Approval and Promulgation of Implementation Plans; Mississippi: Prevention of Significant Deterioration; Greenhouse Gas Tailoring Rule Revision

EPA is taking final action to approve a revision to the State Implementation Plan (SIP), submitted by the State of Mississippi, through the Mississippi Department of Environmental Quality (MDEQ), to EPA on September 14, 2010, for parallel processing. MDEQ submitted the final version of this SIP revision on December 9, 2010. The SIP revision incorporates updates to MDEQ's air quality regulations impacting the regulation of greenhouse gas (GHG) under Mississippi's New Source Review (NSR) Prevention of Significant Deterioration (PSD) program. Specifically, the SIP revision establishes appropriate emission thresholds for determining which new stationary sources and modification projects become subject to Mississippi's PSD permitting requirements for their GHG emissions. The change is necessary because without it, on January 2, 2011, PSD requirements would apply at the 100 or 250 tons per year (tpy) levels otherwise provided under the Clean Air Act (CAA or Act), which would overwhelm Mississippi's permitting resources. EPA is approving Mississippi's December 9, 2010, SIP revision because the Agency has made the determination that this SIP revision is in accordance with the CAA and EPA regulations, including regulations pertaining to PSD permitting for GHGs. Additionally, EPA is responding to adverse comments received on EPA's November 5, 2010, proposed approval of Mississippi's September 14, 2010, draft SIP revision.