[en] The radioactive waste produced by our nuclear industry must be placed in a safe repository. Deep underground storage in a geologic medium is a method proposed to do this. It has been proposed that basalt in the Pasco Basin of the Columbia Plateau would be an excellent underground storage medium for nuclear waste. Thermal and mechanical properties of basalt have been reviewed. The results of this review show that basalt has many characteristics favorable to long-term storage, including strength and thermal stability indicating the ability to isolate the waste from the biosphere in a geologically stable environment. The available computer codes which may be used to simulate the thermo-mechanical behavior of the rock mass surrounding the repository were reviewed and evaluated. There are several codes currently available or under development that can analyze geo-engineering problems and model the repository in order to predict rock mass behavior. Data gathering and demonstration projects were proposed. These include an extensive drilling program, laboratory analysis of core samples, in situ thermo-mechanical studies performed in an excavation in basalt near the surface, and further studies performed in an underground facility in a deep basalt horizon. Possible repository layouts and mining considerations were discussed. Utilization of data from the above programs, plus programs to improve construction techniques and mining cost determinations, will allow development of a final repository that meets long-term radioactive waste isolation requirements