Wellesley College / The Neponset River Restoration Project

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The Neponset River Restoration Project

Dan Brabander, Ph.D
Department Chair and Associate Professor, Geosciences
Wellesley College
21 Wellesley College Rd.
Wellesley, MA 02481

Isabella Gambill
Wellesley College Alumna and Former Brabander Lab Researcher

Initiative Description and Primary Objectives 

The Neponset River Watershed Restoration Project is an ongoing collaboration between the Neponset River Watershed Association (NepRWA), Wellesley College’s Geosciences Department, and a host of local environmental non-profits and conservation groups working towards the revitalization of local ecosystems along the Neponset River in Massachusetts. More specifically, the distinctive cooperation of student research groups, non-profits, and local government agencies in the Neponset River Project is working to:

  • Evaluate options for the restoration of fish runs on the Neponset River, including dam removal, dam modification, and dredging of contaminated river bed sediment in several locations throughout the watershed
  • Engage and empower local communities in the conservation process relating to potential dam removal on the Lower Neponset River, and
  • Provide a holistic approach to localized environmental health risk assessment and management by using historical industrial data to inform and interpret geochemical sampling data in student research.

Neponset River Watershed Background

As one of three main rivers emptying into Boston Harbor, the Neponset River flows through 14 local cities and towns, traveling 30 miles from Foxboro to Dorchester, Massachusetts. Its watershed includes roughly 130 square miles of land southwest of Boston, with a population of about 330,000. Recognized as the second watershed to be industrialized in the United States, the Neponset River Watershed has a complex history of metal loading and contamination from both point and non-point sources. Used historically for hydro-powered factories, the Neponset has been home to the Paul Revere Copper Rolling Mill, Kinglsey Iron and Machine Works, Ames Shovel Shop, and countless other industrial land use ventures, all of which had outflow and discharge pipes pumping toxic industrial waste directly into the river. More recently, local communities along the Neponset River have rallied to reclaim and restore the Neponset in the hopes of a cleaner, more accessible, and more natural river ecosystem.

Lower Neponset River Restoration

The Lower Neponset Restoration Project is strictly focused on the restoration of a five-mile stretch of the Neponset River known as the “Lower Neponset”, passing through the communities of Milton, Hyde Park, Mattapan, and Dorchester, MA.  More specifically, the Lower Neponset Restoration Project has concentrated on the Baker Dam near Dorchester and the Tileston and Hollingsworth (T&H) Dam between Boston and Milton. Ideally, the Lower Neponset Project’s goal is to restore spawning runs of Blueback Herring and American Shad for 17 miles of the Neponset River by removing or modifying the T&H and Baker Dams, which are no longer in use and currently block several migratory fish species from spawning grounds upstream.  If the dams were modified for fish travel, then fish runs would be restored in Norwood, Dedham, Walpole, Westwood, Mattapan, Hyde Park, Quincy, Milton, and Canton, MA. Improvement of these fish runs and habitats for Herring and Shad would not only advance their populations’ health and numbers, but would also have lasting positive effects on the Neponset River food web as a whole. In addition to dam modification and/or removal, the Lower Neponset Project aims to potentially remove and treat Polychlorinated biphenyl (PCB) contaminated river-bottom sediments to create a cleaner and safer river environment.  Furthermore, recent revitalization of local communities along the Neponset River has also created a significant demand for restoration of the river for recreational and development purposes. Even though the Neponset River Restoration Project is primarily a conservation initiative, many local businesses and unconventional conservation advocates, such as the Lower Mills Merchants Association, are invested in the ecological improvement of the land, as healthier river and shore land conditions will be reflected in higher property values and development potential.

Neponset River Baker Dam 

Image 1: Looking Upstream at the Baker Dam (photo courtesy of NepRWA)

According to NepRWA, the Massachusetts Executive Office of Environmental Affairs (EOEA) entered into a cooperative agreement with the Army Corps of Engineers in 1996 to evaluate possibilities for the restoration of fish runs on the Neponset River. The Riverways Program within Massachusetts Fish and Game was then named by the EOEA as the primary agency in charge of coordinating and pursuing studies of the Lower Neponset River. As it became clear to the Riverways Program that Neponset riverbed sediment was severely contaminated with PCBs and industrial waste, the United States Geological Survey (USGS) was contacted to perform detailed sampling of contaminated sediments and determine the severity, extent, and sources of contamination, and to disseminate their results to the public.

A USGS scientist reported the following findings at a January 2008 public meeting in Dorchester.

