Ottawa sits at roughly 70 meters above sea level, on a basin of sensitive Leda clay and glacial till that amplifies seismic motion in ways a standard borehole log doesn't capture. The 2010 Val-des-Bois earthquake — a magnitude 5.0 centered just 60 km north — rattled downtown towers and triggered dozens of slope failures along the Ottawa River, reminding engineers that the capital region is in a moderate seismic zone where site effects matter. A MASW survey measures shear wave velocity directly from the surface, delivering the Vs30 value that the National Building Code of Canada uses to assign site class from A to E. Without that number, you're guessing at the spectral acceleration your structure actually needs to resist. We run the test in parking lots, vacant parcels, and pre-construction pads across Nepean, Kanata, and Orleans, often pairing it with CPT soundings to tie velocity profiles to tip resistance and sleeve friction in the same soil column.
A fifteen percent error in Vs30 can shift your site class from C to D under NBCC, doubling the design spectral acceleration — and the foundation cost.
