A recent excavation near the Lachine Canal uncovered a complex layer of Champlain Sea clay beneath a dense glacial till—a classic Montreal stratigraphy that demands precise classification. Grain size distribution in these soils dictates everything from drainage design to frost heave potential, especially with the city's 140+ freeze-thaw cycles per year. The combination of mechanical sieving for the coarse fraction and hydrometer sedimentation for fines below 75 µm provides the full particle-size curve that geotechnical engineers rely on for permeability estimates and liquefaction screening. In our Montreal-area projects, we often link this analysis with Atterberg limits to establish plasticity characteristics of the silty clay matrix, and with in-situ permeability testing when field hydraulic conductivity values are needed for dewatering system design.
A complete particle-size curve from 75 mm down to 2 µm is the single most useful index for predicting soil behavior in Montreal's mixed glacial and marine deposits.
Service characteristics in Montreal
Critical ground factors in Montreal
Montreal's climate imposes a unique risk factor on grain size interpretation: the severe freeze-thaw cycling that penetrates up to 1.4 m depth in exposed clay. Silts, in particular, are highly frost-susceptible, and a grain size curve showing more than 10% finer than 0.02 mm by mass can indicate potential ice lens formation beneath pavements and shallow foundations. A contractor who skips hydrometer analysis on a silty sand from the Saint-Laurent borough may miss a frost-susceptible fines content that leads to differential heave within two winters. In our experience, the hydrometer fraction also correlates with the clay mineral activity that drives the sensitivity of Champlain Sea deposits—a parameter directly relevant to slope stability assessments along the escarpments of Mount Royal and the Saint-Jacques fault zone.
Our services
For grain size analysis, our dedicated soil classification lab serves the Greater Montreal area, covering Laval to Longueuil, and offers both standard and rapid turnaround. The combined sieve and hydrometer data in each report yields the full particle-size distribution curve, computed uniformity and curvature coefficients, and the USCS classification symbol.
Combined Sieve and Hydrometer Analysis
In Montreal, our comprehensive package for cohesive and mixed soils includes mechanical sieving (75 mm down to 75 µm) and then hydrometer sedimentation reaching the 2 µm clay fraction. The final report provides a merged gradation curve and a complete USCS classification.
Wash Sieve Analysis (Granular Soils)
For sands and gravels characteristic of the Saint-Laurent lowlands, we water-wash samples through a No. 200 sieve to get precise fines content. Because no hydrometer data is needed, we can offer a quicker turnaround.
Hydrometer-Only Fine Fraction Analysis
When dealing with sensitive Champlain Sea silts and clays, the sub-75 µm distribution is essential. To handle Montreal's post-glacial marine deposits, we optimize deflocculation for their unique mineralogy.
Top questions
What does a combined grain size analysis cost for a project in Montreal?
Expect to pay between CA$160 and CA$290 per sample for a standard combined sieve and hydrometer test at our Montreal lab. The cost varies with the number of sieve sizes and the need for expedited reporting. If your project has more than ten samples, we offer volume discounts.
How long does the hydrometer portion of the test take, and why can't it be rushed?
Following Stokes' law, the hydrometer sedimentation phase demands readings at 2, 5, 15, 30, 60, 240, and 1440 minutes. The 1440-minute (24-hour) reading is crucial to capture the clay fraction under 2 µm; omitting it would harm the fine-grained distribution curve's accuracy, vital for classifying Montreal's sensitive marine clays.
Is grain size analysis sufficient for classifying Champlain Sea clay, or do I need additional tests?
While grain size analysis provides particle distribution, Champlain Sea clays also need Atterberg limits to assess plasticity and liquidity index—these correlate with sensitivity and remolded strength. Our recommendation is to combine grain size with Atterberg limits, and for structured clays, perform occasional oedometer consolidation tests to determine the preconsolidation pressure profile.