(a) If the board of commissioners shall have ascertained that the construction, maintenance, and operation of the interstate bridge can be financed in whole or in part by the issuance of revenue bonds payable from the tolls so charged and collected, then the board of commissioners is given and granted the full power and authority to issue revenue bonds for the part or portion which can be so financed, the bonds to be payable over a period of not exceeding thirty (30) years, and shall bear interest at a rate not exceeding six percent (6%) per annum.

(b) To secure the payment of the revenue bonds, together with the interest thereon, the board of commissioners is granted the power and authority to pledge all or any part or portion of the tolls charged and collected or to be collected therefrom as hereinafter provided, and as required to do so in order to finance the bonds. The board of commissioners shall have the right to pledge all or any part or portion of the assessment of benefits as additional security in the event the tolls collected are insufficient to pay the principal and interest of the bonded indebtedness.

(c) If it becomes necessary in order to obtain proper financing of the construction of the bridge, the board of commissioners is granted the power and authority to enter into contracts with the bond-holders or the trustees of the bond issues to guarantee and underwrite the payment of the principal and interest on the bonded indebtedness, and to obligate the board of commissioners and the district to levy or cause to be levied a sufficient tax against the assessment of benefits if the tolls collected in any year shall be insufficient to fully pay off the principal and interest on the bonded debt.

(d) In the event the tolls charged and collected are insufficient to pay the principal and interest of the bonded debt as it matures, then the board of commissioners is required to file a petition in the circuit court setting out the deficiency. Thereupon, the court shall levy a tax of a sufficient amount to make up the deficit with ten percent (10%) added for unforeseen contingencies.

(e) The board of commissioners and the circuit court may be required by mandamus to levy the tax in any proceedings instituted by the trustee or trustees of the bondholders or any individual bond-holder who may hold any unpaid bond or interest coupon. The right to require a levy of tax against the assessment of benefits shall be a continuing right which may be exercised by the trustees or bond-holders until the full amount of the principal and interest of the bonded debt has been paid.