Wash. Rev. Code § 47.60.122
For the purpose of paying the cost of acquiring, constructing, or reconstructing ferries or ferry terminal facilities, and all costs which may be incurred in connection therewith, the department is authorized to issue interim revenue warrants, which shall constitute obligations only of the department, and which shall not be obligations of the state of Washington. Such warrants shall be payable solely out of part or all of the revenues derived from the operation of the Puget Sound ferry system as shall be provided in the resolution authorizing their issuance, and shall be drawn upon, and the principal thereof and interest thereon shall be payable out of, such fund or funds as shall be created in and provided by the resolution. The warrants may be interest-bearing coupon warrants with a fixed maturity date, or may be interest-bearing registered warrants payable in order of their issuance whenever there is sufficient money in the fund upon which they were drawn to redeem any of them.
RCW 47.60.122