and mammals are present in and around the demonstration watershed.” While the lake doesn’t currently discharge to the environment, the long-term plan is for its water to eventually integrate into the regional watershed. Prior to release, water will be monitored and tested to ensure it meets regulated water quality guidelines, Guest said. In the meantime, Suncor adds fresh water and withdraws water for use in its mine operations.
Base Mine Lake. Photo courtesy Pathways Alliance
PASS technology demonstration
Suncor is implementing permanent aquatic storage structure (PASS) technology at a demonstration site that includes Lake Miwasin, a 10-metre-deep lake with a five- metre water cap. PASS uses common treatment agents to help tailings settle and release water more quickly. The process speeds up consolidation and helps improve overall water quality. The company says early results are promising, showing expected improvements in water quality and the re- establishment of vegetation. Insights from local Indigenous communities have helped refine techniques, including influencing landform design and identifying culturally important plants and trees. Confidence in pit lakes “Results from Base Mine Lake and Lake Miwasin give us the confidence that pit lakes are a safe and integral component of our planned closure landscape,” Guest said. The transition to a fully reclaimed boreal landscape in Alberta’s oil sands will take time. Most of the reclaimed area will consist of forests and wetlands, with pit lakes expected to account for less than 10 percent.
Supported by long-term research Numerous pit lakes, with and without tailings, are proposed or planned for the oil sands region. Each is designed to integrate into the final reclaimed landscape, supporting sustainable water management and creating new habitats for aquatic and terrestrial life. Long-term research and monitoring at several sites—some dating back to the 1980s—has shown that water-capped tailings can be effective. Bacteria quickly break down many compounds within the tailings, while the solids settle naturally within weeks. The water layer above largely prevents tailings sediments from migrating back to the surface.
Aquatic technologies contributing to reduction of legacy “
tailings ”
Base Mine Lake performance
At Base Mine Lake, for example, a water cap currently between 10 and 13 metres covers the tailings. Ongoing research and monitoring show it’s performing as expected, Guest said. “The tailings remain contained at the bottom and don’t mix with the water,”he said. “Water quality continues to improve, diverse habitats are forming, and typical boreal lake life, including insects, invertebrates, plants,
*References to land that is reclaimed, permanently reclaimed and surface reclaimed meet the definition of “permanently reclaimed” as defined in the Alberta Energy Regulator Direction for Conservation and Reclamation Submissions (December 2018).
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