Acid Mine Drainage Risk Assessment To Inform Mine And Closure Planning

Alison Hendry, Claire Linklater, Russell Staines and John Chapman
Thursday, May 19, 2016
First presented: 
GEMG Environmental Management Workshop, May 2016

Using drillhole assay data to assess the risk of acid and metalliferous drainage (AMD) early in the planning of a mining operation can have a number of benefits.  These include:

  • Early identification of operational and closure AMD risks;
  • Optimisation of geochemical characterisation programmes
  • Early identification of mitigation and management measures (including engineering design);
  • Early technical input to environmental approval applications;
  • Preventing project delays due to late identification of environmental risks related to AMD and late commencement of lengthy geochemical testing programmes; and,
  • Development and costing of closure strategies early in the planning process.

AMD assessments have been undertaken using drill-hole data (incorporating chemical assays and geological logging information) combined with interpretive geological models and mine planning information for a number of Australian iron ore operations.  The approach has been implemented successfully for mine projects at various stages of development (for example, pre-environmental approvals to post-mining). 

The example discussed herein illustrates the use of geological modelling tools (Vulcan, Leapfrog) to generate 3D visualisations of the distribution of sulfur (a key parameter indicative of AMD risk) within the pit shells.  The final sulfur models were aligned with existing block models to allow examination of past, current and future mine plans in the light of AMD potential.  Volumetric quantities of sulfur-bearing material reporting to waste rock dumps and ore stockpiles respectively were estimated.  Small volumes representing sulfur-bearing ‘hot-spots’ were identified and maps were generated to determine the location of these hot spots on exposed pit walls, and assess closure scenarios with respect to AMD risk and anticipated post-mining water table levels.

This paper describes the overall assessment approach, the benefits of undertaking these assessments as early as possible in mine planning, and how the findings were used to inform the development of closure strategies at the sites.

Feature Author

Alison Hendry

Alison Hendry is a Chartered Geologist with over 10 years’ experience in environmental geochemistry and water quality impact assessments. Alison began her career researching the geochemical soil mineral surface associations of uranium resulting from the use of deplete uranium (DU) munitions in the Balkans, and utilising isotope geochemistry to assess the mobility of uranium from nuclear process plants in the UK. She has worked on a diverse range of geochemical characterisation (acid and metalliferous drainage, AMD) assessments for mine sites, predictive pit lake water quality assessments, water quality compliance reporting, contaminated site investigations, remediation design projects, landfill hydrogeological risk assessments and environmental impact assessments. Alison has extensive field experience of sampling environmental media for assessment, and has gained experience in hydrogeological testing and assessment methods including drilling supervision, well installation design and permeability testing.

Senior Consultant (Geochemistry & Hydrogeology)
PhD (Uranium Geochemistry), BSc (Geology & Environmental Chemistry), CGeol, FGS
SRK Perth
Claire Linklater

Claire Linklater has 22 years’ experience in interpretation of geochemical data, building conceptual models of processes which control in situ geochemical behaviour and the application of geochemical modelling codes.  Her early career was focused on management of radioactive wastes; understanding and quantifying the geochemical behaviour and mobility of radionuclides in the ‘geosphere’ surrounding a proposed underground repository and assessing the long-term stability of engineered and natural barriers.  More recently, she has focused on sulfidic materials management: acid/alkaline rock drainage (ARD) assessment and prediction; water quality and pollutant mobility from waste rock dumps, tailings storage facilities, underground workings and pit walls; assessing the effectiveness of potential mine closure strategies.

Principal Consultant (Geochemistry)
PhD (Geology), FGS, FAusIMM
SRK Sydney
John Chapman

John Chapman has more than 26 years of relevant experience and has developed multi-disciplinary skills relating to mining environmental impacts assessment and environmental controls.  He is a recognised expert in ARD assessment and prediction, mine waste characterisation and management, and mine closure with recent project experience in Australia, South East Asia, Canada, USA and Europe.  John has facilitated enterprise-wide risk assessment workshops, undertaken due diligence and environmental risk assessments for a wide range of mining projects.  Recent projects include detailed geochemical assessment of the tailings properties for the Olympic Dam Project in SA, design and development of the geochemical characterisation program for the Cannington Life Extension project in QLD as well as for the Yeelirrie Project in WA.

Principal Consultant (Geochemistry and Environment)
MSc (Chemical Engineering), P Eng (British Columbia), P.Eng (Yukon Territory)
SRK Brisbane
SRK North America