Construction of the Trans-Alaska Pipeline System for a fifth, should it become necessary. Holding tanks were planned that had a capacity equal to that of the pipeline, allowing the whole pipeline to be emptied if required. As required by the Pipeline Authorization Act, a ballast-water filtration system had to be designed as well. This system removes oil from tankers' ballast water so it is not released into Prince William Sound—something fishermen feared when the pipeline was proposed. Shortly after the permit was signed, convoys of equipment on snow tractors began heading north, using hardened snow roads and an ice bridge over the Yukon River to reach
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