Bacteria Levels Keep Marblehead Beach Closed For Swimming 2 Weeks

MARBLEHEAD, MA — Grace Oliver's Beach in Marblehead remains off-limits for swimming into a third week after recent tests showed sustained unhealthy bacteria levels.

The latest test conducted on Wednesday showed the enterococci colonies were still twice the amount allowable under state guidelines.

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 geometric mean for the last five samples should not exceed 35 colonies per 100 milliliters over a five-test span. The latest test came back at 74 colonies with a five-test mean of 106.19.

Marblehead Director of Public Health said additional samples will be collected for testing later on Friday.

Gas House Beach was also closed with Grace Oliver's Beach on July 2 but has since reopened.

Sandy Beach in Danvers was also closed this week because of high bacteria levels from the stormwater runoff from this week's heavy rains.

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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.)