Thawing permafrost threatens to undermine the supports holding up an elevated section of the Trans-Alaska Pipeline, jeopardizing the structural integrity of one of the world’s largest oil pipelines and raising the potential of an oil spill in a delicate and remote landscape where it would be extremely difficult to clean up.
The slope of permafrost where an 810-foot section of pipeline is secured has started to shift as it thaws, causing several of the braces holding up the pipeline to tilt and bend, according to an analysis by the Alaska Department of Natural Resources. The department has permitted construction of a cooling system designed to keep the permafrost surrounding the vulnerable section of pipeline just north of Fairbanks frozen, as well as to replace the damaged portions of the support structure.
This appears to be the first instance that the pipeline supports have been damaged by “slope creep” caused by thawing permafrost, records and interviews with officials involved with managing the pipeline show.
In response, the Alaska Department of Natural Resources has approved the use of about 100 thermosyphons—tubes that suck heat out of permafrost—to keep the frozen slope in place and prevent further damage to the pipeline’s support structure.
“The proposed project is integral to the protection of the pipeline,” according to the department’s November 2020 analysis.
Alaska officials who oversee the pipeline have been unable to find any records of previous damage to the pipeline caused by slumping permafrost, or of the use of thermosyphons as a defensive safeguard once a slope has begun to slide, and could cite no incidents in which either of those things had occurred.
The installation of the heat pipes builds on an obvious irony. The state is heating up twice as fast as the global average, which is driving the thawing of permafrost that the oil industry must keep frozen to maintain the infrastructure that allows it to extract more of the fossil fuels that cause the warming.
Any spill from the 48-inch diameter pipeline that flows with an average of 20 million gallons of oil a day, and the resulting clean-up activity, could accelerate the thawing of the permafrost even more, environmental experts said.
The extent of the ecological damage would depend on the amount of oil spilled, how deep it saturated the soil and whether the plume reached water sources. But any harm from an oil spill would likely be greater than in most other landscapes because of the fragile nature of the Alaskan land and water.
“This is a wake-up call,” said Carl Weimer, a special projects advisor for Pipeline Safety Trust, a nonprofit watchdog organization based in Bellingham, Washington.
“The implications of this speak to the pipeline’s integrity and the effect climate change is having on pipeline safety in general.”
Weimer said this incident should trigger discussions between regulators and the industry about how to safeguard pipelines from the effects of thawing permafrost and other climate dangers.
“Science points to climate change getting worse. Now is the time to ask what’s being done about it,” Weimer said, referring to the effect of global warming on pipeline safety.
To safeguard the pipeline from possible collapse, the pipeline operator, Alyeska Pipeline Service Company, was granted permission earlier this year by the natural resources department to construct the passive cooling system to arrest the thaw of permafrost that is essential to locking the supports in the ground and keeping the slope from slumping or sliding.
Alyeska is installing approximately 100 free-standing thermosyphons 40 to 60 feet into the ground. Construction is expected to take 120 days and will also include a three-foot layer of insulating wood chips atop the permafrost.