Wash. Rev. Code § 86.09.418
Upon completion of the control works of the district or of any unit thereof, the board of directors of the district may, with the written consent of the county legislative authority of the county within which the major portion of the district is situated, and upon petition signed by landowners representing twenty-five percent of the acreage of the lands in the district or twenty-five percent of the value of the assessments of the district shall, appoint three qualified persons who shall be approved in writing by the county legislative authority, to act as a board of appraisers and who shall reconsider and revise and/or reaffirm the classification and relative percentages, or any part or parts thereof, in the same manner and with the same legal effect as that provided herein for the determination of such matters in the first instance: PROVIDED, That such reexamination shall have no legal effect on any assessments regularly levied prior to the order of appraisal by the reexamining board of appraisers.
RCW 86.09.418