CHARACTERIZATION AND MONITORING OF THE OYSTER,VA BACTERIAL TRANSPORT SITE USING GEOPHYSICAL DATA

To evaluate the importance of heterogeneities in controlling the field-scale transport and stimulation of bacteria used for bioremediation purposes, a multidisciplinary research team has conducted a field-scale study within an uncontaminated sandy Pleistocene aquifer near Oyster, Virginia. Geochemical, hydrological and geophysical data were collected to characterize the site prior to performing several bromide and bacterial tracer test experiments. The first part of the talk will focus on results of the characterization effort at the site performed using hydrological and geophysical data collected across a range of spatial scales, including surface ground penetrating radar (GPR), radar crosshole tomography, seismic crosshole tomography, cone penetrometer (CPT) and borehole electromagnetic flowmeter. These interpreted data were used to constrain the numerical flow and transport models, as well as to reduce the ambiguity often associated with interpretation of field-scale transport experiments due to uncertainties about subsurface physical heterogeneities. Another aspect that we are interested in is the spatio-temporal link between the microbial, hydrological, and physical parameters. Permeability reductions of up to three orders of magnitude have been noted by other researchers during bacterial growth as a result of the formation of a biofilm on the outer surfaces of porous grains, the formation of bacterial aggregates that accumulate and plug pore constrictions, and pore-clogging biogenic gas production. The second part of the talk will focus on efforts that are currently underway at the Oyster Site to investigate the utility of geophysical methods for monitoring physical property variations in porous media caused by bacterial-related phenomena during a biostimulation experiment.