The northbound section of the 170 street bridge over CN’s Bissel Yard had reached the end of its lifespan and required rehabilitation. Interestingly, PCL constructed the bridge originally in 1983. Located above 14 CN tracks, the bridge rehabilitation presented some unusual challenges, including:
- The only sidewalk spanning two bridges was located on the northbound bridge that was going to be rehabilitated by PCL. PCL provided a free taxi service to safely transport people across the bridge when the sidewalk was closed. The industrial nature of the project area meant that foot traffic was minimal and this solution was the most efficient and cost-effective.
- The proximity to CN train tracks placed strictly enforced stipulations on the construction team. For any work being completed within CN Right of Way, a CN flagger was required and all train traffic was given priority over our construction activities. During the project, the PCL team coordinated with CN to efficiently perform bridgework without disrupting ongoing operations below.
The project included complete removal of existing concrete barriers, sidewalk, milling of the structural concrete, and removal of all existing bridge components along the 160-meter bridge, with the exception of the existing precast girders. Once the existing structure was removed, the project team installed new rebar, concrete deck for the bridge, concrete sidewalk, concrete barriers and new bridge deck joints.
The bridge rehabilitation required three deck concrete pours; one for the 150 millimetre structural deck and two for the 50 millimetre concrete topping. The largest structural deck pour took 12 hours and 343 cubic meters of concrete.
Before the concrete barriers were constructed, the project team identified a potential problem in the current design. The southbound bridge rehabilitation, which was completed a few years prior, experienced surface cracking upon completion. Working with a consultant, the team added steel fibers to the mixture to strengthen the barriers and prevent any potential surface cracks. A successful mockup was made and strain tested to ensure proof of concept. The installation was successful – no cracking was found and the solution offered the required finish and quality.
Despite various challenges during the build, and coordinating work with a busy rail yard, the rehabilitation was finished on schedule. The rehabilitated bridge will act as a vital connection within Alberta’s capital city for decades to come.