Wash. Rev. Code § 85.16.190
The decision of the board upon any objections to the determination of benefits and/or apportionment of costs and/or the levy of the assessments therefor, made within the time and in the manner prescribed in RCW 85.16.130, may be reviewed by the superior court of the county in which the district is situated and thereafter by the supreme court or the court of appeals within the time and in the manner and upon the conditions, so far as applicable, provided in RCW 85.08.440, with respect to appeals from and appellate review of the board's apportionment of the cost of construction of the district's system of improvements. The provisions of RCW 85.08.450, shall be controlling as to the regularity, validity, and conclusiveness of all the proceedings hereunder.
RCW 85.16.190
Severability-1988 c 202: See note following RCW 2.24.050.