October 29, 2012

105-year-old bridge nearly demolished

RICHARD GILBERT

staff writer

A local contractor is undertaking the final phase of demolition of the Traffic Bridge in Saskatoon, which was closed by inspectors two years ago due to safety concerns about the oldest bridge in the city.

“(Phase three) involves demolition of the steel bridge span and removal of the demolished materials for disposal, along with cleanup of the site,” stated a City of Saskatoon press release.

“The project is scheduled to be fully complete by mid-November.

Saskatoon-based Saskcon Repair Services Ltd. was awarded the $388,888 contract for the demolition of Span One of the Traffic Bridge.

The project includes salvage and disposal of the structural materials; installation of a new temporary trail to connect the Meewasin Trail around the area near Span 2; installation of permanent chain link fencing around Span 2 and at the top of the south abutment; and modifications to jersey barriers needed to allow Saskatchewan Crescent and Victoria Avenue to be reopened through the area.

Phase Two started earlier this month and included removing the asphalt surface, timber deck and salvageable bridge components.

Phase One included structural shoring of Span One to support demolition equipment.

The Traffic Bridge, which was built in 1907 for horses and carriages, was shut down by Saskatoon city inspectors on Aug. 24, 2010 due to safety concerns.

The decision was made after preliminary results from a scheduled inspection showed serious corrosion and deterioration of some steel members underneath the deck.

At the time of the unexpected closure, the bridge linking the Nutana neighbourhood to downtown was serving about 7,000 vehicles per day, and remained an important and well-used pedestrian and cyclist crossing.

A detailed visual inspection and assessment was undertaken by Stantec on all components of the structure in November 2010.

Initial observations identified significant section loss in the components of the bridge below the deck. The detailed load rating identified many elements that could not support the desired dead and live loads.

As well, Span 4 had reached the point that it can no longer support its own weight safely.

Based on this report, Stantec concluded the only viable future option for the structure was to either replace the bridge with a new facility, or to completely remove and replace the lower portions of the truss and the entire deck structure system.

After a series of public consultations, the Saskatoon City Council faced a choice between rehabilitating the current structure or building a new one.

Council voted on December 2010 to replace the structure through a design-build process with a modern steel truss bridge for vehicle, pedestrian and cyclist use.

The new bridge trusses will be engineered to accommodate a safe minimum vertical clearance for emergency vehicles and transit. The new bridge will be constructed with 3.7 metre driving lane widths and use the existing concrete piers.

An effort will also be made to be sympathetic to the heritage and architecture of the existing bridge.

Construction of the new structure has an estimated time of 18 to 24 months. The cost to replace the Traffic Bridge with a modern steel truss bridge will be between $27 and $34 million.

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