bluuebunny/crossref_metadata_2025_split huggingface dataset:
Simple Derivation of the Retardation Equation and Application to Preferential Flow and Macrodispersion
Authors: Bouwer Herman 
Published: August 2005

AbstractThe equation to calculate the retardation factor of sorbing chemicals moving in aqueous solution through aquifers and vadose zones is derived using a linear sorption isotherm and a mass‐balance approach. The procedure is very simple and clearly illustrates the roles of porosity and water content, including those for saturated flow, unsaturated flow, and preferential flow or other systems with both mobile and immobile phases of the water. Applications of the equation to preferential flow in the vadose zone and macrodispersion in a layered aquifer are illustrated with numerical examples for hypothetical cases.
Aqueous Geochemistry of the Sand‐and‐Gravel Aquifer, Northwest Florida
Authors: Katz Brian G. , Choquette Anne F. 
Published: August 2005

AbstractThe aqueous geochemistry of the sand‐and‐gravel aquifer in northwest Florida was characterized as part of the Florida Ground‐Water Quality Monitoring Network Program, a multiagency cooperative study delineating baseline and/or background water quality for the major aquifer systems throughout the State. The aquifer is the principal source of water in northwest Florida and consists predominantly of quartz sand with smaller amounts of andesine, chlorite, calcite, kaolinite, and illite. Water from 42 wells in the sand‐and‐gravel aquifer sampled during 1986 and 1987 was characteristically low in dissolved solids (median value of 72 milligrams per liter) and of nondistinct water type, although relative concentrations of magnesium and sulfate tended to be lower than those of other major ions. Nonparametric statistical tests of major‐ion concentration variations with depth and relative distance along flow paths indicate that the water chemistry does not change significantly (0.05 significance level) as the water moves vertically and laterally through the aquifer. Mass‐balance calculations indicate that dissolved solids from rainfall and saline‐water sources each account for 13 percent of the concentration of dissolved solids in ground water. Incongruent dissolution of andesine, chlorite, and muscovite to form kaolinite accounts for 94 percent of the neutralization of the total hydrogen ion input from rainfall and from carbonic acid weathering in the subsurface. The remaining neutralization is accounted for by the dissolution of calcite.
Numerical Assessment of a Landfill Compliance Limit
Authors: Mensel Bruce R. , Keefer Donald A. , Griffin Robert A. , Berg Richard C. 
Published: August 2005

AbstractThe PLASM and Random Walk ground‐water flow and contaminant transport models were used to assess the potential impact of various proposed regulatory compliance distances on landfill siting. Contaminant transport modeling was performed for 16 generalized geological sequences representative of hydrogeological conditions over an estimated 90 to 95 percent of Illinois. Results of this modeling indicate that about 50 percent of the state would be hydrogeologically suitable for landfilling of nonhazardous wastes if the compliance distance was 100 feet. With a compliance distance of 500 feet, about 55 percent of the state would be hydrogeologically suitable. This work demonstrates the utility of computer modeling in the development of regulations governing landfill siting.
Prospecting for Zones of Contaminated Ground‐Water Discharge to Streams Using Btottom‐Sediment Gas Bubbles
Authors: Vroblesky Don A. , Lorah Michelle M. 
Published: August 2005

AbstractDecomposition of organic‐rich bottom sediment in a tidal creek in Maryland results in production of gas bubbles in the bottom sediment during summer and fall. In areas where volatile organic contaminants discharge from ground water, through the bottom sediment, and into the creek, part of the volatile contamination diffuses into the gas bubbles and is released to the atmosphere by ebullition. Collection and analysis of gas bubbles for their volatile organic contaminant content indicate that relative concentrations of the volatile organic contaminants in the gas bubbles are substantially higher in areas where the same contaminants occur in the ground water that discharges to the streams. Analyses of the bubbles located an area of previously unknown ground‐water contamination.The method developed for this study consisted of disturbing the bottom sediment to release gas bubbles, and then capturing the bubbles in a polyethylene bag at the water‐column surface. The captured gas was transferred either into sealable polyethylene bags for immediate analysis with a photoionization detector or by syringe to glass tubes containing wires coated with an activated‐carbon adsorbent. Relative concentrations were determined by mass spectral analysis for chloroform and trichloroethylene.
Application of Ground‐Penetrating‐Radar Methods in Hydrogeologie Studies
Authors: Beres Milan , Haeni F. P. 
Published: August 2005

