Somersworth Sanitary Landfill

Overview

The Somersworth Sanitary Landfill is a 26-acre former waste disposal site on Blackwater Road in Somersworth, New Hampshire. It accepted municipal and industrial waste from the mid-1930s until 1981 and burned waste until 1958. EPA added it to the Superfund National Priorities List (NPL) in 1983. The City of Somersworth owns the property.

Groundwater across the site is contaminated with twelve chemicals, including volatile organic compounds (VOCs) such as trichloroethene, tetrachloroethene, vinyl chloride, benzene, and several forms of dichloroethene. Lead, manganese, beryllium, carbon disulfide, chlorobenzene, and dichloromethane are also present in groundwater. Methane has been detected in landfill gas. Per- and polyfluoroalkyl substances (PFAS) are an additional concern, and groundwater monitoring for PFAS has been ongoing since October 2018. Contaminant levels exceed federal drinking water standards. A local zoning ordinance prevents groundwater use in a designated Groundwater Management Zone to protect public health.

EPA selected a cleanup plan in 1994. Workers installed a permeable reactive barrier, a wall filled with granular zero valent iron and sand, which treats VOCs chemically as groundwater flows through it. The wall was completed in 2000. A permeable soil cover, a bedrock extraction well, and a gas collection trench were finished by December 2003, reducing landfill gas to negligible levels. Monitoring after 2004 found periodic breakthrough of chlorinated ethenes in one section of the wall. Investigations from 2015 to 2019 traced the problem to uneven iron distribution, likely from construction. In November 2023, additional zero valent iron was injected into that section using direct push technology. EPA completed its fifth five-year review in September 2025, and a new remedial investigation was scheduled to begin in March 2026.

Human exposure is currently under control across the entire site, with no unacceptable exposure pathways identified. Groundwater contamination is stabilized in its original area. Physical cleanup construction has been completed, and the site achieved ready-for-anticipated-reuse status in 2008. Institutional controls remain in place and restrict land use as long as contamination or cleanup components are present. The site has not yet been deleted from the NPL.

A 10-acre portion of the site is being redeveloped as a ground-mounted solar photovoltaic array with a capacity of about 2.63 megawatts direct current. Construction began in April 2025 and was substantially complete by October 2025, and full operation was expected by December 2025. This is the first Superfund site in New Hampshire to host a solar farm. Community members with questions can contact EPA's Community Involvement Coordinator or Remedial Project Manager, or visit site records at the Somersworth Public Library or EPA Region 1's Records and Information Center in Boston.

(NOTE: This summary was created based on all information available on the EPA's official site profile page as of May 29, 2026. To see the most up-to-date information provided by the EPA, visit the EPA's official profile page for this site. For questions, or to politely encourage the EPA keep their profile pages current, contact the EPA Community Involvement Coordinator or Remedial Project Manager assigned to this site.)