The subsurface environment is an important national resource that is utilized for construction, waste disposal and groundwater supply. Conflicting and unwise use has led to problems of groundwater contamination. Cleanup is often difficult and expensive, and perhaps not even possible in many cases. Construction projects often encounter unanticipated difficulties that increase expenses. Many of the difficulties of predicting mechanical behavior and fluid flow and transport behavior stem from problems in characterizing what cannot be seen. An underground research laboratory, such as can be developed in the nearly 14 miles of tunnel at the Superconducting Super Collider (SSC) site, will provide a unique opportunity to advance scientific investigations of fluid flow, chemical transport, and mechanical behavior in situ in weak and fractured, porous rock on a scale relevant to civil and environmental engineering applications involving the subsurface down to a depth of 100 m. The unique element provided by underground studies at the SSC site is three-dimensional access to a range of fracture conditions in two rock types, chalk and shale. Detailed experimentation can be carried out in small sections of the SSC tunnel where different types of fractures and faults occur and where different rock types or contacts are exposed. …