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9th EEGS Symposium on the Application of Geophysics to Engineering and Environmental Problems
- Conference date: 28 Apr 1996 - 02 May 1996
- Location: Keystone, Colorado, USA
- Published: 28 April 1996
101 - 134 of 134 results
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The Finland Connection
More LessI thought it might be appropriate to provide some background on why we are
having a contingent of geophysicists from Finland at this meeting. The initial contact
was made at the 3rd International Conference on GPR, which was held at Lakewood,
Colorado in 1990. Discussions at that meeting indicated a willingness to provide a true
international aspect to the meetings by having the next one (scheduled for 1992) outside
the United States.
We received two European invitations, one fii and one tentative, and another
tentative invitation from Australia. Discussions about where to hold the 1992 meeting
continued after the sessions, and I found myself in a pub in Lakewood with Mary
Collins, from the University of Florida, and Pauli H%nninen, from the Geological Survey
of Finland. Pauli had been using GPR in mapping peatlands, and the Finland Geological
Survey had a number of GPR units. I was recovering my composure after swallowing
the lime wedge from a bottle of Corona, and Mary and I simultaneously said to Pauli
“Why not Finland”? Pauli gave it a little thought, pounded the table and said “Yes, why
not”?
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Environmental Geoi’Hysics In Finland: State Of The Art
More LessSoil and groundwater contamination has become one of the foremost environmental problems in all industrialized
countries. A recent survey in Finland resulted in a national soil-hazard database of about ten thousand suspect sites.
Although the most problematic sites have been identified, international experiences indicate that further contaminated sites
are likely to be revealed. The biggest groups of problem sites are sawmills and wood impregnation factories, landfills,
scrap-metal and repair shops and gasoline stations, which in total make more than half of the known problem sites. Over
2,000 hazardous sites are located in groundwater reservoir areas, and the most urgent need for remediation is estimated to
involve at least 250 sites with remediation costs totalling US.% 1.3 billion. Although adequate legislation is in effect for
currently existing operators, the hostless and abandoned, contaminated soil sites remain as an unsolved problem.
The most widely applied geophysical techniques in this context in Finland are the seismic refraction method, ground
penetrating radar and earth resistivity/conductivity measurements. Depending on the type of survey problem at hand, even
gravity and magnetic methods can provide useful information. In terms of specific survey problems, the scope of
geophysical techniques has seen a remarkable widening in the last ten years. Of special importance in Finland are the
nuclear waste repository investigations, which have given rise to new survey methods, instrumentation and data
interpretation. The synergistic benefits to environmental surveys from new contributions in mining geophysics should not
be underestimated either. In Finland good examples of this synergy are the spectral induced polarization method, the EM
frequency-sounding method, and an operational method (since early 1980’s) for the measurement of snow-water equivalent
for water reservoir optimization. Currently small but challenging fields of geophysical application are archaeological
surveys and sea-ice thickness determinations with airborne EM techniques, both of which show good promise of increased
importance in the near future.
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Geophysical Surveys At The Oitti Dnapl Spill Site, Southern Finland
In the 1950’s and 1960’s about 10,000 liters of dry cleaning solvents from a dry cleaning establishment near the town
center at Oitti, southern Finland were disposed of in a well and in pits. The groundwater was found to be contaminated in
1992 when a regional groundwater quality survey was done in the region. Among the solvents are trichloroethylene and
tetrachloroethylene. Although the major part of the total amount of solvents were deposited in a condensed form into a
landfill, the storage sites at the dry cleaning establishment became injection wells by default, because of the permeable
nature of the underlying strata (porous sand and gravel, typical of the glacial esker formation overlying the area). The
groundwater has been found to be contaminated within a total area of several square kilometres and the amount of
polluted groundwater in the esker formation is estimated to be 8 million cubic metres. The main water supply well for
the town became contaminated and had to be closed because of high levels of tri- and tetrachloroethylene.
Since 1992, the spill site and the whole esker area have been subject to diverse studies aiming at the delineation of the
polluted area and at the planning of the remediation methods. In 1995 it was decided to perform geophysical surveys at
the site, with two main objectives in mind: first, to delineate the unknown bedrock topography underlying the esker
formation, and secondly, to map variations in the groundwater depth in the vicinity of the establishment. This
information is essential in the delineation of the probable contaminant flow directions. The main geophysical methods
applied were ground penetrating radar and seismic refraction sounding. To a lesser extent, earth resistivity sounding and
inductive sounding (EM3 1) techniques were also applied. On the basis of seismic refraction surveys the depth to bedrock
surface could be determined on the flanks of the esker and results from the ground penetrating radar surveys gave
information about the groundwater depth and overburden quality variations on and around the spill site. A geostatistical
analysis, based on the well-water analyses of the contaminants, proved to be a useful tool in the delineation of the
probable contaminant flow directions.
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Airboiwe Geophysics In Mapping Contaminant Plumes From Landfills
Authors Tarmo Jokinen and Erkki LanneGeological Survey of Finland (GTK) has carried out low altitude airborne geophysical surveys in Finland since
1972. Today 80 % of the country has been measured. The following systems are in use: magnetic, gamma
radiation and vertical coplanar EM and VLF electromagnetic. Airborne geophysics is a fast method to map landfill
areas at regional scale.
A successful example in Finland is the airborne detection of leakage from Rovaniemi landfill, in Northern Finland.
A clear quadrature electromagnetic anomaly (AEM) associated with the landfill was found. The resistivity of
the anomaly source is less than 20 Qm, whereas the surrounding resistivity is 100-300 Qm. In order to explain
the AEM-anomaly sources ground geophysical studies were conducted. Combining geophysical results with
geochemical analyses from peat and ground water, the contaminant plume has been confirmed.
