Alewife Brook Community CSO Elimination Plan web version

Save the Alewife Brook’s Community plan responds to the public health hazard of sewage flooding in the Alewife Brook area by proposing a feasible solution to virtually eliminate CSOs. It integrates Cambridge’s long-established CSO strategy at Alewife Brook with sewer separation and Green Stormwater Infrastructure. In Somerville, it incorporates six projects from the Somerville Citywide 2022 Flood Mitigation and Water Quality Improvements plan and 100 acres of sewer separation, as well as Green Stormwater Infrastructure. It proposes a large underground storage tank and Green Stormwater Infrastructure at the MBTA Alewife station for MWRA’s Little River / Alewife Brook outfall (MWR003). The Community Plan requires, at a minimum, that Green Stormwater Infrastructure should be installed to manage 1-inch of rainfall from 10% of the impervious surfaces in Cambridge and Somerville neighborhoods that drain to Alewife Brook. New constructed stormwater wetlands would attenuate stormwater flows to reduce flooding, while reducing phosphorus in stormwater.

The estimated time to complete the projects in this plan is 15 years. The preliminary cost estimate is $450 million, including the cost of river restoration. It would be funded by the Massachusetts Water Resources Authority.

The Community Plan is different from the MWRA’s plan. MWRA’s plan proposes a reckless waste of $340 million on tanks and a tunnel. MWRA’s tanks and tunnel are not large enough to hold discharge volumes from small 2-year storm events. A single 5-year storm event would result in 15 million gallons of untreated sewage pollution dumping into Alewife Brook. Once undersized tanks and the tunnel are built, they are not easily expandable at a reasonable cost. That means that this plan is not resilient to Climate Change.

MWRA’s plan would continue to flood neighborhoods, homes, yards, parks, and our bike path with nasty sewage. MWRA does not care about public health.

The Community Plan was presented at the January 11, 2026, Community CSO Meeting* in North Cambridge. It was attended in-person and online by 171 community members and area legislators, where it received positive feedback.  Here is a video recording of the January 11, 2026 Community CSO Meeting held in North Cambridge: https://youtu.be/y7tzcgus8SI