OPTIMAL GROUNDWATER REMEDIATION METHODS APPLIED TO A SUPERFUND SITE - FROM FORMULATION TO IMPLEMENTATION

A hydraulic control optimization model is applied to the conceptual and implementation analysis of a ground-water remediation system in coastal New Jersey. The site is modeled using a distributed parameter finite-difference model containing 36,000 nodes within five layers. The conceptual problem is to determine the feasibility of producing a capture zone which encompasses the entire existing plume while recharging all extracted water within property boundaries in such a way that the recharged water satisfies criteria on its fate. The conceptual analysis problem is formulated as a linear program in which the total extraction pumping is minimized, and requirements are placed on hydraulic heads and gradients in both horizontal and vertical directions. A requirement is also made that all extracted water be recharged to the subsurface. The model is used for determination of the feasibility of the remediation concept. Details of constructing constraints for a large-scale formulation are presented. The concept of constraint calibration, using particle tracking to insure that constraints are producing desired results, is introduced and demonstrated. The optimization formulation is used for detailed implementation analysis of the remediation system. A number of techniques for modifying elements of the conceptual model results, such as unrealistically small pump rates, are described. The optimization approach is found to be useful for determining the feasibility of the remedial strategy at this site and for producing results which can be used as a starting point for detailed analysis of the remediation strategy.