Wash. Rev. Code § 17.12.050
The county treasurer shall be ex officio treasurer for each of such districts so formed and the county assessor and other county officers shall take notice of the formation of such district or districts and shall be governed thereby according to the provisions of this chapter. The assessment or the tax levies as hereinafter provided for shall be extended on the tax rolls against the property liable therefor the same as other assessments or taxes are extended, and shall become a part of the general tax against such property and be collected and accounted for the same as other taxes are, with the terms and penalties attached thereto. The moneys so collected shall be held and disbursed as a special fund for such district and shall be paid out only on warrant issued by the county auditor upon voucher approved by the board of county commissioners.
RCW 17.12.050