Investigation of the site of a proposed new road bridge over the River Murray consisted of five hollow spiral auger drillholes totalling 216 feet, geological surface mapping of the floodplain at a scale of 100 feet to 1 inch, and palaeontological examination of selected drillhole samples. The auger drilling suggests that the floodplain is underlain by sandy fossiliferous marl of the Mannum Formation, encountered at a depth of 53 feet in Hole 1 and at about 25 feet in holes 2 to 5. The floodplain sediments are essentially sandy, or somewhat silty below the higher ridge areas. The lagoon areas may contain up to 14 feet of high to low plasticity clay soil in the centre of the depressions. Below 14 feet depth, the alluvial subsoil is essentially sandy over the whole width of floodplain. Groundwater in the drillholes is static at R.L. 127 feet, which is equivalent to pool level in the river. On the geological evidence available, there appears to be little advantage in altering the position or orientation of the bridge and approach embankment from that at present proposed.