Approximately 60% of New York City has a combined sewer system, with 398 CSO outfalls that annually discharge approximately 18 billion gallons of combined sewage, making it one of the largest combined sewer system in the U.S. Since the 1970s, the City has been implementing projects to reduce combined sewer overflows (CSOs) from its sewer system to improve the water quality of its surrounding waters, including Flushing Bay, Jamaica Bay, East River, Hudson River, Harlem River, and the New York Harbor. Overall, the City has completed or committed to complete around $10 billion of grey and green infrastructure projects that will significantly reduce CSOs in these surrounding waterbodies.
CSO Program Regulatory Framework
The New York City Department of Environmental Protection (NYCDEP) is required to abate CSOs in accordance with the federal CSO Policy under the Clean Water Act. Specific requirements for CSO planning and project implementation are defined in State Pollutant Discharge Elimination System (SPDES) permits and administrative consent orders issued by the New York Department of Environmental Conservation (NYSDEC).
Under their SPDES permits, NYCDEP is required to implement with CSO Best Management Practices comprised of 15 BMPs, equivalent to the EPA CSO Policy’s nine minimum CSO control standards. The SPDES permits include additional, more specific BMPs that beyond those required by the EPA policy. For more information on the CSO BMPs, visit the Combined Sewer Overflows (CSOs) page.
Most recent version of NYC CSO Annual BMP Report (PDF)
NYC CSO Consent Orders
The first administrative CSO Consent Order to NYC was issued in 1992. Over the years, as the CSO program has evolved, the CSO Consent Order has been modified and/or superseded by new CSO Consent Orders. The most recent administrative CSO Consent Order was issued in 2005 and has been modified numerous times to include major changes agreed upon between New York City and New York State. Below are links to the 2005 CSO Consent Order, several major modifications to the Order, and the most recent versions of the Appendix A and Appendix C, which define specific projects and milestones under the CSO Consent Order.
