Wash. Rev. Code § 52.14.015
In the event a board of commissioners of any fire protection district determines by resolution that it would be in the best interest of the district to increase the number of commissioners to five or seven, or in the event the board is presented with a petition signed by 10 percent of the registered voters resident within the district who voted in the last general municipal election calling for such an increase in the number of commissioners of the district, the board shall submit a resolution to the county legislative authority or authorities of the county or counties in which the district is located requesting that an election be held. Upon receipt of the resolution, the legislative authority or authorities of the county or counties shall call a special election to be held within the fire protection district at which election the following proposition shall be submitted to the voters substantially as follows:
Shall the board of commissioners of . . . . . county fire protection district no. . . . . . be increased from (three or five) members to (five or seven) members?
Yes . . . ..
No . . . ..
If the fire protection district is located in more than a single county, this proposition shall indicate the name of the district.
If the proposition receives a majority approval at the election, the board of commissioners of the fire protection district shall be increased to five or seven members. The additional members shall be appointed in the same manner as provided in RCW 52.14.020.
RCW 52.14.015