SAUGUS — After elevated levels of bacteria were found in Breakheart Reservation’s Pearce Lake, the lake has now been deemed safe to swim in once again.
As mandated by the Department of Public Health, the Massachusetts Department of Conservation and Recreation conducts weekly water testings.
According to a DCR spokesperson, bacteria making its way into waterfront areas such as beaches and lakes can be common and might occur due to a variety of factors, including rainfall, stormwater outflow, failed septic systems, and nearby wildlife.
When high levels of bacteria are found in the testing samples from bodies of water, signs for visitors are put up informing them that it is currently not safe to swim.
Upon detection of levels of bacteria in the water that are higher than normal, the DCR notifies both state and local boards of health.
As outlined in the DPH guidelines, which the testing is performed according to, the two organisms that are sought as indicators in freshwater, which is present in Pearce Lake, are E. Coli and Enterococci.
Per 100 milliliters of water, no more than 235 colonies of E. Coli can be present in the water, with the average from five tests throughout the “bathing season” not exceeding 126 colonies per 100 milliliters of water.
The number of acceptable colonies in testing for Enterococci is lower than that of E. Coli. There can be no more than 61 colonies per 100 milliliters of water, and the average over a five-test period must not exceed 33 colonies per 100 milliliters of water.
Within 24 to 48 hours of the test in which bacteria is found, an additional test is performed. If the presence of bacteria has returned to a level that is acceptable after the follow-up test, the signage is removed, indicating that swimming in the water is once again safe.
On May 28, there were 1,410 colonies of Enterococci present in a sample of the lake’s water. By May 30, the level of Enterococci had dropped significantly to 79 colonies.
On Wednesday, Breakheart Reservation got the go-ahead to change the lake’s red flags to blue ones, indicating that it is once again safe to swim in Pearce Lake.
