The former Brandywine Defense Reutilization and Marketing Office (DRMO) Yard in Brandywine, MD, is an inactive federal facility on the National Priorities List (NPL). While in operation from 1943-1987, the DRMO yard was used for temporary storage of scrap materials and hazardous waste. The primary groundwater contaminant is trichloroethene (TCE), and the plume in the Brandywine Formation, which is underlain by a regional aquitard (the Calvert Formation), was approximately 20 acres in size. Investigation activities following successful remedy implementation and treatment of the distal plume via in situ bioremediation (ISBR) suggested a contaminant source remained, potentially as sorbed contaminant mass in the underlying Calvert Formation. Membrane interface probe (MIP) technology was used to acquire real-time, nearcontinuous data on the distribution of volatile organic compounds (VOCs) in the subsurface. Following the MIP investigation, additional monitoring wells were installed and passive flux meters (PFMs) were deployed at 5 locations suggested by the MIP results to quantify the magnitude of diffusive flux at the Brandywine/Calvert interface. MIP logging was successful in defining the nature and extent of VOC contamination, as well as subtle geologic differences in the Calvert Formation. Coupling of these data with the PFM data confirmed that residual TCE present in the underlying Calvert Formation was acting as the continuing source of contamination via back diffusion to the Brandywine Formation, and areas of mass flux, mass storage, and mass loading were identified. The combination of these techniques provided high resolution results that have been integral in determining the final remedy for the site.
展开▼
