|Q:||What is a Combined Sewer Overflow (CSO)?|
Like many older cities throughout the Northeastern U.S., Wilmington's sewer pipes carry a combination of sewage from homes and businesses and rainwater runoff to the City's Wastewater Treatment Plant. That works just fine in dry weather, but when heavy rains come, to keep the sudden onslaught of water and sewage from backing up into homes, it is necessary to release some of the combined sewage into local waterways. This release is called a Combined Sewer Overflow, or CSO.
|Q:||Is Wilmington the only city that has CSOs?|
|A:||No. Over 950 of the nation's older Northeast, Great Lakes and Mid-Atlantic cities have CSOs.|
|Q:||Why does this happen?|
indoor plumbing and wastewater treatment plants, older northern industrial
cities built sewer
Even today, during dry weather, the combined sewer pipes are no problem. They carry water to the city's wastewater treatment plant to be treated and released into the Delaware River. However, during heavy rains, the volume of water is too great for Wilmington's interceptor system and treatment plant to process, and the combined system overflows by design into rivers and creeks.
|Q:||Since CSOs only happen during heavy rains, are they really a serious issue?|
|A:||Yes. Because CSOs carry raw sewage with the stormwater, diseasecausing organisms and other pollutants can enter into our area waters.|
|Q:||Has Wilmington warned area residents about these health hazards?|
|A:||Yes. Wilmington has posted signs at every outfall, alerting people to the presence of CSOs and warning against swimming during and after rain events. A contact phone number is provided for additional information.|
|Q:||Why can't we just separate the sanitary sewage from the stormwater run-off?|
|A:||We might be able to, but the cost to channel the two types of flow into separate pipes would be enormous. In Wilmington, every single home in the area would need to have their sewer system disconnected, at an estimated average cost ranging from $3,700-$7,000 per household. As you can imagine, we would need to excavate much of the city streets to duplicate the piping, and this still would not solve the problem of chemicals and other debris that enter our waterways in stormwater.|