March 14, 2023

Avoid Contact with the Charles River in Cambridge and Alewife Brook Through March 16 Due to Potential Harmful Bacteria and Other Pollutants

Public Health Warning in effect through March 16, 2023

People and pets should avoid contact with the lower Charles River,  Alewife Brook, and parts of the Mystic River from March 14-16 due to the release of stormwater mixed with sewage into the river.

The release of mixed stormwater and sewage—known as a “combined sewer overflow (CSO)”—is needed to prevent contaminated water from backing up into homes, businesses and city streets.  

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.

These CSO releases occurred today and the warning is in effect through Thursday, March 16:

  • A release occurred near Magazine Beach (Cottage Farm), which began at 10:18 a.m. and lasted 3 hours and 14 minutes.
  • A release occurred near Eliot Bridge (CAM007), which began at 5:56 a.m. and lasted 4 hours. The impacted areas of the Charles River may include the Cambridge and Boston sides of the river from the Eliot Bridge (near Mount Auburn Hospital) to the Museum of Science.
  • A release occurred in Alewife Brook Reservation in North Cambridge (CAM401A), which began  at 7:11 a.m. and lasted 5 hours and 35 minutes. Impacted areas may include 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 (near the Mystic River State Reservation).

The public should avoid contact with impacted areas of the Charles River, Alewife Brook, and Mystic River for 48 hours from the time the overflow ends because of increased health risks due to bacteria or other pollutants carried by the stormwater, such as fertilizers or pesticides. Contact with this water can make you and your pets sick.  Avoid paddle boarding, boating, fishing, or other activities that can bring you in close contact with this water. 

For more information, go to the Cambridge Department of Public Works’ CSO events web page ( Additional information is available on the Massachusetts Water Resources Authority ( and City of Somerville’s websites ( Translations of the web pages are available using the translate box along the top of the websites. 

The City of Cambridge continues to make major improvements to the city’s sewer and stormwater systems.  As a result, there are fewer CSO events than in the past, but they still occur after heavy rain.  To learn more, please visit:  

If you have questions about potential health risks from contaminated water, contact Sam Lipson at the Cambridge Public Health Department at [email protected] or 617-665-3838.

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ለበለጠ መረጃ፣ እባክዎን ድህረ ገጾቹን ይጎብኙ። በቀኝ በኩል በላይኛው ጥግ ላይ ያለውን “Translate” የሚለውን ሳጥን ይፈልጉ እና ቋንቋዎን ይምረጡ 

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