bluuebunny/crossref_metadata_2025 huggingface dataset:
Ground‐Water Problems in the Mesozoic Pax Mountain Fault Zone
Authors: Snipes David S. , Manoogian Peter R. , Davis Michael W. , Burnett Laura L. , Wylie Jerry A. , Heaton Steven B.
Published: March 2006

More than 100 steeply dipping or vertical Mesozoic fault zones, which cut across Paleozoic igneous and metamorphic rocks, have been reported in the Piedmont and Appalachians of the Carolinas. The present investigation deals with the hydrological problems encountered in exploring for ground water in the Pax Mountain Fault zone. This is the largest known Mesozoic fault in the Carolinas, having a length of more than 75 km and attaining a width of 1 km in places. Subsurface studies of seven wells, which were drilled along the axis of Pax Mountain, South Carolina, show that the composition of the fault rocks is much more complicated than was known heretofore. These rocks consist of angular particles of quartz and feldspar fault breccia enclosed in a kaolinitic clay gouge. They vary greatly in degrees of consolidation and permeability, and these variations were the cause of some serious ground‐water problems. Two wells were dry holes because the intergranular spaces of the breccia were clogged with clay and also because most of the joints were filled with secondary minerals. Three wells, which were drilled in more permeable, but poorly consolidated fault rocks, caved in at a depth of about 80 m just when they had encountered large volumes of water. Two of the seven wells produce potable water, but chemical analyses of the ground water showed that their turbidity values were 6.0 t.u. and 2.0 t.u., which exceed the limit of 1.0 recommended by the South Carolina Department of Health and Environmental Control.
Dependence of Effective Porosity on Fracture Continuity in Fractured Media
Authors: Gordon Matthew J.
Published: March 2006

Fractured geologic media are typically considered to behave as equivalent porous‐media continua for the purposes of hydrologic testing and modeling. The equivalent‐continuum effective porosity of a fractured medium is frequently measured using tracer tests performed over distances that are small relative to the scale of interest in hydrologic and transport modeling. The larger‐scale value of effective porosity can differ from the smaller‐scale measured value by several orders of magnitude, depending in part on the relative degree of fracture continuity between inflow and outflow zones at the different scales. Based on the results of a simplified numerical modeling study for fractured media with poor continuity at the location and scale of interest, flow is dominated by the intact rock matrix, resulting in a higher effective porosity. For fractured media with uninterrupted fracture continuity at the location and scale of interest, the effective porosity may be substantially lower due to the fracture‐dominated nature of the flow.
Hydrogeological Training in the USSR
Authors: Zaltsberg E.
Published: March 2006

This is a short description of undergraduate and graduate hydrogeological training in Soviet universities. Some advantages and disadvantages of this training are pointed out. The necessity of the exchange of ideas and scientific literature between American and Soviet educators in the field of hydrogeology is stressed.
Geochemical Investigations of Three Tropical Karst Drainage Basins in Puerto Rico
Authors: Troester Joseph W. , White William B.
Published: March 2006

The carbonate chemistry was measured at various springs and surface stations along three river basins in the northwestern karst belt of Puerto Rico. Most surface waters are supersaturated with respect to calcite, and carbon dioxide pressures are close to atmospheric value. Spring waters have higher CO2 pressures but also tend to be supersaturated. Water hardnesses are not dramatically greater than those observed in temperate climate karst.
Strata‐Movement Concepts and the Hydrogeological Impact of Underground Coal Mining
Authors: Booth Colin J.
Published: March 2006

A review of mining‐engineering concepts and studies in mine hydrology suggests a conceptual model linking the strata deformation, hydraulic property changes, and ground‐water impacts due to underground coal mining. The pressure‐arch deformation pattern about a small opening creates a local zone of increased permeabilities and dewatering in the seam and immediate roof, but should not hydraulically affect shallower aquifers. Networks of supported headings, rooms, and pillars intensely drain lower aquifers but only slightly affect higher strata except in areas of naturally high permeability. Longwall mining causes extensive, high‐reaching, well‐defined zones of stress, fracturing, and hydraulic impact, the maximum permeability increases being in the tensile zones immediately above the panel and at the sides of the subsidence trough. In shallow aquifers, permeabilities and ground‐water velocities increase, and hydraulic gradients decline independently of mine drainage.

A study of a deep coal mine in the Appalachian Plateau, Pennsylvania indicated: probable hydraulic connections between the mine and shallow aquifers in a principal valley area; no obvious response of water levels in shallow aquifers to undermining by supported headings; and rapid, considerable declines in such water levels in response to nearby longwall mining. These results are consistent with the conceptual model.
Isolation, Identification, and Growth of Well‐Water Bacteria
Authors: Stetzenbach Linda D. , Kelley Lee M. , Sinclair Norval A.
Published: March 2006

