UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

NEW ENGLAND REGION

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

Via electronic

July 16, 2020

Kevin Mooney Senior Project Manager General Electric Company 1 Plastics A venue Pittsfield, MA O1201

Re: Engineering Phase I Inspection/Evaluation Report for Rising Pond Dam Rest of River (GECD850) GE-Pittsfield/Housatonic River Site

Dear Mr. Mooney:

On February 3, 2020, the General Electric Company (GE) submitted a report entitled Engineering Phase I Inspection/Evaluation Report for Rising Pond Dam (the "Report"). In August 2019, the Environmental Protection Agency (EPA) issued a conditional approval letter for Revised Operations, Monitoring, and Maintenance Plan, Rising Pond Dam - MA 00250 (the OM&M Plan), and directed GE to conduct a biennial inspection in 2019, and every two years after. The Report presents the findings of the 2019 Biennial Engineering Phase I Inspection/Evaluation of the Rising Pond Dam.

Pursuant to Section XV of the Consent Decree, after providing reasonable opportunity for review and comment by the State and Connecticut, EPA conditionally approves the Report subject to the following conditions:

General Comments:

1. Cover Page: The owner should be listed as GE and not GZA GeoEnvironmental, Inc.

2. Dam Evaluation Summary Sheet, Item 3: The dam is incorrectly listed as located in Lee/Lenox, Massachusetts. GE shall update the Report with the correct location of Great Barrington, Massachusetts.

3. Dam Evaluation Summary Sheet, Item 6: The OM&M Plan states that Engineering Phase I Inspection/Evaluations will be completed on a biennial basis. The Dam Evaluation Summary Sheet indicates the next inspection is scheduled for November 5, 2024. GE shall update the Report to indicate that the next inspection is scheduled for November 5, 2021.

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4. The Report identifies 13 deficiencies from the 2019 Biennial Engineering Phase I Inspection/ Evaluation. In accordance with Section 4.2.4 of the OM&M Plan, GE was required to address these deficiencies within 60 days of the observance or, for repairs that require a longer time, on a schedule to be submitted to EPA. GE shall update the Report to provide the status ofresponses to these deficiencies . For any deficiencies that have not been resolved and that require corrective action, GE shall complete the corrective actions for these deficiencies no later than 60 days after receipt of this conditional approval letter ( the "CAL"), provided that if GE requires more than 60 days to complete such corrective action, GE shall provide a corrective action schedule to EPA, and provided further that GE may provide a schedule to address the sluice gate deficiency in its report/proposal described in Condition #5.

5. In accordance with section 4.1 of the OM&M Plan, the gate system is required to be inspected biennially by a mechanical/electrical specialist to assess the condition of the gate system and identify any required maintenance. The OM&M plan indicates this will occur concurrently with the Biennial Engineering Phase I Inspection/Evaluation. GE has advised EPA that the gate system was not inspected during the 2019 Biennial Engineering Phase I Inspection/Evaluation but was subsequently inspected by a mechanical/electrical specialist on June 16, 2020. GE shall provide a summary of the findings of that inspection by August 14, 2020, along with a proposal for further investigation, as warranted, in order to develop plans to remedy the deficiency in the sluice gate.

Section 1.0 Description of Project:

6. Section 1.2.2: The Owner and Caretaker information is incorrectly referenced as Section 1 .4. There is no section 1.4 in the report. GE shall revise the report to correct the reference to Section 1.2.6.

7. Section 1.2.3: Although the EPA agrees that a current purpose of the Rising Pond Dam is to impound sediments, the use of the words "may be" in the last sentence of the section downplays the impacts of polychlorinated biphenyls in the sediment. GE shall revise this statement to read "presumably impacted by PCBs".

8. Section 1.2.4 and Figure 5 & 6: The Report describes a 12-inch diameter well drain which provides gate chamber drainage of the pens tock through the left downstream training wall. It is EPA's understanding that this well drain has not been opened in years and is no longer needed because the diversion channel now provides gravity drainage for the penstock. GE shall revise the Report to reflect that the well drain is no longer needed, and that operation of the well valve is not recommended due to its unknown integrity.

9. Section 1.3 .2: Data about pool heights is incorrectly referenced in the section as 1.4. GE shall revise the report to correct the reference in this section to 1.3.4.

10. Section 1.3.8 and Appendix F: This section is lacking detail pertaining to the methods used in the piezometer monitoring, the data collected, and interpretation of the monitoring results. The Figure in Appendix F provides no additional clarity since there is no interpretation or discussion in the Report. In addition, the note on the Figure in Appendix F refers to action

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levels for D-2, P-6 and P-7, however, these piezometers do not correspond to the piezometers in the legend. GE shall update Appendix F to include documentation regarding piezometer monitoring, including: the piezometer monitoring methods; tabular representation of the monitoring results; an updated Figure; a discussion of observed historical levels and their importance; and an interpretation of the monitoring results in relation to the historical levels or action levels, as applicable.

