Why are some parts of the Trans-Alaska oil pipeline raised on stilts?

Hi Talia,

Before we look into the answer, we should know that in many parts of Alaska, the temparature remains below zero throughout the year and so the ground remains frozen solid. Such places are called permafrost.

So one citable reason for elevating parts (in places of permafrost) of the Trans-Alaskan oil pipeline using supporting members is to prevent the frozen ground from warming up (also called thawing) due to the flow of hot oil through the pipeline. If the ground gets heated, the ground might 'melt' ;ie, the physical properties of the ground might change and become more fluid and the pipeline might sink if it was buried underground. This might cause a breakage in the pipeline and even cause a spill which is not a good scenario. So these pipelines are kept elevated above ground using refrigerated supporting members.

In order to prevent the hot oil from melting the permafrost, more than half the pipeline is raised on stilts.

To keep the permafrost from melting.

To stop the permafrost from melting

Hiya! Some parts of the Trans-Alaska pipeline are raised on stilts to allow cool air to circulate underneath therefore preventing the conduction of heat to the permafrost. This in turn reduces the thrawing (melting) of the permafrost (aka frozen ground). Permafrost is actually a huge store of methane (CH4), a potent greenhouse gas, and is stored in what is called methane clathrates (methane stored in ice-crystals). So, stilts reduce the thrawing of permafrost and therefore preserves the store of CH4 and therefore reduces Greenhouse Emissions. Hope this helps!

To stop them from freezing, the cold condition in Alaska means that it can sometimes drop below the melting temperature of oil, causing it to freeze and block the pipeline. Raising the pipe above the ground means the oil isn't in direct contact with the frozen earth and means it is less likely to freeze.