Newmont Boddington Gold Closure Plan
M70/21, M70/22, M70/23, M70/24, M70/25, M70/564, M70/799, M70/1031, ML264SA(1), ML264SA(2), G70/215, G70/218, G70/219, L70/28, L70/95, L70/96
Submission Date December 2012 Version Number CR35945 Contact Details Javier Brodalka, Environment Manager Phone: (08) 9883 4251 Email: [email protected]
Date Revision Description of Originator Reviewer(s) Approval Revision December ‐ ‐ K. De Sousa M. Durack, S. J. Brodalka 2012 Myles, R. Kok, A. James
Newmont Boddington Gold – Closure Plan Closure Plan Checklist
No. Mine Closure Plan Checklist Y/N/NA Section Comments 1 Has the Checklist been endorsed by a senior Y Checklist representative within the tenement holder/ operating company? 2 How many copies were submitted to DMP? Hard copies = 2 Electronic copies = 1 Cover Page, Table of Contents 3 Does the cover page include: Y Cover Page Project title Company name Contact details (including telephone numbers and email addresses) Document ID and version number Date of submission 4 Has a Table of Contents been provided? Y Table of Contents Scope and Project Summary 5 State why the MCP is submitted. Y 1.2 6 Does the project summary include: Y Section 2 Land ownership details 2.2 Location of the project 2.1 Comprehensive site plans 2.4 Background information on the history 2.3 and status of the project Legal Obligations and Commitments 7 Has a consolidated summary or registers of Y Section 3 Appendices 1‐3 closure obligations and commitments been included? Data Collection and Analysis 8 Has information relevant to mine closure been Y Section 4 Appendices 4 ‐ 8 collected for each domain or feature (including pre‐mining baseline studies, environmental and other data)? 9 Has a gap analysis been conducted to determine Y 4.4 if further information is required in relation to closure of each domain or feature? Stakeholder Consultation 10 Have all stakeholders involved in closure been Y 5.1 identified? 11 Has a summary or register of stakeholder Y 5.2 consultation been provided, with details as to who has been consulted and the outcomes? Final Land Use(s) and Closure Objectives 12 Does the MCP include agreed post‐mining land Y Section 6 use(s), closure objectives and conceptual landform design diagram?
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Newmont Boddington Gold – Closure Plan Closure Plan Checklist
No. Mine Closure Plan Checklist Y/N/NA Section Comments 13 Does the MCP identify all potential (or pre‐ Y Section 6 existing) environmental legacies, which may restrict the post‐mining land use (including contaminated sites)? Identification and Management of Closure Issues 14 Does the MCP identify all key issues impacting Y Section 7 Appendix 11 mine closure objectives and outcomes? 15 Does the MCP include proposed management or Y Section 7 mitigation options to deal with these issues? 16 Has the process, methodology and rationale been Y Section 7 provided to justify identification and management of the issues? Closure Criteria 17 Does the MCP include an appropriate set of Y Section 8 specific closure criteria and/or closure performance indicators? Closure Financial Provisioning 18 Does the MCP include costing methodology, Y Section 9 assumptions and financial provision to resource closure implementation and monitoring? 19 Does the MCP include a process for regular Y Section 9 review of the financial provision? Closure Implementation 20 Does the reviewed MCP include a summary of Y 10.2 closure implementation strategies and activities for the proposed operations or for the whole site? 21 Does the MCP contain a closure work program Y 10.3 for each domain or feature? 22 Have site layout plans been provided to clearly Y 10.1 show each type of disturbance? 23 Does the MCP contain a schedule of research and Y 10.3 trial activities? 24 Does the MCP include a schedule of progressive Y 10.3 rehabilitation activities? 25 Does the MCP include details of how unexpected Y 10.3 closure and care and maintenance will be handled? 26 Does the MCP contain a schedule of Y 10.3.5 decommissioning activities? 27 Does the MCP contain a schedule of performance Y Section 11 monitoring and maintenance activities? Closure Monitoring and Maintenance 28 Does the MCP contain a framework, including Y Section 11 methodology, quality control and remedial strategy for closure performance monitoring including post‐closure monitoring and maintenance?
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Newmont Boddington Gold – Closure Plan Table of Contents
Table of Contents 1 Scope and Purpose ...... 1‐1 1.1 Scope ...... 1‐1 1.2 Purpose ...... 1‐1 1.3 Structure ...... 1‐2 1.4 Closure Planning Framework ...... 1‐3 1.4.1 Closure Review Technical Team ...... 1‐3 1.4.2 Closure Plan Review Process ...... 1‐4 1.4.3 Schedule ...... 1‐4 2 Project Overview ...... 2‐1 2.1 Project Location and Tenure ...... 2‐1 2.2 Land Ownership ...... 2‐1 2.3 Project History ...... 2‐2 2.4 Overview of Operations ...... 2‐3 2.4.1 Open Pit Mines ...... 2‐4 2.4.1.1 Wandoo North and South Open Pits ...... 2‐4 2.4.1.2 Satellite Open Pits ...... 2‐4 2.4.2 Jarrah Decline ...... 2‐4 2.4.3 Waste Rock Landforms ...... 2‐5 2.4.3.1 Waste Rock Landforms 7, 8, 9, 10, 11 and 12 ...... 2‐5 2.4.3.2 Q3 Waste Rock Landform ...... 2‐5 2.4.4 ROM Pad and Medium Grade Ore Stockpile ...... 2‐5 2.4.5 Primary Crusher ...... 2‐6 2.4.6 Conveyor Corridor ...... 2‐6 2.4.7 Processing Plant ...... 2‐6 2.4.8 Residue Disposal Areas ...... 2‐6 2.4.8.1 R4 RDA ...... 2‐7 2.4.8.2 F1/F3 RDA ...... 2‐7 2.4.8.3 Future RDA ...... 2‐8 2.4.9 Water Storage Reservoirs and Dams ...... 2‐8 2.4.10 Support Infrastructure ...... 2‐8 2.4.11 Accommodation Village ...... 2‐9 3 Closure Obligations and Commitments ...... 3‐1 3.1 Legislation ...... 3‐1 3.1.1 Mining Act 1978 ...... 3‐1 3.1.2 Environmental Protection Act 1986 ...... 3‐2 3.1.3 Contaminated Sites Act 2003 ...... 3‐3 3.1.4 Environmental Protection and Biodiversity Conservation Act 1999 ...... 3‐3 3.2 Guidelines ...... 3‐3 3.3 Regulatory Approvals ...... 3‐4 3.3.1 Licence for Prescribed Premises ...... 3‐4 3.3.2 Minister for the Environment Approvals ...... 3‐5 3.3.2.1 Environmental Protection Act 1986 ...... 3‐5 3.3.2.2 Environmental Protection and Biodiversity Conservation Act 1999 ...... 3‐5 3.3.3 Department of Mines and Petroleum Approvals ...... 3‐6 4 Closure Data ...... 4‐1 4.1 Environmental and Community Aspects ...... 4‐1 4.1.1 Meteorology...... 4‐1 4.1.2 Geology ...... 4‐2 4.1.3 Landform and Soils ...... 4‐3
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Newmont Boddington Gold – Closure Plan Table of Contents
4.1.3.1 Native Soil Profile ...... 4‐3 4.1.3.1.1 Topsoils and Gravel Subsoils ...... 4‐4 4.1.3.1.2 Oxide Clays ...... 4‐4 4.1.3.2 Rehabilitation Materials ...... 4‐6 4.1.3.2.1 Rehabilitation Materials Inventory and Reconciliation ...... 4‐7 4.1.3.3 Post‐Closure Impacts on Landforms and Soils ...... 4‐11 4.1.4 Surface Water ...... 4‐11 4.1.4.1 Surface Water Flow ...... 4‐11 4.1.4.2 Surface Water Chemistry ...... 4‐12 4.1.4.3 Ecological Values and Beneficial Uses ...... 4‐13 4.1.4.4 Post‐Closure Impacts on Surface Water ...... 4‐13 4.1.5 Groundwater ...... 4‐14 4.1.5.1 Groundwater Systems ...... 4‐14 4.1.5.1.1 Seasonal Shallow Groundwater mSyste ...... 4‐14 4.1.5.1.2 Weathered and Fractured Upper Bedrock Groundwater System ...... 4‐15 4.1.5.1.3 Deep Fractured Bedrock Groundwater System ...... 4‐15 4.1.5.1.4 Influence of Mining ...... 4‐15 4.1.5.2 Groundwater Chemistry ...... 4‐17 4.1.5.3 Post‐Closure Impacts on Groundwater ...... 4‐18 4.1.6 Biodiversity ...... 4‐18 4.1.6.1 Flora and Vegetation ...... 4‐19 4.1.6.1.1 Flora and Vegetation of Thirty‐Four Mile Brook and Hotham River...... 4‐21 4.1.6.1.2 Post Closure Impacts on Flora ...... 4‐21 4.1.6.2 Fauna ...... 4‐21 4.1.6.2.1 Stygofauna and Troglofauna ...... 4‐23 4.1.6.2.2 Short‐Range Endemic Species ...... 4‐23 4.1.6.2.3 Aquatic Fauna ...... 4‐24 4.1.6.2.4 Post Closure Impacts on Fauna ...... 4‐25 4.1.7 Noise ...... 4‐27 4.1.7.1 Post‐Closure Impacts on Noise ...... 4‐27 4.1.8 Air Quality ...... 4‐27 4.1.8.1 Post‐Closure Impacts on Air Quality ...... 4‐28 4.1.9 Land Use ...... 4‐28 4.1.9.1 Post‐Closure Impacts on Land Use ...... 4‐29 4.1.10 Cultural Heritage ...... 4‐29 4.1.10.1 Aboriginal Cultural Heritage ...... 4‐29 4.1.10.2 Other Cultural Heritage ...... 4‐30 4.1.10.3 Post‐Closure Impacts on Cultural Heritage ...... 4‐31 4.1.11 Social Setting and Community ...... 4‐31 4.1.11.1 Post‐Closure Impacts on Social Setting and Community ...... 4‐32 4.2 Research Programs, Studies and Trials ...... 4‐33 4.2.1 Waste Rock Landforms ...... 4‐33 4.2.1.1 Geochemistry and Waste Rock Management ...... 4‐33 4.2.1.2 Landform Design ...... 4‐34 4.2.1.2.1 Waste Rock Landform Placement ...... 4‐35 4.2.1.2.2 Slope Geometry ...... 4‐36 4.2.1.3 Cover Design ...... 4‐37 4.2.1.3.1 Information Review ...... 4‐38 4.2.1.3.2 Modelling of Cover Performance ...... 4‐39 4.2.1.3.3 Steep Slope Trials...... 4‐40
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Newmont Boddington Gold – Closure Plan Table of Contents
4.2.2 Residue Disposal Areas ...... 4‐41 4.2.2.1 Residue Characterisation ...... 4‐41 4.2.2.1.1 Physical Properties ...... 4‐41 4.2.2.1.2 Chemical Properties ...... 4‐41 4.2.2.2 Cover Design ...... 4‐42 4.2.2.2.1 Oxide Residue Cover Trials ...... 4‐43 4.2.3 Open Pits ...... 4‐44 4.2.3.1 Pit Lake Chemistry and Filling Period ...... 4‐44 4.2.3.2 Surface Water Management ...... 4‐50 4.2.4 Rehabilitation Techniques ...... 4‐50 4.2.4.1 Satellite Open Pits ...... 4‐50 4.2.4.2 Trials ...... 4‐52 4.2.4.2.1 Rehabilitation Prescription ...... 4‐52 4.2.4.2.2 Fertiliser Application ...... 4‐52 4.2.4.2.3 Recalcitrant Species ...... 4‐53 4.2.4.2.4 Impact of Grazing ...... 4‐53 4.2.5 Black Cockatoos ...... 4‐54 4.3 Learning’s from Other Mines ...... 4‐55 4.3.1 Relevant Mine Sites...... 4‐55 4.3.1.1 Alcoa World Alumina Australia ...... 4‐56 4.3.1.2 Wesfarmers Premier Coal ...... 4‐56 4.3.1.3 Bemax Resources Limited ...... 4‐57 4.3.1.4 Newmont Waihi Gold ...... 4‐57 4.3.2 Applicable Learning’s ...... 4‐57 4.4 Information Gaps ...... 4‐59 5 Stakeholder Consultation...... 5‐1 5.1 Stakeholder Engagement Process ...... 5‐1 5.2 Stakeholder Engagement Register ...... 5‐2 5.3 Community Visioning for SuperTowns Initiative ...... 5‐8 6 Post‐Mining Land Use and Closure Objectives ...... 6‐1 6.1 Post‐Mining Land Use ...... 6‐1 6.2 Closure Objectives ...... 6‐2 6.3 Closure Strategy and Final Form of Landforms ...... 6‐3 6.3.1 Mining Areas ...... 6‐4 6.3.1.1 Main Open Pits ...... 6‐4 6.3.1.2 Satellite Open Pits ...... 6‐4 6.3.1.3 Jarrah Decline ...... 6‐4 6.3.2 Waste Rock Landforms ...... 6‐5 6.3.3 Residue Disposal Areas ...... 6‐5 6.3.4 Infrastructure and Services ...... 6‐5 6.3.5 Water Management Structures ...... 6‐5 6.3.6 Accommodation Village ...... 6‐6 6.3.7 Temporary Stockpiles ...... 6‐6 6.3.8 Concentrate Storage Shed ...... 6‐6 7 Identification and Management of Closure Issues ...... 7‐1 8 Development of Completion Criteria ...... 8‐1 8.1 Completion Criteria – Mine Operations ...... 8‐1 8.2 Review of Completion Criteria ...... 8‐2 8.3 Completion Criteria – Accommodation Village ...... 8‐7 9 Financial Provision for Closure ...... 9‐1
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Newmont Boddington Gold – Closure Plan Table of Contents
10 Closure Implementation ...... 10‐1 10.1 Closure Management Units ...... 10‐1 10.2 Closure Implementation Strategy and Standard Rehabilitation Approach ...... 10‐2 10.3 Closure Implementation Plans ...... 10‐7 10.3.1 CMU0 – Whole of Operations ...... 10‐9 10.3.1.1 Description ...... 10‐9 10.3.1.2 Closure Implementation Plan ...... 10‐9 10.3.1.3 Unplanned Closure Activities ...... 10‐13 10.3.2 CMU1 – Mining Areas ...... 10‐14 10.3.2.1 Description ...... 10‐14 10.3.2.2 Closure Implementation Plan ...... 10‐16 10.3.2.3 Unplanned Closure Activities ...... 10‐18 10.3.3 CMU2 – Residue Disposal Areas ...... 10‐19 10.3.3.1 Description ...... 10‐19 10.3.3.2 Closure Implementation Plan ...... 10‐21 10.3.3.3 Unplanned Closure Activities ...... 10‐25 10.3.4 CMU3 ‐ Waste Rock Landforms ...... 10‐26 10.3.4.1 Description ...... 10‐26 10.3.4.2 Closure Implementation Plan ...... 10‐28 10.3.4.3 Unplanned Closure Activities ...... 10‐31 10.3.5 CMU4 ‐ Infrastructure ...... 10‐32 10.3.5.1 Description ...... 10‐32 10.3.5.2 Closure Implementation Plan ...... 10‐35 10.3.5.3 Unplanned Closure Activities ...... 10‐39 10.3.6 CMU5 ‐ Water Management Structures ...... 10‐40 10.3.6.1 Description ...... 10‐40 10.3.6.2 Closure Implementation Program ...... 10‐42 10.3.6.3 Unplanned Closure Activities ...... 10‐42 10.3.7 CMU6 ‐ Services ...... 10‐43 10.3.7.1 Description ...... 10‐43 10.3.7.2 Closure Implementation Program ...... 10‐44 10.3.7.3 Unplanned Closure Activities ...... 10‐44 10.3.8 CMU7 ‐ Accommodation Village ...... 10‐45 10.3.8.1 Description ...... 10‐45 10.3.8.2 Closure Implementation Program ...... 10‐47 10.3.8.3 Unplanned Closure Activities ...... 10‐48 10.3.9 CMU8 ‐ Temporary Stockpiles ...... 10‐49 10.3.9.1 Description ...... 10‐49 10.3.9.2 Closure Implementation Program ...... 10‐50 10.3.9.3 Unplanned Closure Activities ...... 10‐50 10.3.10 CMU9 – Storage Shed at Bunbury Port ...... 10‐51 10.3.10.1 Description ...... 10‐51 10.3.10.2 Closure Implementation Program ...... 10‐51 10.3.10.3 Unplanned Closure Activities ...... 10‐51 10.4 Social Responsibility Plan ...... 10‐52 10.4.1 Cultural Heritage Management ...... 10‐52 10.4.2 Stakeholder Engagement ...... 10‐52 10.4.3 Social Impact Management Plan ...... 10‐53 10.4.3.1 SuperTowns Initiative ...... 10‐53 10.5 Workforce Transition Program ...... 10‐54
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Newmont Boddington Gold – Closure Plan Table of Contents
11 Closure Monitoring and Maintenance ...... 11‐1 11.1 Post‐Closure Monitoring Programme ...... 11‐1 11.1.1 Surface Water Monitoring ...... 11‐2 11.1.2 Pit Lake Monitoring ...... 11‐3 11.1.3 Groundwater Monitoring ...... 11‐4 11.1.4 Rehabilitation Monitoring ...... 11‐5 11.2 Remedial Activities ...... 11‐7 11.3 Post‐Closure Maintenance Programme ...... 11‐8 12 Management of Information and Data ...... 12‐1 13 References ...... 13‐1 14 Abbreviations, Acronyms and Glossary ...... 14‐1 14.1 Abbreviations and Acronyms ...... 14‐1 14.2 Glossary ...... 14‐2
Tables Table 2‐1 NBG tenements ...... 2‐1 Table 2‐2 NBG project development approvals ...... 2‐3 Table 2‐3 Wandoo North and Wandoo South open pit slope design parameters ...... 2‐4 Table 2‐4 Waste rock landform footprint areas ...... 2‐5 Table 2‐5 Residue Disposal Areas key parameters ...... 2‐7 Table 3‐1 GNB Minister for the Environment Approvals (State) ...... 3‐5 Table 4‐1 NBG design storm depths (adapted from GHD, 1992) ...... 4‐2 Table 4‐2 Chemical and physical properties of topsoil, subsoil and regolith oxide clay at NBG (from OES, 2010) ...... 4‐5 Table 4‐3 Summary of average physical and chemical properties of rehabilitation materials and topsoil at NBG ...... 4‐7 Table 4‐4 Rehabilitation materials inventory ...... 4‐8 Table 4‐5 Reconciliation of rehabilitation materials for mining area for current disturbance ...... 4‐9 Table 4‐6 Reconciliation of rehabilitation materials for mining area for LOM ...... 4‐9 Table 4‐7 Reconciliation of rehabilitation materials for the RDA area for current disturbance ...... 4‐10 Table 4‐8 Reconciliation of rehabilitation materials for the RDA area for LOM ...... 4‐10 Table 4‐9 Calculated runoff coefficients for rehabilitated slopes at NBG ...... 4‐12 Table 4‐10 Groundwater chemistry at NBG ...... 4‐17 Table 4‐11 Representation of NBG vegetation complexes in conservation estate ...... 4‐19 Table 4‐12 Priority flora species recorded at NBG ...... 4‐20 Table 4‐13 Conservation significant fauna species recorded at NBG ...... 4‐22 Table 4‐14 Short‐range endemic species habitats ...... 4‐23 Table 4‐15 Short‐range endemic species ...... 4‐24 Table 4‐16 Main habitat restoration options for black cockatoo habitat...... 4‐26 Table 4‐17 Aboriginal heritage sites requiring active management ...... 4‐29 Table 4‐18 SIBERIA modelling with assumed parameters – comparison of total eroded volume .... 4‐36 Table 4‐19 SIBERIA modelling with assumed parameters – comparison of gully depth ...... 4‐36 Table 4‐20 SIBERIA modelling with calibrated parameters – comparison of total eroded volume .. 4‐37 Table 4‐21 SIBERIA modelling with calibrated parameters – comparison of average gully depth ... 4‐37 Table 4‐22 Summary of conceptual waste rock landform cover designs ...... 4‐39 Table 4‐23 Summary of outcomes from steep slope trials ...... 4‐40 Table 4‐24 Physical characteristics of oxide and basement residue Gat NB ...... 4‐41 Table 4‐25 Chemical characteristics of oxide and basement residue at NBG ...... 4‐42 Table 4‐26 Total metal concentrations for oxide and basement residue at NBG ...... 4‐42
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Newmont Boddington Gold – Closure Plan Table of Contents
Table 4‐27 Summary of outcomes from oxide residue cover trial ...... 4‐44 Table 4‐28 Closure water balance model climate scenarios ...... 4‐45 Table 4‐29 Base case pit inflows during filling and at steady state ...... 4‐46 Table 4‐30 Results of closure water balance sensitivity analyses ...... 4‐47 Table 4‐31 Indicative post‐closure water quality...... 4‐50 Table 4‐32 Summary of outcomes from fertiliser application trial ...... 4‐53 Table 4‐33 Summary of outcomes from impact of grazing trial ...... 4‐54 Table 4‐34 Summary of learning’s from other mines ...... 4‐58 Table 4‐35 Analysis of information gaps ...... 4‐60 Table 5‐1 Stakeholder engagement tools ...... 5‐3 Table 5‐2 Stakeholder engagement register ...... 5‐4 Table 5‐3 Community visioning for SuperTowns initiative (adapted from Hames Sharley, 2012) ...... 5‐9 Table 6‐1 Closure aspects and objectives ...... 6‐3 Table 8‐1 Completion criteria framework for mine operations ...... 8‐3 Table 10‐1 NBG Closure Managements Units ...... 10‐1 Table 10‐2 Closure implementation strategy ...... 10‐3 Table 10‐3 Standard rehabilitation approach ...... 10‐6 Table 10‐4 Closure Implementation Plan for CMU0 ...... 10‐11 Table 10‐5 Environmental risks to be evaluated for care and maintenance period ...... 10‐13 Table 10‐6 Summary of CMU1 ...... 10‐14 Table 10‐7 Closure Implementation Plan for CMU1 ...... 10‐17 Table 10‐8 Summary of CMU2 ...... 10‐19 Table 10‐9 Closure Implementation Plan for CMU2 ...... 10‐22 Table 10‐10 Area available for progressive rehabilitation of the F1/F3 RDA embankments ...... 10‐24 Table 10‐11 Unplanned closure RDA inspection activities ...... 10‐25 Table 10‐12 Summary of CMU3 ...... 10‐26 Table 10 ‐13 Closure Implementation Plan for CMU3 ...... 10‐29 Table 10‐14 Area available for progressive rehabilitation of the waste rock landforms ...... 10‐30 Table 10‐15 Summary of CMU4 ...... 10‐32 Table 10‐16 Closure Implementation Plan for CMU4 ...... 10‐37 Table 10‐17 Summary of CMU5 ...... 10‐40 Table 10‐18 Closure Implementation Plan for CMU5 ...... 10‐42 Table 10‐19 Summary of CMU6 ...... 10‐43 Table 10‐20 Closure Implementation Plan for CMU6 ...... 10‐44 Table 10‐21 Summary of CMU7 ...... 10‐45 Table 10‐22 Closure Implementation Plan for CMU7 ...... 10‐47 Table 10‐23 Summary of CMU8 ...... 10‐49 Table 10‐24 Closure Implementation Plan for CMU8 ...... 10‐50 Table 10‐25 Summary of CMU9 ...... 10‐51 Table 10‐26 Closure Implementation Plan for CMU9 ...... 10‐51 Table 11‐1 Rehabilitation monitoring programme ...... 11‐6 Table 11‐2 Remedial activities ...... 11‐7
Figures Figure 1‐1 NBG location plan ...... 1‐5 Figure 1‐2 Continuous closure planning (from ICMM, 2008) ...... 1‐6 Figure 2‐1 NBG tenement plan ...... 2‐10 Figure 2‐2 NBG major components ‐ Current ...... 2‐11 Figure 2‐3 NBG major components ‐ LOM ...... 2‐12
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Newmont Boddington Gold – Closure Plan Table of Contents
Figure 2‐4 Waste rock landforms ‐ LOM ...... 2‐13 Figure 2‐5 Oxide pit slope design profile ...... 2‐14 Figure 2‐6 Bedrock pit slope design profile ...... 2‐14 Figure 2‐7 NBG satellite open pits ...... 2‐15 Figure 4‐1 Precipitation and evaporation at NBG ...... 4‐68 Figure 4‐2 Wandoo North geology ...... 4‐69 Figure 4‐3 Wandoo South geology...... 4‐70 Figure 4‐4 Regional surface water regime ...... 4‐71 Figure 4‐5 Catchment boundaries ...... 4‐72 Figure 4‐6 Main water management structures at NBG ...... 4‐73 Figure 4‐7 Groundwater level contours (m) September 2011...... 4‐74 Figure 4‐8 Difference in groundwater level pre‐mining (1987) to 2011 ...... 4‐75 Figure 4‐9 Groundwater salinity contours (TDS mg/L) September 2011 ...... 4‐76 Figure 4‐10 Difference in groundwater salinity pre‐mining (1987) to 2011 ...... 4‐77 Figure 4‐11 Vegetation complexes at NBG ...... 4‐78 Figure 4‐12 Site‐vegetation types at NBG ...... 4‐79 Figure 4‐13 Aboriginal heritage sites at NBG ...... 4‐81 Figure 4‐14 Analysis of waste rock landform placement (a. no secondary constraints; b. existing tenure only) ...... 4‐82 Figure 4‐15 SIBERIA modelling with assumed parameters – slope geometries ...... 4‐83 Figure 4‐16 SIBERIA modelling with calibrated parameters – slope geometries ...... 4‐84 Figure 4‐17 Conceptual waste rock landform cover designs ...... 4‐85 Figure 4‐18 Schematic closure flow circuit ...... 4‐86 Figure 4‐19 Base case pit lake filling curves ...... 4‐87 Figure 4‐20 South pit filling curves for alternative climate scenarios ...... 4‐88 Figure 4‐21 South pit filling curves for alternative evaporation rates ...... 4‐89 Figure 4‐22 Satellite pit rehabilitation areas ...... 4‐90 Figure 4‐23 Tree stocking rate at less than one year ...... 4‐91 Figure 4‐24 Trend in tree stocking rate ...... 4‐92 Figure 4‐25 Species richness at less than three years ...... 4‐93 Figure 4‐26 Trend in species richness ...... 4‐94 Figure 4‐27 Trend in diversity ...... 4‐95 Figure 4‐28 Understorey species live cover at less than three years ...... 4‐96 Figure 4‐29 Understorey species live density at less than three years ...... 4‐97 Figure 4‐30 Trend in native understorey species live density ...... 4‐98 Figure 4‐31 Trend in native understorey species live cover ...... 4‐99 Figure 6‐1 Final form of main open pits and waste rock landforms after cessation of mining ...... 6‐7 Figure 6‐2 Final form of satellite open pits (rehabilitated pits L2 and L3) ...... 6‐8 Figure 6‐3 View from Boonering Hill during operational stage ...... 6‐9 Figure 6‐4 View from Boonering Hill after rehabilitation of RDAs and waste rock landforms ...... 6‐9 Figure 6‐5 View from Pinjarra‐Williams Road during operational stage ...... 6‐10 Figure 6‐6 View from Pinjarra‐Williams Road after rehabilitation of waste rock landforms ...... 6‐10 Figure 10‐1 – NBG Closure Management Units ...... 10‐55 Figure 10‐2 Progressive rehabilitation F1/F3 RDA – saddle dams 1, 2 and 10 ...... 10‐56 Figure 10‐3 Progressive rehabilitation F1/F3 RDA – saddle dams 7, 8, 9 and 10 ...... 10‐57 Figure 10‐4 Progressive rehabilitation F1/F3 RDA – saddle dams 5 and 7 ...... 10‐58 Figure 10‐5 Progressive rehabilitation F1/F3 RDA – saddle dams 3, 4, 5 and 7 ...... 10‐59 Figure 10‐6 Progressive rehabilitation F1/F3 RDA – saddle dams 3 and 4 ...... 10‐60 Figure 10‐7 Rehabilitation zones for waste rock landforms ...... 10‐61 Figure 10‐8 Progressive rehabilitation waste rock landforms ‐ 2024 ...... 10‐62
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Newmont Boddington Gold – Closure Plan Table of Contents
Figure 10‐9 Progressive rehabilitation waste rock landforms ‐ 2027 ...... 10‐63 Figure 10‐10 Progressive rehabilitation waste rock landforms ‐ 2028 ...... 10‐64 Figure 10‐11 Progressive rehabilitation waste rock landforms ‐ 2034 ...... 10‐65 Figure 10‐12 Progressive rehabilitation waste rock landforms ‐ 2037 ...... 10‐66 Figure 10‐13 Progressive rehabilitation waste rock landforms – 2039 ...... 10‐67 Figure 10‐14 Progressive rehabilitation waste rock landforms – 2041 ...... 10‐68 Figure 10‐15 Progressive rehabilitation waste rock landforms – 2042 onwards ...... 10‐69
Plates Plate 4‐1 Mt Wells Fire Tower (from Shire of Boddington, 2011) ...... 4‐30 Plate 4‐2 Tullis Bridge (from Shire of Boddington, 2011) ...... 4‐31
Appendices Appendix 1 – Ministerial Conditions Appendix 2 – Approval Document Commitments Appendix 3 – Tenement Conditions Appendix 4 – Newmont Boddington Gold Mine Rehabilitation Resources Inventory November 2012 Appendix 5 – Research Programs, Studies and Trials Appendix 6 – Newmont Asia Pacific Boddington Gold Mine R4 Oxide Residue Rehabilitation Trial Assessment Appendix 7 – Initial Comparison of the Erosional Performance of Alternative Slope Geometries Appendix 8 – SIBERIA Modelling Calibration of Erosion Parameters and Initial Erosion Assessment Appendix 9 – Information Review – Slope Design and Rehabilitation Parameters Appendix 10 – Newmont Boddington Gold Mine Site Wide Water Balance Model and Hydrochemical Model for Closure Appendix 11 – Learning’s from Other Mines Appendix 12 – Closure Risk Register Appendix 13 – Review of Closure Commitments and Expectations and the Development of Proposed Completion Criteria
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Newmont Boddington Gold – Closure Plan Scope and Purpose
1 SCOPE AND PURPOSE 1.1 Scope Newmont Boddington Gold (NBG) is located in the southwest of Western Australia, within the Darling Plateau (Figure 1‐1). The principal features of the NBG operations are the: Open pits; Waste rock landforms; Residue disposal areas (RDAs); Processing plant; and Associated infrastructure
This Closure Plan (the Plan) covers the tenements in the Boddington area under the control of Newmont Boddington Gold Pty Ltd. The Plan covers the remaining mine life and post‐closure period for the NBG operations and documents the plan for: Closure of the site in 2041 (planned closure); and A cared an maintenance phase (unplanned closure).
This document addresses the following key elements: Closure obligations; Closure risks; Post‐mining land use; Closure objectives and strategy; Process for developing completion criteria; Monitoring programme for the closure and post‐closure phases; Implementation plans for closure and rehabilitation activities to be completed during the operational, closure and post‐closure phases; and Methodology for estimating the cost for closure of the operations.
The following sections provide a summary of the: Purpose and structure of this document (Section 1.2 and 1.3); and Framework within which ongoing closure planning and implementation of closure activities will be conducted for the NBG operations (Section 1.4).
1.2 Purpose This Closure Plan documents the proposed progressive rehabilitation and closure activities for the NBG operations. It also includes details of contingency activities to be undertaken in the situation of unplanned closure. This is a dynamic document that will be regularly reviewed and updated throughout the remaining mine life to ensure changes in areas such as the regulatory environment, stakeholder expectations or technical closure planning information are captured and incorporated into decision making.
This Plan has been developed and submitted as part of approval documentation and to meet Ministerial Statement conditions (MS 591) and tenement conditions. The Plan has been prepared by Newmont to fulfil the requirements of: Stakeholders of the NBG operations; Objectives of Newmont policies and standards; Mining tenement conditions; Ministerial Statement 591; The Australian Minerals Industry Code of Environmental Management;
1‐1 Newmont Boddington Gold – Closure Plan Scope and Purpose
The Strategic Framework for Mine Closure (Australian and New Zealand Minerals and Energy Council and Minerals Council Australia); The Planning for Integrated Mine Closure: Toolkit (International Council on Mining & Metals); and Guidelines for Preparing Mine Closure Plans (Department of Mines and Petroleum and Environmental Protection Authority).
The primary purpose of this Plan is to provide details of the activities and resources required for progressive decommissioning and rehabilitation of all components of the operations. This Plan allows Newmont, stakeholders and regulatory bodies to be aware of and satisfied that the project will be completed in a manner that meets the applicable environmental management standards and sustainable development objectives.
1.3 Structure The structure of this Closure Plan is as follows:
Section 1: Scope and Purpose Describes the purpose of the Closure Plan, the structure of the report and the framework within which the Plan was developed and will continue to be reviewed.
Section 2: Project Overview Provides a summary of the NBG operations, including history and status of the project.
Section 3: Closure Obligations and Commitments Summarises the legal conditions and commitments relevant to mine closure for the NBG operations. This section also lists relevant approvals, leases and licences.
Section 4: Closure Data Describes the key environmental aspects and community values relevant to the NBG operations, summarises the basis for landform designs and studies undertaken to improve understanding of closure of the site and identifies current information gaps.
Section 5: Stakeholder Consultation Outlines the stakeholder engagement process and summarises stakeholder feedback with respect to closure and rehabilitation.
Section 6: Post‐Mining Land Use and Closure Objectives This section describes the post‐mining land use options, closure aspects and objectives for the operations and the final form of landforms and voids.
Section 7: Identification and Management of Closure Issues Provides a summary of the key findings of the closure risk assessment and management measures for major risks identified.
Section 8: Development of Completion Criteria This section describes the completion criteria for the NBG operations.
Section 9: Financial Provision for Closure Summarises the methodology for calculating and updating the closure cost estimate.
1‐2 Newmont Boddington Gold – Closure Plan Scope and Purpose
Section 10: Closure Implementation Summarises the standard decommissioning and rehabilitation approach and the activities required for closure of each domain of the NBG operations for planned and unplanned closure.
Section 11: Closure Monitoring and Maintenance Describes the proposed closure monitoring and maintenance programme and remedial activities.
Section 12: Management of Information and Data Provides details of the system to be used for management of documentation and closure activities.
Section 13: References Lists the references cited throughout this Closure Plan.
Section 16: Abbreviations, Acronyms and Glossary Provides a list of abbreviations and acronyms which are used in this Closure Plan. This section also provides a glossary which defines terms used in the Plan.
1.4 Closure Planning Framework A framework has been developed for ongoing closure planning and implementation of closure and rehabilitation activities at NBG. The closure planning and rehabilitation framework outlines: Responsibilities of the closure review technical team; The closure plan review process; and The current schedule for mine closure and planning.
More detailedn informatio is given on each of these aspects of the framework in the following sections.
1.4.1 Closure Review Technical Team NBG has a closure review technical team (CRT2) to systematically evaluate and coordinate closure planning opportunities, risks and activities that are required to advance the closure planning process. The CRT2 includes key technical disciplines and management personnel from the mining operations including: Regional Environment and Social Responsibility (ESR); Site ESR Mine Planning; Mine Technical Services; and Processing.
The CRT2 meets regularly throughout the mine life cycle to coordinate closure planning, address potential closure and rehabilitation risk and cost issues, foster integration of closure planning into mine operations and evaluate the impacts of changes to the mine plan.
The responsibilities of the CRT2 include: Develop the overall closure vision to guide the planning process; Facilitate communication to all function groups at the mine, to the regional ESR managers and corporate ESR managers;
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Develop closure cost estimates; Prioritise studies and resource needs; Develop and periodically update the closure and rehabilitation specific risk registry; Evaluate and develop opportunities to reduce closure liabilities and reduce risks during the closure and post‐closure periods; and Develop closure and rehabilitation schedules for trials, progressive and final rehabilitation.
1.4.2 Closure Plan Review Process Closure planning is initially conceptual and progressively becomes more detailed over the life of the mine (Figure 1‐2). Successful closure depends on setting, continually reviewing and validating and finally meeting closure goals that align with company and stakeholder requirements (ICMM, 2008).
A program of regular review and revision of the NBG Closure Plan will be undertaken to: Incorporate changes in: o Commitments and obligations; o Life of mine planning; o Areas of disturbance due to expansion of the operation and progressive rehabilitation of disturbed areas; and o Knowledge gained through studies, investigation, trials, monitoring and stakeholder consultation. Track progress against activities in Closure Implementation Plans, ascertain whether incomplete activities are still relevant and develop new activities where appropriate; Review closure objectives and completion criteria to ensure they remain relevant and consistent with stakeholder expectations; and Update the closure cost estimate to an increasing level of accuracy appropriate to the stage of the project.
The NBG Closure Plan will be updated and submitted to the DMP for review every three years. This meets the requirements of the Guidelines for Preparing Mine Closure Plans (DMP/EPA, 2011) and conditions imposed by Ministerial Statement 591. Continued development and review of the NBG Closure Plan will drive progressive rehabilitation on site and the continual improvement cycle for mine closure.
1.4.3 Schedule The timing of closure of the NBG operations depends on a number of factors, including: Economic and environmental costs; Gold eprice and th value of the Australian dollar; and Environmental standards and requirements.
It is currently planned to complete open pit mining and processing of all viable medium grade ore stockpiles at NBG in 2041. However, Newmont will continue to investigate options to extend beyond this estimated mine life.
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Figure 1‐1 NBG location plan
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Figure 1‐2 Continuous closure planning (from ICMM, 2008)
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2 PROJECT OVERVIEW This section provides background information on the NBG operations including: Project location and tenure (Section 2.1); Land ownership (Section 2.2); Project history (Section 2.3); and Overview of operations (Section 2.4).
2.1 Project Location and Tenure NBG is situated in southwest Western Australia within the northern Jarrah forest of the Darling Plateau (Figure 1‐1). The town of Boddington is located 12km southeast of the mine.
NBG is located across nine mining tenements and several miscellaneous licences and general purposes leases (Table 2‐1, Figure 2‐1).e Th mining tenements occur over the BHP Billiton‐Worsley joint venture’s State Agreement ML258SA and Alcoa World Alumina Australia’s State Agreement ML1SA.
Table 2‐1 NBG tenements Tenement Area State Agreement M70/21 Main mining area BHP Billiton‐Worsley ML258SA M70/22 Main mining area BHP Billiton‐Worsley ML258SA M70/23 Main mining area BHP Billiton‐Worsley ML258SA M70/24 Main mining area BHP Billiton‐Worsley ML258SA M70/25 Main mining area BHP Billiton‐Worsley ML258SA M70/564 Main mining area BHP Billiton‐Worsley ML258SA M70/799 Main mining area BHP Billiton‐Worsley ML258SA M70/1031 Main mining area Alcoa ML1SA ML264SA(1) Exploration Alcoa ML1SA ML264SA(2) Main mining area Alcoa ML1SA G70/215 Main mining area BHP Billiton‐Worsley ML258SA G70/218 Main mining area Alcoa ML1SA G70/219 Main mining area Alcoa ML1SA L70/28 Hotham River Pump Station BHP Billiton‐Worsley ML258SA L70/95 Accommodation Village BHP Billiton‐Worsley ML258SA L70/96 Accommodation Village Sewage Treatment Plant BHP Billiton‐Worsley ML258SA
2.2 Land Ownership NBG is managed on behalf of the Newmont Boddington Gold Joint Venture by Newmont Boddington Gold Pty Ltd (NBGPL). The Newmont Boddington Gold Joint Venture ownership comprises: Newmont Boddington Pty Ltd, a wholly owned subsidiary of Newmont Mining Corporation; and Saddleback Investments Pty Ltd, a wholly subsidiary of Newmont Mining Corporation.
The mining operations are largely located on private land owned by NBGPL, with approximately 1,500 ha on the project’s western margin located in State forest. The NBG tenure is underlain largely
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by ML258SA (bauxite mining rights) held by Worsley Alumina and ML1SA (bauxite mining rights) held by Alcoa Australia.
The NBG contact for this Closure Plan is: Javier Brodalka Environmental Manager Phone: (08) 9883 4251 Email: [email protected]
The site and postal addresses for NBG are: Gold Mine Road PO Box 48 Boddington, WA Boddington, WA, 6390
2.3 Project History In 1980, geologists from Reynolds Australia Mines discovered significant gold mineralisation at Boddington when investigating a base metal and gold geochemical anomaly defined by the Geological Survey of Western Australia in 1978. In 1984, a Notice of Intent was submitted to the State government outlining the details of the project and approval for the Boddington Gold Mine (BGM) was given in December 1985. Production commenced at BGM in August 1987 at the design rate of 3 million tonne per annum (Mtpa) based on an ore reserve of 45 million tonne (Mt). First gold was poured on 6 August 1987.
Immediately adjacent to the BGM was the Hedges Gold Mine. An Environmental Review and Management Program was submitted for the Hedges Gold Mine in October 1987 and was subsequently approved in February 1988. Production commenced at Hedges Gold Mine in 1988 at a design rate of 2 Mtpa based on a reserve of .8 Mt First gold was poured in October 1988.
The BGM and Hedges Gold Mines were operated separately until the BGM joint venture partners acquired the Hedges mining area in 1998. After this time the mines became one operation. Since the original approvals there have been several changes and expansions of activities, which are summarised in Table 2‐2.
The BGM went into care and maintenance in December 2001 with the exhaustion of the oxide ore deposit. Over its 15 years of production, the BGM had produced 4.74 million ounces of gold and 6,500 tonnes of copper after processing 105 Mt of ore at a maximum throughput of 8.8 Mtpa. Between December 2001 and May 2006, a small care and maintenance and exploration workforce was maintained to attend to salvage, clean‐up, exploration, environmental statutory obligations, deconstruction and maintenance functions.
In February 2006, the BGM joint venture owners announced the development of a 15 to 20 year 600 Mt expansion processing up to 41 Mtpa. After approximately three and a half years of construction the first copper concentrate was produced on 13 August 2009 and the first gold poured on 29 September 2009.
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Table 2‐2 NBG project development approvals Date Approval December 1985 Boddington Gold Mine project approval. February 1988 Hedges Gold Mine project approval. February 1988 Boddington Gold Mine stage 1 expansion to 4.5 Mtpa. December 1988 Boddington Gold Mine stage 2 expansion to 6 Mtpa with an additional water supply reservoir (D1). November 1989 Boddington Gold Mine mining and processing of basement and supergene ores, expansion to 6.75 Mtpa. January 1993 Boddington Gold Mine mining of oxide ore from the eastern anomalies. January 1995 Boddington Gold Mine rehabilitation strategy for mining area and residue disposal areas. July 1997 Hedges Gold Mine expansion to 4 Mtpa and Section 46 Review. December 1998 Section 46 Review to align existing conditions and commitments. June 2002 Gas‐fired power station and natural gas pipeline approval (now lapsed). March 2006 Section 45C modifications for increased scale of Boddington expansion. September 2006 Boddington Expansion Project Mining Proposal. July 2012 Newmont Boddington Gold Revised Wandoo North and South Pit Modifications and Additional Waste Rock Storage Mining Proposal
2.4 Overview of Operations NBG is a substantial gold and copper project targeting low grade hard rock ore lying beneath existing pits mined during past operations. The main components of the current operations are the (Figure 2‐ 2): Wandoo North and South open pits; Satellite open pits; Jarrah decline; Waste rock landforms; ROM pad and medium grade stockpile; Primary crusher; Conveyor corridor; Processing plant; Residue disposal areas; Water storage reservoirs and dams; Offices and workshops; and Accommodation village.
Future expansion of the operations will include development of an additional RDA and water storage reservoir, extension of the footprint of the waste rock landforms and relocation of some infrastructure (Figure 2‐3).
The following sections provide a summary of the main components of the operations, with more detailed information included in Section 10. A description of the post mining land use, closure strategy and the final form of landforms is summarised in Section 6.
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2.4.1 Open Pit Mines
2.4.1.1 Wandoo North and South Open Pits The Wandoo North and Wandoo South open pits are currently being mined consecutively using face shovels that load Caterpillar 793 haul trucks. A vertical mining rate averaging 60 m/year (12 benches per year) and a peak of up to 108 m/year (9 benches per year) are planned. The pits have strip ratio of 1.2:1 and the total ore and waste mining rate will average 85 Mtpa over the life of the project, with a peak rate of approximately 110 Mtpa.
Mining of the Wandoo South pit is planned to continue until 2041 to a final depth of ‐432 mRL. The pit base at Wandoo North will be reached in 2036 at a depth of ‐252 mRL. Mining takes place below the water table and advance dewatering of pit floors is being achieved through a combination of targeted dewatering bores and tin ‐pi sump pumps.
The design parameters for the open pits are summarised in Table 2‐3 and illustrated in Figure 2‐5 and Figure 2‐6.
Table 2‐3 Wandoo North and Wandoo South open pit slope design parameters Design Criteria Oxide Bedrock Bench height (m) 12 12 Batter height (m) 12 24 Batter angle (°) 47 90 Berm width (m) 14.5 14.5 Inter Ramp Slope Angle (IRSA) (°) 25 59 Maximum slope height at IRSA (m) NA 180 Catch berm width at base of oxide (m) 15 NA Catch berm width (where required) at NA 30 maximum IRSA height (m)
2.4.1.2 Satellite Open Pits The satellite open pits are shallow oxide pits that were mined between 1993 and 2001 (Figure 2‐7). Most of the satellite pits were rehabilitated between 1993 and 2007. The K3/K4 and Q4 pits will be retained for potential use for landfill or trial areas. These pits will be rehabilitated at the end of mine life if not required.
Rehabilitation of the satellite open pits comprised re‐shaping to achieve external drainage, application of between 10 cm and 30 cm of gravel (depending on the slope angle) and 10 cm of topsoil (material depths were optimised based on the volume of material available at each pit), contour ripping, seeding, fertilising and tree planting if required.
2.4.2 Jarrah Decline The Jarrah Decline is located on the northeast side of the Wandoo North open pit. Mining of high‐ grade quartz veins occurred at the Jarrah Decline between 1992 and 1997. After completion, the mine entrance was secured to prevent unauthorised entry and vent shafts were blocked or backfilled.
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2.4.3 Waste Rock Landforms
2.4.3.1 Waste Rock Landforms 7, 8, 9, 10, 11 and 12 From mining of the Wandoo South and Wandoo North open pits, approximately 1.3 Bt of waste rock will be produced. The current operations consist of three waste rock landforms (Figure 2‐2): Waste rock landforms 7 and 8 located to the southwest of the Wandoo North and Wandoo South open pits; and Waste rock landform 9 located to the northeast of the Wandoo North open pit.
Over the life of the mine it is planned to construct an additional landform to the north of Wandoo North open pit (landform 12) and to progressively increase the size of landforms 7 and 8 (landforms 10 and 11) (Figure 2‐3 and Figure 2‐4). At closure these waste rock landforms are planned to have a total footprint of 1,331 ha (Table 2‐4).
Waste rock is transported to designated waste rock landforms based on its geochemical characteristics. Detailed information on the geochemistry and management of the waste rock is included in Sections 4.12 and 4.2.1.1.
Studies have commenced to develop waste rock landform outslope and cover designs that: Maintain their integrity in the long term; Minimise environmental impacts; and Enable progressive rehabilitation.
Detailed information on the studies of the waste rock landform placement, outslope and cover design is included in Sections 4.2.1.2 and 4.2.1.3.
Table 2‐4 Waste rock landform footprint areas Waste Rock Landform Footprint (ha) 7, 8, 10, 11 1,060 9 76 12 195 Total 1,331
2.4.3.2 Q3 Waste Rock Landform The Q3 waste rock landform was constructed in 2001 over the backfilled Q3 South oxide pit. The landform was constructed primarily of diorite, andesite and dolerite and does not contain any hostile materials. The landform has a footprint of 6.5 ha and was designed to blend in with an adjacent hill.
Rehabilitation of the Q3 waste rock landform was completed in 2002 and comprised of application of 3 m of oxide (in most places), 20 cm of gravel and 10 cm of topsoil, contour ripping, seeding, tree and recalcitrant species planting and fertilising.
2.4.4 ROM Pad and Medium Grade Ore Stockpile The ROM pad consists of feed material for the primary crusher and is located adjacent to it to minimise material handling costs.
The medium grade ore stockpile is located immediately south of the primary crusher. This stockpile consists of ore that does not meet optimal revenue functions for earlier mill feed in the mine’s life,
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but is nevertheless economic for mill feed later in the project and when there are short falls in run of mine ore. This stockpile is planned to be re‐handled for processing towards the end of operations.
2.4.5 Primary Crusher The primary crusher is located to the west of the Wandoo North and South open pits and comprises two gyratory crushers which the haul trucks dump ore directly in to. Primary crushed ore is fed onto the overland conveyor to deliver it to the plant site for processing.
2.4.6 Conveyor Corridor The conveyor corridor is located between the Wandoo North and Wandoo South open pits. The conveyor is used to convey crushed ore over the 2.5km from the primary crusher to the coarse ore stockpile located at the processing plant.
2.4.7 Processing Plant Processing at NBG comprises: Three stages of crushing: o Primary; o Closed circuit secondary; and o Tertiary (high pressure grinding rolls). Ball milling; and Hydrocyclone classification.
The ground ore is then floated to produce a gold rich copper concentrate for filtration and sales to overseas smelters. Flotation tailings are then leached for further gold recovery. The ore processing rate is approximately 35 Mtpa or up to 105,000 tonnes per day. Approximately 32 Mtpa of residue is pumped as slurry from the processing plant to the RDAs.
The processing plant is scheduled to continue operating until 2041, when ore from the Wandoo North and Wandoo South pits and viable medium grade ore stockpiles on site are .exhausted
2.4.8 Residue Disposal Areas NBG currently has one active RDA (F1/F3) and one inactive RDA (R4), which are located approximately 5 km north of the processing plant (Figure 2‐2). A third RDA is planned to be constructed to the north of the operations (Figure 2‐3).
The key parameters for the RDAs are summarised in Table 2‐5 with more detailed information included in the sections below.
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Table 2‐5 Residue Disposal Areas key parameters Parameter R4 RDA F1/F3 RDA Future RDA Status Water storage Active Planned Period of Operation 1987 ‐ 2001 1993 – currently active. Construction to Deposition planned to commence 2022 cease 2026. Maximum height (m) 27 70 75 Current height (m) 27 30 NA Maximum 330 1,125 1,650 impoundment area (ha) Current impoundment 330 420 NA area (ha) Maximum 40 x 106 500 x 106 900 x 106 impoundment volume (m3) Current impoundment 40 x 106 66 x 106 NA volume (m3)
2.4.8.1 R4 RDA The R4 RDA is an inactive, unlined valley facility which is currently used: As a water storage facility; For stockpiling of bauxite, rehabilitation and construction materials; As an alternate water source for wildlife; and As the location for a residue rehabilitation trial.
The R4 RDA was active from 1987 to 2001 and contains residue from processing of oxide ore. The RDA was constructed using the upstream method.
Seepage modelling for the R4 RDA indicated that during previous operations and the care and maintenance period, seepage rates through the main embankment and eastern embankment were in the range 750 to 2,200 m3/day. The seepage from the R4 RDA is alkaline (pH of approximately 9) and has a salinity of approximately 8,000 mg/L Total Dissolved Solids (TDS).
2.4.8.2 F1/F3 RDA The F1 RDA is a valley facility which contains residue from the processing of basement rock. Residue produced from basement rock is relatively inert, with very low sulphur levels and a low number of elemental enrichments. The residue settles rapidly to high densities, is relatively incompressible and has permeability at the high end of that which is typical for residue materials. Residue characterisation work indicates there is low risk of acid formation considering the weathering rates that are normally encountered within an RDA.
The F1 RDA was constructed over the existing F3 RDA and O2 water storage reservoir and has been designed for an ultimate storage capacity of 600Mt at a deposition rate of 35 Mt/annum. The F1/F3 RDA is planned to be operated until 2026 when deposition will commence in the future RDA.
Residue discharge is from spigots located around the perimeter. The decant pond is controlled to a concentration of below 30 mg/L for weak acid dissociable cyanide (WAD CN) using a cyanide destruct plant. Decant water recovery is returned to the processing plant for re‐use.
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To control seepage from the facility, the supernatant pond of the F1/F3 RDA is lined with a drainage layer, geomembrane liner and compacted clay liner. The area outside of the supernatant pond is lined with compacted clay. Below the saddle dams, cut‐off trenches extend through the gravel and cap rock to seal into the silt and clay soils.
At closure the F1/F3 RDA will have a footprint of approximately 1,125 ha, a maximum height of 70 m above ground surface and contain approximately 500x106 m3 of residue. The initial two lifts of the embankments will be by downstream construction using local soil. Subsequent lifts will use beached residue material and upstream construction.
2.4.8.3 Future RDA NBG proposes to construct an additional RDA to the east of the existing RDA (Figure 2‐3). The proposed cross valley facility is estimated to be comprised of one main embankment wall of around 75 m high, with a small number of saddle dams between 5 and 16 m high around the remaining perimeter of the facility. The residue would be retained within the natural storage capacity of the valley and will occupy an area of approximately 1,650 ha for storage of 600 Mt.
2.4.9 Water Storage Reservoirs and Dams The main water storage reservoirs and dams at the current NBG operations are the (Figure 2‐2): D1 and D4 water storage reservoirs; North and South clear water ponds; and Impacted water sump.
The principal water storage facilities at NBG are D1 and D4 water storage reservoirs which dam Thirty‐Four Mile Brook. They are used to store raw water for use in the processing plant, including water pumped from the Hotham River. With expansion of the operations NBG plan to construct a new water storage reservoir (D5) to the south of the waste rock landforms (Figure 2‐3). This will replace the D4 water storage reservoir, which will be covered by advancement of the waste rock landforms.
The North and South Clear Water Ponds provide storage for pit dewatering en‐route to the processing plant and other storage structures. The North Clear Water Pond also intercepts Thirty‐ Four Mile Brook runoff.
The impacted water sump is located beneath waste rock landform No. 8 and is used to store mine impacted runoff and seepage for use as process water. It is planned to expand the impacted water sump along the former alignment of the Thirty‐Four Mile Brook as the waste rock landforms expand.
In the early phases of closure, the water storage reservoirs and ponds may be retained for surface water management.
2.4.10 Support Infrastructure Support infrastructure at NBG includes the: Offices; Workshops for servicing of light and heavy vehicles; Electrical and welding workshops; Warehouse; Laboratory; Fuel storage areas; Water treatment plant;
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Sewage treatment plant; Explosives plant and magazine; Hotham River pump station; Pipelines; Booster pump station and cyanide destruct plant; Powerlines; Laydown yards; and Roads and access tracks.
2.4.11 Accommodation Village The accommodation village is located 11 km southeast of the mine and comprises: Transportable accommodation units; Kitchen and dry mess; Wet mess; Recreation room; Gym; Sports courts; Laundry rooms; Administration office; Security hut; and Car parking facilities.
A sewage treatment plant for the village is located at the old camp site on the northern side of Gold Mine Road.
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Figure 2‐1 NBG tenement plan
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Figure 2‐2 NBG major components ‐ Current
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Figure 2‐3 NBG major components ‐ LOM
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Figure 2‐4 Waste rock landforms ‐ LOM
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Figure 2‐5 Oxide pit slope design profile
Figure 2‐6 Bedrock pit slope design profile
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Figure 2‐7 NBG satellite open pits
2‐15 Newmont Boddington Gold – Closure Plan Closure Obligations and Commitments
3 CLOSURE OBLIGATIONS AND COMMITMENTS This section summarises the: Main legislation and guidelines relevant to mine closure from an International, Commonwealth and State perspective (Sections 3.1 and 3.2); and Regulatory approvals under which NBG operates (Section 3.3).
3.1 Legislation Laws and regulations relating to mine closure exist at the State and Commonwealth government levels. The legislation applicable to closure planning and rehabilitation at NBG includes: Rights in Water and Irrigation Act 1914; Soil and Land Conservation Act 1945; Wildlife Conservation Act 1950; Aboriginal Heritage Act 1972; Agriculture and Related Resources Protection Act 1976; Mining Act 1978; Environmental Protection Act 1986; Mines Safety and Inspection Act 1995; Contaminated Sites Act 2003; Native Title Act 1993 (Commonwealth); Environmental Protection and Biodiversity Conservation Act 1999 (Commonwealth).
The legal obligations that Newmont is subject to will change when Acts and Regulations are amended or new legislation is introduced.
The principle legislation that will affect closure of the NBG operations are the Mining Act 1978, Environmental Protection Act 1986, Contaminated Sites Act 2003 and Environmental Protection and Biodiversity Conservation Act 1999, which are discussed in more detail in the following sections.
3.1.1 Mining Act 1978 The Mining Act 1978 regulates mining leases, licences, terms and conditions for mines on private and crown land, surrender of tenements, regulations, litigation and administration of justice issues. All of the tenements issued by the Department of Mines and Petroleum (DMP) have conditions imposed relating to environmental protection, management and, in most cases, mine decommissioning, rehabilitation and submission of Closure Plans. In addition, the Mines Safety and Inspection Act 1995, incorporates specific requirements intended to prevent companies abandoning operations in an unsafe condition.
The main requirements of theP DM with regards to closure and rehabilitation of a mine site can be summarised as follows: Man‐made structures must be removed or otherwise made safe in the long term; Disturbed land is to be left in a condition whereby vegetation can be effected, except those areas where this is deemed to be impractical, such as the solid rock face of an abandoned pit or the outcropping rock in the floor of that pit; Man‐made structures such as waste rock landforms, residue disposal areas, roads and processing plant sites are to be treated so that revegetation is actively promoted; and Revegetated areas should be in keeping with the natural pattern of the surrounding vegetation and be maintained until it is self‐supporting.
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Newmont Boddington Gold – Closure Plan Closure Obligations and Commitments
Under the Mining Act 1978, the DMP has established an Unconditional Performance Bond system applicable to all mining operations. The system ensures that sufficient funds are available if the State Government is required to undertake rehabilitation on mining tenements where the holder failed to comply with environmental conditions placed on its tenements. The bonds for NBG’s leases are reviewed annually through the Annual Environmental Report in light of ongoing rehabilitation undertaken.
The Unconditional Performance Bond system is currently under review and may be replaced by payment of a levy into a Mining Rehabilitation Fund. The purpose of the Fund is to provide a source of funding for the rehabilitation of abandoned mine sites and other land affected by mining operations carried out in, on or under those sites.
