[en] Modeling of transport in the environmental media was performed. Predicting the future performance of any waste site or facility and postulated actions in terms of migration of potential hazardous materials requires mathematical models capable of simulating flow and transport in the groundwater. Three-dimensional groundwater flow and transport models were developed to simulate the groundwater movement and contaminant transport in the Raw Materials Fabrication Area and the Separations Area. The overall objective of the analysis was to develop groundwater flow models that quantifies the rate and direction of the groundwater movement from the waste sites to points of discharge. The USGS Modular 3D model uses the strongly implicit procedure to solve sets of simultaneous finite-difference equations that represent the groundwater flow process. The transport functions, which are the concentration or mass flux at time t due to continuous injection starting at time t', were obtained by solving the three-dimensional advection-dispersion equations using the Sandia Waste Isolation Flow and Transport (SWIFT) model. 5 refs., 7 figs., 2 tabs