10/21/2011

Todd Creek CNR/Galloping Goose Timber Trestle

The cross-braced timber framework of Todd Creek Trestle
The Vancouver Island section of the Canadian National Railway opened in 1911, and it was all about the big trees. Trees had to be cleared for the right of way, ties were cut from the forest, as were the massive beams required to build the many bridges along the route. The Todd Creek Trestle was one such timber bridge that made it possible to navigate through a near-impenetrable, rocky, hilly, forested landscape.


Bridge deck of Todd Creek Trestle


For years the railway allowed people and cargo to travel through the forest between Victoria and Sooke, and to points north toward Lake Cowichan. Lumber trains carrying gargantuan logs, 1-3 per car, rumbled back down from the richly forested hills. There are old-timers in Sooke today that can still remember the lonesome whistle of the timber trains echoing through the hills.




Two major trestles were required to span valleys as the railway travels along the east bank of the Sooke River. Today a steel bridge crosses Charters Creek. Todd Creek trestle, though, is an excellent example of the strength and versatility of wood. Its timbers had to endure the weight of long trains loaded with many tons of huge logs.



When coastal bridge engineers looked for the structural timber for trestles, their first choice was often Douglas fir. Not only was it plentiful, but it also has an excellent strength-to-weight ratio, and performs well when stressed by heavy loads, wind, storms, or earthquakes. The west coast trestles had to endure all of these challenges.



Bear Creek Trestle
One of the most impressive wooden bridges was built in the late 1930s not far from Port Renfrew, in the Bear Creek Valley. Standing a dizzying 74 metres (242 ft) high and spanning 158 metres (517 ft) across, the Bear Creek bridge was at the time the highest wooden trestle in the world.



The Douglas-fir timbers used for bridge building are known for their tough fibre, dense grain structure and strength. Douglas-fir has excellent working properties, and it's wood is moderately durable and rot resistant. An untreated bridge could last 20 years plus, and when treated, much longer. All these advantages combine to explain why Douglas-fir was, and continues to be, the wood of choice for heavy structures.

The trestle carries hikers and cyclists past some remnant old growth trees

 Another important consideration is that Douglas fir is one of the few species available in the large sizes required for the timbers needed for large buildings, or trestles like the one over Todd Creek.

Although trestle fires happen, including two deliberately set (unsuccessful) fires on the Todd Trestle in recent memory, Douglas-fir has an excellent fire rating.

The biggest timbers at the bottom



A walk or bike ride on the Galloping Goose (as the abandoned CNR line is now called) over the Todd Creek trestle gives an excellent view of the valley far below, as well as the forest in the surrounding area.





There are several isolated old growth Douglas-fir along this route, just off the trail. If you look closely you will find them trying to hide among the younger trees surrounding them.




There is a small trail along the Todd Creek trestle to access the creek below. Here you can get a good look at the trestle's amazing structure. Marvel at a form of timber bridge building that has largely faded into the past, along with the big trees that made it all possible.

Todd Creek in the summer

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