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Air Quality

Clean Air Interstate Rule (CAIR)

History of CAIR

The information below includes Federal Register publications, South Carolina State Register publications, and other related materials to CAIR. If you have any questions, please contact Maeve Mason by phone at (803)898-2230 or by email.

Detailed History of CAIR

On March 10, 2005, the United States Environmental Protection Agency (EPA) finalized a rule known as the "Rule to Reduce Interstate Transport of Fine Particulate Matter and Ozone (Clean Air Interstate Rule)," also referred to as CAIR. CAIR was published in the Federal Register on May 12, 2005 (70 FR 25162). South Carolina is one of the 28 states that EPA found to contribute significantly to nonattainment of the National Ambient Air Quality Standards for fine particles (PM2.5) and/or 8-hour ozone in downwind States. Sulfur dioxide (SO2) is a precursor to PM2.5 formation, and nitrogen oxides (NOX) are a precursor to both PM2.5 and ozone formation. The South Carolina Department of Health and Environmental Control (DHEC) was required to revise its State Implementation Plan (SIP) to reduce emissions of SO2 and/or NOX from electric generating units. This required a State rulemaking action and submittal to EPA for review and approval.

EPA coordinated the concurrent release of CAIR with the Clean Air Mercury Rule (CAMR) because a "co-benefit" of implementing the mechanisms for controlling SO2 and/or NOX emissions as required by CAIR is the reduction of mercury (Hg) emissions. Coordinating the development of CAIR with CAMR allowed states to take advantage of the Hg emissions reductions that can be achieved by the air pollution controls designed and installed to reduce SO2 and/or NOX.

DHEC published an initial Notice of Drafting for the State CAIR and CAMR in the South Carolina State Register on July 22, 2005, and a second, extending the drafting period on February 24, 2006. After an extensive stakeholder negotiation process, a Notice of Proposed Regulation was published in the State Register on October 27, 2006. On January 11, 2007, a public hearing was held, wherein DHEC gave approval for the regulation to be presented to the General Assembly.

On March 8, 2007, DHEC submitted CAIR SIP package to EPA for parallel processing. On May 23, 2007, EPA submitted comments on CAIR to DHEC. The State CAIR and CAMR became effective upon the publication of a Notice of Final Regulation in the State Register on June 22, 2007. The final CAIR SIP package was submitted to EPA on August 14, 2007. On October 9, 2007, EPA published in the Federal Register a direct final rule (effective December 10, 2007) that granted abbreviated SIP approval of the majority of the State's CAIR provisions (72 FR 57209).

DHEC moved forward with necessary changes to the State CAIR immediately after receipt of a February 20, 2008, letter from EPA, specifying the necessary modifications for full SIP approval. The State CAIR modifications needed for full SIP approval were addressed in a Notice of Final Regulation published in the October 24, 2008, State Register. A SIP package was sent to EPA on December 4, 2008, for approval.

On July 11, 2008, the United States Court of Appeals for the District of Columbia Circuit (Court of Appeals) vacated CAIR (Case No. 05-1244) after finding "more than several fatal flaws in the rule." Because EPA adopted CAIR as an "integral action," it was vacated in its entirety and remanded to EPA to promulgate a rule that was consistent with the Court of Appeals' opinion. On September 24, 2008, EPA filed a petition for rehearing or, in the alternative, a remand of the case without vacatur. On October 21, 2008, the Court of Appeals issued a motion directing the parties of the case to file a response to EPA's petition.

After considering the parties' respective positions, the Court of Appeals decided to remand the case without vacatur on December 23, 2008. The Court of Appeals' reasoning was that while CAIR was inherently flawed, allowing it to remain in place until EPA could promulgate another rule would at least temporarily preserve the environmental benefits that CAIR provides. Furthermore, the Court of Appeals decided not to impose a deadline by which EPA must correct the flaws within CAIR.

In light of the decision to remand CAIR without vacatur, significant reductions in emissions of SO2 and/or NOX from electric generating units through the State's CAIR will be achieved. A co-benefit of CAIR will be reductions in Hg emissions.


For more information please contact the Bureau of Air Quality at (803) 898-4123 or by email.