bluuebunny/crossref_metadata_2025 huggingface dataset:
Bailing and Construction Considerations for Deep Aquifer Monitoring Wells on Western Oil Shale Leases
Authors: Kelly K. E.
Published: March 2006

Water quality data collected from monitoring wells in the Piceance Creek Basin oil shale area can be significantly influenced by well design and sampling techniques. Many of these influences can be attributed to hydrogeologic complexities, which can have notable variations on a fairly local scale. To adequately address these complexities, a site‐specific characterization of the hydrogeology is necessary. This is particularly important for specifying well construction details of monitoring wells for a ground‐water quality monitoring program.

Data collected during the bailing of deep aquifer wells on Federal Prototype Oil Shale Lease Tract C‐a indicates the need for consistent and representative sample collection depths. Appreciable changes in water quality can be induced by variations in sample collection depths. In addition, unrepresentative data can be obtained due to the incorrect selection of intervals to be sampled in the well. Care must be taken to sample consistently from the same depth and aquifer interval during each and every sampling effort.

Studies such as these provide necessary background information for developing ground‐water monitoring guidelines in the oil shale region. Sampling procedures must be consistent to assure representative data collection. In addition, wells should be designed and completed according to the local hydrogeology and the specific goals of the monitoring program.
A Repeated Pulse Technique for Determining the Hydraulic Properties of Tight Formations
Authors: Walter G. R. , Thompson G. M.
Published: March 2006

Slug and bailer tests are being used increasingly to evaluate the hydraulic properties of “tight” geologic units. Although these pulse methods of stressing a system are used typically only on single wells, the repeated pulse method described here stresses the system in the same manner, but the response is measured in observation wells. This type of pulse test yields much the same information as conventional pumping tests, but it is easier to perform in very low permeability units.

The observation well response hydrographs are analyzed by curve‐matching techniques. In general, a unique set of type curves must be computed for each pulse test. These type curves are computed easily if the pulsed well is treated as a line‐source (or sink). The accuracy of the value of transmissivity (T) determined from the line‐source type curves compared to using the finite‐diameter well solution depends both on the pulsed well radius (rc) and the time interval between pulses (Δt). If TΔt/rc2 is maintained greater than 50, then T determined from the line‐source solution will be within 25% of that determined from more accurate, but computationally inconvenient, finite‐diameter well type curves.

The repeated‐pulse test technique was applied to an experimental well array completed in the Conasauga Shale Formation at Oak Ridge National Laboratory. Values of transmissivity determined by the repeated‐pulse method agreed well with the results of slug tests performed on each well individually, and in addition, provided information on storage coefficients and anisotropy at the site.
Hydrogeology of Pipeline Canyon, Near Gallup, New Mexicoa
Authors: Raymondi Richard R. , Conrad Ronald C.
Published: March 2006

The principal water‐bearing units (in descending stratigraphie order) in Pipeline Canyon are the alluvium, the Dilco Coal Member of the Crevasse Canyon Formation, the Torrivio Sandstone Member of the Gallup Formation, and the Upper and Lower Gallup Sandstones. Presently, the alluvium is recharged by a perennial, southward‐flowing stream sustained by mine dewatering discharge in addition to natural precipitation and runoff. Localized infiltration has created ground‐water mounds in the alluvium. Artesian conditions may exist in sandstone units which are adjacent and hydraulically connected to the alluvium in these areas. Basement faults have produced the Fort Wingate and Pipeline Canyon lineaments which intersect in the area of investigation. Fault‐related fracturing of the sandstones allows for significant ground‐water recharge via the overlying alluvium. Flow in the sedimentary formations is generally to the northeast, while the alluvial system flows to the southwest. The natural water quality for the aquifers in the area is dominated by sodium and sulfate ions. However, complete characterization of the natural water quality is complex because of ground‐water contamination by acidic tailings fluids from a local uranium mill.
Hydraulic Conductivity of a Fine‐Grained Till, Cattaraugus County, New York
Authors: Prudic David E.
Published: March 2006

Hydraulic conductivity of a fine‐grained till was evaluated by field and laboratory techniques as part of a study of the movement of radionuclides at a nuclear‐waste landfill in western New York. In general, both methods produced similar results. Hydraulic conductivity values determined from (a) slug tests of piezometers, (b) several types of laboratory tests on cores, and (c) calculation from mercury porosimeter tests, agreed within a factor of 25.

Slug tests were analyzed by two methods: one assumed horizontal flow to the piezometer screen; the other assumed spherical, isotropic flow. Average horizontal hydraulic conductivity from slug tests of 12 piezometers was 6 × 10−8 cm/s (2 × 10−9 ft/s) by the first method and 2 × 10−8cm/s (7 × 10−10ft/s) by the second.

Laboratory tests of core samples were designed to determine the extent to which anisotropy and increased pressures with depth may affect hydraulic conductivity. Consolidation tests were done on four core samples to determine changes in hydraulic conductivity with pressure. Vertical hydraulic conductivity of the samples decreased by 40 percent as pressure increased from near atmospheric to the 7 kg/cm2 (100 psi), a pressure that would prevail at a depth of 30 m (98 ft). This indicates that hydraulic conductivity of the till decreases with depth in response to overburden pressure.

