Lower Neponset Superfund

The US EPA announced the addition of the Lower Neponset River, between Mother Brook in Hyde Park and the Baker Dam in Milton/Dorchester Lower Mills, to the "National Priorities List" on March 14, 2022.

March 1, 2023—

Update from EPA:

This spring, EPA will begin sampling activities along the Lower Neponset River and riverbanks. Residents may see a small boat with workers wearing protective clothing along the river. This clothing is required because of the workers’ direct contact with sediments likely contaminated with PCBs. EPA will also be working with property owners along some areas of the river to request access to properties for further investigation.

EPA is beginning work on the Riverside Square PCB Site and the Lewis Chemical Site; both smaller removal sites along the river. Removal responses are common at Superfund Sites when contamination poses an immediate threat to human health and the environment.

At the Riverside Square PCB Site, EPA is conducting an investigation of suspected contamination along the banks of the Neponset River. At the Lewis Chemical Site, EPA is preparing for upcoming cleanup work. Look out for a factsheet pertaining to the Lewis Chemicals Site’s upcoming activities in the near future.

For more information on both removal sites please see the attached factsheet or contact ZaNetta Purnell at Purnell.Zanetta@epa.gov or Ashlin Brooks at Brooks.Ashlin@epa.gov.

Background information on the Superfund site can be found here https://www.epa.gov/neponsetriver and in our newly updated factsheet. Please feel free to share this factsheet with any and all interested parties.

March 14, 2022—

EPA designates Lower Neponset River a Superfund site

Listing of the Lower Neponset as a superfund site will bring federal resources to bear on cleaning up PCB contaminated sediments at the bottom of this section of the Neponset River. The process is expected to involve an extensive study of the contamination and potentially responsible parties, opportunities for public input, possible implementation of initial cleanup actions in certain areas, and eventual implementation of comprehensive cleanup efforts.

NepRWA has advocated for the cleanup of this section of the river for almost 20 years and we are excited to see this work getting underway.

Because the contamination is primarily in the mucky organic mud at the bottom of the river many recreational activities along the Lower Neponset and the Neponset Greenway can continue as usual while the cleanup progresses. See below for our FAQ on PCBs and recreation along the river, as well as for a running history of developments and resources related to the cleanup.

For more information, please contact NepRWA Advocacy Director, Kerry Snyder at snyder@neponset.org

View EPA Community Fact Sheets, below. Click here for a printable copy.

Click here to watch the EPA Superfund event announcement at Neponset River/Harvest Bridge

FAQ’s About Superfund and Recreation along the Lower Neponset


What is the EPA Superfund Program?

The Superfund Program protects human health and the environment by investigating and cleaning up often abandoned hazardous waste sites and engaging communities throughout the process. Many of these sites are complex and need long-term cleanup actions. Those responsible for contamination are held liable for cleanup costs. EPA strives to return previously contaminated land and groundwater to productive use.

Is It Safe to Eat FRESHWATER Fish Caught in the Lower Neponset River?

No. People should not eat fish caught in the freshwater portion of the Lower Neponset River. This includes the area from the Baker Dam in Milton / Dorchester Lower Mills to the dam upstream in Walpole at the Hollingsworth and Vose Dam. While the concern over PCB contaminated sediments only extends upstream to Hyde Park, fish that have spent time in the Lower Neponset can easily swim as far upstream as the dam in Walpole. Because of the process of bioaccumulation concentrations of PCBs in the fish can be relatively high compared to levels in the river or the water.

Is it Safe to Go Fishing in the Neponset River? What about Eating Fish From the SALTWATER Portion of the River?

You may enjoy recreational, catch and release fishing in all areas of the Neponset River , so long as you don’t eat FRESHWATER fish caught on the Neponset Mainstem as described above. Touching freshwater fish is not a concern. Saltwater fish caught downstream of the Baker Dam in the portion of the Neponset River known as the Neponset River Estuary, are not exposed to the higher levels of PCB sediments found further upstream and spend much of their lives in areas other than the Neponset River. Follow general guidelines for all saltwater fish when deciding whether to eat saltwater species caught in the Neponset Estuary. There are no special precautions for consumption of saltwater species caught in the Neponset.

Are there PCBs in the Water along the Neponset River?

PCBs do not readily dissolve in water. As a result downstream of Mother Brook there are PCBs in the water, but they are at extremely low levels that are not a concern for human contact. However, you should not drink water taken directly from the Neponset River because of concerns about other pollutants.

May I Walk and Bike along the Lower Neponset River?

Yes, you may safely walk, bike, and engage in other land based activities along the Neponset . PCBs are typically found in the “mucky,” organic mud at the bottom of the river. There should be no human health concerns with land-based recreation along the river, except for eating freshwater fish as discussed above.

May I Canoe, Kayak and Boat along the Neponset?

Yes, you may canoe, kayak and boat along the lower Neponset. PCBs on the Lower Neponset are primarily concentrated in the deep layers of mucky “organic” mud accumulated behind the two dams on the Lower Neponset and a former dam. While boaters might come in contact with mud in the river to a limited degree, this should not be a health concern for several reasons.

