On March 16, 2022, the USEPA formally listed the Lower Neponset River on the National Priorities List (NPL). The Lower Neponset River Site consists of a 3.7-mile section of the Neponset River between its confluence with Mother Brook in Hyde Park and the Walter Baker Dam in Dorchester, affecting the communities of Milton and Boston, MA. As is expected with USEPA’s increased efforts for environmental justice in urban communities, there is a high public involvement and interest at this site, as seen at preliminary public meetings hosted by the USEPA.
EHS Support attended the public workshops hosted by USEPA throughout November 2022 and have garnered information that may be of interest to you including the meeting presentation and key handouts (see below).
To date, the USEPA has begun issuing General Notice Letters, CERCLA 104(e)-Information Requests and an invitation to perform/finance the RI/FS to preliminary parties.
As indicated by USEPA throughout their public workshops, this site may consist of upwards of 100 PRPs. USEPA intends to begin sampling associated with the RI/FS in early 2023 before moving to the EE/CA in late 2023/early 2024. This will likely result in an attempt for cost recovery in future negotiations with the PRPs as the process unfolds. The following figure, provided in a 2009 Technical Assistance Grant Report associated with Mother Brook, depicts the locations of some of the upstream sources.
( Weston and Sampson, Former LE Mason Site- Technical Assistance Grant Report, June 2009)
Though new to the NPL, this site has an extensive investigative history. From 2002 through 2006, the United States Geological Survey (USGS), in cooperation with the Massachusetts Executive Office of Environmental Affairs Riverways Program and the USEPA, conducted studies that detected sediment, surface water and fish tissue contaminated with elevated levels of polychlorinated biphenyls (PCBs). PCB contamination in the lower Neponset River exceeds relevant criteria in both sediment and fish, and concentrations are similar to rivers where mass sediment removals have been required by USEPA. Sediment PCB concentrations range from 28 parts per billion (ppb) in upstream background areas to 11,400 ppb downstream of the confluence with Mother Brook.
USEPA’s Preliminary Site Assessment indicates the USGS determined Mother Brook tributary to be the source of the downstream contamination beginning in the early 1950s. Concentrations in Mother Brook near former industrial facilities ranged up to 24,900 ppb. For context, PCB levels in excess of 1,000 ppb (or 1 part per million) are typically targeted for removal by the USEPA. Concentrations of PCBs in fish tissue in the Lower Neponset River exceeded the 2,000 ng/g USEPA guideline for safe fish levels and reached concentrations similar to those seen at the Fox River in Wisconsin, which was the site of a massive (3.5MM ton) sediment removal due to PCBs. As the RI/FS activities begin, early data indicate an extensive Remedial Action in the future.
Key handouts and presentations:
- Meeting Presentation: USEPA Workshop for the Lower Neponset River Superfund Site
- Fact Sheet: Lower Neponset River Site
- Handout: Government and the Superfund Process
- Handout: Recreational Use of the Neponset River, Community Fact Sheet
- Handout: Superfund Workshop, Glossary of Terms
- Handout: Superfund Workshop, Acronyms and Abbreviations
We will continue to monitor developments on the site and provide additional updates as the information warrants. If you or clients are interesting in learning more about the site’s historical data and future outlook, please reach out to EHS Support’s team:
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