Water and Environment - Amazon S3€¦ · Water and Environment WEST CREEK WATER SUPPLY GROUNDWATER MODELLING Prepared for Toro Energy Ltd Date of Issue 30 June 2010 Our Reference

Water and Environment

WEST CREEK WATER SUPPLY GROUNDWATER MODELLING

Prepared for Toro Energy Ltd

Date of Issue 30 June 2010

Our Reference 1134/C/104a As part of Aquaterra’s commitment to the environment this PDF has been designed for double sided printing and includes blank pages as part of the document.


Prepared for Toro Energy Ltd

Date of Issue 30 June 2010

Our Reference 1134/C/104a



Date Revision Description

Revision A 30/06/2010 Draft

Name Position Signature Date

Originator Iain Marshall Senior Hydrogeologist 30/06/2010

Alan Woodward Principal Hydrogeologist

30/06/2010

Reviewer Kathryn Rozlapa Principal Modeller 30/06/2010

Jeff Jolly Principal Hydrogeologist

30/06/2010

Location Address

Issuing Office Perth Suite 4, 125 Melville Parade, Como WA 6152 Tel +61 8 9368 4044 Fax +61 8 9368 4055


EXECUTIVE SUMMARY


EXECUTIVE SUMMARY

Toro Energy’s (Toro) Lake Way and Centipede uranium deposits are located along the edge of the Lake Way playa, just south of the town of Wiluna, in the Murchison region of Western Australia’s Mid West.

Toro propose to process approximately 2Mt of ore per annum over a project life of 10 years. It is estimated that ~0.70GL/year of moderate salinity water (TDS < 3,000mg/L) will be required to process the ore. This study evaluates the feasibility of sourcing this process water from the West Creek groundwater system, located to the east of Wiluna.

This report presents the following:

▼ A review of the existing environment and hydrogeological conditions of the West Creek area.

▼ Details of the development of a 3 layer regional-scale Modflow/Surfact groundwater model to assess the long-term yield potential of the shallow calcrete aquifer system that extends along the West Creek, in terms of its potential to meet the water demand of Toro’s Wiluna Uranium Project, both in terms of the water quantity and quality requirements. The model is also used to assess the supply potential of the existing West Creek production bores and to determine the optimal borefield configuration required to maximise abstraction from the aquifer within various prescribed water level drawdown constraints.

▼ Results of the modelling.

▼ Borefield development costs.

The following conclusions are reached from the work undertaken:

▼ Water quality within the calcrete aquifer in the study area is marginal at best with respect to the Wiluna Uranium Project water quality constraints.

▼ Water quality within the deeper silty/clayey sediments underlying the calcrete aquifer is unlikely to meet Toro’s water quality constraints.

▼ The modelling indicates that the current West Creek Borefield (installed in the calcrete aquifer) comprising bores P18, P22, P61 and P62 is unlikely to satisfy Toro’s water demand of 0.7GL/year for a project life of ten years.

▼ The modelling indicates that a reconfiguration of the existing West Creek Borefield (comprising P18, P26, P62, P70 and P21) is unlikely supply the required 0.7GL/year for ten years.

▼ The modelling indicates that an expanded West Creek Borefield installed in the calcrete aquifer may meet the Projects water requirements (0.7GL/year) for 8 to 9 years, before declining to ~0.66GL in the tenth year.

▼ The final water quality of the blend of an expanded West Creek Borefield will not be known until further hydrogeological data is collected.

▼ Operation of the Apex Southern Borefield at significant rates is likely to have a deleterious effect on the operation of the West Creek borefield.

▼ The capital costs of developing a 0.7GL/year capacity water supply scheme to pipe water from the West Creek Borefield to the Centipede and Lake Way mines, as well the mine village, is estimated at $12.1M.


EXECUTIVE SUMMARY


A number of recommendations are presented in this report, these are summarised as follows:

▼ A further hydrogeological investigation of the study area should be undertaken.

▼ If the above investigation provides favourable results, a more intensive investigation (including the installation of new production bores and the refurbishment of existing bores) be undertaken.

▼ The groundwater model developed for this study should be updated if the above investigations provide favourable results. The updated model should be used to generate new abstraction predictions.

It should be noted that the modelling results are based on the current model geometry, which has in turn been developed from the current limited hydrogeological dataset, and it assumes average rainfall conditions. The limitations of the modelling work reported here are presented in Section 4.8.


INTRODUCTION

Our Reference 1134/C/104a Page i

CONTENTS

1 INTRODUCTION ...................................................................................................1 1.1 BACKGROUND .............................................................................................1 1.2 SCOPE OF WORK.......................................................................................... 1 1.3 EXISTING ENVIRONMENT .............................................................................. 5

1.3.1 CLIMATE............................................................................................. 5 1.3.2 TOPOGRAPHY ...................................................................................... 5 1.3.3 GEOLOGY............................................................................................ 5 1.3.4 HYDROGEOLOGY.................................................................................. 9

1.4 MINE WATER REQUIREMENTS ........................................................................ 9 1.5 DEVELOPMENT AND UTILISATION OF THE WEST CREEK GROUNDWATER

RESOURCE ................................................................................................ 10 1.5.1 WEST CREEK BOREFIELD .................................................................... 10 1.5.2 APEX SOUTHERN BOREFIELD............................................................... 21

2 CONCEPTUAL HYDROGEOLOGY ..........................................................................25 2.1 PREAMBLE................................................................................................. 25 2.2 DATA REVIEW............................................................................................ 25

2.2.1 DATA SOURCES ................................................................................. 25 2.2.2 OUTCOME OF THE DATA REVIEW.......................................................... 25

2.3 CALCRETE AQUIFER.................................................................................... 25 2.3.1 GEOMETRY........................................................................................ 25 2.3.2 WATER LEVELS AND GROUNDWATER FLOW ........................................... 26 2.3.3 GROUNDWATER RECHARGE AND EVAPOTRANSPIRATION......................... 26 2.3.4 KEY AQUIFER PARAMETERS ................................................................. 26

2.4 ALLUVIUM................................................................................................. 27 2.4.1 ALLUVIUM GEOMETRY......................................................................... 27 2.4.2 WATER LEVELS AND GROUNDWATER FLOW ........................................... 27 2.4.3 GROUNDWATER RECHARGE AND EVAPOTRANSPIRATION......................... 27 2.4.4 KEY AQUIFER PARAMETERS ................................................................. 28

2.5 BASAL CLAYS AND SILT .............................................................................. 28 2.6 FRACTURED ROCK (BEDROCK)..................................................................... 28

3 MINE WATER SUPPLY BOREFIELD OPTIONS ......................................................29 3.1 EXISTING BORES ....................................................................................... 29 3.2 RECOMMENDATIONS FROM PREVIOUS STUDIES............................................. 29 3.3 POSSIBLE NEW DEVELOPMENTS................................................................... 29

4 GROUNDWATER MODEL .....................................................................................30 4.1 MODELLING OBJECTIVES ............................................................................ 30


INTRODUCTION

Page ii Our Reference 1134/C/104a

4.2 MODEL SETUP ........................................................................................... 30 4.2.1 MODEL GRID AND EXTENT .................................................................. 30 4.2.2 MODEL GEOMETRY ............................................................................. 33

4.3 GROUNDWATER INFLOW AND OUTFLOW ....................................................... 45 4.3.1 GROUNDWATER THROUGHFLOW .......................................................... 45 4.3.2 RAINFALL RECHARGE ......................................................................... 45 4.3.3 EVAPOTRANSPIRATION....................................................................... 45 4.3.4 GROUNDWATER ABSTRACTION............................................................ 46

4.4 MODEL CALIBRATION ................................................................................. 51 4.4.1 PREAMBLE ........................................................................................ 51 4.4.2 STEADY-STATE CALIBRATION .............................................................. 51 4.4.3 TRANSIENT CALIBRATION ................................................................... 61

4.5 MODEL PREDICTIONS ................................................................................. 67 4.5.1 SETUP .............................................................................................. 67 4.5.2 PREDICTION RESULTS ........................................................................ 73

4.6 SENSITIVITY ANALYSIS .............................................................................. 89 4.7 GROUNDWATER RECOVERY ......................................................................... 93 4.8 MODEL LIMITATIONS.................................................................................. 97

4.8.1 ABSTRACTION ESTIMATES .................................................................. 97 4.8.2 RECHARGE........................................................................................ 97 4.8.3 AQUIFER CHARACTERISTICS AND CALIBRATION TO TRANSIENT DATA ...... 97

