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7th EEGS Symposium on the Application of Geophysics to Engineering and Environmental Problems
- Conference date: 27 Mar 1994 - 31 Mar 1994
- Location: Boston, Massachusetts, USA
- Published: 27 March 1994
21 - 40 of 76 results
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Digital Impulse Radar And Sonic Testing Of Bridges
Authors M.C. Forde and A.J. BatchelorDigital non-destructive testing techniques available in both the time and frequency domains
are outlined: including digital sonic echo testing, digital sonic frequency domain testing
and digital time domain radar testing. The new non-destructive evaluation techniques are
described in relation to applications to concrete foundation piles and masonry bridges. A
comparison of the techniques with those applied to concrete structures is made.
Case studies are used to illustrate that the techniques of digital sonic impulse hammer
testing and digital impulse radar testing are complementary in nature and can be used to
cost effectively identify the geometries of piles and masonry bridges in addition to fault
detection and location.
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Unconventional Applications Of Terrain Conductivity Logging To Groundwater Investigations
Authors Paul Bauman, Janan Sallomy, Mike Brewster and Anthony BrownConventionally, terrain conductivity logging is used in hydrogeologic studies to map groundwater
contaminant plumes of elevated total dissolved solids (TDS). While well-suited to this
application, terrain conductivity logging is also a tool useful for approaching a wide variety of
other groundwater studies. In this paper, four case studies illustrate the application of borehole
electromagnetic (EM) logging to four different problems. The first case study of EM logging iS
used to identify fractured zones in an otherwise homogeneous cemented sandstone aquifer. The
second case study uses EM logging to establish the connectedness of a fracture or fractures
between two monitoring wells. In the third study, multiple aquifers overlooked during drilling are
clearly delineated by terrain conductivity logging. In the final study, EM logging is used to
describe and delineate paleochannel deposits which are controlling contaminant migration. All
of the above studies are related to light non-aqueous phase liquid (LNAPL) remediation projects.
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High Resolution Flowbeter Lqgging - A Unique Cobbination Of Borehole Geophysks And Hydraulics; Part I: Flwbetrr Techniques And Equipment Deveu)Phent
Authors Robert Crowder, Frederick Paillet and Alfred HessHigh resolution flow logging has the potential to significantly improve
geophysical interpretations in ground-water studies. Surface geophysical
soundings, borehole-to-borehole tomography, and conventional geophysical
logs all provide techniques for the non-invasive characterization of
aquifers on different scales. These techniques generally characterize
aquifers in terms of physical properties such as electrical conductivity or
seismic attenuation that are only indirectly related to hydraulic
parameters. However, borehole flowmetering is a technique included in the
standard suite of well logs that can provide a direct measurement of the
hydraulic properties of sediments and'fractured rocks adjacent to boreholes.
For many years the resolution of available flowmeters severely limited the
application of flowmeter logs in aquifer studies. As a result of recent
emphasis on the application of well logging techniques to aquifer
contamination and remediation projects, a number of different flowmeters
with the potential for making much more accurate flow measurements than
previously possible have been produced. These include techniques based on
laser and acoustic Doppler, electromagnetic, heat-pulse, fluid conductivity
profile, and acoustic scattering measurements.
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High-Resolution Flowmeter Logging - A Unique Combination Of Borehole Geophysics And Hydraulics: Part Ii - Borehole Applications With The Heat-Pulse Flowmeter
Authors Frederick Paillet, Robert Crowder and Alfred HessA number of recently-developed high-resolution flowmeter logging
techniques are described in the well logging literature. These techniques are
now or soon will be capable of measuring flows corresponding to less than 0.01
gallons per minute of borehole discharge. Such measurements have the
potential to significantly improve the interpretation of geophysical logs in
ground water studies by showing how geological structure indicated on logs and
tomographs is related to hydraulic properties of beds, solution openings and
fractures. The potential benefits of such borehole measurements are
illustrated by the results obtained with the U.S. Geological Survey heat-pulse
flowmeter. One of the most potentially useful applications of high-resolution
borehole flow measurements is associated with the disturbance to aquifer
hydraulics induced by the presence of an open borehole. This effect can be
modeled and analyzed to provide a controlled test of aquifer response to
disturbance. Flow measurements can also indicate ground water flow in the
vicinity of the well bore during short, low-capacity aquifer tests. A number
of researchers have shown how such flowmeter profiles can be analyzed to give
rigorous profiles of permeability and specific storage in situ. At the same
time, monitoring of flow transients in cross-borehole pumping tests may be
formulated as a hydraulic tomography study. One useful application of flow
logging is the quick and definitive assessment of flow connections between and
around boreholes within hours after the completion of drilling. Such
measurements could greatly reduce the time and effort involved in the
otherwise expensive and labor intensive procedures of conventional hydraulic
testing and tracer studies.
