Waste encapsulation is an engineering technique used in mining operations to isolate chemically reactive, toxic, or radioactive waste materials within a contained structure that prevents harmful constituents from migrating into the surrounding environment. In bauxite and gold mining, reactive waste such as acid-generating sulphide rock or cyanide-contaminated tailings may be encapsulated within layers of inert overburden, synthetic liners, or compacted clay barriers to cut off contact with oxygen and water — the two main drivers of chemical reactivity. In iron ore mining, encapsulation is used to isolate elevated-manganese or iron-pyrite bearing waste within dump designs that use non-acid-generating (NAG) material as an outer shell around potentially acid-forming (PAF) rock. Diamond mining operations handling kimberlite that contains trace levels of elevated heavy metals or naturally occurring radioactive material (NORM) may use encapsulation methods to prevent these materials from being mobilised by rainfall or groundwater. Encapsulation cells are monitored using lysimeter systems and groundwater bores to confirm the integrity of the barrier over time. This approach is preferred when it is not feasible to treat reactive waste chemically or when long-term passive containment is the most cost-effective solution.
