|  | Tailings Management
Tailings are the water, clay, sand and residual bitumen that remain after the bitumen extraction process. These materials all occur naturally under the surface of the land prior to being mined. Imperial’s tailings process focuses on managing issues associated with the tailings until they can be safely returned back to the environment during ongoing reclamation of the Kearl lease.
At the start of operations, Kearl needs a place to store tailings for about 10 to 12 years until space becomes available to process and then return them into the mined-out pit. During this initial period, the tailings will be held in a carefully engineered external tailings area in the northeast portion of the lease.
Recognizing that Kearl’s external, above-ground tailings area could potentially leak, it is designed with technology to intercept, monitor, and return virtually all seepage back into the tailings area. A series of groundwater wells placed around the perimeter of the pond will collect and recycle water that leaks, or seeps, into the groundwater. A series of groundwater monitoring wells located beyond the pumping wells along the lease boundary will allow us to identify and correct any localized areas where excess off-lease seepage could occur. This system of wells will be in operation for many years until the external tailings area has been fully reclaimed and seepage water is safe to return to the environment. During that time, natural bacteria in the ground and water will bioremediate the residual traces of contaminants, breaking them down into components that are not harmful to the environment. These measures are consistent with Alberta Environment’s strict regulations that ensure groundwater is not affected by any seepage from tailings ponds.
Kearl’s current plans include the use of state-of-the-art technology to make the tailings area as unattractive to water birds as possible. This will include an effective combination of deterrent devices, noises, detection equipment and monitoring efforts.
Once Kearl has been in operation for 10 to 12 years, space will become available to process and then return the tailings to the mined-out pits. At this point, “consolidated tailings technology” will be implemented. From then on, tailings from the extraction process will go directly to the consolidated tailings process and there will no longer be a need for the external tailings area. The external tailings area will be emptied and reclaimed over several decades. The settled fine solids – the mature fine tailings – will be dredged from the bottom of the tailings ponds and sent to the consolidated tailings process. The remaining water will be reused in the extraction process. Over time, the external tailings area will be filled in with sand or overburden to create a contoured landscape incorporating above-ground streams.
Consolidated Tailings (CT) Technology
Consolidated tailings technology involves blending the mature fine tailings from the tailings pond with tailings that come directly from the extraction process – and gypsum – to form a thicker, more solid material that naturally dewaters and forms into a solid landscape. This material will be sent to designated areas within the mined-out pits where it will consolidate over a relatively short time frame and release water. This water will be recycled back to the extraction process.
With time, the resulting consolidated tailings become strong enough for heavy equipment to drive over them to place previously stored soil layers and vegetation over the surface to create a stable landscape for reclamation. Eventually all fine tailings and process-affected water will be removed from the external tailings area, allowing it to be reclaimed. Seepage control measures will remain in place until water quality meets regulated release criteria.
The application of consolidated tailings technology is relatively new, but the technology has been demonstrated. It is the result of over 10 years and $30 million of research and development at Syncrude alone, where the technology has been demonstrated on a commercial scale.
| Consolidated tailings are strong enough to create a stable landscape during reclamation.
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Other Tailings Research
Imperial Oil, in partnership with the University of Alberta and Alberta Ingenuity, has established the Centre of Oil Sands Innovation. One research area is non-water based extraction processes for oil sands mining that would significantly reduce the use of fresh water and could also result in the production of dry tailings. Imperial also participates in the Canadian Oil Sands Network for Research and Development (CONRAD) Tailings Research Programs.
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