poundD sr UNITED STATES ENVIRONMENTAL PROTECTION AGENCY f 2 l S R8 S^^ bull ^ i ^ ^ - REGIONS

I mM bull 1595 Wynkoop street I ^ 5 ^ ^ I DENVER CO 80202-1129 C ^ ^ ^ ^ Phone 800-227-8917

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REF 8EPR-F

MEMORANDUM

SUBJECT Final Explanation of Significant Differences (ESD) for Operable Unit (OU) 2

FROM Maple A Bamard Remedial Project Manager

TO Carol L Campbell Assistant Regional Administrator Office of Ecosystems Protection and Remediation

Attached is the Final ESD 0U2 along with three copies of EPAs signature page The ESD modifies 0U2s source zone treatment system for treatment of ground water on base by eliminating pre-treatment using a steam stripper The Air Stripper Treatment Plant will continue to treat TCE contamination of ground water There are no changes to the applicable or relevant and appropriate requirements (ARAR) but the means of complying has changed The UDEQ provided the required signature pages at the Hill AFB Project Managers Meeting

Attachment

reg Printed on Recycled Paper

FINAL EXPLANATION OF SIGNIFICANT DIFFERENCES

FOR

OPERABLE UNIT 2

fflLL AIR FORCE BASE UTAH

SEPTMEBER 2009

PREPARED BY

Environmental Restoration Branch 75th Civil Engineer Group

Hill Air Force Base UT

HXPIANA riUN OF SIGNIFICANT DIFFERENCES OUl HILL AFB UTAH

Explanation of Significant Differences Operable Unit 2 (OU 2) Hill Air Force Base Utah

INTRODUCTION

This Explanation of Significant Differences (ESD) relates to remedial actions selected by the United States Air Force (USAF) for implementation at Operable Unit 2 (OU 2) at Hill Air Force Base (AFB) Utah in a Record of Decision (ROD) issued in September 1996 (CH2M HILL 1996) Operable Unit 2 is comprised of two Installation Restoration Program (IRP) sites Chemical Pit 3 (WP007) and the Perimeter Road (SS021) Site SS021 included potential disposal sites along Perimeter Road investigated in the late 1980s (Radian 1990) Chemical Pit 3 along with the North Gate Dump Sites (now part of Operable Unit 4) were the only sites where contamination was identified The ROD for OU 2 concluded that no further action was required for SS021 Site WP007 consists of two unlined trenches that were used for the disposal of unknown quantities of chlorinated spent solvents

Operable Unit 2 is addressed in two components the source zone and the non-source zone The source zone is on-Base and is the immediate area around the former Chemical Disposal Pit 3 that is underlain by a dense non-aqueous phase liquid (DNAPL) and affected areas west of Perimeter Road This area has the highest concentrations of contaminants and occupies approximately 6 acres (Figure 1) The non-source zone is north and east of the source zone and Perimeter Road The non-source zone includes shallow groundwater and seep and spring contamination off-Base This area generally has lower contaminant concentrations and occupies approximately 25 acres

An ESD is required to address differences in the following selected remedies for the OU 2 source zone treatment of extracted source zone groundwater with the existing Air Stripper Treatment Plant (ASTP) without pre-treatment by the existing steam stripper

In July 1987 the US Environmental Protection Agency (EPA) placed Hill AFB on the National Priorities List (NPL) under Comprehensive Environmental Response Compensation and Liability Act (CERCLA) In April 1991 Hill AFB entered a Federal Facility Agreement (FFA) with the Utah Department of Environmental Quality (UDEQ) and the EPA Region VIII to establish a procedural framework and schedule for implementing the appropriate response actions in accordance with existing regulations Under the FFA and Executive Order 12580 Hill AFB is the lead agency for all CERCLA actions and UDEQ and the EPA are support agencies Hill AFB seeks concurrence from both the EPA and UDEQ for significant decisions involving cleanup strategy goals and methods

This ESD is issued in accordance with Section 117(c) ofthe CERCLA 42 USC sect 9617(c) and Section 300435(c)(2)(i) ofthe National Oil and Hazardous Substances Pollution Contingency Plan (NCP) which requires the USAF to issue such a document where a remedial action will differ in any significant but not fundamental respect from that selected by the USAF and described in the ROD A significant change to a remedy is one that incrementally changes a component of a remedy (such as cost) but does not fundamentally alter the remedy (such as a change in the selected pump-and-treat remedy) The revised remedy described in this ESD

EXP IAN ATI ON OF SIGNIFICANT DIFFERENCES OUl HILL AFB UTAH

EXPLANATION TCE concentrations In

microsram plaquor Htsr (tilaquo1) frMM X004300

N

Conveyance Line to Central Weber Sewer Improvement

DistrFct

System (UCS) Trench L ^ v

Air Stripper Treatment

(ASTP) Plant r T ^ M (

1 - J A J A i SRS Process r I Building

Figure I Operable Unit 2 site features

complies with the NCP and the statutory requirements of CERLCA The ESD has been prepared to provide the public with an explanation of the nature of the modification to the selected remedy set forth in the ROD and to summarize the infonnation that supports this modification The ESD will become part of the Administrative Record file (40 CFR 300825(a)(2)) and the information repository (40 CFR 300435(c)(2)(i)(A)) for Hill AFB which is located and available for public review at

75CEG CEVR 7274 Wardleigh RD Hill AFB UT 84056-5137

EXIIANA HON UF SIGNIFICANT DIFFERENCES ou 2 HILL AFB UTAH

The Administrative Record is also available for public review at

Weber State University - Ogden Campus Weber State University - Davis Campus Stewart Library Stewart Library 3850 University Circle 2750 University Park Blvd Ogden UT 84408 Layton UT 84041-9099 (801)626-6403

The USAF EPA and UDEQ conclude that the remedy selected in the ROD as modified by this ESD will meet the objectives and performance standards of the ROD

SUMMARY OF THE SITE HISTORY SITE CONDITIONS AND SELECTED REMEDY

Site History

Operable Unit 2 is located along the northeastem boundary of Hill AFB overlooking the Weber River Valley and is one of 13 Operable Units at Hill AFB in various stages ofthe CERCLA process Records indicate that from 1967 to 1975 unknown quantities of chlorinated organic solvents generated during degreasing operations were disposed in trenches (chemical pits) at the site These compounds were placed into two unlined disposal trenches trending north northwest which are estimated to have been approximately 6 to 9 feet deep 10 feet wide and approximately 50 to 100 feet long (Radian 1992) The disposal area is underlain by an alluvial sand aquifer that is composed of a heterogeneous mixture of sand and gravel contained in a narrow buried ancient river channel incised deeply into the underlying clay deposit This clay deposit known as the Alpine Formation forms a barrier to the downward migration of DNAPL

Disposal of the spent chlorinated solvents resulted in DNAPL contaminafion of the underlying shallow aquifer (the Provo Formation) predominantly as one or more pools above the clay (the Alpine Formation) and also as a residual phase held in the aquifers pore spaces (the volume in between individual soil particles) The recovered DNAPL consists primarily of several chlorinated solvents (about 70 percent trichloroethene [TCE] with smaller amounts of 111-trichloroethane [111-TCA] tetrachloroethene [PCE] and methylene chloride) 112 trichloro-122-trifluoroethane (Freon 113) and a lesser amount of oil and grease (URS and DEampS 2001) Contaminated soils near the trenches and the pooled DNAPL are the source of shallow dissolved phase groundwater contamination extending approximately 1500 feet downgradient and beyond the Hill AFB boundary (CH2M HILL 1996) Groundwater contamination appears limited to the shallow unconfined aquifer ofthe Provo Formation

Site Conditions

The on-Base portion of OU 2 sits upon relatively flat lying ground while the off-Base portion of the site consists of a steep terraced north-facing escarpment that is the south wall of the Weber River Valley There is about 300 feet of relief between Hill AFB and the valley below Parts of this hillside are unstable and are known as the Weber Landslide Complex Numerous seeps and

EXIIANA TION OF SIGNIFICANT DIFFERENCES ou 2 HILL AFB UTAH

springs occur along the hillside Depending on water table elevation and the season the springs and seeps discharge water from the shallow groundwater system Depth to groundwater in the shallow system is generally less than 10 feet below ground surface (bgs) in the off-Base area and 20 feet bgs in the on-Base area Along the hillside escarpment and just outside ofthe northeastem Base boundary is the Davis-Weber Canal a privately owned concrete-lined irrigation canal The canal parallels the northeast boundary along most of the Base adjacent to the Weber River Valley The canal provides water from the Weber River for irrigation in the surrounding areas (CH2M HILL 1996)

Selected Remedy

The remedies that were selected for the OU 2 source zone are outlined in the Record of Decision issued in 1996 (CH2M HILL 1996) Those remedies include the following

bull Installadon of a low-permeability vertical barrier around the DNAPL and associated highly contaminated groundwater in the source zone to hinder flow to and from the source zone

bull Continued operation of the Source Recovery System (SRS) to remove DNAPL to the maximum extent practicable and to treat shallow groundwater containing high concentrations of VOCs using steam stripping

bull Completion of planned treatability studies using in-situ steam stripping and surfactant flushing for enhanced DNAPL recovery

bull Soil vapor extraction (SVE) after dewatering of the shallow aquifer to remove VOCs from subsurface soils in what is currently the saturated zone

bull Construction of a surface cap once treatment is completed or it is established the innovative technologies cannot meet remedial action objectives to decrease the inflow of precipitation and prevent erosion of surface soils

bull Environmental monitoring to evaluate the effectiveness of the remedy

bull Institutional controls to minimize exposure by limiting use and preventing access to Contaminated water and soil

One of the remedies specified by the ROD is a low permeability containment wall encircling the source zone to reduce the potential for further contamination of groundwater After the wall was built however an additional accumulation of free-phase DNAPL was identified outside of the wall (URS and DEampS 1999) This accumulation is informally known as either the Griffith Pool or the G-Pool A well field was installed in 1998 to extract mobile DNAPL from the area and to hydraulically contain the groundwater to minimize further contaminant flux to the off-Base plume

DESCRIPTION OF AND BASIS FOR THE DIFFERENCES

The SRS was constructed as an interim remedial action in 1993 to recover DNAPL from the source zone and to treat groundwater containing elevated concentrations of VOCs The SRS consists of a free-product and groundwater recovery well field aboveground pipeline and a process treatment facility (Building 755) Dense nonaqueous phase liquid is recovered during the

EXPLANA TIONOF SIGNIFICANT DIFFERENCES 0U2HIUAFB UTAH

treatment process using three phase separators while dissolved VOCs are removed from the groundwater using a packed-bed steam stripper In 1996 the Air Stripper Treatment Plant (ASTP) was constructed at OU 2 to provide secondary treatment of groundwater frorn the source zone following initial treatment with the steam stripper Prior to 2005 water was discharged from the ASTP to the on-base industrial wastewater treatment plant In 2005 an agreement was signed with Central Weber Sewer Improvement District (CWSID) allowing discharge oftreated water from OU 2 into the sanitary sewer Figure 2 provides a simplified process flow diagram illustrating the difference in the treatment process described in this ESD

Previous process flow

SRS Stop 1 DNAPL

separation

SRS Step 2 Steam

stripping

Pumped water from source zone

Discharge to sanitarYscver

Current process fiovi^

ASTP Air

stripping

Pumped water from source zone

Discharge to sanitary sewer

Figure 2 Simplified process flow diagram for OU 2 water treatment

Since 1992 approximately 44400 gallons of DNAPL have been recovered and over 20 million gallons of contaminated groundwater have been treated by steam stripping Of the total volume of DNAPL recovered 41000 gallons have been recovered primarily as mobile DNAPL via pump-and-treat operations and 3400 gallons have been recovered using enhanced-removal techniques Because the DNAPL recovery from the source zone has been successful DNAPL can no longer be extracted from the existing well field As the amount of DNAPL has decreased within the source zone the average concentration of VOCs in water extracted from the source zone has declined The average concentration of total VOCs in the influent to the SRS historically has ranged from 100 to 300 milligrams per liter (mgL) but concentrations generally have decreased to less than 100 mgL since the beginning of 2006 Hill AFB decided to evaluate

EXPLANA TION OF SIGNIFICANT DIFFERENCES OU 2 HILL AFB UTAH

altemative treatment options because the concentrations of VOCs being treated by the steam stripping process were decreasing

In 2007 Hill AFB proposed testing to determine if source zone water could be treated with the existing ASTP without pre-treatment by the steam stripper (January 25 2007 Project Managers meeting and letter dated March 152007) Piping modifications were completed during the fall of 2007 and initial testing was conducted during January and Febmary 2008 The results of this initial testing clearly showed that the ASTP is capable of achieving the treatment required to maintain compliance with the existing CWSED wastewater discharge permit without preshytreatment by the steam stripper Based on the initial results treatment of source zone water using the ASTP was continued to collect additional data to verify VOC removal efficiency over a one-year prove-out period This prove-out period included increased monitoring of both influent and effluent to the ASTP to allow evaluation of variability in either ASTP operating efficiency andor influent water concentrations

Currently the discharge limit to the CWSID is 2100 ^gL total volatiles (Method E624) The ASTP effluent concentrations remained below this discharge limit during 2008 as shown in Table 1 The calculated treatment efficiency was nominally 100 percent during 24 of 26 sampling events The remaining two sampling events had treatment efficiencies of 998 and 999 percent Figure 3 presents the ASTP effluent concentration over time As is evident from Figure 3 the total VOC concentration in the ASTP effluent has consistentiy been below the discharge limit and has not increased since piping modifications were completed during the fall of 2007

The fact that extracted source zone groundwater at OU 2 is no longer being pre-treated using the steam stripper constitutes a significant but not fundamental difference to the selected remedy outlined in the ROD This modification to the OU 2 source zone treatment system still provides safe and effective groundwater treatment with no additional environmental risk and with no added time to achieve cleanup

PUBLIC PARTICIPATION

This ESD was discussed during the July 30 2009 Restoration Advisory Board (RAB) meeting Discussion will include public notification procedures for ESDs The RAB will be requested to review both the process Hill AFB is using to prepare this ESD and the technical differences documented in this ESD

The RAB will be notified of the submission of the finalized ESD at the first quarterly RAB meeting after the ESD is signed Hill AFB will publish a notice of availability and a brief description ofthe ESD in the local newspaper Ogden Standard Examiner the week following

EXPIANA TION OF SIGNIFICNT DIFFERENCES OU 2 HILL AFB UTAH

TABLE 1 ASTP Total VOC Influent and Effluent Concentrations During 2008

Sample Date

012508

012908

020508

020808

021908

022908

030608

032508

040208

040408

040708

040808

040908

041008

041108

051408

052808

061008

062608

070808

072108

081808

090908

100808

111308

120908

Influent Concentration

(MgL) 104997

14603

159587

209442

3119

63952

72079

637

345

511

462

630

955

1013

1177

1015

1346

940

1342

1644

1239

1318

572

54466

158879

126171

Effluent Concentration

(ugL) 189

182

360

209

130

092

043

000

000

020

000

000

000

000

020

000

000

000

000

140

000

000

000

050

040

080

Treatment Efficiency (percent)

1000

1000

998

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

999

1000

1000

1000

1000

1000

1000

NOTES ngL = Micrograms per Liter VOC = Volatile Organic Compound Total VOCs calculated based on Method E624

