225 ILCS 715/12

(a) The Department may adopt and promulgate reasonable rules respecting the administration of this Act, and in conformity therewith. (b) Rules adopted by the Department shall not apply retroactively. Any operator shall have the right to proceed with operations under this Act until such rules are adopted and no such rules shall be made applicable to any operations prior to the effective date thereof. (c) In addition to the provisions of this Section, and to the extent consistent with this Section, the provisions of the Illinois Administrative Procedure Act apply to the adoption of rules under this Act. (d) Any act authorized to be done by the Director may be performed by the Assistant Director or any employee of the Department when designated by the Director.