Wash. Rev. Code § 88.32.080
Any person interested in any real estate affected by such assessment may appear and file objections to the assessment roll, and the board of county commissioners may make an order regarding the time of filing such objections, as to them seems proper. As to all parcels, lots or blocks as to which no objections are filed within the time so fixed, the assessment thereon shall be confirmed. On the hearing, each party may offer proof and the board shall then have authority to affirm, modify, change and determine the assessment in such sum as to them appears just and right. When the assessment is finally equalized and fixed by the board of county commissioners, the clerk thereof shall certify the same to the county treasurer for collection, or if appeal has been taken from any part thereof, then so much thereof, as has not been appealed from, shall be certified.
RCW 88.32.080