Wash. Rev. Code § 85.06.190
The work on said improvement shall begin and shall be completed with all expedition possible, and said board of commissioners of such drainage district, or any contractor thereunder, shall have no power whatever to change said route or system of improvement or the manner of doing the work therein so as to make any radical changes in said improvement, without the written consent of all the landowners to be benefited thereby, and the landowners which may be damaged thereby. And in case any substantial changes in said system of improvement or the manner of the construction thereof shall be deemed necessary by said board of commissioners at any time during the progress thereof, and if the written consent to such changes cannot be procured from said landowners, then said commissioners, for and on behalf of said district, shall file a petition in the superior court of the county within which said district is located, setting forth therein the changes which they deem necessary to be made in the plan or manner of the construction of said improvement, and praying therein to be permitted to make such changes, and upon the filing thereof, the commissioners shall cause a summons to be served, setting forth the prayer of said petition, under the seal of said court, which summons shall be served in the same manner as the service of summons in the case of the original petition, upon all the landowners or others claiming any lien or interest therein appearing of record in said district, and any or all of said parties so served may appear in said cause and submit their objections thereto, and after the time for the appearance of all of said parties has expired, the court shall proceed to hear said petition at once without further delay, and if it appears during the course of said proceedings that the property rights of any of said landowners will be affected by such proposed change in said improvements, then the court, after having passed upon all preliminary questions as in the original proceedings may call a jury to be impaneled as in the case of the original proceeding for the establishment of said improvements, and upon the final hearing of said cause, the jury shall return a verdict finding the amount of damages, if any, sustained by all persons and corporations, the same as upon the original petition, by reason of such proposed change, and shall readjust the amount of benefits claimed to have been increased or diminished by any of said landowners by reason of said proposed change in said improvements, and the proceedings thereafter shall be the same as to rendering judgment, appeal therefrom, payment of compensation and damages and filing of the certificate with the auditor, as hereinbefore provided for in the proceedings upon the original petition, and said commissioners shall have a right thereafter to proceed with the construction of said improvements according to the changes made therein.
RCW 85.06.190