EXPLANA TION OF SIGNIFICANT DIFFERENCES OU 2 HILL AFB UTAH

j

bull9

c o

5 c o c o o o O gt

o 1 -

1000000

100000

10000

1000

100

10

1

0

i 1

reg Influent

bull Effluent

^ 1 1 1

copy

9 c

raquo copy

CWSID Discharge Permit Concentration 2100 |igL Total Volatiles

s bull bull

c c ra

- 3

reg

regreg reg

1 bull

reg

reg

Jan-04

Jan-05 lt lt

Jan-06 1

Jan-07

1

Jan-08

Jan-09

Figure 3 ASTP Influent and Effluent Total VOC (Method E624) Concentration over Time

that RAB meeting This ESD and the infonnation upon which it is based will be included in the Administrative Record for this Site The Administrative Record also includes the ROD and all documents that formed the basis for USAFs selection and EPA and UDEQs concurrence ofthe remedial action for the Site These components meet the public participation requirement set out in Section 3()0435(c)(2)(i) of the NCP

REFERENCES

CH2M HILL 1996 Record of Decision and Respomiveness Summary for Operable Unit 2 Final Hill AFB Utah September

CH2M HILL 200 Performance Standard Verification Plan Operable Unit 2 Final Hill AFB Utah November

Radian 1990 Site Evaluation Report for Perimeter Road and the Spoils Area Final Hill AFB Utah August

Radian 1992 Remedial Investigation Report for Operable Unit 2 Hill AFB Utah July

URS and DEampS 1999 Dense Nonaqueous Phase Liquid (DNAPL) Source Delineation Project Final Report Operable Unit 2 Hill AFB Utah September

URS and DEampS 2001 SEAR Technology Application at Operable Unit 2 Volumes I and II Hill AFB Utah May

8

EXPIANA TION OF SIGNIFICANT DIFFERENCES OU 2 HILL AFB UTAH

AGENCY COMMENTS

The USAF submitted this ESD to the EPA and UDEQ for their review and comment Comments from both the EPA and UDEQ along with the USAF response are included as follows

UDEQ Comments viith Air Force responses in italics

GENERAL COMMENTS bull Please number all the pages throughout the document bull Please include a figure depicting the 0U2 layout bull Please include separate signature page for each agency It will facilitate the signing

process

Response Page numbers will he added to all pages A figure will be included showing the OUl site The signature pages will be separated as requested

SPECIFIC COMMENTS

i Introduction First Paragraph 5th line Please replace the word ROD with Remedial Investigation

2 Introduction First Paragraph Last line Please insert spent prior to chlorinated solvents 3 Public Participation First Line Please change This ESD will be discussed to This

ESD was discussed

Response Because this part ofthe section caused confusion for multiple reviewers the sentence Based on the ROD Site SS021 is free of contamination with the exception of a few areas being evaluated as part of other Operable Units and this site was recommended for no further remedial action will be replaced with Site SS02I included potential disposal sites along Perimeter Road investigated in the late I980s (Radian J990) Chemical Pit 3 and the North Gate Dump Sites (now part of Operable Unit 4) were the only sites where contamination was identified The ROD for OU 2 concluded that no further action was required for SS021

Response spent will be added as requested

Response The text was updated as requested

EPA Comments with Air Force responses in italics

Introduction First Paragraph states Perimeter Road (SS021) is free of contamination with the exception of a few areas being evaluated else as part of other OUs and this site was recommended for NFRAP Can you state or show on a map the areas being tracked under other OUs

Response Please see response to Specific Comment 1 above

EXPhXNATION OF SIGNIFICANT DIFFERENCES ou 2 HILL AFB UTAH

Fifth Paragraph states that this ESD is issued in accordance with Section 117(c) which requires the USAF to issue a document where a remedial action will differ in any significant but not fundamental respect from the ROD Significant and Fundamental should be defined here instead of under the Description and Basis for the Differences

Response Agreed The sentence A significant change to a remedy is one that incrementally changes a component ofa remedy (such as cost) but does not fundamentally alter the remedy (such as a change in the selected pump-and-treat remedy) will be added after the sentence ending USAF and described in the ROD in the fifth paragraph ofthe Introduction section The sentence will be removed from the fifth paragraph ofthe Description and Basis for the Differences section

STATUTORY DETERMINATIONS

The Applicable or Relevant and Appropriate Requirements (ARARs) addressed by the ROD for OU 2 are not modified by this ESD Considering the clarifications regarding the selected remedies presented in this ESD the USAF EPA and UDEQ all concur that the remedies at OU 2 remain protective of human health and the environment comply with federal and state requirements that were identified in the ROD as ARARs and are cost-effective There are no changes to the anticipated remediation time frame as a result of the Air Forces adoption of these differences from the ROD The remedy satisfies CERCLA Section 121

Signatures

10

EXPUNA TION OF SIGNIFICANT DIFFERENCES OU 2 HILL AFB UTAH

75TH AIR BASE WING (AFMC) HILL AIR FORCE BASE UTAH

^ T R I C K C HI Commander

Date

n

EXPUNA TION OF SIGNIFICANT DIFFERENCES OU 2 HILL AFB UTAH

UNITED STATES ENVIORNMENTAL PROTECTION AGENCY

CAROL L CAMPBELL 0 Date ^ Assistant Regional Administrator Office of Ecosystems Protection and Remediation US EPA Region VIII

12

EXPLANA TION OF SIGNIFICANT DIFFERENCES OU 2 HILL AFB UTAH

STATE OF UTAH DEPARTMENT OF ENVIORNMENTAL QUALITY

)A SMITH Executive Director Utah Department of Environmental Quality

O fCO^L^ Date

13

HXPIANA riUN OF SIGNIFICANT DIFFERENCES OUl HILL AFB UTAH

Explanation of Significant Differences Operable Unit 2 (OU 2) Hill Air Force Base Utah

INTRODUCTION

This Explanation of Significant Differences (ESD) relates to remedial actions selected by the United States Air Force (USAF) for implementation at Operable Unit 2 (OU 2) at Hill Air Force Base (AFB) Utah in a Record of Decision (ROD) issued in September 1996 (CH2M HILL 1996) Operable Unit 2 is comprised of two Installation Restoration Program (IRP) sites Chemical Pit 3 (WP007) and the Perimeter Road (SS021) Site SS021 included potential disposal sites along Perimeter Road investigated in the late 1980s (Radian 1990) Chemical Pit 3 along with the North Gate Dump Sites (now part of Operable Unit 4) were the only sites where contamination was identified The ROD for OU 2 concluded that no further action was required for SS021 Site WP007 consists of two unlined trenches that were used for the disposal of unknown quantities of chlorinated spent solvents

Operable Unit 2 is addressed in two components the source zone and the non-source zone The source zone is on-Base and is the immediate area around the former Chemical Disposal Pit 3 that is underlain by a dense non-aqueous phase liquid (DNAPL) and affected areas west of Perimeter Road This area has the highest concentrations of contaminants and occupies approximately 6 acres (Figure 1) The non-source zone is north and east of the source zone and Perimeter Road The non-source zone includes shallow groundwater and seep and spring contamination off-Base This area generally has lower contaminant concentrations and occupies approximately 25 acres

An ESD is required to address differences in the following selected remedies for the OU 2 source zone treatment of extracted source zone groundwater with the existing Air Stripper Treatment Plant (ASTP) without pre-treatment by the existing steam stripper

In July 1987 the US Environmental Protection Agency (EPA) placed Hill AFB on the National Priorities List (NPL) under Comprehensive Environmental Response Compensation and Liability Act (CERCLA) In April 1991 Hill AFB entered a Federal Facility Agreement (FFA) with the Utah Department of Environmental Quality (UDEQ) and the EPA Region VIII to establish a procedural framework and schedule for implementing the appropriate response actions in accordance with existing regulations Under the FFA and Executive Order 12580 Hill AFB is the lead agency for all CERCLA actions and UDEQ and the EPA are support agencies Hill AFB seeks concurrence from both the EPA and UDEQ for significant decisions involving cleanup strategy goals and methods

This ESD is issued in accordance with Section 117(c) ofthe CERCLA 42 USC sect 9617(c) and Section 300435(c)(2)(i) ofthe National Oil and Hazardous Substances Pollution Contingency Plan (NCP) which requires the USAF to issue such a document where a remedial action will differ in any significant but not fundamental respect from that selected by the USAF and described in the ROD A significant change to a remedy is one that incrementally changes a component of a remedy (such as cost) but does not fundamentally alter the remedy (such as a change in the selected pump-and-treat remedy) The revised remedy described in this ESD

EXP IAN ATI ON OF SIGNIFICANT DIFFERENCES OUl HILL AFB UTAH

EXPLANATION TCE concentrations In

microsram plaquor Htsr (tilaquo1) frMM X004300

N

Conveyance Line to Central Weber Sewer Improvement

DistrFct

System (UCS) Trench L ^ v

Air Stripper Treatment

(ASTP) Plant r T ^ M (

1 - J A J A i SRS Process r I Building

Figure I Operable Unit 2 site features

complies with the NCP and the statutory requirements of CERLCA The ESD has been prepared to provide the public with an explanation of the nature of the modification to the selected remedy set forth in the ROD and to summarize the infonnation that supports this modification The ESD will become part of the Administrative Record file (40 CFR 300825(a)(2)) and the information repository (40 CFR 300435(c)(2)(i)(A)) for Hill AFB which is located and available for public review at

75CEG CEVR 7274 Wardleigh RD Hill AFB UT 84056-5137

EXIIANA HON UF SIGNIFICANT DIFFERENCES ou 2 HILL AFB UTAH

The Administrative Record is also available for public review at

Weber State University - Ogden Campus Weber State University - Davis Campus Stewart Library Stewart Library 3850 University Circle 2750 University Park Blvd Ogden UT 84408 Layton UT 84041-9099 (801)626-6403

The USAF EPA and UDEQ conclude that the remedy selected in the ROD as modified by this ESD will meet the objectives and performance standards of the ROD

SUMMARY OF THE SITE HISTORY SITE CONDITIONS AND SELECTED REMEDY

Site History

Operable Unit 2 is located along the northeastem boundary of Hill AFB overlooking the Weber River Valley and is one of 13 Operable Units at Hill AFB in various stages ofthe CERCLA process Records indicate that from 1967 to 1975 unknown quantities of chlorinated organic solvents generated during degreasing operations were disposed in trenches (chemical pits) at the site These compounds were placed into two unlined disposal trenches trending north northwest which are estimated to have been approximately 6 to 9 feet deep 10 feet wide and approximately 50 to 100 feet long (Radian 1992) The disposal area is underlain by an alluvial sand aquifer that is composed of a heterogeneous mixture of sand and gravel contained in a narrow buried ancient river channel incised deeply into the underlying clay deposit This clay deposit known as the Alpine Formation forms a barrier to the downward migration of DNAPL

Disposal of the spent chlorinated solvents resulted in DNAPL contaminafion of the underlying shallow aquifer (the Provo Formation) predominantly as one or more pools above the clay (the Alpine Formation) and also as a residual phase held in the aquifers pore spaces (the volume in between individual soil particles) The recovered DNAPL consists primarily of several chlorinated solvents (about 70 percent trichloroethene [TCE] with smaller amounts of 111-trichloroethane [111-TCA] tetrachloroethene [PCE] and methylene chloride) 112 trichloro-122-trifluoroethane (Freon 113) and a lesser amount of oil and grease (URS and DEampS 2001) Contaminated soils near the trenches and the pooled DNAPL are the source of shallow dissolved phase groundwater contamination extending approximately 1500 feet downgradient and beyond the Hill AFB boundary (CH2M HILL 1996) Groundwater contamination appears limited to the shallow unconfined aquifer ofthe Provo Formation

Site Conditions

The on-Base portion of OU 2 sits upon relatively flat lying ground while the off-Base portion of the site consists of a steep terraced north-facing escarpment that is the south wall of the Weber River Valley There is about 300 feet of relief between Hill AFB and the valley below Parts of this hillside are unstable and are known as the Weber Landslide Complex Numerous seeps and

EXIIANA TION OF SIGNIFICANT DIFFERENCES ou 2 HILL AFB UTAH

springs occur along the hillside Depending on water table elevation and the season the springs and seeps discharge water from the shallow groundwater system Depth to groundwater in the shallow system is generally less than 10 feet below ground surface (bgs) in the off-Base area and 20 feet bgs in the on-Base area Along the hillside escarpment and just outside ofthe northeastem Base boundary is the Davis-Weber Canal a privately owned concrete-lined irrigation canal The canal parallels the northeast boundary along most of the Base adjacent to the Weber River Valley The canal provides water from the Weber River for irrigation in the surrounding areas (CH2M HILL 1996)

Selected Remedy

The remedies that were selected for the OU 2 source zone are outlined in the Record of Decision issued in 1996 (CH2M HILL 1996) Those remedies include the following

bull Installadon of a low-permeability vertical barrier around the DNAPL and associated highly contaminated groundwater in the source zone to hinder flow to and from the source zone

bull Continued operation of the Source Recovery System (SRS) to remove DNAPL to the maximum extent practicable and to treat shallow groundwater containing high concentrations of VOCs using steam stripping

bull Completion of planned treatability studies using in-situ steam stripping and surfactant flushing for enhanced DNAPL recovery

bull Soil vapor extraction (SVE) after dewatering of the shallow aquifer to remove VOCs from subsurface soils in what is currently the saturated zone

bull Construction of a surface cap once treatment is completed or it is established the innovative technologies cannot meet remedial action objectives to decrease the inflow of precipitation and prevent erosion of surface soils

bull Environmental monitoring to evaluate the effectiveness of the remedy

bull Institutional controls to minimize exposure by limiting use and preventing access to Contaminated water and soil

One of the remedies specified by the ROD is a low permeability containment wall encircling the source zone to reduce the potential for further contamination of groundwater After the wall was built however an additional accumulation of free-phase DNAPL was identified outside of the wall (URS and DEampS 1999) This accumulation is informally known as either the Griffith Pool or the G-Pool A well field was installed in 1998 to extract mobile DNAPL from the area and to hydraulically contain the groundwater to minimize further contaminant flux to the off-Base plume

DESCRIPTION OF AND BASIS FOR THE DIFFERENCES

The SRS was constructed as an interim remedial action in 1993 to recover DNAPL from the source zone and to treat groundwater containing elevated concentrations of VOCs The SRS consists of a free-product and groundwater recovery well field aboveground pipeline and a process treatment facility (Building 755) Dense nonaqueous phase liquid is recovered during the

EXPLANA TIONOF SIGNIFICANT DIFFERENCES 0U2HIUAFB UTAH

treatment process using three phase separators while dissolved VOCs are removed from the groundwater using a packed-bed steam stripper In 1996 the Air Stripper Treatment Plant (ASTP) was constructed at OU 2 to provide secondary treatment of groundwater frorn the source zone following initial treatment with the steam stripper Prior to 2005 water was discharged from the ASTP to the on-base industrial wastewater treatment plant In 2005 an agreement was signed with Central Weber Sewer Improvement District (CWSID) allowing discharge oftreated water from OU 2 into the sanitary sewer Figure 2 provides a simplified process flow diagram illustrating the difference in the treatment process described in this ESD

Previous process flow

SRS Stop 1 DNAPL

separation

SRS Step 2 Steam

stripping

Pumped water from source zone

Discharge to sanitarYscver

Current process fiovi^

ASTP Air

stripping

Pumped water from source zone

Discharge to sanitary sewer

Figure 2 Simplified process flow diagram for OU 2 water treatment

Since 1992 approximately 44400 gallons of DNAPL have been recovered and over 20 million gallons of contaminated groundwater have been treated by steam stripping Of the total volume of DNAPL recovered 41000 gallons have been recovered primarily as mobile DNAPL via pump-and-treat operations and 3400 gallons have been recovered using enhanced-removal techniques Because the DNAPL recovery from the source zone has been successful DNAPL can no longer be extracted from the existing well field As the amount of DNAPL has decreased within the source zone the average concentration of VOCs in water extracted from the source zone has declined The average concentration of total VOCs in the influent to the SRS historically has ranged from 100 to 300 milligrams per liter (mgL) but concentrations generally have decreased to less than 100 mgL since the beginning of 2006 Hill AFB decided to evaluate

