Phase I

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Storm Water Phase I regulations were promulgated by the EPA in 1990.  Phase I uses a permit system set up under the NPDES to regulate storm water discharges from three sources:

  1. Medium and large municipal separate storm sewer systems (MS4s) serving populations of 100,000 or greater;
  2. Construction activity disturbing five acres of land or more; and
  3. Ten categories of industrial activity.