ARRTC38 - May 2017 - Meeting Record · Web viewAlligator Rivers Region Technical Committee Meeting 38 16 – 17 May 2017 Record of meeting Darwin, NT This document is a summary record

ARRTC38 - May 2017 - Meeting Record

http://spire.nt.environment.gov.au/spire/886642/375917/999741/180/arrtc - meeting 37 - 29-30 november 2016/arrtc37 - november 2016 - agenda.docx

Alligator Rivers Region Technical Committee

Meeting 38

16 – 17 May 2017

Record of meeting Darwin, NT

This document is a summary record of the scientific information presented to, and the discussion and actions arising from, the 38th meeting of the Alligator Rivers Region Technical Committee. ARRTC meeting summaries are used to inform planning and prioritisation of scientific research activities.

ARRTC

Dr Simon Barry

Chair, Independent Scientific Member

Ms Jane Coram

Independent Scientific Member

Prof Paul Boon


Dr Jenny Stauber


Assoc Prof Gavin Mudd

Environment NGO stakeholder member

Mr Adam Thompson

Northern Land Council

Ms Sharon Paulka

Energy Resources of Australia

Mr Matthew Whitfort

Supervising Scientist

Apologies

Mr Andrew Johnston


Prof David Mulligan


Presenters and observers

Dr Geoff Pickup

Consultant

Mr Chris Malcolm

Gundjeihmi Aboriginal Corporation

Dr Howard Smith

Northern Land Council

Dr Ian Hollingsworth

Horizon Environmental Soil and Survey Evaluation for Gundjeihmi Aboriginal Corporation (Presenter)

Michelle Iles

Energy Resources of Australia Limited

Ben McTavish

Energy Resources of Australia Limited (Presenter)

Dr Ping Lu

Energy Resources of Australia Limited (Presenter)

Andy McLellan


Toby McGrath

Water Solutions for Energy Resources of Australia Limited (Presenter)

Graeme Esslemont


Peter Anderson


Sally Strohmayr

Department of Primary Industry and Resources

Pete Cotsell

Parks Australia Division

Sally-Ann Atkins

Parks Australia Division (Presenter)

Mr Keith Tayler

Supervising Scientist Branch (Presenter)

Dr Rick van Dam


Dr Chris Humphrey


Mr Peter Baker


Dr Renee Bartolo


Mr John Lowry


Dr Mike Saynor


Ms Berlinda Bowler

Supervising Scientist Branch

Ms Kate Dixon


Dr Andrew Harford


Dr Che Doering


Ms Kate Turner


Mr Mike Welch


Mr John Miller


Ms Lisa Chandler


ACRONYMS

ARPANSAAustralian Radiation Protection and Nuclear Safety Agency

ARRTCAlligator Rivers Region Technical Committee, the Committee

CCLAACorridor Creek Land Application Area

ECElectrical conductivity (of water)

ERAEnergy Resources of Australia Limited

ERISSEnvironmental Research Institute of the Supervising Scientist

ERMEnvironmental Resources Management Australia Pty Limited

GACGundjeihmi Aboriginal Corporation

GCT2Gulungul Creek Tributary 2

KKNsKey Knowledge Needs

OWSOffice of Water Science, Department of the Environment and Energy

RMCPRanger Mine Closure Plan

SSBSupervising Scientist Branch, Department of the Environment and Energy

TSFTailings Storage Facility, Ranger uranium mine

1Welcome and opening session

The meeting commenced at 9.07 am.

The Chair, Dr Simon Barry, welcomed members and observers to the meeting.

1.1Acknowledgement of Country

The Chair acknowledged and paid respect to the Larrakia people, the traditional owners, past and present, on whose country this meeting took place.

1.2Disclosure of conflicts of interests

Dr Stauber noted CSIRO’s ongoing assistance with SSB’s uranium sediment toxicity project.

Dr Mudd noted he continues undertaking consultancy work for GAC.

1.3Attendance and apologies

As recorded above. The resignation of Professor David Mulligan from the Committee was acknowledged.

1.4 Observers

As recorded above.

1.5Correspondence

ARRTC noted the status of correspondence (incoming or outgoing) to 16 May 2016.

1.6Governance

SSB provided an update on committee governance arrangements. ARRTC was advised that formal appointments are expected to be finalised in August 2017, and members notified at that time.

1.7Publications

Publications for the Supervising Scientist Branch and ERA for the period 1 July 2016 to 31 March 2017 are at Attachment E of the ARRTC Report and in the ERA report respectively.

2ARRTC 37 Outcomes

2.1ARRTC 37 – Summary record

ARRTC endorsed the minutes, with verification of a statement to be checked by Mr Andrew Johnston.