Ground water from deep wells was sampled for the presence of heterotrophic bacteria. Over 500 bacteria were isolated from well‐water samples on a low‐nutrient medium (R2A). Gram‐negative, rod‐shaped, nonmotile bacteria predominated, and Acinetobacter spp. comprised 54% of the total number of isolates. Selected isolates were inoculated into unamended and carbon‐enriched well water, and growth was measured by acridine orange direct count (AODC). Carbon sources included glucose, acetate, pyruvate, and succinate in 100 μg carbon/liter and 1,000 μg carbon/liter concentrations. The isolates grew in unamended filtered well water within 24 hours, and growth of an Acinetobacter sp. was further stimulated (greater than two orders of magnitude within five days) in the carbon‐enriched well water.
Inverse Problem in Ground Water: Model Application
Authors: Khan Irfan A.
Published: March 2006

The inverse model developed in the companion paper entitled, “Inverse Problem in Ground Water: Model Development,” has been applied to the Fairfax‐New Baltimore aquifer in the lower Great Miami River Valley, Ohio. The information obtained from U.S. Geological Survey maps showed four distinct zones of differing hydraulic conductivities in the aquifer. The initial guesses for the hydraulic conductivities were made subjectively. The values of storativity were also assigned subjectively. The inverse model converged within five iterations, and an excellent match with the historical data was obtained. A sensitivity analysis was made to determine the response of the model to various initial guesses for the hydraulic conductivity, various assigned values of storativity, and the number of zones. The sensitivity analysis showed that the calculated hydraulic conductivities were insensitive to initial guesses but sensitive to the assigned values of storativity and the number of zones. However, reasonable deviations in the assigned values were absorbed by the surrogate hydraulic conductivity and the model remained a good input‐output model.
Use of a Numerical Ground‐Water Flow Model for Hypothesis Testing
Authors: Krabbenhoft David P. , Anderson Mary P.
Published: March 2006

Field studies along the southeastern shore of Trout Lake, Wisconsin, documented the presence of downward hydraulic gradients in a known discharge area as well as an anomalous distribution of seepage to the lakebed which deviates significantly from the generally accepted dogma that ground‐water seepage rates decrease exponentially with distance from shore. A numerical ground‐water model facilitated identification of the hydrologic control, namely the presence of a unit of high hydraulic conductivity, that accounts for the anomalous data, and is important for understanding the dynamics of the flow system. Field data including seepage measurements, visual inspection of lakebed materials and springs, and information obtained during drilling, indicate that a lens of coarse‐grained material intersects the lake. However, the significance of the coarsegrained material was not fully appreciated until a ground‐water model was used to simulate the flow system. The model indicated that the presence of the coarse‐grained lens has a marked effect on the flow pattern in the nearshore area causing downward hydraulic gradients which divert ground water into the lens and cause the occurrence of a localized high‐seepage area offshore where the lens intersects the lake. The numerical model predicts the anomalous seepage distribution noted in the field and the downward hydraulic gradients demonstrating that numerical models are practical tools for interpreting field data and for use in hypothesis testing.
Parameter Identification of a Ground‐Water Contaminant Transport Model
Authors: Strecker Eric W. , Chu Wen‐sen
Published: March 2006

A parameter identification (PI) procedure is developed and implemented with the United States Geological Survey's Method of Characteristics (USGS‐MOC) model. The PI procedure can be used to estimate selected model parameters from limited observations by quadratic programming. The code combining the PI procedure and the USGS‐MOC model has been tested by two numerical examples from a hypothetical aquifer. The test results show that the proposed algorithm can identify transmissivity and dispersivity accurately under ideal situations. The effects of using a simple characterization of the aquifer on parameter estimation and model are shown. Because of the improved efficiency in model calibration, extended application to field conditions is encouraged. However, it is cautioned that the interested users should be aware of the difficulties in field applications of PI, and it is recommended that sound engineering and scientific judgements are always needed in the use of the proposed, or any other PI method.
A Simplified Analysis of Two‐Well Tracer Tests in Stratified Aquifers
Authors: Güven O. , Falta R. W. , Molz F. J. , Melville J. G.
Published: March 2006

This paper illustrates several interesting effects of aquifer stratification on the results of two‐well tracer tests by means of a simplified computer model. In the model, it is assumed that the aquifer is horizontal, confined, of constant thickness and porosity, and perfectly stratified in the vicinity of the test wells. The nonuniform advection pattern is taken into account in detail by the model, but the local hydrodynamic dispersion is completely neglected. This simplified model has been verified in part by comparisons with available analytical solutions valid for homogeneous aquifers and in part by comparisons with the results of a two‐well field experiment of Pickens and Grisak (1981a) which was performed in a locally stratified aquifer. The applications of the model to several field situations with assumed values of the relevant parameters show that the concentration versus time breakthrough curve measured at the withdrawal well during a standard two‐well test would be very sensitive to variations of the hydraulic conductivity in the vertical. Without the use of supplementary observation wells with isolated multilevel sampling points, the standard test would give little useful information about the hydraulic and dispersive characteristics of an aquifer. Factors such as the length of the tracer injection period, the use of recirculation and the physical size of the experiment all have a strong effect on the breakthrough curve measured at the withdrawal well, making the interpretation of field results difficult unless aquifer stratification is measured and properly taken into account.
Geochemistry of Salt Water Beneath the Rolling Plains, North‐Central Texasa
Authors: Richter Bernd C. , Kreitler Charles W.
Published: March 2006

Sodium‐chloride brine underlies the shallow subsurface and discharges at numerous surface locations in the Rolling Plains of north‐central Texas. According to the ratios of Na/Cl and Br/Cl, and supported by the contribution of other chemical constituents, two major brine types can be distinguished: (1) brine derived from dissolution of halite by fresh ground water, and (2) brine derived from discharge of deep‐basin brine aquifers. All salt‐spring brines as well as shallow subsurface brines in the northern and western parts of the Rolling Plains represent halite‐dissolution brine, whereas deep‐basin brine is represented by samples in the shallow subsurface in the south.

