The alternative technique detailed in this paper, which uses Audio Frequency Domain Magnetics (AFDM), begins by charging the ground water site with a low voltage, low amperage, high frequency electrical current.  As the current moves through the ground water, it emits a magnetic field whose size, shape, magnitude and direction are characteristic of the surrounding aqueous system (Biot-Savart Law).  This field is then read at the surface by a specially tuned receiver.   The data thus generated can be used to create both two-dimensional maps and three-dimensional models of the subsurface network.

The images created by this process highlight those locations where the electrical current has concentrated. Because electricity concentrates in areas of highest conductivity, it is reasonable to infer that either these highlighted locations contain relatively large quantities of water or that the water has a relatively high level of Total Dissolved Solids (TDS).  Since TDS levels often correspond to the prevalence of contaminants, this feature of the AFDM investigation enhances its suitability for the characterization of contaminated groundwater sites, the identification of pollution plumes, and the prediction of contaminant flow.

             This paper relies on information gained in recent karst and fractured-rock characterization cases from various regions of the United States.  It details both the theoretical science behind this technique and the lessons learned from its recent applications.