bluuebunny/crossref_metadata_2025_split huggingface dataset:
Influence of Using Purged and Partially Penetrating Monitoring Wells on Contaminant Detection, Mapping, and Modeling
Authors: Robbins Gary A. 
Published: August 2005

ABSTRACTAn analytical transport model is presented for evaluating vertically averaged concentration data derived from purged and partially penetrating monitoring wells. The model is applicable to continuous contaminant emission from a finite source with longitudinal advection, and three‐dimensional dispersion. The model is used to investigate how screened length may influence contaminant detection, mapping, and modeling. Sensitivity analyses suggest that contaminant concentrations determined from monitoring wells may underestimate the level of aquifer contamination, depending on screened depth, location of the well relative to the contaminant source, the vertical source dimension, and degree of vertical plume spreading. The magnitude of this effect may be comparable to, and in excess of, concentration biases related to construction materials and sampling procedures. Additional screened interval influences may include: underestimates of contamination extent and migration rate; apparent indications of attenuation processes and steady‐state conditions; over‐ estimates of vertical contaminant spreading; increased time of contaminant detection; and poor transport model predictions, owing to well‐biased concentration distributions.
Ground‐Water Modeling for Salinity Management: An Australian Case Study
Authors: Ghassemi Fereidoun , Jakeman Anthony J. , Thomas Geoffrey A. 
Published: August 2005

ABSTRACTRecognition of the severity of land and stream salinity problems in Australia over the past few decades has resulted in the application of a range of mitigation strategies. In terms of stream salinity management, ground‐ water interception has proved the most cost‐effective strategy, and a number of ground‐water interception schemes have now been implemented. In all cases, the scheme design and assessment of feasibility were based on hydrogeological investigations only. This paper presents an analysis of ground‐water behavior associated with the Mildura interception scheme, illustrating the development and use of mathematical models of ground‐water flow in simulating a range of management options for the mitigation of river salinity. The study found that: over the period of simulation, the interception scheme had been operating below its achievable operational effectiveness, 48 compared to 72 percent; effectiveness could be further enhanced to 80 percent by judicious placement of three additional well fields; and improved irrigation practices in the area would significantly reduce the flow of salt to the river. The modeling approach applies to similar river salinity problems elsewhere.
Ground‐Water Assessment of Sinai, Egypt
Authors: Mills Andrew C. , Shata Abdu 
Published: August 2005

ABSTRACTA ground‐water assessment of Sinai, Egypt, was performed by Dames & Moore for the Egyptian Ministry of Development from 1980 to 1983 as a part of the Sinai Development Study. The basic data included existing stratigraphic data from 69 wells and 57 columnar sections, and hydrologic data for 716 water points (wells and springs).Statistical analysis of the data for total dissolved solids (TDS) and for yields from the water points by ground‐water province and by geologic unit showed that the Southern Mountain Province generally has the best quality ground water and the Suez Rift Province the worst. Among all the geologic units, the crystalline rock, the Middle Cretaceous sequence, and the Quaternary deposits yield water of the lowest total dissolved solids. The mean TDS value of ground water from all water points in Sinai for which data were available is 2,800 mg/1. Of all the geologic units, the highest mean yield (200 m3/day, or about 37 gpm) was from Quaternary deposits in the vicinity of El Arish in the north and in the El Qaa plain along the southwest coast.Regional ground‐water flow in the sedimentary aquifers, such as the Lower Cretaceous (and older) sandstone, tends to be strongly influenced by large‐scale folds and faults. In this aquifer, regional flow occurs generally northward and northeastward toward the Arava valley and the Dead Sea in Israel, but another component of flow occurs toward the Gulf of Suez on the western side.
Modeling of Ground‐Water Recharge in Southern Bali, Indonesia
Authors: Nielsen G. L. , Widjaya J. M. 
Published: August 2005

