As controversy continues around the Keystone XL Pipeline that would snake through the U.S., a similar drama plays out north of the border. Canadian officials are deciding whether to green-light a pipeline that would carry a semiliquid hydrocarbon mix for 1,172 kilometers from Alberta's tar sands over the Canadian Rockies to the Pacific coast of British Columbia. Near its proposed terminus, the proposal has met with public outcry and fierce opposition from the Coastal First Nations, a coalition of indigenous tribes.

Calgary, Alberta–based energy company Enbridge's proposed Northern Gateway Pipeline would cross over 1,000 fish-bearing streams and bring 255 oil supertankers each year to the coastline, making the issue highly contentious in Canada's famously outdoor-loving province. Of 1,161 British Columbians to give oral statements as part of the pipeline's federal review process, only two were in favor of the project.

What's more, the pipeline would be carrying an oil product that no one knows much about: diluted bitumen, or dilbit. University and government scientists emphasize an urgent need to fill the knowledge gaps surrounding what diluted bitumen is made of, how it reacts in the environment when spilled, and what its long-term biological effects are.

Answers to those questions are prerequisites to assessing the ecological risks posed by the eight such pipeline projects in Canada alone and to planning for an effective spill-response when things go wrong. “I think it's fair to say, there’s been some purposeful denial that the bitumen is really something different,” says Steve Hamilton, an aquatic ecologist at Michigan State University who worked with the U.S. Environmental Protection Agency (EPA) and Enbridge in 2010 to remediate a diluted bitumen spill in Michigan—work that is still ongoing. “The science has not informed this cleanup very well. There’s a pressing need for research.”

Bitumen is a thick hydrocarbon, the “tar” in Alberta's tar sands, the third largest deposit of hydrocarbons in the world. To flow through a pipeline, the tarlike bitumen is diluted with gas condensates or synthetic oils known as diluents. This mixture of bitumen and diluent is called diluted bitumen, or dilbit for short, but its precise formulation varies widely and is not publicly released.

Finding out what exactly is included under the umbrella term dilbit is an important first step in understanding this unconventional form of oil. “It’s not cast in stone exactly what dilbit is,” says Kenneth Lee, head of Fisheries and Oceans Canada’s (DFO) Center for Offshore Oil and Gas Energy Research in Nova Scotia. “The fate and behavior of the product—the character of the product when it's spilled in the water—will depend on what the final formulation is,” Lee says. Next comes figuring out how dilbit behaves when it is spilled. “We have to understand the physical behavior of the oil before we can design the optimal cleanup technologies,” he adds.

The chronic, long-term effects of bitumen on an ecosystem present a similar blank, although the Michigan spill will provide some information. "In trying to identify research needs, one of the things that's obvious is the lack of toxicity data," says Peter Hodson, a fish toxicologist at Queens University in Ontario. "Neither dilbit nor gas condensates have been tested, and so far I've not been able to find any literature on the environmental impacts of those two products."

Spilled dilbit
The past mishap provides some clues about what might happen. On Sunday, July 25, 2010, one of Enbridge’s pipelines in the U.S. sprung a leak near Marshall, Mich. By the time the spill was contained some three days later, some 20,000 barrels of diluted bitumen had leaked from the pipe and entered a tributary of the Kalamazoo River. At the time the river was in a flood stage, which slowed the oil’s transport downstream. Even then the oil contaminated a 65-kilometer-long stretch of river, overtopped several dams and deposited itself onto the vegetation in the flood plain. The contaminated flora had to be stripped away and taken to landfills, after detergents and water sprays wouldn’t budge the stuff. Ditto with surface soils; once spilled, the dilbit became heavier and thicker as the diluting component of the mix evaporated into the air. “When it loses the diluent it turns back to its original tarry nature and it sticks to things. It's next to impossible to get off,” Michigan State's Hamilton says.

Then there was the oil that became submerged in river sediments. “One of the big questions when we're talking about dilbit is, does it float or does it sink?” DFO’s Lee says. “If you talk to Enbridge or some of the people in industry, they say, ‘well, it floats.’ You look at what happened in the Kalamazoo river, and it sank.”

