bluuebunny/crossref_metadata_2025 huggingface dataset:
Ground‐Water Flow Simulation for Management of a Regulated Aquifer System: A Case Study in the North Carolina Coastal Plain
Authors: Reynolds Jeffrey W. , Spruill Richard K.
Published: August 2005

The State of North Carolina designated a portion of the North Carolina Coastal Plain as its first and only Capacity Use Area in 1969 in response to large‐scale withdrawals from the Castle Hayne aquifer system for phosphate mining operations. Withdrawals from this regulated aquifer require water‐use permits. Applications for water‐use permits require information on the use of the water, including an assessment of the impacts on the source aquifer(s). The U.S. Geological Survey finite‐difference model MODFLOW was used to simulate ground‐water flow in a 1,300 square mile area in the Capacity Use Area to estimate the effects of a proposed mine advance anticipated to require more extensive pumping from the aquifer. In addition, the model was used to evaluate the effects of a proposed municipal wellfield also to be located in the Capacity Use Area. The model provided estimates of required pumping rates for the mining activities. Simulated potentiometric surfaces and hydrographs for the Castle Hayne aquifer resulting from both the mining and the wellfield operations indicated that the Castle Hayne aquifer achieves steady state relatively rapidly and is impacted over a large area as a result of the depressurization pumping. Wellfield pumping has a relatively minor effect. Impacts on ground‐water levels in the Castle Hayne aquifer at nearby communities are mainly dependent on the location of the active mining center. Regional‐scale ground‐water flow models can provide information on the potential effects on the flow system of significant hydrologic stresses and could therefore be useful in assessing the impacts of the stresses as required in the permitting process.
The Geochemistry of Chromium Migration and Remediation in the Subsurface
Authors: Davis Andy , Olsen Roger L.
Published: August 2005

From a human health perspective, knowledge of Cr speciation in soils is important in assessing risk related to ingestion of Cr‐contaminated soils, and in selecting appropriate remedial alternatives that are protective of ground‐water quality. In this study, good agreement was found between Cr (VI) soil concentrations and the mass of Cr (VI) leached from columns over a range of Cr (III):Cr (VI) soil ratios (0.2‐28) and ΣCr concentrations (27–290 mg/kg). In batch tests, adsorption of Cr(VI) to sandy soils was rapid and linear, with a KdCr(VI) of 0.2 liters/kg, suggesting Cr(Vl)‐contaminated vadose‐ and saturated‐zone materials may be remediated by soil flushing or pump‐and‐treat methods. In column tests, soil flushing removed 85% of the soil‐Cr(VI), while pump‐and‐treat leached only 17% of Cr attributable to aquifer contamination. Use of oxidizing agents increased Cr released from Cr(III)‐contaminated soils, but only from 1.3% to 2.3% of ΣCr mass. Based on Cr speciation in soils, Cr(VI) was mobile, while Cr(III)was retained in the soil column, indicating that reduction of Cr(VI) to Cr(III), and the proportion of Cr(III) in the soil, will constrain remedial efficiency. Reduction of Cr(VI) to Cr(III), and subsequent precipitation of CrxFe1−x (OH)3, occurred in a Cr(VI)‐contaminated soil augmented with Fe+2, resulting in < 0.01 mg/1 Cr in the supernatant, suggesting that in situ Cr fixation may mitigate Cr‐contaminated ground water.
Use of Weighted Least‐Squares Method in Evaluation of the Relationship Between Dispersivity and Field Scale
Authors: Xu Moujin , Eckstein Yoram
Published: August 2005

Regression formulas relating dispersivity and field scale have been suggested in the literature by few researchers, among others: Arya (1986) and Neuman (1990). These studies employ conventional statistical techniques that cannot take into account the relative reliability level of a data point. Neuman (1990), using conventional statistics, discarded the low reliability data obtained by calibrating numerical grid models against solute concentrations of large‐scale plumes. Although the numerical modeling data are of low reliability, they are important to consider because of the very limited overall availability of the data. Another problem is with the slope reduction of log10αL versus log10L for large values of L, where L is the field scale, and αL is the longitudinal dispersivity. Neuman (1990) used a different line of best fit with a reduced slope for L ≤ 100 m. Fitting two straight lines on a logarithmic scale, one for L ≤ 100 m and another one for L ≤ 100 m, takes care of the slope change to some extent, but results in loss of data points for both statistical groups. In order to provide a better statistical model using the available data with varying reliabilities, a weighted least‐squares data fitting method was used to define a relationship between dispersivity and field scale. By using this technique, less reliable data points were not simply ignored, but rather assigned a lower weight. The linear model is further improved by fitting a curve through the data drawn on a log10αL versus log10 L diagram. The analysis shows a significant difference between the weighted and the unweighted curves. Further analysis indicated that the increase in longitudinal dispersivity is practically negligible when the scale of flow exceeds 1 km.
Simulations of Flow in Crystalline Rock and Recharge from Overlying Glacial Deposits in a Hypothetical New England Setting
Authors: Harte Philip T. , Winter Thomas C.
Published: August 2005

Cross‐sectional, finite‐difference, steady‐state ground‐water‐flow models of a generalized New England landscape were constructed to examine the effects of hydraulic conductivity and topography on bulk‐fluid flow processes in fractured crystalline rock. The generalized landscape consists of a flat hilltop, a hillside that has a slope of 0.17 ft/ft, and a flat river valley. It includes three hydrogeologic units, stratified drift in the river valley, glacial till, and underlying crystalline rock.

