This study presents a synthesis of information and interpretations relevant to surficial processes at the Yucca Mountain Site. The report is part of the technical basis which will be used to evaluate the suitability of Yucca Mountain, Nevada, as a site for a mined geologic repository for the permanent disposal of high-level radioactive waste and spent nuclear fuel. It provides a description of the surface characteristics, preclosure hydrology, and erosion at the Yucca Mountain Site. This report will provide the technical basis to evaluate three technical guidelines from the U.S.