Bow Valley Gap Wildlife Overpass

Making highways safer for drivers and animals through innovative Wildlife Overpass design

Bridges & Urban Infrastructure

The Trans-Canada Highway (TCH) east of Banff National Park in the Bow River Valley is one of the busiest stretches of roadway in Alberta with current traffic counts exceeding 22,000 vehicles per day on average and up to 30,000 vehicles per day during the summer. It acts as a key access point to the mountain parks of the Canadian Rockies and connects Calgary to local communities and the Stoney Indian Reserve. Historically, this section of highway has been a hot spot for wildlife vehicle collisions (WVCs). Large animals such as deer, elk and bears have been victims of WVCs, along with the drivers of the vehicles. In addition to the high rate of WVCs, the highway acts as a physical barrier to wildlife migration routes and patterns.

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Location: Highway 1, East of Canmore, Alberta
Client: Alberta Transportation and Economic Corridors
Completion: 2024
DIALOG Services
Collaborators: Thurber Engineering
Egis Group

Leading the way

This is the first wildlife overpass constructed in Alberta since 2010, and one of only a handful in North America. The design’s simple, straightforward approach emphasizes safety for drivers as well as a comfortable, ecologically sound experience for the wildlife it will ultimately serve.

Minimizing risk

Wildlife overpasses, in combination with wildlife fencing, are introduced to substantially reduce the rate of wildlife-vehicle collisions (WVCs) while still allowing wildlife to cross the highway in a controlled manner.

A rich local ecosystem

This area is rich in wildlife, from carnivores such as black and grizzly bears to a wide variety of ungulates – bighorn sheep, elk, deer and moose – as well as many other smaller mammals. The exurban growth of residences and businesses in the Bow Valley, increased tourism, and the shipping of goods and services over the TCH combine to create high traffic volumes, noise, artificial lighting and other man-made factors that may make it a deadly gauntlet for wildlife to cross and a potential barrier for their movement.

Future-focused design

Previous wildlife overpasses in Banff National Park were designed to span over 2 travel lanes. This overpass is designed to span over 3 travel lanes to allow for future widening of Highway 1.

Seamless integration

Naturalized planting design that is appropriate to the local ecology and resilient to a changing climate. As the plants first establish and then mature, the bridge will become immersed in, and part of the immediate landscape.

The Team

Neil Robson Partner, Structural Engineer

Steven Prozniak Associate, Structural Engineer

Jill Robertson Partner, Landscape Architect

Graeme JohnstonStructural Engineering Design Lead

Matthew GowResident Engineer

A wildlife-friendly design milestone

To address the high rate of WVCs, DIALOG was contracted to design the Highway 1 Wildlife Overpass. This wildlife overpass is the first of its kind in Alberta outside of the Banff National Park. Simple and straightforward in its design and engineering, the bridge serves two distinct user groups: drivers on Canada’s national Trans-Canada Highway (TCH), and wildlife, a voiceless stakeholder group which is all too often critically impacted by anthropocentric actions. Design considerations sought to balance technical complexity, driver safety and experience, and the ecological needs of the wildlife populations it will connect. The location was selected based on traditional migration patterns, and the design responds to the topography and local ecology of the surroundings to integrate it into the landscape in a manner that is sensitive and thoughtful.

The wildlife overpass structure consists of twin corrugated steel plate arches, one over each direction of travel on Highway 1. The arches are supported by cast-in-place concrete footings and are backfilled with gravel. A thick layer of clay and topsoil on top of the backfill provides opportunity for naturalized landscaping on top of the structure. The overpass structure is over 60m wide and consists of twin steel arches, each with a span greater than 24m. The project also includes approximately 12 km of wildlife fencing.

We’re so excited to see the Bow Valley Gap Wildlife Overpass project completed. DIALOG’s specialized experience and holistic design approach to wildlife crossing projects like this are helping advance a conservation success story that benefits wildlife and people. These projects are a proven solution to reduce deadly and costly wildlife-vehicle collisions while keeping landscapes connected for wildlife to move safely. We look forward to engaging with the DIALOG team on future wildlife crossing projects in the Yellowstone to Yukon region.