Distribution of recharge to and discharge from bedrock is affected by the presence of small topographic features, such as terraces on the hillside. Most of these terraces consist partly or entirely of sand, and they create localized areas of recharge to and discharge from bedrock. Maximum recharge to bedrock commonly occurs at downward inflections of the water table, and discharge occurs at upward inflections of the water table. These inflections of the water table are associated with inflections in topography because the shallow depth of water on hilltops and hillsides resemble the configuration of the land surface.

Regional ground‐water flow in crystalline rock and distribution of bedrock recharge and discharge are also affected by heterogeneities in hydraulic conductivity of the bedrock. Vertical heterogeneity creates short, shallow flow paths in high‐relief terrain. Horizontal heterogeneity causes large variations in the size of bedrock recharge areas; in some cases the difference from homogeneous conditions is more than 50 percent.
A Method for Estimating Field‐Scale Mass Transfer Rate Parameters and Assessing Aquifer Cleanup Times
Authors: Brogan Scott D. , Gailey Robert M.
Published: August 2005

A general method for estimating ground‐water solute mass transfer rate parameters from field test data is presented. The method entails matching solute concentration and hydraulic head data collected during the recovery phase of a pumping test through application of a simulation‐regression technique. Estimation of hydraulic conductivity and mass transfer rate parameter values is performed by fitting model simulations to the data. Parameter estimates are utilized to assess cleanup times for pump‐and‐treat aquifer remediation scenarios. Uncertainty in the cleanup time estimate is evaluated using statistical information obtained with the parameter estimation technique.

Application of the method is demonstrated using a hypothetical ground‐water flow and solute transport system. Simulations of field testing, parameter estimation, and remedial time frames are performed to evaluate the usefulness of the method. Sets of random noise that signify potential field and laboratory measurement errors are combined with the hypothetical data to provide rigorous testing of the method. Field tests are simulated using ranges of values for data noise, the mass transfer rate parameters, the test pumping rates, and the duration of recovery monitoring to evaluate their respective influence on parameter and cleanup time estimates. The demonstration indicates the method is capable of yielding accurate estimates of the solute mass transfer rate parameters. When the parameter values for the hypothetical system are well estimated, cleanup time predictions are shown to be more accurate than when calculated using the local equilibrium assumption.
Slug Tests in Unconfined Formations: An Assessment of the Bouwer and Rice Technique
Authors: Hyder Z. , Butler J. J.
Published: August 2005

The slug test is one of the most common techniques for the in situ estimation of hydraulic conductivity in unconfined flow systems. Recently, a mathematical model describing the flow of ground water in response to a slug test in an unconfined flow system has been proposed. This model incorporates the effects of partial penetration, anisotropy, an upper constant‐head boundary, and, in its most complete form, well skins of either higher or lower permeability than the formation itself. This model is useful in identifying conditions when conventional approaches (i.e., the Bouwer and Rice model) introduce large errors into parameter estimates. For slug tests performed in homogeneous, isotropic formations that would be classified as aquifers, the Bouwer and Rice model provides estimates within 30% of actual field values. In less‐permeable, clay‐rich formations, however, estimates may overpredict formation conductivity by more than 100%. The Bouwer and Rice model introduces the largest error (can easily exceed an order of magnitude) in the presence of a low‐permeability skin. Uncertainty about anisotropy can also be the source of considerable error. The semianalytical solution to the mathematical model described here can be employed for parameter estimation under conditions when the Bouwer and Rice model introduces unacceptably large errors into parameter estimates. This solution can be rapidly evaluated, allowing easy incorporation into an automated well‐test analysis package and/or ready generation of type curves.
Effective Parameter Optimization for Ground‐Water Model Calibration
Authors: Olsthoorn T. N.
Published: August 2005

This paper shows that the Levenberg‐Marquardt method, modified to limit the parameter update steps to within a specified range, effectively optimizes a set of parameters in a ground‐water model. In doing so it performs better than more complicated conjugate gradient algorithms.

The method has been applied to the synthetic ground‐water problem of Carrera and Neuman (1986b), which has been used previously to test calibration method performance. The descent of the error criterion and the simultaneous approach of the parameters to their optimum values are smooth, both with perfect and erroneous head observation data.

