This action approves a revision to the Ohio State Implementation Plan (SIP) submitted on April 17, 2007, and revised on September 26, 2007. This SIP revision incorporates provisions related to the implementation of EPA's Clean Air Interstate Rule (CAIR), promulgated on May 12, 2005, and revised on April 28, 2006, and December 13, 2006, and the CAIR Federal Implementation Plan (CAIR SIP) concerning sulphur dioxide (SO<INF>2</INF>), oxides of nitrogen (NO<INF>X</INF>) annual and NO<INF>X</INF> ozone season emissions for the State of Ohio, promulgated on April 28, 2006, and revised on December 13, 2006. EPA is not making any changes to the CAIR FIP but is amending, to the extent EPA approves Ohio's SIP revision, the appropriate appendices in the CAIR FIP trading rules simply to note that approval. The Ohio SIP revision that was submitted on April 17, 2007, was a full CAIR SIP revision. In a letter submitted on September 26, 2007, Ohio requested that EPA consider the September 26, 2007, submittal as two separate submittals, i.e., as a full CAIR SIP and as an abbreviated CAIR SIP. Ohio requested that EPA act on specific portions of the September 26, 2007, submittal as an abbreviated CAIR SIP. EPA approves Ohio's abbreviated SIP revision that addresses the methodology used to allocate annual and ozone season NO<INF>X</INF> allowances to affected electric generating units (EGUs), and the opt-in provisions, under the CAIR trading programs and the CAIR SIP. This action also contains EPA's response to a comment from the State of Connecticut following publication of the original direct final approval of the Ohio plan on October 16, 2007. We withdrew the original direct final rule on December 5, 2007, because of receipt of this comment. For reasons expressed in the body of this rule, EPA believes the comment from Connecticut is not relevant to this final action and, therefore, we are moving forward to approve the Ohio plan. As such, EPA will populate the compliance accounts of