^ mcmi MEMO

To:

Katharyn Wright (DNREC) Ronald Graeber (DNREC) William Cocke (DNREC)

llllllllllllllllliiiilliiiiiiiiiiiiiiiiiiiii SDMS DocID 2150873

_y

Copies:

Christian Matta (EPA) Robert Asreen (DNREC) Michael Teichman (Parkowski, Guerke & Swayze) John Kindschuh (Bryan Cave)

ARCADIS U.S., Inc.

10 Friends Ln

Suite 300

Newtown

Pennsylvania 18940

Tel 267.685.1800

Fax 267.685.1801

From:

Darren Scillieri

Date:

June?, 2012 ARCADIS Project No.:

NP000686.0005.00005

Subject:

Underground Injection Control (UIC) Class V Well Application Addendum Millsboro TCE Groundwater Contamination Site located in Millsboro, Delaware

This Memorandum has been prepared on behalf of Merck and Co., Inc. (Merck) and Mallinckrodt Veterinary, Inc. (Mallinkrodt) by ARCADIS U.S. Inc. (ARCADIS) as an addendum to the Environmental Control Underground Injection Control (UIC) Class V Well Permit application dated April 5, 2012. This Memorandum provides responses and additional infonnation as requested by Delaware Department of Natural Resources (DNREC) in their April 26, 2012 email and the subsequent telephone conversation between ARCADIS and DNREC on.May 1, 2012. In addition, responses to DNREC Groundwater Protection Branch (GPB) comments to the Preliminary Groundwater Assessment Report (PGIA), provided to ARCADIS in a Memorandum dated May 24 (May 2012 GPB Memo), have been incorporated into this addendum where these comments pertain to the implementation of the reinjection testing.

The May 2012 GPB Memo states that given "the need to resolve the Town's ongoing problem of disposing the treated groundwater; the GPB would recommend the GDS allow ARCADIS to begin testing of the injection well system. The GPB feels this would be an acceptable path fonward with minimal risk due to the fact that the extracted groundwater is currently being treated to remove the TCE, and if any issue arises during the testing phase a contingency plan has been established...." In its Conclusions and Recommendations Section, the May 2012 GPB Memo requires that modifications based on their comments be added to the proposed testing outlined in the April 5, 2012 UIC Class V Well Application Form. As such, this addendum specifically provides responses to the Conclusions /

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Recommendations provided therein, and reflects the subsequent telephone conversation between ARCADIS and DNREC on May 24, 2012. DNREC comments are presented in italics below, along with ARCADIS' responses to those comments.

UIC Comment Responses:

/. Please provide a detailed explanation of any testing phase, and subsequent phases. For example, "Phase I includes: installation of IW-1, to a depth of 90 ft, for the injection of..." Also, please explain future phases of the remediation project. The current application should address the next proposed phase, including the estimated time for completion and estimated duration.

Response: The following provides the main components of each phase of the project. Phase 1 is the installation of the reinjection test well network. Phase 2 is the testing phase and consists of Phase 2a, a Preliminary Step Test and Phase 2b, the Reinjection Test. Phase 3 includes design and construction of the full scale implementation.

Phase 1: Injection Test Well Network

The following injection well and observation well network details have been revised since submission of the UIC permit application dated April 5*, 2012 to better monitor hydraulic effects in the shallow saturated and unsaturated zones. Construction details for the proposed injection and observation wells are provided on the well construction logs included in Attachment 1.

One well will be constructed to enable reinjection pilot testing. Four monitoring wells will be constructed near this well to enable monitoring of water levels in the surrounding and underlying formations. The proposed reinjection and observation wells will be installed by a Delaware-licensed driller, and the test reinjection well will be constructed in accordance with the Delaware Regulations Governing the Construction and Use of Wells, Delaware Division of Water Resources, April 6, 1997. The test injection well and monitoring well network will be installed using mud rotary drilling techniques.

The proposed test injection well will be constructed of a 10-inch steel casing installed to a depth of 5 ft. below ground surface (bgs), and will be completed with a 10-inch diameter stainless steel 50 slot wire-wrap screen from 5 to 85 ft. bgs. The gravel pack will extend from 3 to 90 ft. bgs. The annulus space above 3 ft. bgs will be sealed with neat cement-bentonite to ground surface and will be completed with a flush-mount protective steel cover. Grout will be injected into the annular space of the borehole using a tremie pipe, pressure injection method, to ensure a proper seal.

Observation wells OW-1, OW-2, and OW-3 will be completed in the Columbia Aquifer to monitor effects of the injection test. The shallow observation wells will be constructed of 2-inch PVC to a

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I

depth of 25 feet and completed with a 2-inch diameter PVC 20 slot screen from 5 to 25 feet bgs. The annulus space above the sand pack will be sealed with neat cement and bentonite to ground surface and each well will be completed with a protective steel cover.