The Mines Safety and Inspection Regulations 1995 are specifically related to safety and ensuring the decommissioning and closure of sites is undertaken safely. Regulation 3.16 deals with the requirements that need to be fulfilled by the Registered Manager when a mine is abandoned: “Notification of the abandonment of mining operations at a mine must be in addition to the details set out in regulation 3.12, include the following details: ‐ a. Details of precautionsn take to ensure that access to the underground workings has been secured against unauthorised entry; b. Details of precautions taken to prevent inadvertent access to open pit workings; c. Details of the precautions take to prevent, so far as is practicable, any post mining subsidence into the underground workings, by back‐filling stope voids and by any other appropriate measures; d. Details of precautions taken to ensure that all plant and other equipment have been removed or secured and left in a safe condition; e. Details of any precautions taken to remove or properly dispose of all hazardous substances at the mine; and f. Any plans required to be prepared under Section 88 of the Act…”
Section 88 of the Mining Act 1978 deals with requirements for survey plans to be supplied on abandonment or suspension of operations. In the case of the suspension of mining operations or when a mine is closed, plans must be provided in hard copy form accompanied by a copy in electronic form.
3.1.2 Environmental Protection Act 1986 The Environmental Protection Act 1986 outlines the management requirements for mining projects in Western Australia. Following assessment of a project under Part IV of the Environmental Protection Act 1986, the Western Australian Minister for the Environment issues a Ministerial Statement for Approval which contains the environmental conditions and commitments for the project. Both the environmental conditions and commitments (derived from the project environmental assessment document) must be met by the proponent prior to surrender of a mining lease.
Additionally, management of the NBG operations during operation, closure and post‐closure must meet the requirements of Part V of the Environmental Protection Act 1986, which are to: Not cause pollution and make good any pollution that does occur; Not cause environmental harm and make good any environmental harm that does occur; and Comply with all licences, approvals and notices.
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Newmont Boddington Gold – Closure Plan Closure Obligations and Commitments
3.1.3 Contaminated Sites Act 2003 The Contaminated Sites Act 2003 complements the measures in the Environmental Protection Act 1986 aimed at preventing pollution and environmental harm. The Contaminated Sites Act 2003 and the accompanying Contaminated Sites Regulations 2006 renders the polluter responsible for assuming full liability for contamination of land and groundwater.
Under the Contaminated Sites Act 2003 the following entities are responsible for the reporting of suspected or known contaminated sites to the Department of Environment and Conservation: An owner or occupier of the site; A person who knows, or suspects, that he/she has caused, or contributed, to the contamination; and A contaminated sites auditor engaged to provide a report that is required for the purposes of the Contaminated Sites Act 2003, in respect of the site.
Remediation of a contaminated site will be required when: There is an unacceptable on or off site risk prior to land transfer, alteration of the site suitability, or in lease agreements; or A clean‐up notice is issued by the DEC when sites pose an unacceptable risk to human and/or environmental receptors.
3.1.4 Environmental Protection and Biodiversity Conservation Act 1999 The Environmental Protection and Biodiversity Conservation Act 1999 (the EPBC Act) provides a legal framework to protect and manage matters of national environmental significance, including nationally and internationally important flora, fauna, ecological communities and heritage places. The EPBC Act aims to (Commonwealth of Australia, 2010): Provide for the protection of the environment, especially matters of national environmental significance; Conserve Australia’s biodiversity; Protect biodiversity internationally by controlling the international movement of wildlife; Provide a streamlined environmental assessment and approvals process where matters of national environmental significance are involved; Protect our world and national heritage; and Promote ecologically sustainable development.
Projects that have the potential to impact on “matters of national environmental significance” and are declared a “Controlled Action” under the EPBC Act may be required to meet Conditions of Approval relevant to mine completion.
3.2 Guidelines Commonwealth and State guidelines applicable to closure planning and rehabilitation at NBG include: Strategic Framework for Mine Closure (Australian and New Zealand Minerals and Energy Council and Minerals Council of Australia); Leading Practice Sustainable Development Program for the Mining Industry Handbooks on: Mine Closure and Completion; Mine Rehabilitation; Managing Acid and Metalliferous Drainage and Community Engagement and Development (Australian Department of Industry, Tourism and Resources);
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Newmont Boddington Gold – Closure Plan Closure Obligations and Commitments
Enduring Value – Australian Minerals Industry Framework for Sustainable Development (Minerals Council of Australia); Mine Closure Guideline for Minerals Operations in Western Australia (Chamber of Minerals and Energy of Western Australia); Contaminated Sites Management Series (Department of Environment and Conservation); Guidelines for Preparing Mine Closure Plans (Department of Mines and Petroleum and Environmental Protection Authority); Environmental Notes on Mining: Acid Mine Drainage; Care and Maintenance; and Waste Rock Dumps (Department of Mines and Petroleum); Safety Bund Walls around Abandoned Open Pits (Department of Mines and Petroleum); Safe Design and Operating Standards for Tailings Storage (Department of Mines and Petroleum); Guidance for the Conservation of Mining Industry Heritage in Western Australia (Heritage Council of Western Australia); and Mine Void Water Resources Issues in Western Australia (Water and Rivers Commission).
Newmont is a signatory to a number of international guidelines which are relevant to closure and rehabilitation of the NBG operations: International Council on Mining and Metals (ICMM) Sustainable Development Framework (including the Planning for Integrated Mine Closure: Toolkit); International Cyanide Management Code for the Manufacture, Transport and use of Cyanide in the Production of Gold; Council for Responsible Jewellery Practices; United Nations Global Compact; Extractive Industries Transparency Initiative; Institute of Social and Ethical Accountabilities Standard on Stakeholder Engagement (AA1000); and The Global Sullivan Principles of Social Responsibility.
3.3 Regulatory Approvals NBG is licenced to operate via: Licence for Prescribed Premises; Minister for the Environment Approvals (State and Commonwealth); Department of Mines and Petroleum Approvals; and Department of Water approvals.
3.3.1 Licence for Prescribed Premises NBG operates under Prescribed Premises Licence 8306/1 issued by the Department of Environment and Conservation (DEC) under the authority of the Environmental Protection Act 1986. Licence 8306/1 is valid until 30 April 2014 and authorises the following activities: Processing or beneficiation of metallic ore (Category 5); Mine dewatering (Category 6); Sewage facility (Category 54); Used tyre storage (Category 57); Class I inert landfill site (Category 63); Bulk storage of chemicals (Category 73); and
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Newmont Boddington Gold – Closure Plan Closure Obligations and Commitments
Water desalination plant (Category 85B).
There are no conditions included in this licence related to rehabilitation or closure.
3.3.2 Minister for the Environment Approvals
3.3.2.1 Environmental Protection Act 1986 The NBG operations have been subject to approval via the environmental impact assessment process under Part IV of the Environmental Protection Act 1986 (Table 3‐1). The commitments and Ministerial conditions for these projects specifically related to mine closure and rehabilitation are summarised in Appendix 1.
Table 3‐1 NBG Minister for the Environment Approvals (State) Ministerial Title Comments Statement 596 Gas‐Fired Power Station and Natural Gas Pipeline Approval lapsed 591 Boddington and Hedges Gold Mines 489 Boddington Gold Mine Superseded by Ministerial Statement 591 450 Hedges Gold Project Superseded by Ministerial Statement 591 453 Boddington Gold Mine, Extended Basement Superseded by Ministerial Operation Statement 591 379 Boddington Gold Mine, Enhancement of Facilities, Superseded by 489 and 591 Expansion of Facilities – Stage 2, Mining and Processing of Supergene/Basement Ores, Development of Eastern Anomalies 299 Boddington Gold Mine, Development of Eastern Superseded by Ministerial Anomalies Statements 379, 489 and 591 100 Boddington Gold Mine, Mining and Processing of Superseded by Ministerial Supergene/Basement Ores Statements 379, 489 and 591 85 Boddington Gold Mine, Mining and Processing of Superseded by Ministerial Supergene/Basement Ores Statements 379, 489 and 591 49 Boddington Gold Mine Projects, Expansion of Superseded by Ministerial Facilities – Stage 2 Statement 379, 489 and 591 20 Hedges Gold Project Superseded by Ministerial Statement 379 and 591 19 Boddington Gold Mine Enhancement of Facilities Superseded by Ministerial Statement 379, 489 and 591
3.3.2.2 Environmental Protection and Biodiversity Conservation Act 1999 The NBG project triggered referral under sections 18 and 18A (Listed threatened species and communities) of the Environmental Protection and Biodiversity Conservation Act 1999 in 2006 and 2012 due to the use of the area by Carnaby’s, Baudin’s and Red‐tailed Forest black cockatoos.
The NBG project was assessed by the Commonwealth Minister for Environment as not a controlled action under the Environmental Protection and Biodiversity Conservation Act 199, provided it is
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undertaken in a particular manner. Measures to minimise potential impacts on listed threatened black cockatoos are identified in the NBG Black Cockatoo Management Plan.
3.3.3 Department of Mines and Petroleum Approvals Approval for mining projects has been received from the Department of Mines and Petroleum via the Mining Proposal (formerly Notice of Intent) process. Commitments made within Mining Proposals (formerly Notice of Intents) and letters submitted to the DMP are binding. The commitments that relate to closure and rehabilitation made by NBG (and previous owners) in documents submitted to the DMP are summarised in Appendix 2. NBG is currently in the process of acquiring missing documentation from the DMP. The register of commitments will continue to be updated as documentation becomes available.
Tenement conditions related to mine closure and rehabilitation have been applied to the NBG tenements. The tenement conditions related to closure and rehabilitation are summarised in Appendix 3.
The long history of mining at NBG has led to some commitments and tenement conditions being: Duplicated; No longer relevant; and Contradictory.
Newmont intends to review all of the existing conditions and commitments and propose amendments as required for aspects that are no longer relevant or do note reflect th proposed rehabilitation approach.
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Newmont Boddington Gold – Closure Plan Closure Data
4 CLOSURE DATA This section summarises the data relevant to closure of the site with respect to: The physical and biological environment and key community values at NBG that are critical for successfully meeting closure outcomes (Section 4.1); Outcomes of investigations and trials (Section 4.2); The basis of the design for landforms and how these address the key closure issues identified for the site (Section 4.2); and Learning from the experience of other mine sites (Section 4.3).
Information gaps have been identified and the risk associated with not having this information assessed. Actions required to address information gaps have been prioritised based on risk and are included in the appropriate closure implementation plan (Section 10).
4.1 Environmental and Community Aspects 4.1.1 Meteorology The climate at NBG is typified by hot dry summers with occasional storms and cool wet winters. Weather data has been recorded at NBG since 1984 showing temperature ranges from a mean minimum of 19°C to a mean maximum of 33°C during summer and a mean minimum of 6°C to a mean maximum of 15°C in the winter months. Extreme temperatures range from above 40°C to below 0°C.
Rainfall is typically distributed between the months of May to September, which on average contribute 570 mm or 76% of the annual average of 752 mm (Figure 4‐1). The wettest year at NBG since 1984 has been 1996 when 990 mm of rain was recorded, whilst the driest year was recorded in 2010 with 406 mm of rainfall. Success of rehabilitation can be dependent on rainfall levels in the year following earthworks and seeding, with high rainfall sometimes resulting in excessive erosion.
Evaporation is most pronounced during October to April with 1,133 mm of the annual average of 1,380 mm (or 82%) occurring over this time period. For years which have a complete evaporation history, evaporation has ranged from a minimum of 1,188 mm in 2008 to a maximum of 1,652 mm in 1994. Although annual evaporation exceeds annual precipitation, on a monthly basis average precipitation exceeds average evaporation in the winter months of May to September.
Rainfall intensity and frequency duration data has been calculated for the NBG site following the methodology described in Australian Rainfall and Runoff. Storm depths calculated in this manner are summarised in Table 4‐1. Surface water management structures and RDAs are designed to manage the appropriate rainfall event.
The strongly seasonal rainfall and high evapo‐transpiration contribute to a very high fire risk. Due to its severity and frequency, fire has a major impact on the vegetation, which has the capacity to recover following fires (Worsley, 1999).
Prevailing winds are east‐south‐easterly in summer, with an average velocity of 10 to 22 km/h and west‐north‐westerly in winter with similar velocities.
International global climate models suggest that as atmospheric greenhouse gas concentrations continue to rise, Western Australia will become warmer and rainfall patterns will change. In the southwest of WA, rainfall has already decreased and modelling projects that it will continue to decrease throughout this century (DEC, 2009a). Further increases in temperature and potential
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evaporation are also anticipated. The Indian Ocean Climate Initiative research program project that for south‐west WA (DEC, 2009a): By 2030: o Rainfall will decrease by 2 to 20%; o Summer temperatures will increase by 0.5 to 2.1°C; o Winter temperatures will increase by 0.5 to 2.0°C. By 2070: o Rainfall will decrease by 5 to 60%; o Summer temperatures will increase by 1.0 to 6.5°C; o Winter temperatures will increase by 1.0 to 5.5°C.
A decrease in rainfall and associated increase in evaporation and temperature may affect the success of rehabilitation and the water level and water quality of the post closure pit lakes. Climate change may also necessitate a continuous re‐evaluation of closure objectives and completion criteria (Harris et al, 2006).
Table 4‐1 NBG design storm depths (adapted from GHD, 1992) Recurrence Interval Duration (Years) 6 minutes 1 hour 12 hours 24 hours 72 hours 1 4 mm 12 mm 31 mm ‐ 52 mm 10 10 mm 24 mm 60 mm 76 mm 104 mm 50 16 mm 33 mm 80 mm 102 mm 143 mm 100 18 mm 38 mm 89 mm 115 mm 161 mm 500 27 mm 50 mm 114 mm ‐ 211 mm 1,000 31 mm 56 mm 126 mm ‐ 236 mm 10,000 50 mm 81 mm 175 mm ‐ 334 mm PMP Winter (May) ‐ ‐ ‐ ‐ 688 PMP Winter (June) ‐ ‐ ‐ ‐ 553 PMP Winter (July) ‐ ‐ ‐ ‐ 509 PMP Winter (August) ‐ ‐ ‐ ‐ 464 PMP Winter (September) ‐ ‐ ‐ ‐ 524 PMP Summer ‐ ‐ ‐ ‐ 1,225
4.1.2 Geology NBG is located within the Saddleback Greenstone Belt, a north‐west trending, fault‐bounded sequence of Archaean age. The Saddleback Greenstone Belt comprises three major stratigraphic units. The Hotham Formation at the base of the sequence consists for metasediments including siltstones and minor tuffaceous and agglomeratic rocks. This is overlain by the Wells Formation, comprising felsic to intermediate volcanics. The Marradong Formation, forming the upper unit, comprises metabasalts. The NBG resource lies within a 6 km strike length of the Wells Formation.
Mineralisation is exploited in two discrete zones, Wandoo North and Wandoo South. The former is dominated by porphyritic diorites and occasional fragmental volcanic rocks (Figure 4‐2), the latter by a series of diorite stocks emplaced in a sequence of porphyritic volcanic rocks ranging in composition from andesites to dacites (Figure 4‐3). Mineralisation in both zones is typical of Archean shear‐zone hosted vein and stockwork systems. Gold occurs in association with minor chalcopyrite, pyrrhotite and pyrite. Molybdenite and arsenopyrite are significant accessory phases in Wandoo North.
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Wandoo North and South display several distinctions with respect to alteration. Wandoo North displays relatively intense chlorite alteration plus minor epidote and calcite. Wandoo South is virtually devoid of calcite, with actinolite and albite common.
Information on the geochemistry at NBG is included in Section 4.2.1.1.
4.1.3 Landform and Soils NBG is located on the eastern fringe of the Darling Plateau. The plateau is most strongly dissected in the western area near Boddington with highest remnants reaching 400 mRL. A series of monadnocks in the area includes Mt Wells, which lies immediately northwest of the mine. Landforms comprise relatively broad and shallow valleys with well vegetated swamps in an undulating landscape.
The central part of the Darling Plateau is dissected by a series of major rivers and their tributaries, which originate to the east in the lower rainfall, agricultural region. Flow in most of these rivers is intermittent with water quality ranging from fresh to saline. NBG is located within the catchment of Thirty‐Four Mile Brook, a tributary of the Hotham River.
Three landform‐soil units are found in the Boddington area (Churchward & Dimmock, 1989 as cited in Worsley, 1999): The Dwellingup unit occupies crests and slopes of the Darling Plateau. It is mainly convex in shape and mildly sloping (less that 3° slope), except in saddles where it is concave. Outcrops of laterite are common, especially in the upper slopes. Outcrops of fresh rocks (granites and dolerites) are infrequent and small in extent. The dominant soils are yellowy brown sandy gravels, generally of shallow depth over the lateritc duricrust. They tend to be coarser on the convex slopes and finer in the saddles; The Cooke unit mainly occurs on prominent summits (monadnocks) rising above the general level of the plateau. They are mainly domes of granite which is exposed on crests and steeply sloping flanks. The soils are a mix of light brown gritty sandy loams (lithosols), lateritic sandy gravels and duricrusts. Within the project area it occurs as localised pockets on mid and upper slopes between the Dwellingup and Pindalup units. The nearest major occurrence is Mt Wells to the northwest of the mine site; and The Pindalup unit includes the broad shallow valleys associated with Thirty‐Four Mile Brook and its tributaries. Gravely duplex soils occur on the slopes, with some rock outcropping. The broad valley floors include grey sands, duplex yellow soils and orange earths. Extensive seasonally inundated swamps are located in these broad valley systems. The soils in the swamps tend to be finer in particle size.
More detailed information on the native soil profile and soil materials available for rehabilitation is included in the following sections.
4.1.3.1 Native Soil Profile NBG is located upon a regolith profile typical of the Darling Plateau that has been weathered in situ to a depth of up to 70 m at some locations. Although dependent on topography and landscape position, regolith profiles generally reflect a fairly consistent pedological structure with strong horizonation of: Topsoil nominally 0.1 m thick; Gravel ranging from approximately 0.5 to 8 m in thickness overlying a lateritic caprock that varies in thickness (typically 1 to 5 m); and
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A clay zone, commonly referred to as oxide, averaging around 40 m in thickness, but can reach up to 70 m.
The transition from the oxide material to the underlying variably weathered basement rocks is typically abrupt at NBG.
The following sections provide a summary of the general physical and chemical properties of the: Topsoils and gravel subsoils; and Oxide clays.
4.1.3.1.1 Topsoils and Gravel Subsoils Surface soils of the Darling Plateau are mostly sandy, gravely, often duplex and of lateritic origin. These soils are typically acidic, with approximately 5% organic carbon and low salinity (Table 4‐t2), bu are also low in nutrients (OES, 2010).
Soils located on natural slopes have a coarser texture than those found in valley floors. The dominant physical characteristic is their very high gravel content (up to 90%), which can substantially reduce water holding capacity. These soils are likely to have high hydraulic conductivity typical of Darling Range soils, allowing rainfall to infiltrate quickly.
Topsoils are sometimes moderately dispersive and can display an increase in dispersive behaviour over time, suggesting susceptibility to increased soil structure degradation under saturated or waterlogged conditions (OES, 2007a).
Potential hard setting as a result of soil slaking and dispersion in not likely to be a limiting factor for the soil materials, with Modulus of Rupture values not high enough to limit plant or root growth. In their natural state, the soils can be water‐repellent, which can reduce infiltration and increase runoff and therefore increase the risk of erosion.
Surface soils in the mineralised area reflect the geological anomaly of the greenstone belt. Soil samples taken before the commencement of mining activity demonstrated enriched concentrations of arsenic, copper and zinc.
4.1.3.1.2 Oxide Clays The oxide clay materials comprise red brown to yellow clays, including kaolinitic, ferruginous and limonitic zones. They have low salinity and similar acidity to the surface soils (Table 4‐2). However, unlike the surface soils, little or no gravel is found in these materials.
The water‐storage capacity of jarrah forest soils below the lateritic caprock is high, with this large storage capacity capable of providing water throughout long, dry summers.
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Table 4‐2 Chemical and physical properties of topsoil, subsoil and regolith oxide clay at NBG (from OES, 2010) Soil Landscape pH (1:5 Electrical Organic Carbon Soil Texture Gravel Slaking and Dispersion Potential for Position H2O) Conductivity (Soil Fraction) Content Hard‐Setting Topsoil Slopes 5.4 – 6.5 Non‐saline 4 – 7% Loamy sands – 64 – 76% Range from “Slakes but Very low sandy clay loams does not disperse, unless remoulded” (3a) to “Does not slake nor disperse” (8) Lower slopes 4.6 – 5.8 Non to very 4 – 7% Sandy loams 18 ‐77% ‐ Very low and valley floors slightly saline Subsoil Slopes 6.3 ‐ 7 Non‐saline ‐ Sandy clay loams – 65 – 89% Slakes and partly Low coarse loamy clays disperse after remoulding (3b) In situ ‐ 6.2 Non‐saline ‐ Silty loam Nil ‐ ‐ oxide clay
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4.1.3.2 Rehabilitation Materials During operations oxide, gravel and topsoil have been stockpiled for use during rehabilitation. The expected performance of these materials in rehabilitation based on their physical and chemical properties was assessed by Outback Ecology Services (2011a) and is summarised below.
The topsoil and gravel materials are likely to be relatively resistant to erosion because their high gravel content provides protection from rain splash and surface flow (Table 4‐3). Additionally, the fine fraction of the topsoils and gravels has a relatively high hydraulic conductivity, allowing rainfall to infiltrate. However, the very low hydraulic conductivity of the oxide creates the likelihood that this material will not be able to accept infiltration at a sufficient rate during substantial rainfall events, resulting in saturation of any overlying gravel and topsoil layers. Once saturated, surface runoff could be expected, creating the risk of rilling and gullying of the surface materials.
The oxide materials are, on average, sodic and slightly saline and range from slightly to non‐ dispersive (Table 4‐3). The level of salinity may reduce with leaching over time, and this may in turn allow increased dispersion, leading to greater risk of tunnelling and erosion. As a counter to this, root development through the oxide profile will contribute to enhanced stability.
Some of the topsoils exhibit dispersion upon re‐moulding, indicating a potential to become dispersive and problematic following severe disturbance. Therefore, care needs to be taken to minimise the handling of these soil materials where possible, particularly when wet, to avoid structural degradation which may impact upon the behaviour of these materials when used for rehabilitation (OES, 2010).
There was a wide range of water retention characteristics, with the amount of gravel present being the most influential factor affecting the ability of the material to store and release water. Oxide materials had the highest water holding capacity, with a plant‐available water capacity ranging from 60 to 230 mm/m depth.
Half of the oxide materials sampled had the potential to hard‐set to an extent that may constrict root growth of some plants. However, the bulk densities for the oxide materials when placed in rehabilitated profiles are expected to be lower than when in situ, favouring root growth.
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Table 4‐3 Summary of average physical and chemical properties of rehabilitation materials and topsoil at NBG Parameter Topsoil Gravel Subsoils Laterite Oxide Clays Soil Texture Loamy sand to Clayey sand to Sandy clay loam Sandy clay sandy clay loam sandy clay loam to clay loam loam to clay loam Coarse Material Content 72 77 99 26 (0 to 81) (% >2mm) Emerson Class1 2 to 5 2 to 5 ‐ 1 to6 Modulus of Rupture 8 8 ‐ 76 (9 to 223) (kPa) Hydraulic Conductivity 660 663 ‐ 15 (mm/h) Plant‐Available Water 10.2 4.6 ‐ 17.4 Holding Capacity (%) pH (H20) 6.4 6.6 6.6 5.9 Salinity (dS/m) 0.04 0.04 0.08 1.52 Organic Carbon (%) 2.19 1.05 0.07 0.05 Exchangeable Sodium ‐ ‐ ‐ 11.1 Percentage (%)
4.1.3.2.1 Rehabilitation Materials Inventory and Reconciliation A site wide inventory of rehabilitation materials has been developed for the: Mining area which covers the waste rock landforms, processing plant, all other disturbance associated with mining and processing (including roads) and the unrehabilitated satellite open pits; and RDA area whiche covers th RDAs, Wattle Pit, D1 WSR and associated disturbance (including roads, services and stockpile areas).
The rehabilitation materials inventory includes: Stockpiled material – the volume of material which has been harvested or mined and appropriately stockpiled for use in future rehabilitation activities; and Total available material – the volume of material currently stockpiled plus the estimated volume of gravel subsoil and topsoil to be harvested from future disturbance areas.
1 Emerson Aggregate test classes Class 1 – Dry aggregate slakes and completely disperses Class 2 – Dry aggregate slakes and partly disperses Class 3a – Dry aggregate slakes but does not disperse; remoulded soil disperses completely Class 3b – Dry aggregate slakes but does not disperse; remoulded soil partly disperses Class 4 – Dry aggregate slakes but does not disperse; remoulded soil does not disperse; carbonates and gypsum are present Class 5 – Dry aggregate slakes but does not disperse; remoulded soil does not disperse; carbonates and gypsum are absent; 1:5 suspension remains dispersed Class 6 – Dry aggregate slakes but does not disperse; remoulded soil does not disperse; carbonates and gypsum are absent; 1:5 suspension remains flocculated Class 7 – Dry aggregate does not slake; aggregate swells Class 8 – Dry aggregate does not slake; aggregate does not swell
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Table 4‐4 summarises the volume of oxide, gravel subsoil and topsoil that was stockpiled as of November 2012 and the volume of material calculated to be available for LOM. The volume of gravel subsoil and topsoil that can be harvested from future disturbance areas was calculated based on planned disturbance footprints and known information on the depth of topsoil and subsoil gravel in natural soil profiles within the Boddington area. The likely depth of topsoil and subsoil gravel horizons is known to be dependent on topography and position within the landscape, varying between shallower soils over lateritc duricrust along the crests of ridges to deep sandy colluvial soils in drainage lines and valley floors. Detailed information on the calculation of the volume of topsoil and subsoil gravel to be harvested is included in Appendix 4. The planned assessment of the soil resources within the future disturbance footprints will allow the estimated volumes of topsoil and subsoil gravel within these areas to be further refined.
Table 4‐4 Rehabilitation materials inventory Material Volume (m3) Stockpiled Total Available (LOM) Mining Area Oxide 13,500,000 ‐ Gravel subsoil 3,587,745 6,238,563 Topsoil 1,075,460 2,330,957 RDA Area Gravel subsoil 1,705,785 9,089,997 Topsoil 2,213,057 5,504,970
The reconciliation of the rehabilitation materials for the mining area is summarised in: Table 4‐5 for the current disturbance area; and Table 4‐6 for the LOM disturbance area.
The reconciliation of rehabilitation materials for the RDA area is summarised in: Table 4‐7 for the current disturbance area; and Table 4‐8 for the LOM disturbance area.
For the mining area, reconciliation of the volume of material required for rehabilitation of the current disturbance area against the currently stockpiled rehabilitation materials volumes indicates that while there is enough topsoil and gravel stockpiled there is a shortfall of approximately 2,500,000 m3 of oxide. The additional oxide material could be obtained from the open pits if required in the situation of unplanned closure.
For LOM, reconciliation of the volume of material required for rehabilitation of the planned disturbance areas against the calculated volumes of material available indicates that there will be sufficient volumes of topsoil and gravel subsoil. An additional 16,000,000 m3 of oxide needs to be stockpiled to meet the rehabilitation requirements for the life of mine disturbance areas. This represents 11% of the volume of oxide still to be mined from the Wandoo North and Wandoo South open pits.
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Table 4‐5 Reconciliation of rehabilitation materials for mining area for current disturbance Rehabilitation Rehabilitation Rehabilitation Area Volume of Material Material Thickness (m) (ha) Rehabilitation Material Required (m3) Volume Required Oxide 2.5 640.32 16,008,750 Gravel Subsoil 0.3 690.83 2,072,550 Topsoil 0.1 860.3 860,390 Volume Stockpiled Oxide ‐ ‐ 13,500,000 Gravel Subsoil ‐ ‐ 3,587,745 Topsoil ‐ ‐ 1,075,460 Reconciliation Oxide ‐ ‐ ‐2,508,750 Gravel Subsoil ‐ ‐ 1,515,195 Topsoil ‐ ‐ 215,070
Table 4‐6 Reconciliation of rehabilitation materials for mining area for LOM Rehabilitation Rehabilitation Rehabilitation Area Volume of Material Material Thickness (m) (ha) Rehabilitation Material Required (m3) Volume Required Oxide 2.5 1,180.9 29,522,500 Gravel Subsoil 0.3 1,295.1 3,885,300 Topsoil 0.1 1,464.6 1,464,600 Volume Available Oxide ‐ ‐ 13,500,000 Gravel Subsoil ‐ ‐ 6,283,563 Topsoil ‐ ‐ 2,330,957 Reconciliation Oxide ‐ ‐ ‐16,022,500 Gravel Subsoil ‐ ‐ 2,398,263 Topsoil ‐ ‐ 866,317
For the RDA area, reconciliation of the volume of material required for rehabilitation of the current disturbance area against the currently stockpiled rehabilitation materials volumes indicates that there is a deficit in gravel subsoil of approximately 2,900,000 m3. In the situation of unplanned closure, some of the deficit in gravel subsoil material may be able to be addressed by use of excess material stockpiled for the mining area (Table 4‐5). Alternatively, a borrow pit may be developed as a source of gravel subsoil closer to the RDA area.
For LOM, reconciliation of the volume of material required for rehabilitation of the planned disturbance areas against the calculated volumes of material available indicates that there is a potential shortfall in gravel subsoil of 444,000 m3 for the RDA area. It is possible that additional
2 Oxide not required for rehabilitation of the processing plant and other disturbance areas and satellite open pits. 3 Gravel not required for rehabilitation of the processing plant and other disturbance areas.
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gravel subsoil resources will be available from future disturbance areas to cover the predicted shortage. It may also be possible to substitute some of the gravel subsoil material required with the excess of topsoil material that is likely to be available.
Table 4‐7 Reconciliation of rehabilitation materials for the rRDA area fo current disturbance Rehabilitation Rehabilitation Rehabilitation Area Volume of Material Material Thickness (m) (ha) Rehabilitation Material Required (m3) Volume Required Gravel Subsoil 0.3 1,756,000 4,584,000 Topsoil 0.1 1,756,000 1,756,000 Volume Stockpiled Gravel Subsoil ‐ ‐ 1,705,785 Topsoil ‐ ‐ 2,213,057 Reconciliation Gravel Subsoil ‐ ‐ ‐2,878,215 Topsoil ‐ ‐ 457,057
Table 4‐8 Reconciliation of rehabilitation materials for the RDA area for LOM Rehabilitation Rehabilitation Rehabilitation Area Volume of Material Material Thickness (m) (ha) Rehabilitation Material Required (m3) Volume Required Gravel Subsoil 0.3 3,406 9,534,000 Topsoil 0.1 3,406 3,406,000 Volume Available Gravel Subsoil ‐ ‐ 9,089,997 Topsoil ‐ ‐ 5,504,970 Reconciliation Gravel Subsoil ‐ ‐ ‐444,003 Topsoil ‐ ‐ 2,098,970
The volume of materials stockpiled and required for rehabilitation will vary over the life of the mine as a result of: Use of stockpiled material for rehabilitation; Harvesting of material from future disturbance areas; and Changes to: o Disturbance areas; o Landform designs; and o Rehabilitation prescriptions based on outcomes of trials.
The volume of stockpiled materials is re‐surveyed and updated on an annual basis to incorporate use of materials for rehabilitation and stockpiling of materials from areas disturbed in the previous twelve months. The volume of rehabilitation materials required will be updated as necessary based on changes to the life of mine plan or rehabilitation prescriptions.
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4.1.3.3 Post‐Closure Impacts on Landforms and Soils The potential post‐closure impacts on landforms and soils in the area include: Alteration of landforms through construction of waste rock landforms and RDAs and mining of pits; and Alteration of soil profile and structure in disturbance areas.
Alteration of landforms is being minimised to the extent possible through the incorporation of visual impact in options analysis for the design and placement of the waste rock landforms. The main methods utilised to ensure the landforms fit in with the surrounding topography is to keep them below the maximum height of the surrounding topography and to rehabilitate them with native species so post‐rehabilitation the colour, line and texture of the disturbed areas matches that of the surrounding vegetation.
Alteration of the soil profile in disturbance areas will be amended during the rehabilitation process by reconstruction of a soil profile suitable for the development of the target ecosystem through application of oxide (where required), gravel and topsoil. Rehabilitation areas will also be ripped to a sufficient depth to remove compaction.
4.1.4 Surface Water 4.1.4.1 Surface Water Flow NBG is located within the catchment of Thirty‐Four Mile Brook, a seasonal tributary of the Hotham River (Figure 4‐4). The Thirty‐Four Mile Brook catchment has an areal extent of around 78 km2 and includes some minor tributaries and creeks in the northern part of the catchment and Wattle Hollow Brook towards the southern end of the catchment (Figure 4‐5). Characteristic undisturbed stream morphology of the Thirty‐Four Mile Brook alternates between shallow, narrow riffles over lateritic gravel or cemented lateritic slabs top dee slow‐moving pools.
The site of the future RDA lies within the Gringer Creek catchment, which covers an area of 174.5 km2 (Figure 4‐5).
The topography around NBG is generally smooth, with elevations in the range 200 to 400mRL, and with prominent ridges and troughs present which run northwest to north‐northwest. Undisturbed surface flow within the mining lease is generally from the north and northeast towards the south and southeast.
The project area also contains several small swamps which are shallow depressions which fill in winter and overflow to nearby streams. Overflow from both Eight and Round Swamps reports to Wattle Hollow Brook while water from Pillow and Boomerang Swamps reports to Thirty‐Four Mile Brook. The swamps are dependent on the seasonal shallow groundwater system which does not exhibit responses to mining (Section 4.1.5.1).
Catchment boundaries which occur close to NBG facilities include: The eastern margin of the RDA areas where Boggy Brook and House Brook drainages form a separate tributary to the Hotham River; and Then norther boundary of the RDA areas which marks the limit of the South Dandalup catchment which is used for metropolitan water supply.
The flows in the Hotham River and its tributaries, including Thirty‐Four Mile Brook and Gringer Creek, are seasonal with considerable variation from year to year. In general, the highest stream flow rates are observed in the winter months reducing to negligible flows in summer‐autumn. Low summer
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rates of streamflow are associated with elevated water temperatures, low dissolved oxygen levels, higher total dissolved solids (TDS) and, in many cases, low pH (Worsley, 1999). The approximately 20% decrease in rainfall experienced in the southwest over the last 30 to 40 years has resulted in a 30‐40% decrease in total annual streamflow (WRC, 2000)
The Thirty‐Four Mile Brook catchment has low natural streamflow yield. For the eastern Darling Range low‐rainfall zone, figures of 2‐5% are generally used to predict streamflow, but the relationship is non‐linear with virtually no streamflow recorded in years of below average rainfall (John Consulting Services, 1992). Flow within the Thirty‐Four Mile Brook is ephemeral, generally occurring between July and September. At NBG several impoundments have been constructed along Thirty‐Four Mile Brook, which have also been used to store water pumped from the Hotham River and mine dewatering discharge. As a consequence of damming, hydrology of the ephemeral brook is disrupted, with the only catchment flows occurring between (Figure 4‐6): D1 water storage reservoir and Thirty‐Four Mile Brook Diversion Pond; and Forest to the west of the catchment between Thirty‐Four Mile Brook Diversion Pond and D4 water storage reservoir.
The future RDA has been designed not to extend sufficiently into the catchment to cause ponding of water. However, the downstream embankment arrangement will alter the Gringer Creek stream course. Therefore, it is proposed to divert the river bed into a new channel over a length of 2.4 km to allow the catchment to drain freely back to the Gringer Creek system.
Runoff rates from the landforms at NBG were investigated to identify the relationship between rainfall intensity and duration, and rates of runoff (Table 4‐9). These studies were designed to refine rehabilitation designs and estimate the influence of facility runoff on the final pit void and other closed facilities.
Table 4‐9 Calculated runoff coefficients for rehabilitated slopes at NBG Surface Treatment Runoff Coefficient Mean Maximum Hourly Daily Hourly Daily Rock armour 33% 31% 56% 48% Rock armour under soil 54% 43% 85% 79% Winged rip 47% 43% 63% 60% Conventional rip 32% 30% 48% 50% Smooth surface 39% 37% 60% 60%
4.1.4.2 Surface Water Chemistry Over the length of Thirty‐Four Mile Brook, water quality is variable from year to year and with location in the drainage. For the portion of Thirty‐Four Mile Brook within the mine lease, baseline sampling identified TDS concentrations in the range 100 to 5,000 mg/L. Sampling during the mining period has identified TDS concentrations in a similar range to the baseline values, with small tributaries in vegetated areas recording TDS concentrations as low as 100 mg/L, and the main branch of Thirty‐Four Mile Brook typically 2,000 to 3,000 mg/L both upstream and downstream of nthe ope pits. In the lower reaches of Thirty‐Four Mile Brook, downgradient of the mine leases, TDS concentrations in the range 5,000 to 10,000 mg/L have been measured in areas affected by land clearance for agriculture. Metals which have been regularly analysed in samples from Thirty‐Four
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Mile Brook (cadmium, arsenic, lead, molybdenum and selenium) have typically been low both up‐ gradient and down‐gradient of the mining activities.
Water quality at Gringer Creek is characterised by very hard waters (750 – 1,900 mg/L of CaCO3), high salinity (5,420 – 1,180 µS/cm EC) and high dissolved oxygen levels (80 – 101%) (SWS, 2012). pH ranges from slightly acidic to neutral with levels of 4.7 to 7.1. Baseline conditions for surface water flows in Gringer Creek may contain elevated concentrations of cobalt, zinc and iron (SWS, 2012).
The adjacent House and Boggy Brook catchments appear to be unaffected by the mining operations, with TDS values in samples collected close to the mining area in the 100 to 1,000 mg/L range which is below baseline values (SWS, 2010).
Extensive land clearing for agriculture over the last 100 years has likely led to secondary salinisation and degradation of the Hotham ,River (WRM 2011). Pre‐mining TDS concentrations in the river and adjacent tributaries ranged from 1,000 to 10,000 mg/L over summer and winter months. The brackish water quality in the river may result from a number of factors, including evapoconcentration of pools in the summer months, runoff of nutrients from farmland, and discharge of naturally saline groundwater in zones where water tables have risen as a result of vegetation clearing.
4.1.4.3 Ecological Values and Beneficial Uses The ecological values of the Hotham River and Thirty‐Four Mile Brook have been determined by Streamtec (1990, 1997), Mattiske (2010) and WRM (2010) via vegetation monitoring (Section 4.1.6.1.1) and targeted biological sampling (Section 4.1.6.2.3).
The water quality of the Hotham River is generally considered saline and degraded. Therefore, local farmers tend to rely on surface water runoff into paddock dams for water supply, rather than depend upon the erratic flows and water quality in the Hotham River. Community consultation undertaken by the Boddington River Action Group (BRAG) found that fishing and recreation, the health of the aquatic flora and fauna and the aesthetics of the river were all highly regarded as community values (McLure, 2004).
4.1.4.4 Post‐Closure Impacts on Surface Water The potential post‐closure impacts on the surface water in the area include: Changes to water quality (including sedimentation) caused by runoff from RDAs, waste rock landforms and other disturbed areas; Interruption of surface hydrology by damming and diversion of natural drainage lines which can cause: o Reduction in vegetation health by water logging; o Reduction in vegetation health by reduction in water supply; and o Reduced water supply to soaks, dams and downstream water courses. Changes to long‐term flow patterns and water quality due to overflow of water from pit lakes.
Residue stored within the RDAs will contain a store of salt due to the higher TDS concentration of processing water obtained from the Hotham River compared to groundwater and surface water in the Thirty‐Four Mile Brook and Gringer Creek catchments. If required, the runoff will be treated and discharged directly to the open pits until an acceptable TDS concentration is reached after rehabilitation.
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Runoff from some sections of the waste rock landforms will be released directly to the environment via engineered drainage structures. In the early phases of closure, active management of water control structures will be required. As run‐off coefficients and sediment loads reduce with maturing vegetation cover, sediment ponds and other drainage structures that become redundant will be progressively removed to ultimately result in a passive system where water drains into the open pits or into Thirty‐Four Mile Brook.
Surface water flow in Thirty‐Four Mile Brook has been interrupted by the construction of diversions and dams along its length in the mining area. Flow will be reduced in Thirty‐Four Mile Brook downstream of the operations until the pit lakes fill, which is predicted to be between 40 and 110 years after closure. Some flow will continue to occur in Thirty‐Four Mile Brook from runoff from rehabilitated landforms and sections of the catchment that aren’t diverted into the pit lakes. Changes in the amount of available water may result in changes to the composition of riparian vegetation communities and affect the fauna that use this habitat.
Once dewatering of the mining area ceases pit lakes will develop through inflow of groundwater, runoff from the surrounding waste rock landforms and diversion of the Thirty‐Four Mile Brook. The elevation at which the pit lake will stabilise is set by the elevation of the overflow channel into Wattle Hollow Brook (235mRL). The hydrochemistry of the pit lakes will be a function of: The volume and chemistry of inputs to the pit lakes in the active closure period; The volume and chemistry of seepage and runoff permanently routed to the lakes; Interactions with the materials exposed in the pit slopes; The rate of evapoconcentration at the lake; Thed volume an chemistry of flow from Thirty‐Four Mile Brook; and Chemical reactions and physical stratification occurring within the lake.
Pit water quality is predicted to be slightly alkaline (pH of 7.5) with moderately high salinity (890 mg/L total dissolved solids), consisting mostly of sodium and chloride with trace metals/metalloids at or below analytical detection. Once steady‐state inflow/outflow conditions are established, the saline and constituent concentrations in the pit lake are expected to slowly increase slightly over time due to evapoconcentration in the lake as a result of the large evaporative lake surface. More detailed information of the predicted pit lake hydrochemistry is included in Section 4.2.3.1.
4.1.5 Groundwater 4.1.5.1 Groundwater Systems Groundwater investigations indicate that there are three units which transmit significant quantities of groundwater and occur commonly across the Thirty‐Four Mile Brook catchment: A seasonal shallow groundwater system; A weathered and fractured upper bedrock groundwater system; and A deep fractured bedrock groundwater system.
4.1.5.1.1 Seasonal Shallow Groundwater System The seasonal shallow groundwater system stores and transmits water within the gravel horizon described in Section 4.1.3.1. Infiltration from significant precipitation events potentially saturates this zone and becomes perched above the underlying oxide clays. The pisolitic horizon, which is indicated to be highly permeable, allows water to circulate downslope and using relict vertical passages (e.g. tree roots) it may also potentially percolate downwards. Relict dykes which persist through the oxide clay zone may act either as barriers to horizontal flow in the shallow seasonal groundwater system, or as vertical conduits for infiltration into the deeper system. Groundwater moving through the
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lateritic gravel material predominantly discharges into alluvial sediments along creek channels, as evidenced by the deposition of iron oxides, and is permanently removed via evapotranspiration in vegetated areas.
The seasonal shallow groundwater systems supports swamp areas which are generally sited in topographically low areas and result from the downslope migration of rainfall infiltrating into the shallow gravel horizon. The infiltrated water tends to discharge at topographic lows and has been interpreted to become perched above the oxide clay layer. These swamps areas are therefore not expected to be directly connected to the weathered and fractured upper bedrock groundwater system.
The oxide clay zone which occurs below the gravels hosting the shallow seasonal groundwater system and above the bedrock may potentially provide significant storage of groundwater where it is saturated, but due to the low hydraulic conductivity of this unit it does not act as a major groundwater transmitting system. The active processes in the oxide clay zone are interpreted to be gradual recharge by infiltration from the overlying units and gradual discharge due to under‐drainage by the underlying units.
4.1.5.1.2 Weathered and Fractured Upper Bedrock Groundwater System The weathered and fractured upper bedrock groundwater system is the primary permanently saturated and regionally extensive groundwater unit at the NBG site. Although on a regional basis it is inferred to act and respond as a relatively continuous and connected hydraulic system, on a localised basis the groundwater transmitting properties are highly variable. The primary storage and transmission of groundwater has been inferred to eoccur in th saprolite zone at the upper bedrock surface. In undisturbed conditions the weathered and fractured upper bedrock system is expected to be confined by the overlying oxide unit, except in locations of elevated topography where the unit may approach the surface.
Groundwater elevations in this unit are strongly influenced by seasonal precipitation trends and by long term precipitation trends.
4.1.5.1.3 Deep Fractured Bedrock Groundwater System Discrete isolated broken or fracture zones with potential to transmit groundwater have been identified at depth within the largely competent and intact basement rocks at NBG. In general, hydraulic conductivity along strike have been reported to be 10 to 70 times higher than across strike and it has been suggested that dolerite dykes aligned along strike may retard cross‐strike groundwater flow. Within the granites and gneiss outside of the margins of the Saddleback greenstone belt, fracturing is expected to be very low, which ist consisten with the results of the groundwater investigation programmes conducted within the Yilgarn Craton in the general region. As a result, the main bedrock groundwater system at NBG has generally been interpreted as having limited extend in the northeast southwest direction, extending from around 1 km southwest of the North and South pits to around 4 km northeast of the pits.
4.1.5.1.4 Influence of Mining Key changes to groundwater elevations from pre‐mining levels due to the mining operations are (Figure 4‐7 and Figure 4‐8): Drawdown in the main mining area as a result of dewatering of the open pits; and Mounding in the area of the RDAs as a result of seepage.
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The current dewatering of the open pits draws water from the deep fractured bedrock system. Dewatering of this unit is expected to induce vertical drainage from the weathered and fractured upper bedrock systems near the pits. This is the groundwater system which has the greatest regional extent and the greatest potential to interact with groundwater receptors. Dewatering influences will be observed at groundwater receptors in the NBG region only if: Mining related drawdown in the weathered and fractured upper bedrock system extends as far as the location of the groundwater receptor; and The groundwater receptor is in direct or indirect hydraulic contact with the weathered and fractured upper bedrock groundwater system.
Drilling at Round Swamp, Pillow Swamp and Boomerang Swamp confirms that they are underlain by clayey oxide material ranging from 20 m to 38 m in depth which separates the shallow surface water system from the weathered and fractured upper bedrock groundwater system. There is no direct hydraulic connection between the shallow seasonal groundwater system which supports the swamps at NBG and the dewatering operations, and no mining influence is evident in groundwater elevations in the shallow seasonal groundwater system.
Monitoring of the weathered and fractured groundwater system indicates: that The magnitude of drawdown in this groundwater system is relatively small compared to the drawdown measured in the deep bedrock close to the pits; Regional drawdown appears to extend preferentially to the northwest and southeast, along the direction of geological strike, but is currently limited to an area within around 2 km of the open pits; The position of the southwest margin of the drawdown cone is not well defined as it is currently within the area of disturbance planned for the waste rock landforms where no monitoring bores are located; and Data collected from bores located adjacent to the Hotham River, and in the area between the mine and Hotham River, confirm that the drawdown cone is at least 4 km from the river at the current time.
Future expansion of mining related drawdown in the weathered and fractured upper bedrock groundwater system will be a function of: The rate of groundwater abstraction from the deep bedrock system as the open pits are expanded and deepened; The orientation and location of the discrete zones of fracturing within the deep bedrock which are intersected by the pits and the dewatering bores, and the regional extent and location of these fracture zones; and The degree of vertical hydraulic connection between the weathered and fractured bedrock groundwater system which blankets the area and the underlying deep bedrock system.
The deep bedrock groundwater system has been strongly influenced by mining in the area of the pit slopes. Drawdown within this unit close to the open pit slopes is well defined from a large number of monitoring points and is in the range 35 to 125 m.
Prediction of regional groundwater drawdown in the groundwater system has been highly sensitive to the values of hydraulic conductivity and storage assigned in the model. A conservative approach to modelling, which assumes that all drawdown observed in monitoring bores is attributed to mine dewatering, indicates the cone of drawdown could potentially approach the Hotham River within ten to twelve years.
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The interaction between surface water streams and groundwater systems in the Boddington area are not well defined. The streams in the upper parts of the catchments, including Thirty‐Four Mile Brook, tend to be ephemeral, suggesting that if groundwater discharge to the streams does occur, it is not sufficient to maintain flows through the summer period. Where Thirty‐Four Mile Brook does interact with groundwater, it has been generally interpreted to relate to the shallow seasonal groundwater occurring in the surface gravels.
In the lower catchment areas and along the Hotham River in particular, groundwater discharges to the rivers could potentially occur, and could contribute to base flows observed in the summer months, or recharge from the river into the groundwater system could potentially occur. Field mapping of the Hotham River close to the mine area did not identify any exposures of basement rocks in the streambed which could provide direct hydraulic connection to the groundwater system, but the existence of such a connection could not be definitively ruled out based on the field mapping.
4.1.5.2 Groundwater Chemistry Pre‐mining groundwater quality ranged from 1,000 mg/L to 4,000 mg/L TDS over the mine lease and within the Thirty‐Four Mile Brook catchment. The groundwater is primarily a sodium chloride type with relatively low proportions of sulphate and generally low concentrations of metals (Table 4‐10). The groundwater pH is generally in the range of 5.5 to 8.0.
Table 4‐10 Groundwater chemistry at NBG Analyte Concentration Arsenic Most samples <0.08mg/L, maximum value of 0.16mg/L Cadmium Most samples <0.05mg/L, maximum value of 0.08mg/L Copper Most samples <0.2mg/L, maximum value 0.2mg/L Iron Most samples <10mg/L Molybdenum Most samples <0.1mg/L, maximum value 0.5mg/L Nickel Most samples <0.1mg/L, maximum value 1mg/L Sulphate Most samples <200mg/L, maximum value of 500mg/L Zinc Most samples <0.1mg/L, maximum value of 10mg/L
Salinity has increased up to 10,000 mg/L around the RDAs due to seepage of higher TDS process water obtained from the Hotham River (Figure 4‐9) (NBG, 2012). Localised salinity increases of up to 7,000 mg/L from the pre‐mining baseline levels occur on the south eastern corner of R4A RD (Figure 4‐10).
Salinities have also increased by 1,000 to 2,500 mg/L TDS in the mine area compared to pre‐mining conditions (Figure 4‐10). This could be due to transfer and storage of higher TDS water from the Hotham River around the site. Previously salinity had decreased in the mine area compared to pre‐ mining conditions, which was attributed to removal of saline groundwater by mining and dewatering activities and its subsequent replacement with fresh recharge.
Salinity impacts due to mining activities generally do not appear to extend beyond the Thirty‐Four Mile Brook catchment boundary, with the exception of the salinity increases recorded at the eastern embankment of the R4 RDA located on the boundary of Boggy Brook catchment.
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4.1.5.3 Post‐Closure Impacts on Groundwater The potential post‐closure impacts on the groundwater in the area include: Fluctuation (increase or decrease) in groundwater levels caused by: o Mine dewatering and subsequent recovering of water levels after the completion of mining; o Seepage and seepage recovery from waste rock landforms and RDAs; and o Evaporation from pit lakes. Changes in groundwater quality resulting from: o Seepage from waste rock landforms, RDAs and pit lakes; o Contamination from spills and historic mining activities; and o Exposure of mineralised zones in open pit and underground mines resulting in acid and/or metalliferous drainage.
The zone of groundwater drawdown that will develop due to mine dewatering during operations will recover over the post‐closure period when mine dewatering ceases. A new equilibrium groundwater level will be reached upon completion of filling of the pit lakes.
The water balance model indicates that the pit lakes will act as a groundwater source after filling. The pit water quality is predicted to be slightly alkaline (pH of 7.5) with moderately high salinity (890 mg/L total dissolved solids) with trace metals/metalloids at or below analytical detection.
The RDAs have been lined with a combination of HDPE and clay to minimise seepage. A seepage recovery network is also in place which will continue to be operated during the post‐closure period if required to manage groundwater levels and quality. Groundwater mounding is expected to be restricted to the immediate facility area by the inherent low permeability of the groundwater system, resulting in minimal influence on the groundwater system down‐gradient (SWS, 2012).
After deposition of residue ceases the groundwater mound present beneath the RDAs will gradually subside. Application of a cover on the residue will also reduce infiltration into the residue material to reduce seepage.
The waste rock landforms haven been designed with a layer of compacted clay to reduce seepage. Placement of a cover over the landforms and growth of vegetation will significantly reduce infiltration and resulting seepage in the long term. Modelling of conceptual clover designs by Golder Associates indicates that placement of a cover will reduce seepage to approximately 2% of rainfall.
4.1.6 Biodiversity NBG lies within the Northern Jarrah Forest biogeographic subregion, a duricrusted plateau characterised by Jarrah‐Marri forest on laterite gravels, and in the eastern part, by woodlands of Wandoo‐Marri on clayey soils (Williams and Mitchell, 2001). The region is a centre of endemism for plants (e.g. Eucalyptus marginata), has a locally patchy biota despite the geological and geomorphic uniformity of the lateritic plateau, provides refugia for many threatened species of flora and fauna and has moderate species richness (400‐600 species per km). Remnant populations of several critical weight range4 mammals are now centred in this region.
The Northern Jarrah Forest subregion contains 60 nature reserves, 8 National Parks and 9 Conservation Parks (Williams and Mitchell, 2001).
4 Critical weight range is used to refer to mammals approximately 35 g to 5.5 kg mean adult body weight that have experienced modern decline (Williams and Mitchell, 2001).
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4.1.6.1 Flora and Vegetation NBG is located within the Darling Botanical District of the South‐western Botanical Province (Mattiske Consulting, 2005). Five vegetation complexes occur in the NBG lease areas (Figure 4‐11). An additional two vegetation complexes occur in the land swap area located to the north of the operations. The majority of these vegetation complexes are well represented in the conservation estate (Table 4‐11). The vegetation complexes that are lower than 10% representation in formal and informal reserves reflect the extent of past agricultural clearing in the valley systems near Boddington.
Table 4‐11 Representation of NBG vegetation complexes in conservation estate Vegetation Complex5 Percentage of Pre‐European Representation in Formal and Informal Reserves6 Cooke (Ce) 34.85 Dwellingup (D4) 26.14 Pindalup (Pn) 35.10 Michibin (Mi) 7.10 Yalanbee (Y6) 22.91 Swamp (S) 47.50 Williams (W) 0.45
A total of 21 site‐vegetation types have been mapped for the NBG area (Figure 4‐12). These site‐ vegetation types provide a more local and definitive reflection of local vegetation patterns. The site‐ vegetation types can be grouped as follows: Swamps and valley floors – A and AY; Lower slopes supporting Wandoo Woodlands – Y; Mid and upper slopes supporting Jarrah Forests and Woodlands – M; Lower slopes supporting Jarrah Forests and Woodlands – B, E, J, D, W and Z; Mid and upper slopes supporting Jarrah‐Sheoak Forests – P and SP; Valley slopes supporting Jarrah‐Sheoak Forests with moister soils – SW; Mid and upper slopes supporting Jarrah Forests on sandier soils and less undulating slopes and uplands – H; Mid and upper slopes supporting Jarrah Forests on gravelly soils on upper slopes – S; and Shallow soils supporting a mosaic of Lithic Complexes, Heath and Woodlands on areas on and near granite outcrops – G, R, YG, MG, DG and HG.
The occurrence of natural vegetation complexes in the NBG area and surrounding landscape is strongly correlated with the depth of regolith. While many other factors are also known to influence the ecological structure of vegetation communities, regolith depth can influence many critical site characteristics, particularly soil‐water storage and potential depth of root exploration.
None of the vegetation complexes at NBG are considered Threatened Ecological Communities pursuant to Schedule 2 of the Environmental Protection and Biodiversity Conservation Act 1999 or by
5 Shaded complexes are limited to land swap areas. 6 Based on data in the Forest Management Plan (2004 – 2013) (Conservation Commission of Western Australia).
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the Western Australian Threatened Ecological Communities Scientific Advisory Committee (Mattiske Consulting, 2005).
A total of 660 vascular plant taxa (of which 25 are introduced species) have been recorded on combined survey areas of NBG mining areas (Mattiske Consulting, 2005). The floral values in the NBG area reflect the interface between the eastern sections of the northern Jarrah forest and the flora of the Wheatbelt region. Therefore the range of species is per area relatively higher than in the western Jarrah forest areas. The number of species is also a reflection of the range of site conditions from clay‐loam valley systems to the upland lateritic hills to the shallow granitic soils associated with the greenstone belt.
Mattiske Consulting (2005) noted that only a few species recorded were restricted to the NBG area, with these generally associated with plant communities on the shallow granitic soils. No endangered or vulnerable species, pursuant to Section 178 of the Environmental Protection and Biodiversity Conservation Act 1999, and no Declared Rare Flora species or Threatened Ecological Communities were recorded on the site.
Nine priority species have been recorded in the plant communities on the NBG leases (Table 4‐12). All of these species have been recorded ein th native plant communities and Templetonia drummondii, Lasiopetalum cardiophyllum, Acacia gemina (part of seeding mix) and Senecio leucoglossus have also been recorded in rehabilitated areas within the leases.
Jarrah dieback disease is associated with the introduced water mould Phytophthora cinnamomi and is considered to be the major disease problem of Western Australia’s native forests. The impact of Phytophthora cinnamomi is most significant in the wetter western portion of the Northern Jarrah Forest. NBG is in the drier eastern portion of the Northern Jarrah Forest where incidence and associated impact is markedly less. The NBG lease areas have been mapped for dieback incidence, and a comprehensive forest hygiene programme has been operating successfully since the commencement of the project.
Other forest diseases also occur in the jarrah forest. Infections of Armillaria lutebublina occur infrequently and affect individual plants of small patches of vegetation. Other Phytophthora species are infrequently observed, but are managed using the same forest hygiene procedures.
Table 4‐12 Priority flora species recorded at NBG Species State Conservation Status Acacia gemina7 Priority 2 Eucalyptus latens Priority 4 Gastrolobium sp. Prostrate Boddington (M. Hislop 2130) Priority 1 Halgania corymbosa Priority 3 Lasiopetalum cardiophyllum7 Priority 4 Senecio leucoglossus7 Priority 4 Stenanthemum coronatum Priority 3 Stylidium marradongense Priority 3 Templetonia drummondii7 Priority 4
7 Has been recorded in rehabilitation areas.
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4.1.6.1.1 Flora and Vegetation of Thirty‐Four Mile Brook and Hotham River Riparian vegetation along Thirty‐Four Mile Brook is typically dominated by moderately dense Eucalyptus marginata (Jarrah) with a dense understorey of Melaleuca heath and tall mixed shrub species such as Dodonaea attenuata, Trymalium floribundum and Hakea lissocarpha (Streamtec, 1997).
On the Hotham River there are two main vegetation zones (Mattiske, 2010): Open Melaleuca forest over‐storey across the floodplain with a variable herbaceous understorey; and A narrow zone of Juncus rushes on the outer floodplain forming a transition from floodplain to terrestrial vegetation.
4.1.6.1.2 Post Closure Impacts on Flora The potential post closure impacts on the flora of the region include: Revegetation of disturbed areas; Introduction or spread of jarrah dieback disease; Introduction or spread of weed species; Groundwater drawdown from mine dewatering; and Inundation of vegetation from release of water from pit lakes.
During operations and closure, disturbed areas will be rehabilitated to blend in with the surrounding landforms and vegetation where possible. Rehabilitation species will be selected based on their suitability for the landform and soil profile developed.
Earthmoving activities and vehicle movement associated with rehabilitation have the potential to introduce and spread jarrah dieback and weed species. Continued implementation of the forest hygiene programme during closure will minimise the risk associated with the spread of dieback and other forest diseases as well as weed species.
