South Municipal Water Supply Well

Overview

The South Municipal Water Supply Well site sits in Peterborough, New Hampshire. The well was shut down in December 1982 after chlorinated solvents from the nearby New Hampshire Ball Bearings facility contaminated the groundwater. EPA added the site to the Superfund National Priorities List in September 1984. Today, five businesses operating on site employ 380 people and generate roughly $39.4 million in annual sales.

The main contaminants are chlorinated solvents in groundwater, soil, and sediment. These include trichloroethene, tetrachloroethene, 1,1,1-trichloroethane, 1,1-dichloroethane, 1,1-dichloroethene, cis-1,2-dichloroethene, trans-1,2-dichloroethene, vinyl chloride, toluene, 1,4-dioxane, PCBs (polychlorinated biphenyls), and PAHs (polycyclic aromatic hydrocarbons). The contamination plume extends from the New Hampshire Ball Bearings property to the former well location.

Cleanup has moved through several phases since the original remedy was selected in 1989. Early work included groundwater extraction and treatment, soil vapor extraction, and wetlands restoration. A 2010 amendment to the cleanup plan added thermal treatment of source areas and a permeable reactive barrier (PRB), a wall that passively treats groundwater as it flows through. Thermal treatment finished in November 2016. The first PRB was completed in December 2014 but was found in 2023 to not be working as intended. New Hampshire Ball Bearings completed a replacement PRB in October 2024. Pre-design work for enhanced in-situ bioremediation began in fall 2023. Indoor air sampling inside the NHBB building found some contaminant levels above screening values, but data from 2013 to 2017 showed no unacceptable vapor intrusion risk, as long as vapor extraction and air circulation systems keep running.

EPA has determined that human exposure is under control and that contaminated groundwater migration is stabilized. The municipal water supply protects residents from drinking contaminated groundwater, and institutional controls restrict groundwater use in the area. Physical construction of cleanup work is complete, though the site has not yet met all criteria for full anticipated use. The most recent five-year review was completed in September 2023, and the next is planned for roughly September through November 2028. Remedial action work was completed June 2025.

Community members can review site documents at the Peterborough Town Library at 2 Concord Street or at the EPA Region 1 Records and Information Center in Boston. For questions, contact the Community Involvement Coordinator or the Remedial Project Manager.