Title/Topic/Closure risk management
Executive summaryThis summary draws upon the work of Laurence (2006) on ‘Why do mines close?’ to inform rehabilitation and closure risk management. This study of 800 mine closures over 25 years in Australia provides useful guidance to those managing rehabilitation and closure at mines. This study addresses environmental, socio-economic as well as safety and health aspects of closure.
RationaleThis work is important as it can be very difficult to evaluate rehabilitation and closure risks for a minesite when only site-specific data are used. While there are exceptions to the rule, a mine may only close once. As a consequence, it may be difficult to draw upon direct evidence from that site to identify rehabilitation and closure risks, unless there is a very experienced practitioner leading the process and a good body of knowledge exists. Even then, a wider understanding of closure risks and the probability of an unplanned closure, which Laurence (2006) demonstrates represents 75% of mines studied, provides valuable context for rehabilitation and closure risk management.
Objectives

The outcomes of the research will equip operators and regulators to better manage future mine closures by providing information to help identify key risks and allow companies to mitigate them effectively, early in the mine’s life.

Method/ techniquesLaurence (2006) summarises the early results of a significant and on-going research project investigating the causes and impacts of mine closures over the past 25 years. The closure of the 800 mines provides a wealth of data, obtained from company and government records, interviews with key personnel and other sources. The data includes all Australian States and Territories and all commodities, including metalliferous, coal and industrial minerals. The majority of mine closures were in Western Australia (60%) followed by New South Wales (20%) and Queensland (10%). The most commonly closed mine was a gold mine followed by coal, nickel, base metals and minerals sands operations. Twenty five percent of the mines closed due to resource exhaustion or depletion; 24% due to high costs, price drops, or declining grades; 8% due to open pit resource depletion (but with underground reserves remaining) or underground reserves depleted (but plans to open cut remainder) and 7% due to receivership or voluntary administration. Other significant causes included closure of a downstream industry or loss of markets; adverse geological/geotechnical factors; flooding/inrush; government/political decisions; safety/health or environmental issues or other reasons. The environmental, social and economic impacts of these closures are also significant and include acid mine drainage and impact on mine employees. The outcomes of the research will equip operators and regulators to better manage future mine closures.
Results/Observations

The research was confined to the ‘recent’ area which is considered to begin from the 1980s as this was the time that:

  • Technological improvements, particularly in the gold mining industry rapidly developed.
  • Commodity prices, especially the gold price, increased, creating a boom in exploration as well as the stock market.
  • Environmental legislation was introduced into most jurisdictions.
  • Mine rehabilitation and environmental management practices were implemented in most if not all Australian jurisdictions.
  • Security deposits or bonds were also introduced or significantly increased.

 Mine closures followed a temporal trend shown below:

Mine closures 1981-2005 Laurence.png

Most mine closures were located in WA, followed by NSW, QLD and the NT.

 

Outcomes

What was learned?

 The majority (75%) of mine closures were unplanned and were due to:

 Economic, due to either low commodity price or high costs leading at times to company voluntary administration or receivership.

  • Geological, due, for example, to an unanticipated decrease in grade or size of the ore body.
  • Technical, due to adverse geotechnical conditions or mechanical/equipment failure.
  • Regulatory, due to safety or environmental breaches.
  • Policy changes, which occur from time to time, particularly when governments change.
  • Social or community pressures, particularly from NGOs.
  • Closure of downstream industry or markets.
  • Flooding or inrush.

The primary reason for closure is shown below:

primary reasons for closure 1981-2005 Laurence.png

What were the benefits delivered in terms of new knowledge?

This research highlighted that AMD (Acid and Metalliferous Drainage) was the most significant environmental impact from closure. This was followed by tailings, open pit voids, waste dumps and water quality. Most of the mines were gold mines with coal second in significance.

 

An understanding of primary impacts was derived;

Primary env impacts mine closures 1981-2005.png

 

primary social economic impacts of closure.png

 

primary health and safety impacts mine closure.png

 

References(s)Laurence, D (2006) Why do mines close? In the proceedings of the Mine Closure 2006 Conference, Perth, ACG. (eds Fourie, A. and Tibbett, M)
Date (when )13-15 September 2006
LocationPerth was the venue for the conference, however this research relates to Australia as a whole
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Created by Corinne Unger on 2016/03/01 17:33
    
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