Appendix L – Revised Groundwater Modelling Report | NT EPA

LAppendix L – Revised Groundwater

Modelling Report

D09814A25 December 2017

McArthur River Mining Pty Ltd 2017 MRM EIS Supplementary

Updated Groundwater Impact Assessment

Final Report

McArthur River Mining Pty Ltd

Supplementary EIS

Site Groundwater

Report

171218 R MRM EIS

Supplementary_GW.docx

Page i


EXECUTIVE SUMMARY

This report provides an update of the groundwater assessment completed for the McArthur

River Mine EIS. An assessment of potential groundwater responses to the operations and

proposed management strategies is presented for the Life of Mine and closure scenarios based

on predictions from an improved and re-calibrated numerical groundwater flow and

contaminant transport model. Groundwater impacts are again considered in terms of

dewatering, seepage through overburden emplacement facilities (with a focus on the NOEF),

seepage from water management dams and the Tailings Storage Facility. The corresponding

and integrated Surface Water Impact Assessment, allows MRM to predict and manage the

impacts on the groundwater and surface water system during Life of Mine and closure.

Several important improvements are contained in the proposed project plan and are

considered in this report. The most notable being the changes arising from the predicted NOEF

response, due to a change in the proposed final cover, an alternate modelling approach, and

the final void closure plan. These changes will have long term benefits at MRM and will reduce

loads to the receiving environments.

MRM has undertaken further hydrogeological characterisation for the purposes of improving

the understanding of the site groundwater systems and processes. The program included

further geological characterisation and modelling of the site, additional field geophysics, re-

interpretation of historical data, drilling and hydraulic testing of monitoring bores and sampling

of groundwater for chemical analysis to supplement the existing groundwater information for

the project site. The new data generated from the field program was integrated with the

information presented in the Draft EIS site geological and hydrogeological datasets to refine the

site-wide conceptual hydrogeological model and update the numerical model. Key updates to

the model apart from the project changes were focused on the re-interpreted geological

structures, particularly for the Bald Hills Fault system and the updated hydrogeological

information provided by ongoing field characterisation from MRM’s field program.

The numerical groundwater modelling was completed in MODFLOW using SURFACT and

integrates with both surface water, NOEF unsaturated flow and pit lake (limnology) modelling.

The updated model was calibrated to heads, fluxes and sulphate concentrations over the

monitoring period 2006 to 2014. The calibrated model was again used to simulate the

groundwater responses to life of mine and closure for a period of 1,000 years.

The modeling indicated that groundwater can be impacted by migration of contaminants from

mine sources and natural mineralised sources through aquifer pathways, and aquifer

drawdown as a result of open cut dewatering. As per the Draft EIS, impacts from dewatering

that were assessed include reduction of baseflow and the potential for drawdown at

waterholes. The contaminants of concern that were assessed include sulphate, lead, zinc,

cadmium and arsenic.

A focus of the supplementary modelling was to assess the sensitivity of results to changing

conditions or ranges in the field-determined parameters adopted for the numerical model. This


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involved several alternate simulations completed to better contextualise the contaminant

transport and attenuation processes for the MRM site. Sensitivity analysis included

consideration of the impact of several alternatives for the NOEF (changing the final cover

design, and alternate NOEF foundation conditions), varying aquifer parameters (particularly for

the units associated with the geological structures across the site) and contaminant transport.

The key results from the supplementary EIS groundwater assessment are:

� A focus of the EIS Supplementary was to reduce the contaminant loads arising from the

NOEF through consideration of alternative covers, and as indicated in the concurrent

NOEF Flow and Water Quality report (KCB, 2017), proposed geosynthetic liner (GSL)

cover system reduces cumulative loads to groundwater significantly by a factor of five or

more for sulphate and zinc over the next 100 years, compared to the previously

proposed compacted clay liner (CCL) cover system.

� Dewatering of the open cut pit during operation will largely drain the bedrock aquifer

adjacent to the McArthur River and Barney Creek Diversion Channels, therefore,

reducing baseflow to these structures during the operational phase. After closure, the

rapidly recovering pit lake, as well as rainfall recharge processes allows the bedrock

aquifer hydraulic head to rebound and re-establish a hydraulic connection with the

diversions.

� To mitigate sulphate loads to the Surprise Creek system from the Tailings Storage

Facility (TSF), an interception trench will be constructed on the northern side of the TSF.

Modelling has indicated that this will reduce the loads to Surprise Creek while this

trench is operational. At closure the TSF is removed and will therefore remove loads

from this facility to both Surprise Creek and downstream at the Barney Channel in the

longer term.

� Predicted changes to water levels and flows are of similar magnitude to those reported

by the Draft EIS and previously by the Phase 3 Groundwater Assessment. These include

baseflow discharges to creeks, rivers and diversions that will change due to seepage

from the mine overburden facilities and dewatering of the expanding open cut

operation.

� As indicated in the draft EIS, sulphate plumes are predicted to arise down-gradient of

the NOEF, TSF, and unlined water management facilities during the life of mine

simulations. The loads are primarily associated with long-term seepage from the NOEF

migrating through weathered and fractured bedrock and reporting to the diversion;

modeling results support the benefits of the proposed geosynthetic cover system in

reducing groundwater-driven loads to the receiving surface water.

� As per the Draft EIS, the highest sulphate loads to Barney Creek diversion occur during

closure once aquifer conditions have recovered following mine pit lake rebound. This is

primarily associated with seepage from the NOEF migrating through weathered and

fractured bedrock reporting to the diversion, and will be captured in the Barney Creek

Sumps as required.


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� Metal loads are limited by the maintenance of neutral conditions and by the measures

in place to limit infiltration into the NOEF, i.e. the proposed cover system and NOEF

design and construction.

MRM’s focus for water management is protection of water quality downstream of the site at

SW11. To evaluate environmental impacts from groundwater discharge to surface water

bodies, the predicted groundwater baseflow fluxes and loads throughout Life of Mine and

closure from the model, including the various sensitivity assessments, have been integrated

into the site-wide water quality model. From this integration, MRM has developed monitoring,

mitigation and management plans for mine waste and water. Details of these plans are

included in the main reports for the Draft EIS and Supplementary EIS documents.


Supplementary EIS

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Report

TABLE OF CONTENTS

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1 INTRODUCTION ................................................................................................................. 1

1.1 Project Background ............................................................................................ 1

1.2 Scope of Work .................................................................................................... 3

1.3 Structure of the report ....................................................................................... 3

1.4 Project changes since the Draft EIS .................................................................... 3

1.5 Integration of multiple models ........................................................................... 4

2 UPDATED GROUNDWATER MODEL ................................................................................... 9

2.1 Groundwater model setting ............................................................................... 9

2.2 Model Code ........................................................................................................ 9

2.3 Model Lateral Extents ......................................................................................... 9

2.4 Units and Datum ............................................................................................... 11

2.5 Updated Geology and Hydrogeology ............................................................... 11

2.5.1 Geological Review of MRM 2016 ....................................................... 11

2.6 Natural Mineralisation at McArthur River Mine ............................................... 19

2.7 Expected Behaviour of Groundwater ............................................................... 26

2.8 Model Layers .................................................................................................... 30

2.9 Representing Fractured Media ......................................................................... 31

2.10 Model Exclusions, Assumptions and Limitations .............................................. 31

2.11 Updated Groundwater Modelling Calibration .................................................. 32

2.11.1 Calibration Process, Targets and Metrics .......................................... 32

2.12 Updated Calibration Results and Statistics ....................................................... 33

2.12.1 Transient Calibration Model (2006 to 2014) ..................................... 33

2.12.2 2006 to 2014 groundwater mass transport model ............................ 54

2.13 Approach to Life of Mine simulations .............................................................. 59

2.13.1 Stress periods .................................................................................... 59

2.13.2 Contaminants of Concern .................................................................. 59

2.13.3 Pit drains ............................................................................................ 59

2.13.4 Recharge ............................................................................................ 59

2.13.5 Climate Change .................................................................................. 60

2.13.6 Seepage ............................................................................................. 60

2.13.7 OEF seepage ...................................................................................... 60

2.14 Approach to Site-wide Closure Groundwater Modelling ................................. 61

2.14.1 Stress Periods and Model Scenarios .................................................. 61

2.14.2 Contaminants of Concern .................................................................. 62

2.14.3 Pit ....................................................................................................... 62

2.14.4 Mine Pit Lake Recovery ..................................................................... 62


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TABLE OF CONTENTS (continued)


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2.14.5 Production borefields ........................................................................ 62

2.14.6 Recharge ............................................................................................ 62

2.14.7 Seepage ............................................................................................. 62

3 UPDATED GROUNDWATER MODELLING RESULTS .......................................................... 64

3.1 Life of Mine Simulations ................................................................................... 64

3.1.1 Baseflow estimates to creeks and rivers ........................................... 64

3.1.2 Pit inflow ............................................................................................ 66

Pit inflows are similar to the values observed in the Draft EIS case. ................ 66

3.1.3 Plume extents for Sulphate ............................................................... 66

3.1.4 Plume extents for metals ................................................................... 67

3.1.5 Load estimates to creeks and rivers .................................................. 74

3.1.6 Uncertainty of Load Estimates and Plume Development .................. 76

3.1.7 1-Dimensional Reactive Transport Modelling ................................... 84

3.1.8 Groundwater Inflows ......................................................................... 96

3.1.9 Drawdown beneath Djirrinmini waterhole ........................................ 96

3.1.10 Plume extents for Sulphate and metals ............................................. 96

3.1.11 Water Budget .................................................................................... 97

3.1.12 Summary ............................................................................................ 98

3.2 Closure Simulations .......................................................................................... 98

3.2.1 Baseflow estimates to creeks and rivers ........................................... 98

3.2.2 Plume extents for Sulphate ............................................................. 102

3.2.3 Plume extents for Metals ................................................................ 106

3.2.4 Load Estimates to Creeks and Rivers ............................................... 110

3.2.5 Groundwater inflows ....................................................................... 115

3.2.6 Comparison of Closure Predictions to Expected Groundwater

Behaviour ......................................................................................... 116

3.2.7 Additional sensitivity runs with mitigation ...................................... 117

4 DISCUSSION ON RESULTS AND SENSITIVITY ASSESSMENTS COMPARED TO EIS

SUBMISSION .................................................................................................................. 119

5 CLOSING ........................................................................................................................ 122

List of Tables

Table 1-1 Summary of interactions between models ......................................................... 6

Table 2-1 Summary of model layers .................................................................................. 31

Table 2-2 Summary of transient model calibration metrics: 2006 to 2014 ....................... 34

Table 2-3 Summary of transient model water balance for a representative wet month

(December 2011) of the transient calibration ................................................... 35


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Table 2-4 Summary of transient model water balance for a representative dry month

(September 2011) of the transient calibration .................................................. 35

Table 2-5 Calibration Models “Trial-and-Error” sensitivity ............................................... 37

Table 2-6 Calibration statistics for various model iterations ............................................. 38

Table 2-7 Recalibrated values of model parameters for new fault zones ......................... 38

Table 2-8 Summary of baseflow influences and reliability ................................................ 45

Table 2-9 Calibrated hydraulic conductivity and storage values ....................................... 52

Table 2-10 Sulphate source terms applied to calibration simulation from 2006 to 2014 ... 59

Table 2-11 OEF seepage assumptions for life of mine ........................................................ 60

Table 3-1 Physical, hydraulic and mass transport properties used in 1D analytical model

........................................................................................................................... 76

Table 3-2 Water quality parameters (in mg/L except for pH and Eh) used in the PHREEQC

models ............................................................................................................... 85

Table 3-3 Aquifer mineralogy used in the PHREEQC models ............................................ 86

Table 3-4 Aquifer parameters and partition coefficients used in the model .................... 87

List of Figures

Figure 1 Site Location and General Arrangement ............................................................. 2

Figure 2 Schematic of model interactions used for the assessment ................................. 5

Figure 3 MODFLOW SURFACT model area showing active and inactive cells. ................ 10

Figure 4 Structural framework of the greater mining region, McArthur River (Logan,

2017).................................................................................................................. 13

Figure 5 ERI traverses (GHD 2016, from Logan, 2017) .................................................... 14

Figure 6 ERI traverses along the Barney Diversion (Logan, 2017 based on GHD, 2016) . 14

Figure 7 ERI and location of the 2016 drill holes (MRM,2017) ........................................ 16

Figure 8 ERI traverse Line 1 and drill holes completed in 2016 (MRM, 2017) ................ 16

Figure 9 Update of Model Layers 5- 8 ............................................................................. 18

Figure 10 Interpreted features across the site (KCB – Draft EIS, 2017) ............................. 20

Figure 11 Distribution of the Interpreted HYC Pyritic Shale (after Williams, 1978), location

of other mapped mineralisation, and 2016 sulphate levels in groundwater .... 21

Figure 12 Regional Extent of the HYC Pyritic Shale (after Williams, 1978) ........................ 22

Figure 13 Historical Stream Samples for site (Pb data 1969 to 1988) ............................... 24

Figure 14 Historical Stream Samples for site (Zn data 1969 to 1988) ............................... 24

Figure 15 Historical Soil Geochemical Samples for site (Pb data 1969 to 1994) ............... 25

Figure 16 Historical Soil Geochemical Samples for site (Zn data 1969 to 1994) ............... 26

Figure 17 Scatter plot of modelled versus observed heads for the calibration model

simulation .......................................................................................................... 34

Figure 18 Representative dry stress period and wet stress period for comparison of

model inflows and outflows .............................................................................. 36

Figure 19 The sensitivity of calibration models ................................................................. 38


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Figure 20 Modelled versus observed hydrographs for representative bores for the model

calibration simulation ........................................................................................ 44

Figure 21 Baseflow reaches defined for the project site (consistent with WRM, 2017). .. 48

Figure 22 Model-predicted baseflow during the calibration period 2006-2014 for Surprise

Creek and Barney Creek diversion ..................................................................... 49

Figure 23 Model-predicted baseflow during the calibration period 2006-2014 for Barney

Creek ................................................................................................................. 49

Figure 24 Model-predicted baseflow for 2006-2014 for unnamed creek ......................... 50

Figure 25 Model-predicted baseflow during the calibration period 2006-2014 for

McArthur River and diversion (Initial year values part of model conditioning) 50

Figure 26 Model-predicted baseflow during the calibration period 2006-2014 for Glyde

River and Bull Creek .......................................................................................... 51

Figure 27 Fault and fault corridor parameterisation in Layer 5 and Layer 8 of the upper

bedrock profile .................................................................................................. 53

Figure 28 Calibrated model sulphate loads reporting to Surprise Creek and Barney

diversion ............................................................................................................ 54

Figure 29 Calibrated model sulphate loads reporting to Barney Creek ............................ 55

Figure 30 Calibrated model sulphate loads reporting to unnamed creek ......................... 55

Figure 31 Calibrated model sulphate loads reporting to McArthur River and diversion .. 56

Figure 32 Modelled versus observed sulphate concentrations for representative bores for

the model calibration simulation ...................................................................... 58

Figure 33 Time-series of TSF seepage rates applied to the life of mine model simulations

........................................................................................................................... 61

Figure 34 Life of mine monthly baseflow predictions for Surprise Creek and Barney Creek

diversion ............................................................................................................ 64

Figure 35 Life of mine monthly baseflow predictions for Barney Creek ........................... 65

Figure 36 Life of mine monthly baseflow predictions for McArthur River ........................ 65

Figure 37 Pit inflows over the life of mine and into closure .............................................. 66

Figure 38 Predicted sulphate concentrations in the overburden at four select periods of

the life of mine .................................................................................................. 68

Figure 39 Predicted sulphate concentrations in the weathered bedrock at four select

periods of the life of mine ................................................................................. 69

Figure 40 Predicted sulphate concentrations in the upper bedrock at four select periods

of the life of mine .............................................................................................. 70

Figure 41 Predicted zinc concentrations in the overburden at four select periods of the

life of mine ......................................................................................................... 71

Figure 42 Predicted zinc concentrations in the weathered bedrock at four select periods

of the life of mine .............................................................................................. 72

Figure 43 Predicted zinc concentrations in the upper bedrock at four select periods of the

life of mine ......................................................................................................... 73

Figure 44 Life of mine monthly sulphate load predictions for Surprise Creek and Barney

Creek diversion .................................................................................................. 74


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Figure 45 Life of mine monthly sulphate load predictions for Barney Creek .................... 75

Figure 46 Life of mine monthly sulphate load predictions for McArthur River ................. 75

Figure 47 Sulphate concentration breakthrough at the Barney Creek diversion for base

2067 models ...................................................................................................... 78

Figure 48 Stochastic output for breakthrough sulphate concentrations (in mg/L) at the

Barney Creek diversion using the modified Domenico equation ...................... 79


Barney Creek diversion using the modified Domenico equation, with an

additional module to take account of recharge dilution effects ....................... 79

Figure 50 Stochastic output for sulphate load (in kg/day) using the modified Domenico

equation ............................................................................................................ 80

Figure 51 Tornado sensitivity chart for the stochastic Domenico analytical assessment.

The output is load to the Barney Creek diversion (in kg/day). .......................... 80


diversion using the modified Domenico equation for 100 year simulation ...... 81


diversion using the modified Domenico equation, with an additional module to

take account of recharge dilution effects – for 100 year simulation ................. 82

Figure 54 Stochastic output for sulphate load (in kg/day) at the diversion using the

modified Domenico equation – for 100 year simulation ................................... 82

Figure 55 Tornado sensitivity chart for the stochastic Domenico analytical assessment for

the 100 year simulation. The output is load to the diversion (in kg/day). ........ 83


modified Domenico equation – for 1000 year simulation ................................. 83

Figure 57 Stochastic output for zinc concentration (in mg/L) at the Barney Creek diversion

using the modified Domenico equation – for 1000 year simulation ................. 84

Figure 58 Schematic of the PHREEQC model construction. At each stage of transport

through the column the water quality is in equilibrium with the aquifer

mineralogy and the surface sorption sites ........................................................ 87

Figure 59 Calibrated model bromide concentrations at different times........................... 88

Figure 60 Predicted sulphate breakthrough curve at an observation point 500 m from the

plume source ..................................................................................................... 89

Figure 61 Predicted concentrations after 20 years for arsenic, cadmium, lead and zinc

compared by varying KD values and the solid substrate (between maximum and

minimum values). Note the logarithmic scale. Bromide, a conservative species

used as a tracer in the models, is included for comparison .............................. 90




used as a tracer in the models, is included for comparison .............................. 91


compared using the minimum KD values, minimum solid substrate and 95th


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percentile NOEF input water quality. Note the logarithmic scale. Bromide, a

conservative species used as a tracer in the models, is included for comparison

........................................................................................................................... 92

Figure 64 PHREEQC modelled 1-dimensional reactive transport concentrations after 1 to

20 years for arsenic, cadmium, lead and zinc. Also shown are the

concentrations of the conservative bromide tracer at these time intervals ..... 93

Figure 65 Geochemist’s Workbench modelled 1-dimensional reactive transport

concentrations after 1 to 20 years for arsenic, cadmium, lead and zinc. Also

shown are the concentrations of the conservative bromide tracer at these time

intervals ............................................................................................................. 94

Figure 66 Modflow SURFACT variation /sensitivity of Kd .................................................. 94

Figure 67 2017 SO4 concentrations (EcoLogical, 2017) ..................................................... 95

Figure 68 2017 Zn concentrations (EcoLogical, 2017) ....................................................... 95

Figure 69 Production profile predicted for life of mine .................................................... 96

Figure 70 Water budget summary for December 2037 stress period ............................... 98

Figure 71 TSF Operations period and first 100 years of closure: baseflow predictions for

Surprise Creek and Barney Creek diversion ....................................................... 99

Figure 72 Long-term closure: baseflow predictions for Surprise Creek and Barney Creek

diversion .......................................................................................................... 100


Barney Creek ................................................................................................... 100

Figure 74 Long-term closure: baseflow predictions for Barney Creek ............................ 101


McArthur River ................................................................................................ 101

Figure 76 Long-term closure: baseflow predictions for McArthur River ......................... 102

Figure 77 Predicted sulphate concentrations in the overburden at the end of mining

(2037), once the pit lake has recovered (2067), 120 years closure (2167) and

1000 years closure (3048) ............................................................................... 103

Figure 78 Predicted sulphate concentrations in the weathered bedrock at the end of

mining (2037), once the pit lake has recovered (2067), 120 years closure (2167)

and 1000 years closure (3048) ........................................................................ 104

Figure 79 Predicted sulphate concentrations in the upper bedrock at the end of mining


1000 years closure (3048) ............................................................................... 105

Figure 80 Predicted zinc concentrations in the overburden at the end of mining (2037),

once the pit lake has recovered (2067), 120 years closure (2167) and 1000

years closure (3048) ........................................................................................ 107

Figure 81 Predicted zinc concentrations in the weathered bedrock at the end of mining


1000 years closure (3048) ............................................................................... 108


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Figure 82 Predicted zinc concentrations in the upper bedrock at the end of mining (2037),

once the pit lake has recovered (2067), 120 years closure (2167) and 1000

years closure (3048) ........................................................................................ 109

Figure 83 TSF Operations period and first 100 years of closure: sulphate load predictions

for Surprise Creek and Barney Creek diversion ............................................... 110

Figure 84 Long-term closure: sulphate load predictions for Surprise Creek and Barney

Creek diversion ................................................................................................ 111


for Barney Creek .............................................................................................. 111

Figure 86 Long-term closure: sulphate load predictions for Barney Creek ..................... 112


for McArthur River .......................................................................................... 112

Figure 88 Long-term closure: sulphate load predictions for McArthur River .................. 113

Figure 89 Comparison of projected loads to Barney Diversion in the first 100 years after

pit rebound ...................................................................................................... 113

Figure 89 Long-term closure: zinc load predictions for Surprise Creek and Barney Creek

diversion .......................................................................................................... 114

Figure 90 Long-term closure: zinc load predictions for McArthur River ......................... 114

Figure 91 Water Production profile predicted for closure and early closure .................. 115

List of Appendices

Appendix I Sensitivity Analysis Results

Appendix II Updated TSF Interception Trench Modelling

Appendix III Options for NOEF Plume Interception


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1 Introduction

Klohn Crippen Berger Ltd (KCB) is pleased to provide this report to McArthur River Mining (MRM)

presenting the results of hydrogeology and geochemical studies undertaken to inform the

Supplementary EIS. This work was undertaken to assess contaminant seepage from various site

sources under current and future conditions, and to assess the predicted effectiveness of

proposed site-wide mine waste and water management strategies. The results of this work have

been provided as input for the broader site water balance and surface water impact assessment

being conducted by other consultants.

1.1 Project Background

McArthur River Mine (MRM) is located approximately 720 km south-east of Darwin in the Gulf

Region of the Northern Territory. Mining operations consist of an open-cut mining operation, ore

processing plant, overburden and tailings storage facilities, supporting logistical infrastructure

and, external to the mine area, the Bing Bong Loading Facility (BBLF). The mine targets a large

deposit of multi-seam zinc-lead-silver ore through the current open cut, and previously through

underground extraction techniques.

An Environmental Impact Statement (EIS) was prepared for the MRM underground operation in

1992. The underground operation commenced in 1994, with the first shipment of concentrate

commencing in mid-1995. Up until 2006, MRM was solely an underground operation producing

around 333,000 dry metric tonnes per annum (dmtpa) of bulk lead-zinc-silver concentrate for

overseas and domestic markets (MRM, 2015). The operation expanded to include an open cut

operation following the completion of the 2005 EIS process for the Phase 2 Project (Phase 2). The

MRM Phase 3 Development Project was later approved by the Northern Territory Government in

2013. The Phase 3 project will sustain the long-term future of MRM through extending the life of

This report should be read in conjunction with MRM Draft EIS Hydrogeology Final Report

(KCB, 2017) which provides the background, supporting data, conceptual models and approach to

modelling of the site during operations and closure. In addition, further modelling of the NOEF

using the Tough2 multi-phase modelling software that models both fluid and heat flow for various

states of saturation and accounts for the movement of gaseous and liquid phases, their transport

of latent and sensible heat, and phase transitions between liquid and vapor has been used to

provide an update of flows for a variety of final covers. Tough2 daily water balance results have

been directly linked to GoldSim (supported by PHREEQC and Geochemists Workbench) to

simulate geochemical reactions, loading and the resultant flows and loads of dissolved

contaminants to surface water (toe seeps) and groundwater over the life of mine and closure.

Mine Pit Lake water quality simulations have been updated to account for the proposed final pit

closure arrangement; this includes in-pit placement of the tailings, collection and transfer of NOEF

surface flows after placement, accelerated filling of the pit to submerge mine waste and tailings

placed in the pit, the reactive pit wall materials and consideration of a surface water flows into

and out of the mine pit lake. The potential hydrodynamic changes from these flows have been

included in the Mine Pit Lake water quality assessments to account for the stratification and water

quality changes.

A map of the site location and general infrastructure arrangement is provided in Figure 1.


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Figure 1 Site Location and General Arrangement

GLYDE

RIVER

EMU CREEK

MCARTHURRIVER

BU

LL

CR

EEK

BARNEY C REEK

LITTLE BARNEY CREEK

SURPRI SE CREEK

CARPENTAR

IA H

IGHW

AY

612,000 614,000 616,000 618,000 620,000 622,000

8,1

82

,00

08,1

84

,00

08,1

86

,00

0

0 0.25 0.5 0.75 1

km

PROJECTION1. Horizontal Datum: GDA942. Grid Zone: 533. Vertical Datum: Mean Sea Level

4. Scale: 1:50,000

NOTES:

1. Mine layout as of 2015.

2. Background image: July_2015_MGA53.ecw

3. Surface Water and Road features are based

on published 1:250,000 data that has been

adapted to the background image.

Legend

River/Creek

Diversion

Principal Road

Minor Road

Track

NOEF

Open Cut

TSF

Barney Creek Diversion

McArthur River Diversion

McARTHUR RIVER

MINE

NORTHERN

TERRITORY

QU

EE

NS

LA

ND

WE

ST

ER

N

AU

ST

RA

LIA

KATHERINE

BORROLOOLA

DARWIN

Little Barney Creek Drain

WOEF

SOEF


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1.2 Scope of Work

This project was undertaken to support the Supplementary EIS, and provides MRM with an

estimate of existing and potential groundwater impacts as a consequence of historical and

planned mining operations. To achieve this, the existing site-wide numerical groundwater model

for the MRM site was modified using data and information obtained since the first submission,

this allowed for an updated and recalibrated, and modified from the original Draft EIS submission.

The update of the site-wide groundwater numerical model was based on a revised conceptual

interpretation of the hydrogeological setting of the site. Specific scope items to support the Draft

Supplementary EIS submission included:

1. Further groundwater modelling to address the changes to the project, including the

updated results from the Tough2/GoldSim modelling, provision of further data on metal

attenuation and to address comments raised within the review process of the EIS.

2. Undertaking Tough2 modelling to provide a dynamic water balance and water quality from

the NOEF over life of mine and closure for a variety of scenarios.

3. Undertaking further GoldSim water quality modelling to model water quality from the

NOEF over the life of mine and closure for a variety of scenarios.

4. Undertaking further mine pit lake water quality modelling to provide water qualities

associated with the proposed Mine Pit Lake closure scenario.

1.3 Structure of the report

The report is subdivided into sections as follows:

1. A brief overview of the site;

2. A summary of the updates and changes to the numerical groundwater model;

3. Results of the updated groundwater model;

4. A summary of results, sensitivities and proposed additions to the monitoring and

management plans previously provided in the 2017 Draft EIS submission.

1.4 Project changes since the Draft EIS

The Project changes since the Draft EIS include (Glencore, 2017):

� Open cut domain:

� Incorporation of greater flexibility in the final void closure process and provision of

further clarity on the decision-making process.

� NOEF domain:

� Substitution of the proposed Compacted Clay Layer (CCL) within the NOEF cover

system with a geo-synthetic liner (GSL) for improved performance and greater

consistency;

� Adjustment of the upper NOEF batter slope from a 1V:2.5H slope to a 1V:3H slope to

provide a greater geotechnical factor of safety;

� Optimisation of the NOEF cover system above the GSL to address revised cover system

construction and performance requirements;


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� Optimisation of the NOEF basal CCL thickness to 250mm rather than 500mm based on

improved performance achieved by GSL in the cover system;

� Minor modification of stockpile/ borrow locations to the north of the NOEF;

� Minor modification to the NOEF south eastern boundary to facilitate water

management system infrastructure.

� TSF domain:

� Reconfiguration of the Cell 3 Water Management Dam (WMD) and Process Water Dam

(PWD), essentially swapping their previously proposed locations;

� Incorporation of a HPDE liner to the base of the Cell 3 WMD;

These changes have all been taken into account in this report on site groundwater.

1.5 Integration of multiple models

The water environment at MRM is complex and requires consideration of a variety of sources and

flow types. To provide robust simulations of these interactions during mine life and closure

requires a variety of specialist models to be used conjunctively to provide sufficient detail so that

the changes conditions over time can assessed. The sequence of models is needed to cover the

variety of spatial and temporal domains as well as the physico-chemical processes that cannot be

simulated in sufficient detail by any single modelling code. Since there is interaction and transfers

between these models, the models were linked by using common input data and interactively

using the results from one set of models (for example the groundwater model feeding into the

surface water, waterways model) and allowing feedback between models to occur.

A series of individual models were constructed to address the specific issues within a holistic

watershed and mine site framework (See Figure 2) in a similar manner to approaches followed by

other complex mine sites; see Vandenberg et al, 2016 as an example). The project has used

detailed unsaturated flow modelling in a variable temperature for the NOEF (Tough2) to link to

water quality models (GoldSim/PHREEQC simulations of the daily water quality changes) and to

the groundwater model (Modflow SURFACT). The groundwater modelling results, in terms of base

flow and loads, leaving the system have been integrated into the surface water flow and

contaminant transport model (with consideration of bank storage), which then have provided

flows and contaminant loads to the hydrodynamic modeling and final void water quality models.

For numerical stability, hydrodynamic models require timesteps of seconds at key periods but the

longer-term stratification trends provide important information for the final void water quality

modelling. Through this approach, sufficient detail is provided by a model that is specifically

constructed and well-suited for each aspect of the water system, in a manner that is consistent

across the disciplines required to inform the Supplementary EIS and that allows the various

interactions to be considered.


Supplementary EIS

Site Groundwater

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Page 5


Figure 2 Schematic of model interactions used for the assessment


Supplementary EIS

Site Groundwater

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Page 6


Table 1-1 Summary of interactions between models

Domain Aim Code Detailed

Report Outputs

Results provided

to Model(s) Input from

Site

wide

Site groundwater

and contaminant

transport (life of

mine and closure)

Modflow

Surfact

KCB

Groundwater

Draft EIS,

2017, KCB

Groundwater,

2017 Supp EIS

Groundwater heads; pit

inflow; base flow;

concentrations; loads

WRM Surface

Water

Waterways; Final

Void

Common

climate data;

NOEF model

Site surface water

and contaminant

transport (life of

mine and closure)

GoldSim

WRM, Surface

Water

Waterways

Model, WRM

Surface

Water, 2017

Supp EIS

Flows, concentrations and

loads for dissolved and

suspended parameters

Final void water

quality model;

Hydrodynamic

model for mine

pit lake

Site

groundwater

model; Final

void water

quality model

TSF

TSF Design and

Seepage Mitigation

Design

Modflow

Surfact

KCB

Groundwater

Draft EIS -

Appendix I,

2017, KCB

Groundwater,

2017 Supp EIS

- Appendix I

Groundwater heads; pit

inflow; base flow;

concentrations; loads

Site -wide

groundwater

model; Surface

Water

Waterways

GHD Life of

Mine Design;

common client

data; common

grid alignment

and

hydrogeological

properties as

site

groundwater

model


Supplementary EIS

Site Groundwater

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Page 7


NOEF

Unsaturated flow as

a function of

covers, heat and

NOEF expansion

Tough2

KCB, 2017

Supp EIS -

NOEF model

Daily net infiltration and

dynamic water balance

NOEF WQ Model;

Site Groundwater

Model;

Waterways

Model

Common

hydrogeology

as site

groundwater

model for

underlying

aquifer

Dynamic water

quality as a function

of geochemistry,

NOEF expansion

and water balance

GoldSim

(with

PHREEQC

and GWB for

external

checks and

input)

KCB, 2017

Supp EIS -

NOEF model

Complete water quality

over time; flows and loads

to toe seep and

groundwater

Site Groundwater

Model;

Waterways

Model

Tough2

Final

Void

Water quality in

mine pit lake after

closure (1,000

years)

GoldSim

(with

PHREEQC

and GWB for

external

checks and

input)

KCB, 2017

Supp EIS -

Final void

water quality

Water quality and loads

(flows consistent with

waterways model)

Site Groundwater

Model;

Waterways

Model

TWS

Hydrodynamic

Model;

Site

Groundwater

Model;

Waterways

Model


Supplementary EIS

Site Groundwater

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Page 8


Establish water and

energy balance for

varying pit flow

scenarios and

determine

stratification/mixing

AEM3D

TWS, 2017

Supp EIS -

Hydrodynamic

Model

Mixing depths and

stratification over time

Mine pit lake

Water Quality

Model

Waterways

Model


Supplementary EIS

Site Groundwater

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Page 9


2 UPDATED GROUNDWATER MODEL

2.1 Groundwater model setting

The groundwater model objectives for the Supplementary EIS remain unchanged from the Draft

EIS (KCB,2017; MRM, 2017):

� Assess changes to site-wide groundwater flow patterns due to seepage from mine

infrastructure including the OEFs, water management dams and the TSF.

