Wash. Rev. Code § 47.56.230
When any toll bridge or bridges authorized under this chapter is being built by the department, the department may carry or cause to be carried an amount of insurance or indemnity bond or bonds as protection against loss or damage as the department may deem proper. The department is hereby further empowered to carry such an amount of insurance to cover any accident or destruction in part or in whole to any toll bridge or toll bridges until all bonds sold for the construction of the toll bridge or toll bridges and interest accrued thereon have been fully redeemed and paid. All moneys collected on any indemnity bond or insurance policy as the result of any damage or injury to the toll bridge or toll bridges shall be used for the purpose of repairing or rebuilding the toll bridge or toll bridges as long as there are revenue bonds against any such structure outstanding and unredeemed. The department is also empowered to carry insurance or indemnity bonds insuring against the loss of tolls or other revenues to be derived from any such toll bridge or bridges by reason of any interruption in the use of the toll bridge or toll bridges from any cause whatever, and the proceeds of the insurance or indemnity bonds shall be paid into the fund into which the tolls and other revenues of the bridge thus insured are required to be paid and shall be applied to the same purposes and in the same manner as other moneys in the fund. The insurance or indemnity bonds may be in an amount equal to the probable tolls and other revenues to be received from the operation of the toll bridge or toll bridges during any period of time that may be determined by the department and fixed in its discretion, and be paid for out of the toll revenue fund as may be specified in the proceedings. The department may provide in the proceedings authorizing the issuance of bonds for the carrying of insurance as authorized by this chapter, and the purchase and carrying of insurance as authorized by this chapter, and the purchase and carrying of such insurance shall thereupon be obligatory upon the department and be paid for out of the toll revenue fund as may be specified in the proceedings.
RCW 47.56.230