amec : foster

April 28,2015 wheelef

Mr. Craig Zeller Superfund Remedial and Site Evaluation Branch U.S. Environmental Protection Agency 61 Forsyth Street, S.W. Atlanta, Georgia 30303-8960

Subject: Springs Removal Action Report Addendum Mills Gap Road Groundwater Contamination Site 235 Miiis Gap Road, Asheviiie, Buncombe County, North Caroiina EPA ID: NCD003149556 CERCLA Docket No. CERCLA-04-2004-3755 Amec Foster Wheeler Project 6690-03-9450

Dear Mr. Zeller:

On March 23, 2015, Amec Foster Wheeler Environment & Infrastructure, Inc. (Amec Fester Wheeler) submitted the Springs Removal Action Report (Removal Report) on behalf of GTS Corporation (CIS) In accordance with the 2004 Administrative Order on Consent for Removal Action between the United States Environmental Protection Agency (USEPA) Region 4, CIS, and Mills Gap Road Associates. USEPA provided comments to the Removal Report in an email dated April 14, 2015. USEPA's email also included comments provided by the North Carolina Department of Environment and Natural Resources (NCDENR) to USEPA In an email dated March 24, 2015. This letter addresses USEPA's and NCDENR's comments and serves as an Addendum to the Removal Report.

USEPA's first general comment is regarding estimation of contaminant mass removal rates by the Springs Vapor Removal and Capture System (System). An estimate of the mass removed by the System was determined using the Influent and effluent air samples collected from the System, as well as the System operational parameters. From October 23, 2014, until January 7, 2015 (76 days), approximately 23 pounds of volatile organic compounds (VOCs) were removed, approximately 4 pounds of which was trichloroethene (ICE). From January 7, 2015, until April 17, 2015 (100 days), approximately 19 pounds of VOCs were removed, approximately 7 pounds of which was ICE. Based on the data collected in 2015, after the initial operation period of the system In late 2014, an estimated 6 pounds of VOCs In air are removed by the System on a monthly basis.

USEPA's second general comment Is regarding preparation of a graph showing ICE concentrations In air before and after construction of the System. Attached Is a graph depicting ICE concentrations in ambient, crawlspace, and Indoor air samples collected in the vicinity of the springs from April 2014 to February 2015. The System start-up date is also Indicated on the graph. A figure depicting the air sampling locations is attached.

Correspondence: Amec Foster Wheeler Environment & Infrastructure, Inc. 1308 Patten Avenue Ashevllle, North Carolina 28806 Tel 828.252.8130 License Number: NO Corporate Engineering F-0653

Springs Removal Action Report Addendum April 28. 2015 Miiis Gap Road Groundwater Contamination Site Amec Foster Wheeler Project 6690-03-9450

USEPA's Comment #1 (and NCDENR's second comment) is regarding the analytical results of surface water samples collected downstream of the springs area. The concentration of ICE decreased In the one surface water sample collected after construction of the System, while concentrations of cls-1,2-dlchloroethene (cls-1,2-DCE) and vinyl chloride Increased in the surface water sample. The System Is not Intended to reduce contaminant concentrations in surface water - the System Is Intended to decrease VOC concentrations In Indoor air.

The concentrations of TCE (34.5 micrograms per liter, pg/L) and vinyl chloride (10.8 pg/L) in the post-System construction surface water samples are above the National Recommended Water Quality Criteria (NRWOG) of 2.5 ng/L and 0.025 ng/L, respectively (Note, there Is not a NRWOC for cls-1,2-DCE). The concentration of cls-1,2-DCE (1,130 pg/L) in the post-System construction surface water sample is above the Maximum Contaminant Level (70 pg/L) and the USERA Regional Screening Level for tap water (3.6 gg/L): however, the unnamed tributary from which the surface water sample was collected is not a drinking water source.

Based on concentrations of TCE, cls-1,2-DCE, and vinyl chloride above USEPA's screening level concentrations, USEPA conducted an assessment of risk associated with exposure to the surface water (see attached e-mail dated April 8, 2015). USEPA assumed Ingestion and dermal contact by a recreational receptor. Based on USEPA's assessment, there is not unacceptable risk to recreational receptors from exposure to the surface water.

USEPA's Comment #2 proposes continued quarterly monitoring of ambient air In the vicinity of the springs, while discontinuing monitoring of crawlspace and Indoor air at residences adjacent to the springs. The comment also proposes discontinuing air monitoring at the "outer perimeter" residences. Based on the results of air monitoring data collected over the past year, CTS concurs with the proposed air monitoring strategy. The additional ambient air data collected In the vicinity of the springs through third quarter of 2015 will be evaluated to determine If future ambient air monitoring at the springs Is warranted while the System Is In operation.

In Comment #3, USEPA states that It disagrees with CTS' statement that the System will continue to operate unless the three residences adjacent to the springs become vacant. USEPA stated that the System should continue to operate until a remedy for the source area at the Site Is Implemented. The Intent of CTS' statement was to assert that If residents are no longer living adjacent to the springs, and thus the receptors to Inhalation of TCE removed, discontinuation of the System could be evaluated. CTS agrees that while contaminated groundwater continues to discharge to the springs area at concentrations that might create an unacceptable Indoor air risk to residents adjacent to the springs, the System will continue to operate. Assuming residents continue to live adjacent to the springs area, once the source area remedy Is Implemented and groundwater concentrations in the downgradlent springs area are reduced, discontinuation of the System operation will be evaluated.

