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Development of a NAF/PAF Grade Control Programme for Placement of a WRD Cover

J Chapman, J Jones, K Mandaran, B Luinstra and A Hendry
Monday, November 20, 2017
First presented: 
9th Australian Workshop on Acid and Metalliferous Drainage
Published paper

Mount Isa Mines (MIM) has commenced rehabilitation of the Handlebar Hill Open Cut (HHOC) Waste Rock Dump (WRD). This includes reshaping of the WRD and placement of an interim cover over any exposed potentially acid forming (PAF) and neutral mine drainage (NMD) waste rock exposed following the reshape. The interim cover comprises inert oxide non-acid forming (NAF) material recovered from the adjacent Magazine WRD.  A key requirement of the interim cover was that only NAF non-NMD material was used for the cover placement to limit solute release from the WRD, until a final closure cover is designed and agreed with the Department of Environment and Heritage Protection (EHP) (informed by a comprehensive WRD rehabilitation trial).  Since the Magazine WRD contained some PAF and NMD materials, it was necessary to characterise materials during mining (from the Magazine WRD) and selectively utilise only NAF non-NMD material for cover construction.  

The basis for the development of a sampling and control program to identify suitable material from the Magazine WRD for cover placement is described.  This includes the basis for the recommended sampling frequency and specific testing requirements based on first assessing the maximum tolerance for misclassification (i.e. maximum allowable exposure of NMD and/or PAF materials in the NAF cover), and, relating these to the mining method. 

Feature Author

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
Brian Luinstra

Brian Luinstra has 19 years of experience in the field of geology and hydrogeology working primarily in Canada.  He has executed and managed a wide scope of hydrogeological assessments.  These include regional scale water budgets; water supply assessments; well head protection studies; aquifer hydraulic testing; groundwater monitoring network establishment and program implementation; aquifer conceptualisation and impact assessment; karst investigations and hydrological and hydrogeological modelling.  He is experienced working in remote locations, and has varying levels of proficiency with specialised geological and groundwater modelling packages.  Brian provides technical direction and review on hydrogeological projects, and has been project manager for several key clients.

Principal Consultant (Hydrogeology)
PhD (Earth Science), BSc (Geology)
SRK Perth
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
SRK Turkey