The oxygen and hydrogen isotopic composition of the halite‐dissolution brines indicates a local, meteoric origin for these brines. Shallow subsurface samples from the southeastern Rolling Plains graphically include deep‐basin brine values and meteoric‐water values as end points, suggesting mixing of deep‐basin brine with local meteoric ground water.
Interpretation of Slug Test Data
Authors: Pandit Nitin S. , Miner Robert F.
Published: March 2006

Slug tests offer a quick and inexpensive field method of obtaining localized permeability values. The most commonly used method of interpreting slug test data by Black (1978) requires considerable engineering judgement, and can potentially lead to inconsistency in its application. One of the inconsistencies is usually in the estimation of the initial excess head; the proposed Translation Method offers a way of reducing the inconsistency. Another inconsistency can result from the subjective process of matching actual data with published type curves of expected well response in different aquifers. It is proposed that a standard numerical method should be employed for consistent application and automation of this process. The development of these procedures has led to the implementation of an interactive software package that allows the consistent application of slug test analysis at a lower cost.
Preliminary Evaluation of a Geothermal Aquifer in Southern England
Authors: Burgess W. G.
Published: March 2006

The preliminary evaluation of the first direct‐use (low enthalpy) geothermal well in the United Kingdom included core analysis, geophysical logging, and drill‐stem testing. The effective aquifer is restricted to a few relatively thin loosely cemented bands in the Triassic sandstones at a depth of approximately 1660 m. With an aquifer temperature of at least 67°C the initial assessment of transmissivity, 18 m2/day, suggested that a thermal yield of approximately 2.5 MW would be obtainable. The results are in reasonable agreement with those of a subsequent long‐term production test.
MOC SOLUTIONS OF CONVECTIVE‐DISPERSION PROBLEMS
Authors: Khaleel Raz , Reddell Donald L.
Published: March 2006

Abstract. The method of characteristics is used to solve the one‐ and two‐dimensional convective‐dispersion equations in steady, uniform flow fields. Fully documented listings of the FORTRAN programs are presented. Comparison of numerical results with existing analytical solutions show excellent agreement.
Gaseous Behavior of TCE Overlying a Contaminated Aquifer
Authors: Marrin Donn L. , Thompson Glenn M.
Published: March 2006

Shallow soil gas (<2 meters deep) was collected and analyzed for trichloroethylene (TCE) to determine the relationship with ground‐water contamination directly below. The gaseous TCE plume was mapped with 46 probes and spanned three orders of magnitude in concentration (<0.001 to 2 μg/1). TCE concentrations in water from five monitoring wells around the study site ranged from 4 to 2800 ppb and had a correlation coefficient (r) of 0.90 with TCE concentrations in shallow soil gas. Vertical borings were completed to the water table at four locations in order to obtain profiles of soil gas contamination, air porosity, and water saturation. Gaseous diffusion and air/water partitioning are probably the dominant mechanisms involved in transporting TCE from the ground water to the shallow soil gas.
Characterization of Fracture Permeability with High‐Resolution Vertical Flow Measurements During Borehole Pumping
Authors: Paillet F. L. , Hess A. E. , Cheng C. H. , Hardin E.
Published: March 2006

The distribution of fracture permeability in granitic rocks was investigated by measuring the distribution of vertical flow in boreholes during periods of steady pumping. Pumping tests were conducted at two sites chosen to provide examples of moderately fractured rocks near Mirror Lake, New Hampshire and intensely fractured rocks near Oracle, Arizona. A sensitive heat‐pulse flowmeter was used for accurate measurements of vertical flow as low as 0.2 liter per minute. Although boreholes were spaced at intervals ranging from 10 to 50 meters, acoustic televiewer logs showed little direct continuity of individual fractures from borehole to borehole in either the moderately fractured rocks or intensely fractured rocks. Results indicated that nearly all inflow and outflow to boreholes occurred by means of one or two discrete fractures in both cases. These fractures did not appear very different from other prominent fractures indicated on televiewer and resistivity logs for these boreholes. Hydraulic connections between boreholes apparently were composed of conduits formed by the most permeable portions of intersecting fractures. Most flow in the moderately fractured rocks occurred at isolated fractures at a depth of about 45 meters indicating a nearly horizontal zone of fracture permeability composed of orthogonal, steeply dipping fractures. Previous studies have identified a zone of horizontal permeability in the lower part of the boreholes in the intensely fractured rocks, but flowmeter tests indicated that flow also entered and exited individual boreholes by means of one or two steeply dipping fractures. These results indicate zones of fracture permeability in crystalline rocks are composed of irregular conduits that cannot be approximated by planar fractures of uniform aperture, and that the orientation of permeability zones may be unrelated to the orientation of individual fractures within those zones.
PUMPING TEST ANALYSIS IN LARGE DIAMETER WELLS WITH A SEEPAGE FACE BY KERNEL FUNCTION TECHNIQUE
Authors: Rushton K. R. , Singh V. S.
Published: March 2006

