Rendering of a cross-section of a bioswale in New York City.
If you take a stroll through East Rock next year and stop to admire some curbside tree plantings, you may be looking at more than mere flora.You may be looking at infrastructure.
You’ll see one of the seven “bioswales” being installed as part of the Greater New Haven Water Pollution Control Authority’s ongoing Trumbull Street area sewer separation project, which aims to improve roadway drainage and reduce sewer overflow into the Mill River.
The bioswales, which will resemble ordinary sidewalk tree wells, are depressed areas slightly below street level that divert rainwater that would otherwise run into the sewer. Once in the swale, the water will seep down into the soil, reaching the water table without mixing with contaminated sewage.
Mario Ricozzi, manager of design at GNHWPCA, explained all of this at the City Plan Commission’s regular meeting at City Hall last week. The commission voted to approve the site plan.
The bulk of the sewer separation project is replacing some of New Haven’s old combined sewer pipes, which date to the mid-1800s. When those pipes are overwhelmed, Ricozzi said, the excess water flows into the river. As part of the new project, the authority has installed separate pipes for storm drainage and sanitary sewer water on Trumbull Street.
The bioswales, which will be installed over the next two years, are meant to minimize the need for further pipe replacements. An example of so-called green infrastructure, the bioswales, which rely on natural processes to divert excess rainwater, should be cheaper and more attractive than installing more sewer pipes. “It’s a value proposition,” Ricozzi said.
To test the effectiveness of the bioswales, Clark Street will feature a sort of controlled experiment in which one side of the street gets them and one side doesn’t. (Clark Street will also be a testing ground for permeable sidewalks, which let rain water through to the soil.)
“It’s one of a range of methods to deal with storm water,” said Giovanni Zinn, a project manager in the engineering department.