"..Lawler said the existing Alaskan pipe line was built to hold another four-foot diameter pipe above it, which could be used for natural gas".

This fellow says a gasline was always in the original plan.. until it wasn`t..
A little information about a prospect called "gull Island".  Also very interesting.  I cannot attest to the voracity of the story but it is Alaska folklore based in history. Who`s to say the story isn`t true? http://rense.com/general9/alask.htm