UNITED STATES ENVIRONMENTAL PROTECTION AGENCY New England Office - Region I One Congress Street, Suite 1100 Boston, Massachusetts 02114-2023

August 11, 2009

Mr. Andrew T. Silfer, P.E. General Electric Company 159 Plastics Avenue Pittsfield, Massachusetts 01201 Sent via US Mail and Electronic Mail

RE: Conditional Approval of GE's Revised Conceptual Removal Design/Removal Action Work Plan for Silver Lake

Dear Mr. Silfer:

EPA has completed its reVIew of GE's report entitled "Conceptual Removal Design/Removal Action Work Plan for Silver Lake Sediments" revised and submitted on April 15, 2009 and Attachment I, "Evaluation ofPotential Cap Materials and Controls for the Silver Lake Removal Action Area" received June 1, 2009 (collectively, the Wark Plan).

With respect to any other work plans or submittals related to Silver Lake or Silver Lake Soils, nothing in this conditional approval shall be interpreted to supersede the approval, the conditions in a conditional approval, or the disapproval of such GE submittals, unless expressly stated as such by EPA. EPA reserves all of its review and compliance rights under the Consent Decree regarding such GE submittals including but not limited to, the right to perform and/or require additional sampling or response actions, if necessary, to meet the requirements ofthe Consent Decree.

Pursuant to Paragraph 73 of the CD, EPA, after consultation with the Massachusetts Department of Environmental Protection (MassDEP), approves the Work Plan subject to the following conditions: 1. In summarizing the Performance Standards, GE shall include all standards in the SOW, specifically standards 8 and 9.

2. Section 3.2 - In response to GE's assertions on the ARAR status of the

compensatory mitigation regulations, EPA reserves its right to hold GE In violation of the Consent Decree if GE does not evaluate these regulations as ARARs.

3. Section 3.5.2 - GE shall revise the text to state that if the TOC content [ofthe cap material] is not meeting the required minimum standard, GE shall, in consultation and upon receiving approval from EPA, implement measures to either modify the cap application method or incorporate the addition of supplemental materials to the dry cap mix to enhance the TOC content of the remaining portion of the isolation layer.

4. Section 3.5.4.2 - GE shall state that any significant departures from the methods presented in the Work Plan or any final design documents will be discussed with and are subject to approval from EPA prior to implementation.

5. Section 3.6.3 - There is an inconsistency between the wording in this section describing the armor stone layer as being well-graded rip rap and the Specification provided in Appendix A which describes it as being poorly-graded. GE shall clarify the description ofthe armor stone layer.

6. Section 3.6.3 - The reevaluation of the armor stone layer conducted by GE continues to focus solely on conditions associated with a mean WSE of 975.9, which represents the average elevation of the lake surface over the period for which data have been collected. However, the evaluation does not include either the high water elevation or the low water evaluation. For example, during a 5-yr event the HEC-RAS model simulates a WSE of 979.45 at the outfall.

2 There are more limited data available during drought conditions, as the 5 years of data collection did not include a period ofdrought such as occurred in 2002, 1999, and 1995, however even the limited data demonstrate that the lake level can drop significantly (974.6) below the assumed design elevation of 975.9. Therefore, if wind conditions and resultant wave action occur during periods with low water levels, the armor layer may not provide adequate protection of the shoreline or of the cap due to the potential to undermine the toe ofthe armor protection layer.

EPA agrees that vertical extent of the armor layer below the water line presented in Appendix B should be 1.5 times design wave height. However, EPA believes that the more conservative Protection Manual (SPM; USACE, 1984) calculations of wave height of 1.6 for the east/south shore and 0.7 for the west/north shore are appropriate. GE shall revise the calculations and the design accordingly.

Minimum water levels shall be used by GE to establish the bottom extent of the armor layer. Direct measurements of lake levels during a significant drought are not available to EPA's knowledge, therefore an estimated minimum lake level that could be expected during drought conditions such as those observed in 1995, 1999 and 2002 shall be developed. The vertical extent of the armor layer above the water line shall continue to be based on the mean water surface elevation.

7. Section 4.4.2 - During Post-Construction monitoring, GE shall collect PCB samples from the 3 sampling intervals at all 26 sampling locations for analysis.

