Signs are posted at the Hanford Nuclear Reservation in Benton County in Richland, Washington. Credit: Manuel Valdes | AP

After spending billions of dollars over several decades to remove radioactive waste leaking from a plant where nuclear bombs were made, the Energy Department has come up with a new plan: leave it in the ground.

The shuttered Hanford Nuclear Reservation, which produced plutonium for U.S. atomic weapons from World War II through the Cold War, is the nation’s largest nuclear cleanup site with about 56 million gallons of waste stored in leak-prone underground tanks in south-central Washington State.

The Energy Department has proposed to effectively reclassify the sludge left in 16 nearly empty underground tanks from “high-level” to “low-level” radioactive waste. The re-classification would allow the department to fill the tanks with grout, cover them with an unspecified “surface barrier,” and leave them in place.

But environmental groups and others say the plan amounts to a semantic sleight of hand that will leave as much as 70,000 gallons of remaining nuclear sludge — some of which could be radioactive for millions of years — in the ground.

“This is the most toxic stuff in the world,” said Geoffrey Fettus, a senior attorney with the Natural Resources Defense Council. “You could have a lethal dose in a matter of hours or minutes.”

A similar proposal to reclassify waste at the site was attempted by the George W. Bush administration — prompting a ferocious and protracted legal and legislative battle. The Trump administration revived the idea formally in June and took public comments for five months. A final determination could come as soon as next spring.

The cleanup operations at Hanford are projected to cost more than $100 billion, and the Energy Department has already spent more than $19 billion, according to the Government Accountability Office. The reclassification could save the department billions of dollars. It would also open the door to doing the same for all 177 tanks on the sprawling 586-square-mile reservation.

The Energy Department has already indicated that it intends to use the same approach on other tank farms at Hanford, according to Tom Carpenter, executive director of Hanford Challenge, a Seattle-based watchdog group.

“None of us trust the Department of Energy to make this decision,” Carpenter said in an interview. “None of us trust them that if they get this power to independently re-label this waste that any of it is going anywhere.”

Carpenter added that the area is a terrible place to store the waste because it’s geologically unstable. The Columbia River borders the Hanford land for almost 50 miles and some of the tanks are as close as five miles (eight kilometers) to the river, the largest in the Pacific Northwest and the source of irrigation for agriculture and drinking water for downstream cities.

The department, which declined to comment on the complaints, says in its 300-page plan to conduct the reclassification that about 96 percent of the waste from the 16 tanks — some of which contained more than 500,000 gallons — has been removed.

The reservation, about 200 miles from Seattle, was home to nine nuclear reactors that operated from 1944 until 1987 and produced 74,000 tons of weapons-grade plutonium used to make atomic weapons including the Fat Man bomb that detonated over Nagasaki in 1945. Giant tanks of radioactive waste include a dangerous brew of radioactive elements and have leaked more than a million gallons, threatening water supplies across the state.

Supporters of the Energy Department’s proposal say the method is less risky for workers at the site and that similar techniques have been used successfully to seal up radioactive storage tanks at other Energy Department locations.

Opponents include the Yakama Nation, whose reservation is 20 miles west of the Hanford site and that has treaty rights to the Chinook salmon that spawn in the Columbia River. The nation wrote in comments to the agency that leaving the waste in unstable shallow land is “simply bad policy.”

“It will inevitably result in serious threats to the health of Yakama-enrolled members and the public, both by direct exposure and through consumption of contaminated resources,” the nation said.