Heap Leach Final Draindown Model

Vast inventories of leach solutions unsuitable for direct discharge to the environment are among the legacies of heap leach operations at closure. The final rinsing and subsequent draindown is a complex technical problem often involving significant cost to the operators. To compound the problem, leachate inventory at closure often exceeds the holding capacity of existing ponds. 

The active management phase at closure typically consists of recirculating leach solution to a portion of the heap leach and/or water treatment and discharge, followed by longer-term passive management (without pumping) leveraging evapo-transpiration to continue reducing inventory. Managing the leach solutions represents a significant financial liability. The duration of active management should therefore be carefully planned both technically and financially. SRK has developed a method by which draindown rates and cumulative volumes can be predicted at a daily time scale, enabling the rapid development and comparison of options and scenarios, leading to improved planning.

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