Pearson International: Roads, Bridges and Project Management

When the new passenger terminal at Toronto’s Pearson International Airport opens in October, Canada’s largest concentration of bridges ever built on a Canadian site — 64 in total — will stand as a monument to some challenging engineering design.

Ted Zander, P.Eng., general manager of construction services for the Greater Toronto Airports Authority, says, “I don’t know of any other site that has as many bridges.”

The prime challenge to consulting firms Holmes & Narver Canada and UMA Engineering, which form the Greater Toronto Airport Groundside Association (GTAGA) joint venture, was to replace the old airport access, basically a two-lane road, with a multi-lane road-bridge system capable of accepting future traffic volumes from nearby highways.

The project was divided into two main areas: the “on-site” region close to the three terminal buildings, and the “off-site” section covering the widening of a 1.5 kilometre stretch of Highway 409 leading into the airport.

Because a large portion of the on-site region would be occupied by enormous footprints created by the garage (40,000 m2) and the terminal (80,000 m2), GTAGA designed a new infrastructure that is essentially elevated throughout.

The new road/bridge layout is roughly the shape of a racetrack, with the east end running between the new terminal and garage, and the west end, which will receive traffic from nearby highways, a spaghetti of spans going under and over each other. Some spans are 18 metres high.

The infrastructure, with a construction price tag of $325 million, is enormous. Zander uses “single-lane equivalence” to describe the project’s magnitude: “Everything amounts to 84 kilometres of single lane roadway and 20 kilometres of single-lane bridges.”

The largest structures are the elevated frontage roads, or access ramps, in front of the new terminal. When six-storey concrete bridge columns took shape in the fall of 1999 for the frontage roads, airport visitors thought they were the beginning of the new terminal. Designed by Hatch Mott MacDonald, the 40-metre wide, 900-metre long frontage road system required 60,000 cubic metres of concrete. The structure won a Canadian Consulting Engineering Award in 2001.

The airport’s entire bridge network was divided into structural steel “bathtub” girders and poured-in-place, post-tensioned, concrete voided superstructures. Judy Knight, P.Eng., GTAGA’s project director, says steel was chosen for about 25% of the project where spans would be crossing existing roads, ruling out the erection of deck formwork shoring. The other 75% consists of concrete bridges that curve in every direction. The bridge-road system was fast-tracked so that contractors could mobilize shortly after design work started.

The big challenge was to carry out construction while keeping the airport open. Knight says the key was for the GTAA to tender the work in small packages, interrupting the landscape as little as possible and minimizing detours. “You literally would build 40 feet, divert the traffic, build the next 40 feet, and so on.”

Another important factor was plenty of detour signage. Ironically, traffic accidents were reduced by 60% during the five-year program, no doubt due to establishing workable detours and keeping the speed down.

The terminal, garage and infrastructure are all on the public, or groundside portion of the airport. Everything else — aprons, runways, and hangars and service buildings — are within the airside section.

Part of the airside infrastructure includes a four-lane, 549 metre tunnel that is much stronger than a typical roadway tunnel because it passes beneath three taxiways and a runway, and has a 1,200-mm thick roof. Completed in 2000 under a $40-million contract, the structure took shape in 15-m long sections requiring 60,000 cubic metres of concrete. The twin-cell, four-lane tunnel is used to transfer goods and services throughout the airside region, and more recently, to move passengers to a temporary infield terminal as the old Terminal 1 is decommissioned.

George Peers, P.Eng. is a freelance writer living in Toronto.

Groundside planning and design: GTAGA/UMA Engineering and Holmes & Narver Canada (Judy Knight, P.Eng.)

Groundside review: MGP (MMM/Giffels/Parsons)

Construction administration: Earth Tech, Morrison Hershfield, Cole Sherman/HCIO

Airside underground tunnel design/construction: Morrison Hershfield, Acres, Delcan, Sverdrup Civil

Terminal frontage road bridge, tunnel extension: Hatch Mott MacDonald

Construction: Dufferin Construction, Bot Construction