Wash. Rev. Code § 17.12.020
Whenever ten or more resident freeholders in any county petition the board of county commissioners, asking that their lands be included, either separately or with other lands designated in the petition in a district to be formed for the purpose of preventing, destroying, or exterminating any of the animals, rodents or other such things described in RCW 17.12.010, or that such lands be included within a district already formed by the enlargement of such district, or a new district or districts be formed out of a district or districts then in existence or out of territory partly in districts already formed and not included in any district, and such petition indicating the boundaries of such proposed district, whether all or any part of such county, and stating the purpose of such district, the board shall fix a time for the hearing of such petition and shall give at least thirty days notice of the time and place of such hearing by posting copies of such notice of the time and place of such hearing in three conspicuous places within the proposed district and posting one copy of such notice at the courthouse or place of business of the board, and also by mailing to each freeholder within the proposed district a copy of such notice, to his last known residence, if known, and if not known to the clerk of such board, then and in that event the posting shall be deemed sufficient: PROVIDED, HOWEVER, If the board shall deem it impractical to mail notices to each freeholder, within the proposed district, or if the post office address of all the freeholders are not known, then in that event when recited in a resolution adopted by the board, the notice in addition to posting, shall be published once a week for three successive weeks in the county official paper if there is such, and if there be no official paper, then in some paper published in said county, and if there be no paper published in said county, then in some paper of general circulation within the proposed district. The persons in whose name the property is assessed shall be deemed the owners thereof for the purpose of notice as herein required: PROVIDED, HOWEVER, That for lands belonging to the state, the commissioner of public lands shall be notified, and for lands belonging to the county, the county auditor shall be notified, and if such lands are under lease or conditional sale the lessee or purchaser shall also be notified in the manner above provided. Any person interested may appear at the time of such hearing and may under such rules and regulations as the board may prescribe give his or her reasons for or objections to the creation of such a district.
RCW 17.12.020