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1-Hour Ozone (1979 Standard) Area Information


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On June 15, 2005 the 1 hour ozone standard was revoked for all areas except the 8-hour ozone nonattainment Early Action Compact Areas (EAC) areas (those do not yet have an effective date for their 8-hour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) (PDF) 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.


This page has been modified and is now divided as follows:

  1. Areas With 1-hour Standard Revoked April 15, 2009 or November 20, 2008
  2. Nonattainment and Maintenance Areas No Longer Subject to the 1-hour Standard, as of June 15, 2005
    1. Nonattainment Areas
    2. Maintenance Areas
    3. Historical Summary
  3. Areas with Maintenance Plan Requirements Under Section 110(a)(1) of the CAA
  4. Federal Register Notices Relating to 1-Hour Ozone Designations and Classifications

  1. Areas With 1-hour Standard Revoked April 15, 2009 or November 20, 2008
      These areas are listed in Subpart C

    Fourteen areas were listed in 40 CFR Part 81 Subpart C as participating in an Early Action Compact and designated nonattainment with a deferred effective date.

    The 1-hour standard was revoked for 13 of these areas on April 15, 2009, one year after the effective date (April 15, 2008) of their designation as attainment or nonattainment for the 8-hour ozone standard. By April 2008, 13 of the areas were designated attainment when they met all of their EAC requirements and had clean 8-hour ozone data by December 31, 2007. The Denver, CO Subpart 1 EAC area was designated nonattainment for 8-hour Ozone, effective November 20, 2007 72 FR 53952 (PDF) based on air quality data from 2005, 2006 and the first three quarters of 2007. For Denver, the 1-hour standard was revoked November 20, 2008.

    1. Area Listings Sorted by
      1. Classification
      2. State/Area/County
      3. Area/State/County
    2. Area Maps
      1. U.S. Map
    3. Area Designation Data
      1. Data
    4. Area Summary Report

    History:

    On February 6, 2008, EPA proposed 73 FR 6863 (PDF) and on April 2, 2008, finalized 73 FR 17897 (PDF) 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.




  2. Previous Nonattainment and Maintenance Areas No Longer Subject to the 1-hour Standard (As of June 15, 2005)

    1. Previous Nonattainment Areas No Longer Subject to the 1-hour Standard (As of June 15, 2005) These areas are listed in Subpart C

      1. Area Listings
        1. Classified Areas Sorted by Classification
        2. Sec. 185A Areas (for Sec 185A definition, click here.)
        3. Incomplete or No Data Areas
        4. Sorted by State/Area/County
        5. Sorted by Area/State/County
      2. Area Maps
        1. Classification by County - U.S. Map
        2. Individual Previous Nonattainment Area Maps
      3. Area Designation Data
        1. Classified
        2. Sec. 185A
        3. Incomplete or No Data
      4. Previous Nonattainment Area Summary Report

      78 FR 58189 (PDF), effective 10/23/2013, corrected a boundary for the land of the Morongo Band of Mission Indians, located near Banning Pass in Riverside County, identifying it as a separately designated area for the one-hour Ozone standard, independent of the Los Angeles-South Coast Air Basin Area.


    2. Previous Maintenance Areas (Redesignated from Nonattainnment) No Longer Subject to the 1-hour Standard
      (As of June 15, 2005)

      1. Area Listings
        1. Classified Areas Sorted by Former Classification
        2. Sec. 185A Areas (for Sec 185A definition, click here.)
        3. Incomplete or No Data Areas
        4. Sorted by State/Area/County
        5. Sorted by Area/State/County
      2. Area Maps
        1. Classification by County - U.S. Map
      3. Area Designation Data
        1. Classified
        2. Sec. 185A
        3. Incomplete or No Data
      4. Previous Maintenance Area Summary Report

      Two 1-hour Ozone Maintenance Areas (that were previously nonattainment areas) became Early Action Compact (EAC) areas. As EAC areas, their maintenance plans no longer applied, and they are not listed in the “Previous Maintenance Areas No Longer Subject to the 1-hour Standard” reports. The areas are: Greensboro Winston Salem High Point, NC (initially classified as a Moderate 1-hour Ozone area), and Denver Boulder, CO (initially classified as a Section 185 1-hour Ozone area).


    3. Summary of Previous 1-hour Ozone designations/classifications as June 15, 2005



  3. Areas with a Maintenance Plan Requirement Under Section 110(a)(1) of the CAA

    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.

    1. Area Listings
      1. Classified Areas Sorted by Classification
      2. Sec. 185A Areas (for Sec 185A definition, click here.)
      3. Incomplete or No Data Areas
      4. Sorted by State/Area/County
      5. Sorted by Area/State/County
    2. Area Maps
      1. Classification by County - U.S. Map
    3. Area Designation Data
      1. Classified
      2. Sec. 185A
      3. Incomplete or No Data
    4. Area Summary Report
    5. Federal Register Notices
      1. 110(a)(1) Maintenance Plans

    Until the 1-hour standard no longer applied, the 1-hour Ozone Maintenance Areas (Previously Nonattainment Areas) which were subject to the 1-hour standard had maintenance plans required under section 175A, but were not 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 applied, these areas would be required to submit 110(a)(1) maintenance plans under 40 CFR part 51, section 51.905(a)(3) and (4), if they were attainment for the 8-hour standard.

    The Nashville, TN and Greensboro-Winston Salem-High Point, NC and Denver-Boulder, CO 1-hour Ozone maintenance areas were Early Action Compact (EAC) areas. The 1-hour standard was revoked for the EAC areas on April 15, 2009, one year after the effective date (April 15, 2008) of their designation as attainment for the 8-hour Ozone standard. At that time, the Denver, CO Subpart 1 EAC area was designated nonattainment for 8-hour Ozone, effective November 20, 2007, and the Nashville, TN and Greensboro-Winston Salem-High Point, NC areas were required to submit a 10-year maintenance plan under section 110(a)(1) of the CAA and the Phase 1 Rule.




  4. Federal Register Notices Relating to 1-Hour Ozone Designations and Classifications

    1. November 6, 1991 - 40 CFR PART 81 Air Quality Designations and Classifications (PDF)
    2. August 16, 2005 Correction to August 3 Notice (PDF)
    3. August 3, 2005 Notice Revoking the 1-hour Standard in Most of the Nation
      (Effective September 2, 2005) (PDF)
    4. Other Associated Federal Register Notices
      1. Clean Data Determination/Attainment Determinations
      2. Attainment Date Extensions
        These extensions modify the dates shown in the nonattainment areas above
      3. Changes to a Higher Classification
      4. All Federal Register Notices
        1. Notices Listed By Category
        2. Notices Listed By Area Name
        3. Notices Listed By State then Area
        4. Notices Listed By Date

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