• Transmitted Via Overnight Courier

June 19, 2009

Mr. Richard Fisher U.S. Environmental Protection Agency EPA- New England One Congress Street, Suite 1100 Boston, Massachusetts 02114-2023

Re: GE-Pittsfield/Housatonic River Site Groundwater Management Area 1 (GECD310) Proposed Modifications to Monitoring Well Network

Dear Mr. Fisher:

GE 159 Plastics Avenue Pittsfield, MA 01201 USA

On May 21, 2009, the U.S. Environmental Protection Agency (EPA) issued a letter to the General Electric Company (GE) providing conditional approval of GE's February 27, 2009 Plant Site I Groundwater Management Area NAP L Monitoring Report jar Fall 2008 (Fall 2008 NAPL Monitoring Report). That conditional approval letter provided comments on the Fall 2008 NAPL Monitoring Report. The letter required, among other things, that GE evaluate the usability of East Street Area 2-South monitoring wells 19 and 3-6C-EB-14 (per Condition 2) and Lyman Street monitoring well LS-38 (per Condition 3) for light non-aqueous phase liquid (LNAPL) and groundwater elevation monitoring purposes, and that GE provide the results of that evaluation by electronic mail to EPA within 14 days of receipt of EPA's letter. If the assessment showed that either well was not suitable for LNAPL monitoring, then GE was required to submit, within 30 days of receipt of EPA's conditional approval letter, a proposal to install replacement wells that can properly monitor for LNAPL, which proposal was to include the proposed specifications of the replacement wells and the schedule for installation.

GE performed the required evaluation, which consisted of a review of all available monitoring data from spring 2000 through fall 2008 and a comparison of the monitoring results with the screen setting elevations in each of the wells. That evaluation, which was provided to EPA by e-mail on June 4, 2009, indicated that the wells were not screened to monitor for LNAPL during all occasions. Therefore, in accordance with the requirements contained in EPA's May 21,2009 conditional approval letter, this letter contains a proposal to decommission and replace monitoring wells 19 and 3-6C-EB-14 and to install a shallow well to pair with monitoring well LS-38.

In the June 4, 2009 e-mail, GEstated that this proposal would also discuss other monitoring wells within East Street Area 2-South that may be affected by the upcoming soil-related Response Actions in that area and provide GE's proposed approach to protect, remove, and/or replace those wells. However, since the scope of those Response Actions has yet to be finalized, it would be premature to address the monitoring wells in this area. Therefore, as discussed below, GE will submit an additional proposal to address monitoring wells at East Street Area 2-South once the potential impact of the soil-related activities can be more definitively assessed.

Proposed Replacement of Monitoring Wells Within East Street Area 2-South

Mr. Richard Fisher June 19,2009

Page 2 of 4

As illustrated on attached Figure I, monitoring wells 3-6C-EB-14 and 19 are located in the East Street Area 2-South Removal Action Area and arc proposed to be removed and replaced. We113-6C-EB-14 was included in GE's baseline groundwater quality monitoring program, but additional sampling of this well has been deferred until implementation of a long-term groundwater quality monitoring program at GMA I. It is currently monitored for groundwater elevations and the presence ofNAPL on a semi-annual basis. Well 19 is monitored for groundwater elevations and the presence ofNAPL on a weekly basis.

Based on the results of the evaluation of these two wells provided to EPA on June 4, 2009, and in accordance with the requirements contained in EPA's May 21, 2009 conditional approval letter, GE proposes to decommission these wells and install replacement monitoring wells (to be designated as wells 3-6C-EB-14R and 19R) screened to intercept the water table and allow for LNAPL monitoring under high groundwater conditions. Specifically, the screened sections of each replacement well will be placed at depths between 6 and 16 feet below grade, which is approximately centered around the average groundwater elevations of wells 3-6C-EB-14 (11.5 feet below grade) and 19 (10.9 feet below grade). To ensure that the wells will be appropriately screened to monitor for the presence of LNAPL during all occasions, the tops of the proposed replacement well screens will be at elevations above the historical high groundwater elevations recorded at these wells (i.e., approximately 9 feet below grade at well 3-6C­EB-14 and 8.5 feet below grade at well 19).

Proposed Addition to Existing Well Network Within Lyman Street Area

Well LS-38 is located near the western end of the sheetpile containment barrier at the Lyman Street Area Removal Action Area, as illustrated on Figure 2. This well is monitored for groundwater elevations and the presence ofNAPL on a monthly basis.

