Closed, Illegal and Abandoned (CIA) Disposal Sites

Magnetic Methods

Whether on the surface or below, iron objects or minerals cause local distortions or anomalies in the earth’s magnetic field. Magnetometers measure these variations in the magnetic field. Magnetometers were originally designed for mineral exploration, but are now used in the environmental field for locating buried steel drums, tanks, pipes, and iron debris in trenches and landfills. A magnetometer detects local buried iron objects because the object causes the (locally) uniform magnetic field of the Earth to strengthen or weaken depending on the size, orientation, and magnetic characteristics of the object.

The magnetometer can only sense ferrous materials such as iron and steel.  Other metals like copper, tin, aluminum, and brass are not ferromagnetic and cannot be located with a magnetometer (but may be found with a metal detector). An object with weaker magnetic characteristics may be detected at a maximum depth of about 5-10 feet. On the other hand, large masses of drums may be detected easily to depths of 10-40 feet.

 
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More information on magnetic surveys:

• Northeast Geopysical Services 
• Geovision Geophysical Services 
• Colorado School of Mines

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Last updated: April 18, 2008