A half-dozen bacteria data collection sites in three New Canaan rivers turned up slightly elevated levels of E. coli following tests that commenced this spring, officials said last week.
The results could indicate nitrogen in the water supply, according to members of the New Canaan Conservation Commission.
“I am not looking at these streams and rivers as drinking water supply, but I am looking at them from a wildlife and biodiversity standpoint and I am trying to get a better feel on, are they getting too much nitrogen in the water?” Commission Chair Chris Schipper said during the appointed body’s Aug. 13 meeting, held via videoconference. “I assume E. coli is also related to nitrogen. And are there other chemicals getting into the water supply?”
The Commission referred to data collection and water quality tests from Harbor Watch, part of Westport-based nonprofit organization Earthplace. The group presented to the Commission last spring. The town approved a total of $25,000 for the professional services in the Commission’s budget for the current fiscal year. Harbor Watch has been collecting data at sites along the Noroton, Rippowam and Silvermine Rivers since May. Two testing sites in each waterway showed “slightly elevated” levels of E. coli, the data show, with nine other sites on track to meet a state guideline.
According to marine ecologist Dr. Sarah Crosby, director of Harbor Watch, most of the testing sites in New Canaan “showed only a slightly elevated value relative to the threshold set by the state.”
For each site, Harbor Watch compares a season-long data set—typically eight to 10 samples per site—to two state criteria for recreational use of a waterway, Crosby said in an email to the Commission summarizing results to-date. The organization looks at the “geomean,” which measures “CFU/100 mL” or colony forming units per 100 mL, a measurement for bacteria concentrations. The state Department of Energy and Environmental Protection criteria calls for less than 126 CFU/100 mL for the E. coli geomean.
“Based on the data collected so far, we do not recommend track-down testing for pollution source detection at this time,” Crosby said. “However, we will continue to monitor the data closely and add additional testing sites as needed should elevated bacteria concentrations be observed.”
Commissioner Linda Andros noted at the meeting that testing of local ponds has shown “a lot of nitrogen in the water, and the nitrogen changes all of the ecosystem.”
“Not only the pond, but the pond shores, which are separate ecosystems,” she said. “So it’s important. I think that the use of pesticides is very important to measure as we move toward a healthier, greener planet.”
Schipper noted that where he lives, near a stream, he can hear frogs at night, but not so when he’s walking in the evening at Bristow Bird Sanctuary (one of the elevated E. Coli sites was the Noroton River along Frogtown Road).
“I don’t get quite the same noise level, which makes me wonder is the water in there catching much more residual pollution and pesticides,” he said.
Town Councilman Sven Englund, a guest at the meeting, noted that Bristow gets stormwater runoff from downtown New Canaan.
Schipper said the Commission would ask Harbor Watch what additional testing New Canaan could pursue to get more detailed information on bacteria levels in its water.
New Canaan residents, please consider cutting back on your use of fertilizer on your lawns. Most fertilizer contains high levels of nitrogen which is clearly harmful to our water supply and to our wildlife who use this as their water source.
New Canaan Town Officials, please consider cutting back on the use of pesticides in our for the same reason as cited by Ms. Fagerstal. The run-off of water during heavy rains discharges into storm drains and into our waterways.