Correlation of Water-Bearing Fracture Zones with Stratigraphic Horizons in Sedimentary Rock
Tuesday, September 24, 2019: 8:30 a.m.
James Marolda, CPG, PG
,
Brown and Caldwell
Robert O'Neill, CPG, PG
,
Brown and Caldwell, Upper Saddle River, NJ
In shallow to flat-dipping sedimentary rocks in the Northeast US, lateral groundwater flow is often controlled by open bedding plane fractures. If a readily recognized bed in a stratigraphic sequence (aka, a “marker bed”) can be identified proximal to a bedding plane fracture, that bed can be used to trace, project and predict the position of the fracture. Certain borehole geophysical tools can be used to identify the position of water-bearing fractures in a borehole. Others can be used to assess and correlate stratigraphy between locations. Together, the data from these logs may facilitate correlating water-bearing bedding plane fractures with marker beds. Connectivity of the fractures between locations can then be assessed using hydraulic monitoring.
At a former Manufactured Gas Plant (MGP) site in the northeast, a stratigraphic horizon was identified and correlated across the site using natural gamma logging; this horizon coincides with a water-bearing fracture zone. Hydraulic responses observed in nearby wells during drilling indicate a high degree of fracture connectivity within the zone, which serves as a primary migration pathway for MGP residuals and associated dissolved-phase contaminants. These findings yielded development of a reliable conceptual site model and will add efficiency to supplemental subsurface investigation efforts.
James Marolda, CPG, PG, Brown and Caldwell
James Marolda, CPG, PG, has 14 years of experience as a geologist in the environmental industry. As a geologist/hydrogeologist at Brown and Caldwell, he provides technical and managerial support on hydrogeological investigations including landfill expansion, aquifer testing, and supervision of drilling operations. Responsibilities include directing field activities, data evaluation and manipulation, and preparation of reports that are submitted to various regulatory agencies. Marolda has gained extensive experience in preparing hydrogeologic investigation reports consisting of researching regional and site-specific geologic and hydrogeologic conditions, evaluation of collected field data, and determination of the nature and extent of chemical constituents at numerous sites.
Robert O'Neill, CPG, PG, Brown and Caldwell, Upper Saddle River, NJ
Robert O’Neill, CPG, PG, has 29 years of experience as a geologist in the environmental and petroleum industries. For the past 26 years with Brown and Caldwell he has focused on evaluation of groundwater flow in fractured rock; assessment of DNAPL impacts in rock and soil; evaluation and remediation of impacts related to MGP sites, industrial facilities, and landfills; and the assessment/remediation of contaminated sediments. In the petroleum industry, he conducted detailed analyses of reservoir structure and stratigraphy and geophysical log interpretation. As a reservist in the U.S. Navy Seabees, he has been involved in water well drilling and water supply/treatment projects.
