Cable tool and diamond drilling to depths of up to 185 ft beneath the proposed Adelaide City Festival Hall site have revealed about 60 ft of alluvial materials of Pleistocene to Recent age, overlying about 60 ft of Blanche Point Marls and carbonaceous clays of Upper Eocene age, which are in turn resting on Precambrian weathered siltstone. The Tertiary to Recent beds are near horizontal. The lowermost Tertiary sediments are predominantly paralic, but the Blanche Point Marls are of marine origin. The Quaternary alluvial materials are valley-fill sediments that have been deposited in the Torrens River Valley. The groundwater table is horizontal, and lies about 80 ft below the surface. With the structures proposed, foundation loads will mainly affect the Quaternary alluvial materials and the Blanche Point Marls. The alluvial materials are compact to dense sands and gravels and very stiff to hard clays. The upper part of the Blanche Point Marls has essentially rock-like physical properties, and forms a continuous layer up to 25 ft thick.