No description available.

Water level recovery data collected in wells following controlled pumping tests are affected by both borehole and formation factors. The borehole factors comprise those effects attributed to the presence of the wellbore, such as step-increases in pumping rate, wellbore storage, well efficiency, and skin effects. The formation factors comprise those effects associated with the geologic environment in which an aquifer system occurs, such as variation of the coefficient of storage, and aquifer barrier boundaries. The recovery data should plot as a straight line on a semilogarithmic plot. Step-increases in the discharge rate during the pumping period cause the water level recovery plot to be concave downward. The curvature of the recovery data plot can be eliminated by applying a correction proposed by Harrill in 1970. However, the effect of step-increases in pumping rate on the recovery data is minimal so long as the duration of the pumping steps is less than about one-third of the total duration of pumping. The well efficiency and skin effects cause an additional component of drawdown in a pumped well, which is manifested as an initially rapid recovery rate after pumping stops. The effects of skin and well efficiency are usually dissipated within a few minutes after pumping stops. Wellbore storage effects can be critical in large diameter wells (wellbore radius greater than 0.5 feet) that penetrate aquifers with transmissivities less than about 2,700 feet squared per day. The time required to dissipate wellbore storage effects in the water level recovery data is inversely proportional to the aquifer transmissivity, and directly proportional to the borehole size. Variation of the coefficient of storage during the recovery period results in a semi-logarithmic recovery plot that is concave downward. The curvature of the recovery plot increases as the variation of the coefficient of storage increases. Variation in the coefficient of storage of one order of magnitude during the recovery period introduces an error of more than fifty percent in the transmissivity calculation at late recovery times. The recovery plot of data collected in a well influenced by a barrier boundary defines two straight line segments. The early-time straight line segment has a slope one-half that of the late-time straight line segment. Analysis of the early-time straight line yields the true aquifer transmissivity. Analysis and interpretation of water level recovery data collected in 59 wells following controlled pumping tests in aquifers of various rock types indicate that, in general, the shape of the recovery plot can be used to diagnose the presence of skin effects, low well efficiency, wellbore storage, and variation of the coefficient of storage. Analysis of data from seventeen wells in alluvial aquifers and thirteen wells in sandstone aquifers indicates that the concave downward recovery plot is the most common type of response curve. This shape of recovery curve indicates that the coefficient of storage is commonly smaller during the recovery period than during the drawdown period. Recovery data collected in twenty wells in fractured hard-rock aquifers indicate that the characteristic shape of the recovery plot predicted by Warren and Root in 1963 is generally diagnostic of flow in non-homogeneous, anisotropic, fractured aquifers. When the fracturing approaches being homogeneous and isotropic, the recovery plot can resemble data collected in non-fractured rocks. Recovery data from nine wells in composite limestone-sandstone aquifers indicate that the recovery plot is sometimes similar to the concave downward shape exhibited in sandstone and alluvial aquifers, and sometimes is similar to the shape predicted by Warren and Root for fractured rocks.

Thesis (M.S.)--West Virginia University, 2002. / Title from document title page. Document formatted into pages; contains viii, 71 p. : ill. (some col.). Vita. Includes abstract. Includes bibliographical references (p. 65-70).

This thesis investigated the dissolution of dense non aqueous phase liquids (DNAPL) source zones in the subsurface and the effectiveness of enhanced bioremediation for the treatment of chlorinated ethene DNAPLs, using numerical modeling. For this purpose, an existing multiphase numerical model was extended to include comprehensive models for the processes of dissolution and reaction. The first part of the thesis examined DNAPL dissolution. First, a thermodynamic-based dissolution model was validated using experimental data from two complex heterogeneous DNAPL releases. Model predictions for DNAPL spatial distribution and effluent concentrations agreed well with experimental measurements, without requiring calibration. This is the first successful application of a predictive dissolution model in the literature. Model results showed the important effects of relative permeability and interfacial areas on dissolution rates. Then, the thermodynamic dissolution model was compared to simpler models typically used in the literature. Five Sherwood-Gilland (SG) empirical correlations were evaluated and their limitations were illustrated. A new dissolution model was proposed that combined the predictive ability of the thermodynamic model and the simplicity of SG models, and is applicable for complex source zones. Lastly, the relationship between the DNAPL source architecture and downstream concentrations was investigated, focusing on multistage concentration profiles. A new upscaled model was proposed that is able to capture such complex behavior. In the second part of this thesis the thermodynamic dissolution model was combined with a model for reductive dechlorination of chlorinated ethenes to simulate DNAPL bioremediation. Simulations were conducted for simple DNAPL source zones to investigate the impact of dissolution-related processes on bioremediation effectiveness. Dissolution kinetics and back-partitioning of daughter products in the DNAPL were shown to affect dechlorination. Then, the investigation was extended to DNAPL source zones of complex architectures in heterogeneous domains, illustrating the importance of the source zone architecture for the effectiveness of DNAPL bioremediation. Overall, this thesis presents a comprehensive numerical model that will be an important research tool for evaluating the effectiveness of in-situ bioremediation for DNAPL source zones, and will provide the means for a better understanding and control of the critical factors affecting this technology in the field.

This thesis investigated the dissolution of dense non aqueous phase liquids (DNAPL) source zones in the subsurface and the effectiveness of enhanced bioremediation for the treatment of chlorinated ethene DNAPLs, using numerical modeling. For this purpose, an existing multiphase numerical model was extended to include comprehensive models for the processes of dissolution and reaction. The first part of the thesis examined DNAPL dissolution. First, a thermodynamic-based dissolution model was validated using experimental data from two complex heterogeneous DNAPL releases. Model predictions for DNAPL spatial distribution and effluent concentrations agreed well with experimental measurements, without requiring calibration. This is the first successful application of a predictive dissolution model in the literature. Model results showed the important effects of relative permeability and interfacial areas on dissolution rates. Then, the thermodynamic dissolution model was compared to simpler models typically used in the literature. Five Sherwood-Gilland (SG) empirical correlations were evaluated and their limitations were illustrated. A new dissolution model was proposed that combined the predictive ability of the thermodynamic model and the simplicity of SG models, and is applicable for complex source zones. Lastly, the relationship between the DNAPL source architecture and downstream concentrations was investigated, focusing on multistage concentration profiles. A new upscaled model was proposed that is able to capture such complex behavior. In the second part of this thesis the thermodynamic dissolution model was combined with a model for reductive dechlorination of chlorinated ethenes to simulate DNAPL bioremediation. Simulations were conducted for simple DNAPL source zones to investigate the impact of dissolution-related processes on bioremediation effectiveness. Dissolution kinetics and back-partitioning of daughter products in the DNAPL were shown to affect dechlorination. Then, the investigation was extended to DNAPL source zones of complex architectures in heterogeneous domains, illustrating the importance of the source zone architecture for the effectiveness of DNAPL bioremediation. Overall, this thesis presents a comprehensive numerical model that will be an important research tool for evaluating the effectiveness of in-situ bioremediation for DNAPL source zones, and will provide the means for a better understanding and control of the critical factors affecting this technology in the field.

No description available.

Thesis (Ph. D. - Geosciences)--University of Arizona. / Includes bibliographical references.

Thesis (M.S. - Hydrology and Water Resources)--University of Arizona, 1984. / Includes bibliographical references (leaves 65-68).

Thesis (M.S. - Hydrology and Water Resources)--University of Arizona, 1984. / Includes bibliographical references (leaves 137-149).

Thesis (M.S. - Hydrology and Water Resources)--University of Arizona, 1989. / Includes bibliographical references (leaves 241-248).