70 ILCS 2105/16
All contracts for work other than professional services, to be done by such conservancy district, the expense of which will exceed $10,000 , shall be let to the lowest responsible bidder therefor upon not less than thirty days' public notice of the terms and conditions upon which the contract is to be let, having been given by publication in a newspaper of general circulation published in said district, and the said board shall have the power and authority to reject any and all bids, and readvertise.
And in all other respects such contract shall be entered into and the performance thereof controlled by the provisions of an Act entitled "An Act concerning local improvements," approved June 14, 1897, in force July 1, 1897, and amendments thereto as nearly as may be; provided, that contracts may be let for making proper and suitable connections between the mains and outlets of the respective sewers in said district, with any conduits, main pipe or pipes that may be constructed by such conservancy district.
70 ILCS 2105/16