Using state-of-the-art technology developed by the University of New Hampshire’s Stormwater Center, county staff designed a “subsurface gravel wetland” that was built next to the Bronx River Parkway near Parkway Homes and Virginia roads in June 2011.
The construction site had been mowed lawn, though parts of it are often saturated with water, especially in the spring. The site is the recipient of storm water runoff from a nearby residential neighborhood, local roads, and the parkway. The site is a prime location for this innovative stormwater management system, which will collect runoff and treat it through natural chemical and
biological processes in the plants, soil and gravel that will form the wetland. After most of the pollutants in the runoff have been removed, the water will either seep into the ground or drain out through a pipe toward the Bronx River. The system will help to both improve water quality in the river and soak up excessive runoff, thereby helping to lessen the amount of water getting into the river.
This “subsurface gravel wetland” was created by first digging out in-ground basins, then partially backfilling them with gravel encapsulating perforated pipe, finally topping the gravel with soil. In the soil, moisture-loving vegetation has been planted. The earthen banks surrounding the wetland were planted with grasses and shrubs. The practice is a horizontal-flow filtration system that relies on a dense root mat, crushed stone, and an aerobic, microbe-rich 
environment to improve water quality. Microbes in the gravel break down storm water pollutants, as do those in the soil. The plants soak up the water and capture the pollutants, turning some into less harmful substances. The system will function much like a natural wetland by removing storm water pollutants and providing other benefits, like flood mitigation, surface and ground water recharge during droughts, and wildlife habitat.
To View The Site: The site is next to the Bronx River Parkway between Parkway Homes Road and Virginia Road (between Exits 25 and 26). The site is next to the southbound side of the Bronx River Parkway in the Town of Greenburgh.
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