On March 4, 2013, EPA published “Draft Guidance for PM2.5 Permit Modeling” (“Draft Guidance”) and a series of questions and answers (“Q&A”) in response to the D.C. Circuit Court’s decision on PM2.5 SILs and Significant Monitoring Concentration (“SMC”), Sierra Club v. EPA, ___ F.3d ___, 2013 WL 216018 (D.C. Cir. Jan. 22, 2013). The Court’s decision vacated and remanded the PM2.5 SILs regulations for further consideration and vacated the PM2.5 SMC. These regulations provided PSD permit applicants exemptions from certain preconstruction modeling and ambient air monitoring requirements for PM2.5. The Court rejected the PM2.5 SILs and SMC rules on the grounds that the exemptions did not provide the permitting authority sufficient discretion to determine whether there would be an exceedence of the National Ambient Air Quality Standards (“NAAQS”). For a discussion of the Sierra Club decision, see “PSD Permit Modeling for PM2.5 – EPA Seeking Input Following Federal Court Remand of SILs Permit Exemption.”
After engaging in discussions with states and EPA regional work groups, EPA issued a Q&A paper and Draft Guidance on how to proceed with PM2.5 monitoring requirements during the PSD permit application process. The Draft Guidance and Q&A provide permitting authorities, including states with authorized air programs and authorized states with state approved Implementation Plans (“SIPs”), a path to move forward with pending PSD permits that relied on the PM2.5 SILs and SMC exemptions. The Draft Guidance directs that permitting authorities should not rely on the PM2.5 SMC to allow applicants to avoid compiling air quality monitoring data for PM2.5. Nevertheless, it notes that “in lieu of applicants setting up PM2.5 monitors to collect ambient data, applicants may submit PM2.5 ambient data collected from existing monitoring networks when the permitting authority deems such data to be representative of the air quality . . . for the [preceding year].” Q&A at 2.
As to SILs, it instructs that although a permit authority may not rely solely on PM2.5 SILs to support a conclusion that the source will not cause or contribute to a violation of PM2.5 NAAQS, under certain circumstances a permit authority may rely upon SILs as partial support for such a determination. “If the preconstruction monitoring data shows that the difference between the PM2.5 NAAQS and the monitored PM2.5 background concentrations in the area is greater than the EPA’s PM2.5 SIL value, then . . . it would be sufficient in most cases for permitting authorities to conclude that a proposed source with a PM2.5 impact below the PM2.5 SIL value will not cause or contribute to a violation of the PM2.5 NAAQS and to forego a more comprehensive cumulative modeling analysis for PM2.5.” Q&A at 3. In other words, if the sum of the background PM2.5 and the PM2.5 SILs are less than the PM2.5 NAAQS, then it is reasonable for the permit authority to conclude that the proposed source will not violate the PM2.5 NAAQS if the proposed emissions do not exceed the PM2.5 SILs.
The memorandum accompanying the Draft Guidance states that it is being released for public review and comment for 45 days. The EPA will accept comments through April 17, 2013 and “subsequently engage with the stakeholders on the comments submitted at the 2013 Regional, State, and Local Modeler’s Workshop” on April 22-25 in Dallas, Texas. After that, the EPA intends to revise the Draft Guidance where appropriate and release a final version of the document. Organizations or individuals interested in submitting comments may submit them between now and April 17, 2013, electronically to Mr. George Bridgers of EPA’s Air Quality Modeling Group at Bridgers.George@EPA.gov. In addition, if there are issues or concerns with making an electronic submission, Mr. Bridgers may be contacted at (919) 541-5563.
EPA’s Q&A and the Draft Guidance should provide applicants with pending PSD permits that relied upon the PM2.5 SMC or SILs the opportunity to move forward with the permit process by demonstrating that the PM2.5 impact of the proposed source is less than the PM2.5 SIL and that the PM2.5 ambient background concentrations plus the PM2.5 SIL are less than the PM2.5 NAAQS. This approach will allow permitting authorities to move forward on permits that were stalled by the Sierra Club v. EPA decision. Copies of the Q&A and the Draft Guidance may be found at the EPA New Source Review Website.