In Melbourne, the old landfill sites around Werribee and the Dandenong Valley present a unique challenge: the underlying soils are a mix of Quaternary basalts and Tertiary sediments, often with perched water tables that complicate liner installation. We have run numerous borehole programs on these sites and the key lesson is that you cannot rely on regional data alone — every cell requires its own geotechnical assessment. Before designing the final cover system, we routinely cross-check hydraulic conductivity values with a resistivity survey to map preferential flow paths, and then correlate those results with laboratory permeability tests on undisturbed samples taken from the liner zone.
In Melbourne’s old landfills, a single sand lens can increase vertical permeability by two orders of magnitude — that is why we always run a full core log before finalizing the liner design.