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 the Basin lands. The Uinta Basin was designated a nonattainment in August 2018 and is a unique ozone NAA in many ways. It has a designation area based upon elevation including areas in Uintah and Duchesne County below 6,250 feet above sea level. It is a rural area with a small population, however the geography and weather conditions combined with the presence of significant oil and gas production emissions of VOCs and NOx, creates occasional high levels of ozone exceeding the standard. These ozone events occur in the winter months during a cold air inversion trapping emissions in the basin with snow on the ground and reacting the UV radiation from the sun creating the radiant energy needed to combine VOC and NOx to ozone.
For further information on the scientific research performed in the Basin to better understand the phenomenon of winter time ozone please visit our research pages. There have also been many research projects led by or in coordination with the Utah State University Bingham Research Center. Find summaries and research papers on their website.
Regulatory background
As can be seen in the above monitoring data for the Uinta Basin there are sharp changes in ozone levels which correlate with winters with cold inversions and snow on the ground. Overall there is a slow trend to less exceedances of the standard. This trend with potentially different weather patterns due to climate change have allowed the Division to request two one-year extensions to the original attainment date of August 3, 2021. The first one-year extension was approved in October 2022 extending the attainment date to August of 2022. In April 2024 the EPA proposed approval of the second one-year extension and a determination that the area had attained the 2015 ozone standard and provided an opportunity to comment. On December 16, 2024 EPA issued a final rule that actually denied the second one-year extension request and reclassified the NAA from marginal to moderate classification. The EPA stated that this change in position was due to adverse public comment and re-evaluation of the ozone exceedances in the winter of 2023.
The state of Utah and other partners have filed a petition for reconsideration of the December 2024 decision and EPA has indicated that they are in the process of evaluating the decision of the denial of the second one-year extension and bump up to a moderate classification. The state of Utah has discontinued development of a SIP until EPA finalizes their decision.
Specific regulatory requirements for oil and natural gas operations
The primary source of ozone precursor emissions of VOCs and NOx in the Uinta Basin are from oil and natural gas exploration and production. Under state rules emission inventories are required to be submitted to UDAQ triennially. Information on the state wide and Uinta Basin specific emission inventory for oil and natural gas can be found here. It should be noted that the State of Utah is only responsible for reporting the emission inventory for oil and natural gas sources on state jurisdiction. A large proportion of oil and natural gas operations are in Indian Country and under the jurisdiction of the Ute Tribe and EPA.
There are specific Utah state and federal regulations that are applicable to oil and natural gas sources. The Utah state rules are referred to as the 500 series that spell out how oil and natural gas sources are to register with the Division and to comply with rules to meet permit requirements by rule. The EPA also regulates oil and natural gas sources through the New Source Performance Standards and Emission Guidelines referred to generally as subpart OOOO and specifically the Indian Country in the Uinta Basin are regulated through a Federal Implementation Plan. The federal rules for oil and natural gas sources are still currently undergoing revisions and as such state requirements are also subject to change. To stay updated with ongoing regulatory changes visit the Oil and Natural Gas Regulations webpage where you can sign up for upcoming announcements or rule making.