Today’s subject is the CPR train bridge found in Okotoks Alberta. Spanning the Sheep River, it carries that railway’s Calgary to Lethbridge line. Damaged in the spring of 2013 due to flooding and out of service for a time, the structure is back in use but almost a year later is still under repair.
It’s not known when the bridge was built. I searched books and documents, online and off, and found nothing in respects to that. And examining the bridge turns up nothing either. Often the builder’s will either put a plate on the structure itself, which will list the date, or the year will be cast into one of the concrete abutments or piers. Neither could be found.
Based upon its style one can make a guess as to how old it is. I’d say it dates from the period 1900-1920. Given that the line which it carries came through in the 1890s, this one was clearly a replacement for an earlier structure at the same location. It was common for the railways to put in a cheap-to-construct earlier bridge (often made of wood) which as money would permit, would be replaced by something more permanent and substantial.
The bridge is built to a Pratt Truss design, which is characterized by diagonals, which from the top, slope inwards. When speaking of this type of bridge the word massive comes to mind and the one seen here is no exception. The railway was quite fond of the Pratt Truss it seems and many bridges of this type exist in Western Canada along various CPR lines. They can be used singly or can be set up as multiple spans linked together and supported by intermediate piers, as seen here.
The Pratt Truss dates from the 1840s, but seemed to most popular in the first part of the twentieth century. It has long been superseded by newer designs. So many were built however that they are still very common to this day, most often associated with railways.
As was the case with most things the CPR constructed, this bridge was overbuilt and has no problems supporting the heavier/longer trains of today.
Heavy flooding in June 2013 damaged the structure. The Sheep River cut a new channel in behind the south abutment and went on to wash away a large section of track in that area. That abutment by the way, ended up requiring some repairs, and newspaper photos taken during the flood show parts of it gone. The one on the opposite side along with centre pier looked to have fared better and for the most part appear unscathed.
Once the water levels dropped, repairs were started. Even so, the bridge was out of commission for a time – anywhere from a few weeks to a month or two depending on the source. In the meantime, freights headed between Calgary and Lethbridge had to make their journey using an alternate and much longer route via Medicine Hat.
Lots of fill had to be brought in to replace the washed away roadbed and large boulders were placed near each abutment as a preventative measure against future flooding. Track not washed away but near the bridge got an extra layer of ballast for good measure. Work is still ongoing even though it’s almost been a year since that event. Looking down the track, one can see they have a way to go – the roadbed clearly needs further work and shoring up. I’d venture to guess this section is likely under a slow order and trains travelling here do so at a reduced pace.
The track seen here is along the CPR’s MacLeod Subdivision. From Calgary, the line travels south through Okotoks to a point a few kilometres beyond, where it then connects with the Aldersyde Subdivision in the town of the same name. From there, heading south again, it reaches the Crowsnest Line at a point just northwest of Lethbridge. This is a secondary mainline and sees a modest number of trains per day. Sadly, none showed on our visit.
The Sheep River comes in from the mountains directly to the west. Normally pretty calm and placid, last June, due to heavy snow melt and torrential rains, it became a raging torrent. It cut new channels here and there and deposited lots of rocks and silt and debris. They are still cleaning up the mess.
The bridge is located southeast of downtown and is near a nice wooded natural area. It’s also not far from a stinky sewage treatment plant. A public pathways takes you right to it.
If you’d like to know more about what you’ve seen here, by all means contact us!
Date: April, 2014.
Location: Okotoks, AB.