CLOSURE MANAGEMENT AND REHABILITATION PLAN OLYMPIC DAM May 2019 Copyright BHP is the sole owner of the intellectual property contained in any documentation bearing its name. All materials including internet pages, documents and online graphics, audio and video, are protected by copyright law. Apart from any fair dealing for the purposes of private study, research, criticism or review as permitted under the provisions of the Copyright Act 1968, no part of this document may be reproduced, transmitted in any form or re-used for any commercial purposes whatsoever without the prior written permission of BHP. This document represents the status of the topic at the date shown and is subject to change without notice. The latest version of this document is available from Document Control. © 2019 BHP. All rights reserved. This document is uncontrolled when printed. This Closure and Rehabilitation Plan has been prepared as information only and is not to be relied on as final or definitive. It would continue to be developed and would be subject to change. BHP Olympic Dam Closure Management and Rehabilitation Plan Closure Management Plan Summary Olympic Dam Mine Project Olympic Dam Document Title Olympic Dam Mine Closure Management and Rehabilitation Plan Document Reference 99232 Mining Tenements Special Mining Lease 1 Company Name BHP Billiton Olympic Dam Corporation Pty Ltd Electronic Approval Record Business Role Name Authors Role Name Principal Strategic Planning Don Grant Principal Environment A&I Murray Tyler Principal Closure Planning Craig Lockhart Reviewer Role Name Manager Closure Planning Rebecca Wright Superintendent Environment, Radiation and Occupational Hygiene James Owen Principal Legal Zoe Jones Approver Role Name Head of Environment Analysis and Improvement Gavin Price Head of Geoscience and Resource Engineering Amanda Weir Asset President Olympic Dam Laura Tyler Document Amendment Record Version. Page Change Effected Date of Change No Number 4 Update to 2013 document to reflect current LoA May 2019 Key Stakeholders Department Position Water Planning Superintendent Water Planning Mine Planning Manager Mine Planning Corporate Affairs Head of Corporate Affairs Land and Tenements Superintendent Tenure Environment A&I Manager Environment Page iii BHP Olympic Dam Closure Management and Rehabilitation Plan Table of Contents 1 Executive Summary 1 2 Scope and Purpose 2 2.1 Purpose and Process 2 2.2 Project Overview 2 2.3 Current Mining Tenement 3 2.4 Closure Features and Domains 5 2.5 Current Disturbance 6 3 Roles and Responsibilities 8 4 Closure Obligations and Commitments 9 4.1 Regulatory and Other Requirements 9 4.2 Legal and Statutory Commitments and Obligations 10 4.3 Community Agreements 10 5 Stakeholder Consultation 11 5.1 Stakeholder Identification and Approach 11 5.2 Five Year Engagement Goals 11 5.3 Community Profile 11 5.4 Community Exit Strategy 12 5.5 Stakeholder Register 12 6 Rehabilitation Goals, Objectives and Criteria 13 6.1 Rehabilitation Goals 13 6.2 Final Land Use 13 6.3 Closure Environmental Outcomes and Assessment Criteria 13 7 Collection and Analysis of Closure Data 17 7.1 Climate 17 7.1.1 Existing Climate 17 7.1.2 Climate Change 17 7.1.3 Knowledge Gaps 18 7.2 Waste Material Characteristics 18 7.2.1 Overburden (Rock Storage Facility) 18 7.2.2 Tailings Storage Facilities 18 7.2.3 Knowledge Gaps 19 7.3 Soil Characteristics 19 7.3.1 Soil and Terrain 19 7.3.2 Knowledge gaps 19 7.4 Flora 19 7.4.1 Weeds and Declared Plants 20 7.4.2 Knowledge gaps 20 7.5 Fauna 21 7.5.1 Knowledge gaps 21 7.6 Radiation 21 7.7 Hydrology 22 7.7.1 Conceptual Baseline Understanding 22 7.7.1.1 Surface Water 22 7.7.1.2 Groundwater 22 7.7.2 Change Assessment 22 7.8 Site Contamination 25 7.8.1 Knowledge Gaps 25 Page iv BHP Olympic Dam Closure Management and Rehabilitation Plan 7.9 Visual Amenity 25 7.9.1 Knowledge Gaps 25 7.10 Cultural Heritage 26 8 Risk Assessment 27 9 Closure Implementation 28 9.1 Domain Closure and Rehabilitation Strategies 29 9.1.1 Airport Facilities 29 9.1.2 Contaminated Waste Disposal Facility 29 9.1.3 Metallurgical Plant and Administration 29 9.1.4 Miscellaneous (including the underground mine and administration facilities) 29 9.1.5 Open Pit 30 9.1.6 Pilot Plant 31 9.1.7 Quarry 31 9.1.8 Rock Storage Facility 31 9.1.9 Tailings Retention System 32 9.1.10 Town and Village Facilities 32 9.1.11 Wellfields and Associated Infrastructure 33 9.2 Progressive Rehabilitation 33 9.3 Implementation Schedule 34 10 Post Closure Monitoring and Maintenance 36 10.1 Rehabilitation Monitoring 36 10.2 Tailings Retention System 36 10.3 Open Pit and Rock Storage Facility 36 10.4 Surface Water Monitoring 36 10.5 Groundwater Monitoring 37 10.6 Fauna Monitoring 37 10.7 Weed and Feral Animal Monitoring 37 10.8 Radiation 37 10.9 Air Quality 37 10.10 Great Artesian Basin (GAB) Recovery Monitoring 38 10.11 Safety Monitoring 38 11 Unplanned or Temporary Closure 39 11.1 Unplanned Closure 39 11.2 Temporary Closure (Care and Maintenance) 39 12 Closure Provision 40 13 References 41 14 Appendices 42 Appendix A: Stakeholder Engagement Register 42 Appendix B: Knowledge Gaps and Preliminary Actions 45 Appendix C: Risk Assessment 46 Appendix D: Tailings Investigation 54 Appendix E: Post Closure Monitoring Schedule 55 Figures Figure 2-1: Olympic Dam Location Plan .............................................................................................................................. 