Stimpfl, M, Carrigan, ML, McLeary, MB & Taylor, JR 2009, 'Approaches to acid and metalliferous drainage management — implications of short-term trials for long-term remediation', in AB Fourie & M Tibbett (eds), Mine Closure 2009: Proceedings of the Fourth International Conference on Mine Closure
, Australian Centre for Geomechanics, Perth, pp. 273-264, https://doi.org/10.36487/ACG_repo/908_20
Several waste rock (WR) acid and metalliferous drainage (AMD) management options have been tested at
Brukunga Mine site for their long-term ability to suppress or minimise acidity loads emanating from the WR.
A 12–24 month field demonstration assessed alkaline caps (enhanced caustic magnesia, and natural
limestone), and limestone blends in their long-term capacity to control acidity loads.
The first 12 months of the trial suggest alkalinity producing covers may have significant potential as an
effective and sustainable AMD minimisation strategy. Acidity load produced by the test pile (TP) capped
with enhanced caustic magnesia was considerably decreased when compared with baseline. These results
suggest alkaline covers allow inert neutralisation precipitates to coat preferential flow pathways, minimising
the interface between water and acid salts. Blended limestone did not sustain long-term
minimisation/suppression of acidity loads emanating from the WR, regardless of the ratio of limestone to WR
or grain size. Even though limestone blended test piles showed the highest quality leachate measured
throughout the trials, all test piles showed signs of impending leachate acidification during the latter half of
the trial. In particular, the quality of leachate from all limestone blended test piles showed increasing acidity
and sulphate concentrations, and a decreasing alkalinity and alkalinity to acidity ratio. Little residual
alkalinity remained in the leachate from the limestone blended test piles after 12 months of the trial. The
trend clearly shows, that in the long term, blended test piles are likely to produce leachate of quality
comparable to untreated test piles.
This trial illustrates the necessity for mine closure managers to be cautious in their application of short-term
findings when planning for the longer term, in relation to management of contaminants such as AMD. These
trial results signify that whilst testing of approaches is necessary, the longer the time frame the better the
likely prediction of long-term outcomes. A hasty approach might well result in a failure of remediation, an
inability to complete mine closure, and a hefty cost with little positive outcome.
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Brukunga Pyrite Mine site, South Australia, Earth Systems Pty Ltd, Melbourne, Victoria, Report (unpublished).
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long-term acid rock drainage control at the Grasberg Mine, Papua Province, Indonesia, In Proceedings of the
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Taylor, J., Guthrie, B., Murphy, N. and Waters, J. (2006) Alkalinity producing cover materials for providing sustained
improvement in water quality from waste rock piles, In Proceedings of the Seventh International Conference on
Acid Rock Drainage, ICARD, 26–30 March 2006, St. Louis, USA.
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lowering acidity loads from waster rock piles – A field demonstration, In Proceedings of the Eighth International
Conference on Acid Rock Drainage (ICARD) 22–28 June 2009, Skellefteå, Sweden.