Changes Coming to How You Get CSO Alerts: Re-Register Now!

The Metropolitan Water Reclamation District of Greater Chicago (MWRD) is making changes to how people get updates about Combined Sewer Overflows, or CSOs. A CSO happens during heavy storms when too much rainwater and wastewater flow into the sewer system at the same time. When that happens, untreated water can overflow into the river. Starting June 17, 2025, MWRD is switching to a new system to send CSO notifications. If you already get these alerts, you must re-register at this link to keep getting them.

Please note: This update applies only to MWRD’s alert system. A connected, more dynamic CSO notification system is currently being planned by the City of Chicago, but it is not yet live. We’ll share updates on that effort soon.

CSOs are becoming less common every year thanks to major infrastructure investments, like MWRD’s Tunnel and Reservoir Plan. Only one CSO was documented in the entire Chicago-Calumet system in 2024, and none have occurred so far in 2025.

This change does not affect Overflow Action Day Alerts. Learn more about Overflow Action Day alerts here and register if you have not done so already.