The Wyoming Department of Environmental Quality (WYDEQ) has already issued ozone outlooks and action days this winter for the Upper Green River Basin (UGRB) in southwest Wyoming. Ozone outlooks are issued when meteorological conditions conducive to ozone formation are forecasted to persist for multiple days in the UGRB ozone nonattainment area. Ozone action days are issued to alert companies operating in the UGRB to implement contingency plans to halt, slow, or delay activities that may result in emissions of ozone precursors.

Elevated ozone in the UGRB occurs in the winter when conditions including snow cover, temperature inversions, low winds, and sunlight are coupled with the presence of ozone precursors (nitrogen oxides and volatile organic compounds). In the past, elevated ozone has been noted from late January through March. This year has seen elevated ozone earlier than usual, on January 16 (based on preliminary data).

Companies operating in the UGRB have reduced emissions of ozone precursors over time; new operations must be offset by decreases of emissions elsewhere, with no de minimis thresholds. Companies are also expected to develop and implement contingency plans which lay out measures to be taken when meteorological conditions favor ozone formation. These measures include actions such as postponing construction activities, delaying drilling and completions at well sites, and deferring truck and equipment fueling. There is increased focus this year on sources of precursor emissions southwest of Boulder, Wyoming. Boulder tends to see the highest ozone levels in the basin, and while winds are low prior to and during ozone events, the predominant wind direction is from the southwest.

For more information about Wyoming's ozone and emission reduction efforts, visit the agency's winter ozone webpage. To see real-time data from air quality monitors in the Upper Green and throughout Wyoming, visit the Wyoming Air Quality Monitoring Network. If you are considering doing business in Southwest Wyoming, contact Lori Bocchino at Trinity to find out about the special requirements and considerations for sources of air emissions in that part of the state.