4 Figure 2-2: Olympic Dam disturbance as at June 2018 ....................................................................................................... 7 Figure 7-1: Mean Maximum Temperature and Rainfall (Roxby Downs Olympic Dam Aerodrome Site No. 016096) (BOM 2018) ........................................................................................................................................................... 17 Figure 7-2: Surface Water Features .................................................................................................................................. 24 Page v BHP Olympic Dam Closure Management and Rehabilitation Plan Tables Table 2-1: Olympic Dam Mining Tenements (30 June 2018) ............................................................................................... 3 Table 2-2: LoA Domains and Features ................................................................................................................................ 5 Table 2-3: Current Disturbance ............................................................................................................................................ 6 Table 3-1: Roles and Responsibilities .................................................................................................................................. 8 Table 4-1: Regulatory and Other Commitments and Obligations ......................................................................................... 9 Table 4-2: Legal and Statutory Commitments and Obligations .......................................................................................... 10 Table 5-1: Five Year Engagement Activities ...................................................................................................................... 11 Table 5-2: Roxby Downs Local Government Area Economic Features (ABS, 2018) ......................................................... 12 Table 6-1: Closure Outcomes and Criteria......................................................................................................................... 14 Table 7-1: Climate and Climate Change Knowledge Gaps and Actions ............................................................................ 18 Table 7-2: Waste Material Characteristics Knowledge Gaps and Actions ......................................................................... 19 Table 7-3: Olympic Dam Topsoil Balance (30 June 2018) ................................................................................................. 19 Table 7-4: Soil and Post Mine Land Suitability Knowledge Gaps ...................................................................................... 19 Table 7-5: NRM Act 2004 Declared Weeds ....................................................................................................................... 20 Table 7-6: Vegetation Knowledge Gaps and Actions ......................................................................................................... 20 Table 7-7: Fauna Knowledge Gaps and Actions ................................................................................................................ 21 Table 7-8: Contaminated Land Knowledge Gaps and Actions........................................................................................... 25 Table 7-9: Visual Amenity Knowledge Gaps and Actions .................................................................................................. 25 Table 9-1: Closure Design Principles ................................................................................................................................. 28 Table 9-2: Metallurgical Plant and Administration Infrastructure Closure Design Requirements and Activities ................. 29 Table 9-3: Infrastructure Area Closure Design Requirements and Activities ..................................................................... 29 Table 9-4: Exploration Design Closure Design Requirements and Activities ..................................................................... 30 Table 9-5: Miscellaneous Pond Closure Design Requirements