GTK done airborne measurements at &nmhsuo, the large municipal landfill of Helsinki region. The landfill
area has been mapped in national airborne mapping program (1984) before the operation started (1987). The
second survey was done using tighter flight line spacing. Magnetic anomalies indicated the metallic waste and
human constructions. The attenuation of the gamma radiation revealed wet areas of the landfill. Comparing the
old and new AEM results it was possible to detect accurately and reliably weak conductivity anomaly variations
around the landfill area but there are no evidence of significant leakages.
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Mapping Groundwater Areas With Geophysical Methods
More LessThe application of using geophysical methods to mapping large aquifers has been under expanding interest
during the past few years in Finland. Applying conventional geophysical methods to unconventional targets has
given good results in terms of totally new information and even changed some old presumptions.
The methodology used in several glaciofluvial formations in southwestern Finland has begun with the
interpretation of bedrock structure by locating the fractured zones from low-altitude airborne geophysical and
digital elevation data. After that some gravity profile measurements are made across these fractures to estimate
the thickness of overburden. Refraction seismic soundings and ground penetrating radar are occasionally used
to ensure the bedrock topography and to help estimating in-situ densities.
Combining all the available material (geophysical data, information of groundwater levels) a three-dimensional
estimation of the area is obtained. This is used to conceive decisions of the groundwater storage and flow
capacity of the area surveyed. That has been one part in elaborating regional plan for eskers.
Most cases have been made in co-operation with the Southwest Finland Regional Environment Centre, the
Regional council of Southwest Finland, the Regional Council of Satakunta, Geological Survey of Finland and
industrial plants and communities which take their water from the eskers.
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Mapping Oil Contamination In Glacial Sediments By The Spectral Induced Polarization Method
Authors H. Soininen and H. VanhalaApplication of the spectral induced polarization (SIP) method to mapping oil contaminated soils in glacial
environments has been studied by laboratory and field measurements and by numerical modeling. The
laboratory measurements comprise clean and contaminated sediments and biogenic materials, as well as bedrock
samples. The oils used in the study were clean mineral oil and waste oil. The field tests were carried out at
waste sites in Finland and Estonia.
In the laboratory measurements oils were observed to reduce the resistivity and phase shift immediately after
contamination. After a few days or weeks, however, the phase shift increased and was occasionally higher than
the phase shift in the clean samples. Many contaminated samples from the waste sites had higher phase shifts
and lower resistivities compared to similar uncontaminated samples. The field profiles measured over oil
contaminated soils also showed increased IP effects and decreased resistivities.
The results suggest that detection of oil contamination is possible in the case of homogeneous sand and till
formations. However, layers of silt, fine sand, clay, and biogenic materials may generare phase spectra
resembling those caused by oil contaminated sand and till. Changes in the phase spectra of soils with time can
also be an indication of contamination.
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Monitoring The Integrity Of Liner Construction Using Induced Polarization
More LessAn application of the induced polarization (IP) technique for verification of the integrity of liners installed to
road ditches is considered. Use of the IP technique for leak-detection is based on the changes that saltwater
causes in resistivity and in IP effect in the sediments underlaying a leaking liner. This study is based on
laboratory spectral IP measurements of soil samples contaminated by salt, samples taken at a salt contaminated
road section, and field IP measurements.
IP effect decreases with increasing salt concentration of water, but is fairly independent on the water content
of sediment. This gives a possibility to discriminate the effects caused by the salt from the effects caused by
the changing water content. The IP effect depends - in addition to electrolyte composition - on the grain size
distribution and the mineral composition of the sediment: Fine and medium grained sands show phase shifts
of 10 - 40 mrad at low and medium frequencies (0.01 - 100 Hz), but coarse sand and gravel are practically
unpolarizable. That restricts the use of the IP technique to areas having silt, fine sand or medium sand
sediments.
The heterogeneities in sediment formations, such as a gravel layer with low IP in a sand formation, make the
IP effect an uncertain quantity in detecting a saltwater leak. Monitoring the temporal changes in IP effect
eliminates, however, the the uncertainty due to heterogenous sediments, and seems to make the detection of a
saltwater leak feasible.
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Integration Of Radar, Terrain Conductivity And Radiometric Data In Forest Soil Classification In Lapland
Authors Raimo Sutinen and Pekka HänninenScats pine (Pinus Silvestris) has been favoured in forest management in Lapland for the past four decades. Failures
in the artificial pine regeneration, however, has been occurred especially on previous Norway spruce (Piceu dies)
dominated forests. The present results demonstrate that high water content is typical to tills derived from finegrained
schists of the Central Lapland Greenstone Belt. These tills are typically covered by spruce. Sandy tills,
typical to granitoid areas, tend to be low in water content and are occupied by pine. The in situ dielectric time
domain reflectometry (TDR) radar surface arrival detection (RSAD) measurements provide data on moisture
variations of till soils and thus help forest regeneration at a compartment level. The terrain EM31 conductivity
surveys, along with dielectric measurements, provide necessary data on stratigraphy. A consistent trend between
the terrestial dielectric properties and gamma radiation features in till soils suggests that airborne gamma radiation
data provide an effective tool to regionally classify moisture patterns of forest soils.
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Groundwater Salinity Model Based On Deep Electromagnetic Soundings
Authors Eero Heikkinen, Pauli Saksa, Paula Ruotsalainen, Henry Ahokas, Jorma Nummela and Markku PaananenThis paper describes the compilation of a volumetric model of the salinity distribution of the bedrock groundwaters
in the Olkiluoto island at south-west coast of Finland. The study belongs to the power companies’ programme of
detailed site investigations for disposal of high-level nuclear waste into crystalline bedrock in Finland. The model
was compiled from the interpretations of the geophysical electrical and electromagnetic soundings, which were combined
with hydrogeochemical results to obtain the classification basis for bedrock resistivities. The electromagnetic
interpretations were combined into cross-sections, transferred to a CAD based system and further combined to a 3-D
model for storage, visualisation and further development. Some difficulties occurred when combining the sounding
results with each other and with hydrogeochemical results. Also major simplifications of the observations were necessary.
