It’s a “retirement” nearly 10 years in the making after almost 40 years of service. And it marks a significant milestone for Syncrude and the oil sands industry.

Syncrude has submitted the closure completion report for Coke Cell 5 (CC5) to the Alberta Energy Regulator (AER). Once accepted, Syncrude will remove CC5 from its list of dams.

“These dams are regulated by the AER because they retain fluids and tailings,” says Glen Miller, an Associate Geotechnical Engineer, Regulatory & Lease Development. “We have about 20 fluid-retaining structures on the AER’s registry. Once they are no longer required, we design and implement our closure plan then apply to remove them.”

What will make CC5 different than other dams in the oil sands is it’s the first-ever tailings facility reconfigured into a permanent, reclaimed landform that will be de-registered.

“We’ve had other dams de-registered, but they were in-pit structures submerged under water or tailings,” Glen says. “We are not burying CC5. We’ve physically modified it so it can be regulated in the same way as an inactive overburden dump. It is already revegetated and will eventually be ready to achieve a reclamation certificate, just like Gateway Hill.”

Construction began in 1985 on CC5, a ring dyke built with overburden to hold petroleum coke hydraulically poured into it. Syncrude completed the infilling of coke in late 1999. Ten years later, the AER approved Syncrude’s detailed closure plan showing the modifications required to close CC5, which covers an area of 170 hectares on the north shore of Base Mine Lake.

“After getting approval of our detailed closure plan, it took four years to complete the work, which included the excavation of an outlet in CC5’s southwest corner and recontouring a plateau into a shallow valley that drains environmental runoff towards that outlet,” Glen says. “We submitted the closure completion report in December 2020 and held a thorough field tour of CC5 with the person reviewing the submission for the AER in June. Now we’re just waiting to hear back from the AER soon and are very excited. This will be a significant milestone for Syncrude and for the industry.”

While many people were involved in the shepherding of CC5 towards this historic milestone, Glen singled out a couple key contributors.

“Wayne Mimura, who oversaw each step of this submission, from initial development to final review, as Senior Geotechnical Advisor and Engineer of Record for CC5. And Jack Law, as the Regulatory Affairs Advisor responsible for CC5, served as the point person with the AER and guided the submission’s scope,” Glen says.

As with many of successes here at Syncrude, collaboration helped fuel the success.

– Glen Miller

And Glen, who serves as Syncrude’s closure designer, expects to see the closure of tailings facilities become the norm in the coming decade.

“Folks should look forward to seeing this become routine. We’ve got a few in progress at Aurora and Mildred Lake sites. The East In-Pit detailed closure plan was submitted to AER this past June and we are currently in the process of developing a similar submission for South West In-Pit and then Base Mine Lake is next. To see these closure and reclamation projects accelerate in the areas where we first starting mining in the 1970s, it’s really rewarding to be a part of the final chapters that conclude our use of this land.”

From a mine pit to a tailings pond to an industry-first commercial demonstration of a pit lake, Base Mine Lake has gone through a series of changes over the years.

And much of the monitoring and research by scientists have charted the progress within the lake, right down to the tiny microbial communities that inhabit the 800 hectares of water (Micro-organism ‘hunter’ sees signs of progress in Base Mine Lake’s microbial communities).

Given the amount of research into water-capped tailings management technology since the early 1980s, it was unsurprising to see Syncrude turn to technology to solve the issue of oil sheens on the lake’s surface.

“Residual bitumen from extraction makes up a small portion of fluid fine tailings (FFT). When we placed the FFT into the pit that now forms Base Mine Lake, some of the bitumen was liberated, resulting in mats that formed in two corners of the lake,” says Brandon Kremp, a mining engineer in Tailings & Lease Development. “The initial filling of the pit and the bitumen mats have resulted in a hydrocarbon sheen on the surface and bitumen coating along the shoreline.”

Syncrude first attempted to remove the mats using a hydraulic dredging technology, where a large screw rotated into the tailings bed to disturb the bitumen, which was sucked by a cutter head similar to a vacuum.