� Assess the rate of groundwater seepage and fate of contaminants of concern

(sulphate, zinc, arsenic, cadmium and lead) released from mine sources relative to

sensitive receptors.

� Predict baseflow to site-wide creeks and rivers during current conditions, life of mine

and closure.

� Predict load to site-wide creeks and rivers during current conditions, life of mine and

closure.

� Assess the influence of open cut dewatering and closure mine pit lake filling.

2.2 Model Code

MODFLOW-SURFACT Version 4.0 (HydroGeoLogic, 2016) was again used as the model code to

simulate groundwater flow at the MRM site. The MODFLOW-SURFACT code is based on the

modular groundwater flow code MODFLOW, and contains robust methods and simulation

capabilities to handle complex variably saturated flow and transport processes using the pseudo-

soil function.

2.3 Model Lateral Extents

The model domain is unchanged and extends 12.0 km west-to-east and 10.95 km south-to-north

(Figure 3) and covers an active area of 100,214,630 m2 (100 km2). The model is based on a 50 x 50

metre grid with 240 columns and 219 rows across 14 model layers. The model has 563,346 active

model cells.


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Page 10


Figure 3 MODFLOW SURFACT model area showing active and inactive cells.

MCARTHUR

RIVER

LITTLE BARNEYCR

EEK

EMU CR

E

EK

GLY

DE

R IVER

BU

LLC

RE

EK

BARNEY CR EEK

SURPR ISEC

REEK

612,000 614,000 616,000 618,000 620,000 622,000 624,0008,1

76

,000

8,1

78

,000

8,1

80

,000

8,1

82

,000

8,1

84

,000

8,1

86

,000

8,1

88

,000

8,1

90

,000

0 0.5 1 1.5 2

km

Legend

River/Creek

Diversion

Active Cell

Inactive Cell

NOTES:

1. Background image: McArthur River Mine Merge 50cm.ecw

2. Surface Water and Road features are based on published data that have been adapted from the

background image.3. Mine infrastructure courtesy of MRM.

PROJECTION1. Horizontal Datum: GDA94

2. Grid Zone: 533. Vertical Datum: Mean Sea Level4. Scale: 1:80,000


Supplementary EIS

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Page 11


Major mine operational areas and other natural features of importance represented in the model

are:

� The underground workings

� The LOM open cut

� The Tailings Storage Facility (TSF)

� The NOEF

� All water management dams with leakage rates of greater than 1 L/s

� Emu, Donkey and MIMEX production borefields

� Djirrinmini water hole

� The McArthur River palaeochannel

� McArthur River and diversion

� Ephemeral creeks including Barney Creek and diversion, Surprise Creek, Emu Creek,

Bull Creek, and Glyde River.

2.4 Units and Datum

The time unit for the model is days and the length unit is metres. The horizontal datum for the

project is GDA94 and the projection is MGA Zone 53. The vertical datum is the Australian Height

Datum (AHD) in metres.

2.5 Updated Geology and Hydrogeology

2.5.1 Geological Review of MRM 2016

MRM undertook a project in 2016 to further define the geology and structure of the greater

mining region. Previously the focus was within the mine area and HYC deposit only; however, to

support MRM’s Draft EIS and Supplementary EIS and subsequent future models, it was important

to delineate geological structure and lithology. The principal objective of the 2016/17 geological

and geophysical review was to examine historical data and information culminating in the

construction of a 3D geological interpreted model. This review utilised the following data types;

� Geophysical surveys, in particular airborne QESTEM and magnetics, and ground

MIMDAS and seismic surveys.

� Exploration drill logs and core photographs – located at the Mt Isa exploration office.

� Underground drilling and geological mapping.

� Reports and previous studies including Golder Associates and BFP.

The geological update was also focussed on determining geological features which could impact

groundwater flows and further assist with MRM’s hydrogeological characterisation (MRM, 2017).

After review by Glencore it was concluded that most lithological interpretations were reasonable,


Supplementary EIS

Site Groundwater

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Page 12


however some gaps in the understanding of the structural geology framework on site warranted

investigation.

The review (Logan 2017) addressed the large scale structural framework and the nature of the

faults comprising the framework. The review highlighted six dominant structural features (Figure

4) with the potential to impact on groundwater movement.

� The Emu Fault is the major regional fault in the McArthur area. It is characterised by horst

blocks of Masterton Sandstone, displaced upwards from the base of the McArthur Group.

Seismic data suggest the fault comprises several near vertical faults, is about 150 metres

wide, is deeply weathered, has a low density and is porous with respect to the surrounding

rocks (Golder Associates, 2004). The Emu Fault contact has not been characterised in as

much detail as other structures in terms of groundwater hydraulics, and future works are

planned to drill and investigate the lateral and vertical hydraulic gradients on this contact.

Currently, the available data suggests that the Emu Fault system is a flow barrier across the

fault which is likely to have an enhanced high lateral flow component (MRM, 2017).

� The Western Fault is a series of north-south trending thrusts which dip steeply towards the

east. It abuts the Cooley Dolomite with the HYC Pyritic Shale, the latter host to the bedded

lead and zinc mineralisation. The Cooley Dolomite comprises the Western Fault Block,

which is bounded on the west by the Western Fault and on the east by the Emu Fault.

Previous drilling programs have indicated that the Western Fault, within MRMs levee wall,

has low hydraulic permeability.

� The Western Fault is coincident with the “Cooley Breccia”, interpreted to be a tectonic

breccia formed along the reverse fault planes. The breccia matrix has been interpreted to

be a sedimentary chemical precipitate rather than true matrix sediment. The Cooley

Breccia texture has primarily been re-healed by carbonates and has low hydraulic

conductivity and permeability.

� The Barney Trend is a dominant east-west trending fault corridor which dislocates the

Western Fault, but probably not the Emu Fault. It is interpreted to comprise a series of

north side down steps. Cooley style brecciation and alteration, and lead and zinc

mineralisation occur along the corridor in outcrop and drill hole. The 2016 ERI data

suggest that the faults are conductive, inferring they are porous and/or permeable

(MRM, 2017). The corridor passes beneath the TSF and NOEF.

� Exposures of the Woyzbun Fault in the open cut, underground mine, and drill hole

intersections show a narrow tight fault with minimal gouge or infill. This normal fault,

which dips between 75° to 85° to the south-east, has a throw of approximately 100m, with

the south block down (Logan, 2017).

� Whelans Fault trends north-south with an east side down sense of movement. It is at a

high angle to bedding in the southern wall of the open pit, but appears to be migrate into

the bedding planes of the steeply dipping clay beds of the Teena and WFold Shale in the

northern end of the open pit (Logan, 2017).

� The Woyzbun parallel faults have been identified in several of the historical geophysical

data sets examined in 2017 geological review. Further work is required to confirm their

geometry and significance.


Supplementary EIS

Site Groundwater

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Page 13


Figure 4 Structural framework of the greater mining region, McArthur River (Logan, 2017)

Electrical Resistivity Imaging

GHD completed 24 lines of Electrical Resistivity Imaging (ERI) in the vicinity of the TSF and NOEF,

delineating near surface resistive and conductive domains (Figure 5). The conductive domains are

interpreted to be largely related to permeability induced by the Barney Trend Fault Corridor (GHD,

2016). A selection of conductive features were used by MRM to guide areas of potential drilling

and field testing.


Supplementary EIS

Site Groundwater

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Page 14


Figure 5 ERI traverses (GHD 2016, from Logan, 2017)

An example of the ERI results near the inferred Western Fault is shown on Figure 6.

Figure 6 ERI traverses along the Barney Diversion (Logan, 2017 based on GHD, 2016)

Reinterpretation of 2004 Hummingbird airborne magnetic survey

The 2004 Hummingbird airborne magnetic survey was flown over the open cut, NOEF and TSF to

map the electrical resistivity response of the near surface (effective to less than 80 metres). It was

recognised there were processing issues with the original inversion model, indicated by phase and

amplitude errors (Logan, 2017). As part of the review and to assist with shallow highly conductive

features (e.g. sulphides and water) the data were reprocessed. The reprocessing is still to be fully

interpreted, but early results indicate that some of the known faults are electrically conductive


Supplementary EIS

Site Groundwater

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Page 15


and will assist with further refinement of lithology, structure and other shallow anomalies like the

MRM palaeochannel.

2016 and 2017 Drilling and Field Campaigns

Utilising the ERI and geological reinterpretation described above, MRM undertook a

hydrogeological field campaign in latter part of 2016 to acquire data and information to support

the ongoing hydrogeological conceptualisation for the site. The conceptualisation underpins the

groundwater components of the Environmental Impact Statement (EIS) and the Tailings Storage

Facility (TSF) Seepage Mitigation Project. The campaign comprised drilling, downhole hydraulic

testing (Lugeon, yield and falling head tests) and installation of additional monitoring instruments

(standpipe piezometers and vibrating wire piezometers).

The program objectives of the field campaign outlined in MRM (2016), include:

� Identify zones of relatively elevated hydraulic conductivity representing potential

conduits for groundwater flow and seepage migration from the TSF and NOEF;

� Characterise vertical hydraulic gradients between permeable zones and under/over‐

lying units;

� Quantify hydraulic parameters (particularly aquifer storage);

� Identify potential hydrogeological boundaries (e.g. faults and creeks); and

� Field work concentrated on both the TSF and the NOEF.

There were 37 drill holes completed in 2016 for a total of 1743 metres. Twelve reverse circulation

drill holes into the Reward Dolomite, to a depth of 40 metres, were assayed for 33 elements.

Assays confirmed that the Reward Dolomite generally contains low levels of base metals. The

exception is close to the Barney Trend Fault Corridor, near the southeast corner of the TSF, where

values up to 0.51% zinc and 0.28% lead were intersected over 5 metres. Hydrogeological

characterisation is ongoing with further holes drilled for both characterisation and monitoring.

Eight newly installed, paired, groundwater monitoring bores were also drilled in 2016/17 (GW156

S/D, GW157 S/D, GW158 S/D and GW159 S/D – two bores per site), installed within the alluvial

and bedrock aquifers at the mine.

Figure 7 and Figure 8 shows areas of drilling compared to the ERI survey.


Supplementary EIS

Site Groundwater

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Page 16


Figure 7 ERI and location of the 2016 drill holes (MRM,2017)

Figure 8 ERI traverse Line 1 and drill holes completed in 2016 (MRM, 2017)


Supplementary EIS

Site Groundwater

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Page 17


Updated 3D Geological Model

Glencore compiled a 3D geological model (using Leapfrog Geo 4.0) for the MRM lease area, for

inclusion in future EIS models and assist with future drilling targets. The model integrated varied

data types such as drill hole information, surface mapping, interpreted cross sections and

processed geophysical data, generated by the 2016 geological review. The extended HYC model

covers an area approximately 19km EW x 15km NW, and extends to a vertical depth of 1.7km.

Due to the level of detail available for modelling, the confidence level of the geological output is

understandably highly variable. Therefore, a 25m x 25m x 25m block model was also constructed

in Leapfrog/GEMS to integrate the confidence levels provided by the various data sources

(Glencore, 2017). MRM is using this model to assist in the conceptualisation as it can be

interrogated to determine the confidence relative to the accuracy and precision of the geological

interpretation at a given location.

The lithology and structure used to build this model, was used to support the Supplementary EIS

groundwater modelling by KCB and at that time was considered our best approximation of the

geological settings at MRM (MRM, 2017).

Based on the updated geological understanding, the Bald Hill fault zone was extended to include

two parallel faults, about 700 m apart, oriented around 800 NE towards EMU faults, running

through the footprint of TSF and NOEF.


Supplementary EIS

Site Groundwater

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Page 18


(a) Layer 5 in 2016 model

(b) Layer 5 in 2017 model

(c) Layer 6-7 in 2016 model

(d) Layer 6-7 in 2017 model

(e) Layer 8 in 2016 model (f) Layer 8 in 2017 model

Figure 9 Update of Model Layers 5- 8


Supplementary EIS

Site Groundwater

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Page 19


2.6 Natural Mineralisation at McArthur River Mine

In the Draft EIS, KCB included a short discussion on potential mineralised zones (KCB, 2017). To

further support the observations of areas on the site where groundwater quality has naturally

elevated concentrations, the Draft EIS section is included in this report and supported by further

information provided by the detailed review of the available geological information commissioned

by MRM (Logan, 2017).

2.6.1 Mineralised zones

The MRM deposit was discovered in the 1950s and originally named ‘Here’s Your Chance’ (HYC).

Mineralisation in the area of the mine covers approximately 2 km2. The HYC deposit is comprised

of eight discrete zinc and lead sulphide-rich siltstone horizons largely associated with the presence

of the HYC Pyritic Shale. The total thickness of the mineralised package is around 55 metres and

varies in depth from 0 to 400 metres below the surface. The bedding strike is approximately

north-south and the mineralised beds thin towards the north as waste inter-beds thicken.

The complete extent of the HYC Pyritic Shale extends beyond the proposed open cut extent, and

the potential for this system to affect hydrogeology needs to be considered further. In the area

east of the mine bounded by the McArthur River Diversion in the south, and the Barney Creek

Diversion in the north, lies a zone of several potential natural sources of sulphate (Figure 11).

Within this area are:

� Previously interpreted subcrop of the HYC Pyritic Shale, which also strikes across the

HYC Orebody and current mine.

� A number of satellite sulphide deposits and hence potential sources of sulphate. These

include Cooley I and II, and Ridge I & II. A review of pre-mining soil geochemistry has

indicated a correlation between higher zones of Copper, Lead and Zinc and the

occurrences of these satellite deposits. Measured sulphate concentrations in

groundwater are also high (in excess of 2,000 mg/L) in these areas occupied by the

satellite deposits.

� The alignment of the McArthur River Diversion east of 618,500 is superimposed on

what appears to be the original alignment of Bull Creek. Upstream, Bull Creek strikes

parallel to the interpreted subcrop of the HYC Pyritic Shale.


Supplementary EIS

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Page 20


Figure 10 Interpreted features across the site (KCB – Draft EIS, 2017)

SU

R

PRISEC

RE

EK

MCARTHURRIVER

LITTLE BARNEYC

REE

K

GLY

DE

RIVER

EMUCRE

EK

BULL

CR

EE

K

BARNEY CREEK

BUF

FAL O

CREEK

Qa

-Pmnh

-Pmnh

Cz

Cz

-Clb

-Clb

-Clb

-Clb

-Clb

-Clb

-Prr

-Pmnc

-Prah

-Prah-Pmnh

Qa

Qa

Cz

-Pmx

-Clb-Prr

-Pmnh

-Pmx

-Pmnc-Pmnc

Qa

Qa

-Clb

-Pmnc

-Pmx

-Pru

-Pmx

Kl-Pri

-Pte -Pmo

-Pms-Pmr

-Pmx

-Pmq

-Pmx -Pmnh-Pmq

-Pmr-Pmnh

-Pmq

-Pmp-Pmq

-Pmt

-Pme,-Pmp,-Pmq-Pmnc

-Pmnh

-Pmp -PmpCz

-Pmx

-Pms

-Pmq

-Pmt,-Pmf,-Pmea

-Pri

-Pmnc

-Pmea

-Pnz

-Pmea

-Pmea

-Pms

-Pmt-Pma

-Pmea-Pmea

-Pmt-Pmea -Pri

Mt B

utle

r F

au

lt

Bar

ney

Hill F

ault

Surp

rise F

ault

North Bald Hills FaultBald Hills Fault

Wh

ela

n F

au

lt

Weste

rn F

ault

Woyzbun Fault

CA

RP

EN

TA

RIA

H

IGH

WA

Y

610,000 612,000 614,000 616,000 618,000 620,000 622,000 624,000 626,000

8,1

80

,00

08,1

82

,00

08,1

84

,00

08,1

86

,00

08,1

88

,00

0

0 0.5 1 1.5 2

km

Legend

River/Creek

Diversion

Principal Road

Tailings Facility

NOEF - 2015

Open Cut - 2015


2. Grid Zone: 533. Vertical Datum: Mean Sea Level

4. Scale: 1:75,000

NOTES:

1. Geology: Bauhinia Downs 1:250,000

published geology map.

2. Faults supplied by MRM Geology.




Geology

Fault

Formation, Map Symbol

Cenozoic materials, Qa

Cenozoic materials, Cz

Mesozoic materials, Kl

Bukalara Sandstone, -Clb

Abner Sandstone, -Prah

Crawford Formation, -Prr

Mainoru Formation, -Pru

Limmen Sandstone, -Pri

Balbirini Dolomite, -Pnz

Looking Glass Formation, -Pmo

Stretton Sandstone, -Pmr

Lynott Formation, -Pmnc

Lynott Formation, -Pmnh

Reward Dolomite, -Pmx

Barney Creek Formation, -Pmq

Teena Dolomite, -Pmp

Emmerugga Dolomite, -Pme,-Pmp,-Pmq

Emmerugga Dolomite, -Pmea

Tooganinie Formation, -Pmt,-Pmf,-Pmea

Tooganinie Formation, -Pmt

Amelia Dolomite, -Pma

Masterton Sandstone, -Pms

Settlement Creek Doleri, -Pte


Supplementary EIS Site Groundwater

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Page 21


The hydraulic effect of the McArthur River Diversion, which (along its alignment) has lowered

shallow groundwater to its base (estimated ~15m below ground), is also an important factor to

consider. This has created localised zones of lowered groundwater conditions which, when

aligned with satellite orebodies or sulphide rich subcrop, results in oxidation of previously

saturated geology.

Figure 11 Distribution of the Interpreted HYC Pyritic Shale (after Williams, 1978), location

of other mapped mineralisation, and 2016 sulphate levels in groundwater

In the regional context, Figure 12 provides site wide representation of the extent of the HYC

Pyritic Shale after Williams (1978). The unit extends across the site as far west (and beyond) the

TSF.


Supplementary EIS

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Page 22


Figure 12 Regional Extent of the HYC Pyritic Shale (after Williams, 1978)

CA

RP

EN

TA

RIA

HIG

HW

AY

EMU CREEK

GLYDE

RIVER

MCARTHURRIVER

LITTLE BARNEYC

RE

EK

BARNEY CREEK

S URPRISE CREEK

612,000 614,000 616,000 618,000 620,000 622,000

8,1

82

,00

08,1

84

,00

08,1

86

,00

0

0 0.25 0.5 0.75 1

km



NOTES:

1. Background image: July_2015_MGA53.ecw2. Surface Water and Road features are based

on published 1:250,000 data that has been adapted to the background image.

Legend

River/Creek

Diversion

Principal Road

Minor Road

Track

HYC Ore Body

Pyritic Shale Extent

NOEF

Open Cut

TSF

Barney Creek Diversion

McArthur River Diversion

Little Barney Creek Drain

Cooley II

Cooley II

Ridge II

Ridge I

H.Y.C


Supplementary EIS

Site Groundwater

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Page 23


Historical Soil Geochemistry Data

In 2016 MRM commissioned a project to investigate the historical soil, rock and auger sampling

conducted within and adjacent to the current Mineral Lease (Logan, 2016). This large data set

largely pre-dates MRM mining activities. While these samples cover a large area, varying methods

of analysis and temporal spread are present.

The available soil geochemistry data indicates that sulphate-generating metals in shallow soil,

rivers and outcrop existed pre-mining. At least eight occurrences of lead and zinc mineralisation

were known in the McArthur River region, prior to Mount Isa Mines’ arrival in 1955 (Murray,

1954). Within McArthur River Mining’s mineral leases outcropping sulphide and secondary lead

and zinc mineralisation is documented from the Bulburra, Barney Hill and Cooley Lead prospects.

These were actively eroding and contributing lead and zinc into the soil and stream profiles.

At Bulburra the principle mineralised outcrop formed a 6 metre high hill covering an estimated

area of 5,570 square metres. Outcropping mineralisation comprises galena, sphalerite, cerussite,

smithsonite and hydrozincite with minor pyrite (Murray, 1954; Beresford, 1957). There were

small pits at the prospect and it was drilled during 1952 (Beresford, 1957).

Murray (1954) documents “slugs” of galena occurring in Barney Creek (near the Barney and

Surprise Creek junction), and indicates the prospect was drilled in 1912. A second area of

outcropping galena is documented in Bull Creek, which could be the Cooley I Lead Prospect.

Between 1955 and 1963 Mount Isa Mines and the Bureau of Mineral Resources (now Geoscience

Australia) completed semi-qualitative stream, soil and bedrock sampling within an east-west strip

across the mineral leases, extending from the Emu Fault to west of the mineral leases. The

sampling identified lead and zinc anomalies at the known prospects and discovered areas of

previously unknown mineralisation at W-Fold, Teena and Reward prospects.

Mount Isa Mines completed stream sediment surveys across the mineral leases in 1969, 1981 and

1988 (Figures 13 and 14). The samples were assayed for lead, zinc and copper. Anomalous lead

and zinc, and elevated copper occur along the Barney Trend, specifically in streams draining

Barney Hill, WFold prospect and the southern side of the TSF.


Supplementary EIS

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Page 24


Figure 13 Historical Stream Samples for site (Pb data 1969 to 1988)

Figure 14 Historical Stream Samples for site (Zn data 1969 to 1988)


Supplementary EIS

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Page 25


Soil sampling completed between 1969 and 1994 is biased towards out-cropping and sub-

cropping dolomitic rocks, as earlier sampling had demonstrated that sampling across transported

overburden was not effective. Samples were assayed for lead and zinc and some also for copper.

Lead and zinc soil assays define anomalies near outcropping mineralised dolomites at the Bulburra

and Barney Hill prospects, and over the mineralised shale at the WFold and Wickens Hill prospects

(Figures15 and 16. Assay results from soil across the Bulburra prospect peak at 4.5% lead and

7.5% zinc.

Figure 15 Historical Soil Geochemical Samples for site (Pb data 1969 to 1994)


Supplementary EIS

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Page 26


Figure 16 Historical Soil Geochemical Samples for site (Zn data 1969 to 1994)

2.7 Expected Behaviour of Groundwater

This section is largely unchanged from the Draft EIS submission, with minor changes included to

reflect the slight changes to site knowledge from the 2016 and 2017 geological and

hydrogeological programs completed by MRM.

This section describes the expected behaviour of groundwater across the site for various stages of

the mine life and for closure. The expected behaviour is based on current knowledge of

groundwater flow processes including the site-wide water balance and groundwater – surface

water interactions, and a forecast of how mining infrastructure will alter the groundwater flow

regime. This section is intended to provide a reference point from which to compare model

simulation results, and to gauge the reasonableness of the numerical predictions.

2.7.1 Life of Mine

2.7.1.1 Groundwater Flow Characteristics

The mine plan will alter the groundwater flow regime across the site. Mining of the open cut up to

2023 will be mainly contained within the Barney Creek Formation, a low permeability bedrock

formation with limited permeability associated with faulting and fracture corridors. It is expected

that during this time, pit inflows from the surrounding aquifer units will be similar to current rates

(1 to 5 ML/day), with a majority of flow coming from the McArthur River palaeochannel and minor

contributions coming from fractured bedrock (some fracturing may be associated with the

Woyzbun and Whelan Fault networks). Drawdown caused by pit dewatering will be steep in the

Barney Creek Formation and is not expected to propagate great distances laterally within this rock

unit. Groundwater flow will therefore be diverted locally within 1-2 km of the open cut, varying

spatially as a function of the geology and hydrology. NOEF expansion will lead to a greater surface


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area of rainfall interception and seepage through the dump is expected to rise during the mine life

until the GSL cover is in place. This seepage may cause localised mounding within the shallow

aquifer beneath the foundation and therefore increase velocity vectors away from the facility in

the period prior to cover placement. The installation of the cover system on the NOEF will lead to

a reduction in infiltration into the NOEF. Lining of the PRODs is expected to reduce seepage from

these water management dams compared to historical seepage occurring at the SPROD.

Therefore, these lined dams should only have localised effects on the hydraulic functioning of the

groundwater flow systems.

Mining post-2023 is expected to have a significant effect on the groundwater flow regime. The

highwall of the open cut is expected to breach the lower permeability units to the west (including

the Western Fault) to allow greater hydraulic connection with the higher permeability Cooley

Dolomite bedrock. Dewatering rates are expected to rise over time, and drawdown of the Cooley

Dolomite is expected to be far more widespread than the lower permeability Barney Creek

Formation. Flows currently reporting to the underground workings are also expected to

contribute to the water balance until the open pit reaches the extent of these workings. Given the

north-south orientation of the Cooley Dolomite, the drawdown pattern is expected to be

elongated in this north-south direction. This will lead to drawdown of the bedrock directly to the

east of the NOEF, and divert groundwater flow down-gradient of the NOEF from west-east to

north-south during this period.

2.7.1.2 Source-Pathway-Receptor Processes

It is expected that seepage from the NOEF will migrate predominantly through two major

pathways during the life of mine: one being the more permeable alluvium to the southeast and

south of the NOEF towards Surprise Creek and Barney Creek diversion; the other being the more

permeable Cooley Dolomite to the east of the NOEF, which will flow south towards Barney Creek

diversion. The open cut breaches the Western Fault and dewaters the Cooley Dolomite, it is

expected that the pressures in the Cooley Dolomite will drop significantly and spread laterally

over significant distances. This may influence the path-length and receptor location for NOEF

seepage migrating through the Cooley Dolomite bedrock, with potential for the pathway to now

extend beyond the Barney Creek diversion and continue south towards the open cut.

There are several source terms present at the NOEF site. The facility itself does and will continue

to produce seepage into the foundation that recharges into the underlying shallow geology. As

the dump footprint increases, the rainfall capture of the NOEF will progressively increase and

seepage rates of poor quality water are expected to increase, until the cover systems are

constructed.

The PRODs are also expected to seep poor quality water into the shallow geology. Historically, it

has been demonstrated that the unlined SPROD has produced significant rates of seepage, with

down-gradient hydraulic head rises and sulphate breakthroughs observed in a number of shallow

and deeper monitoring bores. Lining of the PRODs is expected to limit seepage and reduce the

contribution of these sources around the peripheries of the NOEF.

2.7.2 Pathways

There are a number of known permeable pathways which could promote migration of NOEF

seepage towards nearby receptors; the design of the NOEF has been adapted to take these into


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account and to limit the migration of seepage and contaminants. In the shallow overburden, there

are three former drainage systems which contain more permeable unconsolidated sands and

gravels in an interconnected arrangement such that preferential flowpaths are likely. The three

drainage systems are situated in the northeast, southeast and southern extents of the NOEF. The

shallow weathered bedrock is also likely to promote migration of NOEF seepage. The Cooley

Dolomite bedrock, the Western Fault and the fracture network associated with the Western Fault

are situated to the east of the NOEF and are also potential long-term pathways for seepage

migration. The bedrock aquifer/fracture network can sustain a number of production bores and

which confirms aquifer permeability and interconnectivity.

Based on WRM’s water budget analysis, seepage from the historical SPROD has been at rates in

exceedance of 20 L/s, and this seepage will have created localised mounding of the water table in

the shallow hydrostratigraphic units below the dam. This elevated water table will create higher

hydraulic gradients down-gradient of the facility and therefore increase velocity of groundwater

away from the dam. The regional groundwater flow system is generally west to east, with some

localised movement southwards from SPROD towards Barney Creek diversion (this divergence of

flow is likely related to both the influence of the diversion as a discharge feature as well as the

influence of the pit dewatering directly to the south). It is expected that the predominance of

seepage will flow to the east of SPROD (under natural gradients) and to the southeast towards

Barney Creek diversion. Flows from the SPROD to groundwater are expected to decrease over the

immediate to long-term once SPROD is lined with HDPE.

2.7.3 Receptors

The primary receptors for NOEF seepage are Surprise Creek to the southwest of the facility and

Barney Creek diversion to the south and southwest of the facility. These two creeks represent the

lowest points in the topography surrounding the NOEF and existing hydraulic gradients orient

pathlines towards these surface water features. Groundwater levels to the northeast of the NOEF

are up to 5m lower than the topography along Emu Creek to the east. This indicates that

groundwater is not likely discharging as baseflow to the east where Emu Creek trends along the

Bukalara Plateau, but would likely pass underneath Emu creek and flow to the south towards the

McArthur River. The conceptual model indicates that groundwater within the Cooley Dolomite is

currently discharging to the Emu borefield and further south to the Barney Creek diversion. As

mining progresses, dewatering and development of drawdown in the south of the site, will further

promote flow to the south towards these creeks. If significant mounding where to occur in the

northeast, then hydraulic connection may be established. However, given the high permeability of

the Cooley Dolomite aquifer it is highly unlikely that significant mounding in this aquifer will occur.

2.7.3.1 Groundwater – Surface Water Interactions

Natural Inflows

Natural inflows through wet season rainfall recharge and river recharge are expected to be

maintained throughout the life of mine.

Mine-derived Inflows

Seepage to groundwater from the TSF and NOEF are predicted to increase during the life of mine

(OKC, 2016; KCB, 2017) adding impacted water into the groundwater system. Mitigation


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measures in the form of low permeability covers and an engineered lower permeability base for

the NOEF as well as seepage interception between the TSF and Surprise Creek will reduce the

flows and contaminant loads from these facilities during operations.

Groundwater Outflows

It is expected that the groundwater outflow budget will transition during the life of mine.

Evapotranspiration and surface water baseflow discharge will dominate prior to 2023. Post-2023

pit dewatering rates are expected to increase, and the drawdown will lead to changes in pressure

relationships below Barney Creek diversion and McArthur River diversion. This may act to reduce

surface water – groundwater interactions during this period, and therefore lead to a decrease in

baseflow discharge at the Barney Creek diversion and McArthur River diversion. A lowering of the

groundwater table in the east of the site may also lead to a minor reduction in evapotranspiration

losses. Groundwater exiting the site will continue to occur through the McArthur River channel

down-gradient of the site as well as underlying alluvium, weathered bedrock and bedrock in close

proximity to the channel. However, the relative proportion will be diminished post-2023 as pit

dewatering will dominate groundwater outflow.

2.7.4 End of Operations


The proposed GSL cover system established on the completed stages of the NOEF will greatly

reduce foundation seepage from the facility during the closure period (see KCB, 2017 NOEF

Modelling) and therefore result in less seepage to the groundwater system compared to the

operations period. Partial filling of the open cut with tailings and then filling of the remaining void

with surface water will reverse the open cut dynamics from a major sink, depending on the level

to which the pit is managed and the pit closure scenario. The regional drawdown will equilibrate

back to a new equilibrium post-mining more rapidly owing to the dynamic infilling of the mine pit

lake. There will be a return to site-wide west to east groundwater flow processes, with some

potential for short duration flow-through from the mine pit lake to down-gradient aquifers to the

east of the mine void. With pit dewatering no longer dominating the water budget, there is

expected to be a return to the pre-mining conditions.