2.2ARRTC 37 – Actions arising

Actions noted as complete were removed. Outstanding actions were updated.

3Research

3.1Energy Resources of Australia Limited – Ms Sharon Paulka, ERA

Associated presentation: 3.1 ERA operations and closure update

Associated paper: 3.1 Report to the Alligator Rivers Region Technical Committee meeting # 38 Environmental studies and closure

ERA advised that Mr Tim Eckersley, former General Manager Operations, had moved to Rio Tinto, effective January 2017. Ms Lesley Bryce has been formally appointed as General Manager Operations and will commence on 5 June 2017.

Operations

An update on work health and safety performance was provided, with improved performance noted following implementation of enhanced procedures.

An update on environmental performance since January 2017 was provided. Five minor incidents had occurred and will be reported on at the next Routine Periodic Inspection.

An update was provided on rainfall and TSF levels, water management (pond and process water bodies), operational performance, and the 2016 outcomes for the three near-term strategic priorities.

Closure

An update on progressive rehabilitation was provided, including amount spent on rehabilitation and water management to date, status of the feasibility study for the Ranger rehabilitation program in 2017, and progress made on Pit 1 capping, dredging, brine concentrator and brine injection.

An updated schedule of Ranger closure was presented which shows major closure and rehabilitation activities and milestones underway and proposed up to 2026. ERA also provided the timeline for their technical studies up to March 2018 (contained in the ERA report).

ERA noted the Ranger Mine Closure Plan will be made available to the public, most likely in quarter 1, 2018 and updated annually.

The ARRTC commended ERA for its intentions to make the Closure Plan publicly available.

An update on and aerial photographs of the progressive rehabilitation of Jabiluka was provided.

Pit 3 tailings deposition strategy

ERA described the change to its approach for the Pit 3 tailings deposition strategy from subaerial (from top/side of pit) to sub-aqueous, following advice from a tailings consolidation consultant. The change in method included a full risk assessment. SSB advised it was seeking its own independent expert advice on potential longer-term impacts: and was of the view that the change in strategy may have to include review of closure schedule timeframes and water movement. Solute transport and landform subsidence were noted by SSB as the two potential environmental issues of most concern.

ARRTC acknowledged the change in strategy was significant, and requested a presentation on the consolidation work, potential operational challenges including delay to the rehabilitation schedule, and risks associated with having such a large pit full of water requiring rapid consolidation and backfill.

ACTION 38-1: ERA to present at ARRTC 39 (December 2017) an update on the change to the Pit 3 tailings deposition strategy and consolidation work generally, and SSB to present on the results of SSB’s independent review of the potential longer-term operational and environmental risks of the strategy change.

3.2SSB overview and ERISS proposed 2017-18 research and monitoring program – Mr Keith Tayler and Dr Rick van Dam, SSB

Associated presentation: 3.2 Supervising Scientist Branch update

Associated presentation: 3.2 SSB 2016-17 update and ERISS 2017-18 research and monitoring program

Associated paper: 3.2 Supervising Scientist Branch proposed 2017-18 research program

Branch update

SSB provided an update on the status of its review of ERA’s Ranger Mine Closure Plan, the development of the Supervising Scientist’s Rehabilitation Standards, the Branch’s staffing profile, and the Departmental restructure which will result in the Branch joining a newly formed Reef, Heritage and Marine Division.

SSB advised it had developed a 10 year plan: a forward work program for the next 10 years. The Plan arose from the screening level ecological risk assessment from which the KKN’s were derived and endorsed by ARRTC in 2016. The Plan maps out the Branch’s research, monitoring, and supervision activities and projects to 2026, each scheduled, costed, and aligned with ERA rehabilitation activities. The Plan, which will be published in the near future, provides a clear program of work and the ability to report directly against it.

Research and monitoring program

SSB provided a summary of the 2016-17 wet season water quality results and research progress, and the 2017-18 planning process and proposed work program.

Regarding water quality, monitoring has shown an overall trend of improved water quality over the past eight wet seasons. A number of EC spikes were noted in Gulugul Creek in February 2017, but these were not severe enough to trigger exceedance actions. It is thought the spikes were related to the release of water into the Gulungul Creek Tributary 2 (GCT2).

Regarding the 2016-17 research program, significant progress has been made across the following teams:

· Water and Sediment Quality Team: the completion of the multiple lines of evidence assessment for magnesium water quality Rehabilitation Standard, the Magela Creek sand bed sub-surface water quality and ecological pilot study, the development of the freshwater mussel chronic toxicity test, and advice obtained for the Rehabilitation Standard for sulfate.

