Many construction teams in Mackay assume that a standard borehole log is enough to design drainage or dewatering systems. But without in-situ permeability data, you risk oversizing — or undersizing — your groundwater control. That is where the field permeability test (Lefranc/Lugeon) comes in. We run these tests in Mackay on a regular basis, particularly for projects near the Pioneer River or in the low-lying coastal suburbs where water tables sit high. The results feed directly into foundation design, slope stability analysis, and even infiltration system sizing. Getting the coefficient of permeability right from the start saves weeks of rework later.
A single Lugeon test at 10 m depth can reveal whether your excavation will need active dewatering or just passive drainage.
Methodology and scope
We use a trailer-mounted pump unit and double-packer assembly for the Lugeon test, and a simple falling-head setup with standpipe for the Lefranc test in Mackay. The equipment fits through a standard gate and reaches depths up to 30 m. Each test involves sealing off a 1 m section of the borehole with inflatable packers, then injecting water under controlled pressure. We record flow rates and pressure drops at five incremental steps. The team then processes the data to calculate k-values in m/s or cm/s. These numbers are critical for specifying drainage blankets or vertical drains. The whole procedure follows AS 1726-2017 and takes about half a day per test zone.
Technical reference image — Mackay
Local considerations
A retaining wall job on Milton Street in Mackay's CBD taught us a hard lesson. The geotechnical report showed standard soil properties but no permeability data. The contractor designed a gravity wall with weep holes and gravel drains. After the first heavy rain, water built up behind the wall — the gravel drains clogged with fines — and the wall leaned 50 mm in three days. We ran a field permeability test (Lefranc/Lugeon) post-failure and found k values two orders of magnitude lower than assumed. The fix required a full drainage retrofit. That is why we now recommend permeability testing for any wall or excavation below the water table in Mackay.
Lefranc (constant head / falling head) and Lugeon (packer)
Measured parameter
Coefficient of permeability (k) in m/s or cm/s
Test depth range
2 to 30 m (limited by borehole stability)
Pressure stages
5 increments up to 5 bar (Lugeon)
Standards
AS 1726-2017, AS 1289.6.7.3
Typical duration
4–6 hours per test zone
Associated technical services
01
Lefranc Permeability Test
Constant-head or falling-head test in open boreholes or standpipes. Best for low-permeability soils and weathered rock. We use it on Mackay's alluvial terraces to size dewatering systems for basements and sewer trenches.
02
Lugeon Packer Test
Multi-pressure packer test in NQ or HQ diamond-cored holes. Standard for rock masses and high-permeability zones. Common on Mackay dam and bridge projects where grout curtains or cutoff walls are being designed.
Applicable standards
AS 1726-2017 Geotechnical site investigations, AS 1289.6.7.3 Standard Practice for Design and Installation of Groundwater Monitoring Wells, AS 4678-2002 Earth-retaining structures
Frequently asked questions
What is the difference between the Lefranc and Lugeon test?
The Lefranc test uses a single open section of borehole (or a screened standpipe) and measures flow under a constant or falling head. The Lugeon test isolates a section with inflatable packers and applies multiple pressure stages. In Mackay, we choose Lefranc for shallow soils and Lugeon for deeper rock or where the permeability changes rapidly with depth.
How much does a field permeability test in Mackay cost?
A standard field permeability test (Lefranc or Lugeon) in Mackay typically ranges between AU$1,020 and AU$1,550 per test zone, including mobilisation within the Mackay region. The total depends on depth, number of test zones, and site access. We provide a fixed quote before mobilisation.
Do you need a borehole before running the test?
Yes. The test is performed inside a pre-drilled borehole. We can coordinate with a driller to core or auger to the required depth. For shallow tests in Mackay's sandy soils, a hand auger may suffice, but we usually recommend a minimum NQ hole (50 mm diameter) for reliable packer sealing.
What standards does the test follow in Australia?
We follow AS 1726-2017 for the test procedure and AS 1289.6.7.3 for well installation. Our equipment is calibrated annually and the team holds NATA accreditation for field permeability testing. The data is reported in k (m/s) with the corresponding pressure and flow records.
How long does it take to get the results?
Preliminary results are available within 24 hours of the test. A full report with graphs, pressure-flow curves, and calculated k-values is delivered within 5 working days. For urgent projects in Mackay, we can expedite to 2 days at no extra charge.
