Most studies reviewed to this point focus on the important problem of aquifer remediation design. In each of these studies, contaminant transport is modeled for a single contaminant subject to either conservative or linear equilibrium transport. This is an important limitation because groundwater contamination often involves multiple contaminants subject to nonequilibrium, or rate-limited, transport. The first to study the impact of rate-limited mass transfer on groundwater remediation design were Haggerty and Gorelick [1994]. Using a hypothetical aquifer system, they study the simultaneous remediation of three contaminants with different sorption affinities. Their management model combines two-dimensional, linear nonequilibrium solute transport simulation with deterministic, nonlinear optimization to identify optimal well locations and pumping rates for simultaneous cleanup of the three contaminant plumes. A few key results of this study are worth summarizing here: (1) Although strongly sorbing contaminants are difficult to remove, weakly sorbing contaminants are more extensive and faster moving, and both play an important role in defining the optimal design; (2) There is a lower bound on cleanup time that is defined by the mass transfer rate coefficient; and (3) The impact on remediation of rate-limited mass transfer lessens as the time-frame for cleanup increases. Another work of interest is that of Harvey et al. [1994] who present a comparison of pulsed and continuous pumping for removing contaminants subject to rate-limited mass transfer.