The science beneath the surface of Base Mine Lake

To the untrained eye, Base Mine Lake looks like an unremarkable body of water with the sole oddity of having mechanical falcons and other noise-makers floating on buoys to deter waterfowl from landing on its surface.

Beneath that water and surrounding landscape, close to 40 years of research has gone into the lake, a demonstration project of Syncrude’s water-capped tailings technology to turn a former mine pit and tailings pond into a lake capable of supporting aquatic plants and animals.

“Syncrude and its researchers have earned more than 240 patents but we have just one to show for all the research put into the water-capped tailings technology. That’s primarily because we are sharing our intellectual property on our reclamation technologies publicly,” says Mal Carroll, Syncrude’s Manager – Research & Development. “Six universities have conducted research on Base Mine Lake’s progress as part of a very extensive research and monitoring program and they share their findings through peer-reviewed papers. We also share what we’ve found with our industry partners through organizations such as Canada’s Oil Sands Innovation Alliance as well as post that research online.”

Syncrude first began looking at capping fluid tailings – a byproduct of mining and extracting bitumen from oil sands ore – in the early 1980s. Open-pit mines throughout the world have created pit lakes to reclaim their mines, but it had never been attempted in the oil sands.

“Syncrude scales up its research and it was no different with this technology,” says Mal, who has worked for Syncrude for 27 years. “Researchers began with bench-scale experiments in the lab. We then moved into field research by establishing seven small tailings test ponds at the Mildred Lake site in 1989. That work continued with the development of four larger test ponds in 1993.”

Those findings convinced Syncrude to move ahead with Base Mine Lake, a former tailings pond in the original Base Mine, located just south of the Mildred Lake upgrading complex west of Highway 63. Syncrude stopped pouring in fluid tailings at the end of 2012 and began adding fresh water from the Beaver Creek Reservoir, and mine process water in 2013. The lake now covers 800 hectares with about 45 metres of fluid tailings. The tailings were capped by five metres of water, and with dewatering the water cap is now up to 12 metres deep. Syncrude, the University of Toronto (Water is in her blood), McMaster University, University of Alberta, University of Calgary, University of British Columbia and the University of Saskatchewan have conducted research and monitoring on Base Mine Lake to chart the progress in several different areas, including, dewatering of the underlying fluid tailings layer and water chemistry.

“We’re really pleased with what we are seeing.

– Mal Carroll

The fluid tailings are dewatering. Researchers are tracking changes in the water, right down to the microbial level (Micro-organism ‘hunter’ sees signs of progress in Base Mine Lake’s microbial communities),” says Mal. “We’ve made a lot of progress but recognize there’s still work to be done. And going forward, we will continue to have science guide us, just as we have over the previous four decades. And we will continue to share our findings with the public, particularly the Indigenous community members who have visited Base Mine Lake and want to learn more about it. Patents are nice but transparency is very important with this project. We want people to know we are getting this done the right way.”

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