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Alligator Rivers Region Technical Committee

ARRTC Secretariat

GPO Box 461

DARWIN NT 0801

Meeting 41

13 – 14 November 2018

Record of meeting Darwin, NT

This document is a summary record of the scientific information presented to, and the discussion and actions arising from, the 41st meeting of the Alligator Rivers Region Technical

Committee. ARRTC meeting summaries are used to inform planning and prioritisation of scientific research activities.

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ARRTC members

Dr Chris Brady Northern Land Council

Professor Kingsley Dixon Independent Scientific Member

Assoc Professor Gavin Mudd ENGO stakeholder representative

Dr Libby Rumpff Independent Scientific Member

Assoc Professor Fran Sheldon Independent Scientific Member

Dr Jenny Stauber Independent Scientific Member

Dr Wendy Timms Independent Scientific Member

Dr John Woinarski Independent Scientific Member

Prof Craig Simmons Chair, Independent Scientific Member

Apologies

Dr Geoffrey Pickup Independent Scientific Member

Mr Justin O’Brien Gundjeihmi Aboriginal Corporation

Dr Gillian Hirth Independent Scientific Member

Presenters and observers

Ms Michelle Iles Energy Resources of Australia Limited, Presenter

Dr Ping Lu Energy Resources of Australia Limited, Presenter

Ms Sharon Paulka Energy Resources of Australia Limited, Presenter

Prof Lindsay Hutley Charles Darwin University, Presenter

Mr Aiden Wright Energy Resources of Australia Limited

Mr Peter Anderson Energy Resources of Australia Limited

Ms Elmarie Fagan Energy Resources of Australia Limited, Presenter

Ms Linda Pugh Energy Resources of Australia Limited

Ms Imogen Edwards Energy Resources of Australia Limited

Prof Alan Andersen Charles Darwin University

Mr Dave Stark Rio Tinto

Ms Lesley Bryce Energy Resources of Australia Limited

Dr John Sigda INTERA, Presenter

Ms Cindy Ardito INTERA

Mr Roland Lee Department of Primary Industry and Resources, Mines Division

Ms Brooke Cawood Department of Primary Industry and Resources, Mines Division

Mr Peter Waggitt Department of Primary Industry and Resources, Mines Division

Dr Chris Humphrey Supervising Scientist Branch, Presenter

Dr Renee Bartolo Supervising Scientist Branch, Presenter

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Dr Andrew Harford Supervising Scientist Branch, Presenter

Ms Elsa Lee-McGill Supervising Scientist Branch, Secretariat

Ms Samantha Doherty Supervising Scientist Branch, Secretariat

Mr Mike Welch Supervising Scientist Branch, Presenter

Mr Jaylen Nicholson Supervising Scientist Branch, Presenter

Dr Tim Whiteside Supervising Scientist Branch, Presenter

Ms Amie Leggett Supervising Scientist Branch

Ms Kate Turner Acting Supervising Scientist

Dr Mike Saynor Supervising Scientist Branch

Mr John Miller Supervising Scientist Branch

Mr Sean Fagan Supervising Scientist Branch

Ms Stacy MacKenzie Supervising Scientist Branch

Dr Glenn Harrington IGS

Mr Mallory Barnes Supervising Scientist Branch

Mr John Lowry Supervising Scientist Branch

Dr Scott McMaster Supervising Scientist Branch

Dr Sean Bellairs Charles Darwin University, Presenter

Assoc Prof Peter Erskine University of Queensland

ACRONYMS

ARRTC Alligator Rivers Region Technical Committee, the Committee

CDU Charles Darwin University

CERA Cumulative Ecological Risk Assessment

CMLR Centre for Mined Land Rehabilitation

DPIR Department of Primary Industry and Resources, Northern Territory

ECNT Environment Centre Northern Territory

ERA Energy Resources of Australia Limited

ERs Environmental Requirements of the Commonwealth of Australia for the operation of Ranger uranium mine

ERISS Environmental Research Institute of the Supervising Scientist

GAC Gundjeihmi Aboriginal Corporation

INTERA INTERA Geoscience & Engineering Solutions (consultants for ERA)

KKN Key Knowledge Need/s

KNP Kakadu National Park

KNPS Kakadu Native Plan Supplies

LAA Land Application Area

NESP National Environmental Science Program, Department of the Environment and

NLC Northern Land Council

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PAW Plant available water

RMCP Ranger Mine Closure Plan

RPA Ranger Project Area

SSB Supervising Scientist Branch, Department of the Environment and Energy

TLF Trial landform

TSF Tailing storage facility

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1 Welcome and opening session

The meeting commenced at 9.06 am.

Chair introduced himself as the new appointed chairperson.

1.1 Acknowledgement of Country

The Chair acknowledged and paid respect to the Larrakia people who are traditional owners of the

country the meeting took place on, acknowledged their continuing connection to the land, waters

and culture, and paid respects to their elders past, present and emerging.

Chair provided summary of the two day agenda. Noted the meeting is streamed to the Nourlangie

conference room for other SSB staff to observe.

1.2 Disclosure of conflicts of interests

Associate Professor Gavin Mudd noted he continues to undertake small consultancy work.

Dr Jenny Stauber advised CSIRO working closely with ERISS.

1.3 Attendance, apologies and observers

Geoff Pickup and Justin O’Brien were apologies.

Introductions were made by all members and stakeholders and their connection to ARRTC.

1.4 Correspondence

ARRTC noted the status of correspondence (incoming and outgoing) to 12 November 2018.

Kate Turner noted a letter from Drs David Klessa and Ian Hollingsworth to Minister regarding

attendance at ARRTC meetings. Further, Ian Hollingsworth wrote to Secretariat seeking attendance

at ARRTC.

Chair – noted will be further discussed by members.

2 ARRTC 40 Outcomes

2.1 ARRTC 40 – Summary record

ARRTC endorsed the minutes.

2.2 ARRTC 40 – Actions arising

All actions have been completed except for 40-2 and 40-3.

40-2- all four requested reports provided by ERA – on Govdex and noted as complete. Members

might have further request for feedback.

40-3 – Noted sub-group on restoration has been set up and but not yet met. Chair thanked members

for clarification.

