Wash. Rev. Code § 67.38.050
The number of persons on the governing body of the district and how such persons shall be selected and replaced shall be included in the resolution of the county legislative authority providing for the submittal of the proposition to create the district to the voters. Members of the governing body may only consist of a combination of city councilmembers or mayors of the city or cities included within the district, members of the county legislative authority, the county executive of a county operating under a home rule charter, elected members of the governing bodies of municipalities located within the district, and members of the board of regents of a community college district. No governing body may consist of more than nine members. The resolution may also provide for additional, ex officio, nonvoting members consisting of elected officials or appointed officials from the counties, cities, or municipalities which are located all or partially within the boundaries of such a district and who [which] do not have elected or appointed officials sitting on the governing body.
Any member of the governing body, or any ex officio member, who is not an elective official whose office is a full-time position may be reimbursed for reasonable expenses actually incurred in attending meetings or engaging in other district business as provided in RCW 42.24.090.
RCW 67.38.050