Post-Construction Monitoring Results of Green Infrastructure in Neighborhood Demonstration Areas

The New York City Department of Environmental Protection’s (DEP) Office of Green Infrastructure (OGI) identified three neighborhoods in combined sewer overflow (CSO) areas to evaluate the performance of green infrastructure (GI). Sewer flow and rainfall measurements were collected to calculate volumetric runoff coefficients (Cv) before (pre-GI) and after GI practices were constructed (post-GI). The reduction in Cv post-GI showed that the GI practices managed 14.3% of impervious surfaces across the aggregate area of the three areas for a 2.54 cm (1 inch) storm. Concurrent site-scale monitoring at the GI practice level provided insight into the functionality of different elements of the GI practices.With demonstrated performance at the neighborhood-scale and site-scale, GI is expected to serve as a valuable tool in managing stormwater runoff, and the results from the neighborhood demonstration areas will be used to further improve the designs and implementation methodologies of GI practices in New York City.