Tailings dam

A tailings dam is typically an earth-fill embankment dam used to store byproducts of mining operations after separating the ore from the gangue. Tailings can be liquid, solid, or a slurry of fine particles, and are usually highly toxic and potentially radioactive. Solid tailings are often used as part of the structure itself.

Tailings dams rank among the largest engineered structures on earth. The Syncrude Mildred Lake Tailings Dyke in Alberta, Canada, is an embankment dam about 18 kilometres (11 mi) long and from 40 to 88 metres (131 to 289 ft) high. The dam and the artificial lake within it are constructed and maintained as part of ongoing operations by Syncrude in extracting oil from the Athabasca oil sands; it is the largest dam structure on earth by volume, and as of 2001 it was believed to be the largest earth structure in the world by volume of fill.

There are key differences between tailings dams and the more familiar hydroelectric dams. Tailings dams are designed for permanent containment, meaning they are intended to "remain there forever". Copper, gold, uranium, and other mining operations produce varied kinds of waste, much of it toxic, which pose varied challenges for long-term containment.

There are an estimated 29,000 too 35,000 tailings dams around the world with a rate of .011/Mt of world minereal production. (State of World Mine Tailings 2020 www.worldminetailings failures.org. The Responsible Mining Foundation, found that companies have made little or no progress in improving the documentation and safety practices of these ponds.World Mine Tailings Failures has documented that the number of catastrophic tailings dam failures by decade has steadily increased at a statistically significant level since 2000.