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NONDESTRUCTIVE TESTING (NDT) TECHNIQUES TO DETECT CONTAINED SUBSURFACE HAZARDOUS WASTE
Citation:
Lord, A. AND R. Koerner. NONDESTRUCTIVE TESTING (NDT) TECHNIQUES TO DETECT CONTAINED SUBSURFACE HAZARDOUS WASTE. U.S. Environmental Protection Agency, Washington, D.C., EPA/600/2-87/078.
Description:
The project involves the detection of buried containers with NDT (remote-sensing) techniques. Seventeen techniques were considered and four were ultimately decided upon. They were: electromagnetic induction (EMI); metal detection (MD); magnetometer (MAG); and ground penetrating radar (GPR). The containers--both steel and plastic--varying in size from 5 gal to 55 gal were buried in known distributions in a wide variety of soils; also, some were submerged in water. Five diverse field sites were used. As a result of the work at the five field sites, a relatively complete picture has emerged concerning the strengths and weaknesses of the four NDT subsurface container location techniques. Briefly it can be stated: GPR is the only reliable method to detect plastic containers, but it has limitations; GPR, EMI, and MD all suffer severe loss of detection ability when the background electrical conductivity exceeds 40 millimhos/meter; in a dry sandy soil EMI, GPR, and MAG are all capable of picking up a single 55-gal steel drum to a depth of at least 10 feet; the MAG method works well for steel under all subsurface conditions; and GPR can usually pickup the side walls of the excavations where waste is dumped. Application of signal enhancement techniques (background suppression) can be expected to enhance NDT utility.