Description
On November 5, 1991 a VLF geophysical survey was performed on the Campo Indian Reservation, a proposed future landfill location, to determine the degree of subsurface and near-surface fracturing in the immediate vicinity of a pump and tracer test. The survey was performed along four 100 ft long parallel lines 10 ft apart trending N38E (perpendicular to the line between the pumping well and the injection well), and four 100 ft long parallel lines 10 ft apart trending N52W (parallel to the line between the pumping well and the injection well). Plotted data from this survey may indicate a series of fractures, or a fracture zone trending essentially northeast-southwest. Borings drilled at this location also indicate an intensely fractured zone near HG-31, the well used as our pumping well. Although a d.c. resistivity survey was to be performed to obtain a skin depth estimate, a combination of the site conditions and equipment problems prevented the survey from being performed. Since we were unable to obtain any data from our d.c. resistivity survey, it is not possible to estimate a skin depth with any degree of accuracy. Therefore, due to the complications in our VLF survey involving a barbed wire fence, the lack of a skin depth estimate, and an absence of reasonable anomalous trends, I would have to conclude that our survey did not penetrate into the underlying bedrock present at a depth of approximately 100-130 ft.
