FATE AND TRANSPORT OF VOLATILE ORGANICS THROUGH EXTENSIONAL FRACTURE NETWORKS AND STRATIGRAPHIC PARTINGS IN THE PASSAIC FORMATION, CENTRAL NEWARK BASIN OF NEW JERSEY

We have studied the fate and transport of co-mingled volatile organic plumes as they migrate as far as 1,300 meters through extensional fracture networks and stratigraphic partings in mudstones of the Passaic Formation. The study area is located in the central Newark Basin of New Jersey and encompasses a slope-aquifer system. Groundwater and dissolved contaminants flow from a hilltop recharge area downgradient to discharge into a major fault segment and overlying stream. Bedrock structure and groundwater flow generally follows the dipping multi-layered leaky aquifer system model. Several monitoring wells in the fault zone exhibit flowing artesian conditions.

The bedrock in the study area includes the Metlars, Livingston and Kilmer members of the Passaic Formation. The lithology is generally described as red mudstones with intervals of purple mudstone, the latter of which we used as marker beds to correlate boring logs and quantify offsets. Our investigation included determining the fate of contaminants from a source area exposed to volatile organics for several decades. We characterized the stratigraphic and structural controls on groundwater flow and contaminant migration using rock coring, analytical sampling, groundwater elevation data, 3-D visualization techniques, fate and transport modeling, packer testing, acoustic televiewer logging, and other downhole geophysical methods.

Contaminant transport occurs through several types of water-bearing zones. The largest conduits include four major bedding partings extending over 700 meters, a steeply dipping unnamed fault segment with measured offset that is subparallel to the Flemington, Hopewell, New Brunswick and Westons Mill Pond fault systems, and the intersection of these features. Successively smaller water-bearing zones include the steeply dipping tectonic extensional fracture network, minor bedding plane partings, other fractures originating from unloading and weathering, and matrix porosity.