alligator rivers region technical committee meeting 31...

Alligator Rivers Region Technical Committee Meeting 31

27 – 28 November 2013

Meeting Summary

This document is a detailed summary record of the scientific information presented to, and the discussion and actions arising from, the 31st meeting of the Alligator Rivers Region Technical Committee. ARRTC meeting summaries are used to inform planning and prioritisation of scientific research activities.

ARRTC29 Meeting Summary of 24

Alligator Rivers Region Technical Committee - Meeting 31 Agenda

Tuesday, 26 November 2013 (0700 - 1630) Ranger Mine Tour Wednesday, 27 November 2013 (0900 - 1700) 1. PRELIMINARY SESSION (CHAIR)

1.1 Welcome and Introductions 1.2 Apologies and Observers 1.3 Correspondence 1.4 Conflict of Interest Declarations 1.5 Governance

• ARRTC Terms of Engagement 2. ARRTC30 OUTCOMES (CHAIR)

2.1 ARRTC30 - Summary Record 2.2 ARRTC30 - Actions Arising

3. STAKEHOLDER REPORTS 3.1 Uranium Equities Ltd - Nabarlek (Ms Taylor - apology) 3.2 Environment NGOs (Dr Mudd) 3.3 NT Department of Mines and Energy (Ms Strohmayr) 3.4 Northern Land Council (Mr Thompson) 3.5 Supervising Scientist (including Monitoring) (Mr McAllister) 3.6 Parks Australia (South Alligator Valley) (Ms Morgan)

4 RESEARCH STATUS 4.1 ERA Operations/ITWC update (including schedule of key activities and knowledge needs) (Dr Sinclair/Ms Iles/Ms Paulka) 4.2 eriss 2012-13 research outcomes and priorities (Dr van Dam) 4.3 Research addressing Key Knowledge Needs during operational and rehabilitation/closure phases (ERA/eriss)

4.3.1 Operational phase Presentation: Toxicity testing associated with brine concentrator (Dr Harford) Presentation: Mg multiple pulse ecotox study (Dr Harford)

4.3.2 Rehabilitation/closure phase and associated activities Presentation: Ecological Risk Assessment (Dr Bartolo) Presentation: Water quality closure criteria (solutes, suspended sediment) for surface waters (Dr Humphrey) Presentation: Contaminant transport modelling – groundwater (Dr Sigda - Intera Inc.) Presentation: Implications for surface water (Ms Iles) Presentation: Contaminant transport modelling – groundwater (Dr Turner - CSIRO) Presentation: Developing monitoring techniques for onsite/offsite monitoring after rehabilitation (Dr Bartolo) Presentation: Erosion and chemistry studies on trial landform (Dr Erskine/Dr Saynor/Ms Turner) Presentation: Radon exhalation from trial landform (Dr Bollhöfer) Presentation: Radionuclide concentration ratios for bushfood items in the ARR (Dr Bollhöfer) Presentation: Revegetation (Dr Humphrey/Dr Lu)

4.4 Other Key Knowledge Needs Presentation: South Alligator Valley Containment (Dr Bollhöfer)

Thursday, 28 November 2013 (0900 - 1700) 4 RESEARCH STATUS (CONT.) 5. STRATEGIC OVERVIEW

5.1 Presentation: Status of planning and scientific knowledge for development of closure criteria and trajectories (Dr Humphrey/Ms Paulka) 5.2 Summary Discussion (Chair to lead)

6. OTHER BUSINESS 7. NEXT MEETING


Attendance Members Dr Simon Barry Independent Scientific Member and Chairperson Ms Jane Coram Independent Scientific Member Prof Paul Boon Independent Scientific Member Prof David Mulligan Independent Scientific Member Prof Colin Woodroffe Independent Scientific Member Mr Andrew Johnston Independent Scientific Member Dr Gavin Mudd Environment NGO stakeholder member Dr Greg Sinclair Energy Resources of Australia Ltd Mr Adam Thompson Northern Land Council Ms Sally-Ann Strohmayr NT Department of Mines and Energy Mr Richard McAllister A/g Supervising Scientist Apologies Dr Jenny Stauber Independent Scientific Member Ms Melissa Taylor Uranium Equities Limited Mr Russell Ball NT Department of Mines and Energy Mr Justin O’Brien Permanent Observer - Gundjeihmi Aboriginal Corporation Ms Anna Morgan Parks Australia Division Presenters/Observers Ms Melanie Impey Permanent Observer - Gundjeihmi Aboriginal Corporation Ms Brooke Cawood NT Department of Mines and Energy Ms Shelly Iles Energy Resources of Australia Ltd Ms Sharon Paulka Energy Resources of Australia Ltd Dr Ping Lu Energy Resources of Australia Ltd Dr Graeme Esslemont Energy Resources of Australia Ltd Dr Stephen Booth Energy Resources of Australia Ltd Ms Kyla Valdron-Clarke Energy Resources of Australia Ltd Dr John Sigda Intera Inc Dr John Pickens Intera Inc Ms Virginia Leitch Australian Government – Department of Industry Mr Jean-Pierre Issaverdis Parks Australia Division Dr Jeff Turner CSIRO Dr Mike Trefry CSIRO Dr Rick van Dam Environmental Research Institute of the Supervising Scientist Mr Keith Tayler Office of the Supervising Scientist Ms Ally Sinclair Office of the Supervising Scientist Dr Che Doering Environmental Research Institute of the Supervising Scientist Dr Andreas Bollhöfer Environmental Research Institute of the Supervising Scientist Dr Chris Humphrey Environmental Research Institute of the Supervising Scientist Dr Amy George Environmental Research Institute of the Supervising Scientist Dr Renée Bartolo Environmental Research Institute of the Supervising Scientist Dr Mike Saynor Environmental Research Institute of the Supervising Scientist Dr Wayne Erskine Environmental Research Institute of the Supervising Scientist Dr Andrew Harford Environmental Research Institute of the Supervising Scientist Ms Kate Turner Environmental Research Institute of the Supervising Scientist Mr John Lowry Environmental Research Institute of the Supervising Scientist Mr Sean Fagan Environmental Research Institute of the Supervising Scientist SECRETARIAT Mr Scott Parker Office of the Supervising Scientist Ms Shannon Traut Office of the Supervising Scientist


1 Preliminary Session 1.1 WELCOME AND INTRODUCTIONS The Chair (Dr Barry) welcomed members to the 31st meeting of the Alligator Rivers Region Technical Committee (ARRTC). Mr Parker provided members with a facilities and safety briefing. Dr Barry thanked Energy Resources of Australia Ltd (ERA) for arranging the tour of Ranger mine held prior to the meeting and advised all members had found the tour very informative. Dr Barry noted that Prof Woodroffe has advised that he would be resigning from ARRTC following this meeting. ARRTC commended Prof Woodroffe on his significant contribution to the work of ARRTC as the Independent Scientific Member with expertise in geomorphology and wished him well in his future endeavours.

ARRTC31-1: ARRTC commended Prof Woodroffe on his significant contribution to the work of ARRTC as the independent scientific member with expertise in Geomorphology and wished him every success in his future endeavours.

1.2 APOLOGIES Apologies from the following members were noted:

Dr Jenny Stauber Independent Scientific Member Mr Russell Ball NT Department of Mines and Energy Ms Melissa Taylor Uranium Equities Limited Ms Anna Morgan Parks Australia

1.3 CORRESPONDENCE Dr Barry noted that a response from the Minister to his ARRTC30 meeting report had not been received. Mr Parker advised that the Department had forwarded a draft response to the Minister’s Office but this had not been finalised due to the Federal election and subsequent change of government. Dr Barry noted that he would refer to the outcomes from ARRTC30 including the status of the closure/rehabilitation risk assessment and KKN revision work in his report to the Parliamentary Secretary following this meeting.

1.4 CONFLICT OF INTEREST DECLARATIONS There were no conflicts of interest declared. Professor Mulligan advised that the Centre for Mined Land Rehabilitation is assisting SSD with determining the suitability and feasibility of various UAV platforms for use in eriss research and monitoring programs. Dr Barry advised that CSIRO is currently engaged by ERA on a range of technical and rehabilitation related projects, and is also collaborating with eriss on various research activities. Dr Mudd advised that he is contractually engaged by Gundjeihmi Aboriginal Corporation to provide scientific and technical advice on a range of water and rehabilitation related matters in relation to Ranger.

1.5 GOVERNANCE Mr Parker advised that the draft Terms of Engagement (ToE) had been further revised based on comments from members. He advised that once a number of remaining issues have been resolved, the final ToE will be circulated to members for signing out-of-session. It was noted that, under the revised ARRTC governance arrangements, observers at ARRTC meetings will also need to sign a Deed of Confidentiality. A draft Deed is currently being finalised.

2 ARRTC30 Outcomes 2.1 ARRTC30 - SUMMARY RECORD The ARRTC30 draft Meeting Summary was approved as tabled without amendment.

ARRTC31-2: ARRTC approved the ARRTC30 Meeting Summary as tabled.


2.2 ARRTC30 – ACTIONS/OUTCOMES Action/Outcome Status Carried over ARRTC27-4 ARRTC requested Ms Paulka to seek agreement from UEL to provide closure criteria and Hydrogeological review reports to Prof Mulligan, Dr

Mudd and Mr Johnston. ARRTC Secretariat followed up with UEL. Some of the information required was addressed at ARRTC30.

ARRTC27-5 ARRTC agreed that UEL be invited to submit a proposal to amend the (Nabarlek) KKN and that ARRTC then consider based on the evidence that has been provided to support this.

To be addressed as part of KKN review process.

ARRTC30 ARRTC30-1 ARRTC acknowledged Mr Hughes’ significant contribution to the protection of the Alligator Rivers Region through his work as Supervising

Scientist and in previous roles within the NT Government. Complete

ARRTC30-2 ARRTC agreed that the draft ARRTC Terms of Engagement should be finalised out-of-session as soon as possible. Complete ARRTC30-3 ARRTC agreed the Secretariat will follow up actions ARRTC27-4 and ARRTC27-5 (as amended) with Ms Taylor out-of-session. Complete ARRTC30-4 ARRTC agreed that all available, relevant, current and historical information related to the South Alligator Valley rehabilitation activities,

including monitoring data and historical documentation, should be collated into a single reference document. Addressed this meeting – see below

ARRTC30-5 ARRTC commended SSD on the high quality of papers and presentations provided to this meeting and endorsed the proposed eriss 2013-14 research program.

Complete

ARRTC30-6 ARRTC commended ERA staff on the high quality of their scientific work and presentations to this meeting. Complete ARRTC30-7 ARRTC thanked Mr Lowry and Ms Paulka for their high quality presentations. Complete ARRTC30-8 ARRTC noted the proposed approach and timeframe for the Ranger closure risk assessment project and requested that a status report (including

the results from the screening phase) be provided to next meeting. Complete

ARRTC30-9 ARRTC noted the current risk based approach proposed for the revision of the Key Knowledge Needs and requested that a status report be provided to next meeting

Complete

ARRTC30-10 ARRTC agreed that Prof Mulligan would provide suggestions on various suitable modelling packages that could be used by ERA to undertake high run landform evolution modelling for Ranger.

Addressed this meeting - See below

ARRTC30-11 ARRTC requested Dr Sinclair to provide an update on ERA groundwater modelling activities (including associated boundary conditions) to next meeting

Complete

ARRTC30-12 ARRTC requested that ERA provide a presentation on the status (and scientific basis for) the proposed vegetation related closure trajectories for Ranger to next meeting.

Complete

ARRTC30-13 ARRTC requested that ERA provide a presentation on the status (and scientific basis for) the current revegetation strategy for Ranger to next meeting

Complete

ARRTC30-14 ARRTC requested that a presentation on the status of knowledge and planning for the development of closure trajectories be provided to next meeting.

Complete

ARRTC30-15 ARRTC requested that ERA and SSD provide a presentation on the status of erosion modelling for the Ranger to next meeting. Complete ARRTC30-16 ARRTC requested that Dr Lu provide a presentation on the results from his eco-hydrology research at Ranger to next meeting. Complete ARRTC30-17 ARRTC agreed the next meeting (ARRTC31) would be held on a date to be agreed in the second half of November 2013, and may be preceded by

a tour of Ranger mine (subject to confirmation by ERA). Complete


Outstanding Actions ARRTC27-4: Mr Thompson advised NLC had facilitated a workshop in August 2013 with relevant TOs regarding the development of closure criteria for Nabarlek. A report has been drafted and will be provided to Uranium Equities Limited (UEL). It was suggested that ARRTC would be interested in reviewing the scientific basis for the closure criteria. Mr Thompson suggested waiting until UEL has had the opportunity to consider the content of the report and make its proposed modifications. He advised that NLC would appreciate ARRTC’s views on the scientific basis for the proposed closure criteria at some future point. ARRTC noted UEL currently has limited resources for Nabarlek work. ARRTC agreed it would be useful to review the content of the report once finalised and agreed to request a copy from UEL.

ARRTC31-3: ARRTC requested UEL to provide a copy of the Nabarlek vegetation closure criteria report once finalised.

ARRTC30-4 – Mr Issaverdis advised that Parks Australia Division (PAD) would have major difficulties in meeting ARRTC’s request given the massive volume of technical reports and other documentation relating to the SAV rehabilitation work. He suggested that, as PAD doesn’t have the resources available to undertake such a project, other options should be considered such as engaging a postgraduate student.

Dr Barry asked if there was something that could be done as an interim step that wouldn’t require additional resources but would still of value to both PAD and ARRTC. Dr Barry noted ARRTC originally had in mind a synthesis of the approach used at SAV and the various learnings from the process in the form of a knowledge base which could be used to inform future rehabilitation activities. Mr Issaverdis agreed that a synthesis of the available information rather than a collation of the various reports would be more useful. Ms Coram noted the stewardship of scientific knowledge and data is a critical issue in terms of future rehabilitation and closure activities and suggested that a synthesis of the available information would make a good project for an internal graduate within the Department. Mr Tayler advised that SSD would submit a graduate bid next round. Dr van Dam noted that the initial ARRTC request had been for a collation of relevant technical reports rather than a synthesis which would clearly require more work and a higher level of technical proficiency. He suggested that a consolidated bibliography would also be a useful first step in developing such a synthesis. Dr Mudd agreed that a synthesis of ideas and an associated monitoring framework would be useful but noted this would involve a considerable amount of work. He suggested this could be a potential Masters topic for someone and could be done through Charles Darwin University or the Centre for Mined Land Rehabilitation. It was agreed the first step would be for an internal or external graduate to be tasked with developing a scope of work, timeline and consolidated bibliography. Mr Thompson noted this work would also assist the move towards closure certificates and consultation with TO next year in relation to the SAV rehabilitation project. He noted that without such a concise synthesised document it will be challenging to effectively consult TOs on the range of sites in SAV. Mr Issaverdis suggested there is more than sufficient information available already to facilitate the TO consultation process. Mr Thompson suggested that relevant staff from NLC and PAD should spend some time going through what information is available and actually accessible. Mr Issaverdis advised that PAD is keen for the SAV indigenous stakeholder consultation process to commence.

Prof Boon strongly endorsed Ms Coram’s view regarding the importance of knowledge and data stewardship. He noted that this is similar to the process currently underway for the Murray-Darling Basin where one of the key criticisms of the Basin plan had been that there was insufficient collation of available information despite the significant historical investment in generating this knowledge. Mr Issaverdis stressed the need to clearly define the scope of the project to determine whether it is just limited to the rehabilitation process and associated engineering issues or should include broader issues including TO perspectives (given the site is located on Aboriginal owned land managed by the Commonwealth). Mr Thompson agreed the project is potentially very complex. Dr van Dam recalled Mr Waggitt had mentioned at an earlier ARRTC meeting that Dr Mike Fawcett (NTDME) had previously prepared a collated history of the site. Dr Mudd suggested that it’s not just about the history of the site but also contextualising the various learnings and trajectories in terms of water and radionuclides so the document can be used to inform the future rehabilitation of Ranger. He suggested the project would probably require at least two Masters level students, a technical officer and a TO engagement person to have the level of scientific rigour required.