The model will be used for various tasks in the detailed site investigations.
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Application Of Shallow Vertical Seismic Profiles (Vsp) In Interpreting Surface Seismic Dat
Authors Scott Allison and David SchieckThe vertical seismic profile (VSP) is an efficient and accurate method of tying known geology from a borehole given
in depth to the surface seismics ection presentedin time. The VSP enablest he geophysicistt o directly observet he
effects of the geology on the seismic wavelet generated at the surface. At each geological interface the resulting
transmissionr,e flection, conversion and attenuationc haracteristic of the seismicw avelet can be observed directly
from a VSP. Much like common depth point (CDP) reflection techniques VSP’s have been adapted from advances
in petroleum exploration.
VSP data follows a similar processings equenceto CDP data with stepss uch asg eometiy, first break picks,
deconvolution, and stacking. VSP data also has exclusive processing steps such as removal of down going waves
and enhancing upgoing waves. WELLPRO, licensed by GENIX Technology Ltd., was used to process the VSP data.
Displaying VSP data for interpretation includesm ergingw ell logs (measuredin depth) andt he processedV SP along
with a synthetic seismogram into a composite known as an L-plot. VSP data collected by the Geologic Survey of
Canada (GSC) as part of a regional hydrogeological investigation of the Oak Ridges Moraine, north of Toronto,
Ontario, are used as examples in this paper. Synthetic traces were generated by doing a 140 ms corridor stack of the
processedV SP andc an be directly correlated with surfaces eismicd ata acquiredn earby. The VSP verified the
existence of three reflectors at approximate depths of 45 metres, 68 metres, and 88 metres and also produced a
velocity profile based on depth and one-way travel time, This enables an exact time versus depth interpretation of the
surface seismic data at this location.
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Mapping Of Shallow Karstic Aquifers By Electromagnetic Method
More LessEarth resistivities are mapped by an EM-34 electromagnetic terrain conductivity meter in order to
delineate shallow Pliocene reef system which is associated with the potable water in Collier County, Florida.
Relationships between lithofacies, hydrogeologic properties, and geophysical signature are determined. Sixty
three ground water samples drawn from various depths in the area indicate the presence of a zone of wellflushed,
good quality water associated with coralline facies and a zone of lower permeability and relatively poor
quality water. The primary porosity and diagentic history of the coralline facies give them a distinctive
geophysical signature. This signature is the result of the destruction of the primary porosity, high karstic
porosity, and the presence of good quality water.
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Electromagnetic Soundings, Pseudo-Resistivity Logs And Implications For Porosity And Ground Water Salinity
Authors Melvyn E. Best and Brian J. ToddSixteen electromagnetic (EM) soundings were obtained along the dike on the Fraser River Delta (south of
Vancouver, B.C.) that goes from the B.C. Ferry Terminal near the U.S. border to the mouth of the south arm of the
Fraser River (Canoe Passage). The data were collected using a Geonics time-domain electromagnetic (TDEM) EM-
47 system in the central sounding mode. These data were interpreted using the smooth model inversion option
(Occam inversion) from the TEMIXGL software package of Interpex Limited, Golden, Colorado. The TEMIXGL
smooth model inversion can tit up to 19 layers (thicknesses logarithmically increasing with depth) to the apparent
resistivity versus time data. Once the layer thicknesses are fixed, the inversion computes the best fit for the
resistivity of each layer. The smooth model therefore produces a plot of computed resistivity versus depth, somewhat
similar to a resistivity log. It is not a true resistivity log since thicknesses increase with depth. In other words the
resolution of the sounding decreases with depth; hence we shall call them pseudo-resistivity logs. The pseudoresistivity
logs were compared with 3 resistivity (and gamma) logs within the same area. The agreement between
the pseudo-resistivity logs and the downhole logs is remarkably good. Attempts to relate the 3 downhole logs and
the 16 pseudo-resistivity logs to apparent porosity and ground water salinity using a modified Archie’s Law are under
way. Preliminary results indicate that such a relationship may be possible as long as either the pore water salinity
or the porosity is known. Even so, the relationship must be determined empirically. Once a relationship is
developed for a given area the porosity and salinity versus depth can be obtained cheaply and quickly. Such
information is essential for geotechnical applications and understanding ground water flow.
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Geoenvironmental Characterization Of Mine Tailings Using Piezocone Technology And Surface Electromagnetic Geophysics
Authors Elizabeth A. Brown, Michael P. Davies and R.G. CampanellaThe electronic cone penetration test with pore pressure measurement, commonly referred to as the piezocone test or
CPTU, has been established by the worldwide geotechnical community as the premier stratigraphic logging tool for
most soil conditions. Besides stratigraphic information, the piezocone also provides accurate estimates of key
geotechnical parameters and yields extensive information on the physical groundwater regime. Groundwater
parameters assessed include accurate location of the phreatic surface, determination of in-situ gradients, and
estimates of hydraulic conductivity.
The addition of a resistivity module to the piezocone (RCP’I’U) brings a tool to the industry that provides
geoenvironmental characterization which is accurate, rapid, and economical. for most natural and man-made soil
deposits. However, in a consulting engineering environment, new techniques that allow for more expedient yet
accurate site characterization are constantly sought. One such new technique, the use of non-invasive and portable
electromagnetic instruments such as the GeonicsTM EM3 1 as screening tools to guide more thorough investigations
(RCPTU, soil sampling, monitoring wells) shows promise and is the focus of this study.
Two large sulphide tailings impoundments in Western Canada were sites for comparing the ability of the RCPTU
and EM3 1 to geoenvironmentally characterize the tailings. Given the layered geometry of mine tailings, a forward
modeling of the RCPTU conductivity, to yield a predicted EM31 value, is possible. A consistent correlation
between the predicted and obtained data would support and promote the use of the EM31 as a viable tool for use
where an invasive investigation is not possible, cost effective, or where conductive zones need to be targeted for
RCPTU investigation.
