During dry weather and small wet weather events (rainfall and snowmelt), combined sewers are designed to transport all flows to the Water Pollution Control Facility (WPC) for treatment. During larger wet weather events, the volume of storm water entering the combined sewer system may exceed the capacity of the WPC. When this happens, combined sewers are designed to allow a portion of the untreated combined wastewater to overflow into the ditch on E Poe Road This prevents the backing up of sewage into basements, and/or flooding of streets. The location of the discharge of untreated combined wastewater, as well as the discharge event itself, is called a Combined Sewer Overflow (CSO). The City of Bowling Green has one CSO located near the E Poe Road and Mercer Road intersection.