Wash. Rev. Code § 36.69.240
Notice of the adoption of the resolution of intention shall be given each owner or reputed owner of any lot, tract, parcel of land or other property within the proposed improvement district by mailing said notice at least fifteen days before the date fixed for the public hearing to the owner or reputed owner of the property as shown on the tax rolls of the county treasurer at the address shown thereon. The notice shall refer to the resolution of intention and designate the proposed improvement district by number. Said notice shall also set forth the nature of the proposed improvement, the total estimated cost, the proportion of total cost to be borne by assessments, the estimated amount of the cost and expense of such improvement to be borne by the particular lot, tract or parcel, the date, time and place of the hearing before the board of park and recreation commissioners; and in the case of improvements initiated by resolution, the notice shall also state that all persons desiring to object to the formation of the proposed district must file their written protests with the secretary of the board before the time fixed for said public hearing.
RCW 36.69.240