Maralinga is located on the crest of the Ooldea Range, an ancient (Tertiary) coastal dune which is bounded to the south by the Nullarbor Plain and to the north by Tietkens Plain. The dune field of the Great Victoria Desert covers much of the region north of the Nullarbor Plain. The area is underlain by Tertiary sediments of the Eucla Basin and includes the outcropping limestones of the plains. These sediments are in turn underlain by Jurassic - Cretaceous sediments, and by probably flat-lying sediments of the Late Proterozoic - Palaeozoic Officer Basin. Crystalline basement beneath these sediments (Gawler Craton) occurs at depths of 300-550 m. The water table lies 20-30 m below Tietkens Plain and approximately 150 m below siliclastic sands of the Ooldea Range. Water quality is generally poor but one small occurrence of near-potable water is known. The principal water supply for the weapons testing programme comprised bores completed in Officer Basin sediments, with each bore producing up to 5 L/sec. at 15,000-30,000 ppm T.D.S. Engineering geological properties of rock units have been estimated from available data. Materials can be expected to vary from soils to strong rocks above very to extremely strong rocks of the Gawler Craton. Carbonates, particularly the Nullarbor Limestone, may be cavernous. Site investigations, including costings, to provide a small but reliable data base for detailed consideration of available options for waste disposal at Maralinga, are proposed.