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Pacific Southwest, Region 9

Serving: Arizona, California, Hawaii, Nevada, Pacific Islands, Tribal Nations

Air Actions, California - Imperial County

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Imperial County Final Finding of Attainment for the 1997 8-hour Ozone Standard

November 11, 2009 - EPA has signed a final rule determining that the Imperial Valley has attained the 1997 8-hour ozone standard. The finding is based on certified air quality monitoring data from 2006-2008.

Contact Information
Wienke Tax (tax.wienke@epa.gov)
Office of Air Planning
EPA Region 9
(415) 947-4192


Imperial County Proposed Finding of Attainment for the 1997 8-hour Ozone Standard

September 15, 2009 - EPA has signed a propose rule determining that the Imperial Valley has attained the 1997 8-hour ozone standard. The finding is based on certified air quality monitoring data from 2006-2008.

Imperial Valley PM-10 Failure to Attain Final Action

December 4, 2007 - EPA has signed a final rule determining that the Imperial Valley failed to attain the national PM-10 standard for serious nonattainment areas by December 31, 2001. We are finalizing this action based on a 2004 proposed rule that used air monitoring data from 1999-2001. The final rule requires the State to submit a plan to EPA within one year of the rule's publication.


Imperial County Finding of Failure to Attain the 8-hour Ozone Standard

February 13, 2008 - EPA signed a final rule finding that the Imperial County failed to attain the national ambient air quality standard for the 8-hour standard by the statutory attainment date, June 15, 2007. The monitored air quality data for 2004-2006 shows the area is not attaining the standard. The Imperial County is reclassified as a moderate 8-hour ozone nonattainment area with a maximum attainment date of June 15, 2010. The State will need to submit a State Implementation Plan revision that meets the requirements for moderate areas no later than December 31, 2008.

Related Documents
Contact Information

Adrienne Priselac (priselac.adrienne@epa.gov)
Office of Air Planning
EPA Region 9
(415) 972-3285


Historical Actions

August 3, 2004: EPA signed two rules to help bring cleaner air to California's Imperial Valley. First, prompted by a recent Ninth Circuit Court Order, EPA signed a final rule to reclassify the Imperial Valley from a moderate to a "serious" PM-10 nonattainment area. Second, EPA has signed a proposed rule that would find that the Imperial County failed to attain the national PM-10 standard for serious nonattainment areas by December 31, 2001.


  • August 2001: EPA signed a proposal that finds that Imperial County, California, attained the standard for PM-10.
  • October 2001: EPA signed a final notice finding that the Imperial County attained the PM-10 standard.

Imperial County Proposal on Finding of Attainment

On August 6, 2001, EPA signed a proposal that finds that Imperial County, California, attained the standard for PM-10 -- particulate matter, or dust, 10 microns in size or smaller -- by the statutory deadline of December 31, 1994. This proposed finding is based on a technical analysis provided to EPA by the State of California, which EPA has found adequate.

Related Documents

Imperial County Finding of Attainment

On October 9, 2001, EPA signed a final notice finding that the Imperial County attained the PM-10 standard by the statutory attainment date, December 31, 1994. This finding is based on a technical analysis provided to EPA by the State of California, which EPA has found adequate. EPA received adverse comments on the finding of attainment from the Sierra Club. All of the other commenters (including the Imperial County Air District, the agricultural community and mining industry) supported EPA's finding of attainment. EPA's response to comments is provided in the final Federal Register notice.

This final action allows Imperial County to retain its classification as a moderate PM-10 nonattainment area.

Related Information
Contact Information

Adrienne Priselac (priselac.adrienne@epa.gov)
Office of Air Planning
EPA Region 9
(415) 972-3285

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