Wash. Rev. Code § 89.08.370
If the district is ordered dissolved, the supervisors shall forthwith terminate the affairs of the district and dispose of all district property at public auction, and pay the proceeds therefrom to pay any debts of the district and any remaining balance to the state treasurer.
They shall then file a verified application with the secretary of state for the dissolution of the district, accompanied by a certificate of the commission reciting the determination that further operation of the district is impracticable. The application shall recite that the property of the district has been disposed of, that the proceeds therefrom have been used to pay any debts of the district and any remaining balance paid to the treasurer, and contain a full accounting of the property and proceeds. Thereupon the secretary shall issue to the supervisors a certificate of dissolution and file a copy thereof in his or her records.
RCW 89.08.370