5 DISCUSSION......................................................................................................98 5.1 WATER SUPPLY OPTIONS ............................................................................ 98 5.2 PREDICTED DRAWDOWNS........................................................................... 99

6 WEST CREEK BOREFIELD DEVELOPMENT COSTS ..............................................100 6.1 BORE CONSTRUCTION AND TESTING COSTS ................................................100 6.2 PUMP, PIPELINE AND POWER SUPPLY CAPITAL COSTS....................................100

7 CONCLUSIONS .................................................................................................103

8 RECOMMENDATIONS........................................................................................104

9 REFERENCES ....................................................................................................105


INTRODUCTION

Our Reference 1134/C/104a Page iii

TABLES

Table 1.1: Technical and operational information for the West Creek production bores........... 10 Table 1.2: Chemistry of Groundwater from the West Creek Production Bores ....................... 16 Table 1.3: Groundwater chemistry of the production bores in the Apex Southern Borefield ..... 22 Table 2.1: Hydraulic Characteristics of the calcrete aquifer in the West Creek Borefield.......... 27 Table 4.1: Corner Coordinates of the Model Domain ......................................................... 30 Table 4.2: Model Layers ............................................................................................... 33 Table 4.3: Adopted Recharge Values .............................................................................. 52 Table 4.4: Calculated and Adopted Steady-State Calibration Heads for West Creek Borefield .. 52 Table 4.5: Steady State Predicted Water Balance (m3/day)................................................ 52 Table 4.6: Transient Calibration Model Specific Yield and Storage Coefficient Values.............. 61 Table 4.7: Transient Calibration Model Cumulative Mass Balance (m3)................................. 67 Table 4.8: Borefield Prediction Scenarios......................................................................... 68 Table 4.9: Summary of Results for Modelled Scenarios...................................................... 73 Table 4.10: Sensitivity runs .......................................................................................... 89 Table 5.1: Areas of drawdown- Scenarios 6, 8 and 9 ........................................................ 99 Table 6.1: West Creek Borefield Development Costs ........................................................100 Table 6.2: Pumping, pipeline and genset power supply capital costs to Centipede ................101 Table 6.3: Pumping, pipeline and HV power supply capital costs to Centipede .....................101 Table 6.4: Pumping, pipeline and power supply capital costs to Lake Way...........................102

FIGURES

Figure 1.1: Locality plan of the West Creek Groundwater Unit .............................................. 3 Figure 1.2: Simplified Geological Map ............................................................................... 7 Figure 1.3: Location of West Creek and Apex Southern Borefields....................................... 13 Figure 1.4: Water level fluctuations in the West Creek Borefield versus [A] Monthly Rainfall and

[B] Abstraction ........................................................................................... 17 Figure 1.5: Groundwater salinity variations in the West Creek Borefield............................... 19 Figure 1.6: Apex Southern Borefield- Groundwater level fluctuations versus abstraction ........ 23 Figure 4.1: Model Grid and Boundary Conditions .............................................................. 31 Figure 4.2: Aquifer Parameter Distribution Layer 1 ........................................................... 35 Figure 4.3: Aquifer Parameter Distribution Layer 2 ........................................................... 37 Figure 4.4: Aquifer Parameter Distribution Layer 3 ........................................................... 39 Figure 4.5: North-East to South-West Cross-Sections ....................................................... 41 Figure 4.6: North-West to South-East Cross-Section......................................................... 43 Figure 4.7: Modflow Evapotranspiration Package Schematic............................................... 47 Figure 4.8: Evapotranspiration Distribution...................................................................... 49


INTRODUCTION

Page iv Our Reference 1134/C/104a

Figure 4.9: Pumping and Monitoring Bore Locations.......................................................... 53 Figure 4.10: Measured versus Modelled Water Levels........................................................ 55 Figure 4.11: Measured versus Modelled Water Levels and Predicted Steady-State Water Level

Contours .................................................................................................. 57 Figure 4.12: Modelled Recharge Distribution.................................................................... 59 Figure 4.13: Apex Southern Borefield Calibration Hydrographs........................................... 63 Figure 4.14: West Creek Borefield Calibration Hydrographs ............................................... 65 Figure 4.15: Modelled Borefield Configuration .................................................................. 71 Figure 4.16: Total Abstraction for Modelled Borefield Scenarios .......................................... 75 Figure 4.17: Scenario 6- Predicted Watertable after 10 Years............................................. 77 Figure 4.18: Scenario 8- Predicted Watertable after 10 Years............................................. 79 Figure 4.19: Scenario 9- Predicted Watertable after 10 Years............................................. 81 Figure 4.20: Scenario 6- Predicted Drawdown after 10 Years ............................................. 83 Figure 4.21: Scenario 8- Predicted Drawdown after 10 Years ............................................. 85 Figure 4.22: Scenario 9- Predicted Drawdown after 10 Years ............................................. 87 Figure 4.23: Predicted Abstraction Rates- Sensitivity Runs for Scenario 6 ............................ 91 Figure 4.24: Water Levels for Model Cell Containing Bore P62- Scenario 6 and Recovery Run . 95

APPENDICES

Appendix A ACTUAL AREAL EVAPOTRANSPIRATION MAP

Appendix B STEADY-STATE CALIBRATION GROUNDWATER ELEVATIONS

Appendix C PREDICTION MODEL ABSTRACTION VOLUMES


INTRODUCTION

Our Reference 1134/C/104a Page 1

1 INTRODUCTION

1.1 BACKGROUND

Toro Energy’s (Toro) Lake Way and Centipede uranium deposits are located along the edge of the Lake Way playa, just south of the town of Wiluna, in the Murchison region of Western Australia’s Mid West (Figure 1.1). Wiluna is located 750km northeast of Perth and lies along the Goldfields Highway, which connects Wiluna to Leinster (170km to the south-southeast) and to Meekatharra (130km to the west). The nearest regional centre to Wiluna is Kalgoorlie, which is located 500km to the south-southeast of the town.

The Lake Way uranium deposit is located ~15km southeast of Wiluna on the northern shore of the Lake Way playa and lies within exploration licence E53/1132. Toro are currently apply for a mining lease, M53/1090, to cover this deposit. The Centipede deposit is located along the western margin of Lake Way, approximately 30km south-southeast of Wiluna and falls within mining lease M53/224. The uranium mineralisation, consisting mainly of carnotite, is hosted within sheet-like superficial calcrete deposits and associated fluviatile-deltaic sequence of sediments, ranging from thin clay layers to clean coarse sand and gravel.

The Lake Way uranium deposit was discovered in 1972 by Delhi and Vam during exploration for base metals in the Wiluna area. Delhi undertook exploration and initial feasibility work prior to their acquisition by CSR in 1981. The Centipede deposit was discovered in 1977 and CSR acquired the mineral rights to it in 1982. The following year Australia adopted the Three Mines Policy which resulted in the cessation of uranium prospecting. However, the recent reversal of this policy and reconsideration of the national energy policy has resulted in renewed interest in uranium mining across Australia.

During 2006, Toro Energy (then Nova Energy) completed a conceptual mining study that confirmed the technical and economic viability of the Lake Way and Centipede Uranium Project. Preliminary estimates placed the combined resources of both deposits at ~20.2 million tonnes (Mt) of U3O8 (triuranium octaoxide) with an average grade of 0.06% The ore-body generally extends form just below the shallow watertable to a maximum depth of 12 metres below ground level (m.bgl).

Toro propose to process approximately 2Mt of ore per annum over a project life of 10 years, with the Centipede and Lake Way deposits to be mined over years 1 to 6 and 7 to 10, respectively. It is estimated that ~0.70GL/year of moderate salinity water (TDS < 3,000mg/L) will be required to process the ore. Toro Energy propose to rehabilitate and upgrade a disused borefield at West Creek, located on Miscellaneous Lease L53/150, some 18km WNW and 30km NNW from proposed processing plant at Lake Way and Centipede mines, respectively, as the primary water supply for the project.

This report details the development of a groundwater model to assess the long-term yield potential of the shallow calcrete aquifer system that extends along the West Creek, in terms of it’s potential to meet the water demand of Toro’s Wiluna Uranium Project, both in terms of the water quantity and quality requirements. The model is also used to assess the supply potential of the existing West Creek production bores and to determine the optimal borefield configuration required to maximise abstraction from the aquifer within various prescribed waterlevel drawdown constraints.

