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8-Hour Ozone (1997 NAAQS)

November 18 , 2014
January 22 , 2015


In 1997, national ambient air quality standard (NAAQS) for ozone was lowered from 0.12 parts per million of ozone averaged over one hour to 0.08 parts per million of ozone averaged over eight hours. US EPA's Ozone Air Quality Standards

Nonattainment areas are classified as marginal, moderate, serious, severe, or extreme areas depending on the magnitude of the highest 8-hour ozone design value for the monitoring sites in the nonattainment area. In 2004, the Sacramento region was designated nonattainment for the 1997 NAAQS, and classified as a “serious” area with an attainment deadline of June 15, 2013. The Sacramento region includes all of Sacramento and Yolo counties and portions of Placer, El Dorado, Solano, and Sutter counties.

Voluntary Reclassification

Since the Sacramento region needs to rely on the longer term emission reduction strategies from state and federal mobile source control programs, the 2013 attainment date cannot be met. Consequently, on February 14, 2008, CARB, on behalf of the air districts in the Sacramento region, submitted a letter to EPA requesting a voluntary reclassification (bump-up) of the Sacramento Federal Nonattainment Area from a “serious” to a “severe” 8-hour ozone nonattainment area with an extended attainment deadline of June 15, 2019, and additional mandatory requirements. On May 5, 2010 EPA approved the request effective June 4, 2010.