Monitoring of the integrity of electrically non-conductive geomembrane liners installed at waste sites using electrical geophysical techniques has been carried out for a number of years using above-liner leak location surveys and, more recently, below-liner monitoring systems. We compare the theoretical response of both types of survey to a hole in a liner and then compare with measurements made in the field. The theoretical leak response indicates that above-liner surveys are sensitive to leaks over a greater area, though both responses result in comparable leak detectability. However, field data suggest that in practice, measurements made on a sparse grid below the liner have the greater sensitivity to certain leaks. This may be due to the differing leak geometries and background conditions present above and below the liner.
The results indicate that a sparse below-liner monitoring grid, with its long-term monitoring capabilities, combined with above-liner surveys to pinpoint leaks accurately offer a successful approach to ensuring liner integrity throughout the lifetime of a lined waste site.