EPA agreement outlines cleanup of New Hampshire landfill

A new consent decree for the Dover Landfill Superfund site has cleared the way for continued clean up work and better environmental protection, including groundwater remediation, at the site. The consent decree is subject to a 30 day public review and comment period.

The Dover Municipal Landfill Superfund Site, located in Dover, New Hampshire, is a 50-acre uncapped landfill. Ground water beneath the site has been contaminated with arsenic and organic compounds, and the contamination extends well beyond the landfill boundaries, north and eastward to the Cocheco River and south toward the Bellamy Reservoir.

The landfill began operations in 1961 and closed in 1979. While it operated, Dover Municiple landfill accepted household wastes, as well as wastes from local industries that included liquid hazardous wastes. These liquid hazardous wastes consisted of tanning solutions and chlorinated solvents. The site was placed on the National Priorities List on September 8, 1983.

EPA initially outlined a clean up plan for the site in 1991, which was the basis of a 1993 consent decree with the “potentially responsible parties,” all of whom agreed to perform portions of that plan. The 1993 consent decree required the creation of an impermeable cap on top of the 50-acre landfill, but deferred a decision on a ground water remedy until further studies were performed.

Due to the many complexities of cleaning up the site, EPA and the New Hampshire Department of Environmental Services (NHDES) allowed the responsible parties to consider other remedial options for source control that would protect the public health and the environment while remaining cost-effective.

Based on several years of studies, EPA issued an amended “Record of Decision” (ROD) in 2004 that selected a new source control remedy – to capture high-concentration contaminants in selected hot-spots within the landfill, and to capture and treat dissolved contaminants in ground water along the perimeter of the landfill. The high-concentration contaminants within the landfill will be treated on site. The 2004 Amended Record of Decision retained the ground water remedy from the 1991 Record of Decision, including capturing contaminants in the southern plume and discharging the water to the City’s sewer system for treatment. Currently, there are no exposure pathways that pose a hazard to the public or environment. Ground water contamination, however, may pose a threat to public water supplies if it is allowed to continue unchecked.

Since EPA issued the Amended Record of Decision in 2004, the potentially responsible parties have been conducting investigations to accelerate the implementation of the remedy. Portions of the ground water pump and treatment system south of the landfill began operating in April 2008. It is expected that the EPA, NHDES and the potentially responsible parties will continue this collaborative effort to address site contamination and any potential threat to public water supplies.