AN EVALUATION OF 3 REPRESENTATIVE MULTIMEDIA MODELS USED TO SUPPORT CLEANUP DECISION-MAKING AT HAZARDOUS, MIXED, AND RADIOACTIVE-WASTE SITES

The decision process involved in cleaning sites contaminated with haza rdous, mixed, and radioactive materials is supported often by results obtained from computer models. These results provide limits within whi ch a decision-maker can judge the importance of individual transport a nd fate processes, and the likely outcome of alternative cleanup strat egies. The transport of hazardous materials may occur predominately th rough one particular pathway but, more often, actual or potential tran sport must be evaluated across several pathways and media. Multimedia models are designed to simulate the transport of contaminants from a s ource to a receptor through more than one environmental pathway. Three such multimedia models are reviewed here: MEPAS, MMSOILS, and PRESTO- EPA-CPG. The reviews are based on documentation provided with the soft ware, on published reviews, on personal interviews with the model deve lopers, and on model summaries extracted from computer databases and e xpert systems. The three models are reviewed within the context of spe cific media components: air, surface water, ground water, and food cha in. Additional sections evaluate the way that these three models calcu late human exposure and dose and how they report uncertainty. Special emphasis is placed on how each model handles radionuclide transport wi thin specific media. For the purpose of simulating the transport, fate and effects of radioactive contaminants through more than one pathway , both MEPAS and PRESTO-EPA-CPG are adequate for screening studies; MM SOILS only handles nonradioactive substances and must be modified befo re it can be used in these same applications. Of the three models, MEP AS is the most versatile, especially if the user needs to model the tr ansport, fate, and effects of hazardous and radioactive contaminants.