Full of crap: Climate change could cause more sewage pollution for rivers, lakes, and beaches

September 4, 2025

By Bhaamati Borkhetaria

On a nice sunny day in Boston, there are usually people out on the Charles River sailing, kayaking, paddleboarding, canoeing, rowing – coming into contact with the water. You’ll likely find children playing, tourists taking a scenic tour around the river to enjoy a view of Boston, and groups of people learning how to sail.  

It looks idyllic and a far cry from the “dirty water” that the Standells sang about Boston in 1966. It’s even come a long way since former Gov. William Weld jumped face-first and fully clothed into the murky water in 1995 as a vote of confidence in the cleanliness of the river.  

But even on those picturesque sunny days when people are enjoying the river, it’s possible that there is still sewage in the water – especially after heavy rainstorms.  

The Greater Boston area has parts of a legacy combined sewer system where both wastewater and stormwater are collected in shared pipes, and during heavy rains, excess flow bypasses the treatment centers where it is supposed to be cleaned. Instead, it is discharged into local water bodies to prevent backups into people’s homes.  

In 1985, the federal government ordered the Greater Boston area to end wastewater pollution of Boston Harbor and its tributaries, including the Charles and Mystic Rivers. Since then, many combined sewer overflow sites – where wastewater is discharged – have been closed. The average annual average discharge volume from combined sewer overflows into the Charles River basin has decreased by 98 percent since 1988.  

Despite major progress, more than 40 combined sewer overflow sites along the Charles, Mystic, Alewife Brook, and Boston Harbor persist – partly because addressing them comes with more complicated engineering challenges and therefore higher costs. Climate change is expected to double or even quadruple the volume of overflow that is dumped into these water bodies by 2050, according to projections from the Massachusetts Water Resources Authority, and the cities of Cambridge and Somerville. These three entities are collaborating on a draft plan – due this December – to address the remaining sites, balancing the rising overflow risks with the significant costs of remediation. 

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