Development of a Voluntary Early Action Compact to Control Ozone Concentrations in the Austin, Texas Area

摘要

Since 1998, the design value for ozone concentrations averaged over 8 hours in Austin, Texas has exceeded or been close to National Ambient Air Quality Standard (NAAQS). In 2002, the area entered into an O3 Flex agreement, committing to voluntary emission reduction measures intended to maintain compliance with the NAAQS for concentrations averaged over 1 hour. Subsequently, the Austin area has been in the forefront in developing a voluntary Early Action Compact (EAC) to reduce 8-hour averaged ozone concentrations below the NAAQS by 2007, three years before the date required for nonattainment areas. Activities undertaken by the local area pursuant to the EAC have resulted in a voluntary clean air action plan (CAAP) that has been submitted to the Texas Commission on Environmental Quality (TCEQ) and the U.S. Environmental Protection Agency (EPA) for incorporation into the State Implementation Plan (SIP). The EAC has several advantages over the traditional process: it improves the air quality earlier, it permits the local area to select control strategies instead of using EPA prescribed controls, it allows deferreral of nonattainment designation and related requirements and transportation conformity and nonattainment new source review are not required. The EAC CAAP is based on enhanced emissions inventories and photochemical modeling using the Comprehensive Air Quality Model with Extensions (CAMx). The air quality modeling for 2007 indicated that the area would be on the cusp of attainment or nonattainment of the NAAQS. Consequentially, in order to insure that the NAAQS is attained in the future, a suite of control measures have been adopted for implementation in the area. This paper will describe the development of the emissions inventory and the photochemical modeling. Results of the base case modeling will be provided. Sensitivity analyses will be described to assess the role of transport from other areas, the sensitivity to ozone precursors and ozone response to proposed controls. The ozone precursor control measures will be described.