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20th EEGS Symposium on the Application of Geophysics to Engineering and Environmental Problems
- Conference date: 01 Apr 2007 - 05 Apr 2007
- Location: Denver, Colorado, USA
- Published: 01 April 2007
121 - 140 of 164 results
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Test For Detecting An Impermeable Water Barrier In An Earth-Fill Dam In Austria Using Masw Method
Authors Silke Hock, Julian Ivanov and Richard D. MillerSeismic methods were used to locate an impermeable water barrier (density body), constructed in front of a homogenous earth-fill dam (Prätisbach) in Eastern Styria, Austria. This detention reservoir, built in 1985/86, was constructed of locally mined materials. Key to this structures functionality is its impermeable core located within the upstream toe of the dam and parallel to the dam axis. This density body is reported to be composed of the same material as in the main structure, but has undergone intensive artificial compaction. Current pool level in the detention reservoir is consistent with the designed top of the density body, about 2 m below the surface. Seismic methods were attempted because no apparent anomaly was evident on electromagnetic data associated with the density body. Surface wave (MASW) and refraction seismic methods provided compressional (Vp) and shear-wave (Vs) velocities along a profile that should have crossed directly over the density body of the dam. With only a subtle increase in Vp velocity within the designed density body interval, the findings of the seismic survey appear consistent with the electromagnetic data. A loosely fitting relationship was developed providing a better understanding of the internal condition of the dam.
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High Resolution Resistivity Imaging Of Naitwar Bazar Landslide, Garhwal Himalaya, India
Authors Suman K. Mondal, Rambhatla G. Sastry, Param K. Gautam and Ashok K. PachauriAn active landslide investigation using 2D electrical resistivity tomography has been under taken in Garhwal Himalaya. Six electrical resistivity tomography profiles spanning the landslide were
conducted. The resistivity tomograms reveal the presence of slip zones at a depth range of 10 to 20 m from ground level. The inferred lithological depth sections clearly outline the importance of electrical resistivity tomography in landslide studies.
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Practical Methods For Locating Abandoned Wells In Populated Areas
Authors G.A. Veloski, R.W. Hammack and R.J. LynnAn estimated 12 million wells have been drilled during the 150 years of oil and gas production in the United States. Many old oil and gas fields are now populated areas where the presence of
improperly plugged wells may constitute a hazard to residents. Natural gas emissions from wells have forced people from their houses and businesses and have caused explosions that injured or killed people and destroyed property. To mitigate this hazard, wells must be located and properly plugged, a task made more difficult by the presence of houses, businesses, and associated utilities. This paper describes well finding methods conducted by the National Energy Technology Laboratory (NETL) that were effective at two small towns in Wyoming and in a suburb of Pittsburgh, Pennsylvania.
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Characterizing Contaminated Groundwater Sites
Authors Val O. Kofoed and Paul B. RollinsThe greatest challenge in addressing groundwater contamination is gaining an accurate understanding of the complex web of channels and reservoirs which lie hidden below the surface.
Unfortunately, traditional methods for determining the potential flow paths of subsurface pollution require extensive drilling—a time-consuming process which results in significant environmental trauma and high costs. The electromagnetic imaging procedure detailed in this presentation provides exceptionally accurate groundwater maps but requires significantly less drilling. As a result, this method entails fewer costs in terms of time, money and ecological disruption. Initial case studies indicate that this rapid and minimally invasive technique may be particularly well suited to the task of environmental site assessment for the purposes of targeting groundwater cleanup. This procedure relies on the principles of Controlled Source-Frequency Domain Magnetics. First, electrodes are used to charge the groundwater in question with a low voltage electrical current. As the current conducts along the water between the electrodes, it emits a magnetic field whose size, shape, magnitude and direction are characteristic of the surrounding aqueous system. This field is then read at the surface by a specially tuned receiver. The data thus generated can be used to create maps indicating the attributes of the subsurface water network, including potential flow paths. That same data can also form the basis of 3-D models of the site, which provide detailed insight into the depth and character of the aqueous network. Such information is of tremendous value in the difficult effort to remediate groundwater pollution. This technology has recently been deployed in a number of projects involving subsurface contamination. This paper will discuss the results of its deployment at a site where characterizing a plume of contaminated water was a key objective. This presentation will discuss the science behind the methodology and the lessons learned from its recent applications.
