Wash. Rev. Code § 17.28.030
Before a city can be included as a part of the proposed district its governing body shall have requested that the city be included by resolution, duly authenticated.
The petition shall set forth and describe the boundaries of the proposed district and it shall request that it be organized as a mosquito control district. Upon receipt of such a petition, the auditor of the county in which the greater area of the proposed district is located shall be charged with the responsibility of examining the same and certifying to the sufficiency of the signatures thereon. For the purpose of examining the signatures on such petitions, the auditor shall be permitted access to the voters' registration books of each city and county located in the proposed district and may appoint the respective county auditors and city clerks thereof as his or her deputies. No person may withdraw his or her name from a petition after it has been filed with the auditor. Within thirty days following the receipt of such petition, the auditor shall transmit the same to the board of commissioners of the county in which the greater area of the proposed district is located, together with his or her certificate as to the sufficiency thereof.
RCW 17.28.030