1.2 SCOPE OF WORK

In late February 2010, Aquaterra were appointed by Toro Energy (PO TOEP028), to conduct studies to characterise the surface hydrology and groundwater conditions at the Lake Way and Centipede uranium deposits, to allow for the development of an environmentally acceptable water management plan for the Wiluna Uranium Project. Aquaterra’s scope of work also included assessing the potential of the West Creek Borefield to meet the Project’s water requirements of 0.70GL/year. In addition, Toro require information on the likely magnitude and extent of the potential cone of water level drawdown that would develop as a result of abstraction from the West Creek Borefield. In terms of assessing the supply potential of the West Creek borefield, Aquaterra (2010) proposed that the following tasks be undertaken:


INTRODUCTION

Page 2 Our Reference 1134/C/104a

▼ A desktop study to collate all of the available information and to develop a conceptual model of the aquifer system.

▼ Construction of a numerical flow model based on the conceptual aquifer, model calibration, and scenario analysis, to cover a number of potential borefield development options, i.e. using the existing production bores and additional bores. The model will be used to evaluate if and how a given borefield configuration could abstract the required water demand, within potential water level drawdown constraints that may be imposed by the Department of Water (DoW).

▼ Preparation of a report that describes the background hydrogeology, the conceptual hydrogeological model, the design, setup and calibration of the numerical flow model, as well as the results and recommendations for implementation. A preliminary design and costing for the reticulation system / engineering required to deliver the water to the Centipede mine would also be supplied.

LOCALITY PLAN OF THE WEST CREEK GROUNDWATER UNIT FIGURE 1.1

f:\jobs\1134\c\600_report\figures\fig 1.1_locality plan of the west creek groundwater unit .doc


INTRODUCTION


1.3 EXISTING ENVIRONMENT

1.3.1 CLIMATE

The Study area has a semi-arid climate which is characterised by low rainfall and large temperature variations. The closest Commonwealth Bureau of Meteorology (BoM) weather station to the project area is located at Wiluna. The mean annual rainfall is approximately 257mm, but may vary widely from in excess of 700mm to less than 50mm. The highest and most reliable rainfall falls between May and August. Intense tropical cyclone related rainfall events may occur between December and April. Cyclone Bobby is a significant recent example, when in the order of 250mm of rainfall was recorded at Wiluna (in a 9 day period from 19 to 27 February 1995). The mean annual maximum and minimum temperatures for Wiluna are 29 and 14.2°C, respectively.

Potential evaporation is approximately 2400mm/year and exceeds rainfall in all months (Water and Rivers Commission, 1999). Actual areal evapotranspiration is estimated to be between 200 and 300mm/year (BoM, 2010).

1.3.2 TOPOGRAPHY

The study area is largely an alluvial plain and is relatively flat, with a typical elevation of ~500mRL. The area slopes towards the south-east, towards Lake Way with a gradient of about 6x10-4 m/m (Geoscience Australia, 2003).

Zones of bedrock outcrop form low-relief hills and largely compartmentalise the study area from adjoining catchments (Geological Survey of Western Australia, 1999) as follows:

▼ North and north-west: the Finlayson Range, with an elevation of up to about 600mRL.

▼ South and south-west: a range of hills incorporating Mt Wilkinson, with an elevation of up to about 600mRL.

▼ East: a range of hills passing to the east of Wiluna town.

Hydrology

The study area is drained by the south-easterly flowing, ephemeral West Creek and its tributaries, which discharge into the northern edge of the Lake Way salt lake. The Cockarrow and Freshwater tributaries drain the floodplains to the north and south of the West Creek. The extensive Yandil and Paroo catchments, located to the northwest of the area, drain through a narrow valley in the Finlayson Range into the West Creek system. The West Creek catchment is ~32km long and extends over an area of 647km2. Lake Way is a large playa which is ~36km long and ~10km wide, with a surface area of some 245km2. Lake Way forms the drainage basin for an 11,000km2 catchment.

1.3.3 GEOLOGY

The geological map (Sheet SG5109, Geological Survey of Western Australia, 1999) indicates that the study area is largely encircled by bedrock outcrop (Figure 1.2):

▼ Northern and north-western periphery of the study area- the bedrock comprises of the Finlayson Member of the Yerrida Group, described as a quartz arenite with subordinate siltstone.

▼ Southern periphery of the study area- Archean granitoids (Yilgarn Craton).

▼ Eastern periphery of the study area is dominated by metamorphosed Archaean felsic volcanic and volcaniclastic sedimentary rocks (Yilgarn Craton).

The geological map of the area also indicates the following surficial geology in the study area is indicated:

▼ Sheetwash deposits (comprising of clay, silt and sand) are reported to cover most of the study area.

▼ In areas shown to be watercourses, alluvium is indicated.


INTRODUCTION


▼ Calcrete outcrops along the upstream reaches of the West Creek River in the narrow valley passing through the Finlayson Range in the north of the study area. A well developed, relatively extensive delta-shaped body of calcrete extends from the West Creek Borefield to the edge of Lake Way. Exploration drilling in the vicinity of the borefield area indicates that the calcrete is approximately 5 to 20m thick, and that it extends further northwards beneath the soil cover.

In summary, the study area is mostly covered by alluvial sheetwash sediments, with calcrete zones developed along the main drainage system, all underlain by a number of consolidated Archaean and Proterozoic units.

22

5,0

00

mE

7,050,000 mN

7,065,000 mN

7,035,000 mN

21

0,0

00

mE

19

5,0

00

mE

Project

PERTH

KALGOORLIE

ALBANY

DERBY

NEWMAN

FIGURE 1.2

LEGEND

SIMPLIFIED GEOLOGICAL MAP

LOCATION MAP

AUTHOR: REPORT NO:

DRAWN: REVISION:

DATE:

IM ...

MS ...

22/06/2010

Study Area/West Creek Groundwater Unit

Kilometers

Scale: 1:150,000 @A3

GDA 1994 Zone 51

DATA SOURCES:1:250K Scale State Topographicl Map

JOB NO: 1134C

f

Location: F:\Jobs\1134\C\GIS\Vector\MapInfo\Figure 1.2.wor

2 0 2 4

Bubble Well Member: stromatoliticchert and chert breccia

Finlayson Member: quartz areniteand subordinate siltstone

Metasediments/ Metavolcanics

Undifferentiated Granites

Metamorphosed Felsics

Metamorphosed Mafics

Ephemeral Lake andDune Deposits

Sheetwash Deposits

Quaternary Alluvium

Cza

Czb

Qa

Yer

rida

Bas

in

Pyjb

CalcreteCzk

Yilg

an C

rato

n As

Ab

Af

Agf

Pyjf

Ag


INTRODUCTION


1.3.4 HYDROGEOLOGY

Within the Northern Goldfields area, groundwater is reported to occur within the following aquifer units (Waters and River Commission, 1999):

▼ Alluvium. Shallow aquifers with a watertable less than 5m below the ground. The salinity of these aquifers is reported to range from 1,000 to 4,000mg/L on the flanks of palaeo-drainage systems, with higher values encountered along the downstream sections of the drainage system. The hydraulic conductivity of the alluvium aquifers is generally low, with values of less than 2.5m/d. Bore yields vary from 50 to 600m3/day, with higher yields being from unconsolidated clayey basaltic gravels.

▼ Calcrete. Calcrete forms local high-yielding aquifers due to secondary porosity and high permeabilities. Calcrete generally occurs in the lower portions of the drainage system where the watertable is shallow (generally less than 5m below surface). Saturated thicknesses generally range from 5 to 10m. The salinity of groundwater in calcrete is frequently brackish to saline, however can be fresher where they are recharged directly from rainfall, or when inundation occurs. Potential bore yields are reported to range from 100 to 4,400m3/day.

▼ Palaeochannel sand. Tertiary-aged palaeochannel sand aquifers are inferred to be continuous along the major drainage systems throughout the northern Goldfields. However, their continuity is poorly understood and the permeable sand horizons may be absent where palaeochannels transgress greenstone belts. These aquifers are the most important aquifer in the region, providing significant groundwater supplies. The aquifer is up to 1km wide, and up to 40m thick in the main channels, reducing to several hundred metres wide in the tributaries. The sand is confined beneath as much as 80m of structureless kaolinitic clay, although in tributaries the confining layer often contains silt and several sandy horizons. Most of the water within the palaeochannel aquifer is reported to be hypersaline, although fresh to brackish zones may occur in drainage tributaries.

▼ Fractured rock. Fractured rock aquifers comprise greenstones, granitoids and minor intrusives, where permeability and secondary porosity have been produced by fracturing. These hydraulic characteristics are directly related to the fracture intensity, with lithology having limited control.

