Future of Roads | Montreal remodels motorway interchange with carbon cost focus

Montreal’s Turcot Interchange dwarfs Spaghetti Junction at Gravelly Hill Interchange on the M6 in Birmingham. Now that a major remodelling project is complete, it also outdoes the UK interchange’s green credentials.

Main contractor KPH Turcot – comprising Kiewit, Parsons and CRH with WSP as lead designer – recently completed the six year C$3.7bn (£2bn) scheme to rebuild the Canadian motorway junction. The project is not only carbon neutral, it has created 31ha of new green space from what was once a concrete jungle.

Multi-level elevated road system

The interchange is a multi-level elevated road system with multiple structures connecting Autoroutes 15, 20 and 720. It is a vital local and regional link as it is on a key route between Montreal-Trudeau International Airport and the city’s downtown area.

The remodelling project has led to a “major greening” of the area, says Quebec Transport Ministry general manager Sandra Sultana. 

“We really wanted to bring a new look to the interchange,” she says. “It was very concrete before but now it is much greener.”

In total the project has liberated 31ha of space which has been planted with 61,000 shrubs and 9,000 trees.

Beyond the greening, the project’s environmental credentials are pretty astounding – it was the region’s first carbon neutral scheme with the 148,500t of CO₂ emitted during the project offset by planting or carbon credits. 

In addition, Quebec’s transport ministry set KPH Turcot the challenge of reusing or recycling 80% of the materials from demolishing the old structures on site. It beat the target, reusing or recycling 95% of this material.

The need to redevelop the junction was not just born from a desire to improve the environment. The interchange had reached the end of its design life and changes in the local area created an opportunity to do more than simply create a direct replacement.

Work on the original interchange started in 1965 and it opened just before the 1967 Montreal Expo. It was a critical transport link for the 50M expo visitors. 

The elevated design was driven by the need to take traffic over the Lachine Canal, a major railway yard and four rail lines. These meant the main carriageways and slip roads could not be built at ground level. 

Now, more than 50 years later, the canal only carries pleasure craft and the railway yards have been relocated, creating the potential for the remodelled junction to be built at a lower level.

Sultana says: “The current traffic flow is 300,000 vehicles a day.” This is significantly higher than the traffic flows it was designed for in the 1960s.

“The new interchange was built to bring it up to standard and improve traffic flow but not to increase capacity,” she adds.

“The old structure was at the end of its life – it was increasingly needing maintenance. The interchange was built on a number of piers and with very many structures, which were deteriorating. The extreme winter temperatures in Quebec mean that we use a lot of de-icing salt, and that had accelerated the ageing of the structures.”

We really wanted to bring a new look to the interchange. It was very concrete before but now it is much greener

The project to rebuild the Turcot Interchange, and three other junctions within the same road network, started in 2011 and was largely completed late last year with some minor work continuing this year.

It covers an area measuring 7km by 3km and involved rebuilding 145km of traffic lanes, as well as creating 10km of bus lanes and 8km of new cycle lanes. In addition to the new permanent structures, a number of temporary structures were built to allow some parts of the work to be completed while maintaining traffic flow without major road closures.

Parts of the work were designed by the Quebec government and delivered under contract in work packages in a conventional way with the client doing the design and the contractor the building. But 80% of the project was delivered by KPH Turcot under a design and build contract – which goes against the norm in North America.

“Planning for the upgrade project started in early 2000 but it took until 2011 for the scheme to go through all the necessary planning and stakeholder engagement processes. Preparatory work and the conventionally delivered work packages got underway in 2011 and KPH Turcot started the main work in 2015,” says Sultana.

“One of the main challenges was keeping the traffic moving throughout all of the work,” she adds. 

“To reconstruct the four interchanges we needed to carry out work that was beneath or beside the structure and then carry out demolition of the old structures as we were reconstructing.

“Putting forward the mitigation measures during the preparatory phases was important – we encouraged people to use mass transit. As part of that we created reserved bus lanes and redeveloped a bus terminal, as well as constructing a new train station.”

Working with all of the stakeholders was also a major challenge, according to Sultana. “The work was spread across several municipalities and we had to work with the Montreal  Transit Commission and federal government, as well as coordinate with work on other projects,” she says. 

“Just south of the Turcot Interchange, the Champlain Bridge [over the St Lawrence river] was also being rebuilt and the City of Montreal also had projects that it was developing – all of that has an effect on traffic movement.”