ARRTC31-4: ARRTC agreed there would be significant value in having a synthesis of the key learnings from the SAV rehabilitation work and that the next steps are to: a. secure a suitably qualified internal (or external) graduate to develop a high level project scope, timeline and

consolidated bibliography; and b. explore options for funding this work going forward.

ARRTC30-10 – ARRTC noted that Prof Mulligan had provided ERA advice in relation to modelling output requirements as requested last meeting. Prof Woodroffe noted the unique importance of the current landform evolution modelling work and reiterated his previous recommendation to ARRTC that these models should be independently reviewed. He noted that the need to plan and design for a 10,000 year timeframe poses a range of interesting modelling challenges and there are a number of different factors that need to be considered. Prof Woodroffe advised he wasn’t entirely confident commenting on the validity of the current modelling approaches given his level of expertise in the area and suggested an independent expert review would provide ARRTC and stakeholders with a higher level of assurance. Prof Woodroffe commended Mr Lowry on the quality of the landform evolution modelling work to date. Dr van Dam advised that the independent review is already underway and SSD will provide an update to a future ARRTC meeting. Dr Sinclair thanked Prof Mulligan for his advice which ERA found highly valuable. Prof Mulligan reiterated his previous advice that a higher level of computing power may also assist in addressing a number of the current modelling related issues.

ARRTC31-5: ARRTC requested SSD to provide an update on the review of the landform evolution modelling at next meeting.


3 Stakeholder Reports 3.1 URANIUM EQUITIES LTD (NABARLEK) (MS TAYLOR) No report tabled.

3.2 ENVIRONMENTAL NON-GOVERNMENT ORGANSIATIONS (DR MUDD) Dr Mudd provided a report on behalf of environmental NGOs. He noted that Environment NGOs are continuing to closely monitor the current Ranger 3 Deeps EPBC Act assessment process. He advised they still expect that Ranger Mine will close in 2021 as per the current authorisation and move into the full time rehabilitation phase for final closure. Dr Mudd noted the Rum Jungle site and the SAV rehabilitation process both provide valuable case studies for uranium mine rehabilitation so it is critical that the relevant learnings from these processes be used to inform the Ranger rehabilitation process.

3.3 NT DEPARTMENT OF MINES AND ENERGY (MS STROHMAYR) Ms Strohmayr provided an update on NTDME regulatory activities during the reporting period. Key points are summarised below.

Exploration activity – There are currently four exploration operations authorised under the NT Mining Management Act on a number of tenements in the ARR including Cameco Australia Pty Ltd (Arnhem Project), Alligator Energy (Tin Camp Creek Project), Uranium Equities Limited (Nabarlek Uranium Mine) and UXA (Nabarlek Group Project- under administration).

Significant applications – Significant applications for Ranger and Jabiluka for the reporting period included the Pit#1 Closure preload placement (approved 13 August 2013), the ERA Surface Exploration Program 2013 and Notification for Additional Drilling Targets (approved 4 July 2013), an Application to direct distillate from the brine concentrator to Corridor Creek Wetland Filter - Stage 2 (Conditional approval given 30 September 2013) and the Jabiluka IWMP Rehabilitation (approved 2 August 2013).

Pit#1 preload status –Approximately 70% of the tailings surface has been covered with rock. The remaining area is currently too soft to work on safely and will be completed next dry season. Wick drain response is going well with some areas consolidating rapidly with up to 400mm of settlement being observed. Laterite material has been trialled to reduce infiltration and water management is maintaining runoff and process water separation.

Pit#1 seep – During a Regular Periodic Inspection, stakeholders observed a seep from the eastern wall of Pit#1. ERA will undertake an investigation to determine the quality and exact source of this water. Stakeholders have requested that this seep also be considered as part of the groundwater investigations for pit closure.

Jabiluka – IWMP Dewatering Proposal - The discharge of IWMP water to Ngarradj Creek was not completed due to the lower than average wet season during the 2013-2014 period. Cease to flow for Ngarradj Creek was called on 12th June and the remaining 40ML of pond water was released via flood irrigation in the period 27 June to 14 July 2013. Stakeholders inspected the system on 2 July and were satisfied with its design and implementation.

Jabiluka – IWMP Rehabilitation – Following an inspection of the site by stakeholders in July 2013, ERA was requested to provide further information including a materials budget, details of the IWMP rehabilitation design and disposal options and implications for the HDPE membrane. ERA provided a revised application which included removal of the IWMP composite liner for disposal at Ranger in 2014 and placement of embankment material to a depth ranging from 1-3m over the waste dump area and the IWMP disposal area. Engineering works have been completed and erosion control and re-vegetation activities will commence from 30 November 2013. A total of 10,000 tube stock plants comprising of Ranger’s preferred species list are to planted throughout the area at a density of approximately 1000 stems/ha with in-filling if mortality rates within the first 3 months exceed 25%. The fencing will remain in place for approximately 4-5 years to deter grazing animals.

Research topics of interest to NTDME – Topics include updated tailings consolidation model and solute transport model for Pit#1 (from current stage 2) to assist in determining a final permanent tailings level for Pit#1, groundwater investigations being conducted to inform Pit#1 closure agreed to include observed groundwater seep, long term distillate management, brine injection and disposal in Pit#3 and the development of scientific restoration criteria for Jabiluka.

Prof Mulligan thanked Ms Strohmayr for her presentation. He noted the NTDME presentations to each meeting provide a valuable means of ensuring that ARRTC remains well informed in relation to the operational status of uranium mining and exploration activities in the ARR and associated regulatory approvals.

3.4 NORTHERN LAND COUNCIL (MR THOMPSON) Mr Thompson advised NLC has nothing to report.

3.5 SUPERVISING SCIENTIST DIVISION (INCLUDING MONITORING) (MR MCALLISTER) Mr McAllister provided an update on SSD operations. He is currently acting Supervising Scientist while Mr Hughes is on long term leave pending his retirement in early 2014. Mr McAllister advised that SSD has recently lost a number of staff as a result of voluntary redundancies and the current operating environment continues to be impacted by resource constraints. He advised that resources are continuing to be directed towards the highest priority knowledge needs to ensure the Division’s core research activity and associated expertise is maintained.

3.6 PARKS AUSTRALIA (MR ISSAVERDIS PER MS MORGAN) Mr Issaverdis provided an update report on the status of the South Alligator Valley remediation project. Key points are summarised below.

Erosion control - Erosion control was undertaken in June 2013, with remediation of the gullies in the south east corner of the containment in January 2013 and some additional works completed in July 2013. The activities included reinstating the levels that had undergone differential settling and the establishment of a rock armoured runoff diversion to reduce the risk of future erosion. Additional works were undertaken to fill depressions around the monitoring stations and revegetation is planned for the 2013/2014 wet season.


Radiological monitoring – KNP engaged SSD to complete an ‘Acceptable Dose Constraints Report’ which was submitted to ARPANSA in May 2013. A dose constraint level of 30 μSv per annum was proposed and following a site visit in October 2013 was accepted by ARPANSA.

ARPANSA licence - The annual report was submitted to ARPANSA on 23 July 2013 and comprised a Groundwater Monitoring Report, a SSD Inspection Report, the O’Kane site visit report and the Dose Constraints Report. ARPANSA completed a site inspection on 10th October 2013 to assess compliance with the requirements of the ARPANZ Act and licence conditions. ARPANSA’s inspection report concluded that, at the time of inspection, there was no evidence of non-compliance with the licence conditions.

Monitoring - The ARPANSA licence conditions require that an approved environmental monitoring program be undertaken. A program developed in consultation with SSD has been implemented which includes assessment of containment performance, surficial radioactivity, ground water quality and vegetation monitoring. Monitoring of the site is a significant (and unfunded) cost to Parks. Trevlyn Radiation and Environment sampled 11 bores pre (November 2012) and post (May 2013) wet season and analysis results indicate the levels of metals and radionuclides have not increased and are within pre-containment measurements. Groundwater monitoring data will be collected and analysed biannually to establish a ground water baseline. O'Kanes Pty Ltd has been engaged to undertake the cover performance monitoring program, including collection and analysis of cover performance data, vegetation surveys and erosion monitoring. A site visit in May 2013 confirmed that tension cracks and depressions previously observed in the containment surface cover were no longer evident which suggests the differential settling of the containment has decreased and the containment is stabilising.

KNP facility management – NLC has been approached to undertake the Traditional Owner consultations to confirm their satisfaction with the rehabilitation, as per the lease agreement between the Director of National Parks and the Gunlom Land Trust. KNP staff have established a fire break around the perimeter and undertaken weed prevention in the area.

Prof Mulligan asked if the costs associated with the SAV site are a Commonwealth liability or is there a requirement for cost sharing with NT government. Mr Issaverdis advised that PAD is meeting all costs associated with the site but these have not been separately budgeted. Dr Mudd asked if costs are based on staffing or also include infrastructure. Mr Issaverdis advised the main costs relate to ongoing monitoring and data collection. Dr Mudd asked current staffing costs could be reduced by using telemetry and Mr Issaverdis noted this could be looked at. Dr Coram asked what the groundwater monitoring covers. Mr Issaverdis advised that current monitoring includes groundwater levels and water quality (including metals), infiltration and erosion rates and a weather station. Dr Coram suggested it would be valuable for ARRTC to see the groundwater monitoring plan as well as the results. Mr Issaverdis advised PAD could provide the monitoring plan to ARRTC if requested. Dr Barry noted that ARRTC’s interest is related to identifying any associated scientific knowledge requirements. Mr Issaverdis noted that the types of data being collected are primarily determined by the ARPANSA licence conditions and are important for demonstrating the long term stability of the site. Prof Mulligan asked if data from vegetation monitoring on the site was also being reviewed by SSD. Mr Issaverdis confirmed this. He noted PASD is relying on advice from SSD as PAD does not have the necessary technical expertise. Mr Issaverdis advised that ongoing management of vegetation on the site is being done by PAD staff. While the cap is still stabilising, the vegetation is now well established. Mr Tayler noted that during the last inspection of the site PAD staff had advised the site would be subject to a limited burn. Prof Mulligan noted the effects of this will depend on what Acacia species are present and the intensity of the fire. Mr Tayler stressed the importance of ensuring any framework species on the site are protected and the burn is properly controlled.

ARRTC31-6: ARRTC requested that Parks Australia provide a presentation to next meeting on the SAV monitoring approach for groundwater, vegetation management and cap integrity aspects including aims, rationale and results.

4 Research Reports 4.1 ERA OPERATIONS/ITWC UPDATE (INCLUDING SCHEDULE OF KEY ACTIVITIES AND KNOWLEDGE NEEDS) (DR SINCLAIR/MS ILES/MS PAULKA) Dr Sinclair acknowledged the Traditional Owners of the land on which Ranger is located (the Mirarr) and provided the ERA Business Update. Key points are summarised below.

BUSINESS OVERVIEW Business performance and outlook – The uranium market is challenging is the near term but the fundamentals remain positive. ERA considers it is well positioned to re-enter a stronger market post-2015 if the Ranger 3 Deeps underground mine is viable, approved and developed. ERA’s strategic focus remains on improving health safety and environmental performance, increasing the resource base at Ranger, demonstrating ERA’s rehabilitation capabilities, maintaining strong relationships with stakeholders and reducing operational costs. ERA is on track to achieve $150M in savings by the end of 2014. The cash profit from production and sales for H1 2013 was $91M (excluding exploration activities, non cash costs and before tax).

Dr Mudd asked if the figures quoted represent the real costs of doing business as all projects have a bottom line effect and thus impact on profit and loss. Dr Sinclair noted the way the figures are reported is in line with market reporting requirements.

Safety and people – As at the end of September 2013, ERA has 511 employees and contractors (of which 16% were indigenous and 19% female) making it one of the major employers in the West Arnhem region. ERA’s Education Partnership with West Arnhem College continues to strengthen. ERA has a continued focus on safety and achieved a year to date All Injury Frequency Rate of 0.37 (12 month rolling average) and a record number of days without recordable injury of 188 days was achieved on 7 August 2013. Four recordable injuries have occurred to date in 2013. Three employees recovered and returned to full duties and one is recovering.

Environmental/radiation incidents – The unauthorised removal of a controlled vehicle from site is subject to an ongoing investigation by the regulatory authority. The vehicle was not contaminated and the relevant controls were not deficient and had been deliberately breached.


Ms Impey advised that GAC is very concerned that the excursion of the controlled vehicle was actually detected by a contractor employed by ERA and not ERA, and GAC has written to both the NT and Australian Government Minister regarding their concerns.

MAJOR PROJECTS Integrated Tailings, Water & Closure Strategy – The ITWC strategy involves a program of works out to 2026 underpinned by a significant scientific knowledge investment. Key activities for 2014 include the Pit#3 initial fill, tailings transfer and brine management, Pit#3 preload, seepage studies and associated engineering designs, progressive rehabilitation works on LAAs and a range of other scientific studies. All elements in the strategy are temporally linked. Pit backfill of Pit#3 is 62M t not 73 M t. Work to be completed in 2013 includes the Pit#3 underfill and Pit#1 preload (to 70% coverage) and studies for tailing and brine management and support KKNs. The order for the dredge will be finalised shortly. Current scaling issues in the Brine Concentrator are due to changes in process water chemistry. There are also issues with the chemistry of cleaning materials so may need to adjust pH. It was noted that some scaling was expected to occur during commissioning.

Dr Humphrey asked whether there will be discrimination of the material going in Pit#3. Dr Sinclair advised that ERA will ensure that only 2s material and maybe some 1s material will go into the Pit. Dr Mudd asked what amount of material is going back into Pit#3 and Dr Sinclair confirmed that the current design is for 30 Mt of material. He noted the need to accommodate approximately 2GL of brine so a useable void volume plus a safety factor is required, assuming 20% of this would be unavailable. Dr Mudd asked if some of the materials are determined to be ore grade, would more rock material need to be sourced from elsewhere on the lease. Dr Sinclair advised that ERA has high grade and low grade ore stockpiles so is discriminating to ensure no ore grade rock goes into the pit. Mr Thompson asked what volume of 1s was available on the lease and Dr Sinclair advised that about 2 Mt of 1s will go in to Pit#3. He noted the alternative would be to place more laterite in but this would reduce the available void volume. Mr Thompson stressed the need to ensure there is sufficient 1s material left for the cover. Dr Sinclair agreed that it is critical that 1s material is only used for right purposes.

Pit#1 preload – Removal of tailings is a key prerequisite for closing Pit#1. Based on the results of studies during 2013, Pit#1 was divided into 3 areas (A, B and C) based on tailings strength. The initial cover design prepared in May 2013 acknowledged that the lower strength tailings in Area C may not be covered this year due to the state of saturation and rock advance rate in that area. The pre-load has now been successfully placed over the higher strength tailings (approximately 70% of the tailings surface area) and it has been decided to delay completion of the pre-load until the lower strength (Area C) area has received further solar drying. A total of 28 settlement plates will be installed (19 of which are already in place) to provide information on settlement rates to validate/calibrate the consolidation predictions. Learnings from this work will be applied to Pit#3 closure. Results to date (18 Nov) indicate an average settlement of -0.46m. The predicted settlement prior to placing further layers (2014) is 700mm (average) for a 4m thick pre-load. Results to date are encouraging for the 2.5m layer and are not dissimilar to the original model predictions for the 4m pre-load. Settlement and water balance data for Pit#1 will be collected over the 2013-14 wet season and used to re-calibrate the consolidation model. ERA will report back to ARRTC next meeting. Learnings to date will be applied to Pit#3 rehabilitation. These include that in relation to dewatering, moving too quickly can cause mounding in the tailings surface due to pieziometric pressures. Also using a 1m layer leads to undulations across surface and, if removed by grader, will allow tailings to extrude due to underlying pressure. Overall, the design is working. It was noted that there is a spring in the south eastern margin of Pit#1 with a flow rate of about 4 L/sec.

