3D Electrical Resistivity
HGI offers 3D electrical resistivity services to solve large and structurally complex subsurface problems, including mapping geology, fluid flow, contaminant plumes, and leaks from containment systems. There are several strategies that can be employed to map the subsurface with three dimensional resistivity, from combining a set of reasonably close 2D resistivity profiles to designing a full three dimensional grid with electrodes on the surface and within boreholes. The largest survey HGI has collected to date was an investigation of a mine leach dump over an area totaling 876 acres. The modeling results produced using 3D resistivity tomography allowed us to more fully understand the metallurgical conditions up to depths of 700 feet. Other examples of 3D electrode layout from our list of project case studies are presented below. We can accommodate (almost) any geometry and terrain, and depth of investigation of up to 1200 feet.
HGI offers 3D electrical resistivity services to solve large, complex problems within the environmental, ground water, engineering, mining, and petroleum based industries.
Sinkhole mapping of karst terrain is a perfect example of an application that greatly benefits from 3D resistivity tomography. Due to the nature of the targets (closed, resistive sand bodies hosted in conductive limestone), two dimensional resistivity profiling will often distort the true shape and size of the sinkholes. As an example, HGI reprocessed data for a court case in Florida, where the subsurface conditions were being studied for siting a landfill. Specifically, the three dimensional resistivity was being used to map the extent of sinkholes and raveling (loose rock at the edge of the sinkhole). The three dimensional resistivity survey covered approximately 35 acres with over 1800 electrodes. The results are presented below as a slice through the model at a depth of 65 feet. The resistive sinkhole features are shown to have large diameters, in some cases extending over 375 feet across. Borehole data and standard penetrometer testing (locations of each test are presented as squares within the contoured model) validated the three dimensional resistivity survey by confirming the presence (and absence) of competent rock and areas prone to raveling on the edge of sinkholes.