In a first for Edmonton, Marigold Infrastructure Partners is using a large-scale gantry crane originally built for a project in Dubai to build more than two kilometres of elevated track for the Valley Line West LRT, segment by segment.
The west leg of the Valley Line project includes a section that's roughly 2.1 kilometres long where the track will be elevated above existing roadways. The section will connect the West Edmonton Mall transit centre and the Misericordia Community Hospital stop.
The gantry is purpose-built for this task, said Randy Bowman, the project's gantry superintendent.
"With the machine, it's one span at a time, and the machine moves itself," Bowman told Taproot. "So it's less equipment, less logistics, less interruption to the people, the traffic, everything. So the machine gets very efficient at that point."
Efficiency and construction methods used to build the second half of the Valley Line are likely top-of-mind for Edmontonians, who experienced three years of delays on the southeast leg due to faulty piers, river obstructions, supply chain delays, and more.
In response to concerns that the pier problems might reappear, Marigold said in a statement that its teams "monitored the situation on the southeast portion of Valley Line LRT." It said it recognizes its project has similar infrastructure, but "we're being prudent and reviewing our plans to help ensure the infrastructure we're delivering is safe."
The gantry has been shut down until March, when Marigold will resume moving east along the line towards Misericordia.
"Once we get there, then we reconfigure the supports of the machine — the blue beams that everybody sees out there that the machine stands on — we'll reconfigure those, so that the machine can work in the other direction," Bowman said. "Then we'll walk the machine back over the bridge that we just built all the way back to the West Edmonton Mall station."
The Marigold gantry crane is 100 metres long and only requires 10 to 11 crew members, rather than the 30 that would typically be used on projects of this scope. (Supplied)
Marigold currently has 17 out of 47 of the total spans completed. A "span" refers to an area of track that spans a gap between each supporting pier.
"The standard span here is about 36 metres, and we can lift all 11 segments in roughly about seven and a half hours," Bowman said. "So they're all up hanging in the sky on the machine. That's basically one day, then we'll start to do the assembly of the segments."
After raising the segments, each of which weighs 50 tonnes, Marigold applies tension to pre-installed steel cables that will bind the segments together. The gantry then slowly lowers the final piece onto the supporting piers.
Currently, Marigold's average time for the entire cycle is about three days, Bowman said.
The crane was built and used for an LRT project for Expo 2020 Dubai and then sat in storage for a few years before Marigold acquired it from its Italian manufacturer.
The yellow components were shipped to Edmonton directly from Dubai, while the blue electronics and hydraulics were sent to the manufacturer for reconditioning before coming here.
Marigold began construction of the second half of the Valley Line in 2021, and is expected to take five to six years to complete it, according to the city's plan. As of now, Marigold expects to be finished with the gantry and have the elevated portion constructed by the end of 2024. Then, it will lay the track and build the actual stations.
"Odds are it'll be this time next year, between now and Christmas, hopefully, we'll be at the end of the line," Bowman said. "And then in the new year, we'll probably start taking it apart. That's kind of where we are right now with everything as planned."
Marigold Infrastructure Partners is a joint-venture agreement between Colas and Parsons, two international infrastructure developers, specifically created to manage the Valley Line West LRT project. A summary of the progress it has made on the Valley Line project this year is available on their website.