bluuebunny/crossref_metadata_2025 huggingface dataset:
DETECTION OF A PUTATIVE VIRULENCE cadF GENE OF CAMPYLOBACTER JEJUNI OBTAINED FROM DIFFERENT SOURCES USING A MICROFABRICATED PCR CHIP
Authors: POULSEN CLAUS R. , EL‐ALI JAMIL , PERCH‐NIELSEN IVAN R. , BANG DANG DUONG , TELLEMAN PIETER , WOLFF ANDERS
Published: August 2005

A microfabricated polymerase chain reaction (PCR) chip made of epoxy‐based photoresist (SU‐8) was recently designed and developed. In this study, we tested whether the PCR chip could be used for rapid detection of a potential virulence determinant, the cadF gene of Campylobacter jejuni. PCR was performed using published PCR conditions and primers for the C. jejuni cadF gene. DNA isolated from a C. jejuni reference strain CCUG 11284, C. jejuni isolates obtained from different sources (chicken and human), and Campylobacter whole cells were used as templates in the PCR tests. Conventional PCR in tube was used as the control. After optimization of the PCR chip, PCR positives on the chip were obtained from 91.0% (10/11) of the tested chips. A fast transition time was achieved with the PCR chip, and therefore a faster cycling time and a shorter PCR program were obtained. Using the PCR chip, the cadF gene could be detected in 1.5 h in comparison to 3.4 h in the published methods. The PCR chip can be applied for rapid detection of  the virulence cadF gene of C. jejuni obtained from different sources. This is the first PCR chip that has been used to detect Campylobacter virulence genes. Using the chip, the cadF gene of C. jejuni can be detected directly from bacterial whole cells without DNA isolation and purification steps.
Artificial Recharge in Las Vegas Valley, Clark County, Nevada
Authors: Katzer Terry , Brothers Kay
Published: August 2005

Artificially recharging the ground‐water system is one water resource option available to the Las Vegas Valley Water District in response to increasing water demand during summer peak periods. The existing water‐supply system for Las Vegas Valley is limited since peak water‐use demand periods in 10 to 20 years or less will require the construction of additional facilities. To prepare for these short‐term (and longer) demands, the Las Vegas Valley Water District, in cooperation with the U.S. Bureau of Reclamation, conducted a limited ground‐water recharge demonstration project using treated Colorado River water.

A major concern of water managers regarding artificial recharge is the resulting water chemistry when treated (potable) Colorado River water is injected into the ground‐ water system. Both waters are high in calcium creating a potential for calcite precipitation which, in addition to clogging the perforations in the water well casing, could potentially reduce aquifer permeabilities by clogging the pore space of the flow media.

Approximately 525,000 gallons of potable water were injected into a semiconfined ground‐water aquifer over a three‐day period interspersed with two pumping periods. Water chemistry samples taken throughout the injection project showed no imbalance with regard to calcium or any other chemical constituent. Therefore, artificial recharge is feasible and is one water resource technique available to meet an increasing water demand based on the existing water quality of the Colorado River and the quality of the ground water in the area of injection.
Influence of Using Purged and Partially Penetrating Monitoring Wells on Contaminant Detection, Mapping, and Modeling
Authors: Robbins Gary A.
Published: August 2005

An 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

Recognition 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

A 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

The 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

Sixteen 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.
COMPUTING WELL HYDRAULICS SOLUTIONS
Authors: Dougherty David E.
Published: August 2005

Abstract. Type curves, and drawdown analysis curves of other sorts, have a well‐established position in the ground‐water profession. Although a plethora of solutions to well hydraulics problems exists, many of these arc not available in useful type curve formats. lpurthcr, if one wants to perform parameter estimation using many of these solutions, a computer‐based form of the solution is needed. Those who have programmed analytical solutions know the difficulties that will be encountered in coding even the most innocuous‐looking result. In this paper, a computer‐based method of type curve generation is prcscnted based on Stehfest's method of inverting the Laplace transform solution of ground‐water flow problems. The latter are usually easier to obtain than a complete closed‐form solution. The method is very robust for a large class of well hydraulics problems. A companion diskette with FORTRAN source and executable example program is available from the author.
Indicators of Chemical Pollution from Septic Systems
Authors: Alhajjar Bashar J. , Chesters Gordon , Harkin John M.
Published: August 2005