AbstractA ground‐penetrating‐radar system was used to study selected stratified‐drift deposits in Connecticut. Ground‐penetrating radar is a surface‐geophysical method that depends on the emission, transmission, reflection, and reception of an electromagnetic pulse and can produce continuous high‐resolution profiles of the subsurface rapidly and efficiently. Traverse locations on land included a well field in the town of Mansfield, a sand and gravel pit and a farm overlying a potential aquifer in the town of Coventry, and Haddam Meadows State Park in the town of Haddam. Traverse locations on water included the Willimantic River in Coventry and Mansfield Hollow Lake in Mansfield. The penetration depth of the radar signal ranged from about 20 feet in fine‐grained glaciolacustrine sediments to about 70 feet in coarse sand and gravel. Some land records in coarse‐grained sediments show a distinct, continuous reflection from the water table about 5 to 11 feet below land surface. Parallel reflectors on the records are interpreted as fine‐grained sediments. Hummocky or chaotic reflectors are interpreted as cross‐bedded or coarse‐grained sediments. Other features observed on some of the radar records include the till and bedrock surface. Records collected on water had distinct water‐bottom multiples (more than one reflection) and diffraction patterns from boulders. The interpretation of the radar records, which required little or no processing, was verified by using lithologie logs from test holes located along some of the land traverses and near the water traverses.
Tritium as an Indicator of Ground‐Water Age in Centrai Wisconsin
Authors: Bradbury Kenneth R. 
Published: August 2005

AbstractIn regions where ground water is generally younger than about 30 years, developing the tritium input history of an area for comparison with the current tritium content of ground water allows quantitative estimates of minimum ground‐water age. The tritium input history for central Wisconsin has been constructed using precipitation tritium measured at Madison, Wisconsin and elsewhere. Weighted tritium inputs to ground water reached a peak of over 2,000 TU in 1964, and have declined since that time to about 20‐30 TU at present.In the Buena Vista basin in central Wisconsin, most ground‐water samples contained elevated levels of tritium, and estimated minimum ground‐water ages in the basin ranged from less than one year to over 33 years. Ground water in mapped recharge areas was generally younger than ground water in discharge areas, and estimated ground‐water ages were consistent with flow system interpretations based on other data. Estimated minimum ground‐water ages increased with depth in areas of downward ground‐water movement. However, water recharging through thick moraine sediments was older than water in other recharge areas, reflecting slower infiltration through the sandy till of the moraine.
The Depth of Fractures and Active Ground‐Water Flow in a Clayey Till Plain in Southwestern Ontario
Authors: Ruland W. W. , Cherry J. A. , Feenstra Stan 
Published: August 2005

AbstractThe St. Clair Plain in southwestern Ontario is underlain by extensive clayey till deposits which are generally 30 m to 40 m thick. The tills have vertical fractures near the ground surface, and this study investigates the depth of those fractures. Observations in test pits show that most weathering features along fractures reach a depth of only 2.5 m to 4 m, though isolated major fractures extend past the pit bottom depth of 5.6 m at two sites. This study also investigates the depth of active ground‐water flow, which is defined as the ground‐water flow in the clayey deposit which occurs in fractures. Water‐level response tests show bulk hydraulic conductivities of the fractured till ranging from >10−7 to 10−8 cm/s. Seasonal variations in hydraulic head profiles suggest that fractures influence ground‐water flow to maximum depths ranging from 5 m to more than 10 m at the 10 sites studied. The water table is usually within 2 m of the surface, but piezometers went dry to depths of 2 m to 4.9 m during dry periods in 1987 and 1988. Tritium levels greater than l T.U., indicating the presence of post‐1952 water, are found to depths of 7.5 m at all sites and to depths exceeding 12 m in two cases. Tritium has moved to the base of deep, open fractures by active ground‐water flow and has travelled 1 or 2 m beyond that depth by molecular diffusion. Observations of seasonal water‐level variations and tritium sampling show the most promise for determining the maximum depth of hydraulically active, vertical fractures. The maximum depth of active ground‐water flow in fractures varies widely, ranging from 5 m to more than 10 m at the 12 sites studied on the St. Clair Plain.
Statistical Tolerance Limits for Ground‐Water Monitoring
Authors: Gibbons Robert D. 
Published: August 2005

