Integration of ground-penetrating radar and downhole soil moisture data to map the thickness and continuity of landfill capping

Ground-penetrating radar (GPR) and downhole soil moisture readings have been conducted over a former landfill to the north of Adelaide, South Australia, in order to determine and map the thickness and lateral extents of the landfill capping layer over the underlying domestic waste. The study site, Cavan Landfill, is a former landfill undergoing a remediation program including landfill gas extraction and capping. Through the integration of the two data sets, GPR and soil-moisture, accurate information on the thickness and continuity of the capping layer on the landfill has been obtained. Six GPR profiles were collected using a Noggin 500 MHz unit. A time window of 50 nanoseconds was set to give maximum resolution between 0.8 metres and 2.4 metres. Ten shallow wells were installed for characterisation by the 'Diviner 2000' capacitance soil moisture probe along the periphery of the area. Moisture readings were collected in mmH 2 O over time at 10 centimetre intervals up to 1.6 metres in depth. Moisture profiles were superimposed on the GPR profiles for interpretation. The results give accurate information on the capping layer, the degree of heterogeneity and moisture level fluctuations.