been challenged by some states and environmental groups before the D.C. Circuit Court of Appeals.

On the same day that EPA promulgated the NSR revisions summarized above, EPA proposed changes in its rules defining what projects constitute routine maintenance and are exempt from the NSR program. A modified version of the proposal, summarized above, was promulgated in August 2003 and published in October 2003. This rule has also been challenged before the D.C. Circuit Court of Appeals by some states and environmental groups. In December 2003, 2 days before the rule was to become effective in areas where EPA administers the PSD program, the D.C. Circuit Court issued a stay of the rule on the grounds that the petitioners had shown irreparable harm and the likelihood of success on the merits. This stay remains in place and so the new rule has not gone into effect.

On June 30, 2004, EPA announced a 180-day period for reconsideration of the rule. The agency requested comment on the rule’s legality and on the choice of the 20% threshold (69 Fed. Reg. 40278 [2004]).

Following the regulatory overview of the NSR programs presented in this chapter, Chapter 3 examines contributions that emission sources subject to NSR may make to ambient air quality and relationships between specific air pollutants and health effects.