70 ILCS 605/3-31
Owners of lands which require combined drainage or combined drainage and protection from overflow may form a drainage district by mutual agreement, to include lands of their own only, by an instrument in writing duly signed, acknowledged and recorded in the drainage record. This agreement may include the location and character of the work to be done, the method by which the work shall be done, the total amount of the assessment to be levied, the amount of assessments of benefits and damages to be levied against each tract, or so much of these or more as may be agreed upon, and, to the extent provided by the agreement, the proceedings shall be as valid as though the drainage district were organized by petition in court in the manner hereinbefore provided. The appointment, powers and duties of the commissioners of a drainage district organized by mutual agreement shall, except as may be limited by the agreement, be the same as prescribed for drainage districts organized by petition in court, provided, however, that the agreement may include the selection of three drainage commissioners from the signers of the agreement or from others qualified to act. The terms of office of such commissioners shall be until the first Tuesday of the following September and until their successors have been appointed in the manner provided in this Act for the appointment of commissioners of other districts and have qualified. A drainage district organized by mutual agreement shall be subject to the jurisdiction of the circuit court and all such districts shall have all the powers, rights and duties of every kind given to drainage districts organized by petition in court, except as may be limited by the agreement. The above powers, rights and duties shall include, but not be limited to, the power of annexation of lands benefited and the formation of subdistricts as in other drainage districts.
70 ILCS 605/3-31