Wash. Rev. Code § 17.28.070
If the county commissioners deem it proper to include any territory not proposed for inclusion within the proposed boundaries, they shall first cause notice of intention to do so to be mailed to each owner of land in the territory whose name appears as owner on the last completed assessment roll of the county in which the territory lies, addressed to the owner at his or her address given on the assessment roll, or if no address is given, to his or her last known address; or if it is not known, at the county seat of the county in which his or her land lies. The notice shall describe the territory and shall fix a time, not less than two weeks from the date of mailing, when all persons interested may appear before the county commissioners and be heard.
The boundaries of a district lying in a city shall not be altered unless the governing board of the city, by resolution, consents to the alteration.
RCW 17.28.070