Setting up a Lugeon packer assembly in Tauranga's volcanic terrain requires careful attention to borehole stability. The variable rhyolitic tuffs and ignimbrite flows underlying much of the city create distinct hydrogeological compartments that standard percolation tests simply cannot characterise. Our technical team runs the double-packer system down to the target test interval, sealing off the section with inflatable rubber elements before applying staged water pressure through a calibrated flow meter. For the shallower alluvial deposits near the Tauranga Harbour shoreline, we switch to the Lefranc method using a slotted standpipe driven into the bottom of test pits or boreholes. The constant-head or falling-head procedure captures the true hydraulic conductivity of the Tauranga soil profile, which is essential when designing dewatering systems for excavations that encounter the high groundwater table typical of this coastal city. Every test run feeds directly into the geotechnical model, providing engineers with the site-specific permeability values needed to predict seepage rates and pore pressure dissipation.
A properly executed Lugeon profile in fractured ignimbrite reveals the flow regime that a single lab test on a 100 mm core sample will always miss.
