NOVEMber 2008 issue
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NATIONAL ISSUES
Edmonton Bridge Examined For Climate Change Vulnerability
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A BRIDGE WORTH STUDYING |
Edmonton’s Quesnell Bridge is playing a key and early role in a national assessment of public infrastructure and its vulnerability to climate change. In fact a case study of the bridge in the first National Engineering Assessment Report recommends a design review to address deck and drainage systems.
The case study and report come out of a special committee established by Engineers Canada, which represents engineering self-regulating organizations across the country on national issues. The committee, called the Public Infrastructure and Engineering Vulnerability Committee, oversees a broad-based engineering assessment of the vulnerability of Canadian public infrastructure to climate change.
Quesnell Bridge makes a great case study because the City of Edmonton is part way through rehabilitating and upgrading it. Flagged in the study’s executive summary as showing signs of vulnerability are the wearing surface of the bridge’s deck and the drainage system, which includes deck drainage and a retention pond.
“As these components are being replaced as part of the bridge rehabilitation project, the vulnerability is not assessed in terms of existing components, but in terms of potential proposed alternatives, should they be designed according to current standards and processes using typical design climatic data,” says the summary. “It is recommended that applicable design procedures and guidelines be reviewed and further study be conducted, so that design of these components will take into account changing or extreme climatic events.
“Although failure of these components will not lead to catastrophic failure of the bridge, it does constitute a public safety issue, as their performance (such as de-icing effects) can directly impact bridge traffic. Under changing climate conditions, the ability for these components to have consistent performance may be compromised and may require further re-evaluation.”
Engineers Canada released the assessment report in June. It and coming reports are in response to trends suggesting global climate has and will continue to change. Climate variation and weather extremes may impose loads or conditions on Canadian infrastructure it wasn’t designed to sustain, resulting in unacceptable risk.
Currently, the Quesnell Bridge carries Whitemud Drive motor vehicle, pedestrian and bicycle traffic over the North Saskatchewan River. It’s an important and heavily used component of the City of Edmonton’s inner ring road system, with an esti-mated 120,000 vehicles crossing per day, the executive summary explains.
A major river crossing originally constructed in 1968, the bridge was originally designed as a five-lane structure — two traffic lanes southbound and three northbound. The bridge widens to the south, where a ramp from Fox Drive merges with Whitemud Drive, adding a third northbound lane from the south end of Quesnell Bridge towards the west end of the city.
To reduce traffic congestion, the city is widening the bridge by adding two lanes. The widened Quesnell Bridge is due for completion in 2010. The upgraded bridge will be an eight-lane structure, with four southbound and four northbound lanes.
Due to the rehabilitation and upgrade, many of the components assessed in the case study were evaluated for rehabilitation or replacement in the next one to two years. This allowed the study’s authors to consider whether the design criteria being used in the rehabilitation are appropriate. Findings supported by the assessment can help the city make decisions on future operations, maintenance, planning and development, and on potential upgrading and rehabilitation projects.
More Info
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Click on Documents,
First National Engineering Assessment Report
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