Prof Mulligan asked what’s stopping the solutes evaporating and clogging the wicks. Dr Sinclair noted that drying will not occur whilst there is fluid flow from the wick. Also the solutes are highly soluble so are easily rehydrated. Mr Johnston asked if all of the wicks across the site are still functioning and Dr Sinclair confirmed this. He added that following the further capping the fluid will be diverted to decant towers similar to what happens at Nabarlek. Dr Mudd noted that settlement is exponential. It was noted that Intera Inc is also looking at geochemistry and the additional seepage modelling required. Prof Woodroffe asked if the geotextile is sloping or flat. Dr Sinclair advised the geotextile slopes with a height difference across the site of about 1m. Dr Sinclair advised the spring is adjacent to the Pit#1 seepage barrier about 1.5m from the crest. He noted that the spring is about 3m below the barrier so ERA is looking to determine whether water is coming through the barrier. Analysis of the spring water from the top 9 m indicates it’s a mixture of 20-40% pore water and fresh water. ERA will continue to utilise existing nested piezometers and bores to further assess the hydraulic gradient and hydro chemical data to investigate performance of the seepage barrier. Dr Mudd asked when the spring was first identified and Dr Sinclair advised the spring was detected at the beginning of the 2013 dry season and sampling was done at that time. He noted the external 5m differential in head means water is flowing into the pit and that’s why ERA is currently looking at the performance of the seepage barrier. Dr Mudd stressed the importance of determining the source of the spring and associated potential risks as it is a pathway which could reverse direction.

Pit#1 run off trial – A 50m by 50m laterite pad with a compacted laterite base (300-350mm) overlying relatively soft tailings is being used to test the separation of surface run-off from the underlying expression of tailings pore fluids and determine what thickness of laterite capping is required to prevent pore water breakthrough and convert Pit#1 into a pond water catchment. Run off samples will be collected from a 2m by 2m HDPE lined sump during the 2013-14 wet season. If successful the Company will submit an MTC application to transform Pit 1 from a process water catchment to a pond water catchment ahead of the 2014/15 wet season. This plan will involve the placement of a laterite cap over the pre-load layer..

Prof Mulligan asked if the laterite cap will have angle and slope such that water may travel laterally and go over barrier. Dr Sinclair advised surface runoff will drain towards points where it can be collected and there will be two decant towers. Ms Coram asked what is the ultimate fate of collected pore fluids and Dr Sinclair advised these are diverted to the TSF and ultimately to the Brine Concentrator. Ms Coram asked if there will continue to be discharge post closure and Dr Sinclair advised that run off from waste rock will contain solutes so there will be a period when RO units will be required. The brines generated from this will be disposed of underground or injected into the base of Pit#3. Dr Sinclair noted that all process water on the site will need to be treated by 2026. Ms Impey asked where the process water requiring treatment will come from and Dr Sinclair advised process water will come from Pit#3. Dr Sinclair advised that ERA is assuming that all tailings will be placed into Pit#3 by 2021 and the site will be subject to solar drying for 12 months and that wicks will also be required. Dr Sinclair acknowledged that a big wet could hold up the process. Ms Coram noted that the rehabilitation and closure of Pit#3 will be more complex than Pit#1 due to the time issues involved. Dr Sinclair suggested that hydrogeological issues will be the primary concerns in Pit#3 closure. Dr Mudd asked whether ERA has looked at tailings heterogeneity to improve consolidation based on the observed consolidation rates observed so far. Dr Sinclair advised that ERA is currently working on a deposition plan and the results of the work to date are informing this. He noted that once the tailings have been deposited, some further adjustments will be required to ensure maximum density. Prof Woodroffe


asked how often the settlement plates are being measured. Dr Sinclair advised the settlement plates are being surveyed regularly using lasers and as settlement can occur relatively quickly, a higher frequency is required.

Pit#3 under fill (brine management facility) – Approximately 20.7 Mt of material out of a total of 30 Mt has been placed into Pit#3 since December 2012. ERA is on schedule to complete 30Mt placement in Q2/3 2014 which will enable the brine management project to be commissioned from Q1 2015.

Tailings and Brine Management project – Phase 1 – The tailings deposition system will involve dredging, screening, thickening and pumping to Pit#3. Decant will be pumped back to the TSF. The first 2 years dredging will be mainly coarse sands not slimes. Brine injection to Pit#3 will use vertical injection wells and possibly directional drilling if needed. Water displaced from Pit#3 will be pumped to the TSF.

Dr Mudd asked if thickening will involve physical reduction of water volume and Dr Sinclair advised that the thickening is not just chemical agglomeration of fines and there will be a 63% reduction of water volume with thickening. Dr Mudd asked what material will be used for the drainage layer and Dr Sinclair advised probably a 1 to 4m graded rock and geotextile but this was still being determined. Dr van Dam asked when the brine injection to Pit#3 will commence and Dr Sinclair advised probably in May 2015Dr van Dam asked if 18 months of brines going to the TSF will impact on the recovery efficiency in Brine Concentrator and Dr Sinclair advised this may have implications on the operations of the Brine Concentrator and that is why it is important to prepare pit 3 to receive brines from Q2 2015 per the proposed project schedule.. Mr Tayler asked if the contingency pumping units could be used for pumping tailings and Dr Sinclair advised this was feasible depending on the diameter of the pipe

The proposed Pit#3 backfill plan involves 30Mt low grade ore deposited from Nov 2012 to Aug 2014, 41Mt tailings deposited (Mill - 14Mt and TSF - 27Mt) through to Dec 2020, 62Mt waste rock placed in pit over 22 months over 2023/2025 and then covered by waste rock to final landform. Contaminated/unsalvageable plant and infrastructure will also be disposed in Pit#3. It is proposed that the Pit#3 Brine/tailings disposal application will be submitted to MTC for approval in Q3 2014. A number of co-commitments will also need to be achieved.

Ranger 3 Deeps project – The exploration decline project is going well with the face position now 1555m from the surface. Three drill rigs currently operating and 7958 m of drilling has been completed and core recovered. The access road and pad for the ventilation shaft have been completed and pre-consolidation resin injection is underway. ERA is finalising a tender for the vent raise and is awaiting MTC approval to amend the shaft design from 2 to 1 leg. The first cross section of the resource has been completed and initial underground drilling results show significant high grade intersections consistent with the expected continuity of mineralisation within this zone of the mineral resource. The radiometric sorter has been recommissioned (Oct 2013) and is being used to beneficiate high carbonate content R3D ores. Use of the sorter for low grade ore stockpiles is being evaluated.

R3D approval process status – The draft EIS is on track and associated environmental and social studies are ongoing. The draft EIS is expected to be submitted in Q2/3 of 2014 with a final decision on approval expected in 2015. An animal (Fawn antechinus) listed under NT legislation as endangered has been found on the site and ERA is currently looking at habitat requirements and developing a management plan.

Mr Issaverdis asked if Parks Australia was aware of the presence of the endangered species on the mine lease and Dr Sinclair advised he would follow this up.

ARRTC31-7: Dr Sinclair to confirm whether ERA has advised Parks Australia of the presence of the endangered animal (Fawn Antechinus) on the mine lease.

Environmental studies - Ms Iles presented a schedule for scientific studies required to inform the development of closure criteria and support applications for regulatory approval. The priority of each of these studies is based on the date the activity starts and the date the application needs to be made to the regulatory authority. Technical Working Groups (TWG) are being established for each of the closure criteria themes and these will report to the Closure Criteria Working Group which will then report to the MTC. Each TWG will also undertake a gap analysis.

4.2 ERISS 2012-13 RESEARCH OUTCOMES AND PRIORITIES (DR VAN DAM) Dr van Dam provided the eriss overview for 2012-13. Key points are summarised below.

2012-13 water quality – The 2013 wet season was well below average with most of the rainfall occurring towards the end (March – May). There was limited mine discharge into Magela Creek prior to this and upstream (US) and downstream (DS) water quality didn’t diverge until these events. Gulungul Creek followed a similar pattern. It was noted the peak EC event (over 100 u/S/cm) in Gulungul Creek in late May 2013 was very unusual. Investigations by SSD indicate the spike of bicarbonate and U came from a tributary flowing from the area of Anomaly 2. SSD is looking into the possible sources but they are expected to be natural in origin. Overall water quality in Magela and Gulungul Creeks has been good.

2012-13 research priorities – Current SSD research priorities include treated process water management, Pit#3 tailings/closure, Pit#1 closure, LAA remediation, whole of landform design and post-rehabilitation monitoring. SSD also regularly reviews and updates its research priorities to take account of ERA’s rehabilitation/closure priorities and associated knowledge gaps. The SSD commercial research program has been scaled back to enable resources to be directed to high priority research. New knowledge gaps identified as a result of the Rehabilitation/Closure Risk Assessment will also need to be addressed in due course.

ERISS Project summary – The 2012-13 research activities represent a significant program of work so it’s important to assess progress to manage overall resources. Based on this 25% of projects progressed slower than expected and 7% had no progress at all due to various factors including resource constraints, competing priorities, awaiting data/info from others and other program management requirements. Some projects (e.g. monitoring and commercial work) are not negotiable and must continue. Similarly, external projects under contracts have to be done. Key projects delayed included NH3 final water quality trigger values, sediment U trigger values, billabong water quality closure criteria, trial landform erosion and chemistry studies, the UAV demonstration project and the Rehabilitation/Closure Risk Assessment. Despite this, SSD still had a strong year with scientific publications. There is complex interconnectivity between many SSD research projects and ERA rehabilitation activities at Ranger.

Issues – Current staffing and resource constraints at SSD and ERA and the resultant impacts on research programs continue to be of concern. Due to conflicting priorities and resource constraints, the Rehabilitation/Closure Risk Assessment has not progressed as


expected which has impacted on the KKN revision process. However, SSD and ERA continue to report to ARRTC on how current research activities are addressing the KKNs.

Dr Mudd asked what ARRTC can do in relation to the current SSD resource constraints given its statutory role. Dr Barry stated that ARRTC’s primary responsibility is to ensure that all high priority knowledge needs are being appropriately and adequately addressed by the best available scientific research. If this is not the case, then ARRTC has a responsibility to raise this as an issue with the Minister. Dr Barry suggested the issue of who actually undertakes the research is less of a concern. Dr Mudd noted the current linkages between and integration of SSD and ERA research activities is an example of this. Ms Coram agreed but stressed the lack of SSD groundwater research activities continues to be a critical gap which needs to be addressed. Dr van Dam acknowledged that groundwater remains a key knowledge gap for SSD. Ms Coram also suggested that groundwater issues more generally require closer oversight. Mr Tayler advised that SSD is looking to get all of the groundwater research done by ERA and have this then independently reviewed. Dr Sinclair noted there are linkages between SSD and ERA on groundwater research matters but agreed resources are limited. Dr Humphrey noted that for some disciplines, either SSD or ERA may decide to under-resource particular expertise in the knowledge that the other agency has strengths in the discipline (cost-efficiencies).”Dr Sinclair noted the key point is that the critical work is done either using in-house or external expertise as required. Mr Tayler noted in terms of statutory approvals there probably needs to be a formal external independent review process and that SSD would most likely engage the expertise of Geosciences Australia for this.

SSD 2012-13 Research highlights – Key research outcomes included the in- situ toxicity monitoring analyses to correlate EC temp interactions and effects on snail egg production, the development of ecotoxicology/trigger values for process water distillate (Mn, NH3), trial landform solute data analyses (ERA is keen to see results inform Pit#1 and Pit#3 work), work on radon exhalation from rehabilitated landform (jointly with ERA to develop predictive models for radon exhalation in various cap depths) and investigating the feasibility of UAV technologies for remote sensing and analyses.

SSD 2013-14 Research priorities – Current key research priorities include the knowledge to inform development of closure criteria, progressing the rehabilitation/closure risk assessment, the trial landform project, the review and further development of the landform evolution modelling program, the ammonia toxicity work, the revision of the Magela Creek water quality objectives and further development of post rehabilitation monitoring methods.

ARRTC31-8: ARRTC thanked Dr van Dam for his presentation and noted the key outcomes of the SSD 2012-13 research program.

4.3 RESEARCH ADDRESSING KEY KNOWLEDGE NEEDS DURING OPERATIONAL AND REHABILITATION AND CLOSURE PHASES (JOINT ERA/ERISS) 4.3.1 Operational phase

Presentation: Toxicity testing associated with brine concentrator (Dr Harford) This project aims are to assess the toxicity of Brine Concentrator (BC) distillate and to derive site-specific Trigger Values (TV) for manganese and ammonia (interim only).

TV for manganese - A pilot study in 2011 found that BC distillate affected Hydra viridissima population growth due to the deficiency of major ions and that Mn at concentrations found in distillate could also reduce H. viridissima growth. Five local freshwater species were used to assess the toxicity of various concentrations (0 – 100 %) of distillate diluted with Magela Creek water (MCW). The results showed that a 50% dilution in MCW resulted in complete recovery for all species and amendment with Ca, K and Na resulted in 100% recovery, except for H. viridissima (80%) and M. macleayi (60%). It was noted that the addition of magnesium may have assisted recovery. The toxicity effects resulted from the deficiency of major ions which was not unexpected considering the low major ion concentrations in the distillate.

Dr Harford advised that manganese has been a low priority contaminant of concern for many years and that the current water quality guideline of 26 µg L-1 Mn was based on upstream data. He noted that previous work using water from Swift Creek (2008) and BC distillate (2011) had shown that H. viridissima growth is reduced by Mn at concentrations of 130 - 230 µg L-1 Mn. It was also noted the Draft Environmental Quality Standard for Europe is 123 µg L-1 Mn and concentrations in full-scale BC distillate range between 100 - 200 µg L-1. Ms Iles noted that those results were from the ERA laboratory which was also analysing process water and brine. Duplicate samples sent to NTEL had much lower numbers. The method involved exposing 6 local freshwater species to different dilutions of Mn using MCW as the reference (control) water. The results based on the species sensitivity distribution produced a 99% species protection TV of 3.9 µg L-1. Historical upstream data indicated that this TV could not be implemented because it would be exceeded 50% of the time. Therefore, 3 additional chronic exposure toxicity estimates from studies conducted under relevant water conditions were included in the species sensitivity distribution and a 99% species protection TV of 75 µg L-1 was derived. It was concluded that this Mn TV is useable and appears “reasonable” as it is half the lowest IC10 for H. viridissima (160 µg L-1) and below the EU’s EQS of 123 µg L-1. It was noted that Mn speciation is complex and further speciation studies would be useful.

Interim TV for ammonia – It was noted that all results are presented in total ammonia nitrogen (mg L-1 TAN), which includes ammonium ions. There is a significant concentration of ammonia in process water, some in RO-treated permeate from the WTP and some measurements in BC distillate that are higher than background levels. Work on ammonia toxicity testing in Magela Creek has commenced and past toxicity testing has found that H. viridissima is sensitive to ammonia (EC10 = 0.22 mg L-1 TAN @ pH 8). Ammonia toxicity is highly dependent on pH and temperature and statistical analysis of continuous monitoring data was used to calculate the upper 90th percentiles for pH (6.4) and temperature (32oC). Toxicity data, that was used in a recent USEPA ambient water quality criteria report, were used to derive an interim 99% protection trigger value noting however they included primarily temperate species and do not include plant or algae species and were . The species sensitivity distribution (using toxicity estimates pooled by Genus level) derived a 99% TV of 1.4 mg L-1 TAN at pH 7 and 20oC. Adjusting to local conditions (pH 6.4 and temperature of 32°C) derived an interim 99% species protection TV of 0.7 mg L-1 TAN for Magela Creek (MG009). Focus and action levels are still to be determined. The interim TV will be tested against data from local species over the next year. It was noted the


SSD TV is lower than the USEPA value because the USEPA value is based on 95% protection level whereas the SSD work is based on 99% species protection level.

