Cross-borehole flow tests and insights into hydraulic connections in fractured mudstone and sandstone

Cross-borehole flow tests provided insights into hydraulic connections in fractured and dipping mudstone and sandstone that were consistent with the lithostratigraphic and structural framework of a VOCcontaminated bedrock research site in west-central New Jersey. Two cross-borehole flow tests were completed. Each test involved measurement and analysis of transient flow in a newly installed deep corehole with a long open interval during short-term pumping and recovery in an adjacent shallow well with a short open interval. The cross-borehole flow test in the mudstone identified a hydraulic connection through a dipping fractured bed between the pumped interval in the well and a flow zone at an intermediate depth in the corehole. The presence of a hydraulic connection between the pumped well and the corehole was not obvious because the water-level response in the corehole was dominated by a shallow zone of high transmissivity, which was hydraulically isolated from the pumped interval. In the sandstone, the cross-borehole flow test identified a hydraulic connection along dipping fractured beds as well as a connection to a deep high-angle fracture that cuts across bedding. These results suggest that application of cross-borehole flow tests at other contaminated fractured-bedrock sites could provide insights into hydraulic connections useful the design and implementation of monitoring and remediation programs.