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Rail Beds
and
Trestle Bridges
Building the Grand Trunk
Pacific Across the Prairies
Crossing the Prairies:
Rail Beds and Trestle Bridges
Image 1: The Rivers Trestle (Photo
from the Rivers Library Collection)
Railway builders loved the prairies.
Most experienced builders and contractors that came to these plains had
experience with the mountains, hills and rolling country of the eastern
part of the continent. Some had experienced the challenges provided by
the rocky outcrops of the Canadian Shield.
We had the technology to tunnel through mountains, to cross wide deep
valleys, and wind a path through, rather than over, hills and other
obstructions.
What a railway needs is flatness. 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 if you look a map you will notice that a rail line is sometimes
diverted several miles to avoid the expense of going over a hill.
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.
But they did have the survey reports, and knew that there were a few
challenges ahead.
The job of the surveyor is to select the path of least resistance for
the tracks. A walk or bike ride along an abandoned rail line brings
this to life. The trail will twist and turn to avoid hills and valleys.
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 elevations you cut a path through so that the tracks run
through an excavated section lower than the surround ground level. For
modest depressions you build up the grade (sometimes using “fill” from
the last “cut”).
If the depression involves any sort of waterway you need to allow that
water to pass. Small seasonal streams may require only a culvert,
larger ones, a bridge.
And that will get you across quite a bit of the prairies.
Finding the “Best Crossing”
Old carpenters will tell you to measure twice and cut once. That wisdom
applies manifold to the railway construction business. The measuring is
done by a survey.
Long before construction started on Canada’s first Trans-Continental
Railway there was extensive surveying in Western Canada. Of course the
Rocky Mountain presented the biggest barrier, but one couldn’t afford
to make mistakes on the prairies either.
The plains were mapped in a general way quite accurately by the
Palliser and Hind expeditions in from 1857 – 1860. We knew where the
rivers where and quite a bit about elevation, drainage and climate
conditions. As early as 1873, formal surveys started plotting possible
routes. Many options were presented. Geographic considerations were
balanced with political and business considerations and a main route
was chosen. Construction started in 1880 and was completed to the coast
in 1885.
Nearly twenty years later the Grand Trunk Pacific was planning its
competing line. From a business point of view it needed to fill a void
not well served by current lines, so its ideal route was generally
determined. Local decisions about crossing were also easier to make
because of all the surveys already done.
Everyone involved knew exactly what the main challenges were. The first
was at the Pine Creek crossing near the hamlet of Firdale, and the
second was the crossing of the Little Saskatchewan near the village of
Wheatland.
When there is a river to be crossed, a surveyor looks for the place
that it can be most efficiently bridged - the best crossing. The search
for such best crossings has determined the location of many a town and
city as the railways crossed our land.
Designing the Crossing
When faced with a river crossing even after the site is determined
there is still an important decision to make.
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. One
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, and that in itself can be
expensive.
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 C.P.R. that extended a branch from Brandon to Lenore, by way of
Wheatland and Bradwardine.
A look at the following photos of the C.P.R. Bridge at Cossar Crossing
and the current C.N. Bridge near rivers show the difference in
height. The map and Google Earth image shows how the C.P.R used
method 1. They twisted and turned to find a low crossing. While the
Grand Trunk who originally built the Rivers Trestle in 1908, used a
more direct route and a high bridge.
Both companies selected virtually the same ”good crossing” – less than
a kilometre apart.
Image 2: Cossar Crossing. Photo
courtesy the McKee Archives, Brandon
University
Image 3: River Trestle Bridge.
Photo courtesy The Archives of Manitoba
Image 4: The Rivers region in 1915.
Grant’s Cut
Because the contractor chose to build on a fairly direct route spanning
the whole valley some excavation was requited in the hills south of the
trestle to level the rail line. The dirt removed to make the cut was
used to fill in the original trestle, creating a stronger structure and
decreasing the fire hazard. A ravine was cut with a steam shovel to
divert water run-off so the new fill was not washed away. The result to
this day is known as Grant’s Cut likely named after the Resident
Engineer in charge of construction along that stretch of line.
Image 5: The beginning of Grant’s
Cut
Image 6:
Google Earth image showing the CP and Grand Trunk lines
approaching crossing of the Little Saskatchewan River.
Laying the Foundation
The first trestle was built of wood. A slightly longer and higher
bridge built a year later at Duhamel, took over 6 million board feet of
Douglas Fir, with about one third of that going into the piles alone.
