Glossary of abandoned mines terms
Acid and metalliferous drainage
Acid and metalliferous drainage occurs when naturally occurring sulphide minerals oxidise when exposed to air and water, forming sulphuric acid. The acid can leach metals from surrounding rock and, as a result, produce water that has low pH (acidic), high dissolved metals, as well as high sulphate (salt) concentrations.
Capping
Capping refers to a cover placed over contaminated material (such as waste rock or tailings) to minimise water infiltering and reacting with the contaminated material to produce acidic contaminated run-off and seepage. The capping can involve a variety of materials including compacted clay, manufactured liners such as high-density polyethylene (HDPE) or geosynthetic clay liners (GCL) or other soil and rock materials.
Disclaimed
A site that is abandoned though disclaiming of resource tenure as onerous property by liquidators, in accordance with s568 of the Corporations Act 2001 (Commonwealth)
Encapsulate
To surround and cover contaminated material (such as tailings or acid forming waste rock) with clean materials for the purpose of long-term containment as well as minimising water entering and reacting with the material to produce acidic (or contaminated) run-off.
Evaporation ponds
These are large shallow ponds generally used to reduce water volumes by using sunlight, heat and wind to evaporate the water. Water may be clean or mine-affected (contaminated).
Hardstand laydown areas
These are hard-surfaced areas suitable for storing heavy vehicles, machinery or materials.
Heap leach pads
A mining process where mined ore is crushed and heaped on an impermeable plastic or bitumen lined pad and then irrigated with a leach solution to dissolve the valuable metals and produce a leachate that can be collected for further mineral processing.
Mullock heap
A mound of left-over soil or rock from the shaft excavation process, usually associated with small-scale or historic gold or opal mining.
Open-cut pit
A large void left behind after overburden (soil and rock) and the target ore or mineral is excavated.
Pit cutback area
A new area of mining activity adjacent to an existing pit, intended to ultimately connect to and enlarge the size of an existing pit.
Potentially acid forming material (PAF)
Material containing minerals which can oxidise to produce acid through the chemical and biological weathering effects of air, water and microorganisms.
Process water dam
A dam used to store water for use in the extraction process.
Processing plant
Mineral processing equipment used to crush ore and separate or extract target minerals. The process may involve use of industrial chemicals and reagents. The significant volumes of waste product from a processing plant is referred to as tailings.
Seepage collection sump
A constructed storage pond at the toe of a tailings dam, waste rock dump or potential acid forming stockpile to collect any contaminated seepage and allow treatment or pumping to another water storage pond, rather than flowing offsite.
Reprofiling
Earthworks to relocate or reshape material—usually tailings or waste rock—during the remediation process, for the purpose of creating a stable landform with appropriate drainage.
Slag
A non-metallic, glassy by-product formed during the smelting of ore.
Tailings
Residual fine-grained material that has been crushed and ground and/or washed and rejected from a mill or processing plant after the recoverable minerals have been extracted.
Tailings storage facility (TSF)
A dam, containment cell or other storage used for long-term storage of the tailings from a mineral processing plant.
Toe
The lowest section of an embankment or tailings storage facility where any seepage would usually occur.
Undermining
Underground mining which has the potential to affect the surface stability of the overlying and surrounding land.
Waste rock
Rock or material overlying or adjacent to an ore body that needs to be removed in order to access the ore. This material may be benign with minimal environmental impacts, or potentially acid forming (PAF) that needs to be carefully managed. Due to the large volumes, a waste rock dump is commonly constructed during the open cut mining process. Sometimes waste rock is later returned to the original void, but in other cases the waste rock dump is left as a permanent landform.