Data Processing

Literature and Link

Project Staff

Project Home

Project Overview

VSP Recording

Seismic Recording

To use high-resolution seismic reflection profiling techniques to image DNAPL concentrations at the 216 Z-9 Crib, 200 West Area, USDOE Hanford Site, Washington. Delineate subsurface pathways for DNAPL migration.

The Plutonium Finishing Plant (PFP) at Hanford processed plutonium nitrate solutions into plutonium oxide and plutonium metal for defense purposes. During the plutonium recovery process carbon tetrachloride was used in quantity as a heavy liquid separator. Liquid wastes, composed of carbon tetrachloride and residual organic and radioactive compounds, were disposed of in subsurface facilities near PFP.

Between 1955 and 1973 an estimated 360,000 to 580,000 liters of carbon tetrachloride were discharged into waste facilities at 200 West Area. In the mid-1980s dissolved CCl₄ was found in the uppermost aquifer. In 1992 soil vapor extraction was started to remove CCl₄ from the unsaturated zone.

The contamination is concentrated in the vicinity of the 216 Z-9 Crib where it is found throughout the ~ 65 m thick unsaturated zone and in the groundwater. The highest concentrations are found associated with fine-grained, relatively impermeable clastic sedimentary deposits 35-40 m below the surface. Currently, the plume covers 10 square km and is migrating north, south and west of PFP. Approximately 65 percent of the original estimated CCl₄ volume is unaccounted for and might be held as residual saturation in the soil pores of both the unsaturated and saturated zone. Thus, a major component to designing a remediation plan for the area is finding the high concentrations of CCl₄.

The Hanford site is located in eastern Washington State in the rainshadow of the Cascade Mountains. Approximately 150 m of Tertiary and Quaternary fluvial deposits overlie Miocene age Columbia River flood basalts. The fluvial deposits are differentiated into the Ringold Formation (Pliocene) (approx. 110 m thick) and the Hanford Formation (Pleistocene) (approx. 35 m thick). The latter represents gravels, sands, and silts transported by the Lake Missoula floods. At the base of the Hanford Formation is a unit about 8 m thick loosely designated "Plio-Pleistocene" that consists of sand, silt and caliche deposits. The highest CCl₄ soil concentrations (~ 37,800 ppb) are found in the interbedded sands and silts of the lower Hanford "fine" unit and the laminated sands and silts of the Plio-Pleistocene unit above the caliche layer at approximately 34 m depth.