1.4 MINE WATER REQUIREMENTS

Toro proposes to start construction of the Wiluna Uranium Project in 2012, with commercial production of uranium commencing in 2013, and are currently considering two methods for processing of the uranium ore at the Centipede and Lake Way deposits, namely:

▼ Option 1: involves crushing and screening of the ore followed by alkaline heap-leaching with ion exchange uranium recovery.

▼ Option 2: involves crushing and grinding of the ore followed by agitated alkaline leaching and direct precipitation of uranium.

Currently, Option 1 is the preferred method for processing of the ore to produce a uranium oxide concentrate via direct precipitation of sodium di-uranate (SDU). Toro has estimated the process water requirements at 0.70GL/year (~1920m3/day or 22L/s) for a project life of 10 years. For the purposes of this study, Aquaterra have increased the water requirements by 10% (0.77GL/a) to allow for auxiliary water uses, i.e. village consumption, dust suppression etc. It is understood that the water required for this processing option should ideally have a chloride and sulphate concentration of less than 1,000mg/L (pers. comm., D. Kenny, 18 February 2010), which generally corresponds to a TDS content of less than 3,000mg/L (Aquaterra, 2007a).

Recently, Toro (2010) have revised their estimates of the water requirements for processing Options 1 and 2 to up to 0.8 and 2.5GL/a, respectively. Toro propose to construct a water treatment plant to produce 768m3/day (8.9L/s) of demineralised water for steam generation, as well as a reverse-osmosis plant to produce ~120m3/day (1.4L/s) of potable water (<1,000mg/L TDS) for product washing and for camp/plant amenities (Toro, 2010).


INTRODUCTION


1.5 DEVELOPMENT AND UTILISATION OF THE WEST CREEK GROUNDWATER RESOURCE

Two large-scale abstraction schemes have been developed and operated in the West Creek Groundwater Unit since 1986, namely:

▼ The West Creek or Wiluna (Gold Mine) South Borefield.

▼ The Apex (Wiluna Gold Mine) Southern Borefield.

The development and operation of these borefields are discussed below.

1.5.1 WEST CREEK BOREFIELD

Australian Groundwater Consultants (AGC) (1985) describes the RAB drilling of early exploration holes, P9 to P16, in the calcrete aquifer along the West Creek drainage system. During March to May 1986 further exploration drilling took place in the area and production bores P18, P22 and P26 were installed and pump-tested (Figure 1.3). According to AGC (1986), bores P26 and P32 tap clayey sands of a palaeochannel aquifer that underlies the calcrete aquifer. The water quality of the palaeochannel aquifer is highly saline, with measured salinity levels in bore P32 of 140,000mg/L TDS (AGT, 1986).

Production Bore and Operational Specifications

The West Creek Borefield consists of six production bores, P18, P22, P26, P61, P62 and P70. The construction and operational details for these bores are summarised in Table 1.1. Bores P26 and P70 were maintained as standby production holes (Figure 1.3). In 1987, Argent Exploration Services recommended commissioning bores P18, P22, P61 and P62 at a combined pumping rate of 1,789m3/day or 20.7L/s (0.65GL/year). Resource Investigations (1991) increased the combined pumping rate from the four production holes to 1,900m3/day or 22.0L/s (0.694GL/year), after reviewing three years of operational information.

KH Morgan (2006a) estimated that, based on historical abstraction records and work they completed, production bores P18, P26, P61, P62 and P70 should be able to sustain a yield of ~2,400m3/day or 27.7L/s (0.875GL/year).

Table 1.1: Technical and operational information for the West Creek production bores

Bore Number [Date Drilled]

Cased depth (m)

Slotted Interval (m.bgl)

Base of Aquifer (m.bgl)

Original SWLA (m.bgl)

SWL 12-Jun-07 (m.bgl)

Available Drawdown (m)*

Recommended Pumping Rates (L/s)

P18 [Mar 1986]

19.0 4-16 16 (14B) 4.52 4.52 6.3 3.5 C, 3.2A

P22 [Mar 1986]

20.5 5.5-17.5 17 (14B) 4.03 3.99 6.6 5.6 C, 4.9A

P26 [Apr 1986]

35.5 9-17 & 31-33

16B 5.75 5.43 9.8 2.9C

P61 [Nov 1986]

22.0 4-22 19 4.14 4.05 7.8 2.3C, 3.5A

P62 [Nov 1986]

19.0 4-19 16 4.13 - 6.8 9.3 C, 10.4A

P70 [Sep 1988]

19.8 7-19 19 6.10 5.52 7.9 -

Note: A – Resource Investigations (1991). B – Relates to upper calcrete aquifer. C – Argent Exploration Services (1987). * – Available drawdown ≈ 66% of saturated thickness of aquifer (Resource Investigations, 1991).

Resource Investigations (1991) provided estimates of available drawdown in each production bore (Table 1.1), based upon their experience with similar calcrete aquifers in the Eastern Goldfields, which indicated that once waterlevel drawdowns declines below 66% of the saturated


INTRODUCTION


thickness of the aquifer, waterlevels begin to drop more rapidly and bore yields begin to diminish.

Groundwater Abstraction

Chevron Exploration Corporation (CEC) commissioned the West Creek Borefield in April 1987 and it served as the primary mine water supply to their Mt Wilkinson Gold Mine up until April 1989. In May 1989, EON Metals NL (EON) took over operation of the borefield to supply their Matilda Gold Project and operated the borefield up until November 1989. However, detailed production and water quality records for this period are not available (Aquaterra, 2007a). EON was licensed (License No. 32082) to abstract 0.55GL/year (1,507m3/day or 17.4L/s). Subsequently, Asarco and later Wiluna Gold Mines, operated the borefield up until March 1997, whereafter there is no record of the borefield being utilised.

Monthly production information is only available for November 1988 through to January 1991, as well as from April 1993 to March 1997 (Figure 1.4). The following summary of pumping from the borefield is compiled from the above detailed monthly information and other more generalised estimates of borefield abstraction:

▼ April 1987 to April 1989: average borefield production varied between 1,100 and 1,200m3/day (~0.432GL/a) to supply Mt Wilkinson Mine. Resource Investigation (1989) report that 411,823 m3 was abstracted from the borefield over the period April 1988 to April 1989.

▼ May 1989 to January 1991: the average borefield production varied between 767 (8.9L/s) and 1,904 m3/day (22.0L/s). Approximately 0.446GL was abstracted over the 12 months ending in January 1991 (Resource Investigations, 1991).

▼ January 1991 to March 1994: No information is available for this period, but waterlevel records indicate that the borefield was pumped at ~1900 m3/day up until July 1991. Furthermore, it would appear that only standby production bore P26 was pumped between late 1992 and August 1993 (Figure 1.4).

▼ April 1994 to March 1996: apparently only 44m3 of groundwater was abstracted from production P62 (Aquaterra, 2007a).

▼ April 1996 to March 1997: approximately 1,185 m3 of groundwater was pumped from the borefield, which is only 17% of the authorised abstraction of 0.7GL permitted under License 32082 (KH Morgan & Associates, 1997). The water was abstracted from production bores P22 and P62. This licence expired at the end of December 1998.

MINEVILLAGE

22

5,0

00

mE

24

0,0

00

mE

LAKE WAYDEPOSIT

CENTIPEDEDEPOSIT

21

0,0

00

mE

7,050,000 mN

7,035,000 mN

7,065,000 mN

19

5,0

00

mE

P32

TRENNAMANSWELL

DIORITEWELL

MILLIEWELL

NO383 CRITCHESBORE

WARDNO1 WELL

RED HILLWELL

LANAGANBORE

WARDWELL

GARDEN(GOVT NO16)WELL

GARDENWELL

FRESHWATER WELL

GOLDTOOTHWELL

RAILWAYWELL

COCKARROWWELL

DEEP MILLWELL

XP1

XP4

XP3XP2 XP5

N2

N5

N4

P70P26

NO 388

LINDEN BORE

DEEP BORE

HAYES WELL

NO1 WELL

NO 408

P31

LW12

HADJI WELL

BUTCHER WELL

N1

N8

SB1

P18

P22

P61

P62

Project

KALGOORLIE

ALBANY

PERTH

DERBY

NEWMAN

FIGURE 1.3

LEGEND

LOCATION OF WEST CREEK ANDAPEX SOUTHERN BOREFIELDS

LOCATION MAP

AUTHOR: REPORT NO:

DRAWN: REVISION:

DATE:

IM ...

MS ...

