The fight over natural gas drilling in eastern Utah's Nine Mile Canyon and the harm industrial activity causes rock art, ruins, granaries and graves has led to a nationwide policy change on how energy development may proceed on sensitive public lands.

The shift comes with a settlement announced Wednesday in a 2008 lawsuit filed against the U.S. Bureau of Land Management by the Southern Utah Wilderness Alliance, the Nine Mile Canyon Coalition and The Wilderness Society against how the agency approved new gas wells on the West Tavaputs Plateau.

The BLM has agreed that "categorical exclusions" no longer can be used to further full-field development on the plateau. Categorical exclusions, part of the Bush administration's 2005 Energy Policy Act, allowed companies to drill multiple wells after a single environmental impact statement.

The change isn't limited to Denver-based Bill Barrett Corp., whose plans call for 800 wells on the West Tavaputs Plateau. The settlement states that the BLM, first in Utah and then across all the lands it administers, must devise guidance that says the categorical-exclusion shortcut cannot be used without a full evaluation of potential harm to environmental, cultural or historic resources in a project area.

The BLM won't approve any new drilling in Nine Mile Canyon until the agency completes the environmental impact study on Bill Barrett's project. BLM spokeswoman Megan Crandall said the agency anticipates the EIS will be available for public review and comment in August.

The narrow, steep, dirt road that leads through the canyon to the West Tavaputs Plateau gas field winds 40 miles through Carbon and Duchesne counties. Lining it are walls of pictographs and petroglyphs, side canyons and at least 10,000 archaeological sites.

Although Bill Barrett has taken steps to protect rock art, conservationists and the National Trust for Historic Preservation long have protested that the trucks stir up dust that corrodes the etchings in the red sandstone. Attempts to control the dust with magnesium chloride worsened the problem.

In 2008, the BLM issued a draft EIS that acknowledged the project posed potential "adverse effects" on historic resources. That finding triggered legally required deference to the National Historic Preservation Act and a profound change in attitude that led to a pre-settlement agreement in January.

Also critical was a letter from the Hopi nation -- which considers the canyon a traditional and holy cultural land -- asking the national Advisory Council on Historic Preservation to intervene, as required by law. The council persuaded the BLM to invite several groups to new negotiations as consulting parties. The resulting "programmatic agreement" came after a year's negotiations and presaged Wednesday's settlement.

That settlement ends the 2008 lawsuit, which accused the BLM's Price field office of failing to properly analyze the harm caused to rock art and other archaeological artifacts by big-rig traffic churning dust on the steep dirt road leading to the gas field.

The settlement doesn't ban categorical exclusions outright. They still can be used as long as they don't violate the National Environmental Policy Act's list of special circumstances that would prevent quick drilling approval.

The accord says the BLM will study how dust and chemicals affect the rock art and other relics. The evaluation will build on the findings of Constance Silver, a BLM-hired art conservator who found the heavy traffic contributed to corrosion on the rock faces. The agency has not made Silver's study public.

Although Bill Barrett didn't directly participate in the settlement, the company doesn't object to it, said Duane Zavadil, senior vice president for government and regulatory affairs.

The lawsuit targeted 30 Bill Barrett wells approved under the categorical-exclusion statute, but SUWA and the others didn't seek to halt the drilling, which has been completed, Zavadil said. More than 100 wells are producing gas on the plateau, including 15 already in operation when the company acquired the existing leases in 2003.

Bill Barrett hasn't filed any further permit requests with or without categorical exclusions for two years, Zavadil said, partly because gas prices are low and most of the gas-development investment for now has gone to East Coast shale reserves.

A Government Accountability Office report last year criticized the BLM's "inappropriate" use of categorical exclusions, saying the agency's actions led to lawsuits, end runs around environmental laws and dirty air in Vernal.

In January, Interior Secretary Ken Salazar singled out Utah as an example of the agency's improper rush to sell oil and gas leases near national parks, wilderness-quality lands and Nine Mile Canyon's archaeological treasures.

Salazar promised to curb categorical exclusions and lashed out at oil and gas drillers, accusing them of treating public lands in the West like a candy store.

The conservation organizations that brought the lawsuit say they don't oppose drilling on public land, just BLM decisions that fail to consider the many other resources.

Drilling impacts "aren't just going to be the holes in the ground," said Nine Mile Canyon Coalition spokeswoman Pam Miller. "Special places need special treatment."

Steve Bloch, SUWA attorney and conservation director, said the settlement means the BLM will be more thoughtful before it approves natural gas development in Utah.

"It's further acknowledgement," Bloch said, "that the 'drill here, drill now' policies of the Bush administration have been rejected."