Repentigny sits at an elevation of roughly 20 meters above the St. Lawrence River, on unconsolidated sediments of the Champlain Sea that can hide unpredictable bedrock topography. Our field team has applied seismic tomography across dozens of sites along the L'Assomption River corridor, where the contrast between stiff glacial till and underlying shale creates exactly the kind of velocity boundary that refraction surveys resolve. When a recent commercial development near Boulevard Brien encountered 8 meters of soft clay over weathered rock, the seismic refraction profile mapped the bedrock dip in a single morning. That same dataset fed directly into the CPT test layout, positioning soundings where the seismic velocity gradient indicated a transition zone. For deeper targets or urban noise conditions, reflection processing captures horizons beyond 30 meters depth, well past the reach of mechanical borings alone.
A 2D velocity tomogram gives you a continuous image of the subsurface—unlike a borehole that samples a single point.
