10 Risk assessment and management · • Environmental risk management – Principles and processes...

10 Risk assessment and management

Issued Date: October 2019 Revision #: 1.19.0

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TABLE OF CONTENTS1

10 RISK ASSESSMENT AND MANAGEMENT .......................................................................... 10-1

10.1 Risk assessment methodology overview..................................................................... 10-1

10.2 Previous risk assessments ......................................................................................... 10-3

10.3 Closure risk assessment ............................................................................................ 10-4

10.4 Establishing the context and scope ............................................................................. 10-4

10.4.1 Scope of the closure risk assessment ........................................................... 10-5 10.4.2 Purpose and objectives of the closure risk assessment ................................. 10-5 10.4.3 Assumptions of the closure risk assessment ................................................ 10-5 10.4.4 Risk identification and analysis ..................................................................... 10-6

10.5 Discussion of class IV risks ...................................................................................... 10-20

10.5.1 Insufficient volume or quality of viable seed stock available for whole of site revegetation .............................................................................................. 10-20

10.6 Discussion of class III risks ....................................................................................... 10-21

10.6.1 Site condition at 8 January 2026 does not meet stakeholder expectations.. 10-21 10.6.2 Actual consolidation of tailings (Pit 1 and Pit 3) does not match consolidation

modelling and associated closure schedule leading to longer than planned process water treatment ............................................................................ 10-22

10.6.3 No disposal option for high density sludge post tailings deposition (end of 2020) ................................................................................................................. 10-23

10.6.4 TSF wall breached during deconstruction works ........................................ 10-23 10.6.5 Low plant survival rates in the field during establishment and vegetation decline

after/at establishment ................................................................................ 10-24 10.6.6 Exposed land surface contributes to increased weed recruitment, decreasing

revegetation success and spread into Kakadu NP ..................................... 10-24 10.6.7 Groundwater solute transport outcomes do not match modelled behaviour

breaching closure criteria ........................................................................... 10-25 10.6.8 Cannot achieve the desired tailings surface for post-deposition activities in Pit 3

................................................................................................................. 10-25 10.6.9 Large scale fire or natural disaster destroys immature vegetation............... 10-26 10.6.10 Closure activities may introduce new health and safety risks to workforce .. 10-26 10.6.11 Tailings or process water exceeds MOL in Pit 3 ......................................... 10-27 10.6.12 Damage occurs to cultural heritage site during rehabilitation works ............ 10-27

10.7 References............................................................................................................... 10-28

1Cover photograph: Tailings Storage Facility (March 2019)

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FIGURES

Figure 10-1: The ERA HSEQ risk framework (adapted from: AS/NZS ISO 31000:2009) .................10-2

Figure 10-2: Risk class distribution ...............................................................................................10-12

Figure 10-3: Threat risk-profile by non-economic consequence area ............................................10-12

TABLES

Table 10-1: Likelihood classification ...............................................................................................10-7

Table 10-2: Risk assessment matrix ...............................................................................................10-7

Table 10-3: Consequence classes .................................................................................................10-8

Table 10-4: Risk breakdown structure ..........................................................................................10-11

Table 10-5: Summary of class III and IV risks ...............................................................................10-13

APPENDICES

Appendix 10.1: Ranger closure risk assessment

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10 RISK ASSESSMENT AND MANAGEMENT The Energy Resources of Australia Ltd (ERA) overarching approach to potential health, safety and environmental risks is embedded in its Hazard Identification and Risk Management Standard (ERA 2018). ERA has undertaken risk assessments throughout the life of operations at the Ranger Mine. These risk assessments incorporated representation from internal ERA and Rio Tinto stakeholders, ecological, social, engineering and radiation specialists and leading government science bodies (such as Commonwealth Scientific and Industrial Research Organisation (CSIRO) and Environmental Research Institute of Supervising Scientist (ERISS)). The outcomes of these risk assessments are maintained in an ERA risk register.

A risk assessment for specific closure environmental related hazards was undertaken by ERA in August 2016 investigating the best practicable technology (BPT) options described in Section 9. This risk assessment built on previous closure risk assessment conducted since 2008 and was presented in the 2018 Mine Closure Plan (MCP).

During the Ranger closure feasibility study, a series of risk assessment workshops were completed to further develop the Ranger closure risk register. These were conducted in accordance with the ERA hazard identification and risk management standard (ERA 2018) and the Rio Tinto HSEC-C-01 HSEC Risk Assessment Group Procedure.

In June 2019 the environmental risk assessment published in the 2018 MCP was updated with the outcomes of the feasibility study risk assessment and to consider the comments received from the Supervising Scientist on the 2018 MCP risk section.

An overview of the risk assessment methods and process from the ERA Hazard Identification and Risk Management standard is provided in Section 10.1. Section 10.2 provides a summary of previous risk assessments, and Section 10.3 describes the closure risk assessment process. Outcomes of the closure risk assessment is provided in Appendix 10.1. Section 10.6 provides further evaluation of the class III (high) risks, which require active management.

10.1 Risk assessment methodology overview The Hazard Identification and Risk Management Standard (ERA 2018) was developed to ensure that hazards, aspects and opportunities for a particular project or major activity are identified in advance. The resulting risks and impacts to the business, people, property, assets and the environment are recorded and evaluated, and strategies are developed to manage these risks. The ERA Hazard Identification and Risk Management Standard is adopted in element three of the ERA Health, Safety and Environmental Management System which has been certified to meet the requirements of the standard AS/NZ ISO14001:2015 and AS4801. The framework is presented in Figure 10-1, and is consistent with the intent of the following Australian standards, and corporate management standards and practices:

• AS/NZS ISO 14001 Environmental management systems – specification with guidance for use

• AS4801 Occupational health and safety (OHS) management systems – specification with guidance for use


• AS ISO 31000:2018 Risk Management– Principles and guidelines

• Environmental risk management – Principles and processes (HB 203:2012)

• Rio Tinto Risk policy and standard

• Rio Tinto Health, Safety, Environment and Quality (HSEQ) management system – Element 3 hazard identification and risk assessment

• Rio Tinto HSE performance standards, and

• ERA Ranger Mine Environmental Requirements, which require risk controls to safeguard:

o the protection of attributes for which the Kakadu National Park (NP) was inscribed on the World Heritage list

o protection of ecosystem health of wetlands listed under Ramsar Convention on Wetlands

o protection of health of the members of the regional community, and

o maintenance of the nature and biological diversity of aquatic and terrestrial ecosystems of the Alligator Rivers Region, including ecological processes.

Figure 10-1: The ERA HSEQ risk framework (adapted from: AS/NZS ISO 31000:2009)


10.2 Previous risk assessments The risk assessment process implemented by ERA has been used to identify all potential environmental closure risks. Several risk assessments have been undertaken to date on components or aspects of the proposed closure strategy. A review of the respective risk assessments was completed with an objective of incorporating relevant risks from these earlier registers into the 2019 risk assessment, therefore reflecting the current status of the Ranger Mine closure strategy. The risk assessments reviewed included:

• Pit 1 Interim Tailings, Water and Closure (ITWC) Prefeasibility study (PFS) risk register, 2008: The purpose of this risk analysis was to identify and evaluate threats and opportunities associated with the options being considered for Pit 1 closure to PFS level. The output of this risk analysis has been used to help determine the appropriate closure method to be advanced to feasibility level.

• ITWC PFS risk register, 2011: The purpose of this risk analysis was to identify and evaluate threats and opportunities associated with all aspects of closure across a 14-year schedule (2012 to 2026) and 10,000-year tailings containment period.

• Tailings transfer risk register, 2012: The purpose of this risk analysis was to identify and evaluate threats and opportunities associated with elements of the tailings transfer process from the TSF to Pit 3, including dredging, Pit 3 pumping system, power requirements and procurement.

• PFS brine injection prefeasibility operational risk register, 2012: The purpose of this risk analysis was to identify and evaluate the risks associated with the brine injection aspect of the Ranger Mine closure project.

• Feasibility study (FS) tailings and brine management closure risk register, 2013: The purpose of this risk analysis was to identify and evaluate the risks associated with the tailings and brine management aspect of the Ranger Mine closure project. Elements assessed during this risk assessment included brine injection, tailings transfer and implications for both Pit 3 and the tailings dam during the activity, dredging, Pit 3 pumping system and operational readiness.

• Ranger Mine Pit 1 closure risk environmental register, 2016: The purpose of this risk analysis was to identify and evaluate the consequences and significance of the opportunities and threats on the surrounding environment, associated with the closure of Pit 1, and the final average tailings deposition in the pit to a level of 7 mRL. This risk analysis takes into consideration controls.

• Ranger MCP risk assessment, 2016: this risk assessment was presented in the 2018 MCP and at the time incorporated all other risk assessments undertaken over the life of the Ranger Mine at the time. As part of the scoping and in addition to incorporating previous risk assessment outcomes, the BPT options were considered in the risk assessment.

• Ranger Closure Feasibility Study 2018: This risk assessment rolled all previous closure risk assessments up into a single register that is now hosted on the Rio Tinto risk platform “Archer”. This risk register is being activity reviewed and managed as part of the Ranger Closure Project. The risks presented in this MCP are the health, safety, environmental and community risks extracted from this register.


10.3 Closure risk assessment A number of detailed risk assessment workshops were conducted during the Ranger Closure Feasibility Study. The workshops were undertaken to review the previous risk register; identify any additional foreseeable hazards or risk scenarios associated with the closure scope; and identify suitable control measures for implementation. The risk assessment process was facilitated by a competent person and involved the participation of the ERA operations and studies teams, engineering services provider, and other technical experts (as required). Appropriate hazard type prompts were utilised in accordance with the ERA and Rio Tinto hazard identification and risk management requirements.

Risk scenarios were assessed from the perspective that a person could potentially come into contact with, or be exposed to, a specific hazard. Each risk scenario is assigned with a qualitative risk rating by applying the relevant consequence and likelihood scales and descriptors from the Rio Tinto HSEC risk determination matrix (known as the 5x5 qualitative risk matrix). Each closure risk scenario was given a preliminary qualitative risk rating prior to taking control measures into consideration. Control measures were identified for the closure scenarios that resulted in a significant preliminary risk rating (i.e. High - Class III or Critical - Class IV) to further mitigate the risk level to as low as reasonably practical (ALARP). An effectiveness rating was assigned to each control measure to rate suitability for implementation. Subsequently, action plans were developed for control measures that were identified as most effective for mitigating the risk scenarios. All of the significant risks were compiled into an updated risk register including the key control measures. This register was reviewed in June 2019 to provide an update to specific detail relating to environmental and community risks. In June 2019 this risk assessment was reviewed to extract and update any specific environmental and community risks. The following sections describe the process of the closure risk assessment in accordance with AS/NZS ISO 31001:2018 (Figure 10-1).

Outcomes from this risk assessment will continue to be reviewed and additional risks identified during internal or external workshops (e.g. the cumulative risk assessment currently being run by Supervising Scientist Branch (SSB)) will be considered in future iterations of the Ranger MCP. The summary tables included in this section present information considered during the risk assessment including controls and rationale for evaluation. The outcomes of the risk assessment will continue to be used for setting priorities and management strategies. The outcomes of the SSB cumulative risk assessment are to be considered during the next iteration of the MCP risk assessment, and as per Key Knowledge Needs (KKN) Cross Theme 1 (CT1) (Appendix 7.1) will inform other ERA KKN projects, this is indicated to occur in the second half of 2019.

10.4 Establishing the context and scope The purpose, scope, objectives and assumptions of the closure risk assessment are described below.


10.4.1 Scope of the closure risk assessment The scope of the closure risk assessment included the following main categories:

• risks to the ERA ‘Licence to Close’

• risks to engineering and design of mine closure

• risks during implementation of mine closure activities, and

• risks following implementation of closure (post-closure).

10.4.2 Purpose and objectives of the closure risk assessment The purpose of the closure risk analysis was to identify and evaluate the consequences and significance of the threats on the surrounding environment associated with the closure of Ranger Mine, effective 8 January 2026. This risk analysis takes into consideration threats that may occur and relevant controls in place during the three phases of closure: decommissioning, stabilisation and monitoring and post-closure.

Decommissioning commences at the completion of processing, currently scheduled to end in 2020, and will continue to 2026. Decommissioning includes the general works associated with rehabilitating the site to an agreed standard of environmental protection and the re‐contouring and revegetation of the final landform. The stabilisation and monitoring phase is the period post-decommissioning where active works have generally ceased and the progression towards the development of a long-term viable ecosystem and achievement of closure criteria has commenced. This phase may require initial management as landform settling, subsidence and erosion occur, and vegetation establishes. Passive water management techniques will be implemented where required. The post-closure phase occurs when monitoring has demonstrated the closure criteria have been achieved and a close‐out certificate has been issued. It is in this period the site will be returned to the Traditional Owners, and the site may be incorporated within Kakadu NP.

10.4.3 Assumptions of the closure risk assessment The following assumptions were made in considering the analysis and outcomes of the closure risk assessment:

• Technical advice generated from both internal and external sources (e.g. contractors, consultants, associates, government agencies and research partners) was assumed to be appropriate.

• All existing ERA controls will continue to be applied where applicable.

• All standard ERA risk controls will be applied.


The following topics were excluded from the closure risk assessment:

• There is no consideration of socio-economic related risks, as this will be a separate body of work.

• Business economic and reputation risks

• There is no consideration for the closure and rehabilitation of a) the infrastructure immediately south of the Jabiru Airport, identified as the Jabiru field station currently occupied by the ERISS, and b) Jabiru township, as the final use of the township facilities is part of ongoing negotiations.

