As recently as the 1990s, the Price BLM office had put Nine Mile's archaeological treasures front and center, writing a management plan that, according to Miller, would showcase and protect the rock art. 
Then, in 2005, after several years of exploration, geologists for the Bill Barrett Corp. hit a sweet spot in the Tavaputs' ancient bedrock, with extractable gas deposits estimated to be worth $2.5 billion. The company quickly applied for a "full-field" development, which requires an environmental impact statement (EIS) to evaluate potential negative affects. The exhaustive assessment often takes years to complete, but that hasn't slowed down Barrett. To date, the company has drilled 200 of its proposed 800 gas wells, nearly half of them under "categorical exclusions," a provision in the 2005 Energy Act that allows the BLM to give the go-ahead to a variety of projects without doing an environmental review.

By 2006, however, the traffic and dust in Nine Mile Canyon had become so bad that the BLM had to respond to growing complaints by archaeologists and environmentalists. The agency called on Silver to assess the problem. The initiative stalled, though, after the BLM was unable to secure government funding. Barrett then agreed to pay for the study. By the time Silver arrived on the scene last summer, some 350 trucks and rigs were barreling through the canyon on any given day.

In the following months, as Silver worked on the dust study, her worst fears were confirmed by a series of lab analyses. Each time something noteworthy turned up, she e-mailed the person who hired her, Nine Mile Canyon's supervisory archaeologist, Julie Howard, who works out of BLM's Division of Land and Minerals office in Salt Lake City.

In early October of 2007, Silver advised Howard of the likelihood that magnesium chloride was being "tracked all through the canyon." For years, the Barrett Corp. had extensively applied the chemical dust suppressant -- essentially a salt -- along portions of the Nine Mile road. And over the years, the industrial flotilla has pulverized the unstable roadbed, creating an airborne potpourri of silt, diesel fuel and chewed-up magnesium chloride, which is notoriously corrosive to concrete, cars and just about everything else.

In that same e-mail, Silver also told Howard that the dust "all over" the Great Hunt panel -- Nine Mile Canyon's most iconic and frequently photographed image -- had the same chemical "signature" as the dust produced in the air along the adjacent stretch of the road by passing oil and gas trucks. Her other test samples of rock art sites in Nine Mile Canyon had shown a similar pattern. "So, at the very least, dust is getting all over the rock art," Silver wrote. "At the very worst, it is contaminating the rock art with magnesium chloride."

Silver explained to Howard that "the presence of magnesium chloride in dust could become a critical marker for how the Nine-mile road is producing and spreading dust." Puzzling this out -- and determining the extent of the overall problem -- would be huge, but Silver wanted to be sure, so she had the lab run a second set of tests. At the end of October, Silver informed Howard that the final lab results were in: "They found magnesium chloride all over the place, alas."

Two months later, in early January of this year, I met up with Silver in New York City, while she was working on a restoration project at the Guggenheim Museum. Clad in frocky work clothes stained with plaster, the Vermont-based conservator talked proudly of her study at Nine Mile Canyon. Previously, little research had been done on the impacts of dust on rock art -- a worldwide issue -- so she believed her contribution would fill in a significant academic gap.

Silver sounded sure of her findings, stating unequivocally that magnesium chloride-laced dust was being kicked up by trucks and was "going all over the place and settling on the rock art." She was particularly "alarmed" by "all these little crystals of magnesium chloride getting into the pores of the rock art."
"It's such vicious stuff," she added. "It peels concrete, corrodes it."