ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1991.tb00538.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractThe capacity of sandstone to neutralize injected acid was determined for material from a waste disposal well in Jefferson Parish, Louisiana. Injection zone sandstone was found to neutralize approximately 1.51×10−3grams H+ions per gram of sand. Kinetics parameters were determined for reactions of acid with confining layer shale material. Reaction rate coefficients and activation energies of acid‐shale systems agree with values previously determined for reactions of acids with relatively pure clay mine

ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1991.tb00539.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractIn estimating aquifer parameters from pumping test data, it is often found advantageous to use recovery, rather than drawdown, measurements. An equation, derived from Cooper‐Jacob's (1946), is suggested for estimating storativity using residual drawdown measurements from an observation wel

ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1991.tb00540.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractA numerical model is presented which represents both the radial and vertical flow components which usually result from pumping from boreholes in layered aquifers. This model, which is based on finite‐difference approximations, runs on a microprocessor system and can be used for the analysis of pumping test results. A discussion on the interaction between the radial and vertical flow components is followed by a description of the model. A computer program in BASIC and a typical computer output are provided. The application of the model for the analysis of a pumping test in a weathered‐fractured aquifer is described. Three case studies are reviewed where the numerical model is used to gain a greater understanding of the aquifer flow proces

ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1991.tb00541.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractA finite‐difference ground‐water flow model linked to a particle‐tracking routine was used to determine ground‐water flow paths and residence times in the Cambrian‐Ordovician sandstone aquifer of eastern Wisconsin. The modeled region was a cross section along an approximate flow line that included the boundary between unconfmed and confined conditions in the aquifer. Modeling results indicate that lower conductivity units within the sandstone aquifer produce vertically stratified flow in the confined region. These simulation results help explain chemical signatures of ground water in different parts of the aquifer. Three distinct regions of the flow system are identified: the unconfmed zone where vertical mixing across the aquifer yields a homogeneous chemistry, the shallow part of the confined zone where sodium and sulfate charged water from the Maquoketa Shale mixes with water that has migrated from the unconfmed area, and the deeper region of the confined aquifer, containing older water that entered the system in the unconfmed area. Radium activities in ground water increase with distance along flow paths predicted by the simulation, consistent with a low concentration source of solid phase uranium and release of decay products to ground water by desorption and dissolution throughout the sandston

ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1991.tb00542.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractA multiport permeameter was developed for use in estimating hydraulic conductivity over intact sections of aquifer core using the core liner as the permeameter body. Six cores obtained from one borehole through the upper 9 m of a stratified glacial‐outwash aquifer were used to evaluate the reliability of the permeameter. Radiographs of the cores were used to assess core integrity and to locate 5‐ to 10‐cm sections of similar grain size for estimation of hydraulic conductivity. After extensive testing of the permeameter, hydraulic conductivities were determined for 83 sections of the six cores. Other measurement techniques included permeameter measurements on repacked sections of core, estimates based on grain‐size analyses, and estimates based on borehole flowmeter measurements. Permeameter measurements of 33 sections of core that had been extruded, homogenized, and repacked did not differ significantly from the original measurements. Hydraulic conductivities estimated from grain‐size distributions were slightly higher than those calculated from permeameter measurements; the significance of the difference depended on the estimating equation used. Hydraulic conductivities calculated from field measurements, using a borehole flowmeter in the borehole from which the cores were extracted, were significantly higher than those calculated from laboratory measurements and more closely agreed with independent estimates of hydraulic conductivity based on tracer movement near the borehole. This indicates that hydraulic conductivities based on laboratory measurements of core samples may underestimate actual field hydraulic conductivities in this type of stratified glacial‐outw

ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1991.tb00543.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractMultiobjective strategies and models for optimizing the short‐term containment of a 2‐D ground‐water contaminant plume are compared. These are designed for cases in which an appropriate means of treating the contaminated water is unavailable or unauthorized, and the management goal is to prevent plume movement, without pumping contaminated water and without importing or exporting water. Because optimal unsteady strategies are usually more efficient than optimal steady strategies at achieving goals at a prespecified time, the models optimize the needed time‐varying rates of extracting and injecting water. The objective function can use coefficients to consider, one at a time, the objectives of minimizing final hydraulic gradients between observation wells and the plume source, minimizing the cost of pumping, or minimizing the volume of pumping. Alternatively, the model can simultaneously consider the gradient objective and one of the other two objectives in developing a compromise strategy. If the plume must be contained only for the period of optimal unsteady pumping, either the minimizing cost or the minimizing pumping volume objective is most appropriate. For short periods, a minimum pumping strategy, which is the easiest to use, is almost the same as a least‐cost strategy. If the plume must be contained for a longer period, the hydraulic objective becomes increasingly important because it causes a more horizontal potentiometric surface, and less additional pumping is needed to maintain that surface after the end of unstead

ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1991.tb00544.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractTwo case studies are presented as examples of a decision‐analysis approach to engineering design for projects in which the hydrogeological environment plays an important role. This approach to design involves quantifying benefits, costs, and risks for each design alternative under consideration. Risk, which is defined as the expected costs of failure, reflects both performance uncertainties and failure costs. Probabilities of failure are estimated by coupling stochastic ground‐water flow and solute transport models with uncertainty models that represent input parameters as random variables. The case studies that are used to describe the approach involve (1) selecting a pumping rate for an extraction well to capture an existing contaminant plume, and (2) designing a leachate collection system for a soil remediation facility. The examples illustrate that the decision‐analysis approach can be accomplished using relatively simple analytical models to simulate the behaviors of hydrogeological environments and engineering components. The results identify how the preferred design alternative depends upon the regulatory, hydrogeological, and economic environments in which the decision is made. For the extraction well example, the preferred alternative is relatively insensitive to the costs of failure but is dependent upon the expected dimensions of the contaminant plume. For the soil remediation example, the preferred design alternative depends upon the anticipated costs of failure and the regulatory standard for ground‐water contamination. Reducing the variance or uncertainty in dispersivity values by a factor of 3 had a relatively small effect on the overall design of the leachate collection

ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1991.tb00545.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractTidal fluctuations in surface‐water bodies produce progressive pressure waves in adjacent aquifers. As these pressure waves propagate inland, ground‐water levels and hydraulic gradients continuously fluctuate, creating a situation where a single set of water‐level measurements cannot be used to accurately characterize ground‐water flow. For example, a time series of water levels measured in a confined aquifer in Atlantic City, New Jersey, showed that the hydraulic gradient ranged from. 01 to. 001 with a 22‐degree change in direction during a tidal day of approximately 25 hours. At any point where ground water tidally fluctuates, the magnitude and direction of the hydraulic gradient fluctuates about the mean or regional hydraulic gradient. The net effect of these fluctuations on ground‐water flow can be determined using the mean hydraulic gradient, which can be calculated by comparing mean ground‐ and surface‐water elevations. Filtering methods traditionally used to determine daily mean sea level can be similarly applied to ground water to determine mean levels. Method (1) uses 71 consecutive hourly water‐level observations to accurately determine the mean level. Method (2) approximates the mean level using only 25 consecutive hourly observations; however, there is a small error associated with this method. The exact magnitude of this error is usually unknown, and therefore the accuracy of the mean level is also unknown. Method (1) should be used if a higher degree of acc

ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1991.tb00546.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractTidal fluctuation is shown to affect the piezometer readings taken in a nearshore aquifer around a working nuclear power station. Continuous monitoring of a network of 40 piezometers provided relations between the tidal cycle and the piezometer readings. These relations can be expressed in terms of a time lag and amplitude scaling factor. Using these parameters, tidal interference was filtered from the day‐to‐day piezometer readings. The early detection of ground‐water drawdown below the working station caused by construction of a new nuclear power station on an adjacent site could thus be achieved.In parallel with the field work, the theoretical relationship between the tide and piezometric response was shown to be of the same form as that observed in the field. Values of the aquifer characteristics could then be deduced and compared with those measured in conventional pumping tests. The transmission of the pressure oscillation is shown to be faster in areas of higher permeability and in the deeper parts of the aquifer. This second effect is thought to be caused by the presence of the phreatic su

ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1991.tb00547.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY