Areas with a Mandatory Upkeep Agenda Under Section 110(a)(1) of the Clean Air Act are classified as Green Book Sites

Areas with a Mandatory Upkeep Agenda Under Section 110(a)(1) of the Clean Air Act are classified as Green Book Sites

Three Major Cities No Longer Maintain 1-Hour Ozone Maintenance Plans

The Environmental Protection Agency (EPA) revoked the 1-Hour Ozone standard in 2009, transitioning several areas to comply with the more stringent 8-Hour Ozone standard. As a result, formal 1-Hour Ozone maintenance plans for Nashville, TN; Greensboro-Winston Salem-High Point, NC; and Denver-Boulder, CO have been rescinded or are no longer active under EPA policy.

Nashville, TN

After the EPA's 2009 revocation of the 1-Hour Ozone National Ambient Air Quality Standards (NAAQS), the prior 1-Hour Ozone maintenance plan was replaced by 8-Hour Ozone standards and related State Implementation Plans (SIPs). Tennessee's current air quality management targets the 8-Hour standard, so the 1-Hour maintenance plan status is effectively inactive or rescinded.

Greensboro-Winston Salem-High Point, NC

This North Carolina area transitioned to the 8-Hour Ozone standard post-2009. There are no active 1-Hour Ozone maintenance plans, as EPA directed areas to comply with the newer standard, and older 1-Hour plans were either revoked or redesignated.

Denver-Boulder, CO

Colorado's compliance efforts also focus on the 8-Hour Ozone standard since 2009. The 1-Hour maintenance plans were revoked along with the standard, with no current active maintenance plans under the 1-Hour standard.

All three areas, which were Early Action Compact (EAC) areas, were required to submit a 10-year maintenance plan under section 110(a)(1) of the Clean Air Act and the Phase 1 Rule. However, prior to the revocation of the 1-Hour standard, the 1-Hour Ozone Maintenance Areas were not subject to the Section 110(a)(1) maintenance plan provision under 40 CFR part 51, section 51.905(a)(3) and (4). The revocation of the 1-Hour standard allowed these areas to become subject to the Section 110(a)(1) maintenance plan provision if they were attainment for the 1997 8-Hour standard.

The Denver, CO Subpart 1 EAC area was designated nonattainment for the 1997 8-Hour Ozone, effective November 20, 2007.

In summary, all three areas no longer have maintained 1-Hour Ozone maintenance plans post-revocation in 2009, per EPA regulations. Their air quality plans and maintenance now address the 8-Hour Ozone standard as the relevant and enforceable NAAQS for ozone. No recent official documents or state notices indicate any reinstatement or ongoing 1-Hour Ozone maintenance plans for these metropolitan areas. Instead, current efforts and permitting focus on programs aligned with the 8-Hour standard and other air quality measures relevant under current regulations.

The EPA's revocation of the 1-Hour Ozone standard in 2009 mandated compliance with the 8-Hour Ozone standard in numerous areas, including Denver-Boulder, CO. As a result, the active 1-Hour Ozone maintenance plan in Denver-Boulder is no longer in effect.

Nashville, TN, another affected area, also shifted its focus towards the 8-Hour Ozone standard, making the prior 1-Hour maintenance plan effectively inactive or rescinded.

Greensboro-Winston Salem-High Point, NC, similarly transitioned to the 8-Hour Ozone standard, hence there are no active 1-Hour Ozone maintenance plans in this region.

In each of these areas, the primary emphasis is now on the 8-Hour Ozone standard, with no recent indications of reinstatement or ongoing 1-Hour Ozone maintenance plans.

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