U.S. Environmental Protection Agency (EPA) and its contractors performing oversight at Superfund Sites review numerical models developed to simulate contaminant transport. An analytical transport model could be used to check the numerical model results but a practical modeling tool based on a 3D analytical solute transport model is not publicly or commercially available. The roles of an analytical model in Superfund oversight are to simulate the general plume behavior; guide the development of, and provide a check for, a more complex numerical solute transport model; and evaluate smaller scale transport such as during natural gradient tracer tests. EPA tasked APTIM to develop an analytical model for solute transport in a three-dimensional aquifer of finite thickness with uniform flow, dual porosity, sorption, sequential decay, and time-dependent source. The new model was verified against existing analytical models for special cases and against numerical models MT3DMS and RT3D, and published in two journal papers. EPA tasked RTI to develop a graphical user interface (GUI) for the model. Example applications are analysis of tracer tests at the Stringfellow Superfund Site and simulation of TCE plume at the Fresno Sanitary Landfill. To view this archive online or download the slides associated with this seminar, please visit http://www.clu-in.org/conf/tio/ASHTM_061024/