What lies beneath Alberta's man-made lakes?

A plan to store oil sands waste underground

Louis Helbig

From a distance, Base Mine Lake in northern Alberta looks like any other lake in the Athabasca region, with the white spruce of the South Bison Hills surrounding part of the eight-square-kilometre body of water. Off in the distance, though, smokestacks at an oil-sands operation are one reminder why this isn’t the type of place families typically swim or fish. Another lies five metres below the surface, where sits a roughly 13-storey-deep amalgam of tailings, the toxic waste by-product of the oil-sands mining process.

The lake, and the mining effluent below, fill the crater of an old oil-sands mine pit. At this point, Base Mine Lake remains a large-scale experiment, but if all goes according to plan it will one day become reclaimed habitat, home to ducks, geese and fish—the first of dozens of similar sites that will eventually become the largest network of man-made lakes in the world. If not, it risks becoming a symbol for critics of the oil sands’ destructive impact on the landscape. “It’s something [regulators] really better look at carefully before approving one of these,” says Glen Semenchuk, executive director of the Cumulative Environmental Managemental Association (CEMA), an oil-sands advisory group made up of representatives from industry, government, environment and Aboriginal groups that submitted a 400-page report on so-called “end pit lakes” to the Alberta government last year. Semenchuk says it could take between 60 and 80 years before scientists fully understand the effects of the lake on the environment. “If [they] are wrong, the implications could be quite severe.”

The idea of filling old mine pits with tailings and water stems from one of the biggest problems facing the industry—what to do with all the waste it generates. By 2022, the amount of bitumen extracted each month is expected to produce enough toxic liquid to submerge Vancouver’s Stanley Park up to a depth of close to three metres, according to the Pembina Institute, a Calgary-based environmental think tank. Until now, a temporary solution has been to pump the waste into tailings ponds, but those ponds won’t be big enough to contain what’s on the horizon.

Syncrude Canada, one of the world’s largest producers of synthetic crude oil, began conducting the first large-scale commercial demonstration of its kind at Base Mine Lake this summer. The first step was to fill the pit with the tailings slurry—a mix of clay, silt, bitumen, salt and solvents. Syncrude then poured fresh water on top with the idea that over time the water will compress the tailings to the bottom and keep them there. In ponds that were used for testing this technique, scientists discovered naturally forming microbes in the water that could break down the toxic material, paving the way for nature to gradually reclaim the site for wildlife.

“We know that it will work because we’ve tested it on a smaller scale,” says Cheryl Robb, a company spokesperson. The largest of Syncrude’s test ponds is four hectares, while Base Mine Lake is approximately 200 times larger. “This is the next scale up for the technology development,” Robb adds. “We have more than two decades of research that gives us the confidence to test it at this scale.”

But Syncrude’s confidence is not shared by everyone. Among the many concerns scientists have is whether the tailings below the fresh water could leech into other parts of the environment. Reshaping the aquatic landscape could affect an Athabasca drainage system that flows upstream into Arctic waters. There are also worries storms could at some point stir up tailings long thought to be covered. “My preference would be to abandon end-pit lakes as a permanent dump site,” says Jennifer Grant, the oil-sands director at the Pembina Institute. “If we’re in a situation where 20 years out—whoops—Base Mine Lake isn’t representative of the other pit lakes being proposed on the landscape, then we’re on the hook for addressing this volume of tailings.”

There’s also a question of scale, says Semenchuk. According to CEMA, various oil companies have plans for 30 end-pit lakes in northern Alberta. It may be possible for one or two lakes to fit in naturally with the environment, he says, “but can you do 30? The natural system can only tolerate so much.”

The question of waste is, of course, only one of the challenges facing oil-sands developers. To head off criticism, the Harper government announced last week a $40-million taxpayer-funded publicity campaign for the resource sector. At the same time, Natural Resources Minister Joe Oliver asked the Council of Canadian Academies to look at new technologies for extracting bitumen. The 13-member panel will be co-chaired by former Syncrude CEO Eric Newell.

In the meantime, the Base Mine Lake project continues. Those driving by along Alberta’s Highway 63 might not even know what lurks beneath the water. “For all intents and purposes, it looks like a lake,” says Chris Powter, executive director of the Oil Sands Research and Information Network at the University of Alberta. “But we need to see it work in real life.”

And will locals be able to swim in these lakes? “Maybe not right away, but eventually they might,” Powter says. “As soon as you have lakes in an area close to a population, there’s going to be some pressure to use them for something.”

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