When groundwater data matters, a single lab test on a disturbed sample rarely tells the full story. In Brantford, where the glacial stratigraphy shifts from clay-rich Halton Till to sandy Grand River outwash within half a kilometer, we rely on in-situ permeability testing to capture what borehole logs alone miss. The soft-ground-tunnels in this region are particularly sensitive to small changes in hydraulic gradient. The Lefranc method gives us a direct measurement in saturated soils above the water table, while the Lugeon test quantifies the hydraulic conductivity of bedrock intervals, often weathered dolostone of the Guelph or Amabel formations. Both tests have been run across the city’s west-end industrial subdivisions and the older riverbank neighborhoods where foundation drainage can become a recurring issue. When you need a number you can trust for dewatering volume or cutoff wall depth, the data has to come from the field, not a textbook correlation.
A Lugeon test does not just measure permeability—it reveals fracture behavior under pressure, distinguishing laminar flow from hydraulic jacking in real time.
Methodology and scope
Local considerations
The contrast between Brantford’s spring freshet and late-summer low water is extreme; the Grand River can rise two meters in a week during melt, saturating the floodplain silts and completely changing the effective stress regime. A permeability value measured in August may mislead a dewatering plan executed in April. We see this most clearly at sites near the Oxbow, where the groundwater table flips between confined and unconfined conditions depending on river stage. Running a slope-stability analysis with a single “design” k-value, without considering seasonal fluctuation, has caused more than one sheet pile wall to underperform. The Lugeon test’s multi-step pressure cycle also reveals the risk of hydrojacking in low-confinement rock: if the test pressure exceeds the minimum principal stress, the measured permeability becomes an artifact of the test itself, not a formation property. Recognizing that boundary in real time, before it becomes a construction claim, is what separates a paper value from a defensible in-situ measurement.
Applicable standards
ASTM D6391-11: Standard Test Method for Field Measurement of Hydraulic Conductivity Using Borehole Infiltration, ASTM D4630: Standard Test Method for Determining Transmissivity and Storage Coefficient of Low-Permeability Rocks, NBCC 2020: Division B, Part 4, Groundwater and Seepage, CSA A23.3: Commentary on Concrete Water Structures
Associated technical services
Lefranc Variable-Head Tests in Overburden
Run in cased boreholes within the Halton Till and Grand River alluvium, this method records recovery rate after a sudden change in water level. Ideal for calculating k-values between 1x10⁻⁵ and 1x10⁻³ cm/s for dewatering system design.
Lugeon Packer Tests in Bedrock
Single and double packer configurations for the Guelph and Amabel dolostone. Five-step pressure cycle, real-time flow vs. pressure plotting, and analysis of Lugeon unit patterns to identify fracture flow regime and groutability.
Combined Lefranc and Falling-Head Tests
For sites with mixed soil-rock profiles, we sequence Lefranc tests in the overburden and Lugeon tests in the underlying bedrock within the same borehole, reducing mobilization cost and providing a continuous vertical permeability profile.
Pumping Tests and Slug Tests
For higher-yield aquifers in the sand and gravel deposits near the river, a pumping test or slug test provides bulk aquifer parameters (transmissivity, storativity) that complement the point measurements from Lefranc and Lugeon testing.
Typical parameters
Frequently asked questions
What is the difference between a Lefranc test and a Lugeon test?
The Lefranc test measures hydraulic conductivity in soil, typically using a cased borehole with a short open interval. The Lugeon test is a packer test for bedrock, where water is injected under pressure into an isolated section and the flow rate is measured. The Lugeon test also reveals the rock mass’s hydraulic behavior: laminar flow, turbulent flow, dilation, or washout, which is critical for grouting design.
How long does a field permeability test take in Brantford?
A single Lefranc variable-head test in soil may take 30–60 minutes, depending on the hydraulic conductivity and the time needed for water level stabilization. A Lugeon test in bedrock typically requires 60–90 minutes per interval to complete the full five-pressure-step sequence. Including equipment setup and borehole conditioning, a typical program of three to four test intervals is completed in one working day.
What is the typical cost for Lefranc and Lugeon testing in Brantford?
Field permeability testing costs in the Brantford area typically range from CA$850 to CA$1,340 per borehole, depending on whether a single Lefranc test, a single Lugeon interval, or a combined profile is required. The final estimate includes pneumatic packer setup, pressure transducer calibration, data acquisition, and the engineering report with hydraulic conductivity calculations and flow regime interpretation.
Which ASTM standard applies to Lefranc and Lugeon testing?
The Lefranc method follows ASTM D6391-11, «Standard Test Method for Field Measurement of Hydraulic Conductivity Using Borehole Infiltration». For Lugeon testing in low-permeability rock, ASTM D4630 provides the framework for determining transmissivity and storage coefficient. In Brantford’s dolostone, we also reference the International Standard ISO 22282-3:2012 for packer test procedures.