Line: Sewer line

Cities and towns take their water from the Ohio River; in addition, they dump their used water into the Ohio River. One of the major sources of water pollution is combined sewer overflows, abbreviated CSOs.

Water line Sewer line

Number of Combined Sewer Outlets (CSOs)

In most recently built cities the underground pipes which carry waste from people’s houses, offices, and schools to the sewage treatment plant are separate from the underground pipes which capture rain as it runs off roofs, streets, and parking lots (stormwater).

However, when some older cities were building their first water treatment systems in the 19th century, they saved money by combining the sewage pipes with the stormwater pipes. When there was a heavy rain, rainwater would mix with sewage. The resulting volume of water would be too great to flow through the sewage treatment plant and become clean, so it was diverted into pipes which ran directly into streams and rivers, including the Ohio River. Since the passage of the Clean Water Act in 1972, and especially since the establishment of the EPA’s CSO control policy in 1994 cities and towns have been working to eliminate CSOs and the sewage, toxic waste, and trash they dump into streams and rivers.