Wash. Rev. Code § 79.125.040
The department shall prepare plats showing all tidelands and shorelands, surveyed, platted, and appraised by it in the respective counties, on which shall be marked the location of all tidelands and shorelands, with reference to the lines of the United States survey of the abutting upland, and shall prepare a record of its proceedings, including a list of the tidelands and shorelands surveyed, platted, or replatted, and appraised by it and its appraisal of the tidelands and shorelands, which plats and books shall be in triplicate and the department shall file one copy of the plats and records in the department's Olympia office, and file one copy in the office of the county auditor of the county where the lands platted, or replatted, and appraised are situated, and file one copy in the office of the city engineer of the city in which, or within two miles of which, the lands platted, or replatted, are situated.
RCW 79.125.040