Part of the EPA efforts involve sampling under heap leach ponds to determine what's needed to permanently close the ponds.

The EPA also is overseeing two Atlantic Richfield Co. work crews drilling monitoring wells and collecting soil samples around the former mine to assess contamination.

"What we hope to do is to let people know we're trying to move this ahead as best we can," Sickles said, adding that the cleanup process will take years to complete and the costs could exceed $50 million.

After long delays, the EPA ordered ARCO in January to take the first major steps toward cleaning up contamination at the mine.

The order, which replaced voluntary cleanup efforts, stems primarily from 2003 studies that found the soil and groundwater had been contaminated with uranium, a radioactive byproduct of decades of chemical processing of copper at the mine site that covers six square miles, the agency said.

The mine also is polluted with arsenic, beryllium, lead, mercury and selenium.

Cleanup plans have been the source of contentious negotiations between EPA, the Bureau of Land Management, the state of Nevada, Atlantic Richfield, neighboring residents and tribes, as well as a BLM whistle-blower who claims he was fired after he complained that the health and safety risks at the toxic site were being covered up.

EPA officials said the January action didn't put the site on the Superfund list and the agency isn't seeking such status although that remains an option.

Sickles said such a status determination could help in getting funding for the cleanup.

The mine, about 60 miles southeast of Reno, produced copper for about 30 years until 1978. Atlantic Richfield, as a former owner of the mine site, is responsible for the cleanup because the most recent owner, Arimetco of Tucson, Ariz., filed for bankruptcy in 1997 and abandoned the site in 2000.