History and Evolution of Deep Foundations and Excavation Shoring in Toronto, Canada-Paper

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Over the past five decades, Toronto’s deep-foundation and excavation-shoring industry has evolved in response to rapid urban growth, increasingly complex projects, regulatory change, and advances in equipment and design.<br /><br />In the 1970s, most excavations were relatively shallow, and impact-driven piles, sheet piles, and pile-and-lagging systems were common. Rakers and internal bracing supported excavations, while tiebacks gradually gained popularity as projects deepened. Contractors relied on mechanical and crane-mounted rigs, often operated by highly experienced workers. Continuous flight auger piles appeared in the 1990s, but pile driving remained attractive where conditions allowed.<br /><br />A major turning point came with Toronto’s 2008 vibration-control bylaw, prompted by noise and vibration complaints. Monitoring and stricter vibration limits made conventional pile driving and driven casings impractical on many urban sites. Contractors responded by investing in European hydraulic drilling rigs, which offered quieter, more precise installation and could operate in difficult soils and groundwater conditions. These machines helped enable much deeper excavations and foundations, including secant walls extending to about 60 metres and basements with as many as eight parking levels.<br /><br />Modern drilling has also improved wall quality and reduced reliance on wood lagging, helping limit ground movement near adjacent properties. The transition required operators to develop new technical skills and work with increasingly computerized equipment. Diaphragm walls have recently been introduced on sites requiring deep groundwater cutoffs, though their future use in Toronto remains uncertain.<br /><br />The industry has also changed beyond construction methods. Contracts have grown from short, simple agreements to lengthy, risk-focused documents, while hand-drafted drawings have given way to CAD, 3-D, and Revit-based coordination. Overall, Toronto’s experience shows how regulation and urban development accelerated technological change, enabling contractors to meet tighter movement limits and deliver increasingly deep and demanding projects.

Keywords

Toronto deep foundations

excavation shoring

vibration-control bylaw

hydraulic drilling rigs

secant walls

diaphragm walls

tiebacks

continuous flight auger piles

ground movement control

urban excavation projects