bluuebunny/crossref_metadata_2025_split huggingface dataset:
Chemical Leaching Near the Waiawa Shaft, Oahu, Hawaii: 1. Field Experiments and Laboratory Analysis
Authors: Loague Keith , Miyahira Robert N. , Oki Delwyn S. , Green Richard E. , Schneider Randi C. , Giambelluca Thomas W. 
Published: August 2005

AbstractThis paper is the first paper of a two‐part series concerned with assessing the potential for organic chemical leaching to a ground‐water skimming tunnel in the Pearl Harbor Basin, Oahu, Hawaii as a direct result of a proposed urban development. The objective of our simulation‐based assessment was to provide insight into the potential for chemicals, that may be introduced to the recharge areas of the Waiawa Shaft as a result of the proposed developments, to subsequently leach through the unsaturated zone to ground water. In this paper field and laboratory results are presented for experiments designed to support the modeling effort reported in the second paper of this series. The chemical leaching experiments were conducted at two field locations. The chemicals which were applied and then monitored for their downward movement in the near‐surface unsaturated zone are bromide, chlorpyrifos and fenamiphos. We found (1) good mass balance for bromide at both sites, (2) limited mobility of chlorpyrifos and fenamiphos at the field plots, and (3) good agreement between field and laboratory measured degradation rates.
Facilitated Transport of Contaminant Metals Through an Acidified Aquifer
Authors: Kaplan Daniel I. , Bertsch Paul M. , Adriano Domy C. 
Published: August 2005

AbstractA highly acidic aqueous waste containing metals was released into unlined seepage basins between 1955 and 1988 resulting in the contamination of the underlying aquifer. To provide insight about the mechanism (s) responsible for the facilitated movement of several of these contaminant metals, ground‐water samples were recovered from the aquifer along a 1.02‐km transect at approximately the rate of ground‐water flow. Facilitated contaminant transport was attributed primarily to the poor cation‐sorbing capacity of the aquifer matrix and the soluble nature of the metals in the acidic plume. Based on chemical equilibrium calculations of ground‐water ultrafiltrates which agreed with results from cationic and anionic resin‐exchange experiments, over 90% of each contaminant metal (Cr, Ni, Cu, Cd, Pb, and U) existed in cationic forms in the aquifer: either as soluble metals or as sorbates associated with positively charged ground‐water colloids. These cationic species were not retained by the aquifer because the pH of the aquifer matrix was slightly below the measured point‐of‐zero charge, indicating the variable charge sites on the mineral surfaces within the aquifer likely had a net positive charge. Contaminants were associated with recovered ground‐water colloids and this association increased with the pH of the system. However, mobile colloids would likely play only a small role in the transport of contaminants through this aquifer because of their relatively low concentration.
The Effect of Zones of High Porosity and Permeability on the Configuration of the Saline‐Freshwater Mixing Zone
Authors: Wicks Carol M. , Herman Janet S. 
Published: August 2005

AbstractCoastal karst aquifers have highly variable distributions of porosity and permeability. The ability to assess the volume of aquifer occupied by freshwater in coastal karst aquifers is limited by both the lack of understanding of the effect that regions of cavernous porosity and permeability have on the configuration of the saline‐freshwater mixing zone and by the limited knowledge of the location of the cavernous regions. A dual‐density ground‐water flow and solute transport model was used to explore the effect that the depth, lateral extent, and proximity to the coast of zones of high porosity and permeability has on the configuration of the saline‐freshwater mixing zone. These aquifer heterogeneities tend to shift the mixing zone upward relative to the position it would have in aquifers with homogeneous porosity and permeability. Zones of high porosity and permeability located at positions shallow in the aquifer or nearer to the coast had the greatest effect. In fact, for the conditions modeled, position was more important in modifying the configuration of the mixing zone than was changing the ratio of the intrinsic permeability of the cavernous zone to the aquifer matrix from 100 to 1000. Modeling results show that ground‐water flow is concentrated into the zones of high porosity and permeability and that flow configuration results in steep salinity gradients with depth. Field observations of the location of the halocline and of step changes in ground‐water composition coincident with regions of cavernous porosity in coastal karst aquifers corroborate the model results. In a coastal setting with saline water intruding into an aquifer, the effect of cavernous porosity and associated high permeability is to decrease the volume of aquifer in which freshwater occurs by a greater degree than would occur in an aquifer with homogeneous porosity and permeability.
Topographic Influence of Longwall Mining on Ground‐Water Supplies
Authors: Elsworth D. , Liu J. 
Published: August 2005

