOCs ND= not detected WOODARD ampCURRAN Enyinaaring bull Science bull Operations bull

995037wipri reportepa ri interim final feb 2001cadd drawingsfinalfig4mdash16

PLYMOUTH POND

PLYMOUTH POND

1 628Tl7MW-2bB 12135

PLYMOUTH POND

monitoring well Figure 4-20

V total VOC contour (ugl) - June 2000 Distribution of Total VOCs in Shallow Bedrock Groundwater

| 34 | total concentration of detected VOCs ND= not detected NA = not analyzed Supplemental Sampling Event Note SW-113 is located downstream of SEEP-1 Hows Corner Superfund Site

Surface Water Sampling Location these two locations were sampled during the Plymouth Maine Baseline Sampling Event in OctoberNovember 1999 Seep Sampling Location WOODARD amp CURRAN

Engineering bull Science - Operations bull 995037wipri reportepa ri interim final feb 2001 cadd drawingsfinalfig 4-20

residential well Figure 4-22 Distribution of Total VOCs in

monitoring well Deep Bedrock Groundwater

total VOCs contour (ugl) Supplemental Sampling Event

Hows Corner Superfund Site

total concentration of detected VOCs ND= not detected NA = not analyzed Plymouth Maine

WOODARD amp CURRAN

995037wipri reportepa-ri interim final feb 2001cadd drawingsfinalfig 4-22 Engineering bull Science - Operations bull

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

FEET

Shallow Monitoring Well

Deep Monitoring Well

C Detected Concentration ND = Not Detected Figure 1-XS Distribution of Total VOCs in Shallow Bedrock Groundwater

Pumping Well

17-Acre Property Boundary Concentration Contour (ugl)

June 2001 Hows Corner Superfund Site

Plymouth Maine WOODARDampCURRAN

-i^rhvj bull Scbncn bull Operations bull 211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0601 dwg04-20-05

PLYMOUTH POND Hopkins Road V

O

PLYMOUTH POND

PLYMOUTH POND

o

0 300 600 mdashfa FEET

Shallow Monitoring Well bull bull - 17-Acre Property Boundary Figure 1-XD

Deep Monitoring Well 1 I Detected Concentration ND = Not Detected Distribution of Total VOCs in Deep Bedrock Groundwater

-mf- Pumping Well June 2001 Residential Well Hows Corner Superfund Site

Plymouth Maine i h Surface Water Sampling Point

g WOODARD ampCURRAN _ ^ _ ^ _ _ yen_ rj i|Hlaquorlny bull Science bull Opt

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0601 dwg04-20-05

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

Shallow Monitoring Well

Deep Monitoring Well

Detected Concentration ND = Not Detected Figure 1-YS Distribution of Total VOCs in Shallow Bedrock Groundwater

Pumping Well

17-Acre Property Boundary Concentration Contour (ugl)

January 2002 Hows Corner Superfund Site

Plymouth Maine WOODARD amp CURRAN Engineering Science- Operations bull

211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0102dwg04-20-05

PLYMOUTH POND

PLYMOUTH POND

Site Pand^ laquoum-laquoBTuitaraquo tLV

vVlf-(

PLYMOUTH POND

0 300 600 ^ = FEET

Shallow Monitoring Well mdashbullbullbull 17-Acre Property Boundary Figure 1-YD - A - Deep Monitoring Well FT Detected Concentration ND = Not Detected Distribution of Total VOCs in

Deep Bedrock Groundwater Pumping Well January 2002 Residential Well Hows Corner Superfund Site

Plymouth Maine Surface Water Sampling Point

WOODARD ampCURRAN Engineering Sciencs- Operations bulli Si

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0102dwg04-20-05

- m j

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND j A O-shy

Shallow Monitoring Well E Detected Concentration ND = Not Detected Figure 1-ZS Distribution of Total VOCs in

Deep Monitoring Well Shallow Bedrock Groundwater

Pumping Well Hows Corner

April 2003 Superfund Site

17-Acre Property Boundary Plymouth Maine Concentration Contour (ugl) r WOODARD ampCURRAN

Engineering bull Science bull Operations bull 211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0403dwg04-20-05

s S pound

PLYMOUTH POND

PLYMOUTH POND

- -

5 PLYMOUTH POND

Jo

FEET

ft Shallow Monitoring Well mdashbullbullmdash 17-Acre Property Boundary Figure 1-ZD Deep Monitoring Well I 1 I Detected Concentration ND = Not Detected Distribution of Total VOCs in

Deep Bedrock Groundwater Pumping Well April 2003

Q) Residential Well Hows Corner Superfund Site Plymouth Maine

(T) Surface Water Sampling Point WOODARD ampCURRAN poundKk EnginawtirKj bull Science - Operations bull

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0403dwg04-20-05

0 Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

B MW-1B

I 12000

PCE

B 10000 Total VOCs

I

i 2000

i 0 Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

c MW-3B

G 2000

1800

B PCE

1600 Total VOCs

1 I I E

il-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

G E

211941

El

I I z E

80

Concentration Trends shy Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-13DB

Total VOCs

c i i c o

Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

MW-16DB

30

c i c c I c o

Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99

PCE

Total VOCs

Jul-01 Jul-03

211941

O bi

c Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

I MW-16IB

i 35

3

c Total VOCs

lt- 2 5

0 | gt

o

1 sectI

c c 0 4

Jul-90 Jul-92 Jul-94 Jul-96 Jul-98 Jul-00 Jul-02 Jul-04

I I MW-108D

I 12

PCE 10

Total VOCs c oc 3

E E I 0

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

E 211941

c Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

fi MW-108S

I I 40

PCE 35

Total VOCs

30

I f 26

20 I o

I 15

10

c Dec-99 Dec-00 Dec-01 Dec-02 Dec-03 I 0

I MW-112D

c 35 - imdash

I A3 shyTotal VOCs

o c

E 1 2

I

ition

B 1 ^

-i c 3

0 Dec-99 Dec-OO Dec-01 Dec-02 Dec-03

211941

I

i

I

cII

Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-112S

08

PCE

Total VOCs 06

o 04

02

0 Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

MW-114D

o

12000

10000

8000

6000

PCE

Total VOCs

4000

2000

i

ccEIIc

i

i

E

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

211941

Con

cent

ratio

n (

ug

l)

E Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

I MW-114S

E A5000 -- Total VOCs

- 4000

0 3000

2000

i 1000

i n shy

Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

MW-115D

c PCE

Total VOCs

c E

o

C c

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03 I 0

211941

IepoundII

EIEIIGICCIccc

30000

25000

20000

o bullsect 15000 b

o 10000 U

5000

0 Aug-99

25000

20000

5000

0 Aug-99

211941

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-2DB

PCE

Total VOCs

Aug-01 Aug-03

MW-2IB

PCE

Total VOCs

Aug-01 Aug-03

IDIBI

ii EIDIISIBIG C

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-102S

6000

5000 PCE

Total VOCs

4000

O 3000

2000

1000

0 Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

MW-103D

16000

~ 14000 ugt 3- 12000 o

^ 10000

sect 8000

O 6000

4000

2000

PCE

Total VOCs

0Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

211941

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

G MW-103S

I I

ampo

12000

10000

E sectc

S

8000

6000

4000

2000

0Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

G I 6000

MW-104D

i 5000

PCE

Total VOCs

i i c

2000

1000

Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

E I

211941

cIccIG

IIBCccBcIc

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-1041

PCE Total VOCs

a 25000

0 20000

a 15000

10000

5000

0 Jan-OO Jan-01 Jan-02 Jan-03 Jan-04

MW-106D

3000

2500 PCE

Total VOCs

=sect 2000

o bullsect 1500

1000

500

0 Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

211941

c Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

c MW-106S

I PCE

Total VOCs

i

i Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

i

i i i E

C

211941 c

Response to EPA-DEP Comment 5 Dated March 312005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

iiw

EPA-DEP Comment 5

Comment 5 Matrix Diffusion The report as well as other proponents of matrix diffusion suggest that depletion of DNAPL (Section 5112 page 5-15) needs to be achieved While that might be the ideal the goal is to achieve performance standards and that goal may be attainable while there is residual contamination in the rock perhaps even DNAPL globules The low bedrock matrix porosity (page 1-15) the high permeability values (page 4-4) the relative flux of the groundwater (page 5-5) and the decrease in surface area and out of the mainstream pockets (appendix C-4) all suggest that the diffusion out of the rock matrix would be insubstantial relative to the regional flux of groundwater through the Site

Response The TI Evaluation Report does not explicitly consider or rely upon matrix diffusion as a basis for requesting a TI Waiver for a portion of the Hows Corner Site The technical literature provides documentation that matrix diffusion can be a significant process that affects chemical transport and groundwater remediation timeframes in unconsolidated and consolidated media including fractured rock (US EPA 1989 Freeze and Cherry 1979 Pankow and Cherry 1996 Fountain 1998) Back diffusion of contaminants from the matrix porosity of the fractured rock can prolong the time necessary to achieve groundwater cleanup goals particularly for compounds such as PCE for which the cleanup goal is a low concentration It is our expectation that matrix diffusion has occurred at the Hows Corner Site and that back diffusion of PCE from the rock matrix will also occur Although the extent to which matrix diffusion is occurring at the Hows Comer Site has not been determined and that lack of knowledge contributes to uncertainty regarding the cleanup times at the Site the effect of matrix diffusion is to lengthen rather than shorten the time required for remediation

REFERENCES

Fountain JC 1998 Technologies for Dense Nonaqueous Phase Liquid Source Zone Remediation Ground-Water Remediation Technologies Analysis Center Technology Evaluation Report TE-98-02 December

Freeze RA and Cherry JA 1979 Groundwater Prentice-Hall Inc Englewood Cliffs NJ 07632 p 410-412

Pankow J F and Cherry J A 1996 Dense Chlorinated Solvents Waterloo Press Portland OR 97291-1399 p 67-88

US EPA 1989 Transport and Fate of Contaminants in the Subsurface EPA6254-89019 p 17-18

Response to EPA Comment 5 050305doc 1 of 1 Woodard amp Curran (211941)

WOODARD amp CURRAN Maine Massachusetts New Hampshire Connecticut Florida Operational offices across the US 1-800-426-4262 www woodardcurran com

Page 41: SDMS DocID 251749 - Records Collections · 2020-06-13 · CORPORATE OFFICES: Maine, Massachusetts, New Hampshire, Connecticut New, York, Florida Engineering • Science • Operations

Table 2 Repeatability of analysis of foe from one rock core at 55 feet in depth

Statistical Parameter Calculated Value Number of samples analyzed (n) 3 Average foe 00016 Median foe 00015 Geometric Mean foe 00016 Standard deviation of foe measurements 000039 Relative standard deviation 240 -+ 95 Confidence intervals 00008 to 00024

The data in Table 2 shows the following

bull The percent relative standard deviation of these three analyses of foe from the same rock core at Hows Corner is 24

bull The 95 confidence interval of the foes measured in this particular rock core at Hows Conrer is 00008 to 00024

These results show that there is good repeatability in using the Walkley-Black method for analysis of the foe in the rock core at Hows Corner

References Schwarzenbach amp Westall (1981) Transport of nonpolar organic compounds from surface water to groundwater Laboratory sorption studies Environ Sci Tech 15 1360-1367

Walkley A I A Black (1934) An examination of Degtjareff method for determining soil organic matter and a proposed modification of the chromic acid titration method Soil Sci 37 29-37

Hows Corner Tl Evaluation Page S January 13 2005 Appendix B

Woodard and Curran PTS Laboratories PTS File No 34618

ORGANIC CARBON DATA (METHODOLOGY WALKLEY-BLACK)

PROJECT NAME PROJECT NO

SAMPLE ID

203-chip-13 203-chip-23 203-chip-27 203-chip-38 203-chip-42 203-chip-47 203-chip-52 203-chip-58 203-chip-69 203-chip-82 207-chip-11 207-chip-19 207-chip-24 207-chip-29 207-chip-35 207-chip-45 207-chip-55 207-chip-87 207-chip-90

207-chip-55 55-MS

55-MSMSD

Hows Corner NA

DEPTH ft

13 23 27 38 42 47 52 58 69 82 11 19 24 29 35 45 55 87 90

55 NA NA

MATRIX

Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip

Average Median

Geometric Mean Standard Deviation Relative Std Dev

+- 95 Confidence Interval n

Rock Chip Rock Chip Rock Chip

Average Median

Geometric Mean Standard Deviation Relative Std Dev

+- 95 Confidence Interval n

FRACTION ORGANIC CARBON

(gg)

170E-03 185E-03 185E-03 170E-03 240E-03 190E-03 230E-03 180E-03 170E-03 115E-03 195E-03 220E-03 220E-03 235E-03 135E-03 190E-03 205E-03 175E-03 160E-03

188E-03 185E-03 185E-03 327E-04

1739 123E-03 to

19

205E-03 130E-03 150E-03

162E-03 150E-03 159E-03 388E-04

2402 840E-04 to

3

2532E-03

2393E-03

Hows Corner Tl Evaluation Appendix B January 13 2005

Response to EPA-DEP Comment 4 Dated March 31 2005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

EPA-DEP Comment 4

Comment 4 Distribution of contaminants First the TI report seems based on the assertion that there is DNAPL at the source area yet it also appears to represent that the source area is small and the bedrock below 85 is competent (or less fractured) and less impacted by the release of contaminants Some of the confusion may result from using most recent data when that data is from several different sampling events over several years and there is no discernible difference in concentrations between shallow and deep bedrock or as in Section 421 where generally decreased generally increase generally similar and similar concentrations in four consecutive sentences leads to a muddled picture of the contaminant distribution

Second the report asserts that the distribution of contaminants over the entire plume has not changed with time but fails to support this conclusion with data again relying on data that is from different sampling dates for one composite representation

Response The likely presence of dense non-aqueous phase liquid (DNAPL) at the Hows Corner Site and the determination that the source area is small are not mutually exclusive and both are conclusions drawn from information obtained during field investigations The presence of DNAPL in the source area is based on the elevated concentrations of volatile organic compounds (VOCs) detected in the groundwater (WampC 2001 WampC 2002) The conclusion that the source area is small is based on the area in which VOCs in groundwater have been detected at concentrations that are considered to be indicative of the presence of DNAPL nearby Similarly the conclusion that fracture frequency decreases at depths greater than approximately 50 to 85 feet below ground surface was based on field observation during the RI field work The fact that zones with observed fractures exhibited higher hydraulic conductivities than zones without fractures coupled with the decreasing frequency of observed fractures with depth led to the conclusion that the hydraulic conductivity of the bulk rock decreases with depth

The most recent data from all wells were used to provide the maximum VOC data set size During the RI all of the previously-existing and then newly-installed monitoring wells were sampled along with several residential wells The RI sampling included up to 48 monitoring wells Subsequent to the RI and prior to the TI three rounds of monitoring were conducted to verify that the plume was stable 15 monitoring wells were sampled during each of the three rounds During the TI field investigation 29 wells were sampled for VOCs The sampled wells included all of the newly-installed wells and a subset of wells installed during the RI for a total of 29 monitoring wells By using most recent data VOC results from 53 monitoring wells were included in the evaluation (see table labeled Sampling Events for listing of monitoring wells) This approach was selected because there generally was little variation in the data from a particular location between years This is borne out by the attached individual plots of VOCs detected in shallow bedrock and deep bedrock for the Pre-ROD (December 1999January 2000) and Supplemental (May 2000) sampling events and for June 2001 January 2002 and April 2003 sampling events The Pre-ROD and Supplemental plots are similar to the subsequent plots from the 2001 2002 and 2003 sampling events

In addition to maps showing the spatial distribution of VOC data at a given time trend plots of the data from a particular location through time (attached) indicate that since the RI concentrations generally have been stable or have decreased Together the maps and trend plots and the data from which they were developed indicate that the distribution of contaminants over the entire plume has not changed appreciably with time

Response to EPA Comment 4 050305doc 1 of 26 Woodard amp Curran (211941)

REFERENCES

Woodard amp Curran Inc (WampC) 2001 Final Remedial Investigation Report Hows Corner Superfund Plymouth Maine July 2001

Woodard amp Curran Inc (WampC) 2002 Final Feasibility Study Report - Non-Source Area Groundwater Hows Corner Superfund Site Plymouth Maine Hows Corner Superfund Plymouth Maine July 2002

Response to EPA Comment 4 050305doc 2 of 26 Woodard amp Curran (211941)

LIST OF ATTACHMENTS (Response to Comment 4)

Table - Sampling Events 1999 - 2004 (2 pages)

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater Pre-ROD Sampling Event

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater Pre-ROD Sampling Event

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater Supplemental Sampling Event

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater Supplemental Sampling Event

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater June 2001

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater June 2001

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater January 2002

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater January 2002

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater April 2003

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater April 2003

Figure - Concentration Trends - Non-Source Area Wells MW-1B and MW-3B

Figure - Concentration Trends - Non-Source Area Wells MW-13DB and MW-16DB

Figure - Concentration Trends - Non-Source Area Wells MW-16IB and MW- 108D

Figure - Concentration Trends - Non-Source Area Wells MW-108S and MW-112D

Figure - Concentration Trends - Non-Source Area Wells MW-112S and MW-114D

Figure - Concentration Trends - Non-Source Area Wells MW-114S and MW-115D

Figure - Concentration Trends -Source Area Wells MW-2DB and MW-2IB

Figure - Concentration Trends -Source Area Wells MW-102S and MW-103D

Figure - Concentration Trends -Source Area Wells MW-103S and MW-104D

Figure - Concentration Trends -Source Area Wells MW-104I and MW-106D

Figure - Concentration Trends -Source Area Wells MW-106S

Response to EPA Comment 4 050305doc 3 of 26 Woodard amp Curran (211941)

I I

El I

II I I 1 I

I

i

Event Baseline Case ID WC-01 WC-01

Well Date Aug-99 Oct-99 LOT10 1 LOT1-1 1 LOT11-4 LOT14 1 LOT15 1 LOT15-1 1 LOT16 1 LOT16-1 1 LOT17 1 LOT18 1 LOT19 1 LOT2 LOT20 1 LOT21-10 1 LOT21-11 1 LOT21-12 1 LOT21-13 1 LOT21-14 1 LOT21-2 1 LOT21-5 1 LOT21-7 LOT21 -8 1 LOT21-9 1 LOT23 1 LOT24 1 LOT28-1 1 LOT28-2 1 LOT28-3 1 LOT28-4 1 LOT28W 1 LOT30 1 LOT30-1 1 LOT30-2 1 LOT30-3 1 LOT30-4 1 LOT30-5 LOT31 LOT35 1 LOT41 1 LOT42-1 1 LOT43-1 1 LOT43-4 1 LOT6-1 1 LOT67 1 LOT6-7 1 LOT6-8A 1 LOT6-8B 1 LOT80-1 1 LOT82 1 MW-101D MW-1011 MW-101S MW-102D MW-102S MW-103D MW-103S MW-104D MW-1041 MW-104S MW-105D MW-106D

Groundwater Sampling Location Summary 1999 - 2004xls

Sampling Events 1999-2004

Hows Corner Superfund Site Plymouth Maine

Supplemental 2001 2002 2003 Pumping 2004 Pre-ROD Rl Sampling Sampling Sampling Test Sampling WC-03 WC-09 WC-25 WC-30 WC-42B WC-56 WC-58 Dec-99 May-00 Jun-01 Jan-02 Apr-03 Sep-04 Sep-04

1

1 1 1

1 1 1 1 1

1 1

1

1 1

1 1 1

1 1 1 1 1

1

1 1

1 1 1 1

1

1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

Sampling Events 1999-2004

Hows Corner Super-fund Site Plymouth Maine

Supplemental 2001 2002 2003 Pumping Event Baseline Pre-ROD Rl Sampling Sampling Sampling Test

Case ID WC-01 WC-01 WC-03 WC-09 WC-25 WC-30 WC-42B WC-56

ll

Well Date Aug-99 Oct-99 Dec-99 May-00 Jun-01 Jan-02 Apr-03 Sep-04 MW-106S 1 1 1 1 1 MW-107D 1 1 MW-108D 1 1 1 1 1 MW-108S 1 1 1 1 1 MW-110D 1 1 MW-111D 1 1 MW-112D 1 1 1 1 1 MW-112S 1 1 1 1 1 MW-113D 1 1 MW-114D 1 1 1 1 1 MW-114S 1 1 1 1 1 MW-115D 1 1 1 1 1 MW-12DB 1 1 1 MW-12SB 1 1 1 MW-13DB 1 1 1 1 1 1 MW-13SB 1 1 1 MW-14DB 1 1 MW-14SO 1 1 MW-15DB 1 1 1 MW-15SB 1 1 1 MW-16DB 1 1 1 1 1 1 MW-16IB 1 1 1 1 1 1 MW-16SO 1 1 MW-17DO 1 1 1 MW-17SO 1 1 1 MW-1B 1 1 1 1 1 1 MW-203D MW-203S MW-204D MW-204S MW-205 MW-206D

I MW-206S MW-2DB 1 1 MW-2DDB 1 1 MW-2IB 1 1 1 1 1 1 MW-3B 1 1 1 1 1 1

I MW-4O 1 1 1 MW-5B 1 1

II MW-6DB 1 1 1 MW-6SB 1 1 1 MW-8DB 1 1 1 MW-8SB 1 1 1

II PW-207 1 SEEP-1 1 SUBTOTAL - RESIDENTIAL 44 25 0 2 0 3 0 SUBTOTAL - MONITORING 22 48 41 15 15 15 1

Total 3 66 73 41 17 15 18 1

I Included in most recent data

I Notes 1 - Overburden well not included in most recent data for plotting

2 - Tetrahydrofuran and 2-Butanone were the only two compounds detected in this well and are thought to be the result of well repair not included in most recent data for plotting

3 - Not included in most recent data for plotting

2004 Sampling

WC-58 Sep-04

1

1 1

1 1

1 1 1

1

1 1

1 1 1 1 1 1 1 1 1

1 1

1

0 29

29

Groundwatef Sampling Location Summary 1999 - 2004xls

I

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

monitoring well Figure 4-14 total VOC contour (ugl) - December 1999January 2000 Distribution of Total VOCs in

Note SW-113 is located downstream of SEEP-1 Shallow Bedrock Groundwater total concentration of detected VOCs ND= not detected these two locations were sampled during the Pre-ROD Sampling Event

Baseline Sampling Event in OctoberNovember 1999 Hows Corner Superfund Site Surface Water Sampling Location A Plymouth Maine Seep Sampling Location laquo- WOODARD ampCURRAN

995037wipri reportepa ri interim final feb 2001cadd drawingsfinalfig 4-14

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

0 300 600 I

FEET

Q residential well Figure 4-16 monitoring well Distribution of Total VOCs in

Deep Bedrock Groundwater total VOCs contour (ugl) Pre-ROD Sampling Event

active residential wells with lot number Hows Corner Superfund Site 2deg42deg Plymouth Maine total concentration of detected VOCs ND= not detected WOODARD ampCURRAN Enyinaaring bull Science bull Operations bull

995037wipri reportepa ri interim final feb 2001cadd drawingsfinalfig4mdash16

PLYMOUTH POND

PLYMOUTH POND

1 628Tl7MW-2bB 12135

PLYMOUTH POND

monitoring well Figure 4-20

V total VOC contour (ugl) - June 2000 Distribution of Total VOCs in Shallow Bedrock Groundwater

| 34 | total concentration of detected VOCs ND= not detected NA = not analyzed Supplemental Sampling Event Note SW-113 is located downstream of SEEP-1 Hows Corner Superfund Site

Surface Water Sampling Location these two locations were sampled during the Plymouth Maine Baseline Sampling Event in OctoberNovember 1999 Seep Sampling Location WOODARD amp CURRAN

Engineering bull Science - Operations bull 995037wipri reportepa ri interim final feb 2001 cadd drawingsfinalfig 4-20

residential well Figure 4-22 Distribution of Total VOCs in

monitoring well Deep Bedrock Groundwater

total VOCs contour (ugl) Supplemental Sampling Event

Hows Corner Superfund Site

total concentration of detected VOCs ND= not detected NA = not analyzed Plymouth Maine

WOODARD amp CURRAN

995037wipri reportepa-ri interim final feb 2001cadd drawingsfinalfig 4-22 Engineering bull Science - Operations bull

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

FEET

Shallow Monitoring Well

Deep Monitoring Well

C Detected Concentration ND = Not Detected Figure 1-XS Distribution of Total VOCs in Shallow Bedrock Groundwater

Pumping Well

17-Acre Property Boundary Concentration Contour (ugl)

June 2001 Hows Corner Superfund Site

Plymouth Maine WOODARDampCURRAN

-i^rhvj bull Scbncn bull Operations bull 211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0601 dwg04-20-05

PLYMOUTH POND Hopkins Road V

O

PLYMOUTH POND

PLYMOUTH POND

o

0 300 600 mdashfa FEET

Shallow Monitoring Well bull bull - 17-Acre Property Boundary Figure 1-XD

Deep Monitoring Well 1 I Detected Concentration ND = Not Detected Distribution of Total VOCs in Deep Bedrock Groundwater

-mf- Pumping Well June 2001 Residential Well Hows Corner Superfund Site

Plymouth Maine i h Surface Water Sampling Point

g WOODARD ampCURRAN _ ^ _ ^ _ _ yen_ rj i|Hlaquorlny bull Science bull Opt

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0601 dwg04-20-05

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

Shallow Monitoring Well

Deep Monitoring Well

Detected Concentration ND = Not Detected Figure 1-YS Distribution of Total VOCs in Shallow Bedrock Groundwater

Pumping Well

17-Acre Property Boundary Concentration Contour (ugl)

January 2002 Hows Corner Superfund Site

Plymouth Maine WOODARD amp CURRAN Engineering Science- Operations bull

211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0102dwg04-20-05

PLYMOUTH POND

PLYMOUTH POND

Site Pand^ laquoum-laquoBTuitaraquo tLV

vVlf-(

PLYMOUTH POND

0 300 600 ^ = FEET

Shallow Monitoring Well mdashbullbullbull 17-Acre Property Boundary Figure 1-YD - A - Deep Monitoring Well FT Detected Concentration ND = Not Detected Distribution of Total VOCs in

Deep Bedrock Groundwater Pumping Well January 2002 Residential Well Hows Corner Superfund Site

Plymouth Maine Surface Water Sampling Point

WOODARD ampCURRAN Engineering Sciencs- Operations bulli Si

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0102dwg04-20-05

- m j

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND j A O-shy

Shallow Monitoring Well E Detected Concentration ND = Not Detected Figure 1-ZS Distribution of Total VOCs in

Deep Monitoring Well Shallow Bedrock Groundwater

Pumping Well Hows Corner

April 2003 Superfund Site

17-Acre Property Boundary Plymouth Maine Concentration Contour (ugl) r WOODARD ampCURRAN

Engineering bull Science bull Operations bull 211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0403dwg04-20-05

s S pound

PLYMOUTH POND

PLYMOUTH POND

- -

5 PLYMOUTH POND

Jo

FEET

ft Shallow Monitoring Well mdashbullbullmdash 17-Acre Property Boundary Figure 1-ZD Deep Monitoring Well I 1 I Detected Concentration ND = Not Detected Distribution of Total VOCs in

Deep Bedrock Groundwater Pumping Well April 2003

Q) Residential Well Hows Corner Superfund Site Plymouth Maine

(T) Surface Water Sampling Point WOODARD ampCURRAN poundKk EnginawtirKj bull Science - Operations bull

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0403dwg04-20-05

0 Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

B MW-1B

I 12000

PCE

B 10000 Total VOCs

I

i 2000

i 0 Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

c MW-3B

G 2000

1800

B PCE

1600 Total VOCs

1 I I E

il-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

G E

211941

El

I I z E

80

Concentration Trends shy Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-13DB

Total VOCs

c i i c o

Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

MW-16DB

30

c i c c I c o

Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99

PCE

Total VOCs

Jul-01 Jul-03

211941

O bi

c Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

I MW-16IB

i 35

3

c Total VOCs

lt- 2 5

0 | gt

o

1 sectI

c c 0 4

Jul-90 Jul-92 Jul-94 Jul-96 Jul-98 Jul-00 Jul-02 Jul-04

I I MW-108D

I 12

PCE 10

Total VOCs c oc 3

E E I 0

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

E 211941

c Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

fi MW-108S

I I 40

PCE 35

Total VOCs

30

I f 26

20 I o

I 15

10

c Dec-99 Dec-00 Dec-01 Dec-02 Dec-03 I 0

I MW-112D

c 35 - imdash

I A3 shyTotal VOCs

o c

E 1 2

I

ition

B 1 ^

-i c 3

0 Dec-99 Dec-OO Dec-01 Dec-02 Dec-03

211941

I

i

I

cII

Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-112S

08

PCE

Total VOCs 06

o 04

02

0 Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

MW-114D

o

12000

10000

8000

6000

PCE

Total VOCs

4000

2000

i

ccEIIc

i

i

E

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

211941

Con

cent

ratio

n (

ug

l)

E Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

I MW-114S

E A5000 -- Total VOCs

- 4000

0 3000

2000

i 1000

i n shy

Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

MW-115D

c PCE

Total VOCs

c E

o

C c

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03 I 0

211941

IepoundII

EIEIIGICCIccc

30000

25000

20000

o bullsect 15000 b

o 10000 U

5000

0 Aug-99

25000

20000

5000

0 Aug-99

211941

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-2DB

PCE

Total VOCs

Aug-01 Aug-03

MW-2IB

PCE

Total VOCs

Aug-01 Aug-03

IDIBI

ii EIDIISIBIG C

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-102S

6000

5000 PCE

Total VOCs

4000

O 3000

2000

1000

0 Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

MW-103D

16000

~ 14000 ugt 3- 12000 o

^ 10000

sect 8000

O 6000

4000

2000

PCE

Total VOCs

0Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

211941

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

G MW-103S

I I

ampo

12000

10000

E sectc

S

8000

6000

4000

2000

0Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

G I 6000

MW-104D

i 5000

PCE

Total VOCs

i i c

2000

1000

Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

E I

211941

cIccIG

IIBCccBcIc

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-1041

PCE Total VOCs

a 25000

0 20000

a 15000

10000

5000

0 Jan-OO Jan-01 Jan-02 Jan-03 Jan-04

MW-106D

3000

2500 PCE

Total VOCs

=sect 2000

o bullsect 1500

1000

500

0 Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

211941

c Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

c MW-106S

I PCE

Total VOCs

i

i Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

i

i i i E

C

211941 c

Response to EPA-DEP Comment 5 Dated March 312005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

iiw

EPA-DEP Comment 5

Comment 5 Matrix Diffusion The report as well as other proponents of matrix diffusion suggest that depletion of DNAPL (Section 5112 page 5-15) needs to be achieved While that might be the ideal the goal is to achieve performance standards and that goal may be attainable while there is residual contamination in the rock perhaps even DNAPL globules The low bedrock matrix porosity (page 1-15) the high permeability values (page 4-4) the relative flux of the groundwater (page 5-5) and the decrease in surface area and out of the mainstream pockets (appendix C-4) all suggest that the diffusion out of the rock matrix would be insubstantial relative to the regional flux of groundwater through the Site

Response The TI Evaluation Report does not explicitly consider or rely upon matrix diffusion as a basis for requesting a TI Waiver for a portion of the Hows Corner Site The technical literature provides documentation that matrix diffusion can be a significant process that affects chemical transport and groundwater remediation timeframes in unconsolidated and consolidated media including fractured rock (US EPA 1989 Freeze and Cherry 1979 Pankow and Cherry 1996 Fountain 1998) Back diffusion of contaminants from the matrix porosity of the fractured rock can prolong the time necessary to achieve groundwater cleanup goals particularly for compounds such as PCE for which the cleanup goal is a low concentration It is our expectation that matrix diffusion has occurred at the Hows Corner Site and that back diffusion of PCE from the rock matrix will also occur Although the extent to which matrix diffusion is occurring at the Hows Comer Site has not been determined and that lack of knowledge contributes to uncertainty regarding the cleanup times at the Site the effect of matrix diffusion is to lengthen rather than shorten the time required for remediation

REFERENCES

Fountain JC 1998 Technologies for Dense Nonaqueous Phase Liquid Source Zone Remediation Ground-Water Remediation Technologies Analysis Center Technology Evaluation Report TE-98-02 December

Freeze RA and Cherry JA 1979 Groundwater Prentice-Hall Inc Englewood Cliffs NJ 07632 p 410-412

Pankow J F and Cherry J A 1996 Dense Chlorinated Solvents Waterloo Press Portland OR 97291-1399 p 67-88

US EPA 1989 Transport and Fate of Contaminants in the Subsurface EPA6254-89019 p 17-18

Response to EPA Comment 5 050305doc 1 of 1 Woodard amp Curran (211941)

WOODARD amp CURRAN Maine Massachusetts New Hampshire Connecticut Florida Operational offices across the US 1-800-426-4262 www woodardcurran com

Page 42: SDMS DocID 251749 - Records Collections · 2020-06-13 · CORPORATE OFFICES: Maine, Massachusetts, New Hampshire, Connecticut New, York, Florida Engineering • Science • Operations

Woodard and Curran PTS Laboratories PTS File No 34618

ORGANIC CARBON DATA (METHODOLOGY WALKLEY-BLACK)

PROJECT NAME PROJECT NO

SAMPLE ID

203-chip-13 203-chip-23 203-chip-27 203-chip-38 203-chip-42 203-chip-47 203-chip-52 203-chip-58 203-chip-69 203-chip-82 207-chip-11 207-chip-19 207-chip-24 207-chip-29 207-chip-35 207-chip-45 207-chip-55 207-chip-87 207-chip-90

207-chip-55 55-MS

55-MSMSD

Hows Corner NA

DEPTH ft

13 23 27 38 42 47 52 58 69 82 11 19 24 29 35 45 55 87 90

55 NA NA

MATRIX

Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip Rock Chip

Average Median

Geometric Mean Standard Deviation Relative Std Dev

+- 95 Confidence Interval n

Rock Chip Rock Chip Rock Chip

Average Median

Geometric Mean Standard Deviation Relative Std Dev

+- 95 Confidence Interval n

FRACTION ORGANIC CARBON

(gg)

170E-03 185E-03 185E-03 170E-03 240E-03 190E-03 230E-03 180E-03 170E-03 115E-03 195E-03 220E-03 220E-03 235E-03 135E-03 190E-03 205E-03 175E-03 160E-03

188E-03 185E-03 185E-03 327E-04

1739 123E-03 to

19

205E-03 130E-03 150E-03

162E-03 150E-03 159E-03 388E-04

2402 840E-04 to

3

2532E-03

2393E-03

Hows Corner Tl Evaluation Appendix B January 13 2005

Response to EPA-DEP Comment 4 Dated March 31 2005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

EPA-DEP Comment 4

Comment 4 Distribution of contaminants First the TI report seems based on the assertion that there is DNAPL at the source area yet it also appears to represent that the source area is small and the bedrock below 85 is competent (or less fractured) and less impacted by the release of contaminants Some of the confusion may result from using most recent data when that data is from several different sampling events over several years and there is no discernible difference in concentrations between shallow and deep bedrock or as in Section 421 where generally decreased generally increase generally similar and similar concentrations in four consecutive sentences leads to a muddled picture of the contaminant distribution

Second the report asserts that the distribution of contaminants over the entire plume has not changed with time but fails to support this conclusion with data again relying on data that is from different sampling dates for one composite representation

Response The likely presence of dense non-aqueous phase liquid (DNAPL) at the Hows Corner Site and the determination that the source area is small are not mutually exclusive and both are conclusions drawn from information obtained during field investigations The presence of DNAPL in the source area is based on the elevated concentrations of volatile organic compounds (VOCs) detected in the groundwater (WampC 2001 WampC 2002) The conclusion that the source area is small is based on the area in which VOCs in groundwater have been detected at concentrations that are considered to be indicative of the presence of DNAPL nearby Similarly the conclusion that fracture frequency decreases at depths greater than approximately 50 to 85 feet below ground surface was based on field observation during the RI field work The fact that zones with observed fractures exhibited higher hydraulic conductivities than zones without fractures coupled with the decreasing frequency of observed fractures with depth led to the conclusion that the hydraulic conductivity of the bulk rock decreases with depth

The most recent data from all wells were used to provide the maximum VOC data set size During the RI all of the previously-existing and then newly-installed monitoring wells were sampled along with several residential wells The RI sampling included up to 48 monitoring wells Subsequent to the RI and prior to the TI three rounds of monitoring were conducted to verify that the plume was stable 15 monitoring wells were sampled during each of the three rounds During the TI field investigation 29 wells were sampled for VOCs The sampled wells included all of the newly-installed wells and a subset of wells installed during the RI for a total of 29 monitoring wells By using most recent data VOC results from 53 monitoring wells were included in the evaluation (see table labeled Sampling Events for listing of monitoring wells) This approach was selected because there generally was little variation in the data from a particular location between years This is borne out by the attached individual plots of VOCs detected in shallow bedrock and deep bedrock for the Pre-ROD (December 1999January 2000) and Supplemental (May 2000) sampling events and for June 2001 January 2002 and April 2003 sampling events The Pre-ROD and Supplemental plots are similar to the subsequent plots from the 2001 2002 and 2003 sampling events

