Air quality OK around gas field near Pavillion

Oct 28, 2012 By Eric Blom, Staff Writer

The Air Quality Division of the Wyoming Department of Envi-ronmental Quality has found that air around natural gas wells and compression stations near Pavillion is safe.

Officials from the DEQ said at a meeting Oct. 23 that a 14-month study found air pollutants did not exceed standards set by the federal Environmental Protection Agency -- and, in fact, had lower levels of pollutants detected at other oil and gas development locations in the state.

Some area residents, however, were not convinced that the study was accurate.

Air Quality Division administrator Steve Dietrich said the station tested levels of ozone, nitrogen dioxide, hydrocarbons and particulate matter in the air.

Staff compared recorded levels to EPA standards for those pollutants. Dietrich said the EPA thinks that levels of air pollution below their standards do not affect public health or welfare.

Dietrich said his staff found "no exceedances of national air quality standards," and levels of pollutants were "all below the standard."

"So supposedly (the air) is safe in their eyes," Dietrich said, referring to the EPA, "so it has to be safe in our eyes."


Combustion sources such as fires, vehicles, engines and power plants generally produce nitrogen oxide. Ozone is not emitted, but nitrogen oxide, oxygen and volatile organic compounds, such as hydrocarbons, in the air react with sunlight to produce ozone.

"Any natural gas development (produces hydrocarbons) because that's what they're getting out of the ground," Dietrich said.

Larger particulate matter comes from disturbed acreage such as agricultural activity, and smaller particulate matter comes from materials processing.

Dietrich said the EPA does not have standards for hydrocarbons.

"Those have a way of finding their way into other standards like ozone" because hydrocarbons are necessary for ozone formation, he said.

Hydrocarbons can be monitored indirectly and permits for gas wells and compression stations also include hydrocarbon emission limits and require emission controls, Dietrich said.

Good data

He added that third party audits found the station was functioning properly and provided good data.

"We met and exceeded the EPA standard," he said.

In a report on the study, air quality analyst Kirk Billings wrote, "The concentrations measured at the Pavillion station are typically below the concentrations measured at other stations downwind of oil and gas developments in Wyoming."

Residents uncertain

Twelve area residents attended the meeting, and some were unsatisfied with the AQD's conclusion.

"There's two concerns: location and weather patterns that year," Pavillion area resident Jeff Walker said.

The Air Quality Division in-stalled the mobile monitoring station on Powerline Road about one mile west of Tunnel Hill Road. The location is about six miles east of Pavillion, west of most of the gas fields. Monitoring began Jan. 27, 2011, and ended March 31, 2012.

The mobile monitoring station is a small trailer which works by sucking air into the trailer, directly to instruments which test for pollutants. It also monitors meteorological information and has a camera.

"We tried to locate the monitor downwind of as many of the well sites as possible," Dietrich said. "We also look at local topography, how it affects air flow to the monitor."

The AQD found the prevailing winds around Pavillion blow from west to east.

"As you can see, most of the well sites are to the west of the monitor," Dietrich said.

Access to power for the station and landowner permission were also criteria for the location.

A map the AQD provided shows the monitoring site west of most of the southern group of wells, but roughly two miles south of most of the northern group. The monitor was east of one compression station and northeast of another nearby.

Monitor placement

The compression station east of the monitor site "is the only major source of emissions," Dietrich said, meaning it produces 100 tons of emissions or more a year. The monitor was placed upwind of that compression station, he said, because "it's already getting controlled. It's already meeting the best emission standards."

Walker was concerned with the altitude of the monitor.

"Those fumes will come right out and come right down the valley," he said "I don't know how you'll pick that up with a monitor up on that hill."

Billings said the monitor site was located properly because its altitude was within 20 feet of that of the gas field.

Walker was also concerned with wind pushing polluted air toward his home situated in a valley. "When we get those inversions, we get a northeast wind that pushes (the air) up into the valley ... We can notice the odor," he said. "I don't think we're getting a fair sample."

"If you put it in an area where (the air is) funneled too much, you'll get results that aren't indicative of the area in general," Dietrich said.

"There's no such thing as a perfect place," Billings said. "We had to look at power and the monitoring criteria."

"You want to put a monitor everywhere, but your pocket book is only so big," Dietrich said.

$600k price tag

The total cost of study was more than $600,000, Dietrich said.

When asked if residents could receive canisters to collect air samples, Dietrich said results from such collections would be unreliable.

"You get into a host of problems regarding quality controls and delivery times," he said.

Resident Lucille Borushko said this spring was drier than that of 2011.

"If you ran the same tests during this dry period, would we not have gotten exceedances?" she asked.

Billings said dry weather would only affect the particulate matter.

"It comes from dust in the air," said Dietrich.

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