In St. Albert, many geotechnical investigations miss critical transitions between the surficial glaciolacustrine clays and the underlying Cretaceous bedrock. A dozen boreholes can provide discrete data points, but they rarely capture the lateral continuity of buried channels or the irregular bedrock surface shaped by preglacial erosion. Our team addresses this through seismic tomography, deploying both refraction and reflection arrays along proposed infrastructure corridors or beneath future building footprints. While a conventional SPT drilling program defines soil stiffness at specific stations, the tomographic profile interpolates those values continuously across the site, revealing velocity anomalies that could indicate loose infill, fractured shale, or sand lenses within the till. For projects near the Sturgeon River, we often combine this with MASW to extract shear-wave velocity profiles for seismic site class determination per NBCC 2020. The result is a ground model that integrates point data and spatial imaging, reducing the risk of encountering unexpected conditions during excavation or piling in the city's west-end developments.
Tomographic inversion converts travel-time picks into a spatially continuous velocity field, bridging the gap between scattered borehole logs and the true three-dimensional ground structure.
