12 closure monitoring - energy res · 2019. 9. 30. · the closure criteria must represent direct,...

12 Closure monitoring

Issued Date: October 2019 Revision #: 1.19.0

Issued date: October 2019 Page 12-ii Unique Reference: PLN007 Revision number: 1.19.0

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TABLE OF CONTENTS1

12 CLOSURE MONITORING ................................................................................................... 12-1

12.1 Closure monitoring program ....................................................................................... 12-1

12.2 Post-closure monitoring program ................................................................................ 12-3

12.3 Maintenance .............................................................................................................. 12-3

12.4 Landform monitoring .................................................................................................. 12-5

12.5 Water and sediment monitoring ................................................................................ 12-11

12.5.1 Surface water and sediments .................................................................... 12-11

12.5.2 Groundwater ............................................................................................. 12-17

12.6 Radiation monitoring ................................................................................................ 12-28

12.6.1 Closure monitoring .................................................................................... 12-28

12.6.2 Post-closure monitoring ............................................................................. 12-28

12.7 Soils monitoring ........................................................................................................ 12-32

12.8 Flora and fauna monitoring ....................................................................................... 12-32

12.8.1 Native flora and fauna monitoring .............................................................. 12-33

12.8.2 Feral animal monitoring ............................................................................. 12-35

12.8.3 Weed monitoring ....................................................................................... 12-35

12.9 Cultural monitoring ................................................................................................... 12-40

12.10 Trigger, action, response plan (TARP) ...................................................................... 12-41

12.11 References............................................................................................................... 12-45

FIGURES

Figure 12-1: Location of RPA statutory (yellow) and operational surface water monitoring sites ....12-15 Figure 12-2: Proposed location of Pit 1 monitoring bores ..............................................................12-20 Figure 12-3: Location of Pit 3 monitoring bores.............................................................................12-24

TABLES

Table 12-1: Examples of maintenance work that may be required during the closure and/or post-closure phases ...............................................................................................................................12-4 Table 12-2: Landform closure monitoring .......................................................................................12-7

1Cover photograph: Surface water monitoring station in Magela Creek

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Table 12-3: Landform post-closure monitoring ..............................................................................12-10 Table 12-4: Parameters and locations for surface water monitoring to assess compliance with closure criteria..........................................................................................................................................12-16 Table 12-5: Generally identified hydrolithological units on the RPA ...............................................12-18 Table 12-6: Parameters for proposed and existing monitoring bores for Pit 1 and Pit 3 closure .....12-21 Table 12-7: General background groundwater chemistry for the RPA ...........................................12-26 Table 12-8: Groundwater closure and post-closure monitoring .....................................................12-27 Table 12-9: Radiation closure and post-closure monitoring ...........................................................12-30 Table 12-10: Flora and fauna closure & post-closure monitoring ...................................................12-36 Table 12-11: Suggested indicators of cultural health of rehabilitated site (Garde 2015) .................12-40 Table 12-12: An example of a bilingual, scalar cultural index score for cultural criteria monitoring .12-41 Table 12-13: Trigger, action, response plan..................................................................................12-42

APPENDICES

Appendix 12.1: Pit 1 Progressive Rehabilitation Monitoring Framework

Appendix 12.2: Plume and Contaminated Site Management Plan

Issued date: October 2019 Page 12-1 Unique Reference: PLN007 Revision number: 1.19.0


12 CLOSURE MONITORING

This section describes the monitoring programs developed for the Ranger Mine to assess performance against the closure criteria (Section 8) and to address the requirements of the Ranger Authorisation. In accordance with clause 13.3 of the Ranger Authorisation: “… the company must carry out a monitoring program approved by the Supervising Authority or the Minister with the advice of the Supervising Scientist following cessation of operations until such time as a relevant close-out certificate is issued”.

The closure criteria must represent direct, measurable and quantifiable target values or tiered assessment processes, based on industry best practice frameworks to develop suitable monitoring programs. The closure criteria have been developed to demonstrate achievement of the closure objectives (Section 6.2) and desirable outcomes (Section 8). The monitoring programs discussed within this section apply to the closure and post-closure phases as defined in Section 1.3. The monitoring programs discussed below align with the six closure themes described in Section 8.8:

• landform

• radiation

• water and sediment

• soil

• flora and fauna, and

• cultural.

Within each closure theme is a description of the proposed monitoring as it will occur during the closure and post-closure phases. The proposed closure monitoring programs build on the existing, extensive monitoring regimes established during mining operations at the Ranger Mine. The closure monitoring program is required to assess rehabilitation success, including determination of the protection of potentially impacted ecosystems and environmental values.

Both the monitoring programs and closure criteria are subject to review as the outcomes of studies and/or new information become available and stakeholder feedback is considered. As such, some aspects of post-closure monitoring require finalisation of the closure criteria to develop further. This is an adaptive management process designed to remove uncertainty and meet the closure objectives. Where necessary, amendments will be incorporated into future iterations of the Mine Closure Plan (MCP).

12.1 Closure monitoring program

Monitoring to evaluate performance against closure criteria will begin during the progressive rehabilitation activities during operations and continue into closure. The closure monitoring program will enable an adaptive management approach to site rehabilitation to inform performance strategy. The monitoring program will provide ongoing feedback of the site rehabilitation performance and indicate improvement for implementation before applying to the broader scale rehabilitation.

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Operational monitoring programs will provide input into the closure monitoring programs, as required. Technical working groups and programs that have taken place over recent years (e.g. the Independent Surface Water Working Group) have informed the development of the monitoring programs outlined in this section. The Monitoring Evaluation and Research Review Group provides oversight of ongoing development and refinement of monitoring and research programs during the closure period, ensuring adequate data is being collected as required for validation of various models and collaboratively improving confidence that the proposed Ranger Mine closure progressive rehabilitation will achieve the environmental requirements (ERs). This helps ensure the proposed monitoring for the closure phase also meets the endorsed Key Knowledge Needs (KKNs).

Monitoring programs associated with closure studies will also continue throughout the operation and closure phases. The research related monitoring programs are captured within the summary of each research project in Section 7.

In recognition of the interrelationship between closure related studies undertaken by both Energy Resources of Australia Ltd (ERA) and Supervising Scientist Branch (SSB), the Monitoring Evaluation and Research Review Group was established in 2019. The group, represented by members of ERA and SSB, as well as subject matter experts as required, is tasked with the ongoing development and refinement of monitoring and research programs during the progressive rehabilitation period. Outstanding closure monitoring programs, and further studies related monitoring, will be developed in collaboration with and/or reviewed by this group.

A Ranger Mine Rehabilitation Monitoring Workshop was held on 4 September 2018 to ‘agree on high-level monitoring, to avoid missing information that is needed to inform the progressive rehabilitation process’ (SSB 2018). Progressive rehabilitation is ongoing from present operations through to 2026 and encompasses the following monitoring themes:

• landform

• water (groundwater and surface water)

• radiation, and

• ecosystem rehabilitation.

An overarching Pit 1 Progressive Rehabilitation Monitoring Framework (Appendix 12-1) and subsequent management plan will be developed and refined during the rehabilitation of Pit 1, commencing in late 2019. Success of the Pit 1 rehabilitation will be driven by adaptive management, research and monitoring to establish the overarching framework for ongoing rehabilitation across the Ranger Mine. A number of stakeholders, including the SSB and Alligator Rivers Region Technical Committee (ARRTC), have provided recommendations towards the Pit 1 monitoring objectives and requirements.


The Pit 1 Rehabilitation Monitoring Framework will extend from May 2019 to 2026 to address the full scope of monitoring for Pit 1 rehabilitation works through to post-closure. A broad range of monitoring scopes, as detailed within the Ranger Authority, are applicable during the construction of Pit 1 landform. In particular, the construction and ecosystem establishment aspects will be monitored to evaluate landform performance.

12.2 Post-closure monitoring program

The post-closure monitoring program is initiated following the successful completion of decommissioning and rehabilitation. This monitoring phase will occur after January 2026 where the site is progressing towards the development of a long-term stable landform and self-sustaining ecosystem that meets the closure objectives. The adaptive management approach implemented during the transitional monitoring phase (from operations to closure to post-closure) will continue, whereby the monitoring program will provide ongoing feedback of the site rehabilitation performance, identify any issues and inform maintenance activities. However, under the current legislative framework, (Ranger Authorisation under the Atomic Energy Act 1953 - section 41c (5) of the Authority (Nov 1999) (Section 3.1.2) the access of ERA to the Ranger Project Area (RPA) ceases on 8 January 2026. Discussions are currently underway with key stakeholders to enable ongoing access to the RPA after this date, to undertake monitoring and, if required, minor remedial or maintenance works.

12.3 Maintenance

The post-closure monitoring program commences in 2026 and will continue until results of the monitoring demonstrate that the site has met the required closure objectives and relinquishment of the RPA is achieved. As the length of this time is unknown, ERA have currently assumed 25 years of monitoring.

During this phase, the landform may settle over time, and there is the potential for subsidence and/or erosion to occur. Revegetation should progress towards a self-sustaining ecosystem. Potential remedial management practices in this phase are described in Table 12-1.

Monitoring the rehabilitation progress of site access tracks and service corridors will be assessed by aerial photography, as it will not be practical to undertake traditional monitoring in the field once tracks are removed. Remedial action will be undertaken where necessary.


Table 12-1: Examples of maintenance work that may be required during the closure and/or post-closure phases

Action Description

Minor earthworks

• Will be undertaken to repair any ongoing erosion or other stability issues, identified by landform monitoring.

• May include localised maintenance of passive water management structures or sediment basins.

Infill planting

• Highest rates of plant mortality will most likely occur soon after initial planting and routine monitoring will allow for timely remediation through infill planting (timed to occur with annual wet seasons). Infill planting will be undertaken where high mortality of ‘initial’ tubestock is observed in the first 6-24 months.

• ‘Secondary’ introductions of additional species will occur once suitable conditions develop.

• May also be required when an unplanned large-scale event such as a fire or cyclone causes significant additional mortality.

Weed control

• Weeds may out-compete and smother tubestock, or may increase the risk of fire, and thus increase mortality.

• ERA will monitor and maintain a weed control buffer zone around the rehabilitated site. Targeted weed monitoring, and also the routine revegetation monitoring will record if any weed infestations occur on the rehabilitation.

• Weed control methods will be situation and species-specific, with the most effective controls determined from ERA experience and input from specialists. Weeds are likely to be controlled by a combination of chemical and physical methods (including application of residual or short acting chemicals, seed head cutting and burning, or fuel-load reduction by fire).

Fire management

• Fire is a part of the current land management of Kakadu NP but is a risk to the initial development of rehabilitation; and therefore, needs to be controlled.

• In an effort to avoid fire in revegetated areas, only low-biomass native grasses and herbs will be introduced, along with trees and shrubs, at initial establishment. Fire will be excluded for the first 5-8 years until revegetated species have established a level of resilience (defined in the Ranger Mine Revegetation Strategy, Appendix 11-4) and after which low intensity ‘cool burns’ will be promoted in the wet and early dry seasons.

Application of fertiliser

• Some of the growth media to be used in rehabilitation may be deficient in nutrients. To improve optimum growing conditions, tubestock will be planted with fertiliser pellets and, approximately 6-12 months later, a second application of fertiliser will be applied.

• Plant health and development will be the primary indicator of soil and plant nutrition, however five-yearly soil monitoring will assist with interpretation, and amelioration, of any determined nutrient deficiency, if required (e.g. addition of further fertiliser inputs).


Action Description

Pest control

• High levels of insect damage can cause plant mortality; young plants may also be impacted by native and feral vertebrate fauna (e.g. wallabies or pigs).

• Routine vegetation monitoring will identify impacts from the range of potential pest species.

• Management of pests may involve spraying with insecticides, temporary fencing, or direct management of feral vertebrate fauna (carried out in accordance with the ERA Fauna Management Plan and in accordance with relevant licences).

Water management

• Passive water and sediment management ponds may require maintenance.

• Structures may also need to be decommissioned when no longer required

12.4 Landform monitoring

A number of landform studies have been undertaken to address key closure issues and risks to inform the design parameters of the final landform. In particular, the construction of the trial landform in 2009 and subsequent studies used to validate design attributes such as landform stability, erosion, topography and visual amenity; and inform the current landform model predictions (Sections 7.5). The outcomes of these studies have resulted in a final landform topography that incorporates low elevation and slopes to enhance landform stability and visual aesthetics to blend with the surrounding landscape. The focus of landform the monitoring and maintenance program is erosion control.

Landform monitoring occurs during progressive rehabilitation and throughout closure to assess the condition of the landform. Specific landform parameters are monitored during and after construction to assess stability and suitability for revegetation. The primary objective of monitoring during construction is to assess adherence to the planned landform design; including material transfer and placement. Following construction, parameters such as settlement and subsidence performance; surface topography; surface ripping; erosion and erosion controls; bedload and sediment control; and suspended sediment will be monitored. Further detail on these parameters are included in the Table 12-2.

The design of the landform including erosion and drainage control will minimise the development of gully erosion. Sediment basins and drainage channels will be inspected post wet season to confirm operation according to design. Inspections will assess the absence or presence of unplanned gully erosion and channels and inform subsequent maintenance, if required, as well as validate modelling outputs. The Supervising Scientist has indicated that whilst it is expected that gullies will form on the landform within the modelled 10,000 years, the tailings will be below the natural landscape and are therefore not expected to be exposed (Supervising Scientist 2017). It is expected that the need for maintenance should progressively decrease as the landform stabilises and dynamic equilibrium is reached. When drainage channels are considered to have reached or trending towards functional dynamic equilibrium,


the outcome criterion will be achieved. At functional dynamic equilibrium there will be no unplanned gully erosion and the landform will be comparable to the surrounding landscape.

An important parameter for assessment of site-wide erosion is event load suspended sediment, tracked on a whole of wet season basis. Suspended sediment loads from the landform are expected to reduce over time, trending towards background suspended sediment loads. The Supervising Scientist has demonstrated turbidity can be used as an indicator for suspended sediment (Moliere & Evans 2010). Turbidity monitoring up and down stream of the RPA will be applied as a measure of suspended sediment loads leaving the landform and entering Magela Creek or Gulungul Creek. Sediment loads are expected to decrease over time and achievement of the outcome criterion will be based on trending towards background loads. Post-wet season inspections for bedload in Magela Creek and Gulungul Creek will also be conducted to assess erosion and inform maintenance.

Subsidence or slumping, deformation and/or settlement will be assessed via monitoring of geotechnical conditions to track progress towards the closure objectives and be addressed with maintenance, if necessary. Settlement plates (54 are proposed) will be installed ahead of the secondary capping layer and measure consolidation to 300 mm settlement, with corrections for the capping layers. Use of Satellite based synthetic Aperture Radar (SAR) for monitoring settlement. Tailings will be monitored for excess pore water pressures via vibrating piezometers.

Monitoring to measure progress towards landform closure criteria will also include final landform topography after completion. It is expected that either airborne and/or terrestrial LiDAR (or equivalent) technology will be used to survey and capture the final landform topography. If the final landform varies significantly from the design, the topography will be used to rerun the 10,000 year landscape evolution model. Specific details on which LiDAR techniques will be utilised have yet to be determined; and new information will be incorporated into future iterations of the MCP.

Landform monitoring for closure is presented in Table 12-2 and post-closure monitoring in Table 12-3.


Table 12-2: Landform closure monitoring

Aspect Methodology Analysis Location Frequency Duration Closure Criteria (Table 8-1)

Material placement*

Material characteristics and volume.

Dynamic mine model with associated tracking methods. Within landform levels during construction.

Whole of final landform via tracking system.

Ongoing Until landform is built.

Pit 1 Progressive Rehabilitation Monitoring Framework (Table 4*)

Subsidence or slumping, deformation and/or settlement

Geotechnical monitoring (As described in Section 12.4)

Identify any subsidence or deformation of landform areas

TSF, pits and landfill walls

Quarterly Until final landform is stable and has met final criteria.

Closure criteria L1

Surface topography*

Topography survey

Comparison of DEM and survey to planned landform.

Whole of final landform.

Once. When practical upon completion of final landform.

Not applicable.

Closure criteria L1

Quantify landform settlement

Year on year DEM change and topographic survey.


Annual Until final landform is stable and has met final criteria.

Closure criteria L1/L4

Surface micro-topography*

Micro-topography survey

Comparison of DEM and survey to planned landform.


Annual Until final landform is stable and has met final criteria.


High resolution DEM and field survey


After land forming and annual after wet season.

Until final landform is stable and has met final criteria.


Surface ripping*

Map ripped areas

Mapping via GPS tracking, field survey or remote sensing.

Planned ripped areas.

Once, after landform creation.

Not applicable.

Closure criteria L4



Erosion (encapsulated tailings)*

Capture digital elevation model (DEM) of the final constructed landform using either airborne and/or terrestrial LiDAR (or equivalent) technology.

Describe the final landform against planned landform. Assess LEM results for critical erosion over tailings areas. Potentially provide updated information to rerun the 10,000 year landscape evolution model (LEM) and confirm LEM predictions for tailings encapsulation.

All disturbed areas.

Once. When practical upon completion of final landform (closure phase).

Not applicable.


Erosion (local scale post-wet season)

Field inspection* of erosion and sedimentation, notes, photographs DEM analysis

Identify significant erosion – rill erosion > 30 cm depth, sheet erosion or prevention of revegetation (>0.1 ha) Identify erosion around drainage channels.

Erosion of drainage channels Sedimentation of sensitive receptors

Annually after wet season

Until final landform is stable and has met final criteria L2 and L3

Closure criteria L2 and L3

Erosion Control Structures*

Confirm erosion control structure function through field inspection.

Ensure erosion structures function effectively.

All erosion control structures.

Annually post-wet season.

Until final landform is stable and has met final criteria L3.

Closure criteria L3

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Bedload (Access Roads and Creeks)

Field inspection* of erosion, notes, photographs

Identify any erosion on roads that may be source of bedload moving offsite.

Access roads Magela and Gulungul creeks

Biannually and after each significant rain event


Closure criteria L5

Bedload (sediment traps)*

Quantify sub-catchment bedload sediment movement.

Measurement from sediment traps.

All sediment traps.

Annually post-wet season.


Closure criteria L5

Suspended Sediment

Assessment of turbidity (fine suspended sediment)

BACIP analysis (Moliere & Evans 2010) after end wet season Inform assessment of site denudation rates. Turbidity trajectory transitioning to control environment levels after 5 years.

Monitoring points upstream and downstream of site (Magela and Gulungul creeks).

Continuous turbidity monitoring during wet season.

Until suspended sediment loads are approaching background values.

Closure criteria L6

*Adapted from Pit 1 Progressive Rehabilitation Monitoring Framework (Appendix 12-1)


Table 12-3: Landform post-closure monitoring


Erosion (local scale post-wet season)

Field inspection* of erosion and sedimentation, notes, photographs

Identify significant erosion – rill erosion > 40 cm depth, sheet erosion or prevention of revegetation (>0.1 ha) Identify erosion around drainage channels.

Erosion of drainage channels Sedimentation of sensitive receptors



Closure criteria L3

Erosion (general)


General inspection for localised scouring and damage.

All disturbed areas

Biannually 2026-2031**

Closure criteria L3

Annually 2031-2051**

Closure criteria L3

Bedload (Access Roads and Creeks)


Identify any erosion on roads that may be source of bedload moving offsite.

Access roads Magela and Gulungul creeks

Biannually and after each significant rain event


Closure criteria L5

Bedload (Sediment Basins)

Field inspection* of sediment control basins, notes, photographs

Sediment volumes in sediment control basins. Structural integrity of sediment control basins.

All sediment control basins

Quarterly 2026-2029**

Closure criteria L5

Biannually 2030-2051**

Closure criteria L5



Suspended Sediment

Assessment of turbidity (fine suspended sediment)

BACIP analysis (Moliere and Evans 2010) after end wet season Inform assessment of site denudation rates Turbidity trajectory transitioning to control environment levels after 5 years.

Monitoring points upstream and downstream of site (Magela and Gulungul creeks)

Continuous turbidity monitoring during wet season

Until suspended sediment loads are approaching background values

Closure criteria L6

*Erosion field study methodology to be developed prior to closure and being trialled as part of the Pit 1 Rehabilitation Monitoring Strategy.

12.5 Water and sediment monitoring

12.5.1 Surface water and sediments

Closure monitoring

Surface water monitoring is currently undertaken at a number of sites within and outside the RPA by ERA, SSB and the Northern Territory Department of Primary Industry and Resources (DPIR). The ERA surface water monitoring program is reviewed and updated annually in the Ranger Mine Water Management Plan (RWMP). The RWMP is subject to a stakeholder review and approval process each year. The program includes monitoring for both compliance and operational purposes, i.e. active water management information.

The surface water compliance monitoring program and interpretation and reporting framework is very mature (Turner et al. 2015). The compliance monitoring program consists of continuous monitoring of electrical conductivity (EC) and turbidity, weekly grab samples for a range of key variables and event-based sampling upstream and mid/downstream of the mine on Magela Creek and Gulungul Creek. In line with recommendations from the Independent Surface Water Working Group (Hart & Taylor 2013) and the SSB (Turner et al. 2015) ERA is planning to transition to an event triggered auto-sampling regime and phase out weekly grab sampling.


Water quality results are compared to a three-tier system of management and compliance trigger values, this approach aligns with the National Water Quality Management Framework. The upper tier Limit, which represents the water quality objective for high level ecosystem protection, is the compliance value. The framework also includes Focus, Action and Guideline values which prompt management and reporting actions. These lower tier management trigger values also provide criteria to assess the acceptability of, or suitable conditions for, planned active discharges of water from the Ranger Mine site to Magela Creek.

Once the mine enters the post-closure phase discharges of water from the rehabilitated site will be passive so the three-tiered approach with discharge management responses will not be the most appropriate regime to implement. To assess site contribution to nutrient loading within creeks, water flow volumes will be measured at upstream and downstream sites at GCC, Gulungul Creek lease boundary (GCLB), upstream Magela Creek solute load site (MCUS) and Magela Creek water quality compliance point (MG009).

Post-closure monitoring

Monitoring in the post-closure period is required to assess rehabilitation success including identifying any unexpected events or Constituents of Potential Concern (COPC) concentrations (compared to model predicted results), and assessing the protection of ecosystems, human health and environmental values by comparison of water quality against closure criteria (when agreed).

Groundwater solute transport modelling has predicted long time lags between closure of the mine and delivery of peak solute loads to the creek system. The delivery time frames are dependent on the source of the contaminant, and transport pathway (Section 7.7.1).

Timeframes for the peak loads from the different source terms (INTERA 2016) are:

• waste rock runoff – < 20 years

• waste rock seepage – ~ 270 years

• tailings and brines – ~10,000 years

• expressed process water (pit tailings flux) from Pit 1, removed and treated currently and throughout closure phase (i.e. prior to 2026).

The surface water model (Section 7.8) will predict concentrations of COPCs the creeks and billabongs will be exposed to as a result of these loads. Accumulation of COPCs in sediments will be calculated based on predicted water quality results. Risks to water quality also include those in the immediate post-rehabilitation time frame when the landform is stabilising and most prone to erosion and poor-quality runoff from freshly worked waste rock surfaces (Section 10). Predicted concentrations of COPCs delivered to the creek from these events are also included in the surface water model.


