How is Stormwater Regulated?

In 1987, Congress changed the federal Clean Water Act by declaring the discharge of stormwater from certain industries and municipalities to be a point source of pollution. Due to this change, certain stormwater discharges now require a National Pollutant Discharge Elimination System (NPDES) permit or water quality discharge permit. The U.S. Environmental Protection Agency (EPA) gave the Department of Ecology the authority to implement these permits in Washington State.

The EPA stormwater regulations establish two phases (Phase I and Phase II) for the stormwater permit program:

Phase I

Phase I stormwater NPDES permits cover stormwater discharges from certain industries, construction sites involving more five or more acres, and municipalities with a population of more than 100,000.

Ecology regulates stormwater discharges from industries and construction sites under separate general permits. These permits require the development and implementation of a Stormwater Pollution Prevention Plan (SWPPP). The SWPPP for construction sites is primarily a temporary erosion and sediment control plan. The SWPPP for industrial facilities is a documented plan to identify, prevent, and control the contamination of stormwater discharges.

The municipal stormwater permits require the implementation of a Stormwater Management Program. The Stormwater Management Program is a plan to reduce the discharge of pollutants, reduce impacts to receiving waters, eliminate illegal discharges, and progress towards meeting surface water, groundwater and sediment standards. Ecology reissued the current municipal Phase I permit in December 2006. Ecology will issue a separate general permit for Washington State Department of Transportation in 2007.

The public entities covered under Phase I Municipal Stormwater NPDES permits include:

Phase II

In 1999, EPA issued the final Phase II stormwater regulations. The Phase II regulations expand the requirement for stormwater permits to all municipalities located in urbanized areas and to construction sites between one and five acres. The rule also requires an evaluation of cities outside of urbanized areas that have a population over 10,000, to determine if a permit is necessary for some or all of these cities.

In December 2006 Ecology finalized the general permits to cover the additional cities and counties included by the Phase II rule. Two separate general permits cover eastern and western Washington Phase II communities. Additionally, special purpose districts located in Phase I and Phase II areas may need permit coverage. Special districts include ports, flood control districts, diking and drainage districts, prison complexes, public universities, and parks and recreation districts.

EPA rules require local governments to develop stormwater programs that address the following six main elements:

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

For More Information, please see the following Ecology publications:


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