“We pumped that material into a nearby holding pond in 2018 and 2019,” says Brandon, who joined Syncrude in 2019 after starting as a co-op student three years earlier. “Syncrude had used that technology to transfer materials being holding ponds for several years but it didn’t work as well on the bitumen mats due to the viscosity of the material.”
A team began researching alternatives and came up with another solution, an underwater mechanical excavator that could scoop material from the tailings bed.
“We began using this method when we started dredging in the middle of August and will use it until the end of the season, which typically comes near the end of October when the lake starts to freeze over,” says Sebastian Lastra Valenzuela, Team Leader, Mildred Lake Tailings Planning.

It’s very exciting to be involved in proving this concept and making sure it’s successful to show end-of-mine lakes are suitable closure features for both Syncrude and oil sands as a whole.

– Sebastian Lastra Valenzuela

Every operator has this type of lake in their closure plan and we are proud to be the ones pioneering it.”

As with proving any ground-breaking technology, the team has faced some challenges. “But we’ve learned from them and are gratified to see the result of a lot of hard work. We are at the very early stages but the technology is showing real promise,” says Sebastian, who joined Syncrude in 2014.

And the success to date has many authors as collaboration with other business units, including Research & Development, Tailings & Lease Development – Expense Projects and Operations – helped Sebastian’s team unlock the solutions.

“There’s a lot of people who deserve to share the credit for driving this project forward, including Keith Baker, Sandra Armstrong and Robert Trettenero,” says Sebastian. “Our work has also been strongly supported by Trevor Finlayson, Barry Bara, Dallas Heisler and Carla Wytrykush.”

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.”

Growing up in Saskatchewan, Dallas Heisler understood the importance of water from an early age.

“Water is prized given the prominence of farming where I grew up,” says Dallas, Syncrude’s Pit Lake Co-ordinator. “But we also recognize the value of water in the Wood Buffalo region. While agriculture isn’t a major industry here, the lakes, rivers and wetlands are very important. People want them to be protected. That’s no different than back home.”

Syncrude is bringing those values to managing Base Mine Lake, the demonstration project for its water-capped tailings The lake, which covers 800 hectares just south of Syncrude’s Mildred Lake upgrading complex, was a former mine pit prior to being a tailings pond.

“Syncrude completed tailings infilling at the end of 2012 and began importing fresh water from the Beaver Creek Reservoir starting in 2013 so there is now approximately 40 metres of fluid tailings covered with about 10 metres of water,” says Dallas. “Researchers from Syncrude (Medical equipment helps solve Base Mine Lake monitoring mysteries) as well as several universities, including the University of Toronto (Water is in her blood) and the University of Calgary (Micro organism hunter sees signs of progress in Base Mine Lakes microbial communities) have monitored the progress of Base Mine Lake since then. What they’ve found is the fluid tailings are dewatering, which reduces their volume. We’re also seeing promising changes in the water quality, which is in line with the 40 years of previous research we’ve done on water capping.”

Because Base Mine Lake is designed to function as part of a wider reclaimed landscape, it operates as a flow-through system with inflows and outflows similar to natural lakes.

“The inflow comes from the Beaver Creek Reservoir from the south. Right now, the outflow water is returned to Syncrude’s recycle water system,” Dallas says. “While the goal is to eventually have the lake flow out to the Athabasca River, we need to store that water on site at the present time until the federal governments establish regulatory criteria for treated mine water into the environment.”

Syncrude is working on demonstrating two technologies – water-capped tailings technology and coke-treatment (Warren’s innovation will help reclaim tailings ponds faster. – Syncrude) to eventually allow the release of mine water into the environment. Those releases are anticipated to be managed consistently with other releases approved from other industries in Alberta and Canada. Until then, all water – including Base Mine Lake’s outflow – must remain stored on site. “We are operating close to our capacity for mine water and tailings so we are looking at all options as we do not want to build a new tailings facility,” Dallas says. “As a result, we have decided not to bring in fresh water from Beaver Creek Reservoir to Base Mine Lake for this year. It is the responsible thing to do in order to manage our water inventory on site.”

The extensive monitoring program will continue to track changes within the lake through the year to determine how the change in water inflow influences Base Mine Lake’s performance.

We have a solid plan in place.

– Dallas Heisler

“We’ve tied this into all the work being done on the monitoring and research. We’ll continue collecting samples and getting researchers out on the lake and reporting those findings.”

