Flexible time-varying optimization methodology for the solution of groundwater management problems

An outer approximation based, time-varying optimization methodology to obtain a least-cost groundwater remediation design based upon a multi-period, pump-and-treat strategy is introduced. In this novel approach, the remediation design is modified, or updated, from time to time in order to obtain cost-effective removal of contaminants from the subsurface subject to the requirement of respecting upper-bound contaminant concentration constraints at target locations and times. Concentration constraints are defined at the end of each management period, the duration of which is calculated by the optimization algorithm in such a way as to ensure maximum mass removal and to prevent further off-site migration of the contaminant plume. At each stage, the pumping strategy is modified and constraints are relocated in response to the changes in the plume geometry. A penalty term is added to the objective function to assure the performance of the proposed remediation-pumping scheme at a pre-selected time beyond the end of the design period. The utilization of the suggested approach to a field application illustrates the effectiveness of the proposed strategy.