EXPLANA TION OF SIGNIFICANT DIFFERENCES OU 2 HILL AFB UTAH

altemative treatment options because the concentrations of VOCs being treated by the steam stripping process were decreasing

In 2007 Hill AFB proposed testing to determine if source zone water could be treated with the existing ASTP without pre-treatment by the steam stripper (January 25 2007 Project Managers meeting and letter dated March 152007) Piping modifications were completed during the fall of 2007 and initial testing was conducted during January and Febmary 2008 The results of this initial testing clearly showed that the ASTP is capable of achieving the treatment required to maintain compliance with the existing CWSED wastewater discharge permit without preshytreatment by the steam stripper Based on the initial results treatment of source zone water using the ASTP was continued to collect additional data to verify VOC removal efficiency over a one-year prove-out period This prove-out period included increased monitoring of both influent and effluent to the ASTP to allow evaluation of variability in either ASTP operating efficiency andor influent water concentrations

Currently the discharge limit to the CWSID is 2100 ^gL total volatiles (Method E624) The ASTP effluent concentrations remained below this discharge limit during 2008 as shown in Table 1 The calculated treatment efficiency was nominally 100 percent during 24 of 26 sampling events The remaining two sampling events had treatment efficiencies of 998 and 999 percent Figure 3 presents the ASTP effluent concentration over time As is evident from Figure 3 the total VOC concentration in the ASTP effluent has consistentiy been below the discharge limit and has not increased since piping modifications were completed during the fall of 2007

The fact that extracted source zone groundwater at OU 2 is no longer being pre-treated using the steam stripper constitutes a significant but not fundamental difference to the selected remedy outlined in the ROD This modification to the OU 2 source zone treatment system still provides safe and effective groundwater treatment with no additional environmental risk and with no added time to achieve cleanup

PUBLIC PARTICIPATION

This ESD was discussed during the July 30 2009 Restoration Advisory Board (RAB) meeting Discussion will include public notification procedures for ESDs The RAB will be requested to review both the process Hill AFB is using to prepare this ESD and the technical differences documented in this ESD

The RAB will be notified of the submission of the finalized ESD at the first quarterly RAB meeting after the ESD is signed Hill AFB will publish a notice of availability and a brief description ofthe ESD in the local newspaper Ogden Standard Examiner the week following

EXPIANA TION OF SIGNIFICNT DIFFERENCES OU 2 HILL AFB UTAH

TABLE 1 ASTP Total VOC Influent and Effluent Concentrations During 2008

Sample Date

012508

012908

020508

020808

021908

022908

030608

032508

040208

040408

040708

040808

040908

041008

041108

051408

052808

061008

062608

070808

072108

081808

090908

100808

111308

120908

Influent Concentration

(MgL) 104997

14603

159587

209442

3119

63952

72079

637

345

511

462

630

955

1013

1177

1015

1346

940

1342

1644

1239

1318

572

54466

158879

126171

Effluent Concentration

(ugL) 189

182

360

209

130

092

043

000

000

020

000

000

000

000

020

000

000

000

000

140

000

000

000

050

040

080

Treatment Efficiency (percent)

1000

1000

998

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

999

1000

1000

1000

1000

1000

1000

NOTES ngL = Micrograms per Liter VOC = Volatile Organic Compound Total VOCs calculated based on Method E624

EXPLANA TION OF SIGNIFICANT DIFFERENCES OU 2 HILL AFB UTAH

j

bull9

c o

5 c o c o o o O gt

o 1 -

1000000

100000

10000

1000

100

10

1

0

i 1

reg Influent

bull Effluent

^ 1 1 1

copy

9 c

raquo copy

CWSID Discharge Permit Concentration 2100 |igL Total Volatiles

s bull bull

c c ra

- 3

reg

regreg reg

1 bull

reg

reg

Jan-04

Jan-05 lt lt

Jan-06 1

Jan-07

1

Jan-08

Jan-09

Figure 3 ASTP Influent and Effluent Total VOC (Method E624) Concentration over Time

that RAB meeting This ESD and the infonnation upon which it is based will be included in the Administrative Record for this Site The Administrative Record also includes the ROD and all documents that formed the basis for USAFs selection and EPA and UDEQs concurrence ofthe remedial action for the Site These components meet the public participation requirement set out in Section 3()0435(c)(2)(i) of the NCP

REFERENCES

CH2M HILL 1996 Record of Decision and Respomiveness Summary for Operable Unit 2 Final Hill AFB Utah September

CH2M HILL 200 Performance Standard Verification Plan Operable Unit 2 Final Hill AFB Utah November

Radian 1990 Site Evaluation Report for Perimeter Road and the Spoils Area Final Hill AFB Utah August

Radian 1992 Remedial Investigation Report for Operable Unit 2 Hill AFB Utah July

URS and DEampS 1999 Dense Nonaqueous Phase Liquid (DNAPL) Source Delineation Project Final Report Operable Unit 2 Hill AFB Utah September

URS and DEampS 2001 SEAR Technology Application at Operable Unit 2 Volumes I and II Hill AFB Utah May

8

EXPIANA TION OF SIGNIFICANT DIFFERENCES OU 2 HILL AFB UTAH

AGENCY COMMENTS

The USAF submitted this ESD to the EPA and UDEQ for their review and comment Comments from both the EPA and UDEQ along with the USAF response are included as follows

UDEQ Comments viith Air Force responses in italics

GENERAL COMMENTS bull Please number all the pages throughout the document bull Please include a figure depicting the 0U2 layout bull Please include separate signature page for each agency It will facilitate the signing

process

Response Page numbers will he added to all pages A figure will be included showing the OUl site The signature pages will be separated as requested

SPECIFIC COMMENTS

i Introduction First Paragraph 5th line Please replace the word ROD with Remedial Investigation

2 Introduction First Paragraph Last line Please insert spent prior to chlorinated solvents 3 Public Participation First Line Please change This ESD will be discussed to This

ESD was discussed

Response Because this part ofthe section caused confusion for multiple reviewers the sentence Based on the ROD Site SS021 is free of contamination with the exception of a few areas being evaluated as part of other Operable Units and this site was recommended for no further remedial action will be replaced with Site SS02I included potential disposal sites along Perimeter Road investigated in the late I980s (Radian J990) Chemical Pit 3 and the North Gate Dump Sites (now part of Operable Unit 4) were the only sites where contamination was identified The ROD for OU 2 concluded that no further action was required for SS021

Response spent will be added as requested

Response The text was updated as requested

EPA Comments with Air Force responses in italics

Introduction First Paragraph states Perimeter Road (SS021) is free of contamination with the exception of a few areas being evaluated else as part of other OUs and this site was recommended for NFRAP Can you state or show on a map the areas being tracked under other OUs

Response Please see response to Specific Comment 1 above

EXPhXNATION OF SIGNIFICANT DIFFERENCES ou 2 HILL AFB UTAH

Fifth Paragraph states that this ESD is issued in accordance with Section 117(c) which requires the USAF to issue a document where a remedial action will differ in any significant but not fundamental respect from the ROD Significant and Fundamental should be defined here instead of under the Description and Basis for the Differences

Response Agreed The sentence A significant change to a remedy is one that incrementally changes a component ofa remedy (such as cost) but does not fundamentally alter the remedy (such as a change in the selected pump-and-treat remedy) will be added after the sentence ending USAF and described in the ROD in the fifth paragraph ofthe Introduction section The sentence will be removed from the fifth paragraph ofthe Description and Basis for the Differences section

STATUTORY DETERMINATIONS

The Applicable or Relevant and Appropriate Requirements (ARARs) addressed by the ROD for OU 2 are not modified by this ESD Considering the clarifications regarding the selected remedies presented in this ESD the USAF EPA and UDEQ all concur that the remedies at OU 2 remain protective of human health and the environment comply with federal and state requirements that were identified in the ROD as ARARs and are cost-effective There are no changes to the anticipated remediation time frame as a result of the Air Forces adoption of these differences from the ROD The remedy satisfies CERCLA Section 121

Signatures

10

EXPUNA TION OF SIGNIFICANT DIFFERENCES OU 2 HILL AFB UTAH

75TH AIR BASE WING (AFMC) HILL AIR FORCE BASE UTAH

^ T R I C K C HI Commander

Date

n

EXPUNA TION OF SIGNIFICANT DIFFERENCES OU 2 HILL AFB UTAH

UNITED STATES ENVIORNMENTAL PROTECTION AGENCY

CAROL L CAMPBELL 0 Date ^ Assistant Regional Administrator Office of Ecosystems Protection and Remediation US EPA Region VIII

12

EXPLANA TION OF SIGNIFICANT DIFFERENCES OU 2 HILL AFB UTAH

STATE OF UTAH DEPARTMENT OF ENVIORNMENTAL QUALITY

)A SMITH Executive Director Utah Department of Environmental Quality

O fCO^L^ Date

13

EXP IAN ATI ON OF SIGNIFICANT DIFFERENCES OUl HILL AFB UTAH

EXPLANATION TCE concentrations In

microsram plaquor Htsr (tilaquo1) frMM X004300

N

Conveyance Line to Central Weber Sewer Improvement

DistrFct

System (UCS) Trench L ^ v

Air Stripper Treatment

(ASTP) Plant r T ^ M (

1 - J A J A i SRS Process r I Building

Figure I Operable Unit 2 site features

complies with the NCP and the statutory requirements of CERLCA The ESD has been prepared to provide the public with an explanation of the nature of the modification to the selected remedy set forth in the ROD and to summarize the infonnation that supports this modification The ESD will become part of the Administrative Record file (40 CFR 300825(a)(2)) and the information repository (40 CFR 300435(c)(2)(i)(A)) for Hill AFB which is located and available for public review at

75CEG CEVR 7274 Wardleigh RD Hill AFB UT 84056-5137

EXIIANA HON UF SIGNIFICANT DIFFERENCES ou 2 HILL AFB UTAH

The Administrative Record is also available for public review at

Weber State University - Ogden Campus Weber State University - Davis Campus Stewart Library Stewart Library 3850 University Circle 2750 University Park Blvd Ogden UT 84408 Layton UT 84041-9099 (801)626-6403

The USAF EPA and UDEQ conclude that the remedy selected in the ROD as modified by this ESD will meet the objectives and performance standards of the ROD

SUMMARY OF THE SITE HISTORY SITE CONDITIONS AND SELECTED REMEDY

Site History

Operable Unit 2 is located along the northeastem boundary of Hill AFB overlooking the Weber River Valley and is one of 13 Operable Units at Hill AFB in various stages ofthe CERCLA process Records indicate that from 1967 to 1975 unknown quantities of chlorinated organic solvents generated during degreasing operations were disposed in trenches (chemical pits) at the site These compounds were placed into two unlined disposal trenches trending north northwest which are estimated to have been approximately 6 to 9 feet deep 10 feet wide and approximately 50 to 100 feet long (Radian 1992) The disposal area is underlain by an alluvial sand aquifer that is composed of a heterogeneous mixture of sand and gravel contained in a narrow buried ancient river channel incised deeply into the underlying clay deposit This clay deposit known as the Alpine Formation forms a barrier to the downward migration of DNAPL

Disposal of the spent chlorinated solvents resulted in DNAPL contaminafion of the underlying shallow aquifer (the Provo Formation) predominantly as one or more pools above the clay (the Alpine Formation) and also as a residual phase held in the aquifers pore spaces (the volume in between individual soil particles) The recovered DNAPL consists primarily of several chlorinated solvents (about 70 percent trichloroethene [TCE] with smaller amounts of 111-trichloroethane [111-TCA] tetrachloroethene [PCE] and methylene chloride) 112 trichloro-122-trifluoroethane (Freon 113) and a lesser amount of oil and grease (URS and DEampS 2001) Contaminated soils near the trenches and the pooled DNAPL are the source of shallow dissolved phase groundwater contamination extending approximately 1500 feet downgradient and beyond the Hill AFB boundary (CH2M HILL 1996) Groundwater contamination appears limited to the shallow unconfined aquifer ofthe Provo Formation

Site Conditions

The on-Base portion of OU 2 sits upon relatively flat lying ground while the off-Base portion of the site consists of a steep terraced north-facing escarpment that is the south wall of the Weber River Valley There is about 300 feet of relief between Hill AFB and the valley below Parts of this hillside are unstable and are known as the Weber Landslide Complex Numerous seeps and

EXIIANA TION OF SIGNIFICANT DIFFERENCES ou 2 HILL AFB UTAH

springs occur along the hillside Depending on water table elevation and the season the springs and seeps discharge water from the shallow groundwater system Depth to groundwater in the shallow system is generally less than 10 feet below ground surface (bgs) in the off-Base area and 20 feet bgs in the on-Base area Along the hillside escarpment and just outside ofthe northeastem Base boundary is the Davis-Weber Canal a privately owned concrete-lined irrigation canal The canal parallels the northeast boundary along most of the Base adjacent to the Weber River Valley The canal provides water from the Weber River for irrigation in the surrounding areas (CH2M HILL 1996)

Selected Remedy

The remedies that were selected for the OU 2 source zone are outlined in the Record of Decision issued in 1996 (CH2M HILL 1996) Those remedies include the following

bull Installadon of a low-permeability vertical barrier around the DNAPL and associated highly contaminated groundwater in the source zone to hinder flow to and from the source zone

bull Continued operation of the Source Recovery System (SRS) to remove DNAPL to the maximum extent practicable and to treat shallow groundwater containing high concentrations of VOCs using steam stripping

bull Completion of planned treatability studies using in-situ steam stripping and surfactant flushing for enhanced DNAPL recovery

bull Soil vapor extraction (SVE) after dewatering of the shallow aquifer to remove VOCs from subsurface soils in what is currently the saturated zone

bull Construction of a surface cap once treatment is completed or it is established the innovative technologies cannot meet remedial action objectives to decrease the inflow of precipitation and prevent erosion of surface soils

bull Environmental monitoring to evaluate the effectiveness of the remedy

bull Institutional controls to minimize exposure by limiting use and preventing access to Contaminated water and soil

One of the remedies specified by the ROD is a low permeability containment wall encircling the source zone to reduce the potential for further contamination of groundwater After the wall was built however an additional accumulation of free-phase DNAPL was identified outside of the wall (URS and DEampS 1999) This accumulation is informally known as either the Griffith Pool or the G-Pool A well field was installed in 1998 to extract mobile DNAPL from the area and to hydraulically contain the groundwater to minimize further contaminant flux to the off-Base plume

DESCRIPTION OF AND BASIS FOR THE DIFFERENCES

The SRS was constructed as an interim remedial action in 1993 to recover DNAPL from the source zone and to treat groundwater containing elevated concentrations of VOCs The SRS consists of a free-product and groundwater recovery well field aboveground pipeline and a process treatment facility (Building 755) Dense nonaqueous phase liquid is recovered during the

