‘Ozone outlooks’ for March 17-21

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UGRB predicts higher levels

SUBLETTE COUNTY – It’s difficult to imagine that the Upper Green River Basin’s mountain air might contain something harmful to people of certain ages with respiratory concerns.

But some of these calm, sunny days with rays reflecting off abundant, unbroken snow fields can create an excess of winter ozone.

The Wyoming Department of Environmental Quality’s Air Quality Division (AQD) scientists and forecasters issued an ozone outlook from Friday, March 17, through Tuesday, March 21.

AQD issues an ozone outlook when weather conditions appear to be shaping up to create unhealthy levels of the invisible, tasteless gas.

Winter ozone

Winter ozone was first discovered in the UGRB’s oil and gasfields and studied to determine what conditions lead to levels higher than the federal air-quality standards limit of 70 parts per billion during an 8-hour rolling period.

Nitrogen oxides (NOx) and volatile organic compounds (VOC) are manmade emissions from combustion that are called precursors, held closer to the ground during temperature inversions. When low wind speeds and bright sunlight are forecasted to follow, these mix to create winter ozone. The UGRB is designated as a federal “ozone nonattainment” area.

The UGRB is going through an annual spell of state-issued “ozone outlooks” this month. Earlier this month, AQD asked operators and combustion-engine users, including private vehicles, to voluntarily observe two Ozone Action Days. 

Ozone outlook

During ozone outlooks, people around the UGRB are asked to reduce precursor emissions by not idling vehicles, making deliveries later in the day, postponing construction and open burning and reduce engine uses.

DEQ-AQD monitors ozone, precursor and other emission levels “live” at UGRB stations around the Pinedale Anticline where higher levels appear most often at Boulder, as well as Big Piney, Daniel South, Pinedale and Juel Spring.

Ozone outlooks were also issued for March 12-14.

If rising ozone levels are measured that could affect health, AQD will announce an Ozone Action Day (OAD) to request even stricter – and still voluntary – emission reductions.

Ozone Action Day

The AQD issued OAD status for March 7 and March 8, and with that notified “ozone contingency plan participants” to implement plans to reduce ozone precursor emissions, said AQD’s Kimberly Mazza.

“If an Ozone Action Day is determined to be warranted, it is issued by the AQD by noon, alerting all stakeholders with one day of notice,” she said.

PureWest did take action quickly, according to Kelly Bott.

“With respect to ozone days, we’ve definitely reduced our activity levels and have been deferring things like deliveries and work-overs, but I wouldn’t say our production is way down,” she said this week. “Rather, folks are working late hours to avoid the peak ozone/sunlight hours and working long hours to make up for things we’ve been deferring.”

Voluntary OAD participation is paramount while PureWest is also “working hard to navigate the myriad emerging regulatory issues so we can increase production and get additional supply to the market,” Bott added. 

For more

To learn more about the Upper Green River Basin and winter ozone, visit the Wyoming DEQ at https://deq.wyoming.gov/aqd/. One free informative report is the 35-page “UGRB: The Power of Partnership” that can be downloaded.

To observe real-time and “historical data” winter ozone trends at each of the AQD’s air-quality monitoring stations, visit wyvisnet.com.

For answers to ozone questions, email [email protected].





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