The simple Single Resident Well (SRW) Model has been used to calculate groundwater movement since Fermilab`s inception. A new Concentration Model is proposed which is more realistic and takes advantage of computer modeling that has been developed for the siting of landfills. Site geologic and hydrologic data were given to a consultant who made the migration calculations from an initial concentration that was based upon the existing knowledge of the radioactivity leached out of the soil. The various components of the new Model are discussed, and numerical examples are given and compared with DOE/EPA limits.