Repentigny sits at roughly 10 meters above sea level, stretched along the St. Lawrence River's north shore on a deep sequence of post-glacial marine clays. With over 86,000 residents and steady growth pushing development eastward into Le Gardeur and beyond, the question of seismic amplification keeps coming up in geotechnical reports. The 1988 Saguenay earthquake, a magnitude 5.9 event centered 300 km away, sent enough long-period energy through the region to remind engineers that distance doesn't guarantee safety. National Building Code of Canada (NBCC 2020) now requires site-specific shear wave velocity data for Site Class determination on projects exceeding certain occupancy thresholds. Our approach to seismic site classification integrates the MASW survey directly into the broader geotechnical investigation, eliminating guesswork when the borehole log hits stiff clay at 25 meters and you need to know what lies beneath.
In Repentigny, the difference between Site Class C and D often comes down to the shear wave velocity of just a few meters of desiccated crust overlying the Champlain Sea clay.
