Wash. Rev. Code § 87.03.480
Any desired special construction, reconstruction, betterment or improvement or purchase or acquisition of improvements already constructed, for any authorized district service, including but not limited to the safeguarding of open canals or ditches for the protection of the public therefrom, which are for the special benefit of the lands tributary thereto and within an irrigation district may be constructed or acquired and provision made to meet the cost thereof as follows:
The holders of title or evidence of title to one-quarter of the acreage proposed to be assessed, may file with the district board their petition reciting the nature and general plan of the desired improvement and specifying the lands proposed to be specially assessed therefor. A local improvement district may include adjoining, vicinal, or neighboring improvements even though the improvements and the properties benefited are not connected or continuous. Such improvements may be owned by the United States, the state of Washington, the irrigation district, or another local government. Upon approval of the board of an adjoining irrigation district, an irrigation district may form local improvement districts or utility local improvement districts that are composed entirely or in part of territory within that adjoining district. Upon the filing of the petition the board, with the assistance of a competent engineer, shall make an investigation of the feasibility, cost, and need of the proposed local improvement together with the ability of the lands to pay the cost, and if it appears feasible, they may elect to have plans and an estimate of the cost prepared. If a protest against the establishment of the proposed improvement signed by a majority of the holders of title in the proposed local district is presented at or before the hearing, or if the proposed improvement should be found not feasible, too expensive, or not in the best interest of the district, or the lands to be benefited insufficient security for the costs, they shall dismiss the petition.
RCW 87.03.480
Safeguarding open canals or ditches: RCW 35.43.040, 35.43.045, 35.44.045, 36.88.015, 36.88.350, 36.88.380 through 36.88.400, and 87.03.526.