Post closure it is predicted that it will take between 40 and 110 years for groundwater levels in the NBG area to recover to pre‐mining levels. However, groundwater drawdown by mine dewatering or the release of excess water is unlikely to significantly affect native vegetation or wetlands because: Seasonal wetlands are sustained by perched aquifers. The lower water tables in the weathered and fractured groundwater system induced by dewatering will not significantly affect leakage from these perched aquifers. A practical example of this can be seen where mining has impinged on one corner of Eight Swamp without any noticeable impact upon the remainder of the swamp; and Most of the water used by jarrah forest species is rainfall stored in the top 5 to 10 m of soil. There is negligible movement of water upwards from the oxide aquifer to the roots of plants. Moreover, the depth of the oxide water table is often greater than the maximum recorded depth of roots.
The release of water from the pit lakes to Wattle Hollow Brook will occur via a constructed channel. Due to the long time‐frame predicted for the pit lakes to overflow, vegetation may establish in the overflow channel. This vegetation will become intermittently inundated after the pit lakes fill, which will result in an adaptation of the vegetation type to that more suited to swamps and valley floors.
4.1.6.2 Fauna Fauna surveys and monitoring have been conducted in the NBG area since the early 1980s. These surveys have recorded 91 species of birds, 14 native and 5 introduced mammals, 13 amphibians and
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22 reptiles. The fauna of conservation significance that have been located at the site are described in Table 4‐13. All these fauna have a geographical range that extends well beyond the NBG project area and the eastern Darling Range forest.
The fauna of NBG are very similar to the more arid eastern areas of the Darling Range. However, it also supports elements which are outliers from their main distribution in the higher rainfall forests of the western Darling Range (Worsley Alumina Pty Ltd, 1999). This effect appears to be brought about by narrow fauna corridors extending from the western Darling Range to the eastern zone along the wetter valley systems and is more evident in plant communities lowest in the landscape. Upland areas are more typical representatives of the eastern zone and barely distinguishable from other locations along the eastern periphery of the Darling Range.
The NBG project area can be divided into two main faunal habitats (Worsley, 1999): Areas dominated by shrubland; and Areas dominated by woodland.
Valley Wandoo woodland and lower slope heath has the richest faunal communities and is highly significant to many species of animals, particularly birds, as the trees provide a large number and variety of nesting and/or refuge hollows and when flowering they are a rich source of nectar for honeyeaters. Mid‐slope Jarrah and lower slope Yarri has the most diverse faunal communities.
Table 4‐13 Conservation significant fauna species recorded at NBG Species Status8 Mammals Chuditch (Dasyurus geoffroii) Schedule 1 – WC Act Vulnerable – EPBC Act Woylie (Bettongia penicillata ogilbyi) Schedule 1 – WC Act Endangered – EPBC Act Southern Brush Tailed Phascogale (Phascogale tapoatafa) Schedule 1 – WC Act Southern Brown Bandicoot (Isoodon obesulus fusciventer) Priority 5 – DEC Priority Fauna List Western Brush Wallaby (Macropus irma) Priority 4 – DEC Priority Fauna List Water Rat (Hydromys chrysogaster) Priority 4 – DEC Priority Fauna List Birds Baudin’s Black Cockatoo (Calyptorhynchus baudinii) Schedule 1 – WC Act Carnaby’s Black Cockatoo (Calyptorhynchus latirostris) Schedule 1 – WC Act Endangered – EPBC Act Forest Red‐tailed Black Cockatoo (Calyptorhynchus banksii Schedule 1 ‐ WC Act naso) Peregrine Falcon (Falco peregrinus) Schedule 4 – WC Act Crested Shrike‐tit (Falcunuculus frontatus) Priority 4 – DEC Priority Fauna List Rainbow Bee‐eater (Merops ornatus) Schedule 3 – WC Act Reptiles Carpet Python (Morelia spilota imbricata) Schedule 4 – WC Act Priority 4 – DEC Priority Fauna List Dell’s Skink (Ctenotus delli) Priority 4 ‐ DEC Priority Fauna List
8 WC – Western Australia Wildlife Conservation Act 1950 EPBC – Commonwealth Environmental Protection and Biodiversity Conservation Act 1999
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4.1.6.2.1 Stygofauna and Troglofauna Significant stygofauna and troglofauna communities are unlikely to occur in the NBG area due to lack of potential subterranean habitat (OES, 2011b). Previous studies in the southwest of Western Australia suggest that stygofauna are likely to be present in karst geologies, while troglofauna occur in vuggs and voids within suitable geology. These characteristics are absent from the NBG area, which is dominated by a granite geology and contains both a seasonal shallow aquifer and a deeper, permanent bedrock aquifer.
4.1.6.2.2 Short‐Range Endemic Species Endemism refers to the restriction of a species to a particular area, at a continental, national or local scale (Allen et al, 2002). The short‐range endemic (SRE) invertebrate fauna of Western Australia is typically associated with sheltered and mesic microhabitats, such as the southeast aspect of slopes, trees, boulders and rockpiles, outcrops, mesas, drainage systems, deep gorges, natural springs and fire refuges (EPA, 2009). Two habitats with high potential to support SRE species have been identified in the NBG area on the basis of the habitats forming sheltered microhabitats or by forming habitat isolates (Table 4‐14).
A level two SRE invertebrate fauna survey yielded 24 species considered potential SRE species (Table 4‐15). Sixteen of these species are only know from the NBG area. A review of relevant literature and databases identified seven additional species that are likely to occur in the area.
Table 4‐14 Short‐range endemic species habitats Habitat Potential to Rationale for Classification Support SRE Species Jarrah/Marri Low Jarrah/Marri woodlands provide little shelter when compared to woodland other habitats in the landscape. Additionally, they form a habitat that is extensive and contiguous in the landscape. Previously Low Areas of land previously disturbed by farming and mining disturbed activities. Wandoo Medium These areas of low elevation tend to form around Melaleuca woodland swampland isolates, providing sheltered environments with elevated soil water content. Plantation Low Highly disturbed areas, limited habitat variability due to monoculture of Pinus radiata or Eucalyptus georgei and deep litter layer which poses a high fire risk. Melaleuca High These low lying swamp areas form isolated, sheltered swampland environments with elevated soil water content providing a source of moisture, even during the dry summer months. Granite outcrop High Granite outcrops can form habitat isolates (EPA, 2009). The granite outcrops in the NBG area form sheltered refuge areas that are isolated from similar habitats in the surrounding landscape. Allocasuarina Medium These areas have a deep leaf litter layer providing a sheltered environment for relictual species. These habitats are isolated and distinct from other sheltered areas within the landscape.
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Table 4‐15 Short‐range endemic species Species Individuals Collected Mygalomorph spiders Aganippe ‘MYG187’ Synothele mullaloo Scorpion Urodacus planimanus Millipedes Antichiropus ‘sp. Boddington’9 Antichiropus ‘sp. Goldmine’8 Antichiropus ‘sp. Marradong’ Antichiropus ‘sp. Saddleback 1’ Slaters Acanthodillo sp. Nov. A8 Trichorhina sp. Nov Snails Luinodiscus cf. repens Bothriembryon cf. serpentines Earthworms ‘sp. 009’8 ‘sp. 010’8 ‘sp. 013’8 ‘sp. 015’8 ‘sp. 016’8 ‘sp. 020’8 ‘sp. 025’8 ‘sp. 027’8 ‘sp. 032’8 ‘sp. 034’8 ‘sp. 035’8 ‘sp. 036’8 ‘sp. 037’8
4.1.6.2.3 Aquatic Fauna In Northern Jarrah Forest streams three dominant habitats are likely, although not all habitats may be present in each season: Channel – areas of the stream where surface water flow is unbroken and macrophytes are not present; Macrophyte – areas where riparian vegetation drape into the water or where the stream flows through beds of submerged or emergent macrophytes; and Riffle – areas where surface stream flow is “broken” by obstructions such as gravel beds, cobbles, large woody debris and rocks.
As a result of degraded water quality, the Hotham River is characterised by a low biodiversity of macroinvertebrates and fish. Low biodiversity in Thirty‐four Mile Brook is even more apparent because of its ephemeral nature and is only suitable for species that are able to colonise from more permanent sites or have short aquatic life‐stages.
Streamtec (1997) recorded a total of 76 species of macroinvertebrates from the Hotham River and Thirty‐Four Mile Brook. This included a large number of Coleopteran (beetle) species which have features which enable them to take advantage of temporary waters or waters which may become temporarily unsuitable (e.g. due to excessive salinity or low dissolved oxygen levels). Species more sensitive to environmental degradation, such as Plecoptera and Ephemeroptera, were not
9 Only known from NBG area.
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widespread. Diversity was within the range measured for forested uplands of the jarrah forest and no species considered rare or restricted were recorded. The majority of species collected were endemic to the jarrah forest with many Gondwandic elements to the fauna. At the time of the study there was no evidence of an impact on the Hotham River originating from activities at the NBG mine.
In 2010 WRM (2011) recorded a total of 111 macroinvertebrate taxa from the Hotham River and Thirty‐Four Mile Brook. Of the taxa recorded, 9% were endemic to the southwest and a further 4% had distributions restricted to Western Australia.
Five native freshwater fish species and two introduced species were recorded from the Hotham River and Thirty‐Four Mile Brook. Native species recorded were regional endemics, but are common throughout south‐western Australia.
The functional organisation of jarrah forest stream invertebrates is dominated by the detritivore feeding group10 (mostly collectors) with shredders co‐dominant, except in riffle areas. The functional organisation of the fauna also varies seasonally, with collectors dominant in summer, when low flows facilitate the settlement of fine particulate matter. Filter‐feeders increase in winter, when higher flows suspend organic matter in the water column. Predators show no consistent seasonal pattern, but their abundances are positively correlated with the abundance of other invertebrates.
4.1.6.2.4 Post Closure Impacts on Fauna Closure of NBG will result in no further impact to fauna and rehabilitation of disturbed areas will result in restoration of feeding and breeding habitat over time. Monitoring has shown that black cockatoos start using rehabilitation areas as a food resource within eight years post‐revegetation (Lee et al, 2010).
The habitat requirements of black cockatoos and other priority fauna will be considered in the development of rehabilitation prescriptions where relevant. The main habitat restoration options for black cockatoo habitat are summarised in Table 4‐16 (Finn, 2010).
10 Functional feeding groups: ‘shredders’ feed on coarse particulate matter (>1 mm); ‘collectors’ feed on fine particulate matter (<1 mm); ‘filterers’ filter suspended particles from the water column and are often viewed as a subset of collectors; ‘grazers’ graze or scrape algae and diatoms attached to the substrate; ‘predators’ capture live prey.
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Table 4‐16 Main habitat restoration options for black cockatoo habitat Feeding Habitat Ecological Function Comment Typical jarrah forest Provides Jarrah and Marri as Rehabilitation sites eventually return to a vegetation structure similar to the forest habitats in vegetation food source, but also other the surrounding area. These habitats are used by all three black cockatoo species, with Jarrah species in lesser amounts. and Marri the main sources of food for Baudin’s cockatoos and Forest Red‐Tailed black cockatoos. Typical jarrah forest Provide Jarrah and Marri as Marri is a key food source for Baudin’s cockatoos and Forest Red‐Tailed black cockatoos, and vegetation but with richer food source, but with greater areas richer in Marri are high‐value feeding habitats. mix of Marri concentrations of Marri. Heath woodland Provide food source for Dryandra, Hakea and Banksia spp. are key food sources for Carnaby’s cockatoos. dominated by mid‐canopy Carnaby’s cockatoos, but also Woodland/heath habitats occur only infrequently in the Jarrah forest, but provide habitat for species (Dryandra, Hakea, habitat used by range of a range of bird and mammal species. Thus, creating areas of woodland/heath habitat may Banksia) other fauna. have broad biodiversity benefits. Stands or strips of non‐ Provide food source for Pine is a key food source for Carnaby’s cockatoos and is used wherever it is found, with some native species (Pine) Carnaby’s cockatoos. flocks exhibiting a preference for pine over native vegetation. The main ecological advantage of pine is that pine treesd an pine stands provide a dense, high energy source of food. Breeding Habitat Ecological Function Comment Typical jarrah forest Provide large hollow‐bearing Rehabilitation sites with a typical Jarrah forest vegetation will provide large hollow‐bearing vegetation trees. trees in >150 years at a density similar to other Jarrah forest landscapes. Jarrah is not a good source of large hollows, meaning that large hollows tend to occur disproportionately in other tree species, particularly Marri and Wandoo. Typical jarrah forest Provide large hollow‐bearing Rehabilitation sites with greater concentrations of Marri and Wandoo would provide large vegetation but with richer trees. hollow‐bearing trees in >150 years, but at a density higher than other Jarrah forest complex of Marri and landscapes. Marri and Wandoo (as well as other similar species such as Yarri) are much better Wandoo sources of hollow than Jarrah. Artificial nest hollows Provide short‐term source of Artificial nest hollows would provide short‐term mitigation for the loss of natural hollows and hollows. may also support breeding near rehabilitation areas, particularly if food is abundant in these areas. Water Ecological Function Comment Artificial water points Provide source of water. Black cockatoos must drink daily, so sources of water improve habitat suitability.
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4.1.7 Noise Mining and processing activities conducted at NBG can generate noise. The significant noise sources are: Mobile equipment in the open pits and on route to the crusher and waste rock landforms; Primary crusher; Overland conveyor from primary crusher to crushed ore stockpile; and Processing plant (consisting of conveyors, screening, crushing, milling and grinding).
Modelling has indicated that noise levels at the nearest noise sensitive premises will comply with the assigned noise levels in the Environmental Protection (Noise) Regulations 1997 at all times.
NBG has developed a Noise and Vibration Management Plan to minimise impacts to the environment, local residents and the wider community. The Noise and Vibration Management Plan will continue to be updated as required and will form the basis for managing noise at the site during closure and rehabilitation works.
4.1.7.1 Post‐Closure Impacts on Noise The main sources of noise will cease with the expected cessation of open pit mining and mineral processing. Continued implementation of the Noise and Vibration Management Plan during closure will ensure the ongoing management of the impact of noise on the residents of Boddington and neighbours of the mine.
4.1.8 Air Quality The primary source of air emissions from the NBG project are: Greenhouse gases produced as a result of electricity production and consumption, combustion of diesel and LPG, the use of explosives and the clearing of vegetation; and Dust generated from both fugitive and point sources.
The primary sources of air emissions from NBG will reduce upon the cessation of open pit mining and mineral processing. However, closure and rehabilitation activities such as earthmoving have the potential to contribute to dust emissions from the site during the closure and post closure phases along with wind erosion from waste rock landforms, RDAs and disturbed areas.
NBG implements an Air Quality Management Plan which is applicable to all activities which generate particulate, gaseous or fugitive air emissions at all stages of mining from design, construction and operation through to mine closure. NBG’s air quality management strategy involves the following stages: Systematically identifying sources; Identifying relevant legal and other requirements; Assessing the significance of each point and diffuse source in terms of: o Potential effects on the environment o The quantity and frequency of emission o The conditions under which the emission occurs o Any relevant community concerns Prevention, minimisation and/or control of emissions.
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Air emission controls implemented at NBG include: Road sealing; Limiting clearing of land to that required; Watering of unsealed roads; Dust collection systems; and Preventative maintenance.
4.1.8.1 Post‐Closure Impacts on Air Quality Air quality may be adversely affected post‐closure due to: Dust generation from earthmoving activities and erosion of disturbed areas; and Emission of greenhouse gases from mobile equipment.
The key closure and rehabilitation activities that may result in the generation of dust during earthmoving activities are: Transportation and application of rehabilitation materials; Shaping of landforms; and Ripping, seeding and fertilising of landforms.
The Air Quality Management Plan will continue to be updated as required and will form the basis for managing air emissions at the site during closure and rehabilitation works.
Excessive delays in rehabilitation of the RDAs or poor rehabilitation performance may contribute to dust emissions from the site during the closure and post‐closure phases due to wind erosion of disturbed surfaces. Undertaking progressive rehabilitation where possible will minimise the risk of dust generation from disturbed areas.
4.1.9 Land Use The primary major surrounding land uses near NBG are: Agriculture; Mining; Production Forestry; Nature Conservation; Recreation and Culture; and Surface Water Supply (Catchment).
Much of the land to the south of the project area has been cleared for agriculture and is commonly used for grazing and mixed cropping. The growth of hobby farms, plantations and specialised products is resulting in a move away from the traditional broad‐acre farming in the region.
The Boddington Bauxite Mine is located 30km to the south‐west of NBG. Bauxite mining is expected to continue in the Boddington area for many years.
To the north and east of NBG is private forest managed for timber. The forested area has been subject to selective logging for many decades.
The Monadnocks Conservation Park is located to the north of operations. This is an area of high concentration of rock outcrops, which display high levels of plant endemism and species assemblages that contrast with the surrounding landscape (DEC, 2009b).
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There are three principle areas of forest that are used for recreational purposes: The area around Tullis Bridge; Around Long Gully Bridge; and Along the Bibbulmun Track.
The Department of Environment and Conservation manages the Bibbulmun track, which is a popular route with hikers and those interested in seeing these areas. Additionally, the Hotham River is used for recreational pursuits including bird watching, fishing, kayaking, swimming, picnicking and walking. Redfin, perch and cobbler (catfish), along with marron (freshwater crayfish) are caught in season in the river.
South Dandalup water catchment lies to the northwest of the project area.G NB is located within the catchment of Thirty‐Four Mile Brook, which is not used for human consumption other than NBG employees and contractors.
4.1.9.1 Post‐Closure Impacts on Land Use It is believed that of the existing land uses, future mining, production forestry, nature conservation, recreation and culture and surface water supply can be managed in a compatible manner beyond closure at NBG. Livestock grazing is considered incompatible post‐closure due to risks associated with destabilising vegetation covers on rehabilitated surfaces. More detailed information on post‐mining land use is included in Section 6.
4.1.10 Cultural Heritage 4.1.10.1 Aboriginal Cultural Heritage A large number of Aboriginal heritage surveys have been conducted at NBG since the 1980’s. A number of Aboriginal heritage sites are recorded within the Department of Indigenous Affairs databases, the majority of which are quartz scatters and mythological sites (Figure 4‐13). Four of the registered sites require active management (Table 4‐17).
Table 4‐17 Aboriginal heritage sites requiring active management Site Description Round Swamp (DIA A very sparse scatter of quartz artefacts around the south and west margins of 4230) Round Swamp. The artefact assemblage included mainly quartz with some dolerite and one backed tool. Forest (DIA 4300) A fairly sparse scatter of artefacts on the surface near the head of a creek. The artefact assemblage consisted of mainly quartz with some dolerite, mainly chips and flakes and two fabricators. Hotham River (DIA The Hotham River is significant in terms of customary use and a number of 27935) historic camps and ceremonial grounds were present on its embankments from where the Thirty‐Four Mile Brook intersects the Hotham River to the bridge on Bannister Road. Forest (DIA 4277) A sparse scatter of about 150 artefacts on the edge of House Brook.
The Gnaala Karla Booja Native Title Claim encompasses the NBG area, with representation managed by South West Aboriginal Land and Sea Council (SWALSC). In August 2006, the Gnaala Karla Booja People (GKB), SWALSC and Newmont Boddington Gold signed the Moorditj Booja Community Partnership Agreement which acknowledges the GKB People as Traditional Owners of the area and their relationship to the land. The Community Partnership Agreement provides a process through which mutual respect and common interests can be achieved and a strong economic base can be
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built for the future generations of the GKB People. The parties to the Community Partnership Agreement are also committed to the Preservation of Aboriginal Heritage Agreement which sets out the process to be followed for the management of Aboriginal heritage sites within a 20 km buffer around the NBG operational area.
4.1.10.2 Other Cultural Heritage The Shire of Boddington identified two cultural heritage sites in the area of NBG in their Municipal Heritage Inventory (Shire of Boddington, 2011): Mt Wells Fire Tower; and Tullis Bridge.
The Mt Wells Fire Tower is located at the top of Mt Wells ands wa constructed as a fire lookout for the surrounding timber milling industry (Plate 4‐1). The tower was renovated in 1997 but was extensively damaged during storms in July 2012. The tower is utilised for recreational use, a weather station and fire lookout. Installation of huts has also allowed overnight usage by walkers of the Bibbulmun Track. The Mt Wells Fire Tower is an important feature of past industry practices in the Boddington area and conservation is recommended. Mining operations at NBG will not affect the Mt Wells Fire Tower.
Plate 4‐1 Mt Wells Fire Tower (from Shire of Boddington, 2011)
Tullis Bridge occurs across the Hotham River at the site of the Hotham River pump station. Tullis Bridge was constructed in 1912 as a rail link between Pinjarra and Narrogin and was in service until 1968. In 1969, rejuvenation work was undertaken so pedestrians could continue to cross the river on the bridge. However, it was extensively damaged by fire in 2008 and is no longer in use. Tullis Bridge has significant associations with the local timber industry and the connection between Narrogin and
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Pinjarra. It is rates as having an exception level of significance and conservation is highly recommended.
Tullis Bridge is also identified as a European heritage site in the Heritage Commission of Western Australia database.
Plate 4‐2 Tullis Bridge (from Shire of Boddington, 2011)
4.1.10.3 Post‐Closure Impacts on Cultural Heritage Continued implementation of the Cultural Heritage Management Plan during closure will ensure the ongoing protection of cultural heritage sites.
4.1.11 Social Setting and Community The project site falls within the Peel Region which covers 5,500 km2 and comprises the area defined by the boundaries of the City of Mandurah and the Shires of Boddington, Murray, Serpentine‐ Jarrahdale and Waroona. The region is lightly populated and most of the inhabitants are employed in bauxite mining, quarrying, forestry, agriculture and general servicing of these industries.
The town of Boddington is located 12 km southeast of the mine. Between the town and mine are several residences and NBG’s accommodation village. The nearest residence is approximately 7 km northeast of the project.
The Shire of Boddington has a predominantly agricultural economic base, with a focus on sheep, wheat and other cereal crops. This economic base changed with the influence of bauxite and gold mining industries, which were established there in the late 1970s and mid‐1980s. In recent times, the Shire is experiencing a growth in timber plantations (particularly after the restrictions placed upon
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felling of old growth timber), hobby farmers and new agricultural markets such as stone fruit, avocadoes, and viticulture olives.
In the 2011 census, the population of Boddington was recorded as 1,908 people. Of these, 72.9% were employed full‐time, 15.6% were employed part‐time and 2.5% were unemployed. Mining is the largest industry for employment in Boddington with 36.8% of employed people working in metal ore mining. Other major industries of employment included heavy and civil engineering construction (6.5%), land development and site preparation services (4.4%), school education 93.7%) and cafes, restaurants and takeaway food services (2.9%).
Boddington, while not having a large population, has very good facilities. The commercial centre includes a supermarket, post office, chemist, deli, bank and petrol stations. Community health is served by doctors and a child health centre as well as a district hospital and ambulance centre. Other emergency services include Police, Country Fire Brigade and State Emergency Service.
The Boddington township has a library, child care facilities and a district junior high school catering for students from pre‐school to year 10. The closest senior high school is in Pinjarra approximately 80 km away.
4.1.11.1 Post‐Closure Impacts on Social Setting and Community The potential post‐closure impacts on the community and social setting include: Reduction in population in Boddington and surrounding townsites; Reduction in business and income for local businesses; and Reduction in support and sponsorship of local activities and sporting teams.
The temporary closure of the Boddington operations in 2001 provided a useful set of statistics for predicting the future impact of mine closure. Boddington experienced a drop in population between 1996 and 2001, which is likely to have been influenced by the Boddington operations going into care and maintenance and the downturn in associated activities during this time (Q&A Communications, 2004). At the time of going into care and maintenance, the Boddington Gold Mine employed approximately 76 individuals directly and 205 contractors (the majority of whom resided in Perth). Of the 76 direct employees, the majority (90%) resided in Boddington (with the remainder residing in Mandurah (2%), Williams (1%), Perth (5%) and other towns within the Peel region (2%)).
After mine closure, 57% of the direct employees left the area. Stakeholder interviews confirmed a noticeable decrease in population immediately following cessation of mining activity, but the impact was not reflected in property sales or rental sales data and school attendance figures (Q&A Communications, 2004). This data supports the conclusion that at this time the impact of the temporary mine closure on the population was offset by a growth in the residential population due to other lifestyle considerations.
Following the temporary closure of the operations, two local businesses (one engineering firm and one laboratory) closed and two restaurants changed hands (Q&A Communications, 2004).
Closer to the end of mine life the Social Responsibility Plan will be refined to address the potential impacts of closure, particularly on the local community (Section 10.4). The projects and programs implemented for closure of NBG will be based upon the requirements of the local community at the time and will consider what has been successful in other communities.
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4.2 Research Programs, Studies and Trials Research programs, studies and trials have been conducted over the life of the NBG project to address key closure issues identified for the site. These programs will be continued in order to facilitate ongoing refinement of closure and rehabilitation techniques and costs. Progress and findings of research, studies and trials will be reported in the Annual Environmental Report.
The following sections summarise the key results of research programs, studies and trials that are relevant to rehabilitation and closure of the: Waste rock landforms (Section 4.2.1); RDAs (Section 4.2.2); and Open pits (Section 4.2.3).
Rehabilitation techniques are relevant to all disturbance areas and learning’s from previous rehabilitation at NBG are summarised in Section 4.2.4. Research undertaken into black cockatoos is summarised in Section 4.2.5.
More detailed information on the research programs, studies and trials that have been undertaken is included in Appendix 5.
4.2.1 Waste Rock Landforms The key areas of investigation for the waste rock landforms at NBG are: Geochemistry and management of potentially acid forming material; Landform design; and Cover design.
A summary of the key outcomes of the research, studies and trials conducted in these areas is included in the following sections.
4.2.1.1 Geochemistry and Waste Rock Management Investigations of geochemical conditions at NBG have been undertaken at various stages during mine development and operation. In general, the main objectives of the geochemical assessments have been to: Identify and characterise materials which will be mined and dispatched to waste rock landforms; and Determine the future acid and/or metalliferous mine drainage (AMD) potential of the various materials and facility areas.
NBG currently employ conventional Net Acid Generation (NAG) test and acid base accounting (ABA) indices for the differentiation of potentially acid forming (PAF) and non‐acid forming (NAF) components of the run of mine waste rock stream. The applicability of these indices to the material at NBG is however questionable due to its very low sulphide‐S content and negligible carbonate neutralisation capacity. This results in the majority of waste rock being conservatively classified and managed as PAF.
ABA and NAG test data provide reliable determinants of waste rock behaviour only for the relatively small fraction of the NBG waste stream which is either: Definitively NAF in character due to the presence of carbonate buffering capacity which significantly exceeds acid production potential; or
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Definitively PAF in character due to the prevalence of acid production potential or NAG acidity levels which, regardless of sulphide oxidation kinetics exceed aluminosilicate buffering capacity.
Run of mine NAG data compiled for waste grade material analysed to date indicates that the above characteristics are likely to apply to only a small percentage of the total waste stream.
The presence of non‐carbonate buffering capacity in a significant proportion of the intrusive lithologies at NBG is signified by the tendency for sample materials classified as PAF on the basis of NAG tests to maintain circum‐neutral leachate pH during prolonged weathering in column tests. Acid contact water in the majority of instances may be mitigated in NBG waste rock lacking carbonate buffering through reaction with aluminosilicates, chiefly biotite and feldspars. However, this non‐ carbonate buffering is only effective to a threshold sulphide oxidation rate and/or within a pH range which is probably delimited by a lower bounding value of around 5.
Results derived from the kinetic testing program commenced in 2000 suggest that the threshold rate of sulphide oxidation beyond which non‐carbonate buffering is ineffective is of the order of 2 to 2.5 mg/kg/day sulphate yield (BGM, 2003). In the specific sample suite subject to testing sulphide oxidation rates in excess of 2.5 mg/kg/day were produced in materials with sulphide‐S abundances as low as 0.2%.
Kinetic testing commenced in 2010 indicates that the sulphide oxidation rate threshold beyond which effective aluminosilicate buffering may be inhibited is around 3 mg/kg/day (Campbell et al, 2012). In the specific sample suite subject to testing, this threshold corresponds to a sulphide‐S abundance of around 0.3%.
Based on the entire sulphide block model for NBG, it is estimated that around 54% of the model area is characterised by sulphide‐S levels of <0.1%, with a total of 74% containing sulphide‐S at <0.2%. This is broadly analogous to the distribution evident in run of mine samples from both the North and South pits to date. While sulphide‐S constitutes only one of a range of possible controls on AMD generation propensity in the life of mine waste stream, this level of analogy, coupled with the relative homogeneity of the principal waste lithologies throughout the block model area, suggest that the use of a sulphide‐S threshold for differentiation of NAF and PAF material behaviour is likely to be applicable throughout the mine life.
NBG has commenced developing a revised waste rock handling plan and medium grade management plan based on improved understanding of the long‐term AMD and metal leaching potential of waste rock and medium grade ore. The overall approach to characterisation of the AMD potential of the waste rock and medium egrad ore will be based on collection of representative samples for use in laboratory static and kinetic testing. In parallel with this work, field testing will be undertaken to demonstrate that conclusions drawn from laboratory scale tests are fully applicable to the behaviour of waste rock in the field setting. The field tests established are intended to serve as a source of long term data to guide validation of operational waste rock management protocols and the refinement of closure designs for the waste rock landforms at NBG.
4.2.1.2 Landform Design The closure strategy for the waste rock landforms is to create physically stable and safe landforms that are consistent with the existing variable topography. To achieve this strategy, landform design for NBG has focussed on: Optimal placement of the waste rock landforms (Section 4.2.1.2.1); and Slope geometry (Section 4.2.1.2.2).
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4.2.1.2.1 Waste Rock Landform Placement A specialist mining planning consultant was engaged to conduct comprehensive analyses of the options available for optimising waste rock storage. Evaluation of approximately 20 alternative landform designs was undertaken by applying a series of constraints (primary and secondary) either in isolation or collectively and assessing the outcomes. Primary constraints are restrictions to construction of the waste rock landform at a physical location that will apply under all conditions. The primary constraints included during the evaluation of the landform design for NBG were the locations of the: Processing plant; Open pits; Stockpile and ROM pad; and Conveyor corridor.
Secondary constraints are restrictions for construction of the waste rock landform at a physical location that may or may not be applied depending on requirements. Their main use is for undertaking “what if” analyses. The secondary constraints considered in the evaluation of the landform design forG NB included: Current cleared footprint; Existing tenure; Location of: o State forest; o Black cockatoo habitat; o A potentially significant woylie population; o Locally restricted vegetation communities such as swamps; o Bauxite; o Infrastructure such as powerlines. Visual amenity; Maximum elevation; and Regional drainage.
As an example, Figure 4‐14 shows the results of restricting expansion of the waste rock landforms to existing tenure compared with the application of no secondary constraints.
The above factors posed challenges to the planning process for the waste rock landforms as they interact to result in conflicting outcomes. For example, constructing a landform with an increased maximum height results in a smaller footprint and less clearing of jarrah forest for the volume of waste rock being stored. However, this also results in increased visual impact and a higher long term closure risk due to the long slopes to be stabilised during rehabilitation.
After several iterations, preferred landform locations, heights and sizes were selected and integrated with the NBG mine planning process. The waste rock dumping schedule was also assessed to ensure that materials that require encapsulation can be segregated and that rehabilitation materials such as oxide can be stored in locations where they can be accessed when required at later stages of the mine life to minimise the area required for stockpiling of materials.
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4.2.1.2.2 Slope Geometry Due to the large area of the waste rock landforms, slope geometry and surface water management is a critical component of long term stability. SIBERIA11 modelling was conducted to compare the relative performance of alternative slope geometries. A copy of the reports on SIBERIA modelling undertaken are included in Appendix 7 and Appendix 8.
Initial modelling was undertaken using parameters considered to be realistic for the site conditions. The slope geometries modelled were (Figure 4‐15): Single slope with benches – 14 m wide benches with 1 m high bunds and 1 m deep water diversion channels with 17° interbench slopes; Single slope ‐ 17° slope with no benches; Concave slope – concave slope with grades of 15.3°, 13.4°, 9.2° and 4.8°; and Concave slope with benches – 40m wide benches with 3 m high bunds and 5° back slope with concave interbench slopes with grades of 25° and 15°. Crest bund height set to provide sufficient storage volume to retain material eroded from the slope above the bench.
The erosion simulation results indicated that a concave slope with wide benches and sized bunds performs better than the other slope geometries with respect to total eroded volume and gully depth (Table 4‐18 and Table 4‐19).
Table 4‐18 SIBERIA modelling with assumed parameters – comparison of total eroded volume Slope Geometry Total Eroded Volume (% compared to single slope with benches geometry) Single slope with benches 100% Single slope 116% Concave slope 67% Concave slope with sized benches 26%
Table 4‐19 SIBERIA modelling with assumed parameters – comparison of gully depth Slope Geometry Gully Depth (% compared to single slope with benches geometry) Maximum Gully Depth Average Gully Depth Single slope with benches 100% 100% Single slope 202% 197% Concave slope 152% 141% Concave slope with sized benches 97% 120%
Further modelling was undertaken of three slope geometries identified in the previous study using erosion parameters calibrated to the materials at NBG. Modelling also took into account a range of vegetation covers from no vegetation to full forest cover. The slope geometries modelled were (Figure 4‐16): Single slope with benches – 14 m wide benches with 1 m high bunds and 1 m deep water diversion channels with 17° interbench slopes;
11 SIBERIA is a long‐term erosion model developed to simulate the linkages between the time evolving geomorphic form of natural landscapes and the hydrology and erosion processes occurring on them, and how these processes, in turn, determine the future evolution of the natural landform.
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Concave slope with benches (30 m lifts) – 40m wide benches with 5 m high bunds and 5° back slope with concave interbench slopes with grades of 25° and 15°. Crest bund height set to provide sufficient storage volume to retain material eroded from the slope above the bench; and Concave slope with benches (20 m lifts) – 40m wide benches with 5 m high bunds and 5° back slope with concave interbench slopes with grades of 25° and 15°. Crest bund height set to provide sufficient storage volume to retain material eroded from the slope above the bench.
Comparison of the three slope profiles showed that a slope geometry where benches are sized to retain water and slope erosion perform significantly better in terms of total eroded volume and average gully depth (Table 4‐20 and Table 4‐21). It is also evident that vegetation has a significant effect on the total erosion.
Table 4‐20 SIBERIA modelling with calibrated parameters – comparison of total eroded volume Slope Geometry Total Eroded Volume (% compared to single slope with benches geometry) Little or No Grasses, Shrubs Well Established Vegetation and Small Trees Vegetation Single slope with benches 100% 100% 100% Concave slope with sized benches 16.6% 7.3% 1.6% (30 m lifts) Concave slope with sized benches 12.2% 5.4% 1.1% (20 m lifts)
Table 4‐21 SIBERIA modelling with calibrated parameters – comparison of average gully depth Slope Geometry Average Gully Depth (% compared to single slope with benches geometry) Little or No Grasses, Shrubs Well Established Vegetation and Small Trees Vegetation Single slope with benches 100% 100% 100% Concave slope with sized benches 70% 22.7% 13.3% (30 m lifts) Concave slope sized with benches 26% 9.7% 6.0% (20 m lifts)
4.2.1.3 Cover Design The cover design for the waste rock landforms needs to ensure that closure objectives and completion criteria are going to be met with regards to landform stability, management of mine wastes and establishment of vegetation that resembles that of the region. The combined requirements of landform stability, minimisation of infiltration of surface water into the landform and revegetation with local native species presents a significant challenge, particularly given the large size of the landforms.
Cover design for the waste rock landforms has focussed on: Review of available information; Modelling of cover performance; and
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Trials of rehabilitation on steep slopes.
4.2.1.3.1 Information Review An information review was undertaken to assist in the development of suitable rehabilitation parameters for NBG. The information review incorporated: Assessment of: o Current design and rehabilitation criteria; o Information available from other mine sites pertaining to landform and slope geometry (slopes, shapes, materials, drainage); o Characteristics influencing the erodibility and successful rehabilitation of constructed slope Evaluation of rehabilitation undertaken on site in terms of slope stability and revegetation success, materials used and slope parameters; Identification of influential parameters to be considered for cover design at NBG; Development of slope geometry and rehabilitation prescriptions to be incorporated into SIBERIA modelling; and Recommendations for field based evaluation of slope geometry, erosion and drainage parameters.
A copy of the information review is included in Appendix 9.
Successful rehabilitation of the waste rock landforms will need to take into account: Soil and waste material characteristics; Vegetation characteristics; Scheduling and placement of waste materials; Slope design; Surface treatments; Surface water and drainage; and Climatic factors.
The most relevant information relating to rehabilitation at NBG can be drawn from existing rehabilitation and trial work. A summary of the results of rehabilitation of the satellite open pits at NBG is included in Section 4.2.4. The key outcomes of the steep slope trials that have been undertaken at NBG are summarised in Section 4.2.1.3.3.
The key observations of an inspection of rehabilitated slopes undertaken at NBG were: The growth of vegetation in existing rehabilitation areas is substantial, with a 30 cm layer of topsoil/gravel over oxide material supporting adequate vegetation in the satellite open pits; Plant roots readily penetrate the oxide material below the surface gravel/topsoil in the reconstructed profiles; The growth of vegetation is less in areas of shallow gravel cover and/or exposed oxide material; and Erosion has occurred where the depth of gravel at the surface is insufficient, where oxide is exposed at the surface or where surface water flow is concentrated.
A waste rock landform rehabilitation trial is proposed to evaluate and potentially refine design parameters under field conditions. The performance of the selected slope design and rehabilitation prescriptions will be evaluated to augment the existing knowledge base on the most suitable rehabilitation methods for NBG.
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The rehabilitation materials (i.e. topsoil, gravel and oxide) have differing erodibility, infiltration and water storage capacities. Different combinations of these materials will be tested under field conditions to optimise the water holding, erodibility and vegetation growth potential of the cover. Potential prescriptions that may be evaluated as part of a lfield tria include: 0.3 m of topsoil/gravel over 2 m of oxide; 0.3 m of topsoil/gravel over 0.5 m of waste rock/oxide (i.e. waste rock ripped into oxide surface) over 1.5 m of oxide; and 0.3 m of topsoil/gravel over 2 m of waste rock/oxide (i.e. waste rock and oxide mixed).
4.2.1.3.2 Modelling of Cover Performance Modelling of cover design was undertaken using VADOSE/W12 to assess the performance of cover options. Two conceptual cover designs were considered which were both designed to be store‐and‐ release cover systems (Table 4‐22 and Figure 4‐17). The key conclusions from the modelling were: The effectiveness of a 5 m thick cover is expected to be similar to a 2 m thick cover. However, the seepage rates could be higher if the oxide cover thickness is less than 2 m thick; The incorporation of a compacted layer in the cover system is not expected to improve the effectiveness of the cover system. The seepage rates through a cover system with a compacted layer are expected to be similar to the cover system without such a layer; The compacted layer would not impede oxygen ingress significantly. The compacted oxide material is expected to dry out once the plant roots become established in the cover and this will allow oxygen to diffuse into the waste rock; Almost all of the rainfall water that infiltrates the cover system is stored within the upper 2 m of the cover system. This water is removed during the dry season through evapotranspiration. There is not a gradual build‐up of soil‐water content, even after very wet seasons; Leaf litter reduces direct evaporation from the ground surface, thereby allowing more water to be stored in the soil profile which will be available for vegetation; and A gravel and topsoil layer would promote infiltration into cover material and limit run‐off from the landforms. This would inhibit erosion and allow more water to be stored in the covers, which would become available for the vegetation.
Table 4‐22 Summary of conceptual waste rock landform cover designs Layer Cover Option A Cover Option B Layer 1 (top) 30 to 50 cm mixed gravel or laterite 30 to 50 cm mixed gravel or laterite and topsoil. and topsoil. Layer 2 200 to 500 cm uncompacted kaolinitic 100 to 400 cm uncompacted kaolinitic oxide material. oxide material. Layer 3 None. 60 to 100 cm of compacted kaolinitic oxide material. Layer 4 (bottom) Waste rock. Waste rock.
12 VADOSE/W is a two‐dimensional finite‐element saturated and partially saturated flow model with the ability to simulate soil‐atmospheric interactions, including infiltration, evaporation, transpiration and run‐off. VADOSE/W can be used to model the movement of water, vapour and gas through saturated and partially saturated soils in response to rainfall, evaporation and transpiration.
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4.2.1.3.3 Steep Slope Trials. A series of trials has been undertaken at NBG on rehabilitation of slopes at angles of up to 25° (referred to as steep slope trials). The focus of this research has been to examine the performance of different surface treatments on steep slopes using surface water runoff, erosion and vegetation as performance indicators. The outcomes of these trials are summarised in Table 4‐23.
Table 4‐23 Summary of outcomes from steep slope trials Year Treatments Outcomes 1995 200 mm of topsoil and gravel over Increased gravel thickness in the cover backfilled oxide material. profile reduced the severity of gully 300 mm of topsoil and gravel over erosion. backfilled oxide material. The increased gravel thickness is thought 400 mm of topsoil and gravel over to increase the water storage capacity of backfilled oxide material. the cover, which reduces the potential for the cover to saturate which results in flow of excess water over the surface. 1997 Rock armour over 100 mm of topsoil and Rehabilitation is most susceptible to 200 mm of gravel. erosion during the first year before Rock armour under 100 mm of topsoil vegetation is established when the soil and 200 mm of gravel. profile is most unstable. 100 mm of topsoil and 200 mm of gravel. Rehabilitation was most successful on 100 mm of topsoil and 200 mm of gravel treatments with a degree of surface ripped with a winged tyne to a depth of roughness (either ripping or rock 1 m. armouring). 100 mm of topsoil and 200 mm of gravel Where very large gullies were not ripped with a conventional tyne to a present, erosion had stabilised by the end depth of 1 m. of the fourth year. Moonscaping. 2007 100 mm of topsoil and 150 mm of gravel Erosion was lowest on the treatment with ripped with a conventional tyne to a the least gravel, which does not support depth of 600 mm. previous trial findings that increased 100 mm of topsoil and 200 mm of gravel gravel thickness reduces erosion. ripped with a conventional tyne to a Comparison of trials between 1995 (wet depth of 600 mm. year), 1997 (dry year) and 2007 (slightly 100 mm of topsoil and 300 mm of gravel wetter than average year) indicates that ripped with a conventional tyne to a rainfall intensity may have a greater depth of 600 mm. impact on erosion than surface Application of paper based hydromulch treatments. at approximately 3 mm thickness. Application of woodchips appears to be a Application of woodchipped forest useful treatment for prevention and debris at approximately 3 mm thickness. potentially mitigation of erosion. Application of a layer of jutemat (a However, application of woodchips is commercial geosynthetic stabilising currently limited to a 40 m slope length. material). Hydromulch does not appear to be effective at significantly reducing erosion.
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4.2.2 Residue Disposal Areas The key areas of investigation for the RDAs at NBG are: Residue characterisation; and Cover design.
A summary of the key outcomes of the research, studies and trials conducted in these areas is included in the following sections.
4.2.2.1 Residue Characterisation 4.2.2.1.1 Physical Properties The basement residue is classified as having a loamy sand texture, which is coarser than the oxide residue which is classed as a clay loam (Table 4‐24). The fine particle size of the oxide residue is reflected in high water storage potential (40% volumetric water content at field capacity), but this high pore water suction may lead to decreased water availability for plants. Basement residue contains a lower proportion of clay‐sized material than the oxide residue at NBG, leading to a lower expected field capacity, higher hydraulic conductivity, less reactive surface area and thus less capacity to absorb nutrients.
The basement residue is slightly dispersive while the oxide residue partly dispersed after remoulding. While the basement residue had some capacity to hard set, the Modulus of Rupture (MOR) value recorded was below that considered potentially limiting to root growth (60 kPa). By contrast, the oxide residue was found to have a very high capacity for hard setting with a MOR value of around 240 kPa.
Table 4‐24 Physical characteristics of oxide and basement residue at NBG Parameter Oxide Residue Basement Residue Texture (of <2mm fraction) Clay loam Loamy sand Emerson Test Class 3b – Dry aggregate slakes but 2 – Dry aggregate slakes and does not disperse; remoulded partly disperses soil partly disperses Modulus of Rupture (kPa) 240 43.9
4.2.2.1.2 Chemical Properties Oxide residue is characterised by (Table 4‐25): High salinity and alkalinity due to the ore extraction process; High exchangeable sodium percentage (ESP); Poor nutrient status and availability due to the high alkalinity; and Extremely low organic carbon levels.
Application of soil treatments in the rehabilitation trial undertaken on the R4 RDA resulted in conditions changing to be generally less hostile for plant growth, with salinity and pH decreasing (Section 4.2.2.2.1).
In comparison to the oxide residue, the basement residue contains lower levels of sodium, is less saline and alkaline, has lower cation exchange capacity and higher extractable micronutrients (Table 4‐25). Therefore, in terms of chemical properties the basement residue is more suitable for plant growth.
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Total metal concentrations in both oxide and basement residues are low with the exception of copper, which was measured up to 1,200 mg/kg in an oxide residue sample (Table 4‐26). These high copper concentrations reflect the copper mineralisation in the NBG ore body, and that copper was not extracted during processing of the oxide ore.
The basement residue is deficient in both sulphide and carbonate minerals, and is thus classified as Non‐Acid Forming. Geochemical assessment indicates that bismuth is the only minor element which is enriched in the basement residue solids. Bismuth is incorporated into the crystal lattice of primary silicates and is thus “fixed” and has negligible bioavailability and solubility (OES, 2007b).
Table 4‐25 Chemical characteristics of oxide and basement residue at NBG Parameter Oxide Residue Basement Residue
Soil pH (H2O) 8.6 8.1 Electrical Conductivity (dS/m) 0.72 0.6 Organic Carbon (%) 0.13 0.13 ‐ Plant‐Available NO3 3 3 + Nutrients (mg/kg) NH4 2 3.5 P 5.5 3 K 463 3,298 S 136 256 Exchangeable Ca2+ 1.2 2.51 Cations (meq/100g) Mg2+ 0.7 <0.1 Na+ 0.8 <0.1 K+ 0.1 0.1 Exchangeable Sodium Percentage (%) 29.4 Below limits of reporting
Table 4‐26 Total metal concentrations for oxide and basement residue at NBG Parameter (mg/kg) Oxide Residue Basement Residue EIL13 Arsenic 8.0 11.0 20 Cadmium <1 <1 3 Chromium 76.5 39.5 400 Copper 791 156 100 Lead 11.0 <5 600 Nickel 23.5 28.0 60 Zinc 38.5 28.5 200 Mercury <0.1 0.25 1
4.2.2.2 Cover Design The cover design for the RDAs needs to ensure that closure objectives and completion criteria are going to be met with regards to landform stability, management of mine wastes and establishment of vegetation that resembles that of the region.
Trials undertaken on the R4 RDA (oxide residue) and successful rehabilitation of the neighbouring Hedges RDA indicate that oxide residue can be successfully rehabilitated (Section 4.2.2.2.1). However, further work is required to understand rehabilitation of the basement tailings and
13 EIL – Ecological Investigation Limit for soils (DEC, 2010).
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Newmont has made commitments regarding establishment of residue rehabilitation trials to develop an appropriate prescription for revegetation of the basement residue surface.
A basement residue rehabilitation trial is proposed to be conducted with the following objectives: To evaluate the behaviour of basement residue after rehabilitation, particularly in relation to its capacity to support productive vegetation; To evaluate the effect of decreasing the thickness of gravel subsoil on vegetation establishment and productivity; To assess if particular plant species are better adapted to the rehabilitated residue profile; and To provide an opportunity to assess root exploration and water use by vegetation on rehabilitated residue.
4.2.2.2.1 Oxide Residue Cover Trials The Gold Residue Rehabilitation Project was a field research program conducted between NBG, Hedges Gold Mine, the University of Western Australia and Murdoch University. The project was initiated to: Test the rehabilitation prescription developed from pot trials and field experiments at an operational scale; and Assess the impact of modifications to the prescription to enhance environmental, logistical and economic outcomes.
The principal variable in the trial was the thickness of the gravel layer placed over the residue. The three treatments were: 30 cm of gravel and 10 cm of topsoil; 15 cm of gravel and 10 cm of topsoil; and 10 cm of topsoil only.
The project also incorporated two soil amendments, gypsum (30 t/ha and 60 t/ha) and organic compost (50 m3/ha), as experimental variables.
Re‐sampling of the R4 RDA trial area was undertaken in 2011, twelve years after establishment of the trial, to assess long term trends in vegetation growth and soil properties. The outcomes of this trial are summarised in Table 4‐27.
A copy of the 2011 investigation is included in Appendix 6.
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Table 4‐27 Summary of outcomes from oxide residue cover trial Monitoring Year Outcomes 2001 During the first year and a half, vegetation performance was similar in all treatments, though growth, foliage cover and seedling height were greater in the topsoil only treatment. After two years, species richness and plant density declined in the topsoil only treatment compared to gravel and topsoil treatments. Organic sources of nutrients are not necessary for rehabilitation. Gypsum applied at 30 t/ha effectively improved alkalinity by lowering pH and improved sodicity by lowering exchangeable sodium. Root growth in the residue layers was observed to favour planes of weaknesses and voids in cracks, and layers of coarser material. Residue areas appear likely to be able to be revegetated by endemic species. 2011 A substantial reduction in the salinity of the residue material occurred between 1999 and 2011, both at the surface and at depth. The residue within the top 0.5 m of the profile is now classed as ‘non’ to ‘slightly’ saline. There has been no upward movement of salts into the topsoil/gravel cover materials from the residue materials. The pH of the residue material decreased from being extremely alkaline at the surface in 1999 to neutral in 2011. There was a similar reduction in alkalinity deeper in the residue material with pH increasing with depth. There has been a decrease in the concentration of nitrate, plant‐available phosphorus, potassium and sulphur in the residue materials, as would be expected with the high rate of vegetation growth within the trial area. The initially very high levels of exchangeable sodium within the upper (i.e. top 0.5 m) residue material have declined substantially. This, in combination with an increase in the exchangeable calcium present, has resulted in a decrease in the exchangeable sodium percentage of the residue materials to a depth of approximately 0.5 m. There was little consistent difference in the physical and chemical characteristics of the soil cover and residue materials within the different depth of soil/gravel cover treatments.
4.2.3 Open Pits The key areas of investigation for the open pits at NBG are: Pit lake chemistry and filling period; and Surface water management.
The key outcomes of the research, studies and trials conducted in these areas is summarised in the following sections.
4.2.3.1 Pit Lake Chemistry and Filling Period A site wide closure water balance and hydrochemical model has been developed to be used as a predictive tool to support the ongoing development of the NBG Closure Plan and the design of mine facilities. The model was developed using the software GoldSim, which is a graphical, object oriented program for performing dynamic, deterministic or stochastic simulations. A summary of the
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outcomes from the water balance model with respect to the pit lake filling period and chemistry are summarised below. A copy of the report is included in Appendix 10.
The following facilities are modelled in the closure water balance: F1/F3 RDA; R4 RDA; Future RDA; Cyanide destruct plant; D1 water storage reservoir; Upper Thirty‐Four Mile Brook diversion pond; Waste rock landforms 7, 8, 9, 10, 11 and 12; Medium grade ore and ROM footprint; Impacted water sump (seepage management system); Acid rock drainage treatment plant; North and South pits; South pit drainage channel; and D5 water storage reservoir.
Natural flow processes and flows between the facilities at closure are illustrated in the conceptual flow diagram in Figure 4‐18. In the model it is assumed that the existing cyanide destruct plant will operate for ten years post‐closure and seepage from waste rock landforms 7, 8, 10 and 11 will be treated for twenty years post‐closure.
Base case predictions from the water balance model were generated using daily data measured at the Marradong precipitation station from the period 1960 to 2010 (the drier portion of the longm ter record at this station), factored based on comparison with the NBG site station for the period for which they overlap. This results in an annual average precipitation of 788 mm and an annual average evaporation of 1,380 mm in the base case model.
Sensitivity analyses were undertaken to evaluate: Alternative climate scenarios (Table 4‐28). The possibility that the pit will never discharge to the downstream environment; Uncertainty in pit lake evaporation estimates; Rehabilitation effectiveness; and Optimum AMD treatment rate.
Table 4‐28 Closure water balance model climate scenarios Climate Scenario Model Input Extremely dry Precipitation reduced to 50% of long term averages, resulting in an annual average of 419 mm. Climate change Based on climate model predictions which indicate a maximum reduction of 20% in annual precipitation and a maximum increase of 6% in annual evaporation by 2070, resulting in an annual average precipitation of 620 mm. Very dry Precipitation reduced to 80% of long term averages, resulting in an annual average of 679 mm. Wet conditions Based on the wetter part of the historical record, resulting in an annual average precipitation of 888 mm. Very wet conditions Long term precipitation data increased by 20% to give an annual average of 1,019 mm.
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Under base case conditions, the North pit is expected to spill to the South pit after 32 years, and the South pit is expected to discharge to the downstream environment after 80 years (Figure 4‐19). After the pits fill they are expected to discharge every winter, with a predicted average spilling rate of 415 L/s (35,852 m3/day). During the summer months, when evaporation from the lake surface and groundwater outflows are greater than the combined inputs, the pit lake elevation is predicted to decline by up to about 0.7 m.
During filling of the pit lakes, runoff from the waste rock landforms and discharge from the up‐ gradient catchment containing the R4 and F1/F3 RDAs dominate the inflows (Table 4‐29). Once the pit lakes have filled and discharge from the South pit drainage channel is occurring, discharge from the up‐gradient catchment and rehabilitated F1/F3 and R4 RDAs is the dominant control on pit lake discharge. Most of the remaining inflows come from direct precipitation on the lake, runoff from waste rock landform 12 and the up‐gradient catchment and runoff from waste rock landforms 7, 8, 10 and 11.
During most of the pit lake filling period, the pit lake is modelled to act as a groundwater sink, with groundwater inflow contributing to lake filling. In the final stages of lake filling, as the lake rises from around 225 mRL to the South Pit spillway elevation at 235 mRL, the pit lakes is expected to switch to acting as a groundwater source, with some outflow of lake water into the groundwater system occurring. The water balance model predicts that ouflow to the groundwater system (around 7L/s) will be a small component of the pit lake water balance model compared to runoff entering the lake, so the lake will continue to fill to the spillway elevation.
Table 4‐29 Base case pit inflows during filling and at steady state Inflows % of Total during Filling % of Total at Steady Period State Direct precipitation 14.5 23.1 Catchment runoff 0.3 0.5 Pit wall runoff 10.3 7.6 Groundwater inflow 8.2 0.0 Waste rock landforms 7, 8, 10 and 11 runoff 20.5 18.7 Runoff from up‐gradient catchment and waste 12.9 16.4 rock landform 1214 Runoff from up‐gradient catchment and R4 and 28.2 32.1 F1/F3 RDAs15 Cyanide destruct plant discharge 2.3 0.0 AMD treatment plant discharge 1.2 0.0 Waste rock landform 9 seepage 1.5 1.5 Total 100 100
Table 4‐30 provides a summary of the model results for the sensitivity analysis undertaken. The results indicate that: The pits will discharge under all realistic future climate conditions, with filling times ranging from 44 to 127 years;
14 Modelled as Upper Thirty‐Four Mile Brook Diversion Pond and New Pond 2. 15 Modelled as New Pond 1.
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Reducing precipitation to as low as an average of 419 mm/year (less than the lowest annual total in the 100 year synthetic record) still results in the pit lakes discharging, although the filling time is extended to 250 years; The pit lake is relatively insensitive to the evaporation rates applied to the lake. This is due to the large catchment area reporting to the pit lakes and the relatively wet winter conditions compared to pit lakes in most other areas across Australia; Storage exceedance events from the seepage management system can be prevented by operating the AMD treatment plant at capacities between 9 and 26 L/s; and If rehabilitation of the waste rock landforms is poor and settlement and erosion potentially result in infiltration rates which reach 15% of precipitation, the capacity of the AMD treatment plant would potentially need to exceed 120 L/s.
Table 4‐30 Results of closure water balance sensitivity analyses Purpose Scenario Results Evaluate alternative Very dry: Natural precipitation Figure 4‐20 illustrates the predicted climate scenarios rate reduced by 20% and pond variation in the South pit filling rate evaporation coefficient increased for the climate scenarios analysed. to 90% of pan evaporation rate. Filling times range from Wet: The first 50 years of wetter approximately 44 years to 127 data from the early 1900’s years, compared to the base case of repeated. 80 years. Very wet: Natural precipitation rate increased by 20% and pond The typical range for lowering of the evaporation coefficient reduced to pit lake elevation in summer for the 60% of pan evaporation. base case model is 0.3 to 0.7 m. For Climate change: Natural the climate scenarios considered precipitation rate in 1990 reduced this movement reduces to 0.2 to by 20%, monthly pan evaporation 0.5 m in the very wet case and estimates for 1990 increased by increases to 0.6 to 0.9 m in the 6%, based on high emissions climate change case. predictions for 2070 and pond evaporation coefficient increased to 90% of pan evaporation. Evaluate the possibility Long term precipitation reduced Inputs to the pit lakes still exceed that the pit will never by 50%. outflows via groundwater outflow discharge. and evaporation. The pit lakes will discharge, but the filling period is increased to approximately 250 years. Evaluate uncertainty in Reduce pond evaporation Figure 4‐21 illustrates the predicted evaporation estimates. coefficient from 70% of pan variation in the South pit filling rate evaporation to 60%. for the evaporation rates analysed. Filling times range from 77 years to 86 years, compared to the base case Increase pond evaporation of 80 years. Once the pit fills and coefficient from 70% of pond begins to discharge there is no evaporation to 90%. observable difference in discharge rate or timing.
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Purpose Scenario Results Evaluate success of Increase evapotranspiration from Average seepage reduces from 3 L/s rehabilitation. RDAs from 70% to 130% of pan to 2 L/s for R4 RDA, 14 L/s to 7 L/s evaporation (assumes for F1/F3 RDA and 20 L/S to 10 L/s revegetation is very successful). for the future RDA. Pit slake discharge during year 82 rather than year 80. Reduce waste rock landform Slightly decreased inflow to pit from runoff from 45% to 35% of waste rock landform runoff. Pit precipitation (assumes poor lakes discharge during year 82 rehabilitation outcomes). rather than year 80.
Determine required Seepage management system With a storage volume of AMD treatment rate for storage volume of 100,000 m3. 100,000 m3 there should be no an assumed storage storage exceedance events if the capacity in the seepage AMD plant operates at a rate of management system for 26 L/s or more. base case scenario waste Seepage management system With an increased storage volume rock landform infiltration storage volume of 200,000 m3. of 200,000 m3, the AMD plant rate (2%). treatment rate may operate at a rate of 9 L/s or more to prevent storage exceedance events. Determine required Seepage management system With poor rehabilitation outcomes, AMD treatment rate storage volume of 100,000 m3. seepage to the seepage with worst case waste management system would increase rock landform infiltration significantly. However, storage Seepage management system (15%). 3 exceedance events within the storage volume of 200,000 m . seepage management system could be minimised with an AMD Seepage management system treatment plant operating rate in storage volume of 300,000 m3. the range 60 to 120 L/s for system storage capacities of 300,000 m3 to 100,000 m3.
