As the only airport within Toronto’s boundaries, Billy Bishop Toronto City Airport prides itself on convenience. It’s located just minutes from the downtown core, "on the doorstep of the financial district," and accessible by car, public transit, bike and foot…and then a 90-second ferry ride.
The airport is located 121m away from downtown Toronto on an island on Lake Ontario. To put this in perspective, the gold medalist at this summer’s London 2012 Olympics, Nathan Adrian of team USA, swam the 100m freestyle in 47.52 seconds.
In March, a groundbreaking ceremony announced financial close on the Billy Bishop project.
Along with Toronto mayor, Tom Ford, Canada’s Prime Minister Stephen Harper attended the event to express his support for the project. "Toronto is a world-class city and airports in world class cities must provide world-class service," he said in announcing regulatory changes to help clear the way for construction.
"As much as we all like the ferries, and I have all kinds of great memories riding them as a boy, lining up for one when you are rushing for a plane does not qualify as world class."
While the airport is much smaller compared the city’s international airport, limited to flights in and out of Canada and the US, in 2011 alone 1.55M passengers went through Billy Bishop and that number is expected to grow.
In 2014, passengers at the city airport will arrive from the mainland through a pedestrian tunnel with a total of four moving sidewalks. The ferries will still run every 15 minutes as they do now to transport materials needed at the airport, such as fuel.
Paying the way
In proposal documents, the Toronto Port Authority (TPA), which owns and operates the airport and the tunnel project, explained, "the ferry service creates inherent problems with airport operations, particularly on the mainland side. Passenger activity here is highly peaked as it is linked to the ferry schedule, which discharges all passengers from single or multiple flights at the mainland terminal at the same time. Pick-up activity associated with a ferry arrival extends for five minutes or less, followed by 10 minutes of inactivity until the next ferry arrival (or longer, if there has been no subsequent flight)."
TPA chose to procure the project through a public-private partnership (PPP) because it would reduce costs, ensure on-time and on-budget delivery of the project and enhance the potential for innovations in public infrastructure, according to planning documents.
Construction is being financed over time by passengers, through an Airport Improvement Fee of CAD 20 (USD 20.4) included in their flight cost. The TPA selected Forum Infrastructure partners for the PPP in December 2011. A shortlist of consortia had been previously announced in April.
Forum Infrastructure Partners is responsible for the design, construction, financing and maintenance of the tunnel and will be responsible for operating the project for a period of 20 years. The consortium is led by Forum Equity Partners, a privately-owned Canadian infrastructure development and investment firm that specialises in PPPs and other public sector development. Construction responsibilities are contracted with PCL Constructors, with Technicore Underground as the tunnelling subcontractor. Project design is led by U-based firm Arup, with ZAS Architects and Exp geotechnical engineers. Facility management responsibilities are contracted with Johnson Controls.
The tunnel project will be privately financed at a cost of CAD 82.5M (USD 82.9M). It is scheduled to open in Spring 2014.
"Forum is very proud to be partnered with the Toronto Port Authority on the Billy Bishop Toronto City Airport Tunnel project," said Richard Abboud, president and CEO of Forum in March. "The Billy Bishop Toronto City Airport is today one of the most important and highest profile assets in our City. It is a key business and travel gateway bringing Torontonians and the world closer together. We are excited that in partnering with the Toronto Port Authority to deliver the Tunnel project, Forum can contribute to the Billy Bishop ‘success story’, and the quality of life and economic vibrancy of our City."
Professional advisors for the TPA include Dillon Consulting, NORR Architects, Hatch Mott MacDonald, Brookfield Financial, Deloitte & Touche LLP, Gowlings LLP, P3 Canada, Marsh Canada and P1 Consulting.
Digging the way
The tunnel will be constructed by excavating shafts on both the mainland and island sides of the airport to be connected by the tunnel. The mainland shaft will eventually house six elevators and the island side will have three banks of escalators and two elevators. The contract also includes building additional facilities adjacent to the terminals.
