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Objective:
To test the feasibility of using high-resolution seismic techniques and direct hydrocarbon indicator analyses to image free-phase and dissolved phase DNAPLs at the M-Area seepage basin, USDOE Savannah River Site, South Carolina.
Another objective is to map the subsurface geology and determine the geologic controls on the distribution of the DNAPL plume.
Background:
From 1952 to 1982 an estimated 13 million pounds of chlorinated solvents composed of mostly trichloroethylene
(TCE), tetrachloroethylene (PCE), and trichloroethane
(TCA) were used at the Savannah River Site (SRS) M-Area to degrease reactor fuel and target elements. Residual solvents, and estimated 2 million pounds, were released into the M-Area process sewer lead to the M-Area seepage basin
(MSB). The original M-Area seepage basin, constructed in 1958, was an eight million gallon unlined surface impoundment designed to contain uranium wastes and waste solvents. The basin was closed in 1988, subsequently backfilled and covered with an impermeable cap.
Chlorinated solvents have been detected in the groundwater near MSB since 1981. The contamination occurs in weakly consolidated Eocene age sediments above a confining clay layer know as the "Green Clay" at depths of 180 feet. The water table occurs at a depth of 120+ feet. Environmental remediation strategies have included: groundwater pump and treat, soil vapor extraction, in situ air stripping, and in situ bioremediation. |
