Wash. Rev. Code § 54.16.140
Any such improvement shall be ordered by resolution of the commission either upon petition or resolution therefor. When a petition, signed by ten percent of the owners of land in the district to be therein described, is filed with the commission, asking that the plan or improvement therein set forth be adopted and ordered, and defining the boundaries of a local improvement district to be assessed in whole or in part to pay the cost thereof, the commission shall fix the date of hearing thereon, and give not less than two weeks notice thereof by publication. The commission may deny the petition or order the improvement, unless a majority of the owners of lands in the district file prior to twelve o'clock noon of the day of the hearing, with the secretary a petition protesting against the improvement. If the commission orders the improvement, it may alter the boundaries of the proposed local district and prepare and adopt detail plans of the local improvement, declare the estimated cost thereof, what proportion thereof shall be borne by the local improvement district, and what proportion, if any shall be borne by the entire public utility district.
RCW 54.16.140