Volume 105, Number 10 - March 6, 2008
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Ozone levels spark advisory
Some might wonder how significant Sublette County’s first Air Pollution Advisory for excessive ozone levels actually was. After all, the advisory, issued by the Air Quality Division (AQD) for the Department of Environmental Quality (DEQ) on Feb. 27, only lasted three days, during which ozone levels never rose above average, harmless levels.
The real problem actually occurred the week before, when ozone levels escalated well above legal limits to the highest levels Sublette County has ever seen. Yet the DEQ waited until days later to issue an advisory.
“It seems the DEQ was a bit slow in reacting,” said Perry Walker, an air quality scientist in Daniel.
Both the DEQ and Walker’s individual monitoring recorded eight-hour ozone averages of 122 parts per billion (ppb) in Boulder on Feb. 21 and 103 ppb on the Jonah Field on Feb. 22, shockingly above the National Ambient Air Quality Standard of 80 ppb.
“I think the DEQ probably waited [to issue the advisory] because it’s still exploring new ground,” Walker said. “The DEQ isn't used to situations like this.” Exactly right, said Dave Finley, AQD administrator. The agency is still struggling to pin down the cause behind the county’s rare surges of ozone — an irritant that causes respiratory problems for children, elderly and those with breathing problems — as well as how much local gas fields have contributed.
“The reason we didn’t issue the advisory in early February is because we didn’t expect to see those levels,” Finley said. All the agency could do was try to forecast if it would happen again. “Even though we don’t have complete answers on the conditions that lead to the formation of high levels of ozone, we thought, ‘we’re forecasting similar conditions in late February. We’d better let the public know.’”
The public shouldn’t blame the DEQ too much for getting the forecast wrong, or for letting the real ozone surge catch the agency off guard.
The monitored levels on Feb. 21 and 22 are rarely seen outside of urban metropolise, and for them to occur in rural areas is nothing short of baffling. Yet it’s happened before in Sublette County.
Since the DEQ started monitoring ozone levels in the Upper Green River Basin in 2005, the agency has seen levels average at over 80 ppb in February 2005, and again in February 2006.
“It was a surprise to most air quality professionals — prior to that, ozone was only a summertime pollutant, people thought it needed hot conditions like in L.A.,” Finley said. “And ozone was thought to be an urban air pollutant. There are no urban areas in Sublette County … Nobody thought it would be a problem.”
In an effort to seek out why it had become an issue, the DEQ launched an intensive air quality study in 2005 measuring temperature and pressure variations in the atmosphere, which the agency has continued every winter since.
Now the AQD theorizes, but has yet to confirm, that the ozone escalations occur during the marriage of a few precise weather conditions.
First, uniform snow cover. Ozone is created when the sun’s ultraviolet rays break up the nitrous oxide (NOx) emissions created by cars and other diesel-burning machines. This is why ozone is uncommon in the winter, when cloud cover is common.
But scientists reason that if snow covers the ground, then the sun’s rays pass once through the atmosphere toward the ground and are reflected back up again by the snow, providing two opportunities for UV rays to break up the NOx.
This would explain why ozone didn’t rise above normal levels in Sublette County last year, when there was no snow on the ground. Other conditions for winter ozone escalations include strong temperature inversions, where cold air on the ground is trapped by hot air above it, preventing ventilation. Low winds are also necessary to minimize ventilation.
Finley said the advisory probably proved incorrect because of unexpected wind activity. “We didn’t issue the advisory to alarm folks — it was just meant to show the information we had,” Finley said.
For now, the DEQ can only give such uncertain predictions until continuing studies confirm the agency’s theory.
“Our real objective is to collect enough information so that air quality scientists can understand what’s forming the ozone, and more importantly, what we can do to prevent ozone levels from forming,” Finley said. Reducing ozone isn’t as easy as simply capping a few smoke stacks. It’s an ambiguous waste, produced when NOx mixes with combusted volatile organic compounds (VOC), making ozone difficult to predict and to reduce.
Many conservationists point out that a likely place to start would be limiting drilling on the gas fields of the Pinedale Anticline, the largest VOC producer in the county and a source of NOx emissions.
“This used to be the most pristine area in the world,” said Linda Baker, grassroots coordinator for the Upper Green River Valley Coalition. “In just 10 years, the accelerated pace of development has caused us to be concerned about our health.”
But operators on the anticline argue that they could reduce emissions considerably if the Bureau of Land Management (BLM) approves their request to drill an additional 4,000 wells with year-round drilling, instead of the current seasonal stipulations. “The fact that there will be more wells doesn’t necessarily mean there will be more emissions,” said Jim Sewell, Shell Exploration and Development environmental engineer. With permission to drill year-round, operators can obtain contracts for better drilling technologies, like natural-gaspowered rigs that reduce NOx emissions by 80 percent.
It’s a good start for now, Finley said. “If you ask me to list five things we’ll do tomorrow [to decrease ozone levels], I couldn’t,” he said. “We don’t completely understand what’s going on out there. We’re trying to be aggressive at getting information on the conditions conducive to forming ozone levels, and I’m certain that we’re going to be working with gas companies to figure out strategies to lower and prevent ozone levels from occurring in future Februaries. So stay tuned.”
To check current ozone levels in Sublette County, go to the DEQ Web site: www.wyvisnet.com.
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