Stormwater runoff picks up pollution as it travels over our developed landscapes and is a major source of water quality problems. In 1987, the Federal Clean Water Act was amended to address stormwater problems. As a result, the United States Environmental Protection Agency (EPA) created the National Pollutant Discharge Elimination System (NPDES) to address stormwater runoff. States are then required to administer permits to local jurisdictions to regulate runoff as part of the NPDES Program. Larger jurisdictions, such as the City of Seattle, King County and Snohomish County, are considered “Phase I permittees”. Moderate sized jurisdictions, such as Whatcom County, are considered “Phase II permittees”.
Areas of more urban density have been designated by the Washington State Department of Ecology as “Phase II Areas”, or areas that must adhere to the local jurisdictions’ Phase II permit. The Phase II areas are shown here.
If your project is located within an NPDES Phase II area, a stormwater design that is consistent with the 2012 Washington State Department of Ecology Stormwater Management Manual For Western Washington must be proposed with any development application. Generally, if your project results in new plus replaced hard surface of more than 2,000 sq. ft., a stormwater plan that is consistent with the 2012 Manual will be required. It is highly encouraged that you consult with a licensed Civil Engineer to determine what level of stormwater plan you will need for your project.