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CSO Public Notification Program

Why are there CSOs?

When sewer systems throughout the country were first built, overflows were considered an acceptable way to manage excess water. However, untreated wastewater can contain microorganisms, bacteria and chemicals. To address this concern, MSD is actively working to reduce and eliminate sewer overflows located within the MSD service area.

MSD has already remedied 20 CSOs within the MSD service area since 1990. We also are developing an aggressive plan to address remaining CSOs by 2022. It will be a tough job, but one we're committed to doing well.

The Metropolitan Sewer District of Greater Cincinnati (MSD) has launched a program to notify Hamilton County residents when existing or predicted weather conditions are likely to cause combined sewer overflows (CSOs). The CSO advisories will be issued by email and recorded on a new CSO telephone information line.

A CSO is a discharge of untreated storm and wastewater from a combined sewer into the environment. CSOs typically occur when combined sewers fill up with too much water for the system to handle, most often during heavy rains, and the excess water is released into a stream or river. Power failures and pipe blockages also can cause CSOs.

CSOs are a concern for all of us. MSD is making much-needed improvements to the sewer system to reduce and control these overflows. This program is designed to let residents know in advance when CSOs are likely to occur, thus enabling them to guard against coming in contact with the water.

Under the new notification program, MSD will issue a CSO advisory when a rainfall of .25 inches or more is predicted or recorded for Hamilton County, or when water levels in area rivers and streams are elevated such that a CSO is likely to occur. Advisories will remain in place for 72 hours after a rainfall and 72 hours after water levels in area waterways have returned to normal and CSOs are believed to have ceased.

To protect themselves and their families from the health concerns of sewer overflows, MSD recommends avoiding contact with water near a CSO discharge location, particularly after rainstorms. This includes activities such as boating, wading, fishing and swimming. Signs are already posted along local waterways identifying sewer discharge locations.

Receiving CSO Advisories

By phone: Call the CSO Information Line at (513) 244-5116 to listen to the latest notification.
By email: You can receive CSO Advisories in your inbox by subscribing to the CSO Public Notification mailing list. Subscriptions are free and easy to setup.