[en] This volume, Volume 1, ''Executive Summary,'' is the first of a 23-volume series, ''Technical Support for GEIS: Radioactive Waste Isolation in Geologic Formations,'' Y/OWI/TM-36, which supplements the ''Contribution to Draft Generic Environmental Impact Statement on Commercial Waste Management: Radioactive Waste Isolation in Geologic Formations,'' Y/OWI/TM-44. The series provides a more complete technical basis for the preconceptual designs, resource requirements, and environmental source terms associated with isolating commercial LWR wastes in underground repositories in salt, granite, shale, and basalt. Wastes are considered from three fuel cycles; uranium and plutonium recycling, no recycling of spent fuel, and uranium-only recycling. This volume briefly describes the Alternate Repository Preconceptual Design Studies that led to the generic repository designs and the determination of the repository's resource requirements and environmental effluents