When EPA finalized the Cross-State Air Pollution Rule (CSAPR) on July 6, it also announced a supplemental notice of proposed rulemaking entitled "Federal Implementation Plans for Iowa, Kansas, Michigan, Missouri, Oklahoma, and Wisconsin," which was published in the Federal Register on July 11. In the supplemental action, EPA sought comment on its conclusion that "emissions from Iowa, Kansas, Michigan, Missouri, Oklahoma, and Wisconsin significantly contribute to downwind nonattainment or interfere with maintenance of the 1997 ozone National Ambient Air Quality Standards (NAAQS) in other states." 76 Fed. Reg. 40662. EPA also proposed to implement CSAPR's ozone season nitrogen oxide program as Federal Implementation Plans (FIPs) for Iowa, Kansas, Michigan, Missouri, Oklahoma, and Wisconsin to address emissions from those states that significantly contribute to nonattainment or interfere with maintenance of the 1997 ozone NAAQS in downwind states. 

Under EPA's proposal to include the six states in CSAPR's seasonal ozone nitrogen oxide program, the affected states would be required to reduce their nitrogen oxide emissions between May and September beginning in 2012. In the supplemental action, EPA proposes to create ozone season nitrogen oxide emission budgets for affected units (generally large electric generating units) in the six states. Under this "state budget" concept, each affected state will be allocated an emissions budget for nitrogen oxide during the summertime ozone season, and each state's budget will then be allocated among the various electric generating units within the each state according to a prescribed allocation methodology. Five of the states, except Oklahoma, are already included in CSAPR's fine particulate program, which requires year-round nitrogen oxide emissions reductions, and will have to comply with the seasonal ozone nitrogen oxide program on top of the fine particulate requirements. The comment period on EPA's supplemental action closes on August 22, 2011. EPA hopes to finalize the proposed rulemaking by November 1, 2011 so that the rule can be implemented in time for the 2012 ozone season.