The Wyoming Department of Environmental Quality reported a reduction in industrial activities in response to last week’s ozone alerts in Sublette County, but still found some emissions-causing activities taking place.
DEQ spokesman Keith Guille said crews were performing county road construction work, which will be addressed with county commissioners.
Ozone levels in the county exceeded national air quality standards for five days last week, according to monitoring sites administered by DEQ, according to Guille.
Some area residents have suggested that local vehicle traffic or emissions from outside the region may degrade air quality in Sublette County, but the effect from those sources is unknown, according to Guille.
“We do not regulate mobile sources like cars, so we don’t know what those emissions levels are at,” he said. “And obviously pollution doesn’t stop at county or state lines.
“What we can control, and what we regulate, is industry,” he said.
The air quality monitoring station near Boulder is located near the crest of the Pinedale Anticline and north of the Jonah natural gas field. The station consistently has the highest ozone levels detected on days when the federal standard is exceeded.
A technical document submitted by DEQ to the Environmental Protection Agency in 2009 noted: “The analysis conclusively shows that elevated ozone at the Boulder monitor is primarily due to local emissions from oil and gas development activities: drilling, production, storage, transport, and treating.”
The DEQ report was submitted to the EPA in support of an ozone nonattainment designation for Sublette County and smaller adjacent areas in Sweetwater and Lincoln counties. Areas of the country where air pollution levels persistently exceed the national ambient air quality standards may be designated “nonattainment,” according to the EPA. The report stated that “sources outside the recommended nonattainment area would not have a significant impact on the Boulder monitor due to the presence of an inversion and very low wind speeds, which significantly limit precursor and ozone transport from sources located outside of the Upper Green River Basin.”
DEQ prepared an estimated inventory of emissions for the nonattainment area. It showed 94 percent of volatile organic compound emissions in the basin and 60 percent of oxides of nitrogen are attributable to oil and gas production and development. Of the 11 major sources in the basin, all were oil and gas related.
The inventory also divided the emissions into those associated with construction, drilling and completion of wells, well site production, and major sources. Oil and gas production was the largest source of volatile organic compounds, while the largest nitrogen oxide emission sources were from rigs drilling the natural gas wells, natural gas compressor stations and gas-fired production equipment.
Guille noted that from 2008 to 2010, gas production in the area increased 8 percent, but emissions inventories decreased during that time, with nitrogen oxides dropping 25 percent and volatile organic compounds falling 20 percent. He attributed the reductions to tighter regulatory controls and to contingency plans implemented by industry.
QEP Resources spokeswoman Emily Kelley said Ultra, Shell and QEP met with DEQ officials on Monday to discuss ozone and what was being done to reduce emissions.
“We all agree that we’ve made important progress in reducing emissions on the Pinedale Anticline, but everyone recognizes that across the basin there is still work to do,” she said.
Kelley said the companies identified more voluntary actions that they will undertake immediately to further reduce emissions through the end of this ozone season.
Ultra will continue to suspend all completion operations that require flaring, and will provide only recycled water to its completion operations via pipeline to reduce trucking and associated emissions. Ultra pledged to continue to look at every facet of its operation to see where additional reductions can be made.
Shell agreed to suspend ongoing completions activities when an ozone advisory is issued, as it did last week.
“That includes securing the well and shutting down hydraulic fracturing operations to reduce the associated emissions,” Kelley said. “Shell will keep a minimal crew on site to ensure safety and well integrity and to prevent equipment from freezing while operations are shut down.”
Shell’s action also eliminates emissions associated with the engines on the hydraulic fracturing trucks, trucking materials to the location for the completions activities, and transporting workers to and from the site.
Shell will keep the approximately 70 workers who typically support these activities on stand-by in order to resume operations when the advisory ends.
QEP pledged to continue to defer all completions until mid-March, as well as shut down all work-over rig operations not related to production maintenance, Kelley said.