bluuebunny/crossref_metadata_2025 huggingface dataset:
Experiments to Assess the Hydraulic Efficiency of Well Screens
Authors: Clark L. , Turner P. A.
Published: March 2006

The hydraulic properties of commercial well screens were investigated to determine which screen design features affected head loss. The test program began with laboratory experiments and continued as a field‐scale experiment with the installation of a well field in the Thames Valley Gravel Aquifer.

The laboratory experiments indicated that, for all practical purposes, the head loss attributable to all of the screens tested was negligible. The experimental head loss, however, did vary from screen to screen, particularly at high intake velocities, and the screens could be ranked on the basis of their hydraulic efficiencies. This efficiency hierarchy is explained tentatively in terms of the screen construction methods and slot geometry. The field experiments showed that the hydraulic performance of all well screens is independent of screen design provided that the open area of the screen is above about 10%. The field experiments also indicated that the development capacity of a screen in a gravel aquifer is not wholly dependent on screen design, but that progressive development does increase the hydraulic efficiency of a well.
Aquifer Tests and Well Field Performance, Scioto River Valley, Ohio: Part Ia
Authors: Norris Stanley E.
Published: March 2006

Based on 13 aquifer infiltration tests at 11 sites, aquifer transmissivity ranged from 17,000 to 40,000 square feet per day, and the streambed infiltration rate ranged from 0·06 to 0·19 million gallons per day per acre along a seven‐mile reach of the Scioto River in south‐central Ohio. Despite these wide ranges, the sand and gravel aquifer, 40 to 65 feet thick, underlying 10–20 feet of river alluvium south of the glacial boundary, is fairly homogeneous due largely to the absence of till interbeds.

Performance of a major well field designed on the basis of the tests has been about as predicted, validating the techniques of data collection and analysis.

At each site, a well for pumping was drilled on the floodplain, 150 to 750 feet from the river, and an array of observation wells was installed on lines extending through the pumped well, one line perpendicular to the river and the other parallel.

Values of drawdown measured in the observation wells at the end of constant‐rate pumping periods, usually of three days duration, were used to determine line‐source distance and aquifer transmissivity. The rate of streambed infiltration and the streambed‐leakage factor, the latter term relating the infiltration rate to drawdown beneath the stream, also were determined at all but one site. Drive‐point wells installed in the riverbed, or along the near bank, in the vicinity of the pumped well were used to determine drawdown beneath the river due to pumping.
Ground‐Water Model for a Thick Fresh‐Water Lens
Authors: Liu Clark C. K. , Lau L. Stephen , Mink John F.
Published: March 2006

The Pearl Harbor aquifer, an important ground‐water resource for southern Oahu, Hawaii, contains an enormous fresh‐water lens, up to 300 m (1,000 ft) thick, floating above saline water. The upper boundary of the fresh‐water lens is confined near the coast and phreatic inland, whereas its lower boundary is not confined. A finite‐difference flow model was used to simulate the Pearl Harbor aquifer system. The location of the fresh‐water/salt‐water interface, which constitutes the lower boundary of the flow system model, was estimated by Hubbert's formula. Known geohydrologic boundaries and aquifer parameters were also simulated. First, formation of the lens by filling the aquifer with fresh water from natural recharge was simulated to reconstruct the initial conditions before exploitation of the lens and to partially calibrate the model against the hydraulic‐head distribution in 1879. The model then was calibrated fully by simulating the lens’reponse to actual historical pumping patterns covering a time span of 100 years (1880 to 1980). Simulated heads compared favorably with the observed heads over time and space. The calibrated flow model may serve as a useful tool in the management of the Pearl Harbor aquifer.
Ground‐Water Systems Simulation by Time‐Series Techniques
Authors: Houston J.F.T.
Published: March 2006

Time‐series techniques have been widely used in economic and environmental contexts. This paper explores their use in ground‐water systems. The basic techniques are considered in relation to hydrogeology and two case histories show their application to real systems. Water level fluctuations in a well field are shown to be dependent upon pumping rates and prior rainfall and can be simulated by a multiple linear regression model. The rate of dewatering of a mine is shown to be dependent upon pumping rates and prior rainfall and can be simulated by a multiple linear regression model. The rate of dewatering of a mine is shown to be dependent upon antecedent mine size and rainfall, and can also be simulated by a multiple linear regression model. Such models can be used for forecasting and control of the ground‐water systems, and once formulated are ideally suited to the management of ground‐water systems where more costly and complex methods cannot be used.
Geophysical Logging in Carbonate Aquifersa
Authors: MacCary L. M.
Published: March 2006

Some logging methods are inherently superior to others for the analysis of limestone and dolomite aquifers. Three such systems are the density, neutron, and acousticvelocity logs.

Relative percentages of limestone and dolomite, average matrix (grain) densities of the rock mixtures, and porosity of the rock mass can be calculated from density, neutron, and acoustic‐velocity logs. Wells drilled before the 1960's generally were logged with an uncalibrated neutron tool. In some instances, the resultant curve can be empirically calibrated.

