"You can blow a channel bank out in a heartbeat. We need to know what conditions it takes to make that occur," University of Arizona geosciences professor John Dohrenwend told about 40 Atlas tailings "stakeholders," representatives of federal and state agencies, environmental and tribal advocates and Moab residents.

The Moab meeting was in anticipation of public hearings this month and a final decision by the federal government later in the year on what to do with the huge pile. The Energy Department's ultimate decision will affect 25 million people in four states who rely on the Colorado River for drinking water.

Dohrenwend, an adjunct professor who worked for the U.S. Geological Survey for 25 years, used satellite imagery and historical data to compare the river in 1944 to how it looked in 1962 and 1983, a flood year that sent the river 4 feet up the banks of the tailings pile. He concluded that a so-called probable maximum flood, when the river would flow at 300,000 cubic feet per second, could surround the tailings and inundate much of Moab.

Dohrenwend's research, funded by a DOE grant, determined that despite a study cited in DOE's preliminary environmental impact study released in November, the river is not moving steadily away from the tailings pile, which holds 12 million tons of Cold War-era uranium mining leftovers.

The U.S. Geological Survey also weighed in with an early look at a yet-to-be published study that found that a 100-year flood of 97,600 cubic feet per second would cover 4 feet of tailings. At 300,000 cfs, the river would climb 25 feet up the tailings pile.

Both studies found it feasible that the flood waters would deepen and narrow the channel, making the water move more swiftly. That finding undermines the data the DOE relied on for its draft environmental study, Moab resident Sarah Fields said after the meeting.

"It calls into question the assumption that if there's a big flood, [the river] will just turn into a big lake, that there wouldn't be any damage or erosion," she said. "The water would be moving at such a rate, there not only would be erosion but the pile would be undercut."

The very uncertainty of determining what the river might do was enough for Grand County Commissioner Rex Tanner.

"If we can't speculate with some kind of certainty what happens to the pile in the next 1,000 years," he said, "that's the reason to move it."

Loren Morton, who is overseeing the Atlas tailings project for the Utah Department of Environmental Quality, said the new data from the U.S. Geological Survey are "more robust" than the 1994 study the DOE relied on.

But Don Metzler, the Grand Junction, Colo.-based DOE project manager, defended the data used in the draft EIS.

"We built on what we inherited," he said. "We had conclusions we could stand behind."

The Energy Department released its 1,000-page draft environmental impact statement in November, but in an unusual decision didn't include a preferred solution for the tailings. The study outlined five possibilities, including capping the debris from where it sits, moving it to one of three locations or doing nothing, which is unlikely.

The 90-day comment period ends Feb. 18. The DOE will hold four public hearings Jan. 25-27 in Green River, Moab, White Mesa and Blanding.

The Friday meeting was billed as a chance for those with an interest in the decision to have a briefing session before the public hearings. A final EIS is expected in summer, with a decision by autumn.

The cleanup is estimated to cost $10.75 million for design and construction plus an annual cost of $906,000.

Capping the tailings in place would cost $166 million and take seven to 10 years to complete. Moving the tailings would cost between $329 million and $464 million.

Moving the tailings, either by slurry pipeline, truck or train, would take about eight years, the DOE says.