AbstractThe extent of potential aquifer dewatering resulting from underground longwall mining is determined through application of a nonlinear finite‐element model. The model represents the form of the body strain field that accompanies mining‐induced subsidence, and uses strain magnitudes to define the modified hydraulic conductivity field. The model is applied to test the sensitivity of the induced strain field to ground surface topography. The location and extent of three characteristic zones of conductivity enhancement are defined, representing gravitational detachment above the panel, shear failure above the abutment, and extensile deformation at the ground surface. Correspondingly, well completion locations are ranked with their potential for dewatering representing relatively high potential in upland areas and relatively low potential in valley base locations. These results amplify and offer a phenomenological explanation of observational data. Modeling results are compared with several documented studies in the Appalachian coal fields and favorable agreement achieved.
Distribution of Transmissivity in the Dammam Limestone Formation, Kuwait
Authors: Mukhopadhyay Amitabha 
Published: August 2005

AbstractThe transmissivity (T) distribution in the Dammam Formation aquifer within the State of Kuwait was investigated. It was found that up to 29% of the spatial variation in the log10 T values could be explained by a multiple linear relation with the coordinates of the observation site, whereby the log10 T showed a decreasing trend towards north and east. The deviations of the log10 T from the first degree trend were kriged using the semivariogram constructed on the basis of the available T data. The resulting values were added to the logio T values estimated from the linear relation with the coordinates, to derive the most likely values of log10 T at prespecified points. The technique provides estimates of transmissivity in areas away from the existing water fields. The T distribution with respect to the structure of the Dammam Formation was also investigated. The hypothesis that the transmissivity of the Dammam Formation was higher on the structural highs could not be substantiated, mostly because not enough data were available from such areas.
Localized Anisotropic Transmissivity in a Karst Aquifer
Authors: Greene Earl A. , Rahn Perry H. 
Published: August 2005

AbstractMaps of cave passageways in the outcrop area of the uplifted Madison Limestone in the Black Hills, South Dakota, show that principal cavern development is oriented in the major direction of ground‐water flow, roughly radial to the Black Hills. Fracture‐trace analysis and measuremnt of joints in the Wind Cave area show that these orientations coincide with cave passageways. Aquifer testing at Rapid City indicates that a local principal transmissivity tensor is oriented in the direction of cave development and along the strikes of bedding‐plane fractures. This indicates that much of the permeability of the Madison aquifer is modern karst (post‐Laramide‐Orogeny).From the above, we conclude that a localized anisotropic permeability (principal direction of transmissivity) is developed by ground water flowing through fractures, dissolving the rock, and producing dissolution‐enhanced conduits along the direction of ground‐water flow. This localized principal direction of transmissivity can be deduced from analysis of the potentiometric surface, stream‐aquifer hydrographs, mapped cave passageways, aquifer tests, fracture traces, and measurements of joints in the field.
MacWateqf: The Classic Speciation and Saturation Program Adapted to Macintosh Computers
Authors: Román F. Javier Sánchez San 
Published: August 2005

