Environmental Rules in King County, WA (2026)

King County Code § 9.04.030

Drainage review is required when any proposed project is subject to a King County development permit or approval and: 1. Would result in two thousand square feet or more of new impervious surface, replaced impervious surface or new plus replaced impervious surface; 2. Would involve seven thousand square feet or more of land disturbing activity; 3. Would construct or modify a drainag...

King County Code § 16.82.095

A. A person who clears, grades or otherwise disturbs a site shall provide erosion and sediment control that prevents, to the maximum extent practicable, the transport of sediment from the site to drainage facilities, water resources and adjacent properties. Erosion and sediment controls shall be applied as specified by the temporary erosion and sediment control measures and performance criter...

King County Code § 21A.24.271

Before initiating any new floodplain development, the person proposing the development shall obtain a floodplain development permit from King County. Exceptions to other permit requirements do not apply to floodplain development. The applicant shall ensure that all necessary permits have been obtained from those federal, state or local government agencies from which prior approval is required...

King County Code § 21A.25.180

Docks, piers, moorage piles or buoys, floats or launching facilities are allowed only for water dependent uses or for public access and shall be limited to the minimize size necessary to support the use. New private boat launch ramps are not allowed; ... Only one dock, pier, moorage pile or buoy, float or launching facility may be allowed for a single detached residential lot and only if the ap...

King County Code § 16.82.051.E.23

Clearing for the purposes of wildfire preparedness ..., as follows: a. understory clearing within fifteen feet of a residential structure containing habitable space or an attached deck; ... c. within thirty feet of a residential structure ..., understory clearing and tree pruning underneath a tree crown to provide up to ten feet of vertical clearance from the ground to remove ladder fuels. Tree...

King County Code § 21A.06.490; § 21A.24.240(E)(1)

Flood protection elevation: an elevation that is three feet above the base flood elevation. ... New, substantially improved or converted residential buildings and flood mitigation home elevations shall meet the following standards: 1. Elevate the lowest floor, including basement, to or above the flood protection elevation;