AbstractStatistical tolerance limits can play a useful role in ground‐water detection monitoring programs at waste disposal facilities; however, their properties are often misunderstood or confused with statistical prediction limits. The purpose of this paper is to describe when, where, and why statistical tolerance limits should be used in ground‐water monitoring applications and how they relate to alternatives, such as statistical prediction limits. In addition, a two‐stage procedure that involves the use of both tolerance and prediction limits is described and is shown to have particularly desirable properties for waste disposal facilities for which large numbers of statistical comparisons are performed on a regular basis (e.g., 100 or more comparisons per quarter).
Influence of Vertical Flow on Ground‐Water Transport
Authors: Brainard Edward C. , Gelhar Lynn W. 
Published: August 2005

AbstractTwo‐dimensional analysis of ground‐water flow using graphical flow net analysis or numerical modeling is applied to many field settings. However, the assumption of hydrostatic head conditions, implicit in two‐dimensional depth‐averaged planimetric analyses, is not correct for situations where there is vertical flow such as near a partially penetrating stream. Vertical flow is particularly important when predicting flow paths for contaminant transport. An analytical solution is presented, which calculates the flow paths in the vicinity of a partially penetrating stream. The derivation assumes radial flow towards the stream in the vicinity of the stream, and predominantly horizontal Dupuit flow in the remainder of the region. The analytical solution may be used as a correction to apply to flow paths generated by two‐dimensional analysis, or as a screening tool to determine the error when vertical flow is neglected by two‐dimensional analysis. To verify the analytical solution, it is compared to numerical simulations of three‐dimensional flow in an idealized aquifer for a number of cases with varying degrees of hydraulic conductivity anisotropy. An example illustrates the use of the analytical solution. For the example presented, two‐dimensional analysis can underestimate the distance which a contaminant travels before discharging into the stream by almost a mile.
An Evaluation of Lithium Sorption Isotherms and Their Application to Ground‐Water Transport
Authors: Newman Brent D. , Fuentes Hector R. , Polzer Wilfred L. 
Published: August 2005

AbstractBatch adsorption and desorption equilibrium experiments were used to evaluate lithium sorption on crushed tuff in contact with ground water. The laboratory studies were conducted in support of saturated zone characterization field tests to be performed near Yucca Mountain, Nevada. These studies included equilibrium experiments conducted at 38° C (expected subsurface temperature) for a 1‐ to 2,000‐mg/l range of initial lithium solution concentrations. Data from the equilibrium experiments were used in the evaluation of Linear, Langmuir, Freundlich, and Modified Freundlich isotherm expressions.Comparisons of adsorption and desorption isotherms showed that lithium adsorption was reversible for solution concentrations up to 150 mg/l. This conclusion was based on F‐test comparisons of predicted adsorption and desorption data from Langmuir isotherms.Lithium sorption was best represented by the nonlinear isotherms where the Langmuir gave the best fit followed by the Modified Freundlich and Freundlich. When these isotherms were used in a one‐dimensional, column adsorption transport code, differences occurred in the predicted breakthrough curves. The transport results showed differences of as much as a factor of five in the time of arrival of lithium for the various isotherms depending on the influent concentration chosen. The differences in the simulation breakthrough curves indicate the importance of isotherm selection. Statistical discrimination and column experiments are suggested as better evaluations of isotherms that are to be incorporated into field‐scale transport simulations.
The Modeling Process and Model Validation
Authors: Tsang Chin‐Fu 
Published: August 2005