In Comment #4, USEPA Indicates that the Rice family requested consideration be given to painting the System piping a more neutral color. CTS Intends to paint the System piping a more neutral color.

NCDENR requested clarification regarding the two sparge points Installed at SP-3 and SP-6. Based on the historic laboratory analytical results of surface water samples collected In the vicinity of sparge 'sumps' SP-3 and SP-6 (Immediately downstream of Sprlngs-02/03 and Sprlng-04), two sparge point assemblies (I.e., two slotted pipes with solid risers and separate piping to the air compressor) were Installed In these sumps to provide additional sparging

Springs Removal Action Report Addendum Miiis Gap Road Groundwater Contamination Site Amec Foster Wheeler Project 6690-03-9450

April 28, 2015

capacity. These dual sparge point assemblies were designated 'a' and 'b' at the SP-3 and SP-6 locations. The other sparge points each have one sparge point assembly.

If you have questions regarding this Removal Report Addendum, please contact us at (828) 252-8130.

Sincerely,

Amec Foster Wheeler Environment & Infrastructure, Inc.

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

SEK/MEW:sek

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

Matthew E. Wallace,^. %% Principal Engineer r f 24 9'3'"3 ^

attachments: Graph of TCE Concentrations in Air Samples Collected in the Area of the Springs Springs Area Air Sampling Locations Risk Evaluation e-mail from Ofia Hodoh of USEPA, dated April 8, 2015

TCE Concentrations in Air Samples Collected in the Area of the Springs Mills Gap Road Groundwater Contamination Site

Asheville, North Carolina Amec Foster Wheeler Project 6690-03-9450

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Sample ID/ Location

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Document: P:\Proiects\CTSCorpofation\4.0 Project DellverablesU.S Databases\GIS\MapDocumentsVCTS_AIR_2015_11>:17LS.m»l PDF: P:\Pro|ects\CTS Corporatlon\4.0 Project Dellverables\4.5 Databases\GIS\Figures\VI 2Q15\SpnngsArea AirSampling.pdf 04/28/2015 3:34 PM brlan.pelers

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amec foster wheeler

CTS of Asheville, Inc. Superfund Site Asheville, North Carolina

Prepared/Date: BRP 04/28/15 Checked/Date: SEK 04/28/15

Springs Area Air Sampling Locations

Project 6690039450

Zellei^rai^

From: Hodoh, Ofia Sent: Wednesday, April 08, 2015 4:19 PM To: Zelier, Craig; Adams, Glenn; Thoms, Sharon Cc: Koporec, Kevin; Bentkowski, Ben; Miller, Angela; Haire, Stacey; Rigger, Don; Young,

Nestor Subject: Re: CIS of Asheville - Spring Removal Action Report

Craig,

Concerning the surface water pathway, TCE, VC and 1,2-DCE were screened against the National Recommended Water Quality Critera (NRWQC) human health consumption for water plus organism. The maximum level of TCE at 34.S ug/L exceeds its NRWQC (2.5 ug/L); VC at 10.8 ug/L exceeds its NRWQC (0.025 ug/L); and cls-l,2-DCE at 1,310 ug/L exceeds its tapwater RSL (3.6 ug/L) and the MCL (70 ug/L). In the absence of a NRWQC, the tapwater RSL was used as the screening value for cis-1,2-DCE.

Utilizing very conservative exposure assumptions, the cancer risk for TCE (2E-06) and VC (5E-05) were within the EPA acceptable risk range of lE-06 to lE-04 for the recreational receptor, based on the combined ingestion and dermal pathway. The child non-cancer HI was less than 1.0, for cis-l,2-DCE, TCE and VC. The ambient air sample collected on 10/24/14 (between the springs and Mills Gap Road) indicate that TCE and VC are below EPA's acceptable risk range. EPA's IRIS no longer supports the derivation of inhalation toxicity value for the cis and trans isomers of DCE.

Ofia Hodoh, M.S. EPA Region 4 404.562.9176 hodoh.ofia@epa.gov

From: Zelier, Craig Sent; Wednesday, April 8, 2015 2:39 PM To: Adams, Glenn; Hodoh, Ofia; Thoms, Sharon Cc: Koporec, Kevin; Bentkowski, Ben; Miller, Angela; Haire, Stacey; Rigger, Don; Young, Nestor Subject: FW: GTS of Asheville - Spring Removal Action Report

TSS Folks-

The Springs Removal Action Report for GTS/Rice Family Compound is attached. I have one specific question for you. Table 4 shows the analytical results for surface water as it exists the remediation system. As expected, TCE has been reduced from 461 ppb to 34.5 ppb (e.g. the good news). Also as expected, as we degrade TCE, we are producing Cis-1,2 DCE and Vinyl Chloride. Cis concentrations went from 161 ppb to 1,270 ppb. VC concentrations went from 3.2 ppb to 10.6 ppb. Is this a concern from a Human Health (e.g. air and/or recreational scenario) and/or Eco scenario? In other words, how does it compare to our screening values?

Thanks for your input.