Oil & Water: Line 61 Pipeline Carries Oil That Could Sink if Spilled in the St. Croix Headwaters

Authoritative new study confirms that diluted bitumen can complicate clean-up by submerging and sticking to surfaces.




6 minute read

Map of Line 61 pipeline's route across the St. Croix River headwaters
Map of Line 61 pipeline’s route across the St. Croix River headwaters.

Much of the oil flowing through Line 61 – the pipeline passing under the St. Croix River’s headwaters that St. Croix 360 first reported on in October 2014 – is “unconventional.”

Unlike regular crude, it isn’t pumped out of the ground, but is mined. In its raw form, it isn’t really fluid – it resembles hot asphalt. It is diluted with other chemicals so it will flow through pipelines.

The mixture is known as diluted bitumen, or “dilbit.” Up to 50 million gallons of it is pumped each day through Enbridge’s pipelines across the St. Croix and three of its tributaries in northern Wisconsin. 

It turns out that its environmental impacts are also unconventional.

The dilbit dilemma

For five years, debate has surrounded the question of whether or not dilbit spills are harder to clean up than regular crude oil. Environmental groups say it sinks in water; the pipeline industry says it doesn’t.

A new report from a panel of experts may have finally answered the question.

An independent committee of scientists and engineers recently confirmed that dilbit can sink to the bottom of lakes and rivers, unlike traditional oil. Because the lightweight petroleum products quickly evaporate, the heavy bitumen left behind sinks and sticks to just about anything (like fish, birds, soil, plants, rocks).

“For any crude oil spill, lighter, volatile compounds begin to evaporate promptly; in the case of diluted bitumen, a dense, viscous material with a strong tendency to adhere to surfaces begins to form as a residue,” the report reads.

The study was performed by the National Academies of Sciences, Engineering, and Medicine, a Congressionally-designated organization that advises the government on scientific issues. It was reviewed by other experts, and included input from industry representatives. The two-year project was funded by the U.S. Department of Transportation.

Enbridge representative Jennifer Smith says the company is currently reviewing the report, and is focused on making sure spills don’t happen.

“Our priority is preventing an incident from ever occurring,” Smith told me. “We have robust emergency response plans in place. That is why we focus our efforts on providing the training, equipment and personnel to be able to act quickly in coordination with local, state and – if warranted – federal responders in order to protect people, property, and the environment.”

Debate follows disaster

A great blue heron stained by oil in the Kalamazoo River (Michigan DEQ)
A great blue heron stained by oil in the Kalamazoo River (Michigan DEQ)

The concerns of sinking dilbit first came to light after the Kalamazoo River spill in 2010, when an Enbridge pipeline spilled almost a million gallons of dilbit in Michigan.

Clean-up crews discovered that much of the oil did not float on top of the water, where it could be relatively easily skimmed off, but created “tar balls” that sank to the bottom. It also stuck to everything it touched, including living creatures.

The river had to be dredged and 36 miles of it were closed for two years.

The spill sounded an alarm. America suddenly became aware that much of the oil being dug out of the Canadian oil sands was flowing through pipelines across the country, and that it possibly posed unique new risks.

The Natural Resources Defense Council issued a report a year after the Kalamazoo spill describing the threat of dilbit. “Unlike conventional crude oils, the majority of dilbit is composed of raw bitumen which is heavier than water,” the report stated. A subsequent study funded by the oil industry found that dilbit does not in fact sink. 

The company that owns the tar sands pipeline crossing Wisconsin previously disputed that dilbit sinks. In October 2014, Enbridge spokesperson Becky Haase told St. Croix 360 that when the Kalamazoo River spill happened, the river was in the midst of a major flood and the oil stuck to twigs, branches and sediment, which then sank, carrying the oil down with it.

Settling the question

Processes affecting the composition, amount, and behavior of diluted bitumen.
Processes affecting the composition, amount, and behavior of diluted bitumen. (Via NAS report)

In 2013, Congress directed the federal Pipeline and Hazardous Materials Safety Administration to study the problem, and the results of its research were released on Dec. 8.

Carl Whiting, one of the founders of the fledgling Wisconsin Safe Energy Alliance (WiSE), has been tracking the impact of Line 61 on private property and public waters.

“This long-awaited study confirms what clean-up crews discovered on the Kalamazoo River in 2010. Namely; tar sands sinks. Unlike a typical boom-and-skim response, the bottom of the Kalamazoo had to be dredged, making this tragic river spill the most expensive on-shore oil disaster in United States history,” Whiting said.

The authors of the report did indeed confirm the claim.

“[S]pills of diluted bitumen pose particular challenges when they reach water bodies. In some cases, the residues can submerge or sink to the bottom of the water body.” If clean-up doesn’t happen before the oil sinks, it is “highly problematic” because of limited ways to detect, contain, or recover oil below the surface.

