A common oversight in Medicine Hat is treating the drift deposits and Bearpaw Formation shale as impermeable without running a verified field test. We have seen dewatering systems fail because designers relied on lab permeability from remolded samples, forgetting that slickensided shale fractures can open up during excavation. The Lefranc test gives you a direct measurement of hydraulic conductivity in soil and weathered rock, while the Lugeon test quantifies water take in jointed bedrock. Getting these numbers right matters when you are working near the river, where a few liters per minute of unexpected inflow can stall a deep excavation for days. We run these tests with a truck-mounted drill rig that handles the variable cobble layers common in the valley fill, ensuring the test interval is stable before injection begins.
A five-step Lugeon test in Bearpaw shale can reveal whether fractures are erodible or self-healing under rising reservoir head.
Our approach and scope
Local considerations
In Medicine Hat, we often notice that boreholes advanced with air rotary can smear the shale borehole wall, temporarily masking open joints. If you run the Lugeon test immediately without flushing the hole with clear water and surging the packer, you can get a false low-permeability reading that looks safe on paper but leads to a blowout during excavation. The steep valley walls along the South Saskatchewan River create artesian conditions in some buried gravel channels; a Lefranc test in a borehole that is not casing-supported through the upper gravel can collapse and give you a misleadingly high head loss. Our technicians record water temperature and barometric pressure at each test, correcting for viscosity effects that shift k values by up to 15% between a cold spring morning and a hot July afternoon.
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Reference standards
CSA A23.3: Design of Concrete Structures (water-retaining structures), ASTM D4630: Standard Test Method for Determining Transmissivity and Storage Coefficient of Low-Permeability Rocks, NBCC 2020: National Building Code of Canada (geotechnical site investigation requirements), Canadian Dam Association (CDA) guidelines for dam foundation permeability assessment, ASTM D5092: Standard Practice for Design and Installation of Groundwater Monitoring Wells
Complementary services
Lefranc variable-head testing
Constant or falling head tests in granular overburden using a slotted standpipe and gravel pack. We measure k values from 10^-4 to 10^-7 m/s, critical for construction dewatering design in river terrace deposits.
Lugeon multi-stage packer testing
Downhole testing in NQ core holes using a pneumatic packer and five-step pressure sequence. We interpret the P-Q curve for laminar, turbulent, dilation, washout, or fracture-filling behavior per Houlsby.
Combined permeability and grouting verification
Pre- and post-grouting Lugeon tests to verify grout curtain effectiveness. We correlate water take reduction with grout volume injected, providing acceptance curves for the engineer of record.
Typical parameters
Common questions
What is the difference between a Lefranc test and a Lugeon test?
The Lefranc test measures hydraulic conductivity (k) in soil or highly weathered rock using a short test section, typically 0.5 to 1 meter, with a constant or falling head method. The Lugeon test is designed for fractured bedrock and uses a packer to isolate a longer test section, usually 3 to 5 meters, applying stepped water pressures while measuring the flow rate. The Lugeon value quantifies water take in Lugeon units; Lefranc gives you k in m/s. In Medicine Hat, we use Lefranc in the glacial drift and Lugeon in the Bearpaw shale and Oldman sandstone.
How much does a field permeability test cost in Medicine Hat?
A full-day field program including one Lefranc test and one multi-stage Lugeon test, with a technical interpretation report, typically ranges from CA$960 to CA$1,300 depending on borehole depth, access conditions, and the number of pressure steps required. Additional tests on the same borehole reduce the unit cost significantly.
How do you interpret a Lugeon P-Q curve?
We plot the effective pressure against the flow rate for each step and classify the resulting curve shape. Laminar flow gives a straight line through the origin. Turbulent flow curves concave downward. Dilation shows a concave-upward shape with increasing permeability at higher pressures. Washout curves show a hysteresis loop with higher flow on the descending pressure steps. A curve that starts high and drops indicates fracture clogging. This interpretation, developed by Houlsby, tells us whether the fractures are stable, erodible, or self-healing under pressure.
How deep can you run a Lugeon test in Medicine Hat formations?
We routinely test to depths of 60 meters in the Bearpaw and Oldman formations using an NQ wireline system. The limiting factor is usually the packer seating depth in competent rock; if the shale is highly weathered near the surface, we case off the upper section and seat the packer in fresh rock below. For deeper investigations exceeding 80 meters, we switch to an HQ hole to maintain packer seal integrity. More info.