3. ERA and SSB Updates

3.1 ERA overview report – Sharon Paulka, ERA

Associated presentation (on Govdex): ERA overview report

Associated paper (on Govdex): Report to the ARRTC Meeting # 41

Overview by ERA. Acknowledged Mirrar people, the Traditional Owners of the land Ranger operates on.

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ERA provided an overview of operations and noted that safety is number one priority to ensure the people and environment are taken care of. Noted that there have been a couple of minor injuries. More significant injury sustained by electrician in April –flash burn. Safety improved this year compared to previous year.

The fire and weed management plan most relevant leading into closure was described. There was a significant weed issue five to six years ago. By comparison weeds in 2018 had significantly reduced through the use more specific sprays and burning techniques which have been successful.

ARRTC were interested in / noted:

Whether native grass was returning after weed eradication. ERA cannot really say at this point in time as sprays can kill native grass.

Glyphosate sprays will be banned in the EU soon and that this could have implications for similar bans across Australia.

In relation to rainfall, ERA noted there has been a slow start to the coming Wet season. Forecasts are for a dry November and average December, with monsoons not starting until January.

ERA advised that they are ahead in operational performance, and are ahead of schedule to meet production guidance. Ore processing at Ranger is heading towards the tail of the stockpile now.

Regarding process water treatment, the brine concentrator has been performing consistently above nameplate following a number of improvements that have been implemented over the past year. A feasibility study is being completed on upgrading the fan in vessel 3 to increase performance.

Recommissioning of the High Density Sludge Plant is currently in the final stages of construction and a brine squeezer is currently being installed.

ARRTC discussed the history of pond water treatment.

In relation to Pit 1, backfill is ongoing. The small amount of earthworks remaining to construct the final cover have stopped pending final approval. ERA is currently seeking this approval by April 2019. Approval of the Pit 1 application is contingent on additional information, particularly with respect to vegetation establishment (e.g. plant available water). Agreement on what studies are critical before construction of Pit 1 is crucial, with a need to commence these studies and associated monitoring as soon as possible.

In relation to TSF tailing transfer, the second dredge will arrive in May 2019 and start operation in late May/early June 2019. A trial will commence shortly to assess sub-aqueous deposition. Notching of the northern TSF wall will be progressive, with dredging completed by the end of 2020.

There are many activities and studies underway in relation to Pit 3. These include seismic surveys, bathymetric surveys, CPT testing, and ongoing independent consolidation modelling.

ERA noted that a delegation from the Niger Ministry of Mines visited Ranger with interests in mine closure. ARRTC was supportive and positive about the visit.

Moving to closure, ERA is implementing a program, ‘My Future Plan’, to enable employees to move to different jobs. A training package has been developed to assist in re-deployment. Some employees may relocate within Rio Tinto, others are seeking redundancies in order to retire, while others again are undertaking training in a different career.

The ARRTC was interested in:

The mapping and management of weeds. ERA advised that they have a consultant providing advice and more detailed maps will be loaded to a GIS system.

The main risks associated with weed management. ERA noted that they are confident in their weed management, and that significant resources have been used to map and control weeds on RPA.

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The Supervising Scientist noted that SSB is working particularly hard with ERA to improve, and keep open, lines of communication. SSB will expedite wherever possible approvals processes by having more face to face meetings. ERA noted they are communicating regularly with relevant experts and SSB.

[Agenda item 3.3 discussed before 3.2.]

3.3 Ranger closure, feasibility study and schedule, Dave Stark, Rio Tinto

Associated presentation (on Govdex): Ranger Closure Feasibility Study update

Mr Stark provided an update on the feasibility study and schedule.

The ARRTC was interested in/noted:

The closure schedule appeared to be very tight. Mr Stark advised that there is a good level of

confidence with the schedule as contingencies were built in to the cost estimate to recover

activities as needed. Mr Stark noted approvals are tight and there are pre-requisites for

activities. However, collaborative forums are helping with scheduling. The Supervising

Scientist noted that it is vital to gather sufficient and appropriate information to feed into

applications seeking approval.

The schedule is based on 50% probability of success. ERA advised that analysis is based on

best and worst case scenarios, with Monte Carlo methods used.

The potential uncertainty in rainfall estimates and questions whether ERA had accounted for

external ‘black swan’ surprises which may affect critical path completion dates. Mr Stark

advised that a central estimate rainfall scenario was used.

The type of dredge to be used in the TSF for tailings excavation. ERA advised that a technical

assurance panel engaged a dredge specialist to advise on selecting the right dredge. A

dredge master has been engaged from Mozambique to develop a dredging plan.

Whether the stockpile block model developed is based on samples too. ERA advised that the

block model was based on hundreds of samples taken during a 2008 stockpile drilling

campaign for historical material and since this time a detailed geochemical analysis program

during operations.

Whether the schedule for the revegetation plan used the same process for understanding

probabilities of success. Mr Stark advised that internal and external experts were consulted

in developing the methodology. There are sound plans for irrigation of newly-established

vegetation and allowance made for pre-treatment of weeds.

SSB queried:

the timing for consolidation of Pit 3. ERA advised April/May 2025

whether there would be any resolution on planning/activities in next version of RMCP. This

will give SSB and regulators more confidence. Mr Stark advised that the outcomes of the FS

will be included in the next version of the MCP.

whether a minimum amount of consolidation is required before the geotextile material is

placed. Mr Stark advised that no consolidation is required prior to placing geotextile material

as this is planned to occur sub-aqueously.

ENGO member noted that extending long-term monitoring to 25 years is a positive step. The

commitment that Rio Tinto has shown is noticed locally and internationally.

3.2 Ranger Mine Closure Plan (RMCP) update, Sharon Paulka, ERA

Associated presentation (on Govdex): RMCP Update

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ERA provided an overview of the RMCP and noted that it outlines the strategy for closure. Further, it

supports the environmental requirements (ERs) to ensure the rehabilitated site is similar to adjacent

land so that the site may eventually be incorporated back into Kakadu National Park.

The plan ensures ERA meets obligations under the NT Mining Management Act and is based on the

WA mine closure guidelines.

The ARRTC was interested in whether approval of the RMCP would come with conditions. Mr Waggitt

(DPIR) advised that approval will probably be with conditions.

In relation to the closure criteria developed to address the objectives of the ERs, the Supervising

Scientist noted that all criteria were either assessed as acceptable or partially acceptable and ERA is

on track to receive full acceptance.

