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16th EEGS Symposium on the Application of Geophysics to Engineering and Environmental Problems
- Conference date: 06 Apr 2003 - 10 Apr 2003
- Location: San Antonio, Texas, USA
- Published: 06 April 2003
1 - 20 of 139 results
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Using Analytic Signal Analysis On Aeromagnetic Data To Constrain Amt Inversions, Sonora San Pedro Basin, Mexico
Authors J.C. Wynn, Floyd Gray, T.E. Nordstrom, Dexin Liu, E.V. Reed, F.A. Villaseñor and Gerry ConnardAirborne geophysical studies on the American side of the San Pedro Valley of Arizona
and Mexico have allowed us to map depth to crystalline basement in this area where
groundwater is critically important (Alley and others, 1999; Leake and others, 2000; Wynn and
others, 2000; Wynn, 2000/2003). This basin, whose head lies in northern Mexico, hosts a major
US-Mexico migratory bird fly-way. A desire to preserve the surface water in the San Pedro
River led to the creation of the San Pedro National Riparian Conservation Area in 1988. To
preserve the surface water, one must know something about the aquifer underlying it. On the
American side of the basin, time-domain airborne geophysical methods were used to map the
relatively conductive groundwater typical of an arid region to depths of 150 - 400 meters in the
absence of human cultural interference. In order to better understand the hydrology of the basin
as a whole, geophysical surveying has been extended southward into the Sonoran San Pedro
Valley of northern Mexico. An airborne magnetic survey in northern Mexico has been processed
to depth-to-magnetic-source, and concatenated to a magnetic data set from southern Arizona to
show depth to basement for the San Pedro Valley drainage. We then conducted a scalar Audio-
MagneTotelluric (AMT) survey over four different lines in the Sonoran San Pedro basin, and
processed these data using a smooth-model inversion to conductivity-vs-depth profiles. As we
view the conductivity inversion results, we are in fact visualizing the highly conductive water
typical of an arid climate - in effect, we broadly image the saturated sediments. We then used an
analytic signal depth-to-source algorithm on magnetic data along the same profiles to constrain
the AMT inversion. The result is a unique set of geophysical profiles that clearly show basement
structure beneath the Sonoran San Pedro basin to depths of up to 800 meters. These constrained
profiles help resolve basement controls on groundwater flow in northern Mexico leading to the
US frontier. It is impossible to understand the groundwater regime except in the context of the
volcanic and sedimentary history of the region, and neither the geology nor the geophysics can
be carried out independently of the other, but the whole together contribute substantially more
than the parts.
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Aster Imagery And Aeromagnetic Data - Powerful Tools To Aid Reconnaissance Geologic Mapping Of The Sierra San José Mountain Range, Northern Sonora State, Mexico
Authors J.C. Wynn, J.L. Mars, Floyd Gray, A.P. Schultz, F.A. Maldonado, F.A. Villaseñor and L.M. Brady-NormanAeromagnetic and Advanced Spaceborne Thermal Emission and Reflection Radiometer
(ASTER) data are currently being used to assist in geologic mapping of the Sierra San José
region in the Sonoran San Pedro River basin. Lithologic contacts have also been mapped using
Euler deconvolution of aeromagnetic data. A lithologic classification map consisting of quartzfeldspar,
clay-muscovite-sericite, and carbonate was produced using thresholded match filter
ASTER data and relative band depth absorption analysis (RBD). A minimum noise transform
(MNF) false color composite image was used to map lithologic units. A false color composite
image of ASTER bands 1 (blue), 2 (green) and 3 (red) was also used to determine the extent of
vegetation and assist in mapping structural features, although most of the structural features
could be mapped using high altitude stereo pair imagery. To date, field studies indicate that
ASTER data have successfully mapped carbonates, sericite, and muscovite and with lesser
success have also helped characterize quartz-rich rocks. In addition, our field studies, along with
ASTER and Landsat data, have confirmed lithologic contacts at the surface mapped by Euler
deconvolution of the aeromag.
