Arlington Warns Residents To Avoid Alewife Brook After Sewer Overflow

ARLINGTON, MA — Town officials are warning residents and pets to stay out of portions of Alewife Brook after Cambridge reported a combined sewer overflow following heavy rainfall Wednesday.

The report involved CAM401A, a discharge point upstream of the confluence of the Little River and Alewife Brook and upstream of the Route 2 Bridge. According to the Massachusetts Department of Environmental Protection, combined sewer overflows can occur when heavy rain overwhelms a sewer system, causing stormwater to mix with wastewater and discharge into a nearby river or lake. They can also occur because of obstructions or breaks in sewer lines.

The Arlington Health Department is advising residents and pets not to swim, wade or stand in the water because of possible health risks from bacteria and other pollutants associated with urban stormwater runoff and combined sewer overflows.

The latest overflow followed a day of steady rainfall across the region that caused localized flooding in several communities. It also came two days after the Massachusetts Water Resources Authority presented the Arlington Select Board with proposed solutions aimed at reducing the decades-long problem of combined sewer overflows affecting Alewife Brook and nearby neighborhoods.

The overflows originate from combined sewer systems in Cambridge and Somerville, where stormwater and wastewater share the same pipes. During periods of heavy rainfall, the systems can exceed capacity, sending excess flow into waterways such as Alewife Brook to help prevent sewage from backing up into streets, homes and businesses.

Town officials have received multiple overflow notifications this summer following heavy rain, including several earlier this month involving the same Cambridge outfall. The recurring overflows have prompted continued advocacy from Save the Alewife Brook and ongoing discussions among Arlington officials, Cambridge, Somerville and the MWRA about long-term infrastructure improvements.

MassDEP has required public notification of combined sewer overflows since July 2022, with municipalities notifying residents when discharges occur so they can avoid contact with affected waterways.

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