This time lag and its relevance to monitoring and assessing if closure criteria will be met is recognised in the SSB rehabilitation standard series2 which states:

Given the potentially long timeframe between the completion of rehabilitation and the peak delivery of contaminants to surface water, this Rehabilitation Standard will most likely be used to assess predicted magnesium3 concentrations from modelled scenarios. Ongoing surface water and groundwater monitoring will be required after rehabilitation to continue to ensure the environment is being protected, and to validate and assess confidence in the models.

Thus, the aims of the post-closure surface water monitoring program can be described as:

• assess whether closure criteria are met, or if water quality is transitioning toward meeting criteria

• provide assurance that the environment is being protected, and

• validate and assess confidence in, the solute transport predictive models.

The proposed post-closure monitoring program, summarised in Table 12-3, provides a basis of determining if the environment and human health continues to be protected in the post-closure phase, and if the surface water model predictions for that phase are being met.

Water quality parameters and draft guideline values have been proposed for each of the objectives of the surface water and sediment closure theme (Section 7.4, particularly Section 7.4.3). Review and acceptance or refinement of these for water quality criteria will be considered by a stakeholder water quality working group. The draft monitoring program to assess if the criteria are being met in the post-closure period will be reviewed by the same group following agreement on criteria and indicators.

The locations and monitoring frequencies for current surface water monitoring forms the basis of the proposed initial post-closure monitoring strategy (Table 12-4). Sub-catchment monitoring exit points have been included as part of surface water monitoring during Pit 1 rehabilitation. Consideration of onsite and sub-catchment exit points will be discussed in future planning meetings with SSB, with new information included within updates to the MCP. The rationale for monitoring at these locations (Figure 12-1) are:

• current compliance points MG009 and GCLB, just inside the boundary of the RPA: comparison of water quality at the current compliance points in Magela and Gulungul creeks against agreed water quality objectives will continue to provide the basis of assessing protection of the aquatic environment, human health and recreational values in creeks and billabongs downstream of the RPA

2 http://www.environment.gov.au/science/supervising-scientist/publications/ss-rehabilitation-standards 3 The same statement is made in the rehabilitation standard for each COPC

http://www.environment.gov.au/science/supervising-scientist/publications/ss-rehabilitation-standards


• upstream and downstream on Magela and Gulungul creeks: continuous turbidity during the wet season to enable suspended sediment comparison with natural distribution (suspended sediment landform criteria and aesthetic values of clarity)

• onsite billabongs: comparison of water quality and sedimentation in Coonjimba and Georgetown billabongs with criteria accepted as representing impacts that are as low as reasonably achievable (ALARA), to demonstrate acceptable levels of protection for ecosystems on the RPA

• offsite billabong: comparison of sedimentation levels in Gulungul Billabong with criteria (TBC), and

• comparison of results against model predictions for all above sites for validation purposes.

As discussed above, ERA is planning to shift to event-based monitoring in the near future, with sample collection triggered by changes in continuous EC data. A similar approach could be suitable for the post-closure monitoring program and will be considered by the stakeholder working group based on the success of the program to be implemented during operations and closure phase.

The proposed initial monitoring program will evolve based on changes in methods and technology (some currently planned), feedback by the stakeholder working group and if results collected in the initial years of the post-closure monitoring period demonstrate a reduction in risk. Feedback from SSB regarding the Pit 1 Progressive Rehabilitation Monitoring Framework will be addressed in the next iteration of the MCP. All discussions and improvements to this framework will likely be adapted into the broader site-wide closure monitoring programs as planning progresses. It is anticipated that the post-closure monitoring program could be carried out by a local service provider.

The results from the surface water monitoring program and any triggered investigations and actions will be provided to stakeholders (as available) with an interpretive report of all results at the end of each wet season. The trigger value system used during the operational phase can be adapted to provide agreed EC and turbidity thresholds to trigger investigation and reporting and the possible need for maintenance. This will be considered by the stakeholder working group.


Figure 12-1: Location of RPA statutory (yellow) and operational surface water monitoring sites

The proposed surface water monitoring program details are summarised in Table 12-4 and is applicable to both the closure and post-closure phases. Monitoring during the closure phase will identify the potential opportunity to decrease the monitoring scope during post-closure.


Table 12-4: Parameters and locations for surface water monitoring to assess compliance with closure criteria

Location Parameter Closure criteria Frequency

MG009, GCLB, MCUS*, GCC*

Turbidity W2, W3, L11 Continuous

EC W3

Mn, U, SO4 W1, W2, W3, W5

Monthly grab sampling during the wet season with frequency reduced over time based on performance and risk review.

Al, Cu, Cd, Cr, Fe, Pb, V, Zn, Mg, Ca, Mg:Ca, NH3-N

W3

Nitrogen-N, PO4-P loads W3

NO3, NO2 W1, W2

Visual clarity and surface films W2, C7

Observations at each grab sampling collection. Also undertaken as part of cultural criteria monitoring.

Gulungul Billabong

Sediment concentrations S, U, Sb, Cd, Cr, Cu, Pb, Hg, Ni, Ag, Zn, As

W4

Accumulation in sediments limited by U in water criteria. Sediment sampling to demonstrate current4 compliance via scheduled projects in closure phase.

Sedimentation W3

Event-based triggered by results of landform monitoring. TBC in consultation with Landform criteria and Water quality stakeholder groups.

Coonjimba and Gulungul Billabongs

Turbidity W2, W5 Continuous

EC W5

Al, Cu, Cd, Cr, Fe, Pb, V, Zn, Mg, Ca, Mg:Ca, NH3-N

W5

Monthly grab sampling during the wet season with frequency reduced over time based on performance and risk review.

NO3, NO2 W1, W2

Monthly (if recreational and drinking water identified as community value for these sites).

4 Long-term compliance demonstrated by calculating accumulation based on predicted water quality results and water-sediment distribution coefficients.


Location Parameter Closure criteria Frequency

Visual clarity and surface films W2, C7

Observations at each grab sampling collection. Also undertaken as part of cultural criteria monitoring.

Sediment concentrations S, U, Sb, Cd, Cr, Cu, Pb, Hg, Ni, Ag, Zn, As (W4, W5)

W5

Accumulation in sediments limited by U in water criteria. Sediment sampling to demonstrate current5 compliance via scheduled projects in closure phase.

Sedimentation W5

Event-based triggered by results of landform monitoring. TBC in consultation with Landform criteria and Water quality stakeholder groups.

* The parameter list for MCUS and GCC upstream sites may be reduced in future where criteria does not include comparison against natural distributions.

12.5.2 Groundwater

Closure monitoring

Environmental Requirement (ER) 2.3 "… provides for minimum restrictions on the use of the area." However, it was agreed during the Closure Criteria Working Group meeting of 19 August 2008 that groundwater extraction for purposes other than monitoring would not be allowed on the RPA, post-closure. The minutes of the meeting state: "… that a constraint on groundwater abstraction from Ranger operational area and some surrounds will be needed to prevent bores being sunk in areas where water may be unsuitable for use."

In this context, the primary objective of the closure groundwater monitoring program will be to confirm that measured time series changes to water quality are consistent with the hydrogeological model predictions and the regional groundwater environment remains protected. The results of solute transport modelling (INTERA 2014a, 2014b, 2018) indicate that solutes at depth in the backfilled pits will enter low-permeability hydrogeological units (non-aquifers) and migrate away from solute sources at very low rates. The modelled flux rates from these units to shallow and deep aquifers and surface water bodies are very low. It is thus not appropriate to set concentration-based groundwater closure criteria for these units. Ongoing monitoring of groundwater will provide data to validate these solute transport model predictions and assumptions.

5 See footnote against sediment concentration for onsite billabongs.


Monitoring 'envelopes' in the four sub-catchments; Gulungul, Coonjimba, Djalkmarra and Corridor creeks, will be progressively refined during decommissioning. The ‘envelopes’ will comprise new and/or existing monitoring bores.

Groundwater on the RPA is generally described through discrete hydrolithological units (HLU). These HLUs are defined based on similar geological and groundwater flow and transport characteristics. The HLUs are split into four typical zones and are summarised in Table 12-5.

Table 12-5: Generally identified hydrolithological units on the RPA

Hydrolithological Zone

Geological Description and Typical Depth

Hydrological Description

Alluvial HLUs The surficial alluvial HLUs include the alluvial sediments (sands, gravels and transported sediments). Alluvial HLUs are present in proximity to the to the creek channels across the RPA. Typical thickness of the alluvial HLUs are between 8 m to 12 m.

Ephemeral wetting in wet season. Hosts the water table in the wet season. Likely to behave as a porous medium with relatively higher permeability.

Shallow Weathered Rock HLUs

Weathered rock is the mantle of parent rock that has been decomposed or altered to contain a large clay or sandy clay fraction. In general, the thickness of weathered across the RPA is about 25 to 30 m but it can be thicker or thinner in local areas.

Ephemeral wetting in wet season. Hosts the water table in the wet season. Likely to behave as a porous medium with relatively moderate to high permeability.

Deep Bedrock HLUs

The deep HLUs are not exposed at the surface. The deep HLUs are those located in the fresh bedrock of the Cahill Formation and the Nanambu Complex. In general, these units start at base of the weathered rock HLUs and extend beyond the base of the groundwater model (700 m+ depth).

Fully saturated at all times (unless affected locally by dewatering associated with mine activities). Typically low permeability with the exception of several discrete zones that have been identified with moderate to high permeability. These higher permeability zones include the Deeps Water Producing Zone (DWPZ), MBL zone, depressurised upper mine sequence (D-UMS) and Zone C shallow bedrock. The DWPZ is higher permeability region located below Pit 3 along a geological contact associated with the Deeps Fault Zone. The MBL zone higher permeability conceptualised strip of higher yielding rock that was defined to explain high groundwater yields near the south-eastern edge of Pit 1. The D-UMS is a higher permeability zone that extends to the north of Pit 3


Hydrolithological Zone

Geological Description and Typical Depth

Hydrological Description

and is defined by an area where groundwater heads responses were observed as a result of Pit 3 mining. The Zone C is a higher permeability shallow bedrock unit that is a relatively small zone to the south of Pit 3 and is defined by an area where groundwater head responses were observed as a result of Pit 3 mining.

Mine Backfill HLUs

Mine backfill HLUs consist of the material used to backfill Pit 1, Pit 3 and the final landform. This material consists waste rock and tailings. The thickness of these HLUs varies greatly depending on location, the Pit 1 and Pit 3 backfill HLUs extend from ground level to the base of the pit excavations whilst the final landform extends from the natural ground surface to the maximum height of the final landform.

The mine backfill HLUs consist of materials with both high permeability (waste rock) and lower permeability (tailings).

The overall objective of the groundwater monitoring program is to monitor changes in groundwater head and solute concentrations for comparison against expected changes in the groundwater system (i.e. changes in groundwater heads and flow direction and changes in concentrations of selected solutes). This monitoring regime is intended to demonstrate that solute transport velocities and concentrations are consistent with modelling predictions and that the receiving environment remains protected.

Groundwater monitoring programs have been proposed for both Pit 3 (Djalkmarra catchment) and Pit 1 (Corridor Creek), as a component of the Ranger Water Management Plan (2018). Both programs have been designed to target pathways for transport of solutes into the environment and the various hydrolythic units defined in the groundwater conceptual model.

The Pit 1 groundwater monitoring program is intended to demonstrate that solute transport velocities and concentrations, within each hydrolithological unit are consistent with modelling predictions, and that the receiving environment is being protected in this area. The long-term monitoring program consists of two existing bores, MB-L and R1C3-1, along with three new bores to be drilled in 2019.

The Pit 3 groundwater monitoring program is to monitor changes in groundwater head and solute concentrations, within each hydrogeological unit, for comparison against expected changes in the groundwater system between Pit 3 and Magela Creek, both during Pit 3 backfilling and after Pit 3 closure. Adjacent Pit 3, 13 existing bores are monitored biannually to capture pre and post-wet season groundwater quality. An additional six monitoring bores are planned to be drilled in the second half of 2019 along identified potential flow pathways from Pit 3 to Magela Creek. An additional seventh monitoring bore will be installed following


completion of backfilling of Pit 3 to monitor head and solute concentration changes in the Pit 3 shallow waste rock backfill, which is expected to be a source for solutes of potential concern.

Both programs include the installation of new bores and have utilised existing bores where possible. The location and screening parameters of the proposed Pit 1 and Pit 3 monitoring bores are provided in Table 12-6, Figure 12-2 and Figure 12-3.

The site-wide post-closure groundwater monitoring network will be based on the existing network as outlined in the 2017/18 annual GWR (ERM 2018). However, bores within the final landform will be decommissioned when no longer required. This program will also include the proposed Pit 1 and Pit 3 monitoring bores identified above.

Figure 12-2: Proposed location of Pit 1 monitoring bores


Table 12-6: Parameters for proposed and existing monitoring bores for Pit 1 and Pit 3 closure

Bore ID Location Easting (MGA94)

Northing (MGA94)

Depth (m)

Screen Interval (mbgl) Monitoring

23562 Magela Ck 274404 8598253 5.5 0 to 5.5 m Biannual WQ & SWL

MB-L Pit 1 273933 8595935 50 14 to 16 m Biannual WQ & SWL**

R1C3-1 Pit 1 273977 8595978 22.25 16.25 to 22.25 m Biannual WQ & SWL

New Bore 1 Pit 1 273963 8596488 35* 2 to 35 m Biannual WQ & SWL



MS4 Pit 3 274311 8598255 9.25 6 to 9.25 m Biannual WQ & SWL

MS4-A Pit 3 274311 8598255 5.25 1.45 to 5.25 m Biannual WQ & SWL

NWOB003 Pit 3 274012 8598271 11 1 to 11 m Biannual WQ & SWL

P3-4B Pit 3 273822 8598301 100 60 to 99.5 m Biannual WQ & SWL

P3-8 Pit 3 274292 8598235 81 42 to 69 m Biannual WQ & SWL

P3-9 Pit 3 274240 8598515 48.5 15 to 48.5 m Biannual WQ & Data Logger SWL

P3-11 Pit 3 274362 8598122 25.6 11 to 25.6 m Biannual WQ & SWL

P3-12 Pit 3 273893 8598467 75.6 56 to 71 m Biannual WQ & SWL

P3-13 Pit 3 274477 8597921 39 24.6 to 39 m Biannual WQ & SWL

P3-14 Pit 3 274575 8597995 49.3 32 to 46 m Biannual WQ & SWL



Northing (MGA94)

Depth (m)


P3-15A Pit 3 274651 8598250 57 39 to 54 m Biannual WQ & SWL

P3-15B Pit 3 274677 8598252 30 22 to 30 m Biannual WQ & SWL

P3-16 Pit 3 274117 8598323 57.7 34.7 to 57.7 m Biannual WQ & SWL








FI1 Pit 3 273663 8598557 6 0 to 6 m Data Logger SWL

FI2 Pit 3 273768 8598629 6 0 to 6 m Data Logger SWL

MC11 Pit 3 275039 8598056 3.5 0.3 to 3.5 m Data Logger SWL



P3-3A Pit 3 273686 8598892 57.6 36 to 52 m Data Logger SWL

P3-3C Pit 3 273687 8598898 16.5 8.5 to 16.5 m Data Logger SWL

P3-7 Pit 3 273968 8598296 97.5 90 to 97.5 m Data Logger SWL

R3D49S R3 Deep 274800 8597799 294 258 to 294 m Biannual WQ & SWL



Northing (MGA94)

Depth (m)


R3D51D R3 Deep 274662 8597631 468 385 to 468 m Biannual WQ & SWL


R3D52D R3 Deep 274446 8598214 373 345 to 373 m Biannual WQ & SWL


R3D54 R3 Deep 274562 8597836 396 350 to 396 m Biannual WQ & SWL

R3D56A R3 Deep 274557 8598065 349 open hole Biannual WQ & SWL

* Final depths are likely to change depending on the depth of observed geology during drilling.

** Additional monitoring undertaken to support operational requirements.


Figure 12-3: Location of Pit 3 monitoring bores


A similar monitoring regime will be implemented across the other sub-catchments. This may be in the form of monitoring bores within hydrolithic units; or in the form of primary, secondary and tertiary bores staged at various distances down-gradient of each potential contaminant source to provide background water quality data, expeditious verification of model predictions or to detect longer range effects of solute migration.

Monitoring of existing bores, as per Table 12-6, is currently underway with results to be presented in the annual groundwater report. Assessment of this monitoring program will undergo continuous review to ensure it remains suitable for supporting closure studies and validating modelling results. Updates of the groundwater monitoring plan to support closure ongoing closure studies are detailed in the Annual RWMP and subsequent MCPs.

The proposed monitoring will comprise monthly measurements of standing water level and quarterly sampling and chemical analysis (Table 12-8). The aim of post-closure groundwater monitoring is to demonstrate that solute transport velocities and concentrations are consistent with modelling predictions and that the receiving environment will remain protected from defined COPCs. A representative sample of bores will remain for the groundwater monitoring program post-closure. As the post-closure groundwater environment stabilises, it is proposed that monitoring frequency requirements will decrease over time if no risks are identified.

COPCs are constituents considered to be a potential concern to the environment, and can be a concern for humans, biota and/or fauna. The Ranger Authorisation stipulates environmental monitoring of groundwater for the solutes magnesium (Mg), sulfate (SO4), manganese (Mn), uranium (U) and radium-226 (226Ra). Organic contaminates such as total petroleum hydrocarbon (TPH) are potential COPCs for the historical processing plant area.

COPC trigger levels for all parameters must be determined from suitable background collection sites, and these will inform the criteria for ongoing management. These figures will be updated in the post-closure monitoring report as received. Weaver et al. (2010) provided a general review of background groundwater chemistry of the TSF, and this is intended as a guide below in Table 12-7.

The proposed monitoring will comprise measurements of standing water level plus sampling and chemical analysis at defined frequencies of, for example, pH, EC, Ca, Cl, HCO3

-, K, Mg, Mn, Na, SO4

2-, 226Ra and U.

Updates of the groundwater monitoring plan to support closure are detailed in the Annual RWMP.

The final groundwater monitoring program for post-closure will be developed with continued stakeholder engagement and advice from INTERA upon completion of the post-closure solute transport modelling. Development of the post-closure groundwater monitoring plan will be detailed in subsequent mine closure plans.

Groundwater monitoring for closure and post-closure is presented in Table 12-8.


Table 12-7: General background groundwater chemistry for the RPA

Parameter Alluvial HLUs Shallow Weathered HLUs Deep Bedrock HLUs

EC <500 μS/cm

Sulfate

< 5 mg/L Higher concentrations in the dry may result from evapotranspiration. Fluctuating concentrations may relate to input from surface water or runoff.

<5 mg/L Steadily rising concentrations through time are likely to indicate seepage from the TSF or stockpiles.

<5 mg/L Steadily rising concentrations through time are likely to indicate seepage from the TSF or stockpiles.

Magnesium < 30 mg/L with no indications or steadily rising concentrations.

Calcium < 40 mg/L with no indications or steadily rising concentrations.

Manganese <5 to approximately 2000 μg/L, Fluctuating concentrations

<10 to approximately 2000 μg/L with no indication of steadily rising concentrations

Radium-226 Variable, <5 to approximately 100 mBq/L Variable activities <5 to approximately 300 mBq/L

Uranium <10 μg/L


Table 12-8: Groundwater closure and post-closure monitoring

Aspect Methodology Analysis Location Frequency Duration Compliance Reference

Standing water level

Monthly manual standing water level measurements

Compare to adopted background levels to confirm groundwater level is behaving according to modelled predictions, within the documented uncertainties. To determine hydraulic gradients and potential movement of COPCs.

Groundwater monitoring locations listed in Table 12-6

Monthly (year 1) Quarterly (years 2-4 if no changes) Annually during wet season (ongoing if no changes)

Until criteria have been achieved

Ranger Authorisation Annex A, ERA Water Management Plan 2018

Chemical analysis In situ parameters (pH, EC) Major ions and cations (Mg, Na, K, Ca, Cl, SO4, HCO3, CO3) Filterable metals (U, Mn, Fe) Total nitrogen (NOx-N (NO2-N+NO3-N), NH3-N) Ra-226

Compare to adopted background levels to confirm groundwater chemistry is not being adversely impacted by COPCs from former RPA activities. Where COPC impacts are already present, to ensure these are not migrating into additional impact areas.

Groundwater monitoring locations listed in Table 12-6

Quarterly (years 1-3 if no exceedances) Annually during wet season (ongoing if no exceedances)

Until criteria have been achieved

Ranger Authorisation Annex A

Additional trace metals (Cd, Cr, Cu, Hg, Pb, Zn, Fe, Al) Total Petroleum Hydrocarbons (TPH)

Sites in Process Plant Area


12.6 Radiation monitoring

12.6.1 Closure monitoring

The current operational radiation monitoring program will continue throughout the closure phase in accordance with the requirements of the Authorisation. The purpose of this monitoring is to confirm that radiation exposure of workers on the Ranger Mine site and members of the community is kept ALARA and below the relevant dose limits. Variations to the monitoring program will be necessary as rehabilitation progresses beyond the cessation of uranium processing.

Radiation monitoring, undertaken for the purposes of assessment of closure criteria, will be limited during the closure phase. Detail will be provided in future MCPs following the outcomes of the Monitoring Evaluation and Research Review Group.

12.6.2 Post-closure monitoring

The proposed post-closure monitoring for radiological performance has been structured around the exposure pathways for radiation due to the potential access to and final land use of the area. These pathways are:

• inhalation of Long Lived Alpha Activity (LLAA e.g. radioactive dust)

• inhalation of radon progeny (Potential Alpha Energy Concentration; PAEC)

• ingestion of radioactive material in (or with) food or water, and

• external irradiation from gamma rays (and beta particles).

Given the possible post-closure use of the landform, the critical group will be Aboriginal people using the site for traditional activities including transient camping and the gathering of traditional bush foods for consumption.

LLAA and PAEC will be measured towards the end of the dry season for the initial five-year period following construction of the final landform, the details of the monitoring program are outlined in Table 12-9. During the dry season lower soil moisture results in increased Rn exhalation rates and higher dust concentrations in air. Monitoring will be undertaken over at least a minimum one-week period each dry season using either:

• more volume samplers (LLAA) or Alpha Prisms (PAEC) targeting areas with increased activity present in the sediments, or

• more passive techniques that integrate over a longer time period, such as track etch detectors (PAEC) or passive dust samplers (LLAA) over a three- to six-month period.

Potentially contaminated waters will be monitored in conjunction with the water and sediment monitoring program with grab samples taken upstream and downstream of Ranger Mine in Magela Creek and Gulungal Creek and at key receptor locations. Samples will initially be taken monthly during creek flow, this will reduce to annually once low levels have been confirmed.


Results of this monitoring program will be used to determine ingestion dose from drinking water and eating bush foods.