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Use Of Azimuthal Electrical Resistivity Method Used For Determining Joint Orientations In Glacial Tills Around Milwaukee, Wisconsin
Authors Douglas A. Carlson, Robert W. Taylor and Douglas S. CherkauerJoints in unconsolidated material can be the primary avenues
for the flow of both electrical charge and water. Therefore
methods which can efficiently map anisotropic distribution of
electrical pathways should also provide a good indication of
hydraulic anisotropy. In particular, azimuthal resistivity surveys
are useful for observing the joint sets within glacial tills. For
this study, 26 azimuthal resistivity surveys were conducted at 18
sites around Milwaukee, Wisconsin. The sites were usually
characterized Oak Creek Till, 8 surveys, or the Ozaukee Till, 11
surveys. The azimuthal resistivity surveys revealed a systematic
pattern to the trend of joints within tills. The pattern appeared
to be independent of saturation levels. The azimuthal resistivity
survey method detected the difference between the average trend of
joints parallel to the ice flow direction within, the Oak Creek and
Ozaukee Tills. The joint set which is approximately parallel to
the ice flow direction is often the dominant set and is one of the
three joint sets that other workers have observed. These joint
sets are: parallel, perpendicular and conjugate to ice flow
direction. These joint sets may have a major impact on the
hydraulic conductivity of glacial tills. The results of this study
indicate that it is important to consider the trend of joint sets
when modeling ground water flow in till material. As this study's
results indicate, the tills are not electrically isotropic and
hence, may have horizontal anisotropy of hydraulic conductivity.
Azimuthal resistivity surveys appear to be a reliable method
for determining the trend of the dominant joint set within glacial
tills around Milwaukee, Wisconsin. Results compare favorably with
direct observation of joint traces. Furthermore, azimuthal
resistivity surveys are cheaper, faster and easier than aquifer
tests and do not require excavations, which are necessary for
direct observation of joint traces.
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Detectlon And Mapping Of Mine Subsidence Fractures In Glacial Drift Using Surface Electrical Methods
More LessFracturing caused by coal mine subsidence disrupts surface structures, alters drainage
patterns, changes the hydraulic properties of overburden rocks and soil and may
expose shallow aquifers to contamination from surface sources. In this study electrical
resistivity soundings and frequency-domain electromagnetic (EM) surveys were made
before, during and after subsidence of a 40-70 ft section composed of loess, till and
glaciolacustrine deposits in the southern Illinois coal basin. During subsidence,
resistivity increased from approximately 60 to 140 ohm-m in the upper 5 ft along the
south margin of the panel. This “layer” of elevated resistivity may reflect air-filled
fractures penetrating the soil to the water table and shallow drift aquifer. Sounding
lines oriented parallel to fractures measured resistivity increases averaging 90 ohm-m,
whereas those oriented perpendicular to fractures exhibited resistivity increases
averaging 30 ohm-m. After subsidence, resistivity of near-surface materials declined
dramatically (100 ohm-m in some areas), reflecting closure of shallow fractures and
seasonal increases in soil moisture. Postsubsidence EM measurements recorded a
low-conductivity zone over the south panel margin 5 months after subsidence, probably
as a result of fractured soil between depths of 8 to 20 ft. These zones may represent
areas of locally dewatered drift which had not yet received rech,arge from winter
precipitation due to low permeabilities in the overlying clay-rich sections of the
overburden. This experiment illustrates how electrical geophysical methods provide a
viable and cost-effective means to assess fracturing and the hydrogeologic impact of
subsidence on shallow aquifers overlying longwall coal mines.
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A New Approach To In Situ Determination Of The Hydraulic Conductivity
Authors F. Efferssø and K.I. SørensenIncreasing demands for detailed ground water and transport models as remedies to planning of water abstraction
and prevention of ground water pollution have accentuated an integrated application of hydraulic and geophysical
data. This integration requires that relations between hydraulic and geophysical properties becomes better known,
but also that detailed methods become accessible.
In this context, a new method (Injection Method) for detailed in situ determination of apparent hydraulic
conductivity has been developed as an alternative to pumping tests and piezometer tests. The measurements are
carried out in connection with down drilling of a hollow stem auger, where a transducer mounted inside the drilling
stem measures the rise in hydraulic head outside the drilling stem due to injection of a controlled water flow. By
measuring the hydraulic head in situ, the method is expected to provide close estimates of the apparent hydraulic
conductivity.
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Assessing Soil Properties For Site-Specific Agriculture Using Ground Penetrating Radar
Authors R.S. Freeland, L.G. Wells and R.B. DoddGround penetrating radar (GPR) was evaluated by a research team of university and USDA agricultural scientists as a
noninvasive method of measuring soil properties. Near-surface images were obtained using a Geophysical Survey
Systems, Inc.4 (GSSI), SIR@ System-1OA radar mainframe and four GSSI antenna models, which included one GSSI
prototype antenna. Antennas having center frequencies ranging from 300 to 900 MHz were used to scan a soil depth of
~7.5 ft to limestone bedrock. Soil horizon classifications by depth were compared with the radar images.
Calibration techniques, small and large area survey methods, data interpretation, and a field’s identifiable subsurface
features of one farm site detected by GPR are presented. Three-dimensional visualization mapping is also presented that
illustrates the subsurface soil characteristics detected by using GPR at the site. Promising applications of the technology
for site-specific agriculture are presented.