In addition to maps showing the spatial distribution of VOC data at a given time trend plots of the data from a particular location through time (attached) indicate that since the RI concentrations generally have been stable or have decreased Together the maps and trend plots and the data from which they were developed indicate that the distribution of contaminants over the entire plume has not changed appreciably with time

Response to EPA Comment 4 050305doc 1 of 26 Woodard amp Curran (211941)

REFERENCES

Woodard amp Curran Inc (WampC) 2001 Final Remedial Investigation Report Hows Corner Superfund Plymouth Maine July 2001

Woodard amp Curran Inc (WampC) 2002 Final Feasibility Study Report - Non-Source Area Groundwater Hows Corner Superfund Site Plymouth Maine Hows Corner Superfund Plymouth Maine July 2002

Response to EPA Comment 4 050305doc 2 of 26 Woodard amp Curran (211941)

LIST OF ATTACHMENTS (Response to Comment 4)

Table - Sampling Events 1999 - 2004 (2 pages)

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater Pre-ROD Sampling Event

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater Pre-ROD Sampling Event

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater Supplemental Sampling Event

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater Supplemental Sampling Event

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater June 2001

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater June 2001

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater January 2002

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater January 2002

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater April 2003

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater April 2003

Figure - Concentration Trends - Non-Source Area Wells MW-1B and MW-3B

Figure - Concentration Trends - Non-Source Area Wells MW-13DB and MW-16DB

Figure - Concentration Trends - Non-Source Area Wells MW-16IB and MW- 108D

Figure - Concentration Trends - Non-Source Area Wells MW-108S and MW-112D

Figure - Concentration Trends - Non-Source Area Wells MW-112S and MW-114D

Figure - Concentration Trends - Non-Source Area Wells MW-114S and MW-115D

Figure - Concentration Trends -Source Area Wells MW-2DB and MW-2IB

Figure - Concentration Trends -Source Area Wells MW-102S and MW-103D

Figure - Concentration Trends -Source Area Wells MW-103S and MW-104D

Figure - Concentration Trends -Source Area Wells MW-104I and MW-106D

Figure - Concentration Trends -Source Area Wells MW-106S

Response to EPA Comment 4 050305doc 3 of 26 Woodard amp Curran (211941)

I I

El I

II I I 1 I

I

i

Event Baseline Case ID WC-01 WC-01

Well Date Aug-99 Oct-99 LOT10 1 LOT1-1 1 LOT11-4 LOT14 1 LOT15 1 LOT15-1 1 LOT16 1 LOT16-1 1 LOT17 1 LOT18 1 LOT19 1 LOT2 LOT20 1 LOT21-10 1 LOT21-11 1 LOT21-12 1 LOT21-13 1 LOT21-14 1 LOT21-2 1 LOT21-5 1 LOT21-7 LOT21 -8 1 LOT21-9 1 LOT23 1 LOT24 1 LOT28-1 1 LOT28-2 1 LOT28-3 1 LOT28-4 1 LOT28W 1 LOT30 1 LOT30-1 1 LOT30-2 1 LOT30-3 1 LOT30-4 1 LOT30-5 LOT31 LOT35 1 LOT41 1 LOT42-1 1 LOT43-1 1 LOT43-4 1 LOT6-1 1 LOT67 1 LOT6-7 1 LOT6-8A 1 LOT6-8B 1 LOT80-1 1 LOT82 1 MW-101D MW-1011 MW-101S MW-102D MW-102S MW-103D MW-103S MW-104D MW-1041 MW-104S MW-105D MW-106D

Groundwater Sampling Location Summary 1999 - 2004xls

Sampling Events 1999-2004

Hows Corner Superfund Site Plymouth Maine

Supplemental 2001 2002 2003 Pumping 2004 Pre-ROD Rl Sampling Sampling Sampling Test Sampling WC-03 WC-09 WC-25 WC-30 WC-42B WC-56 WC-58 Dec-99 May-00 Jun-01 Jan-02 Apr-03 Sep-04 Sep-04

1

1 1 1

1 1 1 1 1

1 1

1

1 1

1 1 1

1 1 1 1 1

1

1 1

1 1 1 1

1

1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

Sampling Events 1999-2004

Hows Corner Super-fund Site Plymouth Maine

Supplemental 2001 2002 2003 Pumping Event Baseline Pre-ROD Rl Sampling Sampling Sampling Test

Case ID WC-01 WC-01 WC-03 WC-09 WC-25 WC-30 WC-42B WC-56

ll

Well Date Aug-99 Oct-99 Dec-99 May-00 Jun-01 Jan-02 Apr-03 Sep-04 MW-106S 1 1 1 1 1 MW-107D 1 1 MW-108D 1 1 1 1 1 MW-108S 1 1 1 1 1 MW-110D 1 1 MW-111D 1 1 MW-112D 1 1 1 1 1 MW-112S 1 1 1 1 1 MW-113D 1 1 MW-114D 1 1 1 1 1 MW-114S 1 1 1 1 1 MW-115D 1 1 1 1 1 MW-12DB 1 1 1 MW-12SB 1 1 1 MW-13DB 1 1 1 1 1 1 MW-13SB 1 1 1 MW-14DB 1 1 MW-14SO 1 1 MW-15DB 1 1 1 MW-15SB 1 1 1 MW-16DB 1 1 1 1 1 1 MW-16IB 1 1 1 1 1 1 MW-16SO 1 1 MW-17DO 1 1 1 MW-17SO 1 1 1 MW-1B 1 1 1 1 1 1 MW-203D MW-203S MW-204D MW-204S MW-205 MW-206D

I MW-206S MW-2DB 1 1 MW-2DDB 1 1 MW-2IB 1 1 1 1 1 1 MW-3B 1 1 1 1 1 1

I MW-4O 1 1 1 MW-5B 1 1

II MW-6DB 1 1 1 MW-6SB 1 1 1 MW-8DB 1 1 1 MW-8SB 1 1 1

II PW-207 1 SEEP-1 1 SUBTOTAL - RESIDENTIAL 44 25 0 2 0 3 0 SUBTOTAL - MONITORING 22 48 41 15 15 15 1

Total 3 66 73 41 17 15 18 1

I Included in most recent data

I Notes 1 - Overburden well not included in most recent data for plotting

2 - Tetrahydrofuran and 2-Butanone were the only two compounds detected in this well and are thought to be the result of well repair not included in most recent data for plotting

3 - Not included in most recent data for plotting

2004 Sampling

WC-58 Sep-04

1

1 1

1 1

1 1 1

1

1 1

1 1 1 1 1 1 1 1 1

1 1

1

0 29

29

Groundwatef Sampling Location Summary 1999 - 2004xls

I

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

monitoring well Figure 4-14 total VOC contour (ugl) - December 1999January 2000 Distribution of Total VOCs in

Note SW-113 is located downstream of SEEP-1 Shallow Bedrock Groundwater total concentration of detected VOCs ND= not detected these two locations were sampled during the Pre-ROD Sampling Event

Baseline Sampling Event in OctoberNovember 1999 Hows Corner Superfund Site Surface Water Sampling Location A Plymouth Maine Seep Sampling Location laquo- WOODARD ampCURRAN

995037wipri reportepa ri interim final feb 2001cadd drawingsfinalfig 4-14

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

0 300 600 I

FEET

Q residential well Figure 4-16 monitoring well Distribution of Total VOCs in

Deep Bedrock Groundwater total VOCs contour (ugl) Pre-ROD Sampling Event

active residential wells with lot number Hows Corner Superfund Site 2deg42deg Plymouth Maine total concentration of detected VOCs ND= not detected WOODARD ampCURRAN Enyinaaring bull Science bull Operations bull

995037wipri reportepa ri interim final feb 2001cadd drawingsfinalfig4mdash16

PLYMOUTH POND

PLYMOUTH POND

1 628Tl7MW-2bB 12135

PLYMOUTH POND

monitoring well Figure 4-20

V total VOC contour (ugl) - June 2000 Distribution of Total VOCs in Shallow Bedrock Groundwater

| 34 | total concentration of detected VOCs ND= not detected NA = not analyzed Supplemental Sampling Event Note SW-113 is located downstream of SEEP-1 Hows Corner Superfund Site

Surface Water Sampling Location these two locations were sampled during the Plymouth Maine Baseline Sampling Event in OctoberNovember 1999 Seep Sampling Location WOODARD amp CURRAN

Engineering bull Science - Operations bull 995037wipri reportepa ri interim final feb 2001 cadd drawingsfinalfig 4-20

residential well Figure 4-22 Distribution of Total VOCs in

monitoring well Deep Bedrock Groundwater

total VOCs contour (ugl) Supplemental Sampling Event

Hows Corner Superfund Site

total concentration of detected VOCs ND= not detected NA = not analyzed Plymouth Maine

WOODARD amp CURRAN

995037wipri reportepa-ri interim final feb 2001cadd drawingsfinalfig 4-22 Engineering bull Science - Operations bull

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

FEET

Shallow Monitoring Well

Deep Monitoring Well

C Detected Concentration ND = Not Detected Figure 1-XS Distribution of Total VOCs in Shallow Bedrock Groundwater

Pumping Well

17-Acre Property Boundary Concentration Contour (ugl)

June 2001 Hows Corner Superfund Site

Plymouth Maine WOODARDampCURRAN

-i^rhvj bull Scbncn bull Operations bull 211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0601 dwg04-20-05

PLYMOUTH POND Hopkins Road V

O

PLYMOUTH POND

PLYMOUTH POND

o

0 300 600 mdashfa FEET

Shallow Monitoring Well bull bull - 17-Acre Property Boundary Figure 1-XD

Deep Monitoring Well 1 I Detected Concentration ND = Not Detected Distribution of Total VOCs in Deep Bedrock Groundwater

-mf- Pumping Well June 2001 Residential Well Hows Corner Superfund Site

Plymouth Maine i h Surface Water Sampling Point

g WOODARD ampCURRAN _ ^ _ ^ _ _ yen_ rj i|Hlaquorlny bull Science bull Opt

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0601 dwg04-20-05

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

Shallow Monitoring Well

Deep Monitoring Well

Detected Concentration ND = Not Detected Figure 1-YS Distribution of Total VOCs in Shallow Bedrock Groundwater

Pumping Well

17-Acre Property Boundary Concentration Contour (ugl)

January 2002 Hows Corner Superfund Site

Plymouth Maine WOODARD amp CURRAN Engineering Science- Operations bull

211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0102dwg04-20-05

PLYMOUTH POND

PLYMOUTH POND

Site Pand^ laquoum-laquoBTuitaraquo tLV

vVlf-(

PLYMOUTH POND

0 300 600 ^ = FEET

Shallow Monitoring Well mdashbullbullbull 17-Acre Property Boundary Figure 1-YD - A - Deep Monitoring Well FT Detected Concentration ND = Not Detected Distribution of Total VOCs in

Deep Bedrock Groundwater Pumping Well January 2002 Residential Well Hows Corner Superfund Site

Plymouth Maine Surface Water Sampling Point

WOODARD ampCURRAN Engineering Sciencs- Operations bulli Si

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0102dwg04-20-05

- m j

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND j A O-shy

Shallow Monitoring Well E Detected Concentration ND = Not Detected Figure 1-ZS Distribution of Total VOCs in

Deep Monitoring Well Shallow Bedrock Groundwater

Pumping Well Hows Corner

April 2003 Superfund Site

17-Acre Property Boundary Plymouth Maine Concentration Contour (ugl) r WOODARD ampCURRAN

Engineering bull Science bull Operations bull 211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0403dwg04-20-05

s S pound

PLYMOUTH POND

PLYMOUTH POND

- -

5 PLYMOUTH POND

Jo

FEET

ft Shallow Monitoring Well mdashbullbullmdash 17-Acre Property Boundary Figure 1-ZD Deep Monitoring Well I 1 I Detected Concentration ND = Not Detected Distribution of Total VOCs in

Deep Bedrock Groundwater Pumping Well April 2003

Q) Residential Well Hows Corner Superfund Site Plymouth Maine

(T) Surface Water Sampling Point WOODARD ampCURRAN poundKk EnginawtirKj bull Science - Operations bull

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0403dwg04-20-05

0 Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

B MW-1B

I 12000

PCE

B 10000 Total VOCs

I

i 2000

i 0 Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

c MW-3B

G 2000

1800

B PCE

1600 Total VOCs

1 I I E

il-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

G E

211941

El

I I z E

80

Concentration Trends shy Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-13DB

Total VOCs

c i i c o

Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

MW-16DB

30

c i c c I c o

Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99

PCE

Total VOCs

Jul-01 Jul-03

211941

O bi

c Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

I MW-16IB

i 35

3

c Total VOCs

lt- 2 5

0 | gt

o

1 sectI

c c 0 4

Jul-90 Jul-92 Jul-94 Jul-96 Jul-98 Jul-00 Jul-02 Jul-04

I I MW-108D

I 12

PCE 10

Total VOCs c oc 3

E E I 0

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

E 211941

c Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

fi MW-108S

I I 40

PCE 35

Total VOCs

30

I f 26

20 I o

I 15

10

c Dec-99 Dec-00 Dec-01 Dec-02 Dec-03 I 0

I MW-112D

c 35 - imdash

I A3 shyTotal VOCs

o c

E 1 2

I

ition

B 1 ^

-i c 3

0 Dec-99 Dec-OO Dec-01 Dec-02 Dec-03

211941

I

i

I

cII

Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-112S

08

PCE

Total VOCs 06

o 04

02

0 Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

MW-114D

o

12000

10000

8000

6000

PCE

Total VOCs

4000

2000

i

ccEIIc

i

i

E

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

211941

Con

cent

ratio

n (

ug

l)

E Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

I MW-114S

E A5000 -- Total VOCs

- 4000

0 3000

2000

i 1000

i n shy

Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

MW-115D

c PCE

Total VOCs

c E

o

C c

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03 I 0

211941

IepoundII

EIEIIGICCIccc

30000

25000

20000

o bullsect 15000 b

o 10000 U

5000

0 Aug-99

25000

20000

5000

0 Aug-99

211941

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-2DB

PCE

Total VOCs

Aug-01 Aug-03

MW-2IB

PCE

Total VOCs

Aug-01 Aug-03

IDIBI

ii EIDIISIBIG C

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-102S

6000

5000 PCE

Total VOCs

4000

O 3000

2000

1000

0 Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

MW-103D

16000

~ 14000 ugt 3- 12000 o

^ 10000

sect 8000

O 6000

4000

2000

PCE

Total VOCs

0Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

211941

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

G MW-103S

I I

ampo

12000

10000

E sectc

S

8000

6000

4000

2000

0Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

G I 6000

MW-104D

i 5000

PCE

Total VOCs

i i c

2000

1000

Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

E I

211941

cIccIG

IIBCccBcIc

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-1041

PCE Total VOCs

a 25000

0 20000

a 15000

10000

5000

0 Jan-OO Jan-01 Jan-02 Jan-03 Jan-04

MW-106D

3000

2500 PCE

Total VOCs

=sect 2000

o bullsect 1500

1000

500

0 Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

211941

c Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

c MW-106S

I PCE

Total VOCs

i

i Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

i

i i i E

C

211941 c

Response to EPA-DEP Comment 5 Dated March 312005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

iiw

EPA-DEP Comment 5

Comment 5 Matrix Diffusion The report as well as other proponents of matrix diffusion suggest that depletion of DNAPL (Section 5112 page 5-15) needs to be achieved While that might be the ideal the goal is to achieve performance standards and that goal may be attainable while there is residual contamination in the rock perhaps even DNAPL globules The low bedrock matrix porosity (page 1-15) the high permeability values (page 4-4) the relative flux of the groundwater (page 5-5) and the decrease in surface area and out of the mainstream pockets (appendix C-4) all suggest that the diffusion out of the rock matrix would be insubstantial relative to the regional flux of groundwater through the Site

Response The TI Evaluation Report does not explicitly consider or rely upon matrix diffusion as a basis for requesting a TI Waiver for a portion of the Hows Corner Site The technical literature provides documentation that matrix diffusion can be a significant process that affects chemical transport and groundwater remediation timeframes in unconsolidated and consolidated media including fractured rock (US EPA 1989 Freeze and Cherry 1979 Pankow and Cherry 1996 Fountain 1998) Back diffusion of contaminants from the matrix porosity of the fractured rock can prolong the time necessary to achieve groundwater cleanup goals particularly for compounds such as PCE for which the cleanup goal is a low concentration It is our expectation that matrix diffusion has occurred at the Hows Corner Site and that back diffusion of PCE from the rock matrix will also occur Although the extent to which matrix diffusion is occurring at the Hows Comer Site has not been determined and that lack of knowledge contributes to uncertainty regarding the cleanup times at the Site the effect of matrix diffusion is to lengthen rather than shorten the time required for remediation

REFERENCES

Fountain JC 1998 Technologies for Dense Nonaqueous Phase Liquid Source Zone Remediation Ground-Water Remediation Technologies Analysis Center Technology Evaluation Report TE-98-02 December

Freeze RA and Cherry JA 1979 Groundwater Prentice-Hall Inc Englewood Cliffs NJ 07632 p 410-412

Pankow J F and Cherry J A 1996 Dense Chlorinated Solvents Waterloo Press Portland OR 97291-1399 p 67-88

US EPA 1989 Transport and Fate of Contaminants in the Subsurface EPA6254-89019 p 17-18

Response to EPA Comment 5 050305doc 1 of 1 Woodard amp Curran (211941)

WOODARD amp CURRAN Maine Massachusetts New Hampshire Connecticut Florida Operational offices across the US 1-800-426-4262 www woodardcurran com

Page 43: SDMS DocID 251749 - Records Collections · 2020-06-13 · CORPORATE OFFICES: Maine, Massachusetts, New Hampshire, Connecticut New, York, Florida Engineering • Science • Operations

Response to EPA-DEP Comment 4 Dated March 31 2005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

EPA-DEP Comment 4

Comment 4 Distribution of contaminants First the TI report seems based on the assertion that there is DNAPL at the source area yet it also appears to represent that the source area is small and the bedrock below 85 is competent (or less fractured) and less impacted by the release of contaminants Some of the confusion may result from using most recent data when that data is from several different sampling events over several years and there is no discernible difference in concentrations between shallow and deep bedrock or as in Section 421 where generally decreased generally increase generally similar and similar concentrations in four consecutive sentences leads to a muddled picture of the contaminant distribution

Second the report asserts that the distribution of contaminants over the entire plume has not changed with time but fails to support this conclusion with data again relying on data that is from different sampling dates for one composite representation

Response The likely presence of dense non-aqueous phase liquid (DNAPL) at the Hows Corner Site and the determination that the source area is small are not mutually exclusive and both are conclusions drawn from information obtained during field investigations The presence of DNAPL in the source area is based on the elevated concentrations of volatile organic compounds (VOCs) detected in the groundwater (WampC 2001 WampC 2002) The conclusion that the source area is small is based on the area in which VOCs in groundwater have been detected at concentrations that are considered to be indicative of the presence of DNAPL nearby Similarly the conclusion that fracture frequency decreases at depths greater than approximately 50 to 85 feet below ground surface was based on field observation during the RI field work The fact that zones with observed fractures exhibited higher hydraulic conductivities than zones without fractures coupled with the decreasing frequency of observed fractures with depth led to the conclusion that the hydraulic conductivity of the bulk rock decreases with depth

The most recent data from all wells were used to provide the maximum VOC data set size During the RI all of the previously-existing and then newly-installed monitoring wells were sampled along with several residential wells The RI sampling included up to 48 monitoring wells Subsequent to the RI and prior to the TI three rounds of monitoring were conducted to verify that the plume was stable 15 monitoring wells were sampled during each of the three rounds During the TI field investigation 29 wells were sampled for VOCs The sampled wells included all of the newly-installed wells and a subset of wells installed during the RI for a total of 29 monitoring wells By using most recent data VOC results from 53 monitoring wells were included in the evaluation (see table labeled Sampling Events for listing of monitoring wells) This approach was selected because there generally was little variation in the data from a particular location between years This is borne out by the attached individual plots of VOCs detected in shallow bedrock and deep bedrock for the Pre-ROD (December 1999January 2000) and Supplemental (May 2000) sampling events and for June 2001 January 2002 and April 2003 sampling events The Pre-ROD and Supplemental plots are similar to the subsequent plots from the 2001 2002 and 2003 sampling events

In addition to maps showing the spatial distribution of VOC data at a given time trend plots of the data from a particular location through time (attached) indicate that since the RI concentrations generally have been stable or have decreased Together the maps and trend plots and the data from which they were developed indicate that the distribution of contaminants over the entire plume has not changed appreciably with time

Response to EPA Comment 4 050305doc 1 of 26 Woodard amp Curran (211941)

REFERENCES

Woodard amp Curran Inc (WampC) 2001 Final Remedial Investigation Report Hows Corner Superfund Plymouth Maine July 2001

Woodard amp Curran Inc (WampC) 2002 Final Feasibility Study Report - Non-Source Area Groundwater Hows Corner Superfund Site Plymouth Maine Hows Corner Superfund Plymouth Maine July 2002

Response to EPA Comment 4 050305doc 2 of 26 Woodard amp Curran (211941)

LIST OF ATTACHMENTS (Response to Comment 4)

Table - Sampling Events 1999 - 2004 (2 pages)

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater Pre-ROD Sampling Event

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater Pre-ROD Sampling Event

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater Supplemental Sampling Event

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater Supplemental Sampling Event

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater June 2001

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater June 2001

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater January 2002

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater January 2002

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater April 2003

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater April 2003

Figure - Concentration Trends - Non-Source Area Wells MW-1B and MW-3B

Figure - Concentration Trends - Non-Source Area Wells MW-13DB and MW-16DB

Figure - Concentration Trends - Non-Source Area Wells MW-16IB and MW- 108D

Figure - Concentration Trends - Non-Source Area Wells MW-108S and MW-112D

Figure - Concentration Trends - Non-Source Area Wells MW-112S and MW-114D

Figure - Concentration Trends - Non-Source Area Wells MW-114S and MW-115D

Figure - Concentration Trends -Source Area Wells MW-2DB and MW-2IB

Figure - Concentration Trends -Source Area Wells MW-102S and MW-103D

Figure - Concentration Trends -Source Area Wells MW-103S and MW-104D

Figure - Concentration Trends -Source Area Wells MW-104I and MW-106D

Figure - Concentration Trends -Source Area Wells MW-106S

Response to EPA Comment 4 050305doc 3 of 26 Woodard amp Curran (211941)

I I

El I

II I I 1 I

I

i

Event Baseline Case ID WC-01 WC-01

Well Date Aug-99 Oct-99 LOT10 1 LOT1-1 1 LOT11-4 LOT14 1 LOT15 1 LOT15-1 1 LOT16 1 LOT16-1 1 LOT17 1 LOT18 1 LOT19 1 LOT2 LOT20 1 LOT21-10 1 LOT21-11 1 LOT21-12 1 LOT21-13 1 LOT21-14 1 LOT21-2 1 LOT21-5 1 LOT21-7 LOT21 -8 1 LOT21-9 1 LOT23 1 LOT24 1 LOT28-1 1 LOT28-2 1 LOT28-3 1 LOT28-4 1 LOT28W 1 LOT30 1 LOT30-1 1 LOT30-2 1 LOT30-3 1 LOT30-4 1 LOT30-5 LOT31 LOT35 1 LOT41 1 LOT42-1 1 LOT43-1 1 LOT43-4 1 LOT6-1 1 LOT67 1 LOT6-7 1 LOT6-8A 1 LOT6-8B 1 LOT80-1 1 LOT82 1 MW-101D MW-1011 MW-101S MW-102D MW-102S MW-103D MW-103S MW-104D MW-1041 MW-104S MW-105D MW-106D

Groundwater Sampling Location Summary 1999 - 2004xls

Sampling Events 1999-2004

Hows Corner Superfund Site Plymouth Maine

Supplemental 2001 2002 2003 Pumping 2004 Pre-ROD Rl Sampling Sampling Sampling Test Sampling WC-03 WC-09 WC-25 WC-30 WC-42B WC-56 WC-58 Dec-99 May-00 Jun-01 Jan-02 Apr-03 Sep-04 Sep-04

1

1 1 1

1 1 1 1 1

1 1

1

1 1

1 1 1

1 1 1 1 1

1

1 1

1 1 1 1

1

1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

Sampling Events 1999-2004

Hows Corner Super-fund Site Plymouth Maine

Supplemental 2001 2002 2003 Pumping Event Baseline Pre-ROD Rl Sampling Sampling Sampling Test

Case ID WC-01 WC-01 WC-03 WC-09 WC-25 WC-30 WC-42B WC-56

ll

Well Date Aug-99 Oct-99 Dec-99 May-00 Jun-01 Jan-02 Apr-03 Sep-04 MW-106S 1 1 1 1 1 MW-107D 1 1 MW-108D 1 1 1 1 1 MW-108S 1 1 1 1 1 MW-110D 1 1 MW-111D 1 1 MW-112D 1 1 1 1 1 MW-112S 1 1 1 1 1 MW-113D 1 1 MW-114D 1 1 1 1 1 MW-114S 1 1 1 1 1 MW-115D 1 1 1 1 1 MW-12DB 1 1 1 MW-12SB 1 1 1 MW-13DB 1 1 1 1 1 1 MW-13SB 1 1 1 MW-14DB 1 1 MW-14SO 1 1 MW-15DB 1 1 1 MW-15SB 1 1 1 MW-16DB 1 1 1 1 1 1 MW-16IB 1 1 1 1 1 1 MW-16SO 1 1 MW-17DO 1 1 1 MW-17SO 1 1 1 MW-1B 1 1 1 1 1 1 MW-203D MW-203S MW-204D MW-204S MW-205 MW-206D

I MW-206S MW-2DB 1 1 MW-2DDB 1 1 MW-2IB 1 1 1 1 1 1 MW-3B 1 1 1 1 1 1

I MW-4O 1 1 1 MW-5B 1 1

II MW-6DB 1 1 1 MW-6SB 1 1 1 MW-8DB 1 1 1 MW-8SB 1 1 1

II PW-207 1 SEEP-1 1 SUBTOTAL - RESIDENTIAL 44 25 0 2 0 3 0 SUBTOTAL - MONITORING 22 48 41 15 15 15 1

Total 3 66 73 41 17 15 18 1

I Included in most recent data

I Notes 1 - Overburden well not included in most recent data for plotting

2 - Tetrahydrofuran and 2-Butanone were the only two compounds detected in this well and are thought to be the result of well repair not included in most recent data for plotting

3 - Not included in most recent data for plotting

2004 Sampling

WC-58 Sep-04

1

1 1

1 1

1 1 1

1

1 1

1 1 1 1 1 1 1 1 1

1 1

1

0 29

29

Groundwatef Sampling Location Summary 1999 - 2004xls

I

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

monitoring well Figure 4-14 total VOC contour (ugl) - December 1999January 2000 Distribution of Total VOCs in

Note SW-113 is located downstream of SEEP-1 Shallow Bedrock Groundwater total concentration of detected VOCs ND= not detected these two locations were sampled during the Pre-ROD Sampling Event

Baseline Sampling Event in OctoberNovember 1999 Hows Corner Superfund Site Surface Water Sampling Location A Plymouth Maine Seep Sampling Location laquo- WOODARD ampCURRAN

995037wipri reportepa ri interim final feb 2001cadd drawingsfinalfig 4-14

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

0 300 600 I

FEET

Q residential well Figure 4-16 monitoring well Distribution of Total VOCs in

Deep Bedrock Groundwater total VOCs contour (ugl) Pre-ROD Sampling Event

active residential wells with lot number Hows Corner Superfund Site 2deg42deg Plymouth Maine total concentration of detected VOCs ND= not detected WOODARD ampCURRAN Enyinaaring bull Science bull Operations bull

995037wipri reportepa ri interim final feb 2001cadd drawingsfinalfig4mdash16

PLYMOUTH POND

PLYMOUTH POND

1 628Tl7MW-2bB 12135

PLYMOUTH POND

monitoring well Figure 4-20

V total VOC contour (ugl) - June 2000 Distribution of Total VOCs in Shallow Bedrock Groundwater

| 34 | total concentration of detected VOCs ND= not detected NA = not analyzed Supplemental Sampling Event Note SW-113 is located downstream of SEEP-1 Hows Corner Superfund Site

Surface Water Sampling Location these two locations were sampled during the Plymouth Maine Baseline Sampling Event in OctoberNovember 1999 Seep Sampling Location WOODARD amp CURRAN

Engineering bull Science - Operations bull 995037wipri reportepa ri interim final feb 2001 cadd drawingsfinalfig 4-20

residential well Figure 4-22 Distribution of Total VOCs in

monitoring well Deep Bedrock Groundwater

total VOCs contour (ugl) Supplemental Sampling Event

Hows Corner Superfund Site

total concentration of detected VOCs ND= not detected NA = not analyzed Plymouth Maine

WOODARD amp CURRAN

995037wipri reportepa-ri interim final feb 2001cadd drawingsfinalfig 4-22 Engineering bull Science - Operations bull

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

FEET

Shallow Monitoring Well

Deep Monitoring Well

C Detected Concentration ND = Not Detected Figure 1-XS Distribution of Total VOCs in Shallow Bedrock Groundwater

Pumping Well

17-Acre Property Boundary Concentration Contour (ugl)

June 2001 Hows Corner Superfund Site

Plymouth Maine WOODARDampCURRAN

-i^rhvj bull Scbncn bull Operations bull 211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0601 dwg04-20-05

PLYMOUTH POND Hopkins Road V

O

PLYMOUTH POND

PLYMOUTH POND

o

0 300 600 mdashfa FEET

Shallow Monitoring Well bull bull - 17-Acre Property Boundary Figure 1-XD

Deep Monitoring Well 1 I Detected Concentration ND = Not Detected Distribution of Total VOCs in Deep Bedrock Groundwater

-mf- Pumping Well June 2001 Residential Well Hows Corner Superfund Site

Plymouth Maine i h Surface Water Sampling Point

g WOODARD ampCURRAN _ ^ _ ^ _ _ yen_ rj i|Hlaquorlny bull Science bull Opt

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0601 dwg04-20-05

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

Shallow Monitoring Well

Deep Monitoring Well

Detected Concentration ND = Not Detected Figure 1-YS Distribution of Total VOCs in Shallow Bedrock Groundwater

Pumping Well

17-Acre Property Boundary Concentration Contour (ugl)

January 2002 Hows Corner Superfund Site

Plymouth Maine WOODARD amp CURRAN Engineering Science- Operations bull

211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0102dwg04-20-05

PLYMOUTH POND

PLYMOUTH POND

Site Pand^ laquoum-laquoBTuitaraquo tLV

vVlf-(

PLYMOUTH POND

0 300 600 ^ = FEET

Shallow Monitoring Well mdashbullbullbull 17-Acre Property Boundary Figure 1-YD - A - Deep Monitoring Well FT Detected Concentration ND = Not Detected Distribution of Total VOCs in

Deep Bedrock Groundwater Pumping Well January 2002 Residential Well Hows Corner Superfund Site

Plymouth Maine Surface Water Sampling Point

WOODARD ampCURRAN Engineering Sciencs- Operations bulli Si

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0102dwg04-20-05

- m j

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND j A O-shy

Shallow Monitoring Well E Detected Concentration ND = Not Detected Figure 1-ZS Distribution of Total VOCs in

Deep Monitoring Well Shallow Bedrock Groundwater

Pumping Well Hows Corner

April 2003 Superfund Site

17-Acre Property Boundary Plymouth Maine Concentration Contour (ugl) r WOODARD ampCURRAN

Engineering bull Science bull Operations bull 211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0403dwg04-20-05

s S pound

PLYMOUTH POND

PLYMOUTH POND

- -

5 PLYMOUTH POND

Jo

FEET

ft Shallow Monitoring Well mdashbullbullmdash 17-Acre Property Boundary Figure 1-ZD Deep Monitoring Well I 1 I Detected Concentration ND = Not Detected Distribution of Total VOCs in

Deep Bedrock Groundwater Pumping Well April 2003

Q) Residential Well Hows Corner Superfund Site Plymouth Maine

(T) Surface Water Sampling Point WOODARD ampCURRAN poundKk EnginawtirKj bull Science - Operations bull

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0403dwg04-20-05

0 Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

B MW-1B

I 12000

PCE

B 10000 Total VOCs

I

i 2000

i 0 Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

c MW-3B

G 2000

1800

B PCE

1600 Total VOCs

1 I I E

il-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

G E

211941

El

I I z E

80

Concentration Trends shy Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-13DB

Total VOCs

c i i c o

Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

MW-16DB

30

c i c c I c o

Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99

PCE

Total VOCs

Jul-01 Jul-03

211941

O bi

c Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

I MW-16IB

i 35

3

c Total VOCs

lt- 2 5

0 | gt

o

1 sectI

c c 0 4

Jul-90 Jul-92 Jul-94 Jul-96 Jul-98 Jul-00 Jul-02 Jul-04

I I MW-108D

I 12

PCE 10

Total VOCs c oc 3

E E I 0

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

E 211941

c Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

fi MW-108S

I I 40

PCE 35

Total VOCs

30

I f 26

20 I o

I 15

10

c Dec-99 Dec-00 Dec-01 Dec-02 Dec-03 I 0

I MW-112D

c 35 - imdash

I A3 shyTotal VOCs

o c

E 1 2

I

ition

B 1 ^

-i c 3

0 Dec-99 Dec-OO Dec-01 Dec-02 Dec-03

211941

I

i

I

cII

Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-112S

08

PCE

Total VOCs 06

o 04

02

0 Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

MW-114D

o

12000

10000

8000

6000

PCE

Total VOCs

4000

2000

i

ccEIIc

i

i

E

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

211941

Con

cent

ratio

n (

ug

l)

E Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

I MW-114S

E A5000 -- Total VOCs

- 4000

0 3000

2000

i 1000

i n shy

Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

MW-115D

c PCE

Total VOCs

c E

o

C c

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03 I 0

211941

IepoundII

EIEIIGICCIccc

30000

25000

20000

o bullsect 15000 b

o 10000 U

5000

0 Aug-99

25000

20000

5000

0 Aug-99

211941

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-2DB

PCE

Total VOCs

Aug-01 Aug-03

MW-2IB

PCE

Total VOCs

Aug-01 Aug-03

IDIBI

ii EIDIISIBIG C

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-102S

6000

5000 PCE

Total VOCs

4000

O 3000

2000

1000

0 Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

MW-103D

16000

~ 14000 ugt 3- 12000 o

^ 10000

sect 8000

O 6000

4000

2000

PCE

Total VOCs

0Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

211941

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

G MW-103S

I I

ampo

12000

10000

E sectc

S

8000

6000

4000

2000

0Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

G I 6000

MW-104D

i 5000

PCE

Total VOCs

i i c

2000

1000

Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

E I

211941

cIccIG

IIBCccBcIc

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-1041

PCE Total VOCs

a 25000

0 20000

a 15000

10000

5000

0 Jan-OO Jan-01 Jan-02 Jan-03 Jan-04

MW-106D

3000

2500 PCE

Total VOCs

=sect 2000

o bullsect 1500

1000

500

0 Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

211941

c Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

c MW-106S

I PCE

Total VOCs

i

i Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

i

i i i E

C

211941 c

Response to EPA-DEP Comment 5 Dated March 312005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

iiw

EPA-DEP Comment 5

Comment 5 Matrix Diffusion The report as well as other proponents of matrix diffusion suggest that depletion of DNAPL (Section 5112 page 5-15) needs to be achieved While that might be the ideal the goal is to achieve performance standards and that goal may be attainable while there is residual contamination in the rock perhaps even DNAPL globules The low bedrock matrix porosity (page 1-15) the high permeability values (page 4-4) the relative flux of the groundwater (page 5-5) and the decrease in surface area and out of the mainstream pockets (appendix C-4) all suggest that the diffusion out of the rock matrix would be insubstantial relative to the regional flux of groundwater through the Site

Response The TI Evaluation Report does not explicitly consider or rely upon matrix diffusion as a basis for requesting a TI Waiver for a portion of the Hows Corner Site The technical literature provides documentation that matrix diffusion can be a significant process that affects chemical transport and groundwater remediation timeframes in unconsolidated and consolidated media including fractured rock (US EPA 1989 Freeze and Cherry 1979 Pankow and Cherry 1996 Fountain 1998) Back diffusion of contaminants from the matrix porosity of the fractured rock can prolong the time necessary to achieve groundwater cleanup goals particularly for compounds such as PCE for which the cleanup goal is a low concentration It is our expectation that matrix diffusion has occurred at the Hows Corner Site and that back diffusion of PCE from the rock matrix will also occur Although the extent to which matrix diffusion is occurring at the Hows Comer Site has not been determined and that lack of knowledge contributes to uncertainty regarding the cleanup times at the Site the effect of matrix diffusion is to lengthen rather than shorten the time required for remediation

REFERENCES

Fountain JC 1998 Technologies for Dense Nonaqueous Phase Liquid Source Zone Remediation Ground-Water Remediation Technologies Analysis Center Technology Evaluation Report TE-98-02 December

Freeze RA and Cherry JA 1979 Groundwater Prentice-Hall Inc Englewood Cliffs NJ 07632 p 410-412

