A House subcommittee chairman is telling Energy Department officials to "do your homework" before pushing Congress to approve the opening of an underground nuclear waste disposal facility.

Rep. Mike Synar, D-Okla., made the statement Tuesday after his Government Operations Environment, Energy and Natural Resources subcommittee was told that major questions remain about the Waste Isolation Pilot Plant (WIPP) in New Mexico.The department wants to begin putting waste into the underground facility next month, but it has not adequately proven that it can operate it safely, according to witnesses and documents at the hearing.

Among those raising questions were the department's office of safety appraisals, its Brookhaven National Laboratory and an environmental consultant it hired to review WIPP.

At the same time, the congressional General Accounting Office said it would be premature for Congress to approve the Energy Department's request to pass legislation needed to launch the $700 million project.

"There are many uncertainties involving WIPP performance that must be addressed before DOE can demonstrate that the facility is suitable," GAO's Keith Fultz said.

Synar called the hearing to look into the department's plan to place 125,000 barrels of so-called transuranic waste into the repository 2,150 feet below the ground near Carlsbad.

Transuranic waste, a byproduct of nuclear weapons production, is a combination of radioactive material and a wide variety of hazardous substances. The waste proposed for WIPP represents approximately half the amount now stored above ground in about half a dozen states.