Wash. Rev. Code § 35A.02.060
When a petition which is sufficient under the rules set forth in RCW 35A.01.040 is filed with the legislative body of an incorporated city or town, signed by qualified electors of such municipality in number equal to not less than ten percent of the votes cast at the last general municipal election, seeking adoption by the city or town of the classification of noncharter code city and the reorganization of the city or town under one of the plans of government authorized in this title, the county auditor shall file with the legislative body thereof a certificate of sufficiency of such petition. Thereupon, the legislative body shall cause such proposal to be submitted to the voters at the next general municipal election if one is to be held within one hundred eighty days after certification of the sufficiency of the petition, or at a special election to be held for that purpose not less than ninety days nor more than one hundred and eighty days from such certification of sufficiency. Ballot titles for elections under this chapter shall be prepared by the city attorney.
RCW 35A.02.060