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A Direct Comparison Of Airborne And Ground Magnetometer Array Data Collected Over A Seeded Uxo Site
Authors David J. Wright, J.R. McDonald, Nagi Khadr and H.H. NelsonThe airborne MTADS adjunct, a helicopter-mounted magnetometer array, was recently evaluated
in a demonstration on 1,685 acres of a live-fire range previously used for ground-fired projectiles at the
Badlands Bombing Range in South Dakota. Performance was evaluated by blind-seeding a ten-acre site
with inert 105-mm, 155-mm, and 8-in projectiles. The seeded test area, and an additional 100 acres of
the airborne survey area, were also surveyed using the vehicular MTADS magnetometer array. Based
upon the vehicular and airborne surveys, 26 inert projectiles, and an additional 9 HE-filled projectile
duds were recovered in this area. The airborne survey system detected all the projectiles identified in the
vehicular survey. These data provide a unique opportunity for both qualitative and quantitative
comparison of the performance of these systems. The two data sets differ with respect to survey altitude
above ground and data sample density. The effect of the altitude difference on the character of target
anomalies with respect to amplitude and width are immediately apparent. Relative production rates,
location accuracies, identification and classification capabilities of the two systems are compared.
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Modeling Aquifer Structures With Airborne Em In The Boteti Area, Botswana
Authors Daniel Sattel and Lesego KgotlhangAs part of a project by the Department of Water Affairs, Botswana to evaluate groundwater
resources in the Boteti River area in Botswana airborne EM data were acquired with the TEMPEST
system with the objective to map prospective lithologies and structures containing freshwater aquifers.
The project area is characterized by a palaeolake system bordered to the south by elevated terrain. Most
of the lower-lying area is covered by a thick layer of Kalahari Beds with saline groundwater generally
situated less than 20 m below surface. Elevated terrain to the south have Karoo sediments outcropping
in places.
In the north of the project area AEM data were acquired across palaeolake terrain to locate fresh
water zones associated with recharge pans above the saline water table. The derived conductivity
structure outlines several shallow, resistive zones that appear to correspond to dry sand; fresh water
pockets above the saline water were not located by the boreholes drilled. Further, the AEM results
indicate the outline of a brackish to saline aquifer at a depth of 30 m beneath a clay layer. Preliminary
borehole data from this aquifer indicate high yields (20-64 m3/h) with TDS values in the range 1550-
2700 mg/l. A comparison of borehole information with the modeled conductivity structure indicates the
conductivities to be dominated by clay content, water saturation and salinity.
In the southeast of the project area AEM data were acquired across elevated terrain to delineate
fresh sandstones sandwiched in-between dry alluvium or basalt and mudstone. The comparison of
airborne EM and magnetic data with drillhole information indicates that the basalts are characterized by
very low conductivities and a strong magnetic response. The underlying sand- and mudstones have
intermediate and high conductivities, respectively, and are characterized by horst-graben structures,
reflected in the magnetic data and conductivity-depth sections. Resistivity isosurfaces generated from
the 3D conductivity data facilitate the spatial appreciation of the geometry of the interpreted structures.
Favorable locations for freshwater exploitation interpreted from the TEMPEST data include a shear zone
and sandstone units fully preserved beneath basalt caps. Preliminary borehole data indicate yields of 15-
54 m3/h of brackish to saline water (TDS 1000-3000 mg/l) in the depth range 56-180 m with the highest
yield obtained from fractured sandstone at 180 m depth. The results indicate the conductivities of Karoo
lithologies to be dominated by clay content, water salinity and, locally, by the presence of quartz.
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Practical Inversions For Helicopter Electromagnetic Data
By Greg HodgesDiscrete-layer inversions are the most accurate method of converting geophysical
data to a geoelectrical model of the earth. Smooth-model inversions and transforms
(Occam’s inversions and CDI sections) are more robust to execute, but only discretelayer
inversions can provide direct measurement of depth to a target layer, which is
necessary for engineering purposes. However, there can be a problem with non-unique
solutions – there may be two or more solutions that fit the data within the specified
accuracy. Also, discrete-layer inversions tend to be model specific. They generally use
a constant number of layers, similar conductivity contrast for the starting model, etc.
This can present a problem when the geological model changes within a data set,
changing the conditions or dropping data from high signal down to zero, for example.
An inversion process with built-in geological and geophysical “intelligence” can
overcome many of these limitations. Input data are weighted based on the signal level.
Questionable data, or data clearly influenced by non-target effects (e.g. power lines) are
rejected. Existing data, such as drill holes, are used to generate the best possible starting
model and the inversion process constrained to honour these data. Known geophysical
parameters, such as the conductivity of bedrock, or conductivity of a water layer, can be
fixed. Any of these factors can change across a data set or region, and the inversion will
adjust itself to match the changes.