The ARRTC noted/queried:

The timeline regarding assessment of 2018 MCP: ERA advised that all comments and

responses are being uploaded to a database and will be provided to individual experts to

ensure each study has addressed comments. Still awaiting feedback in next month or two.

The next plan will be submitted on 1 October 2019. Need to determine cut-off date for

updates, possibly June 2019.

Whether ERA is expecting the Committee to look at the revised version before it goes to the

Minister. ERA advised that the committee’s review is not a required step in the MCP

approval. However, ARRTC will be advised when the plan is available for review (expected

prior to the second ARRTC meeting of the year). Given the size of the document ERA

suggested that the committee focus on the sections discussing the science/KKNs and closure

criteria.

Whether ERA has considered climate change risks. ERA advised this was taken into account

with the erosion modelling scenarios and also covered in KKNs that deal with landscape scale

influences. Peter Bayliss (CSIRO) has also addressed the issue in the cumulative risk

assessment.

3.4 Supervising Scientist’s Update Report, Kate Turner, SSB

Associated presentation (on Govdex): 3.4 Supervising Scientist Branch Update

The Supervising Scientist gave an update on Key Knowledge Needs, project planning and other key

activities.

The Supervising Scientist advised:

the KKNs have been reviewed and refined and SSB is seeking endorsement of these changes

by ARRTC at the end of the meeting.

SSB still in the process of working with ERA closure team to refine project scopes and

milestones so that SSB projects can be included in ERA’s closure schedule.

SSB have developed a project management system to help manage timing and delivery of

key outputs of projects.

The ARRTC were interested in:

The process if SSB and ERA do not agree on the adequacy of the science used to address a

KKN. The Supervising Scientist advised that, as far as possible, the intent is to ensure SSB and

ERA both agree that sufficient information has been gathered prior to closing out KKNs. The

amendment and close-out process for KKNs is documented in the protocol provided

previously to ARRTC (meeting ARRTC40) (ie SSB/ERA completion of the close

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out/amendment form, then MTC review, then ARRTC review). SSB has the final decision on

KKN close out.

Whether all contingencies will be captured.

[Agenda item 3.5 was discussed before 3.4 SSB 2018-19 Research update]

3.5 SSB’s RMCP Assessment Report, Kate Turner, SSB

Associated presentation (on Govdex): Ranger Mine Closure Plan Assessment Report

Associated paper (on Govdex): Assessment Report: Ranger Mine Closure Plan 2018 Supervising Scientist

The Supervising Scientist:

Provided an overview of SSB’s assessment report and noted that her role in the planning

process is to ensure that rehabilitation activities can be achieved and also to ensure that ERA

has provided evidence that best practice technology has been adequately considered.

Noted that ERA’s RMCP included knowledge gaps and areas with high degree of uncertainty

both linked closely with closure themes and KKNs.

SSB’s assessment focused on future achievement of environmental requirements. Many

detailed questions were raised by SSB with all comments distilled into recommendations.

This approach provides a framework that highlights the key concerns and knowledge gaps,

the KKNs required to address these, and thereby a good level of confidence going forward.

SSB’s main requirement is to have a high level of confidence in the surface water modelling

so we can understand potential surface water contaminant concentrations.

In relation to assessment outcomes, SSB has advised ministers that we support approval of

the plan and have made recommendations to ERA on contingency plans, water treatment

and contaminant modelling, revegetation, closure criteria and long-term monitoring

programs.

The Chair was interested in an estimate on how much resourcing is required to reasonably capture all

the future work and whether it is feasible. The Supervising Scientist advised that SSB is limited in its

annual budget but is reviewing its ongoing and proposed projects now. At the next meeting we will

seek ARRTC’s guidance or agreement on the project prioritisation process. SSB will link projects to

ERAs schedule.

3.4 SSB update report, Chris Humphrey, SSB

Associated presentation (on Govdex): 3.4 SSB 2018-19 Research update

Associated paper (on Govdex): Status of SSB 2018-19 research program

SSB provided a proposal for ARRTC reporting going forward and an update and status of its 2018-19

research program.

For future meetings, ARRTC will be asked to comment on current research projects against the

combined SSB/ERA project schedule, endorse pre-distributed research project proposals and endorse

modifications/additions to, close-out of, KKNs as required.

SSB described the progress in research as of November 2018 across the major program areas,

Ecosystem restoration and landform, Radiation and Water and sediment quality. Ecosystem

restoration projects (i.e. related to landform properties that will enable the establishment of a

sustainable vegetation community) continue to be a high priority for ARRTC and this is the reason for

continuing focus for ARRTC41 on related research on this topic.

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3.6 SSB rehabilitation standards, Chris Humphrey, SSB

Associated presentation (on Govdex): SSB’s Rehabilitation Standards.

SSB provided an overview of the status of its nine rehabilitation standards published to date and

explained each standard by theme. The rehabilitation standards have been revised on the basis of

ERA and ARRTC feedback, much of this feedback and associated revision described in the

presentation.

The NLC member (Chris Brady) commended SSB on its Standards noting that they provide the key

supporting criteria against which successful rehabilitation of the Ranger mine will be assessed.

The ARRTC were also interested in:

Whether the risk of climate change was factored into the rehabilitation standards. SSB

advised that climate change and implications for erosion (runs of wet years) and plant

available water (runs of dry years) have been recognised in the KKNs.

Dr Stauber noted SSB’s decision not to publish separate sediment standards, instead focusing

on the water quality that prevents sediment contaminants potentially accumulating to

unacceptable concentrations.

Dr Humphrey also clarified for ARRTC, SSB’s intent re metals guideline values (GVs) (for cases where ambient water quality exceeds published (default) national GVs, i.e. apply the median of ambient water quality (but not apply the original ANZECC (2000) recommendation of the 80th percentile of water quality as the GV). SSB noted they have sought external statistical advice on the metals Standard.

4 Groundwater

4.1 Groundwater studies update (past, present and future studies), John Sigda, INTERA

Associated presentation and images (on Govdex): Ranger Groundwater Flow Model for the Sitewide

Domain

John Sigda prefaced his presentation with the qualification that Intera’s work is scope driven. He

provided an update on Intera’s groundwater modelling as follows:

- Ranger closure planning and deliverables – conceptual model presented to the Committee.

