Updated 3:30 pm, Thursday, August 18
West Tisbury announced Thursday morning that Lambert’s Cove Beach is open to swimming following a closure Wednesday due to high levels of bacteria. Seth’s Pond remains closed.
In Oak Bluffs, Medeiros Cove, on the Oak Bluffs side of Lagoon Pond near Sailing Camp Park was also reopened for swimming, after a water sample taken Wednesday met both state standards for water quality.
Island health agents in three towns closed beaches on Wednesday after water quality tests detected unsafe levels of bacteria in the water. Heavy rain Monday is the likely cause of the unsatisfactory test results.
Lambert’s Cove Beach and Seth’s Pond in West Tisbury, Medeiros Cove near the Sailing Camp in Oak Bluffs, and Chilmark Pond in Chilmark were closed Wednesday to swimming.
Water taken at those sampling points all tested higher than the allowable limit of enterococci bacteria. Enterococci are an indicator organism that signal the presence of other harmful bacteria.
State health regulations require the closing of ocean beaches if the bacteria amounts exceed 104 colony forming units per 100 millilitres (cfu/100 ml) of sample water.
Water samples collected Monday, August 15, showed Chilmark Pond with 400 cfu/100ml. Lambert’s Cove, at the north sampling point, tested at 280, and Medeiros Cove at 150. All other beaches on the Island tested well below the allowable limits.
The National Weather Service recorded 1.75 inches of rain on Martha’s Vineyard the day health agents collected the samples. State health officials said heavy rainfall often contributes to beach closings, when bacteria wash from roads and beaches into the ocean.