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McIntosh Perry

Stokely Creek Bridge proves McIntosh Perry up for the challenge

For McIntosh Perry structural engineers, the design of the Stokely Creek Bridge replacement was all about being adaptable while finding creative solutions for unique challenges.

Starting as a rehabilitation project, McIntosh Perry was originally retained to restore the structure. However, it was soon discovered that the bridge, located about 35 km north of Sault St. Marie on Lake Superior, was not at all typical.

McIntosh Perry Project Manager, Laura Donaldson, said since Highway 7088 (Havilland Shores Drive) is a dead-end road, closing the bridge and providing a detour route was not feasible.

“Widening the existing structure to provide a wider construction lane width was considered, but was not preferred as it would have resulted in a further reduction in the already deficient live load capacity,” Donaldson said. “The bridge had to remain open during construction to service the residences located on Lake Superior.”

The single-span, concrete bridge is more than 13 m long and a narrow 8 m wide. It carries two lanes of traffic over Stokely Creek. The small bridge had never been rehabilitated during its 70 years of service. In October 2012, the Ministry agreed with McIntosh Perry’s recommendation that full replacement was required.

That came with its own intricacies, as the bridge is being replaced without being closed to traffic. With the narrow structure width, rehabilitating the centre portion of the bridge deck while maintaining traffic operations would not have been possible.

As such, the installation of the bridge is being undertaken in two stages, while maintaining a one-lane, two-way traffic operation, with yield to oncoming traffic implemented at the site during construction.

But it’s not only the on-bridge traffic that needed to be considered for this project. Water traffic also had to be accounted for, as the bridge spans a small navigable waterway.

Donaldson said as with any project involving a navigable waterway, approval from Transport Canada was required.

“The temporary works required to demolish the old bridge do not allow for maintaining a navigational channel during construction,” she said. “There simply is not enough room. The solution was to provide a portage route

adjacent to the structure throughout the duration of construction.”

The Stokely Creek Bridge also proved to be an inhabitable area for wildlife. Donaldson said McIntosh Perry’s ecologists identified the presence of an existing wetland, fish habitat, species at risk, migrant bird species, and critical habitat areas. Not only were used nests of the Eastern Pheobe observed on the underside of the bridge, but the creek also falls within general range for the species-at-risk, Common Snapping Turtle.

All that, combined with background information obtained from the Ministry of the Natural Resources which indicated that Stokely Creek is a cold-water tributary stream of Lake Superior with a large fish community, meant McIntosh Perry professionals were dealing with an environmentally sensitive area.

Donaldson said work restrictions and control measures were put in place to ease to effects of the bridge replacement on local wildlife. As such, the period when in-water works are permitted is limited to the period between July 1 and Aug. 15 each year, Donaldson said. “To mitigate the potential impact on wildlife by the construction, bird netting and reptile exclusion fencing will be installed prior to contractor start-up. These control measures will prevent the Eastern Pheobe and the reptiles from nesting within the construction zone.”

With numerous traffic, waterway, and environmental factors contributing to the overall replacement strategy of the project, it required McIntosh Perry staff to be proactive and forward thinking to achieve success in the design process.

Construction was awarded last fall to a firm from Sudbury, Ont. The bridge is being fabricated throughout the winter and a fixed construction completion date is set for June 27, 2014.

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McIntosh Perry’s ecologists identified the presence of an existing wetland, fish habitat, species at risk, migrant bird species, and critical habitat areas.