Electromagnetics

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Electromagnetic (EM) methods are widely used for environmental and geotechnical investigations. EM methods employ active-sensing technology in which a generated EM field is used to induce a secondary EM response in the mediums being investigated. EM sensors can be divided into two categories: frequency domain, which measures the amplitude and phase of the induced electromagnetic field, and time domain, which measures the decay time of the induced field. EM instruments measures variability in subsurface conductivity, which can be naturally occurring (differing lithologic materials), or man-made (soil/groundwater contaminants or buried metal) and have the added capability of detecting non-ferrous as well as ferrous metallic objects. 

Applications of EM methods:

• Identifying unexploded ordnance (UXO)
• Locating buried metallic objects (drums, tanks, etc)
•  Mapping leachate plumes
• Mapping soil salinity and saltwater intrusions
• Delineating landfill and trench boundaries
• Mapping soil and groundwater contaminants
• Detecting the locations and orientations of faults
• Mapping lateral and vertical distributions of soil types
• Locating water resources
• Identifying karst bedrock features
• Predicting areas prone to slope failure