May 21,2014

Richard Gates

UNITED STATES ENVIRONMENTAL PROTECTION AGENCY NEW ENGLAND REGION

FIVE POST OFFICE SQUARE, SUITE 100, BOSTON, MA 02109

Remediation Project Manager General Electric Company 159 Plastics A venue Pittsfield, MA 01201

Sent via electronic and U.S. First Class Mail

Re: Conditional Approval ofGE's April2014 Revised Final Removal Design/Removal Action Work Plan for Unkamet Brook Area-Remainder, GE-Pittsfield/Housatonic River Site

Dear Mr. Gates:

EPA has completed its review ofGE's Revised Final Removal Design/Removal Action Work Plan for Unkamet Brook Area-Remainder, dated April 2014 (the "Revised Work Plan"). This Revised Work Plan is subject to the terms and conditions specified in the Consent Decree that was entered in U.S. District Court on October 27, 2000. Pursuant to Paragraph 73 of the Consent Decree governing the response action, EPA, after consultation with the Massachusetts Department of Environmental Protection (MassDEP), approves this Revised Work Plan subject to the following Conditions.

1. p. 15, pt full paragraph, 2nd sentence and footnote 7: GE, EPA and MassDEP are continuing to discuss the form of institutional control for the Berkshire Community College (BCC) property (Parcel L 12-2-1 ). In the event that it is determined that neither an ERE nor a Notice ERE can be executed for this property, GE shall advise EPA and MassDEP, and the parties will discuss how to proceed.

2. p.46, 2nd bullet: GE shall clarify in the forthcoming Supplemental Information Package (SIP) for the project that "constructability considerations" will not be used to determine the lowest existing elevation within a brook section, but may be used by the Remediation Contractor to determine the specific relevant section of the brook to be remediated at one time. The lowest existing elevation within that section of the brook channel (which will be the basis for determining the depth of excavation in that section) shall be determined in the field based on survey methods.

3. p.4 7, 1st full paragraph, last sentence: consistent with footnote # 16 in the April 2013 Work Plan, GE shall attempt to remove all sediment in the eastern pipe of Culvert# 1 prior to slip­lining, not just conduct "any necessary sediment removal."

4. p.47, 3rd full paragraph, 3rd sentence: the phrase "similar to those in Culverts # 1 and #2" is incorrect (Culverts # 1 and #2 are 4' diameter CMP, not 3' by 3' box culverts). GE shall clarify in the SIP.

5. p.48, 1st paragraph, 2"d to last sentence: 1n accordance with Condition #1 of the 12/16/09 CAL, GE shall remove all sediment, not just the top foot of sediment, from Cui verts # 1, #2, and #4. For Culvert #3, GE shall conduct an evaluation to assess whether all sediment in that culvert can be removed using available technologies and without compromising the safety of the workers engaged in the cleaning. As part of those efforts, GE shall research potential culvert cleaning technologies to determine if removal of all sediment in Culvert #3 is technical ly practicable given its length, construction, and safety considerations. In addition, if removal of all sediment from Culvert #3 is determined to be technically impracticable or unsafe, GE shall further evaluate the extent to which sediment can be removed from that culvert, as well as the practicability and safety of placing a cover of non-erodible material over the remaining sediment. GE shall provide the results of these evaluations to EPA in the SIP, along with a specific proposal regarding the cleaning of Culvert #3, and shall discuss the proposed procedures with EPA.

In addition, to the extent that the culvert cleaning procedures will result in different post­construction conditions from those assumed in the existing Unkamet Brook flow modeling, the modeling shall be revised using the new post-construction conditions to estimate the impacts on local flows and flooding. GE shall provide the results of that revised modeling to EPA and shall discuss those results with EPA prior to the implementation of the remediation activities.

6. p.49, 1n Parking Lot Portion: GE has proposed to continue to use half of the existing parking lot that is within the former interior landfill (in two phases) during project implementation. GE shall provide in the SIP a discussion of how this proposal will be implemented safely. ·

7. p.63, P1 full paragraph, item "(3)": for areas east of the new brook channel, to maximize flood storage capacity, rather than the proposed placement of one foot of topsoil in permanently inundated areas GE shall place topsoil in these areas to match approximate original grade (but not to exceed one foot of topsoil placement). GE shall clarify in the SIP.

