Liquid wastes . This technique allows liquids to be evaporated, or solid wastes to be concentrated, prior to disposal by other means. An IEPA survey in 1980 counted 7,450 active or abandoned waste impoundments in Illinois. Unlined or improperly lined impoundments are considered by some authorities to be the most significant source of chemical pollution of Illinois groundwater. It is not clear how many waste impoundments are in use today, but tighter regulations are making the practice of storing officially designated hazardous wastes on land less attractive.
Mining wastes .
Slurry ponds contain very fine-grained clay and minerals cleaned from coal. Untended gob piles and dried-out slurry ponds are a source of airborne pollutants, and erosion from unstable piles can clog drainage ditches and flood nearby farm fields. Illinois land is used to dispose of assorted organic matter, mainly agricultural wastes such as crop residues and animal manures. Farm land also is the preferred site for the disposal of sludge from publicly-owned sewage treatment works and certain cannery wastes generated by commercial food processors. Most of the former are small works, located in rural areas with immediate access to large amounts of land.