chevron-down Created with Sketch Beta.


From Chocolate to PCBs: The Lower Neponset River's Industrial Past Places It on the National Priorities List

Christen Maccone and Stephan A Maranian


  • Provides historical information about the Neponset River.
  • Discusses how despite the lack of heavy industry on the Neponset River today, pollutants from the early industrial days remain.
  • Indicates that a restored Lower Neponset River would serve as a recreational and environmental resource for nearby communities with environmental justice concerns.
From Chocolate to PCBs: The Lower Neponset River's Industrial Past Places It on the National Priorities List Parsons

The headwaters of the Neponset River start some 30 miles southwest of Boston, and the river meanders downstream until it empties into Boston Harbor. The history of the Neponset includes over 10,000 years of human habitation and more than 375 years of industrialization.

The flowing river offered great opportunity to the people who inhabited the region, including food and transportation. Early in the life of the United States, the Neponset River played an intricate role in the preservation of our young nation’s history. In the 1820s the nation’s first commercial railway was constructed to transport granite from the quarries of Quincy, Massachusetts, to the Neponset River, where it then traveled through Boston Harbor to Charlestown, to build the Bunker Hill Monument.

Dams also harnessed the Neponset’s energy, the first of which—likely among the first in the New World—was constructed in 1634. The dams furthered innovation and supported some of the first mills in the United States, including those for paper, gun powder, and chocolate production. Over time, the size and power of larger rivers such as the Merrimack surpassed the Neponset, but industrial development continued along the banks of the Neponset all the way into the 19th century. Today, the more than 100 dams along the Neponset River watershed are remnants of the era of waterpower, which ended in the 20th century, when the fossil fuel era began. However, the Neponset River remained a critical water source and continued to serve as a means for disposing industrial waste products, during a time when dilution was the solution to pollution.

The Neponset experienced momentous change over the years. In the 1930s the Neponset River hosted modern industry, which used polychlorinated biphenyls (PCBs) to manufacture things such as electronic mechanisms and carbonless copy paper. Factories released PCBs and other pollutants into the river, which floated downstream and became trapped in sediment behind dams. Yet when industry left, its pollution remained. Today, no heavy industry remains on the Neponset.

The Baker Chocolate Factory dam was constructed in the 1960s by the Walter Baker Chocolate Company. The company built a network of brick mills, which still stand today and are used as commercial and residential spaces. However, the factory closed its doors in 1965. Other than holding back contaminated sediment from years of industrial pollution and providing a nostalgic view of what the Industrial Neponset once was, the Baker Dam serves little to no purpose. The dam is not considered significant by historians, but the buildings and the rivers industrial past are. Any dam removal project must incorporate measures to protect and document adjoining historic resources and to actively interpret the key role of waterpower as the driving force behind the river’s industrial period.

PCBs are a designated hazardous substance under the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA). Both section 311(b) and 307(a) of the Clean Water Act, and section 112 of the Clean Air Act are statutory sources for the designation of PCBs as hazardous substances under CERCLA. Pursuant to CERCLA, the owners and operators of facilities with PCBs, in amounts exceeding a specified threshold, are required to annually report releases of PCBs and to immediately report these releases if the amount exceeds the reportable quantity. In response to a request from the Massachusetts Department of Environmental Protection, the Environmental Protection Agency (EPA) formally proposed to add a 3.7 mile stretch of the Lower Neponset River to the National Priorities List (NPL) in September of 2021.

On Wednesday, March 16, 2022, EPA published a final rule, adding the Lower Neponset River to the NPL. The removal of the Baker Dam (as well as the Tileston & Hollingsworth Dam seven miles upstream), and remediation of the contaminated sediment would open 17 miles of historic spawning runs of herring and shad. In addition to restoring fish passage and river flow, this project would reduce flood risk and restore the river channel to a more natural shape and flow, thereby enhancing wildlife, aesthetics, and recreation.

In addition to protecting public health and restoring the environment, Superfund cleanups support positive economic and social outcomes in communities. The Biden administration has prioritized environmental justice (EJ), and the EPA has worked to include EJ in its programs. CERCLA is no outlier; 72 programs by EPA were initially determined as covered by the initiative with Superfund being one of the six pilot programs. The Superfund Redevelopment Initiative (SRI) is a key feature of addressing environmental justice concerns. While cleaning up contamination to levels that pose no risk to human health or the environment is certainly beneficial, redevelopment and reuse of a site utilizes a valuable resource, land. Superfund sites, after cleanup efforts have been completed, have been redeveloped for a wide range of purposes: housing, retail, park/green space.

Deborah Szaro, EPA New England acting regional administrator said, "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." EJ has been a concern for the communities surrounding the Lower Neponset River site, such as Mattapan. These same communities, which have been heavily affected by climate change, could have the redeveloped Lower Neponset River site as a natural space, or other resource. In addition to ecological benefits, a restored Lower Neponset River would serve as a recreational and environmental resource for nearby communities with environmental justice concerns.