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High Resolution Geophysical Technologies
ARM Geophysics performs Terrain Conductivity Surveys for a variety of applications.
To perform Terrain Conductivity Surveys, ARM uses a Geonics EM-31DL conductivity meter.
For environmental applications the EM-31 data can be used to map landfills, buried
drums, and shallow groundwater contamination. It also has geotechnical applications
such as soil thickness and possible sinkhole or pinnacle locations in karst terrain.
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Where possible, ARM integrates the data collection with Global Positioning Systems
(GPS) with at least sub-meter accuracy. Depending on how the data are collected, the
effective depth of the system is approximately 7.5 or 18 feet. The system is a non-intrusive
conductivity measuring device, and data can be collected almost as fast as the operator
can walk. The system provides two measurements, Quadrature (apparent conductivity)
and In-phase data (metallic response). The data are digitally recorded and periodically
down-loaded to a field computer for quality assurance and preliminary interpretation.
At the conclusion of a survey, the EM-31 data are interpreted and mapped as shown
in the example. The EM-31 data are contoured, and presented in a fashion that will
show the interpreted subsurface features (ie; areas of concern).
An EM-31 survey, which measures the apparent conductivity of the subsurface, can
be used to estimate the relative amounts of soil and rock within the area of measurement.
Higher apparent conductivities measurements imply a thicker soil cover, while
lower apparent conductivities suggest a greater effect from bedrock, therefore
indicating a thinner soil cover. Discrete areas of elevated conductivity within
a limited areal extent can be an indicator of subsurface sinkhole development activity.
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| ARM EM31 Towed System |
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