[en] AEC 7 is a borehole drilled in western Lea County, New Mexico, in section 31, T.21S.,R.32E. AEC 7 was drilled to 3918 feet in 1974 by Oak Ridge National Laboratory; Sandia deepened the hole to 4732 ft in 1979. The borehole provided stratigraphic and lithologic information in the initial and final drilling. The borehole was used extensively for tests of borehole plugs and plugging operations. AEC 7 penetrated, in descending order, Holocene sands and Mescalero caliche (8 ft), Santa Rosa Sandstone (109 ft), Dewey Lake Red Beds (542 ft), Rustler Formation (325 ft), Salado Formation (2014 ft), Castile Formation (1521 ft), and the upper Bell Canyon Formation (197 ft). Cores were obtained from much of the borehole. An extensive suite of geophysical logs provides information on stratigraphy, lithology, and structure. Beds were in normal stratigraphic sequence and without structural deformation except in the lower Castile. Anhydrite II and Halite II appear to be repeated in the borehole. This section was penetrated during deepening by Sandia; the structural complication is consistent with deformation found nearby in ERDA 6. The potential site on which AEC 7 is located was abandoned in 1976 after ERDA 6 was drilled. The WIPP is a demonstration facility for the disposal of transuranic (TRU) waste from defense programs. The WIPP will also provide a research facility to investigate the interactions between bedded salt and high level wastes