ANDOVER — A few weeks ago after a heavy storm, Dan Graovac was kayaking near the mouth of the Merrimack River when he began to smell something foul.
The emerald waters had turned the color of mud, with clumps of fecal matter floating on the surface. Graovac, a recreational fisherman, decided it wasn’t a good day to be angling for striped bass.
The sewage had come from waste-water treatment plants along the Merrimack, which provides drinking water to more than 600,000 people as it meanders some 125 miles from central New Hampshire into Newburyport Harbor.
“It’s appalling and crazy — really crazy,” said Graovac, 48, who joined scores of concerned residents at a recent meeting here about the river pollution.
Nearly 50 years after the Clean Water Act, the Merrimack has become one of the most polluted waterways in New England, one of dozens of rivers in the region that are repeatedly inundated with raw sewage from treatment plants overwhelmed by heavy rains.
With rainfall in the area as much as 50 percent above average this year, the Merrimack is expected to be deluged with an estimated 750 million gallons of sewage from the six treatment plants that feed into it — more than it has received in a decade, said Rusty Russell, executive director of the Merrimack River Watershed Council.
On one September day alone, about 120 million gallons of sewage were released into the river, which has the most overflow outlets of any waterway in New England.
While federal and state laws have curbed such pollution in recent decades, sewage discharges remain a persistent problem that could worsen in the coming years, with climate change expected to bring more heavy precipitation to the Northeast.
“Massachusetts prides itself on being a modern, state-of-the-art, progressive state, yet we’re still dealing with a 15th-century problem — sewage in our water,” said Julia Blatt, executive director of the Massachusetts Rivers Alliance. “People think that our sewage spill issues ended when Boston Harbor was cleaned up. They didn’t.”
The court-ordered cleanup of Boston Harbor, polluted for years by sewage, cost billions and took decades. But now the area’s beaches rarely close and the waters are considered relatively pristine for an urban area.
While most communities have separate systems for sewage and rainwater, some older areas have combined sewer systems that handle both at once, leaving them vulnerable to storms and forcing them to release a mix of storm water and sewage to avoid dangerous backups.
Most plants that rely on what are known as combined sewer overflow systems are required by the 1972 Clean Water Act to remedy the problem. But the cost of building holding tanks or overhauling sewer systems is so high that it could take decades.
There are an estimated 772 communities around the country, including 19 in Massachusetts, that routinely discharge sewage into rivers or other waterways, according to the Environmental Protection Agency. In a 2016 survey, the agency found that $271 billion is needed to maintain and improve the nation’s waste-water infrastructure, including $48 billion to replace combined sewer overflow systems.
In Springfield, for example, the city’s water and sewer commission estimated a few years ago that it would cost more than $180 million over the next 20 years to stop its sewage from flowing into the Connecticut River.
Despite the costs, there has been progress.
Over the past 15 years, five communities in Massachusetts have eliminated the old sewer systems, and the state’s number of overall outfall sources is decreasing, according to the Department of Environmental Protection. For instance, on the Connecticut, there were 149 locations in Massachusetts where sewage flowed into the river in the 1990s. Today, there are 54 such outlets left, said Andrea Donlon, steward of the Connecticut River Conservancy in Greenfield.
But the ongoing vulnerability of the system remains concerning. Earlier this month, a sewer line break led to sewage flowing into the Connecticut at a rate of 100 gallons a minute. And some systems that have been upgraded continue to discharge sewage during intense storms.
“We’d like to see a continued, concerted effort to fix these as soon as possible,” Donlon said. “But we understand there are costs and difficulties.”
Given the scope of the problem, environmental advocates have urged lawmakers to require plants to notify nearby residents when they release sewage into the rivers, similar to laws in at least 14 other states, they said.
“People have to know when the river is heavily polluted and they should stay out of it,” said Russell, who has hosted a series of meetings in the area about the dangers of sewage in rivers. “The bacteria can cause havoc with human health.”
Previous notification measures have stalled in the Legislature, but the new proposal is less stringent. It would require treatment plants to notify local health officials and the state departments of Environmental Protection and Public Health within two hours of a release. They would also be required to notify residents who sign up for alerts within four hours.
The state Senate passed the bill over the summer, but it remains in committee in the House.
“It isn’t dead yet, but we’re running out of time,” said state Representative Linda Dean Campbell, a Methuen Democrat, at the meeting in Andover. “We know these storms are going to be more frequent and more intense. Ultimately, we’re going to need to do more than just notify residents.”
Some communities and treatment plants have opposed the legislation, saying the requirements are too onerous.
“We’re opposed to requirements that communities can’t meet,” said Philip Guerin, president of the Massachusetts Coalition for Water Resources Stewardship, which represents the interests of municipalities.
Guerin, the director of water and sewer operations in Worcester, acknowledged that “many communities could do a better job in notifying the public” about sewage releases, but he worried that such alerts risked “misleading” residents that the rivers were clean the rest of the time.
“We just don’t want people to be falsely advised that a river is safe,” Guerin said, noting that runoff from agricultural lands, urban areas, and construction sites can also taint water quality.
Baker administration officials declined to comment on whether they support the notification measure, but they noted that more than $2 billion has been spent in recent decades to reduce the amount of sewage discharged into state rivers, from roughly 9.5 billion gallons a year in the 1990s to less than 3.5 billion gallons in 2015.
Clean water advocates called the towns’ objections absurd and urged them to expedite their infrastructure improvements before climate change and increasing development make the situation worse.
“We shouldn’t expect to be notified that these sewage spills are still happening? That doesn’t seem right,” Blatt said. “As long as billions of gallons of sewage are still flowing into the water, we should strive for something better.”
At the meeting in Andover, Russell cited a 2015 study in the journal Environmental Health Perspectives that found a 13 percent increase in emergency room visits for gastrointestinal issues after heavy rainfalls in the Lawrence area. The study found no similar increase in emergency room visits in neighboring communities that receive drinking water from uncontaminated sources.
He called the increase “statistically significant,” and others at the meeting shared stories about health issues they attributed to the fouled water.
The water from the river remains potable, as it’s treated before making it to faucets. Still, there are considerable health risks.
Graovac no longer eats what he catches near where the Merrimack flows into Newburyport Harbor, the endpoint of all the river’s outfalls. A friend who surfs in the area routinely experiences sinus infections after sewage is released in the river, while another friend’s dog developed lesions on its legs after coming into contact with the polluted water, he said.
He shared pictures of the mud-colored murk surrounding his kayak after a recent storm.
“This needs to stop,” Graovac said. “But short of that, we need to know when it happens.”