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EPA Proposes Modifications to Cleanup of the Kearsarge Metallurgical Corporation Superfund Site in Conway, NH
Release Date: 10/07/2003
Contact Information: Alice Kaufman, EPA Community Involvement Office, 617-918-1064
BOSTON - The U.S. Environmental Protection Agency and the New Hampshire Department of Environmental Services is proposing to alter the cleanup strategy for the Kearsarge Metallurgical Corporation Superfund site in Conway, NH. Since the original cleanup decision, issued in a 1990 Record of Decision, EPA has gathered additional information about the site which makes it necessary to alter the original remedy to ensure the protection of human health and the environment.
- Excavation of additional source materials. The 1990 ROD addressed sources of contamination by requiring the removal of a septic tank and its contents and the excavation of leach field soils at the site. These sources of contamination were removed during 1992. Recent investigations indicate that chlorinated solvents moved beyond the leach field source area and downward through the soils and accumulated in the low permeability silt and clay soils in the culvert area where they are acting as an ongoing source of contamination to the groundwater. EPA has funded the NHDES through a cooperative agreement to have a contractor excavate the remaining highly contaminated soils located at depths of 8 to 15 feet below the ground surface, all of which are below the water table. The soils will be disposed of at an approved offsite facility.
- Improve the existing extraction system by installing a larger trench in the source area. A ground water extraction trench will be constructed where the contaminated source materials are removed. This will result in an improved ground water capture system.
- Correct site-specific groundwater cleanup level. Due to a previous computational error in establishing the groundwater cleanup level that is necessary to protect people's health, EPA writing in the ESD corrects the site-specific ground water cleanup goals for 1,1 - Dichloroethane (1, 1 - DCA) to 3650 ppb so that it is consistent with current toxicity data. The original remedy incorrectly established a groundwater cleanup goal of 4 ppb for 1,1-DCA.
The original cleanup plan set out to control the source of contamination and manage the migration of contamination by excavating and treating contaminated soils, extracting and treating contaminated groundwater and providing long-term groundwater monitoring. Four extraction wells were installed west of Hobbs Street and ten extraction wells were installed east of the former KMC building. A groundwater treatment plant has been operating continuously since 1993 to treat the water before discharging it to the local publicly owned treatment plant. However, contaminated ground water concentrations in the culvert area ground water have not decreased significantly since approximately 1997 and are still higher than the cleanup goals. Additional investigations revealed a concentrated source of chlorinated organic solvents in the culvert area of the site which are acting as an ongoing source of contamination to the groundwater.
This modified remedy, detailed in a document called Explanation of Significant Differences (ESD), addresses this newly identified ongoing source of contamination. The significant differences between the remedy as presented in the 1990 Record of Decision and the action now being proposed include:
Questions can be sent to: Richard Goehlert, Remedial Project Manager, U.S. EPA, 1 Congress St., Suite 1100 (HBO), Boston MA 02114 or Andrew Hoffman, Remedial Project Manager, NHDES, 6 Hazen Dr., Concord NH 03301.
The Administrative Record, containing information supporting this proposal, is available for public review at the locations listed below:
US Environmental Protection Agency
One Congress Street
Boston, MA 02114
M-F 10:00 am - 1:00 pm
and 2:00 pm - 5:00pm
Conway Public Library
Conway, NH 03818
M - Th 10:00 a.m. - 8:30 p.m.
F - Saturday 10:00 a.m. - 5:30 p.m.