Despite evidence of higher horizontal than vertical permeability in one set of laboratory tests of till samples, other laboratory and field tests as well as analyses of ground‐water flow by a computer model indicate that the till is nearly isotropic.

Hydraulic conductivity of the till was estimated with reasonable accuracy from mercury‐porosimeter tests. However, estimating hydraulic conductivity of fine‐grained samples from some regions by this method may be inappropriate because the method uses dry samples, which could severely affect the results if swelling clays are present.
RISING GROUND WATER – PROBLEM OR RESOURCE?
Authors: Hagerty D. J. , Lippert K.
Published: March 2006

Abstract. Ground water rising to within 6 m (20 feet) of average ground surface elevations in Louisville, Kentucky caused concern to municipal officials and building owners in the central urban area. An average rise of more than 11 m (35 feet) occurred between 1969 and 1980.

An evaluation of foundation conditions and structural configurations in central Louisville indicated rising ground water could create:

1. slight but significant possibilities of structural settlement problems;

2. high possibilities of damage to basement floors and walls; and

3. very high possibilities for disruption of utility conduits.

Efforts to determine the cause of this rise in ground‐water level have focused on the historical relationships between ground‐water levels, pumpage rates and precipitation values.

Historical data indicated that ground‐water levels in a system undisturbed by man could reach ground surface elevations in central Louisville. Preliminary studies indicated a strong relation between average ground‐water levels and changes in pumping rates and incident precipitation. A further detailed study showed extremely high correlation (R = 0.995) between average ground‐water levels in 1966–1980 and cumulative departures in precipitation and pumping rates from 1950–1965 average precipitation and pumping rates.

A study of the feasibility of lowering ground‐water levels while simultaneously storing energy in the aquifer system was begun but was interrupted by devastating explosions of hexane in the sewers beneath south‐central Louisville on February 13, 1981. Although a dry year in 1980 and no change in pumping rate have slowed the rise in ground‐water level temporarily, long‐term solutions to this problem need to be developed.
Regional Study of the Dakota Aquifer (Darton's Dakota Revisited)
Authors: Helgesen J. O. , Jorgensen D. G. , Leonard R. B. , Signor D. C.
Published: March 2006

In 1905, N. H. Darton described the geology and underground‐water resources of the central Great Plains in his classic report that emphasized the importance of the Dakota aquifer to this region of the United States. Since Darton's work, many investigators have studied Dakota‐aquifer hydrology with regard to development of local or statewide resources. Preliminary mapping of relatively recent fluid‐level data by the U.S. Geological Survey indicates regional potentiometric trends similar to those interpreted by Darton, but altitudes substantially lower in part of the area. The classic artesian‐system concept of the Dakota aquifer is not consistent with some of the data and observations of the past several decades. The simple aquifer geometry and effective lateral hydraulic continuity normally associated with that concept do not appear to characterize the Dakota aquifer regionally.
Permeability of Grout Seals Surrounding Thermoplastic Well Casing
Authors: Kurt Carl E. , Johnson Roy C.
Published: March 2006

An experimental test program was conducted to measure the longitudinal permeability of a grouted thermoplastic water well casing system. A neat cement grout, with and without calcium chloride or bentonite admixtures, was placed in the annulus of a simulated well. Test pressure and specimen configuration was shown to influence the measured coefficient of permeability. A neat grout with a water/cement ratio of 2.0 had a much higher permeability coefficient than the same grout with a water/cement ratio of 0.46.

Once the bond line between the grout and casing was broken, the permeability of the system was generally higher than for the initial test. Specimens with a bell coupling included had a slightly higher permeability than specimens with straight pieces of casing. The effect on permeability of the admixtures in the grout was not conclusive. However, the addition of a bentonite slurry to the test water was observed to decrease the permeability coefficient when tested under low pressure.

The permeability coefficient of the basic neat grout casing system ranged from 20 – 100 × 10 −5 cm/sec at low test pressure. It was concluded that the casing has an impact on the longitudinal permeability of the system since the coefficients of permeability measured were significantly higher than other published values. However, the coefficients of permeability measured were in the range of soils with low permeability such as silts.
A Lumped Parameter Model of a Chalk Aquifer‐Stream System in Hampshire, United Kingdom
Authors: Keating T.
Published: March 2006

A field investigation into low flow augmentation using seasonal ground‐water abstraction from the unconfined Chalk aquifer in Hampshire, United Kingdom, revealed the presence of a thin, highly transmissive and storative zone in the Chalk close to the water table. A lumped parameter model of the aquifer‐stream system incorporating a variable transmissivity and storativity distribution has been developed to explain the unusual hydrogeological features of the catchment observed during the investigation.
The Nature and Source of Arsenic in Northeastern Ohio Ground Watera
Authors: Matisoff Gerald , Khourey Christopher J. , Hall John F. , Varnes Arthur W. , Strain William H.
Published: March 2006

