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Public Health Warning Issued Related to Recent Sewage Discharge

BOSTON – September 18, 2023 – The following is a public health warning related to a recent sewage discharge, also known as a combined sewer overflow CSO). State regulations require local public health departments to provide notice to the public when these discharges may create a risk to public health, including when a discharge lasts for more than two hours.  

Massachusetts Water Resources Authority Outflow MWR203, located at Prison Point in Charlestown near the Charles River Dam, experienced a discharge or overflow starting on Monday, September 18th at 2:45pm, creating a potential public health risk. The overflow is ongoing, and this advisory will expire 48 hours after the overflow has ended. Note that this data is preliminary and may be revised. Check the Massachusetts Water Resources Authority website here and the Boston Water and Sewer Commission here for current updates.   This event impacts the waters of the Upper Inner Harbor and Charlestown.

The public is advised to avoid contact with affected water bodies for at least 48 hours after a sewage discharge or overflow, during rainstorms, and for 48 hours after rainstorms end, due to increased health risks from bacteria or other pollutants associated with urban stormwater runoff and discharges of untreated or partially treated wastewater.  

A combined sewer overflow occurs when a large storm overwhelms the combined sewerage system causing rainwater to mix with wastewater and discharge to a nearby water body. This prevents sewage backups into homes and businesses.  

More information about CSOs and public health is available at   



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