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  Additional Information
CSO control or Regional Stormwater Management: What is the difference?
What is a CSO? [PDF]

View a map of our combined sewer outfalls and any active CSO alerts

To report an overflow, call (216) 432-7333

 CSO CONTROL | Your Sewer District: Keeping our Great Lake great.

Understanding combined sewers

As in most urban areas across the nation, Greater Cleveland's earliest sewers (primarily within the city and its inner-ring suburbs) are combined sewers. Built around the turn of the nineteenth century, these sewers carry sewage, industrial waste, and stormwater in a single pipe.

What is a Combined Sewer Overflow (CSO)?

During a rain storm, water flowing over hard surfaces rushes quickly into sewers. This flow is known as runoff, and can cause a dramatic increase of water flowing into and through the combined sewers. When this happens, control devices may allow some of the flow (a combination of stormwater and sewage) to overflow into area waterways to prevent urban flooding and damage to wastewater treatment facilities. This event is called a combined sewer overflow or CSO.

Locations, Frequencies, and Occurrences of Overflows

The Northeast Ohio Regional Sewer District has 124 permitted locations, known as outfalls, where overflows may discharge in the Greater Cleveland area. The permitted total includes one outfall at our Easterly plant and one at our Westerly plant.

In addition to predicted CSO frequencies, the District also monitors discharges on a daily basis at various CSO locations. You can view our CSO Alerts Map for the latest CSO activity or notifications.

What has the Sewer District done to alleviate combined sewer overflows?

Since its inception, the District has invested nearly $900 million in projects that have reduced CSOs. In certain locations, computer-controlled gates and inflatable dams store CSO flow in large pipes during rain events. The stored combined flow is released to a District wastewater treatment plant following the rain event.

Adjacent to the District's Westerly Wastewater Treatment Center, a Combined Sewer Overflow treatment facility stores and treats CSOs. Construction of the District's Heights Hilltop, Northwest and Southwest Interceptors has reduced CSO discharges in various locations. Floatables control netting facilities have been constructed at ten locations to reduce the amount of litter and debris being discharged from CSOs.

Recently, the District has overseen the construction of a number of CSO control "early action" projects in the Easterly and Westerly Treatment Plant areas, and more are planned in the Southerly Treatment Plant district. And ongoing construction of the Mill Creek Tunnel has dramatically reduced CSOs to Mill Creek.

Yet there is still more work to do, and Project Clean Lake will help us address this serious water-quality issue.