On October 3, 2016, the United States Environmental Protection Agency ("EPA") published a Proposed Rule titled Revisions to the Prevention of Significant Deterioration (PSD) and Title V Greenhouse Gas (GHG) Permitting Regulations and Establishment of a Significant Emissions Rate (SER) for GHG Emissions Under the PSD Program ("Proposed Rule"). EPA explains that the Proposed Rule is intended to further conform its regulations to the U.S. Supreme Court's 2014 decision in UARG v. EPA (134 S. Ct. 2427) and the 2015 judgment by the D.C. Circuit in Coalition for Responsible Regulation v. EPA (Nos. 09-1322, 10-073, 10-1092, and 10-1167).

The most noteworthy change is that the Proposed Rule would establish a Significant Emissions Rate ("SER") for GHGs. Specifically, EPA is proposing to establish a 75,000 tpy CO2e SER. The agency concluded that this level represents a de minimis level of GHG emissions for purposes of determining whether a GHG Best Available Control Technology ("BACT") review should be required as part of an "anyway source" PSD permit. An "anyway source" is a source that is otherwise required to obtain a PSD permit based on its emissions of one or more regulated New Source Review pollutants other than GHGs. UARG limited the scope of the PSD permitting program to "anyway sources" and held that the EPA may exempt an "anyway source" from the GHG BACT requirement if the source emits a de minimis amount of GHGs.

The Proposed Rule would also revise several definitions. For example, the Proposed Rule would exclude GHG emissions from "major source" and "major modification" determinations. The Proposed Rule would also add a definition of "GHGs": "the air pollutant defined in § 86.1818–12(a) of this chapter as the aggregate group of six greenhouse gases: Carbon dioxide, nitrous oxide, methane, hydrofluorocarbons, perfluorocarbons and sulfur hexafluoride. To represent an amount of GHGs emitted, the term tpy CO2 equivalent emissions (CO2e) shall be used and computed as follows: (a) Multiply the mass amount of emissions (tpy), for each of the six greenhouse gases in the pollutant GHGs, by the gas's associated global warming potential published at Table A–1 to subpart A of part 98 of this chapter—Global Warming Potentials. (b) Sum the resultant value for each gas to compute a tpy CO2e."

If finalized, the Proposed Rule would amend several other regulations that EPA reasons are no longer necessary after UARG . Comments on the Proposed Rule are due by December 2, 2016. Additional information about GHG permitting under the Clean Air Act is available here.

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