las vegas -- Engineers moved some structures at the Yucca Mountain nuclear waste dump after rock samples indicated a fault line unexpectedly ran beneath their original location, an Energy Department official said Monday.
Allen Benson, a spokesman for the U.S. Department of Energy in Las Vegas, said project adjustments were made in June.
"In the spring we discovered the true course of the Bow Ridge fault line. As a result we moved locations several hundred feet" to the east, he said. "That's why we do studies, to come up with information to make the repositories safer."
The department responded to a published report that cited a May 21 letter in which U.S. Geological Survey maps showed the Bow Ridge fault "may be farther east than projected."
The Las Vegas Review-Journal said it obtained the documents last week.
Robert R. Loux, head of the Nevada Agency for Nuclear Projects and the state's chief anti-Yucca administrator, said he was not reassured by "just-in-time engineering."
"This represents a complete lack of understanding about the site's characteristics," Loux said. "They've been out there for 25 years or longer. And they get surprises like this. This is basic geology, stuff they should have known all along."
The May 21 letter and maps show the fault beneath where officials hoped to build concrete pads to store spent radioactive fuel canisters for cooling before they are entombed in tunnels inside the mountain, about 90 miles northwest of Las Vegas.
Core samples from 250 feet below the surface showed the fault was hundreds of feet east of where scientists thought it was, and that it passed beneath the initial site for the storage pads, forcing their relocation, Benson said.
Recent rock core sampling has spurred a legal battle in federal court in Las Vegas.
State Engineer Tracy Taylor had asked U.S. District Judge Roger L. Hunt to order the Energy Department to stop using Nevada water for cooling and lubricating drill rigs collecting rock samples. Hunt denied the state request last week.
Congress in 2002 picked Yucca Mountain to become the nation's nuclear waste dump, with plans calling for entombing 77,000 tons of spent radioactive fuel hauled to Nevada from 39 states. But the plan has been delayed by legal challenges, money shortages, scientific controversies and political opposition. Planners now concede the dump won't open before 2017.
Project officials say they are continuing to develop repository design, construction and operating plans in preparation for applying next year for a Nuclear Regulatory Commission license.