May/June 2021 Water Quality Report (CWMN)

Read the latest Water Quality Results from the Neponset River Watershed CWMN Program.

Volunteer water sampler, Win Burr, enthusiastically drops off his water samples from Beaver Meadow Brook in June.

Thanks to our Community Water Monitoring Network (CWMN) volunteers, who gave up their early mornings in May and June to take water samples!

E. coli

E. coli is a bacteria that often indicates contamination from human and animal waste. Typical sources include leaking sewer infrastructure and dog waste. High levels of the bacteria associated with this waste can make people sick.

  • In May, 85% of the sites sampled were safe for swimming and all sites were safe for boating.
  • In June, only 53% of the sample sites had E. coli levels safe for swimming.
  • Unquity Brook in Milton had especially high E. coli levels this June.

Of those sites, five failed to meet the bosting standard. E. coli concentrations typically increase from May to June because the bacteria grow faster in warmer water.

Residents can help reduce the amount of E.coli bacteria in the water by always picking up after their dog and throwing the waste in a trash can.

The E. coli results are summarized in the maps and graph below.


Algal growth caused by excessive Phosphorus pollution at Crack Rock Pond, Foxborough, July 2021. Photo by Mike Smith.

Phosphorus is a key nutrient for plants and is present in leaves, pollen, dirt, and some fertilizers.

Unfortunately, when any of these materials wash off of lawns or roads and into storm drains, the phosphorus ends up in streams and ponds. Too much phosphorus can lead to harmful algal blooms, cyanobacteria blooms, and fish kills.

  • In May, 85% of samples collected had healthy phosphorus levels.
  • In June, this dropped to 15%.

Phosphorus pollution is a huge issue for most of the watershed and typically increases by about 60% from May to June. This increase is largely the result of low dissolved oxygen leading to a chemical reaction that releases phosphorus from lake sediments. Another factor is phosphorus-rich organic material such as leaves and pollen washing off of paved surfaces and into storm drains.

You can help reduce phosphorus pollution by supporting investments in green stormwater infrastructure and stormwater utilities in your neighborhood.

The Phosphorus results are summarized in the graph below.

Note levels at NER002 (Crack Rock Pond) are extremely high and could not reasonably fit on the graph (May: 0.365 mg/L, June: 0.591 mg/L)

For comment or questions please contact NepRWA’s Environmental Fellow, Declan Devine

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