The Jaffrey Recreation Department is reporting high levels of E. coli bacteria at Shattuck Beach on Thorndike Pond, following water testing.
While the beach is not currently closed to residents, swimming and contact with the water are not advised. Advisories have been posted at the beach.
Recreation Director Samantha Bontempo said water at the beach is tested regularly in two spots twice a month. The most recent round of testing found 167 MPN (Most Probable Number) per 100 milliliters in one spot and 117 MPN per 100 milliliters in the other.
E. coli in lakes can result from fecal contamination. Primary causes include wildlife populations near the shore — particularly waterfowl — leaking septic tanks or sewage infrastructure near the shore, or fertilizer entering the water through stormwater runoff.
Bontempo said the cause of the spike is not known but may be related to runoff from a recent heavy rain event.
The water at Shattuck Beach was expected to be retested Friday and regularly thereafter until E. coli levels dissipate. Swimming advisories will remain in effect until then.
Swallowing water with high levels of E. coli can cause illness, with symptoms including nausea, vomiting, diarrhea, stomach cramps, fever and headache.
Children, older adults and people with weakened immune systems are at greater risk.
Steps to reduce risk include showering after swimming or contact with the water, keeping children from swallowing lake water, and keeping pets out of the water and away from the beach area.
Water quality will continue to be monitored, and follow-up testing will determine when the water is safe for swimming again. Notices will be posted on the town website, the town’s Facebook page and the Parks and Recreation Facebook page.