Small MS4 Program Requirements


Operators of regulated small MS4s are required to design their programs to:

  • Reduce the discharge of pollutants to the “maximum extent practicable” (MEP)
  • Protect water quality
  • Satisfy the appropriate water quality requirements of the Clean Water Act

Implementation of the MEP standard will typically require the development and implementation of BMPs and the achievement of measurable goals to satisfy each of the six minimum control measures. The Phase II Rule defines a small MS4 Storm Water management program as a program comprising six elements that, when implemented in concert, are expected to result in significant reductions of pollutants discharged into receiving water bodies. 

Minimum Control Measures

The six MS4 program elements, termed “minimum control measures,” are:

  • Construction Site Runoff Control
  • Illicit Discharge Detection and Elimination
  • Pollution Prevention/Good Housekeeping
  • Post-Construction Runoff Control
  • Public Education and Outreach
  • Public Participation/Involvement