Invest Saint Lucia Headquarters, Pointe Seraphine
Challenge
The proposed seven-storey headquarters site spans two markedly different ground environments: a steep volcanic rock slope intended to carry the main structure, and an adjoining reclaimed waterfront taxi-stand area, beneath which reclamation fill of unknown thickness was suspected to extend to significant depth.
Scope
Test pit excavation and block rock sampling along the slope; DPSH soundings and an MASW survey across the reclaimed taxi-stand platform.
Methodology
Along the slope, a mini-excavator fitted with a hydraulic rock breaker exposed the underlying rock mass at five locations, recovering representative block samples for strength testing. Across the reclaimed platform, three DPSH soundings assessed penetration resistance and fill thickness, while MASW testing established the shear-wave velocity profile and seismic site classification of the reclaimed ground.
Findings
The rock slope was confirmed as a competent, high-strength founding material, with unconfined compressive strengths ranging from approximately 17 to 143.5 MPa, and classified as Seismic Site Class C. The reclaimed taxi-stand platform was found to comprise loose to medium-dense granular fill extending beyond 20 m depth in places, with a Vs30 of approximately 212 m/s corresponding to Site Class D, and shallow groundwater connected to the surrounding marine system.
Outcome
The investigation established that the rock slope can support shallow foundations directly, while the reclaimed platform requires deep foundations, giving Invest Saint Lucia a clear, site-specific foundation strategy for two structurally distinct portions of a single development.