EXPLANA TIONOF SIGNIFICANT DIFFERENCES 0U2HIUAFB UTAH

treatment process using three phase separators while dissolved VOCs are removed from the groundwater using a packed-bed steam stripper In 1996 the Air Stripper Treatment Plant (ASTP) was constructed at OU 2 to provide secondary treatment of groundwater frorn the source zone following initial treatment with the steam stripper Prior to 2005 water was discharged from the ASTP to the on-base industrial wastewater treatment plant In 2005 an agreement was signed with Central Weber Sewer Improvement District (CWSID) allowing discharge oftreated water from OU 2 into the sanitary sewer Figure 2 provides a simplified process flow diagram illustrating the difference in the treatment process described in this ESD

Previous process flow

SRS Stop 1 DNAPL

separation

SRS Step 2 Steam

stripping

Pumped water from source zone

Discharge to sanitarYscver

Current process fiovi^

ASTP Air

stripping

Pumped water from source zone

Discharge to sanitary sewer

Figure 2 Simplified process flow diagram for OU 2 water treatment

Since 1992 approximately 44400 gallons of DNAPL have been recovered and over 20 million gallons of contaminated groundwater have been treated by steam stripping Of the total volume of DNAPL recovered 41000 gallons have been recovered primarily as mobile DNAPL via pump-and-treat operations and 3400 gallons have been recovered using enhanced-removal techniques Because the DNAPL recovery from the source zone has been successful DNAPL can no longer be extracted from the existing well field As the amount of DNAPL has decreased within the source zone the average concentration of VOCs in water extracted from the source zone has declined The average concentration of total VOCs in the influent to the SRS historically has ranged from 100 to 300 milligrams per liter (mgL) but concentrations generally have decreased to less than 100 mgL since the beginning of 2006 Hill AFB decided to evaluate

EXPLANA TION OF SIGNIFICANT DIFFERENCES OU 2 HILL AFB UTAH

altemative treatment options because the concentrations of VOCs being treated by the steam stripping process were decreasing

In 2007 Hill AFB proposed testing to determine if source zone water could be treated with the existing ASTP without pre-treatment by the steam stripper (January 25 2007 Project Managers meeting and letter dated March 152007) Piping modifications were completed during the fall of 2007 and initial testing was conducted during January and Febmary 2008 The results of this initial testing clearly showed that the ASTP is capable of achieving the treatment required to maintain compliance with the existing CWSED wastewater discharge permit without preshytreatment by the steam stripper Based on the initial results treatment of source zone water using the ASTP was continued to collect additional data to verify VOC removal efficiency over a one-year prove-out period This prove-out period included increased monitoring of both influent and effluent to the ASTP to allow evaluation of variability in either ASTP operating efficiency andor influent water concentrations

Currently the discharge limit to the CWSID is 2100 ^gL total volatiles (Method E624) The ASTP effluent concentrations remained below this discharge limit during 2008 as shown in Table 1 The calculated treatment efficiency was nominally 100 percent during 24 of 26 sampling events The remaining two sampling events had treatment efficiencies of 998 and 999 percent Figure 3 presents the ASTP effluent concentration over time As is evident from Figure 3 the total VOC concentration in the ASTP effluent has consistentiy been below the discharge limit and has not increased since piping modifications were completed during the fall of 2007

The fact that extracted source zone groundwater at OU 2 is no longer being pre-treated using the steam stripper constitutes a significant but not fundamental difference to the selected remedy outlined in the ROD This modification to the OU 2 source zone treatment system still provides safe and effective groundwater treatment with no additional environmental risk and with no added time to achieve cleanup

PUBLIC PARTICIPATION

This ESD was discussed during the July 30 2009 Restoration Advisory Board (RAB) meeting Discussion will include public notification procedures for ESDs The RAB will be requested to review both the process Hill AFB is using to prepare this ESD and the technical differences documented in this ESD

The RAB will be notified of the submission of the finalized ESD at the first quarterly RAB meeting after the ESD is signed Hill AFB will publish a notice of availability and a brief description ofthe ESD in the local newspaper Ogden Standard Examiner the week following

EXPIANA TION OF SIGNIFICNT DIFFERENCES OU 2 HILL AFB UTAH

TABLE 1 ASTP Total VOC Influent and Effluent Concentrations During 2008

Sample Date

012508

012908

020508

020808

021908

022908

030608

032508

040208

040408

040708

040808

040908

041008

041108

051408

052808

061008

062608

070808

072108

081808

090908

100808

111308

120908

Influent Concentration

(MgL) 104997

14603

159587

209442

3119

63952

72079

637

345

511

462

630

955

1013

1177

1015

1346

940

1342

1644

1239

1318

572

54466

158879

126171

Effluent Concentration

(ugL) 189

182

360

209

130

092

043

000

000

020

000

000

000

000

020

000

000

000

000

140

000

000

000

050

040

080

Treatment Efficiency (percent)

1000

1000

998

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

999

1000

1000

1000

1000

1000

1000

NOTES ngL = Micrograms per Liter VOC = Volatile Organic Compound Total VOCs calculated based on Method E624

EXPLANA TION OF SIGNIFICANT DIFFERENCES OU 2 HILL AFB UTAH

j

bull9

c o

5 c o c o o o O gt

o 1 -

1000000

100000

10000

1000

100

10

1

0

i 1

reg Influent

bull Effluent

^ 1 1 1

copy

9 c

raquo copy

CWSID Discharge Permit Concentration 2100 |igL Total Volatiles

s bull bull

c c ra

- 3

reg

regreg reg

1 bull

reg

reg

Jan-04

Jan-05 lt lt

Jan-06 1

Jan-07

1

Jan-08

Jan-09

Figure 3 ASTP Influent and Effluent Total VOC (Method E624) Concentration over Time

that RAB meeting This ESD and the infonnation upon which it is based will be included in the Administrative Record for this Site The Administrative Record also includes the ROD and all documents that formed the basis for USAFs selection and EPA and UDEQs concurrence ofthe remedial action for the Site These components meet the public participation requirement set out in Section 3()0435(c)(2)(i) of the NCP

REFERENCES

CH2M HILL 1996 Record of Decision and Respomiveness Summary for Operable Unit 2 Final Hill AFB Utah September

CH2M HILL 200 Performance Standard Verification Plan Operable Unit 2 Final Hill AFB Utah November

Radian 1990 Site Evaluation Report for Perimeter Road and the Spoils Area Final Hill AFB Utah August

Radian 1992 Remedial Investigation Report for Operable Unit 2 Hill AFB Utah July

URS and DEampS 1999 Dense Nonaqueous Phase Liquid (DNAPL) Source Delineation Project Final Report Operable Unit 2 Hill AFB Utah September

URS and DEampS 2001 SEAR Technology Application at Operable Unit 2 Volumes I and II Hill AFB Utah May

8

EXPIANA TION OF SIGNIFICANT DIFFERENCES OU 2 HILL AFB UTAH

AGENCY COMMENTS

The USAF submitted this ESD to the EPA and UDEQ for their review and comment Comments from both the EPA and UDEQ along with the USAF response are included as follows

UDEQ Comments viith Air Force responses in italics

GENERAL COMMENTS bull Please number all the pages throughout the document bull Please include a figure depicting the 0U2 layout bull Please include separate signature page for each agency It will facilitate the signing

process

Response Page numbers will he added to all pages A figure will be included showing the OUl site The signature pages will be separated as requested

SPECIFIC COMMENTS

i Introduction First Paragraph 5th line Please replace the word ROD with Remedial Investigation

2 Introduction First Paragraph Last line Please insert spent prior to chlorinated solvents 3 Public Participation First Line Please change This ESD will be discussed to This

ESD was discussed

Response Because this part ofthe section caused confusion for multiple reviewers the sentence Based on the ROD Site SS021 is free of contamination with the exception of a few areas being evaluated as part of other Operable Units and this site was recommended for no further remedial action will be replaced with Site SS02I included potential disposal sites along Perimeter Road investigated in the late I980s (Radian J990) Chemical Pit 3 and the North Gate Dump Sites (now part of Operable Unit 4) were the only sites where contamination was identified The ROD for OU 2 concluded that no further action was required for SS021

Response spent will be added as requested

Response The text was updated as requested

EPA Comments with Air Force responses in italics

Introduction First Paragraph states Perimeter Road (SS021) is free of contamination with the exception of a few areas being evaluated else as part of other OUs and this site was recommended for NFRAP Can you state or show on a map the areas being tracked under other OUs

Response Please see response to Specific Comment 1 above

EXPhXNATION OF SIGNIFICANT DIFFERENCES ou 2 HILL AFB UTAH

Fifth Paragraph states that this ESD is issued in accordance with Section 117(c) which requires the USAF to issue a document where a remedial action will differ in any significant but not fundamental respect from the ROD Significant and Fundamental should be defined here instead of under the Description and Basis for the Differences

Response Agreed The sentence A significant change to a remedy is one that incrementally changes a component ofa remedy (such as cost) but does not fundamentally alter the remedy (such as a change in the selected pump-and-treat remedy) will be added after the sentence ending USAF and described in the ROD in the fifth paragraph ofthe Introduction section The sentence will be removed from the fifth paragraph ofthe Description and Basis for the Differences section

STATUTORY DETERMINATIONS

The Applicable or Relevant and Appropriate Requirements (ARARs) addressed by the ROD for OU 2 are not modified by this ESD Considering the clarifications regarding the selected remedies presented in this ESD the USAF EPA and UDEQ all concur that the remedies at OU 2 remain protective of human health and the environment comply with federal and state requirements that were identified in the ROD as ARARs and are cost-effective There are no changes to the anticipated remediation time frame as a result of the Air Forces adoption of these differences from the ROD The remedy satisfies CERCLA Section 121

Signatures

10

EXPUNA TION OF SIGNIFICANT DIFFERENCES OU 2 HILL AFB UTAH

75TH AIR BASE WING (AFMC) HILL AIR FORCE BASE UTAH

^ T R I C K C HI Commander

Date

n

EXPUNA TION OF SIGNIFICANT DIFFERENCES OU 2 HILL AFB UTAH

UNITED STATES ENVIORNMENTAL PROTECTION AGENCY

CAROL L CAMPBELL 0 Date ^ Assistant Regional Administrator Office of Ecosystems Protection and Remediation US EPA Region VIII

12

EXPLANA TION OF SIGNIFICANT DIFFERENCES OU 2 HILL AFB UTAH

STATE OF UTAH DEPARTMENT OF ENVIORNMENTAL QUALITY

)A SMITH Executive Director Utah Department of Environmental Quality

O fCO^L^ Date

13

EXIIANA HON UF SIGNIFICANT DIFFERENCES ou 2 HILL AFB UTAH

The Administrative Record is also available for public review at

Weber State University - Ogden Campus Weber State University - Davis Campus Stewart Library Stewart Library 3850 University Circle 2750 University Park Blvd Ogden UT 84408 Layton UT 84041-9099 (801)626-6403

The USAF EPA and UDEQ conclude that the remedy selected in the ROD as modified by this ESD will meet the objectives and performance standards of the ROD

SUMMARY OF THE SITE HISTORY SITE CONDITIONS AND SELECTED REMEDY

Site History

Operable Unit 2 is located along the northeastem boundary of Hill AFB overlooking the Weber River Valley and is one of 13 Operable Units at Hill AFB in various stages ofthe CERCLA process Records indicate that from 1967 to 1975 unknown quantities of chlorinated organic solvents generated during degreasing operations were disposed in trenches (chemical pits) at the site These compounds were placed into two unlined disposal trenches trending north northwest which are estimated to have been approximately 6 to 9 feet deep 10 feet wide and approximately 50 to 100 feet long (Radian 1992) The disposal area is underlain by an alluvial sand aquifer that is composed of a heterogeneous mixture of sand and gravel contained in a narrow buried ancient river channel incised deeply into the underlying clay deposit This clay deposit known as the Alpine Formation forms a barrier to the downward migration of DNAPL

Disposal of the spent chlorinated solvents resulted in DNAPL contaminafion of the underlying shallow aquifer (the Provo Formation) predominantly as one or more pools above the clay (the Alpine Formation) and also as a residual phase held in the aquifers pore spaces (the volume in between individual soil particles) The recovered DNAPL consists primarily of several chlorinated solvents (about 70 percent trichloroethene [TCE] with smaller amounts of 111-trichloroethane [111-TCA] tetrachloroethene [PCE] and methylene chloride) 112 trichloro-122-trifluoroethane (Freon 113) and a lesser amount of oil and grease (URS and DEampS 2001) Contaminated soils near the trenches and the pooled DNAPL are the source of shallow dissolved phase groundwater contamination extending approximately 1500 feet downgradient and beyond the Hill AFB boundary (CH2M HILL 1996) Groundwater contamination appears limited to the shallow unconfined aquifer ofthe Provo Formation

Site Conditions

The on-Base portion of OU 2 sits upon relatively flat lying ground while the off-Base portion of the site consists of a steep terraced north-facing escarpment that is the south wall of the Weber River Valley There is about 300 feet of relief between Hill AFB and the valley below Parts of this hillside are unstable and are known as the Weber Landslide Complex Numerous seeps and

EXIIANA TION OF SIGNIFICANT DIFFERENCES ou 2 HILL AFB UTAH

springs occur along the hillside Depending on water table elevation and the season the springs and seeps discharge water from the shallow groundwater system Depth to groundwater in the shallow system is generally less than 10 feet below ground surface (bgs) in the off-Base area and 20 feet bgs in the on-Base area Along the hillside escarpment and just outside ofthe northeastem Base boundary is the Davis-Weber Canal a privately owned concrete-lined irrigation canal The canal parallels the northeast boundary along most of the Base adjacent to the Weber River Valley The canal provides water from the Weber River for irrigation in the surrounding areas (CH2M HILL 1996)

Selected Remedy

The remedies that were selected for the OU 2 source zone are outlined in the Record of Decision issued in 1996 (CH2M HILL 1996) Those remedies include the following

bull Installadon of a low-permeability vertical barrier around the DNAPL and associated highly contaminated groundwater in the source zone to hinder flow to and from the source zone

bull Continued operation of the Source Recovery System (SRS) to remove DNAPL to the maximum extent practicable and to treat shallow groundwater containing high concentrations of VOCs using steam stripping

bull Completion of planned treatability studies using in-situ steam stripping and surfactant flushing for enhanced DNAPL recovery

bull Soil vapor extraction (SVE) after dewatering of the shallow aquifer to remove VOCs from subsurface soils in what is currently the saturated zone

bull Construction of a surface cap once treatment is completed or it is established the innovative technologies cannot meet remedial action objectives to decrease the inflow of precipitation and prevent erosion of surface soils

bull Environmental monitoring to evaluate the effectiveness of the remedy

bull Institutional controls to minimize exposure by limiting use and preventing access to Contaminated water and soil

One of the remedies specified by the ROD is a low permeability containment wall encircling the source zone to reduce the potential for further contamination of groundwater After the wall was built however an additional accumulation of free-phase DNAPL was identified outside of the wall (URS and DEampS 1999) This accumulation is informally known as either the Griffith Pool or the G-Pool A well field was installed in 1998 to extract mobile DNAPL from the area and to hydraulically contain the groundwater to minimize further contaminant flux to the off-Base plume

DESCRIPTION OF AND BASIS FOR THE DIFFERENCES

The SRS was constructed as an interim remedial action in 1993 to recover DNAPL from the source zone and to treat groundwater containing elevated concentrations of VOCs The SRS consists of a free-product and groundwater recovery well field aboveground pipeline and a process treatment facility (Building 755) Dense nonaqueous phase liquid is recovered during the

