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Underground Detection Equipment Limitations

  • Ground penetrating radar does has limited penetration through very dense compacted material, saturated soil or soils covered in reinforced concrete
  • Where the dielectric value of the surrounding soil and the service you are looking for are close to each other, a very weak or no reflection will be visible
  • The GPR unit has to be in contact with the soil surface and irregular surfaces cannot be scanned
  • Outside interference from high voltage underground or overhead lines
  • Detected underground services cannot always be service-specifically identified unless they are visible at a termination point, manhole or according to existing information
  • In areas where underground services are densely concentrated in sub-metre areas, services will be indicated as a band of services. Equipment used in the proposed survey can’t distinguish between individual services in such areas if ground conditions do not allow it
  • Services buried on top of each other can often not be distinguished using electrical or radar detection methodologies
  • Depth of detected services can be supplied by the avoidance tool if a good signal connection can be made or by GPR within a 10% accuracy
  • Dense clay formations, high water tables, rubble used as backfill, excessive steel reinforcement in concrete or even load shedding can influence the accuracy of the equipment used and the outcome of the survey
  • Whilst employing appropriate equipment, processes and best endeavors at all times, no guarantee can be made that any particular element of buried infrastructure will be properly detected or parameterized by the proposed survey due to the large number of variables encountered on different sites. For critical applications it is always recommended that a survey be followed by careful hand excavation and air knife probing