What are Combined Sewer Overflows

Combined Sewer Overflows ate discharges from combined sewer systems into a receiving stream. A combined sewer system collects both stormwater runoff and sanitary sewage in the same pipes and conveys the water to the WWTF. During dry weather, the combined sewer system transports all wastewater directly to the North WWTF. However, during wet weather events, the volume of wastewater entering the WWTF occasionally exceeds the pumping capacity and is discharged directly to the Illinois River with either partial or no treatment.

Are CSO’s legal?

Yes, CSO’s are legal and permitted by the IEPA and USEAP. The City of Marseilles was permitted to operate a CSO by the Illinois Pollution Control Plan on February 26, 1986, under PCB 85-211. The City of Marseilles submits monthly DMR reports outlining the duration and flow of the CSO event, amount of precipitation leading to the event, and various water quality parameters required by the IEPA.

Are any health risks associated with CSO’s?

CSO’s contain highly diluted sewage with bacteria that may cause illness. Therefore, swimming, canoeing, or other activities that result in bod contact with the Illinois River should be avoided during a CSO event.

CSO occurrences 1997-Present

Where is the CSO located?

The City of Marseilles’ CSO is located at the WWTF, discharging into the Illinois River.

How can residents help in the reduction of CSO’s?

Residents can assist in preventing CSO’s by ensuring that no additional water is being discharged into the sanitary sewer during a rain event. Sump pumps, downspouts, and other drainage tiles are illegal discharges if they are connected to the sanitary sewer. Discharges from these items should be rerouted to your yard or a storm sewer if available. For questions regarding a possible illegal connection, please contact a licensed plumber or the City of Marseilles WWTF.

Wastewater Treatment Facility

Wastewater Treatment Facility Links