[en] This paper describes in detail the geomechanical instrumentation system and the data base that has been established from the geomechanical monitoring program. In addition, it describes the quality assurance and control measures that are in place to ensure that the data from the underground is accurate, traceable, and defensible. The system is installed at the Waste Isolation Pilot Plant in Carlsbad, New Mexico. This facility is being developed for the disposal of transuranic nuclear wastes in underground excavations in salt 2150 feet below the surface. The purpose of the instrumentation system is to monitor the deformations and stress changes that are occurring in the rock with time. This information is needed to routinely assess conditions in the facility and to ensure that safe operating conditions are maintained