65 ILCS 5/9-2-106

Except as otherwise provided in Section 9-2-113, whenever any contract has been awarded to any bidder for the construction of any waterworks system, bridge, or viaduct referred to in Section 9-2-19, the bid of the party to whom the contract has been awarded and the award therefor shall be treated as provisional and shall not be binding upon the party to whom the contract is awarded, or upon the municipality, until the levying of the tax provided for in Section 9-2-38 has been authorized by the electors of that municipality voting at an election to be held as provided in Section 9-2-38. The provisions of this Section 9-2-106 shall not apply to any city having a population of 500,000 or more.