225 ILCS 720/6.05

In lieu of a performance bond, the operator may deposit as security cash, negotiable government securities, or negotiable certificates of deposit of any bank organized or transacting business in the United States, or any combination thereof, with the Department in an amount equal to or greater than the amount of the surety bond required by Section 6.02. Such deposits shall be made, held and disposed of as provided in this Act and by the Department by rule.