It is shown that least‐squares optimization can be done effectively in a simple manner and that it can be easily integrated with practical ground‐water modeling. No changes have to be made to the model code. This ease of implementation is emphasized by the fact that all modeling presented here was done using an ordinary spreadsheet program on a PC.
Optimal Ground‐Water Remediation Methods Applied to a Superfund Site: From Formulation to Implementation
Authors: Ahlfeld David P. , Page Roger H. , Pinder George F.
Published: August 2005

1. Abstract

A hydraulic control optimization model is applied to the conceptual and implementation analysis of a ground‐water remediation system in coastal New Jersey. The site is modeled using a distributed parameter finite‐difference model containing 36,000 nodes within five layers. The conceptual problem is to determine the feasibility of producing a capture zone which encompasses the entire existing plume while recharging all extracted water within property boundaries in such a way that the recharged water satisfies criteria on its fate. The conceptual analysis problem is formulated as a linear program in which the total extraction pumping is minimized, and requirements are placed on hydraulic heads and gradients in both horizontal and vertical directions. A requirement is also made that all extracted water be recharged to the subsurface. The model is used for determination of the feasibility of the remediation concept. Details of constructing constraints for a large‐scale formulation are presented. The concept of constraint calibration, using particle tracking to insure that constraints are producing desired results, is introduced and demonstrated. The optimization formulation is used for detailed implementation analysis of the remediation system. A number of techniques for modifying elements of the conceptual model results, such as unrealistically small pump rates, are described. The optimization approach is found to be useful for determining the feasibility of the remedial strategy at this site and for producing results which can be used as a starting point for detailed analysis of the remediation strategy.
Geothermal‐Water Characteristics in the Surdulica Aquifer
Authors: Hadzisehović Munevera , Dangić Adam , Miljević Nada , Sipka Vojislava , Golobocanin Dusan
Published: August 2005

The Surdulica‐Bujanovac geothermal region of southeastern Serbia, with granodiorite (Surdulica) and granite (Bujanovac) aquifers (water temperatures of 125°C and 46°C, respectively) was hydrogeologically and geochemically studied using environmental isotopes from 1986 to 1990. In the Surdulica system, water, rock, and vegetation samples from 35 locations (springs, rivers, and boreholes) representing all parts of the hydrogeological system (recharge area, transition zone, and terminus with hot deep‐circulated waters) were collected for geochemical and isotope analyses (D, 18O,3H, 13C, 14C). From the recharge area to the terminus of the system, ground‐water temperatures and ionic concentrations increase two to three orders of magnitude: temperature from 3–126°C, Na+ 2.3–1127 mg/1; HCO3− 30.5–2989 mg/1; SO42− 4.8–480 mg/1; SiO2 3–90 mg/1. The hot waters, appearing at the terminus of the system (Vranjska and Bujanovac Spas locations) are the oldest, based on 14C and 3H. The δ13C attains the low negative value of −0.4‰ for hot waters, approaching those in the aquifer matrix, which are in the range between −8.4 and + 2 ‰. The δ18O and δD values in precipitation and ground water indicate that recharge takes place predominantly at the higher elevations (more than 500 m asl) and in the cold seasons. A dual‐porosity system comprised of fissures and intergranular storage controls fluid transport. The deepest flows are hydraulically isolated from fresh waters. Low 14C contents (1–6 pMC) and the absence of3 H suggest the mean residence times for the older water up to 20,000 years. A 18O shift and chemical geothermometers suggest that their base temperatures of more than 200°C are not likely.
Fracture Density Distributions and Well Yields in Coastal Maine
Authors: Loiselle Marc , Evans David
Published: August 2005

Understanding the distribution of water‐bearing fractures in crystalline rock is an important component in evaluating the availability and vulnerability of water resources throughout the northeastern U.S. The State of Maine requests well drillers to report estimates of fracture depths and fracture yields for all bedrock wells drilled in the state. Using these data we analyze fracture‐depth and fracture‐yield data from 227 bedrock wells in coastal Maine in order to understand how fracture locations and yields are distributed with depth. Numerical simulations and statistical tests show that it is not possible to infer how fractures are distributed with depth: fracture depths are consistent with several distributions, including uniform fracture density with depth. In order to understand how fracture yield varies with depth, we group yield data into 50 foot depth intervals and compare distributions in each interval using nonparametric statistical tests. These tests show that the distribution of fracture yield in different depth intervals are statistically equivalent. These results imply that there is no empirical justification for limiting well depth when drilling for water resources in fractured bedrock in coastal Maine.
Analytical Solutions for Water Flow and Solute Transport in the Unsaturated Zone
Authors: Nachabe Mahmood H. , Islas Alvaro L. , Illangasekare Tissa H.
Published: August 2005

Analytical solutions for the water flow and solute transport equations in the unsaturated zone are presented. We use the Broadbridge and White nonlinear model to solve the Richards’ equation for vertical flow under a constant infiltration rate. Then we extend the water flow solution and develop an exact parametric solution for the advection‐dispersion equation. The method of characteristics is adopted to determine the location of a solute front in the unsaturated zone. The dispersion component is incorporated into the final solution using a singular perturbation method. The formulation of the analytical solutions is simple, and a complete solution is generated without resorting to computationally demanding numerical schemes. Indeed, the simple analytical solutions can be used as tools to verify the accuracy of numerical models of water flow and solute transport. Comparison with a finite‐element numerical solution indicates that a good match for the predicted water content is achieved when the mesh grid is one‐fourth the capillary length scale of the porous medium. However, when numerically solving the solute transport equation at this level of discretization, numerical dispersion and spatial oscillations were significant.
Dampening of Transverse Dispersion in the Halocline in Karst Limestone in the Northeastern Yucatan Peninsula
Authors: Stoessell Ronald K.
Published: August 2005

