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1.1 Purpose and Application:
1.1.1 This guide summarizes the equipment, field procedures, and
interpretation methods for the assessment of the electrical
properties of subsurface materials and their pore fluids, using the
direct current (DC) resistivity method. Measurements of the
electrical properties of subsurface materials are made from the
land surface and yield an apparent resistivity. These data can then
be interpreted to yield an estimate of the depth, thickness, and
resistivity of subsurface layer(s).
1.1.2 Resistivity measurements as described in this guide are
applied in geological, geotechnical, environmental, and hydrologic
investigations. The resistivity method is used to map geologic
features such as lithology, structure, fractures, and statigraphy;
hydrologic features such as depth to water table, depth to
aquitard, and ground water salinity; and to delineate ground water
contaminants. General references are, Keller and Frischknecht (1),
Zohdy et al (2), Koefoed (3), EPA (4), Ward (5), Griffiths and King
(6), and Telford et al(7).
1.2 Limitations:
1.2.1 This guide provides an overview of the Direct Current
Resistivity Method. It does not address in detail the theory, field
procedures, or interpretation of the data. Numerous references are
included for that purpose and are considered an essential part of
this guide. It is recommended that the user of the resistivity
method be familiar with the references cited in the text and with
the Guide D 420, Practice D 5088, Practice D 5608, Guide D 5730,
Test Method G 57, D 6429, and D 6235.
1.2.2 This guide is limited to the commonly used approach for
resistivity measurements using sounding and profiling techniques
with the Schlumberger, Wenner, or dipole-dipole arrays and
modifications to those arrays. It does not cover the use of a wide
range of specialized arrays. It also does not include the use of
spontaneous potential (SP) measurements, induced polarization (IP)
measurements, or complex resistivity methods.
1.2.3 The resistivity method has been adapted for a number of
special uses: on land, in a borehole, or on water. Discussions of
these adaptations of resistivity measurements are not included in
this guide.
1.2.4 The approaches suggested in this guide for the resistivity
method are the most commonly used, widely accepted, and proven.
However, other approaches or modifications to the resistivity
method that are technically sound may be substituted if technically
justified and documented.
1.2.5 This guide offers an organized collection of information or a
series of options and does not recommend a specific course of
action. This document cannot replace education, experience, and
should be used in conjunction with professional judgment. Not all
aspects of this guide may be applicable in all circumstances. This
ASTM document is not intended to represent or replace the standard
of care by which the adequacy of a given professional service must
be judged, nor should this document be applied without
consideration of a project's many unique aspects. The word
"Standard" in the title of this document means only that the
document has been approved through the ASTM consensus process.
1.3 Precautions:
1.3.1 It is the responsibility of the user of this guide to follow
any precautions in the equipment manufacturer's recommendations and
to consider the safety implications when high voltages and currents
are used.
1.3.2 If this guide is used at sites with hazardous materials,
operations, or equipment, it is the responsibility of the user of
this guide to establish appropriate safety and health practices and
determine the applicability of any regulations prior to use.
1.3.3 This standard does not purport to address all of the safety
concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety and
health practices and to determine the applicability of regulatory
limitations prior to use.
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