Book excerpt: Project Pre-Schooner II consisted of a 100-ton chemical explosive detonated in hard, dry rock at a depth of 71 feet. The primary purpose of the project was to increase the knowledge of crater dimensions in hard, dry rock as a function of depth of burst and type of explosive. This report describes the proportioning of a concrete mixture used in stemming the access hole of the shot cavity, the design of the stem configuration, laboratory tests conducted on core samples from the site and on specimens of the concrete mixture required for design of the stem, and placement of the concrete at the job site. Based on observations of the detonation, fractured pieces of the reinforced concrete stem, and the size of the crater, it is believed that the stem acted effectively to stem the detonation. (Author).