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The CTS of Asheville, Inc., Superfund Site is located at 235 Mills Gap Road in Asheville, North Carolina. International Resistance Company owned and operated the site from 1952 to 1959. It manufactured electronic components. CTS Corporation manufactured electronic components used in auto parts and hearing aids at the site from 1959 to April 1986.

Mills Gap Road Associates (MGRA) purchased the 53.54-acre site in 1987. MGRA sold 44.89 acres to the Biltmore Group, LLC in 1997, which developed the 44.59 acres into a residential subdivision. The remaining 8.65 acres where the old facility was located is fenced and has been vacant since the mid-1990s. The building was demolished in December 2011.

Historical use of solvents in the manufacturing of electronic components contaminated the CTS Site with trichloroethylene (TCE) and fuel oil (non-aqueous phase liquid, or NAPL). 

The EPA proposed the site to the National Priorities List (NPL) in March 2011 and finalized it on the NPL in March 2012.

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What Has Been Done to Clean Up the Site?

The EPA is the lead federal Agency at this site. The EPA and the North Carolina Department of Environmental Quality (NCDEQ) provide oversight of work performed by CTS Corporation and its contractors under legal agreements and EPA-approved work plans. The EPA’s top priority is to eliminate potential human exposure to TCE via drinking water and air inhalation pathways.

In 2004, the EPA entered into an Administrative Order on Consent (AOC) for Removal Action with CTS Corporation and Mills Gap Road Associates. Removal of contaminant mass from the subsurface was initiated in 2004. 

2006 - 2010
A soil vapor extraction (SVE) system was installed to vacuum VOCs from the soils above the water table. From July 2006 to July 2010, the SVE system removed an estimated 6,473 pounds of VOCs from the unsaturated zone.

2012 – 2014
On January 26, 2012, the EPA and CTS Corporation entered into an Administrative Order and Settlement Agreement on Consent (AOC) for Remedial Investigation and Feasibility Study (RI/FS).

From September 2012 to August 2014, CTS installed 101 water supply filtration systems in residences located within a one-mile radius of the Site who relied on groundwater as their drinking water supply. The filtration systems were installed as a precautionary measure.

2014 – 2015
During the 2014-2015 timeframe, Buncombe County installed municipal water supply lines in the vicinity of the site. Of the 101 residences with filtration systems, 87 home owners elected to connect to the municipal water line. CTS will continue to maintain the remaining water filtration systems until they are no longer warranted. Residential wells within the one-mile radius whose owners did not connect to county water service are monitored annually.

In September 2014, CTS installed a springs remediation system on property immediately to the east of the site to reduce TCE concentrations in outdoor/indoor air. The remediation system includes a combination of air sparging and vapor extraction. Air sparging pumps air into the surface water and subsurface at seven locations. These vapors are extracted using vacuums at 12 locations and then treated by carbon canisters. The area was covered with a low-density polyethylene liner to increase the system’s efficiency.

Construction began on September 10, 2014 and the system has been in continuous operation since October 21, 2014.

In June 2015, additional samples were collected on the western side of the site, near the Southside Village neighborhood and an undeveloped tract of land south of Mills Gap Road. This investigation delineated a narrow plume of TCE-impacted groundwater extending from the western fence line of the CTS plant site. The results of this data collection are compiled in the Western Area Remedial Investigation Report and Addendum.

In February, the EPA issued an Interim Action Record of Decision (ROD) specifying the interim cleanup remedy for the site. The NCDEQ concurred with the EPA remedy decision. The interim remedy is a source control action for Non-Aqueous Phase Liquid (NAPL) and TCE in the groundwater beneath the former CTS plant site. The interim action will address a 3.1-acre area. Approximately 208,250 cubic yards of material in the saturated zone between the observed water table and top of competent bedrock will be cleaned up.

ERH took place on a 1.2-acre area between December 2017 and November 2018. ERH is a technology that heats the ground to extract and treat hazardous substances. Electricity runs through electrodes, heating the soil and groundwater to vaporize the contaminants. The vapors are captured and removed through extraction wells, then treated above ground before being discharged to the air. The goal of the ERH cleanup was to reduce the TCE pre-treatment concentrations in saturated soil and groundwater by 95 percent in the treatment area beneath the former CTS plant. The average TCE concentration in saturated soil was reduced from 59,496 parts per billion (ppb) to 1,318 ppb, a 97.8% reduction. The average TCE concentration in groundwater was reduced from 16,523 ppb to 736 ppb, a 95.5 percent reduction. ERH removed approximately 5,600 pounds of TCE and over 12,000 gallons of NAPL safely from the subsurface.

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What Is the Current Site Status?

ISCO is being used to treat contamination in a 1.9-acre area that is north of the area that was successfully treated by ERH. 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 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.

A final site-wide cleanup will be selected in the future to address any contamination remaining after the ERH and ISCO technologies have had a chance to work over several years.

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Activity and Use Limitations

At this site, activity and use limitations that EPA calls institutional controls are in place. Institutional controls play an important role in site remedies because they reduce exposure to contamination by limiting land or resource use. They also guide human behavior. For instance, zoning restrictions prevent land uses – such as residential uses – that are not consistent with the level of cleanup.

For more background, see Institutional Controls.

Fencing surrounds the former plant and the area where the vapor extraction system is operating. The former plant area has been vacant since the mid-1990s.


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Sampling and Monitoring

Drinking water is sampled annually at homes where the owners declined to connect to the extended municipal water line. Ambient air is sampled quarterly on the eastern and western sides of the site to ensure the springs treatment system is working as intended. Influent and effluent air samples are also collected every six weeks to monitor contaminant removal efficiency of the system.

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Enforcement Information


Enforcing environmental laws is a central part of EPA’s mission to protect human health and the environment. When warranted, EPA will take civil or criminal enforcement action against violators of environmental laws.

In 2004, EPA entered into an Administrative Order on Consent (AOC) for Removal Action with CTS Corporation, the former operator at the time of disposal for the Site, and Mills Gap Road Associates, the current owner of the Site. On January 26, 2012, EPA and CTS Corporation entered into an Administrative Order and Settlement Agreement on Consent (AOC) for Remedial Investigation and Feasibility Study (RI/FS).

On May 10, 2016, EPA issued Special Notice Letters to three Potentially Responsible Parties (PRPs) at the CTS of Asheville, Inc. Superfund Site: Mills Gap Road Associates; CTS Corporation; and Northrop Grumman Systems Corporation. Issuing Special Notice Letters is an important first step in the legal process by which the EPA formally requests that PRPs perform remedial work at a site under EPA oversight and according to EPA-approved work plans. The Interim Remedial Action for the CTS of Asheville, Inc. Superfund Site was selected by the EPA in a Record of Decision (ROD) finalized on February 11, 2016. The Interim Remedial Action calls for a combination of Electrical Resistance Heating (ERH) and In-Situ Chemical Oxidation (ISCO) treatment to address Non-Aqueous Phase Liquid (NAPL) and trichloroethene (TCE) beneath 3.1 acres of the former CTS facility. The estimated cost of this interim source control remedy is approximately $9 Million.

On March 7, 2017, the judge signed the settlement agreement for the Interim Remedial Action at the CTS of Asheville, Inc. Superfund Site.



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