Updated

An Energy Department (search) investigation found no evidence of criminal misconduct by contractors accused of trying to cover up evidence of worker illnesses at the Hanford nuclear site (search) in Washington state, the department's inspector general said Wednesday.

The IG report said the investigation "did not substantiate criminal misconduct" related to any of the charges against the contractors that provide health services and are involved in cleaning up highly radioactive waste in 177 underground tanks at the facility near Richland, Wash.

A private watchdog group, citing complaints from some of the workers, had accused the contractors of altering or destroying health records, filing false injury reports and hiding questionable ammonia vapor readings involving the tank cleanup.

But Inspector General Gregory Friedman said Wednesday, in summarizing the report, that none of these charges could be substantiated, despite interviews with more than 70 current and former Hanford workers, managers and health specialists.

"Therefore, absent additional relevant and compelling information, we intend to close this case," wrote Friedman in a memo to Energy Secretary Spencer Abraham. He said he turned the report over to the U.S. attorney's office.

Nevertheless, Friedman said the investigation revealed some concerns in the way Hanford Environmental Health Foundation, the contractor in charge of occupational medicine and hygiene services at the facility, has handled illness and injury complaints.

Noting that many workers interviewed "had unresolved concerns" about safety, Friedman said that "management needs to intensify its efforts to improve employee confidence in the occupational health and safety program at Hanford."

But on the allegations of criminal misconduct, the report said it found no evidence that HEHF altered or destroyed medical records, filed false injury reports or inflated the results of an annual performance assessment report to downplay illnesses and injuries.

The report also cleared CH2M Hill (search), the contractor in charge of the tank cleanup program, of any criminal conduct involving ammonia vapor readings at the tank farm. Some workers had charged that the company had covered up excessively high vapor exposure readings.

"The facts developed during the investigation did not substantiate criminal misconduct relating to alleged cover-ups of vapor readings," wrote Friedman. He said that the investigation produced "conflicting testimony" on the issue but that investigators could find "no independent corroborating evidence" to support the charges.

Based on worker complaints, the Government Accountability Project (search), a nonprofit watchdog group, in September 2003 listed 45 incidents of workers exposed to chemical vapors from underground tanks. In a previous report the IG said it had found two of the 45 incidents improperly classified and nonreportable.