Hanford contractors have wrapped up a project to stabilize a waste storage tunnel that partially collapsed in May of 2017.
Crews started filling the tunnel with engineered grout early in October. Crews poured several thousand cubic yards of engineered grout into Tunnel 1 near the Plutonium Uranium Extraction (PUREX) Facility. Grouting reduces the risk of further collapse and increases the protection for workers, the public, and the environment from radiological hazards, without preventing future work to clean up the site.
Department of Energy contractor CH2M HILL Plateau Remediation Company (CH2M) began grouting Oct. 3 and placed the last truckload of grout Nov. 11.
“Stabilizing Tunnel 1 was achieved safely and quickly, due to our skilled workers, solid planning, and extensive coordination,” said Doug Shoop, manager, DOE Richland Operations Office in a press release. “Our contractor not only completed this work safely, but also ahead of the Department’s projected completion timeframe of late December.”
Approximately 521 truckloads (4,434 cubic yards) of grout were placed in the tunnel. Crews lowered cameras in the tunnel ensured the grout flowed the length of the tunnel and around the contaminated equipment inside. The grout was injected in several lifts, or layers, and each lift was allowed to set up before the next began. Approximately a foot of space was left between the topmost layer and the ceiling of the tunnel.
“Now that Tunnel 1 is secure, we can focus on our evaluation and determining the appropriate course of action for stabilizing Tunnel 2,” Shoop said.
An integrity analysis completed earlier this year showed nearby Tunnel 2 is at risk for experiencing a similar collapse, and may not be able to bear the weight of the soil above the tunnel. Like Tunnel 1, Tunnel 2 contains railcars with contaminated pieces of plutonium processing equipment. Enhanced surveillance is in place to detect any changes to the structural integrity of the 1960s-era waste tunnel. Plans to stabilize Tunnel 2 are under evaluation and should be finalized in the coming weeks.