An additional monitoring well will be installed in the Bethany formation per the request of GPB in the May 2012 GPB Memo. As requested in the GPB letter, this well will be installed to approximately 135 feet bgs. The well will be constructed of 1-inch diameter schedule 40 PVC and completed with 10 slot PVC screen from 125 to 135 feet bgs. The gravel pack will extend from 120 to 135 ft. bgs. The annulus space above 120 ft. bgs will be sealed with neat cement-bentonite to ground surface and will be completed with a protective steel cover. Grout will be injected into the annular space of the borehole using a tremie pipe, pressure injection method, to ensure a proper seal is installed to hydraulically isolate the well from the overlying and/or underlying aquifer/formation.

Following reinjection pilot testing, the data will be evaluated to determine whether additional reinjection wells are necessary for the full scale system, and the appropriate design of such wells, if necessary.

Phase 2a: Preliminary Step Test Prior to implementing the longer term test a short-term preliminary test of the reinjection well will be conducted. Water from the Town of Millsboro supply wells PW-1 and/or PW-2 will be utilized to facilitate the reinjection testing.

The step test will be used to select an appropriate reinjection rate for the longer term reinjection test as well as to evaluate mounding effects within the aquifer at various reinjection rates. The step test will be run at four evenly spaced injection rates to determine the maximum sustainable rate for implementing the longer term test. 200 gpm is the maximum rate that can be pumped from each of PW-1 and PW-2. If higher rates are needed, additional water will be routed from either PW-1 or PW-2, if Town water demand allows.

Each rate implemented during the step test will be run for an estimated 30 to 120 minutes. Following the completion of each step, the reinjection rate will be increased for the subsequent step. The reinjection rates and total gallons reinjected willbe measured and recorded after each step. This procedure will be repeated for each of the steps of the step test.

Phase 2b: Reinjection Test After completion of the step test and after the test well has recovered, a longer term reinjection test will be conducted. Prior to initiating the longer term reinjection test, the groundwater levels will be allowed to equilibrate to within 90% of the initial water level. The longer term reinjection

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test will be conducted at the maximum sustainable reinjection rate determined during the step test. A constant reinjection rate will be maintained during testing. The pumping rate and total gallons pumped will be measured and recorded before each water level measurement. The effect this pilot-test will have on local water levels in the Columbia Aquifer will be evaluated by measuring the water levels in the three observation wells installed around the reinjection well.

The test will be run until injection dynamics and groundwater conditions have stabilized to the degree that the design parameters have been established. Stability will be considered to have been achieved once mounding effects on the water table have reached equilibrium; i.e., no change in water levels over an extended period of time (several hours). However, complete stability (no change in groundwater level) is rarely achievable in practice. For testing purposes, it

. will be assumed that water level stabilization within 5% of the total vertical distance available for mounding, maintained over a four hour period, is adequate to determine the design parameters needed to complete the full-scale system design. It is anticipated that the design parameters will be established within an estimated 72-hours of initiating the test; however, the permit for reinjection is being requested for a 30-day active injection period to allow for 1) a step test to be conducted and the results evaluated prior to beginning the longer-term test; 2) to address the potential that a longer timeframe will be required before the design parameters are established; and 3) to accommodate potential mechanical or logistical issues that may prolong testing.

Phase 3: Full scale design and Implementation Data collected during the injection testing will be used to design the full scale reinjection system. Upon completion of the full scale design, a final UIC permit will be prepared to facilitate full scale implementation. Detailed design for the full-scale system will be provided in the final UIC Permit Application.

ii. Do you intend for the test well to be utilized for injection In the future? The decision impacts the construction standards for the well.

Response: It is intended that the test well will be a component of the final full scale reinjection system. As discussed during the May 1, 2012 call, the well will be installed in accordance with the Delaware Regulations Governing the Construction and Use of Wells, Delaware Division of Water Resources, April 6, 1997.

/;/. Has the 'new treatment system' (page 8 of 16) been selected? If so, please provide details.

Response: The new treatment system to be utilized in the full-scale reinjection system has not been selected; rather, it will be selected and designed following the injection testing. Details regarding this system will be included in the final UIC Permit Application. Water being utilized for the reinjection testing will be post-treatment from the existing carbon treatment system being implemented at the Town supply wells (PW-1 and PW-2).

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iv. Where is documentation (approval letter) from the DNREC Site Investigation & Restoration Section (SIRS) or EPA, regarding the remediation project (page 9 of 16), providing wntten approval of the remediation method?

Response: A work plan summarizing activities to be performed to support the pilot testing and design of a reinjection system was submitted to DNREC SIRB and EPA on May 8, 2012 for review. The information provided in the work plan is consistent with information provided in the UIC Class V Well Application dated April 5, 2012. The work plan provides details of the installation of the reinjection test well network and performance of the reinjection test, which are the first two phases of work related to the reinjection system. It is our understanding that DNREC SIRB and EPA are expediting review of the work plan and will provide approvals of the remediation method to you shortly.

V. The Drilling Contractor information must be included in the UIC application (page 10 of 16).

Response: A drilling contractor has not been selected for the project. The drilling contractor will be selected based on cost and availability. However, ARCADIS has obtained quotes from the two contractors listed below. If a drilling contractor other than one from the below list is selected ARCADIS will ensure the contractor is licensed in the State of Delaware and will provide the contractor information to DNREC prior to initiating drilling activities at the site.

