Charles River Sewer Overflow Plan

At a glance

What: the City's long-term plan to end combined sewer overflows (storm and sewage mixed, discharged to the Charles River), developed with the MWRA and Somerville. The City Manager's December 2025 report responded to a September 29, 2025 Council vote calling for a more ambitious and collaborative approach (Order 309 in the speakers' reference). It describes a "Hybrid 2" control plan whose pieces include a tank at 135 Sherman Street, part of an integrated system of about 5.3 million gallons.
Where it stands: report placed on file 9-0 on December 22, 2025. The State granted a 120-day extension for the draft plan to Cambridge, the MWRA and Somerville; the final plan is still due December 31, 2026.
Next: a City advisory committee (initially called a CSO commission; a Stormwater Management Advisory Committee with a wider scope, starting with CSOs in its first six months) to convene in January 2026; draft stormwater regulations out for public comment in the first months of 2026; cost share with MWRA and Somerville still to be worked out.
Related: the MWRA's separate proposal for a tank at Magazine Beach, see Magazine Beach CSO Storage Tank (October 2026).

Deputy Commissioner Nardone (Public Works) said the extension came after the memo. The Cambridge piece will cost "hundreds of millions of dollars," depending on the design storm (a five-year storm or larger); much of the infrastructure would sit on land the City does not own; the cost share with the MWRA and Somerville is not settled.
City Engineer Wilcox: since 2000 the City has built 13 stormwater holding tanks alongside sewer separation, and none could be sized to a 25-year storm because of space in the public way; the memo concluded that building overflow control to a 2050, 25-year storm level may provide limited public health and water quality benefit given widespread flooding, though it would still be modeled in the draft plan.
Stormwater regulations are being revised to match the new zoning density; the old trigger of 10 parking spaces no longer works, and Public Works reviews about 300 building permit applications a year for stormwater.
Nolan asked for the draft plan to include costs and benefits (health, recreation, flood mitigation), for the advisory committee recruitment to start soon, and for the regulations to be brought back to the Council.
Toner asked for the total cost and funding source and for regular updates to the public ("one huge ticket item"); Zusy welcomed putting storage on private developers, worried about density in wet areas, asked about MWRA's reported $2.1 billion of new borrowing capacity; Nardone said the cost-share analysis will follow.

Anas El-Turabi (neighbor of 135 Sherman Street) asked the Council to accept the report with an explicit recommendation that the new committee include at least one seat for abutters and residents near the facility, and said the December 11 community meeting lacked remote access and translation. Michael Siegel, a long-time neighbor, said at a meeting a few weeks earlier neighbors were told the project was inevitable, after years of being told there were no plans for the parcel. Nolan supported the abutter seat.
Emily Norton (executive director, Charles River Watershed Association) criticized the memo: the logic for not designing to the 2050 storm, the stormwater rules (Waltham and Watertown are stronger), the absence of green infrastructure from the long-term plan, and outreach she described as meetings "for the sake of meetings." She offered to help draft a scope for the cost-benefit accounting and hoped to sit on the new committee.

Report from the City Manager placed on file 9-0 on a motion by Nolan; discussion with Public Works; three public speakers.