Electrical Resistivity (ER) applies direct current or low-frequency alternating current into the subsurface to determine the potential difference between two points revealing the resistivity and conductivity of the geological subsurface units. This exploration technique is a quick and inexpensive way to image the subsurface while leaving the ground surface unscathed. A number of electrical resistivity arrays can be utilized depending on the scope and goals of the project and can be used independently or in conjunction with other exploration techniques including borehole drilling. Uses of ER exploration include: geologic mapping of shallow bedrock and permafrost, volume estimates of shallow subsurface leaks and liquid bodies, locating mine shafts and voids, mapping the extent of aquifers, aquifer contamination evaluations, and archaeological studies. NGE-TFT has successfully used ER to gather resistivity data to be used for the design in grounding systems for electrical substations and cell towers. We also employ the soil box resistivity test as a laboratory analysis of the resistivity of soil samples from the field. This method is mainly used to determine the potential for corrosion of pipes and other metals buried in the tested soils. Electrical Resistivity is limited to summer use and should be employed in soils that are unsaturated with rain water. Generally, a brief site assessment should be conducted prior to the commissioning of an ER survey to evaluate the site conditions and determine if ER technology may be a suitable exploration/inspection method for a given project. New and/or unproven applications for Electrical Resistivity are constantly being discovered and tested, so contact NGE-TFT and let us work together to determine if ER is a suitable technology for your next project!