Wash. Rev. Code § 85.08.880
If a majority of the votes cast favor merger, the board or boards of county commissioners shall enter an order approving the petition and ordering the merger and file a certified copy thereof with the county auditor or auditors of the county or counties in which the district is situated, and the drainage improvement district, joint drainage improvement district, or consolidated drainage improvement district shall thereupon be dissolved and its system of improvements vested in the irrigation district or irrigation districts without further proceedings. If a majority of the votes cast are against merger, the board of commissioners shall enter an order dismissing the proceedings. If the merger is approved, the expenses of the county or counties in connection with the election will be paid by the irrigation district or irrigation districts, with each irrigation district, if there is more than one, paying the same portion of the expenses as that portion of the drainage improvement district, joint drainage improvement district, or consolidated drainage district which is merged into the irrigation district. If the merger is not approved, the expenses of the county or counties in connection with the election will be paid by the drainage improvement district, joint drainage improvement district, or consolidated drainage improvement district.
RCW 85.08.880