With supporting data from resistivity logs, apparent water resistivity (Rwa) can be estimated. Depending on rock and mud resistivities, the two most useful resistivity curves for water‐quality studies are the deeply‐focused laterolog and the induction log. For older wells, the standard electric log may be used, if the drilling mud is not salt‐saturated.

Rwa contour maps derived from geophysical data are useful to outline areas of recharge, direction of probable ground‐water flow, and location and salinity of brine areas. Another useful application of well logs is estimation of ground‐water temperature. These temperatures are obtained from maximum‐reading thermometer data that generally are recorded on each logging run. Maps of porosity can be used to outline potential areas for completing large‐yield wells.
Aquifer Tests and Well Field Performance, Scioto River Valley, Ohio: Part IIa
Authors: Norris Stanley E.
Published: March 2006

The streambed‐leakage factor ranged from 0.11 to 1.68 million gallons per day per acre per foot of head loss. Most values for the streambed infiltration rate and the streambed‐leakage factor for six tests before 1970 were higher than for six tests in 1976–79, suggesting a change in streambed permeability in the intervening time.

A well field to serve a government‐owned uranium enrichment facility, consisting initially of 4 wells, later increased to 15 wells, was designed to yield up to 20 million gallons per day. The wells are on a line parallel to the river at distances from the stream ranging from 122 to 330 feet. Distance between wells ranges from 190 to 303 feet. Specific capacities of the wells, based on 24‐hour acceptance tests, ranged from 63 to 147 gallons per minute per foot of drawdown and averaged 100 gallons per minute per foot of drawdown. By late Summer of 1976, pumpage from all 15 wells ranged from 12 to 15 million gallons per day. Drawdown was about as expected, based on design criteria developed from the aquifer tests, except that pumping levels were lower than expected in the Fall and Winter of 1976–77, resulting from low streamflow and low river temperature.
LET THE MATTER DROP!: THE ROOTS OF WASTE DISPOSAL PROBLEMS
Authors: Donovan R. Nowell , Pettyjohn Wayne A.
Published: March 2006

. Observations on the collapse of a medieval castle built on an artificial mound testify that contemporary slippage was adroitly accommodated by building adjustments. However, 300 years of continuous usage without an effective waste disposal system eventually caused the latrine tower to collapse.
GROUND‐WATER UNIT STEP AND RECTANGULAR PULSE RESPONSES WITH A PROGRAMMABLE CALCULATOR
Authors: Kelly William E.
Published: March 2006

A programmable calculator program is given along with examples for a general impulse response function for calculating step and rectangular pulse response for stream‐aquifer interaction, pumping in leaky and nonleaky artesian aquifers, and two‐dimensional dispersion.
Ground‐Water Flow Model Determinations of Areal Hydrogeology and Geology
Authors: Pennequin Didier F. E.
Published: March 2006

The two‐dimensional ground‐water flow model developed by Trescott et al. (1976) was used to determine several important parameters needed to compute the ground‐water flow component to and from Lake Wingra, Madison, Wisconsin; these include horizontal hydraulic conductivity (Kh), ratio of horizontal hydraulic conductivities between two layers (Kh1/Kh2), average anisotropy of the sediments in each layer (Kh/Kv), and average depth of interaction between a lake and an aquifer. In addition to gaining hydrogeologic information, the model was used successfully to estimate general geologic relationships (i.e., location and configuration of geologic contacts) in part of the northeast shore area of Lake Wingra.
The Study of a Pseudomonad Infestation in a Well at Shilo, Manitoba
Authors: Cullimore D. R.
Published: March 2006

Water from a newly installed well (4A) at the Canadian Forces Base, Shilo in Manitoba, Canada was reported to be producing a hydrocarbon smell and sporadic turbidity which was shown to be caused by the generation of a significant population of the bacterium Pseudomonas aureofaciens. In this investigation, the pseudomonad was isolated, identified and found to be able to degrade mineral oil (as a source of organic carbon) aerobically but was not capable of nitrate respiration or of anaerobic growth. The generation of high populations (and turbidity) of Pseudomonas aureofaciens in the well water was linked to the presence of dissolved oxygen in the water along with sufficient hydrocarbons to support growth. The maximum population recorded was 8 × 105 C.F.U./ml. The origin of the hydrocarbons in the ground water was postulated to have been long‐term solvent spills from a nearby paint shop.
Regional Trends in Transmissivity and Hydraulic Conductivity, Lower Cretaceous Sands, North‐Central Texasa
Authors: Macpherson Gwendolyn L.
Published: March 2006

Depositional and structural history control regional trends in transmissivity and hydraulic conductivity in Lower Cretaceous‐age sandstones along the Balcones‐Ouachita trend in north‐central Texas. Because of a scarcity of pumping tests, delineation of trends was possible only by incorporating transmissivities estimated from specific capacities. Statistical comparison of estimated and pumping‐test transmissivities confirmed the validity of this approach. The resulting contour maps should be useful in evaluating these aquifers as potential low‐temperature geothermal resources. The method can also be applied to other aquifers to facilitate ground‐water management programs.
Gravity Exploration of a Buried Valley in the Appalachian Plateau
Authors: Wilson Michael P. , Peterson Donald N. , Ostrye Thomas F.
Published: March 2006

