A tailings ponds primer

Alan Fair, director of COSIA’s EPA, discusses tailings ponds, challenges and efforts to reduce the tailings pond footprint. Q: What are tailings ponds?

A: Tailings ponds provide the opportunity to recycle 85% to 90%-plus of the water used in the extraction process that liberates bitumen from oil sands ore. They are also where residual material (tailings) from extraction is stored. Tailings are

composed of sand, silt, clay, residual bitumen and other naturally occurring substances. There are two types of tailings — coarse tailings and fluid fine tailings (FFTs). Coarse tailings are made up of silica sand particles which, when discharged into a pond, settle out quickly. The sand can then be used as construction material and the water recycled. FFTs contain fine clay particles that do not settle out but remain in suspension, creating a water solution the consistency of runny yogurt. These FFTs are contained within the oil sands tailings ponds. Q: What will happen to tailings ponds? A: At the end of a mine’s life, all tailings will be treated and by law all disturbed areas must be reclaimed, including all tailings ponds. Q: What has been reclaimed?

A: Significant areas of tailings pond dikes have and are being reclaimed at a number of sites, including Suncor’s Pond 1 (Wapisiw Lookout), the first tailings pond in the oil sands which was decommissioned and reclaimed in 2010. The surface of the pond is now revegitated. When reclamation is complete, Wapisiw Lookout

will span an area of over 540 acres with mixed forest and wetland that support a diversity of plants and wildlife.

Q: How is technology helping to speed up reclamation?

A: Every site is unique, so there’s not a one-size-fits-all solution. However, there are a number of technologies employed to greatly accelerate the reclamation process. They include: Tailings reduction technology; Tailings centrifuges that accelerate dewatering and the drying of tailings fines that can be mixed with sand and soil to support plant life;

Accelerated dewatering which allows the dewatered FFTs to be placed in mined-out pits and reclaimed over

time. The waste water can be recycled more quickly;

Cross-flow filtration that removes water from the extraction tailings stream before it reaches the tailings pond, thereby reducing the need for tailings ponds; and,

A filter press process that renders FFTs dense enough for use in land reclamation. In 2013, COSIA members contributed in excess of $79-million to collective research and development devoted to tailings management. Working together the companies can do better work, faster and more cost effectively.