First, PCBs in the river are bound to organic matter in the mud and the primary hazard would be eating mud rather than touching mud. Second, areas of the river that have sandy or rocky bottoms without accumulations of mucky organic mud will have minimal if any PCBs because there is little or no organic matter with which the PCBs can bind. Lastly even in areas of the river that have organic mud deposits near formal canoe launches, the PCB concentrations in surface sediments are generally low. Higher PCB concentrations are found behind the dams several feet or more below the surface of the mud. While the risk of PCB exposure to boaters via mud is limited, we do recommend washing hands and shoes after recreation if you get muddy, as much because of other pollutants as because of PCBs.

Can I Swim in the Lower Neponset River?

While our goal is to get all of the Neponset and its tributaries to be safe for swimming all the time, the Lower Neponset River does not yet meet this goal consistently. This is primarily because of remaining problems with sewage pollution and untreated rain runoff from surrounding streets and neighborhoods, though potential exposure to PCB’s in mud deposits would also be a concern with swimming in the area between Mother Brook and the Baker Dam. That said, the Lower Neponset often does meet bacterial pollution standards for swimming and almost always meets bacterial standards for boating.

Is there a project website, email list, or some other mechanism to keep track of the project and receive timely notice of meetings or document releases?

In the event the site is added to the NPL, an official Superfund epa.gov website will be created, where overall information will be posted. At this time, you can view documents such as the factsheets, etc. at: https://go.usa.gov/xd9mE

Project Site Description


The Lower Neponset River “site” which is being nominated for “superfund” status is defined by the U.S. Environmental Protection Agency (EPA) as the 3.7-mile stretch of the Neponset River from the confluence with Mother Brook in Hyde Park just upstream of Dana Avenue, extending downstream to the Walter Baker Dam located upstream of Adams Street, Dorchester, and Milton.

View EPA documents, such as factsheets, etc. at: https://go.usa.gov/xd9mE

Key EPA Contacts


ZaNetta Purnell
U.S. EPA Community Involvement Coordinator 617-918-1306

Meghan Cassidy
U.S. EPA Supervisory Environmental Engineer 617-918-1387

General Information

Notes from EPA Community Meeting on October 5, 2021


On October 5th, EPA held an informational Community Meeting to provide information and answer questions about the Superfund process. More than 165 people participated in the meeting and asked some great questions, although EPA could not accept or consider formal comments on the proposal during the meeting, they were soliciting formal comments from the public on the proposed addition of the Lower Neponset River to the National Priorities list.

View Oct 5 2021 EPA presentation

Some key points gleaned from both the documents and the context of the site include:

  • The EPA’s assessment of the Lower Neponset from the confluence of the Neponset River and Mother Brook to the Baker Dam identify clear evidence of extensive PCB contamination of river bottom sediments.
  • EPA’s assessment also concludes that there is no readily identifiable source of the contamination.
    • This is a major issue for the Commonwealth and a key reason federal resources are necessary. Neither the Commonwealth nor the affected municipalities of Boston and Milton have the resources to investigate and identify the numerous potential “responsible parties”–those prior landowners and industrial operators that contributed to the contamination. Nor do they have the resources to clean up the contaminated sediments themselves.
  • Leaving the contaminated sediments in place is not an option.
    • PCBs contaminate the fish from the Lower Neponset upstream to Walpole, causing a significant public health risk to those who fish for food. (The EPA’s assessment confirmed “subsistence fishing.” See Section of the HRS Documentation Record for Lower Neponset, p.57.)
    • The EPA’s assessment indicates that PCBs threaten groundwater, potentially a source of drinking water for more than 40,000 people. (While the surface drinking water threat was not scored because people don’t get their water directly from the Neponset, EPA concludes that future groundwater contamination is a possibility. See the EPA’s Narrative Summary of the project.)
    • The contamination makes it impossible for the Commonwealth to begin several community-supported projects to modify the Baker Dam and remove the Tileston and Hollingsworth Dam within the site. These projects would not only improve the health of the river and existing and potential fisheries, but also would reduce a public safety risk for environmental justice communities should the dams fail. (And the impacts of climate change, including increased precipitation and flooding events, make such dam failure a significant concern as time goes on).
    • While secondary recreation activities–such as boating, catch-and-release fishing, and sitting, walking, biking and playing along the banks of the river–are safe and encouraged, there may be a perception that the river is an unsafe place due to the contamination. Such a perception, in practice, makes the river and its many benefits inaccessible for some.
    • Lack of access to a critical water resource is a significant equity issue for the environmental justice communities surrounding the site.
  • Based on the supporting documentation for the Lower Neponset site, the inclusion of the site on the NPL is necessary to ensure  (1) further investigation into the legacy pollution of sediments within the Lower Neponset; (2) identification of responsible parties; and (3) eventual cleanup of the pollution to permit necessary restoration activities and increased access to the Lower Neponset.

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