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Erosion and Sediment Control

IDOT ensures that highway construction projects and highway separate storm sewer systems in urbanized areas comply with the National Pollutant Discharge Elimination System (NPDES). This is a permitting program, under the federal Clean Water Act, which regulates construction, industrial activities and both large and small metropolitan separate storm sewer systems to reduce the discharge of pollutants into waters of the United States. Whenever an acre or more of ground is disturbed for roadwork, it is IDOT's responsibility to implement measures to control the discharge of sediment and other pollutants into nearby rivers, streams and wetlands. This is done through the use of an Erosion and Sediment Control Plan, which implements a variety of temporary and permanent measures (e.g. perimeter silt fence, ditch checks, temporary and permanent seeding) to prevent soil and other pollutants from leaving the construction site.

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.  


IDOT and its contractors utilize several manuals and guides to comply with the requirements of the ILR10 and ILR40 NPDES Permits.


IDOT staff and/or consultants are responsible for designing the Erosion and Sediment Control plan for a project. This plan typically uses a variety of Best Management Practices (BMPs) to control erosion and sediment at a project. In addition, a storm water Pollution Prevention Plan (SWPPP) is prepared, submitted to the IEPA, and kept at the project site. The SWPPP describes the project site conditions, what controls and practices are to be followed, as well as a contractor certification statement. The guidance used to design the Erosion and Control Plan and SWPPP is in Chapter 41 of the IDOT BDE Manual.


IDOT is actively involved in assuring compliance of NPDES requirements for state highway projects. We feel one of the best ways to do this is educating its staff, consultants and contractors. This is why we have regularly scheduled classes on NPDES requirements through the Illinois Center for Transportation (ICT).

Contact Us

Contact IDOT Stormwater Committee:

Scott Marlow (Design)
(217) 782-3195

Michael Copp (Construction)
(217) 782-6143