Vol. 17 No. 3
March, 1987
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Stay Safe in 87
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Replacing Six Bridge Spans Called for Much
Ingenuity
Above the Harrison River: A
custom-built, portable gantry crane was required to replace six double-tracked spans that
make up the Harrison River bridge. The span replacement work had to be done in stages in order not to hamper regular
train movements.
Harrison Mills, British
Columbia - Ingenuity. That's the stuff solutions are made of - and plenty of ingenuity went into the Harrison
River railway bridge replacement project.
The double-track bridge, about 113 km east of Vancouver on CP Rail's Cascade subdivision, had served
well for more than 70 years. But, its time had come.
Enter CP Rail's bridge experts.
It was going to be a tough job. Just how do you replace a bridge quickly yet still allow for regular train
operations? The answer: devise a system that replaces bridge spans in stages and, while your at it, have a
contractor come up with a brand new type of crane to get the job done.
Canron Inc., under contract to CP Rail, replaced six 23-metre spans and two 26-metre spans
weighing 122 tonnes and 145 tonnes respectively.
To do this, Canron designed and built a portable gantry crane, custom made for the Harrison River project. Built in
Vancouver and assembled on site, the crane was supported by six columns which rested on the tops of the bridge's
piers. The columns had to be moveable to allow for the varying distances between the piers.
Using six giant hooks, the crane was able to lift an entire double-track span, move it adjacent to the
span and lower it onto waiting flat cars which then were pulled clear of the work area.
METHOD FLEXIBLE
A new span was then brought in on flat cars, positioned under the gantry crane and then placed in position.
"The construction method devised by Canron was not only attractive economically, but it also allowed a flexible
construction schedule. The other alternative was to use cranes on barges, but the construction period would have
been restricted to coincide with high water on the Harrison River to permit the barges access to the bridge,"
said Fred Cummings, of CP Rail's Vancouver engineering office.
A second delicate manoeuvre was moving the old span clear of the tracks into the space at the work area that the new
span had occupied.
Due to space limitations, cranes could not be used, so a winch and pully system was devised. The span was jacked up
off the rail cars and blocked on dollies at either end, then pulled straight across into the clear. The steel from
the spans was cut up, loaded into gondola cars and recycled by a Vancouver manufacturer.
Replacing the spans meant the track had to be closed for 11 hours. Once a change out was completed, the gantry crane
was moved forward on rail cars to the next span.
"The ease with which the gantry crane could be moved to the next location facilitated a one-week
turnaround. The average replacement time for a span was every seven days. There were a few set backs, but these were
minor. The speed that the bridge was completed and uniqueness of the scheme made this project distinctive from any
other I've worked on", Mr. Cummings said.
The lion's share of the project was completed in January. Another two specially-designed spans are
slated to be installed in 1988. The total tab for the project will top $6 million.
The Harrison River bridge was originally a timber trestle built in 1885. In 1913, a new steel structure on concrete
piers was constructed.
This CP Rail News article is copyright
1987 by the Canadian Pacific Railway and is reprinted here with their
permission. All photographs, logos, and trademarks are the property of the Canadian Pacific Railway
Company.
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