ABSTRACTThe major aquifers in Southern Bali include a Pliocene lower calcareous sequence and a Quaternary upper volcanic sequence. Both exhibit rapid lateral and vertical facies changes, and hence hydrogeologic parameters are highly variable. Yields of up to 90 l/s are known from the calcareous system and up to 60 l/s from the volcanic formations.Ground‐water recharge was estimated by five different techniques. Analysis of well hydrographs gave 468 mm per annum for 1984–85. Annual infiltration of 25 percent of rainfall gave an average recharge of 437 mm. Baseflow separation of five years of stream discharge data gave 272 mm/annum discharge, approximately equal to recharge, much of which, however, is removed for irrigation upstream of the gauge. A flownet analysis gave 492 mm/annum average discharge, approximately equal to annual recharge.A model for recharge was prepared, using all relevant available soil, land use, hydrogeological, and meteorological data for calibration. It calculated annual recharge in a year of above average rainfall to be 645 mm for light soils, 538 mm for medium soils, and 376 mm for heavy clay soils. Annual recharge in an average rainfall year (1980, 1983) was 605 mm for light soils, 504 mm for medium soils, and 308 mm for heavy soils. In a drought year (1976), recharge was 481 mm in light soils, 401 mm in medium soils, and 267 mm in heavy soils.
Ground‐Water Quality Variations in a Silty Alluvial Soil Aquifer, Oklahoma
Authors: Hoyle Blythe L. 
Published: August 2005

ABSTRACTSixteen wells in a residential area in central Oklahoma were monitored from mid‐April 1986 to early February 1987 to characterize natural water quality variations in a shallow, fine‐grained alluvial soil aquifer. The wells are in four clusters, each with four wells, which range in depth from 8 to 14 feet. Two clusters are adjacent to a row of large deciduous trees and two are in grass‐covered areas.Considerable spatial and seasonal variations occurred in bicarbonate (the major ion in the ground water) and in electrical conductance. Both parameters were generally higher in wells adjacent to the trees than in the grassy areas. Carbon dioxide partial pressure values (Pco2) calculated for ground‐water samples ranged from 10−2·34 to 10−0·42 atm. For a given pH, Pco2 values were higher in the shallower wells under the trees than in grassy areas. These data suggest that more carbon dioxide was produced by tree respiration or associated microbial processes than by grass, resulting in higher bicarbonate concentrations and conductances.Statistical analyses of conductance and bicarbonate data indicated that sample variances were not always equal and that sample distributions were either normal, skewed, or polymodal. These results violate the assumptions of normal distribution and homogeneous variances underlying parametric statistical tests, such as Student's t test, which some regulatory agencies use to compare sample means. Results of this study suggest that more than one well is required to characterize background water quality, and that innovative statistical methods are needed to evaluate monitoring data.
Indicators of Chemical Pollution from Septic Systems
Authors: Alhajjar Bashar J. , Chesters Gordon , Harkin John M. 
Published: August 2005

AbstractThe median‐polish statistical method was used to test and quantify chloride (Cl‐), electrical conductivity (EC), pH, and fluorescence of laundry detergent optical brighteners as indicators of ground‐water pollution from septic systems. The septic systems were located in coarse‐textured soils over a high water table close to discharge areas in south‐central Wisconsin. Parameters were measured monthly for two years in septic tank effluent samples and in water samples collected downgradient from 17 septic systems and from upgradient background samples. The median‐polish technique was excellent for comparing hydrochemical data: Cl‐was a conservative tracer and the most suitable indicator of contaminant plumes; EC was semiconservative and EC and pH were only acceptable; and fluorescence was unacceptable. Fluorescence as an optical brightener in septic tank effluents ranged between 0.14 and 0.98 mg/1 with an average value of 0.40 ± 0.16 mg/l. In ground water downgradient from the septic systems, fluorescence levels were within the background levels. Natural substances such as humic and fulvic acids were probably the sources of fluorescence in ground water, not optical brighteners, because optical brighteners did not pass through septic systems drainfields. Fluorescence of naturally occurring compounds in ground water was between >0.01 and 260 μ/1 with a mean of ≤51± 14 μ/1 expressed as optical brightener. Nitrification in the soil below the drainfields caused ground‐water pH values to decrease within a few meters of the drainfields.
Ground‐Surface Delineation of Fractures Over Mined‐Out Openings Using Carbon Dioxide Emissions
Authors: Kirschner F. E. , Williams R. E. , Ralston D. R. 
Published: August 2005

