We were on a cut-to-fill site out near Kamo, and the retaining wall design was stalled because nobody had verified the actual drainage capacity of the residual clay. Whangarei’s geology shifts fast—basalt flows, alluvial pockets, weathered greywacke—and guessing permeability from a borelog rarely ends well. That job needed a CPT test to map the soft layers and a Lefranc test at the footing level, so the contractor could size the drainage blanket without over-engineering the whole thing. Across Whangarei, from Onerahi to Tikipunga, we run field permeability tests that give you a real K value, not a textbook assumption. The Whangarei District Council land use consent process often triggers this when infiltration or groundwater control is part of the resource consent package.
In Whangarei’s layered volcanic terrain, a single in-situ permeability test at the right depth replaces a hundred conservative assumptions.
Questions and answers
When does the Whangarei District Council require a field permeability test?
Typically when a resource consent application involves on-site stormwater disposal—soak pits, infiltration trenches, or rain gardens. The Council wants to see in-situ hydraulic conductivity data to prove the ground can accept the design infiltration rate. We test at the exact depth and location of the proposed device.
What’s the difference between a Lefranc test and a Lugeon test?
A Lefranc test measures permeability in soil using falling or constant head methods inside a borehole. A Lugeon test is a packer test for fractured rock, injecting water under pressure to calculate Lugeon units. In Whangarei, we often run both on the same borehole when the profile transitions from soil into basalt or greywacke.
How much does a field permeability test cost in Whangarei?
For a Lefranc or Lugeon test package, you’re generally looking at NZ$1,090 to NZ$1,780, depending on depth, access, and whether we need to install packers in rock. The price includes the borehole setup, the test run, and the signed report with K values and field logs.
How long does it take to get results?
The field work usually wraps up in a day, assuming the borehole is already drilled and stable. We submit the preliminary K values within 48 hours so your designer can keep moving. The full signed report with test plots and interpretation follows within a week.
