Resistivity surveys have proven to be an extremely useful tool throughout its years of application. Within the past year or so major improvements have occurred in the utilization of this technique; instrumentation now allows for greater productivity in data acquisition and software used in the analysis of the data is far more sophisticated. This same software brings a marked improvement over earlier investigations; true resistivity distribution may now be depicted (i.e imaged) below a survey line or traverse, facilitating therebye, interpretation of the nature of materials and structure located there.
The illustration below shows results obtained over granitic rock where we sought to locate faults or sizable fracture systems containing potable water. The survey depth was approximately 50 meters; the length of the survey line is about 359 meters. The survey line's topography is shown to be undulating over a range of 5 meters. A large fault zone is shown extending to the full depth of the survey. Water zones were detected at a depth of approximately 10 meters.
The field work involved here was about a half day's duration. It compares favorably with a traditional boring exploration which would have occupied several weeks -- considering the environment. The associated magnified costs of the latter approach would have been deemed excessive by most.
The exhibit below shows three parallel traverses and the results realized therefrom. Here the survey depth is approximately 60 feet over a sand and gravel environment. The length of these traverses is approximately 1200 feet. The purpose of this work was to ascertain the areal extent and direction of migration of a contaminant plume suspected in the ground water at this site's location. The dashed line connects the areas of maximum concentration in this plume.
Here the field work occupied a total of a day's time for the three survey lines. Again this compares favorably costwise with an alternative boring, water sampling and water analysis program commonly utilized.