It is expected that seepage from the NOEF will continue to migrate predominantly through two

major pathways during the closure period: one being the more permeable alluvium to the

southeast and south of the NOEF towards Surprise Creek and Barney Creek diversion; the other

being the more permeable Cooley Dolomite to the east of the NOEF, which will flow south

towards Barney Creek diversion. It is expected that drawdown in the Cooley Dolomite will recover

over a period of decades owing to rainfall recharge. As the Cooley Dolomite recovers, it is

expected that a hydraulic connection between the Cooley Dolomite and the Barney Creek

diversion will be re-established. When this hydraulic connection is established, the seepage

pathway from the NOEF will become shorter and Barney Creek diversion will again become the

primary receptor for down-gradient NOEF seepage.


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2.7.5 Closure- Long-term


Long-term performance of the cover system on the NOEF will limit seepage to the groundwater

system and allow the regional west-east groundwater flow system to dominate as per pre-mining

conditions. The mine pit lake will behave as a variable flow-through system, acting as a constant

head recharge source to the McArthur River palaeochannel and down-gradient weathered

bedrock and fractured rock, in periods when the elevation of the mine pit lake is higher than these

units. The proposed spillways will control the seasonal variation in the open cut. Long-term, there

is not expected to be significant residual drawdown in the aquifers situated around the

peripheries of the mine pit lake, and only minor loss to groundwater under the proposed closure

case. Site-wide west to east groundwater flow processes will dominate. With a recovery of

aquifers post-mining, there is expected to be a return to the pre-mining conditions where

groundwater exits the system at the McArthur River.


It is expected that seepage from the NOEF will continue to migrate predominantly through two

major pathways during the closure period. The first of these will be the more permeable alluvium

to the southeast and south of the NOEF towards Surprise Creek and Barney Creek diversion; the

other being the more permeable Cooley Dolomite to the east of the NOEF, which will flow south

towards Barney Creek diversion. With the Cooley Dolomite recovering, it is expected that a

hydraulic connection between the Cooley Dolomite and the Barney Creek diversion will be re-

established and Barney Creek diversion will again become the primary receptor for down-gradient

NOEF seepage.

2.8 Model Layers

The model was vertically discretized into 14 layers to represent different aquifers, aquitards and

mining features. Table 2-1 presents a summary of the individual model layers and the various

hydrostratigraphic units and mine features that they represent. Originally, the groundwater flow

model had 12 layers, however, during early runs of the mass transport model it was decided to

further discretize the upper bedrock layer (layer 5) into three layers to better simulate the

transport of mass through the upper bedrock aquifer. The layers and structure have been

amended since the Draft EIS, based on the update geological understanding of the site.


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Table 2-1 Summary of model layers

Model

Layer Hydrostratigraphic Unit

Mining

Features (Pre-

2006)

Mining Features

(Post-2006)

Layer Base

Elevation (mAHD)

1 Overburden TSF OEFs, WMDs, TSF,

Open cut 11.2~119.5

2 Overburden

Open cut

4.8~119.4

3 Overburden – McArthur River

palaeochannel -10.8~119.3

4 Weathered Bedrock -29.7~119.2

5

Upper Bedrock, Faulting

-35.9~98.1

6 -42.1~76.9

7 -54.6 ~34.7

8 -92

9

Lower Bedrock, Faulting

Underground workings

Open cut, underground void

-146

10

Underground void

-225

11 -307

12 -384

13 -400

14 -600

2.9 Representing Fractured Media

Consistent with the Draft EIS, an Equivalent Porous Media (EPM) approach has been used. The

shallow and deep bedrock is a fractured rock aquifer with some karstic conditions in dolomite

units. EPM was used to represent the fracture networks (depths, orientations and extents etc.)

and karst conduits and to characterise these permeable zones. This approach represents the

primary and secondary porosity and hydraulic conductivity (K) distributions of the fracture

network as having effective hydraulic properties (Anderson and Woessner, 1991).

The EPM is a suitable approach for replicating the behavior of a regional flow system such as the

shallow Cooley Dolomite bedrock aquifer and meets the overall objectives of the study in defining

groundwater drawdown and impacts at the aquifer scale.

2.10 Model Exclusions, Assumptions and Limitations

The following exclusions, assumptions and limitations are associated with the groundwater

modelling completed for this investigation and are consistent with the Draft EIS:

� The numerical model has been developed as an impact assessment tool. The conceptual

model was based on available geological and hydrogeological data. Simplifications to the

geological structure have been made to translate a complex physical environment into a

workable numerical framework; for the updated model the data outlined in Section 2.5.1

was used.


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� The fractured bedrock groundwater flow system has been represented by the EPM

method.

� The presence of regional and local faults has been represented as vertical features with

varying hydraulic properties. These hydraulic properties were adjusted during calibration

to achieve the best fit of modelled heads and flows. A corridor of broken rock has been

simulated on either side of each fault to represent a more permeable zone that will

enhance groundwater flow and allow for migration of contaminants.

� The groundwater flow model assumes that the hydraulic properties are uniform for each

hydrostratigraphic layer or zone. In the field, the hydraulic properties will vary significantly

across a given hydrogeological unit. As a result, the simplified model will predict a more

uniform zone of depressurisation, contamination and flows.

� Seepage from the various water management dams on-site has been simulated as time-

varying recharge to the uppermost aquifer system in the groundwater flow model. The

dam seepage rates have been estimated using both hydraulic equations and a water

balance approach.

� Historical water quality data for the various mine water storages such as the TSF and the

PRODs have been used as the basis for life of mine water quality source terms for these

facilities.

2.11 Updated Groundwater Modelling Calibration

A similar calibration process was followed as for the Draft EIS groundwater model (KCB, 2017).

2.11.1 Calibration Process, Targets and Metrics

Transient model calibration was performed by manually adjusting boundary conditions, hydraulic

conductivity (2017) values, storage properties and model recharge. The model was initially run in

long-term steady-state mode to prepare starting heads for the various model layers and transient

modelling. Steady state calibration however was not undertaken due to the limited value this

would provide considering the strong seasonality effects on groundwater across the site. The

steady-state groundwater levels were established as the starting conditions for the transient

models.

The following performance metrics were used to judge the quality of the model conditioning and

calibration simulations:

� The Scaled Root Mean Squared (RMS) Error for the model-predicted versus observed

hydraulic heads for 29 primary monitoring bore locations from the 1990 to 2005

simulation and 206 primary monitoring bore locations from the 2006 to 2014 simulation.

� The variance of modelled to measured hydraulic heads at 206 calibration targets

(observation points).

� Time-series hydrographs of modelled versus measured heads at representative monitoring

bores across shallow and deeper aquifers in key locations (such as the receiving aquifer

pathways between mine sources and surface water receptors).

� Groundwater level contour patterns for shallow and deeper aquifers.

� The model predicted base flow (flux) to key surface water bodies.

� The model predicted inflow rate to the active underground workings till 2005.


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� The model predicted inflow rate to the active open cut mine from 2006 to 2014. This

includes the contribution of the palaeochannel to mine inflows.

� Strategies to reduce model non-uniqueness included:

� Incorporation of all available shallow and deep geology information to constrain the

three-dimensional limits of the major hydrostratigraphic zones within the model

domain. This constrains the measured heads as a function of specific geological units

and also relies strongly on the inferred geological and hydrogeological units that have

been developed independently by KCB and by Glencore for geology.

� Setting calibration targets for hydraulic conductivity based on measured values from

field-based aquifer testing. This constrains the bounds of the calibration to the field-

measured ranges for each unit so that implausible parameter ranges are not assigned

on the basis of achieving a better statistical fit.

� Adjusting aquifer parameters within field-measured ranges.

� Adjusting aquifer parameters within plausible bounds to achieve a reasonable

calibration match to measured groundwater fluxes to the underground mine voids

(deep geology influences flux) and to the open cut (both shallow and deep geology

influences flux).

� Calibrating to multiple distinct hydrological conditions, including rainfall variation, river

diversions, response to leakage from water management dams, and underground and

open pit dewatering. Application of multiple stresses to the system prevents numerical

forcing of the flows to meet calibration metrics and allows the processes to be

mimicked as a key part of the calibration process.

2.12 Updated Calibration Results and Statistics

2.12.1 Transient Calibration Model (2006 to 2014)

2.12.1.1 Groundwater Levels and Statistical Calibration Performance

After calibration, and, similar to the Draft EIS groundwater model, a good correlation between the

modelled regional flow patterns and the interpreted flow patterns based on measured

groundwater level data.

Updated calibration statistics show an improved degree of calibration compared to the Draft EIS

model. Figure 17 presents a scatter plot of observed versus modelled heads for the calibration

simulation. The scaled RMS over the simulation period (2006 to 2014) was calculated to be 7.48 %

with an RMS of 3.70 m. The water balance error was less than 0.01 % and indicates a well

converged solution with a reliable mass balance (see Table 2-2 and Figure 18).



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Figure 17 Scatter plot of modelled versus observed heads for the calibration model

simulation

Table 2-2 Summary of transient model calibration metrics: 2006 to 2014

Statistical Metric Calibration Metrics: Transient Calibration Model

(units)

Number of primary head calibration targets 206 sites and 5143 head observations

Root Mean Square Error (RMS) 3.60

Scaled RMS 7.27%

Mean Sum of Residuals (MSR) 0.77

Scaled MSR 4.78%

Transient water balance error 0.01%


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Table 2-3 Summary of transient model water balance for a representative wet month

(December 2011) of the transient calibration

Water Budget Component Inflow (m3/day) Outflow (m3/day)

Storage 621.3 24,796.6

Constant Head 16,841.7 257.1

Bores 0 9,888.51

Drains 0 10,490.1

Recharge 45,372.8 18,047.72

ET 0 15,191.8

River leakage 11,781.9 5,394.5

General Head Boundary 9,451.8 0

TOTAL 84,069.4 84,066.3 1Includes pumping from the underground vent shaft. 2Recharge outflow is rejected recharge where water would pond above surface if the extra recharge were forced into

the model.

Table 2-4 Summary of transient model water balance for a representative dry month

(September 2011) of the transient calibration

Water Budget Component Inflow (m3/day) Outflow (m3/day)

Storage 9228.7 1405.4

Constant Head 17296.8 65.2

Bores 0.0 11772.311

Drains 0.0 8629.3

Recharge 6323.1 10836.222

ET 0.0 11849.8

River leakage 3026.8 2746.6

General Head Boundary 11428.4 0.0

TOTAL 47303.9 47304.8 1Includes pumping from the underground vent shaft. 2Recharge outflow is rejected recharge where water would pond above surface if the extra recharge were forced into

the model.



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Figure 18 Representative dry stress period and wet stress period for comparison of model

inflows and outflows

The sensitivity of the model hydraulic properties and mass transport properties were tested

during trial-and-error model calibration runs and the results are reported as part of the broader

reporting on sensitivity cases (Appendix I).

The updated model was recalibrated with previous monitored data over the period between 2006

and 2015. The calibration was focused on the parameters in the upper level of the new fault zones

in response to the target observed heads, contaminant concentrations as well as the fluxes to

underground workings. Five “trial-and-error” initial models with the variation of parameters listed

in Table 2-5 were used for recalibration. Sensitivity analysis was completed to assess the potential

impact of change of hydraulic properties in the updated geological interpretation faults location

and the hydraulic properties of these faults. A key aspect tested was to assess whether the core of

each fault acted as a higher or lower permeability zone compared to the surrounding rock, as well

as the zones adjacent to the fault. The properties of the zones between faults were also assessed.

The “Trial and Error” sensitivity cases were selected to:

� Analyse the potential impact of the updated locations of faults on groundwater system;

� Examine the impact of K value variation between south and northern Bald Hill Faults on

model calibration;

� Examine the impact of K value variation between west and east Bald Hill Faults (Emu

Zone) on model calibration;

� Clarify the impact of hydraulic properties on model calibration for bedrock for zones

between the inferred fault lineaments.

The sensitivity of calibration results on the variation of model parameters was analyzed and

shown in tabulated and figure form below (Table 2-6 and Figure 19).


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Table 2-5 Calibration Models “Trial-and-Error” sensitivity

Calibration BHF (N) K zone BHF (S) K zone BHF Inner zone BHF in Emu zone Other Zones

Northern part of Bald Hill Fault Northern part of Bald Hill Fault Zone between two

strands of fault Bald Hill Fault near Emu Fault N/A

Location Core K_Z39 Buffer K_Z40 Core K_Z41 Buffer K_Z42 K_Z43_Between Core K_Z44 Buffer K_Z45 Recharge Storage

Values in Draft EIS

2016 K_Z8 / Z10 K_Z8 / Z11 K_Z10 K_Z11 K_Z8 K_Z34 K_Z35 Z14/Z9 Z14/Z9

K (m/d) K_Z10=0.088 K_Z11=1.31 K_Z10=0.088 K_Z11=1.31 K_Z8=1.51 K_Z34=10 K_Z35=5

M001 0.1X 0.1X 0.1X 0.1X 0.1X 0.1X 0.1X

M002 10X 10X 10X 10X 10X 10X 10X

M003 0.1X 0.1X 1X 1X 5X 1X 1X

M004 1X 1X 0.1X 0.1X 0.5X 0.1X 0.1X 0.5X 0.1X

M005 0.1X 0.1X 0.2X 0.5X 0.4X 0.2X 0.2X 2X 10X



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Figure 19 The sensitivity of calibration models

Based on the model sensitivity analysis and the best match with the hydrography of monitored

heads and concentration data, the final calibration results were obtained (Table 2-6).

Table 2-6 Calibration statistics for various model iterations

Statistical Metric Error 2016

Model M001 M002 M003 M004 M005

Number of primary head calibration

targets 5143 5143 5143 5143 5143 5143

Root Mean Square Error (RMS - m) 3.49 3.46 3.54 3.50 3.47 3.23

Scaled RMS (%) 7.07% 6.78% 7.15% 7.07% 6.89% 6.48%

Mean Sum of Residuals (MSR - m) 0.77 0.71 0.72 0.69 0.44 0.39

Scaled MSR (%) 4.75% 4.72% 4.76% 4.80% 4.76% 4.49%

Water balance error (%) 0.009% 0.009% 0.009% 0.007% 0.009% 0.008%

Table 2-7 Recalibrated values of model parameters for new fault zones

Features Hydrostratigraphic Unit Kh(m/day) Kv(m/day) Ss (1/m) Sy (-)

Bald Hill Fault - North Core – Zone 39 0.01 0.01 1.0E-06 0.05

Buffer – Zone 40 0.13 0.13 1.0E-05 0.05

Bald Hill Fault - South Core – Zone 41 0.02 0.02 1.0E-06 0.05

Buffer – Zone 42 0.26 0.26 1.0E-05 0.05

BHF Inner Zone Zone 43 0.60 0.60 1.0E-05 0.08

BHF in EMU zone Core – Zone 44 1 1 1.0E-05 0.08

Buffer – Zone 45 5 5 1.0E-05 0.08


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2.12.1.2 Updated Transient Calibration Hydrographs

Figure 20 presents modelled versus observed water level hydrographs for selected monitoring

bores across the 2006 to 2014 simulation period. A reasonable correlation has been achieved for

bores at the TSF (e.g. Bores GW92A, GW62, GW20A), around the perimeter of the NOEF (e.g.

GW133S, GW105, GW124D), south of SPROD (e.g. GW65S, GW64D), south of SEPROD (e.g.

GW88D, GW102), the Barney Creek Plain (e.g. GW109) and Djirrinmini (e.g. GW74).

The assessment of calibration performance using transient hydrographs compares model

predicted output with measured data for a total of 38 sites. Monitoring locations with brief or

incomplete temporal records were not included in the presentation of hydrographs but were

included in the statistical analysis for completeness.

Calibration locations are again compared for six broad zones:

1. The perimeter of the TSF with 11 bores selected in the western, northern and eastern

perimeters at different aquifer depths.

2. Around the perimeter of the NOEF with 11 bores selected in the western, northern and

eastern perimeters at different aquifer depths.

3. Down-gradient of the SPROD and SEPROD with 8 bores selected at different aquifer depths.

4. At Djirrinmini waterhole with 4 bores selected at different aquifer depths.

5. Within the Barney Creek plain with two bores selected.

6. Within the mining area with two bores selected.



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TSF Area



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NOEF Area


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Southern NOEF: down-gradient of SPROD and SEPROD

30

31

32

33

34

35

0 365 730 1,095 1,460 1,825 2,190 2,555 2,920 3,285 3,650

Gro

un

dw

ate

r H

ea

d (

m)

Time (Days)

GW65S Observed

GW65S Modelled

30

32

34

36

0 365 730 1,095 1,460 1,825 2,190 2,555 2,920 3,285 3,650

Gro

un

dw

ate

r H

ea

d (

m)

Time (Days)

GW94S Observed

GW94S Modelled

10

15

20

25

30

35

40

0 365 730 1,095 1,460 1,825 2,190 2,555 2,920 3,285 3,650

Gro

un

dw

ate

r H

ea

d (

m)

Time (Days)

GW64D Observed

GW64D Modelled

10

15

20

25

30

35

40

0 365 730 1,095 1,460 1,825 2,190 2,555 2,920 3,285 3,650

Gro

un

dw

ate

r H

ea

d (

m)

Time (Days)

GW117D Observed

GW117D Modelled

30

31

32

33

34

35

36

37

0 365 730 1,095 1,460 1,825 2,190 2,555 2,920 3,285 3,650

Gro

un

dw

ate

r H

ea

d (

m)

Time (Days)

GW94D Observed

GW94D Modelled

0

10

20

30

0 365 730 1,095 1,460 1,825 2,190 2,555 2,920 3,285 3,650

Gro

un

dw

ate

r H

ea

d (

m)

Time (Days)

GW88D Observed

GW88D Modelled

30

31

32

33

34

35

0 365 730 1,095 1,460 1,825 2,190 2,555 2,920 3,285 3,650

Gro

un

dw

ate

r H

ea

d (

m)

Time (Days)

GW65D Observed

GW65D Modelled

0

10

20

30

0 365 730 1,095 1,460 1,825 2,190 2,555 2,920 3,285 3,650

Gro

un

dw

ate

r H

ea

d (

m)

Time (Days)

GW102 Observed

GW102 Modelled


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Djirrinmini Area

10

15

20

25

30

0 365 730 1,095 1,460 1,825 2,190 2,555 2,920 3,285 3,650

Gro

un

dw

ate

r H

ea

d (

m)

Time (Days)

GW76 Observed

GW76 Modelled10

15

20

25

30

0 365 730 1,095 1,460 1,825 2,190 2,555 2,920 3,285 3,650

Gro

un

dw

ate

r H

ea

d (

m)

Time (Days)

GW74 Observed

GW74 Modelled

10

15

20

25

30

35

40

0 365 730 1,095 1,460 1,825 2,190 2,555 2,920 3,285 3,650

Gro

un

dw

ate

r H

ea

d (

m)

Time (Days)

GW77 Observed

GW77 Modelled10

15

20

25

30

35

40

0 365 730 1,095 1,460 1,825 2,190 2,555 2,920 3,285 3,650

Gro

un

dw

ate

r H

ea

d (

m)

Time (Days)

GW72 Observed

GW72 Modelled

10

20

30

40

0 365 730 1,095 1,460 1,825 2,190 2,555 2,920 3,285 3,650

Gro

un

dw

ate

r H

ea

d (

m)

Time (Days)

GW109 Observed

GW109 Modelled0

5

10

15

20

25

30

0 365 730 1,095 1,460 1,825 2,190 2,555 2,920 3,285 3,650

Gro

un

dw

ate

r H

ea

d (

m)

Time (Days)

GW67 Observed

GW67 Modelled

10

15

20

25

30

35

40

0 365 730 1,095 1,460 1,825 2,190 2,555 2,920 3,285 3,650

Gro

un

dw

ate

r H

ea

d (

m)

Time (Days)

GW110B Observed

GW110B Modelled

0

5

10

15

20

25

30

0 365 730 1,095 1,460 1,825 2,190 2,555 2,920 3,285 3,650

Gro

un

dw

ate

r H

ea

d (

m)

Time (Days)

SS7-1 Observed

SS7-1 Modelled


Supplementary EIS

Site Groundwater

Report


Page 44


Barney Creek Plain Area

Open Cut Area

Figure 20 Modelled versus observed hydrographs for representative bores for the model

calibration simulation

Baseflow estimates in calibration period

The baseflow estimates for the calibration period show slight changes to the previous calibration.

The most significant change is a marginal increase in the distribution of flows in Surprise Creek

section because of the adjustment of the Bald Hill geological structures to the east of the TSF.

The individual creek reaches are provided in Figure 21.

Table 2-8 provides a breakdown of the features of each baseflow reach and its relevance in terms

of site-wide surface water-groundwater interactions.


Supplementary EIS

Site Groundwater

Report


Page 45


Table 2-8 Summary of baseflow influences and reliability

Creek/River Baseflow

Reach ID

Mine seepage sources and

activities with potential to

influence baseflow

Natural Influences

on baseflow

Factors influencing

baseflow estimate

reliability

Surprise Creek

17_1

This reach of Surprise Creek is

the receptor for shallow TSF

seepage from Cells 1 and 2 of

the TSF.

Limited surface water

flow monitoring in this

reach.

17_2

This reach of Surprise Creek is

the receptor for shallow

seepage from SPROD.



reach.

Barney Creek

22

This reach of Little Barney

Creek is situated directly

south of the TSF water

management dam.

Limited groundwater

head data to constrain

aquifers beneath and

adjacent to the creek.



reach.

16_1

This reach of Barney

Creek is present along the

western boundary of the

model domain and as

such is heavily influenced

by the western constant

head boundary condition.

For this reason, the

estimate of baseflow for

this reach is not

considered reliable.

16_2

These reaches of

Barney Creek pass

through where

groundwater quality

is naturally saline

and believed to be a

result of shallow

mineralisation

Limited groundwater






reach.

16_3

This reach of Barney Creek is

situated down-gradient of

WOEF.

Barney Creek

Diversion 3

This reach represents the

length of the Barney Creek

diversion and is the potential

receptor for southward

seepage from SPROD, SEPROD

and the NOEF, as well as ELS

seepage migrating north.



reach.

Unnamed

Creek

18_2

This reach of unnamed creek

extends across the northern

perimeter of the NOEF

18_3

This reach of unnamed creek

is present to the north of the

TSF, however, most TSF

seepage migrating north is

expected to discharge to

Surprise Creek before it

reaches unnamed creek.

Limited groundwater






reach.


Supplementary EIS

Site Groundwater

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Page 46


Creek/River Baseflow

Reach ID

Mine seepage sources and

activities with potential to

influence baseflow

Natural Influences

on baseflow

Factors influencing

baseflow estimate

reliability

Emu Creek

18_1

These reaches of Emu Creek

are situated down-gradient of

the NOEF.

These reaches of

Emu Creek pass

through an area

where groundwater

quality is naturally

saline and believed

to be a result of

shallow

mineralisation

Limited groundwater



adjacent to the creek. A

number of bores up-

gradient of the creek

show groundwater

elevations 4 to 5 m below

the elevations in the

creek.

a. 20

McArthur

River

Upstream

11

Limited groundwater



adjacent to the creek

12 MIMEX production bore

abstraction may result in head

reduction along these reaches

13

McArthur

River Diversion

25

Mine dewatering will

significantly affect the

hydraulic heads beneath the

diversion. SOEF is present

between the pit and the

diversion.



reach.

4

Seepage from ELS creates a

significant increase in the

head gradient towards the

diversion, as well as a

potential plume migration

from the dam itself.



reach.

McArthur

River

Downstream

14

This zone represents a

significant outflow for

groundwater passing through

the mine site.

Limited groundwater






reach.

15

This zone represents a

significant outflow for

groundwater passing through

the mine site.

Glyde Glyde

No groundwater head

data to constrain aquifers

beneath and adjacent to

the creek.



reach.

Bull 19

No groundwater head

data to constrain aquifers

beneath and adjacent to

the creek.

No surface water flow

monitoring in this reach.


Supplementary EIS

Site Groundwater

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Page 47


Modelled baseflow for Emu Creek within the model domain is zero, consistent with the

conceptual model and measurements of groundwater levels on site.


Supplementary EIS

Site Groundwater

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Page 48


Figure 21 Baseflow reaches defined for the project site (consistent with WRM, 2017).

MC

AR

TH

UR

RIV

E

R

LITTLE BARNEYCR

EEK

EMUCR

EEK

GLY

DE

RIVER

BU

LLC

RE

EK

BARNEY CR EEK

Zone 19

Zone 14

Zone

18_2

Zone

17_2

Zone

16_1

Glyde Rv

Zone

17_1

Zone 15

Zone

16_2

Zone 3_3

Zone 20

Zone 12

Zone

16_3

Zone 4_1

Zone 22

Zone 11

Zone 11

Zone 13

Zone

18_3

Zone 25

Zone 25

Suprise

Creek U/S2

Zone

3_1Zone 3_2

Zone 4_2

Zone

18_1

612,000 614,000 616,000 618,000 620,000 622,000 624,0008,1

76

,000

8,1

78

,000

8,1

80

,000

8,1

82

,000

8,1

84

,000

8,1

86

,000

8,1

88

,000

8,1

90

,000

0 0.5 1 1.5 2

km

Legend

River/Creek

Diversion

Model Domain

Catchment Zone

River Cell

NOTES:

1. Background image: McArthur River Mine Merge 50cm.ecw

2. Surface Water and Road features are based on published data that have been adapted from the

background image.3. Topography: MRM 2015 Lidar Survey





Report


Page 49


Figure 22 Model-predicted baseflow during the calibration period 2006-2014 for Surprise

Creek and Barney Creek diversion

Figure 23 Model-predicted baseflow during the calibration period 2006-2014 for Barney

Creek



Report


Page 50


Figure 24 Model-predicted baseflow for 2006-2014 for unnamed creek

Figure 25 Model-predicted baseflow during the calibration period 2006-2014 for McArthur

River and diversion (Initial year values part of model conditioning)



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Page 51


Figure 26 Model-predicted baseflow during the calibration period 2006-2014 for Glyde

River and Bull Creek

2.12.1.3 Calibrated Hydraulic Parameters

Material Parameters

Table 2-9 summarises the calibrated hydraulic conductivity and storage values used for the

fourteen layers of the model. The change since the Draft EIS model are minor changes to assigned

aquifer parameters and the updated alignment of the fault structures running NW/SE in the TSF

area toward the NOEF; consistent with the updated geological interpretation. As per the

conceptual understanding of aquifer conditions at the site, there is a general decreasing trend in

permeability with increasing depth in each hydrostratigraphic unit. Figure 27 presents the

hydraulic conductivity of Layer 5 and Layer 8 of the upper bedrock profile. Most of the

groundwater flow in the bedrock occurs between layer 5 and layer 8. This figure shows that the

fault planes are all represented as a low permeability barrier to flow. On either side of the faults is

a fault corridor which has relatively high permeability in the uppermost bedrock layers (e.g. Layer

5), and decreases in permeability with depth (e.g. Layer 8).


Supplementary EIS

Site Groundwater

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Page 52


Table 2-9 Calibrated hydraulic conductivity and storage values

Layer Hydrostratigraphic Unit Kh(m/day) Kv(m/day) Ss (1/m) Sy (-)

1,2,3 Fine-grained overburden 0.2 0.1 1.E-03 0.02

1,2 Coarse-grained overburden 2.6 0.3 1.E-03 0.02

1 Tailings 9.0E-03 9.0E-04 1.E-05 0.2

3 McArthur River palaeochannel 9.7 1.0 1.E-03 0.02

4 Weathered bedrock 1.2 0.1 1.E-04 0.08

4 Weathered epikarst of the Reward Dolomite 5 5 1.E-04 0.08

5 Karstic Reward Dolomite 10 10 1.E-05 0.1

5,6,7,8 Bulk Reward Dolomite 0.3 to 1.5 0.3 1.E-05 0.1

5,6,7,8 Barney Creek Formation 3.5E-04 3.5E-05 1.E-06 0.005

5,6,7,8 Cooley Dolomite South 1 1 1.E-05 0.1

5,6,7,8 Cooley Dolomite North 5 5 1.E-05 0.1

5,6,7,8 Masterton Sandstone 0.2 0.02 1.E-06 0.1

5,6,7,8 Woyzbun, Whelan, Western Faults 3.5E-04 3.5E-05 1.E-06 0.005

8 North Fractured bedrock along fault zones 1.3 1.3 1.E-04 0.1

9,10 Western Dolomite 2.3E-02 2.3E-03 1.E-05 0.1

9,10 Barney Creek Formation 9.4E-03 9.4E-03 1.E-06 0.005

9,10 Cooley Dolomite 9.8E-02 9.8E-03 1.E-05 0.1

9,10 Masterton Sandstone 1.9E-02 1.9E-03 1.E-06 0.1

11,12,13,14 Woyzbun, Whelan, Western Faults 5.0E-04 5.0E-04 1.E-06 0.005

11,12,13,14 Western Dolomite 2.7E-03 2.7E-04 1.E-06 0.025

11,12,13,14 Barney Creek Formation 1.0E-03 1.0E-03 1.E-06 0.005

11,12,13,14 Cooley Dolomite 3.6E-03 3.6E-04 1.E-06 0.025

11,12,13,14 Masterton Sandstone 3.7E-03 3.7E-04 1.E-06 0.025

8,9,10,11,12,13,14 Fractured bedrock along fault zones 3.5E-03 3.5E-04 1.E-06 0.005

5,6,7,8 Bald Hill Fault - North Core 0.01 0.01 1.0E-06 0.05

5,6,7,8 Bald Hill Fault - North Buffer 0.13 0.13 1.0E-05 0.05

5,6,7,8 Bald Hill Fault - South Core 0.02 0.02 1.0E-06 0.05

5,6,7,8 Bald Hill Fault - South Buffer 0.26 0.26 1.0E-05 0.05

5,6,7,8 Reward Dolomite between BHF 0.60 0.60 1.0E-05 0.08

5,6,7,8 Bald Hill Fault Core in EMU zone 1 1 1.0E-05 0.08

5,6,7,8 Bald Hill Fault Buffer in EMU zone 5 5 1.0E-05 0.08


Supplementary EIS

Site Groundwater

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Page 53


Figure 27 Fault and fault corridor parameterisation in Layer 5 and Layer 8 of the upper bedrock profile

BU

LL

C

REEK

SURPRISE CREEK

616,000 618,000 620,000

8,1

82

,00

08,1

84

,00

0

BU

LL

C

REEK

SURPRISE CREEK

Bar

ney

Hill F

ault

Bald Hills Fault

616,000 618,000 620,000

8,1

82

,00

08,1

84

,00

0

0 0.25 0.5 0.75 1

km



4. Scale: 1:40,000

NOTES:




2. Mine infrastructure courtesy of MRM.

Legend

River/Creek

Diversion

Fault

NOEF (2015)

Open Cut (2018)

LAYER 5 LAYER 8

North CooleyDolomites

Kxy = 5 m/day

South Cooley

DolomitesKxy = 0.98 m/day

Fault

Kxy = 3.5 x10 m/day-4

Fault Corridor

Kxy = 1.31 m/day

Fault

Kxy = 3.5 x10 m/day-4

Barney Creek

Formation

Kxy = 3.5x10 m/day-4

Barney Creek

Formation

Kxy = 3.5 x 10 m/day

Fault CorridorKxy = 0.0036 m/day

North Cooley

Dolomites

Kxy = 0.98 m/day

South CooleyDolomites

Kxy = 0.098 m/day

-4

Fault Corridor

Kxy = 1.306 m/day



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Page 54


Rainfall Recharge

Recharge rates were applied consistently with the Draft EIS groundwater model (KCB, 2017).

2.12.2 2006 to 2014 groundwater mass transport model

Two measures of contaminant transport calibration were applied:

� Visual review of the model predicted sulphate plume at the end of the calibrated

model scenario with 2016 averaged data to check that source-pathway-receptor

relationships were being honoured; and,

� Visual comparison of predicted versus observed sulphate time-series concentration

profiles at key monitoring locations, in positions consistent with those used in the Draft

EIS model.

2.12.2.1 Sulphate loads to creeks and rivers

Figure 28 to Figure 31 presents the predicted sulphate loads reporting to creeks and rivers across

the calibration simulation period. Sulphate loads vary seasonally and increase in Surprise Creek

(17_1 and 17_2), and Barney Creek diversion (3) as a result of mine-site activities such as TSF and

SPROD operation.

