Because most of the pipeline was built above permafrost, each of the pipes holding up the raised sections of pipeline contained a sealed tube of ammonia. As the permafrost below the pipeline warms, the ammonia absorbs the heat and rises to a radiator on top of each stanchion. The ammonia is cooled by the outside air, condenses, and falls back to the bottom of the tube, where the process repeats.[10]
The surveyed route crossed hundreds of streams and rivers. To cross these with the pipeline, engineers designed concrete "jackets" to surround the pipe and weight it down so it would sink to the bottom of the stream or river. Because oil is lighter than water, the pipeline would float without the concrete jackets. Dredging rivers and burying the pipeline in the streambed was not allowed due to environmental concerns. In several places—either out of fear of disturbing the river or because of the river's characteristics—pipeline bridges were constructed. The most notable of these are over the Yukon River and the Tanana River.[11] To protect against corrosion in these wet environments, the pipeline was designed with cathodic protection.[12]