Wash. Rev. Code § 36.88.060
Whether the improvement is initiated by petition or resolution the board shall conduct a public hearing at the time and place designated in the notice to property owners. At this hearing, the board may make such changes in the boundaries of the district or such modifications in the plans for the proposed improvement as shall be deemed necessary: PROVIDED, That the board may neither so alter the improvement as to increase the estimated cost by an amount greater than ten percent above that stated in the notice, nor increase the proportionate share of the cost to be borne by assessments from the proportion stated in the notice, nor change the boundaries of the district to include property not previously included therein without first passing a new resolution of intention and giving a new notice to property owners, in the manner and form and within the time herein provided for the original notice.
At said hearing, the board shall select the method of assessment, ascertain whether the plan of improvement or construction is feasible and whether the benefits to be derived therefrom by the property within the proposed district, together with the amount of any county road fund participation, exceed the costs and expense of the formation of the proposed district and the contemplated construction or improvement and shall make a written finding thereon. In case the proceedings have been initiated by petition, the board shall find whether the petition including all additions thereto or withdrawals therefrom made prior to five o'clock p.m. of the day before the hearing is sufficient within the boundaries of the district so established at said hearing by the board. If said petition shall be found insufficient the board shall by resolution declare the proceedings terminated. In case the proceedings have been initiated by resolution if the board shall find the improvement to be feasible, it shall continue the hearing until a day not more than fifteen days after the date for returning ballots for the purpose of determining the results of said balloting.
After the hearing the board may proceed to adopt a resolution creating the district and ordering the improvement. Such resolution shall establish such district as the ". . . . . . county road improvement district No. . . . ." Such resolution shall describe the nature and territorial extent of the improvement to be made and the boundaries of the improvement district, shall describe the method of assessment to be used, shall declare the estimated cost and the proportion thereof to be borne by assessments, and shall contain a finding as to the result of the balloting by property owners in case the improvement shall have been initiated by resolution.
Upon the adoption of the resolution establishing the district, the board shall have jurisdiction to proceed with the improvement. The board's findings on the sufficiency of petitions or on the results of the balloting shall be conclusive upon all persons.
RCW 36.88.060