Abstract. A method of analyzing the pumping and recovery phases of large diameter wells based on a Kernel function method is presented. Consideration is given to the effect of the seepage face, which is the difference between the well‐water level and the aquifer level on the well face. A computer program for the Kernel function method written in BASIC, is provided. In the analysis of a representative field test, the importance of including the seepage face is demonstrated; if the seepage face is ignored, both the transmissivity and storage coefficient are underestimated.
Reverse Pathline Calculation of Time‐Related Capture Zones in Nonuniform Flow
Authors: Shafer John M.
Published: March 2006

A simple to understand and easy to implement numerical technique, based on reverse calculation of ground ‐water flow paths, is applied to delineation of time‐related capture zones around water‐supply wells. The areal extent of a t‐year capture zone in a two‐dimensional regional flow domain is approximated by a large set of reverse pathlines all with t‐year travel times. The numerical approach is suitable for calculation of time‐related capture zones in steady, nonuniform flow with inhomogeneous, anisotropic aquifer conditions. The example applications show the sensitivity of this technique to the influence of multiple wells in a block inhomogeneous flow regime.
Diffusivity of Glacial‐Outwash Aquifer by the Floodwave‐Response Technique
Authors: Reynolds Richard J.
Published: March 2006

Aquifer diffusivity (transmissivity divided by storage coefficient) was calculated for three sites in a glacial‐autwash valley aquifer near Cortland, New York from water‐level fluctuations induced by rises in stream stage. The observed response data were analyzed through use of a one‐dimensional floodwave‐response model to calculate the theoretical head response in the aquifer generated by a floodwave in the stream, and then matched to the observed head response. Diffusivity values computed from sharply peaked flood rises ranged from 6.08 to 8.68 ft2. The closest match between observed and calculated heads was obtained from a site where the aquifer is confined and the saturated thickness (and thus the diffusivity) remains constant with the passage of a floodwave. Arrival time of the observed flood‐peak seems to be the most useful criterion for curve matching, especially under unconfined conditions, where a match to the rising limb and floodpeak is difficult because of changes in the saturated thickness.

A transmissivity value of 14,700 ft2/d for the glacial‐outwash aquifer, calculated from specific capacity data from a nearby industrial well, combined with diffusivity calculated by the floodwave‐response method, indicates a storage coefficient between the normal ranges for unconfined and confined aquifers. Calculated storage coefficients were 0.015, 0.027, and 0.034 at the three sites.

The floodwave‐response method of calculating aquifer diffusivity is relatively inexpensive compared to standard aquifer tests and is effective in glacial‐valley fill aquifers that are hydraulically connected to a major stream or river.
Monitoring Well Installation, Purging, and Sampling Techniques ‐ Part 1: Conceptualizations
Authors: Keely Joseph F. , Boateng Kwasi
Published: March 2006

Commonly employed techniques for the installation, purging, and sampling of monitoring wells are examined. The degree to which hollow‐stem augering disturbs the near‐borehole environment, and how this may result in the movement of contaminated solids or fluids from one stratum to another is discussed. The desirability of driving temporary casing to shield one stratum from another, and to improve the general quality of the monitoring well installation (especially the effectiveness of the filter pack emplaced), is argued. A call for further testing of sampling devices, based on limited field comparisons and a lack of reports of conclusive tests elsewhere, is given.
A Comparison of Field and Laboratory Methods for Determining Contaminant Flow Parameters
Authors: Taylor S. R. , Moltyaner G. L. , Howard K.W.F. , Killey R.W.D.
Published: March 2006

In situ estimates of advective and dispersive properties of ground‐water flow systems are essential for the adequate prediction of solute flow. Field tracer tests provide the best estimates of these properties; however, this approach is often precluded by the expense and time involved. Various laboratory techniques have been developed to circumvent these problems and provide convenient estimates of hydraulic conductivity and dispersivity. Although these techniques are used extensively in hydrogeological investigations, very few attempts have been made to compare their estimates with field values.

A detailed investigation was performed on an unconfined sand aquifer using a combination of routine laboratory techniques and an innovative field tracer test. The extensive data set provided a unique opportunity to compare field results with those obtained by a variety of laboratory techniques.

