section_path: Environmental effects/Waste
section_name: Waste
paragraph_text: Waste
  
  Ore mills generate large amounts of waste, called tailings. For example, 99 tons of waste is generated per ton of copper, with even higher ratios in gold mining – because only 5.3 g of gold is extracted per ton of ore, a ton of gold produces 200,000 tons of tailings. (As time goes on and richer deposits are exhausted – and technology improves – this number is going down to.5 g and less.) These tailings can be toxic. Tailings, which are usually produced as a slurry, are most commonly dumped into ponds made from naturally existing valleys. These ponds are secured by impoundments (dams or embankment dams). In 2000 it was estimated that 3,500 tailings impoundments existed, and that every year, 2 to 5 major failures and 35 minor failures occurred. For example, in the Marcopper mining disaster at least 2 million tons of tailings were released into a local river. In 2015, Barrick Gold Corporation spilled over 1 million liters of cyanide into a total of five rivers in Argentina near their Veladero mine. Since 2007 in central Finland, the Talvivaara Terrafame polymetal mine's waste effluent and leaks of saline mine water have resulted in ecological collapse of a nearby lake. Subaqueous tailings disposal is another option. The mining industry has argued that submarine tailings disposal (STD), which disposes of tailings in the sea, is ideal because it avoids the risks of tailings ponds. The practice is illegal in the United States and Canada, but it is used in the developing world.
  
  The waste is classified as either sterile or mineralized, with acid generating potential, and the movement and storage of this material form a major part of the mine planning process. When the mineralised package is determined by an economic cut-off, the near-grade mineralised waste is usually dumped separately with view to later treatment should market conditions change and it becomes economically viable. Civil engineering design parameters are used in the design of the waste dumps, and special conditions apply to high-rainfall areas and to seismically active areas. Waste dump designs must meet all regulatory requirements of the country in whose jurisdiction the mine is located. It is also common practice to rehabilitate dumps to an internationally acceptable standard, which in some cases means that higher standards than the local regulatory standard are applied.