Waste exhumation at a landfill at the U.S. Department of Energy’s desert site is paused following a partial collapse of the dig area Thursday that caused a large excavator to partially slide into the pit.
No one was injured and no radiation was released during the accident, Fluor Idaho spokesman Erik Simpson said. Contractor Fluor is in charge of the Idaho Cleanup Project.
The operator remained in the slumped excavator for about 90 minutes before he could be safely removed. The machine slid several feet into the pit, which is 21 feet deep at its lowest point. The pit is located in the dome-shaped Accelerated Retrieval Project 8 enclosure.
The enclosure, located at the 97-acre Subsurface Disposal Area, contains transuranic waste generated at the Rocky Flats nuclear weapons plant outside Denver. The waste was buried in Idaho in the 1950s and ’60s; it includes plutonium-laced sludges, graphite materials and filters. The enclosure also contains Rocky Flats uranium waste often referred to as “roaster oxides.”
Fluor is working on a plan to safely remove the excavator and continue waste exhumation at the enclosure, Simpson said.
“When you have an incident, you have a fact-finding meeting where you discuss what happened. Then there’s a lessons learned discussion: what did we learn and how do we move forward,” he said. “Now we’re in the corrective actions stage. Once we’ve implemented those and it’s deemed responsible to resume operations we will.”
Fluor officials aren’t yet sure what caused the pit face to slough. The contractor likely will look at “excavator positioning enhancements” to improve safety precautions going forward, Simpson said.
Crews had been removing buried waste for about 30 minutes when the accident occurred. The excavator was stationed 4 to 6 feet from the pit — about 2 feet farther than procedure dictates — when the side of the pit collapsed, a Fluor statement said.
This is the first such incident since waste exhumation began at the Subsurface Disposal Area in 2005, the statement said.
Waste exhumation at the 1.72-acre Accelerated Retrieval Project 8 enclosure began in 2013, and is 77 percent complete.
The enclosure is the only Accelerated Retrieval Project building where waste is actively being removed.
A ninth enclosure is expected to finish construction soon, otherwise there are Advanced Mixed Waste Treatment Project support and waste characterization activities being conducted at the fifth and seventh enclosures.
Reporter Kevin Trevellyan can be reached at 542-6762.