The existence of high‐density, nearly‐structureless bedrock buried by relatively low‐density sediments makes gravity prospecting a very informative technique for bedrock‐topography studies of the northern Appalachian Plateaus. Locating bedrock exposures and using available well data reduces the area of the gravity search. Depths to bedrock from wells correlate excellently with depths from gravity anomalies. The minimum anomaly detected was 0·18 milligal, corresponding to a depth of approximately 40 feet.
Drawdowns in Large‐Diameter Wells Due to Decreasing Abstraction Rates
Authors: Rushton K. R. , Singh V. S.
Published: March 2006

Due to characteristics of centrifugal pumps, most pumping tests in large‐diameter wells exhibit a decreasing abstraction rate with increasing drawdown. Type curves are obtained for the case of abstraction rates which are functions of the well drawdown; values for the type curves are obtained from a numerical model. For the case of constant abstraction, these curves provide an alternative to the classical approach. By plotting the ratio of drawdowns at different times, it is possible to identify more easily when the aquifer begins to contribute to the well discharge. The practical application of the technique is illustrated by a field example.
Evaluation of Surface Impoundment Assessment in New Mexico
Authors: Person Mark , Antle Rebecca , Stephens Daniel B.
Published: March 2006

Surface Impoundment Assessment (SIA) is a methodology for determining the potential for ground‐ water contamination from pits, ponds and lagoons. SIA produces a numerical rating of a site, based on the sum of scores assigned to four categories: vadose zone properties, ground‐water availability, ground‐water quality, and waste characteristics. The SIA for New Mexico was conducted as part of a nationwide survey of potentially hazardous waste‐disposal sites. Comparisons of the contamination potential scores and observed ground‐water contamination from mining, milling, and industrial impoundments in New Mexico using histograms, Mann‐Whitney U‐Test, and linear logistic regression indicate that vadose zone properties and the nature of the waste contribute most to the general success of the SIA method to predict contamination. The remaining two categories which rate ground‐water availability and natural ground‐water quality do not appear to be reasonable measures of ground‐water contamination potential. Rather, these categories are more indicative of the value of the ground‐water resources.
Evaluating System for Ground‐Water Contamination Hazards Due to Gas‐Well Drilling on the Glaciated Appalachian Plateau
Authors: Harrison Samuel S.
Published: March 2006

Recent drilling for natural gas in the Glaciated Appalachian Plateau area of northwestern Pennsylvania has caused limited, but increasing ground‐water contamination. By evaluating hydrogeologic parameters at a proposed gas well site, such as the ground‐water flow system, permeability of surficial sediments, and the presence of fracture zones, the contamination hazard of the site can be assessed. Three case studies document that the most hazardous sites are generally located on or near valley walls of major drainageways. The relatively steep hydraulic gradient, the frequent presence of highly permeable surficial sediments, and the low to moderate dilution of contaminants along the intermediate‐length flow paths at these sites all contribute to a relatively high pollution hazard. In addition to locating gas wells in high‐hazard hydrogeologic zones, allowing the annulus of gas wells to become pressurized is the other major factor contributing to aquifer contamination.
An Examination of Scale‐Dependent Dispersion Coefficients
Authors: Molz Fred J. , Güven Oktay , Melville Joel G.
Published: March 2006

Many hydrologists have observed that dispersion coefficients, when measured in the field, turn out to be scale‐dependent. That is, the greater the travel distance in a tracer test used to measure dispersivity, the larger the dispersivity value that is calculated. Recently, Güven et al.(1983) presented a study which contains a basis for understanding the phenomenon of scale‐dependent dispersion within a deterministic framework. The results of that study are used as a basis for defining a scale‐dependent macro‐ dispersion coefficient for unidirectional flow in a stratified aquifer. Theoretical expressions are then obtained for the macrodispersivity, its various components, and its small time and large time limits. Using the data of Pickens and Grisak (1981a, b), numerical values are calculated for the macrodispersivity, and estimates are made of the travel distance required in order to reach Fickian conditions. Asymptotic large time macrodispersivity values of 49.5 m to 990 m and travel distances of 5.4 km to 109 km result for the particular aquifer studied. Based on these results it appears that Fickian conditions will seldom apply in practice to porous media flow. This study and previous studies show that the primary physical mechanism that causes spreading of a solute near the source is different advection rates at different elevations in the aquifer. Present results and comparisons with field data indicate that this phenomenon is not represented well by a scale‐ dependent dispersion coefficient. In modeling dispersion phenomena, it appears that more emphasis should be placed on field study and the accurate determination of hydraulic conductivity variations and other nonhomogeneities, and less on incorporating somewhat arbitrary dispersion coefficients into complex mathematical models.
Ground‐Water Modeling in a Southwestern Alluvial Basin
Authors: Hawkins David B. , Stephens Daniel B.
Published: March 2006