The hydraulic conductivity results from two different methods of grain‐size analysis (Hazen, 1893; and Masch and Denny, 1966) were observed to be quite well correlated, although their absolute values did not correspond with the hydraulic conductivities determined from the tracer test. However, contrary to previous studies, the results from grain‐size analysis were the same order of magnitude as the in situ values. In addition, the two grain‐size methods appear to provide upper and lower boundaries within which lie the hydraulic conductivity estimates determined from the tracer test. Thus, grain‐size analysis of moderately to well sorted sands may provide reasonable and convenient approximations of hydraulic conductivities of the aquifer.

No correlation was observed between field tracer test longitudinal dispersivity values and those determined from laboratory column tracer tests. The latter, however, differed by only an order of magnitude from the in situ point measurements, a difference which is considerably smaller than has been previously reported. This is largely attributed to the accuracy of the sampling methods used in the tracer tests.
PERFORMANCE AND ANALYSIS OF AQUIFER TRACER TESTS WITH IMPLICATIONS FOR CONTAMINANT TRANSPORT MODELING–A PROJECT SUMMARY
Authors: Molz Fred J. , Güven Oktay , Melville Joel G. , Keely Joseph F.
Published: March 2006

The scale‐dependence of dispersivity values used in contaminant transport models to estimate the spreading of contaminant plumes by hydrodynamic dispersion processes was investigated and found to be an artifact of conventional modeling approaches (especially, vertically averaged parameters in two‐dimensional plume simulations). The work reported here shows that variations in hydraulic conductivity with depth result in significant variations in ground‐water flow and contaminant transport velocities; it is the resulting velocity variations that, if vertically averaged, give rise to apparent scale‐dependency of dispersion (e.g., increased dispersion with increasing travel distance). Special depth‐selective observation well designs are recommended by the authors for use in tracer tests, so that detailed estimates of the variations in hydraulic conductivity, and flow and transport velocities can be obtained. Innovative modeling techniques that take advantage of the detailed information obtainable from such tests (by emphasizing advective transport, as opposed to dispersive transport), have been developed by the authors. These modeling techniques are shown to have an element of true predictive ability, being able to closely simulate actual results with little or no calibration.
Effect of Water‐Level Recoveries on Fault Creep, Houston, Texas
Authors: Holzer Thomas L. , Gabrysch Robert K.
Published: March 2006

Fault creep has stopped or slowed in the eastern part of the Houston, Texas, land subsidence area where reductions in pumping of ground water have allowed water levels to recover partially. Creep has continued across faults in the western part where heavy pumping causes water levels to continue to decline. The observations support the long‐suspected relation between historical faulting and withdrawal of ground water and indicate that partial water‐level recoveries can reduce fault movement and structural damage.
Beneficial Aspects of Sea‐Water Intrusion
Authors: Howard Ken W. F.
Published: March 2006

The Permo‐Triassic sandstone aquifer of northwest England has been a major source of ground‐water supply since the early 19th century. Between Liverpool and Manchester, ground‐water resource development has led to a considerable lowering of the water level inland and intrusion of sea water from the Mersey Estuary and Manchester Ship Canal. As part of a detailed investigation of resource management, a two‐dimensional finite‐difference flow model was developed to represent aquifer behavior for the period 1840 to 1980. Subsequently, this model was used to predict the effects of implementing various management strategies over a 40‐year period ending 2020.

Results indicate that ground‐water withdrawals have exceeded natural replenishment by an average of 100% during the past 50 years. In this time the potentiometric heads have responded remarkably slowly to the flow imbalance, a resilience that is largely attributed to the inflow of sea water at rates only marginally less than recharge from meteoric sources. Careful development of the fresh ground‐water resources has minimized water quality problems along the estuary and ship canal, and the model clearly shows how controlled inflow of saline water can considerably enhance the recovery of fresh ground‐water reserves. Difficulties arise only when excessive exploitation accelerates water quality deterioration. Model calculations indicate that inflow of saline water would continue for over 10 years following complete cessation of fresh ground‐water production.
Large Data Bases and Regional Ground‐Water Quality Assessments ‐ An Iowa Case Study
Authors: Rajagopal R.
Published: March 2006

Many state and federal agencies routinely collect ground‐water quality data to meet a variety of objectives. The WATSTORE (Water Data Storage and Retrieval System) data files of the U.S. Geological Survey containing raw ground‐water quality data from 4,388 wells and the MSIS (Model State Information System) data files of the U.S. EPA containing finished (blended and/or treated) ground‐water quality data from 2,137 public water‐supply sources are the only two large computer‐coded data files on Iowa ground‐water quality. These two data bases, by themselves, provide significant insights regarding the distribution of chemicals in different hydrogeological environments and the compliance status of PWS sources with reference to drinking‐water quality standards in Iowa. With minor modifications, these two data bases can be integrated to: (a) provide statistical, spatial, temporal, and geological summaries of observed ground‐water quality; (b) determine the extent of exposed populations to various contaminants in their different concentrations; (c) provide necessary information to reduce the existing list of contaminants and include some of those that are not being monitored now; (d) identify gaps in current data‐gathering efforts and prioritize the various components of future monitoring programs; (e) identify potential linkages for the combined use of ground‐water quantity and quality, socioeconomic, land‐use, and public health data; and (f) alert policy makers to potential ground‐water quality problems facing the state. Some of the limitations of the two data bases and the need for integrating them is demonstrated by a comparative analysis and evaluation.
Design of a Ground‐Water Sampler for Collecting Volatile Organics and Dissolved Gases in Small‐Diameter Wellsa
Authors: Johnson Richard L. , Pankow James F. , Cherry John A.
Published: March 2006

