Wash. Rev. Code § 35A.09.030
On the petition of a number of qualified electors of a charter code city equal to ten percent of the total votes cast at the last preceding municipal general election, the legislative body of such charter code city shall, or without such petition, may, by resolution, cause an election to be held for the election of a charter commission of fifteen freeholders for the purpose of preparing a new or revised charter for the city by altering, revising, adding to, or repealing the existing charter including all amendments thereto. The members of the charter commission shall be qualified and nominated as provided by chapter 35A.08 RCW. At such election the proposition of whether or not a charter commission shall be created at all shall be separately stated on the ballots and unless a majority of the votes cast upon that proposition favor it, no further steps shall be taken in the proceedings.
RCW 35A.09.030
Sufficiency of petition in code city: RCW 35A.01.040.