EXPLANA TIONOF SIGNIFICANT DIFFERENCES 0U2HIUAFB UTAH

treatment process using three phase separators while dissolved VOCs are removed from the groundwater using a packed-bed steam stripper In 1996 the Air Stripper Treatment Plant (ASTP) was constructed at OU 2 to provide secondary treatment of groundwater frorn the source zone following initial treatment with the steam stripper Prior to 2005 water was discharged from the ASTP to the on-base industrial wastewater treatment plant In 2005 an agreement was signed with Central Weber Sewer Improvement District (CWSID) allowing discharge oftreated water from OU 2 into the sanitary sewer Figure 2 provides a simplified process flow diagram illustrating the difference in the treatment process described in this ESD

Previous process flow

SRS Stop 1 DNAPL

separation

SRS Step 2 Steam

stripping

Pumped water from source zone

Discharge to sanitarYscver

Current process fiovi^

ASTP Air

stripping

Pumped water from source zone

Discharge to sanitary sewer

Figure 2 Simplified process flow diagram for OU 2 water treatment

Since 1992 approximately 44400 gallons of DNAPL have been recovered and over 20 million gallons of contaminated groundwater have been treated by steam stripping Of the total volume of DNAPL recovered 41000 gallons have been recovered primarily as mobile DNAPL via pump-and-treat operations and 3400 gallons have been recovered using enhanced-removal techniques Because the DNAPL recovery from the source zone has been successful DNAPL can no longer be extracted from the existing well field As the amount of DNAPL has decreased within the source zone the average concentration of VOCs in water extracted from the source zone has declined The average concentration of total VOCs in the influent to the SRS historically has ranged from 100 to 300 milligrams per liter (mgL) but concentrations generally have decreased to less than 100 mgL since the beginning of 2006 Hill AFB decided to evaluate

EXPLANA TION OF SIGNIFICANT DIFFERENCES OU 2 HILL AFB UTAH

altemative treatment options because the concentrations of VOCs being treated by the steam stripping process were decreasing

In 2007 Hill AFB proposed testing to determine if source zone water could be treated with the existing ASTP without pre-treatment by the steam stripper (January 25 2007 Project Managers meeting and letter dated March 152007) Piping modifications were completed during the fall of 2007 and initial testing was conducted during January and Febmary 2008 The results of this initial testing clearly showed that the ASTP is capable of achieving the treatment required to maintain compliance with the existing CWSED wastewater discharge permit without preshytreatment by the steam stripper Based on the initial results treatment of source zone water using the ASTP was continued to collect additional data to verify VOC removal efficiency over a one-year prove-out period This prove-out period included increased monitoring of both influent and effluent to the ASTP to allow evaluation of variability in either ASTP operating efficiency andor influent water concentrations

Currently the discharge limit to the CWSID is 2100 ^gL total volatiles (Method E624) The ASTP effluent concentrations remained below this discharge limit during 2008 as shown in Table 1 The calculated treatment efficiency was nominally 100 percent during 24 of 26 sampling events The remaining two sampling events had treatment efficiencies of 998 and 999 percent Figure 3 presents the ASTP effluent concentration over time As is evident from Figure 3 the total VOC concentration in the ASTP effluent has consistentiy been below the discharge limit and has not increased since piping modifications were completed during the fall of 2007

The fact that extracted source zone groundwater at OU 2 is no longer being pre-treated using the steam stripper constitutes a significant but not fundamental difference to the selected remedy outlined in the ROD This modification to the OU 2 source zone treatment system still provides safe and effective groundwater treatment with no additional environmental risk and with no added time to achieve cleanup

PUBLIC PARTICIPATION

This ESD was discussed during the July 30 2009 Restoration Advisory Board (RAB) meeting Discussion will include public notification procedures for ESDs The RAB will be requested to review both the process Hill AFB is using to prepare this ESD and the technical differences documented in this ESD

The RAB will be notified of the submission of the finalized ESD at the first quarterly RAB meeting after the ESD is signed Hill AFB will publish a notice of availability and a brief description ofthe ESD in the local newspaper Ogden Standard Examiner the week following

EXPIANA TION OF SIGNIFICNT DIFFERENCES OU 2 HILL AFB UTAH

TABLE 1 ASTP Total VOC Influent and Effluent Concentrations During 2008

Sample Date

012508

012908

020508

020808

021908

022908

030608

032508

040208

040408

040708

040808

040908

041008

041108

051408

052808

061008

062608

070808

072108

081808

090908

100808

111308

120908

Influent Concentration

(MgL) 104997

14603

159587

209442

3119

63952

72079

637

345

511

462

630

955

1013

1177

1015

1346

940

1342

1644

1239

1318

572

54466

158879

126171

Effluent Concentration

(ugL) 189

182

360

209

130

092

043

000

000

020

000

000

000

000

020

000

000

000

000

140

000

000

000

050

040

080

Treatment Efficiency (percent)

1000

1000

998

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

999

1000

1000

1000

1000

1000

1000

NOTES ngL = Micrograms per Liter VOC = Volatile Organic Compound Total VOCs calculated based on Method E624

EXPLANA TION OF SIGNIFICANT DIFFERENCES OU 2 HILL AFB UTAH

j

bull9

c o

5 c o c o o o O gt

o 1 -

1000000

100000

10000

1000

100

10

1

0

i 1

reg Influent

bull Effluent

^ 1 1 1

copy

9 c

raquo copy

CWSID Discharge Permit Concentration 2100 |igL Total Volatiles

s bull bull

c c ra

- 3

reg

regreg reg

1 bull

reg

reg

Jan-04

Jan-05 lt lt

Jan-06 1

Jan-07

1

Jan-08

Jan-09

Figure 3 ASTP Influent and Effluent Total VOC (Method E624) Concentration over Time

that RAB meeting This ESD and the infonnation upon which it is based will be included in the Administrative Record for this Site The Administrative Record also includes the ROD and all documents that formed the basis for USAFs selection and EPA and UDEQs concurrence ofthe remedial action for the Site These components meet the public participation requirement set out in Section 3()0435(c)(2)(i) of the NCP

REFERENCES

CH2M HILL 1996 Record of Decision and Respomiveness Summary for Operable Unit 2 Final Hill AFB Utah September

CH2M HILL 200 Performance Standard Verification Plan Operable Unit 2 Final Hill AFB Utah November

Radian 1990 Site Evaluation Report for Perimeter Road and the Spoils Area Final Hill AFB Utah August

Radian 1992 Remedial Investigation Report for Operable Unit 2 Hill AFB Utah July

URS and DEampS 1999 Dense Nonaqueous Phase Liquid (DNAPL) Source Delineation Project Final Report Operable Unit 2 Hill AFB Utah September

URS and DEampS 2001 SEAR Technology Application at Operable Unit 2 Volumes I and II Hill AFB Utah May

8

EXPIANA TION OF SIGNIFICANT DIFFERENCES OU 2 HILL AFB UTAH

AGENCY COMMENTS

The USAF submitted this ESD to the EPA and UDEQ for their review and comment Comments from both the EPA and UDEQ along with the USAF response are included as follows

UDEQ Comments viith Air Force responses in italics

GENERAL COMMENTS bull Please number all the pages throughout the document bull Please include a figure depicting the 0U2 layout bull Please include separate signature page for each agency It will facilitate the signing

process

Response Page numbers will he added to all pages A figure will be included showing the OUl site The signature pages will be separated as requested

SPECIFIC COMMENTS

i Introduction First Paragraph 5th line Please replace the word ROD with Remedial Investigation

2 Introduction First Paragraph Last line Please insert spent prior to chlorinated solvents 3 Public Participation First Line Please change This ESD will be discussed to This

ESD was discussed

Response Because this part ofthe section caused confusion for multiple reviewers the sentence Based on the ROD Site SS021 is free of contamination with the exception of a few areas being evaluated as part of other Operable Units and this site was recommended for no further remedial action will be replaced with Site SS02I included potential disposal sites along Perimeter Road investigated in the late I980s (Radian J990) Chemical Pit 3 and the North Gate Dump Sites (now part of Operable Unit 4) were the only sites where contamination was identified The ROD for OU 2 concluded that no further action was required for SS021

Response spent will be added as requested

Response The text was updated as requested

EPA Comments with Air Force responses in italics

Introduction First Paragraph states Perimeter Road (SS021) is free of contamination with the exception of a few areas being evaluated else as part of other OUs and this site was recommended for NFRAP Can you state or show on a map the areas being tracked under other OUs

Response Please see response to Specific Comment 1 above

EXPhXNATION OF SIGNIFICANT DIFFERENCES ou 2 HILL AFB UTAH

Fifth Paragraph states that this ESD is issued in accordance with Section 117(c) which requires the USAF to issue a document where a remedial action will differ in any significant but not fundamental respect from the ROD Significant and Fundamental should be defined here instead of under the Description and Basis for the Differences

Response Agreed The sentence A significant change to a remedy is one that incrementally changes a component ofa remedy (such as cost) but does not fundamentally alter the remedy (such as a change in the selected pump-and-treat remedy) will be added after the sentence ending USAF and described in the ROD in the fifth paragraph ofthe Introduction section The sentence will be removed from the fifth paragraph ofthe Description and Basis for the Differences section

STATUTORY DETERMINATIONS

The Applicable or Relevant and Appropriate Requirements (ARARs) addressed by the ROD for OU 2 are not modified by this ESD Considering the clarifications regarding the selected remedies presented in this ESD the USAF EPA and UDEQ all concur that the remedies at OU 2 remain protective of human health and the environment comply with federal and state requirements that were identified in the ROD as ARARs and are cost-effective There are no changes to the anticipated remediation time frame as a result of the Air Forces adoption of these differences from the ROD The remedy satisfies CERCLA Section 121

Signatures

10

EXPUNA TION OF SIGNIFICANT DIFFERENCES OU 2 HILL AFB UTAH

75TH AIR BASE WING (AFMC) HILL AIR FORCE BASE UTAH

^ T R I C K C HI Commander

Date

n

EXPUNA TION OF SIGNIFICANT DIFFERENCES OU 2 HILL AFB UTAH

UNITED STATES ENVIORNMENTAL PROTECTION AGENCY

CAROL L CAMPBELL 0 Date ^ Assistant Regional Administrator Office of Ecosystems Protection and Remediation US EPA Region VIII

12

EXPLANA TION OF SIGNIFICANT DIFFERENCES OU 2 HILL AFB UTAH

STATE OF UTAH DEPARTMENT OF ENVIORNMENTAL QUALITY

)A SMITH Executive Director Utah Department of Environmental Quality

O fCO^L^ Date

13

EXIIANA TION OF SIGNIFICANT DIFFERENCES ou 2 HILL AFB UTAH

springs occur along the hillside Depending on water table elevation and the season the springs and seeps discharge water from the shallow groundwater system Depth to groundwater in the shallow system is generally less than 10 feet below ground surface (bgs) in the off-Base area and 20 feet bgs in the on-Base area Along the hillside escarpment and just outside ofthe northeastem Base boundary is the Davis-Weber Canal a privately owned concrete-lined irrigation canal The canal parallels the northeast boundary along most of the Base adjacent to the Weber River Valley The canal provides water from the Weber River for irrigation in the surrounding areas (CH2M HILL 1996)

Selected Remedy

The remedies that were selected for the OU 2 source zone are outlined in the Record of Decision issued in 1996 (CH2M HILL 1996) Those remedies include the following

bull Installadon of a low-permeability vertical barrier around the DNAPL and associated highly contaminated groundwater in the source zone to hinder flow to and from the source zone

bull Continued operation of the Source Recovery System (SRS) to remove DNAPL to the maximum extent practicable and to treat shallow groundwater containing high concentrations of VOCs using steam stripping

bull Completion of planned treatability studies using in-situ steam stripping and surfactant flushing for enhanced DNAPL recovery

bull Soil vapor extraction (SVE) after dewatering of the shallow aquifer to remove VOCs from subsurface soils in what is currently the saturated zone

bull Construction of a surface cap once treatment is completed or it is established the innovative technologies cannot meet remedial action objectives to decrease the inflow of precipitation and prevent erosion of surface soils

bull Environmental monitoring to evaluate the effectiveness of the remedy

bull Institutional controls to minimize exposure by limiting use and preventing access to Contaminated water and soil

One of the remedies specified by the ROD is a low permeability containment wall encircling the source zone to reduce the potential for further contamination of groundwater After the wall was built however an additional accumulation of free-phase DNAPL was identified outside of the wall (URS and DEampS 1999) This accumulation is informally known as either the Griffith Pool or the G-Pool A well field was installed in 1998 to extract mobile DNAPL from the area and to hydraulically contain the groundwater to minimize further contaminant flux to the off-Base plume

DESCRIPTION OF AND BASIS FOR THE DIFFERENCES

The SRS was constructed as an interim remedial action in 1993 to recover DNAPL from the source zone and to treat groundwater containing elevated concentrations of VOCs The SRS consists of a free-product and groundwater recovery well field aboveground pipeline and a process treatment facility (Building 755) Dense nonaqueous phase liquid is recovered during the

EXPLANA TIONOF SIGNIFICANT DIFFERENCES 0U2HIUAFB UTAH

treatment process using three phase separators while dissolved VOCs are removed from the groundwater using a packed-bed steam stripper In 1996 the Air Stripper Treatment Plant (ASTP) was constructed at OU 2 to provide secondary treatment of groundwater frorn the source zone following initial treatment with the steam stripper Prior to 2005 water was discharged from the ASTP to the on-base industrial wastewater treatment plant In 2005 an agreement was signed with Central Weber Sewer Improvement District (CWSID) allowing discharge oftreated water from OU 2 into the sanitary sewer Figure 2 provides a simplified process flow diagram illustrating the difference in the treatment process described in this ESD

Previous process flow

SRS Stop 1 DNAPL

separation

SRS Step 2 Steam

stripping

Pumped water from source zone

Discharge to sanitarYscver

Current process fiovi^

ASTP Air

stripping

Pumped water from source zone

Discharge to sanitary sewer

Figure 2 Simplified process flow diagram for OU 2 water treatment

Since 1992 approximately 44400 gallons of DNAPL have been recovered and over 20 million gallons of contaminated groundwater have been treated by steam stripping Of the total volume of DNAPL recovered 41000 gallons have been recovered primarily as mobile DNAPL via pump-and-treat operations and 3400 gallons have been recovered using enhanced-removal techniques Because the DNAPL recovery from the source zone has been successful DNAPL can no longer be extracted from the existing well field As the amount of DNAPL has decreased within the source zone the average concentration of VOCs in water extracted from the source zone has declined The average concentration of total VOCs in the influent to the SRS historically has ranged from 100 to 300 milligrams per liter (mgL) but concentrations generally have decreased to less than 100 mgL since the beginning of 2006 Hill AFB decided to evaluate

EXPLANA TION OF SIGNIFICANT DIFFERENCES OU 2 HILL AFB UTAH

altemative treatment options because the concentrations of VOCs being treated by the steam stripping process were decreasing

In 2007 Hill AFB proposed testing to determine if source zone water could be treated with the existing ASTP without pre-treatment by the steam stripper (January 25 2007 Project Managers meeting and letter dated March 152007) Piping modifications were completed during the fall of 2007 and initial testing was conducted during January and Febmary 2008 The results of this initial testing clearly showed that the ASTP is capable of achieving the treatment required to maintain compliance with the existing CWSED wastewater discharge permit without preshytreatment by the steam stripper Based on the initial results treatment of source zone water using the ASTP was continued to collect additional data to verify VOC removal efficiency over a one-year prove-out period This prove-out period included increased monitoring of both influent and effluent to the ASTP to allow evaluation of variability in either ASTP operating efficiency andor influent water concentrations

