Sts. & Hy. Code, § 31183

Any surplus which exists in the acquisition and construction fund shall be applied to the retirement, by purchase or call, of bonds issued for the acquisition or construction of the toll tunnel. If such bonds cannot be purchased at a price satisfactory to the authority and are not by their terms callable prior to maturity, the surplus shall be paid into the fund applicable to the payment of principal and interest of such bonds and shall be used for that purpose. The proceedings authorizing the issuance of bonds may provide limitations and conditions upon the time and manner of applying the surplus to the purchase and call of outstanding bonds and the terms upon which they shall be purchased or called, and such limitations and conditions shall be followed and observed in the application and use of the surplus. All bonds retired by purchase or call shall be immediately canceled.