A two‐dimensional finite‐difference computer code was used to model the ground‐water flow system in an alluvial basin in southwest New Mexico. A three‐step approach was used to determine the transmissivity distribution for the model. First, values of the natural logarithm of transmissivity (In T) were interpolated from existing data using the kriging technique. This interpolation scheme also produced a map of standard deviations of the kriging errors. Second, a conventional flow net was drawn from steadystate water levels with the aid of the kriged hydraulic head distribution. Third, the approximate transmissivity map, the standard deviation map of the kriged In T values, and flow net were used to select the segment of each streamtube where transmissivity was known with greatest certainty (smallest In T kriging error). Then, transmissivities in other segments of the stream tubes were calculated from Darcy's Law. This distribution, when input to the numerical model, did not have to be altered appreciably during the calibration for a steady‐state and seven‐year transient period. Most of the transient calibration was accomplished by adjusting storage coefficients. Considering the uncertainty in the available pumping data, very good agreement was found between observed and predicted water levels during a four‐year model verification period.
Matrix Diffusion Effects on Contaminant Migration from an Injection Well in Fractured Sandstone
Authors: Feenstra Stan , Cherry J. A. , Sudicky E. A. , Haq Zia
Published: March 2006

Deep‐well injection into fractured sandstone is an option for the disposal of contaminated mine dewatering discharge from an open pit uranium mine. As part of the assessment of potential contaminant migration from deep‐well injection, the effect of matrix diffusion was evaluated. An analytical mathematical model was developed for the simulation of the radial movement of a contaminant front away from an injection point under steady flow conditions in a planar fracture with uniform properties. The model includes the effects of advection in the fracture, diffusion of contaminants from the fracture into the rock matrix, and equilibrium adsorption on the fracture surface as well as in the rock matrix. Effective diffusion coefficients obtained from laboratory experiments on 11 intact core samples varied from 3.4 × 10−8 to 3.2 × 10−7 cm2/s. Model simulations were made with diffusion coefficient values in this range and with single‐fracture injection rates estimated from fracture frequencies in boreholes, and from bulk hydraulic conductivity values obtained from field tests. Because of matrix diffusion, the rate of outward movement of the front of the nonreactive contaminants from the injection well is much slower than the rate of water flow in the fractures. Simulations of the movement of contaminants that undergo adsorption indicate that even a small distribution coefficient for the rock matrix causes the contaminants to remain very close to the injection well during the one‐year period. The results of the simplified model demonstrate that matrix diffusion is an important process that cannot be neglected in the assessment of a waste disposal scheme located in fractured porous rock. However, in order to make a definitive assessment of the capability of matrix diffusion and associated matrix adsorption to significantly limit the extent of contaminant migration around injection wells, it would be necessary to conduct field tests such as a preliminary or experimental injection.
Ground‐Water Quality at a Creosote Waste Site
Authors: Bedient P. B. , Rodgers A. C. , Bouvette T. C. , Tomson M. B. , Wang T. H.
Published: March 2006

An abandoned creosote facility in Conroe, Texas, has become a field site for the National Center for Ground Water Research (NCGWR) at Rice University. Ground‐water contamination in the shallow aquifer beneath the site was characterized by sampling soils and water quality at 14 monitoring wells and 35 boreholes.

Results from six sampling trips over two years for inorganic and organic chemical concentrations in the ground water show wells around the site were contaminated to levels above 800 μg/l for naphthalene, 400 μg/1 for methyl naphthalene, and 150 μg/1 for dibenzofuran. Conservative constituents, traced by chloride concentrations up to 75 mg/l, have migrated 300 ft (90 m) downgradient of the site. Organic contaminants have been adsorbed and microbially degraded in their migration from the waste source as evidenced by their attenuated concentrations. Detailed field pump tests have been performed to evaluate hydraulic conductivity at several of the shallow wells. The U.S. Geological Survey (USGS) Solute Transport Model (Konikow and Bredehoeft, 1978) has been used to predict chloride plume patterns and evaluate parameters which govern transport processes at the Conroe waste site.
A Syringe and Cartridge Method for Down‐Hole Sampling for Trace Organics in Ground Water
Authors: Pankow James F. , Isabelle Lome M. , Hewetson Janet P. , Cherry John A.
Published: March 2006

A newly developed technique which allows the down‐hole sampling and subsequent analysis of ground water for trace organic contaminants was tested during an investigation of contaminant migration at an inactive landfill site in Burlington, Ontario, Canada. The sampling device, which is lowered down piezometers with a tube, consists of a small cylindrical cartridge of sorbent material attached to a syringe. Vacuum or pressure applied at the surface controls the movement of the plunger in the syringe. The volume of the syringe determines the volume of sample water that passes through the cartridge. The cartridge is removed from the syringe at the surface. One cartridge is used for each sampling; the syringe is reusable. The residual water in the cartridge is removed in the laboratory, and the cartridge is desorbed to a fused silica capillary column for analysis by gas chromatography (GC). The analyses discussed here were performed on a GC/mass spectrometer/data system (GC/MS/DS). Of the many organic compounds that were identified in the samples, three compounds were clearly landfill‐related: 1,1,1‐trichloroethane, chlorobenzene, and para‐dichlorobenzene. The three compounds were found at levels substantially above blank levels in 9, 5, and 5 piezometers, respectively. The average concentrations were 14., 5.3, and 0.88μg/1 (ppb), respectively. The pooled coefficients of variation for the analyses for the three compounds were 27., 6.9, and 6.4%, respectively. The volatility of 1,1,1‐trichloroethane was probably the cause of the greater variability in its analytical data. The main advantages of the technique over most conventional sampling methods include: (1) down‐hole sampling in a manner which minimizes the potential for volatilization losses; (2) avoidance of passage of the sample through long sections of tubing that may contaminate the sample or cause adsorptive losses; (3) convenience of sample handling, storage, and shipping; and (4) high sensitivity.
Subsurface Injection of Treated Sewage into a Saline‐Water Aquifer at St. Petersburg, Florida — Water‐Quality Changes and Potential for Recovery of Injected Sewage
Authors: Hickey John J. , Ehrlich Garry G.
Published: March 2006

