amec September 1, 2015 fOStGP

wheeler Mr. Craig Zeller, P.E. Superfund Remedial and Site Evaluation Branch U.S. Environmental Protection Agency 61 Forsyth Street, S.W. Atlanta, Georgia 30303-8960 via e-mail: zeller.craig@epa.gov

Subject: Preliminary Response to USEPA's Review Comments on the NAPL Area Focused Feasibility Study Report GTS of Asheville, Inc. Superfund Site 235 Mills Gap Road, Asheville, Buncombe County, North Carolina EPA ID: NCD003149556 CERCLA Docket No. CERCLA-04-2012-3762 Amec Foster Wheeler Project 6252-12-0006

Dear Mr. Zeller:

As we discussed this morning, we have reviewed your August 26, 2015, Review Comments on the NAPL Area Focused Feasibility Study (FFS) and have set forth below some preliminary observations concerning several of those comments.

CIS is pleased that USEPA agrees that electrical resistivity heating (ERH) is appropriate as an interim source control remedy for the approximate one-acre NAPL Area. This interim remedy will allow us to move forward on the cleanup of the Site on an expedited basis which, as you know, was one of the primary objectives of the FFS.

In USEPA's comments, the presence of dissolved phase ICE in the area of MW-6 and MW-7 was referenced. However, monitoring wells MW-6, MW-6A and MW-7A (non-NAPL locations) identified in your letter were not part of the FFS, although there were data at those locations at the same relative concentrations^ noted when the FFS Work Plan was prepared in the fall of 2014. Remedial efforts at those areas were not included because CIS and USEPA agreed that those areas were outside of the identified NAPL Area. Thus, the FFS was not designed to, nor did it evaluate, the feasibility of any technology at those non-NAPL locations. The intent of the FFS was to select a remedial alternative that would "cut off" the source area, so that concentrations in the downgradient plume (such as at MW-6, MW-6A, and MW-7A) would begin to decrease.

^ We agree that the TOE concentrations are relatively high at the non-NAPL locations, but the highest concentrations are within the NAPL source area, not at the non-NAPL locations as stated in your letter. [NAPL Investigation Report dated May 5, 2014] Correspondence: Amec Foster Wheeler Environment & Infrastructure, Inc. 1308 Patton Avenue Asheville, North Carolina 28806 Tel 828.252.8130 License Number: NC Corporate Engineering F-1253

CTS of Asheville, Inc. Superfund Site September 1,2015 Preliminary Response to USEPA's Review Comments on the NAPL Area Focused Feasibility Study Report Amec Foster Wheeier Project 6252-12-0006

Based on our preliminary evaluation, the pH of groundwater at the site is lower than what is optimal for biodegradation without some type of geochemical alteration. Such considerations were not evaluated in the FFS, as bioremediation is not typically evaluated In source areas with elevated contaminant concentrations. We do not know if enhanced thermal bioremediation, as suggested in your comments, would be feasible as a remedy in those non-NAPL locations. Thus, implementation of enhanced thermal bioremediation for the downgradient non-NAPL area as USEPA suggests is not appropriate at this time.

Concerning the DRO (i.e., diesel range organics), the FFS was neither designed nor approved to evaluate any remedial technologies for what is, in actuality (as explained In our prior reports), weathered No. 2 fuel oil. The work done by TRS Group, Inc. and set forth as TRS's ERH Bench Testing Report simply noted in passing the observation that there had been a 60 percent reduction in the petroleum fraction coincident with the TOE removal objective, which was the stated purpose of the bench test.

Of course, CTS will provide available data concerning any observed fuel oil reduction resulting from the implementation of the ERH interim remedial measure. But the weathered No. 2 fuel oil has never been designated as a contaminant of concern at the site and, therefore, the FFS was neither designed nor intended to provide for a remedial action objective (RAO) for fuel oil.

As you requested, we will submit a revised FFS report addressing USEPA's comments by September 10, 2015.

Sincerely,

Amec Foster Wheeler Environment & Infrastructure, Inc.

Susan E. Kelly, P.E., L.G. Senior Engineer

SEK/MEW:sek

Matthew E. Wallace, P.E. Principal Engineer

cc: Daniel Harper, CTS Corporation Michael Dolan, Jones Day William Clarke, Roberts & Stevens, P.A. Nile Testerman, NCDENR