10.4.4 Risk identification and analysis As required by the ERA Hazard Identification and Risk Management standard, ERA risk assessments are conducted by teams with relevant qualifications and experience relating to the activity of concern and area of risk. Threats are considered in context of potential causes, controls and the potential impacts. The risk rankings were determined for each risk using a severity matrix. The matrix is a tabular portrayal of risk as the combination of the probability of occurrence (likelihood) and consequence severity.

During the identification of the closure risks, consideration was given to results and issues raised in past and recent risk assessments and modelling studies (solute transport, tailings consolidation etc.). The sources, stressors, pathways and endpoints discussed previously with stakeholders (Bartolo et al. 2013) were also considered.

The aim of risk identification is to generate a comprehensive list of credible risks related to mine closure, based on the previous and current operational and planned closure activities. The hazards were analysed to identify any significant risk to human health, safety or the natural environment with all current and proposed mitigation measures in place. Risk is measured in terms of consequence and likelihood of the adverse impact occurring in accordance with AS ISO 31000:2018 and ERA Standard: HSEQ Hazard Identification and Risk Management

Both hazards and risks are an element or action giving rise to a condition that may cause harm, whereas potential impacts (consequences) are the effect or result triggered if the risk does occur.

The likelihood (Table 10-1) and severity of consequences (Table 10-2) were defined for each environmental aspect and factor (receptor) relevant to the closure of the Ranger Mine. Risk scenarios are evaluated using the HSEQ 5x5 risk matrix (Table 10-2) to identify the consequence, likelihood and resulting risk class (refer to Attachment 2 – ERS003a HSEQ Risk Matrix). Additional definitions for long-term risks (e.g. those that may need to be considered over 10,000 years such as tailings exposure) (Table 10-1) were considered in the risk assessment. The consequence definitions are based on the ERA risk scheme and were customised to align with the particular environmental, radiation and cultural aspects of the Ranger Mine (Table 10-3).

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Table 10-1: Likelihood classification

Likelihood Rare Unlikely Possible Likely Almost

certain Frequency interval (multiple events)

Less than once per 100 years

Once in ten to once in 100 years

Once per year to once in ten years

Twice per year to once

per year

More than twice per

year

Probability (single events) <0.1% 0.1% – 1% 1% – 10% 10% – 25% >25%

Long term aspects (i.e. items relevant to 10,000 years)

Less than once per 10,000 years

Once in 1,000 to once in 10,000 years

Once per 100 to once in 1,000 years

Twice per 100 years to once per 100 years

More than twice per 100 years

The risk rankings are determined for each risk using the risk matrix are shown in Table 10-2. The matrix is a tabular portrayal of risk as the combination of the probability of occurrence and consequence severity.

Table 10-2: Risk assessment matrix

Severity Very low Low Moderate High Very high

Almost certain Class II Class III Class IV Class IV Class IV

Likely Class II Class III Class III Class IV Class IV

Possible Class I Class II Class III Class IV Class IV

Unlikely Class I Class I Class II Class III Class IV

Rare Class I Class I Class II Class III Class III

Risk scenarios that result in the highest ranked potential impacts (class III and class IV) were identified for consideration of additional risk controls (Section 10.4). The consequences assessed included both impacts to the natural environment and to the health and safety of the workforce and the public based on the definitions provided in Table 10-3.

Whilst risks with lower ranked potential impacts are predominantly subject to normal operational controls and ongoing improvement processes, the risk assessment also identified additional treatments for some class I and class II risks (Appendix 10.1).


Table 10-3: Consequence classes

Consequence

Consequence Type Very Low Low Moderate High Very High

Licence to Operate / Stakeholders (reputation with external stakeholders)

Informal disapproval from local stakeholders, manageable by site personnel with limited additional effort. No significant residual impact on reputation.

Stakeholder actions resulting in operational or commercial impacts equivalent in value to days to weeks of operational inefficiency at a tier 1 asset. Formal public disapproval from local stakeholder(s) requiring specific local management response. Some residual local reputational impact, with potential accumulate over time.

Stakeholder actions resulting in operational or commercial impacts equivalent in value to days to weeks of production from a tier 1 asset. Organised local action / prolonged formal high-profile disapproval influencing policy, regulation, commercial and / or social activity at the local level. Reputation damage requiring significant local management intervention and concessions. Prolonged scrutiny by local stakeholders contributing to cumulative reputation harm.

Stakeholder actions and / or rent seeking resulting in operational or commercial impacts equivalent in value to weeks to months of production from a tier 1 asset, but not compromising financial viability. Organised formal action influencing relevant policy, regulation, commercial and / or social activity at the national level. Reputation damage on a national scale, credibly constraining future business activities at that level for around six months due to prolonged scrutiny by stakeholders.

Stakeholder actions and / or rent seeking resulting in operational or commercial impacts equivalent in value to months to years of production from a tier 1 asset, compromising the financial viability of the asset and driving a minor formal impairment disclosure. Organised formal action at the international level influencing relevant policy, regulation, commercial or social activity across multiple jurisdictions. Reputation damage on an international (~ one year) or national (multiple years) scale, credibly preventing realisation of a major future opportunity or prolonged scrutiny of the Group assets and business activities. Severe reputation damage on a local scale, requiring a transformational change in strategy / leadership to maintain ongoing viability of an asset.

Health & Safety

Low-level short-term inconvenience or symptoms. Typically a first aid case with no medical treatment.

Injury or illness requiring medical treatment, that does not lead to restricted duties or lost time. Typically a medical treatment case injury or illness. Also includes diagnosed occupational illnesses that do not require medical treatment e.g., Dermatitis, laceration requiring suturing, NIHL, pneumoconiosis or other diagnosis without significant impairment or disability.

Injury / illness with moderate damage or impairment (<30% on impairment scale) to one or more persons. Typically a restricted duties or lost time injury/illness. e.g., Loss of finger, broken leg, injury requiring in-patient care, severe asthma attack, mental illness (with lost time), NIHL, pneumoconiosis or other diagnosis with significant impairment or disability.

Single fatality or severe permanent impairment to a person (>30%) e.g. loss of hand or lower limb (at knee), paraplegia.

Multiple fatalities or severe permanent impairment to multiple people (<5 people).


Consequence

Consequence Type Very Low Low Moderate High Very High

Environment

An unplanned or unpermitted or unintended event; or a series of chronic or cumulative events results in: Harm to the environment that is localised, of short-duration, effects no sensitive receptors and is quickly and easily rectified (e.g. within a shift). (For impacts to groundwater – a few days to weeks of natural recovery.)

An unplanned or unpermitted or unintended event; or a series of chronic or cumulative events results in: Harm on the environment that is localised, effects no sensitive receptors and is rectified or reversed within a few days to weeks of work effort, or a few days to weeks of natural recovery. (For impacts to groundwater – weeks to months of natural recovery.)

An unplanned or unpermitted or unintended event; or a series of chronic or cumulative events results in: Harm on the environment that is largely localised but starts to be unconfined, effects sensitive receptors and is rectified or reversed within weeks to months of work effort, or weeks to months of natural recovery. (For impacts to groundwater – months to years of natural recovery.)

An unplanned or unpermitted or unintended event; or a series of chronic or cumulative events results in: Harm on the environment that is unconfined, effects sensitive receptors and is rectified or reversed within months to years of work effort, or months to years of natural recovery. (For impacts to groundwater – years to decades of natural recovery.)

An unplanned or unpermitted or unintended event; or a series of chronic or cumulative events results in: Widespread, environmental harm that is rectified or reversed within several years to decades of work effort, or years to decades of natural recovery. Irreversible harm to localised but sensitive receptors. (For impacts to groundwater – multiple decades of natural recovery.)

Communities & Social Performance

Short term loss of trust with communities, repaired within days. Damage to cultural heritage site or item of low significance.

Loss of trust with communities taking weeks to months to resolve. Non-disruptive organised opposition. Damage to cultural heritage site or item of moderate significance. Ad hoc complaints about some aspects of agreement or commitments.

Loss of trust with communities that cannot be resolved through routine procedures. Disruptive organised opposition. Mitigatable damage to cultural heritage site of high local or national significance. Material non-conformance with agreements or commitments.

Widespread, sustained opposition from communities. Blockades resolved with routine procedures. Major negative impact on communities’ economic viability. Irreparable damage to cultural heritage site of high local significance. Most aspects of agreements or commitments not met and independent mediation required to resolve the impasse.

Sporadic or short term (i.e. weeks) interruptions to operations and projects, due to: Systemic opposition from communities that impacts community trust at other Rio Tinto assets. Blockades not resolved by routine procedures. Sporadic outbreaks of violence, directed at company assets or people. One-off deployment of public security as a result of a communities’ issue. Loss of community economic viability. Irreparable damage to cultural heritage site/s of national significance. Complete failure of agreement or commitment.

Legal & Regulatory Compliance

Non-compliance with agreements or laws that can be resolved via informal discussion or direct engagement.

Breaches of agreements or laws resulting in formal notices or written warnings to Rio Tinto.

Breaches of agreements or laws resulting in low-level fines or payments by Rio Tinto.

Breaches of agreements or laws or legal action resulting in fines, settlements or payments that are material at the site level, or short-term suspension of operations.

Breaches of agreements or laws or legal action resulting in fines, settlements or payments that are material at the business unit level, long-term suspension of operations or sanctions against responsible managers.

Radiation (employees, contractors or public)

Measurable increase in radiation dose with outcomes remaining below dose constraints.

Increase in radiation dose above the dose constraints but still below international limits.

Increase in radiation dose to above international limits.

Radiation doses above 100 mSv to an individual and likely to significantly increase the risk of cancer to that individual.

Radiation doses to multiple individuals above 100 mSv or acute radiation syndrome to an individual.


Potential credible risks were identified by considering the activities and phases associated with the closure of the Ranger Mine. For each risk (threat), one or more possible causes (triggers/indicators) were identified and together these were used to define the potential impacts (consequences) of each risk scenario.

Each risk scenario was assigned a unique identification number and assessed by using the risk matrix, applying a consequence and likelihood rating to the potential impact. This step of the assessment process considered operational controls to generate a risk ranking established for the aspect anticipated as having the highest potential impact (e.g. environmental impacts, compliance and community impact)

The Ranger Mine has been in operation for over 35 years and has an extensive suite of existing environmental management controls, processes, standards and stakeholder consultation such controls (e.g. bunds and water diversion controls) will continue to operate during and potentially beyond closure. As outlined previously, controls are taken into account when determining the risk ranking, thus it is the “residual” rather than the “inherent” (simple) risk that is ranked (as per ISO 31000).

A risk breakdown structure was established from the key areas of risk identified in previous risk assessments and to form the basis of the closure risk assessment (Table 10-4). The risk breakdown structure underpins the process of risk identification and subsequent processes of risk analysis, risk evaluation and risk treatment. It focuses the risk assessment process on mine closure to ensure that risk identification is undertaken at a sufficient level of detail.


Table 10-4: Risk breakdown structure

Category (risk code) Subcategory

Licence to Close (TA)

Regulatory & Statutory Obligations Commitments & Agreements Stakeholder Expectations Environmental Communities & Social Performance Local Economics Tenure & Leases Communications

Engineering / Design (TB) Assumptions

Decommissioning (TC)

Decommissioning

Landform

Revegetation

Biodiversity

Hydrology and Hydrogeology

Emissions

Waste disposal

Implementation (TD)

Implementation Planning Health & Safety Environment Communities

Post-Closure (TF) Health & Safety Environment Communities

The risk assessment identified a total of 47 risks, of which 19 risks related to project schedule, four to radiation, five to health and safety, 19 to environment, 20 to legal and regulatory compliance, 27 to licence to operate and 20 to communities and social performance.

Of these 47 risks, 14 were identified as class III (high) risks requiring active management, and one was identified as class IV (critical), which need urgent and immediate attention. Figure 10-2 and Figure 10-3 show the breakdown of risks.

All risks and risk controls are provided in Appendix 10.1. Table 10-5 provides a summary of class III (high) and class IV (critical) risks. The controls are included in Section 10.5 and Section 10.6.


Figure 10-2: Risk class distribution

Figure 10-3: Threat risk-profile by non-economic consequence area


Table 10-5: Summary of class III and IV risks

Threat code Threat title Causes (Triggers / indicators)

Impacts (Consequences) Controls Additional information Evaluation rationale

T A 02 01 Site condition at 8 Jan 2026 does not meet stakeholder expectations.

Previous commitments made are not embedded within scope. Insufficient stakeholder engagement. Insufficient scientific basis to support closure criteria. Inconsistent expectations from different stakeholders. Misalignment SSB closure standards and ERA closure criteria. Assessed closure elements viewed as not meeting "Best Practicable Technology" (BPT). Poor environment performance onsite. Closure studies and the outcomes presented in reports, undertaken by relevant experts, are complex and difficult to communicate to stakeholders. Significant changes to pre-communicated/approved closure strategy. The community may be concerned about what infrastructure is retained or lost as a result of the closure. Community expectations for the retained infrastructure are different to that remaining. Misunderstanding of the Authorisation by the community. RPA perceived to be contaminated. Perception of ERA failing to comply with UN Conventions, for instance, those relating to Traditional Owners/World Heritage areas

Traditional Owners do not return to country. Community dissatisfied with final landform. Inability to obtain final close-out.

