RICHLAND, WA – Department of Energy contractor CH2M Hill Plateau Remediation Company (CHPRC) has selected a subcontractor to design, engineer, and install a system to stabilize three underground structures at the Hanford Site’s Central Plateau by filling the structures with engineered grout. CHPRC is managing the stabilization project and awarded a $3.9 million subcontract to a small, disadvantaged company, White Shield, of Pasco, Washington.
The three underground structures are the 216-Z-2 Crib, 216-Z-9 Crib and 241-Z-361 Settling Tank, and are located near the former Plutonium Finishing Plant. The structures received liquid waste during Hanford’s plutonium production operations and contain residual radioactive and chemical contamination. A 2019 report indicates the structures are at risk of age-related failure.
Consistent with the Hanford Site’s essential mission critical operations posture, initial work on the subcontract will be conducted via email or conference call. White Shield will begin working on designs for an engineered grout mix and a conveyance system that will be used to move grout from trucks into the structures.
Following the resumption of normal operations at Hanford and completion of some post-demolition activities at the Plutonium Finishing Plant, trucks will deliver engineered grout to be pumped into the structures using a conveyance system connected to pipes, called “risers” that stick out of the top of the structures. Workers will also lower lighting and cameras through the risers so they can monitor grout flow during placement.
The 216-Z-2 Crib will be filled with about 75 cubic yards of grout; the 241-Z-361 Settling Tank will receive 125 cubic yards; and 4,000 cubic yards will be delivered to the 216-Z-9 Crib. The grout will stabilize the structures, while not precluding future remedial actions or final closure decisions.
Crews will monitor radiological conditions before and during work, to ensure workers and the environment are protected.
Grout has been used safely to stabilize other structures at Hanford, including two waste storage tunnels next to the Plutonium Uranium Extraction Plant in 2017 and 2019. PUREX Tunnel 1 was filled with 4,000 cubic yards of grout, and Tunnel 2 was filled with 40,000 cubic yards.
For more information, visit the Aging Structures Stabilization Project website.