The hydrologic water balance model was used as the basis for a hydrochemical model to provide preliminary estimates of post‐closure waste quality at specific locations at discrete time periods. The hydrochemical model was developed using the geochemical thermodynamic equilibrium code PHREEQC based on the results obtained from the base case water balance model developed in GoldSim.
The level of precision in the inputs to the current hydrochemical model is not at sufficient detail to allow detailed characterisation of surface water chemistry in the receiving environment, particularly for metals concentrations. However, the model provides an indication of the relative importance and influence of the various components in the water balance and has been constructed to allow the predictions to be improved as the input chemistries become defined in more detail.
During early filling, the North pit lake water quality is influenced by the up‐gradient sources (R4 and F1/F3 RDAs, waste rock landform 9 and up‐gradient catchment) as well as the discharge from the cyanide destruct plant and groundwater inflow. The water quality will be slightly alkaline with elevated TDS concentrations of around 2,800 mg/L (Table 4‐31).
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The North pit lake will fill to the notch excavated between the two pits after approximately 33 years. At this time, the TDS in the North pit lake is indicated to be around 1,200 mg/L (mainly composed of sodium, chloride and sulphate), with trace metals/metalloids at or below analytical detection limits with the exception of copper. Over time, the TDS in the North pit lake is predicted to further decrease as the lake continuously overflows to South pit and the water quality is more significantly influenced by natural catchment runoff and direct precipitation inflows than by treatment plant outflows.
During the yearl filling period (0 to 33 years post‐closure), the South pit lake water quality will be mostly influenced by groundwater quality inflow (high TDS), pit wall runoff and some runoff from the rehabilitated waste rock landforms. During this period, the pH is indicated to be slightly alkaline with moderately elevated TDS mainly composed of sodium and chloride. After approximately 33 years, the South pit lake water quality will be more significantly influenced by the North pit lake overflow water quality, and the TDS concentration is indicated to increase as the South pit lake fills to the notch elevation at approximately 79 years. Throughout this period, trace metals/metalloid concentrations are predicted to increase slightly but continue to be low or below analytical detection limits.
Throughout the filling period the South pit lake is indicated to have around 25 to 40 mg/L alkalinity. This suggests there is some capacity for assimilation of additional acidic inflows if the volume or concentration of either pit wall runoff or the portion of waste rock landform seepage that reaches the pit lake is greater than modelled.
After approximately 79 years post‐closure, the North and South pit lakes will join to become the combined pit lake ande th predicted water quality after this time reflects a complete mixture of the two lakes. The pit lake is predicted to fill to the discharge point after approximately 81 years post‐ closure. At this time, the pit lake is indicated to be slightly alkaline, total alkalinity remaining at around 40 /Lmg and moderate TDS. Once steady‐state inflow/outflow conditions are established, the TDS and constituent concentrations in the pit lake are expected to increase slightly over time due to evapoconcentration in the lake as a result of the large evaporative lake surface.
The D5 water storage reservoir is the point at which discharge from the pit lakes and seepage from the waste rock landforms after 20 years will be released to the environment. The water quality to be discharged to the environment during the early closure period (<20 years), is predicted to be of neutral pH and low TDS with trace metals/metalloids at or below analytical detection limits.
Once discharges from the seepage management system are diverted into D5 reservoir after 20 years, TDS concentrations increase slightly to 350 mg/L, whilst pH is maintained neutral. Subsequent to discharge from the combined pit lake, the water quality predicted at D5 reservoir indicates a two‐ fold increase in TDS concentrations.
After 120 years post‐closure (equivalent to 39 years of pit lake overflow), the TDS is predicted to be moderately high at approximately 800 mg/L (consisting mostly of sodium, chloride and sulphate) with trace metals/metalloids at or below analytical detection limits.
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Table 4‐31 Indicative post‐closure water quality Analyte (mg/L) Years Post‐Closure 2 years 10 years 33 years 79 years 81 years 120 years North Pit Lake pH 7.8 7.7 7.7 7.6 ‐ ‐ TDS 2,769 1,572 1,218 1,052 ‐ ‐
Alkalinity (as CaCO3) 82 63 55 51 ‐ ‐ Chloride 1282 723 549 459 ‐ ‐ Sodium 762 431 333 294 ‐ ‐ 2‐ Sulfate (as SO4 ) 404 225 183 171 ‐ ‐ South Pit Lake pH 7.4 7.3 7.4 ‐ ‐ ‐ TDS 921 864 924 ‐ ‐ ‐
Alkalinity (as CaCO3) 27 24 28 ‐ ‐ ‐ Chloride 505 474 506 ‐ ‐ ‐ Sodium 223 211 226 ‐ ‐ ‐ 2‐ Sulphate (as SO4 ) 65 62 65 ‐ ‐ ‐ Combined Pit Lake pH ‐ ‐ ‐ 7.5 7.6 7.5 TDS ‐ ‐ ‐ 955 980 894
Alkalinity (as CaCO3) ‐ ‐ ‐ 37 41 36 Chloride ‐ ‐ ‐ 468 460 408 Sodium ‐ ‐ ‐ 253 265 248 2‐ Sulfate (as SO4 ) ‐ ‐ ‐ 113 133 133 D5 Water Storage Reservoir pH 7.2 7.1 7.2 7.1 7.1 7.1 TDS 279 220 349 279 475 803
Alkalinity (as CaCO3) 17 13 16 13 12 14 Chloride 150 118 196 154 238 379 Sodium 89 70 115 92 144 230 2‐ Sulfate (as SO4 ) 6 5 7 6 49 116
4.2.3.2 Surface Water Management Robust designs are required for surface water management to ensure the integrity of the NBG landforms is protected. To prevent flooding of the surrounding forest and the waste rock landforms, a drainage channel is required from the pit lakes. Overflow from the pit lakes will discharge via a drainage channel at 235 mRL into Wattle Hollow Brook, a tributary of Thirty‐Four Mile Brook.
SLR Consulting (formerly Metago Environmental Engineers) were engaged to design drainage structures for the pit inlet and outlet structures, notch cut between the North and South pit and drainage channel.
4.2.4 Rehabilitation Techniques 4.2.4.1 Satellite Open Pits The satellite open pits are shallow oxide pits that were mined between 1993 and 2001. Most of the satellite pits were rehabilitated between 1992 and 2002 (Figure 4‐22 and Figure 2‐7). Rehabilitation of the satellite pits generally consisted of: Landscaping, application of topsoil, ripping and seeding during later summer;
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Planting of seedlings in winter; and Application of fertiliser by helicopter.
Rehabilitation monitoring currently consists of assessment of trees and understorey vegetation and has been undertaken as approximately nine months, three years, seven years and twelve years of age.
The tree stocking rate for the satellite open pits for the first year ranges from 364 to 3,925 stems/ha (Figure 4‐23). All of the satellite open pits except one (Pit C East) exceeded the completion criteria for the tree stocking rate of 400 stems/ha within the first year. The tree stocking rate in rehabilitation areas is also greatly exceeding ywhat ma be expected in native forest of similar site‐vegetation types.
Factors which have been found to affect the stocking rate of the rehabilitation areas at NBG include: Seasonal conditions in the first year after planting. A long and/or dry first summer places greater stress on seedlings at a susceptible age; Burning of seedlings by fertiliser; Soil compaction which may be caused by timing of site preparation and ripping during wet weather. Soil compaction appears to predominantly affect the establishment of E. marginata. This may be expected as this species typically develops a large lignotuber that penetrates the soil profile early in development; and Local site conditions such as aspect which affect exposure to the wind and sun.
The abundance of both seeded and planted trees in the rehabilitation areas shows that both seeding and planting can result in successful tree seedling establishment. Continued recording of seedlings in the rehabilitation areas also indicates that the vegetation is producing viable seed as the seeds of eucalypts do not persist in the soil seed bank for long periods.
A trend of increasing tree stocking rates to a peak level, followed by a slight decline after seven years is generally observed (Figure 4‐24). Tree death is expected as communities settle through competition and shading to achieve steady community composition. Monitoring has identified a general pattern that E. marginata deaths are more prevalent two years after revegetation than either one year or three years in rehabilitation areas at NBG, indicating that this species is particularly susceptible at two years.
Within three years all of the satellite open pits had achieved the species richness completion criteria of 27 plants/80m2 (Figure 4‐25). Species richness is initially expected to rise as the amount of seed stored in the topsoil or blowing in from adjacent vegetated areas increases and then decrease slightly as the community stabilises. This trend is generally observed for the NBG rehabilitation areas (Figure 4‐26).
Succession of understorey species dominance is apparent between assessment years. Initially a high proportion of seeded legumes provides soil stability and assists in the restoration of nutrient cycles during the establishment of rehabilitated areas. However, they often out‐complete other less viable species and reduce diversity in the rehabilitated areas. Monitoring indicates that although in the early stages of rehabilitation legumes are dominant, with the senescence of Acacia spp. in the older rehabilitated areas this dominance collapses and the diversity increases with the fall in competition. The death of some early colonising species (e.g. Kennedia species) allows for litter accumulation, nutrient accumulation and opening of the soil surface which can accommodate the establishment of new seedlings with time. Shannon‐Wiener Index values remain the same or increase slightly with
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time indicating the progression and development of the rehabilitated areas into that of a more complex species rich forest (Figure 4‐27).
Understorey growth measurement parameters of percentage foliage cover (Figure 4‐28) and plant density (Figure 4‐29) for three‐year old NBG rehabilitation compares favourably with three year‐old Boddington Bauxite Mine (BBM) rehabilitation.
A decrease in alive understorey plant density after seven years is not an unexpected response for rehabilitation of this age (Figure 4‐30). As the foliage of understorey species increases, particularly the cover of the large dominant species such as Acacia celastrifolia, competition increases which results in the loss of the more vulnerable species. Such a pattern will continue until the community reaches equilibrium. An increasing diversity index based on plant density assures that although the number of individual stems per square metre may have decreased, there is a greater range of plant species comprising this density (Figure 4‐27).
An overall increase in tree stocking rates and heights and concurrent decrease in understorey foliage cover (Figure 4‐31) indicate the increasing influence of shading on understorey species by overstorey species. This is part of the succession process and has been observed in other rehabilitation areas in the northern jarrah forest.
Of the 238 species that have been seeded or planted within the satellite pit rehabilitation areas, 127 species have failed to return and are potential recalcitrant species. An additional 42 species have returned 25% or less of the times they have been seeded or planted. Recalcitrant species may be failing to establish due to the absence of specific germination requirements. This may be overcome with time as the plant succession of the rehabilitation becomes more suitable.
4.2.4.2 Trials 4.2.4.2.1 Rehabilitation Prescription In 1996/97 a trial was established to test the effect of 20 rehabilitation treatments consisting of combinations of the following variables on plant establishment (Mattiske, 1998a, 1999a): Seeding (seeded or non‐seeded); Season of topsoil placement and seeding (winter or summer); Topsoil handling (direct return or stockpiled); Ripping method (conventional or winged tyne); and Gravel depth (0, 10 or. 20 cm)
The key findings from the trial were: Rehabilitation areas should be seeded with native plant species; Direct return rather than stockpiled topsoil should be applied to rehabilitation areas where possible; and Gravel depth of 10 cm appears optimal for native perennial plant density and foliage cover.
4.2.4.2.2 Fertiliser Application In 1998, a trial was conducted at NBG to assess the effects of four different methods of fertiliser application on rehabilitation performance (Mattiske, 1998b, 1999b). The four methods of fertiliser application assessed were: Spreading on the surface of the oxide before gravel and topsoil spreading in March (summer); Spreading on the surface of the gravel before topsoil spreading in March (summer);
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Spreading on the topsoil surface before ripping and seeding in March (summer); and Spreading on the topsoil surface after ripping and seeding in October (spring).
The outcomes of this trial are summarised in Table 4‐32.
Table 4‐32 Summary of outcomes from fertiliser application trial Monitoring Year Outcomes 1998 Based on the performance measures of density, foliage cover, species richness and diversity the most successful fertiliser treatment was the application of fertiliser on the topsoil in summer. Based on these parameters, the least successful fertiliser treatment was the application of fertiliser on the topsoil in spring. The poor performance of the rehabilitation where the fertiliser was applied on the topsoil in October 1998 can be attributed to the comparatively short duration of time between applying the fertiliser and the monitoring which was carried out in November 1998. A comparison of the three fertiliser treatments applied in March demonstrates that the topsoil application was the most successful of these fertiliser treatments. The benefits of the fertiliser decreased with increasing depth at which the fertiliser was applied. 1999 The treatment in which fertiliser is spread on topsoil in spring ranks highest in 5 of 8 aspects of rehabilitation performance measured. However, the apparent success of the treatment is compromised by low foliage cover and a high abundance of introduced species.
4.2.4.2.3 Recalcitrant Species Trial areas were established at NBG in 1997 to investigate establishment and survival of Macrozamia riedlei, Xanthorrhoea preissii and Xanthorrhoea gracilis in rehabilitation (Worsley Alumina, 1997). The trial investigated the survival of seed versus seedlings of M. Riedlei and survival of X. preissii and gracilis seed.
The trial concluded that seedling survival was higher than seed for M. riedlei. Low survival rates were noted for X. preissii and gracilis seed.
4.2.4.2.4 Impact of Grazing In 2001, a trial was established to test the impact of grazing on seedling survival (Mattiske, 2001). The trial comprised a fenced area of 1 ha and a similar area that was not fenced. Each area was planted with 13 species of seedlings or cuttings from recalcitrant species. Re‐monitoring of the trial area was undertaken in 2003, (Mattiske, 2003).
The outcomes of this trial are summarised in Table 4‐33.
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Table 4‐33 Summary of outcomes from impact of grazing trial Monitoring Year Outcomes 2001 During the first growing season there was no benefit to plants excluded from grazing. Seeded/planted and non‐seeded species richness, density and foliage cover, as well as species diversity, were greater in the unfenced areas than in the fenced areas. Similarly, the average progress of cutting/seedlings was greater in the unfenced area than the fenced area. 2003 Exclusion of grazers has increased the success of a greater number of seedlings than in the unfenced area. Grazing (or exclusion of it) is more than likely a major factor contributing to the survival success of recalcitrant species in rehabilitation. Foliage cover and native species richness was higher in the fenced area than the unfenced area. However, alive plant density was greater in the unfenced area. The combination of these results suggest that although the unfenced areas had a more successful initial growth period, the fenced areas may now be establishing better than the unfenced areas.
4.2.5 Black Cockatoos The jarrah forest in which NBG is located is habitat for three species of nationally threatened black cockatoos: Carnaby’s Black Cockatoo Calyptorhynchus latirostris (CBC); Forest Red‐tailed Black Cockatoo Calyptorhynchus banksia naso (FRTBC) ; and Baudin’s Black Cockatoo Calyptorhynchus baudinii (BBC).
Research on black cockatoos on site and within the surrounding jarrah forest is undertaken in close collaboration with researchers from Murdoch University. The research focuses on: Black cockatoo ecology; Feeding and habitat value; and Feeding in rehabilitation.
Biggs (2008) studied the feeding and nesting resources for black cockatoos within the jarrah forest at NBG. The aim of this study was to improve the knowledge of habitat requirements for black cockatoos by assessing the occurrence of food plants and large hollows and how their distribution varies across the landscape. Recommendations from this study relevant to closure and rehabilitation are: Propagation of preferred food species such as marri should be maximised; Allow for spatially and temporally varying food resources for the three species and ensure a constant supply of suitable feeding resources are available by establishing fast growing food plants in rehabilitated forest while waiting for marri to mature; and Where necessary, provide artificial nest boxes near or within high quality feeding habitat.
To better understand the features of rehabilitation areas that are important to black cockatoos, Lee et al (2010) undertook field observations and vegetation sampling in rehabilitation areas. The key findings of the study are:
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Rehabilitation areas at NBG are starting to provide food for black cockatoos, with CBC eating seeds from proteaceous shrubs (Banksia and Hakea spp.) and BBC and FRTBC eating seeds of regenerating Marri; and All three species fed in rehabilitation areas eight years old, indicating that food resources starte to becom available within this time frame post‐revegetation.
In a similar study, Doherty (2010) examined how black cockatoos use mine restoration as a feeding resource at Aloca’s Huntly bauxite mine. Doherty (2010) determined that future management of rehabilitation should aim to: Improve establishment of Persoonia longifolia and Allocasuarina fraseriana; Retain and possibly increase the proportion of Hakea species in the seed mix; Maintain and/or increase seeding rates of C. calophylla relative to E. marginata; and Investigate management options for maximising growth and food production of eucalypt stems in restoration, such as reducing the tree stand density and consequently the seeding rate and/or thinning over dense restoration.
4.3 Learning’s from Other Mines This section summarises learning’s from the closure and rehabilitation experience of other mines in the areas of: Rehabilitation techniques; Sustainability of rehabilitation; Fire and silvicultural management; Monitoring techniques; Formation of pit lakes; Development of completion criteria; Community consultation and participation in closure planning.
4.3.1 Relevant Mine Sites NBG has the benefit of being able to learn from the experience of: Adjacent mines with respect to rehabilitation and closure of mines in the unique environment of the Northern Jarrah forest; and Mines in the region with respect to more general issues such as formation of pit lakes and development of completion criteria.
The experience gained from the management of other Newmont sites with respect to closure and rehabilitation has also formed the basis of this Closure Plan.
Mines from which NBG has gained information regarding rehabilitation and closure include: Huntly, Willowdale and Jarrahdale (closed) bauxite mines operated by Alcoa World Alumina Australia (Alcoa); Coal mines of the Collie area operated by Wesfarmers Premier Coal (Premier Coal); Mineral sands mines operated by Bemax Resources Limited (Bemax); and Newmont Waihi Gold.
A description of these operators and sites is included below with relevant learning’s regarding closure and rehabilitation summarised in Section 4.3.2.
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4.3.1.1 Alcoa World Alumina Australia Alcoa has been undertaking bauxite mining in the Northern Jarrah forest since 1963 and have a well‐ developed mining and restoration process. The original Alcoa mine at Jarrahdale has been rehabilitated and in 2005 975 ha of the mine received a “certificate of completion” and was dreturne to the management control of the State of Western Australia (Gardner & Bell, 2007). Alcoa also operated and rehabilitated the Hedges Gold Mine and retain responsibility for the Hedges RDA.
Alcoa has the aim of achieving the best mine restoration and environmental performance in the world (Koch & Hobbs, 2007). Providing the basis for this aim is (Koch, 2007a): The current restoration objective “To restore a self‐sustaining jarrah forest ecosystem, planned to enhance or maintain water, timber, recreation and conservation values”; and The target that “The average number of indigenous plant species in 15‐month‐old restoration is 100% of the number found in representative jarrah forest sites, with at least twenty per cent of these from the recalcitrant species priority list”.
Alcoa has an extensive research and development program which covers: Minimising the spread of Phytophthora cinnamomi; Restoring jarrah forest trees and understorey; Nutrient cycling, soil processes and beneficial soil microorganisms; Fauna return; Regolith strength, root architecture and implications for ripping as part of the restoration process; and Fire and silviculture management.
Alcoa has also developed a set of completion criteria that has been agreed upon with the DMP and DEC (DoIR, 2007).
4.3.1.2 Wesfarmers Premier Coal Premier Coal has been mining in the Collie Basin since 1950, with major open cut mining commencing in 1970. Revegetation of completed landforms and mining areas commenced in 1975 and by 2004 1,020 ha had been rehabilitated (47% of the area disturbed by mining operations) (Premier Coal, 2011). The primary aim of Premier Coal’s rehabilitation program is to establish stable, compatible landforms revegetated with local, native species. The second aim is to leave a positive legacy for future generations, such as recreation areas, aquaculture options or conservation outcomes.
Due to the style, scale and depth of mining by Premier Coal, a final void remains at the end of mine life despite careful mine planning to minimise the size of final voids through backfilling. The resulting pit lakes have become important tourist attractions for visitors to the region (Shire of Collie, 2011) and are used for recreational and tourism purposes both intentionally (Lake Kepwari) and unintentionally (Stockton Lake and Black Diamond Lake) (McCullough et al, 2009a).
Premier Coal developed the Lake Kepwari pit lake as a major recreation and conservation facility (McCullough et al, 2009a). Wesfarmers demonstrated its commitment to sustainability principles with three innovative rehabilitation programs which included the development of (DMP, 2006): A recreational lake; A motor sports and driver training complex; and An aquaculture precinct for research and economic development.
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As a result of these rehabilitation programs Premier Coal were Golden Gecko award winners in 2005 for leadership in sustainable development. The company set a new environmental standard by establishing assets of lasting social, economic and environmental value at its old open cut pits in the Collie region (DMP, 2006).
Premier Coal has undertaken extensive research and modelling of pit lakes in collaboration with the Mine Water and Environment Research Centre.
4.3.1.3 Bemax Resources Limited Bemax Resources undertook mining for mineral sands within Ludlow State Forest No. 2 in the southwest of Western Australia. The post‐mining land use for the mining area was identified as conservation of biological, physical, cultural and landscape values, consistent with that of the unmined parts of the Ludlow State Forest and the adjacent National Park. Bemax developed a detailed integrated mining and rehabilitation management plan that included recreating the soil profile within the mine pits to achieve rehabilitation that would restore the previously degraded Ludlow Tuart Forest (Cable Sands, 2006; Bemax, 2009).
As part of the integrated mining and rehabilitation management plan, Bemax developed completion criteria and associated targets and have been undertaking monitoring since 2005 to track progress against these criteria.
4.3.1.4 Newmont Waihi Gold Newmont Waihi Gold is situated close to the town of Waihi (population 4,500 people) in New Zealand. The direct and indirect impacts of the Newmont Waihi Gold operations account for approximately 25% of the town’s economy (CSRM, 2009). In 2002 Newmont initiated a community consultation process to prepare the town for the closure of the mining operations. From this emerged the Vision Waihi Trust which has the role of implementing projects which are developed by the Waihi Community Vision. The biggest project under development is the Gold Discovery Centre.
In 2009 undertook a Social Impact Assessment (SIA) focussed on the potential impacts on the community of closure of the mine within two years (the life of the mine was extended after completion of the SIA).
4.3.2 Applicable Learning’s The applicability of learning’s from other sites needs to be carefully considered for NBG as the site specific characteristics of construction materials, rehabilitation resources, climatic factors, vegetation and closure requirements create a relatively unique situation. The level of disturbance associated with mining at NBG is much more intense than the mining of bauxite and minerals sands which typically remove <10 m of material and do not result in the formation of waste rock landforms and residue disposal areas.
Key learning’s from other sites are summarised in Table 4‐34 with more detailed information provided in Appendix 11.
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Table 4‐34 Summary of learning’s from other mines Aspect Key Learning’s Rehabilitation techniques The Alcoa rehabilitation process has successfully returned a modified jarrah forest ecosystem after mining. The rehabilitation process includes: o Stripping of soil in two layers (topsoil and subsoil); o Pushing down pit walls to create a smooth rolling landscape and manage runoff; o Deep ripping of the pit floor to break up compaction; o Return of overburden and topsoil (by direct placement where possible); o Placement of fauna habitat structures; o Contour ripping to reduce compaction and create furrows; o Seeding of 78‐113 species in summer and autumn; o Planting of plant species that do not return from the soil seed bank of broadcast seed; and o Application of fertiliser. Sustainability of rehabilitation Based on 30 years of monitoring Alcoa have found that: o All ecosystem function (including nutrient cycling and nutrient accumulation) appears to be successful or developing on an appropriate trajectory; o Structural attributes of the restored vegetation are controlled by the floristic composition and growth of the vegetation and are developing favourably with time; and o Biodiversity measures show some deficiencies, which should be resolved with time (e.g. lack of rotting wood and tree hollows for fauna) or are the subject of ongoing research and development (e.g. imbalance of seeder/re‐sprouter species). Topsoil seed stores rapidly accumulate in rehabilitated areas, indicating that plants are flowering and setting viable seed. Rehabilitation areas that are older than 12‐15 years can be integrated with the prescribed burning of the surrounding unmined forest. Monitoring techniques A species count provides a quick and easy measurement that is easily understood and correlates well with Shannon‐ Weiner diversity. Monitoring occurs when rehabilitation is 15 months old as research shows that species richness and floristic similarity of restored sites to intact vegetation does not increase over one or two decades. Formation of pit lakes The current demand for water in Western Australia means that pit lakes represent a potentially valuable resource to both the environment and the community.
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4.4 Information Gaps The closure data for NBG has been analysed to identify any information gaps which may affect the outcomes of rehabilitation and closure. The risk associated with not having the missing information has been assessed and a plan developed for appropriately addressing the information gap. The tasks identified in Table 4‐35 have been included in the appropriate Closure Implementation Plan in Section 10.
Closure planning is an ongoing process, and Closure Plans are periodically reviewed to maintain currency. The actions outlined in Table 4‐35 have been identified as having the ability to improve closure outcomes by: Filling gaps in the knowledge base; Validating assumptions made in this conceptual closure plan; or Predicting the impacts of closure strategy implementation.
Table 4‐35 is unlikely to represent a complete list of actions that will be undertaken prior to closure of the site and will be updated with each revision of the Closure Plan.
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Table 4‐35 Analysis of information gaps Information Gap Associated Risk Task Relevant Closure Management Unit or Section of Closure Plan Geology The extent to which non‐ Incomplete understanding of silicate Undertake laboratory testing of waste grade CMU3 carbonate buffering capacity is buffering capacity of waste rock. material encompassing: influenced by lithology or Increase in closure cost due to a) All major litho‐alteration assemblages in alteration across the deposit area. requirement to modify cover design or the life of mine waste rock stream The kinetics of non‐carbonate treat contaminated groundwater or b) A sulphide S range which will facilitate buffering reactions and their surface water. effective demarcation of the total‐sulphide resultant dependence on the threshold below which silicate buffering duration of solid‐solution may afford reliable AMD mitigation. interactions. Behaviour of waste rock under Incomplete understanding of the Undertake field‐scale testing of waste rock and CMU3 field conditions. effects of concurrent acid generation medium grade ore. and buffering under field conditions. Monitor seepage from medium grade stockpile Increase in closure cost due to (operational activity). requirement to modify cover design or treat contaminated groundwater or surface water. Landform and Soils Soil resources in the expanded Incomplete understanding of soil Undertake soil characterisation when RDA design CMU2 RDA footprint. properties and volumes. finalised and mining tenure in place. Materials inventory and reconciliation Update rehabilitation material inventory and CMU0 based on estimation of types and reconciliation. volumes of rehabilitation materials available.
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Information Gap Associated Risk Task Relevant Closure Management Unit or Section of Closure Plan Optimal cover depth for RDAs and Performance of rehabilitation Undertake rehabilitation trial on basement residue CMU2, CMU3 waste rock landforms. impacted. and waste rock landform. Increase/decrease in closure cost due to requirement to modify cover design. Rehabilitation takes longer to meet completion criteria. Acceptable rate of erosion of Rehabilitation does not meet Undertake rehabilitation trial on waste rock CMU3 cover materials to prevent impact completion criteria due to excessive landform. to stability, vegetation growth erosion. Undertake erosion monitoring on rehabilitated CUM0 (incorporate and management of surrounding Increase in closure cost due to areas. into monitoring areas. requirement to undertake repairs programme) and/or modify cover design. Develop erosion standard for completion criteria. CMU0 Landforms impact management of surrounding land. Monitoring method for erosion. Unable to demonstrate that Develop method for monitoring erosion. CMU0 rehabilitation meets completion criteria. Surface Water Detailed design for surface water Increase/decrease in closure cost Develop detailed surface water management CMU2, CMU3 management. based upon detailed design. design for site, including waste rock landforms and RDAs. Evolution of pit lake water quality. Pit lake water quality varies from post‐ Update post‐closure water balance model as CMU1 closure water balance model understanding of hydrological and hydrochemical prediction. parameters improves during operations.
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Information Gap Associated Risk Task Relevant Closure Management Unit or Section of Closure Plan Water quality of runoff from RDAs Surface water quality completion Monitor quality of runoff from waste rock landform CMU2, CMU3 and waste rock landforms. criteria aren’t met. and basement residue rehabilitation trial. Pit lake water quality varies from post‐ closure water balance model prediction. Volume of runoff from RDAs and Site‐water balance model based on Investigate water balance for proposed oxide layer CMU3 waste rock landforms. estimation of runoff rates based on in cover systems. expected vegetation cover and cover Monitor quantity of runoff from waste rock CMU3 design. landform rehabilitation trial. Drainage structures not appropriately sized resulting in excessive erosion or failure. Increased closure cost due to requirement to repair or modify drainage structures. Water quality guidelines for Incomplete understanding of water Develop water quality guidelines for runoff water CMU0 release of water to receiving quality required to prevent runoff exiting mining areas. environment. from adversely affecting the receiving Consult with relevant stakeholders to get CMU0 environment. agreement. Groundwater Quality of post‐closure seepage. Groundwater quality criteria aren’t Investigate post‐closure seepage water quality. CMU2 met. Increase/decrease in closure cost due to change in requirement for treatment of seepage. Post deposition seepage period Increase/decrease in closure cost due Investigate post‐deposition seepage period. CMU2 for RDAs. to change in requirement for treatment of seepage.
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Information Gap Associated Risk Task Relevant Closure Management Unit or Section of Closure Plan Water quality guidelines for Incomplete understanding of Develop groundwater quality criteria. CMU0 protection of beneficial use. groundwater quality required to Consult with relevant stakeholders to get CMU0 protect beneficial use. agreement. Flora and Vegetation Capacity of basement tailings to Rehabilitation does not meet Undertake rehabilitation trial on basement residue. CMU3 support vegetation. completion criteria. Increased closure cost for identifying, harvesting and application of suitable cover material. RDA not suitable for agreed upon post‐closure land use. RDA cannot be managed in accordance with surrounding land use. If particular plant species are Reduced success of vegetation Include a variety of local native species in CMU2 better adapted to the establishment and productivity. rehabilitation trial on basement residue. rehabilitated residue profile. Increased cost for seeding of RDA. Rehabilitation takes longer period to meet completion criteria. Performance of rehabilitation on Rehabilitation does not meet Undertake rehabilitation trial on waste rock CMU3 waste rock landforms. completion criteria. landform. Waste rock landforms not suitable for agreed upon post‐closure land use. Waste rock landforms cannot be managed in accordance with surrounding land use.
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Information Gap Associated Risk Task Relevant Closure Management Unit or Section of Closure Plan Target seed mix and ecosystem Rehabilitation does not meet Undertake rehabilitation trial on basement residue CMU2, CMU3 for RDAs and waste rock completion criteria. and waste rock landform. landforms. Increase in closure cost due to use of Include a variety of local native species in CMU2, CMU3 inappropriate seed. rehabilitation trials. Identify target ecosystem and document in CMU0 Rehabilitation Management Plan. Completion criteria for Incomplete understanding of Undertake rehabilitation trial on basement residue CMU2, CMU3 performance of rehabilitation of performance of rehabilitation for and waste rock landform. areas with significant disturbance areas with significant disturbance of Develop completion criteria for rehabilitation of CMU0 of the in situ soil profile (e.g. the in situ soil profile. disturbance areas with significant disturbance of waste rock landforms and RDAs). the in situ soil profile. CMU0 Consult with relevant stakeholders to get agreement. Requirement for post‐ Rehabilitated areas cannot be Monitor development of rehabilitation. Section 11 revegetation management such integrated with management of the as thinning/burning. surrounding land. Seed bank required for key plant Incomplete understanding of soil seed Investigate level of seed required in soil seed bank CMU0 groups to be self‐sustaining. bank required for key plant groups to for key plant groups to be self‐sustaining. be self‐sustaining. Monitoring method for soil seed Unable to demonstrate that Develop method for monitoring soil seed bank. CMU0 bank. rehabilitation meets completion criteria. Weed density of target Rehabilitated areas cannot be Investigate weed density of target ecosystem. CMU0 ecosystem. integrated with management of the surrounding land. Definition of native tree species Rehabilitation susceptible to forest Investigate and define native tree species which are CMU0 which are resistant to forest disease. resistant to forest disease. disease.
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Information Gap Associated Risk Task Relevant Closure Management Unit or Section of Closure Plan Fauna Level of usage of artificial nesting Rehabilitation does not meet habitat Annual monitoring of usage of nesting hollows hollows by Black Cockatoos. requirements of Black Cockatoos. (operational activity).
Proportion of plant species with Rehabilitation does not meet Identify proportion of plant species with attributes CMU0 attributes contributing to black completion criteria. contributing to Black Cockatoo habitat in target cockatoo habitat in target Rehabilitation does not provide ecosystem. ecosystem. habitat for black cockatoos. Land Use Defined post‐closure land use. Areas not appropriately managed for Consult with relevant stakeholders to get CMU0 post‐closure land use. agreement. Potential post‐closure land uses limited by inappropriate management. Capacity of landforms to support Rehabilitated areas not suitable for Undertake rehabilitation trials. CMU2, CMU3 potential post‐closure land uses. post‐closure land use. Suitability of long term pit water Post‐closure value of pit lakes Update post‐closure water balance model as CMU1 quality for potential post‐closure reduced. understanding of hydrological and hydrochemical land uses. Water requires treatment for post‐ parameters improves during operations. closure use. Community Capacity of community to adapt Incomplete understanding of potential Refine Social Responsibility Plan to address the Section 10.4 to closure. impacts of closure on community. potential impacts of closure. Projects and programs not focussed on addressing community needs, building local capacity and fostering resilience to change. Identification of areas where Effort expended in areas which do not Refine Social Responsibility Plan to address the support required. reduce impacts of closure. potential impacts of closure. Areas of risk not identified. Include closure in Social Impact Assessment.
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Information Gap Associated Risk Task Relevant Closure Management Unit or Section of Closure Plan Post‐closure vision of Boddington Understanding of post‐closure vision Undertake visioning process with Boddington community. of Boddington community currently community. based on visioning undertaken as part Investigate options for supporting the post‐closure of SuperTowns Initiative. vision such as setting up a trust fund and advisory committee. Infrastructure to be retained post‐ Opportunity for re‐use of Consult with community two years prior to closure closure for use by community. infrastructure lost. to identify infrastructure to be retained. Delay in relinquishment as transfer of Develop asset transfer agreement for infrastructure legal responsibility to third party for to be retained for use by the community. infrastructure to be retained not in place. Workforce Transition Program. Employees not provided with Develop Workforce Transition Program one year Section 10.5 information, support and training to prior to closure. minimise the impacts of closure. General Post‐Closure Access Plan. Incomplete understanding of post‐ Develop Post‐Closure Access Plan. CMU0 closure access required for monitoring Consult with relevant stakeholders to get CMU0 and management of fire, forest agreement. disease, weeds and maintaining access to freehold land. Post‐closure access does not meet completion criteria. Rehabilitation Management Plan. Loss of opportunity for progressive Develop Rehabilitation Management Plan. CMU0 rehabilitation. Consult with relevant stakeholders to get CMU0 Rehabilitation does not meet agreement. completion criteria. Extent of contaminated sites and Increase/decrease in closure cost. Audit of contaminated sites and development of CMU0 requirements for remediation. Relinquishment delayed. remediation plan if required.
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Information Gap Associated Risk Task Relevant Closure Management Unit or Section of Closure Plan Detailed decommissioning plans Unidentified risks result in increased Develop detailed decommissioning plans for RDAs. CMU2 for RDAs. closure cost.
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Figure 4‐1 Precipitation and evaporation at NBG
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Figure 4‐2 Wandoo North geology
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Figure 4‐3 Wandoo South geology
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Figure 4‐4 Regional surface water regime
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Figure 4‐5 Catchment boundaries
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Figure 4‐6 Main water management structures at NBG
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Figure 4‐7 Groundwater level contours (m) September 2011
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Figure 4‐8 Difference in groundwater level pre‐mining (1987) to 2011
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Figure 4‐9 Groundwater salinity contours (TDS mg/L) September 2011
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Figure 4‐10 Difference in groundwater salinity pre‐mining (1987) to 2011
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Figure 4‐11 Vegetation complexes at NBG
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Figure 4‐12 Site‐vegetation types at NBG
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Figure 4‐12 – Site‐vegetation types at NBG ‐ Legend
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Figure 4‐13 Aboriginal heritage sites at NBG
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a) b)
Figure 4‐14 Analysis of waste rock landform placement (a. no secondary constraints; b. existing tenure only)
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Figure 4‐15 SIBERIA modelling with assumed parameters – slope geometries
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Figure 4‐16 SIBERIA modelling with calibrated parameters – slope geometries
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Figure 4‐17 Conceptual waste rock landform cover designs
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Figure 4‐18 Schematic closure flow circuit
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Figure 4‐19 Base case pit lake filling curves
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Figure 4‐20 South pit filling curves for alternative climate scenarios
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Figure 4‐21 South pit filling curves for alternative evaporation rates
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Figure 4‐22 Satellite pit rehabilitation areas
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Figure 4‐23 Tree stocking rate at less than one year
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Figure 4‐24 Trend in tree stocking rate
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Figure 4‐25 Species richness at less than three years
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Figure 4‐26 Trend in species richness
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Figure 4‐27 Trend in diversity
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Figure 4‐28 Understorey species live cover at less than three years
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Figure 4‐29 Understorey species live density at less than three years
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Figure 4‐30 Trend in native understorey species live density
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Figure 4‐31 Trend in native understorey species live cover
4‐99 Newmont Boddington Gold – Closure Plan Stakeholder Consultation
5 STAKEHOLDER CONSULTATION This section details the: Stakeholder engagement process (5.1); and Register of stakeholder engagement and Newmont responses to topics raised by stakeholders (5.2).
Relevant information from stakeholder consultation undertaken by the Shire of Boddington as part of the SuperTowns initiative has also been incorporated into development of this Closure Plan. A summary of the outcomes of the community visioning process is included in Section 5.3.
5.1 Stakeholder Engagement Process Effective closure planning involves bringing together the views, concerns, aspirations, efforts and knowledge of various internal and external stakeholders to achieve outcomes that are beneficial to the operating company and the community that hosts it (ICMM, 2008). Participants in closure planning may hold different views on what can and cannot be achieved in closure, and expectations may vary between stakeholders. Understanding these views and expectations (which may change over time) and formulating with stakeholders a balanced, realistic and achievable closure outcome that can be funded and supported by the relevant parties is a fundamental aspect of closure planning (ICMM, 2008). The process of engagement with internal and external stakeholders may not result in full consensus on closure outcomes, but it should be considered successful if it leads to fully informed decisions.
For NBG a stakeholder engagement process has been developed, which prioritises target audiences and identifies the key issues of concern for each group. The overarching objectives of the stakeholder engagement process are: To identify NBG stakeholders and manage the relationships in a consistent way, including marginalised groups; To provide sufficient information to interested stakeholders such that they are able to make informed decisions, raise issues and concerns and obtain feedback as part of the closure planning process; To establish relationships with key stakeholders that enable ongoing dialogue through implementation of the Closure Plan; and Ensure effective monitoring, measurement and tracking processes for all stakeholder interactions.
Key stakeholders were identified through experience in the Boddington region. The key stakeholders identified were: Department of Environment and Conservation (DEC); Department of Mines and Petroleum (DMP); Department of State Development (DSD); Department of Water (DoW); Officee of th Environmental Protection Authority (OEPA); Traditional Owners; South West Aboriginal Land and Sea Council (SWALSC); Shire of Boddington; Local landowners; Boddington and Dwellingup communities; Local businesses; Employees;
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Service providers; and Regional organisations.
The key tools employed by Newmont to engage with stakeholders in the development of this Closure Plan were: Face‐to‐face meetings with the: o Boddington Gold Mine Environmental Management Liaison Group (BGMEMLG); o Boddington and Dwellingup communities; and o Gnaarla Karla Booja Working Party. Community and employee newsletters; Annual Environmental Report; and Social Impact Assessment.
The target audience, engagement frequency and information provided or sought via each tool is summarised in Table 5‐1. Due to the incorporation of closure planning in life of mine planning for re‐ permitting of expansion of the project, stakeholder engagement for closure was often done in conjunction with that for re‐permitting.
5.2 Stakeholder Engagement Register Stakeholder input aided the development of this Plan throughout the engagement process. Newmont views the continuation of established stakeholder engagement as an integral part of managing closure ofe th site in the future.
The stakeholder engagement activities undertaken over the last two years, topics raised by stakeholders and Newmont responses are summarised in Table 5‐2. Any outcomes of the PER public comment period that are relevant to closure will be subsequently considered and addressed in future versions of this Plan.
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Table 5‐1 Stakeholder engagement tools Stakeholder Target Audience Frequency Information Provided/Sought Engagement Tool Meetings with DEC, DMP, DSD, DoW, 6‐monthly Update on environmental BGMEMLG OEPA activities and performance on site over the previous six months, including closure and rehabilitation. Community Boddington and Quarterly Update on operational meetings Dwellingup performance, including closure communities and rehabilitation when relevant. Meetings with Traditional Owners 6‐monthly Focus on Community Gnaarla Karla Partnership Agreement, Booja Working particularly heritage Party management and future livelihood. The Golden Employees 6‐monthly Activities on site, including Scoop closure and rehabilitation. newsletter Boddington Boddington Approximately NBG activities (including News newsletter community monthly closure and rehabilitation) and upcoming stakeholder engagement opportunities. Annual DEC, DMP, DSD, DoW, Annually Update on environmental Environmental OEPA activities on site, including Report (AER) closure and rehabilitation. Social Impact Local residents, local Every 5 years during Identify positive and negative Assessment businesses, the operation phase social impacts associated with employees and plus 3 years prior to NBG’s presence in the contractors, suppliers, decommissioning. community (including aspects local Indigenous of closure and community community, visioning). Closure focus from government and 3 years prior to institutional decommissioning. stakeholders
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Table 5‐2 Stakeholder engagement register Date Stakeholder(s) Description of Consultation Topics Raised Response 17/3/2010 BGMEMLG 6‐monthly update meeting Opportunity to complete rehabilitation of R4 eastern embankment. Cross section of planned None required. rehabilitation presented. 27/10/2010 BGMEMLG 6‐monthly update meeting Final rehabilitation on the R4 eastern embankment was completed in July. A section of the old 1. Feedback provided at meeting that from a chemical camp site which was scarified in 2008 was hand seeded in July 2010. Steep slopes around the perspective the tailings properties will remain the same. primary crusher, process water pond main gate security and coarse ore stockpilen have bee Geochemistry studies undertaken on the ore body by stabilised with mulch and hydromulch. Graeme Campbell and Associates indicate that the material is very homogeneous. Plan to conduct basement residue trial in the northwest section of F1 RDA. 2. Feedback provided at meeting that on‐site mulch wasn’t used in case of dieback risk. At next BGMEMLG meeting Eugene Bouwhuis (DMP) queried: (13/5/2011), feedback provided that mulch supplier was 1. What quality controls in place with the hydromulch to ensure it is from a disease‐free confirmed as disease free following testing. and weed‐free supplier; and 2. If tailings properties will change as the project progresses. Ian Freeman (DEC) commented: 3. Karri mulch has risks with Armillaria disease. 16/6/2011 BGMEMLG Newmont Boddington Gold Mine Summary provided of: None required. Annual Environmental Report ‐ Rehabilitation strategy; 2010 Completion criteria; Rehabilitation status; Activities undertaken in 2010 (rehabilitation at site of old village, R4 RDA eastern embankment and main embankment); and Rehabilitation monitoring results. October Employees The Golden Scoop Information provided on why closure planning occurs so far in advance of mine closure. None required. 2011 November Local residents, Social Impact Assessment (SIA) Uncertainty of Life of Mine (LOM) planning and lack of communication leads to poor Stakeholder Engagement Plan re‐developed. 2011 local businesses, community understanding and knowledge of mine’s vision for the future. Information on LOM Plan, extension of mine life and approvals employees and process provided via: contractors, Golden Scoop and Boddington News suppliers, local Presentations to Shire, BST and Non‐Government Indigenous Organisations community, Community meetings government and Mail outs institutional Face‐to‐face meetings. stakeholders Summary of SIA outcomes made available to public. 13/5/2011 BGMEMLG 6‐monthly update meeting Overview provided on planned basement residue rehabilitation trial and closure studies in None required. progress. NBG awaiting letter from DMP on submission date for Closure Plan, however aiming for late 2012/early 2013.
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Date Stakeholder(s) Description of Consultation Topics Raised Response 7/11/2011 BGMEMLG 6‐monthly update meeting Information provided on change in submission date for Closure Plan to 31 December 2012 Feedback provided to DEC at meeting: (approved by DMP) and update on closure studies (completion criteria, geochemistry and 1. Outback Ecology is helping with development of completion waste rock management, landform and cover design for waste rock landforms, cover design for criteria. All queries to be addressed to Katina De Sousa RDAs, re‐sampling of rehabilitation trial on oxide residue, design of rehabilitation trial on (Senior Closure Planner). DEC invited to workshop on basement residue, development of Strategic Decommissioning Plan for RDAs, post‐closure site completion criteria conducted on 12/7/2012; and water balance and regional groundwater assessment). 2. Compaction rate is not yet known. Will be tested to check effectiveness of dry placement in residue in trial area instead Grant Lamb (DEC) queried: of placement via spigots. 1. Who is developing completion criteria for the Closure Plan as he would like to be in contact with them prior to plan submission; and 2. What compaction rate is expected for basement residue rehabilitation trial. 6/12/2011 Dwellingup Quarterly community update Community members queried Life of Mine impact on: Feedback provided at meeting that: community meeting 1. Mt Wells 1. No impact on Mt Wells. 2. Noise 2. Noise modelling would occur and NBG Noise Management 3. Water use Strategy Working Group has been convened. 4. Aesthetics 3. Water allocations and peak flow requirements were discussed. Water extraction is compliant with surface water Community member asked if waste rock dump would extend to the river. extraction licence. Water is extensively re‐used through the operations. 4. Visual impact assessment studies commissioned. 5. Waste rock dump would not extend to the river. 7/12/2011 Boddington Quarterly community update Community member indicated that proposed RDA on Saddleback Tree Farms would be very Feedback provided at meeting that: community meeting close to their property and residence. Noise modelling and visual impact assessment studies have been commissioned. General comments were made in relation to likely impact on noise and aesthetics. NBG Noise Management Strategy Working Group has been convened. Community member/Shire Councillor asked if NBG would need to increase water abstraction Water allocations and peak flow requirements were from the Hotham River. discussed. Increase in water harvest (above current licence level) would not be required for the Life of Mine Extenstion Project but it may be considered for the Optimisation Project. NBG has been approached the State Government to determine interest in piping treated waste water from Woodman Point to the mine via Alcoa at Pinjarra. 8/2/2012 Boddington Community announcement via Update on Life of Mine permitting and answers to questions raised at last community meeting None required. community Boddington News on: Operational noise; Vehicle noise and safety; and Visual impact. 21/3/2012 Dwellingup Quarterly community update Information provided on Life of Mine permitting and SIA results. None required. community meeting 22/3/2012 Boddington Quarterly community update Information provided on Life of Mine permitting and SIA results. None required. community meeting 1/5/2012 BGMEMLG 6‐monthly update meeting Information provided on progress on closure related projects (landform and cover design, 2 hour workshop on completion criteria arranged for BGMEMLG. materials management for larger waste rock landforms, rehabilitation materials Consultation to be undertaken on a one‐on‐one basis if required. characterisation and inventory, post‐closure water balance, RDA rehabilitation trials, Preliminary RDA Decommissioning Plan and completion criteria) and asked about preferred format for consultation on completion criteria.
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Date Stakeholder(s) Description of Consultation Topics Raised Response 11/5/2012 Boddington Phone call Request for more information on possible impact of Life of Mine on the value of property. Meeting held with resident to discuss Life of Mine and future resident expansion. 16/5/2012 Boddington Community announcement via Update on Life of Mine referral to EPA. None required. community Boddington News 22/5/2012 Newmont ESR, Workshop on completion criteria Draft completion criteria reviewed. Revision to wording discussed at workshop incorporated into Mining and completion criteria. Revised criteria distributed to attendees plus Technical site General Manager for review. Services Departments 6/6/2012 DEC Email DEC need to be consulted on all aspects of closure planning where DEC estate is involved and is ConsultationC with DE tailored to cover the identified areas. neighbouring NBG’s mine with regard to, but not limited to; final land use, visual impact assessment, flora/fauna management, final land forms, access management, infrastructure removal, rehabilitation and ongoing monitoring. 5/7/2012 DEC Meeting Final land use, visual impact assessment, flora/fauna management, final landforms, access Meeting minutes provided to DEC. management infrastructure removal, rehabilitation and ongoing monitoring, grant of mining tenure over State forest, DEC preference for areas of disturbance to be excised from State forest, classification and management of waste rock and post‐closure use of eth Western Power substation located in State forest. 12/7/2012 BGMEMLG Workshop on completion criteria Draft completion criteria reviewed. Revision to wording discussed at workshop incorporated into completion criteria. Meeting minutes and revised completion criteria distributed to BGMEMLG members for review. 6/8/2012 DMP Email DMP feedback on revised completion criteria. Revision to completion criteria to take into account feedback from DMP where appropriate. Revised completion criteria distributed to BGMEMLG members for review with invite to discuss in person. 15/8/2012 Gnarla Karla Working Party Meeting Overview of closure strategy, post‐closure land use and completion criteria relating to None required. Boodja stakeholder consultation, indigenous heritage and post‐closure access.
GKB Working Party advised that they have the opportunity to provide input to the Closure Plan if desired. GKB Working Group to advise tNewmon of best forum for engagement. 10/9/2012 BGMEMLG Email Members of BGMEMLG provided with: No further comments from DEC (email from Grant Lamb Summary of how DMP feedback on completion criteria addressed; and 10/9/2012) Updated completion criteria to be included in the Closure Plan. The Office of the Environmental Protection Authority has no BGMEMLG members were invited to meet to discuss the updated completion criteria. further comments on the completion criteria (email from Mark Rust 10/9/2012) 9/10/2012 Gnarla Karla Working Party Heritage Site Visit Overview of closure strategy, post‐closure land use, completion criteria relating to stakeholder None required. Boodja consultation, indigenous heritage, post‐closure access and input invited from the Working Party. Meeting minutes distributed to South West Aboriginal Land and Sea Council and GKB Working Party. 11/10/2012 EPA Meeting Discussion on the success of existing or previous rehabilitation works and learnings to be Feedback provided at meeting that this information would be applied to the proposed expansion. provided in the Closure Plan to be submitted with the PER. 12/10/2012 DMP Email and phone call Follow up on whether the DMP will be providing further feedback on the updated completion None required (no response received from the DMP). criteria.
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Date Stakeholder(s) Description of Consultation Topics Raised Response 1/11/2012 BGMEMLG 6‐monthly update meeting Information provided on post‐mining land use, closure objectives and completion criteria, Feedback provided to DMP at meeting: closure strategy and final form of landforms, closure implementation, monitoring and 1. The lined section of the RDA will remain lined. The RDAs maintenance, stakeholder consultation and knowledge gaps. will be water shedding at closure to minimise infiltration of water into the residue. Revegetation of the residue DMP (Eugene Bouwhuis) queried: with native species will also reduce infiltration. 1. How is the lined section of the RDA going to be managed? Will it stay lined?
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5.3 Community Visioning for SuperTowns Initiative SuperTowns is a Royalties for Regions initiative aimed at encouraging regional communities located in the southern half of WA to plan and prepare for the predicted doubling of the State’s population over the next 40 years (Department of Regional Development and Lands, 2011). The aim is to build on the unique character and economic drivers of nominated project towns, and put in place funding structures and planning support for sustainable industry, development, services and infrastructure. The SuperTowns initiative ties in with Newmont’s goal of making Boddington socially and economically stable after closure of the mining operations and NBG is a member of the Project Team (Section 10.4).
The Shire of Boddington undertook a formal visioning process to identify the community’s future aspirations and priorities for their Town and District and to better understand the values and hopes of residents in order to create a great place for people to live, work and visit. The visioning workshops involved participation from residents, community groups, business people, the District High School, the Shires of Boddington, Williams and Wandering and many State Government departments and agencies (120 people participated). Consultation involved public workshops in Boddington, Williams and Wandering, individual discussions, an online survey and information forwarded by individuals direct to the project consultants.
The key findings from the visioning process are summarised in Table 5‐3 with aspects particularly relevant to closure of the NBG operations highlighted. During the visioning process it was recognised that to offset the risk of NBG closing the local economy needs to be diversified, such as: Tourism (Sovereign Hill and Mining Hall of Fame); Gourmet foods (Swan Valley); and Branding (Margaret River).
The following business and industry development opportunities were identified: Mining – value added services; Construction – affordable, green technology; Manufacturing – services to Bunbury and Mandurah; Agriculture – high end produce, gourmet food, wine, agri‐products; Retail – high street convenience, tourism product; Tourism – visitor services, accommodation, food, leisure; and Emerging: o Waste/resource management, renewable energy; o Creative industries; and o Health and well ‐being.
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Table 5‐3 Community visioning for SuperTowns initiative (adapted from Hames Sharley, 2012) Theme Outcomes Economic Workshop participants’ keen to see town grow and proposer. development Locals understand that an increase in population would support more services and business and consequent improvement in infrastructure. It was acknowledged that the lives of the mines (Newmont and BHP‐Billiton) are finite and the economy ofe th district must be diversified, suggestions included tourism and high value‐added agriculture. Challenges understood in attracting businesses that provide or support tourist offerings (accommodation and food). Strength of Many clubs and activities. community Low crime – safe for kids (freedom). Casual country atmosphere. History – family connections. People look out for each other. Strong community spirit. Welcoming community. Good level of volunteerism. Low stress lifestyle. Aging population – how do they stay in town with no facilities and little support. Access to Commercial/Retail – very poor choice, small range of offerings and many items not available (e.g. petrol on Sunday). facilities Bank finance – onerous deposit required for a home loan in ‘Rural zone’. Health services. Residential aged care. Retirement accommodation. Recreation and youth centre. More childcare provision. Transport Lack of public transport to the highway. options Lack of transport between towns in the District. Drive In/Drive Out encourages people to choose to live elsewhere and drive/bus to work.
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Theme Outcomes Sense of Place Quiet peaceful place. Nice scale to town, with room to grow and protect current values. Demolished buildings in the main street – negative impact on streetscape. Desire for stronger main street design guidelines to control look and feel – create something special about the town centre. Infrastructure Poor technology infrastructure (broadband/phone). provision Limited access to medical facilities. Difficulty accessing medical specialists. Keen for a Recreation Centre (need facilities as a place to connect to foster social interaction). No Senior High School – families leave rather than send kids to boarding school. Water supply constraints on larger lots. Housing Key worker housing. Housing affordability. Housing availability. Housing choice – larger lifestyle blocks preferred. High school Without a Senior High School families leave rather than send kids to boarding school. Low quality of education provided in middle years – families are moving away, mine incentive for employees to base in Mandurah or Bunbury and qualify for “Away Schooling”. Environment Importance of environment, trees, river and stars. Promoting the clean green environment. Mines buying up farming country. Governance Increasing expectations of people wishing to be involved in the future development (look and feel) of the place. Social equality in the community – mine workers and others. Emergence of future leaders. Management the transition to a SuperTown. Promoting the District as a great place to live – live in Boddington and FIFO to work. Managing expectations – locals want to see the benefits of growth.
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6 POST‐MINING LAND USE AND CLOSURE OBJECTIVES This section outlines the closure approach for the NBG operations, including the: Post‐mining land use (Section 6.1); Closure aspects and objectives (Section 6.2); and Closure strategy and final form of landforms (Section 6.3).
The post‐mining land use and closure objectives form the basis for the development of completion criteria and performance indicators for the operations. The development of completion criteria is detailed in Section 8.
6.1 Post‐Mining Land Use The post‐mining land use for the NBG operations has not yet been finalised and will continue to be refined as part of the ongoing closure planning process. It is unlikely that a single land use option will be suitable for the area. A flexible approach, in which changing preferences and attitudes for land use can be accommodated, is required due to the long life of the mine, rapid population growth in the region and changing priorities of stakeholders over time. Potential post‐mining land uses have been identified based on: Existing land uses in the area; The expected capacity of the land after completion of rehabilitation activities; Opportunities for use of infrastructure established as part of the mine; and Consultation with stakeholders.
The existing jarrah forest surrounding NBG is managed for multiple land uses, including: Nature conservation; Recreation; Forestry; Water catchment; and Mining activities
Other land uses in the Boddington region include livestock grazing and plantations in cleared areas.
The land uses identified above may be applicable to areas of the NBG operations post‐closure as the rehabilitated landscape evolves, with some land values being achievable before others. Livestock grazing is considered an incompatible post‐mining land use at NBG, except at the accommodation village site, due to risks with destabilising vegetative covers of rehabilitation surfaces.
The return of flora and fauna to disturbed areas and the creation of a compatible forest system will re‐introduce the nature conservation land use to the area. The habitat requirements of black cockatoos and other priority fauna will be considered in the development of rehabilitation prescriptions where relevant. The value of rehabilitation as a feeding habitat can potentially be increased by including a richer mix of Marri in the typical Jarrah forest.
Recreational use of the native forest areas in the Boddington region includes bushwalking, mountain biking, camping and public firewood collection. It is expected that once the rehabilitation has matured and is integrated with the surrounding environment, appropriate recreational land uses could be introduced to the area. These uses would need to be compatible with, and consider the impact upon, the other land uses.
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Forestry is the principal land use of the surrounding native forest, with forestry activities conducted on private land and in State forest. It is expected that once the rehabilitation has matured it can be managed with the surrounding forestry land use.
The land use water catchment refers to the contribution of runoff from the mining operations to streamflow into the Hotham River via the House Brook, Thirty‐Four Mile Brook and Wattle Hollow Brook. Additionally, House Brook, Thirty‐Four Mile Brook and the Hotham River all flow through agricultural areas and have some limited use for livestock at certain times of the year. The Hotham River is a tributary of the Murray River, which flows to the Peel Inlet near Mandurah. Contribution of runoff from rehabilitated areas will not be achieved until it is of suitable quality for release into the environment.
A large proportion of the current mining area is situated on bauxite mining leases controlled by BHP Billiton‐Worsley and Alcoa World Alumina Australia. Thus, some areas of the NBG operations will be used for future bauxite mining.
Other land uses that may be compatible with the post‐closure rehabilitated landscape and infrastructure available include habitat/species management, manufacturing and industrial, water storage and treatment, renewable energy generation and managed resource protection. Population growth in the region and increasing demand for water and power may result in alternative land uses such as water storage and treatment and renewable energy generation being viewed as valuable sustainable land uses for areas of the NBG operations in the future.
The accommodation village exists on privately owned land leased from a farmer. For this area, livestock grazing will be the targeted post‐mining land use. The accommodation village site will be returned to a condition that approximates the pre‐construction land use of agricultural pastoral land.
