The largest and most costly U.S. environmental cleanup project has been dogged for years by worries about an accidental nuclear reaction or a spill of toxic materials that could endanger residents nearby, as well as a history of contractor retaliation against workers who voice worries about persistent safety risks.

But it hasn’t fully turned the corner yet, according to recent comments by the federal officials now overseeing its operation.

“Changing the culture takes time,” said Mark Whitney, the Department of Energy’s assistant secretary for environmental management, at a special hearing last week before members of an independent federal watchdog group that monitors safety problems at federal nuclear facilities. “I’m not going to sit here today and tell you we have everything solved.”

Whitney spoke inside a ballroom at the Three Rivers Convention Center in Kennewick, Washington, 17 miles from the Hanford Site where generators churned out plutonium, the lifeblood of the U.S. nuclear arsenal, for a half-century during the Cold War. More than 55 million gallons of pasty waste now lie in decomposing barrels beneath the ground at Hanford, posing a potential safety hazard to thousands of people who rely on the nearby Columbia River for drinking water.

The Waste Treatment and Immobilization Plant project there, known as WTP, is meant to exhume the waste, freeze it in glass, and give it a proper burial. But it’s been plagued by delays. It was expected to cost $4.3 billion and be built by 2011. Instead, the cost has swelled past $12 billion to date, with an estimated $7 billion in work left to be done. So far, not a drop of waste has been processed.

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Nuclear reactors line the riverbank at the Hanford Site along the Columbia River in January 1960. The N Reactor is in the foreground, with the twin KE and KW Reactors in the immediate background. The historic B Reactor, the world's first plutonium production reactor, is visible in the distance. (image: U.S. Department of Energy/Wikimedia Commons)

The Department of Energy has been constructing facilities to house the glassification work, including a plant that prepares the waste for storage by mixing it with materials to dilute its radioactivity. But the technology was flawed, creating a risk that explosive gases could pool in the pipes. According to a Government Accountability Office report released in May, contractors relied on obsolete safety guidelines, leaving the site vulnerable to accidents involving dangerous nuclear materials.

A 2014 draft report by the Energy Department’s Office of River Protection on the status of the project was obtained by the nonprofit nuclear watchdog group Hanford Challenge and released by the group last week. It said engineers have identified more than 360 design weaknesses that could impede the operation of the Low-Activity Waste Facility, where the waste will be encased in glass. They also said the design led by contractor Bechtel National Incorporated fell short of acceptable safety standards. The ventilation system hadn’t been adequately tested to assure it would stop widespread radioactive contamination in the building. Without a detailed plan for operation and maintenance, workers are at risk of exposure to searing heat and chemical and radiological hazards, the report said.

Asked about the report and about progress toward resolution of the longstanding problems facing the WTP project at last week’s meeting of the Defense Nuclear Facilities Safety Board, Energy Department representatives said they had imposed stricter oversight of contractors, and made a concentrated effort to assure workers they can report problems without retribution.

But safety board member Sean Sullivan, a retired Navy officer who spent 26 years commanding submarines, questioned what the department claims are signs of improvement. He pointed to a January 2013 Energy Department review at the Waste Isolation Pilot Plant, a federal nuclear waste repository in New Mexico known as WIPP, which missed some key safety problems.

When a truck fire and a radiation leak inside WIPP halted operations there a year later, independent experts identified even more gaping holes in the plant’s safety precautions than the department’s previous examinations had found, Sullivan said. “The safety culture at WIPP was not fine,” Sullivan said. “In fact, it was not good at all.”

In June, Bechtel, the contractor the Energy Department hired for the WTP project, agreed to pay a fine of $800,000 after investigators concluded Bechtel had failed to follow safety guidelines it agreed to more than a decade earlier, or to update them when problems were found, “in some cases, for many years,” according to the company’s settlement agreement with the Office of Enterprise Assessments.

The Government Accountability Office in May said that the Energy Department’s cost estimates for the project can’t be trusted, and also asserted that “significant, unresolved design issues remain” with Bechtel’s nuclear safety standards compliance. Correcting the problems could add to the expense of the project and delay its completion, the GAO concluded.

In 2012, then-Energy Secretary Steven Chu concluded that the project was progressing but still had significant flaws. A report by the Defense Nuclear Facilities Safety Board concluded that problems flagged by a whistleblower in the planning and design of the waste mixing center persisted, raising the possibility of a nuclear chain reaction. Chu halted work on the project in late 2012 and ordered a large-scale testing operation meant to detect when nuclear materials become so concentrated that that they threaten to trigger an accidental reaction.

These problems were flagged in 2010 by Walter Tamosaitis, who worked for Bechtel subcontractor URS Energy and Construction and headed a team that sought to find and fix the waste plant’s design problems. At a critical juncture, Tamosaitis said the project should be suspended until serious safety concerns with the planned waste mixing operation could be resolved.

Delaying milestones on the project jeopardized $55 million that Bechtel stood to gain by meeting certain deadlines. “There’s only one thing standing in the way,” Tamosaitis, 68, recalled telling his colleagues. “That’s me.” He was removed from the project within days and then fired in 2013.

He filed a whistleblower retaliation lawsuit, and after years of hearings and resistance by URS, he won a settlement this month of $4.1 million from Aecom, the company that acquired URS in October 2014.

“This is sweet, deeply-deserved and long overdue justice for a whistleblower who may have changed the course of history by preventing a nuclear tragedy,” Tom Devine, legal director for the whistleblower advocacy organization the Government Accountability Project in Washington, D.C., said. “It was absolutely terrifying what Bechtel was planning at Hanford. It was a complete gamble with public health and safety, all to earn millions in bonus money for getting a job done, regardless of whether it was disastrous for the Pacific Northwest. Bechtel was willing to take that chance. Walt wasn’t.”

Aecom did not admit to treating Tamosaitis unfairly, according to the agreement filed in court. Spokesmen for Aecom, Bechtel and the Energy Department all said safety is a foremost concern for the project, and that workers are encouraged to speak up when they recognize hazards.

In 2008, however, the Energy Department levied fines against Bechtel for retaliation against a whistleblower on the WTP project. And last year, the Department of Labor reinstated an environmental specialist at Hanford after she filed a whistleblower complaint against URS alleging that she was fired in 2011 for reporting nuclear safety deficiencies and environmental noncompliance.

Tamosaitis’ firing spurred a congressional hearing in 2014, and a letter he wrote to the Defense Nuclear Facilities Safety Board soon after his safety worries were ignored triggered an inquiry. The safety board’s chair at the time, Peter Winokur, wrote to Chu that it uncovered a broken safety culture at Hanford.