New York City has 14 water treatment plants, and on a dry day, these plants collect and treat approximately 1.3 billion gallons of sewage and stormwater runoff. On a rainy day, that amount increases considerably—often well beyond the plants' combined 2.5-billion-gallon capacity. The city has been plagued with frequent combined sewer overflow (CSO) incidents as a result, which negatively impact the area's rivers, streams, and bays. Ultimately, the water quality of the city's renowned New York Harbor has been diminished by this chronic problem—a challenge that many of our nation's cities face today.

Reducing Runoff

The city's Department of Environmental Protection (DEP) has taken a significant step forward to reduce the amount of runoff entering the water system, which, in turn, will decrease CSOs and ultimately improve the region's water quality. The NYC Green Infrastructure Plan is targeting a ten percent reduction in runoff from impervious surfaces by 2030, largely as a result of the construction of approximately 5,500 Right-of-Way Bioswales (ROWBs).

ROWBs are tree pits that are designed to absorb a significant amount of runoff—more than 2,200 gallons of stormwater at a time. These curbside gardens are engineered with a three-foot layer of soil and sand atop a two-foot layer of gravel. They feature native trees and plants, and serve as attractive urban amenities—stretching 20 feet long and five feet wide.

DEP Priority Areas

We are currently tasked with designing ROWBs for the NYC Department of Design + Construction in several locations in the Borough of Queens. Others have been constructed or are planned for Brooklyn and the Bronx. All are to be located in DEP Priority CSO tributary areas.

The NYC Green Infrastructure Plan is an ambitious yet common sense approach to improving water quality in the region. We'll see cleaner waterways and more attractive communities.