• A.C. Shultes PO BOX 188 Bridgeville, DE 19933 State of Delaware Contractor Water Well License #14

• Uni-Tech Drilling Co., Inc. 61 Grays Ferry Road P.O. Box 407 . Franklinville, NJ 08322 State of Delaware Contractor Water Well License #928

vi. The proposed operational data contains a maximum injection rate of 300 gpm (based on the current system); will the current remediation system be able to process additional flows from a new injection well?

Response: The current remediation system is proposed to be used for reinjection testing only. The full-scale system will employ one or more extraction well(s) located within the TCE plume, and the treatment system will be designed to accept flow rates up to an estimated 300 gpm.

vii. The Injection Related Equipment diagrams did not provide any Indication of pumps, meters, piping/tubing (from start to finish).

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Response: The groundwater to be reinjected into the Columbia Aquifer during the pilot testing will consist solely of groundwater extracted from the Columbia Aquifer. The extracted groundwater will be treated to remove TCE (and any other VOC potentially present) prior to re­injection. As discussed, no modifications will be made to the current treatment system in place to treat water from PW-1 and PW-2. The water from these wells will simply be diverted to the reinjection test well post-treatment. Specifications and diagrams depicting the equipment to be used during reinjection testing, for those components of the system between the effluent of the treatment system for Town supply wells PW-1 and PW-2 and the test injection well to be installed on the Q by the C Properties, LLC, are provided as Attachment 2.

viii. The Contingency Plan (page 14 of 16) should address what actions/steps will be taken in the case of failure of the injection well, along with back-up plans. The GWDS understands that the injection well will need to be taken off-line for routine maintenance and expects to see plans to address both routine and emergency maintenance.

Response: In case of failure during reinjection testing, the testing will be suspended (i.e., water will no longer be diverted from PW-1 or PW-2), and will only be restarted upon troubleshooting and repair of the cause for failure. Detailed plans for both routine and emergency maintenance will be provided for the full-scale system in the final UIC Permit Application.

ix. Please be aware of UIC Mechanical Integrity Testing requirements (UIC Regulations §146.08).

Response: Mechanical integrity testing of the injection well will be implemented in accordance with the above referenced regulation.

PGIA Comment Responses - Conclusions/Recommendations:

• Testing shall last a minimum of 60 days at the proposed rate of 300 gpm

Response: Scott Strohmeler (DNREC GBP) indicated during the May 24 telephone conversation that this comment was intended to reiterate what was provided in the UIC permit application; however, the proposal from the UIC permit application was misinterpreted. ARCADIS clarified that the 300 gpm referenced in the UIC permit application is the estimated pumping rate necessary to control plume migration, not the single-well reiniection rate for the test. Further, the 60-day testing period referenced by DNREC was a misinterpretation. The May/June 2012 timeframe was provided in the UIC permit application as a referenced timeframe for conducting the testing, not to imply that the entire 60-dav period would be used for testing. As discussed above on page 4, it is anticipated that the design parameters will be established within an estimated 72-hours of initiating the test, and the permit for reinjection is being requested for a 30-day active injection period.

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• Monitoring shall include the three (3) monitor wells indicated on Figure 3 of the PGIA at the proposed depth of 40 feet (Columbia): along with three (3) additional deep monitor wells (Bethany Formation sand) to accompany each of the 40-foot wells proposed; and PW-3 (Manokin). The deep monitor wells shall each be approximately 135 feet in depth with a 10-foot screen.

Response: DNREC and ARCADIS agreed that a single monitoring well screened within the Bethany is adequate to evaluate of impacts to hydraulic head in this unit. As agreed, the well to be installed in the Bethany will be installed proximal to either proposed observation well OW-2 or OW-3.

• Monitoring of the deep monitor wells must also be continuously monitored as proposed for the shallow monitor wells;

Response: The additional well to be installed in the Bethany as discussed in the above response will be continuously monitored.

• Contingency plan calls for shutdown in a "high-high" level, but is not defined. The GPB assumes this level is deeper than 2 feet below ground surface; however, if it is not the GPB would suggest including test shutdown to occur if the monitor wells indicate groundwater mounding grossly exceeds the anticipated levels and comes within two (2) feet of the land surface;

Response: ARCADIS is in agreement with this recommendation.

• Calibration of the groundwater model shall be performed using the injection well test data;

Response: ARCADIS is in agreement with this conclusion/recommendation and plans to conduct recalibration of the groundwater model using the reinjection well test data.

• Submit a report of all findings to the GDS prior to permitting the permanent system.

Response: A final UIC permit application to DNREC is required to enable permitting of the full-scale reinjection system. The reinjection system design will be based upon the findings of the reinjection test, and these findings will be included in the UIC permit application.

Attachments:

Attachment 1: Revised reinjection test well network construction logs Attachment 2: Reinjection test engineering design specifications

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Well Purpose Reinjection Well

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