The Chicago River was once a heavily industrialized waterway, but nowadays the prime source of pollution in the river is the wastewater released from the three enormous sewage treatment plants along the Chicago and the Calumet rivers. Sewage is treated at these plants but is not fully disinfected of bacteria before being released into the river system. For many years the Water Reclamation District has argued that the river is too dirty for recreational use, and therefore the released wastewater need not be cleaned to the higher standards of a more pristine waterway.
The EPA argues that deindustrialization and the miles of trails constructed along the river have indeed transformed it into a recreational river, and any wastewater released should be held to a higher standard of water quality.
Fully disinfecting wastewater from all three sewage treatment plants could cost up to $1 billion according to the Water Reclamation District, but the EPA estimates the cost will be much less. The current EPA decision will affect only the Howard Avenue and Calumet plants, not the big Stickney plant, costing even less.