70 ILCS 2905/5-4
All contracts for work to be done and supplies and materials to be purchased by the sanitary district, the expense of which will exceed $10,000, shall be let to the lowest responsible bidder therefor, upon not less than 21 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 the district, and the board may reject any and all bids and readvertise. All purchases or sales of $10,000 or less may be made in the open market without publication in a newspaper as above provided, but whenever practical shall be based on at least 3 competitive bids. No person may be employed on the work except citizens of the United States, or those who in good faith have declared their intention to become citizens, and 8 hours constitutes a day's work.
If a unit of local government performs non-emergency construction, alteration, repair, improvement, or maintenance work on the public way, the sanitary district may enter into an intergovernmental agreement with the unit of local government allowing similar construction work to be performed by the sanitary district on the same project, in an amount no greater than $100,000, to save taxpayer funds and eliminate duplication of government effort. The sanitary district and the other unit of local government shall, before work is performed by either unit of local government on a project, adopt a resolution by a majority vote of both governing bodies certifying work will occur at a specific location, the reasons why both units of local government require work to be performed in the same location, and the projected cost savings if work is performed by both units of local government on the same project. Officials or employees of the sanitary district may, if authorized by resolution, purchase in the open market any supplies, materials, equipment, or services for use within the project in an amount no greater than $100,000 without advertisement or without filing a requisition or estimate. A full written account of each project performed by the sanitary district and a requisition for the materials, supplies, equipment, and services used by the sanitary district required to complete the project must be submitted by the officials or employees authorized to make purchases to the board of trustees of the sanitary district no later than 30 days after purchase. The full written account must be available for public inspection for at least one year after expenditures are made.
70 ILCS 2905/5-4