Why does permafrost make construction difficult in the Northwest Territories?

Permafrost creates significant construction challenges in the Northwest Territories because it acts as a delicate, frozen foundation that is highly sensitive to thermal disturbance. When the ground is disturbed—such as by compacting vegetation or constructing heated buildings—the permafrost can thaw, leading to surface subsidence and a loss of structural bearing strength.12

Key engineering difficulties include:

• Subsidence: Thawing of ice-rich permafrost causes the ground to sink, which can destabilize roads, airfields, and buildings.13
• Frost Action: The freezing and thawing of ground moisture causes frost heaving in winter, which displaces structures, and leads to a loss of soil strength in summer.23
• Poor Drainage: Permafrost prevents water from draining into the ground, which exacerbates frost action and further weakens the soil.12
• Temperature Sensitivity: Buried infrastructure, such as water and sewer lines, is at constant risk of freezing.1

To mitigate these issues, engineers must often use specialized techniques, such as placing thick gravel pads to insulate the ground or employing "passive" construction methods designed to keep the permafrost frozen and stable.12