Sts. & Hy. Code, § 31158

If a bond issue for the acquisition or construction of the toll tunnel is authorized and sold in whole or in part and the authority deems it advisable and advantageous to enlarge or extend the toll tunnel or to change the structure or design thereof in order to afford new or greater facilities for any type or class of traffic, the authority may issue additional bonds for the purpose of enlarging or extending the toll tunnel or changing the structure or design thereof in order to afford such new or greater facilities. Such additional bonds shall be issued only if the surrender and cancellation of all outstanding bonds issued for the acquisition or construction of the toll tunnel as originally designed can be assured or obtained by call or by consent of the holders thereof. Such additional bonds shall not constitute a debt or obligation of the state or of El Dorado County but shall be bonds of the authority of the same character and payable from the same funds as other bonds authorized pursuant to this chapter. The pledge of the tolls and other revenues to be received from the operation of the toll tunnel to the payment of outstanding bonds shall not be lessened, diminished, or affected in any way by the issuance of such additional bonds.