The beauty of Sandhill Fen is more than skin deep. It goes deeper than the beauty of the plants and animals that thrive in its carefully designed wetland valleys and forested hills.

It penetrates some 60 metres below the surface landscape, where a Syncrude-developed technology enabled the use of oil sands mine tailings to fill this former mine pit back up to grade. In fact, the Fen and its surrounding watershed is the oil sands industry’s first example of mine reclamation over a foundation of treated tailings.

The Fen’s creation was part of Syncrude’s multi-pronged research spanning more than 20 years to design ways to construct the landforms that overlie the treated tailings; and foster the growth of peatlands, which are common in the natural landscape of the oil sands region of Northern Alberta. In essence, Syncrude set out to do what had never been done before. Syncrude has now published a Research Synthesis on its two decades of study.

The Fen was built in Syncrude’s former East Mine, an 11.5 sq. kilometre area at the company’s Mildred Lake site north of Fort McMurray, Alberta. Mining here ended in 1997 and the 57-hectare Fen watershed was commissioned in 2012, in the northern section of this site.

Before that topography could be created, the empty mine pit needed to be filled up, a process that was completed using Composite Tailings (CT) technology. This gargantuan task took more than a decade.

The CT process takes fluid fine tailings from tailings ponds (a mixture of water and suspended clay material) and mixes it with coagulant to create a slurry that is hydraulically deposited into the pit. The coagulant causes the tailings to quickly consolidate and release water to the surface of the deposit. This water is siphoned off and recycled; what remains is a soft sand-and-clay material. Too soft, for example, to support the heavy construction equipment needed to bring in the sand, soil and other landform materials that will overlie the tailings and allow later-stage reclamation and revegetation.

That meant a capping strategy also had to be developed. Wayne Mimura, Senior Associate Geotechnical Engineer, says, “Capping is a process of constructing a safe trafficable cap or cover over the softer CT deposit to minimize risk for people, animals and equipment. It allows the construction of topographic features such as hummocks (small hills) and swales (lowland areas) for reclamation and vegetation using sand. In particular, we wanted to form the sand cap such that the hills and lowlands would direct surface and ground water in a way that allows wetlands and forests to develop.”

Capping soft tailings deposits is done all over the world; while it hadn’t yet been done in the oil sands industry, there was a body of CT research created by the University of Alberta in the 1980s that Syncrude had supported. Based on that knowledge, a series of small-scale capping tests were initiated to study both hydraulic sand placement (via pipeline) and mechanical sand placement (using large mobile equipment); these tests informed Syncrude’s commercial-scale application in the East Mine, where both techniques were used.

The capping technology creates a surcharge load over the underlying CT deposit. This allows the CT to dewater and gain strength over time, and minimizes the amount of settlement of the closure topography.

“This was the first in the oil sands industry,” says Wayne, who has been working for Syncrude for 32 years.

Successfully capping CT using conventional tailings technology has allowed Syncrude to reclaim and revegetate the land for its intended land uses.

– Wayne Mimura

The technology is now also being transferred to successfully cap and reclaim other soft deposits.”

While R&D work to address the capping issue was underway, the parallel challenge of CT tailings reclamation was also being addressed. This involved engineers working together with natural resource scientists.

“Whenever scientists and engineers are faced with a new challenge, we start with what we know,” says Syncrude ecologist Carla Wytrykush. “Although we had never reclaimed CT before, we had a lot of experience reclaiming overburden landforms and the tailings sand slopes of external tailings facilities. We knew that the CT and sand cap would release pore water to the surface of the land. We also knew that other experts could help us.”

Syncrude involved researchers from several scientific disciplines in the design of the CT reclamation pilot.

By inviting these diverse perspectives on the challenge, the opportunity to create the Fen was identified. Tailings researchers and engineers explained CT and its properties. Wetland ecologists shared how different wetlands form.

We knew we needed to develop CT reclamation practices, and we knew that fen reclamation was important to government and Indigenous stakeholders.

– Carla Wytrykush

Through collaboration, we brought these two challenges together into an incredible opportunity to advance CT and fen reclamation at the same time; the result is the Sandhill Fen Research Watershed.”

