Wash. Rev. Code § 87.03.670
If there be outstanding bonds of the district, or consolidated district, as the case may be, or if such district shall have entered into a contract with the United States, or the state of Washington, then the board may adopt a resolution to the effect that the board deems it to the best interest of the district that the lands mentioned in the petition, or some portion thereof, or the former district mentioned in the petition, as the case may be, should be excluded from the district, or consolidated district, and the former district reestablished. The resolution shall describe such lands so that the boundaries can readily be traced, or shall give the corporate name and number of the former district. The holders of such outstanding bonds may give their assent, in writing, to the effect that they severally consent that the board may make an order by which the lands, or the former district, mentioned in the resolution may be excluded from the district, and in case contract has been made with the United States, or the state of Washington, the secretary of the interior or the director of ecology may assent to such change. The assent must be acknowledged by the several holders of such bonds in the same manner and form as is required in case of a conveyance of land, and the acknowledgment shall have the same force and effect, as evidence, as the acknowledgment of such conveyance. The assent of the secretary of the interior need not be acknowledged. The assent shall be filed with the board, and in the office of the county clerk in each county comprised within the district and must be recorded in the minutes of the board; and said minutes, or certified copy thereof, shall be admissible in evidence with the same effect as the said assent; but if such assent of the bondholders, and in case of contract with the United States, or the state of Washington, such assent of the secretary of the interior or the director of ecology, be not filed, the board shall deny and dismiss said petition.
RCW 87.03.670
Acknowledgments: Chapter 64.08 RCW.
Board's powers and duties generally (contracts with state and United States): RCW 87.03.140.
Certificate of acknowledgment-Evidence: RCW 64.08.050.