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Determiniation Of Manning'S Roughness Coefficients For Natural Channels And Rivers
By M. AhmadiAlthough much research has been done on Manning's roughness coefficient, n, for stream channels, very little has been done concerning the roughness values for natural channels and rivers. The n value is determined from the values of the factors that affect the roughness of natural channels and rivers.
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Resistivity Structure Of Rainier Mesa- Shoshone Mountain, Nevada Test Site, Nevada
Authors Ted Asch and Brian RodriguezThe U. S. Department of Energy and the National Nuclear Security Administration are addressing ground water contamination resulting from historical underground nuclear testing. Most of
these tests, limited to specific areas of the Nevada Test Site, were conducted hundreds of feet above the groundwater table; however, more than 200 of the tests were in proximity of, or within, the water table. One issue of concern is the nature of the somewhat poorly constrained pre-Tertiary geology and its effects on ground water flow in the area. Magnetotelluric data collected by the U.S. Geological Survey in 2003 and in 2005 have helped to characterize the resistivity structure in the pre-Tertiary geology beneath Rainier Mesa, Buckboard Mesa, northern Mid Valley, Shoshone Mountain, the Eleana Range, and the Yucca Flat areas of the Nevada Test Site. The character, thickness, and lateral extent of the Chainman Shale and Eleana Formation that comprise the Upper Clastic Confining Unit (UCCU) are generally characterized in the upper 5 km. The interpretation is not well determined where conductive volcanic tuff confining unit (TCU) overlies conductive Chainman Shale, where resistive Eleana Formation overlies resistive lower carbonate aquifer (LCA) units, or where resistive vitric tuff aquifer (VTA) rock overlies units of the Eleana Formation. The nature of the volcanic units in the west has been refined, as are large and small fault structures such as the CP Thrust Fault, the Carpetbag Fault, and the Yucca Fault that cross Yucca Flat. The subsurface electrical resistivity distribution and inferred geologic structures determined by this investigation should help constrain the ydrostratigraphic framework model that is under development for the Rainier Mesa/Shoshone Mountain Corrective Action Unit and areas to the west and in understanding the effects on ground water flow in the area.
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Interrogating Levees In Texas, New Mexico, And New Orleans Using Various Seismic Metho
Authors Julian Ivanov, Richard D. Miller, Joseph B. Dunbar, John W. Lane and Steve SmullenCompressional- (Vp) and shear-wave (Vs) velocities were determined within earthen levees on the Rio Grande River in south Texas, south New Mexico and New Orleans. A loosely fitting relationship was developed to better characterize the internal condition of the levees. Seismic data were incorporated with surface observations, existing core taken from the levee, and airborne EM data acquired. Several different components of the seismic wavefield were recorded at each levee site. Several seismic data-analysis techniques were appraised including, P- and S-wave refraction, P- and S-wave refraction tomography, Rayleigh and Love-wave surface-wave analysis using multi-channel analysis of surface waves (MASW), and P- and S-wave cross-levee tomography. In addition, at each of the sites compressional- (Vp) and shear-wave (Vs) velocity changes were measured. Each of the levee sites had a unique seismic response that was related to levee material, shape, velocity model, and time of the evaluation (most likely related to varying moisture content). Clearly, no one property relationship to characterize levees can be established for all levee systems, each needing a unique norm defined.
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Wellfield Exploration For An Ethanol Plant Using Photo-Lineament Analysis In Conjunction With 2-D Resistivty: A Case History
Authors Gabriel J. Hebert and Gregory B. ByerRecently, the ethanol industry has grown in the Midwestern United States. Because a large ethanol plant consumes over 1000 gallons of water per minute, an abundant water source is critical. Unfortunately, the geology of a potential plant site is not always suitable for such extraction, as was the case for a possible site in northwestern Indiana. In this region, the bedrock consists of shale, siltstone, sandstone, and limestone; while the unconsolidated material above bedrock consists predominantly of fine grained glacial till. Overall, this is a difficult area geologically to find abundant groundwater yielding formations. Prior to the conduction of the geophysical investigation, a local drilling company drilled eight (8) water wells on the site, all with minimal yields (less than 20 gal/min). The geophysical survey performed, consisted of a preliminary photo-lineament analysis of the site to locate potential fracture zones, which were then further investigated using two-dimensional vertical resistivity profiling to characterize the electrical properties of the upper subsurface. Using these methods, several water bearing zones were detected, the best of these sustainably yielding up to 800 gal/min.
