RICHLAND, Wash. – As Hanford Site workers prepare to stabilize a waste storage tunnel at risk of collapse, crews are getting roads ready, setting up grout-mixing operations, and testing equipment and procedures using mockups.
EM Richland Operations Office (RL) contractor CH2M HILL Plateau Remediation Company (CHPRC) is preparing the site and mobilizing equipment to place engineered grout inside the Plutonium Uranium Extraction Plant (PUREX) Tunnel 2. The 54-year-old tunnel contains railcars with contaminated pieces of plutonium processing equipment from PUREX placed in the tunnel beginning in the 1960s.
Following the May 2017 partial collapse of an adjacent waste tunnel, PUREX Tunnel 1, an engineering evaluation showed Tunnel 2 at risk of collapse. Crews filled Tunnel 1 with grout last year; grouting Tunnel 2 will prevent collapse of the structure and address the risk of another potential emergency situation.
“Stabilizing the tunnel is important to protecting workers, the public, and the environment from a potential spread of contamination,” RL Manager Doug Shoop said. “And filling the tunnel with grout will not preclude future cleanup decisions, such as removing the equipment encased in grout in the future.”
Crews recently finished preparing roads and an area to mix grout. Trucks will bring in enough raw material to the site to mix the 43,000 cubic yards of grout needed to fill the 1,688-foot tunnel. The engineered grout is a mixture of water, cement, fly ash, and sand used to fill void spaces in and around the stored waste. This animation shows how pipes inserted into existing tunnel risers will place the grout inside.
“The entire project team has done a great job preparing to begin grouting,” said Mark Wright, vice president of CHPRC’s project technical services. “From procurement, to safety, to engineering, every aspect of our company has been involved in helping to make sure we are poised to do this safely and efficiently.”
Grout placement is expected to take between three and four months. RL has asked the Washington State Department of Ecology for authorization to begin placing grout in September due to the potential risk of collapse and to avoid coming winter weather that could impact operations.
The department is also working with the state on a requested change to the Hanford Site Dangerous Waste Permit that includes a public comment period from mid-August through September.