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Electromagnetic Conductivity And Magnetic Surveys For Characterization Of An Abandoned Nuclear Reactor Facility
Authors Arthur J. Fromm, Robert W. Taylor, Kenneth Skinner, Joseph Litehiser and Paul LinleyElectromagnetic conductivity and total field magnetic surveys were conducted over a 14 acre
portion of a site used during the Manhattan Project for nuclear research and plutonium
production. While the facility was decommissioned and abandoned in 1953, there is presently
some concern related to the potential for movement of radioactively contaminated ground water
and sediments through high permeability underground features, such as tunnels or pipes. In
addition, a number of underground storage tanks were left in place when the site was abandoned.
The objectives of the surveys were to enhance the available data base related to the locations of
underground features. The electromagnetic results clearly defined the presence of steam lines,
water mains, electrical utility lines, building foundations, underground storage tanks, and a tunnel.
The magnetic results were ineffective in detecting elongated subsurface features and provided
relatively poor definition of building foundations. However, the magnetic results did detect
disposal areas and reactor remains that were poorly defined by the electromagnetic data. The
differences in the two data sets demonstrate the need for both electromagnetic and magnetic
surveys in site characterization studies.
A combined total of 41 conductivity and magnetic anomalies were identified as potentially
significant. Ten of these anomalies resulted from vegetation covered surface debris. Eight of the
anomalies were spatially associated with documented building foundations or underground utility
lines. The remaining 23 anomalies of unknown origin were excavated to determine the source
material. Thirteen of the excavated anomalies were associated with buried utility features that
could serve as high permeability conduits for ground water or sediment movement. The deepest
of these was a 6 inch water main at a depth of 6 feet. The remainder of the utilities were at depths
of 4 feet or less. Three of the anomalies resulted from underground storage tanks that ranged in
size from 1000 gallons to 5000 gallons. Seven of the anomalies resulted from general waste
disposal areas. The use of historical documentation combined with electromagnetic and magnetic
surveys provided a cost effective method for baseline characterization of the complex
underground features associated with a nuclear reactor facility.
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Application Of Dig-Face Monitoring During Excavation Of A Radioactive Plume
Authors N.E. Josten, R. Gehrke, R. Stanley and K. MacMahanDig-face characterization is a concept for improving the safety and efficiency of hazardous waste retrieval. A
dig-face characterization system consists of onsite hardware for collecting detailed information on the changing
chemical, radiological, and physical conditions in the subsurface during the entire course of a hazardous site
excavation. The dig-face characterization concept originated at the Idaho National Engineering Laboratory and has
been under development there since 1992. During August 1995, a prototype dig-face system was taken to Mound
Laboratory, Ohio, for a first attempt at monitoring a hazardous excavation. Mound Area 7 was the site of historical
disposals of 232Th, 227A c, and assorted debris. The dig-face characterization system was used to monitor a 20-ft x
20-ft x 5-ft-deep excavation aimed at removing 227A~ contaminated soils. Radiological, geophysical, and
topographic sensors were scanned across the excavation dig-face at four successive depths as soil was removed in 1 -ft
to 2-ft lifts. The geophysical and topographic sensors located metallic debris and mapped the dig-face topography in
great detail as the excavation advanced. The radiation sensors produced high-fidelity images showing the location of
radioactive contaminants and clearly identified and delineated separate 232Th and 227A~ plumes. By combining the
radiation data from all four levels, a three-dimensional image of the contamination plumes was developed. The
radiation sensor data indicated that only a small portion of the excavated soil volume was contaminated. The spatial
information produced by the dig-face system was used to direct the excavation activities into the area containing the
227A~ and to evaluate options for handling the separate 232Th plume.
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Em Induction And Magnetic Surveys At Large Landfill Sites Using Gps For Positional Control
Authors Jeffrey B. Hackworth, Thomas M. Kirkpatrick and D. Randal HoltzclawElectromagnetic (EM) induction and magnetic surveys were conducted at two large landfill sites, totaling 76
acres, using a global positioning system (GPS) as the positional control method. The surveys were conducted at
Tinker AFB in Oklahoma, as part of a Phase II Resource Conservation and Recovery Act (RCRA) facility
investigation. The objectives of the investigation were to delineate the boundaries of known landfill trenches and
determine whether features seen in aerial photographs represented previously unidentified trenches. The GPS
method of survey control was chosen rather than the conventional local grid approach because site conditions
included extremely rugged surface topography, thick vegetation, and several swampy areas that precluded the
establishment of precisely spaced, straight lines. The alternative would have required civil surveying and
extensive vegetation removal. The GPS allowed local navigation and reorientation to avoid obstacles and field
hazards while continuing to collect valid, accurately located geophysical data.
The use of differentially corrected GPS data for this investigation proved to be an excellent way to obtain
geophysical survey control at a reduced level of effort; however, it added complexity to the surveys that had to be
planned for both in the field and during data processing. Specialized processing techniques were developed to
overcome minor satellite signal “dropouts, ” and to allow for proper time-synchroniuttion and merging of the
geophysical and GPS data.
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Keys To Marketing And Selling Environmental & Engineering Geophysics
Authors Douglas E. Laymon and Martin MieleMuch of the time as practicing geophysicists we have rightly focused our attention on
refining and developing our craft, technical ability, and know-how. Throughout our early
education and early technical work, geophysicists gain the necessary tools to be good practitioners
of their science. However, we are most often left to our own devices to learn the business and
selling skills required to obtain and maintain the work that brings satisfaction to our careers as
geophysicists. This paper focuses on some of the essential tools that can be used in selling and
marketing geophysics to others (e.g., engineers, attorneys, and developers).
Three essential keys are important to selling. First, you must have a sellable commodity.
As geophysicists this is our technical know-how, ability, and experience. Secondly, you must have
enthusiasm for what you are doing. You must genuinely enjoy and believe in geophysics and what
it can do for your client. Your clients and potential clients will see this and will get caught up in
your enthusiasm. Thirdly, you must have a strategy for your approach, or a marketing plan which
outlines your approach to selling and provides you with a road map to follow. Additionally, you
must be able to understand your client’s needs. It is important to keep the lines of
communication open with clients, as communication is paramount and will determine the amount
of follow-on work and types of referrals you receive.
