70 ILCS 2205/16
Subject to the referendum provided for in Section 16.1, the board of trustees may borrow money for corporate purposes on the credit of the corporation, and issue bonds therefor, in such amounts and form, and on such conditions as it shall prescribe, but shall not become indebted in any manner, or for any purpose, to an amount, including existing indebtedness, in the aggregate to exceed 5.75% of the value of the taxable property in said district, to be ascertained by the last assessment for state and county taxes previous to the incurring of such indebtedness or, until January 1, 1983, if greater, the sum that is produced by multiplying the district's 1978 equalized assessed valuation by the debt limitation percentage in effect on January 1, 1979; and before or at the time of incurring any indebtedness, shall provide for the collection of a direct annual tax sufficient to pay the interest on such debt, as it falls due, and also to pay and discharge the principal thereof, within 20 years after contracting the same.
The bonds shall be sold to the highest and best responsible bidder therefor. Notice of the time and place bids will be publicly opened shall be given by publication in a newspaper having general circulation in the district, once each week for 3 successive weeks, the last publication to be at least one week prior to the time specified in the notice for the opening of bids.
70 ILCS 2205/16