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The Spiral Tunnels

Updated: Sep 9, 2019

This one goes out to all the road-trippers out there! On our journey from Kelowna to Canmore we had some fun stopping at various sites along the way. The Spiral Tunnels historic site is a perfect stop for Canadian history junkies and train lovers.

Trains don’t run on a regular schedule but if you’re there at the right time it’s awesome! As the trains snake their way up the Kicking Horse Pass and over the continental divide, they circle deep into the mountains on both sides of this valley. The two giant underground loops they follow are the Spiral Tunnels. Because each tunnel makes a complete spiralling turn, trains actually cross over themselves. From this viewpoint you might see an engine emerge from the upper portal while 15 m below it, the last cars are still entering the lower portal! It's a bit of an engineering marvel to help deal with a terrain with too steep an incline, and there's some interesting history behind it.

Here's a video fo the train exiting the upper tunnel. Wait to the end; you'll catch a glimpse of the lead locomotive's headlight for just a moment:

Here's a quick description of how the spiral tunnel works:

And now watch the whole thing in action:

The Kicking Horse Corridor: In the narrow, steep-sided Kicking Horse valley, wildlife and people compete for precious space. Valley bottoms are the best places to live and the easiest routes to travel - for people and wildlife.

For people, the Kicking Horse valley contains the Trans-Canada Highway, the Canadian Pacific Railway, the village of Field, and visitor facilities. such as campgrounds.

For wildlife, the valley is a conduit of life that allows travel from one habitat or population to another - to find food, shelter and mates. Clear movement corridors are essential for their long-term survival.

Why did the Canadian Pacific Railway ever choose such a precipitous route for their main track through the Rockies? Certainly, James Hecor, who mapped the Kicking Horse pass in 1858, never recommended it as a major transportation corridor. Running out of food, getting kicked by his horse, and then struggling up the final steep pitch convinced him this route was a poor one.

Despite Hector’s warnings and the misgivings of early surveyors, the railway did choose the Kicking Horse Pass in 1881. While the long-favoured Yellowhead Pass, 200 km to the north offered a gentle passage through he mountains, the Kicking Horse line was far enough south to block competition from American branch railroads. The route across the southern prairies was also 122 km shorter than the Yellowhead line.

So significant was the choice of Kicking Horse Pass to the transportation history of Canada, it was designated a national historic site in 1971.

Steep Track Approved In 1884, the Canadian Pacific Railway could spare neither time nor money to carve a gradual descent down the west side of the Kicking Horse Pass. Instead, the CPR obtained the federal government's permission for a steep but temporary line. The proposed Big Hills rack dropped at a dizzying 4.5 % grade - twice the maximum allowed in their government contract.

The Big Hill was notorious. You drive it today as you follow the Trans-Canada Highway through the Kicking Horse Pass… but it was also the route of the original CPR line. With a 4.5% grade, this was the steepest section of mainline on the entire continent - so steep that when a five-car train descended, the front of the locomotive was 5m below the rear of the train.

Danger and Death Hired at $2.25 for a ten-hour day, thousands of workers braved spring snow, avalanches and summer forest fires while they laboured on the Big Hill. Men blanched on the trestle timbers over the foaming river. Blasting the cliffs with nitro-glycerine was unpredictable and the men working below dodged rocks knocked loose by workers above. Deaths averaged one a week. After a day’s work men returned to their tents and shanties at the site of the present Kicking Horse Campground.

Train Wrecks and Bottlenecks A 15-car train needed four extra pusher engines to climb the Big Hill. Shunting engines and inching up the grade took time and created bottlenecks. But downgrade traffic was another matter. The first train to run the Big Hill derailed, plunged into the river, and killed three men. The C.P.R built three spur lines on the Big Hill to catch runaway trains. Switches were left set for the spurs; they weren’t reset for the main line until the switchman knew that an oncoming train was in control.

It took a combination of spur lines, safety switches and signals to keep the trains under control; going up, it took extra engines to push them over the pass. The line was costly to operate - and dangerous!

Riding A Runaway

An old-timer described spur lines on the Big Hill as places “where wrecks could take place without hindering traffic on the mainline.” One engineer decided not to use them to stop his runaway train. He whistled loudly at each switch - the signal for each switchman to let him through. The train sped crazily down the track. Arriving triumphantly in Field, the engineer discovered a telegram marked “RUSH” waiting for him. He was, it stated, fired for disregarding the rules!

Schwitzer’s Solution: Frustrated by accidents and congested uphill traffic, the CPR sought an easier grade for the Big Hill trains. Designing a better line in the narrow valley posed a tremendous challenge. In Switzerland, engineers had solved a similar problem by using tunnels that spiralled into a mountain. Railway engineer J.E. Schwitzer modelled the Spiral Tunnels after the Swiss design. Extra length gained by his new figure-eight track would cut the steepness of the Big Hill in half.

Spiral tunnels were the answer! Where the old line plunged straight down the flanks of Cathedral Mountain, the new line makes gentle zigzags across the entire valley. A tunnel in Cathedral Mountain and a lower one in Mount Ogden allow trains to make their turns in giant, spiralling loops.

Blasting The Spirals: In 1907, thundering explosions once again echoed in the Kicking Horse valley. Blasting in from either end, crews met with near-perfect alignment in both tunnels. More than 1,000 men and 75 carloads of dynamite (70 tonnes) were used to blast 686,000 cubic meters of rock from within Mt. Ogden and Cathedral Crags. A few workers were killed when their shovels struck stray dynamite. After nearly 25 years of use, the “temporary” Big Hill was abandoned. Parts of it became a carriage road, and later, the Trans-Canada Highway.

In 1909 a new route was completed. It was twice as long but only half as steep. On the original Big Hill line, four engines were required to haul 762 tons (14 cars) uphill. One the spiral Tunnels were completed, two engines could haul 980 tons (18 cars) uphill at five times the speed. Safety improved for downhill trains, runaway spur lines were no longer required, rear pusher locomotives were no longer needed, scheduling delays were reduced and operating costs went down.

Mudslides and Bravery August 1925: A gully high on Cathedral Mountain began to move. The engineer of a pusher locomotive saw the mudslide heading straight for the Yoho Siding house. He ran downslope to warn those inside, just in time to avert disaster.

Mudlides and avalanches are a fact of life on the Big Hill. Modern technology tries to keep pace. A concrete snowshed beneath Mount Stephen divers snow and ice avalanches. Pumps on Cathedral Glacier divert excess melt water. But the forces of nature still prevails in this extreme mountain terrain.

Water and Ice In the cold winter days of steam locomotives, condensed steam would freeze and cause ice to build up in the tunnels. Large wooden doors at the portals of the Upper Spiral Tunnel helped keep the cold air out.

Water seeping through cracks in the bedrock is another cause of ice build-up. Work crews used to chip away at the ice with pickaxes. Today, foam insulation lining the tunnel walls helps minimize the problem. As well, metal bars mounted on the lead box car of some freight trains knock ice from the ceilings.