C.S.O. Project

Welcome letter from Mayor John B. O'Reilly, Jr.

Click on any of the numbered locations on the map below for more information

(Currently only site #8 has available information)

What is the CSO Project?

It is a project to meet the requirements of the Federal Clean Water Act of 1972 pertaining to correcting water quality problems caused by discharges from combined sanitary/storm water sewers. The United States Environmental Protection Agency has cited combined sanitary/storm water sewer overflow (CSO) discharges as a significant source of pollution to the nation’s surface waters.

In our nation’s history, combined sanitary/storm water sewer systems were built in the mid to late 1800s and early 1900s at a time when wastewater treatment plants did not exist. Nearly all the combined sanitary/storm water sewer systems built in this era are still in use. At that time construction of combined sanitary/storm sewer systems was encouraged to help eliminate emerging widespread safety and health concerns in our growing urban centers. Construction of this type of sewer was abandoned in the 1940s-50s with the advent of construction of wastewater treatment plants built to handle separated sanitary sewerage. Approximately sixty six percent of Dearborn is served by a combined sewer system.

The Federal Clean Water Act of 1972 now requires the overflows from combined sewers to be eliminated or treated to meet federal water quality discharge standards for body contact and for supporting healthy aquatic life.

Dearborn ’s CSO Project will meet the federal requirements by a combination of:

• Separating combined sanitary/storm sewer where practicable and

• Where separation is not practicable construct retention/treatment facilities that store and treat discharges to meet federal water quality standards for body contact and for supporting healthy aquatic life when discharges occur.

Dearborn ’s CSO facilities are constructed using a large concrete cylindrical shaft that is sunk into the earth through a coordinated excavation process. The result is referred to as a “treatment shaft” that temporarily captures a large volume of the CSO discharge for later treatment at the Detroit sewage treatment plant. Any CSO volumes that exceed the capacity of the treatment shaft receive “settling, skimming and disinfection” prior to being discharged to the Rouge River . The result is that the vast majority of CSO discharges will no longer reach the river and the relatively small amount of remaining CSO volumes will be properly treated before entering the river.

Frequently asked questions

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