AbstractThis article presents MacWateqf, a version for Macintosh computers of the classic WATEQF program. This version of WATEQF can be used easily, as entry data do not need a rigid format, permitting the use of integer or real numbers, whether real or in scientific notation, with any quantity of decimals. Furthermore, a new program is also presented here: Mac Wat‐Intro, which makes it possible to create a datafile for WATEQF input with absolute ease.
Reducing Uncertainty Associated with Ground‐Water Flow and Transport Predictions
Authors: Poeter Eileen P. , McKenna Sean A. 
Published: August 2005

AbstractEffective evaluation of ground‐water flow and transport problems requires consideration of the range of possible interpretations of the subsurface given the available, disparate types of data. Geostatistical simulation (using a modified version of ISIM3D) of hydrofacies units produces many realizations that honor the available geologic data and represent the range of subsurface interpretations of unit geometry. Hydraulic observations are utilized to accept or reject the geometric configurations of hydrofacies units and to estimate ground‐water flow parameters for the units (using MODFLOWP). These realizations are employed to evaluate the uncertainty of the resulting value of the response function (ground‐water flow velocity and contaminant concentration) using MT3D. The process is illustrated with a synthetic data set for which the “truth” is known, and produces a striking reduction in the distribution of predicted contaminant concentrations. The same system is evaluated three times: first with only hard data, then with both hard and soft data, and finally with only the realizations that honor the hydraulic data (i.e., those accepted after parameter estimation via inverse flow modeling). Using only hard data, the mean concentration predicted for all realizations at the point of interest is nearly two orders of magnitude lower than the true value and the standard deviation of the log of concentration is two. The addition of soft data brings the mean concentration within one order of magnitude of the true value and reduces the standard deviation of the log of concentration to one. After eliminating realizations using inverse flow modeling, the mean concentration is one‐third of the true value and the standard deviation of the log of concentration less than 0.5.
Correction for Temperature Effect in the Recovery of a Pumped Well
Authors: Kawecki M. W. 
Published: August 2005

AbstractWater levels measured in tests on pumped or flowing wells tapping confined aquifers are generally affected by temperature changes in the water column. This temperature effect becomes significant in deep wells, making direct hydraulic analysis of test data meaningless. The problem can be avoided by using an observation well or by monitoring bottom‐hole pressure in the test well, but both these options are costly and consequently not always available. Therefore, a temperature correction method is proposed based on a simple model assumed to describe the cooling in the test well during recovery. The method is designed to determine the aquifer transmissivity from recovery data and to calculate the true drawdown during pumping. The only additional test data requirements are measurements of the initial and stabilized discharge temperatures. Despite several approximating assumptions in the cooling model, the method has given apparently successful results in a number of case studies. Although further testing of its effectiveness is still required, the method may prove to be a useful secondary alternative in many cases if observation wells and bottom‐hole pressure monitoring facilities are not available.
Ground‐Water Contaminant Plume Differentiation and Source Determination Using BTEX Concentration Ratios
Authors: Yang Y. Jeffrey , Spencer Rick D. , Mersmann Mark A. , Gates Todd M. 
Published: August 2005

AbstractConcentration ratios of benzene, toluene, ethylbenzene, and xylenes (BTEX) in ground water can be used for ground‐water contaminant plume differentiation and source determination. Computer modeling utilizing BTEX soil‐water partitioning coefficients and biodegradation rates shows that hydraulic dispersion, retardation, and biodegradation do not significantly modify the BTEX concentration ratios in ground water, particularly those of ethylbenzene and xylenes. Therefore, the BTEX concentration ratios are similar in the contaminant plumes that are derived from a common source or sources of similar BTEX compositions. In the vadose zone, the BTEX concentration ratios in downward‐migrating contaminant free‐product remain essentially unchanged because of the dynamic nature of soil adsorption and restricted natural soil ventilation. The only significant change in the BTEX concentration ratios occurs in the partitioning between ground water and contaminant free‐product as the result of differential BTEX solubilities in water. In the partitioning, benzene/toluene and toluene/ethylbenzene concentration ratios of ground water are 3.6 and 3.3 times greater respectively than the ratios at the source, while the ratios of ethylbenzene and xylenes remain unchanged.The geochemical methods were successfully applied and tested at two sites where multiple ground‐water contaminant plumes from different sources were superimposed. The conclusions of geochemical analysis are consistent with the site‐specific hydraulic characteristics and facility operation histories.
Analysis of Hydraulic Conductivity Averaging Schemes for One‐Dimensional, Steady‐State Unsaturated Flow
Authors: Srivastava Rajesh , Guzman‐Guzman Amado 
Published: August 2005