The city of St. Petersburg is testing subsurface injection of treated sewage into the Floridan aquifer as a means of eliminating discharge of sewage to surface waters and as a means of storing treated sewage for future nonpotable reuse. The injection zone at the test site at the start of injection contained saline water with chloride concentrations ranging from 14,000 to 20,000 milligrams per liter (mg/1).

Treated sewage with a mean chloride concentration of 170 mg/1 was injected through a single well for 12 months at a mean rate of 4.7 × 105 cubic feet per day. The volume of water injected during the year was 1.7 × 108 cubic feet. Dissolved oxygen was contained in the sewage prior to injection. Water removed from the injection zone during injection was essentially free of oxygen. Probable growth of denitrifying bacteria and, thus, microbial denitri‐fication, was suggested by bacterial counts in water from two observation wells that were close to the injection well.

The volume fraction of treated sewage in water from wells located 35 feet and 733 feet from the injection well and open to the upper part of the injection zone stabilized at about 0.9 and 0.75, respectively. Chloride concentrations stabilized at about 1,900 mg/1 in water from the well that was 35 feet from the injection well and stabilized at about 4,000 mg/1 in water from the well that was 733 feet from the injection well. These and other data suggest that very little near injection‐quality treated sewage would be recoverable from storage in the injection zone.
Hydrogeology of Wadi Al‐Yammaniyah, Saudi Arabia
Authors: Memon Bashir A. , Kazi Asadullah , Bazuhair Abdulghafar S.
Published: March 2006

Quaternary alluvium, ranging in thickness from a few to 100 meters underlain by Precambrian rocks of metamor‐phic and igneous origin, constitutes an important source of ground water in Wadi Al‐Yammaniyah, Saudi Arabia. The purpose of this report is to assess the hydraulic properties, quality of water, and estimated change in storage in waterbearing rocks in the area.

The results of eight pumping tests carried out in hand‐dug, large‐diameter wells, indicate that the hydraulic conductivity of the alluvial aquifer ranges from 5.6 × 10−5 to 1.85 × 10−3 cm/second (3.36 × 10−5 to 1.11 × 10−3 m/minute) and that its storativity varies from 8.23 × 10−2 to 1.17 × 10−1.

The aquifer is replenished by sporadic but intensive rainfall of short duration. The present withdrawal is only about 10 percent of the annual recharge which is estimated at 52 × 106 m3. It is shown that there is a substantial potential for the future development of potable ground water which would be required for the development of the area.
Modeling of Trace Organics Biotransformation in the Subsurface
Authors: Bouwer Edward J. , McCarty Perry L.
Published: March 2006

Biofilm processes are potentially important for transformations of organic micropollutants in ground water. Some theoretical hypotheses and empirical observations suggest that a concentration threshold exists for some compounds below which the concentration cannot be reduced by bacterial action. However, in the presence of one compound at a relatively high concentration, termed the primary substrate, another compound present at trace concentrations, termed the secondary substrate, can be biotransformed as well. These concepts were evaluated through laboratory column studies with several halogenated organic compounds of importance in ground water. A biofilm model can successfully describe utilization of trace substrates, and application to modeling the subsurface is discussed. A simplified batch model with first‐order kinetics may be adequate for describing subsurface microbial processes when low active organism and pollutant concentrations exist over a large scale.
An Idealized Ground‐Water Flow and Chemical Transport Model (S‐PATHS)
Authors: Oberlander Phil L. , Nelson R. W.
Published: March 2006

The number of studies on the actual and potential environmental consequences of contaminated ground water is growing. One means of studying these consequences is through an idealized flow and transport model, S‐PATHS, which allows the hydrologist to determine the salient features of contaminant migration with a minimum of data.

The transport of contaminants by ground water from many waste disposal sites can be geometrically idealized as flow between a line and a circle. The flow system adjacent to the disposal site can be represented as a contaminant line source, and a downgradient pumping well as a circular sink. To study waste disposal sites on a larger scale the model geometry is reversed and the disposal site is represented as a circular source, and a river or other convenient line of evaluation is represented as a line sink. This idealization allows S‐PATHS to describe the flow and transport process directly by a single partial differential expression. S‐PATHS considers transmissivity, effective porosity, sorption, source strength, source concentration, decay, potentiometric gradient, circle size, and distance to the line. Coding for the model is not lengthy and can be run on a large‐capacity, hand‐held calculator.
Field Testing the Hypothesis of Darcian Flow Through a Carbonate Aquifer
Authors: Hickey John J.
Published: March 2006

The acceptability of the hypothesis of Darcian flow through a semiconfined carbonate aquifer was tested prior to running a multiple‐day aquifer test in Pinellas County, Florida. The approach used to test the hypothesis was to run a number of hour‐long aquifer tests at different discharges with drawdown measured at the same time during each test in two observation wells, one at 35 feet and the other at 733 feet from the pumped well. If the hypothesis were acceptable, a plot of drawdown versus discharge should describe a straight line.