Figure 28 Calibrated model sulphate loads reporting to Surprise Creek and Barney diversion



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Figure 29 Calibrated model sulphate loads reporting to Barney Creek

Figure 30 Calibrated model sulphate loads reporting to unnamed creek



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Figure 31 Calibrated model sulphate loads reporting to McArthur River and diversion

Sulphate Plume Development

Figure 32 indicates observed and modelled sulphate concentration breakthrough curves at key

representative bores situated down-gradient of the TSF, NOEF, SPROD and SEPROD.

The model is again replicating the development of plumes to the south of the SPROD and SEPROD.

There are excellent correlations in the breakthrough of sulphate at bores GW94S, GW64S, GW95S,

GW87D, GW65D, GW64D, GW95D, GW98D, and GW97.



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Page 58


Figure 32 Modelled versus observed sulphate concentrations for representative bores for

the model calibration simulation

2.12.2.2 Calibrated Mass Transport Parameters

Source Terms

Table 2-10 shows various natural and mine-related sources present within the model domain for

the calibration period. These values are based on average values over the period of monitoring up

to 2014 and have been kept consistent with the Draft EIS.


Supplementary EIS

Site Groundwater

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Table 2-10 Sulphate source terms applied to calibration simulation from 2006 to 2014

Sulphate Source Concentration (mg/L)

TSF Cells 1 and 2 15,000

Barney Creek mineralised zone 2,500

Emu Creek mineralised zone 1500

Cooley mineralised zone 600-2,000

NOEF 12,000

SPROD 2,500

SPSD 3,500

SEPROD 5,200

WOEF 6,500

ELS 2,300

VDD 2,100

OMR 530

2.13 Approach to Life of Mine simulations

Life of mine (LOM) model runs were established for the period 2015 to 2037 to represent the

transient conditions of the mine as defined by the project description snapshots for 2018, 2022,

2027, 2032 and 2037. These have been kept consistent with the Draft EIS.

2.13.1 Stress periods

The model was simulated at monthly stress periods for the LOM period. The monthly stress

periods allow seasonal recharge rates to be applied to the model such that baseflow discharge to

creeks and rivers adequately represented the wet and dry season conditions, including the

transition periods between seasons.

2.13.2 Contaminants of Concern

Sulphate, zinc, arsenic, cadmium and lead were modelled as parameters of interest, consistent

with the Draft EIS.

2.13.3 Pit drains

Pit shell snapshots were provided by MRM for 2018, 2022, 2027, 2032 and 2037 for the

progressively expanding open cut mine. The open pit was modelled as drain cells placed across all

model layers which exist between the base of the open cut and the ground surface, for each time

snapshot in the project description. The same approach was applied as for the Draft EIS.

At the completion of mining (and after tailings have been placed in-pit), drain cells were

deactivated and the material properties of the void reinstated as a high storage value (Specific

Yield of 0.99) and a high hydraulic conductivity of 100 m/day in the pit void above the tailings. This

is consistent with the Draft EIS.

2.13.4 Recharge

Natural recharge rates were applied at the calibrated infiltration rates, consistent with the Draft

EIS. The long-term 125 year SILO climate dataset was used to define monthly average values for

recharge.


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2.13.5 Climate Change

Climate change projections for MRM were developed by WRM (2016). These have been applied

consistently for the groundwater modelling assessments as per the Draft EIS (Appendix D of the

Draft EIS).

2.13.6 Seepage

2.13.6.1 Water management dam seepage

Monthly time-varying seepage rates were provided for each water management dam for the LOM

(see WRM, 2017). The seepage rates were applied directly to the water table as time-varying

recharge with a source term for each contaminant of concern. This approach is deemed

conservative from a mass transport perspective, as all of the load seeping from each dam is input

directly to the aquifer without any loss in the unsaturated zone

2.13.7 OEF seepage

There are five major OEFs in the mining area over the LOM: NOEF, SOEF, WOEF, EOEF PAF(HW)

and LGO. Table 2-11 summarises the OEFs that have been modelled and the assumptions for

seepage and water quality.

Table 2-11 OEF seepage assumptions for life of mine

OEF

Net

percolation

(% of rainfall)

Foundation

seepage Toe seepage

Source of

foundation

seepage

water quality

Start time End Time

NOEF

Based on

TOUGH2

foundation

seepage

Assigned

based on

TOUGH2

Assigned

based on

TOUGH2

NOEF Water

Quality Model

results

LOM Permanent

SOEF 35% 50% of NP 50% of NP

NOEF Water

Quality Model

results

2015 2042

WOEF

25% from

2006 to 2042;

6% from 2042

onwards after

cover

100% of NP -

NOEF Water

Quality Model

results

LOM Permanent

EOEF

PAF(HW) 5.5% 50% of NP 50% of NP

NOEF Water

Quality Model

results

2019 2042

LGO 15% 50% of NP 50% of NP

NOEF Water

Quality Model

results

2022 2038

2.13.7.1 TSF seepage

Monthly time-varying seepage rates for the LOM were extracted from the TSF seepage mitigation

design groundwater model for Cell 1 and Cell 2 of the TSF, as well as the water management dams

(Figure 33). Details of this modelling are documented in Appendix II of the Draft EIS. Seepage from



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Page 61


Cells 1 and 2 increase with time as the tailings pond increases and the mound under the pond

develops. Additional mitigation/interception designs are underway and have been included to

indicate that more efficient capture of these rates is possible. For this Supplementary EIS, the

improved interception has only been considered as an alternative sensitivity case and the

approach to the water management conservatively assumes the Draft EIS approach is put in place.

The seepage rates were applied directly to the water table as time-varying recharge with a source

term for each contaminant of concern (sulphate held at 15,000 mg/L for TSF cells 1 and 2). This

approach is deemed conservative from a mass transport perspective, as all of the load seeping

from each tailings cell and dam is input directly to the aquifer without any loss to any unsaturated

zones that may arise. Figure 33 provides the time-series of seepage rates that were modelled as

recharge across the LOM.

Figure 33 Time-series of TSF seepage rates applied to the life of mine model simulations

2.14 Approach to Site-wide Closure Groundwater Modelling

2.14.1 Stress Periods and Model Scenarios

To allow for the 1,000 year simulations, the closure period was simulated with increasing stress

intervals (longer time intervals) in the longer term. In the period immediately after operations

have ceased, the model was simulated at monthly stress periods from 2037 to 2067. The monthly

stress periods allowed seasonal recharge to be applied so that baseflow discharge to creeks and

rivers adequately represented wet and dry season conditions.

From 2068 to 2167, the model was simulated into 200 stress periods to represent six months of

wet season conditions and six months of dry season conditions for a 100-year period. Following


Supplementary EIS

Site Groundwater

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Page 62


this 100-year closure simulation a final long-term simulation was run from 2168 to 3048, to

present results for the 1,000 years of closure. The rest of the long-term simulation is consistent

with the Draft EIS model (KCB, 2017) and considers the changes to the groundwater environment,

ongoing contaminant migration (which includes consideration of diffusion over the entire

simulation period).

2.14.2 Contaminants of Concern

Sulphate, zinc, arsenic, cadmium and lead were again modelled for the closure simulations.

2.14.3 Pit

Active dewatering of the open cut was simulated with pit drains until 2047. After tailings

placement, the open cut drains are switched off and the pit is modelled as an open void with a

high permeability (100 m/day in the void above the tailings) and high storage (SY of 0.99).

2.14.4 Mine Pit Lake Recovery

A time-varying constant head boundary was activated at the base of the open cut void to match

the recovering mine pit lake level that was modelled in the GoldSim final void model. This

included iterations between the final void model and the groundwater model to align heads and

groundwater inflow rates between the models. A seasonally variable mine pit lake was modelled

from 2048 to 2167. After 2168, the mine pit lake level was held constant at ~16.9 mAHD (based on

the water ways and final void model); the final void model and the waterways model provide the

detailed water balance after this period.

2.14.5 Production borefields

The borefields are considered to be decommissioned in 2037.

2.14.6 Recharge

The values used were the same as the Draft EIS model. For the closure simulation, the climate

sequence was consistent with the base case climatic sequence used for the surface water (WRM,

2017) modelling; this is consistent with the final void modelling.

2.14.7 Seepage

2.14.7.1 Water management dam seepage

Water management is consistent with the Draft EIS groundwater model, apart from the changes

to the WMD and PWD adjacent to the TSF. These facilities have been modelled consistently with

the design values for liners and seepage (see WRM, 2017).

2.14.7.2 OEF seepage other than the NOEF

Values used in the Draft EIS model have been implemented for this round of modelling.

2.14.7.3 TSF seepage

Monthly time-varying seepage for the closure period was extracted from the updated TSF seepage

mitigation design groundwater model for the TSF, as well as the water management dams (KCB,


Supplementary EIS

Site Groundwater

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Page 63


2016). These seepage rates take account of the decreasing decant pond height as tailings is

reprocessed and disposed of in the open cut. Post-2047, the model simulations assume that the

tailings have been completely removed and that natural recharge conditions return once the area

has been rehabilitated.

The seepage rates from 2038 to 2047 were applied directly to the water table as time-varying

recharge with a source term for each contaminant of concern.



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3 UPDATED GROUNDWATER MODELLING RESULTS

3.1 Life of Mine Simulations

3.1.1 Baseflow estimates to creeks and rivers

Transient creek baseflow was predicted for reaches of the various surface water features across

the site. The individual creek reaches are again consistent with the WRM nomenclature.

Model-predicted groundwater discharge to creeks and rivers over the LOM simulations for

selected river and creek reaches is presented in Figure 34 to Figure 36. These are similar to the

Draft EIS Case.

Figure 34 Life of mine monthly baseflow predictions for Surprise Creek and Barney Creek

diversion



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Page 65


Figure 35 Life of mine monthly baseflow predictions for Barney Creek

Figure 36 Life of mine monthly baseflow predictions for McArthur River



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3.1.2 Pit inflow

Pit inflows are similar to the values observed in the Draft EIS case.

Figure 37 Pit inflows over the life of mine and into closure

Sensitivity assessments were undertaken to provide bounds on these values; these are included in

Appendix I.

3.1.3 Plume extents for Sulphate

Sulphate plumes occur at several key locations. Figure 38, Figure 39, and Figure 40 show that TSF,

NOEF, and WOEF seepage are expected to result in down-gradient plumes in the weathered

bedrock and upper bedrock at various stages of the life of mine. These plumes are less

predominant in the overburden, and report mainly to Surprise Creek and Barney Creek (although

WOEF seepage diverges with some seepage migrating west toward Barney Creek and the majority

of seepage migrating east towards the open cut void. There is also a significant plume beneath

Barney Creek diversion, however, this is not reporting to the diversion as load (Section 9.1.3 for

details), but rather is continuing below the diversion under gradients imposed by dewatering

operations, and discharges to the open cut drains.

Seepage from EOEF and SOEF migrates to the open cut void owing to steep hydraulic gradients

between these facilities and the dewatered open cut.

There are naturally-derived sulfate plumes associated with mineralisation in the Barney Creek

plain, the Emu Creek plain (north of Barramundi Dreaming), and the Cooley mineralisation along

the McArthur River diversion.

There are also minor sulfate plumes associated with various mine water management dams

across the site. These plumes are less prominent than simulated during the calibration period, a

reflection of higher dam seepage rates during the calibration periods. An emphasis on improved

dam management has seen significantly reduced dam seepage rates forecast for the LOM.


Supplementary EIS

Site Groundwater

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Page 67


3.1.4 Plume extents for metals

The migration of the contaminants of concern will be primarily controlled by advection and

dispersion within the aquifer pathways. Sulphate is a conservative parameter (i.e. not assumed to

be subject to reaction processes and attenuation) and as such its plume migration will represent

the maximum extents for the given source-pathway-receptor model. The metal parameters (As,

Cd, Pb and Zn), however, are attenuated in the aquifer matrix during migration through the

aquifer pathway and therefore, their plume extents are contracted in comparison to sulphate. To

illustrate the influence of attenuation, select LOM snapshots of the Zn1 plume have been

presented in Figure 41, Figure 42, and Figure 43. Comparison of sulphate plumes (Figure 38 to

Figure 40 ) with the migration of Zn (Figure 41 to Figure 43) shows that the sulphate plume has

migrated from the various mine sources (TSF, NOEF) to the down-gradient creeks and rivers

relatively quickly (i.e. in the order of several years), while the metal plumes have not migrated far

beyond the original sources during mining operations in the same period.

Additional contour plots to show concentrations over time are provided in Appendix IV for:

� Sulphate in the overburden and weathered bedrock every decade up to 2100.

� Sulphate in the upper and lower bedrock at 2030, 2050 and 2100 (reduced intervals due to

lower rates of migration in these deeper units).

� Zinc in the overburden and weathered bedrock every decade up to 2100.

� Zinc in the upper and lower bedrock at 2030, 2050 and 2100 (reduced intervals due to

lower rates of migration in these deeper units).

1 Zinc has the lowest Kd values of the four metals modelled, and as such will show the onset of plume migration

before the other three metals, as As, Cd and Pb all exhibit a greater tendency to sorb, based on the site-specific Kd

values.


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Figure 38 Predicted sulphate concentrations in the overburden at four select periods of the life of mine


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Figure 39 Predicted sulphate concentrations in the weathered bedrock at four select periods of the life of mine


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Figure 40 Predicted sulphate concentrations in the upper bedrock at four select periods of the life of mine


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Figure 41 Predicted zinc concentrations in the overburden at four select periods of the life of mine


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Figure 42 Predicted zinc concentrations in the weathered bedrock at four select periods of the life of mine


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Figure 43 Predicted zinc concentrations in the upper bedrock at four select periods of the life of mine



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3.1.5 Load estimates to creeks and rivers

3.1.5.1 Sulphate Load

Model-predicted sulphate load discharged to creeks and rivers over the LOM for selected river

and creek reaches is presented in Figure 44 to Figure 46. Results are similar to the Draft EIS with

the following comments:

� Sulphate load increases for Surprise Creek at station 17_1 as TSF seepage increases

throughout the LOM.

� For station 17_2 the sulphate load reduces significantly in the first three years due to

improved management practices at SPROD. Load remains below 500 kg/day for the life

of mine.

� Sulphate load reduces for Barney Creek diversion throughout the LOM. This is primarily

related to baseflow reductions post-2023 (see Section 9.1.1 for details).

� Barney Creek contributes <500 kg/day during the dry season throughout the LOM.

Figure 44 Life of mine monthly sulphate load predictions for Surprise Creek and Barney

Creek diversion



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Figure 45 Life of mine monthly sulphate load predictions for Barney Creek

Figure 46 Life of mine monthly sulphate load predictions for McArthur River

3.1.5.2 Metal Loads

Appendix I presents individual graphs for zinc, arsenic, cadmium and lead loads to all creek and

river reaches for the LOM simulations. Metal load trends are very similar to baseflow trends as the

concentrations of the metals reaching each creek stay relatively consistent over the simulations.

The reason for the similarity is that the concentrations typically remain at background across the

LOM for each metal modelled, resulting in level predictions showing strong parallels with

baseflow trends.


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Most of the metal load is attenuated in the aquifer matrix during this short-term 23 year period,

Additional modelling using several approaches including 1-D mass transport analytical solutions

and reactive transport modeling applied to Barney Creek and Surprise Creek predicted hundreds

to thousands of years for concentration breakthroughs to occur at the creeks largely due to the

retardation expected due to the relatively high Kd values for these aquifers. These are provided in

more detail in the section which follows.

Metal load predictions for the LOM varies coincident with base flow. Concentration changes are

negligible so flow changes are the largest drivers on metal load variation over the life of mine

simulations.

3.1.6 Uncertainty of Load Estimates and Plume Development

A review of the particle tracking streamlines migrating from the NOEF to surface water (Barney

Creek diversion) was conducted to establish the major pathways for mass transport. There are

two main transport pathways for NOEF seepage: one set of streamlines that migrate from the

southern NOEF and SPROD towards Surprise Creek and Barney Creek diversion through

permeable overburden and weathered bedrock; and another set that migrate from the central

and eastern NOEF eastward towards the Cooley Dolomite and then travel south through the

Cooley Dolomite and Western Fault fracture corridor, and discharge to either the Barney Creek

diversion, or the open cut (post-2023 until pit lake recovery). The second transport pathway also

includes flow through permeable overburden in the southeast corner of the NOEF. The first of

these two pathways constitute the major long-term groundwater pathway for NOEF seepage. For

this reason, the first pathway was analysed using a 1D Domenico (1987) equation to detail the

uncertainty of baseflow loads to the receptor as well as the most sensitive parameters that

influence the predictions of load. The 1D approach was selected so that a stochastic review could

be undertaken.

The physical, hydraulic and mass transport properties required for the 1D analytical model were

taken directly from the 3D model so that consistency was achieved for key inputs including

hydraulic gradient, hydraulic conductivity, effective porosity, and dispersion. These properties

were set to the calibrated model parameters for the base analytical model and allowed to vary

between upper and lower bounds for the stochastic simulations.

Table 3-1 Physical, hydraulic and mass transport properties used in 1D analytical model

Parameter Units Pathway 1: Southeast corner of NOEF

Min Max Mean

Hydraulic Conductivity m/s 1.2E-05 2.9E-04 5.8E-05

Hydraulic gradient 0.0025 0.00625 0.00375

Bulk density g/cm3 1.5 2.6 2.0

Effective porosity 0.05 0.15 0.1

Source term – Sulphate mg/L 8125

Source term – Zinc mg/L 6.35

Representative stress period

Date Steady-state at 2067 conditions


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The Domenico analytical equation is used due to its versatility and widespread use in many

attenuation assessment tools (e.g., in BIOCHLOR; Aziz et al. 2003), and the fact that degradation

and retardation can be included.

Understanding model assumptions is crucial to simulate transport process for a specific

contaminant in a groundwater system such as this. The Domenico Analytical Model assumes:

i. A finite source dimension,

ii. A steady state source,

iii. Homogeneous aquifer properties,

iv. One dimensional flow,

v. Contaminant concentration estimated at the centreline of the plume,

vi. Molecular diffusion2 based on concentration gradient is considered as part of the

dispersivity, and

The degree of retardation depends on both aquifer and constituent properties. The retardation

factor is the ratio of the groundwater seepage velocity to the rate that dissolved chemicals

migrate in the groundwater. As an alternative, results were also compared to the Ogata-Banks

approximation (Ogata and Banks, 1961). The Ogata-Banks equation was used to determine

concentration breakthrough curves at the same points as the Domenico equations, with

consideration of advection, dispersion and retardation for the metals.

These 1-D models assume a uniform, constant aqueous phase source concentration. For this, the

contaminant source does not vary spatially, and is fixed over the duration of the simulation time.

The source takes the form of a vertical plane oriented perpendicular to the groundwater flow

direction located at the downgradient limit of the NOEF. For this assessment, source

concentrations were selected to be consistent for each period of the equivalent numerical model.

To further understand the influences that could impact on loads and concentrations, stochastic

modelling approaches were used. Stochastic modelling follows a Monte Carlo simulation

technique which allow multiple realisations of different "what if" cases where the ranges and

distributions of the parameters are assessed. This allows the range of possible outcomes, their

probability of occurring, and the inputs that have the greatest impact on the contaminant plumes

model, to be assessed.

The Monte Carlo probability capability of GoldSim was used to assign distributions and assess the

impact of different input parameters. The approach allows definition of the assumptions for each

input and the 1-D contaminant transport equations to be assessed for multiple scenarios. This

approach provides a broad understanding of the model variability, with results typically provided

as ranges associated with a probability of occurrence rather than single values as provided by the

well–calibrated 3D numerical model.

2 Diffusion has been included as part of the dispersivity for the analytical approach; for the numerical model diffusion

was explictly.


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Two types of results are again provided in this report; the probability plots of each contaminant

plume and interpretive diagrams (Tornado plots). The stochastic concentration/time graphs with

probabilities are useful in indicating the variability and the range of outcomes. The Tornado

diagrams indicate which parameters have the greatest impact on the results.

Short-term sensitivity for sulphate (10 years)

Figure 47 presents the sulphate breakthrough concentrations for the 2067 conditions in the

southeast corner of the NOEF using the various 1D analytical equations. The concentrations at the

creek discharge point in the numerical model are around 3000 mg/L, which is a good match to the

analytical outputs, and demonstrates that the analytical equation is a useful tool for representing

this linear source-pathway-receptor system in the southeast corner of the NOEF.

Figure 47 Sulphate concentration breakthrough at the Barney Creek diversion for base 2067

models

A stochastic analysis of the modified Domenico equation was used to determine the sensitivity of

model outputs to modifications to the input parameters. Figure 48 presents the probability of

sulphate concentration breakthrough curves at the diversion, with each of the colour bands

representing the probability of the concentration being in that envelope based on the ranges

provided for aquifer and mass transport properties (i.e. the plausible range of each parameter).

The very low and very high values have lower probability with greater probabilities nearer the

median of the graph. Figure 49 presents the same modified Domenico stochastic analysis as

described above, however, dilution from rainfall recharge is taken into account. Figure 50

presents the probability of sulphate load reporting to the diversion. The median value presented

is similar to the 3D numerical model output for load at 2067 (being 1200 to 1500 mg/L).

One way of summarising the sensitivity is by using a Tornado diagram (see Figure 51). In this case,

the effect of varying each parameter can be shown visually for the ranges provided. For the short-

term 2067 case, the most sensitive parameters (in terms of influencing sulphate load at the

0

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Modified Domenico _Summary Domenico_Recharge_DiluteDomenico (1987) Ogata & Banks (1961)


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diversion) are hydraulic conductivity, then hydraulic gradient, effective porosity and source

concentration. The least sensitive parameter is dispersion (longitudinal and transverse).


Barney Creek diversion using the modified Domenico equation


Barney Creek diversion using the modified Domenico equation, with an

additional module to take account of recharge dilution effects

0

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4000

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2050 2052 2054 2056 2058 2060 2062 2064 2066

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Statistics for Modified Domenico _Summary

Min..1% / 99%..Max 1%..5% / 95%..99% 5%..15% / 85%..95%15%..25% / 75%..85% 25%..35% / 65%..75% 35%..45% / 55%..65%45%..55% 50%

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2050 2052 2054 2056 2058 2060 2062 2064 2066

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Statistics for Domenico_Recharge_Dilute

Min..1% / 99%..Max 1%..5% / 95%..99% 5%..15% / 85%..95%15%..25% / 75%..85% 25%..35% / 65%..75% 35%..45% / 55%..65%45%..55% 50%


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Figure 50 Stochastic output for sulphate load (in kg/day) using the modified Domenico

equation

Figure 51 Tornado sensitivity chart for the stochastic Domenico analytical assessment. The

output is load to the Barney Creek diversion (in kg/day).

Note: K is hydraulic conductivity; i is the hydraulic gradient; por is the effective porosity; long_dispersion

is the longitudinal dispersion; trans_dispersion is the transverse dispersion.

0

1000

2000

3000

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2050 2052 2054 2056 2058 2060 2062 2064 2066

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(kg

/da

y)

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Statistics for Max_load_into_river_domenico

Min..1% / 99%..Max 1%..5% / 95%..99% 5%..15% / 85%..95%15%..25% / 75%..85% 25%..35% / 65%..75% 35%..45% / 55%..65%45%..55% 50%

0 1000 2000 3000 4000 5000

Stochastic_conc

Trans_dispersion

Long_dispersion

Source_Concentration

Por_Stochastic

i_Stochastic

K_Stochastic

Ind

ep

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ble

s

Low High


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Medium-term sensitivity for sulphate (100 years)

The same stochastic analytical assessment was also undertaken for a medium-term simulation

(100 years) to assess whether the probability of outcomes and sensitivity of parameters are

influenced once the sulphate plume reaches a steady-state condition (Figure 52 to Figure 55).

Compared to the loads and concentrations in the short-term, there is a far narrower envelope of

loading results due to the convergence of the concentration breakthroughs. The numerical model

results for this period indicate a steady load of approximately 3, 500 kg/day of sulphate to this

location in the same period.

Considering the impact of plausible outcomes, the impact of the original source concentration

now becomes a far greater contributor in terms of the variance in load. The importance of a

thorough understanding of the long-term closure concentrations is illustrated in the 100-year

Tornado plot (Figure 55).


diversion using the modified Domenico equation for 100 year simulation

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diversion using the modified Domenico equation, with an additional module to

take account of recharge dilution effects – for 100 year simulation


modified Domenico equation – for 100 year simulation

0

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Statistics for Domenico_Recharge_Dilute

Min..1% / 99%..Max 1%..5% / 95%..99% 5%..15% / 85%..95%15%..25% / 75%..85% 25%..35% / 65%..75% 35%..45% / 55%..65%45%..55% 50%


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Figure 55 Tornado sensitivity chart for the stochastic Domenico analytical assessment for

the 100 year simulation. The output is load to the diversion (in kg/day).

Note: K is hydraulic conductivity; i is the hydraulic gradient; por is the effective porosity; long_dispersion

is the longitudinal dispersion; trans_dispersion is the transverse dispersion.

Long-term sensitivity for sulphate (1000 years)

With the plumes reaching a pseudo-steady state with a source fixed concentration, the 1,000 year

sulphate load results (see Figure 56) look similar to the 100 year sulphate load results for this

plume.


modified Domenico equation – for 1000 year simulation

1000 2000 3000 4000 5000 6000 7000

Stochastic_conc

Long_dispersion

Por_Stochastic

Trans_dispersion

i_Stochastic

K_Stochastic

Source_ConcentrationIn

de

pe

nd

en

t V

ari

ab

les

Low High

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Max_lo

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ay)

Time

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5000

Statistics for Max_load_into_river_domenico

10%..15% / 85%..90% 15%..25% / 75%..85% 25%..35% / 65%..75%35%..45% / 55%..65% 45%..55% 50%


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Long-term sensitivity for metals (1,000 years)

A stochastic analysis of the modified Domenico equation was undertaken to determine the

sensitivity of model outputs to modifications to the input parameters for the metal CoC’s that are

sourced from the NOEF. Figure 57 presents the probability of zinc concentration breakthrough

curves at the diversion over a 1,000 year simulation period. The analytical model shows that there

is no probability of any breakthrough occurrence in the first 500 years of closure conditions. In the

latter 500 years of the 1,000 year simulation, there is only an upper probability of 20% or less that

any breakthrough occurs. The median probability has no concentration breakthrough at 1,000

years. The controlling parameter that influences whether any breakthrough occurs is the Kd value.

Figure 57 Stochastic output for zinc concentration (in mg/L) at the Barney Creek diversion

using the modified Domenico equation – for 1000 year simulation

3.1.7 1-Dimensional Reactive Transport Modelling

To provide additional sensitivity analysis on the Modflow Surfact model-predicted results,

simulations were constructed using the hydrogeochemical software PHREEQC (Parkhurst and

Appelo, 2013). The software was utilised to develop a 1-dimensional reactive transport model to

predict the potential for migration of contaminants from NOEF seepage through the subsurface

lithology towards the Barney Creek diversion drain. The PHREEQC results were calibrated with the

model results, and compared to the independently-derived transport simulations calculated using

the Domenico equation and the Geochemist’s Workbench. The construction of the PHREEQC

model, its calibration and the predicted outcomes, are outlined below.

Model Data

The following information, provided by MRM, was used to populate the PHREEQC model:

1. Water quality (Table 3-2):

� Bore GW148D, located to the southeast of the NOEF close to the Barney Creek

diversion, to represent water in the subsurface (aquifer).

0

1

2

3

4

5

6

2100 2200 2300 2400 2500 2600 2700 2800 2900 3000 3100 3200

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10%..15% / 85%..90% 15%..25% / 75%..85% 25%..35% / 65%..75% 35%..45% / 55%..65% 45%..55% 50%


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� NOEF groundwater seepage, calculated at the median and 95th percentile values from

the NOEF GoldSim simulated output (See NOEF Modelling, KCB, 2017).

� A nominal 10 mg/L of bromide was added to the NOEF seepage water to act as a

conservative tracer (i.e., no attenuation) to calibrate the transport model.

2. Aquifer mineralogy from the X-ray diffraction (XRD) results of the weathered bedrock

reported by (KCB, 2017) (Table 3-3). The mineralogy consists primarily of dolomite, quartz

and kaolinite with minor quantities of pyrite. Hydrous-ferric-oxide surfaces (Hfo), which

provide the primary sorption sites in the PHREEQC model (Smith, 1999), are present in

chlorite, clay minerals and other hydrated iron-bearing silicates within the aquifer

mineralogy; these are represented by goethite (FeOOH) and ferrihydrite (Fe(OH)3) in the

model.

3. Initial redox conditions were calculated from the GW148D measured dissolved oxygen

concentrations, oxygen reduction potentials, and GoldSim calculated values. These were

then equilibrated with the prevailing aquifer mineralogy during the simulation.

4. The “wateq4f.dat” database was used as this database contains thermodynamic data for

the aqueous species according to the compilation of (Nordstrom and Archer, 2003) and

the surface complexation constants from (Dzombak and Morel, 1990).

Table 3-2 Water quality parameters (in mg/L except for pH and Eh) used in the PHREEQC

models

Parameter

NOEF Seepage GW148D

Median 95th

Percentile Median

pH 8.2 8.0 8.4

Eh (mV) 200 200 150

Aluminium 0.003 0.015 0.006

Alkalinity 1174 824 555

Arsenic 0.35 0.40 0.004

Bismuth 0.0003 0.001 0.00001

Cadmium 0.001 0.003 0.00002

Calcium 431 428 76

Chloride 109 951 78

Copper 0.14 0.59 0.001

Fluoride 0.75 0.87 0.70

Iron 0.29 0.60 0.002

Lead 0.033 0.072 0.001

Magnesium 8459 9353 67

Manganese 0.46 1.00 0.11

Mercury 0.003 0.003 0.00002

Molybdenum 0.081 0.099 0.014

Nickel 0.37 0.73 0.002

Potassium 135 277 19

Selenium 0.002 0.002 0.001

Sodium 110 769 80

Sulphate 34356 37630 65

Thallium 0.18 0.39 0.002

Zinc 1.52 1.54 0.04

Bromide 10 10 ̶


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Table 3-3 Aquifer mineralogy used in the PHREEQC models

Mineral Formula

Dolomite CaMg(CO3)2

Gibbsite Al(OH)3

Goethite, Ferrihydrite FeOOH, Fe(OH)3

Kaolinite Al2Si2O5(OH)4

Pyrite FeS2

Quartz SiO2

Model Concepts and Construction

The model is constructed using the 1-dimensional reactive transport module in PHREEQC. This

simulates advective-dispersive transport and reactions expected to occur as a contaminant plume

from the NOEF seepage travels along a ~ 550 m pathway into the subsurface lithology (the

aquifer), a path length that is consistent with the outcomes of the TOUGH2 model.

The reactive transport model is constructed with the following physical parameters:

� A column of ~ 550 m, which is based on the straight line distance between the southeast

edge of the NOEF to the Barney Creek diversion channel, designed to be consistent with

the site-wide groundwater models.

� The selected PHREEQC column consists of 20 cells to represent the plume path. The first

10 cells are 2-10 m length. This is to simulate the interactions close to the southeast corner

of the NOEF, where the seepage meets the aquifer water, which may be expected to

produce the highest initial change in water quality. Subsequent cells are 50 m in length.

� Dispersivities of 0.2 to 5 m reflect the scales of the different columns following Gelhar et

al. (1992).

� The column, as the aquifer, initially contains aquifer water (from GW148D), which is

displaced as the plume (represented by the GoldSim NOEF water) is shifted along each

column. 35 shifts are used to provide enough shifts to transport the seepage along all of

the cells.

A schematic conceptual diagram of the column set up is shown in Figure 58.



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Figure 58 Schematic of the PHREEQC model construction. At each stage of transport

through the column the water quality is in equilibrium with the aquifer

mineralogy and the surface sorption sites

At each stage, the water quality is modelled to be in equilibrium with the prevailing physical,

chemical and mineralogical conditions outlined above. Each cell within the column also contains

surface binding sites that allow sorption of dissolved species as the water travels through the

column. These are constructed using PHREEQC’s surface master species applications:

Values of KD have been determined from laboratory batch experiments (ASTM C1733-10) for

arsenic, cadmium, lead and zinc partitioning between solution and weathered bedrock (KCB,

2017); thus the surface sorption reactions in PHREEQC are constrained by MRM site-specific

values. The KDs used in the PHREEQC are consistent with the groundwater model and the Draft

EIS.