Site specific recognised scientific research undertaken against identified knowledge gaps. Alligator Rivers Region Technical Committee (ARRTC) process and KKN developed. Closure Criteria Working Group(CCWG) was re-engaged in 2016 and produced set of draft closure criteria. Nominated resource for stakeholder engagement in place - Chief Advisor. Stakeholder Engagement Plan developed. Trial landform (TLF) established and results transparent to Traditional Owners (TOs). Jabiluka rehabilitation provides precedent. BPT and approvals process. Tiered assessment framework. Closure Plan updates to incorporate stakeholder recommendations. Contingencies for closure included in Closure Plan. Early engagement with stakeholders. Application of BPT process. Communication forums (e.g. ARRTC, Alligator Rivers Region Advisory Committee (ARRAC), MTC, stakeholder workshops). External commitments register. Socio-economic impact assessment. Stakeholder engagement has occurred to understand their needs and the ability to meet these needs. GIS study undertaken to model the potential view lines, which has been approved by stakeholders.

Threat of closure criteria not being agreed prior to works being approved is covered by other risk. For example, possible reinstatement of Djalkmarra Billabong.

This risk is rated as rare likelihood due to the multiple controls, however the scheduling to complete closure within the nominated timeframe is a high risk.




T B 01 02 Actual consolidation of tailings (Pit 1 and Pit 3) does not match consolidation modelling and associated closure schedule leading to longer than planned process water treatment.

Poor management of deposition of tailings causes segregation effects including from 2nd dredge. Poor installation of wick drains. Poor performance of underdrain pump. Delay in backfilling Pit 3. Tailings consolidation outcomes do not match modelling behaviour. Inadequate characterisation of tailings properties. Delays to tailings transfer from the Tailings Storage Facility (TSF).

Process water treatment required beyond closure date to treat process water to achieve 95% consolidation. Landform subsidence causes delays and impacts to the success of revegetation. Differential settlement of final landform. Solute transport different to predicted. Changes to waste rock volumes in Pit, resulting in changes to landform design.

Specialist consultant employed on consolidation modelling. Assurance of consolidation model being completed by stakeholders (2 independent reviews). ERA developing separate consolidation model. Pit 1 actual consolidation rates known and model adjusted to suit; ongoing monitoring. Cone penetration testing (CPT) Testing to inform consolidation model and wick design. Ongoing presentations to stakeholders through Mine Site Technical Committee (MTC) and Ranger Closure Consultative Forum (RCCF). ERA progressing stakeholder actions for subaqueous deposition. MTC correspondence accepting 95% for Pit 1. Placement of the underfill in Pit 3 to reduce the rate of rise of tailings during deposition, maximising potential consolidation and minimised risk of differential settlement of tailings. Pit 3 design is based on the learnings of Pit 1. Prefabricated vertical drains (wicks) installed to maximise consolidation. Placement of bulk backfill will be undertaken to lead to timely completion of consolidation. Adaptive application of bulk backfill based on survey and actual consolidation. Active management post-2026 of landform surface (e.g. minor subsidence). Tailings deposition plan. Ongoing monitoring and modelling of tailings during deposition phase.

This risk is limited to consolidation only - late completion of tailings transfer covered by other risk. Current schedule has water treatment from consolidation on critical path (95% consolidation in May 2025). Base case scope requires BC to finish operating May 2025.

Bulk material movement (BMM) is completed on time. Additional 6-12 months of process water treatment from consolidation or disagreement with stakeholders. Do not invest in another post-BC treatment plant. This is not known until very late in the schedule so that the large scale high density sludge (HDS) contingency is not available.

T B 01 03 No disposal option for high density sludge (HDS) sludge post tailings deposition. (end of 2020)

A portion of HDS cannot be stored in Pit 3 during subaqueous capping, due to quantity or timing of HDS production. Placing HDS in waste rock layers may result in leaching and increased solute transport (assumed).

Potential high cost. Process and disposal off site. Cease HDS operations at end of 2020. Potential downstream environmental impact. Engineered storage solution in waste rock drives additional cost and time (BMM).

Sludge characteristics established. Preliminary approval for HDS plant. Testings of sludge material completed.

HDS cell impacts Pit 3 Backfill, e.g. capping of HDS cell. Assume filter press plant is part of base scope. Evaluation based on constructing a cell outside of Pit 3.




T C 02 02 TSF wall breached during deconstruction works whilst still in use.

Draw down rates within the facility cause instability and slumping of the walls. Wall demolition sequencing causes uncontrolled release of material. Seepage of water occurs through or under wall during water storage; potential for piping erosion leading to failure. Damage to wall rock armouring during tailings removal (dredge/machinery). Excessive erosion on dam walls. Over topping of dam leading to failure.

Significant compliance impact and legal prosecution. Reputation severely impacted. Clean up and remediation costs. Environmental impact. Schedule impact.

Dedicated dam engineer overseeing and approving all plans (Coffey). Independent review of all engineering. Engineering supervision of construction works. Process safety, Closure Construction Management Plans (CCMPs) include TSF failure which references drawdown rates on facility. Interception trenches installed around west wall of the TSF. Compliance and auditing against compliance to RT D5 Standard. Advanced notice through bore monitoring. Process safety controls for dredging. Successful completion of Eastern wall notch. Maintain appropriate maximum operating level (MOL). Technical review complete for use of TSF as a water storage facility. Additional monitoring and instrumentation for drawdown. Downstream raise dam constructed with clay core. Modelling to understand impact.

Major compliance and reputation impact if was to occur.

T C 04 01 Low plant survival rates in the field during establishment and vegetation decline after/at establishment.

Low plant available water in waste rock substrate. Competition from weedy species. Seasonal availability of landform is not optimum for planting. Plant disease or poor health in nursery stock e.g. disease or root:shoot ratio. Lack of nutrient cycling. Lack of local accumulation of litters and fines (sediments). Fauna grazing on tube stock/seedlings. Elevated magnesium sulfate concentrations in groundwater. Inadequate irrigation. Note this risk does not include fire or extreme weather events - these are included in TD.01.10.

Reduction in floristic diversity and density. Delay in revegetation schedule or resources taken from primary planting to support additional infill planting requirements. Revegetation does not support fauna diversity. Unable to meet cultural criteria for a sustainable food and medicinal source. Increased mortality rate from 20% to 40% (60% survival).

TLFs completed to demonstrate viability of vegetation in waste rock. Criteria established with stakeholders on species and seed gathering area. Plant available water modelling predictions indicate sufficient water holding capacity of waste rock to support vegetation. Sub-surface compaction layers increase water holding capacity of waste rock. Construction of landform using various techniques to make sure particle size distribution is to design and paddock dumping to get better compaction. Watering of plants (irrigation) in early stages but not long-term. Ripping of landform. Use of biodegradable pots. Irrigation for first six months post-planting. Compliance with National Standard for Nursery Management.

The Revegetation Management Plan will be updated with experience from Pit 1 in 2020.

Additional 20% of plants die. Sufficient seed and plant stock available to replant so only low schedule impact. Potential for up to $10M additional cost. Revegetation plan will be updated with experience on Pit 1 in 2020 - following this it is anticipated the likelihood will be reduced.




T C 04 02 Insufficient volume or quality of viable seed stock available for whole of site revegetation.

Changes in seasonality - e.g. dryer wet season leads to less flowering and fruiting. Size of areas to be revegetated concurrently, exceed stock capacity. Late seasonal fires impacts seed collection. Predation (birds). Local provenance area may still be too restrictive. Availability of contractor/labour force to meet demand. Limited seed harvesting capacity. Loss of seed (fire, theft, disease, vermin, fungus). Loss of licence to collect seed. Air conditioning fails in seed store. Variable seed viability after collection. Inadequate land access. Inadequate resources for seed collection.

Reduction in floristic diversity and density. Delay in revegetation schedule. Revegetation does not support fauna diversity. Reputation damage. Unable to meet cultural criteria for a sustainable food and medicinal source.

Commenced collection and storage of seed stock. (approximately 7%). Renewed seed collection permit with Kakadu NP. Contractor purchased required equipment. Seed collection metric. Revegetation management plan draft. Agreed species list. Site environment team collecting on lease. MoU with Greening Australia. (support with plant germination and propagation) Nursery expansion including seed storage facility. Backup air conditioning in seed storage room. ERA conducting seed collection on RPA. Schedule of seed requirements complete (including by species). Revegetation Management Plan. 95% of stems for shrubs and trees will be planted via tubestock rather than direct seeding (significantly less seed required).

(Risk ID was D09.02, Subcategory name was D09 Rehabilitation). Kakadu NP eligible for government assistance once contract in place.

One year delay to the completion to the revegetation program to achieve the desired density and floristic diversity.

T C 04 03 Exposed land surface contributes to increased weed recruitment decreasing revegetation success and spread into Kakadu NP.

Unsuitable growth medium to sustain framework species. Weed recruitment from surrounding Kakadu NP. Seedbank in landform medium. Vectors leaving site - e.g. machinery, vehicles, animals, or wind or water-borne.

Additional costs required during post-closure period to manage weeds. Additional time period for post-closure management. Reduction in floristic diversity and density. Reduction in faunal diversity and density. Unable to meet cultural criteria for a sustainable food and medicinal source. Increase in Kakadu NP weed density and species diversity. Introduction of new weed species into Kakadu NP.

Spray final landform surface prior to planting to reduce weed recruitment. Ongoing weed management (including research and trialling). Ongoing liaison with Kakadu NP regarding fire, weed and feral animal management strategies. Material selection for surface cover - e.g. limited laterite at the surface and use of weeds-free material. Weed and seed inspections. Implementation of post-decommissioning access tracks for ongoing weed and fire management.

Opened for MCP, but is well managed.

This threat managed.




T C 06 01 Groundwater solute transport outcomes do not match modelled behaviour breaching closure criteria.

Higher than estimated solute load from interred tailings in Pit 1 and Pit 3. Higher than estimated solute load from brine injection into Pit 3 underfill. Higher than estimated solute load from Pit 1 and Pit 3 backfill methodology. TSF deconstruction plan (leaving contaminated material and plume in situ). Higher than estimated solute load from final land form. Tailings consolidation modelling underestimates pore water expressed. Failure of decant structures to remove expressed pore water. Incorrect assumptions of hydraulic properties. Incorrect hydrolithologic units (HLUs). Incorrect assumptions of source concentrations. Higher than estimated solute load from leaving mill plume and other contaminants in situ. Mineralised material left out of Pit 3. Seepage rates from pit tailings/waste rock are higher than predicted. Active water treatment ceases too early. Volumes of process water and pit tailings flux are not recovered and treated, as predicted.

Downstream environmental impact. Additional scope and cost required to address solute transfer. Ongoing long-term water treatment required. Prosecution due to lack of compliance. Reputation impacts. Impact to cultural heritage sites. Non-compliance with ER 3.1 & 11.3 (ii) (e.g. Kakadu NP values are compromised; Ramsar status is compromised, aquatic biodiversity of Alligator Rivers Region (ARR) is compromised). Water quality closure criteria is not met. Potential toxicity to downstream aquatic biota. Bioaccumulation in bush tucker rendering it unfit for consumption.

Solute transport and balance study ongoing by stakeholder recognised experts (INTERA). Existing solute management experience. Contingency Plan for excessive solute transfer developed (i.e. interception trenches). Peer review of INTERA Study. Monitoring of bores and review and validation of INTERA model. Sensitivity analysis. Update of conceptual model to include all geological knowledge. Calibrating all the bores over 35 years. Updated geochemical model and drilling of stockpiles to improve understanding of source concentration. Baseline groundwater concentrations determined. Landform flood study informs sedimentation controls design.

Low probability due to inherent conservatism in the model. Water quality in Magella Creek causes environmental harm and reputation impact on national level; recovery period one year plus.

T C 08 03 No disposal option for HDS sludge post tailings deposition. (end of 2020).

A portion of HDS cannot be stored in Pit 3 during subaqueous capping, due to quantity or timing of HDS production. Placing HDS in waste rock layers may result in leaching and increased solute transport (assumed).

Potential high cost. Process and disposal off site. Cease HDS operations at end of 2020. Potential downstream environmental impact. Engineered storage solution in waste rock drives additional cost and time (BMM).

Sludge characteristics established. Preliminary approval for HDS plant. Testings of sludge material completed.

HDS cell impacts Pit 3 Backfill, e.g. capping of HDS cell. Assume filter press plant is part of base scope. Evaluation based on constructing a cell outside of Pit 3.

T D 01 01 Cannot achieve the desired tailings surface for post-deposition activities in Pit 3.

Uneven deposition of tailings. Excessive segregation. Uneven consolidation.

Delay in Pit 3 capping works. Difficulty collecting process water expressed from tailings (impacts dewatering). Extended consolidation. Failure of geotextile material (tearing). Eruptions of tailings through capping.

Consolidation modelling. Tailings deposition Plan (draft). Pit 3 capping methodologies. Pit 3 wicking design complete.

Final engineering to be completed. Potential for several additional decant wells. Additional three month schedule delay.




T D 01 02 Large scale fire or natural disaster (e.g. cyclone) destroys immature vegetation.