- Constructing a site-wide hydrogeologic framework

- Creating a site-wide groundwater flow model

- Flow calibration and preliminary results

- Groundwater-surface water interactions.

The ARRTC was interested in:

Why averages were not used to measure rainfall. INTERA said rainfall can be very patchy.

Whether there is any consideration as to whether the data are biased one way or another.

How groundwater discharge affects surface water quality.

The Supervising Scientist queried how variability and uncertainty in recharge rates, hydraulic

parameters and boundary construction was captured. It was further queried if using a mean recharge

to represent spatial variability was appropriate.

Dr Glenn Harrington followed up on SSB’s queries. The approach of averaging recharge rates across all

bores to yield a single estimate for uniform application to the calibration model domain neglects the

expected spatial variability in recharge due to differences in soil, vegetation and topography, and so

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requires further investigation. Dr Harrington believed that a quantitative, calibration-constrained

uncertainty analysis will be required to inform the post-closure groundwater flow and solute transport

model. Such analysis is critical to quantify and communicate the level of confidence in (1) flow model

calibration, and (2) solute transport model predictions

ARRTC was interested in/noted that:

There may be opportunities to use other models.

There is always uncertainty in numerical model assumptions. Current industry practice is to

quantify the uncertainty in the model. This is a useful information that is used to

demonstrate the confidence in model results to stakeholders.

ARRTC was interested in solute transport and how the model will be approached to address

this.

The Chair summarised that the Committee is expressing concern that the uncertainty in the model is

not being adequately addressed and presented.

5 Key Knowledge Needs

5.1 Consolidation (gap analysis) and 5.2 KKN close out – recap and potential candidate KKNs

Associated presentation (on Govdex): KKNs Final Consolidation November 2018

Associated paper (on Govdex): KKN Final Consolidation November 2018

SSB provided a summary of the KKN consolidation process, with the current revisions based on

recent ARRTC and ERA review. SSB collaborated with ERA to refine KKN questions, resolve points of

difference and agree on allocation of responsibilities.

Updated narrative descriptions for each KKN question have been compiled and provided to ARRTC.

SSB is now seeking endorsement from ARRTC of the final consolidated KKNs and questions, noting

that these will be updated periodically if new KKNs are identified and as existing KKNs are amended

or closed out.

SSB noted that (i) the narratives were still in draft and were provided to ARRTC to give context to the

KKNs, (ii) ERA were still reviewing the recently provided narratives, and (iii) endorsement was not

being sought on the narratives at this stage only on the KKNs themselves.

As part of the presentation, SSB summarised past agreement on the KKN amendment process, and

provided examples of several KKNs that are candidates for imminent close-out. The close out process

seeks endorsement of the Ranger MTC, followed by ARRTC.

5.3 SSB/ERA project allocation to KKNs

SSB described their process for allocation of projects against KKNs, how these would be

amalgamated with ERA’s projects and against ERA’s rehabilitation schedules, and indicated that at

the next meeting (ARRTC42) the Committee will be asked to assess the adequacy of the joint project

list in addressing the KKNs. A draft template was presented, which will be used to list and summarise

SSB and ERA projects against each KKN question.

ERA advised the committee that closure-supporting studies have been identified and integrated into

the closure master schedule. There are links in the schedule to the Key Knowledge Needs.

The master schedule also highlights studies that require peer review, best practicable technology and

all related assessment requirements.

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A snapshot of closure supporting studies for WBS1000 (with links back to master schedule) was

presented to the Committee. This is a live schedule which gets updated as activities change.

ARRTC noted for the consolidated KKNs:

Great improvement but a few inconsistencies in the level of detail in narrative descriptions

between themes e.g. Radiation KKNs have a higher level of detail in the descriptions not

evident in many of the KKNs for other themes. Thus while it is good to see that KKNs were

being narrowed in their focus, further detail is still required on the KKN for contaminants (for

example) to convey the full intent. The Supervising Scientist advised she prefers members to

focus on key project outputs and SSB will focus on consistency between the descriptions.

The template was good but more detail may be required for some individual projects to

demonstrate how they address a given KKN.

Because many KKNs are linked to multiple objectives, will there be a process to track and

ensure all the objectives have been met?

The Chair noted there was strong support for the consolidated KKNs, the Committee was

comfortable that nothing has been lost with consolidation or closed out prematurely. However, his

fellow-members are looking for more detail in the KKNs to better understand

outcomes/outputs/deliverables.

ACTION 41-1: ARRTC to provide final feedback on the Key Knowledge Needs to the Secretariat by 7

December 2018

Day 1 meeting ended at 4.10pm

6 Ecosystem restoration: Presentations requested by ARRTC arising from ARRTC 40

6.1 ERA’s Restoration Operational Plan, Ping Lu, ERA

Associated presentation (on Govdex): ERA’s Restoration Operational Plan

Dr Lu noted that ARRTC requested the presentation at the last meeting (ARRTC 40). The focus of this

agenda item is ERA’s revegetation management plan which needs to be finalised for the final

landform application.

The revegetation plan is in final stages of drafting and is the product of ERA’s feasibility study. The

plan addresses environmental settings, statutory and non-statutory environmental requirements and

objectives and provides a re-articulation of the Ranger revegetation strategy discussed at ARRTC 40.

The plan covers implementation, revegetation activities and monitoring.

The revegetation works include details on planting site preparation, establishment of vegetation and

planting (tube stock and supplemented by direct seeding) and maintenance and monitoring of the

revegetation. A temporal flow chart of the overall revegetation process was presented to the

Committee.

Dr Lu advised the Committee on plans for the species mix and initial planting density according to

landform topography e.g. large number of Acacia mimula planned for open forest habitat with

Eucalytpus tetrodonta also planted in high numbers in open forest because they don’t like ‘wet feet’.

Eucalyptus miniata has been assessed as more suitable for planting on concave slopes than on rocky

and dry locations, or at the toes of the landform where the “wet feet” issue might develop.

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The revegetation stages include:

- Herbicide spraying to treat weeds

- Initial planting (1000 stems / hectare)

- Irrigation set up before planting then for up to 6-months post-planting

- Infill planting (200 stems / hectare)

Seed collection and nursery production of tube stock will occur prior to these works.

Bio-degradable pots will be used to increase plant success rate by reducing ‘transplanting shock’.