AbstractThe Bunker Hill Mine, located near Kellogg, Idaho, is situated within highly fractured metasediments comprised of quartzites and argillites. Fractures, faults, and joints are the preferentially permeable pathways for ground‐water flow. Identifying and grouting such features in an attempt to control ground‐water recharge to the mine is a potential method for acid production abatement. In order to implement an effective grouting program, preferential pathways for ground‐water recharge must be identified, delineated, and evaluated.Other researchers have identified the major flow paths and acid mine drainage producing zones within the mine. The objective of this project is to investigate the occurrence of minor structural features (fractures) that may constitute recharge pathways from unsaturated mountain slopes to underlying acid‐producing rocks in or adjacent to mined‐out areas. To accomplish this objective, a soil‐gas measuring technique was employed to measure gaseous emissions that are hypothesized to be produced by chemical reactions between the acid mine drainage and carbonate‐bearing rocks located within the mine. Carbon dioxide (CO2) was selected as a tracer for recharge pathways from mined‐out openings to the ground surface; CO2 was measured using the probe extracted static grab sample/onsite analysis method. The method was tested over an observable fault. Three surficially unobservable fractures were identified within the study area. We hypothesize that these discontinuities are capable of transmitting water to the mine during recharge events.
Influence of Aquifer Heterogeneity on Contaminant Transport at the Hanford Site
Authors: Poeter Eileen , Gaylord David R. 
Published: August 2005

AbstractAquifer heterogeneities defined by mapping and correlating lithofacies derived from existing geologic and borehole geophysical data at the U.S. Department of Energy's (DOE) Hanford Site (south–central Washington) were compared to tritium migration trends within the unconfined aquifer. Lithofacies percentage maps proved useful in defining large–scale (on the order of miles) tritium migration pathways at Hanford but were not sufficiently detailed to serve as unambiguous predictors of these pathways. Results suggest that: (1) incorporation of geologic parameters more closely related to hydraulic properties (e.g., quantified grain size and sorting, degree of cementation, packing arrangement, sedimentary structures, and grain shape), and (2) conscientious integration of all hydrogeologic data at the Hanford Site (and elsewhere) will allow definition of three‐dimensional aquifer elements termed “hydrofacies” and enhance reliable prediction of contaminant migration pathways. Strict reliance on standard fluvial models in the evaluation of lithofacies at Hanford is not appropriate for predicting plume migration because of the complex depositional and erosional history of the sediments comprising the unconfined aquifer. Use of “hydrofacies” ultimately may serve as the appropriate conceptual framework for predicting plume migration.
Selection of Surfactants for the Removal of Petroleum Products from Shallow Sandy Aquifers
Authors: Abdul Abdul S. , Gibson Thomas L. , Rai Devi N. 
Published: August 2005

AbstractSoil and ground‐water contamination by petroleum products, such as gasoline and oils, is widespread. A laboratory study was conducted to evaluate the relative suitability of 10 commercial surfactants for washing residual levels of automatic transmission fluid (ATF) from sandy material. The surfactants included at least one example for each of four main groups of commercial surfactants: (1) ethoxylated alcohols (nonionic), (2) ethoxylated nonylphenols (nonionic), (3) sulfates (anionic), and (4) sulfonates (anionic).Several properties of aqueous solutions of the surfactants (0.00001 to 5.0% v/v) were measured and used in evaluating their suitability. The extent of dispersion of soil colloids was measured as the turbidity (in formazin turbidity units, FTU) of soil/surfactant solution mixtures. The detergency of the surfactant solutions and the extent to which they solubilized the ATF were measured. The critical micelle concentration, which ranged from 0.05 to 5.0 percent, was measured and used to select the aqueous concentration of the surfactants in washing experiments. The amount of ATF removed from the sand ranged from about 23% by washing with water to more than 80% by washing with ethyoxylated alcohol surfactants. ATF was best removed from the soil by washing with a 0.5% aqueous solution of either alkoxylated alcohol ether, ethoxylated alcohol, or nonylphenol ether sulfate. An ethoxylated alcohol surfactant was selected for scale‐up laboratory and field tests because this surfactant caused low soil‐colloid dispersion and high ATF dispersion and solubilization, and was effective in washing ATF from the soil
An Analysis Technique for Multilevel and Partially Penetrating Slug Test Data
Authors: Widdowson Mark A. , Molz Fred J. , Melville Joel G. 
Published: August 2005

