July 06, 2010


Posted on July 6, 2010 by Roger Ferland

Concern is growing in western states about EPA’s recent refusal to adequately  consider elevated PM-10 levels resulting from natural events as a factor in determining nonattainment.In 2005, Congress amended Clean Air Act Section 319 to require EPA to adopt rules for states to petition to exclude certain measured or modeled ambient air quality data from the determination whether a state was attaining National Ambient Air Quality Standards (“NAAQS”), because the data was affected by “exceptional events.” In general, exceptional events are those caused by natural, rather than anthropogenic sources. On March 22, 2007, EPA adopted a rule establishing the procedures and criteria to “exclude, discount, weigh, or make adjustments” to data based on the exceptional event finding. 72 Fed. Reg. 13561, 13562. 

From its adoption, the rule was criticized either for going too far to find exceptional events or not far enough. Particularly unhappy with the rule was the Western States Air Resources Council or WESTAR, an association of air quality managers from the western states. Criticisms include the charge that the rule did not contain clear criteria for making an exceptional event demonstration and generally ignored the real world natural conditions in the western deserts. In addition, WESTAR and others maintained that EPA acted much too slowly and inconsistently on state petitions for exceptional event determinations. In response, EPA has promised to issue guidance that would address these concerns.

On May 25, 2010, EPA rejected a petition for exceptional event status covering four high wind-related PM-10 NAAQS exceedances at a single monitor in Phoenix, Arizona. As a result, EPA will be compelled to disapprove the CAA Section 189(d) PM-10 nonattainment area plan for the Phoenix area. State officials expressed shock at the rejection because they believed that they had worked closely with EPA technical staff to develop a data package that would satisfy the rule criteria. They complained that their data had either been ignored or summarily dismissed. 

Officials from other western states attacked the EPA decision immediately and demanded new rules rather than the less legally-binding guidance promised by EPA. Although the controversy over EPA’s exceptional events rule and its implementation has been generally confined to PM-10 issues in the arid west, the adoption of a significantly more stringent 8-hour ozone NAAQS in August, and the huge increase in the size and number of nonattainment areas that will result from the new standard is likely to make the dysfunctional rule a national concern.

Tags: Air


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