70 ILCS 2805/77
Except as otherwise provided in Section 9-2-113 of the Illinois Municipal Code, as now or hereafter amended, any work or other public improvement, to be paid for in whole or in part by special assessment or special taxation, when the expense thereof will exceed $10,000, shall be constructed by contract let to the lowest responsible bidder in the manner prescribed in this Act.
In case of any work which it is estimated will not cost more than $10,000, if, before or after receiving bids, it appears to the committee of local improvements that the work can be performed better and cheaper by the district, the committee may perform that work and employ or contract for the necessary help or contractor without the necessity of obtaining bids therefor.
70 ILCS 2805/77