Subsurface Condition Assessment, Syncrude Refinery Canada, AB
Alberta, Canada
Incident Overview
A mobile crane collapse occurred at Syncrude Refinery due to an unseen underground void beneath the concrete crane pad (See Pictures 1, 2 and 3). No Ground Penetrating Radar (GPR) scan had been conducted by plant engineering or the crane and rigging department prior to crane setup. Additionally, outrigger positions were not evaluated to confirm that the ground conditions could adequately support the crane’s dead weight and load distribution.
Picture 1
Pictures 2 and 3
To prevent similar incidents, pre-placement load-bearing capacity investigations and subsurface condition assessments should be performed on crane pad locations before lifting operations.
Scan Area & Methodology
Following the collapse, GPR scanning was conducted to assess the perimeter of the void and determine its lateral extent. A 350MHz Hyper Stacking System was deployed to collect high-resolution radar data, ensuring a thorough subsurface evaluation.
Scan Line Spacing - 16-inch intervals, allowing for dense data collection and detailed imaging.
Safe Work Practices - All scans were conducted with adherence to refinery safety protocols.
Radar Image Analysis - The collected data provided a visual representation of subsurface anomalies.
Pictures 4 (typical sinkhole formation) and 5
Findings & 3D Imaging Analysis
Sinkhole Formation Detected - The radar cross-section revealed a distinct V-shaped void, indicative of sinkhole formation beneath the surface.
3D GPR Image Processing - After data collection, a 3D radar image was generated onsite, allowing for immediate analysis (See Picture 6).
Void Outline Marking - The hidden void was mapped and marked on the surface, guiding the mitigation response.
Underground Utility Mapping - The rader image also identified and marked buried pipelines (represented by blue lines in the imaging results, See Picture 6).
Pictures 6 - Interpolated 3D GPR image rotated in plan view
Engineering Response & Risk Mitigation
A licensed geotechnical engineer assessed the site and implemented remediation measures to stabilize the affected area. Moving forward, subsurface assessments should be integrated into standard pre-lift procedures to:
Verify ground stability at crane pad locations.
Identify voids, sinkholes and underground hazards before setup.
Prevent structural failure and minimize operational risks.
By utilizing non-destructive evaluation (NDE) methods, including GPR scanning, load-bearing capacity assessments and utility mapping, facilities can significantly reduce the risk of crane failures and enhance safety in heavy lifting operations.
