The northern shore of Lake Ontario conceals a granular stratigraphy that changes behavior radically during a seismic event. In Ajax, post-glacial sands and silts deposited by the Duffins Creek system sit over a shallow water table, often less than three meters deep. When a moderate earthquake—say a magnitude 5.5 to 6.0 from the Western Quebec Seismic Zone—hits these saturated loose layers, pore pressure can spike and erase the soil's effective stress within seconds. That is the liquefaction mechanism, and mapping it requires more than a simple borehole log. Our team correlates field data from SPT drilling with lab grain-size curves to calculate the factor of safety at each critical depth, following the NCEER workshop framework and the NBCC 2020 seismic hazard values for the Ajax-Pickering corridor. For projects where continuous profiling is mandatory, we integrate CPT soundings to detect thin liquefiable seams that split-spoon intervals might miss.
A clean sand with 5% fines and an N60 of 8 at six meters depth, under a PGA of 0.25g, will liquefy in Ajax unless the site is improved—that is not an opinion, it is the NCEER math.
Process and scope
Local ground factors
Take two projects, one on Harwood Avenue North near the 401 and another on Lake Driveway West by Rotary Park. The Harwood site might show dense silty sand with N-values above 25 and a water table at five meters: liquefaction risk is negligible under the design earthquake. The Lake Driveway site, however, sits on hydraulically-placed fill over natural beach sand, with groundwater at 1.8 meters and corrected blow counts in the single digits. The difference in foundation cost between the two can exceed sixty percent once seismic mitigation enters the equation. Ignoring this contrast during the planning phase is the fastest way to a stop-work order once the geotechnical peer review flags the missing liquefaction chapter. Our reports quantify the risk with a factor of safety for every sublayer, so the structural engineer can decide between ground improvement, deep foundations, or a mat slab with controlled settlement expectations.
Video overview
Reference standards
NCEER Workshop (Youd & Idriss 2001) — Liquefaction triggering procedure, ASTM D1586-18 — Standard Penetration Test, ASTM D422 / D6913 — Grain-size analysis for fines content, NBCC 2020 — Seismic hazard values for Ajax, Ontario, Ontario Building Code (O.Reg 332/12) — Site Class and foundation requirements
Other technical services
SPT-Based Liquefaction Triggering
We run the Youd-Idriss (2001) procedure on each blow-count interval, correcting N60 for hammer energy, overburden, and fines content—then report the cyclic stress ratio versus cyclic resistance ratio for your site.
Post-Liquefaction Settlement and Lateral Spread
Using Zhang et al. (2002) and empirical lateral displacement curves, we estimate vertical settlements and horizontal deformations under the design earthquake, critical for infrastructure near Duffins Creek marshlands.
Ground Improvement Verification
After treatment with stone columns or vibrocompaction, we re-test with CPT to confirm that the densified soil exceeds the target safety margin specified in the geotechnical report.
Site-Specific Seismic Hazard Assessment
For Class 3 and 4 buildings under the Ontario Building Code, we prepare the Site Class determination and liquefaction chapter required by the peer reviewer, including PGA and magnitude scaling per NBCC.
Typical parameters
Questions and answers
How much does a liquefaction analysis cost for a single-family home in Ajax?
For a residential lot in Ajax, a complete liquefaction assessment including two SPT boreholes, lab grain-size testing, and the NCEER analysis report typically falls between CA$3,840 and CA$5,440. The range depends on access conditions, depth to refusal, and whether we need to add CPT soundings for thin-layer detection.
What soil types in Ajax are most susceptible to liquefaction?
The clean to slightly silty sands found in the Duffins Creek floodplain and along the Lake Ontario waterfront are the most susceptible. These are geologically recent deposits—post-glacial and alluvial—with low relative density and a shallow water table that keeps them permanently saturated.
Does the Ontario Building Code require a liquefaction study for my project?
Under the OBC, a liquefaction assessment is triggered when the site is classified as Site Class F or when the geotechnical investigation reveals loose saturated sands within the top 15 meters in a moderate-to-high seismic zone. Ajax falls within the Western Quebec influence region, so most commercial and multi-residential projects on the south side will require it as part of the foundation design submission.