A new single family house is being constructed on a lakefront foreshore lot off Crabapple Drive in Whistler, BC. The proposed residence consists of two separate buildings connected by an overhead walkway. The property is bounded by residential lots to the north and south, Crabapple Drive to the east and Alta Lake to the west.
The proposed lakefront residential buildings are located on the north shore of Alta Lake. Stability of the lakeshore slope was assessed for seismic loading conditions by the geotechnical consultant. The analyses concluded the set back line from the crest of the lakeshore slope extended well into the building envelope, making it unfeasible to maintain foundation support if a flow slide event were to occur following the design earthquake. Restrictions on working within the riparian zone prevented the construction of an in-ground seismic dike along the waterfront. Therefore, lateral displacements due to a flow slide were mitigated by densification of the ground beneath, and some distance beyond, the building envelope. Vibro stone columns spaced on a uniform equilateral grid were considered the most appropriate method of ground improvement. Stone columns were installed using wet top-feed methods to a treatment depth of 18m below working site elevations. The ground improvement work was carried out within approximately 10m from the adjacent residences to the north and south. Vibration monitoring performed by the consultant verified peak particle velocities were maintained below the specified threshold levels. The Vibro stone column work achieved the specified performance criteria as measured by the Cone Penetration Test.