This volume describes and discusses oil shale deposits of the U.S., applicable methods for mining the shale, and the environmental concerns associated with oil shale technologies. Mining is required to supply shale to the retorts of aboveground processes. The majority of oil shale mining is expected to be by the underground room-and-pillar method. Surface mining (i.e., open pit mining) may also be used to supply material for surface retorts and may be appropriate for up to 15 to 20% of the oil shale resources. Principal environmental issues unique to true and modified in situ oil shale processing include disposal of retort water and drill cuttings, migration of fluids during and after in situ processing, surface thermal changes, and hazardous materials that may be leached from spent shale. Other site-specific problems of in situ processing include off-gas emissions, fugitive dust generation, land disturbance, and water usage. The environmental issues are similar for oil shale surface processes, except for surface thermal changes. The degree of impact, however, is expected greater than that for either the true or the modified in situ process.