At the completion of decommissioning activities, an airborne radiometric survey with targeted ground surveys for external gamma dose rate and 226Ra in soils will be undertaken to determine the gamma dose from the final landform.

Radiation monitoring for closure and post-closure is presented in Table 12-9.


Table 12-9: Radiation closure and post-closure monitoring

Aspect Methodology Analysis Location Frequency Duration Long Lived Alpha Activity (LLAA) – Radionuclides in dust

High volume samplers or deposited dust samplers to monitor

Confirm radiation doses to members of the public are below limits (as defined in closure criteria)

RPA and key receptor locations off site

Initial continuous 3-month period, then continuous one-week period each dry season Deposited dust monitoring every 3-6 months (for years 1-5)

Five years following 8 January 2026

Radon Decay Products (RDP)

Continuous radon decay product monitors or more passive techniques such as radon track etch detectors


RPA and key receptor locations off site

Initial continuous 3-month period, then continuous one-week period each dry season Deposited dust monitoring every 3-6 months (for years 1-5)

Five years following 8 January 2026

External gamma radiation Airborne radiometric survey with ground gamma survey and soil sampling


final landform

Once at the completion of rehabilitation activities

NA

Radionuclides in bushfood Gamma spectrometry analysis of samples for Ra-226, U


RPA To be refined based on fruit and seed production seasons

Until demonstrated progression towards closure criteria, i.e. low levels have been confirmed


Aspect Methodology Analysis Location Frequency Duration Bushfood – water Gamma spectrometry

analysis of samples for Ra-226, U

Confirm radiation doses to members of the public are below limits (as defined in closure criteria). Confirm radionuclide concentrations used in concentration ratios for ERICA assessment

MG009 and GCLB

Monthly during wet season flow decreasing to annually over time

Until demonstrated progression towards closure criteria, i.e. low levels have been confirmed Duration or timeline for ERICA assessment (5 years post-closure)

Soil radionuclide analysis Gamma spec analysis of samples for Ra-226, U-238

Confirm radionuclide concentrations used in concentration ratios for tier 2 ERICA assessment

RPA other than final landform waste rock areas

Once Immediately post-closure


12.7 Soils monitoring

Soil remediation across the RPA will occur prior to decommissioning and will be based on the Plume and Contaminated Site Management Plan CDM.03-0000-EG-REP-00024 (Appendix 12-2), developed during the feasibility study, and the Ranger Mine contaminated site register and identified sites where contamination could occur as a result of the storage of inorganic and organic chemicals, and solute migration from mine-related activities. This register has been developed in conjunction with a number of targeted assessments undertaken at known contaminated sites on the RPA (Sections 7.4.2 and 7.9.9).

The key environmental receptors of the Ranger Mine are the surface water bodies adjacent to the mine site. These receptors are far away from contaminated sites. Groundwater velocities in the underlying formations are low, and the weathered rock underlying the site tends to retard most contaminants. Nevertheless, further characterisation of contaminants at some contaminated sites on the RPA may be required to determine vertical extent, lateral extent and/or mass of contamination.

It is intended that the degree of remediation required for each contaminated site will be based on soil concentrations at these locations compared to local background concentrations or the published investigation levels (i.e. Health Investigation Level (HIL) and/or Environment Investigation Levels (EIL)). If soil concentrations in each site are shown to be below the screening levels then no further remediation or assessment will be required.

However, if concentrations of contaminants are above screening levels then a detailed site investigation and/or remediation plan will be developed. Under this scenario, monitoring and reporting may be required to demonstrate that the risk is ALARA.

12.8 Flora and fauna monitoring

Monitoring is an integral part of the revegetation process. It is used to determine the initial success of revegetation efforts in establishing the desired species density and composition and evaluate the progress of older revegetation in terms of growth rates, structural development, ecological function and tracking along a trajectory towards longer-term sustainability. It provides feedback to identify problems and inform adaptive management or intervention. It is also needed to demonstrate acceptable performance against criteria and standards, ultimately leading into stakeholder acceptance of the revegetation (Reddell & Meek 2004).

Flora and fauna monitoring undertaken during the operation of Ranger Mine is presented in Section 7 and has included:

• almost ten years of revegetation monitoring on the TLF and at Jabiluka, focused on assessment of growth, performance and survival of plants and vegetation communities under different conditions (substrate type, substrate depth and planting method, understorey establishment and response to fire) (Section 7.3.4)


• many historical small-scale revegetation trials in relation to landform morphology, substrate characteristics, revegetation and ecosystem establishment methods, species-specific establishment and seed provenance (Section 7.6.1)

• limited monitoring of progressive rehabilitation for establishment, development and weeds

• over 16 years of reference site monitoring in areas adjacent to the Ranger Mine lease considered relevant to the waste rock final landform (Section 7.4.5 & 7.4.6). This monitoring has focused on characterising the composition, structure and function of these ecosystems to inform revegetation practices and objectives (in particularly closure criteria). A subset of long-term reference monitoring plots has been maintained to obtain information on the natural dynamics of these ecosystems, including in response to disturbance events such as cyclones and fire, and

• opportunistic and structured fauna monitoring has been undertaken on rehabilitated sites (e.g. TLF) and reference sites (Section 7.4.5).

From this operational experience, and drawing on decades of industry best practice, a comprehensive closure revegetation monitoring program has been developed.

The current proposed program allows for potential improvements following a number of investigations proposed for the Pit 1 revegetation works, such as optimised species-specific establishment methods, the influence of substrate characteristics (and soil water availability) on plant success, success of rock structures to enhance fauna site utilisation. Thus, the monitoring of Pit 1 will comprise a combination of research structured monitoring along with routine revegetation monitoring methods. A collaborative technical working group of key stakeholders has been formed and continues to refine the research trials and aligned associated monitoring for Pit 1 revegetation. The flora and fauna monitoring program presented in Table 12-10 represents the routine tasks anticipated for the overall revegetation program, regardless of additional research activities, which will be developed separately. Completion criteria relevant to flora and fauna are in Table 8-5.

12.8.1 Native flora and fauna monitoring

The scope and frequency of monitoring is largely dependent upon the stage of development of the revegetation. An initial assessment soon after planting (one to three months) assesses will capture any mortality caused by planting stress or other revegetation execution problems. The highest mortality is anticipated to occur in the first six to twelve months post-planting, due to drought conditions during the dry season. Thus, the determination of the requirement for infill planting will typically be able to be made six to eight months after planting. Ongoing annual monitoring of establishment success will continue until all initial establishment and subsequent infill plantings have developed sufficiently and attrition rates have dropped to a recoverable level. This initial monitoring will focus on survival rates for tubestock and germination rates for direct seeding, species composition, density, height, health and other opportunistic observations such as weeds, fauna, pests and erosion. Subsets of individual plants will be identified and recorded each year to allow assessment of individual species development.


Initial annual monitoring may involve recording every planted stem, though this will depend on the size of the area revegetated. Alternatively, belt transects, point centred quarter or other techniques may be used to sample a subset of the stems. Some permanent plots will be established within the revegetation area and monitor all plants within the plots monitored, as this reduces “white noise” variation in results over time. Fixed photo points will be used to provide a visual representation of revegetation progress. For the initial monitoring attributes, consistent methods will be used each year, to enable comparisons over time and between sites, and into the long-term monitoring program.

As the vegetation matures, monitoring of species composition and density will remain essential, whilst other aspects related to ecosystem structure and function will become increasingly important. Attributes to be measured as part of this long-term monitoring program may include occurrence of flowering and fruiting, presence of understorey (including weeds) and leaf litter, canopy cover, tree height and diameter at breast height. Monitoring will also include aspects other than vegetation, such as surveys for fauna, pests, weeds and erosion.

Monitoring of these established, maturing revegetated ecosystems will focus on comparison with completion criteria attributes, and will gradually provide a developmental trajectory including predictive trends towards achieving the criteria.

As secondary introductions of additional plant species and plants occur, additional 'initial' monitoring of these plants will need to occur in addition to the routine vegetation monitoring of the already established vegetation.

Long-term revegetation monitoring will need to continue on an annual basis, until the developmental trajectory can be seen to be steadying and the risk of deviation (due to mortality, weeds or fire) and any requirement for active management intervention is sufficiently reduced. As development stabilises, the frequency, intensity and potentially the scope of the monitoring program can be adjusted to allow more effective use of resources. Monitoring of some attributes, such as fauna recolonisation, may be more suitable on a campaign (e.g. five year) basis in the mature revegetation (along with similar surveys of the reference sites).

Areas that receive remediation treatment will require a targeted monitoring program, independent of the surrounding areas, to assess the effectiveness of the remedial action and progress back towards the desired trajectory.

Flora and fauna monitoring and maintenance for post-closure will begin following initial planting. The majority of the infill planting and understorey planting activities will occur during this phase. The flora and fauna monitoring will utilise the information provided by the monitoring of established reference sites and will comprise vegetation plots and fauna trapping transects to address terrestrial flora and fauna closure criteria.

The flora and fauna monitoring program to be implemented will be developed to capture relevant information as the revegetation progresses. For example, the early fauna monitoring (e.g. years one to three), is likely to focus on incidental observations of vertebrates and invertebrates. As the vegetation establishes, there will be an increase in monitoring to include trapping and systematic observation-based surveys to determine the presence of major functional groups. In the initial stages of revegetation (e.g. years one to five), the flora


monitoring will focus on species survival rates, which will inform remediation works.6 As saplings develop, a more comprehensive suite of parameters addressing ecosystem development and closure criteria will be introduced (Section 8, Table 8-5).

The proposed survey frequency of flora and fauna across the final landform is: three, six and twelve months (year one); annually (years two to five, inclusive); one-off surveys every five years (e.g. at years 10, 15, etc). Some routine surveys, such as weed, will be annual, and every five years a more comprehensive monitoring will be required to demonstrate the trajectory. The details are presented in Table 12-10.

12.8.2 Feral animal monitoring

ERA currently undertakes feral animal monitoring and culling to manage densities of particular species on the RPA, such as pigs. This practice will continue during the initial maintenance period after commencement of post-closure monitoring (e.g. years one to five). Feral animals will be culled if densities become too high and other remedial actions will be taken if feral animals are adversely affecting physical works (e.g. damaging wetlands or revegetation on the final landform) or significantly compromising recolonisation by native fauna. As the landform develops, feral animal monitoring and management will revert to that which is followed within Kakadu National Park (NP).

12.8.3 Weed monitoring

ERA has undertaken fine scale annual weed surveys and mapping across the RPA since 2003 (Section 4.3.3.2). This mapping provides data to assess the effectiveness of weed control measures and to inform the ongoing weed monitoring and subsequent corrective actions required to meet closure criteria, particularly within the first five years, whilst the revegetation is establishing.

Weeds may out-compete with and/or smother tubestock, or may increase the risk of fire, and thus potentially increase mortality. ERA will monitor and maintain a weed control buffer zone around the rehabilitated site. Targeted weed monitoring, and also the routine revegetation monitoring will record if any weed infestations occur on the rehabilitation.

Weed control methods will be situation and species-specific, with the most effective controls determined from ERA experience and input from specialists. Weeds are likely to be controlled by a combination of chemical and physical methods, including application of residual and or short acting chemicals, seed head cutting and burning, or fuel-load reduction by fire.

6 Infill planting requirements will be informed by frequent site inspections over the course of the first

1 – 2 years until vegetation establishment.


Table 12-10: Flora and fauna closure & post-closure monitoring

Type Aspect Methodology /Analysis Location Frequency Duration Initial Establishment Monitoring.

Species composition, density and species relative abundance

Use standard NT vegetation survey methods.

In specific plots to provide representative samples within the RPA. Also to be used following infill planting and of remediation that involves introduction of new plants.

3, 6 and 12 months after planting, and then annually each post-wet / early dry season.

To transition to ‘long-term’ vegetation monitoring program once rates of attrition reduce and structural and functional attributes begin to develop, e.g. 3-5 years.

Survival rates (incl. height and health) for tubestock and germination rates for direct seeding

Rapid assessment of broadscale plant survival using tubestock planting data (location / species). Permanent plots, individual plants assessed over repeat monitoring events. % of planted (or sown) plants.

Opportunistic observations such as weeds, fauna, pests and erosion

Opportunistic observations as part of flora monitoring program. Aerial / LiDAR assessment of erosion and/or weeds.

Long-term Revegetation Monitoring.

Species composition (tree and shrubs) and species relative abundance

Bray-Curtis similarity index >25%. Total species richness 90% of midstorey and overstorey framework species.

In specific plots to provide representative samples within the RPA.

Annually each post-wet / early dry season. Frequency, scope, intensity to be reduced, based on assessment of risk of deviation (due to mortality, weeds or fire) and any requirement for active management intervention.

Until closure criteria F2 achieved

Canopy architecture

Presence of multi-strata. Presence of understorey shrubs and grasses developed appropriate to the substrate.


Canopy cover index, ground cover index

Use standard NT vegetation survey methods.



Type Aspect Methodology /Analysis Location Frequency Duration Comparable to appropriate reference sites.

Tree distribution

Trees are planted in a manner to appear ‘natural’.


Reproduction (flowering and seeding)

Evidence of flowering and fruiting of 80% of framework species or characteristic species (based on species present).


Recruitment & regeneration

Presence of seedlings and/or suckers of 100% of framework species (based on species present).


Nutrient cycling

Accumulation of litter and organic matter. Evidence of decomposition of litter. Presence of soil, animals and saprophytic fungi. The above criteria occur in 90% of the survey plots.


Fire resilience

Following a recent fire (within the previous five years), all other closure criteria must be shown to have been met, demonstrating recovery.



Type Aspect Methodology /Analysis Location Frequency Duration Wind & drought resilience

Woodland ecosystem demonstrates survival under natural condition, similar to appropriate reference sites.


Weed composition and abundance

Survey for Class A weeds and Class B weeds and other introduced species. No Class A7 weeds. Class B2 weeds similar to surrounding Kakadu NP (defined by monitoring). Presence of other introduced species would not require a maintenance regime significantly different from that appropriate to adjacent areas of Kakadu NP.

Spatial mapping of priority species and density scoring across the RPA

Annual, within the disturbed area and buffer zone


Presence of native fauna

Development of habitat suitable for native fauna species that utilise appropriate reference sites: the following habitat features must be present: multi-strata layers; coarse woody debris (10 cm in diameter), trending towards development of hollows, rock features Local native mammals, birds, reptiles & invertebrates using the site (or likely to).

Opportunistic observations included as part of initial vegetation monitoring method. One-off comprehensive surveys every 5 years (including reference sites).


7 Class A Weeds are to be eradicated. Class B weeds growth and spread to be controlled


Type Aspect Methodology /Analysis Location Frequency Duration An effective termite decomposer fauna has developed: Recent termite constructs (mounds, arboreal nests, earthen workings in litter, on wood and on tree stems) are present, and there is evidence of termite‐mediated decomposition of woody and other plant materials.

One-off surveys every 5 years (ongoing). Early monitoring to focus on incidental observations, moving to trapping /systematic-based observation studies as vegetation establishes.

Exotic fauna Feral animals (specifically buffalo, horses and pigs) are similar in density on the RPA compared to the adjacent areas of Kakadu NP



12.9 Cultural monitoring

Alongside the development of the cultural closure criteria (Section 8.7), linguist Murray Garde (Garde 2015) proposed a number of indicators that could be used to reflect the Traditional Owner attitudes towards rehabilitation progress and by extension the satisfication of the cultural closure criteria during the closure and post-closure phases (Table 12-11). A number of these indicators are largely based on visual and aesthetic values, as viewed through the lens of Mirarr culture. These indicators represent the overall cultural health of the ecosystem, which needs to be assessed by Mirarr Traditional Owners.

Table 12-11: Suggested indicators of cultural health of rehabilitated site (Garde 2015)

Landscape surface Vegetation Riparian zone Biodiversity

Size of rocks Growth rate Presence or absence of artificial water bodies

Natural species numbers and diversity

Presence/absence of erosion Botanical diversity

Visual impressions of water quality, sedimentation, silting of rehabilitated water courses

Impressions of hunting potential

Accessibility Correct species for ecological zone

Condition of water course margins, creek banks

Impressions of vegetable food availability

General aesthetic (does it look ‘natural’)

Presence/absence of weeds

Garde (2015) states that there are very few established models or methodologies to inform programs that assess cultural health. One notable example comes from New Zealand: Cultural Health Index for Streams and Waterways: Indicators for Recognising and Expressing Maori Values (Tipa & Teirney, 2003, 2006). The index attempts to apply indicators that Maori land owners use to assess the health of waterways.

In the absence of an established best practice methodology in an Australian context, Garde (2015) described a proposed process by which to monitor the success of rehabilitation using a set of cultural health indices. The process described a scalar score generally out of ten that allowed impressionistic responses to be quantified. A key aspect of the indices is the bilingual format, including information in both Kundjeyhmi and English (an example is in Table 12-12).


Table 12-12: An example of a bilingual, scalar cultural index score for cultural criteria monitoring

ga-djalbolkwarre yerre

ga-bolkwarre yiga ga-bolkmakmen gun-yahwurd

kareh ga-bolkmakmen gare lark

ga-bolkmakmen wurd

bon, ba-bolkmakminj wanjh

no improvement yet noticed

some minor improvements

some areas improved, some

areas not

noticeable return to healthy state in

most areas

satisfactory return to natural state

1 | 2 3 | 4 5 | 6 7 | 8 9 | 10

It was suggested that the cultural monitoring assessments could be carried out at specific locations that collectively provide a cross section of rehabilitation and include a number of significant cultural areas. An assessment of cultural health and rehabilitation progress will be conducted at each location on an annual basis. The proposed locations include:

• TSF rehabilitated landform

• Pit 3 rehabilitated landform

• Retention Pond 2 (RP2) rehabilitated landform

• Pit 1 rehabilitated landform

• Retention Pond 1 (RP1)

• Kundjinba Billabong (Coonjimba Billabong)

• Georgetown Billabong (Madjawulu)

• Brockman irrigation area (i.e. Corridor Creek LAA)

• Karnbowh Djang (Tree Snake Dreaming), and

• Ranger Mine 34 archaeological site (quartz outcrop with grinding holes).

The Gundjeihmi Aboriginal Corporation (GAC) and the Northern Land Council (NLC) have provided feedback that the MCP is to include a compliance and monitoring process for meeting the cultural closure criteria and that they would propose a process for ERA consideration that included direct involvement of Traditional Owners with technical support. The GAC and the NLC have been working with Traditional Owners and Murray Garde to build on previous work completed. Once GAC and NLC have finalised the proposed process, it will be reviewed by ERA and incorporated into future revisions of the MCP.

12.10 Trigger, action, response plan (TARP)

The monitoring program described in Sections 12.4 to 12.9 have been summarised into a preliminary TARP, which will also be updated in future iterations of the MCP based on agreement of closure criteria and the outcomes of ongoing studies. The TARP is presented in Table 12-13.

Issued date: October Page 12-42 Unique Reference: PLN007 Revision number: 1.19.0 Documents downloaded or printed are uncontrolled.

Table 12-13: Trigger, action, response plan

Aspect Monitoring Response Methodology Purpose Trigger Action Responsibility

Landform

Final landform surface (topography, erosion and settlement)

Sites: RPA Parameters: Landform terrain Analysis: LiDAR or drone survey Frequency: Annual

To inform landform settling rate and erosion rates

Change from previous Comparison to modelled

Site-based plan and action as required

Site Environmental Officer (or delegate)

Erosion (local scale)

Sites: Sensitive receptor areas and drainage channels Parameters: Field inspection, notes and photographs Analysis: Identify erosion problem areas Frequency: Annually after the wet season

Identify erosion problem areas and any maintenance required to drainage channels

Significant erosion – rill erosion > 40 cm depth, sheet erosion or hostile soil environment prevents revegetation (>0.1 ha) Erosion around drainage channels

Site-based plan and action as required Repairs to area identified


Subsidence, slumping, deformation, and/or settlement

Sites: Identified geotechnical sites Parameters: Geotechnical monitoring of pits, landfill walls, TSF Analysis: Identify any changes (subsidence or deformation) of landform Frequency: Quarterly

Identify any subsidence or deformation of landform areas

Subsidence, deformation, or settlement of final landform are noted

Site-based plan and action as required. May require additional works including modifying the sediment control basis


Bedload

Sites: Water courses that direct water off site and associated sediment basins Parameters: Field inspection, notes and photographs Analysis: Identify bedload moving off site Frequency: Biannually before and after the wet season

Identify bedload being transferred off site Bedload identified moving offsite



Bedload (sediment basins)

Sites: 18 temporary sediment basins Parameters: Sediment volume and structural stability Analysis: Design requirements Frequency: Annual

To maintain basins in operational condition Outside operational design criteria Site-based plan and action as

required Site Environmental Officer (or delegate)

Suspended Sediment

Sites: Monitoring points upstream and downstream of site Parameters: Turbidity (fine suspended sediment (FSS)) Analysis: BACIP analysis (Moliere & Evans, 2010) Frequency: Ongoing monitoring, analysis after wet season

Assess site denudation rates Turbidity trajectory not transitioning to control environment levels after 5 years

Site-based plan and action as required May require additional surface stabilisation and/or revegetation or works including modifying the sediment control basin


Water and sediment

Surface water and sediment – turbidity and aesthetic

Sites: GCC, GCLB, MCUS, MG009, Gulungul, Coonjimba and Georgetown Billabongs Parameters: Turbidity at both sites and other aesthetic parameters (e.g. surface films, odour) Analysis: Physical and observational analysis of samples Frequency: Continuous monitoring for turbidity

Identify erosion issues and conformance with ecosystem and recreational quality of surface water

Results exceed specific agreed closure criteria

Monitor trends and develop site specific action plan as required


Surface water and sediment – other parameters

Sites: GCC, GCLB, MCUS, MG009, Gulungul, Coonjimba and Georgetown Billabongs Parameters: Various parameters (e.g. EC, major ions, nutrients and metals)

Assess compliance with closure criteria and ecosystem protection. Validate surface water model predictions. Identify surface water and sediment quality issues

Samples exceed specific screening criteria defined in closure criteria

Monitor trends, identify cause and develop site specific action plan as required



Aspect Monitoring Response Methodology Purpose Trigger Action Responsibility Analysis: Chemical analysis of samples and continuous EC Frequency: Ongoing monitoring for EC (Mg), scheduled grab sampling

Review model assumptions and outputs

Surface water and sediment – metals and S in sediment

Sites: Gulungul, Coonjimba and Georgetown Billabongs: Parameters: Metals and S in sediment Analysis: Chemical analysis of samples Frequency: Sample prior to and at end of decommissioning

Characterise contaminants in sediments on and off the RPA. Inform decommissioning of onsite billabongs and confirm success of decommissioning activity (if conducted)

Samples exceed specific screening criteria defined in closure criteria

Monitor trends, identify causes and develop site specific action plan as required Develop best practicable technology decommissioning plans for onsite water bodies


Groundwater

Sites: Monitoring bores Parameters: Standing water level and in situ parameters (pH, EC) Major ions and cations, filterable metals and total nitrogen Analysis: Physical and chemical analysis of samples Frequency: Standing water level monthly, chemical analysis quarterly

To confirm groundwater level and chemistry is behaving according to modelled predictions, within the documented uncertainties

Analysis indicates that groundwater is not tracking according to model predictions



Radiation

LLAA and PAEC inhalation

Sites: RPA Parameters: LLAA and PAEC (mSv per year) Analysis: High volume samplers and continuous radon decay product monitors or more passive techniques such as radon track etch detectors and passive dust samplers Frequency: High volume samplers and continuous radon decay product monitors over a one-week period each dry season, passive techniques over a three to six-month period. Monitoring for the initial five year period following construction of the final landform.

