3D VISUALIZATION OF CONTAMINANT TRANSPORT IN A FRACTURED BEDROCK AQUIFER

This study focuses on a 60-acre dissolved solvent plume located within the Farmhaven Brook Fault Zone. Multiple sources have contributed dissolved solvents to this comingled plume that has migrated 4,000 feet. General groundwater flow in bedrock occurs preferentially along strike within discrete intensely fractured bedding planes. The bedrock in this New Jersey study area is the Passaic Formation of the Newark Basin consisting of interbedded shales, siltstones, mudstones, and sandstones. Due to the complexity of the fault zone fracture system and multiple offsite sources, Mining Visualization System (MVS) software was utilized in order to gain a better understanding of contaminant transport in the fractured bedrock aquifer. MVS software uses advanced gridding and geostatistical analysis to create 3D models of geologic setting and analyte spatial data.

3D visualization of contaminant transport was accomplished by generating volumetric geologic and plume models. Using well boring logs, geophysical data, and downhole bedrock logging, a 3D geologic model of the Farmhaven Brook Fault Zone (overburden and bedrock lithology) was constructed in MVS, incorporating the fault structures and the dipping and fractured bedding planes. Groundwater chemistry data from monitoring wells generated representative 3D dissolved solvent plumes by applying kriging techniques in MVS.

Simultaneous display of both the geologic and plume models within MVS visually illustrated plume migration along the fractured bedding planes, position of subcropping discrete fracture zones, plume convergence areas, and the lithologic influence on plume geometry. The geostatistically rendered plume geometries showed a strong correlation to the location of steeply-dipping extensional fractures. In the vicinity of the steeply-dipping fractures the plume geometry is oriented more vertically, displaying the vertical gradients induced by the fractures. Areas with similar vertical plume geometry indicate existing preferential pathways and possible locations for unmapped steeply-dipping fractures. The ability to display volumetric plume models within a 3D geologic model provided a powerful tool in understanding contaminant transport in the Farmhaven Brook Fault Zone and has provided insight to possible unmapped fracture zones.