Marketing and selling is the “work of getting work.” Networking and the development of
relationships is the bottom line in sales and marketing. People work with people and generally
contract people they trust and like. Winning at sales takes common sense and diligent effort.
The fruit of this labor is continued success and growth of your business. To the geophysicist, sales
is a means to an end which allows you to be involved in the work you enjoy and to help bring
fulfillment to your career as a geophysicist.
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The Value Of Two-Component Gpr Data: Identifying The Polarization Contribution In Amplitude Anomalies
Authors Rob D. Luzitano and Tad J. UlrychMost of the current research in ground penetrating radar (GPR) relating reflection strength to material properties,
such as soil moisture and the existence of contaminants, involves only single component data, i.e., the component
with transmitter and receiver antennas parallel. This scalar view of a vector phenomenon leaves most of the
information contained in the reflected wavelet untapped. Moreover, an amplitude anomaly in the parallel component
may be largely, or at least in part, due to a polarization effect. Anomalous polarization of the returned wavelet
degrades the coupling with the receiver antenna since the match between wavelet and antenna polarizations is
decreased. This polarization contribution is ignored by the common scalar approach which ascribes the amplitude
anomaly entirely to such properties as water saturation or a suspected contaminant plume. Wavelet depolarization
occurs, to some degree, for most cases of reflection and refraction. Indeed, the depolarizing character of a scatterer
can aid in its identification. Although complete depolarization, causing reflections to extinguish, was confirmed 20
years ago in sea ice, little attention has been given to possible depolarization effects in soil or rock.
We investigate the power loss in the parallel component due to anomalous polarization by using a new instantaneous
attribute: polarization match. The instantaneous polarization match estimates how severely depolarization
is affecting amplitudes while also identifying the responsible depolarizing structure. In this initial investigation
the instantaneous polarization match estimate is applied to data from sites of two different structural complexities.
Field experiments at an abandoned overpass ramp investigated depolarization for the simple cases of smooth
shallow dipping interfaces and a lateral change in material. Both profiles and common midpoint (CMP) soundings
demonstrated that the transverse magnetic (TM) wavelet depolarizes more than the transverse electric (TE) wavelet.
This difference is, at least in part, explained by the occurrence of the Brewster angle in the TM mode. At the
sites investigated, the most significant mechanisms for depolarization appear to be scattering from rough spots (a
S-20% power loss) and at points of wavefront interference. These surveys provide only an initial investigation, and
other traverse orientations, environments, and target types should be investigated, some of which are likely better
depolarizers than the targets in this study.
Although degraded polarization match is usually a secondary amplitude effect, in some cases this problem
could become significant. When pursuing targets of anomalous amplitude, or any other attribute, at least one
two-component profile should be acquired to characterize the depolarization nature of the field site.
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An Integrated Geophysical Investigation Of An Inactive Wood Treatment Facility
Authors Jyotiranjan Kar and Peter T. MillerFive geophysical methods were used to characterize the subsurface at an inactive wood treatment facility. Seismic refraction,
electromagnetic conductivity (EM-3 1 and EM-34), very low frequency (VLF), and spontaneous potential (SP) methods were used to
locate potential water-bearing zones and to help understand the driving mechanisms for the movement of groundwater and chemical
constituents below the site. The investigation was successful in delineating areas where gravity drainage, groundwater seepage, and
preferential groundwater movement was occurring. Typically, these areas were characterized by lower bedrock elevations, decreased
bedrock velocities, increased electrical conductivity values, and anomalous VLF and SP deflections. The data were incorporated into
the generation of site models, the determination of critical geologic information, and the placement of seven proposed monitoring
wells.
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2D Inversion Of Resistivity Profile Data
Authors Ingelise Møller, Niels B. Christensen and Bo H. JacobsenProfile oriented geoelectrical data can now be collected with considerable speed and with short sample
length resulting in huge amounts of data values per day. For dense galvanic profile measurements we
have developed a 2D inversion algorithm; a deconvolution based on the Born approximation and the 2D
FrCchet kernel. The translational invariance of the problem allows the development of an algorithm in
the wave number domain, whereby the inversion problem decouples into many small linear problems.
The deconvolution algorithm is demonstrated on a theoretical data set and a CVES (continuous vertical
electrical sounding) profile of field data. Besides these vertical sections, data are presented as traditionally
iso-resistivity maps of apparent resistivity and of layer resistivity - results of the deconvolution algorithm.
The deconvolution algorithm works almost instantaneously with computation times in order of seconds
on an ordinary PC for 500 measurements in 10 configurations.
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A Site Characterization Of The Soda Butte Creek Drainage, Yellowstone National Park
Authors Eric Nyberg, Wayne L. Hamilton, William R. Sill and Marvin A. SpeeceGeophysical techniques were applied in the Soda Butte Creek study in an attempt to characterize the area’s
groundwater resource. The head of this drainage is located near the northeastern boundary of Yellowstone
National Park; furthermore, Soda Butte Creek is a major tributary of the Lamar River--which in turn is a
major tributary of the Yellowstone River. The National Park Service is concerned with potential development
along the Park’s boundary which may adversely affect both surf&l and groundwater recharge into the Park.
Seismic refraction surveys and Schhnnberger resistivity soundings have been used to define the area’s valley
Ii11 composition and thickness. The techniques were also used to determine the valley’s saturated thickness.
By obtaining these parameters through geophysical means, important insights pertaining to the area’s
hydrogeology can be developed. Since no previous hydrogeologic studies (i.e., pump tests) have been
performed in this environmentally sensitive location--due, in part, to the costs and impacts associated with
drilling water wells--the use of cost effective, low-impact geophysical methods is a viable means of obtaining
subsurface information.
