Construction of the Trans-Alaska Pipeline System with the Denali Fault, a major cause of earthquakes, and with large amounts of permafrost. In 1969, the unincorporated Trans-Alaska Pipeline System group drilled a series of core samples north of the Brooks Range that demonstrated how ubiquitous the permafrost was along the route. This forced the design of an elevated pipeline, which was tested in a loop built near Barrow. This elevation required the pipeline to be insulated, since extreme cold temperatures caused the metal to become brittle, even when hot oil was being pumped through the pipeline. After ecological objections forced subterranean pipeline crossings (in order to allow
Central Asia–Center gas pipeline system proposed to renovate existing systems and construct a new parallel pipeline to the western branch. On 12 May 2007, Vladimir Putin of Russia, Nursultan Nazarbayev of Kazakhstan and Gurbanguly Berdimuhamedow of Turkmenistan signed a memorandum for renovation and expansion of the western branch of the pipeline. On 20 December 2007, Russia, Turkmenistan and Kazakhstan finalized agreement on construction of the Caspian Coastal Pipeline parallel to the existing CAC-3 pipeline (known as Bekdash–Europe pipeline or Okarem–Beineu pipeline). Almost all Uzbek and Turkmen natural gas is delivered through the CAC pipeline system, mainly through the eastern branch due to location of production