The CPT rig sets up fast on Clarington’s glacial till. A 20-ton truck with hydraulic rams pushes a cone penetrometer at 2 cm per second, recording tip resistance and pore pressure every 10 mm. No drilling, no cuttings. For sandy zones near the Lake Ontario shoreline, we pair this with SPT drilling to capture split-spoon samples for grain-size distribution. The cone tells us the soil’s density and drainage potential; the sample tells us whether the fines content is high enough to suppress excess pore pressure. Clarington sits on a complex mix of glacial sediments where sand layers, silty clay, and occasional gravel lenses alternate across short distances. The seismic hazard is real. Southern Ontario has a 2% in 50-year probability of significant ground shaking, and the NBCC 2020 maps assign a PGA around 0.12 to 0.15 g for the area. That is enough to trigger liquefaction in loose, saturated sands below the water table.
Loose sand below the water table at PGA above 0.12 g is not a theoretical risk in Clarington — it shows up in SPT N-values under 6 at 3 to 4 meters depth in Courtice.
Methodology and scope
Local ground factors
We see a recurring issue in Clarington: builders treat the upper 1.5 m of stiff clay as proof the site is fine, then hit saturated sand at 3 m during excavation. That sand layer, if loose, can liquefy and cause differential settlement that cracks slabs and tilts shallow footings. The risk is not uniform across the municipality. Areas east of Oshawa Creek and south of Highway 401 have thicker sand deposits from the former glacial Lake Iroquois shoreline. The water table in low-lying zones near Bond Head and Port Darlington is often within 1.5 m of grade in spring. That combination — shallow water, loose sand, and moderate seismicity — produces a site that requires either deep foundations bearing below the liquefiable layer or ground improvement. Stone columns, vibrocompaction, or compaction grouting can densify the sand and increase the Factor of Safety. We provide the pre- and post-treatment verification data that the geotechnical engineer of record needs to sign off on the design.
Relevant standards
NBCC 2020 (National Building Code of Canada), Ontario Building Code O.Reg. 332/12 as amended, ASTM D1586-18 (Standard Test Method for Standard Penetration Test), ASTM D5778-20 (Standard Test Method for Electronic Friction Cone and Piezocone Penetration Testing), Youd et al. (2001) NCEER/NSF Liquefaction Evaluation Procedures, Robertson & Wride (1998) CPT-based Soil Behavior Type and Liquefaction Assessment, CSA A23.3-14 (Design of Concrete Structures, seismic provisions)
Associated technical services
Field Investigation — SPT and CPT
We mobilize truck-mounted CPT rigs and hollow-stem auger SPT rigs across Durham Region. The CPT provides continuous tip resistance (qc), sleeve friction (fs), and pore pressure (u2) profiles. The SPT delivers split-spoon samples for index testing and fines content. Together they produce the data needed for a defensible CSR-CRR analysis per Youd et al. (2001) or Boulanger & Idriss (2014).
Laboratory Index and Liquefaction Screening
Our ISO/IEC 17025-accredited lab runs grain-size distribution (ASTM D6913), Atterberg limits (ASTM D4318), and natural moisture content on every sample from potentially liquefiable layers. Fines content and plasticity index are key inputs to the CRR correction factors. We can also run cyclic triaxial or cyclic simple shear tests for high-importance structures requiring project-specific CRR curves.
Typical parameters
Common questions
At what depth is liquefaction a concern in Clarington?
Liquefaction typically occurs within the upper 15 m of soil, and is most common between 2 m and 10 m depth. In Clarington, the water table in spring can be as shallow as 1.5 m in areas near Bond Head and Port Darlington. Any loose sand below the water table and above 15 m depth should be evaluated. The NBCC requires liquefaction assessment when the site has sand with SPT N-values below 15, the water table is within 3 m of the foundation, and the PGA exceeds 0.12 g.
What is the difference between SPT-based and CPT-based liquefaction analysis?
SPT-based analysis uses the N-value corrected for energy, overburden, and fines content to compute the Cyclic Resistance Ratio (CRR). The method follows Youd et al. (2001) and is well-calibrated to field case histories. CPT-based analysis uses tip resistance (qc) and friction ratio to derive the Soil Behavior Type (Ic) and compute CRR via Robertson & Wride (1998) or Boulanger & Idriss (2014). CPT provides a continuous profile with no sample disturbance, and is faster and less expensive per meter. We often combine both: SPT for sample recovery and index testing, CPT for detailed stratigraphy and liquefaction screening across the full depth.
How much does a soil liquefaction analysis cost in Clarington?
What ground improvement methods work for liquefiable soils in Clarington?
The most common methods are vibrocompaction for clean sands, stone columns for silty sands, and compaction grouting for soils with higher fines content. Vibrocompaction uses a vibrating probe to densify sand to a target relative density, typically 70–85%. Stone columns provide drainage and reinforcement, reducing excess pore pressure buildup. Dynamic compaction is less common in Clarington due to proximity to residential areas. We provide pre- and post-treatment SPT or CPT verification to confirm the improvement has achieved the required Factor of Safety against liquefaction.
Does the Ontario Building Code require liquefaction analysis for residential buildings?
The Ontario Building Code references NBCC 2020 seismic provisions. For standard single-family homes classified as low importance (Category I), a full liquefaction analysis is not always triggered by code. However, if the geotechnical investigation identifies loose sand below the water table and the site is in a moderate seismic zone like Clarington, the engineer of record may recommend a liquefaction screening to satisfy due diligence. For multi-unit residential, schools, and any post-disaster buildings, the analysis is mandatory under NBCC.