Open pit mining in context
Open pit mines are surface mines where rock and minerals are extracted in large volumes and then sorted into valuable and non-valuable materials afterwards. Open pit mines are used when tunnelling is not viable because the valuable materials are too spread out or the ground is not structurally suitable for digging tunnels. These mines are used in hard rock mining for metal ores such as copper, gold, silver, iron, and aluminum.
The rock materials that are not processed (overburden) need to be relocated once the pit is created. When the valuable materials have been processed, tailings are created from the uneconomic parts of the ore. These tailings are placed into a pond or dam which can lead to a toxic environment due to the concentration of the unextracted sulfide minerals.
Reclamation of the mine has many concerns including the preservation of the top soil, segregation of waste material from tailings ponds, erosion control, drainage control, control of dust, regrading, and restoration. During the mining operation, vibration and impacts on water have the potential to cause problems as well.