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Monitoring Well Completion Evaluation With Borehole Geophysical Methods
Authors Robert Crowder and William HenrichGeophysical logs amenable to the evaluation of well completion features in monitoring wells
have included acoustic, gamma-gamma dual density, natural gamma, caliper and video. Well
completion features surveyed have consisted of validation the vertical position and physical
integrity of slotted micro screen and the identification and extent of annular materials behind casing
such as sand pack, bentonite seals and sanitary cement grout seals.
Traditional oil field logging methods of well evaluation such as the Cement Bond Log
(acoustic) can be used under certain conditions in PVC cased monitoring wells, however the
interpretation emphasis is placed on acoustic velocity as a diagnostic means to identify various
annular materials. This is in contrast to oil field cement bond log methodology which focuses on
amplitude reduction in the first sonic wave arrivals as a measure of 1) the presence of cement
grout and 2) subjective estimate of the degree of bond (e.g. casing to cement, cement to
formation). These interpretation disparities are primarily the result of differences in construction
materials, geologic setting and construction procedures between oil & gas well and environmental
monitoring wells.
A number of case histories utilizing acoustic, gamma-gamma dual density and natural
gamma logs are presented to show well completion aspects of polyvinyl chloride cased monitoring
wells in a variety of shallow geologic settings. The case histories show the importance of
combining complementary logging techniques to help validate final interpretation and demonstrate
certain limitations and constraints characteristic of geophysical methods in general.
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Modeling Borehole Stoneley Wave Propagation Across Permeable In-Situ Fractures
Authors C.H. Cheng and X.M. TangThe characterization of the hydraulic transmissivity of permeable fractures is a very important
task in the study of ground water flow in basement rocks. Previous studies that model the permeable
structure as a single fluid-filled fracture failed to explain the observed significant Stoneley
wave attenuation across the permeable structure. In this paper, the structure is modeled as a
permeable fracture zone. The results show that Stoneley waves can be strongly attenuated or
even eliminated without significant reflection, because of the dissipation of wave energy into the
permeable zone. Three field cases are modeled and the theoretical results are compared with
the field data. It is shown that low- and medium-frequency Stoneley waves (1 - 5 kHz) are very
sensitive to the permeability of the fractures and can be used to assess permeability from in-situ
logging data, if the fracture porosity and zone thickness can be measured. At higher frequencies,
however, Stoneley waves are not very sensitive to permeability but are mainly affected by the sum
of the fracture openings expressed as the product of fracture zone thickness and porosity in the
fracture zone. This finding is demonstrated by a logging data set obtained using high-frequency
Stoneley waves at 34 kHz.
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Use Of Borehole Electromagnetic-Induction And Natural-Gamma Logs To Delineate A Contaminant Plume In Ground Water
More LessElectromagnetic-induction and natural-gamma borehole logs were used to delineate the
vertical extent of contamination in ground water at a former plating facility. The facility
discharged plating wastes, including volatile organic compounds and numerous metals, into
unlined lagoons. These wastes leached into an unconsolidated glacial aquifer and formed an
electrically conductive contaminant plume that is flowing towards surface-water bodies.
