Wash. Rev. Code § 87.80.050
Notice of the hearing on the petition shall be given by the clerk of the board of county commissioners by publishing the same, at the cost of the board of control, if created, otherwise at the cost of the petitioners, in the official newspaper of each county containing lands irrigated from the source of supply of the entities signing the petition. The notice shall be published in at least three weekly issues thereof. However, the time of the hearing shall not be less than thirty days from the date of the first publication of the notice. A copy of the notice shall be posted at the regular meeting place of the board of directors of each irrigation entity concerned in the granting or denial of the petition and a copy of the notice shall be mailed to the department of ecology at Olympia at least thirty days prior to the day of the hearing.
RCW 87.80.050