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.
![](images/P11Map.jpg)
Two
crossings of the Little Saskatchewan, Method #1 on the Pendennis –
Wheatland line, Method #2 at Rivers.
|