Calgary sits on a mix of glacial till, alluvial sands, and bedrock shales. The bedrock aquifer beneath the city supplies most of the municipal water. Builders here often underestimate how variable the permeability can be across even a single lot. A field permeability test (Lefranc/Lugeon) gives you the actual hydraulic conductivity in the ground — not a table value. For deep excavations near the Bow River, knowing inflow rates is critical. We combine this test with drainage geotechnical studies to design effective dewatering systems. That data saves weeks of schedule delays.
One test section can reveal a 100-fold difference in permeability between adjacent till layers. That is the difference between dry excavation and a flooded pit.
Methodology and scope
A common mistake contractors make in Calgary is assuming all till behaves the same. It does not. Glacial till here has lenses of sand and gravel that create unpredictable flow paths. A field permeability test (Lefranc/Lugeon) isolates each layer. We drill a borehole, seal off the test section with packers, then inject or withdraw water at controlled pressures. The Lefranc method works for low-permeability soils like till. The Lugeon test suits rock joints and fractures. Both follow CSA Z768. The result is a reliable k-value for seepage analysis. If you are designing a permanent foundation drain, pair this with a consolidation test to predict settlement under seepage forces.
Technical reference image — Calgary
Local considerations
Calgary's groundwater table fluctuates seasonally by up to 4 m in some neighborhoods like Capitol Hill. That means permeability measured in July can be half the value in March. If your project relies on a single dry-season reading, you risk undersizing the dewatering system. The consequence is a flooded excavation during spring melt. A field permeability test (Lefranc/Lugeon) captures the range, not just a snapshot. We also recommend wet-season re-testing for high-risk sites near the Elbow River. That extra step has saved clients from costly emergency pumping.
Lefranc (constant/falling head) or Lugeon (multi-stage pressure)
Typical depth range
3 m to 60 m below ground surface
Measured parameter
Hydraulic conductivity (k) in m/s
Applicable soils
Silt, clay till, sand, gravel, fractured bedrock
Packer type
Single or double pneumatic packers
Reporting units
cm/s or m/day with confidence interval
Standard
CSA Z768, CSA A23.3 references
Associated technical services
01
Constant-Head Lefranc Test
For saturated soils below the water table. Uses a constant water level to measure steady-state flow. Best for till and silt layers.
02
Falling-Head Lefranc Test
For low-permeability soils above the water table. Water column drops over time. Suitable for clay-rich till.
03
Lugeon Packer Test
Multi-stage pressure test in rock. Measures permeability and joint response under increasing pressure. Used for grout curtain design.
04
Single vs Double Packer Configurations
Single packer isolates the bottom of the hole. Double packer isolates a specific interval. We recommend double packer for multi-layer till sequences.
Applicable standards
CSA Z768 (Standard Practice for Design and Installation of Groundwater Monitoring Wells), ASTM D6391 (CFEM Ch 4) (CFEM Ch 4) (CFEM Ch 4) (CFEM Ch 4) (CFEM Ch 4) (Field Measurement of Hydraulic Conductivity Using Borehole Infiltration), CSA A23.3-14 (Design of Concrete Structures — references to permeability requirements)
Frequently asked questions
What is the difference between the Lefranc and Lugeon test?
The Lefranc test is used in soils and uses constant or falling head with low injection pressures. The Lugeon test is designed for rock and applies multiple pressure stages to evaluate fracture behavior and grout acceptance. Both measure hydraulic conductivity but under different conditions.
How much does a field permeability test cost in Calgary?
The typical cost for a field permeability test (Lefranc/Lugeon) in Calgary ranges from CA$890 to CA$1,470 per test section. This includes mobilization, drilling, packer installation, and a laboratory report. Volume discounts apply for multiple test sections on the same site.
When should I order a field permeability test instead of a lab test?
Order a field test when the soil is undisturbed, when you need in-situ conditions (natural stress, saturation), or when the material is too coarse for lab sampling. Lab tests are cheaper but only measure remolded or small samples. For excavation dewatering design, field tests are the standard.
