Updated 12:34 pm, Friday
The Chilmark board of health reported Friday that the pond at Lucy Vincent Beach (LVB) is open.
The pond was closed Thursday after water test results were above the state limit of 104 colony forming units per 100 milliliters of water (cfu/100 mil) of enterococci bacteria.
Result from water samples tested Wednesday were 214. On Friday, Marina Lent, board of health administrator/inspector, said the number was 41.
There were no reported problems at Lucy Vincent Beach test result (10), and Squibnocket Beach (less than ten).
Lucy Vincent Pond has no swimming beach and sits to the west of Chilmark Pond behind the beach dunes. It is connected to brackish Chilmark Pond, which is frequently opened to the ocean, by a weed-choked channel.
Last week, health officials in Chilmark and Oak Bluffs reopened beaches closed earlier due to water samples above the state minimum for enterococci bacteria, an indicator organism for more dangerous bacteria.
Although recent single tests fell within state standards, both towns 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.
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 geometric mean trend. The major factor was an exceedingly high result, received July 5, of 2,420 cfu/100 mil, the limit of the measurement chart.
While the single-day result 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.