Wash. Rev. Code § 87.03.085
Fifteen days before any election held under this chapter, subsequent to the organization of any district, the secretary of the board of directors shall cause notices to be posted in three public places in each election precinct, of the time and place of holding the election. The secretary shall also post a general notice of the same in the office of the board, which shall be established and kept at some fixed place to be determined by the board, specifying the polling places of each precinct. Prior to the time for posting the notices, the board must appoint for each precinct, from the electors thereof, one inspector and two judges, who shall constitute a board of election for the precinct. If the board fails to appoint a board of election, or the members appointed do not attend at the opening of the polls on the morning of election, the electors of the precinct present at that hour may appoint the board, or supply the place of an absent member thereof. The board of directors must, in its order appointing the board of election, designate the house or place within the precinct where the election must be held. However, in any irrigation district that is less than two hundred thousand acres in size and is divided into director divisions, the board of directors in its discretion may designate one polling place within the district to serve more than one election precinct. The board of directors of any irrigation district may designate the principal business office of the district as a polling place to serve one or more election precincts and may do so regardless of whether the business office is located within or outside of the boundaries of the district. If the board of directors does designate a single polling place for more than one election precinct, then the election officials appointed by the board of directors may serve more than one election precinct and the election officials may be electors of any of the election precincts for which they are the election board.
RCW 87.03.085