Model sensitivity analysis was performed by varying the physical parameters and KD values within

the limits in Table 3-4. Model run durations were varied from 20 years (the groundwater model

breakthrough time) and 100 years (to assess longer-term changes).

Table 3-4 Aquifer parameters and partition coefficients used in the model

Parameter Units Minimum Value Maximum Value

Bulk density, ρ g/cm3 1.5 2.7

Porosity, φ ̶ 0.1 0.3

KD(arsenic) mL/g 0.6 52.9

KD(cadmium) mL/g 2.1 45.8

KD(lead) mL/g 49 124

KD(zinc) mL/g 1.8 13

Results

Model Calibration

The 1-Dimensional reactive transport model was first calibrated with groundwater model results

using a bromide tracer: bromide is a conservative species and a nominal concentration of 10 mg/L

was introduced into the NOEF seepage prior to the transport run. The transport column

properties were adjusted until a bromide breakthrough concentration was observed at 500 m

after 20 years. Figure 59 shows the calibrated model bromide concentrations after 1, 10 and 20

years.



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Figure 59 Calibrated model bromide concentrations at different times

Sulphate, a conservative species, is not expected to attenuate as it is transported through the

aquifer, but it may interact with the equilibrium aquifer mineralogy. Figure 60 shows that the

sulphate breakthrough concentrations from the calibrated 1-dimensional reactive transport

model are comparable to those from the Domenico simulations, with the breakthrough predicted

to be similar to that for bromide and to occur at 500 m after ~ 20 years.



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Figure 60 Predicted sulphate breakthrough curve at an observation point 500 m from the

plume source

Sensitivity Analysis

Dissolved species that are expected to attenuate, were assessed by varying the sorption

parameters. Figure 61 compares the modelled median outputs for arsenic, cadmium, lead and

zinc following variations in the partition coefficients and aquifer solid parameters. In Figure 61, as

expected, lower partition coefficients result in higher predicted concentrations as the dissolved

species are favoured. The predicted concentrations show, however, that these species are still

strongly attenuated compared to the conservative bromide tracer, with values generally predicted

to be close to, or below limits of detection (KCB, 2017). Figure 61 also shows that the amount of

aquifer substrate (i.e., the sites available for sorption), has a minor effect on the predicted

concentrations, with only small variations between concentrations influenced by the minimum

and maximum substrate values. Figure 62 shows predicted concentrations from a model run

calibrated at 100 years with almost identical outcomes. Predicted concentrations using the 95th

percentile values for the NOEF seepage, also show little variation from those predicted from

median values (Figure 63).



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used as a tracer in the models, is included for comparison



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used as a tracer in the models, is included for comparison



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compared using the minimum KD values, minimum solid substrate and 95th

percentile NOEF input water quality. Note the logarithmic scale. Bromide, a

conservative species used as a tracer in the models, is included for comparison

Comparison with Other Models- Geochemist’s Workbench

Simulated outputs from the calibrated PHREEQC 1-dimensional reactive transport model were

compared to those from a calibrated model set up in the Geochemist’s Workbench. PHREEQC and

the Geochemist’s Workbench use the same thermodynamic database to calculate equilibria at

each transport step. The PHREEQC model differs, however, by using the MRM laboratory-derived

partition coefficients to calculate sorption, whereas standard Hfo equilibrium constants are used

for calculations in the Geochemist’s Workbench. Figure 64 and Figure 65 compare the predicted

concentrations of arsenic, cadmium, lead and zinc and the conservative tracer bromide, using the

two models. The PHREEQC model outputs shown in Figure 64 result from the ‘least expected’

substrate parameters, with the minimum partition coefficients and minimum available sorption

sites. As Figure 64 and Figure 65 show, there is excellent agreement between the two models: for

a bromide breakthrough of ~ 20 years, arsenic, cadmium, lead and zinc are strongly attenuated

with low concentrations predicted and only close to the plume source.



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Figure 64 PHREEQC modelled 1-dimensional reactive transport concentrations after 1 to 20

years for arsenic, cadmium, lead and zinc. Also shown are the concentrations of

the conservative bromide tracer at these time intervals



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Figure 65 Geochemist’s Workbench modelled 1-dimensional reactive transport

concentrations after 1 to 20 years for arsenic, cadmium, lead and zinc. Also

shown are the concentrations of the conservative bromide tracer at these time

intervals

Comparison with Other Models- SURFACT Sensitivity Testing

A sensitivity run was completed using the site groundwater model to compare. This provided a

check on the possible impact of Kd values, using bore GW64D as comparative value. The results

indicate that the values used in the assessment are consistent with expected Kd values and that at

a larger scale using a three-dimensional model, similar responses are obtained as provided by the

analytical and reactive transport assessments in the preceding sections.

Figure 66 Modflow SURFACT variation /sensitivity of Kd

Comparison with MRM 2017 Monitoring

As an independent and measured comparison to the modelling, the most recent monitoring data

from MRM for sulphate and zinc concentrations (EcoLogical 2017) can be used to illustrate that

these process are occurring on site to attenuate metal migration in the groundwater (Figure 67

and Figure 68).


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Figure 67 2017 SO4 concentrations (EcoLogical, 2017)

Figure 68 2017 Zn concentrations (EcoLogical, 2017)



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3.1.8 Groundwater Inflows

Inflows to the open cut and underground workings for the LOM are presented in Figure 69. These

are very similar to the Draft EIS case, with a slight reduction in the predicted inflow from the

paleochannel.

Figure 69 Production profile predicted for life of mine

3.1.9 Drawdown beneath Djirrinmini waterhole

The Djirrinmini waterhole is a culturally-significant section of the McArthur River that is

groundwater-fed and relies on sufficient hydraulic head within shallow and deep groundwater

systems to maintain its existence. Drawdown of hydraulic head at Djirrinmini was assessed for the

Phase 3 Project EIS, with the impact assessment model predicting up to 0.7 m of drawdown at

Djirrinmini waterhole associated with pit dewatering. The Draft OMP EIS groundwater impact

assessment predicts up to 0.4m of drawdown in the overburden and weathered bedrock and up

to 0.65m of drawdown in the fresh bedrock adjacent to the waterhole. This magnitude of impact

to Djirrinmini is consistent with the previously approved Project impacts.

3.1.10 Plume extents for Sulphate and metals

Based on the hydrogeological conceptual model, sulphate plumes from the NOEF were expected

to migrate to the south and southeast of the NOEF via the shallow overburden (where coarser-

grained deposits are present in old drainage lines) and through the fractured Cooley Dolomite.

The model predictions showed that sulphate sourced from the NOEF migrates south and

southeast of the NOEF through the shallow overburden, weathered bedrock and upper Cooley

Dolomite bedrock, reporting to Surprise Creek and Barney Creek diversion prior to 2023 and the

open cut void post-2023. This is similar to the Draft EIS.

The life of mine model predictions indicate that the metal (Zn, As, Cd, and Pb) plumes have not

migrated far beyond the source locations. As described in section 3.1.6, it was expected that


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natural attenuation processes would greatly restrict the migration of the metal plumes in the

aquifer pathways.

3.1.10.1 Load reporting to creeks and rivers

Sulphate load reduces for Barney Creek diversion throughout the LOM, relating primarily to a

reduction in baseflow rates post-2023 during the operational period. The sulphate plume front

extents and concentrations migrating from the NOEF through the overburden, weathered bedrock

and shallow bedrock increase during the life of mine, however the receptor shifts from the Barney

Creek diversion to the open cut, leading to an extension of the plume further south to the open

cut void.

Sulphate load progressively increases throughout life of mine for the reach of Surprise Creek that

is adjacent to the TSF. This is expected as shallow seepage from the TSF will increase as the facility

develops, and the bulk of this seepage passes through the permeable shallow strata and reports

to Surprise Creek in the immediate north. This reach of Surprise Creek flows during the dry

season, whereas there is no flow immediately up-gradient and down-gradient of the TSF. These

current field observations support the conceptual and numerical models, in that shallow seepage

will sustain dry season flows in the immediate reach that passes the TSF. To mitigate these loads,

an interception trench is proposed (see Draft EIS). The results used for the impact assessment

consider the influence of the mitigation as described in the Draft EIS.

3.1.11 Water Budget

Figure 70 presents the water budget for the last stress period (December 2027) in the 2023-2027

life of mine simulation. The water budget shows that the dominant inflow is recharge and aquifer

throughflow, followed by the injection of water that reports to the underground workings through

a general head boundary condition. There is a commensurate abstraction of this underground

inflow via pumping well abstraction out of the underground void. The major natural outflows from

the model are evapotranspiration, rejected recharge and baseflow discharge to ephemeral creeks

(represented by drains). For the selected stress period there was a 1.16% error in the overall

water balance.



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Figure 70 Water budget summary for December 2037 stress period

3.1.12 Summary

The life of mine predictions of baseflow discharges, plume extents for sulphate and metals, and

the loads reporting to the creeks and rivers appear to be reasonable and are consistent with the

conceptual understanding of the groundwater flow systems at the MRM site, and of a similar

magnitude to the Draft EIS.

3.2 Closure Simulations

3.2.1 Baseflow estimates to creeks and rivers

Model-predicted groundwater discharge to creeks and rivers during closure and closure

simulations for selected river and creek reaches is presented in Figure 71 to Figure 76 below.

These are similar to the Draft EIS case and can be summarised:

� Barney Creek diversion has a sudden increase in baseflow post-2062. This timing is

coincident with the development of the mine pit lake and recovery of groundwater

conditions in the dewatering affected Cooley Dolomite aquifer. The baseflow reaches a

new equilibrium post-2067 at ~20-25 L/s with subtle fluctuations in wet and dry periods up

to 2167, and then steady at ~23 L/s post-2167.

� Surprise Creek at reach 17_1 is no longer hydraulically influenced by a head at the TSF and

by 2070 the dry season baseflow generally reduces to less than 2 L/s. Surprise Creek at

reach 17_2 has a low long-term dry season baseflow rate of generally less than 2 L/s.

McArthur River diversion has increases in baseflow to three prominent reaches:

� At reach 14 (downstream of diversion) the baseflow increases from 2-3 L/s in 2037-2070

up to 5 L/s post-2070. This is likely related to a new equilibrium condition in aquifers



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down-gradient of the open cut once the mine pit lake level has recovered, and local and

regional groundwater conditions reach their new equilibrium.

� At reach 12 (up-gradient of diversion) the baseflow increases from 1-2 L/s in 2037-2070 up

to 5-10 L/s post-2070. This is likely attributed to two main factors: 1) pit dewatering effects

start to rebound post-2047; and 2) the MIMEX borefield no longer operates post-2037.

There is a lag associated with aquifer rebound and baseflow increases on the order of 10-

20 years.

� At reach 4 (in the diversion) there is steady increase in baseflow from 2054 to 2067 as the

mine pit lake recovers and the Cooley Dolomite and overlying aquifers also recover. Long-

term the diversion baseflow stabilises at ~8 L/s baseflow.


Surprise Creek and Barney Creek diversion



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Figure 72 Long-term closure: baseflow predictions for Surprise Creek and Barney Creek

diversion


Barney Creek



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Figure 74 Long-term closure: baseflow predictions for Barney Creek


McArthur River



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Figure 76 Long-term closure: baseflow predictions for McArthur River

3.2.2 Plume extents for Sulphate

Sulphate plumes are evident at several key locations throughout closure. Snapshots of sulphate

plumes at 2037 (end of open cut mining), 2067, 2167 and 3048 are presented for the overburden,

weathered bedrock and upper bedrock in Figure 77, Figure 78, and Figure 79. These figures

indicate a similar pattern to the Draft EIS, with some increase in sulphate in the areas between the

NOEF and Barney Creek in the long-term as the water levels recover after the pit refills, with a

resulting interception of the plumes at the creek line.


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Figure 77 Predicted sulphate concentrations in the overburden at the end of mining (2037), once the pit lake has recovered (2067), 120 years closure (2167) and 1000 years closure (3048)


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Figure 78 Predicted sulphate concentrations in the weathered bedrock at the end of mining (2037), once the pit lake has recovered (2067), 120 years closure (2167) and 1000 years closure (3048)


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Figure 79 Predicted sulphate concentrations in the upper bedrock at the end of mining (2037), once the pit lake has recovered (2067), 120 years closure (2167) and 1000 years closure (3048)


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3.2.3 Plume extents for Metals

Metals continue to be attenuated during closure with a progressive increase in the spatial (lateral

and vertical) extent of the plumes. Zinc plume maps have again been used to show the indicative

extent of the metal migration between the sources and the receptors during various time

snapshots throughout closure. Figure 80, Figure 81, and Figure 82 show the zinc plumes at 2037,

2067, 2167 and 3048 for the overburden, weathered bedrock and upper bedrock. It is evident

from these figures that metal migration is a much slower process than sulphate migration, and

that the 1,000-year closure snapshot starts to show the extents of the metal plumes from source

to receptor. The closure simulations are based on Tough2/GoldSim results.


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Figure 80 Predicted zinc concentrations in the overburden at the end of mining (2037), once the pit lake has recovered (2067), 120 years closure (2167) and 1000 years closure (3048)


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Figure 81 Predicted zinc concentrations in the weathered bedrock at the end of mining (2037), once the pit lake has recovered (2067), 120 years closure (2167) and 1000 years closure (3048)


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Figure 82 Predicted zinc concentrations in the upper bedrock at the end of mining (2037), once the pit lake has recovered (2067), 120 years closure (2167) and 1000 years closure (3048)


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3.2.4 Load Estimates to Creeks and Rivers

3.2.4.1 Sulphate

Model-predicted sulphate load discharged to creeks and rivers during closure and closure

simulations for selected river and creek reaches is presented in Figure 83 to Figure 88 below. A

complete set of sulphate load graphs for all creek and river reaches is provided in Appendix 1. A

summary of important sulphate load predictions includes:

� Sulphate load increases significantly for Barney Creek diversion from 2062 (where

loads are <500 kg/day) to post-2090 (where loads increase to 2,500 to 4,000 kg/day).

This increase relates to the recovery of groundwater levels in the Cooley Dolomite

after mine pit lake rebound. As the aquifer levels recover to levels above the base of

the diversion, there is hydraulic connection to allow baseflow to re-emerge in this

reach (rather than bypassing under the reach when the aquifer levels where below the

diversion invert).

� Sulphate load to Surprise Creek decreases at reach 17_1 as the TSF source is removed

and local aquifers are ‘flushed’ by fresh rainfall recharge post-2047.

� Sulphate load to Surprise Creek at reach 17_2 is generally low throughout closure.

� Sulphate load reduces for Barney Creek throughout long-term closure (post 2168). This

is primarily related to a cleaning up of water quality in the shallow aquifers discharging

to Little Barney Creek in the immediate south of the TSF.

� McArthur River and McArthur River diversion are predicted to have low sulphate loads

during closure.

Figure 83 TSF Operations period and first 100 years of closure: sulphate load predictions for

Surprise Creek and Barney Creek diversion


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Figure 84 Long-term closure: sulphate load predictions for Surprise Creek and Barney Creek

diversion


Barney Creek


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Figure 86 Long-term closure: sulphate load predictions for Barney Creek


McArthur River


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Figure 88 Long-term closure: sulphate load predictions for McArthur River

3.2.4.2 Comparison of loads to Barney Creek Diversion between GSL cover and Draft EIS

The change in sulphate loads to the surface water as a result of the implementation of the GSL

cover is most clearly indicated by considering the loads to this section in the 100 years after the

pit lake has recovered (i.e 2068 to 2167). The time series over this period is shown on Figure 89.

Figure 89 Comparison of projected loads to Barney Diversion in the first 100 years after pit

rebound


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3.2.4.3 Zinc Load

Subtle increases in zinc load are noted on the long-term closure simulation for Surprise Creek,

Barney Diversion, and McArthur River. Figure 90 presents the long-term zinc loads to Surprise

Creek and Barney Creek diversion. There is a small increase in zinc load over an 880-year period in

the Barney Creek diversion.

Figure 91 presents the long-term zinc loads to McArthur River. There is a subtle increase in zinc

load over an 880-year period for the diversion (at reach 4).

Figure 90 Long-term closure: zinc load predictions for Surprise Creek and Barney Creek

diversion

Figure 91 Long-term closure: zinc load predictions for McArthur River


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3.2.4.4 Arsenic, Cadmium and Lead Load

Arsenic, cadmium and lead show similar subtle increases for the long-term closure simulation for

Surprise Creek, Barney Diversion, and McArthur River. Appendix I presents individual graphs for

arsenic, cadmium and lead loads to all creek and river reaches for the closure period.

3.2.5 Groundwater inflows

Inflows to the open cut and underground workings for the closure and early closure (up to 2067)

are presented in Figure 92.

The major features of the predicted inflows are as follows:

� Underground inflows remain steady at 10 ML/day, buffered by a general head set at below

the base of the open cut. This inflow was maintained in the model to mimic the inflow

contributions experienced by the underground working post-2009.

� Palaeochannel inflow starts at around 20 L/s in 2038 and progressively reduces throughout

closure as the mine pit lake slowly recovers. There is a distinct seasonality in the

palaeochannel inflow rate with up to 5 L/s difference between peak wet season rates and

dry season rates.

� Upper bedrock (model layers 5 to 8) inflow reduces to less than 10 L/s as the mine pit lake

recovers.

� Lower bedrock (model layers 9 to 14) inflow is typically less than 10 L/s.

� The underground flows have been assumed to be resolved once the pit expands to

consume most of the previous underground workings.

Figure 92 Water Production profile predicted for closure and early closure


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3.2.6 Comparison of Closure Predictions to Expected Groundwater Behaviour

This section of the report compares the model predictions for closure with expected groundwater

behaviour, which is largely based on site knowledge used to develop the site conceptual

hydrogeological model.

3.2.6.1 Baseflow Discharges

The most significant prediction for closure baseflow discharge is the appreciable increase in

baseflow in the Barney Creek diversion post-2062. This increase is consistent with the conceptual

understanding of groundwater-surface water interactions influenced by dewatering of the

permeable Cooley Dolomite shallow bedrock (which causes hydraulic disconnection between the

shallow groundwater and the diversion). Post-mining recovery of drawdown is expedited by the

rapid infilling of the Mine Pit Lake. By 2070, the groundwater flow system has reached a quasi-

steady-state condition with stable groundwater levels, baseflow discharge rates and sulphate

loads to the surface water systems. The long-term equilibrium of ~23 L/s (baseflow to Barney

Creek diversion) shows that the contribution of NOEF seepage has increased the baseflow

discharge rate in comparison to pre-2014 conditions. This is reasonable as the seepage

contribution from NOEF will lead to an increased hydraulic gradient facilitated by the short path-

length between the NOEF and the diversion.

Without continued seepage from the TSF, Surprise Creek baseflow discharge rates are reduced for

the long-term closure condition. This is considered to be a reasonable prediction, as it backs the

conceptual understanding that the TSF currently supports baseflow discharge to Surprise Creek,

and the creek is mainly dry in the dry season directly up-gradient and down-gradient of the TSF

(where the influence of TSF seepage is not present).

The McArthur River diversion baseflow discharge rates are predicted to recover during the closure

period and sustain the new equilibrium levels for the long-term closure condition. This recovery in

baseflow is conceptually sound since pit dewatering effects will be reversed post-mining and

groundwater elevations will rise and re-establish gradients towards the river/diversion and

increase baseflow.

3.2.6.2 Plume extents for sulphate

The sulphate plume originating at the TSF flushes out progressively from 2067 to 3048. This is a

rational prediction given that: i) the TSF source is removed from 2037 to 2047; ii) 1,000 years of

rainfall recharge will force the plume to push through the aquifer pathway and report to the

nearest down-gradient receptor; iii) sulphate is a conservative parameter and will tend to not be

subject to reaction processes and attenuation, and as such, will readily migrate through a given

source-pathway-receptor system.

The NOEF contributes long-term sulphate-rich seepage to the groundwater systems situated

down-gradient of the NOEF. The long-term sulphate plume concentrates to the southeast of the

NOEF in an area between the Haul Bridge and Barramundi Dreaming up-gradient of the Barney

Creek diversion. The long-term plume extents are consistent with the conceptual model for

groundwater flow systems at this part of the site:

� Seepage from the NOEF is reduced during the closure period due to the effectiveness of

the cover system.


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� The reduction in seepage leads to a re-instatement of dominant west-to-east flow

conditions under the facility.

� Recovery of the regional drawdowns associated with the open cut remove the driving

gradient from north-to-south between the NOEF and the open cut.

� Groundwater seepage from the NOEF should, therefore, migrate to the east and southeast

of the facility and discharge to the lowest point in the topography – being the Barney

Creek diversion. Therefore, the plume should be logically concentrated in the southeast

corner of the NOEF.

3.2.6.3 Plume extents for metals

Metal plumes emerge from the NOEF and TSF over the 1,000-year closure simulations. These

plumes are much slower in their migration than the conservative sulphate species, which is

attributed to natural attenuation to the aquifer matrix. The following observations are made from

the current site knowledge which support this delay in metal plume emergence:

5. The TSF and NOEF plumes are expected to stay neutral.

6. There is relatively high iron content and clay content in the units underlying the two

sources (TSF and NOEF) facilitating an abundance of sorption surfaces for attenuation to

occur.

7. Laboratory analysis of field samples have determined Kd values that support point 2

above.

8. Field monitoring through MRM’s groundwater monitoring program has shown that there is

strong attenuation of metals, and to date, there is no metal plume coincident with the

current sulphate plume.

3.2.6.4 Load reporting to creeks and rivers

Sulphate load increases at the Barney Creek diversion commensurate with the re-establishment of

hydraulic connection between the aquifer and the diversion, and a marked increase in baseflow

discharge post-2062. As described above, this increase in baseflow and load is consistent with the

understanding of groundwater flow processes at the site. Given that the long-term sulphate

source term for NOEF seepage is high, it makes sense that the plume concentrations would not

decrease over the long term.

Subtle increases in zinc load are noted in the long-term closure simulation for Surprise Creek,

Barney diversion, and McArthur River. Arsenic, cadmium and lead show similar subtle increases

for the long-term closure simulation for Surprise Creek, Barney Diversion, and McArthur River.

Dissolved metal plumes may develop over very long periods of time (thousands of years and

greater) but breakthrough of more conservative contaminants like sulphate would be expected to

indicate development of preferential pathways and act as an early warning system for the metal

plumes.

3.2.7 Additional sensitivity runs with mitigation

Two additional mitigation scenarios have been considered. Appendix 2 provides the results of

additional modelling for an updated interception trench for the TSF/Surprise Creek system, while

Appendix 3 provides an outline of potential groundwater interception in the area between the

NOEF and Barney Creek (based on the Draft EIS results with a CCL cover). These results


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demonstrate the effectiveness of the potential mitigation strategies, which, if deemed to be

necessary, would be effective in reducing loads reaching the Barney Creek diversion.

These options can be implemented, if required, but do not form part of the base case, as the

surface water modelling results with the groundwater and other results included have provided

the basis for the water management plans proposed to be implemented to meet the water quality

objectives of the downstream monitoring point in the McArthur River (see WRM, 2017).


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4 DISCUSSION ON RESULTS AND SENSITIVITY ASSESSMENTS COMPARED TO EIS

SUBMISSION

The modelling presented in this report has been undertaken to include specific updates to MRM’s

proposed project plan and to address feedback received subsequent to the Draft EIS submission.

While most of the conceptual understanding of the site is largely consistent with the Draft EIS

reporting, several changes to the approach have been included in the modelling to better reflect

the expected site conditions over the life of mine and into closure. The most significant changes

relate to the how the NOEF water balance has been simulated and the resultant water quality

from this facility under conditions of elevated temperatures and low water content. In addition,

the final void water quality modelling approach has accounted for the establishment of

stratification in the mine pit lake over time, under variety of flow conditions. As previously, the

outcomes from all of these models has been used conjunctively in the surface water modelling

and broader impact assessments that have been completed for this Supplementary EIS

submission.

A further change to the report, has been the more explicit consideration of alternative scenarios

and completion of sensitivity analyses in the various models. The impact on calibration of altering

the permeabilities has been indicated in Section 2. A key consideration has been the potential for

metal migration and a detailed section has been included which considers several different

approaches (ranging from simplified 1-D analytical models to reactive transport models with

different hydrogeochemical codes) to better assess the potential for metal attenuation and metal

migration. This assessment indicated that based on the site characterisation and consistent with

MRM’s groundwater monitoring results, under neutral conditions metal attenuation will continue

to play an important role in reducing the mobility of the metals of concern in the aquifers. The

modelling of the NOEF (See separated report on the NOEF water quality, KCB, 2017) suggest that

neutral conditions are expected over the long-term duration of the simulations.

Further sensitivity results that have been included in this regard for the Supplementary EIS include

(see Appendix 1 for details of these assessments):

� Inclusion of a variety of alternative scenarios for the NOEF modelling to provide a broad

understanding of a range of potential outcomes. While the proposed base case will be a

GSL integrated into the cover, with a low permeability engineered base, several

alternatives to this were considered, including assessment of a partial cover failure of the

GSL (which would then act more like a compacted clay liner) and several iterations of

alternative engineered bases. Both the flows and resultant water quality and contaminant

loads were assessed for these cases; more importantly the more extreme case has been

included in a surface water modelling sensitivity assessment so that an appropriate water

management plan could be developed to allow for this extreme eventuality as part of

MRM’s adaptive management approach.

� As indicated in the concurrent NOEF Flow and Water Quality report (KCB, 2017), proposed

geosynthetic liner (GSL) cover system reduces cumulative loads to groundwater

significantly by a factor of five or more for sulphate and zinc over the next 100 years,

compared to the previously proposed compacted clay liner (CCL) cover system

� Several iterations of the water quality modelling for the NOEF have been considered. The

most important of these (apart from the changes to the cover which impact on reactivity,


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water quality and loads) were assessments which consider scenarios under which acid

leachate/seepage may arise in NOEF. A case where one of the High PAF zones completely

acidifies has been considered to assess the change to loads to groundwater, as well as a

case where the proportion of PAF material is doubled in the NOEF. These results have

again been considered in the broader context of the site so that sufficient contingency is

available in the management plans should these conditions unexpectedly arise.

The transient calibration of the updated model provided a sound basis for the predictive

simulations:

� Transient predicted heads are replicated in trend and elevation to measured hydrograph

data, and show strong prediction of the seasonal effects on groundwater across the model

domain. This head response to dam seepage from the PRODs is replicated in terms of

timing and magnitude of head change.

� Dewatering rates predicted during the conditioning model (underground) and calibration

model (open cut) match observed and anecdotal dewatering rates over the same period.

� Statistical assessment of model calibration has improved since the Draft EIS, exceeds

industry standard, and supports the visual calibration performance observed in the

hydrographs.

� Baseflow predictions mimic dry and wet season conditions, respecting the ephemeral

nature of these systems.

� Predicted changes to water levels and flows are of similar magnitude to those reported by

the Draft EIS and previously by the Phase 3 Groundwater Assessment. These include

baseflow discharges to creeks, rivers and diversions that will change due to seepage from

the mine overburden facilities and dewatering of the expanding open cut operation.

� Predicted sulphate plumes are consistent with the site understanding with respect to

source-pathway-receptor relationships, with conservative levels of sulphate being

predicted and natural sources of sulphate generation being included in the transient

simulations. Inferred flow directions and plume migrations are consistent with the

conceptual source-pathway-receptor model for the site.

� Acceptable calibration performance and sound translation of the conceptual setting into

the numerical environment are both considered to have been achieved with this model.

Groundwater modelling results indicate similar responses to those outlined in the Draft EIS. The

most significant changes are due to the updated structural geology and more importantly the

updated understanding of the long-term response of the NOEF from the Tough2 and associated

water quality modelling.

Contaminant transport modelling has been completed for a variety of scenarios related to options

for the management of NOEF. The outcomes from these scenarios are changes to flows and

especially concentrations and loads that report to receptors, with the MRM surface water system

the most important of these. All of these results have been considered in the surface water

assessments and management plans to cover the range of results (other than just the base case)

developed by MRM to protect water quality downstream of the site. While sulphate

concentrations are expected to continue to increase due to the high concentrations expected

from the NOEF, concerns about long-term metal migration have been addressed through


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modelling of various flow and NOEF scenarios and the sensitivity analysis described above. For

these metals, with zinc used as an example, the Kd value is the controlling influence on the long-

term migration and emergence of a plume at the receptor. Using field-derived values of Kd, there

is little to no breakthrough of Zn at the receptors for the selected aquifer pathways, in the closure

design period.

The major impact to surface water systems is again predicted at the Barney Creek diversion during

closure. Sulphate loads into this section of the creek, are predicted to increase from <500 kg/day

at closure to between 2500-4000 kg/day 20 years after operations closure. The increase in load is

primarily associated with long-term seepage from the NOEF migrating through weathered and

fractured bedrock reporting to the diversion (as previously reported in the Draft EIS). The

proposed NOEF design with a low permeability GSL as part of the cover system and the

engineered base greatly restricts the loads emanating from the NOEF and reaching the creek,

however a generous allowance for defects has been included to provide some conservatism to the

results. Dewatering of the open cut during operations results in a gradient towards the open cut

in the bedrock aquifer in the vicinity of the diversion, therefore, reducing baseflow to the

diversion during mining, and drawing the contaminant plume below the level of the diversion (see

Draft EIS reporting, KCB, 2017). After operations, the engineered rapid recovery pit lake water

level, supported by natural recharge to the aquifers, allows the bedrock aquifer hydraulic head to

rebound and re-establish a hydraulic connection with the diversion.

A subtle increase in metal load (e.g. Zinc load at Barney diversion increases from 0.04 to 0.05

kg/day over 1000 years) is also predicted in the Barney Creek diversion after 400 years of closure.

This delayed plume migration to the diversion is a result of the sorption of the metals in the

aquifer matrix; this is consistent with current site observations and the results from the Draft EIS.

There is an increase in sulphate load reporting to Surprise Creek during the life of mine. This

increase is associated with tailings seepage migrating a short distance north towards Surprise

Creek, in spite of the proposed interception trench put in place to capture the majority of the

load. This sulphate load diminishes during closure as the tailings is removed and placed in-pit.

After approximately 100 years the sulphate load in Surprise Creek is reduced from 2,000 kg/day

back to <500 kg/day. An alternative and more effective mitigation plan is currently in the design

phase and this should act to limit the loads to Surprise Creek further.

The hydrological impact assessment completed by WRM, considers the environmental impact of

baseflow discharge loads for sulphate and metals, particularly in the dry season when the

baseflow constitutes the major surface water flow component.

Closure waste and water management for the site was considered in an integrated manner. By

considering the same scenarios and drivers on water volumes and water quality using the

groundwater model, the mine pit lake model and the site-wide surface water quality model, a

holistic assessment of the closure impacts has been obtained. The results have been used by

WRM to develop water management strategies that limit the impact on downstream surface

water for the 1,000 year periods simulated (WRM, 2017).


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5 CLOSING

All water quality modelling is inherently based upon a number of assumptions that reduce the

number of governing factors to manageable proportions given the typical limitations in availability

of site-specific data and information. Based upon the assumptions listed in this report and in

agreement with MRM, the water quality predictions presented herein should be viewed at a level

of accuracy required to assess the likelihood of large scale changes or applicable mine effluent

quality guidelines being exceeded, rather than the results being intended as a precise estimation

of all parameter concentrations over the 1,000 year closure period.

This report is an instrument of service of Klohn Crippen Berger Ltd. The report has been prepared

for the exclusive use of McArthur River Mining Pty Ltd (Client) for the specific application to the

MRM EIS. The report's contents may not be relied upon by any other party without the express

written permission of Klohn Crippen Berger. In this report, Klohn Crippen Berger has endeavoured

to comply with generally-accepted professional practice common to the local area. Klohn Crippen

Berger makes no warranty, express or implied.

KLOHN CRIPPEN BERGER LTD.

Brent Usher, PhD. PrSciNat Chris Langton, PGeo

Project Manager, Senior Hydrogeochemist & Associate Senior Reviewer, Principal Hydrogeologist


Supplementary EIS

Site Groundwater

Report


Page 123


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and Proposed Mitigation Options, McArthur River Mine. Report prepared for Hatch

Associates Pty Ltd, May 2011.

Aziz C.E., Newell C.J., Gonzales J.R., Haas P., Clement T.P. and Y-W. Sun. 2000. BIOCHLOR Version 1.0 User’s Manual. EPA/600/R-00/008.

