CFR›Title 40›Chapter I›Part 51›Subpart Y ContainsSection 51.930CorpusDaily eCFRDisplayed edition2026-05-18Last updated2026-05-18 Subpart Y—Mitigation Requirements Sections 51.930 § 51.930 Mitigation of Exceptional Events. Previous W Subpart W—Determining Conformity of General Federal Actions to State or Federal Implementation Plans Next Z Subpart Z—Provisions for Implementation of PM<sub>2.5</sub> National Ambient Air Quality Standards