· Revegetation and Landform Team: attainment of Beyond Visual Line of Sight qualifications for drone operations, the modelling of effects of riplines on a rehabilitation surface project now in the write-up phase, and refinements to CAESAR-LisFlood modelling.

· Environmental Radioactivity Team: attainment of the first measurement of 231Pa in mussel flesh, the measurement of 226Ra and metals in mussel shells to establish tissue-to-whole organism conversion factors for biota dose modelling, and refinement of radon dispersion modelling of final landform.

The proposed 2017-18 work program, aligned with SSB 10 year plan, is focussed on KKNs, and is made up of 54 research projects (29 of which are new) and eight monitoring projects (Figure 1). Recognising the need for continual improvement, a component of the proposed 2017-18 work program will be dedicated to undertaking development, review and refinement of monitoring and research methods.

Figure 1. SSB 2017-18 research projects, by theme.

SSB thanked ARRTC for its feedback on the Supervising Scientist Branch Report. The SSB has provided responses to the feedback.

3.3 Specific presentations

3.3.1 Over-arching

Rehabilitation ecological risk assessment update (Renee Bartolo, SSB)

Associated paper: 3.3.1 Project scope, methods and timelines for Cumulative Ecological Risk Assessment (CERA) for the rehabilitation and closure of Ranger uranium mine (Bayliss, 2017)

Associated presentation: 3.3.1 Rehabilitation ecological risk assessment – project update

At its 37th meeting (November 2016) ARRTC requested SSB:

· Screen the moderate and low risks identified in the Ecological Risk Assessment, and identify (i) where those moderate and low risks are covered by the KKNs (based on the critical and high risks) and (ii) reference relevant existing KKNs; and

· Present on the method to be used for the cumulative ecological risk assessment (CERA).

Screening

From the 69 moderate and low risks identified in the Ecological Risk Assessment, a total of 12 risks overall (two in the decommissioning phase, 10 in the post-decommissioning phase) were identified as having no corresponding KKN. The management of these 12 risks was discussed. The remaining 57 risks have now been mapped against a corresponding KKN.

CERA method

This project is a collaboration between ERISS, CSIRO (Peter Bayliss) and consultant Dave Walden.

The scope of the first phase of the CERA is to model on-site risks associated with landform development/stabilisation and revegetation, and the interaction between the two (refer associated paper by Bayliss, 2017). The project aims are to: determine the most appropriate method for undertaking a CERA; to identify and catalogue datasets that will be used in the risk assessment; develop an agreed conceptual model and supporting narrative to undertake a risk assessment; undertake qualitative modelling on the conceptual models developed through the rehabilitation and closure ecological risk assessments to date; and complete a CERA for the on-site risks (landform, revegetation, and contaminants and sediments). SSB presented the conceptual model of on-sight risks, and the framework for the CERA (Figure 2). The second phase of the CERA (in 2018) will model off-site risks and in particular, in relation to surface water and groundwater interactions. The ‘whole of site’ surface water model, tentatively due for completion by ERA by the end of the year, is critical for the second phase.

With respect to timing for phase 1, a qualitative modelling workshop is scheduled for August 2017. Complete quantitative risk analysis, modelling and assessments is expected to be complete by November 2017, and the draft risk assessment report expected by December 2017.

Figure 2. Framework for the cumulative ecological risk assessment.Based on AS/NZS ISO 31000:2009 risk management principles and guidelines,ISO IEC 31010:2009 risk management risk assessment techniques, and theUS EPA Guidelines for Ecological Risk Assessment.

3.3.2 Water and Sediment

Magela Creek sand bed water quality and ecology studies (Chris Humphrey, SSB)

Associated presentation: 3.3.2 Magela Creek sand bed water quality and ecology studies.

Project title: Assessing the ecological risks of mine water contaminants in the dry season, subsurface waters of Magela Creek sand channel. ARRTC 38 report, page 135-137.

Project publications to date: Chandler L, Tomlinson M & Humphrey C 2017. Water quality and biota in the subsurface sands of Magela Creek - report of a pilot study. Internal Report. Supervising Scientist Branch, Darwin. In review.

Dr Humphrey provided an update on the progress of this project, last presented at ARRTC 36 (August 2016). The design of this current study, commencing in July 2017, is being informed by the 2016 pilot study which examined water quality (including current mine water contamination) and biota of subsurface saturated sands of Magela Creek. The results of the pilot study were presented, and are reported in Chandler et al 2017 (in review). The forward work plan includes monthly collection of biota and water chemistry samples, investigations into habitat variables (such as subsurface flow rates and hydraulic conductivity) and genomics and morphological analysis of biota samples.

ARRTC commended the techniques and approach taken by the project, supported the project’s forward work program in its current form, and endorsed the project.