Electromagnetic-induction and natural-gamma borehole surveys were conducted in eight
monitoring wells to delineate zones of electrically conductive ground water indicative of the
contaminant plume. Three contaminated zones delineated at two wells immediately
downgradient of the plating facility were 5 to 15 ft thick. At monitoring wells farther
downgradient from the site, contaminant zones were more than 20 ft thick in places.
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Analysis Of Wellbore Image Data Applied To Environmental And Geotechnical Case Studies
Authors Colleen A. Barton and Jerry WrightThe application of borehole televiewer (BHTV) data analyses recorded in the shallow crust
to environmental and hydrological investigations is fourfold: 1) fracture characterization, 2) in-situ
stress measurement, 3) providing site geologic and lithologic constraints, and 4) geotechnical
monitoring. One of the primary uses of the borehole televiewer data since the tool became
operational in geophysical logging has been measurement of the orientation and distribution of
planar features in a drillhole. The resolution of the borehole televiewer is capable of detecting a
wide range of fracture sizes and these data can provide a wealth of information pertinent to
understanding the mechanical behavior of the Earths crust at a drillsite. Fractures provide
permeable pathways for fluids and affect rock properties by chemical alteration of the surrounding
rock mass. Fracture geometry is therefore important to fluid flow and permeability in reservoirs
and waste disposal sites and to the safety of groundwater aquifers. In situ stresses play a major
role in the stability of natural and man made structures. The measurement of stress orientation and
magnitude, possible through the analysis of BHTV image data, can provide information about the
ambient tectonic stresses and information crucial to the design, construction and monitoring of
dams, tunnels or aqueducts. Stress orientation and magnitude also has a major impact on the
development of natural fractures and subsequent movement along preexisting fault surfaces. In
shallow crustal wells the constraints placed on in-situ stress from the analysis of BHTV data are
important to interpreting the interaction between pore pressure and hydrostatic pressure in a well
and subsequent wellbore stability.
Case studies from wells that exemplify the application of BHTV data analysis to
geotechnical and environmental issues are presented. The first study involved in the siting and
construction of a major aqueduct/tunnel in central Utah. The objectives of this study were to
characterize the natural fractures within the shallow crust at the drillsite and to determine the
orientation of in-situ stresses. A second study, conducted in two phases, concerned the analysis of
fractures developed in a concrete dam abutment in Colorado. Detailed measurements of the aperture
of fractures detected by BHTV imaging were made at a ten month interval to help establish the
integrity of the dam. Finally, a study of wellbore image data recorded at county landfill in Oregon
was performed to measure the orientation, aperture and depth distribution of fractures at the site.
The image data was used in conjunction with geophysical logs to discriminate between bedding
plane fractures and through-going fractures in siltstone units and fractures in basalt units.
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Downhole Shearwave Studies Enhanced By Gamma Log Litholocic Interpretations
Authors Alan C. Samuelson, Donald L. Eggert and William R. EckhoffOver the past fifteen years the Indiana Geological Survey has routinely used gamma logs in
its investigations of unconsolidated sediments: These logs have become powerful tools that allow
interpretation of the distribution of particle sizes in a sedimentary column. Thus, interpretations of
the depositional setting and correlations of Quaternary deposits have been improved.
In 1990 the Indiana Geological Survey began investigation of the particle and shearwave
velocity of Quaternary deposits in Indiana as part of the Survey’s seismic hazards reduction program.
Over a hundred downhole velocity records from southern and central Indiana have been recorded
and analyzed over the past three years. Each of these holes have been gamma logged. Based on
sample description and log signatures; eolian, Iacustrine, fluvial, and glacial till deposition have been
recognized.
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Preliminary Results Of A Seismic Borehole Test Using Downhgle Shaped Charges At The Doe Hanford Site
Authors Susan Narbutovskih and Finn MichelsenGeophysical site characterization studies can be important steps in the process of designing and
monitoring remediation at hazardous waste storage facilities. However, use of seismic techniques for
subsurface characterization at the DOE Hanford Site has been limited for several reasons. One reason
is the lack of borehole velocity control, which is valuable to the development of initial geologic
models and seismic data processing. Current drilling procedures result in steel-cased boreholes which
are poorly coupled to the surrounding sediments. In addition, these low-velocity sediments are highly
attenuative. Consequently, standard techniques to provide velocity control are not adequate. Both
Vertical Seismic Profiling (VSP) and reversed VSP (RVSP) surveys are currently being investigated
to provide velocity control and for subsurface imaging capabilities.
