Wash. Rev. Code § 35.58.540
Upon receipt of a duly certified petition calling for an election on the annexation of territory to a metropolitan municipal corporation, or if the metropolitan council shall determine without a petition being filed, that an election on the annexation of any adjacent territory shall be held, the metropolitan council shall fix a date for a public hearing thereon which shall be not more than sixty nor less than forty days following the receipt of such petition or adoption of such resolution. Notice of such hearing shall be published once a week for at least four consecutive weeks in one or more newspapers of general circulation within the territory proposed to be annexed. The notice shall contain a description of the boundaries of the territory proposed to be annexed and shall state the time and place of the hearing thereon and the fact that any changes in the boundaries of such territory will be considered at such time and place. At such hearing or any continuation thereof, any interested person may appear and be heard on all matters relating to the proposed annexation. The metropolitan council may make such changes in the boundaries of the territory proposed to be annexed as it shall deem reasonable and proper, but may not delete any portion of the proposed area which will create an island of included or excluded lands and may not delete a portion of any city. If the metropolitan council shall determine that any additional territory should be included in the territory to be annexed, a second hearing shall be held and notice given in the same manner as for the original hearing. The metropolitan council may adjourn the hearing on the proposed annexation from time to time not exceeding thirty days in all. At the next regular meeting following the conclusion of such hearing, the metropolitan council shall, if it finds that the annexation of such territory will be conducive to the welfare and benefit of the persons and property therein and the welfare and benefit of the persons and property within the metropolitan municipal corporation, adopt a resolution fixing the boundaries of the territory to be annexed and causing to be called a special election on such annexation to be held not more than one hundred twenty days nor less than sixty days following the adoption of such resolution.
RCW 35.58.540