Compliance with the National Building Code of Canada (NBCC) and CSA A23.3 requires accurate subsurface hydraulic data, particularly in Sault Ste Marie where infrastructure interacts with both glacial overburden and fractured Shield rock. The field permeability test, executed via the Lefranc method in soils or the Lugeon method in rock, delivers direct in-situ hydraulic conductivity values that lab tests on disturbed samples cannot reproduce. With the St. Marys River shaping local groundwater flow and the city sitting at approximately 46.5°N latitude, seasonal frost penetration and spring melt infiltration heavily influence drainage design. Our team runs these tests using standardized packer systems and constant/variable head configurations, providing engineers with the reliable data needed for dewatering plans, cutoff wall design, and seepage analysis under NBCC 2020 structural requirements.
A single packer test in fractured rock reveals more about actual seepage paths than a dozen lab permeameter tests on intact core samples.
Local considerations
In Sault Ste Marie, many foundation bid packages still rely on textbook permeability ranges instead of site-specific data. We have seen cases where the assumed hydraulic conductivity of a glacial till was off by an order of magnitude, leading to undersized sump pumps and a flooded excavation that delayed the project by three weeks during a wet October. The cost of a Lefranc or Lugeon test is negligible compared to emergency dewatering or, worse, a basal heave failure in a deep shaft. For rock sockets under the St. Marys River influence, a Lugeon value above 10 Lu signals the need for curtain grouting before proceeding with the permanent lining. Skipping this step because the rock core looks competent on the rack is a gamble that no geotechnical engineer in the Algoma District should take.
Frequently asked questions
What is the difference between a Lefranc test and a Lugeon test?
A Lefranc test measures hydraulic conductivity in soil using a slotted casing section, typically under constant or variable head conditions. A Lugeon test is a packer test performed in rock boreholes where water is injected at stepped pressures; results are expressed in Lugeon units, where 1 Lu approximates 1 litre per minute per metre of test section at 1 MPa pressure. Lefranc follows ASTM D6391, Lugeon follows ASTM D4630.
How much does a field permeability test cost in Sault Ste Marie?
For a standard Lefranc or Lugeon test program with a single test interval, pricing typically ranges from CA$970 to CA$1,570 depending on borehole depth, number of pressure stages, and access conditions. A multi-interval packer test program with five or more stages is priced accordingly and includes the full report with flow-versus-pressure plots.
When does the NBCC require in-situ permeability testing?
The NBCC 2020, under Part 4, requires that foundation design account for groundwater conditions. In-situ permeability data becomes essential when designing permanent dewatering systems, evaluating seepage forces on retaining structures, or assessing the need for cutoff walls and grout curtains. The geotechnical engineer of record determines the required testing scope based on the site investigation findings.
Can you perform Lugeon tests through casing in unstable ground?
Yes. In Sault Ste Marie's variable overburden, we often advance casing through the soil and weathered zone to seat into competent rock. The Lugeon test is then performed below the casing shoe using a single or double packer assembly, isolating the test interval from the cased section above.