22/06/2010

Study Area/ West Creek Groundwater Unit

Kilometers

Scale: 1:150,000 @A3

GDA 1994 Zone 51

DATA SOURCES:1:250K Scale State Topographicl Map

JOB NO: 1134C

f

Location: F:\Jobs\1134\C\GIS\Vector\MapInfo\Figure 1.3.wor

Existing West Creek Production Bores

Notional Production Bores

2 0 2 4

Apex Southern Production Bores

Monitoring Bores

Processing Plant

Mine Village

Pipeline


INTRODUCTION


Groundwater Quality

The groundwater quality in the calcrete aquifer system is generally brackish, with measured salinities ranging between 2,000 to 3,500 mg/L TDS. The available groundwater chemistry for the production bores is summarised in Table 1.2, where it is evident that:

▼ In terms of Toro’s process water requirements, the groundwater quality is marginal, with TDS and chloride concentrations generally exceeding 3,000 and 1,000mg/L, respectively. The sulphate content of the groundwater is below the 1,000mg/L constraint level.

▼ In general, the groundwater salinity in the borefield increases downstream from the most north-westerly production bore, P26 (2,344mg/L TDS), to the most south-easterly hole P62 (TDS 3,100mg/L TDS). Further southwards, towards Lake Way, the TDS of groundwater in the Apex Southern Borefield (Section 1.5.2) increases to ~4,500mg/L.

▼ The quality of the groundwater in the low permeability sand units of the underlying palaeochannel aquifer is hypersaline, i.e. the TDS of groundwater in P32 is 134,550mg/L.

▼ The nitrate levels of the water in the calcrete aquifer often exceeds the Australian Drinking Water (2004) health limits, and should be treated if it is to be used for domestic consumption.

▼ The salinity of the groundwater in the shallow calcrete aquifer shows short-term variations associated with significant rainfall recharge events. Figure 1.5 shows the TDS of groundwater from production bores P18 and P22 rising by 2,200 and 3,800mg/L, respectively, over a period of 9 months following the February 1995 flood event (cyclone ‘Bobby’), when 250mm of rain fell in the area. This may be due to flushing of salt from unsaturated zones of the soil/aquifer profile.


INTRODUCTION


Table 1.2: Chemistry of Groundwater from the West Creek Production Bores

Bore No.

Sample Period

Statistic pH TDS (mg/L) Na (mg/L)

Ca (mg/L)

Mg (mg/L)

K (mg/L)

Cl (mg/L)

HC03

(mg/L) SO4

(mg/L) NO3

(mg/L) F (mg/L)

Si (mg/L)

Number 8 8 8 8 8 8 7 7 6 6 2 4

Mean 7.6 2,877 642 115 144 70 1,055 249 520 78 0.1 65

Std Dev. 0.2 315 43 14 28 12 155 17 33 18 - 22

P18 Apr 96 – Jan 10

Min/Max 7.2/7.8 2,300/3,260 570/700 83/130 91/190 56/90 730/1,200 220/275 465/560 52/95 - 32/77

Number 7 7 7 7 7 7 6 6 5 5 1 3

Mean 7.6 3,578 777 157 208 90 1,287 311 809 61 0.1 65

Std Dev. 0.4 322 59 18 22 5 86 22 102 12 - -

P22 Apr 96 – Jan 10

Min/Max 7.1/8.1 3,215/4,230 725/891 130/180 165/230 85/98 1,175/1,400 285/340 640/890 47/75 - 33/85

Number 5 5 5 5 5 5 4 4 4 3 1 2

Mean 7.6 2,344 501 110 129 53 866 231 380 78 0.1 54

Std Dev. 0.3 301 46 7 20 7 84 33 22 - - -

P26 Apr 96 – Jan 10

Min/Max 7.3/7.9 1,900/2,620 460/570 100/120 120/165 49/65 790/955 210/280 360/410 47/95 0.1 32/75

P61 Jan 10 1 sample 5.8 4,110 885 138 165 84 1,374 230 699 - -

P62 Jul 96 1 sample 7.6 3,100 750 100 140 70 1,400 170 - 40 0 28.0

P32 May-86 1 sample 7.35 134,550 36,400 350 5,230 3,160 64,790 180 21,710 45 0.3 35

Australian Drinking Water Guideline (2004)

6.5 – 8.5 A A N/S N/S N/S A N/S 500 50 1.5 N/S

Notes: A – No guideline, as not considered necessary. N/S – Not supplied.

500 – Exceeds Australian drinking water health limit (Underlined). 500 – Exceeds Toro’s processed water quality requirements for alkaline heap-leach treatment (Boldfaced).

WATER LEVEL FLUCTUATIONS IN THE WEST CREEK BOREFIELD VERUS [A] MONTHLY RAINFALL AND [B] ABSTRACTION FIGURE 1.4

document2

GROUNDWATER SALINITY VARIATIONS IN THE WEST CREEK BOREFIELD FIGURE 1.5

document1


INTRODUCTION


1.5.2 APEX SOUTHERN BOREFIELD

The Apex (Wiluna Gold Mine) Southern Borefield is located 9.5km south of Wiluna town (Figure 1.1) and taps the shallow calcrete aquifer in this area, some 4.5km downstream of production bore P62 in the West Creek Borefield. The borefield comprises five production bores, XP1 to XP5, which provided water to the Wiluna Gold Mine up until early 2008. The borefield is currently not being utilised by Apex Gold. The bore construction details and hydrogeological logs could not be located. There is also no information available on the sustainability of the borefield, although the borefield was licensed to abstract up to a maximum of 1.13GL/year. The borefield layout is shown in Figure 1.3.

Groundwater Abstraction

Monthly groundwater abstraction information is only available for the following two operational periods (Figure 1.6):

▼ January 1987 to April 1991: Over this period ~1.563GL of groundwater was abstracted from the five production bores. Approximately 76% of this water was pumped from bores XP2, XP4 and XP5. During this time abstraction rates varied between 0.155 and 0.572GL/year.

▼ April 2005 to March 2007: Total abstraction from the borefield over the periods April 2005 to March 2006 and April 2006 to March 2007 was 7.86GL and 7.43GL, respectively.

Groundwater Quality

The groundwater abstracted from production bores in the Apex Southern Borefield is brackish, with TDS concentrations averaging between 4,000 to 5,000mg/L (Table 1.3).


INTRODUCTION


Table 1.3: Groundwater chemistry of the production bores in the Apex Southern Borefield

Bore No.

Sample Period

Statistic pH TDS (mg/L)

Na (mg/L)

Ca (mg/L)

Mg (mg/L)

K (mg/L)

Cl (mg/L)

HC03

(mg/L) SO4

(mg/L) NO3

(mg/L) F (mg/L)

Si (mg/L)

Number 14 14 14 14 14 14 14 14 14 14 8 12

Mean / Std Dev

7.9 4964 /980 1208/274 142/19 250/56 121/29 1969/535 384/54 1014/128 30/7 1.5/0.8 66/26

XP1 Jul 94 – Jun 06

Min /Max 7.4/8.8 3400/6200 805/1500 110/170 320/150 81/200 1070/2800 265/475 750/1200 18/39 0.7/3.4 1/88

Number 16 16 16 16 16 16 16 16 16 16 8 14

Mean 7.8/0.3 3959/522 918/159 126/16 189/24 99/16 1424/246 412/31 867/97 30/8 1.6/0.9 68/22

XP2 May 94 - Dec 05

Min 7.2/8.7 3300/5000 775/1300 100/160 150/230 76/130 1060/1900 350/465 750/1090 15/46 1.0/3.8 32/90

Number 18 18 18 17 18 18 18 18 18 18 9 16

Mean / Std Dev

7.8/0.4 4931/604 1162/153 136/13 229/20 122/19 1850/292 438 1036/128 28/10 1.7/0.6 65/28

XP3 May 94 - Jun 06

Min 7.2/8.7 3970/6300 900/1400 120/170 195/280 89/170 1270/2500 360/560 775/1300 6/46 1.2/3.3 2/94

Number 17 17 17 17 17 17 17 17 17 17 8 15

Mean / Std Dev

7.7 4472/1142 1026/319 146/13 225/48 118/28 1616/482 469/38 1023/210 26/9 1.9/0.7 64/29

XP4 May 94 - Jun 06

Min 7.2/8.0 3400/8500 790/2000 120/170 180/400 88/180 1160/3100 420/550 840/1700 14/46 1.4/3.7 2/96

Number 16 16 16 16 16 16 16 16 16 16 7 14

Mean / Std Dev

7.7/0.2 4741/512 1111/163 145/12 216/20 124/24 1795/267 455/53 944/82 35/9 1.9/0.8 62/30

XP5 May 94 - Jun 06

Min 7.2/8.2 3970/6000 885/1370 130/170 180/250 94/190 1170/2200 390/560 775/1100 17/47 1.3/3.7 2/96

Australian Drinking Water Guideline (2004)

6.5 – 8.5

A A N/S N/S N/S A N/S 500 50 1.5 N/S

Notes: A – No guideline, as not considered necessary. N/S – Not supplied. 500 – Exceeds Australian drinking water health limit (Underlined). 500 – Exceeds Toro’s processed water quality requirements for alkaline heap-leach treatment (Boldfaced).

