70 ILCS 2105/15.5
Whenever any land or facilities financed by the issuance of bonds under Section 15.1 is combined with any other land or facilities to be financed by the issuance of bonds under Section 15.1, and there are outstanding unpaid obligations previously issued which are payable solely from the revenue derived from the operation of the land or facilities to finance which the bonds were issued, the unpaid obligations may be refunded by the issuance and exchange therefor of revenue bonds with the consent of the respective holders of the unpaid obligations if such obligations are not by their terms then callable for redemption in advance of their stated maturities. Whenever any such outstanding unpaid obligations are refunded, the unpaid obligations shall be surrendered and exchanged for revenue bonds of a total principal amount which shall not be more but may be less than the principal amount of the obligations exchanged and the interest thereon to the date of exchange.
70 ILCS 2105/15.5