To confirm radiation doses to members of the public are below limits

Exceedance of the baseline radiation dose as defined in the closure criteria

Action plan to mitigate identified pathway to ALARA Apply additional restrictions on the use of the land in consultation with Traditional Owners

Radiation Safety Officer (or delegate)

Food and water contamination

Sites: Magela Creek at MG009 and GCLB, , also upstream sites Parameters: Ra-226, U-238 (other isotopes if risk identified) Analysis: Gamma spec analysis Frequency: initially monthly during the wet season, decreasing to annually over time

As above As above As above Radiation Safety Officer (or delegate)

External gamma radiation

Sites: RPA Parameters: Radiation dose rate (µGy/h) Analysis: Airborne radiometric survey with ground gamma survey and soil sampling for Ra-226 for ground-truthing Frequency: At the completion of rehabilitation activities

As above As above As above Radiation Safety Officer (or delegate)

Flora and fauna

Flora species composition

Sites: Vegetation plots and transects across the RPA Parameters: Species composition (tree and shrubs) and species relative abundance, canopy architecture, canopy cover index, ground cover index and tree distribution Analysis: vegetation survey analysis

To determine whether species composition and community structure is similar to adjacent areas of Kakadu NP

Exceedance of final criteria defined in closure criteria




Aspect Monitoring Response Methodology Purpose Trigger Action Responsibility Frequency: three, six and 12 months (year 1); annually (years 2 – 5, inclusive); one-off surveys every five years (e.g. at years 10, 15, etc)

Ecosystem maintenance

Sites: vegetation plots and fauna trapping transects across the RPA Parameters: Reproduction (flowering and seeding), recruitment / regeneration, nutrient cycling, fire resilience, resilient to wind and drought, plant available water, weed composition and abundance and presence of native fauna. Analysis: vegetation and fauna survey analysis. Frequency: three, six and 12 months (year 1); annually (years 2 – 5, inclusive); one-off surveys every five years (e.g. at years 10, 15, etc).

To determine whether the long term, viable ecosystem requiring maintenance is similar to adjacent areas of Kakadu NP

As above As above Site Environmental Officer (or delegate)

Fauna surveying

Sites: Fauna trapping transects across the RPA Parameters: Species diversity and abundance Analysis: Fauna survey analysis Frequency: three, six and 12 months (year 1); annually (years 2 – 5, inclusive); one-off surveys every five years (e.g. at years 10, 15, etc)

To determine the presence of major functional species groups in comparison to surrounding Kakadu NP

As above As above

Weed surveying and mapping

Sites: RPA Parameters: Weed density and priority Analysis: Spatial mapping and density scoring Frequency: Annual

To determine the spread of weeds and invasive flora within the revegetation areas

As above As above

Cultural

Cultural values To be determined (see Section 12.9)

To determine whether Traditional Owners are satisfied that the rehabilitated environment supports cultural land uses

Conditions identified in closure criteria not met



Soils

Contamination

Sites: Sites in the Ranger Mine contaminated site register Parameters: Various contaminants Analysis: Contaminated soil assessment based on local background concentrations or published investigation levels Frequency: Prior to decommissioning and as identified by assessment.

To ensure impacted soils are remediated to as low as reasonably achievable to protect the environment

Screening levels for intended land use are exceeded

If concentrations of contaminants are above screening levels then a detailed site investigation and/or remediation plan will be developed, requiring further monitoring


Nutritional Assessment

Sites: Stratified sampling sites across the rehabilitated landform. Parameters: Macro and micro-nutrients, pH, EC, OC% etc. Analysis: Soil chemical (and physical) parameters compared with known reference sites and vegetation requirements Frequency: Five-yearly surveys (at years 0, 5, 10, 15, etc).

To assess the development of the soil profile and inform follow-up fertiliser application type, quantity and timing

Conditions required for development of rehabilitation not met

Develop soil amelioration plan, such as fertiliser application



12.11 References

Alarcon Leon, E., Gellert, C., and Pillai, M. 2007, Groundwater contamination in the Ranger Mine Plant area – Phase 2 investigations, for ERA Ranger Mine by EWL Sciences Pty Ltd.

Garde, M. 2015. Closure Criteria Development - Cultural. ERA Ranger Integrated Tailings, Water & Closure. Confidential report, Northern Territory. April 2015, p 160.

INTERA Incorporated. 2014a. Final Report: Solute Egress Mitigation Modelling for ERA Ranger Pit 3 Closure. Prepared for Energy Resources of Australia Ltd by INTERA Incorporated, Albuquerque, NM USA, Commercial in Confidence. 1 July 2014.

INTERA Incorporated. 2014b. Solute Egress Modelling for ERA Ranger Pit 1 Closure. Prepared for Energy Resources of Australia Ltd by INTERA Incorporated, Albuquerque, NM USA. 1 July 2014, p 112.

INTERA 2016, Final Report: Conceptual Model for Ranger Mine, Report for Energy Resources of Australia Ltd. 30 September 2016, p 5

INTERA 2018, Assessment of Effect of Tailings Deposition Method on Post-Closure Solute Loading from Pit 3 Tailings to Magela Creek, Prepared for ERA, 13 June 2018

Gellert, C. 2009a, Ranger contaminated sites investigation: 2008 groundwater sampling, for ERA Ranger Mine by EWL Sciences Pty Ltd.

Gellert, C. 2009b, Short Report, Addendum to Ranger contaminated sites investigation 2008 groundwater sampling report, for ERA Ranger Mine by EWL Sciences Pty Ltd.

Gellert, C. & Jones, C. 2008, Draft Short Report: Status of Contaminated Sites at the Ranger Mine as of December 2007, by EWL Sciences Pty Ltd.

Golder 2016, ERA Ranger Mine – Processing Area Groundwater Contamination Assessment.

Hollingsworth, I. 2006, Contaminated Soil Investigation Ranger Mine, Report for ERA Ranger Mine by EWL Sciences Pty Ltd.

Lu, P, Riaz, A & Bollhöfer, A. 2009. Challenges in estimating public radiation dose resulting from land application of waters of elevated natural radioactivity at Ranger uranium mine, Australia. International Conference on Remediation of Land Contaminated by Radioactive Material Residues. Astana, Kazakhstan.

Moliere, D & Evans, K 2010. Development of trigger levels to assess catchment disturbance on stream suspended sediment loads in the Magela Creek, Northern Territory, Australia. Geographical Research, 48. pp 370-385.

Tipa, G & Teirney, L. 2003. A Cultural Health Index for Streams and Waterways: Indicators for Recognising and Expressing Maori Values. Report prepared for the Ministry for the Environment, Wellington, New Zealand. April 2006, p 72. https://www.mfe.govt.nz/sites/default/files/cultural-health-index-for-streams-and-waterways-tech-report-apr06.pdf

Tipa, G & Teirney, L. 2006. A Cultural Health Index for Streams and Waterways: A tool for nationwide use. A report prepared for the Ministry for the Environment by Gail Tipa and Laurel Teirney, Wellington, New Zealand. April 2006, p 58. https://www.mfe.govt.nz/sites/default/files/cultural-health-index-for-streams-and-waterways-tech-report-apr06.pdf

http://www.mfe.govt.nz/sites/default/files/cultural-health-index-for-streams-and-waterways-tech-report-apr06.pdf




APPENDIX 12.1: PIT 1 PROGRESSIVE REHABILITATION MONITORING FRAMEWORK

Pit 1 Progressive Rehabilitation Monitoring Framework

April 2019

Author(s):

Issued Date:

Revision:

Dr Paul Frazier (2rog)

9 April 2019

V2

Issued date: 09/04/19 Page 2

Unique Reference: ERA-002 Revision number: V2


Document Details

Company 2rog Consulting

Status Final Project Reference 2rog – ERA-002

Name Position Date

Originator Dr Paul Frazier Director 12/12/18

Checked Dr Julian Wall Director 14/12/18

Approved Dr Paul Frazier Director 14/01/19




Revision History

Revision # Issued date Description By (initials)

Checked (initials)

Approved

V0 17/12/18 Initial draft PF JW PF

V0a 22/12/18 Revised Draft PF PF PF

V1 14/01/19 Final PF SP/EF PF

V1a 24/01/19 Final PF EF/MI PF

V1b 4/02/19 Final PF EF PF

V2 9/04/19 Following SSB review PF EF PF

This report has been produced by or for Energy Resources of Australia Limited (ERA). The report and its contents are the property of ERA. Duplication or reproductions of the report or any part of its contents are not permitted without the express written permission of the current approver listed above.




TABLE OF CONTENTS

1 INTRODUCTION ........................................................................................................................... 5 2 PIT 1 REHABILITATION SCHEDULE .......................................................................................... 9 3 CONSTRUCTION PHASE MONITORING .................................................................................. 10 4 ECOSYSTEM ESTABLISHMENT PHASE ................................................................................. 17 5 PIT 1 RESEARCH PLANNING - PRESENT TO 2026 ................................................................ 29

5.1 Whole of site studies ......................................................................................................... 33 6 REHABILATION FRAMEWORK REVIEW AND STAKEHOLDER COLLABORATION .............. 34 7 REFERENCES ............................................................................................................................ 35

FIGURES

FIGURE 1 RANGER URANIUM MINE LOCATION ................................................................. 6

FIGURE 2 AERIAL IMAGERY OF RANGER MINE LAYOUT WITH PIT 1 IDENTIFIED (PHOTO CAPTURE JUNE 2018) ............................................................................................ 7

FIGURE 3 HIGH-RESOLUTION IMAGE OF PIT 1 AREA (PHOTO CAPTURE JUNE 2018) . 8

TABLES

TABLE 1 PIT 1 REHABILITATION SCHEDULE (INDICATIVE PENDING APPROPRIATE

APPROVALS) PROVIDES INFORMATION AS PROVIDED FROM CLOSURE EXECUTION

SCHEDULE. ............................................................................................................................. 9

TABLE 2 INDICATIVE ORE GRADES AND MINERAL TYPE ............................................... 11

TABLE 3 PIT 1 CONSTRUCTION PHASE MONITORING FRAMEWORK (MAY 2019-AUG

2020) ...................................................................................................................................... 12

TABLE 4 PIT 1 CONSTRUCTION PHASE: TRIGGER, ACTION, RESPONSE PLAN (TARP) ............................................................................................................................................... 14

TABLE 5 PIT 1 ECOSYSTEM ESTABLISHMENT PHASE MONITORING (AUG 2020 – NOV 2022) ...................................................................................................................................... 18

TABLE 6 ECOSYSTEM ESTABLISHMENT PHASE TARP .................................................. 23

TABLE 7 PIT 1 TARGETED RESEARCH TASKS ................................................................. 30




Abbreviations

Abbreviation Description AARTC Alligators Rivers Region Technical Committee

BACIP Before After Control Impact Paired

DEM Digital Elevation Model

ERA Energy Resources of Australia

LEM Landscape Evolution Model

SSB Supervising Scientist Branch


Unique reference: ERA-002 Revision number: V2


1 INTRODUCTION

The Ranger Progressive Rehabilitation Monitoring Workshop was held on 4 September 2018

to ‘agree on high-level monitoring, to avoid missing information that is needed to inform the progressive rehabilitation process’ (SSB 2018).

This workshop defined the progressive rehabilitation period as being from present to 2026 and

identified key monitoring themes that included:

• Landform • Water (groundwater and surface water) • Radiation • Ecosystem restoration.

The workshop also identified that rehabilitation of Pit 1 is planned to proceed in late 2019 and

presents an opportunity to develop and refine the Progressive Rehabilitation Monitoring Framework.

Following the initial workshop, a subsequent workshop was held with Energy Resources of

Australia (ERA) staff on 27 November 2018, to develop a monitoring and research framework specifically focussing on the Pit 1 area. This team reviewed and incorporated knowledge and

advice from the Ranger Progressive Rehabilitation Monitoring Workshop meeting notes, subsequent stakeholder meetings, best practice monitoring procedures and the wealth of

knowledge and research available for the site.

Supervising Scientist Branch (SSB) held a Pit 1 monitoring objectives workshop on 23 November 2018. The outcomes of this workshop were shared with ERA on 26 November

2018 (Leggett, Amie. 26 November 2018) and discussed at the internal ERA workshop held

on 27 November 2018.

Parallel to these workshops, the 41st Alligator Rivers Region Technical Committee (ARRTC)

meeting was held in Darwin on 13-14 November 2018. ARRTC members were actioned to

provide input recommendations to the Pit 1 monitoring requirements.

• ACTION 41.2: ARRTC to consider what parameters should be monitored on the Ranger Trial Landform to inform relevant KKNs. While this would include parameters informing plant available water modelling (WAVES), they should also be broadened if necessary to consider parameters informing the design of future research and monitoring for Pit 1 rehabilitation

• ACTION 41-4: ARRTC to provide input into planning and implementing an adaptive management approach to Pit 1 rehabilitation, including reviewing the detailed plans of ERA/SSB for any additional studies and monitoring that are required to inform the Key Knowledge Needs and the broader rehabilitation project.

Subsequent communication and feedback via email and meetings was also incorporated into

the design of this framework (Dixson, Kingsley. 11 December 2018, Leggett, Amie. 18 December 2018, Leggett, Amie. 20 December 2018, Leggett, Amie. 21 December 2018,

Rumpff, Libby. 13 December 2018, Zichy-Woinarski, John. 11 December 2018).




This framework focusses on monitoring and research activities that may be conducted to ensure successful rehabilitation of the Pit 1 area (Figures 2-3) and inform ongoing progressive

rehabilitation across the Ranger site.

To ensure clarity throughout this document the terms monitoring and research have been defined as:

Monitoring – repeated measurement of target indicator parameters that are linked to

trigger/threshold values that may invoke a management action.

Research – a defined study with a clear hypothesis and defined objective/s that is designed to inform a specific knowledge gap.

Monitoring data may be incorporated into a research program with properly constructed

hypotheses. Likewise, research activities may be incorporated into a monitoring program with suitable action triggers established.

The Pit 1 Rehabilitation Monitoring Framework consists of two distinct monitoring phases:

construction; and ecosystem establishment. A separate section on defined research studies associated with Pit 1 is also included.

It is intended that the Pit 1 monitoring framework provides the basis for the progressive

rehabilitation monitoring plan for the Ranger site. Lessons learned from the monitoring and research outcomes from Pit 1 will be incorporated into the site monitoring plan as required

under an adaptive management framework.

The location and set out of the Ranger Mine and Pit 1 is shown in Figures 1-3.

Figure 1 Ranger uranium mine location




Figure 2 Aerial imagery of Ranger Mine layout with Pit 1 identified (Photo capture June 2018)




Figure 3 High-resolution image of Pit 1 area (Photo capture June 2018)




2 PIT 1 REHABILITATION SCHEDULE

The Pit 1 rehabilitation schedule comprises two main phases: construction; and ecosystem

establishment (Table 1). The construction phase consists of:

• Backfill with detailed tracking of fill material in regard to material grade (3112-01) • Construction of the final landform topography (3112-03/04) • Survey and sign-off of final landform topography (3112-05).

Once the final landform has been created and meets required specifications the ecosystem

establishment phase will be undertaken, although some activities such as tube-stock growth

and weed spraying will be undertaken between the two phases as required.

At this time the construction phase extends from 01-May-19 through to 25-Aug-20 and the

ecosystem establishment phase extends from 15-May-20 to 04-Nov-22 (Table 1).

The Pit 1 rehabilitation monitoring framework will extend from May 2019 to 2026 to provide for a continuous monitoring framework from rehabilitation to closure.

Table 1 Pit 1 rehabilitation schedule (indicative pending appropriate approvals) provides information as provided from Closure Execution schedule.

Project code

Activity Identifier code

Scheduled Start date

Scheduled End date

Pit 1, backfill and capping and final landform (3110, 3111, 3112) 3112-01 1s to Pit 1 Backfill 275 01-May-19 01-Feb-20

3112-03 1s to Final Landform Pit 1 120 05-May-20 07-Jul-20

3112-04 Final Landform Details by Dozer Pit 1 34 14-Jul-20 15-Aug-20

3112-05 As-Built Surveying Pit 1 10 15-Aug-20 25-Aug-20

Revegetation – Pit 1 (3113) 3113-01 Handover of site – Pit 1 Area 0 15-Aug-20

3113-02 Seed Planting and Growing – Pit 1 Area 92 15-May-20 15-Aug-20

3113-03 Initial Weed Spraying – Pit 1 Area 24 15-Aug-20 08-Sep-20

3113-04 Cultivation Period – Pit 1 Area 48 08-Sep-20 24-Oct-20

3113-05 Irrigation Installation – Pit 1 Area 90 24-Oct-20 04-Feb-21

3113-06 Initial Planting – Pit 1 Area 375 04-Feb-21 06-May-22

3113-07 Irrigation Starts (First 3 Months) – Pit 1 Area

90 06-May-22 04-Aug-22

3113-08 Irrigation for 3-6 Months – Pit 1 Area 90 04-Aug-22 04-Nov-22

3113-08 Inspection/Monitoring for Mortality – Pit 1 Area

1 04-Nov-22 04-Nov-22




3 CONSTRUCTION PHASE MONITORING

The construction phase will result in a final landform that complies with the planned landform design. Key elements include:

• Burial of all tailings materials to designed depths • Staged back fill with higher grade material (grade 2) buried deeper and lower grade

material (grade 1) forming the landform surface layer (Table 2). • Shaping into the planned landform topography • Installation of water and sediment traps at landscape outflow locations • Micro-topography construction that may include ripping and placement of surface

materials.

Ranger mine is currently operating under the requirements detailed in the Ranger

Authorisation to Operate (current version 0108 issued June 2018). The requirements provide

a comprehensive set of monitoring and reporting schedules that help to ensure the protection of the surrounding environment and communities. The Ranger Authorisation requirements

will continue throughout the construction phase of Pit 1 rehabilitation and they will be

enhanced with the additional monitoring and research described in this Framework. As per the requirements in the Ranger Authorisation to Operate, the following reporting and

monitoring will continue as normal during the construction of Pit 1:

• Mining Management Plan

• Annual Radiation and Atmospheric Monitoring Interpretative Report

• Tailings Dam Surveillance Reports

• Water Management Plan

• Annual Groundwater Report

• Whole of Site Groundwater Conceptual Model

• Groundwater Monitoring Plan

• Provision of Monitoring Data, including routine Water Quality Reports

• Surface Water Wet Season Report

• Rehabilitation Progress Report

Further detail on Pit 1 construction is provided in the Ranger Mine Closure Plan (MCP 2018).




Table 2 Indicative ore grades and mineral type

Grade Grade (% U3O8) Material type

1980-1997 1998-2009 2010-Current 1 <0.02 <0.02 <0.02 Un-mineralised rock

2 0.02-0.05 0.02-0.08

Low 2

0.02-0.06 Very low grade ore

High 2

0.06-0.08 Low grade ore

3 0.05-0.10 0.08-0.12 0.08-0.12 ore

4 0.10-0.20 0.12-0.20 0.12-0.20 ore

5 0.20-0.35 0.20-0.35 0.20-0.35 ore

6 0.35-0.50 0.35-0.50 0.35-0.50 ore

7 >0.50 >0.50 >0.50 ore

The Pit 1 Construction Phase monitoring framework focusses on all aspects relevant to Pit 1 rehabilitation (Table 3), thus key elements relating to the physical construction approach and

final landscape shape are the focus of this framework. A Trigger, Action, Response, Plan

(TARP) is presented in Table 4 and includes management actions should a threshold be exceeded.

Issued date: 09/04/19 Page 12 Unique reference: ERA-002 Revision number: V2


Table 3 Pit 1 Construction Phase Monitoring Framework (May 2019-Aug 2020)

Aspect Objective/s Method Variable Frequency Tailings consolidation

Confirm tailings consolidation Settlement monitoring plates Change in level of settlement

Monthly

Material placement

Confirm 2s material placed at basal levels

Implementation of the dynamic mine model created for ERA, (AMC, 2018)

Material load placement log Daily

Survey Regular surface levels Weekly

Confirm 1s material placed as surface layer

Implementation of the dynamic mine model created for ERA, (AMC, 2018)

Material load placement log Daily

Survey Regular surface levels Weekly

Surface topography

Confirm final surface topography for Landscape Evolution Model (LEM). Confirm built to design requirements

High resolution DEM Surface Elevation Annual post wet season LEM rerun if required

Topographic survey Cross-sections and/or levels

Once; post construction

Quantify landscape settlement Year on year DEM change detection Surface level change Annual

Topographic survey Cross-sections and/or levels

Annual

Quantify sediment transport Year on year DEM change detection DEM change Annual

Surface micro-topography

Describe surface micro-topography High resolution DEM and field survey Surface DEM and surface complexity

After land forming and annually after wet season

GPS on ripping machinery, field mapping or remote sensing

Ripped areas Once, after ripping is complete



Aspect Objective/s Method Variable Frequency

Landscape denudation and erosion

Quantify site denudation rate (suspended load)

BACIP designed turbidity monitoring (Moliere and Evans 2010)

Stream turbidity Continuous logged in flowing water

Quantify gully erosion High resolution DEM Surface DEM Annual post wet season

Field assessment Field notes Annually after wet season

Quantify sub-catchment bedload sediment movement

Measurements from sediment traps Transported sediment volume


Surface water management

Ensure all surface water runoff is captured and managed

Pumping of water from Pit 1 pond water sump to RP2

Continuous monitoring During and following rainfall periods



Table 4 Pit 1 Construction Phase: Trigger, Action, Response Plan (TARP)


Materials placement

Site: Whole of landscape via tracking system. Parameters: Material character and volume. Analysis: Dynamic mine model with associated tracking methods. Within landform levels during construction. Frequency: Ongoing, as per Table 3, as landscape is built.