Dr Humphrey noted that the issue of high level background concentrations is also covered in the National Water Quality Guidelines. Dr Mudd asked if it is possible to get lower detection limits for major ions and what the results mean in terms of Total Dissolved Solids. Dr Harford advised that the lowest detection level possible is about 0.1 µg L-1. Dr Mudd asked about the effect of the Mg:Ca ratio and Dr Harford noted this was not a relevant factor in these waters. Prof Boon noted this toxicity work has potential broader application to the use of other treated waters. Dr Harford noted there is a paucity of detail in the literature on the topic and the Ecotoxicology Program is currently publishing a paper on 10 years of treated mine water toxicity work. Dr Harford advised the mussels are highly sensitive and Dr Erskine asked how this sensitivity is dealt with in interpreting results. Dr Harford advised that there are rules in the revised Water Quality Guidelines on how to deal the reliability of results when using highly sensitive species. Dr Mudd asked how it is determined that the test has measured the more sensitive species in the ecosystem. Dr Barry suggested this shouldn’t be a concern as the sample is supposed to be representative. Dr Harford indicated he is looking at whether mussels should be added to the suite of local species used in ARR ecotoxicology analyses and also snails as they are known to be sensitive to ammonia. Dr Mudd suggested it comes back to baseline conditions and if values are far exceeding natural values. He noted it also demonstrates the value of having more species tested and how sensitive these curves are to the number of species in the dataset.

Presentation: Mg multiple pulse ecotox study (Dr Harford) Work by SSD in 2010 using lab based experiments found higher magnesium (Mg) toxicity in H. viridissima than identified in earlier work due to the soft water in the ARR. Later work by SSD in 2013 comparing effects of pulse exposures over a number of different exposure durations found a relationship between Mg toxicity and exposure duration, leading to the derivation of pulse-duration TV framework that is used to interpret the effects of pulse exposure in Magela creek. The aim of this study was to determine if H. viridissima was more sensitive to a second pulse and the time required for full recovery following a pulse exposure. The study was undertaken as an Honours project by Ms Andrea Prouse from RMIT-University. Modified 96-h toxicity tests were used with sensitivity to a single pulse as the positive control. An apparent recovery period for H. viridissima was determined to be about 4 days. True recovery was observed in all groups and growth rates were greater in double pulse treatments. The study also determined if concentration multiplied by duration equals a constant effect and whether multiple pulses need to be treated as separate or single events. It was noted that some regulators use concentration duration time (e.g. USEPA). Results indicated that H. viridissima benefits from inter-pulse recovery periods. Key findings from this work included that after non-lethal Mg pulses H. viridissima recovers rapidly once returned to non-toxic media and organisms exhibit less sensitivity to a 2nd pulse than to a single pulse (not clear if due to resistant individuals or tolerance development). A minimum recovery time was not determined because there were no recovery periods tested where organisms did not recover. Future work will include shortening recovery periods to find a non-recovery period and assessing if similar response in other species (e.g. Cladoceran).

Prof Boon asked how the specific mechanism of toxicity is determined and if this known in this case. Dr Harford advised the mechanism of toxicity is unknown at this stage but suggested it could be related to ion toxicity. Dr van Dam noted that considerable research on this question has been done by others, and suggests a key mechanism of action is due to Mg’s property as a Ca antagonist. This has been shown for mammals and some aquatic organisms. Prof Boon noted that exposure time is also an important factor and thatin the analyses should include repeated measures.statistical analysis, and Dr Harford noted he would look at using a repeated measures design analysis.

4.3.2 Rehabilitation/closure phase and associated activities

Presentation: Ecological Risk Assessment (Dr Bartolo) ERA and SSD are collaborating on an Ecological Risk Assessment for the rehabilitation and closure of Ranger. This project comprises 3 phases: (1) problem formulation, (2) risk analysis and (3) interpretation of results. The problem formulation and related conceptual models will inform the development of closure criteria and associated compliance metrics, and will inform the revision of the Key Knowledge Needs. External facilitators (CSIRO) were engaged to guide and assist the problem formulation phase. The aims of the problem formulation phase included determining relevant ecological assessment endpoints, identifying the key sources, stressors and ecological assets during the relevant temporal (decommissioning, stabilisation, monitoring and post-closure) and spatial (Ranger minesite, Ranger lease, Magela Creek catchment, KNP and ARR) scales, develop associated conceptual models and design the methodology for the risk analysis phase of the assessment. The temporal scale includes having to address cultural requirements of TOs over 7 generations (300 years). The approach used is consistent with the AS/NZS ISO 31000:2009 Risk management-principles and guidelines and the risk assessment components are consistent with the Guidelines for Ecological Risk Assessment (USEPA, 1998). The assessment endpoints have been redrafted from the original management objectives. A total of 19 conceptual models were drafted. There are 3 assessment endpoints that are yet to have models redrafted and finalised: 2 for aquatic ecosystems (which will be addressed upon completion of the ecological processes definition) and 1 for human health (which will be addressed by combining the human health and terrestrial (RPA) model. During the review of the models it became apparent that ecological processes were not clearly defined and required further clarification. A small focus group from the aquatic ecosystems breakout group has drafted a paper discussing ecological processes and how these can be measured. This issue will be further addressed through the Closure Criteria WG. The risk analysis phase of the project will commence in 2013-14. It was noted that progress to date has been hampered due to staff availability (resourcing) for the project, both within SSD and ERA.

Prof Woodroffe questioned the appropriateness of having Erosion characteristics of the rehabilitated landform meets agreed closure criteria as the assessment endpoint in the causal model covering Risks to landform stability on Ranger mine site as these are in fact different issues. He asked where significant issues such as gully erosion are being captured in the models. Dr Bartolo advised that the final models will be supported by explanatory narratives setting out the rationale for the selected endpoints. Mr Tayler noted the current models are still drafts and will be reviewed by the Closure Criteria Working Group to identify any inconsistencies and revised accordingly. Prof Mulligan thought the soil erosion pathway in the example model presented would include gullying. Dr Barry noted that the models are still in draft form but suggested it is a potential concern at this stage that some stressors or pathways may be missing. He noted that ideally a complete process of identifying and prioritising all relevant risks and hazards should be done but acknowledged a full assessment for each model is not possible and further filtering will be required. Prof Mulligan asked what the next steps are in progressing the project. Dr van Dam advised that it is proposed that external expertise be engaged to assist with the screening process. Ms Iles noted that further discussions are required about how to


resource this. Dr Barry noted that the screening process is critical to ensure all relevant risks are identified and incorporated in the models. Prof Mulligan asked how ARRTC could assist at this stage and Dr Barry suggested that ARRTC could review the outcomes of the screening process. Dr Sinclair noted the CCWG TWGs will have primary responsibility for reviewing the screening process but agreed ARRTC’s comments on the outcomes would be valuable. Ms Iles noted the TWGs will include people who were involved in the initial workshops. Dr Sinclair noted that the Cultural TWG membership also needs to be able to provide stakeholder endorsement of outcomes as well.

Presentation: Water quality closure criteria (solutes, suspended sediment) for natural waterbodies adjacent to Ranger (Dr Humphrey) Dr Humphrey noted work in this area has been underway for several years using a field effects approach complementary to a laboratory approach. He noted Georgetown Billabong (GTB) provides a good test bed for deriving solute (including MgSO4) and turbidity closure criteria for billabongs (using turbidity-phytoplankton relationships). Data from Jim Jim Creek are being used to derive turbidity closure criteria for creek channels (using turbidity-macroinvertebrate responses).

Water quality closure criteria for Billabongs – Both Coonjimba and Georgetown Billabongs have historically received runoff from very low grade and waste rock stockpiles, polished wetland filtration waters and/or land application (irrigated) areas. Also there has been some contamination of surface waters by MgSO4 and to a much lesser extent by U. It was noted that Coonjimba Billabong surface waters are more contaminated than Georgetown Billabong. The closure objectives for billabongs are linked to the closure objective that surface water discharges from Ranger should not compromise the biodiversity of aquatic ecosystems in the ARR. The current approach is guided by ANZECC/ARMCANZ (2000) philosophy that where there is low contamination present, but biological communities are still intact, the water quality record should be used to derive closure criteria to protect aquatic ecosystems. This work involved collection of macroinvertebrates from macrophyte habitat in 14 waterbodies. Family-level rank-abundance data were analysed using univariate and multivariate techniques, and GTB was compared with reference waterbodies. For the years 1995, 1996, 2006 and 2009, community structure in GTB was similar to reference but was significantly different in 2011. Taxa number in GTB has declined over time and was significantly lower in 2011 while Mg levels also increased over the same period. This indicated that a Mg value of < 5 mg/L would be protective of biota. Where GTB biota was equivalent with reference, corresponding water quality data were used to derive closure criteria. The biological field effects of < 5 Mg/L is similar to the laboratory derived limit of ~ 3 mg/L Mg, although the field effect is actual and the laboratory value is extrapolated using different exposures for 99% species protection. In relation to EC, water quality was poor in the years prior to 2009 and 2011, so water quality from 1995, 1996 and 2006 are being considered in the derivation of closure criteria. The derived criteria are less conservative than had values been based upon a reference condition approach but are still protective to the standard of reference condition. The very different (natural) water quality in GTB between wet (Jan to May) and dry (Sept to Dec) seasons, however, suggests that two sets of criteria are required. The 80 percentile values of EC, Mg and U for the wet and dry season data relevant to those years in which macroinvertebrate data are akin to reference. Further work will be done to determine whether the results of sampling post 2011, including periods of improved water quality, are consistent with the field effects relationship observed to date. The Mg threshold will be reassessed and ecological models of threshold response/recovery will also be assessed. Based on this work, it is suggested that extended periods (i.e. longer than 3 months) of Mg greater than 4 mg/L should be avoided. Alternative and corroborative approaches to determining thresholds in biological community responses will also be explored. The closure criteria and supporting evidence will be reviewed by the Closure Criteria WG.

Deriving turbidity closure criteria for billabongs and creek channels – Turbidity in GTB usually increases over the dry season to a threshold at which light and subsequent photosynthesis and phytoplankton growth are reduced. Based on turbidity-chlorophyll relationship data from 1981, 2009 and 2012, phytoplankton inhibition in GTB occurs in the range of 50 – 70 NTU. Turbidity-macroinvertebrate data from an unformed road crossing in Jim Jim Creek in 1996 were analysed using multivariate techniques. Original data analyses indicated that in the absence of disturbance, communities become more similar over the recessional flow period (early dry season) in reference streams while impacted sites indicate higher dissimilarity. In the case of Jim Jim Creek, similarity was higher than what would be expected for a given flow regime. Results indicated that increased turbidity in Jim Jim Creek led to impacts on the downstream communities but a threshold value could not be determined. MDS ordination and ANOSIM of community data indicated that sustained turbidity levels of >30 NTU resulted in impairment to downstream macroinvertebrate communities. Group separation showed a high proportion of predatory taxa which don’t have external gills which would be clogged by suspended sediment. There was also a corresponding decline in a Hardyhead fish species which has a visual feeding strategy and would've normally consumed these taxa.

Based on this work, thresholds for biological effects of high and sustained turbidity in ARR ecosystems are between 50 -70 NTU for phytoplankton in GTB and 30 NTU for macroinvertebrate communities in the Jim Jim Creek channel. However, there is a need to decide whether to combine, keep separate or take the most conservative values. Also need to keep in mind that the values are derived from dry season studies whereas erosion-induced, elevated turbidity associated with rehabilitation will occur during the wet season and that sources of turbidity for the two studies reported above differ from those to be expected to arise from erosion of rehabilitated mine landforms (i.e. laterite and Cahill schists). Also sustained elevated turbidity is unlikely in the wet season, but there is potential for sedimentation in billabongs from ‘short-sharp’ events. Further work will look at the effects of short term turbidity peaks in GTB and sedimentation effects. It is expected this will be further examined in the newly formed TWG.

Ms Iles asked if there is a SSD report on this work and Dr Humphrey advised a report is currently being finalised (Dr George noted the report is 70% drafted). Ms Iles noted the work will be valuable for informing the work of the Closure Criteria Working Group. Ms Iles advised that ERA has questions about the Mg criteria and the need to look at other variables. (i.e. the relationship is correlative but is it causal and have other variables such as hydrology (high flow through system and high water levels around that time) been assessed?) Dr Humphrey noted the values derived are less conservative than had they been derived using a referential approach, and that they are consistent with (and less conservative than) lab values.. Prof Boon asked to what extent turbidity and chlorophyll a are correlated. Dr Humphrey advised that, as sampling occurred at the very beginning of the wet season, turbidity is low and turbidity then increases to the point where phytoplankton decreases. Prof Boon queried if turbidity is affected by the chlorophyll in phytoplankton and Mr Tayler queried whether the phytoplankton itself might impact on turbidity. Prof Woodroffe asked if turbidity responses vary between organisms (i.e. wouldn’t there be a pattern between some taxa that can tolerate turbidity and those which are sensitive). Dr Humphrey advised this was just an example of an indirect ecological effect. Prof Woodroffe asked if there are species (e.g. mussels) that are not sensitive to turbidity. Dr van Dam asked whether the focus is more on communities rather than species. Dr Humphrey agreed and advised this is a community level response (phytoplankton and macroinvertebrate communities).


Dr George advised the current work had looked at macro-invertebrates as those data were available and that other biotic groups will be looked at in the future. Dr Mudd asked how important the link between turbidity and dissolved oxygen is. Dr Humphrey advised that turbidity is the main driver in responses and the results are essentially dealing with biological response. Prof Boon noted that previous studies in billabongs in Victoria had shown there was diurnal stratification. Mr Tayler noted the diurnal temperature variation is higher in tropical systems. Dr Humphrey noted that dissolved oxygen levels vary on a diurnal basis. Dr Mudd asked if turbidity was a factor in reducing dissolved oxygen and Dr Humphrey indicated this wasn’t the case. Mr Johnston asked if studies on the trial landform are also looking at potential turbidity impacts. Mr Tayler noted than the closure criteria need to be based on ecological effects rather than just on physico-chemical factors.