The 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

The 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

Aquifer 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

Soil 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

The 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

The 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

A 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.
A Program to Calculate Hydraulic Conductivity Using Slug Test Data
Authors: Wylie Allan , Wood Thomas R.
Published: August 2005

Abstract. During the execution of a slug test, the water level in a well is instantaneously raised or lowered and changes in the water level are monitored as it seeks its equilibrium position. SLUGTST is a program, written in TURBO BASICb for IBM PCc microcomputers and compatibles, which calculates hydraulic conductivity using data obtained during such a test.
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

Forty 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

A 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

From 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

A 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.
Simple Derivation of the Retardation Equation and Application to Preferential Flow and Macrodispersion
Authors: Bouwer Herman
Published: August 2005

The equation to calculate the retardation factor of sorbing chemicals moving in aqueous solution through aquifers and vadose zones is derived using a linear sorption isotherm and a mass‐balance approach. The procedure is very simple and clearly illustrates the roles of porosity and water content, including those for saturated flow, unsaturated flow, and preferential flow or other systems with both mobile and immobile phases of the water. Applications of the equation to preferential flow in the vadose zone and macrodispersion in a layered aquifer are illustrated with numerical examples for hypothetical cases.
Aqueous Geochemistry of the Sand‐and‐Gravel Aquifer, Northwest Florida
Authors: Katz Brian G. , Choquette Anne F.
Published: August 2005

The aqueous geochemistry of the sand‐and‐gravel aquifer in northwest Florida was characterized as part of the Florida Ground‐Water Quality Monitoring Network Program, a multiagency cooperative study delineating baseline and/or background water quality for the major aquifer systems throughout the State. The aquifer is the principal source of water in northwest Florida and consists predominantly of quartz sand with smaller amounts of andesine, chlorite, calcite, kaolinite, and illite. Water from 42 wells in the sand‐and‐gravel aquifer sampled during 1986 and 1987 was characteristically low in dissolved solids (median value of 72 milligrams per liter) and of nondistinct water type, although relative concentrations of magnesium and sulfate tended to be lower than those of other major ions. Nonparametric statistical tests of major‐ion concentration variations with depth and relative distance along flow paths indicate that the water chemistry does not change significantly (0.05 significance level) as the water moves vertically and laterally through the aquifer. Mass‐balance calculations indicate that dissolved solids from rainfall and saline‐water sources each account for 13 percent of the concentration of dissolved solids in ground water. Incongruent dissolution of andesine, chlorite, and muscovite to form kaolinite accounts for 94 percent of the neutralization of the total hydrogen ion input from rainfall and from carbonic acid weathering in the subsurface. The remaining neutralization is accounted for by the dissolution of calcite.
Numerical Assessment of a Landfill Compliance Limit
Authors: Mensel Bruce R. , Keefer Donald A. , Griffin Robert A. , Berg Richard C.
Published: August 2005

The PLASM and Random Walk ground‐water flow and contaminant transport models were used to assess the potential impact of various proposed regulatory compliance distances on landfill siting. Contaminant transport modeling was performed for 16 generalized geological sequences representative of hydrogeological conditions over an estimated 90 to 95 percent of Illinois. Results of this modeling indicate that about 50 percent of the state would be hydrogeologically suitable for landfilling of nonhazardous wastes if the compliance distance was 100 feet. With a compliance distance of 500 feet, about 55 percent of the state would be hydrogeologically suitable. This work demonstrates the utility of computer modeling in the development of regulations governing landfill siting.
Prospecting for Zones of Contaminated Ground‐Water Discharge to Streams Using Btottom‐Sediment Gas Bubbles
Authors: Vroblesky Don A. , Lorah Michelle M.
Published: August 2005

