The federal government on Wednesday proposed adding the portion of the Neponset River that winds through Milton, Dorchester, Mattapan and Hyde Park to the list of the nation's most serious uncontrolled or abandoned contaminated sites.
Citing sediment contamination stemming from the former operation of industrial mills and dams built to turn grinding wheels, the U.S. Environmental Protection Agency on Wednesday included a 3.7-mile stretch of the Lower Neponset River on its list of 13 newly proposed Superfund sites. If the river section is deemed a Superfund site, the designation could lead to more investigations and an eventual cleanup using federal resources and expertise.
The Lower Neponset River channel ranges from approximately 40 to 300 feet wide and comprises an estimated 40 acres running through the four communities. Preliminary studies that date back to 2002 have indicated its sediments are contaminated with elevated levels of PCBs, or polychlorinated biphenyls.
The site is bordered by residential, commercial areas and industrial areas, as well as public parcels including the Neponset River Greenway.
"EPA continues to protect public health and the environment in communities where industrial activities have left behind a legacy of contamination," EPA New England Acting Regional Administrator Deborah Szaro said late Wednesday. "By proposing to add the Lower Neponset River site to Superfund, EPA is taking concrete steps to address a legacy of contamination in this urban river that will lead to a cleaner and healthier environment for nearby citizens."
According to the EPA, Superfund site cleanups around the country have been credited for "significant reductions in both birth defects and blood-lead levels among children living near sites and research has shown residential property values increase up to 24 percent within three miles of sites after cleanup."
There are 1,134 Superfund sites in the United States, including 31 in Massachusetts, according to the EPA.
The Massachusetts Department of Environmental Protection, which is overseen by Gov. Charlie Baker, in 2015 requested that the river section be added to the Superfund list "as the surface water, sediment, and fish within the Neponset River and Estuary are contaminated with PCBs," according to the EPA.
PCB concentrations were identified in studies dating back to the 2002 to 2006 period conducted by the United States Geological Survey, which reported increased PCB concentrations in sediment samples collected downstream of the Mother Brook in Hyde Park, which feeds into the river. In 2006 and 2008, the state oversaw a "large removal of contaminated sediments" in Mother Brook, according to the EPA.
An August 2018 final report prepared for the EPA on PCB contamination in the river noted that water flowing through the Lower Neponset discharges at the Baker Dam and continues to flow downstream through a marsh and estuary and into Dorchester Bay and Boston Harbor.
The EPA has opened a 60-day public comment period that will include a virtual public meeting on Tuesday, Oct. 5.
"The Baker-Polito Administration continues to prioritize returning the Lower Neponset River back to a healthy state and ensuring that it remains a recreational and environmental resource for years to come," Baker said in a statement. "We are eager to see the cleanup and restoration of the waterbody, which flows through a portion of Milton, and the Environmental Justice communities of Dorchester, Mattapan and Hyde Park."
In a June 25 letter to Szaro, Baker wrote that the site warrants Superfund status due to the "serious nature of the contamination."
The EPA said its proposed Superfund site updates reflect President Joe Biden's commitment to updating the National Priorities List more regularly, with the goal of "cleaning up and returning blighted properties to safe and productive reuse in areas where environmental cleanup and jobs are needed most."
EPA Administrator Michael Regan said in a statement Wednesday that Superfund site additions will deliver protections to people who "live, work, pray and go to school" in communities near contaminated sites. A pending infrastructure bill, Regan said, could address a backlog of Superfund sites awaiting cleanups.
The larger Neponset River drains about 101 square miles of land and flows 29 miles from its headwaters in Foxborough into the Neponset River Estuary east of Dorchester Avenue and Adams Street in Dorchester.