The Eliot Bridge near Mount Auburn Hospital on the Charles River, seen in June 2011. (Photo: Scott Dexter via Flickr)

For the second time this winter, people are warned to avoid contact with local bodies of water due to the presence of sewage in stormwater overflow.

Humans and pets should stay away from, the lower Charles River, Alewife Brook and parts of the Mystic River through Thursday, according to Cambridge’s departments of public works and public health.

Releases of mixed stormwater and sewage – known as a combined sewer overflow – are needed to prevent contaminated water from backing up into homes, businesses and city streets. Overflows Tuesday from a late-winter storm included releases near Magazine Beach, which began at 10:18 a.m. and lasted three hours and 14 minutes; near the Eliot Bridge near Mount Auburn Hospital, which began at 5:56 a.m. and lasted four hours; and in the Alewife Brook Reservation in North Cambridge, which began at 7:11 a.m. and lasted five hours and 35 minutes.

The Charles River may be affected by the Eliot Bridge area release down to the Museum of Science. The Alewife area release could affect the Alewife Brook and Little River in Cambridge, Somerville and Arlington, as well as the Mystic River from the intersection of Alewife Brook Parkway and Mystic Valley Parkway in Somerville to the Fellsway/Route 28 bridge in Medford.

Avoiding the water for 48 hours from the time the overflow ends decreases health risks from bacteria or other pollutants carried by the stormwater, such as fertilizers or pesticides, said Suzy Feinberg, the city’s public information officer for health.

Contact with the water can make you and your pets sick, health officials said, calling for people to avoid paddle boarding, boating, fishing or other activities that could lead to contact. 

There was another two-day warning starting Jan. 26 about contact with water potentially tainted by an overflow.

Major work is underway to prevent the overflows; residents from more than a half-dozen communities learned a new timeline for the work at a Dec. 15 meeting organized by Cambridge and Somerville governments and the Massachusetts Water Resources Authority. A draft plan due by June 2023 and a final plan sue by December 2023 have been delayed by three years for more public input and analysis, health officials said.

This post took significant amounts of material from a press release.