Wild fires from external sources. Wild fire from ongoing operational management practices. Lightning strikes. Inadequate weed management. Inadequate response capability. Extreme weather event - flood, wind, drought

Reduction in floristic diversity and density. Resprouting from lignotubers post fire, delays the maturation of the final landform revegetation. Increased active management of revegetation. Low representation of fauna taxa. Increased weed densities. Increased erosion due to lower revegetation success across landform. Potential water quality impacts from increased erosion. Large scale damage to new vegetation

Delayed introduction of ground spp. reduces fire risk. Weed control and fire management, including buffer zones (~ 200 m surrounding revegetation). Ongoing active management of revegetation. Introduction of cool burns five to seven years post-planting. Revegetation strategy designed to meet closure criteria for resilience (e.g. species mix, irrigation, weed monitoring etc.). Ongoing liaison with Kakadu NP regarding fire, weed and feral animal management strategies. Waste rock surface has low fire risk for 5-7 years post-planting. Irrigation strategy creates cyclone resistance (encourages deep root development). Fire breaks and access tracks.

TLF informs ongoing landform management strategies.

Evaluation based on meeting rehabilitation requirements in Jan 2026. Cyclone or bushfire event destroys large areas of revegetated zone.

T D 02 03 Closure activities may introduce new health and safety risks to workforce.

Rehabilitation works have tasks that have not been completed before on site introducing new hazards and controls. New contractors on site that do not know the ERA Health, Safety, Environment and Community (HSEC) systems.

Workers injured. Current HSEC Management System. Level 2 risk assessment, JHA, Take 5 for all higher risk tasks. MOC for any changes to systems and/or processes. Engagement of experienced contractors in unknown tasks. Contractor induction process.

Assumed case of fatality, high consequence low probability.

T D 03 02 Large scale fire or natural disaster (e.g. cyclone) destroys immature vegetation.

Wild fires from external sources. Wild fire from ongoing operational management practices. Lightning strikes. Inadequate weed management. Inadequate response capability. Extreme weather event - flood, wind, drought.

Reduction in floristic diversity and density. Resprouting from lignotubers post fire, delays the maturation of the final landform revegetation. Increased active management of revegetation. Low representation of fauna taxa. Increased weed densities. Increased erosion due to lower revegetation success across landform. Potential water quality impacts from increased erosion. Large scale damage to new vegetation.

Delayed introduction of ground spp. reduces fire risk. Weed control and fire management, including buffer zones (~ 200 m surrounding revegetation). Ongoing active management of revegetation. Introduction of cool burns five to seven years post-planting. Revegetation strategy designed to meet closure criteria for resilience (e.g. species mix, irrigation, weed monitoring etc.). Ongoing liaison with Kakadu NP regarding fire, weed and feral animal management strategies. Waste rock surface has low fire risk for 5-7 years post-planting. Irrigation strategy creates cyclone resistance (encourages deep root development). Fire breaks and access tracks.

TLF informs ongoing landform management strategies.

The likelihood is unlikely (due to controls), but with a high consequence rating.




T D 03 06 Tailings or Process water exceeds MOL in Pit 3.

Very high rainfall event. Additional tailings/material transferred from TSF to Pit 3. Additional tailings from mill. Notching of TSF reduces volume that can be stored in TSF.

Overflow of Pit 3. Transport of solutes to Magela Creek through weathered zone. Requirement to store water in TSF stops dredging operations. Modelling completed to demonstrate no impact from high flood event overtopping Pit 3.

MOL proposed to stakeholders based on surrounding head data to ensure Pit 3 remains a sink. Tailings quantities well understood - production data and Fugro survey. Regular bathymetric surveys to determine process water inventory. Ongoing survey of the TSF floor.

Schedule delay on cleaning TSF due to water remaining in TSF. Overtopping pit is 1:1000 yr flood event.

T D 04 01 Damage occurs to cultural heritage site during rehabilitation works.

Vehicle movement in restricted areas. Non-conformance with the land disturbance permit process. Breach to the Cultural Heritage Management System. Not all sites identified. Indirect impact from closure activities e.g. water runoff, erosion, sedimentation, changes to landforms. Not meeting agreed mitigations. Increased dust from closure activities.

Breach of NT Heritage Act and Sacred Sites Act. Reputation impacted. Cost of remediation. Fines. Civil/criminal action. Loss of trust.

Cultural Heritage Management system including general induction and heritage induction. AAPA certificate. Land Disturbance Permit system. Database of cultural heritage sites. Access restricted to sites through signage and / or fencing. Cultural Heritage Management Plan for closure includes mitigation measures, incident process and additional security of sensitive sites.

Breakdown of multiple administrative controls leads to vehicle/equipment damaging site.


10.5 Discussion of class IV risks There was only one class IV risk identified which is described in Section 10.5.1.

10.5.1 Insufficient volume or quality of viable seed stock available for whole of site revegetation

Potential causes for insufficient volume or quality of viable seed stock include seasonality (e.g. dryer wet season leading to less flowering and fruiting), areas to be revegetated exceed stock capacity, late seasonal fires impact seed collection, predation (e.g. birds), local provenance area is restrictive, inadequate availability of contractor/labour force to meet demand, loss of seed (fire, theft, disease, vermin, fungus), loss of licence to collect seed, air conditioning fails in seed store, natural variability in seed viability and inadequate land access. This risk has been assessed as being possible with moderate to high consequences for impacting timing of rehabilitation, and therefore is a class IV risk. Controls to mitigate this risk include:

• seed collection and storage underway, with approximately 7% of required seed stock in storage

• seed collection permit in Kakadu NP has been renewed

• Revegetation Plan developed with agreed species list, contract for collection and schedule of seed requirements complete

• site environment team collecting on lease

• Memorandum of Understanding (MoU) with Greening Australia to provide support with plant germination and propagation

• nursery expansion underway including dedicated air-conditioned seed storage facility, and

• approximately 95% of stems for shrubs and trees will be planted via tubestock rather than direct seeding which will significantly reduce seed requirements.


10.6 Discussion of class III risks

10.6.1 Site condition at 8 January 2026 does not meet stakeholder expectations The status of the Ranger Project Area (RPA) at the legally required date for closure of 8 January 2026 may not meet stakeholder expectations. The likelihood of this risk is rated as rare due to the multiple controls, however there is uncertainty regarding ability to meet closure tasks within the nominated timeframe. Causes of this risk may result from a number of factors centred on the following key themes:

• commitments not embedded within closure scope

• insufficient communication and engagement with relevant stakeholders

• misaligned or inconsistent expectations and standards between ERA and stakeholders

• inadequate rehabilitation performance, and

• inaccurate perceptions of obligations, outcomes and/or RPA condition.

The controls identified during the risk assessment to mitigate this risk include:

• site specific recognised scientific research undertaken against identified knowledge gaps

• Alligator River Regions Technical Committee (ARRTC) process and KKNs were developed

• Closure Criteria Working Group (CCWG) was re-engaged in 2016 and developed a set of closure criteria

• nominated resource for stakeholder engagement in place (Chief Advisor)

• Stakeholder Engagement Plan developed

• Trial landform (TLF) established and results transparent to Traditional Owners

• Jabiluka rehabilitation provides precedent for successful rehabilitation

• application of BPT and approvals process

• tiered assessment framework

• MCP updates to incorporate stakeholder recommendations

• contingencies for closure included in MCP

• early engagement with stakeholders

• ongoing communication forums (e.g. ARRTC, Alligator Rivers Region Advisory Committee (ARRAC), Minesite Technical Committee (MTC), stakeholder workshops)

• external commitments register, and

• socio-economic impact assessment.


10.6.2 Actual consolidation of tailings (Pit 1 and Pit 3) does not match consolidation modelling and associated closure schedule leading to longer than planned process water treatment

The potential consequences of this risk occurring include a delay in the success of the revegetation, a delay in the completion of process water treatment by 2026 or result in a change in the landform design. This risk has been considered unlikely, however, delays may have a high impact on the project schedule and therefore this risk is ranked class III.

Controls to mitigate this risk include:

• specialist consultant employed on consolidation modelling

• assurance of consolidation model being completed by stakeholders along with two independent reviews

• ERA developing separate consolidation model which has been calibrated with Pit 1 actual consolidation rates

• ongoing monitoring and Cone Penetration Testing (CPT) to inform consolidation model and wick design

• ongoing presentations to stakeholders through MTC and Ranger Closure Consultative forum (RCCF)

• ERA progressing stakeholder actions for subaqueous deposition

• MTC correspondence accepting 95% for Pit 1

• placement of the underfill in Pit 3 to reduce the rate of rise of tailings during deposition, maximising potential consolidation and minimising risk of differential settlement of tailings

• Pit 3 design is based on the learnings of Pit 1

• prefabricated vertical drains (wicks) installed to maximise consolidation

• placement of bulk backfill will be undertaken to lead to timely completion of consolidation

• adaptive application of bulk backfill based on survey and actual consolidation

• active management post-2026 of landform surface (e.g. minor subsidence)

• tailings deposition plan, and

• ongoing monitoring and modelling of tailings during deposition phase.


10.6.3 No disposal option for high density sludge post tailings deposition (end of 2020)

The risk of no disposal option for high density sludge (HDS) may be caused by inability to utilise Pit 3 during subaqueous capping due to quantity or timing of HDS production or leaching and increased solute transport preventing storage in waste rock layers. This risk has been assessed as possible with low to moderate consequences. Identified controls to mitigate this risk include:

• sludge characteristics are established

• preliminary approval for HDS plant achieved, and

• sludge material testing has been completed.

10.6.4 TSF wall breached during deconstruction works A breach of the Tailings Storage Facility (TSF) wall during deconstruction works could be triggered by instability due to draw down, direct impact on wall during demolition, excessive erosion of the wall or overtopping. The likelihood of this risk is considered rare, however, the consequences would be high, resulting in a class III characterisation. Identified controls to mitigate this risk include:

• dedicated dam engineer overseeing and approving all plans

• independent review of all engineering

• engineering supervision of construction works

• process safety Closure Construction Management Plans (CCMPs) include TSF failure which references drawdown rates on facility

• interception trenches installed around west wall of the TSF

• compliance and auditing against compliance to RT D5 Standard

• advanced notice through bore monitoring

• process safety controls for dredging

• successful completion of Eastern wall notch

• maintain appropriate maximum operating level (MOL)

• technical review complete for use of TSF as a water storage facility

• additional monitoring and instrumentation for drawdown, and

• downstream raise dam constructed with clay core modelling to understand impact.


10.6.5 Low plant survival rates in the field during establishment and vegetation decline after/at establishment

Low plant survival rates could occur due to low plant available water, weed competition, nutrient deficiency or excess, fauna grazing on tube stock/seedlings, or inadequate irrigation or rainfall. This risk does not consider fire or extreme weather events which are assessed separately (TD.01.10). This risk has been assessed as low likelihood but moderate consequences, which ranks this risk as class III. It is envisaged that learnings from rehabilitation of Pit 1 can be used to update the Revegetation Plan and will likely reduce the risk class. Controls to mitigate this risk include:

• TLFs completed to demonstrate viability of vegetation in waste rock

• criteria established with stakeholders on species and seed gathering area

• plant available water (PAW) modelling predictions indicate sufficient water holding capacity of waste rock to support vegetation

• sub-surface compaction layers increase water holding capacity of waste rock

• construction of landform using various techniques to make sure particle size distribution is to design and paddock dumping to get better compaction

• watering of plants (irrigation) in early stages but not long-term

• ripping of landform

• use of biodegradable pots

• irrigation for first six months post-planting, and

• compliance with National Standard for Nursery Management.

10.6.6 Exposed land surface contributes to increased weed recruitment, decreasing revegetation success and spread into Kakadu NP

Increased weed recruitment from exposed land surface may result from unsuitable growth medium to sustain framework species, weed recruitment from surrounding Kakadu NP and natural seedbank in landform medium, or from vectors entering and/or leaving RPA (e.g. machinery, vehicles, animals, or wind, water-borne). This risk has been assessed as unlikely with potential high consequences, and therefore is a class III risk. Controls to mitigate this risk include:

• spray final landform surface prior to planting to reduce weed recruitment

• ongoing weed management, including research and trials

• ongoing liaison with Kakadu NP regarding fire, weed and feral animal management strategies

• material selection for surface cover (e.g. limited laterite at the surface and use of weeds-free material)


• weed and seed inspections, and

• implementation of post-decommissioning access tracks for ongoing weed and fire management.

10.6.7 Groundwater solute transport outcomes do not match modelled behaviour breaching closure criteria

Groundwater solute transport breaching closure criteria may result from incorrect assumptions or inputs into the model including solute load from Pit 1 and Pit 3 and final landform, hydraulic properties, HLUs and source concentrations. Other possible causes include ineffective tailings deconstruction, ineffective removal of expressed pore water, higher than estimated solute load from leaving mill plume and other contaminants in situ, active water treatment ceases too early, or from volumes of process water and pit tailings flux not being recovered and treated. This risk has been assessed as unlikely with potential high consequences, and therefore is a class III risk. Controls to mitigate this risk include:

• peer reviewed solute transport and balance study ongoing by stakeholder recognised experts (INTERA), including sensitivity analysis

• existing extensive project solute management experience

• baseline groundwater concentrations are known

• landform flood study informing sedimentation controls design

• contingency plan for excessive solute transfer (i.e. interception trenches)

• 35 years of bore monitoring data has been used to review and validate the INTERA model

• updated conceptual model to include all geological knowledge, and

• updated geochemical model and drilling of stockpiles to improve understanding of source concentrations.

10.6.8 Cannot achieve the desired tailings surface for post-deposition activities in Pit 3

The risk of not achieving the desired tailings surface for post-deposition activities in Pit 3 may result from uneven deposition of tailings, excessive segregation or uneven consolidation. This risk has been assessed as being possible with low to moderate consequences and therefore is a class III risk. Controls to mitigate this risk include:

• consolidation modelling

• preparation of draft tailings deposition plan, and

• Pit 3 capping methodologies and wicking design complete.


