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The double-decker Tobin Bridge—the largest in New England—looms overhead as I bob on the waves of the Mystic River in my 10-foot Tucktec folding kayak. I am paddling the length of one of the most industrialized rivers in America, if not the world, as it flows from the suburban beaches of Medford to the smokestacks and shipping platforms at the mouth of Boston Harbor.

For thousands of years, the Massachusetts, Nipmuc, and Pawtucket peoples relied on the “Missi-tuk,” or Great Tidal River, and the migration of the river herring to sustain their way of life. Beginning in the 1600s, European colonizers filled in surrounding marshland and built dams, shipyards, tanneries, and other industrial infrastructure, releasing untold quantities of toxins, like arsenic and polychlorinated biphenyls, or PCBs, into the watershed.

The Mystic River is cleaner today than it was 50 years ago, thanks in large part to the Clean Water Act, passed 50 years ago this month, in October of 1972. The Act was a game changer for urban waterways like the Mystic, long a dumping ground for industrial waste.

“The Clean Water Act is a foundational environmental law,” says Katharine Lange, policy specialist at the Massachusetts Rivers Alliance. “Having clean water gives us clean forests, clean agricultural products, clean recreational opportunities.”

However, the Mystic River faces new threats today from stormwater pollution, climate change, and the potential for lost protections.

In the days leading up to my expedition, the anniversary project took on new urgency, as the Supreme Court heard oral arguments in Sackett v. Environmental Protection Agency. The case, brought by an Idaho couple and backed by polluting industries and represented by the pro-industry Pacific Legal Foundation, challenges the very definition of a protected waterway. A decision in favor of the Sacketts would not only jeopardize the recovery of America’s rivers, but also make surrounding communities more vulnerable to climate change.

But if the EPA prevails, rivers like the Mystic hold promise of cleaner futures.

The morning I set out from the river’s headwaters in the Mystic Lakes, I see little evidence of environmental degradation. As the river winds through the suburban neighborhoods of Arlington, Medford, and Somerville, I paddle alongside swans and painted turtles sunning themselves on logs. The fall foliage reflects in the water, which is clear enough to see striped fish darting between the lily pads.

In 2021, the main body of the Mystic River earned a grade of B+ on its annual EPA Water Quality Report Card. The assessment is based on how often waters meet bacterial standards for safe fishing, swimming, and boating. This grade is up from the D the river earned in 2007, when the EPA began compiling data.

The improvement is largely thanks to the Clean Water Act, which gave the EPA authority to crack down on “point source pollution” from single, traceable sources, like factories and chemical plants. However, the key to successful enforcement has been the energy and activism of local nonprofits, residents, and volunteers.

Andrew Hrycyna is a watershed scientist at the Mystic River Watershed Association, a nonprofit committed to the protection of the Mystic and adjacent wetlands. He oversees a dedicated corps of 40 to 50 trained volunteers who are on call to monitor the river’s baseline water quality once a month. From 2008 to 2016, the Mystic River Watershed Association partnered with the EPA to organize a hot-spot monitoring program, which dispatched volunteers during heavy rainstorms to collect samples from stormwater outfalls. This real-time data has helped the EPA pinpoint contamination from leaky pipes and illicit discharges, including from the Suffolk Downs Racetrack and ExxonMobil’s Everett Terminal.

“That was a way of our investing effort that wasn’t being done by other people, by government, using our status as nonprofit to contribute data that then got the regulators to start putting pressure of various kinds on municipalities,” Hrycyna says.

Yet many toxic discharges originate far above the Mystic’s main channel, in the smaller tributaries, streams, and swamps that feed into it. This is why the impact of the Sackett case is so potentially devastating; it would narrow the scope of the Clean Water Act to apply only to navigable bodies of water, leaving adjacent wetlands open to contamination or to being filled in altogether.

“Not only are [wetlands] a source for water quantity, they also play a big role in the water quality in the rest of the river,” says Lange of the Massachusetts Rivers Alliance. “Wetlands in particular are really good at filtering off gross stuff from water.”

According to Lange, wetlands also help build climate resilience by protecting surrounding communities from flooding associated with severe storms and rising sea levels. “Swamplands absorb even an abnormal rain or snowmelt in a way that our streets and basements cannot,” she says.

Such precipitation events will only become more frequent and intense as climate change accelerates. Rainfall is already overwhelming Boston’s “combined” sewer system, which transports both raw sewage and stormwater to wastewater treatment facilities. These combined sewer overflows, or CSOs, release excess bacteria, nutrients, and other non-source pollution into the watershed, causing toxic Cyanobacteria blooms and other unsafe conditions.

Once I pass under the Mystic Valley Parkway, the river widens, revealing the Boston skyline. I am nearing the end of my 7-mile journey from the Mystic’s source in the northern suburbs to its mouth at Boston Harbor.

Ahead of me lies the Amelia Earhart Locks, which separates the upper freshwater segment of the Mystic from the lower tidal reaches. I’d been advised to buy an airhorn to get the attention of the lock master, who is unaccustomed to small vessels like mine. But even after repeated blasts, there’s no sign of acknowledgment in the control tower. I end up carrying my 28-pound plastic kayak up and around the dike, to the astonishment of dog walkers on the Assembly Square bike path.

Prior to 1877, this lower portion of the Mystic was surrounded by saltwater marsh. The entire area was then filled in to make way for the loading docks and industrial lots now lining the broad channel between Charlestown and Everett. Above the locks, I had encountered other kayakers, but now the only other vessel in sight is a ferry from the new Encore Casino, which was built atop a former Monsanto Superfund site.

Only a few stray nips and fishing bobs litter the stony shoreline, a testament to the success of the Mystic River Watershed Association’s Trash-Free Mystic initiative. The water doesn’t appear dirty, but rather deep blue and bottomless, the reflections of smokestacks rippling across the surface. This is the Mystic River made famous by the 2003 crime-noir film starring Sean Penn, where intergenerational trauma played out in the shadow of the Tobin Bridge.

By the time I reach Boston Harbor, the sun is sinking behind the city skyline. One week earlier, Massachusetts lawmakers had gathered on the waterfront to mark the 50th anniversary of the Clean Water Act. Speaking at the event, Sen. Edward Markey said, “I look forward to working with the EPA to continue to protect our waterways and expand access to historically underserved communities.”

The new Bipartisan Infrastructure Law appropriates $43 billion for sewer upgrades, wetland restoration, and green infrastructure. That includes rain gardens and bioswales, which filter nutrients from stormwater runoff. But a decision in favor of the Sacketts could undermine these potential solutions. 

Still, more than political promises, what gives me hope for the future of this post-industrial river and so many like it is Hrycyna’s quiet army of tireless volunteers, and groups like theirs across the country, huddled over sewer drains in the rain.

“Cities change rivers in a lot of ways that negatively affect the ecosystem,” Hrycyna says. “But urban rivers are nonetheless living systems, and so they’re still filled with aquatic life. It’s a cool thing to notice when you’re out on the river in a canoe.”