Pankow J F and Cherry J A 1996 Dense Chlorinated Solvents Waterloo Press Portland OR 97291-1399 p 67-88

US EPA 1989 Transport and Fate of Contaminants in the Subsurface EPA6254-89019 p 17-18

Response to EPA Comment 5 050305doc 1 of 1 Woodard amp Curran (211941)

WOODARD amp CURRAN Maine Massachusetts New Hampshire Connecticut Florida Operational offices across the US 1-800-426-4262 www woodardcurran com

Page 44: SDMS DocID 251749 - Records Collections · 2020-06-13 · CORPORATE OFFICES: Maine, Massachusetts, New Hampshire, Connecticut New, York, Florida Engineering • Science • Operations

EPA-DEP Comment 4

Comment 4 Distribution of contaminants First the TI report seems based on the assertion that there is DNAPL at the source area yet it also appears to represent that the source area is small and the bedrock below 85 is competent (or less fractured) and less impacted by the release of contaminants Some of the confusion may result from using most recent data when that data is from several different sampling events over several years and there is no discernible difference in concentrations between shallow and deep bedrock or as in Section 421 where generally decreased generally increase generally similar and similar concentrations in four consecutive sentences leads to a muddled picture of the contaminant distribution

Second the report asserts that the distribution of contaminants over the entire plume has not changed with time but fails to support this conclusion with data again relying on data that is from different sampling dates for one composite representation

Response The likely presence of dense non-aqueous phase liquid (DNAPL) at the Hows Corner Site and the determination that the source area is small are not mutually exclusive and both are conclusions drawn from information obtained during field investigations The presence of DNAPL in the source area is based on the elevated concentrations of volatile organic compounds (VOCs) detected in the groundwater (WampC 2001 WampC 2002) The conclusion that the source area is small is based on the area in which VOCs in groundwater have been detected at concentrations that are considered to be indicative of the presence of DNAPL nearby Similarly the conclusion that fracture frequency decreases at depths greater than approximately 50 to 85 feet below ground surface was based on field observation during the RI field work The fact that zones with observed fractures exhibited higher hydraulic conductivities than zones without fractures coupled with the decreasing frequency of observed fractures with depth led to the conclusion that the hydraulic conductivity of the bulk rock decreases with depth

The most recent data from all wells were used to provide the maximum VOC data set size During the RI all of the previously-existing and then newly-installed monitoring wells were sampled along with several residential wells The RI sampling included up to 48 monitoring wells Subsequent to the RI and prior to the TI three rounds of monitoring were conducted to verify that the plume was stable 15 monitoring wells were sampled during each of the three rounds During the TI field investigation 29 wells were sampled for VOCs The sampled wells included all of the newly-installed wells and a subset of wells installed during the RI for a total of 29 monitoring wells By using most recent data VOC results from 53 monitoring wells were included in the evaluation (see table labeled Sampling Events for listing of monitoring wells) This approach was selected because there generally was little variation in the data from a particular location between years This is borne out by the attached individual plots of VOCs detected in shallow bedrock and deep bedrock for the Pre-ROD (December 1999January 2000) and Supplemental (May 2000) sampling events and for June 2001 January 2002 and April 2003 sampling events The Pre-ROD and Supplemental plots are similar to the subsequent plots from the 2001 2002 and 2003 sampling events

In addition to maps showing the spatial distribution of VOC data at a given time trend plots of the data from a particular location through time (attached) indicate that since the RI concentrations generally have been stable or have decreased Together the maps and trend plots and the data from which they were developed indicate that the distribution of contaminants over the entire plume has not changed appreciably with time

Response to EPA Comment 4 050305doc 1 of 26 Woodard amp Curran (211941)

REFERENCES

Woodard amp Curran Inc (WampC) 2001 Final Remedial Investigation Report Hows Corner Superfund Plymouth Maine July 2001

Woodard amp Curran Inc (WampC) 2002 Final Feasibility Study Report - Non-Source Area Groundwater Hows Corner Superfund Site Plymouth Maine Hows Corner Superfund Plymouth Maine July 2002

Response to EPA Comment 4 050305doc 2 of 26 Woodard amp Curran (211941)

LIST OF ATTACHMENTS (Response to Comment 4)

Table - Sampling Events 1999 - 2004 (2 pages)

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater Pre-ROD Sampling Event

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater Pre-ROD Sampling Event

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater Supplemental Sampling Event

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater Supplemental Sampling Event

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater June 2001

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater June 2001

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater January 2002

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater January 2002

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater April 2003

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater April 2003

Figure - Concentration Trends - Non-Source Area Wells MW-1B and MW-3B

Figure - Concentration Trends - Non-Source Area Wells MW-13DB and MW-16DB

Figure - Concentration Trends - Non-Source Area Wells MW-16IB and MW- 108D

Figure - Concentration Trends - Non-Source Area Wells MW-108S and MW-112D

Figure - Concentration Trends - Non-Source Area Wells MW-112S and MW-114D

Figure - Concentration Trends - Non-Source Area Wells MW-114S and MW-115D

Figure - Concentration Trends -Source Area Wells MW-2DB and MW-2IB

Figure - Concentration Trends -Source Area Wells MW-102S and MW-103D

Figure - Concentration Trends -Source Area Wells MW-103S and MW-104D

Figure - Concentration Trends -Source Area Wells MW-104I and MW-106D

Figure - Concentration Trends -Source Area Wells MW-106S

Response to EPA Comment 4 050305doc 3 of 26 Woodard amp Curran (211941)

I I

El I

II I I 1 I

I

i

Event Baseline Case ID WC-01 WC-01

Well Date Aug-99 Oct-99 LOT10 1 LOT1-1 1 LOT11-4 LOT14 1 LOT15 1 LOT15-1 1 LOT16 1 LOT16-1 1 LOT17 1 LOT18 1 LOT19 1 LOT2 LOT20 1 LOT21-10 1 LOT21-11 1 LOT21-12 1 LOT21-13 1 LOT21-14 1 LOT21-2 1 LOT21-5 1 LOT21-7 LOT21 -8 1 LOT21-9 1 LOT23 1 LOT24 1 LOT28-1 1 LOT28-2 1 LOT28-3 1 LOT28-4 1 LOT28W 1 LOT30 1 LOT30-1 1 LOT30-2 1 LOT30-3 1 LOT30-4 1 LOT30-5 LOT31 LOT35 1 LOT41 1 LOT42-1 1 LOT43-1 1 LOT43-4 1 LOT6-1 1 LOT67 1 LOT6-7 1 LOT6-8A 1 LOT6-8B 1 LOT80-1 1 LOT82 1 MW-101D MW-1011 MW-101S MW-102D MW-102S MW-103D MW-103S MW-104D MW-1041 MW-104S MW-105D MW-106D

Groundwater Sampling Location Summary 1999 - 2004xls

Sampling Events 1999-2004

Hows Corner Superfund Site Plymouth Maine

Supplemental 2001 2002 2003 Pumping 2004 Pre-ROD Rl Sampling Sampling Sampling Test Sampling WC-03 WC-09 WC-25 WC-30 WC-42B WC-56 WC-58 Dec-99 May-00 Jun-01 Jan-02 Apr-03 Sep-04 Sep-04

1

1 1 1

1 1 1 1 1

1 1

1

1 1

1 1 1

1 1 1 1 1

1

1 1

1 1 1 1

1

1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

Sampling Events 1999-2004

Hows Corner Super-fund Site Plymouth Maine

Supplemental 2001 2002 2003 Pumping Event Baseline Pre-ROD Rl Sampling Sampling Sampling Test

Case ID WC-01 WC-01 WC-03 WC-09 WC-25 WC-30 WC-42B WC-56

ll

Well Date Aug-99 Oct-99 Dec-99 May-00 Jun-01 Jan-02 Apr-03 Sep-04 MW-106S 1 1 1 1 1 MW-107D 1 1 MW-108D 1 1 1 1 1 MW-108S 1 1 1 1 1 MW-110D 1 1 MW-111D 1 1 MW-112D 1 1 1 1 1 MW-112S 1 1 1 1 1 MW-113D 1 1 MW-114D 1 1 1 1 1 MW-114S 1 1 1 1 1 MW-115D 1 1 1 1 1 MW-12DB 1 1 1 MW-12SB 1 1 1 MW-13DB 1 1 1 1 1 1 MW-13SB 1 1 1 MW-14DB 1 1 MW-14SO 1 1 MW-15DB 1 1 1 MW-15SB 1 1 1 MW-16DB 1 1 1 1 1 1 MW-16IB 1 1 1 1 1 1 MW-16SO 1 1 MW-17DO 1 1 1 MW-17SO 1 1 1 MW-1B 1 1 1 1 1 1 MW-203D MW-203S MW-204D MW-204S MW-205 MW-206D

I MW-206S MW-2DB 1 1 MW-2DDB 1 1 MW-2IB 1 1 1 1 1 1 MW-3B 1 1 1 1 1 1

I MW-4O 1 1 1 MW-5B 1 1

II MW-6DB 1 1 1 MW-6SB 1 1 1 MW-8DB 1 1 1 MW-8SB 1 1 1

II PW-207 1 SEEP-1 1 SUBTOTAL - RESIDENTIAL 44 25 0 2 0 3 0 SUBTOTAL - MONITORING 22 48 41 15 15 15 1

Total 3 66 73 41 17 15 18 1

I Included in most recent data

I Notes 1 - Overburden well not included in most recent data for plotting

2 - Tetrahydrofuran and 2-Butanone were the only two compounds detected in this well and are thought to be the result of well repair not included in most recent data for plotting

3 - Not included in most recent data for plotting

2004 Sampling

WC-58 Sep-04

1

1 1

1 1

1 1 1

1

1 1

1 1 1 1 1 1 1 1 1

1 1

1

0 29

29

Groundwatef Sampling Location Summary 1999 - 2004xls

I

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

monitoring well Figure 4-14 total VOC contour (ugl) - December 1999January 2000 Distribution of Total VOCs in

Note SW-113 is located downstream of SEEP-1 Shallow Bedrock Groundwater total concentration of detected VOCs ND= not detected these two locations were sampled during the Pre-ROD Sampling Event

Baseline Sampling Event in OctoberNovember 1999 Hows Corner Superfund Site Surface Water Sampling Location A Plymouth Maine Seep Sampling Location laquo- WOODARD ampCURRAN

995037wipri reportepa ri interim final feb 2001cadd drawingsfinalfig 4-14

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

0 300 600 I

FEET

Q residential well Figure 4-16 monitoring well Distribution of Total VOCs in

Deep Bedrock Groundwater total VOCs contour (ugl) Pre-ROD Sampling Event

active residential wells with lot number Hows Corner Superfund Site 2deg42deg Plymouth Maine total concentration of detected VOCs ND= not detected WOODARD ampCURRAN Enyinaaring bull Science bull Operations bull

995037wipri reportepa ri interim final feb 2001cadd drawingsfinalfig4mdash16

PLYMOUTH POND

PLYMOUTH POND

1 628Tl7MW-2bB 12135

PLYMOUTH POND

monitoring well Figure 4-20

V total VOC contour (ugl) - June 2000 Distribution of Total VOCs in Shallow Bedrock Groundwater

| 34 | total concentration of detected VOCs ND= not detected NA = not analyzed Supplemental Sampling Event Note SW-113 is located downstream of SEEP-1 Hows Corner Superfund Site

Surface Water Sampling Location these two locations were sampled during the Plymouth Maine Baseline Sampling Event in OctoberNovember 1999 Seep Sampling Location WOODARD amp CURRAN

Engineering bull Science - Operations bull 995037wipri reportepa ri interim final feb 2001 cadd drawingsfinalfig 4-20

residential well Figure 4-22 Distribution of Total VOCs in

monitoring well Deep Bedrock Groundwater

total VOCs contour (ugl) Supplemental Sampling Event

Hows Corner Superfund Site

total concentration of detected VOCs ND= not detected NA = not analyzed Plymouth Maine

WOODARD amp CURRAN

995037wipri reportepa-ri interim final feb 2001cadd drawingsfinalfig 4-22 Engineering bull Science - Operations bull

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

FEET

Shallow Monitoring Well

Deep Monitoring Well

C Detected Concentration ND = Not Detected Figure 1-XS Distribution of Total VOCs in Shallow Bedrock Groundwater

Pumping Well

17-Acre Property Boundary Concentration Contour (ugl)

June 2001 Hows Corner Superfund Site

Plymouth Maine WOODARDampCURRAN

-i^rhvj bull Scbncn bull Operations bull 211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0601 dwg04-20-05

PLYMOUTH POND Hopkins Road V

O

PLYMOUTH POND

PLYMOUTH POND

o

0 300 600 mdashfa FEET

Shallow Monitoring Well bull bull - 17-Acre Property Boundary Figure 1-XD

Deep Monitoring Well 1 I Detected Concentration ND = Not Detected Distribution of Total VOCs in Deep Bedrock Groundwater

-mf- Pumping Well June 2001 Residential Well Hows Corner Superfund Site

Plymouth Maine i h Surface Water Sampling Point

g WOODARD ampCURRAN _ ^ _ ^ _ _ yen_ rj i|Hlaquorlny bull Science bull Opt

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0601 dwg04-20-05

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

Shallow Monitoring Well

Deep Monitoring Well

Detected Concentration ND = Not Detected Figure 1-YS Distribution of Total VOCs in Shallow Bedrock Groundwater

Pumping Well

17-Acre Property Boundary Concentration Contour (ugl)

January 2002 Hows Corner Superfund Site

Plymouth Maine WOODARD amp CURRAN Engineering Science- Operations bull

211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0102dwg04-20-05

PLYMOUTH POND

PLYMOUTH POND

Site Pand^ laquoum-laquoBTuitaraquo tLV

vVlf-(

PLYMOUTH POND

0 300 600 ^ = FEET

Shallow Monitoring Well mdashbullbullbull 17-Acre Property Boundary Figure 1-YD - A - Deep Monitoring Well FT Detected Concentration ND = Not Detected Distribution of Total VOCs in

Deep Bedrock Groundwater Pumping Well January 2002 Residential Well Hows Corner Superfund Site

Plymouth Maine Surface Water Sampling Point

WOODARD ampCURRAN Engineering Sciencs- Operations bulli Si

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0102dwg04-20-05

- m j

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND j A O-shy

Shallow Monitoring Well E Detected Concentration ND = Not Detected Figure 1-ZS Distribution of Total VOCs in

Deep Monitoring Well Shallow Bedrock Groundwater

Pumping Well Hows Corner

April 2003 Superfund Site

17-Acre Property Boundary Plymouth Maine Concentration Contour (ugl) r WOODARD ampCURRAN

Engineering bull Science bull Operations bull 211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0403dwg04-20-05

s S pound

PLYMOUTH POND

PLYMOUTH POND

- -

5 PLYMOUTH POND

Jo

FEET

ft Shallow Monitoring Well mdashbullbullmdash 17-Acre Property Boundary Figure 1-ZD Deep Monitoring Well I 1 I Detected Concentration ND = Not Detected Distribution of Total VOCs in

Deep Bedrock Groundwater Pumping Well April 2003

Q) Residential Well Hows Corner Superfund Site Plymouth Maine

(T) Surface Water Sampling Point WOODARD ampCURRAN poundKk EnginawtirKj bull Science - Operations bull

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0403dwg04-20-05

0 Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

B MW-1B

I 12000

PCE

B 10000 Total VOCs

I

i 2000

i 0 Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

c MW-3B

G 2000

1800

B PCE

1600 Total VOCs

1 I I E

il-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

G E

211941

El

I I z E

80

Concentration Trends shy Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-13DB

Total VOCs

c i i c o

Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

MW-16DB

30

c i c c I c o

Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99

PCE

Total VOCs

Jul-01 Jul-03

211941

O bi

c Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

I MW-16IB

i 35

3

c Total VOCs

lt- 2 5

0 | gt

o

1 sectI

c c 0 4

Jul-90 Jul-92 Jul-94 Jul-96 Jul-98 Jul-00 Jul-02 Jul-04

I I MW-108D

I 12

PCE 10

Total VOCs c oc 3

E E I 0

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

E 211941

c Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

fi MW-108S

I I 40

PCE 35

Total VOCs

30

I f 26

20 I o

I 15

10

c Dec-99 Dec-00 Dec-01 Dec-02 Dec-03 I 0

I MW-112D

c 35 - imdash

I A3 shyTotal VOCs

o c

E 1 2

I

ition

B 1 ^

-i c 3

0 Dec-99 Dec-OO Dec-01 Dec-02 Dec-03

211941

I

i

I

cII

Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-112S

08

PCE

Total VOCs 06

o 04

02

0 Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

MW-114D

o

12000

10000

8000

6000

PCE

Total VOCs

4000

2000

i

ccEIIc

i

i

E

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

211941

Con

cent

ratio

n (

ug

l)

E Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

I MW-114S

E A5000 -- Total VOCs

- 4000

0 3000

2000

i 1000

i n shy

Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

MW-115D

c PCE

Total VOCs

c E

o

C c

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03 I 0

211941

IepoundII

EIEIIGICCIccc

30000

25000

20000

o bullsect 15000 b

o 10000 U

5000

0 Aug-99

25000

20000

5000

0 Aug-99

211941

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-2DB

PCE

Total VOCs

Aug-01 Aug-03

MW-2IB

PCE

Total VOCs

Aug-01 Aug-03

IDIBI

ii EIDIISIBIG C

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-102S

6000

5000 PCE

Total VOCs

4000

O 3000

2000

1000

0 Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

MW-103D

16000

~ 14000 ugt 3- 12000 o

^ 10000

sect 8000

O 6000

4000

2000

PCE

Total VOCs

0Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

211941

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

G MW-103S

I I

ampo

12000

10000

E sectc

S

8000

6000

4000

2000

0Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

G I 6000

MW-104D

i 5000

PCE

Total VOCs

i i c

2000

1000

Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

E I

211941

cIccIG

IIBCccBcIc

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-1041

PCE Total VOCs

a 25000

0 20000

a 15000

10000

5000

0 Jan-OO Jan-01 Jan-02 Jan-03 Jan-04

MW-106D

3000

2500 PCE

Total VOCs

=sect 2000

o bullsect 1500

1000

500

0 Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

211941

c Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

c MW-106S

I PCE

Total VOCs

i

i Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

i

i i i E

C

211941 c

Response to EPA-DEP Comment 5 Dated March 312005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

iiw

EPA-DEP Comment 5

Comment 5 Matrix Diffusion The report as well as other proponents of matrix diffusion suggest that depletion of DNAPL (Section 5112 page 5-15) needs to be achieved While that might be the ideal the goal is to achieve performance standards and that goal may be attainable while there is residual contamination in the rock perhaps even DNAPL globules The low bedrock matrix porosity (page 1-15) the high permeability values (page 4-4) the relative flux of the groundwater (page 5-5) and the decrease in surface area and out of the mainstream pockets (appendix C-4) all suggest that the diffusion out of the rock matrix would be insubstantial relative to the regional flux of groundwater through the Site

Response The TI Evaluation Report does not explicitly consider or rely upon matrix diffusion as a basis for requesting a TI Waiver for a portion of the Hows Corner Site The technical literature provides documentation that matrix diffusion can be a significant process that affects chemical transport and groundwater remediation timeframes in unconsolidated and consolidated media including fractured rock (US EPA 1989 Freeze and Cherry 1979 Pankow and Cherry 1996 Fountain 1998) Back diffusion of contaminants from the matrix porosity of the fractured rock can prolong the time necessary to achieve groundwater cleanup goals particularly for compounds such as PCE for which the cleanup goal is a low concentration It is our expectation that matrix diffusion has occurred at the Hows Corner Site and that back diffusion of PCE from the rock matrix will also occur Although the extent to which matrix diffusion is occurring at the Hows Comer Site has not been determined and that lack of knowledge contributes to uncertainty regarding the cleanup times at the Site the effect of matrix diffusion is to lengthen rather than shorten the time required for remediation

REFERENCES

Fountain JC 1998 Technologies for Dense Nonaqueous Phase Liquid Source Zone Remediation Ground-Water Remediation Technologies Analysis Center Technology Evaluation Report TE-98-02 December

Freeze RA and Cherry JA 1979 Groundwater Prentice-Hall Inc Englewood Cliffs NJ 07632 p 410-412

Pankow J F and Cherry J A 1996 Dense Chlorinated Solvents Waterloo Press Portland OR 97291-1399 p 67-88

US EPA 1989 Transport and Fate of Contaminants in the Subsurface EPA6254-89019 p 17-18

Response to EPA Comment 5 050305doc 1 of 1 Woodard amp Curran (211941)

WOODARD amp CURRAN Maine Massachusetts New Hampshire Connecticut Florida Operational offices across the US 1-800-426-4262 www woodardcurran com

Page 45: SDMS DocID 251749 - Records Collections · 2020-06-13 · CORPORATE OFFICES: Maine, Massachusetts, New Hampshire, Connecticut New, York, Florida Engineering • Science • Operations

REFERENCES

Woodard amp Curran Inc (WampC) 2001 Final Remedial Investigation Report Hows Corner Superfund Plymouth Maine July 2001

Woodard amp Curran Inc (WampC) 2002 Final Feasibility Study Report - Non-Source Area Groundwater Hows Corner Superfund Site Plymouth Maine Hows Corner Superfund Plymouth Maine July 2002

Response to EPA Comment 4 050305doc 2 of 26 Woodard amp Curran (211941)

LIST OF ATTACHMENTS (Response to Comment 4)

Table - Sampling Events 1999 - 2004 (2 pages)

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater Pre-ROD Sampling Event

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater Pre-ROD Sampling Event

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater Supplemental Sampling Event

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater Supplemental Sampling Event

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater June 2001

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater June 2001

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater January 2002

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater January 2002

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater April 2003

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater April 2003

Figure - Concentration Trends - Non-Source Area Wells MW-1B and MW-3B

Figure - Concentration Trends - Non-Source Area Wells MW-13DB and MW-16DB

Figure - Concentration Trends - Non-Source Area Wells MW-16IB and MW- 108D

Figure - Concentration Trends - Non-Source Area Wells MW-108S and MW-112D

Figure - Concentration Trends - Non-Source Area Wells MW-112S and MW-114D

Figure - Concentration Trends - Non-Source Area Wells MW-114S and MW-115D

Figure - Concentration Trends -Source Area Wells MW-2DB and MW-2IB

Figure - Concentration Trends -Source Area Wells MW-102S and MW-103D

Figure - Concentration Trends -Source Area Wells MW-103S and MW-104D

Figure - Concentration Trends -Source Area Wells MW-104I and MW-106D

Figure - Concentration Trends -Source Area Wells MW-106S

Response to EPA Comment 4 050305doc 3 of 26 Woodard amp Curran (211941)

I I

El I

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Event Baseline Case ID WC-01 WC-01

Well Date Aug-99 Oct-99 LOT10 1 LOT1-1 1 LOT11-4 LOT14 1 LOT15 1 LOT15-1 1 LOT16 1 LOT16-1 1 LOT17 1 LOT18 1 LOT19 1 LOT2 LOT20 1 LOT21-10 1 LOT21-11 1 LOT21-12 1 LOT21-13 1 LOT21-14 1 LOT21-2 1 LOT21-5 1 LOT21-7 LOT21 -8 1 LOT21-9 1 LOT23 1 LOT24 1 LOT28-1 1 LOT28-2 1 LOT28-3 1 LOT28-4 1 LOT28W 1 LOT30 1 LOT30-1 1 LOT30-2 1 LOT30-3 1 LOT30-4 1 LOT30-5 LOT31 LOT35 1 LOT41 1 LOT42-1 1 LOT43-1 1 LOT43-4 1 LOT6-1 1 LOT67 1 LOT6-7 1 LOT6-8A 1 LOT6-8B 1 LOT80-1 1 LOT82 1 MW-101D MW-1011 MW-101S MW-102D MW-102S MW-103D MW-103S MW-104D MW-1041 MW-104S MW-105D MW-106D

Groundwater Sampling Location Summary 1999 - 2004xls

Sampling Events 1999-2004

Hows Corner Superfund Site Plymouth Maine

Supplemental 2001 2002 2003 Pumping 2004 Pre-ROD Rl Sampling Sampling Sampling Test Sampling WC-03 WC-09 WC-25 WC-30 WC-42B WC-56 WC-58 Dec-99 May-00 Jun-01 Jan-02 Apr-03 Sep-04 Sep-04

1

1 1 1

1 1 1 1 1

1 1

1

1 1

1 1 1

1 1 1 1 1

1

1 1

1 1 1 1

1

1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

Sampling Events 1999-2004

Hows Corner Super-fund Site Plymouth Maine

Supplemental 2001 2002 2003 Pumping Event Baseline Pre-ROD Rl Sampling Sampling Sampling Test

Case ID WC-01 WC-01 WC-03 WC-09 WC-25 WC-30 WC-42B WC-56

ll

Well Date Aug-99 Oct-99 Dec-99 May-00 Jun-01 Jan-02 Apr-03 Sep-04 MW-106S 1 1 1 1 1 MW-107D 1 1 MW-108D 1 1 1 1 1 MW-108S 1 1 1 1 1 MW-110D 1 1 MW-111D 1 1 MW-112D 1 1 1 1 1 MW-112S 1 1 1 1 1 MW-113D 1 1 MW-114D 1 1 1 1 1 MW-114S 1 1 1 1 1 MW-115D 1 1 1 1 1 MW-12DB 1 1 1 MW-12SB 1 1 1 MW-13DB 1 1 1 1 1 1 MW-13SB 1 1 1 MW-14DB 1 1 MW-14SO 1 1 MW-15DB 1 1 1 MW-15SB 1 1 1 MW-16DB 1 1 1 1 1 1 MW-16IB 1 1 1 1 1 1 MW-16SO 1 1 MW-17DO 1 1 1 MW-17SO 1 1 1 MW-1B 1 1 1 1 1 1 MW-203D MW-203S MW-204D MW-204S MW-205 MW-206D

I MW-206S MW-2DB 1 1 MW-2DDB 1 1 MW-2IB 1 1 1 1 1 1 MW-3B 1 1 1 1 1 1

I MW-4O 1 1 1 MW-5B 1 1

II MW-6DB 1 1 1 MW-6SB 1 1 1 MW-8DB 1 1 1 MW-8SB 1 1 1

II PW-207 1 SEEP-1 1 SUBTOTAL - RESIDENTIAL 44 25 0 2 0 3 0 SUBTOTAL - MONITORING 22 48 41 15 15 15 1

Total 3 66 73 41 17 15 18 1

I Included in most recent data

I Notes 1 - Overburden well not included in most recent data for plotting

2 - Tetrahydrofuran and 2-Butanone were the only two compounds detected in this well and are thought to be the result of well repair not included in most recent data for plotting

3 - Not included in most recent data for plotting

2004 Sampling

WC-58 Sep-04

1

1 1

1 1

1 1 1

1

1 1

1 1 1 1 1 1 1 1 1

1 1

1

0 29

29

Groundwatef Sampling Location Summary 1999 - 2004xls

I

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

monitoring well Figure 4-14 total VOC contour (ugl) - December 1999January 2000 Distribution of Total VOCs in

Note SW-113 is located downstream of SEEP-1 Shallow Bedrock Groundwater total concentration of detected VOCs ND= not detected these two locations were sampled during the Pre-ROD Sampling Event

Baseline Sampling Event in OctoberNovember 1999 Hows Corner Superfund Site Surface Water Sampling Location A Plymouth Maine Seep Sampling Location laquo- WOODARD ampCURRAN

995037wipri reportepa ri interim final feb 2001cadd drawingsfinalfig 4-14

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

0 300 600 I

FEET

Q residential well Figure 4-16 monitoring well Distribution of Total VOCs in

Deep Bedrock Groundwater total VOCs contour (ugl) Pre-ROD Sampling Event

active residential wells with lot number Hows Corner Superfund Site 2deg42deg Plymouth Maine total concentration of detected VOCs ND= not detected WOODARD ampCURRAN Enyinaaring bull Science bull Operations bull

995037wipri reportepa ri interim final feb 2001cadd drawingsfinalfig4mdash16

PLYMOUTH POND

PLYMOUTH POND

1 628Tl7MW-2bB 12135

PLYMOUTH POND

monitoring well Figure 4-20

V total VOC contour (ugl) - June 2000 Distribution of Total VOCs in Shallow Bedrock Groundwater

| 34 | total concentration of detected VOCs ND= not detected NA = not analyzed Supplemental Sampling Event Note SW-113 is located downstream of SEEP-1 Hows Corner Superfund Site

Surface Water Sampling Location these two locations were sampled during the Plymouth Maine Baseline Sampling Event in OctoberNovember 1999 Seep Sampling Location WOODARD amp CURRAN

Engineering bull Science - Operations bull 995037wipri reportepa ri interim final feb 2001 cadd drawingsfinalfig 4-20

residential well Figure 4-22 Distribution of Total VOCs in

monitoring well Deep Bedrock Groundwater

total VOCs contour (ugl) Supplemental Sampling Event

Hows Corner Superfund Site

total concentration of detected VOCs ND= not detected NA = not analyzed Plymouth Maine

WOODARD amp CURRAN

995037wipri reportepa-ri interim final feb 2001cadd drawingsfinalfig 4-22 Engineering bull Science - Operations bull

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

FEET

Shallow Monitoring Well

Deep Monitoring Well

C Detected Concentration ND = Not Detected Figure 1-XS Distribution of Total VOCs in Shallow Bedrock Groundwater

Pumping Well

17-Acre Property Boundary Concentration Contour (ugl)

June 2001 Hows Corner Superfund Site

Plymouth Maine WOODARDampCURRAN

-i^rhvj bull Scbncn bull Operations bull 211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0601 dwg04-20-05

PLYMOUTH POND Hopkins Road V

O

PLYMOUTH POND

PLYMOUTH POND

o

0 300 600 mdashfa FEET

Shallow Monitoring Well bull bull - 17-Acre Property Boundary Figure 1-XD

Deep Monitoring Well 1 I Detected Concentration ND = Not Detected Distribution of Total VOCs in Deep Bedrock Groundwater

-mf- Pumping Well June 2001 Residential Well Hows Corner Superfund Site

Plymouth Maine i h Surface Water Sampling Point

g WOODARD ampCURRAN _ ^ _ ^ _ _ yen_ rj i|Hlaquorlny bull Science bull Opt

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0601 dwg04-20-05

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

Shallow Monitoring Well

Deep Monitoring Well

Detected Concentration ND = Not Detected Figure 1-YS Distribution of Total VOCs in Shallow Bedrock Groundwater

Pumping Well

17-Acre Property Boundary Concentration Contour (ugl)

January 2002 Hows Corner Superfund Site

Plymouth Maine WOODARD amp CURRAN Engineering Science- Operations bull

211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0102dwg04-20-05

PLYMOUTH POND

PLYMOUTH POND

Site Pand^ laquoum-laquoBTuitaraquo tLV

vVlf-(

PLYMOUTH POND

0 300 600 ^ = FEET

Shallow Monitoring Well mdashbullbullbull 17-Acre Property Boundary Figure 1-YD - A - Deep Monitoring Well FT Detected Concentration ND = Not Detected Distribution of Total VOCs in

Deep Bedrock Groundwater Pumping Well January 2002 Residential Well Hows Corner Superfund Site

Plymouth Maine Surface Water Sampling Point

WOODARD ampCURRAN Engineering Sciencs- Operations bulli Si

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0102dwg04-20-05

- m j

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND j A O-shy

Shallow Monitoring Well E Detected Concentration ND = Not Detected Figure 1-ZS Distribution of Total VOCs in

Deep Monitoring Well Shallow Bedrock Groundwater

Pumping Well Hows Corner

April 2003 Superfund Site

17-Acre Property Boundary Plymouth Maine Concentration Contour (ugl) r WOODARD ampCURRAN

Engineering bull Science bull Operations bull 211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0403dwg04-20-05

s S pound

PLYMOUTH POND

PLYMOUTH POND

- -

5 PLYMOUTH POND

Jo

FEET

ft Shallow Monitoring Well mdashbullbullmdash 17-Acre Property Boundary Figure 1-ZD Deep Monitoring Well I 1 I Detected Concentration ND = Not Detected Distribution of Total VOCs in

Deep Bedrock Groundwater Pumping Well April 2003

Q) Residential Well Hows Corner Superfund Site Plymouth Maine

(T) Surface Water Sampling Point WOODARD ampCURRAN poundKk EnginawtirKj bull Science - Operations bull

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0403dwg04-20-05

0 Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

B MW-1B

I 12000

PCE

B 10000 Total VOCs

I

i 2000

i 0 Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

c MW-3B

G 2000

1800

B PCE

1600 Total VOCs

1 I I E

il-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

G E

211941

El

I I z E

80

Concentration Trends shy Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-13DB

Total VOCs

c i i c o

Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

MW-16DB

30

c i c c I c o

Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99

PCE

Total VOCs

Jul-01 Jul-03

211941

O bi

c Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

I MW-16IB

i 35

3

c Total VOCs

lt- 2 5

0 | gt

o

1 sectI

c c 0 4

Jul-90 Jul-92 Jul-94 Jul-96 Jul-98 Jul-00 Jul-02 Jul-04

I I MW-108D

I 12

PCE 10

Total VOCs c oc 3

E E I 0

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

E 211941

c Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

fi MW-108S

I I 40

PCE 35

Total VOCs

30

I f 26

20 I o

I 15

10

c Dec-99 Dec-00 Dec-01 Dec-02 Dec-03 I 0

I MW-112D

c 35 - imdash

I A3 shyTotal VOCs

o c

E 1 2

I

ition

B 1 ^

-i c 3

0 Dec-99 Dec-OO Dec-01 Dec-02 Dec-03

211941

I

i

I

cII

Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-112S

08

PCE

Total VOCs 06

o 04

02

0 Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

MW-114D

o

12000

10000

8000

6000

PCE

Total VOCs

4000

2000

i

ccEIIc

i

i

E

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

211941

Con

cent

ratio

n (

ug

l)

E Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

I MW-114S

E A5000 -- Total VOCs

- 4000

0 3000

2000

i 1000

i n shy

Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

MW-115D

c PCE

Total VOCs

c E

o

C c

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03 I 0

211941

IepoundII

EIEIIGICCIccc

30000

25000

20000

o bullsect 15000 b

o 10000 U

5000

0 Aug-99

25000

20000

5000

0 Aug-99

211941

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-2DB

PCE

Total VOCs

Aug-01 Aug-03

MW-2IB

PCE

Total VOCs

Aug-01 Aug-03

IDIBI

ii EIDIISIBIG C

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-102S

6000

5000 PCE

Total VOCs

4000

O 3000

2000

1000

0 Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

MW-103D

16000

~ 14000 ugt 3- 12000 o

^ 10000

sect 8000

O 6000

4000

2000

PCE

Total VOCs

0Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

211941

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

G MW-103S

I I

ampo

12000

10000

E sectc

S

8000

6000

4000

2000

0Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

G I 6000

MW-104D

i 5000

PCE

Total VOCs

i i c

2000

1000

Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

E I

211941

cIccIG

IIBCccBcIc

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-1041

PCE Total VOCs

a 25000

0 20000

a 15000

10000

5000

0 Jan-OO Jan-01 Jan-02 Jan-03 Jan-04

MW-106D

3000

2500 PCE

Total VOCs

=sect 2000

o bullsect 1500

1000

500

0 Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

211941

c Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

c MW-106S

I PCE

Total VOCs

i

i Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

i

i i i E

C

211941 c

Response to EPA-DEP Comment 5 Dated March 312005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

iiw

EPA-DEP Comment 5

Comment 5 Matrix Diffusion The report as well as other proponents of matrix diffusion suggest that depletion of DNAPL (Section 5112 page 5-15) needs to be achieved While that might be the ideal the goal is to achieve performance standards and that goal may be attainable while there is residual contamination in the rock perhaps even DNAPL globules The low bedrock matrix porosity (page 1-15) the high permeability values (page 4-4) the relative flux of the groundwater (page 5-5) and the decrease in surface area and out of the mainstream pockets (appendix C-4) all suggest that the diffusion out of the rock matrix would be insubstantial relative to the regional flux of groundwater through the Site

Response The TI Evaluation Report does not explicitly consider or rely upon matrix diffusion as a basis for requesting a TI Waiver for a portion of the Hows Corner Site The technical literature provides documentation that matrix diffusion can be a significant process that affects chemical transport and groundwater remediation timeframes in unconsolidated and consolidated media including fractured rock (US EPA 1989 Freeze and Cherry 1979 Pankow and Cherry 1996 Fountain 1998) Back diffusion of contaminants from the matrix porosity of the fractured rock can prolong the time necessary to achieve groundwater cleanup goals particularly for compounds such as PCE for which the cleanup goal is a low concentration It is our expectation that matrix diffusion has occurred at the Hows Corner Site and that back diffusion of PCE from the rock matrix will also occur Although the extent to which matrix diffusion is occurring at the Hows Comer Site has not been determined and that lack of knowledge contributes to uncertainty regarding the cleanup times at the Site the effect of matrix diffusion is to lengthen rather than shorten the time required for remediation

