SALT LAKE CITY (AP) – An agreement signed Tuesday is aimed at safeguarding thousands of prehistoric American Indian drawings and carvings from truckers’ dust in a famed Utah canyon near where a Colorado company wants to dramatically increase energy development.

The pact signed at the Utah Capitol is the first major attempt to address concerns over dust in Nine Mile Canyon, whose miles of decorated walls are sometimes called the world’s longest art gallery.

The canyon has been the focus of intense debate for several years after Denver-based Bill Barrett Corp. proposed developing 800 natural gas wells on West Tavaputs Plateau, which sits above Nine Mile Canyon. The Bureau of Land Management has not made a final decision on Bill Barrett’s proposal.

The primary concern has been concern over dust from the unpaved road being kicked up by an increasing number of trucks ferrying equipment and workers.

Some worry the dust could hurt the ancient art panels depicting bighorn sheep, owls, a two-headed snake, spear-wielding hunters and warriors engaged in hand-to-hand combat.

The agreement is meant to lay out protections for the rock art if Bill Barrett’s proposal is approved. It was signed by BLM officials, Utah Gov. Gary Herbert, Bill Barrett Corp., as well as environmental and archaeological groups and advocates for the 78-mile-long canyon.

The deal, affecting some 233 square miles, including the canyon and the West Tavaputs Plateau, includes a list of tasks such as more dust suppression and studies to determine if the rock art is being harmed.

Much of the agreement’s financial burden will be shouldered by Bill Barrett.

Duane Zavadil, the company’s vice president for government affairs, said the company could end up spending nearly $1 million a year for dust suppression, contractors to research and monitor rock art and other steps.

“We want to document and be sure we’re leaving that rock art in as good a shape as we found it,” he said.

The plan for 800 more would likely mean about 200 trucks per day using the canyon’s winding road during the peak of development, Zavadil said, adding that estimates of 1,000 trucks a day were used primarily for government’s analysis of the project.

Tuesday’s agreement gives the company some regulatory certainty if their project moves ahead, he said.

“Hopefully we have the biggest stumbling block out of the way,” Zavadil said.

Herbert praised the agreement, which was a year in the making by a long list of politically diverse participants, as a triumph of the “reasonable and rationale.”

Selma Sierra, BLM’s director for Utah, said it would ensure that Nine Mile’s artifacts “will be protected for generations to come.”

Canyon advocates called it an important first step but said its success will be measured in how it’s implemented.

Pam Miller, chair of the Nine Mile Canyon Coalition, said she’s happy to see efforts to tamp down dust and study its potentially adverse effects. Whether the BLM cracks down when problems crop up will be something her group will be watching for.

“We haven’t always been listened to before when we’ve reported problems,” Miller said. “But we’re hopeful. We sincerely hopes it’s going to work.”

In Carbon County, which includes a portion of the canyon, officials are hopeful the deal not only protects the rock art but also allows the energy project to move ahead.

Commissioner John Jones said about 60 percent of the county’s property taxes come from energy development.

Jones said there’s been consideration of paving the Nine Mile Canyon road but it’s pricey – roughly $70 million for 40 to 50 miles.

Although much of the canyon’s traffic today is from the mineral industry, dust has been flying ever since curious tourists began tramping through to see the rock art, which was first discovered in the late 1800s.

Some of the carvings and drawing are believed to be the work of the mysterious Fremont people, who lived in present-day Utah, Idaho, Colorado and Nevada from 700 to 1300 A.D.

Other inscriptions in the canyon’s walls are from the Ute Indians, early explorers and members of the U.S 9th Cavalry.