The National Combined Sewer Overflow Inventory was first published to ECHO in May 2023 to reflect the most current inventory of CSOs across the United States.

These data are updated weekly.

ICIS - NPDES is an information management system maintained by the EPA Office of Compliance to track permit compliance and enforcement status of facilities regulated by the

National Pollutant Discharge Elimination System (NPDES) under the Clean Water Act (CWA). ICIS - NPDES is designed to support the NPDES program at the state, regional, and national levels.

Please note that states are actively working to update and correct data in ICIS - NPDES.

EPA estimates that approximately 80% of CSOs are included in the National Combined Sewer Overflow Inventory (as of May 2023).

This feature service contains data from Active CSOs only. 

A zipped Comma Separated Value (CSV), zipped download file of both active and closed CSOs is available for download at https://echo.epa.gov/tools/data-downloads#downloads.

Search for the term "CSO" to find the link.  Also at https://echo.epa.gov/tools/data-downloads/cso-inventory-summary,

a data dictionary on the data used in this feature service can be found.