Studies of geology and hydrology in the Basin and Range Province, Southwestern United States, for isolation of high-level radioactive waste - Evaluation of the regions

Six regions in the Basin and Range province, ranging in size from 21,600 to 80,000 square kilometers, were evaluated to identify prospective hydrogeologic environments for isolation of high-level radioactive waste. Prospective hydrogeologic environments were evaluated on the basis of the surface distribution of potential host rocks, late Cenozoic tectonic activity, hydrogeologic characteristics, and mineral and energy resources. These regions were selected as prospective for this study from a screening of the Basin and Range province.

The six regions have certain characteristics that appear favorable for isolation of radioactive waste. The scant precipitation and great potential for water loss by evaporation and transpiration results in little surface runoff and ground-water recharge. This, combined with other hydrogeologic factors, results in areas within the regions that have thick unsaturated zones and long ground-water flow paths and traveltimes.

Potential host media in the unsaturated zone include crystalline rocks, volcanic rocks, and basin fill. Potential host media in the saturated zone are predominantly crystalline igneous rocks but also include argillaceous rocks, evaporitic rocks, intracaldera tuffs, and laharic breccias.