Wash. Rev. Code § 58.17.080
Notice of the filing of a preliminary plat of a proposed subdivision adjacent to or within one mile of the municipal boundaries of a city or town, or which contemplates the use of any city or town utilities shall be given to the appropriate city or town authorities. Any notice required by this chapter shall include the hour and location of the hearing and a description of the property to be platted. Notice of the filing of a preliminary plat of a proposed subdivision located in a city or town and adjoining the municipal boundaries thereof shall be given to appropriate county officials. Notice of the filing of a preliminary plat of a proposed subdivision located adjacent to the right-of-way of a state highway or within two miles of the boundary of a state or municipal airport shall be given to the secretary of transportation. In the case of notification to the secretary of transportation, the secretary shall respond to the notifying authority within fifteen days of such notice as to the effect that the proposed subdivision will have on the state highway or the state or municipal airport.
RCW 58.17.080