3.3.3 Groundwater

Corridor Creek Land Application Area (CCLAA) to Gulungul Creek upper tributary groundwater plume delineation (Ben McTavish, ERA)

Associated presentation: 3.3.3 CCLAA to Gulungul Creek upper tributary groundwater study.

Associated report: 3.1 Report to the Alligator Rivers Region Technical Committee meeting # 38 Environmental studies and closure, section 1.4, pages 9-11.

Associated report: Ranger Annual Groundwater Report 2015/16. Environmental Resources Management Australia Pty Limited, December 2016.

The aim of this investigation was to assess the potential causes of elevated EC spikes measured in surface water from Gulungul Creek upper tributary, and the potential relationship between irrigation activities at the CCLAA, where concentrations of sulfate and several other ions in groundwater exceed adopted background values. Potential interactions between groundwater and surface water between the south-western portion of the CCLAA and surrounding catchments are being assessed. The findings were presented to ARRTC, and are reported on in the Ranger Annual Groundwater Report 2015/16 (ERM, 2016). The assessment indicates that due to the cessation of irrigation in the southern portion of the CCLAA, hydraulic loading in this area has declined thus reducing the potential for migration of contaminants of potential concern from this area (ERM, 2016).

A conceptual hydrological model for the CCLAA and Gulungul Creek upper tributary area based on the source-pathway-receptor framework, is being developed. Mitigation measures were presented and include limiting irrigation rates in the south-west corner of the CCLAA and continued groundwater monitoring.

ACTION 38-2: ERA to present at ARRTC 41 (November 2018) an update on the CCLAA to Gulungul Creek upper tributary groundwater plume delineation.

ACTION 38-3: SSB to present at ARRTC 39 (November 2017) an update on Gulungul Creek water quality investigations.

Gulungul Creek tributary 2 interception system update (Ben McTavish, ERA)

Associated presentation: 3.3.3 GCT2 interception system update.

Associated paper: 3.1 Report to the Alligator Rivers Region Technical Committee meeting # 38 Environmental studies and closure, section 2.2.1, pages 22-24.

Associated report: Ranger Annual Groundwater Report 2015/16. Environmental Resources Management Australia Pty Limited, December 2016.

The GCT2 interception system consists of a seepage interception trench, a cut-off wall, seven shallow dewatering bores along the GCT2 alignment, and the periodic capture and pumping of GCT2 surface flow. The system was installed over 2014-15, and is designed to reduce further migration of impacted groundwater from the TSF into the GCT2 alignment, remove impacted groundwater already present down gradient of the TSF west wall sump, and reduce discharge of impacted shallow groundwater into the GCT2 channel.

To date, the interception system has been very effective at drawing out salt, and hence reducing EC in associated monitoring bores, since dewatering commenced in January 2016.

ARRTC was interested to know about the chemical characteristics of the intercepted waters, as this would provide useful insights to form an understanding of the chemical composition of groundwater moving through and beyond the rehabilitated site and how representative they are considered to be of the post-closure groundwater.

ERA presented the review of system performance completed by ERM between January and October 2016. Nine megalitres of groundwater and 22 tons of salt were removed from the GCT2 channel. Next steps are to continue to monitor the systems performance, and review recommendations made by ERM to improve the operation and optimisation of the system.

ERA contend the GCT2 area hydrology is different to that expected post-closure, so believe the two are not readily comparable. As identified in the Ranger conceptual model, post-closure hydrology is expected to be less head-driven with longer solute transport timelines. Currently, the tailings dam embankments provide significantly greater storage of waste rock leachate, and this in turn, significantly increases driving head.

A detailed assessment of the GCT2 system is provided in section 9 of the Ranger Annual Groundwater Report (ERM, 2016). ERA advised it intends to provide the learnings from the assessment to INTERA.

ARRTC was interested to know:

· The potential source of the impacted groundwater, as this is important in demonstrating preferential pathways. ERA advised the water quality indicates a small presence of some process water, but the precise mechanism seems to be from a relatively shallow and narrow alluvial pathway.

· How much can be learnt from this system and applied to knowledge of recharge through the final landform and forward modelling. ERA reiterated that INTERA has a predicated zone, timing and amounts, and modelling to date based on a 10,000 year recharge and related processes, do not influence the peak loadings to the Gulungul Creek. ERA is providing information to INTERA as it comes to hand.

ARRTC noted the importance of the work associated with the interception system and its expectations in ensuring learnings from it are made and incorporated into INTERA modelling and reporting.

Review of Pit 3 hydrogeological aspects (Peter Baker, SSB)

Associated presentation: 3.3.3 Review of Pit 3 hydrogeological aspects.