Within 13 days of a spill, the authors found that the light diluent chemicals mixed with the bitumen evaporate. The bitumen does not. Water has a density of 1 gram per cubic centimeter. After being exposed to the elements, bitumen can reach a density of 1.004 grams per cubic centimeter. Heavier than water, it sinks.

The authors say it is thus imperative to clean up dilbit quickly, before the light chemicals evaporate and the bitumen starts to submerge.

Changes to meet challenges

Cover of National Academies of Science report on diliuted bitumen
Click to download or purchase the report.

Right now, dilbit is treated like any other oil flowing through pipelines, with no special requirements to prepare for its unique clean-up challenges.  The new report includes a long list of ways to reduce the risk of another spill like the Kalamazoo River incident.

“Broadly, regulations and agency practices do not take the unique properties of diluted bitumen into account, nor do they encourage effective planning for spills of diluted bitumen,” the report reads.

The detailed recommendations for new policies and procedures are grounded in findings about the particular problems of cleaning up dilbit.

The changes start with simply identifying dilbit when it is being transported, requiring plans for cleaning up submerged oil, developing new tools and techniques that can recover submerged oil, and more research to better understand how dilbit behaves in waterways. It also calls on the federal agency in charge of pipelines to review response plans thoroughly.

“The recommendations set forth in our report represent a practical and pragmatic approach to mitigating the unique concerns associated with spills of diluted bitumen,” said committee chair Diane McKnight in a news release.

At least one pipeline safety advocate seems skeptical that the report will lead to significant change. Rebecca Craven at the Pipeline Safety Trust wrote in a blog post that changing the regulations “will be no easy feat.” She pointed to a 2011 report that called for an audit of the federal agency in charge of pipelines, reviewing its spill response program. That audit has still not been released.

“This NAS study identifies a number of major corrections that are needed specific to improving plans that relate to potential spills of dilbit. Let’s hope it doesn’t take another four years to enact these recommendations,” Craven writes.

The long-underfunded agency in charge of the vast web of pipelines criss-crossing the country responded to the report by declaring it would suggest operators voluntarily adopt recommendations in the report; advocate for the changes with policy-makers; continue working with industry to improve clean-up plans; and host a public meeting next spring to gather ideas on the topic.

The Natural Resources Defense Council, feeling vindicated after criticisms of its 2011 report stating the same dangers, believes the debate is now over and it is time for action. In a blog post about the report, Joshua Axelrod, a policy analyst, called for comprehensive dilbit oversight – managing its unique risks when being carried by pipelines, trains, trucks, and boats.

Answers before expansion

A slide from a presentation delivered to investors on Oct. 7, 2015 by Enbridge president of liquid pipelines Guy Jarvis
A slide from a presentation delivered to investors on Oct. 7, 2015 by Enbridge president of liquid pipelines
Guy Jarvis

Enbridge division head Guy Jarvis recently told investors that the company is in the early stages of building a “Line 61 twin,” to run along the same route, carrying more dilbit. No official proposal has yet been presented.

Whiting, from WiSE, says the damage done by a rupture in Line 61 would be much worse than the catastrophic Kalamazoo River spill. The Michigan pipeline leaked about a million gallons in 17 hours – that much oil flows through Line 61 every half-hour.

“What do we do when a flow rate nearly 35 times greater than what spilled into the Kalamazoo explodes into the St. Croix, or some other sensitive waterway?” Whiting asks. “This is a question which should be answered before we allow any further expansion of the largest pipeline corridor in North America.”

“It is time that regulators acknowledge the pressing need to address the threats that tar sands oil pose to all forms of oil transportation infrastructure, so much of which is built beside our nation’s critical water bodies and adjacent to sensitive communities.”


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2 responses to “Oil & Water: Line 61 Pipeline Carries Oil That Could Sink if Spilled in the St. Croix Headwaters”

  1. Mike Priaro, P.Eng. Avatar

    There is one glaring error in this piece (second sentence.)

    Until Imperial/ExxonMobil’s Kearl mining project (the first strip mine without an upgrader) started up in 2015, all mined bitumen from the oil sands was upgraded to syncrude, equivalent to a 31 degree API light/medium crude, which has far less tendency to sink than bitumen which has a density greater than fresh water.

    The bitumen which is diluted with diluent to make it pumpable as dilbit entirely came from in-situ operations before Kearl.

    See my “Bitumen and Dilbit Primer” on my Behance website or on my LinkedIn pages.

    Mike Priaro, P.Eng.

    1. Greg Seitz Avatar

      Mike – Thank you. Was the oil flowing through Line 6B in Michigan when the Kalamazoo Spill happened (and the oil sank) syncrude?

      Greg Seitz
      St. Croix 360