Seeing into the Earth Noninvasive Characterization of the Shallow Subsurface for Environmental and Engineering Applications (2000) / Chapter Skim
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1 Introduction
1 Introduction
Pages 6-17
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From page 6... ...
Subsurface applications of public health and safety are dominated by regulatory concerns, whereas resource extraction is driven by economic returns. These four general applications form a continuum of sometimes interrelated and sometimes competing objectives.
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Indirect or noninvasive methods hold the promise for rapid, low-impact, and relatively inexpensive characterization of the earth's subsurface just as X-rays, sonograms, and other medical imaging technologies have reduced the necessity for invasive diagnostic surgery and have revolutionized medical practice. As in medicine, there are many situations in which invasive methods are required to characterize the shallow subsurface.
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Realizing this potential will require concerted interdisciplinary efforts by earth scientists, geotechnologists, government agencies and regulators, and the user community. PURPOSE OF THIS REPORT A variety of noninvasive techniques for subsurface characterization may offer distinct advantages over traditional invasive methods.
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assesses current capabilities for characterizing the nearsurface environment using noninvasive technologies, (2) identifies weak links in current capabilities and the potential for new and improved methods, and (3)
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NEAR-SURFACE APPLICATIONS OF NONINVASIVE TECHNIQUES Noninvasive characterization of the shallow subsurface can serve many ends (see Box 1.3~. Many of the techniques have been developed from the decades-old geophysical methods used to explore for petroleum and other mineral resources.
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A survey of the evolution of geophysical methods applied to engineering and environmental problems is available through a series of manuals produced by the U.S. Army Corps of Engineers (Department of the Army, 1948, 1979, 1995~.
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Increasingly, geophysical methods are being used prior to construction to help assess the subsurface integrity of proposed locations for industrial and government facilities such as chemical plants and facilities for waste storage and disposal. Geophysical and other noninvasive methods continue to be developed for near-surface resource exploration, particularly mineral resources and groundwater.
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From page 14... ...
Where there is the need, the noninvasive characterization can be checked by invasive "ground truth" measurements, which may allow further calibration of the noninvasive methods and help in modeling the specific site's subsurface conditions. Resulting characterizations provide critical input to the development of a conceptual model for a site, which is the initial step in an "expedited site characterization process" (American Society for Testing and Materials, 1997~.
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For example, groundwater flow calculations depend on estimates of hydraulic conductivity for which direct noninvasive measurement techniques currently do not exist. Other examples of parameters that cannot be unambiguously determined include porosity, grain size and orientation, and clay content and mineral
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, 1997. Provisional Standard Guide for Expedited Site Characterization of Hazardous Waste Contaminated Sites, ASTM PS 85-96.
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, 1997. Expedited Site Assessment Tools for Underground Storage Tank Sites: A Guide for Regulators, EPA Office of Underground Storage Tanks, EPA510-B-97-001, Washington, D.C.
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