The application of both seismic refraction surveys and Schlumberger resistivity soundings was done in an
attempt to verify the results of each technique. By accomplishing this feat, the problem of “nonuniqueness”
associated with each method can be significantly reduced.
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Environmental Geophysics And Sequential Air Photo Study At Sunfish Lake Twin Cities Army Ammunition Plant
Authors C.A. Padar, L.D. McGinnis, M.D. Thompson, A.W. Anderson, M.A. Benson, J.E. Stefanov, C.R. Daudt, S.F. Miller and D.E. KnightGeophysical and air photo studies at the Twin Cities Army Ammunition Plant (TCAAP), Minnesota,
were conducted to establish a chronology of dumping and waste disposal. This study was undertaken to aid in the
assessment of the amount of remediation needed to reclaim a wetland area. An integrated analysis of
electromagnetic, magnetic and ground-penetrating RADAR (GPR) measurements over a 25acre site, provided the
information necessary to define waste disposal events. These events are observed on a sequence of aerial photos
taken between 1940 and 1993.
The former southwestern embayment of the lake, filled in during the original construction of the base,
has been clearly defined. Two burn cages and their surrounding debris have been delineated. The area1 extent of
another waste site has been defined along the northern shoreline. Depth estimates determined from EM-61
analysis, and depths to original lake bottom, derived from GPR, have yielded volumetric estimates of the amount
of material that would need removal if excavation is required. Magnetic and electromagnetic data have pin pointed the locations of mounds, observed from historical air photos. Except for these areas along the northwestern shore, there is no evidence of waste disposal along the shoreline or within the present-day lake margins. The ability to date the anomalous regions is
significant, in that different production demands upon TCAAP, during the time periods of WWII, The Korean War, and The Vietnam Conflict, have resulted in different types of waste. The ability to categorize areas with distinct time periods of operation and waste disposal can greatly aid the environmental cleanup effort with regard to the type of contaminants that might be expected at these poorly documented disposal sites.
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Small-Scale Mineral Cavity Exploration Utilizing High-Resolution Ground-Penetrating Radar
Authors J.L. Petruccione, C.E. Papadakis, R.W. Welhrer, MA. Becker, R.R. Franke and P.S. MosesIn order to test the exploration potential of ground-penetrating radar (GPR) for mineral-lined cavity
detection, a GPR survey was conducted over a relatively smooth, -5 m2 bedding plane surface located within
an open-pit limestone mine, east-central New York State. Mineral cavities within the siliceous limestone are
observed on near-vertical surfaces and range between 0.2 to 0.8 m below the exposed bedding surface, upon
which the survey was performed. For this investigation, a hand-held, shielded 1000 megahertz (MHz) transceiver
antenna was utilized, and subsurface reflections were sampled over a 20 nanosecond (ns) time window which
provided a maximum penetration depth of -1 m. A 1 x 1 ft (0.3 x 0.3 m) grid was marked on the exposed
bedding surface, and GPR profile data were then collected by sliding the 1000 MHz antenna at a relatively
constant rate over the established grid lines in perpendicular, intersecting directions.
All GPR data were collected as analog chart records which allowed real-time, in-field interpretations.
Radar facies observed during this survey include laterally continuous, high-amplitude reflections that have a
subparallel to parallel geometry. These reflections are prominent between 4 and 14 ns two-way travel time
(TWT), and are interpreted as either internal bedding plane interfaces, fractures, or solution (stylolite) surfaces.
Several high-amplitude reflectors between -4 and 10 ns TWT were observed and characterized by an arching,
hyperbolic-shaped geometry. Steeply inclined diffractions that cross-cut prominent lateral, parallel reflections
are also associated with the hyperbolic reflections. This facies relationship is attributed to the contact between
bedrock and air-filed voids within bedrock. A total of 10 air-filed voids were predicted from the GPR survey.
Physical sampling of these GPR anomalies uncovered a total of six, near-circular to ovoid, dome-shaped, minerallined
cavities. Based on the survey fmdmgs, the high-resolution 1000 MHz GPR system can be used to accurately
map internal bedrock structures, in particular, shallow (c 1 m subsurface) air-filled vugs.
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Dielectric Properties Of Polluted Soils As A Potential Tool To Detect Low Level Organic Pollution In Unsaturated Soils
Authors Sylvie Porokhovoï, Jean du Mouza and M. ReiterThe detection of organic pollution in soils is usually made by chemical analysis. Some geophysical methods are
available to detect massive and transient pollution. But the standards used in Europe to define a non polluted soil
are very strict : some organic compounds (as Polycyclic Aromatic Hydrocarbons) have to be less than 10 ppm.
Hence, a geophysical tool allowing to prospect large areas with low rate organic pollution has to be developed.
In this aim, our work is the first step of the evaluation of a geophysical method based on the dielectric
characteristics of soils, our final goal being in situ measurementso f those parameters.
Several geophysical methods are already used to monitor organic pollution of groundwater. Both electric
(Olhoeft G.R., 1985) and dielectric properties of these pollutants can be used. Conventional DC resistivity
measurementsa nd EM methodsc an provide good results when polluted groundwater is linked with high salinity,
while GPR and radiowave EM can be used to detect hydrocarbons by measuring soil dielectric properties. The
problem of detecting organic compounds is different for saturated and unsaturated media because the dielectric
constant E, of water (- 80, depending on temperature and frequency) is higher than that of dry soils (2<&,<6) and
organic liquids (E,, < 6 if the compound is not polar). For saturated soils or rocks, the presence of organic liquid
reduces the water saturation component and, consequently, the global dielectric constant of the soil in
comparison with non-polluted soil or rock. GPR method can detect contrasting dielectric permittivities due to
such phenomena. This method is efficient for high levels of pollution ( > 30% by weight) in a saturated zone and
for transient flow because it is easier to compare several GPR sections versus time than to interpret one section
without references. Our bibliographic study indicated the lack of geophysical methods to detect low level
organic pollution, but some papers appear to be optimistic (Yong R.N. and Hoppe ES., 1989, Vanhala H. and
al, 1992) concerning the detection of pollutants in soils measuring the dielectric behavior in polluted soils.