8. pp.l23-126: approval of this Work Plan, including but not limited to Section 8.5, shall not preclude EPA from modifying or adding to the Post-Removal Site Control Activities or the NRR/E monitoring and maintenance activities described in the Work plan when EPA approves the fmal plan for such activities.

9. Figure 3-1: the storm water outfall numbering here is inconsistent with Figure 7-1 and the technical drawings. GE shall clarify in the SIP.

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10. Tech. Drawing #3: the small soil removal area from Unkamet Brook-West which abuts excavation cell #8 should be shown on the drawing. GE shall clarify in the SIP.

11 . Tech. Drawing #3: excavation cell "31" appears to be unnecessary. GE shall clarify in the SIP.

12. Tech. Drawing #4, Note 4: due to the potential for flooding upstream of the Dalton Avenue culvert, GE shall NOT allow use of a temporary water barrier at this location. Rather, GE shall require either a) use of a bypass pumping system set up just upstream of Dalton Avenue (with piping routed through one of the culverts) or b) excavation "in the wet" just downstream of Dalton Avenue limited to that amount required to set up a bypass system just downstream of Dalton A venue.

13. Tech. Drawing # 12: the label "PHASE 2 DRAINAGE COLLECTION PIPE" is unclear, and no similar label appears on Tech. Drawing # 13. GE shall clarify in the SIP.

14. Tech. Drawing # 14: GE is showing a different location for the existing sewer line, but the arrow for the "EXISTING SANITARY SEWER ALIGNMENT" label was not shifted accordingly. GE shall correct in the SIP.

15. Tech. Drawing #15: it appears that the station designations (i.e., 0+50) were inadvertently shifted to the left compared to the previous sewer profile. As a result the tabulated manhole stations on Tech. Drawing #32, Detail 4 do not match those shown here. GE shall submit a revised Tech. Drawing # 15 in the SIP (i.e., the correction is to return to the previous station designations on the sewer profile rather than changing Tech. Drawing #32).

Also, this revised Tech. Drawing #15 shall correct the typo/editing note in Detail 1: "DELETE ANCHOR TRENCH AND" appears to be part of a reviewer's note that should be deleted.

16. Tech. Drawing #24: at parcel L12-1-101, the field-verified existing surface at the excavation area along the southwestern side of the building is a combination of either asphalt or concrete pavement, thus the partial vegetative restoration currently called for needs to be removed and replaced with asphalt pavement restoration. GE shall clarify in the SIP.

17. Tech. Drawing #26: the excavation cell ID's here duplicate those on the north side of Merrill Road. GE shall clarify in the SIP whether it will either renumber these cells or track them as being either north or south of Merrill Road.

Also, in Note 9, the phrase" ... OF THE AREMA MANUAL FOR RAILWAY ENGINEERED AND WILL BE ... " does not make sense as written. GE shall clarify in the SIP.

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18. Tech. Drawing #32, Detail 2: per Detail4, Tech. Drawing #33, the continuous concrete footer is 4" thicker for a total of 12" thick where the helical piles are located. However, this Detail 2 on qrawing #32 shows no such increase in thickness at pile locations.

A thin soil cushion layer or cushion geotextile shall be placed underneath manhole #3 so that it does not sit directly on the cap system.

Also, the label for detail "5/29" for manhole pipe penetration needs to be changed to "5/32", and the pointer for the rectangular 8" deep continuous footer under the manhole points to the bottom of the manhole itself~ rather than the footer.

GE shall clarify and correct in the SIP.

19. Tech. Drawing #32, Detail 3: this manhole foundation detail is unclear as it does not indicate the total length and width of the foundation, and it appears that errant solid lines have been included beyond where the continuous footer (shown in dashed lines) flares down to the 5' width (as inferred from Drawing #33). GE shall clarify in the SIP.

