How to Find Buried
(The text in this article has been extracted from a publication by the United States Environmental Protection Agency.)
Metal detectors, also referred to as pipeline and cable detectors, are widely used for locating buried metal objects in a process called metal detection (MD). MD can be used to locate steel and composite (i.e., fiberglass-coated steel) tanks; metal piping; and utilities.
The response of MD decreases dramatically with depth. As a target depth is doubled, the response decreases by a factor of as much as 64 (the response to small objects decreases more rapidly than the response to large objects).
Metal detectors are capable of detecting metal utilities up to 3 feet below ground surface (bgs), a 55-gallon metal drum up to 10 feet bgs, or a 10,000-gallon steel tank up to 20 feet bgs.
Stakes or paint marks are typically placed over targets as the survey proceeds.
The diagram below presents a schematic drawing of MD operating principles.
Care must be taken to minimize noise from metal fences, vehicles, buildings, and buried pipes.
Rebar in concrete is perhaps the most common problem for this method.