A sampling device is described which collects ground‐water samples containing volatile organic compounds and dissolved gases. The device protects the samples from volatilization losses from the time of collection until the time of analysis. It can be produced in a wide range of sizes and allows access to wells with inside diameters as small as one centimeter. The sampler is designed to be lowered in a well to the desired depth, depressurized to slightly below the in situ pressure to allow entry of the sample, and then repressurized prior to being returned to the surface. During collection and storage, the sample is exposed only to copper and stainless steel. An optional quartz prefilter can also be used. Crimping sections at either end of the sample reservoir seal the pressurized sample during its return to the laboratory. The sampler is designed to be interfaced to analytical instruments for the direct, quantitative transfer of all analytes.
Seismic Reflection Study of a Shallow Aquifer During a Pumping Test
Authors: Birkelo Bradley A. , Steeples Don W. , Miller Richard D. , Sophocleous Marios
Published: March 2006

Seismic reflection surveys were used to follow the drawdown in a shallow aquifer during a pumping test. Using severe analog low‐cut filters and 1/4‐m geophone spacings, 335 Hz reflections were obtained from the top of the saturated zone 2.7 m deep. The reflections moved down in time as the saturated zone dropped in response to pumping. The dominant frequency and bandwidth both dropped during pumping indicating a more diffuse reflecting boundary. Slight pullups of reflectors at specific locations on the CDP sections may indicate a higher elevation of the capillary fringe and therefore finer sediments in those locations. Other potential applications of this technique include mapping cones of depression and detecting and delineating perched‐water tables.
An Analysis of Hillside Seepage
Authors: Melville Joel G. , Sims Paul N.
Published: March 2006

A steady‐state hillside seepage problem is solved analytically. Subject to the Dupuit‐Forchheimer assumption, one‐dimensional seepage with uniform recharge over an inclined impervious bed is analyzed. Results are presented graphically showing the profile dependence on a single parameter. Properties of the profiles arc investigated. Profiles are also calculated numerically and plotted to improve the physical interpretation.
The Use of Marine Electromagnetic Conductivity as a Tool in Hydrogeologic Investigations
Authors: Duran Philip B.
Published: March 2006

Field procedures for collecting marine electromagnetic (EM) conductivity data were developed by the U.S. Geological Survey as part of a hydrogeologic investigation of the Delaware River shipping channel. Eighty miles of marine EM data collected along the border between Pennsylvania and New Jersey were used to help interpret results from high‐resolution, continuous seismic‐reflection surveys done in the Summer of 1984.

Comparison of EM data with lithologic logs from river borings showed a direct relationship. EM conductivity of sand or bedrock ranged from 4 to 10 millimhos per meter (mmhos/m). Extensive clay beneath the shipping channel generally gave readings exceeding 20 mmhos/m. Conductivity readings over silts were almost always between these values (11 to 20 mmhos/m). This relation was used to help interpret the continuous seismic‐reflection data.
Gravity Modeling of the Brimfield Township Buried Valley and Associated Aquifer, Portage County, Ohio
Authors: Culek Thomas E. , Palmer Donald F.
Published: March 2006

A detailed gravity survey of 295 points was conducted in Brimfield Township, Ohio to map buried bedrock topography with a higher degree of resolution than was possible by well data alone. The survey included a subset of 40 stations where both gravity and bedrock depth were determined. Partial correlation analysis allowed identification of a regional gravity trend, and multiple linear regression led to quantitative estimates of depth to bedrock throughout the surveyed area in a manner different from the standard method of gravity interpretation that employs models of different shapes, sizes, and density contrasts. Glacial sediments range in thickness from 10 to 150 feet, with the thickest portions generally over the axis of the buried valley. Some variations in predicted versus measured bedrock depth may be a function of variation in density of the glacial sediments or of topographic effects of the buried bedrock surface. The results of the analysis led to an improved estimate for the bedrock elevation and thickness of valley fill. The interpretation has implications with regard to the volume of glacial sediments in the area and their potential productivity as sources of ground water in the future.
Analysis of Steady‐State Salt‐Water Upconing with Application at Truro Well Field, Cape Cod, Massachusetts
Authors: Reilly Thomas E. , Frimpter Michael H. , LeBlanc Denis R. , Goodman Alvin S.
Published: March 2006

