How are tailings stored/contained?

Tailings are typically stored in engineered structures called tailings storage facilities (TSFs) or more colloquially, a tailings dam. A TSF comprises of physical impoundment that stores the solid material, as well the supporting infrastructure for managing the water. Considering the amount of tailings produced relative to the commodity produced from mining, TSF can cover vast swathes of land. In fact TSFs are among the largest engineered structures on earth.
The tailings material is generally stored behind an embankment that can be engineered from other materials (borrow material from the earth, or waste rock from the mine development) or self-raised using the tailings material itself. The latter method is the most economical, however, introduces its own risks.
The water collected in these facilities from the slurry and from precipitation must be managed to control seepage through the placed solid material – that inherently make them less stable or have dedicated storage dams that hold water that has been in contact with the tailings is no longer safe for environmental release (in most cases).

While some dewatering technologies are fast becoming mainstreamed in mining today, such as filtration, the use of water in mining, and their presence in tailings is still a fundamental concern that must be addressed in their design.