The U.S. Environmental Protection Agency (EPA) has selected a cleanup plan for the first mile of the Lower Neponset River Superfund Site, marking a major milestone in the effort to address decades of industrial contamination in Boston and Milton, Massachusetts.

The selected plan targets the stretch of river between the Dana Avenue Bridge—where the Neponset merges with the Mother Brook—and the Tileston and Hollingsworth Dam. The area has long been contaminated by polychlorinated biphenyls (PCBs) and other hazardous substances, a legacy of centuries of industrial activity along the river.

"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 a statement.

What the Cleanup Will Include

Following a detailed Engineering Evaluation and Cost Analysis (EE/CA) completed in June 2025, the EPA held a public comment period from June 13 through August 1, including a virtual public hearing on July 9. After reviewing public input, the agency finalized its approach, which includes:

• Dredging and excavation of sediment and floodplain soil with PCB levels exceeding 1 part per million.
  
  
• Construction of a permanent cap on the riverbed to stabilize the area, protect aquatic habitats, and isolate remaining contamination.
  
  
• Off-site transport and disposal of contaminated sediment and soil.
  
  
• Removal of the Tileston and Hollingsworth Dam, a step expected to improve water flow and ecosystem health

The cleanup design phase will begin in 2026, with construction scheduled to start in 2027. EPA estimates the full removal action will take approximately four years to complete.

Full documentation, including the EPA’s responses to public comments, is available in the Action Memorandum

A River with a Long Industrial History

The Lower Neponset River Superfund Site spans a 3.7-mile segment of the river from the confluence with Mother Brook in Hyde Park to the Walter Baker Chocolate Dam upstream of Adams Street in Dorchester/Milton. It was added to the EPA's National Priorities List (NPL) in March 2022 due to widespread contamination.

Once a hub of early American industrialization dating back to the 1630s, the Neponset River was historically used to power factories and hosted numerous industrial operations, many of which discharged waste directly into the water. As a result, toxic substances—including PCBs, banned in the U.S. since the late 1970s - settled into the sediment and soil, posing long-term risks to public health and aquatic ecosystems.

The upcoming work represents just the first phase of a broader cleanup of the entire Lower Neponset River Superfund Site. Future plans will address additional contaminated segments downstream. EPA officials say continued community engagement and environmental justice considerations will remain central to the process.