f DC resistivity monitoring of the unsaturated zone beneath a lined landfill site in the UK

Characterisation of the properties of the unsaturated or vadose zone enables better prediction of contaminant and interstitial water distribution and transport. This is important especially at sites where there is a perceived risk of contamination to groundwater. At such sites, suitable monitoring should be undertaken to ensure that the incidence of pollutant escape is minimised and that any pollution is tracked. This is essential if remedial procedures are to be targeted and effective. An electrode grid permanently installed beneath an HDPE plastic lined landfill in the UK is not only capable of monitoring for holes in the liner, but also enables DC resistivity monitoring of the Triassic Sandstone aquifer which underlies the landfill (Taylor et. al., 1997). Should a hole develop in the liner late on in the life of the landfill where repair would be unfeasible, two-dimensional electrical image sections of the vadose zone can be used to indicate not only the location of any escaping leachate but also its extent and direction of migration. Knowledge of the electrical and physical properties of the partially saturated sandstone beneath the landfill as well as seasonal variations in the sandstone resistivity distribution should enable better interpretation of any data collected after a leak of this kind occurs.