MINERAL PRODUCTION STAGE
At the production stage the mineral producer (miner) will extract minerals from the area of their production lease by digging open cut, underground or long-wall mines as well as construct associated infrastructure.
Preparing to mine
Once a miner has received development consent and a production lease from the NSW Government to undertake mining, the proponent will develop a mine site.
Developing a mine site may involve various components including the construction of access roads, site preparation and clearing, the disposal of overburden and waste rock, and the development of facilities for processing the mined resource, and then active mining.
Construction of access roads
Access roads might be constructed to provide access for heavy equipment and supplies to the mine site or to ship out processed metal and ores.
Under the Mining Act 1992, the holder of a Mining Lease is entitled to a right of way between a mine site and a public road to allow access to the mine site.[ii]
Wherever practical the route of the right of way should follow the route of existing roads or tracks[iii], and gates or grids must be constructed (including dog or rabbit proof gates where the fence intersected is a dog or rabbit proof fence) wherever the right of way intersects with fence lines.[iv]
Any grids or gates constructed must be of adequate quality to prevent stock from straying[v] and any costs associated with the installation and maintenance of the gates and grids must be met by the miner.[vi]
Site preparation and clearing
A miner may need to clear land for the construction of staging areas that would house project personnel and
Disposal of waste rock and overburden
Metallic ores are buried under a layer of ordinary soil or rock (called ‘overburden’ or ‘waste rock’) that must be moved or excavated to allow access to the metallic ore deposit.
For most mining projects, the quantity of overburden generated by mining is enormous.
The ratio of the quantity of overburden to the quantity of mineral ore (called the ‘strip ratio’) is usually greater than one, and can be much higher.
For example, if a proposed mining project involves the extraction of 100 million metric tons of mineral ore, then the project could generate more than one billion metric tons of overburden and waste rock.
These high-volume wastes, sometimes containing significant levels of toxic substances, are usually deposited on-site, either in piles on the surface or as backfill in open pits, or within underground mines.
Development of processing and tailings disposal facilities
Large volumes of waste can be generated from mining operations, for example, the copper content of a good grade copper ore may be only one quarter of one percent. Likewise, the gold content of a good grade gold ore may be only a few hundredths of a percent.
Raw mined minerals will need to be processed and waste materials separated from the useable ore.
Processing includes physical and/or chemical separation techniques such as gravity concentration, magnetic separation, electrostatic separation, flotation, solvent extraction, electrowinning, leaching, precipitation and amalgamation.
Tailings are what remains following the processing of the raw materials and the extraction of mineral. Tailings are distinct from overburden, which is the waste rock or materials overlying an ore or mineral body that are displaced during mining without being processed.
Tailing ponds will need to be constructed to store tailings prior to disposal.
What mining methods may be used?
For mineral mining, you can expect any of the following:
Open-cut mining, or
underground mining (including bord and pillar, longwall mining).
The mining technique utilised will vary depending on the resource which is targeted and the particular geology of the area amongst other considerations.
Open cut mining
Open-cut mining is generally used where resource deposits are close to the surface. Open cut mining will involve blasting and removing layers of rock and soil to access the deposit.[vii] This will allow the company to recover more of the resource. The NSW Minerals Council reports that 65% of coal mining in NSW is done through open-cut mining.
As a result of the magnitude of the impacts of open-cut mining, an explorer may offer to purchase your land. It may be a condition of the explorer’s approval that they offer to purchase your land or purchase your land if you ask them to.[viii]
Underground mining techniques are also used. These can involve long-wall mining or bord and pillar techniques.
Long-wall mining is an underground mining technique which involves mining along the coal-seam in long corridors. Once coal has been removed from the corridor, the corridor will collapse in on itself. This will cause surface subsidence of the land in which underground long-wall mining is taking place.
Bord and pillar mining
The bord and pillar mining technique different to long-wall mining as instead of underground mining in corridors, mining takes place in block or grid pattern with pillars of rock left as walls.
[i] Environmental Law Alliance Worldwide Guidebook for Evaluating Mining Project EIAs (July 2010)
[ii] Mining Act 1992 (NSW) s 164
[iii] Ibid s 164 (3) (b)
[iv] Ibid s 164 (3)
[v] Ibid s 164 (4)
[vi] Ibid s 164 (5)
[vii] NSW Minerals Council Mining Methods (Accessed July 2014)
[viii] Environmental Defenders Office Mining Law in New South Wales: A Guide for the Community (2012)