The goal of the project was to enhance the transportation functions of the station, implement capital improvements and revitalize it as a destination by preserving and restoring its heritage character as a designated national historic site.
The site’s considerable spatial limitations and heritage conservation constraints made expanding the concourse, improving its services and creating viable retail space an enormous challenge.
Norr, the project architect and engineer, engaged WSP to consolidate existing geotechnical and geo-environmental reports for Union Station. This phase of the $900 M project involved the ‘dig-down’ of the existing basement of the historical building by an additional three to four metres to accommodate a new retail concourse and linkage with the adjoining TTC Station.
As with many projects in Toronto’s downtown, it was necessary to consider rock creep as a potential source of exceptionally high lateral pressure on tunnel walls as a result of a phenomenon called rock-squeeze. Soil-structure interaction analysis was undertaken to quantify the true impact of a possible rock movement on the tunnels. This was augmented by detailed monitoring of actual rock movement in the tunnel trenches. To mitigate the impact of excavating in rock close to the existing foundations an ingenious approach was improvised involving drilling holes roughly three metres apart to the desired excavation depth and running steel wires to saw cut the shale. This method produced perfectly intact, almost polished, vertical surfaces in the rock.
The initial project scope was broadened to include value-engineering of many aspects of the work including the micropiling support of the existing columns (carrying rail traffic above), excavation support for perimeter shoring and internal egress tunnel and soil waste classification. The project team also conducted construction quality assurance services including concrete and grout testing, inspection of waterproofing, reinforcing and anchor proof/performance load testing.
WSP provided inspection and testing services for structural steel, fireproofing, concrete and building envelope services for the below-grade and above-grade components as related to waterproofing and glass moat cover and re-roofing installations in addition to condition assessment services of existing structure column, walls and floor slab. Structure-proof load testing services was also provided at various site locations to determine of loading capacity. Vibration and settlement monitoring services were provided for the excavation of proposed basement structure and the demolition of all existing structures within the site.
- Geotechnical Investigation
- Environmental Investigations
- Quality Assurance
- Materials Inspection and Testing