Decomposition of organic‐rich bottom sediment in a tidal creek in Maryland results in production of gas bubbles in the bottom sediment during summer and fall. In areas where volatile organic contaminants discharge from ground water, through the bottom sediment, and into the creek, part of the volatile contamination diffuses into the gas bubbles and is released to the atmosphere by ebullition. Collection and analysis of gas bubbles for their volatile organic contaminant content indicate that relative concentrations of the volatile organic contaminants in the gas bubbles are substantially higher in areas where the same contaminants occur in the ground water that discharges to the streams. Analyses of the bubbles located an area of previously unknown ground‐water contamination.

The method developed for this study consisted of disturbing the bottom sediment to release gas bubbles, and then capturing the bubbles in a polyethylene bag at the water‐column surface. The captured gas was transferred either into sealable polyethylene bags for immediate analysis with a photoionization detector or by syringe to glass tubes containing wires coated with an activated‐carbon adsorbent. Relative concentrations were determined by mass spectral analysis for chloroform and trichloroethylene.
Application of Ground‐Penetrating‐Radar Methods in Hydrogeologie Studies
Authors: Beres Milan , Haeni F. P.
Published: August 2005

A ground‐penetrating‐radar system was used to study selected stratified‐drift deposits in Connecticut. Ground‐penetrating radar is a surface‐geophysical method that depends on the emission, transmission, reflection, and reception of an electromagnetic pulse and can produce continuous high‐resolution profiles of the subsurface rapidly and efficiently. Traverse locations on land included a well field in the town of Mansfield, a sand and gravel pit and a farm overlying a potential aquifer in the town of Coventry, and Haddam Meadows State Park in the town of Haddam. Traverse locations on water included the Willimantic River in Coventry and Mansfield Hollow Lake in Mansfield. The penetration depth of the radar signal ranged from about 20 feet in fine‐grained glaciolacustrine sediments to about 70 feet in coarse sand and gravel. Some land records in coarse‐grained sediments show a distinct, continuous reflection from the water table about 5 to 11 feet below land surface. Parallel reflectors on the records are interpreted as fine‐grained sediments. Hummocky or chaotic reflectors are interpreted as cross‐bedded or coarse‐grained sediments. Other features observed on some of the radar records include the till and bedrock surface. Records collected on water had distinct water‐bottom multiples (more than one reflection) and diffraction patterns from boulders. The interpretation of the radar records, which required little or no processing, was verified by using lithologie logs from test holes located along some of the land traverses and near the water traverses.
Tritium as an Indicator of Ground‐Water Age in Centrai Wisconsin
Authors: Bradbury Kenneth R.
Published: August 2005

In regions where ground water is generally younger than about 30 years, developing the tritium input history of an area for comparison with the current tritium content of ground water allows quantitative estimates of minimum ground‐water age. The tritium input history for central Wisconsin has been constructed using precipitation tritium measured at Madison, Wisconsin and elsewhere. Weighted tritium inputs to ground water reached a peak of over 2,000 TU in 1964, and have declined since that time to about 20‐30 TU at present.

In the Buena Vista basin in central Wisconsin, most ground‐water samples contained elevated levels of tritium, and estimated minimum ground‐water ages in the basin ranged from less than one year to over 33 years. Ground water in mapped recharge areas was generally younger than ground water in discharge areas, and estimated ground‐water ages were consistent with flow system interpretations based on other data. Estimated minimum ground‐water ages increased with depth in areas of downward ground‐water movement. However, water recharging through thick moraine sediments was older than water in other recharge areas, reflecting slower infiltration through the sandy till of the moraine.
The Depth of Fractures and Active Ground‐Water Flow in a Clayey Till Plain in Southwestern Ontario
Authors: Ruland W. W. , Cherry J. A. , Feenstra Stan
Published: August 2005