A linear relation was described in 15‐minute and 1‐hour data plots of drawdown versus discharge for both observation wells. Thus, the hypothesis of Darcian flow through the semiconfined carbonate aquifer was deemed acceptable. Drawdown data from the distant observation well collected during the following multiple‐day aquifer test were then analyzed for aquifer‐property values of transmissivity, storage coefficient, and leakance coefficient using standard methods. Discharge for the multiple‐day test was within the discharge range of the hour‐long tests.
Simulation of Ground‐Water Flow in a Mined Watershed in Eastern Ohioa
Authors: Weiss Jonathan S. , Razem Allan C.
Published: March 2006

A 43‐acre watershed in Muskingum County, Ohio, was studied to determine the hydrologic consequences of strip mining for coal. A quantitative description of the effects on the ground‐water flow components of the hydrologic system has been obtained using digital models.

The premining watershed was characterized by nearly flat‐lying sedimentary rocks of the Pennsylvanian System. Underclay beneath the two major coal beds formed bases for perched zones, creating three separate aquifers. Recharge to the ground‐water system occurred mainly by percolation of precipitation. Most of the discharge from the top and middle aquifers occurred by downward leakage to the underlying aquifers. A smaller amount of discharge occurred as springflow or streamflow near the intersections of the underclays and land surface.

Mining has destroyed the top aquifer, and has replaced the bedrock by spoil material. Water levels in the spoils are at a much lower altitude than existed in the premining top aquifer because of a combination of (1) a larger hydraulic conductivity, (2) areal variations of the hydraulic characteristics of the confining bed, and (3) a slower rate of recharge from precipitation caused by removal of vegetation and soil compaction. Covering of previously exposed portions of the middle aquifer and a lower hydraulic head in the spoils has allowed less recharge to the middle aquifer. Additional flow is induced across the western boundary of the watershed and has reduced the outflow across the eastern boundary. Discharge from the middle aquifer as downward leakage and streamflow is less than before mining.
The Optimal Spacing of Interfering Wells: An Analytic Solution
Authors: Briscoe John
Published: March 2006

An exact expression is derived for the optimal spacing between interfering wells in a rectangular well field in an ideal confined aquifer. A simple, practical method for determining the optimal spacing is presented. The optimal spacing is shown to be substantially different from the spacing determined by use of the Theis formulation. The economic savings resulting from use of the revised approach are evaluated and found to be considerable, especially when the number of wells is large and the transmissivity of the aquifer low.
Detection of an Impermeable Boundary in an Anisotropic Formation: A Case Study
Authors: Way S. C. , McKee C. R.
Published: March 2006

Direct mirror‐well image theory to locate an impermeable boundary does not apply in anisotropic formations because the relationship between flow lines and equipotential lines is distorted due to directional transmissivity. A simple approach enables an impermeable boundary to be located in anisotropic formations, and it can be verified with a field example.
Modeling Organic Contaminant Partitioning in Ground‐Water Systems
Authors: Miller Cass T. , Weber Walter J.
Published: March 2006

Effective management of a ground‐water system requires description and prediction of the transport and fate of contaminants in that system. This can be facilitated by using mathematical models which accurately represent the physical phenomena operative in the system. One of the most significant phenomena impacting the transport of many organic pollutants is partitioning between the solid (soil) and aqueous (ground‐water) phases.

The tendency of a contaminant to partition may be roughly approximated from measurements of such constitutive properties as the octanol: water partition coefficient of the contaminant and organic carbon content of the soil. Such rough approximations provide a basis for cursory appraisal, but are inadequate for quantitative system descriptions, particularly where nonlinear equilibrium sorption, kinetically dependent partitioning, or irreversible and/or hysteretic phase distribution phenomena are operative. Accurate simulation of solute transport frequently requires the incorporation of kinetic parameters and/or a nonlinear isotherm relationship to define transport phenomena in the fundamental equations governing mass transport. Laboratory measurements may be utilized to assess sorptive factors of importance, kinetic properties of an organic solute and a soil system, and equilibrium partitioning relationships. Such measurements can be utilized to provide more accurate modeling of contaminant transport.
Migration of Chlorophenolic Compounds at the Chemical Waste Disposal Site at Alkali Lake, Oregon —1. Site Description and Ground‐Water Flow
Authors: Pankow James F. , Johnson Richard L. , Houck James E. , Brillante Susan M. , Bryan W. Jerry
Published: March 2006

