We present two problems of dewatering where the use of analytical solutions to groundwater flow problems provide insight that is important for engineering practice. The first problem concerns the dewatering of a section of the Mississippi river for the purpose of building a lock. As the case was settled in court, the problem will be presented without mentioning details such as the company and agency involved; we will focus instead on the conclusion that resulted from the analysis. The contractor, responsible for installing a cofferdam, was required to fill the dam with sand from a specific location. The cofferdam performed very poorly in that excessive leakage occurred, resulting in extremely high dewatering cost. The second problem concerned the dewatering of the divide-cut section of the Tennessee-Tombigbee waterway. The hydrogeology of the formations through which the waterway was cut was such that the contractor was advised to install pressure-relieve wells to ensure stability of the bottom of the pit as well as its embankments. Failure to operate the wells in an effort to save cost resulted in a surprising amount of piping along the bottom part of the embankment.
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