Wash. Rev. Code § 87.04.030
When a new irrigation district comprising more than two hundred thousand acres has been authorized, pursuant to law, the board of county commissioners shall, within thirty days from the canvassing of the returns, divide the district into director divisions equal to the number of directors, and in the resolution organizing the district, they shall include an order designating the director divisions and describing the boundaries thereof. When a petition for the formation of a new irrigation district comprising less than two hundred thousand acres has been filed pursuant to law and said petition includes a request that the district be divided into director divisions, the board of county commissioners shall divide the district into director divisions as provided in this section unless objections to director divisions are made at the hearing held pursuant to RCW 87.03.020; and in the event objections to director divisions are made and not withdrawn, the board of county commissioners may deny the request for director divisions or if it determines that it is to the best interests of the district that director divisions be established, it may, in its order calling an election for organization of the district, include a separate proposition on the question of director divisions; and if a majority of the votes cast on said proposition are in favor of director divisions, then the resolution organizing the district shall include an order designating the director divisions and describing the boundaries thereof.
RCW 87.04.030