A waste dump, also referred to as a waste rock dump, overburden dump, or spoil pile, is a surface structure where non-economic or sub-grade rock materials removed during open-pit or underground mining are permanently deposited. In bauxite mining, waste dumps typically contain stripped lateritic overburden and low-grade ore that does not meet cut-off grade criteria. These structures must be designed and managed to prevent erosion, slope instability, and surface water contamination. In gold mining, waste dumps may contain sulphide-bearing rock capable of generating acid mine drainage (AMD), making their engineering design and environmental monitoring particularly critical. Iron ore waste dumps are often massive structures containing billions of tonnes of banded iron formation, shale, and low-grade mineralised rock, requiring elaborate drainage, compaction, and revegetation programs. In diamond mining, kimberlite waste dumps accumulate material that has been processed and found to contain insufficient diamonds or no diamonds at all. All waste dumps are subject to geotechnical design criteria governing slope angle, lift height, foundation conditions, and drainage infrastructure. Progressive rehabilitation of waste dump surfaces — including topsoil replacement and revegetation — is increasingly required to minimise long-term environmental liabilities.