Presentation: Revegetation (Dr Humphrey/Dr Lu) For the past 20 years, ERA has disposed of excess pond water using natural woodland Land Application Areas (LAA) on the mine lease. There 8 LAA on the Ranger lease covering a total area of approx 340Ha. These LAAs will be progressively rehabilitated commencing with trials in the Magela and Djalkmarra LAAs in 2014. This will require the development of closure criteria for radiation, soil quality and flora and fauna. Over the past 4 years, ERA has undertaken extensive field investigations looking at radioactivity and heavy metals in LAAs and various remediation strategies, including two collaborative projects with SSD and Safe Radiation Pty Ltd (Dr Riaz Akber). These investigations showed that the level of heavy metals (Cu, Mn, Ni, Pb and Zn) in LAAs are less than the Health Investigation Levels (HIL) for relevant land use types stipulated under the National Environment Protection Measures (NEPM) guidelines. The level of sulfur is also below the NEPM Ecological Investigation Levels (there being no HIL for S). Uranium contamination in LAAs is restricted to the range of the sprinkler systems and contamination from leaf litter is insignificant. Magela Creek LAA (as the oldest LAA) has the highest contamination (mainly U and some Mn). The annual radiation dose via four key radiation pathways was assessed for each of the LAAs. Dose contribution from entire LAAs is quite low at 80 µSv yr-1, which is about 27% of the dose constraint (assuming RPA overall public dose constraint is 300 µSv/yr). Magela LAA contributes majority of the dose (>72%). The key pathways are direct irradiation and inhalation of dust. During 2011-12, collaborative work with SSD was done to test the effectiveness of 4 soil remediation methods (baseline, soil mixing, soil removal and both) and to refine associated parameters (e.g. extent of soil removal required and soil erosion measures). Soil mixing is the preferred option for Magela LAA “Area B” with erosion and overland flow controls. It is proposed that the revegetation of LAAs will be consistent with the revegetation strategy developed by ERA (Reddell & Meek 2004; Gellert 2012) which requires the early establishment of framework trees and exclusion of fire for at least three years. Reference and analogue sites will be used to inform species selection and development of closure criteria. Stakeholder expectations regarding final landform use will also need to be taken into account. It was noted that LAAs in the Magela Creek catchment have high incidences of Acacia holosericea, which is not endemic to Ranger and an aggressive species which responds well to disturbance including fire. Data from ERA and SSD from vegetation analogue areas was combined and classified using multivariate techniques. The classification indicates that, historically, vegetation of the LAAs was likely the common mixed Eucalypt woodland community. Modelling of plant-environment relationships indicated that the woodland trees and shrub species making up this community are ubiquitous and have no strong preference for any particular environment conditions. This suggests that the revegetation strategy for eucalypt woodlands on LAAs could involve planting in similar densities and frequencies as found on adjacent woodland areas. The original radius of 30km previously proposed as provenance for seed collection is considered to be too restrictive and following a technical review it is proposed that a much broader zone be used subject to stakeholder agreement. It was noted that species selection and development of closure and assessment criteria for monitoring and sign-off will be considered by a Revegetation Technical Working Group, reporting to the Ranger Closure Criteria Working Group.

Dr Mudd asked if there is a plan to do follow up assessment of rehabilitated LAAs to ensure the sites are stable. Dr Lu advised that remediated LAAs will be resurveyed over time. Ms Paulka advised that the sites will be monitored on an ongoing basis leading up to closure and she expects that the gamma measurements should remain fairly stable. Dr Humphrey noted that ERA has undertaken considerable work on LAA remediation, particularly the vegetation aspects. He noted the LAA rehabilitation process provides the first opportunity to apply the analogue vegetation rehabilitation approach. He welcomed ERA’s commitment to adhere to the original revegetation strategy developed by Reddell et al (and updated in 2012), particularly the focus on framework species and the exclusion of fire for first 3 years. Dr Humphrey noted the high incidence of Acacia species on the sites poses a number of challenges. Dr van Dam asked if the high incidence of Acacias may be due to prior disturbance of these areas. Dr Humphrey agreed that this could be related to prior disturbance. Dr Lu noted that Acacia holosericea was used in trials to control mission grass conducted by CDU in 2006-2007. Dr George asked if it is planned to review the population modelling in terms of planting strategies, as planting in same densities as analogue areas doesn’t take account of mortality effects. Mr Tayler advised that ERA will need to ensure they plant sufficient trees to allow for mortality. Dr Barry asked how vegetation analogue areas will inform the development of closure criteria. Mr Tayler noted that the closure criteria will not specify a planting rate. Prof Mulligan noted that the initial discussion focused on revegetation of LAAs, but obviously this also has implications for revegetation strategies for the final landform. Prof Boon asked what strategies will be used to avoid having a single cohort of vegetation on LAAs and Dr Lu advised that planting will need to occur over a number of years.

Presentation: Developing monitoring techniques for onsite/offsite monitoring after rehabilitation (Dr Bartolo) Dr Bartolo noted that her group has been renamed the Revegetation and Landscape Ecology Group. There are a number of research projects addressing monitoring requirements during the operational and rehabilitation phases and establishing baseline data on natural variation. One such research project is looking at demonstrating the utility of unmanned aerial systems (UASs) for monitoring rehabilitation and revegetation of the Ranger mine site. The project is trialling the feasibility of using UASs to obtain very high resolution imagery that can be used to monitor site rehabilitation in a time and cost effective way. The project aims to demonstrate that UASs can be used successfully at Ranger and to gather the necessary data from test sites. This is a collaborative project with the University of Queensland, Centre for Mined Land Rehabilitation (CMLR) which shares common research objectives with SSD. This is the first time the Swampfox (Skycam NZ) technology has been tested under extreme tropic climatic conditions and for monitoring ground features such as savanna, floodplains and billabongs. UAS tests were conducted at four sites during the period 8-10 October 2013 when temperatures exceeded 40oC. All areas flown were outside the 3 nm restriction around Jabiru air strip which includes a large portion of the minesite. CMLR research team and the manufacturer of Swampfox conducted the tests with ERISS staff present. Swampfox was used for all sites except the Georgetown Analogue area where a TekSumo flying wing was used due to the increased tree cover and restricted launch space. Due to the high temperatures, the cameras stopped working. A number of modifications were made to reduce the internal temperatures in the airframe. Savannas have few features for


registration which results in poor results when processing orthomosaics. A forward 75% forward overlap was used but a >90% forward overlap is probably required for savannas during the late dry season. There also could be problems with the Pix4D software. The poor results in the Djarr Djarr test were due to a combination of low altitude (~80m AGL) and slow frame rate (1.8 secs) which should be remedied by increasing forward overlap and frame rate. Key findings included that UAS systems provide a flexible and cost effective means of image capture subject to temporal and climatic factors and a resolution of 5cm GSD is required for mine site applications. It was noted that a hyperspectral sensor (camera) would provide increased spectral resolution and thus enhance the monitoring applications and science questions that can be considered. CMLR are working on increasing the trigger rate of the cameras and the data processing issues. SSD is currently considering whether further testing is required before making the decision to proceed with purchasing a system. Current testing indicates that object based segmentation can be used to produce classification of cover type quickly and cost effectively.

Prof Boon asked about the implications of the speed of technological change noting that companies are continually bringing out new cameras. Dr Bartolo noted that technology is relatively inexpensive enough to update as required but agreed this may pose issues with calibration. Prof Mulligan noted that newer cameras can capture JPEG images and Dr George noted that options for LiDAR capture are also available down to 5cm resolution. Dr Bartolo noted this depends on the footprint involved but agreed very high resolution imaging is possible. Dr Barry suggested that, as the UAV space is very well populated with various technologies and support systems, some degree of caution is needed when investing in proprietary technologies when much of this is now available off the shelf. Prof Mulligan noted a key benefit with UAVs is the frequency of sampling. Dr Bartolo noted that lower cost is also a key consideration. Dr Barry suggested there is also a need to integrate this technology with existing plot based measurement systems. Dr Bartolo advised the UAV technology fits within a broader integrated multi scaled approach. Prof Woodroffe indicated that he is pleased the technology is being looked at for application in the ARR and asked if any other agencies have expressed interest in using the technology. He noted that outputs from the system may need to be integrated with the information requirements of other agencies (e.g. Parks). Prof Mulligan declared that the Centre for Mine Land Rehabilitation has a commercial interest in promoting this technology, but is only providing SSD with advice at this stage. Dr Mudd agreed the technology has potential broader application for other sites in the ARR and could provide very useful data in terms of remote monitoring of rehabilitation. Dr Bartolo suggested the technology could be used for monitoring the rehabilitation of Nabarlek. Dr Mudd noted there has already been 18 years of revegetation at Nabarlek but there may be value in doing this. Dr Barry noted the potential benefits of the technology but underscored the need to clearly define the scientific rationale for using the technology and what specific research questions are being addressed. It was also noted that UAV systems can potentially carry radiometric monitoring equipment.

Presentation: Contaminant transport modelling – groundwater (Dr Sigda - Intera Inc.) Dr Sinclair advised that Intera and CSIRO have been doing groundwater and solute modelling around Pit#1 and Pit#3 which is feeding into Ranger rehabilitation/closure planning processes. Dr Turner has been focusing on Pit#1 solute fluxes and feeding this into the hydrodynamic model while Intera is doing Pit#3 seepage estimates over 10K years and also looking at potential catchment effects. Dr Sinclair noted that the work still needs to be integrated but will be critical in informing the design of the final landform. He noted that ERA would welcome ARRTC’s comments on the work and results to date.

Dr Sigda advised that Intera Inc has undertaken significant work during 2013 which has enhanced the current level of understanding of features and drivers of solute transport across the site. He noted the key changes from 2012 to 2013 included updates to the conceptual model, 3D groundwater flow calibration model, source term models for conservative (Mg2+) and reactive (U, Mn, and Ra-226) solutes, a 3D predictive groundwater flow and transport model for Mg2+ and a 1D reactive transport model for U, Mn, and Ra-226. While there is good understanding of solute generation from tailings, there is still some uncertainty regarding solute generation from waste rock. The new Pit#3 closure plan 1B now has tailings sitting 26m higher in the pit. The billabong on top has now been removed and there is a drainage basin on the eastern side of the pit. The performance of new mitigation elements (caps for waste rock and tailings at depth, cut-off wall between Pit#3 and Magela Creek) has also been investigated. The new 3D and 1D predictive models based on updated conceptual and flow calibration models and sources have reduced uncertainty in source term behaviour for all solutes and enable the loadings to Magela Creek from waste rock, tailings, and brine to be quantified. Changes to the Ranger conceptual model include expanded review and evaluation of site specific information (hydraulic properties and geochemistry), revised spatial extent and properties of existing hydrolithologic units (ancestral Magela sands characterised and Djalkmarra fault zone replaced by deep carbonate unit), addition of new hydrolithologic units (waste rock stockpiles, waste rock in final landform and 2 bedrock units near Pit#1) and surface seepage (ground surface) as a key process. The key driving forces for flow and transport are recharge, evapo-transpiration, surface-groundwater interactions and topographic flow. The extent of the ancestral Magela Sands has been expanded (approximately doubled) following the review of old bore logs. A number of new bores and piezometers have been installed and sampled to determine geochemical properties.

Dr Mudd asked if in-situ density and porosity were also measured in the bores and Dr Sigda confirmed this. Dr Mudd agreed all of the right things appear to have been measured. Dr Sigda noted that the bore is only about 150m deep so only thing that would change is timing not loading. Dr van Dam asked if the depth of the sand unit in the model has also changed and Dr Sigda advised that depth has changed by up to 8m in some areas. Prof Woodroffe asked if the sands are Pleistocene or Holocene or a mixture and Dr Sigda advised that the age of the sands is currently not known.

Dr Sigda noted that landform waste rock was added as a new hydrolithologic unit to the post-closure model. This increases recharge outside of the pits and its thickness varies from < 2m to 14m. The groundwater flow model was recalibrated to address the new and revised hydrolithologic units, correct coordinates for 17 calibration bores and increase the number of targets from 54 to 73 around Pit#1. Field tests using the new bores were used to constrain hydraulic conductivity for the ancestral Magela sands. The model was calibrated using the same approach as the previous model. Modelled seasonal head variations are captured in shallow and deep calibration bores, but rises and declines are less steep than those observed. Final calibration has good residual statistics and there is a good cross-plot between observed and simulated values.

Dr Mudd asked about the interaction between shallow and deeper groundwater and if the model will pick up the dynamics occurring in the deeper aquifers. Dr Sigda noted the deeper groundwater systems move much slower than shallow groundwater systems. He noted the model has been calibrated based on 80m depth but the actual model goes to a depth of 120m. As the transport time in deeper systems is so slow, this would have negligible impact over a 10k year period. Dr Sigda noted that if recharge is driving solutes downward they wouldn’t surface and flows have been forced to local in the model so the creek gets an event. Dr Mudd noted that the carbonate unit goes much deeper and expressed concern that this wasn’t covered in the model. Dr


Sigda noted that Packer testing on the carbonate unit lower in the sequence indicates that it has a much lower conductivity (2-3 orders of magnitude lower than weathered rock and 4-5 lower than shallow weathered rock). Ms Coram asked what the recharge values used were based on and Dr Sigda advised the recharge rates had been taken from the literature on ET and recharge work in Howard River Basin. He added that Intera wanted to confine the range but ensure consistency with other work. Dr Mudd asked if calibration involved testing and Dr Sigda advised that a calibration used a computational cluster with 20 machines running for a week.

Numerical modelling tools were used to predict differences in solute loading to Magela Creek for “base case” (no mitigation) and with mitigation scenarios. These included a 3D numerical flow and transport model of Mg2+ (constructed from the calibrated flow model and the source term models) and a 1D reactive transport model of U, Mn, and Ra-226 (with reactive loadings scaled from Mg2+ loading results). These models provide an indication of how much solute migrates to Magela Creek via which pathways over time and also what reactive chemistry is involved. The model includes groundwater discharged to the creek surface water, surface seepage in the NE margin of Pit#3 and also solute transport from the brines from Pit#3 underfill. The source and mitigation elements were identified with waste rock divided into time-varying leaching and steady leaching vadose zones. Recharge in waste rock is higher (10% monthly precipitation) versus 5% for weather rock and 3% for the low permeability cap. In the predictive model domain the creek is the only boundary removing water from system. Recharge in the riparian zone is 100% in first 2 months of wet season then nil. Evapo-transpiration is 25% on both weather and waste rock. ET in the riparian zone is 80% in first 3 months of dry season and then 10%. The model indicates that ponding of surface seepage will occur in the NE margin of Pit#3, so drainage would be required in these areas. It is assumed that these drains would transport solutes to Magela Creek. Mitigation scenarios can be assessed using either time-varying or average (steady) driving forces for groundwater flow. Over 10K years it is considered best to look at steady driving forces as solutes travel very slowly. To assess potential impacts associated with Pit#3 closure, a number of different closure scenarios were modelled using different mitigation elements. The various source terms for conservative and reactive solutes in Pit#3 were quantified. Time-varying leaching from the vadose zone in shallow waste rock in pit generates high loads of solutes until exhausted while steady leaching much less. Tailings have steady uniform leaching and contain 88% of all Mg produced. It was assumed that the landform waste rock does not leach and vegetation was taken into account. The leaching of Mg2+ in waste rock backfill was presented. Dr Sigda summarised the key findings from this work noting they are different to the findings from the 2012 work. Updated conceptual and numerical models were used to assess performance of low-K caps and cut-off wall. The modelling approach allows efficient simulation of solute loading to Magela Creek over 10,000 years. The increased recharge up-gradient of Pit#3 and topographic gradient drive flow across the backfill towards the creek, potentially causing surface seepage near the pit toe. There is little attenuation of reactive solutes during transport through the ancestral Magela sands after 60 years. Brine has negligible solute loading over 10,000 years and low-permeability caps are very effective in reducing loading, but not the cut-off wall. A combination of low-permeability caps reduces solute loading by 77% to 98% over 10,000 years.

Ms Coram asked if any sensitivity analysis of the model has been undertaken, particularly in relation to changes in K values given the importance of groundwater modelling in underpinning the rehabilitation design. Dr Sigda advised that no sensitivity analyses have been done as measurements are 1m or lower. He advised that, if looking at 10K year loading, as long as the relative difference is known and the driving forces are steady, there is limited value in looking at sensitivity. He also noted that waste rock is highest conductivity material in system and given the revisions to the model since last ARRTC, a higher K value would mean more flow through the tailings but still not a lot of mass. Dr Sigda noted the tailings are not the constriction, it’s the surrounding rock. He noted the Packer test data are currently being analysed and that K values for the bedrock are equal or 2 orders of magnitude lower than the tailings. He acknowledged it may be useful to look at doing a sensitivity analysis on weathered rock. Dr Sigda asked Ms Coram why she was concerned about having a faster rate and she advised if the solute is released faster, there would be a higher concentration in creek.

