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Ozone Standards and Development of a State Implementation Plan (SIP): Uinta Basin

Proposed changes to the existing ozone standard combined with increasing incidences of high ozone values in the Uinta Basin could require further reductions in emissions from oil and gas operations. If ozone levels exceed federal air quality standards, the Basin could be designated as a nonattainment area, requiring preparation of a State Implementation Plan (SIP).

Elevated Ozone Levels

Beginning in 2005, periods of high ozone in the Upper Green River Basin of southwestern Wyoming pointed to oil and gas operations as a major source of precursor emissions. The same phenomenon was discovered in the Uinta Basin during the winters of 2009-2010 and 2010-2011—when ozone levels exceeded the 8-hour 75 parts per billion (ppb) Environmental Protection Agency (EPA) air quality standard—raising concerns about the increasing frequency of elevated ozone concentrations in the Basin.

The 2013 Uinta Basin Ozone Study (UBOS) showed that the maximum 8-hour average ozone concentrations at the air monitor in Ouray exceeded the EPA standard by 89 percent, and 17 of the 20 monitoring sites recorded exceedances of the standard during the study period. During the 2013 study, ozone values exceeded the National Ambient Air Quality Standards (NAAQS) for 22 days in Vernal and 29 days in Roosevelt. Individual episodes of elevated ozone ranged from 3 to nearly 15 days in length.

These exceedances don’t constitute a violation of the EPA ozone standards by themselves. A violation only occurs when the three year average of the fourth-highest daily maximum 8-hour average is greater than 75 ppb. However, elevated levels of ozone impact the health of Basin residents and increase the possibility that the area will be designated as nonattainment for ozone by the EPA.

Ozone Standards

The Clean Air Act (CAA) requires the EPA to set NAAQS for ozone and five other criteria pollutants. If areas in a state fail to meet these NAAQS, the area is designated as nonattainment, and the state is required to submit a State Implementation Plan (SIP) to demonstrate how the area will be brought back into attainment, or compliance, with the NAAQS.

The CAA requires the EPA to review the standards every five years to ensure that they are protective of human health and the environment. The EPA began its review of ozone standards in 2008 and released draft rules in 2010 that recommended lowering the 75 parts per billion (ppb) limit to between 60 to 70 ppb. For a variety of reasons, this recommendation was put on hold in 2011. EPA staff conducted scientific studies and policy assessments on the standards in 2012 and 2014, releasing their findings in the Integrated Science Assessment for Ozone and Related Photochemical Oxidants in June 2014. EPA staff concluded that, based on comprehensive scientific evidence that proved stronger than previous reviews, the current standard of 75 ppb should be lowered to between 60 ppb to 70 ppb to protect public health and the environment. On November 25, 2014, the EPA proposed to update the 8-hour standard to between 65 and 70 ppb, and the agency is seeking comments on levels as low as 60 ppb. The Administrator of the EPA will make the final decision on this proposed revision of the standard by October, 2015.

State Implementation Plan (SIP) for Ozone

When the EPA revises the NAAQS, it has two years to designate areas as meeting the standards (attainment) or not meeting them (nonattainment) based on local monitored data. Once the NAAQS are revised, the clock starts for nonattainment designation for the area along with the SIP process:

  • The governor has one year to recommend nonattainment status.
  • The EPA has one year to publish final nonattainment designation.
  • The state has three years to write the SIP.
  • The state has one year to have controls in place.
  • Each of the next three years must meet the standard or the area will be classified as a more severe nonattainment area. If an area is designated as moderate, serious, or severe, it has a longer time frame to meet the standard.

SIPs must include a description of control strategies and measures to control pollution and include a program to enforce the measures specified to bring the area into attainment. The SIP must also contain contingency measures that will require further emission reductions if the control strategies are not sufficient to attain the standard.

Early Emission Reductions

Over the past several years, DAQ has been working actively with industry, local governments, and the Ute Tribe to reduce emissions ahead of an EPA designation for the area and collect scientific data that can be used to guide future emission reduction efforts. State and tribal participation in Ozone Advance, voluntary seasonal controls, and new state rules for oil and gas operations will improve existing ozone levels and help the Basin achieve early emission reductions.

The CAA classifies nonattainment areas according to severity. Marginal or Moderate nonattainment areas for ozone have fewer SIP requirements than Serious or Severe areas. Early emission reductions can reduce pollution concentrations, resulting in a lower classification that would allow greater flexibility to develop emission reduction strategies that are effective in the area.  The CAA requires areas with a higher classification to implement strategies that were designed for major urban areas and would not be effective in rural areas where vehicle emissions are not a significant issue.

Early emission reductions will lower emission reduction requirements under the SIP. Once a SIP is in development, sources that made reductions before the base year will have fewer obligations under the SIP and will have greater control over the timing and methods used to reduce emissions. Once the state implements SIP strategies, however, sources that did not make early reductions will generally face higher costs and reduced flexibility.

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