8. Section 4.5.2 - During the first five years following installation ofthe armor layer and completion of restoration activities, if an excessive wind event occurs in Pittsfield, GE shall, in consultation with EPA, inspect the shoreline armor and adjacent isolation materials for wave damage, irrespective of the semi-annual monitoring schedule.

3 9. Appendix A ~ GE shall consider the use of Mirafi 500X or 600X rather than 100X, as these geotextiles are more suitable for the placement of coarse angular material and heavy loads.

10. GE shall propose an approach to addressing the deficiencies noted in the Pilot Study Area (e.g. areas where TOC and cap thickness do not meet Performance Standards, detection ofsurficial PCB concentrations).

Specific conditions on Attachment I

11. Page 4 ~ 6. The availability the potential organic carbon sources is only discussed as being available from a local supplier or not. There are no references to the name or location of suppliers, local or elsewhere, to allow for evaluation of the true availability of the material. GE shall identify potential suppliers of material in the Final Work Plan.

12. Page 4 - 6. Settling properties of each potential organic carbon source were assessed based on observations of settling during Coagulation-Flocculation Jar Tests (ASTM 2035-08) in which turbidity is observed after potential cap materials are mixed with water and shaken. Because of the lack of data provided for this study, there is no evidence to support any of GE's conclusions based on differences in settling rates among the different cap materials. Settling results are not described in terms of rate (cm/s) or duration (hours, minutes, days) for all cap materials to settle. Turbidity is not quantified. Instead, settling is qualitatively described as "turbidity in the jar starting to diminish shortly after placement" or as taking "several days" to clear. In contrast to the qualitative method chosen, there are quantitative, easily performed methods for evaluating settling of particles, including SM2540 and EPA 160.5. In both methods, an Imhoff (graduated) cone, is used to quantify settleable solids after specified time points. This method can easily be modified to determine the maximum settleable solids and associated settling rates and times.

4 13. GE indicates that density and particle SIze were factors included in their comparison of cap materials. However, there is no quantitative comparison of the densities ofthe di fferent cap materials, even though the particle densities of sand, soil, granular active carbon, and clay-based composite materials (Aquablok®, 2009; Murphy et aI., 2004; 2006). Additional information about the properties and performance of cap materials has been described by Reible, 2005. GE shall provide a tabulated comparison of the densities, porosities, and particle size(s) of these materials to inform an assessment of the likely differences in settling rates and resulting turbidity upon placement.

14. GE also indicates that the distribution of TOC within cap materials following placement was one of the factors included in their comparison of cap materials. For organo-clay and GAC materials, GE presents the argument that to achieve a TOC content of 1%, sand would have to be mixed with organo-clay and GAC materials at a ratio of 9: 1 and 20: 1. In the case of clay-based composite materials, this is not valid because organic carbon is amended into and clay-based composite materials such as Aquablok® in variable amounts and as a consequence, the percent of organic carbon may not only be adjusted for each application, but also likely differs among organo-clay products from different suppliers (Aquablok, CETCO, BioSoil, Biomin, Chinese organo-clay suppliers, etc.). Also, particle size can be varied to also promote homogenous distribution.

15. GE suggests that the costs are higher for using and clay-based composite materials and GAC materials in a cap as compared to using topsoil. However, the methodology used to generate costs and the costs associated with different cap materials are not provided and thus this statement can not be validated. GE shall provide a cost estimate, including all assumptions, for all materials evaluated in the Final Work Plan.

16. Page 7, Paragraph 3. GE indicates that "During the final design process, GE will continue to review commercially available turbidity curtains, and with input from manufacturers, would identify the most appropriate fabric (e.g., fabric ,

5 apparent opening size, filtration area) and installation location and approach. In addition, GE will, in consult with material manufacturers, consider other turbidity curtain options, including placement around smaller sub-areas of the lake to isolate areas of active capping and/or use of impermeable turbidity curtains to divert or isolate storm water flow from the rest of the lake during cap placement activities." While conceptually this is acceptable, the details have not yet been provided. The most appropriate fabrics and specific types of turbidity curtains (i.e., gunderbooms) should be considered in advance of full-scale cap placement. A detailed comparison of several well-defined approaches (Francingues et aI., 2005) for controlling turbidity within the area being capped as well as the area of removal shall be reviewed and the review shall be summarized in the Final Work Plan.