Layer extraction algorithms have been developed to measure the depth to specific
layers from smooth sections, or to provide starting models from smoothed sections for
discrete-layer inversions.
This “intelligent” inversion process was used to generate depth-to-bedrock maps
over a sink-hole where the overburden changed from conductive clay to resistive sand.
Drill and seismic information was used to help generate the starting model for each data
point, and the inversion was constrained when close to these data points. Magnetically
permeable geology and cultural interference were identified, and the input data were
adjusted to minimize the effects of these non-conductivity effects.
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Geophysical Investigations In Support Of Archeological Studies At The Fredericksburg Civil War Battleground
Authors William Frangos and Clarence R. GeierGeophysical work at the Fredericksburg Battlefield site of the Fredericksburg and
Spotsylvania National Military Park has assisted in directing archeological studies
undertaken in preparation for restoration work. Extensive ground penetrating radar
(GPR) surveying has helped pinpoint infantry trenches and artillery emplacements, as
well as locating long disappeared farm buildings on the site. Data were gathered on a
series of grids organized around areas of archeological interest using 250, 500, and 1,000
MHz antennae. A number of features were identified and subsequently excavated; all
were verified and several proved to be of Civil War relevance.
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Use Of Precision Mapping And Multiple Geophysical Methods At The Historic Reese Cemetery In Muncie, Indiana
Authors Gregory B. Byer and John A. MundellMany privately owned historical cemeteries are found throughout the countryside in the United
States. One such cemetery, known as the Reese Cemetery, dates back to the pioneer settlement of
Indiana in the early 1800’s, and is located near Muncie, Indiana. As is often the case, documentation of
the individual graves is often incomplete or even non-existent, and as a result many of the oldest graves
become lost because they are either completely unmarked or have illegible or broken headstones. The
cemetery association responsible for the care of the Reese Cemetery determined that it was necessary to
map the entire cemetery and find as much out as practical about the locations of unmarked graves.
Because of strict regulations regarding the disturbance of historic cemeteries, it was deemed necessary
to locate the unmarked graves, buried headstones, etc. using non-intrusive methods whenever possible.
In July 2002, a detailed mapping project was performed on this one-acre (0.4-hectare) cemetery.
Precision survey mapping of topography and individual headstones, written and photographic
documentation of each headstone, and the completion of a geophysical survey were all performed to
provide a lasting record of the cemetery. The techniques used included ground penetrating radar, terrain
conductivity, and metal detection. This approach provided value both in terms of preserving the identity
and locations of the graves and in offering insight into the locations of some unmarked graves. Ground
penetrating radar amplitude mapping appears to have provided the single greatest insight and level of
detail pertaining both to graves containing metallic objects (vaults and caskets) and graves retaining
little more than disrupted soil strata and human remains.
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Geophysical Investigations At The Archaeological Site Of Fort Saint Joseph, Niles, Mi
Authors Laura A. Sherrod, Daniel Lynch and William SauckFort St. Joseph in SW Michigan was utilized as a trading post from 1691 until 1781. The exact
location of the fort had been unknown for over a century until archaeological investigations during the
spring of 1998 recovered numerous 18th Century artifacts along the southeast bank of the St. Joseph
River. The site is located between an abandoned mid-20th Century landfill and the St. Joseph River.
Shallow geology is comprised of an organic rich surface layer of 0.3m overlying a 19th century silty
gray plow zone. Magnetic gradiometer, ground-penetrating radar (GPR), electrical resistivity, and
electromagnetic induction (EMI) surveys were employed in the spring of 2002 to guide archaeological
excavations. The results of these applications are very encouraging. Intact cultural deposits were
recorded from depths ranging between 0.35m and 1.80m. All but one of the five archaeological
excavation units opened under the guidance of the geophysical surveys yielded physical evidence of the
fort. Cultural deposits associated with the geophysical anomalies include burnt pit features, hearth
stones, and a charcoal layer associated with a burnt structure. There are numerous locations on site that
require further investigation.
