Boston Takes On Dirty Stormwater
Rain is a hurdle in the city’s decades-long quest to clean up the Charles River
By Saima Sidik
The Charles River in Cambridge, Massachusetts. | Photo courtesy of Sergi Reboredo/VWPics via AP Images
There was a time, in the 1960s, when Boston’s Charles River was so notoriously filthy that rock stars sang about how dirty it was and falling in was seen as cause for a tetanus shot.
The problem was that Boston’s plumbing was ill-equipped to handle both sewage and natural storms. When stormwater flowed down roads and into storm drains, it joined the same system already handling the city’s sewage. This often overwhelmed the system, and the excess water flowed directly into nearby waterways.
Today, the Charles is much cleaner, largely because Boston has separated most of its systems for handling sewage and stormwater. Yet poor water quality still makes the river unsafe for swimming about 30 percent of the time. That’s partly because storms bring new threats to the river’s system—bacteria, pathogens, and waste from the city’s streets.
As the city worked to remove sewage from the river, it shunted rainwater directly off streets and into waterways. The cleanliness of that rainwater “was kind of an afterthought,” said Kate England, a deputy assistant commissioner at the Massachusetts Department of Environmental Protection. But when rain flows over streets, it picks up all manner of grit and grime. And, now, all those pollutants flow directly into waterways, including the Charles.
One of the biggest problems is the nutrient phosphorus, which is abundant in plant fertilizers, pet waste, goose poop, leaf litter, and many other forms of debris found around the city. Increased storms, supercharged by climate change, exacerbate the issue by causing more frequent and destructive stormwater runoff. When rainwater carries phosphorus into the Charles, it leads to toxic algal blooms, which make the water unsafe. In 2007, the Environmental Protection Agency directed the Boston Sewer and Water Commission to reduce the amount of phosphorus in the lower Charles by between 48 percent and 96 percent.
The city is still working toward that goal, and officials plan to let nature do the heavy lifting. Plans are afoot to let rainwater meander through natural environments that will clean it before it enters the river—a type of green stormwater infrastructure.
The approach is catching on in cities across the United States and beyond. Not only can green infrastructure clean water, but it can also reduce the risk of floods and reduce urban heat, said Lisa Kumpf, the senior restoration program manager for the Charles River Watershed Association. Her organization’s main goal is to get the city to clean up the Charles River by completely separating sewer and stormwater pipes. In the meantime, green infrastructure, which the group also advocates for, is another tool that can be used to filter our toxins.
In part, green infrastructure is catching on because there aren’t a lot of other ways to clean stormwater, short of sending it all to a water treatment facility, which would require extensive new infrastructure. There are proprietary filters for removing nutrients from stormwater, but they’re expensive.
Boston’s plan to use green infrastructure to clean stormwater is “a completely reasonable place to start,” said Ashlynn Stillwell, a civil and environmental engineering professor from the University of Illinois Urbana-Champaign. But monitoring water quality will be important to make sure the system is delivering on its promises.
The city’s approach involves a mix of small, distributed green infrastructure and large, centralized features. The small stuff blends in with the cityscape such that a passerby might not even notice it. In Codman Square, for instance, rain gardens replace small sections of the sidewalk. Here and there, segments of the curb have been cut away to allow water to flow off the road and seep into the soil. In other places, green infrastructure is truly incognito. City Hall Plaza, for example, is paved with porous pavement that looks like a typical city sidewalk but allows water to pass through.
Larger features, on the other hand, will look very unlike a normal city street. I logged onto Zoom to discuss one such feature with Kumpf on a muggy July morning when, appropriately enough, rain had forced us to abandon our in-person interview.
We’d planned to meet on the border of Boston’s Mission Hill neighborhood and the neighboring town of Brookline, where Leverett Pond serves as a catchment for runoff before it enters the Muddy River and then the Charles. Rainwater that falls over about four and a half square miles drains into Leverett Pond, bringing an unpleasant mixture of city debris along with it. Oil slicks are a common occurrence. Adding to the mess is raw sewage from houses in which the plumbing has been erroneously connected to the stormwater system, although the sewage system is supposed to be separate. When you approach the pond, “you will smell it!” Kumpf said.
Instead of Leverett Pond being just a quick stop, the Charles River Watershed Association would like to remake it into a natural wetland where water would slowly meander through a circuitous path, allowing time for plants to sop up excess nutrients and bacteria to die in the bright sunlight before the water flows into the Charles. This might reduce phosphorus flowing through the Muddy River by 25 percent, the association estimates.
THE MUDDY RIVER
Who would fund the redevelopment and when it would be finished are still open questions. Kumpf hopes that a combination of municipal, state, and—perhaps one day—federal funding could get the project off the ground. Meanwhile, similar plans are afoot in other parts of the city, although federal funding cuts could complicate matters. One such spot is a new community slated for construction in Boston’s Allston neighborhood. Rainwater from this area currently drains directly into the Charles, but the new development will include green stormwater infrastructure, England said. The verdict is still out on whether the community will include one large feature, like a wetland, or many small features.
Across the Charles, in the town of Cambridge, there’s a model for what the final sites could look like. In 2013, the city completed a 3.4-acre wetland within a state park. Today, the wetland, called Alewife Stormwater Wetland, collects and cleans rainwater from 420 acres before it enters a nearby waterway called the Little River.
As I walked the perimeter of the Alewife Wetland with Patrick Herron, executive director of the Mystic River Watershed Association, we stopped next to a tree-lined pond about the size of an Olympic swimming pool. Branches drooped over still, brown water, providing shade for insects that skimmed the surface on this hot June afternoon.
This is a settling pond where grit and rocks settle so they won’t “muck up the system,” Herron said. From there, rainwater flows into a much larger pool where lily pads and ducks dot the surface and red-winged blackbirds flit overhead. Here, phosphorus and other nutrients settle out and are taken up by plants before the water continues on in the watershed, Herron explained.
Although it’s “magnificent,” in Herron’s words, building the wetland was a challenge. The project cost over $150 million and required forging relationships between a variety of stakeholders. There was also pushback from locals who opposed turning public land into a site for water treatment, resulting in years of lawsuits.
Now, 12 years after construction was completed, the Mystic River Watershed Association is collaborating with a researcher from Northeastern University to study the wetland’s impact on water quality. Results are still pending, but in other places, constructed wetlands have removed between 45 and 90 percent of the phosphorus from urban stormwater.
Herron can easily envision Boston creating something analogous to the Alewife Stormwater Wetland. According to him, once people spend time in its tranquil environment, creating similar sites becomes “really hard to argue against.”
Saima Sidik is science journalist based in Somerville, Massachusetts. She writes mostly about biology and earth science.