Coupled seepage-thermal effects and adaptation measures for an arctic bridge

Climate warming as well as anthropogenic effects are disturbing subsurface thermal and water regimes in northern regions. As an arctic nation, Canada continues to expand all-season transportation linkages to improve access to remote communities, natural resources, and emerging marine corridors. While these investments provide substantial societal, economic, and strategic benefits, the ground-infrastructure-climate interactions can prove complicated on the local and regional scale. The Inuvik–Tuktoyaktuk Highway (ITH), located within the continuous permafrost zone, is Canada’s first all-season road to reach the Arctic coast and represents an important transition toward climate-adaptive infrastructure design. The highway incorporates numerous drainage crossings where bridges are founded on deep foundations embedded in frozen ground.  Hans Creek Bridge, located at 57 km along ITH, is a three-span structure with abutments and piers founded on adfreeze piles in permafrost. Adfreeze pile foundations require cold temperatures (<-1oC) to support the overlying super-structure, making them highly sensitive to changes in ground temperature. The bridge as also constructed to be climate adaptation–ready, allowing for future installation of thermosyphons should mitigation become necessary. Ground temperature monitoring, correlated with near-surface geophysics, indicates that thermal conditions at the abutments are cooling as intended; however, temperatures of the pier foundations have increased over time, potentially due to localized groundwater seepage effects. This spatial variability highlights the importance of site-specific coupled thermal-seepage processes affecting the permafrost response. Preliminary coupled seepage-thermal modelling results indicate seepage velocities greater than approximately 1 cm / day could significantly reduce thermosyphon efficiency. Thermosyphon installation can be customized to increase effectiveness of passive ground cooling under complex thermal and hydrological conditions. The combined approach using ground temperature measurements and near surface geophysics as well as coupled seepage-thermal modeling highlights the coupled climate change–anthropogenic effects on critical arctic infrastructure and the owner’s plan to stave off these same effects.