Wash. Rev. Code § 47.56.130
The department is hereby empowered to issue bonds for the construction of any toll bridge or toll bridges authorized under the provisions of this chapter. Any and all bonds issued for the construction of any toll bridge or toll bridges under the authority of the department shall be issued in the name of the department, shall constitute obligations only of the department, shall be identified as . . . . . . toll bridge bonds, and shall contain a recital on the face thereof that the payment or redemption of the bonds and the payment of the interest thereon is secured by a direct and exclusive charge and lien upon the tolls and other revenues of any nature whatever received from the operation of the particular toll bridge or bridges for the construction of which the bonds are issued and that neither the payment of the principal or any part thereof nor of the interest thereon or any part thereof constitutes a debt, liability, or obligation of the state of Washington. The department is empowered to receive and accept funds from the state of Washington or the federal government upon a cooperative or other basis for the construction of any toll bridge authorized under this chapter and is empowered to enter into such agreements with the state of Washington or the federal government as may be required for the securing of such funds.
RCW 47.56.130