Consequently, we made some laboratory measurementso f the dielectric properties of both polluted and non
polluted soils.
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Gravimetric Mapping Of An Abandoned Underground Limestone Mine In Clark County, Indiana
By R.M. RenéAn underground limestone mine near the center of Clark Military Grant 48 in Clark County, Indiana, was in
operation from 1892 to 1896. This mine, here referred to as the Gheen’s Mill Cementville Mine, was abandoned and
became flooded before the slope shaft entrance was back-filled. The roof of the mine is at a depth of about 8.2 m (27
feet). An interval of 4.3 m (14 ft) or less of limestone was mined to make a natural cement. A map of the mine was
needed because undermined areas might be unsafe for buildings. The area is presently being developed as a business
park. Fifty-six holes were drilled several years ago to map the mine, but their precise locations were unknown.
Seventeen holes found cavities, 32 holes penetrated the mined interval but did not encounter cavities, and 7 holes did
not find bedrock within a depth of 11 m (33 ft). A gravity survey was made to help locate these holes and to better
define the bounds of the mine. One hole was successfully exhumed and identified on the basis of the gravimetry.
Gravity was measured at 837 stations in nineteen east-west and north-south profiles with 3.05-m (loft) station
spacing. Inflection points of a negative 140~pgal Bouguer gravity anomaly located edges of the mine. First and second
horizontal derivatives of the gravity profiles helped locate these edges. Gravity profiles around the mine perimeter
did not detect any tunnels extending between the boreholes. A large negative residual Bouguer gravity anomaly south
of the mine defines a buried valley that limited the area available for mining. The gravity method should be practical
in mapping similar underground mines in the region. Approximately 40 percent of one of these mines, the Falls City
Mine, has collapsed (Ren6, et al., 1994). The gravity survey of the Gheen’s Mill Cementville Mine probably indicates
that a lesser proportion of the limestone was mined within the perimeter of this mine than in the case of the Falls City
Mine.
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3-D D.C. Electrical Resistivity Inversion With Application To A Contamination Site In The Aberjona Watershed
Authors Weiqun Shi, William Rodi, Randall L. Mackie and Jie ZhangWe have developed an inversion algorithm that finds smooth, three-dimensional models of the earth’s electrical
resistivity from d.c. pole-pole or dipole-dipole potential field data. The algorithm, based on Tikhonov’s
regularization method, computes models that fit the data and have minimum structure in the sense that second
spatial derivatives of resistivity are minimized. A nonlinear conjugate gradient (NLCG) algorithm with
pre-conditioning is employed to solve the minimization problem involved. Numerical experiments with synthetic
and real data show that our version of the NLCG algorithm is more efficient than the commonly used
Gauss-Newton method. We demonstrate the inversion algorithm on a large dipole-dipole data set collected
at a groundwater contamination site in the Aberjona Watershed in Massachusetts. Our Aberjona inversion
model correlates well with other geophysical results at the site (GPR sections and cone penetrometer logs)
and serves to extrapolate the sparse stratigraphic information previously available into a full 3-D model of
the study area.
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An Integrated Geophysical Study Of The Yarmony Archeological Site, Colorado
Authors C. Skokan, C. Edwards, J. Holt and A. VaughanIn a joint project between the Colorado School of Mines
Department of Geophysics and Colorado State University Department
of Archeology, and sponsored by the Bureau of Land Management, an
integrated survey of the Yarmony 5EA759 site was undertaken. The
Yarmony archaeological site was discovered in April, 1987, during
a routine examination for a proposed road improvement and during
that month excavations began. A pit house was discovered which
dated to 6300 years before present. This pit house is the oldest
known dwelling, to date, located in Colorado. Human remains
approximately the same age as the pit house were also found at
Yarmony (Metcalf and Black, 1991). These discoveries have led to
the need to determine the nature and extent of subsurface
cultural deposits at the site in a quick, cost effective,
reliable, and non-intrusive manner. Geophysics is an effective
and proven method for finding the locations of archaeological
features in many areas (Vaughan, 1985) and was therefore applied
at the Yarmony Site.
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Engineering Soil Parameters From Seismic Cone Penetrometer Tests - An Overview
Authors T.A. Terry, D.J. Woeller and P.K. RobertsonSince the introduction of the seismic cone penetrometer test in the early 1980s significant progress has been made in
the analysis and interpretation of the collected data. The basic equipment, test and data reduction are reviewed. The
current methods available for evaluating liquefaction using penetration resistance and normalized shear wave velocity
are presented and discussed, as is the recently developed method for evaluating sand compressibility from penetration
resistance and shear wave velocity.
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Recent Applications Of Electrical Imaging Surveys In The United Kingdom
By Ron D.BarkerRecent developments in electrical tomography field acquisition and data inversion technology
have resulted in the production of electrical images which more accurately mirror the subsurface than is
possible with conventional resistivity surveys. The technique is particularly suitable for shallow site
investigation where understanding the complexities of the subsurface structure is important. This is
demonstrated with examples of its application in determining depth to bedrock, in resource and contaminant
studies, the study of shallow fracture systems, and in monitoring subsurface fluid flow.
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Two Layer Depth Analysis Of Em-3 1 Conductivity Data
More LessThe Geonics Eh4-3 1 Inductively Coupled Ground Conductivity A4eter is a very
useful instrument for rapid and sensitive area1 coverage for site characterization. It
responds to a number of important environmental variables such as soil or rock
type, pore fluid content, and fluid conductivity, and often produces very useful
plan maps. It would be helpful if the results could be augmented with depth
information along selected traverse lines. It is often important to know, for
example, whether an apparent conductivity anomaly arises above or below the
bedrock surface or water table.
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