Wash. Rev. Code § 53.34.070
Revenue bonds and notes issued under the provisions of this chapter shall be payable solely from the revenues, income, receipts, profits, charges, fees, rentals, and moneys received or derived by or through the ownership, operation, sale, lease, or other disposition in whole or in part of any project or projects authorized under the provisions of this chapter, or through the issuance of refunding bonds or notes, and the commission of any district issuing revenue bonds or notes under the authority of this chapter shall establish, maintain, and collect rates, tolls, rents, and charges from time to time so long as any of such revenue bonds are outstanding and unpaid for all services sold, furnished, or supplied by or through any such project or projects sufficient to produce an amount, together with any other moneys of the district available and dedicated to such purpose, to pay the principal of and interest and premium, if any, on all revenue bonds and notes payable from the revenues of any project or projects as the same may respectively fall due in accordance with the terms of the resolution or resolutions or trust agreement authorizing the issuance and securing the payment of such obligations.
RCW 53.34.070