REFERENCES

Fountain JC 1998 Technologies for Dense Nonaqueous Phase Liquid Source Zone Remediation Ground-Water Remediation Technologies Analysis Center Technology Evaluation Report TE-98-02 December

Freeze RA and Cherry JA 1979 Groundwater Prentice-Hall Inc Englewood Cliffs NJ 07632 p 410-412

Pankow J F and Cherry J A 1996 Dense Chlorinated Solvents Waterloo Press Portland OR 97291-1399 p 67-88

US EPA 1989 Transport and Fate of Contaminants in the Subsurface EPA6254-89019 p 17-18

Response to EPA Comment 5 050305doc 1 of 1 Woodard amp Curran (211941)

WOODARD amp CURRAN Maine Massachusetts New Hampshire Connecticut Florida Operational offices across the US 1-800-426-4262 www woodardcurran com

Page 46: SDMS DocID 251749 - Records Collections · 2020-06-13 · CORPORATE OFFICES: Maine, Massachusetts, New Hampshire, Connecticut New, York, Florida Engineering • Science • Operations

LIST OF ATTACHMENTS (Response to Comment 4)

Table - Sampling Events 1999 - 2004 (2 pages)

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater Pre-ROD Sampling Event

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater Pre-ROD Sampling Event

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater Supplemental Sampling Event

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater Supplemental Sampling Event

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater June 2001

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater June 2001

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater January 2002

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater January 2002

Figure - Distribution of Total VOCs in Shallow Bedrock Groundwater April 2003

Figure - Distribution of Total VOCs in Deep Bedrock Groundwater April 2003

Figure - Concentration Trends - Non-Source Area Wells MW-1B and MW-3B

Figure - Concentration Trends - Non-Source Area Wells MW-13DB and MW-16DB

Figure - Concentration Trends - Non-Source Area Wells MW-16IB and MW- 108D

Figure - Concentration Trends - Non-Source Area Wells MW-108S and MW-112D

Figure - Concentration Trends - Non-Source Area Wells MW-112S and MW-114D

Figure - Concentration Trends - Non-Source Area Wells MW-114S and MW-115D

Figure - Concentration Trends -Source Area Wells MW-2DB and MW-2IB

Figure - Concentration Trends -Source Area Wells MW-102S and MW-103D

Figure - Concentration Trends -Source Area Wells MW-103S and MW-104D

Figure - Concentration Trends -Source Area Wells MW-104I and MW-106D

Figure - Concentration Trends -Source Area Wells MW-106S

Response to EPA Comment 4 050305doc 3 of 26 Woodard amp Curran (211941)

I I

El I

II I I 1 I

I

i

Event Baseline Case ID WC-01 WC-01

Well Date Aug-99 Oct-99 LOT10 1 LOT1-1 1 LOT11-4 LOT14 1 LOT15 1 LOT15-1 1 LOT16 1 LOT16-1 1 LOT17 1 LOT18 1 LOT19 1 LOT2 LOT20 1 LOT21-10 1 LOT21-11 1 LOT21-12 1 LOT21-13 1 LOT21-14 1 LOT21-2 1 LOT21-5 1 LOT21-7 LOT21 -8 1 LOT21-9 1 LOT23 1 LOT24 1 LOT28-1 1 LOT28-2 1 LOT28-3 1 LOT28-4 1 LOT28W 1 LOT30 1 LOT30-1 1 LOT30-2 1 LOT30-3 1 LOT30-4 1 LOT30-5 LOT31 LOT35 1 LOT41 1 LOT42-1 1 LOT43-1 1 LOT43-4 1 LOT6-1 1 LOT67 1 LOT6-7 1 LOT6-8A 1 LOT6-8B 1 LOT80-1 1 LOT82 1 MW-101D MW-1011 MW-101S MW-102D MW-102S MW-103D MW-103S MW-104D MW-1041 MW-104S MW-105D MW-106D

Groundwater Sampling Location Summary 1999 - 2004xls

Sampling Events 1999-2004

Hows Corner Superfund Site Plymouth Maine

Supplemental 2001 2002 2003 Pumping 2004 Pre-ROD Rl Sampling Sampling Sampling Test Sampling WC-03 WC-09 WC-25 WC-30 WC-42B WC-56 WC-58 Dec-99 May-00 Jun-01 Jan-02 Apr-03 Sep-04 Sep-04

1

1 1 1

1 1 1 1 1

1 1

1

1 1

1 1 1

1 1 1 1 1

1

1 1

1 1 1 1

1

1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

Sampling Events 1999-2004

Hows Corner Super-fund Site Plymouth Maine

Supplemental 2001 2002 2003 Pumping Event Baseline Pre-ROD Rl Sampling Sampling Sampling Test

Case ID WC-01 WC-01 WC-03 WC-09 WC-25 WC-30 WC-42B WC-56

ll

Well Date Aug-99 Oct-99 Dec-99 May-00 Jun-01 Jan-02 Apr-03 Sep-04 MW-106S 1 1 1 1 1 MW-107D 1 1 MW-108D 1 1 1 1 1 MW-108S 1 1 1 1 1 MW-110D 1 1 MW-111D 1 1 MW-112D 1 1 1 1 1 MW-112S 1 1 1 1 1 MW-113D 1 1 MW-114D 1 1 1 1 1 MW-114S 1 1 1 1 1 MW-115D 1 1 1 1 1 MW-12DB 1 1 1 MW-12SB 1 1 1 MW-13DB 1 1 1 1 1 1 MW-13SB 1 1 1 MW-14DB 1 1 MW-14SO 1 1 MW-15DB 1 1 1 MW-15SB 1 1 1 MW-16DB 1 1 1 1 1 1 MW-16IB 1 1 1 1 1 1 MW-16SO 1 1 MW-17DO 1 1 1 MW-17SO 1 1 1 MW-1B 1 1 1 1 1 1 MW-203D MW-203S MW-204D MW-204S MW-205 MW-206D

I MW-206S MW-2DB 1 1 MW-2DDB 1 1 MW-2IB 1 1 1 1 1 1 MW-3B 1 1 1 1 1 1

I MW-4O 1 1 1 MW-5B 1 1

II MW-6DB 1 1 1 MW-6SB 1 1 1 MW-8DB 1 1 1 MW-8SB 1 1 1

II PW-207 1 SEEP-1 1 SUBTOTAL - RESIDENTIAL 44 25 0 2 0 3 0 SUBTOTAL - MONITORING 22 48 41 15 15 15 1

Total 3 66 73 41 17 15 18 1

I Included in most recent data

I Notes 1 - Overburden well not included in most recent data for plotting

2 - Tetrahydrofuran and 2-Butanone were the only two compounds detected in this well and are thought to be the result of well repair not included in most recent data for plotting

3 - Not included in most recent data for plotting

2004 Sampling

WC-58 Sep-04

1

1 1

1 1

1 1 1

1

1 1

1 1 1 1 1 1 1 1 1

1 1

1

0 29

29

Groundwatef Sampling Location Summary 1999 - 2004xls

I

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

monitoring well Figure 4-14 total VOC contour (ugl) - December 1999January 2000 Distribution of Total VOCs in

Note SW-113 is located downstream of SEEP-1 Shallow Bedrock Groundwater total concentration of detected VOCs ND= not detected these two locations were sampled during the Pre-ROD Sampling Event

Baseline Sampling Event in OctoberNovember 1999 Hows Corner Superfund Site Surface Water Sampling Location A Plymouth Maine Seep Sampling Location laquo- WOODARD ampCURRAN

995037wipri reportepa ri interim final feb 2001cadd drawingsfinalfig 4-14

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

0 300 600 I

FEET

Q residential well Figure 4-16 monitoring well Distribution of Total VOCs in

Deep Bedrock Groundwater total VOCs contour (ugl) Pre-ROD Sampling Event

active residential wells with lot number Hows Corner Superfund Site 2deg42deg Plymouth Maine total concentration of detected VOCs ND= not detected WOODARD ampCURRAN Enyinaaring bull Science bull Operations bull

995037wipri reportepa ri interim final feb 2001cadd drawingsfinalfig4mdash16

PLYMOUTH POND

PLYMOUTH POND

1 628Tl7MW-2bB 12135

PLYMOUTH POND

monitoring well Figure 4-20

V total VOC contour (ugl) - June 2000 Distribution of Total VOCs in Shallow Bedrock Groundwater

| 34 | total concentration of detected VOCs ND= not detected NA = not analyzed Supplemental Sampling Event Note SW-113 is located downstream of SEEP-1 Hows Corner Superfund Site

Surface Water Sampling Location these two locations were sampled during the Plymouth Maine Baseline Sampling Event in OctoberNovember 1999 Seep Sampling Location WOODARD amp CURRAN

Engineering bull Science - Operations bull 995037wipri reportepa ri interim final feb 2001 cadd drawingsfinalfig 4-20

residential well Figure 4-22 Distribution of Total VOCs in

monitoring well Deep Bedrock Groundwater

total VOCs contour (ugl) Supplemental Sampling Event

Hows Corner Superfund Site

total concentration of detected VOCs ND= not detected NA = not analyzed Plymouth Maine

WOODARD amp CURRAN

995037wipri reportepa-ri interim final feb 2001cadd drawingsfinalfig 4-22 Engineering bull Science - Operations bull

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

FEET

Shallow Monitoring Well

Deep Monitoring Well

C Detected Concentration ND = Not Detected Figure 1-XS Distribution of Total VOCs in Shallow Bedrock Groundwater

Pumping Well

17-Acre Property Boundary Concentration Contour (ugl)

June 2001 Hows Corner Superfund Site

Plymouth Maine WOODARDampCURRAN

-i^rhvj bull Scbncn bull Operations bull 211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0601 dwg04-20-05

PLYMOUTH POND Hopkins Road V

O

PLYMOUTH POND

PLYMOUTH POND

o

0 300 600 mdashfa FEET

Shallow Monitoring Well bull bull - 17-Acre Property Boundary Figure 1-XD

Deep Monitoring Well 1 I Detected Concentration ND = Not Detected Distribution of Total VOCs in Deep Bedrock Groundwater

-mf- Pumping Well June 2001 Residential Well Hows Corner Superfund Site

Plymouth Maine i h Surface Water Sampling Point

g WOODARD ampCURRAN _ ^ _ ^ _ _ yen_ rj i|Hlaquorlny bull Science bull Opt

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0601 dwg04-20-05

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

Shallow Monitoring Well

Deep Monitoring Well

Detected Concentration ND = Not Detected Figure 1-YS Distribution of Total VOCs in Shallow Bedrock Groundwater

Pumping Well

17-Acre Property Boundary Concentration Contour (ugl)

January 2002 Hows Corner Superfund Site

Plymouth Maine WOODARD amp CURRAN Engineering Science- Operations bull

211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0102dwg04-20-05

PLYMOUTH POND

PLYMOUTH POND

Site Pand^ laquoum-laquoBTuitaraquo tLV

vVlf-(

PLYMOUTH POND

0 300 600 ^ = FEET

Shallow Monitoring Well mdashbullbullbull 17-Acre Property Boundary Figure 1-YD - A - Deep Monitoring Well FT Detected Concentration ND = Not Detected Distribution of Total VOCs in

Deep Bedrock Groundwater Pumping Well January 2002 Residential Well Hows Corner Superfund Site

Plymouth Maine Surface Water Sampling Point

WOODARD ampCURRAN Engineering Sciencs- Operations bulli Si

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0102dwg04-20-05

- m j

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND j A O-shy

Shallow Monitoring Well E Detected Concentration ND = Not Detected Figure 1-ZS Distribution of Total VOCs in

Deep Monitoring Well Shallow Bedrock Groundwater

Pumping Well Hows Corner

April 2003 Superfund Site

17-Acre Property Boundary Plymouth Maine Concentration Contour (ugl) r WOODARD ampCURRAN

Engineering bull Science bull Operations bull 211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0403dwg04-20-05

s S pound

PLYMOUTH POND

PLYMOUTH POND

- -

5 PLYMOUTH POND

Jo

FEET

ft Shallow Monitoring Well mdashbullbullmdash 17-Acre Property Boundary Figure 1-ZD Deep Monitoring Well I 1 I Detected Concentration ND = Not Detected Distribution of Total VOCs in

Deep Bedrock Groundwater Pumping Well April 2003

Q) Residential Well Hows Corner Superfund Site Plymouth Maine

(T) Surface Water Sampling Point WOODARD ampCURRAN poundKk EnginawtirKj bull Science - Operations bull

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0403dwg04-20-05

0 Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

B MW-1B

I 12000

PCE

B 10000 Total VOCs

I

i 2000

i 0 Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

c MW-3B

G 2000

1800

B PCE

1600 Total VOCs

1 I I E

il-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

G E

211941

El

I I z E

80

Concentration Trends shy Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-13DB

Total VOCs

c i i c o

Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

MW-16DB

30

c i c c I c o

Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99

PCE

Total VOCs

Jul-01 Jul-03

211941

O bi

c Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

I MW-16IB

i 35

3

c Total VOCs

lt- 2 5

0 | gt

o

1 sectI

c c 0 4

Jul-90 Jul-92 Jul-94 Jul-96 Jul-98 Jul-00 Jul-02 Jul-04

I I MW-108D

I 12

PCE 10

Total VOCs c oc 3

E E I 0

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

E 211941

c Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

fi MW-108S

I I 40

PCE 35

Total VOCs

30

I f 26

20 I o

I 15

10

c Dec-99 Dec-00 Dec-01 Dec-02 Dec-03 I 0

I MW-112D

c 35 - imdash

I A3 shyTotal VOCs

o c

E 1 2

I

ition

B 1 ^

-i c 3

0 Dec-99 Dec-OO Dec-01 Dec-02 Dec-03

211941

I

i

I

cII

Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-112S

08

PCE

Total VOCs 06

o 04

02

0 Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

MW-114D

o

12000

10000

8000

6000

PCE

Total VOCs

4000

2000

i

ccEIIc

i

i

E

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

211941

Con

cent

ratio

n (

ug

l)

E Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

I MW-114S

E A5000 -- Total VOCs

- 4000

0 3000

2000

i 1000

i n shy

Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

MW-115D

c PCE

Total VOCs

c E

o

C c

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03 I 0

211941

IepoundII

EIEIIGICCIccc

30000

25000

20000

o bullsect 15000 b

o 10000 U

5000

0 Aug-99

25000

20000

5000

0 Aug-99

211941

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-2DB

PCE

Total VOCs

Aug-01 Aug-03

MW-2IB

PCE

Total VOCs

Aug-01 Aug-03

IDIBI

ii EIDIISIBIG C

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-102S

6000

5000 PCE

Total VOCs

4000

O 3000

2000

1000

0 Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

MW-103D

16000

~ 14000 ugt 3- 12000 o

^ 10000

sect 8000

O 6000

4000

2000

PCE

Total VOCs

0Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

211941

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

G MW-103S

I I

ampo

12000

10000

E sectc

S

8000

6000

4000

2000

0Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

G I 6000

MW-104D

i 5000

PCE

Total VOCs

i i c

2000

1000

Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

E I

211941

cIccIG

IIBCccBcIc

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-1041

PCE Total VOCs

a 25000

0 20000

a 15000

10000

5000

0 Jan-OO Jan-01 Jan-02 Jan-03 Jan-04

MW-106D

3000

2500 PCE

Total VOCs

=sect 2000

o bullsect 1500

1000

500

0 Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

211941

c Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

c MW-106S

I PCE

Total VOCs

i

i Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

i

i i i E

C

211941 c

Response to EPA-DEP Comment 5 Dated March 312005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

iiw

EPA-DEP Comment 5

Comment 5 Matrix Diffusion The report as well as other proponents of matrix diffusion suggest that depletion of DNAPL (Section 5112 page 5-15) needs to be achieved While that might be the ideal the goal is to achieve performance standards and that goal may be attainable while there is residual contamination in the rock perhaps even DNAPL globules The low bedrock matrix porosity (page 1-15) the high permeability values (page 4-4) the relative flux of the groundwater (page 5-5) and the decrease in surface area and out of the mainstream pockets (appendix C-4) all suggest that the diffusion out of the rock matrix would be insubstantial relative to the regional flux of groundwater through the Site

Response The TI Evaluation Report does not explicitly consider or rely upon matrix diffusion as a basis for requesting a TI Waiver for a portion of the Hows Corner Site The technical literature provides documentation that matrix diffusion can be a significant process that affects chemical transport and groundwater remediation timeframes in unconsolidated and consolidated media including fractured rock (US EPA 1989 Freeze and Cherry 1979 Pankow and Cherry 1996 Fountain 1998) Back diffusion of contaminants from the matrix porosity of the fractured rock can prolong the time necessary to achieve groundwater cleanup goals particularly for compounds such as PCE for which the cleanup goal is a low concentration It is our expectation that matrix diffusion has occurred at the Hows Corner Site and that back diffusion of PCE from the rock matrix will also occur Although the extent to which matrix diffusion is occurring at the Hows Comer Site has not been determined and that lack of knowledge contributes to uncertainty regarding the cleanup times at the Site the effect of matrix diffusion is to lengthen rather than shorten the time required for remediation

REFERENCES

Fountain JC 1998 Technologies for Dense Nonaqueous Phase Liquid Source Zone Remediation Ground-Water Remediation Technologies Analysis Center Technology Evaluation Report TE-98-02 December

Freeze RA and Cherry JA 1979 Groundwater Prentice-Hall Inc Englewood Cliffs NJ 07632 p 410-412

Pankow J F and Cherry J A 1996 Dense Chlorinated Solvents Waterloo Press Portland OR 97291-1399 p 67-88

US EPA 1989 Transport and Fate of Contaminants in the Subsurface EPA6254-89019 p 17-18

Response to EPA Comment 5 050305doc 1 of 1 Woodard amp Curran (211941)

WOODARD amp CURRAN Maine Massachusetts New Hampshire Connecticut Florida Operational offices across the US 1-800-426-4262 www woodardcurran com

Page 47: SDMS DocID 251749 - Records Collections · 2020-06-13 · CORPORATE OFFICES: Maine, Massachusetts, New Hampshire, Connecticut New, York, Florida Engineering • Science • Operations

I I

El I

II I I 1 I

I

i

Event Baseline Case ID WC-01 WC-01

Well Date Aug-99 Oct-99 LOT10 1 LOT1-1 1 LOT11-4 LOT14 1 LOT15 1 LOT15-1 1 LOT16 1 LOT16-1 1 LOT17 1 LOT18 1 LOT19 1 LOT2 LOT20 1 LOT21-10 1 LOT21-11 1 LOT21-12 1 LOT21-13 1 LOT21-14 1 LOT21-2 1 LOT21-5 1 LOT21-7 LOT21 -8 1 LOT21-9 1 LOT23 1 LOT24 1 LOT28-1 1 LOT28-2 1 LOT28-3 1 LOT28-4 1 LOT28W 1 LOT30 1 LOT30-1 1 LOT30-2 1 LOT30-3 1 LOT30-4 1 LOT30-5 LOT31 LOT35 1 LOT41 1 LOT42-1 1 LOT43-1 1 LOT43-4 1 LOT6-1 1 LOT67 1 LOT6-7 1 LOT6-8A 1 LOT6-8B 1 LOT80-1 1 LOT82 1 MW-101D MW-1011 MW-101S MW-102D MW-102S MW-103D MW-103S MW-104D MW-1041 MW-104S MW-105D MW-106D

Groundwater Sampling Location Summary 1999 - 2004xls

Sampling Events 1999-2004

Hows Corner Superfund Site Plymouth Maine

Supplemental 2001 2002 2003 Pumping 2004 Pre-ROD Rl Sampling Sampling Sampling Test Sampling WC-03 WC-09 WC-25 WC-30 WC-42B WC-56 WC-58 Dec-99 May-00 Jun-01 Jan-02 Apr-03 Sep-04 Sep-04

1

1 1 1

1 1 1 1 1

1 1

1

1 1

1 1 1

1 1 1 1 1

1

1 1

1 1 1 1

1

1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

Sampling Events 1999-2004

Hows Corner Super-fund Site Plymouth Maine

Supplemental 2001 2002 2003 Pumping Event Baseline Pre-ROD Rl Sampling Sampling Sampling Test

Case ID WC-01 WC-01 WC-03 WC-09 WC-25 WC-30 WC-42B WC-56

ll

Well Date Aug-99 Oct-99 Dec-99 May-00 Jun-01 Jan-02 Apr-03 Sep-04 MW-106S 1 1 1 1 1 MW-107D 1 1 MW-108D 1 1 1 1 1 MW-108S 1 1 1 1 1 MW-110D 1 1 MW-111D 1 1 MW-112D 1 1 1 1 1 MW-112S 1 1 1 1 1 MW-113D 1 1 MW-114D 1 1 1 1 1 MW-114S 1 1 1 1 1 MW-115D 1 1 1 1 1 MW-12DB 1 1 1 MW-12SB 1 1 1 MW-13DB 1 1 1 1 1 1 MW-13SB 1 1 1 MW-14DB 1 1 MW-14SO 1 1 MW-15DB 1 1 1 MW-15SB 1 1 1 MW-16DB 1 1 1 1 1 1 MW-16IB 1 1 1 1 1 1 MW-16SO 1 1 MW-17DO 1 1 1 MW-17SO 1 1 1 MW-1B 1 1 1 1 1 1 MW-203D MW-203S MW-204D MW-204S MW-205 MW-206D

I MW-206S MW-2DB 1 1 MW-2DDB 1 1 MW-2IB 1 1 1 1 1 1 MW-3B 1 1 1 1 1 1

I MW-4O 1 1 1 MW-5B 1 1

II MW-6DB 1 1 1 MW-6SB 1 1 1 MW-8DB 1 1 1 MW-8SB 1 1 1

II PW-207 1 SEEP-1 1 SUBTOTAL - RESIDENTIAL 44 25 0 2 0 3 0 SUBTOTAL - MONITORING 22 48 41 15 15 15 1

Total 3 66 73 41 17 15 18 1

I Included in most recent data

I Notes 1 - Overburden well not included in most recent data for plotting

2 - Tetrahydrofuran and 2-Butanone were the only two compounds detected in this well and are thought to be the result of well repair not included in most recent data for plotting

3 - Not included in most recent data for plotting

2004 Sampling

WC-58 Sep-04

1

1 1

1 1

1 1 1

1

1 1

1 1 1 1 1 1 1 1 1

1 1

1

0 29

29

Groundwatef Sampling Location Summary 1999 - 2004xls

I

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

monitoring well Figure 4-14 total VOC contour (ugl) - December 1999January 2000 Distribution of Total VOCs in

Note SW-113 is located downstream of SEEP-1 Shallow Bedrock Groundwater total concentration of detected VOCs ND= not detected these two locations were sampled during the Pre-ROD Sampling Event

Baseline Sampling Event in OctoberNovember 1999 Hows Corner Superfund Site Surface Water Sampling Location A Plymouth Maine Seep Sampling Location laquo- WOODARD ampCURRAN

995037wipri reportepa ri interim final feb 2001cadd drawingsfinalfig 4-14

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

0 300 600 I

FEET

Q residential well Figure 4-16 monitoring well Distribution of Total VOCs in

Deep Bedrock Groundwater total VOCs contour (ugl) Pre-ROD Sampling Event

active residential wells with lot number Hows Corner Superfund Site 2deg42deg Plymouth Maine total concentration of detected VOCs ND= not detected WOODARD ampCURRAN Enyinaaring bull Science bull Operations bull

995037wipri reportepa ri interim final feb 2001cadd drawingsfinalfig4mdash16

PLYMOUTH POND

PLYMOUTH POND

1 628Tl7MW-2bB 12135

PLYMOUTH POND

monitoring well Figure 4-20

V total VOC contour (ugl) - June 2000 Distribution of Total VOCs in Shallow Bedrock Groundwater

| 34 | total concentration of detected VOCs ND= not detected NA = not analyzed Supplemental Sampling Event Note SW-113 is located downstream of SEEP-1 Hows Corner Superfund Site

Surface Water Sampling Location these two locations were sampled during the Plymouth Maine Baseline Sampling Event in OctoberNovember 1999 Seep Sampling Location WOODARD amp CURRAN

Engineering bull Science - Operations bull 995037wipri reportepa ri interim final feb 2001 cadd drawingsfinalfig 4-20

residential well Figure 4-22 Distribution of Total VOCs in

monitoring well Deep Bedrock Groundwater

total VOCs contour (ugl) Supplemental Sampling Event

Hows Corner Superfund Site

total concentration of detected VOCs ND= not detected NA = not analyzed Plymouth Maine

WOODARD amp CURRAN

995037wipri reportepa-ri interim final feb 2001cadd drawingsfinalfig 4-22 Engineering bull Science - Operations bull

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

FEET

Shallow Monitoring Well

Deep Monitoring Well

C Detected Concentration ND = Not Detected Figure 1-XS Distribution of Total VOCs in Shallow Bedrock Groundwater

Pumping Well

17-Acre Property Boundary Concentration Contour (ugl)

June 2001 Hows Corner Superfund Site

Plymouth Maine WOODARDampCURRAN

-i^rhvj bull Scbncn bull Operations bull 211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0601 dwg04-20-05

PLYMOUTH POND Hopkins Road V

O

PLYMOUTH POND

PLYMOUTH POND

o

0 300 600 mdashfa FEET

Shallow Monitoring Well bull bull - 17-Acre Property Boundary Figure 1-XD

Deep Monitoring Well 1 I Detected Concentration ND = Not Detected Distribution of Total VOCs in Deep Bedrock Groundwater

-mf- Pumping Well June 2001 Residential Well Hows Corner Superfund Site

Plymouth Maine i h Surface Water Sampling Point

g WOODARD ampCURRAN _ ^ _ ^ _ _ yen_ rj i|Hlaquorlny bull Science bull Opt

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0601 dwg04-20-05

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

Shallow Monitoring Well

Deep Monitoring Well

Detected Concentration ND = Not Detected Figure 1-YS Distribution of Total VOCs in Shallow Bedrock Groundwater

Pumping Well

17-Acre Property Boundary Concentration Contour (ugl)

January 2002 Hows Corner Superfund Site

Plymouth Maine WOODARD amp CURRAN Engineering Science- Operations bull

211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0102dwg04-20-05

PLYMOUTH POND

PLYMOUTH POND

Site Pand^ laquoum-laquoBTuitaraquo tLV

vVlf-(

PLYMOUTH POND

0 300 600 ^ = FEET

Shallow Monitoring Well mdashbullbullbull 17-Acre Property Boundary Figure 1-YD - A - Deep Monitoring Well FT Detected Concentration ND = Not Detected Distribution of Total VOCs in

Deep Bedrock Groundwater Pumping Well January 2002 Residential Well Hows Corner Superfund Site

Plymouth Maine Surface Water Sampling Point

WOODARD ampCURRAN Engineering Sciencs- Operations bulli Si

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0102dwg04-20-05

- m j

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND j A O-shy

Shallow Monitoring Well E Detected Concentration ND = Not Detected Figure 1-ZS Distribution of Total VOCs in

Deep Monitoring Well Shallow Bedrock Groundwater

Pumping Well Hows Corner

April 2003 Superfund Site

17-Acre Property Boundary Plymouth Maine Concentration Contour (ugl) r WOODARD ampCURRAN

Engineering bull Science bull Operations bull 211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0403dwg04-20-05

s S pound

PLYMOUTH POND

PLYMOUTH POND

- -

5 PLYMOUTH POND

Jo

FEET

ft Shallow Monitoring Well mdashbullbullmdash 17-Acre Property Boundary Figure 1-ZD Deep Monitoring Well I 1 I Detected Concentration ND = Not Detected Distribution of Total VOCs in

Deep Bedrock Groundwater Pumping Well April 2003

Q) Residential Well Hows Corner Superfund Site Plymouth Maine

(T) Surface Water Sampling Point WOODARD ampCURRAN poundKk EnginawtirKj bull Science - Operations bull

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0403dwg04-20-05

0 Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

B MW-1B

I 12000

PCE

B 10000 Total VOCs

I

i 2000

i 0 Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

c MW-3B

G 2000

1800

B PCE

1600 Total VOCs

1 I I E

il-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

G E

211941

El

I I z E

80

Concentration Trends shy Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-13DB

Total VOCs

c i i c o

Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

MW-16DB

30

c i c c I c o

Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99

PCE

Total VOCs

Jul-01 Jul-03

211941

O bi

c Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

I MW-16IB

i 35

3

c Total VOCs

lt- 2 5

0 | gt

o

1 sectI

c c 0 4

Jul-90 Jul-92 Jul-94 Jul-96 Jul-98 Jul-00 Jul-02 Jul-04

I I MW-108D

I 12

PCE 10

Total VOCs c oc 3

E E I 0

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

E 211941

c Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

fi MW-108S

I I 40

PCE 35

Total VOCs

30

I f 26

20 I o

I 15

10

c Dec-99 Dec-00 Dec-01 Dec-02 Dec-03 I 0

I MW-112D

c 35 - imdash

I A3 shyTotal VOCs

o c

E 1 2

I

ition

B 1 ^

-i c 3

0 Dec-99 Dec-OO Dec-01 Dec-02 Dec-03

211941

I

i

I

cII

Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-112S

08

PCE

Total VOCs 06

o 04

02

0 Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

MW-114D

o

12000

10000

8000

6000

PCE

Total VOCs

4000

2000

i

ccEIIc

i

i

E

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

211941

Con

cent

ratio

n (

ug

l)

E Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

I MW-114S

E A5000 -- Total VOCs

- 4000

0 3000

2000

i 1000

i n shy

Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

MW-115D

c PCE

Total VOCs

c E

o

C c

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03 I 0

211941

IepoundII

EIEIIGICCIccc

30000

25000

20000

o bullsect 15000 b

o 10000 U

5000

0 Aug-99

25000

20000

5000

0 Aug-99

211941

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-2DB

PCE

Total VOCs

Aug-01 Aug-03

MW-2IB

PCE

Total VOCs

Aug-01 Aug-03

IDIBI

ii EIDIISIBIG C

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-102S

6000

5000 PCE

Total VOCs

4000

O 3000

2000

1000

0 Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

MW-103D

16000

~ 14000 ugt 3- 12000 o

^ 10000

sect 8000

O 6000

4000

2000

PCE

Total VOCs

0Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

211941

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

G MW-103S

I I

ampo

12000

10000

E sectc

S

8000

6000

4000

2000

0Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

G I 6000

MW-104D

i 5000

PCE

Total VOCs

i i c

2000

1000

Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

E I

211941

cIccIG

IIBCccBcIc

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-1041

PCE Total VOCs

a 25000

0 20000

a 15000

10000

5000

0 Jan-OO Jan-01 Jan-02 Jan-03 Jan-04

MW-106D

3000

2500 PCE

Total VOCs

=sect 2000

o bullsect 1500

1000

500

0 Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

211941

c Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

c MW-106S

I PCE

Total VOCs

i

i Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

i

i i i E

C

211941 c

Response to EPA-DEP Comment 5 Dated March 312005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

iiw

EPA-DEP Comment 5

Comment 5 Matrix Diffusion The report as well as other proponents of matrix diffusion suggest that depletion of DNAPL (Section 5112 page 5-15) needs to be achieved While that might be the ideal the goal is to achieve performance standards and that goal may be attainable while there is residual contamination in the rock perhaps even DNAPL globules The low bedrock matrix porosity (page 1-15) the high permeability values (page 4-4) the relative flux of the groundwater (page 5-5) and the decrease in surface area and out of the mainstream pockets (appendix C-4) all suggest that the diffusion out of the rock matrix would be insubstantial relative to the regional flux of groundwater through the Site

Response The TI Evaluation Report does not explicitly consider or rely upon matrix diffusion as a basis for requesting a TI Waiver for a portion of the Hows Corner Site The technical literature provides documentation that matrix diffusion can be a significant process that affects chemical transport and groundwater remediation timeframes in unconsolidated and consolidated media including fractured rock (US EPA 1989 Freeze and Cherry 1979 Pankow and Cherry 1996 Fountain 1998) Back diffusion of contaminants from the matrix porosity of the fractured rock can prolong the time necessary to achieve groundwater cleanup goals particularly for compounds such as PCE for which the cleanup goal is a low concentration It is our expectation that matrix diffusion has occurred at the Hows Corner Site and that back diffusion of PCE from the rock matrix will also occur Although the extent to which matrix diffusion is occurring at the Hows Comer Site has not been determined and that lack of knowledge contributes to uncertainty regarding the cleanup times at the Site the effect of matrix diffusion is to lengthen rather than shorten the time required for remediation

REFERENCES

Fountain JC 1998 Technologies for Dense Nonaqueous Phase Liquid Source Zone Remediation Ground-Water Remediation Technologies Analysis Center Technology Evaluation Report TE-98-02 December

Freeze RA and Cherry JA 1979 Groundwater Prentice-Hall Inc Englewood Cliffs NJ 07632 p 410-412

Pankow J F and Cherry J A 1996 Dense Chlorinated Solvents Waterloo Press Portland OR 97291-1399 p 67-88

US EPA 1989 Transport and Fate of Contaminants in the Subsurface EPA6254-89019 p 17-18

Response to EPA Comment 5 050305doc 1 of 1 Woodard amp Curran (211941)

WOODARD amp CURRAN Maine Massachusetts New Hampshire Connecticut Florida Operational offices across the US 1-800-426-4262 www woodardcurran com

Page 48: SDMS DocID 251749 - Records Collections · 2020-06-13 · CORPORATE OFFICES: Maine, Massachusetts, New Hampshire, Connecticut New, York, Florida Engineering • Science • Operations

Sampling Events 1999-2004

Hows Corner Super-fund Site Plymouth Maine

Supplemental 2001 2002 2003 Pumping Event Baseline Pre-ROD Rl Sampling Sampling Sampling Test

Case ID WC-01 WC-01 WC-03 WC-09 WC-25 WC-30 WC-42B WC-56

ll

Well Date Aug-99 Oct-99 Dec-99 May-00 Jun-01 Jan-02 Apr-03 Sep-04 MW-106S 1 1 1 1 1 MW-107D 1 1 MW-108D 1 1 1 1 1 MW-108S 1 1 1 1 1 MW-110D 1 1 MW-111D 1 1 MW-112D 1 1 1 1 1 MW-112S 1 1 1 1 1 MW-113D 1 1 MW-114D 1 1 1 1 1 MW-114S 1 1 1 1 1 MW-115D 1 1 1 1 1 MW-12DB 1 1 1 MW-12SB 1 1 1 MW-13DB 1 1 1 1 1 1 MW-13SB 1 1 1 MW-14DB 1 1 MW-14SO 1 1 MW-15DB 1 1 1 MW-15SB 1 1 1 MW-16DB 1 1 1 1 1 1 MW-16IB 1 1 1 1 1 1 MW-16SO 1 1 MW-17DO 1 1 1 MW-17SO 1 1 1 MW-1B 1 1 1 1 1 1 MW-203D MW-203S MW-204D MW-204S MW-205 MW-206D

I MW-206S MW-2DB 1 1 MW-2DDB 1 1 MW-2IB 1 1 1 1 1 1 MW-3B 1 1 1 1 1 1

I MW-4O 1 1 1 MW-5B 1 1

II MW-6DB 1 1 1 MW-6SB 1 1 1 MW-8DB 1 1 1 MW-8SB 1 1 1

II PW-207 1 SEEP-1 1 SUBTOTAL - RESIDENTIAL 44 25 0 2 0 3 0 SUBTOTAL - MONITORING 22 48 41 15 15 15 1

Total 3 66 73 41 17 15 18 1

I Included in most recent data

I Notes 1 - Overburden well not included in most recent data for plotting

2 - Tetrahydrofuran and 2-Butanone were the only two compounds detected in this well and are thought to be the result of well repair not included in most recent data for plotting

3 - Not included in most recent data for plotting

2004 Sampling

WC-58 Sep-04

1

1 1

1 1

1 1 1

1

1 1

1 1 1 1 1 1 1 1 1

1 1

1

0 29

29

Groundwatef Sampling Location Summary 1999 - 2004xls

I

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

monitoring well Figure 4-14 total VOC contour (ugl) - December 1999January 2000 Distribution of Total VOCs in

Note SW-113 is located downstream of SEEP-1 Shallow Bedrock Groundwater total concentration of detected VOCs ND= not detected these two locations were sampled during the Pre-ROD Sampling Event

Baseline Sampling Event in OctoberNovember 1999 Hows Corner Superfund Site Surface Water Sampling Location A Plymouth Maine Seep Sampling Location laquo- WOODARD ampCURRAN

995037wipri reportepa ri interim final feb 2001cadd drawingsfinalfig 4-14

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

0 300 600 I

FEET

Q residential well Figure 4-16 monitoring well Distribution of Total VOCs in

Deep Bedrock Groundwater total VOCs contour (ugl) Pre-ROD Sampling Event

active residential wells with lot number Hows Corner Superfund Site 2deg42deg Plymouth Maine total concentration of detected VOCs ND= not detected WOODARD ampCURRAN Enyinaaring bull Science bull Operations bull

995037wipri reportepa ri interim final feb 2001cadd drawingsfinalfig4mdash16

PLYMOUTH POND

PLYMOUTH POND

1 628Tl7MW-2bB 12135

PLYMOUTH POND

monitoring well Figure 4-20

V total VOC contour (ugl) - June 2000 Distribution of Total VOCs in Shallow Bedrock Groundwater

| 34 | total concentration of detected VOCs ND= not detected NA = not analyzed Supplemental Sampling Event Note SW-113 is located downstream of SEEP-1 Hows Corner Superfund Site