Prof Woodroffe thanked Dr Sigda for his presentation and noted he is particularly interested in the ancestral Magela sands. He noted there appears to be a Holocene floodplain nested in a Pliocene terrace and he is therefore interested in what has been deposited in the Magela sands over the past 10k years, and whether this is broader than the white sands observed in the Magela Creek floodplain. He suggested if there is more ancestral sand it may be important to determine where the boundary is and what effect this may have on the spatial extent of solute transport. Dr Sigda advised there is little neck effect. He noted that the work by Nanson et al is important in characterising Magela Creek sediments which are located in highly incised old lithofied sediments. He also noted that the Magela Creek sediments are treated as a whole body so the model probably assumes the sands are more conductive than they actually are. It was noted that silty sands are a common observation in bore logs. Dr Sigda advised the sand units in the model are not constrained. Prof Woodroffe asked how confident Intera is regarding the bottom of the sand unit and if it is irregular. Dr Sigda advised the bottom of the sand unit is irregular but thickness wasn’t an issue in terms of solute loading/transport. Dr Barry asked if there were other explanations that are equally plausible. Dr Sigda advised that, as the head remained the same, if the cross section is narrower then the flow rate will be faster and the inverse if thicker. Dr Mudd suggested if the cross section is thicker the load will be greater as conductivity affects flow and thus load. He asked if the total head in the system (elevated head and osmotic pressure) was considered and Dr Sigda advised this was not factored into MODFLOW. Dr Mudd noted that in terms of the Pit#3 cross section there is a rebound in groundwater levels during the early years and asked how long it takes for the system to reach a quasi-steady state. Dr Sigda advised Intera had taken a simple view that the system reaches equilibrium in 2025 and didn’t simulate the ramp up. Prof Mulligan asked why the model has water running across the top of the pit if there is so much existing contribution from the surrounding landform, and wouldn’t the infiltration risk reduction strategy be to not do this. Dr Sigda advised he wasn’t sure as this wasn’t addressed in the groundwater model. He noted there is no surface/groundwater interaction during the wet season. Dr Sinclair advised the aim is to divert as much water around the infiltration points as possible.

Ms Coram noted that, as there is evidence of minor structural features, one issue may be that these structures provide preferential flow pathways. She asked how extensively this issue has been addressed under modelling and if there has been conceptual


groundwater modelling to identify areas of preferential pathways. Dr Sinclair noted that the key structures around Pit#3, including the pit wall, have been mapped. Dr Sigda noted that as the scale of the model is 25m these features have essentially been averaged in. If there was a fault running from the pit to the creek, the model provides an overall average flow rate. He advised he was not sure what the implications of any such structures might be in terms of solute transport. He suggested that preferential flow paths are of probably limited importance over the 10K year period. Ms Coram agreed these factors may not be significant over a 10K year timeframe, however there may be issues over the short term and at smaller scale that may not be being picked up on a model of this magnitude. Dr Sigda advised the Packer testing looked at the flow path in the existing fault line and determined this is in the order of the weathered bedrock. Dr Sinclair noted these are the main ore bearing sequences. Ms Coram stated that she was not necessarily critiquing the model, but, in terms of a small seep for example, there may implications in terms of environmental impacts even if not being picked up by the model. Dr Barry agreed and suggested the model needs to explicitly state that it cannot assess the impact of small scale structures. Ms Coram noted that the model is being informed by expert opinion but stressed the need to ensure all potential risks are identified and quantified. Dr Barry noted it’s not so much about the model per se, but rather the decisions that can be made on the basis of what the model is showing. Dr Sinclair advised that ERA is confident that the effect of small scale structures are not an issue in terms of solute transport but ERA will have another look at this.

Dr Sigda welcomed the various questions being raised by ARRTC members as these are valuable inputs for refining the tool. Dr Mudd suggested it may be useful to better conceptualise the situation by including geological mapping and overlaying the map of aquifers and their associated pressures. Dr Sigda advised this has been done as a matter of course. Mr Tayler noted that he is not convinced that the cap will last 10k years so there will need to be a high degree of confidence in the final landform design. Dr Sigda advised that the cap surface has been simulated assuming a growth medium and vegetation.

Dr Sinclair advised that the modelling is showing that seepage mitigation is definitely required but ERA is not committing to a cap for the final landform because the model is currently forcing all solutes through an artificial boundary condition. There is a need to better understand the deeper system and link yield analysis to hydrodynamics to look at impacts on water quality in Magela Creek. He also noted that ERA is concerned whether a 99% ecosystem protection target is actually reasonable and achievable on the footprint of the site. The other issue is whether there is sufficient laterite available to have a cap. He suggested therefore a Best Practicable Technology analysis needs to be done. He stressed again that at this point ERA is not committing to capping the entire site.

Mr Tayler noted the point made by Ms Coram regarding the impact of solute loading on the concentration of solutes in the creek. He suggested that concentration in the creek will vary due to seasonal fluctuations so can’t just focus on loads and need to factor in flow conditions as well. He suggested there is likely to be a period following rehabilitation when the closure criteria cannot be met. Dr van Dam noted that while there may be a period when closure criteria will not be able to be met, it will still be critical to ensure there are no environmental impacts during this period. He asked if the current solute modelling will be integrated with the hydrological modelling and also the Pit#1 modelling. Ms Iles advised the models are not yet combined but it is planned to do this. Dr Mudd noted the need to also consider the potential effects at a regional scale.

Mr Johnston asked if the abandoned underground mine work has been included in the model in terms of the performance of the cap. Dr Sinclair advised that this will need to be looked at as part of the EIS, particularly whether brines will access the underground workings. Data are being collected so this can be modelled.

ARRTC31-9: ARRTC thanked Dr Sigda for his presentation and requested the final reports arising from this work be provided to ARRTC members for information.

Presentation: Pit#3 modelling - Implications for surface water (Ms Iles) Ms Iles advised that this hydrodynamic modelling work follows on from the results presented by Intera. The modelling work focused on Mg and assumed that other solutes have conservative behaviour. This work, and the surface water work, will be revised and updated results presented at a future ARRTC meeting. It was noted that the data for Mg were based on the 2012 Intera work. ERA staff are being provided with training on the model. The modelling used operational criteria as closure criteria are currently not available. This work is looking at how loads from Pit #3 compare to existing loads and the implications in terms of compliance at the downstream monitoring site MG009. The current operational water quality criteria for Magela Creek including the ecotox derived TV for Mg and the interim limit for ammonia and annual additional load limits (as included in authorisation) were presented.. Average annual loads of Mg to Magela Creek from groundwater seepage based on work by Intera were presented. It was noted that following recent changes to the model, the estimated unmitigated combined load of 210,000 kg/yr was significantly higher that what was calculated in the 2012 Intera work (38,000 kg/yr), but the annual load reduces to 16,000 kg/yr in the combined mitigated scenario. The modelled results for Annual Average Solute Loading for 10K yr period from waste rock, tailings and combined for both Magela Creek surface water and surface seepage were presented. It was noted that in the unmitigated scenario there is a probability of having a load of manganese 10 times higher than current limits, but this is significantly reduced in the mitigated scenario. Loads for U and Ra226 remained below current limits. The model predicted surface water concentration results for Magela Creek (Williams 2013) based on Intera 2012 predicted seepage results was presented. The model is based on mean flows in Magela Creek over 10 year period (1996-2006) at MG009. Contributions from Gulungul Creek (8% of MC flow) and Corridor Creek (1% MC flow) were also factored in. The model was run over 2 years to assess flushing and residual build up in the creek. Groundwater inputs to Magela Creek were calculated using average of 100 years monthly groundwater flows interpolated to hourly which better matches the creek hydrograph boundary condition data. The model used a constant magnesium concentration of 160mg/L and evaporation rate of 0.005 metres/day (from regional literature). Magnesium dispersion during the recessional period using Intera 2012 data in the unmitigated case was presented which showed that Mg concentrations lower than the ecotox value of 3 mg/L. During the wet season in the unmitigated case, Mg concentrations were also lower than the ecotox value of 3 mg/L, 2.4 mg/L in the first flush reducing to about 1.2 mg/L after 24 hours. It was noted that once creek depth reaches 0.5m, Mg concentrations drops to 1/10th of the original level. Dr van Dam noted that first flush water may also contain a higher major ion concentration anyway. The predicted concentrations of U, Mn, Mg and 226Ra at MG009 for both mitigated and unmitigated scenarios during the three flow states (first flush, early wet and recessional flow) using Intera 2013 data were presented. This showed that manganese levels (not magnesium as initially thought) could potentially cause detrimental impacts in the no mitigation scenario as they are significantly higher than current limits. The Intera 2013 work also shows that in the unmitigated scenario, 60-70% of seepage occurs at the surface. This could have potential for evaporite formation as has occurred previously in LAAs, surface runoff and seepage sites. The evaporite is mostly epsomite but may contain heavy metals and radionuclides and would dissolve in the first flush of the wet season. ERA will construct drainage lines but further modelling needs to be done to look


at when solutes are actually likely to wash into the creek and at what concentrations. Detrimental impacts could occur if the ecotox limits or annual additional loads limits are exceeded. Magnesium loads are likely to be similar to current operations but manganese loads will be orders of magnitude higher that annual limits if there are no mitigating caps installed. The loads of potential nutrients (N, P) and 210Po are unknown at present. Manganese and magnesium concentrations are greater than current criteria in the unmitigated case and manganese in the first flush will be higher than referenced site based criteria in the mitigated case. Potential ammonia concentrations and ecotox based criteria are currently unknown. It is clear that capping will reduce potential salt formation from expressed seepage.

Dr van Dam noted that magnesium levels will be significantly higher after 300 years and Dr Sigda advised that the 2012 data had assumed a plateau after 300 years. Ms Iles advised the model had not been updated as Intera was finalising its new modelling results. Dr Harford asked if manganese would also be attenuated and Ms Iles advised that ERA is currently looking at various mitigation options.

Presentation: Contaminant transport modelling – groundwater (Dr Turner - CSIRO) Dr Turner provided a presentation on the key findings from his work on groundwater modelling for Ranger Pit#1 closure. He acknowledged his collaborators from the US Geological Survey (uranium transport and absorption modelling) and CSIRO on the project. The work was conducted over four year period (2009-2013) and involved a comprehensive investigation of Pit#1 tailings solids and pore fluid diagenesis and the long-term geochemical stability of tailings in Pit#1, a characterisation of the reactivity of Pit#1 backfill material (waste rock) and solute source strength (revised downward in 2013), a hydrogeological and mineralogical characterisation of bounding lithologies of Pit#1 and a complex groundwater flow and reactive transport modelling analysis (time frame up to 10,000 years).

The key outcomes and learnings from this work are outlined below:

Pit#1 tailings diagenesis – Long Term Geochemical Stability in Pit#1 - Diagenetic crystallization and redox processes are already apparent in reducing SO4, Fe, Mn and U by formation of secondary solid phases: gypsum, Fe oxyhydroxides, rhodochrosite and uraninite respectively. The net mass transfer effect on the pore fluid solute inventory for these elements is not yet significant, except possibly for U. Mg and NH4 concentrations in pore fluids do not appear to undergo alterations that result in any change to their pore fluid concentrations caused by formation of diagenetic solid phases. In-Pit chlorite dissolution is predicted within Pit#1 and will raise the pH such that the pH of the porewater within Pit#1 is predicted to increase from 4.4 to 7.1 within 300 years.

Pit Solute Source Strength (PSSS) - The most recent estimation of the PTF (ATC Williams, 2013) shows the PTF discharge will result in the PTF declining to effectively zero within six years of commencement of the backfill loading. Removal and treatment of the relatively rapid mode egress component in minimizing the environmental impact of fluid egress from Pit #1 is highlighted. In the absence of removal and treatment of PTF, model projections indicate that accumulating backfill groundwater will have a significant effect on groundwater concentrations at surface water boundaries. Transport modelling was based on the condition of 90% PTF recovery and removal from Pit#1 – with action under way following the recent backfill preload. The primary driver determining the solute mass accumulation within the backfill is the PTF. Water rock interaction with the waste rock is a secondary factor.

Conservative Solute transport - The (effective) mobile porosity of 0.6% determined form the R1C3 tracer test leads to a bi-modal pathway of solute– i) relatively rapid initial phase from pit solute source strength ii) slow moving phase from tailings mass. In the base case model, solute transport in the first 100 years mainly occurs at shallow depths up to 50m due to relatively fast groundwater flow near the surface. Once the solutes that were initially located/expressed above tailings sediments are flushed and transported to the discharge area (Georgetown Billabong), the slowly moving solutes in the deeper parts of the aquifer provide an increasing fraction of the total mass flux. Model variants investigated including effective porosity, dual domain exchange coefficient, hydraulic conductivity profile and 50% reduction in Pit#1 source strength showed that PSSS management has greatest potential to reduce breakthrough concentrations at surface water boundaries.

Reactive Solute Transport – The reactive transport model successfully reconstructed a stable hydrogeochemical transport modelling framework consistent with observed ambient hydrogeochemistry at Ranger (e.g. the groundwater pH distribution, Mg, SO4 generated after 10,000 years). Results allow comparison of predicted groundwater concentrations at surface water boundaries of reactive and non reactive species with operational water quality criteria. Conversion of such results into solute loads to surface requires combination with groundwater discharge estimates – this will be a next step.

Results - Impacts on water quality at boundaries Magnesium – Response in groundwater Mg concentrations at the GTB boundary (1600m) are indicated to rise by a maximum factor of about 2 at about 120 years over their current baseline concentration of about 14mg/L. Given surface flow dilution and groundwater convergence dilution the groundwater contribution of Mg is not expected to cause exceedence of the Mg toxicity TV for Magela Creek.

Sulfate – Response in groundwater SO4 concentrations are indicated to rise by a maximum factor of about 5 from the current baseline concentration of about 12 mg/L. This will be further diluted by groundwater convergence and surface flow and has some, but likely low, probability of exceeding the previously proposed criteria for GTB (10.7mg/L, Jones et al., 2005)

Uranium - Responses in groundwater U concentration are complex. Current indications are a rise by a factor of about 15 from the current baseline concentrations of about 2-3 μg/L. The site-specific uranium toxicity TV is 6 μg/L. It was noted that the model overshoots baseline U concentrations by a factor of 5.

Manganese – The previously proposed criteria for Mn in GTB is indicated as 0.01 mg/L (Jones et al., 2005). Response in groundwater Mn concentrations in groundwater are indicated to rise to about 0.08 mg/L with a long lag time of 1000 years. This will be further diluted by surface flow thus there is a very low probability of exceeding the proposed annual maximum closure criteria limit for Mn.

Ms Coram noted the conservative nature of Mg highlights the need to understand the transport mechanisms involved. Dr Mudd noted that regional control on deeper groundwater systems is also an important consideration.

ARRTC31-10: ARRTC thanked Dr Turner for his informative presentation.

ARRTC31-11: ARRTC commended ERA, Intera Inc and CSIRO on the high quality of the groundwater and solute modelling research to date.


Presentation: Erosion and chemistry studies on trial landform (Dr Erskine/Dr Saynor/Ms Turner) Dr Erskine acknowledged his SSD co authors and noted this is a collaborative project with ERA. It was noted that direct seeding on the Trial Landform (TLF) had been unsuccessful so additional tubestock and fill in planting was undertaken. As a result, most vegetation on the TLF is from tubestock planting during the period 2009-10. Dr Lu noted that, while direct seeding did not meet ERA’s revegetation expectations in terms of rate of growth and capturing the ground surface, there are still large numbers of plants on the site which were direct seeded. He noted these will have an increasing effect on surface erosion although this effect might be negligible in the first 2-3 years. It was noted that the different age of vegetation in different plots is potentially confounding. There are four erosion plots on the TLF. Annual rainfall over the period 2009-13 was variable with year 2 being above average. Year 4 was initially looking to be a below average year, but total rainfall for that year was boosted by a significant rainfall event (with 22.4% of annual rainfall occurring over a 4 day period). Intense rainfall events cause problems due to damage to the plots. In February 2011, medium coarse sand was transported onto the plots and a failure of the concrete bund in Plot 2 resulted in additional run-on from the adjacent area entering the plot. Plot 2 has an additional peak which is therefore not rainfall related and methods were developed to adjust the run-off results accordingly. The 2 largest events in 2010-11 were removed and regression of run-off was recalculated based on corrected volumes. It was noted every event over 1.5mm generates run-off and that Plot 2 generates almost double the run-off of Plot 1. Based on results from the largest rainfall event (1 in 200 year) found there is usually higher run-off from Plot 2 than Plot 1 due to upper slope plot boundary failing and piping during the event. Plot 1 has a hydrologic threshold of 30mm and well defined rip lines (30mm is required to fill the gaps between rip lines before runoff occurs). Plot 2 has a hydrologic threshold of 15 mm and has less defined rip lines and also a few boulders resulting in a lower storage capacity. Further work is required to look at discharges from larger storms and results from Plots 3 and 4.