AbstractThe safety assessment of underground disposal of nuclear or toxic wastes requires the use of models. Such models need to be validated to ensure, as much as possible, that they are a good representation of the actual processes occurring in the real system. In this paper an attempt is made to take a broad view by reviewing step by step the modeling process and bringing out the need for validating every step of this process. Thus, model validation includes not only comparison of modeling results with data from selected experiments, but also evaluation of procedures for the construction of conceptual models and calculational models as well as methodologies for studying data and parameter correlation. The need for advancing basic scientific knowledge in related fields, for multiple assessment groups, and for presenting our modeling efforts in open literature for public scrutiny is also emphasized.
Modeling Variations in Annular Pressure Due to Fluid Injection
Authors: Arnold Fredric C. 
Published: August 2005

AbstractMonitoring of the liquid pressure in a casing‐tubing annulus confined by the wellhead at the surface and by a packer above the injection interval is a simple and inexpensive method of detecting the loss of mechanical integrity in wells used for disposal of liquid wastes. However, variations in annular pressure which occur in response to changes in injection rate and injected fluid temperature complicate the interpretation of annular pressure data. The variation of fluid and formation temperatures with depth, the expansion and contraction of fluids and metal tubing with pressure and temperature, and wellbore depth and geometry, have been combined in a model of annular pressure response to fluid injection. The response to changes in injected fluid rate and temperature have been simulated with the model and verified by field experiment. Although the response to a change in injection rate or temperature is greatest in the first two hours following the change, annulus pressure continues to vary with time and a true steady‐state was not attained.
Embedded Knowledge in Software: 2. Demonstration and Preliminary Evaluation
Authors: McClymont G. L. , Schwartz F. W. 
Published: August 2005

AbstractThis paper demonstrates the operation of EXPAR, a knowledge‐based system designed to assist in preparing a set of data for a contaminant transport model. The accompanying evaluation exercise provides preliminary indications of the usefulness of EXPAR. The exercise tested the ability of participants to simulate the distribution of three organic compounds at a hazardous waste site near Ottawa, Canada. A modest set of basic information was provided together with one of four sets of supplementary data. The embedded knowledge in the EXPAR system appeared to provide valuable assistance in modeling, and the system itself met our expectations in terms of the user‐friendliness and robustness. Additional work will be required to remove the weaknesses found in the evaluation particularly with respect to biodégradation data and guidance in establishing flow directions. The results of the project have shown that knowledge‐based systems show promise in solving problems associated with the implementation of a transport model.
Field‐Scale Investigation of Infiltration Into a Compacted Soil Liner
Authors: Panno Samuel V. , Herzog Beverly L. , Cartwright Keros , Rehfeldt Kenneth R. , Krapac Ivan G. , Hensel Bruce R. 
Published: August 2005

AbstractLittle field‐scale research has been done to evaluate the effectiveness of compacted soil barriers in retarding the movement of water and leachates. In response to this need, the Illinois State Geological Survey constructed and instrumented an experimental compacted soil liner. Infiltration of water into the liner has been monitored for two years. The objectives of this investigation were to determine whether a soil liner could be constructed to meet the U.S. EPA's requirement for a saturated hydraulic conductivity of less than or equal to 1.0×10−7 cm/s, to quantify the areal variability of the hydraulic properties of the liner, and to determine the transit time for water and tracers through the liner.The liner measures 8 m×15 m×0.9 m and was designed and constructed to simulate compacted soil liners built at waste disposal facilities. The surface of the liner was flooded to form a pond on April 12, 1988. Since flooding, infiltration has been monitored with four large‐ring (LR) and 32 small‐ring (SR) infiltrometers, and a water‐balance (WB) method that accounted for total infiltration and evaporation. Ring‐infiltrometer and WB data were analyzed using cumulative‐infiltration curves to determine infiltration fluxes. The SR data are lognormally distributed, and the SR and LR data form two statistically distinct populations. Small‐ring data are nearly identical with WB data; because there is evidence of leakage in the LRs, the SR and WB data are considered more reliable.Geostatistical analysis of the SR infiltration data revealed that the infiltration‐flux data were unstructured (random) at scales greater than 0.8 m. This analysis shows that it is possible to construct a compacted soil liner with a uniformly low saturated hydraulic conductivity, and that classical statistics should adequately estimate the mean infiltration flux of the liner and the associated uncertainty in that value.Saturated hydraulic conductivity of the liner was estimated using Darcy's Law and the Green‐Ampt Approximation; the average values for these calculations, based on the first and second years of SR data, were 4.0×10−8 and 3.4×10−8 cm/s, respectively. Breakthrough of water at the liner's bottom is expected to occur approximately six years after the initial ponding of the liner.
Water Quality Response to the Partial Casing of a Well
Authors: Grundl Tim , Delwiche Jim 
Published: August 2005

