![[logo] US EPA](https://webarchive.library.unt.edu/eot2008/20090511082541im_/http://www.epa.gov/epafiles/images/logo_epaseal.gif){kind=logo}
8-Hour Ground-Level Ozone Designations in EPA Region 9
National Links
On April 15, 2004, EPA implemented the final designations of areas for the 8-hour ozone national ambient air quality standard, or NAAQS. Almost 500 counties across the country were designated as nonattainment for the standard. There are 17 nonattainment areas located in Region 9, shown in the chart below, and in the designation map for 8-hour ground-level ozone in Region 9.
| Arizona | ||
| Area | Classification | Maximum Attainment Date |
Phoenix-Mesa |
Subpart 1 (Basic) | 2009 |
California |
||
| Area | Classification | Maximum Attainment Date |
Central Mountain Counties (Amador/Calaveras Cos.) |
Subpart 1 (Basic) | 2009 |
Chico (Butte Co.) |
Subpart 1 (Basic) | 2009 |
Coachella Valley |
Serious | 2013 |
Eastern Kern |
Subpart 1 (Basic) | 2009 |
Imperial Co. |
Marginal | 2007 |
Sacramento Region |
Serious | 2013 |
San Diego |
Subpart 1 (Basic) | 2009 |
San Francisco Bay Area |
Marginal | 2007 |
San Joaquin Valley |
Serious | 2013 |
South Coast |
Severe-17 | 2021 |
Southern Mountain Counties (Mariposa/Tuolumne Cos.) |
Subpart 1 (Basic) | 2009 |
Sutter Buttes (Sutter Co., part) |
Subpart 1 (Basic) | 2009 |
Ventura |
Moderate | 2010 |
Western Mojave Desert |
Moderate | 2010 |
Western Nevada Co. |
Subpart 1 (Basic) | 2009 |
| Nevada | ||
| Area | Classification | Maximum Attainment Date |
Las Vegas (Clark Co.) |
Subpart 1 (Basic) | 2009 |
EPA also finalized Phase I of the implementation rule for the 8-hour standard, which includes a system for classifying areas according to the severity of their air quality violation, and explains how areas will transition from the 1-hour to the 8-hour ozone standard. More information about the standard and its implementation is available on EPA's National 8-Hour Ground-level Ozone Designations Web site. Additional information about how this standard affects the Pacific Southwest is available on the Region 9: State and Tribal Recommendations and EPA Response Web page.