GEM-300 Multi-frequency EM

 

Multi-frequency Electromagnetic (EM) Method

Electromagnetic (EM) induction is a standard tool for delineation of contaminated waste sites and measures variation in electrical conductivity (EC) levels. The output of an EM survey is a generally a map, or 3D surface, showing the variation in EC across a site in units of mS/m.

The GEM-300 is a frequency domain, electromagnetic profiling system manufactured by GSSI. It can be configured to simultaneously measure up to 16 user defined frequencies between 330Hz and 20kHz with a fixed coil separation. By acquiring multiple frequencies the user can select the frequency(ies) which provide the best results for a specific application. Both in-phase and quadrature measurements are recorded with time-stamp. Output is mutual coupling ratio (Q) in part/per million (ppm) and apparent conductivity in mS/m.

ScanTec have used the GEM-300 for the following applications;

  • detection of cavities / tomos
  • mapping the extent of contamination plumes
  • mapping isolated zones of buried waste
  • detection of military waste (metallic waste)
  • detection of burial sites
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    (Below) GEM-300 Multifrequency EM instrument


    Example of GEM-300 data collected at a contaminated site in NZ showing zones of metallic waste

    (Below) Example of conductivity survey to map the extent of landfill within a former basalt quarry, Auckland, New Zealand.

    Example of GEM-300 survey data showing the extent of wood waste / contaminant deposit, New Zealand