This application is based solely on rainfall data and the resulting Combined Sewer Outfall prediction models established, and does not reflect realtime dry-weather discharges or actions taken by DEP in emergency events. Please check DEP homepage for any additional advisory information.
Combined Sewer Overflows (CSOs) happen when a wastewater treatment plant or parts of the sewer get too full, usually when there’s a big rain event or snowstorm. When this occurs, wastewater is sent straight into our waterways, without being treated. DEP supplies an online Waterbody advisory application to see how rainfall has impacted NYC Waterways.