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.”