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Ground Penetrating Radar In The Search For Ancient Helike, Greece
Authors Doria L. Kutrubes, Steven Soter, Dora Katsonopoulou and Ariane HeinzThe coastal city of Helike in Greece was destroyed by an earthquake in 373 BC and submerged in a
lagoon. The site was later silted over and reoccupied. Surveys in the area using ground penetrating radar
detected targets of potential archaeological interest. Exploratory trenches to investigate some targets
uncovered Byzantine, Roman and Hellenistic structures. However, the ruins of Classical and older
settlements, at 3 m depth and deeper, are probably beyond the range of radar in this area, due to the
prevalence ofconductingclay-rich lagoonalsediments.Herewediscuss theradar results,and briefly note
the identification of some radar targets by excavations.
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Dnapl Detection Sensitivity Of A High-Resolution Directional Borehole Radar
Authors Craig W. Moulton and David L. WrightThe U.S. Geological Survey has developed a directional borehole radar system (DBOR) for
high-resolution imaging close to borehole wells. We have conducted physical and numerical modeling
to assess the ability of this radar to detect and map the location of dense non-aqueous phase liquids
(DNAPLs) near a borehole.
Physical modeling was conducted in a water-saturated silica sand-filled tank. Model targets
included silica sand saturated with mineral oil and a paraffin cylinder. The oil-sand mixtures were
sealed in plastic bags of the desired shape and placed in the sand at various distances and orientations
relative to the borehole. Physical modeling showed that the paraffin and oil-sand rectangular targets and
the thick wedge against the borehole imaged well. The thick and thin wedges away from the borehole
were more difficult to discern.
Finite-difference time-domain (FDTD) numerical modeling was done for some geometries and
electrical properties that were physically modeled and will also include additional cases in the future.
Results indicate that the radar system will be able to detect and map the location of small amounts of
DNAPL in a controlled spill experiment to be conducted by the U.S. Environmental Protection Agency.
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Effects Of Borehole Fill On Resistivity Investigations
Authors Robin E. Nimmer, James L. Osiensky and Andrew M. BinleyDrilled boreholes generally are the only feasible means to access the subsurface for the
emplacement of downhole electrodes for most hole-hole and hole-surface resistivity
experiments. However, the very existence of the borehole itself creates the potential for
significant noise due to the inevitable conductivity contrast that develops between the borehole
walls and the formation. Borehole effects develop whenever a current source is placed in a
drilled borehole. Borehole geometries may range from nearly perfect cylinders to highly,
irregular, rugose holes in consolidated rock, to relatively minor, collapsed, disturbed zones in
caving sediments. Boreholes in non-caving formations generally are filled with artificial
materials to afford crucial, electrical continuity between downhole electrodes and the borehole
walls. Filled boreholes form cylindrically shaped heterogeneities that create significant noise
due to preferential current flow up and down the conductive columns. Selected conditions are
simulated with a finite difference model to illustrate the significance of borehole effects on holehole
and hole-surface mise-à-la-masse electrical potentials near a current electrode. Preliminary
modeled results of borehole effects for electrical resistance tomography (ERT) suggest the
existence of an inhomogeneity between the two boreholes which may cause misinterpretation of
the data, depending on the resistivity contrast of the borehole fill and earth material.
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The Value Of Borehole -To-Surface Information In Near-Surface Crosswell Seismic Tomography
Authors Geoff J.M. Moret and Michael D. KnollDetailed information about the spatial distribution of subsurface properties is important in
many fields. One method that can image the seismic velocity structure of the shallow
subsurface is crosswell seismic tomography. By including rays traveling from the
boreholes to the surface, the angular coverage of crosswell tomograms can be
significantly improved. We investigated the effects of these borehole-to-surface rays on
synthetic and field data. The tests on synthetic data showed that including borehole-tosurface
information did not significantly change the tomogram’s resolution.
Tomographic inversion of a field data set collected at the Boise Hydrogeophysical
Research Site, however, showed that including borehole-to-surface information improves
a tomogram’s ability to image layer boundaries, and improves the velocity estimates for
slow layers. The tomogram generated using the crosswell and borehole-to-surface
information is consistent with the previously interpreted hydrostratigraphic units at the
site.
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Continuous Full-Wave Sonic Logging In A Dry Hole
Authors Toshiyuki Kurahashi and Tomio InazakiThis paper describes a new concept of continuous full-wave sonic logging (FWS) in a dry hole. The
continuous FWS in a tube provides physical properties at narrow intervals under the dry condition. The
method uses a synthetic rubber tube that enables continuous FWS to be conducted in a dry hole, by
sealing the dry hole wall and preventing water leakage. The addition of water made the tube expand and
contact firmly to the hole wall. FWS collects sonic signals as waveforms through the tube, and
successively provides a larger quantity of higher resolution data than conventional downhole
measurement under the dry condition by receiving sonic signals more precisely and effectively.
