The climate recorded at Yellowknife Airport was considered representative of the climate across of the Highway 3 study area, and data on various elements were collected and examples of the potential impacts on affected infrastructure are summarized below:
- Ground temperature changes that can cause frost heaving or permafrost thaw may deform the embankment through differential movements, shoulder rotation, or sloughing.
- Intense rain events may exceed the design flow capacities for culverts and bridges, resulting in water ponding against, overtopping, or flowing uncontrollably through the road embankment. Water that accumulates to develop ponds could form a heat sink that alters the geothermal regime and potentially develop into a talik.
- Snow storms reduce visibility and affect maintenance, i.e., snow clearing. Furthermore, thick snow covers act as a thermal insulator, preventing cold winter air temperatures from penetrating the ground and resulting in ground warming. On the other hand, reduced snow cover could result in ground cooling.
- Groundwater temperatures, levels and flow rates may affect the geothermal regime of the road embankment and foundation. Changing ground water levels may also cause subgrade settlement of unfrozen foundation soils.
- Changes in surface water flows due to increased flooding or ice formation can result in thermal or mechanical erosion of the road embankment and its foundation.
Two categories of climate change information were considered: Climate change projections based on global and regional climate model simulations; and analysis of historical climate data from Yellowknife. Climate change projections for the Yellowknife area from eighteen global circulation models (GCM) and one regional climate model (RCM) were evaluated considering a moderate greenhouse gas emission scenario (SRA25). BGC also reviewed previous geotechnical assessments of the highway, aerial photographs as well as several as-built construction and design drawings for the reconstructed highway as part of the assessment.