Currently the discharge limit to the CWSID is 2100 ^gL total volatiles (Method E624) The ASTP effluent concentrations remained below this discharge limit during 2008 as shown in Table 1 The calculated treatment efficiency was nominally 100 percent during 24 of 26 sampling events The remaining two sampling events had treatment efficiencies of 998 and 999 percent Figure 3 presents the ASTP effluent concentration over time As is evident from Figure 3 the total VOC concentration in the ASTP effluent has consistentiy been below the discharge limit and has not increased since piping modifications were completed during the fall of 2007

The fact that extracted source zone groundwater at OU 2 is no longer being pre-treated using the steam stripper constitutes a significant but not fundamental difference to the selected remedy outlined in the ROD This modification to the OU 2 source zone treatment system still provides safe and effective groundwater treatment with no additional environmental risk and with no added time to achieve cleanup

PUBLIC PARTICIPATION

This ESD was discussed during the July 30 2009 Restoration Advisory Board (RAB) meeting Discussion will include public notification procedures for ESDs The RAB will be requested to review both the process Hill AFB is using to prepare this ESD and the technical differences documented in this ESD

The RAB will be notified of the submission of the finalized ESD at the first quarterly RAB meeting after the ESD is signed Hill AFB will publish a notice of availability and a brief description ofthe ESD in the local newspaper Ogden Standard Examiner the week following

EXPIANA TION OF SIGNIFICNT DIFFERENCES OU 2 HILL AFB UTAH

TABLE 1 ASTP Total VOC Influent and Effluent Concentrations During 2008

Sample Date

012508

012908

020508

020808

021908

022908

030608

032508

040208

040408

040708

040808

040908

041008

041108

051408

052808

061008

062608

070808

072108

081808

090908

100808

111308

120908

Influent Concentration

(MgL) 104997

14603

159587

209442

3119

63952

72079

637

345

511

462

630

955

1013

1177

1015

1346

940

1342

1644

1239

1318

572

54466

158879

126171

Effluent Concentration

(ugL) 189

182

360

209

130

092

043

000

000

020

000

000

000

000

020

000

000

000

000

140

000

000

000

050

040

080

Treatment Efficiency (percent)

1000

1000

998

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

999

1000

1000

1000

1000

1000

1000

NOTES ngL = Micrograms per Liter VOC = Volatile Organic Compound Total VOCs calculated based on Method E624

EXPLANA TION OF SIGNIFICANT DIFFERENCES OU 2 HILL AFB UTAH

j

bull9

c o

5 c o c o o o O gt

o 1 -

1000000

100000

10000

1000

100

10

1

0

i 1

reg Influent

bull Effluent

^ 1 1 1

copy

9 c

raquo copy

CWSID Discharge Permit Concentration 2100 |igL Total Volatiles

s bull bull

c c ra

- 3

reg

regreg reg

1 bull

reg

reg

Jan-04

Jan-05 lt lt

Jan-06 1

Jan-07

1

Jan-08

Jan-09

Figure 3 ASTP Influent and Effluent Total VOC (Method E624) Concentration over Time

that RAB meeting This ESD and the infonnation upon which it is based will be included in the Administrative Record for this Site The Administrative Record also includes the ROD and all documents that formed the basis for USAFs selection and EPA and UDEQs concurrence ofthe remedial action for the Site These components meet the public participation requirement set out in Section 3()0435(c)(2)(i) of the NCP

REFERENCES

CH2M HILL 1996 Record of Decision and Respomiveness Summary for Operable Unit 2 Final Hill AFB Utah September

CH2M HILL 200 Performance Standard Verification Plan Operable Unit 2 Final Hill AFB Utah November

Radian 1990 Site Evaluation Report for Perimeter Road and the Spoils Area Final Hill AFB Utah August

Radian 1992 Remedial Investigation Report for Operable Unit 2 Hill AFB Utah July

URS and DEampS 1999 Dense Nonaqueous Phase Liquid (DNAPL) Source Delineation Project Final Report Operable Unit 2 Hill AFB Utah September

URS and DEampS 2001 SEAR Technology Application at Operable Unit 2 Volumes I and II Hill AFB Utah May

8

EXPIANA TION OF SIGNIFICANT DIFFERENCES OU 2 HILL AFB UTAH

AGENCY COMMENTS

The USAF submitted this ESD to the EPA and UDEQ for their review and comment Comments from both the EPA and UDEQ along with the USAF response are included as follows

UDEQ Comments viith Air Force responses in italics

GENERAL COMMENTS bull Please number all the pages throughout the document bull Please include a figure depicting the 0U2 layout bull Please include separate signature page for each agency It will facilitate the signing

process

Response Page numbers will he added to all pages A figure will be included showing the OUl site The signature pages will be separated as requested

SPECIFIC COMMENTS

i Introduction First Paragraph 5th line Please replace the word ROD with Remedial Investigation

2 Introduction First Paragraph Last line Please insert spent prior to chlorinated solvents 3 Public Participation First Line Please change This ESD will be discussed to This

ESD was discussed

Response Because this part ofthe section caused confusion for multiple reviewers the sentence Based on the ROD Site SS021 is free of contamination with the exception of a few areas being evaluated as part of other Operable Units and this site was recommended for no further remedial action will be replaced with Site SS02I included potential disposal sites along Perimeter Road investigated in the late I980s (Radian J990) Chemical Pit 3 and the North Gate Dump Sites (now part of Operable Unit 4) were the only sites where contamination was identified The ROD for OU 2 concluded that no further action was required for SS021

Response spent will be added as requested

Response The text was updated as requested

EPA Comments with Air Force responses in italics

Introduction First Paragraph states Perimeter Road (SS021) is free of contamination with the exception of a few areas being evaluated else as part of other OUs and this site was recommended for NFRAP Can you state or show on a map the areas being tracked under other OUs

Response Please see response to Specific Comment 1 above

EXPhXNATION OF SIGNIFICANT DIFFERENCES ou 2 HILL AFB UTAH

Fifth Paragraph states that this ESD is issued in accordance with Section 117(c) which requires the USAF to issue a document where a remedial action will differ in any significant but not fundamental respect from the ROD Significant and Fundamental should be defined here instead of under the Description and Basis for the Differences

Response Agreed The sentence A significant change to a remedy is one that incrementally changes a component ofa remedy (such as cost) but does not fundamentally alter the remedy (such as a change in the selected pump-and-treat remedy) will be added after the sentence ending USAF and described in the ROD in the fifth paragraph ofthe Introduction section The sentence will be removed from the fifth paragraph ofthe Description and Basis for the Differences section

STATUTORY DETERMINATIONS

The Applicable or Relevant and Appropriate Requirements (ARARs) addressed by the ROD for OU 2 are not modified by this ESD Considering the clarifications regarding the selected remedies presented in this ESD the USAF EPA and UDEQ all concur that the remedies at OU 2 remain protective of human health and the environment comply with federal and state requirements that were identified in the ROD as ARARs and are cost-effective There are no changes to the anticipated remediation time frame as a result of the Air Forces adoption of these differences from the ROD The remedy satisfies CERCLA Section 121

Signatures

10

EXPUNA TION OF SIGNIFICANT DIFFERENCES OU 2 HILL AFB UTAH

75TH AIR BASE WING (AFMC) HILL AIR FORCE BASE UTAH

^ T R I C K C HI Commander

Date

n

EXPUNA TION OF SIGNIFICANT DIFFERENCES OU 2 HILL AFB UTAH

UNITED STATES ENVIORNMENTAL PROTECTION AGENCY

CAROL L CAMPBELL 0 Date ^ Assistant Regional Administrator Office of Ecosystems Protection and Remediation US EPA Region VIII

12

EXPLANA TION OF SIGNIFICANT DIFFERENCES OU 2 HILL AFB UTAH

STATE OF UTAH DEPARTMENT OF ENVIORNMENTAL QUALITY

)A SMITH Executive Director Utah Department of Environmental Quality

O fCO^L^ Date

13

EXPLANA TIONOF SIGNIFICANT DIFFERENCES 0U2HIUAFB UTAH

treatment process using three phase separators while dissolved VOCs are removed from the groundwater using a packed-bed steam stripper In 1996 the Air Stripper Treatment Plant (ASTP) was constructed at OU 2 to provide secondary treatment of groundwater frorn the source zone following initial treatment with the steam stripper Prior to 2005 water was discharged from the ASTP to the on-base industrial wastewater treatment plant In 2005 an agreement was signed with Central Weber Sewer Improvement District (CWSID) allowing discharge oftreated water from OU 2 into the sanitary sewer Figure 2 provides a simplified process flow diagram illustrating the difference in the treatment process described in this ESD

Previous process flow

SRS Stop 1 DNAPL

separation

SRS Step 2 Steam

stripping

Pumped water from source zone

Discharge to sanitarYscver

Current process fiovi^

ASTP Air

stripping

Pumped water from source zone

Discharge to sanitary sewer

Figure 2 Simplified process flow diagram for OU 2 water treatment

Since 1992 approximately 44400 gallons of DNAPL have been recovered and over 20 million gallons of contaminated groundwater have been treated by steam stripping Of the total volume of DNAPL recovered 41000 gallons have been recovered primarily as mobile DNAPL via pump-and-treat operations and 3400 gallons have been recovered using enhanced-removal techniques Because the DNAPL recovery from the source zone has been successful DNAPL can no longer be extracted from the existing well field As the amount of DNAPL has decreased within the source zone the average concentration of VOCs in water extracted from the source zone has declined The average concentration of total VOCs in the influent to the SRS historically has ranged from 100 to 300 milligrams per liter (mgL) but concentrations generally have decreased to less than 100 mgL since the beginning of 2006 Hill AFB decided to evaluate

EXPLANA TION OF SIGNIFICANT DIFFERENCES OU 2 HILL AFB UTAH

altemative treatment options because the concentrations of VOCs being treated by the steam stripping process were decreasing

In 2007 Hill AFB proposed testing to determine if source zone water could be treated with the existing ASTP without pre-treatment by the steam stripper (January 25 2007 Project Managers meeting and letter dated March 152007) Piping modifications were completed during the fall of 2007 and initial testing was conducted during January and Febmary 2008 The results of this initial testing clearly showed that the ASTP is capable of achieving the treatment required to maintain compliance with the existing CWSED wastewater discharge permit without preshytreatment by the steam stripper Based on the initial results treatment of source zone water using the ASTP was continued to collect additional data to verify VOC removal efficiency over a one-year prove-out period This prove-out period included increased monitoring of both influent and effluent to the ASTP to allow evaluation of variability in either ASTP operating efficiency andor influent water concentrations

Currently the discharge limit to the CWSID is 2100 ^gL total volatiles (Method E624) The ASTP effluent concentrations remained below this discharge limit during 2008 as shown in Table 1 The calculated treatment efficiency was nominally 100 percent during 24 of 26 sampling events The remaining two sampling events had treatment efficiencies of 998 and 999 percent Figure 3 presents the ASTP effluent concentration over time As is evident from Figure 3 the total VOC concentration in the ASTP effluent has consistentiy been below the discharge limit and has not increased since piping modifications were completed during the fall of 2007

The fact that extracted source zone groundwater at OU 2 is no longer being pre-treated using the steam stripper constitutes a significant but not fundamental difference to the selected remedy outlined in the ROD This modification to the OU 2 source zone treatment system still provides safe and effective groundwater treatment with no additional environmental risk and with no added time to achieve cleanup

PUBLIC PARTICIPATION

This ESD was discussed during the July 30 2009 Restoration Advisory Board (RAB) meeting Discussion will include public notification procedures for ESDs The RAB will be requested to review both the process Hill AFB is using to prepare this ESD and the technical differences documented in this ESD

The RAB will be notified of the submission of the finalized ESD at the first quarterly RAB meeting after the ESD is signed Hill AFB will publish a notice of availability and a brief description ofthe ESD in the local newspaper Ogden Standard Examiner the week following

EXPIANA TION OF SIGNIFICNT DIFFERENCES OU 2 HILL AFB UTAH

TABLE 1 ASTP Total VOC Influent and Effluent Concentrations During 2008

Sample Date

012508

012908

020508

020808

021908

022908

030608

032508

040208

040408

040708

040808

040908

041008

041108

051408

052808

061008

062608

070808

072108

081808

090908

100808

111308

120908

Influent Concentration

(MgL) 104997

14603

159587

209442

3119

63952

72079

637

345

511

462

630

955

1013

1177

1015

1346

940

1342

1644

1239

1318

572

54466

158879

126171

Effluent Concentration

(ugL) 189

182

360

209

130

092

043

000

000

020

000

000

000

000

020

000

000

000

000

140

000

000

000

050

040

080

Treatment Efficiency (percent)

1000

1000

998

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

999

1000

1000

1000

1000

1000

1000

NOTES ngL = Micrograms per Liter VOC = Volatile Organic Compound Total VOCs calculated based on Method E624

EXPLANA TION OF SIGNIFICANT DIFFERENCES OU 2 HILL AFB UTAH

j

bull9

c o

5 c o c o o o O gt

o 1 -

1000000

100000

10000

1000

100

10

1

0

i 1

reg Influent

bull Effluent

^ 1 1 1

copy

9 c

raquo copy

CWSID Discharge Permit Concentration 2100 |igL Total Volatiles

s bull bull

c c ra

- 3

reg

regreg reg

1 bull

reg

reg

Jan-04

Jan-05 lt lt

Jan-06 1

Jan-07

1

Jan-08

Jan-09

Figure 3 ASTP Influent and Effluent Total VOC (Method E624) Concentration over Time

that RAB meeting This ESD and the infonnation upon which it is based will be included in the Administrative Record for this Site The Administrative Record also includes the ROD and all documents that formed the basis for USAFs selection and EPA and UDEQs concurrence ofthe remedial action for the Site These components meet the public participation requirement set out in Section 3()0435(c)(2)(i) of the NCP

REFERENCES

CH2M HILL 1996 Record of Decision and Respomiveness Summary for Operable Unit 2 Final Hill AFB Utah September

CH2M HILL 200 Performance Standard Verification Plan Operable Unit 2 Final Hill AFB Utah November

Radian 1990 Site Evaluation Report for Perimeter Road and the Spoils Area Final Hill AFB Utah August

Radian 1992 Remedial Investigation Report for Operable Unit 2 Hill AFB Utah July

URS and DEampS 1999 Dense Nonaqueous Phase Liquid (DNAPL) Source Delineation Project Final Report Operable Unit 2 Hill AFB Utah September

URS and DEampS 2001 SEAR Technology Application at Operable Unit 2 Volumes I and II Hill AFB Utah May

8

EXPIANA TION OF SIGNIFICANT DIFFERENCES OU 2 HILL AFB UTAH

AGENCY COMMENTS

The USAF submitted this ESD to the EPA and UDEQ for their review and comment Comments from both the EPA and UDEQ along with the USAF response are included as follows

UDEQ Comments viith Air Force responses in italics

GENERAL COMMENTS bull Please number all the pages throughout the document bull Please include a figure depicting the 0U2 layout bull Please include separate signature page for each agency It will facilitate the signing

process

Response Page numbers will he added to all pages A figure will be included showing the OUl site The signature pages will be separated as requested

SPECIFIC COMMENTS

i Introduction First Paragraph 5th line Please replace the word ROD with Remedial Investigation

2 Introduction First Paragraph Last line Please insert spent prior to chlorinated solvents 3 Public Participation First Line Please change This ESD will be discussed to This

ESD was discussed

Response Because this part ofthe section caused confusion for multiple reviewers the sentence Based on the ROD Site SS021 is free of contamination with the exception of a few areas being evaluated as part of other Operable Units and this site was recommended for no further remedial action will be replaced with Site SS02I included potential disposal sites along Perimeter Road investigated in the late I980s (Radian J990) Chemical Pit 3 and the North Gate Dump Sites (now part of Operable Unit 4) were the only sites where contamination was identified The ROD for OU 2 concluded that no further action was required for SS021

