70 ILCS 605/6-1
Whenever the cost of any work to be performed by the district or the cost of any machinery, equipment, materials or supplies to be purchased by the district will exceed $20,000 , the commissioners shall advertise for sealed bids for the performance of such work or the furnishing of such machinery, equipment, materials or supplies by publishing a notice in a newspaper published or having general circulation in the county in which the district was organized not less than once each week for 3 successive weeks. The first such publication shall be made not less than 17 days prior to the date set for opening the bids. The notice shall particularly set out the time when and the place where the bids will be opened, the nature of the work to be performed or the machinery, equipment, materials or supplies to be purchased and the terms of payment. The commissioners may reject any and all bids, may waive any informality in bids received and may continue the letting from time to time. The commissioners may accept any bid they deem most favorable, but if the bid accepted is not the lowest bid, they shall enter in their minutes their reason for not accepting the lower bid or bids. If any person to whom a contract has been let after notice as herein required fails to perform his contract, the same may be relet in such a manner as the commissioners deem best, with or without advertisement for bids.
The provisions of this Section, however, shall not apply to the contracting, letting or doing of any repair or maintenance work the cost of which will be payable from the annual maintenance fund of the district.
70 ILCS 605/6-1