We drilled a test hole last year on a commercial site near the Bendigo railway station. The gravelly clay at 4 m depth had an apparent permeability of 3×10⁻⁵ m/s under falling-head conditions. That data changed the design of the basement drainage system. For any excavation below the water table in Bendigo, a field permeability test (Lefranc/Lugeon) is the only way to measure in-situ hydraulic conductivity. Without it, you guess the seepage rate and risk flooding the pit. We run the test in accordance with AS 4678, using constant-head for sands and falling-head for clays. The procedure is straightforward but the interpretation requires experience with local geology.
Field permeability in Bendigo's gravelly clays can be 10 to 100 times higher than lab tests indicate — measure it in situ.
Methodology and scope
A common mistake we see in Bendigo is relying solely on laboratory permeability tests on remoulded samples. Those results can be an order of magnitude off from real field values. The soil fabric, fissures, and gravel lenses that dominate groundwater flow in Bendigo are destroyed during sampling. A field permeability test (Lefranc/Lugeon) preserves the in-situ structure. We use a single-packer system in open boreholes drilled with a solid-stem auger. The test interval is isolated with a pneumatic packer, and water is injected under controlled pressure. Flow rate and pressure are logged continuously. For projects near the Bendigo Creek, we supplement the program with infiltration testing to evaluate surface recharge rates alongside the deeper Lefranc results.
Technical reference image — Bendigo
Local considerations
AS 4678 requires that groundwater control measures be based on measured rather than estimated permeability. In Bendigo, where the weathered bedrock and alluvial terraces create highly variable hydraulic conditions, a single assumption can lead to undersized dewatering systems. We have seen temporary works fail on two local sites because the design permeability was taken from a textbook table. A field permeability test (Lefranc/Lugeon) reduces that risk to a known value. It also provides the data needed for grouting programs, slope stability analysis, and settlement predictions. The cost of testing is trivial compared to a delayed excavation or a structural claim.
Lefranc (falling/constant head) or Lugeon (packer)
Typical K range in Bendigo
1×10⁻⁴ to 1×10⁻⁷ m/s
Test interval length
0.5 m to 3.0 m (single packer)
Pressure stages (Lugeon)
3-5 stages up to 1.5 MPa
Data output
K (m/s), transmissivity (m²/s), flow regime type
Applicable standard
AS 4678, AS 1289
Associated technical services
01
Lefranc Permeability Test
Constant-head and falling-head methods in open boreholes. Suitable for soils and weak rocks. Reported as K (m/s) with flow regime notes.
02
Lugeon Packer Test
Multi-stage pressure injection in single- or double-packer configuration. Used for rock masses and stiff clays. Delivers Lugeon values and permeability classification.
03
In-Situ Flow Logging
Combined with geophysical logging to identify discrete permeable zones. Provides depth-specific transmissivity profiles for complex hydrogeological settings.
Applicable standards
AS 4678:2002, AS 1289, Australian Drilling Industry Training Committee (ADITC) Manual
Frequently asked questions
What is the difference between Lefranc and Lugeon tests?
The Lefranc test is used in soils and weak rock where the borehole remains open. Water is injected under constant or falling head, and permeability is calculated from the flow rate and head difference. The Lugeon test is designed for rock masses with a packer system. Water is injected at increasing pressure stages, and the Lugeon value (litres per minute per metre of test interval at 1 MPa) is recorded. The Lugeon test also reveals whether the flow regime is laminar, turbulent, or dilation-controlled.
How much does a field permeability test cost in Bendigo?
The typical cost for a single Lefranc or Lugeon test in Bendigo ranges from AU$1080 to AU$1.610, depending on depth, packer configuration, and number of test stages. For multiple tests on the same borehole, the per-test cost decreases. We provide a fixed-price quote after reviewing the borehole log and project scope.
At what depth do you perform the test in Bendigo soils?
The test interval is selected based on the target stratum. In Bendigo, the weathered bedrock often occurs between 3 m and 12 m depth. We place the packer just above the zone of interest. For shallow alluvial deposits near the Bendigo Creek, the test is run at 2 m to 6 m. The borehole is advanced to total depth first, then we conduct the tests upward from the lowest interval.
