Stormwater Quality

In the latter part of the 20th century, pollution had become so prevalent in our streams, rivers and lakes, Congress amended the Clean Water Act requiring the Environmental Protection Agency (EPA) to address storm water runoff. As a result, the National Pollutant Discharge Elimination System (NPDES) was developed. 

In 1990 Phase I of the program was implemented to address water pollution and focused on storm water discharges from industrial sources and larger municipal separate storm sewer systems, or MS4s. By the turn of the century, with storm water pollution continuing to be a problem, Phase II of the program was developed and implemented with the focus being on smaller MS4s and construction sites disturbing one or more acres. In Colorado, the Phase II rule is administered by the Colorado Department of Public Health and Environment. Compliance with the NPDES Phase II rule became a requirement for Grand Valley MS4's, including the City of Grand Junction, in March of 2003.

NPDES Permit Coverage

EPA's Phase II rule specifies that MS4's must apply for NPDES permit coverage. To obtain this coverage, an MS4 operator must develop, implement, and enforce a storm water management program that is designed to reduce the discharge of pollutants to the maximum extent practicable, protect water quality, and satisfy the applicable water quality requirements of the Clean Water Act. EPA's Storm Water Phase II Final Rule states that this storm water management program must include the following six minimum control measures :

  • Construction site stormwater runoff control
  • Illicit discharge detection and elimination (IDDE)
  • Pollution prevention and good housekeeping for municipal operations
  • Post-construction stormwater management in new development and redevelopment
  • Public education and outreach on stormwater impact
  • Public involvement and participation

As part of their applications for permit coverage, MS4 operators must identify the best management practices they will use to comply with each of the six minimum control measures and the measurable goals they have set for each measure.