Second waste storage tunnel at Hanford is at risk of cave-in, regulators say

A second tunnel containing radioactive waste at the Hanford Nuclear Reservation is “structurally deficient by almost every measure” and at risk of caving in, state and federal regulators said Friday.

A 400-square-foot hole opened May 9 in the roof of a waste storage tunnel at the defunct Plutonium Uranium Extraction Facility, known as PUREX. The collapse prompted the state to demand a review by the U.S. Department of Energy, which manages the 580-square-mile nuclear site near the Tri-Cities.

The department found that both of the PUREX tunnels, including the much larger one that hasn’t collapsed, are inadequate for storing hazardous defense waste. It came as no surprise to regulators, who in recent years have dealt with leaking storage tanks and occasional releases of radiation.

“All of these structures that are holding onto waste at the site are starting to get older, and they’re all getting past their useful life,” Alex Smith, the state Department of Ecology’s nuclear waste program manager, said during a recorded news conference Friday morning. “These issues highlight the importance of having adequate funding for the site, and we’ll be talking to our members of Congress about that, as we always do.”

The Department of Energy has an annual budget of $2.3 billion for cleaning up Hanford, which supplied most of the plutonium for the U.S. nuclear arsenal during World War II.

Doug Shoop, who runs the agency’s operations office at Hanford, said earlier in June it will cost at least $100 billion to finish cleaning the millions of gallons of toxic waste on the site.

On Friday, Shoop explained how the tunnels were built and how the agency intends to stabilize them until a permanent solution is achieved. One option is to fill both tunnels with a cement-like grout, encasing the flatbed rail cars and contaminated equipment that are stored inside.

Shoop said that equipment includes large nuclear storage vessels that Hanford workers drained “as best they could” before loading them into the tunnels decades ago.

“There’s in all likelihood some residual contamination that’s inside these vessels,” he said.

The tunnel that collapsed in May, Tunnel No. 1, is about 360 feet long and holds eight rail cars. It was built in 1956 out of pressure-treated Douglas fir timbers and an 8-foot layer of soil.

Smith said it’s still unclear what caused the cave-in, although age was certainly a factor.

“It’s hard to figure out exactly what may have caused it,” Smith said. “There’s a lot of different stressors and potential reasons for that collapse.”

No release of radiation was detected from the collapse, and the hole was later filled with sand and dirt. Shoop said the Department of Energy installed cameras to monitor both tunnels and now conducts daily inspections. A thick sheet of plastic was spread over the top of Tunnel No. 1 to prevent further deterioration from rain or snow.

Tunnel No. 2 is about 1,700 feet long and holds 28 rail cars. Workers in 1965 formed the arch-shaped tunnel out of corrugated metal sheets, then tried to put an 8-foot layer of soil on top of it. Shoop said the metal caved in twice during construction, so workers added concrete braces before applying the dirt again.

“We in particular wanted to know about the structural integrity of Tunnel No. 2 because it had never been assessed to our knowledge,” Smith said.

Shoop said no one has entered the tunnels since they were built, and because of the radiation, engineers have been unable to inspect many structural components. The findings released Friday are based largely on records of the tunnel designs.

“The records, as you might imagine, 50 years ago, might not have been as good as we’d like them,” he said, adding that the engineers need to know what types of soil were used to build the tunnels, and how much that soil was compacted.

During a soon-to-be-scheduled public forum, Shoop said, “We also may get some information from former workers that we don’t have in the records.”

The state’s order also requires the Department of Energy to submit a plan for stabilizing both tunnels by Aug. 1. The Department of Ecology already has approved a proposal to fill Tunnel No. 1 with grout; plans haven’t been finalized for Tunnel No. 2.

By Oct. 1, the Department of Energy must propose safety modifications to its existing long-term cleanup permit.