Municipal stormwater general permits regulate discharges from municipal stormwater systems. These drainage systems are separated from sanitary sewer systems and are owned or operated by cities, counties, and other public entities.
Stormwater is rain and snow melt that runs off surfaces such as rooftops, paved streets, highways, and parking lots. As water runs off these surfaces, it can pick up pollutants that contaminate local water bodies.
The Washington State Department of Ecology manages Storm Water Permits.
>> Environmental Storm Water Permits at Department of Ecology