Response spent will be added as requested

Response The text was updated as requested

EPA Comments with Air Force responses in italics

Introduction First Paragraph states Perimeter Road (SS021) is free of contamination with the exception of a few areas being evaluated else as part of other OUs and this site was recommended for NFRAP Can you state or show on a map the areas being tracked under other OUs

Response Please see response to Specific Comment 1 above

EXPhXNATION OF SIGNIFICANT DIFFERENCES ou 2 HILL AFB UTAH

Fifth Paragraph states that this ESD is issued in accordance with Section 117(c) which requires the USAF to issue a document where a remedial action will differ in any significant but not fundamental respect from the ROD Significant and Fundamental should be defined here instead of under the Description and Basis for the Differences

Response Agreed The sentence A significant change to a remedy is one that incrementally changes a component ofa remedy (such as cost) but does not fundamentally alter the remedy (such as a change in the selected pump-and-treat remedy) will be added after the sentence ending USAF and described in the ROD in the fifth paragraph ofthe Introduction section The sentence will be removed from the fifth paragraph ofthe Description and Basis for the Differences section

STATUTORY DETERMINATIONS

The Applicable or Relevant and Appropriate Requirements (ARARs) addressed by the ROD for OU 2 are not modified by this ESD Considering the clarifications regarding the selected remedies presented in this ESD the USAF EPA and UDEQ all concur that the remedies at OU 2 remain protective of human health and the environment comply with federal and state requirements that were identified in the ROD as ARARs and are cost-effective There are no changes to the anticipated remediation time frame as a result of the Air Forces adoption of these differences from the ROD The remedy satisfies CERCLA Section 121

Signatures

10

EXPUNA TION OF SIGNIFICANT DIFFERENCES OU 2 HILL AFB UTAH

75TH AIR BASE WING (AFMC) HILL AIR FORCE BASE UTAH

^ T R I C K C HI Commander

Date

n

EXPUNA TION OF SIGNIFICANT DIFFERENCES OU 2 HILL AFB UTAH

UNITED STATES ENVIORNMENTAL PROTECTION AGENCY

CAROL L CAMPBELL 0 Date ^ Assistant Regional Administrator Office of Ecosystems Protection and Remediation US EPA Region VIII

12

EXPLANA TION OF SIGNIFICANT DIFFERENCES OU 2 HILL AFB UTAH

STATE OF UTAH DEPARTMENT OF ENVIORNMENTAL QUALITY

)A SMITH Executive Director Utah Department of Environmental Quality

O fCO^L^ Date

13

EXPLANA TION OF SIGNIFICANT DIFFERENCES OU 2 HILL AFB UTAH

altemative treatment options because the concentrations of VOCs being treated by the steam stripping process were decreasing

In 2007 Hill AFB proposed testing to determine if source zone water could be treated with the existing ASTP without pre-treatment by the steam stripper (January 25 2007 Project Managers meeting and letter dated March 152007) Piping modifications were completed during the fall of 2007 and initial testing was conducted during January and Febmary 2008 The results of this initial testing clearly showed that the ASTP is capable of achieving the treatment required to maintain compliance with the existing CWSED wastewater discharge permit without preshytreatment by the steam stripper Based on the initial results treatment of source zone water using the ASTP was continued to collect additional data to verify VOC removal efficiency over a one-year prove-out period This prove-out period included increased monitoring of both influent and effluent to the ASTP to allow evaluation of variability in either ASTP operating efficiency andor influent water concentrations

Currently the discharge limit to the CWSID is 2100 ^gL total volatiles (Method E624) The ASTP effluent concentrations remained below this discharge limit during 2008 as shown in Table 1 The calculated treatment efficiency was nominally 100 percent during 24 of 26 sampling events The remaining two sampling events had treatment efficiencies of 998 and 999 percent Figure 3 presents the ASTP effluent concentration over time As is evident from Figure 3 the total VOC concentration in the ASTP effluent has consistentiy been below the discharge limit and has not increased since piping modifications were completed during the fall of 2007

The fact that extracted source zone groundwater at OU 2 is no longer being pre-treated using the steam stripper constitutes a significant but not fundamental difference to the selected remedy outlined in the ROD This modification to the OU 2 source zone treatment system still provides safe and effective groundwater treatment with no additional environmental risk and with no added time to achieve cleanup

PUBLIC PARTICIPATION

This ESD was discussed during the July 30 2009 Restoration Advisory Board (RAB) meeting Discussion will include public notification procedures for ESDs The RAB will be requested to review both the process Hill AFB is using to prepare this ESD and the technical differences documented in this ESD

The RAB will be notified of the submission of the finalized ESD at the first quarterly RAB meeting after the ESD is signed Hill AFB will publish a notice of availability and a brief description ofthe ESD in the local newspaper Ogden Standard Examiner the week following

EXPIANA TION OF SIGNIFICNT DIFFERENCES OU 2 HILL AFB UTAH

TABLE 1 ASTP Total VOC Influent and Effluent Concentrations During 2008

Sample Date

012508

012908

020508

020808

021908

022908

030608

032508

040208

040408

040708

040808

040908

041008

041108

051408

052808

061008

062608

070808

072108

081808

090908

100808

111308

120908

Influent Concentration

(MgL) 104997

14603

159587

209442

3119

63952

72079

637

345

511

462

630

955

1013

1177

1015

1346

940

1342

1644

1239

1318

572

54466

158879

126171

Effluent Concentration

(ugL) 189

182

360

209

130

092

043

000

000

020

000

000

000

000

020

000

000

000

000

140

000

000

000

050

040

080

Treatment Efficiency (percent)

1000

1000

998

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

999

1000

1000

1000

1000

1000

1000

NOTES ngL = Micrograms per Liter VOC = Volatile Organic Compound Total VOCs calculated based on Method E624

EXPLANA TION OF SIGNIFICANT DIFFERENCES OU 2 HILL AFB UTAH

j

bull9

c o

5 c o c o o o O gt

o 1 -

1000000

100000

10000

1000

100

10

1

0

i 1

reg Influent

bull Effluent

^ 1 1 1

copy

9 c

raquo copy

CWSID Discharge Permit Concentration 2100 |igL Total Volatiles

s bull bull

c c ra

- 3

reg

regreg reg

1 bull

reg

reg

Jan-04

Jan-05 lt lt

Jan-06 1

Jan-07

1

Jan-08

Jan-09

Figure 3 ASTP Influent and Effluent Total VOC (Method E624) Concentration over Time

that RAB meeting This ESD and the infonnation upon which it is based will be included in the Administrative Record for this Site The Administrative Record also includes the ROD and all documents that formed the basis for USAFs selection and EPA and UDEQs concurrence ofthe remedial action for the Site These components meet the public participation requirement set out in Section 3()0435(c)(2)(i) of the NCP

REFERENCES

CH2M HILL 1996 Record of Decision and Respomiveness Summary for Operable Unit 2 Final Hill AFB Utah September

CH2M HILL 200 Performance Standard Verification Plan Operable Unit 2 Final Hill AFB Utah November

Radian 1990 Site Evaluation Report for Perimeter Road and the Spoils Area Final Hill AFB Utah August

Radian 1992 Remedial Investigation Report for Operable Unit 2 Hill AFB Utah July

URS and DEampS 1999 Dense Nonaqueous Phase Liquid (DNAPL) Source Delineation Project Final Report Operable Unit 2 Hill AFB Utah September

URS and DEampS 2001 SEAR Technology Application at Operable Unit 2 Volumes I and II Hill AFB Utah May

8

EXPIANA TION OF SIGNIFICANT DIFFERENCES OU 2 HILL AFB UTAH

AGENCY COMMENTS

The USAF submitted this ESD to the EPA and UDEQ for their review and comment Comments from both the EPA and UDEQ along with the USAF response are included as follows

UDEQ Comments viith Air Force responses in italics

GENERAL COMMENTS bull Please number all the pages throughout the document bull Please include a figure depicting the 0U2 layout bull Please include separate signature page for each agency It will facilitate the signing

process

Response Page numbers will he added to all pages A figure will be included showing the OUl site The signature pages will be separated as requested

SPECIFIC COMMENTS

i Introduction First Paragraph 5th line Please replace the word ROD with Remedial Investigation

2 Introduction First Paragraph Last line Please insert spent prior to chlorinated solvents 3 Public Participation First Line Please change This ESD will be discussed to This

ESD was discussed

Response Because this part ofthe section caused confusion for multiple reviewers the sentence Based on the ROD Site SS021 is free of contamination with the exception of a few areas being evaluated as part of other Operable Units and this site was recommended for no further remedial action will be replaced with Site SS02I included potential disposal sites along Perimeter Road investigated in the late I980s (Radian J990) Chemical Pit 3 and the North Gate Dump Sites (now part of Operable Unit 4) were the only sites where contamination was identified The ROD for OU 2 concluded that no further action was required for SS021

Response spent will be added as requested

Response The text was updated as requested

EPA Comments with Air Force responses in italics

Introduction First Paragraph states Perimeter Road (SS021) is free of contamination with the exception of a few areas being evaluated else as part of other OUs and this site was recommended for NFRAP Can you state or show on a map the areas being tracked under other OUs

Response Please see response to Specific Comment 1 above

EXPhXNATION OF SIGNIFICANT DIFFERENCES ou 2 HILL AFB UTAH

Fifth Paragraph states that this ESD is issued in accordance with Section 117(c) which requires the USAF to issue a document where a remedial action will differ in any significant but not fundamental respect from the ROD Significant and Fundamental should be defined here instead of under the Description and Basis for the Differences

Response Agreed The sentence A significant change to a remedy is one that incrementally changes a component ofa remedy (such as cost) but does not fundamentally alter the remedy (such as a change in the selected pump-and-treat remedy) will be added after the sentence ending USAF and described in the ROD in the fifth paragraph ofthe Introduction section The sentence will be removed from the fifth paragraph ofthe Description and Basis for the Differences section

STATUTORY DETERMINATIONS

The Applicable or Relevant and Appropriate Requirements (ARARs) addressed by the ROD for OU 2 are not modified by this ESD Considering the clarifications regarding the selected remedies presented in this ESD the USAF EPA and UDEQ all concur that the remedies at OU 2 remain protective of human health and the environment comply with federal and state requirements that were identified in the ROD as ARARs and are cost-effective There are no changes to the anticipated remediation time frame as a result of the Air Forces adoption of these differences from the ROD The remedy satisfies CERCLA Section 121

Signatures

10

EXPUNA TION OF SIGNIFICANT DIFFERENCES OU 2 HILL AFB UTAH

75TH AIR BASE WING (AFMC) HILL AIR FORCE BASE UTAH

^ T R I C K C HI Commander

Date

n

EXPUNA TION OF SIGNIFICANT DIFFERENCES OU 2 HILL AFB UTAH

UNITED STATES ENVIORNMENTAL PROTECTION AGENCY

CAROL L CAMPBELL 0 Date ^ Assistant Regional Administrator Office of Ecosystems Protection and Remediation US EPA Region VIII

12

EXPLANA TION OF SIGNIFICANT DIFFERENCES OU 2 HILL AFB UTAH

STATE OF UTAH DEPARTMENT OF ENVIORNMENTAL QUALITY

)A SMITH Executive Director Utah Department of Environmental Quality

O fCO^L^ Date

13

EXPIANA TION OF SIGNIFICNT DIFFERENCES OU 2 HILL AFB UTAH

TABLE 1 ASTP Total VOC Influent and Effluent Concentrations During 2008

Sample Date

012508

012908

020508

020808

021908

022908

030608

032508

040208

040408

040708

040808

040908

041008

041108

051408

052808

061008

062608

070808

072108

081808

090908

100808

111308

120908

Influent Concentration

(MgL) 104997

14603

159587

209442

3119

63952

72079

637

345

511

462

630

955

1013

1177

1015

1346

940

1342

1644

1239

1318

572

54466

158879

126171

Effluent Concentration

(ugL) 189

182

360

209

130

092

043

000

000

020

000

000

000

000

020

000

000

000

000

140

000

000

000

050

040

080

Treatment Efficiency (percent)

1000

1000

998

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

999

1000

1000

1000

1000

1000

1000

NOTES ngL = Micrograms per Liter VOC = Volatile Organic Compound Total VOCs calculated based on Method E624

EXPLANA TION OF SIGNIFICANT DIFFERENCES OU 2 HILL AFB UTAH

j

bull9

c o

5 c o c o o o O gt

o 1 -

1000000

100000

10000

1000

100

10

1

0

i 1

reg Influent

bull Effluent

^ 1 1 1

copy

9 c

raquo copy

CWSID Discharge Permit Concentration 2100 |igL Total Volatiles

s bull bull

c c ra

- 3

reg

regreg reg

1 bull

reg

reg

Jan-04

Jan-05 lt lt

Jan-06 1

Jan-07

1

Jan-08

Jan-09

Figure 3 ASTP Influent and Effluent Total VOC (Method E624) Concentration over Time

that RAB meeting This ESD and the infonnation upon which it is based will be included in the Administrative Record for this Site The Administrative Record also includes the ROD and all documents that formed the basis for USAFs selection and EPA and UDEQs concurrence ofthe remedial action for the Site These components meet the public participation requirement set out in Section 3()0435(c)(2)(i) of the NCP

REFERENCES

CH2M HILL 1996 Record of Decision and Respomiveness Summary for Operable Unit 2 Final Hill AFB Utah September

CH2M HILL 200 Performance Standard Verification Plan Operable Unit 2 Final Hill AFB Utah November

Radian 1990 Site Evaluation Report for Perimeter Road and the Spoils Area Final Hill AFB Utah August

Radian 1992 Remedial Investigation Report for Operable Unit 2 Hill AFB Utah July

URS and DEampS 1999 Dense Nonaqueous Phase Liquid (DNAPL) Source Delineation Project Final Report Operable Unit 2 Hill AFB Utah September

URS and DEampS 2001 SEAR Technology Application at Operable Unit 2 Volumes I and II Hill AFB Utah May

8

EXPIANA TION OF SIGNIFICANT DIFFERENCES OU 2 HILL AFB UTAH

AGENCY COMMENTS

The USAF submitted this ESD to the EPA and UDEQ for their review and comment Comments from both the EPA and UDEQ along with the USAF response are included as follows

UDEQ Comments viith Air Force responses in italics

GENERAL COMMENTS bull Please number all the pages throughout the document bull Please include a figure depicting the 0U2 layout bull Please include separate signature page for each agency It will facilitate the signing

process

Response Page numbers will he added to all pages A figure will be included showing the OUl site The signature pages will be separated as requested

SPECIFIC COMMENTS

i Introduction First Paragraph 5th line Please replace the word ROD with Remedial Investigation

2 Introduction First Paragraph Last line Please insert spent prior to chlorinated solvents 3 Public Participation First Line Please change This ESD will be discussed to This

ESD was discussed

Response Because this part ofthe section caused confusion for multiple reviewers the sentence Based on the ROD Site SS021 is free of contamination with the exception of a few areas being evaluated as part of other Operable Units and this site was recommended for no further remedial action will be replaced with Site SS02I included potential disposal sites along Perimeter Road investigated in the late I980s (Radian J990) Chemical Pit 3 and the North Gate Dump Sites (now part of Operable Unit 4) were the only sites where contamination was identified The ROD for OU 2 concluded that no further action was required for SS021

