RC105 MarApr2023 - Magazine - Page 28
CONSTRUCTION
WATER
UNDER
THE BRIDGE
Gantry cranes keep
vital bridge open during
complete reconstruction
by George Koch
HE CITY OF EDMONTON’S Groat Road Bridges
and Road Renewal project set challenging
requirements. Despite approaching the
end of its service life, the City wanted
the nearly 65-year-old, 330-metre-long
four-lane bridge forming a critical transportation route over the North Saskatchewan
River repaired rather than replaced. The entire
superstructure’s deck, girders and portions of
piers and abutments—13,000 tonnes of concrete—was to be demolished. Traffic normally
averaging approximately 40,000 vehicles per day
had to flow throughout construction. Widening
of the shared use path from 2.4 to 4.2 metres on
the bridge was completed to meet the City’s
requirements. In-stream work faced regulatory
hurdles including schedule restrictions for fish
spawning, and physical constraints to how much
of the River could be impacted at any given time.
And the project needed to be completed in under
three years.
Although many factors and people contributed to the project’s completion on-budget at
$45.6 million and within the 33-month schedule,
Graham Construction’s successful execution
hinged on a temporary works innovation conceived before the project even began. In brief:
the superstructure demolition and reconstruction were
completed from above instead of below. There, project
execution centred on a custom-designed and constructed,
rail-mobile gantry crane system—the first such solution
ever used in Canada.
“The process amounted to sawing the old bridge down
the middle, repairing one half of the bridge, keeping
two-way traffic open on the other side, then flipping the
process and repeating,” explains Jim Murray, the City
of Edmonton’s project manager. “This was no easy task,
people driving by don’t realize how complex it is.” And
continues Murray, “In the first half we struggled, this was
something new, it was quite stressful because we knew
if we didn’t get that first half flipped over for traffic, we
weren’t going to be successful.”
In addition to the river bridge itself, the contract called
T
George Koch is a
researcher and writer
based in Calgary who
has written extensively
about construction and
public infrastructure.
28
RENEW CANADA – MARCH/APRIL 2023
for rehabilitating two bridges, one to the north of the river
and one to the south of the river along with the rehabilitation of five kilometres of roadway and on/off ramps. The
City had previously selected DIALOG as designer and
engineer of record, and the firm would later remain on-site
through contract administration. Graham was selected as
general contractor in January 2018. “On a project with this
kind of complexity and risks—a critical river bridge in the
centre of Edmonton – we don’t hire somebody for whom
this is their first try at it,” says Murray.
In 2017 Graham began delivering an equally complex project in its widening of Calgary’s Crowchild Trail
bridge. The company resolved similar in-stream restrictions concerning the Bow River by hanging temporary
works off the bridge sides, averting the need for traditional in-stream berms. “Groat Bridge couldn’t be executed
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