Role of Geophysics in Expedited Site Characterization: Case History

Expedited site characterization (ESC) is an environmental investigation approach that focuses on using nonintrusive and minimally intrusive investigative techniques synergistically to efficiently and thoroughly characterize hazardous waste sites. Unlike traditional approaches, ESC uses a dynamic (i.e., flexible) work plan with an on-site decision-making team of senior-level technical staff. Another key feature of the ESC process is the emphasis on understanding site geology and hydrogeology at a high level of detail before searching for the contaminants. Geophysical techniques were successfully incorporated into an ESC project at an oil seepage basin site on the U.S. Department of Energy's Savannah River site to define the limits of buried wastes, to detect and map an inorganic plume emanating from the waste trenches, and to define the approximate depth and lateral continuity of major stratigraphic units across the site. The geophysical techniques, integrated with minimally intrusive direct push technologies, provided the framework for the development of the conceptual site model. The refined conceptual site model was then successfully used to guide ground water contaminant sampling to define the spatial extent of the inorganic and organic plume emanating from the waste trenches.