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Time Series Resistivity Analysis Of Water Content Vatiation In Karst Terrain, Edwards Limestone, San Anstonio, Texas
Authors Marla M. Roberts and Alan DuttonAs San Antonio is one of the fastest-growing metropolitan areas in the United States the strain on its water source has increased accordingly. Unlike many other large cities, San Antonio relies solely on groundwater as a single source for its water needs. Urban sprawl now affects sensitive areas within the recharge zone of the Edwards Aquifer. Better definition of where and how recharge occurs is needed.
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Gravity, Magnetic & Gpr Surveys For Massive Gold Deposits At A Philippine Treasure Site
By Ralph SouleBeginning in December 2002 GeoPotential Philippines, Inc. (GPI) in conjunction with the International Recovery Group Philippines, Inc. (IRGPI) conducted a series of geophysical surveys over several potential treasure sites in the Philippines. The purpose of the geophysical surveys was to locate massive gold deposits that had been buried by the Japanese military during the occupation of the Philippines in World War II. This paper discusses the geophysical surveys conducted at one of the treasure sites (Figure 1 INDEX MAP) called the “Waterfall Site”.
At the Waterfall site Gravity, Magnetic and Ground Penetrating Radar (GPR) Surveys were conducted to search for 250 metric tons of Gold buried at a depth of 10 to 15 meters. An initial Gravity Profile indicated a possible massive Gold deposit. The GPR Survey produced an anomaly indicative of a buried chamber. However subsequent excavation of the feature indicated a hoax. The follow up Gravity Survey produced a Gravity Anomaly consistent with a massive deposit of gold. Excavation at the Site is currently suspended due to environmental and political concerns.
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Successful Application Of Geophysics At The Aganoa Archaeological Site, Island Of Tutuila, American Samoa
Authors William A. Sauck, Frederic B. Pearl and Suzanne L. EckertGPR and magnetometry were used at a site on the SE shore of Tutuila in search of the deepest, relatively undisturbed occupation level. The general purpose of the archaeological research was to further elaborate the nature of Ancestral Polynesian Culture and to obtain datable materials representative of the oldest habitation of this island. This was also to serve as another data point toward determining the nature of Polynesian origins; whether it was an in situ cultural evolution from the earliest colonists, or possibly due to outside cultural influences much later, as some would now suggest. The several-hectare site occupies a re-entrant into the otherwise steep shoreline of the island. Magnetometry was used to attempt to locate buried basalt blocks (walls or tools) encased in nonmagnetic coral sands. GPR in the form of long, shore-perpendicular transects was able to show the accretionary history of this beach and ridge area. Surprisingly, it revealed that the earlier ridges were directly below the modern ridge, ie, progradation of this geomorphic feature had not occurred. Hence, exploration was re-directed to the modern topographic high (between modern houses of the village), and resulted in the GPR discovery of a 5m x 5m compacted floor at 1.5m depth, containing numerous and datable artifacts.
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Geophysical Investigations At An Archaeological Site In Marcus Hook, Pennsylvania
Authors Hiromi Hamajima and Kelly A. WeyerOn March 18, 2006, geophysical investigations were conducted at an archeological site in Marcus Hook, Pennsylvania. The purpose of the investigations was to attempt to identify any
anomalous features that may be associated with the Marcus Hook Plank Log House. During renovation of the house, the landowner discovered the plank log construction of the house and began recovering artifacts from the fill beneath the kitchen floor. As interesting as the facts about this site are the legends. There is a local oral tradition that this house was once the home of a mistress of the notorious pirates, Blackbeard. Another local legend associated with the house is the underground tunnels which supposedly connected the house to the Delaware River.
The equipment used for this investigation included a Geonics EM-61 electromagnetic metaldetector and a Sensors & Software Nogginplus 250 SmartCart ground penetrating radar (GPR) system. The results indicated an anomalous area measuring approximately 20 by 25 feet with a strong reflection at 2 to 3 feet below ground surface. This anomaly may represent a foundation, possibly a garage or carriage house, shown in this location on an early 20th century map. The results will be used to guide for future excavations.
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3D Visualization Of 2D Electrical Surveys Integrated In Seismic And Gpr Interpretation Softwares
Authors Daniel F.S. Maia and Guilherme P. CastilhoGeophysics is never done with just one kind of data, and integration of all data is crucial for a good interpretation. Electrical methods are commonly combined with Potential (shallow) or
Seismic (deep) methods for subsurface investigation. Most commonly used Seismic and GPR interpretation software packages do have good 3d visualization capabilities but do not provide the capability of importing electrical data into them. In this paper, we show how it is possible to integrate a series of 2d electrical images into a 3d block for visualization in these interpretation
software package.
