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EPA Issues “Questions and Answers” Document Regarding Impact of Decision by U.S. Court of Appeals for the D.C. Circuit to Remand EPA’s Implementation Rule for the PM2.5 NAAQS


As reported in last quarter’s issue of the Air Quality Letter, the U.S. Court of Appeals for the District of Columbia Circuit recently vacated the significant monitoring concentration (SMC) established for PM2.5 in EPA’s October 2010 rulemaking on the grounds that there is no authority for SMCs under the Clean Air Act.  Additionally, the court vacated and remanded the significant impact levels (SILs) for PM2.5 that were established in EPA’s October 20, 2010 rulemaking on the grounds that the SILs may not be protective of the PM2.5 NAAQS in all circumstances.  On March 4, 2013, EPA issued a “Questions and Answers” guidance document to provide states and regulated entities with EPA’s preliminary answers to the most common questions regarding the impact of the court’s ruling on pending and recently issued PSD permits.  In general, the Questions and Answers document states that PSD permitting authorities should “immediately align their permitting actions with the [court’s] decision.”

With respect to the SMCs for PM2.5, EPA explained that delegated state and local permitting authorities should not rely on the PM2.5 SMC to allow applicants to avoid the need to compile ambient air quality monitoring data for PM2.5.  Rather, all applicants seeking a PSD permit where direct PM2.5 or any PM2.5 precursor is emitted in a significant amount should either: (1) collect and submit the necessary ambient PM2.5 monitoring data; or (2) submit PM2.5 ambient data collected from existing monitoring networks where the permitting authority deemed such data to be representative of the air quality in the area of the source for the year preceding receipt of the application.

With respect to reliance on the PM2.5 SILs, EPA cautioned that reliance on the SILs alone to demonstrate that a source will not cause or contribute to a violation of the PM2.5 NAAQS is inadequate.  However, EPA stated that permitting authorities have the discretion to select and utilize a PM2.5 SIL value if the record provides sufficient justification for the selected SIL value and the manner in which it will be used.  The SIL values for PM2.5 in EPA regulations could continue to be used if the permitting authority also takes background concentrations of PM2.5 into account.  For example, in situations where the difference between the PM2.5 NAAQS and the monitored PM2.5 background concentrations in the area is greater than the SIL value, in most cases, EPA expects that modeled impacts below the PM2.5 SIL would be adequate to demonstrate that the project will not cause or contribute to a violation of the PM2.5 NAAQS (which allows the source to forego a comprehensive cumulative modeling analysis for direct PM2.5 and precursors).  EPA also explained that as part of the cumulative analysis, an applicant may continue to show that the proposed source does not contribute to an existing violation of the PM2.5 NAAQS by demonstrating that the proposed source’s PM2.5 impact does not significantly contribute to an existing violation of the PM2.5 NAAQS.  EPA expects permitting authorities to consult with EPA before using SIL values for this purpose.

With respect to state implementation plans (SIPs) that contain SILs and SMCs that are inconsistent with the court’s ruling, EPA recommends that the states begin to take steps to remove those provisions from the SIPs.  As noted above, EPA also warned that permits issued on the basis of such provisions going forward may be inconsistent with the Clean Air Act and subject to challenge.  EPA also noted that it does not believe the court’s ruling will affect sources with final PSD permits that relied on such SIP provisions.  Such permits were issued in accordance with regulations that were in effect at the time of permit issuance.

For SIP provisions that are currently pending before EPA for approval, EPA noted it would not approve any SIP provisions that are inconsistent with the court ruling.  Thus, EPA encouraged states that have already made such SIP submissions to withdraw those portions of the submissions that were inconsistent with the court’s ruling.

To view a complete PDF of the First Quarter 2013 issue of the Air Quality Letter, click HERE.

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