APEX SOUTHERN BOREFIELD – GROUNDWATER LEVEL FLUCTUATIONS VERSUS ABSTRACTION FIGURE 1.6

document3


CONCEPTUAL HYDROGEOLOGY


2 CONCEPTUAL HYDROGEOLOGY

2.1 PREAMBLE

The conceptual hydrogeology for the modelled area, outlined below, is based on the integration of all available information. The conceptual hydrogeology represents a simplified understanding of the geometry, hydraulic characteristics and flow dynamics of the aquifer systems, and provides the technical foundation for the compilation of the numerical flow model.

2.2 DATA REVIEW

2.2.1 DATA SOURCES

In addition to the documents cited in Section 1, a number of other data sources were reviewed to increase our understanding of the extent and thicknesses of the geological/hydrogeological units in the study area. These data include the following:

▼ Water and Rivers Commission, 1999. Groundwater Resources of the Northern Goldfields, Western Australia. Report HG2.

▼ Geological Survey of Western Australia, 2001.Explanatory notes. Geological sheet SG51-09, Wiluna (2nd Edition).

▼ Published digital 1/100,000 and 1/250,000 geological and topocadastral map-sheets.

▼ Hydrogeological and water supply reports prepared by consultants.

▼ Available LANDSAT satellite imagery and the 90m resolution SRTM digital elevation model.

▼ Electronic data supplied to Aquaterra by the Department of Water on 9th March 2010.

▼ Lithological logs of mineral exploration holes, hi-resolution aerial-photographs, digital geophysical and LIDAR elevation data supplied by Toro.

▼ Waterlevel and groundwater quality data supplied by Toro.

2.2.2 OUTCOME OF THE DATA REVIEW

In terms of potential water resources, the calcrete aquifer represents a significant source of fresh to marginally brackish water in the study area. Published data (Water and Rivers Commission, 1999) indicates that calcrete aquifers in the area to the south of Wiluna may store up to 190GL of water, of which 5GL/year is renewable.

Examination of the data suggests that a significant palaeochannel groundwater source does not underlie the calcrete aquifer present within the study area.

Further discussion of the geological units in the study area is presented below.

2.3 CALCRETE AQUIFER

2.3.1 GEOMETRY

Following the review of available data, Aquaterra consider that it is plausible that the calcrete extends as an aquifer (with variable width) along the full length of West Creek drainage system. In the north-west of the study area the calcrete is estimated to be approximately 1km wide, broadening to ~4km in the south-east.

Aquaterra’s interpretation of the thickness of the calcrete aquifer is mainly based on hydrogeological information available from on a limited number of exploration bores drilled to establish the West Creek Borefield (Australian Groundwater Consultants, 1986 and 1987). This information indicates the presence of an extensive body of calcrete that extends from between 0 to 5m below surface to maximum recorded depths of 20 to 25m below surface. Groundwater levels in this area range between 3 and 7m below surface, providing an average saturated thickness of 10 to 15m and a maximum saturated thickness of ~20m. The calcrete is assumed to thin towards the north, with an estimated thickness ranging from 5 to 10m. In the southern portion of the study area the calcrete is interpreted as being ~10 to 15m thick, increasing in thickness towards Lake way in the south-east.




Extensive alluvial sediments, which are predominantly clayey, with occasional sand horizons, occur adjacent to and extend beneath the calcrete deposits. The main calcrete aquifer in the vicinity of the West Creek Borefield is underlain by a clay-rich unit.

According to AGC (1986), production bores P26 and P32 intercepted water in clay-rich sand horizons which form part of a palaeochannel deposit that underlies the calcrete aquifer. They reported that P32 intercepted only 3m of calcrete at 2m, but intersected clayey sands at depths of 85-93m and 98-102m, before penetrating the meta-basalt bedrock at 102m. Subsequent, airlift testing showed that the sands have a relatively low permeability and therefore a lower yield potential than the overlying calcrete. The authors, however, believe that it is plausible that the logged sequence of silty sand and clay represents highly sheared, deeply weathered and decomposed, volcaniclastic sedimentary rocks associated with the north-west trending Erawalla Fault system that passes directly below the West Creek Borefield.

The above interpreted calcrete thicknesses are consistent with published data in Water and Rivers Commission (1999) which indicates that the thickness of calcrete aquifers in the area is highly variable, up to 30m thick with an estimated average of 5m.

2.3.2 WATER LEVELS AND GROUNDWATER FLOW

Groundwater data from existing reports and supplied by the Department of Water were examined. Aquifer responses to pumping from the calcrete can be can be observed within the dataset (Section 1.5.1).

Based on this data, interpreted static waterlevels in the calcrete aquifer are ~4m below ground surface. Groundwater elevations confirm that flow within the calcrete is essentially from the north-west to the south-east of the study area, where it discharges at Lake Way. Essentially Lake Way is considered to act as ‘drain’, acting to remove groundwater from the system via evaporation.

Based on the geometry of the outcropping Finlayson Member sandstone in the north-east of the study area, there would appear to be limited opportunity for groundwater inflow into the study area from the north-west via the calcrete. It is possible that during high rainfall events that greater flow takes through the calcrete at this locality. However, on a long-term average this is not expected to provide significant inflows into the catchment.

2.3.3 GROUNDWATER RECHARGE AND EVAPOTRANSPIRATION

Direct groundwater recharge to the calcrete aquifer would be expected to occur in response to rainfall events.

Published data suggests that recharge directly from rainfall or via infiltration of runoff in areas of out cropping calcrete would constitute at least 1%, possibly as much as 5% of total rainfall. Rainfall events in excess of 50mm would generate significant runoff that would rapidly inundate the calcrete via solution cavities (Water and Rivers Commission, 1999). Rockwater (1978) estimated rainfall recharge rates of 0.74 - 1.2% of MAP (228mm/a) for the alluvial aquifers developed along the Negrara and Kukabubba Creeks to the north of Wiluna.

Indirect recharge of the calcrete aquifer would also be expected to take place via lateral inflow from the flanking alluvial sediments. Induced recharge would occur in response to groundwater abstraction from the calcrete and would be subject to a time lag as groundwater flowed from neighbouring less permeable sediments into the calcrete.

Australian Groundwater Consultants (1986) found that localised recharge of the West Creek aquifer system is only likely to occur following significant runoff events and that historical records reveal several extended periods of five years or more without any significant runoff producing rainfall events.

Evapotranspiration would be expected to occur where groundwater levels are shallow, perhaps within 2-3m of the ground surface.

2.3.4 KEY AQUIFER PARAMETERS

The hydraulic conductivity of the calcrete aquifer is expected to be variable, due to the likely presence of solution cavities and the entrapment of fine grained clasts within the aquifer.




AGC (1986) present the results of pump-testing on production bores P18, P22 and P26 that tap the calcrete aquifer in the West Creek borefield, which provided transmissivity and specific yield values in the range of 135 to 350m2/day (average 250m2/day) and 3 to 8% (average 5%), respectively.

The hydraulic parameters as determined from test-pumping of the West Creek production bores are summarised in Table 2.1.

The specific yield of calcrete is reported to be highly variable due to its karstic nature, ranging from 5 to 25%. Specific yields are reported to be highest around the watertable and generally decreases with depth. Groundwater storage estimates presented in Water and Rivers Commission (1999) were based on 10%, this value being derived from pumping tests around Wiluna.

Table 2.1: Hydraulic Characteristics of the calcrete aquifer in the West Creek Borefield

Bore No.

Static Water Level (m.bgl)

Pump-test Yield (L/s)

Transmissivity (m2/day) [Recovery]

Storativity Recommended Production Yield (L/s)

Aquifer / Comments

P18 4.52 4.3 130 [135] 0.001 3.5 Calcrete, 42hr test in April 86, max. drawdown of 4.5m.

P22 4.03 4.4 290 250 – 350

0.094 0.077

5.8 Calcrete, 50hr test in April 86, max. drawdown of 1.59m.

P26 5.75 3.5 110 135 – 320

0.030 0.27

2.9 43.3hr test in April 86, max. drawdown of 5.3m. Deep Clayey Sands T = 30-80 m2/d

P61 4.14 2.8 690 107 [682]

0.001

2.3 Calcrete. Duration Test 4080min, Max. Drawdown = 14.53m.

P62 4.13 16.9 740 737 [950]

0.003 9.3 Calcrete. Duration Test 4080min, Max. Drawdown = 2.38m.