Recently a jet perforating gun was used to perforate a double-cased borehole in the 200 West Area.
During this operation, acoustic emissions were recorded from numerous depths to obtain velocity
control for a previous surface survey conducted in the same area. Both P- and S-wave data were
recorded simultaneously from multiple horizons using the DAS-1 seismograph and 3-component
geophones. The data were analyzed for a variety of uses besides velocity control. Signal attenuation
was studied as a function of source depth and offset distance to evaluate formation absorption while
vertical resolution was determined from the frequency spectrum.
Preliminary results indicate that adequate P-wave velocity control can be obtained even though the
near-surface sediments are very attenuative. However, we conclude that the perforating gun produces
little SH energy. Preliminary velocities indicate that reflection coefficients should be great enough to
use surface techniques. Results from the frequency study suggest that a swept source for both surface
and borehole surveys may be necessary to obtain required resolutions. Finally, signal attenuation as a
function of formation facies suggest that seismic techniques may be useful in mapping perched water
zones and for long term vadose zone monitoring.
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Resistivity Surveying For Planning Of Infrastructure
Authors Torleif Dahlin, Sam Johansson and Ola LandinResistivity surveying can play an important role for providing a geotechnical planning basis
for infrastructure projects if used in an early stage of the pre-investigations. The result can
then guide the selection of geotechnical drilling and sounding points, to ensure that the
selected points are representative. It can also decrease the total number of drilling points
needed. In order to be an attractive method which complements the traditional geotechnical
methods resistivity surveying has to give an area1 cover, be economically efficient and provide
easily accessible presentations. This in turn makes it necessary to automate data collection,
interpretation and presentation as far as possible, and an approach for this is presented
together with results from two field sites.
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Urban Geophysics - Seeking The Difficult And Hidden
Authors P.J. Fenning, D. McCann and K. VenessEnvironmental Geophysics is defined by Steeples and Miller
(1993) as the use of geophysical measurements of part of the
earth to evaluate or remediate problems in the earth's
environment. A reveiw of environmental geophysical literature
shows a substantial pre-occupation with localities or targets
that will require future remediation. Greenhouse (1992)
comments that the term environmental geophysics is "not
descriptive so much of methodology or target as it is of a
context. It is usually practiced in association with
hydrogeology and hydrogeologists.
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Sasw & Gpr To Detect Buried Objects
Authors Naser Al-Shayea, Richard Woods and Park GilmoreThe spectral-analysis-of-surface-waves (SASW) technique is compared with the ground
penetration radar (GPR) method for detection of buried objects. Tests were performed in a 7 m
diameter by 2 m deep sand bin in the G. G. Brown Lab of the University of Michigan. The bin is
filled with uniform silica sand compacted to a uniform density of about 16 kN/m³. During the
filling process, a three-cell void was buried at a depth of 305 mm to the top in the center of the bin.
SASW and GPR tests were performed with all three cells empty, one cell (center cell) empty, and
all cells full of sand. The two experimental techniques are being compared with each other for
eflicacy of void detection.
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Locating Railroad Track Bed Subsurface Defects Utilizing Nondestructive Remote Sensing Technologies
Authors Richard J. Graf, Leann M. Forister and Gary J. WeilThe railroad is a vital transportation link with tracks traversing thousands of miles throughout the United States.
When this link fails, the resultant damage costs millions of dollars. Track failure, attributed to moisture trails and
erosion voids in the rock ballast and subsoils that support the tracks, slowly deteriorate the railbed to a critical
point in which iron rail shifts occur. All railroad lines experience failures on a regular basis, but the recent Flood
of ‘93, that inundated thousands of square miles of land and hundreds of miles of railroad tracks in the midwestem
United States, brought a new impetus to quickly locate and repair these hidden subsurface defect areas.
