Scientist performs hydrology experiment at underground lab at Yucca Mountain. (Photo courtesy of Dept. of Energy)

Nevada officials have threatened another lawsuit to challenge the Environmental Protection Agency's newly recommended radiation exposure cap at the nuclear waste repository proposed to be built beneath Yucca Mountain, about 100 miles northwest of Las Vegas.

EPA, responding to a 2004 federal appeals court decision, on Aug. 9 announced a proposed radiation limit extending up to 1 million years in the future at the Yucca Mountain site. In July 2004, the U.S. Court of Appeals for the District of Columbia Circuit said the 10,000-year radiation cap that EPA proposed in 2001 wasn't consistent with recommendations of the National Academy of Sciences.

In 2001, the Dept. of Energy estimated the project's cost at $57.5 billion, including $4.5 billion for design and construction.

EPA's new proposal limits radiation from the repository at 350 millirems per year in the period between 10,000 and 1 million years from now. The new EPA standard also retains the 10,000-year limit of 15 millirems per year that it issued in 2001.

EPA Assistant Administrator for Air and Radiation Jeffrey Holmstead told reporters that the agency's new standard is consistent with the National Academy's study "and will be protective of human health even a million years from now." He conceded that in setting a standard that far in the future "the uncertainties become much bigger" than looking ahead 10,000 years. But he said the 350 millirem level is no greater than the background radiation level now in cities such as Denver.

But Nevada Attorney General Brian Sandoval called EPA's recommended radiation level "an obscenely lax and dangerous new standard." He says that if EPA adopts its new standard, or something like it, "Nevada will sue them again."

Holmstead said that EPA has produced a standard in a way that's consistent with the science. He also says he is "quite confident" that the radiation level, if challenged, will be upheld in court.

The 2004 appellate court ruling in Nuclear Energy Institute v. Environmental Protection Agency, combined four challenges brought by Nevada, Clark County, the city of Las Vegas, the Natural Resources Defense Council and other environmental groups and NEI to elements of the decision to locate the repository at Yucca Mountain and the facility's requirements.

The Dept. of Energy plans to file a licensing application with the Nuclear Regulatory Commission for Yucca Mountain. In that application DOE must show, among other things, that the planned repository will meet EPA's recommended radiation limits.