The Trans-Alaska Pipeline, one of the world’s largest oil pipelines, could be in danger.
Thawing permafrost threatens to undermine the supports holding up an elevated section of the pipeline, jeopardizing its structural integrity and raising the potential of an oil spill in a delicate and remote landscape.
The slope of permafrost where an 810-foot section of the pipeline is secured has started to shift as it thaws, causing several of the braces holding up the pipeline to twist and bend.
This appears to be the first instance that 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.
“The implications of this speak to the pipeline’s integrity and the effect climate change is having on pipeline safety in general.”
While the use of these tubes is common along the pipeline’s expanse, available records show that they have never been previously used as a defensive safeguard once a slope has begun to slide.
“This is a wake-up call,” said Carl Weimer, a special projects adviser 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.”
Permafrost is ground that has remained completely frozen for at least two years straight and is found beneath nearly 85 percent of Alaska. In the last few decades, permafrost temperatures there have warmed as much as 3.5 degrees Fahrenheit.
The state’s average temperature is projected to increase 2 to 4 degrees more by the middle of the century, and a study published in the journal Nature Climate Change projects that with every 2 degree increase in temperature, 1.5 million square miles of permafrost could be lost to thawing.
In seeking permission in February 2020 to install the thermosyphons on the slope northwest of Fairbanks near the Dalton Highway in the central part of the state, the Alyeska Pipeline Service Co., which operates the pipeline, confirmed that thawing permafrost posed a threat.
“The purpose of this project is to protect the integrity of the Trans-Alaska Pipeline (mainline) from permafrost degradation,” according to the company’s application.
Michelle Egan, a spokeswoman for Alyeska, an association of oil companies that includes a subsidiary of Hilcorp Energy Co., as well as ConocoPhillips and ExxonMobil, declined to talk about the condition of the weakened section of pipe or the extent of permafrost thawing.
Egan said that “permafrost changes were anticipated during the original design” of the 800-mile pipeline, which opened in 1977 and runs from Prudhoe Bay in the north to Valdez on Prince William Sound in the south.
There are about 124,000 thermosyphons arrayed along the path of the pipeline — a nod from its engineers to the importance of keeping the ground below it frozen. The tubes are bored from 15 to 70 feet into the permafrost in areas where warming might cause it to thaw. But those chillers only cool the permafrost directly below the pipeline, which holds the supports.
The new project, in which Alyeska is installing about 100 free-standing thermosyphons 40 to 60 feet into the ground, is required to keep a broader slope from collapsing or sliding and damaging the supports.
Construction began last month and is expected to take 120 days and will also include a three-foot layer of insulating wood chips atop the permafrost.
To avoid problems with the permafrost, 420 miles of the pipeline were built on an elevated support system that keeps the pipe about 6 feet above the ground. The frames that hold the pipeline, called vertical support members, look like a capital H with the pipeline resting on the cross stroke.
Tony Strupulis, the pipeline coordinator for the Alaska Department of Natural Resources, said there is no reason for panic — the support structures are not in immediate danger of collapse. But he added that the department remains “very mindful” about the implications of thawing permafrost for pipeline safety.
“The design philosophy is, ‘If it’s frozen, keep it frozen,’” he said.
Trans-Alaska’s safety record: 18 oil spills in 20 years
As the melting permafrost threatens pipeline supports and raises the potential of an oil spill, Alyeska says in its emergency response plans that cleaning up a spill could accelerate the thawing.
Alyeska’s plan to chill the permafrost with additional thermosyphons in the face of global warming, as Alaska heats up twice as fast as the global average, underscores an obvious irony: The oil industry must act to keep the permafrost frozen to maintain an infrastructure that allows it to extract more of the fossil fuels that cause the warming.
There have been 18 breaches of the Trans-Alaska Pipeline in the last 20 years, according to data from the Pipeline Hazardous Material Safety Administration (PHMSA).
Spills have ranged from less than one barrel to 6,800 barrels. In all, the pipeline has spilled 9,784 barrels of oil, resulting in $52.7 million in damages and costs, according to the PHMSA records.
Causes of the spills include breaks in corroded pipe to equipment failure and operator error. None of the spills recorded by PHMSA were attributed to permafrost thaw.
The extent of ecological damage from another spill 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.
“A massive oil spill would be impossible to clean up in the Alaskan environment,” said Kristen Monsell, a senior attorney for the Center for Biological Diversity, a nonprofit organization focused on protecting wild animals and plants.
Future safety efforts must factor in climate change
Federal and Alaska state regulators do not have specific guidelines for addressing safety issues related to thawing permafrost. Instead, they rely on general rules that require pipeline operators to evaluate stress factors, such as earthquakes, vibration and thermal expansion and contraction.
“While there is no way to make transporting oil safe, the regulatory agencies need to be doing everything they can to protect from the potential harms,” Monsell said.
The Alaska Department of Environmental Conservation said its focus is on ensuring that operators maintain pipeline integrity by adhering to state-mandated inspections that follow industry safety standards.
“Pipeline subsidence, regardless of cause, should be addressed through a maintenance and inspection program,” spokeswoman Laura Achee said in an email. “DEC does not have guidelines that are specific to permafrost.”
Richard Kuprewicz, president of Accufacts Inc., a pipeline consulting firm, said it wouldn’t be wise for pipeline operators to count on permafrost remaining solid in the same way as in the past.
Assessing pipelines to determine if years-old structural designs can withstand the changing conditions and accelerated rate of permafrost thaw is prudent, he said.
“Operators need to understand this new world being brought about by climate change,” he said. “What was true in the past may not be true today.”
Doug Goering, dean emeritus of the University of Alaska at Fairbanks College of Engineering and Mines, credits the Trans-Alaska Pipeline for its robust safety design.
Yet, he said thawing permafrost can pose considerable risk to the structural integrity of pipelines. “If the permafrost thaws, the ground loses its grip on the piling,” he said. “You can understand the consequences.”