NPDES Phase II

Phase II of the NPDES Stormwater Program began in March 2003 and applies to additional MS4s and construction sites disturbing equal to or greater than one but less than five acres of land. Phase II also expands the industrial "no exposure" exemption covered under NPDES Phase I. Illinois Environmental Protection Agency (Illinois EPA) is in charge of implementing both phases of the NPDES Stormwater Program. The Phase II regulations were published in the December 8, 1999, Federal Register.

Summary of December 8, 1999, Stormwater Phase II Rule:

• Municipalities located in urban areas as defined by the Census Bureau are required to obtain NPDES permit coverage for discharges from their municipal separate storm sewer systems (MS4s). Municipalities located outside of urbanized areas may need to comply within 180 days notice or as determined by the NPDES Permitting Authority.
• Beginning on March 10, 2003, construction sites that disturb one acre or more are required to have coverage under the NPDES general permit for stormwater discharges from construction site activities.
• Municipalities under 100,000 population will no longer be exempt from the construction site stormwater requirements and the industrial stormwater requirements effective March 10, 2003. (WWTPs 1.0 mgd or more will need a General Stormwater Permit for Industrial Activities)
• Definition of industrial stormwater has been revised to expand the "no-exposure" exemption to all industrial categories except construction.