AQD: Ozone Outlook through Wednesday

Courtesy image

People asked to limit combustive emissions

SUBLETTE COUNTY – Air-quality conditions in the Upper Green River Basin continue to lead to predictions of heightened winter ozone levels in Sublette County.

Another “Ozone Outlook” was issued for those affected by breathing in the invisible pollutant, running from Monday, March 27, through Wednesday, March 29. Winter ozone is a byproduct of combustive emissions from oil and gas development, temperature inversions and sunlight reflecting off heavy snow cover – all of which are current conditions in Sublette County in March.

Sublette County and the Upper Green River Basin oil and gas are produced at the Pinedale Anticline by PureWest, formerly Ultra Resources, and the Jonah Infill by Jonah Energy.

On Saturday, March 25, Wyoming Department of Environmental Quality’s Air Quality Division sent out the Ozone Outlook notice, based on their own forecasters’ weather conditions.

The main precursors to winter ozone are heightened emissions of nitrogen oxides (NOx) and volatiles organic compounds (VOC) that result from combustion.

During optimum ozone conditions, AQD asks the operators, public facilities and citizens to reduce outdoor fires, engine idling, construction and delivery activities and nonessential driving.

“The AQD will continue forecasting daily to determine if an Ozone Action Day (OAD) should be issued to implement Ozone Contingency Plans” by noon, if winter ozone levels appear to on the rise.

During the recent March 19 OAD, PureWest’s Kelly Bott explained that the operator voluntarily deferred many activities to reduce the chance of ozone formation. Jonah Energy’s Paul Ulrich did not respond.

AQD’s previous Ozone Outlooks this winter included Feb. 16-18, March 7-10 and March 12-14. Ozone Action Days were declared on March 7-8 and March 19.

Quick looks at AQD’s air-quality monitoring stations’ data for March 19 show one-hour and eight-hour average ozone levels that approached but did not exceed the federal safety standard of 70 parts per billion.

These levels have been shown to exacerbate breathing problems in young, old and outdoor active people.

On March 19, the highest one-hour standards shown for the day were about 60 ppb at South Pass, about 58 ppb at Big Piney, 71 ppb at Boulder, 59 ppb at Daniel South, 69 ppb at Juel Spring and 68 ppb at Pinedale Gaseous.

If operators’ ozone contingency plans were not voluntarily observed that day, it is not possible to tell what the levels might have been, on the Wyoming Visibility Network at

More information on ozone and health effects are at Wyoming DEQ, and the Wyoming Department of Health website, https://health.wyo.