OPTIMIZATION OF REMEDIAL PUMPING SCHEMES FOR A GROUNDWATER SITE WITH MULTIPLE CONTAMINANTS

This paper presents mr optimization analysis of the remedial pumping d esign for a contaminated aquifer located in Elmira Ontario, Canada. Th e remediation task presented in the paper is to remove two ground-writ er contaminant species, NDMA (N-nitrosodimethylamine) and chlorobenzen e 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 qu ality standard for NDMA is five orders of magnitude smaller than the i nitial peak concentration. The objective is to minimize total pumping and the constraints incorporate ground-water quality requirements on t he maximum and the spatially averaged residual concentrations, with co ntaminant source control being considered. On the combination of simul ation and optimization, the results of this study indicate that the pe rformance of an optimization algorithm based on gradient search is con troled by the specified cleanup levels, and that contaminant concentra tions can be nonconvex and nonsmooth for some pumping schemes.