In Project GNOME, a 5-KT nuclear device was detonated at the end of a 335-m-long buttonhooked and self-sealing tunnel excavated at a 366-m depth in a salt formation in New Mexico. The primary purposes of the project were to explore (a) the feasibility of recovering, and converting for electric-power generation, energy from heat reservoirs formed underground by nuclear explosions, and (b) the practicability of recovering radiosotopes for peaceful uses. The U.S. Army Engineer Waterways Experiment Station furnished drilling consultant services, and performed cotesting and grouting operations in connection with Project GNOME. The latter included (a) performing physical tests and petrographic examinations on salt cores from the project site; (b) designing grout mixtures, to match physical properties of the salt, for use in grouting instruments in place and in connection with installing underground structural appurtenances; and (c) drilling and grouting at the site to embed scientific instruments and in connection with structural work within the tunnel.