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Ozone in the Uinta Basin

The Uinta Basin lies in the northeast corner of Utah and is bounded on the north by the Uinta Mountains, on the south by the Tavaputs Plateau, on the west by the Wasatch Range, and on the east by elevated terrain that separates it from Piceance Basin in Colorado. Duchesne and Uintah Counties occupy most of the Basin, and the Uintah and Ouray reservation covers a significant portion of basin lands.

Increased oil and gas development in the Uinta Basin have led to environmental issues regarding air quality, water quality, and management of drilling wastes.

In recent years, concentrations of wintertime ozone in the Uinta Basin have reached or exceeded the National Ambient Air Quality Standards (NAAQS), raising concerns about the health and environmental impacts of elevated ozone levels in the Basin.

Increased oil and gas exploration and production in the Uinta Basin has contributed to the increase in the precursor gases that lead to the formation of ozone. In addition, the Environmental Protection Agency (EPA) plans to tighten ozone standards by the end of 2015, making it more likely that the Basin will be designated as a nonattainment area for ozone. Areas designated as nonattainment are required to submit a State Implementation Plan (SIP) that demonstrates emissions reductions to bring the area into compliance with the NAAQS.

The Division of Air Quality (DAQ), in partnership with local governments, industry, local health departments, the Bureau of Land Management (BLM), EPA, the Ute Tribe, and various scientific research organizations, has been working diligently to determine the causes of wintertime ozone, identify control strategies to reduce emissions, and encourage industry to take proactive steps to cut emissions ahead of statutory deadlines (53 KB).

Emissions Reductions

Ozone pollution in the Basin is being addressed through a wide range of regulatory and voluntary emission reduction strategies.

Federal Regulatory Measures

  • EPA’s 2012 rulemaking for New Source Performance Standards (NSPS) for the oil and gas industry is predicted to cut VOC emissions by nearly one-fourth across the oil and gas industry, including a nearly 95 percent reduction in VOCs emitted from new and modified hydraulically fractured gas wells.
  • EPA updates to VOC performance standards for storage tanks will ensure that tanks likely to have the highest emissions are controlled first while tank owners and operators will have time to install VOC controls.
  • EPA Minor Source Permitting in Indian Country provides a permitting method for emissions sources not previously subject to regulation on tribal lands.
  • National Environmental Standards for Hazardous Air Pollutants (NESHAPS) regulations establishing standards for reciprocating internal combustion engines at oil and gas sources will significantly lower emissions, particularly from VOC sources.
  • New Source Performance Review (NSPS) standards for compression ignition engines and spark ignition engines will regulate VOC and NOx emissions from these types of engines.

State Regulatory Measures

  • New statewide rules (R307-500 Series, Oil and Gas) were adopted in 2014 to ensure that existing oil and gas equipment is maintained and operated as designed, and to reduce emissions from pneumatic controllers and oil tank trucks.
  • Existing DAQ source compliance action for permitted oil and gas operations and coordination with the Utah Division of Oil, Gas, and Mining (DOGM) on drilling permits provides more comprehensive compliance coverage of oil and gas activities.
  • State Approval Orders (AO) for permitted oil and gas operations use a projected production/well decline analysis as a surrogate for a demonstration of no significant impact from new or modified sources to ensure that new sources are not increasing ozone levels in the Basin.

Voluntary Measures


Jurisdictional issues complicate air pollution regulation in the Basin. Energy production areas are scattered over federal, state, and tribal lands. Each of these agencies has jurisdiction over the production areas located on their respective lands, and each have air regulations that apply depending on the amount of pollution emitted.

Indian Country

Approximately two-thirds of currently producing oil and gas wells, three quarters of the gas production, and half of the oil production in the Uinta Basin is located in reviewing and permitting oil and gas production air emissions on tribal lands. On December 12, 2013, EPA proposed extending the deadline for oil and gas sources in Indian Country for an additional 1 to 1 ½ years to provide additional time to develop general permits for this source category. On July 2, 2013, the Ute Indian Tribe of the Uintah and Ouray Reservation requested to enroll in the Ozone Advance program. DAQ is currently coordinating with the Ute Tribe to improve air quality and reduce emissions from oil and gas activities on tribal land.

State Lands

Utah has jurisdictional responsibility for the lands outside of Indian Country, where approximately 90 percent of the population is located. Normally, the State uses a program called New Source Review (NSR) to regulate oil and gas emissions. NSR is effective because sources are subject to Best Available Control Technology (BACT) review, National Ambient Air Quality Standards (179 KB) and public comment before sources receive a permit. To qualify for NSR, sources must meet a minimum threshold of emissions: 5 tons per year of any criteria pollutant, less than 500 pounds per year of any single hazardous air pollutant, or less than 2,000 pounds per year of combined hazardous air pollutants. If the source emits less than the threshold, they fall outside of NSR regulations.

