Nipigon River Bridge: Nipigon River Bridge a first for Ontario.

• Author: Strong, Graham
• Position: Top Infrastructure Projects

It's one of the most technically challenging --and dramatic--bridges ever built in Ontario.

The Nipigon River Bridge, now being built just outside of the northwestern Ontario town of Nipigon, is part of a larger project to twin the Trans-Canada Highway between Nipigon and Thunder Bay. Part of what makes the project so complex is its location. The rocky terrain of the Canadian Shield, the irregular river banks near the mouth to Lake Superior, the need to maintain traffic over the river, and the delicate environmental ecosystem around it all led to creative solutions using the latest technologies.

"This project had to be built in a very narrow corridor with the (trout) spawning beds just north of the bridge and a CPR railway structure directly south," said Annemarie Piscopo, northwestern region communications co-ordinator for the Ontario Ministry of Transportation.

Previous work, years ago, showed how disturbing the waters could seriously impact trout population. For that reason, the bridge could not have footings within the river itself.

"The environmental challenges at this location were part of the constraints that facilitated the need for a long span structure. A number of bridge structures and types were reviewed during the design phase of the project," Piscopo said.

The solution was to build a cable-stayed bridge--the first such bridge in Ontario --which uses towers to hold up the bridge deck with a series of cables, similar to a suspension bridge. The advantage of this design at the Nipigon River is that it allows a fairly lengthy span to be supported by just one set of towers built on dry land, not in the river itself.

When completed, the bridge will span 252 metres. The three-tower centre pier rises 51 metres above the bridge deck, which is supported by 66 steel cables anchored to the towers. A pedestrian pathway separated from traffic will allow people to safely walk across the river.

The construction itself incorporated some of the latest bridge-building materials including glass fibre-reinforced polymers (GFRP) to make it lighter and less susceptible to corrosion. Further, the latest building techniques are helping make...