Salt‐water upconing describes the phenomenon where salt water is transported vertically upward under a well in response to pumpage in a fresh‐water aquifer underlain by salt water. Sharp interface methods have been used successfully to describe the physics of upconing. A finite‐element model is developed to simulate a sharp interface for determination of the steady‐state position of the interface and maximum permissible well discharges. The model developed is compared to previous published electric‐analog model results of Bennett and others (1968). Both methods are applied to a test case at Truro, Massachusetts, where maximum permissible discharges are determined by the finite‐element model to range from 0.47 to 1.05 cubic feet per second for the Test Site No. 4 location.
Hydrogeology of an Alkaline Fly Ash Landfill in Eastern Iowa
Authors: Le Seur Spencer Linda , Drake Lon D.
Published: March 2006

The hydrogeology and chemical quality of the shallow ground‐water regime at a coal fly ash landfill was investigated near Montpelier, Iowa. An embankment dam retains the two‐hectare deposit of silt‐sized alkaline coal fly ash in an upland ravine. The fly ash landfill was operated between 1964–;1973 and was subsequently capped with a thin loess layer and seeded to pasture. The ash is underlain by loess, over clay‐rich till, over sandstone. Ground water now saturates the lower one‐half of the ash.

Nineteen shallow monitoring wells were installed around and within the landfill. Sampling in 1983–;1984 was conducted for water levels, temperature, pH, alkalinity, specific conductance, calcium (Ca2+), magnesium (Mg2+), sodium (Na+), potassium (K+), sulfate (SO42−), chloride (Cl−), arsenic (As), and selenium (Se).

Calculated ion balances for 30 analyses had an error of less than 4%. Native loess‐derived ground water of a calcium bicarbonate type enters the landfill, and then shifts to a calcium sulfate type. A distinct leachate plume presently extends at least 46 meters downgradient from the landfill, passing under and through the dam, then discharging into a small pond. SO42− and Se concentrations in the plume exceed EPA drinking‐water standards, and trace As was detected.

Although ground‐water pH increased after entering the landfill, bicarbonate alkalinity declined. Results of equilibrium solubility calculations suggest that this condition evolved from calcite supersaturation within the landfill, precipitating calcium carbonate. Dissolution of calcium and magnesium oxides on the glassy fly ash spheres sustains the highly alkaline leachate strength.
Ground‐Water Contamination Near a Uranium Tailings Disposal Site in Colorado
Authors: Goode Daniel J. , Wilder Russell J.
Published: March 2006

Contaminants from uranium tailings disposed of at an active mill in Colorado have seeped into the shallow ground water onsite. This ground water discharges into the Arkansas River Valley through a superposed stream channel cut in the resistant sandstone ridge at the edge of a synclinal basin. In the river valley, seasonal surface‐water irrigation has a significant impact on hydrodynamics. Water levels in residential wells fluctuate up to 20 ft and concentrations of uranium, molybdenum, and other contaminants also vary seasonally, with highest concentrations in the Spring, prior to irrigation, and lowest concentrations in the Fall. Results of a simple transient mixing cell model support the hypothesis that lateral ground‐water inflow, and not irrigation recharge, is the source of ground‐water contamination.
Monitoring Moisture Migration in the Vadose Zone with Resistivity
Authors: Kean William F. , Waller Muriel Jennings , Layson H. Richard
Published: March 2006

Studies of moisture migration in the vadose zone were conducted at four field sites using a reverse Schlumberger resistivity array. Gravimetric moisture measurements on soil samples taken at each of the field sites were made to a maximum depth of 1.83 meters, and these results were correlated with resistivity values. Tensiometer measurements were also taken at two of the four sites. The soils at the sites have combined clay and silt content (less than .0625 mm grain size) which varies from 13% to 84%. Three of the sites are underlain by sand or gravel in the unsaturated zone. The fourth site has fractured but relatively impermeable shales and siltstones under the surface soils. Depths to water table varied from 1.58 m to 13.7 m. Resistivity and gravimetric moisture measurements were carried out prior to the addition of water to the surface, and following the application of water, either by watering of the site (at two sites) or during and after rainfall events (at two sites). Monitoring was carried out for periods of one to three weeks. Results indicate that (1) moisture is retained for long periods of time in clay/silt‐rich soils; (2) moisture migration is slow below a moist soil zone and is not readily detected by surface resistivity measurements; and (3) near‐surface moisture changes can be defined by surface resistivity.
Representative Sampling of Ground Water from Short‐Screened Boreholes
Authors: Barber C. , Davis G. B.
Published: March 2006

Boreholes terminated with a short (1–3 m) length of screen are often used in ground‐water quality monitoring, although to obtain representative samples, pumping is often required to overcome the effects of stagnant casing storage. Methods for estimating pumping time prior to sampling from a pumped discharge, presented graphically and in summary equations, show that for most requirements, pumping time (ta) to purge well storage (where mixing of casing storage and ground water takes place within the casing) or to overcome casing storage effects (where little mixing occurs within the casing) is given by

image

Here V is the volume of well storage, Q is the average pumping rate, and m is given by

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where Ct, Cg, and Cc are concentrations of some substance in pumpage, and ground water, and the initial concentration in casing storage, respectively. In boreholes which have been developed and which are regularly pumped and where a relative sampling error of 2.5% is considered to be acceptable, then m has a value of 0.1. Pumping time then equates to the time necessary to pump 2.3 volumes of well storage from the borehole.

