Title/Topic/Long term water management
Executive summaryResearch by Byrne highlighted that the majority of mining operations do not prepare for long term water management and as a consequence are faced with longer time periods between cessation of operations and relinquishment of mining tenure. In some instances they may realise that water may need to be managed in perpetuity.
Current situation  Operational mining activites involve water management systems. Often too little attention is given to designing water management systems which will be sustainable in the long term with little or no management requirements post-cessation of mining.
Objectives  The purpose of this study was to raise awarenss of the need to design for long term water management as an integral component of mine design.
Method/ techniques

 Bryne studied 73 mine closure plans dating from 2007 to 2013. He also reviewed 57 mines in actual closure to evaluate how long it took from completion of mining to relinquishment.

Results/ObservationsThe average time period predicted for relinquishment from the 73 mines was 11 years. The actual time period to relinquishment of 57 undergoing closure was quite different. Only five had so far achieved relinquishment with an average closure period of 14 years after production cessation. The remaining sites in closure have an average closure duration to date of 21 years – and were still going.
Outcomes

Byrne observed that long term water management is typically ignored in mine closure planning. He noted that there is also an underestimation of time to achieve relinquishment, based on this focus on long term water management.  only five have so far achieved relinquishment with an average closure period of 14 years after production cessation. The remaining 91% of sites in closure have an average closure duration to date of 21 years – and still going.

 A common issue among those sites in closure is water management, with a further common issue being acid and metaliferous drainage (AMD). Of the closure plans that were reviewed only one site had allowance for long term (>50 years) of water treatment. Of the sites in actual closure 25% have reported that they expect such long term water treatment, with many acknowledging that in perpetuity treatment is probable.

 Clearly there is a gap between what is being allowed in closure plans and the reality of closure. There are a number of factors leading to the optimism of the closure plans, including unrealistic assumptions, pressures to reduce closure cost provisions and the technical complexity of many AMD issues.

Long term water management is a reality that needs to be acknowledged and addressed. If addressed early in the mine life cycle the impacts for mining companies can be reduced.

References(s)

Byrne, G. (2013) Long term water management – the forgotten legacy of mine closure

Date (when )2013
LocationMelbourne, Water in Mining Conference, AusIMM
KeywordsWater management, long term, relinquishment, post-closure management
    
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