Hwy 11A Bridge at Rocky Mountain House

About This Project

The Highway 11A Bridge over the North Saskatchewan River was a major infrastructure replacement project undertaken for Alberta Transportation near Rocky Mountain House, Alberta. The existing bridge had reached the end of its service life, requiring a new structure that would improve long-term performance while minimizing impacts on the surrounding environment.

As Prime Consultant, ISL provided comprehensive services including route evaluation, preliminary and detailed design, construction inspection, and contract administration. Five potential alignments were reviewed before selecting an optimal location immediately downstream of the existing bridge. To encourage competitive bidding and construction flexibility, two bridge design alternatives were developed: a steel plate girder structure and a post-tensioned concrete girder option.

The final bridge was constructed as a 173-metre, three-span crossing with only two river piers, reducing impacts on the North Saskatchewan River channel and adjacent floodplain. Extensive geotechnical investigations identified challenging water-bearing bedrock conditions, leading to the use of drilled pile foundations that simplified construction and reduced risk.

Additional design considerations included a specialized sidewalk system to improve drainage through the bridge crest curve and architectural treatments inspired by the surrounding mountain landscape. The completed bridge provides a safe, durable, and visually distinctive transportation link for the region while respecting the sensitive river environment.

• 173 m replacement bridge over the North Saskatchewan River
• Three-span steel girder structure
• Two-pier configuration minimizing environment impacts
• Optimized alignment selected through a comprehensive alternatives assessment