Elevated arsenic concentrations were found in ground water near Canal Fulton, Ohio. The hydrologie and chemical properties of the area were studied to determine the source of the arsenic and evaluate the possibility of a similar problem occurring elsewhere. Two major aquifer systems exist within the study area: the Sharon Sandstone of the upland areas; and the outwash sand and gravel deposits of the buried valleys. Ground‐water flow is generally from the north, but local variations are caused by the Tuscarawas River valley on the south and west of the study area. Within the study area, there is no evidence for an anthropogenic source of arsenic to the ground water. Agricultural soils, abandoned underground coal mines, industrial impoundments to the north, and an abandoned industrial dump site within the study area were all eliminated as possible sources for the arsenic. The arsenic in Canal Fulton ground water is entirely inorganic, consisting of about equal parts of arsenate and arsenite. Reduction‐oxidation (redox) considerations suggest that arsenic is controlled by an adsorption equilibrium with ferric hydroxides, and that the reduction of the ferric hydroxides by a recent lowering of Eh and/or pH in the aquifer has liberated both iron and arsenic to solution. A high correlation between ferrous iron and total dissolved arsenic supports this model. It is hypothesized that Eh conditions have been lowered in the aquifer by either the recent introduction of methane gas or the deposition of a thick layer of till during the last glacial retreat. The methane gas could be leaking from deep underground storage at the site and reducing oxidized compounds. The deposition of till would have eliminated local recharge of oxygenated waters.
A Computer Program for a Trilinear Diagram Plot and Analysis of Water Mixing Systemsa
Authors: Morris Michael D. , Berk Jeffrey A. , Krulik Joseph W. , Eckstein Yoram
Published: March 2006

The Piper (1953) trilinear diagram has been widely used to graphically represent the dissolved constituents of natural waters and to test for apparent mixtures of waters from different sources. Because of the time required to plot points and calculate the proportional values of mixing, this treatment of data was often quite tedious, particularly in studies involving large numbers of chemical analyses. The PIPER program was written in BASIC to be run on a Hewlett‐Packard desktop computer with an X‐Y plotter. Data input is in ppm units. The program plots points in all three fields of the trilinear diagram, draws at each point within the central diamond field a circle with a radius correspondent to the concentrations expressed in meq/1, checks for points that fall on a straight line (or within a predetermined tolerance of a straight line) representing postulated mixtures with two end members, and/or within a triangle representing mixtures of three end members. Finally, the program does a numerical analysis of the mixing ratios of the constituents for postulated mixing systems according to the methodology as presented by Piper (1953).
Enumeration and Characterization of Bacteria Indigenous to a Shallow Water‐Table Aquifer
Authors: Wilson J. T. , McNabb J. F. , Balkwill D. L. , Ghiorse W. C.
Published: March 2006

Regions of the earth below the root zone of soil have conventionally been considered void of life. However, widespread pollution of ground water in the U.S. by organic compounds has kindled interest in the numbers of microbes that might be found in aquifers and associated regions of the deeper unsaturated zone, and in their ability to degrade organic pollutants.

Newly developed techniques in microbial ecology allow the direct enumeration and examination of soil microbes without recourse to their cultivation on growth media. These techniques reduce many uncertainties associated with the use of culture media, such as the growth of contaminants or the failure of indigenous forms to grow on a particular medium. Samples were recovered aseptically from depths of 1·2, 3·0, and 5·0 meters (m) at the margin of a small floodplain near Lula, Oklahoma. Depth to the water table was 3·6 m; depth to bedrock was 6·0 m. Numbers of microbes were surprisingly similar at all three depths (3 to 9 × 106/g dry material). Although both Gram‐positive and Gram‐negative bacteria were encountered, small Gram‐positive coccoid forms predominated. No protozoa, yeasts, or other fungi were seen. The indigenous bacteria could rapidly degrade toluene. Chlorobenzene was degraded in material from the vadose zone, while bromodichloromethane was degraded in material from the saturated zone. There was no detectable degradation of 1,2‐dichloroethane, 1,1,2‐trichloroethane, trichloroethylene, or tetrachloroethylene.
The Practical Application of Surface Electrical Resistivity to Detection of Ground‐Water Pollution
Authors: Urish Daniel W.
Published: March 2006

One of the primary problems in field investigations of ground‐water pollution is locating the contaminant plume. Drilling of sampling holes on a hit‐or‐miss basis is both time‐consuming and expensive. Under many subsurface conditions, surface electrical resistivity profiling can quickly and cheaply locate the general position of the plume and identify areas most feasible for sampling and monitoring. Many contaminants contain an ionic concentration considerably higher than the background level of native ground water. When such a contaminant is introduced into an aquifer, the electrical resistivity of the saturated soil is reduced. Surface electrical resistivity profiling across a suspected area can identify this reduced resistivity zone as an anomaly. The sensitivity of the method depends on relative uniformity of geology and topography as well as minimal extraneous electrical interferences. It is also essential that the “A” spacing used in the profiling procedure be carefully selected. If the resistivity contrast between contaminated and uncontaminated ground water is high, detection of at least the central part of the plume is likely within expected geologic variation. The method has been successfully used in the location of plumes from contaminants including brine, uranium reprocessing liquid wastes and landfill leachate in glacial deposits of New England.
Harmonizing Ghyben‐Herzberg Interface with Rigorous Solutions
Authors: Kashef Abdel‐Aziz I.
Published: March 2006

Ground‐water management in coastal aquifers is becoming highly complex due to the increase in water demand coupled with the threat of salt‐water encroachment. The salt‐/fresh‐water interface produced by the natural flow of the aquifer is distorted as a result of ground‐ water exploitation. The solution of these problems includes several simplifications of unknown effects. This paper deals with the first phase in ground‐water management, namely locating the interface due to natural flow by simple equations which give results practically the same as the rigorous solution.

