TWIN FALLS, Idaho (AP) - A federal appeals court has upheld an earlier federal district court decision that requires the U.S. Department of Energy to clean up buried nuclear waste at the Idaho National Laboratory.

A three-judge panel from the 9th U.S. Circuit Court of Appeals last week upheld a ruling by U.S. District Judge Edward J. Lodge, who sided with Idaho in a disagreement between the state and federal government over a 1995 deal involving nuclear waste at the 890-square-mile nuclear research area in eastern Idaho.

The state argued that the agreement to settle a long-standing legal battle between Idaho and the Energy Department means what state leaders thought it meant: that DOE must remove all "transuranic" waste - rags, gloves and dirt contaminated with radioactive material like plutonium - from INL by 2018.

The Energy Department argued that the agreement only covered transuranic waste that was stored in barrels on asphalt pads above ground since 1970, not the toxic transuranics that were put into drums and cardboard boxes and dumped into pits and trenches for burial between 1954 and 1970.

"We're happy about this, of course," Curt Fransen, deputy director of the state's Department of Environmental Quality, told The Times-News.

He said the 1995 agreement involves thousands of truckloads of transuranic waste shipped to Idaho in the 1950s and 1960s from the Rocky Flats nuclear weapons plant near Golden, Colo.

State officials fear the aquifer beneath the site that is the source of drinking water for thousands of people is threatened by the transuranic waste.

"Over this period of time, the drums have disintegrated," said Fransen. "Identifying and digging this stuff up and containerizing it is not a simple process. Most of it is done remotely."

He said the state and DOE are working on an agreement on cleaning up the waste. Lodge would have to approve the agreement.

Estimated cost of the cleanup, based on doing little, to digging up all buried waste at the site, not just transuranic waste, ranges from $57 million to $13.5 billion, Fransen said.

The Department of Justice has 45 days to ask for a rehearing, and up to 90 days to appeal the decision.

Justice Department spokesman Andrew Ames said the agency is reviewing the ruling.