McKnight Boulevard Pedestrian Overpass

Calgary, AB

Located near 44 Street in northeast Calgary, a pedestrian overpass was needed to allow pedestrians to safely reach a school and a commercial district on either side of the busy, multi-lane McKnight Boulevard.

Project Services

ISL provided preliminary engineering, detailed design and construction administration for a twin girder pedestrian bridge, as well as the associated regional pathway extensions, utility diversions and drainage and landscape elements.

Slender Design

To cross 55 metres of roadway with a depth-to-span ratio of greater than 20, ISL configured the union of two steel plate girders with a maximum depth of 2.4 metres, thereby exceeding the design criteria for a slender bridge profile.

Overnight Installation

To minimize traffic disruptions on the busy McKnight Boulevard, it was decided to erect the twin bridge girders in just one night. Carefully planned and executed, temporary traffic control and lighting allowed both the girders and the precast decking units to be installed successfully with minimal disturbances.

Winter Conditions

To stay on schedule, much of the abutment concrete pours and bridge construction took place during harsh winter conditions. Special portable industrial heaters and insulated tarpaulins protected the freshly poured concrete from the cold weather.

Project Completion

The McKnight Boulevard Pedestrian Overpass opened to the public in September 2009.

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Calgary Zoo Pedestrian Suspension Bridge

Calgary, AB

After being closed for several years due to safety concerns and 2013 flood damage, the pedestrian bridge at the Calgary Zoo was demolished as part of the flood mitigation work.

An Iconic Structure

ISL designed a 60 m replacement suspension bridge of a similar nature that is set to become a destination and iconic structure, much like the former bridge was.


While the bridge had to be extended to ensure a 3 m clear inside width to meet modern standards for accessibility, ISL designed it with the same abutment locations so that the new abutments actually straddle the original ones leaving the original abutments in place for posterity.

Balancing Aesthetics with the Budget

Despite a tight overall budget, the Zoo wanted an aesthetically pleasing and architecturally striking signature structure that would offer lively and dynamic characteristics for its pedestrian users. To meet these requirements, ISL was efficient in both the design and details, using lightweight superstructure elements that trickle down to smaller substructure and foundations, as well as advanced analysis of structural dynamics and a lightweight FSC certified Alaskan Yellow Cedar deck.

Withstanding Future Floods

The team ensured the geometry of the new bridge can accommodate high flood water levels of 2013 and higher.

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Kingswood Pedestrian Bridge

Brackendale, BC

In fall 2009, ISL was commissioned to prepare a conceptual and detailed design of the 200-metre Kingswood Pedestrian Bridge across the new Sea to Sky Highway 99 near the Township of Brackendale in the District of Squamish, British Columbia.

Improved Safety

The new highway had virtually disconnected pedestrian crossing and access to the nearby school and residential areas in this section of the town. The bridge was proposed as a safety measure to accommodate pedestrian, cyclist and wheelchair traffic across the highway.

Recycled and Reused

ISL elected to re-use existing precast pre-stressed concrete flanged box and Double T beam members, which had been in storage from the dismantling of the Centennial Way Pedestrian Bridge Overpass. Modifying the design to use these superstructure beams helped reduce the capital cost of the bridge by 25 percent while providing a more sustainable solution.

Environmental Care

The bridge was designed and constructed to minimize environmental impacts on the nearby creek and a protected pond. A new culvert was installed to replace a dented and overgrown culvert on site.

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100 Avenue Bridge Rehabilitation

Grande Prairie, AB

The City of Grande Prairie selected ISL for this bridge rehabiliation project, which involved structural assessment and recommendation of rehabilitation options, followed by design, tendering and construction administration for the selected option.

State of Disrepair

Built in 1958 with only small fixes thereafter, the 100 Avenue Bridge was in a state of disrepair with reinforcing bar corrosion and numerous spalls of concrete along the deck curb. Bridge expansion joints were buried under six inches of Asphalt Concrete Pavement (ACP).

Rehabilitation Program

Inspections and assessments led ISL to recommend replacing the 39.5-metre long deck and rebuilding the wing wall, guard rail, abutments, bearings and approach slabs. Construction staging enabled two lanes of traffic to remain open for most of the construction, even though the work was extensive. A new High Performance Concrete (HPC) topping slab will increase the deck's durability and service life.

Girder Reuse

Analysis showed that the existing girders complied with bridge code loading, allowing ISL to develop a plan for girder reuse by rehabilitating their corroded ends. Construction efficiencies were maximized by lifting the girders and rehabilitating them off their supports, which enabled access to the abutment/piers for its rehabilitation at the same time. These measures resulted in substantial time and capital cost savings for the City.

Rehab Benefits

With the completion of these rehabilitations in December 2014, the service life of the bridge has been extended by 50 years or more.

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32 Street Crossing

Okotoks, AB

This project was the largest infrastructure project ever undertaken by Okotoks and was designed and built within one year to satisfy tight timelines set by the federal Infrastructure Stimulus Fund.

Vital Connection

This project involved constructing 1.4 kilometres of new arterial roadway including regional pathways, two bridges over the CPR track and Sheep River and a major river diversion within the flood plain. The project provides the only local route that will remain passable when trains cross or in major flood events, significantly improving network capacity for all modes of transportation.

River Relocation

ISL led a multi-disciplinary consulting team that included Golder Associates, who contributed significantly in hydraulics, flood management and biophysical science. A key innovation of the project was the 750 metre relocation of the Sheep River, returning the river to a course it had historically followed from the 1950s to the 1970s. This had numerous benefits, including mitigating the risk of flood damage on downstream lands, reducing bank erosion and allowing the new bridge to be constructed efficiently over dry land.

Environmental Stewardship

As the largest recorded diversion of a meandering alluvial mountain river, the project required careful design and extension of the current state of technical knowledge. Environmental monitoring and mitigation included extensive on-site fish habitat compensation measures, and an active relocation program that helped more than 11,000 fish migrate to the new river channel. All impacted areas within the river valley have also been completely re-naturalized, leaving Okotoks a lasting legacy of sustainable transportation design.

Award Winner

This project won two Consulting Engineers of Alberta awards: an Award of Excellence for Water Resources and Energy Production and an Award of Merit for Transportation Infrastructure.

"A multi-faceted project that has shown very high results in key elements of technical excellence, value, innovation and environmental protection. An impressive project of significant benefit to the Town of Okotoks."
— CEA Showcase Award judges' comments, Alberta Innovators magazine, Spring 2011

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