—Yellowstone to Yukon Conservation Initiative (Y2Y)

A seamless extension of the natural landscape

The design references the surrounding landscape context so seamlessly that it feels like a continuation of the natural environment. Its location was strategically chosen for being a significant pathway in wildlife migration routes, but the natural topography also encourages integration into the surrounding landscape. The landscape-facing elements of the design seek to minimize the impacts of the highway, including considerations for noise mitigation, visual screening, and clustered plantings to provide areas of respite for wildlife. The highway-facing design is sleek and functional, emphasizing safety for vehicles while still illustrating to drivers the unique nature of the structure.

Challenges and solutions

Two key challenges for this project included the final highway lane arrangement and its effect on the overpass design and cost, and the potential for traffic impacts due to the overpass construction. Both challenges were identified in the Concept Design phase.

The existing lane arrangement on Highway 1 at the overpass location consisted of a 4-lane divided highway (2 lanes in each travel direction). At the Concept Design phase, several highway lane arrangements were reviewed which could accommodate a future widening to 6-lanes or 8-lanes. The ultimate lane arrangement would have a direct impact on the overall project cost as a significantly larger and more expensive structure would be required to span a widened highway. Construction of an overpass that had suitable width only for the existing lane arrangement would be the least costly, but could not accommodate a highway widening. DIALOG found that traffic volumes did not warrant consideration of the highway increasing to 8-lanes for close to 50 years, and there are also substantial physical constraints nearby the project site which would need to be considered, so this option was not recommended.

Ultimately, the 6-lane divided highway was recommended to Alberta Transportation as this provided a reasonable balance between accommodation for a future highway widening and additional project cost. The selection of a 6-lane divided highway split into twin arches, each with 3 lanes and associated shoulders, was also made to mitigate potential traffic impacts during the overpass construction. The relatively wide arch design ultimately allowed four lanes of existing traffic to be rerouted onto one side of the divided highway via a temporary median crossing while the construction of an arch was occurring over the closed section of highway. During construction of the second arch, the traffic was rerouted through the first completed arch via a temporary median crossing.

During the design phases, a conceptual detour design was reviewed to ensure the feasibility of constructing and implementing a detour. This traffic accommodation strategy was ultimately used by the Contractor to successfully keep all existing lanes of traffic flowing throughout the construction period, substantially reducing traffic impacts and delays.

Similar Projects

2024
George Price Highway Wildlife Crossings, Belize

The George Price Highway Upgrade Project encompasses the extensive rehabilitation and upgrading of 80 km of highway extending from Belize City to Belmopan. This highway presents varying environmental and engineering constraints, necessitating specific considerations for wildlife crossing structures (WCS) design. A total of five wildlife crossings are recommended as part of the highway upgrade. The primary crossings are a large span dry underpass and a medium span seasonally wet underpass to ensure safe passage of jaguar, tapir, white-lipped peccary, puma, white-tailed deer, and red brocket deer. Three secondary underpass crossings are proposed to ensure safe passage of wary species such as puma, ocelot, jaguarundi and gray fox by providing crossing opportunities between primary crossings. DIALOG has completed the concept design for each structure, working closely with the environmental expert to determine the appropriate crossing location, type, and size.

2010/11
Highway 1 Wildlife Overpasses, Banff National Park km 49 and km 54

DIALOG was the prime consultant for the design team of the animal overpass structures at km 49 and km 54 which were delivered through a design-build model with Bremner Construction Ltd. The structures at these locations consisted of twin CSP arches (17m span x 60 m length), complete with mechanically stabilized earth headwalls.

2008/09
Highway 1 Wildlife Overpasses, Banff National Park km 64 and km 74

The animal overpass structures at km 65 and km 74 were delivered through a design-build model. DIALOG was the structural engineers for the larger consultant team retained by Public Works Government Services Canada to prepare the indicative design for the structures and administer the contract. Two design options were developed for these structures – twin corrugated steel arches, and twin precast concrete arches – with the steel arches being constructed.

1996/97
Highway 1 Wildlife Overpasses, Banff National Park km 27 and km 36

In 1996, DIALOG and Lafarge Construction Materials developed arch-bridge structures over the Trans-Canada Highway at two locations between Banff and Lake Louise. The intent of the structures was to restore natural travel routes for wildlife while reducing collisions between vehicles and animals. The structure consists of buried twin precast concrete arches covered with rock, soil, and restored natural vegetation. At each of the overpass locations, the eastbound and westbound structures span 17 m and are 52 m long.