Wash. Rev. Code § 35.92.260
When a city or town makes local improvements for any of the purposes specified in RCW 35.92.220 and 35.92.230, as now or hereafter amended, the proceedings relative to the creation of districts, financing of improvements, levying and collecting assessments and all other procedure shall be had, and the legislative authority shall proceed in accordance with the provisions of the laws relating to local improvement districts in cities of the first class: PROVIDED, That when the improvement is initiated upon petition, the petition shall set forth the fact that the signers are the owners according to the records in the office of the county auditor, of property to an aggregate amount of a majority of the surface area within the limits of the assessment district to be created: PROVIDED FURTHER, That when an assessment is made for any purpose other than the construction or reconstruction of any system or means of distribution or delivery of water, it shall not be necessary for the legislative authority to be furnished with a statement of the aggregate assessed valuation of the real estate exclusive of improvements in the district according to the valuation last placed upon it for purposes of general taxation, or the estimated amount of the cost of the improvement to be borne by each tract of land or other property, but a statement by the engineer or other officer, showing the estimated cost of the improvement per square foot, shall be sufficient: PROVIDED FURTHER, That when the legislative authority of a city or town shall deem it necessary to levy special assessments for the purposes specified in RCW 35.92.230, as now or hereafter amended, other than for the purpose of paying the costs of acquiring, constructing or reconstructing any system or means of distribution or delivery of water for irrigation or domestic purposes, the legislative authority for such city or town may hold a single hearing on the assessment rolls for all irrigation local improvement districts within the city or town. Such legislative authority shall fix the date of such hearing and shall direct the city or town clerk to give notice thereof, in the form prescribed by RCW 35.44.080, by publication thereof in a legal newspaper of general circulation in the city or town, once, not less than fifteen days prior to the date fixed for hearing; and by mailing, not less than fifteen days prior to the date fixed for hearing, notice thereof to the owner or reputed owner of each item of property described on the assessment roll whose name appears on such roll at the address of such owner or reputed owner shown on the tax rolls of the county treasurer for each such item of property: PROVIDED FURTHER, That when an assessment roll is once prepared and does not include the cost of purchase, construction, or reconstruction of works of delivery or distribution and the legislative authority of such city or town decides to raise a similar amount the ensuing year, it shall not be necessary to prepare a new assessment roll, but the legislative authority may pass a resolution of intention estimating the cost for the ensuing year to be the same as the preceding year, and directing the clerk to give notice stating the estimated cost per square foot of all land within the district and refer persons interested to the books of the treasurer, and fixing the date for a hearing on such assessment roll. Notice of such hearing shall be given by the city or town clerk in the form and manner required in the preceding proviso. The treasurer shall be present at the hearing and shall note any changes on his or her books. The legislative authority shall have the same right to make changes in the assessment roll as in an original assessment, and after all changes have been made it shall, by ordinance, confirm the assessment and direct the treasurer to extend it on the books of his or her office.
RCW 35.92.260