Background
The “good neighbor provision” under Clean Air Act (CAA or Act) section 110(a)(2)(D)(i)(I) requires states to address the interstate transport of air pollution. Specifically, it requires that each state’s implementation plan (SIP) contain adequate provisions to prohibit air pollutant emissions from within the state that will significantly contribute to nonattainment of the national ambient air quality standards (NAAQS), or that will interfere with maintenance of the NAAQS, in any other state. To address this provision, the EPA has finalized a series of complex federal regulatory programs imposing increasingly stringent controls on emissions, starting with the “NOX SIP Call” rule in 1998, then the Clean Air Interstate Rule in 2005, followed by the Cross-State Air Pollution Rule (CSAPR) in 2011, the 2016 “CSAPR Update” rule, and further updates to CSAPR. While the EPA discontinued administration of the NOX Budget Trading Program, the requirements for the NOX SIP Call continued to apply.
South Carolina’s Electric Generating Units (EGUs) currently participate in the CSAPR trading programs for annual emissions of NOX and SO2 , but the EGUs in the state are no longer subject to a NOX ozone season trading program under either CSAPR or the CSAPR Update as the air quality modeling for the CSAPR Update projected that South Carolina would not contribute significantly to nonattainment or interfere with maintenance in downwind areas for either the 1997 ozone NAAQS or the 2008 ozone NAAQS. Because South Carolina’s EGUs and non-EGUs no longer participate in any CSAPR or CSAPR Update trading program for ozone season NOX emissions, the NOX SIP Call regulations at 40 CFR 51.121(r)(2) as well as anti-backsliding provisions at 40 CFR 51.905(f) and 40 CFR 51.1105(e) require these sources to maintain compliance with the NOX SIP Call requirements. The requirements are outlined in the original 1998 rule and the NOX SIP Call Update rule published on March 8, 2019. This update to the NOX SIP Call provides states flexibility to establish alternative monitoring and reporting requirements for certain sources not otherwise required to perform Part 75 monitoring under other programs such as the Acid Rain Program or CSAPR.
On July 11, 2019, the Department submitted a SIP revision to comply with the requirements of the NOX SIP Call, requesting EPA approval to remove from the SIP the CAIR program repealed from S.C. Regulation 61-62.96. South Carolina will continue to meet its transport obligation under the NOX SIP Call through incorporation of applicable NOX SIP Call requirements into S.C. Regulation 61-62.96. The Department’s removal of CAIR from its regulations and adoption of an alternative monitoring option is appropriate and consistent with applicable federal law, including the NOX SIP Call and Section 110(l) of the Clean Air Act. The EPA published a final rule in the Federal Register approving this revision on July 29, 2020 (85 FR 45541).
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Mary Peyton Wall, Manager, (803) 898-4064