Carla says, “The Fen was built at the north end of the East Mine as soon as we could drive on it. Today, after nine years of intensive research and monitoring, it has an incredible story to tell: The wetland supports a range of plants typical of peatlands in the region; we’ve got peat formation; and we’ve got carbon accumulation. Those are huge wins in my mind. It’s informing how we are reclaiming the rest of the East Mine area. This work will be fully completed in the next few years and it will be the first fully reclaimed mine in the oil sands.”

The next time you hear about the Sandhill Fen, think about the beauty enshrined deep beneath the lush, green wetland.

Those interested in the synthesis of Syncrude’s Composite Tailings Capping Knowledge, which includes learnings from the Sandhill Fen Watershed, can download the materials here. The Synthesis includes research summary reports and a bibliography of scientific publications. Syncrude thanks the University of Alberta for making the Synthesis accessible to everyone on their Education and Research Archive online library.

When Dustin Stuyt and his team sought solutions to extend the life of tertiary sizer teeth in Syncrude’s ore crushing units, they looked internally to the Research and Development department for ideas.

The collaboration resulted in new technologies that could see oil sands mining and extraction equipment of all kinds running for years before they need maintenance.

Syncrude has been tackling material wear issues since production began in 1978. The abrasive nature of oil sand combined with the extreme temperatures throughout the year in Northern Alberta have played havoc on shovel teeth, grader blades, and tertiary sizer teeth in particular. As equipment and technology have changed, so have the solutions to these issues. The ultimate goal is to extend equipment performance as long as possible before replacement is required.

The company’s Leading Edge Advanced Performance (LEAP) project was created five years ago to look at extending the life of equipment in direct contact with oil sand and rock materials. Dan Wolfe, senior associate, Mechanical with R&D, leads the project and their work on tertiary sizer teeth has revealed viable solutions including friction welding technology adapted from the aerospace industry.

Tertiary sizers are the final step in wet crushing technology used at Syncrude’s North Mine operation to process oil sand and prepare it for hydrotransport. After oil sand is broken down by crushers in the field to about the size of a beach ball, the material has water added to it while it passes through two sets of sizers before being sent to Extraction. In secondary sizing, those beach ball pieces become the size of a volleyball, and after tertiary sizing the pieces are softball size or smaller.

Syncrude’s North Mine uses a wet crushing technology that mixes crushed oil sands with water through secondary and tertiary sizers to produce a slurry for bitumen extraction. New technology developed for the sizer teeth has the potential to extend unit run life 10 times longer than is currently achieved.

The magic happens in the tertiary sizers.

– Dustin Stuyt

“It’s the last step where oil sand is mixed with water and chemicals to convert it to a slurry of finer particles that can be easily transported to Extraction,” says Dustin Stuyt, a senior engineer with Equipment & Reliability Engineering.

Unlike other extraction technologies on site where screens reject materials larger than a specified maximum before the remainder enters the hydrotransport system, the use of sizers allows everything to be fed into the system allowing for greater bitumen recovery and fewer maintenance issues along the way to Extraction. There are four of these systems operating in parallel at North Mine.

The sizers consist of four rotating shafts about five metres long with fist-sized teeth. There are 432 teeth on each of the shafts on the tertiary sizers for a total of 1,728 in a machine. Over a typical run of 2,000 hours, more than 10 million tonnes of oil sand will pass through the system before the teeth will need maintenance, with the tertiary sizers taking the brunt of the wear.

The wear issue is significant in the sizers, because if you lose one inch off the teeth, larger materials get through and you’ll start damaging equipment downstream.

– Dan Wolfe

Dustin’s Extraction team and R&D tested a number of options for the tertiary sizer teeth with various degrees of success – including a test that both he and Dan referred to as a horrific failure – until they discovered two tungsten carbide options with serious potential.

Tungsten carbide is a dense, metal-like substance about two times heavier than steel and up to 10 times harder. It’s the hardest material commercially available to Syncrude and wears extremely well, but it is prone to cracking when attached to steel with traditional joining processes.

The first option to the team was teeth sourced from a US-based company specializing in tungsten carbide products. They developed a sizer tooth with broken bits of tungsten carbide recycled from hard rock drills embedded in the first centimetre of the tooth.
“These teeth cost less than what we’re currently using and so far the results have shown they can last about twice as long,” says Dustin.