A range of hydrodynamic dispersion coefficients was estimated for fracture‐fluid and combined fracture and pore‐fluid flow within the halocline of the limestone aquifer forming the surface of the northern Yucatan Peninsula. The coefficients are fit parameters in a model reproducing observed halocline profiles in a sinkhole and in a borehole near the northeastern coast. Fitted coefficients range from 10−7 to 10−4 cm2/sec, of which molecular diffusion, without transverse (vertical) dispersion, can account for 10−7 to 10−5 cm2/sec. The mechanical stability of the vertical density gradient in the halocline dampens transverse dispersion in pore fluids and in fracture fluids that are transitional between laminar and turbulent flow. The dampening is proportional to the ratio of the energy needed for the fluid to rise and displace a less dense fluid to the vertical component of the kinetic energy of the fluid. The ratio of these two energies is at a maximum during the initial stage of development of a halocline and decreases as the halocline widens.
Retardation of Dissolved Oxygen Due to a Trapped Gas Phase in Porous Media
Authors: Fry Virginia A. , Istok Jonathan D. , Semprini Lewis , O'Reilly Kirk T. , Buscheck Timothy E.
Published: August 2005

Information on the transport of dissolved gases in ground water is needed to design ways to increase dissolved gas concentrations in ground water for use in in situ bioremediation (e.g., O2 and CH4) and to determine if dissolved gases are conservative tracers of ground‐water flow (e.g., He). A theoretical model was developed to describe the effect of small quantities of trapped gas bubbles on the transport of dissolved gases in otherwise saturated porous media. Dissolved gas transport in porous media can be retarded by gas partitioning between the mobile aqueous phase and a stationary trapped gas phase. The model assumes equilibrium partitioning where the retardation factor is defined as R = 1 + H′(Vg/Vw) where H' is the dimensionless Henry's Law constant for the dissolved gas, and Vg and Vw are the volumes of the trapped gas and water phases, respectively. At 15°C and with Vg/ Vw= 0.05, the predicted retardation factors for He, O2, and CH4 are 5.8, 2.4, and 2.3, respectively. The validity of the model was tested for dissolved oxygen in small‐scale column experiments over a range of trapped gas volumes. Retardation factors of dissolved oxygen increased from 1 to 6.6 as Vg/Vw increased from 0 to 0.123 and are in general agreement with model predictions except for the larger values of Vg/Vw. The theoretical and experimental results suggest that gas partitioning between the aqueous phase and a trapped gas phase can greatly influence rates of dissolved gas transport in ground water.
Flow of Gasoline‐in‐Water Microemulsion Through Water‐Saturated Soil Columns
Authors: Ouyang Ying , Mansell Robert S. , Rhue R. Dean
Published: August 2005

Much consideration has been given to the use of surfactants to clean up nonaqueous phase liquids (NAPLs) from contaminated soil and ground water. Although this emulsification technique has shown significant potential for application in environmental remediation practices, a major obstacle leading to low washing efficiency is the potential formation of macroemulsions with unfavorable flow characteristics in porous media. This study investigated influences of the flow of leaded‐gasoline‐in‐water (LG/W) microemulsion upon the transport of gasoline and lead (Pb) species in water‐saturated soil columns. Two experiments were performed: (1) the immiscible displacement of leaded gasoline and (2) the miscible displacement of LG/W microemulsion through soil columns, followed by sequentially flushing with NaCl solution and a water/surfactant/cosurfactant (W/S/CoS) mixture. Comparison of breakthrough curves (BTC) for gasoline between the two experiments shows that about 90% of gasoline and total Pb were removed from the soil columns by NaCl solution in the LG/W microemulsion experiment as compared to 40% removal of gasoline and 10% removal of total Pb at the same process in the leaded gasoline experiment. Results indicate that gasoline and Pb species moved much more effectively through soil during miscible flow of LG/W microemulsion than during immiscible flow of leaded gasoline. In contrast to the adverse effects of macroemulsion on the transport of NAPLs, microemulsion was found to enhance the transport of gasoline through water‐saturated soil. Mass balance analysis shows that the W/S/CoS mixture had a high capacity for removing residual gasoline and Pb species from contaminated soil. Comparison of water‐pressure differences across the soil columns for the two experiments indicates that pore clogging by gasoline droplets was greatly minimized in the LG/W microemulsion experiment.
Estimating DNAPL Composition and VOC Dilution from Extraction Well Data
Authors: Jackson R. E. , Marine P. E.
Published: August 2005