6.2 Closure Objectives Closure objectives must set out the long term goals for closure outcomes (DMP/EPA, 2011). With respect to the rehabilitation aspects of closure, the EPA proposes the following standard objectives (EPA, 2006): Safe, stable and resilient landforms and soils; Appropriate hydrology; Providing visual amenity, retaining heritage values and suitable rfo agreed land uses; Resilient and self‐sustaining vegetation comprised of local provenance species; Reaching agreed numeric targets for vegetation recovery; and Comprising habitats capable of supporting all types of biodiversity.
The closure objectives for NBG have been developed to support a framework of aspects for which management is fundamental for effective closure of the operations (Table 6‐1). The framework incorporates aspects ranging from physical elements (e.g. stability, drainage, erosion, suitability of materials to support plant growth) through to biological aspects (e.g. vegetation, ecosystem processes, fauna habitat) and post‐closure management. The closure objectives are general goals relating to each aspect which provide a guiding set of principles for progressive rehabilitation and mine closure planning. The closure objectives are supported by completion criteria and a measurement approach (Section 8).
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Table 6‐1 Closure aspects and objectives Aspect Objective Community and other Stakeholders will be consulted in relation to post‐closure outcomes. stakeholders Indigenous heritage features have been identified and will be respected and protected. Appropriate land tenure will be in place prior to relinquishment. Geotechnical stability Landforms will be safe and structurally stable. Infrastructure removal Infrastructure will be removed, except as agreed with key stakeholders, and the area rehabilitated for integration into the surrounding landscape. Topography and drainage Landforms will be consistent with the landscape, will facilitate a return to the regional drainage function and will not adversely affect the surrounding natural environment. Managing mine wastes Mine waste materials with potential for environmental impact are appropriately contained. Contaminated sites will be appropriately managed. Access Retain access as agreed with key stakeholders and restrict access to high risk areas. Surface stability Final landform surfaces develop resistance to erosive forces. Forest disease All practicable measures will be taken to limit the spread of forest disease. Soil fertility and surface The soil profile will be suitable for the development of the target profile ecosystem. Fauna habitat Rehabilitated areas provide appropriate habitat for native fauna. Vegetation Vegetation will resemble that of the region and enable integration into the surrounding landscape. Ecosystem function Ecosystem function will resemble that of target ecosystem.1 Management after closure Rehabilitated areas will be able to be managed as required for the post‐mining land use. 2
6.3 Closure Strategy and Final Form of Landforms To facilitate the planning of closure activities, the site has been divided into domains on the basis of location, environmental and physical attributes and the key activities to be conducted to achieve effective closure. The closure strategy and final form of landforms for each domain is based on: Previous commitments and legal requirements; Feedback received from stakeholders; Location of the landform with respect to: o Visibility; and o Risk relating to public access post‐closure. Volume of the landform and cost associated with altering the final form; Requirement to encapsulate materials with adverse properties;
1 The northern jarrah forest in which the NBG operations are located is a heterogeneous ecosystem. Due to disturbance of the geology during the process of mining and the formation of waste rock landforms and residue disposal areas, the post‐closure ecosystem is likely to be a modified jarrah forest ecosystem, as found by Alcoa World Alumina Australia after rehabilitation of bauxite mines in the northern jarrah forest (Koch & Hobbs, 2007). 2 The major broad scale management strategies applied in the unmined jarrah forest are prescribed burning and silvicultural operations (Burrows, 2004 cited in Grant et al, 2007a).
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Requirement to achieve long term stability of the landform; Type and volume of material available for rehabilitation; Minimisation of long term erosion; Management of surface water; Potential post‐mining use of the landform; and Requirements of the post‐mining land use.
The closure strategy and final form of landforms for each of the domains is described in the following sections. These closure strategies will continue to be reviewed and refined to incorporate improved knowledge and understanding gained through ongoing research, trials and experience.
6.3.1 Mining Areas The mining areas domain covers the main open pits, satellite open pits and the Jarrah Decline. The closure strategy and final form of landforms for each of these areas is described below.
6.3.1.1 Main Open Pits The NBG open pits are of too large a scale to be readily backfilled. Therefore, the final form of the main open pits at the cessation of mining will be a void (Figure 6‐1). Modelling indicates that the pits will fill with water to form pit lakes over a period of approximately 80 years after dewatering operations have ceased.
The closure strategy for the main open pit voids is the formation of interconnected pit lakes by diverting the upper catchment of Thirty‐Four Mile Brook into the Wandoo North pit. The pit voids will fill up to about 235mRL, with an overflow to Wattle Hollow Brook occurring at this level. The pit walls will be left at the as‐mined angle of 25° in oxide and 59° in bedrock. An abandonment bund will be installed around the open pits, consistent with DMP guidelines, to prevent uncontrolled access.
In a country with limited water resources and demand for water continuing to increase as a result of population growth and expansion of mining operations, pit lake water may be of significant potential use to both industry and surrounding communities (Kumar et al, 2009). The potential use of pit lake water is dependent on the water quantity and quality (Doupé & Lymbery, 2005). Although water quality may initially, or eventually, restrict potential uses of pit lake water, current and emerging technologies may enable remediation of these mine waters to a standard that can be used for beneficial purposes such as irrigation, aquaculture, livestock water or industrial water (McCullough & Lund, 2006).
6.3.1.2 Satellite Open Pits The closure strategy for the shallow satellite open pits is backfilling and/or reshaping to achieve external drainage. Slopes will generally be rehabilitated to less than 15°. The landformed slopes will be revegetated with local species of the surrounding jarrah forest. Fauna habitat structures will be established to provide appropriate habitat for native fauna.
The final form of the satellite open pits will be shallow voids that have been shaped and revegetated to be compatible with the surrounding landforms (Figure 6‐2).
6.3.1.3 Jarrah Decline For the Jarrah Decline the closure strategy is to backfill the portal and box cut to blend in with the slopes of the main open pits.
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6.3.2 Waste Rock Landforms For the waste rock landforms, the closure strategy is to create physically stable and safe landforms that that are consistent with the existing variable topography and vegetation. The final form of the waste rock landforms will be as illustrated in Figure 6‐1. The footprint of the landforms has been determined based on the regional topography and surface water drainage. The maximum height of the landforms has been set at 360mRL so as not to exceed the surrounding topography (Mt Wells is in excess of 400mRL).
The waste rock landforms will have a cover to minimise infiltration of water, manage erosion and provide a suitable soil profile for vegetation growth. Surface water from the majority of the rehabilitated landforms will be directed into the final pit voids with the remainder discharging to the Thirty‐Four Mile Brook and Hotham River system when suitable water quality is achieved.
The waste rock landforms will be rehabilitated with native species so post‐rehabilitation the colour, line and texture of the disturbed areas matches that of the surrounding vegetation. Visual impact assessment undertaken for expansion of the project indicates that from key view points along the Bibbulmum Track, Marradong Road and Pinjarra‐Williams Road the visual impact of the waste rock landforms is minimal even during the operation phase (Figure 6‐3 and Figure 6‐5) (ecoscape, 2012). The visual impact of the waste rock landforms becomes even less once they are vegetated (Figure 6‐4 and Figure 6‐6).
6.3.3 Residue Disposal Areas The closure strategy for the R4, F1/F3 and future residue disposal areas is to create water shedding landforms. Runoff will be directed to the Thirty‐Four Mile Brook and report to the North Pit for the R4 and F1/F3 RDAs. For the future RDA, runoff will be directed to Gringer Creek when appropriate water quality is achieved.
The final form of the RDA’s will be relatively flat elevated landforms with some external embankments. The landforms will be rehabilitated and revegetated, with wetlands potentially developing in depression areas (Figure 6‐4). The vegetation cover is likely to resemble the swamp and wandoo site‐vegetation types of the forest found in the jarrah forest. Over time, the vegetation may experience succession towards the site‐vegetation types of the forest surrounding the perimeter of the RDA’s.
6.3.4 Infrastructure and Services The closure strategy for disturbance associated with infrastructure and services is to re‐shape disturbance areas to blend in with the surrounding topography and revegetate with local species of the surrounding jarrah forest. All infrastructure will be removed unless the following is in place: Appropriate tenure; and A signed agreement regarding post‐closure legal responsibility by a third party.
For roads the closure strategy will be removal, unless required for post‐closure management of the site. Power and water lines will be removed unless required or owned by third parties.
6.3.5 Water Management Structures The closure strategy for the water management structures will generally consist of removal and re‐ shaping to blend in with the surrounding topography. Some structures may be retained post‐closure for ongoing management of regional surface water.
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The final form of the outflow channel from Wandoo South open pit to Wattle Hollow Brook will be an open surface water management structure.
6.3.6 Accommodation Village The closure strategy for the accommodation village is to return the site to a condition that approximates the pre‐construction land use of agricultural‐pastoral land. All infrastructure will be removed unless retention of select facilities, amenities or materials is agreed upon with the Owner.
If the sewage treatment plant is not retained, the closure strategy will be removal of all infrastructure and returning the site to a condition that approximates the condition prior to occupying the land.
6.3.7 Temporary Stockpiles The standard closure strategy for temporary stockpiles is removal to natural ground level and re‐ shaping to blend in with the surrounding topography if required.
Bauxite ore that is disturbed during the mining operations will be left in a suitable state for recovery by Worsley when they undertake mining in the area.
6.3.8 Concentrate Storage Shed The closure strategy for the concentrate storage shed located at the Bunbury Port is to sell it to a third party. If the storage shed cannot be sold it will be removed in order to return the area to a condition that approximates the pre‐construction condition.
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Figure 6‐1 Final form of main open pits and waste rock landforms after cessation of mining3
3 Final form of waste rock landforms does not show revegetation.
6‐7 Newmont Boddington Gold – Closure Plan Post‐Mining Land Use and Closure Objectives
Figure 6‐2 Final form of satellite open pits (rehabilitated pits L2 and L3)
6‐8 Newmont Boddington Gold – Closure Plan Post‐Mining Land Use and Closure Objectives
Waste rock landform (beyond) RDA
Figure 6‐3 View from Boonering Hill during operational stage
Waste rock landform (beyond) RDA
Figure 6‐4 View from Boonering Hill after rehabilitation of RDAs and waste rock landforms
6‐9 Newmont Boddington Gold – Closure Plan Post‐Mining Land Use and Closure Objectives
Waste rock landform
Figure 6‐5 View from Pinjarra‐Williams Road during operational stage
Waste rock landform
Figure 6‐6 View from Pinjarra‐Williams Road after rehabilitation of waste rock landforms
6‐10 Newmont Boddington Gold – Closure Plan Identification and Management of Closure Issues
7 IDENTIFICATION AND MANAGEMENT OF CLOSURE ISSUES This section provides a summary of the key findings of the closure risk assessment and management measures for major risks identified
A risk register has been developed for the NBG operations to identify risks and opportunities related to closure. The risk register is updated on an annual basis in accordance with the principals outlined in AS/NZS ISO 31000:2009 Risk Management – Principles and Guidelines. A copy of the risk assessment in included in Appendix 11.
The major risk areas identified for closure of the NBG operations and key management measures are summarised in Table 7‐1. The management measures are included in the relevant closure implementation plan or are incorporated into operational activities where appropriate.
Table 7‐1 Major risk areas and key management measures Risk Description Management Measures Changing stakeholder Undertake ongoing stakeholder consultation. expectations over life of Obtain stakeholder agreement on completion criteria. project. Agreed completion criteria Develop completion criteria for areas where the in situ soil are unachievable at closure. profile is not disturbed based on the results of rehabilitation of satellite pits. Conduct field trials and develop quantitative standards based on results for disturbance areas where in situ soil profile is disturbed. Benchmark completion criteria and rehabilitation against neighbouring mines. Develop completion criteria to level of detail appropriate for the age of the operations and refine as more data becomes available. Undertake monitoring for groundwater, surface water and rehabilitation. Review monitoring program to ensure required data being collected. Track progress against completion criteria in AER. Public safety on landforms Restrict public access via ripping of tracks, bunding, fencing and post‐closure. signage. Re‐shape landforms to reduce slope angle and minimise erosion. Public access to open pit void Restrict public access via ripping of tracks and pit ramps, and underground workings. bunding, paddock dumping top of pit ramp, fencing and signage. Seal portal and obtain sign off by DMP.
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Newmont Boddington Gold – Closure Plan Identification and Management of Closure Issues
Risk Description Management Measures Underestimation of closure Annually revise closure provision. cost. Base closure provision on third‐party rates. Annually internally and externally review closure provision. Identify, record, report and manage contaminated sites. Undertake rehabilitation trials to guide cover design. Obtain stakeholder agreement on completion criteria. Undertake ongoing stakeholder consultation. Include Social Responsibility in closure planning process. Develop detailed landform and drainage design. Operational decisions and Update closure provision annually to reflect current operations. activities compromise closure Integrate closure planning with life of mine planning. outcomes. Regular audit of landform construction against design. Integrate closure into RDA design. Communicate closure strategy to personnel. Develop progressive rehabilitation plan. Inadequate surface water Construct perimeter drains around waste rock landforms to management. prevent release of surface water to surrounding environment. Remove surface water from RDAs. Diversion management plan for Thirty‐Four Mile Brook. Rehabilitate disturbed areas. Develop detailed drainage design for waste rock landforms and RDAs. Excessive erosion of Undertake erosion modelling for design of waste rock landforms landforms. considering outslope design and cover material. Investigate physical and chemical properties of rehabilitation materials. Design drains for appropriate flow volume. Undertake rehabilitation trial for waste rock landforms. Develop quantitative standard for erosion based on results of trials. Develop work instruction for rehabilitation earthworks. Regular audit of landform construction against design. Incorporate closure into landform design. Develop detailed drainage design for waste rock landforms and RDAs.
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Newmont Boddington Gold – Closure Plan Identification and Management of Closure Issues
Risk Description Management Measures Integrity of landform design Include management of surface water in options analysis for compromised by excessive waste rock landforms. erosion and/or settlement. Design drainage on waste rock landforms to minimise erosion. Design drains for appropriate rainfall event. Survey control of construction of drains. Undertake options analysis for surface water management for RDAs. Consider settlement during design of drains for top surface of waste rock landforms. Develop detailed drainage design for waste rock landforms and RDAs. Develop integrated site water management. Delay rehabilitation of RDAs until majority of consolidation has occurred. Excessive infiltration through Investigate physical and chemical properties of rehabilitation covers on waste rock materials. landforms and RDAs. Develop cover design based on material properties and results of trials. Design landforms to be water shedding rather than water retaining. Direct seepage from waste rock landforms to Impacted Water Sump. Successful rehabilitation trial on R4 RDA. Undertake rehabilitation trial on waste rock landform and basement residue. Develop work instruction for rehabilitation earthworks. Monitor seepage and runoff from waste rock landforms and RDAs. Conduct oxide water balance trial. Geotechnical instability of Design of RDAs by a geotechnical engineer. landforms and open pit. Review of RDA design in approval process by DMP. QA/QC of RDA construction. Annual geotechnical audit of RDAs. Prepare civil construction report for each stage of RDA construction. Geotechnical review oft pi design. Visual assessment of open pit and waste rock landforms. Regular audit of landform construction against design.
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Newmont Boddington Gold – Closure Plan Identification and Management of Closure Issues
Risk Description Management Measures Poor rehabilitation Successful rehabilitation trial on R4 RDA and rehabilitation of performance. Hedges RDA. Investigate physical and chemical properties of rehabilitation materials. Investigate properties of native soil profile. Learn from rehabilitation of satellite pits and from Alcoa. Develop covers design based on material properties, vegetation requirements and results of trials. Reconstruct soil profile via application of oxide, topsoil and gravel where required. Apply local provenance seed at rate required for target ecosystem. Cut and germination testing of seed. Apply fertiliser. Plant recalcitrant species. Rip on the contour to break up compaction. Construct fauna habitat structures. Research use of rehabilitation areas by black cockatoos. Develop quantitative standards for rehabilitation based on results of trials and rehabilitation of satellite pits. Undertake rehabilitation trial on waste rock landform and basement residue. Develop Rehabilitation Management Plan. Develop progressive rehabilitation plan. Inadequate management of Geochemical characterisation of waste rock and residue. potentially hostile material. Review classification of non‐acid forming and potentially acid forming material. Develop waste rock and medium grade management plan. Line footprint of waste rock landform with low permeability oxide and direct seepage to Impacted Water Sump. Encapsulate high‐capacity potentially acid forming material. Line supernatant pond of F1/F3 RDA with HDPE and remainder with low permeability clay. Undertake rehabilitation trial on waste rock landform and basement residue. Track placement of waste rock via Fleet Management System (FMS). Regular audit of landform construction against design.
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Newmont Boddington Gold – Closure Plan Identification and Management of Closure Issues
Risk Description Management Measures Medium grade stockpiles not Medium grade not placed within 100 m of edge of landform to located or constructed with leave space for encapsulation. closure considered as it is Survey control of medium grade stockpile. assumed they will be Track placement of medium grade via FMS. processed. Regular audit of landform construction against design. Incorporate medium grade stockpile into waste rock landform design. Develop medium grade management plan which covers processing and non‐processing scenarios. Monitor seepage and surface water runoff from medium grade stockpile. Alteration of surface water Design landforms to re‐establish regional drainage function for regime. Thirty‐Four Mile Brook catchment. Post‐closure discharge from pit lakes to Hotham River via Wattle Hollow Brook after filling. Assess impact of new or expanded RDAs on new catchment areas. Cone of depressurisation from Monitor groundwater levels. dewatering impacts Undertake study on ecological impacts on Hotham River. groundwater and surface Review regional groundwater model and impacts of dewatering. water resources. Decrease in impact post‐closure due to recovery of groundwater levels over the long term. Pit lake water quality poorer Develop post‐closure water balance model based on best data than predicted. available. Ongoing revision of post‐closure water balance model as more information becomes available on quality and quantity of inputs from trials. Personnel injury during Develop decommissioning plan. decommissioning. Update cyanide facilities decommissioning plan. Implement safety procedures developing during operations phase. Use experts for high risk tasks. Ore and potential ore traps Include in decommissioning plan. overlooked during decommissioning.
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Newmont Boddington Gold – Closure Plan Identification and Management of Closure Issues
Risk Description Management Measures Seepage impacts receiving Monitor groundwater and undertake annual hydrological environment. review. Adhere to Newmont policies and standards. Store hydrocarbons in appropriate facilities consistent with Australian standards. Predict volume and quality of water requiring post‐closure treatment with post‐closure water balance model. Geochemical characterisation of waste rock. Develop waste rock and medium grade management plan. Line footprint of waste rock landform with low permeability oxide and direct seepage to Impacted Water Sump. Encapsulate high‐capacity potentially acid forming material. Line supernatant pond of F1/F3 RDA with HDPE and remainder with low permeability clay. Operate seepage recovery network for R4 RDA. Locate RDAs in separate catchment to South Dandalup Dam. Include water treatment in closure provision. Track placement of waste rock via FMS. Develop quantitative standard for groundwater. Install covers on RDAs and waste rock landforms to reduce infiltration. Design landforms to be water shedding rather than water retaining. Update post‐closure water balance model with more refined inputs for seepage rates and runoff from results of trials. Review cost for post‐closure water treatment. Regular audit of landform construction against design. Assess impact of new or expanded RDAs on new catchment areas. Undertake risk assessment of impact to groundwater from R4 RDA. Improve understanding of impact of salt load in RDAs on quality of post‐closure seepage and runoff. Assess requirement for treatment of salinity for RDAs post‐ closure.
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Newmont Boddington Gold – Closure Plan Development of Completion Criteria
8 DEVELOPMENT OF COMPLETION CRITERIA This section describes the completion criteria for the NBG operations.
Completion criteria provide the basis on which successful rehabilitation and mine closure, and achievement of closure objectives are determined (DMP/EPA, 2011). With respect to completion criteria, the Strategic Framework for Mine Closure (ANZMEC/MCA, 2000) advises that: Completion criteria are specific to the mine being closed, and should reflect its unique set of environmental, social and economic circumstances; Completion criteria are the basis on which successful reclamation is determined, and should be developed in consultation with stakeholders. This ensures that there is broad agreement on both the end land use objectives and the basis for measuring the achievement of that objective. Ideally, completion criteria should reflect the specific environmental and socio‐economic circumstances of the site; and Completion criteria should be flexible enough to adapt to changing circumstances without compromising the agreed end objective. This provides certainty of process and outcome (relinquishment of tenement when the conditions have been met). There should be an agreed process for the periodic review and modification of completion criteria in light of improved knowledge or changed circumstances.
For the NBG operations completion criteria have been developed for the: Mine operations (8.1); and The accommodation village (8.3).
Development of completion criteria for NBG has taken into account (Appendix 12): Closure objectives and post‐mining land use; The physical environment and consequences of permanent changes to landforms, soils and hydrology; Existing completion criteria; Legal requirements and obligations; Newmont Environmental Policy and standards; Feedback from stakeholders; and Completion criteria of other sites in the south‐west region of WA, such as the Ludlow and Jarrahdale mines.
8.1 Completion Criteria – Mine Operations The closure completion developed for the mine operations at NBG consists of a framework of aspects supported by closure objectives, completion criteria and measurement approaches (Table 8‐1). As physical elements of rehabilitated landforms are planned and constructed before biological components can be established the framework of completion criteria relate to three sequential phases: Planning and landform construction; Surface preparation and vegetation establishment; and Monitoring, remediation and relinquishment.
The success of revegetation is typically compared against natural (un‐mined) analogues, which is the approach taken for the completion criteria framework. The northern jarrah forest in which the NBG operations are located is a heterogeneous ecosystem. Different jarrah forest site vegetation types exist (Havel, 1975) which are the result of the underlying geology and consequent moisture and nutrient conditions of the soils. Due to disturbance of the geology during the process of mining and
8‐1 Newmont Boddington Gold – Closure Plan Development of Completion Criteria
the formation of waste rock landforms and residue disposal areas, the post‐closure ecosystem will never be identical to the pre‐mining state. The post‐closure ecosystem is likely to be a modified jarrah forest ecosystem, as found by Alcoa World Alumina Australia after rehabilitation of bauxite mines in the northern jarrah forest (Koch & Hobbs, 2007).
8.2 Review of Completion Criteria Completion criteria developed now may no longer be appropriate at the time of closure due to: Changes in environmental and social values (e.g. due to the impacts of climate change or changes to population dynamics or land use); Improvements in the closure knowledge base; Changes in stakeholder expectations; and Modifications to the mine plan having a significant impact on closure strategies and outcomes.
For these reasons, development of completion criteria for NBG will be an iterative process and will continue to be reviewed and refined overe the lif of the mine. Further refinement or variations to the completion criteria will be documented in the reviewed Closure Plan to be resubmitted every three years. Agreement with stakeholders on quantitative standards developed will be reached through ongoing consultation, refinement of the Closure Plan and resubmission every three years.
8‐2 Newmont Boddington Gold – Closure Plan Development of Completion Criteria
Table 8‐1 Completion criteria framework for mine operations Aspect Objective Phase1 Completion Criteria Measurement Approach Quantitative Standard Community and Stakeholders will be consulted in relation Phase 1 As set out in Social Responsibility Plan, key Evidence of stakeholder consultation Compliance with Social Responsibility Plan and other to post‐closure outcomes. stakeholders will be provided with the activities prior to. closure Community Partnership Agreement with Gnaala Karla stakeholders opportunity to provide input which will be Booja Traditional Owners. incorporated in the Closure Plan where feasible. Indigenous heritage features have been Phase 1‐3 Heritage features will be managed in Review against agreed outcomes with Compliance with NBG Cultural Heritage Management identified and will be respected and consultation with stakeholders and in stakeholders and NBG Cultural Heritage Plan and outcomes agreed with stakeholders. protected. compliance with NBG Cultural Heritage Management Plan. Management Plan. Appropriate land tenure will be in place Phase 1‐3 In collaboration with the Department of Review of areas of mining disturbance and No waste rock landforms, residue disposal areas or prior to relinquishment. Environment and Conservation (or equivalent tenure. open pits located in State forest at relinquishment regulatory agent), areas disturbed by mining unless agreed with Department of Environment and excised from State forest. Conservation (or equivalent regulatory agent). Appropriate tenure will be in place for gazetted Review areas of gazetted roads, Tenure appropriate to post‐closure land use. Signed roads and any infrastructure transferred to a infrastructure transfer and tenure. agreement in place regarding post‐closure responsibility third party prior to relinquishment or prior to transfer of infrastructure to a third party. handover. Geotechnical Landforms will be safe and structurally Phase 1 Final landforms and constructed drainage Evidence that final landform construction Compliance with approved designs and specifications. stability stable. features conform to approved designs and meets approved designs and specifications. specifications which incorporate appropriate Review undertaken against Newmont factors of safety to ensure design intent is standards. maintained for the long term. Phase 1 A geotechnical review of each residue disposal Evidence of acceptance from State Mining Acceptance of geotechnical review and final as‐built area and waste rock landform by an Engineer (or equivalent) of residue disposal documentation by State Mining Engineer (or appropriate specialist is accepted by the State area and waste rock landform as‐built equivalent). Mining Engineer (or equivalent), on completion reports. of decommissioning works. End of Permanent landforms are not located within Review zone of potential pit instability and Acceptance of geotechnical review by State Mining Phase 1 the zone of potential pit instability. landform placement by an appropriate Engineer (or equivalent). specialist. Infrastructure Infrastructure will be removed, except as Phase 2 Infrastructure is removed from site or buried, Review infrastructure removal works. Infrastructure removed unless otherwise agreed and removal agreed with key stakeholders, and the area except where an asset transfer agreement is in asset transfer agreement in place for infrastructure rehabilitated for integration into the place with key stakeholders for retention. retained. surrounding landscape. Topography and Landforms will be consistent with the Phase 1 Landforms will fit within the surrounding Survey of height (mRL). Landforms will not exceed an average maximum height drainage landscape, will facilitate a return to landscape in terms of height and where of 380mRL. regional drainage function and will not practicable in terms of overall topography. adversely affect the surrounding natural Phase 3 Regional surface drainage to downstream Review of designs and specifications. Landform design and placement minimises downstream environment. environments is not prevented following the effects. completion of rehabilitation works. Phase 3 Runoff water quality will be suitable for the Water analyses for at least three years prior Runoff water exiting mining areas to comply with receiving environment. to release of water to the environment. agreed water quality guidelines. Managing mine Mine waste materials with potential for Phase 1‐3 Potentially hostile wastes are identified, Evidence of materials characterisation and Compliance with designs and management plans. wastes environmental impact are appropriately managed and contained within landforms audit of mine waste management and contained. according to approved landform design and containment within landforms in relation of mine waste management plans. approved designs.
1 Phase 1 – Planning and landform construction; Phase 2 – Surface preparation and vegetation establishment; Phase 3 – Monitoring, remediation and relinquishment.
8‐3 Newmont Boddington Gold – Closure Plan Development of Completion Criteria
Aspect Objective Phase1 Completion Criteria Measurement Approach Quantitative Standard Monitoring groundwater throughout Groundwater quality to comply with agreed water landform construction and until quality guidelines. relinquishment. Contaminated sites will be appropriately Phase 2 Contaminated sites will be managed in Audit of contaminated sites. Compliance with Contaminated Sites Act 2003. managed. 2 accordance with the Contaminated Sites Act 2003. Access Retain access as agreed with key Phase 1 Light vehicle access on to bauxite stockpiles is Audit of bunds against Department of Mines Bund construction compliant with Department of Mines stakeholders and restrict access to high risk restricted by bunds. and Petroleum guidelines. and Petroleum guideline Safety Bund Walls around areas. Abandoned Open Pit Mines (DoIR 1997). Phase 2 Access maintained according to a Post‐Closure Review against agreed Post‐Closure Access Compliance with Post‐Closure Access Plan. Access Plan agreed with key stakeholders, Plan. including consideration of ongoing monitoring, and management of fire, forest disease, weeds and maintaining access to freehold land. Phase 2 Access roads not required for agree post‐ Review against agreed Post‐Closure Access Compliance with Post‐Closure Access Plan. closure access are rehabilitated. Plan. Phase 2 Access to open pits is restricted by Audit works against Department of Mines Compliance with Department of Mines and Petroleum abandonment bunds, built to regulatory and Petroleum guidelines and Newmont guideline Safety Bund Walls around Abandoned Open guidelines and Newmont Standards. Standards. Pit Mines (DoIR 1997) and Newmont Standards. Surface stability Final landform surfaces develop resistance Phase 1 Landform slope parameters and material Review slopes and surface profile against Compliance with approved landform designs. to erosive forces. characteristics are consistent with those set approved landform designs. out in approved landform designs. Phase 2 Final surface materials and treatments, and Review final surfaces and drainage controls Compliance with approved landform designs. drainage control structures, as matched to the against approved landform designs. characteristics of the slope and are consistent with those set out in approved landforms designs. Phase 3 Erosion features should not threaten the Conduct erosion inspection following No uncontrolled water runoff. Quantitative standard to integrity of landform design, and not create completion of rehabilitation works, and be developed based on outcomes of rehabilitation hazards that may unreasonably impede land continued observation until relinquishment. trials. management. Forest disease All practicable measures will be taken to Phase 1‐2 Management strategies applied during soil Review Land Management Plans to ensure Areas mapped for Phytophthora cinnamomi and limit the spread of forest disease. stripping, stockpiling and replacement to disease mapping is incorporated. Armillaria within 12 months prior to disturbance. minimise disease spread from soils known to Review of landform design and Rehabilitation planned so that no runoff from contain forest disease. specifications. Phytophthora cinnamomi infected areas entering areas rehabilitated with disease‐free soil. Review of topsoil management practices and Topsoil from areas with incidence of Phytophthora Rehabilitation Management Plan. cinnamomi and Armillaria managed separately from disease‐free soil and not place upslope of disease‐free soil. Phase 2‐3 There is an adequate establishment of native Audit seed mixtures and conduct monitoring For satellite pits and areas with minimal disturbance of tree species on rehabilitation that are resistant in accordance with current monitoring the in situ soil profile: at least 100 stems/ha of resistant to Phytophthora cinnamomi. regime. native tree species to be present within the first 12 months. For waste rock landforms, residue disposal areas and areas of significant disturbance of the in situ soil profile: standard to be defined based on outcomes of rehabilitation trials.
2 Management of landfills will be managed in accordance with the Contaminated Sites Act 2003.
8‐4 Newmont Boddington Gold – Closure Plan Development of Completion Criteria
Aspect Objective Phase1 Completion Criteria Measurement Approach Quantitative Standard Soil fertility and The soil profile will be suitable for the Phase 2 A suitable soil profile is in place to facilitate Review rehabilitation works against Soil profile to consist of topsoil to a thickness of 10 cm surface profile development of the target ecosystem.3 plant establishment and growth, as defined in approved Rehabilitation Management Plan. and subsoil gravel to a depth of at .least 30 cm approved Rehabilitation Management Plan. Rehabilitation areas have been ripped sufficient to remove compaction and create surface roughness. For satellite pits and areas with minimal disturbance of the in situ soil profile: rehabilitation areas ripped to a depth of 1.5m. For waste rock landforms, residue disposal areas and areas of significant disturbance of the in situ soil profile: standard to be defined based on outcomes of rehabilitation trials. Fertiliser has been applied at an appropriate rate. Fauna habitat Rehabilitated areas provide appropriate Phase 2‐3 Fauna habitat structures have been established Review of rehabilitated areas. An average of one fauna habitat per hectare re‐ habitat for native fauna. on rehabilitated areas. established across the reconstructed landscape. Phase 2‐3 On maturity, vegetation will provide foraging Review seeding list in relation to species Proportion of plant species with attributes contributing and longer term potential nesting habitat for composition and seed quality, and confirm to Black Cockatoo habitat resembles that of the target Black Cockatoos. with vegetation monitoring following the ecosystem. second winter after seeding. Vegetation Vegetation will resemble that of the region Phase 1 Investigate strategies to encourage recruitment Review of research programs. Demonstrated research and/or trials on establishment and enable integration into the of priority and recalcitrant flora into of priority and recalcitrant species in rehabilitation. surrounding landscape. rehabilitated areas to levels consistent with target ecosystem. Phase 2 Viable seed has been broadcast at rates Review seeding list in relation to seed quality For satellite pits and areas with minimal disturbance of sufficient to achieve the target ecosystem. and confirm with vegetation monitoring the in situ soil profile: vegetation should include trees Seed mix to contain at least 60 native forest within the first 12 months. (≥400/ha), legumes (≥4,000/ha) and other understorey species supplemented by seedlings. plants (≥10,000/ha). For waste rock landforms, residue disposal areas and areas of significant disturbance of the in situ soil profile: standard to be defined based on outcomes of rehabilitation trials. Phase 3 Species richness to resemble that of the target Review seeding list and conduct vegetation For satellite pits and areas with minimal disturbance of ecosystem as defined in the Rehabilitation monitoring within the first three years. the in situ soil profile: species richness to achieve at Management Plan. least 27 species/80m2. For waste rock landforms, residue disposal areas and areas of significant disturbance of the in situ soil profile: standard to be defined based on outcomes of rehabilitation trials. Phase 3 Populations of key plant groups will be self‐ Measurement of soil seed bank. Viable seed of trees, legumes and other understorey sustaining. plants will be present in soils at levels sufficient to maintain these key groups. Phase 1‐2 NBG fire component of the Land Management Review of Land Management Plan and Compliance with Land Management Plan. Plan, including response capability, is adequate response capability. for rehabilitation protection. Ecosystem Ecosystem function will resemble that of Phase 3 Retention and availability of critical ecosystem Assessment of infiltration and nutrient Measures of infiltration and nutrient cycling are function target ecosystem. resources will resemble that of the target cycling through appropriate analysis. adequate to achieve target ecosystem. Quantitative ecosystem as defined in the Rehabilitation standard to be developed based on outcomes of Management Plan. rehabilitation trials.
3 The target ecosystem will consist of the local species which grow best in the modified soil profile created. The target ecosystem will be defined in the Rehabilitation Management Plan for NBG based on the outcomes of rehabilitation trials.
8‐5 Newmont Boddington Gold – Closure Plan Development of Completion Criteria
Aspect Objective Phase1 Completion Criteria Measurement Approach Quantitative Standard Management Rehabilitated areas will be able to be Phase 3 Rehabilitation is of an age where it has the Age of revegetation as determined through The site is capable of regeneration after being burnt as after closure4 managed as required for the post‐mining potential to regenerate after a wildfire. research. part of fire management within the surrounding forest. land use. Phase 3 Weed populations do not required specific Visual inspection and quantitative Density of weed species is less than target ecosystem, management above that of the surrounding monitoring where appropriate. as defined in the Rehabilitation Management Plan. land.
4 The aspect Management after closure addresses developing the land appropriately for the post‐mining land use. After relinquishment by Newmont rehabilitated areas are expected to be managed by the new owner(s) as per the surrounding jarrah forest.
8‐6 Newmont Boddington Gold – Closure Plan Development of Completion Criteria
8.3 Completion Criteria – Accommodation Village The Accommodation Village is located on privately owned farm land. The Accommodation Village site will be returned to a condition that approximates the pre‐construction land use of agricultural pastoral land in consultation with the land owner in accordance with the following completion criteria: 1. Removal of all infrastructure on the land or, in consultation with the Owner, retention of select facilities, amenities or materials in accordance with the terms and conditions of the compensation agreement; 2. Rehabilitation of all disturbed areas to a condition that approximates that prior to occupation of the site; 3. Identification and rehabilitation of any contaminated areas, including provision of evidence of notification and proposed management measures to relevant statutory authorities; 4. A certificate signed by the Owner releasing Boddington Gold Mine Management Co Pty Ltd of any future liability associated with the site upon attainment of the following completion criteria: a. Ensure land is physically safe for people to access and does not pose a human health risk; b. Re‐establishment of vegetation within disturbed areas of land with plant species using a seed mix and native tree species selected in consultation with the Owner; and c. Up to 4 live trees per hectare (126 total trees) shall exist on the land to achieve the pre‐disturbance tree density of the land. Planting to supplement the removal of trees during construction of the Accommodation Village shall be coordinated with the Owner.
8‐7 Newmont Boddington Gold – Closure Plan Financial Provision for Closure
9 FINANCIAL PROVISION FOR CLOSURE This section summarises the methodology for calculating and updating the closure cost estimate.
Newmont Mining Corporation recognises that it is essential to its long term financial planning that all costs associated with closure and rehabilitation are systematically, accurately and consistently evaluated and reported. On an individual site basis closure costs are estimated annually through Newmonts’ CRTT process. The CRTT process uses templates to ensure that the methodology used to estimate closure and rehabilitation costs is consistent across all Newmont interests. As described below, share market reporting requirements for closure and rehabilitation costs are legally binding, with a requirement to meet rigorous standards and be subject to independent auditing.
As well as estimating LOM closure costs, the CRTT process serves as Newmont’s governance model for compliance with U.S. Financial Accounting Standard Board’s Statement No. 143 (FASB 143) regarding closure and rehabilitation liability reporting. FASB 143 liability estimates are required to legally comply with the regulations dictated by the United States Generally Accepted Accounting Principles (“US GAAP”) and the Securities and Exchange Commission (“SEC”) reporting requirements. The estimate is filed with the SEC as part of the Company’s Annual Report on Form 10‐K in line items “Other Current Liabilities” and “Reclamation and Remediation Liabilities”. It is meant to accurately represent an accounting estimate of the end of year “On‐The‐Ground” liability appropriately distributed over the life of the asset (the mine). Annual cash flows are used to calculate a single line term net present value of the liability in order to communicate this information to the current and potential company shareholders through the annual report. Each year the CRTT estimates are rigorously reviewed at a corporate level to ensure that the estimated costs are realistic and can be justified and are audited by an independent registered public accounting firm. Newmont accrues funds on an annual basis for closure and rehabilitation liabilities through charges to earnings.
The methods of calculation used in the CRTT templates are based on: First‐principle approaches for volume and distance calculations and productivity estimation; and Third party cost rates.
Productivity calculations used in the templates are largely derived from published sources such as the Caterpillar Performance Handbook. Post‐closure monitoring and maintenance obligations are also accounted for in the calculation of the closure and rehabilitation cost.
Within the Newmont CRTT templates closure costs are calculated on an area basis (Table 9‐1). Activities that are costed for each area are based on the requirements of the Closure Plan and may include those listed in Table 9‐1.
The NBG closure and rehabilitation cost will continue to be reviewed and refined on an annual basis or where a significant project change has occurred to take into account: Inflation; Additional site data collected as part of the monitoring program, trials, investigations and studies; Site experience with closure and rehabilitation activities; Improvements in industry knowledge and practices; Modifications to the Plan and work requirements; and Changes to regulatory or financial reporting requirements.
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Newmont Boddington Gold – Closure Plan Financial Provision for Closure
Assumptions and parameters used during preparation of the closure and rehabilitation cost estimate for NBG are: Mining ceases in 2041; Mineral processing ceases in 2041; All medium‐grade stockpiles will be processed and therefore rehabilitation of these will not be required; Current rehabilitation techniques are used to the end of mine life; Costs have been estimated by the best available means, which includes historic cost data available at NBG and experience at other operations; Nominal values based on experience have been used where costs were not available; and The costs comprise only those costs over and above normal mining costs.
Table 9‐1 – Newmont CRTT template cost areas and potential closure activities Newmont CRTT Template Cost Area Potential Closure Activities Roads, railroads and airstrips Pushing in shoulders, transport and application of rehabilitation materials, ripping, seeding, fertilising Drill sites, drill pads and exploration Audit of exploration disturbance trenches Drill hole abandonment Removal of casing and infrastructure, backfilling Open pits, borrow areas and trenches Re‐profiling, application of rehabilitation materials, ripping, seeding, fertilising, construction of abandonment bunding Portals/Adits underground mines Backfilling, transport and application of rehabilitation materials, ripping, seeding, fertilising Non‐process ponds and reservoirs Removal of infrastructure and embankments, establishment of spillway, re‐profiling, transport and application of rehabilitation materials, ripping, seeding, fertilising Water treatment Power costs, operating costs, maintenance costs, reagent consumption, by‐product handling and disposal Waste rock landforms Re‐profiling, transport and application of rehabilitation materials, ripping, seeding, fertilising Residue disposal areas Transport and application of rehabilitation materials, ripping, seeding, fertilising Surface drainage Clearing, excavation, rock lining, installation of geofabric Demolition of facilities ‐ Monitoring Water, soil, rehabilitation, fauna Consultants costs Geotechnical assessment, annual reporting, model validation, data management, relinquishment reporting Socio‐economic Employee re‐training, career outplacement services, community consultation/programmes Mobilisation and demobilisation ‐ Contingency ‐
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Newmont Boddington Gold – Closure Plan Closure Implementation
10 CLOSURE IMPLEMENTATION This section provides detailed information on the implementation of closure and rehabilitation activities at NBG, including: Domains for mine closure planning and implementation (Section 10.1); Closure implementation strategies and key activities for each domain and the standard rehabilitation approach (Section 10.2); Closure Implementation Plans for each domain that detail activities to be completed during the operational, decommissioning, monitoring and post‐closure phases (Section 10.3); Refinement of the Social Responsibility Plan to address the potential impacts of closure (Section 10.4); and Development of a workforce transition program to ensure that employees are provided with information, support and training to minimise the effect of the closure of the operations (Section 10.5).
10.1 Closure Management Units To facilitate the planning of closure activities and the development of Closure Implementation Plans, the site has been divided into nine domains referred to as Closure Management Units (CMUs). The CMUs have been identified based on location, environmental and physical attributes and the key activities to be conducted in each location to achieve effective closure of the NBG operations.
The CMUs identified for NBG are summarised in Table 10‐1 and shown in Figure 10‐1.
Table 10‐1 NBG Closure Managements Units CMU Name Features CMU0 Whole of Operations All of site, exploration drill holes CMU1 Mining Areas Main open pits, satellite open pits, Jarrah Decline CMU2 Residue Disposal Areas R4 RDA, F1/F3 RDA, future RDA, Wattle Pit area CMU3 Waste Rock Landforms Waste rock landforms 7, 8, 9, 10, 11, 12 and Q3 South CMU4 Infrastructure Mill, primary crusher, conveyor, workshops, offices, security gate, fuel farm, magazine, explosives/emulsion batching plant, core yard, laydown areas, roads and tracks, warehouse, landfill, monitoring bores, production bores, booster pump station, Caro’s acid plant, Hotham River pump station CMU5 Water Management Water supply reservoirs, pit lake outflow channel, dams and Structures turkeys nests, drainage control structures CMU6 Services Power lines, water lines (including residue delivery and decant recovery lines) CMU7 Accommodation Village Accommodation village and sewage treatment plant CMU8 Temporary stockpiles Bauxite, gravel, oxide and topsoil stockpiles, medium grade ore stockpile, ROM pad CMU9 Concentrate storage shed Concentrate storage shed at Bunbury Port.
10‐1 Newmont Boddington Gold – Closure Plan Closure Implementation
10.2 Closure Implementation Strategy and Standard Rehabilitation Approach This section outlines the closure implementation strategy for each CMU (Table 10‐2) and the standard rehabilitation approach (Table 10‐3) that will generally be utilised during closure of the NBG operations in order to ensure that the requirements of the closure objectives and post‐mining land use are met. The implementation strategy and standard rehabilitation approach form the basis for decommissioning and rehabilitation activities included in the Closure Implementation Plans for the CMUs. Where this standard approach will not be followed for specific areas, details will be included in the relevant Closure Implementation Plan.
The standard rehabilitation approach utilised atG NB is based on previous experience (Section 4.2) and learning’s from neighbouring mine sites (Section 4.3). Rehabilitation prescriptions will vary across the NBG site because of the different characteristics of the underlying substrates and rehabilitation objectives. However, the rehabilitation approach summarised in Table 10‐3 is likely to be applicable to most disturbance areas. Where non‐standard rehabilitation techniques are required this will be specified in the relevant Closure Implementation Plan and detailed in work instructions prior to activity commencing.
All closure work will be conducted in accordance with NBGs’ Health and Safety Policy, procedures and work instructions. Specific Safety Management Plans will be developed before undertaking hazardous works such as dismantling and demolition of plant sites. The requirements of the Cultural Heritage Management Plan will also be considered and addressed throughout the closure process.
Practical planning for sudden closure cannot be done in detail, as the circumstances surrounding the reasons for closure may dictate possible closure scenarios (ICMM, 2008). In the case of unplanned closure, the standard decommissioning and rehabilitation approach during the care and maintenance period will consist of: The preparation, preservation and care and maintenance of plant and equipment; and Disposal of redundant assets not required.
Specific tasks for the case of unplanned closure are included in the Closure Implementation Plans.
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Table 10‐2 Closure implementation strategy Domain Area Closure Implementation Strategy Whole of Contaminated sites Manage in accordance with Contaminated Sites Act 2003 and Contaminated Sites Regulations 2006. Operations Exploration drill Collar and plug hole. holes Mound dirt over plugged hole. Rip and seed with local provenance species if required. Mining Areas Main open pits Where possible and practicable backfill with waste rock. Construct abandonment bunds from competent rock. Satellite open pits Backfill and/or re‐shape to achieve external drainage. Cover with topsoil and gravel. Rip on the contour and seed with local provenance species. Underground mines Salvage any saleable plant/equipment. Seal off all access points. Residue Disposal R4, F1/F3 and Continue dewatering until active management is no longer required for groundwater levels and quality to Areas future RDAs meet agreed completion criteria. Backfill all seepage collection trenches and ponds when no longer required. Profile outer embankments of landform to reduce long term erosion and promote stability. Construct water management structures. Cover embankments and surfaces with gravel and topsoil. Rip on the contour and seed with local provenance species. Seepage recovery Retain selected bores for compliance monitoring. bores Backfill remaining bores with appropriate material. Waste Rock Waste rock Selectively place waste rock for encapsulation of material with adverse properties. Landforms landforms 7, 8, 9, Profile outer batters of landform to reduce long term erosion and promote stability. 10, 11 and 12 Construct water management structures. Cover outer surface with oxide, graveld an topsoil. Rip on the contour and seed with local provenance species.
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Domain Area Closure Implementation Strategy Infrastructure Mill, primary Salvage remaining gold in applicable areas. crusher, conveyor, When no longer required, dismantle/demolish all structures to below ground level unless specified otherwise workshops, offices, by appropriate approvals. security gate, Break up concrete and bury or dispose of. warehouse, core Break up scrap metal and recycle where possible. yard, laydown, fuel The strategy for usable infrastructure and plant will be: farm, magazine, Offer to other Newmont sites; explosives/emulsion Consult with community about possible use; and batching plant, Auction to the public. booster pump Signed agreements must be in place for all infrastructure to be retained. station, Hotham Place saleable materials/plant in sales yard and auction. River pump station, Audit contaminated sites and develop remediation plan if required. Caro’s acid plant Re‐shape surface and sheet with rehabilitation material where required. Deep rip on the contour and seed with local provenance species. Monitoring bores Retain selected bores for compliance monitoring. Backfill bores that are no longer required with appropriate material. Production bores Decommission and retain as sealed bores. Roads and tracks Remove windrows and reinstate natural drainage function. Retain some sumps and reconfigure as water holes for fauna. For sealed roads: Rip and dispose of material unless specified otherwise by appropriate approvals; and Mine compacted layer and re‐place material as loose fill. For unsealed roads: Mine compacted layer and re‐place material as loose fill. Sheet with rehabilitation material. Rip on the contour. Seed with local provenance species.
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Domain Area Closure Implementation Strategy Water Lined water storage Slash liner and bury during backfilling of dam. Management dams Re‐shape surface and sheet with rehabilitation material. Structures Rip on the contour and seed with local provenance species. Unlined water Re‐shape surface and sheet with rehabilitation material. storage dams Rip on the contour and seed with local provenance species. Water supply tanks Remove tank and either sell or dispose of. Break up concrete base and bury or dispose of. Sheet with rehabilitation material if required. Rip on the contour and seed with local provenance species. Services Pipelines, For above ground lines, remove and sell where possible or dispose of unless specified otherwise by powerlines appropriate approvals. For buried pipelines, leave buried unless they pose a future risk. Reinstate areas along routes and revegetate as appropriate. Accommodation Accommodation Remove all infrastructure or, in consultation with the Owner, retain select facilities, amenities or materials in Village village and sewage accordance with terms and conditions of the compensation agreement. treatment plant Identify and rehabilitate any contaminated areas, including provision of evidence of notification and proposed management measures to statutory authorities. Rehabilitate all disturbed areas to a condition that approximates that prior to occupation of the site. Re‐establish vegetation within disturbed areas of land with plant species using a seed mix and native tree species selected in consultation with the Owner. Temporary Medium grade ore Either process at end of mining or rehabilitate in situ. Stockpiles stockpile and ROM Remove all contaminated material and sheet with rehabilitation material where required. pad Deep rip on the contour and seed with local provenance species. Bauxite stockpiles Leave in a suitable state for recovery by Worsley. Install bunding to restrict access. Scale to make safe and round off top edge. Gravel, oxide and Remove to natural ground level. topsoil stockpiles Re‐shape and sheet with rehabilitation material. Rip on the contour and seed with local provenance species.
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Table 10‐3 Standard rehabilitation approach Aspect Standard Rehabilitation Approach Timing Spreading of topsoil and gravel should be conducted in the months between October and March, although extension of dry conditions may allow spreading to occur beyond this time frame. Ripping should be restricted to dry soil conditions to maximise the effectiveness of ripping. Seeding is to be undertaken in summer/autumn after ripping. Planting of seedlings and recalcitrant/priority species is to be undertaken in winter. Fertilising should be conducted in August/September after planting. Dieback If it is necessary to spread dieback infected soil it should be applied to the lowest infected soil point of the rehabilitated landscape to minimise the risk of disease spread. Strict hygiene practices will need to be observed. Seed Seed must be collected from the native forest surrounding NBG including: o George, Wells, Duncan, Bombala, Hedges and Gyngoorda forest blocks; o NBG property; and o Vegetation on private land bounded to the west by the aforementioned forest blocks and to the east by a line that extends from Crossman to the Saddleback timber reserve (though excluding the Saddleback timber reserve). Seed will not be accepted from outside the specified provenance areas and cannot be mixed with seed from outside these areas. Seed is to be cut and germination tested for calculation of quantities required for the seed mix and rate of application. Seed is to generally cast at a rate of approximately 3 kg/ha (~1 kg/ha legumes, 0.9 kg/ha trees and 1.1 kg/ha understorey species). Seeding areas should have grids surveyed to ensure uniform seed application. Seedlings Tree seedlings should be applied at a rate of between 200 and 400 stems/ha, to provide reliable and rapid tree cover. Recalcitrant/ Recalcitrant/priority flora shall be incorporated into rehabilitation areas as priority successful propagation methods are developed (subject to availability and species geographical suitability of the rehabilitation landscape). Fertiliser Phosphate‐based fertiliser is usually spread via helicopter or hand at a rate of approximately 450 kg/ha in August and September. Planted seedlings are hand fertilised with Diammonium Phosphate fertiliser tablets. Fauna Fauna habitats should be created at an average density of one per hectare habitats (subject to availability of material and accessibility of rehabilitation area). Fauna habitats should be formed from a variety of materials, including piles of rocks, hollow logs, high limbs, nesting boxes, tree stumps and other scattered forest debris.
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10.3 Closure Implementation Plans The Closure Implementation Plan for each CMU comprises the following information: A description which includes: o The features of the CMU; o Area of disturbance; o Current status; o Closure date; o Key potential closure risks; o Potential post‐mining land use; o Closure strategy; o Landform design (where applicable); o Rehabilitation prescription; and o Completion criteria. Timing and responsibility for activities to be completed in the following areas; o Planning and reporting; o Construction; o Rehabilitation; and o Decommissioning. Unplanned closure activities.
Monitoring, remedial activities and maintenance programmes for each CMU are covered in Section 11. Identification and management of information gaps is covered in Section 4 with tasks included in the Closure Implementation Plan for the appropriate CMU.
Practical planning for unplanned closure cannot be done in detail; however, this Closure Plan provides the basis for rapid evaluation of the remaining unknowns and risks associated with closure and development of an appropriate decommissioning plan if the site goes into a care and maintenance period. Care and maintenance is a period following temporary cessation of operations when infrastructure remains largely intact and the site continues to the managed (ICMM, 2008). The care and maintenance period will be identified by the following characteristics: No earthmoving activities other than those required for limited rehabilitation works; No processing of ore; A reduced workforce comprising a care and maintenance team; Revised monitoring activities; and Potentially exploration activities.
Experience gained during temporary closure of the NBG site between 2001 and 2006 was utilised during the development of this Closure Plan.
The Closure Implementation Plans provide an estimated schedule for progressive rehabilitation and closure activities. Progressive rehabilitation is based upon the mining plan and will continue to be revised and refined in response to variables such as: The price of gold and copper; Inflation rate; and Advances in mining, processing and rehabilitation techniques.
The timing of rehabilitation at NBG will likely proceed as follows: Satellite pits and associated haul roads as they become available and are sterilised; Sections of the waste rock landforms as they are completed, with final surfaces rehabilitated after the completion of mining;
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Sections of the embankments of the RDAs as they are completed and the top surface when they consolidate sufficiently to allow access by earthmoving equipment; The main open pits after the completion of mining; The processing plant after the completion of processing; Infrastructure progressively as it is no longer required; The accommodation village progressively as the work force reduces; and Water management structures progressively as they are no longer required.
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10.3.1 CMU0 – Whole of Operations 10.3.1.1 Description CMU0 covers the entire NBG site and includes closure activities that are common to many of the CMUs.
10.3.1.2 Closure Implementation Plan The key closure activities for CMU0 are: Ongoing engagement with stakeholders; Annual review of the: o Closure risk register; o Closure provision in accordance with the requirements of the United States Financial Accounting Standard Board’s Statement No. 143 (FASB 143); o Rehabilitation material inventory; and o Closure activities undertaken. Review and re‐submission of the Closure Plan every three years in accordance with the requirements of the Guidelines for Preparing Mine Closure Plans (DMP/EPA, 2011); Management of closure data and activities; Development of management plans; Development of quantitative standards for completion criteria; Notification of the district inspector before the suspension of mining operations in accordance with the requirements of the Mines Safety and Inspection Regulations 1995 (Section 3.1.1); Contaminated sites audit; Post‐closure reporting; and Archiving of documentation.
More information on these key closure activities is included below. Details of the timing and responsibility for closure and rehabilitation activities to be carried out for CMU0 are summarised in Table 10‐4.
Engagement with stakeholders will continue to be undertaken as required and will include: Refinement of completion criteria; Finalisation of post‐mining land use; and Establishment of formal closure, sign‐off and relinquishment mechanisms with lead regulatory agencies that outline the responsibilities and accountabilities and proposed methodologies required to achieve sign‐off.
The review of the closure risk register, closure provision and Closure Plan will take into account any changes to legislation, stakeholder expectations or the site operations which may affect closure of the site. The Closure Plan will continue to be updated as more information becomes available and will become more detailed as closure of the site approaches (as described in Section 1.4.2). The closure provision will be adjusted to take into account any closure activities undertaken in the previous year and any changes to the Life of Mine Plan (i.e. timing of closure activities based on operational activities).
Upon finalisation and approval of this Closure Plan, the Closure Implementation Plans will be loaded into the PRAC database and tracked. Documentation relevant to closure and rehabilitation of the site will continue to be uploaded to PRAC as required.
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A Rehabilitation Management Plan will be developed which will include details of the target ecosystem for rehabilitation, management of rehabilitation materials (including dieback infected material) and the progressive rehabilitation schedule. Prior to closure of the site a Post‐Closure Access Plan will be developed in consultation with stakeholders. The Post‐Closure Access Plan will include consideration of ongoing monitoring, management of fire, forest disease and weeds, and maintenance of access to freehold land.
Quantitative standards will be developed for the following completion criteria: Groundwater quality; Runoff water quality exiting mining areas; Erosion; Infiltration and nutrient cycling; Weed density; Soil seed bank; Habitat for black cockatoos; Native species resistant to forest disease; and For waste rock landforms, residue disposal areas and areas of significant disturbance of the in situ soil profile: o Ripping depth; o Stocking rate; and o Species richness.
A target ecosystem to be used as the basis for ecosystem monitoring will be identified based on the outcomes of rehabilitation trials. Quantitative standards will be developed on an ongoing basis as understanding improves during operations through experience, research and trials. A monitoring method will also be investigated for erosion, infiltration and nutrient cycling to be incorporated into the monitoring programme.
During closure of the operations a contaminated sites audit will be undertaken to address any sites which are not dealt with during the operational period. The contaminated sites audit will also include an investigation for any further unidentified contaminated sites that may be uncovered during the decommissioning process.
If the contaminated sites audit indicates that decontamination of a site may be required, a sampling and analysis program will be developed and results compared with the assessment levels for soil, sediment and water set out by the DEC (2010). Contaminated sites will be dealt with in accordance with the administrative and technical guidelines of the DEC. The development of a sampling and analysis program for a contaminated site may also be initiated by the classification by the DEC of a site as Potentially Contaminated – Investigation Required and will be incorporated into future revisions of this Plan as required.
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Table 10‐4 Closure Implementation Plan for CMU0 Activity Timing Responsibility1 Planning and Reporting Upload Closure Implementation Plans into the PRAC 2013 Senior Closure Planner database. Develop Rehabilitation Management Plan. 2013 Environment Manager Investigate and define native tree species which are 2013 Senior Closure Planner resistant to forest disease. Commence investigating soil seed bank required for 2014 Senior Closure Planner key plant groups to be self‐sustaining. Develop monitoring method and incorporate into monitoring programme. Identify target ecosystem and document in 2019 Senior Closure Planner Rehabilitation Management Plan. Investigate weed density, proportion of plant species 2020 Senior Closure Planner with attributes contributing to Black Cockatoo habitat, infiltration and nutrient cycling of target ecosystem. Upload documentation into the PRAC database. Ongoing Senior Closure Planner Develop quantitative standards for completion Ongoing Senior Closure Planner criteria. Engage with stakeholders as required, including Ongoing as Senior Closure Planner refinement of completion criteria. required. Review and update closure risk register. Annually until Senior Closure Planner relinquishment. Review and update closure provision in accordance Annually until Senior Closure Planner with the requirements of FASB 143. relinquishment. Record and report closure activities undertaken in Annually until Environment Manager the Annual Environmental Report. relinquishment. (Op) / Closure Superintendent (Post‐Op) Review rehabilitation materials inventory, including: Annually until Senior Closure Planner Stockpiles depleted through use for completion of (Op) / Closure rehabilitation activities; rehabilitation Superintendent (Post‐)Op New stockpiles created from stripping of new activities. disturbance areas; Stockpiles relocated; and Re‐classification of stockpiles based on materials characterisation undertaken. Update and re‐submit Closure Plan. Every three years Senior Closure Planner until (Op) / Closure relinquishment. Superintendent (Post‐Op) Prepare and submit Annual Environmental Report, Annually until Environment Manager including an Annual Hydrological Review. relinquishment. (Op) / Closure Superintendent (Post‐Op) Develop Post‐Closure Access Plan. 2039 Environment Manager
1 Op – Operational period Post‐Op – Post‐operational period
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Activity Timing Responsibility1 Develop Workforce Transition Program. 2040 Human Resources Manager Notify the district inspector before the suspension of 2041 Site General Manager operations. Archive documentation required to be retained. 2041 Closure Superintendent Undertake contaminated sites audit. 2042 Closure Superintendent Prepare and submit Relinquishment Report. At Closure Superintendent relinquishment.
