A refraction seismic survey was employed to determine depths to bedrock in the northern St. Vincent Basin. The aim was to assist siting drillholes of a coal exploration programme within a down faulted trough. Time-distance curves did not directly delineate the sedimentary - weathered bedrock interface, due to the presence of undetectable intermediate velocity zones. However, using "blind-zone" calculations in association with the few weathered bedrock velocities recorded, troughs in the weathered bedrock were indicated. Results from the seismic survey compare well with drill logs from the subsequent drilling programme.