Applying base isolation seismic design in New Westminster goes well beyond standard structural detailing—it demands a thorough understanding of local ground response shaped by deep alluvial deposits and the proximity of the Fraser River. The city sits within a high-hazard zone under the National Building Code of Canada (NBCC 2020), with Site Class D and E profiles dominating the lowland areas and long-period amplification that can penalize conventional fixed-base construction. In our experience reviewing projects near the Skytrain corridor and the downtown densification belt, the decision to isolate the superstructure is often driven by the need to protect critical functions and control interstory drift, not just to meet base shear targets. A well-designed isolation system reduces floor accelerations and allows the building to ride out the long-duration shaking that characterizes Cascadia Subduction Zone events. For sites where borehole data confirms soft cohesive soils extending past 30 m, we often recommend coupling the isolation analysis with a seismic microzonation study to refine the site-specific spectra before finalizing the isolator properties.
Long-period amplification on New Westminster’s deep alluvial soils can turn a fixed-base structure into a resonant oscillator—base isolation decouples the building from that specific hazard.