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10.3.1.3 Unplanned Closure Activities In the situation of NBG going into unplanned closure, as soon as possible after the decision is made to place the site on care and maintenance an environmental audit will be carried out. The audit will seek to establish the status of all landforms and infrastructure with respect to the environmental risk of each element during the expected period of care and maintenance. If this time is not known, then the environmental risk would be evaluated over a minimum period of two years. The audit would include the risks summarised in Table 10‐5 .
Table 10‐ 5 Environmental risks to be evaluated for care and maintenance period Area Environmental Risks Waste rock Dispersal of waste material to the surrounding environment as a result of erosion. landforms Pollution of the surrounding environment as a result of chemicals or other materials coming out of the landform. Residue Dispersal of waste material to the surrounding environment as a result of erosion. Disposal Areas Pollution of the surrounding environment as a result of chemicals or other materials coming out of the landform. Release of liquor from the facility as seepage through the containment walls, directly into groundwater through the base of the facility, through over‐topping of the facility and through any under drainage or gravity out‐fall from the decant pond. Catastrophic failure of the containing wall through a structural weakness in the wall because of a design or construction fault, or erosion of the wall, particularly through over‐topping in the event of heavy rainfall. Processing Dispersal of process‐related materials and chemicals outside of the plant area if plant not stored or disposed of correctly. Hydrocarbon Dispersal of hydrocarbons to the environment if not stored or disposed of storage areas correctly. Open pit mines Diversion of surface water into pits depriving vegetation systems downstream of their normal supply of water. Underground Diversion of surface water into shafts and decline portals depriving vegetation mines systems of their normal supply of water. Surface Erosion of the natural land surface or constructed landforms due to natural and drainage engineered drainage structures becoming ineffective due to erosion, sedimentation and other factors.
Based on the outcomes of the audit, a plan would be developed to manage/ameliorate the environmental risks identified. The site Emergency Response Plan will also be revised in response to the change in risk associated with the site in a care and maintenance phase.
During care and maintenance, ongoing monitoring and maintenance of perimeter fencing and security patrols of the site would continue. The management of forest disease would be continued through: Continued observance of the forest hygiene policy and procedures; Maintaining availability of washdown units; and Re‐mapping known forest disease area boundaries every three years.
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10.3.2 CMU1 – Mining Areas 10.3.2.1 Description CMU1 covers the main open pits, satellite open pits and Jarrah Decline. A summary of these areas is included in Table 10‐6.
Table 10‐6 Summary of CMU1 Aspect Description Main Open Pits Feature Wandoo North, Wandoo South and Mine South pits Area of Disturbance 770 ha Current Status Active mining. Estimated Closure 2041 Date Key Potential Public access to open pit void and underground workings. Closure Risks Inadequate surface water management. Geotechnical instability of landforms and open pit. Alteration of surface water regime. Cone of depressurisation from dewatering impacts groundwater and surface water resources. Seepage impacts receiving environment. Potential Post‐ Nature conservation, recreation, water catchment, habitat/species Mining Land Use management, water storage and treatment Closure Strategy Formation of interconnected lakes with an overflow to Wattle Hollow Brook. The following water sources will be directed into the pit voids post‐closure: Runoff from the upper portion off the Thirty‐Four Mile Brook catchment; Runoff from the R4 and F1/F3 RDAs; Runoff from sections of the waste rock landforms; and Discharge from the cyanide destruct and acid and/or metalliferous drainage treatment plants in the initial post‐closure period of 10 to 20 years. Construction of abandonment bunds to prevent inadvertent public access. Landform Design Pit walls will be left at the as‐mined angle of 25° in oxide and 59° in bedrock. Completion Criteria Access to open pits is restricted by abandonment bunds, built to regulatory guidelines and Newmont standards. Satellite Open Pits Feature C, D, K, L, M and Q pits Area of Disturbance Total – 224 ha Rehabilitated ‐ 173 ha Current Status C pit – Rehabilitated 1992. Incorporated into Main Open Pits. D pits – Rehabilitated 1998. Incorporated into Main Open Pits. K1/K2 pit – Rehabilitated 2000. K3 pit – Retained for potential use for landfill or trial areas. K4 pit – Retained for potential use for landfill or trial areas. K5/K6 pit – Rehabilitated 2000. K6 pit – Rehabilitated 1998. K7/K9 pit – Rehabilitated 2000. K8 pit – Rehabilitated 2002. L1 pit – Rehabilitated 1999.
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Aspect Description L1 Nth/Sth – Rehabilitated 2001 L2‐4 pits – Rehabilitated 2001. M1 pit – Rehabilitated 2002. M2‐5 pits – Rehabilitated 2001. Q1‐3 pits – Rehabilitated 2002. Q4 – Retained for potential use for landfill or trial areas. S pits (Wattle Pit) – Incorporated into F1/F3 RDA (Section 10.3.3). Key Potential Inadequate surface water management. Closure Risks Alteration of surface water regime. Potential Post‐ Nature conservation, forestry, habitat/species management, water Mining Land Use catchment Closure Strategy Backfilling and/or reshaping to achieve external drainage. Landform Design Slopes generally rehabilitated to <15°. For rehabilitation slopes exceeding 15° and 5 ha geotechnical analysis undertaken. Rehabilitation Application of approximately 30 cm of gravel and 10 cm of topsoil, contour Prescription ripping, seeding and fertiliser application. Fauna habitats created at an approximate density of one habitat per hectare, subject to material availability. Completion Criteria Regional surface drainage to downstream environments is not prevented following the completion of earthworks. Runoff water quality will be suitable for the receiving environment. Erosion features should not threaten the integrity of landform design, and not create hazards that may unreasonably impede land management. There is an adequate establishment of native tree species that are resistant to Phytophthora cinnamomi. A suitable soil profile is in place to facilitate plant establishment and growth, as defined in approved Rehabilitation Management Plan. Fauna habitat structures have been established on rehabilitated areas. On maturity, vegetation will provide foraging and longer term potential nesting habitat for black cockatoos. Investigate strategies for recruitment of priority and recalcitrant flora into rehabilitated areas to levels consistent with the target ecosystem. Viable seed has been broadcast at rates sufficient to achieve the target ecosystem. Seed mix to contain at least 60 native forest species supplemented by seedlings. Species richness to resemble that of the target ecosystem as defined in the Rehabilitation Management Plan. Populations of key plant groups will be self‐sustaining. Retention and availability of critical ecosystem resources will resemble that of the target ecosystem as defined in the Rehabilitation Management Plan. Rehabilitation is of an age where it has the potential to regenerate after a wildfire.
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Aspect Description Jarrah Decline Feature Portal and underground workings for Jarrah Decline Area of Disturbance No disturbance as located within Wandoo North pit. Current Status Closed. Mine entrance secured to prevent unauthorised access and vent shafts blocked or backfilled. Notice of abandonment of the Jarrah Decline and plans of underground workings submitted to the District Inspector in 1997. District Inspector visited underground mine on 1 April 1997 and stated that measures employed to preclude unauthorised access were fully adequate. Closure Date 1997 Key Potential Public access to open pit void and underground workings. Closure Risks Potential Post‐ As for Main Open Pits. Mining Land Use Closure Strategy Backfill box cut.
10.3.2.2 Closure Implementation Plan The key closure activities for CMU1 are: Updating the post‐closure water balance model; Reshaping and rehabilitation of remaining satellite open pits; and Construction of abandonment bunds and paddock dumping the top of pit ramps of the main open pits.
Details of the gtimin and responsibility for closure and rehabilitation activities to be carried out for CMU1 are summarised in Table 10‐7.
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Table 10‐7 Closure Implementation Plan for CMU1 Activity Timing Responsibility Planning and Reporting Complete sterilisation drilling of satellite pits K3, K4 2013 Geology Manager and Q4. Update post‐closure water balance model as Ongoing Senior Closure Planner required when more detailed information becomes available (e.g. quality and quantity of water inputs). Develop work instructions2 for rehabilitation works Progressively as Senior Closure Planner for K3, K4, Q4 and main open pits. required. (Op) / Closure Superintendent (Post‐Op) Review of zone of pit instability and landform 2042 Closure Superintendent placement by an appropriate specialist. Construction Construct abandonment bund for main open pits Ongoing, to be Load and Haul and paddock dump top of pit ramp. completed by Superintendent (Op) / 2043 (two years Closure Superintendent after completion (Post‐Op) of mining) Rehabilitation Backfill and/or reshape satellite pits K3, K4 and Q4 to 2035 Environment Manager achieve external drainage. Apply gravel and topsoil in accordance with rehabilitation prescription for satellites pit K3, K4 and Q4. Rip on the contour for satellite pits K3, K4 and Q4. Apply local provenance seed and fertiliser for satellite pits K3, K4 and Q4. Construct fauna habitats for pits K3, K4 and Q4. Backfill box cut for Jarrah Decline. 2042 Closure Superintendent
Survey final landform of satellite pits and main open Ongoing as Mine Technical Services pits. rehabilitation Manager (Op) / Closure earthworks Superintendent (Post‐Op) completed.
2 Detailed work instructions will be developed prior to rehabilitation activities commencing. These work instructions will include information such as: Type and depth of capping material; Any additional treatments required and how they are to be applied; Locations of all rehabilitation materials to be used; and QA/QC procedures to be followed during rehabilitation earthworks.
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10.3.2.3 Unplanned Closure Activities The three main activities required for CMU1 in the case of unplanned closure are: Visual inspections of the main open pits; Minor rehabilitation activities for stabilisation and management of surface water; and Monitoring of rehabilitation.
The current programme of visual inspections of the open pits would be continued until a determination is made regarding restarting or closure of the site. Visual inspections would focus on identifying: Areas of deformation failure; and Zones of cracking or slumping.
Minor rehabilitation earthworks may be required to ensure stabilisation of sections of the mining area andm for interi management of surface water to prevent erosion. The earthworks required would be dependent upon the timing of unplanned closure.
Monitoring of rehabilitated areas would continue in accordance with the current monitoring programme (Section 11.1).
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10.3.3 CMU2 – Residue Disposal Areas 10.3.3.1 Description CMU2 covers the R4, F1/F3 and future RDAs and the Wattle pit area. The Wattle pit area is included in CMU2 as it is immediately adjacent to the F1 RDA so synergies exist to combine construction of the RDA with rehabilitation of the. oxide pits A summary of these areas is included in Table 10‐8.
Table 10‐8 Summary of CMU2 Aspect Description Key Potential Public safety on landforms post‐closure. Closure Risks Inadequate surface water management. Excessive erosion of landforms. Integrity of landform design compromised by excessive erosion and/or settlement. Excessive infiltration through covers on waste rock landforms and RDAs. Geotechnical instability of landforms and open pit. Poor rehabilitation performance. Inadequate management of hostile material. Alteration of surface water regime. Seepage impacts receiving environment. Potential Post‐ Nature conservation, forestry, habitat/species management, water Mining Land Use catchment, renewable energy generation Closure Strategy Formation of a water shedding landform with runoff reporting to North Pit or Gringer Creek. Landform Design Relatively flat elevated landforms with water shedding top surface. Embankments rehabilitated to 15°. Completion Criteria Final landforms and constructed drainage features conform to approved designs and specifications which incorporate factors of safety to ensure design intent is maintained for the long term. A geotechnical review of each residue disposal area and waste rock landform by an appropriate specialist is accepted by the State Mining Engineer (or equivalent) on completion of decommissioning works. Regional surface drainage to downstream environments is not prevented following the completion of earthworks. Runoff water quality will be suitable for the receiving environment. Potentially‐hostile wastes are identified, managed and contained within landforms according to approved landform design and mine waste management plans. Erosion features should not threaten the integrity of landform design, and not create hazards that may unreasonably impede land management. There is an adequate establishment of native tree species that are resistant to Phytophthora cinnamomi. A suitable soil profile is in place to facilitate plant establishment and growth, as defined in approved Rehabilitation Management Plan. Fauna habitat structures have been established on rehabilitated areas. On maturity, vegetation will provide foraging and longer term potential nesting habitat for black cockatoos. Investigate strategies for recruitment of priority and recalcitrant flora into
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Aspect Description rehabilitated areas to levels consistent with the target ecosystem. Viable seed has been broadcast at rates sufficient to achieve the target ecosystem. Seed mix to contain at least 60 native forest species supplemented by seedlings. Species richness to resemble that of the target ecosystem as defined in the Rehabilitation Management Plan. Populations of key plant groups will be self‐sustaining. Retention and availability of critical ecosystem resources will resemble that of the target ecosystem as defined in the Rehabilitation Management Plan. Rehabilitation is of an age where it has the potential to regenerate after a wildfire. R4 RDA Feature R4 RDA Area of Disturbance 322 ha Current Status Inactive oxide residue storage area. Currently used for water storage and as an alternative water source for wildlife. Rehabilitation trial constructed in 1999 to investigate the effects of topsoil, gypsum and compost application rates over various depths of gravel cover on revegetation performance and rehabilitation success. Closure Date 2041 Rehabilitation Application of 30 cm of gravel and 10 cm of topsoil, contour ripping, seeding Prescription and fertiliser application. F1/F3 RDA Feature F1/F3 RDA Area of Disturbance 1,250 ha Current Status Active basement residue deposition. Estimated Closure 2041 Date Rehabilitation Application of 30 cm of gravel and 10 cm of topsoil, contour ripping, seeding Prescription and fertiliser application. In addition, application of 2 m of oxide residue if field trials do not demonstrate successful growth of vegetation in basement residue. Wattle Pit Area Feature S1, S2 (backfilled), S4, S5 and S7 (backfilled) oxide pits, a cleared open area for a pit that was never developed (S3), a temporary waste stockpile, topsoil and gravel stockpiles Area of Disturbance 42 ha Current Status Utilised for mining of construction materials for the adjacent F1/F3 RDA. Sterilisation drilling has been conducted confirming no further prospect for extraction of ore from the pit. Consent to backfill has been obtained from the Geological Survey of WA. Estimated Closure 2041 Date Closure Strategy Backfilling and/or re‐shaping to achieve drainage to F1/F3 RDA. Landform Design Slopes generally rehabilitated to <15°. Rehabilitation Application of up to 30 cm of gravel and 10 cm of topsoil, contour ripping, Prescription seeding and fertiliser application.
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Aspect Description Future RDA Feature Future RDA Area of Disturbance Planned – 1,650 ha Current Status Not yet constructed. Potential Closure 2041 Date Rehabilitation As for F1/F3 RDA Prescription
10.3.3.2 Closure Implementation Plan The key closure activities for CMU2 are: Ongoing development of the RDA Decommissioning Plan from the current conceptual form, including investigation of; o Post‐closure seepage period and water quality; o Inventory of salt within residue profile and mobility post‐closure; and o Detailed drainage design. Construction of a basement residue rehabilitation trial to assess: o Rehabilitation prescriptions; o Rate of infiltration and runoff; and o Chemistry of runoff from rehabilitated landforms. Baseline soil assessment for footprint of future RDA; Ongoing management and treatment of seepage and underdrainage until no longer required; Progressive rehabilitation of the embankments and top surface of the RDAs; and Documentation of final form of the RDAs after completion of rehabilitation.
Details of the timing and responsibility for closure and rehabilitation activities to be carried out for CMU2 are summarised in Table 10‐9.
Rehabilitation of the embankments of the RDAs can be undertaken progressively as they are constructed. Table 10‐10 summarises the estimated area available for progressive rehabilitation of the embankments of the F1/F3 RDA on an annual basis. The zones of the RDA available for rehabilitation are shown in Figure 10‐2 to Figure 10‐6. The scheduling of progressive rehabilitation of the embankments of the RDAs is based upon the residue deposition schedule and timing may change in response to changes in the mine plan.
Timing for rehabilitation of the top surface of the RDAs has been estimated in Table 10‐9, but is dependent on the time taken for the residue to consolidate sufficiently for safe access by earthmoving machinery.
A progressive rehabilitation schedule for the future RDA will be developed as part of detailed design.
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Table 10‐9 Closure Implementation Plan for CMU2 Activity Timing Responsibility Planning and Reporting Investigate post‐closure seepage period and water 2013 Senior Closure Planner quality. Undertake baseline soil assessment for footprint of 2018 Senior Closure Planner the future RDA and update rehabilitation materials inventory. Investigate inventory of salt within residue profile of 2026 Senior Closure Planner F1/F3 RDA and mobility post‐closure. Refine RDA Decommissioning Plan (including surface Ongoing Senior Closure Planner water management design) as more detailed information becomes available. Develop work instructions for rehabilitation works Progressively as Senior Closure Planner for RDAs. required. (Op) / Closure Superintendent (Post‐Op) Review of RDAs by a geotechnical/ engineering Prior to Closure Superintendent specialist and submit report to the State Mining completion of Engineer to meet the requirements of tenement operations conditions for M70/21, M70/22, M70/23 and and/or M70/799. Assessment to include: rehabilitation of The status of the structure and its contained the residue. tailings; An examination of the implications of the physical and chemical characteristics of the materials; The results of all environmental monitoring; and A discussion of any stabilisation and on‐going remedial works. Document completion of rehabilitation earthworks 2051 (after Closure Superintendent in as‐built report for R4, F1/F3 and future RDAs, completion of including geotechnical review by an appropriate rehabilitation specialist. earthworks). Construction Construct basement residue rehabilitation trial. 2013 Environment Manager Rehabilitation Apply gravel and topsoil to embankments for R4, Progressively as Environment Manager F1/F3 and future RDA. completed. (Op) / Closure Superintendent (Post‐Op) Ongoing management of underdrainage and 2041‐2051 Closure Superintendent seepage and treatment at cyanide destruct plant until no longer required (estimated at 10 years). Treatment of surface runoff from RDAs at cyanide 2041‐2051 Closure Superintendent destruct plant during rehabilitation of top surface (estimated at 10 years).
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Activity Timing Responsibility Construct drainage features on the top surface of 2044 onwards Closure Superintendent RDAs in accordance with surface water management design. Apply gravel and topsoil in accordance with rehabilitation prescription on top surface of RDAs. Apply local provenance seed and fertiliser to RDAs. Construct fauna habitats on RDAs. Backfill seepage interception trenches around RDAs. 2051 (upon Closure Superintendent completion of seepage recovery).
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Table 10‐10 Area available for progressive rehabilitation of the F1/F3 RDA embankments Year Construction Phase Saddle Dam Area (ha) 2013/2014 7 3 1.67 4 0.75 5 3.15 7 2.34 8 5.46 Total 13.37 2014/2015 8 9 1.93 10 2.71 Total 4.64 2015/2016 9 ‐ 0 2016/2017 10 8 5.99 Total 5.99 2017/2018 11 3 6.51 4 2.29 5 4.39 7 5.69 Total 18.87 2018/2019 12 2 0.20 9 3.40 10 4.28 Total 7.88 2019/2020 13 ‐ 0 2020/2021 14 8 5.73 Total 5.73 2021/2022 15 1 13.78 3 7.09 4 2.65 5 4.32 7 5.76 Total 55.60 2022/2023 16 2 1.42 9 3.70 10 4.89 Total 10.01 2023/2024 17 ‐ 0 2024/2025 18 1 2.64 2 1.71 3 6.00 4 2.32 5 3.79 7 5.28 8 4.74 9 2.79 10 3.67 Total 32.94 Total 133.04
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10.3.3.3 Unplanned Closure Activities The main activities required for CMU2 in the case of unplanned closure are: Continuing regular inspections of the RDAs; Ongoing water management; Groundwater monitoring and reporting; and Audit of the RDAs by a qualified engineer.
In the case of unplanned closure, regular inspections of the RDAs would continue in the care and maintenance phase as outlined in Table 10‐11. Inspections of the RDAs would continue until a determination is made regarding restarting or closure of the site.
Table 10‐11 Unplanned closure RDA inspection activities Inspection Frequency Activities Daily Visual check of: Pipeline integrity Embankment integrity Seepage from embankments Residue level Fauna mortality Evidence of dusting Location of decant pond Condition of access ramps Monthly Record volume of water transfers Monitor for o Pond area, wall and beach freeboard o Piezometer pore pressures Annually Monitor water quality for decant pond Annually (one year post‐ Operational review by qualified engineer closure) As required Silt removal from return water ponds
Ongoing management of underdrainage and seepage would be required during the care and maintenance phase. The water balance of the RDAs would continue to be managed to maintain levels as low as possible.
Groundwater monitoring and reporting would continue as per current schedules and procedures until alternative arrangements are agreed upon with relevant stakeholders (currently the Department of Environment and Conservation and Department of Water).
Tenement conditions require the RDAs to be inspected by a qualified engineer on an annual basis whilst the RDA is active. A review of the RDAs would need to be undertaken in the year following unplanned closure of the site in order to fulfil the requirement of this tenement condition. A copy of the audit report prepared by the inspecting engineer would be submitted to the Department of Mines and Petroleum with the Annual Environmental Report.
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10.3.4 CMU3 ‐ Waste Rock Landforms 10.3.4.1 Description CMU3 covers waste rock landforms No. 7, 8, 9, 10, 11, 12 and Q3 South. A summary of these areas is included in Table 10‐12.
Table 10‐12 Summary of CMU3 Aspect Description Key Closure Risks Public safety on landforms post‐closure. Inadequate surface water management. Excessive erosion of landforms. Integrity of landform design compromised by excessive erosion and/or settlement. Excessive infiltration through covers on waste rock landforms and RDAs. Geotechnical instability of landforms and open pit. Poor rehabilitation performance. Inadequate management of hostile material. Medium grade stockpiles not located or constructed with closure considered as it is assumed they will be processed. Alteration of surface water regime. Seepage impacts receiving environment. Potential Post‐ Nature conservation, forestry, habitat/species management, water Closure Land Use catchment, managed resource protection, renewable energy generation Closure Strategy Formation of a physically stable and safe landform that is consistent with the existing topography and vegetation. Completion Criteria Final landforms and constructed drainage features conform to approved designs and specifications which incorporate factors of safety to ensure design intent is maintained for the long term. A geotechnical review of each residue disposal area and waste rock landform by an appropriate specialist is accepted by the State Mining Engineer (or equivalent) on completion of decommissioning works. Permanent landforms are not located within the zone of potential pit instability. Landforms will fit within the surrounding landscape in terms of height and where practicable in terms of overall topography. Regional surface drainage to downstream environments is not prevented following the completion of earthworks. Runoff water quality will be suitable for the receiving environment. Potentially‐hostile wastes are identified, managed and contained within landforms according to approved landform design and mine waste management plans. Landform slope parameters and material characteristics are consistent with those set out in approved landform designs. Final surface materials and treatments, and drainage control structures, are matched to the characteristics of the slope and are consistent with those set out in approved landform designs. Erosion features should not threaten the integrity of landform design, and not create hazards that may unreasonably impede land management.
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Aspect Description There is an adequate establishment of native tree species that are resistant to Phytophthora cinnamomi. A suitable soil profile is in place to facilitate plant establishment and growth, as defined in approved Rehabilitation Management Plan. Fauna habitat structures have been established on rehabilitated areas. On maturity, vegetation will provide foraging and longer term potential nesting habitat for black cockatoos. Investigate strategies for recruitment of priority and recalcitrant flora into rehabilitated areas to levels consistent with the target ecosystem. Viable seed has been broadcast at rates sufficient to achieve the target ecosystem. Seed mix to contain at least 60 native forest species supplemented by seedlings. Species richness to resemble that of the target ecosystem as defined in the Rehabilitation Management Plan. Populations of key plant groups will be self‐sustaining. Retention and availability of critical ecosystem resources will resemble that of the target ecosystem as defined in the Rehabilitation Management Plan. Rehabilitation is of an age where it has the potential to regenerate after a wildfire. Waste Rock Landforms 7, 8, 9, 10, 11, 12 Feature Waste rock landforms 7, 8, 9, 10, 11 and 12 Area of Disturbance 1,331 ha
Status Active. Zones used for storage of oxide required for rehabilitation. Estimated Closure 2041 Date Landform Design Slope geometry, benches and crest bunds designed to optimise performance with respect to erosion and gully depth. Rehabilitation Application of at least 2 m of oxide, 30 cm of gravel and 10 cm of topsoil, Prescription contour ripping, seeding and fertiliser application. Q3 South Waste Rock Landform Feature Small oxide waste rock landform constructed over the backfilled Q3 South satellite open pit. Area of Disturbance 6.5 ha Status Rehabilitated 2002. Closure Date 2001 Landform Design Single lift of 20m blended into adjacent hill. Rehabilitation Application of approximately 3 m of oxide, 20 cm of gravel and 10 cm of Prescription gravel, contour ripping, seeding, tree planting, recalcitrant species planting and fertilising.
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10.3.4.2 Closure Implementation Plan The key closure activities for CMU3 are: Development of outslope, drainage and cover design for waste rock landforms; Research into non‐carbonate buffering capacity of waste rock and development of management plans; Construction of a rehabilitation trial to assess: o Rehabilitation prescriptions; o Rate of infiltration and runoff; and o Water quality of runoff from rehabilitated landforms. Investigation of water balance in oxide material; Progressive rehabilitation of the waste rock landforms; and Documentation of final form of the waste rock landforms after completion of rehabilitation.
Development of the outslope, drainage and cover design for the waste rock landforms commenced in 2011 and is ongoing. In 2012, a trial was commenced on the water balance for the proposed oxide layer in the cover system. A rehabilitation trial will be constructed to identify the optimal cover design.
To improve understanding of the non‐carbonate buffering capacity and kinetics of the waste rock at NBG the following research programme commenced in 2012: Laboratory testing of waste rock encompassing major litho‐alteration assemblages and a sulphide range which will facilitate demarcation of the threshold below which silicate buffering may afford reliable AMD mitigation; and Field testing of waste rock and medium grade ore.
Based on the initial results of the research programme the Waste Rock Management Plan will be updated and a Medium Grade Ore Management Plan will be developed. These management plans will be updated in 2014 based on the outcomes of the completed laboratory programme and testing in the field over a period of years.
Rehabilitation of the outer slopes of the landforms will be conducted progressively as construction of sections is completed. Table 10‐14 summarises the estimated area available for progressive rehabilitation of the outer slopes of waste rock landforms 7, 8, 9, 10, 11 and 12. The zones of the landforms available for rehabilitation are shown in Figure 10‐8 to Figure 10‐15. The scheduling for progressive rehabilitation of the outer slopes is based upon the mining schedule and timing may change in response to changes in the minee plan. Th top surface and some embankments of the waste rock landforms will be active until the completion of mining in 2041. Rehabilitation of these areas will commence from 2041 onwards.
The medium‐grade ore stockpile is incorporated into waste rock landform No. 9. Processing of the medium‐grade ore will be undertaken during the final stages of mining. Sections of the waste rock landform abutting the medium‐grade stockpile will be rehabilitated progressively where possible concurrent with the removal of the medium‐grade ore. Rehabilitation of these areas will be completed after the completion of processing, which is planned for 2041. If processing of the medium‐grade ore does not occur, this area will be rehabilitated as part of the waste rock landform.
Details of the timing and responsibility for closure and rehabilitation activities to be carried out for CMU3 are summarised in Table 10‐13.
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Table 10‐13 Closure Implementation Plan for CMU3 Activity Timing Responsibility Planning and Reporting Develop outslope, drainage and cover design. Commenced Senior Closure Planner 2011 Undertake laboratory and field‐scale testing of waste Commenced Senior Closure Planner rock and medium grade ore. 2012 Investigate oxide layer water balance. Commenced Senior Closure Planner 2012 Update Waste Rock Management Plan and develop 2013 Senior Closure Planner Medium Grade Ore Management Plan. Update Waste Rock and Medium Grade Ore 2015 Senior Closure Planner Management Plans. Develop work instructions for rehabilitation works. Progressively as Senior Closure Planner required. (Op) / Closure Superintendent (Post‐Op) Feotechnical review of waste rock landforms by an 2042 Closure Superintendent appropriate specialist. Construction Construct rehabilitation trial. 2014 Environment Manager Rehabilitation Construct drains in accordance with approved Progressively as Environment Manager design. sections of (Op) / Closure Batter outer slopes to final angle. landforms Superintendent (Post‐Op) Apply oxide, gravel and topsoil under dry conditions completed. in accordance with the rehabilitation prescription. Rip on the contour. Apply local provenance seed and fertiliser. Construct fauna habitats. Survey landforms. Ongoing as Mine Technical Services rehabilitation Manager (Op) / Closure earthworks Superintendent (Post‐Op) completed. Undertake a controlled burn around rehabilitation As required. Environment Manager area to prevent damage from wild fires if required. A (Op) / Closure controlled burn may be conducted through each Superintendent (Post‐Op) rehabilitation area after the youngest rehabilitation has been rehabilitated for 15 years.
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Table 10‐14 Area available for progressive rehabilitation of the waste rock landforms Year Reclamation Stage Panel RL (m) Area (ha) 2024 R12 R12.a 240 ‐ 300 97.0 R11.1 R11.1.a 260 ‐ 300 21.1 Total 118.2 2027 R12 R12.b 300 ‐ 340 69.8 R11.1 R11.1.b 300 ‐ 340 17.2 Total 87.0 2028 R12 R12.c 340 ‐ 360 32.5 Total 32.5 2034 R11.2 R11.2.a 240 ‐ 300 14.1 Total 14.1 2037 R11.2 R11.2.b 300 ‐ 340 17.0 R10.1 R10.1.a 240 ‐ 300 18.4 R10.2 R.10.2.a 220 ‐ 300 39.7 Total 75.1 2041 R10.1 R10.1.c 320 ‐ 340 7.2 R10.2 R10.2.c 320 ‐ 340 8.3 Total 15.5 2042 onwards R7.1 R7.1 280 ‐ 360 50.1 R7.2 R7.2 280 ‐ 360 57.9 R8.1 R8.1 380 ‐ 360 31.5 R8.2 R8.2 240 ‐ 360 103.0 R9 R9 255 ‐ 315 63.7 R10.1 R10.1.d 340 ‐ 360 5.4 R10.2 R10.2.d 340 ‐360 5.4 R10.3 R10.3.a 260 ‐ 360 50.0 R10.3.b 340 ‐ 360 11.1 R11.1 R11.1.c 340 ‐ 360 5.4 R11.2 R11.2.c 340 ‐ 360 6.7 R13 R13 360 324.7 R14 R14 280 118.6 R15 R15 280 52.2 Total 885.7 Total 1,244.3
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10.3.4.3 Unplanned Closure Activities In the case of unplanned closure, the main activities required for CMU3 are: Minor rehabilitation activities for stabilisation and management of surface water; Monitoring of rehabilitation; and Maintenance of drainage structures.
Minor rehabilitation earthworks may be required to ensure stabilisation of the waste rocks landform and for interim management of surface water to prevent erosion. The earthworks required would be dependent on the timing of unplanned closure.
Monitoring of rehabilitated areas would continue in accordance with the current monitoring programme (Section 11.1).
Maintenance of drainage structures would need to continue in the case ofd unplanne closure. This would include: Regular inspections to check integrity and for excessive erosion; Fixing areas of excessive erosion or where drainage function is failing; and Removal of sediment from ponds and drains.
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10.3.5 CMU4 ‐ Infrastructure 10.3.5.1 Description CMU4 covers infrastructure at NBG. A summary of these areas is included in Table 10‐15.
Table 10‐15 Summary of CMU4 Aspect Description Area of 170 ha Disturbance Key Closure Poor rehabilitation performance. Risks Personnel injuring during decommissioning. Ore and potential ore traps overlooked during decommissioning. Potential Post‐ Nature conservation, recreation, forestry, water catchment, habitat/species Mining Land management, manufacturing and industrial, renewable energy generation Use Closure Dismantle/demolish all structures to below ground level unless specified otherwise Strategy by appropriate approvals. Break up concrete and bury or dispose of. Re‐shape disturbance areas to blend in with the surrounding topography and revegetate with local species. Rehabilitation Application of 10 cm of topsoil, contour ripping and seeding. Prescription Completion Appropriate tenure will be in place for gazetted roads and any infrastructure Criteria transferred to a third party prior to relinquishment or handover. Infrastructure is removed from site or buried, except where an asset transfer agreement is in place with key stakeholders for retention. Contaminated sites will be managed in accordance with the Contaminated Sites Act 2003. A suitable soil profile is in place to facilitate plant establishment and growth, as defined in approved Rehabilitation Management Plan. Fauna habitat structures have been established on rehabilitated areas. On maturity, vegetation will provide foraging and longer mter potential nesting habitat for black cockatoos. Investigate strategies for recruitment of priority and recalcitrant flora into rehabilitated areas to levels consistent with the target ecosystem. Viable seed has been broadcast at rates sufficient to achieve the target ecosystem. Seed mix to contain at least 60 native forest species supplemented by seedlings. Species richness to resemble that of the target ecosystem as defined in the Rehabilitation Management Plan. Populations of key plant groups will be self‐sustaining. Retention and availability of critical ecosystem resources will resemble that of the target ecosystem as defined in the Rehabilitation Management Plan. Rehabilitation is of an age where it has the potential to regenerate after a wildfire.
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Aspect Description Primary Crusher Feature Two gyratory crushers located to the west of the Wandoo North and South open pits. Current Status Active Estimated 2041 Closure Date Closure As the primary crusher is substantial and partially buried it is not feasible to break Strategy it up for removal. Therefore, the closure strategy is to bury it and re‐shape to blend in with the surrounding topography. Rehabilitation Remove structural steel and bury foundation concrete in situ with at least 3 m of Prescription oxide. Conveyor Feature Conveyor for crushed ore between the primary crusher and processing plant. Current Status Active – may be relocated to accommodate future mining. Estimated 2041 Closure Date Processing Plant Feature Processing plant consisting of: Crushing circuit; Ball milling; Hydrocyclone classification; and Supporting infrastructure. Current Status Active Estimated 2041 Closure Date Buildings Feature Workshops, offices, security gate, magazine, explosives/emulsion batching plant, core yard, warehouse Current Status Active Estimated 2041. Some buildings will be retained for rehabilitation activities. Closure Date Fuel Farm Feature Fuel storage area and waste oil storage tank. Current Status Active. Estimated 2041. Some fuel storage areas will be retained for rehabilitation activities. Closure Date Roads and Tracks Feature Haul roads and access tracks. Current Status Active. Haul roads and access tracks have been progressively rehabilitated as they are no longer required. Estimated 2041. Some roads and tracks will be: Closure Date Progressively rehabilitated as they are no longer required; or Maintained post‐closure for access for monitoring and maintenance activities.
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Aspect Description Laydown Areas Feature Laydown areas for temporary storage of infrastructure and equipment. Current Status Active Estimated 2041 Closure Date Bores Feature Monitoring and production bores. Current Status Active Estimated 2041 Closure Date Pump Stations and Caro’s Acid Plant Feature Booster pump station for F1/F3 RDA, Hotham River pump station and Caro’s acid plant. Current Status Active Estimated 2041 – Hotham River pump station Closure Date 2051 – Caro’s acid plant Landfill Feature Inert landfill facility. Current Status Active Estimated 2046 Closure Date
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10.3.5.2 Closure Implementation Plan The key closure activities for CMU4 are: Development of: o Agreements with stakeholders for retention of infrastructure or equipment; o An inventory reduction plan for stores of hydrocarbons and chemicals; o Decommissioning Plans Decommissioning and removal or demolition of infrastructure and equipment; and Rehabilitationd of disturbe areas.
Details of the timing and responsibility for closure and rehabilitation activities to be carried out for CMU4 are summarised in Table 10‐16 below. Decommissioning will be undertaken progressively where possible if areas of infrastructure are no longer required.
Before the commencement of decommissioning, the responsibility for removal of areas of infrastructure (such as fuel tanks) by third parties will be established by checking contracts and other documentation. Where equipment and infrastructure is to be decommissioned and removed from site by third parties a suitable plan will be required by NBG to ensure the task is completed safely.
Prior to commencing decommissioning of infrastructure and equipment a detailed Decommissioning Plan will be developed. The requirements of the Cyanide Facility Decommissioning Management Plan (summarised below) will be incorporated into the development of the overall Decommissioning Plan. The Decommissioning Plan will detail the following where appropriate: Risks and hazards associated with decommissioning works; Dangerous Goods stored on site; Equipment and infrastructure to be: o Removed for use by other Newmont sites; o Removed for use by third parties; o Retained on site (for which signed agreements are in place); and o Demolished. Temporary storage areas for equipment and infrastructure to be removed; Methods for disposal of: o Goods that can be returned, recycled or re‐used; and o Scrap material. Infrastructure that will require decontamination before re‐use or removal from site; Description of how equipment and infrastructure is to be: o Decommissioned; and o Demolished. The methods used will meet the requirements of the current standard (at present Australian Standard AS2601‐2001‐The demolition of structures). Tasks for which: o A Standard Operating Procedure is in place; o A Standard Operating Procedure is to be developed prior to commencing; o A Job Safety Analysis will be required prior to commencing; and o Extra safety precautions are required (i.e. tasks only conducted by specialised personnel with relevant past experience). Clearances required for tasks (i.e. confined space entry, dig permit); and Responsibilities and accountabilities for decommissioning works.
Infrastructure will be decommissioned in accordance with the standard decommissioning and rehabilitation approach (Section 10.2) unless specified otherwise in the Decommissioning Plan.
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The Cyanide Facilities Decommissioning Management Plan for NBG was developed to satisfy elements of Principle 5 of the International Cyanide Management Code for the Manufacture, Transport and use of Cyanide in the Production of Gold (the Cyanide Code) (International Cyanide Management Institute, 2002). Principle 5 addresses: Protection of personnel, communities and the environment from cyanide during decommissioning; and The establishment of adequate provisioning to undertake decommissioning.
The Cyanide Facilities Decommissioning Management Plan contains detailed information with respect to: System amendments, including: o Risk assessment; o Review of operational plans, procedures and work instructions; o Revision of Emergency Response Plan; and o Induction and training focused on changes to systems of work, new hazards posed by closure and an overview of cyanide decommissioning work. Project and task scheduling; Reagent stock reduction; Processing water inventory reduction; RDA Pre‐Decommissioning Audit; Pre‐closure clean up; Tanks and confined spaces; Cyanide disposal; Groundwater management; Post deconstruction contamination removal; and Site security.
The Cyanide Facilities Decommissioning Management Plan for NBG was last updated in 2010. Updating the Cyanide Facilities Decommissioning Plan at least every five years or when changes occur that impact strategies in the Plan is managed as part of operation of the site and hence is not included in the Closure Implementation Plan for CMU4.
Over the life of the operation several landfills have been created for the disposal of putrescible and non‐putrescible waste. One landfill is currently in operation. This landfill will be covered and rehabilitated as part of the rehabilitation of this domain.
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Table 10‐16 Closure Implementation Plan for CMU4 Activity Timing Responsibility Planning and Reporting Consult with stakeholders (including the local 2039 (two years Social Responsibility community) about retention of infrastructure and prior to Manager equipment. completion of processing) Prepare inventory reduction plan for stores of 2039 Processing Manager hydrocarbons and chemicals. Conduct risk assessment for infrastructure proposed 2040 HSLP Manager to be retained on site. Prepare agreements for infrastructure to be retained 2040 Site Business Manager on site or utilised by stakeholders. Signed agreements to detail: Responsibility for infrastructure post hand over; and Required condition of infrastructure at hand over. Establish responsibility for removal of infrastructure 2040 by third parties. Obtain permit to disturb beds and banks for removal 2041 Closure Superintendent of Hotham River pump station. Locate suitable storage location for drill core 2041 remaining at core yard. Prepare Decommissioning Plan 2041 Review plans submitted by third parties for removal 2041 of equipment and infrastructure. Develop work instructions for rehabilitation works 2042 onwards for disturbed areas. Decommissioning Relocate or dispose of drill core. 2042 Closure Superintendent Valuation of salvageable equipment and 2042 infrastructure by auctioneers. Decommission and salvage equipment and 2042 infrastructure. Auction equipment and infrastructure not needed by 2042 Newmont. Removal of auctioned equipment and infrastructure 2043 by third parties. Demolish and dispose of remaining infrastructure 2043 and equipment. Decommission and seal production bores. Ongoing as no Environment Manager longer required. (Op) / Closure Superintendent (Post‐Op)
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Activity Timing Responsibility Rehabilitation Backfill monitoring bores. Ongoing as Environment Manager Rip sealed roads and dispose of material. required. (Op) / Closure Mine compacted layer for sealed and unsealed roads Superintendent (Post‐Op) and re‐place material as loose fill. Break up and bury concrete. Break up bitumen areas. Remove contaminated soil and dispose of appropriately. Backfill with clean, competent material if required for surface water management. Reinstate drainage function where practical. Spread rehabilitation material over required areas. Deep rip disturbed areas on the contour to reduce compaction. Apply local provenance seed.
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10.3.5.3 Unplanned Closure Activities Considerable experience was gained at NBG regarding activities required for infrastructure in the situation of unplanned closure when the site was in care and maintenance between 2001 and 2006. The main activities required for CMU4 in the case of unplanned closure are the preparation, preservation and care and maintenance of infrastructure and equipment to sustain its usability and value.
In a care and maintenance period the following activities may be undertaken for the processing plant: Loaded carbon would be advanced through the system and stripped. The stripped carbon would then be surface dried to reduce the risk of galvanic corrosion, spontaneous combustion and accretion into carbon agglomerates due to salt egress. The dried carbon would be stored with earthing rods installed. Prior to re‐use the stored carbon may require cleaning and sizing to remove stone and grit material and carbon fines; During processing of the remaining carbon in the system the amount of reagents, hydrocarbons, consumables and spare parts stored on site would be reduced to meet minimum operating requirements; Equipment would be shut down appropriately to ensure minimal impact on start‐up; Tanks would be drained of slurry and filled with water to prevent corrosion; Pumps would be cleaned out and the barrels filled with grease to prevent corrosion; The mills would have all rocks removed from them and be turned over regularly; Hydraulic and pressurised lubrication systems would be treated with vapour phase inhibitors; Electrical Distribution Centre (EDC) rooms and switch panels would be cleaned, pest treatment maintained and air conditioners left running; General lighting would be maintained for security access purposes and safety at night; Essential power supplies would be left on. Emergency power supply and electrical circuits would be fully maintained and tested regularly; Security would be maintained around the magazine and explosives/emulsion batching plant; The processing plant area and laydown yards would be cleaned up; Roads and drains would be inspected and maintained; Productions bores would be inspected and maintained; and General repairs would be undertaken as required and opportunistic maintenance may be completed (such a replacing mill liners).
The care and maintenance activities undertaken would continue to be reviewed and amended as required until a decision is reached on re‐starting the mine or decommissioning the infrastructure.
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10.3.6 CMU5 ‐ Water Management Structures 10.3.6.1 Description CMU5 covers water management structures at NBG. A summary of these areas is included in Table 10‐17.
Table 10‐17 Summary of CMU5 Aspect Description Area of Disturbance 202 ha Key Potential Inadequate surface water management. Closure Risks Poor rehabilitation performance. Alteration of surface water regime. Potential Post‐ Nature conservation, recreation, forestry, water catchment, mining activities, Mining Land Use habitat/species management, manufacturing and industrial, managed resource protection Closure Strategy Remove and re‐shape to blend in with surrounding topography. Rehabilitation For lined facilities, slash liner and bury. Prescription For all facilities, re‐shape surface, application of 20 cm of gravel and 10 cm of topsoil, contour ripping and seeding. Completion Criteria Final landforms and constructed drainage features conform to approved designs and specifications which incorporate appropriate factors of safety to ensure design intent is maintained for the long term. Regional surface drainage to downstream environment is not prevented following the completion of earthworks. A suitable soil profile is in place to facilitate plant establishment and growth, as defined in approved Rehabilitation Management Plan. Fauna habitat structures have been established on rehabilitated areas. On maturity, vegetation will provide foraging and longer term potential nesting habitat for black cockatoos. Investigate strategies for recruitment of priority and recalcitrant flora into rehabilitated areas to levels consistent with the target ecosystem. Viable seed has been broadcast at rates sufficient to achieve the target ecosystem. Seed mix to contain at least 60 native forest species supplemented by seedlings. Species richness to resemble that of the target ecosystem as defined in the Rehabilitation Management Plan. Populations of key plant groups will be self‐sustaining. Retention and availability of critical ecosystem resources will resemble that of the target ecosystem as defined in the Rehabilitation Management Plan. Rehabilitation is of an age where it has the potential to regenerate after a wildfire.
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Aspect Description Water Storage Reservoirs Feature Water storage reservoirs D1, D4 and D5. Current Status D1 WSR ‐ Active. D4 WSR ‐ Active. Will be incorporated into footprint of waste rock landforms. D5 WSR ‐ Planned. Estimated Closure D1 WSR ‐ 2051 Date D4 WSR ‐ 2017 D5 WSR ‐ 2061 Dams and Turkeys Nests Feature Site dams and turkeys nests (including North and South clear water ponds). Current Status Active Estimated Closure 2042 Date Drainage Control Structures Feature Drains, sediment ponds Current Status Active Estimated Closure Some drainage structures will be retained post‐closure. Drainage structures Date not being retained will be progressively rehabilitated as they are no longer required. Pit Lake Outflow Channel Feature Post closure outflow channel from Wandoo South pit to Wattle Hollow Brook Current Status Not yet constructed. Estimated Closure Channel constructed and retained post‐closure. Date Landform Design Side slopes of 1V:3H. Depth of excavation for spillway varies between 0 and 35 m. Rehabilitation 300 mm of rock on side slopes to prevent erosion. Prescription
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10.3.6.2 Closure Implementation Plan The key closure activity for CMU5 is progressive rehabilitation of facilities as they are no longer required. Details of the timing and responsibility for closure and rehabilitation activities to be carried out for CMU5 are summarised in Table 10‐18 below. Decommissioning of any infrastructure associated with water management structures is included in CMU4.
In the early phases of closure, active management of surface water will be required to control runoff and sediment loads as earthworks are completed and vegetation establishes. As rehabilitation matures and sediment loads decrease, the requirement for water management will be reduced. The fate of the major water management structures is likely to be: North Clear Water Pond and Thirty‐Four Mile Brook Diversion Pond currently overflow via a spillway into the Wandoo North open pit in an upstream emergency or excessive rainfall. These facilities will be modified to permanently direct flow from Thirty‐Four Mile Brook into Wandoo North pit; South Clear Water Pond will be incorporated into the footprint of the open pit during mining; The Impacted Water Sump will be allowed to passively drain into Thirty‐Four Mile Brook once water quality is satisfactory for release; D1 WSR will initially be retained during closure for water storage and management of runoff from the upstream RDAs. Once the quality of runoff from the RDAs is suitable for discharge D1 WSR will be breached and flow will be directed directly to the open pits; and D5 WSR will initially be retained during closure for water storage and management of runoff and seepage from the upstream waste rock landforms. Once the quality of runoff and seepage from the waste rock landforms is suitable for discharge D5 WSR will be breached and flow will be directed to Thirty‐Four Mile Brook.
Table 10‐18 Closure Implementation Plan for CMU5 Activity Timing Responsibility Decommissioning Decommissioning of any infrastructure associated with water management structures included in CMU4. Construction Construct pit lake outflow channel. 2042 Closure Superintendent Rehabilitation For lined storage facilities, slash liner and bury Ongoing as no Environment Manager during backfilling. longer required. (Op) / Closure Breach or backfill storage facility. Superintendent (Post‐Op) Re‐shape storage facility to blend in with surrounding topography. Apply rehabilitation material to disturbed areas. Rip on the contour. Apply local provenance seed.
10.3.6.3 Unplanned Closure Activities In the case of unplanned closure, inspections and maintenance of water management structures would continue to prevent leakage and overtopping. Drainage structures would be inspected and sediment removal and erosion repair conducted as required.
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10.3.7 CMU6 ‐ Services 10.3.7.1 Description CMU6 covers services at NBG. A summary of these areas is included in Table 10‐19.
Table 10‐19 Summary of CMU6 Aspect Description Estimated Closure Some services will be: Date Progressively rehabilitated as they are no longer required; or Maintained post‐closure for monitoring and maintenance activities. Key Potential Personnel injuring during decommissioning. Closure Risks Potential Post‐ Nature conservation, recreation, forestry, water catchment, habitat/species Mining Land Use management, manufacturing and industrial, renewable energy generation Closure Strategy Remove and re‐shape disturbance areas to blend in with the surrounding topography. Rehabilitation Application of 20 cm of gravel and 10 cm of topsoil, contour ripping and Prescription seeding. Completion Criteria Appropriate tenure will be in place for gazetted roads and any infrastructure transferred to a third party prior to relinquishment or handover. Infrastructure is removed from site or buried, except where an asset transfer agreement is in place with key stakeholders for retention. A suitable soil profile is in place to facilitate plant establishment and growth, as defined in approved Rehabilitation Management Plan. Fauna habitat structures have been established on rehabilitated areas. On maturity, vegetation will provide foraging and longer term potential nesting habitat for black cockatoos. Investigate strategies for recruitment of priority and recalcitrant flora into rehabilitated areas to levels consistent with the target ecosystem. Viable seed has been broadcast at rates sufficient to achieve the target ecosystem. Seed mix to contain at least 60 native forest species supplemented by seedlings. Species richness to resemble that of the target ecosystem as defined in the Rehabilitation Management Plan. Populations of key plant groups will be self‐sustaining. Retention and availability of critical ecosystem resources will resemble that of the target ecosystem as defined in the Rehabilitation Management Plan. Rehabilitation is of an age where it has the potential to regenerate after a wildfire. Power Lines Feature Power lines and poles owned by NBG. Current Status Active. Pipelines Feature Water, residue and decant return pipelines. Current Status Active. Pipelines have been progressively rehabilitated as they are no longer required.
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10.3.7.2 Closure Implementation Plan The key closure activity for CMU6 is the progressive decommissioning and removal of power lines and pipelines as they are no longer required. Details of the timing and responsibility for closure and rehabilitation activities to be carried out for CMU6 are summarised in Table 10‐20.
Table 10‐20 Closure Implementation Plan for CMU6 Activity Timing Responsibility Planning and Reporting Confirm and document location of all NBG owned 2041 Business Manager power lines. Decommissioning For underground power lines, disconnect and leave Progressively as Environment Manager buried unless they pose a future risk. no longer (Op) / Closure For overhead power lines, isolate and remove required. Superintendent (Post‐Op) infrastructure in consultation with the Office of EnergySafety. Sell or recycle infrastructure where possible. For buried pipelines, flush and seal where they come to the surface unless the pose a future risk. Remove any above ground infrastructure related to buried pipelines (e.g. breather valves). For above ground pipelines, flush, cut into sections, remove and sell or recycle where possible. All pipe sections will be inspected to ensure clean‐out has been effective prior to removal from site. Appropriately dispose of all material not sold or recycled. Rehabilitation Doze in windrows on access corridors. Progressively as Environment Manager Backfill catchpits and sediment ponds which aren’t no longer (Op) / Closure required. required. Superintendent (Post‐Op) Apply rehabilitation material to disturbed areas if required. Rip on the contour. Apply local provenance seed.
10.3.7.3 Unplanned Closure Activities In the case of unplanned closure, inspections and maintenance of power lines and pipelines would continue until a decision is made on the future of the site. Cleaning of pole top insulators would need to continue to manage the risk of fire due to build‐up of dust.
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10.3.8 CMU7 ‐ Accommodation Village 10.3.8.1 Description CMU7 covers the accommodation village and sewage treatment plant. A summary of these areas is included in Table 10‐21.
Table 10‐21 Summary of CMU7 Aspect Description Accommodation Village Feature Accommodation units, kitchen, dry mess, wet mess, recreation room, gym, sports courts, parking facilities, security and administration offices. Area of Disturbance 36 ha Current Status Active Estimated Closure 2051. The accommodation village will be progressively decommissioned from Date 2041 as the work force decreases. Key Potential Poor rehabilitation performance. Closure Risks Personnel injuring during decommissioning. Post‐Mining Land Agricultural‐pastoral land. Use Closure Strategy Remove all infrastructure (unless retention of select facilities agreed upon with the Owner) and return the site to a condition that approximates the pre‐ construction land use. Rehabilitation Removal of trees and shrubs not native to the local area. Application of Prescription topsoil. Completion Criteria Land will be physically safe for people to access and not pose a human health risk. Vegetation will be re‐established within disturbed areas of land with plant species using a seed mix and native tree species selected in consultation with the Owner. Up to 4 live trees per hectare (126 total trees) shall exist on the land to achieve the pre‐disturbance tree density of the land. Planting to supplement the removal of trees during construction of the Accommodation Village shall be coordinated with the Owner.
A completion inspection shall be undertaken by the Owner and NBG on or before the first day of the thirteenth month following NBG’s notice to the Owner that the land has been rehabilitated. The completion certificate shall be signed by the Owner following the inspection or deficiencies with criteria will be actioned by NBG. Sewage Treatment Plant Feature Sewage treatment plant and ponds. Current Status Active. Estimated Closure 2046 Date Key Potential Poor rehabilitation performance. Closure Risks Personnel injuring during decommissioning.
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Aspect Description Potential Final Land The sewage treatment plant may be retained for ongoing use and Use management by the Shire of Boddington or Water Corporation. If the treatment plant is not retained, potential final land uses are nature conservation, recreation, forestry, water catchment and manufacturing and industrial Closure Strategy Removal of all infrastructure (unless retention is agreed upon) and return the site to a condition that approximates the condition prior to occupying the land. Rehabilitation Application of topsoil (if available), rip on the contour and seed with local Prescription provenance species. Completion Criteria Appropriate tenure will be in place for gazetted roads and any infrastructure transferred to a third party prior to relinquishment or handover. Infrastructure is removed from site or buried, except where an asset transfer agreement is in place with key stakeholders for retention.
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10.3.8.2 Closure Implementation Plan The key closure activities for CMU7 are: Consultation with the Owner to determine: o Facilities to be retained on site; and o Species to include in seed mix. Removal of all infrastructure not to be retained; Rehabilitation of disturbed areas; and Undertaking completion inspection with the Owner.
Details of the timing and responsibility for closure and rehabilitation activities to be carried out for CMU7 are summarised in Table 10‐22.
Table 10‐22 Closure Implementation Plan for CMU7 Activity Timing Responsibility Planning and Reporting Prepare agreement with the Owner for facilities to 2050 (one year prior Site Business Manager be retained on site of Accommodation Village. to decommissioning Signed agreement to detail: of Accommodation Responsibility for facilities post hand over; and Village) Required condition of facilities at hand over. Consult with the Owner regarding species to include 2050 Closure in seed mix for the Accommodation Village. Superintendent Consult with the Shire of Boddington and Water 2050 Closure Corporation regarding retention of sewage Superintendent treatment plant. Notify relevant authorities of any contaminated In accordance with Environment Manager areas at the Accommodation Village. requirements of (Op) / Closure Contaminated Sites Superintendent (Post‐ Act 2003 Op) Prepare completion certificate after inspection of 2052 (12 months Closure site by the Owner of the Accommodation Village. after completion of Superintendent rehabilitation) Decommissioning Remove all infrastructure at the Accommodation 2051 Closure Village for which there is not a signed agreement Superintendent with the Owner to retain. Remove all infrastructure from the sewage treatment plan for which there is not a signed agreement to retain. Rehabilitation Identify and rehabilitate any contaminated areas at 2051 Closure the Accommodation Village. Superintendent Remove trees and shrubs at the Accommodation Village not native to the local area. Apply stockpiled topsoil to disturbed areas at the Accommodation Village. Deep rip on the contour to reduce compaction at the Accommodation Village.
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Activity Timing Responsibility Re‐establish vegetation at the Accommodation Village using seed mix and native tree species selected in consultation with Owner. Apply topsoil to disturbed areas at sewage treatment plant if available. Deep rip on the contour to reduce compaction at the sewage treatment plant. Apply local provenance seed to the sewage treatment plant area. Undertake completion inspection of the On or before the first Accommodation Village with the Owner. day of the thirteenth month following NBG’s notice that the land has been rehabilitated.
10.3.8.3 Unplanned Closure Activities In the case of unplanned closure, sections of the Accommodation Village not being utilised would be cleaned, sanitised and secured. Areas of the Village such as the kitchen, dry mess, wet mess and sporting facilities would continue to be utilised for the reduced workforce in place during the care and maintenance period.
The sewage treatment plant would continue to be inspected and maintained during care and maintenance.
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10.3.9 CMU8 ‐ Temporary Stockpiles 10.3.9.1 Description CMU8 covers stockpiles of materials planned to be removed during the operational or post‐closure periods. A summary of the features of CMU8 is included in Table 10‐23
Table 10‐23 Summary of CMU8 Aspect Description Area of Disturbance 207 ha Key Closure Risks Medium grade stockpiles not located or constructed with closure considered as it is assumed they will be processed. Poor rehabilitation performance. Potential Final Land Use Nature conservation, recreation, forestry, water catchment, mining activities, habitat/species management, manufacturing and industrial, managed resource protection Closure Strategy Remove to natural ground level and re‐shape to blend in with surrounding topography if required. Landform Design Incorporate into surrounding landform. Rehabilitation Prescription Apply topsoil, deep rip on the contour and seed with local provenance species. Completion Criteria Light vehicle access on to bauxite stockpiles is restricted by bunds. A suitable soil profile is in place to facilitate plant establishment and growth, as defined in approved Rehabilitation Management Plan. Fauna habitat structures have been established on rehabilitated areas. On maturity, vegetation will provide foraging and longer term potential nesting habitat for black cockatoos. Investigate strategies for recruitment of priority and recalcitrant flora into rehabilitated areas to levels consistent with the target ecosystem. Viable seed has been broadcast at rates sufficient to achieve the target ecosystem. Seed mix to contain at least 60 native forest species supplemented by seedlings. Species richness to resemble that of the target ecosystem as defined in the Rehabilitation Management Plan. Populations of key plant groups will be self‐sustaining. Retention and availability of critical ecosystem resources will resemble that of the target ecosystem as defined in the Rehabilitation Management Plan. Rehabilitation is of an age where it has the potential to regenerate after a wildfire. Medium Grade Stockpile Feature Stockpile of medium grade ore. Current Status Active Estimated Closure Date 2041
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Aspect Description Bauxite Stockpiles Feature Stockpiles of bauxite disturbed during NBG mining operations. Current Status Bauxite stockpiles will be left in a state suitable for recovery by Worsley. Rehabilitation of the footprint of the stockpiles will be the responsibility of Worsley. Estimated Closure Date Dependent on mining schedule of Worsley. Gravel Stockpiles Feature Gravel material stockpiled for rehabilitation use. Current Status Active Estimated Closure Date 2051 Topsoil Stockpiles Description Topsoil material stockpiled for rehabilitation use. Status Active Estimated Closure Date 2051
10.3.9.2 Closure Implementation Plan The key closure activity for CMU8 is the progressive rehabilitation of the footprint of the stockpiles as they are removed. Details of the timing and responsibility for closure and rehabilitation activities to be carried out for CMU8 are summarised in Table 10‐24.
