Gas field emissions, weather conditions combine to create Sublette problem, DEQ says
CHRIS MERRILL Star-Tribune environment reporter | Posted: Thursday, February 28, 2008 12:00 am
LANDER - Elevated levels of a potentially toxic air pollutant in the Pinedale region prompted the Department of Environmental Quality to issue an air pollution advisory Wednesday.
Relatively high levels of ozone, a noxious gas and respiratory irritant, have been recorded by DEQ monitors at Boulder, Daniel and at the Jonah natural gas field this past week.
Boulder registered an eight-hour ozone level of 122 parts per billion - well above the 85- to 105-parts-per-billion range, which the Environmental Protection Agency considers an "unhealthy" concentration.
The Air Quality Division of DEQ is advising people who might be sensitive to ozone - including children, the elderly and those with existing respiratory conditions - to avoid any extended, strenuous outdoor activity while the advisory is in effect.
The Upper Green River Basin has registered at least slightly elevated levels of ozone in three out of the past four winters, and researchers now recognize that natural gas development in the region has a lot to do with that trend. There are an estimated 5,000 oil and gas wells in the basin, which includes the bustling Jonah and Pinedale Anticline fields.
The ozone warning - the first issued in Sublette County by DEQ - is expected to persist for at least the next few days. Recent weather forecasts say the cold air mass over the valley will be trapped by warm air above it and continue to hang stagnant over the valley, according to David Finley, the air quality administrator for DEQ.
Elevated levels of ozone can cause respiratory problems in people and animals, and can trigger headaches and burning eyes.
"It's really our recommendation that especially people with respiratory conditions, and those who are susceptible to respiratory ailments, be aware of the conditions before they choose to do extended activities outdoors," Finley said.
'Something strange going on'
When DEQ first recorded the wintertime ozone phenomenon in 2005, air quality experts were baffled, Finley said. Elevated ozone levels were thought to be strictly a summertime occurrence, usually in large metropolitan areas.
The agency has been researching the trend for going on three years, and Finley said the department has begun to pinpoint the cause.
"The elevated levels occurred in the winter months of '05 and '06, and when they occurred again in '06, we decided that there was something strange going on," Finley said. "Ozone is typically a summer pollutant, because it requires solar energy and heat to drive the reaction that forms ozone, so we and others were surprised to see elevated levels in the dead of winter in Sublette County."
The dead of winter in the Pinedale region, it turns out, can in fact provide perfect conditions for ozone creation, if those conditions are combined with pollutants from energy development and other human activities.
One of those prerequisites is fairly complete snow cover in the valley, Finley said. Sunlight reflects off the snow, providing additional ultraviolet energy to drive the ozone reaction. Ozone gas is created when sunlight hits hydrocarbons and nitrogen oxides in the air - pollutants created chiefly by the burning of fossil fuels at ground level.
If nearly complete snow cover is combined with strong temperature inversions - which have the effect of trapping air in the valley - and that is coupled with slow wind speeds, it all leads to increased ozone production in the valley, Finley said.
"The study is not complete yet, but it seems to us, based on what we know today, the ozone is locally generated and is only generated when those specific meteorological conditions exist," Finley said. "If there's a breeze blowing 10 or 15 miles per hour, it's not going to form in these concentrations. If we don't have the temperature inversions, if there's no snow cover, we won't see it either."
That understood, the entire phenomenon is made possible because of human-caused pollution in the valley, Finley said.
"Pollutants are most certainly being created by gas production activities there," he said. "They're also emitted by cars and by fossil fuel combustion - but the oil and gas development activities out there are a large source of the volatile organic compounds."
Limiting emissions
Finley said he spoke with representatives of each of the major companies active in gas production in the Upper Green River Basin and informed them that DEQ believes there will be high ozone levels in the next several days.
He asked the companies to be particularly vigilant in maintaining equipment to limit emissions, Finley said, and he asked them to defer any planned maintenance activities which would have resulted in increased emissions until weather conditions have changed.
"Each of the companies has agreed to cooperate. Every company out there has taken every step necessary to reduce pollution during this episodic condition," Finley said.
Environment reporter Chris Merrill can be reached at chris.merrill@trib.com or at (307) 267-6722.