The Phase 1 final rule to implement the 1997 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 1997 8-Hour Ozone standard; and that were - at the time of the 1997 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 1997 8-Hour Ozone standard.

1. Area Listings
   1. Classified Areas Sorted by Classification
   2. Section 185A Areas
   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. Section 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 1997 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 The 1-Hour standard was revoked for the EAC areas on April 15, 2009, one year after the effective date (April 15, 2008) of their designation as attainment for the 1997 8-Hour Ozone standard. At that time, the Denver, CO Subpart 1 EAC area was designated nonattainment for 1997 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.