bluuebunny/crossref_metadata_2025_split huggingface dataset:
Detection of an Impermeable Boundary in an Anisotropic Formation: A Case Study
Authors: Way S. C. , McKee C. R. 
Published: March 2006

ABSTRACTDirect 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

ABSTRACTEffective 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

ABSTRACTThe 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.
Hydraulic Properties of Stony Vadose Zonesa
Authors: Bouwer Herman , Rice R. C. 
Published: March 2006

ABSTRACTHydraulic 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

ABSTRACTMost 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

ABSTRACTThe 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

ABSTRACTUnlined 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
Fluoride in the Ground Water of Northeastern Ohio
Authors: Corbett Robert G. , Manner Barbara M. 
Published: March 2006

ABSTRACTFluoride 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

ABSTRACTHydrogeologists 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

ABSTRACTThe 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.
Determination of Horizontal Aquifer Anisotropy with Three Wells
Authors: Neuman Shlomo P. , Walter Gary R. , Bentley Harold W. , Ward John J. , Gonzalez Don Diego 
Published: March 2006

ABSTRACTExisting methods for the determination of horizontal aquifer anisotropy by means of pumping tests require a minimum of four wells, one for water withdrawal and three for drawdown observations. This paper shows how the same methods can be used to determine anisotropy with as few as three wells, if at least two of them can be pumped in sequence. A field example is included. A method of analyzing data from more wells than the above minimum, by least squares, is also described.
Microcomputer Model of Artificial Recharge Using Glover's Solution
Authors: Molden D. , Sunada D. K. , Warner J. W. 
Published: March 2006

ABSTRACTAn interactive program written for an APPLE II+ 48K computer is presented which solves Glover's (1960) analytical solution for recharge from a rectangular basin. The program is capable of graphically displaying the rise and decline of the recharge mound for either an infinite homogeneous medium or for a stream aquifer system.
Relationships Between Ground‐Water Silica, Total Dissolved Solids, and Specific Electrical Conductivity
Authors: Day Barbara A. , Nightingale Harry I. 
Published: March 2006

ABSTRACTSpecific electrical conductivity (SEC), total dissolved solids (TDS), and silica (SiO2) are ground‐water quality parameters routinely measured in a laboratory. Electrical conductivity measurements are made quickly and are less costly than TDS measurements. Once the relationship between the parameters is determined by regression analysis, TDS can be estimated quickly from the SEC and SiO2 measurements. Water quality data from 25 city wells in Fresno, California, and historical ground‐water quality data from the adjacent San Joaquin River/Kings River alluvial interfan (central San Joaquin Valley, California), the Kaweah River alluvial fan, and the Kern River alluvial fan (southern San Joaquin Valley) were used in this investigation. For the specific hydrologic areas studied, the model's TDS predictive ability is improved when SiO2 is included with SEC as the independent variables.
Comparison of Aquifer Characteristics Derived from Local and Regional Aquifer Testsa
Authors: Randolph R. B. , Krause R. E. , Maslia M. L. 
Published: March 2006

ABSTRACTA comparison of the aquifer parameter values obtained through the analysis of a local and a regional aquifer test involving the same area in southeast Georgia is made in order to evaluate the validity of extrapolating local aquifer‐test results for use in large‐scale flow simulations. The case study involves an increase in pumpage of 6.3 Mgal/d (million gallons per day) for the local test and a reduction in pumpage of 66 Mgal/d for the regional test, each involving the same well field. The test involved the Floridan aquifer system, a limestone sequence characterized predominantly by secondary permeability in this area. Time‐drawdown and time‐recovery data were analyzed by using both graphical and least‐squares fitting of the data to the Theis curve. Additionally, directional transmissivity, transmissivity tensor, and angle of anisotropy were computed for both tests. The major and minor axes of the transmissivity ellipse determined from the regional test show general agreement with those determined from the local test. A slightly higher ratio of anisotropy was observed on the regional scale: 2.1:1, than on the local scale: 1.5:1. Regional storage coefficients ranged from 3.4 × 10−4 to 7.2 × 10−4 as compared with local storage coefficients ranging from 1.8 × 10−4to 5.3 × 10−4.
Simulation of Ground‐Water Flow in Southeastern Oahu, Hawaii
Authors: Eyre Paul Richard 
Published: March 2006