Tertiary sizer teeth ready for action. The teeth are made from solid blocks of 25-millimetre thick tungsten carbide clad with a Kovar coating and attached to the segments using a friction welding technique.

The new teeth are being attached to the sizer segments as maintenance rebuilds take place. Using the previous teeth, the team budgeted for nine rebuilds per year but the new, lower-cost sizer teeth could reduce rebuilds to as few as three per year – meaning millions of dollars in annual savings.

“We think the teeth could process up to 30 million tonnes of ore before they need replacement,” says Dustin. “With the addition of small tungsten carbide studs between the teeth, we are seeing better product for hydrotransport and our wear rates have dropped off by 50 per cent since the wet crusher was commissioned.”

A second option, while more complex, is showing even greater potential. It involves cladding solid blocks of 25-millimetre thick tungsten carbide with a Kovar coating, and attaching them to the segments using a friction welding technique. Kovar is a unique iron-nickel-cobalt alloy that expands and contracts like the tungsten carbide material. When Kovar cools from the cladding operation it doesn’t create residual stress at the bond line. Without the Kovar coating, a crack forms when the tungsten carbide is welded to the steel and it doesn’t take long for the block to break off.

Hugh Roth is a senior associate, Metallurgy at R&D, who tested this new technology and introduced the Kovar coating/friction welding solution. “With friction welding the weld takes seconds to make. It is only hot at the interface and the carbide doesn’t know it’s being welded,” he says.

Syncrude is the first company to evaluate this technology and we anticipate it having benefits for a wide range of earth engaging equipment.

– Hugh Roth

Syncrude is analyzing results as they come in and is looking to evaluate the technology for other applications. R&D tested friction welding on grader blades and tertiary sizers this winter with extremely positive results. While regular grader blade edges last about two weeks before they need to be replaced, the test showed potential for them to last an entire season. Additionally, 66 of the friction welded sizer teeth were put into service and all of them showed little to no wear after two months. It’s possible the teeth could last 10 times longer than current teeth, or 20,000 hours.

“It’s a totally different level of capability,” said Hugh. “We can design and operate equipment in a completely different way now that we know materials can last 20,000 hours or more and we can rely on the metal keeping its shape. Outage schedules don’t have to be what they were, and we may not have to build redundancy into our operating equipment.”

While there is excitement for the results to come from this collaboration, Dan believes more can be done to improve wear rates in the future. Developing two parallel solutions for a big problem and applying those ideas to other leading edge issues, means there is more testing to do. And with that, more innovations to come for R&D and Bitumen Production to extend wear life on machinery and equipment.

Warren Zubot is leading the team behind an exciting innovation that’s targeting faster, more effective reclamation of tailings areas.

Syncrude takes its environmental responsibilities seriously. That’s why we’re always looking for new and better ways to improve our sustainability and environmental performance. Take Warren, a Senior Engineering Associate who is on a mission to find a way to treat tailings water for safe release.

Tailings, a byproduct of extracting bitumen from oil sand, are stored in tailings ponds and are a mixture of water, sand, clay, fine solids, residual hydrocarbons and salts. Although these ponds are the source of water that is recycled and used in our production processes, their growth is something we want to avoid. Having the ability to treat and safely release tailings water will eliminate the need for long-term storage and allow faster and more effective return of land to a natural state.

That’s where Warren’s innovation comes in.

Applying principles that are similar to a home water filter using activated carbon, Warren’s technology uses petroleum coke from Syncrude’s upgrader to remove the unwanted compounds from tailings water, transforming it so that it can safely support aquatic life and other downstream uses. Once tailings water becomes safe for release, tailings areas can be returned back to a productive natural state, making this water treatment innovation a huge step in solving a major reclamation challenge.

After a successful small-scale pilot in 2012, Syncrude contracted one of the region’s leading Indigenous businesses to design and construct a full-scale pilot treatment facility, as well as manage the ongoing monitoring of treated water. The facility began operation in June 2019.

It takes a lot of outside-the-box thinking to create something that’s never been done before. It took a lot of collaboration across Syncrude teams, along with the skills of a local Indigenous business to make it possible.

– Warren zubot

Syncrude has engaged Indigenous communities and other regional stakeholders to educate them about the project, seek feedback and ensure we work with our neighbours to mitigate their concerns.

