EPA Selects Cleanup Plan for Portion of Lower Neponset River Superfund Site

EPA Selects Cleanup Plan for Portion of Lower Neponset River Superfund Site

November 10, 2025

BOSTON (November 10, 2025) - U.S. Environmental Protection Agency (EPA) has selected a cleanup plan for the first mile of the Lower Neponset River Superfund Site, located in Boston and Milton, Massachusetts. This covers the area of the Neponset River from where it merges with the Mother Brook near the Dana Avenue Bridge, to the Tileston and Hollingsworth Dam.

"This represents another great milestone for the Lower Neponset River Superfund Site and is a reflection of this administration's priorities to move cleanup activities along swiftly, efficiently and fulfill the agency's core mission of protecting human health and the environment," said EPA New England Regional Administrator Mark Sanborn.

In June 2025, EPA completed an Engineering Evaluation/Cost Analysis (EE/CA). This analysis evaluated cleanup alternatives and presented EPA's recommended cleanup plan to address contamination from polychlorinated biphenyls (PCBs) and other hazardous substances. EPA held a public comment period from June 13 through August 1, 2025, which included a virtual public hearing on July 9, 2025. All public comments were considered before selecting the cleanup plan.

The cleanup plan includes:

• Dredging and excavating contaminated sediment and floodplain soil with total PCB levels exceeding 1 part per million;
• Constructing a permanent cap in the first mile of the river to stabilize and restore the riverbed, minimizing surface water elevation changes, providing habitats, and isolating any remaining contamination in deeper sediment;
• Transporting and disposing of contaminated sediment and soil off-site; and
• Removing the Tileston and Hollingsworth Dam.

Cleanup design will begin in 2026, and construction is anticipated to begin in 2027. The removal action is estimated to take approximately four years to complete.

A copy of the Action Memorandum, which includes EPA's responses to public comments on the EE/CA, can be found here: https://semspub.epa.gov/src/document/01/697312 (pdf) (28.7 MB).

Background

The Lower Neponset River Superfund Site was added to the National Priorities List (NPL) on March 16, 2022, and is currently identified by EPA as a 3.7-mile stretch of the Neponset River. The Site begins at the point where it merges with the Mother Brook (a tributary to the Neponset River located upstream of Dana Avenue in Hyde Park), extends downstream through City of Boston neighborhoods of Hyde Park, Mattapan, Dorchester, and the Town of Milton, and ends at the Walter Baker Chocolate Dam (located upstream of Adams Street in Dorchester/Milton).

Industrialization and subsequent urbanization began in the Neponset River Basin as early as the 1630s. Recognized as the second watershed to be industrialized in the United States, the Neponset River has a complex history of contamination from both point and non-point sources. Used historically for hydro-powered factories, the Neponset River has been home to countless industrial land use ventures, most, if not all, of which likely had outflow and discharge pipes pumping industrial waste directly into the river.

To learn more about EPA's work at the Lower Neponset River Superfund Site, visit: https://www.epa.gov/neponsetriver