Snohomish County, WA Environmental Rules: Boat Dock Permits (2026)

517 governs docks, piers, floats, boathouses and mooring buoys anywhere within shoreline jurisdiction (the area regulated by the county's Shoreline Management Program). On marine shorelines, a single-family pier or dock cannot exceed 90 feet measured perpendicularly from the ordinary high water mark (OHWM); shared moorage may reach 110 feet if the applicant demonstrates the extra length is necessary. Every pier or dock is capped at six feet wide, with walkway ramps limited to four feet wide and required to be fully grated. On lake shorelines the waterward intrusion cannot exceed the average intrusion of neighboring docks, and in no case may it extend past 80 feet from the OHWM or the point where the water is eight feet deep, whichever comes first; the first 30 feet of any dock on a salmon-bearing lake must narrow to four feet wide.

Floats are limited to one per single-family residence, no more than 100 square feet, and may not sit more than 45 feet waterward of the OHWM on lakes. Decking on any dock, pier or float must allow at least 40 percent open spacing (grating, gapped boards, or light prisms) to let light reach the water below. Private boathouses are capped at 12 feet high, 500 square feet total, no wider than 25 percent of the shoreline lot's width, and may extend no more than 25 feet beyond the mean low waterline; side walls are prohibited and covered boathouses need a three-foot side setback unless shared with the neighbor.

None of these structures may impede navigation, sit over critical saltwater habitat or spawning areas, or use toxic-treated materials in contact with the water. Whether a facility is even allowed depends on the shoreline's environment designation: all boat mooring is permitted in the Urban designation, conditionally permitted for public/commercial docks in Urban Conservancy, and prohibited outright in the Natural and Municipal Watershed Utility designations.