Marblehead Beach Remains Closed To Swimming

MARBLEHEAD, MA — Grace Oliver Beach in Marblehead remained closed to swimming Thursday morning after the latest bacteria testing showed its geometric mean over the past two weeks remained above acceptable levels.

The beach was closed Friday, along with Gas House Beach, for elevated levels of Enterococci in recent tests. Gas House Beach has since reopened, but Grace Oliver remains closed with additional testing planned for Thursday.

According to the Centers for Disease Control and Prevention: "Enterococci are a type of bacteria mainly found in the gut and feces of animals. They are used as an indicator organism for groundwater because they closely link water quality with contamination by human feces. Some enterococci can cause disease in humans."

The average of Enterocci colonies exceeded the maximum of 35 per 100 milliliters at Grace Oliver Beach. The geometric mean at Grace Oliver was 76.58 through the most recent test on Wednesday after a spike around June 23.

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(Scott Souza is a Patch field editor covering Beverly, Danvers, Marblehead, Peabody, Salem and Swampscott. He can be reached at Scott.Souza@Patch.com. Twitter: @Scott_Souza.)