Toronto’s historic Union Station, which has been the city’s rail hub since 1927, is currently undergoing four concurrent, but separate, revitalization projects. Together, the projects will expand passenger amenities and increase the capacity of the station. Courtesy of Vahagn Stepanian, NORR Limited
Toronto’s historic Union Station is undergoing significant revitalization work that includes simultaneous work above and below the existing tracks.
October 22, 2013—The City of Toronto is one of Canada’s most densely populated, a fact that would make any major transportation infrastructure project difficult. Layering major construction projects atop one other—in terms of both time and space—has the potential to bring movement in an urban environment to a complete standstill. But that fate has been avoided at the city’s historic Union Station, the city’s primary rail hub since its construction in 1927 and now undergoing a number of concurrent, but separate, revitalization projects.
The station is recognized as a historic site by the country’s cultural and resource heritage protection agency, Parks Canada. According to the agency, the station’s heritage value “lies in both its architectural presence as the country’s most outstanding example of Beaux-Arts railway architecture and its historical role as one of the most significant hubs in the Canadian transportation network.”
Most days typically see 250,000 passengers pass through the multimodal station, according to the city’s website, so limiting or shuttering rail service while completing the work on each of the construction projects was not an option. The design teams came up with complementary renovation schedules that enabled the rail hub to remain fully operational while work on each of the projects was completed—including work directly below and directly above fully operational rail beds.
The revitalization effort of the five-story station is being completed by the City of Toronto, and includes excavation work under the existing train beds so that 125,000 sq ft of new concourse space can be added. At the same time this work is being completed, Toronto-based, regional transportation agency GO Transit is replacing the train shed roof that covers its tracks at the station.
When the station was initially built, it contained a sunken “moat”
around its perimeter edges. One of the projects involves
constructing a glass roof over the moat to create a comfortable
space for pedestrians. Courtesy of NORR Limited
“Usually in renovations of train stations, service to the station is reduced or eliminated altogether; this is particularly possible in cities with multiple stations,” said Lesley Thompson, the manager of the Union Station train shed project at GO Transit, who wrote in response to questions posed by Civil Engineering online. “In this case, not only are we renovating the station around operating trains, including building a whole new roof, but the city is altering the foundations of the station under operating trains.”
As the trains approach Union Station, they finish their journey atop track beds located on a suspended concrete slab, Thompson explained. Above the slab, the GO Transit engineering team was responsible for creating a new 300,000 sq ft, light-filled, atrium-like roof to cover the trains. Below the slab, the city’s engineers were responsible for reinforcing the existing 447 columns that supported the concrete slab on which the train tracks lay so that the earth could be excavated an additional 4 m in depth, the columns extended, and new foundations constructed in a “dig down” project.
The level of “coordination between two distinct engineering teams—one for the structure and systems above the suspended slab supporting the tracks and another for the structure and systems below the slab—is unusual,” Thompson said. “The teams had to become very good at sharing ideas and information back and forth.”
“When you excavate several meters below the floor or start tearing through walls of a nearly 100-year-old building, you will find unexpected things,” said Rick Tolkunow, P.Eng., the principal engineer of the Union Station revitalization project for the City of Toronto. Tolkunow responded in writing to questions posed by Civil Engineering online. Each night, between 600 and 900 metric tons of soil are excavated from the site as part of the underground work, according to the city’s website.
“There’s really no way of knowing what’s underground or behind a wall until you actually go in and start working,” Tolkunow said. “Unforeseen site conditions have to be dealt with as they come up, and this often takes time. But the city’s biggest challenge continues to be maintaining full station operations throughout construction for the convenience of the travelling public, while maintaining a safe environment for pedestrians and workers.”
Excavation work under the station is carefully choreographed
because each column needs to be supported and then extended
while trains continue to operate atop the concrete slab. A total of
125,000 sq ft of new space will be added to the station as a result
of the “dig down” project. Courtesy of Vahagn Stepanian,
Additional work taking place at the station includes a new subway platform within the underground portion of the station, which is being added by the Toronto Transit Commission, and a new underground pedestrian connection to the station from Toronto’s existing 29 km long underground shopping and entertainment network, called PATH. The new connection is being added by the city.
The global engineering firm Arup was brought on board to model pedestrian movements through the station in the preconstruction stage through the four major stages of construction. “We built some quite sophisticated models of the train schedules, the three-dimensional layouts of the station, [and] the surrounding neighborhood—the total area modeled was probably a kilometer and a half by a kilometer and a half,” says Erin Morrow, LEED-AP, a senior consultant in the Toronto office of Arup and the firm’s project manager for the modeling work on the station.
“Basically, what we were doing with the models was providing feedback to the designers and the stakeholders on where things were going to be working, where they weren’t going to be working, and problems that could be expected, and then using that information to come up with solutions,” Morrow says. “And then, testing those solutions to make sure that they actually would work.” (Videos of the modeling are available online.)
The program his team created, on Arup’s proprietary MassMotion simulation software, was so successful at modeling the three-dimensional environment—including individual passengers who could each make their own impromptu decisions in response to congestion—that the software was released to the market for sale, according to Morrow. Arup developed the software for the Union Station project as well as for the Fulton Center transportation hub in New York City.
The aboveground and belowground work being completed at Union Station is expected to be fully complete by 2016. Currently, the “dig down” portion of the revitalization is nearing the end of its first stage, which includes column modifications, according to Tolkunow.