  • Most PCBs were found in the sediments behind T&H Dam in Milton/Hyde Park and, to a lesser extent, behind Baker Dam in Lower Mills.
  • PCBs in sediments behind dams were found to be highly unstable and to become suspended in the water column after storms.
  • PCBs were found in the flesh of freshwater fish at levels that pose a significant risk to human health. Based on these findings, the state Department of Public Health (DPH) issued a health warning for certain types of fish caught between Walpole and Baker Dam. DPH spent the summer of 2008 testing additional fish species and tributaries of the Neponset River for possible health risks.
  • Storms regularly wash large quantities of PCBs over the dams and into the Neponset River Estuary. PCBs were found in the water column all the way to its mouth at Dorchester Bay.
  • PCBs were found in the flesh of saltwater fish, though not at levels which pose a risk to human health. (Source: “Lower Neponset River Restoration”, Neponset River Watershed Association. See: www.neponset.org/projects/ecological-restoration/lower-neponset-restoration/.)  

In addition to data collected and published by the USGS, the Riverways Program also funded two studies with the private consulting firm Milone & MacBroom in order to perform a cost-benefit analysis of the 28 proposed alternatives for restoration, including “do nothing”, dam removal and/or modification, and dredging of contaminated river bed sediments. Although most of the alternatives were found to be technically infeasible, the dredging of contaminated sediments and permanent “capping” of sediments behind the two dams were found to be viable PCB cleanup alternatives. After the results of the environmental consulting and USGS studies were made public, recommendations from both the Neponset River Restoration Technical Advisory Committee and the Citizens Advisory Committee -collectively representing federal agencies, local government agencies, private organizations, and local neighborhood associations- forwarded the removal or partial removal of the Baker and T&H dams, along with the dredging and removal of contaminated sediments as their preferred mode of action for Neponset restoration. Several Massachusetts environmental and watershed groups, including the Mass Audubon, Sierra Club, Conservation Law Foundation, and the Charles River Watershed Association, gave additional support for full dam removal at both dam sites.

Upper Neponset River Restoration

The Upper Neponset River Restoration Project involves a partnership with NepRWA and Wellesley College to include student research in the environmental health risk assessment and management of the Upper Neponset River, specifically focusing on the East Branch of the Neponset. Dr. Daniel Brabander’s geochemistry lab at Wellesley College conducted field sampling of over 190 sediment samples, representing 17 ponds and tributaries throughout the watershed (see Figure 1, below).

Neponset River Watershed 


Figure 1: Map of the Neponset River Watershed, Indicating Land Use Practice, Wellesley College Sampling Locations, and the Two Dams of Interest for Removal on the Lower Neponset River. (Source:  Hatem, Alex, Gambill, Isabella, Sedlack, Casey, and Willis-Norton, Ellen. “Inventory Analysis and Transport of Legacy Metals in River and Millpond Sediments: An Example from the Neponset River Watershed, Massachusetts”. Poster Presented at: 63rd Annual Geological Society of America Conference, May 18-20, 2011) .

Geochemical sampling involved the collection of Russian cores (Figure 2), freeze cores, and dredge surface samples, which were then analyzed using x-ray fluorescence spectroscopy (XRF).

Wellesley Figure 2 

Figure 2: Russian Core Collected in Factory Pond; Note the Color Stratification that Indicates a Shifting Geochemical Makeup. (Source: Brabander Lab).      

Brabander’s lab utilized a holistic approach that combined targeted industrial history and land use data with geochemical flow conditions in order to guide sampling at priority sites expected to be “hot spots” of contamination. For example, historical research conducted via government documents, Sanborn maps, and census data including the statistics of manufacturing in Norfolk County (where the East Branch of the Neponset is located), revealed that the presence of the Revere Copper Rolling Mill, Ames Shovel Shop, and Kingsley Iron and Machine Company resulted in point source pollution of arsenic, copper, iron, chlorine, lead, chromium, zinc, and several other heavy metals directly into the river via factory discharge pipes. Once students were able to identify the location of factory discharge pipes, sampling of sediments directly in front of the pipes yielded more accurate measurements of the highest levels of heavy metal contamination in the East Branch of the Neponset River. Further investigations of historical peaks in production were linked with peaks in contamination within the sediment core, causing Brabander’s lab to read each core as a historical archive documenting the presence and severity of the various contaminates and when they were introduced into the ecosystem.

