Arlington, MA, February 25, 2026 — At their monthly meeting this afternoon, the Massachusetts Water Resources Authority (MWRA) Board of Directors voted to approve a plan that would ensure the ongoing release of combined sewer overflows (CSOs) to the Mystic River, Charles River, and Alewife Brook for a generation or more. Though the new plans are an incremental improvement over an October 2025 proposal, which was shelved after public backlash, they still fall short of what our rivers and public health deserve.
“The Mystic River and Alewife Brook, just like the Charles, are treasured resources for hundreds of thousands of people across greater Boston,” says Patrick Herron, Executive Director for the Mystic River Watershed Association (MyRWA). “But MWRA is still proposing projects that have us running in place against climate change as opposed to outlining the investments necessary to create a modernized, 21st-century water infrastructure to match our world-class cities. MWRA’s own financial models show that more ambitious plans are affordable, so why are we holding back on solving this problem once and for all?”
The new proposal promises “Zero CSOs in a 2050 typical year” in the Mystic, Charles, and Alewife, but this description gives a rosier picture than the reality bears out. We know that MWRA’s draft plan would ensure the release of CSOs to all three waterbodies, including the Alewife Brook, in some, if not most, years. We also know that 2050 conditions will not last forever. Climate change is bringing bigger, more intense storms that will cause more CSO activations as time goes on.
MWRA, Cambridge, and Somerville have presented alternatives that go further, and these plans are not budget-breaking. In the data they presented, even the most expensive plans would amount to only about a 10% increase above average base MWRA rates – the cost of an extra lunch out every month. And this rate change would be rolled out slowly, over decades. MWRA’s own Financial Capability Analysis found the projects to have “low impact” for even the most ambitious plans.
With approval from the MWRA board, plans will move next to the Massachusetts Department of Environmental Protection (Mass DEP) and to the US Environmental Protection Agency (EPA), which hold the regulatory authority to approve or amend it. As this process moves forward, MyRWA will continue to advocate for the virtual elimination of CSOs.