Bethke, C. M. 2008. “The Board of Trustees of the University of Illinois (2008) The Geochemists

Workbench Programmes Rxn.” Act2, Tact, SpecE8, Aqplot, React, Gtplot, X1t, X2t, and Xtplot.

Debye P and Hückel E (1923) Zur Theorie der Elektrolyte.- Phys.Z.; 24: pp 185-206.

Connell Hatch. 2007. Detailed Design Report, Barney Creek Haul Road Bridge – McArthur River

Mine Expansion. Report submitted to Xstrata Zinc Pty Ltd, 1 June 2007.

Crabb, D M, 1956, “Geochemical Survey 1956”, Appendix I to “Report on Bauhinia and McArthur

River Areas NT – Field Season 1956” Report to Mt Isa Mines Ltd, February, 1957.

Domenico P.A. and G.A. Robbins. 1985. A new method of contaminant plume analysis. Ground Water, Vol. 23, No. 4, pp. 476–485.

Domenico P.A. 1987. An Analytical Model for Multidimensional Transport of a Decaying Contaminant Species. Journal of Hydrology, Vol. 91, pp. 49-58.

Eco Logical Australia (2017). McArthur River Mining Groundwater, Surface Water & Fluvial

Sediment Monitoring Report 2016/17. Prepared for McArthur River Mining, Glencore

Elberling Bo and Damgaard Lars Riis (2001) Microscale measurements of oxygen diffusion and

consumption in subaqueous sulfide tailings, In Geochimica et Cosmochimica Acta, Volume

65, Issue 12

ESI, 2016. Groundwater Vistas Version 6.59 Build 2.

GHD, 2017. MRM 2016 ERI Survey. Report to MRM, November 2017.

Gleisner M 2005. Quantification of mineral weathering rates in sulfidic mine tailings under water-

saturated conditions. PhD thesis. Stockholm University, Faculty of Science, Department of

Geology and Geochemistry.

Glencore, 2017. Project Definition for Supplementary EIS.

Goldsim Techonology Group 2011. Goldsim Version 11.1 User’s Guide’ Volumes 1 and 2, Goldsim

Technology Group, Issaquah, Washington USA, May 2014.

HydroGeoLogic, 2016. MODHMS/MODFLOW-SURFACT: A comprehensive MODFLOW-based

Hydrologic Modelling System.

Hatch, 2011a. Review of Seepage Mitigation Options. Report prepared for Xstrata Zinc, 26 July

2011.

Hatch, 2011b. Water Balance Review. Report prepared for Xstrata Zinc, 26 May 2011.

KCB, 2016. MRM groundwater Report: Monitoring Report 2014-2016. Report prepared for MRM,

9 September 2016.

KCB, 2017. MRM Draft EIS Groundwater Impact Assessment Report Report prepared for MRM,

February 2017.


Supplementary EIS

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Langmiur (1997). Aqueous Environmental Geochemistry. PRENTICE HALL Upper Saddle River, New

Jersey 07458.

Lapakko KA (1994) Subaqueous disposal of mine waste: laboratory investigation. Bureau of Mines

Special Publication, SP 06 A-94, pp 270–278

Limousin et al (2007). Sorption isotherms: A review on physical bases, modelling and

measurement. Applied Geochemistry, v22, p249–275.

Logan, R (2017) Summary of Geological Investigations completed at MRM during 2016. Report

prepared for McArthur River Mine.

Murray, W J, 1964, Background information on the HYC Lead-Zinc Deposit, McArthur River,

Northern Territory, Carpentaria Exploration Company Pty Ltd, Technical Report No 80.

Murray, W J, 1975, McArthur River HYC lead-zinc and related deposits, NT., The Australian

Institute of Mining and Metallurgy, Monograph Series, No 5, pp329-339.

MEND (1989) SUBAQUEOUS DISPOSAL OF REACTIVE MINE WASTES: AN OVERVIEW. MEND Project

2.11.1a

Parkhurst, D.L., Appelo, C.A.J., 2013. Description of input and examples for PHREEQC version 3 - A

computer program for speciation, batch-reaction, one-dimensional transport, and inverse

geochemical

Pruess, K., C.M. Oldenburg, and G.J. Moridis. 2012. TOUGH2 user’s guide, Version 2. Revised ed.

Rep. LBNL-43134. Lawrence Berkeley Natl. Lab., Berkeley, CA.

http://esd.lbl.gov/files/research/projects/tough/documentation/

TOUGH2_V2_Users_Guide.pdf (accessed August 2014).

RPS. 2012a. Shallow Groundwater Investigation, McArthur River Mine. Report prepared for

Xstrata Zinc, 4 December 2012.

RPS. 2012b. Groundwater Modelling of Seepage from MRM SEPROD. Report prepared for AMDD

and METSERVE, 16 July 2012.

RPS. 2013a. McArthur River Mine, Deep Groundwater Investigation. Report prepared for Xstrata

Zinc, 8 April 2013.

RPS. 2013b. McArthur River Mine Site-wide Groundwater Model. Report prepared for Xstrata

Zinc, 15 November 2013.

Rutqvist, J. & O. Stephansson. 2003. “The Role of Hydromechanical Coupling in Fractured Rock

Engineering.” Hydrogeology Journal. 11(1): 7-40.

Smith, J.W. 1972. Bauhinia Downs, Northern Territory: 1:250,000 Geological Series - Explanatory

Notes. SE5303. Bureau of Mineral Resources, Geology and Geophysics, Canberra.

USEPA (1999a). UNDERSTANDING VARIATION IN PARTITION COEFFICIENT, Kd, VALUES, Volume I:

The Kd Model, Methods of Measurement, and Application of Chemical Reaction Codes.


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USEPA (1999b). UNDERSTANDING VARIATION IN PARTITION COEFFICIENT, Kd, VALUES, Volume II:

Review of Geochemistry and Available Kd Values for Cadmium, Cesium, Chromium, Lead,

Plutonium, Radon, Strontium, Thorium, Tritium (3H), and Uranium.

USEPA (2004). UNDERSTANDING VARIATION IN PARTITION COEFFICIENT, Kd, VALUES, Volume III:

Review of Geochemistry and Available Kd Values for Americium, Arsenic, Curium, Iodine,

Neptunium, Radium, and Technetium.

URS. 2004. McArthur River Mine, Tailings Storage Facility Rehabilitation – Cell 1 Concept Design.

Report submitted to Xstrata McArthur River Mines, 10 December 2004.

URS. 2005a. MRM Expansion EIS – Groundwater Investigations to Determine the Potential Impacts

of Dewatering. Report submitted to Xstrata Plc, 29 April 2005.

URS. 2005b. Groundwater and Surface Water Investigations of the McArthur River. Report

prepared for Xstrata Plc, 9 December 2005.

URS. 2006. Simulation of Proposed Tailings Storage Facility to Assess Potential Seepage Impacts,

McArthur River Mine. Report submitted to Xstrata Plc, 20 June 2006.

URS. 2012. MRM Phase 3 Development Project EIS – Groundwater. Report prepared for Mining &

Energy Technical Services Pty Ltd, 16 January 2012.

Tropical Water Solutions, 2017 McArthur River Mine open cut: 3D Hydrodynamic Modelling for a

Mine Pit Lake System. November 2017.

Vandenberg, J.A., Herrell, M., Faithful, J.W. et al. Mine Water Environ (2016) 35: 350.

https://doi.org/10.1007/s10230-015-0337-5

WRM Water and Environment (2017). Surface water impact assessment for the McArthur River

Mine Overburden Management Project Environmental Impact Statement. Report prepared

for METServe on behalf of McArthur River Mining. Brisbane: WRM Water and

Environment, pp.1-443.

WRM Water and Environment (2017). Updated Base Case Waterways model impact assessment

for the MRM OMP EIS



Report



APPENDIX I

Sensitivity Results

McArthur River Mining Pty Ltd Supplementary EIS

Appendix Sensitivity Analyses Draft

Appendix_I.docx

Page I-1


Appendix I

I-1 GROUNDWATER MODEL RESULTS FROM DIFFERENT SCENARIOS

I-1.1 Results from GSL cover case

I-1.1.1 Surprise & Barney Creek diversion

Figure A1- 1: Simulated flow rate over LOM to Surprise and Barney Creek diversion

Figure A1- 2: Simulated SO4 load rate over LOM to Surprise and Barney Creek diversion



Appendix_I.docx

Page I-2


Figure A1- 3: Simulated Zn load rate over LOM to Surprise and Barney Creek diversion

Figure A1- 4: Simulated As load rate over LOM to Surprise and Barney Creek diversion



Appendix_I.docx

Page I-3


Figure A1- 5: Simulated Cd load rate over LOM to Surprise and Barney Creek diversion

Figure A1- 6: Simulated Pb load rate over LOM to Surprise and Barney Creek diversion



Appendix_I.docx

Page I-4


Figure A1- 7: Simulated flow rate over closure and 100yrs into closure to Surprise and Barney Creek diversion

Figure A1- 8: Simulated SO4 load rate over closure and 100yrs into closure to Surprise and Barney Creek diversion



Appendix_I.docx

Page I-5


Figure A1- 9: Simulated Zn load rate over closure and 100yrs into closure to Surprise and Barney Creek diversion

Figure A1- 10: Simulated As load rate over closure and 100yrs into closure to Surprise and Barney Creek diversion



Appendix_I.docx

Page I-6


Figure A1- 11: Simulated Cd load rate over closure and 100yrs into closure to Surprise and Barney Creek diversion

Figure A1- 12: Simulated Pb load rate over closure and 100yrs into closure to Surprise and Barney Creek diversion



Appendix_I.docx

Page I-7


Figure A1- 13: Simulated flow rate for long term into closure to Surprise and Barney Creek diversion

Figure A1- 14: Simulated SO4 load rate for long term into closure to Surprise and Barney Creek diversion



Appendix_I.docx

Page I-8


Figure A1- 15: Simulated Zn load rate for long term into closure to Surprise and Barney Creek diversion

Figure A1- 16: Simulated As load rate for long term into closure to Surprise and Barney Creek diversion



Appendix_I.docx

Page I-9


Figure A1- 17: Simulated Cd load rate for long term into closure to Surprise and Barney Creek diversion

Figure A1- 18: Simulated Pb load rate for long term into closure to Surprise and Barney Creek diversion



Appendix_I.docx

Page I-10


I-1.1.2 Barney Creek

Figure A1- 19: Simulated flow rate over LOM to Barney Creek

Figure A1- 20: Simulated SO4 load rate over LOM to Barney Creek



Appendix_I.docx

Page I-11


Figure A1- 21: Simulated Zn load rate over LOM to Barney Creek

Figure A1- 22: Simulated As load rate over LOM to Barney Creek



Appendix_I.docx

Page I-12


Figure A1- 23: Simulated Cd load rate over LOM to Barney Creek

Figure A1- 24: Simulated Pb load rate over LOM to Barney Creek



Appendix_I.docx

Page I-13


Figure A1- 25: Simulated flow rate over closure and 100 yrs into closure to Barney Creek

Figure A1- 26: Simulated SO4 load rate over closure and 100 yrs into closure to Barney Creek



Appendix_I.docx

Page I-14


Figure A1- 27: Simulated Zn load rate over closure and 100 yrs into closure to Barney Creek

Figure A1- 28: Simulated As load rate over closure and 100 yrs into closure to Barney Creek



Appendix_I.docx

Page I-15


Figure A1- 29: Simulated Cd load rate over closure and 100 yrs into closure to Barney Creek

Figure A1- 30: Simulated Pb load rate over closure and 100 yrs into closure to Barney Creek



Appendix_I.docx

Page I-16


Figure A1- 31: Simulated flow rate for long term into closure to Barney Creek

Figure A1- 32: Simulated SO4 load rate for long term into closure to Barney Creek



Appendix_I.docx

Page I-17


Figure A1- 33: Simulated Zn load rate for long term into closure to Barney Creek

Figure A1- 34: Simulated As load rate for long term into closure to Barney Creek



Appendix_I.docx

Page I-18


Figure A1- 35: Simulated Cd load rate for long term into closure to Barney Creek

Figure A1- 36: Simulated Pb load rate for long term into closure to Barney Creek



Appendix_I.docx

Page I-19


I-1.1.3 McArthur River

Figure A1- 37: Simulated flow rate over LOM to McArthur River

Figure A1- 38: Simulated SO4 load rate over LOM to McArthur River



Appendix_I.docx

Page I-20


Figure A1- 39: Simulated Zn load rate over LOM to McArthur River

Figure A1- 40: Simulated As load rate over LOM to McArthur River



Appendix_I.docx

Page I-21


Figure A1- 41: Simulated Cd load rate over LOM to McArthur River

Figure A1- 42: Simulated Pb load rate over LOM to McArthur River



Appendix_I.docx

Page I-22


Figure A1- 43: Simulated flow rate over closure and 100 yrs into closure to McArthur River

Figure A1- 44: Simulated SO4 load rate over closure and 100 yrs into closure to McArthur River



Appendix_I.docx

Page I-23


Figure A1- 45: Simulated Zn load rate over closure and 100 yrs into closure to McArthur River

Figure A1- 46: Simulated As load rate over closure and 100 yrs into closure to McArthur River



Appendix_I.docx

Page I-24


Figure A1- 47: Simulated Cd load rate over closure and 100 yrs into closure to McArthur River

Figure A1- 48: Simulated Pb load rate over closure and 100 yrs into closure to McArthur River



Appendix_I.docx

Page I-25


Figure A1- 49: Simulated flow rate for long term into closure to McArthur River

Figure A1- 50: Simulated SO4 load rate for long term into closure to McArthur River



Appendix_I.docx

Page I-26


Figure A1- 51: Simulated Zn load rate for long term into closure to McArthur River

Figure A1- 52: Simulated As load rate for long term into closure to McArthur River



Appendix_I.docx

Page I-27


Figure A1- 53: Simulated Cd load rate for long term into closure to McArthur River

Figure A1- 54: Simulated Pb load rate for long term into closure to McArthur River



Appendix_I.docx

Page I-28


I-1.2 Results from CCL cover case

I-1.2.1 Surprise & Barney Creek diversion

Figure A1- 55: Simulated flow rate over LOM to Surprise and Barney Creek diversion

Figure A1- 56: Simulated SO4 load rate over LOM to Surprise and Barney Creek diversion



Appendix_I.docx

Page I-29


Figure A1- 57: Simulated Zn load rate over LOM to Surprise and Barney Creek diversion

Figure A1- 58: Simulated As load rate over LOM to Surprise and Barney Creek diversion



Appendix_I.docx

Page I-30


Figure A1- 59: Simulated Cd load rate over LOM to Surprise and Barney Creek diversion

Figure A1- 60: Simulated Pb load rate over LOM to Surprise and Barney Creek diversion



Appendix_I.docx

Page I-31


Figure A1- 61: Simulated flow rate over closure and 100yrs into closure to Surprise and Barney Creek diversion

Figure A1- 62: Simulated SO4 load rate over closure and 100yrs into closure to Surprise and Barney Creek diversion



Appendix_I.docx

Page I-32


Figure A1- 63: Simulated Zn load rate over closure and 100yrs into closure to Surprise and Barney Creek diversion

Figure A1- 64: Simulated As load rate over closure and 100yrs into closure to Surprise and Barney Creek diversion



Appendix_I.docx

Page I-33


Figure A1- 65: Simulated Cd load rate over closure and 100yrs into closure to Surprise and Barney Creek diversion

Figure A1- 66: Simulated Pb load rate over closure and 100yrs into closure to Surprise and Barney Creek diversion



Appendix_I.docx

Page I-34


Figure A1- 67: Simulated flow rate for long term into closure to Surprise and Barney Creek diversion

Figure A1- 68: Simulated SO4 load rate for long term into closure to Surprise and Barney Creek diversion



Appendix_I.docx

Page I-35


Figure A1- 69: Simulated Zn load rate for long term into closure to Surprise and Barney Creek diversion

Figure A1- 70: Simulated As load rate for long term into closure to Surprise and Barney Creek diversion



Appendix_I.docx

Page I-36


Figure A1- 71: Simulated Cd load rate for long term into closure to Surprise and Barney Creek diversion

Figure A1- 72: Simulated Pb load rate for long term into closure to Surprise and Barney Creek diversion



Appendix_I.docx

Page I-37


I-1.2.2 Barney Creek

Figure A1- 73: Simulated flow rate over LOM to Barney Creek

Figure A1- 74: Simulated SO4 load rate over LOM to Barney Creek



Appendix_I.docx

Page I-38


Figure A1- 75: Simulated Zn load rate over LOM to Barney Creek

Figure A1- 76: Simulated As load rate over LOM to Barney Creek



Appendix_I.docx

Page I-39


Figure A1- 77: Simulated Cd load rate over LOM to Barney Creek

Figure A1- 78: Simulated Pb load rate over LOM to Barney Creek



Appendix_I.docx

Page I-40


Figure A1- 79: Simulated flow rate over closure and 100 yrs into closure to Barney Creek

Figure A1- 80: Simulated SO4 load rate over closure and 100 yrs into closure to Barney Creek



Appendix_I.docx

Page I-41


Figure A1- 81: Simulated Zn load rate over closure and 100 yrs into closure to Barney Creek

Figure A1- 82: Simulated As load rate over closure and 100 yrs into closure to Barney Creek



Appendix_I.docx

Page I-42


Figure A1- 83: Simulated Cd load rate over closure and 100 yrs into closure to Barney Creek

Figure A1- 84: Simulated Pb load rate over closure and 100 yrs into closure to Barney Creek



Appendix_I.docx

Page I-43


Figure A1- 85: Simulated flow rate for long term into closure to Barney Creek

Figure A1- 86: Simulated SO4 load rate for long term into closure to Barney Creek



Appendix_I.docx

Page I-44


Figure A1- 87: Simulated Zn load rate for long term into closure to Barney Creek

Figure A1- 88: Simulated As load rate for long term into closure to Barney Creek



Appendix_I.docx

Page I-45


Figure A1- 89: Simulated Cd load rate for long term into closure to Barney Creek

Figure A1- 90: Simulated Pb load rate for long term into closure to Barney Creek



Appendix_I.docx

Page I-46


I-1.2.3 McArthur River

Figure A1- 91: Simulated flow rate over LOM to McArthur River

Figure A1- 92: Simulated SO4 load rate over LOM to McArthur River



Appendix_I.docx

Page I-47


Figure A1- 93: Simulated Zn load rate over LOM to McArthur River

Figure A1- 94: Simulated As load rate over LOM to McArthur River



Appendix_I.docx

Page I-48


Figure A1- 95: Simulated Cd load rate over LOM to McArthur River

Figure A1- 96: Simulated Pb load rate over LOM to McArthur River



Appendix_I.docx

Page I-49


Figure A1- 97: Simulated flow rate over closure and 100 yrs into closure to McArthur River

Figure A1- 98: Simulated SO4 load rate over closure and 100 yrs into closure to McArthur River



Appendix_I.docx

Page I-50


Figure A1- 99: Simulated Zn load rate over closure and 100 yrs into closure to McArthur River

Figure A1- 100: Simulated As load rate over closure and 100 yrs into closure to McArthur River



Appendix_I.docx

Page I-51


Figure A1- 101: Simulated Cd load rate over closure and 100 yrs into closure to McArthur River

Figure A1- 102: Simulated Pb load rate over closure and 100 yrs into closure to McArthur River



Appendix_I.docx

Page I-52


Figure A1- 103: Simulated flow rate for long term into closure to McArthur River

Figure A1- 104: Simulated SO4 load rate for long term into closure to McArthur River



Appendix_I.docx

Page I-53


Figure A1- 105: Simulated Zn load rate for long term into closure to McArthur River

Figure A1- 106: Simulated As load rate for long term into closure to McArthur River



Appendix_I.docx

Page I-54


Figure A1- 107: Simulated Cd load rate for long term into closure to McArthur River

Figure A1- 108: Simulated Pb load rate for long term into closure to McArthur River



Report



APPENDIX II

Updated TSF Interception Trench Modelling

171012 LR MRM_TSF Seepage Mitigation Modelling_Update.docx D09814A23

Klohn Crippen Berger Ltd. • Level 5, 43 Peel St • South Brisbane QLD 4101 • Australia +617.3004.0244 t • +617.3004.0299 f • www.klohn.com

October 12, 2017

McArthur River Mine Karen Heazlewood Project Engineer Dear Ms Heazlewood: TSF Interception Modelling 2017 Comparison of alternative trench designs

1 INTRODUCTION

MRM, KCB and GHD held a discussion on the outcomes of the groundwater modelling to date for the Life of Mine TSF, on 26 September 2017. Outcomes from this discussion included a request for KCB to investigate the role that additional pressure relief drains constructed into the aquifer unit underlying the proposed trench would have on performance, and a comparison of the 2017 trench alternatives to the unmitigated case.

This letter is provided to accompany the raw data provided to MRM and GHD on the model outcomes and provides a series of figures, from the latest scenarios, without any further discussion.

2 MODEL SETTING

2.1 Elevations

Figure 1: West to East section - GHD Sept. Trench, with 3 Pressure Relief Drains on Segment 5

MRM TSF Interception Modelling 2017

Comparison of alternative trench designs

171012 LR MRM_TSF Seepage Mitigation Modelling_Update.docx

Page 2 D09814A23 October 2017

2.2 Additional drains

Figure 1a, Trench Segment 5 was modelled by adding three pressure relief drains connecting the underlying aquifer.

Pressure relief drain hydraulic conductivity assigned as 5 m/day, the same value as the underlying aquifer.

2.3 Seepage zones and segments

Figure 2. Seepage Zones and Segments





3 SUMMARY OF RESULTS

3.1 Flows

Figure 3: Trench Seepage Rates with 3 Pressure Relief Drains

Figure 4: Surprise Creek Segment Seepage





3.2 Wet and Dry Season flows (2037)

Figure 5: Seepage comparison

between segments of Trench with 3 pressure relief

drains and Surprise Creek.

Figure 6: Seepage comparison

between segments of Trench (with 3

pressure relief drains) and

Surprise Creek.





3.3 Mass load

Figure 7: Trench (with 3 Chimney drains) segment mass load

Figure 8: Surprise Creek Segment Mass Load





Figure 9: Mass load comparison

between segments of

Trench (with 3 pressure relief

drains) and Surprise Creek.

Figure 10: Mass load comparison

between segments of

Trench (with 3 pressure relief

drains) and Surprise Creek.





3.4 Head Contours

Figure 11: Head

Contour in Layer 1

Figure 12: Head

Contour in Dolomitic

Layer





Figure 13: Comparison of Trench elevations with model layers

4 COMPARISON OF TRENCH DESIGNS

4.1 Seepage volumes

Figure 14: Seepage to Trench





Figure 15: Seepage to Surprise Creek

5 COMPARATIVE LOADS

Figure 15: Mass Load of Surprise Creek (Max load 3.7 kg/d for Pressure Relief Drain Case)





6 CLOSURE

This report is an instrument of service of Klohn Crippen Berger Ltd. The report has been prepared for the exclusive use of McArthur River Mines (Client) for the specific application to the 2017 TSF Seepage Modelling project. The report's contents may not be relied upon by any other party without the express written permission of Klohn Crippen Berger. In this report, Klohn Crippen Berger has endeavoured to comply with generally-accepted professional practice common to the local area. Klohn Crippen Berger makes no warranty, express or implied.

Yours truly,

KLOHN CRIPPEN BERGER LTD.

Brent Usher, PhD, PrSciNat Senior Hydrogeochemist and Associate

GW:BU



Report



APPENDIX III

Options for NOEF Plume Interception

170215LR_NIRB Concept Mitigation.docx

D09814A10

Klohn Crippen Berger Ltd. • www.klohn.com

February 15, 2017


PO Box 36821,

Winnellie, NT

0821

Mr. Gary Taylor Environmental Manager: MRM Dear Mr. Taylor MRM NOEF EIS Overburden Management EIS: NOEF Mitigation Concept Modelling Letter Report

Please find enclosed KCB’s letter report summarising the groundwater modelling assessment of

GHD’s concept design for an interception trench situated immediately down-gradient of the

southern and eastern perimeters of the NOEF. We understand that these assessments are

required for the NOEF Independent Review Board (NIRB) to assess the efficacy of the proposed

interception trench.

1 INTRODUCTION

KCB built and calibrated a numerical groundwater model for the MRM site that was used for the

2017 OMP EIS (KCB, 2017). The model was developed in MODFLOW-SURFACT Version 4.0

(HydroGeoLogic, 2016), and has both groundwater flow and mass transport capabilities. For the

OMP EIS the model was used in transient simulation mode to predict changes to groundwater

conditions, including variation in baseflow and load contributions during life of mine, closure and

long-term post-closure.

We understand that the NIRB have reviewed KCB’s groundwater impact assessment report and

GHD’s concept design for an interception trench down-gradient of the NOEF, and are seeking to

understand the hydraulic effectiveness of GHD’s proposed concept design.

Given the expedited timeframes for the NIRB to present the impact assessment to DME, it was

agreed between the NIRB and KCB that the existing groundwater model would be used, without

changes to the model grid. The model would be used to assess the conceptual effectiveness of the

interception trench to capture NOEF seepage predicted to occur in the southeast corner of the

NOEF and discharge to either the pit or the Barney Creek diversion. This letter report summarises

the outcomes of the proposed interception trench mitigation scenarios.

McArthur River Mining Pty Ltd Overburden Management EIS

NOEF Mitigation Concept Modelling Draft Letter Report


Page 2

D09814A10 February 2017

2 MODIFICATIONS TO EXISTING MODEL

2.1 Representing the Interception Trench

An AutoCAD design file “3d Trench.dwg” was provided by GHD on 02 February 2017, with an accompanying draft report titled “65368DraftB.pdf” and associated design figures within “32-17428-Fig01-Fig07.pdf”. These drawing and report files provided the conceptual design for the interception trench. The key features of the trench (as reported by GHD) relevant to the mitigation modelling scenarios are shown in Figure 1 and include:

An excavated trench at 1.5:1. The base of the trench has been set at the 2087 dry season groundwater level as modelled by the EIS groundwater model. Typically the crest to crest distance of the trench is less than 55 m.

An excavated deeper slot through the base of the trench.

The basal slot is conceptually 2m deep (and therefore intersects two metres below the 2087 dry season groundwater levels) and has clean, screened rockfill emplaced within.

The trench is backfilled with soil/earthfill.

Eight sumps/pump stations are nominally configured to remove water from the backfilled slot via a common recovery pipeline.

Figure 1: Conceptual cross section of the NOEF interception trench (adapted from GHD Figure: 32-1742805-FIG04)

A centre-line for the rockfill slot base was provided in the design drawing “3D Trench.dwg”. This design line was imported into ArcGIS v10.3.1 (ESRI, 2015) and overlain with the model grid cells. A linear selection of grid cells was selected so that a continuous linear drain feature could be established in the model. This linear selection of grid cells was one cell wide (50m cells) as shown on Figure 2. Where needed, the interception trench drain cells were adjusted one cell northwards to allow grid cell space between the trench and Surprise Creek and Barney Creek diversion to the


Overburden Management EIS

NOEF Mitigation Concept Modelling

Draft Letter Report


Page 3


immediate south. This was deemed necessary to allow for potential reversal of groundwater flow

from the south of the diversion to flow under the diversion and report to the trench, and to

prevent creek flows from directly reporting to the trench.

The existing model mesh cell size of 50m x 50m was used. Ideally, the model mesh would be

modified to allow more accurate representation of the actual scale of the interception trench,

however, this would have taken significant effort in terms of adjusting adjacent boundary

conditions for creeks, rivers, and diversions, which would necessitate model recalibration. It was

agreed between KCB, MRM and the NIRB that for the current assessment, these changes would

not be required for the model.

The reference head for each individual interception trench drain cell was inferred from the

nearest point on the centre line of the base of the rockfill slot. For this conceptual design

modelling, it was assumed that the drains are able to remove all water from within the rockfill. In

reality, a head will develop within the basal slot. The reference head was then correlated with the

top and bottom of each model layer to determine each drain’s model layer. The geology

intersected by the base of the drains varied from overburden in Layer 2 to upper bedrock in Layer

5.

The conductance of each drain cell was calculated based on the cell length (50m), the slot width

(1.5m width of slot) and height of the drainage slot (2m), as well as a Kz for the clean rockfill. A Kz

of 10 m/day was assumed to allow ready inflow to the trench at this conceptual stage of design.

2.2 Zone Budget Updates

Groundwater Vistas zone budget requires hydrostratigraphic zones to be established for each

zone of interest. For the mitigation modelling scenarios, new zones were established as follows:

� The model cells directly up-gradient of the interception trench (to quantify flow from NOEF

towards trench).

� The model cells directly underneath the trench (to quantify trench underflow and vertical

flow upwards to the trench).

� The trench cells themselves.

� The model cells directly down-gradient of the interception trench (to quantify NOEF

seepage bypassing the trench and reversal of down-gradient flow towards the trench).

2.3 Mass Transport Modifications

The mass transport functionality in MODFLOW SURFACT was modified to model only a single

dissolved constituent, sulphate, which is the most conservative component considered in the

OMP EIS groundwater impact assessment.




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Figure 2: Location of interception trench drain cells with reference to the NOEF, existing model mesh and creek/diversion drain cells




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2.4 Selected Model Simulations

Two model time periods were selected to represent end-member groundwater flow system

conditions in the aquifer pathways down-gradient of the NOEF. These pathways are primarily in the

upper Cooley Dolomite bedrock with minor contributions from the overburden and weathered

bedrock. The EIS simulations for the Life of Mine, closure, and post-closure have shown that the

Cooley Dolomite bedrock is significantly drawn down by pit dewatering post-2023. This drop in

hydraulic head leads to sulphate plumes migrating beneath Barney Creek in the direction of the pit.

Plumes from the NOEF migrate southeast, flow beneath the diversion and continue through to the

northeast corner of the open cut.

Following cessation of pit dewatering, the open cut is refilled with tailings and ex-pit waste and then

is rapidly filled with water to form a pit lake. This transition period between active dewatering and

development of a filled pit lake modifies the groundwater flow system significantly. Given this

transition period it is necessary to test the efficacy of the trench under both groundwater flow

conditions: one case during maximum dewatering conditions when there is potential for hydraulic

disconnection between the trench and phreatic surface, resulting in groundwater passing underneath

the base of the trench; and, another case where the aquifers have recovered post-dewatering and

achieve a new state of equilibrium with the filled mine void and pit lake. The simulation periods

selected for this mitigation modelling assessment are:

� 2038 to 2047 which represents maximum dewatering of the Cooley Dolomite.

� 2068 to 2167 which represents the establishment of a new equilibrium in groundwater heads

post-mining. This 100 year simulation also takes account of annual wet and dry seasons which

may influence the functionality of the interception trench.

3 MITIGATION MODEL CASES

Six mitigation cases were defined by the NIRB to evaluate the conceptual efficacy of the proposed

interception trench design. The six cases are defined in Table 1, and show that three cases have been

developed for each simulation period. All six cases include an interception trench, with the major

differentiation being the NOEF foundation seepage (as determined by DumpSim and TOUGH2): Cases

1 and 2 are based on the EIS NOEF foundation seepage rate; Cases 3 and 4 simulate the response of

doubling the NOEF foundation seepage rate; Cases 5 and 6 simulate the effect of halving the NOEF

foundation seepage rate.

The 2038 to 2047 model runs (Model Cases 1, 3, and 5) use monthly stress periods for a ten year time

interval (120 stress periods total) with monthly rainfall recharge varying according to the EIS project

climate database. The drain boundary reference head in the trench was maintained at a constant

elevation assuming efficient and complete removal of water from the rockfill slot. In reality, some

head may build up in the slot, however, for this conceptual assessment, the level was held at the base

of the slot.




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The 2068 to 2167 model run was used for Model Case 2, 4, and 6. These cases utilise six monthly

stress periods for a one hundred year interval (200 stress periods total) with seasonal rainfall

recharge varying according to project climate database. Again, the drain boundary condition and the

reference head in the drain cells was held to the base of the slot.