Field data from a large‐scale ground‐water extraction system at the Savannah River Site in South Carolina indicate that considerable dilution of volatile organic compounds (VOCs) occurs at extraction wells when compared with the effective solubilities of the VOC components (TCE and PCE) in the dense, nonaqueous phase liquid (DNAPL) source zone. This dilution is believed to be due to the convergence of both contaminated and uncontaminated streamtubes on the extraction wells studied. Thus, the measured concentrations of dissolved VOCs in extraction wells appear to be principally functions of (1) the effective solubilities of the DNAPL components, and (2) the dilution due to streamtube convergence on the extraction wells. A simple method for computing DNAPL composition and the dilution factor from extraction well data is presented for the case when dilution is the dominant mechanism that causes the measured ground‐water concentrations of dissolved VOC components to be significantly less than their respective effective solubilities relative to the DNAPL mixture. This method successfully computes the molar composition of a PCE/ TCE DNAPL, bailed from a pair of monitor wells at the Savannah River Site, using the measured concentrations of PCE and TCE in ground waters from the same pair of wells. The method is then used to predict the variation of DNAPL composition within the aquifer from VOC data sampled at all 11 extraction wells. Such information is of considerable use in choosing solvent‐specific surfactants for enhanced remediation operations.
Measurements of Aquifer‐Storage Change and Specific Yield Using Gravity Surveys
Authors: Pool D. R. , Eychaner J. H.
Published: August 2005

Pinal Creek is an intermittent stream that drains a 200‐square‐mile alluvial basin in central Arizona. Large changes in water levels and aquifer storage occur in an alluvial aquifer near the stream in response to periodic recharge and ground‐water withdrawals. Outflow components of the ground‐water budget and hydraulic properties of the alluvium are well‐defined by field measurements; however, data are insufficient to adequately describe recharge, aquifer‐storage change, and specific‐yield values. An investigation was begun to assess the utility of temporal‐gravity surveys to directly measure aquifer‐storage change and estimate values of specific yield.

The temporal‐gravity surveys measured changes in the differences in gravity between two reference stations on bedrock and six stations at wells; changes are caused by variations in aquifer storage. Specific yield was estimated by dividing storage change by water‐level change. Four surveys were done between February 21, 1991, and March 31, 1993. Gravity increased as much as 158 microGal ± 1 to 6 microGal, and water levels rose as much as 58 feet. Average specific yield at wells ranged from 0.16 to 0.21, and variations in specific yield with depth correlate with lithologic variations. Results indicate that temporal‐gravity surveys can be used to estimate aquifer‐storage change and specific yield of water‐table aquifers where significant variations in water levels occur. Direct measurement of aquifer‐storage change can eliminate a major unknown from the ground‐water budget of arid basins and improve residual estimates of recharge.
Use of a Square‐Array Direct‐Current Resistivity Method to Detect Fractures in Crystalline Bedrock in New Hampshire
Authors: Lane J. W. , Haeni F. P. , Watson W. M.
Published: August 2005

Azimuthal square‐array direct‐current (dc) resistivity soundings were used to detect fractures in bedrock in the Mirror Lake watershed in Grafton County, New Hampshire. Soundings were conducted at a site where crystalline bedrock underlies approximately 7 m (meters) of glacial drift. Measured apparent resistivities changed with the orientation of the array. Graphical interpretation of the square‐array data indicates that a dominant fracture set and (or) foliation in the bedrock is oriented at 030° (degrees). Interpretation of crossed square‐array data indicates an orientation of 027° and an anisotropy factor of 1.31. Assuming that anisotropy is due to fractures, the secondary porosity is estimated to range from 0.01 to 0.10.

Interpretations of azimuthal square‐array data are supported by other geophysical data, including azimuthal seismic‐refraction surveys and azimuthal Schlumberger dc‐resistivity soundings at the Camp Osceola well field. Dominant fracture trends indicated by these geophysical methods are 022° (seismic‐refraction) and 037° (dc‐resistivity). Fracture mapping of bedrock outcrops at a site within 250 m indicates that the maximum fracture‐strike frequency is oriented at 030°.

The square‐array dc‐resistivity sounding method is more sensitive to a given rock anisotropy than the more commonly used Schlumberger and Wenner arrays. An additional advantage of the square‐array method is that it requires about 65 percent less surface area than an equivalent survey using a Schlumberger or Wenner array.
Research Borehole‐Geophysical Logging in Determining Geohydrologic Properties
Authors: Jorgensen Donald G. , Petricola Mario
Published: August 2005

A research borehole‐geophysical logging program was implemented to assess specific yield, aquifer mineralogy, and water resistivity more accurately and economically than can be done using conventional aquifer testing and coring procedures. The logging program was part of the Ground‐Water Research Project for Abu Dhabi Emirate.

A method of determining specific yield using data from a thermal decay‐time (TDT) log was developed and tested. This technique relates the capture cross section of the fluid in the invaded zone to specific yield. A second new method uses data from density and neutron logs in a program “LOGAN2” to determine specific yield. Results from both methods were compared to the specific yield derived from the neutron log as well as a specific yield determined by a complex analysis of data from a set of research borehole‐geophysical logs, including a gamma‐gamma log for density, neutron, sonic, gamma‐ray, induction, microresistivity, photoelectric, caliper, and spontaneous‐potential logs. The agreement was good.

