Closed, Illegal and Abandoned (CIA) Disposal Sites

Ground Penetrating Radar (GPR)

Ground penetrating radar is a geophysical method that generates a continuous profile of the subsurface. GPR’s radiate a very short burst of radio-frequency energy into the ground to detect discontinuities. A transmitter antenna generates high frequency radio waves that propagate into the earth in a broad beam. An echo from various subsurface interfaces is reflected back to the observer from a remote target. The strength of the echo is dependent on the absorption of the signal on the path to and from the target, the size and shape of the target, and the degree of discontinuity at the reflecting boundary. GPR’s detect a boundary between rock and air (a cave or cavity) or between one type of soil and another (for example undisturbed soil to waste). The dielectric properties of the subsurface materials correlate with many of the mechanical and geologic parameters of these materials. The performance GPR is limited by attenuation. The signals in moist soils, especially soils having high clay content, can be significantly attenuated. GPR is most useful in detecting changes in the geometry of subsurface interfaces.

In-depth website describing GPR:

• GPR Usage and Limitations, by Lambert Dolphin, SRI International

Quick information on GPR:

• Northeast Geophysical Services
• Advanced Geologic Services
• Geovision Geophysical Services

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Last updated: April 18, 2008