Mr Baker provided an update review, in light of ERA’s change to its tailings deposition strategy for Pit 3, from sub-aerial to subaqueous. SSB has undertaken a preliminary review to determine the likelihood of short-term risks associated with the projected level of free water.

Four potential groundwater pathways have been identified and were presented: the north face fracture zone; Djalkmara Sands, carbonate, and sub-horizontal drains. The maximum operating level for the pit is being assessed by INTERA, and SSB will, in turn, review INTERA’s assessment and geotechnical report.

The ARRTC noted this was largely an operational issue, but were concerned about how the change in strategy may impact on rehabilitation objectives, notably potential permeability issues. SSB noted three projects will investigate permeability: Pit 3 Transmissivity Assessment; Djalkmara Sands Transmissivity Assessment; and Magela Creek surface water-groundwater interactions. ERA contended that the sub-aqueous method had lower risks than the subaerial method, as demonstrated by learnings from Pit 1.

ARRTC recognised the significance of the issue, and requested it be updated in due course.

Nabarlek groundwater summary (Peter Baker, SSB)

Associated presentation: 3.3.3 Review of Nabarlek groundwater data.

Mr Baker presented a summation of two reviews conducted by the OWS on Nabarlek groundwater data, requested by ARRTC at its 37th meeting. The two reviews are:

· Barnes and Zimmerman (June 2016), which provided a preliminary review of the data; and

· Lawson (November 2016) extending on the June 2016 review, looking at uncertainty and ongoing issues.

The key matters arising out of the reviews are:

· Bore integrity: casing and annulus walls have compromised integrity, impacting on sampling adequacy. The installation of new and deeper bores is a recommendation.

· Bore metadata: discrepancies on applied bore naming conventions has resulted in missing information, and a bore audit is recommended. The discrepancies flow through to other databases where there are inconsistences between the Bureau of Meteorology’s database and other records.

· Hydrochemistry anomalies (sulfate, magnesium and uranium across 3 transects measured from ~1980 to 2012): in Transect 1, sulfate concentrations were found to be overall reducing over time, assisted by rainfall flushing, but magnesium levels were found to be elevated in the sampling bore located near the former pit. Transect 2 had increased levels of sulfate, but there is insufficient data to know whether this is occurring at an increased geographical distance from the pit. Transect 2 also had uranium levels increasing above reference levels over the last 10 years. Transect 3 had increasing levels of magnesium, but stable levels of sulfate but also require further monitoring to assess potential impacts to Cooper Creek.

Recommendations arising from the reviews included a bore audit, continued annual monitoring, resolution of data discrepancies, assessment of background concentrations, and further transport modelling of deep solute loads. Although environmental impact in the future cannot be discounted, presently there is limited evidence to suggest any impact on the environment.

The ARRTC endorsed the recommendations arising from the reviews and supported their implementation. The ARRTC recommended adding the broader Alligator Rivers Region into the KKNs. The SSB noted that there are placeholders in the KKNs for the other key sites within the Alligator Rivers Region, with the intention to populate these when time is available, but that Ranger currently remains the highest priority. Also, the SSB noted that it deployed several water quality (electrical conductivity) loggers in streams at Nabarlek for the 2016-17 wet season, and will be able to provide an update at ARRTC39.

3.3.4 Landform

Status of landform evolution modelling (John Lowry and Mike Saynor, SSB)

Associated presentation: 3.3.4 Status of landform evolution modelling, CAESAR-Lisflood model

Mr Lowry and Dr Saynor presented an update of the CAESAR-Lisflood sensitivity analysis, the vegetation model, particle size ranges, and the application of synthetic rainfall data sets, requested by ARRTC at its 37th meeting.

CAESAR-Lisflood (landform evolution model that simulates runoff, erosion and deposition, used to assess landform stability) sensitivity analysis

CAESAR-Lisflood has been used to simulate a range of scenarios, which has been reported in a variety of peer-reviewed publications and conference proceedings.

The sensitivity analysis applied the highly recognised and extensively applied Morris Method (Morris, 1991). The analysis tested the sensitivity of 15 parameters. The sensitivity analysis found the sediment transport equation parameter to be the most non-linear and have the greatest impacts/cause the most variability. The vegetation critical sheer stress parameter was found to become most important when modelling geomorphic parameters. The sediment grain size sets parameter was shown to be influential in the short-term (up to 1000 years), but diminishing over time.

Vegetation model update

The SSB has trialled a different vegetation model within the CAESAR-Lisflood model based on that of Saco et al (2007), which is more dynamic and intuitive, and better suited to the Northern Territory climate and landscape. Comparison between the existing static and the new dynamic models showed that output amounts were similar, with the exception that the dynamic model incised much less in main streams and resulted in more eroded headwaters. Hence, increased predicted erosion (sediment yield) was found with the dynamic model. An issue hampering the progress of the dynamic vegetation model is missing information on how biomass relates to erosion (the same issue identified in the sensitivity analysis – specifically, what shear stresses were required for erosion to occur).

