65 ILCS 5/11-134-2
The city council of any city availing itself of the provisions of this Division 134, shall adopt an ordinance, incorporating therein the contract to be entered into and authorizing the execution thereof on behalf of the city. The contract, among other things, (1) shall describe in a general way the plans and equipment to be constructed for the purpose of such filtration and treatment, (2) shall refer to and make a part thereof the plans and specifications for the plants and equipment, (3) shall provide for the manner, terms, and conditions upon which the water is to be filtered and treated, (4) shall provide for and fix the rate at which the water will be filtered and treated, and (5) may prescribe a method of redetermining that rate in the event such redetermination is provided for by the terms of the contract. The rate so fixed and the method so prescribed for redetermining the rate shall not be modified during the term of the contract without the consent of both the city and the other contracting party.
65 ILCS 5/11-134-2