A method of computer‐assisted interpretation of mineralogy was developed by correlating results of direct examination of the mineralogy of sidewall cores with data from a nuclear activated spectral‐gamma log (GLT). The GLT log allows the mineralogy to be assessed in a comprehensive manner. These computer interpreted results were used to develop another method of computer‐assisted interpretation of holes logged not using the GLT. The second method was applied to the more than 50 other test holes that did not include GLT and TDT logs.

Resistivity of the water in the formation was conceptualized using a dual‐water model, which is especially suited for clayey aquifers. Water resistivities were calculated by two methods—first using data from the suite of logs without the GLT and again using the data from the research suite of logs, which included the GLT. The agreement of calculated water resistivities was excellent
Bottled Water, Spas, and Early Years of Water Chemistry”
Authors: Back William , Landa Edward R. , Meeks Lisa
Published: August 2005

Although hot springs have been used and enjoyed for thousands of years, it was not until the late 1700s that they changed the course of world civilization by being the motivation for development of the science of chemistry. The pioneers of chemistry such as Priestley, Cavendish, Lavoisier, and Henry were working to identify and generate gases, in part, to determine their role in carbonated beverages. In the 18th century, spas in America were developed to follow the traditional activities of popular European spas. However, they were to become a dominant political and economic force in American history on three major points: (1) By far the most important was to provide a place for the leaders of individual colonies to meet and discuss the need for separation from England and the necessity for the Revolutionary War; (2) the westward expansion of the United States was facilitated by the presence of hot springs in many locations that provided the economic justification for railroads and settlement; and (3) the desire for the preservation of hot springs led to the establishment of the National Park Service. Although mineral springs have maintained their therapeutic credibility in many parts of the world, they have not done so in the United States. We suggest that the American decline was prompted by: (1) the establishment of The Johns Hopkins School of Medicine in 1893; (2) enactment of the Pure Food and Drug Act of 1907; and (3) the remarkable achievement of providing safe water supplies for American cities by the end of the 1920s. The current expanding market for bottled water is based in part on bottled water being an alternative beverage Ito alcohol and sweetened drinks and the inconsistent palatability and perceived health hazards of some tap waters.
Relation Between Topography and Well Yield in Boreholes in Crystalline Rocks, Sogn og Fjordane, Norway
Authors: Henriksen Helge
Published: August 2005

Well data from about 760 wells drilled in lower Paleozoic and Precambrian hard rocks have been integrated in a database with topographic and lithologic data thought to be of importance for well yield. The database is mainly based on already existing well records supplemented by desk studies of maps. The wells were initially assigned to nine hydrogeological settings determined by rock type, and into five hydrogeological settings according to their topographic position. Statistical tests were performed to determine whether the median well yields of these groups were significantly different. Boreholes in valley bottoms and flatlands had higher well yields. The data analysis suggests that the lithologic effect on well yield may be of less importance than topography.
Analysis of Temporal Environmental Isotopic Variation in Ground Water of the Georgia Piedmont
Authors: Rose Seth
Published: August 2005

Time‐series analyses were made of environmental tritium (3H) concentrations, the stable oxygen isotopic (δ18O) and major‐ion composition of natural waters from the southeastern Piedmont Province of Georgia. The sampling network consisted of four fractured rock production wells (utilized at variable rates), one regolith monitoring well, two streams, and rainfall. Although the isotopic composition of rainfall was highly variable (−11.8‰≤δ18O ≤−l.l‰ and 2.3 ≤ TU ≤ 125), only minor isotopic variation (δl8O generally ≤ 1.0‰ and 3H generally ≤ 2 TU) was observed during the sampling period (∼ 1 year) within ground water at a given well site. The coefficients of isotopic variation for ground water within the bedrock aquifers (δ18Ocv and 3H cv < 10%) were similar to those of ground water within the shallow regolith (δ18Ocv= 5.6% and 3Hcv= 3.3%).

Ground water from the most extensively used production well was nearly isotopically and geochemically invariant throughout most of the year. Other than a 0.3–0.5‰δ18O depletion observed during the late spring and early summer, there were few temporal trends and little to suggest the presence of a seasonal component of recharge within ground water extracted from the fractured bedrock aquifers. This is consistent with the 3H‐modeled mean residence time of this ground water which is ∼ 20–40 years. The isotopic composition becomes well‐homogenized by the time ground water infiltrates a few meters below the water table, and ground‐water pumping does little to alter these mixing processes.
Pump‐and‐Treat Remediation of Heterogeneous Aquifers: Effects of Rate‐Limited Mass Transfer
Authors: Berglund Sten , Cvetkovic Vladimir
Published: August 2005

