Wash. Rev. Code § 36.94.030
Whenever the county legislative authority deems it advisable and necessary for the public health and welfare of the inhabitants of the county to establish, purchase, acquire, and construct a system of sewerage and/or water, or make any additions and betterments thereto, or extensions thereof, the board shall adopt a sewerage and/or water general plan for a system of sewerage and/or water for all or a portion of the county as deemed necessary by the board. If the county has adopted a comprehensive plan for a physical development of the county pursuant to chapter 36.70 RCW and/or chapter 35.63 RCW, then the sewerage and/or water general plan shall be adopted as an element of that comprehensive plan pursuant to the applicable statute.
RCW 36.94.030
Severability-1981 c 313: See note following RCW 36.94.020.