AbstractThe multilevel slug test is a technique that provides data for determining the local value of hydraulic conductivity at a specific elevation. However, existing data analysis techniques developed for fully screened and/or partially screened slug tests (Cooper et al., 1967; and Bouwer and Rice, 1976) and packer slug tests (Dagan, 1978) are not adequate for application to the general multilevel case. Through the application of a numerical flow model to the problem, a new means to analyze multilevel slug test data is developed. Simulations performed for both confined and unconfined cases using a finite‐element model yield values of dimensionless discharge for a complete range of multilevel slug test geometries. Effects of anisotropy and location of instrumentation relative to aquifer boundaries are also considered. The method allows for values of horizontal hydraulic conductivity to be determined directly from slug test data. Application to experimental data is provided in an outline of the procedure
Infiltration of Immiscible Contaminants in the Unsaturated Zone
Authors: Reible Danny D. , Illangasekare Tissa H. , Doshi Dharmesh V. , Malhiet Mark E. 
Published: August 2005

AbstractThe presence of a nonaqueous liquid phase in the subsurface often controls the rate and magnitude of ground‐water contamination. In addition, remediation efforts that do not directly address the nonaqueous phase material are unlikely to provide cost‐effective or timely solutions to the ground‐water contamination risk. Practical modeling tools that describe the fate and transport of a separate contaminant phase are described. Simple models such as those described are appropriate for regulatory development and preliminary site assessment and remediation planning.The current work is focused on the one‐dimensional infiltration of a nonaqueous phase liquid through an unsaturated zone initially at residual water saturation. Laboratory experiments examining the infiltration of the water immiscible organics, automatic transmission fluid and isooctane, were used to develop and validate the simple models of the infiltration process. The models described herein are applicable to large spills where the infiltration is essentially one‐dimensional and driven by gravity and capillary forces.
A Hydrogeologic Database for Ground‐Water Modeling
Authors: Newell Charles J. , Hopkins Loren P. , Bedient Philip B. 
Published: August 2005

AbstractA new hydrogeologic database, the HGDB, was developed from a national survey of National Water Well Association (NWWA) members. The database contains general hydrogeologic information from 400 field site investigations across the country and detailed statistical summaries of five ground‐water parameters: hydraulic conductivity, seepage velocity, hydraulic gradient, saturated thickness, and depth to top of aquifer. The HGDB was developed to verify and expand statistical distributions used in a Monte Carlo ground‐water model developed by EPA for land disposal regulation (Federal Register, 1986,1988).The database structure is a unique application of the aquifer classification method used in the NWWA's DRASTIC system (Aller et al., 1987). Respondents were asked to classify their aquifers as one of 111 different DRASTIC hydrogeologic settings, and 12 groupings of settings were analyzed to produce statistical distributions of hydrogeologic data based on site geology and geomorphology. Three examples of the hydrogeologic groupings are coastal beaches; alluvial basins, valleys and fans; and outwash settings.The HGDB can be used for several purposes. First, the HGDB results indicate that the EPA's distributions of seepage velocity and hydraulic conductivity used in the land disposal model are sound. These are the most important hydrogeologic parameters in the model. The HGDB goes a step further, and provides a set of statistical distributions that can be used to make the land disposal regulations more site‐specific than the national approach now being used. Finally, the HGDB data can be used for general site characterization and for educational purposes. The database is available as a detailed written report and spreadsheet file from the American Petroleum Institute, and is contained in a graphical computerized decision support system for ground‐water modeling called OASIS. The HGDB serves as a framework for organizing hydrogeologic information from different site investigations and can be expanded easily beyond the 400 sites now in the database.
Mapping Zones of Contaminated Ground‐Water Discharge Using Creek‐Bottom‐Sediment Vapor Samplers, Aberdeen Proving Ground, Maryland
Authors: Vroblesky Don A. , Lorah Michelle M. , Trimble Stephen P. 
Published: August 2005

