Wash. Rev. Code § 68.54.100
A part of one district may be transferred and merged with an adjacent district whenever such area can be better served by the merged district. To effect such a merger a petition, signed by not less than fifteen percent of the qualified electors residing in the area to be merged, shall be filed with the commissioners of the merging district. Such petition shall be promoted by one or more qualified electors within the area to be transferred. If the commissioners of the merging district act favorably upon the petition, then the petition shall be presented to the commissioners of the merger district. If the commissioners of the merger district act favorably upon the petition, an election shall be called in the area merged.
In the event that either board of cemetery commissioners should not concur with the petition, the petition may then be presented to a county review board established for such purposes, if there be no county review board for such purposes then to the state review board and if there be no state review board, then to the county commissioners of the county in which the area to be merged is situated, who shall decide if the area can be better served by such a merger; upon an affirmative decision an election shall be called in the area merged.
A majority of the votes cast shall be necessary to approve the transfer.
RCW 68.54.100