Describe and verify material strata within final Pit 1 landform

Internal strata vary in a manner that increases risk of higher-grade materials exposure

Stop construction. Remove or reshape current level to conform with design plan


Surface topography

Site: Whole of landscape Parameters: Topography Analysis: Comparison of DEM and survey to planned landform Frequency: Once off. When practical upon completion of final landform

Describe final landform against planned landform. Confirm LEM predictions for tailings encapsulation Potentially provide updated information for LEM

Final landform varies significantly from planned landform and subsequent LEM results show critical erosion over tailings areas

Reshape landform or armour potential erosion areas until LEM results comply with 10,000 year requirement


Surface settlement

Site: Whole of landscape Parameters: Topography Analysis: Comparison of DEMs and survey Frequency: Annual

Quantify topographic settlement rates







Sediment transport

Site: Whole of landscape Parameters: Topography Analysis: Comparison of DEMs and survey Frequency: Annual

Quantify site scale denudation rates

Site denudation rate is significantly higher than predicted




Site: Whole of landscape Parameters: Topography Analysis: Comparison of DEMs and field survey Frequency: Annual

Describe site scale micro-topography

Microtopography does not conform to planned landscape distribution pattern

Alter microtopography through ripping, grading, placement of material or other works


Surface ripping

Site: Planned ripped areas Parameters: Area Analysis: mapping via GPS tracking, field survey or remote sensing Frequency: Once after landform creation

Map ripped areas Ripping does not conform to planned ripped area

Undertake works to amend ripping area


Landscape erosion (gullying)

Sites: Sensitive receptor areas and drainage channels Parameters: DEM analysis and field inspection, notes and photographs Analysis: Identify erosion problem areas Frequency: Annually after the wet season



Site-based plan and action as required. Repairs to area identified





Bedload

Sites: Watercourses that direct water off site and associated sediment basins Parameters: Field inspection, notes and photographs Analysis: Identify bedload moving off site Frequency: Biannually before and after the wet season

Identify bedload being transferred to sediment traps

Bedload transport rates significantly beyond those of trial landform

Site-based plan and action as required. May require additional works including modifying the sediment control basins


Landscape erosion (turbidity)

Sites: Monitoring points upstream and downstream of site Parameters: Turbidity (fine suspended sediment (FSS) Analysis: BACIP analysis (Moliere & Evans, 2010) Frequency: Ongoing monitoring, analysis after wet season

Identify site scale erosion rates

Turbidity trajectory not transitioning to control environment levels after 5 years



Surface water management during construction

Site: Whole of landscape Parameters: EC Analysis: Surface water runoff management Frequency: During and after rainfall periods.

Monitor surface water quality

EC trigger; As per section 5.8 Pit 1 Catchment Management in RWMP 2018/19

Investigation as per section 5.8 Pit 1 Catchment Management in RWMP 2018/19


Issued date: 09/04/19 Page 17 Unique Reference: ERA-002 Revision number: V2


4 ECOSYSTEM ESTABLISHMENT PHASE

This section describes the Pit 1 monitoring framework for the ecosystem establishment phase (15 May 2020 to closure in 2026), noting that it is a part of the planned whole-of-site monitoring for landform, water (ground and surface), radiation and ecosystem processes.

The Pit 1 Ecosystem Establishment monitoring framework focusses on those aspects relevant to this phase of Pit 1 rehabilitation (Table 5). A Trigger, Action, Response, Plan (TARP) is presented in Table 6 and includes management actions should a threshold be exceeded.

During the ecosystem establishment phase of Pit 1, monitoring of radiation will continue to be undertaken as per the Ranger Authorisation to operate and those plans will be in effect. However, specific radiation assessment research tasks will be undertaken (Table 7).



Table 5 Pit 1 Ecosystem establishment phase monitoring (Aug 2020 – Nov 2022)

Theme: Landform


Surface topography

Quantify landscape settlement Year on year DEM change DEM change Annual

Topographic survey Cross-sections and levels Annual


Describe surface micro-topography High resolution DEM and field survey

Surface DEM and field notes After land forming and annual after wet season

Landscape denudation and erosion

Quantify site denudation rate (suspended load)

BACIP designed turbidity monitoring (Moliere and Evans 2010)

Stream turbidity Continuous logged in flowing water

Quantify gully erosion High resolution DEM Surface DEM Annual post wet season

Field assessment Field notes Annually after wet season

Quantify sub-catchment bedload sediment movement

Measurements from sediment traps

Transported sediment volume Annually after wet season

Erosion control

Confirm erosion control structure function

Field inspection Field notes and records Annually after wet season



Theme: Water


Surface water quality

Confirm water leaving Pit 1conforms to the approved Water Management Plan

Multiple telemetered probes

Designed sub-catchment water and sediment traps

Grab samples from sumps etc with lab analysis

Solutes, EC, TSS, COPC, Total P, Total N, NH4, Turbidity, radionuclides

Continuous and grab samples

Confirm water quality in adjacent/connected water sources

Multiple telemetered probes

Grab samples from sumps etc with lab analysis

Solutes, EC, TSS, COPC, Total N, Total P, NH4, Turbidity, radionuclides

Continuous and grab samples as per WMP

Surface water quantity

Monitoring discharge leaving landform Designed sub-catchment water and sediment traps

Discharge Continuous with flow

Model surface water runoff DEM based rainfall/runoff model

Discharge As required to correlate with discharge measurement and provide input to water balance

Groundwater seepage and contaminant transport

Define groundwater movement and quality dynamics

Monitor bore network develop new bores as required

Groundwater modelling (INTERA project)

Groundwater flow and quality Continuous sampling and dynamic model



Theme: Water


Groundwater heads

Monitor ground water heads Monitor bore network develop new bores as required

Groundwater modelling (INTERA project)

Bore level Continuous sampling

GW surface water interaction

Better understand GW-SW interaction if any

Bore logging (INTERA project)

Bore level and water quality

Grab samples

Continuous sampling and as sampled

Theme: Ecosystem


Plant species distribution and survival

Confirm species distribution conforms to plan

Document plant survival

Planting plan and log of species planting location

Plant species, stems per species

During planting

Survey quadrats, field transects

Plant species and survival 3 month, 6 months, annually

Plant growth rate

Document plant growth rate Survey quadrats Height, DBH 3 month, 6 months, annually

Canopy Cover Document canopy cover Survey quadrats Canopy cover % 3 month, 6 months, annually

Plant recruitment

Document plant recruitment Survey quadrats Recruitment occurrence and species (flowering, fruiting, emergence)

3 month, 6 months, annually



Theme: Ecosystem


Weather monitoring

Determine site weather conditions Weather station and observation

Rainfall, temperature, humidity, ET

Ongoing

Irrigation Confirm irrigation performance Inspection Irrigation function Daily/weekly

Weed management

Control and/or eliminate all priority weeds Visual inspection Weed presence and abundance

Daily/weekly with other checks

Flora pests and diseases

Monitor plant pests and diseases Visual Presence of pest or disease Daily/weekly with other checks

Ground cover Monitor development of groundcover Survey quadrats Species, % cover, litter % 3 month, 6 months, annually

Nutrient cycling

Understand edaphic process Soil/sediment survey and analysis

Soil nutrients, microbes, soil chemistry

Baseline and 5 years

Fauna colonisation

Document fauna on site Opportunistic observation during other surveys

Species Opportunistic

Fauna pests Monitor and control fauna pests Visual inspection for animals and animal impacts

Fauna pest species Ongoing



Theme: Ecosystem


Fire exclusion Confirm fire exclusion Visual inspection Presence/absence (location) As required

Tube-stock quality

Confirm tube-stock quality and viability Inspection of tube-stock in nursery and upon planting

Root binding, disease ongoing

Bush foods (aquatic and terrestrial)

Document contaminants levels in bushfoods

Field sampling Laboratory analysis for contaminants

Baseline and every 2nd year



Table 6 Ecosystem establishment phase TARP

Theme: Landform

Aspect Monitoring Response

Method Purpose Trigger Action Responsibility

Surface topography Site: Whole of landscape Parameters: Topography Analysis: Comparison of DEMs and survey Frequency: Annual

Quantify topographic settlement rates





Site: Whole of landscape Parameters: Topography Analysis: Comparison of DEMs and field survey Frequency: Annual

Describe site scale micro-topography

Micro-topography does not conform with planned landscape distribution pattern

Alter microtopography through ripping, grading, placement of material or other works


Bedload

Sites: Water courses that direct water off site and associated sediment basins Parameters: Field inspection, notes and photographs Analysis: Identify bedload moving off site Frequency: Bi-annually before and after the wet season

Identify bedload being transferred to sediment traps

Bedload transport rates significantly beyond those of trail landform





Theme: Landform



Landscape erosion (gullying)

Sites: Sensitive receptor areas and drainage channels Parameters: DEM analysis and Field inspection, notes and photographs Analysis: Identify erosion problem areas Frequency: Annually after the wet season



Site-based plan and action as required Repairs to area identified


Landscape erosion (Turbidity)

Sites: Monitoring points upstream and downstream of site Parameters: Turbidity (fine suspended sediment (FSS) Analysis: BACIP analysis (Moliere & Evans, 2010) Frequency: Ongoing monitoring, analysis after wet season

Identify site scale erosion rates

Turbidity trajectory not transitioning to control environment levels after 5 years



Erosion control structures

Sites: Site structures and works Parameters: Field inspection, notes and photographs Analysis: Identify problem areas Frequency: Annually after the wet season

Confirm function of erosion control structures

Structures not function or compromised

Site-based plan and action as required. Repairs to area identified




Theme: Water



Surface water quality (Pit 1)

Sites: sub-catchment designed exit points Parameters: water quality Analysis: Probe and grab sample Frequency: Continuous and grab sample


Water quality does not meet release water quality standards

Divert away from release water circuit. Evaluate reason for exceedance and implement remediation and amelioration works


Surface water quality (offsite receiving environments)

Sites: Defined receiving site Parameters: water quality Analysis: Probe and grab sample Frequency: Regular sampling through year


Samples exceed Magela Creek trigger values (As per Annex C.1 of the Authorisation “Water Quality Objectives for Magela Creek and Gulungul Creek”)

As per Turner et al 2015


Groundwater seepage and contaminant transport

Sites: Bore network Parameters: Water levels and water quality Analysis: Physical and chemical analysis of samples Frequency: Standing water level monthly, chemical analysis quarterly

To confirm groundwater level, movement and chemistry is behaving according to modelled predictions, and to increase model performance and power through additional data input

Analysis indicates that groundwater is exceeding model predictions





Theme: Water



GW surface water interaction

Sites: Bore network Parameters: Water level and water quality Analysis: Physical and chemical analysis of samples Frequency: Standing water level monthly, chemical analysis quarterly

To confirm groundwater interaction, if any, with key surface water sites

Analysis indicates groundwater ingress into surface water sites

Site-based plan and action as required.


Theme: Ecosystem



Flora composition performance and distribution

Sites: Vegetation plots across entire site Parameters: Provenance, species composition (tree and shrubs) and species relative abundance, survival, canopy architecture, canopy cover index, ground cover index, tree distribution, flowering fruiting, seeding, juveniles, overall condition. Analysis: vegetation survey analysis Frequency: three, six and 12 months (year 1); annually

To determine whether species composition and community structure is similar to adjacent areas of KNP

Values do not conform with closure criteria


Principal Advisor Rehabilitation and Ecology (or delegate)



Theme: Ecosystem



Irrigation Sites: associated with planting Parameter: Functioning irrigation system Analysis: inspection Frequency: ongoing until irrigation removed

Ensure functional irrigation system

Irrigation failure or poor performance

Mend irrigation system


Weed management

Sites: Pit 1 site Parameter: Priority weed presence Analysis: Field survey and inspection Frequency: Prior to planting and ongoing associated with vegetation surveys and other site traverses

Assess weed presence, species and abundance

Priority or other weeds present

Weed management (generally spraying) until weeds are no longer present


Nutrient cycling Sites: Pit 1 and TLF Parameter: soil edaphic processes Analysis: Soil pit and analysis Frequency: year 1 and 5

Understand soil formation processes and nutrient cycling

Poor soil formation and nutrient processes affecting plant development

Site-based analysis and ameliorant plan and application


Fauna pests Sites: Pit 1 Parameter: Fauna pest present Analysis: Visual survey Frequency: Ongoing, all staff to report signs of fauna pests

Minimise impact of feral pests on rehabilitation

Presence of pests Implement appropriate pest management




Theme: Ecosystem



Bush foods (aquatic and terrestrial)

Sites: Onsite and selected offsite targets Parameter: Food pollutants and toxins Analysis: Field sampling and analysis Frequency: year 1 and 5

Understand potential for contamination of aquatic species

Trigger levels of contaminants found

Remove access to food source and undertake site and source amelioration




5 PIT 1 RESEARCH PLANNING - PRESENT TO 2026

Ranger mine has developed a list of targeted research projects to inform the creation of a safe and stable final environment. The research tasks listed here are targeted specifically to inform rehabilitation success and are focussed on Pit 1 relevant studies.



Table 7 Pit 1 targeted research tasks

Theme: Landform

Aspect Objective/s Method

Particle size distribution

Understand Pit 1 surface and top layer particle size distribution

Measures of surface sediment calibre distribution profile appropriate for material type.

Stock pile drilling

To describe the release behaviour and source concentrations of all COPCs over time from each of the waste rock and tailings-derived source materials

INTERA project

Theme: Water


Water balance

Develop Pit 1 water balance model

Identify key parameters that require additional studies (e.g. evaporation and ET, runoff, infiltration, deep drainage and recharge, changes in soil water at key depths related to roots and waste rock dump levels)

Undertake targeted studies to complete water balance model

Undertake a specific pit 1 water balance study. Identify key parameters that require additional verification and undertake specific studies to measure these parameters.



Herbicide fate Understand the fate of glyphosate herbicide in the environment following application and run-off

Develop a trial water quality sampling and analysis program with stakeholders to examine the fate of glyphosate herbicide when it has been applied to an area of weed/grass cover and bare rehabilitation landscape and subjected to watering/rainfall and run off.

Groundwater Understand Pit 1 groundwater processes Develop additional bores and undertake site scale monitoring and modelling of groundwater quality, quantify and movement.

Wetland filter process

Understand the water and sediment condition of receiving wetland filter areas

A water and sediment sampling and analysis program to understand the current condition of the Pit 1 wetland filter receiving areas.

Theme: Ecosystem


Fauna colonisation

Understand fauna colonisation at early stages of rehabilitation

Targeted fauna studies after year 1 and 5 of Pit 1 planting. Surveys developed to specifically early stage fauna such as insects and birds. Field design could follow the pattern established for flora quadrat surveys.

Opportunistic records of fauna observations undertaken during regular surveys and inspections.



Fauna translocation

Understand efficacy of translocating critical ecosystem engineer species

In conjunction with fauna studies at other sites develop a study to understand colonisation of critical ecosystem engineering species within rehabilitated areas on site and, if necessary, develop a plan to translocate these species if required. If translocation is required a translocation monitoring study should be developed.

Disturbance Understand recovery from disturbance No disturbance is planned during the period covered by this plan. However, should disturbance through fire, disease, wind or other cause occur a disturbance specific assessment and knowledge capture study will be developed and implemented.

Theme: Radiation


Radon-222 exhalation flux densities

To verify that radon-222 exhalation flux densities Radon-222 exhalation surveys

Gamma dose rates, waste rock radium-226 activity concentration

To validate predictions on the surface waste rock uranium content

Ground-based gamma dose rate survey



5.1 Whole of site studies

In addition to the studies (research and monitoring) designed specifically considering Pit 1 rehabilitation, several whole of site studies are progressing as parallel programs. These include:

• Nursery establishment and management processes to ensure the quantity and quality of seed and tube-stock

• Trial Landform studies will continue to examine ecosystem establishment processes including:

O Soil development O Plant survival O Native species recruitment O Fauna establishment and usage O Pest and weed treatment

• Trial landform excavation studies O Two pits were excavated in March 2019 on the trial landform to collect samples and

information to inform further particle size distribution studies and root observation studies.

• ERA is currently undertaking waste rock stockpile oxidation rate studies.



6 REHABILATION FRAMEWORK REVIEW AND STAKEHOLDER COLLABORATION

To ensure the continued refinement of the proposed monitoring framework, the framework will be reviewed by ERA staff in consultation with stakeholders every 12 months and a review outcomes report provided to stakeholders.

A Ranger Rehabilitation – Monitoring Evaluation and Research Review Group will be formed by ERA and include stakeholder group representatives. This review group will be chaired by ERA and will enable collaboration between key stakeholder groups to ensure research programs are developed and refined during the progressive rehabilitation of the Ranger mine. Implementation of additional studies outside of Pit 1 (TLF, nursery etc.) will also be discussed, developed and refined in this review group.



7 REFERENCES

ERA 2018. Ranger Water Management Plan (1 October 2018), Energy Resources of Australia.

MCP 2018. Ranger Mine Closure Plan, Energy Resources of Australia.

Moliere, D & Evans, K 2010. Development of trigger levels to assess catchment disturbance on stream suspended sediment loads in the Magela Creek, Northern Territory, Australia. Geographical Research, 48 370-385.

SSB 2018. Ranger Progressive Rehabilitation Monitoring Workshop Meeting Notes (4 September 2018).

Turner K, Tayler K & Tyrrell JWR 2015. Revised Ranger Mine Water Quality Objectives for Magela Creek and Gulungul Creek. Internal Report 638, December, Supervising Scientist, Darwin.

Personal communications

Dixson, Kingsley. 11 December 2018. Re: ARRTC 41 – Action Item 41.2 (Due 13 Dec ’18). (Curtin University).

Leggett, Amie. 26 November 2018. Pit 1 Monitoring Objectives – information for ERA. (Supervising Scientist Branch).

Leggett, Amie. 18 December 2018. FW: Pit 1 Monitoring. (Supervising Scientist Branch).

Leggett, Amie. 20 December 2018. FW: Pit 1 monitoring. (Supervising Scientist Branch).

Leggett, Amie. 21 December 2018. FW: Pit 1 monitoring. (Supervising Scientist Branch).

Rumpff, Libby. 13 December 2018. Re: ARRTC 41 – Action Item 41.2 (Due 13 Dec ’18). (University of Melbourne).

Zichy-Woinarski, John. 11 December 2018. Re: ARRTC 41 – Action Item 41.2 (Due 13 Dec ’18). (Charles Darwin University).

APPENDIX 12.2: PLUME AND CONTAMINATED SITE MANAGEMENT PLAN

ERA Project Management Plan Ranger Closure Feasibility Study Project Management H355334 Plume and Contaminated Site Management Plan

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Ver: 03.04 © Hatch 2018 All rights reserved, including all rights relating to the use of this document or its contents.

Plume and Contaminated Site Management Plan

H355334-00000-201-230-0006

2018-10-08 0 Approved for Use C. Hart-Davies D. Bademosi B. Smyth S. Gallagher

DATE REV. STATUS PREPARED BY CHECKED BY APPROVED BY APPROVED BY

Discipline Lead Functional Manager Client


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Table of Contents

1. Introduction ..................................................................................................................................... 1

2. Purpose ........................................................................................................................................... 2

3. Scope ............................................................................................................................................... 3

4. Contaminated Land Management Objectives and Requirements ............................................. 4

4.1 Preferred Closure Strategy ..................................................................................................... 4 4.2 Final Land Use ........................................................................................................................ 4 4.3 Regulatory Requirements ....................................................................................................... 5

4.3.1 Northern Territory Contaminated Land Requirements .............................................. 5 4.3.2 National Contaminated Land Guidelines ................................................................... 7 4.3.3 Closure Objectives and Criteria ................................................................................. 8

4.4 Best Practicable Technology Assessment ........................................................................... 16 4.5 Rio Tinto Requirements ........................................................................................................ 17

5. Existing Knowledge Base ............................................................................................................ 18

5.1 Surface Water and Sediment ................................................................................................ 18 5.2 Constituents of Potential Concern ........................................................................................ 19 5.3 Groundwater Contamination ................................................................................................. 20 5.4 Ranger Conceptual Model .................................................................................................... 21

5.4.1 Processing Plant Area Conceptual Model ............................................................... 22 5.4.2 Land Application Areas Conceptual Model ............................................................. 24

6. Contaminated Land Management at Closure ............................................................................ 27

6.1 Summary ............................................................................................................................... 27 6.2 Final Landform Construction ................................................................................................. 27

7. Contaminated Land and Plume Register ................................................................................... 31

8. Future Work Programs ................................................................................................................. 38

8.1 Future BPT assessments ..................................................................................................... 38 8.2 Further Site Assessment Required ....................................................................................... 39

9. Validation ....................................................................................................................................... 41

10. Monitoring for Closure ................................................................................................................. 42

11. Reporting ....................................................................................................................................... 43

11.1 Accountability and Ownership .............................................................................................. 44

12. References .................................................................................................................................... 45


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List of Tables Table 4-1: Closure Criteria - Soils ........................................................................................................ 11 Table 4-2: Closure Criteria - Radiation ................................................................................................ 12 Table 4-3: Closure Criteria - Water and Sediments ............................................................................. 13 Table 4-4: Closure Criteria - Cultural ................................................................................................... 15 Table 6-1: Summary values for reclamation areas .............................................................................. 27 Table 7-1: Contaminated Site Remediation Options ........................................................................... 35

List of Figures Figure 5-1: U and Mn soil concentration versus depth; generally decreasing over depth (ERA & ELA 2018) ..................................................................................................................................................... 24 Figure 5-2: Location of LAAs and associated monitoring bores discussed herein .............................. 25 Figure 6-1: Reclamation areas ............................................................................................................. 28 Figure 6-2: Processing plant area, including ROM pad ....................................................................... 29 Figure 6-3: Backfill contour map .......................................................................................................... 30 Figure 7-1: Major Site Areas ................................................................................................................ 32 Figure 7-2: Processing Plant Area ....................................................................................................... 33 Figure 7-3: Contaminated Sites Register ............................................................................................. 34

List of Appendices

Appendix A Contaminated Site Register

Appendix B Natural Attenuation Requirements


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1. Introduction The Ranger uranium mine (Ranger/Ranger mine) is located within the Ranger Project Area (RPA) adjacent to Jabiru, approximately 260 kilometres (km) east of Darwin in the Alligator Rivers Region of the Northern Territory (NT). Energy Resources of Australia Ltd (ERA) has owned and operated the Ranger mine since the commencement of operations in 1980. The RPA is surrounded by Kakadu National Park (KNP). Under current operational approvals, ERA is permitted to undertake mining and milling activities in the RPA until 8 January 2021, with final rehabilitation and closure activities to be completed by 8 January 2026.

Soils and sediments on the RPA have become contaminated through treatment of pond water in wetlands and bunds, irrigation of pond water in the land application areas (LAAs), the accumulation of low level contaminants in waters passing through billabongs, and seeps and spills in the plant areas. Groundwater plumes associated with the existing tailings dam and the process plant area have also been identified as a potential source of contamination.

ERA have developed and implemented a Hazardous Material and Contamination Control Plan to ensure that contaminated sites are appropriately characterized and managed in accordance with the Rio Tinto Environmental Standards and relevant regulatory requirements. In accordance with this plan a Contaminated Sites Register (CSR) has been developed and maintained to identify all sites that have supported land use activity that has potential to contaminate. The CSR was initially developed in 2004 and has been regularly updated. The CSR is warehoused in GIS format and includes, but is not limited to, information on the location, land use activity, potential contaminants and an assessment of the risk the contaminants pose to the surrounding environment, including human health.

In combination with the register development, a number of targeted assessments were undertaken on the RPA at known contaminated sites. While the focus of these assessments was predominantly identifying groundwater contamination, soil profiles were completed at known contaminated sites to define the lateral extent of contamination in the soils and shallow groundwater. This data has been used to develop conceptual site models for known areas of contamination, which are used to understand migration of Contaminants of Potential Concern (COPC) through soils, groundwater, and surface water under current and post-closure conditions. The contamination risks and remediation requirements of other sites have not yet been fully assessed.