This paper illustrates a new technology combination of nondestructive, remote sensing Computer Enhanced
Infrared llennography and Ground Penetrating Ruder that was used to detect buried moisture trails and erosion
voids of railroad track beds. This technology combination is described in theory and by discussion of a case study
based upon a successful project, conducted immediately following the flood, for Burlington Northern Railroad.
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Automated, Rapid, Comprehensive Non-Destructive Tunnel Testing
Authors P. Fisk, R. Holt, H. Russell and B. BohlkeAutomated seismic/sonic wave velocity, frequency and reflection measurements and radar profiling
measurements are obtained to provide a rapid, comprehensive and efficient non-destructive
evaluation of tunnel liner conditions. The automated seismic/sonic system acquires overlapping
(continuous data) at 6,18, and 30 inch intervals at a rate of 500 to 2,000 feet per hour. Radar profiling
data are acquired simultaneously to provide a complete suite of non-destructive data to evaluate the
following critical tunnel parameters:
. strength of the tunnel liner;
. identification and mapping of weak, deteriorated, cracked, delaminated tunnel liner;
. identification of metal structural or functional members such as rebars, pipes, ribs etc.;
. identification of thinner tunnel liner areas;
. identification and mapping of voiding behind the liner.
All data are displayed in the field for quality and recorded on digital disks for future analysis,
processing and playback on analog chart recordings for on-site interpretation.
The seismic/sonic/ultrasonic measurements provide data to calculate the moduli values (Young’s, bulk
and shear) and an evaluation of the strength/mechanical properties of tunnel liner materials (concrete
and masonry). The seismic/sonic/ultrasonic results identify and quantify areas of interior
deterioration, as well as liner thinning and voiding behind the liner. Radar profiling is used to
identify metal within the liner, areas of increased moisture or water infiltration, as well as water filled
void conditions behind the liner.
This system has been utilized on a number of projects throughout the United States and abroad
including: rapid transit, water supply, railway, automobile, and hydroelectric tunnels as well as
pipelines.
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Inspection Of Cast-In-Place Piles By Ultrasonic And Radiometric Testing
By Olli T. OkkoThe possible existence of casting defects in cast-in-place piles in Finland has been
systematically inspected by ultrasonic cross-hole testing in tubes installed beforehand in the
pile. In order to analyze the accuracy of the method a test pile was built up. The internal
structure of the pile was tested also by nuclear logging and water injection tests carried out in
the PVC-sleeve tubes installed in the pile.
Small cracks in the concrete pile were clearly detected on the analog sonograms of the
ultrasonic cross-hole records. On the other hand the largest casting defect was not well
identified, probably due to the homogeneity of the weak concrete. The density and the water
content in the large volume of concrete was measured by back-scattering techniques of
gamma rays and thermal neutrons. By means of these methods casting defects thicker than 5
cm were detected. After the pile was grouted, only the nuclear methods could be used to
inspect the quality of the grouted pile. The sonograms were similar to those obtained before
the grouting.
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The Use Of Geophysical Techniques For The Detection Of - Partially Collapsed - Mine Shafts
Authors Jan Brouwer and Vincent NijhofDuring the past centuries the Southernmost part of the Netherlands has been known for
extensive marl recovery. Systems of galleries and mine shafts exist over - assumed - areas
of several hundred km2. At some locations mine galleries have recently collapsed causing
severe damage to the roads and buildings in the surrounding urban areas. Due to these
collapsed galleries parts of the system of mining shafts have become unreachable making it
but impossible to determine the exact lateral extent of the collapse features and the galleries
from within the mining system and leaving only surface methods to locate the shafts and to
determine the potential hazard for similar collapse features.
In this paper we present a feasibility study that addresses the use of three surface geophysical
investigation techniques - Resistivity Image Profiling (RIP), Ground Probing Radar (GPR),
and Reflection Seismic Profiling - to locate the mine shafts and to determine whether the
shafts are collapsed or intact.
