70 ILCS 3705/9
Every public water district organized under this Act and every non-profit private water company is authorized to construct, maintain, alter and extend its water mains and wastewater lines as a proper use of highways along, upon, under and across any highway, street, alley or public ground in the State, but so as not to inconvenience the public use thereof, and the right and authority are hereby granted to any such district or non-profit private water company to construct, maintain and operate any conduit or conduits, water pipe or pipes, wholly or partially buried or otherwise in, upon and along any of the lands owned by said State under any of the public waters therein; provided that the right, permission and authority hereby granted shall be subject to all public rights of commerce and navigation and the authority of the United States in behalf of such public rights, and also to the laws of the State of Illinois to regulate and control the same.
70 ILCS 3705/9