An analytical solution for the radial mass flux in a stratified aquifer is presented. The solution refers to a simple case of aquifer remediation by the pump‐and‐treat method using one extraction well. Initially, the contaminant mass is distributed between the mobile phase and “subsurface sources,” from which mass is transferred to the ground water by a rate‐limited process. The transport of the dissolved contaminants is assumed to be by advection only. The results show that both the heterogeneity in hydraulic conductivity and the mass transfer process have impact on the predicted cleanup times. The rate of mass transfer and the mass distribution are concluded to be the most important parameters and, therefore, the mass transfer process should be the prime subject of further investigations.
Optimization of Remedial Pumping Schemes for a Ground‐Water Site with Multiple Contaminants
Authors: Xiang Yanyong , Sykes Jon F. , Thomson Neil R.
Published: August 2005

This paper presents an optimization analysis of the remedial pumping design for a contaminated aquifer located in Elmira, Ontario, Canada. The remediation task presented in the paper is to remove two ground‐water contaminant species, NDMA (N‐nitrosodimethylamine) and chlorobenzene, to such extent that the specified ground‐water quality standards are met. The contaminants, NDMA and chlorobenzene, have different initial plume configurations and retardation characteristics. The required quality standard for NDMA is five orders of magnitude smaller than the initial peak concentration. The objective is to minimize total pumping, and the constraints incorporate ground‐water quality requirements on the maximum and the spatially averaged residual concentrations, with contaminant source control being considered. On the combination of simulation and optimization, the results of this study indicate that the performance of an optimization algorithm based on gradient search is controlled by the specified cleanup levels, and that contaminant concentrations can be nonconvex and nonsmooth for some pumping schemes.
Geochemical Reactions During Biodegradation/Vapor‐Extraction Remediation of Petroleum Contamination in the Vadose Zone
Authors: Capuano Regina M. , Johnson Mark A.
Published: August 2005

Hydrocarbon concentrations in soil water and vapor are generally used to evaluate the progress of biodegradation and vapor extraction of petroleum contamination in the unsaturated zone. This study shows that changes in the inorganic composition of vadose zone water samples can be used to evaluate the reactions that occur in the unsaturated zone during such a remediation effort. Chemical analyses were completed on water samples collected from alluvial sediments contaminated with diesel fuel and gasoline at the Gallatin Farmers Cenex, Belgrade, Montana. The samples were collected from 7 suction lysimeters for 3 months after fertilization, but before vapor extraction, and then for 6 months following the start of vapor extraction. The geochemical reaction progress code SOLMINEQ.88 is used to calculate the aqueous equilibria in the samples and to simulate possible reaction pathways.

Reduction in TPH and BTEX concentrations indicated that biodegradation of the petroleum began after fertilization, prior to vapor extraction, and continued after the start of vapor extraction. SO4=, HCO3‐, pH, and PCO2 show large systematic variations with both time and depth. These variations are independent of evaporation, mixing, sample extraction time, and soil moisture content and thus appear to be a direct consequence of bioremediation and vapor extraction. PCO2 is found to be a measure of the effectiveness of vapor extraction. The chemical mass transfer calculations also show that if vapor extraction occurs alone removing CO2 from solution without coupling of a process to buffer the solution pH, large amounts of carbonate minerals could precipitate, significantly reducing sediment permeability. These data suggest that analyses of inorganic compounds in lysimeter samples can be used to evaluate geochemical changes during vadose zone remediation and can be used to improve remediation design.
A Ground‐Water Flow Mathematica Tool Package
Authors: Cheng Alexander H‐D. , Sidauruk Paston
Published: August 2005

Mathematica, a symbolic computer mathematics program, is used to construct a tool package for ground‐water flow and contaminant transport simulations. High level, mnemonic functions are designed that allow users to plot type curves, to animate ground‐water flow fields, to perform parameter determination, and to visualize the movement of contaminant cloud.
Integrated Optimal Management of Ground‐Water Pollution and Withdrawal
Authors: Keshari Ashok K. , Datta Bithin
Published: August 2005

An integrated ground‐water management model is formulated as a multivariable constrained nonlinear optimization problem. To simulate the physical and chemical processes occurring within a leaky confined aquifer system, the finite‐difference forms of the flow and transport equations are embedded in the management model. The Hooke‐Jeeves method, a nonlinear programming technique, in conjunction with the exterior penalty function method is used to solve this management model. The suitability and capability of this method to solve the management problems for study areas of different sizes and different numbers of management periods are demonstrated. The performance evaluation of this proposed methodology establishes its potential applicability for the solutions of different kinds of ground‐water management problems. The developed methodology also demonstrates the suitability of the embedding technique to solve a dimensionally large nonlinear ground‐water management problem. The proposed methodology does not require the linking of simulation and optimization models externally. It is shown that global optimality of obtained solutions is dependent on the extensive identification of local optimal solutions and the accuracy in prescribed aquifer characteristics.
Evaluation of the Variations in Borehole Yield From a Fractured Karoo Aquifer, South Africa
Authors: Sami K.
Published: August 2005

