Local firefighters and helicopters were already on the scene when Jim McLeod, chief engineer of design and construction at the Canadian National Railway Company (CN), learned the company’s 1,200-foot wooden trestle bridge in Mayerthorpe, Alta., was on fire on April 26, 2016.
Although the firefighters put up a valiant fight, the fire moved swiftly due to the wind direction that day. Within an hour and a half, flames completely consumed the bridge. It soon became apparent it would be a total loss.
As the bridge burned, the CN team began analyzing how to best restore train operations. The bridge connects to a line that runs east-west, providing rail service to forestry, energy, agriculture and aggregate customers between Edmonton and the Kaybob area. (According to Millar Western Forest Products, 10 per cent of the province’s forest products are shipped on the line.) With no detour for rail traffic coming out of Whitecourt, Alta., it is a vital connection. The fire even left railcars stranded west of the bridge.
“There’s significant traffic that comes out of Whitecourt,” McLeod says. “With the bridge down, there was no other access for customers.”
Even while the fire still smouldered through the night, supplies were being shipped into Mayerthorpe to begin work on a replacement. CN’s engineering team first looked at the potential for a culvert-and-fill replacement, but due to the hydrology and soil conditions of the site, the team ruled out that option. They also looked at another option involving a reinforced earth wall and span. Ultimately, the team decided to do a hybrid.
CN has a supply of strategically located materials across its networks for situations like Mayerthorpe. As a result, the team used standard concrete voided double-box spans that had already been fabricated for other projects.
They also looked at available steel spans. The trestle bridge’s previous steel span, which was supported on a timber foundation, fell during the fire and could not be repaired. The team located a suitable second-hand span in Kamloops, B.C. As the fill work took place, the team repaired and strengthened the span.
“The biggest challenge we faced were the soil conditions throughout the valley,” McLeod says. “It’s a relatively soft clay, and the local fill material sourced was unsuitable for the structure. So we used granular fill out of Whitecourt.”
When McLeod initially assessed the situation, he anticipated the bridge would be out for at least four weeks. To expedite completion of the project, the CN team broke the construction down into three subprojects: east-end fill, west-end fill and bridge construction in the middle. CN and contract crews worked 24-7 to complete the project.
Mayerthorpe’s own Barsi Enterprises did the fill on the west end, while Universal Rail Systems – Frontline worked on the east end. CN crews as well as Remcan Projects undertook the bridgework.
The team completed the project in 20 days—eight days ahead of the original estimated completion time. “The success of the project wasn’t just that it was done in a very short period of time, but it was done with no safety incidents. It was a very busy, active site with a lot of equipment moving around,” McLeod says.
He attributes the project’s success—both the impeccable safety record and the speed of completion—to the contractors and CN crews all working together. “The team pulled together and worked diligently to do a quality job,” McLeod explains. “We had safety briefings before each shift—and re-briefing as the work changed on site.”
The team drove a total of 76 steel piles. Constructed from 195,000 tonnes of steel, concrete and fill material (6,500 loads), the new bridge structure is 292 feet long, with the fill portion stretching 860 feet. At 46 feet high, it stands the same height as the trestle bridge, with a total of nine spans.
On May 15th, the stranded railcars finally crossed the bridge and continued on their way.
However, the story does not quite end there. The Mayerthorpe bridge fire was just one of a rash of fires in the area. The fire department responded to 18 separate incidents beginning on April 19 through April 29, 2016, in and around the town. All of the fires were deemed suspicious.
The RCMP would later charge Lawson Michael Schalm, a Mayerthorpe firefighter and the son of a former town mayor, with 18 counts of arson. Schalm was one of the firefighters who fought the fire.