10.6.9 Large scale fire or natural disaster destroys immature vegetation The risk of a large-scale fire or natural disaster (e.g. cyclone) destroying immature vegetation may result from wild fires caused by external sources or from ongoing operational activities, lighting strikes, inadequate weed management, inadequate response capability, or extreme weather event (flood, wind, drought). This risk has been assessed as possible with low to moderate consequences and therefore is a class III risk. Controls to mitigate this risk include:

• delayed introduction of groundcover species to reduce fire risk

• weed control and fire management including buffer zones of approximately 200 m surrounding revegetation, firebreaks and access tracks

• ongoing active management of revegetation

• introduction of cool burns every five to seven years post-planting

• revegetation strategy designed to meet closure criteria for resilience (e.g. species mix, irrigation, weed monitoring etc.)

• ongoing liaison with Kakadu NP regarding fire, weed and feral animal management strategies

• waste rock surface has an inherent low fire risk for 5-7 years post-planting, and

• irrigation strategy creates cyclone resistance by encouraging deep root development.

10.6.10 Closure activities may introduce new health and safety risks to workforce

The risk of closure activities introducing new health and safety risks to the workforce may be a result of new tasks that have not been undertaken previously or new contractors that are not familiar with the ERA Health, Safety, Environment and Community (HSEC) systems. This risk has been assessed as unlikely with high consequences and therefore is a class III risk. Controls to mitigate this risk include:

• current HSEC Management System, including implementation requirements

• Critical Risk Management (CRM) commenced in 2015 (designed to ensure each work area has clear understanding of what potentially fatal risks are associated with work activities, and ensure there are effective controls in place, and managed)

• Management of Change process for any changes to systems and/or processes

• engagement of experienced contractors in new tasks, and

• contractor induction process.


10.6.11 Tailings or process water exceeds MOL in Pit 3 The risk of tailings or process water exceeding MOL in Pit 3 may result from a very high rainfall event, additional tailings/material transferred from the mill or TSF to Pit 3, or from notching the TSF and reducing volume that can be stored in TSF. This risk has been assessed as rare with low to high consequences and therefore is a class III risk. Controls to mitigate this risk include:

• MOL is based on surrounding head data to ensure Pit 3 remains a sink

• tailings quantities are well understood from production data and Fugro survey

• regular bathymetric surveys to determine process water inventory, and

• ongoing survey of the TSF floor.

10.6.12 Damage occurs to cultural heritage site during rehabilitation works

The risk of damage to a cultural heritage site during rehabilitation works may result from vehicle movement in restricted areas, non-conformance with the land disturbance permit process, breach to the Cultural Heritage Management System, indirect impacts from closure activities (e.g. water runoff, erosion, sedimentation, changes to landforms), increased dust from closure activities, or a new site is identified during rehabilitation and closure. This risk has been assessed as possible with moderate consequences and therefore is a class III risk. Controls to mitigate this risk include:

• Cultural Heritage Management System including general induction and heritage induction

• Aboriginal Areas Protection Authority (AAPA) certificate

• Land Disturbance Permit system

• database of cultural heritage sites

• access restricted to sites through signage and / or fencing, and

• Cultural Heritage Management Plan for closure includes mitigation measures, incident process and additional security of sensitive sites.

Issued date: October 2019 Page 10-28 Unique Reference: PLN007 Revision number: 1.19.0 Documents downloaded or printed are uncontrolled.

10.7 References Bartolo, R, Parker, S, van Dam, R, Bollhöfer, A, Kai-Nielsen, K, Erskine, W, Humphrey, C

& Jones, D. 2013. Conceptual models of stressor pathways for the operational phase of Ranger Uranium Mine. Supervising Scientist, Darwin. January.

Department of Industry, Innovation and Science (DIIS) 2016. Leading Practice handbook: Risk Management. Leading Practice Sustainable Development Program in the Mining Industry produced by the Department of Industry, Innovation and Science, Canberra.

Energy Resources of Australia Ltd 2018. HSEQ Hazard Identification and Risk Management. ERA Standard ER003. Energy Resources of Australia Ltd, 12 July 2018.

APPENDIX 10.1: RANGER CLOSURE RISK ASSESSMENT

CDM.03-0000-MR-REG-00001 - Modified for MCP risks only - August 2019

Risk Description Count

Threat Title IV III II I Risk Status

T AT A 01 Commitments & AgreementsT A 01 01 ERA is not meeting community

expectations for local employment

Number of total jobs available are reduced through closure.

Some jobs require specialised skillsets.

Lack of engagement with local community

Reduced economic and social benefit to

community

FS Closure Implementation Plan identifies packages of work

suitable for local employment.

Requirements defined under mining agreement.

Engagement with local community to identify opportunities

under each work package. Potential for business to be formed

and/or opportunity for existing businesses to grow

For example, as roles become more

specialised there may not be the

opportunities for entry level roles for

local people. Very low local

employment during closure due to

skills gap, unavailability of local

labour, or poor planning.

Unlikely due to intensive

stakeholder consultation

U M II 0 0 1 0 II Open

T A 02 Stakeholder ExpectationsT A 02 01 Site condition at 8 Jan 2026 does not

meet Stakeholder expectations

Previous commitments made are not embedded within

scope.

Insufficient stakeholder engagement.

Insufficient scientific basis to support closure criteria.

Inconsistent expectations from different stakeholders

Misalignment SSB closure standards and ERA closure

criteria.

Assessed closure elements viewed as not meeting "Best

Practicable Technology" (BPT).

Poor environment performance onsite.

Closure studies and the outcomes presented in reports,

undertaken by relevant experts, are complex and difficult to

communicate to stakeholders.

Significant changes to pre-communicated/approved

closure strategy.

The community may be concerned about what

infrastructure is retained or lost as a result of the closure.

Community expectations for the retained infrastructure are

different to that remaining.

Misunderstanding of the Authorisation by the community.

RPA perceived to be contaminated.

Perception of ERA failing to comply with UN Conventions,

for instance, those relating to Traditional Owners/World

Heritage areas

Traditional owners do not return to country.

Community dissatisfied with final landform.

Inability to obtain final close-out.

Site specific recognised scientific research undertaken against

identified knowledge gaps.

ARRTC process and key knowledge needs developed.

Closure Criteria Working Group was re-engaged in 2016 and

produced set of draft closure criteria.

Nominated resource for stakeholder engagement in place -

Chief Advisor.

Stakeholder Engagement Plan developed.

Trial landform established and results transparent to TO's.

Jabiluka rehabilitation provides precedent.

BPT and approvals process.

Tiered assessment framework.

Closure Plan updates to incorporate stakeholder

recommendations

Contingencys for closure included in Closure Plan.

Early engagement with stakeholders.

Application of BPT process.

Communication fora (e.g. ARRTC, ARRAC, MTC, stakeholder

workshops, etc).

External commitments register.

Socio-economic impact assessment.

Stakeholder engagement has occurred to understand their

needs and the ability to meet these needs.

GIS study undertaken to model the potential view lines, which

has been approved by stakeholders.

Threat of closure criteria not being

agreed prior to works being approved

is covered by other risk.For example

possible reinstatement of Djalkmarra

billabong.

This risk is rated as rare

likelihood due to the multiple

existing controls, however the

scheduling to complete closure

within the nominated timeframe

is a high risk.

R H M H III II III 0 2 1 0 III Open

T A 02 02 Airport is unable to be retained and

handed over to stakeholders

Lack of agreement between government and stakeholders

on a future state and funding arrangement for airport.

Increased rehabilitation costs.

Inability to maintain FIFO arrangement to end

of Closure activities.

Involvement in Jabiru Stakeholder Planning Group. Current scope assumes airport is

retained, but not discussed within the

MCP

Agreement likely due to the

essential services provided by

the airport, and the active

pariticipation within the Jabiru

Stakeholder Planning Group.

R L I 0 0 0 1 I Open

T A 03

T A 03 01 Perception amongst local community

of downstream contamination from

Ranger closure impacting ability to

engage in traditional activities.

Includes radiation, contamination.

Poor/lack of communication with stakeholders

Historical incidents and lack of trust

Traditional owners not able to collect bush

foods and/or interact with country for cultural

practices

Damage to relationship with key stakeholders.

Loss of community trust

Water monitoring program. External Relations team is on

mailing list for enviro water monitoring to proactively manage

media.

Relationship committee meeting.

Actions to manage this issue included in the Communities and

Stakeholder Engagement Plan.

There is a low risk that the TO

perceptions do not match that

which has been achieved in

rehabilitation.

L VL VL II II 0 0 2 0 II Open

T A 03 02 Landform does not meet the values

(e.g. land uses) that are expected

from the stakeholders.

Broad definition in the legislation interpreted differently by

authorities.

Insufficient consultation with traditional owners.

Landform may block the view of Mt Brockman.

Traditional owners do not return to the land

and/or end land use unfit for cultural purposes.

ERA will not be released from the legal

responsibilities.

Stakeholder communication strategy and management - e.g.

traditional owners, MTC, ARRAC, ARRTC, technical working

groups, community engagement.

Landform design cultural closure criteria informed by Murray

Garde consultations with Mirarr (2015).

3D printed physical model of final landform used to

demonstrate final landform topography.

GIS study undertaken to model the potential view lines.

Defined in s. 44 approval agreement.

Follow recommendations of post

closure land use report.

This is unlikely due to the

significant consultation with

stakeholder on the landform,

and on expectations.


T A 04

T A 04 01 Closure of Ranger Mine inpacts on

local economics

Removal of subsidies.

Removal of services.

Lack of consultation.

Lack of understanding of timeline of closure.

Lack of understanding of impact on population of Ranger

closure.

No future plan for the region by government.

Businesses become unviable.

Social dislocation.

Loss of leasehold to operate businesses.

SIA (Social impact assessment).

Engagement with stakeholders on future state.

Public updates through Town Hall meetings and local media.

Closure schedule developed.

It is possible that this will occur,

but ERA is working closely with

the community to ensure the

transition is transparent

P L L II II 0 0 2 0 II Open

T A 05 Tenure & LeasesT A 05 01 No mechanism available from 9th Jan

2026 to allow access to RPA for any

further closure activities or monitoring

and management of post closure

activities.

Section 44 agreement does not allow access to RPA

beyond January 2026.

Standard of site closure cannot be maintained

in early years causing legacy issues.

Acknowledgement by stakeholders that certain monitoring and

maintenance activites are required for a number of years post

January 2026.

Initial discussions with DIIS

representatives regarding appropriate

access arrangements have

commenced. Parties have agreed to

progress in more detail following

conclusion of the FS.

Long lead time until 2026 and

good working relationship

therefore unlikely the ability

access will not be available.

U L M I II 0 0 1 1 II Open

T B Engineering / DesignT B 01 Assumptions

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Threat Title IV III II I Risk StatusLe

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T B 01 01 Rainfall is greater than planned in the

Water Model (P50) increasing the

process water inventory to

manage/treat leading to later

completion of process water

treatment than planned.

Rainfall exceeds the P50 as modelled.

Extreme "one off" rainfall event (particularly later in the

closure schedule).

Additional process water treatment increases

schedule beyond closure date - cost +

legal/regulatory & reputational impacts.

Increased cost from additional process water

treatment through the BC.

Increased cost from requirement to implement

process water contingency (large scale HDS).

Delay in rehabilitating the TSF/RP6 due to need

to use for process water storage for longer.

High water inventory in 2020-21 prevents TSF

being cleaned as process water cannot all fit in

Pit 3.

Industry established tool used (water model) with model

assured.

Water Model rainfall assumption based on median 50% trace

over a significant data base (>100 years of data).

Water Model uses significant historical data records from local

monitoring location.

Contingency plan for higher-than-planned rainfall (large scale

HDS plant)

Regular Water Model update.

Additional 6 months of BC operation available over and above

current model (reduces size of HDS plant required).

BC production currently higher than planned in model (Sept

2018).

Scenario of extreme weather event late in the closure

schedule assessed during feasibility study and included in

water management plans.

Process water volume tracked against water model prediction

This risk is related to higher than

planned rainfall only.

The current forecast inventory trace,

with planned process water treatment

and management tactics in place, is

on critical path (i.e. has no float).

Higher than planned rainfall

(P70) early in the project

schedule (prior to 2022-23 wet

season) results in

implementation of HDS

contingency at approx. 2 Ml/d.

Rationale includes effect of

updated BC productivities

(Sept 2018) and additional 6

months of BC operation at end

of schedule.

P L L L II II II 0 0 3 0 II Open

T B 01 02 Actual consolidation of tailings (Pit 1

and Pit 3) does not match

consolidation modelling and

associated closure schedule leading

to longer than planned process water

treatment.

Poor management of deposition of tailings causes

segregation effects including from 2nd dredge.

Poor installation of wick drains.

Poor performance of underdrain pump.

Delay in backfilling Pit 3.

Tailings consolidation outcomes do not match modelling

behaviour

Inadequate characterisation of tailings properties.

Delays to tailings transfer from the tailings dam

Process water treatment required beyond

closure date to treat epressed process water to

achieve 95% consolidation

Landform subsidence causes delays and

impacts to the success of revegetation.

Differential settlement of final landform.

Solute transport different to predicted.

Changes to waste rock volumes in Pit, resulting

in changes to landform design.

Specialist consultant employed on consolidation modelling.

