The Massachusetts Water Resources Authority is leaning toward a plan that puts it on a trajectory to keep putting sewage into the Charles and Mystic Rivers over the coming decades — though less than it does right now.
The MWRA and the cities of Cambridge and Somerville are developing new plans to control combined sewer overflows into the rivers. These happen when there’s too much runoff from heavy rains, and untreated stormwater and sewage flow into waterways. They can be prevented with costly upgrades, like separating the systems, building underground runoff storage or installing wider pipes.
Advocacy groups are disappointed by the sewer infrastructure plans presented at a MWRA board meeting Wednesday.
The recommended upgrades allow for a limited number of sewage overflows in some Cambridge and Somerville locations.
“The most aggressive infrastructure improvements that they have showed us would either take care of the problem or largely take care of the problems,” said Emily Norton, the executive director of the Charles River Watershed Association.
But those aren’t the plans the MWRA ultimately picked.
Cambridge City Councilor Patricia Nolan told GBH News she appreciates the city’s plans to improve a problematic part of Alewife’s sewer system by installing an underground tank to store runoff. But she added in an email, “We want there to be no sewage overflows and stand united in wanting an accelerated timeline for addressing the [combined sewer overflows].”
With this more limited plan, the MWRA would also pursue what’s known as reclassification. The water quality in those portions of the Charles and Mystic Rivers could be legally downgraded and categorized as sites that are occasionally closed to swimming and other recreation because of untreated sewage discharges. Right now, they are generally safe for recreation, irrigation, drinking water and wildlife habitat.
Norton worries about downgrading the classification.
“We would lose the legal leverage that we have now to force MWRA and Cambridge and Somerville to make further improvements to the river. And we’re not OK with that,” she said.
Patrick Herron, executive director of the Mystic River Watershed Association, said his organization and others were “really disappointed” by the proposals. He said they want to see these combined sewer overflows eliminated and, like Norton, the most rigorous infrastructure improvements.
He worries that sewer and stormwater pipes couldn’t accommodate the huge amount of water expected in a 25-year storm event by 2050 — the highest benchmark used by the water authority in planning for climate change.
MWRA and the cities of Cambridge and Somerville must submit an updated plan to state and federal regulators by December 31. It will be open to public comment starting in January, before it is finalized in early 2027, and would require approval by the MassDEP and U.S. Environmental Protection Agency.
System upgrades will be paid for, in part, by higher water bills to customers.
In a statement to GBH News, the MWRA said, “the draft plan as presented reflects a responsible approach that balances potential environmental benefits with rate impacts to all MWRA customer communities.”
The price tags between plans vary. For example, the MWRA’s recommended plan for sites along the Charles would be $360 million.
What Norton and the CRWA want is a plan with a $2.6 billion cost, although Norton notes the MWRA can bond projects over decades and there could be future federal funding to support these projects.
“They’re more expensive,” she said. “So that’s a question for the public, is that what you want? Public dollars going to getting sewage out of our rivers? My guess is that yes, that is what people want.”
