AS 1726:2017 sets the standard for geotechnical site investigations in Australia, and in Canberra, getting the permeability parameters right is non-negotiable. The city sits on a complex mix of Silurian volcanics, deeply weathered shales, and alluvial deposits along the Molonglo River corridor. A desktop estimate won't cut it. We run Lefranc tests in boreholes to quantify hydraulic conductivity in soil and highly fractured rock, and Lugeon tests in cored sections where water loss must be measured under pressure. These in-situ measurements feed directly into dewatering strategies, basement retention designs, and seepage analyses for cuts on projects stretching from Gungahlin to Tuggeranong. For sites where the water table interacts with reactive clays, the permeability profile often dictates the entire earthworks specification. We often pair this with a test pits program to visually log the fracture network before assigning packer zones.
A single Lugeon value reflects fracture connectivity, not just rock mass porosity. In Canberra's faulted volcanics, that distinction matters.
Q&A
When do I need a Lugeon test instead of a Lefranc test?
Lefranc is for soil and very weak rock where the borehole stands open below a casing. Lugeon applies to cored rock sections (dacite, ignimbrite, fresh shale) where you need a packer to isolate a test interval and apply pressure. In Canberra we often run both on the same borehole: Lefranc in the colluvium and weathered top, Lugeon from the rockhead down.
How much does a field permeability test cost in Canberra?
A single Lefranc or Lugeon test package typically ranges from AU$1,050 to AU$1,590 depending on depth, number of pressure stages, and packer configuration. Mobilisation and drill rig day rate are separate. We quote per borehole with a clear breakdown so you know what each test interval costs.
How long does it take to get permeability test results?
The field test itself takes 30 to 90 minutes per interval once the borehole is prepared. We report preliminary k values the same day if needed for construction decisions. The final AGS-compliant report with interpretation and plots is delivered within five working days.
Which AS 1726 sections cover permeability testing?
AS 1726:2017 references in-situ permeability testing in Section 6 (field investigations) and Appendix D for test procedures. We follow the Houlsby method for Lugeon interpretation and the variable/constant head procedures detailed in the standard for Lefranc tests.
