Through a 2-year effort known as the Ozone Transport Assessment Group (OTAG), EPA worked in partnership with the 37 easternmost States and the District of Columbia, industry representatives, and environmental groups to address ozone transport. From May 1995 to June 1997, the OTAG held meetings to identify and evaluate flexible and cost-effective strategies for reducing long-range transport of ozone and ozone precursors. This multi-year collaboration resulted in the most comprehensive analysis of ozone transport ever conducted. In June 1997, the OTAG States voted 32-5 in favor of a strategy to reduce NO_x emissions from utilities and other major sources. Reductions ranged from those currently required by the Clean Air Act, up to an 85% reduction in emissions rate (or 0.15 lbs NO_x /MMBtu, whichever is less stringent) from 1990 utility levels in a number of States in the OTAG region. In November 1997, building on the recommendations of OTAG, EPA proposed to require 22 States and the District of Columbia to submit State implementation plans (SIP) that address the regional transport of ground-level ozone. EPA proposed to require implementation of NO_x control measures by May 2003 to eliminate the significant contribution of emissions from upwind States, and set Statewide NO_x emissions budgets reflecting those reductions In May 1998, EPA issued a supplemental notice which proposed a model NO_x budget trading program and State reporting requirements and provided the air quality analyses of the proposed Statewide NO_x emissions budgets. In October 1998 EPA published the final version of the SIP call, which included additional air quality analyses and revised inventories based on public comments. This paper focuses on the development of the emission inventory and projection data developed to support EPA's rule. The starting point for the emission and projection data was the OTAG Study. OTAG emissions and projections were revised by selecting a more recent base year, developing a new inventory and projection data set for electric generating units (EGUs), and by incorporating comments from States, industry, and other stakeholders. This paper documents the development of the 2007 base case emissions and the development of the State-level 2007 NO_x budgets.
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