The St. Clair Plain in southwestern Ontario is underlain by extensive clayey till deposits which are generally 30 m to 40 m thick. The tills have vertical fractures near the ground surface, and this study investigates the depth of those fractures. Observations in test pits show that most weathering features along fractures reach a depth of only 2.5 m to 4 m, though isolated major fractures extend past the pit bottom depth of 5.6 m at two sites. This study also investigates the depth of active ground‐water flow, which is defined as the ground‐water flow in the clayey deposit which occurs in fractures. Water‐level response tests show bulk hydraulic conductivities of the fractured till ranging from >10−7 to 10−8 cm/s. Seasonal variations in hydraulic head profiles suggest that fractures influence ground‐water flow to maximum depths ranging from 5 m to more than 10 m at the 10 sites studied. The water table is usually within 2 m of the surface, but piezometers went dry to depths of 2 m to 4.9 m during dry periods in 1987 and 1988. Tritium levels greater than l T.U., indicating the presence of post‐1952 water, are found to depths of 7.5 m at all sites and to depths exceeding 12 m in two cases. Tritium has moved to the base of deep, open fractures by active ground‐water flow and has travelled 1 or 2 m beyond that depth by molecular diffusion. Observations of seasonal water‐level variations and tritium sampling show the most promise for determining the maximum depth of hydraulically active, vertical fractures. The maximum depth of active ground‐water flow in fractures varies widely, ranging from 5 m to more than 10 m at the 12 sites studied on the St. Clair Plain.
A Method for Installing Miniature Multilevel Sampling Wells
Authors: Stites Will , Chambers Lucy W.
Published: August 2005

Abstract. A method has been developed to install miniature multilevel ground‐water sampling wells in shallow, unconsoli‐dated aquifers at sites without truck access. An advantage of these wells over the traditional bundle‐type multilevel is that this type of installation causes minimal aquifer disturbance. Thus, miniature multilevels can be installed while a tracer test is in progress. Furthermore, only hand tools are needed in the field, and equipment and materials are easily obtained and inexpensive. The time required for installation is comparable to other methods.
Statistical Tolerance Limits for Ground‐Water Monitoring
Authors: Gibbons Robert D.
Published: August 2005

Statistical tolerance limits can play a useful role in ground‐water detection monitoring programs at waste disposal facilities; however, their properties are often misunderstood or confused with statistical prediction limits. The purpose of this paper is to describe when, where, and why statistical tolerance limits should be used in ground‐water monitoring applications and how they relate to alternatives, such as statistical prediction limits. In addition, a two‐stage procedure that involves the use of both tolerance and prediction limits is described and is shown to have particularly desirable properties for waste disposal facilities for which large numbers of statistical comparisons are performed on a regular basis (e.g., 100 or more comparisons per quarter).
Influence of Vertical Flow on Ground‐Water Transport
Authors: Brainard Edward C. , Gelhar Lynn W.
Published: August 2005

Two‐dimensional analysis of ground‐water flow using graphical flow net analysis or numerical modeling is applied to many field settings. However, the assumption of hydrostatic head conditions, implicit in two‐dimensional depth‐averaged planimetric analyses, is not correct for situations where there is vertical flow such as near a partially penetrating stream. Vertical flow is particularly important when predicting flow paths for contaminant transport. An analytical solution is presented, which calculates the flow paths in the vicinity of a partially penetrating stream. The derivation assumes radial flow towards the stream in the vicinity of the stream, and predominantly horizontal Dupuit flow in the remainder of the region. The analytical solution may be used as a correction to apply to flow paths generated by two‐dimensional analysis, or as a screening tool to determine the error when vertical flow is neglected by two‐dimensional analysis. To verify the analytical solution, it is compared to numerical simulations of three‐dimensional flow in an idealized aquifer for a number of cases with varying degrees of hydraulic conductivity anisotropy. An example illustrates the use of the analytical solution. For the example presented, two‐dimensional analysis can underestimate the distance which a contaminant travels before discharging into the stream by almost a mile.
An Evaluation of Lithium Sorption Isotherms and Their Application to Ground‐Water Transport
Authors: Newman Brent D. , Fuentes Hector R. , Polzer Wilfred L.
Published: August 2005