Surface Water Sampling Location these two locations were sampled during the Plymouth Maine Baseline Sampling Event in OctoberNovember 1999 Seep Sampling Location WOODARD amp CURRAN

Engineering bull Science - Operations bull 995037wipri reportepa ri interim final feb 2001 cadd drawingsfinalfig 4-20

residential well Figure 4-22 Distribution of Total VOCs in

monitoring well Deep Bedrock Groundwater

total VOCs contour (ugl) Supplemental Sampling Event

Hows Corner Superfund Site

total concentration of detected VOCs ND= not detected NA = not analyzed Plymouth Maine

WOODARD amp CURRAN

995037wipri reportepa-ri interim final feb 2001cadd drawingsfinalfig 4-22 Engineering bull Science - Operations bull

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

FEET

Shallow Monitoring Well

Deep Monitoring Well

C Detected Concentration ND = Not Detected Figure 1-XS Distribution of Total VOCs in Shallow Bedrock Groundwater

Pumping Well

17-Acre Property Boundary Concentration Contour (ugl)

June 2001 Hows Corner Superfund Site

Plymouth Maine WOODARDampCURRAN

-i^rhvj bull Scbncn bull Operations bull 211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0601 dwg04-20-05

PLYMOUTH POND Hopkins Road V

O

PLYMOUTH POND

PLYMOUTH POND

o

0 300 600 mdashfa FEET

Shallow Monitoring Well bull bull - 17-Acre Property Boundary Figure 1-XD

Deep Monitoring Well 1 I Detected Concentration ND = Not Detected Distribution of Total VOCs in Deep Bedrock Groundwater

-mf- Pumping Well June 2001 Residential Well Hows Corner Superfund Site

Plymouth Maine i h Surface Water Sampling Point

g WOODARD ampCURRAN _ ^ _ ^ _ _ yen_ rj i|Hlaquorlny bull Science bull Opt

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0601 dwg04-20-05

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

Shallow Monitoring Well

Deep Monitoring Well

Detected Concentration ND = Not Detected Figure 1-YS Distribution of Total VOCs in Shallow Bedrock Groundwater

Pumping Well

17-Acre Property Boundary Concentration Contour (ugl)

January 2002 Hows Corner Superfund Site

Plymouth Maine WOODARD amp CURRAN Engineering Science- Operations bull

211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0102dwg04-20-05

PLYMOUTH POND

PLYMOUTH POND

Site Pand^ laquoum-laquoBTuitaraquo tLV

vVlf-(

PLYMOUTH POND

0 300 600 ^ = FEET

Shallow Monitoring Well mdashbullbullbull 17-Acre Property Boundary Figure 1-YD - A - Deep Monitoring Well FT Detected Concentration ND = Not Detected Distribution of Total VOCs in

Deep Bedrock Groundwater Pumping Well January 2002 Residential Well Hows Corner Superfund Site

Plymouth Maine Surface Water Sampling Point

WOODARD ampCURRAN Engineering Sciencs- Operations bulli Si

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0102dwg04-20-05

- m j

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND j A O-shy

Shallow Monitoring Well E Detected Concentration ND = Not Detected Figure 1-ZS Distribution of Total VOCs in

Deep Monitoring Well Shallow Bedrock Groundwater

Pumping Well Hows Corner

April 2003 Superfund Site

17-Acre Property Boundary Plymouth Maine Concentration Contour (ugl) r WOODARD ampCURRAN

Engineering bull Science bull Operations bull 211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0403dwg04-20-05

s S pound

PLYMOUTH POND

PLYMOUTH POND

- -

5 PLYMOUTH POND

Jo

FEET

ft Shallow Monitoring Well mdashbullbullmdash 17-Acre Property Boundary Figure 1-ZD Deep Monitoring Well I 1 I Detected Concentration ND = Not Detected Distribution of Total VOCs in

Deep Bedrock Groundwater Pumping Well April 2003

Q) Residential Well Hows Corner Superfund Site Plymouth Maine

(T) Surface Water Sampling Point WOODARD ampCURRAN poundKk EnginawtirKj bull Science - Operations bull

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0403dwg04-20-05

0 Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

B MW-1B

I 12000

PCE

B 10000 Total VOCs

I

i 2000

i 0 Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

c MW-3B

G 2000

1800

B PCE

1600 Total VOCs

1 I I E

il-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

G E

211941

El

I I z E

80

Concentration Trends shy Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-13DB

Total VOCs

c i i c o

Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

MW-16DB

30

c i c c I c o

Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99

PCE

Total VOCs

Jul-01 Jul-03

211941

O bi

c Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

I MW-16IB

i 35

3

c Total VOCs

lt- 2 5

0 | gt

o

1 sectI

c c 0 4

Jul-90 Jul-92 Jul-94 Jul-96 Jul-98 Jul-00 Jul-02 Jul-04

I I MW-108D

I 12

PCE 10

Total VOCs c oc 3

E E I 0

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

E 211941

c Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

fi MW-108S

I I 40

PCE 35

Total VOCs

30

I f 26

20 I o

I 15

10

c Dec-99 Dec-00 Dec-01 Dec-02 Dec-03 I 0

I MW-112D

c 35 - imdash

I A3 shyTotal VOCs

o c

E 1 2

I

ition

B 1 ^

-i c 3

0 Dec-99 Dec-OO Dec-01 Dec-02 Dec-03

211941

I

i

I

cII

Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-112S

08

PCE

Total VOCs 06

o 04

02

0 Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

MW-114D

o

12000

10000

8000

6000

PCE

Total VOCs

4000

2000

i

ccEIIc

i

i

E

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

211941

Con

cent

ratio

n (

ug

l)

E Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

I MW-114S

E A5000 -- Total VOCs

- 4000

0 3000

2000

i 1000

i n shy

Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

MW-115D

c PCE

Total VOCs

c E

o

C c

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03 I 0

211941

IepoundII

EIEIIGICCIccc

30000

25000

20000

o bullsect 15000 b

o 10000 U

5000

0 Aug-99

25000

20000

5000

0 Aug-99

211941

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-2DB

PCE

Total VOCs

Aug-01 Aug-03

MW-2IB

PCE

Total VOCs

Aug-01 Aug-03

IDIBI

ii EIDIISIBIG C

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-102S

6000

5000 PCE

Total VOCs

4000

O 3000

2000

1000

0 Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

MW-103D

16000

~ 14000 ugt 3- 12000 o

^ 10000

sect 8000

O 6000

4000

2000

PCE

Total VOCs

0Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

211941

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

G MW-103S

I I

ampo

12000

10000

E sectc

S

8000

6000

4000

2000

0Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

G I 6000

MW-104D

i 5000

PCE

Total VOCs

i i c

2000

1000

Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

E I

211941

cIccIG

IIBCccBcIc

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-1041

PCE Total VOCs

a 25000

0 20000

a 15000

10000

5000

0 Jan-OO Jan-01 Jan-02 Jan-03 Jan-04

MW-106D

3000

2500 PCE

Total VOCs

=sect 2000

o bullsect 1500

1000

500

0 Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

211941

c Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

c MW-106S

I PCE

Total VOCs

i

i Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

i

i i i E

C

211941 c

Response to EPA-DEP Comment 5 Dated March 312005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

iiw

EPA-DEP Comment 5

Comment 5 Matrix Diffusion The report as well as other proponents of matrix diffusion suggest that depletion of DNAPL (Section 5112 page 5-15) needs to be achieved While that might be the ideal the goal is to achieve performance standards and that goal may be attainable while there is residual contamination in the rock perhaps even DNAPL globules The low bedrock matrix porosity (page 1-15) the high permeability values (page 4-4) the relative flux of the groundwater (page 5-5) and the decrease in surface area and out of the mainstream pockets (appendix C-4) all suggest that the diffusion out of the rock matrix would be insubstantial relative to the regional flux of groundwater through the Site

Response The TI Evaluation Report does not explicitly consider or rely upon matrix diffusion as a basis for requesting a TI Waiver for a portion of the Hows Corner Site The technical literature provides documentation that matrix diffusion can be a significant process that affects chemical transport and groundwater remediation timeframes in unconsolidated and consolidated media including fractured rock (US EPA 1989 Freeze and Cherry 1979 Pankow and Cherry 1996 Fountain 1998) Back diffusion of contaminants from the matrix porosity of the fractured rock can prolong the time necessary to achieve groundwater cleanup goals particularly for compounds such as PCE for which the cleanup goal is a low concentration It is our expectation that matrix diffusion has occurred at the Hows Corner Site and that back diffusion of PCE from the rock matrix will also occur Although the extent to which matrix diffusion is occurring at the Hows Comer Site has not been determined and that lack of knowledge contributes to uncertainty regarding the cleanup times at the Site the effect of matrix diffusion is to lengthen rather than shorten the time required for remediation

REFERENCES

Fountain JC 1998 Technologies for Dense Nonaqueous Phase Liquid Source Zone Remediation Ground-Water Remediation Technologies Analysis Center Technology Evaluation Report TE-98-02 December

Freeze RA and Cherry JA 1979 Groundwater Prentice-Hall Inc Englewood Cliffs NJ 07632 p 410-412

Pankow J F and Cherry J A 1996 Dense Chlorinated Solvents Waterloo Press Portland OR 97291-1399 p 67-88

US EPA 1989 Transport and Fate of Contaminants in the Subsurface EPA6254-89019 p 17-18

Response to EPA Comment 5 050305doc 1 of 1 Woodard amp Curran (211941)

WOODARD amp CURRAN Maine Massachusetts New Hampshire Connecticut Florida Operational offices across the US 1-800-426-4262 www woodardcurran com

Page 49: SDMS DocID 251749 - Records Collections · 2020-06-13 · CORPORATE OFFICES: Maine, Massachusetts, New Hampshire, Connecticut New, York, Florida Engineering • Science • Operations

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

monitoring well Figure 4-14 total VOC contour (ugl) - December 1999January 2000 Distribution of Total VOCs in

Note SW-113 is located downstream of SEEP-1 Shallow Bedrock Groundwater total concentration of detected VOCs ND= not detected these two locations were sampled during the Pre-ROD Sampling Event

Baseline Sampling Event in OctoberNovember 1999 Hows Corner Superfund Site Surface Water Sampling Location A Plymouth Maine Seep Sampling Location laquo- WOODARD ampCURRAN

995037wipri reportepa ri interim final feb 2001cadd drawingsfinalfig 4-14

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

0 300 600 I

FEET

Q residential well Figure 4-16 monitoring well Distribution of Total VOCs in

Deep Bedrock Groundwater total VOCs contour (ugl) Pre-ROD Sampling Event

active residential wells with lot number Hows Corner Superfund Site 2deg42deg Plymouth Maine total concentration of detected VOCs ND= not detected WOODARD ampCURRAN Enyinaaring bull Science bull Operations bull

995037wipri reportepa ri interim final feb 2001cadd drawingsfinalfig4mdash16

PLYMOUTH POND

PLYMOUTH POND

1 628Tl7MW-2bB 12135

PLYMOUTH POND

monitoring well Figure 4-20

V total VOC contour (ugl) - June 2000 Distribution of Total VOCs in Shallow Bedrock Groundwater

| 34 | total concentration of detected VOCs ND= not detected NA = not analyzed Supplemental Sampling Event Note SW-113 is located downstream of SEEP-1 Hows Corner Superfund Site

Surface Water Sampling Location these two locations were sampled during the Plymouth Maine Baseline Sampling Event in OctoberNovember 1999 Seep Sampling Location WOODARD amp CURRAN

Engineering bull Science - Operations bull 995037wipri reportepa ri interim final feb 2001 cadd drawingsfinalfig 4-20

residential well Figure 4-22 Distribution of Total VOCs in

monitoring well Deep Bedrock Groundwater

total VOCs contour (ugl) Supplemental Sampling Event

Hows Corner Superfund Site

total concentration of detected VOCs ND= not detected NA = not analyzed Plymouth Maine

WOODARD amp CURRAN

995037wipri reportepa-ri interim final feb 2001cadd drawingsfinalfig 4-22 Engineering bull Science - Operations bull

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

FEET

Shallow Monitoring Well

Deep Monitoring Well

C Detected Concentration ND = Not Detected Figure 1-XS Distribution of Total VOCs in Shallow Bedrock Groundwater

Pumping Well

17-Acre Property Boundary Concentration Contour (ugl)

June 2001 Hows Corner Superfund Site

Plymouth Maine WOODARDampCURRAN

-i^rhvj bull Scbncn bull Operations bull 211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0601 dwg04-20-05

PLYMOUTH POND Hopkins Road V

O

PLYMOUTH POND

PLYMOUTH POND

o

0 300 600 mdashfa FEET

Shallow Monitoring Well bull bull - 17-Acre Property Boundary Figure 1-XD

Deep Monitoring Well 1 I Detected Concentration ND = Not Detected Distribution of Total VOCs in Deep Bedrock Groundwater

-mf- Pumping Well June 2001 Residential Well Hows Corner Superfund Site

Plymouth Maine i h Surface Water Sampling Point

g WOODARD ampCURRAN _ ^ _ ^ _ _ yen_ rj i|Hlaquorlny bull Science bull Opt

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0601 dwg04-20-05

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

Shallow Monitoring Well

Deep Monitoring Well

Detected Concentration ND = Not Detected Figure 1-YS Distribution of Total VOCs in Shallow Bedrock Groundwater

Pumping Well

17-Acre Property Boundary Concentration Contour (ugl)

January 2002 Hows Corner Superfund Site

Plymouth Maine WOODARD amp CURRAN Engineering Science- Operations bull

211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0102dwg04-20-05

PLYMOUTH POND

PLYMOUTH POND

Site Pand^ laquoum-laquoBTuitaraquo tLV

vVlf-(

PLYMOUTH POND

0 300 600 ^ = FEET

Shallow Monitoring Well mdashbullbullbull 17-Acre Property Boundary Figure 1-YD - A - Deep Monitoring Well FT Detected Concentration ND = Not Detected Distribution of Total VOCs in

Deep Bedrock Groundwater Pumping Well January 2002 Residential Well Hows Corner Superfund Site

Plymouth Maine Surface Water Sampling Point

WOODARD ampCURRAN Engineering Sciencs- Operations bulli Si

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0102dwg04-20-05

- m j

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND j A O-shy

Shallow Monitoring Well E Detected Concentration ND = Not Detected Figure 1-ZS Distribution of Total VOCs in

Deep Monitoring Well Shallow Bedrock Groundwater

Pumping Well Hows Corner

April 2003 Superfund Site

17-Acre Property Boundary Plymouth Maine Concentration Contour (ugl) r WOODARD ampCURRAN

Engineering bull Science bull Operations bull 211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0403dwg04-20-05

s S pound

PLYMOUTH POND

PLYMOUTH POND

- -

5 PLYMOUTH POND

Jo

FEET

ft Shallow Monitoring Well mdashbullbullmdash 17-Acre Property Boundary Figure 1-ZD Deep Monitoring Well I 1 I Detected Concentration ND = Not Detected Distribution of Total VOCs in

Deep Bedrock Groundwater Pumping Well April 2003

Q) Residential Well Hows Corner Superfund Site Plymouth Maine

(T) Surface Water Sampling Point WOODARD ampCURRAN poundKk EnginawtirKj bull Science - Operations bull

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0403dwg04-20-05

0 Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

B MW-1B

I 12000

PCE

B 10000 Total VOCs

I

i 2000

i 0 Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

c MW-3B

G 2000

1800

B PCE

1600 Total VOCs

1 I I E

il-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

G E

211941

El

I I z E

80

Concentration Trends shy Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-13DB

Total VOCs

c i i c o

Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

MW-16DB

30

c i c c I c o

Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99

PCE

Total VOCs

Jul-01 Jul-03

211941

O bi

c Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

I MW-16IB

i 35

3

c Total VOCs

lt- 2 5

0 | gt

o

1 sectI

c c 0 4

Jul-90 Jul-92 Jul-94 Jul-96 Jul-98 Jul-00 Jul-02 Jul-04

I I MW-108D

I 12

PCE 10

Total VOCs c oc 3

E E I 0

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

E 211941

c Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

fi MW-108S

I I 40

PCE 35

Total VOCs

30

I f 26

20 I o

I 15

10

c Dec-99 Dec-00 Dec-01 Dec-02 Dec-03 I 0

I MW-112D

c 35 - imdash

I A3 shyTotal VOCs

o c

E 1 2

I

ition

B 1 ^

-i c 3

0 Dec-99 Dec-OO Dec-01 Dec-02 Dec-03

211941

I

i

I

cII

Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-112S

08

PCE

Total VOCs 06

o 04

02

0 Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

MW-114D

o

12000

10000

8000

6000

PCE

Total VOCs

4000

2000

i

ccEIIc

i

i

E

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

211941

Con

cent

ratio

n (

ug

l)

E Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

I MW-114S

E A5000 -- Total VOCs

- 4000

0 3000

2000

i 1000

i n shy

Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

MW-115D

c PCE

Total VOCs

c E

o

C c

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03 I 0

211941

IepoundII

EIEIIGICCIccc

30000

25000

20000

o bullsect 15000 b

o 10000 U

5000

0 Aug-99

25000

20000

5000

0 Aug-99

211941

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-2DB

PCE

Total VOCs

Aug-01 Aug-03

MW-2IB

PCE

Total VOCs

Aug-01 Aug-03

IDIBI

ii EIDIISIBIG C

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-102S

6000

5000 PCE

Total VOCs

4000

O 3000

2000

1000

0 Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

MW-103D

16000

~ 14000 ugt 3- 12000 o

^ 10000

sect 8000

O 6000

4000

2000

PCE

Total VOCs

0Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

211941

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

G MW-103S

I I

ampo

12000

10000

E sectc

S

8000

6000

4000

2000

0Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

G I 6000

MW-104D

i 5000

PCE

Total VOCs

i i c

2000

1000

Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

E I

211941

cIccIG

IIBCccBcIc

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-1041

PCE Total VOCs

a 25000

0 20000

a 15000

10000

5000

0 Jan-OO Jan-01 Jan-02 Jan-03 Jan-04

MW-106D

3000

2500 PCE

Total VOCs

=sect 2000

o bullsect 1500

1000

500

0 Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

211941

c Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

c MW-106S

I PCE

Total VOCs

i

i Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

i

i i i E

C

211941 c

Response to EPA-DEP Comment 5 Dated March 312005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

iiw

EPA-DEP Comment 5

Comment 5 Matrix Diffusion The report as well as other proponents of matrix diffusion suggest that depletion of DNAPL (Section 5112 page 5-15) needs to be achieved While that might be the ideal the goal is to achieve performance standards and that goal may be attainable while there is residual contamination in the rock perhaps even DNAPL globules The low bedrock matrix porosity (page 1-15) the high permeability values (page 4-4) the relative flux of the groundwater (page 5-5) and the decrease in surface area and out of the mainstream pockets (appendix C-4) all suggest that the diffusion out of the rock matrix would be insubstantial relative to the regional flux of groundwater through the Site

Response The TI Evaluation Report does not explicitly consider or rely upon matrix diffusion as a basis for requesting a TI Waiver for a portion of the Hows Corner Site The technical literature provides documentation that matrix diffusion can be a significant process that affects chemical transport and groundwater remediation timeframes in unconsolidated and consolidated media including fractured rock (US EPA 1989 Freeze and Cherry 1979 Pankow and Cherry 1996 Fountain 1998) Back diffusion of contaminants from the matrix porosity of the fractured rock can prolong the time necessary to achieve groundwater cleanup goals particularly for compounds such as PCE for which the cleanup goal is a low concentration It is our expectation that matrix diffusion has occurred at the Hows Corner Site and that back diffusion of PCE from the rock matrix will also occur Although the extent to which matrix diffusion is occurring at the Hows Comer Site has not been determined and that lack of knowledge contributes to uncertainty regarding the cleanup times at the Site the effect of matrix diffusion is to lengthen rather than shorten the time required for remediation

REFERENCES

Fountain JC 1998 Technologies for Dense Nonaqueous Phase Liquid Source Zone Remediation Ground-Water Remediation Technologies Analysis Center Technology Evaluation Report TE-98-02 December

Freeze RA and Cherry JA 1979 Groundwater Prentice-Hall Inc Englewood Cliffs NJ 07632 p 410-412

Pankow J F and Cherry J A 1996 Dense Chlorinated Solvents Waterloo Press Portland OR 97291-1399 p 67-88

US EPA 1989 Transport and Fate of Contaminants in the Subsurface EPA6254-89019 p 17-18

Response to EPA Comment 5 050305doc 1 of 1 Woodard amp Curran (211941)

WOODARD amp CURRAN Maine Massachusetts New Hampshire Connecticut Florida Operational offices across the US 1-800-426-4262 www woodardcurran com

Page 50: SDMS DocID 251749 - Records Collections · 2020-06-13 · CORPORATE OFFICES: Maine, Massachusetts, New Hampshire, Connecticut New, York, Florida Engineering • Science • Operations

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

0 300 600 I

FEET

Q residential well Figure 4-16 monitoring well Distribution of Total VOCs in

Deep Bedrock Groundwater total VOCs contour (ugl) Pre-ROD Sampling Event

active residential wells with lot number Hows Corner Superfund Site 2deg42deg Plymouth Maine total concentration of detected VOCs ND= not detected WOODARD ampCURRAN Enyinaaring bull Science bull Operations bull

995037wipri reportepa ri interim final feb 2001cadd drawingsfinalfig4mdash16

PLYMOUTH POND

PLYMOUTH POND

1 628Tl7MW-2bB 12135

PLYMOUTH POND

monitoring well Figure 4-20

V total VOC contour (ugl) - June 2000 Distribution of Total VOCs in Shallow Bedrock Groundwater

| 34 | total concentration of detected VOCs ND= not detected NA = not analyzed Supplemental Sampling Event Note SW-113 is located downstream of SEEP-1 Hows Corner Superfund Site

Surface Water Sampling Location these two locations were sampled during the Plymouth Maine Baseline Sampling Event in OctoberNovember 1999 Seep Sampling Location WOODARD amp CURRAN

Engineering bull Science - Operations bull 995037wipri reportepa ri interim final feb 2001 cadd drawingsfinalfig 4-20

residential well Figure 4-22 Distribution of Total VOCs in

monitoring well Deep Bedrock Groundwater

total VOCs contour (ugl) Supplemental Sampling Event

Hows Corner Superfund Site

total concentration of detected VOCs ND= not detected NA = not analyzed Plymouth Maine

WOODARD amp CURRAN

995037wipri reportepa-ri interim final feb 2001cadd drawingsfinalfig 4-22 Engineering bull Science - Operations bull

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

FEET

Shallow Monitoring Well

Deep Monitoring Well

C Detected Concentration ND = Not Detected Figure 1-XS Distribution of Total VOCs in Shallow Bedrock Groundwater

Pumping Well

17-Acre Property Boundary Concentration Contour (ugl)

June 2001 Hows Corner Superfund Site

Plymouth Maine WOODARDampCURRAN

-i^rhvj bull Scbncn bull Operations bull 211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0601 dwg04-20-05

PLYMOUTH POND Hopkins Road V

O

PLYMOUTH POND

PLYMOUTH POND

o

0 300 600 mdashfa FEET

Shallow Monitoring Well bull bull - 17-Acre Property Boundary Figure 1-XD

Deep Monitoring Well 1 I Detected Concentration ND = Not Detected Distribution of Total VOCs in Deep Bedrock Groundwater

-mf- Pumping Well June 2001 Residential Well Hows Corner Superfund Site

Plymouth Maine i h Surface Water Sampling Point

g WOODARD ampCURRAN _ ^ _ ^ _ _ yen_ rj i|Hlaquorlny bull Science bull Opt

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0601 dwg04-20-05

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

Shallow Monitoring Well

Deep Monitoring Well

Detected Concentration ND = Not Detected Figure 1-YS Distribution of Total VOCs in Shallow Bedrock Groundwater

Pumping Well

17-Acre Property Boundary Concentration Contour (ugl)

January 2002 Hows Corner Superfund Site

Plymouth Maine WOODARD amp CURRAN Engineering Science- Operations bull

211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0102dwg04-20-05

PLYMOUTH POND

PLYMOUTH POND

Site Pand^ laquoum-laquoBTuitaraquo tLV

vVlf-(

PLYMOUTH POND

0 300 600 ^ = FEET

Shallow Monitoring Well mdashbullbullbull 17-Acre Property Boundary Figure 1-YD - A - Deep Monitoring Well FT Detected Concentration ND = Not Detected Distribution of Total VOCs in

Deep Bedrock Groundwater Pumping Well January 2002 Residential Well Hows Corner Superfund Site

Plymouth Maine Surface Water Sampling Point

WOODARD ampCURRAN Engineering Sciencs- Operations bulli Si

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0102dwg04-20-05

- m j

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND j A O-shy

Shallow Monitoring Well E Detected Concentration ND = Not Detected Figure 1-ZS Distribution of Total VOCs in

Deep Monitoring Well Shallow Bedrock Groundwater

Pumping Well Hows Corner

April 2003 Superfund Site

17-Acre Property Boundary Plymouth Maine Concentration Contour (ugl) r WOODARD ampCURRAN

Engineering bull Science bull Operations bull 211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0403dwg04-20-05

s S pound

PLYMOUTH POND

PLYMOUTH POND

- -

5 PLYMOUTH POND

Jo

FEET

ft Shallow Monitoring Well mdashbullbullmdash 17-Acre Property Boundary Figure 1-ZD Deep Monitoring Well I 1 I Detected Concentration ND = Not Detected Distribution of Total VOCs in

Deep Bedrock Groundwater Pumping Well April 2003

Q) Residential Well Hows Corner Superfund Site Plymouth Maine

(T) Surface Water Sampling Point WOODARD ampCURRAN poundKk EnginawtirKj bull Science - Operations bull

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0403dwg04-20-05

0 Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

B MW-1B

I 12000

PCE

B 10000 Total VOCs

I

i 2000

i 0 Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

c MW-3B

G 2000

1800

B PCE

1600 Total VOCs

1 I I E

il-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

G E

211941

El

I I z E

80

Concentration Trends shy Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-13DB

Total VOCs

c i i c o

Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

MW-16DB

30

c i c c I c o

Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99

PCE

Total VOCs

Jul-01 Jul-03

211941

O bi

c Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

I MW-16IB

i 35

3

c Total VOCs

lt- 2 5

0 | gt

o

1 sectI

c c 0 4

Jul-90 Jul-92 Jul-94 Jul-96 Jul-98 Jul-00 Jul-02 Jul-04

I I MW-108D

I 12

PCE 10

Total VOCs c oc 3

E E I 0

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

E 211941

c Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

fi MW-108S

I I 40

PCE 35

Total VOCs

30

I f 26

20 I o

I 15

10

c Dec-99 Dec-00 Dec-01 Dec-02 Dec-03 I 0

I MW-112D

c 35 - imdash

I A3 shyTotal VOCs

o c

E 1 2

I

ition

B 1 ^

-i c 3

0 Dec-99 Dec-OO Dec-01 Dec-02 Dec-03

211941

I

i

I

cII

Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-112S

08

PCE

Total VOCs 06

o 04

02

0 Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

MW-114D

o

12000

10000

8000

6000

PCE

Total VOCs

4000

2000

i

ccEIIc

i

i

E

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

211941

Con

cent

ratio

n (

ug

l)

E Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

I MW-114S

E A5000 -- Total VOCs

- 4000

0 3000

2000

i 1000

i n shy

Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

MW-115D

c PCE

Total VOCs

c E

o

C c

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03 I 0

211941

IepoundII

EIEIIGICCIccc

30000

25000

20000

o bullsect 15000 b

o 10000 U

5000

0 Aug-99

25000

20000

5000

0 Aug-99

211941

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-2DB

PCE

Total VOCs

Aug-01 Aug-03

MW-2IB

PCE

Total VOCs

Aug-01 Aug-03

IDIBI

ii EIDIISIBIG C

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-102S

6000

5000 PCE

Total VOCs

4000

O 3000

2000

1000

0 Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

MW-103D

16000

~ 14000 ugt 3- 12000 o

^ 10000

sect 8000

O 6000

4000

2000

PCE

Total VOCs

0Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

211941

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

G MW-103S

I I

ampo

12000

10000

E sectc

S

8000

6000

4000

2000

0Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

G I 6000

MW-104D

i 5000

PCE

Total VOCs

i i c

2000

1000

Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

E I

211941

cIccIG

IIBCccBcIc

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-1041

PCE Total VOCs

a 25000

0 20000

a 15000

10000

5000

0 Jan-OO Jan-01 Jan-02 Jan-03 Jan-04

MW-106D

3000

2500 PCE

Total VOCs

=sect 2000

o bullsect 1500

1000

500

0 Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

211941

c Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

c MW-106S

I PCE

Total VOCs

i

i Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

i

i i i E

C

211941 c

Response to EPA-DEP Comment 5 Dated March 312005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

iiw

EPA-DEP Comment 5

Comment 5 Matrix Diffusion The report as well as other proponents of matrix diffusion suggest that depletion of DNAPL (Section 5112 page 5-15) needs to be achieved While that might be the ideal the goal is to achieve performance standards and that goal may be attainable while there is residual contamination in the rock perhaps even DNAPL globules The low bedrock matrix porosity (page 1-15) the high permeability values (page 4-4) the relative flux of the groundwater (page 5-5) and the decrease in surface area and out of the mainstream pockets (appendix C-4) all suggest that the diffusion out of the rock matrix would be insubstantial relative to the regional flux of groundwater through the Site

Response The TI Evaluation Report does not explicitly consider or rely upon matrix diffusion as a basis for requesting a TI Waiver for a portion of the Hows Corner Site The technical literature provides documentation that matrix diffusion can be a significant process that affects chemical transport and groundwater remediation timeframes in unconsolidated and consolidated media including fractured rock (US EPA 1989 Freeze and Cherry 1979 Pankow and Cherry 1996 Fountain 1998) Back diffusion of contaminants from the matrix porosity of the fractured rock can prolong the time necessary to achieve groundwater cleanup goals particularly for compounds such as PCE for which the cleanup goal is a low concentration It is our expectation that matrix diffusion has occurred at the Hows Corner Site and that back diffusion of PCE from the rock matrix will also occur Although the extent to which matrix diffusion is occurring at the Hows Comer Site has not been determined and that lack of knowledge contributes to uncertainty regarding the cleanup times at the Site the effect of matrix diffusion is to lengthen rather than shorten the time required for remediation

REFERENCES

Fountain JC 1998 Technologies for Dense Nonaqueous Phase Liquid Source Zone Remediation Ground-Water Remediation Technologies Analysis Center Technology Evaluation Report TE-98-02 December

Freeze RA and Cherry JA 1979 Groundwater Prentice-Hall Inc Englewood Cliffs NJ 07632 p 410-412

Pankow J F and Cherry J A 1996 Dense Chlorinated Solvents Waterloo Press Portland OR 97291-1399 p 67-88

US EPA 1989 Transport and Fate of Contaminants in the Subsurface EPA6254-89019 p 17-18

Response to EPA Comment 5 050305doc 1 of 1 Woodard amp Curran (211941)

WOODARD amp CURRAN Maine Massachusetts New Hampshire Connecticut Florida Operational offices across the US 1-800-426-4262 www woodardcurran com

Page 51: SDMS DocID 251749 - Records Collections · 2020-06-13 · CORPORATE OFFICES: Maine, Massachusetts, New Hampshire, Connecticut New, York, Florida Engineering • Science • Operations

PLYMOUTH POND

PLYMOUTH POND

1 628Tl7MW-2bB 12135

PLYMOUTH POND

monitoring well Figure 4-20

V total VOC contour (ugl) - June 2000 Distribution of Total VOCs in Shallow Bedrock Groundwater

| 34 | total concentration of detected VOCs ND= not detected NA = not analyzed Supplemental Sampling Event Note SW-113 is located downstream of SEEP-1 Hows Corner Superfund Site

Surface Water Sampling Location these two locations were sampled during the Plymouth Maine Baseline Sampling Event in OctoberNovember 1999 Seep Sampling Location WOODARD amp CURRAN

Engineering bull Science - Operations bull 995037wipri reportepa ri interim final feb 2001 cadd drawingsfinalfig 4-20

residential well Figure 4-22 Distribution of Total VOCs in

monitoring well Deep Bedrock Groundwater

total VOCs contour (ugl) Supplemental Sampling Event

Hows Corner Superfund Site

total concentration of detected VOCs ND= not detected NA = not analyzed Plymouth Maine

WOODARD amp CURRAN

995037wipri reportepa-ri interim final feb 2001cadd drawingsfinalfig 4-22 Engineering bull Science - Operations bull

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

FEET

Shallow Monitoring Well

Deep Monitoring Well

C Detected Concentration ND = Not Detected Figure 1-XS Distribution of Total VOCs in Shallow Bedrock Groundwater

Pumping Well

17-Acre Property Boundary Concentration Contour (ugl)

June 2001 Hows Corner Superfund Site

Plymouth Maine WOODARDampCURRAN

-i^rhvj bull Scbncn bull Operations bull 211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0601 dwg04-20-05

PLYMOUTH POND Hopkins Road V

O

PLYMOUTH POND

PLYMOUTH POND

o

0 300 600 mdashfa FEET

Shallow Monitoring Well bull bull - 17-Acre Property Boundary Figure 1-XD

Deep Monitoring Well 1 I Detected Concentration ND = Not Detected Distribution of Total VOCs in Deep Bedrock Groundwater

-mf- Pumping Well June 2001 Residential Well Hows Corner Superfund Site

Plymouth Maine i h Surface Water Sampling Point

g WOODARD ampCURRAN _ ^ _ ^ _ _ yen_ rj i|Hlaquorlny bull Science bull Opt

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0601 dwg04-20-05

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

Shallow Monitoring Well

Deep Monitoring Well

Detected Concentration ND = Not Detected Figure 1-YS Distribution of Total VOCs in Shallow Bedrock Groundwater

Pumping Well

17-Acre Property Boundary Concentration Contour (ugl)

January 2002 Hows Corner Superfund Site

Plymouth Maine WOODARD amp CURRAN Engineering Science- Operations bull

211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0102dwg04-20-05

PLYMOUTH POND

PLYMOUTH POND

Site Pand^ laquoum-laquoBTuitaraquo tLV

vVlf-(

PLYMOUTH POND

0 300 600 ^ = FEET

Shallow Monitoring Well mdashbullbullbull 17-Acre Property Boundary Figure 1-YD - A - Deep Monitoring Well FT Detected Concentration ND = Not Detected Distribution of Total VOCs in

Deep Bedrock Groundwater Pumping Well January 2002 Residential Well Hows Corner Superfund Site

Plymouth Maine Surface Water Sampling Point

WOODARD ampCURRAN Engineering Sciencs- Operations bulli Si

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0102dwg04-20-05

- m j

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND j A O-shy

Shallow Monitoring Well E Detected Concentration ND = Not Detected Figure 1-ZS Distribution of Total VOCs in

Deep Monitoring Well Shallow Bedrock Groundwater

Pumping Well Hows Corner

April 2003 Superfund Site

17-Acre Property Boundary Plymouth Maine Concentration Contour (ugl) r WOODARD ampCURRAN

Engineering bull Science bull Operations bull 211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0403dwg04-20-05

s S pound

PLYMOUTH POND

PLYMOUTH POND

- -

5 PLYMOUTH POND

Jo

FEET

ft Shallow Monitoring Well mdashbullbullmdash 17-Acre Property Boundary Figure 1-ZD Deep Monitoring Well I 1 I Detected Concentration ND = Not Detected Distribution of Total VOCs in

Deep Bedrock Groundwater Pumping Well April 2003

Q) Residential Well Hows Corner Superfund Site Plymouth Maine

(T) Surface Water Sampling Point WOODARD ampCURRAN poundKk EnginawtirKj bull Science - Operations bull

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0403dwg04-20-05

0 Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

B MW-1B

I 12000

PCE

B 10000 Total VOCs

I

i 2000

i 0 Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

c MW-3B

G 2000

1800

B PCE

1600 Total VOCs

1 I I E

il-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

G E

211941

El

I I z E

80

Concentration Trends shy Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-13DB

Total VOCs

c i i c o

Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

MW-16DB

30

c i c c I c o

Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99

PCE

Total VOCs

Jul-01 Jul-03

211941

O bi

c Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

I MW-16IB

i 35

3

c Total VOCs

lt- 2 5

0 | gt

o

1 sectI

c c 0 4

Jul-90 Jul-92 Jul-94 Jul-96 Jul-98 Jul-00 Jul-02 Jul-04

I I MW-108D

I 12

PCE 10

Total VOCs c oc 3

E E I 0

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

E 211941

c Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

fi MW-108S

I I 40

PCE 35

Total VOCs

30

I f 26

20 I o

I 15

10

c Dec-99 Dec-00 Dec-01 Dec-02 Dec-03 I 0

I MW-112D

c 35 - imdash

I A3 shyTotal VOCs

o c

E 1 2

I

ition

B 1 ^

-i c 3

0 Dec-99 Dec-OO Dec-01 Dec-02 Dec-03

211941

I

i

I

cII

Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-112S

08

PCE

Total VOCs 06

o 04

02

0 Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

MW-114D

o

12000

10000

8000

6000

PCE

Total VOCs

4000

2000

i

ccEIIc

i

i

E

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

211941

Con

cent

ratio

n (

ug

l)

E Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

I MW-114S

E A5000 -- Total VOCs

- 4000

0 3000

2000

i 1000

i n shy

Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

MW-115D

c PCE

Total VOCs

c E

o

C c

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03 I 0

211941

IepoundII

EIEIIGICCIccc

30000

25000

20000

o bullsect 15000 b

o 10000 U

5000

0 Aug-99

25000

20000

5000

0 Aug-99

211941

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-2DB

PCE

Total VOCs

Aug-01 Aug-03

MW-2IB

PCE

Total VOCs

Aug-01 Aug-03

IDIBI

ii EIDIISIBIG C

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-102S

6000

5000 PCE

Total VOCs

4000

O 3000

2000

1000

0 Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

MW-103D

16000

~ 14000 ugt 3- 12000 o

^ 10000

sect 8000

O 6000

4000

2000

PCE

Total VOCs

0Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

211941

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

G MW-103S

I I

ampo

12000

10000

E sectc

S

8000

6000

4000

2000

0Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

G I 6000

MW-104D

i 5000

PCE

Total VOCs

i i c

2000

1000

Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

E I

211941

cIccIG

IIBCccBcIc

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-1041

PCE Total VOCs

a 25000

0 20000

a 15000

10000

5000

0 Jan-OO Jan-01 Jan-02 Jan-03 Jan-04

MW-106D

3000

2500 PCE

Total VOCs

=sect 2000

o bullsect 1500

1000

500

0 Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

211941

c Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

c MW-106S

I PCE

Total VOCs

i

i Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

i

i i i E

C

211941 c

Response to EPA-DEP Comment 5 Dated March 312005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

iiw

EPA-DEP Comment 5

Comment 5 Matrix Diffusion The report as well as other proponents of matrix diffusion suggest that depletion of DNAPL (Section 5112 page 5-15) needs to be achieved While that might be the ideal the goal is to achieve performance standards and that goal may be attainable while there is residual contamination in the rock perhaps even DNAPL globules The low bedrock matrix porosity (page 1-15) the high permeability values (page 4-4) the relative flux of the groundwater (page 5-5) and the decrease in surface area and out of the mainstream pockets (appendix C-4) all suggest that the diffusion out of the rock matrix would be insubstantial relative to the regional flux of groundwater through the Site

Response The TI Evaluation Report does not explicitly consider or rely upon matrix diffusion as a basis for requesting a TI Waiver for a portion of the Hows Corner Site The technical literature provides documentation that matrix diffusion can be a significant process that affects chemical transport and groundwater remediation timeframes in unconsolidated and consolidated media including fractured rock (US EPA 1989 Freeze and Cherry 1979 Pankow and Cherry 1996 Fountain 1998) Back diffusion of contaminants from the matrix porosity of the fractured rock can prolong the time necessary to achieve groundwater cleanup goals particularly for compounds such as PCE for which the cleanup goal is a low concentration It is our expectation that matrix diffusion has occurred at the Hows Corner Site and that back diffusion of PCE from the rock matrix will also occur Although the extent to which matrix diffusion is occurring at the Hows Comer Site has not been determined and that lack of knowledge contributes to uncertainty regarding the cleanup times at the Site the effect of matrix diffusion is to lengthen rather than shorten the time required for remediation

REFERENCES

Fountain JC 1998 Technologies for Dense Nonaqueous Phase Liquid Source Zone Remediation Ground-Water Remediation Technologies Analysis Center Technology Evaluation Report TE-98-02 December

Freeze RA and Cherry JA 1979 Groundwater Prentice-Hall Inc Englewood Cliffs NJ 07632 p 410-412

Pankow J F and Cherry J A 1996 Dense Chlorinated Solvents Waterloo Press Portland OR 97291-1399 p 67-88

US EPA 1989 Transport and Fate of Contaminants in the Subsurface EPA6254-89019 p 17-18

Response to EPA Comment 5 050305doc 1 of 1 Woodard amp Curran (211941)

WOODARD amp CURRAN Maine Massachusetts New Hampshire Connecticut Florida Operational offices across the US 1-800-426-4262 www woodardcurran com

Page 52: SDMS DocID 251749 - Records Collections · 2020-06-13 · CORPORATE OFFICES: Maine, Massachusetts, New Hampshire, Connecticut New, York, Florida Engineering • Science • Operations

residential well Figure 4-22 Distribution of Total VOCs in

monitoring well Deep Bedrock Groundwater

total VOCs contour (ugl) Supplemental Sampling Event

Hows Corner Superfund Site

total concentration of detected VOCs ND= not detected NA = not analyzed Plymouth Maine

WOODARD amp CURRAN

995037wipri reportepa-ri interim final feb 2001cadd drawingsfinalfig 4-22 Engineering bull Science - Operations bull

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

FEET

Shallow Monitoring Well

Deep Monitoring Well

C Detected Concentration ND = Not Detected Figure 1-XS Distribution of Total VOCs in Shallow Bedrock Groundwater

Pumping Well

17-Acre Property Boundary Concentration Contour (ugl)

June 2001 Hows Corner Superfund Site

Plymouth Maine WOODARDampCURRAN

-i^rhvj bull Scbncn bull Operations bull 211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0601 dwg04-20-05

PLYMOUTH POND Hopkins Road V

O

PLYMOUTH POND

PLYMOUTH POND

o

0 300 600 mdashfa FEET

Shallow Monitoring Well bull bull - 17-Acre Property Boundary Figure 1-XD

Deep Monitoring Well 1 I Detected Concentration ND = Not Detected Distribution of Total VOCs in Deep Bedrock Groundwater

-mf- Pumping Well June 2001 Residential Well Hows Corner Superfund Site

Plymouth Maine i h Surface Water Sampling Point

g WOODARD ampCURRAN _ ^ _ ^ _ _ yen_ rj i|Hlaquorlny bull Science bull Opt

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0601 dwg04-20-05

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

Shallow Monitoring Well

Deep Monitoring Well

Detected Concentration ND = Not Detected Figure 1-YS Distribution of Total VOCs in Shallow Bedrock Groundwater

Pumping Well

17-Acre Property Boundary Concentration Contour (ugl)

January 2002 Hows Corner Superfund Site

Plymouth Maine WOODARD amp CURRAN Engineering Science- Operations bull

211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0102dwg04-20-05

PLYMOUTH POND

PLYMOUTH POND

Site Pand^ laquoum-laquoBTuitaraquo tLV

vVlf-(

PLYMOUTH POND

0 300 600 ^ = FEET

Shallow Monitoring Well mdashbullbullbull 17-Acre Property Boundary Figure 1-YD - A - Deep Monitoring Well FT Detected Concentration ND = Not Detected Distribution of Total VOCs in

Deep Bedrock Groundwater Pumping Well January 2002 Residential Well Hows Corner Superfund Site

Plymouth Maine Surface Water Sampling Point

WOODARD ampCURRAN Engineering Sciencs- Operations bulli Si

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0102dwg04-20-05

- m j

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND j A O-shy

Shallow Monitoring Well E Detected Concentration ND = Not Detected Figure 1-ZS Distribution of Total VOCs in

Deep Monitoring Well Shallow Bedrock Groundwater

Pumping Well Hows Corner

April 2003 Superfund Site

17-Acre Property Boundary Plymouth Maine Concentration Contour (ugl) r WOODARD ampCURRAN

Engineering bull Science bull Operations bull 211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0403dwg04-20-05

s S pound

PLYMOUTH POND

PLYMOUTH POND

- -

5 PLYMOUTH POND

Jo

FEET

ft Shallow Monitoring Well mdashbullbullmdash 17-Acre Property Boundary Figure 1-ZD Deep Monitoring Well I 1 I Detected Concentration ND = Not Detected Distribution of Total VOCs in

Deep Bedrock Groundwater Pumping Well April 2003

Q) Residential Well Hows Corner Superfund Site Plymouth Maine

(T) Surface Water Sampling Point WOODARD ampCURRAN poundKk EnginawtirKj bull Science - Operations bull

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0403dwg04-20-05

0 Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

B MW-1B

I 12000

PCE

B 10000 Total VOCs

I

i 2000

i 0 Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

c MW-3B

G 2000

1800

B PCE

1600 Total VOCs

1 I I E

il-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

G E

211941

El

I I z E

80

Concentration Trends shy Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-13DB

Total VOCs

c i i c o

Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

MW-16DB

30

c i c c I c o

Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99

PCE

Total VOCs

Jul-01 Jul-03

211941

O bi

c Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

I MW-16IB

i 35

3

c Total VOCs

lt- 2 5

0 | gt

o

1 sectI

c c 0 4

Jul-90 Jul-92 Jul-94 Jul-96 Jul-98 Jul-00 Jul-02 Jul-04

I I MW-108D

I 12

PCE 10

Total VOCs c oc 3

E E I 0

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

E 211941

c Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

fi MW-108S

I I 40

PCE 35

Total VOCs

30

I f 26

20 I o

I 15

10

c Dec-99 Dec-00 Dec-01 Dec-02 Dec-03 I 0

I MW-112D

c 35 - imdash

I A3 shyTotal VOCs

o c

E 1 2

I

ition

B 1 ^

-i c 3

0 Dec-99 Dec-OO Dec-01 Dec-02 Dec-03

211941

I

i

I

cII

Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-112S

08

PCE

Total VOCs 06

o 04

02

0 Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

MW-114D

o

12000

10000

8000

6000

PCE

Total VOCs

4000

2000

i

ccEIIc

i

i

E

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

211941

Con

cent

ratio

n (

ug

l)

E Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

I MW-114S

E A5000 -- Total VOCs

- 4000

0 3000

2000

i 1000

i n shy

Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

MW-115D

c PCE

Total VOCs

c E

o

C c

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03 I 0

211941

IepoundII

EIEIIGICCIccc

30000

25000

20000

o bullsect 15000 b

o 10000 U

5000

0 Aug-99

25000

20000

5000

0 Aug-99

211941

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-2DB

PCE

Total VOCs

Aug-01 Aug-03

MW-2IB

PCE

Total VOCs

Aug-01 Aug-03

IDIBI

ii EIDIISIBIG C

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-102S

6000

5000 PCE

Total VOCs

4000

O 3000

2000

1000

0 Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

MW-103D

16000

~ 14000 ugt 3- 12000 o

^ 10000

sect 8000

O 6000

4000

2000

PCE

Total VOCs

0Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

211941

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

G MW-103S

I I

ampo

12000

10000

E sectc

S

8000

6000

4000

2000

0Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

G I 6000

MW-104D

i 5000

PCE

Total VOCs

i i c

2000

1000

Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

E I

211941

cIccIG

IIBCccBcIc

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-1041

PCE Total VOCs

a 25000

0 20000

a 15000

10000

5000

0 Jan-OO Jan-01 Jan-02 Jan-03 Jan-04

MW-106D

3000

2500 PCE

Total VOCs

=sect 2000

o bullsect 1500

1000

500

0 Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

211941

c Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

c MW-106S

I PCE

Total VOCs

i

i Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

i

i i i E

C

211941 c

Response to EPA-DEP Comment 5 Dated March 312005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

iiw

EPA-DEP Comment 5

Comment 5 Matrix Diffusion The report as well as other proponents of matrix diffusion suggest that depletion of DNAPL (Section 5112 page 5-15) needs to be achieved While that might be the ideal the goal is to achieve performance standards and that goal may be attainable while there is residual contamination in the rock perhaps even DNAPL globules The low bedrock matrix porosity (page 1-15) the high permeability values (page 4-4) the relative flux of the groundwater (page 5-5) and the decrease in surface area and out of the mainstream pockets (appendix C-4) all suggest that the diffusion out of the rock matrix would be insubstantial relative to the regional flux of groundwater through the Site

Response The TI Evaluation Report does not explicitly consider or rely upon matrix diffusion as a basis for requesting a TI Waiver for a portion of the Hows Corner Site The technical literature provides documentation that matrix diffusion can be a significant process that affects chemical transport and groundwater remediation timeframes in unconsolidated and consolidated media including fractured rock (US EPA 1989 Freeze and Cherry 1979 Pankow and Cherry 1996 Fountain 1998) Back diffusion of contaminants from the matrix porosity of the fractured rock can prolong the time necessary to achieve groundwater cleanup goals particularly for compounds such as PCE for which the cleanup goal is a low concentration It is our expectation that matrix diffusion has occurred at the Hows Corner Site and that back diffusion of PCE from the rock matrix will also occur Although the extent to which matrix diffusion is occurring at the Hows Comer Site has not been determined and that lack of knowledge contributes to uncertainty regarding the cleanup times at the Site the effect of matrix diffusion is to lengthen rather than shorten the time required for remediation

REFERENCES

Fountain JC 1998 Technologies for Dense Nonaqueous Phase Liquid Source Zone Remediation Ground-Water Remediation Technologies Analysis Center Technology Evaluation Report TE-98-02 December

Freeze RA and Cherry JA 1979 Groundwater Prentice-Hall Inc Englewood Cliffs NJ 07632 p 410-412

Pankow J F and Cherry J A 1996 Dense Chlorinated Solvents Waterloo Press Portland OR 97291-1399 p 67-88

US EPA 1989 Transport and Fate of Contaminants in the Subsurface EPA6254-89019 p 17-18

Response to EPA Comment 5 050305doc 1 of 1 Woodard amp Curran (211941)

WOODARD amp CURRAN Maine Massachusetts New Hampshire Connecticut Florida Operational offices across the US 1-800-426-4262 www woodardcurran com

Page 53: SDMS DocID 251749 - Records Collections · 2020-06-13 · CORPORATE OFFICES: Maine, Massachusetts, New Hampshire, Connecticut New, York, Florida Engineering • Science • Operations

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

FEET

Shallow Monitoring Well

Deep Monitoring Well

C Detected Concentration ND = Not Detected Figure 1-XS Distribution of Total VOCs in Shallow Bedrock Groundwater

Pumping Well

17-Acre Property Boundary Concentration Contour (ugl)

June 2001 Hows Corner Superfund Site

Plymouth Maine WOODARDampCURRAN

-i^rhvj bull Scbncn bull Operations bull 211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0601 dwg04-20-05

PLYMOUTH POND Hopkins Road V

O

PLYMOUTH POND

PLYMOUTH POND

o

0 300 600 mdashfa FEET

Shallow Monitoring Well bull bull - 17-Acre Property Boundary Figure 1-XD

Deep Monitoring Well 1 I Detected Concentration ND = Not Detected Distribution of Total VOCs in Deep Bedrock Groundwater

-mf- Pumping Well June 2001 Residential Well Hows Corner Superfund Site

Plymouth Maine i h Surface Water Sampling Point

g WOODARD ampCURRAN _ ^ _ ^ _ _ yen_ rj i|Hlaquorlny bull Science bull Opt

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0601 dwg04-20-05

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

Shallow Monitoring Well

Deep Monitoring Well

Detected Concentration ND = Not Detected Figure 1-YS Distribution of Total VOCs in Shallow Bedrock Groundwater

Pumping Well

17-Acre Property Boundary Concentration Contour (ugl)

January 2002 Hows Corner Superfund Site

Plymouth Maine WOODARD amp CURRAN Engineering Science- Operations bull

211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0102dwg04-20-05

PLYMOUTH POND

PLYMOUTH POND

Site Pand^ laquoum-laquoBTuitaraquo tLV

vVlf-(

PLYMOUTH POND

0 300 600 ^ = FEET

Shallow Monitoring Well mdashbullbullbull 17-Acre Property Boundary Figure 1-YD - A - Deep Monitoring Well FT Detected Concentration ND = Not Detected Distribution of Total VOCs in

Deep Bedrock Groundwater Pumping Well January 2002 Residential Well Hows Corner Superfund Site

Plymouth Maine Surface Water Sampling Point

WOODARD ampCURRAN Engineering Sciencs- Operations bulli Si

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0102dwg04-20-05

- m j

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND j A O-shy

Shallow Monitoring Well E Detected Concentration ND = Not Detected Figure 1-ZS Distribution of Total VOCs in

Deep Monitoring Well Shallow Bedrock Groundwater

Pumping Well Hows Corner

April 2003 Superfund Site

17-Acre Property Boundary Plymouth Maine Concentration Contour (ugl) r WOODARD ampCURRAN

Engineering bull Science bull Operations bull 211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0403dwg04-20-05

s S pound

PLYMOUTH POND

PLYMOUTH POND

- -

5 PLYMOUTH POND

Jo

FEET

ft Shallow Monitoring Well mdashbullbullmdash 17-Acre Property Boundary Figure 1-ZD Deep Monitoring Well I 1 I Detected Concentration ND = Not Detected Distribution of Total VOCs in

Deep Bedrock Groundwater Pumping Well April 2003

Q) Residential Well Hows Corner Superfund Site Plymouth Maine

(T) Surface Water Sampling Point WOODARD ampCURRAN poundKk EnginawtirKj bull Science - Operations bull

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0403dwg04-20-05

0 Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

B MW-1B

I 12000

PCE

B 10000 Total VOCs

I

i 2000

i 0 Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

c MW-3B

G 2000

1800

B PCE

1600 Total VOCs

1 I I E

il-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

G E

211941

El

I I z E

80

Concentration Trends shy Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-13DB

Total VOCs

c i i c o

Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

MW-16DB

30

c i c c I c o

Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99

PCE

Total VOCs

Jul-01 Jul-03

211941

O bi

c Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

I MW-16IB

i 35

3

c Total VOCs

lt- 2 5

0 | gt

o

1 sectI

c c 0 4

Jul-90 Jul-92 Jul-94 Jul-96 Jul-98 Jul-00 Jul-02 Jul-04

I I MW-108D

I 12

PCE 10

Total VOCs c oc 3

E E I 0

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

E 211941

c Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

fi MW-108S

I I 40

PCE 35

Total VOCs

30

I f 26

20 I o

I 15

10

c Dec-99 Dec-00 Dec-01 Dec-02 Dec-03 I 0

I MW-112D

c 35 - imdash

I A3 shyTotal VOCs

o c

E 1 2

I

ition

B 1 ^

-i c 3

0 Dec-99 Dec-OO Dec-01 Dec-02 Dec-03

211941

I

i

I

cII

Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-112S

08

PCE

Total VOCs 06

o 04

02

0 Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

MW-114D

o

12000

10000

8000

6000

PCE

Total VOCs

4000

2000

i

ccEIIc

i

i

E

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

211941

Con

cent

ratio

n (

ug

l)

E Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

I MW-114S

E A5000 -- Total VOCs

- 4000

0 3000

2000

i 1000

i n shy

Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

MW-115D

c PCE

Total VOCs

c E

o

C c

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03 I 0

211941

IepoundII

EIEIIGICCIccc

30000

25000

20000

o bullsect 15000 b

o 10000 U

5000

0 Aug-99

25000

20000

5000

0 Aug-99

211941

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-2DB

PCE

Total VOCs

Aug-01 Aug-03

MW-2IB

PCE

Total VOCs

Aug-01 Aug-03

IDIBI

ii EIDIISIBIG C

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-102S

6000

5000 PCE

Total VOCs

4000

O 3000

2000

1000

0 Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

MW-103D

16000

~ 14000 ugt 3- 12000 o

^ 10000

sect 8000

O 6000

4000

2000

PCE

Total VOCs

0Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

211941

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

G MW-103S

I I

ampo

12000

10000

E sectc

S

8000

6000

4000

2000

0Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

G I 6000

MW-104D

i 5000

PCE

Total VOCs

i i c

2000

1000

Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

E I

211941

cIccIG

IIBCccBcIc

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-1041

PCE Total VOCs

a 25000

0 20000

a 15000

10000

5000

0 Jan-OO Jan-01 Jan-02 Jan-03 Jan-04

MW-106D

3000

2500 PCE

Total VOCs

=sect 2000

o bullsect 1500

1000

500

0 Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

211941

c Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

c MW-106S

I PCE

Total VOCs

i

i Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

i

i i i E

C

211941 c

Response to EPA-DEP Comment 5 Dated March 312005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

iiw

EPA-DEP Comment 5

Comment 5 Matrix Diffusion The report as well as other proponents of matrix diffusion suggest that depletion of DNAPL (Section 5112 page 5-15) needs to be achieved While that might be the ideal the goal is to achieve performance standards and that goal may be attainable while there is residual contamination in the rock perhaps even DNAPL globules The low bedrock matrix porosity (page 1-15) the high permeability values (page 4-4) the relative flux of the groundwater (page 5-5) and the decrease in surface area and out of the mainstream pockets (appendix C-4) all suggest that the diffusion out of the rock matrix would be insubstantial relative to the regional flux of groundwater through the Site

Response The TI Evaluation Report does not explicitly consider or rely upon matrix diffusion as a basis for requesting a TI Waiver for a portion of the Hows Corner Site The technical literature provides documentation that matrix diffusion can be a significant process that affects chemical transport and groundwater remediation timeframes in unconsolidated and consolidated media including fractured rock (US EPA 1989 Freeze and Cherry 1979 Pankow and Cherry 1996 Fountain 1998) Back diffusion of contaminants from the matrix porosity of the fractured rock can prolong the time necessary to achieve groundwater cleanup goals particularly for compounds such as PCE for which the cleanup goal is a low concentration It is our expectation that matrix diffusion has occurred at the Hows Corner Site and that back diffusion of PCE from the rock matrix will also occur Although the extent to which matrix diffusion is occurring at the Hows Comer Site has not been determined and that lack of knowledge contributes to uncertainty regarding the cleanup times at the Site the effect of matrix diffusion is to lengthen rather than shorten the time required for remediation

REFERENCES

Fountain JC 1998 Technologies for Dense Nonaqueous Phase Liquid Source Zone Remediation Ground-Water Remediation Technologies Analysis Center Technology Evaluation Report TE-98-02 December

Freeze RA and Cherry JA 1979 Groundwater Prentice-Hall Inc Englewood Cliffs NJ 07632 p 410-412

Pankow J F and Cherry J A 1996 Dense Chlorinated Solvents Waterloo Press Portland OR 97291-1399 p 67-88

US EPA 1989 Transport and Fate of Contaminants in the Subsurface EPA6254-89019 p 17-18

Response to EPA Comment 5 050305doc 1 of 1 Woodard amp Curran (211941)

WOODARD amp CURRAN Maine Massachusetts New Hampshire Connecticut Florida Operational offices across the US 1-800-426-4262 www woodardcurran com

Page 54: SDMS DocID 251749 - Records Collections · 2020-06-13 · CORPORATE OFFICES: Maine, Massachusetts, New Hampshire, Connecticut New, York, Florida Engineering • Science • Operations

PLYMOUTH POND Hopkins Road V

O

PLYMOUTH POND

PLYMOUTH POND

o

0 300 600 mdashfa FEET

Shallow Monitoring Well bull bull - 17-Acre Property Boundary Figure 1-XD

Deep Monitoring Well 1 I Detected Concentration ND = Not Detected Distribution of Total VOCs in Deep Bedrock Groundwater

-mf- Pumping Well June 2001 Residential Well Hows Corner Superfund Site

Plymouth Maine i h Surface Water Sampling Point

g WOODARD ampCURRAN _ ^ _ ^ _ _ yen_ rj i|Hlaquorlny bull Science bull Opt

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0601 dwg04-20-05

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

Shallow Monitoring Well

Deep Monitoring Well

Detected Concentration ND = Not Detected Figure 1-YS Distribution of Total VOCs in Shallow Bedrock Groundwater

Pumping Well

17-Acre Property Boundary Concentration Contour (ugl)

January 2002 Hows Corner Superfund Site

Plymouth Maine WOODARD amp CURRAN Engineering Science- Operations bull

211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0102dwg04-20-05

PLYMOUTH POND

PLYMOUTH POND

Site Pand^ laquoum-laquoBTuitaraquo tLV

vVlf-(

PLYMOUTH POND

0 300 600 ^ = FEET

Shallow Monitoring Well mdashbullbullbull 17-Acre Property Boundary Figure 1-YD - A - Deep Monitoring Well FT Detected Concentration ND = Not Detected Distribution of Total VOCs in

Deep Bedrock Groundwater Pumping Well January 2002 Residential Well Hows Corner Superfund Site

Plymouth Maine Surface Water Sampling Point

WOODARD ampCURRAN Engineering Sciencs- Operations bulli Si

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0102dwg04-20-05

- m j

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND j A O-shy

Shallow Monitoring Well E Detected Concentration ND = Not Detected Figure 1-ZS Distribution of Total VOCs in

Deep Monitoring Well Shallow Bedrock Groundwater

Pumping Well Hows Corner

April 2003 Superfund Site

17-Acre Property Boundary Plymouth Maine Concentration Contour (ugl) r WOODARD ampCURRAN

Engineering bull Science bull Operations bull 211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0403dwg04-20-05

s S pound

PLYMOUTH POND

PLYMOUTH POND

- -

5 PLYMOUTH POND

Jo

FEET

ft Shallow Monitoring Well mdashbullbullmdash 17-Acre Property Boundary Figure 1-ZD Deep Monitoring Well I 1 I Detected Concentration ND = Not Detected Distribution of Total VOCs in

Deep Bedrock Groundwater Pumping Well April 2003

Q) Residential Well Hows Corner Superfund Site Plymouth Maine

(T) Surface Water Sampling Point WOODARD ampCURRAN poundKk EnginawtirKj bull Science - Operations bull

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0403dwg04-20-05

0 Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

B MW-1B

I 12000

PCE

B 10000 Total VOCs

I

i 2000

i 0 Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

c MW-3B

G 2000

1800

B PCE

1600 Total VOCs

1 I I E

il-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

G E

211941

El

I I z E

80

Concentration Trends shy Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-13DB

Total VOCs

c i i c o

Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

MW-16DB

30

c i c c I c o

Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99

PCE

Total VOCs

Jul-01 Jul-03

211941

O bi

c Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

I MW-16IB

i 35

3

c Total VOCs

lt- 2 5

0 | gt

o

1 sectI

c c 0 4

Jul-90 Jul-92 Jul-94 Jul-96 Jul-98 Jul-00 Jul-02 Jul-04

I I MW-108D

I 12

PCE 10

Total VOCs c oc 3

E E I 0

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

E 211941

c Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

fi MW-108S

I I 40

PCE 35

Total VOCs

30

I f 26

20 I o

I 15

10

c Dec-99 Dec-00 Dec-01 Dec-02 Dec-03 I 0

I MW-112D

c 35 - imdash

I A3 shyTotal VOCs

o c

E 1 2

I

ition

B 1 ^

-i c 3

0 Dec-99 Dec-OO Dec-01 Dec-02 Dec-03

211941

I

i

I

cII

Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-112S

08

PCE

Total VOCs 06

o 04

02

0 Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

MW-114D

o

12000

10000

8000

6000

PCE

Total VOCs

4000

2000

i

ccEIIc

i

i

E

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

211941

Con

cent

ratio

n (

ug

l)

E Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

I MW-114S

E A5000 -- Total VOCs

- 4000

0 3000

2000

i 1000

i n shy

Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

MW-115D

c PCE

Total VOCs

c E

o

C c

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03 I 0

211941

IepoundII

EIEIIGICCIccc

30000

25000

20000

o bullsect 15000 b

o 10000 U

5000

0 Aug-99

25000

20000

5000

0 Aug-99

211941

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-2DB

PCE

Total VOCs

Aug-01 Aug-03

MW-2IB

PCE

Total VOCs

Aug-01 Aug-03

IDIBI

ii EIDIISIBIG C

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-102S

6000

5000 PCE

Total VOCs

4000

O 3000

2000

1000

0 Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

MW-103D

16000

~ 14000 ugt 3- 12000 o

^ 10000

sect 8000

O 6000

4000

2000

PCE

Total VOCs

0Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

211941

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

G MW-103S

I I

ampo

12000

10000

E sectc

S

8000

6000

4000

2000

0Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

G I 6000

MW-104D

i 5000

PCE

Total VOCs

i i c

2000

1000

Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

E I

211941

cIccIG

IIBCccBcIc

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-1041

PCE Total VOCs

a 25000

0 20000

a 15000

10000

5000

0 Jan-OO Jan-01 Jan-02 Jan-03 Jan-04

MW-106D

3000

2500 PCE

Total VOCs

=sect 2000

o bullsect 1500

1000

500

0 Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

211941

c Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

c MW-106S

I PCE

Total VOCs

i

i Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

i

i i i E

C

211941 c

Response to EPA-DEP Comment 5 Dated March 312005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

iiw

EPA-DEP Comment 5

Comment 5 Matrix Diffusion The report as well as other proponents of matrix diffusion suggest that depletion of DNAPL (Section 5112 page 5-15) needs to be achieved While that might be the ideal the goal is to achieve performance standards and that goal may be attainable while there is residual contamination in the rock perhaps even DNAPL globules The low bedrock matrix porosity (page 1-15) the high permeability values (page 4-4) the relative flux of the groundwater (page 5-5) and the decrease in surface area and out of the mainstream pockets (appendix C-4) all suggest that the diffusion out of the rock matrix would be insubstantial relative to the regional flux of groundwater through the Site

Response The TI Evaluation Report does not explicitly consider or rely upon matrix diffusion as a basis for requesting a TI Waiver for a portion of the Hows Corner Site The technical literature provides documentation that matrix diffusion can be a significant process that affects chemical transport and groundwater remediation timeframes in unconsolidated and consolidated media including fractured rock (US EPA 1989 Freeze and Cherry 1979 Pankow and Cherry 1996 Fountain 1998) Back diffusion of contaminants from the matrix porosity of the fractured rock can prolong the time necessary to achieve groundwater cleanup goals particularly for compounds such as PCE for which the cleanup goal is a low concentration It is our expectation that matrix diffusion has occurred at the Hows Corner Site and that back diffusion of PCE from the rock matrix will also occur Although the extent to which matrix diffusion is occurring at the Hows Comer Site has not been determined and that lack of knowledge contributes to uncertainty regarding the cleanup times at the Site the effect of matrix diffusion is to lengthen rather than shorten the time required for remediation

REFERENCES

Fountain JC 1998 Technologies for Dense Nonaqueous Phase Liquid Source Zone Remediation Ground-Water Remediation Technologies Analysis Center Technology Evaluation Report TE-98-02 December

Freeze RA and Cherry JA 1979 Groundwater Prentice-Hall Inc Englewood Cliffs NJ 07632 p 410-412

Pankow J F and Cherry J A 1996 Dense Chlorinated Solvents Waterloo Press Portland OR 97291-1399 p 67-88

US EPA 1989 Transport and Fate of Contaminants in the Subsurface EPA6254-89019 p 17-18

Response to EPA Comment 5 050305doc 1 of 1 Woodard amp Curran (211941)

WOODARD amp CURRAN Maine Massachusetts New Hampshire Connecticut Florida Operational offices across the US 1-800-426-4262 www woodardcurran com

Page 55: SDMS DocID 251749 - Records Collections · 2020-06-13 · CORPORATE OFFICES: Maine, Massachusetts, New Hampshire, Connecticut New, York, Florida Engineering • Science • Operations

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND

Shallow Monitoring Well

Deep Monitoring Well

Detected Concentration ND = Not Detected Figure 1-YS Distribution of Total VOCs in Shallow Bedrock Groundwater

Pumping Well

17-Acre Property Boundary Concentration Contour (ugl)

January 2002 Hows Corner Superfund Site

Plymouth Maine WOODARD amp CURRAN Engineering Science- Operations bull

211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0102dwg04-20-05

PLYMOUTH POND

PLYMOUTH POND

Site Pand^ laquoum-laquoBTuitaraquo tLV

vVlf-(

PLYMOUTH POND

0 300 600 ^ = FEET

Shallow Monitoring Well mdashbullbullbull 17-Acre Property Boundary Figure 1-YD - A - Deep Monitoring Well FT Detected Concentration ND = Not Detected Distribution of Total VOCs in

Deep Bedrock Groundwater Pumping Well January 2002 Residential Well Hows Corner Superfund Site

Plymouth Maine Surface Water Sampling Point

WOODARD ampCURRAN Engineering Sciencs- Operations bulli Si

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0102dwg04-20-05

- m j

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND j A O-shy

Shallow Monitoring Well E Detected Concentration ND = Not Detected Figure 1-ZS Distribution of Total VOCs in

Deep Monitoring Well Shallow Bedrock Groundwater

Pumping Well Hows Corner

April 2003 Superfund Site

17-Acre Property Boundary Plymouth Maine Concentration Contour (ugl) r WOODARD ampCURRAN

Engineering bull Science bull Operations bull 211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0403dwg04-20-05

s S pound

PLYMOUTH POND

PLYMOUTH POND

- -

5 PLYMOUTH POND

Jo

FEET

ft Shallow Monitoring Well mdashbullbullmdash 17-Acre Property Boundary Figure 1-ZD Deep Monitoring Well I 1 I Detected Concentration ND = Not Detected Distribution of Total VOCs in

Deep Bedrock Groundwater Pumping Well April 2003

Q) Residential Well Hows Corner Superfund Site Plymouth Maine

(T) Surface Water Sampling Point WOODARD ampCURRAN poundKk EnginawtirKj bull Science - Operations bull

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0403dwg04-20-05

0 Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

B MW-1B

I 12000

PCE

B 10000 Total VOCs

I

i 2000

i 0 Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

c MW-3B

G 2000

1800

B PCE

1600 Total VOCs

1 I I E

il-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

G E

211941

El

I I z E

80

Concentration Trends shy Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-13DB

Total VOCs

c i i c o

Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

MW-16DB

30

c i c c I c o

Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99

PCE

Total VOCs

Jul-01 Jul-03

211941

O bi

c Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

I MW-16IB

i 35

3

c Total VOCs

lt- 2 5

0 | gt

o

1 sectI

c c 0 4

Jul-90 Jul-92 Jul-94 Jul-96 Jul-98 Jul-00 Jul-02 Jul-04

I I MW-108D

I 12

PCE 10

Total VOCs c oc 3

E E I 0

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

E 211941

c Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

fi MW-108S

I I 40

PCE 35

Total VOCs

30

I f 26

20 I o

I 15

10

c Dec-99 Dec-00 Dec-01 Dec-02 Dec-03 I 0

I MW-112D

c 35 - imdash

I A3 shyTotal VOCs

o c

E 1 2

I

ition

B 1 ^

-i c 3

0 Dec-99 Dec-OO Dec-01 Dec-02 Dec-03

211941

I

i

I

cII

Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-112S

08

PCE

Total VOCs 06

o 04

02

0 Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

MW-114D

o

12000

10000

8000

6000

PCE

Total VOCs

4000

2000

i

ccEIIc

i

i

E

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

211941

Con

cent

ratio

n (

ug

l)

E Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

I MW-114S

E A5000 -- Total VOCs

- 4000

0 3000

2000

i 1000

i n shy

Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

MW-115D

c PCE

Total VOCs

c E

o

C c

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03 I 0

211941

IepoundII

EIEIIGICCIccc

30000

25000

20000

o bullsect 15000 b

o 10000 U

5000

0 Aug-99

25000

20000

5000

0 Aug-99

211941

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-2DB

PCE

Total VOCs

Aug-01 Aug-03

MW-2IB

PCE

Total VOCs

Aug-01 Aug-03

IDIBI

ii EIDIISIBIG C

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-102S

6000

5000 PCE

Total VOCs

4000

O 3000

2000

1000

0 Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

MW-103D

16000

~ 14000 ugt 3- 12000 o

^ 10000

sect 8000

O 6000

4000

2000

PCE

Total VOCs

0Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

211941

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

G MW-103S

I I

ampo

12000

10000

E sectc

S

8000

6000

4000

2000

0Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

G I 6000

MW-104D

i 5000

PCE

Total VOCs

i i c

2000

1000

Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

E I

211941

cIccIG

IIBCccBcIc

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-1041

PCE Total VOCs

a 25000

0 20000

a 15000

10000

5000

0 Jan-OO Jan-01 Jan-02 Jan-03 Jan-04

MW-106D

3000

2500 PCE

Total VOCs

=sect 2000

o bullsect 1500

1000

500

0 Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

211941

c Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

c MW-106S

I PCE

Total VOCs

i

i Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

i

i i i E

C

211941 c

Response to EPA-DEP Comment 5 Dated March 312005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

iiw

EPA-DEP Comment 5

Comment 5 Matrix Diffusion The report as well as other proponents of matrix diffusion suggest that depletion of DNAPL (Section 5112 page 5-15) needs to be achieved While that might be the ideal the goal is to achieve performance standards and that goal may be attainable while there is residual contamination in the rock perhaps even DNAPL globules The low bedrock matrix porosity (page 1-15) the high permeability values (page 4-4) the relative flux of the groundwater (page 5-5) and the decrease in surface area and out of the mainstream pockets (appendix C-4) all suggest that the diffusion out of the rock matrix would be insubstantial relative to the regional flux of groundwater through the Site

