What is a Combined Sewer Overflow (CSO)?
During large rainfalls when stormwater overwhelms the capacity of the pipes, combined sewer systems are designed to discharge the overflow into rivers and lakes. The overflow points are regulated and permitted through the United States Environmental Protection Agency in cooperation with the Illinois Environmental Protection Agency.

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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?