Illinois Statutes Chapter 415. Environmental Safety § 5/28.2. Federally required rules

(a) For the purposes of this Section, “required rule” means a rule that is needed to meet the requirements of the federal Clean Water Act,  1 Safe Drinking Water Act,  2 Clean Air Act  3 (including required submission of a State Implementation Plan), or Resource Conservation and Recovery Act,  4 other than a rule required to be adopted under subsection (c) of Section 13, Section 13.3, Section 17.5, subsection (a) or (d) of Section 22.4, subsection (a) of Section 22.7, or subsection (a) of Section 22.40.

(b) When the Agency proposes a rule that it believes to be a required rule, the Agency shall so certify in its proposal, identifying the federal law to which the proposed rule will respond and the rationale upon which the certification is based. If the certification is accompanied by a written confirmation from USEPA, the certification shall be under the signature of the regional administrator, the deputy regional administrator, the appropriate division director or a responsible senior official from USEPA headquarters. The Board shall either accept or reject the certification within 45 days and shall reference the certification in the first notice of the proposal published in the Illinois Register as provided by the Illinois Administrative Procedure Act.  5 First notice of the proposal shall be submitted for publication in the Illinois Register as expeditiously as is practicable, but in no event later than 6 months from the date the Board determines whether an economic impact study should be conducted. Should the Board reject an Agency certification, the proposal shall not be considered a required rule. If the Board fails to act within the requisite 45 day period, the certification shall be deemed granted.

(c) Whenever a required rule is needed, the Board shall adopt a rule (i) that fully meets the applicable federal law and (ii) that is not inconsistent with any substantive environmental standard or prohibition that is specifically and completely contained and fully set forth within any Illinois statute, except as authorized by this Act. In determining whether the rule fully meets the applicable federal law, the Board shall consider all relevant evidence in the record.