Dianne Nielson, executive director of the Utah Department of Environmental Quality, called the EPA's comments significant, saying, "If the Department of Energy chose to leave the pile in place, it would have to produce significantly more information to the EPA to address the concerns. And frankly, there isn't a cost-effective way to do that."

The EPA joined mounting opposition from Western governors, bipartisan members of Congress, water agencies and others who say leaving the waste pile from an abandoned uranium mill would threaten drinking water for millions of people downstream.

"The impact of the EPA's decision, we hope, will be to convince the Department of Energy it ought to move the tailings off the banks of the Colorado River," Nielson said.

The Department of Energy proposal, which would cap the waste onsite -- near several popular national parks -- is one of four approaches under consideration by the agency. Others include shipping the uranium tailings and other contaminants offsite by rail or truck to arid, rocky sites to the north, or sucking them out via a giant pipe to a site to the south.

The EPA report is one of more than 1,400 sets of comments sparked in large part by the department's decision not to make moving the waste the preferred option in its draft environmental impact statement for the site.

"The idea that any responsible government would take the risk of leaving 12 million tons of radioactive waste on the Colorado River, that supplies water to 26 million people, is absolutely irresponsible," said Judy Carmichael, a Grand County councilwoman. "It's just that simple. There is no way they can prove that's safe. We can't experiment with the next five generations. It doesn't make any sense."

Brad Hiltscher, a Washington, D.C., staff lobbyist for the Los Angeles-based Metropolitan Water District, agreed. "No water agency is going to want to deliver radioactive water to its customers. . . . As of today, there is no known treatment for removing radioactive waste from water. Period."

While EPA staff had some concerns about transporting the waste, they gave the lowest possible rating to capping it and leaving it next to the flood-prone, meandering river.

"The basis for our environmental unsatisfactory rating . . . is the potential for prolonged environmental and public health risk that could result from the continued release of toxic contaminants to ground and surface waters," the staff wrote in comments signed by Robert Roberts, the EPA's regional administrator in Denver. The report was filed last month before the end of the public comment period.

Giving such an adverse rating to a proposed federal project is "fairly rare," said Larry Svoboda, the EPA's director of National Environmental Policy Act review for the region. In this case it required approval by then-deputy administrator Stephen Johnson, who was nominated Friday by President Bush to head the agency.

Don Metzler, the department's onsite project manager, said it was decided several years ago that there would be no preferred option initially, precisely so that a wide range of comments could be gathered.

Metzler said he wasn't surprised by the reaction, the bulk of which favors moving the waste away from the river.

"It's an important subject. The Colorado River is the lifeblood of the Southwest," he said.

While critics point to studies showing the flood-prone river might be migrating toward the site, Metzler said other studies have shown that the river might be moving away from it. He said it would be cheaper to cap the material in place, with projected costs of $166 million. To move it would cost between $400 million and $500 million, he said.

But after years of negotiation, most officials had assumed the unanimous choice was to move the enormous, leaking, gooey mound elsewhere.

"At this juncture in the process, after many years of technical review and study . . . we want to make it clear that any remediation other than an off-site option is unacceptable," wrote outgoing Utah Gov. Olene Walker on Dec. 29, on behalf of herself and four other governors.

In the past month, members of Congress, including Sen. Orrin Hatch, R-Utah, have written to new Secretary of Energy Samuel Bodman or his staff expressing strong opposition to leaving the waste in place.

Bodman, who was sworn in last month, is "aware of the issues involving the Moab site," spokesman Joe Davis said, and might end up making the decision himself on what should be done.

Although that decision could come as soon as March 18, it probably won't be made until summer, Davis said.

Moab Mayor David Sakrison said Saturday he was encouraged by the EPA's comments.

"We were promised by the Clinton administration . . . it was going to be moved and somehow it got forgotten," he said. "We're ecstatic about the news, to be quite honest. . . . Having the EPA weigh in on this is huge. We're pretty excited."

-----

Tribune staff writer Lisa Rosetta contributed to this report.