This style of “bioswale” is coming to East Rock.
A mile of new stormwater drainage pipes. Thirty-seven manholes and 24 new catch basins. Three hundred feet of pervious concrete sidewalk, and seven “bioswales.”
The Greater New Haven Water Pollution Control Authority (GNHWPCA) plans to bring those public improvements to East Rock to capture roadway drainage north of Trumbull Street to about Humphrey and between Whitney Avenue and State Street.
The yellow are the proposed pipes, and the green dots the bioswales.
Tuesday night two dozen East Rockers gathered at the monthly meeting of the SoHu Neighborhood Association on Pearl Street to hear a presentation about the plan by Giovanni Zinn, the project manager with the city’s engineering department, and Mario Ricozzi, the GNHWPCA’s manager of design.
The project is a continuation of an ongoing Yale Campus/Trumbull Street sewer separation project, and part of the city’s continuing program to separate storm draining from the sanitary sewer system. The overall goal of that effort is to prevent “combined sewer overflows” (CSOs) that periodically, during flooding storms, cause unseparated lines to mix the sludge water with the stormwater and send sewage into the rivers.
The new pipes — currently there are no separate storm drainage pipes, only sewer lines in the area — - will be installed on Whitney, Lincoln, Bradley, and Pearl. They will stormwater down to culverts at State Street that will send it into the Mill River.
On smaller smaller streets such as Clark and along Orange, instead of the “grey infrastructure” of new piping, the WPCA will install “green infrastructure,” namely the bioswales.
Area environmentalists have long called for more “green” as opposed to “grey” infrastructure in the GNHWPCA’s plans to reduce overflows and upgrade the East Shore sewage treatment facility.
New Haven’s bioswales will follow models (pictured at the top of the story) from New York City, which has installed about 200 of a planned 1,000, said Zinn.
The bioswales are planned to be low-fenced areas about five by 20 feet between curb and sidewalk. They will leave at least five feet of unimpeded sidewalk.
Zinn and Ricozzi.
The design pitches the bioswales slightly below street level and with a curb cut to receive water flow from the gutter. They will contain trees and plantings, chosen for their ability to absorb, along with layers of dirt and gravel that will intercept the flow of water from the street gutter and infiltrate it down, mimicking nature, thereby reducing the amount of water that reaches the catch basin.
The plan calls for seven of these along Orange Street and a double-sized bioswales on Clark. The project’s managers will monitor the bioswales on Clark to see how much they reduce water reaching the catch basin.
That aspect of the plan drew the most interest from the audience on Tuesday night.
“You’re brilliant,” said Judy Nugent of Clark Street. She specifically complimented the placement of the bioswales in some of the no-parking areas along Clark Street.
In addition to pipes and bioswales, the third feature of the Phase 2A project will feature pervious concrete sidewalks on both sides of Clark Street beginning at State and moving west. Pervious sidewalks are concrete, but more porous than regular concrete and designed to send the water down into the ground below instead of letting it wash into the streets.
Zinn said that one small bioswale was installed on Trumbull Street, which had a specific drainage problem in connection with the previous phase of work, the years-long sewer separation project around the intersection of Trumbull and Prospect.
Similarly a small stretch of sidewalk on Court Street was redone three years ago in pervious concrete.
The East Rock project will be the first to employ green infrastructure of this kind on a larger scale. The bioswales will be monitored and function as pilots for other streets in the area and for other phases of sewer separation work in the future.
If the bioswales work, they may be installed on the narrower streets, avoiding the need to tear up the roadways for new piping, along particularly narrow streets such as Eld and Bradley.
Half the $13 million for the project will come half from a grant from the state, Department of Energy and Environmental Protection(DEEP) and the other half from borrowing, according to Ricozzi. The GNHWPCA will repay 60 percent of the debt, the city, 40 percent. That’s been the deal ever since the city arranged to fold its operations in with the new regional organization, said Ricozzi. The city did that to solve a one-time budget hole.
The GNHWPCA serves the New Haven, East Haven, Hamden, and Woodbridge.
The inconvenience is not expected to be grievous, said the officials.
As crews work on approximately 100-foot length pieces of the project at a time, portions of the smaller one-way streets like Clark and Pearl will need to be closed during the day, with some detouring; they will be opened at night. Work on Whitney will not impede two-way traffic on that avenue, officials said.
Green infrastructure is now required of new developments in the New Haven Combined Sewer area to reduce the impact of new developments on combined sewer overflows, according to the GNHWPCA.
“We’re one of the first” communities to deploy green infrastructure like bioswales, Zinn said.
He and Ricozzi both attributed that to greater comfort of the regulators such as U.S. Environmental Protection Agency with green infrastructure; the state’s Clean Water Fund‘s willingness to set aside a percentage of funding for green infrastructure for waste water management; and proven advances in the technology.
If the money comes through, work should commence this summer and finish by the fall of 2015, said Ricozzi.