October 2020 Water Quality Report (CWMN)

Moderate rainfall leads to above-average October water pollution

On October 8th, NepRWA’s team of volunteers left their homes under the cloak of night, an hour before sunrise. Braving the darkness and chilly temperatures they scrambled down to the banks of the Neponset River and its many tributaries to collect the last water samples of the 2020 sampling season.

Read on to learn what their work has revealed about water quality in the Neponset River Watershed this October.

Long-time CWMN volunteer, Jim Cianci, tests water samples.

E. coli Results

E. coli is a bacteria that often indicates contamination from human and animal waste. The bacteria associated with this waste can make people sick.

In October, 50% of samples met the EPA “safe for swimming” standard while 70% met the “safe for boating” standard.

Typically, in October, 71% of samples meet the swimming standard. The lower than average results this year are likely due to the 0.11 inches of rain that fell within 24 hours of collecting the samples. The precipitation washes bacteria into the river through the stormwater system and contributes to leaking septic systems and wastewater infrastructure.

High E. coli levels continue to impact Pine Tree Brook, Unquity Brook, Germany Brook, and Meadow Brook

Residents can help reduce the amount of E.coli bacteria in the water by always picking up after your dog and throwing the waste in a trash can — and by making sure that your septic system is working properly.

Phosphorus Results

Phosphorus is a key nutrient for plants and is a large component of most fertilizers. Unfortunately, when fertilizer washes off lawns it can end up in streams and ponds. Too much phosphorus can lead to harmful algal blooms, cyanobacteria blooms and fish kills.

In October, 43% of the sites sampled had healthy levels of Phosphorous. These levels are slightly higher than the typical October however they are still within the range of what we typically see this time of year.

For tips on how to reduce your phosphorus impact on the River visit www.yourcleanwater.org/lawn

How do these results compare to past October samplings?

The plot below illustrates the percent of samples meeting the standards for healthy levels of E. coli and Phosphorous over the last 13 Octobers. Larger values indicate better overall water quality.

We see that both the E. coli and Phosphorous compliance rates were low compared to the average due to the precipitation prior to sampling. However, the Phosphorous levels were within the expected range while the E. coli levels are uncharacteristically low for October. For comparison purposes, 2008 and 2019 also received a similar amount of precipitation prior to the sampling event and exhibited lower than average E. coli compliance.

If you have any questions about this report, please contact NepRWA Environmental Fellow, Declan Devine at devine@neponset.org

As always, thank you to our tireless team of volunteers who make the collection of this invaluable data possible!

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