Paleo-Depositional Environment Controls Modern Day Groundwater Flow and Contaminant Migration

The anisotropy imparted by a heterogeneous aquifer complicated the development of a CSM for a former industrial facility in the Newark Basin, where past operations resulted in DNAPL releases to fractured bedrock. Understanding the heterogeneity was critical to understanding the control it exerted on contaminant transport and groundwater flow. The coarse grain size and poor sorting of the basal sandstones and conglomerates within upward fining sequences underlying the site, and the geometry of the sequences indicated paleo-deposition occurred in channels formed on terminal fans of steep gradient braided rivers. Conceptualizing this setting helped our interpretation of these small-scale sequences as being lens-shaped and laterally discontinuous in all directions, with overlapping depositional geometry. This interpretation and other investigative data allowed us to develop a reliable CSM of non-uniform, partially interconnected fracture networks (not continuous individual fractures) between sequences that extended down-dip beneath the site and offsite. The fracture networks within sequences pinched out like the depositional geometry of the small-scale lithologic sequences in which they developed. As a result, these fracture networks even if interconnected, occurred at different depths along strike and down dip. When made up of sufficiently interconnected openings these networks were groundwater bearing zones in which contaminants migrated.