A shallow seismic refraction survey was carried out around the disposal lagoons at the Naracoorte Saleyards to determine the depth to the underlying Gambier Limestone bedrock. If the floors to existing effluent disposal lagoon excavations are near to, or extend into this rock unit, the effluent could pollute the limestone aquifer. The Oligo-Miocene Gambier Limestone was found to occur at a depth of 4-18 m. It is overlain by Pliocene Parilla Sands, the porosity and permeability of which will prove important in determining whether the aquifer is being polluted.