Ill. Admin. Code tit. 2, § 2175.540
Under Section 28.2 of the Act [415 ILCS 5/28.2], the Board may adopt a "required rule." A "required rule" means a rule that is needed to meet the requirements of the federal Clean Water Act, SDWA, Clean Air Act (including required submission of a State Implementation Plan), or RCRA, other than a rule required to be adopted as an identical-in-substance rule (see Section 2175.535) [415 ILCS 5/28.2(a)].
(Source: Amended at 44 Ill. Reg. 14166, effective August 21, 2020)