AbstractForty passive vapor samplers were placed in creek‐bottom sediment in an area where ground water contaminated with volatile organic compounds is discharging to surface water. The vapor samplers were composed of activated carbon fused to a ferromagnetic wire in a test tube. The samplers were analyzed in a laboratory using an extranuclear quadrupole mass spectrometer. Data from the samplers reveal distributions of chloroform, tetrachloroethylene, trichloroethylene, and benzene in the bottom sediment that closely correspond to the distribution of those compounds in the adjacent ground water. Moreover, concentrations of tetrachloroethylene in bottom sediment estimated from the samplers are similar to those measured in observation wells near the shoreline. Thus, the passive vapor samplers may be used to locate and map areas where contaminated ground water is being discharged to surface water and to determine the approximate concentrations of specific contaminants in the discharging ground water.
Applications of Forward Modeling Resistivity Profiles
Authors: Radstake F. , Geirnaert W. , Kleinendorsf T. W. , Terhell J. C. 
Published: August 2005

AbstractA simple numerical two‐dimensional interpretation model for resistivity profiles and soundings, similar to the one presented by Mufti (1976, 1978, 1980), has been developed for a PC. With the aid of the computer program, a synthetic response of Wenner and Schlumberger soundings or profiles can be generated for two‐dimensional subsurface structures. The possibility of calculating a resistivity response in advance offers a tool to optimize electrode configurations and spacings, and hence greatly improves the value of the measurements. A better insight is also obtained into how geological structures may affect the size and shape of anomalies in resistivity profiles. With the aid of the model, the sensitivity of Schlumberger and Wenner arrays to the weathered layer thickness in a granitic environment is illustrated, and a case study of the quantitative interpretation for a resistivity profile from a schistose environment in Burkina Faso is presented.
On a One‐Dimensional Tracer Model
Authors: Huang Heqing 
Published: August 2005

AbstractFrom the analytical solution to the instantaneous injection model, two sets of equations are given for calculating the three important parameters V, D, and E (effective initial concentration) from two or three points on the tracer breakthrough curve. If two points are used, one must be the maximum concentration on the tracer breakthrough curve. The effective initial concentration (E) calculated from the tracer breakthrough must be less than the initial injection concentration (M/PS) (M is the tracer mass being injected, P is the porosity of the reservoir, and S is the cross‐sectional area of the flow for an injection). The difference between the initial injection concentration and the calculated effective initial concentration might be used to evaluate the degree of tracer loss resulting from a combined effect of multidirectional dispersion, adsorption, and/or decomposition.
Estimating Recharge Rates Through Unsaturated Glacial Till by Tritium Tracing
Authors: Daniels Douglas P. , Fritz Steven J. , Leap Darrell I. 
Published: August 2005

AbstractA tritium profile obtained from a core located on the Tipton Till Plain near West Lafayette, Indiana, showed a “tritium reversal” (corresponding to a low‐high‐low activity of tritium relative to depth) at 7 m, indicating the present position of recharge water derived from 1963/64 precipitation. The average recharge rate calculated using the tritium data is 3.5 cm/yr for the “mass‐balance” method and 4.7 cm/yr for the “transit‐time” method. The average of 4.1 cm/yr is in reasonable agreement with Arihood's (1982) estimate of 5.1 cm/yr for tills, based on numerical modeling of data from a water‐budget study in the White River basin of Indiana. Two other cores, located on a nearby topographically lower slope, showed no definite reversal in tritium activity, probably because of lateral flow components at these locations.To be applied, the tritium technique should assess the contribution of summer and winter precipitation to recharge because tritium activities tend to peak in spring and summer precipitation. Contrary to the usual assumptions that recharge to aquifers in temperate zones of the northern hemisphere occurs between October and April, stable isotopic data of well water in the study area indicate that an appreciable amount of annual recharge (about 34%) actually occurs between April and October.