70 ILCS 2305/18.5

The sanitary district may enter into contracts with municipalities or other parties outside the sanitary district that may request service from the sanitary district at higher rates than the existing rates for like consumers within the sanitary district to allow the sanitary district to obtain a fair return to cover the costs of financing, constructing, operating, and maintaining its facilities. In the event that thereafter such rates are not agreed upon by the parties or are not otherwise provided for by contract, such rates shall be fixed and determined by the circuit court of Lake County after a petition has been filed with that court.