The famous Great Hunt Panel stands near a road traveled by trucks April 30 in Nine Mile Canyon northeast of Wellington, Utah. A preservation study says that kicked-up dust that lands on the panel creates a

Wellington, Utah ? Along Utah’s Nine Mile Canyon lies what some call the longest art gallery in the world – thousands of prehistoric rock carvings and paintings of bighorn sheep and other wildlife, hunters wielding spears, and warriors engaged in hand-to-hand combat.

But now, a dramatic increase in natural gas drilling is proposed on the plateau above the canyon, and preservationists fear trucks will kick up dust that will cover over the images. And they worry that one possible solution – a chemical dust suppressant – could make things worse by corroding the rock.

“They’re irreplaceable,” said Steve Tanner, a member of the Nine Mile Canyon Coalition, which wants more done to funnel industrial traffic away from the canyon to protect the art on the sandstone walls. “When they’re gone, they’re gone.”

The more than 10,000 petroglyphs have been a source of fascination and speculation since their discovery in the late 1800s. The art is believed to be the work of the Fremont people, who lived in present-day Utah, Idaho, Colorado and Nevada from 700 to 1300 A.D., and the ancestors of modern-day Ute Indians.

(The canyon – a mix of private and public land – is actually 78 miles long; it might have gotten its name because a cartographer for the 19th-century explorer John Wesley Powell used a nine-mile section in mapping the passage.)

The federal Bureau of Land Management has pronounced it “the greatest concentration of rock art sites” in the country.

But the scrubby, rugged landscape around the canyon is also rich in minerals. Oil and gas development along the West Tavaputs Plateau has been going on since the 1950s, though for most of that time consisted of no more than several dozen wells.

Then, in 2002, Denver-based Bill Barrett Corp. paid about $8 million for more than 47,000 acres of oil and gas leases in and around the plateau. The area now has 100 to 110 active natural gas wells by the BLM’s estimate, and the agency is proposing to allow roughly 700 to 800 more to be drilled over eight years.

Traffic along the narrow gravel road through the canyon would increase from about 107 vehicles per day now to a maximum of 441 per day during peak development, which would probably last two to three years, according to BLM estimates.

As for the effect on the artwork, some warn it would be akin to driving a truck through the Louvre. Others expect the drilling to be fairly benign.

“I don’t think we really know what the damage might be being caused right now,” said Kevin Jones, Utah’s state archaeologist. “I think the resource is valuable enough that we ought to find out.”

In 2006, the Bill Barrett Corp. agreed to pay for a study of the possible effects of the dust. Constance Silver of Preservar Inc., which conducted the study, said she found that kicked-up dust that lands on a rock art panel creates “a very serious conservation problem.”

At one of the canyon’s most famous spots, a scene depicting a great hunt, dust clouds from passing trucks travel more than 100 feet and linger in the air for at least 10 minutes before settling on the rock carvings, she found.

Another issue raising concern: the use of magnesium chloride on the road to harden the dirt and keep dust down. The salt compound is already being applied in an agreement between the county and the company.

Magnesium chloride has damaged concrete buildings and works of art before, according to Silver’s report, and its use around Nine Mile Canyon ought to be “carefully considered.” The fear is that it will collect in the pores of the rock and eat away its surface.

This summer, two other kinds of dust suppressants will be tried on the road.

“While there’s no definitive information on the effect of magnesium chloride on the art itself, we have enough information we’re concerned to the point where we’re looking for alternatives,” said Brad Higdon, a BLM environmental coordinator.

Company spokesman Jim Felton defended the project, saying if drilling does not go forward, the implications will be “immediate, dire and drastic” given the demand for energy in the U.S. The project would also create nearly 1,000 jobs in the area, according to the BLM.