Tree filters planned to treat stormwater in downtown Niantic

A test of the tree filters, planned for the Grand Street area, was installed Friday on Hope Street in Niantic. (Courtesy of East Lyme engineering)
A test of the tree filters, planned for the Grand Street area, was installed Friday on Hope Street in Niantic. (Courtesy of East Lyme engineering)

East Lyme — Plans are underway to install tree filters this fall in the Grand Street area of town, with the goal of improving the environmental quality of the Niantic River and its watershed.

About 20 tree filters will be installed in October in conjunction with the town's repaving project for the Grand Street area, Town Engineer Victor Benni said. The area includes Grand, Smith, Lincoln and Beckwith streets, and N. Washington and York avenues, as well as the eastern section of Hope Street, from approximately the Ring's End section to Pennsylvania Avenue.

"The overall purpose is to provide water quality treatment prior to stormwater entering the Niantic River," Benni said.

The project will be paid for through a $92,500 grant that the Eastern Connecticut Conservation District applied for from the state Department of Energy and Environmental Protection through the Clean Water Act, said Judy Rondeau, coordinator for the Niantic River watershed with the Eastern Connecticut District.

The town won't spend money on the project, but plans to provide a 40 percent in-kind match, including from part of the paving project that already was planned, improvements the town made to stormwater basins in the area and the design of the tree filters, Benni said.

Benni said the town is designing tree filters with a two-system approach to treat the stormwater. The top portion will feature a soil media in which soils and microbes will break down pollutants and nutrients in the stormwater. A crushed stone layer, underneath the top portion, will provide a storage area for the stormwater and further treat it. After being treated by those two components, the stormwater then will infiltrate into the existing sandy soil below the system.

Overflow from the system will move to the next tree filter or stormwater structure, he said.

"What we’re really trying to get is the first inch of rainfall that falls," Rondeau said. "The first inch is going to pick up all the pollutants that are lying on the ground."

Once that first flush of rain has gone into the tree filters, the additional stormwater that falls on the ground won't be carrying the first load of pollutants, she said.

The tree filters will be installed within the town's right-of-way along the frontage of properties in that area, though the exact locations are still to be determined, Benni said. The filters will be landscaped into the area and feature granite curbs and a decorative layer of native beach stone, he said.

Rondeau said that once potential locations are identified for the tree filters, the Eastern Connecticut Conservation District plans to contact neighbors to try to encourage them to "adopt" the trees and potentially weed them twice during the summer. The filters' stone top treatment will discourage weeds.

The Board of Selectmen on Wednesday authorized First Selectman Mark Nickerson to enter into an agreement with the Eastern Connecticut Conservation District for the stormwater management improvements.

The storm sewer system in the Grand Street area collects stormwater from about 55 acres in downtown, Benni said.

The Niantic River Watershed Protection Plan, adopted in 2006, recommends identifying means to reduce stormwater discharges to the Niantic River, and the Eastern Connecticut Conservation District is always looking for opportunities to do that, Rondeau said. The opportunity to improve stormwater practices in the Grand Street area arose when Benni mentioned that the town was planning a repaving project.

The town also is facing requirements from the Department of Energy and Environmental Protection to reduce within the next five years some of the paved surfaces in urbanized areas, including the Grand Street area, in which stormwater directly runs off into water bodies, such as the Niantic River.

Benni said low-impact stormwater management measures will help achieve that.

There are already about eight tree filters in town, located on Pennsylvania Avenue in Niantic and on Colony Road in Flanders, Benni said.

He said stormwater testing has shown that tree filter systems have the effect of lowering E. coli levels in stormwater.


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