The provisions of this act shall never be construed as authorizing any levee or drainage system for agricultural or mining purposes, but shall be liberally construed for the prevention of overflows and drainage of lands for sanitary purposes, with any sanitary district organized hereunder: Provided, nothing herein contained shall be held to constitute a contract between the state and any municipal corporation organized hereunder, or to prevent the alteration, amendment or repeal of this act, or of any amendment thereof, at any time thereafter.
70 ILCS 2205/28