Rousseau, PDS 2010, 'Providing context to acid metalliferous drainage assessments', in R Jewell & AB Fourie (eds), Proceedings of the First International Seminar on the Reduction of Risk in the Management of Tailings and Mine Waste
, Australian Centre for Geomechanics, Perth, pp. 333-344.
The why, what, how, when, where and whom questions with respect to completing an acid metalliferous
drainage (AMD) assessment are outlined in this discussion.
Why? AMD has been recognised as the most significant potential long-term liability associated with mining,
particularly post closure. The requirement to understand AMD is thus driven by corporate governance,
financing and regulatory considerations.
What? The current definition (GARD Guide, 2009; and other guideline documents) of what an AMD
assessment should include is broad. It includes acidity that is released through sulphide oxidation, but also
covers release of other elements that are mobile under acidic, neutral, or alkaline conditions, as well as
introduced contaminants. The purpose of these assessments is thus to identify all mining-related sources of
How? To achieve a realistic AMD assessment, specialist knowledge about geochemistry, hydrogeology,
engineering and management details of a project is necessary to evaluate AMD risk, to model systems in
question, and to develop mitigation strategies. To evaluate the potential for impacts it is necessary that
contaminant sources, transport pathways and receptors be identified and that their physical and
geochemical properties must be adequately quantified. These properties must also be related to the mining
operation using a suitable site conceptual model.
When? AMD assessment should commence at the exploration stage, once sufficient geological information
and sample material is available to obtain a realistic view of ore and waste geochemistry. The earlier the
evaluation starts, the sooner AMD related liabilities and technical challenges associated with geochemistry
for a mining project become known.
Where? The AMD assessment should consider all materials to be disturbed by mining that could potentially
result in significant geochemical changes and associated mobilisation of acidity or other potentially harmful
Whom? An AMD assessment should be carried out by technical specialists, suitably knowledgeable about
geochemical and hydrogeological processes. Sufficient geological background is required to conceptualise
relevant geological factors associated with a mining operation. It is also necessary for geological, mining
and engineering personnel associated with a project to provide input to these assessments, as their
information and activities can have a major influence on AMD related outcomes associated with material
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