Assurance of consolidation model being completed by

stakeholders (2 independent reviews).

ERA developing separate consolidation model.

Pit 1 actual consolidation rates known and model adjusted to

suit; ongoing monitoring.

CPT Testing to inform consolidation model and wick design.

Ongoing presentations to stakeholders through MTC and

RCCF.

ERA progressing stakeholder actions for sub-aqueous

deposition.

MTC correspondence accepting 95% for Pit 1.

Placement of the underfill in Pit 3 to reduce the rate of rise of

tailings during deposition, maximising potential

consolidationand minimised risk of differential settlement of

tailings.

Pit 3 design is based on the learnings of Pit 1.

Prefabricated vertical drains (wicks) installed to maximise

consolidation.

Placement of bulk backfill will be undertaken to lead to timely

completion of consolidation.

Adaptive application of bulk backfill based on survey and

actual consolidation.

Active management post 2026 of landform surface (e.g. minor

subsidence).

Tailings deposition plan

Ongoing monitoring and modelling of tailings during deposition

phase.

This risk is limited to consolidation

only - late completion of tailings

transfer covered by other risk.

Current schedule has water treatment

from consolidation on critical path

(95% consolidation in May 2025).

Base case scope requires BC to

finish operating May 2025.

BMM is completed on time.

Additional 6-12 months of

process water treatment from

consolidation or disagreement

with stakeholders. Do not

invest in another post-BC

treatment plant.

This is not known until very late

in the schedule so that the

large scale HDS contingency is

not available.

U H M M III II II 0 1 2 0 III Open

T B 01 03 No disposal option for HDS sludge

post tailings deposition. (end of 2020)

A portion of HDS cannot be stored in Pit 3 during

subaqueous capping, due to quantity or timing of HDS

production.

Placing HDS in waste rock layers may result in leaching

and increased solute transport (assumed).

Potential high cost.

Process and disposal off site.

Cease HDS operations at end of 2020.

Potential downstream enviromental impact.

Engineered storage solution in waste rock

drives additional cost and time (BMM).

Sludge characteristics established.

Preliminary approval for HDS plant.

Testings of sludge material completed.

HDS cell impacts Pit 3 Backfill,

e.g. capping of HDS cell.

Assume filter press plant is part

of base scope.

Evaluation based on

constructing a cell outside of

Pit 3.

P M L L III II II 0 1 2 0 III Open

T B 01 04 Assumptions made in the process

water water model are not realised

leading to longer than planned

process water treatment (critical path)

Over-optimistic assumptions used in Water Model - current

basis is an interpretation of measured free process water

inventories vs modelled inventories.

Climatic conditions do not deliver planned evaporation

rates (longer wet season, less wind).

Closure activities & timing do not allow evaporative areas

to be realised.

Future 'active' evaporation tactics do not perform as

planned.

Water Model does not directly duplicate real-world

scenarios.

Water Model assumptions are inaccurate (only includes

assumptions not included in other risks).

Process water treatment rates not achieved

Surface water inflows to process water are greater than

expected (including from additional pond water captured)

Groundwater inflows to process water are greater than

expected

Additional process water treatment increases

schedule beyond closure date.

Delay in rehabilitating the TSF/RP6 due to need

to use for process water storage for longer.

Pan evaporation tests.

Regular monitoring free process water inventory.

Implement water evaporation tactics.

BC evaporator vessel scaling issue understood and

addressed.

BC seed cyclones upgraded.

BC operation has reached a sustained rate of 115% with no

fan upgrade and is operating consistently at a higher rate than

in the current water model.

BC fan upgrade study planned.

Brine squeezer being implementated - schedule in Water

Model.

HDS plant refirbished

Plan for pilot work for membrane process water treatment.

Flowsheet for lime dosing developed; established the

technical viability of lime dosing option - to be incorporated

into future studies work.

Sensitivity analysis on current water model complete.

Annual water model validation

Current evaporation rates based on

2016-17 measurements.

Further validation to be completed by

April 2019.

Lower evaporation rates lead

to a 12 month schedule

extension for process water

treatment.

Requires implementation of

additional HDS contingency to

meet closure schedule (approx.

2 Ml/d).

P L L L II II II 0 0 3 0 II Open

T C 02 Decommissioning

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T C 02 01 Unplanned contaminated materials

found on RPA.

Unknown asbestos materials.

Unknown radioactive material.

Unknown hydro-carbons plume.

Unknown PCBs.

Additional closure scope required to manage

material, may impact achieving 2026 closure

date

Asbestos register available.

Schedule of radiation sources available.

Learnings from previous decommissioning activities (acid

plant).

Disposal for areas of contaminated material available.

Contaminated sites register.

Risk based CLM approach.

Staged implentation.

Asbestos and fibrous materials management plan.

Closure Contaminated sites management plan.

Treatment solution is to

dispose into Pit 3.

P 0 0 0 0 Open

T C 02 02 Tailings Storage Facility wall

breached during deconstruction

works while still in use.

Draw down rates within the facility cause instability and

slumping of the walls.

Wall demolition sequencing causes uncontrolled release of

material.

Seepage of water occurs through or under wall during

water storage; potential for piping erosion leading to

failure.

Damage to wall rock armouring during tailings removal

(dredge/machinery).

Excessive erosion on dam walls.

Over topping of dam leading to failure.

Significant compliance impact and legal

prosecution.

Reputation severely impacted.

Clean up and remediation costs.

Environmental impact.

Schedule impact.

Dedicated dam engineer oversiting and approving all plans

(Coffey).

Independent review of all engineering.

Engineering supervision of construction works.

Process safety CCMP's include TSF failure which references

drawdown rates on facility.

Interception trenches installed around west wall of the TSF.

Compliance and auditing against compliance to RT D5

Standard.

Advanced notice through bore monitoring.

Process safety controls for dredging.

Successful completion of Eastern wall notch.

Maintain appropriate MOL.

Technical review complete for use of TSF as a water storage

facility.

Additional monitoring and instrumentation for drawdown

Downstream raise dam constructed with clay core

Modelling to understand impact

Major compliance and

reputation impact if was to

occur.

R H VH VH VH VH III III III III III 0 5 0 0 III Open

T C 03 Land FormT C 03 01 Excessive erosion impacts landform

stability and revegetation success.

Final landform not matched to rainfall characteristics.

Insufficient sedimentation controls.

Insufficient erosion controls.

Tailings not fully consolidated.

Rainfall is greater than anticipated (eg Climate Change

scenarios)

Revegetation insufficient or ineffective in minimising

erosion

Revegetation requires ongoing management.

Extensive cracking and subsidence occurs over

the landform leading to an increased

maintenance regime.

Stability issues occur along the developing

gullies causing excessive erosion.

Tailings or Low 2 material becomes exposed.

Landform Evolution Model (LEM) model has informed both

landform design, erosion controls and sediment traps.

LEM has climate change scenarios and a synthetic rainfall

data set for 10,000 years.

Controls on Material Movement to ensure built landform

matches design.

Validation of consolidation models.

Final designed landform does not contain slopes > 4%.

Updated consolidated model with Pit 1 validation from

monitoring data and CPT testing. Ongoing updates.

Flood study used to design erosion controls.

Revegetation strategy tailored to landform elements (e.g.

slopes, gullies, etc).

Contour ripping in high erosion areas.

Access tracks will be designed to minimise erosion and/or not

cause erosion.

Ongoing rectification works

during post-closure -

earthworks and reveg.

No impact to closure schedule

as in post-closure

U M L M L II I II I 0 0 2 2 II Open

T C 03 02 Erosion and gully formation across

landform surface exposes contained

tailings.

Rainfall is greater than anticipated (eg Climate Change

scenarios)

Failure of proposed erosion controls.

Erosion rates do not match modelled

Final landform not constructed to design

Non-compliance with ER 2.1, ER 5 and ER

11.3(i).

Potentially increases solute transport on/off

site.

Potentially increases radiation dose to

members of the public.

Limits access by traditional owners to post

decommissioning site.

Iterative/adaptive landform design based on landform stability

modelling.

Establishment of vegetative surfaces to reduce erosion.

Erosion structures are incorporated into landform design - e.g.

ripping and armouring where required.

Ongoing maintenance of erosion structures and mitigation of

gully formation, post decommissioning.

Implementation of a QA program for landform construction

and erosion controls.

Design of Pit backfill has tailings low in the Pit with thick waste

rock cap.

Landform designed with drainage channels diverted away

from in Pit tailings.

A post closure monitoring program for

gully formation will be implemented.

Most predicted erosion occurs within

the first 50 years.

Magela Creek 10 mRL; Pit 3

consolidated tailings -30 mRL.

Rare likelihood due to existing

controls are extensive

R L L M I I II 0 0 1 2 II Open

T C 04 RevegetationT C 04 01 Low plant survival rates in the field

during establishment and vegetation

decline after/at establishment

Low plant available water in waste rock substrate.

Competition from weedy species.

Seasonal availability of landform is not optimum for

planting.

Plant disease or poor health in nursery stock e.g. disease

or root:shoot ratio.

Lack of nutrient cycling.

Lack of local accumulation of litters and fines (sediments).

Fauna grazing on tube stock/seedlings.

Elevated magnesium sulfate concentrations in

groundwater.

Inadequate irrigation.

Note this risk does not include fire or extreme weather

events - these are included in TD.01.10.

Reduction in floristic diversity and density.

Delay in revegetation schedule or resources

taken from primary planting to support

additional infill planting requirements.

Revegetation does not support fauna diversity.

Unable to meet cultural criteria for a sustainable

food and medicinal source.

Increased mortality rate from 20% to 40% (60%

survival).

Trial landforms completed to demonstrate viability of

vegetation in waste rock.

Criteria established with stakeholders on species and seed

gathering area.

Plant available water modeling predictions indicate sufficient

walter holding capacity of wase rock to support vegetation

Sub-surface compaction layers increase water holding

capacity of waste rock

Construction of landform using various techniques to make

sure particle size distribution is to design and paddock

dumping to get better compaction.

Watering of plants (irrigation) in early stages but not long term.

Ripping of landform.

Use of biodegradable pots.

Irrigation for first 6 months post-planting.

Compliance with National Standard for Nursery Management.

The Revegetation Management Plan

will be updated with experience from

Pit 1 in 2020.

Additional 20% of plants die.

Sufficient seed and plant stock

available to replant so only low

schedule impact. Potential for

up to $10m additional cost.

Reveg plan will be udpated

with experience on Pit 1 in

2020 - following this it is

anticipated the likelihood will

be reduced.

L L M M M M III III III III III 0 5 0 0 III Open

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T C 04 02 Insufficient volume or quality of viable

seed stock available for whole of site

revegetation.

Changes in seasonality - e.g. dryer wet season leads to

less flowering and fruiting.

Size of areas to be revegetated concurrently, exceed stock

capacity.

Late seasonal fires impacts seed collection.

Predation (birds).

Local provenance area may still be too restrictive.

Availability of contractor/labour force to meet demand.

Limited seed harvesting capacity.

Loss of seed (fire, theft, disease, vermin, fungus)

Loss of license to collect seed.

Air conditioning fails in seed store.

Variable seed viability after collection.

Inadequate land access.

Inadequate resources for seed collection.


Delay in revegetation schedule.


Reputation damage.



Commenced collection and storage of seed stock. (approx

7%)

Renewed seed collection permit with KNP.

Contractor purchased required equipment.

Seed collection metric.

Revegetation management plan draft.

Agreed species list.

Site environment team collecting on lease.

MOU with Greening Australia. (support with plant germination

and propogation)

Nursery expansion including seed storage facility.

Backup airconditioning in seed storage room.

ERA conducting seed collection on RPA.

MTO and schedule of seed requirements complete (including

by species).

Revegetation Management Plan.

95% of stems for shrubs and trees will be planted via

tubestock rather than direct seeding (significantly less seed

required)

(Risk ID was D09.02, Sub-category

name was D09 Rehabilitation).

KNP eligible for government

assistance once contract in place.

1 year delay to the completion

to the reveg program to

achieve the desired density

and floristic diversity.

P H M M M M IV III III III III 1 4 0 0 IV Open

T C 04 03 Exposed land surface contributes to

increased weed recruitment

decreasing revegetation success and

spread into KNP

Unsuitable growth medium to sustain framework species.

Weed recruitment from surrounding KNP.

Seedbank in landform medium.

Vectors leaving site - e.g. machinery, vehicles, animals, or

wind or water-borne.

Additional costs required during post closure

period to manage weeds.

Additional time period for post closure

management.


Reduction in faunal diversity and density.



Increase in KNP weed density and species

diversity.

Introduction of new weed species into KNP.

Spray final landform surface prior to planting to reduce weed

recruitment.

Ongoing weed management (including research and trialling).

Ongoing liaison with KNP regarding fire, weed and feral

animal management strategies.

Material selection for surface cover - e.g. limited laterite at the

surface and use of weeds-free material.

Weed and seed inspections.

Implementation of post decommissioning access tracks for

ongoing weed and fire management.

Opened for MCP, but is well

managed

This threat managed.

Confirmed with S. Paulka

U H III 0 1 0 0 III Open

T C 05 BiodiversityT C 05 01 Final landform fails to meet

biodiversity "similarity" indices

Insufficient diversity and abundance of flora and fauna to

meet defined trajectories.

Changes in biodiversity survey techniques.

Lack of artificial habitat to encourage fauna.

Non-compliance with ER 2.1.

Requires adjustment to flora species list.

