The Jaffray Overhead and Big Sand Creek Bridge are vital bridges along Highway 3 in the Kootenays, a critical corridor in the National Highway System connecting British Columbia, Alberta, and the USA. Built in the 1950s, these structures accommodate an average of 6,000 vehicles daily, with traffic surging to 8,000 during the busy summer months, playing a critical role in regional connectivity and economic activity.

Historically, this section of Highway 3, located just east of Jaffray, presented challenges with its narrow roadway and substandard S-curve alignment. The original design reduced the speed limit to 80km/h within a 100km/h speed zone, creating safety hazards for drivers. Frequent wildlife crossings from nearby forests also increased the risk of collisions, posing dangers to drivers and animals.

The 73-year-old bridges were nearing the end of their service life, facing rising maintenance costs and the risk of closures for major repairs. Recent inspections revealed ongoing issues, recommending significant rehabilitation or replacement. With limited alternative routes around the project area, closures would severely impact traffic flow, emphasizing the need to address these issues while minimizing disruptions.

The Ministry of Transportation and Transit (Ministry) engaged McElhanney Ltd (McElhanney) to design critical upgrades to address these issues and improve the highway alignment to raise the design speed to 100km/h, enhance safety, replace aging infrastructure, and improve resiliency against climate change.

The project included the widening and realignment of approximately 1km of Highway 3 and the construction of two new bridges:

• The 112m, three-span Jaffray Overhead, spanning one active rail line with space for a second line in the future.
• The 61m, three-span Big Sand Creek Bridge, crossing an environmentally sensitive watercourse and providing a freeboard to accommodate the impacts of climate change and two wildlife corridors.

McElhanney evaluated multiple highway options to strike the optimal balance between key project objectives: achieving a 100km/h design speed, maintaining roadway width consistency with other Highway 3 segments, minimizing traffic disruption during construction, and maximizing cost efficiency. The new alignment achieves the design speed and geometry by removing the existing S-curve between the two bridge crossings, allowing both new bridges to be built while maintaining traffic flow on the previous existing highway and eliminating the need for temporary bridges.

A large volume of roadway fill was required to raise the highway for improved sight lines and to meet the necessary clearances beneath the bridges for trains, water depths impacted by climate change, and large animals. Our team minimized fill volume by reducing the depth of the approach span girders at Big Sand Creek. This approach required a bespoke concrete diaphragm at the piers to accommodate different girder depths while maintaining superstructure continuity. The result was a lower bridge with a continuous superstructure over the piers and a jointless deck for reduced maintenance.

We mobilized a multi-disciplinary team across six BC offices, implementing two parallel design tracks under experienced senior bridge engineers. This ensured customized solutions for each site while avoiding a one-size-fits-all approach that could compromise efficiency. The design manager oversaw both teams to ensure consistency.

• Improved safety for 6,000 daily highway users (8,000 during summer months) by straightening the alignment, widening the lanes and shoulders, and adding flares at the bridge approaches.
  
• The new Big Sand Creek bridge improves flood capacity, reduces scour risk, and supports wildlife passage.
  
• The project was completed on schedule and under the Ministry’s tender budget thanks to McElhanney’s high level of documentation and exceptional engineering expertise.