The Problem with Permafrost
One of the main problems construction crews had to deal with was permafrost. Permafrost is caused when the vegetation that insulated the frozen ground was stripped and removed in order to make way for the road. This allowed the frozen ground to melt into a cold slush that left an unstable surface. Through consultations with local road builders, the soldiers learned that they could prevent the ground from thawing by leaving the stripped vegetation where it fell. They then doubly-insulated the roadbeds by laying brush and log corduroy along the surface. Much of today’s Alaska Highway still has an under layer of local spruce and poplar corduroy beneath it.