EVALUATION OF BENEFITS OF PARTIAL SOURCE ZONE TREATMENT USING INTERMEDIATE-SCALE PHYSICAL MODEL TESTING AND NUMERICAL ANALYSIS

A debate has started recently within the scientific and remediation community on benefits of partial source zone treatment of NAPL contaminated sites (not fully removing the entrapped free phase NAPL sources), with respect to achieving clean up goals as measured by the reduction in the downstream plume concentrations. The uncertainty associated with the removal of NAPLs from source zones could be attributed to a number of factors that include lack of data or information on the extent and timing of the spill, complex entrapment configurations created by the unstable behavior (fingering), geologic heterogeneity, and unavailability of accurate techniques for characterization of these heterogeneities and location of the sources. Data for the resolution of issues related benefits of partial source zone treatment is not expected to come from field sites. Laboratory studies in intermediate-scale test tanks provide accurate data sets to investigate this issue, as it is possible to conduct controlled spill experiments under known conditions of aquifer heterogeneity. The source depletion and the downstream concentrations in the dissolved plume can be monitored during remediation. The data generated in controlled experiments are used to validate numerical models to conduct theoretical analysis. This paper discusses this approach and presents results from such a study where benefits of partial source zone treatment using surfactants was evaluated using intermediate-scale testing and numerical modeling.