RICHLAND, Wash. – U.S. investigators have said that problems first identified six years ago at a Washington state plant where deadly nuclear waste would be treated continue to plague the multi-billion dollar facility.

The Tri-City Herald reports that the Government Accountability Office said in a report released Tuesday that the site’s contractor, Bechtel National, has not fully completed planned actions.

And the corrections that have been made have not prevented continuing quality assurance problems. The report also criticized the Department of Energy for its oversight of the project.

The $17 billion plant has been under construction since 2002 to turn up to 56 million gallons of radioactive waste into a glass form that would be buried at another site. The waste is a leftover from the past production of plutonium for the nation’s nuclear weapons program.

The sprawling Hanford site in Eastern Washington state is temporarily storing the radioactive and toxic wastes in underground tanks. It’s owned by the Energy Department, which hires private contractors to manage the cleanup work.

Hanford was established during World War II and made the plutonium for the atomic bomb dropped on Nagasaki, Japan. The 560-square-mile site also made most of the plutonium for the nation’s nuclear arsenal during the Cold War.

The accountability office recommended ordering Bechtel to find out the full extent of problems at the vitrification plant that would turn the waste into molten glass.

The office’s report also said Energy Department employees are under pressure to get part of the plant up and running and that two quality assurance experts said department managers and Bechtel prioritize cost and sticking to schedules more than identifying potential problems.

The investigators said Energy Department officials should halt work in areas in construction quality problems are recurring.

In a written response to the report, Energy Department Assistant Secretary for Environmental Management Anne White said plant working conditions meet all established requirements.

Bechtel did not comment, referring the Energy Department’s response to the report.