Batch adsorption and desorption equilibrium experiments were used to evaluate lithium sorption on crushed tuff in contact with ground water. The laboratory studies were conducted in support of saturated zone characterization field tests to be performed near Yucca Mountain, Nevada. These studies included equilibrium experiments conducted at 38° C (expected subsurface temperature) for a 1‐ to 2,000‐mg/l range of initial lithium solution concentrations. Data from the equilibrium experiments were used in the evaluation of Linear, Langmuir, Freundlich, and Modified Freundlich isotherm expressions.

Comparisons of adsorption and desorption isotherms showed that lithium adsorption was reversible for solution concentrations up to 150 mg/l. This conclusion was based on F‐test comparisons of predicted adsorption and desorption data from Langmuir isotherms.

Lithium sorption was best represented by the nonlinear isotherms where the Langmuir gave the best fit followed by the Modified Freundlich and Freundlich. When these isotherms were used in a one‐dimensional, column adsorption transport code, differences occurred in the predicted breakthrough curves. The transport results showed differences of as much as a factor of five in the time of arrival of lithium for the various isotherms depending on the influent concentration chosen. The differences in the simulation breakthrough curves indicate the importance of isotherm selection. Statistical discrimination and column experiments are suggested as better evaluations of isotherms that are to be incorporated into field‐scale transport simulations.
The Modeling Process and Model Validation
Authors: Tsang Chin‐Fu
Published: August 2005

The safety assessment of underground disposal of nuclear or toxic wastes requires the use of models. Such models need to be validated to ensure, as much as possible, that they are a good representation of the actual processes occurring in the real system. In this paper an attempt is made to take a broad view by reviewing step by step the modeling process and bringing out the need for validating every step of this process. Thus, model validation includes not only comparison of modeling results with data from selected experiments, but also evaluation of procedures for the construction of conceptual models and calculational models as well as methodologies for studying data and parameter correlation. The need for advancing basic scientific knowledge in related fields, for multiple assessment groups, and for presenting our modeling efforts in open literature for public scrutiny is also emphasized.
Modeling Variations in Annular Pressure Due to Fluid Injection
Authors: Arnold Fredric C.
Published: August 2005

Monitoring of the liquid pressure in a casing‐tubing annulus confined by the wellhead at the surface and by a packer above the injection interval is a simple and inexpensive method of detecting the loss of mechanical integrity in wells used for disposal of liquid wastes. However, variations in annular pressure which occur in response to changes in injection rate and injected fluid temperature complicate the interpretation of annular pressure data. The variation of fluid and formation temperatures with depth, the expansion and contraction of fluids and metal tubing with pressure and temperature, and wellbore depth and geometry, have been combined in a model of annular pressure response to fluid injection. The response to changes in injected fluid rate and temperature have been simulated with the model and verified by field experiment. Although the response to a change in injection rate or temperature is greatest in the first two hours following the change, annulus pressure continues to vary with time and a true steady‐state was not attained.
Embedded Knowledge in Software: 2. Demonstration and Preliminary Evaluation
Authors: McClymont G. L. , Schwartz F. W.
Published: August 2005

This paper demonstrates the operation of EXPAR, a knowledge‐based system designed to assist in preparing a set of data for a contaminant transport model. The accompanying evaluation exercise provides preliminary indications of the usefulness of EXPAR. The exercise tested the ability of participants to simulate the distribution of three organic compounds at a hazardous waste site near Ottawa, Canada. A modest set of basic information was provided together with one of four sets of supplementary data. The embedded knowledge in the EXPAR system appeared to provide valuable assistance in modeling, and the system itself met our expectations in terms of the user‐friendliness and robustness. Additional work will be required to remove the weaknesses found in the evaluation particularly with respect to biodégradation data and guidance in establishing flow directions. The results of the project have shown that knowledge‐based systems show promise in solving problems associated with the implementation of a transport model.