A project is underway to replace the North Channel Bridge between Cornwall, Ontario, and Cornwall Island. This endeavor’s success will not only revitalize this component of a critical border crossing for the U.S. and Canada, but will also serve as a pilot project for a number of new construction techniques.
Canada’s Federal Bridge Corporation Ltd. (FBCL) owns the bridge, part of the greater Seaway International Bridge, and serves as project management for the four-phase replacement project, but building an entirely new bridge structure adjacent the existing bridge requires extensive logistical coordination with the various construction crews and a number of public authorities. The first phase of the North Channel Bridge replacement was overseen by American Bridge Canada Company and involved the construction of all in-water works, including the three new bridge piers, while the second phase is being helmed by AECON, a Toronto, Ontario-based company.
Formed from the consolidation of companies active for more than a century, AECON ranks first among the country’s largest publicly traded construction companies, and the company boasts a landmark-heavy portfolio of completed projects, especially in the transportation sector. AECON has successfully completed its fair share of infrastructure landmarks, including the new 16 Mile Creek Bridge located west of Toronto, and it has provided local construction expertise to build the $1.6 billion Autoroute 30 Extension south of Montreal, which is slated for completion in late 2012. AECON’s result-oriented approach and strong safety record caught the eye of FBCL, helping the company land the Phase II contract in 2011.
“This is an exceptionally technical job, but AECON has extensive experience in bridge building, not just from a construction standpoint but from a consulting standpoint as well,” adds John Almeida, senior contracts manager at AECON and project manager for the second phase of the North Channel Bridge Replacement project.
“Technically AECON will be building three separate brides [in the second phase] because you have to cross Cornwall Canal to get to the North Channel Bridge and we’re also adding a pedestrian bridge to link both sides of Cornwall Canal,” expands Almeida.
An Opportunity to Innovate
Though a smaller bridge, the Canal Bridge has made headlines for its use of high-performance, self-curing Hydrocure concrete on an otherwise standard rigid-frame bridge structure. The National Research Council’s Institute for Research in Construction is spearheading the experimental concrete’s development. Early studies show the advanced product can extend the lifespan of bridge deck by up to 20 years when compared to standard high-strength concrete formulations and by more than 40 years when compared to conventional strength concrete.
Hydrocure concrete’s formulation uses a lightweight porous shale aggregate that can hold up to 20-percent of its own water weight, essentially curing the concrete from within. The product’s formulation manages to minimize shrinkage – a typical problem with standard high-strength concrete – while also reducing cracking and the subsequent damage and corrosion of the bridge’s substructure at a cost roughly five-percent higher than standard high-strength concrete. Sustainability and safety sit at the center of AECON’s operations, so this new approach to concrete has been welcomed.
One Step at a Time
Even before AECON could begin work on the North Channel replacement bridge, though, the company was tasked with reconstructing some of the existing water mains and deep sewers. “The truth is the sewer element is equally as challenging as the bridge work, involving some comprehensive shoring some 10- to 11-metres deep, right in the middle of Brookdale Avenue,” admits Almeida. “So far, though, we have been able to successfully manage the water infiltration and stay on schedule.”
Brookdale Avenue leads to the Canal Bridge and ultimately to the North Channel Bridge and Three Nations Crossing, so AECON has enlisted the help of Miwel, a highly experienced sewer and water main contractor, to carry out the deep sewer work, while leveraging its extensive experience to coordinate with local authorities to minimize any impact to the surrounding community.
In the meantime, AECON has coordinated crews to begin preparation for the actual bridge construction using a sequential launch of the bridge’s steel box girders that began in May 2012. The site’s close proximity to the existing bridge, compounded with security concerns, rules out the possibility of using a traditional barge crane to erect each box girder segment. Instead, AECON tapped Structal-Bridges to fabricate the bridge’s box girders and devise a system using lightweight steel launching nose to gingerly slide each girder section out, working from north to south.
Counterweights are carefully arranged to ensure the gently sloping launch nose supports the weight of the girder piece being installed. Once the assembled bridge section is halfway out, crews carefully remove the counterweights to lower the section to a flush horizontal position. The section is then rolled along the girders of the launching nose and slide safely into place. At that point, crews carefully raise the installed section enough to remove the rollers, place final bearings and return the piece down in its final position, and repeat the process for each of the 22 box girder sections.
“This is a really unique installation approach that requires a lot of highly precise modeling to ensure we’re not going to overstress any part of the structure during the launch sequence,” explains Almeida. “It’s a hugely critical component and highly technical so the site is really just overrun with engineers and modeling experts who take great care to make sure their calculations are being realized.”
Once a section had been placed, crews mobilize to begin building the bridge deck, ensuring work progresses smoothly for an on-time delivery in September 2013. AECON also opted to have the pedestrian bridge prefabricated offsite and it will be delivered for installation in two separate shipments and constructed atop footings AECON previously constructed. The bridge will link pedestrians to a network of trails on both sides of the canal and create an entirely separate space for safe pedestrian travel.
As soon as the bridge opens to traffic, Phase Three will commence and the existing North Channel Bridge will be demolished, with the fourth and final phase wrapping up in 2016 with additional roadway realignment components. The new North Channel Bridge will facilitate international travel and trade while simultaneously costing taxpayers less to maintain, securing the bridge’s place in a critical border crossing and reinforcing AECON’s reputation for building things that matter.