Although all three techniques gave at least some indication to the location of the shafts, the
RIP was found to be superior to both other methods since it did not merely prove to correctly
reveal the location of the mine-shafts, it also gave some indication to whether the shafts were
collapsed or not.
GPR measurements clearly showed diffracted energy in areas where shafts were expected. The
use of GPR methods, however, was limited to it’s application on roads and other areas of
relatively flat surface conditions.
Seismic measurements highly suffered from low-velocity layer effects. Although diffracted
energy could be noticed that possibly correlates to some of the mine-shafts, data were
obscured by the occurrence of strong refraction multiples.
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The Integration Of Imaging And Parameter Estimation In Shallow Geophysics
Authors Alan Witten and Stephen NortonThis paper presents two related approaches to signal processing of shallow geophysical
data based on the concept of geophysical diffraction tomography. While both methods can be
considered imaging, one is imaging in the traditional sense where images of spatial variations
in subsurface physical properties are reconstructed. The second method is one of parameter
estimation based upon known characteristics of targets of interest. This technique yields a
reconstruction of the spa.tial variations in the likelihood of a specified target being present,
the log likelihood function, and, consequently, this method can also be considered an imaging
procedure. Several examples are given of the results of selected signal processing algorithms
applied to actual data.
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Large Scale Hydrogeological Investigation In The Beder Area - A Case Study
Authors Esben Auken, Niels B. Christensen, Kurt I. Sørensen and Flemming EffersøBy the integrated use of geophysical methods a ltydrogeological investigation with a very
high r~~solution of the geology has heen carried out in Denmark. llsing newly developed
methods such as auger Ellog drilling with levrl specific Water sampling and pulled array
contitttlous electric profiling together along with more Ouniliar techniques such as transient
electromagnetic sounding we have perfortned a general exantinatiott of the vulnerability,
the volumetric extent and the chemical properties of the aquifer itt the area. The
protection of the aquifer was less than expected. There was a rorrelation between the water
quality and the lithology of the aquifer.
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Use Of Ground-Penetrating Radar To Determine The Depositional Environment Of Glacial Deposits In Southern New Hampshire
More LessGround-penetrating-radar (GPR) surveys were made along more than 8 miles of land and
water within the Flints Pond and Lyle Reed Brook areas in southern New Hampshire. The GPR
data revealed thick sequences of continuous reflectors that represent stratified drift. Surficial
geologic mapping of the area indicates that the stratified-drift deposits are graded to the various
levels of glacial Lake Nashua. Four distinct signatures were apparent on the GPR profiles and
were correlated with various glacial depositional environments: (1) thin, relatively flat-lying,
continuous reflectors draped over the underlying till or bedrock topography, which represent
fine-grained lacustrine sediment; (2) medium-grained, subparallel to slightly chaotic, continuous
reflectors, steeply dipping in places, which represent predominantly medium- to coarse-grained
sands deposited as deltaic sediments in a lacustrine environment; (3) subparallel to hummocky,
chaotic, coarse-grained reflectors, steeply dipping in places, which represent coarse-grained icecontact
deposits, such as eskers or crevasse fillings; and (4) sharply diffracted, fine-grained,
chaotic reflectors, which represent till and (or) till over bedrock. The signatures were correlated
with geologic structures by comparing the radar records to analyses of undisturbed sediment
samples collected at six test-boring sites in the area. Correlation of radar signatures with
geologic structures can be used to indicate the depositional environment of the structure.
Land and water surveys using GPR detected glacially scoured valleys in bedrock that have
been subsequently filled with stratified drift. Geologic structures are visible in greater detail
from GPR surveys on land than on water. Penetration depths of greater than 80 feet (800
nanoseconds) were common on land surveys done over stratified drift. Penetration depths of
approximately 45 feet (400 nanoseconds) were common on water surveys as a result of the
attenuation of the radar signal by the water column.
GPR also was used to delineate the surface contact between stratified drift and the adjacent
till and (or) bedrock. Typically, the signal was attenuated as the survey passed from the
stratified-drift surface to the till surface because of the increased electrical conductivity of the till.
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