Sudbury sits on complex glacial lake deposits. The old Lake Algonquin left thick sequences of silty sand here. A 5.0 magnitude earthquake in 2000 reminded everyone the region is seismically active. In our experience, loose saturated sands in the Valley area raise immediate liquefaction flags under NBCC 2020. The challenge is not just the shaking. It is the high groundwater tied to the 330 lakes within city limits. When we run a liquefaction analysis, we look at the full picture. A CPT test gives us the continuous profile needed to spot thin loose layers. For sites near tailings or filled ground, we also run grain size analysis to check the fines content against the seed criteria. The data drives everything.
A dense sand layer can hide loose sand beneath it. Sudbury's glacial history creates exactly these hidden profiles.
Our approach and scope
Site-specific factors
NBCC 2020 Article 4.1.8.16 mandates liquefaction assessment for Site Class F soils. Sudbury has plenty of those. Loose saturated sands in the Valley and around Ramsey Lake classify as Site Class E or F. Miss that assessment and you risk differential settlement of up to 200 mm in a design earthquake. We see it mostly in older neighborhoods where fill was placed directly over swampy ground. The consequence is structural damage to foundations and buried utilities. Our reports provide a clear FS against liquefaction. We also calculate post-shaking settlement. The guidance from the Canadian Foundation Engineering Manual is our baseline. For critical infrastructure, we push the analysis further with advanced laboratory testing on undisturbed samples.
Reference standards
NBCC 2020 (National Building Code of Canada), CSA A23.3: Design of Concrete Structures, ASTM D6066: Standard Practice for Determining the Normalized Penetration Resistance of Sands, Canadian Foundation Engineering Manual (4th Edition)
Complementary services
CPTu Sounding
Piezocone testing to capture continuous tip resistance and pore pressure. Ideal for identifying thin liquefiable seams in Sudbury's layered glacial deposits.
Laboratory Cyclic Testing
Cyclic triaxial or direct simple shear tests on undisturbed samples. We determine the actual CRR for high-sensitivity silts found near Junction Creek.
Ground Improvement Verification
Post-treatment CPT checks to confirm that vibrocompaction or stone columns have achieved the target density. Required for building permit closure in high-risk zones.
Typical parameters
Frequently asked questions
What triggers a mandatory liquefaction study in Sudbury?
The Ontario Building Code references NBCC 2020. A study is mandatory when the water table is within 3 m of the surface and the soil profile contains loose sands with N60 below 15. Large areas of the Valley and floodplain meet this condition.
How much does a soil liquefaction analysis cost for a residential lot?
For a standard single-family lot in Sudbury, a complete analysis including CPT soundings and a signed engineering report typically falls between CA$3,810 and CA$5,820. The final figure depends on access constraints and the depth of investigation required.
Can shallow bedrock eliminate the liquefaction risk completely?
Yes. Bedrock at less than 3 m depth eliminates the risk. However, we must verify that the 'rock' is not a boulder pavement. A seismic refraction line confirms the true bedrock depth and rules out floating boulders in the till.