20. Tech. Drawing #32, Detail4: see Condition 15 above (i.e., edit Tech. Drawing #15 so that it matches the station designations in this detail).

21. Tech. Drawing #33, Detail2: Rather than having the cap system sit directly on top of the continuous concrete foundation, GE shall require either that a thin soil cushion layer be placed between the cap system and this foundation or that a cushion geotextile be used instead of the lower non-woven geotextile above this foundation. GE shall clarify in the SIP.

22. Tech. Drawing #33, Detail 2, Note 3: soil/material resulting from the required excavation for the ~ontinuous footer within the former interior landfill shall be disposed off-site. Similarly, soil/material resulting from the required excavation for manhole #5 and for the relocated sewer north and south of the former landfill shall be disposed off-site.

Also, the 2' HDPE liner overlap shall be fusion welded.

GE shall clarify in the SIP.

23. Tech. Drawing #34, Detail 9: since the north outlet drainage channel now has the larger Type III riprap, GE shall clarify in the SIP ifthe specified 15" thickness (unchanged from the 2013 work plan) is sufficient.

24. Tech. Drawing #36, Detail 6: GE shall revise to require that a thin soil cushion layer or cushion geotextile be placed underneath the concrete fence footer so that it doesn't sit directly on the cap system. GE shall provide the minimum thickness of this soil cushion layer and/or the . manufacturer's specifications for the cushion geotextile in the SIP for EPA review and approval.

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25. Tech. Drawing #38, first detail: GE shall clarify in the SIP that the indicated sewer line is the existing, not the relocated, sewer line.

26. Tech. Drawing #39, Detail 1: see Condition 24 above (a thin soil cushion layer or cushion geotextile shall be placed between the cap system and the concrete fence footer).

27. Given the comments above regarding various Technical Drawings, GE shall issue a complete set of revis·ed drawings to ensure that all project personnel, including potential contractors bidding on the work, are working from the same plans. For all revised drawings, per Condition 117 of the February 2014 CAL, GE shall ensure that the line type used for the limits of the former interior landfill matches that on the drawings' legends. GE shall provide this full set of revised drawings to EPA as an attachment to the SIP.

28. Appendix E, Section 02200, 3.03, J: as noted in Condition 165 ofthe February 2014 CAL, the requirement that the first lift of backfill over geosynthetics be at least 12 inches will not apply in many cases in this project. GE shall clarify in the SIP.

29. The SIP shall address the steps that GE will take to comply with Paragraphs 55 and 123.b of the Decree, which relate to the approval, execution, and recording of a Conservation Easement and Restriction on ten acres of wetlands located in the GE Plant Area to the east of the Unkamet Brook landfill.

GE shall address each of the above Conditions in writing in the forthcoming project SIP, which shall be submitted within 120 days from the date of this letter.

EPA reserves all of its review and compliance rights under the Consent Decree regarding all submittals, including but not limited to, the right to perform and/or require additional sampling or response actions, if necessary, to meet the requirements of the Consent Decree. If there is any conflict between the Performance Standards as stated in the Revised Work Plan and the Performance Standards as stated in the Consent Decree and SOW, the Consent Decree and SOW shall control.

Please do not hesitate to contact me at 617 918 1329 or at dickerson.dave@epa.gov should you have any questions in this regard.

Sincerely,

David Dickerson Unkamet Brook Proj-ect Manager

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cc: Dean Tagliaferro, EPA John Kilborn, EPA Tim Conway, EPA Chris Ferry, ASRC John Ziegler, MassDEP Michael Backunas, MassDEP Robert Leitch, USACE Linda Palmieri, Weston Solutions Michael Gorski, MassDEP Eva Tor, MassDEP Karen Pelto, MassDEP Nancy Harper, MA AG Mayor Daniel Bianchi, City of Pittsfield James McGrath, City of Pittsfield Corydon Thurston, PEDA Barbara Landau, Noble & Wickersham James Gagnon, O 'Reilly, Talbot & Okun Rod McLaren, GE Andrew Silfer, GE James Bieke, Sidley Austin Mark Gravelding, ARCADIS Public Repositories

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