During the last four decades, the use of the Ghyben‐Herzberg (G‐H) principle to determine the salt‐/fresh‐water interface in coastal aquifers was questioned by many investigators due to the neglect of the water movement. Some of the highly complex solutions which were later introduced are reviewed in this paper and compared with the G‐H results for a very wide range of parameters. It has been found that the G‐H principle is valid for practical purposes and that the differences between location of the interface predicted by the G‐H principle and those determined by the rigorous solutions may be less than the differences resulting from small errors in the field records of water levels.

For exceptionally high natural velocities and/or for more precision within the zones very close to the shore, two simple equations derived on the basis of the rigorous solutions are given. Each equation is written in terms of the practically popular G‐H solution with a correction factor added. The results of these equations are tabulated in dimensionless values for practical use. Moreover, the extent and size of the fresh‐water lens can be determined from the field records of one or two shallow observation wells. An illustrative example is given to clarify the procedure.
Hydrogeology of the Littlefield Springs, Arizona
Authors: Trudeau Douglas A. , Hess John W. , Jacobson Roger L.
Published: March 2006

A hydrogeologic investigation was conducted to determine the source of recharge to the Littlefield Springs, a series of carbonate springs occurring along a 10 km (6 mile) reach of the Virgin River in northwestern Arizona. The most probable sources of recharge to the springs were determined to be influent Virgin River water and precipitation within the springs hydrologic basin. These recharge sources could account for the total discharge of the springs. The Littlefield Springs have essentially constant discharge 1.84 cms (65 cfs), and quality 2940 mg/L TDS. Tritium analyses of the spring and river water indicate that there are at least two different sources of recharge to the Littlefield Springs–one a minimum of 22 years old and the other younger than 22 years old. Analysis of the influent Virgin River upstream from the springs indicates a 1·42 cms (50 cfs) loss at 2130 mg/L TDS and the same ionic ratio of dissolved constituents as the springs. The travel time of this recharge source is interpreted to be a minimum of 22 years. Local recharge to the springs has been estimated to be 0·31 cms (11 cfs). The presence of local recharge is indicated by pulse train gaging of the springs, and by water quality at a well upstream of the springs and at the first upstream occurrence of the springs. The travel time of this recharge source is interpreted to be less than 22 years.
Aqueous Geochemistry and the Exchangeable Cation Composition of Glauconite in the Aquia Aquifer, Maryland
Authors: Chapelle Francis H. , Knobel LeRoy L.
Published: March 2006

The cation composition of water in the Aquia aquifer of southern Maryland changes systematically in the direction of ground‐water flow. In the upgradient parts of the aquifer, calcium is the dominant cation in solution. Between 10 and 20 miles downgradient, calcium and magnesium are dominant. Between 20 and 35 miles downgradient, magnesium and potassium are dominant, and, beyond 40 miles downgradient, sodium is the most abundant cation in solution. The exchangeable cation composition of glauconite in the Aquia aquifer changes systematically in the direction of flow in a manner similar to the changes in water chemistry. These observations are interpreted as evidence that cation exchange reactions are processes that simultaneously alter water composition and glauconite composition along the flowpath.

Exchange parameters K’and n for glauconite in the Aquia aquifer were determined for the reactions:
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The exchange parameters for each reaction were tested by an indirect method. Molar ratios of exchangeable cations or glauconite were calculated from water chemistry data using the derived k’and n values. In each case, the trend of calculated molar ratios compared favorably with measured molar ratios. The calculated exchange parameters demonstrate that the exchange process is not linear for the Ca2+ ‐Na+ and Mg2+ ‐Na+ ion pairs.

The sum of exchangeable cations on glauconite samples is significantly lower in the outcrop area than downgradient. Corresponding to this, the concentration of dissolved silica and dissolved oxygen in Aquia water is high near the outcrop area and decreases downgradient. This pattern suggests that incongruent dissolution of glauconite is an additional process that modifies glauconite composition near the outcrop area but is less important downgradient.
INSTALLATION OF SHALLOW SAND‐PACKED PIEZOMETERS IN LOOSE SATURATED SEDIMENT
Authors: Garrett Mary Keith , Carter Virginia
Published: March 2006

Abstract. Installation of shallow sand‐packed piezometers in auger holes with caving saturated sands in the Great Dismal Swamp of Virginia and North Carolina was greatly facilitated by freezing the piezometer and sand pack together. The frozen unit made it possible to install up to three wells per day with little difficulty.
Survival of Pathogenic and Indicator Organisms in Ground Water
Authors: Bitton G. , Farrah S. R. , Ruskin R. H. , Butner J. , Chou Y. J.
Published: March 2006

A comparative study was undertaken on the decay rates of three bacterial types (S. typhimurium, E. coli and S. faecalis), an enterovirus (poliovirus type 1) and a bacterial phage (f2) in ground water maintained under laboratory conditions. Except for f2 phage, all the microorganisms tested were relatively stable in ground water. S. faecalis survived best among all the bacteria tested and its decay rate was similar to that of poliovirus type 1.