That’s been an interesting challenge for the project’s lead designer, Jon Hurt, associate principal with Arup’s tunnel practice. "The shafts and the tunnel are being fitted like an airport standard building," he says. "For me that’s been a bit different from a normal tunnel project. It has architectural finishes, it has moving walkways in it, HVAC systems, fire alarm systems and things like that."
Shaft excavation started this summer. The mainland shaft has a depth of 45m while the island shaft will be more in the range of 35m to 45m. Excavations under the lake will progress uphill with a one per cent gradient in the first half, and four per cent for the second half. Both shafts are secant pile, reinforced with I-beams.
"What the contractor decided to do, rather than just dig out the width of the shaft and then bell all out at the bottom and mine it all out, they’re just going to dig the whole shaft down the full width of the lobby to the bottom and then we’ll build the elevator core and backfill around it," says Hurt.
On the mainland side the contractor will install a gantry crane above the shaft to remove spoil. Because the only way to access the island side of the project is by ferry, all cement trucks, cranes and other construction vehicles and equipment must wait and board, just like Billy Bishop passengers. Though not for the entirety of the project – cement will be piped through the tunnel from the mainland worksite.
Once the shafts are complete the contractor will first drive a pipe arch of smaller 1.8m diameter tunnels, which will be filled with concrete to form a protective canopy. Depth beneath the lake is between 25m and 45m.
"Just given the unknowns of going beneath the channel we wanted to be sure we’re in pretty good rock so we gave ourselves extra cover," Hurt says.
The ground is mostly shale with 8m of overburden materials. The rock gets slightly deeper as the alignment goes out to the lake. "It’s slightly more fractured on the island side, in the upper sections," says Hurt, "But the depths we are in, it should be pretty consistent."
There aren’t any major concerns for ground water ingress either. "It’s always a risk that we’ll hit some fault or something," he says. "It’s very difficult to pick up a horizontal feature, so is a vertical feature even on land, but on a lake it’s even harder. That’s why we are going through first with the 1.8m bores. They can be much more easily controlled than a 10m-wide face."
Technicore has two TBMs available for the five drifts, which should each take only a few weeks to excavate (figure 2). The sequence may change depending on whether the second machine is used. "It’s very much like a secant pile wall," says Hurt. "The aim is to either do it so it’s completely in rock or it has a concrete filled tunnel on each side, and to mine through and fill it with concrete pretty quickly once it’s through."
PCL is installing a concrete batching plant on the Malting Lands (adjacent to the airport), which will virtually eliminate cement trucks on the already congested streets near the airport. Once the drifts are complete, concrete will be pumped through a sleeve in one of the five bores to be used on the island. Cement trucks will no longer need to catch the ferry. Running parallel to the tunnel alignment is a utility tunnel from the early 1900s roughly 2m in diameter. This is really the only notable excavation under the lake and near the project site prior to the tunnel project. There aren’t many details from its construction and it’s currently flooded, says Hurt. "Not because the tunnel failed, but the water main running through it eventually got so old that it leaked. I think they patched it up, but one of the things we’re doing is we’re putting in a new sewage main as part of our project."
He adds, "the good thing is we know they got across okay."
The biggest concern for the shale is time dependent formation and how much pressure the swelling will put on the cast in place concrete lining. "Understanding the exact parameters of how it’s going to work is a big focus," Hurt explains. He adds, "We did some additional boreholes since we got the job. We’ve been running tests at the University of Western Ontario."
The tunnel will be excavated using the sequential excavation method and will have a 10m inside diameter. Lining is likely to be 200mm, with the invert and side walls conventionally reinforced and steel fiber in the crown. Though there are different scenarios depending on the swell and the time duration between the excavation and lining installation.
Tunnels visited the project’s work site in August as the shaft excavations were underway. At the mainland shaft, the crew was about 3m into the rock. On the island side, crews had completed all the female secant piles and were going around filling in the holes. Hurt provided an update as Tunnels went to press. Work on the mainland shaft was continuing, and bracing was being installed in the island side excavation