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.
In the meantime, advocates for eliminating the combined sewer overflow sites entirely – including the river watershed associations – are pushing for the plan to be ambitious, while others are pushing for a plan that prioritizes affordability.
“If this new long-term control plan just has some sort of incremental reductions or makes things a little bit better, that’s going to be a big problem because climate change will just reverse those efforts,” said Julie Wood, climate resilience director at the Charles River Watershed Association. “We’d like to see essentially the combined sewer overflows eliminated because that’s really the only way you won’t start to go backwards.”
Wood’s nonprofit is running a campaign with the slogan “Cut the Crap” with poop emojis on posters and costumes to get raw sewage out of the Charles. They have put up signs on MBTA trains and a large banner on the pedestrian bridge over the Massachusetts Turnpike in Allston.
“We need to end this problem,” said Wood. “The Charles is a beloved resource. People should be able to use it without worrying about getting sick. As our climate changes and it gets hotter, people should be able to swim there.”
At a public meeting in January, the MWRA, Somerville, and Cambridge presented several proposals to tackle the remaining overflows. The projects presented have timelines that span 40 to 50 years and could cost up to $4 billion, depending on which alternative is chosen.
Matt Romero, the head of the MWRA advisory board, called for an approach that would be the least cost to sewage ratepayers.
“If we could wave a magic wand and make all the combined sewer overflows disappear, we obviously would,” said Romero. “But we live in the real world. And these are real dollars from real families and real rate payers. What we really need to always take into account is looking at what level of control [over the combined sewer overflows] that is going to be the right balance for the dollars that are being spent.”
Wood said that it is possible that funding for the remaining combined sewer overflows can be secured from sources other than ratepayers like state-issued bonds.
In July, wastewater flowed into the Charles twice, and both occurred during rainfalls with less than an inch of rain. On August 14, there was another alert that wastewater went into the river.
Mark Jacobson, vice president of Charles River Recreation, which rents boats on the Charles and Mystic, offers boating classes on both rivers including a class that teaches people how to turn a kayak right side up if it capsizes. That involves being fully submerged in the water.
He said that overflow events and poor water quality caused by cyanobacteria have meant his company had to turn customers away and reschedule bookings.
Jacobson said he sees people out on the river the next day after overflow events. Public health officials recommend avoiding contact with contaminated water for 48 hours after an overflow event because there might still be a risk of bacteria and other pollutants.
“Very few people know about combined sewer overflows,” said Jacobson. “People figure that this is many years after the Clean Water Act and are surprised. They really don’t expect that that’s happening in Massachusetts in 2025.”
Even with the occasional overflows, the Charles River is a relatively clean body of water in comparison with other places around the state. Across Massachusetts, there are about 190 remaining overflow sites, and many are located within lower-income communities. In the municipalities that have an overflow site, 85 percent of the total population lives within an environmental justice area, according to the Department of Environmental Protection
Research has shown that exposure to waterbodies following combined sewer overflow events can result in public health issues. A 2024 study focusing on the Merrimack Valley, an area with more than 30 remaining combined sewer overflow sites, found that these events are linked to an increase in emergency department visits due to acute gastrointestinal illness.
Nathan Sanders, a data scientist affiliated with the Berkman Klein Center for Internet and Society at Harvard University, has done research on how low-income communities face an increased risk of exposure to sewage. He points out that other parts of the state haven’t made nearly the progress that the Charles has.
“There are many more water bodies, beaches, rivers, and lakes, around Massachusetts that don’t yet enjoy the same water quality that the Charles does,” said Sanders. “Environmental justice communities experience a significantly higher burden of sewage pollution than comparable watersheds that have whiter and richer and more English-speaking demographics. That is the state of things today after having a decade of really substantial investment into controlling sewage pollution. And so that’s what I think needs to change.”
The state tried to address the lack of public information in 2021 with a law that required the operators of the combined sewer overflow sites to notify the public with alerts when untreated sewage is released into the water. Through that law, the state began collecting more robust data on combined sewer overflow events in mid-2022 and compiling an annual report.
In 2023, which was a particularly rainy year, there were 606 overflow events where 2,847 million gallons of untreated sewage were dumped into water bodies across the Commonwealth. In 2024, there were far fewer events – 137 overflows – and 1,948 million gallons dumped.
Rep. Greg Schwartz of Newton and Rep. David Rogers of Cambridge have sponsored a bill that would require all owners of combined sewer systems to eliminate all combined overflows into the state’s waterways by the year 2050.
“This is not a problem that is going to go away,” said Schwartz, who also enjoys boating on the Charles. “While we’ve had some success in reducing the large amount of the combined sewer overflow problem, it still exists in many of our rivers and waterways. It’s only going to get worse with the climate change impact on weather and specifically rainfall.”
According to Schwartz, setting a 25-year goal of elimination is important to get momentum behind addressing the public health impacts of combined sewer overflows.
“We should be setting our sights and aspirations to achieve a future where we can actually be confident that people will not have to avoid the water when it’s hot, and if they do go boating or swimming, they don’t have to end up in an emergency room,” said Schwartz.