Under field conditions, bacterial indicators were also found to be stable in the ground‐water environment. The decay rate for fecal streptococci was lower than for fecal or total coliforms in the shallow wells.
Field Determination of Cation Exchange Properties for Calcareous Sand
Authors: Reardon E. J. , Dance J. T. , Lolcama J. L.
Published: March 2006

A technique has been developed for the determination of the exchangeable cation population of calcareous sandy material with cation exchange capacities of less than 1 meq/100 g. The technique involves the addition of exchange salt in the dry state to samples of porous media using original pore water as the exchange salt solvent. In applying this technique to samples from below the water table, the amount of pore water available for reaction is reduced by centrifuging in the field to bring the moisture content close to field capacity values. By utilizing the minimum amount of pore water, interferences during the exchange process due to calcite precipitation or dissolution are minimized. The extent of calcite dissolution or precipitation that occurs can be appraised by measuring alkalinity or total carbon on the pore water before and after addition of the exchange salt. Three salts, NH4C1, CsCl and LiCl were tested for their suitability for this technique. CsCl was found to be preferable because of its low tendency to dissolve carbonate and the preference of Cs+ on exchange sites.

Application of the method to a field site in southern Ontario yielded a value of 0.51 ± 0·09 meq/100 g over 15 samples for the cation exchange capacity of a near surface glaciofluvial sand deposit. It is believed that this technique could be applied with reasonable accuracy and reproducibility to materials with exchange capacities of as low as 0·1 meq/100 g.
Analysis of Flow to a Large‐Diameter Well Discrete Kernel Approach
Authors: Patel S. C. , Mishra G. C.
Published: March 2006

Unsteady flow to a large‐diameter well has been analyzed by a discrete kernel approach, taking well storage into consideration. The variation of drawdown with time has been obtained at the well and inside the aquifer. The validity of the new method has been verified by comparing the drawdown at the well with the drawdown given by Papadopulos and Cooper (1967). The aquifer contribution to discharge at various times has been estimated.
Rapid Solution of the Nonlinear Step‐Drawdown Equation
Authors: Miller Cass T. , Weber Walter J.
Published: March 2006

The step‐drawdown test is frequently utilized by hydrogeologists as an aid in assessing well efficiency and approximate pumping capacity. Unfortunately, the analysis of step‐drawdown data presently requires either a solution to a system of highly nonlinear equations or the application of tenuous assumptions relative to the solution form. A method for solution is derived which does not require limiting assumptions, type‐curve methods or extensive computer facilities.
Effects of Aquifer Interconnection Resulting from Underground Coal Gasification
Authors: Stone Randolph , Raber Ellen , Winslow Alan M.
Published: March 2006

An investigation was conducted to evaluate the effects of aquifer interconnection caused by the collapse of cavities formed in coal seams by two small underground coal gasification experiments in the Powder River Basin, Wyoming. The main objective of the work was to assess the magnitude and extent of changes in the ground‐water flow patterns near the sites of the two experiments. Hydraulic head measurements in the three affected aquifers were used to calibrate a steady‐state ground‐water flow model of the interconnection zone at each site. Flow modeling and field measurements show that water from one or both of the upper aquifers enters the collapse rubble and flows down to the lowest aquifer (the gasified coal seam) where it flows away from the collapse zones. The hydraulic conductivity of the collapse rubble is less than that of the aquifers and provides only a very moderately permeable interconnection between them. A marked reduction in the hydraulic conductivity of the gasified coal seam near the collapse zones causes restriction of flow in the seam, away from them. Changes in hydraulic head and flow patterns caused by aquifer interconnection extend generally only 200–300 ft (60–90 m) away from the experiment sites. Flow in the uppermost aquifer at one of the sites may be influenced as far as 400 ft (122 m) away. At both experiment sites, aquifer interconnection allows water from the uppermost (sand) aquifer, which contains the poorest quality water of the three aquifers, to enter one or both of the underlying coal aquifers.
AN APPLICATION OF GEOSTATISTICS TO DETERMINE REGIONAL GROUND‐WATER FLOW IN THE SAN ANDRES FORMATION, TEXAS AND NEW MEXICOa
Authors: Orr Elizabeth D. , Dutton Alan R.
Published: March 2006

