The 2020 National Building Code of Canada (NBCC), together with CSA A23.3, places clear emphasis on Site Class determination based on shear-wave velocity profiles, and in Burlington this becomes particularly relevant where the Queenston Shale transitions into limestone and dolostone of the Lockport Formation. The Halton till that blankets much of the Niagara Escarpment corridor masks the true bedrock surface, making borehole-only investigations incomplete. We run seismic tomography lines—both refraction and high-resolution reflection—to map the overburden-bedrock interface continuously, rather than inferring it from scattered point data. The 43.3°N latitude means we deal with a distinct freeze-thaw cycle that affects near-surface velocities seasonally, so we document ground conditions at time of acquisition for defensible interpretation. When the objective includes rippability assessment or mapping fracture zones within the upper bedrock, combining tomography with seismic refraction profiling gives us the P-wave velocity structure, while a MASW survey provides the complementary Vs profile needed for Site Class E or D evaluations under NBCC Table 4.1.8.4.A.
A continuous velocity cross-section from seismic tomography reveals the bedrock topography that scattered boreholes miss—critical in Burlington’s escarpment terrain.