The Mine Closure Plan (MCP) (ERA & ELA 2018) has identified that contaminated soils pose a potential risk to the surrounding environment, including human health. An objective for closure is that, where needed, soils will be remediated to a level where their environmental impact is as low as reasonably achievable to protect the environment.

A plan for the management of plumes and contaminated land at closure, and a plan for further contaminated site assessment work, are required as an input to the Ranger Mine Closure Project Execution Plan.


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2. Purpose The purpose of this document is to present:

• An updated CSR that identifies potentially contaminated sites and plumes; and

• A plan for the management of contaminated land and plumes.

These will be inputs to the Project Execution Plan.

This document also details further work to be undertaken to determine risks from contaminated land and plumes and develop plans for their management during closure.


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3. Scope The CSR includes sites at the following locations:

• Jabiru East

• LAAs

• Mining Footprint

• Operation Footprint

• Pit 1

• Retention Ponds

This plan excludes management of contaminated land at sites at the Jabiru Township and Jabiru airport and the remediation of Ranger 3 Deeps (R3D) will be addressed separately. The management of waste rock and tailings is also addressed elsewhere.


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4. Contaminated Land Management Objectives and Requirements An MCP (ERA & ELA 2018) has been prepared as part of ERA's obligations under the NT Mining Management Act 2001 (Mining Management Act)and details the closure strategy for the RPA, closure objectives and legal and other requirements for closure. Closure objectives and requirements and closure implementation activities relevant to contaminated land and plume management are summarised in this section.

4.1 Preferred Closure Strategy The preferred closure strategy involves backfilling of Pit 1 and Pit 3 following tailings deposition, starting with the most contaminated materials (grade 2 very low grade ore) and then the residual waste material remaining on the land surface at closure, including contaminated soils. The final landform will be constructed using waste rock with specific design features to minimise erosion and sediment discharge from the final landform. The designed final landform will also ensure a sufficient growth substrate. Temporary passive water and sediment management structures (e.g. sumps and sediment traps) will be constructed around the perimeter of the landform, designed to manage runoff during the early years of establishment (ERA & ELA 2018).

4.2 Final Land Use The Ranger Environmental Requirements (ERs) specify that the RPA needs to be returned to a state in which it could be incorporated in the KNP:

“….the company must rehabilitate the Ranger Project Area to establish an environment similar to the adjacent areas of Kakadu National Park such that, in the opinion of the Minister with the advice of the Supervising Scientist, the rehabilitated area could be incorporated into the Kakadu National Park.”

Any decision on the actual incorporation of the site to KNP will be made by the relevant authority and may not eventuate until some time after closure. Therefore, the use of the final landform by local Aboriginal people (on the condition that they are satisfied that the area is safe) is considered to be the most likely final land use. A detailed consultation with traditional owners regarding their planned use of the site by has been conducted (Garde, 2015) and identified the following land uses:

• Customary harvesting of bush foods and medicine;

• Recreation;

• Land management activities; and

• Cultural site visitation and ritual responsibilities (ERA & ELA 2018).


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4.3 Regulatory Requirements Operations at Ranger are governed by both Australian and Northern Territory legislation and regulations. The key instrument that governs operations at the Ranger mine on a day-to-day basis is the Ranger Authorisation issued under the Mining Management Act (Authority 0108). The Ranger Authorisation incorporates the Environmental Requirements (ERs), which are attached to the section 41 (s.41) Authority issued by the Australian Government under the Atomic Energy Act 1953 (Cth) (Atomic Energy Act). Final signoff on rehabilitation of the site will be provided by the Northern Territory Minister for Primary Industry and Resources and Commonwealth Minister for Industry Innovation and Science acting on advice from the Supervising Scientist.

ERA has prepared the Ranger Mining Management Plan 2018 (ERA 2018) in accordance with the requirements of both the Department of Primary Industry and Resources ‘Template for the Preparation of a Mining Management Plan’ the Mining Management Act, and the ‘Ranger Annual Environment Report’ to comply with the requirements of Annex C of the Ranger Authorisation 0108. Activities carried out on the RPA continue to be consistent with the approved MMP.

The primary environmental legislation dealing with contaminated sites in NT is the NT Waste Management and Pollution Control Act 2016 (WMPC Act). The WMPC Act “does not apply in relation to a contaminant or waste that results from, directly or indirectly, the carrying out of a mining activity”. However, the ER 3.2.3 requires the operation to conform with the most recently published and relevant Australian standards, codes of practice and guidelines. One of the objectives of the WMPC Act is to facilitate the implementation of the National Environment Protection (Assessment of Site Contamination) Measure 1999 (NEPM ASC or NEPM), made under the National Environment Protection Council Act 1994 (NEPC Act). Therefore, the contaminated land assessment and management at Ranger conforms with the WMPC Act and relevant national environment protection measures.

4.3.1 Northern Territory Contaminated Land Requirements The objectives of the WMPC Act are:

• To protect, and where practicable to restore and enhance the quality of, the territory environment by:

preventing pollution

reducing the likelihood of pollution occurring

effectively responding to pollution

avoiding and reducing the generation of waste

increasing the re-use and re-cycling of waste

effectively managing waste disposal


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to encourage ecologically sustainable development

to facilitate the implementation of national environment protection measures made under the NEPC Act.

The Northern Territory (NT) Environment Protection Authority (EPA) requires contaminated sites that pose or threaten to pose serious or material environmental harm as defined in the WMPC Act to be assessed in accordance with the NEPM ASC.

The NT Contaminated Land Guideline (NT EPA 2017) has been developed by the NT EPA to describe the framework for the assessment and remediation of contaminated land.

The current approach to contaminated land management in NT is to deal with contaminated sites on a case-by-case basis, generally following guidance set out in the NEPM during the investigation stages (Scott & McInerny 2014). Remediation goals and strategies are site specific and based upon factors including risk, cost and proposed use of the land. Site specific remediation criteria can be developed, but largely, the NEPM ASC investigation levels form the remediation targets.

In cases where no readily available or economically feasible method is available for remediation, it may be possible to adopt appropriate regulatory controls or develop other forms of remediation. In the case of remediation of groundwater, a risk-based ‘clean up to the extent practicable’ approach is used but this is driven by the use of the receiving waters.

Generally, sites require the generation of a Remedial Action Plan (RAP), including;

• Set remediation goals that ensure the area of the activity or contaminated site will be suitable for the proposed use and will pose no unacceptable risk to human health or to the environment.

• Document in detail all procedures and plans to be implemented to reduce risks to acceptable levels for the proposed site use, these can include:

if practicable, on-site treatment of the contamination so the associated risk is reduced to an acceptable level.

off-site treatment of excavated soil, so that associated risk is reduced to an acceptable level, after which soil is returned to the site.

consolidation and isolation of the soil on site by containment with a properly designed barrier.

removal of contaminated material to an approved site or facility, followed, where necessary, by replacement with appropriate material.


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where the assessment indicates remediation would have no net environmental benefit or would have a net adverse environmental effect, implementation of an appropriate management strategy.

• Establish the environmental safeguards required to complete the remediation in an environmentally acceptable manner.

• Identify and include proof of the necessary approvals and licences required by regulatory authorities.

Once remedial work is complete, a report should be prepared detailing the site work conducted and regulatory decisions made, as well as the monitoring program proposed. An assessment of contamination may result in the issue of a Statement of Environmental Audit (the professional opinion of an independent, accredited Auditor, assessed on the basis that they posed or threatened to pose serious or material environmental harm and were known to the NT EPA). This process is discussed in Section 9.

4.3.2 National Contaminated Land Guidelines The NEPM ASC was developed under the NEPC Act and is enforced by state and territory specific legislation. In the NT, NEPM ASC is enforced by the WMPCA Act.

The desired environmental outcome for the NEPM ASC is to provide adequate protection of human health and the environment, where site contamination has occurred, through the development of an efficient and effective national approach to the assessment of site contamination.

Site contamination principles included in the NEPM ASC and particularly relevant to contaminated site management at RPA are:

• “There should be a consistent approach to the assessment of site contamination across Australia but each participating jurisdiction may implement the necessary controls in its own manner”.

• “Industries, including mining and mineral processing industries, are responsible for ensuring that, when equipment on a site is dismantled or a site is otherwise decommissioned, appropriate measures are taken to leave the site in a safe and stable condition in order to prevent or, as far as practical, minimise adverse long-term environmental (physical, social and economic) impacts”.

The NEPM ASC also states “…in observing the principles and guidelines in this Measure, each participating jurisdiction should give consideration to the most current advice and best practice”. NEPM also states “In general, to achieve the desired environmental outcome, the process of the assessment of site contamination should be placed within the context of the broader site assessment and management process”.


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The NEPM recommended general process for the assessment of site contamination is published in Schedule A of NEPM. The purpose of site assessment is to determine whether site contamination poses an actual or potential risk to human health and the environment, either on or off the site, of sufficient magnitude to warrant remediation appropriate to the current or proposed land use. Schedule A shows the staged site assessment process indicating which general guidelines are applied to preliminary and detailed site investigations. The preliminary investigation should be sufficient to identify whether contamination exists on the site. Contamination may not be completely delineated at this stage. A detailed investigation is required when the results of preliminary investigation are insufficient to enable site management strategies to be devised.

The work undertaken at RPA to date which has involved identifying constituents of potential concern (COPC) and potential risks to human health and the environment and development of conceptual site models (CSMs) is consistent with the NEPM recommended general process for the assessment of site contamination. Much work related to site contamination and risks has already been undertaken at RPA and for some or many areas sufficient information is available for site management strategies to be devised.

4.3.3 Closure Objectives and Criteria The Ranger ERs contain a number of primary and secondary objectives for the rehabilitation and closure of Ranger, which the closure objectives and criteria are based on.

The overall objective for rehabilitation and closure has been based on the rehabilitation goal outlined in the Ranger Authorisation and the ERs.

“….the company must rehabilitate the Ranger Project Area to establish an environment similar to the adjacent areas of Kakadu National Park such that, in the opinion of the Minister with the advice of the Supervising Scientist, the rehabilitated area could be incorporated into the Kakadu National Park.” ER 2.1.

It is recognised in the wording of Primary Objective 2.1 that there will be differences between the ecosystem of the broader KNP and that of the final landform on the RPA. Specifically, any impacts within the RPA must be as low as reasonably achievable (ALARA) to protect the environment. These differences are reflected within the closure criteria.

Proposed closure criteria are presented in the MCP (ERA & ELA 2018) and have been developed from closure criteria studies and reports, including work completed by the Closure Criteria Working Group (CCWG) and the technical working groups. The closure criteria are based on substantial research and studies, stakeholder consultation and risk assessments over the life of the mine.


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The specific closure objectives and/or outcomes relevant to contaminated land and plume management include:

• R1 and R2 – Radiation doses to members of the pubic are below limits and ALARA.

• W1 – Mine derived analytes will not cause dietary (food and water) resources to exceed limits for human consumption in Magela Creek outside the RPA.

• W2 – Mine derived hazards will not cause designated recreational water resources to become unsafe for their designated recreational use in Magela Creek outside the RPA and Gulungul Creek secondary contact sites.

• W3 – Mine derived analytes from surface or ground waters discharged to surface waters outside the RPA do not cause detrimental impact to the ecosystem health of the Alligators River Region.

• W4 – Mine sourced solutes do not cause increased uranium in sediments off the RPA to levels detrimental to ecosystem health of the region.

• W5 – Surface water quality on the RPA meets the highest ecosystem protection level that is demonstrated to be as low as reasonably achievable.

• S1 – Impacted soils are remediated to as low as reasonably achievable to protect the environment.

• C7 – Traditional owners satisfied with the water quality and that no silting or sedimentation is occurring.

Table 4-1, Table 4-2, Table 4-3, and Table 4-4 provide a summary of the closure objectives, the outcomes derived from these objectives, parameters used to measure the outcome and the proposed closure criteria, as presented in the MCP (ERA & ELA 2018). For some objectives, corrective action is also provided in the case the expected outcome is not accomplished.

Determining if water and sediment closure outcomes are met is by an assessment process, rather than compliance with a single numeric criterion. Tiered assessment approaches are included in the NEPM ASC Schedule B(4) and B(7) (NEPM 2013); the Australian drinking water (NHMRC & NRMMC, 2011) and recreational (NHMRC, 2008); and national water and sediment guidelines (ANZECC & ARMCANZ, 2000, Simpson et al., 2013). The assessment effort of these tiered approaches increases with each tier. In assessing potential environmental and/or health impacts of concentrations greater than the screening value, consideration is given to both the ensuing potential for exposure and consequences of such exposures.


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The closure criteria assessment approach for water and sediment has been developed using a combination of site specific and national water quality guidelines within a risk-based, tiered assessment process. The tiered assessment process continues to be refined through stakeholder workshops in collaboration with ERA and consultants BMT WBM Pty Ltd. Constituents of potential concern (COPC) present in tailings/process water or waste-rock sources and other key variables have been used in determining the analytes of concern/interest. First tier screening criteria are derived from (i) national drinking water and recreations guidelines values; and (ii) site-specific and ANZECC guidelines values for ecosystem protection.

The assessment of contaminated soils is based on the framework outlined in NEPM ASC Schedule A. A Tier 1 preliminary site investigation will be completed for all identified contaminated soils that are not already in the process of remediation as part of the larger decommissioning works (i.e. land application areas). If soil concentrations in these locations are shown to be below the screening levels, no further remediation or assessment will be required. If they are above the screening levels, a Tier 1 detailed site investigation will be required. If adequate information is already available, a remediation plan will be developed (ERA & ELA 2018).

Achievement of closure criteria for soils will be either through demonstration that contamination levels are currently or remediated to be low enough that no action is required or through development of a site management plan based on ALARA (ERA & ELA 2018).


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Table 4-1: Closure Criteria - Soils

ER Objective Outcome Parameter Final criteria ID

1.2 (e)

The company must ensure that operations at Ranger do not result in: (e) environmental impacts within the Ranger Project Area which are not as low as reasonably achievable, during mining excavation, mineral processing, and subsequently during and after rehabilitation.

Impacted soils are remediated to as low as reasonably achievable to protect the environment.

Contaminated soil assessment for uranium and manganese in LAA. Demonstrate risk is ALARA

S1

Contaminated assessment of identified COPCs for other soils identified as not being part of the larger decommissioning works

Demonstrate risk is ALARA S2

(ERA & ELA 2018)


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Table 4-2: Closure Criteria - Radiation

ER Objective Outcome Parameter Final criteria Corrective actions ID

2.2 (b) and 11.3 (iii)

Stable radiological conditions on areas impacted by mining so that, the health risk to members of the public, including traditional owners, is as low as reasonably achievable; members of the public do not receive a radiation dose which exceeds applicable limits recommended by the most recently published and relevant Australian standards, codes of practice, and guidelines; and there is a minimum of restrictions on the use of the area

Radiation doses to members of the pubic are ALARA

Using the agreed restrictions on land use the total above-baseline radiation dose from pathways: External gamma Inhalation of Radon decay products Inhalation of dust Ingestion of bush food (including water)

0.3 mSv per year

Modify the design and/or action plan to mitigate identified pathway to ALARA (societal and economic considerations taken into account). Apply additional restriction on the use of the land in consultation with Traditional Owners (using the agreed method).

R1

Radiation doses to members of the public are below limits

Should land use restrictions fail, the total above-baseline radiation dose from pathways: External gamma Inhalation of RDP Inhalation of dust Ingestion of bush food (including water)

1 mSv per year

Modify the design of the landform or other relevant parameters in the decommissioning plan to reduce radiation dose for the specific pathway of concern. Post closure develop an action plan to mitigate identified pathway to ALARA (societal and economic considerations taken into account).

R2

(ERA & ELA 2018)


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Table 4-3: Closure Criteria - Water and Sediments

ER Objective Outcome Parameter Final and screening criteria ID

3.1 and 1.1(c) and 1.2 (c)

The company must not allow either surface or ground waters arising or discharged from the Ranger Project Area during its operation, or during or following rehabilitation, to compromise the achievement of the primary environmental objectives. The company must ensure that operations at Ranger are undertaken in such a way as to be consistent with the following primary environmental objectives: (c) Protect the health of Aboriginals and other members of the regional community

Mine derived analytes will not cause dietary (food and water) resources to exceed limits for human consumption in Magela Creek outside the RPA

Drinking water: Mn, NO3, NO2, SO42-, U Diet: Mn,

A risk assessment of water quality in Magela Creek outside of the RPA demonstrates mine derived analytes do/will not cause intake levels of those COPC to become intolerable. First tier screening criteria – drinking water: Drinking water quality in Magela Creek outside the RPA meets the national drinking water health guidelines. SO42- 500 mg/L, Mn 500 µg/L, NO3 50 mg/L, NO2 3 mg/L, U 17 µg/L (NHMRC & NRMMC, 2011; v3.4). First tier screening criteria – diet: Local diet model demonstrates that ingestion of mine derived COPC via aquatic bush foods and drinking water does not cause annual intakes to exceed national/international tolerable intake levels. Refer to Figure 6-3 for higher tier assessment approaches.

W1


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ER Objective Outcome Parameter Final and screening criteria ID

The company must ensure that operations at Ranger do not result in: (c) An adverse effect on the health of Aboriginals and other members of the regional community by ensuring that exposure to radiation and chemical pollutants is as low as reasonably achievable and conforms with relevant Australian law, and in particular, in relation to radiological exposure, complies with the most recently published and relevant Australian standards, codes of practice, and guidelines.

Mine derived hazards will not cause designated recreational water resources to become unsafe for their designated recreational use in Magela Creek outside the RPA and Gulungul Creek secondary contact sites.

Toxic or irritant chemicals Visual clarity and surface films

Water quality in Magela and Gulungul creeks at secondary contact sites is safe for secondary contact. First tier screening criteria: Water quality at MG009 and GCH meets the following the following recreational guidelines: NO3 500 mg/L, NO2 30 mg/L, U 170 µg/L (i.e., drinking water COPC x 10: NHRMC, 2008) SO42- 400 mg/L, Mn 100 µg/L (ANZECC & ARMCANZ, 2000 irritants, no guidelines for irritants/toxicants in NHMRC, 2008). Refer to Figure 6.4 for higher tier assessment approaches. No mine related change to water quality in Magela and Gulungul creeks causes turbidity to be significantly increased over natural background values. Oil and petrochemicals not to be noticeable as a visible film on the water or be detectable by odour.

W2

(ERA & ELA 2018)


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Table 4-4: Closure Criteria - Cultural

ER Objective Outcome Parameter Final criteria ID #

1.1 (a) 2.1

The company must ensure that operations at Ranger are undertaken in such a way as to be consistent with the following primary environmental objectives: (a) maintain the attributes for which Kakadu National Park was inscribed on the World Heritage list; The company must rehabilitate the Ranger Project Area to establish an environment similar to the adjacent areas of Kakadu National Park such that, in the opinion of the Minister with the advice of the Supervising Scientist, the rehabilitated area could be incorporated into the Kakadu National Park.

Traditional owners satisfied with the water quality and that no silting or sedimentation is occurring

Visual impressions of water quality (colour, flow, expected clarity, visible contaminants), silting, sedimentation.

≥7 Water quality verified by Bininj monitoring – water appears to be of high quality in most areas, only very minor water quality concerns

C7

(ERA & ELA 2018)


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4.4 Best Practicable Technology Assessment ERA & ELA (2018) describe the identification and use of Best Practicable Technologies (BPTs) as a key component of the ERs for Ranger mine, which specify that:

12.1 All aspects of the Ranger Environmental Requirements must be implemented in accordance with BPT.

12.2 Where there is … agreement … that the primary environmental objectives can be best achieved by … (an) action which is contrary to the Environmental Requirements …and which has been determined in accordance with BPT, that proposed action should be adopted.

12.3 All environmental matters not covered by these Environmental Requirements must be dealt with by the application of BPT.

The definition of BPT in the ERs establishes a framework to assess currently available technology. The BPT assessment ranks, weights and scores technology options. The final BPT score for each technology option was calculated using the rank of the option against each of the criteria. The BPT score summarises performance of the option against current international performance standards. The intent behind BPT is to ensure that choices between different operational and closure designs/mitigation methods made at any point during the mine life, utilise technology that ranks highest when assessed against the factors below;

• World's best practice.

• Cost-effectiveness.

• Proven effectiveness.

• Age of equipment.

• Social factors.

• Is consistent with the Primary Environmental Objectives.

The BPT also removes the necessity for the ERs specifying particular technologies which may become obsolete.

ERA have revised and expanded the original BPT matrix published by the Supervising Scientist in 2000. The revised BPT matrix enables technical staff to assess individual components of a project, as well as assess the overall BPT for the final closure proposal.

There are currently 25 criteria used in the matrix, which can be categorised under the following headings:

• Traditional owner culture and heritage.

• Protection of people and the environment (operational phase).

• Fit for purpose.


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• Operational adequacy.

• Rehabilitation and closure.

• Constructability

Like risk assessments, BPTs undergo review from time to-time to ensure options remain fit for purpose.

BPT assessments will be required for some of the remediation options identified in this plan.

4.5 Rio Tinto Requirements The relevant RT standard for contaminated land and plume management is “E15 - Hazardous materials and non-mineral waste management November 2017”. Requirements of the E15 standard that are particularly relevant to this plan are:

• 2.12 Dispose non-mineral waste in permanent, engineered, controlled and approved facilities, whether onsite or offsite, that are designed and operated in accordance with local laws and regulations or internal performance criteria.

• 2.14 Evaluate and document potential hazardous materials, contaminated sites and non- mineral waste risks and impacts as part of the technical and financial preparation and evaluation of capital projects. Develop appropriate mitigation strategies for all significant impacts and risks.

• 2.18 Perform verification assessments of contractors who transport or recycle waste materials and facilities used for treatment, storage and disposal to confirm that the wastes are being managed appropriately

Clauses 2.12 and 2.14 are addressed in this plan. The requirements of clause 2.18 will be addressed in the closure Environmental Management Plan (EMP).


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5. Existing Knowledge Base The MCP (ERA & ELA 2018) provides detailed information on ERA's most relevant supporting studies undertaken over the past 35 years at the Ranger mine, to inform both the development of the overarching closure strategy and design, and closure criteria. The outcomes of supporting studies presented in the MCP (ERA & ELA 2018) and relevant to contaminated land and plume management are summarised in this section.

5.1 Surface Water and Sediment Surface water quality monitoring has been ongoing at Ranger and in the surrounding environment for several decades providing a significant volume of reference data for surface water quality within the creeks and billabongs. Studies have collected baseline water quality data to describe background conditions in billabongs and creeks within the Magela catchment.

Sediment quality has been studied at a number of wetlands (both natural and constructed) within the RPA, including routine annual sediment monitoring conducted by ERA between 1982 and 2001. A review of all sediment data was undertaken during 2013, which recommended resumption of the sediment monitoring program to provide a pre-closure baseline assessment for sediments both inside and outside of the RPA.

Uranium was identified as the primary COPC based on the available data (1982 to 2013). This data showed a consistent trend in uranium concentration at the following billabongs relevant to the RPA (in order of highest concentration to lowest): Georgetown Billabong; Coonjimba (approximately equal to Georgetown Billabong); Gulungul Billabong; and, Mudginberri.