Source: Argent (1987) and AGC (1986)

2.4 ALLUVIUM

2.4.1 ALLUVIUM GEOMETRY

Laterally the alluvium is constrained by the presence of the calcrete aquifer through the central part of the study area, and the bedrock on the periphery.

Based our experience of similar settings, we have assumed that, where present, the alluvium is approximately 5m thick over the majority of the area, with the thickness being increased where appropriate, to ‘tie-in’ with the calcrete thickness.

It is likely that a lateral transition zone exists between the calcrete and the alluvium, where finer grained sediments are interlayered with the calcrete.

2.4.2 WATER LEVELS AND GROUNDWATER FLOW

The data indicates that groundwater levels in the alluvium to the east of the West Creek are approximately 4 to 9m below ground surface. It is likely that groundwater within the alluvium drains towards the calcrete aquifer in the centre of the study area and ultimately discharges to Lake Way.

2.4.3 GROUNDWATER RECHARGE AND EVAPOTRANSPIRATION

Groundwater within the alluvium is recharged from irregular and episodic rainfall events. Published data suggests that the alluvium receives between 0.09 and 1% of total rainfall as recharge (Water and Rivers Commission, 1999). It is possible that enhanced recharge occurs in the alluvium along the flanks of outcropping bedrock, however we have no data to confirm or quantify this recharge mechanism.




Evapotranspiration would be expected to occur where groundwater levels are shallow, perhaps within 2-3m of the ground surface.

2.4.4 KEY AQUIFER PARAMETERS

Published data for alluvial aquifers in the northern Goldfields indicate low permeability values for these units. Data from the Albion Downs borefield provides hydraulic conductivity values of less than 2.5m/d. Bore yields from alluvium aquifers in the region are reported to range from 50 to 600m3/day, indicating variable permeability (Water and Rivers Commission, 1999).

An average specific yield of 0.05 was proposed by the Water and Rivers Commission (1999) as an appropriate value for water resource calculations, however other data suggests that a value of 0.1 is may be more appropriate (Geological Survey of WA, 1992).

2.5 BASAL CLAYS AND SILT

In general, the calcrete aquifer is underlain by a layer of clay-rich sediments with thin intercalations of sand or occasional silty gravel layers. This clayey horizon is also present below the calcrete at the Centipede and Lake Way deposits. The thickness of this horizon is highly variable and is assumed to vary between 5 to 10m. Little or no information is available on the hydraulic properties of this horizon which, where present, acts as an aquitard. AGC (1986) report a transmissivity of 13m2/day for a clayey sand layer intercepted between 85 and 102m in bore P32 (i.e. hydraulic conductivity ~ 0.77m/d). They report transmissivity values of 30 to 80m2/day for a 13m thick unit of interbedded fine sand and clayey sand intercepted at 20m in production bore P26 (i.e. K-values of 2.3 to 6.0m/d).

2.6 FRACTURED ROCK (BEDROCK)

Permeability in fractured bedrock aquifers in the study area is believed to be largely derived from secondary porosity derived from structural features, although the Finlayson Member may have a primary porosity component. Literature reviewed indicates that the local geological structure is the dominant feature controlling the occurrence and flow of groundwater in fractured rocks; the lithology is considered to have only limited influence in this respect.

Fractured rock aquifers are recharged infrequently by rainfall and ephemeral drainages into open fractures and weathered zones. Higher recharge rates may occur where elevated laterite occur (Water and Rivers Commission, 1999).

Aquaterra anticipate the bulk hydraulic conductivity and storativity values to be low for fractured rock aquifers in the study area. Hydraulic conductivity and specific yield values would be expected to be in the region of 0.01m/day and 0.001 respectively.

Groundwater flow within fractured rocks would discharge to either overlying unconsolidated units, or as throughflow to Lake Way. In either case it is assumed that groundwater flow through fractured rock aquifer system within the study area would represent a small proportion of the overall water budget.


MINE WATER SUPPLY BOREFIELD OPTIONS


3 MINE WATER SUPPLY BOREFIELD OPTIONS

3.1 EXISTING BORES

Two borefields currently exist in the Study area:

▼ West Creek Borefield, comprising of production bores P18, P22, P26, P61, P62 and P70 (Section 1.5.1).

▼ The Apex Southern Borefield, which is currently inactive. This borefield comprises production bores XP1 to XP5 (Section 1.5.2).

The locations of these borefield and individual production bores are shown in Figures 1.1 and 1.3, respectively.

As indicated in Section 1.5, previous studies have recommended that the West Creek Borefield can be operated at a rate of between 0.65 - 0.875GL/year. The data available also suggests that the water quality from this borefield is marginally acceptable, in terms of Toro’s requirements. Data for the Apex Southern Borefield indicates that water quality closer to Lake Way is too saline to be considered for Toro’s purposes. On this basis, Aquaterra consider that Toro would need to source water from the existing, or a reconfigured, West Creek Borefield only.

3.2 RECOMMENDATIONS FROM PREVIOUS STUDIES

Sanders (1972, in Rockwater, 1978) recommends the exploring the narrow band of outcropping calcrete along the upper reaches of the West Creek, just south of the Bubble Well, which has a salinity of 2500mg/L TDS.

Currently we have little information concerning the hydrogeology of the far north-western portion of the Study Area. It is possible that good groundwater prospects exist in this area, however, given the current data gaps we believe that this option represents a strategy with a higher risk.

3.3 POSSIBLE NEW DEVELOPMENTS

Aquaterra considered that one potential approach to meet Toro’s bulk water volume and water quality requirements, was to spread the required abstraction over areas of the calcrete aquifer where we have the highest level of existing data.

Given the low rainfall for the area, combined with an anticipated low throughflow, we would expect such an approach to essentially provide abstraction volumes via the withdrawal groundwater from storage. The thin saturated thickness of the aquifer would necessitate the distribution of production bores across as wide an area as possible, to limit drawdown to an acceptable level. Unfortunately, the increasing salinity as one moves downstream in the catchment places a limit as to how far abstraction bores could be developed towards Lake Way.

Given the above, Aquaterra currently considers that a distributed borefield, located in the general area of the existing West Creek Borefield presents the most promising water supply prospect for the Wiluna Uranium Project. .


GROUNDWATER MODEL


4 GROUNDWATER MODEL

4.1 MODELLING OBJECTIVES

The main objective of the modelling study was to develop a numerical groundwater flow model to assess the feasibility of a proposed water supply borefield for Toro’s Wiluna Uranium Project. The anticipated water demand for ore processing and handling and mining operations is estimated to be up to 0.7GL/year for the 10 year life of the project. The calibrated numerical groundwater model was used to determine sustainable abstraction rates and to evaluate potential impacts of a borefield drawing groundwater from the shallow calcrete aquifer for the life of the project.

A regional numerical groundwater model was developed to assess the water supply potential and impacts of the proposed borefield abstraction on the calcrete aquifer. The extent of the model domain also makes it suitable to assess interaction with future groundwater development in the calcrete aquifer if required.

The key features of the numerical groundwater model are discussed in detail in the following sections, and may be summarised as follows:

▼ Groundwater recharge from incident rainfall.

▼ Groundwater evapotranspiration from phreatophytic vegetation and near surface water tables.

▼ Groundwater inflow from the upstream catchment and groundwater outflow to the Lake Way playa system.

▼ Groundwater pumping from the proposed water supply borefield.

4.2 MODEL SETUP

4.2.1 MODEL GRID AND EXTENT

The numerical groundwater modelling package Modflow-Surfact (Version 3.0, Hydrogeologic, Inc. 1996) was used to develop the model operating under the Groundwater Vistas graphical user interface (Version 5.40, Rumbaugh and Rumbaugh, 1996-2007). Modflow-Surfact is one of the industry’s leading groundwater flow modelling packages and was chosen for its ability to simulate a shallow water table aquifer with potential for desaturation and re-saturation.

The upper right-hand corner of the model is positioned approximately 18km NNW of Wiluna, and extends 40km to the west and 45km north (Figure 4.1). The model grid was rotated 42 degrees anti-clockwise from the MGA grid to align the model grid with the inferred preferential flow direction in the calcrete aquifer. The corner coordinates of the model are shown in Table 4.1.