Kiewit project director Jean François Poulin adds: “It was a very complex project. Rebuilding the entire interchange below the existing one while keeping 300,000 vehicles moving and mitigating all the impacts.”

Communicating each stage of the work was something that the Quebec Transport Ministry and KPH Turcot took seriously. 

“Maintaining a good dialogue was important,” says Sultana. “We needed to be communicating with stakeholders, communicating with road users and communicating with other projects in the area. We made it an objective throughout the project to keep everyone informed of what was happening, of the progress being made, of the work to come and the anticipated obstacles.”

Communication with residents was also key as the interchange is spread through five different boroughs of Montreal. Some of the work to replace the interchange required work in people’s backyards – a particular challenge with the work going on around the clock. 

The Quebec Transport Ministry established “good neighbourhood” committees, which held meetings every six to eight weeks, to support the residents during the work and create constant dialogue.

In total 56 of the structures were rebuilt, resulting in 65% fewer structures than the original Turcot Junction. An 8M.m³ earthmoving operation within the site was also undertaken during the project. 

Closures of sections of the interchange were mostly limited to weekends and nights and there was only one four day closure of the whole junction during the six year project.

Poulin says the Lachine Bridge is an example of the challenge of building around the existing infrastructure. 

“The Lachine Bridge is a cable-stayed structure that carries the road over the Lachine Canal,” he says. 

“We had to build it in stages and a number of phases to fit with the schedule. The bridge passes under the existing highway 15 and had to be built around a forest of existing piers.”

At another location, Poulin says that a pier had to be saw cut so that a steel beam could be moved into position for a new structure. 

“The complexity of the work required a lot of planning,” he adds.

One of the main challenges was keeping the traffic moving throughout all of the work

If that was not enough, the main Canadian National railway corridor goes right through the middle of the site. The four railway lines carry 50 trains a day.

Relocating 7km of railway track was also part of the project. Despite this major work, Sultana says that train services were never interrupted.

Relocating the track did not remove the challenge for the KPH Turcot team as the new lines were still close to the parts of the rebuilding work. As a result, the work still had to be coordinated around train movements.

Utilities were also a challenge, given the size of the site. There were water pipes, sewers, gas pipes, electricity lines and fibre optics to contend with. 

Most of it was relocated on a small scale or protected but a 1km length of a wastewater collection system had to be rerouted and reconstructed so that contractors could undertake the interchange work.

Sultana says that the work may have looked easy on paper but the reality was more complicated.

Poulin adds that a lot of innovation was needed to protect traffic using the old structures while the new parts were built. 

We used both design and build and traditional but we need to move fully to design and build on future major projects

New structures also required protection. They were built over the warmer summer months, and the old structures were dismantled during the colder winter period. 

Poulin says that although the project was spread over six years, every year had a fast track schedule due to the weather and phasing. 

“You cannot miss the window,” he says. “During the good season we had to build detours and permanent infrastructure to switch the traffic onto and to free up the existing structures so that in the winter we could dismantle those. If you miss the deadline, you could jeopardise the project calendar for a year.”

In a number of locations, sections of new bridge deck were built around the existing piers with the deck completed at a later stage, once demolition of the old structure had taken place. 

The project team used a whole host of deflectors, a temporary bridge over the railway tracks and shipping containers around new piers to protect the new structures while the old ones were demolished. 

At one location, the project team took full advantage of the cold winter weather in Quebec and built an ice so demolition could be done safely without damaging the new structures.

Challenging earthworks

Earthworks were a major part of the challenge, with 8M.m³ of material to be moved – and trying to do that without double handling the material wherever possible to maximise efficiency. 

In addition, around 65% of the soil had to be dried out with lime to allow it to be re-used, which meant that the material movements had to be carefully planned around storage space, handling operations and infill operations.

At the peak of the project there were 1,200 people from KPH Turcot on site as well as those employed by the other Quebec Transport Ministry contractors. Up to 700 pieces of construction equipment were also in use. Now most of the work is finished and with only landscaping to be completed.

Sultana is clearly proud that the work was finished on time, despite challenges from the pandemic in the final stages. It was also completed on budget.

Nonetheless, she feels there are lessons to be learned in the approach to communication and in terms of the need to avoid relocating railway tracks on such a scale. 

“We can also learn from our procurement approach,” she says. “We used both design and build and traditional but we need to move fully to design and build on future major projects to fully realise the benefits from that approach.”

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