Safety 1st Advancer Manual del operador descargar pdf (Pagina 21)

Environmental Remediation Drilling

Safety Guidelines

Page 21 of 132

2.6.1 - Ground Penetrating Radar cont.

Figure 2.1 - Ground Penetrating Radar Being Demonstrated in a Non- Environmental Remediation

Work Area. (Photo courtesy of Enviroscan, Inc.)

Limitations of GPR

Exploration depth can be limited by soil or water with high conductivity. Detection depends upon a

dielectric contrast between the subsurface feature and the surrounding material.

GPR can be a very effective tool for location of subsurface structures, especially shallow obstructions.

Although GPR has been applied at greater depths, it is generally considered to be more effective down to

approximately 10 to 15 feet below the ground surface in most lithologies. Resolution is degraded with

depths exceeding 20 to 30 feet. For utility locating, depth is usually limited to 10 feet or less to ensure safe

drilling operation. Transducers exist that can penetrate to greater depths, but these use a lower frequency.

Lower frequency means lower resolution, and narrow objects like utilities cannot be seen.

Some things to consider when evaluating GPR:

• Closely spaced survey lines are required to locate small objects,

• A relatively smooth surface is also necessary, and

• As with most utility locating technologies, GPR is not as effective where the ground surface is paved

with highly reinforced concrete due to interference from the presence of the metal rebar. Interference is

also prevalent if surface structures are immediately adjacent to the area.

Recent advances in radar antennae and computer software have made GPR more effective in difficult

situations.

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Safety 1st Advancer Manual del operador Pagina 21