Dr Mudd asked if the sequencing of storm events is important in terms of run-off (i.e. in terms of intensity and interval) and Dr Saynor advised there probably is a sequencing factor involved relating to the level of saturation. Prof Woodroffe asked if when storms occur during the wet season was also factor and Dr Erskine advised that, due to antecedent conditions, run-off was usually higher later in the wet season but the net result was the same.

Bedload from the plots was measured using a half pipe on the down slope with a flume and filling basin. Anything in the half pipe and basin is considered bedload. The results indicate that bedload has declined dramatically over time with the highest bedload yield coming from Plot 2 which has the lowest level of vegetative cover. It was noted that in Year 4, Plots 1 and 4, which were originally planted with tubestock and have greatest density of vegetation, had the lowest yields. This is due to canopy protection and leaf litter. Plot 4 also has significant weed invasion. All of the plots are dominated by sand, with some gravel and smaller amounts of silt and clay. Plots 3 and 4 (with laterite) have had the lowest silt production. Silt and clay are normally flushed over the flume. Bedload is therefore dominated by coarse material. Based on results from the smallest measuring station over the four years, there is a good correlation between turbidity and suspended sediment. Further work will be done to start average to determine if there is a significant relationship between system sediment and turbidity.

Prof Boon asked why the coefficient was 0.5 for early years and 1.7 for the whole period. Dr Mudd noted the results for 2004-05 appears to have more data points than other years and Dr Erskine indicated this depends on the total number of events in the year and that more data will affect r2. Dr Erskine also noted that the amount of fine sediment generated varies from year to year and that the large rainfall event in a year (e.g. 1 in 600 in 2007) will affect all relationships. Dr Erskine also noted that land slips can have a longer term influence as the may continue to act as sediment sources.

For Plot 1, the types of solutes present, their concentrations, exported loads and behaviour over time for the first three years were examined. It was noted that the EC located at the inflow to the flume doesn’t sample every event. EC was used to calculate TDS which was then multiplied by discharge to determine load. Results indicate solute loads in surface run-off are very low. Cu and Ni increased in annual mean concentration while Ca, K, Na, SO4, Mn, Si and Al decreased in annual mean concentration. There were no significant changes in Pb, Zn, U, Mg and Ba. Changes in solute loads within the wet season (concentration vs. cumulative runoff) indicated a first flush effect which was not unexpected. As there was no alkalinity measurements it was decide to focus on cations. Concentrations of K, Na and SO4 were exhausted by 2011-12. K concentration is usually low anyway due to plant uptake. In 2009-10 the majority of samples were Na/K dominated but in 2010-11 and 2011-12 Ca was dominant ion. EC was used to calculate Mg and Ca concentrations as both have linear relationship with EC. Loads were then calculated which indicated the greatest load was exported during 2010-11.

On a related matter, it was noted that there has been international recognition of the landform evolution modelling work and that Dr Geoff Pickup had commenced his independent review of the work to date. Dr van Dam advised that Dr Greg Hancock and Dr Tom Coulthard have also been retained to undertake some consultancy work and that funding has been allocated for this. Further processing of discharge, suspended sediment and solute loads from the TLF will be done.

Dr Mudd asked how many more years of monitoring of the TLF are required. Dr Erskine suggested that at least one more year of monitoring is required, but noted there should be no problem with ceasing this research after 5 years. He noted that ERA is considering burning the plot to measure fire impacts on the vegetation. Prof Woodroffe indicated he is pleased to see the work continuing on the TLF as this has significant importance in terms of overall Ranger rehabilitation. He commended the pioneering work done on small scale erosion on the TLF and asked what the key knowledge gaps associated with transferring this knowledge to a larger scale are (i.e. is it slope or materials etc). Dr Erskine agreed that little is known about issues associated with scale and this is the subject of a current paper looking at extrapolating results from the TLF to the larger scale. He noted there is certainly a threshold issue as runoff and erosion results from the TLF are different to those measured in the creek systems, which suggests there are real differences between the small scale overland flows to the larger scale, once channelised flow is evident. Prof Mulligan asked if a water balance has been done for the TLF and Dr Erskine advised that Dr Lu has been using a gross estimate of evapotranspiration from the TLF plots and more precise measurements of tree transpiration losses which are combined. ERA also has 2 sumps measuring chemistry but not sure if volumes are also measured. Dr Mudd asked if Class A evaporation pan data are available on the TLF and Dr Sinclair confirmed this1

1 ERA (Dr Lu) noted in reviewing the draft meeting summary that the Class A evaporation pan is located at Jabiru Airport not on the

TLF. However, potential evaporation on the TLF can be calculated from the range of other weather parameters collected.

. Dr Sinclair noted ERA encourages the collection of empirical data from the TLF. It was asked if historical data from work by Riley has been looked at and Dr Erskine advised that Dr Riley had provided his data which are being looked at. Dr Sinclair advised that the landform model previously provided to Mr Lowry was incorrect and


suggested that SSD hold off doing further landform evolution modelling until ERA has further refined the landform model. ARRTC commended SSD on their cooperative approach with ERA to date in relation to landform modelling. Dr Barry asked if there is an opportunity to use the TLF to do further studies on erosion using different slopes. Dr van Dam advised that SSD has looked at this but it would be subject to the necessary resources being available. It was noted that the TLF was not designed to study slope erosion but such studies could be included as part of Pit#1 rehabilitation works.

Presentation: Radon exhalation from trial landform (Dr Bollhöfer) This project is investigating long-term changes and variability in radon (222Rn) exhalation for the four different treatments on the TLF, and the effects of season, cover type and thickness, weathering and compaction. This will inform the determination of a long term 222Rn exhalation flux from the rehabilitated landform and assist in developing relevant closure criteria. As radon emanates from soil grains there is usually a much higher concentration in soil than in the atmosphere. Radon can escape the soil via convection (described by Dacy’s law) or diffusion (described by Fick’s Law). A background 222Rn exhalation flux has been estimated (Bollhöfer et al 2014) and will be used to compare with fluxes post rehabilitation. Radon is a decay product of Radium- 226 (226Ra) so the magnitude of 222Rn exhalation flux is proportional to the concentration of 226Ra in the soil. Although average soil radioactivity is not markedly different across the four erosion plots, there is a difference in average 222Rn flux densities for the two different surface treatments. In the dry season, typical average radon flux densities from the surface of the waste rock–laterite treatment are higher than radon flux densities from waste rock only, and they decrease markedly in the wet. In contrast, there was no obvious seasonal trend observed for radon exhalation fluxes from waste rock only in the first couple of years after trial landform construction. Analysis using volumetric water content data from ERA indicates a typical wet season flux density of 10-100 mBq·m-

2·s-1 per Bq·g-1 and a dry season flux density of 350 mBq·m-2·s-1 per Bq·g-1. In comparison, flux densities measured at Nabarlek were 240 – 530 mBq·m-2·s-1 per Bq·g-1.

Over the past 6 months, work progressed in collaboration with ERA and Safe Radiation Pty Ltd on using PVC columns filled with waste rock material (1s). Results from this work indicated a 222Rn flux density (using diffusion length of 2.3 m and Fick’s Law) of 320 mBq·m-2·s-1 per Bq·g-1. Once the radon exhalation rate for the final landform is known this can be factored into atmospheric transport models to derive an estimate of inhalation doses to the public. It is already predicted the post rehabilitation dose will be negligible for Jabiru residents but will obviously be higher for people on or in the immediate vicinity of the final landform. The main conclusions from this work are that 222Rn activity flux density is higher during the dry season, dry season 222Rn exhalation from waste rock has increased, potentially due to weathering of substrate and the difference between waste rock and waste rock-laterite mix has decreased over the years. The dry season RE-R: ~ 350 mBq m-2 s-1 per Bq g-1 is lower than at natural analogues (~600-1000 mBq.m-2.s-1 per Bq.g-1). There is good agreement between results from experimental and field studies. Further work is planned to investigate change in diffusion length over time. EnRad staff have continued to input to the Radiation Health Committee (safety guide for contaminated sites) and IAEA (MODARIA – models for assessing impacts from NORM and contaminated sites supporting remediation) activities.

Mr Johnston commended SSD and ERA on the high quality of the radon exhalation work to date.

Presentation: Radionuclide concentration ratios for bush food items in the ARR (Dr Bollhöfer) This project aims to derive reference concentration ratios (CR) for terrestrial bushfoods in the ARR and involved investigating radionuclide uptake in terrestrial plants and animals, identifying knowledge gaps and prioritising radionuclide-bushfood combinations for further research. Key activities included a literature review, review of unpublished data from eriss and ERA, using the BRUCE tool to determine CRs and summarising relevant plant and animal tissue data.

The BRUCE tool is based on ARR biota and media activity concentration data collected over the past 30 years and contains over 5000 records. It was noted that not all nuclides were measured in every sample. In the BRUCE tool, areas are referred to as sites (i.e. disturbed areas, such as past or present uranium mine sites) or locations (i.e. environmental areas from where bushfoods have been collected - may be on or off a site). BRUCE enables the average CR for bushfood items collected at all locations around a specific site to be calculated, as well as the average CR for bushfood items collected at a specific location. Average CR across the whole of the region can also be calculated. Bushfood samples are assumed to have been collected a defined point in space and time. In the case of animal samples, BRUCE allows a test to determine whether a soil sample has been collected within the specific home range for that animal. Complications can arise when the home range of an animal partially overlaps with the area of a site as the radionuclide activity concentration in media samples collected onsite may be different to that for media samples collected offsite and the ‘straight’ average of the media values may not be a representative measure of the actual media activity concentrations to which the animal is exposed. In this situation it is proposed that an appropriate weighting be applied to media samples collected onsite and offsite based on the fraction of time spent in each area by the animal.

CRs for individual bushfood items are calculated using BRUCE using a standard formula. The results for Buffalos were that 210Po is the highest CR for all tissue types, 210Po and 210Pb are generally higher in organs than in flesh and U and Th accumulate generally less in organs than the other radionuclides. The results for pigs were that 210Po CR in flesh was about 2 orders of magnitude higher than other radionuclides and about 1 order of magnitude higher than in buffalo. Organ data are generally lacking for pigs. In the case of Wallaby, 226Ra and 238U CR in wallaby flesh was smaller than that for buffalo and pig, 226Ra and 238U CR in wallaby organs is very similar to buffalo organs. There is a lack of 210Po and 210Pb data for wallaby generally. Work on CRs in fruits and yams was discontinued as there are sufficient data and these foods do not contribute significantly to overall dose. It was noted that yams have higher CRs than fruit probably due to the fact that some elements when absorbed by plants are retained and accumulated in the root system.

Ingestion dose can be calculated from information on diet and radionuclide activity concentrations in food items and using dose conversion factors recommended by the ICRP. Information on diet composition and typical quantities of food items consumed can be gleaned from local indigenous people. Radionuclide activity concentrations in food items can be determined by direct measurement or estimated using transfer factors applied to radionuclide activity concentrations in environmental media such as soil or water. The potential radiological importance was calculated for various bushfoods-radionuclide combinations. Conclusions from this work include that 210Po poses by far the largest potential risk (with high CF and DCF) for terrestrial food items, and more 210Po data are needed for wallaby. In addition the components of the reference diet need to be agreed so that actual ingestion doses can be calculated. The BRUCE tool will be populated with metals data and reviewed. EnRad is involved in a number of international (IAEA MODARIA working groups) and national (ARPANSA/DRET review of CRs for non-human biota; Radiation Health Committee safety guide) initiatives.


Prof Mulligan thanked Dr Bollhöfer for his presentation and asked if there is a control on how high background levels for particular animals can go. Dr Bollhöfer advised that there is no distinguishing between uptake at background and contaminated sites, as it’s a simplified approach. Dr Barry asked if NHB exposure varies across the site depending on whether the soil is contaminated or uncontaminated. Dr Sinclair advised that background varies across the site due to the presence of several radiological anomalies, and as a result the level being measured in animals will vary depending on sampling location. It was noted that there is also natural background and that aradon baseline map of 226Rais the same as radon 226 soil activity concentration exists.

4.4 Other Key Knowledge Needs

Presentation: South Alligator Valley Containment (Dr Bollhöfer) No presentation due to time limitations.

5.0 Strategic Overview (ERA/eriss) Presentation: Status of planning and scientific knowledge for development of closure criteria and trajectories (Dr Humphrey/Ms Paulka) Dr Humphrey noted that the development of science-based trajectories for ecosystems establishment is required to inform rehabilitation and regulatory decisions regarding closure. This work is being overseen by the Closure Criteria Working Group comprising staff from ERA and SSD. It was noted that there is evidence that ecosystems in the NT have potential to move into altered states following disturbance. There is a long history of work on revegetation and ecosystem establishment trajectories by ERA scientists. An ARRTC-led workshop (organised by then ARRTC member Dr Carl Grant and Dr Peter Bayliss) was also held in 2005. Other relevant work includes the ERA revegetation strategy developed by Reddell and other work by Bayliss (ex SSD) and Zimmerman (ex ERA).

Ms Paulka noted that Dr Humphrey had raised a number of high order issues regarding closure criteria and trajectories at ARRTC30 but these have not yet been endorsed through the CCWG. She noted in an overall closure context, concepts around the trajectory approach are being considered in developing the framework.

Prof Mulligan asked if the CCWG also includes mine planners and water management staff and Ms Paulka advised that the CCWG comprises relevant staff from ERA, SSD, GAC and other stakeholders, but staff with specific line responsibilities for mine planning and water management were not involved.

Ms Paulka provided an overview on the framework for, and status of, developing closure criteria (CC) and associated trajectories for Ranger. The overall closure process for Ranger comprises 3 main phases. The Plan phase involves the development of CC by the CCWG and feeding these into rehabilitation/closure design and planning, The Approval phase involves the regulators determining whether the final closure design will achieve the CC. The Execute phase involves monitoring until the CC have been achieved and ERA has been released from liability. Technical Working Groups (TWG) have been formed for each of a number of themes and a scope of work and set of deliverables has been drafted for each. Each TWG will determine parameter values for which CC are required. Relevant baseline and reference datasets (and any knowledge gaps) will then be identified and a method for setting each parameter threshold value will be agreed, taking into account any relevant spatial and temporal issues. Parameter values and projected trajectories (and action plans for deviate trajectories) will then be derived. Once the CC and associated mitigation arrangements are agreed, monitoring plans will then be developed for each parameter. Each TWG will need to report back to the CCWG at each step of the process. A final report will be presented to the CCWG which will then submit the closure design and associated CC to the MTC for approval. Ms Paulka noted ERA will need to demonstrate that the CC are achievable.

