How many cities have Combined Sewer Overflows (CSO)?
Combined Sewer Overflows (CSO) are common among industrial cities that developed along the East Coast and Great Lakes regions in the mid 1800s. Nationwide, there are approximately 775 CSO communities. According to the U.S. Environmental Protection Agency (EPA) there are 108 combined sewer systems within Illinois. In addition to Aurora, the following Illinois cities have combined sewers:
- Chicago
- Elgin
- Evanston
- Hinsdale
- Joliet
- Morris
- Ottawa
- Peoria
- Rock Island

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1. What is a Combined Sewer System?
2. What is a Combined Sewer Overflow (CSO)?
3. How many cities have Combined Sewer Overflows (CSO)?
4. Does Aurora have Combined Sewer Overflows (CSOs)?
5. What challenges do Combined Sewer Overflow (CSO) communities face?
6. What has Aurora done to improve the Combined Sewer System (CSO) and prevent sewer backups and overflows?
7. Does anyone regulate Combined Sewer Overflows?