The hydrogeology of the chemical waste disposal site in the closed basin at Alkali Lake, Oregon has been examined. Interest in the site is due to the burial (November 1976) of 25,000 drums of herbicide manufacturing residues in unlined trenches on the playa of the basin. Included in the wastes were large amounts of chlorophenols and polymeric chlorophenoxyphenols. The flow of the alkaline (pH ∼10) ground water in the site area is driven by: (1) springs which create a mound east of the site; and (2) the sump effect of “West Alkali Lake,” a topographic low to the west of the site. Porosity, bulk mass densities, and grain‐size distributions were determined. At one piezometer, the depth to ground water ranged between 0.9 m and 2.2 m. With the bottoms of the trenches in which the chemicals were buried between 0.60 and 0.75 m below the level of the ground surface, the bottom portions of the trenches may, at least occasionally, be in direct contact with the ground water.
NUMERICAL METHOD OF PUMPING TEST ANALYSIS USING MICROCOMPUTERS
Authors: Rathod K. S. , Rushton K. R.
Published: March 2006

Abstract. This paper describes how a numerical method of pumping test analysis, which has proved to be useful in many practical situations, can be run on microcomputers. Full details of a program in BASIC and a test problem are provided. The need to perform all the calculations to a sufficient accuracy is stressed, and the choice of suitable mesh spacings and time steps is discussed.
Hydraulic Properties of Stony Vadose Zonesa
Authors: Bouwer Herman , Rice R. C.
Published: March 2006

Hydraulic properties of saturated and unsaturated stony soils were studied on a 3.35 m long column, 1.24 m in diameter, filled with alternating sand and boulder layers. The boulders averaged 6.2 × 15 × 20 cm in size and were laid down on their flat side. Tensiometers and a neutron probe access tube were placed in the column for measuring pressure heads and water contents, respectively. Saturated conditions were obtained by ponding the column. The resulting hydraulic conductivity K was 5.1 m/day. This value could also be calculated from the measured K for the sand alone on separate samples, using a simple equation that takes into account the void ratio of the sand alone and that of the boulder‐sand mixture. Unsaturated K was determined by applying water at less than ponded infiltration rates. Resulting relations between the unsaturated K and water content or negative pressure head could also be estimated from the relation between unsaturated K and pressure head for the sand alone and the calculated saturated K of the boulder‐sand mixture. The method of Millington and Quirk for calculating the relation between unsaturated K and water content also gave reasonable results. The dispersivity of the boulder‐sand column was 18 times that of the sand alone. Pore velocity was accurately estimated as the Darcy velocity divided by the volumetric water content. Hydraulic properties of stony vadose zones are difficult to determine. This work shows that they can be estimated from K relations measured in the laboratory on samples of the soil between the rocks. Knowledge of hydraulic properties of vadose zones is important in predicting movement of water and pollutants to the underlying ground water.
An Explicit Finite Difference Model for Unconfined Aquifers
Authors: Chu Wen‐sen , Willis Robert
Published: March 2006

Most of the current simulation models for unconfined aquifers are based on the assumption that the free surface variation is small so that it can be combined with permeability to reduce the nonlinear Boussinesq equation to a linear partial differential equation (PDE). One of the most obvious reasons for using the linearization assumption is for the ease of numerical solution. This work presents a simpler alternative which permits an easy direct solution of the Boussinesq equation. A forward in time, central in space (FTCS) explicit finite difference method is used in the simulation model. The model was first validated by comparing its results with known analytical solution. It was then applied to an actual situation in which the short‐term responses (from pumping) of an unconfined aquifer were simulated. The study shows that the stability of the model can be easily controlled, and because of the simple algorithm used, the code can be expeditiously developed and economically run on smaller machines. Due to the uncertainties in the calibration results, it is recommended here that more data be collected to improve the calibration before the model is used as a real‐time simulation tool.
An Integrated Hydrochemical Approach to Deduce the Response of an Aquifer System During Its History of Abstraction
Authors: Jackson D. , Lloyd J. W.
Published: March 2006

The investigation of the regional flow characteristics of aquifers is important with respect to aquifer management. To determine regional flows, use can be made of hydraulic and hydrochemical data. In a study of a Chalk Aquifer System in the south of Lincolnshire, England, a combined hydrochemical approach using major, minor and isotope chemistry is described. The chemical data have been used because hydraulic information is difficult to interpret both locally and regionally as a consequence of multi‐layered hydraulic zones, nonhomogeneous fissure zones, and variable erosional features. By characterizing ground‐water types on the basis of major ion chemistry, and subsequently interrelating with minor ion distributions (notably iodide supported by strontium), a reasonable assessment of operative flow paths and mechanisms has been made. Substantiation of the conclusions reached using major and minor ion chemistry is provided by the environmental isotope data of carbon and tritium.
Hydrogeochemical Interaction Between a Municipal Waste Stabilization Lagoon and a Shallow Aquifer
Authors: Kehew Alan E. , Schwindt Francis J. , Brown David J.
Published: March 2006

