Welideniya, S, Tucker, N & Mesquita, A 2023, 'Open pits, underground mines and tailings storage facilities—geotechnical and legislative aspects at closure in Western Australia', in B Abbasi, J Parshley, A Fourie & M Tibbett (eds), Mine Closure 2023: Proceedings of the 16th International Conference on Mine Closure
, Australian Centre for Geomechanics, Perth, https://doi.org/10.36487/ACG_repo/2315_045
All mining proposals (MP) submitted with mine closure plans (MCP) to be accepted by the Department of Mines, Industry Regulation and Safety (DMIRS) in Western Australia (WA) must comply with strict engineering, environmental and legislative requirements, as overseen by the regulatory agency, WorkSafe Western Australia. To meet all legislative requirements, including engineering and environmental laws, mine closures must face and meet these challenges. The Work Health and Safety Act 2020 (WHS Act), the Work Health and Safety (Mines) Regulations 2022 (WHS Mines Regulations), the Mining Act 1978, the Mining Regulations 1981 and the Environmental Protection Act 1986 provide clear and consistent guidelines for exploration, design and construction, operation, and closure of mines across WA. The Mining Act 1978 requires mining activities to be rehabilitated and closed in a manner that leaves the land safe, stable and non-polluting without unacceptable liability to the state. A mine closure plan is required under the Mining Act 1978 and enforced via tenement conditions applicable to the mining lease. Traditional land owner’s involvement on the land used for mining applies from the beginning of the project during the exploration and mining phases and continues onto the closure considering post mining land use which may also include the land access for cultural and ceremonial use. The legislation regarding mining and environmental protection were also developed with the intention of minimising environmental damage, enforcing professional commitments on ore reserve exploitation and upholding traditional land owner’s interests to their lands.
When planning the post mining closure of open pit mining operations many geotechnical engineering aspects related to perpetual pit slope stability, the stability of waste dumps, pit lakes and access controls using abandonment bunding for the safety of people as well as wildlife will need to be applied. Planning for the closure of underground mines, depending on the mining method, will need to address the elimination of any potential unplanned subsidence by well-proven geotechnical modelling. Other areas to address may be impacts on changes to the surface water flow and ground water table and inadvertent access to any mining areas through shafts or portals. Dealing with tailings facilities could be the most challenging aspect of a mine closure. The mine closure plan regarding tailings will need to address embankment stability, ground water contamination and liquefaction potentials, seepage and dust. The closure will be required to promote the regrowth of natural endemic plants that were impacted by the mining operation in order to bring the location back to the pre-mining natural environment as much as possible. Tailings could contain materials having the potential of acid mine drainage (AMD) which will need to be effectively managed to prevent any environmental impacts.
Keywords: geotechnical, underground, open pit, tailings, subsidence, mine closure, WHS, environmental, AMD, stability, liquefaction, tenements
Aboriginal Heritage Act 1972
Department of Industry and Resources 1997, Geotechnical considerations in underground mines – Guideline, Perth,
Department of Mines, Industry Regulation and Safety 2009, Waste rock dumps – Environmental Notes on Mining, Perth
Department of Mines, Industry Regulation and Safety 2013, Tailings storage facilities in Western Australia – Code of practice, Perth,
Department of Mines, Industry Regulation and Safety 2019, Ground control management in Western Australian mining operations – Guideline, Perth,
Department of Mines, Industry Regulation and Safety 2019, Ground control for Western Australian mining operations – Code of practice, Perth.
Department of Mines, Industry Regulation and Safety 2021, Waste Rock Dumps Version 2.1, Perth,
Department of Mines, Industry Regulation and Safety, Mining Industry Advisory Committee, Work Health and Safety Commission 2022, Mine safety management system – Code of practice, Perth
Government of Western Australia 2022, Work Health and Safety Act 2020, Australia
Government of Western Australia 2022, Work Health and Safety (Mines) Regulations 2022, Australia.
Government of Western Australia 1978, Mining Act 1978, Australia.
Government of Western Australia, Mining Regulations 1981.
Government of Western Australia 1986, Environmental Protection Act 1986, Australia.
International Commission on Large Dams (ICOLD) 2013, Bulletin 153 Sustainable design and post-closure performance of tailings dams.
International Commission on Large Dams, Australian National Committee (ANCOLD) 2019, Guidelines on tailings dams - Planning, design, construction, operation and closure, Revision 1
International Commission on Large Dams (ICOLD) 2020, Bulletin 181 Tailings dam design – Technology update.
Laubscher, D H, 2000. A practical manual on block caving, Prepared for International Caving Study, JKMRC and Itasca Consulting Group, Brisbane, 500p.
Mathews, K E, Hoek, E, Wyllie, D C and Stewart, S B V, 1980. Prediction of stable excavation spans for mining at depths below 1000 meters in hard rock. Golder Associates Report to Canada Centre for Mining and Energy Technology (CANMET), Department of Energy and Resources, Ottawa, Canada.
Mining Industry Advisory Committee (MIAC) 2019, Ground control management in Western Australian mining operation, Perth.
Native Title Act 1993