BC Hydro is addressing the growing demand for reliable energy capacity through the Site C Clean Energy Project. When the reservoir filling begins, the Site C reservoir will widen the Peace River by 2-to-3 times, inundating parts of Highway 29. This vital highway, tracing the north bank of the Peace River in northeastern BC, serves as a crucial link connecting Hudson’s Hope with the Alaska Highway and Fort St. John.

To minimize the impact on the local community and enhance transportation connectivity, BC Hydro collaborated with BC MoTI to realign segments of Hwy 29. The realignment work involves designing & constructing 26 km of highway, including 5 major highway bridges at Cache Creek (590m), Halfway River (1042m), Farrell Creek (411m), Dry Creek (160m), and Lynx Creek (150m).

Ensuring timely project completion was paramount for the team, aligning with critical milestones in the Site C Project timeline, particularly the reservoir filling slated for September 2023. Equally important was the safety, community benefit, and sustainability of the new bridges, in accordance with BC MoTI standards.
Located in an area with challenging ground conditions and exposed to significant shifts in local climate, wind, and hydrology during reservoir filling, the bridges faced unique challenges. These included the rare (1:10,000 year) risk of landslide-generated waves (LGW) from the southern valley wall, as well as the scarcity of high-quality granular material and riprap in the Peace Region for construction.

The bridge design incorporated environmental enhancements for fish, snakes, and amphibians, along with safety features for cyclists and motorcycles. Challenges arising from the reservoir included scenarios of normal and emergency rapid drawdown impacting bridge embankment slope stability, the formation of thicker ice sheets in embayments imposing substantial loads on bridge piers, and the vulnerability of hydraulic erosion from wind, boat waves, and ice on banks and slopes.

TECHNICAL EXCELLENCE: Each bridge crossing is different in site conditions and had to be completed by the given end-date which links to the Site C Project timeline. Our approach was to create a design solution that was adaptable to five unique sites, consistent in aesthetics and performance, cost-effective and time efficient for construction, sustainable for climate change, and resilient for natural hazards.

INNOVATION: Four bridges are susceptible to tsunami-intensity (up to 18m high) waves from catastrophic landslides of the riverbanks (volume up to 10+ million m3). No design codes and criteria are available. Traditional approach (uniform hazards) was cost prohibitive. Hence, a risk-based approach was adopted, in which higher risk elements were designed for high level of hazard (1:10000 yr) & high-performance criteria, and lower risk elements were designed for low level of hazard (1:2500 yr) & low-performance criteria.

SUSTAINABILITY: All valuable environmental habitats at each site were protected and preserved during and after construction by avoiding permanent and temporary works in watercourse and any environmental sensitive areas, using diversion channels, temporary culverts, and bridges as required.

COMMUNITY: Bridge alignments and crossing locations were thoroughly studied and carefully selected to minimize impacts on agricultural lands, private properties, cultural and historical sites, and to enhance recreation and tourism opportunities for local communities.

Hwy 29 Realignment is a key component for the Site C project and all 5 replacement bridges were successfully completed on schedule which was critical to filling the reservoir and to putting generation station, spillways, turbines and generation into operation. The new bridges met all project requirements, overcame complex and difficult technical challenges, and demonstrated WSP’s commitment in actions to deliver sustainable & resilient bridges to our clients, general public & local communities.