Response The TI Evaluation Report does not explicitly consider or rely upon matrix diffusion as a basis for requesting a TI Waiver for a portion of the Hows Corner Site The technical literature provides documentation that matrix diffusion can be a significant process that affects chemical transport and groundwater remediation timeframes in unconsolidated and consolidated media including fractured rock (US EPA 1989 Freeze and Cherry 1979 Pankow and Cherry 1996 Fountain 1998) Back diffusion of contaminants from the matrix porosity of the fractured rock can prolong the time necessary to achieve groundwater cleanup goals particularly for compounds such as PCE for which the cleanup goal is a low concentration It is our expectation that matrix diffusion has occurred at the Hows Corner Site and that back diffusion of PCE from the rock matrix will also occur Although the extent to which matrix diffusion is occurring at the Hows Comer Site has not been determined and that lack of knowledge contributes to uncertainty regarding the cleanup times at the Site the effect of matrix diffusion is to lengthen rather than shorten the time required for remediation

REFERENCES

Fountain JC 1998 Technologies for Dense Nonaqueous Phase Liquid Source Zone Remediation Ground-Water Remediation Technologies Analysis Center Technology Evaluation Report TE-98-02 December

Freeze RA and Cherry JA 1979 Groundwater Prentice-Hall Inc Englewood Cliffs NJ 07632 p 410-412

Pankow J F and Cherry J A 1996 Dense Chlorinated Solvents Waterloo Press Portland OR 97291-1399 p 67-88

US EPA 1989 Transport and Fate of Contaminants in the Subsurface EPA6254-89019 p 17-18

Response to EPA Comment 5 050305doc 1 of 1 Woodard amp Curran (211941)

WOODARD amp CURRAN Maine Massachusetts New Hampshire Connecticut Florida Operational offices across the US 1-800-426-4262 www woodardcurran com

Page 56: SDMS DocID 251749 - Records Collections · 2020-06-13 · CORPORATE OFFICES: Maine, Massachusetts, New Hampshire, Connecticut New, York, Florida Engineering • Science • Operations

PLYMOUTH POND

PLYMOUTH POND

Site Pand^ laquoum-laquoBTuitaraquo tLV

vVlf-(

PLYMOUTH POND

0 300 600 ^ = FEET

Shallow Monitoring Well mdashbullbullbull 17-Acre Property Boundary Figure 1-YD - A - Deep Monitoring Well FT Detected Concentration ND = Not Detected Distribution of Total VOCs in

Deep Bedrock Groundwater Pumping Well January 2002 Residential Well Hows Corner Superfund Site

Plymouth Maine Surface Water Sampling Point

WOODARD ampCURRAN Engineering Sciencs- Operations bulli Si

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0102dwg04-20-05

- m j

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND j A O-shy

Shallow Monitoring Well E Detected Concentration ND = Not Detected Figure 1-ZS Distribution of Total VOCs in

Deep Monitoring Well Shallow Bedrock Groundwater

Pumping Well Hows Corner

April 2003 Superfund Site

17-Acre Property Boundary Plymouth Maine Concentration Contour (ugl) r WOODARD ampCURRAN

Engineering bull Science bull Operations bull 211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0403dwg04-20-05

s S pound

PLYMOUTH POND

PLYMOUTH POND

- -

5 PLYMOUTH POND

Jo

FEET

ft Shallow Monitoring Well mdashbullbullmdash 17-Acre Property Boundary Figure 1-ZD Deep Monitoring Well I 1 I Detected Concentration ND = Not Detected Distribution of Total VOCs in

Deep Bedrock Groundwater Pumping Well April 2003

Q) Residential Well Hows Corner Superfund Site Plymouth Maine

(T) Surface Water Sampling Point WOODARD ampCURRAN poundKk EnginawtirKj bull Science - Operations bull

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0403dwg04-20-05

0 Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

B MW-1B

I 12000

PCE

B 10000 Total VOCs

I

i 2000

i 0 Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

c MW-3B

G 2000

1800

B PCE

1600 Total VOCs

1 I I E

il-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

G E

211941

El

I I z E

80

Concentration Trends shy Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-13DB

Total VOCs

c i i c o

Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

MW-16DB

30

c i c c I c o

Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99

PCE

Total VOCs

Jul-01 Jul-03

211941

O bi

c Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

I MW-16IB

i 35

3

c Total VOCs

lt- 2 5

0 | gt

o

1 sectI

c c 0 4

Jul-90 Jul-92 Jul-94 Jul-96 Jul-98 Jul-00 Jul-02 Jul-04

I I MW-108D

I 12

PCE 10

Total VOCs c oc 3

E E I 0

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

E 211941

c Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

fi MW-108S

I I 40

PCE 35

Total VOCs

30

I f 26

20 I o

I 15

10

c Dec-99 Dec-00 Dec-01 Dec-02 Dec-03 I 0

I MW-112D

c 35 - imdash

I A3 shyTotal VOCs

o c

E 1 2

I

ition

B 1 ^

-i c 3

0 Dec-99 Dec-OO Dec-01 Dec-02 Dec-03

211941

I

i

I

cII

Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-112S

08

PCE

Total VOCs 06

o 04

02

0 Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

MW-114D

o

12000

10000

8000

6000

PCE

Total VOCs

4000

2000

i

ccEIIc

i

i

E

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

211941

Con

cent

ratio

n (

ug

l)

E Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

I MW-114S

E A5000 -- Total VOCs

- 4000

0 3000

2000

i 1000

i n shy

Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

MW-115D

c PCE

Total VOCs

c E

o

C c

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03 I 0

211941

IepoundII

EIEIIGICCIccc

30000

25000

20000

o bullsect 15000 b

o 10000 U

5000

0 Aug-99

25000

20000

5000

0 Aug-99

211941

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-2DB

PCE

Total VOCs

Aug-01 Aug-03

MW-2IB

PCE

Total VOCs

Aug-01 Aug-03

IDIBI

ii EIDIISIBIG C

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-102S

6000

5000 PCE

Total VOCs

4000

O 3000

2000

1000

0 Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

MW-103D

16000

~ 14000 ugt 3- 12000 o

^ 10000

sect 8000

O 6000

4000

2000

PCE

Total VOCs

0Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

211941

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

G MW-103S

I I

ampo

12000

10000

E sectc

S

8000

6000

4000

2000

0Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

G I 6000

MW-104D

i 5000

PCE

Total VOCs

i i c

2000

1000

Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

E I

211941

cIccIG

IIBCccBcIc

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-1041

PCE Total VOCs

a 25000

0 20000

a 15000

10000

5000

0 Jan-OO Jan-01 Jan-02 Jan-03 Jan-04

MW-106D

3000

2500 PCE

Total VOCs

=sect 2000

o bullsect 1500

1000

500

0 Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

211941

c Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

c MW-106S

I PCE

Total VOCs

i

i Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

i

i i i E

C

211941 c

Response to EPA-DEP Comment 5 Dated March 312005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

iiw

EPA-DEP Comment 5

Comment 5 Matrix Diffusion The report as well as other proponents of matrix diffusion suggest that depletion of DNAPL (Section 5112 page 5-15) needs to be achieved While that might be the ideal the goal is to achieve performance standards and that goal may be attainable while there is residual contamination in the rock perhaps even DNAPL globules The low bedrock matrix porosity (page 1-15) the high permeability values (page 4-4) the relative flux of the groundwater (page 5-5) and the decrease in surface area and out of the mainstream pockets (appendix C-4) all suggest that the diffusion out of the rock matrix would be insubstantial relative to the regional flux of groundwater through the Site

Response The TI Evaluation Report does not explicitly consider or rely upon matrix diffusion as a basis for requesting a TI Waiver for a portion of the Hows Corner Site The technical literature provides documentation that matrix diffusion can be a significant process that affects chemical transport and groundwater remediation timeframes in unconsolidated and consolidated media including fractured rock (US EPA 1989 Freeze and Cherry 1979 Pankow and Cherry 1996 Fountain 1998) Back diffusion of contaminants from the matrix porosity of the fractured rock can prolong the time necessary to achieve groundwater cleanup goals particularly for compounds such as PCE for which the cleanup goal is a low concentration It is our expectation that matrix diffusion has occurred at the Hows Corner Site and that back diffusion of PCE from the rock matrix will also occur Although the extent to which matrix diffusion is occurring at the Hows Comer Site has not been determined and that lack of knowledge contributes to uncertainty regarding the cleanup times at the Site the effect of matrix diffusion is to lengthen rather than shorten the time required for remediation

REFERENCES

Fountain JC 1998 Technologies for Dense Nonaqueous Phase Liquid Source Zone Remediation Ground-Water Remediation Technologies Analysis Center Technology Evaluation Report TE-98-02 December

Freeze RA and Cherry JA 1979 Groundwater Prentice-Hall Inc Englewood Cliffs NJ 07632 p 410-412

Pankow J F and Cherry J A 1996 Dense Chlorinated Solvents Waterloo Press Portland OR 97291-1399 p 67-88

US EPA 1989 Transport and Fate of Contaminants in the Subsurface EPA6254-89019 p 17-18

Response to EPA Comment 5 050305doc 1 of 1 Woodard amp Curran (211941)

WOODARD amp CURRAN Maine Massachusetts New Hampshire Connecticut Florida Operational offices across the US 1-800-426-4262 www woodardcurran com

Page 57: SDMS DocID 251749 - Records Collections · 2020-06-13 · CORPORATE OFFICES: Maine, Massachusetts, New Hampshire, Connecticut New, York, Florida Engineering • Science • Operations

- m j

PLYMOUTH POND

PLYMOUTH POND

PLYMOUTH POND j A O-shy

Shallow Monitoring Well E Detected Concentration ND = Not Detected Figure 1-ZS Distribution of Total VOCs in

Deep Monitoring Well Shallow Bedrock Groundwater

Pumping Well Hows Corner

April 2003 Superfund Site

17-Acre Property Boundary Plymouth Maine Concentration Contour (ugl) r WOODARD ampCURRAN

Engineering bull Science bull Operations bull 211941 Hows CornerwipDrawingsTI EVALtotalvocs-shallow-0403dwg04-20-05

s S pound

PLYMOUTH POND

PLYMOUTH POND

- -

5 PLYMOUTH POND

Jo

FEET

ft Shallow Monitoring Well mdashbullbullmdash 17-Acre Property Boundary Figure 1-ZD Deep Monitoring Well I 1 I Detected Concentration ND = Not Detected Distribution of Total VOCs in

Deep Bedrock Groundwater Pumping Well April 2003

Q) Residential Well Hows Corner Superfund Site Plymouth Maine

(T) Surface Water Sampling Point WOODARD ampCURRAN poundKk EnginawtirKj bull Science - Operations bull

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0403dwg04-20-05

0 Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

B MW-1B

I 12000

PCE

B 10000 Total VOCs

I

i 2000

i 0 Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

c MW-3B

G 2000

1800

B PCE

1600 Total VOCs

1 I I E

il-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

G E

211941

El

I I z E

80

Concentration Trends shy Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-13DB

Total VOCs

c i i c o

Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

MW-16DB

30

c i c c I c o

Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99

PCE

Total VOCs

Jul-01 Jul-03

211941

O bi

c Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

I MW-16IB

i 35

3

c Total VOCs

lt- 2 5

0 | gt

o

1 sectI

c c 0 4

Jul-90 Jul-92 Jul-94 Jul-96 Jul-98 Jul-00 Jul-02 Jul-04

I I MW-108D

I 12

PCE 10

Total VOCs c oc 3

E E I 0

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

E 211941

c Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

fi MW-108S

I I 40

PCE 35

Total VOCs

30

I f 26

20 I o

I 15

10

c Dec-99 Dec-00 Dec-01 Dec-02 Dec-03 I 0

I MW-112D

c 35 - imdash

I A3 shyTotal VOCs

o c

E 1 2

I

ition

B 1 ^

-i c 3

0 Dec-99 Dec-OO Dec-01 Dec-02 Dec-03

211941

I

i

I

cII

Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-112S

08

PCE

Total VOCs 06

o 04

02

0 Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

MW-114D

o

12000

10000

8000

6000

PCE

Total VOCs

4000

2000

i

ccEIIc

i

i

E

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

211941

Con

cent

ratio

n (

ug

l)

E Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

I MW-114S

E A5000 -- Total VOCs

- 4000

0 3000

2000

i 1000

i n shy

Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

MW-115D

c PCE

Total VOCs

c E

o

C c

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03 I 0

211941

IepoundII

EIEIIGICCIccc

30000

25000

20000

o bullsect 15000 b

o 10000 U

5000

0 Aug-99

25000

20000

5000

0 Aug-99

211941

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-2DB

PCE

Total VOCs

Aug-01 Aug-03

MW-2IB

PCE

Total VOCs

Aug-01 Aug-03

IDIBI

ii EIDIISIBIG C

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-102S

6000

5000 PCE

Total VOCs

4000

O 3000

2000

1000

0 Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

MW-103D

16000

~ 14000 ugt 3- 12000 o

^ 10000

sect 8000

O 6000

4000

2000

PCE

Total VOCs

0Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

211941

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

G MW-103S

I I

ampo

12000

10000

E sectc

S

8000

6000

4000

2000

0Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

G I 6000

MW-104D

i 5000

PCE

Total VOCs

i i c

2000

1000

Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

E I

211941

cIccIG

IIBCccBcIc

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-1041

PCE Total VOCs

a 25000

0 20000

a 15000

10000

5000

0 Jan-OO Jan-01 Jan-02 Jan-03 Jan-04

MW-106D

3000

2500 PCE

Total VOCs

=sect 2000

o bullsect 1500

1000

500

0 Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

211941

c Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

c MW-106S

I PCE

Total VOCs

i

i Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

i

i i i E

C

211941 c

Response to EPA-DEP Comment 5 Dated March 312005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

iiw

EPA-DEP Comment 5

Comment 5 Matrix Diffusion The report as well as other proponents of matrix diffusion suggest that depletion of DNAPL (Section 5112 page 5-15) needs to be achieved While that might be the ideal the goal is to achieve performance standards and that goal may be attainable while there is residual contamination in the rock perhaps even DNAPL globules The low bedrock matrix porosity (page 1-15) the high permeability values (page 4-4) the relative flux of the groundwater (page 5-5) and the decrease in surface area and out of the mainstream pockets (appendix C-4) all suggest that the diffusion out of the rock matrix would be insubstantial relative to the regional flux of groundwater through the Site

Response The TI Evaluation Report does not explicitly consider or rely upon matrix diffusion as a basis for requesting a TI Waiver for a portion of the Hows Corner Site The technical literature provides documentation that matrix diffusion can be a significant process that affects chemical transport and groundwater remediation timeframes in unconsolidated and consolidated media including fractured rock (US EPA 1989 Freeze and Cherry 1979 Pankow and Cherry 1996 Fountain 1998) Back diffusion of contaminants from the matrix porosity of the fractured rock can prolong the time necessary to achieve groundwater cleanup goals particularly for compounds such as PCE for which the cleanup goal is a low concentration It is our expectation that matrix diffusion has occurred at the Hows Corner Site and that back diffusion of PCE from the rock matrix will also occur Although the extent to which matrix diffusion is occurring at the Hows Comer Site has not been determined and that lack of knowledge contributes to uncertainty regarding the cleanup times at the Site the effect of matrix diffusion is to lengthen rather than shorten the time required for remediation

REFERENCES

Fountain JC 1998 Technologies for Dense Nonaqueous Phase Liquid Source Zone Remediation Ground-Water Remediation Technologies Analysis Center Technology Evaluation Report TE-98-02 December

Freeze RA and Cherry JA 1979 Groundwater Prentice-Hall Inc Englewood Cliffs NJ 07632 p 410-412

Pankow J F and Cherry J A 1996 Dense Chlorinated Solvents Waterloo Press Portland OR 97291-1399 p 67-88

US EPA 1989 Transport and Fate of Contaminants in the Subsurface EPA6254-89019 p 17-18

Response to EPA Comment 5 050305doc 1 of 1 Woodard amp Curran (211941)

WOODARD amp CURRAN Maine Massachusetts New Hampshire Connecticut Florida Operational offices across the US 1-800-426-4262 www woodardcurran com

Page 58: SDMS DocID 251749 - Records Collections · 2020-06-13 · CORPORATE OFFICES: Maine, Massachusetts, New Hampshire, Connecticut New, York, Florida Engineering • Science • Operations

s S pound

PLYMOUTH POND

PLYMOUTH POND

- -

5 PLYMOUTH POND

Jo

FEET

ft Shallow Monitoring Well mdashbullbullmdash 17-Acre Property Boundary Figure 1-ZD Deep Monitoring Well I 1 I Detected Concentration ND = Not Detected Distribution of Total VOCs in

Deep Bedrock Groundwater Pumping Well April 2003

Q) Residential Well Hows Corner Superfund Site Plymouth Maine

(T) Surface Water Sampling Point WOODARD ampCURRAN poundKk EnginawtirKj bull Science - Operations bull

211941 Hows CornerwipDrawingsTI EVALtotvocs-deep-0403dwg04-20-05

0 Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

B MW-1B

I 12000

PCE

B 10000 Total VOCs

I

i 2000

i 0 Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

c MW-3B

G 2000

1800

B PCE

1600 Total VOCs

1 I I E

il-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

G E

211941

El

I I z E

80

Concentration Trends shy Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-13DB

Total VOCs

c i i c o

Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

MW-16DB

30

c i c c I c o

Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99

PCE

Total VOCs

Jul-01 Jul-03

211941

O bi

c Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

I MW-16IB

i 35

3

c Total VOCs

lt- 2 5

0 | gt

o

1 sectI

c c 0 4

Jul-90 Jul-92 Jul-94 Jul-96 Jul-98 Jul-00 Jul-02 Jul-04

I I MW-108D

I 12

PCE 10

Total VOCs c oc 3

E E I 0

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

E 211941

c Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

fi MW-108S

I I 40

PCE 35

Total VOCs

30

I f 26

20 I o

I 15

10

c Dec-99 Dec-00 Dec-01 Dec-02 Dec-03 I 0

I MW-112D

c 35 - imdash

I A3 shyTotal VOCs

o c

E 1 2

I

ition

B 1 ^

-i c 3

0 Dec-99 Dec-OO Dec-01 Dec-02 Dec-03

211941

I

i

I

cII

Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-112S

08

PCE

Total VOCs 06

o 04

02

0 Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

MW-114D

o

12000

10000

8000

6000

PCE

Total VOCs

4000

2000

i

ccEIIc

i

i

E

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

211941

Con

cent

ratio

n (

ug

l)

E Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

I MW-114S

E A5000 -- Total VOCs

- 4000

0 3000

2000

i 1000

i n shy

Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

MW-115D

c PCE

Total VOCs

c E

o

C c

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03 I 0

211941

IepoundII

EIEIIGICCIccc

30000

25000

20000

o bullsect 15000 b

o 10000 U

5000

0 Aug-99

25000

20000

5000

0 Aug-99

211941

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-2DB

PCE

Total VOCs

Aug-01 Aug-03

MW-2IB

PCE

Total VOCs

Aug-01 Aug-03

IDIBI

ii EIDIISIBIG C

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-102S

6000

5000 PCE

Total VOCs

4000

O 3000

2000

1000

0 Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

MW-103D

16000

~ 14000 ugt 3- 12000 o

^ 10000

sect 8000

O 6000

4000

2000

PCE

Total VOCs

0Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

211941

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

G MW-103S

I I

ampo

12000

10000

E sectc

S

8000

6000

4000

2000

0Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

G I 6000

MW-104D

i 5000

PCE

Total VOCs

i i c

2000

1000

Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

E I

211941

cIccIG

IIBCccBcIc

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-1041

PCE Total VOCs

a 25000

0 20000

a 15000

10000

5000

0 Jan-OO Jan-01 Jan-02 Jan-03 Jan-04

MW-106D

3000

2500 PCE

Total VOCs

=sect 2000

o bullsect 1500

1000

500

0 Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

211941

c Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

c MW-106S

I PCE

Total VOCs

i

i Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

i

i i i E

C

211941 c

Response to EPA-DEP Comment 5 Dated March 312005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

iiw

EPA-DEP Comment 5

Comment 5 Matrix Diffusion The report as well as other proponents of matrix diffusion suggest that depletion of DNAPL (Section 5112 page 5-15) needs to be achieved While that might be the ideal the goal is to achieve performance standards and that goal may be attainable while there is residual contamination in the rock perhaps even DNAPL globules The low bedrock matrix porosity (page 1-15) the high permeability values (page 4-4) the relative flux of the groundwater (page 5-5) and the decrease in surface area and out of the mainstream pockets (appendix C-4) all suggest that the diffusion out of the rock matrix would be insubstantial relative to the regional flux of groundwater through the Site

Response The TI Evaluation Report does not explicitly consider or rely upon matrix diffusion as a basis for requesting a TI Waiver for a portion of the Hows Corner Site The technical literature provides documentation that matrix diffusion can be a significant process that affects chemical transport and groundwater remediation timeframes in unconsolidated and consolidated media including fractured rock (US EPA 1989 Freeze and Cherry 1979 Pankow and Cherry 1996 Fountain 1998) Back diffusion of contaminants from the matrix porosity of the fractured rock can prolong the time necessary to achieve groundwater cleanup goals particularly for compounds such as PCE for which the cleanup goal is a low concentration It is our expectation that matrix diffusion has occurred at the Hows Corner Site and that back diffusion of PCE from the rock matrix will also occur Although the extent to which matrix diffusion is occurring at the Hows Comer Site has not been determined and that lack of knowledge contributes to uncertainty regarding the cleanup times at the Site the effect of matrix diffusion is to lengthen rather than shorten the time required for remediation

REFERENCES

Fountain JC 1998 Technologies for Dense Nonaqueous Phase Liquid Source Zone Remediation Ground-Water Remediation Technologies Analysis Center Technology Evaluation Report TE-98-02 December

Freeze RA and Cherry JA 1979 Groundwater Prentice-Hall Inc Englewood Cliffs NJ 07632 p 410-412

Pankow J F and Cherry J A 1996 Dense Chlorinated Solvents Waterloo Press Portland OR 97291-1399 p 67-88

US EPA 1989 Transport and Fate of Contaminants in the Subsurface EPA6254-89019 p 17-18

Response to EPA Comment 5 050305doc 1 of 1 Woodard amp Curran (211941)

WOODARD amp CURRAN Maine Massachusetts New Hampshire Connecticut Florida Operational offices across the US 1-800-426-4262 www woodardcurran com

Page 59: SDMS DocID 251749 - Records Collections · 2020-06-13 · CORPORATE OFFICES: Maine, Massachusetts, New Hampshire, Connecticut New, York, Florida Engineering • Science • Operations

0 Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

B MW-1B

I 12000

PCE

B 10000 Total VOCs

I

i 2000

i 0 Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

c MW-3B

G 2000

1800

B PCE

1600 Total VOCs

1 I I E

il-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

G E

211941

El

I I z E

80

Concentration Trends shy Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-13DB

Total VOCs

c i i c o

Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

MW-16DB

30

c i c c I c o

Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99

PCE

Total VOCs

Jul-01 Jul-03

211941

O bi

c Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

I MW-16IB

i 35

3

c Total VOCs

lt- 2 5

0 | gt

o

1 sectI

c c 0 4

Jul-90 Jul-92 Jul-94 Jul-96 Jul-98 Jul-00 Jul-02 Jul-04

I I MW-108D

I 12

PCE 10

Total VOCs c oc 3

E E I 0

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

E 211941

c Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

fi MW-108S

I I 40

PCE 35

Total VOCs

30

I f 26

20 I o

I 15

10

c Dec-99 Dec-00 Dec-01 Dec-02 Dec-03 I 0

I MW-112D

c 35 - imdash

I A3 shyTotal VOCs

o c

E 1 2

I

ition

B 1 ^

-i c 3

0 Dec-99 Dec-OO Dec-01 Dec-02 Dec-03

211941

I

i

I

cII

Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-112S

08

PCE

Total VOCs 06

o 04

02

0 Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

MW-114D

o

12000

10000

8000

6000

PCE

Total VOCs

4000

2000

i

ccEIIc

i

i

E

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

211941

Con

cent

ratio

n (

ug

l)

E Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

I MW-114S

E A5000 -- Total VOCs

- 4000

0 3000

2000

i 1000

i n shy

Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

MW-115D

c PCE

Total VOCs

c E

o

C c

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03 I 0

211941

IepoundII

EIEIIGICCIccc

30000

25000

20000

o bullsect 15000 b

o 10000 U

5000

0 Aug-99

25000

20000

5000

0 Aug-99

211941

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-2DB

PCE

Total VOCs

Aug-01 Aug-03

MW-2IB

PCE

Total VOCs

Aug-01 Aug-03

IDIBI

ii EIDIISIBIG C

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-102S

6000

5000 PCE

Total VOCs

4000

O 3000

2000

1000

0 Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

MW-103D

16000

~ 14000 ugt 3- 12000 o

^ 10000

sect 8000

O 6000

4000

2000

PCE

Total VOCs

0Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

211941

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

G MW-103S

I I

ampo

12000

10000

E sectc

S

8000

6000

4000

2000

0Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

G I 6000

MW-104D

i 5000

PCE

Total VOCs

i i c

2000

1000

Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

E I

211941

cIccIG

IIBCccBcIc

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-1041

PCE Total VOCs

a 25000

0 20000

a 15000

10000

5000

0 Jan-OO Jan-01 Jan-02 Jan-03 Jan-04

MW-106D

3000

2500 PCE

Total VOCs

=sect 2000

o bullsect 1500

1000

500

0 Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

211941

c Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

c MW-106S

I PCE

Total VOCs

i

i Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

i

i i i E

C

211941 c

Response to EPA-DEP Comment 5 Dated March 312005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

iiw

EPA-DEP Comment 5

Comment 5 Matrix Diffusion The report as well as other proponents of matrix diffusion suggest that depletion of DNAPL (Section 5112 page 5-15) needs to be achieved While that might be the ideal the goal is to achieve performance standards and that goal may be attainable while there is residual contamination in the rock perhaps even DNAPL globules The low bedrock matrix porosity (page 1-15) the high permeability values (page 4-4) the relative flux of the groundwater (page 5-5) and the decrease in surface area and out of the mainstream pockets (appendix C-4) all suggest that the diffusion out of the rock matrix would be insubstantial relative to the regional flux of groundwater through the Site

Response The TI Evaluation Report does not explicitly consider or rely upon matrix diffusion as a basis for requesting a TI Waiver for a portion of the Hows Corner Site The technical literature provides documentation that matrix diffusion can be a significant process that affects chemical transport and groundwater remediation timeframes in unconsolidated and consolidated media including fractured rock (US EPA 1989 Freeze and Cherry 1979 Pankow and Cherry 1996 Fountain 1998) Back diffusion of contaminants from the matrix porosity of the fractured rock can prolong the time necessary to achieve groundwater cleanup goals particularly for compounds such as PCE for which the cleanup goal is a low concentration It is our expectation that matrix diffusion has occurred at the Hows Corner Site and that back diffusion of PCE from the rock matrix will also occur Although the extent to which matrix diffusion is occurring at the Hows Comer Site has not been determined and that lack of knowledge contributes to uncertainty regarding the cleanup times at the Site the effect of matrix diffusion is to lengthen rather than shorten the time required for remediation

REFERENCES

Fountain JC 1998 Technologies for Dense Nonaqueous Phase Liquid Source Zone Remediation Ground-Water Remediation Technologies Analysis Center Technology Evaluation Report TE-98-02 December

Freeze RA and Cherry JA 1979 Groundwater Prentice-Hall Inc Englewood Cliffs NJ 07632 p 410-412

Pankow J F and Cherry J A 1996 Dense Chlorinated Solvents Waterloo Press Portland OR 97291-1399 p 67-88

US EPA 1989 Transport and Fate of Contaminants in the Subsurface EPA6254-89019 p 17-18

Response to EPA Comment 5 050305doc 1 of 1 Woodard amp Curran (211941)

WOODARD amp CURRAN Maine Massachusetts New Hampshire Connecticut Florida Operational offices across the US 1-800-426-4262 www woodardcurran com

Page 60: SDMS DocID 251749 - Records Collections · 2020-06-13 · CORPORATE OFFICES: Maine, Massachusetts, New Hampshire, Connecticut New, York, Florida Engineering • Science • Operations

I I z E

80

Concentration Trends shy Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-13DB

Total VOCs

c i i c o

Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99 Jul-01 Jul-03

MW-16DB

30

c i c c I c o

Jul-89 Jul-91 Jul-93 Jul-95 Jul-97 Jul-99

PCE

Total VOCs

Jul-01 Jul-03

211941

O bi

c Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

I MW-16IB

i 35

3

c Total VOCs

lt- 2 5

0 | gt

o

1 sectI

c c 0 4

Jul-90 Jul-92 Jul-94 Jul-96 Jul-98 Jul-00 Jul-02 Jul-04

I I MW-108D

I 12

PCE 10

Total VOCs c oc 3

E E I 0

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

E 211941

c Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

fi MW-108S

I I 40

PCE 35

Total VOCs

30

I f 26

20 I o

I 15

10

c Dec-99 Dec-00 Dec-01 Dec-02 Dec-03 I 0

I MW-112D

c 35 - imdash

I A3 shyTotal VOCs

o c

E 1 2

I

ition

B 1 ^

-i c 3

0 Dec-99 Dec-OO Dec-01 Dec-02 Dec-03

211941

I

i

I

cII

Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-112S

08

PCE

Total VOCs 06

o 04

02

0 Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

MW-114D

o

12000

10000

8000

6000

PCE

Total VOCs

4000

2000

i

ccEIIc

i

i

E

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

211941

Con

cent

ratio

n (

ug

l)

E Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

I MW-114S

E A5000 -- Total VOCs

- 4000

0 3000

2000

i 1000

i n shy

Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

MW-115D

c PCE

Total VOCs

c E

o

C c

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03 I 0

211941

IepoundII

EIEIIGICCIccc

30000

25000

20000

o bullsect 15000 b

o 10000 U

5000

0 Aug-99

25000

20000

5000

0 Aug-99

211941

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-2DB

PCE

Total VOCs

Aug-01 Aug-03

MW-2IB

PCE

Total VOCs

Aug-01 Aug-03

IDIBI

ii EIDIISIBIG C

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-102S

6000

5000 PCE

Total VOCs

4000

O 3000

2000

1000

0 Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

MW-103D

16000

~ 14000 ugt 3- 12000 o

^ 10000

sect 8000

O 6000

4000

2000

PCE

Total VOCs

0Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

211941

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

G MW-103S

I I

ampo

12000

10000

E sectc

S

8000

6000

4000

2000

0Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

G I 6000

MW-104D

i 5000

PCE

Total VOCs

i i c

2000

1000

Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

E I

211941

cIccIG

IIBCccBcIc

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-1041

PCE Total VOCs

a 25000

0 20000

a 15000

10000

5000

0 Jan-OO Jan-01 Jan-02 Jan-03 Jan-04

MW-106D

3000

2500 PCE

Total VOCs

=sect 2000

o bullsect 1500

1000

500

0 Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

211941

c Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

c MW-106S

I PCE

Total VOCs

i

i Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

i

i i i E

C

211941 c

Response to EPA-DEP Comment 5 Dated March 312005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

iiw

EPA-DEP Comment 5

Comment 5 Matrix Diffusion The report as well as other proponents of matrix diffusion suggest that depletion of DNAPL (Section 5112 page 5-15) needs to be achieved While that might be the ideal the goal is to achieve performance standards and that goal may be attainable while there is residual contamination in the rock perhaps even DNAPL globules The low bedrock matrix porosity (page 1-15) the high permeability values (page 4-4) the relative flux of the groundwater (page 5-5) and the decrease in surface area and out of the mainstream pockets (appendix C-4) all suggest that the diffusion out of the rock matrix would be insubstantial relative to the regional flux of groundwater through the Site

Response The TI Evaluation Report does not explicitly consider or rely upon matrix diffusion as a basis for requesting a TI Waiver for a portion of the Hows Corner Site The technical literature provides documentation that matrix diffusion can be a significant process that affects chemical transport and groundwater remediation timeframes in unconsolidated and consolidated media including fractured rock (US EPA 1989 Freeze and Cherry 1979 Pankow and Cherry 1996 Fountain 1998) Back diffusion of contaminants from the matrix porosity of the fractured rock can prolong the time necessary to achieve groundwater cleanup goals particularly for compounds such as PCE for which the cleanup goal is a low concentration It is our expectation that matrix diffusion has occurred at the Hows Corner Site and that back diffusion of PCE from the rock matrix will also occur Although the extent to which matrix diffusion is occurring at the Hows Comer Site has not been determined and that lack of knowledge contributes to uncertainty regarding the cleanup times at the Site the effect of matrix diffusion is to lengthen rather than shorten the time required for remediation

REFERENCES

Fountain JC 1998 Technologies for Dense Nonaqueous Phase Liquid Source Zone Remediation Ground-Water Remediation Technologies Analysis Center Technology Evaluation Report TE-98-02 December

Freeze RA and Cherry JA 1979 Groundwater Prentice-Hall Inc Englewood Cliffs NJ 07632 p 410-412

Pankow J F and Cherry J A 1996 Dense Chlorinated Solvents Waterloo Press Portland OR 97291-1399 p 67-88

US EPA 1989 Transport and Fate of Contaminants in the Subsurface EPA6254-89019 p 17-18

Response to EPA Comment 5 050305doc 1 of 1 Woodard amp Curran (211941)

WOODARD amp CURRAN Maine Massachusetts New Hampshire Connecticut Florida Operational offices across the US 1-800-426-4262 www woodardcurran com

Page 61: SDMS DocID 251749 - Records Collections · 2020-06-13 · CORPORATE OFFICES: Maine, Massachusetts, New Hampshire, Connecticut New, York, Florida Engineering • Science • Operations

O bi

c Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

I MW-16IB

i 35

3

c Total VOCs

lt- 2 5

0 | gt

o

1 sectI

c c 0 4

Jul-90 Jul-92 Jul-94 Jul-96 Jul-98 Jul-00 Jul-02 Jul-04

I I MW-108D

I 12

PCE 10

Total VOCs c oc 3

E E I 0

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

E 211941

c Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

fi MW-108S

I I 40

PCE 35

Total VOCs

30

I f 26

20 I o

I 15

10

c Dec-99 Dec-00 Dec-01 Dec-02 Dec-03 I 0

I MW-112D

c 35 - imdash

I A3 shyTotal VOCs

o c

E 1 2

I

ition

B 1 ^

-i c 3

0 Dec-99 Dec-OO Dec-01 Dec-02 Dec-03

211941

I

i

I

cII

Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-112S

08

PCE

Total VOCs 06

o 04

02

0 Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

MW-114D

o

12000

10000

8000

6000

PCE

Total VOCs

4000

2000

i

ccEIIc

i

i

E

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

211941

Con

cent

ratio

n (

ug

l)

E Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

I MW-114S

E A5000 -- Total VOCs

- 4000

0 3000

2000

i 1000

i n shy

Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

MW-115D

c PCE

Total VOCs

c E

o

C c

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03 I 0

211941

IepoundII

EIEIIGICCIccc

30000

25000

20000

o bullsect 15000 b

o 10000 U

5000

0 Aug-99

25000

20000

5000

0 Aug-99

211941

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-2DB

PCE

Total VOCs

Aug-01 Aug-03

MW-2IB

PCE

Total VOCs

Aug-01 Aug-03

IDIBI

ii EIDIISIBIG C

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-102S

6000

5000 PCE

Total VOCs

4000

O 3000

2000

1000

0 Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

MW-103D

16000

~ 14000 ugt 3- 12000 o

^ 10000

sect 8000

O 6000

4000

2000

PCE

Total VOCs

0Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

211941

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

G MW-103S

I I

ampo

12000

10000

E sectc

S

8000

6000

4000

2000

0Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

G I 6000

MW-104D

i 5000

PCE

Total VOCs

i i c

2000

1000

Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

E I

211941

cIccIG

IIBCccBcIc

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-1041

PCE Total VOCs

a 25000

0 20000

a 15000

10000

5000

0 Jan-OO Jan-01 Jan-02 Jan-03 Jan-04

MW-106D

3000

2500 PCE

Total VOCs

=sect 2000

o bullsect 1500

1000

500

0 Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

211941

c Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

c MW-106S

I PCE

Total VOCs

i

i Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

i

i i i E

C

211941 c

Response to EPA-DEP Comment 5 Dated March 312005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

iiw

EPA-DEP Comment 5

Comment 5 Matrix Diffusion The report as well as other proponents of matrix diffusion suggest that depletion of DNAPL (Section 5112 page 5-15) needs to be achieved While that might be the ideal the goal is to achieve performance standards and that goal may be attainable while there is residual contamination in the rock perhaps even DNAPL globules The low bedrock matrix porosity (page 1-15) the high permeability values (page 4-4) the relative flux of the groundwater (page 5-5) and the decrease in surface area and out of the mainstream pockets (appendix C-4) all suggest that the diffusion out of the rock matrix would be insubstantial relative to the regional flux of groundwater through the Site

Response The TI Evaluation Report does not explicitly consider or rely upon matrix diffusion as a basis for requesting a TI Waiver for a portion of the Hows Corner Site The technical literature provides documentation that matrix diffusion can be a significant process that affects chemical transport and groundwater remediation timeframes in unconsolidated and consolidated media including fractured rock (US EPA 1989 Freeze and Cherry 1979 Pankow and Cherry 1996 Fountain 1998) Back diffusion of contaminants from the matrix porosity of the fractured rock can prolong the time necessary to achieve groundwater cleanup goals particularly for compounds such as PCE for which the cleanup goal is a low concentration It is our expectation that matrix diffusion has occurred at the Hows Corner Site and that back diffusion of PCE from the rock matrix will also occur Although the extent to which matrix diffusion is occurring at the Hows Comer Site has not been determined and that lack of knowledge contributes to uncertainty regarding the cleanup times at the Site the effect of matrix diffusion is to lengthen rather than shorten the time required for remediation

