Reducing CSOs in the Big Apple – NYC’s Green and Gray Approach

On March 8, 2012, the New York State Department of Environmental Conservation (DEC) and the New York City Department of Environmental Protection (DEP) signed a groundbreaking agreement to reduce combined sewer overflows (CSOs) using a hybrid green and gray infrastructure approach (DEC, 2012). As part of this agreement, DEP will develop 10 waterbody-specific CSO long term control plans (LTCPs) and a citywide LTCP to reduce CSOs and improve water quality of New York City’s (NYC’s) waterbodies and waterways. The goal of each LTCP is to identify appropriate CSO controls necessary to achieve waterbody-specific water quality standards, consistent with the Federal CSO Policy and the water quality goals of the Clean Water Act (CWA). This paper provides an overview of the City’s current and future efforts to cost-effectively reduce CSO in NYC and the challenges of implementing this program