The City's 120-year-old sewer collection system is a network of 300 miles of buried pipe. Approximately 90% of these pipes handle both sanitary sewer flow and stormwater runoff, directing it to the City-owned wastewater treatment plant. However, during high-intensity storm events, the volume of runoff from rainfall exceeds the capacity of the collection system. Consequently, a portion of the combined stormwater and sanitary sewer flow overflows into the Brandywine and Christina Rivers. These occurrences are termed combined sewer overflows (CSOs).
More information can be found by visiting the Wilmington CSO website or viewing it below.