Clarification of definition of modifications and modified and applicability to construction for nonattainment areas

(a) Definition Section 171 of the Clean Air Act (42 U.S.C. 7501) is amended by striking paragraph (4) and inserting the following: (4) The terms modifications and modified mean a modification as defined in section 111(a), except that such terms do not include a change at a major emitting facility that does not result in a significant emissions increase, or a significant net emissions increase, in annual actual emissions at such facility.. (b) Applicability to construction Section 172(c)(5) of the Clean Air Act (42 U.S.C. 7502(c)(5)) is amended by adding at the end the following: The construction for which a permit is required under this paragraph is construction that involves physical construction of the discrete parts of an emissions unit (as defined in section 165(f)(2)) at a major stationary source, regardless of whether the construction involves other physical on-site activities at the major stationary source, including any such other physical on-site activity that— (A) may be costly; (B) may significantly alter the site; (C) is permanent in nature; or (D) is to accommodate an installation to an emissions unit..