[en] This report presents the assumptions, methods, and results of a probabilistic approach to the calculation of groundwater travel times to the water table below Yucca Mountain, Nevada. Data to support the analyses were abstracted from formal and informal reports generated by the staff of several organizations participating in the Nevada Nuclear Waste Storage Investigations (NNWSI) Project activities. Because flow in the portion of the unsaturated zone below the proposed repository is probably nearly steady state and vertical, the hydraulic gradient was assumed to equal minus one (/minus/1) in our model. This means that the flow was assumed to be driven vertically downward solely by elevation head along the direction of gravity. On the basis of this assumption, a reasonable approximation of the velocity of water through the unsaturated zone was obtained by dividing the flux by an effective porosity. 3 refs., 2 figs