Optimization of Remedial Pumping Schemes for a Ground‐Water Site with Multiple Contaminants

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Abstract
This paper presents an optimization analysis of the remedial pumping design for a contaminated aquifer located in Elmira, Ontario, Canada. The remediation task presented in the paper is to remove two ground‐water contaminant species, NDMA (N‐nitrosodimethylamine) and chlorobenzene, to such extent that the specified ground‐water quality standards are met. The contaminants, NDMA and chlorobenzene, have different initial plume configurations and retardation characteristics. The required quality standard for NDMA is five orders of magnitude smaller than the initial peak concentration. The objective is to minimize total pumping, and the constraints incorporate ground‐water quality requirements on the maximum and the spatially averaged residual concentrations, with contaminant source control being considered. On the combination of simulation and optimization, the results of this study indicate that the performance of an optimization algorithm based on gradient search is controlled by the specified cleanup levels, and that contaminant concentrations can be nonconvex and nonsmooth for some pumping schemes.