Those piles, that end up supporting the full weight of the structure
and the trains that cross it were sunk deep into the ground. A visible
reminder is available at the site of the Pine Creek crossing. The
original trestle, was replaced by a “big fill” when the bridge was
barely a decade old. The following photos show the site today.
Image 7: The newly built Pine
Creek trestle (Photo from the Archives of
Manitoba)
Image 8:
The replacement fill is to the left while the old Pine Creek
trestle was near the centre of this photo.
Image 9:
This close-up shows the standing
remains of the piles of the Pine Creek
Trestle. They were sunk deep into the boggy ground. When the trestle
was dismantled these pile were cut off at ground level and they have
been working their way slowly out ever since.
Building the Structure
The engineering principals and construction procedures were tried and
true by 1900.
The Grand Trunk Pacific chose a C.P.R. veteran Horace Haney to
supervise the building of trestles in the west. Haney had extensive
experience in trestle bridge construction for the C.P.R., including
work in the Rocky Mountains.
Image 10:
Horace Haney and his Granddaughter, Edith Bonner
Image 11:
Horace Haney (second from the right) and his work crew at
Battle River (Duhamel Bridge).
From the
collection of W.J. Bonner, Miniota Mb. And donated by his son,
John Horace Bonner
Working from an appropriately wide base, and supported by the
aforementioned piles, a series wooden beams called bents, are connected
by horizontal beams, walers and crossbracing, are fastened with
bolts to create a framework upon which a deck is set and tracks are
laid. The format used can be seen in all the photos of western
trestles, the variables being length and height.
Image12:
Wood Trestle Bridge Construction. From the collection of W.J.
Bonner, Miniota Mb. And donated by his son, John Horace Bonner
Along with the massive initial investment, the Rivers bridge, like most
railway bridges, required considerable ongoing maintenance and upgrades.
In some cases, such as at Battle River (Duhamel Bridge), a crossing was
abandoned and a track re-routed to a neighbouring track (In that case
the CNR line was nearby,) In other cases such as Pine Creek a fill
replaced the trestle.
In Rivers, period improvements were made over a long span of time
beginning almost immediately.
The filling of the trestle started almost as soon as the trestle was
completed. This was standard practice as the fill stabilized the whole
structure. The temporary bents on either approach would have been
filled as soon as possible. As seen on the big image of the trestle
(taken pre-1910—the locomotive #507 was renumbered #807 in 1910), the
filling has already started at both ends of the permanent structure.
The bulk of the filling occurred between 1921 and 1922. As one CNR
report, dated 27 August 1921, stated. "Fair progress is being made on
this work (Tilling). We are averaging about 1800 cubic yards per day."
The main filling was done over the course of two seasons. Cars were
loaded with
fill by steam shovel at Grant's cut. A locomotive hauled the loaded
cars to the
bridge site where they were emptied along either side and both ends of
the bridge.
As the height of the embankment increased, the horizontal elements of
the bridge
(walers and crossbracing) were removed. Once the embankment reached the
level
of the deck at the top of the bridge, the fill was allowed to settle
for one season.
The next year the filling was completed and the deck was removed.
Image 13.
Loading material taken from a fill. From the collection of
W.J. Bonner, Miniota Mb. And donated by his son, John Horace Bonner
So, if you dug into the embankment today you would find the vertical
parts of the
bridge (the bents), exactly as they were when the filling started! Even
though the
timbers were untreated, they should be quite well preserved as they
have not been
exposed to the air.
The Steel Structure
In 1924, a portion of the unfilled trestle over the roadway diversion
and the
river was replaced with a short piece of steel bridging. The steel was
fabricated and erected by the Dominion Bridge Company.
In the following years there were ongoing problems with the earth
embankment, nothing unusual for such a large fill. In the early 1930s,
it was noted that the embankment was shoving too hard on the end bents
of the timber approaches, and it was considered necessary to extend the
bridge. In 1937, one bent was added to the west approach and two bents
were added to the east approach.
Over the years, the timber approaches were replaced. Finally in 1970,
the timber approaches were replaced with steel. Steel spans and towers
similar to what had been installed in 1924, were installed at both ends
of the existing steel bridge, bringing the bridge to the appearance we
are familiar with today.
Image 14. The Rivers Trestle
Bridge, serving today after many
modifications over the years.
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