Response spent will be added as requested

Response The text was updated as requested

EPA Comments with Air Force responses in italics

Introduction First Paragraph states Perimeter Road (SS021) is free of contamination with the exception of a few areas being evaluated else as part of other OUs and this site was recommended for NFRAP Can you state or show on a map the areas being tracked under other OUs

Response Please see response to Specific Comment 1 above

EXPhXNATION OF SIGNIFICANT DIFFERENCES ou 2 HILL AFB UTAH

Fifth Paragraph states that this ESD is issued in accordance with Section 117(c) which requires the USAF to issue a document where a remedial action will differ in any significant but not fundamental respect from the ROD Significant and Fundamental should be defined here instead of under the Description and Basis for the Differences

Response Agreed The sentence A significant change to a remedy is one that incrementally changes a component ofa remedy (such as cost) but does not fundamentally alter the remedy (such as a change in the selected pump-and-treat remedy) will be added after the sentence ending USAF and described in the ROD in the fifth paragraph ofthe Introduction section The sentence will be removed from the fifth paragraph ofthe Description and Basis for the Differences section

STATUTORY DETERMINATIONS

The Applicable or Relevant and Appropriate Requirements (ARARs) addressed by the ROD for OU 2 are not modified by this ESD Considering the clarifications regarding the selected remedies presented in this ESD the USAF EPA and UDEQ all concur that the remedies at OU 2 remain protective of human health and the environment comply with federal and state requirements that were identified in the ROD as ARARs and are cost-effective There are no changes to the anticipated remediation time frame as a result of the Air Forces adoption of these differences from the ROD The remedy satisfies CERCLA Section 121

Signatures

10

EXPUNA TION OF SIGNIFICANT DIFFERENCES OU 2 HILL AFB UTAH

75TH AIR BASE WING (AFMC) HILL AIR FORCE BASE UTAH

^ T R I C K C HI Commander

Date

n

EXPUNA TION OF SIGNIFICANT DIFFERENCES OU 2 HILL AFB UTAH

UNITED STATES ENVIORNMENTAL PROTECTION AGENCY

CAROL L CAMPBELL 0 Date ^ Assistant Regional Administrator Office of Ecosystems Protection and Remediation US EPA Region VIII

12

EXPLANA TION OF SIGNIFICANT DIFFERENCES OU 2 HILL AFB UTAH

STATE OF UTAH DEPARTMENT OF ENVIORNMENTAL QUALITY

)A SMITH Executive Director Utah Department of Environmental Quality

O fCO^L^ Date

13

EXPLANA TION OF SIGNIFICANT DIFFERENCES OU 2 HILL AFB UTAH

j

bull9

c o

5 c o c o o o O gt

o 1 -

1000000

100000

10000

1000

100

10

1

0

i 1

reg Influent

bull Effluent

^ 1 1 1

copy

9 c

raquo copy

CWSID Discharge Permit Concentration 2100 |igL Total Volatiles

s bull bull

c c ra

- 3

reg

regreg reg

1 bull

reg

reg

Jan-04

Jan-05 lt lt

Jan-06 1

Jan-07

1

Jan-08

Jan-09

Figure 3 ASTP Influent and Effluent Total VOC (Method E624) Concentration over Time

that RAB meeting This ESD and the infonnation upon which it is based will be included in the Administrative Record for this Site The Administrative Record also includes the ROD and all documents that formed the basis for USAFs selection and EPA and UDEQs concurrence ofthe remedial action for the Site These components meet the public participation requirement set out in Section 3()0435(c)(2)(i) of the NCP

REFERENCES

CH2M HILL 1996 Record of Decision and Respomiveness Summary for Operable Unit 2 Final Hill AFB Utah September

CH2M HILL 200 Performance Standard Verification Plan Operable Unit 2 Final Hill AFB Utah November

Radian 1990 Site Evaluation Report for Perimeter Road and the Spoils Area Final Hill AFB Utah August

Radian 1992 Remedial Investigation Report for Operable Unit 2 Hill AFB Utah July

URS and DEampS 1999 Dense Nonaqueous Phase Liquid (DNAPL) Source Delineation Project Final Report Operable Unit 2 Hill AFB Utah September

URS and DEampS 2001 SEAR Technology Application at Operable Unit 2 Volumes I and II Hill AFB Utah May

8

EXPIANA TION OF SIGNIFICANT DIFFERENCES OU 2 HILL AFB UTAH

AGENCY COMMENTS

The USAF submitted this ESD to the EPA and UDEQ for their review and comment Comments from both the EPA and UDEQ along with the USAF response are included as follows

UDEQ Comments viith Air Force responses in italics

GENERAL COMMENTS bull Please number all the pages throughout the document bull Please include a figure depicting the 0U2 layout bull Please include separate signature page for each agency It will facilitate the signing

process

Response Page numbers will he added to all pages A figure will be included showing the OUl site The signature pages will be separated as requested

SPECIFIC COMMENTS

i Introduction First Paragraph 5th line Please replace the word ROD with Remedial Investigation

2 Introduction First Paragraph Last line Please insert spent prior to chlorinated solvents 3 Public Participation First Line Please change This ESD will be discussed to This

ESD was discussed

Response Because this part ofthe section caused confusion for multiple reviewers the sentence Based on the ROD Site SS021 is free of contamination with the exception of a few areas being evaluated as part of other Operable Units and this site was recommended for no further remedial action will be replaced with Site SS02I included potential disposal sites along Perimeter Road investigated in the late I980s (Radian J990) Chemical Pit 3 and the North Gate Dump Sites (now part of Operable Unit 4) were the only sites where contamination was identified The ROD for OU 2 concluded that no further action was required for SS021

Response spent will be added as requested

Response The text was updated as requested

EPA Comments with Air Force responses in italics

Introduction First Paragraph states Perimeter Road (SS021) is free of contamination with the exception of a few areas being evaluated else as part of other OUs and this site was recommended for NFRAP Can you state or show on a map the areas being tracked under other OUs

Response Please see response to Specific Comment 1 above

EXPhXNATION OF SIGNIFICANT DIFFERENCES ou 2 HILL AFB UTAH

Fifth Paragraph states that this ESD is issued in accordance with Section 117(c) which requires the USAF to issue a document where a remedial action will differ in any significant but not fundamental respect from the ROD Significant and Fundamental should be defined here instead of under the Description and Basis for the Differences

Response Agreed The sentence A significant change to a remedy is one that incrementally changes a component ofa remedy (such as cost) but does not fundamentally alter the remedy (such as a change in the selected pump-and-treat remedy) will be added after the sentence ending USAF and described in the ROD in the fifth paragraph ofthe Introduction section The sentence will be removed from the fifth paragraph ofthe Description and Basis for the Differences section

STATUTORY DETERMINATIONS

The Applicable or Relevant and Appropriate Requirements (ARARs) addressed by the ROD for OU 2 are not modified by this ESD Considering the clarifications regarding the selected remedies presented in this ESD the USAF EPA and UDEQ all concur that the remedies at OU 2 remain protective of human health and the environment comply with federal and state requirements that were identified in the ROD as ARARs and are cost-effective There are no changes to the anticipated remediation time frame as a result of the Air Forces adoption of these differences from the ROD The remedy satisfies CERCLA Section 121

Signatures

10

EXPUNA TION OF SIGNIFICANT DIFFERENCES OU 2 HILL AFB UTAH

75TH AIR BASE WING (AFMC) HILL AIR FORCE BASE UTAH

^ T R I C K C HI Commander

Date

n

EXPUNA TION OF SIGNIFICANT DIFFERENCES OU 2 HILL AFB UTAH

UNITED STATES ENVIORNMENTAL PROTECTION AGENCY

CAROL L CAMPBELL 0 Date ^ Assistant Regional Administrator Office of Ecosystems Protection and Remediation US EPA Region VIII

12

EXPLANA TION OF SIGNIFICANT DIFFERENCES OU 2 HILL AFB UTAH

STATE OF UTAH DEPARTMENT OF ENVIORNMENTAL QUALITY

)A SMITH Executive Director Utah Department of Environmental Quality

O fCO^L^ Date

13

EXPIANA TION OF SIGNIFICANT DIFFERENCES OU 2 HILL AFB UTAH

AGENCY COMMENTS

The USAF submitted this ESD to the EPA and UDEQ for their review and comment Comments from both the EPA and UDEQ along with the USAF response are included as follows

UDEQ Comments viith Air Force responses in italics

GENERAL COMMENTS bull Please number all the pages throughout the document bull Please include a figure depicting the 0U2 layout bull Please include separate signature page for each agency It will facilitate the signing

process

Response Page numbers will he added to all pages A figure will be included showing the OUl site The signature pages will be separated as requested

SPECIFIC COMMENTS

i Introduction First Paragraph 5th line Please replace the word ROD with Remedial Investigation

2 Introduction First Paragraph Last line Please insert spent prior to chlorinated solvents 3 Public Participation First Line Please change This ESD will be discussed to This

ESD was discussed

Response Because this part ofthe section caused confusion for multiple reviewers the sentence Based on the ROD Site SS021 is free of contamination with the exception of a few areas being evaluated as part of other Operable Units and this site was recommended for no further remedial action will be replaced with Site SS02I included potential disposal sites along Perimeter Road investigated in the late I980s (Radian J990) Chemical Pit 3 and the North Gate Dump Sites (now part of Operable Unit 4) were the only sites where contamination was identified The ROD for OU 2 concluded that no further action was required for SS021

Response spent will be added as requested

Response The text was updated as requested

EPA Comments with Air Force responses in italics

Introduction First Paragraph states Perimeter Road (SS021) is free of contamination with the exception of a few areas being evaluated else as part of other OUs and this site was recommended for NFRAP Can you state or show on a map the areas being tracked under other OUs

Response Please see response to Specific Comment 1 above

EXPhXNATION OF SIGNIFICANT DIFFERENCES ou 2 HILL AFB UTAH

Fifth Paragraph states that this ESD is issued in accordance with Section 117(c) which requires the USAF to issue a document where a remedial action will differ in any significant but not fundamental respect from the ROD Significant and Fundamental should be defined here instead of under the Description and Basis for the Differences

Response Agreed The sentence A significant change to a remedy is one that incrementally changes a component ofa remedy (such as cost) but does not fundamentally alter the remedy (such as a change in the selected pump-and-treat remedy) will be added after the sentence ending USAF and described in the ROD in the fifth paragraph ofthe Introduction section The sentence will be removed from the fifth paragraph ofthe Description and Basis for the Differences section

STATUTORY DETERMINATIONS

The Applicable or Relevant and Appropriate Requirements (ARARs) addressed by the ROD for OU 2 are not modified by this ESD Considering the clarifications regarding the selected remedies presented in this ESD the USAF EPA and UDEQ all concur that the remedies at OU 2 remain protective of human health and the environment comply with federal and state requirements that were identified in the ROD as ARARs and are cost-effective There are no changes to the anticipated remediation time frame as a result of the Air Forces adoption of these differences from the ROD The remedy satisfies CERCLA Section 121

Signatures

10

EXPUNA TION OF SIGNIFICANT DIFFERENCES OU 2 HILL AFB UTAH

75TH AIR BASE WING (AFMC) HILL AIR FORCE BASE UTAH

^ T R I C K C HI Commander

Date

n

EXPUNA TION OF SIGNIFICANT DIFFERENCES OU 2 HILL AFB UTAH

UNITED STATES ENVIORNMENTAL PROTECTION AGENCY

CAROL L CAMPBELL 0 Date ^ Assistant Regional Administrator Office of Ecosystems Protection and Remediation US EPA Region VIII

12

EXPLANA TION OF SIGNIFICANT DIFFERENCES OU 2 HILL AFB UTAH

STATE OF UTAH DEPARTMENT OF ENVIORNMENTAL QUALITY

)A SMITH Executive Director Utah Department of Environmental Quality

O fCO^L^ Date

13

EXPhXNATION OF SIGNIFICANT DIFFERENCES ou 2 HILL AFB UTAH

Fifth Paragraph states that this ESD is issued in accordance with Section 117(c) which requires the USAF to issue a document where a remedial action will differ in any significant but not fundamental respect from the ROD Significant and Fundamental should be defined here instead of under the Description and Basis for the Differences

Response Agreed The sentence A significant change to a remedy is one that incrementally changes a component ofa remedy (such as cost) but does not fundamentally alter the remedy (such as a change in the selected pump-and-treat remedy) will be added after the sentence ending USAF and described in the ROD in the fifth paragraph ofthe Introduction section The sentence will be removed from the fifth paragraph ofthe Description and Basis for the Differences section

STATUTORY DETERMINATIONS

The Applicable or Relevant and Appropriate Requirements (ARARs) addressed by the ROD for OU 2 are not modified by this ESD Considering the clarifications regarding the selected remedies presented in this ESD the USAF EPA and UDEQ all concur that the remedies at OU 2 remain protective of human health and the environment comply with federal and state requirements that were identified in the ROD as ARARs and are cost-effective There are no changes to the anticipated remediation time frame as a result of the Air Forces adoption of these differences from the ROD The remedy satisfies CERCLA Section 121

Signatures

10

EXPUNA TION OF SIGNIFICANT DIFFERENCES OU 2 HILL AFB UTAH

75TH AIR BASE WING (AFMC) HILL AIR FORCE BASE UTAH

^ T R I C K C HI Commander

Date

n

EXPUNA TION OF SIGNIFICANT DIFFERENCES OU 2 HILL AFB UTAH

UNITED STATES ENVIORNMENTAL PROTECTION AGENCY

CAROL L CAMPBELL 0 Date ^ Assistant Regional Administrator Office of Ecosystems Protection and Remediation US EPA Region VIII

12

EXPLANA TION OF SIGNIFICANT DIFFERENCES OU 2 HILL AFB UTAH

STATE OF UTAH DEPARTMENT OF ENVIORNMENTAL QUALITY

)A SMITH Executive Director Utah Department of Environmental Quality

O fCO^L^ Date

13

EXPUNA TION OF SIGNIFICANT DIFFERENCES OU 2 HILL AFB UTAH

75TH AIR BASE WING (AFMC) HILL AIR FORCE BASE UTAH

^ T R I C K C HI Commander

Date

n

EXPUNA TION OF SIGNIFICANT DIFFERENCES OU 2 HILL AFB UTAH

UNITED STATES ENVIORNMENTAL PROTECTION AGENCY

CAROL L CAMPBELL 0 Date ^ Assistant Regional Administrator Office of Ecosystems Protection and Remediation US EPA Region VIII

12

EXPLANA TION OF SIGNIFICANT DIFFERENCES OU 2 HILL AFB UTAH

STATE OF UTAH DEPARTMENT OF ENVIORNMENTAL QUALITY

)A SMITH Executive Director Utah Department of Environmental Quality

O fCO^L^ Date

13

EXPUNA TION OF SIGNIFICANT DIFFERENCES OU 2 HILL AFB UTAH

UNITED STATES ENVIORNMENTAL PROTECTION AGENCY

CAROL L CAMPBELL 0 Date ^ Assistant Regional Administrator Office of Ecosystems Protection and Remediation US EPA Region VIII

12

EXPLANA TION OF SIGNIFICANT DIFFERENCES OU 2 HILL AFB UTAH

STATE OF UTAH DEPARTMENT OF ENVIORNMENTAL QUALITY

)A SMITH Executive Director Utah Department of Environmental Quality

O fCO^L^ Date

13

EXPLANA TION OF SIGNIFICANT DIFFERENCES OU 2 HILL AFB UTAH

STATE OF UTAH DEPARTMENT OF ENVIORNMENTAL QUALITY

)A SMITH Executive Director Utah Department of Environmental Quality

O fCO^L^ Date

13