Idaho Site Building Demolition Closes Chapter on Underlying Disposal Pit

EM Idaho Cleanup Project Manager Connie Flohr and EM Principal Deputy Assistant Secretary Jeff Avery stand in front of the site where EM crews completed demolition of the waste exhumation facility that overlaid Pit 9, part of the Subsurface Disposal Area

The legacy of a pit that held radioactive and hazardous waste for 56 years at DOE’s Idaho National Laboratory Site has ended.

EM and decontamination and decommissioning (D&D) crews with cleanup contractor Idaho Environmental Coalition (IEC) recently took down the waste exhumation facility that overlaid Pit 9, bringing its long history to a close.

IEC’s operations and radiological controls teams prepared the facility overlaying the one-acre Cold War-era disposal pit for teardown. They created an engineered approach to pull the steel-framed structure to the ground in several sections and reduce it in size for disposal. Workers then placed the resulting debris in the Subsurface Disposal Area (SDA) and covered it with clean soil.

From 2005 to early 2022, EM crews removed targeted waste from Pit 9 and six other pits — a combined 5.69 acres of the SDA. Known as the Accelerated Retrieval Project (ARP), waste exhumation and repackaging took place in nine waste exhumation facilities. Workers have completed demolition of three of the previous waste exhumation facilities following the completion of waste exhumation, and the additional buildings remaining will be demolished in the near future. The building over Pit 9 was called ARP V.

Once all ARP buildings are demolished, the debris will be left in place and covered with clean gravel. It will serve as the base of an earthen cover to be constructed over the entire SDA to protect the underlying Snake River Plain Aquifer.

An area at the INL site before and after demolition of a waste exhumation facility

At top is a waste exhumation facility that had been built overlaying Pit 9, part of the Subsurface Disposal Area (SDA) at DOE’s Idaho National Laboratory. Immediately above is a view of the demolition of that facility. EM crews separated the waste exhumation facility into two portions that were pulled over individually. Debris from the facility was reduced in size and covered with fill material. Once the remaining structures at SDA are demolished, an engineered cover will be constructed over the entire 97-acre landfill.

Pit 9’s complex story began in the late 1960s, when it received waste primarily from the Rocky Flats Plant, a former nuclear weapon production plant and the site of one of EM’s largest, most successful cleanups.

The pit was earmarked for cleanup in the early 1990s using a physical-separation, chemical-extraction process in a record of decision signed by EM, the U.S. Environmental Protection Agency and state of Idaho.

Pit 9 then came under a fixed-price cleanup contract that failed, resulting in construction of two buildings which, following the outcome of a yearslong lawsuit, were demolished. A portion of the landfill was then used for a pilot-scale effort in which buried waste was probed and removed.

Those events over the decades led to the ARP and the targeted waste removal from Pit 9 and the broader SDA. After workers finished exhuming waste from Pit 9, an ARP facility was used to treat sludge waste. In 2018, a breach of four waste drums occurred there. Although it caused contamination in the building’s airlock interior, no external contamination was detected and there were no personnel injuries.

EM then moved the sludge treatment process to an adjacent facility as crews decontaminated the ARP V facility, removed its inner fabric and applied fixative to the inner building framework.

With the ARP V facility over Pit 9 demolished, D&D crews are now focused on the next ARP structure to be removed later this year.

By Erik Simpson - Reprinted from EM Update (8/22/23)