The planned nuclear waste dump at Yucca Mountain (search) in Nevada won't be built unless the Energy Department is confident of the supporting science after investigating e-mails that showed workers discussing fabricating data, an official said Tuesday.

Under angry questioning from Nevada lawmakers, deputy director Theodore Garrish said the department was preparing to apply for a license to run the dump, but "we have not made a final decision yet as to when or whether to file those documents, and some of that will be based on this investigation."

"I can assure you we will not go forward unless we can have the feeling ourselves first that this repository will be safe," said Garrish.

Reassurances from Garrish and Charles Groat, the director of the U.S. Geological Survey (search), didn't satisfy the Nevadans. They have seized on the e-mails, written by USGS employees, as the latest reason to kill the dump planned for 90 miles north of Las Vegas. Officials from Gov. Kenny Guinn (search) on down expressed outrage Tuesday during a House Government Reform subcommittee hearing.

"The fact that data may have been intentionally fabricated in service of shoring up predetermined and politically driven conclusions calls into question the very legitimacy of this entire program," Guinn said.

The Energy Department (search) disclosed March 16 that e-mails written between 1998 and 2000, principally by two USGS scientists, suggested the workers might have falsified documents. Porter's committee has released redacted versions of dozens of the e-mails that show workers discussing concocting facts and keeping two sets of figures, one for themselves and one to show quality assurance officers.

In one e-mail a USGS scientist wrote: "I don't have a clue when these programs were installed. So I've made up the dates and names. ... This is as good as it's going to get. If they need more proof, I will be happy to make up more stuff."

The workers were studying how water moved through the desert site where the government wants to store 77,000 tons of commercial and defense nuclear waste for at least 10,000 years. The USGS validated Energy Department conclusions that water seepage was relatively slow, so radiation would be less likely to escape.

In written testimony, Garrish downplayed the significance of the e-mails. "This appears to be a lapse in quality assurance protocol and, at this time, we have no evidence that the underlying science was affected," his written testimony said.

He seemed to soften his position when he addressed the subcommittee, suggesting more study was needed.

"The impact of this issue is yet to be determined, and yes, we are concerned about the integrity of the data, and what was done was inexcusable," Garrish said.

The inspectors general of the Energy and Interior departments are conducting criminal investigations with help from the FBI, and the Energy Department is studying the impact on the scientific underpinnings of the planned waste dump site.

But Nevada lawmakers called Tuesday for additional reviews. Rep. Jon Porter, R-Nev., who chaired Tuesday's hearing, said he wanted an independent commission similar to the presidential commission that investigated the 1979 accident at Pennsylvania's Three Mile Island (search).

Porter also said he was summoning the two main USGS workers who wrote the e-mails to testify at a hearing next week. Their identities have not been released. Groat said Tuesday they are no longer on the Yucca project but are still employed by USGS.

John Mitchell Jr., president and general manager of Bechtel SAIC (search), the Energy Department's managing contractor on the Yucca project, also testified Tuesday. He said the e-mails were originally discovered by Bechtel workers in early December and were discussed by high-ranking company officials, but weren't turned over to the Energy Department until March.

Porter was the only member of the House Government Reform federal work force and agency organization subcommittee to attend Tuesday's panel. He invited Nevada's other two House members, Republican Jim Gibbons and Democrat Shelley Berkley, to join him in questioning witnesses. That turned the three-hour hearing into a face-off between Nevadans adamantly opposed to Yucca and government officials committed to it, and there was little budging on either side.

A planned completion date of 2010 for the Yucca project was recently abandoned by Energy Department officials. A new date has not yet been set.