Reports Highlight Unevaluated Spill Risk from Keystone XL

New Market Condition Makes Keystone XL Riskier Than Previously Thought. Here's Why.

Reports from industry and government sources show that TransCanada’s troubles finding enough tar sands production to fill Keystone XL is not just a potential problem for the company’s bottom line—it makes for a more dangerous, leak prone pipeline. As studies by the federal pipeline regulators, the State Department and industry experts reveal, operating pipelines below their full capacity creates significant new hazards—as low flow rates both increase the likelihood of pipeline ruptures due to internal corrosion while also making leaks far more difficult to detect and locate due to “slack line’ conditions. These risks are only aggravated by the unusual properties of tar sands crude oil, which led the National Academy of Sciences to conclude pose an even greater set of risks to the environment than conventional oil when spilled. None of these factors were considered in previous environmental reviews for the project, which assumed Keystone XL would be fully filled. 

TransCanada has publicly acknowledged that it may not enough customers  to justify building Keystone XL to build the pipeline, This new dynamic has occurred as low oil prices have halted new tar sands projects and led major oil companies to divest their tar sands reserves. However, Keystone XL’s environmental reviews have always assumed that the 830,000 barrel per day (bpd) pipeline would operate at full capacity, as the pipeline had originally secured long term contracts for well over 90% of its capacity. Now many of those oil producers have backed out of the project and the company is struggling to find shippers to fill Keystone XL’s capacity. As industry studies of the TransAlaska pipeline as will as federal studies of leak detection technology and other pipelines show, moving forward with Keystone XL without securing its full capacity creates new safety risks for the pipeline.

These risks include: 

1. Increased likelihood of spills due to internal corrosion. Pipelines operating at less than full capacity are at greater risk of internal corrosion. As the State Department’s 2017 environmental review of Enbridge’s Line 3 pipeline observed “corrosion caused by sludge formation is more common in pipelines with low flow rates, in which there is greater separation of water from oil, and when solids accumulate within the pipeline."[1] A 2011 study of lower pipeline flow conditions in the TransAlaska pipeline also highlighted this risk, stating “[T]he team recognized the change in water behavior in the pipeline at lower flow rates as a potential high risk to the system.”[2] This study came several years after internal corrosion on the TransAlaska pipeline resulted in a 267,000 gallon spill in Alaska Prudhoe Bay and investigators later found areas of internal corrosion throughout the pipeline.   

BP TransAlaska Pipeline Spill

Alaska Department of Environmental Quality

2. Decreased ability to detect and locate leaks. Pipeline leak detection systems can be notoriously unreliable even in the best of situations. When operating at full capacity, Keystone XL’s leak detection system is only able to identify leaks greater than 500,000 gallons per day in real time.[3] However, as a 2011 study of the TransAlaska pipeline notes, pipelines operating at lower flow have a much greater incidence of “slack line” conditions, which “affects the time to detect a leak (increases it) and locate a leak (degrades it).” PHMSA’s 2012 study on leak detection describes how slack line conditions create significant challenges for leak detection stating:

“Because of the slack line conditions, low pressure, and changing density of the crude oil being transported, there are times during normal routine operations where the metering can show positive for hours and alternatively can show negative for hours.”[4]

3. Tar sands diluted bitumen spills present greater risks. The combined hazards of an increased risk of corrosion and hard to detect leaks are intensified by the fact that Keystone XL will transport diluted bitumen tar sands. In a 2016 study, the National Academy of Sciences (NAS) highlighted the fact that tar sands diluted bitumen spills have greater impacts on the environment and pose challenges that spill responders are not yet prepared to address. The NAS concluded:

“When all risks are considered systematically, there must be a greater concern associated with spills of diluted bitumen compared to spills of commonly transported crude oils.”[5]

None of these developments were evaluated in past environmental reviews of Keystone XL. As Nebraska's Public Service Commission (PSC) considers the route for the pipeline, its decision to exclude testimony concerning the need for the project or its safety risks may leave one of its greatest risks to the state unconsidered—that the lack of need for Keystone XL may result in a far more dangerous pipeline through Nebraska's lands and waters.

[1] State Department, Line 67 Draft Environmental Impact Statement, 5-18, available at

[2] Alyeska Pipeline Service Company, Low Flow Impact Study, June 15, 2011, pg. 17, available at

[3] "The SCADA system, in conjunction with Computational Pipeline Monitoring or model-based leak detection systems, would detect leaks to a level of approximately 1.5 to 2 percent of the pipeline flow rate. Keystone has stated it could detect a leak of this size within 102 minutes. Computer-based, non-real-time, accumulated gain/loss volume-trending would be used to assist in identifying low-rate or seepage releases below the 1.5 to 2 percent by volume detection thresholds. Smaller leaks may also be identified by direct observations by Keystone or the public". State, FSEIS, 3.13-34, available at

[4] Pipeline and Hazardous Materials Safety Administration, Leak Detection Study - DTPH56-11-D-000001, Dec. 12, 2012, pg. 3-71 available at

[5] National Academy of Sciences, Spills of Dilute Bitumen from Pipelines: A Comparative Study of Environmental Fate, Effects, and Response, Jan. 2016, pg. 82, available at

About the Authors

Anthony Swift

Director, Canada Project, International program

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