NPDES Phase II Regulations

What are the NPDES Phase II Stormwater Regulations?

  • In 1969 the Cuyahoga River in Cleveland, Ohio became so polluted and full of oily trash and residue that it caught on fire.  The fire brought attention to other environmental problems across the country and helped lead to the passage of the Clean Water Act (CWA) in 1972.  The CWA established the objective to restore and maintain the chemical, physical, and biological integrity of the nation’s waters.
  • Phase I of the US EPA stormwater program was promulgated in 1990 under the CWA. Phase I relies on National Pollutant Discharge Elimination System (NPDES) permit coverage to address storm water runoff from:
    • Municipal separate storm sewer systems (MS4s) generally serving populations of 100,000 or greater
    • Construction activity disturbing 5 acres of land or greater
    • Ten categories of industrial activity.
  • The Stormwater Phase II Final Rule (1999) was the next step in US EPA’s effort to help protect the Nation’s water resources from polluted stormwater runoff.
    • Expands the Phase I program by requiring additional operators of MS4s in urbanized areas and operators of small construction sites (greater than 1 acre), through the use of NPDES permits, to implement stormwater programs.
    • Permit coverage is obtained from the North Carolina Department of Environment and Natural Resources (NCDENR).

NPDES Phase II goal:

  • A regulated small MS4 operator must develop, implement, and enforce a stormwater management program designed to reduce the discharge of pollutants from their MS4 to the “maximum extent practicable,” to protect water quality, and to satisfy the appropriate water quality requirements of the CWA. The rule requires the implementation of best management practices (BMPs) to protect water quality.


NPDES Phase II requirements:

  • The stormwater management program must include the following six (6) minimum control measures:
    • Public education and outreach
    • Public participation/involvement
    • Illicit discharge detection and elimination
    • Construction site runoff control
    • Post-construction runoff control
    • Pollution prevention/good housekeeping


  • The small MS4 operator must identify its selection of BMPs and measurable goals for each minimum measure in the permit application. Must evaluate and assess the chosen BMPs and measurable goals in periodic reports to NCDENR.