Stormwater Permits | Region 10 | US EPA

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Stormwater Permits

Most stormwater discharges are considered point sources of pollution and require coverage by an NPDES permit. There are three types of regulated stormwater discharges:

  1. Construction
  2. Industrial
  3. Municipal
About Stormwater Permits

The 1987 Water Quality Act (WQA) added section 402 (p) to the Clean Water Act, requiring that EPA issue National Pollutant Discharge Elimination System (NPDES) permits for the following five categories of stormwater discharges:

  • discharges permitted prior to February 4, 1987
  • discharges associated with industrial activity
  • discharges from large Municipal Separate Storm Sewer Systems (MS4s) (systems serving a population of 250,000 or more)
  • discharges from medium MS4s (systems serving a population of 100,000 or more, but less than 250,000)
  • discharges judged by the permitting authority to be significant sources of pollutants or which contribute to a violation of a water quality standard
The five categories listed above are generally referred to as Phase I of the stormwater program. On November 16, 1990, as a first step in carrying out the requirements of the 1987 WQA, EPA promulgated final regulations (40 CFR 122.26) for stormwater discharges from MS4s serving a population over 100,000, and for storm water discharges associated with industrial activity (55 Fed. Reg. 47990). The Phase I industrial stormwater program requires permitting for construction sites which disturb five or more acres and for numerous types of industrial facilities which are identified in the regulations by standard industrial classification (SIC) code or narrative description.

The stormwater program also includes a Phase II, which addresses discharges not covered by Phase I. U.S. EPA issued final Phase II regulations on December 8, 1999 (64 Fed. Reg. 68722). These regulations require stormwater permits by March 10, 2003 for numerous small MS4s, construction sites of one to five acres, and industrial facilities owned or operated by small MS4s which were previously exempted under the Intermodal Surface Transportation Efficiency Act.

Additional background information on the stormwater program and numerous guidance documents may be found at EPA's national stormwater Web site. Copies of stormwater program materials may also be obtained by from EPA's Office of Water Resource Center at (202) 566-1729.

Permitting Authorities

EPA Region 10 is the National Pollutant Discharge Elimination System (NPDES) permitting authority in Idaho, Indian Country in Oregon and Washington, Metlakatla & Denali National Park in Alaska, and for federal operators in Washington.

State Permitting Authorities:

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