Dr Lu advised the ARRTC on the rate of planting productivity— four stems per six minutes per team of four and half people resulting in nine productive hours per day, 12 working hours per day. Work can be scaled up to cover nine hectares per week. During the wet season—eight hours per day due to WHS related to working in the heat. Reduced productivity for difficult or wet weather also factored into the plan.

A planting organisational chart was presented to Committee – ERA is trialling the organisational structure and planting process for the earlier revegetation of areas including Pit 1. Any inefficiencies will be recognised early and modifications can be applied for the peak planting period.

Irrigation is a key component of revegetation. A stadium type system will be used and each irrigation panel/system can cover eight hectares. 53 systems are required to operate at the peak period based on the current execution schedule.

Dr Lu noted that one of the key risks to the revegetation plan is having enough good quality seeds and tube stock. ERA have partnered with Kakadu Native Plants in the last 13 years and have harvested seeds to ensure enough seeds are available for whole project.

Mr Wright added that they have established a database of the harvest to determine whether adequate seed has been harvested and to assess viability. ERA is also recruiting a specialist for ecosystem restoration to focus on seeds, tube stock and revegetation logistics and planning.

Dr Lu noted that ERA is converting an exploration yard to a large nursery with a contractor commencing this week for its construction. ERA is aiming to grow 250,000 plus plants per year. The nursery also encompasses an area for seed storage.

6.2 ERA’s Revegetation Strategy (update), Ping Lu, ERA

Associated presentation (on Govdex): ERA’s Revegetation Strategy Update Dr Lu advised the ARRTC that ERA have engaged a consultant, Dr Ingrid Meek, to review ERA’s revegetation studies and write up the supporting document to the proposed Revegetation Strategy that members are wanting to review, with the aim of providing supporting document before the next ARRTC meeting.

The ARRTC queried/was interested in:

The total number of species targeted for establishment. Dr Lu advised there are 49 trees and

shrubs.

Whether there were similar targets for understorey species. Dr Lu advised that the necessary

research is being undertaken (presentation by Dr Bellairs to follow) and that ERA was still

considering species suited to the waste rock substrate. Furthermore, some plants will

volunteer (i.e. be naturally recruited).

Whether the scheduling includes understorey planting. Dr Lu advised understorey tube stock

will be planted during the infill planting stage, starting at 6 months after initial planting.

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Whether the irrigation regime will be the same as used for the trial landform. Dr Lu advised

that it will be at a similar rate but will adopt a stadium grade system for better water

efficiency and reduced runoff.

Whether plants that have died will be replaced during the infill planting stage and whether

replanting of the same species will occur. Dr Lu agreed this would be the case.

In relation to adaptive management, whether ERA has itemised what might, or is likely to, go

wrong and has carried out risk assessments. Dr Lu advised ERA has looked at risk

assessments but will use Pit 1 revegetation as the basis for further adaptive management

and learnings.

Whether one of the risks is the change in water quality from surface (low ionic strength) to

bore water. Dr Lu advised that ERA would use bore water of suitable water quality and

probably drinking water quality.

The nature of irrigation water that was used for the trial landform. Dr Lu advised that ERA used collected rain water supplemented with bore water

SSB was interested in:

Whether the plant list was biased towards those more tolerant of drier conditions. Dr Lu

advised that the final landform will not be uniform – and nor is the natural landscape – and

that as shown by ERA/SSB’s reference vegetation studies and especially ERA’s ecohydrology

and revegetation studies, vegetation is naturally variable and different species prefer

different ‘terrain’ depending on local topographic and edaphic conditions. ERA’s

revegetation strategy has taken this into consideration, assigning plants to their most

suitable niche to increase survival potential while ensuring the overall species composition

will meet the closure criteria.

The recommendation in the 2005 Ranger Revegetation Strategy was that Acacias should be underrepresented in the initial planting. Dr Lu advised that the earlier recommendation was based on issues identified in earlier studies which used aggressive Acacia species. The results from the trial landform indicated that selected Acacia species can be used appropriately. Acacia only has six to eight years of life – once they die they provide space for other plants to thrive but in their period of growth are an important source of soil nutrients. The trial landform data demonstrated that with the right selection of species, Acacia can play a major role in overall vegetation establishment and development without becoming dominant. Nevertheless, ERA is re-assessing the recommendation.

The ARRTC was further interested in:

Following from above, whether there has been any consideration on how to deal with fires in six to eight year’s time when the Acacia cohort has died. Dr Lu advised there is a buffer zone with the surrounding natural bush, ERA is not using high fuel grasses, and as shown on the trial landform, while Acacias may be prone to fire, in the absence of grass fuel loads this risk is minimal.

The time period over which ERA will maintain a fire break. Dr Lu advised this has been budgeted for 25 years.

Whether risk assessment protocols applied to this project. Dr Lu advised they are.

Whether the risk assessment can be shared with the Committee. ERA advised the risk assessment is still in draft form but will be incorporated into the next RMCP. CSIRO has also undertaken a cumulative risk assessment of risks to the final landform (SSB funded project). ERA will get back to the Committee on these outputs.

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The target number of species for the understory (as species richness of understorey is typically much higher than overstorey) and associated seed availability are potential concerns. Dr Lu advised that ERA has engaged Sean Bellairs and his graduate to work on understorey issues—commencing March 2019.

Whether biodegradable pots have been used widely elsewhere and whether they pose toxicity risks as they break down. Dr Lu was not aware of any documented risks of this type. Trials on site and those by other clients of KNPS have not shown signs of toxicity.

ERA noted they had a correction to make on ARRTC 40 minutes associated with their revegetation

studies reported at the time and will provide a correction to the Secretariat.

6.3 Specific topics and updates from ERA Plant available water, Lindsay Hutley

Associated presentation (on Govdex): Plant Available Water Professor Hutley advised his work with ERA focused on:

typical water balance of natural savanna in terms of rainfall, storage, evapotranspiration, runoff and drainage

TLF soil properties – whether the material can support a mature savanna ecosystem, in particular, whether there is enough water storage capacity in waste rock to support vegetation, especially in dry years.

A schematic representation of the annual water balance in the Howard River Basin near Darwin was presented to the Committee which provides a reference for estimates of savanna water balance in the NT. The Ranger mine site area has lower rainfall, a likelihood of shallower soils in the lease area, lower canopy cover, with tree water use more seasonal and a lower tree canopy water use than the Howard River location.

