On the evening of February 24, the United States Environmental Protection Agency (EPA) described its plan to nominate the “Lower Neponset River” for “superfund” status at a well-attended community meeting in Mattapan.

EPA is proposing to nominate the “Lower Neponset River” to the National Priority List, better known as the superfund list. The “Lower Neponset River” includes the area from the confluence of the Neponset River and Mother Brook in Hyde Park (near Dana Ave) down to the Baker Dam in Milton/Dorchester Lower Mills (near Adams Street).

At issue is the longstanding problem of river-bottom sediments contaminated with Poly-Chlorinated Biphenyls (PCBs). PCB’s are a category of chemicals that were widely used by industry until they were banned in the early 1970s.

Several companies along Mother Brook used PCBs and discharged them to the Brook. The companies in question cleaned up the brook itself, but have declined to take responsibility for PCBs found in the river’s main stem downstream of Mother Brook.

Process and Timeline

The proposed action by EPA is being initiated in response to a request by the Mass Department of Environmental Protection (MassDEP). MassDEP supervised the cleanup of Mother Brook and has been studying PCBs in the Neponset River for more than a decade with assistance from the United States Geological Survey (USGS).

MassDEP has recently concluded that it lacks the resources to take enforcement against the parties responsible for discharging the PCBs, and has asked EPA to take over the cleanup and enforcement efforts.

EPA has completed additional assessment which has confirmed that the Lower Neponset River meets the criteria for superfund listing, and EPA expects to nominate the Lower Neponset River for listing in the fall or winter of 2020.

Once the Lower Neponset has been nominated and if it is designated as a superfund site, EPA will undertake additional studies to detail the extent of the pollution and identify responsible parties. They will then seek to have responsible parties complete the cleanup, or if there are no responsible parties, undertake a cleanup using federal funds. The timeline to complete a cleanup is unknown at this time, and is likely to span a decade, if not more.

Is It Safe to Recreate Along the River?

EPA will not reach its own conclusions about pollution risks until it has completed additional studies which will likely take several years.

However, the MassDEP and the USGS have already completed a number of studies along the river over the last decade that provide good guidance for people recreating in or along the river. Based on these studies we make the following recommendations.

Don’t Eat the Fish

Don’t eat fish caught in the Neponset River or its tributaries between Walpole, Canton and Lower Mills. The main human health risk from the PCBs is fish consumption, because of bio-accumulation. Fish in Lower Neponset area can swim from the Baker Dam all the way up to Hollingsworth and Vose Pond in Walpole, Factory Pond on the East Branch in Canton and up several smaller tributaries. Don’t eat fish caught in this area. However, recreational catch and release fishing is not a concern.

Concentrations are lower in the Neponset Estuary and sport fish generally move around to other areas of Boston Harbor much of the time. Species such as striped bass and bluefish as well as other species that are caught downstream of the Baker Dam in the Neponset River Estuary should be similar to fish found in other areas of Boston Harbor, and the same rules apply for the Neponset as for other areas.

Bike Path and Banks are Safe

DEP conducted studies of soil contamination along the Neponset Greenway Bike Path and key publicly accessible riverbank areas such as canoe launches along the Lower Neponset and found no PCBs. Small areas of other pollutants (lead and arsenic) we found and have been cleaned up. Biking, walking, picnicking, etc. along the river in these areas is safe.

Take Sensible Precautions When Canoeing and Fishing

It is very unlikely that people canoeing, fishing or wading along the Lower Neponset will encounter high levels of PCBs. PCBs are not in the air, and they are at extremely low concentrations in the water itself (below drinking water standards). PCB concentrations in areas of the river bottom that have rocks, gravel or clean sand should be minimal. The banks have been tested at all canoe launches and found to be clean. Washing hands or taking a shower is an appropriate precaution if you get wet or muddy in the river. Wearing boots or waders when wading in the river is also recommended.

Minimize Contact with Deep Black Mud

PCBs bind to small organic particles (decomposing leaves, etc) in the mud, which means they are mostly found in squishy, dark black mud areas, which most people will naturally avoid. The highest concentrations in the river bottom are well below the surface and located behind the T&H and Baker Dams and in the Rice Islands area. Surface layers of black mud in the river have much lower concentrations of PCBs. In the unlikely event that you do find yourself in deep mud, take a hot shower, and you should be fine.

Further Reading

• EPA Lower Neponset Fact Sheet
• EPA Lower Neponset Presentation Slides 2-24-2020