Modeling Natural Attenuation with Source Control at a Chlorinated Solvents Dry Cleaner Site

Abstract

AbstractA ground water flow and solute transport model was developed for a site contaminated with chlorinated solvents to simulate the site remediation activities that included natural attenuation and source control. MODFLOW was used to model the flow field, and RT3D was employed to simulate the sequential decay reactions involving perchloroethene, trichloroethene, dichloroethene, and vinyl chloride (VC). Predictive simulations were completed for two conditions: natural attenuation alone and source excavation followed by natural attenuation. Results demonstrated the feasibility of site remediation for both conditions with the latter one occurring in a shorter time frame. A detailed sensitivity analysis was performed to assess the uncertainty in model predictions. The most sensitive model parameters (i.e., initial contaminant concentrations, reaction rate constants, and source release rates) were perturbed and combined to form a number of parameter sets for use in the predictive simulations. The maximum plume length, the maximum plume concentration, and the persistence time for the noncompliance plume area were assessed to identify the possible failure scenarios and the most likely future plume configuration. Results indicated that further VC plume expansion or migration beyond site boundaries is unlikely.