Dr Pickup expressed concern about the ability of the vegetation model to effectively simulate run-on and run-off effects of water, movement and transport of particles and nutrients in the landscape, and sediment trap effects, and noted these effects remain applicable even to low elevations and flat topographies. Dr Pickup flagged this as a significant issue on the trial land form that should be addressed. Dr Pickup suggested there was a relatively simple way to deal with this issue, which he will discuss with SSB and Professor Tom Coulthard, fluvial geomorphologist. Dr Pickup acknowledged that significant work had gone into developing and enhancing the CAESAR-Lisflood model to date and that model results were sound.

The influence of surface material particle size ranges on erosion rates

This project looked at determining the most suitable surface material size ranges for input into the CAESAR-Lisflood model, that can accommodate the three different surface types (waste rock, natural surface, and armoured) across the Ranger site.

Dr Pickup noted that sediment transport theory remains rough and quite limited, and models are poor at handling sediment mixes. Given the limitations of the theory, Dr Pickup suggested 2 grain size distributions (composed of 9 classes each) would be adequate. Further, given the limitations, Dr Pickup suggested the only way to improve modelling was to incorporate spatial vegetation parameters.

Application of synthetic rainfall data sets

Climate analogues are a useful tool to assess sensitivity of mine sites to potential future climates where little data exists. SSB’s synthetic rainfall datasets will be used to develop rainfall scenarios for periods of up to 10,000 years. The range of rainfall scenarios developed to date show the potential for rapid erosion over a simulated period of 1000 years, and increased sediment output is likely with increased rainfall and storm intensity. The results provide a guide to areas of improvement in the landform design, and increased confidence that applying stochastic synthetic rainfall datasets in landform modelling will improve the long-term predictions of landform stability.

The ARRTC:

· Was interested to know, irrespective of timeframes, whether or not tailings might be exposed if there is continual erosion. ARRTC was advised that within the modelled 10,000 years tailings are not expected to be exposed, however gullies will form. Tailings will be below the natural landscape, so are not expected to be exposed.

· Agreed that the CAESAR-Lisflood modelling development phase has probably gone as far as it could go. ARRTC suggested testing the improvement suggested (above) by Dr Pickup.

· Was interested to know how groundwater would be prevented from intercepting tailings. ERA noted this is incorporated into the Ranger Conceptual Model and erosion control design, and if gullies form, they will be mitigated and actively managed, in accordance with the Environmental Requirements.

· Was interested to know if there was benefit in exploring catastrophic climatic events (worse case scenarios) noting that synthetic rainfall data do not take into account events that come in from another population, i.e. flood events that sit above the linear trend. SSB noted it is looking at palaeoflood records to ascertain if there are any large catastrophic events above the historical record that could be incorporated into the model; and that Dr Verdon Kidd and Professor Hancock were investigating both climate analogues and palaeoclimate sources for additional information.

Landform flood modelling to inform sediment/erosion management (Toby McGrath, Principal Engineer Water Solutions for ERA)

Associated presentation: 3.3.4 Landform flood modelling

Associated report: 3.1 Report to the Alligator Rivers Region Technical Committee meeting # 38 Environmental studies and closure, section 1.5.2, pages 13-14.

Water Solutions were engaged by ERA to estimate design flood hydrographs for the final landform sub-catchments, develop a concept hydraulic design for the final landform drainage and sediment control system, and develop design criteria to guide the final design of the system. The work is directly aligned with the landform-related closure criteria and associated KKNs. This presentation provided ARRTC with the preliminary findings. Features of the project are outlined in the associated report.

ARRTC:

· Noted, having regard to the proposed network of 16 leaky rock weir sediment basins, that a complex road network would be required to accommodate access, and not only sediment would accumulate, but also vegetation debris.

· Was interested in, noting these are designed to be deconstructed, when it was proposed to remove the leaky rock weirs. Mr McGrath stated that was an operational decision rather than a closure related decision, and would be dependent on a number of factors including decommissioning criteria timeframes on sediment movements and turbidity levels in creeks.

· Noted, having regard to the modelled flood visualisations, that inflow from upstream of the Magela catchment has not been taken into account. Mr McGrath stated in response that the Water Solutions report contains a number of recommendations, including taking into account flooding from Coonjimba Creek catchment.

· Were interested in how the captured sediment would be disposed of. ERA advised this was yet to be determined.