Table 1: Mitigation Model Cases

Model Case Simulation Period Stress Periods Interception Trench NOEF Foundation

Seepage Rate

Case 1 2038 to 2047 Monthly Yes As per EIS

Case 2 2068 to 2167 Wet season/Dry season Yes As per EIS

Case 3 2038 to 2047 Monthly Yes Double EIS rate

Case 4 2068 to 2167 Wet season/Dry season Yes Double EIS rate

Case 5 2038 to 2047 Monthly Yes Half EIS rate

Case 6 2068 to 2167 Wet season/Dry season Yes Half EIS rate

4 RESULTS

4.1 Mitigated sulphate load to Barney Creek diversion

Model-predicted sulphate loads discharged as baseflow to Barney Creek diversion are presented in

Figure 3 and Figure 4. These figures show that limited reduction in sulphate load occurs during the

maximum dewatering scenario when most of the sulphate plume bypasses the trench and migrates

beneath the diversion, whereas a significant reduction in sulphate load is achieved for the 100 year

post-closure scenario, where hydraulic connection permits the trench to operate in accord with its

intended purpose.

There is very little differentiation in sulphate load reporting to Barney Creek diversion between the

three mitigated cases for each time period. This indicates that the hydraulic properties of the Cooley

Dolomite aquifer are controlling the rate at which sulphate migrates through the aquifer pathway

and the rate at which sulphate discharges to the diversion. This is consistent with the 1D modified

Domenico analytical sensitivity analysis completed for the groundwater impact assessment (KCB,

2017).




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Figure 3: Monthly sulphate load (kg/day) predictions for Barney Creek diversion for unmitigated

case and mitigated Cases 1, 3 and 5 over the period 2038 to 2047

Figure 4: Seasonal sulphate load (kg/day) predictions for Barney Creek diversion for unmitigated

case and mitigated Cases 2, 4 and 6 over the period 2068 to 2167

0

100

200

300

400

500

600

700

1/2038 1/2039 1/2040 1/2041 1/2042 1/2043 1/2044 1/2045 1/2046 1/2047

Lo

ad

Ra

te (

Kg

/D

ay

)

Simulation Time (Date)

Unmitigated (EIS Case 3) Case 1 Case 3 Case 5

0

500

1000

1500

2000

2500

3000

3500

4000

4500

5000

1/2068 1/2077 1/2086 1/2095 1/2104 1/2113 1/2122 1/2131 1/2140 1/2149 1/2158 1/2167

Lo

ad

Ra

te (

Kg

/D

ay

)


Unmitigated (EIS Case 3) Case 2 Case 4 Case 6




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4.2 Discharge to Trench

Figure 5 and Figure 6 present the discharge rate to the interception trench drain cells for the various

model cases. The trench intercepts more groundwater post-closure once the head in the Cooley

Dolomite and overlying aquifers has recovered to a new equilibrium condition post-mining. Figure 7

presents the zone budget analysis for the interception trench in Mitigation Case 2 (Base mitigation

case from 2068 to 2167). The zone budget analysis shows that some bypass of the trench system

occurs (difference between “UG to Below Trench” and “Below Trench to DG”). There is also a

component of reversal of flow with down-gradient groundwater drawn back towards the trench.

Figure 5: Interception trench drain outflow for Mitigated Cases 1, 3 and 5 (2038 to 2047)

0

200

400

600

800

1000

1200

1400

1600

1/2038 1/2039 1/2040 1/2041 1/2042 1/2043 1/2044 1/2045 1/2046 1/2047

Tre

nch

Ou

tflo

w (

m3

/d

ay

)


Case 1 Case 3 Case 5




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Figure 6: Interception trench drain outflow for Mitigated Cases 2, 4 and 6 (2068 to 2167)

0

500

1000

1500

2000

2500

3000

1/2068 1/2077 1/2086 1/2095 1/2104 1/2113 1/2122 1/2131 1/2140 1/2149 1/2158 1/2167

Tre

nch

Ou

tflo

w (

m3

/d

ay

)


Case 2 Case 4 Case 6




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Figure 7: Zone budget for interception trench in Model Case 2 (2068 to 2167).

Note: “Below Trench to Trench” represents vertical upward flow to the trench; “DG to Trench” represents flow from south

and east of the trench back towards the trench; “DG to Below Trench” represents flow from south and

east of the trench back underneath the trench; “UG to Below Trench” represents flow from NOEF

towards trench; “Below Trench to DG” represents flow from beneath the trench to down-gradient of the

trench.

4.3 Flow net Sections

A flow net section was established in a north-south orientation through the dominant aquifer

pathway in the southeast corner of the NOEF. The section was orientated so that it starts within the

NOEF footprint, cuts through the interception trench in the southeast corner of the NOEF, cuts across

the Barney Creek diversion where maximum sulphate load is discharging post-closure and finishes in

close proximity to the open cut /pit lake limits. The location of the flow net section is shown on Figure

8. The individual flow net sections for each mitigation case are presented sequentially from Figure 9

to Figure 14.

Mitigation cases 1, 3 and 5 show:

� that the water table (shown as red line) is lowered by pit dewatering in the south of the

section. The water table is situated below the invert of both Barney Creek diversion and the

interception trench.

� There are strong downwards vertical gradients owing to pit dewatering.

0

200

400

600

800

1000

1200

1400

1600

1/2068 1/2077 1/2086 1/2095 1/2104 1/2113 1/2122 1/2131 1/2140 1/2149 1/2158 1/2167

Flu

x (

m3

/d

ay

)


Below Trench to Trench DG to Trench DG to Below Trench

UG to Below Trench Below Trench to DG




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� NOEF seepage has a dominant lateral flow component in the Cooley Dolomite underneath the

NOEF itself.

Mitigation cases 2, 4 and 6 show:

� Pit lake throughflow drives lateral groundwater flow north towards the Barney Creek

diversion.

� There is a reversal of flow with groundwater that previously would have discharged to the

diversion being drawn north towards the interception drain.

� NOEF seepage flowpaths are directed towards the interception trench.




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Figure 8: Location of flow net section with reference to the interception trench drain cells and the 2167 sulphate concentrations in

the upper bedrock




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Figure 9: Flow net section A-A’ for mitigation case 1 (2038 to 2047). Upper section shows head equipotentials only, while lower

section shows both head equipotentials plus sulphate concentrations (lower limit set at 0.6 kg/m3 or 600 mg/L)




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4.4 Particle tracking

Particle tracking using the semi-analytical equations of Pollock (1988) was undertaken to visualise the

influence of groundwater velocity vectors and hydraulic head distributions on source-pathway-

receptor systems in the vicinity of the proposed interception trench. A network of particle seeds was

deployed from the base of the weathered bedrock for the NOEF footprint. Streamlines were

generated for each of the mitigation cases with forward projection of ten years for cases 1, 3 and 5,

and one hundred years for cases 2, 4 and 6. The individual streamline outputs are presented in Figure

15 to Figure 20. The key features interpreted from the streamlines are:

� The interception trench is largely ineffective for model cases 1, 3 and 5 when dewatering has

lowered the hydraulic heads and established a direct pathway from the NOEF to discharge to

the open cut.

� The interception trench along the eastern perimeter of the NOEF is ineffective during the

post-closure simulations (cases 2, 4 and 6) with particles flowing beneath the trench.

However, the interception trench in the southeast corner of the NOEF captures most of the

particles that have bypassed the eastern trench system. The southern interception trench

system captures most of the particles that migrate from the NOEF.

Figure 15: Forward tracking 10 year streamlines for Mitigation Case 1




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4.5 Sulphate plume visualisation

The sulphate concentration at 13 mAHD (within Layer 5 - upper bedrock in the southeast corner of

NOEF) is presented for the six model cases in Figure 21 to Figure 26. The key features interpreted

from the sulphate plume maps are:

� As with the streamlines figures, the interception trench is largely ineffective for model cases 1,

3 and 5 when dewatering has lowered the hydraulic heads and established a disconnected

pathway between the trench and the water table, from the NOEF to discharge to the open

cut.

� The interception trench along the eastern perimeter of the NOEF is ineffective during the

post-closure simulations (cases 2, 4 and 6) with sulphate migrating beneath the trench.

However, the interception trench in the southeast corner of the NOEF captures most of the

sulphate plume that has bypassed the eastern trench system. The southern interception

trench system captures most of the sulphate plume that migrates from the NOEF.




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Figure 21: Sulphate concentrations at elevation 13 mAHD (within upper bedrock in southeast

corner of NOEF) for Case 1






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5 LIMITATIONS AND ASSUMPTIONS

The following limitations and assumptions associated with the mitigation modelling assessment are

noted:

� This modelling should be regarded as an indicative simulation of the conceptual design. Detail

of the interception system has been broadly approximated using the existing EIS model.

� Only modelling two snapshot simulations is not a true indication of progressive capture of the

sulphate plume. Using this snapshot approach there is no conditioning of heads or

concentrations from the time of construction onwards. Rather, the trench is assumed to

become instantaneously active at the start of each model simulation, and highly efficient in its

performance. To conceptually assess the efficacy of the mitigation system, this snapshot

approach is conservative (i.e. the trench would likely impact water levels sooner than shown

in this modelling).

� The interception trench is coarsely represented with the existing 50m x 50m grid cells. For

design, further discretisation of the model grid in the vicinity of the trench will be required to

more accurately represent this feature.

� The EIS groundwater model was built to represent source-pathway-receptor systems at a

catchment scale. For this reason, the equivalent porous media (EPM) method used to

represent zones of fracturing and for karstic features in the Cooley Dolomite/Reward

Dolomite was deemed to be appropriate. EPM is suitable at this catchment-scale because it

represents the broad pathway from source to receptor. However, for local-scale problems,

EPM may be less suitable. If significant fracture zones or solution cavities at depth within the

Cooley Dolomite are a primary conduit for NOEF seepage, there is a potential for seepage to

migrate under the trench through one or more of these features. During design of the trench,

investigations on the nature of the Cooley Dolomite system would provide a better

understanding of the physical and hydraulic nature of the preferential flow systems within this

aquifer pathway.

� The reference head in the rockfill slot was assumed to be at the base of the slot. In reality,

there will be a head of water in the rockfill which will influence the performance of the drain.

Depending on the underlying aquifer conditions, sections of head in the drain may locally

discharge back into the regional system.

� The vertical permeability of the trench system has been assumed to be sufficient for

groundwater to migrate without limitation to the trench, under the influence of the hydraulic

gradients.

� The trench capture performance is assumed to be highly efficient in the current model

simulations. No reduction in capture rate was accounted for natural processes such as

siltation of the rockfill and precipitation on the rockfill and material immediately surrounding

the trench.




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6 CLOSING

This letter report is an instrument of service of Klohn Crippen Berger Ltd. The report has been

prepared for the exclusive use of McArthur River Mine (Client) for the specific application to the 2017

EIS. The report's contents may not be relied upon by any other party without the express written

permission of Klohn Crippen Berger. In this report, Klohn Crippen Berger has endeavoured to comply

with generally-accepted professional practice common to the local area. Klohn Crippen Berger makes

no warranty, express or implied.

Yours truly,

KLOHN CRIPPEN BERGER LTD

Brent Usher, PhD

Geosciences Manager/ Project Manager

170620LR_Concept_Mitigation_Update.docx D09814A10

Klohn Crippen Berger Ltd. • www.klohn.com

June 19, 2017

McArthur River Mining Pty Ltd PO Box 36821, Winnellie, NT 0821 Mr. Jamie Hacker MRM 2017 EIS Dear Mr. Hacker MRM NOEF EIS Overburden Management EIS: NOEF Mitigation Concept Modelling- June 2017 Update At MRM’s request, KCB completed modelling of GHD’s concept design for an interception trench situated immediately down-gradient of the southern and eastern perimeters of the NOEF in January/February 2017. In May 2017, the NOEF Independent Review Board (NIRB) requested further groundwater modelling to assess the efficacy of the proposed interception trench.

This letter reports provides a summary of the updated modelling, summarising the groundwater modelling assessment of MRM/GHD’s updated concept designs for plume interception down-gradient of the southern and eastern perimeters of the NOEF.

1 INTRODUCTION

KCB built and calibrated a numerical groundwater model for the MRM site that was used for the 2017 OMP EIS (KCB, 2017). The model was developed in MODFLOW-SURFACT Version 4.0 (HydroGeoLogic, 2016), and has both groundwater flow and mass transport capabilities. For the OMP EIS the model was used in transient simulation mode to predict changes to groundwater conditions, including variation in baseflow and load contributions during life of mine, closure and long-term post-closure.

To meet the immediate time frames of NIRB’s initial submissions to the regulators, it was agreed the KCB’s EIS model would be used without refinement to assess the conceptual effectiveness of the interception trench to capture NOEF seepage predicted to occur in the southeast corner of the NOEF and discharge to either the pit or the Barney Creek diversion.

In May 2017, the NIRB requested further modelling to be undertaken, to include the following tasks:

1. Refine the EIS model grid to optimise the model response with the proposed interception trench and additional collection bores.

It was agreed that the grid would be refined as far as is practical, in the area surrounding the proposed trench to a grid spacing of ~ 12.5 m and adjacent to the trench to ~ 6m.



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D09814A10 June 2017

2. Re-run the refined model for similar conditions that were considered in KCB’s “NOEF Mitigation Concept Modelling Draft Letter Report” (15 February 2017).

3. Assess the sensitivity of these results by halving and doubling the hydraulic conductivity of the fault zone to the east of the NOEF.

4. Account for interception of the predicted deeper water table conditions in the southeast area by modelling selectively located collection bores.

From this provide an indication of the location, depths and abstraction rates required to contain seepage during operations.

5. Assess the fate of the COPC loadings that may by-pass the interception system after operations.

2 MODELLING APPROACH

As previously, KCB has modelled the interception ditch using a drain boundary condition inserted into the refined model mesh (grid cells refined to 12.5 m resolution and 6.25 m) along the proposed drain alignment. The proposed pumping interception wells located downstream of the drain alignment would be positioned based on the initial results. As previously, the drain condition extends across the gaps in the ditch, working on the assumption that interception well pumping will be successful in reducing the phreatic surface to the specified water elevation in the drain adjacent to these locations.

To reduce model simulation run times, contaminant transport modelling was limited to sulphate (SO4) as a conservative ion. Particle tracking showing streamlines has been used to assess seepage pathways and drain capture efficiency. In addition, for each of the simulations, sulphate loads and fluxes for the reach of the Barney Channel previously reported on, as well as to the trench have been extracted from the model for each model run provided.

2.1 Model Simulation Periods

For consistency, KCB proposed that the same periods modelled previously were repeated. Two time periods were modelled:

2038 to 2047 – this period represents a time when dewatering of the open pit is at a maximum stress state and groundwater elevations in the Cooley Dolomite have been lowered causing a degree of disconnection between the NOEF seepage and Barney Channel, leading to reduced flow from the NOEF directly to Barney Channel in this period.

2068 to 2167 – to reflect the groundwater conditions after pit lake development and groundwater levels have recovered to near steady state conditions in the NOEF footprint area. This model simulation period will provide an indication of the interception performance of the trench for the post-closure condition, and any loads reporting to Barney Channel.

These existing transient scenarios include seasonality in the rainfall recharge relationship in accordance with the EIS climate data set. The 2038 to 2047 model uses monthly stress periods for




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D09814A10 June 2017

rainfall recharge, while the longer-term 2068 to 2167 post-closure scenario uses six monthly stress periods which alternate between average wet season and average dry season conditions for the given EIS climate data set.

Similar limitations in terms of timing of the interception trench commissioning period will apply as previously reported (KCB, February 2017).

2.2 Sensitivity Analysis

KCB previously provided sensitivity analysis by varying the NOEF foundation seepage flux. Based on our discussions with MRM and the NIRB, for this update, KCB has focused the sensitivity analysis on hydraulic conductivity of the north-south trending fault zone to the east of the NOEF.

3 MODIFICATIONS TO EXISTING MODEL

3.1 Grid refinement

The previous model grid spacing of 50 m has been refined in the model. This reduced the grid size to 12.5 m near the proposed interception alignments, and down to ~ 6.25 m along the proposed alignments). The refined grid is shown in Figure 1.

Figure 1: Refinement of model grid (zones of refinement are shown)




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3.2 Representing the interception system

The interception system was represented as reported previously (KCB, 2017), using the alignments and .dxf files provided to KCB by GHD in May 2017. The same assumptions used previously have been included. Additional options simulated for the May 2017 round of modelling included abstraction bores. These were modelled with specific locations and with drain elevations included to simulate the reduction in water level to a specified elevation/depth below surface. Where bores are included in the main alignment to mimic the impact of an equivalent trench, the elevation of the drains were set to approximately the proposed trench invert elevation. For the deeper capture bores, the depth was iterative and based on the hydrogeological conditions and the predicted depths of the major flow lines obtained from the unmitigated EIS model case for sulphate.


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Figure 2: Location of interception trench drain cells with reference to the NOEF, refined model mesh and creek/diversion drain cells




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3.3 Zone Budget Updates

Groundwater Vistas zone budget requires hydrostratigraphic zones to be established for each zone of interest. For the mitigation modelling scenarios, zones were established to be consistent with the January 2017 mitigation modelling as follows:

The model cells directly up-gradient of the interception trench (to quantify flow from NOEF towards trench).

The model cells directly underneath the trench (to quantify trench underflow and vertical flow upwards to the trench).

The trench cells themselves (or bores where these have been simulated).

The model cells directly down-gradient of the interception trench (to quantify NOEF seepage bypassing the trench and reversal of down-gradient flow towards the trench).

3.4 Selected interception system design

MRM provided KCB with several additional alignments to consider before the detailed modelling was completed. The alignment of MRM’s preferred design is shown on Figure 3. The depths and alignments provided by GHD were used in the modelling.

Figure 3: Illustration of May 2017 design alignment (from GHD)




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The modelled mitigation design has the following elements:

An interception trench at approximately 12m below surface in the west of design. This trench runs along the south of SEPROD, extending from west of the PROD trench to the start of the defined AAP protected area to the west of Barramundi Dreaming.

Shallow bores with a drain condition at a maximum depth of 15 m across the protected zone.

Based on the results of the February 2017 mitigation modelling, additional deep bores have been included in the mitigation system. These bores have a drain condition specified at a depth of approximately 45 m, and are located immediately south of the interception trench in this design. The intent of these bores is to assist in capturing the plume below the deeper water table in period while the pit lake is recovering. Water balances were recorded for each bore to assess the volume that the drain condition removes, as an initial estimate of required abstraction rates.

3.5 Mass Transport

Consistent with the January 2017 modelling, the mass transport functionality in MODFLOW SURFACT was modified to model only sulphate as a dissolved constituent.

3.6 Summary of model cases presented

Table 1: Model Cases presented in this memo

Model Case Simulation

Period Interception

NOEF Foundation Seepage Rate

EIS (to 2047) 2038 to 2047 No As per EIS

EIS (to 2167) 2068 to 2167 No As per EIS

Mitigation Concept ( to 2047)

2038 to 2047 Yes – as per Feb 2017 concept As per EIS

Mitigation Concept ( to 2167)

2068 to 2167 Yes – as per Feb 2017 concept As per EIS

2017 Mitigation Design (to 2047)

2038 to 2047 GHD May 2017 Design As per EIS

2017 Mitigation Design (to 2167)

2068 to 2167 GHD May 2017 Design As per EIS

Design Sensitivity 1 2038 to 2167 GHD May 2017 Design As per EIS (Hydraulic conductivity in plume path doubled)

Design Sensitivity 2 2038 to 2167 GHD May 2017 Design As per EIS (Hydraulic conductivity in plume path halved)




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4 RESULTS

4.1 Particle tracking

Particle tracking using the semi-analytical equations of Pollock (1988) was undertaken to visualise the influence of groundwater velocity vectors and hydraulic head distributions on source-pathway-receptor systems in the vicinity of the proposed interception trench. A network of particle seeds was deployed from the base of the weathered bedrock for the NOEF footprint. Streamlines were generated for each of the mitigation cases with forward projection of 10 years and 100 years respectively.

4.1.1 Comparison to coarser grid

Particle tracking results from the refined grid, showed that similar results are obtained with the fine and coarser grids. The refined grid (with 6m spacing in the in the area of interest) provides a more accurate representation of the proposed trench design. The results from the May 2017 design showed very similar results to the January 2017 simulation. The simulations again suggest that shallow interception options were somewhat ineffective in the short term when the water table is deeper in some areas as a result of the dewatering of the open cut, but significantly more effective in the longer term once the water levels recover after when the pit lake is established. (Figure 4).




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Figure 4: Comparative Streamlines at 2047 (EIS grid and January 2017 trench)




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Figure 5: Comparative Streamlines at 2047 (Refined Grid; trench only)




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4.1.2 Enhancement of Mitigation Options to include deeper bores

Deeper bores were added to the mitigation design. The deep bores were placed along the predicted flow path with the drain condition at a depth of ~45m below surface (Figure 5). Several iterations of deeper bores were tested for efficacy.

Figure 6: Positions of the bores overlain on the refined grid (sizes exaggerated for clarity)

Deep bores were simulated as being operational up to 2047, with the shallower interception system assumed to remain operational throughout the longer-term simulation (i.e. up to 2168).

Flow lines for a selection of these scenarios is shown on Figures 7 to 9.




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Figure 7: Inclusion of deep bores for the immediate post-closure period




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Figure 8: Streamlines for the mitigation design for the immediate post-closure period with deeper bores (2047 view from West)




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Figure 9: Streamlines for the mitigation design at 2168 (with trench only in place)




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Inclusion of the deep bores is effective in the immediate post-closure period, with the shallower interception systems becoming more effective in the longer-term post-closure.

4.2 Flows and loads summaries for mitigation design

Flows and loads to the Barney Creek diversion (and to the mitigation system) have been extracted from the models. Results from the proposed 2017 mitigation design (with deeper bores in place for the period 2038-2067 as outlined in the preceding sections) have been compared to the EIS assessment to illustrate the impact that these measures could have on flows and loads.

Comparison to the unmitigated case, shows that the 2017 design is effective in reducing flows (Figure 10 and Figure 11) and loads (Figure 12 and Figure 13) to Barney Creek Diversion for the section of interest.

Figure 10: Comparison of mitigated (bores and trench) and unmitigated flows to Barney Creek (2038-2047)

Inclusion of deeper bores maintaining the water levels at between 35 m and 40 m below surface showed that significant reduction in loads could be achieved in the immediate post-closure period.




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Figure 11: Comparison of mitigated and unmitigated flows to Barney Creek (up to 2167)

Model-predicted sulphate loads discharged as baseflow to Barney Creek diversion are presented in Figure 12 and Figure 13.

Figure 12: Comparison of mitigated and unmitigated loads to Barney Creek (2038-2047)




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Figure 13: Comparison of mitigated and unmitigated loads to Barney Creek (up to 2167)

4.2.1 Results of sensitivity testing

Two additional simulations were undertaken to test whether changes in the hydraulic conductivity of the north-south trending zone of higher permeability would have a meaningful impact on the efficacy of the mitigation. For this assessment, the hydraulic conductivity of was varied by doubling, and then halving the K-value in this zone of the model grid.

Results for the loads to Barney Creek, indicate that the proposed mitigation system is insensitive to the changes in K applied in the model and that the system would still be effective in reducing loads to the surface water system in the shorter and longer post-closure periods (Figure 14 and Figure 15). With changes aquifer parameters, the volume of water intercepted changes and confirmation of these values will be key to the integrated closure mitigation plan and water handling system.




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Figure 14: Sensitivity testing for 2017 mitigation case loads to Barney Creek (2038-2047)

Figure 15: Sensitivity testing for 2017 mitigation case loads to Barney Creek (up to 2167)




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5 DISCUSSION

Key aspects from modelling using the refined grid and May 2017 mitigation design include:

Modelling with the refined grid provides more precise inclusion of the mitigation design. The unmitigated results from the EIS model and the refined model results show that model grid refinement does not change the model results to any significant degree.

During the early post-closure period (~ 2047), shallow interception options have limited effect as the flow lines are deeper than the proposed interception, i.e. a significant portion of seepage flows south, below the invert of the Barney Creek Diversion.

The trench/shallow bores are significantly more effective in post-closure, after the pit lake is established.

Inclusion of deeper bores in the model suggests interception pumping will be effective in mitigating the plume in the early post-closure period. Drain cells were included to simulate pumping to achieve water level depths of ~ 45 m were simulated.

Deeper bores could also be used to good effect in the closure period. The practical implications of continued pumping of deep bores after closure will need to be weighed up against the reduction in loads.

Conceptually, the 2017 mitigation design indicates that significant reduction in load to Barney Creek Diversion can be achieved. In the shorter-term (prior to pit lake rebound), deeper bores in combination with the shallow interception are also effective at reducing loads to the Barney Diversion.

Sensitivity analysis suggests that the hydraulic conductivity of the north-south structure influences the results but that the proposed mitigation option would still be effective.

6 LIMITATIONS AND ASSUMPTIONS

The following limitations and assumptions associated with the mitigation modelling assessment are noted:

This modelling should be regarded as an indicative simulation of the conceptual design. Detail of the interception system has been broadly approximated.

Only modelling two snapshot simulations is not a true indication of progressive capture of the sulphate plume. Using this snapshot approach there is no conditioning of heads or concentrations from the time of construction onwards. Rather, the trench/bore is assumed to become instantaneously active at the start of each model simulation, and highly efficient in its performance. To conceptually assess the efficacy of the mitigation system, this snapshot approach is conservative (i.e. the trench would likely impact water levels sooner than shown in this modelling).




Page 20

D09814A10 June 2017

The EIS groundwater model was built to represent source-pathway-receptor systems at a catchment scale. For this reason, the equivalent porous media (EPM) method used to represent zones of fracturing and for karstic features in the Cooley Dolomite/Reward Dolomite was deemed to be appropriate. EPM is suitable at this catchment-scale because it represents the broad pathway from source to receptor. However, for local-scale problems, EPM may be less suitable. If significant fracture zones or solution cavities at depth within the Cooley Dolomite are a primary conduit for NOEF seepage, there is a potential for seepage to migrate under the trench through one or more of these features. During design of the mitigation system, investigations on the nature of the Cooley Dolomite system would provide a better understanding of the physical and hydraulic nature of the preferential flow systems within this aquifer pathway.

The reference head in the rockfill slot was assumed to be at the base of the slot for the trenches. In reality, there will be a head of water in the rockfill which will influence the performance of the drain. Depending on the underlying aquifer conditions, sections of head in the drain may locally discharge back into the regional system.

The vertical permeability of the trench system has been assumed to be sufficient for groundwater to migrate without limitation to the trench, under the influence of the hydraulic gradients.

The trench capture performance is assumed to be highly efficient in the current model simulations. No reduction in capture rate was accounted for natural processes such as siltation of the rockfill and precipitation on the rockfill and material immediately surrounding the trench.

No optimisation of the options has been undertaken, and the results presents are provided with the specifications from GHD, and/or agreed to between KCB and MRM. It is expected that further reductions in loads can be obtained by changing depths or rates of pumping from these options.




Page 21

D09814A10 June 2017

7 CLOSING

This letter report is an instrument of service of Klohn Crippen Berger Ltd. The report has been prepared for the exclusive use of McArthur River Mine (Client) for the specific application to the 2017 EIS. The report's contents may not be relied upon by any other party without the express written permission of Klohn Crippen Berger. In this report, Klohn Crippen Berger has endeavoured to comply with generally-accepted professional practice common to the local area. Klohn Crippen Berger makes no warranty, express or implied.

Yours truly,

KLOHN CRIPPEN BERGER LTD

Brent Usher, PhD Geosciences Manager/ Project Manager

McArthur River Mining Ltd

MRM OMP EIS

2017 EIS Supplementary

171215DR Appendix IV Concentration Figures

GSL Model.docx Page -1


APPENDIX IV

GSL case concentration plots: Multiple aquifers & smaller intervals up to 2100


MRM OMP EIS


171215DR Appendix IV Concentration Figures

GSL Model.docx

Page -2


Figure 1: Predicted sulphate concentrations in the overburden at 2020, 2030, 2040 and 2050

SURPRISE

C

REEK

MCARTHUR

RIVER

BU

LL

CR

EE

K

BARNEYCREEK

EMUCREE

K

LITTLE BARNEYCR

EEK

BU

F

FALO CRE E K

610,000 612,000 614,000 616,000 618,000 620,000

8,1

82

,000

8,1

84

,000

8,1

86

,000

0 0.5 1 1.5 2

km

NOTES:

1. Background image: McArthur River Mine

Merge 50cm.ecw

2. Surface Water features are based on

published data that have been adapted from the background image.

