The Eglinton Crosstown LRT (light rail transit) Line project, the cornerstone of the overall C$8.4 billion investment, was announced in 2007 as part of the Transit City plan, which included the development and implementation of six other light rail lines across Toronto. The Eglinton Crosstown project is a 19 kilometres (11.8 miles) long LRT line that will bring much-needed relief to the transit woes of the residents of Toronto. The impact of this highly anticipated project on commuters in the Greater Toronto Area (GTA) is expected to be dramatic and immediate once the first train leaves the station in 2021 (anticipated). In fact, Metrolinx is estimating that, within its first 10 years of service, the Crosstown line will be carrying 5,500 passengers per hour (peak times) and making 100 million passenger trips annually. As with many of today’s mega public transportation projects, the Crosstown LRT follows the Public-Private-Partnership (P3) model. Aecon is an equal partner in the C$5.3 billion Crosslinx Transit Solutions (Crosslinx) consortium (along with partners ACS Infrastructure Canada, Ellis Don, and SNC-Lavalin). Upon the Crosstown LRT’s completion, Metrolinx, the region’s transit authority and project client/owner, will turn to the Toronto Transit Commission (TTC) to operate the line.
As one of the largest transit projects currently underway in North America, the Crosstown LRT involves a combination of 15 underground stations and 10 at-grade surface stops. Traversing the city in an east-west direction across the midtown artery of Eglinton Avenue, the line will run underground for more than 10 kilometres (6.2 miles), from Keele Street to Laird Avenue, then will continue for more than eight kilometres (five miles) on the surface to Kennedy Station.
Because of its enormous size, the overall construction project was divided into five different segments, with each segment valued between C$600 million and C$1.1 billion. Essentially, each segment operated as its own entity. Aecon Foundations was awarded four stations of Segment No. 2: Dufferin/Fairbanks, Bathurst/Forest Hill, Chaplin, and Mt. Pleasant. For the underground stations, a considerable amount of specialty foundation works was needed, including secant pile walls, soldier piles and wooden lagging, ground anchors, utility support structures, micropiles for underpinning working platforms, guidewalls, and struts/ steel bracing. The general scope and time constraints resulted in the following work being performed:
• Total of 2,157 piles installed
• 48,519 linear metres or Lm (159,183 linear feet or LF) of drilling
• 2,760 Lm (9,055 LF) of wall installed
• Pile lengths ranging from 10 to 42 metres (33 to 138 feet)
• Up to eight drilling rigs operating at the same time
• Up to six tie-back machines operating at the same time
Design Management and Project Concerns
Because of the numerous stakeholders involved, design management was one of the most challenging parts for this project. Aecon Foundations subcontracted the needed design work to Pedelta Engineering. The utilities required a significant amount of attention and coordination, as it was not intended to relocate them per the design concept. Another challenge was working around and not causing disturbance to the tunnels already installed under a separate contract prior to the installation of the shoring work for the new segments. The available right of way didn’t allow enlarging the station. In several areas, the piles for the shoring wall were as close as 12 centimetres (five inches) from the existing tunnel segments.
The project requirement for the drilling of the secant piles around and adjacent to the existing tunnel segments was a verticality tolerance of less than 0.5 per cent. The level of accuracy could be achieved using the support provided by the equipment suppliers and the Jean Lutz system. During drilling, the verticality was measured at three different levels, at the minimum. If the required tolerance was achieved at a depth of 15 metres (49 feet), only then could drilling be continued.