Under a 2013 Record of Decision (ROD), Hanford was initially to take a coupled remediation approach, removing the soil beneath the 324 Building using existing equipment within the facility before it is demolished. The DOE, however, is now proposing as its preferred alternative a decoupled approach, whereby the building is demolished first. A temporary containment structure would then be erected over the 300-296 waste site while it is remediated.
According to a DOE fact sheet, the decoupled approach will be safer for workers while reducing risks posed by the aging building. It is estimated that the work will take 8.5 years and cost $202 million. The coupled approach, in comparison, has been estimated to take 12 years at a cost of $438 million.
The DOE and EPA are currently holding a public comment period until July 9 on a Comprehensive Environmental Response, Compensation, and Liability Act proposed plan to amend the 2013 ROD. During the comment period, the two agencies will collect input on each remediation alternative. A hybrid meeting also will be held on June 30 at 5:30 p.m. (PDT) at the Richland Public Library in Richland, Wash.
Background: Located in Hanford’s 300 Area, the 324 Building supported research on radioactive materials from 1966 to 1996. Due to its proximity to the Columbia River and the city of Richland, demolition and remediation of the building and 300-296 waste site are priorities for the DOE and its contractor Central Plateau Cleanup Company (CPCCo).
Demolition operations were postponed in 2010 after workers detected significant radionuclide contamination in the soil under the building’s B Cell. Radioactive solutions are thought to have seeped through a hole in a sump liner and into the ground through an expansion joint in the concrete floor. According to a CPCCo report, radiological measurements approaching 13,000 R/hr were detected approximately seven feet under the expansion joints.
As per the 2013 ROD, remote excavation arms within the 324 Building would be used for the initial excavation of contaminated soil through the B Cell floor. Once the limits of the excavation arms were reached, the building would be demolished and the remaining excavation work would then be completed under a temporary enclosure.
While stabilizing the 324 Building in 2022 before beginning excavation, however, CPCCo crews detected additional soil contamination. A 2023 analysis by CPCCo and the Pacific Northwest National Laboratory confirmed the area of contaminated soil is wider and deeper than previous measurements indicated.
According to the DOE, the contaminated soil beneath the 324 Building has remained stable for decades, and underground monitoring shows the contamination has not migrated toward groundwater.
