Ground Penetrating Radar - Team Delta - Damien Watt

Investigations of contaminated soils may require use of what is known GPR or Ground Penetrating Radar. Ground penetrating radar (GPR) is a electromagnetic geophysical technique for subsurface investigation, characterization and monitoring that does not require digging or excavation. The ground penetrating radar can be deployed multiple ways. Some the methods of deployment are illustrated with the attached photos. Other methods of deployment from the surface include hand deployment or using a vehicle, placement in boreholes, between boreholes, from aircraft and from satellites. It has the highest resolution of any geophysical method for imaging the subsurface. Resolution as high as centimeter scaled resolution is possible in some cases.
GPR is widely used to locate lost utilities, perform environmental site characterization and monitoring, archaeological and forensic investigation, unexploded weapons and land mine detection, groundwater, pavement and infrastructure. The way the GPR works is similar to seismic reflection methods, the down and back pass through (or two way travel) times of the reflected, and pulse is gauged. Resolution is controlled by of the propagating electromagnetic wavelength in the ground. Resolution increases with increasing frequency and decreases with a decreasing frequency, all depending on the length of the wavelength. With approximation of radar wave velocities, the method results in vertical cross-sections that demonstrates reflecting layers of objects at depth. Depth of investigation varies from less than one meter to more than 5,400 meters depending on the media being explored. Any irregularities in the soil can either focus or scatter the wavelength depending on orientation. Scatter losses occur when the irregularity sends the wavelength in a different direction of the antenna or the electrochemical property of the soil causing low amplitude of the wavelength.
In conducting both phase I and phase II investigations GPR can be effective in finding sources of ground contamination. GPR is also very capable of to find inconsistencies in the soil as well or a boundary of Non aqueous phase liquids or NAPL in the soil due to the electrochemical properties of contaminats. GPR together with other methods such as terrain conductivity help give insight to what is going on in the ground without any digging.


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Pictures (2009, October 6). Ground Penetrating Radar Surveys Retrieved October 6, 2009, from http://www.geomodel.com/; GEOmodel TM

Lawrence Conyers (2009, October 6). Ground Penetrating Radar Retrieved October 6, 2009, from http://mysite.du.edu/~lconyer/: Conyers, Lawrence, University of Denver

Ground-Penetrating Radar (2009 October). Retrieved October 6, 2009, from http://en.wikipedia.org/wiki/Ground-penetrating_radar;