Impacts of physical and chemical heterogeneities on aquifer remediation design

2004-07-01
Aksoy, Ayşegül
Culver, Teresa B.
The impacts of physical and chemical aquifer heterogeneities on optimal remediation design, costs, and time to compliance are investigated by linking a genetic algorithm with a contaminant transport simulation model. Physical and chemical aquifer heterogeneities were grouped into three levels as follows: (1) hydraulic conductivity (K) heterogeneity only; (2) combined heterogeneity of K and the distribution coefficient (Kd); and (3) combined heterogeneity of K, Kd, and the mass transfer rate (α). Various degrees of heterogeneity were considered, ranging from slightly heterogeneous to strongly heterogeneous. Impacts were evaluated using two different optimization models: the optimal design model and the time-to-compliance model. The first model focused on finding optimal aquifer remediation designs and costs under various heterogeneity conditions, and the second model optimized the time needed to meet the water quality goals for a fixed pumping schedule. Results show that the variability in the remediation costs and time to compliance for different realizations of a heterogeneous K-field increases as K-heterogeneity increases. Consideration of Kd- and α-heterogeneities results in different policies and costs compared to cases where sorption heterogeneity is neglected. In general, time to compliance increases for systems with both chemical and physical heterogeneity as compared to systems with only physical heterogeneity. The impact of α-heterogeneity on remediation strategies is most apparent when Kd-heterogeneity is high. Although an increase in K-heterogeneity decreases the impact of Kd- and α-heterogeneities on remediation costs and time to compliance, sorption heterogeneity could still significantly impact the performance of a remediation system, especially when sorption heterogeneity is high.