Photos were presented of canopy development on the Ranger TLF which showed good growth of tube stock, reasonable eucalypt establishment and non-eucalypt survival. Photos also showed good litter development, reproduction and regeneration.

The conclusions suggest waste rock material can sustain savanna tree species, however, vegetation on the TLF is not yet at maturity and no understorey vegetation is being supported. The question remains as to whether a mature savanna ecosystem be sustained.

Prof Hutley noted that, amongst the world’s tropical savanna climates, north Australia has one of the most seasonal. Soil water holding capacity is critical for dry season survival, with all water provided during the wet season. There is also a need to couple understanding of available moisture of the TLF material with nutrient studies (available N, P) to see if there are enough nutrients to support long-term tree growth.

To address the issue of whether waste rock can hold sufficient water for long-term sustainability of vegetation, it is necessary to 1) measure savanna tree water use at analogue sites, 2) investigate the TLF soil properties for potential soil moisture storage, and 3) then apply models to assess the impact of long-term rainfall variability. These have been investigated.

Plant available water (PAW) is the stored moisture vegetation can typically extract from soil. PAW is the amount of water held between the free drainage and permanent wilting points and can be estimated from TLF soil texture data. The TLF has limited ability to store moisture given the high rock volume and limited mass of fine earth fractions (<2 mm fraction - sand, silts, clays). Based on particle

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size analysis of the TLF fine earth fractions, waste rock can deliver a maximum of 400 mm of plant available moisture to vegetation over 4000 mm depth of waste rock substrate.

Calculations were shown for typical TLF PAW at the end of the wet season / beginning of the dry and, through WAVES modelling, which assesses whether or not vegetation can survive through a poor (dry) year based upon long-term regional weather data. This analysis showed that the TLF has a net surplus of moisture assuming a mean dry season tree transpiration rate of 0.5 mm d-1 and that tree survival is possible in 4 m of waste rock. Construction to 5 m adds a 20% buffer for PAW.

While the final landform appears likely to be able to support a typical savanna ecosystem similar to surrounds, Prof Hutley indicated a sensitivity analysis was still required (considering PAW and rock volume, rate of weathering, spatial variability of TLF fine earth fraction and rock volumes) and that climate change implications also needed to be considered, as higher temperatures will increase potential evaporation in the dry season and higher or lower rainfall will change PAW.

The ARRTC was interested in:

Committee – how deep were soil moisture probes placed in the TLF. Prof Hutley and Dr Lu advised probes were installed down the TLF profile to 4 meters in the waste rock only Section 1A which the simulation was based on.

The accuracy of the WAVES model and risks involved in using the model. Prof Hutley advised that modelled vs observed PAW estimates on the TLF were in reasonably good agreement. However, PAW calculations may be overestimated if rock volume is underestimated and void space is significant.

Whether the model is suggesting there is enough water and whether tree density would affect results. Prof Hutley confirmed that fewer trees would provide more PAW.

How the results inform survival of understorey/shrubs in dry season. Prof Huxley noted the occurrence of species that naturally survive on skeletal soils, such as Calytrix may be suitable for the site. Prof Hutley noted that Eucalyptus phoenicea is an overstory species that grows in skeletal rocky soils and is also potentially suitable for the TLF. Dr Lu commented that Eucalyptus phoenicea has established successfully on the TLF. Prof Hutley suggested it would be useful to acquire baseline data to determine where the (species-specific) risks lie.

Prof Hutley advised that climate change was a consideration in the study i.e. warmer climate means higher evaporation. However, this may be partially offset by the fact that there is an increasing trend in North Australian rainfall. A late dry season heat wave is something to consider – die backs in savannas are a concern and although uncommon in the Top End, do occur in north Queensland savannas.

SSB commented that the concern with the TLF is that you need such a large sample size to determine the total particle size distribution accurately. Samples for later laboratory measurement are very difficult to collect and process, because coarse rock fragments may be up to 1 m or more in diameter. Recently SSB used a Grid by Number method to measure over 700 particles on erosion plots 1 & 2. With the large percentage of rock content present there will be more pore spaces between the larger rocks. The TLF is like a sieve, water passes straight through. The issue is rock content (> 2 mm) may be greater than 70% whereas the PAW calculations assumed 66%.

The ARRTC noted:

The need to address the risk of plant survival during the first five years and measure soil moisture. ERA noted they will be measuring PAW.

It would be good if modelling looked at different eucalypt species.

SSB asked whether there was any additional monitoring that could be conducted on the TLF and/or Pit 1 to inform ecosystem restoration planning and thereby tighten up uncertainties. This discussion related to the need to 1) continue monitoring of soil moisture, and 2) capture typical spatial variation

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in void space, fine earth fraction mass and rock volumes of material in Pit 1, all critical parameters to estimate PAW storage. Prof Hutley advised that they could look at stress of trees, thermal stress etc.

On the basis of all the preceding discussion on PAW, the Supervising Scientist indicated that at this stage she is comfortable with the information provided on this subject, and provided the assessment of the Pit 1 application contains all relevant information, would recommend approval.

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 - recommendations to

be provided to the Secretariat by 7 December 2018.

Understory research, Sean Bellairs

Associated presentation (on Govdex): Rehabilitation and Revegetation of Ranger Uranium Mine

Dr Bellairs advised that his CDU research examined native understorey establishment on the TLF.

Nearly 80% of species on the Ranger lease are understorey, this strata being important for controlling

erosion, increasing water infiltration, trapping resources (seed, litter, fine earth particles), improving

soil fertility (particularly legumes), improving soil biota, ensuring there are nutrients for growth, and

provide nesting sites and food for fauna.

Waste rock has high rock and sand content, lower fines content, and poor water holding capacity. It

also has low total organic carbon, available nitrogen and cation exchange capacity, and minimal soil

biological activity.

Amelioration strategies to improve soil development and formation were examined: apply fertiliser,

increase the proportion of fines, incorporate ground-up organic matter, apply surface litter. As the

organic matter or litter breaks down, this will help improve nutrient concentrations and provide food

sources for microbes, fungi and invertebrates.