Section 2.0 Inspection:

11. Section 2.1.2: Figures currently do not illustrate the locations of the monitoring wells and piezometers. GE shall update the report and provide a figure with the locations of all monitoring wells and piezometers illustrated.

12. Section 2.1.3, Primary Spillway: While the sluice gate was opened during the 2019 Biennial Engineering Phase I inspection/Evaluation, due to the short length of time the sluice gate was open, the water level in the pond did not reach a level which would allow for the spillway to fully dry. This prevented the inspectors from safely traversing and observing the spillway. The OM&M Plan requires: (i) operation of the sluice gate annually during the summer quarterly inspection at a time of low flow; (ii) inspection of the gate system (including operation) during Biennial Engineering Phase I Inspections by a mechanical/electrical specialist; (iii) clearing of the weep holes within the spillway during Biennial Engineering Phase I Inspections conducted during low-flow conditions; and (iv) inspection of the spillway's condition during Biennial Engineering Phase I Inspections. In order to reconcile all inspection requirements, GE has advised EPA that it would like to conduct spillway inspections and weep hole clearing under low-flow conditions during alternate future Engineering Phase I Inspection/Evaluations. To do so, GE shall submit an OM&M Plan Amendment Letter proposing a new Biennial Engineering Phase 1 Inspection/Evaluation schedule to reflect the proposed alternating low-flow inspection frequency for the spillway (beginning in 2021). That OM&M Amendment Letter shall be submitted to EPA within 60 days ofreceipt of this CAL and propose new schedules consistent with the following:

a. In years when a Biennial Engineering Phase I Inspection/Evaluation is to be scheduled, GE may elect to combine the Phase I inspection with an appropriate quarterly inspection (with normal-flow or low-flow conditions), and the annual operation of the sluice gate and inspection by the mechanical/electrical specialist will occur during the Phase I Inspection regardless of flow (normal- or low-flow).

b. In years without a Biennial Engineering Phase I Inspection/Evaluation, the sluice gate will be exercised during the summer quarterly low-flow inspection.

c. Weep hole clearing and spillway apron inspections will be performed during Biennial Engineering Phase I Inspections/Evaluations scheduled during low-flow conditions ( every four years) so that the spillway can be dewatered via the sluice gate operation, or more frequently if deemed necessary by a dam safety engineer.

d. Prior to the Biennial Engineering Phase I Inspections/Evaluations scheduled during low-flow conditions (every four years), GE shall provide a proposal for lowering the water level in the impoundment and dewatering the spillway, in accordance

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with Section 2.4 of the approved OM&M Plan. That plan shall include opening the sluice gate prior to the inspection/evaluation to provide sufficient time for the pond to drain and the spillway to dry adequately. These preemptive efforts should control the pond's flow through the penstock and allow drying of the spillway for observation and maintenance (e.g., cleaning out the weep holes).

13 . Section 2.1.3, Low-Level Outlet: The OM&M Plan requires that the penstock be inspected every four years, and EPA's August 29, 2019 CAL required that GE conduct an inspection of the penstock in 2019 and every four years thereafter. However, a penstock inspection was not completed during the 2019 Phase I Biennial Dam Inspection/ Evaluation because of high water levels due to the sluice gate either not seating properly or mechanical deficiency.

GE shall:

a. inspect the penstock in conjunction with its further investigation of the sluice gate, as discussed in Condition #5 above, and on a schedule to be proposed in its August 14, 2020 report required by that condition;

b. submit a pens tock summary report to EPA within 60 days upon completion of the penstock inspection; and

c. conduct future penstock inspections (beginning in 2023) in accordance with the OM&M Plan and in conjunction with alternating Biennial Engineering Phase I Inspection/Evaluations.

14. Section 2.3: GE shall include in future Engineering Phase I Inspection/Evaluation reports a chronological listing (identifying date and type of inspection) completed at the Rising Pond Dam for all inspections over the two-year period between Engineering Phase I Inspection/Evaluation reports in accordance with section 3.0 of the OM&M plan.

15 . Section 2.3.2: The Report indicates that GE will perform maintenance activities pending any findings from their routine inspections. GE shall provide a summary of scheduled and completed maintenance activities in future quarterly inspection reports .

