Nonlinearity and nonconvexity are two major characteristics of groundwater quality management models. The classical solutions of such problems require enormous computational effort without ensuring a global optimum. To circumvent this problem, the outer approximation method, a global optimization technique, was introduced to solve groundwater quality management problems characterized by a nonconvex objective function with minima at the boundary of the feasible region and constraints that have convex or nonconvex behavior. In this paper, a more sophisticated and computationally efficient approach for the case of the nonconvex constraints is presented. To illustrate the efficacy and efficiency of this new approach, a hypothetical and a field-scale problem are considered.