The U.S. Environmental Protection Agency (EPA) issued guidance on March 4, 2013, on permitting for fine particulate matter (PM2.5) in light of a court decision vacating portions of its rules. Sierra Club v. EPA (D.C. Cir., No. 10-1413, 1/22/13), summarized in Issue 441 of this Update, overturned rules that would have allowed sources with expected emissions below Significant Impact Levels (SILs), or in locations with monitored PM2.5 levels below Significant Monitoring Concentration (SMC), to forego obtaining one year of monitoring data as otherwise required under the Clean Air Act (CAA).

The court remanded the affected regulatory provisions to allow EPA to develop new rules, but that process is not complete. The new guidance is intended to address some of the issues that may arise in light of the court’s ruling. EPA suggests that any State Implementation Plan which contains PM2.5 provisions that are similar to the vacated provisions will likely require a rulemaking to remove them. EPA encourages states with pending applications for approval of a PM2.5 Prevention of Significant Deterioration (PSD) provision to remove any references to SMC and SIL in their pending applications, although it suggests that if the provisions remain, EPA could potentially approve everything but the SMC and SIL provisions.

According to EPA, for now, permit applicants must provide PM2.5 monitoring data with their PSD permit applications. It states, however, that “applicants will generally be able to rely on existing representative monitoring data” in their applications. EPA also notes that permits previously issued in response to applications that relied on SILs and SMCs to support a determination not to monitor are unlikely to require further action since they complied with applicable law when they were issued. But EPA says that applying either the SIL or SMC rules in reviewing currently pending permit applications “may be inconsistent with the Clean Air Act and may be difficult to defend in administrative and judicial challenges.” EPA requires that ongoing reviews contain adequate information to justify a conclusion that the proposed emission source will not violate the National Ambient Air Quality Standard for PM2.5.