AbstractThe evaluation of average properties over a block or element is required for most numerical methods used for the solution of unsaturated flow equations. In this study, it is shown that the accuracy of a particular averaging scheme depends on the type of model used for unsaturated material properties. A systematic and thorough error analysis of the averaging techniques for some commonly used soil characteristic curves is performed. It is shown that the two‐point Gaussian quadrature is consistently more accurate than the arithmetic, geometric, and harmonic means for all types of constitutive models.
Delineation of a Saline Ground‐Water Boundary from Borehole Geophysical Data
Authors: Schnoebelen Douglas J. , Bugliosi Edward F. , Krothe Noel C. 
Published: August 2005

AbstractThis study uses borehole geophysical data to calculate the total dissolved solids (TDS) concentration of ground water in Devonian and Silurian carbonate aquifers in northern and southwestern Indiana and specifically, to delineate the 10,000 mg/l (milligrams per liter) TDS boundary. The 10,000 mg/l TDS boundary as used here refers to the transitional zone in the Devonian rocks where the TDS concentration of saline ground water changes from less than 10,000 mg/l to 10,000 mg/l or greater. The 10,000 mg/l boundary not only defines the maximum allowable TDS concentration recommended by the U.S. Environmental Protection Agency for potentially potable water, but also establishes an internal “limit” for the Silurian and Devonian carbonate aquifers in Indiana where density differences may be important for ground‐water flow modeling. The study demonstrated that geophysical log data can provide a useful means of estimating TDS concentration in areas where water‐quality data are lacking, found an excellent correlation between the resistivity‐porosity method and measured TDS concentrations, and found several anomalous areas in Indiana where TDS concentration in Devonian and Silurian aquifers were higher or lower than expected.The TDS content of ground water in Devonian and some Silurian units was estimated by using three independent geophysical methods: static spontaneous‐potential, mud‐filtrate‐resistivity, and resistivity‐porosity. Each method yields values for formation‐water resistivity (Rw), from which TDS concentrations can be estimated. Calculated concentrations from each method were compared to available water‐quality analyses. Use of the resistivity‐porosity method produced the most accurate results. To help quantify the values used in the resistivity‐porosity method, 19 samples cut from cores were evaluated by laboratory analyses. The static spontaneous‐potential method was used only where data were not available for the resistivity‐porosity method. The mud‐filtrate‐resistivity method yielded poor results and was not used. Chemical analyses of ground water and TDS concentrations estimated from borehole geophysical log data (resistivity‐porosity and static spontaneous potential methods) were used to establish areas where TDS concentrations in ground water are less than or greater than 10,000 mg/l.The concentrations of TDS of water from the Silurian and Devonian carbonates were generally found to increase in a consistent trend downdip with depth into the Illinois and Michigan Basins; however, this trend was not observed in several anomalous areas where the 10,000 mg/l TDS boundary becomes more irregular in shape. There are also areas where the underlying Silurian carbonates have TDS concentrations that are less saline than the overlying Devonian carbonates. These anomalous areas may be the result of nonuniform recharge during Pleistocene time or more recent times, or from differences in permeability that control flow paths and rates.
Site Characterization Using 3H/3 He Ground‐Water Ages, Cape Cod, MA
Authors: Solomon D. K. , Poreda R. J. , Cook P. G. , Hunt A. 
Published: August 2005

