Preparing for the New PM2.5 NAAQS

EPA released the 2024 PM2.5 revisions today in pre-Federal Register draft form. The new primary annual PM2.5 NAAQS is set at 9 ug/m3, annual arithmetic mean. EPA retained the 15 ug/m3 secondary annual NAAQS for PM2.5 welfare effects. EPA retained the 24-hour PM2.5 primary and secondary NAAQS at 35 ug/m3 and the primary and secondary annual PM10 NAAQS of 150 ug/m3. The revised primary NAAQS will take effect 60 days after publication in the Federal Register. Importantly for NSR Law Blog readers, EPA did provide some initial transition guidance on NSR permitting under the new NAAQS.

Transition Guidance

EPA provided the following transition guidance to assist sources in navigating the permitting changes resulting from the revised NAAQS and the possible designation of additional areas as nonattainment in the future.

New Sources and Modifications in Areas that Will Be Designated Nonattainment

"until ... nonattainment designation occurs, proposed new major sources and major modifications located in any area currently designated attainment or unclassifiable for all preexisting PM2.5 NAAQS will continue to be subject to the PSD program requirements for PM2.5. Any proposed major stationary source or major modification triggering PSD requirements for PM2.5 that does not receive its PSD permit by the effective date of a new nonattainment designation for the area where the source would locate would then be required to satisfy applicable NNSR preconstruction permit requirements for PM2.5.

New Sources and Modifications in Attainment Areas that Exceed the Revised NAAQS

In areas where air pollution exceeds the level of the revised primary annual PM2.5 NAAQS, a PSD permit applicant must demonstrate that the source or modification will not cause or contribute to a violation of the NAAQS. Section 165(a)(3)(B) of the CAA states that a proposed source may not construct unless it demonstrates that it will not cause or contribute to a violation of any NAAQS. This statutory requirement is implemented through a provision contained in the PSD regulations at 40 CFR 51.166(k) and 52.21(k).226 If a source cannot make this demonstration, or if its initial air quality impact analysis shows that the source’s impact would cause or contribute to a violation, the reviewing authority may not issue a PSD permit to that source. However, a PSD permit applicant may be able to make this demonstration if it compensates for the adverse impact that would otherwise cause or contribute to a violation of the NAAQS. In contrast to the NSR requirements for nonattainment areas, the PSD regulations do not explicitly specify remedial actions that a prospective source must take to address such a situation, but the EPA has historically recognized that sources applying for PSD permits may utilize offsetting reductions in emissions as part of the required PSD demonstration under CAA section 165(a)(3)(B).

In an accompanying footnote, EPA notes some examples of such offsets.

Finally, because of the lag time in developing SIPs for newly designated nonattainment areas, EPA notes that states may use the interim program at Part 51, Appendix S to enable major source/major modification permitting in newly designated nonattainment areas prior to the time the state's nonattainment area SIP for the area is approval. EPA also reminded sources that in "serious" nonattainment areas, the "major source" threshold for both primary PM2.5 and its precursors becomes 70 tons/year while remaining 100 tons/year in "moderate" areas.

There is no "grandfathering" period any more as a result of the D.C. Circuit decision in Murray Energy Corp. v. EPA, 936 F.3d 597 (D.C. Cir. 2019). You can read more about Murray Energy in NSR Law Blog's article "DC Circuit: No PSD 'Grandfathering'".

SILs change

In a somewhat unexpected development, EPA stated that it will develop and release an "updated" significant impact level for the revised primary annual PM2.5 NAAQS "on or before the effective date" of the final NAAQS, so in about sixty to seventy days. Given the 25% reduction in the primary NAAQS, a reduction in the SIL, potentially at a similar magnitude, is likely. A decrease in the SIL will expand modeling requirements for future projects and make "no contribution" findings more difficult.

NSR Law Blog will review implementation guidance details affecting new source review permitting and keep readers up-to-date as this important development progresses.