The Fine Art of Crossing the River

 
Railway builders must have loved the prairies.

A train hates a steep grade, in fact a rise of even 2 metres for every hundred travelled (a 2% grade) is considered unacceptable. The whole efficiency of the locomotive is lost if you have to provide enough power to just step on the accelerator like you would in a car to get over the hill. For the builder, negotiating hills and valleys in such a way that we keep the trains on a low grade add great cost to the process of railway building. That’s why a rail line is sometimes diverted several kilometres to avoid the expense of going over a hill or through a valley. 

So when the earliest railway builders arrived on the prairies, say, at Winnipeg, and started travelling west, over those flat plains towards Portage, they must have been quite happy.
 
The job of the railway construction crew is to take that path of least resistance and work with it. That means it’s a process of levelling using what came to be known as cuts and fills. For small hills you cut a path through so that the tracks run through an excavated section lower than the surround ground level. For modest depressions or ravines you build up the grade.

That will get you across much of the prairies.

Designing the Bridge

The Little Saskatchewan is a little river in a big valley, a valley left over from the huge streams that drained the meltwater from the last ice age. There are two accepted ways to cross a deep valley. Method #1 is to plot a gentle decline along the edge of the valley, cross the river on modest bridge, then plot an equally gentle climb up the other side. This can take one on quite a detour.

Or one can cross at the top by building a bridge from rim to rim of the valley, far above the stream.

The Little Saskatchewan had already been crossed once in this area, by the CPR. Comparing their former bridge at Cossar Crossing and the current CN Bridge near Rivers shows the difference in height. 

 

Cossar Crossing. Photo courtesy the McKee Archives, Brandon University
 

The Rivers Trestle

The CPR used twisted and turned to find a low crossing, while the Grand Trunk Pacific used a more direct route and a high bridge.

Both companies selected virtually the same ”good crossing” – less than a kilometre apart.


Two crossings of the Little Saskatchewan, Method #1 on the Pendennis – Wheatland line, Method #2 at Rivers.