AbstractExploratory drilling to locate new water‐supply wells on Cape Cod, Massachusetts encountered fuel‐related organic contaminants in a shallow unconfined aquifer. However, the plume could not be traced back to the water table and estimates of ground‐water velocities were not consistent with plausible contaminant releases, and thus the source of contamination was not located. In conjunction with an expanded hydrogeologic investigation, tritium and helium isotope analyses were performed to delineate ground‐water ages and flow rates. Vertical profiles of ground‐water age were used to determine recharge rates that range from 70 to 115 cm/yr. The age of water near the leading edge of the contaminant plume along with estimates of dispersion were used to estimate when the contaminant release occurred (1975 ± 3 years). Recharge estimates, the geometry of the aquifer, and contaminant data were used in a simple mass balance model to determine both the location of the contaminant source and the horizontal ground‐water velocity (ranging from 20 ± 12 m/y to 90 ± 20 m/y across the site). Concurrent site investigations revealed fuel floating on the water table within the area (± 250 m) determined by the model. The configuration of the water table and recharge estimates were used to estimate a horizontal hydraulic conductivity of 130 ± 30 m/d. The mean hydraulic conductivity from a subsequent 72 hr, 12 well pumping test was 100 m/d.
Preparation of Specific‐Yield Logs for Clastic Bedrock Aquifers
Authors: Robson S. G. 
Published: August 2005

AbstractSpecific yield is the principal aquifer characteristic needed to estimate the volume of recoverable ground water in storage in an aquifer. Determination of specific yield can be difficult and costly, particularly in deep, confined aquifers where core drilling and core analyses may be needed to define specific yield. A method has been developed for preparation of specific‐yield geophysical logs that could greatly ease the determination of specific yields in such aquifers.Three geophysical logs that were investigated as potential indicators of specific yield were the free fluid index log, the effective‐porosity log, and the apparent grain‐density log. The free fluid index log did not accurately represent conditions at the test site in central Colorado and may not be suitable for application in other shallow and permeable aquifers. The effective‐porosity and apparent grain‐density logs were each used in least‐squares linear regressions to correlate log response to specific yield measured in core samples. The resulting regression equations have coefficients of correlation (R) of 0.84 and 0.90, and were used to successfully prepare specific‐yield logs from the effective‐porosity and apparent grain‐density logs.
Theis Solution Under Aquifer Parameter Uncertainty
Authors: Cheng A. H‐D. , Ouazar D. 
Published: August 2005

AbstractThe Theis solution is one of the most widely used ground‐water flow solutions for the prediction of drawdown caused by a pumping well in a confined compressible aquifer. This paper extends the classical solution with the consideration of information uncertainty of aquifer parameters. The goal is to present a simple and practical theory that can be easily utilized by practicing hydrogeologists.
Soil‐Gas Signatures from Volatile Chlorinated Solvents: Borden Field Experiments
Authors: Rivett Michael O. 
Published: August 2005

AbstractField experiments have been conducted at the Borden research site to evaluate the widely applied soil‐gas survey method. In particular, the ability of surveys to delineate DNAPL chlorinated solvent sources and associated ground‐water plumes has been investigated. Field experiments indicated that dissolved‐phase plumes from DNAPL pools or residual located about a meter or more below the water table are unlikely to be directly detected by soil‐gas surveys. Soil‐gas plumes observed at real sites are attributed to volatilization of source material in the vadose zone and consequent formation of very shallow interface zone ground‐water contamination that is able to partition to the soil gas as it transports downgradient. The distribution of DNAPL sources and dissolved‐phase plumes deeper in the ground‐water zone may often bear little resemblance to the shallow interface zone ground‐water plume above, and hence the location of this deeper contamination will remain highly difficult to identify by soil‐gas surveys. Field observations are confirmed with simple analytical 1‐D diffusion modeling and the implications of the results to the practice of soil‐gas surveys at contaminated sites indicated.