 |
| |
 |
| |
 |
| |
 |
| |
 |
| |
 |
| |
 |
| |
 |
| |
 |
| |
 |
| |
 |
| |
 |
| |
 |
Ground Penetrating Radar for Environmental Site Assessment
ESI INC. offers both ground penetrating radar (GPR) and Side Scan Sonar (for marine
underwater mapping) services. We also have underwater cameras and salvage capabilities.
Our GPR units can map out and view a wide range of underground conditions.
Left:
On the left is an example of how a
GPR unit can view underground
conditions. In this image you can
clearly see where a series of tanks are
located.
Right:
The image on the left is one taken
using the Ground Penetrating Rador
Method. You can clearly see where
the pipes are located underground.
The Ground Penetrating Radar (GPR) Method
The GPR method provides information, which can be used to help determine construction
conditions without disrupting the site. GPR will image a wide range of subsurface conditions
such as:
• Bedrock topography
• Depth to the water table
• Depth and thickness of soil strata on land and water
• Location of subsurface cavities and fractures in bedrock
• Location of buried objects such as pipes, storm drains and cables
• Underground tanks (UST) oil and gas
• Buried drums
• Boundaries of buried landfills
• Extent of contaminant plumes and if groundwater is impacted
• Condition of concrete, brick and masonry structures
• Conditions of sub-grades beneath roads and railroad beds
• Presence of rebar in concrete
• Mapping and inspections of septic systems and fields
• Location of archeological sites
Ground Penetrating Radar Applications:
• Pipes and utilities
• Underground tanks (UST) oil and gas
• Buried Drum location
• Septic tank inspections
• Landfill and burial trenches
• Cemetery and gravesites
• Buried objects
Ground Penetrating Radar (GPR)
The depth of ground penetrating radar (GPR) can be as deep as 100 feet (30 meters). Detail
can be determined based on the antenna and settings used. A low frequency antenna will
examine the surface at great depths. A higher frequency antenna can examine the near
surface in great detail. GPR can image any underground installation regardless of construction
material. The on-site printout allows for immediate referencing and mark outs.
Ground Penetrating Radar (GPR) uses FM-frequency radio energy to echolocate subsurface
features. The technique was originally developed to investigate subsurface features below ice
sheets. The GPR method has since been adapted for use over land and water. Over-water
surveys are done by passing the radar antenna over the area in a small wooden or fiberglass
boat. The signal is then sent through the hull and water column to the sub-bottom material.
Signal strength is adjusted depending on type of water, fresh or salt, and depth of the water.
As on land, the image is stored on-board in the main computer for printing and review. In a
GPR survey, high frequency (10mhz to 3,OOOMHz) electromagnetic (EM) pulses are used
to detect changes in EM properties (dielectric permitivity, conductivity and magnetic
permeability) as a function of depth. Energy is propagated into the ground, from a
transmitting antenna and is reflected back to a receiving antenna from subsurface boundaries
at which there are EM property contrasts. As the antennas are moved along the survey line,
a series of scans are collected and positioned side by side to form a profile of the subsurface.