AbstractThe computer model MODFLOW was used to model the water quality effects caused by casing off a contaminated layer in a well screened across multiple hydrogeologic units. Water produced from the contaminated layer is initially prevented from entering the well, but eventually a new concentration steady state is reached in which the contamination returns to the original level. The time needed for establishment of the new concentration steady state is primarily a function of aquifer conductivity and is essentially independent of aquitard conductivity. Under the modeled conditions, pressure steady state was reached in less than 100 days. Under the same conditions, concentration steady state was reached in less than 6000 days.
Results of Two Pumping Tests in Wisconsin Age Weathered Till in Iowa
Authors: Jones LaDon , Lemar Tracy , Tsai Chin‐Ta 
Published: August 2005

AbstractGlacial till overlies many bedrock aquifers in Iowa, and a number of landfills and leaking underground storage tank sites are located in weathered and unweathered till. To investigate the potential for significant lateral ground‐water flow in Wisconsin age weathered loam till in Iowa, two 24‐hour pumping tests were performed in the shallow unconfined ground water present in the weathered till, a constant flowrate pumping test and a constant drawdown pumping test. The saturated thickness in the weathered till at the research site is less than 3 m, and choosing a constant flowrate sufficient for significant drawdown in the monitoring wells without dewatering the pumping well was difficult. In a low conductivity medium with a thin saturated thickness, the constant drawdown pumping test was found to be a more practical field technique. In the constant drawdown test, a chosen level of constant drawdown is maintained in the pumping well for the duration of pumping, and the flowrate decreases with time. The changing flowrate of the constant drawdown pumping test was approximated as a series of step decreases, and superposition of the Theis solution was used for simulation. Both types of pumping tests yielded similar parameter estimates for the weathered loam till region in Iowa, with an average bulk horizontal hydraulic conductivity of around 5×10‐4 cm/s and an average specific yield of about 0.032. Single well response (bail) tests produced comparable estimates for hydraulic conductivity, with a mean of 3×10‐4 cm/s. The results imply significant lateral ground‐water flow is possible, and the weathered till should not be considered a significant barrier to the lateral spread of shallow ground‐water contamination.
Straight‐Line Intercept Method in Aquifer Volume Calculations
Authors: Şen Zekâi , Sabtan Abdullah A. 
Published: August 2005

AbstractVolume calculations in various aspects of ground‐water resources evaluation play a significant role. However, these calculations are made by different classical techniques, each of which employs the finite element concept. A common requirement in these techniques is the adaptation of a basic height—like contour interval. The accuracy of the estimated volume is influenced by the subjectivity on the part of the person doing the contouring on a specified contour interval. It is observed that there is a linear relationship between the contour interval and the estimated volume. The basic idea of this paper is to use a simple drawing procedure of a few points of different contour intervals versus the resulting volumes. A regression line is fitted through the scatter of these points. The best volume estimate corresponds to zero contour interval, i.e., the intercept of the straight line with the volume axis. This technique provides a common basis in that different researchers arrive at exactly the same conclusion for a given data set. The proposed method is verified by calculating the reservoir volume of a laboratory dam model with the known reservoir volume. It was found that the estimated volume was off by only 5% of the measured one. Further applications of the method are given for some observed data from the Floridan aquifer and a Black Hills dam reservoir.