Oil drilling hits a preservation snag A Denver energy company's plan to drill more than 800 natural-gas wells in eastern Utah's relic-rich Nine Mile Canyon is in trouble with a top federal historical preservation agency. In letters sent this week to Bureau of Land Management officials in Washington and Salt Lake City, the Advisory Council on Historic Preservation questions whether the BLM adequately evaluated potential damage from the drilling project on ancient art and archaeological sites. The agency's involvement likely will slow the project and buttresses claims from tribal and conservation groups that Bill Barrett Corp.'s big-rig traffic along canyon's dirt roads will destroy some of the West's most stunning ancient American Indian rock art. "This is welcome news," said Jerry Spangler, of the Colorado Plateau Archaeological Alliance. "It's pretty tough to ignore the advisory council when they get involved." The advisory council acts as a kind of appeals agency that can step in and require a federal agency to reconsider its historical-preservation actions....