Washington State Department of Ecology

Municipal Stormwater Map Resources

Maps of Phase I and Phase II Permit Coverage Areas
Flow Control Guidance for Highly Urbanized Basins
Contains maps and information on areas that potentially meet the 40% Impervious/20 Year criterion.
Western Washington Land Cover Change
GIS data layers showing changes in land cover and impervious surface for Western Washington for 1991, 1996, and 2001.
Ecology's Washington Coastal Atlas
An interactive mapping tool for Washington’s marine shorelines and the land areas near Puget Sound, the outer coast, and the estuarine portion of the Columbia River.
Industrial Facilities Site Database
GIS maps to download and database for industrial stormwater and other permitted facilities.
Ecology GIS Data Standards
Data standards for GIS maps of stormwater system maps that are required in municipal stormwater permits.