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Public advised to avoid Boston Harbor following sewage overflow

The harbor seen after sunset last month from East Boston.Michael Dwyer/Associated Press

The Massachusetts Water Resources Authority advised the public Thursday to avoid a section of Boston Harbor for at least 48 hours following an overflow of sewage related to Wednesday’s rainstorm.

The area of concern is part of the inner harbor, upstream of North Washington Street Bridge, the authority said. Interacting with affected waters can cause illness and creates a potential public health risk, it said.

Boston received two-thirds of an inch of rain by midnight Dec. 1, according to the National Weather Service. Heavy rain can overwhelm parts of the city’s sewerage system. When this happens, rainwater mixes with wastewater and discharge to a nearby body of water, preventing sewage backups into homes and businesses.


The MWRA advised residents avoid water activities like swimming, boating, and fishing as well as any contact with affected waters during rainstorms and for 48 hours after a rainstorm ends.

“Massachusetts Water Resource Authority owns combined sewer outfalls that discharge a mixture of stormwater and sewage to the Charles and Mystic Rivers, Alewife Brook, and Boston Harbor,” according to its website. When overflow occurs at an MWRA-owned outfall, there is a notification displayed on a map on its website.

The authority’s Prison Point combined sewage overflow facility in Charlestown, as well as two Somerville Marginal CSO Treatment Facility Outfalls also experienced discharge of sewage treated within the last two days Nov. 30, according to the map on the website.

Data about the sewage overflow are preliminary and may be updated, the MWRA said in a statement. The public can monitor updates on the status of the sewage overflow on the authority’s website.

Katie Mogg can be reached at katie.mogg@globe.com. Follow her on twitter @j0urnalistkatie