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1-Hour Ozone Information
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This page provides detailed information on designations and classifications of 1-hour ozone nonattainment areas, maintenance plan requirements and anti-backsliding requirements. It reflects the current status of 1-hour nonattainment areas and does not reflect the 8-hour standard. For information about the 8-hour ozone areas, click on the "8-Hour Ozone" link on the left sidebar. On June 15, 2005 the 1 hour ozone standard was revoked for all areas except the 8-hour ozone nonattainment Early Action Compact Areas (EAC) areas (those do not yet have an effective date for their 8-hour designations). This happened by virtue of 40 CFR 50.9(b). Due to the revocation of the 1-hour ozone standard, effective June 15, 2005, a recent notice [70 FR 44470] removed from 40 CFR part 81 the 1-hour designations and classifications for all areas except EAC areas that have deferred effective dates for their designations under the 8-hour ozone standard. The former 1-hour ozone designations and classifications as of June 15, 2004, are being retained in subpart C of Part 81 for purposes of the anti backsliding provisions of 40 CFR 51.905. 40 CFR 51.905(c) references subpart C of part 81 for the areas affected by the anti-backsliding regulation. The final phase 1 rule that implements the 8-hour ozone standard provides generally that only the portion of the designated area for the 8-hour NAAQS that was designated nonattainment for the 1-hour NAAQS is required to comply with the anti-backsliding obligations in 40 CFR 51.905(a). Consult the rule for additional detail. The maintenance plans required under section 51.905(a)(3)(iii) and (4)(ii) must demonstrate maintenance only for the area designated nonattainment (or attainment with a section 175A maintenance plan) for the 1-hour NAAQS at the time of designation of the 8-hour NAAQS.
History: On February 6, 2008, EPA proposed (73 FR 6863) and on April 2, 2008, finalized (73 FR 17897) the designation of the remaining 13 Early Action Compact (EAC) Areas as attainment for the 8-hour ozone National Ambient Air Quality Standard (NAAQS), effective April 15, 2008. The States in which these 13 areas are located had submitted quality-assured data indicating that the areas are in attainment for the 8-hour ozone NAAQS based on ambient air monitoring data from 2005, 2006 and 2007. In addition, consistent with EPA's implementing regulations, the 1-hour ozone NAAQS will no longer apply in each of these areas one year after the effective date of the designation. The 8-hour ozone NAAQS tables will be modified in the regulations to reflect the attainment designation for the 13 EAC areas and the 1-hour ozone NAAQS tables in the regulations to reflect that the 1-hour standard will no longer apply in these areas as of April 15, 2009.
The phase 1 final rule to implement the 8-hour ozone standard was published on April 30, 2004. The anti backsliding provisions in that rule set forth specific requirements for areas that are designated attainment for the 8-hour ozone standard; and that were - at the time of the 8-hour designations (generally June 15, 2004) - either attainment areas with maintenance plans for the 1-hour standard; or nonattainment for the 1-hour standard. Specifically, 40 CFR part 51, section 51.905(a)(3) and (4) requires these areas to submit a maintenance plan under section 110(a)(1) of the CAA. That maintenance plan must demonstrate maintenance out to 10 years after designation. This maintenance plan does not, however, carry with it any conformity obligations (unlike maintenance plans required under section 175A of the Act. The section 110(a)(1) maintenance plan must be submitted within 3 years after designation for the 8-hour ozone standard.
The Maintenance Areas listed below (Previously Nonattainment Areas) which are still subject to the 1-hour standard have maintenance plans required under section 175A, but are not at this time subject to the Section 110(a)(1) maintenance plan provision under 40 CFR part 51, section 51.905(a)(3) and (4). When the 1-hour standard no longer applies, they will be required to submit 110(a)(1) maintenance plans under 40 CFR part 51, section 51.905(a)(3) and (4), if they are attainment for the 8-hour standard. The areas are: Nashville, TN, Greensboro Winston Salem High Point, NC, and Denver Boulder, CO.
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