Flora similarity indices currently

based on 20 m x 20 m quadrats. SSB

proposed to change analogue

quadrats to 100 m x 100 m. Also no

current fauna monitoring.

Unlikely due to the KKNs

planned to address any gaps in

understanding prior to

finalisation of rehabilitation


T C 06 Hydrology & HydrogeologyT C 06 01 Groundwater solute transport

outcomes do not match modelled

behaviour breaching closure criteria.

Higher than estimated solute load from interred tailings in

Pit 1 and Pit 3.

Higher than estimated solute load from Brine injection into

Pit 3 underfill.

Higher than estimated solute load from Pit 1 and Pit 3

backfill methodology.

TSF deconstruction plan (leaving contaminated material

and plume in situ).

Higher than estimated solute load from final land form.

Tailings consolidation modelling underestimates pore water

expressed.

Failure of decant structures to remove expressed pore

water.

Incorrect assumptions of hydraulic properties.

Incorrect HLUs.

Incorrect assumptions of source concentrations.

Higher than estimated solute load from leaving Mill plume

and other contaminants in situ.

Mineralised material left out of Pit 3.

Seepage rates from pit tailings/waste rock are higher than

predicted.

Active water treatment ceases too early.

Volumes of process water and pit tailings flux are not

recovered and treated, as predicted.

Downstream environmental impact.

Additional scope and cost required to address

solute transfer.

Ongoing long term water treatment required.

Prosecution due to lack of Compliance.

Reputation impacts.

Impact to cultural heritage sites.

Non-compliance with ER 3.1 & 11.3 (ii)

(e.g. KNP values are compromised; Ramsar

status is compromised, aquatic biodiversity of

ARR is compromised).

Water quality closure criteria isn't met.

Potential toxicity to downstream aquatic biota.

Bioaccumulation in bush tucker rendering it

unfit for consumption.

Solute transport and balance study ongoing by stakeholder

recognised experts (Intera).

Existing solute management experience.

Contingency Plan for excessive solute transfer developed (i.e.

interception trenches).

Peer review of Intera Study.

Monitoring of bores and review and validation of Intera model.

Sensitivity analysis.

Update of cenceptual model to include all geological

knowledge.

Calibrating all the bores over 35 years.

Updated geochemical model and drilling of stockpiles to

improve understanding of source concentration.

Baseline groundwater concetrations determined.

Landform flood study informs sedimentation controls design.

Low probability due to inherent

conservatism in the model.

Water quality in Magella creek

causes environmental harm

and reputation impact on

national level; recovery period

1 year plus.

U M H H H H II III III III III 0 4 1 0 III Open

T C 06 02 Solutes and sediments from surface

runoff from final rehabilitated site

enters off-site water bodies at greater

than closure criteria. (surface water)

Poor quality water shedding from waste rock is released

offsite.

Uncontrolled erosion on the final landform (e.g. gullying).

Water management structures undersized and/or unable to

cope with extreme events.

Poor quality water from legacy contaminated sites

(LAA/contaminated sediments) enters offsite waterbodies

at greater than predicted quantities/qualities.

Exposed ASS releases contaminants to water column.

Sediments and/or solutes entering offsite

environment at greater than closure criteria.

Billabong sedimentation.

Ecosystem damage.

Closure criteria not met; no lease

relinquishment.

Ranger Conceptual Model (RCM) and solute transport

modelling completed.

Landform flood study informs sedimentation controls design.

Historic and ongoing studies into erosion.

TSF solute transfer study completed by Intera.

Characterisation of LAA and billabong sediments (partially

complete).

Post-closure Management Plan.

Need to complete sediment

characterisation studies and ASS

studies and surface water models.

Surface water runoff is a very

low source of contaminants.

Failure of sediment controls in

first 3 years leads to bed load

in creek.

U M M II II 0 0 2 0 II Open

T C 07 Emissions

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T C 07 01 Increased dust from rehabilitation

activities impacts environment

Earth moving operations associated with closure activities. Exceedance of dust level criteria.

Non-compliance/ prosecution.

Impact on adjacent vegetation health

Water trucks.

Exposure limits understood through operations


managed

Dust generation will not

increase above current

operations. Existing

management practices will

suffice to manage threat.

U L L I I 0 0 0 2 I Open

T C 08 Waste DisposalT C 08 01 Disposal location for contaminated

material not available following

backfill of Pit 3.

Pit 3 no longer available for disposal of contaminated

material (water treatment plants, HME, construction

facilities).

Inability to agree upon location with stakeholders.

Water treatment infrastructure is required post backfill of

Pit 3.

Schedule overrun.

Cost overruns.

Potential offsite disposal (higher cost).

Master schedule developed recognising this risk.

RP2 planned for Phase 2 demolition material.

Decontaminate and transport off-site.


managed now RP2 will be used for

disposal

U L VL VL I I I 0 0 0 3 I Open

T C 08 02 Unable to inject brine into underfill. Scaling in pipelines associated with wells causes sufficient

back pressure to prevent well operating (caused by scale

and brine TSS).

All 5 wells may block.

The use of cold process water to flush blocks the pipe from

scale being detached.

Floating Brine injection pipeline is kinked and stops/slows

flow.

Blocking underfill around wellheads.

Failure of underdrain bore or inability to reinstate bore.

Delay in reinstatement of underdrain bore.

Insufficient injection flow rate capacity.

Brine does not fill voice space as planned.

Lack of operating data on brine injection due to underdrain

not operational.

Brine detected in underdrain.

Insufficient brine void space

Brine recycling leads to increased TDS in

process water, causing increased cost of

treatment.

Requirement for additional wells to be drilled.

Significant additional maintenance costs.

Additional cost for replacement underdrain

pumping infrastructure.

Significant capital cost associated with

contingent brine disposal.

Extended water treatment duration (with risk of

additional process water from rainfall).

Ability to directional drill additional steel-cased wells with

postive-displacement pumps.

Assurance Plan with production metrics developed.

Infrastructure built.

Water model model capable of forecasting TDS.

Pigging and flushing.

Have additional pipe on-site to allow faster installation of

replacement.

Full pump replacement held on-site as critical spare.

Data gathering plan for performance of brine injection.

Underfill engineered with a 20% contingency for brine storage

(based on 100% of process water treated via BC).

Underfill volume review of as-built undertaken (Mark Coghill

Nov. 2016) and determined contingency of 20%.

HDS plant incorporated into water model, removes salt from

circuit.

Conductivity meter on the underdrain water flow.

Brine injection rates are a metric

reviewed in ERA CSC on monthly

basis.

Current Scope includes 3 new

bores.

Evaluation based on potential

for additional injection bores.

No impact on water treatment

schedule as brine recirculated.

Additional work for underdrain

is lower risk.

Rationale does not consider

alternative salt disposal.

P L II 0 0 1 0 II Open

T C 08 03 No disposal option for HDS sludge

post tailings deposition. (end of 2020)

A portion of HDS cannot be stored in Pit 3 during

subaqueous capping, due to quantity or timing of HDS

production.

Placing HDS in waste rock layers may result in leaching

and increased solute transport (assumed).

Potential high cost.

Process and disposal off site.

Cease HDS operations at end of 2020.

Potential downstream enviromental impact.

Engineered storage solution in waste rock

drives additional cost and time (BMM).

Sludge characteristics established.

Preliminary approval for HDS plant.

Testings of sludge material completed.

HDS cell impacts Pit 3 Backfill,

e.g. capping of HDS cell.

Assume filter press plant is part

of base scope.

Evaluation based on

constructing a cell outside of

Pit 3.


T C 08 04 Offsite disposal of blackjack is not

possible due to inability of waste

contractor to gain the necessary

approvals.

Contractor cannot demonstrate facility meets

environmental requirements.

Incident at facility causes loss of operating license.

On site disposal option required Contractor has received approvals

Active engagement with contractor

Approvals recived, risk

managed

2nd option from BPT is

implemented - onsite

incineration

P 0 0 0 0 Open

T D ImplementationT D 01 Implementation Planning

T D 01 01 Cannot achieve the desired tailings

surface for post-deposition activities

in Pit 3

Uneven deposition of tailings.

Excessive segregation.

Uneven consolidation.

Delay in Pit 3 capping works.

Difficulty collecting process water expressed

from tailings (impacts dewatering).

Extended consolidation.

Failure of geotextile material (tearing).

Eruptions of tailings through capping.

Consolidation modelling.

Tailings deposition Plan (draft).

Pit 3 capping methodologies.

Pit 3 wicking design complete.

Final engineering to be

completed.

Potential for serveral additional

decant wells.

Additional 3 month schedule

delay.


T D 01 02 Large scale fire or natural disaster

(e.g. cyclone) destroys immature

vegetation.

Wild fires from external sources.

Wild fire from ongoing operational management practices.

Lightning strikes.

Inadequate weed management.

Inadequate response capability.

Extreme weather event - flood, wind, drought


Resprouting from lignotubers post fire, delays

the maturation of the final landform

revegetation.

Increased active management of revegetation.

Low representation of fauna taxa.

Increased weed densities.

Increased erosion due to lower revegetation

success across landform.

Potential water quality impacts from increased

erosion.

Large scale damage to new vegetation

Delayed introduction of ground spp. reduces fire risk.

Weed control and fire management, including buffer zones (~

200 m surrounding revegetation).

Ongoing active management of revegetation.

Introduction of cool burns 5 - 7 years post planting.

Revegetation strategy designed to meet closure criteria for

resilience (e.g. species mix, irrigation, weed monitoring etc.).



Waste rock surface has low fire risk for 5-7 years post-

planting.

Irrigation strategy creates cyclone resistance (encourages

deep root development).

Fire breaks and access tracks.

Trial landform informs ongoing

landform management strategies.

Evaluation based on meeting

rehabilitation requirements in

Jan 2026.

Cyclone or bushfire event

destroys large areas of

revegetated zone.


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T D 01 03 Insufficient volume or quality of trees

from nursery for revegetation.

Higher than expected mortality in the nursery due to

disease, fire, theft.

Under skilled propagators.

Lack of viable seed.

Technical issues in the nursery - e.g. disease, procedures,

equipment failures.

Poor production rates.

Poor nursery implementation planning.

Low plant propogation success

Delay to revegetation.

Unable to get stakeholder acceptance.


Delay in revegetation schedule.


Unable to meet cultural criteria.

20% allowance for infill.

30% allowance for unviable seeds.

Nursery secured.

Management of combustables in nursery area.

Disease control activities in nursery.

Planting and propogation trials successfully completed.

Learnings from Pit 1 will be taken into remaining work - lead

time for additional seeds & seedlings.

Expert propagation knowledge and implementation provided

by existing contractor.

Nursery constructed on site

Alterntive off site nursery(s) available if required

Insufficient volume leads to 6

month delay in revegetation.

Stakeholder acceptance

achieved through continued

active management during post-

closure.

U M L L II I I 0 0 1 2 II Open

T D 01 04 Cannot achieve revegetation planting

production rates

Insufficient rest provisions in schedule.

Dehydration.

Assumed cycle times are optimistic.

No cool rooms available.

Little precedent for proposed process - semi-mechanised,

waste rock.

Cultural requirements for random planting pattern.

Workforce not acclimatised to local conditions.

Commercial payment structure.

Workforce unfit for work - medical conditions, etc.

Unknown medical conditions.

Larger plants from nursery than planned.

Schedule delay.

Additional cost for larger crews/additional

resources to maintain schedule.

H&S incident.

Poor quality planting leading to higher mortality.

Existing H&S processes and procedures. Lower productivity leads to

increased resources to meet

schedule. Increases

revegetation costs by 25%.

L VL II 0 0 1 0 II Open

T D 02 Health & SafetyT D 02 01 Contaminated material leaves site

during closure activities.

Equipment and tooling is not appropriately decontaminated

and taken off site by contractors.

Inadequate checks undertaken.

Poor communications with contractors.

New contractors not familiar with processes.

Not continuing induction processes.

Breach of Licence.

Prosecution.

Impact on community health.

Impact to reputation.

ERA Radiation Management Plan.

RSO's within org structure.

Gated security.

Contractor induction process.

Physical radiation induction checklist.

Random testing by RSO's.

Changes to controlled areas summarised in CIP.

Likelihood is Unlikely,

moderate reputational impact

(limited to NT based on last

incident).

U L M M I II II 0 0 2 1 II Open

T D 02 02 Exposure of people to radioactive

materials during demolition and

decommissioning.

Dust hang-up in Mill.

Calciner residual material.

SX tanks residual material.

Poor decommissioning and cleaning post Mill closure.

Incorrect demolition methodology.

Lack of radiation support.

Removal of density gauges.

Workers exposed have negative health

impacts.

Breaches of Licence conditions.

Reputational impact.

Schedule impact pending investigation.

Established standards of protection from radiation. (e.g

radiation protection system,PPE)

Org structure currently includes RSO roles.

Significant corporate knowledge and experience.(still a control

post 2020?)

Membership of professional networks.

Medicals and monitoring.

Controlled areas.

Inductions and training.

Decommissioing and demolition plan.

Linked to org structure risk

particularly associated with Radiation

support people.

New activities during

decommissioning, only

administrative controls

therefore liklelihood greater

than Rare.

U L M M M L I II II II I 0 0 3 2 II Open

T D 02 03 Closure activities may introduce new

heath and safety risks to workforce

Rehabilitation works have tasks that have not been

completed before on site intorcucing new hazards and

controls.

New contractors on site that do not know our HSEC

systems.