Although the Brabander/NepRWA collaboration is ongoing, results from data over the past 5 years suggest that sedimentation and depositional processes in the East Branch have led to deep (>30cm) burial of heavy metals in some historic millponds along the Upper Neponset, resulting in partial natural attenuation and sequestration of contaminated sediments if left alone. Therefore, Brabander’s lab cautions against dredging, dam removal, or dam modification at dam sites in the Upper Neponset where contaminated sediments are found, since each of those alternatives if pursued may result in the uncontrolled mobilization of otherwise sequestered heavy metals. Once previously contained heavy metals become mobilized in the water column, there is the possibility of redistributing legacy metals downstream, thereby posing serious threats to the entire Neponset watershed ecosystem. It is worth noting that the mobility potential of legacy metals varies considerably, creating a significant challenge for watershed-wide recommendations.

The combination of geochemical analyses of sediment composition and historical industrial output data utilized by Brabander’s lab suggests that historical research can serve as a first order tool for predicting heavy metal distributions in the watershed, and identifying major polluters for potential prosecution. Additionally, in light of potential dam removal on the Upper Neponset River, the identification of heavy metal inventories in the sediment by depth can help to guide remediation efforts, since surface metal concentrations may not adequately reflect contained pollutants that may become mobile with dredging or dam modification. 

Key Academic Disciplines 

Environmental Studies, Geochemistry, Biology

Key Partner Organizations and Individuals 

Neponset River Watershed Association (NepRWA)

Boston Environment Department

Milton Conservation Commission

Massachusetts Department of Conservation and Recreation

Riverways Program and Massachusetts Department of Fish and Game

Lower Mills Merchants Association

Citizens Advisory Committee

Milone & MacBroom Consulting

Wellesley College, Dr. Daniel Brabander and Dr. James Turner

DJB Geochemistry Lab Group, Wellesley College

Olin College of Engineering and Dr. Robert Martello

Initiative History and Champions 

The continuously positive reception and support of both the Lower and Upper Neponset Restoration Projects allowed for a large-scale collaboration between local government agencies, non-profits, community organizations, watershed associations, and student researchers at Wellesley College. A project of this scope and nature would not have been possible without the constant coordination and leadership by the Neponset River Watershed Association. Additional funding allowed for a holistic and comprehensive project that focuses on location-specific restoration and remediation.

Distinctiveness and Strategic Significance of the Initiative 

As more communities move to reclaim and restore local rivers and watersheds formerly occupied by industry, effective watershed management is essential to pursuing alternatives that are safe for both human and environmental health. The inclusion of a host of environmental organizations and research institutions in this project ensures that a thorough and accurate assessment of environmental risk is performed, and that the best alternative is pursued for restoration. With the time and dedication put forth by NepRWA and its collaborators, the Neponset River Restoration Project is an excellent example of a thorough and integrative approach to watershed restoration that also allows for the constant feedback and empowerment of the local community. The inclusion of student research facilitates an interdisciplinary approach to watershed restoration and management that is location-specific, involves targeted conservation efforts, and aids greater communication between scientists and community members. 

Measurable Effectiveness of the Initiative 

Although the Neponset Restoration Project has been a work in progress for over 15 years, its thorough investigations of viable alternatives for conservation have prioritized the Baker and T&H dams for modification and/or removal in the next few years. The collaboration between NepRWA and Wellesley College ensured that similar dam modification would not be pursued in the Upper Neponset’s East Branch without considering the extremely harmful effects of mobilizing contained pollutants in river sediment. Additionally, the identification of point-source polluters along the Neponset can result in current owners being responsible for funding of cleanup activities, and may aid in obtaining federal funding for dam removal and/or modification. 

Transferability of the Initiative 

The research model put forth by the Wellesley College/NepRWA collaboration allowed for a more comprehensive assessment of metal inventories and relative transport potentials in urban watersheds. Within the context of watershed restoration, this model can be used to more effectively address environmental health risks, identify the effects of targeted dam removal, and perform impartial watershed management research. The wide range of organizations and partnerships involved in the Neponset Restoration Project allows for broad dissemination of results and recommendations, and has the potential to influence and inform local watershed conservation in the future. 

The Initiative’s Ability to Endure 

The full and far-reaching local support from businesses, conservation groups, and community organizations for Neponset River cleanup and restoration will ensure that preferred conservation actions are pursued, and that similar efforts continue throughout the Neponset River watershed until the job is done.  

Engagement Strategies 
  • Poster presentations and talks at Geological Conferences (GSA, Bridgewater State), Wellesley College, and NepRWA meetings
  • Presentations of findings to public committees and forums
  • Publication and report distribution.