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Barnstable County staff weigh in on recent beach closures at Cooks Brook in Eastham

Bacterial growth could have been encouraged by beach erosion

BY AMELIA ROTH-DISHY, The Provincetown Independent | JUL 26, 2023

Photo Credit: Amelia Roth-Dishy, The Provincetown Independent

EASTHAM — The closure of Cooks Brook Beach on the Cape Cod Bay side of Eastham from July 8 to 21 seems to have been caused by natural bacterial flourishing — rather than the usual culprit, contamination from human and pet waste.

In Massachusetts, as in most states, public health officials measure the safety of water at public beaches by testing for enterococci bacteria. Beach water must fall below the single-sample standard, which is no more than 104 colonies per 100ml, and the geometric mean standard, which is no more than 35 colonies per 100ml across the past five samples.

A single test over 35 colonies would not close a beach on its own. But at Cooks Brook, the sample collected by Barnstable County monitors failed on July 6, passed on July 7, and then failed on all five weekdays from July 10 to 14.

Eastham Health Agent Hillary Greenberg-Lemos wrote to town staff during that period that the previous five samples had been “all over the place,” ranging from under the single-test limit of 104 colonies all the way up to 2,000 colonies.

The next week, all five samples passed. By Friday, the geometric mean of the test results had fallen back under 35, and the town could reopen the beach.

To read the article in its entirety, please visit Cooks Brook Beach Reopens After a Two-Week Closure – The Provincetown Independent.