A scientist who wrote e-mails about falsifying work on the Yucca Mountain (search) nuclear waste project was paid $4,900 for a Yucca assignment he got after the e-mails became known, the U.S. Geological Survey (search) said Tuesday.

Last week, the Energy Department said the scientist — a USGS hydrologist identified by USGS Tuesday as Joe A. Hevesi (search) — never billed for the work.

Hevesi was a principal author of e-mails written between 1998 and 2000 by scientists studying how water moved through the proposed waste dump 90 miles northwest of Las Vegas.

In the e-mails to colleagues, Hevesi discussed making up facts, deleting inconvenient data and keeping two sets of files — "the ones that will keep (quality assurance) happy and the ones that were actually used."

USGS Director Charles Groat assured lawmakers at a hearing last week that the scientists involved were no longer working on Yucca Mountain. A day later, USGS and the Energy Department disclosed that Hevesi had actually been given a new, 40-hour assignment in March, several days after Energy learned of the e-mails. An Energy spokeswoman said last week that Hevesi never actually billed any hours for the assignment.

On Tuesday, USGS spokeswoman A.B. Wade said officials had learned that Hevesi had in fact completed the 40 hours of work on the assignment, which was to help reconstruct a computer file needed to run models of water infiltration through the proposed dump site.

Hevesi was paid his normal weekly salary of $4,900 for the work, and USGS is billing the Energy Department for the amount, Wade said.

Energy spokeswoman Anne Womack Kolton said the department was still gathering information and she couldn't comment further. A message for Hevesi left at his USGS office in Sacramento, Calif., was not returned.

USGS scientists validated Energy Department (search) conclusions that water seeped relatively slowly through the proposed dump site, which would result in less radiation release — a finding disputed by Yucca critics.

Meanwhile, a congressional panel chaired by Rep. Jon Porter, R-Nev., was pushing forward with plans to seek testimony from Hevesi and two other USGS scientists involved with the e-mails.

The Interior Department last week turned down a request for the scientists to testify before Porter's House Government Reform federal work force and agency organization subcommittee. The department cited ongoing criminal investigations by the FBI and inspectors general at the Energy and Interior departments.

Yucca Mountain is planned as a national repository for 77,000 tons of high-level commercial and defense nuclear waste, to be buried for 10,000 years and beyond in the Nevada desert. The project is strongly opposed by Nevada officials, and the most recent completion date of 2010 was recently abandoned by the Energy Department.