Workers injured Current HSEC Management System.

Level 2 risk assessment, JHA, Take 5 for all higher risk tasks.

MOC for any changes to systems and/or processes.

Engagement of experieneced contractors in unknown tasks.

Contractor induction process

Assumed case of fatality, high

consequence low probability

U H III 0 1 0 0 III

T D 03 EnvironmentT D 03 01 Uncontrolled release of contaminated

material into the onsite environment

during tailings transfer to Pit 3.

Failure or damage is incurred to tailings transfer pipeline.

Poorly managed transport of tailings and contaminated

material post dredging.

Truck deviates from planned course.

Changing environment during closure with respect to

controlled ares.

Inadequate identification of controlled areas.

Release of contaminated material to ground

causes environmental incident.

Onsite water is contaminated.

Non-compliance with Ranger Authorisation and

ERs.

Tailings transfer pipeline design incorporates:

• Bunded pipe corridor.

• Routine inspections & maintenance.

• Process safety management.

• 24/7 visual inspection (e.g. line walkers).

• Quarterly non-destructive (thickness) testing undertaken.

Pipeline actively managed through ERA's process safety

management system.

Existing ERA procedures for contaminated material

management.

Closure implementation plan includes expanded controlled

area for all hazardous materials handling activities.

Spillage is contained, no offsite

environmental impact.

U VL L I I 0 0 0 2 I Open

T D 03 02 Large scale fire or natural disaster

(e.g. cyclone) destroys immature

vegetation.

Wild fires from external sources.

Wild fire from ongoing operational management practices.

Lightning strikes.

Inadequate weed management.

Inadequate response capability.

Extreme weather event - flood, wind, drought


Resprouting from lignotubers post fire, delays

the maturation of the final landform

revegetation.

Increased active management of revegetation.

Low representation of fauna taxa.

Increased weed densities.

Increased erosion due to lower revegetation

success across landform.

Potential water quality impacts from increased

erosion.

Large scale damage to new vegetation

Delayed introduction of ground spp. reduces fire risk.

Weed control and fire management, including buffer zones (~

200 m surrounding revegetation).

Ongoing active management of revegetation.

Introduction of cool burns 5 - 7 years post planting.

Revegetation strategy designed to meet closure criteria for

resilience (e.g. species mix, irrigation, weed monitoring etc.).



Waste rock surface has low fire risk for 5-7 years post-

planting.

Irrigation strategy creates cyclone resistance (encourages

deep root development).

Trial landform informs ongoing

landform management strategies.

The likelihood is unlikely (due

to existing controls), but with a

high consequence rating

U H III 0 1 0 0 III Open

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T D 03 03 Major functional groups of native

fauna do not return to landform.


Fire damage to habitat.

Competition from feral animals and weeds.

Acutely toxic onsite waterbodies.

No appropriate habitat types preventing adequate shelter

food and/or breeding opportunity

Reduced representation in functional groups.



No fertilization some animal pollinated of flora

groups

Lack of sustainabiliy of established ecosystems

Revegetation strategy well defined.

Onsite water quality meets international guidelines for wildlife

drinking water.

Active weed and fire management, including treatments and

monitoring.



Implementation of rocky habitat areas.

Islands of translocated leaf litters and hummus (containing

invertebrates)

Eventual removal of site fence (physical barriers) allowing

egress on to site.

Creation of faunal habitats on the landform, including nesting

Corbett (1999) investigated the

recolonisation of 6 experimental

revegetation sites on the Ranger

mine waste rock dump and found that

most taxa were well represented

within 5 years of revegetation.

Arboreal (e.g. possums) are absent

Evidence of fauna on 7 year old trial

landform supports these data.

Unlikely probability due to the

ability of fauna to egress from

adjacent NP to rehabilitation

sites

U L M I II 0 0 1 1 II Open

T D 03 04 Feral animals occur at higher

densities than in surrounding KNP.

Lack of management.

Open disturbed area.

Weed infestation.

RPA becomes a source of feral animals to

KNP.

Impacts natural recruitment of fauna.

Impacts revegetation success.

Spreads weeds.

Impact to waterways (eg buffalo)

Active feral animal management aligned with current

operational practices.

Ongoing liaison with KNP regarding feral animal management

strategies.

Feral populations in the surrounding

KNP are high.

Unlikely probability that feral

numbers will be higher than

surrounding as will be

managed initially and then

likely to be similar to

surrounding populations as aim

is to achieve similar environs

U M L II I 0 0 1 1 II Open

T D 03 05 Increased aquatic weed

establishment in RPA billabongs

impacts KNP

Transfer from surrounding environment, vehicles, transient

fauna.

Transport of weeds from surrounding KNP.

Decrease in downstream aquatic biodiversity /

habitat leading to Ramsar status and aquatic

biodiversity of ARR being compromised.

Weeds will be managed in accordance with existing

operational management plans and strategies.

Early warning monitoring and subsequent adaptive

management.

No known infestations of aquatic

weeds on RPA - e.g. paragrass,

salvinia.

Would have to be on an excessively

large scale to have an impact on

existing weed diversity and density in

downstream environment.

All downstream (offsite) wetlands

currently weed impacts.

Currently no aquatic weed

infestations on the RPA.

Existing invasion risk in KNP.

Weed management in surrounding

KNP (not in ERA's control).

Paragrass is in the Kakadu NP -

but not upstream from Ranger

Mine

U L I 0 0 0 1 I Open

T D 03 06 Tailings or Process water exceeds

MOL in Pit 3.

Very high rainfall event.

Additional tailings/material transferred from TSF to Pit 3.

Additional tailings from mill.

Notching of TSF reduces volume that can be stored in

TSF.

Overflow of Pit 3.

Transport of solutes to Magela Creek through

weathered zone.

Requirement to store water in TSF stops

dredging operations.

Modelling completed to demonstrate no impact

from high flood event overtopping Pit 3.

MOL proposed to stakeholders based on surrounding head

data to ensure Pit 3 remains a sink.

Tailings quantities well understood - production data and

Fugro survey.

Regular bathymetric surveys to determine process water

inventory.

Ongoing survey of the TSF floor.

Schedule delay on cleaning

TSF due to water remaining in

TSF.

Overtopping pit is 1:1000 yr

flood event.

R M L H H II I III III 0 2 1 1 III Open

T D 04 CommunitiesT D 04 01 Damage occurs to cultural heritage

site during rehabilitation works

Vehicle movement in restricted areas.

Non-conformance with the land disturbance permit

process.

Breach to the cultural heritage management system.

Not all sites identified.

Indirect impact from closure activities e.g. water run-off,

erosion, sedimentation, changes to landforms.

Not meeting agreed mitigations.

Increased dust from closure activities.

Breach of NT Heritage Act and Sacred Sites

Act.

Reputation impacted.

Cost of remediation.

Fines.

Civil/criminal action.

Loss of trust.

Cultural Heritage Management system including general

induction and heritage induction.

AAPA certificate.

Land Disturbance Permit system.

Database of cultural heritage sites.

Access restricted to sites through signage and / or fencing.

Cultural Heritage Management Plan for closure includes

mitigation measures, incident process and additional security

of sensitive sites.

Breakdown of multiple

administrative controls leads to

vehicle/equipment damaging

site.

P M M M III III III 0 3 0 0 III Open

T D 04 02 Bad behaviour/social tension in

Jabiru from contractors/FIFO

workforce engaged during closure.

Large influx of contractor/FIFO workforce.

Pressure on existing local accommodation and other

services.

Contractors/FIFO workers behaving inappropriately.

Local community unrest.

Reputational impact to ERA, negative publicity.

Community incidents.

Community health.

CSP management plan.

ERA Community policy.

Contractor terms and conditions - code of conduct.

General induction.

No take-away alcohol.

Police in Jabiru.

Combination of Jabiru housing and

FIFO camp to be used for

accommodation.

Any issues managed locally. L VL II 0 0 1 0 II Open

T F Post ClosureT F 01 Health & SafetyT F 01 01 Radiation doses from the final

landform exceed dose constraint.

Mineralised material left on surface (gamma, dust and

radon).

Exposed tailings - see risk TD08-01.

Solutes expressed to surface water and mobilised.

Non-compliance with ER 5. Material movement planning and stockpile resource model to

identify location of 1s and 2s rock.

Dust control during decommissioning.

Final landform thickness reduces the likelihood of exposing

tailings and radon emanation from tailings.

Access restrictions to particular areas of the RPA may apply

post closure to keep doses below dose constraint.

Engineering dose constraint of 300 µSv per year will be

applied.

Storm water and erosion control, design and management

structures.

Iterative landform design informed by LEM.

Data from trial landform studies has informed the landform

design and LEM.

Active water management strategy and inventory control.

Air quality assessment completed.

This is possible due to the

material to be used on the FLF.

P L L II II 0 0 2 0 II Open

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T F 01 02 Radiation doses to the public exceed

annual dosage limits.

Mineralised material left on surface (gamma, dust and

radon).

Exposed tailings - see risk TD08-01.

Solutes expressed to surface water and mobilised.

Non-compliance with ER 5.

Increased dose to public.

Material movement planning and stockpile resource model to


Dust control during decommissioning.

Final landform thickness reduces the likelihood of exposing

tailings and radon emanation from tailings.

Access restrictions to particular areas of the RPA may apply

post closure to keep doses below dose constraint.


structures.

Iterative landform design informed by LEM.

Data from trial landform studies has informed the landform

design and LEM.

Active water management strategy and inventory control.

Would require restrictions on

use - these would be

minimised.

U M L M II I II 0 0 2 1 II Open

T F 01 03 Elevated levels of contaminants

(metals) in bush tucker.

Bioaccumulation of contaminants from surface

water/sediments, and/or soils.

Localised areas of higher uptake coinciding with higher

harvesting rates.

Non-compliance with ER 3.1.

Increased uptake of metals.

Minimise contamination of aquatic systems refer to controls in

TA1-01 and TA2-01.

Minimise contamination of pit surface, refer controls in TB2-

02.

Bush food consumption restrictions to particular areas of the

RPA may apply post closure.

Community engagement plan.

Likelihood based on

bioaccumulation potential in

aquatic organisms on

site.Small contribution of bush

tucker from RPA to overall

diet.Communication to address

community concerns.

P VL L I II 0 0 1 1 II Open

T F 01 04 Levels of contamination in offsite

drinking water exceed health

guidelines.

Transport of mine derived contaminants from RPA to

downstream water supplies at significantly higher rates

than models predict.

Non-compliance with ER 3.1. Minimise contamination of aquatic systems refer to controls in

TA1-01 and TA2-01.

Minimise contamination of pit surface, refer controls in TB2-

02.

Bush food consumption restrictions to particular areas of the

RPA may apply post closure.

Community engagement plan.

May already exceed health

guidelines at some

downstream locations from

natural or non-mining sources.

P VL L I II 0 0 1 1 II Open

T F 02 EnvironmentT F 02 01 Rehabilitated Landform fails to

become a self-sustaining ecosystem

Ecosystem processes/functions are not adequately

estabished eg nutrient recycling, recruitment, carbon flow

Ecosystem does not continue on trajectories to

completion criteria.

Ecosystem is more vulnerable to decline due to

events such as fire or weeds or climate change.

Site requires more active management than

KNP

PING to Add Unlikely due to the controls is

place and quantity of scientific

trials to ensure ecosystem

functioning is self-sustaining


T F 02 02 Legacy erosion areas persist post

2026.

Inadequate controls are implemented during the mine's

operational phase.

Ongoing erosion and deposition in downstream

drainage lines.

Implementation of stabilisation works. Monitoring Needs to be actively management

during operations.

Unlikely as legacy erosion

areas will be addressed in

closure activities and

monitoring will determine if

there are erosion issues

requiring remedial earthworks

U M L II I 0 0 1 1 II Open

T F 02 03 Total above baseline radiation dose

to plants and animals exceed

UNSCEAR values.

Dust transported to local soils (terrestrial).

Waste rock on final landform (terrestrial).

Land application area (terrestrial).

Run-off from the landform to creeks (aquatic).

Controlled water releases to creeks (aquatic) during

stabilisation phase.

Groundwater contaminants expressed to surface water

(aquatic).

Increase in radionuclide concentrations in soil

affecting terrestrial biota.

Increase in radionuclide concentrations in water

and/or billabong sediments affecting aquatic

biota.

Active dust suppression during decommissioning phase.

Establishment of vegetation across landform to minimise

erosion and runoff.

Material movement planning and stockpile resource model to



structures.

100 µGy/h terrestrial spp.

400 μGy/h aquatic spp.

Unlikely probability as existing

controls effective


T F 03 CommunitiesT F 03 01 Direct and indirect impact to cultural

heritage sites during monitoring -

especially if signage/demarcation is

decommissioned.

Inappropriate access on lease area by contractors

Remediation works carried out without consideration of

cultural heritage (process not followed)

Breach of NT Heritage Act and Sacred Sites

Act.

Reputation impacted.

Cost of remediation.

Fines.

Civil/criminal action.

Loss of trust.

AAPA certificate

Land disturbance process

The post-rehab monitoring plan will

inform what areas will need to be

accessed throughout the monitoring

phase. This will then inform the

phased decommissioning of

protection measures

Unlikely probability as

management plans effective in

preventing such a risk during

operations, and will continue

during closure works

U M M II II 0 0 2 0 II Open

27End of record

CDM.03-0000-MR-REG-00001

H355334-00000-140-060-0001

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10 Risk assessment and management · • Environmental risk management – Principles and processes...

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