There are knowledge gaps in establishing understorey species in mine waste rock in north Australia,

with limited amelioration treatments investigated nor comparisons of tube stock to broadcast

seeding. Protocols for understorey establishment are also unclear.

The overall aim of the CDU study is to assess whether the establishment of native understorey

species on Ranger mine waste rock is improved by the application of physical/chemical amelioration

treatments or planting techniques.

Study site areas are plots 1 and 2 on TLF with controls, using tube stock and direct seeding on waste

rock and treatments described above.

In relation to species selection, 46 species were sought, but seed from only eight could be obtained

in sufficient quantity and quality. Eight understorey species were trialled in the CDU shade house (4

grasses and 4 legumes) and 5 understorey species were trialled on the TLF (3 grasses and 2 legumes).

Seed supply is a challenge. Protocol for obtaining seed is also a consideration.

Greater emergence was shown for litter additions (possibly due to increased moisture retention)

while fines and incorporated organic matter resulted in lower emergence. Understorey growth was

improved by fertiliser additions in well-watered conditions and by litter additions in water-limited

conditions. On the TLF, plants grown with litter additions had greatest survival. Tubestock plantings

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had greater establishment success and may be a viable establishment approach when applied as

‘ecological islands’.

The ARRTC noted/were interested in:

The low germination rate, noting the poor viability of seeds from most species (38 out of 46 species).

Whether seed supply chain is a real risk.

Whether seeds were planted in fine material.

Whether seeds were under water stress.

Temperature was not measured.

ARRTC also noted that the areas used for the TLF trials were very small and indicative that further

work is required. They also suggested that preparation and other treatments, e.g. plant hormones,

could be looked into.

Dr Bellairs noted that at both trials:

Most species did not experience significant differences in survival between treatments, with control plots having the lowest proportion of plants surviving.

At the TLF seedlings from seeds sown into litter tended to have the greatest survival, while

those sown with fertiliser, as well as control plants, tended to have the lowest survival.

The ARRTC were interested in:

Whether fertiliser affected emergence/survival. Dr Bellairs noted that sand had a negative effect and organic matter incorporated into waste rock may have a (negative) hydrophobic effect.

The effects on plants from continuous watering for these species i.e. root rotting

Whether nitrogen could be a limiting factor.

In relation to order of establishment: whether canopy cover will increase or decrease success rate of the understorey.

If early understorey establishment favoured grasses which may then lead to greater fire risk

The possibility of scaling up, by adding litter and adding microbes.

ERA advised that there are very strict controls on what ERA can bring on site/into KNP because of

cultural and biological considerations and the introduction of biological amelioration agents will need

GAC/KNP approval.

ACTION 41-3: ARRTC to work with SSB on a process for identifying which of the committees’ original

questions and comments on the Ranger Mine Closure Plan require ERA responses.

6.4 SSB/NESP restoration research progress, Renee Bartolo/Alan Anderson

Associated presentation (on Govdex): 6.4i SSB/NESP Ecosystem Restoration Research Progress

SSB provided a briefing on its ecosystem restoration research, deriving metrics for its ecosystem

restoration standard. It is proposing to use interim metrics, based on data it has (e.g. 1 ha plots), but

derive final metrics from larger range, at-scale, measurement, where possible. The interim metric

values will be within the range of the environmentally more realistic, at-scale values. The derived

metrics are consistent with a five star recovery rating as outlined in the SERA national restoration

standards

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Phase 2 plantings for wet/seasonally inundated areas on the landform won’t happen for a number of

years pending development of such ecosystem conditions so metrics associated with these are not as

higher priority.

SSB’s priorities will be aligned with ERA’s rehabilitation schedule which governs the ‘time required’

for the information. Examples of Restoration Standard attributes, the priority ‘score’ and rationale

for the priority ranking were provided.

The ARRTC were interested in:

From a planning perspective for species and planting densities, whether it’s possible to say

this is what we think based on what we currently have and based on what literature says.

SSB noted that species density information (stems per ha) is a priority and staff are providing interim

measures for revegetation planning from the 1 ha savanna reference sites. The transitional riparian

(seasonally inundated savanna) is not as urgent because of the longer lead time.

SSB provided the Committee with an update on the 1 ha plot survey results; 245 species were

recorded across all plots, with 78% of species classified as understorey. The understorey is diverse

but there are a small number of dominant species. Four broad understorey vegetation groups were

identified from multivariate analysis, with functional diversity described for life span, method of

persistence and life form. Interim metrics for the restoration standard attributes relevant to

understorey will be derived from the 1 ha plot survey results.

The ARRTC were interested in:

A recalculation of functional diversity of life forms excluding perennials

In relation to dynamics, what may shift overtime? Need to know if we’re heading towards a state that is undesirable

Spatial and temporal differences in vegetation composition and structure

Use of spatial variation data to drive decision making

Examining low frequency-occurrence species, and whether there is opportunity to culture these from tube stock rather than broadcast seeding.

SSB provided an update on spatial and temporal change in the surrounds (savanna) based on

historical aerial photo archives. The variation in canopy cover over time was described for the

distribution of cover classes. These data and the envelope of variation may be used as restoration

standard metrics for the relevant structural attributes.

Associated presentation (on Govdex): 6.4ii Faunal rehabilitation at Ranger Uranium Mine

Prof Andersen provided a presentation to the Committee on faunal rehabilitation at Ranger. He

noted the ambitious goal to rehabilitate Ranger so that the environment is similar to adjacent areas

of Kakadu National Park. Faunal recolonization is the acid test to inform whether revegetation is

successful.

Prof Andersen noted that fauna played a key functional role —sustainable ecosystems need and are

maintained by fauna. The importance of fauna recognised by ERA rehabilitation objective 2 and SSB’s

rehabilitation standards.

The project goals are to develop faunal measures of rehabilitation success (closure criteria) and to

assess invertebrate recolonization at the Ranger trial revegetation sites. These goals address KKN

ESR2. Part of the first goal is to characterise reference vertebrate assemblages using historical data

for the region and to design a robust sampling methodology for monitoring of vertebrate fauna.

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Closure criteria for invertebrates are to be derived from new surveys conducted at 7 of SSB’s

reference sites surrounding the mine together with data from the Ranger TLF sites. Early results from

2018 are as expected, i.e. given the young age and isolation of the TLF, ant species richness and

composition at revegetation trials is not yet similar to that in surrounding Kakadu NP. Ongoing

monitoring is required to assess a trajectory while the sampling intensity needs to be appropriate for

species detection.

