The original village centre on Wilson Street of historic, Ancaster, Ontario, is filled with trendy boutiques, cafes, and shops housed in 1850's era stone and wood structures. The 249 Wilson St. W. site slopes toward the Dundas Valley with a 7 metre elevation variation from the highest to lowest point. A proposed expansion of the existing commercial space featured construction of a multi-story building and parking garage at the rear of the site. Excavation depths up to 10 metres below street grade and 5 metres below existing foundations were required, and the proposed excavation extended to within 2 metres of an adjacent property. Excavation support up to 10 m high was required to retain the adjacent property, and underpinning of existing footings to a depth of 5 m was also required while maintaining the building in service. Site topography and access restrictions precluded the use of conventional piling equipment.
Construction Manager Arguson Projects selected Geo-Foundations to provide a design-build excavation support and underpinning system for the project consisting, in both cases, of anchored shotcrete, constructed in a 'top down' fashion using light, compact drilling and excavating equipment. The mesh-reinforced shotcrete face was restrained by hollow-bar, grout-flushed soil anchors spaced at 1.5 m (both vertically and horizontally) for the earth support and 1.2 m for the underpinning. The highest section of earth support required 7 tiers of anchors; 3 tiers of anchors were required to restrain the deepest underpinning. Grouted vertical dowels were installed on 0.6 m centers at the underpinning wall in advance of shotcrete and anchor installation in order to provide vertical support in the final condition and temporary soil support during excavation. In total, 115 shotcrete panels, 115 soil anchors, and 20 grouted dowels were installed over a 6 week period. The building was completed in March 2011.
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