Following this study, sediment data collected between 2002 and 2006 was reviewed, to identify the ecological risk associated with sediments at the onsite water bodies. The results showed the following trend in ecological risk (highest to lowest): RP1 wetland filter; Corridor Creek wetland filter; RP1; Georgetown Billabong; Coonjimba Billabong (approximately equal to Georgetown Billabong).

The Supervising Scientist has also conducted a sediment sampling and analysis program during 2007, 2011 and 2013, at billabongs within the Alligator Rivers Region. The data obtained shows a clear distinction between the water bodies within the RPA, and non-impacted offsite water bodies (outside the RPA).

A comprehensive sediment study reported in 2015, provided sediment core data in addition to surface sediment data. The study included metal concentration data and lead (Pb) isotope ratios, 206Pb/207Pb and 208Pb/207Pb. The study demonstrated that measurement of lead isotope ratios in the sediments is a powerful tool to determine whether erosion products from uranium rich sources are being transported downstream, albeit at relatively low concentrations.


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5.2 Constituents of Potential Concern Previous studies for the Ranger mine and RPA have identified COPC in the ore and milling processes and waste rock, and their presence and/or risk to receiving waters. The following COPC have been identified for assessment:

• COPC from waste rock: total mono-nitrogen oxides (NOx); total suspended solids (TSS); turbidity; magnesium; calcium; sulfate; manganese; and, uranium.

• COPC from tailings / process water: Ammoniacal nitrogen (NH3-N); phosphorus (Total P / PO4-P); copper; lead; cadmium; iron; zinc; chromium; vanadium; and, potentially nickel.

The studies indicated that the COPC generated from the tailings / process water pose a negligible risk compared to contributions from waste rock and natural sources, and hence, do not require formal closure criteria. Monitoring and management should instead focus on the COPC from the waste rock.

Other COPC that are considered to be low risk but require established closure criteria include:

• Ammoniacal nitrogen (NH3-N): no risk expected however this COPC contains a Site specific guideline.

• Metals that may originate from the ore / mill, including:

Copper, cadmium, lead and uranium enriched greater than 10 times background concentration.

Manganese and vanadium as process additives.

Nickel and chromium from stainless steel used in the mill and iron from the mill grinder.

Zinc and cadmium from galvanised roofing.

Groundwater modelling shows that contaminants from the tailings/process water source peaks at approximately 12 years for Pit 1 tailings flux and 10,000 years for the combined Pit 1 and Pit 3 tailings. Predicted loads of tailings sourced COPC entering Magela and/or Corridor Creek are compared with the ANZECC/ARMCANZ guidelines and NT detection levels and are significantly lower than guidelines or below detection limits.

Acid Sulfate Soils:

The presence (and extent) of acid sulfate soils within the black soil of Coonjimba Billabong has been confirmed through studies undertaken at this site during 2009. The Coonjimba Billabong is a landscape sump which collects water and solutes from the surrounding catchment. The studies indicate that these soils are formed via recharge from surface water, due to a sulfur concentration gradient extending from the surface to the


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base of the soil profile, and barriers to vertical water/ solute movement within the profile. Furthermore, annual wetting and drying of areas of the billabong enables oxidation (and generation of acid) during the dry season, and re-mineralisation of the acid during the wet season when the billabong becomes inundated with water. As a result, acid sulphate soils should not be disturbed as the low landscape profile provides natural containment when the billabong evaporates during the dry season, acidic water from the Coonjimba Billabong cannot flow to Magela Creek due to disconnection between both water sources during the dry season, and due to this, there is low environmental risk to the billabong ecosystem or to downstream water quality and ecosystems.

5.3 Groundwater Contamination Studies into the existing groundwater contamination on site have been undertaken by Environmental Resources Management (ERM) and Golder Associates in conjunction with ERA. A characterisation of groundwater contamination was undertaken, along with identification of potential sources and transport mechanisms in areas where contamination occurs. Monitoring programs were also developed to further understand and manage contaminated groundwater.

ERM recently developed a conceptual hydrological model for the Corridor Creek LAA and Gulungul Creek upper tributary area based on the source-pathway-receptor framework. The conceptual hydrologic model consolidates recent and historical groundwater elevation and groundwater quality data and considers those data in the context of the ground surface elevation in the vicinity of the Gulungul Creek upper tributary.

ERM concluded that “based on the data review conducted for the preparation of the [Annual Ranger Groundwater Report], the migration of impacts in groundwater away from potential source areas at the [Ranger Project Area] is, overall, limited. This has been illustrated particularly in Aquifer 2 at the [tailings dam] where impacts to Aquifer 2 are largely delineated even in areas where they appear to have migrated further (e.g. along the GCT2 and RP1 alignments)”.

In relation to the Corridor Creek LAA potential impacts on upper Gulungul Creek, ERM state "Potential interactions between groundwater and surface water between the south-western portion of the Corridor Creek LAA and surrounding catchments is currently being assessed as the south-west corner of the Corridor Creek LAA is located near the divide between Corridor Creek and the upper portions of GCT1 and the upper tributary of Gulungul Creek. This assessment indicates that due to the cessation of irrigation in the southern portion of the Corridor Creek LAA, hydraulic loading in this area has declined thus reducing the potential for migration of COPC from this area. Additionally, the majority of residual impact from former Corridor Creek LAA activities is located in the Corridor Creek catchment."


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There is an existing plume from the tailings dam which has the potential to transport elevated concentrations of COPC to surface water. The location and pathways for the transport of elevated concentrations of COPC from the tailings dam plumes have been the subject of numerous studies, informing the Ranger conceptual site model. Key decommissioning activities and events that will lead to a reduction in the localized hydraulic heads and migration of COPC from the tailings dam to down gradient creeks and tributaries have been identified.

The risks identified are related to potential migration of contaminants from other legacy plumes and poor water quality from cumulative sources entering offsite water bodies. The site conceptual model developed for Ranger mine considers the information gained from these studies in relation to areas of interest or concern within the RPA to identify the COPC present, the predicted receptors and contaminant transport pathways post-closure.

5.4 Ranger Conceptual Model The Ranger mine conceptual model was developed by ERA in 2016. The report includes a comprehensive executive summary, which summarises the complex nature of the conceptual model framework. ERA requested that INTERA develop a conceptual model that focuses on groundwater and surface water flow and transport of COPC within the Ranger mine area and out into its surroundings. Further hydrogeological studies have been commissioned in 2018 that will be included in subsequent updates of the closure plan.

The primary objective of the Ranger conceptual model is to describe the elements of Ranger’s hydrogeologic and surface water environment that are important to understanding groundwater and surface water flow and solute migration within and out of the Ranger mine area at the appropriate time and space scales. It is intended to provide a scientific framework based on the available evidence by which ERA can assess and implement decommissioning and closure activities consistent with regulatory environmental controls and rehabilitation requirements.

The Ranger conceptual model is a descriptive distillation of the groundwater and surface water systems at and in the vicinity of the Ranger mine and of solute migration resulting from mine-related activities. Developed as a tool for understanding migration of Ranger COPC through soils, groundwater, and surface water under current and post-closure conditions, the Ranger conceptual model can also be used as a guide for developing future numerical models and as input to support decision making for decommissioning activities. The Ranger conceptual model was created following best practices for development of conceptual models, including those found in the Australian groundwater modelling guidelines. ERA created the Ranger conceptual model using existing information, data, and studies that provided valuable insight into Ranger groundwater hydrology, solute transport, geochemistry, topography, and surface water hydrology.


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The important elements for the Ranger conceptual model are classified into features, events, and processes. Features of the Ranger mine area comprise the key physical characteristics of the site, such as the topography, hydrogeologic framework and its properties, vegetative cover, and the design for backfill materials in the pits. Events include the timing of changes to the Ranger area, such as the start and end of mining and completion of decommissioning and rehabilitation. Processes are the forces driving movement of surface water, groundwater, and solutes within the Ranger area.

The Ranger conceptual model comprises multiple interrelated conceptual models spanning three different spatial scales the regional scale model, the site-wide scale model and the area of concern/interest conceptual models. Individual mine workings or features are areas of interest/concern for COPC sources and migration within and from the Ranger mine site and include the processing plant area and LAAs.

Each of the conceptual model's identifies the receptors and transport pathways for the appropriate COPC. Soil, groundwater, and surface water are considered to be receptors for COPC, based on the environmental requirements and objectives put in place for operation and closure of the Ranger mine, as well as transport pathways.

Conceptual models for the areas of interest/concern examined the operational and decommissioning period and the post-closure period. Steps for developing the area of interest/concern conceptual models included describing the setting, identifying the source(s) and COPC, and identifying the transport pathways and receptors, including soil, groundwater, and surface water.

The Ranger conceptual model describes the elements of Ranger's hydrogeologic and surface water environment that are important to understanding groundwater and surface water flow and solute migration within and out from the Ranger mine at the appropriate time and space scales. Conceptual models were developed for the regional scale, sitewide scale, and the scale of individual areas of interest/concern where the COPC sources are located.

The Ranger conceptual model provides a scientific framework based on the available evidence by which ERA can assess and implement decommissioning and closure activities consistent with regulatory environmental controls and rehabilitation requirements.

5.4.1 Processing Plant Area Conceptual Model The source of COPC in the process plant area and some non-point (areal) sources associated with dust and dispersion from operational activities that have occurred at the site over many years are summarised in the MCP.


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As planned in the closure strategy, shallow contaminated soil in the processing plant area will be removed during decommissioning. Studies between 2006 and 2009 revealed that groundwater beneath the processing plant area had been affected by Mg, Mn, SO4, U, and organic contaminants, primarily total petroleum hydrocarbons, released by operational activities. Water quality data for the nine down-gradient bores OA03 through OA11, installed and sampled in 2009, did not show impacts from the processing plant area. This lack of impact to the nearby down-gradient bores suggests that migration of contaminants from the processing plant area is extremely slow.

Current impacts to groundwater from operational activities appear to be minimal and located in the near vicinity of the processing plant area. The lack of recent water quality data throughout much of the processing plant area leaves uncertainty about current groundwater conditions. Reclamation is expected to remove much of the COPC sources in the shallow soil, so groundwater concentrations are expected to decrease over time. Thus, the processing plant area is not expected to be an area of concern for groundwater after mine closure.

Based on the distance from the affected groundwater beneath the processing plant area to Corridor Creek and Georgetown Billabong and the low COPC concentrations seen in bores adjacent to Corridor Creek and Georgetown Billabong, contaminated runoff and/or groundwater discharge from the processing plant area are not expected to be of concern for surface water after closure.


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Figure 5-1: U and Mn soil concentration versus depth; generally decreasing over depth

(ERA & ELA 2018)

5.4.2 Land Application Areas Conceptual Model The five areas of land application distributed across the Ranger mine area are the Magela LAA (MLAA) and MLAA extension; the Djalkmarra LAA (east) and Djalkmarra LAA extension (west); the RP1 LAA and RP1 LAA extension; the Jabiru East LAA; and the Corridor Creek LAA.

As described in the MCP, uranium and radium-226 have been shown to be retained in the shallow soil; however, any future transport into surface water by erosion and runoff would be diluted to very low levels by the large creek flows. Irrigation with the dilute water produced by the treatment plants and natural recharge has been flushing out the conservative COPC in recent years and will continue to do so prior to closure. For all LAAs, the groundwater chemistry is expected to show limited to no impacts by the time of site closure.


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Figure 5-2: Location of LAAs and associated monitoring bores discussed herein

Several studies have been undertaken of individual or grouped LAAs between 1993 and 2010 investigating various soil contamination levels, radiological status of soils and other soil properties.

In one of the studies (Akber et al. 2011), over 200 soil samples collected from across all of the LAAs found that radionuclides applied to the LAAs have been retained in the soil profile between depths of 5 and 10 centimetres. These bound radionuclides have a low leachability and will therefore be unlikely to impact the aquatic environment downstream.


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Akber (2015) also conducted a study of the uranium distribution in the LAAs. The study found that sprinkler irrigation of RP2 water has resulted in an increased concentration of uranium (and other radioisotopes) in the soils of the LAAs. Uranium load varies in the LAAs, depending upon the site use duration, concentration in the applied water and the applied water volume. Averaged over the entire 338 ha of LAAs at Ranger, the additional external gamma dose rate due to land application is 0.03 micro-Sieverts per hour. It was found that the contribution of land application areas to the terrestrial diet for adult radiation dose is only 2.5 micro-Sieverts per year. This has been used to calculate the increase in dose rate received via the inhalation of radon decay products from land application. On average, the increase due to land application is small and only 0.0003 micro-Sieverts per hour above background (this increase is higher in Magela A (0.03 micro-Sieverts) and Magela B (0.02 micro-Sieverts)).

The dose was calculated for an adult, 10 year old (juvenile) and 1 year old (infant), according to radioactivity of different radioisotopes applied to the land until 2008, and modified radioactivity 100 years and 1000 years in the future.

The data shows that the dose contribution from all LAAs to be very low and below the exemption levels published in the ARPANSA National Directory (ARPANSA 2017), with the exception of Magela A and B. Magela A and B are only slightly above the exemption level of 10 micro Sieverts per year and present very minimal risk to members of the public; being only 4 percent and 2 percent respectively of the annual member of the public limit (1,000 micro Sieverts per year).These results indicate that no remediation for radiological contamination will be required.

However, additional soil sampling has recently been completed in the land application areas to supplement these findings. The outcomes of this additional work will be reported in the next iteration of the MCP.

Uranium distribution is non-uniform both in the vertical and horizontal direction. In the vertical direction, the uranium concentration decreases exponentially with depth and little applied uranium is expected to reach below 0.2 metres depth from the surface. In the horizontal direction, the applied uranium loads seem to exist in strips along the irrigation lines. The leaf litter in the LAAs has elevated uranium concentration which is likely due to both the foliar uptake during the sprinkler irrigation with RP2 water and the root uptake.

The LAAs are not considered to be areas of concern for groundwater or surface water post-closure for various reasons including (but not limited to): nearly 20 years of wet season flushing between when the LAAs were decommissioned and when the site will be closed; groundwater chemistry has improved in some LAAs since switching from the application of RP2 water to clean water; and transport of U and/or 226Ra on sediment in surface water runoff is possible, but will likely result in small quantities entering surface water bodies and will be diluted on entry.

Further information on the outcomes of the radiation studies completed in the LAAs is provided in the MCP (ERA & ELA 2018).


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6. Contaminated Land Management at Closure 6.1 Summary

Once the tailings deposition into Pit 3 has concluded in 2020, prefabricated vertical drains (wicks) will be installed, similar to those which have been installed in Pit 1. This is estimated to be completed by 2022 and will be followed by the installation of a geotextile layer to provide the required geotechnical strength and allow access for backfill. The geotextile layer will then be covered with a preload layer of waste rock, to activate the wicks. The remainder of Pit 3 will be backfilled with waste rock from the remaining stockpiles, concurrent with the deposition of the deconstructed mill and other site infrastructure (and contaminated soil) into the pit. The surface of the pit will then be contoured to the final landform shape, and revegetation will commence in 2024 (Section 10.7).

6.2 Final Landform Construction Construction of the final landform will involve significant backfill into pits and the redistribution of appropriate materials to ensure the final landform meets closure requirements. The activities to be undertaken to construct the final landform can be grouped into areas of the RPA based on the timing of their availability to be used for reclamation. The reclamation consists of four main areas; the Pit 1 area, the tailings dam area, the processing plant area and the Pit 3 area (including the stockpile area). The reclamation areas were published in the 2016 Draft Mine closure plan, and are presented in Figure 6-1 and Table 6-1 provides summary quantitative values for each area.

Table 6-1: Summary values for reclamation areas

Reclamation area Cut m3 Fill

m3 Net m3

Net (cut/fill)

Area (ha) Tonnes

Pit 3 void 8,000 30,432,000 -30,424,000 Fill 75 -60,848,000

Processing plant 1,701,000 3,838,000 -2,137,000 Fill 116 -4,274,000

Pit 1 area 1,831,900 6,510,000 -4,678,100 Fill 84 -9,356,200

Tailings dam area 8,517,000 6,258,000 2,259,000 Cut 286 4,922,000

Under stockpiles 36,257,000 955,000 35,302,000 Cut 237 70,604,000

Total 48,314,900 47,993,000 321,900 Cut 798 1,047,800

Table 6-1 shows that approximately 1.5 metres of cut is taken from the processing plant area, which has been used as a basis for assumptions in Table 7-1.


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The data in Table 6-1 shows that the final landform is designed to a near perfect material balance. However, these volumes do not illustrate the total movements. This is due to the need for a cut of mineralised material to be made underneath the stockpiles, and the remaining voids subsequently being refilled with non-mineralised material.

Figure 6-1: Reclamation areas

Waste rock that will be placed as part of the final landform construction, including pit backfill, will be made up of grade 2 and grade 1 waste rock. The surface layer (or landform cover) will be made up of entirely grade 1 material. The thickness of this material above any grade 2 material will need to be at least 2 metres, to ensure any gamma radiation is sufficiently attenuated. The maximum uranium content of grade 1 material currently planned to form this surface layer is 200 parts per million U3O8 (170 parts per million uranium or 2 Becquerels per gram) with an average of 80 parts per million U3O8 (68 parts per million uranium or 0.8 Becquerels per gram). This is below that currently considered to be radioactive according to the Australian Radiation Protection and Nuclear Safety Agency (ARPANSA 2014). The use of grade 1 material (<0.02 percent U3O8) for this final layer will be confirmed using both the stockpile grade block model and truck load gamma analysis via a discriminator.


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Once decommissioning of the plant and all demolition and disposal of the processing plant infrastructure into Pit 3 has concluded in approximately 2024, backfilling of the plant area will commence.

The total rock fill required for the plant area is significant (2.1 million cubic metres or 4.1 million tonnes), mostly due to the height of the final landform over RP2 (approximately 23 to 28 metres). The backfill material for the processing plant area will be sourced from the last stages of stockpile in the stockpile area, which will all be grade 1 material. The run-of-mine (ROM) pad will be reclaimed and made contiguous with the Pit 1 area in 2021.

Figure 6-2: Processing plant area, including ROM pad

A backfill contour map is provided as Figure 6-3. It shows the contour depths of the final rehabilitated footprint, that correspond to the plan view backfill sections 1 to 5. Proposed landform cuts are shown in tan regardless of the length or depth of cut that is required.


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Figure 6-3: Backfill contour map


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7. Contaminated Land and Plume Register An operational Contaminated Site Register (CSR) has been developed and maintained by the site Environment Team at Ranger, in accordance with the site Hazardous Material and Contamination Control Plan (ERA 2016). The site Hazardous Material and Contamination Control Plan is appended to the approved Ranger Mining Management Plan (ERA 2018). The operational CSR (2016) identifies all sites where activities have occurred that have the potential to contaminate land.

The register has been updated throughout 2018, with additional sites being added. The register has been reviewed by the closure team to identify the contamination volume and clean up requirements, and the potential impact of the contamination outside of the Ranger mining lease. Additionally, a sampling program was undertaken in late 2017 to confirm the presence of contamination on the LAA’s and billabongs.

A risk review was held to identify further work required to scope and assess potentially contaminated sites to the correct level to satisfy the closure objectives and relevant legislation. A workshop was later held to identify the areas requiring remediation, the remediation approach and any further work required. The register was updated to include total area, depth under landform (m), is there current sufficient information, option for remediation, pros and cons, and, go forward/ next steps.

During the workshop on the 30 and 31 May the following broad remediation strategies were defined prior to being assigned to each site:

• Leave in-situ (i.e. no treatment, do nothing).

• Leave in-situ (i.e. treat through natural attenuation).

• Dispose of in pit (i.e. scrape 1.5m soil and dispose of in pit as part of planned landform construction works).

• Off-site disposal (i.e. certain goods and substances require offsite disposal through licensed contractors).

• Dispose in other location (i.e. a purpose-built landfill).

• Encapsulate and dispose of on-site (i.e. asbestos requires encapsulation prior to disposal).

It was discussed that these options would require a BPT assessment to determine if they are reasonable for the management of contaminated sites. Additionally, for sites to be left in situ, those individual sites may not require a BPT assessment.

The updated Contaminated Land and Plume register is provided in Appendix A. This register describes the location and potential contaminants at each site, a comment on the basis for this assumption, describes the information known to date regarding each site, and provides the next steps for the management of each site.


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The contaminated sites have been grouped into major site areas, based on location, contamination risk and proposed remediation strategies. The major site areas are shown on Figure 8-1.

Figure 7-1: Major Site Areas


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Figure 7-2: Processing Plant Area


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Figure 7-3: Contaminated Sites Register


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The management of contaminated land within each major site area is summarised in the following table:

Table 7-1: Contaminated Site Remediation Options

Area Sites included Proposed Treatment Further Work

Ranger Mine Area

Processing Plant Area

Processing plant area including all sites identified in Figure 7-2.

Remove surface infrastructure, a selective 1.5m scrape of surface soil and place in pit (see Table 6-1).

Natural attenuation of groundwater plumes and ongoing monitoring. Further sampling and BPT assessments are required for remediation approach to sulfur stockpile, power station, the CCD circuit, emergency dump tank and the Shellsol USTs (discussed in section 8)

Pit 1 Area Current Domestic Landfill, Bioremediation Pad, Historic/ decommissioned and buried Industrial Landfills, Corridor Road

Remove surface infrastructure, Leave sites in-situ, corridor road will require surface scrape during demolition and the topsoil will be placed in pit. Records from sampling at bio-remediation pad indicate all soil has been remediated.

Standalone approval is required for the Pit 1 backfill, which is already being progressed

Tailings Dam Tailings Storage Facility and Sumps

Once tailings are removed, assumption that the head pressure of the plume will be released, and no remediation is required.

Decide whether to extend interception trenches to protect Gulungul creek (BPT assessment required). No triggers have been exceeded in Gulungul in 2017/18. Natural attenuation of groundwater plume. Ongoing monitoring and INTERA to cover plume in next conceptual model


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Pit 3 Pit 3 All tailings and surface mill infrastructure, including hazardous materials and contaminated soil to be disposed of in pit, on top of a geotextile layer, and covered with waste rock.

Standalone application to MTC and approval for backfill and closure of Pit 3 is required. Disposal of contaminated soil in pit will be approved through Pit 3 application approval. Waste remaining post-closure of Pit 3 will be disposed of in RP2. A register is to be kept detailing contents and stratification of Pit 3 and RP2.

Stockpile area

Stockpile areas, Mine maintenance Workshop, Mine Wash-down Bay, Historical Landfill and Dredge diesel unloading storage and pumping

Workshop areas (including washdown bay, diesel unloading, storage and pumping) will be treated similar to processing plant area: surface infrastructure removed, 1.5m scrape of soil and disposed of in pit. Area will be covered in waste rock. Remainder of stockpile area requires no remediation.

Need new groundwater and soil samples for historical landfill to confirm no migration of hydrocarbons and to identify receptors. Landfill site may require an engineered cap and will undergo BPT assessment.

