Explain the difficulties of building Trans-Alaskan pipeline through tundra?
The Trans-Alaska Pipeline, or TAP, was a huge undertaking. The TAP is about 800 miles long; it took two years to build, and cost 32 lives. There were many issues to be contended with simply because of the size of the pipeline. It had to cross many rivers and streams, and construction had to be earthquake-proof. The TAP runs in long sweeping bends, rather than a straight line, so that it will not kink or break when it expands and contracts in length in response to temperature changes.
Building anything in Alaska can be challenging, due to the extremely long, dark winters, which are cold and windy. However building directly on the tundra presents an even greater challenge. Tundra is underlain by permanently frozen soil, and keeping that soil frozen was vital to the TAP. The pipe itself is raised up in the air, and an innovative solution was engineered for preserving the frost beneath the pipe. The pipe's supports are hollow, and are filled with an ammonia-based refrigerant. The refrigerant helps draw heat out of the soil and disperse it into the air above. The pipeline also has more than 500 sections where the pipe is raised 10 feet in the air to allow caribou herds to pass through during their annual migrations.