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The Utility Of Multi-Electrode Resistivity Data In Geotechnical Investigations – A Case Study
Authors Param K. Gautam, Rambhatla G. Sastry and Suman K. MondalFor any major civil engineering construction, traditional geotechnical investigations like, standard penetration test (SPT), dynamic cone penetration test (DCPT) and static cone penetration test (SCPT) are carried out to assess the suitability of a site. These tests provide point information depthwise. However, non-invasive geoelectrical site investigations can provide subsurface resisistivity information in 1-D, 2-D and 3-D scales. Here, through a case study, an effort is made to relate the 2-D resistivity/IP sections to field geotechnical results and extend the scope of geoelectric sections to geotechnical site characterization. The available geotechnical test results like SPT, DCPT and SCPT for a multi-storeyed building in Indo-Gangetic Alluvial Plains are correlated with 2-D resistivity sections gained from two multielectrode resistivity-imaging experiments. The good correlation between SPT and IP sections allowed us to predict synthetic SPT from an interpreted IP section. The actual and synthetic SPT (normalized) match well in phase but differ in amplitude, which means that IP and SPT relationship is non-linear. In future, we hope that by a proper non-linear transformation the limitations of point mode geotechnical tests can be overcome.
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Comaparison Of Survey Results From Em-61 And Beep Mat For Uxo In Basaltic Terrain
Authors Les P. Beard, Jacob Sheehan, William E. Doll, Pierre Gaucher, Regis Desbiens and Wayne MandellSite S-12 is one of several World War II era bombing targets found on the Pueblos of Laguna and Isleta in New Mexico. Magnetometry results from a low-altitude helicopter magnetometry survey at S-12 were inconclusive as to the extent and density of the ordnance debris field because underlying basalt flows created such a strong background signal. Subsequently, a team from Battelle and GDD Inc. carried out ground geophysical surveys to test the effectiveness of a geophysical instrument called Beep Mat. Beep Mat is mounted in a rugged sled and is designed to be towed over the ground or through snow. Originally developed for Canadian mineral prospecting, it has the ability to distinguish between conductive and non-conductive materials and between magnetic and non-magnetic materials. It is therefore a potentially useful instrument for UXO detection and discrimination. At Site S-12, a 100m x 50m grid was established in an area thought to be on the periphery of the bombing target. Geophysical data using EM-61, and Beep Mat were collected over the grid at one meter line spacing. Both the EM-61 and the Beep Mat data produced similar maps showing locations of scrap and UXO, but Beep Mat anomaly peaks were randomly offset about 2m from EM-61 anomaly peaks.
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A Practical And Autonomous Geophysical Platform
Authors R.J. Bowers and Eric CloseThe US Government spends millions of dollars every year on unexploded ordnance remediation. A large portion of that funding goes to collecting geophysical data. When possible, geophysical data is collected by vehicles pulling arrays of geophysical sensors. The tow vehicles are driven by people following navigational aids. These people are often susceptible to errors that are system inherent. Human shortcomings lead to errors in driving a precise course, variations in speed, and limitations in endurance. Recent developments in robotics have resulted in the development of an autonomous tow vehicle that can overcome these shortcomings. The “Tugbot” robot works with any geophysics array. In the summer and fall of 2006 the robot was proven at an 1800-acre site where production was improved dramatically by 100% over similar projects where humans were operating the vehicle. Additionally, due to Tugbot’s precise control and positioning capabilities, superior throughput, operational quality control, data integrity, and safety results resulted,. Improved precision in geophysical data may allow discrimination of UXO targets in geophysical data. This document briefly describes the Tugbot and its operation.
