Updated 3:08 pm, Friday
On a day of broiling heat, Friday health officials in Chilmark and Oak Bluffs reopened beaches closed earlier this week due to water samples above the state minimum for enterococci bacteria.
Late Thursday, Oak Bluffs health official agent Shirley Fauteux reopened Inkwell Beach to swimming. Late Friday morning, Ms. Fauteux reopened Pay Beach, Medeiros Cove near the Sailing Camp, and Eastville Beach near the drawbridge after the results of water tests on July 21 met state standards.
Although recent single tests fell within state standards, Oak Bluffs needed to continue testing until the average of the five most recent samples, called a geometric mean trend, met the state standard. The state requires beaches be closed to swimming if water samples do not meet both standards.
On Saturday, July 16, Ms. Fauteux opened all the town beaches when tests showed they met the daily standard, though they did not meet the geometric mean standard. On Tuesday, July 20, the state ordered Oak Bluffs to close the beaches again, until they meet both standards for water quality.
Friday, one day after Chilmark health officials closed Squibnocket, on Friday the beach was reopened to swimming.
Marina Lent, board administrator/inspector, said the single day results and geometric mean both met state standards. “We’re in the clear for now,” she said in an email to The Times Friday.
The most recent water test for enterococci bacteria, an indicator organism for more dangerous bacteria, taken on Monday, July 18, was well under the state limit of 104 colony forming units per 100 milliliters of water (cfu/100 mil).
However, the average bacteria count did not meet the state standard called “geometric mean trend.” The major factor was an exceedingly high result received on July 5 of 2,420 cfu/100 mil, the limit of the measurement chart.
While the single day standard provides a “snapshot” of water quality, the geometric mean measurement is based on the most recent five test results, and computes trends in water quality over time.
Until Thursday, the board of health was only testing on a weekly basis. Ms. Lent said she was not aware of the need to fall under the geometric mean until she received a call from the DPH.
In an email to The Times Thursday morning, Ms. Lent said DPH official Irena Draksic telephoned the Chilmark board of health Thursday morning, July 21, and said the town is required to post a closure for Squibnocket Beach, because the average bacterial count is still higher than is allowed.
Ms. Lent said, had she known of that requirement she would have begun testing daily after July 5 in order to move the 2,420 result out of the equation. Oak Bluffs encountered a similar situation, closing, reopening and then closing beaches.
The latest results showed a single count of 20 and geometric mean of 27.7 she said.