Unlined municipal waste stabilization lagoons are potential sources of ground‐water contamination. Fourteen monitoring wells were installed around the McVille, North Dakota lagoon, a site at which the impoundment is excavated into permeable sediments of an unconfined glacio‐fluvial aquifer with a shallow water table. One cell at the site, Cell I, retains waste water continuously, while another, Cell II, is used for periodic overflow discharges from Cell I. Seepage through the bottom of Cell I passes through a strongly reducing organic sludge layer. Sulfate in the waste water is reduced to sulfide and possibly precipitated as sulfide minerals in or below this sludge layer. In the unsaturated or shallow saturated zone beneath the pond, the infiltrating waste water reduces ferric iron in iron oxide minerals to more soluble ferrous iron. Proximal down‐gradient well analyses indicate high iron concentrations and very low sulfate levels. Downgradient wells near the lagoon have very high ammonium concentrations. The source of the ammonium is either rapid infiltration from Cell II or denitrification of the nitrate present in ground water upgradient from the lagoon. About 300 feet downgradient from Cell I, ammonium concentrations decline to near zero. The most likely mechanism for this decrease is cation
COMPUTING DRAWDOWN DISTRIBUTIONS USING MICROCOMPUTERS
Authors: King James M.
Published: March 2006

Abstract. Using known or estimated values of trans‐missivity and storativity, the distribution of drawdowns at any time within a discretized flow field can be generated by applying simple trigonometry and numerical approximations of the exponential integral to the Theis equation. Single‐ and multiple‐well systems, as well as image boundaries, are readily simulated with this method. A program employing this technique is presented in BASIC for use with microcomputers. The availability, low cost, and computational power of many small computers makes them ideal for this type of application. Their user‐oriented features allow many possible combinations of wells, boundaries, and hydraulic properties to be analyzed in a short time.
Fluoride in the Ground Water of Northeastern Ohio
Authors: Corbett Robert G. , Manner Barbara M.
Published: March 2006

Fluoride contents range from <0.05 to 5.9 milligrams per liter (mg/1) based upon 255 water samples collected from wells in nine counties of northeastern Ohio. Only 16 samples had fluoride contents exceeding 1 mg/1, and all are from the southern trio of counties. Furthermore, all samples high in fluoride are from wells close to or penetrating the contact between the Allegheny and Pottsville Formations.

Data from a line of 34 wells for which logs were obtained indicate that high fluoride water occurs in either the lower part of the Allegheny Formation, or more probably, in the upper part of the Pottsville Formation.

Ground waters high in fluoride are related to the bedrock geology. Fluoride data, particularly in the area of potentially high values, are important to health professionals in the prescription of fluoride supplements for children. Such prescriptions should be made only after the water has been tested.
Contamination Analysis — Flow Nets and the Mass Transport Equation
Authors: Watson Ian
Published: March 2006

Hydrogeologists are being asked increasingly to analyze ground‐water contamination problems in a quantitative, rather than a descriptive way. Similarly, in providing input for the site selection and design of proposed waste‐disposal facilities, quantitative analyses help to optimize the interplay of environmental, practical, and economic factors that the hydrogeologist must contend with.

This paper introduces a simple, analytical procedure for achieving this. Critical input data include the geohydrologic properties of the aquifer, the permeability and chemical characteristics of the waste materials, and the seepage velocity governing the rate of migration of the leachate plume within the aquifer. The geohydrologic setting assumed and inferred by way of example, typifies that of most disposal scenarios, an anisotropic unconsolidated aquifer.

The analytical methodology outlined employs an extension of flow‐net theory to determine seepage velocity and a derivation of the chemical mass transport equation to predict the attenuation of leachate constituents in the ground‐water regime. The mathematical expressions derived take into account both transient and steady‐state development of the plume, but are based on sufficiently simplifying assumptions to facilitate convenient manipulation on a scientific calculator. The solutions obtained, although approximate, compare favorably with more costly computer‐generated results. A comparison of results is presented. User application relates to the solution of first‐order problems and in cases where a more sophisticated analysis is required, provides input for selecting the appropriate technique.
Subsurface Injection of Treated Sewage into a Saline‐Water Aquifer at St. Petersburg, Florida —Aquifer Pressure Buildup
Authors: Hickey John J.
Published: March 2006

The city of St. Petersburg has been testing subsurface injection of treated sewage into the Floridan aquifer as a means of eliminating discharge of sewage to surface waters and as a means of storing treated sewage for future non‐potable reuse. The injection zone originally contained native saline ground water that was similar in composition to sea water. The zone has a transmissivity of about 1.2 X 106 feet squared per day (ft2/d) and is within the lower part of the Floridan aquifer.

Treated sewage that had a mean chloride concentration of 170 milligrams per liter (mg/1) was injected through a single well for 12 months at a mean rate of 4.7 X 105 cubic feet per day (ft3/d). The volume of water injected during the year was 1.7 X 108 cubic feet.

Pressure buildup at the end of one year ranged from less than 0.1 to as much as 2.4 pounds per square inch (lb/in2) in observation wells at the site. Pressure buildup in wells open to the upper part of the injection zone was related to buoyant lift acting on the mixed water in the injection zone in addition to subsurface injection through the injection well.

Calculations of the vertical component of pore velocity in the semiconfining bed underlying the shallowest permeable zone of the Floridan aquifer indicate upward movement of native water. This is consistent with the 200‐ to 600‐mg/l increase in chloride concentration observed in water from the shallowest permeable zone during the test.