. The construction of a contour map of hydraulic head for ground water in the San Andres Formation in west Texas and eastern New Mexico is problematic due to variability in quality and distribution of data. The direction of regional ground‐water flow can be inferred from raw data only in the northern part of the study area where reliable drill‐stem tests and water‐level measurements make up most of the data. In the southern area, where unreliable and highly variable drill‐stem tests comprise the bulk of the data, variogram analysis and kriging successfully remove the effects of high measurement error. This allows the regional trend to be seen. However, kriged block estimates cannot be computed for a critical region with sparse data in the northeastern part of the study area. The most complete potentiometric surface can be contoured from hybrid data: kriged block estimates from the southern region, and original head measurements in the northern region.
Heat Convection in Warm Springs Valley, Virginia
Authors: Severini Anthony P. , Huntley David
Published: March 2006

Warm Springs Valley, located in northwestern Virginia, is characterized by the discharge of springs from cavernous limestone at temperatures up to 40°C, although the measured geothermal gradient is a normal 10°C/km. The area is therefore hypothesized to be an important example of a situation where thermal convection is sufficient to produce high‐temperature surface waters. A finite‐difference numerical model was constructed to simulate the simultaneous transport of heat and fluid under combined forced and free convection conditions. This model was used to test the hypothesized heat flow system for Warm Springs Valley.

The results of the testing show that, within the hydrogeological constraints found at Warm Springs Valley, convection with a normal geothermal gradient is capable of producing 40°C hot springs. The conditions required a zone of enhanced vertical hydraulic conductivity in the area of ground‐water discharge and a deep zone of enhanced horizontal hydraulic conductivity. The enhanced zones are consistent with the geology found in the basin.
A CONSTANT DISCHARGE DEVICE FOR AQUIFER TESTS ON LARGE‐DIAMETER WELLS
Authors: Athavale R. N. , Singh V. S. , Subrahmanyam K.
Published: March 2006

Abstract. The discharge in pumping tests conducted on large‐diameter wells declines with the fall of water level. This violates the basic requirement of pumping tests that the discharge should remain constant. A simple device to keep the discharge constant has therefore been developed. This device is also useful in keeping the discharge much lower than the rated capacity of the farmer's pump, and thus in increasing the total test period.

The discharge from the farmer's pump is released in a barrel having a V‐notch at the top and an arrangement for returning a part of the discharge to the well. The return flow is gradually reduced through a control valve, and thus the net outflow is kept constant.

This device has been used for conducting pumping tests on several dug wells.
Assessment of the Effectiveness of Barriers for the Retardation of Pollutant Migration
Authors: Knox Robert C.
Published: March 2006

Currently, one of the most popular methods of containing contaminated ground water is through use of subsurface impermeable barriers. These barriers can take one of three forms: slurry walls, grout curtains, or steel sheet piles. Successful operation of these barrier systems is dependent upon three basic criteria. First, the barrier must be truly impermeable and remain so over time even upon exposure to the contaminated ground water. Second, there must exist an underlying impermeable formation, at a reasonable depth, to which the barrier can be connected. Third, an adequate connection between the barrier and the underlying formation must be assured.

This paper presents the results of the analysis of the movement of contaminated ground water under or through an imperfect barrier. The first phase of the analysis consists of the development of an analytical solution for the flow of ground water under a barrier and a simple numerical integration technique for developing concentration breakthrough curves. This simple solution algorithm was applied to the cases of variable recharge rates and lengths, variable depths of penetration of the barrier, and anisotropic soils. The second phase of the analysis involves applying a numerical solute transport model to analyze the performance of a barrier with and without the effects of hydrodynamic dispersion, and in the presence of a layered soil, and finally the performance of a fully penetrating but partially permeable barrier.
Aquifer Testing, Mathematical Modeling, and Regulatory Risk
Authors: Wang Ching‐Pi , Williams Roy E.
Published: March 2006

Mathematical modeling founded on a strong field data base can be a valuable tool for the analysis of ground‐water contamination problems. The purposes of this paper are threefold: (1) we demonstrate the dilemma of a knowledgeable ground‐water quality regulator whose regulatory decision‐making process is confronted with the output of a mathematical model that is based on very limited field test data; (2) we demonstrate a method available to a knowledgeable regulator for assessing approximately a range of possible performances of a contaminated ground‐water recovery well field using a range of input data derived from a very limited data base; and (3) we present a strong case for presenting mathematical model outputs as ranges of values rather than as unique solutions. A range is determined by an examination of the level of sophistication of the field data base. Our experience with 12 field sites wherein ground‐water contamination has occurred has led us to conclude that field data are seldom, if ever, adequate to defend a unique solution from a mathematical model. Regulatory decisions generally can be reduced to minimization of risks based on the smallest range of model outputs that can be defended on the basis of the field data base. The more limited the field data base, the greater must be the range of defensible model outputs, and consequently, the greater the risk inherent in subsequent regulatory decisions. The knowledgeable regulator can assess the risks in the regulatory decision‐making process only if he is able to assess the extent to which the field data base for the mathematical model output reflects state‐of‐the‐art data collection and analysis technologies and methodologies. If an applicant for a permit or license submits a less than adequate data base and concomitantly a broad range of defensible model outputs, he inherently requests that the knowledgeable regulator accept a risk greater than that required if adequate aquifer testing techniques had been employed.
Ground‐Water Chemistry of Dibdiba Formation, North Kuwait
Authors: AI‐Ruwaih Fawzia
Published: March 2006

