SALT LAKE CITY — Researchers looking to study the formation of ozone in the Uinta Basin in 2013 were not disappointed, logging dozens of instances in which the federal standard was breached, including one by 89 percent.
A final report from the 2013 Uinta Basin Ozone Study released Tuesday details how emissions from the 10,000 producing oil and gas wells in the region become trapped, setting up a complex chemical reaction typically seen in urbanized areas in the summer.
The standard set by the Environmental Protection Agency for ozone is 75 parts per billion, and one monitor at Ouray had a recording of 142 parts per billion. The study, however, is careful to note that the high number is not considered a violation of the standard per se because it did not hit an eight-hour average over a three-year period.
Monitors documented those instances on 22 days in Vernal and 29 days in Roosevelt. Those bumps happened during seven separate multiday ozone occurrences in episodes that were three to 15 days in length.
The recurrent phenomenon of wintertime ozone trapped in the Uinta Basin is driven by strong temperature inversions that coincide with snow on the ground. Chemical reactions are driven by ultraviolet solar radiation from the snow and are accompanied by high levels of methane.
Ozone buildups occur during half of the winters in the basin — and during the first year of the study, 2012, researchers came up with no data because of the lack of snow cover.
This latest field study period turned out to be incredibly fruitful, providing a wealth of data that will help lay the foundations for studies in the future, said Brock LeBaron, deputy director of the Utah Division of Air Quality.
The multi-pronged study is the most ambitious air pollution probe carried out in Utah, tapping a variety of researchers from the National Oceanic and Atmospheric Administration, researchers from five Western states and the Utah Department of Environmental Quality.
Several other entities or agencies have thrown in support and funding for the $5.5 million study, including the Bureau of Land Management and the oil and gas industry, to determine the type of chemistry at play in the formation of the ozone.
Researchers point out that emission reductions at the 500-megawatt Bonanza power plant are unlikely to have a significant impact in curtailing the problem.
The ozone rests in a layer between 200 feet above the ground to 1,300 feet. The stack from the plant sits at 600 feet, and its plume penetrates through the layer of pollutants. The report also notes that in winters when ozone levels have not spiked to extremes, there has not been an accompanying decrease in oil and gas activity.
Those operations continue at a regular or unvarying pace year-round, but the report notes episodic or seasonal controls may be useful in the quest to control ozone.
The report said studying ozone formation is particularly challenging because of the lack of a full-fledged emissions inventory in the area. And unlike the ozone that forms as summer smog due to the interaction of chemicals, ozone occurs in the basin with help from nitrous acid and formaldehyde, or HONO.
Multiple recommendations on what steps to be taken next include designing a robust way to measure HONO and developing a more comprehensive inventory of the emissions in the basin.
LeBaron said regulators are working closely with the Ute Indian Tribe because of the concentration of natural gas production that occurs in the eastern part of the basin. The study has revealed that there are thousands of places where volatile organic compounds — precursors to ozone — could be captured more effectively to reduce the potential for ozone concentrations.
He said it will be interesting to determine in the future if the predictive models for ozone — developed based on the summer occurrences — will work for additional research in the basin.