Bioswales Come To Dwight

Lucy Gellman Photo In a quest to clean up the West River and green the city’s response to rainfall, four new bioswales are coming to the Dwight neighborhood.

That was the story Wednesday morning at Troup School, where representatives from Save The Sound, Schumack Construction and the City of New Haven gathered to work on three bioswales on Platt Street and one on Edgewood Avenue.

The first bioswales in that specific stretch of Dwight, they join one bioswale and two rain gardens built by Save The Sound, and close to 20 by the City of New Haven and Urban Resources Initiative.

All of those are part of a commitment that the city has made to install 200 bioswales between 2015 and spring 2019.

City of New Haven Schematc Bioswales are deeply dug, landscaped developments filled with gravel, stones, mulch and soil and planted with native perennials; several have popped up across the city in the last couple years. They are intended to absorb storm runoff that would otherwise go into storm drains, and join sewage in the city’s “grey infrastructure” or underground network of tubes and pipes. Calling them “the perfect green infrastructure for urban space,” Save The Sound representative Kendall Barbery said that these bioswales will include a variety of heavy metal switch grass, inkberry, and redosier dogwood, among other plants.   

In Dwight, Edgewood and the West River neighborhood, the bioswales — as well as shallower rain gardens and porous pavement — are part of an effort to revitalize the West River. In the years leading up to 2015, the Greater New Haven Water Pollution Control Authority (WPCA) estimated that 45 million gallons of storm runoff were going into the West River every year. Because of the way New Haven’s grey infrastructure is designed, sewage and storm runoff find their way into the same collection pipes, including a major one under Ella T. Grasso Boulevard. During periods of heavy rainfall—periods that the city is seeing more of with climate change, Barbery said—spots along that collection pipe drain off into the West River. Some of the storm runoff never gets to a water treatment facility, and carries with it the salt, sediment, and diesel residues that build up on city streets.   

Looking over those statistics, community members from the West River Watershed Coalition (WRWC) began to voice concern. With both the city and organizations like Save The Sound, they began to brainstorm ways to better manage the storm system. Around the same time, the WPCA launched into work on citywide projects to bring runoff numbers down to 14.5 million gallons per year. The bioswales are part of conquering that remaining number.

These newest additions come out of a $100,000 grant from the Environmental Protection Agency (EPA) administered by the state’s Department of Energy & Environmental Protection (DEEP). At several thousand dollars each, they are in various states of done-ness—two have been finished, one is still under construction, and one has yet to be started. As they take about two days each, Barbery estimated that it will be done by the end of the week. To construct each at a regulation size of five by 15 feet, construction crews mark off the area, remove the sidewalk panels, dig out a mix of concrete and dirt that is beneath the sidewalk, prepare it with sand, and then lay it with gravel, larger stones, mulch, and soil in that order. Plants are then added to improve drainage further, keeping the soil loose and absorbent with their roots. As a final touch, Save the Sound adds a metal fence, to mark the area as a piece of green infrastructure that neighborhood residents can recognize.   

They’re increasingly in demand, said Dawn Henning, sustainability project manager with the City of New Haven. As climate change shifts storm patterns and outcomes in New Haven’s coastal environment, city officials have observed more short, intense spurts of rainfall that leave areas of the city flooded. 

“All of the storm sewer system is underground and no one really thinks about it,” she said as construction workers primed the bioswale-to-be on Platt Street with sand. “I think this brings it into greater consciousness.”

To work on that consciousness in the greater community, Barbery and Henning are planning two community-focused planting days in early May, one for Troup School students and another for neighbors and churchgoers who live and pray in the area.

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