Electrical Resistivity Imaging (ERI) is a noninvasive electrical sounding technique that produces profiles showing a virtual cross-section of soil, sediment and bedrock layers. It works well in electrically conductive materials such as clay and saltwater-saturated materials where GPR signals are rapidly absorbed. 

Transects may be laid in a straight line to generate a 2D cross-sectional image or in a grid pattern to generate a 3D image.   Depth of penetration is typically 20% of line length.  Good data to 100 feet is typical for 550 foot long lines.

Applications

Used to map soil and rock thickness and elevation of subsurface interfaces.  Determine lateral continuity of soil and sediment layers.  Delineate geologic features such as buried sinkholes, lenses of organic soil, soil voids, caves, mineralized veins and fractures.  Can be used to map pollution plumes and saltwater intrusion. Since 1999, SEI has used Advanced Geosciences, Inc. (AGI), resistivity imaging equipment to evaluate sites across the United States.  All operators have completed the manufacturer’s training course.

Equipment

Super Sting R8/IP with 56 passive electrodes (121 electrical smart switches also available) manufactured by AGI.  Data is processed using RES2DINV and RES3DINV, and EarthImager software with finite element or finite difference models to produce colorized cross-sections.  Data is verified and optionally processed onsite to ensure survey integrity.