16. Section 2.3.2: The OM&M Plan requires that sediment be removed from the Rising Pond Dam when observations indicate build-up of excess sediment within conveyances that may interfere with water flow. The Report mentions removal of sediment as a potential maintenance item but does not discuss whether sediment is accumulating at the Rising Pond Dam. GE shall update the report to clarify if sediment build-up was observed, any observations of conveyance of sediment, or if there is observed sediment interference with the flow of water. GE shall clarify in the revised report how sediment build-up is assessed and whether corrective action is required.

17. Section 2.5: EPA disagrees that all embankments will not be overtopped by a 500-year storm. GE shall update the fourth sentence of the first paragraph of this section to indicate that the right embankment would not be overtopped by the 500-year storm; however, the concrete forebay section and left embankment would be overtopped. GE has submitted a

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report entitled Design for Raising Portions ofthe Rising Pond Dam Above the 500-Year Flood Elevation ( the "Design") on January 31 , 2020, and a conditional approval letter for the Design was issued by EPA on July 10, 2020.

Section 3.0 Assessment and Recommendations:

18. Section 3 .1, embedded table: The table identifies that no change in condition has occurred for the following items since the 2016 Engineering Phase I Inspection/ Evaluation:

a. Rust on the forebay trashrack

b. Crack in the forebay concrete below upstream end of the abandoned operator

c. The poorly seated sluice gate

d. The eroded area (off dam) at downstream end of the left masonry training wall

In accordance with Section 4.2.4 of the OM&M Plan, GE was required to address these deficiencies within 60 days of the observance or, for repairs that require a longer time, on a schedule to be submitted to EPA. GE shall update the Report to provide the status ofresponses to these deficiencies. For any deficiencies that have not been resolved and that require corrective action, GE shall complete the corrective actions for these deficiencies no later than 60 days after receipt of this CAL, provided that if corrective actions will require a longer period, GE shall provide a schedule as to when these corrective actions will be completed, and provided further that GE will provide a schedule to address items a and c above in its proposal for a further investigation of the sluice gate system, as discussed in Condition #5 . When operating the sluice gate, GE shall make best efforts to attempt to physically clear any entrapped debris, including having methods and equipment in place, so that the debris does not prevent closure of the sluice gate.

19. Section 3 .2 .1: The Report does not provide a schedule for the listed monitoring and investigation items. GE shall revise the report to include a schedule of maintenance and/or corrective action for each of the items described in this section.

Figures :

20. GE shall include a Figure illustrating the grout bag monitoring plan at the right downstream training wall in future Biennial Engineering Phase I Inspection/Evaluation reports .

GE shall submit a revised report within 30 days of the date of this letter.

EPA's conditional approval of this Plan does not supersede or affect GE's other legal obligations and requirements, including but not limited to such requirements set forth by the Massachusetts Office of Dam Safety.

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EPA reserves all of its review and compliance rights under the Consent Decree and the RCRA Permit 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 letter and the Performance Standards as stated in the Consent Decree or the RCRA Permit, the Consent Decree or RCRA Permit shall control.

Please do not hesitate to contact me at (617) 918-1720 or at fontaine.joshua@epa.gov should you have any questions in this regard.

Sincerely, Digitally signed by JOSHUA JOSHUA FONTAINE Date: 2020.07.16 FONTAINE 07:37:16 -04'00'

Josh Fontaine Project Manager

cc: Dean Tagliaferro, EPA Tim Conway, EPA Chris Ferry, ASRC Robert Leitch, USACE Emily Caruso, Mass Department of Conservation and Recreation - Office of Dam Safety John Ziegler, MassDEP Elizabeth Steinhart, MassDEP Ben Guidi, MassDEP Michael Gorski, MassD EP Cathy Kiley, MassDEP Mark Tisa, MA DFG Traci Iott, CT DEEP Susan Peterson, CT DEEP Deb Jones, Bluestone Environmental Lori DiBella, Connecticut Attorney General ' s Office Field Supervisor, U.S . Department oflnterior Mark Barash, U.S . Department oflnterior Ken Finkelstein, NOAA Molly Sperduto, USFWS Nancy Harper, MA AG Melissa Provencher, BRPC Mayor Linda Tyer, City of Pittsfield James McGrath, City of Pittsfield Christopher J Ketchen, Chief Administrative Officer, Lee and Lenox Town Administrator, Stockbridge Town Manager, Great Barrington

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Town Administrator, Sheffield Eric Merrifield, GE Andrew Silfer, GE Pamela Brown, GE Jonathan Andrews and Laurie Gibeau, GZA James Bieke, Sidley Austin Michael Coakley, PEDA MA Public Information Repository Public Information Repository at David M. Hunt Library in Falls Village, CT

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