On Friday, specialists from the state Division of Natural Resources began moving fish from a 50-year-old pond at the site to a new pond constructed in a noncontaminated area nearby.

The fish - mostly carp and black bullhead - have likely lived in the pond for years, and were probably deposited there as water from the Colorado River was pumped into the pond, said Ed Baker, environmental compliance lead worker for S.M. Stoller, Corp., the site contractor.

Radioactive tailings have contaminated soil surrounding the pond, but the water inside the pond does not appear to be contaminated, Baker said.

As part of the Energy Department's plan to move the tailings away from the banks of the Colorado River, all contaminated soil found on the 400-acre property will be hauled to a permanent disposal cell that will be constructed near Crescent Junction, about 30 miles north.

Workers must drain the pond to remove the surrounding soil. Because of the pond's age, wildlife experts were concerned that it might contain endangered fish such as the humpback chub.

"We wanted to make sure there were no endangered fish in there," said fish recovery specialist Darek Elverud. "It would be unusual, but it's possible since the pond is connected to the river."

Using electrified probes to temporarily stun the fish, Elverud and Colleen Blaine pulled about 25 carp and five bullheads from the pond on Friday before afternoon heat forced them to stop for the day. The pair will return Tuesday to complete the job. Through the process, known as "electrofishing," a pair of probes is inserted into the water, creating a mild electric shock - about 200 volts, or three amps - stunning the fish and causing them to rise to the surface. Elverud and Blaine net the fish, and place them in a five-gallon bucket for transfer to a new location.

"It causes muscle contraction that makes them rise to the surface and swim toward the boat," Elverud said. "That allows us to capture the fish. If it's done right, it doesn't harm the fish in any way."

Workers began filling the new pond, about 200 yards to the south, with water, pumped from the Colorado River, on Wednesday morning. By Friday, the pond held more than 1.5 million gallons of murky river water that will now be new fish habitat. The new pond will be maintained at a depth of about 9 feet, said Fred Smith, project supervisor.