The ARRTC was interested in:

The plan for vertebrates and trajectories. Prof Andersen advised that there is an issue with the TLF plots not being suitable for this purpose because their scale is too small to assess vertebrates. However, interesting data can be gleaned from lizards. Absence of fauna maybe a dispersal problem, not that the habitat is not right.

Ants disperse through flight, other groups don’t disperse through flight and limited dispersion may be an issue (that is, habitat itself is not the reason for differences in diversity and the lower species number).

Lack of understorey which may help fauna through provision of key habitat. ERA’s planting sequence is for understorey to be established last. Prof Andersen noted that planting everything at once may not be the best strategy. There are no studies to draw from for successful faunal recolonization

The fact that many vertebrate reference sites will include introduced species/pest species and whether this has been assessed. Prof Andersen advised this is not part of his NESP project.

How long will the Ranger minesite fence be managed? ERA noted the fence is not going to keep things out, and is not designed to restrict feral animals. There are no plans for additional fencing for this purpose.

Whether another metric on degree of naturalness would be useful. Mr Anderson noted

metrics about abundance of feral animals will be a third approach.

7 Stakeholder update reports

7.1 Department of Primary Industry and Resources

DPIR apologised that their report has not been cleared for release.

DPIR is progressing through the approval process for the Ranger mine closure plan and is hoping that

this will be resolved in near future.

DPIR is looking at various proposals on ongoing closure-related activities. Some can be approved at

departmental level, some require ministerial approval, the latter taking a bit longer to go through

process.

No major environmental incidents that require investigation noted. A few minor incidents ie. oil

spills.

DPIR will submit report to the ARRTC Secretariat for uploading to Govdex in due course.

7.2 Environment NGOs

Associated presentation (on Govdex): Ranger’s Mine Closure Plan: Some perspectives from

environmental stakeholders

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Associate Professor Mudd provided a presentation to the Committee which covered the history of

mining in the Alligators River Region.

Dr Mudd noted this is the first time environmental groups, Traditional Owners and governments are

on the same page wanting to work towards successful rehabilitation.

Dr Mudd expressed his concerns about the closure plan including surface and groundwater

resources, the final rock layer and associated revegetation and erosion risks and that climate change

does not appear to be factored into the plan. He also noted that most of the focus of water quality

criteria looks at drinking and recreational water standards – which could allow for significantly higher

solutes (like ~100 times) given the tolerance of humans. Environmental protection aspects refer only

to work in progress to determine specific limits.

Dr Mudd also raised regulatory concerns and associated risks including liability, funding, post-closure

monitoring and the legal status of the rehabilitated site beyond 2026. He pointed to legacy issues

associated with upper South Alligator River and Nabarlek.

DPIR noted the RMCP is in recent authorisation and will be updated annually.

ERA advised they had issued closure models in the past, since 2002, and the RMCP is not the first to

be presented to mine site technical committees.

Dr Stauber questioned Dr Mudd’s claim that the RMCP’s focus was predominately on human health

criteria for water quality, noting that CSIRO have always used Australian guidelines to set criteria for

ecosystem health. ERA also contested the human health focus, noting that drinking water guidelines

are included in MCP for regulatory/legal purposes, but so too are other values such as ecosystem

protection, which might have confused people. ERA highlighted that environmental protection

aspects did not just refer only to work in progress to determine specific limits but that there are

criteria in the plan for ecosystem protection as well. The next update will provide additional

clarification.

The ARRTC noted it was a timely reminder that the Committee has a role to scrutinise Narbarlek – should be a standing item

POST-MEETING annotation

On the basis of ERA and ARRTC’s disagreement with Dr Mudd that the RMCP did not provide

sufficient focus on water quality criteria for ecosystem health, Dr Mudd amended his

presentation immediately after the ARRTC41 meeting. The amendment acknowledged that the

Plan does refer to the ANZECC freshwater guidelines for ecosystem health. The amended

presentation was uploaded to Govdex.

7.3 Northern Land Council

Mr Brady noted there has been a lot of progress since last meeting and that ERA’s feasibility study

provides NLC with a lot more confidence.

SSB’s rehabilitation standards also provide stakeholders with enhanced confidence.

In relation to the RMCP, NLC and GAC have already recommended to the Minister for Resources and

Northern Australia that the plan be approved but that there are still outstanding issues. There is a

need to focus on risk management and contingency.

From the perspective of Traditional Owners, the 2026 timeframe is not as important as a good

environmental outcome.

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8 Meeting outcomes

Summary of key outcomes and actions arising from meeting

The Chair advised the Committee that the wording of the action items will need careful consideration

and actions will be provided in the coming days.

Post meeting it, the Chair and ARRTC agreed on the following additional action items:

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.

ACTION 41-5: ARRTC requested a standing agenda item be added to review the status of research,

supervision and/or monitoring activities being conducted for other uranium sites in the broader

Alligator Rivers Region.

ACTION 41-6: ARRTC requested that other Key Knowledge Needs be included to cover the other

uranium sites in the broader Alligator Rivers Region. The additional KKNs would inform the

environmental status of the sites themselves but through cross-referencing, would also inform

rehabilitation at Ranger particularly given the relatively long durations since initial rehabilitation (e.g.

over 30 years for Nabarlek).

ACTION 41-7: ARRTC to respond to Ian Hollingsworth’s request to attend ARRTC meetings.

ACTION 41-8: ARRTC to clearly document and submit a comprehensive and coordinated information

request to ERA. This may take the form of specific reports, studies, questions, data and information

that enable ARRTC to fulfil its technical advisory functions.

ACTION 41-9: ARRTC to seek clarification on outstanding INTERA groundwater modelling questions

and issues.

NEW ACTION 41-10: ARRTC to form a sub-group for groundwater modelling using the ToR from the

restoration subgroup as a template. The sub-groups will meet on an ad-hoc basis out of session

(where possible) to follow up on key scientific issues and provide feedback to ARRTC/ERA/SSB if and

as necessary

11 Other Business

Confirmation of next meeting dates:

ARRTC 42: Darwin 14 - 15 May – agreed

ARRTC 43: Darwin 12 - 13 November - agreed

Meeting concluded at 15:35