Solutions being studied to reduce the negative effects of Dams

September 27, 2012

To improve water quality, the Assabet’s nutrient study (known as a TMDL Total Maximum Daily Load) showed that reducing the phosphorus discharge from the wastewater treatment plants will help reduce the recycling but not enough. Phase 1 of stricter phosphorus discharge limits has been set, and major investments in upgrading the treatment plants have been made to meet these limits. If this is not enough to allow the river to meet its water quality standard, what next? The TMDL required that in addition to reducing new input of phosphorus, phosphorus recycling from the sediment must be reduced by 90% in order to meet standards.

Could removing dams and/or the sediment behind them reduce phosphorus recycling and eliminate the need for even stricter discharge limits?

The State DEP, in a collaborative effort with the six Assabet River sewered communities, funded and oversaw a study to address this question. This collective initiative underscores the shared commitment to improving water quality in the region.

The $1 million study was funded by 50% state funding, with a 50% match of federal funding through the Army Corps of Engineers, who were in charge of the study. A large modeling component was subcontracted to Camp Dresser & McKee.
Six of the nine Assabet dams were included in the Corps study. Not included in the study were two flood control dams (Nichols Dam in Westborough and Tyler Dam in Marlborough) and a breach (Damonmill Dam in West Concord) that have little impact on water quality.

The Assabet Sediment and Dam Removal Study was published in September 2010, entitled “Assabet River, Massachusetts: Sediment and Dam Removal Feasibility Study.“

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River Log

~30%

of the SuAsCo rivers watershed is wetlands, crucial for wildlife habitat and water quality

~30%

of water samples in the SuAsCo rivers watershed contain PFAS, leading to increased monitoring and remediation by local authorities and environmental groups

~70%

of dams in the SuAsCo watershed are over a century old, requiring extensive upkeep and presenting obstacles to river restoration and fish passage

>40%

of the land within the watershed is publicly accessible, offering recreational opportunities such as hiking, boating, and birdwatching to the community

~15%

of the land in the SuAsCo rivers watershed is covered by impervious surfaces such as roads, rooftops, and parking lots. This contributes to stormwater runoff and water pollution issues

Solutions being studied to reduce the negative effects of Dams

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