Dr Mudd asked where KNP fits into the framework given the need for future incorporation of the rehabilitated site into the park. Ms Paulka noted that the issue of incorporation into KNP was not an issue for ERA, given this would logically occur after final closure and signoff. Dr van Dam noted that closure criteria are required for each of the phases. Dr Mudd noted that a single document outlining the closure plan had previously been produced and asked if this would be done again. Dr Sinclair advised that a master document is being developed as part of the pre-feasibility work which sets out the various packages of work involved in rehabilitation and closure and this is reviewed each year. Prof Mulligan asked if there is a timeline for the development of closure criteria which aligns with the overall closure process. Ms Paulka confirmed this and advised that discrete packages of work will be submitted for approval and executed as required. She noted all of the closure criteria can’t be finalised at the same time as it depends on the issues involved (e.g. Pit#1 rehabilitation/closure focusing on GTB and Pit#3 rehabilitation/closure focusing on Magela Creek but also includes Pit#1 aspects). It was noted the Environmental Requirements and closure objectives are also being fed into the Rehabilitation/closure Risk Assessment. Dr Barry asked where the current process is up to and Ms Paulka advised that scopes of work for each TWG are being completed. She advised the Radiation TWG has held its first meeting and the Cultural and Water TWG will commence in January. Other TWGs will be established in early 2014. Dr Bartolo asked where the rehabilitation objectives come from and Ms Paulka advised these are based on the ERs and values used in the Rehabilitation/Closure Risk Assessment.

Ms Paulka advised a trajectory approach will be used where this is considered relevant for the parameter, otherwise the standard CC approach will be used. A decision will also be made as to whether any trajectory approach will be used to inform management decisions to determine pathways to achieve a CC or used instead of a CC. Where a trajectory will be used instead of a CC, the supporting models will need to be peer reviewed and agreement reached regarding what point on the trajectory will be used as the final closure condition as well as any associated milestones.

Presentation: Ecological basis to trajectory approach using vegetation (Dr Humphrey) Dr Humphrey noted there are various trajectory approaches that can be used for ecosystem restoration. In identifying the right approach, it is important to understand the recovery/establishment/restoration trajectories, the potential thresholds and the nature and timing of any management interventions, if required. It was noted that trajectory approaches for ecosystem restoration have been used in a number of settings internationally, and in Australia they have mainly been informed by rangelands ecology research. Dr Humphrey outlined different models depicting the shift between natural and degraded states which included gradual recovery (unassisted recovery), threshold systems, alternative stable states (e.g. lakes that alternate between clear /macrophytes to turbid/eutrophic) and stochastic dynamics (highly variable/no equilibria). Prof Boon noted that it is easier for an ecosystem to shift to an altered state but much harder to revert back. Alternative state models have been used in rangelands ecology in the form of


state and transition models of vegetation dynamics. These involve splitting rangeland systems into various discrete states with defined processes that cause the transition between states (e.g. overgrazing leading to woody vegetation). Restoration thresholds may prevent recovery (e.g. may be biotic (invasive spp/weeds), abiotic (fire) or biotic-abiotic positive feedbacks). Dr Humphrey noted state and transition models (STMs) have been applied to minesite establishment and revegetation in the past (e.g. work by Dr Carl Grant in relation to bauxite mine rehabilitation in WA and on Groote Eylandt). It was noted that STMs are not regarded as useful in rehabilitation contexts where significant disturbance has occurred and trajectory ecosystems are unknown. Dr Humphrey noted in the case of Ranger there is substantial small scale experimental and serendipitous research and evidence from the ARR. Undesirable pathways for Ranger and their causes have been identified (e.g. Nabarlek), the reference (target ) condition is relatively well characterised and there are indications that an ecosystem similar in appearance to surrounding natural ecosystems is achievable. Dr Humphrey provided examples of deviation states in the ARR including at Nabarlek where the revegetation was unsuccessful in achieving the original rehabilitation goal of “blending in with surrounding savanna woodland” and current vegetation is characterised by high density of grassy weeds and very low density of trees, and an Acacia shrubland nearing the end of its successional life. The impacts of fire and weeds on successful revegetation were also noted. Dr Humphrey referred to work by Bayliss et al (2004) at Nabarlek on an informed conceptual model of rehabilitation outcomes. He also noted work by Redell & Meek (2005) at Ranger which showed that initial floristic composition is crucial (i.e. using Acacias to ‘initiate’ succession doesn’t work) and that framework species that rely on a persistence strategy are uncompetitive in establishing from seed in these situations. Other examples referred to included the Mudginberri pastoral trials where a ‘do nothing’ approach had been applied after exotic grass plantings in the mid 1970s.

Dr Humphrey noted ERA had submitted a Revegetation Strategy for the final landform at Ranger Mine at the 13th ARRTC meeting in March 2004 (Reddell & Meek 2004). The strategy has subsequently been refined (Gellert 2012) and the revegetation strategy for Ranger is now consistent with state-transition models. The strategy comprises 14 steps including excluding ‘pioneer’ species, grasses and ‘aggressive’ acacias from initial establishment (because they out-compete framework species and increase fire risk), establishing framework eucalypt species from tubestock and excluding fire until framework plants are of sufficient size to survive. It was noted that possible knowledge gaps may include the fact that the performance of vegetation establishment on steeper slopes hasn’t been tested on the TLF nor has the use of mycorrhizal fungi or soil development been looked at.2

Dr Humphrey also noted that there is a need to look at establishment/restoration of aquatic ecosystems on the rehabilitated landform. There are risks to rehabilitation, predominately from water quality and potentially acid sulfate sediments. For natural systems, models of ecosystem dynamics in response to disturbance require further development, especially in response to water quality (e.g. unassisted recovery from poor water quality (‘gradual continuum’) or alternative stable states (with no guarantee that significant intervention will assist)). It was noted that the current closure studies and aquatic ecosystems establishment projects will further inform this.

Each element of the strategy will require closure criteria, monitoring guidelines for acceptance, performance standards and identified corrective actions and/or interventions. Risk associated with the strategy will also need to be assessed and key knowledge gaps identified. Dr Humphrey presented an example on how the strategy might be applied for a mixed eucalypt woodland.

It was noted the Environment Requirements for closure of the Ranger Uranium mine includes the need to ‘maintain the natural biological diversity of aquatic and terrestrial ecosystems of the Alligator Rivers Region, including ecological processes’. The TWG looking at this has adopted the following definition of ecosystem processes: ‘The interactions and connections between living and non living systems, including movements of energy, nutrients and species.’ Ecological processes are essential in rehabilitation programs because they underpin the key assets to be maintained or re-established. It was noted this requires further definition, delineation and prioritisation to be successfully incorporated into the current Ranger Closure and Rehabilitation Ecological Risk Assessment Framework. It is also not clear which ecological processes are currently being measured directly or through proven surrogates or not being measured at all. This is a cross cutting theme for further CCWG consideration. Dr Humphrey noted that closure criteria/ monitoring protocols/standards/actions and interventions will be further developed and refined for ecosystem establishment through the CCWG. These criteria will need to be based on best science and agreed by key stakeholders (including TOs). The underlying key principles will be subject to ongoing approval through ARRTC and MTC.

Prof Boon noted the current trajectory approach and advised that international work on deviant pathways indicates that “flickering” can be used as early warning signal that the system is moving into an unstable state. Prof Mulligan noted the work on trajectories for site revegetation was further advanced than he had imagined and some draft criteria could probably be identified at this stage. He noted that the main limiting factor will probably be related to plant nutrition. Water shouldn’t be a problem given climatic conditions and the nature of substrate material and weathering rates based on the TLF work appear to be typical of across the site.3 Prof Boon noted the lack of a native grass component on the final landform may be an issue and it was noted that native grass species would be allowed to establish on the site. There was some discussion about the importance of vegetation on slopes from a revegetation and rehabilitation point of view. Dr Humphrey noted there is no guidance in the early work done on this issue. Prof Mulligan noted the differential success of tubestock planting versus direct seeding. Dr Humphrey suggested the first 3-4 years of revegetation will require intensive management. Dr Sinclair advised that ERA will be progressively revegetating the site and Pit#1 would probably be done first. It was noted that there are issues associated with sourcing sufficient seedlings given the scale of the revegetation task. Dr van Dam noted that progressive revegetation won’t necessarily alleviate the problem of sourcing sufficient seedlings and further work on how to scale up seedling production will be required.4

Dr Barry asked if ARRTC has specific interests in relation to the actual closure trajectories or just the fact that they are based on relevant and adequate scientific evidence. Prof Mulligan suggested the key issue is for ARRTC to be comfortable that the science

2 ERA (Dr Lu) noted in reviewing the draft meeting summary that mycorrhizal fungi had not been specifically included in the TLF

study because earlier studies by CSIRO/ERA had shown it was not promising. However, mycorrhizal fungi are used in the potting mix as a normal nursery practice.

3 ERA (Dr Lu) noted in reviewing the draft meeting summary that water is a key limiting factor for waste rock substrate over the dry season.

4 ERA (Dr Lu) noted in reviewing the draft meeting summary that he is confident that progressive revegetation will mitigate against seed-sourcing limitations.


underpinning the development of trajectories is sound and that appropriate interventions for deviant trajectories are available (and are achievable). He noted that this will provide the required level of assurance to stakeholders that the approach is scientifically sound and all risks have been considered and addressed. Ms Coram suggested ARRTC doesn’t necessarily have a role in shaping the general closure criteria, but ARRTC definitely has responsibility to review the science underpinning the closure criteria and any proposed trajectory components. Prof Mulligan agreed that ARRTC definitely should have a view as to whether identified end points are overly aspirational or if there are other end points that would better address stakeholder expectations. Dr Barry noted that the issue of closure criteria has been on ARRTC’s agenda for the past five years and it appears that the current thinking is that the final landform will be somewhat different to the surrounding landform. He agreed the development of closure criteria and associated trajectories will require close consultation with stakeholders going forward. Dr Barry asked if there has been previous work on trajectories that could inform the development of closure trajectories for Ranger. Dr van Dam noted that previous work on fire has been looked at in the context of Ranger. Mr Tayler advised that further detail on the trajectories approach should be available by next ARRTC meeting.

Prof Mulligan asked if there are opportunities to trial any of the closure trajectories and Dr van Dam advised that this depends mainly on resource availability. He added however that ARRTC should feel free to provide feedback on any of the science underpinning the approach. Prof Boon asked about the possible implications of plant pathogens on rehabilitation and Dr Barry suggested that weeds are probably a greater issue.

Prof Woodroffe advised he was pleased to see some progress in the closure criteria development but stressed this work needs to be supported by the outcomes of the Ecological Risk Assessment process, which should also inform the whole landscape design process. He noted the availability of laterite and soil development on the final landform requires further attention. Prof Woodroffe stressed the importance of having a holistic approach to the development of closure criteria and taking account of cultural and social requirements as well. Given this, Prof Woodroffe queried why the current risk assessment was focused on ecological rather than environmental aspects. Dr Sinclair advised the BPT process has been established to balance ecological aspects with the engineering aspects of the rehabilitation process. Ms Paulka suggested that the ecological risk assessment didn’t strictly follow the specific guidelines of the ISO standard (using USEPA guidelines) so in her opinion it is actually in fact an environmental risk assessment.

Prof Mulligan suggested the issue of integration is also an important point. He noted that one reason why the trial landform is growing well is because it’s flat and water isn’t a problem, however it is unrealistic to expect ecosystem development to occur as part of rehabilitation unless it’s fully integrated into the landform design process. Dr Barry asked if data are available to facilitate this and Ms Paulka advised that data on aspect and slope from previous work by Unger et al are available. Dr George agreed it is important that an ecosystem approach be used which hopefully will include an aquatic ecosystem component.

ARRTC31-12: ARRTC requested ERA and SSD to provide an update on the status of the development of Closure Criteria (including trajectories) to next meeting.

ARRTC31-13: Dr Mudd requested that an update on the status of the Ranger 3 Deeps EIS and assessment process be provided to the next meeting.

5.2 SUMMARY DISCUSSION (CHAIR) ARRTC members noted that while SSD and ERA are operating under significant resource constraints, highest priority research addressing the Key Knowledge Needs is being maintained. While there are no critical gaps at this stage, ARRTC will continue to monitor the situation and will consider raising its concerns with the Minister (Parliamentary Secretary) if necessary. ARRTC agreed it is important that work on the Rehabilitation/Closure Risk Assessment be expedited to enable the KKN revision process to continue. ARRTC commended ERA on the quality of the groundwater and solute modelling work being done by CSIRO and Intera. ARRTC also noted and endorsed the SSD and ERA research publications since last meeting. Dr Barry noted that he would include these matters in his report to the Minister on the outcomes of this meeting. Dr Sinclair noted there is good clarity regarding the key critical tasks and associated priorities involved in the closure strategy and ERA and SSD will continue to work collaboratively to ensure highest priority research required to de-risk the closure strategy continues.

ARRTC31-14: ARRTC agreed to monitor the effects of current resource constraints on SSD and ERA research activities to ensure the highest priority knowledge needs continue to be addressed. ARRTC31-15: ARRTC noted the status of the Rehabilitation/Closure Risk Assessment project and requested that this work be expedited.

6 Other Business There was no other business raised.

ARRTC31-16: ARRTC noted and endorsed the scientific publication lists provided by SSD and ERA.

7 Next Meeting

The meeting closed at 5.30 pm.

ARRTC Secretary 28 November 2013

ARRTC31-17: ARRTC agreed the next meeting (ARRTC32) would be held on 7 – 8 May 2014.


No. ARRTC31 ACTIONS ARISING Responsibility

ARRTC31-1 ARRTC commended Prof Woodroffe on his significant contribution to the work of ARRTC as the independent scientific member with expertise in Geomorphology and wished him every success in his future endeavours.

ARRTC

ARRTC31-2 ARRTC approved the ARRTC30 Meeting Summary as tabled. ARRTC

ARRTC31-3 ARRTC requested UEL to provide a copy of the Nabarlek vegetation closure criteria report once finalised. UEL

ARRTC31-4 ARRTC agreed there would be significant value in having a synthesis of the key learnings from the SAV rehabilitation work and that the next steps are to (a) secure a suitably qualified internal graduate to develop a high level project scope, timeline and consolidated bibliography; and (b) explore options for funding this work going forward.

PAD/SSD

ARRTC31-5 ARRTC requested SSD to provide an update on the review of the landform evolution modelling at next meeting. SSD

ARRTC31-6 ARRTC requested that Parks Australia provide a presentation to next meeting on the SAV monitoring approach for groundwater, vegetation management and cap integrity aspects including aims, rationale and results.

PAD

ARRTC31-7 Dr Sinclair to confirm whether ERA has advised Parks Australia of the presence of the endangered animal (Fawn Antechinus) on the mine lease. ERA

ARRTC31-8 ARRTC thanked Dr van Dam for his presentation and noted the key outcomes of the SSD 2012-13 research program. ARRTC

ARRTC31-9 ARRTC thanked Dr Sigda for his presentation and requested the final reports arising from this work be provided to ARRTC members for information. ERA

ARRTC31-10 ARRTC thanked Dr Turner for his informative presentation. ARRTC

ARRTC31-11 ARRTC commended ERA, Intera Inc and CSIRO on the high quality of the groundwater and solute modelling research to date. ARRTC

ARRTC31-12 ARRTC requested ERA and SSD to provide an update on the status of the development of Closure Criteria (including trajectories) to next meeting. ERA/SSD

ARRTC31-13 Dr Mudd requested that an update on the status of the Ranger 3 Deeps EIS and assessment process be provided to the next meeting. ERA

ARRTC31-14 ARRTC agreed to monitor the effects of current resource constraints on SSD and ERA research activities to ensure the highest priority knowledge needs continue to be addressed.

ARRTC

ARRTC31-15 ARRTC noted the status of the Rehabilitation/Closure Risk Assessment project and requested that this work be expedited. ERA/SSD

ARRTC31-16 ARRTC noted and endorsed the scientific publication lists provided by SSD and ERA. ARRTC

ARRTC31-17 ARRTC agreed the next meeting (ARRTC32) would be held on 7 – 8 May 2014. ARRTC

alligator rivers region technical committee meeting 31...

Documents