Air Quality Division: Plans: 8-Hour Ozone

The U.S. EPA is charged with developing air quality standards for the protection of human health and welfare. U.S. EPA is also required to evaluate those standards periodically and revise them as needed (see U.S. EPA: Ozone ). In 1997, U.S. EPA completed an analysis of the 1-hour ozone standard, and adopted a new, more protective 8-hour standard to address the impacts of exposure of the public to longer periods of elevated ozone pollution. On June 13, 2007, ADEQ adopted and submitted to U.S. EPA, under the 1997 8-hour ozone standard, the Eight Hour Ozone Plan for the Maricopa Nonattainment Area . This plan, developed by the Maricopa Association of Governments (MAG), demonstrated attainment of the 1997 8-hour ozone standard and attainment with that standard has been achieved. Because the nonattainment area is now in attainment, MAG developed the Final 8-Hour Ozone Redesignation Request and Maintenance Plan for the Maricopa Nonattainment Area adopted by ADEQ and submitted to U.S. EPA on March 25, 2009.

In 2008, U.S. EPA again revised the ozone standard and lowered the previous 8-hour standard from 0.08 parts per million (ppm) to 0.075 ppm . U.S. EPA has provided nine factors that states must consider when recommending boundaries for attainment, nonattainment, and unclassifiable areas. The major factors include consideration of sources of ozone precursor emissions, meteorological conditions, jurisdictional boundaries, and monitors currently measuring ozone at nonattainment levels. ADEQ developed a Technical Support Document (TSD) to explain to U.S. EPA the recommendations of the Governor for revising the boundaries of the ozone nonattainment area to address the new 2008 standard. The Governor's recommendations were submitted to U.S. EPA Region 9 in March 2009.

In 2009, U.S. EPA reconsidered the ozone standard established in 2008 and delayed action on boundary designations. U.S. EPA withdrew the reconsideration in September 2011 and indicated it will move forward with boundary designations for the 2008 standard. Since the submittal of State recommendations in 2009, changes have occurred in air quality and emissions information that was used to develop those recommendations. Based on those changes, revised boundary recommendations were submitted to U.S. EPA in December 2011. EPA completed area designations for the 2008 ozone standards effective July 20, 2012.

Technical Analysis for 8-Hour Ozone Boundary Designation (submitted in 2009 and revised in 2011 based on new 2008 Standard)

Technical Analysis for 8-Hour Ozone Area Boundary Designation (submitted in 2003 based on old 1997 Standard)