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Lester, George

Civil Engineering

2013

MS

The pump-and-treat method, which is often used for contaminated groundwater remediation, while largely effective, has some drawbacks. Tailing, which is the continued occurrence of residual low level contaminant concentration for extended periods of time, is an example. Tailing occurs because contaminants are removed from low permeability lithological units very slowly, causing the concentration versus time curve to have a long tail. Through an experimental investigation of contaminant transport in a heterogeneous soil column in which the tailing phenomena was observed, pulsed pumping has proven to be an effective alternative to traditional pump-and-treat methods using a continuous discharge strategy. Contaminant transport across sharp soil interfaces has been previously described as non-Fickian. In an effort to determine the physical processes underlying the tailing. phenomena, an axisymmetric finite-element-volume code in cylindrical coordinates has been developed to determine the effect of the dispersion coefficient on accurately mpdeling experimental data. The experimental results suggest that pulsed pumping removes the same levels of contamination as continuous pumping for a given amount of time while pumping less water. An optimization analysis shows a clear trade-off between fInal concentration, time of pumping, and total remediation time; therefore, an optimal solution exists to minimize cost based on the management goals for remediation time and fInal concentration.