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U.S. Court of Appeals for the D.C. Circuit Remands EPA’s Implementation Rule for its PM2.5 NAAQS and Separately Vacates PM2.5 Significant Impact Levels and Significant Monitoring Concentrations


On January 4, 2013, the U.S. Court of Appeals for the District of Columbia Circuit ruled that two EPA final rules establishing implementation requirements for the PM2.5 NAAQS were inconsistent with the Clean Air Act.  The two rules at issue were EPA’s April 25, 2007 and May 16, 2008 implementation rules and specifically, the components of those rules that applied to nonattainment New Source Review (NSR).

In promulgating the implementation rules, EPA relied upon the general nonattainment NSR provisions of Subpart 1 of Part D of Title I of the Clean Air Act, rather than the particulate-matter specific provisions of Subpart 4 of Part D of Title I.  The Natural Resources Defense Council and Sierra Club challenged the rulemakings on the basis that the more specific and more stringent provisions of Subpart 4 of Part D should have been applied.  Under Subpart 1, EPA has more flexibility in extending the deadlines for achieving attainment with the NAAQS.

EPA argued that because Subpart 4 of Part D repeatedly refers to PM10 rather than to PM2.5 or particulate matter, it was reasonable for it to interpret Subpart 1 as applying to nonattainment implementation provisions for the PM2.5 NAAQS.  The court, however, found that PM10 includes PM2.5 and therefore, under a plain reading of Subpart 4, it applies to PM2.5.  Because the court found the statute is plain on its face, EPA’s interpretation was not entitled to deference.  The court therefore remanded to EPA the two rulemakings to repromulgate the nonattainment NSR provisions pursuant to Subpart 4 of Part D, consistent with the court’s opinion.  Because the court did not invalidate the rulemakings, which also included provisions relating to PSD review in attainment areas, the ruling should not affect the aspects of the regulations that relate to PSD review of permit applications with respect to PM2.5.

On January 22, 2013, the U.S. Court of Appeals ruled on the challenge brought by the Sierra Club to the significant impact levels (SILs) and significant monitoring concentration (SMC) established for PM2.5 in EPA’s October 20, 2010 rulemaking. The court found there is no authority for SMCs under the Clean Air Act, and therefore, vacated the PM2.5 SMC. The SMCs that have been established for other pollutants were not at issue in the case and were not addressed by the court’s ruling. However, assuming the ruling stands, it creates uncertainty as to what action EPA may take in the future with respect to existing SMCs. The ruling calls into question EPA’s authority to preclude promulgation of new SMCs for any pollutant.

With respect to the PM2.5 SIL, the court vacated and remanded the SIL to EPA, at the agency’s request. EPA noted the SIL may not be protective of the PM2.5 NAAQS in all circumstances, such as where PM2.5 concentrations in ambient air are already close to the NAAQS, and the court agreed with that assessment. The Sierra Club argued SILs were universally invalid and unauthorized under the Clean Air Act, but the court found that issue was not ripe for a decision. The claim, however, will almost certainly be reasserted in a challenge to any revised PM2.5 NAAQS. The SIL ruling raises a question as to whether EPA will, in any future rulemaking, also attempt to clarify when other SILs may not be protective of NAAQS. SILs and SMCs have been important screening tools that were used to prevent unnecessary PSD permitting delays where impacts of emissions are considered de minimis. Accordingly, the court’s ruling will likely result in significant delays in some major industrial projects.

To view a complete PDF of the Fourth Quarter 2012 issue of the Air Quality Letter, click HERE.

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