Based on the results of the evaluation of Lyman Street Area well LS-3 8 provided to EPA June 4, 2009, and in accordance with the requirements contained in EPA's May 21, 2009 conditional approval letter, GE proposes to install a shallow monitoring well adjacent to existing well LS-38 (which will continue to be utilized for DNAPL monitoring purposes). The new monitoring well (to be designated as well LS-3 8S) will be screened to intercept the water table and allow for LNAPL monitoring at the western edge of the sheetpile containment barrier in this area. Specifically, GE proposes to install the screened section of the well at a depth between 6- and 16-feet below grade, which is approximately centered around the average groundwater elevation of well LS-38 (12.6 feet below grade) and above the historical high groundwater elevation recorded at this well (i.e., approximately 8.5 feet below grade).

Although groundwater is typically observed between 11 and 13 feet below grade in this area, the base elevation of the proposed LS-38S well screen is approximately equal to the lowest groundwater elevations observed in well LS-38, indicating that the well may be dry on ce1tain occasions. In that event, well LS-38 will be utilized for LNAPL monitoring in this area, since the screen zone in that well will overlap the lower pmtion of proposed well LS-38S.

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Schedule

Mr. Richard Fisher June 19, 2009

Page 3 of 4

Following EPA approval of this proposal, GE will initiate plans to install well LS-38S at the Lyman Street Area in accordance with the procedures described in Appendix S of GE's FSP/QAPP, with the intention of installing and developing the well in advance of the fall 2009 semi-annual monitoring event. Following installation and development, well LS-38S will immediately be added to GE's NAPL monitoring program utilizing the same monitoring protocols as well LS-38 (i.e., monitored on a monthly basis with any recoverable quantities of LNAPL manually removed).

Since wells 3-6C-EB-14 and 19 are located within the paved p01tion of East Street Area 2-South where a liner will be installed beneath the vegetative engineered barrier, these wells and any replacements would likely be destroyed during removal of the pavement and construction of the barrier. Therefore, GE proposes to continue to utilize the existing wells until construction activities in this area are scheduled (since the high groundwater elevation season has passed for this year, each well should be usable for LNAPL monitoring purposes during most occasions). At that time, GE will decommission the monitoring wells in accordance with the general procedures described in Appendix GG of GE's FSP/QAPP for the GE-Pittsfield/Housatonic River Site. During construction of the vegetative engineered barrier, openings will be constructed in the liner and sealed to a circular form (e.g., Sonotube) that will be left open following liner installation to facilitate installation of the replacement wells following completion of the response action activities without penetrating the newly-installed liner.

On April 21, 2009, GE submitted the Second Addendum to Conceptual Removal Design/Removal Action Work Plan for East Street Area 2-South (Second Addendum), which provided responses to the comments included in EPA's April II, 2008 letter and presented supplemental information supporting those responses. The Conceptual Work Plan and Addenda describe the need for and proposed scope of soil­related response actions for East Street Area 2-South. Groundwater at East Street Area 2-South is included within the Plant Site I Groundwater Management Area (GMA I). In general, the response actions for soil at East Street Area 2-South are anticipated to include soil removal/replacement, pavement enhancement, installation of a vegetative engineered barrier, and restoration activities. Following EPA approval of the Second Addendum (and assuming that no additional addenda to the Conceptual Work Plan are required), GE will submit a letter to EPA summarizing proposed modifications to the monitoring well network and the ongoing groundwater quality and non-aqueous phase liquid (NAPL) monitoring programs at East Street Area 2-South, particularly in regard to monitoring wells that are no longer utilized or needed by GE and/or are located within or adjacent to areas subject to soil-related response actions where modifications will be necessary to accommodate the implementation of the soil response actions.

Please call me if you have any questions regarding this proposal.

Richard W. Gates Remediation Project Manager

Attachments

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GENERAL ELECTRIC COMPANY PITISFIELD, MASSACHUSETIS

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ARCADIS 2 FIGURE

cc: D. Tagliaferro, EPA T. Conway, EPA* 1-l. Inglis, EPA R. Howell, EPA* K.C. Mitkevicius, USACE L. Palmieri, Weston (2 copies) E. Tor, MDEP* J. Rothchild, MDEP* M. Gorski, MDEP J. Ziegler, MDEP* S. Steenstrup, MDEP (2 copies) J. Ruberto, Mayor, City of Pittsfield Pittsfield Commissioner of Public Health William Hines, Director, PEDA B. Landau, Noble & Wickersham T. Bowers, Gradient N. E. Harper, MA AG D. Young, MA EOEA M. Carroll, GE* R. McLaren, GE* J. Nuss, ARCADJS J. Bieke, Goodwin Procter J. Ciampa, SPECTRA J. P01ter, Mintz, Levin R. Nasman, Berkshire Gas M. Booher, Dewey & LeBoeuf* !. Murarka, Ish, Inc. K. Hylton, KHES, LLC* D. Mauro, META* Public Information Repositories GE Internal Repositories

*cover letter only

Mr. Richard Fisher June 19, 2009

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