The SSB noted that vegetation management presented in Mr McGrath’s proposal was different to what has been proposed by ERA before. Mr McGrath noted Water Solutions was working closely with ERA to consider a number of aspects related to vegetation, including increasing the water availability for plants, but not solute transport.

ARRTC noted the parameterisation and assumptions presented by Mr McGrath were consistent with how the landform is expected to be. ARRTC thanked Mr McGrath for the presentation.

Ranger closure – cover design for ecosystem reconstruction (Dr Ian Hollingsworth, Horizons Environmental and Soil Survey, presentation for GAC)

Associated presentation: 3.3.4 Cover design for ecosystem restoration.

Associated paper: Ranger uranium mine final landform cover design for ecosystem reconstruction (2017). Hollingsworth, I.D. and Klessa, D. Horizon Environmental Soil Survey and Evaluation.

This study was commissioned by GAC to review and advise on what it believed to be design issues with ERA’s current landform construction plans and final landform, namely in relation to:

· Issue identification and impact assessment: restoring water balance processes at site and catchment scale is an essential KKN representing best practice science for ensuring environmental protection;

· Development and validation of standards: landform cover design for ecosystem restoration;

· Monitoring and assessment needs: water balance monitoring parameters and endpoints;

· Traditional owner aspirations: significant cultural and natural features in the landscape and Mirarr expectations in relation to traversability, land capability, contour ripping, subsoil drainage, water balance modelling design and monitoring; and

· Ecosystem recovery and function, and ecohydrological factors and endpoints.

Full details are provided in the associated paper. An alternative cover design basis was presented by Dr Hollingsworth.

The following topics were raised and discussed:

· The extent to which ERA considered water retention in the trial landform. ERA informed that particle size analysis were undertaken in 2009, 2013 and 2014 for the waste rock treatment on the trial landform. Between 2009 and 2013 both the clay and silt percentages of the surface soil were significantly different (increased). In 2014, two pits in the waste-rock treatment were sampled. When combined pit 1 and pit 2 together there was not a significant difference in the clay percentage between 2009 and 2014 samples. However when treated separately, Pit 1 (2014) was significantly different to 2009 samples but Pit 2 (2014) was not, though the two were significantly different from each other. In 2014, silt was significantly increased but sand (%) was significantly decreased. This would increase the soil water holding capacity in the top 3m soil by about 9% (Jill Segura, 2017, unpublished, CDU PhD student).

· The use and availability of laterite. The use of laterite was part of an earlier design, but now there is limited laterite available, and trails showed poor revegetation success in the laterite plots. This has been taken into account in the final landform design. The approach raised questions regarding what vegetation will be supported. ARRTC noted it has already (previously) considered the lack of laterite and what that means for vegetation regrowth.

· The feasibility of using blasting to obtain an appropriate particle size distribution of rock. ERA noted the advancements in this field and environmental benefits, but informed it had ceased blasting and had no intentions of resuming. Waste rock will now only be moved.

· How the issues raised by Dr Hollingsworth will be addressed. It was noted ARRTC will continue to discuss KKN gaps in this space, while SSB will continue to work with ERA on its closure strategy in relation to landform cover conditions that can sustain a vegetation community. ERA has such information in the RMCP, but will provide a more detailed case and strategy in its application to the MTC to construct the final landform. SSB reiterated it will not support ERA’s proposed construction of the landform, until ERA can demonstrate it will support plant growth and that the process for such approvals was through the MTC. GAC will provide its concerns on the RMCP to ERA for consideration.

· ARRTC noted it has not yet seen the RMCP so was unable to comment on how the plan lends itself to address the issue of cover design for ecosystem restoration.

· On issue of KKNs, SSB agreed to review these for specific consideration of ecological processes and advise ARRTC accordingly. SSB had previously assessed whether the ecological risk assessment and subsequent KKNs had covered ecological processes. It was thought that the ecological endpoints were broad enough that ecological processes were covered. Nonetheless, SSB will review.

· ERA conceded that the RMCP lacks detail in this context, and studies are underway to inform and better articulate its landform design approach. Understory development is a key priority for ERA. It advised an updated approvals schedule will be available for stakeholders by the end of quarter 2, 2017, and an updated Closure Plan available for discussion at ARRTC 39 (November 2017). ERA advised it will make the RMCP available to the public.

· SSB noted that from its observations, waste rock remains competent for a long period of time and does not weather as quickly as has been proposed by Milnes 1989. The influence of any difference between the materials mined from Pit 1 and Pit 3 (i.e. more chlorite schist compared to more mica schist respectively) on weathering rates should be taken into account. Further, that there had been no observed soil development on the trial landform after eight wet seasons, indicating that soils are unlikely to develop in five years, as proposed by ERA in its RMCP.