17. Page 8, top. As discussed in Condition 16, turbidity control measures proposed do not include the use of specialty turbidity curtains. There are a variety of curtains that could be used to reduce turbidity including floating and hanging, solid diversion baffle, permeable or filter, standing frame, specialty boom. GE shall include a discussion of which type of curtain will be used and the rationale for selection ofthe curtain in the Final Work Plan.

18. Page 8, top. The discussion of turbidity control measures does not include alternative methods for placement of cap material. The choice of cap placement method is known to have an effect on turbidity (Bailey et aI., 2005). In the pilot study in Silver Lake, a barge-mounted spreader-box was used to broadcast a slurry of cap material to the water surface; however, there are alternative placement methods that should be considered and evaluated to reduce turbidity. Specifically, as part of the Anacostia capping demonstration project, a conventional clamshell bucket was successfully used to place a cap layer uniformly in thin (~6"+/- 2") lifts of sand, apatite soil and Aquablok® using a digital GPS for bucket location and with controlled opening of the bucket using an experienced operator (http://www.hsrc-ssw.org/ana-index.html; McDonough et al., 2007). In addition, as part of a pilot study in the lower Grasse ,

6 construction of a subaqueous cap was evaluated using various combinations of capping materials and placement techniques. Optimal results were achieved with a I: I sand/topsoil capping material applied at either just above or several feet below the water surface via a clamshell attached to a barge-mounted crane (Quandrini et aI., 2003). Other methods that may help to control turbidity during placement include the use of a submerged diffuser system with a barge or a gravity-fed downpipe or (Bailey et aI., 2005). A variation of a submerged diffuser system was used in Calumet Harbor, Illinois. This diffuser significantly reduced pipeline exit velocity, confined the discharged material to the lower portion of the water column, and reduced suspended solids in the upper portion of the water column. Similar methods were used by the ACE to lower turbidity in Brazil ftp://erdcftp.erdc.usace.army.mil/pub/el/Sehroeder/Brazil/. As part of the lower Grasse River (Massena, NY) pilot study, the clamshell bucket (both surface and subsurface) and tremie-pumping application techniques were compared; both methods resulted in sufficient cap coverage but subsurface clamshell bucket and tremie-pumping applications led to a more uniform grain size distribution in the placed material (Quandrini et aI., 2003). GE acknowledges that final design considerations related to the actual spreader assembly and conveyance of cap material will be made in consultation with the selected remedial contractor. However, GE shall evaluate and consider alternative placement methods to reduce turbidity in the final Work Plan.

19. Pages 8 to 10. GE provided four additional descriptions and initial evaluations of turbidity control measures: bypass, lowering of lake levels, pump and ex-situ treatment, and coagulationlflocculation added to cap materials. a. Stomwater bypass - this section is incomplete and GE acknowledges that additional flow data would be necessary to determine the utility of bypassing the Fourth Street outfall. However, EPA agrees that this is likely not a practical to managing the lake elevation.

7 b. Lowering ofLake Levels and Pump and Ex-Situ Treatment - Based on the evaluations presented by GE, EPA agrees that these techniques are not feasible as turbidity control measures, at least until such time that GE selects final cap materials. c. Coagulation/Flocculation - GE's evaluation of this potential treatment is inadequate based on the information presented. At a minimum, GE should have provided a qualitative evaluation of using this technique for potential reduction in turbidity. For each of the potential cap materials, GE should have provided additional investigations/descriptions as to how the coagulant/flocculent agent might influence the availability and/or distribution of organic carbon. There are numerous vendors that deal directly in the contaminated sediment and water treatment market that likely can provide information regarding the application of coagulantlflocculent agents. GE further discounts this process on the basis that these agents are typically applied in different environments and therefore the uncertainty associated with applying this process in Silver Lake is too high.

22. GE shall develop a addressing conditions 12-21 listed above for Attachment I that can be implemented ifthe Performance Standard for TOC is not achieved or if unacceptable concentrations of suspended solids are discharged to the river through the Silver Lake outfall.

