After the director issues his or her final decision approving the issuance, amendment, or termination of a marketing order, the director shall determine by a referendum whether the affected parties or producers assent to the proposed action or not. The director shall conduct the referendum among the affected parties or producers based on the list as provided for in RCW
15.66.060 or
15.66.143, as applicable, and the affected parties or producers shall be deemed to have assented to the proposed issuance or termination order if fifty-one percent or more by number reply to the referendum within the time specified by the director, and if, of those replying, sixty-five percent or more by number and fifty-one percent or more by volume assent to the proposed order. The producers shall be deemed to have assented to the proposed amendment order if sixty percent or more by number and sixty percent or more by volume of those replying assent to the proposed order. The determination by volume shall be made on the basis of volume as determined in the list of affected producers created under provisions of RCW
15.66.060, subject to rules and regulations of the director for such determination. The director shall consider the approval or disapproval of any cooperative marketing association authorized by its producer members to act for them in any such referendum, as being the approval or disapproval of the producers who are members of or stockholders in or under contract with such association of cooperative producers: PROVIDED, That the association shall first determine that a majority of the membership of the association authorize its action concerning the specific marketing order. Results of the referendum shall be mailed to all affected parties in the form of a postcard. If the requisite assent is given, the director shall adopt the order.