Although the method could identify individual fractures in bedrock in all hazards, it cannot be used at a
low velocity part of less than 1.5 km/sec in water due to the structure of the tube.
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Borehole Radar Attenuation-Difference Tomography During The Tracer/Time-Lapse Test At The Boise Hydrogeophysical Research Site
More LessA tracer test and time-lapse radar imaging experiment was conducted at the Boise
Hydrogeophysical Research Site to investigate the utility of crosswell radar in imaging an electrically
conductive tracer plume. A multilevel water sampling system down gradient from the tracer injection
well and in the radar imaging plane was used to collect detailed, 1-dimensional, fluid electrical
conductivity data during the tracer test. We compare the spatial and temporal position and concentration
variations of the plume as indicated by the fluid conductivity data to those suggested by radar level run
attenuation differences, shot-receiver attenuation difference crossplots, and an attenuation-difference
tomogram. We find that attenuation differences generally correlate well with changes in fluid
conductivity. Where correlations are not so strong, the discrepancies can be explained by the difference
in support volumes for the radar and chemistry measurements, and also by regularization of the radar
tomogram. Our results indicate that crosswell radar imaging coupled with hydrologic tracer testing can
provide useful information about subsurface fluid flow and mass transport in complex fluvial aquifers.
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Tracer/Time-Lapse Radar Imaging Test At The Boise Hydrogeophysical Research Site
A combined tracer and time-lapse radar imaging experiment was conducted in the unconfined
coarse fluvial aquifer at the Boise Hydrogeophysical Research Site in August, 2001. Two tracers
(bromide and uranine) were injected to form a plume over a 4-m interval that spanned the contact
between hydrostratigraphic units with contrasting permeability. The tracer plume traveled 6.9 m to well
B6, passing through well A1 instrumented with 20 sampling zones over a 5-m interval that spanned the
injection interval. Radar tomographic data were collected periodically on cross-sectional and
longitudinal planes, two of which passed through well A1 for quantitative calibration of radar
attenuation tomograms in terms of solute concentration. Pre-test three-dimensional modeling was used
to provide estimates of bromide concentration distributions under a variety of scenarios to help optimize
(a) radar responses in tomographic planes, and (b) pumping rate from B6 to minimize influence on the
plume while ensuring plume passage through A1 and complete breakthrough in two weeks. Bromide
breakthrough occurred first and with greatest concentration in the higher permeability unit as expected.
Time-lapse cross-hole radar data show plume-related differences in expected regions with time-lapse
level runs and time-lapse attenuation-difference tomograms. Uranine breakthrough was significantly
diminished and delayed relative to bromide; follow-up experiments suggest biological activity
associated with cottonwood roots caused the non-conservative uranine behavior.
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Investigations Into Contaminant Plumes: Using Aem Profiling For Groundwater Modeling Input
More LessIn order to realize the vision for the environment contained in the South African Constitution,
national environmental policy processes had to be established to ensure regular collection and updating
of the environmental data needed for effective management, monitoring, regulation, enforcement and
participation. Information systems on chemical hazards and toxic releases needed to be set up to help
co-ordinate the administration of an integrated pollution control and waste management policy.
Moreover, within this policy, open disclosure, accessibility and effective dissemination of environmental
data and information had to be ensured.
This paper presents an example of some of the pro-active work done using an integrated
information systems approach that is in line with research and development into establishing such an
environmental policy. Contaminant pollution plumes due to acid mine drainage from tailings storage
facilities were defined with high resolution airborne electromagnetic (AEM) profiling and traced out by
digitizing subsurface contact zones from conductivity depth imagery in a 3D visualization environment.
In combination with various spatial data sets derived plume characteristics were used as input in creating
3D groundwater models.
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Study Of Oil Pollution In Airports With Resistivity Sounding
In this work we consider the resistivity sounding method based on tomograpic technoloqy applied for mapping contamination of geological environment with aviation fuel in two airports in Mexico. Vertical electrical sounding allows to map polluted zone in plan and with depth and to estimate qualitatively the contamination grade. The resistivity survey was supplemented by drilling and chemical analysis of oil concentration. The data of direct and indirect measurements have good correspondence with each other.