As always, Syncrude will share insights with our industry partners through COSIA, as well as with academic institutions to advance knowledge and ensure results are transparent and publicly available in peer-reviewed scientific literature.

When Rochelle Young first started working at Syncrude 20 years ago, she heard about plans to turn the west in-pit tailings pond into a lake.

“I remember wondering, ‘How is that actually possible? I was working as an environmental scientist and it was hard to imagine.”

Today, Rochelle works as a Regulatory Affairs Advisor and that tailings pond is now Base Mine Lake, an eight-square-kilometre pit lake that borders Highway 63 to the west as you travel south from the Mildred Lake site.

Syncrude stopped using it as a tailings facility close to 10 years ago – on Dec. 31, 2012. The lake now plays a critical role in Syncrude’s reclaimed landscape as the first commercial-scale demonstration of water-capped tailings technology and the oil sands industry’s first pit lake.

But, why pit lakes? Surface mining results in large pits that must be reclaimed. Some mine pits are filled with mine materials such as overburden or tailings to form a solid surface, which is then reclaimed to forests and wetlands. Other mine pits are reclaimed to lakes.

Due to the nature and timing of mine material movement and use, the overburden that was removed to initiate the pit is reclaimed as soon as practical on Syncrude’s site. This is part of our commitment to progressive reclamation and meeting our goal of minimizing the effect of disturbance.

However, this leaves insufficient material available to fill one or more of the mine pits at the completion of mining. These pits may be partially or fully filled with water (mine and/or fresh water) and reclaimed as a lake (pit lake). Pit lakes reduce the need for material re-handling, which would result in increased emissions from material transportation (such as greenhouse gases or nitrogen oxides), lengthen reclamation timelines and success, and increased costs.

Pit lakes are used at open-pit mine sites around the world, and are a global mining industry best practice for reclamation and closure. Pit lakes support a variety of plants and animals typical of aquatic ecosystems and are integrated into the reclaimed landscape.

“Syncrude has included water-capped fluid tailings in pit lakes since its earliest closure plan designs,” says Rochelle. “The Alberta regulator gave our company approval to have Base Mine Lake as a demonstration to prove that pit lakes are viable.”

Developing a successful pit lake requires planning, monitoring and research to learn and guide lake management.

Pit lake designs and plans have changed over time to reflect the state of knowledge of oil sands mine waters and tailings, technology advances, changing regulations and inputs from local stakeholders and Indigenous communities.

Base Mine Lake’s water capping technology includes filling the empty mine pit with fluid tailings (a mixture of clay, fine solids, water and residual bitumen), and then capping it with water to form a lake. The demonstration intends to show that the water quality will improve over time while the tailings solids remain isolated at the bottom of the lake.

Rochelle, who is working on several tailings projects, explains pit lakes are just one of a suite of reclamation methods that are used today and that like with any reclamation project, there are challenges. However, she believes that this is a challenge that Syncrude will meet.

“Results of the water-capped tailings technology are very positive so far. Syncrude is demonstrating we have physically sequestered the tailings from the water body,” says Rochelle. “We are also showing the water quality is improving over time, which is supporting natural biological communities to develop.”

With roughly 40 years of rigorous research on pit lakes among Canadian oil sands producers, Rochelle is confident and optimistic about Syncrude’s reclamation that includes Base Mine Lake and future pit lakes to come.

It is amazing to see the progress over the past 20 years. The Base Lake Mine project demonstrates what can be achieved with research, experience and hard work. It shows what seems impossible is within your reach.

– Rochelle Young

Peter Dunfield has spent a long and distinguished career poking around rice paddies, peatlands, volcanoes and tailings ponds searching for nature’s tiniest grazers, single-celled micro-organisms that chew up methane.

That quest led the University of Calgary microbiologist to Syncrude’s west in-pit tailings pond in 2012, where he and his team isolated, identified and described two new micro-organisms – Methylicorpusculum oleiharenae and Oleiharenicola alkalitolerans.

“You have to use Latin when describing new species. The first means small-bodied methyl-eater while the second one is alkali-tolerating oil sands dweller,” says Peter. “Identifying these new species is fun, although our main job is to monitor the microbial communities in Base Mine Lake using DNA signatures, and compare them to an active tailings pond and a natural lake. Isolating and describing new microbial species is a sideline and takes a lot of tedious lab work. But when we find something interesting, we do it.”