The physical and chemical properties of oil products change as they are exposed to the open environment in a process known as weathering. Typically oils float, Lee says, but evidence from the Kalamazoo spill, and results of early lab tests, suggest that as dilbit interacts with fine particles suspended in the water column, like the sediments found in river water, it sinks. "Dilbit in its initial form for a period of days to weeks is not an unusual product,” says Jeff Green, a consultant to Enbridge’s Northern Gateway and technical coordinator for its environmental assessment. “If it does take on heavy sediment loads and weathers, it can sink, and so it can become a nonfloating hydrocarbon.”

Knowing whether dilbit sinks or floats and under what environmental conditions remains a key step to planning an effective spill response. If dilbit sinks, what clean up strategies and technologies exist to recover it from the river bottom or ocean floor? In the Kalamazoo dilbit spill, Enbridge stirred up the river bottom to loosen and recover the oil. Lee points out that this approach was not effective in conditions colder than 4.4 degrees Celsius, which could pose a problem in colder northern river systems. “In my mind, this is an unproven technique,” Hamilton says. The results of EPA-commissioned experiments testing its effectiveness last summer have yet to come in.

No one knows what fraction of the 3.1 million liters of spilled dilbit in Michigan became what has since been termed “submerged oil,” but it was enough to contaminate hundreds of acres of river sediment. Three years and nearly $800 million dollars of cleanup efforts later, Enbridge and the EPA still have more work to do. As a last resort, they will likely dredge the river bottom and dispose of the contaminated sediment in landfills this summer. “We've basically had to destroy the environment to recover the submerged oil,” Hamilton says.

The ecosystem has bounced back quite well, however. Along the river, fish, aquatic insects, birds or mammals appear healthy, Hamilton reports. “You have to remember that thousands of workers stripped every visible patch of oil off the landscape. So if it were in an environment where you couldn't do that, then it wouldn't be bouncing back like it is now,” he notes. “I can't imagine what sort of environment that might be but it could be anywhere along the proposed route of the [Northern Gateway] Pipeline where you've got rugged terrain or rivers or steep gradients, or it could be in the port where it goes into deep bays. It would be next to impossible to clean up.”

And, even after this costly lesson, he points out that no one knows what causes the oil to sink, nor does anyone know its ecological cost, toxicity, environmental persistence or whether there are things that can be done to accelerate its biodegradation. “I believe that the world would have been better off if we had done some more focused directed research during the last couple years to ask these questions and get some answers,” Hamilton says.

Gateway to disaster?
In 2011 Canadian oil production reached 2.9 million barrels a day and by 2020 that number is expected to reach 4.2 million. Enbridge’s Northern Gateway alone would transport 525,000 barrels of dilbit daily, in addition to 193,000 barrels of imported condensate that would flow through a second pipe alongside leading back to the tar sands in Alberta.

“If we look at the historical record, it's clear that Canada has never had a system of pipelines that are leakproof or spill-proof,” says Sean Kheraj, a historian at York University in Toronto. Kheraj points to the telling statistic that in 2010 Alberta’s pipeline network alone spilled 3.4 million liters of liquid hydrocarbon product (which is the fancy name for oil and gas products). “We can anticipate historically that there will likely be spills along any new pipeline network, whether it’s Keystone XL or Northern Gateway.”

In testimony to the Joint Review Panel assessing Northern Gateway back in September 2012 in Edmonton, Enbridge spill expert and economist Jack Ruitenbeek reported that the probability of a tanker, pipeline rupture or terminal spill—of any size, large or small—across the pipeline’s 50-year lifetime was 93 percent. The National Energy Board and Canadian Environmental Assessment Agency’s Joint Review Panel that is currently assessing the environmental effects of Northern Gateway will reach their decision on the pipeline by the end of 2013.

But if the proposed pipeline spills in British Columbia, aquatic ecosystems along its path will be most at risk. “Once you get over the [Continental] Divide virtually every stream that would be crossed turns into a salmon-bearing stream. There are no streams that are of trivial significance from an ecosystem context,” says Mark Boyce, a fisheries and wildlife biologist at the University of Alberta in Edmonton. “At the end, at the far reaches of these pipelines are the most pristine marine environments on the planet, and to go mucking that up is just outrageous.”