Chemical studies have been carried out on a number of water wells from the Dibdiba Formation northeast of Kuwait. Water salinity of this formation ranges between 3,300 mg/l to 7,000 mg/l, increasing with depth. The water entrapped in Dibdiba Formation is mainly sodium chloride type which can be differentiated into three different groups according to the ranges of concentration of the main cations and anions. These groups are: (3331113) sodium chloride water type in which Cl > Na, group (3333113) sodium chloride water type in which Na > Cl. In both groups the sequence of dominant cations is Na > Ca > Mg. Group (3333111) sodium chloride water type has Na > Cl and the sequence of dominant cations is Na > Mg > Ca. Chemical ratios of Ca/Mg, Na/Cl, and C1/HCO3 were worked out for Dibdiba ground water. The ratio of Ca/Mg Dibdiba Formation ranges from 0.4 to 8.58, the ratio of Na/Cl ranges between 0.98 to 1.33, and the ratio of C1/HCO3 is 232.

A plot of chemical analysis on a trilinear diagram shows that Dibdiba Formation ground‐water chemical properties are dominated by alkalies (Na > Ca) and strong acid (Cl > SO4). Water chemistry may reflect the history of the flow path, indicating regional flow as shown by increasing Na+, Cl‐, SO–4 and where Ca+, Mg+ achieve equilibrium.
Sources of Nitrate in Ground Water in a Sewered Housing Development, Central Long Island, New York
Authors: Flipse William J. , Katz Brian G. , Lindner Juli B. , Markel Richard
Published: March 2006

Nitrate concentrations in ground water on Long Island, New York, have increased markedly in the last 30 years. A significant amount of this increase has been attributed to lawn and garden fertilizers in addition to cesspool and septic‐tank discharges. The increase in nitrate concentration is of particular concern in the central and eastern part of the island, where ground water is the sole source of drinking water.

Ground‐water samples were collected from 14 wells screened near the water table in the sewered Twelve Pines housing development constructed in Medford, Suffolk County, in 1970. Samples were collected during 1972–79 and analyzed for total ammonium, organic nitrogen, and nitrate.

Statistical analyses indicate that concentrations of nitrate‐nitrogen in water from 10 of the wells increased significantly during 1972–79; those in water from the other four wells did not.

Nitrogen loads were estimated to be 2,300 kg/yr from fertilizers, less than 80 kg/yr from irrigation water, 200 kg/yr from animals, and less than 670 kg/yr from precipitation. Leakage from sewers was considered negligible.

Nitrate‐nitrogen isotope ratios also suggest that the greatest source of nitrogen is from cultivation sources (either mineralized soil nitrogen or fertilizers) rather than human or animal wastes.
Bedrock Depth Estimates from Ground Magnetometer Profiles
Authors: Birch F. S.
Published: March 2006

Bedrock depths can be calculated readily from ground magnetic profiles using either Werner deconvolution or Fourier spectral analysis. For crystalline basement rocks of New England and eastern Canada, a vertical dike is a useful magnetic source model. Formulae for these methods are presented along with some practical guidelines for implementing them.

Six field examples from metamorphic and igneous areas in New Hampshire show that bedrock depths from spectral analysis agree well with estimates from seismic refraction, from wells and from outcrops. The Werner estimates are much more variable but commonly bracket the others. At several of these sites, measurements by other geophysical methods would be impractical, more expensive, or restricted to certain times of the year.
Land Subsidence Near Oil and Gas Fields, Houston, Texasa
Authors: Holzer Thomas L. , Bluntzer Robert L.
Published: March 2006

Subsidence profiles across 29 oil and gas fields in the 12,200‐km2 Houston, Texas, regional subsidence area, which is caused by decline of ground‐water level, suggest that the contribution of petroleum withdrawal to local land subsidence is small. Despite large volumes of petroleum production, subsidence at most fields was not increased by oil and gas withdrawal. Local increases of subsidence were detected at only six fields—Alco‐Mag, Chocolate Bayou, Goose Creek, Hastings, Mykawa, and South Houston. With the exception of the 1‐m subsidence from 1917 to 1925 at Goose Creek, differential subsidence across oil and gas fields was smaller by a factor of two or more than subsidence caused by aquifer compaction. At four fields—Barbers Hill, Cedar Bayou, Humble, and Pierce Junction—subsidence was substantially less than in the surrounding area. Except for Cedar Bayou, these fields are associated with shallow salt domes that partly occupy the aquifer system; for the three fields, subsidence during the periods of record came to less than half the subsidence in the surrounding area.

In addition to land subsidence, faults with an aggregate length of more than 240 km (150 mi) have offset the land surface in historical time. Natural geologic deformation, ground‐water pumping, and petroleum withdrawal have all been considered as potential causes of the historical offset across these faults. The minor amount of localized land subsidence associated with oil and gas fields, however, suggests that petroleum withdrawal is not a major cause of the historical faulting, at least by a differential compaction mechanism.
Field and Laboratory Analyses of Water from the Columbia Aquifer in Eastern Maryland
Authors: Bachman L. Joseph
Published: March 2006

Field and laboratory analyses of pH, alkalinity, and specific conductance from water samples collected from the Columbia aquifer on the Delmarva Peninsula in eastern Maryland were compared to determine if laboratory analyses could be used for making regional water‐quality interpretations.

