This report is the result of work performed under the third part (Task C) of a four-part contract to gather technical information to evaluate environmental acceptability of various options for disposal of high-level wastes. The other risks are: A-Source Term Characterization; B-Effectiveness of Engineering Controls; and D-Assessment of Accidental Pathways. Task C report has three principal objectives; to assess geologic site selection factors; to review available information and quantify the potential for the migration of nuclides through the geosphere to the biosphere, and to consider dose-to-man implications of a repository for high-level waste containing large quantities of radionuclides in high concentrations that might become dispersed into the biosphere over geologic times. Task C attempts to summarize the influences on nuclide migration potential and thereby identify critical inadequacies in the data and analytical method.