REFERENCES

Fountain JC 1998 Technologies for Dense Nonaqueous Phase Liquid Source Zone Remediation Ground-Water Remediation Technologies Analysis Center Technology Evaluation Report TE-98-02 December

Freeze RA and Cherry JA 1979 Groundwater Prentice-Hall Inc Englewood Cliffs NJ 07632 p 410-412

Pankow J F and Cherry J A 1996 Dense Chlorinated Solvents Waterloo Press Portland OR 97291-1399 p 67-88

US EPA 1989 Transport and Fate of Contaminants in the Subsurface EPA6254-89019 p 17-18

Response to EPA Comment 5 050305doc 1 of 1 Woodard amp Curran (211941)

WOODARD amp CURRAN Maine Massachusetts New Hampshire Connecticut Florida Operational offices across the US 1-800-426-4262 www woodardcurran com

Page 62: SDMS DocID 251749 - Records Collections · 2020-06-13 · CORPORATE OFFICES: Maine, Massachusetts, New Hampshire, Connecticut New, York, Florida Engineering • Science • Operations

c Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

fi MW-108S

I I 40

PCE 35

Total VOCs

30

I f 26

20 I o

I 15

10

c Dec-99 Dec-00 Dec-01 Dec-02 Dec-03 I 0

I MW-112D

c 35 - imdash

I A3 shyTotal VOCs

o c

E 1 2

I

ition

B 1 ^

-i c 3

0 Dec-99 Dec-OO Dec-01 Dec-02 Dec-03

211941

I

i

I

cII

Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-112S

08

PCE

Total VOCs 06

o 04

02

0 Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

MW-114D

o

12000

10000

8000

6000

PCE

Total VOCs

4000

2000

i

ccEIIc

i

i

E

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

211941

Con

cent

ratio

n (

ug

l)

E Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

I MW-114S

E A5000 -- Total VOCs

- 4000

0 3000

2000

i 1000

i n shy

Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

MW-115D

c PCE

Total VOCs

c E

o

C c

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03 I 0

211941

IepoundII

EIEIIGICCIccc

30000

25000

20000

o bullsect 15000 b

o 10000 U

5000

0 Aug-99

25000

20000

5000

0 Aug-99

211941

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-2DB

PCE

Total VOCs

Aug-01 Aug-03

MW-2IB

PCE

Total VOCs

Aug-01 Aug-03

IDIBI

ii EIDIISIBIG C

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-102S

6000

5000 PCE

Total VOCs

4000

O 3000

2000

1000

0 Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

MW-103D

16000

~ 14000 ugt 3- 12000 o

^ 10000

sect 8000

O 6000

4000

2000

PCE

Total VOCs

0Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

211941

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

G MW-103S

I I

ampo

12000

10000

E sectc

S

8000

6000

4000

2000

0Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

G I 6000

MW-104D

i 5000

PCE

Total VOCs

i i c

2000

1000

Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

E I

211941

cIccIG

IIBCccBcIc

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-1041

PCE Total VOCs

a 25000

0 20000

a 15000

10000

5000

0 Jan-OO Jan-01 Jan-02 Jan-03 Jan-04

MW-106D

3000

2500 PCE

Total VOCs

=sect 2000

o bullsect 1500

1000

500

0 Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

211941

c Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

c MW-106S

I PCE

Total VOCs

i

i Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

i

i i i E

C

211941 c

Response to EPA-DEP Comment 5 Dated March 312005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

iiw

EPA-DEP Comment 5

Comment 5 Matrix Diffusion The report as well as other proponents of matrix diffusion suggest that depletion of DNAPL (Section 5112 page 5-15) needs to be achieved While that might be the ideal the goal is to achieve performance standards and that goal may be attainable while there is residual contamination in the rock perhaps even DNAPL globules The low bedrock matrix porosity (page 1-15) the high permeability values (page 4-4) the relative flux of the groundwater (page 5-5) and the decrease in surface area and out of the mainstream pockets (appendix C-4) all suggest that the diffusion out of the rock matrix would be insubstantial relative to the regional flux of groundwater through the Site

Response The TI Evaluation Report does not explicitly consider or rely upon matrix diffusion as a basis for requesting a TI Waiver for a portion of the Hows Corner Site The technical literature provides documentation that matrix diffusion can be a significant process that affects chemical transport and groundwater remediation timeframes in unconsolidated and consolidated media including fractured rock (US EPA 1989 Freeze and Cherry 1979 Pankow and Cherry 1996 Fountain 1998) Back diffusion of contaminants from the matrix porosity of the fractured rock can prolong the time necessary to achieve groundwater cleanup goals particularly for compounds such as PCE for which the cleanup goal is a low concentration It is our expectation that matrix diffusion has occurred at the Hows Corner Site and that back diffusion of PCE from the rock matrix will also occur Although the extent to which matrix diffusion is occurring at the Hows Comer Site has not been determined and that lack of knowledge contributes to uncertainty regarding the cleanup times at the Site the effect of matrix diffusion is to lengthen rather than shorten the time required for remediation

REFERENCES

Fountain JC 1998 Technologies for Dense Nonaqueous Phase Liquid Source Zone Remediation Ground-Water Remediation Technologies Analysis Center Technology Evaluation Report TE-98-02 December

Freeze RA and Cherry JA 1979 Groundwater Prentice-Hall Inc Englewood Cliffs NJ 07632 p 410-412

Pankow J F and Cherry J A 1996 Dense Chlorinated Solvents Waterloo Press Portland OR 97291-1399 p 67-88

US EPA 1989 Transport and Fate of Contaminants in the Subsurface EPA6254-89019 p 17-18

Response to EPA Comment 5 050305doc 1 of 1 Woodard amp Curran (211941)

WOODARD amp CURRAN Maine Massachusetts New Hampshire Connecticut Florida Operational offices across the US 1-800-426-4262 www woodardcurran com

Page 63: SDMS DocID 251749 - Records Collections · 2020-06-13 · CORPORATE OFFICES: Maine, Massachusetts, New Hampshire, Connecticut New, York, Florida Engineering • Science • Operations

I

cII

Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-112S

08

PCE

Total VOCs 06

o 04

02

0 Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

MW-114D

o

12000

10000

8000

6000

PCE

Total VOCs

4000

2000

i

ccEIIc

i

i

E

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

211941

Con

cent

ratio

n (

ug

l)

E Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

I MW-114S

E A5000 -- Total VOCs

- 4000

0 3000

2000

i 1000

i n shy

Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

MW-115D

c PCE

Total VOCs

c E

o

C c

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03 I 0

211941

IepoundII

EIEIIGICCIccc

30000

25000

20000

o bullsect 15000 b

o 10000 U

5000

0 Aug-99

25000

20000

5000

0 Aug-99

211941

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-2DB

PCE

Total VOCs

Aug-01 Aug-03

MW-2IB

PCE

Total VOCs

Aug-01 Aug-03

IDIBI

ii EIDIISIBIG C

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-102S

6000

5000 PCE

Total VOCs

4000

O 3000

2000

1000

0 Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

MW-103D

16000

~ 14000 ugt 3- 12000 o

^ 10000

sect 8000

O 6000

4000

2000

PCE

Total VOCs

0Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

211941

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

G MW-103S

I I

ampo

12000

10000

E sectc

S

8000

6000

4000

2000

0Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

G I 6000

MW-104D

i 5000

PCE

Total VOCs

i i c

2000

1000

Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

E I

211941

cIccIG

IIBCccBcIc

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-1041

PCE Total VOCs

a 25000

0 20000

a 15000

10000

5000

0 Jan-OO Jan-01 Jan-02 Jan-03 Jan-04

MW-106D

3000

2500 PCE

Total VOCs

=sect 2000

o bullsect 1500

1000

500

0 Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

211941

c Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

c MW-106S

I PCE

Total VOCs

i

i Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

i

i i i E

C

211941 c

Response to EPA-DEP Comment 5 Dated March 312005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

iiw

EPA-DEP Comment 5

Comment 5 Matrix Diffusion The report as well as other proponents of matrix diffusion suggest that depletion of DNAPL (Section 5112 page 5-15) needs to be achieved While that might be the ideal the goal is to achieve performance standards and that goal may be attainable while there is residual contamination in the rock perhaps even DNAPL globules The low bedrock matrix porosity (page 1-15) the high permeability values (page 4-4) the relative flux of the groundwater (page 5-5) and the decrease in surface area and out of the mainstream pockets (appendix C-4) all suggest that the diffusion out of the rock matrix would be insubstantial relative to the regional flux of groundwater through the Site

Response The TI Evaluation Report does not explicitly consider or rely upon matrix diffusion as a basis for requesting a TI Waiver for a portion of the Hows Corner Site The technical literature provides documentation that matrix diffusion can be a significant process that affects chemical transport and groundwater remediation timeframes in unconsolidated and consolidated media including fractured rock (US EPA 1989 Freeze and Cherry 1979 Pankow and Cherry 1996 Fountain 1998) Back diffusion of contaminants from the matrix porosity of the fractured rock can prolong the time necessary to achieve groundwater cleanup goals particularly for compounds such as PCE for which the cleanup goal is a low concentration It is our expectation that matrix diffusion has occurred at the Hows Corner Site and that back diffusion of PCE from the rock matrix will also occur Although the extent to which matrix diffusion is occurring at the Hows Comer Site has not been determined and that lack of knowledge contributes to uncertainty regarding the cleanup times at the Site the effect of matrix diffusion is to lengthen rather than shorten the time required for remediation

REFERENCES

Fountain JC 1998 Technologies for Dense Nonaqueous Phase Liquid Source Zone Remediation Ground-Water Remediation Technologies Analysis Center Technology Evaluation Report TE-98-02 December

Freeze RA and Cherry JA 1979 Groundwater Prentice-Hall Inc Englewood Cliffs NJ 07632 p 410-412

Pankow J F and Cherry J A 1996 Dense Chlorinated Solvents Waterloo Press Portland OR 97291-1399 p 67-88

US EPA 1989 Transport and Fate of Contaminants in the Subsurface EPA6254-89019 p 17-18

Response to EPA Comment 5 050305doc 1 of 1 Woodard amp Curran (211941)

WOODARD amp CURRAN Maine Massachusetts New Hampshire Connecticut Florida Operational offices across the US 1-800-426-4262 www woodardcurran com

Page 64: SDMS DocID 251749 - Records Collections · 2020-06-13 · CORPORATE OFFICES: Maine, Massachusetts, New Hampshire, Connecticut New, York, Florida Engineering • Science • Operations

Con

cent

ratio

n (

ug

l)

E Concentration Trends - Non-Source Area Wells Hows Corner Superfund Site Plymouth Maine

I MW-114S

E A5000 -- Total VOCs

- 4000

0 3000

2000

i 1000

i n shy

Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

MW-115D

c PCE

Total VOCs

c E

o

C c

Dec-99 Dec-00 Dec-01 Dec-02 Dec-03 I 0

211941

IepoundII

EIEIIGICCIccc

30000

25000

20000

o bullsect 15000 b

o 10000 U

5000

0 Aug-99

25000

20000

5000

0 Aug-99

211941

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-2DB

PCE

Total VOCs

Aug-01 Aug-03

MW-2IB

PCE

Total VOCs

Aug-01 Aug-03

IDIBI

ii EIDIISIBIG C

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-102S

6000

5000 PCE

Total VOCs

4000

O 3000

2000

1000

0 Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

MW-103D

16000

~ 14000 ugt 3- 12000 o

^ 10000

sect 8000

O 6000

4000

2000

PCE

Total VOCs

0Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

211941

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

G MW-103S

I I

ampo

12000

10000

E sectc

S

8000

6000

4000

2000

0Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

G I 6000

MW-104D

i 5000

PCE

Total VOCs

i i c

2000

1000

Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

E I

211941

cIccIG

IIBCccBcIc

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-1041

PCE Total VOCs

a 25000

0 20000

a 15000

10000

5000

0 Jan-OO Jan-01 Jan-02 Jan-03 Jan-04

MW-106D

3000

2500 PCE

Total VOCs

=sect 2000

o bullsect 1500

1000

500

0 Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

211941

c Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

c MW-106S

I PCE

Total VOCs

i

i Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

i

i i i E

C

211941 c

Response to EPA-DEP Comment 5 Dated March 312005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

iiw

EPA-DEP Comment 5

Comment 5 Matrix Diffusion The report as well as other proponents of matrix diffusion suggest that depletion of DNAPL (Section 5112 page 5-15) needs to be achieved While that might be the ideal the goal is to achieve performance standards and that goal may be attainable while there is residual contamination in the rock perhaps even DNAPL globules The low bedrock matrix porosity (page 1-15) the high permeability values (page 4-4) the relative flux of the groundwater (page 5-5) and the decrease in surface area and out of the mainstream pockets (appendix C-4) all suggest that the diffusion out of the rock matrix would be insubstantial relative to the regional flux of groundwater through the Site

Response The TI Evaluation Report does not explicitly consider or rely upon matrix diffusion as a basis for requesting a TI Waiver for a portion of the Hows Corner Site The technical literature provides documentation that matrix diffusion can be a significant process that affects chemical transport and groundwater remediation timeframes in unconsolidated and consolidated media including fractured rock (US EPA 1989 Freeze and Cherry 1979 Pankow and Cherry 1996 Fountain 1998) Back diffusion of contaminants from the matrix porosity of the fractured rock can prolong the time necessary to achieve groundwater cleanup goals particularly for compounds such as PCE for which the cleanup goal is a low concentration It is our expectation that matrix diffusion has occurred at the Hows Corner Site and that back diffusion of PCE from the rock matrix will also occur Although the extent to which matrix diffusion is occurring at the Hows Comer Site has not been determined and that lack of knowledge contributes to uncertainty regarding the cleanup times at the Site the effect of matrix diffusion is to lengthen rather than shorten the time required for remediation

REFERENCES

Fountain JC 1998 Technologies for Dense Nonaqueous Phase Liquid Source Zone Remediation Ground-Water Remediation Technologies Analysis Center Technology Evaluation Report TE-98-02 December

Freeze RA and Cherry JA 1979 Groundwater Prentice-Hall Inc Englewood Cliffs NJ 07632 p 410-412

Pankow J F and Cherry J A 1996 Dense Chlorinated Solvents Waterloo Press Portland OR 97291-1399 p 67-88

US EPA 1989 Transport and Fate of Contaminants in the Subsurface EPA6254-89019 p 17-18

Response to EPA Comment 5 050305doc 1 of 1 Woodard amp Curran (211941)

WOODARD amp CURRAN Maine Massachusetts New Hampshire Connecticut Florida Operational offices across the US 1-800-426-4262 www woodardcurran com

Page 65: SDMS DocID 251749 - Records Collections · 2020-06-13 · CORPORATE OFFICES: Maine, Massachusetts, New Hampshire, Connecticut New, York, Florida Engineering • Science • Operations

IepoundII

EIEIIGICCIccc

30000

25000

20000

o bullsect 15000 b

o 10000 U

5000

0 Aug-99

25000

20000

5000

0 Aug-99

211941

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-2DB

PCE

Total VOCs

Aug-01 Aug-03

MW-2IB

PCE

Total VOCs

Aug-01 Aug-03

IDIBI

ii EIDIISIBIG C

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-102S

6000

5000 PCE

Total VOCs

4000

O 3000

2000

1000

0 Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

MW-103D

16000

~ 14000 ugt 3- 12000 o

^ 10000

sect 8000

O 6000

4000

2000

PCE

Total VOCs

0Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

211941

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

G MW-103S

I I

ampo

12000

10000

E sectc

S

8000

6000

4000

2000

0Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

G I 6000

MW-104D

i 5000

PCE

Total VOCs

i i c

2000

1000

Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

E I

211941

cIccIG

IIBCccBcIc

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-1041

PCE Total VOCs

a 25000

0 20000

a 15000

10000

5000

0 Jan-OO Jan-01 Jan-02 Jan-03 Jan-04

MW-106D

3000

2500 PCE

Total VOCs

=sect 2000

o bullsect 1500

1000

500

0 Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

211941

c Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

c MW-106S

I PCE

Total VOCs

i

i Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

i

i i i E

C

211941 c

Response to EPA-DEP Comment 5 Dated March 312005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

iiw

EPA-DEP Comment 5

Comment 5 Matrix Diffusion The report as well as other proponents of matrix diffusion suggest that depletion of DNAPL (Section 5112 page 5-15) needs to be achieved While that might be the ideal the goal is to achieve performance standards and that goal may be attainable while there is residual contamination in the rock perhaps even DNAPL globules The low bedrock matrix porosity (page 1-15) the high permeability values (page 4-4) the relative flux of the groundwater (page 5-5) and the decrease in surface area and out of the mainstream pockets (appendix C-4) all suggest that the diffusion out of the rock matrix would be insubstantial relative to the regional flux of groundwater through the Site

Response The TI Evaluation Report does not explicitly consider or rely upon matrix diffusion as a basis for requesting a TI Waiver for a portion of the Hows Corner Site The technical literature provides documentation that matrix diffusion can be a significant process that affects chemical transport and groundwater remediation timeframes in unconsolidated and consolidated media including fractured rock (US EPA 1989 Freeze and Cherry 1979 Pankow and Cherry 1996 Fountain 1998) Back diffusion of contaminants from the matrix porosity of the fractured rock can prolong the time necessary to achieve groundwater cleanup goals particularly for compounds such as PCE for which the cleanup goal is a low concentration It is our expectation that matrix diffusion has occurred at the Hows Corner Site and that back diffusion of PCE from the rock matrix will also occur Although the extent to which matrix diffusion is occurring at the Hows Comer Site has not been determined and that lack of knowledge contributes to uncertainty regarding the cleanup times at the Site the effect of matrix diffusion is to lengthen rather than shorten the time required for remediation

REFERENCES

Fountain JC 1998 Technologies for Dense Nonaqueous Phase Liquid Source Zone Remediation Ground-Water Remediation Technologies Analysis Center Technology Evaluation Report TE-98-02 December

Freeze RA and Cherry JA 1979 Groundwater Prentice-Hall Inc Englewood Cliffs NJ 07632 p 410-412

Pankow J F and Cherry J A 1996 Dense Chlorinated Solvents Waterloo Press Portland OR 97291-1399 p 67-88

US EPA 1989 Transport and Fate of Contaminants in the Subsurface EPA6254-89019 p 17-18

Response to EPA Comment 5 050305doc 1 of 1 Woodard amp Curran (211941)

WOODARD amp CURRAN Maine Massachusetts New Hampshire Connecticut Florida Operational offices across the US 1-800-426-4262 www woodardcurran com

Page 66: SDMS DocID 251749 - Records Collections · 2020-06-13 · CORPORATE OFFICES: Maine, Massachusetts, New Hampshire, Connecticut New, York, Florida Engineering • Science • Operations

IDIBI

ii EIDIISIBIG C

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-102S

6000

5000 PCE

Total VOCs

4000

O 3000

2000

1000

0 Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

MW-103D

16000

~ 14000 ugt 3- 12000 o

^ 10000

sect 8000

O 6000

4000

2000

PCE

Total VOCs

0Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

211941

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

G MW-103S

I I

ampo

12000

10000

E sectc

S

8000

6000

4000

2000

0Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

G I 6000

MW-104D

i 5000

PCE

Total VOCs

i i c

2000

1000

Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

E I

211941

cIccIG

IIBCccBcIc

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-1041

PCE Total VOCs

a 25000

0 20000

a 15000

10000

5000

0 Jan-OO Jan-01 Jan-02 Jan-03 Jan-04

MW-106D

3000

2500 PCE

Total VOCs

=sect 2000

o bullsect 1500

1000

500

0 Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

211941

c Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

c MW-106S

I PCE

Total VOCs

i

i Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

i

i i i E

C

211941 c

Response to EPA-DEP Comment 5 Dated March 312005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

iiw

EPA-DEP Comment 5

Comment 5 Matrix Diffusion The report as well as other proponents of matrix diffusion suggest that depletion of DNAPL (Section 5112 page 5-15) needs to be achieved While that might be the ideal the goal is to achieve performance standards and that goal may be attainable while there is residual contamination in the rock perhaps even DNAPL globules The low bedrock matrix porosity (page 1-15) the high permeability values (page 4-4) the relative flux of the groundwater (page 5-5) and the decrease in surface area and out of the mainstream pockets (appendix C-4) all suggest that the diffusion out of the rock matrix would be insubstantial relative to the regional flux of groundwater through the Site

Response The TI Evaluation Report does not explicitly consider or rely upon matrix diffusion as a basis for requesting a TI Waiver for a portion of the Hows Corner Site The technical literature provides documentation that matrix diffusion can be a significant process that affects chemical transport and groundwater remediation timeframes in unconsolidated and consolidated media including fractured rock (US EPA 1989 Freeze and Cherry 1979 Pankow and Cherry 1996 Fountain 1998) Back diffusion of contaminants from the matrix porosity of the fractured rock can prolong the time necessary to achieve groundwater cleanup goals particularly for compounds such as PCE for which the cleanup goal is a low concentration It is our expectation that matrix diffusion has occurred at the Hows Corner Site and that back diffusion of PCE from the rock matrix will also occur Although the extent to which matrix diffusion is occurring at the Hows Comer Site has not been determined and that lack of knowledge contributes to uncertainty regarding the cleanup times at the Site the effect of matrix diffusion is to lengthen rather than shorten the time required for remediation

REFERENCES

Fountain JC 1998 Technologies for Dense Nonaqueous Phase Liquid Source Zone Remediation Ground-Water Remediation Technologies Analysis Center Technology Evaluation Report TE-98-02 December

Freeze RA and Cherry JA 1979 Groundwater Prentice-Hall Inc Englewood Cliffs NJ 07632 p 410-412

Pankow J F and Cherry J A 1996 Dense Chlorinated Solvents Waterloo Press Portland OR 97291-1399 p 67-88

US EPA 1989 Transport and Fate of Contaminants in the Subsurface EPA6254-89019 p 17-18

Response to EPA Comment 5 050305doc 1 of 1 Woodard amp Curran (211941)

WOODARD amp CURRAN Maine Massachusetts New Hampshire Connecticut Florida Operational offices across the US 1-800-426-4262 www woodardcurran com

Page 67: SDMS DocID 251749 - Records Collections · 2020-06-13 · CORPORATE OFFICES: Maine, Massachusetts, New Hampshire, Connecticut New, York, Florida Engineering • Science • Operations

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

G MW-103S

I I

ampo

12000

10000

E sectc

S

8000

6000

4000

2000

0Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

G I 6000

MW-104D

i 5000

PCE

Total VOCs

i i c

2000

1000

Jan-00 Jan-01 Jan-02 Jan-03 Jan-04

E I

211941

cIccIG

IIBCccBcIc

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-1041

PCE Total VOCs

a 25000

0 20000

a 15000

10000

5000

0 Jan-OO Jan-01 Jan-02 Jan-03 Jan-04

MW-106D

3000

2500 PCE

Total VOCs

=sect 2000

o bullsect 1500

1000

500

0 Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

211941

c Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

c MW-106S

I PCE

Total VOCs

i

i Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

i

i i i E

C

211941 c

Response to EPA-DEP Comment 5 Dated March 312005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

iiw

EPA-DEP Comment 5

Comment 5 Matrix Diffusion The report as well as other proponents of matrix diffusion suggest that depletion of DNAPL (Section 5112 page 5-15) needs to be achieved While that might be the ideal the goal is to achieve performance standards and that goal may be attainable while there is residual contamination in the rock perhaps even DNAPL globules The low bedrock matrix porosity (page 1-15) the high permeability values (page 4-4) the relative flux of the groundwater (page 5-5) and the decrease in surface area and out of the mainstream pockets (appendix C-4) all suggest that the diffusion out of the rock matrix would be insubstantial relative to the regional flux of groundwater through the Site

Response The TI Evaluation Report does not explicitly consider or rely upon matrix diffusion as a basis for requesting a TI Waiver for a portion of the Hows Corner Site The technical literature provides documentation that matrix diffusion can be a significant process that affects chemical transport and groundwater remediation timeframes in unconsolidated and consolidated media including fractured rock (US EPA 1989 Freeze and Cherry 1979 Pankow and Cherry 1996 Fountain 1998) Back diffusion of contaminants from the matrix porosity of the fractured rock can prolong the time necessary to achieve groundwater cleanup goals particularly for compounds such as PCE for which the cleanup goal is a low concentration It is our expectation that matrix diffusion has occurred at the Hows Corner Site and that back diffusion of PCE from the rock matrix will also occur Although the extent to which matrix diffusion is occurring at the Hows Comer Site has not been determined and that lack of knowledge contributes to uncertainty regarding the cleanup times at the Site the effect of matrix diffusion is to lengthen rather than shorten the time required for remediation

REFERENCES

Fountain JC 1998 Technologies for Dense Nonaqueous Phase Liquid Source Zone Remediation Ground-Water Remediation Technologies Analysis Center Technology Evaluation Report TE-98-02 December

Freeze RA and Cherry JA 1979 Groundwater Prentice-Hall Inc Englewood Cliffs NJ 07632 p 410-412

Pankow J F and Cherry J A 1996 Dense Chlorinated Solvents Waterloo Press Portland OR 97291-1399 p 67-88

US EPA 1989 Transport and Fate of Contaminants in the Subsurface EPA6254-89019 p 17-18

Response to EPA Comment 5 050305doc 1 of 1 Woodard amp Curran (211941)

WOODARD amp CURRAN Maine Massachusetts New Hampshire Connecticut Florida Operational offices across the US 1-800-426-4262 www woodardcurran com

Page 68: SDMS DocID 251749 - Records Collections · 2020-06-13 · CORPORATE OFFICES: Maine, Massachusetts, New Hampshire, Connecticut New, York, Florida Engineering • Science • Operations

cIccIG

IIBCccBcIc

Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

MW-1041

PCE Total VOCs

a 25000

0 20000

a 15000

10000

5000

0 Jan-OO Jan-01 Jan-02 Jan-03 Jan-04

MW-106D

3000

2500 PCE

Total VOCs

=sect 2000

o bullsect 1500

1000

500

0 Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

211941

c Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

c MW-106S

I PCE

Total VOCs

i

i Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

i

i i i E

C

211941 c

Response to EPA-DEP Comment 5 Dated March 312005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

iiw

EPA-DEP Comment 5

Comment 5 Matrix Diffusion The report as well as other proponents of matrix diffusion suggest that depletion of DNAPL (Section 5112 page 5-15) needs to be achieved While that might be the ideal the goal is to achieve performance standards and that goal may be attainable while there is residual contamination in the rock perhaps even DNAPL globules The low bedrock matrix porosity (page 1-15) the high permeability values (page 4-4) the relative flux of the groundwater (page 5-5) and the decrease in surface area and out of the mainstream pockets (appendix C-4) all suggest that the diffusion out of the rock matrix would be insubstantial relative to the regional flux of groundwater through the Site

Response The TI Evaluation Report does not explicitly consider or rely upon matrix diffusion as a basis for requesting a TI Waiver for a portion of the Hows Corner Site The technical literature provides documentation that matrix diffusion can be a significant process that affects chemical transport and groundwater remediation timeframes in unconsolidated and consolidated media including fractured rock (US EPA 1989 Freeze and Cherry 1979 Pankow and Cherry 1996 Fountain 1998) Back diffusion of contaminants from the matrix porosity of the fractured rock can prolong the time necessary to achieve groundwater cleanup goals particularly for compounds such as PCE for which the cleanup goal is a low concentration It is our expectation that matrix diffusion has occurred at the Hows Corner Site and that back diffusion of PCE from the rock matrix will also occur Although the extent to which matrix diffusion is occurring at the Hows Comer Site has not been determined and that lack of knowledge contributes to uncertainty regarding the cleanup times at the Site the effect of matrix diffusion is to lengthen rather than shorten the time required for remediation

REFERENCES

Fountain JC 1998 Technologies for Dense Nonaqueous Phase Liquid Source Zone Remediation Ground-Water Remediation Technologies Analysis Center Technology Evaluation Report TE-98-02 December

Freeze RA and Cherry JA 1979 Groundwater Prentice-Hall Inc Englewood Cliffs NJ 07632 p 410-412

Pankow J F and Cherry J A 1996 Dense Chlorinated Solvents Waterloo Press Portland OR 97291-1399 p 67-88

US EPA 1989 Transport and Fate of Contaminants in the Subsurface EPA6254-89019 p 17-18

Response to EPA Comment 5 050305doc 1 of 1 Woodard amp Curran (211941)

WOODARD amp CURRAN Maine Massachusetts New Hampshire Connecticut Florida Operational offices across the US 1-800-426-4262 www woodardcurran com

Page 69: SDMS DocID 251749 - Records Collections · 2020-06-13 · CORPORATE OFFICES: Maine, Massachusetts, New Hampshire, Connecticut New, York, Florida Engineering • Science • Operations

c Concentration Trends - Source Area Wells Hows Corner Superfund Site Plymouth Maine

c MW-106S

I PCE

Total VOCs

i

i Dec-99 Dec-00 Dec-01 Dec-02 Dec-03

i

i i i E

C

211941 c

Response to EPA-DEP Comment 5 Dated March 312005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

iiw

EPA-DEP Comment 5

Comment 5 Matrix Diffusion The report as well as other proponents of matrix diffusion suggest that depletion of DNAPL (Section 5112 page 5-15) needs to be achieved While that might be the ideal the goal is to achieve performance standards and that goal may be attainable while there is residual contamination in the rock perhaps even DNAPL globules The low bedrock matrix porosity (page 1-15) the high permeability values (page 4-4) the relative flux of the groundwater (page 5-5) and the decrease in surface area and out of the mainstream pockets (appendix C-4) all suggest that the diffusion out of the rock matrix would be insubstantial relative to the regional flux of groundwater through the Site

Response The TI Evaluation Report does not explicitly consider or rely upon matrix diffusion as a basis for requesting a TI Waiver for a portion of the Hows Corner Site The technical literature provides documentation that matrix diffusion can be a significant process that affects chemical transport and groundwater remediation timeframes in unconsolidated and consolidated media including fractured rock (US EPA 1989 Freeze and Cherry 1979 Pankow and Cherry 1996 Fountain 1998) Back diffusion of contaminants from the matrix porosity of the fractured rock can prolong the time necessary to achieve groundwater cleanup goals particularly for compounds such as PCE for which the cleanup goal is a low concentration It is our expectation that matrix diffusion has occurred at the Hows Corner Site and that back diffusion of PCE from the rock matrix will also occur Although the extent to which matrix diffusion is occurring at the Hows Comer Site has not been determined and that lack of knowledge contributes to uncertainty regarding the cleanup times at the Site the effect of matrix diffusion is to lengthen rather than shorten the time required for remediation

REFERENCES

Fountain JC 1998 Technologies for Dense Nonaqueous Phase Liquid Source Zone Remediation Ground-Water Remediation Technologies Analysis Center Technology Evaluation Report TE-98-02 December

Freeze RA and Cherry JA 1979 Groundwater Prentice-Hall Inc Englewood Cliffs NJ 07632 p 410-412

Pankow J F and Cherry J A 1996 Dense Chlorinated Solvents Waterloo Press Portland OR 97291-1399 p 67-88

US EPA 1989 Transport and Fate of Contaminants in the Subsurface EPA6254-89019 p 17-18

Response to EPA Comment 5 050305doc 1 of 1 Woodard amp Curran (211941)

WOODARD amp CURRAN Maine Massachusetts New Hampshire Connecticut Florida Operational offices across the US 1-800-426-4262 www woodardcurran com

Page 70: SDMS DocID 251749 - Records Collections · 2020-06-13 · CORPORATE OFFICES: Maine, Massachusetts, New Hampshire, Connecticut New, York, Florida Engineering • Science • Operations

Response to EPA-DEP Comment 5 Dated March 312005 On the Draft Technical Impracticability Evaluation

Hows Corner Superfund Site Plymouth Maine

iiw

EPA-DEP Comment 5

Comment 5 Matrix Diffusion The report as well as other proponents of matrix diffusion suggest that depletion of DNAPL (Section 5112 page 5-15) needs to be achieved While that might be the ideal the goal is to achieve performance standards and that goal may be attainable while there is residual contamination in the rock perhaps even DNAPL globules The low bedrock matrix porosity (page 1-15) the high permeability values (page 4-4) the relative flux of the groundwater (page 5-5) and the decrease in surface area and out of the mainstream pockets (appendix C-4) all suggest that the diffusion out of the rock matrix would be insubstantial relative to the regional flux of groundwater through the Site

Response The TI Evaluation Report does not explicitly consider or rely upon matrix diffusion as a basis for requesting a TI Waiver for a portion of the Hows Corner Site The technical literature provides documentation that matrix diffusion can be a significant process that affects chemical transport and groundwater remediation timeframes in unconsolidated and consolidated media including fractured rock (US EPA 1989 Freeze and Cherry 1979 Pankow and Cherry 1996 Fountain 1998) Back diffusion of contaminants from the matrix porosity of the fractured rock can prolong the time necessary to achieve groundwater cleanup goals particularly for compounds such as PCE for which the cleanup goal is a low concentration It is our expectation that matrix diffusion has occurred at the Hows Corner Site and that back diffusion of PCE from the rock matrix will also occur Although the extent to which matrix diffusion is occurring at the Hows Comer Site has not been determined and that lack of knowledge contributes to uncertainty regarding the cleanup times at the Site the effect of matrix diffusion is to lengthen rather than shorten the time required for remediation

REFERENCES

Fountain JC 1998 Technologies for Dense Nonaqueous Phase Liquid Source Zone Remediation Ground-Water Remediation Technologies Analysis Center Technology Evaluation Report TE-98-02 December

Freeze RA and Cherry JA 1979 Groundwater Prentice-Hall Inc Englewood Cliffs NJ 07632 p 410-412

Pankow J F and Cherry J A 1996 Dense Chlorinated Solvents Waterloo Press Portland OR 97291-1399 p 67-88

US EPA 1989 Transport and Fate of Contaminants in the Subsurface EPA6254-89019 p 17-18

Response to EPA Comment 5 050305doc 1 of 1 Woodard amp Curran (211941)

WOODARD amp CURRAN Maine Massachusetts New Hampshire Connecticut Florida Operational offices across the US 1-800-426-4262 www woodardcurran com

Page 71: SDMS DocID 251749 - Records Collections · 2020-06-13 · CORPORATE OFFICES: Maine, Massachusetts, New Hampshire, Connecticut New, York, Florida Engineering • Science • Operations

EPA-DEP Comment 5

Comment 5 Matrix Diffusion The report as well as other proponents of matrix diffusion suggest that depletion of DNAPL (Section 5112 page 5-15) needs to be achieved While that might be the ideal the goal is to achieve performance standards and that goal may be attainable while there is residual contamination in the rock perhaps even DNAPL globules The low bedrock matrix porosity (page 1-15) the high permeability values (page 4-4) the relative flux of the groundwater (page 5-5) and the decrease in surface area and out of the mainstream pockets (appendix C-4) all suggest that the diffusion out of the rock matrix would be insubstantial relative to the regional flux of groundwater through the Site

Response The TI Evaluation Report does not explicitly consider or rely upon matrix diffusion as a basis for requesting a TI Waiver for a portion of the Hows Corner Site The technical literature provides documentation that matrix diffusion can be a significant process that affects chemical transport and groundwater remediation timeframes in unconsolidated and consolidated media including fractured rock (US EPA 1989 Freeze and Cherry 1979 Pankow and Cherry 1996 Fountain 1998) Back diffusion of contaminants from the matrix porosity of the fractured rock can prolong the time necessary to achieve groundwater cleanup goals particularly for compounds such as PCE for which the cleanup goal is a low concentration It is our expectation that matrix diffusion has occurred at the Hows Corner Site and that back diffusion of PCE from the rock matrix will also occur Although the extent to which matrix diffusion is occurring at the Hows Comer Site has not been determined and that lack of knowledge contributes to uncertainty regarding the cleanup times at the Site the effect of matrix diffusion is to lengthen rather than shorten the time required for remediation

REFERENCES

Fountain JC 1998 Technologies for Dense Nonaqueous Phase Liquid Source Zone Remediation Ground-Water Remediation Technologies Analysis Center Technology Evaluation Report TE-98-02 December

Freeze RA and Cherry JA 1979 Groundwater Prentice-Hall Inc Englewood Cliffs NJ 07632 p 410-412

Pankow J F and Cherry J A 1996 Dense Chlorinated Solvents Waterloo Press Portland OR 97291-1399 p 67-88

US EPA 1989 Transport and Fate of Contaminants in the Subsurface EPA6254-89019 p 17-18

Response to EPA Comment 5 050305doc 1 of 1 Woodard amp Curran (211941)

WOODARD amp CURRAN Maine Massachusetts New Hampshire Connecticut Florida Operational offices across the US 1-800-426-4262 www woodardcurran com

Page 72: SDMS DocID 251749 - Records Collections · 2020-06-13 · CORPORATE OFFICES: Maine, Massachusetts, New Hampshire, Connecticut New, York, Florida Engineering • Science • Operations

WOODARD amp CURRAN Maine Massachusetts New Hampshire Connecticut Florida Operational offices across the US 1-800-426-4262 www woodardcurran com