Dr. Dunfield examining water samples from Base Mine Lake.
Photo Credit: Nadya Dunfield.

In the case of Methylicorpusculum oleiharenae – the small-bodied methane eater – what interests Dunfield is the micro-organism that was abundant in the west in-pit tailings pond in 2012 is now almost nonexistent in Base Mine Lake eight years later.

“That one has now almost disappeared from Base Mine Lake, which is an indication the lake is no longer a tailings pond.”

People should not be concerned that new species are evolving in tailings ponds, because microbial species generally do not evolve over short periods of time.

– Peter Dunfield

With these kind of species, we are talking about tens or hundreds of millions of years of evolution. What we isolated have already existed somewhere. My suspicion is they existed in oil sands seeps or other petroleum deposits but they found a really nice home in the tailings ponds. But they have already existed in nature.” he says. “There are still methane-eating bacteria in Base Mine Lake but different ones have colonized the lake because the conditions have changed and that’s a sign of progress. There have been dramatic changes in the microbes in the lake over the past six years – it really doesn’t resemble a tailings pond any more. It’s somewhere in between a tailings pond and a natural lake now.”

PhD student Chantel Biegler extracts microbial DNA from Base Mine Lake water samples. The DNA will be sequenced to determine what microbes are present in the lake.

Photo Credit: Nadya Dunfield.

Peter and a team of 10 present and former graduate and post-doctoral students have monitored Base Mine Lake since 2014 as part of a group of outside experts from different universities and research institutions working on different areas.

“We’ve enjoyed working on this project – Syncrude has been really good to work with as a partner. It’s a lot of fun – they have a diverse group assembled to look at this lake – we have limnologists, micro-climatologists, geochemists, biologists among other disciplines,” he says. “We’ve learned a lot from each other.”

Base Mine Lake has also provided lessons of its own.

“We’re quite surprised. We thought it might take decades for things to change. We certainly are seeing changes already.

– Peter Dunfield

“There have been dramatic changes, not only in the species of methane oxidising bacteria, but also in other key players such as phototrophic algae. The overall microbial biodiversity appears to be increasing. The lake is trending in a positive direction.”

Learn more about research at Syncrude.

A need to solve monitoring mysteries for Base Mine Lake prompted one Syncrude researcher to turn to medical equipment and the results have been great.

Barry Bara, a senior technical specialist with the Mine Closure Research Team needed to measure the bitumen and gases on the surface of the lake. He also wanted to locate mats – deposits of bitumen formed after tailings were placed into the lake bottom – so they could be removed.

The lake is a former mine pit now reclaimed as an aquatic landscape feature that sequesters the tailings material underneath the water layer. Syncrude completed the placement of tailings into the pit at the end of 2012 and began adding fresh water.

Research dating back to the late 1970s showed the technology would turn the area into a lake capable of sustaining aquatic life, which will be incorporated into the reclaimed landscape. Syncrude had already demonstrated this through a series of test ponds. Base Mine Lake is the first time the technology is being used on a large scale in the oil sands.

Researchers have conducted extensive monitoring and testing to check the progress of the lake since 2012. One important but difficult measurement is the amount of bitumen and gas in the lake. But the team discovered you could find those elements in the ice that formed on the lake during the winter

Last winter, Barry and his team harvested 200 ice cores 60 to 70 centimetres thick from the lake.

These cores may contain gas and bitumen, which rise to the surface. During the winter, they are frozen into the ice. We want to get an idea of what is coming up in different areas of the lake.

– Barry Bara

“If you keep doing that year after year, you can identify the areas where to concentrate your remediation. Then you can demonstrate you’ve reduced the bitumen because you have the actual measurements.”

With the use of a computed tomography (CT) scanner – a medical imaging machine – Barry and his team were able to find out from the samples how much bitumen came to the surface.

In collaboration with Coanda Research and Development, Barry also pursued another piece of medical imaging equipment to locate bitumen mats at the bottom of the lake. Ultrasound machines use sound waves to see inside the human body. He saw an opportunity because ultrasound works the same as sonar-based fish finders used by recreational anglers. Syncrude bought a commercial sonar unit and Barry hopes it can identify bitumen mats.