All conditions listed above shall be addressed in the final combined Work Plan for Silver Lake Sediments and Bank Soil within 5 months of receipt of this letter or within two months of approval of the submittal of the Responses to Trustee Comments Regarding Natural Resource Restoration/Enhancement Measures for Banks of Silver Lake. If you have any questions please give me a call.

8 Sincerely,

i l "'/..["<'-~ C'

Susan C. Svirsky, Project Manager cc: Mike Carroll, GE Dick Gates, GE Rod McLaren, GE James Bieke, Goodwin Procter Mike Gorski, MassDEP Eva Tor, MassDEP John Ziegler, MassDEP Susan Steenstrup, MassDEP Dale Young, MAEOEEA Susan Peterson, CTDEP Kenneth Munney, USFWS Ken Finkelstein, NOAA James Owens, EPA Holly Inglis, EPA Tim Conway, EPA Dean Tagliaferro, EPA Mark Otis, USACE Mayor James Ruberto, City ofPittsfield William Hines Jr., PEDA Jim McGrath, City ofPittsfield Caleb Mitchell, City ofPittsfield Scott Campbell, Weston Linda Palmieri, Weston Solutions Public Information Repositories

References:

Aquablok®. 2009. Product Test Documents. Available at: http://www.aquablokinfo.com/index.php?option=com content&task=view&id=4 3&Itemid=141. Aquablok®, Ltd. Bailey, S.E., Engler, RM., Clausner, J.E., and Palermo, M.R 2005. Equipment and Placement Techniques for Subaqueous Capping. Engineer Research and Development Center. Vicksburg, MS. ERDC TN-DOER-R9. September. Francingues, N. R, and Palermo, M.R 2005. Silt Curtains as a Dredging Project Management Practice. Army Engineer Research and Development Center. Vicksburg, MS. ERDC TN-DOER-E21.

9 Jersak, J. 2000. Sediment Capping Demonstration Project on the Ottawa River: An Impacted Lake Erie . Hull & Associates, Inc. Presented at the Sediments Remediation Action Team Meeting. January 13. Available online at: http://www.rtdf.org/PUBLIC/SEDIMENT/MINUTES/011300/jjpres/index.htm. McDonough, K.M., Murphy, P., 01sta, J., Zhu, Y., Reib1e, D. and Lowry, G.V. 2007. Development and Placement ofa Sorbent-Amended Thin Layer Sediment Cap in the Anacostia River. Soil and Sediment Contamination, 16:313-322. Murphy, P.l, and Lowry, G.V. 2004. In Place Management ofPCB-Contaminated Sediments: Performance Evaluation and Field Placement of Sorbent-Amended Sediment Caps. Symposia Papers Presented Before the Division ofEnvironmental Chemistry. American Chemical Society. Philadelphia, PA. August 22-26. Murphy, PJ., Marquette, A., Reib1e, D., Lowry, G.V. 2006. Predicting the Performance ofActivated Carbon-, Coke-,and Soil-Amended Thin Layer Sediment Caps. Journal ofEnvironmental Engineering, 132:787-794. Quadrini, J.D., VanDewalker, H.M., Mihm, J.E., McShea, L.J. 2003. Pilot-Scale Demonstration of In Situ Capping ofPCB-Containing Sediments in the Lower Grasse River. Remediation, Winter Volume. Reib1e, D. 2005. In Situ Sediment Remediation Through Capping: Status and Research Needs. Hazardous Substance Research Center/South and Southwest. Available on at: http://www.hsrc-ssw.org/pdf/cap-bkgd.pdf. U.S. Army Corps ofEngineers (USACE). 1984. Shore Protection Manual. U.S. Army Corps ofEngineers (USACE). Updated 2003. Eagle River Flats (ERF) Website Available at: http://www.crrel.usace.army.mil/erf/history/#Remediation. U.S. Environmental Protection Agency (USEPA). 2007. Demonstration ofthe AquaBlok® Sediment Capping Technology. Innovative Technology Evaluation Report. EPA/540/R-07/008. National Risk Management Research Laboratory, Office ofResearch and Development, Cincinnati, Ohio. September.

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