 The City of Peoria is developing a long-term plan to reduce combined sewer overflows to the Illinois River, as required by the U.S. Environmental Protection Agency and the Illinois Environmental Protection Agency.During dry weather, sewage flows safely through the city's sewers to the Greater Peoria Sanitation District wastewater treatment plant.However, about 28 times a year, melting snow or rainwater can overwhelm the sewers, causing untreated sewage to overflow into the Illinois River.