Neponset River Report Card: 2021

Mattapan bank and head of Marsh Islands, Neponset River

On July 15, 2022, the U.S. Environmental Protection Agency (EPA) issued the 2021 Water Quality Report Card for the Neponset River and the bacteria “grades”, which can be seen on the map below.

The report card shows the result of water samples taken from various locations across the 120-square mile Neponset River Watershed and is made possible through NepRWA’s Community Water Monitoring Network (CWMN).

For bacterial pollution in the Neponset Watershed, most streams and river segments earned grades of “A” or “B.” Only Unquity Brook, Germany Brook, and Meadow Brook received grades of “D” or “F.” All monitored ponds earned “A’s” and the mainstem of the River, where most recreation occurs, got “B” grades. (Scroll down to learn what A, B, C, D, and F mean.)

NepRWA also tracks dissolved oxygen and phosphorus, which are important for fish, wildlife, and recreation.

The grades in the Neponset are similar to the previous year. (See 2020 Report Card.)  The biggest challenge in the Neponset is polluted rain runoff from streets, parking lots, and yards. When it is raining, grades drop by 22% on average, nearly two full letter grades.

If you have any questions about the Water Quality Report Card, please contact NepRWA River Restoration Director, Sean McCanty at

What’s in a grade?

The report card grades are based on Massachusetts standards for swimmable water and a less stringent criteria for boating, defined by all 3 of the Boston Harbor watershed associations.

The grades reflect the number of sampling events that either met boating standards (50% compliance) or both swimming and boating standards (100% compliance) over the last 3 years.

While useful, we caution that compliance scores can only tell you how often the standards are met on average and cannot replace your own good judgment about the safety of recreation.

In general, we recommend avoiding water-based recreation, especially swimming, directly following rainy days, as E. coli levels typically spike then.

The multiple factors that affect water quality and the bacteria “grade” of the Neponset River include:

  • Stormwater runoff occurs during rain events and washes contaminants such as dog waste into streams and ponds via storm drain systems.
  • Leaking sewer pipes or sanitary sewer overflows, which allow raw sewage to flow into streams and ponds.
  • Poorly maintained septic systems, which allow bacteria and chemicals to flow from groundwater into streams and ponds.

Partnerships Make a Difference

NepRWA relies on volunteers and municipal partnerships to help fulfill our mission to clean up and protect the Neponset River, its tributaries, and surrounding watershed lands.

Our Community Water Monitoring Network (CWMN) involves the help of dozens of dedicated volunteers, who take water samples from May through October from 41 sites across the Neponset River Watershed.

The water quality data gathered from the volunteer samples provides valuable insight into the health of the River and helps to identify where we need to focus remediation efforts.

Click here to view the interactive CWMN Data Viewer.

Our Neponset Stormwater Partnership (NSP) is a regional program that aims to reduce the cost and increase the effectiveness of municipal stormwater management programs through regional cooperation and resource sharing. Partners include the towns of Canton, Dedham, Foxborough, Medfield, Milton, Norwood, Quincy, Randolph, Sharon, Stoughton, and Westwood, along with the Metropolitan Area Planning Council (MAPC).

Residents and business owners can take the following steps to reduce polluted rain runoff:

  • Always pick up after their dog and throw the waste into a trash can.
  • Reduce the use of lawn chemicals.
  • Build a rain garden that naturally filters pollutants.
  • Redirect downspouts toward the lawn, garden, and shrubs.
  • Clean up spills, like fertilizer, pesticides, and motor oil, from driveways and sidewalks.
  • Wash cars on the lawn so that water filters into the grass.
  • Use pervious materials when building walkways, patios, or driveways.
  • Install a rain barrel to capture roof runoff.

Learn more at

If you spot pollution in a waterway or see any dumping, please email or give us a call at 781-575-0354 x 300



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