27 June 2008
Canada Commemorates the National Historic Significance of the Construction of the Lethbridge Viaduct
The Lethbridge Viaduct - Date/photographer
unknown.
Lethbridge Alberta - Mr. Rick Casson, Member of Parliament
for Lethbridge, today unveiled a Historic Sites and Monuments Board of Canada plaque commemorating the national historic significance
of the Construction of the Lethbridge Viaduct.
"This Government is proud to commemorate the magnificent engineering achieved in the construction of this high-level
railway crossing," said Mr. Casson. "We are proud to acknowledge this as Canada's largest steel viaduct and to recognize that
it was built under very challenging conditions".
In contrast to other high level viaducts of its era, the Lethbridge Viaduct has not required any additional strengthening or
reconstruction to meet modern live load demands. The ongoing service of the Lethbridge Viaduct in spite of increasingly heavy moving
loads, the impact of severe wind forces, and dramatic temperature changes, is a testament to the excellence of its design and
construction.
Today, the Lethbridge Viaduct remains the largest steel tower bridge in the world in its overall length, weight, and uncommon height.
It is far longer than any other high-level viaduct of its type and is the only North American viaduct over 90m (300 feet)
in height to remain in service.
"Today's commemoration will help Canadians appreciate and understand the importance of the construction of the bridge and its
contribution to the transportation of goods across the entire country," said Mr. Casson.
The Historic Sites and Monuments Board of Canada, created in 1919, advises the Minister of the Environment about the national historic
significance of places, people and events that have marked Canada's history. The placement of a commemorative plaque represents the
official recognition of historic value. It is one means of educating the public about the richness of our culture and heritage, which
must be preserved for future generations.
The Lethbridge Viaduct - July 2003 Brian
Switzer.
The Construction of the Lethbridge Viaduct
The Lethbridge Viaduct crosses the Oldman River (formerly Belly River) at Lethbridge, Alberta, on the Crow's Nest Pass branch of the
Canadian Pacific Railway. It was built in 1907-1909 to shorten and improve the railway line between Lethbridge and Fort
Macleod. The viaduct spans the entire width of the Oldman River Valley at Lethbridge, where the river flows through a deep, wide,
steeply banked coulee. Considered the world's largest steel viaduct, it is a structure 1,534m (5,327 feet) long and 96m (314 feet) high
from the bed of the river. The Lethbridge Viaduct is an outstanding engineering achievement in the surmounting of stupendous
construction challenges presented by its immense size, and the strong winds, dry soils, and extremes of temperature in the Oldman River
Valley.
In its general configuration, appearance, and structural design, the Lethbridge Viaduct conformed closely to "classic" steel
railway viaducts of the era. It also incorporated advanced design details derived from other outstanding high level viaducts. The
highest and largest bridge in Canada, its construction greatly improved the hauling capacity and transit time of trains on the Crow's
Nest Pass rail line.
With the exception of a minor intervention to stabilize one tower column, the structure remains as designed and constructed in
1907-1909.
In contrast to other high level viaducts of its era, the Lethbridge Viaduct has not required any strengthening or ultimate replacement
to meet modern live load demands. Today, it carries the largest of the Canadian Pacific Railway's modern diesels and freight cars,
which are much heavier and longer than envisaged by its builders. The continuance of the Lethbridge Viaduct in service
as-built, in spite of increasingly heavy moving loads, the impact of severe winds forces, and dramatic temperature
changes is a testament to the excellence of its design and construction.
Today, the Lethbridge Viaduct remains the largest steel tower bridge in the world in its overall length, weight, and uncommon height.
It is far longer than any other high level viaduct of its type, and is the only North American viaduct over 90m (300 feet) in height to
remain in service.
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