The geophysical responses of buried drums ? field tests in weathered Hawkesbury Sandstone, Sydney Basin, NSW

Abstract

Field and laboratory experiments and tests were carried out to investigate the response of buried steel and plastic drums to the magnetic, transient electromagnetic and resistivity profiling techniques in a magnetically quiet weathered Hawkesbury Sandstone environment in the central Sydney Basin. Steel drums, 200 l, 50 l, 20 l, and 5 l in size, and plastic containers, 70 l, and 20 l in size, were used as buried targets in controlled profiling surveys. The proton precession magnetic method located individual drums buried at shallow depths but with increasing difficulty as drum size decreased. The survey profiles provided data that could be modelled by sphere or dipole sources magnetized by induction as viscous and permanent maqnetization contributions were minor. Clusters of buried drums were readily detected by magnetometry and the data successfully modelled with an array of dipole sources. The TEM method clearly located individual steel drums, but the drum anomaly was less evident in the Wenner resistivity data. Plastic drums were not detected by any of the methods applied. Magnetic surveying is the primary method of choice for the location of shallowly buried steel drums in environmental studies.