JACKSON - For the first time, public land officials acknowledged that increased natural gas drilling in Sublette County will possibly reduce visibility in Wyoming's two national parks - as well as five wilderness areas and a roadless area.

The Bureau of Land Management, in a supplemental air quality study for the Jonah Infill Drilling Project released this week, said the cumulative effects of more drilling will likely lead to haze above acceptable threshold levels in the national parks in the early stages of drilling. Haze would be caused by both release of pollutants from drilling and from increased traffic and wood stove smoke.

That haze will affect Yellowstone and Grand Teton national parks, the Bridger, Popo Agie, Fitzpatrick, Teton and Washakie wilderness areas, and the Wind River roadless area.

The BLM made its assessments based on its preferred alternative for the Jonah drilling project. That alternative calls for 3,100 new gas wells.

Grand Teton could experience eight days of haze, and Yellowstone could see three.

Linda Baker, a Pinedale resident and member of the Upper Green River Valley Coalition, said this, combined with the study's report that Pinedale could see haze up to 113 days a year, is "amazing."

"That is just flagrant disregard for the lungs of people with sensitivities or people who like to bike," she said. "It just blows my mind."

She said people live in Wyoming in part for the air quality, and it used to be you could see all the way to the Uintas from the Upper Green River Valley - but not anymore.

"When people start seeing the Winds disappear, I'm afraid there's going to be some pretty angry people and some pretty angry letters," Baker said. "I'm not sure people understand what's coming."

Florence Murphy, spokeswoman for Encana Oil and Gas Inc. - the company looking to do most of the additional drilling in the Jonah Field - said her team has not had a chance to review the air-quality document, but generally the analysis represents a "worst-case scenario."

"What's really important is the ongoing air monitoring that provides the hard data that demonstrates the trends," Murphy said. "That is clearly what will allow for mitigation to respond."

Encana is mandated to monitor air quality, she said, and that monitoring allows the company to mitigate any problems as they arise.

In its study, the BLM looked at air quality and visibility impacts to wilderness areas and surrounding communities under different emissions scenarios. Those scenarios included low emission, high emission, and mitigation scenarios based on mitigation percentages, such as 80 percent or 60 mitigation. It also examined effects from the first few years of development.

The agency also examined impacts from just the drilling operation, and cumulative impacts from increased population in the area. Impacts were estimated for 2017, when the field is expected to be running fully, except for the "early stage" impacts.

During the early stages of drilling, all neighboring communities - Big Piney, Big Sandy, Boulder, Bronx, Cora, Daniel, Farson, LaBarge, Merna and Pinedale - can expect visibility impacts above wilderness threshold levels. There are no visibility regulation thresholds at the state or federal levels for these towns. So, in its analysis, the BLM used criteria established for wilderness areas it also examined. The agency said using the same criteria as wilderness areas as background likely results in an "overestimate" of air quality impacts on regional towns.

Boulder residents, for example, can expect to be living under hazy skies for 131 days - about a third of the year - because of the cumulative impacts of drilling. Pinedale residents could see 113 days of haze, with a maximum air quality change of levels more than 10 times accepted levels in the short term.

Although the BLM's analyzed cumulative impacts show some serious changes in air quality, Baker questioned whether those impacts are adequately measured.

"When we wake up and see this brown smudge and yellow haze around (the Jonah Field) every day? To me that's 100 percent change," she said. "I believe people live here because of quality of life. That quality of life is attached to clear skies and clean air, and we're losing that. It is more than unfortunate. It's a crime."

The supplemental air quality report was developed to analyze the estimated effect on air quality in a variety of scenarios under the BLM's preferred alternative.

Public comment for the Jonah Infill Drilling Project analysis closed in April. The BLM is expected to release a final plan later this year.

The Jonah Field is about 32 miles southeast of Pinedale, on about 30,500 acres.

Environmental reporter Whitney Royster can be reached at (307) 734-0260 or at royster@trib.com.