Superfund Designation for the Lower Neponset

On September 8th, the EPA formally proposed to add the Lower Neponset (3.7 miles between Mother Brook and the Baker Dam) to the National Priorities List.

Updated October 6, 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.

View Oct 5 EPA presentation

EPA will consider comments made in writing and email until November 8, 2021.

Currently, the EPA is looking for comments on the documentation supporting the listing of the Lower Neponset as a Superfund site.

  • To send via the post office, mail to:

U.S. Environmental Protection Agency
EPA Docket Center, Superfund Docket
Mail Code 28221T
1200 Pennsylvania Avenue NW
Washington, DC 20460

All comments must:
  • Reference the docket number of the proposal EPA-HQ-OLEM-2021-0457
  • Be submitted or postmarked by November 8, 2021.

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.

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:

For more information, please contact NepRWA Advocacy Director, Kerry Snyder at


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 Fish Caught in the FRESHWATER Portion of 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 next dam upstream which is located 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?

Recreational, catch and release fishing in all areas of the Neponset River is safe, so long as you don’t eat FRESHWATER fish caught on the Neponset Mainstem as described above. Touching freshwater fish is not a concern, and as discussed below land by the river, the riverbanks, the water, and the air near the river are not hazardous. 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 Air along the Neponset?

No, PCBs are not in the air near the river. PCB’s are attached to organic mud in certain areas of the river bottom. People recreating along the river should have no concerns about PCB air pollution.

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. The PCB concentrations are so low in Neponset River water that they are well below human drinking water quality standards for PCB contamination. However, that obviously doesn’t mean you should drink water taken directly from the Neponset River because of concerns about other pollutants. People enjoying the river should have no health concerns about coming in contact with the water as a result of PCBs. In terms of other types of pollution besides PCBs, almost everywhere on the Neponset River meets “boatable” water quality standards and in fact most areas meet “swimmable” water quality standards most of the time. Read more about water quality elsewhere on this site.

Is Walking, Biking and Sitting along the Lower Neponset River Safe?

Yes, walking, cycling, sitting, picnicking and other land based activities along the Neponset are all safe. PCBs are found in the “mucky,” organic mud at the bottom of the river, not on land along the river and not on the riverbanks. When PBCs were first discovered in the River, the MA Department of Environmental Protection conducted extensive testing along the Neponset River Greenway Trail, in parks along the river, and at canoe launches along the river and did not find PCBs in these on-land recreation areas. There should be no human health concerns with land-based recreation along the river, except for eating freshwater fish as discussed above.

Is Canoeing, Kayaking and Boating along the Neponset Safe?

Yes, canoeing, kayaking and boating along the lower Neponset are safe. As discussed above, PCBs are not in the air, and the water meets drinking water quality standards in terms of PCB contamination. Land along the river and at canoe launches has also been tested and found free of PCBs. 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 PCBs do not easily move through human skin. As such, 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 canoe launches, the PCB concentrations in surface sediments are 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 after recreation if you get muddy, as much because of other pollutants as because of PCBs.

Is it Safe to 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 exposure to PCB’s in deeper mud deposits would also be a concern with swimming. 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 listed to the NPL, an official Superfund website will be created, where overall information will be posted. At this time, you can view documents such as the factsheets, etc. at:

How have you distributed notification of the meeting and would you object if we were to pass the information on to additional people that we know are interested?

EPA is collaborating with the City of Boston/Neighborhood Services on outreach. Per their request, they have translated the factsheet into five languages.

In addition, City of Boston/Neighborhood Services liaisons for each neighborhood are assisting on getting the word out. They are working on sending it to their e-mailing lists, posting it in weekly newsletters, having hard copies at community centers, providing the meeting info at community meetings and such. Please do not hesitate to share information with others who are interested.

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

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