The South Saskatchewan River carved through thick deposits of glacial Lake Regina and Lake Agassiz, leaving Saskatoon with extensive layers of silty clay and clay till. These fine-grained lacustrine soils can hold water like a sponge. When we run an Atterberg test on a sample from the city’s east side, the liquid limit often lands between 45 and 75 percent, and the plastic limit between 20 and 30. That range tells us exactly how the material will behave when a contractor excavates in spring or when a basement slab cures through a dry August. The standard method follows ASTM D4318, and our lab runs it daily on material taken from boreholes across the city. For projects where the clay fraction dominates, we often pair this with a grain-size analysis to confirm the silt-clay split before signing off on foundation recommendations.
A plasticity index above 25 in Saskatoon’s native clay signals seasonal movement that no amount of compaction can fully suppress.
Technical details of the service in Saskatoon
Typical technical challenges in Saskatoon
The mistake we see too often is a site investigation that stops at grain size and moisture content, skipping the Atterberg limits because the budget feels tight. Then the contractor places a footing on a clay that looks stiff in the cut but has a liquid limit of 60 and a plasticity index of 35. The soil saturates during the first heavy rain, loses strength, and the foundation settles differentially. In Saskatoon’s lacustrine clays, that scenario is not hypothetical; it happens in new subdivisions around Rosewood and Evergreen. Classifying the soil with just a visual-manual method is not enough. ASTM D2487 and the Unified Soil Classification System require the Atterberg limits to correctly label a soil as CL, CH, or MH. Without that label, the bearing capacity assumptions are guesswork, and the repair costs later dwarf the price of the lab test.
Our services
Our Saskatoon lab runs the full Atterberg suite as part of routine geotechnical characterization, but we also support specialized investigations where the plasticity data feeds into larger design questions.
Liquid and Plastic Limit Testing
Complete ASTM D4318 procedure on disturbed samples from auger holes, test pits, or Shelby tubes. We report LL, PL, and PI on every certificate.
Shrinkage Limit and Linear Shrinkage
Supplementary testing for clay liners and road subgrades where volume change potential is critical. We follow ASTM D427 and D4943 procedures.
Soil Classification Packages
Combined grain-size distribution and Atterberg limits to assign USCS group symbols. We return a unified lab report suitable for foundation design submissions.
Moisture Conditioning Curves
Multiple-point Atterberg runs across a moisture range to map the soil’s consistency envelope for projects requiring detailed shrink-swell modeling.
Top questions
How long does Atterberg testing take for a Saskatoon project?
Standard turnaround is 24 to 48 hours from sample drop-off. We log every sample on arrival at the Saskatoon lab, dry and prepare it the same day, and run the Casagrande cup and plastic limit thread the following morning. If the project is time-sensitive, we can report results within 24 hours for a small rush fee. The limiting step is usually the overnight air-drying required by ASTM D4318 for wet preparation.
What sample size do you need for Atterberg limits?
We need at least 300 grams of material passing the No. 40 sieve. In practice, that means a one-liter jar or a sealed plastic bag of disturbed soil from the auger or test pit. The sample must be representative of the fine fraction; if there is significant gravel, we note it on the report but the Atterberg test itself runs on the minus-425-micron portion.
What does Atterberg testing cost in Saskatoon?
A single-point Atterberg test (liquid limit and plastic limit) typically runs between CA$100 and CA$140 per sample, depending on whether it is part of a larger geotechnical package. Discounts apply for batch submissions of six or more samples from the same project.
Why do Saskatoon clays show such high plasticity indices?
The glacial Lake Regina and Lake Agassiz sediments that underlie much of the city are rich in smectite and illite clay minerals. These minerals have extremely small particle sizes and high specific surface area, which lets them bind a large amount of water. That water-binding capacity drives the liquid limit up and creates the wide gap between LL and PL that we measure as a high plasticity index.