Dedham Stormwater Project

Planned BMPs will help to reduce pollution, including bacteria, from reaching Mother Brook.

August 2015 — Thanks to a grant from MassDEP and EPA, Dedham is planning to construct three stormwater treatment structures (also known as Best Management Practices, or BMPs) on town property.  NepRWA partnered with the town to apply for and secure this funding.

The BMPs include bioretention cells (similar to rain gardens), a subsurface infiltration system, and a water quality swale.  Each of these structures will allow runoff water to filter through the ground and be naturally treated by plants and soil, rather than running straight into Mother Brook and carrying pollution with it.

Mother Brook, the Neponset River, and the Charles River in Dedham are all listed as impaired waterbodies for a variety of pollutants, including bacteria and nutrients, such as nitrogen and phosphorus, by MassDEP.

Data from our Citizen’s Water Monitoring Network (CWMN) shows that Mother Brook has high levels of bacteria when it rains.  This presents a risk of illness to anyone boating, fishing, or swimming in the water.  Additionally, nutrients such as nitrogen and phosphorus have been high, which can lead to other issues such as harmful algal blooms and low dissolved oxygen.  Algae blooms can produce toxins that can make people and pets sick, and when the algae dies and decays, it consumes the oxygen in the water that the fish need to breathe.

The proposed treatment structures will capture the runoff and remove up to 90% of pollution from the tributary area before the stormwater makes its way to Mother Brook!

Construction is expected to take place this fall on Colburn Street, Avery Street, and Sawmill Lane.

Update – Dec. 2016

The Avery Street swale is the last of three structures built to collect and filter stormwater runoff before it reaches Mother Brook. A stormwater swale is a linear trench that is intended to manage stormwater runoff. The other two structures are located on the corner of Sawmill Lane and Emmet Ave, and on the corner of Colburn St. and Hyde Park St.

In the Neponset Watershed, stormwater runoff is a major source of bacteria and nutrient pollution. This poses a major health risk for anyone who recreates in the water immediately following a rain event, or for anyone who comes in contact with a cyanobacteria bloom driven by excess-nutrients.

The stormwater structures built in Dedham collect stormwater runoff before it enters the drain system and filter the runoff using special soils and plants to remove many of the pollutants. If properly maintained these structures will help clean up Mother Brook every time it rains.

The Dedham Stormwater Project is a collaboration between the town of Dedham and NepRWA, utilizing 319 grant funds from MassDEP.  For any questions about the project, please contact NepRWA Executive Director, Ian Cooke at

From left to right: Avery Street, Colburn Street, Sawmill Lane

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