Laboratory and field evaluations using boreholes in transmissive and low permeability formations generally validate the theoretical approach. The theory can be used as a basis for estimating and optimizing pumping times for monitoring programs where ground‐water samples are recovered from short‐screened boreholes. Additionally, the theory allows the determination of an optimum pumping rate.
PUMPTEST.BAS: A PROGRAM TO CALCULATE TRANSMISSIVITY AND STORATIVITY
Authors: Smith Stephen M.
Published: March 2006

Abstract. PUMPTEST.BAS is a BASIC program for IBM PCb microcomputers and compatibles that calculates transmissivity and storativity of confined aquifers using the Cooper‐Jacob method.
Leachate Generated by an Oil‐and‐Gas Brine Pond Site in North Dakota
Authors: Murphy Edward C. , Kehew Alan E. , Groenewold Gerald H. , Beal William A.
Published: March 2006

Two unlined ponds were used for holding and evaporation of brines produced with oil and gas at a well site in north‐central North Dakota. The brine‐evaporation ponds were in use from 1959 up to the late 1970s when they were backfilled and leveled. Continued salt‐water migration at this site since closure has decreased crop yields in surrounding fields and has killed trees in a shelterbelt within an area of approximately 10 acres.

An apparent resistivity survey delineated a 360,000‐ft2 area of extremely low resistivity. Isoconcentration maps indicate that a highly saline leachate plume extends laterally in a 500‐foot radius around the ponds and vertically to a depth of 70 feet below the surface.

Ground‐water recharge at this site is low because of the semiarid climate and the low hydraulic conductivity of the near‐surface sediments and, as a result, very little flushing of the brine from the sediment beneath the ponds has occurred. Pore water within the unsaturated zone beneath the reclaimed ponds contains essentially the same ionic concentrations as that: of brine impounded in these pits 10 to 25 years ago.

Based upon the results of this research, we estimate that brine leachate will continue to migrate at slow rates from this site for tens and possibly hundreds of years if no action is taken. The construction of a mound over the site and/or an infiltration gallery around the perimeter would minimize the spread of brine and make it possible to return this land to production in the foreseeable future.
Combined Use of Hydraulic and Electrical Properties of an Aquifer in a Geostatistical Estimation of Transmissivity
Authors: Ahmed Shakeel , de Marsily Ghislain , Talbot Alain
Published: March 2006

Many previous attempts have been made to establish an empirical relation between the electrical and hydraulic properties of aquifers. However, only regression models between transmissivity or permeability and a few electrical parameters have been used on the basis of the available pairs of data. Kriging, a geostatistical technique, estimates a regionalized variable at any point in space, and multivariate geostatistical techniques allow one to use several variables together to estimate any ‘spatial parameter. One such method, cokriging, is used to estimate the transmissivity based not only on measurements of transmissivity, but also on measurements of specific capacity and electrical transverse resistance. The studied aquifer is situated in the Medjerda Valley in Tunisia where very few data on transmissivity and specific capacity are available, but resistivity data are relatively abundant. It is shown that with the geostatistical technique, one can: (1) use several electrical or elastic properties, which are easily measured, in the estimation of the desired parameter without establishing any empirical relation; and (2) make the estimation at any point where none of these properties has been sampled and, at the same time obtain a variance of the estimation error. The method is also compared with the usual regression method.
A Remotely Operated Seepage Meter for Use in Large Lakes and Rivers
Authors: Cherkauer Douglas A. , McBride John M.
Published: March 2006

The many seepage meter designs presented to date are generally fragile and require direct installation by divers. On large surface‐water bodies, such as the Great Lakes, storm wave size, water depth, temperature, and turbidity make these previous seepage meters ineffective. A design is presented in this paper which is heavy and sturdy enough to withstand Great Lakes storms and which can be remotely installed from the water surface. These UWM meters require stabilization on the bottom of 15 to 25 minutes before activation and must be corrected for slow settling and hydraulic inefficiency. Such correction is straightforward, and corrections are presented for sand beds. Field testing shows that corrected seepages from these meters have a maximum deviation of 33% and a standard deviation of 22% from the observed mean. The meter has had over a 90% success rate in installations throughout the Great Lakes. It does not function on rock or soft sediment.
Measurement of Ground‐Water Parameters Using Salt‐Water Injection and Surface Resistivity
Authors: White Paul A.
Published: March 2006

1. ABSTRACT

A method of determining the direction and velocity of ground‐water flow by injecting a salt‐water slug into an aquifer, and tracing its movement with surface resistivity measurements is described. Aquifer hydraulic conductivity can be derived from the measured velocity, the hydraulic gradient, and the aquifer porosity. The method is examined using theoretical considerations and New Zealand field examples.

This method of measuring ground‐water velocities has several advantages over conventional well‐to‐well tracer experiments. Only a single access to the aquifer is required. Velocity estimates are more representative of true ground‐water velocities. The method is inexpensive and straightforward to perform. It is applicable to investigating freshwater aquifers within 20 m of the ground surface and when highly conductive materials do not occur above the aquifer.