Sewage overflows in Boston and Cambridge trigger warnings

Heavy rain over the weekend caused a number of sewage overflows in Boston and Cambridge, prompting authorities to alert the public to the dangers of contaminated water.

State regulations require local public health departments to alert residents whenever a combined sewer overflow (CSO) event may create a public health risk.

A CSO occurs when a large storm overwhelms a sewer system. Rainwater mixes with sewage and is discharged into nearby water bodies so that homes and businesses do not experience sewage backup.

The spillover events in Boston and Cambridge were not directly related. Both were simply caused by heavy rains during the same period, a Boston Public Health Commission spokesperson said.

Three locations in Boston have experienced CSO events, and public health advisories are due to expire on Tuesday.

A sewage outlet located at Porter Street in East Boston overflowed at 11:40 p.m. Saturday. It ended Sunday at 1:55 a.m. Another outing located in the Fort Point Channel at Albany Street occurred Sunday at 12:20 a.m. It lasted until 3:25 a.m. A third CSO occurred in the Upper Inner Harbor, above the North Washington St. Bridge at 12:20 a.m. Sunday. it lasted until 3:25

“The public is advised to avoid contact with affected water bodies for at least 48 hours after a sewage spill or overflow, during thunderstorms, and for 48 hours after thunderstorms end, due to increased health risks from bacteria or other pollutants associated with urban stormwater runoff. and discharges of untreated or partially treated sewage,” Boston officials said in a statement.

Cambridge officials are warning people to keep themselves and their pets away from Alewife Creek and parts of the Mystic River until Tuesday.

Two CSO events occurred overnight on Saturday evening and Sunday morning. The two happened at Alewife Brook Reserve in North Cambridge, officials said.

Alewife Brook and Little River in Cambridge, Somerville and Arlington could be affected, as well as portions of the Mystic River from the intersection of Alewife Brook Parkway and Mystic Valley Parkway in Somerville to the Fellsway/Route 28 bridge in Medford.

Paddleboarding, boating, fishing, and other activities that can bring you closer to the water should be avoided at this time. Cambridge officials have recently been working to control CSO events, and the frequency of such events is decreasing, officials said.