Spiral Tunnels in Yoho National Park

So after a fun morning in Moraine Lake, we went to Laggan’s Mountain Bakery and Delicatessen for lunch.  That place is amazing and if you are ever driving by Lake Louise, make sure you stop there for something.

Instead of turning back towards the Johnston Canyon Campground or Banff, I went west towards British Columbia and we spent the rest of the day in Yoho National Park where the plan was to see Takakkaw Falls.  Soon after heading across the border into B.C. and the park, I saw the sign for the Spiral Tunnels.  The inner nerd in me forced me to turn out as we checked them out.

Spiral Tunnels near Field B.C. in Yoho National ParkSpiral Tunnels near Field B.C. in Yoho National ParkSpiral Tunnels near Field B.C. in Yoho National ParkSpiral Tunnels near Field B.C. in Yoho National Park

Quick nerd break to explain why this was so cool. 

To complete the Pacific railway as quickly as possible, a decision was made to delay blasting a lengthy 1,400 feet (430 m) tunnel through Mount Stephen and instead build a temporary 8-mile (13 km) line over it. Instead of the desired 2.2% grade (116 feet to the mile) a steep 4.5% (some sources say 4.4%) grade was built in 1884. This was one of the steepest railway lines anywhere. It descended from Wapta Lake to the base of Mount Stephen, along the Kicking Horse River to a point just west of Field, then rose again to meet the original route.

Three safety switches were built to protect against runaway trains. These switches led to short spurs with a sharp reverse upgrade and they were kept in the uphill position until the operator was satisfied that the train descending the grade towards him was not out of control. Speed was restricted to eight miles per hour (13 km/h) for passenger trains and six (10 km/h) for freight, and elaborate brake testing was required of trains prior to descending the hill. Nevertheless, disasters occurred with dismaying frequency.

Field was created solely to accommodate the CPR’s need for additional locomotives to be added to trains about to tackle the Big Hill. Here a stone roundhouse with turntable was built at what was first known simply as Third Siding. In December 1884 the CPR renamed it Field after C.W. Field, a Chicago businessman who, the company hoped, might invest in the region after he had visited on a special train they had provided for him.

At that time, standard steam locomotives were 4-4-0s, capable enough for the prairies and elsewhere, but of little use on the Big Hill. Baldwin Locomotive Works was called upon to build two 2-8-0s for use as Field Hill pusher engines in 1884. At the time they were the most powerful locomotives built. Two more followed in June 1886. The CPR began building its own 2-8-0s in August 1887, and over the years hundreds more were built or bought.

The Big Hill “temporary” line was to remain the main line for twenty-five years, until the famous Spiral Tunnels were opened on September 1, 1909.

The improvement project was started in 1906, under the supervision of John Edward Schwitzer, the senior engineer of CPR’s western lines. The first proposal had been to extend the length of the climb, and thus reduce the gradient, by bypassing the town of Field at a higher level, on the south side of the Kicking Horse river valley. This idea had quickly been abandoned because of the severe risk of avalanches and landslips on the valley side. Also under consideration was the extension of the route in a loop northwards, using both sides of the valley of the Yoho river to increase the distance, but again the valley sides were found to be prone to avalanches. It was the experience of severe disruption and delay caused by avalanches on other parts of the line (such as at the Rogers Pass station, which was destroyed by an avalanche in 1899) that persuaded Schwitzer that the expensive solution of digging spiral tunnels was the only practical way forward.

The route decided upon called for two tunnels driven in three-quarter circles into the valley walls. The higher tunnel, “number one,” was about one thousand yards in length and ran under Cathedral Mountain, to the south of the original track. When the new line emerged from this tunnel it had doubled back, running beneath itself and 50 feet (15 m) lower. It then descended the valley side in almost the opposite direction to its previous course before crossing the Kicking Horse River and entering Mount Ogden to the north. This lower tunnel, “number two,” was a few yards shorter than “number one” and the descent was again about fifty feet. From the exit of this tunnel the line continued down the valley in the original direction, towards Field. The constructions and extra track would effectively double the length of the climb and reduce the ruling gradient to 2.2%. The new distance between Field and Wapta Lake, where the track levels out, is 11.5 miles (18.5 km).

The contract was awarded to the Vancouver engineering firm of MacDonnell, Gzowski and Company and work started in 1907. The labor force amounted to about a thousand and the cost was about 1.5 million Canadian dollars.

Even after the opening of the spiral tunnels, Field Hill remained a significant challenge and it was necessary to retain the powerful locomotives at Field locomotive depot.

Even though the Spiral Tunnels eliminated the Big Hill, the mountains remained and so too did the Field Hill. The Ottertail revision of 1902 and the five-mile (26,518 feet or 8.083 kilometres) long double track Connaught Tunnel of 1916 were other improvements made to the original line in British Columbia. It was not until the late 20th century when a major new project of 20 miles (32 km) including the 9.1-mile (14.6 km) Mount Macdonald Tunnel reduced the grade to a very manageable average of 0.82%, (maximum 1%) opened in December 1988.

There is a hike along there that we did not take but I intend to next year that should be a lot of fun.

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