Project Spotlight: Imperial Street, Burnaby

Project type: 30-storey residential tower with four levels of below-grade parking. The parkade is close to the property lines on all sides, so excavation support, groundwater control, and foundation recommendations were coordinated from the outset.

What we did

• Deeper subsurface program for a 4-level parkade: We advanced sonic drilling to approximately 15 m (about 50 ft) to characterize the bearing horizons and groundwater behavior at the bottom of excavation, building on the earlier investigation and groundwater review for the site. Findings are consistent with dense to very dense silty sand and till-like soils suitable for conventional foundations where verified.  
• Seismic site characterization (MASW): Two MASW lines were completed for code-based seismic inputs. The measured Vs30 values were about 518–524 m/s, supporting a stiff profile for design.
• Shoring and excavation strategy: On three sides, shotcrete with tie-back anchors was planned, with removable anchors within 10 ft of existing grade to meet municipal requirements. On the restricted side, where non-encroaching shoring was required due to neighbour constraints, we used internal rakers and walers to keep all support within the property boundary, then staged excavation to the design subgrade elevation.

Groundwater and construction staging

Low-permeability soils and perched water were anticipated at times. The plan relied on weepholes through the shoring face, local sumps and pumps, and erosion and sediment control compliant with City requirements. This approach keeps the prepared foundation subgrade workable and limits softening of fine-grained soils prior to concrete placement.

Foundation recommendations and field reviews

Conventional pads and strips on verified very dense native soils were targeted, with service settlements estimated within typical limits when bearing levels are protected and approved during geotechnical field reviews at the bottom of excavation. Bearing checks, blinding where needed, and clean release memos kept the excavation moving on schedule.

Results

The combined program provided site-specific seismic inputs, a deeper characterization for the four-level parkade, and a shoring scheme that respected neighbour constraints on one side without encroachment, while maintaining practical groundwater management and buildable bearing recommendations