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Variability Of Real Uxo
Authors Jonathan T. Miller and Tom FuruyaReal UXO are often dented, bent, broken, rusted-out, or otherwise damaged. This generates variability in their Electromagnetic Induction (EMI) response and complicates the job of UXO/clutter
discrimination. This SERDP-funded project was aimed at quantifying UXO variability by measuring a large number of real UXO and expressing variability in physically meaningful terms. Over 600 items were measured in air using both Time-Domain (EM63) and Frequency-Domain (GEM3) instruments and response was quantified by fitting a response model to both time-domain and frequency-domain data simultaneously. Four physically meaningful parameters are derived from the fits: 1) response magnitude, which relates to target size, 2) late time fundamental decay time constant, which relates to conductivity and maximum diameter, 3) magnetic cross-over time, which relates to quadrature peak, and 4) the static-field asymptote, which relates to target permeability and demagnetization factor. First and second order moments of variability for these parameters are estimated within each UXO class, along with uncertainties of those estimates found by Jackknife and Bootstrap re-sampling.
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Repeatability Of Common Uxo Detection & Discrimination Instruments
Authors Ryan E. North, Eric W. Smith and Andrew B. SchwartzIn support of UXO detection and discrimination, considerable effort has been and is being devoted to (1) understanding the operating characteristics of currently deployed EMI sensor systems, (2) characterizing the sensor system response as a function of location of a given ordnance target relative to the system, (3) characterizing the sensor signatures of given EMI systems to a wide variety of ordnance types, and (4) currently an effort to characterize the variation in signatures of given EMI sensors with a statistically significant sampling of representatives of the same ordnance type. Complementary to the fourth item, there has not been a similar effort to characterize and understand the signature variation to a given ordnance item among various geophysical systems of the same type. Even differences in the 5 to 10 % range between the same type systems over a given ordnance item, while perhaps insignificant from the perspective of detection, could lead to erroneous classification/identification from the perspective of discrimination. Production geophysical surveys for UXO detection and discrimination typically use two technologies: electromagnetic induction (EMI) systems and total field magnetometry (TFM). EMI systems are the most versatile of the geophysical methods used for surveys for buried UXO, leading to environmental restoration. The EMI systems are versatile due to the capability of broad bandwidth operation and variable transmitter and receiver configurations. TFM sensors are the most reliable and simplest systems to operate while also having the ability to detect large targets at greater depths than EMI. One new unit, if possible, of each of the three most common instruments used in UXO remediation projects: the Geonics EM61-MK1 and EM61-MK2 metal detectors, and the Geometrics G-858 magnetometer; were tested as reference instruments. The
response of the instruments was monitored as a function of time versus the following parameters: battery voltage, system current draw, transmitted power (where applicable), electronics temperature, battery temperature, and ambient weather conditions. The measurements have been repeated multiple times in one day as well as on subsequent days while using a regulated power supply to attempt to determine which parameters have the most significant affect on system response. Currently we have tested four EM61-MK1 units, two EM61-MK2 units and two G-858 units. A total of ten units of each type will be tested for this project. The surprising result that has been observed is that the signal to noise ratio of the EM61 series instruments is a function of the battery voltage, which indicates that the transmitted current is not regulated.
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A Comparison Of The Repeatability Of Different Methods For Determining Electromagnetic Time Decay Constants Of Mec
Authors Craig Murray, Richard J. Grabowski, Harry Wagner and Nathan HarrisonDiscriminating between MEC-like and non-MEC-like objects is currently one of the most important challenges facing ordnance geophysicists. The apparent decay constant measured by time
domain electromagnetic sensors such as Geonics’ EM61-MK2 has proven to be a useful tool for this type of discrimination. While more sophisticated inversion methods may provide better discrimination results than simple decay constant analysis, measurements using the decay constant can be implemented efficiently and are relatively insensitive to positioning errors typical of data collected in large-scale production projects. The apparent decay constant can be extracted from EM61-MK2 datasets in several ways, such as locating the individual peak measurements over the item for each time gate, calculating the decay constant for each data point, or extracting the different time gate measurements from gridded data. Several methods of measuring the decay constant were compared to determine which provided the most repeatable values from multiple datasets collected over the same objects. The repeatability of the
measured decay constant over several of the same type of object buried at different depths and orientations was also compared for the different methods.
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Operator Influence On Uxo Sensor Technologies
More LessThe primary objective of this test program was to quantitatively determine the level of influence that individual operators have on unexploded ordnance (UXO) sensors. This level of influence was first evaluated by observing the performance of expert and novice operators engaged in a blind search for a variety of UXO targets. Empirical data was collected for both novice and expert performance levels with a commercial handheld magnetometer. Data recorded was scored on traditional metrics such as probability of detection (Pd), false alarm rates (BAR), and time during the course of traversing a onethird acre test plot. This information was intended to provide insight into maximizing operator performance.
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