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Ozone State Implementation Plan (SIP) Process Ozone SIP


Within two years after setting or revising NAAQS for criteria pollutants, the EPA must designate areas as meeting (attainment) or not meeting (nonattainment) the air-quality standard. The EPA’s final designations are based on the most recent three years of air-quality monitoring data, recommendations from the state, and additional technical information. State recommendations are made by the governor and consider air-quality data, emissions, meteorology, topography, and jurisdictional boundaries.

If an area is not meeting the standard, the state is required to prepare a SIP. The SIP is a comprehensive document that identifies how the state will attain or maintain the NAAQS to comply with the provisions of the Clean Air Act. The SIP includes regulatory and non-regulatory control measures for reaching attainment by a specific deadline.

Marginal SIP Requirements

All or parts of seven counties in Utah were designated as Marginal nonattainment, the least stringent nonattainment designation, for the 2015 8-hour ozone standard. These areas were required to attain the ozone standard by August 3, 2021. The Clean Air Act requires the following actions for areas designated as Marginal nonattainment:

  • A baseline emission inventory must be completed
  • A nonattainment new source review (NNSR) program must be implemented, with a NSR emission offset ratio of 1.1:1
  • Emission statements from sources with a threshold of 25 tons per year of NOx or VOCs must be completed

Serious SIP Requirements

Areas that fail to attain the standard by the moderate attainment date will be further reclassified to serious nonattainment status and will be required to attain the standard by August 3, 2027. Based on recent monitoring data, it is likely that the Northern Wasatch Front nonattainment area will be reclassified as serious nonattainment in 2025. The Clean Air Act requires the following actions for areas designated as serious nonattainment:

  • All requirements for marginal and moderate nonattainment areas
  • A NNSR program must be implemented, with a NSR emission offset ratio of 1.2:1
  • Major sources of VOCs/NOx (sources with emissions greater than 50 tons per year) must complete a reasonably available control technology (RACT) analysis and implement identified controls that meet this threshold
  • An attainment demonstration identifying if the area will attain the standard by the attainment date 
  • A 3% annual reduction in VOCs or NOx to demonstrate reasonable further progress (RFP)
  • An enhanced emissions inspection and maintenance (I/M) program 
  • Vehicle Miles Traveled reporting

Contingency measures for failure to attain must be determined

SIP Timeline

These are approximate deadlines that will be confirmed when EPA bumps Utah’s ozone nonattainment areas to moderate, which will most likely affect this schedule.

Stakeholder Meetings

The DAQ wants to ensure an inclusive public involvement and stakeholder process and involve both industry and advocates for clean air. As DAQ staff progresses in the SIP process, public meetings will be held to provide information regarding regulatory timelines and the actions that DAQ will be obligated to take to meet the new requirements for a moderate classification, as well as provide an opportunity for questions regarding the SIP process. This section will be updated as public meetings are scheduled.

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