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Induced Polarization (Ip) Measurements Of Soils From An Aged Hydrocarbon Contaminated Site
Authors Gamal Z. Abdel Aal, Estella A. Atekwana, Lee D. Slater and Craig UlrichProducts of hydrocarbon biodegradation are organic acids, CO2, and water. Organic acids and
carbonic acids formed from CO2 enhance soil dissolution. Therefore, biodegradation results in
enrichment of ions, increasing electrolyte concentration and changing fluid chemistry. Further,
dissolution is expected to induce physical changes in the surface area of soil particles, potentially
impacting their electrical response. To test the above hypothesis, induced polarization (IP)
measurements in the frequency range (0.1-1000 Hz) were made on samples from an aged hydrocarbon
contaminated site where intrinsic bioremediation occurs.
Results from the saturated zone indicate that real conductivity (σ') is unable to distinguish
contaminated from uncontaminated samples. However, using imaginary conductivity (σ"), contaminated
samples are distinguished from uncontaminated samples by their higher magnitudes. Further, the
dissolved phase samples cluster in the intermediate σ", whereas residual phase samples show highest σ".
Although σ' results from the unsaturated zone are complicated by variable soil moisture content, σ"
shows similar patterns as for the saturated zone. We infer from the strong response exhibited by residual
phase samples that biodegradation is most active in this zone. Scanning electron microscope images
from the depth interval of residual hydrocarbon phase samples show that this zone had extensive etching
and pitting of quartz and feldspar grains. It is possible that etching and pitting results in an increase in
the surface area of the mineral grains, producing the strong polarization observed for the residual phase
samples. These results suggest that IP is potentially a better indicator of contamination and
biodegradation than DC resistivity. However, more laboratory and field investigations are required to
better understand the effect of biodegradation processes on the measured SIP response and the surface
conduction mechanism.
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Preliminary Characterization Of A Napl-Contaminated Site Using Borehole Geophysical Techniques
We present preliminary results from an on-going geophysical investigation of the former DOE Pinellas
site, a site with confirmed non-aqueous phase liquid (NAPL) contamination. Our eventual goal
is the effective use of integrated crosswell geophysical methods, specifically seismic and radar tomography,
to remotely detect zones of high NAPL saturation. In this paper we discuss our motivation
and early efforts at using a combination of seismic and radar information to understand site geology
and possible contaminant signatures. We also present our current approach to consistent
acquisition, preprocessing, tomographic inversion, and interpretation of joint seismic/radar profiles.
Although direct geophysical evidence of NAPL pools has not yet been obtained, several regions of
anomalous seismic attenuation were detected. These attenuating regions could not be explained
by borehole effects or lithology and may be caused by regions of partial gas or NAPL saturation.
Possible gas sources include biogenic production from contaminated regions and side-effects from
previous remediation activities. Continuing research at the Pinellas site will focus on constraining
the mechanism responsible for the observed seismic attenuation, developing a more complete model
of site soil properties, and applying more quantitative approaches to the integration and analysis
of our seismic and radar images.
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The Use Of Ground Penetrating Radar For Site Characterization At Hanford
Authors Rosemary Knight, James Irving, Eugene Freeman and Paulette TercierAccurate information is needed about the hydrogeologic properties at the Department of Energy
Hanford site in southeastern Washington. This information is required in order to model the fate and
transport of subsurface contaminants. Ground penetrating radar (GPR) data were collected in two areas
at Hanford to assess the potential usefulness of GPR for site characterization. The sediments at Hanford
are such that we found the penetration depth of the radar measurement to be limited to approximately 10
m, in most locations, when using 100 MHz antennas. This means that GPR can only be used to obtain
information about the sediments in the top of the vadose zone.
One survey objective involved the use of GPR to locate clastic dikes, which can have a large
impact on contaminant transport. The dikes were clearly imaged as diffraction hyperbolae in the GPR
data. The second objective was to test the use of GPR to describe the spatial variability in water content.
Geostatistical analysis of GPR data from a test site yielded a correlation length comparable to that
obtained from analysis of neutron probe data from the site. This result suggests that GPR data can be
used to quantify the subsurface distribution in water content at Hanford.
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