Wetlands

Pond Water SED2B, RP1WLF, RP1, RP2, RP3, RP1WLF-Sumps, RP6, Corridor Creek Wetland Filter Network (6xcells), Georgetown Billabong, Coonjimba Billabong

Currently assumed that sites do not require scraping or waste rock on top. Surface infrastructure to be removed and sites to be left as is.

Sampling results required to provide indication of whether areas need to be scraped and covered with waste rock.

Sampling to confirm whether remediation is required for billabongs and RP1WLF. BPT assessments will be


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undertaken for these areas.

LAAs and Irrigation Areas

Magela A, Magela B, Djalkmara, Jabiru East, RP1LAA, Corridor Ck LAA,

With the exception of Magela, all LAAs are considered non-contaminated. Magela Land Application Area will undergo progressive rehabilitation that includes removing and disposing of the remaining irrigation infrastructure, remediation of soil containing elevated concentration of applied radionuclides and heavy metals via mixing to depth of 40cm, and revegetation of the remediated area with local native species. All other LAAs will only require infill revegetation.

Sampling to confirm contamination of other LAAs, and a BPT assessment is required to confirm approach for LAA remediation.

Other Infrastructure

Infrastructure in Jabiru East

USTs, Exploration Wash bay, Septic Tanks at Ranger Mine Village, Gagadju Workshops

Surface infrastructure to be removed and a 10-20cm scrape of surface soil will be required. Soil to be disposed of in pit.

Exploration wash bay will remain for duration of revegetation activities and to be removed post closure (post- 2026).

Further work programs, such as BPT assessments, are required and ongoing monitoring programs are discussed in section 8. Natural attention is described in more detail in Appendix B.


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8. Future Work Programs 8.1 Future BPT assessments

As an outcome of the contaminated sites register and workshop, and as agreed at the workshop and documented in spreadsheet in Appendix A, the following sites are identified as requiring a BPT assessment:

• Historical Landfill (as this is a historical site, the contents and past management of this landfill is uncertain. There was reported disposal of paints, solvents and hydrocarbons. It is assumed that this site will require an engineered cap and further soil and groundwater testing to identify receptors and migration of contaminants from the landfill).

• Former Sulfur Stockpile and Acid Plant (monitoring shows contamination and impacted groundwater with a plume moving towards RP2. The site is contaminated with waste oil, acidic water overflow and sulfur. The site was redeveloped for the Brine Concentrator, during which, surface contaminated soil was disposed in Pit 1. The plume will require ongoing monitoring and sampling, and the site will be included in an Acid Sulphate Soil Assessment in 2018).

• CCD Circuit and Neutral Thickener (this site has actual contamination of soils and surface water by process slurry. The plume underneath this area will be addressed in the next conceptual model and updated annually based on sampling. Further modelling is required to understand this groundwater contamination).

• Shellsol USTs (This site has actual contamination of hydrocarbons, however it is uncertain whether the source is from a plume coming from the bulk diesel tanks or if the contamination is from bore construction. The farthest bore from the site detects contamination, however the closest does not, therefore a re-test is recommended. The current treatment of this site is assumed to be to leave the plume in situ and allow natural attenuation of the plume).

• Power Station Area (this site contains moderate level contamination and there is an assumed plume of hydrocarbon contamination under the power station. There is history of a separator pipe leaking and additional monitoring is required).

• Emergency Dump Tank (this site has potential low-level contamination of soils and groundwater. Annual testing of pungent liquor kerosene was conducted here and the potential of a concrete leak means there is potential for an organics plume in groundwater. This site will be treated the same as the SX, and will have 1.5m soil stripped and waste rock on top. Natural attenuation is assumed to be sufficient for the treatment of the plume, however further studies are recommended).


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• Tailings Dam (this site will have high level contamination and radioactivity. Comprehensive modelling of its contamination exists however, there is concern over the plume existing underneath the site. It is assumed that once the tailings are removed, the head pressure of the plume is removed and natural attenuation will be sufficient to control the migration of the plume. Natural attenuation will then allow for the plumes remediation. There may be a requirement to extend the interception trenches and pumps to protect Gulungul creek. No triggers have been exceeded in Gulungul in 2017/18. However, ongoing monitoring is required).

• RP1 Wetland Filter (RP1 WF has previously received pond water and gets run off from the Western Stockpile, which contained radionuclides and is understood to have actual contamination. As there are areas that may not be covered by waste rock, further sampling is required to understand what, if any, remediation is required).

• Georgetown and Coonjimba Billabongs (these areas are understood to have actual contamination due to mine water. Sampling will confirm the remediation required).

• Land Application Areas (these areas are understood to have actual contamination due to irrigation with pond water. Sampling will confirm the remediation required).

8.2 Further Site Assessment Required In addition to BPT assessments, there is further work required in order to gain enough data to assess a remediation approach.

Sampling

Additional sampling is required at the bioremediation pad, the sulfur stockpile, the power station, the emergency dump tank, shellsol USTs, CCD circuit, the historical landfill and on all irrigated areas and water bodies to confirm remediation requirements.

Plumes

Studies between 2006 and 2009 reveal that groundwater beneath the processing plant area had been affected by magnesium, manganese, sulfate, uranium and organic contaminants, primarily total petroleum hydrocarbons released by operational activities. Water quality data for the nine down-gradient bores installed and sampled in 2009 did not show impacts from the processing plant area. This lack of impact to nearby downgradient bores suggests that migration of contaminants from the processing plant area is extremely slow. However, the lack of recent water quality data throughout much of the processing plant area leaves uncertainty about current groundwater conditions. Annual groundwater sampling and reporting should continue throughout closure to ensure any migration of contaminants is captured. Reclamation is expected to remove much of the COPC sources in the shallow soil, so groundwater concentrations are expected to decrease overtime.


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The contaminant plume that is present in the processing plant area has migrated to the south and south east, towards Corridor Creek, consistent with local groundwater flow directions. There is some uncertainty with this analysis given that it is based primarily on four monitoring locations with limited water quality data available (Golder 2016). A 2016 study from Golder Associates has recommended that two additional monitoring wells be installed to the west of OA10 and south of OA09 to confirm that contaminant plumes have only migrated marginally.

Additionally, uncertainty still exists with regards to the solute concentrations and transport of the plume from the tailings dam, therefore additional groundwater studies are proposed to gain a better understanding of the system. Currently, natural attenuation will be the method for management of these plumes (See Appendix B).

ERA installed 14 new groundwater monitoring bores and extended the groundwater monitoring program to additional existing bores in the process plant area during the 2016 dry season (ERM 2017). Petroleum hydrocarbons were not identified in groundwater from monitoring bores near the diesel fuel tanks, which were a major focus of investigations conducted in 2016/17 in this area. A sulfate plume was identified to extend towards the south from the south-western portion of the process plant area and has not been completely delineated. Therefore further assessment is required.

LAA Sampling

Magela LAA will require remediation due to the application of pond water and contamination levels. The data presented shows that radiation dose contribution from the LAAs is quite low, at 8% of the RPA overall public dose limit. Magela LAA contributes the majority of the dose (>72%), and soil remediation trials indicate that as over 80% of the contaminants are within the top 10cm of soil layer, soil mixing down to 30-40cm depth would significantly reduce radiation levels and bring heavy metals concentration down to ambient levels. It is proposed that Magela LAA will require removal of irrigation infrastructure, to be disposed of in the pit, and remediation of soil by mixing to a depth of 40cm. Re-vegetation of the remediated area with local plant species will follow. Further sampling could be required on other LAAs.

RAP

A Remedial Action Plan (RAP) will be developed for the sites following the BPT studies. Once a BPT identifies whether or not a site requires remediation, a remediation plan will be proposed. The development of a RAP should set remediation goals that ensure the remediated site will pose no unacceptable risk to human health or to the environment, and impacted soils within the RPA are as remediated to as low as reasonably achievable to protect the environment. The RAP should document in detail all procedures and plans to be implemented to remediate contaminated soil (for uranium, manganese or identified COPCs in order to demonstrate the risk is ALARA.


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9. Validation Following remediation, it must be proven that all contamination has been removed or successfully treated. This includes sampling treated soil or, where soil material has been excavated, sampling the sites where it was removed from. Validation of groundwater requires ongoing groundwater monitoring over a pre-determined period of time.

Where remedial action has been carried out, the site must be ‘validated’ to ensure that the objectives stated in the RAP have been achieved.

The extent of validation required will depend on:

• the degree of pollutant originally present

• the type of remediation processes that have been carried out

• the proposed land use.

Validation must confirm statistically that the remediated site complies with the clean-up criteria set for the site. The validation report must assess the results of the post-remediation testing against the clean-up criteria stated in the RAP. Where targets have not been achieved, reasons must be stated and additional site work proposed to achieve the original RAP objectives.

A report detailing the results of the site validation is required. Where targets have not been achieved, reasons must be stated and additional site work proposed to achieve the original RAP objectives. The validation report should also include information confirming that all regulatory authorities' licence conditions and approvals have been met. In particular, documentary evidence is needed to confirm that any disposal of soil offsite is done in accordance with the RAP. The report should include:

• rationale and justification for the validation strategy including:

clean-up criteria and statistically based decision-making methodology

validation sampling and analysis plan

• details of a statistical analysis of validation results and evaluation against the clean-up criteria

• verification of compliance with regulatory requirements

CRC CARE, a cooperative research centre for contamination assessment and remediation of the environment, has a guideline for reporting which provides instruction as to the way ongoing site monitoring must be reported, outlined in Section 11 (Scott & McInerny 2012).


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10. Monitoring for Closure Where full clean-up is not feasible, or on-site containment of contamination is proposed, the need for an ongoing monitoring program should be assessed. If a monitoring program is needed, it should detail the proposed monitoring strategy, parameters to be monitored, monitoring locations, frequency of monitoring, and reporting requirements.

Where in-situ (on-site) remediation methods are used, ongoing monitoring of the remediation process is required to ensure contamination levels are dropping (i.e. the remediation is working). This is generally in the form of regular soil or groundwater monitoring.

Monitoring events are often conducted at regular intervals to take into account seasonal changes in groundwater levels. A contingency plan is often required (i.e. a change in remedial method or further remediation) if the chemical levels identified during monitoring exceed a pre-determined trigger level.

The post-closure management plan (H355334-00000-201-230-0013) will include documentation on:

• Timeframes, e.g. commencement and expected length of the program

• Details about ongoing site monitoring requirements (soil, groundwater, surface water, air emissions), including monitoring locations, parameters and frequency

• Methodology of monitoring, including field and laboratory techniques

• Results of monitoring analyses including relevant Quality Analysis/Quality Control reporting

• Any pre-determined trigger levels for further action, i.e. to trigger active remediation

• details of party(s) responsible for the monitoring program

• Details of reporting frequency

• Details of what should be reported and to whom

The parameters outlined in the Ranger closure criteria can be used to monitor closure and rehabilitation performance (See section 4.3.3). The closure parameters and corrective actions for the monitoring of contaminated land and soils is also outlined in the MCP. For further detail on the post-closure monitoring management, refer to post-closure monitoring plan.


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11. Reporting It is important to document both the methodologies used for rehabilitation of contaminated soils and the results of monitoring against the closure criteria.

Where remedial action has been carried out, the validation report must include;

• The nature and location of chemical substances remaining on the site

• The objectives of long-term management of the site

• How the site in general, and remaining chemical substances will be managed and monitored

• Who will be responsible for implementation

• Evidence of acceptance by the responsible party to implement the plan

• Contingency plans in the case of unsuccessful management measures

• Time frames for action and for reporting to relevant government regulatory agencies

Reporting for each contaminated site area will be produced after remediation is undertaken. The report will discuss the initial results of the testing and results of any remediation that may have occurred, year to year. The report will discuss the longer-term monitoring of the site to ensure no contamination occurs. After 5 years of annual reporting, the report will include an assessment of how the site is tracking against the overall closure criteria on a biennial basis.

The monitoring report should include information about:

• ongoing site monitoring requirements (if any), including monitoring parameters and frequency

• results of monitoring analyses including all relevant quality assurance/quality control (QA/QC) reporting requirements stated above

• ongoing site/equipment maintenance, e.g. containment cap integrity

• details of party(ies) responsible for maintenance and monitoring program.

The monitoring report must include sufficient information on the location of the site, site history and surrounding environment (including geology and hydrogeology) field and laboratory sampling and analysis plans, quality control and assurance to enable robust regulatory decision-making.

Reporting of the site validation and ongoing monitoring should also be conducted, as per Section 9.and 10.


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Additionally, in relation to environmental and radiation monitoring on site, the Ranger Authorisation states that ‘the company shall carry out a monitoring program approved by the Director following cessation of operations until such time as a relevant close-out certificate is issued’. Environmental monitoring including radiation and contamination monitoring, groundwater, potable water, surface water, atmospheric monitoring, and constituent monitoring shall continue as per the Ranger Authorisation, until a close-out certificate is issued.

11.1 Accountability and Ownership All coordination of contaminated land management will be undertaken by ERA. The Closure and Projects team will be the owner of the contaminated land projects; however, sampling and remediation may be carried out by other ERA departments as per this plan.

This plan shall be reviewed and revised if necessary, at least once every two years or when:

• Any site register is updated or an action measure is implemented.

• Any further testing or annual sampling is implemented and different findings are presented

• Any changes are made to final landform areas or requirements.

• The plan is no longer adequate for managing contaminated land works.

• An Environmental representative requires a review if they believe that any of the above points affects Environmental matters.


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12. References

Akber, R & Lu, P. 2012. A model for radiation dose assessment during future occupancy of land application areas at ERA Ranger uranium mine. Report by Safe Radiation for Energy Resources of Australia Ltd. March 2012, p 39.

Akber, R, Lu, P & Bollhofer, A. 2011. Distribution of radioactivity in the land application areas assessed via direct measurement. Report for Energy Resources of Australia Ltd, Darwin. March 2011, p 91.

ARPANSA 2017. National Directory for Radiation Protection, Incorporating Amendment 7;

Republished 13 June 2017. Radiation Protection Series No. 6. Commonwealth of

Australia.

ERA (2016b). Hazardous Material and Contamination Control Plan, HPM001 22 June

2016. Energy Resources of Australia Ltd.

ERA (2018). Ranger Mining Management Plan 2018. Energy Resources of Australia Ltd.

ERM (2017) Ranger Annual Groundwater Report 2016/2017, for Energy Resources of

Australia Ltd, Environmental Resources Management Australia Pty Ltd (ERM).

Energy Resources of Australia Ltd & Ecological Australia (2016). DRAFT Ranger mine

closure plan, issued December 2016. Revision #:0.16.0,

Energy Resources of Australia Ltd & Ecological Australia (2018). Ranger mine closure

plan, issued May 2018. Revision #:0.18.0,

http://www.energyres.com.au/sustainability/closureplan/

Garde, M. 2015. Closure Criteria Development - Cultural. ERA Ranger Integrated

Tailings, Water & Closure. Confidential report, Northern Territory. April 2015, p 160.

Golder Associates, 2016 Groundwater Contamination Assessment, ERA Ranger Mine

Processing Plant Area, Golder Associates, 1543087-002-R-Rev0.

INTERA Incorporated. 2016. Final report: Conceptual model for Ranger mine. Report by

INTERA Incorporated for Energy Resources of Australia Ltd. September 2016


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NEPC. 2015. National Environment Protection (Ambient Air Quality) Measure. National

Environment Protection Council (NEPC). Available:

http://www.nepc.gov.au/nepms/assessment-site-contamination, accessed: 26th

September 2018.

NTEPA. 2016. Waste Management and Pollution Control Act. Darwin, NT.

Scott K, & McInerny, M. 2012, Developing a national guidance framework for Australian remediation and management of site contamination: Review of Australian and international frameworks for remediation, CRC for Contamination Assessment and Remediation of the Environment, Technical Report no. 22.


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Appendix A Contaminated Site Register

ERA Ranger Mine Contaminated Land Risk Register

Risk Register ReviewDeveloped: 2004Last Reviewed: Jul-18

Review Date Reviewed By Review Comments2004 ERA ERA developed this contaminated site register in 2004

2011 ERA

2017

2018

2018 24-Apr

2018 31-May-18

2018 31-May-18

During the workshop on the 30 and 31 May the following broad remediation strategies were defined prior to being assigned to each site:-Leave in-situ (i.e. no treatment, do nothing).-Leave in-situ (i.e. treat through natural attenuation).-Dispose of in pit (i.e. scrape 1.5m soil and dispose of in pit as part of planned landform construction works.-Off-site disposal (i.e. certain goods and substances require offsite disposal through licensed contractors).-Dispose in other location (i.e. a purpose built landfill).-Encapsulate and dispose of on-site (i.e. asbestos requires encapsulation prior to disposal).It was discussed that these options would require a BPT assessment to determine if they are reasonable for the management of contaminated sites. Additionally, for sites to be left in situ, those individual sites may not require a BPT assessment.

Section 7.4.2 of the 1400 Ranger Mine Closure Plan states: This Contaminated Sites Register is maintained in accordance with ERAs HMP001 Hazardous Material Management Plan . This register identifies all sites (including Jabiluka and Djarr Djarr) that have supported land use activity having the potential to contaminate land. This register includes, but is not limited to, information on the location, land use activity, potential contaminants and risk. The register is maintained by the Environment Team. The Contaminated Site Register is also in GIS format.

Section 7.4.2 of the 1400 Ranger Mine Closure Plan states: In combination with the register development, a number of targeted assessments were undertaken on the RPA until 2011 at known contaminated sites, including but not limited to the: counter current decantation and lime tank sites; bulk diesel tower site; historic acid plant and sulfur stockpile sites; solvent extraction plant, chlorine tank and ammonia deposits sites; mine maintenance workshop; power station; historical landfill; the tailings dam (e.g. Humphrey & Chandler, in review, McCullough, 2006, Parry, 2016, Richardson et al., 2017, Supervising Scientist, 2017a, b, Trenfield et al., 2017) and land application areas (e.g. Hart et al., 1983, Zimmermann & Lu, 2011). While the focus of these assessments was predominantly identifying groundwater contamination, soil profiles were completed at known contaminated sites to define the lateral extent of contaminating processes on site in the soils and shallow groundwater. In addition to this work, ERA has completed an assessment of the risk of generation of acid sulfate soils in Coonjimba Billabong. The outcomes of this study are presented in Section 7.4.2.3.

In early 2018 the operational Contaminated Sites Register was updated by ERA to provide a current register for closure planning purposes. The updated register included sediment sampling sites including retention ponds, billabongs and other water bodies, wash bays, exploration facilities, the septic tanks at Ranger Mine Village, additional warehouses and areas within with mill area. No data or reports were reviewed during the update. Where the risk rating is low, but the sampling data is N/A- the ratings were left unchanged from previous risk register.

The closure study team reviewed the CSR and risk ranked the sites using a traffic light system. Green were items that were low risk and low cost, yellow were moderate, and red were high. Additionally, a sampling program was undertaken in late 2017 to confirm the presence of contamination on the LAA’s and billabongs.

p g p y g (costs of remediation) and knowledge of contamination and agree and document ‘go forward’ options and future works required for each site. The following people attended the meeting:•Bernard Smyth (Chair) – Project Manager, Hatch•Doyin Bademosi – Project Coordinator, Hatch•Sean Gallagher – ERA Study Manager•Anthony Reid – Specialist Environment, ERA•Peter Lander – Environmental Superintendent, ERA•Sharon Paulka – ERA Closure Manager, ERA•Stefan Djordjic – Project Controls, HatchThe outcomes of this review included identification of further work required to scope and assess potentially contaminated sites to the correct level to satisfy the level of accuracy for the FS, and to develop a scope and plan to treat the Contaminated sites to satisfy the closure objectives and relevant legislation. The potentially contaminated sites were reviewed, and it was decided that a process was required to establish a set of criteria to treat the contaminated land, that would be similar to NEPM guidelines, and a workshop would be held in Darwin to reach agreement on site treatment.A follow up workshop was held on 30 and 31 May 2018 at ERA’s Darwin office. The following people attended the meeting:•Bernard Smyth (Chair) – Project Manger, Hatch•Sean Gallagher – ERA Study Manager•Anthony Reid – Specialist Environment, ERA•Peter Lander – Environmental Superintendent, ERA•Sharon Paulka – ERA Closure Manager, ERA•Linda Pugh – Specialist Approvals, ERA•Elmarie Fagan – Specialist Closure Strategy, ERA•Michelle Iles – Principal Advisor Environmental Studies, ERA•Robyn Skinner – Environmental Lead, Alan Irving & Associates•Clare Hart-Davies – Environmental Specialist, Hatch•Ping Lu – Principal Advisor – Rehabilitation and Ecology, ERADuring the workshop, every site identified that was coloured green or yellow was reviewed and discussed. The purpose of the workshop was to populate the agreed sites on register with the following information:•Area•Depth under Landform (m) •Is there sufficient information?•Option•Pros and Cons•Go Forward and Next steps.The areas that were updated include all sites in the processing plant area, Pit 1, Pit 3, Tailings Dam, Stockpile area/ mining footprint, Jabiru East and Airport, Pond Water and LAA’s and Irrigation areas. The sites removed from the register include the snake pit or southern stockpile seepage sump and the green waste dump as they were not considered areas with contamination concern

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Appendix B Natural Attenuation Requirements


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Natural Attenuation National Framework for Remediation and Management of Contaminated Sites in

Australia (CRC Care 2018)

CRC CARE produced a technical report with GHD to provide guidance on how monitored natural attenuation (MNA) can be applied as a remediation or management strategy for addressing potential environmental and human health risks associated with petroleum hydrocarbon contamination in groundwater.

The guidance outlines an approach to the implementation of MNA, to optimise efficiency and economics of the process, which includes:

• preliminary assessment, including addressing potential legal and liability issues

• initial evaluation of natural attenuation

• detailed characterisation, through multiple lines of evidence, of natural attenuation

• verifying the performance of natural attenuation, including the development of a comprehensive monitoring plan, and

• achieving closure, including documentation.

Ongoing monitoring is also required where groundwater is contaminated, to determine the performance of the remedial works or support natural attenuation, or where on-site containment (‘cap and contain’) is proposed. The development of an ongoing monitoring program is recommended to ensure the effective management of the contamination. The ongoing monitoring program should document the following:

• identify all responsible parties and detail commitments to the monitoring program

• provide timeframes (e.g. commencement and expected length of program)

• monitoring locations

• frequency of monitoring

• methodology of monitoring, including field and laboratory techniques

• monitoring parameters

• any pre-determined trigger levels for further action, i.e. to trigger active remediation

• frequency of reporting

• parties to be reported to (this may include certain community groups).


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The use of monitored natural attenuation (MNA) as a remediation and/or site management approach requires a sound understanding of natural attenuation mechanisms in order to evaluate their potential efficacy in achieving remedial goals. Many regulatory agencies recognize MNA as a viable remediation or management approach, but this alternative must be supported by adequate evidence of its effectiveness. Such evidence requires adequate site characterization to determine solute plume behavior and includes an evaluation of natural attenuation processes, making realistic estimates of attenuation rates and source decay rates, and designing an adequate monitoring program to show that natural attenuation is occurring as expected.