INVESTIGATING A FRACTURED BEDROCK AQUIFER BENEATH MULTI-SOURCES OF TRICHLOROETHENE AND OTHER CONTAMINANTS IN A MAJOR METROPOLITAN SUBURB

Contamination from a reported five sources was investigated in groundwater of the Brunswick and Lockatong Formations in a study area of approximately 10 square kilometers in suburban Philadelphia, Pennsylvania. The contamination is mainly trichloroethene (TCE) and other organic compounds. The Brunswick Formation is composed of red beds of siltstone and shale with interbeds of sandstone; the Lockatong Formation is typically referred to as a gray argillite. Data from borehole geophysics, discrete zone wellbore tests, synoptic water levels and groundwater chemistry were used to develop a hydrogeologic framework. The hydraulic data were used to conceptualize fracture interconnectedness, gradients and possible pathways. Also, data from stream samples collected in the area aided in the development of the framework so that the relationship between the surface and subsurface system is assessed. Thirty-four (34) existing wells consisting of industrial wells, supply wells, residential wells, and monitoring wells in addition to 40 newly installed monitoring wells were used during this investigation. Although the technical procedures implemented were substantial, their importance was rivaled by the administrative and logistical procedures that were followed. During the course of the investigation access to numerous private properties was gained to reach existing wells and install new wells. Administrative accomplishments for gaining access to private property, drilling during residential and commercial construction activities, and locating existing wells was significant to the success of the investigation in this bustling area. An investigation summary describes the degree of data and logistics that are needed to characterize a fractured aquifer beneath a sub-regional study area of a major metropolitan suburb.