Wash. Rev. Code § 87.53.140
Upon the dissolution of the district the county commissioners shall determine from the records the remaining bond and other indebtedness of the district, and shall determine the proper number of annual assessments, not over five, necessary to discharge the debt. They shall cause the county assessor to prepare the annual assessment roll for the lands in the district, based upon the acreages shown on the last district assessment roll. The commissioners shall levy annual assessments, not exceeding five, upon all property in the district assessed for the bond fund on the district's last assessment roll and according to the ratios of benefits there shown, sufficient to pay any remaining claims, including bonds. They shall levy and equalize the assessments, after the same notice of hearing as are required of district directors on irrigation assessments. The county auditor shall perform the duties of the secretary of the district and the county treasurer shall be ex officio treasurer of the district and shall collect the assessments. In all other respects the general irrigation district laws shall govern.
Any funds remaining after all assessments have been collected and all indebtedness and costs liquidated shall be paid over to the bondholders in cases where they have accepted a compromise settlement. Otherwise the surplus shall be distributed as by law provided.
RCW 87.53.140
General irrigation district laws: Chapter 87.03 RCW.