On the basis of 170 field pH and specific conductance measurements, 165 laboratory pH and specific conductance measurements, and 86 field and 135 laboratory alkalinity measurements, a significant difference at the 0.1‐percent level was found between laboratory and field analyses of pH and specific conductance. No significant difference was found between laboratory and field analyses of alkalinity. In most samples, laboratory pH was greater than field pH, laboratory specific conductance was less than field specific conductance, and laboratory alkalinity was equally likely to be less than, the same as, or greater than field alkalinity.

Kruskal‐Wallis tests of field and laboratory data grouped by north‐south and east‐west coordinates and by land use indicate that the difference between field and laboratory values is usually not enough to affect the outcome of the statistical tests. Thus, laboratory measurements of these constituents may be adequate for making certain regional water‐quality interpretations, although they may result in errors if used for geochemical interpretations.
Anisotropy in the Ironton and Galesville Sandstones Near a Thermal‐Energy‐Storage Well, St. Paul, Minnesota
Authors: Miller R. T.
Published: March 2006

The U.S. Geological Survey is studying the potential for storage of heated water in a sandstone aquifer in St. Paul, Minnesota. The efficiency of the aquifer to store thermal energy is related, in part, to the hydrogeologic characteristics of the aquifer. The movement of heat away from the injection well is directly related to the anisotropy. Aquifer tests were conducted to determine the anisotropy near the heated‐water injection well. The maximum and minimum values of transmissivity along the principal directions of the hydraulic conductivity tensors of the Ironton and Galesville Sandstones in St. Paul, Minnesota are approximately 1,090 and 480 feet squared per day. The storage coefficient is 4.5 × 10−5. These values represent the average of four determinations of nonsteady flow to a well in an idealized infinite anisotropic aquifer. Analysis of the values of transmissivity and storage coefficient for hypothetical changes in location of two of the monitoring wells where depth‐deviation surveys were not available indicates that computed transmissivities vary less than 5 percent and storage coefficients vary less than ±6 percent.
Aquifer Studies Using Flow Simulations
Authors: Puri S.
Published: March 2006

Flow simulations supplemented resource evaluation studies of the Lower Greensand aquifer. The annual recharge has hitherto been considered to be the resource available for development although a large confined storage exists. Pumping is principally in urban areas but recent monitoring suggests that the aquifer may have suffered excessive drawdowns. Therefore, simulation studies were carried out to refine the annual recharge estimate, to define the past effects of pumping and to obtain an indication of future trends. Catchment water balance indicates average annual recharge of 28 × 106 m3. One‐dimensional (ID) ground‐water flow simulation suggests that regional abstractions affect outcrop‐water levels. The study showed that the aquifer reached a new equilibrium with the current pumping regime. An improved insight to the aquifer has permitted the formulation of strategies for future resource development.
SIMPLE ANALYTICAL SOLUTIONS FOR THE HP41CV PROGRAMMABLE CALCULATOR
Authors: Baker Stephen J.
Published: March 2006

Abstract. Two useful programs have been developed for the Hewlett Packard HP41CV programmable calculator. The THEIS program is designed to simulate a well pumping from a confined or unconfined aquifer. Drawdown, residual drawdown, t/t1 and t/r2 are calculated. The BOUN program is designed to solve for drawdown in a well pumping from an aquifer bounded by two parallel impermeable barriers. The programs can be used in aquifer pumping test design, pumping test analysis, and aquifer response predictions.
Hydrogeologic Characteristics of Shallow Glacial Drift Aquifers in Dissected Till Plains (North‐Central Missouri)
Authors: Sharp John M.
Published: March 2006

The dissected till plains physiographic province contains extensive areas of pre‐Illinoian drift in Kansas, Nebraska, Iowa, and Missouri. The drift is typically a clay‐rich, oxidized, and highly weathered till. In many areas of Missouri, this shallow drift represents the only readily available aquifer suitable for domestic and small agricultural users. There are, however, only few published data on the region's hydrogeology. Water budget analyses indicate that approximately 30% of mean annual rainfall is discharged by stream flow and 70% by evapotranspiration. The shallow drift flow systems are best considered unconfined, steady‐state systems. Each watershed corresponds roughly to a local ground‐water system. There is, typically, little hydraulic connection between the shallow drift systems and underlying strata. The drift hydraulic conductivity varies from approximately 1011 m/sec (laboratory tests) to 10−6 to 10−7 m/sec (field tests) when permeable sand lenses or joints are intersected. Ground‐water discharge is concentrated in the immediate vicinity of stream channels, and recharge is concentrated on nearly horizontal hillslope summits. The ground water is generally potable (averaging 455 mg/1 total dissolved solids), but may be high in iron or polluted locally by organic wastes.