Boreholes in an interbedded and fractured sandstone/mudstone Karoo aquifer were classified according to their position relative to structural features identified on a photogeologic map. The yields of boreholes located adjacent to dolerite intrusions, or on the limbs of folds where changes in bedding dip occur, were found to be significantly higher than the yields of boreholes located where no structural deformation could be observed. No statistical difference was found between the yields of boreholes located adjacent to faults or along fold axes and those in undeformed sections. No significant correlation exists between yield and saturated depth penetrated, suggesting that borehole productivity is primarily dependent on the permeability of intercepted fractures rather than on borehole depth. Yields from boreholes located in higher order catchments were also considerably greater than yields in first and second order catchments. Yield probability curves have been derived for the different structural features identified. These show that locating boreholes adjacent to dolerite intrusions or changes in bedding dip significantly increases the probability of obtaining a high yielding borehole. The identification of these features from air photos, therefore, provides an economical means of locating boreholes without expensive geophysical surveys.
The In Situ Permeable Flow Sensor: A Ground‐Water Flow Velocity Meter
Authors: Ballard Sanford
Published: August 2005

A new technology called the In Situ Permeable Flow Sensor has been developed at Sandia National Laboratories. These sensors use a thermal perturbation technique to directly measure the direction and magnitude of the full three‐dimensional ground‐water flow velocity vector in unconsolidated, saturated, porous media. The velocity measured is an average value characteristic of an approximately 1 cubic meter volume of the subsurface. The sensors are permanently buried in direct contact with the formation at the point where the velocity measurement is to be made. While this deployment strategy means that the approximately $2500 instruments are not recovered, borehole effects which can negatively influence the quality of the measurement are avoided. The sensors can be connected to a data acquisition system which can be monitored remotely, via modem and telephone connection, for extended periods of time. The technology is able to measure flow velocities in the range of 5 × 10‐6 to 1 × 10‐3 cm/s, depending on the thermal properties of the medium in which it is buried.
Modeling Cationic Surfactant Transport in Porous Media
Authors: Hayworth Joel S. , Burris David R.
Published: August 2005

Laboratory and field experiments have shown that cationic surfactants can be used to modify aquifer materials, and thereby form zones of enhanced sorption for hydrophobic organic contaminants (HOC's) migrating in ground water. Coupled to a contaminant degradation or removal process, this concept has potential as a remediation technology. In order to apply enhanced sorption in a remediation scheme, an ability to predict the transport and partitioning behavior of cationic surfactants in the subsurface is necessary. In this paper we present the results of a numerical modeling study in which the transport and partitioning behavior of the cationic surfactant hexadecyltrimethylammonium chloride (HDTMA) in porous media is investigated. Modeling of previously published batch and column HDTMA sorption experimental results for Columbus Air Force Base aquifer material indicates that, under certain conditions, kinetic effects will dominate the transport process with slow desorption of HDTMA being the likely rate‐controlling step. The results suggest that a significant departure from equilibrium will exist under natural gradient conditions for the Columbus aquifer material. Low aqueous surfactant concentrations can be expected to persist within a surfactant‐enhanced sorption zone, even after considerable flushing with surfactant‐free ground water. The low aqueous concentration may have implications in terms oftoxicityto microorganisms.
Bench‐Scale Evaluation of Bioaugmentation to Remediate Carbon Tetrachloride‐Contaminated Aquifer Materials
Authors: Mayotte Timothy J. , Dybas Michael J. , Criddle Craig S.
Published: August 2005

Pseudomonas sp. strain KG is a denitrifying bacterium that, under iron‐limited conditions and in the presence of sufficient quantities of growth substrate, rapidly transforms carbon tetrachloride (CCl4) to carbon dioxide and nonvolatile products without production of chloroform. Bench‐scale laboratory methods were used to evaluate the feasibility of bioaugmentation with strain KC to remediate aquifer materials from an aquifer of documented CCl4 contamination at Schoolcraft, Michigan. Nine glass columns packed with uncontaminated aquifer materials from the site were used to simulate aquifer conditions. Columns were alternately exchanged with ground water from the site in a rapid (20–30 minute) displacement of the pore fluid, then incubated under static conditions for a period of days to weeks. The exchange and incubation procedure continued until CCl4 removal began to plateau, indicating equilibration of the sorbed CCl4 with CCl4 in the pore fluid. Information obtained during this period was used to evaluate porosity (total and effective) and CCU sorption. In subsequent exchanges, base, acetate, and phosphorus were added to the exchange fluids to create conditions favorable for growth of strain KC and expression of its CCU transformation activity (niche adjustment). Three columns were inoculated with strain KC; three were not inoculated; and three were chemically disinfected with thimersol. Strain KC was transported more rapidly than the average linear velocity of the exchange fluids in the inoculated columns. Protein levels measured in the effluent of the inoculated columns during subsequent exchanges indicated that niche adjustment enabled rapid growth and colonization of the aquifer solids by strain KC. Little or no protein was detected in the effluent of uninoculated columns. CCl4 mass balances on the inoculated, noninoculated, and chemically disinfected columns indicated that niche adjustment and inoculation with strain KC created conditions favorable for CCl4 removal from the aquifer solids. Up to 70% removal of soluble CCl4 (30–50 μg/l) occurred in inoculated columns over a period of seven to nine days.