Wash. Rev. Code § 87.03.735
The board of directors of the irrigation district, if it deems it not for the best interest of the irrigation district that the proposed merger take place, shall enter an order refusing to assent to the merger. But, if it deems it to be to the best interest of the irrigation district that the merger take place and, if twenty-five or more persons interested in the irrigation district have not shown cause in writing why the proposed merger should not take place, or, if having shown cause, withdraw the same, the board of directors of the irrigation district may enter an order assenting to the proposed merger.
If twenty-five or more persons interested in the irrigation district shall show cause, as aforesaid, why the proposed merger should not take place and shall not withdraw the same, and if the irrigation district board nevertheless deems it for the best interest of the irrigation district that the proposed merger take place, the board shall adopt a resolution to that effect.
RCW 87.03.735