About 20 per cent of Alberta’s oil sands reserves are recoverable by surface mining, where oil sands are excavated using trucks and shovels and transported to extraction plants to separate the bitumen. This bitumen can be sold as a product or further upgraded to synthetic crude oil. Operators must manage and mitigate the impacts of mining projects and ensure that the resource is not wasted.
Tailings are what remain after about 90 per cent of bitumen has been removed from the ore that was excavated from the ground. It consists of water, silt, sand, clay, and residual bitumen. To protect the environment, tailings are deposited in man-made tailings ponds surrounded by dikes and collection and monitoring systems.
When a mine begins operation, external tailings ponds with above-ground dikes are constructed. Once a mined-out pit becomes available, tailings are stored there. The majority of tailings are currently stored this way.
Tailings ponds are essential to oil sands mining operations as they act as both holding areas, where the majority of the water needed for bitumen extraction can be recycled, and as settling basins for solids.
While sand tends to settle quickly in tailings ponds, the smaller particles of clay and silt, with a size equal to or less than 44 micrometres, tend to remain suspended, forming fluid tailings. Without intervention, fluid tailings take decades to slowly settle, and even then only to a consistency of soft mud, making the management of these fluid tailings an ongoing challenge for the oil sands mining industry.
When fluid tailings are not managed effectively, their volumes increase and more tailings ponds are needed to store them. Over time, the AER noted that operators were failing to meet tailings performance commitments made in project applications, contributing to the proliferation of tailings ponds and delayed reclamation. The AER responded in 2009 by introducing Directive 074: Tailing Performance Criteria and Requirements for Oil Sands Mining Schemes, which set out clear and measureable targets to reduce fluid tailings and form trafficable deposits.
Significant progress in tailings management has been made since Directive 074 was released in 2009.
In response to Directive 074, oil sands mining operators have:
These benefits are an important step to the continued advancements in the management and reclamation of fluid tailings. The release of the Government of Alberta’s Tailings Management Framework is the next progression of tailings management in Alberta.
Part of the AER’s mandate is to ensure that Alberta’s resources are not wasted. Directive 082: Operating Criteria; Resource Recovery Requirements for Oil Sands Mine and Processing Plan Operations sets out operating criteria to identify the oil sands that an operator is required to mine and estimate the volume of bitumen that an operator is required to recover. The AER strives to allow industry appropriate operational flexibility, while at the same time ensuring the conservation of Alberta’s oil sands resource.