From the EPA report: Field work for the second phase of interim cleanup at the CTS of Asheville Site at 235 Mills Gap Road was completed during the first week of March 2020. This phase of the cleanup used In-Situ Chemical Oxidation (ISCO) to treat contamination in a 1.9-acre area. The area treated by ISCO is north of the area that was successfully treated by Electrical Resistance Heating (ERH) in 2018. The EPA expanded the interim cleanup to include this second phase in response to public input.
The ISCO treatment involved injection of potassium permanganate into the ground to oxidize and break down trichloroethylene (TCE) into harmless byproducts like carbon dioxide and water. A total of 76 injection wells were installed between October and December 2019. The injection wells were installed to the top of bedrock, which ranged from 55 to 90 feet below ground surface. From December 2019 through March 2020, approximately 350,000 pounds of potassium permanganate were injected into the subsurface via 380 vertical intervals at the 76 injection wells.
The injected potassium permanganate is expected to take three to five years to reduce TCE in groundwater by 95% to meet the Remedial Action Objective (RAO). Groundwater monitoring will be conducted every six months in the treatment area until the RAO is achieved. If a 95% TCE reduction is not achieved, additional ISCO treatment might be necessary.
The ERH and ISCO cleanup strategies at the CTS of Asheville Site were required under a March 7, 2017 settlement between EPA, the U.S. Department of Justice, CTS Corporation, Mills Gap Road Associates and Northrop Grumman Systems Corporation. To date, the companies have spent $5 million on the ERH component, and $4 million on the ISCO treatment.
More information regarding the CTS Superfund Site can be found at: https//www.epa.gov/superfund/cts-millsgap.