ACTION 38-4: ERA to present at ARRTC 39 its cover design including water balance, vegetation growth, material balance for the landform with an emphasis on evidence to support the long-term sustainability of vegetation.

ACTION 38-5: If available, ERA to present at ARRTC 39 the Ranger Mine Closure Plan for discussion – refer outstanding Action 37.2.

ACTION 38-6: SSB to review the Key Knowledge Needs for consideration of ecological processes, in light of Dr Hollingsworth paper and presentation on cover design.

ACTION 38-7: SSB to provide at ARRTC 39 a presentation on waste rock weathering.

3.3.5 Flora & fauna

Vegetation understorey trial (Ping Lu, ERA)

Associated presentation: 3.3.5 Understory establishment in waste rock.

Associated report: 3.1 Report to the Alligator Rivers Region Technical Committee meeting # 38 Environmental studies and closure, section 1.3, pages 5-9.

This project is investigating the establishment of understory species in waste rock to determine factors limiting success and optimum establishment protocols. It involves monitoring emergence and survival on the Ranger trial landform and in waste rock trials at the Charles Darwin University. Further details are provided in the associated report. Sowing and planting will occur in January 2018.

ARRTC was interested to know how ERA is taking into account the development/presence of mycorrhizal fungi and dormancy. ERA advised it was incorporating mycorrhizal fungi into the potting mixtures, and working on a protocol for mimicking dormancy.

SSB were interested to know why ERA was not undertaking understory trials on laterite-waste rock mixed plots. ERA noted it had found understory to establish quite quickly in waste rock in land application areas, and viewed weed invasion as more of a critical issue than the establishment of understory.

3.3.6 Radiation

No presentation requested.

Having regard to research overall, ARRTC endorsed the work program.

4Key Knowledge Needs

Overview of ARRTC expertise review (Rick van Dam, SSB)

Associated presentation: 4 Key Knowledge Needs – ARRTC expertise review

SSB is conducting an assessment of the expertise required on ARRTC as Ranger moves into the closure and rehabilitation phases. Specifically, SSB is seeking an appropriate blend of expertise on ARRTC to advise on and review Ranger rehabilitation-related research and monitoring required to meet the Environmental Requirements, Ranger operational research/monitoring needs, and relevant research and monitoring needs elsewhere within the Alligator Rivers Region.

SSB advised it is preparing the expertise assessment as an Internal Report, which will be circulated for consultation shortly, and ARRTC was invited to provide comments.

5Stakeholder update reports

5.1Department of Primary Industry and Resources – including regulatory decisions and supporting science.

Report tabled, no presentation given.

5.2Environment NGOs

Dr Mudd on behalf of Environmental Non-Government Organisations noted usual concerns regarding progress on the rehabilitation of the Ranger mine.

5.3Northern Land Council

No report.

5.4Parks Australia (Sally-Ann Atkins)

Associated presentation: Parks Australia Division South Alligator Valley containment update

The South Alligator Valley containment facility is located in the Gunlom Land Trust Area of Kakadu National Park. The facility was purpose built in 2009 to encapsulate various waste from abandoned uranium mines in the region. Parks Australia Division (with assistance from Envirotech) conducts ongoing monitoring to ensure the facility is working and meeting its intensions.

Parks presented an assessment of containment performance for 2015-16 (also reportable to ARPANSA. Results are provided in the associated presentation. In short, subsidence is one of the biggest issues. Subsidence impacts on monitoring stations and is causing water percolation and infiltration (seepage). Chemical analysis of the seepage shows this to be relatively benign. Groundwater monitoring shows no contamination, when compared to drinking water guidelines.

Parks also provided ARRTC with an update on the settling of the facilities cap following 2010 and 2013 remediation efforts.

ARRTC noted the many lessons to be learnt from the ongoing monitoring and revegetation efforts at the site, and thanked Parks for their detailed presentation.

7Meeting outcomes

7.1Summary of key outcomes and actions arising from meeting

ARRTC 38 actions were reviewed and agreed to by ARRTC.

7.2Matters for Chair’s report to the Minister

Matters for the Chair’s post-meeting letter to the Minister were noted.

8Other Business

Confirmation of next meeting dates:

ARRTC 39: Darwin, Tuesday 14 and Wednesday 15 November 2017

Mid-cycle interim teleconference dates indicatively Tuesday 29 August 2017 - 10-12 pm EST and March 2018

ARRTC 40: Darwin, May 2018

ARRTC 41: Darwin, November 2018

Meeting closed at 4.27 pm.

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Documents

ARRTC38 - May 2017 - Meeting Record · Web viewAlligator Rivers Region Technical Committee Meeting 38 16 – 17 May 2017 Record of meeting Darwin, NT This document is a summary record