Legend

River/Creek

Diversion

SURPRISE

CREEK

MCARTHUR

RIVER

BU

LL

CR

EEK

BARNEYCREEK

LITTLE BARNEYCR

EEK

EMUCREE

K

BU

F

FALO

CREEK

8,1

82

,000

8,1

84

,000

8,1

86

,000

SURPRISE

CREEK

MCARTHUR

RIVER

BU

LL

CR

EE

K

BARNEYCREEK

LITTLE BARNEYCR

EEK

EMUCREEK

BU

F

FALO CRE E K

8,1

82

,000

8,1

84

,000

8,1

86

,000

SURPRISECR

EEK

MCARTHUR

RIVER

BU

LL

CR

EEK

BARNEY CRE EK

EMUCREEK

LITTLE BARNEYCR

EE

K

BU

F

FALO CRE EK

610,000 612,000 614,000 616,000 618,000 620,000

8,1

82

,000

8,1

84

,000

8,1

86

,000



4. Scale: 1:65,000

2020 2030

20502040

SulphateConcentration(mg/L)

300 - 1000

1000 - 2000

2000 - 3000

3000 - 4000

4000 - 5000

5000 - 6000

6000 - 7000

7000 - 8000

8000 - 9000

9000 - 10000

10000 - 11000

11000 - 12000

12000 - 13000

13000 - 14000

14000 - 15000

15000 - 16000

16000 - 17000

17000 - 18000

18000 - 19000

19000 - 20000

>20000


300 - 1000

1000 - 2000

2000 - 3000

3000 - 4000

4000 - 5000

5000 - 6000

6000 - 7000

7000 - 8000

8000 - 9000

9000 - 10000

10000 - 11000

11000 - 12000

12000 - 13000

13000 - 14000

14000 - 15000

15000 - 16000

16000 - 17000

17000 - 18000

18000 - 19000

19000 - 20000

>20000


300 - 1000

1000 - 2000

2000 - 3000

3000 - 4000

4000 - 5000

5000 - 6000

6000 - 7000

7000 - 8000

8000 - 9000

9000 - 10000

10000 - 11000

11000 - 12000

12000 - 13000

13000 - 14000

14000 - 15000

15000 - 16000

16000 - 17000

17000 - 18000

18000 - 19000

19000 - 20000

>20000


300 - 1000

1000 - 2000

2000 - 3000

3000 - 4000

4000 - 5000

5000 - 6000

6000 - 7000

7000 - 8000

8000 - 9000

9000 - 10000

10000 - 11000

11000 - 12000

12000 - 13000

13000 - 14000

14000 - 15000

15000 - 16000

16000 - 17000

17000 - 18000

18000 - 19000

19000 - 20000

>20000


MRM OMP EIS


Appendix

171215DR Appendix IV Concentration Figures GSL Model.docx

Page -3


Figure 2: Predicted sulphate concentrations in the overburden at 2060, 2070, 2080 and 2090

SURPRISE

C

REEK

MCARTHUR

RIVER

BU

LL

CR

EE

K

BARNEYCREEK

EMUCREE

K

LITTLE BARNEYCR

EEK

BU

F

FALO CRE E K

610,000 612,000 614,000 616,000 618,000 620,000

8,1

82

,000

8,1

84

,000

8,1

86

,000

0 0.5 1 1.5 2

km

NOTES:


Merge 50cm.ecw



Legend

River/Creek

Diversion

SURPRISE

CREEK

MCARTHUR

RIVER

BU

LL

CR

EEK

BARNEYCREEK

LITTLE BARNEYCR

EEK

EMUCREE

K

BU

FFA

LOCREEK

8,1

82

,000

8,1

84

,000

8,1

86

,000

SURPRISE

CREEK

MCARTHUR

RIVER

BU

LL

CR

EE

K

BARNEYCREEK

LITTLE BARNEYCR

EEK

EMUCREEK

BU

F

FALO CRE E K

8,1

82

,000

8,1

84

,000

8,1

86

,000

SURPRISECR

EEK

MCARTHUR

RIVER

BU

LL

CR

EEK

BARNEY CRE EK

EMUCREEK

LITTLE BARNEYCR

EE

K

BU

F

FALO CRE EK

610,000 612,000 614,000 616,000 618,000 620,000

8,1

82

,000

8,1

84

,000

8,1

86

,000


4. Scale: 1:65,000

2060 2070

20902080


300 - 1000

1000 - 2000

2000 - 3000

3000 - 4000

4000 - 5000

5000 - 6000

6000 - 7000

7000 - 8000

8000 - 9000

9000 - 10000

10000 - 11000

11000 - 12000

12000 - 13000

13000 - 14000

14000 - 15000

15000 - 16000

16000 - 17000

17000 - 18000

18000 - 19000

19000 - 20000

>20000


300 - 1000

1000 - 2000

2000 - 3000

3000 - 4000

4000 - 5000

5000 - 6000

6000 - 7000

7000 - 8000

8000 - 9000

9000 - 10000

10000 - 11000

11000 - 12000

12000 - 13000

13000 - 14000

14000 - 15000

15000 - 16000

16000 - 17000

17000 - 18000

18000 - 19000

19000 - 20000

>20000


300 - 1000

1000 - 2000

2000 - 3000

3000 - 4000

4000 - 5000

5000 - 6000

6000 - 7000

7000 - 8000

8000 - 9000

9000 - 10000

10000 - 11000

11000 - 12000

12000 - 13000

13000 - 14000

14000 - 15000

15000 - 16000

16000 - 17000

17000 - 18000

18000 - 19000

19000 - 20000

>20000


300 - 1000

1000 - 2000

2000 - 3000

3000 - 4000

4000 - 5000

5000 - 6000

6000 - 7000

7000 - 8000

8000 - 9000

9000 - 10000

10000 - 11000

11000 - 12000

12000 - 13000

13000 - 14000

14000 - 15000

15000 - 16000

16000 - 17000

17000 - 18000

18000 - 19000

19000 - 20000

>20000


MRM OMP EIS


Appendix


Page -4


Figure 3: Predicted sulphate concentrations in the overburden at 2100

SURPRISE

C

REEK

MCARTHUR

RIVER

BU

LL

CR

EE

K

BARNEYCREEK

EMUCREE

K

LITTLE BARNEYCR

EEK

BU

F

FALO CRE E K

610,000 612,000 614,000 616,000 618,000 620,000

8,1

82

,000

8,1

84

,000

8,1

86

,000

0 0.5 1 1.5 2

km

NOTES:


Merge 50cm.ecw



Legend

River/Creek

Diversion


4. Scale: 1:65,000

2100SulphateConcentration(mg/L)

300 - 1000

1000 - 2000

2000 - 3000

3000 - 4000

4000 - 5000

5000 - 6000

6000 - 7000

7000 - 8000

8000 - 9000

9000 - 10000

10000 - 11000

11000 - 12000

12000 - 13000

13000 - 14000

14000 - 15000

15000 - 16000

16000 - 17000

17000 - 18000

18000 - 19000

19000 - 20000

>20000


MRM OMP EIS


Appendix


Page -5


Figure 4: Predicted sulphate concentrations in the weathered bedrock at 2020, 2030, 2040 and 2050

SURPRISE

C

REEK

MCARTHUR

RIVER

BU

LL

CR

EE

K

BARNEYCREEK

EMUCREE

K

LITTLE BARNEYCR

EEK

BU

F

FALO CRE E K

610,000 612,000 614,000 616,000 618,000 620,000

8,1

82

,000

8,1

84

,000

8,1

86

,000

0 0.5 1 1.5 2

km

NOTES:


Merge 50cm.ecw



Legend

River/Creek

Diversion

SURPRISE

CREEK

MCARTHUR

RIVER

BU

LL

CR

EEK

BARNEYCREEK

LITTLE BARNEYCR

EEK

EMUCREE

K

BU

FFA

LOCREEK

8,1

82

,000

8,1

84

,000

8,1

86

,000

SURPRISE

CREEK

MCARTHUR

RIVER

BU

LL

CR

EE

K

BARNEYCREEK

LITTLE BARNEYCR

EEK

EMUCREEK

BU

F

FALO CRE E K

8,1

82

,000

8,1

84

,000

8,1

86

,000

SURPRISECR

EEK

MCARTHUR

RIVER

BU

LL

CR

EEK

BARNEY CRE EK

EMUCREEK

LITTLE BARNEYCR

EE

K

BU

F

FALO CRE EK

610,000 612,000 614,000 616,000 618,000 620,000

8,1

82

,000

8,1

84

,000

8,1

86

,000


4. Scale: 1:65,000

2020 2030

20502040


300 - 1000

1000 - 2000

2000 - 3000

3000 - 4000

4000 - 5000

5000 - 6000

6000 - 7000

7000 - 8000

8000 - 9000

9000 - 10000

10000 - 11000

11000 - 12000

12000 - 13000

13000 - 14000

14000 - 15000

15000 - 16000

16000 - 17000

17000 - 18000

18000 - 19000

19000 - 20000

>20000


300 - 1000

1000 - 2000

2000 - 3000

3000 - 4000

4000 - 5000

5000 - 6000

6000 - 7000

7000 - 8000

8000 - 9000

9000 - 10000

10000 - 11000

11000 - 12000

12000 - 13000

13000 - 14000

14000 - 15000

15000 - 16000

16000 - 17000

17000 - 18000

18000 - 19000

19000 - 20000

>20000


300 - 1000

1000 - 2000

2000 - 3000

3000 - 4000

4000 - 5000

5000 - 6000

6000 - 7000

7000 - 8000

8000 - 9000

9000 - 10000

10000 - 11000

11000 - 12000

12000 - 13000

13000 - 14000

14000 - 15000

15000 - 16000

16000 - 17000

17000 - 18000

18000 - 19000

19000 - 20000

>20000


300 - 1000

1000 - 2000

2000 - 3000

3000 - 4000

4000 - 5000

5000 - 6000

6000 - 7000

7000 - 8000

8000 - 9000

9000 - 10000

10000 - 11000

11000 - 12000

12000 - 13000

13000 - 14000

14000 - 15000

15000 - 16000

16000 - 17000

17000 - 18000

18000 - 19000

19000 - 20000

>20000


MRM OMP EIS


Appendix


Page -6


Figure 5: Predicted sulphate concentrations in the weathered bedrock at 2060, 2070, 2080 and 2090

SURPRISE

C

REEK

MCARTHUR

RIVER

BU

LL

CR

EE

K

BARNEYCREEK

EMUCREE

K

LITTLE BARNEYCR

EEK

BU

F

FALO CRE E K

610,000 612,000 614,000 616,000 618,000 620,000

8,1

82

,000

8,1

84

,000

8,1

86

,000

0 0.5 1 1.5 2

km

NOTES:


Merge 50cm.ecw



Legend

River/Creek

Diversion

SURPRISE

CREEK

MCARTHUR

RIVER

BU

LL

CR

EEK

BARNEYCREEK

LITTLE BARNEYCR

EEK

EMUCREE

K

BU

FFA

LOCREEK

8,1

82

,000

8,1

84

,000

8,1

86

,000

SURPRISE

CREEK

MCARTHUR

RIVER

BU

LL

CR

EE

K

BARNEYCREEK

LITTLE BARNEYCR

EEK

EMUCREEK

BU

F

FALO CRE E K

8,1

82

,000

8,1

84

,000

8,1

86

,000

SURPRISECR

EEK

MCARTHUR

RIVER

BU

LL

CR

EEK

BARNEY CRE EK

EMUCREEK

LITTLE BARNEYCR

EE

K

BU

F

FALO CRE EK

610,000 612,000 614,000 616,000 618,000 620,000

8,1

82

,000

8,1

84

,000

8,1

86

,000


4. Scale: 1:65,000

2060 2070

20902080


300 - 1000

1000 - 2000

2000 - 3000

3000 - 4000

4000 - 5000

5000 - 6000

6000 - 7000

7000 - 8000

8000 - 9000

9000 - 10000

10000 - 11000

11000 - 12000

12000 - 13000

13000 - 14000

14000 - 15000

15000 - 16000

16000 - 17000

17000 - 18000

18000 - 19000

19000 - 20000

>20000


300 - 1000

1000 - 2000

2000 - 3000

3000 - 4000

4000 - 5000

5000 - 6000

6000 - 7000

7000 - 8000

8000 - 9000

9000 - 10000

10000 - 11000

11000 - 12000

12000 - 13000

13000 - 14000

14000 - 15000

15000 - 16000

16000 - 17000

17000 - 18000

18000 - 19000

19000 - 20000

>20000


300 - 1000

1000 - 2000

2000 - 3000

3000 - 4000

4000 - 5000

5000 - 6000

6000 - 7000

7000 - 8000

8000 - 9000

9000 - 10000

10000 - 11000

11000 - 12000

12000 - 13000

13000 - 14000

14000 - 15000

15000 - 16000

16000 - 17000

17000 - 18000

18000 - 19000

19000 - 20000

>20000


300 - 1000

1000 - 2000

2000 - 3000

3000 - 4000

4000 - 5000

5000 - 6000

6000 - 7000

7000 - 8000

8000 - 9000

9000 - 10000

10000 - 11000

11000 - 12000

12000 - 13000

13000 - 14000

14000 - 15000

15000 - 16000

16000 - 17000

17000 - 18000

18000 - 19000

19000 - 20000

>20000


MRM OMP EIS


Appendix


Page -7


Figure 6: Predicted sulphate concentrations in the weathered bedrock at 2100

SURPRISE

C

REEK

MCARTHUR

RIVER

BU

LL

CR

EE

K

BARNEYCREEK

EMUCREE

K

LITTLE BARNEYCR

EEK

BU

F

FALO CRE E K

610,000 612,000 614,000 616,000 618,000 620,000

8,1

82

,000

8,1

84

,000

8,1

86

,000

0 0.5 1 1.5 2

km

NOTES:


Merge 50cm.ecw



Legend

River/Creek

Diversion


4. Scale: 1:65,000


300 - 1000

1000 - 2000

2000 - 3000

3000 - 4000

4000 - 5000

5000 - 6000

6000 - 7000

7000 - 8000

8000 - 9000

9000 - 10000

10000 - 11000

11000 - 12000

12000 - 13000

13000 - 14000

14000 - 15000

15000 - 16000

16000 - 17000

17000 - 18000

18000 - 19000

19000 - 20000

>20000


MRM OMP EIS


Appendix


Page -8


Figure 7: Predicted sulphate concentrations in the upper bedrock at 2030, 2050 and 2100

SURPRISE

C

REEK

MCARTHUR

RIVER

BU

LL

CR

EE

K

BARNEYCREEK

EMUCREE

K

LITTLE BARNEYCR

EEK

BU

F

FALO CRE E K

610,000 612,000 614,000 616,000 618,000 620,000

8,1

82

,000

8,1

84

,000

8,1

86

,000

0 0.5 1 1.5 2

km

NOTES:


Merge 50cm.ecw



Legend

River/Creek

Diversion

SURPRISE

CREEK

MCARTHUR

RIVER

BU

LL

CR

EE

K

BARNEYCREEK

LITTLE BARNEYCR

EEK

EMUCREEK

BU

F

FALO CRE E K

8,1

82

,000

8,1

84

,000

8,1

86

,000

SURPRISECR

EEK

MCARTHUR

RIVER

BU

LL

CR

EEK

BARNEY CRE EK

EMUCREEK

LITTLE BARNEYCR

EE

K

BU

F

FALO CRE EK

610,000 612,000 614,000 616,000 618,000 620,000

8,1

82

,000

8,1

84

,000

8,1

86

,000


4. Scale: 1:65,000

2030 2050

2100


300 - 1000

1000 - 2000

2000 - 3000

3000 - 4000

4000 - 5000

5000 - 6000

6000 - 7000

7000 - 8000

8000 - 9000

9000 - 10000

10000 - 11000

11000 - 12000

12000 - 13000

13000 - 14000

14000 - 15000

15000 - 16000

16000 - 17000

17000 - 18000

18000 - 19000

19000 - 20000

>20000


300 - 1000

1000 - 2000

2000 - 3000

3000 - 4000

4000 - 5000

5000 - 6000

6000 - 7000

7000 - 8000

8000 - 9000

9000 - 10000

10000 - 11000

11000 - 12000

12000 - 13000

13000 - 14000

14000 - 15000

15000 - 16000

16000 - 17000

17000 - 18000

18000 - 19000

19000 - 20000

>20000


300 - 1000

1000 - 2000

2000 - 3000

3000 - 4000

4000 - 5000

5000 - 6000

6000 - 7000

7000 - 8000

8000 - 9000

9000 - 10000

10000 - 11000

11000 - 12000

12000 - 13000

13000 - 14000

14000 - 15000

15000 - 16000

16000 - 17000

17000 - 18000

18000 - 19000

19000 - 20000

>20000


MRM OMP EIS


Appendix


Page -9


Figure 8: Predicted sulphate concentrations in the lower bedrock at 2030, 2050 and 2100

SURPRISE

C

REEK

MCARTHUR

RIVER

BU

LL

CR

EE

K

BARNEYCREEK

EMUCREE

K

LITTLE BARNEYCR

EEK

BU

F

FALO CRE E K

610,000 612,000 614,000 616,000 618,000 620,000

8,1

82

,000

8,1

84

,000

8,1

86

,000

0 0.5 1 1.5 2

km

NOTES:


Merge 50cm.ecw



Legend

River/Creek

Diversion

SURPRISE

CREEK

MCARTHUR

RIVER

BU

LL

CR

EE

K

BARNEYCREEK

LITTLE BARNEYCR

EEK

EMUCREEK

BU

F

FALO CRE E K

8,1

82

,000

8,1

84

,000

8,1

86

,000

SURPRISECR

EEK

MCARTHUR

RIVER

BU

LL

CR

EEK

BARNEY CRE EK

EMUCREEK

LITTLE BARNEYCR

EE

K

BU

F

FALO CRE EK

610,000 612,000 614,000 616,000 618,000 620,000

8,1

82

,000

8,1

84

,000

8,1

86

,000


4. Scale: 1:65,000

2030 2050

2100


300 - 1000

1000 - 2000

2000 - 3000

3000 - 4000

4000 - 5000

5000 - 6000

6000 - 7000

7000 - 8000

8000 - 9000

9000 - 10000

10000 - 11000

11000 - 12000

12000 - 13000

13000 - 14000

14000 - 15000

15000 - 16000

16000 - 17000

17000 - 18000

18000 - 19000

19000 - 20000

>20000


300 - 1000

1000 - 2000

2000 - 3000

3000 - 4000

4000 - 5000

5000 - 6000

6000 - 7000

7000 - 8000

8000 - 9000

9000 - 10000

10000 - 11000

11000 - 12000

12000 - 13000

13000 - 14000

14000 - 15000

15000 - 16000

16000 - 17000

17000 - 18000

18000 - 19000

19000 - 20000

>20000


300 - 1000

1000 - 2000

2000 - 3000

3000 - 4000

4000 - 5000

5000 - 6000

6000 - 7000

7000 - 8000

8000 - 9000

9000 - 10000

10000 - 11000

11000 - 12000

12000 - 13000

13000 - 14000

14000 - 15000

15000 - 16000

16000 - 17000

17000 - 18000

18000 - 19000

19000 - 20000

>20000


MRM OMP EIS


Appendix


Page -10


Figure 9: Predicted zinc concentrations in the overburden at 2020, 2030, 2040 and 2050

SURPRISE

C

REEK

MCARTHUR

RIVER

BU

LL

CR

EE

K

BARNEYCREEK

EMUCREE

K

LITTLE BARNEYCR

EEK

BU

F

FALO CRE E K

610,000 612,000 614,000 616,000 618,000 620,000

8,1

82

,000

8,1

84

,000

8,1

86

,000

0 0.5 1 1.5 2

km

NOTES:


Merge 50cm.ecw



Legend

River/Creek

Diversion

SURPRISE

CREEK

MCARTHUR

RIVER

BU

LL

CR

EEK

BARNEYCREEK

LITTLE BARNEYCR

EEK

EMUCREE

K

BU

FFA

LOCREEK

8,1

82

,000

8,1

84

,000

8,1

86

,000

SURPRISE

CREEK

MCARTHUR

RIVER

BU

LL

CR

EE

K

BARNEYCREEK

LITTLE BARNEYCR

EEK

EMUCREEK

BU

F

FALO CRE E K

8,1

82

,000

8,1

84

,000

8,1

86

,000

SURPRISECR

EEK

MCARTHUR

RIVER

BU

LL

CR

EEK

BARNEY CRE EK

EMUCREEK

LITTLE BARNEYCR

EE

K

BU

F

FALO CRE EK

610,000 612,000 614,000 616,000 618,000 620,000

8,1

82

,000

8,1

84

,000

8,1

86

,000


4. Scale: 1:65,000

2020 2030

20502040

ZincConcentration(mg/L)

0.02 - 0.025

0.025 - 0.05

0.05 - 0.075

0.075 - 0.1

0.1 - 0.25

0.25 - 0.5

0.5 - 0.75

0.75 - 1

1 - 2.5

2.5 - 5

5 - 7.5

7.5 - 10

10 - 30

>30


0.02 - 0.025

0.025 - 0.05

0.05 - 0.075

0.075 - 0.1

0.1 - 0.25

0.25 - 0.5

0.5 - 0.75

0.75 - 1

1 - 2.5

2.5 - 5

5 - 7.5

7.5 - 10

10 - 30

>30


0.02 - 0.025

0.025 - 0.05

0.05 - 0.075

0.075 - 0.1

0.1 - 0.25

0.25 - 0.5

0.5 - 0.75

0.75 - 1

1 - 2.5

2.5 - 5

5 - 7.5

7.5 - 10

10 - 30

>30


0.02 - 0.025

0.025 - 0.05

0.05 - 0.075

0.075 - 0.1

0.1 - 0.25

0.25 - 0.5

0.5 - 0.75

0.75 - 1

1 - 2.5

2.5 - 5

5 - 7.5

7.5 - 10

10 - 30

>30


MRM OMP EIS


Appendix


Page -11


Figure 10: Predicted zinc concentrations in the overburden at 2060, 2070, 2080 and 2090

SURPRISE

C

REEK

MCARTHUR

RIVER

BU

LL

CR

EE

K

BARNEYCREEK

EMUCREE

K

LITTLE BARNEYCR

EEK

BU

F

FALO CRE E K

610,000 612,000 614,000 616,000 618,000 620,000

8,1

82

,000

8,1

84

,000

8,1

86

,000

0 0.5 1 1.5 2

km

NOTES:


Merge 50cm.ecw



Legend

River/Creek

Diversion

SURPRISE

CREEK

MCARTHUR

RIVER

BU

LL

CR

EEK

BARNEYCREEK

LITTLE BARNEYCR

EEK

EMUCREE

K

BU

FFA

LOCREEK

8,1

82

,000

8,1

84

,000

8,1

86

,000

SURPRISE

CREEK

MCARTHUR

RIVER

BU

LL

CR

EE

K

BARNEYCREEK

LITTLE BARNEYCR

EEK

EMUCREEK

BU

F

FALO CRE E K

8,1

82

,000

8,1

84

,000

8,1

86

,000

SURPRISECR

EEK

MCARTHUR

RIVER

BU

LL

CR

EEK

BARNEY CRE EK

EMUCREEK

LITTLE BARNEYCR

EE

K

BU

F

FALO CRE EK

610,000 612,000 614,000 616,000 618,000 620,000

8,1

82

,000

8,1

84

,000

8,1

86

,000


4. Scale: 1:65,000

2060 2070

20902080


0.02 - 0.025

0.025 - 0.05

0.05 - 0.075

0.075 - 0.1

0.1 - 0.25

0.25 - 0.5

0.5 - 0.75

0.75 - 1

1 - 2.5

2.5 - 5

5 - 7.5

7.5 - 10

10 - 30

>30


0.02 - 0.025

0.025 - 0.05

0.05 - 0.075

0.075 - 0.1

0.1 - 0.25

0.25 - 0.5

0.5 - 0.75

0.75 - 1

1 - 2.5

2.5 - 5

5 - 7.5

7.5 - 10

10 - 30

>30


0.02 - 0.025

0.025 - 0.05

0.05 - 0.075

0.075 - 0.1

0.1 - 0.25

0.25 - 0.5

0.5 - 0.75

0.75 - 1

1 - 2.5

2.5 - 5

5 - 7.5

7.5 - 10

10 - 30

>30


0.02 - 0.025

0.025 - 0.05

0.05 - 0.075

0.075 - 0.1

0.1 - 0.25

0.25 - 0.5

0.5 - 0.75

0.75 - 1

1 - 2.5

2.5 - 5

5 - 7.5

7.5 - 10

10 - 30

>30


MRM OMP EIS


Appendix


Page -12


Figure 11: Predicted zinc concentrations in the overburden at 2100

SURPRISE

C

REEK

MCARTHUR

RIVER

BU

LL

CR

EE

K

BARNEYCREEK

EMUCREE

K

LITTLE BARNEYCR

EEK

BU

F

FALO CRE E K

610,000 612,000 614,000 616,000 618,000 620,000

8,1

82

,000

8,1

84

,000

8,1

86

,000

0 0.5 1 1.5 2

km

NOTES:


Merge 50cm.ecw



Legend

River/Creek

Diversion


4. Scale: 1:65,000

2100


0.02 - 0.025

0.025 - 0.05

0.05 - 0.075

0.075 - 0.1

0.1 - 0.25

0.25 - 0.5

0.5 - 0.75

0.75 - 1

1 - 2.5

2.5 - 5

5 - 7.5

7.5 - 10

10 - 30

>30


MRM OMP EIS


Appendix


Page -13


Figure 12: Predicted zinc concentrations in the weathered bedrock at 2020, 2030, 2040 and 2050

SURPRISE

C

REEK

MCARTHUR

RIVER

BU

LL

CR

EE

K

BARNEYCREEK

EMUCREE

K

LITTLE BARNEYCR

EEK

BU

F

FALO CRE E K

610,000 612,000 614,000 616,000 618,000 620,000

8,1

82

,000

8,1

84

,000

8,1

86

,000

0 0.5 1 1.5 2

km

NOTES:


Merge 50cm.ecw



Legend

River/Creek

Diversion

SURPRISE

CREEK

MCARTHUR

RIVER

BU

LL

CR

EEK

BARNEYCREEK

LITTLE BARNEYCR

EEK

EMUCREE

K

BU

FFA

LOCREEK

8,1

82

,000

8,1

84

,000

8,1

86

,000

SURPRISE

CREEK

MCARTHUR

RIVER

BU

LL

CR

EE

K

BARNEYCREEK

LITTLE BARNEYCR

EEK

EMUCREEK

BU

F

FALO CRE E K

8,1

82

,000

8,1

84

,000

8,1

86

,000

SURPRISECR

EEK

MCARTHUR

RIVER

BU

LL

CR

EEK

BARNEY CRE EK

EMUCREEK

LITTLE BARNEYCR

EE

K

BU

F

FALO CRE EK

610,000 612,000 614,000 616,000 618,000 620,000

8,1

82

,000

8,1

84

,000

8,1

86

,000


4. Scale: 1:65,000

2020 2030

20502040


0.02 - 0.025

0.025 - 0.05

0.05 - 0.075

0.075 - 0.1

0.1 - 0.25

0.25 - 0.5

0.5 - 0.75

0.75 - 1

1 - 2.5

2.5 - 5

5 - 7.5

7.5 - 10

10 - 30

>30


0.02 - 0.025

0.025 - 0.05

0.05 - 0.075

0.075 - 0.1

0.1 - 0.25

0.25 - 0.5

0.5 - 0.75

0.75 - 1

1 - 2.5

2.5 - 5

5 - 7.5

7.5 - 10

10 - 30

>30


0.02 - 0.025

0.025 - 0.05

0.05 - 0.075

0.075 - 0.1

0.1 - 0.25

0.25 - 0.5

0.5 - 0.75

0.75 - 1

1 - 2.5

2.5 - 5

5 - 7.5

7.5 - 10

10 - 30

>30


0.02 - 0.025

0.025 - 0.05

0.05 - 0.075

0.075 - 0.1

0.1 - 0.25

0.25 - 0.5

0.5 - 0.75

0.75 - 1

1 - 2.5

2.5 - 5

5 - 7.5

7.5 - 10

10 - 30

>30


MRM OMP EIS


Appendix


Page -14


Figure 13: Predicted zinc concentrations in the weathered bedrock at 2060, 2070, 2080 and 2090

SURPRISE

C

REEK

MCARTHUR

RIVER

BU

LL

CR

EE

K

BARNEYCREEK

EMUCREE

K

LITTLE BARNEYCR

EEK

BU

F

FALO CRE E K

610,000 612,000 614,000 616,000 618,000 620,000

8,1

82

,000

8,1

84

,000

8,1

86

,000

0 0.5 1 1.5 2

km

NOTES:


Merge 50cm.ecw



Legend

River/Creek

Diversion

SURPRISE

CREEK

MCARTHUR

RIVER

BU

LL

CR

EEK

BARNEYCREEK

LITTLE BARNEYCR

EEK

EMUCREE

K

BU

FFA

LOCREEK

8,1

82

,000

8,1

84

,000

8,1

86

,000

SURPRISE

CREEK

MCARTHUR

RIVER

BU

LL

CR

EE

K

BARNEYCREEK

LITTLE BARNEYCR

EEK

EMUCREEK

BU

F

FALO CRE E K

8,1

82

,000

8,1

84

,000

8,1

86

,000

SURPRISECR

EEK

MCARTHUR

RIVER

BU

LL

CR

EEK

BARNEY CRE EK

EMUCREEK

LITTLE BARNEYCR

EE

K

BU

F

FALO CRE EK

610,000 612,000 614,000 616,000 618,000 620,000

8,1

82

,000

8,1

84

,000

8,1

86

,000


4. Scale: 1:65,000

2060 2070

20902080


0.02 - 0.025

0.025 - 0.05

0.05 - 0.075

0.075 - 0.1

0.1 - 0.25

0.25 - 0.5

0.5 - 0.75

0.75 - 1

1 - 2.5

2.5 - 5

5 - 7.5

7.5 - 10

10 - 30

>30


0.02 - 0.025

0.025 - 0.05

0.05 - 0.075

0.075 - 0.1

0.1 - 0.25

0.25 - 0.5

0.5 - 0.75

0.75 - 1

1 - 2.5

2.5 - 5

5 - 7.5

7.5 - 10

10 - 30

>30


0.02 - 0.025

0.025 - 0.05

0.05 - 0.075

0.075 - 0.1

0.1 - 0.25

0.25 - 0.5

0.5 - 0.75

0.75 - 1

1 - 2.5

2.5 - 5

5 - 7.5

7.5 - 10

10 - 30

>30


0.02 - 0.025

0.025 - 0.05

0.05 - 0.075

0.075 - 0.1

0.1 - 0.25

0.25 - 0.5

0.5 - 0.75

0.75 - 1

1 - 2.5

2.5 - 5

5 - 7.5

7.5 - 10

10 - 30

>30


MRM OMP EIS


Appendix


Page -15


Figure 14: Predicted zinc concentrations in the weathered bedrock at 2100

SURPRISE

C

REEK

MCARTHUR

RIVER

BU

LL

CR

EE

K

BARNEYCREEK

EMUCREE

K

LITTLE BARNEYCR

EEK

BU

F

FALO CRE E K

610,000 612,000 614,000 616,000 618,000 620,000

8,1

82

,000

8,1

84

,000

8,1

86

,000

0 0.5 1 1.5 2

km

NOTES:


Merge 50cm.ecw



Legend

River/Creek

Diversion


4. Scale: 1:65,000


300 - 1000

1000 - 2000

2000 - 3000

3000 - 4000

4000 - 5000

5000 - 6000

6000 - 7000

7000 - 8000

8000 - 9000

9000 - 10000

10000 - 11000

11000 - 12000

12000 - 13000

13000 - 14000

14000 - 15000

15000 - 16000

16000 - 17000

17000 - 18000

18000 - 19000

19000 - 20000

>20000


MRM OMP EIS


Appendix


Page -16


Figure 15: Predicted zinc concentrations in the upper bedrock at 2030, 2050 and 2100

SURPRISE

C

REEK

MCARTHUR

RIVER

BU

LL

CR

EE

K

BARNEYCREEK

EMUCREE

K

LITTLE BARNEYCR

EEK

BU

F

FALO CRE E K

610,000 612,000 614,000 616,000 618,000 620,000

8,1

82

,000

8,1

84

,000

8,1

86

,000

0 0.5 1 1.5 2

km

NOTES:


Merge 50cm.ecw



Legend

River/Creek

Diversion

SURPRISE

CREEK

MCARTHUR

RIVER

BU

LL

CR

EE

K

BARNEYCREEK

LITTLE BARNEYCR

EEK

EMUCREEK

BU

F

FALO CRE E K

8,1

82

,000

8,1

84

,000

8,1

86

,000

SURPRISECR

EEK

MCARTHUR

RIVER

BU

LL

CR

EEK

BARNEY CRE EK

EMUCREEK

LITTLE BARNEYCR

EE

K

BU

F

FALO CRE EK

610,000 612,000 614,000 616,000 618,000 620,000

8,1

82

,000

8,1

84

,000

8,1

86

,000


4. Scale: 1:65,000

2030 2050

2100


0.02 - 0.025

0.025 - 0.05

0.05 - 0.075

0.075 - 0.1

0.1 - 0.25

0.25 - 0.5

0.5 - 0.75

0.75 - 1

1 - 2.5

2.5 - 5

5 - 7.5

7.5 - 10

10 - 30

>30


0.02 - 0.025

0.025 - 0.05

0.05 - 0.075

0.075 - 0.1

0.1 - 0.25

0.25 - 0.5

0.5 - 0.75

0.75 - 1

1 - 2.5

2.5 - 5

5 - 7.5

7.5 - 10

10 - 30

>30


0.02 - 0.025

0.025 - 0.05

0.05 - 0.075

0.075 - 0.1

0.1 - 0.25

0.25 - 0.5

0.5 - 0.75

0.75 - 1

1 - 2.5

2.5 - 5

5 - 7.5

7.5 - 10

10 - 30

>30


MRM OMP EIS


Appendix


Page -17


Figure 16: Predicted zinc concentrations in the lower bedrock at 2030, 2050 and 2100

SURPRISE

C

REEK

MCARTHUR

RIVER

BU

LL

CR

EE

K

BARNEYCREEK

EMUCREE

K

LITTLE BARNEYCR

EEK

BU

F

FALO CRE E K

610,000 612,000 614,000 616,000 618,000 620,000

8,1

82

,000

8,1

84

,000

8,1

86

,000

0 0.5 1 1.5 2

km

NOTES:


Merge 50cm.ecw



Legend

River/Creek

Diversion

SURPRISE

CREEK

MCARTHUR

RIVER

BU

LL

CR

EE

K

BARNEYCREEK

LITTLE BARNEYCR

EEK

EMUCREEK

BU

F

FALO CRE E K

8,1

82

,000

8,1

84

,000

8,1

86

,000

SURPRISECR

EEK

MCARTHUR

RIVER

BU

LL

CR

EEK

BARNEY CRE EK

EMUCREEK

LITTLE BARNEYCR

EE

K

BU

F

FALO CRE EK

610,000 612,000 614,000 616,000 618,000 620,000

8,1

82

,000

8,1

84

,000

8,1

86

,000


4. Scale: 1:65,000

2030 2050

2100


0.02 - 0.025

0.025 - 0.05

0.05 - 0.075

0.075 - 0.1

0.1 - 0.25

0.25 - 0.5

0.5 - 0.75

0.75 - 1

1 - 2.5

2.5 - 5

5 - 7.5

7.5 - 10

10 - 30

>30


0.02 - 0.025

0.025 - 0.05

0.05 - 0.075

0.075 - 0.1

0.1 - 0.25

0.25 - 0.5

0.5 - 0.75

0.75 - 1

1 - 2.5

2.5 - 5

5 - 7.5

7.5 - 10

10 - 30

>30


0.02 - 0.025

0.025 - 0.05

0.05 - 0.075

0.075 - 0.1

0.1 - 0.25

0.25 - 0.5

0.5 - 0.75

0.75 - 1

1 - 2.5

2.5 - 5

5 - 7.5

7.5 - 10

10 - 30

>30

Appendix L – Revised Groundwater Modelling Report | NT EPA

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Transcript of Appendix L – Revised Groundwater Modelling Report | NT EPA