Wash. Rev. Code § 36.70.040
By ordinance a board may, as an alternative to and in lieu of the creation of a planning commission as provided in RCW 36.70.030, create a planning department which shall be organized and function as any other department of the county. When such department is created, the board shall also create a planning commission which shall assist the planning department in carrying out its duties, including assistance in the preparation and execution of the comprehensive plan and recommendations to the department for the adoption of official controls and/or amendments thereto. To this end, the planning commission shall conduct such hearings as are required by this chapter and shall make findings and conclusions therefrom which shall be transmitted to the department which shall transmit the same on to the board with such comments and recommendations it deems necessary.
RCW 36.70.040