Montreal’s subsoil isn’t just dirt. It’s a layered record of glacial retreat and marine invasion. The Champlain Sea deposited sensitive clays across the island, then the glaciers left compact till underneath. Standard boreholes can miss thin silt seams between those layers. That’s why we run the cone penetration test — CPT — to get a continuous resistance profile without sample disturbance. We see contractors lose weeks when a design assumes uniform clay and hits a sand lens at 14 meters. A single CPT sounding can map those transitions in an afternoon, even in the tight access alleys of Rosemont or the industrial lots of Montréal-Est. For sites near the St. Lawrence, where the water table sits barely two meters down, we combine CPT data with in-situ permeability measurements to separate drainage behavior from strength.
In Montreal’s sensitive clays, a CPT dissipation curve tells you more about foundation performance than any lab consolidation test.
Service characteristics in Montreal
Demonstration video
Critical ground factors in Montreal
Montreal sits in a moderate seismic zone — the last significant event, the 1732 M5.8 quake, was centered near the island itself. Combine that with sensitive clay and the risk isn’t just settlement. It’s cyclic softening. A CPT run through Champlain Sea deposits gives us the normalized tip resistance and friction ratio needed to run a liquefaction trigger analysis. We use the Robertson (2009) method because it handles silty clays better than the standard Youd-Idriss approach. For deep excavations in the downtown core, where cut-and-cover stations intersect multiple till layers, missing a thin liquefiable silt seam can lead to base instability during dewatering. The cone picks up that seam when an SPT split spoon would have blown through it unnoticed. In a city building 20,000 new housing units a year, many on infill or former industrial land, that level of resolution isn’t optional.
Our services
Our CPT services cover the full range of Montreal geotechnical needs — from quick site class determinations to detailed liquefaction assessments.
Standard Piezocone Sounding
Continuous qc, fs, and u2 profiling to 30 meters depth. Includes dissipation tests at bearing layer and soil behavior type classification per Robertson charts. Ideal for foundation design in Ville-Marie and Plateau.
Seismic CPT (SCPTU)
Piezocone with downhole geophone for direct Vs measurement. Used where NBCC site class E or F is suspected, or when the structural team needs shear wave velocity for dynamic analysis of mid-rise buildings on Montreal's east end clays.
Frequently asked questions
How much does a CPT sounding cost in Montreal?
A standard piezocone sounding to 20 meters with one dissipation test typically runs between CA$260 and CA$340 per meter. Mobilization for the truck rig adds a line item that depends on distance from our base and site access conditions — tight residential streets or island sites can require smaller track-mounted equipment.
How deep can the CPT rig push through Montreal's glacial till?
It depends on the till density. In the central plateau, we often hit refusal between 18 and 25 meters when the cone tip exceeds 30 MPa. In the West Island where till is looser, soundings can reach 35 meters. When refusal is shallow, we pre-drill through the crust and continue with a seismic cone, or transition to a mud-rotary borehole with SPT sampling for the deeper layers.
Do you need traffic control permits for CPT work on Montreal streets?
Yes. Any work on the public right-of-way in Montreal requires a permit from the arrondissement, and for arterial roads, a traffic control plan approved by the City. We handle the permit application as part of the mobilization scope. For sidewalk or lane closures in dense neighborhoods like Le Plateau, we coordinate with Stationnement Montréal to reserve the space. Lead time is usually five to seven business days.
Can CPT data be used for seismic site classification under NBCC?
Absolutely. The NBCC 2020 allows site class determination from CPT data using correlations between tip resistance and shear wave velocity. Our piezocone soundings include the friction ratio and pore pressure measurements needed to identify soil behavior type, which feeds directly into the Vs30 estimate. For sites near the boundary between class C and D — common in Montreal's transition from till to clay — we recommend a seismic CPT to get direct Vs measurements and remove the correlation uncertainty.