Wash. Rev. Code § 85.08.230
Whenever the board of county commissioners has passed a resolution establishing a district, the county commissioners may at their meeting on the first Monday in October next ensuing and at the same time in each year thereafter until the improvement has been completed and a statement of total costs has been filed, levy an assessment against the property within the district to defray the preliminary expenses of the district, the levy to be based upon the estimated benefits as shown by the report of the county engineer on file in the auditor's office. The assessment so made shall be considered and credited to the respective pieces of property by the board of appraisers and by the county commissioners at the hearing on the assessment roll and the final apportionment. The preliminary assessments herein provided for shall be levied and collected in the same manner as the final assessment and shall be credited to the construction fund and used for the redemption of warrants issued against the same. Preliminary expenses shall mean all of the expenses incurred in the proceedings for the organization of the district and in other ways prior to the beginning of the actual construction of the improvement.
RCW 85.08.230