Wash. Rev. Code § 85.08.890
None of the indebtedness of the drainage improvement district, joint drainage improvement district, or consolidated drainage improvement district, or of the drainage improvement districts taken into the consolidated drainage improvement district, shall be affected by the merger and dissolution, and all lands liable to be assessed to pay such indebtedness shall remain liable to the same extent as if the merger and dissolution had not taken place, and all assessments theretofore levied shall remain unimpaired and shall be collected in the same manner as if no merger had taken place. The board or boards of directors of the irrigation district or irrigation districts with which the drainage improvement district, joint drainage improvement district, or consolidated drainage improvement district was merged shall have all the powers possessed at the time of the merger by the board of supervisors of the drainage improvement district, joint drainage improvement district, or consolidated drainage improvement district and the board or boards of county commissioners may levy and cause to be collected any and all assessments against any of the lands formerly within the drainage improvement district, joint drainage improvement district, or consolidated drainage improvement district necessary for the payment of all indebtedness thereof, and of the drainage improvement districts taken into the consolidated drainage improvement district. Until the assessments are collected and all indebtedness of each drainage improvement district or joint drainage improvement district included in the merger, either as such or, in the case of the former, as a part of a consolidated drainage improvement district, is paid, separate funds shall be maintained for each such drainage improvement district or joint drainage improvement district as were maintained before the merger.
RCW 85.08.890