As the Hanford Site continues a phased remobilization of site operations, the Department of Energy’s Office of Environmental Management and its contractor CH2M HILL Plateau Remediation Company (CHPRC) recently began designing and constructing a full-scale, off-site mock-up to support the stabilization of three underground structures with engineered grout, the DOE announced on July 7.
Located near the former Plutonium Finishing Plant, the structures—the 216-Z-2 Crib, 216-Z-9 Crib, and 241-Z-361 Settling Tank—received liquid waste during Hanford’s plutonium production operations and contain residual radioactive and chemical contamination. A 2019 report indicates that the structures are at risk of age-related failure.
The following video shows an engineering walk-down of the stabilization project.
The system: Construction of the mock-up includes a conveyance system that will be used to move more than 4,500 cubic yards of engineered grout from trucks into the structures. The grout will be pumped through more than 1,500 feet of pipe, helping to keep workers out of high-contamination areas. Mock-ups are used extensively at Hanford to allow crews to troubleshoot processes and safely train on tools and equipment in a clean environment before work begins in the field. Located near Richland, Wash., the Hanford Site is the focus of the largest environmental cleanup project in the United States.
According to CHPRC, which is managing the stabilization project, 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.
In April, CHPRC awarded a $3.9 million subcontract to a small, disadvantaged company, White Shield, of Pasco, Wash., to design, engineer, and install the grout conveyance system. The DOE expects the stabilization project to be completed by the end of 2020.
Grout has been used safely to stabilize other structures at Hanford, including two waste storage tunnels next to the Plutonium Uranium Extraction Plant (PUREX) 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.
They’re saying: “The conveyance system is going to help us tremendously because all three structures are in high radiological areas,” said Delise Savior, CHPRC project manager. “This will minimize our time in these areas while allowing us to safely and efficiently stabilize the structures. Crews will also monitor radiological conditions before and during work to further ensure our workers and the environment are protected.”
“We are making good progress on the mock-up for the stabilization project following appropriate health and safety protocols as we continue our phased remobilization,” said Al Farabee, DOE Richland Operations Office assistant manager. “This work is critical to Hanford’s mission to reduce risk to workers, the public, and the environment.”