Under the Massachusetts Department of Public Health (MDPH) regulations for beach guidelines, beach operators must test all public ocean beaches for bacteria each week using the enterococcus indicator organism. Under that guideline beach sampling will be weekly during the swim season (June to September). Single-sample test results cannot exceed a specified number of bacteria colonies per 100/milliliter sample. If they exceed the specified levels the beach is required to be closed to swimming. The maximum contamination is 104 enterococci/100 milliliter for ocean waters. There are 6 recreation water bodies that the health department tests:
Black Rock Beach
Cohasset Yacht Club
Cohasset Sailing club
When the beach is closed in the harbor, the Harbormaster will post a yellow flag for closed and all other locations will have a sign posted. The Harbor is automatically closed after 0.5 inches of rain within a 24 hour period of time.