A federal judge has hit the brakes on a nuclear renaissance, ruling that U.S. Department of Energy officials violated environmental laws when they re-launched a program to mine uranium and produce yellowcake fuel in Colorado.

U.S. District Judge William Martinez ordered DOE officials to stop approving exploration, mining and all other activities on 31 sites leased to uranium companies. The ruling affects about 25,000 acres southwest of Grand Junction along the Dolores and San Miguel rivers.

A 53-page opinion filed late Tuesday said the DOE "acted arbitrarily and capriciously in failing to analyze site-specific impacts" on people and the environment — especially given the history of uranium mining in the region.

Martinez also found DOE officials violated the Endangered Species Act by failing to consult with U.S. Fish and Wildlife Service biologists about the impact of leasing uranium lands.

The decision means federal overseers of the nation's push to develop fuel for nuclear energy must proceed far more carefully and conduct a detailed analysis — with full public participation — of the likely effects that renewed uranium mining and milling would have on air, land, water and people.

Extraction of uranium over 60 years left Colorado and other Western states pocked with toxic scars, tainted water and legal obligations to former workers and survivors.

A Government Accountability Office study found the U.S government approved 5,777 radiation-exposure claims by uranium workers, mostly miners, between 1992 and 2007 and paid $577 million in settlements. There were 2,970 claims denied.

While world market prices for uranium have remained low, a Canadian company's proposal to build the nation's first new uranium mill since the Cold War in southwestern Colorado has kindled interest in renewed production of uranium fuel for nuclear power plants.

State health regulators this year issued a final permit, which local residents are challenging in court. The mill proposal led to several companies expressing interest in mining uranium.

DOE officials responded by reconfiguring lease tracts in 2007, then issuing leases for 31 tracts in 2008 to six companies — Cotter Corp., Golden Eagle Uranium, Energy Fuels Resources, Gold Eagle Mining, U.S. Uranium Corp. and Zenith Minerals.

The DOE has estimated 13.5 million pounds of uranium ore could be extracted and began approving exploration plans on five lease tracts in 2009.

"We've been saying, since 2006, that these environmental studies need to be done before the Department of Energy acts to re-invigorate uranium mining and milling in western Colorado. Now a federal judge's order is in place," said attorney Travis Stills of the Durango-based Energy Minerals Law Center, who argued the case for the Colorado Environmental Coalition and other local and national groups. "Now, maybe we'll finally get protections for the Dolores River Basin and the people who live in the region."

DOE officials have argued they were planning to do a thorough environmental study once they knew more about specific proposed mines.

It is unclear whether the agency will appeal the judge's decision, said Laura Kilpatrick, manager of the DOE Office of Legacy Management's uranium leasing program.

Kilpatrick said she could not comment on the ruling because "it is a pending litigation. There are such things as appeals."

She said DOE officials did not cut corners on environmental requirements.

"There's not a soul who thought they did not do everything that was required," she said.

DOE officials embarked on a full environmental-impact study in July that will involve ecologists, engineers and others, she said. It probably will take about two years to complete.

"We're obviously going to continue with what we are doing with the uranium leasing programs," with the environmental study in progress, she said. "To my knowledge, nothing has changed at all."

Bruce Finley: 303-954-1700 or bfinley@denverpost.com