oa Geophysical Evaluation Of Potential Refuse Disposal Sites A Case Study from George Town, Northern Tasmania

Geophysical techniques were applied at the George Town municipal refuse disposal site in northern Tasmania to delineate areas of thick Jurassic dolerite -derived clays and colluvial material for future waste disposal trenches. A variety of techniques were applied including seismic refraction, magnetics and frequency domain electromagnetics (EM31).

Seismic refraction surveys effectively discriminate zones of thick clay and colluvial sediments from near-surface dolerite bedrock and residual core stones. Travel-time curves are typically complex due to the irregular dolerite surface and data was interpreted by tomographic inversion. Correlation of refraction tomograms with engineering data, auger drilling and point load measurements suggest that the boundary between "easy" and "difficult" excavation corresponds to a seismic velocity of ~2000m/s.

Areas of near-surface dolerite are characterised by high total magnetic intensity and low apparent conductivity while zones of thick colluvial material and clay are conductive and have lower total magnetic intensity. The results of magnetic and EM surveys are complementary and correlate closely with the seismic interpretation.

In this geological environment the combination of magnetic and frequency-domain EM surveys provide the most cost-effective geophysical exploration strategy for rapid delineation of suitable sites for waste disposal.