Ecological and Best Management Practices Planning to Address Combined Sewer Overflows in New York City

Water quality in New York Harbor is currently impacted by combined sewage and stormwater overflows during rain events. As part of the Mayor's PlaNYC 2030 program, New York City Environmental Protection (NYCDEP) is spearheading the Ecological and Best Management Practices (BMPs) Planning to Address Combined Sewer Overflows (CSOs) initiative. Among the ecological pilots being implemented are algal turf scrubbers and constructed ribbed mussel beds, oyster habitat reefs, and eelgrass beds. They will be monitored for potential water quality improvements in New York Harbor. NYCDEP is also currently piloting innovative and long-term sustainable source controls to evaluate their effectiveness in reducing the quantity of stormwater runoff entering the sewer system in various types of ultra-urban environments. These BMP pilots are located within highway medians, park-and-ride lots, public parks, street-side sidewalks, and public housing facilities throughout the City. The stormwater pilots being implemented and monitored include enhanced tree pits, stormwater infiltration swales, bioretention cells, pervious pavements, blue roofs, and subsurface retention systems. Flow measurements, weather data, and physical observation are being used to evaluate the effect of these pilots on storm hydrology. Basic water quality analyses are expected to indicate whether these pilots function similarly to BMPs in other regions and to identify potential maintenance concerns. Monitoring data for both ecological pilots and BMPs will be collected and analyzed over the course of two years after completion of each pilot construction. This information will ultimately be utilized in combination with stormwater modeling efforts to evaluate the impact of watershed-level implementation, revise sewer codes and regulations, and develop guidelines for implementing green-infrastructure throughout the City.