ABSTRACTOn the leeward side of southeastern Oahu, Hawaii, near‐vertical dikes have intruded the gently dipping and highly permeable lava flows of the Koolau mountain. These dikes bound the study area on the north and west and internally divide it into the Waialae and Wailupe‐Hawaii Kai aquifers. Recharge to these aquifers, 6 and 9 million gallons per day respectively, has created Ghyben‐Herzberg lenses that freely float on sea water and discharge to the sea through coastal sediments. In the Waialae area, where rainfall is high and where thick (poorly permeable) coastal sediments inhibit the discharge of fresh water, heads are 8 to 15 feet above sea level. Lower rainfall and thin coastal sediments that allow easy discharge cause heads to be only 1 to 5 feet in the Wailupe‐Hawaii Kai area.The flow of ground water and the effects of future water development were simulated using AQUIFEM, a two‐dimensional finite‐element flow model, modified for aquifers containing a sea‐water interface. The model provides accurate simulation of observed heads averaged over several years and predicts an additional area‐wide head decline of about 1 foot when three recently drilled wells are put into production.
Rejection of Recharge Water from Madison Aquifer Along Eastern Perimeter of Bighorn Artesian Basin, Wyoming
Authors: Huntoon Peter W. 
Published: March 2006

ABSTRACTApproximately half of the perimeters of Wyoming foreland artesian basins are characterized by structural continuity of the Paleozoic aquifers between the recharge areas and the interior parts of the artesian basins. A significant percentage of the ground water which circulates through such recharge areas is rejected through springs because there is a marked decrease in transmissivity basin‐ward from the recharge areas. The transmissivity contrasts have developed since the recharge areas became morphologically differentiated from the basin interiors during post‐Laramide time. Secondary enhancement of permeabilities is occurring in the recharge areas through dissolution of the rock matrix and cement, and in some locations the rocks were tectonically fractured. In contrast, the rates of dissolution within the basin interiors are substantially decreased, or processes of recrystallization, cementation, or compaction are operating to destroy permeability. The result is that in the case treated here, net recharge to the basin interior is a small fraction of measured stream losses in the headwaters of the recharge area.
Distribution of Volatile Organic Compounds in a New Jersey Coastal Plain Aquifer System
Authors: Fusillo Thomas V. , Hochreiter Joseph J. , Lord Deborah Grant 
Published: March 2006

ABSTRACTSamples for analysis of volatile organic compounds were collected from 315 wells in the Potomac‐Raritan‐Magothy aquifer system in southwestern New Jersey and a small adjacent area in Pennsylvania during 1980–82. Volatile organic compounds were detected in all three aquifer units of the Potomac‐Raritan‐Magothy aquifer system in the study area. Most of the contamination appears to be confined to the outcrop area at present. Low levels of contamination, however, were found downdip of the outcrop area in the upper and middle aquifers.Trichloroethylene, tetrachloroethylene, and benzene were the most frequently detected compounds. Differences in the areal distributions of light chlorinated hydrocarbons, such as trichloroethylene, and aromatic hydrocarbons, such as benzene, were noted and are probably due to differences in the uses of the compounds and the distribution patterns of potential contamination sources.The distribution patterns of volatile organic compounds differed greatly among the three aquifer units. The upper aquifer, which crops out mostly in less‐developed areas, had the lowest percentage of wells with volatile organic compounds detected (10 percent of wells sampled). The concentrations in most wells in the upper aquifer which had detectable levels were less than 10 /μg/1. In the middle aquifer, which crops out beneath much of the urban and industrial area adjacent to the Delaware River, detectable levels of volatile organic compounds were found in 22 percent of wells sampled, and several wells contained concentrations above 100 μ/1. The lower aquifer, which is confined beneath much of the outcrop area of the aquifer system, had the highest percentage of wells (28 percent) with detectable levels. This is probably due to (1) vertical leakage of contamination from the middle aquifer, and (2) the high percentage of wells tapping the lower aquifer in the most heavily developed areas of the outcrop.
Interference Due to Neighboring Wells During Pumping Tests
Authors: Rushton K. R. 
Published: March 2006

ABSTRACTWhen other wells are pumping from an aquifer in which a pumping test is being carried out, they can interfere with the observed data. Even if the interfering wells are several kilometers away, they can have a significant effect on test results. The effect of the interfering wells on the drawdown can be misinterpreted .as boundary effects. By combining the series expansions for the Theis expression for the pumped and interfering wells, it is shown that the magnitude of the interference depends primarily on the length of time for which the interfering well pumps before the start of the test. An important finding of the analysis is that the distance between the test and interfering wells has a small effect. A method of correcting for the effect of an interfering well during both pumping and recovery phases is introduced.
Estimating Vertical Soil Moisture Flux at a Land Treatment Site
Authors: Dreiss S. J. , Anderson L. D. 
Published: March 2006

ABSTRACTEstimation of rates of contaminant movement at land treatment sites requires accurate measurements of water movement through the soil zone. A moisture balance method that employs the zero flux plane concept and several simplifying assumptions about saturated and unsaturated flow conditions gives reasonable estimates of evapotranspiration and percolation fluxes when applied to a land treatment site in central coastal California. The technique requires measurements of the saturated hydraulic conductivity of field soils as well as soil matric suction and moisture content at regular time intervals. Replicate monitoring clusters for matrix suction and moisture content are necessary in spatially variable soils but a detailed knowledge of the spatial variability of saturated hydraulic conductivity is not warranted.