Table 10‐24 Closure Implementation Plan for CMU8 Activity Timing Responsibility Rehabilitation If any material is remaining, re‐shape to blend in Ongoing as areas Environment Manager with surrounding topography. become (Op) / Closure Reinstate drainage function where practical. available. Superintendent (Post‐Op) Apply topsoil if required. Deep rip to break up compacted soils. Apply local provenance seed.
10.3.9.3 Unplanned Closure Activities In the case of unplanned closure of the site, the inventory of rehabilitation material balances would be updated to verify the availability of suitable material for rehabilitation of disturbed areas.
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10.3.10 CMU9 – Storage Shed at Bunbury Port 10.3.10.1 Description CMU9 covers the concentrate storage shed at the Bunbury Port. A summary of CMU9 is included in Table 10‐25.
Table 10‐25 Summary of CMU9 Aspect Description Concentrate Storage Shed Feature Concentrate storage shed located at Bunbury Port. Current Status Active Estimated 2042 Closure Date Closure Sell to a third party. Strategy
10.3.10.2 Closure Implementation Plan The key closure activity for CMU9 is to find a third‐party to purchase the storage shed. Details of the timing and responsibility for closure and rehabilitation activities to be carried out for CMU9 are summarised in Table 10‐26.
Table 10‐26 Closure Implementation Plan for CMU9 Activity Timing Responsibility Planning and Reporting Prepare agreement for storage shed to be 2040 Site Business Manager purchased. Decommissioning Clean storage shed to remove residual copper 2042 Closure Superintendent concentrate.
10.3.10.3 Unplanned Closure Activities In the case of unplanned closure, ongoing maintenance of the concentrate storage shed would be required in the care and maintenance phase
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10.4 Social Responsibility Plan The NBG Social Responsibility Plan currently focuses on: Cultural heritage management; Stakeholder consultation; Social investment; Moorditj Booja Community Partnership Agreement; and Live, hire and buy local.
The Social Responsibility Plan is: Based on engagement with a wide range of external stakeholders; Informed by Social Impact Assessments; Guided by Newmont standards; and Supportive of wider community, regional and national development plans beyond the life of mine, particularly social and economic diversification and sustainability.
Closer to the end of mine life the Social Responsibility Plan will be refined to address the potential impacts of closure, particularly on the local community. More information on each area of the Social Responsibility Plan is included in the following sections.
10.4.1 Cultural Heritage Management The NBG Cultural Heritage Management Plan stipulates the management requirements that are to be applied to all activities that occur within the Heritage Area of Influence from exploration to mine closure. NBG is required to ensure that all Aboriginal heritage sites are managed and protected in accordance with legislation, and will meet its responsibilities by: Engaging with the Gnaala Karla Booja People who are recognised as having authority to speak for country; and Designing all activities from exploration through to life of mine to avoid damage to Aboriginal heritage sites.
10.4.2 Stakeholder Engagement Efficient and inclusive stakeholder engagement fosters a sense of trust and security within the community that their needs and concerns relating to the environmental, social and economic issues will be addressed in the event of mine closure. Other benefits of informing stakeholders and allowing them to participate in the closure process include: Improvement to the planning process; Improved staff motivation; Improved interagency relations; Better acceptance of closure decisions among stakeholders and community members; Enhanced mine reputation; and Community receptiveness to future proposals.
Stakeholder engagement can also assist in mitigating the impacts of change during and after mine closure.
Stakeholder mapping and engagement has been undertaken during development of this Closure Plan (Section 5). Stakeholders will continue to be consulted in relation to post‐closure outcomes during the operation of the project. Feedback from stakeholders will be incorporated into the Plan where feasible.
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10.4.3 Social Impact Management Plan Studies of communities affected by mine closure have shown that there will almost always be impacts on the local community in the form of the removal of some or all of the positive contributions made by the mine during its life (Andrews‐Speed et al., 2005, Browne et al., 2009a, b, CSRM, 2009, Haney & Shkaratan, 2003, Readford, 2010). Common impacts experienced by communities can include: Loss or decrease in incomes; Increased unemployment; Local economic decline; Population decline; Depressed real estate market; Decline in infrastructure (reduced demand for childcare, organised recreation, health services and schooling); Disruption to family relationships; and Loss of community participation and identity.
By considering mine closure early, operations are in a better position to ensure the long term sustainability of the community by avoiding creating dependency on the mine for social and community services and economic benefit. If planning processes are implemented prior to closure, mining communities will be better positioned to effectively manage these impacts by preparing before they occur. Impact assessment has the potential to provide information that can inform closure planning by directing attention to key areas of potential impact. Such nstudies ca also be used as a basis to engage with communities to understand perceived impacts, identify how best to manage adverse impacts and explore opportunities that mine closure may bring.
Assessing the communities’ capacity to adapt to change might also help with understanding how they respond to the impacts of mine closure for community planning purposes. This can guide the objectives for community planning through implementation of projects and programs that address community needs, build local capacity for self‐management and foster resilience to change, such as: Establishing a closure committee/advisory panel comprising relevant stakeholders; Stimulating alternative economic activity during the mining operation in order to diversify the local economy; Capacity building for organisations and groups with responsibilities and interests in post‐closure issues; Progressively releasing company homes into private ownership in order to preserve local real estate markets; Developing infrastructure that will last a long time; Establishing a community trust fund; and Articulation of a future social or regional identity that may not include mining.
The projects and programs implemented for closure of NBG will be based upon the requirements of the local community at the time and will consider what has been successful in other communities, such as setting up a trust fund and advisory committee at Newmont Waihi Gold.
10.4.3.1 SuperTowns Initiative Newmont is part of the Project Team for the SuperTowns initiative for Boddington. This initiative is aimed at encouraging regional communities located in the southern half of Western Australia to plan and prepare for doubling of the State’s population of the next 40 years (Department of Regional Development and Lands, 2011). The aim of SuperTowns is to prepare communities for natural population expansion and to give them the capacity, vibrancy and commercial and industrial base
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that will provide an attractive choice for people wanting to live in regional towns. The key focus areas of the program are: Governance, strategic planning and community engagement; Development of healthy, attractive and well‐planned communities (including streetscape, business and revitalisation programs); Sustainable communities; Economic activity and employment opportunities (including industry attraction, workforce planning, skills development and technology and innovation); Community engagement Aboriginal participation; Maximisation of the benefits of technology and innovation; Asset and infrastructure management; Integrated transport and key infrastructure linkages; and Marketing and strengthening of identity.
The SuperTowns initiative ties in with Newmont’s goal of making Boddington socially and economically sustainable after closure of the mining operations. As part of the private sector Newmont can participate in the initiative by providing support for economic growth in the region by supporting growth and improving quality of life in order to attract and retain staff (Department of Regional Development and Lands, 2011).
10.5 Workforce Transition Program A workforce transition program will be developed at least one year prior to the closure of the site to ensure that employees are provided with information, support and training to minimise the effect of the closure of the operations. Development and implementation of the workforce transition program is likely to include the following activities.
Prior to closure a questionnaire may be distributed to all NBG employees in order to gain their input into the matters of: Redundancy timing; Transfers; Closure concerns; Training; Advice required to deal with closure; and Access to counselling.
The responses to this questionnaire will form the basis for establishment of the communication, training and counselling services. Programs and services established for employees may include: Career and financial advice to prepare for work prospects and other opportunities after closure; Appraisals to provide employees with a record of their performance and skills; Training to ensure that operating tickets are renewed; Communication to ensure that work opportunities within Newmont and externally with contactors are known; Job skills workshops to provide participants with the knowledge, skills and confidence to conduct their job search; Services of a typist for curriculum vitae preparation; Increased access to counselling services; and Incentives for retention of key employees.
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Figure 10‐1 – NBG Closure Management Units
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Figure 10‐2 Progressive rehabilitation F1/F3 RDA – saddle dams 1, 2 and 10
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Figure 10‐3 Progressive rehabilitation F1/F3 RDA – saddle dams 7, 8, 9 and 10
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Figure 10‐4 Progressive rehabilitation F1/F3 RDA – saddle dams 5 and 7
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Figure 10‐5 Progressive rehabilitation F1/F3 RDA – saddle dams 3, 4, 5 and 7
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Figure 10‐6 Progressive rehabilitation F1/F3 RDA – saddle dams 3 and 4
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R12 199.3ha
R9 63.7ha
R15 52.2ha
R8.2 103ha R14 118.6ha
R8.1 R11.1 31.5ha 43.7ha R7.2 57.9ha R11.2 37.8ha
R13 R10.1 324.7ha R7.1 38.2ha 50.1ha
R10.2 62.9ha R10.3 61.0ha
Figure 10‐7 Rehabilitation zones for waste rock landforms
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R12.a 97ha
R11.1.a 21.1ha
Figure 10‐8 Progressive rehabilitation waste rock landforms ‐ 2024
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R12.b 69.8ha
R11.1.b 17.2ha
Figure 10‐9 Progressive rehabilitation waste rock landforms ‐ 2027
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R12.c 32.5ha
Figure 10‐10 Progressive rehabilitation waste rock landforms ‐ 2028
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R11.2.a 14.1ha
Figure 10‐11 Progressive rehabilitation waste rock landforms ‐ 2034
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R11.2.b 17ha
R10.1.a 18.4ha
R10.2.a 39.7ha
Figure 10‐12 Progressive rehabilitation waste rock landforms ‐ 2037
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R10.1.b 7.2ha
R10.2.b 9.6ha
Figure 10‐13 Progressive rehabilitation waste rock landforms – 2039
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R10.1.c 7.2ha
R10.2.c 8.3ha
Figure 10‐14 Progressive rehabilitation waste rock landforms – 2041
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R15 52.2ha
R14 118.6ha
R9 63.7ha
R7.1, R7.2, R8.1, R8.2, R10.1.d, R10.2.d, R10.3.a, R10.3.b, R11.1.c, R11.2.c 651.2ha
Figure 10‐15 Progressive rehabilitation waste rock landforms – 2042 onwards
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11 CLOSURE MONITORING AND MAINTENANCE This section summarises the post‐closure monitoring (Section 11.1), remedial activities (Section 11.2) and maintenance programme (Section 11.3) for NBG.
11.1 Post‐Closure Monitoring Programme Following closure there will be a period of monitoring to demonstrate: Progress towards and the final achievement of completion criteria; That the operation is approaching a safe and sustainable state; and There are no persistent adverse impacts.
The post‐closure monitoring programme utilises pre‐mining and operational information as its foundation and is based upon the Environmental Monitoring Management Plan. The proposed monitoring programme includes: Surface water monitoring; Pit lake monitoring; Groundwater monitoring; and Rehabilitation monitoring.
A summary of each component of the proposed monitoring programme is included below.
The ultimate objective of post‐closure monitoring is to achieve lease relinquishment. This can only be considered when it is clearly shown that approved completion criteria have been met. For NBG, the post‐closure monitoring period has been nominated as 20 years. However, monitoring will be conducted until such time as it can be established that there are no significant ongoing impacts from the site. As monitoring data trends approach completion criteria or stabilise, the intensity of monitoring will be reduced in accordance with the decreasing risk. The results of post‐closure monitoring will be submitted to the appropriate regulatory authorities in annual reports.
If monitoring indicates completion criteria are not being met, or are not likely to be met, monitoring and annual reporting will continue and an appropriate investigation will be undertaken to determine the likely causes of the failure and to assist in the development of remedial actions if required.
Appropriate Quality Assurance/Quality Control (QA/QC) for field sampling will be required to ensure the absence of possible exposure to contamination. Quality control will be based upon the system developed and implemented during operation of NBG. QA/QC will include the use of: Field blanks to estimate contamination during the sample collection procedure; Transport blanks to estimate the amount of contamination introduced during the transport and storage of samples from the time of sampling until the time of analysis; and Duplicate samples to measure the sampling error and precision.
All field instruments will be calibrated before use and documented in a log sheet. All sampling equipment will be rinsed with distilled water before and after use. Field filtration will be undertaken for samples that need to be stabilised.
Standard metadata such as the date, time, location and climate information will be recorded.
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Water and sediment samples are susceptible to change as a result of physical, chemical and biological reactions which may take place between the time of sampling and analysis. Sample preservation is intended to retard the chemical and biological changes that continue after sample collection. Sample bottles will be supplied by the external National Association of Testing Authorities (NATA) accredited laboratory that undertakes the sample analysis. Sample bottles will be pre‐ prepared to preservation requirements.
A properly designed and executed chain of custody procedure will ensure sample integrity from collection to data reporting, including the ability to track possession and handling of samples from the time of collection through to analysis. The chain of custody procedure will cover the following aspects: Sample labels; Field log books; Chain of custody record; Shipping papers; Delivery to the laboratory; and Tracking system.
All data will be checked for: Compliance with internal requirements and licence conditions; and Unusual results or possible trends.
Once the data has been final checked it will be imported into the environmental monitoring database.
Risks associated with the monitoring programme will be identified and adequately controlled. The monitoring programme will be conducted in accordance with Newmont’s Health, Safety & Loss Prevention Policy, Standard Operating Procedures (SOPs) and work instructions.
11.1.1 Surface Water Monitoring The potential impacts of mining activities at NBG on surface water may include: Changes to water quality (including sedimentation) caused by runoff from RDAs, waste rock landforms and other disturbed areas; Interruption of surface hydrology by damming and diversion of natural drainage lines which can cause; o Reduction in vegetation health by water logging; o Reduction in vegetation health by reduction in water supply; and o Reduced water supply to soaks, dams and downstream water courses. Changes to long‐term flow patterns and water quality due to overflow of water from pit lakes.
Monitoring of surface water will be targeted at detecting these potential impacts during the post‐ closure period.
11.1.1.1 Monitoring Sites Post‐closure surface water monitoring will be conducted at the following locations: Decant ponds until water is no longer present; RDA underdrainage and Leak Collection Recovery System (LCRS) until decommissioned or dry; Water storage facilities (i.e. D1 WSR) until they are breached;
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Sediment sumps (including waste rock landform sediment ponds); Runoff from rehabilitated landforms; and Boggy Brook, Wattle Hollow Brook, House Brook, South Dandalup Streams, Thirty‐ Four Mile Brook and Hotham River at locations upstream and downstream of the operations.
11.1.1.2 Monitoring Procedure Surface water monitoring will comprise water level (where relevant) and water quality measurements. Water levels will be measured by either manual readings or automated telemetry.
For water quality monitoring, water samples will be collected and preserved in accordance with the requirements of the current Australian Standard (at present AS/NZS 5667.1‐1998 (Water Quality – Sampling – Guidance on the design of sampling programs, sampling techniques and the preservation and handling of samples)). Water samples will be submitted to a laboratory with current NATA accreditation for the analysis undertaken. Samples will be analysed in accordance with the current “Standard Methods for Examination of Water and Wastewater – APHA‐AWWA‐WEF” or other methods endorsed as appropriate by regulatory authorities. Parameters to be analysed will be site dependent and may include: pH; Electrical conductivity (EC); Total dissolved solids (TDS); Total suspended solids (TSS); Metals; and Cyanide.
At the time of sampling, field pH, EC and dissolved oxygen will be measured using portable instruments where required. Field analysis will be undertaken in accordance with the requirements of the instrument manufacturer.
11.1.2 Pit Lake Monitoring Pit lakes can have a wide range of water chemistries depending on factors such as local geology, climate, pit morphometry, rate of filling and the type of water used to fill the lake (Gammons & Tucci, 2011). Newmont has undertaken modelling to determine the predicted post‐closure water quality and filling time of the open pit voids. Pit lake monitoring will be conducted to: Compare the filling rate with the model predictions; and Analyse and track changes in the water quality during initial filling of the pit lake.
The pit lake sampling regimen will be initiated immediately after pit filling commences so that any developing water quality problems can be recognised as soon as possible and early enough that management intervention can be successfully implemented. The Australia and New Zealand Guidelines for Fresh and Marine Water Quality (ANZECC/ARMCANZ 2000) provide guidance on limits and trigger values for various standard end uses.
Pit lakes and their surrounding environment represent a significant health and safety risk to workers. The pit lake monitoring programme will take into account: Acute risks such as drowning; and Chronic risks such as inappropriate and sustained physical exertion.
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11.1.2.1 Monitoring Sites Pit lake monitoring will be conducted from areas of the open pit voids that are safe to access post‐ closure. The best location to collect long‐term data will be in the deepest portion of the pit lake (if horizontal gradients in chemistry are minimal). Enough water samples will be collected to represent each of the vertical compartments of the pit lake.
The composition of groundwater springs, permanent or transient surface water and runoff from pit walls after a major rain event may also be sampled for predictions of water chemistry.
11.1.2.2 Monitoring Procedure Pit water quality monitoring will be incorporated into the existing water monitoring procedures prior to closure of the site. Water samples will be collected and preserved in accordance with the requirements of the current Australian Standard (at present AS/NZS 5667.1‐1998 (Water Quality – Sampling – Guidance on the design of sampling programs, sampling techniques and the preservation and handling of samples)).
Water samples will be collected using point samplers (e.g. a Van Dorn sampler) or by pumping water to the surface with a submersible or peristaltic pump. At the time of sampling, field pH, EC and dissolved oxygen will be measured using a submersible meter. Field analysis will be undertaken in accordance with the requirements of the instrument manufacturer.
Water samples will be submitted to a laboratory with current NATA accreditation for the analysis undertaken. Samples will be analysed in accordance with the current “Standard Methods for Examination of Water and Wastewater – APHA‐AWWA‐WEF” or other methods endorsed as appropriate by regulatory authorities. Parameters to be analysed may include: pH; EC; TDS; TSS; Nutrients (nitrate, phosphate, nitrite and ammonium); and Metals.
Monitoring will also include general observations recording information about the pit lake and the surrounding environment such as water colour and changed landscape features such as erosion.
11.1.3 Groundwater Monitoring The potential impacts of mining activities at NBG on groundwater may include: Fluctuation (increase or decrease) in groundwater levels caused by: o Mine dewatering and subsequent recovering of water levels after the completion of mining; o Seepage and seepage recovery from waste rock landforms and RDAs; and o Evaporation from pit lakes. Changes in groundwater quality resulting from: o Seepage from waste rock landforms, RDAs and pit lakes; o Contamination from spills and historic mining activities; and o Exposure of mineralised zones in open pit and underground mines resulting in acid and/or metalliferous drainage.
Groundwater monitoring will be targeted at detecting these potential impacts during the post‐ closure period.
11‐4 Newmont Boddington Gold – Closure Plan Closure Monitoring and Maintenance
11.1.3.1 Monitoring Sites Monitoring bores are located throughout the region of the NBG operations with concentration of sites in the vicinity of the residue disposal areas, open pits, waste rock landforms and water supply reservoirs. The sites to be monitored post‐closure will be determined using a risk‐based approach based upon bores monitored during operations.
11.1.3.2 Monitoring Procedure Groundwater monitoring will comprise water level and water quality measurements. Groundwater levels will be measured by automated depth sensors or manually using a portable water level meter.
Water quality monitoring will be consistent with the current Australian Standard (at present AS/NZS 5667.1‐1998 (Water quality – Sampling Part 1: Guidance on the design of sampling programs, sampling techniques and the preservation and handling of samples) and AS/NZS 5667.1‐1998 (Water quality – Sampling Part 1.1: Guidance on sampling of groundwaters)). Water samples will be submitted to a laboratory with current NATA accreditation for the analysis undertaken. Samples will be analysed in accordance with the current “Standard Methods for Examination of Water and Wastewater – APHA‐AWWA‐WEF” or other methods endorsed as appropriate by regulatory authorities. Parameters to be analysed will be site dependent and may include: pH; EC; TDS; Metals; and Cyanide.
At the time of sampling, field pH and EC will be measured using portable instruments. Field analysis will be undertaken in accordance with the requirements of the instrument manufacturer.
11.1.4 Rehabilitation Monitoring Rehabilitation monitoring is undertaken to: Ensure: o The soil profile constructed during rehabilitation is suitable for the development of the target ecosystem; o Rehabilitated areas provide habitat for native fauna; o Vegetation will resemble that of the region and enable integration into the surrounding landscape; and o Ecosystem function resembles that of the target ecosystem. Detect areas of rehabilitation in need of repair or re‐treatment; and Determine that rehabilitation has stabilised sufficiently prior to the removal of drainage protection.
11.1.4.1 Monitoring Sites Monitoring will be conducted on rehabilitation areas based on the year in which it is rehabilitated. The size and shape of future rehabilitation areas will be dependent on the advancement of progressive rehabilitation of current and future disturbance areas. Monitoring locations will be added over time as new areas of rehabilitation are completed.
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11.1.4.2 Monitoring Procedure The rehabilitation monitoring programme is summarised in Table 11‐1.
Assessment of topsoil and gravel depth, ripping depth and fauna habitat density will be undertaken following completion of rehabilitation earthworks. Vegetation monitoring will be conducted through installation of monitoring plots, which can be re‐assessed over time as vegetation develops and matures. Data collected will include: Density of: o Trees; o Legumes; o Understorey species; o Weeds; and o Native trees resistant to Phytophthora cinnamomi. Proportion of plant species with attributes contributing to black cockatoo habitat.
Vegetation monitoring will commence progressively as revegetation of disturbance areas is completed.
An appropriate monitoring method will be determined for erosion, infiltration and nutrient cycling and monitoring of the soil seed bank. Erosion monitoring may consist of rill assessment, erosion pin monitoring, photo point monitoring or LiDAR (Light Detection and Ranging). Infiltration and nutrient cycling may be assessed by conventional quantitative procedures or Landscape Function Analysis. Monitoring of the soil seed bank may involve taking soil samples and conducting germination testing to determine the number of viable seed and the species represented.
Table 11‐1 Rehabilitation monitoring programme Parameter Units Monitoring Frequency Topsoil and gravel depth cm Assess once following rehabilitation earthworks. Fauna habitat density Number of Record at establishment or at habitats/ha 9 months. Ripping depth m Assess once following rehabilitation earthworks. Density of trees Stems/ha At approximately: Density of legumes Stems/ha 9 months Density of understorey species Stems/ha 3 years Density of weeds Stems/ha 7 years Density of native tree species resistant to Stems/ha 12 years Phytophthora cinnamomi 20 years Proportion of plant species with attributes % contributing to black cockatoo habitat. Species richness Species/80m2 Nutrient Cycling Dependent on Infiltration method used Erosion Viable seed of trees, legumes and Number/m2 At 7 years understorey species
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11.2 Remedial Activities For each CMU potential trigger events have been identified that may require remedial activities to prevent or mitigate impacts (Table 11‐2). Remedial activities cannot be planned in detail as the most appropriate action will be dependent on the factors contributing to the trigger event; however, anticipated remedial activities have been identified.
Table 11‐2 Remedial activities CMU Trigger Event Anticipated Remedial Activities 1 Access restrictions fail. Undertake remedial earthworks to reconstruct and/or relocate abandonment bund. Replace and/or increase signage. 1‐8 Revegetation does not meet Conduct chemical and/or physical assessment of the topsoil completion criteria or not to determine the cause of revegetation failure. trending towards Apply viable soil material appropriate to the location’s sustainability. conditions, if available. Undertake additional seeding or planting of seedlings. Consult with the key stakeholders regarding amendment to completion criteria and/or post‐mining land use objectives. 1‐8 Weeds impacting Investigate and implement control methods where rehabilitated ecology. appropriate. 1‐8 Excessive ponding of surface Investigate surface water management and conduct water or runoff. earthworks to resolve where possible. 1‐8 Excessive erosion. Improve drainage control mechanisms or undertake repairs to ensure water is controlled from a “top‐down” approach. This could include directing water away from bunds and constructing catchment cells. Armour with competent material if material type is contributing to erosion. Re‐work rehabilitated areas to re‐instate appropriate ground levels or construct bunds. 1‐3 Integrity of ripping fails or Re‐rip on the contour. contributes to the concentration of water in some areas. 1‐3, 5 Areas of subsidence or Backfill with competent material and monitor. instability. 2 Covers are inadequate and Investigate and apply a suitable cover where possible. impacts of the exposed underlying material are unsustainable. 2, 4, Excessive sedimentation. Implement suitable repair and control methods. 5, 7, 8 2, 3 Failure of berms. Undertake repairs to restore capacity. Angle berms towards landform to prevent run‐off. Re‐rip the bottom of the berm to increase infiltration. Increase bund dimensions to prevent over‐topping. 2, 3 Long term water quality does Undertake risk assessment. not meet completion criteria. Undertake investigations to identify the source of any contamination.
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CMU Trigger Event Anticipated Remedial Activities Revise rehabilitation approach in the area. Restrict water usage. 3 Poor quality seepage. Install pumps and bores to intercept and recover seepage. Install cut‐off trenches. 4, 7 Cover material over buried Investigate and apply a suitable cover material where foundations inadequate. possible. 4, 6, 7 Overlooked infrastructure Remove infrastructure from site. identified post‐closure. 4 Subsidence of rehabilitated Excavate and compact voids to ensure further subsidence bores. does not occur. 8 Storage shed at Bunbury port Remove all infrastructure and return site to a condition that cannot be sold. approximates the condition prior to occupying the land.
11.3 Post‐Closure Maintenance Programme Post‐closure management requirements typically include (DITR, 2006): Weed control Exclusion or control of grazing animals; Control of public access; Fire management; and Maintenance of safety signs and fences.
The objective of rehabilitation of the NBG site is that active management other than that normally required for the agreed post‐closure land uses should not be required.
The NBG post‐closure maintenance programme will include the following activities until they are no longer required or responsibility is transferred to another party: Residue Disposal Areas o Inspections and auditing of the RDAs to ensure compliance with DMP guidelines for tailings storage; o Maintenance of RDA freeboard; and o Maintenance of drainage, pumpback and underdrainage facilities until decommissioned or dry. Water Storage Reservoirs o Annual geotechnical audits until breached. Security o Maintenance of fencing and signage. Reporting o Submission of Annual Environmental Report, including an Annual Hydrological Review; o Monitoring and reporting for National Pollutant Inventory (NPI) (if trigger level reached). Stakeholder Engagement o Ongoing liaison with stakeholders (including the local community and regulatory authorities); and o Participation in joint fire control plan and feral animal control programs. General o Continuation of weed management program, feral animal control and fire management;
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o Maintenance of surface water management structures until no longer required (including sediment removal and erosion repair as required). The level of maintenance required is expected to decrease as revegetation establishes; o Maintenance of necessary roads and tracks (including dust management where required); o Maintenance of vehicle wash‐down units; o Maintenance of management systems (EMS, IMS); o Updating of Emergency Response Plan; and o Servicing of fire extinguishers.
11‐9 Newmont Boddington Gold – Closure Plan Management of Information and Data
12 MANAGEMENT OF INFORMATION AND DATA The retention of mine records is important as they provide (ANZMEC/MCA, 2000); A history of: o Past developments; and o Closure implementation at the site Information for incorporation into state and national resource databases; and The potential for improved future land use planning and/or site development.
The Progressive Rehabilitation and Closure (PRAC) system developed by Outback Ecology will be utilised at NBG to manage: Documentation relating to rehabilitation and closure; and Planned rehabilitation and closure activities.
The PRAC system is a Geographic Information System (GIS) based mine closure planning tool that provides a systematic approach for planning and closure as a dynamic and continuous process.
Documentation relevant to closure and rehabilitation is stored within the PRAC system and linked to the applicable domain(s) to provide an information database. Relevant documentation will continue to be uploaded to the PRAC system as it becomes available and more knowledge is gathered.
Storing documentation in the PRAC system facilitates easy accessibility, including remotely, as it is stored on a secure remote server. The PRAC system also creates a repository of information that can be handed over to regulatory authorities upon the relinquishment of the site if necessary.
The PRAC system will also be set up to manage closure activities, such as investigations, monitoring and rehabilitation tasks, for each domain. Upon finalisation and approval of this Closure and Rehabilitation Management Plan, the Closure Implementation Plans detailed in Section 10 will be loaded into the PRAC system to help with management of activities and tracking of progress over time.
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Newmont Boddington Gold – Closure Plan References
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Australian and New Zealand Minerals and Energy Council (ANZMEC) and Minerals Council of Australia (MCA) (2000), Strategic Framework for Mine Closure.
Bemax Resources Incorporating Cable Sands (Bemax) (2009), Status of Completion Criteria at the Ludlow Mine Site, February 2009.
Biggs, E. (2008), Habitat Selection by South‐West Cockatoos: Carnaby’s Cockatoo (Calyptorhynchus latirostris), Baudin’s Cockatoo (Calyptorhynchus baudinii) and the Forest Red‐Tailed Black Cockatoo (Calyptorhynchus banksii naso) in the Eastern Ecotone of Jarrah Forest, Western Australia.
Boddington Gold Mine (BGM) (2003), Boddington Gold Mine Acid Mine Drainage Study – Kinetic Testwork Final Report October 2003.
Browne, A.L., Buckely, A. and Stehlik, D. (2009a), A Rapid Rural Appraisal of the Closure of the Ravensthorpe Nickel Operation: A focus on the social, environmental and economic impacts for Ravensthorpe, Hopetoun and Jerdacuttup, Western Australia.
Browne, A.L., Stehlik, D. and Buckley, A. (2009b), The Mega‐Projects Paradox and the Politics of Risk, Hope and Mistrust: Capturing localised impacts of the boom/bust cycles of Australian mining.
Campbell, G., Haymont, R. and Amoah, N. (2012), A Testing Approach to Assess the Weathering Behaviour of Lithotypes Characterised by e a Trac ‐sulphide/Carbonate‐deficient Mineralogy: Application to Altered Andesites/Diorites at the Boddington Gold Mine, Western Australia. In: ICARD 2012, Ottawa, Canada.
Centre for Social Responsibility in Mining (CSRM) (2009), Social Impacts of Closure of Newmont Waihi Gold Operations. Sustainable Minerals Institute, The University of Queensland.
Commonwealth Department of Industry, Tourism and Resources (2006), Mine Closure and Completion.
Commonwealth of Australia (1996), National Strategy for the Conservation of Australia’s Biological Diversity.
Commonwealth of Australia (2010), EPBC Act – Frequently Asked Questions.
Department of Environment and Conservation (DEC) (2009a), Fact Sheet 4: Climate Change Projections for Western Australia.
Department of Environment and Conservation (DEC) (2009b), Information Sheet 17/2009 – Wildfires can be Bad for Biodiversity.
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Department of Environment and Conservation (DEC) (2010), Assessment Levels for Soil, Sediment and Water. Contaminated Sites Series. Version 4, Revision 1.
Department of Industry and Resources (DoIR) (1997), Safety Bund Walls around Abandoned Open Pit Mines – Guideline.
Department of Industry and Resources (DoIR) (2007), Alcoa World Alumina Australia Darling Range Bauxite Mine Rehabilitation Completion Criteria.
Department of Industry Tourism and Resources (DITR) (2006), Leading Practice Sustainable Development Program for the Mining Industry Mine Closure and Completion.
Department of Mines and Petroleum (DMP) (2006), 15 Years Golden Gecko Awards for Environmental Excellence Commemorative Booklet.
Department of Mines and Petroleum (DMP) and Environmental Protection Authority (EPA) (2011), Guidelines for Preparing Mine Closure Plans.
Department of Regional Development and Lands (2011), Regional Centres Development Plan (SuperTowns) Framework 2011‐2012.
Doherty, T.S. (2010), Restoration of Black‐Cockatoo Feeding Habitat at a Bauxite Mine in the Jarrah Forest: The Effects of Vegetation Succession and Thinning.
Doupé, R.G. and Lymbery, A.J (2005), Environmental Risks Associated with Beneficial End Uses of Mine Lakes in Southwestern Australia. Mine Water and the Environment 24: 134‐138. ecoscape (2012), NBG LOM Extension Project Visual Impact Assessment.
Environmental Protection Authority (EPA) (2006), Guidance for the Assessment of Environmental Factors (in accordance with the Environmental Protection Act 1986) Rehabilitation of Terrestrial Ecosystems.
Environmental Protection Authority (EPA) (2009), Guidance for the Assessment of Environmental Factors: Sampling of Short Range Endemic Invertebrate Fauna for Environmental Impact Assessment in Western Australia, No 20. May 2009.
Farrell, T.P. (1993), Some Considerations in Planning for Mine Decommissioning. In: Australian Mining Industry Council Environmental Workshop 1993 Proceedings.
Finn, H. (2010), Draft NBG Black‐Cockatoo Project Report.
Gammons, C. H. and Tucci, N. (2011) Monitoring the water quality of pit lakes. In: Mine Pit Lakes: Closure and Management, C.D. McCullough (ed).
Gardner, J.H and Bell, D.T. (2007), Bauxite Mining Restoration by Alcoa World Alumina in Western Australia: Social, Political, Historical, and Environmental Contexts. Restoration Ecology 15 (Supplement): S3‐S10.
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Grant, C.D., Norman, M.A. and Smith, M.A. (2007a), Fire and Silvicultural Management of Restored Bauxite Mines in Western Australia. Restoration Ecology 15 (Supplement): S127‐S136.
Gutteridge Haskins and Davey Pty Ltd (GHD) (1992), Boddington Gold Mine Residue Disposal System 5 Year Plan 1992‐1996.
Hames Sharley (2012), Community Vision Presentation 24 January 2012, Shire of Boddington, viewed 13 June 2012. http://www. boddington.wa.gov.au/supertowns/communityconsultation/
Haney, M and Shkaratan, M. (2003), Mine Closure and Its Impact on the Community – Five Years After Mine Closure in Romania, Russia and Ukraine.
Harris, J.A., Hobbs, R.J., Higgs, E. and Aronson, J. (2006), Ecological Restoration and Global Climate Change. Restoration Ecology 14: 170‐176.
International Cyanide Management Institute (2002), International Cyanide Management Code for the Manufacture, Transport and use of Cyanide in the Production of Gold (the Cyanide Code).
International Council on Mining & Metals (ICMM) (2008), Planning for Integrated Mine Closure: Toolkit.
John Consulting Services (1992), Boddington Gold Mine F3 Residue Storage Area Management of Salinity Impacts.
Koch, J.M. (2007a), Alcoa’s Mining and Restoration Process in South Western Australia. Restoration Ecology 15 (Supplement): S11‐S16.
Koch, J.M. and Hobbs, R.J. (2007), Synthesis: Is Alcoa Successfully Restoring a Jarrah Forest Ecosystem after Bauxite Mining in Western Australia? Restoration Ecology 15 (Supplement): S26‐S39.
Kumar, R.N., McCullough, C.D. and Lund, M.A. (2009), Water Resources in Australian Mine Pit Lakes. In: Water in Mining Conference 2009.
Lee, J., Finn, H. and Calver, M. (2010), Mine‐Site Revegetation Monitoring Detects Feeding by Threatened Black‐Cockatoos Within 8 Years. Ecological Management & Restoration 11, 141‐143.
Mattiske Consulting Pty Ltd (Mattiske) (1998a), Boddington Gold Mine Assessment of Vegetation Establishment in Pit C – Central Rehabilitation Trial, November 1997.
Mattiske Consulting Pty Ltd (Mattiske) (1998b), Assessment of Pit L Fertiliser Trial Boddington Gold Mine 1998.
Mattiske Consulting Pty Ltd (Mattiske) (1999a), Assessment of Vegetation Establishment in Pit C – Central Rehabilitation Trial Boddington Gold Mine.
Mattiske Consulting Pty Ltd (Mattiske) (1999b), Assessment of Pit L1 Fertiliser Trial Boddington Gold Mine.
Mattiske Consulting Pty Ltd (Mattiske) (2001), 2001 Assessment of 1999 and 2001 Mine‐Pit Rehabilitation Areas and Kangaroo Exclusion Trial Area, Boddington Gold Mine.
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Mattiske Consulting Pty Ltd (Mattiske) (2003), 2003 Assessment of 2001 Kangaroo Exclusion Trial Area Planted Recalcitrant and Priority Species, Boddington Gold Mine.
Mattiske Consulting Pty Ltd (Mattiske) (2005), Review of Flora and Vegetation Located in the Boddington Gold Mine and Hedges Lease Areas.
Mattiske Consulting Pty Ltd (Mattiske) (2010), Review of Flora and Vegetation on Hotham River and Thirty‐Four Mile Brook.
McCullough, C.D. and Lund, M.A. (2006). Pit Lakes: Benefit or Bane to Companies, Communities and the Environment? In: Proceedings of the Goldfields Environmental Management Group Workshop on Environment Management 2006.
McCullough, C., Hunt, D. and Evans, L (2009a), Sustainable Development of Open Pit Mines: Creating Beneficial End Uses for Pit Lakes. In: Mine Pit Lakes Characteristics, Predictive Modeling, and Sustainability Volume 3.
McLure (2004), Hedges Gold Community Monitoring Program – Community Values of the Hotham River.
Newmont Boddington Gold (NBG) (2012), Newmont Boddington Gold Annual Environmental Report – 2011.
Outback Ecology Services (OES) (2007a), Closure Planning for the Boddington Gold Mine – Soil Cover Profiles and Vegetation Outcomes.
Outback Ecology Services (OES) (2007b), Closure Planning for the Boddington Gold Mine – Properties of Primary Tailings.
Outback Ecology Services (OES) (2010), Review of Existing Information on Soils and Waste Materials in Relation to Landform Design and Rehabilitation.
Outback Ecology Services (OES) (2011a), Properties and Inventory of Soil and Mine Wastes for Rehabilitation at the Boddington Gold Mine.
Outback Ecology Services (OES) (2011b), Newmont Asia Pacific Boddington Gold Mine Waste Rock Dump & Residue Disposal Area Expansion: Subterranean Fauna Desktop Assessment.
Outback Ecology Services (OES) (2012), Boddington Gold Mine Short‐ranged Endemic Invertebrate Fauna Baseline Survey.
Premier Coal (PC) (2011), Mine Rehabilitation. Website: http://www.premiercoal.com.au/Environment/Mine_Rehabilitation.aspx. Accessed 13 February 2011.
Q&A Communications (2004), Social Atlas and Stakeholder Mapping for Boddington Gold Mine Expansion Company.
Readford, A. (2010), Social tImpac Assessment, Adaptive Capacity and Mine Closure: A case study of Kandos, N.S.W.
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Schlumberger Water Services (SWS) (2010), Boddington Gold Mine Summary of Groundwater, Surface Water and Geochemical Conditions and Implications for Closure.
Schlumberger Water Services (SWS) (2012), Newmont Boddington Gold Baseline Studies for Expanded RDA Facilities.
Shire of Boddington (2011), Municipal Heritage Inventory 2011.
Shire of Collie (2011), Discovery Drives. Website: http://collie.wa.gov.au/visit/discovery‐drives/. Accessed 13 February 2011.
Streamtec Pty Ltd (1990), Aquatic Monitoring Study of the Hotham River System in Relation to Gold Mining Operations in the Boddington Area of Western Australia 1988/1989.
Streamtec Pty Ltd (1997), Aquatic Ecosystem Monitoring in Thirty Four Mile Brook and the Hotham River.
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Williams, K. and Mitchell, D (2001) Jarrah Forest 1 (JF1 – Northern Jarrah Forest subregion. Website: www.dec.wa.gov.au/pdf/science/bio_audit/jarrah_forest01_p369‐381.pdf. Accessed 6 July 2012.
Worsley Alumina Pty Ltd (Worsley) (1997), Boddington Gold Mine Recalcitrant Species Trial Monitoring January 1997.
Worsley Alumina Pty Ltd (Worsley) (1999), Worsley Alumina Boddington Gold Mine Project Flora and Fauna Studies.
13‐5 Newmont Boddington Gold – Closure Plan Abbreviations, Acronyms and Glossary
14 ABBREVIATIONS, ACRONYMS AND GLOSSARY 14.1 Abbreviations and Acronyms AMD Acid and/or metalliferous drainage ANC Acid Neutralisation Capacity ANZMEC Australian and New Zealand Minerals and Energy Council APP Acid Production Potential BGMEMLG Boddington Gold Mine Environmental Management Liaison Group C Celcius CMU Closure Management Unit CN Cyanide Cyanide Code International Cyanide Management Code for the Manufacture, Transport and Use of Cyanide in the Production of Gold DEC Department of Environment and Conservation DIA Department of Indigenous Affairs DMP Department of Mines and Petroleum DoW Department of Water DSD Department of State Development EC Electrical Conductivity EPBC Act Environmental Protection and Biodiversity Conservation Act 1999 ESP Exchangeable Sodium Percentage FAS 143 Financial Accounting Standards Board Statement No. 143: Accounting for Obligations Associated with the Retirement of Long‐lived Assets FMS Fleet Management System GIS Geographic Information System GKB Gnaala Karla Booja HDPE High Density Polyethylene LOM Life of Mine mbgl Metres below ground level MCA Minerals Council of Australia mg/L Milligrams per litre Mt Million tonne Mtpa Million tonne per annum NAF Non Acid Forming NBG Newmont Boddington Gold Newmont Newmont Asia Pacific Limited OEPA Office of the Environmental Protection Authority
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Newmont Boddington Gold – Closure Plan Abbreviations, Acronyms and Glossary
OES Outback Ecology Services PAF Potentially Acid Forming PRAC Progressive Rehabilitation and Closure RDA Reside Disposal Area ROM Run of Mine SRE Short‐range Endemic SWALSC South West Aboriginal Land and Sea Council SWS Schlumberger Water Services TDS Total Dissolved Solids WA Western Australia WAD Weak Acid Dissociable
14.2 Glossary Angle of repose The maximum slope or angle at which loose, cohesionless material remains stable. Aquifer A geological formation, group of formations or part of a formation capable of yielding a significant amount of water to a well or spring. Backfill The material used to refill an excavation. Baseline surveys The gathering of data to describe the existing physical, biological, socio‐ economic, health, labour, cultural heritage, or any other variable considered relevant before mine development as a basis for estimating the impact of development, planning measures to avoid, manage or mitigate impacts and establish baseline conditions and indicators against which change resulting from the presence of a mining project can be measured (www.pdac.ca). Batter The inclination of an artificially created slope. Berm See bench. Bench A relatively flat, horizontal surface, elevated within an open pit or a waste rock landform. Bench height The vertical distance between adjacent benches in an open pit or waste rock landform. Measured from the toe of one bench to the crest of the connecting slope. Blast A single pattern of holes that are fired in a sequence to fracture the rock to enable the digging by hydraulic shovels. Bund A mound of earth, rock or dirt. Care and maintenance Phase following temporary cessation of mining operations where infrastructure remains largely intact and the site continues to be managed. All mining operations suspended, site being maintained and monitored (DMP/EPA, 2011).
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Newmont Boddington Gold – Closure Plan Abbreviations, Acronyms and Glossary
Catchment area The area that contributes water to a particular watercourse; a watershed. Closure A whole of life process which includes rehabilitation and decommissioning and culminates in tenement relinquishment (EPA, 2006). Closure Planning A process that extends of the mine life cycle and that typically culminates in tenement relinquishment. It includes decommissioning and rehabilitation (ICMM, 2008) Closure completion Result of all activities required to attain site relinquishment/surrender. This includes rehabilitation, closure and decommissioning works. A completed mine has progressed to a state where mining lease ownership can be surrendered/relinquished and responsibility accepted by the next land user (DITR, 2006). Community There are many ways to define “community”. In mining industry terms, community is generally applied to the inhabitants of immediate and surrounding areas who are affected by a company’s activities. ‘Local community’ usually indicates a community in which operations are located and may include Indigenous or non‐Indigenous people. Community engagement An ongoing process of relationship building that includes the disclosure of information, consultation with affected communities and creation of a grievance mechanism, and that provides a framework within which mutual trust may evolve over time (www.pdac.ca). Completion The goal of mine closure. A completed mine has reached a state where mining lease ownership can be relinquished and responsibility accepted by the next land user. Completion criteria Qualitative or quantitative standards of performance used to measure success or otherwise of rehabilitation actions required for closure of a site (Farrell, 1993). Consolidation A process by which loose, soft or liquid materials become firm and coherent. Consolidation typically results from tighter packing with greater inter‐particle cohesion or friction and less pore water holding particles apart. Consultation A process of two‐way communication between the operator and the affected communities and other stakeholders. Consultation should be undertaken in a manner that is inclusive, respectful, and culturally appropriate and that provides affected communities and other stakeholders with opportunities to express their views on project risks, impacts and mitigation measures, and allows the explorer to consider and respond to them (www.pdac.ca). The act of providing information or advice, on and seeking responses to, an actual or proposed event, activity or process. Cultural heritage Unique and non‐renewable resource that posses cultural, historic, scientific, spiritual or religious value and includes immovable objects, sites, structures, natural features or landscapes that have archaeological, paleontological, historical, cultural, artistic and religious values, as well
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Newmont Boddington Gold – Closure Plan Abbreviations, Acronyms and Glossary
as unique environmental features that embody cultural values (www.pdac.ca). Cyanide Code, The A voluntary program from the gold mining industry to promote responsible management of cyanide used in gold mining, enhance protection of human health and reduce the potential for environmental impacts. Decline Downward sloping underground workings. Includes adits and passages connecting different levels (ramps). Decommissioning The decontamination, dismantling, removal and/or demolition of infrastructure/equipment. Process by which a mining operation is shut down. The process that begins near or at the cessation of mineral production and ends with the removal of all unwanted infrastructure and services. (DMP/EPA, 2011). Demolition The complete or partial dismantling of a building or structure, be pre‐ planned and controlled methods or procedures (AS 2601). Dewatering The process of removing water from an underground mine or open pit, or from the surrounding rock or non‐lithified materials. Disturbed Area where vegetation has been cleared and/or topsoil (surface cover) removed (DMP/EPA, 2011). Disturbance type A feature created during mining or exploration activity (e.g. waste rock landforms, haul roads, access roads, plant site, tailings storage facility, borrow pits, drill pads, stockpiles, office blocks, accommodation village etc) (DMP/EPA, 2011). Domain A group of landform(s) or infrastructure that has similar rehabilitation and closure requirements and objectives (DMP/EPA, 2011). Drainage The manner in which the waters of an area exist and move, including surface streams and groundwater pathways. A collective term for all concentrated and diffuse water flow. Earthworks Reshaping, capping, water/wind erosion control, rock armouring (DMP/EPA, 2011). Ecologically sustainable Meeting the goal and principles of the National Strategy for Ecologically Sustainable Development, endorsed by all Australian jurisdictions in 1992, to ensure that development improves the total quality of life, both now and in the future, in a way that maintains the ecological processes on which life depends (DMP/EPA, 2011). Ecosystem The biota (plants, animals, fungi and microorganisms) occurring in a given area, along with the abiotic environment that sustains it (landforms, soils, hydrology) and their interactions. Environment Living things, their physical, biological and social surroundings and interactions between all of these (DMP/EPA, 2011). Environmental value A beneficial use and/or ecosystem health condition (DMP/EPA, 2011).
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Newmont Boddington Gold – Closure Plan Abbreviations, Acronyms and Glossary
Erosion The detachment and subsequent removal of either rock or surface material by wind, rain, wave action, freezing, thawing or other processes. Evaporation The process by which a liquid is changed into a gas. Evapotranspiration The loss of moisture to the atmosphere due to evaporation and transpiration by vegetation. Facility All portions of a mining operation, including, but not limited to, the mine, waste rock stockpiles, beneficiation process components, processed ore disposal sites and all associated buildings and structures. Geochemistry Study of the distribution and abundance of elements in minerals, rocks, soils, water and the atmosphere. Geology The study of the earth, its history and the changes that have occurred or are occurring, and the rocks and non‐lithified materials of which it is composed and their mode of formation and transformation. Groundwater All subsurface water comprising the zone of saturation, including perched zones of saturation, which could produce usable water. Gully erosion The modification of unconsolidated and consolidated surface by processes such as running water, mass movement and snow avalanching, resulting in the formation of parallel and sub‐parallel long, narrow ravines. Gullies have steep or gently sloping sides, and steep or gently sloping longitudinal profiles (www.inap.com.au) Habitat The natural environment of an organism or community, including all biotic and abiotic elements; a suitable place for it to live (Commonwealth of Australia, 1996). Impact Any effect, whether anticipated or unanticipated, positive or negative, (www.pdac.ca). Kinetic testing Procedure used to measure the magnitude and/or effects of dynamic processes, including reaction rates (such as sulphide oxidation and acid generation), material alteration and drainage chemistry and loadings that result from weathering. Unlike static tests, kinetic tests measure the behaviour of a sample over time (DMP/EPA, 2011). Laterite A red, highly‐weathered residual soil, usually rich in oxides of iron and aluminium. Legal obligations register A register of legally binding conditions and commitments relevant to rehabilitation and closure at a given mine site (DMP/EPA, 2011). Liability All outstanding work requirements or equivalent monetary requirements. Life of Mine Expected duration of mining and processing operations (DMP/EPA, 2011). Liner A continuous layer of man‐made or reconstructed natural materials, or a combination thereof, which restricts the downward or lateral movement of liquids.
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Newmont Boddington Gold – Closure Plan Abbreviations, Acronyms and Glossary
Lithology A rock type defined by a distinct set of physical and mineralogical characteristics. Local provenance Material used to propagate plants collected from narrowly defined geographical area, which closely matches the plant types and physical environment where it is to be used (EPA, 2006). Low grade ore Ore that is relatively deficient in the target metals/minerals. A term usually used for materials that could be ore under favourable economic conditions. Low grade ore stockpile A mined rock pile containing low grade ore segregated to permit milling at some later date when economic conditions become more favourable. Maintenance The preservation of the functional integrity and efficiency of the equipment and structures of a mine closure project and includes, without limitation, any necessary preventative maintenance, corrective maintenance and replacement of equipment or structures. Mill A piece of grinding equipment using a revolving drum. Mine A mine includes: a) a place where mechanical disturbance of the ground or an excavation is made to explore for or produce coal, metallic ore, industrial minerals or placer minerals, b) all cleared areas, machinery and equipment for use in servicing a mine or for use in connection with a mine and buildings other than residential facilities, c) excavation and any associated activities including exploration drilling, processing, concentrating, waste disposal and site reclamation) closed and abandoned mine sites (www.inap.com.au). Mining The process of extracting ores from the earth. Mining Operations Any method of working by which the earth or any rock structure, coal seam, stone, fluid or mineral bearing substance is disurbed, removed, washed, sifted, crushed, leached, roasted, floated, distilled, evaporated, smelted, refined, sintered, pelletised, or dealt with for the purpose of obtaining any mineral or rock from it for commercial purposes or for subsequent use in industry, whether it has been previously disturbed or not, and includes: (a) exploration activities; (m) operations undertaken for the environmental rehabilitation of the mine site during production operations and after their completion; (o) operations undertaken to leave a mine safe to be abandoned. (Mines Safety and Inspection Act 1994, Provision 4). Open pit A surface depression created by the excavation of near surface metallic ore, industrial minerals, placer minerals or coal. In open pit mining, overburden covering the deposit is removed, exposed rock is blasted and moved to a mill, and waste rock is placed in one or more waste rock landforms (www.inap.com.au).
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Newmont Boddington Gold – Closure Plan Abbreviations, Acronyms and Glossary
Operating cost The expenses incurred during the normal operation of a facility, or component, including labour, materials, utilities, and other related costs. Includes all fuel, lubricants, and normally scheduled part changes in order to keep a subsystem, system, particular item, or entire project functioning. Operating costs may also include general building maintenance, cleaning services, taxes and similar items. Ore Rock, sediments or non‐lithified materials that contain economically recoverable levels of coal, metals or minerals (www.inap.com.au). Piping Subterranean erosion of non‐lithified materials caused by flowing water. Results in the formation of conduits due to the removal of particles. Plan A predetermined course of action over a specified period of time which represents a projected response to an anticipated environment in order to accomplish a specific set of adaptive objectives. Pond A process component which stores, confines or otherwise significantly impedes the horizontal movement of process fluids. Portal Surface entrance to an adit, level, incline or decline. Post‐mining land use Term use to describe a land use that occurs after the cessation of mining operations (DMP/EPA, 2011). Processing plant Includes all processing facilities for ore treatment including crushing plants, grinding, vat leach, heap leach, dump leach and tailings disposal facilities (DMP/EPA, 2011). Project The total integrated mining operations in which a number of sites contribute to the overall operation to supply ore, processing facilities and disposal of waste products (DMP/EPA, 2011). Quality assurance All those planned or systematic actions necessary to provide adequate confidence that a product, process or service will conform to established requirements and specifications. Quality control Inspection, test, evaluation or other necessary action to verify that a product, process or service conforms to established requirements and specifications. Quality management Concerns the optimisation of the quality activities involved in producing a product, process or service. As such, it includes appraisal, training and prevention activities. Reference ecosystem An ecosystem used as a guide for closure outcomes. Measurements from reference systems are used to set appropriate measurable targets for rehabilitation. Rehabilitated Areas are safe, have demonstrated stability under representative climatic conditions, non‐polluting and support a functioning, self sustaining ecosystem comprising local native species (DMP, 2010). Rehabilitation A process where disturbed land is returned to a stable, productive and self‐sustaining condition consistent with the post‐mining land use (DMP/EPA, 2011). Actions performed during or after an exploration project or mining operation to shape, stabilise, revegetate or otherwise treat the land in order to return it to a safe, stable condition consistent
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Newmont Boddington Gold – Closure Plan Abbreviations, Acronyms and Glossary
with the establishment of a productive post mining land use of the land and the safe abandonment of a facility in a manner which ensure the public safety, as well as the encouragement of techniques which minimise that adverse visual effects. Relinquishment Final approval by the relevant regulating authority that agreed targets have been met (EPA, 2006). Remediation To clean up or mitigate contamination of soil or water. Residue The ground rock waste product from a mill or process plant, the materials remaining after the economically valuable elements are removed from the ore. Residue disposal area The final storage location for processed ore discharged from a mill. Revegetation The deliberate planting of vegetation. An activity aimed at re‐ establishing vegetation on cleared surfaces. Risk The probably and consequence of failure. Runoff The part of precipitation that does not infiltrate but moves as overland flow. Safe A condition where the risk of adverse effects to people, livestock, other fauna and the environment in general have been reduced to a level acceptable to all stakeholders (DMP/EPA, 2011). Sample A representative fraction, usually relatively small, collected for analysis or description. Schedule The plan for completion of a project based on a logical arrangement of activities, resources available, imposed dates or funding budgets. Sediment Solid fragmental materials which have been deposited after being transported by air, water or ice or precipitated from solution. Soil The upper portion of non‐lithified materials that has been altered over a period of time, as a result of plant growth, climate (including moisture and temperature effects), drainage, macro‐ and microorganism activity or topographical position, producing a product that differs from the parent material (regolith) in many physical, chemical, biological processes and morphological properties. Soil either serves or has the potential to serve as a medium for the growth of terrestrial or wetland plants (www.inap.com.au). Stable A condition where rates of change of specified parameters meet agreed criteria (DMP/EPA, 2011). Stakeholder A person, group or organisation with the potential to affect or be affected by the process or outcome of mine closure (ICMM, 2008). Static testing Procedure for characterising the physical or chemical status of a geological sample at one point in time. Static tests include measurements of chemical and mineral composition and the analyses required for Acid Base Calculations (DMP/EPA, 2011). Stockpile A pile of excavated rock or naturally non‐lithified materials placed in anticipation of later use or re‐handling.
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Newmont Boddington Gold – Closure Plan Abbreviations, Acronyms and Glossary
Stygofauna Aquatic fauna inhabiting groundwater. Surface water All water open to the atmosphere and subject to surface runoff. Task Smallest unit of work planned. It must have an identifiable start and finish, and usually produces some recognisable results. Tenement Land tenure granted under the Mining Act 1978 (e.g. Mining Lease, Exploration Lease, Prospecting Lease, Miscellaneous Licence and General Purpose Lease) (DMP/EPA, 2011). Topsoil The material at or near the surface of the earth which has been modified and acted upon by natural, physical, chemical or biological agents in a manner which will allow it to support revegetation. Troglofauna Fauna inhabiting air‐filled caves or small voids underground. Updating The regular review, analysis, evaluation and reporting of progress of the project, including recomputation of an estimate or schedule. Vuggs Small to medium‐sized cavities within rock. Waste rock Rock with insufficient amounts of the economically valuable elements to warrant its extraction, but which has to be removed to allow physical access to the ore. Waste rock is typically blasted into smaller particles to allow its removal by truck and shovel. Waste rock landform A mine rock pile containing waste rock. Water balance A term used in the context of mining to describe an inventory of drainage inputs and outputs, water volumes and the rate of flow. Weed Any species which has the potential to have detrimental effects on economic, social or conservation values.
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Newmont Boddington Gold – Closure Plan Appendices
15 APPENDICES
Appendix 1 – Ministerial Conditions
Appendix 2 – Approval Document Commitments
Appendix 3 – Tenement Conditions
Appendix 4 – Newmont Boddington Gold Mine Rehabilitation Resources Inventory November 2012
Appendix 5 – Research Programs, Studies and Trials
Appendix 6 – Newmont Asia Pacific Boddington Gold Mine R4 Oxide Residue Rehabilitation Trial Assessment
Appendix 7 – Initial Comparison of the Erosional Performance of Alternative Slope Geometries
Appendix 8 – SIBERIA Modelling Calibration of Erosion Parameters and Initial Erosion Assessment
Appendix 9 – Information Review – Slope Design and Rehabilitation Parameters
Appendix 10 – Newmont Boddington Gold Mine Site Wide Water Balance Model and Hydrochemical Model for Closure
Appendix 11 – Learning’s from Other Mines
Appendix 12 – Closure Risk Register
Appendix 13 – Review of Closure Commitments and Expectations and the Development of Proposed Completion Criteria
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Closure Risk Register
Consequence Likelihood
Risk Description Current Controls Future Controls Risk Level
Newmont policies and standards. Ongoing consultation with stakeholders throughout life of Inadequate stakeholder consultation. Closure included in BGMEMLG and community meetings. mine. 4 1 10 Medium Register of stakeholder consultation. Approval of Closure Plan by regulators. Changing stakeholder expectations over life of BGMEMLG meetings. Get stakeholder agreement on completion criteria. 4 2 14 High project. Development of completion criteria. Ongoing stakeholder consultation. Include closure in Social Impact Assessment. Social Impact Assessment does not include closure Include Social Responsibility in Closure Planning process. Target community spending on projects which develop ability 3 2 9 Medium risks and opportunities. of Boddington to cope with closure. Assessed during development of PER. Include interpretive signage on Bibbulmun Track. Reshaping and rehabilitation of landforms. Move track (if necessary). Visual impact of landforms. 2 2 5 Low Limited height of waste rock landforms to 360mRL. Screen view points from roads with tree planting. Gold sponsor of Bibbulmun track. Conduct visual impact assessment. Completion criteria developed with support from Outback Ecology. Outcomes of rehabilitation of satellite pits basis for completion criteria for disturbance areas where in situ soil profile not disturbed. Develop quantitative standards based on outcomes of Benchmarking of completion criteria and rehabilitation at neighbouring sites. Agreed completion criteria are unachievable at rehabilitation trials for disturbance areas where the in situ Level of detail in completion criteria appropriate for age of site and allow for 4 2 14 High closure. soil profile is disturbed. refinement when more information available. Track progress against completion criteria in AER. Monitoring undertaken for groundwater, surface water and rehabilitation. Monitoring data stored in database. Review of monitoring program to ensure required data being collected. Potential post‐mining land uses identified based on existing land uses in area. Grazing not included as post ‐mining land use in Closure Plan based on land capability. Post‐mining land use not appropriate with respect Finalisation of post‐mining land use based on the outcomes Post‐mining land use not finalised within Closure Plan. 4 1 10 Medium to land capability. of rehabilitation trials. RDA rehabilitation trial and success of rehabilitation of Hedges RDA. Research by Alcoa indicates rehabilitation can be integrated with management of surrounding jarrah forest. Restrict public access (ripping tracks, bunding, fencing, signage). Public safety on landforms post‐closure. Access to site controlled during operations. 3 3 13 High Re‐shape landforms to reduce slope angle and minimise erosion. Construct abandonment bund (cost included in closure Closure provision includes construction of abandonment bund, signage, provision). Public access to open pit void and underground blocking access tracks. Rip access tracks and pit ramps. 5 1 15 High workings. Portal sealed and signed off by DMP. Padock dump top of pit ramps. Put up signage about risks in the area. AER review of Ministerial Statement Conditions. Non‐compliance with conditions and commitments, Spread sheet of compliance requirements. Supersede previous closure commitments with new Closure 4 1 10 Medium Newmont Standards and relevant signatory codes. Education of personnel. Closure commitments register. Plan. Involvement of mining department in closure planning.
