Wash. Rev. Code § 36.94.350
In the event the agreement of the parties provides for the transfer to the county of all the property of the municipal corporation or all such property except bond redemption funds in the possession of the county treasurer from which outstanding bonds of the municipal corporation are payable, and the agreement also provides for the assumption and payment by the county of all the indebtedness of the municipal corporation including the payment and retirement of all its outstanding bonds, and if the petition of the parties so requests, the court in the decree approving and directing the transfer of property, or in a subsequent decree, may dissolve the municipal corporation effective as of the time of transfer of property or at such time thereafter as the court may determine and establish.
RCW 36.94.350