BOARD MEETING DATE: November 5, 2004
AGENDA NO. 31

End-of-Season Air Quality Report

SYNOPSIS:

In 2004, the South Coast Air Basin recorded the lowest number of violations of the federal ozone standard since the inception of the District and its predecessor agencies. The improvement in ozone air quality in 2004 is in direct contrast to the 2003 summer ozone season which exhibited severe weather conditions and correspondingly higher ozone concentrations. Favorable weather conditions which led to cooler temperatures and weaker inversions, together with continued implementation of the air pollution control strategy, have contributed to this year's observed trend.

COMMITTEE:

Not Applicable

RECOMMENDED ACTION:

Receive and file.

Barry R. Wallerstein, D.Env.
Executive Officer

Background

After two decades of steady improvement in air quality, from the late 1990's through 2001 the South Coast Basin (Basin) entered a period where a slower rate of reductions was observed in the number of days exceeding the federal 1-hour and 8-hour ozone air quality standards. Of greater concern, in 2002 and 2003, the trend of air quality improvement was reversed, leaving 2003 with the worst air quality in a seven-year span. As a consequence, much focus was placed on the observed air quality trend in 2004 to determine whether this inflection point in the trend was real or would 2004 signal a return to the long-term trend. More specifically: were the higher ozone concentrations observed in the preceding two years a response to stagnant weather and or short-term changes in mobile source emissions due to the process of implementing California fuel reformulation or were they more indicative of a flattening trend in air quality?

Year 2004 Ozone Air Quality

In 2004, the Basin recorded the lowest number of violations of the federal ozone standard (27) and the lowest peak 1-hour concentration (0.163 parts per million) since the inception of the District and its predecessor agencies. Moreover, the Basin relinquished the nationwide titles for most days above the federal 1- and 8-hour standard and peak 1-hour concentration. Favorable weather conditions which led to cooler temperatures (and a slower rate of ozone formation and less evaporative emissions) and weaker inversions played a major role in this year's observed ozone air quality. Completion of the statewide fuel reformulation program (i.e., eliminating higher evaporative emissions due to co-mingling of two fuels during transition) together with the continued implementation of the air pollution control strategy also contributed.

Staff will provide a presentation at the Board Meeting summarizing the ozone air quality in 2004.

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