1
Closure Risk Register
Consequence Likelihood
Risk Description Current Controls Future Controls Risk Level
Annual review of LOM and FASB closure provision. Closure provision based on third‐party rates. Review of contaminated sites. Internal and external review of closure provision annually. Get agreement with stakeholders on completion criteria. Underestimation of closure cost. Contaminated sites identified, recorded and reported to DEC. Ongoing consultation with stakeholders. 4 2 14 High High risk contaminated sites remediated during care and maintenance period. Include Social Responsibility in closure planning process. Undertake rehabilitation trials to guide cover design. Develop detailed landform and drainage designs. BGMEMLG meetings. Continued integration of closure planning and life of mining planning. LOM & FASB closure provision updated annually to reflect current operations. Operational decisions and activities compromise Regular audit of landform construction against design. Closure planning integrated with life of mine planning. 4 2 14 High closure outcomes. Integrate closure into RDA design and communicate to Mining Department attend closure update meetings. personnel. Develop progressive rehabilitation plan. Develop work instructions for rehabilitation works. QA/QC program in place during construction. Covers and drainage structures not constructed to Draft Rehabilitation Materials SOP. Adequate supervision of earthworks. 3 2 9 Medium specifications. Construction report for each stage of RDA construction. Survey of earthworks. Regular audit of landform construction against design. Integrate into RDA design with Knight Piesold. Include topsoil stripping in future budgets and planning. Include consideration of rehabilitation materials Identification and encapsulation of PAF material. requirements and management in RDA and waste rock Selection of NAF material for building of drains. landform design. Materials with inappropriate physical or chemical Harvesting and stockpiling of gravel and topsoil for rehabilitation. Materials characterisation undertaken prior to stripping for properties used for construction of drainage 3 2 9 Medium Inventory of rehabilitation materials undertaken and reconciled with new disturbance areas. structures and covers. requirements. Develop Rehabilitation Management Plan. Draft Rehabilitation Materials SOP. Review of PAF/NAF classification. Develop waste rock management plan. Annual testing of residue. Perimeter drains around waste rock landforms so no water released to Rehabilitation of disturbance areas. environment. Inadequate surface water management. Develop detailed drainage system for waste rock landforms 3 3 13 High Surface water removed from RDAs. and RDAs. 34 Mile Brook diversion management plan. Include topsoil stripping and storage in future budgets and planning. Include consideration of rehabilitation materials requirements and management in RDA and waste rock All currently cleared areas have topsoil harvested and stockpiled. landform design. Inventory of rehabilitation materials undertaken and reconciled with Inadequate rehabilitation materials. Materials characterisation undertaken prior to stripping for 3 2 9 Medium requirements. new disturbance areas. Draft Rehabilitation Materials SOP. Develop Rehabilitation Management Plan. Ongoing reconciliation of materials inventory against requirements. Tracking of oxide stockpiling via Fleet Management System.
2
Closure Risk Register
Consequence Likelihood
Risk Description Current Controls Future Controls Risk Level
Annual survey of stockpile volumes. Establish owner for stockpiles who authorises what they are utilised for. Rehabilitation trial for waste rock landforms. Develop quantitative standard for erosion based on Erosion modelling for design of waste rock landform considering outslope outcomes of trials. design and cover material. Excessive erosion of landforms Develop work instructions for rehabilitation works. 4 2 14 High Investigation of physical and chemical properties of rehabilitation materials. Regular audit of landform construction against design. Drains designed for peak flow. Incorporate closure into RDA design. Develop detailed drainage design. Management of surface water included in options analysis for design of waste rock landforms. Drainage on waste rock landforms designed to minimise erosion. Detailed design for drainage on RDA embankments and Drains designed for appropriate rainfall event. waste rock landforms. Integrity of landform design compromised by Survey control of construction of drains. Develop integrated site water management. 3 3 13 High excessive erosion and/or settlement. Options analysis for surface water management for RDAs. Rehabilitation of RDA delayed until majority of consolidation Drains designed for peak outflows based on appropriate Annual Return has occurred. Interval. Drainage design for top surface of waste rock landforms considered settlement. Investigation of physical and chemical properties of rehabilitation materials. Design cover for RDA and waste rock landforms. Landforms designed to be water shedding rather water holding. Rehabilitation trial on waste rock landform. Seepage directed to Impacted Water Sump. Excessive infiltration through covers on waste rock Rehabilitation trial on basement residue. Success of R4 RDA rehabilitation trial. 4 2 14 High landforms and RDAs. Develop work instructions for rehabilitation works. Closure Plan currently includes oxide cover on F1/F3 RDA if trial does not Monitoring of seepage and surface runoff from medium demonstrate that vegetation will grow on oxide residue. grade stockpile. Oxide water balance trial. R4 RDA rehabilitation trial and success of rehabilitation of Hedges RDA. Investigation of physical and chemical properties of basement residue. Learnings from rehabilitation of satellite pits and from Alcoa. Obtain seedlings from Alcoa. Reconstruction of soil profile (application of oxide, gravel and topsoil where Basement residue rehabilitation trial. required). Waste rock landform rehabilitation trial. Application of local provenance seed at rate required for target ecosystem. Develop cover design for basement residue and waste rock Cut and germination testing of seed. landforms based on material properties, vegetation Poor rehabilitation performance. Planting of recalcitrant species. Application of fertiliser. 4 2 14 High requirements and outcomes of trials. Contour ripping to break up compaction. Develop quantitative standards for areas with disturbance of Quantitative rehabilitation standards developed for areas with minimal the in situ soil profile based on outcomes of trials. disturbance of in situ soil profile. Develop Rehabilitation Management Plan. Rehabilitation monitoring. Investigations of native soil profile and properties of rehabilitation materials. Fauna habitat structures constructed in rehabilitation areas. Research on black cockatoos indicates use of rehabilitation areas within 6‐8 years.
3
Closure Risk Register
Consequence Likelihood
Risk Description Current Controls Future Controls Risk Level
Design of RDAs by geotechnical engineer. Review of RDA design in approval process by DMP. QA/QC of RDA construction. Geotechnical instability of landforms and open pit. Annual geotechnical audit of RDAs. Regular audit of landform construction against design. 4 2 14 High Civil construction report for each stage of RDA construction. Geotechnical review of pit design. Visual assessment of open pit and waste rock landforms. Geochemical characterisation of waste rock and residue. Development of management plan for PAF material. Review of PAF/NAF classification. Footprint of waste rock landform lined with low permeability oxide and Develop waste rock and medium grade management plan. Inadequate management of potentially hostile seepage directed to IWS. Rehabilitation trial for waste rock landform. 4 2 14 High material (PAF, residue). Encapsulation of PAF‐HC. Track placement of material via FMS. Supernatant pond at F1/F3 RDA lined with HDPE. Regular audit of landform construction against design. Remainder of RDA lined with low permeability clay. Current waste rock landform design process incorporates encapsulation of medium grade stockpile for LOM and re‐ Medium grade not placed within 100m of edge of landform (leaves room for permitting scenarios. Medium grade stockpiles not located or encapsulation with NAF material if required). Development of medium grade management plan which constructed with closure considered as it is 4 2 14 High Tracking of material placement via FMS. covers processing and non‐processing scenarios. assumed they will be processed. Survey control of medium grade stockpile. Regular audit of landform construction against design. Monitoring of seepage and surface runoff from medium grade stockpile. Design landforms to re‐establish regional drainage function (Thirty‐Four Mile Brook catchment discharges to Hotham River). Alteration of surface water regime. Accepted and approved impact of project (EPA). 3 3 13 High Discharge from pit lakes to Hotham River via Wattle Hollow Brook after filling. Assess impact of expansion of RDAs on new catchments. Review of regional groundwater and impacts of dewatering. Cone of depressurisation from dewatering impacts Groundwater monitoring program. Impacts will be less after dewatering ceases due to recovery 2 4 12 High groundwater and surface water resources. Study on ecological impacts on Hotham River. of groundwater level over the long term. Ongoing updating of model as more information becomes Pit lake water quality poorer than predicted. Post‐closure water balance model based on best data available. available on quality and quantity of inputs from trials. 4 2 14 High Likely improvements with model capability over time. Post‐closure water balance model based on best data available. Ongoing updating of model as more information becomes Water level in pit lake different to predicted. Model includes assessment of potential climate change scenarios. available on quantity of inputs from trials. 3 1 6 Medium Pit outlet structure designed to prevent flooding of surrounding area. Likely improvements with model capability over time.
4
Closure Risk Register
Consequence Likelihood
Risk Description Current Controls Future Controls Risk Level
Develop quantitative standard for release of surface water. Rehabilitation of disturbance areas. Develop detailed drainage system design for waste rock Perimeter drains around waste rock landforms so no water released to landforms and RDAs. environment. Surface water runoff impacts receiving Majority of runoff directed to open pit void post‐closure. Surface water removed from RDAs. 3 2 9 Medium environment. Treatment of runoff from RDAs until quality suitable for Thirty‐Four Mile Brook diversion management plan. release to Thirty‐Four Mile Brook. Closure provision includes 10 years of water treatment. Update post‐closure site water balance model with more refined inputs for seepage rates and runoff from outcomes of rehabilitation trials. Newmont policies and standards. Hydrocarbons stored in appropriate facilities consistent with appropriate Australian standards. Groundwater monitoring program and annual hydrological review. Develop quantitative standard for groundwater. Post‐closure site water balance predicts volume and quality of water requiring Installation of cover to reduce infiltration for waste rock treatment. landform. Geochemical characterisation of waste rock. Water shedding design for RDAs and installation of cover. Development of management plan for PAF material. Update post‐closure site water balance model with more Footprint of waste rock landform lined with low permeability oxide and refined inputs for seepage rates and runoff from outcomes of seepage directed to IWS. rehabilitation trials. Seepage impacts receiving environment. Supernatant pond at F1/F3 RDA lined with HDPE. Review cost for post‐closure water treatment. 5 2 19 Extreme Remainder of RDA lined with low permeability clay. Regular audit of landform construction against design. Seepage recovery network operational for R4 RDA. Assess impact of RDAs on new catchment areas. RDAs located in separate catchment to South Dandalup Dam. Risk assessment of impact to groundwater to date from R4 Closure provision includes 10 years of water treatment. RDA. Monitoring downstream of R4 RDA at Wattle Hollow Brook. Improve understanding of impacts of salt load in RDAs on Tracking of waste rock location using Fleet Management System. quality of post‐closure seepage and runoff. 10 years of post‐closure treatment of AMD from waste rock landforms Assess need for treatment of salinity from RDAs post‐closure. included in closure provision. 10 years of treatment of underdrainage for cyanide destruction included in closure provision. Include areas of usage for infected topsoil in Closure Plan. Dieback Management Plan ‐ mapping, research, segregation of infected topsoil Include management of infected stockpiles in Rehabilitation Closure and rehabilitation activities introduce or stockpiles, vehicle hygiene and control of access to infected areas, education of Management Plan. 4 1 10 Medium spread forest disease. personnel. Included in completion criteria. Dieback Management Plan implemented during Reported on at BGMEMLG meetings and in AER. rehabilitation activities. Signage of infected stockpiles and rehabilitation areas. Include rehabilitation areas in Burn Plan in future (including Interagency agreement in place with DEC and Shire (updated annually) for prescription for age of rehabilitation and how often to be controlled burning and control of wildfire in forest areas. burnt). Fire impacts rehabilitation. "Burn Plan" included in AER. Consider access requirements for fire management in Post‐ 3 2 9 Medium Research by Alcoa into how rehabilitation copes with fire. Closure Access Plan. Protection of rehabilitation from fire included in completion criteria. Develop integrated Fire Management Plan for plantation, Hotham Farm and mine site.
5
Closure Risk Register
Consequence Likelihood
Risk Description Current Controls Future Controls Risk Level
Finalise Land Management Plan. Weed SOP. Continue management during rehabilitation and closure Weeds and/or feral animals impact surrounding Baseline species list for rehabilitation. activities. 2 3 8 Medium land. Site entry and vehicle hygiene procedure. Consider access requirements for weed and feral animal Participation in feral animal trapping. management in Post‐Closure Access Plan. Incorporate new land into current management plans. Impact will be less than current mining activities due to reduced fleet size and Use water carts to keep materials damp. Dust impacts community and surrounding smaller equipment. Move or undertake alternative activities in adverse wind 2 2 5 Low environment. Progressive rehabilitation of disturbance areas. conditions. Existing monitoring program (groundwater, surface water, rehabilitation). Review of rehabilitation monitoring with respect to completion criteria. Inadequate monitoring (groundwater, surface Revise rehabilitation monitoring program (if required). Data stored in MonitorPro. 3 2 9 Medium water, rehabilitation, weeds, feral animals). Update Environmental Monitoring Management Plan. Post‐closure monitoring included in closure provision. Monitoring programme included in Closure Plan. Third‐party demolition cost prepared for major infrastructure. Development of Decommissioning Plan. Surface and sub‐surface infrastructure not removed Location of infrastructure recorded. Removal of infrastructure in accordance with Plan. 3 2 9 Medium or adequately covered. Disturbance areas rehabilitated progressively when no longer required. Updating of demolition cost by third‐party. Development of Decommissioning Plan. Exposure of personnel to hazardous materials Update of Cyanide Facilities Decommissioning Plan. NA ‐ decommissioning not yet occurring. 3 2 9 Medium during decommissioning. Implementation of safety procedures from operations phase. Use of experts for high risk tasks. Development of Decommissioning Plan. Update of Cyanide Facilities Decommissioning Plan. Personnel injury during decommissioning. NA ‐ decommissioning not yet occurring. 4 2 14 High Implementation of safety procedures from operations phase. Use of experts for high risk tasks. Ore and potential gold traps overlooked during NA ‐ decommissioning not yet occurring. Include in Decommissioning Plan. 4 2 14 High decommissioning. Include in Decommissioning Plan. Equipment stolen during decommissioning. NA ‐ decommissioning not yet occurring. 2 3 8 Medium Security on site during decommissioning.
6
Closure Risk Register
7
Closure Risk Register
Level Description Criteria (read as either/or) The event will occur 5 Certain The event occurs daily The event is expected to occur 4 Likely The event occurs weekly/monthly The event will occur under some circumstances 3 Possible The event occurs annually The event has occurred elsewhere 2 Unlikely The event occurs every 10 years The event may occur in exceptional circumstance 1 Rare The event has rarely occurred in the industry
Consequence Likelihood 1 2 3 4 5 Insignificant Minor Moderate Major Catastrophic 5 11 16 20 23 25 Certain 4 7 12 17 21 24 Likely 3 4 8 13 18 22 Possible 2 2 5 9 14 19 Unlikely 1 1 3 6 10 15 Rare
8
Tenement Conditions
TENEMENT CONDITIONS Condition Tenements The lessee at his expense, shall rehabilitate all areas effected by mining M70/21, M70/22, including rehabilitation enrichment of dieback and other forest disease M70/24 affected areas, resulting from the lessee’s operations associated with mining to the satisfaction of the Executive Director of the Department of Environment and Conservation and the State Mining Engineer. The lessee at his expense rehabilitating all areas effected by mining or M70/264SA operations associated with mining including the rehabilitation of dieback or other forest disease affected areas resulting from the lessee’s mining or operations associated with mining. Rehabilitation being to the satisfaction of the Regional Mining Engineer and in agreement the Regional Manager CALM. All surface holes drilled for the purpose of exploration are to be capped, M70/21, M70/22, filled or otherwise made safe after completion. M70/23, M70/24, M70/25, M70/564, M70/799, M70/1031 All costeans and other disturbances to the surface of the land made as a M70/21, M70/22, result of exploration, including drill pads, grid lines and access tracks, M70/23, M70/24, being backfilled and rehabilitated to the satisfaction of the M70/25, M70/564, Environmental Officer, Department of Industry and Resources (DoIR). M70/799, M70/1031 Backfilling and rehabilitation being required no later than 6 months after excavation unless otherwise approved in writing by the Environmental Officer, DoIR. All waste materials, rubbish, plastic sample bags, abandoned equipment M70/21, M70/22, and temporary buildings being removed from the mining tenement prior M70/23, M70/24, to or at the termination of exploration program. M70/25, M70/564, M70/799 Unless the written approval of the Environmental Office, DoIR is first M70/21, M70/22, obtained, the use of scrapers, graders, bulldozers, backhoes or other M70/24 , M70/799, mechanised equipment for surface clearing or the excavation of costeans M70/1031 is prohibited. Following approval, all topsoil being removed ahead of mining operations and separately stockpiled for replacement after backfilling and/or completion of operations. Unless the written approval of the Environmental Office, DoIR, and the M70/564 Water Authority of Western Australia is first obtained, the use of scrapers, graders, bulldozers, backhoes or other mechanised equipment for surface clearing or the excavation of costeans is prohibited. Following approval, all topsoil being removed ahead of mining operations and separately stockpiled for replacement after backfilling and/or completion of operations. The lessee at his expense rehabilitating all areas affected by mining or M70/21, M70/22, operations associated with mining conducted during the term of lease. M70/23, M70/24, Rehabilitation being to the satisfaction of the State Mining Engineer and M70/25, M70/1031 in agreement with the Regional Manager CALM and in accordance with CALM Policy No. 10 (Rehabilitation of Disturbed Lands).
1
Tenement Conditions
Condition Tenements The lessee at his/her expense rehabilitating all areas affected by mining G70/215, G70/218, or operations associated with mining conducted during the term of the G70/219 lease. Rehabilitation being to the satisfaction of the Director, Environment, DMP and in agreement with the Regional/District Manager, DEC and in accordance with DEC Policy No. 10 (Rehabilitation of Disturbed Lands). The lessee designating to the Regional Manager, CALM a responsible M70/21, M70/22, officer to direct and control the rehabilitation. M70/23, M70/24, M70/25, M70/1031, M70/264SA The lessee designating to the Regional/District Manager, DEC a G70/215, G70/218, responsible officer to direct and control the rehabilitation program. G70/219 All topsoil being removed ahead of all mining operations from sites such M70/21, M70/22, as pit areas, waste disposal areas, ore stockpile areas, pipeline, haul M70/23, M70/24, roads and new access roads and being stockpiled for later respreading or M70/25, M70/564, immediately respread as rehabilitation progresses. M70/799, G70/215, L70/96, M70/1031, G70/218, G70/219, M70/264SA All topsoil being removed ahead of all mining operations from sites such L70/95 as waste disposal areas, mine camp areas and new access roads and being stockpiled for later respreading or immediately re‐spread as rehabilitation progresses. At completion of operations, all buildings and structures being removed M70/21, M70/22, from site or demolished and buried to the satisfaction of the State M70/23, M70/24, Mining Engineer. M70/25, M70/564, M70/799, G70/215, M70/264SA At completion of operations, all buildings and structures being removed L70/95, L70/96, from site or demolished and buried to the satisfaction of the Director, M70/1031, G70/218, Environment Division, DoIR. G70/219 At the completion of operations or progressively where possible all M70/21, M70/22, access roads and other disturbed areas being covered with topsoil, deep M70/23, M70/24, ripped and revegetated with local native grasses, shrubs and trees to the M70/25, M70/564, satisfaction of the State Mining Engineer and on freehold land, the M70/799, G70/215, landholder. M70/1031, G70/218, G70/219 The lessee submitting to the State Mining Engineer and Boddington Gold M70/21, M70/22, Mine Liaison Group in March of each year, for the reporting period of M70/23, M70/24, November and October, an annual report outlining the project M70/25, M70/799 operations, minesite environmental management and rehabilitation work undertaken in the previous 12 months and the proposed operations, environmental management plans and rehabilitation programmes for the next 12 months.
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Tenement Conditions
Condition Tenements The lessee submitting to the Director, Environment Division, DoIR, a brief M70/564, G70/215, annual report outlining the project operations, minesite environmental L70/95, L70/96, management and rehabilitation work undertaken in the previous 12 G70/219, M70/264SA months and the proposed operations, environmental management plans and rehabilitation programmes for the next 12 months. This report to be submitted each year in: March The lessee submitting to the Director, Environment, DMP and the G70/215, G70/218, Regional/District Manager, DEC in March of each year, a brief annual G70/219 report outlining the project operations, minesite environmental management and rehabilitation work undertaken in the previous 12 months and the proposed operations, environmental management plans and rehabilitation programs for the next 12 months. Following receipt of the annual report a site inspection by the Regional Environmental Officer, Department of Mines and Petroleum and Regional/District Manager, DEC may be required. The lessee submitting to the State Mining Engineer and the M70/1031 Regional/District Manager, CALM, a brief annual report outlining the project operations, minesite environmental management and rehabilitation work undertaken in the previous 12 months and the proposed operations, environmental management plans and rehabilitation programs for the next 12 months. This is to be lodged at the time annual reports are due in accordance with Clause 5A(3) of the Alumina Refinery (Worsley) Agreement Act 1973. Following receipt of the annual report a site inspection by the Regional Environmental Officer, Department of Minerals and Energy and Regional/District Manager, CALM may be required. Prior to the completion of the operations and/or rehabilitation of the M70/21, M70/22, tailings facility, a review by a geotechnical/engineering specialist of the M70/23, M70/799 tailings facility being submitted to the Statement Mining Engineer for his assessment and is required to include:‐ The status of the structure and its contained tailings; An examination of the implications of the physical and chemical characteristics of the materials; The results of all environmental monitoring; and A discussion of any stabilisation and on‐going remedial works. Waste dumps must be located outside of the zone of potential pit M70/22, M70/24, instability. M70/25, M70/1031, G70/218, M70/264SA Tailings dams, disposal areas and dumps being sited so as to pose no M70/564, M70/1031 threat to water course stability to groundwater and surface water quality, and being constructed so as to be stable on decommissioning. With the exception of the material used in road construction, mine M70/264SA waste being returned as backfill to mine pits during the life of the project. If it is decided not to process marginal ore, this material also being returned to mined out pits. Should a decision to mine bedrock be made in the future, then detailed plans must be submitted to the EPA for further assessment.
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Tenement Conditions
Condition Tenements The lessee providing decommissioning plans for the removal of waste M70/264SA and equipment. These plans being finalised at least twelve months prior to the proposed date for decommissioning and being to the satisfaction of the EPA and appropriate Government agencies. The lessee presenting proposals for rehabilitation of areas affected by the project within 12 months of commissioning, as follows: i. Rehabilitation of landscape, soils and vegetation appropriate for the land use priority for that area within State Forest and to standards appropriate to bauxite mining, to the satisfaction of CALM. ii. Rehabilitation of areas affected by chemical spills should they occur and monitoring or chemical concentration until they decline to background levels, to the satisfaction of the State Mining Engineer. iii. Rehabilitation of the haul road to the satisfaction of CALM. A Mine Closure Plan is to be submitted by the date specified below, G70/215, G70/219, unless otherwise directed by an Environmental Officer, DMP. The Mine L70/95, L70/96, Closure Plan is to be prepared in accordance with the “Guidelines for M70/21, M70/22, Preparing Ming Closure Plans” available on DMP’s website M70/23, M70/24, 30 December 2012 M70/25, M70/564, M70/799
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Ministerial Conditions
MINISTERIAL CONDITIONS Ministerial Statement 591, Boddington and Hedges Gold Mines (Assessment 1409, Bulletin 1035) Page Commitment 2 2‐1 The proponent shall implement the consolidated environmental management commitments documented in schedule 2 of this statement. 2‐2 The proponent shall implement subsequent environmental management commitments which the proponent makes as part of the fulfilment of conditions in this statement. 4 7‐1 Prior to 31 October 2003, the proponent shall prepare, and subsequently implement, a Preliminary Closure Plan, which provides the framework to ensure that the site is left in an environmentally acceptable condition to the requirements of the Minister for the Environment and Heritage on advice of the Environmental Protection Authority.
This Plan shall be reviewed every five years, and shall address: 1. Rationale for the siting and design of plant and infrastructure as relevant to environmental protection, and conceptual plans for the removal or, if appropriate, retention of plant and infrastructure; 2. A conceptual rehabilitation plan for all disturbed areas and description of a process to agree on the end land use(s) with all stakeholders; 3. A conceptual plan for a care and maintenance phase; and 4. Management of noxious materials to avoid the creation of contaminated areas. 7‐2 At least six months prior to the anticipated date of closure, or at a time agreed with the Environmental Protection Authority, the proponent shall prepare a Final Closure Plan designed to ensure that the site is left in an environmentally acceptable condition to the requirements of the Minister for the Environment and Heritage on advice of the Environmental Protection Authority.
The Final Closure Plan shall address: 1. Removal, or if appropriate, retention of plant and infrastructure in consultation with relevant stakeholders; 2. Rehabilitation of all disturbed areas to a standard suitable for the agreed new land uses(s); 3. Identification of contaminated areas, including provision of evidence of notification and proposed management measures to relevant statutory authorities; 4. Long term management of mined‐out pits, residue disposal areas, process water ponds, non‐mineralised rock stockpiles, water supply dams, processing plant and associated infrastructure; and 5. Long term management measures for groundwater and surface waters affected by the project. 5 7‐3 The proponent shall implement the Final Closure Plan required by condition 7‐2 until such time as the Minister for the Environment and Heritage determines, on advice of the Environmental Protection Authority, that the proponent's closure responsibilities are complete. 7‐4 The proponent shall make the Final Closure Plan required by condition 7‐2 publicly available, to the requirements of the Minister for the Environment and Heritage on the advice of the Environmental Protection Authority.
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Ministerial Conditions
Ministerial Statement 591, Boddington and Hedges Gold Mines (Assessment 1409, Bulletin 1035) Page Commitment Proponent’s 4. Prepare and submit to the BGM Environmental Management Liaison Group Commitments annual environmental reports which will incorporate environmental management plans and include details of environmental management measures and commitments, rehabilitation plans, internal auditing plans, compliance reports and research for the BGM project. 8. Carry out regular monitoring of the abundance and distribution of flora and fauna in rehabilitation and forest areas adjacent to mined and residue disposal areas in consultation with CALM. 9. Encourage recruitment of local rare or priority flora and threatened fauna into rehabilitation areas. 10. Research will be conducted into priority species which occur naturally on the BGM site but which have not been recorded in rehabilitation, with the aim of establishing these species in suitable rehabilitation areas. 24. Undertake studies to determine acceptable conditions for the release of excess water to Thirty‐Four Mile Brook. 25. Participate in catchment management activities that are aimed at protecting or enhancing the ecological values of Hotham River and Thirty‐ Four Mile Brook in the vicinity of the BGM Project Area. 29. Develop rehabilitation and decommissioning plans for the BGM Project Areas in consultation with the BGM Environmental Management Liaison Group. 30. Continue field trials for rehabilitation of residue disposal areas. 31. Undertake a research and development programme to identify alternative techniques for residue rehabilitation. 32. Undertake detailed studies to determine management options for the lake(s) in consultation with the BGM Liaison Group. 33. Undertake a comprehensive study to characterise the ecology and human dependencies on Thirty‐Four Mile Brook in order to establish a baseline for evaluation of rehabilitation strategies. 34. Develop water release and water quality targets for the decommissioned phase of the mine in consultation with the BGM Environmental Management Liaison Group. 36. Prepare a scheme to assist revegetation of the Hotham catchment that includes sponsorship of: - Research, planting or revegetation trials on farming land; - Re‐establishment of riparian vegetation in degraded areas; and - Enhancement of biodiversity in degraded areas. 37. Implement the vegetation scheme described in commitment 36. 39. Investigate rehabilitation of forested areas affected by jarrah dieback. 43. Maximise salvage of forest products from clearing in the BGM project area. 44. Participate in regional feral animal and weed control programmes in association with CALM.
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Ministerial Conditions
Ministerial Statement 590, Hedges Gold Project (Assessment 1410, Bulletin 1035) Page Commitment 5 15‐1 Within twelve months following commissioning, the proponent shall prepare a rehabilitation program which addresses: 1. The rehabilitation of landscape, soils and vegetation appropriate for the land use priority for that area within State Forest and to standards appropriate to bauxite mining; 2. The rehabilitation of areas affected by chemical spills should they occur and monitoring of chemical concentrations until they decline to background levels; 3. The rehabilitation of haul roads in State Forest; 4. The rehabilitation of the water supply dam; and 5. The rehabilitation of the tailings dam to the requirements of the Minister for the Environment an Heritage, on the advice of the Environmental Protection Authority, the Department of Conservation and Land Management, the Forest Products Commission, the Department of Mines and Petroleum Resources and the Water and Rivers Commission as appropriate. 15‐2 The proponent shall implement the rehabilitation program required by condition 15‐1. 7 18‐1 The proponent shall carry out the satisfactory decommissioning of the project, removal of the plant and installations and rehabilitation of the site and its environs. 18‐2 At least twelve months prior to decommissioning, the proponent shall prepare a final decommissioning and rehabilitation plan to achieve the objectives of condition 18‐1, to the requirements of the Minister for the Environment and Heritage on advice of the Environmental Protection Authority, the Department of Conservation and Land Management, the Water and Rivers Commission and the Department of Mineral and Petroleum Resources.
This Plan shall address: 1. The tailings dam; 2. The water supply dam; and 3. The removal of waste and equipment. 18‐3 The proponent shall implement the plan required by condition 18‐2.
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Ministerial Conditions
Ministerial Statement 489, Boddington Gold Mine (Assessment 1053, Bulletin 850)1 Page Commitment 2 5‐1 Within twelve months following the notification of the decision‐making authorities under Section 45(7) of the Environmental Protection Act, and prior to any decommissioning, the proponent shall prepare a report which indicates rehabilitation and decommissioning objectives and performance for the project site, to the requirements of the Environmental Protection Authority on advice of the Department of Environmental Protection.
After preparation of the initial report, the proponent shall revise the above‐ mentioned report every five years. 5‐2 At least twelve months prior to decommissioning, or at such later time considered appropriate by the Minister for the Environment on advice of the Department of Environmental Protection, the proponent shall prepare a decommissioning and rehabilitation plan which: 1. Provides for the long‐term management of mined‐out pits, the residue disposal areas, process water ponds, non‐mineralised rock stockpiles, water supply dams, processing plant sites and associated infrastructure; 2. Outlines long‐term management measures of ground and surface waters affected by the project that ensure waters discharged from the project site will not adversely affect the existing beneficial uses and ecosystems of the South Dandalup catchment, the Hotham River and the Thirty‐Four Mile Brook in the vicinity of the Boddington Gold Mine Project; 3. Provides for the development of a 'walk away' solution for the decommissioned mine pits, the residue disposal areas, process water ponds, non‐mineralise rock stockpiles, water supply dams, processing plant site and associated infrastructure; and 4. Takes into consideration the findings arising from the report prepared according to the requirements of condition 5‐1, to the requirements of the Minister for the Environment on advice of the Boddington Gold Mine Environmental Management Liaison Group and the Environmental Protection Authority.
Note: A 'walk away' solution means that the site shall either no longer required management at the time the proponent ceases mining operations, or if further management is deemed necessary, the proponent shall make adequate provision so that the required management is undertaken with no liability to the State. 5‐3 The proponent shall implement the decommissioning and rehabilitation plan required by condition 5‐2. Proponent’s 2. Top soil from areas cleared for project activities will be salvaged for use in Commitments decommissioning and other rehabilitation programmes. 6. Carry out regular monitoring of the abundance and distribution of flora and fauna in rehabilitation and forest areas adjacent to mined and residue disposal areas in consultation with CALM.
1 The conditions and procedures of this Ministerial Statement were replaced by the conditions and procedures of Ministerial Statement 591. The conditions of this Ministerial Statement replace all previous conditions for the following proposals; 19 published on 15 February 1988, 49 published on 8 December 1988, 85 published on 22 November 1989, 100 published on 8 June 1990, 299 published on 21 January 1993 and 379 published on 25 January 1995.
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Ministerial Conditions
Ministerial Statement 489, Boddington Gold Mine (Assessment 1053, Bulletin 850)1 Page Commitment Proponent’s 8. Conduct a programme which aims to establish priority flora, which occur Commitments naturally on the BGM site but which have not been recorded in rehabilitation, with the aim of establishing these species in suitable rehabilitation areas. 17. Drainage will be installed around mine pits, haul‐roads and stockpiles, water (other than acidic mine drainage) from these will either be used for dust suppression, or will drain via silt traps into natural watercourses. 19. Shallow mine pits will be contoured to slopes generally consistent with natural landforms. 20. Deeper pits will be rehabilitated if, at the time of completion of mining the weathered profile, no decision to mine bedrock has been made. 21. Should a decision to mine bedrock to be [sic] made, detailed plans will be submitted to the State for approval. 22. Final rehabilitation will ensure that run‐off will drain to natural watercourses or into the deeper pits. 24. Develop rehabilitation and decommissioning plans for the BGM Project Area in consultation with the BGM Liaison Group. 25. Continue field trials for rehabilitation and decommissioning plans for the BGM Project Area in consultation with the BGM Liaison Group. 26. Undertake a research and development programme to identify alternative techniques for residue rehabilitation in consultation with the BGMLG. 27. Undertake detailed studies to determine management options for the lake(s) in consultation with the BGM Liaison Group. 28. Detailed rehabilitation prescriptions for the mining area will be developed with the primary objectives of stabilising surfaces, minimising erosion, minimising risk of saline groundwater seepage, and providing a sustainable vegetation system. 29. Local provenance native species will be used where possible, although other species may be used where they provide advantages in meeting the primary objectives.
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Ministerial Conditions
Ministerial Statement 450, Hedges Gold Project (Assessment 1057, Bulletin 851)2 Page Commitment 4 13‐1 Within twelve months following commissioning, the proponent shall prepare a rehabilitation programme which addresses: 1. The rehabilitation of landscape, soils and vegetation appropriate for the land use priority for that area within State Forest and to standards appropriate to bauxite mining, to the requirements of the Department of Conservation and Land Management; 2. The rehabilitation of areas affected by chemical spills should they occur and monitoring of chemical concentrations until they decline to background levels, to the requirements of the Department of Minerals and Energy; 3. The rehabilitation of haul roads in State Forest, to the requirements of the Department of Conservation and Land Management; 4. The rehabilitation of the water supply dam, to the requirements of the Waters and Rivers Commission; and 5. The rehabilitation of the tailings dam, to the requirements of the Departments of Minerals and Energy. 13‐2 The proponent shall implement the rehabilitation programme required by condition 13‐1. 5 14‐1 With the exception of the material used in road construction, the proponent shall return mine waste, as backfill, to mine pits during the life of the project. 14‐2 If it is decided not to process marginal ore, the proponent shall also return this material to mined‐out pits. 19‐2 At least twelve months prior to decommissioning, the proponent shall prepare a final decommissioning and rehabilitation plan to achieve the objectives of condition 19‐1, to the requirements of the Environmental Protection Authority on advice of the Department of Conservation and Land Management, the Water and Rivers Commission and the Department of Miners and Energy.
This plan shall address, but not be limited to: 1. The tailings dam; 2. The water supply dam; and 3. The removal of waste and equipment. The proponent shall implement the plan required by condition 19‐2. Proponent’s 6. Progressively rehabilitation mined areas during the project, if mining Commitments sequence and production drilling data indicate that this is possible. Alternatively, rehabilitate all areas after project completion. 7. Where practicable, return waste to mined areas. Landscape and rehabilitate the remaining waste stockpile according to principles in (8). 8. Return affected areas to appropriate and achievable land uses in accordance with agreements with the State Government and Worsley Timber Company, using prescriptions developed in consultation with relevant State Government authorities. 9. Monitor and maintain rehabilitated pits, waste stockpile, haul road and residue disposal areas until such time as it is agreed, with the State, that the objectives of such rehabilitation have been met.
2 The conditions and procedures of this Ministerial Statement were replaced by the conditions and procedures of Ministerial Statement 591.
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Ministerial Conditions
Ministerial Statement 450, Hedges Gold Project (Assessment 1057, Bulletin 851)2 Page Commitment Proponent’s 10. Design and operate a water quality, drainage and stormwater management Commitments system throughout the project area which will minimise the discharge of turbid water, plant chemicals or tailings spills into nearby streams, and minimise erosion. 11. Ensure mining operations do not have a negative impact on the long term quality of water in the BGM water supply reservoir, by developing and implementing appropriate drainage control and rehabilitation programmes. 15. Conduct forest upgrading planting in disease affected State Forest immediately adjacent to operations, if required and considered appropriate by CALM. 29. Remove contaminated material and carry out appropriate rehabilitation if a tailings pipeline failure occurs. 30. Establish surface contouring and drainage to prevent the rise of contaminated waters in residue disposal areas during rehabilitation, and permit vegetation establishment. Establish a drainage collection system to retain runoff so that it can be monitored and if necessary treated prior to discharge. 31. Continue monitoring the water residue system until it is decided, in consultation with the State, that such activity is no longer required. 44. Ensure that mining of the stream zone orebody only took place during summer months and that rehabilitation of this part of the pit would commence immediately mining was completed.
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Ministerial Conditions
Ministerial Statement 453, Boddington Gold Mine, Extended Basement Operation (Assessment 1033, Bulletin 453)3 Page Commitment 4 8‐1 Within the first five years following the commencement of mining, and prior to any decommissioning of the site, the proponent shall a report which indicates rehabilitation and decommissioning objectives and performance for the site, to the requirements of the Environmental Protection Authority on advice of the Department of Environmental Protection, the Department of Conservation and Land Management and the Department of Minerals and Energy.
After preparation of the initial report, the proponent shall revise the above‐ mentioned report every five years. 8‐2 At least five years prior to decommissioning, or at such later time considered appropriate by the Minister for Environment on advice of the Department of Environmental Protection, the proponent shall prepare a decommissioning and rehabilitation plan which: 1. Provides for the long‐term management of the mined‐out pits, the residue disposal areas, process water ponds, non‐mineralised rock stockpiles, water supply dams, processing plant site and associated infrastructure; 2. Outlines the long‐term management of ground and surface waters affected by the project that ensure waters discharged from the project site will not adversely affect the existing beneficial uses and ecosystems in the South Dandalup catchment, the Hotham River and the Thirty‐Four Mile Brook in the vicinity of the Boddington Gold Project; 3. Provides for the development of a 'walk away' solution for the decommissioned mine pits, the residue disposal areas, the process water ponds, the non‐mineralised rock stockpiles, the water supply dams, processing plant site and associated infrastructure; and 4. Takes into consideration the findings arising from the report prepared according to the requirements of condition 8‐1, to the requirements of the Minister for the Environment on advice of the Boddington Gold Mine Environmental Management Liaison Group and the Environmental Protection Authority.
Note: A 'walk away' solution means that the site shall either no longer require management at the time the proponent ceases mining operations, or if further management is deemed necessary, the proponent shall make adequate provision so that the management is undertaken with no liability to the State. The proponent shall implement the decommissioning and rehabilitation plan required by condition 8‐2. Proponent’s 5. A. Prepare and submit to the BGM Liaison Group annual environmental Commitments reports which will incorporate environmental management plans and include details of environmental management measures and commitments, rehabilitation plans, internal auditing plans, compliance reports and research for the BGM project.
3 The conditions and procedures of this Ministerial Statement were replaced by the conditions and procedures of Ministerial Statement 591.
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Ministerial Conditions
Ministerial Statement 453, Boddington Gold Mine, Extended Basement Operation (Assessment 1033, Bulletin 453)3 Page Commitment 5. B. Prepare and submit plans to the BGM Liaison Group through the annual environmental reporting process which incorporates plans and measures to reduce as far as practicable the out‐of‐pit placement of non‐mineralised rock for the BGM project. 8. Carry out regular monitoring of the abundance and distribution of flora and fauna in rehabilitation and forest areas adjacent to mined and residue disposal areas in consultation with CALM. 9. Encourage recruitment of local rare or priority flora and threatened fauna into rehabilitation areas. 10. Research will be conducted into priority species which occur naturally on the BGM site but which have not been recorded in rehabilitation, with the aim of establishing these species in suitable rehabilitation areas. 20. Undertake studies to determine acceptable conditions for the release of excess water to Thirty‐Four Mile Brook. 21. Participate in catchment management activities that are aimed at protecting or enhancing the ecological values of Hotham River and Thirty‐ Four Mile Brook in the vicinity of the BGM Project Area. 25. Develop rehabilitation and decommissioning plans for the BGM Project Areas in consultation with the BGM Liaison Group. 26. Continue field trials for rehabilitation of residue disposal areas. 27. Undertake a research and development programme to identify alternative techniques for residue rehabilitation. 28. Undertake detailed studies to determine management options for the lake(s) in consultation with the BGM Liaison Group. 29. Undertake a comprehensive study to characterise the ecology and human dependencies on Thirty‐Four Mile Brook in order to establish a baseline for evaluation of rehabilitation strategies. 30. Develop water release and water quality targets for the decommissioned phase of the mine in consultation with the BGM Liaison Group.
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Ministerial Conditions
Ministerial Statement 379, Boddington Gold Mine, Enhancement of Facilities, Expansion of Facilities – Stage 2, Mining and Processing of Supergene/Basement Ores, Development of Eastern Anomalies (Assessment 901, Bulletin 766)4 Page Commitment 2 4‐1 At least 12 months prior to decommissioning the mine pits, the proponent shall prepare an Environmental Management Programme for the inclusion of lakes as final landform features within the mine pit areas, to the requirements of the Department of Environmental Protection on advice of the Water Authority of Western Australia, the Department of Minerals and Energy and the Department of Conservation and Land Management.
This programme shall include, but not be limited to, the following: - Lake design, including: a) The proposed connection to Thirty‐Four Mile Brook; b) The partial return of mine waste as backfill to mine pits where required for the necessary creation of shallow water areas or islands for wildlife use; c) Inflow and outflow options for the management of water quality and quantity in the lakes and Thirty‐Four Mile Brook, including options for isolating the lakes; and d) Slopes and proposed vegetation types, including wetlands plant species; - Target minimum, maximum and optimum water levels in the lakes based on stream flow in Thirty‐Four Mile Brook, groundwater flow and run‐off from surrounding areas; - Water quality criteria to ensure the maintenance of appropriate water quality in the lakes and Thirty‐Four Mile Brook; - Predicted groundwater and surface water hydrological responses and impacts on long term salinity in the lakes and Thirty‐Four Mile Brook; and - The development of a comprehensive monitoring, management and reporting programme 4‐2 The proponent shall implement the Environmental Management Programme required by condition 4‐1 to the requirements of the Department of Environmental Protection on advice of the Water Authority of Western Australia, the Department of Minerals and Energy and the Department of Conservation and Land Management. 3 5‐1 The proponent shall rehabilitate the Boddington Gold Mine site and environs and remove associated infrastructure, to the requirements of the Department of Environmental Protection and the State Mining Engineer with advice from other agencies, as appropriate. 6‐1 The proponent shall ensure that waters discharged to the Hotham River from the residue disposal areas and the D1 Dam permit the maintenance of the identified beneficial uses and the existing ecosystems of the River.
4 The conditions and procedures of this Ministerial Statement were replaced by the conditions and procedures of Ministerial Statements 489 and 591. The conditions of this Ministerial Statement replace all previous conditions for the following proposals; Enhancement of Facilities (Assessment 156), Expansion of Facilities ‐ Stage 2 (Assessment 182), Mining and Processing of Supergene/Basement Ores (Assessment 238/238‐1) and Development of Eastern Anomalies (Assessment 700).
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Ministerial Conditions
Ministerial Statement 379, Boddington Gold Mine, Enhancement of Facilities, Expansion of Facilities – Stage 2, Mining and Processing of Supergene/Basement Ores, Development of Eastern Anomalies (Assessment 901, Bulletin 766)4 Page Commitment 3 6‐2 The proponent shall ensure that waters discharged to the Thirty‐Four Mile Brook from the residue disposal areas and the D1 Dam permit the maintenance of the identified beneficial uses and the existing ecosystems of the Brook. 6‐3 At least six months prior to discharge of waters from the residue disposal areas or the D1 Dam, the proponent shall demonstrate in a report to the Department of Environmental Protection how the discharges will be managed to meet conditions 6‐1 and 6‐2, to the requirements of the Department of Environmental Protection on advice of the Water Authority of Western Australia.
This report shall address, but not be limited to, the following; - Provision of further details on the water management programme, referred to in the proponent's documentation of 1994, for the residue disposal areas and the D1 Dam; - Further characterisation of the receiving environments of the Hotham River and Thirty‐Four Mile Brook; and - Determination of the likely effectiveness of the water management programme in meeting the objectives of conditions 6‐1 and 6‐2. 6‐4 In the event that matters addressed in the report required by condition 6‐3 demonstrate the need for variation o the programme referred to in the proponent's documentation of 1994, the proponent shall modify the water management programme to the requirements of the Department of Environmental Protection on advice of the Water Authority of Western Australia. 6‐5 The proponent shall implement the modified water management programme arising from condition 6‐4. 4 7‐1 At least twelve months prior to decommissioning, the proponent shall prepare a decommissioning and rehabilitation plan, including development of a 'walk away' solution for the site, to the requirements of the Department of Environmental Protection and the State Mining Engineer.
Note: A 'walk away' solution means that the site shall either no longer require management at the time the proponent ceases mining operations, or if further management is deemed necessary, the proponent shall make adequate provision so that the required management is undertaken with no liability to the State. This could be in the form of an environmental bond such as those routinely held against mining rehabilitation success by the Department of Minerals and Energy. 7‐2 The proponent shall implement the plan required by condition 7‐1 to the requirements of the Department of Environmental Protection and the State Mining Engineer. Proponent’s 2. Topsoil from areas cleared for project activities will be salvaged for use in Commitments decommissioning and other rehabilitation activities. 16. Shallow mine pits will be contoured to slopes generally consistent with natural landforms. 17. Deeper pits will be rehabilitated if, at the time of completion of mining the weathered profile, no decision to mine bedrock has been made. Should a decision to mine bedrock to be [sic] made, detailed plans will be submitted to the State for approval.
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Ministerial Conditions
Ministerial Statement 379, Boddington Gold Mine, Enhancement of Facilities, Expansion of Facilities – Stage 2, Mining and Processing of Supergene/Basement Ores, Development of Eastern Anomalies (Assessment 901, Bulletin 766)4 Page Commitment Proponent’s 18. Final rehabilitation will ensure that runoff will drain to natural watercourses Commitments or into the deeper pits. 19. Life‐of‐project land use plans will be prepared and submitted to the State on an annual basis. 21. Prior to the commencement of rehabilitation BGM will develop detailed prescriptions for the residue areas which will be aimed at stabilising the residue surface, providing a sustainable vegetation system, and optimise [sic] the quality of any future runoff from those areas. 22. As a temporary measure following decommissioning, D1 Dam will be used to capture and control saline runoff from the BGM Residue Disposal Areas, which will be diverted to the Hotham River. This diversion of water will not cause an increase of more than 10% in the salinity of Hotham River at any time. Other than salinity this discharge will not exceed statutory guidelines for water used for livestock watering. 23. Unless authorised by the State, residue area runoff water which is released from D1 Dam into Thirty‐Four Mile Brook will not exceed 3000mg/L Total Dissolved Solids. This discharge will not exceed statutory guidelines for recreational waters. 24. During the initial period of lake filling following rehabilitation, BGM will endeavour to manage water flows so as to minimise drought stress in riparian vegetation in Thirty‐Four Mile Brook. 25. When the quality of residue area runoff meets the criteria for discharge to Thirty‐Four Mile Brook, BGM will continue to monitor and manage further runoff until sufficient data are available to demonstrate to the satisfaction of the State that (notwithstanding seasonal effects) the quality of this runoff has stabilised or is continuing to improve below those criteria. Final rehabilitation of D1 dam will not commence until this has been demonstrated. 26. BGM will include in the final landform lakes in the Pit G and Pit B areas, which will be linked to Thirty‐Four Mile Brook. Detailed plans will be developed in consultation with and to the satisfaction of the State showing lake design, inflow and outflow structures, slopes, and proposed vegetation types, prior to final rehabilitation commencing. Measures to maximise the area of shallows in the lakes will be investigated and implemented where practicable. The design will include predicted hydrological responses and impacts on long‐term salinity in Thirty‐Four Mile Brook. 27. Detailed rehabilitation prescriptions for the mining area will be developed with the primary objectives of stabilising surfaces, minimising erosion, minimising risk of saline groundwater seepage, and providing a sustainable vegetation system. Local provenance native species will be used where possible, although other species may be use where they provide advantages in meeting the primary objectives. 30. BGM will develop rehabilitation strategies and prescriptions in consultation with the State, and monitor and report on the success of rehabilitation.
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Ministerial Conditions
Ministerial Statement 299, Boddington Gold Mine, Development of Eastern Anomalies (Assessment 700, Bulletin 661)5 Page Commitment 1 3‐1 At least six months prior to decommissioning, the proponent shall prepare a decommissioning and rehabilitation plan to the requirements of the State Mining Engineer and the Environmental Protection Authority. 3‐2 The proponent shall implement the plan required by condition 3‐1 to the requirements of the State Mining Engineer and the Environmental Protection Authority. Proponent’s 6. Develop rehabilitation strategies and prescriptions in consultation with the Commitments State, and monitor and report on the success of rehabilitation.
5 The conditions and procedures of this Ministerial Statement were replaced by the conditions and procedures of Ministerial Statement 379, 489 and 591.
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Ministerial Conditions
Ministerial Statement 100, Boddington Gold Mine, Mining and Processing of Supergene/Basement Ores (Assessment 238‐B, Bulletin 430)6 Page Commitment 1 In implementing this proposal (including the documented modifications of 1 March 1990) the proponent shall fulfil the commitments made in the Notice of Intent of July 1989 (as amended) and shall carry out the mining and processing of the Supergene/Basement Ores in accordance with the relevant commitments documented in the Environmental Management Programme for the Boddington Gold Mine of April 1997.
6 The conditions and procedures of this Ministerial Statement were replaced by the conditions and procedures of Ministerial Statement 379, 489 and 591.
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Ministerial Conditions
Ministerial Statement 85, Boddington Gold Mine, Mining and Processing of Supergene/Basement Ores (Assessment 238‐A, Bulletin 408)7 Page Commitment 2 To maintain the water quality of Thirty‐Four Mile Brook so that the Water Supply Reservoirs will be a viable long‐term source of public water supply and to leave the site in an environmentally stable condition, the proponents shall undertake rehabilitation of the site and its environs in consultation with the Water Authority of Western Australia, the Department of Mines and, where appropriate, the land owner, to the satisfaction of the Environmental Protection Authority upon advice from the Water Authority of Western Australia and the Department of Mines. Proponent’s 2. Topsoil from areas cleared for project activities will be salvaged for use in Commitments decommissioning and other rehabilitation activities. 9. Rehabilitation of project areas will be carried out in consultation with the State and, where appropriate, the land owner, with the aim of maintaining the water quality of Thirty‐Four Mile Brook so that the downstream Water Supply Reservoir could be a viable long‐term source of public water supply. If, at the time of decommissioning, the State requires the Water Supply Reservoir as a potable water source, the water quality in the reservoir will be reassessed and, should it prove to be unsuitable, the Joint Venturers will drain the dam, allowing it to refill naturally. 18. Perimeter drains will be installed around mine pits and stockpiles; water (other than acid mine drainage water) from these and from haul roads will drain through silt traps into natural watercourses. 20. Mine waste not used in road construction will be returned as backfill to mine pits during the life of the project 21. If it is decided not to process marginal ore, this material will be returned to mined‐out pits. 22. Shallow mine pits will be contoured to slopes generally consistent with natural landforms. 23. Deeper pits will be rehabilitated if, at the time of completion of mining the weathered profile, no decision to mine bedrock has been made. Should a decision to mine bedrock to be made, detailed plans will be submitted to the State for approval. 24. Final rehabilitation will ensure that runoff will drain to natural watercourses or into the deeper pits. 25. Life‐of‐project land use plans will be prepared and submitted to the State on an annual basis.
7 The conditions and procedures of this Ministerial Statement were replaced by the conditions and procedures of Ministerial Statement 379, 489 and 591.
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Ministerial Conditions
Ministerial Statement 49, Boddington Gold Mine, Expansion of Facilities – Stage 2 (Assessment 182, Bulletin 361)8 Page Commitment Proponent’s Topsoil from areas cleared for project activities will be salvaged for use in Commitments decommissioning and other rehabilitation programmes. Rehabilitation of project areas will be carried out in consultation with the State and, where appropriate, the land owner, with the aim of maintaining the water quality of Thirty‐Four Mile Brook so that the Water Supply Reservoir would be a viable source of public water supply. If, at the time of decommissioning, the State requires the Water Supply Reservoir as a potable water source, the water quality in the reservoir will be reassessed and, should it prove to be unsuitable, the Joint Venturers will drain the dam, allowing it to refill naturally. Perimeter drains will be installed around mine pits and stockpiles, water from these and haul roads will drain through silt traps into natural watercourses. Mine waste not used in road construction will be returned as back fill to mine pits during the life of the project. If it is decided not to process marginal ore, this material will be returned to mined‐ out pits. Shallow mine pits will be contoured to slopes generally consistent with natural landforms. Deeper pits will be rehabilitated if, at the time of completion of mining the weathered profile, no decision to mine bedrock has been made. Should a decision to mine bedrock be made, detailed plans will be submitted to the State for approval. Final rehabilitation will ensure that runoff will drain to natural watercourses or into deeper pits.
8 The conditions and procedures of this Ministerial Statement were replaced by the conditions and procedures of Ministerial Statement 379, 489and 591.
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Ministerial Conditions
Ministerial Statement 20, Hedges Gold Project (Assessment 148, Bulletin 314) 9 Page Commitment 2 13. The proponent shall present proposals for rehabilitation of areas affected by the project within 12 months of commissioning, as follows; - Rehabilitation of landscape, soils and vegetation appropriate for the land use priority for that area within State forest and to standards appropriate to bauxite mining, to the satisfaction of the Department of Conservation and Land Management; - Rehabilitation of areas affected by chemical spills should they occur and monitoring of chemical concentrations until they decline to background levels, to the satisfaction of the Department of Mines; - Rehabilitation of haul roads in State Forest, to the satisfaction of the Department of Conservation and Land Management; - Rehabilitation of the water supply dam, to the satisfaction of the Water Authority of Western Australia; and - Rehabilitation of the tailings dam, to the satisfaction of the Department of Mines. 3 14. With the exception of the material used in road construction, mine waste shall be returned as backfill to mine pits during the life of the project. If it is decided not to process marginal ore, this material shall also be returned to mined out pits. Should a decision to mine bedrock be made in the future, then detailed plans must be submitted to the Environmental Protection Authority for further assessment. 18. The proponent shall provide decommissioning plans for: - The tailings dam; - The water supply dam; and - The removal of waste and equipment.
Plans shall be finalised at least twelve months prior to the proposed date for decommissioning and be to the satisfaction of the Environmental Protection Authority and appropriate Government agencies. Proponent’s 6. Progressively rehabilitate mined areas during the project, if mining sequence Commitments and production drilling data indicate that this is possible. Alternatively, rehabilitate all areas after project completion. 7. Where practicable, return waste to mined areas. Landscape and rehabilitate the remaining waste stockpile according to principles in (8). 8. Return affected areas to appropriate and achievable land uses in accordance with agreements with the State Government and Worsley Timber Company, using prescriptions developed in consultation with relevant State Government authorities. 9. Monitor and maintain rehabilitated pits, waste stockpile, haul road and residue disposal areas until such time as it is agreed, with the State, that the objectives of such rehabilitation have been met. 11. Ensure mining operations do not have negative impact on the long term quality of water in the BGM water supply reservoir, by developing and implementing appropriate drainage control and rehabilitation programmes. 15. Conduct forest upgrading planting in disease affected State Forest immediately adjacent to operations, if required and considered appropriate by CALM.
9 The conditions and procedures of this Ministerial Statement were replaced by the conditions and procedures of Ministerial Statement 379 and subsequently Ministerial Statement 591.
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Ministerial Conditions
Ministerial Statement 20, Hedges Gold Project (Assessment 148, Bulletin 314) 9 Page Commitment Proponent’s 30. Establish surface contouring and drainage to prevent the rise of contaminated Commitments waters in residue areas during rehabilitation, and permit vegetation establishment. Establish a drainage collection system to retain runoff so that it can be monitored and if necessary treated prior to discharge. 31. Continue monitoring the water residue system until it is decided, in consultation with the State, that such activity is no longer required. 44. Ensure that mining of the stream zone orebody only took place during summer months and that rehabilitation of this part of the pit would commence immediately mining was completed.
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Ministerial Conditions
Ministerial Statement 19, Boddington Gold Mine Enhancement of Facilities (Assessment 156, Bulletin 313)10 Page Commitment Proponent’s Topsoil from areas cleared for project activities will be salvaged for use in Commitments decommissioning and other rehabilitation programmes. Rehabilitation of project areas will be carried out in consultation with the State and, where appropriate, the land owner, with the aim of maintaining the water quality of Thirty‐Four Mile Brook so that the Water Supply Reservoir would be a viable source of public water supply. If, at the time of decommissioning, the State requires the Water Supply Reservoir as a potable water source, the water quality in the reservoir will be reassessed and, should it prove to be unsuitable, the Joint Venturers will drain the dam, allowing it to refill naturally. Perimeter drains will be installed around mine pits and stockpiles, water from these and haul roads will drain through silt traps into natural watercourses. Mine waste not used in road construction will be returned as back fill to mine pits during the life of the project. If it is decided not to process marginal ore, this material will be returned to mined‐ out pits Shallow mine pits will be contoured to slopes generally consistent with natural landforms. Deeper pits will be rehabilitated if, at the time of completion of mining the weathered profile, no decision to mine bedrock has been made. Should a decision to mine bedrock be made, detailed plans will be submitted to the State for approval. Final rehabilitation will ensure that runoff will drain to natural watercourses or into deeper pits.
10 The conditions and procedures of this Ministerial Statement were replaced by the conditions and procedures of Ministerial Statements 379, 489 and 591.
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