Wash. Rev. Code § 85.16.150
When the board shall have determined that the schedule or schedules of benefits and/or apportionment of costs as filed or as changed and modified by it are fair, just and equitable and, if estimated costs have been apportioned, that said benefits equal or exceed said costs apportioned, the members of the board approving the same shall sign said schedule or schedules and cause the clerk of the board to attest their signatures under his or her seal, and shall enter an order in the journal approving and confirming the final determination of such benefits and apportionment of costs and all proceedings leading thereto and in connection therewith. If separate schedules be established for maintenance of the diking system and of the drainage system, the board shall by order establish two separate maintenance funds, one for the maintenance of the diking system and one for the maintenance of the drainage system.
RCW 85.16.150