In the Basin, many of the oil and gas emission sources, including wellheads and tanks, do not meet the NSR threshold and are not regulated through this program. DAQ and its partners in the Basin are working with stakeholders to determine the feasibility of other regulatory measures for sources that fall outside of NSR to establish better pollution controls for smaller sources.

Ozone Basics

Ozone is a colorless gas comprised of three oxygen atoms. It is not emitted directly into the air as a gas but is formed through a chemical reaction between nitrogen oxides (NOx) and volatile organic compounds (VOCs) in the presence of sunlight. Ozone exposure causes respiratory inflammation and irritation often described as “a sunburn on the lungs” and is a trigger for increased symptoms of asthma. While the same ozone molecule protects the earth from harmful radiation in the upper atmosphere, at ground level it is considered an air pollutant, with national standards for allowable concentrations in the ambient air.

Most scientific studies have focused on summertime ozone in urban areas. Summer ozone formation chemistry is well characterized. Wintertime ozone, on the other hand, is a relatively new phenomenon, limited to a few isolated basins in the Intermountain West, and its causes are not fully understood. Preliminary evidence suggests that high concentrations of ozone in the Basin during the winter only occur when the ground is snow covered, a temperature inversion traps emissions close to the ground, and the skies are sunny. The traditional strategies for solving summertime ozone pollution won’t work in the Uinta Basin because of the unique nature of wintertime ozone.


Partnerships with stakeholders are critical to the success of efforts to reduce emissions in the Basin. The Uinta Basin Ozone Study, Three-State Pilot Project, Ozone Advance, and voluntary seasonal controls are examples of the collaboration with state and local governments, federal land management agencies, state agencies, local health departments, researchers, universities, the Ute Indian tribe, and industry that are ongoing in the Uinta Basin.


While the Uinta Basin is still officially in attainment for ozone, elevated ozone levels over recent years and tighter ozone standards point to a nonattainment designation by the EPA. This will require the state to prepare a State Implementation Plan (SIP) to bring state lands in the Basin into attainment. The tribe and EPA would also be required to develop a plan for Indian Country. A nonattainment designation creates a process for the state and federal government to prepare consistent plans for emissions reductions. The practical result is a delay in real emission controls until the plans are developed and adopted. It will take at least three years of regulatory monitoring for the EPA to make a determination that the Basin is in nonattainment for ozone. Development of a SIP would take another three years. A nonattainment designation could bring mandatory mitigation strategies designed to address traditional, urban, summertime ozone—strategies that could be ineffective or even counterproductive in the Basin.

The state has adopted new rules to reduce emissions from the oil and gas industry statewide, and is working to ensure that existing sources are meeting all existing permitting requirements. The state is currently engaged in productive discussions with industry on voluntary reductions—reductions that would take place before mandatory measures could be implemented and improve air quality in the Basin now. Should the Basin go into nonattainment, these reduction measures could minimize the severity of the ozone pollution. Since ozone nonattainment areas are classified across a spectrum from Marginal to Extreme and regulated accordingly, reducing emissions now could result in a lower classification. This would provide the state with greater flexibility in addressing elevated ozone concentrations, which is critical, because ozone control strategies prescribed under nonattainment may not be appropriate for the Basin’s winter ozone problem.


The Division of Air Quality (DAQ) is leading a multi-year effort to bring together knowledgeable scientists to study this phenomenon. Participants include the Environmental Protection Agency (EPA), National Oceanic Atmospheric Administration (NOAA), Utah State University, University of Utah, and a number of other universities in both the United States and Canada. The Uinta Basin Winter Ozone Study (UBOS) began in 2011 to characterize emission sources, identify chemical pathways unique to the Basin, and develop effective mitigation measures. This collaborative study continues to bring together the best and the brightest in the fields of atmospheric research, air modeling, and emissions source testing, and analysis.

The ongoing Uinta Basin Ozone Study (UBOS) is important for understanding the atmospheric chemistry responsible for winter ozone and developing control strategies that reduce the precursor gases that contribute to its formation. Over the past few years of study, much has been learned about the unique winter chemistry that exists in the Basin. Research has shown that VOCs are the most effective ozone precursor to reduce. Scientists are working to determine which VOCs are key to forming ozone in the Basin, where these emissions are located in the atmosphere, how their location impacts their ability to mix and react, and which meteorological conditions set the stage for the formation of ozone.

Due to the complex chemistry that creates ozone and the vast variation in VOC reactivity, reductions must be targeted to specific emissions. Otherwise, there is the potential that emissions reductions will not be effective or even be counterproductive.

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