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Regulation and Permitting

In 1972, Congress amended the Clean Water Act to prohibit the discharge of any pollutants into waters of the United States from a point source (e.g. industrial wastewater, municipal sewage, etc.) unless the discharge was authorized by a National Pollutant Discharge Elimination (NPDES) permit. In 1987, the Clean Water Act was further amended to require a comprehensive NPDES program that occurred in two separate phases.

Phase I, which was started on November 16, 1990, addressed the most significant sources of pollution in storm water runoff, primarily the municipal storm sewers of medium and larger cities and construction projects that disturbed more than five acres of land. Under this phase, IDOT received a separate permit, ILR10, from the IEPA for each project that met NPDES requirements.

Under Phase II, which began on March 1, 2003, the requirements became more stringent. The threshold to trigger the NPDES permitting process was lowered to one acre of disturbance. Also under Phase II, operators of small municipal separate storm sewer systems or MS4s were required to have authorization to discharge pollutants from construction and maintenance operations as well as their storm sewer systems. These requirements were accomplished through the issuance of the ILR40 permit.

Approximately every 5 years, the IEPA reissues the ILR10 and ILR40 NPDES stormwater permits.   Each reissue updates the language in the permit based upon guidance from the USEPA and comments from the public as well as other state and local government agencies. 

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