Table 4.1: Corner Coordinates of the Model Domain

Easting* (m) Northing* (m)

Top left 186031 7044373

Top right 216260 7072073

Bottom left 207650 7020780

Bottom right 237875 7048482

Notes: *- Indicates GDA 94 Zone 51

A uniform model cell size 500m by 500m was employed. The model grid comprises 3 layers, 64 rows, and 82 columns, resulting in a total of 15,744 cells with 7,875 active cells (Figure 4.1).

F:\Jobs\ Fig 1.1.srf

MODEL GRID AND BOUNDARY CONDITIONSFIGURE 4.1

ConstantHead (CH)

No FlowBoundary

Grid

LEGEND

190000 195000 200000 205000 210000 215000 220000 225000 230000 235000

7025000

7030000

7035000

7040000

7045000

7050000

7055000

7060000

7065000

7070000

Const

ant H

ead

Inflo

w

(522 m

RL)Hadji Well

Vincent Bore


GROUNDWATER MODEL


4.2.2 MODEL GEOMETRY

Model layer elevations were set to follow surface topography or aquifer/aquitard geometry within the model boundary consistent with available data (bore logs and regional geological information) as detailed in Table 4.2.

Layer 1 represents the calcrete, surrounding calcrete/alluvium transition, alluvium and fractured bedrock. Three hydraulic zones are represented in the calcrete aquifer consistent with:

▼ A decrease in the permeability of the calcrete aquifer as a result of increased silt/clay content with distance away from the groundwater discharge zone at Lake Way.

▼ Monitoring data associated with groundwater pumping from the calcrete from the Apex Southern Borefield (bores XP1 to XP5) and the West Creek Borefield (P18, P22, P62, etc) suggests varying responses to pumping that may be described by varying aquifer transmissivity. This is discussed further in Section 4.4.3.

Surrounding the calcrete aquifer is a transition zone of interbedded alluvium/calcrete, with alluvium adjoining the transition zone.

Layer 2 represents a smaller deeper-seated area of calcrete in the northern extremities of the model, a silty/clay unit underlying the calcrete aquifer and fractured bedrock surrounding the calcrete. Layer 3 represents the underlying and surrounding fractured rock.

The hydrogeological units represented in each layer are illustrated in Figures 4.2 to 4.4. Cross sectional views of the hydrogeological units modelled are shown in Figures 4.5 and 4.6.

Table 4.2: Model Layers

Layer Hydrogeological Units

Layer Geometry

Elevation of Ground Surface

Top of active cells in layer follows surface topography based on Shuttle Radar Topography Mission (SRTM) elevation data (90m resolution), and/or LIDAR survey data supplied by Toro.

Calcrete (3 zones)

Calcrete thicknesses consistent with available data to a maximum thickness of 20m (in the vicinity of bores P26, P18, P70, P61 and P62), 15m adjacent to Lake Way, with a minimum thickness of approximately 5m.

Calcrete/Alluvium Transition

Generally assigned a thickness of 5 to 10 m to provide a smooth hydraulic transition to the adjacent calcrete and alluvial areas. Thickness increases to approximately 13m in some localised areas.

Alluvium

Generally assigned a thickness of 5m with a maximum of up to 10m in some localised areas.

1 (Top of Model)

Fractured Rock Assigned a thickness of approximately 5m.

Silt/clay Generally assigned a thickness of 5m, increasing to approximately 12.5m below the main body of the calcrete aquifer.

Calcrete Assigned to a limited area in north-east of Layer 2. Approximate thickness of 5m.

2

Fractured Rock Assigned a nominal thickness of approximately 5m.

3 (Base of Model)

Fractured Rock Assigned a thickness of between 70 and 190 m with the base of the model set at an elevation of 400m RL.

AQUIFER PARAMETER DISTRIBUTION: LAYER 1 FIGURE 4.2F:\Jobs\1134\C\600_Report\Figures\104a Figures\Fig 4.2.srf

190000 195000 200000 205000 210000 215000 220000 225000 230000 235000

7025000

7030000

7035000

7040000

7045000

7050000

7055000

7060000

7065000

7070000

Easting (m)

Nor

thin

g (m

)

Eastern Alluvium


Western Alluvium

No Flow Cells

Northern Calcrete

Middle Calcrete

LEGEND

Fractured Bedrock

Southern Calcrete

1/0.1

2/0.2

1/0.1

2/0.2

12.5/1.25

0.005/0.0005

25/2.5

0.0001/0.2

0.0001/0.05

0.0001/0.2

0.0001/0.05

0.0001/0.1

0.00001/0.001

0.0001/0.1

Kh/Kv (m/d) S/Sy

Projection: MGA94 Z51

AQUIFER PARAMETER DISTRIBUTION: LAYER 2 FIGURE 4.3

190000 195000 200000 205000 210000 215000 220000 225000 230000 235000

7025000

7030000

7035000

7040000

7045000

7050000

7055000

7060000

7065000

7070000

Fractured Bedrock

Northern Calcrete

Clay/Silt

No Flow Cells

LEGEND

0.005/0.0005

2/0.2

0.5/0.05

0.00001/0.001

0.0001/0.05

0.00001/0.001

Kh/Kv (m/d) S/Sy

F:\Jobs\1134\C\600_Report\Figures\104a Figures\Fig 4.3.srf

Easting (m)

Nort

hin

g (

m)


AQUIFER PARAMETER DISTRIBUTION: LAYER 3 FIGURE 4.4

190000 195000 200000 205000 210000 215000 220000 225000 230000 235000

7025000

7030000

7035000

7040000

7045000

7050000

7055000

7060000

7065000

7070000

Bedrock

No Flow Cells

LEGEND

0.005/0.0005 0.00001/0.001

Kh/Kv (m/d) S/Sy


Nort

hin

g (

m)

Easting (m)


SCHEMATIC CROSS-SECTIONS: NORTH-EAST TO SOUTH-WEST FIGURE 4.5

Note: Vertical Exaggeration Not to Scale.

190000 200000 210000 220000 230000

7030000

7040000

7050000

7060000

7070000

A

A'

A A'

B B'

B

B'

W E


Key as per Figures 4.2 and 4.3

Easting (m)

Nort

hin

g (

m)


NORTH-WEST TO SOUTH-EAST CROSS-SECTION FIGURE 4.6

A' A

NS

Note: Vertical Exaggeration Not to Scale.


Key as per Figures 4.2 and 4.3

190000 195000 200000 205000 210000 215000 220000 225000 230000 235000

7025000

7030000

7035000

7040000

7045000

7050000

7055000

7060000

7065000

7070000

A

A'

Nort

hin

g (

m)

Easting (m)



GROUNDWATER MODEL


4.3 GROUNDWATER INFLOW AND OUTFLOW

4.3.1 GROUNDWATER THROUGHFLOW

The general direction of groundwater flow within the calcrete in the study area is from the north-west towards Lake Way in the south-east. Groundwater flow from the alluvial units in the periphery of the Study area flows to Lake Way via the calcrete.

Two fixed-head boundaries simulate groundwater flow into and out of the model domain as outlined below:

▼ Groundwater inflow from the northwest of the model domain is simulated by a fixed head boundary set at an elevation of 522mRL. This elevation value is consistent with a groundwater elevation based on monitoring data supplied by DoW for Vincents Bore.

▼ Groundwater outflow from the south-west of the model domain is simulated by a fixed-head boundary set at an elevation of 489mRL. The elevation of this boundary was based on monitoring data for bore LW12 (490mRL). This value is consistent with groundwater elevations in the Hadji Bore estimated from DoW gauging data.

The location of the above bores and the assigned fixed-head boundaries are shown in Figure 4.1.

4.3.2 RAINFALL RECHARGE

In addition to the inflow boundary described in Section 4.3.1, inflow into the modelled groundwater system is also provided via rainfall recharge, assigned as a proportion of rainfall recorded at Wiluna town. Recharge is incorporated in the model using the Recharge (RCH) package.

The average annual rainfall recorded at the Wiluna monitoring station (since recording began in 1899) is around 257mm/year. Rainfall recharge applied in the model was calculated as a percentage of average measured monthly rainfall rates for the following units:

▼ Calcrete (3 recharge Zones).

▼ Calcrete/Alluvium Transition Zone.

▼ Fractured Rock.

▼ Alluvium (2 recharge Zones).

The areal distribution of rainfall recharge assigned to the calibrated model is discussed in detail in Section 4.5.2.

4.3.3 EVAPOTRANSPIRATION

Evapotranspiration (ET) is a collective term for the transfer of water, as water vapour, to the atmosphere from both vegetated and un-vegetated land surfaces (BoM). The Actual Areal Evapotranspiration1 for the Wiluna area is between 200 and 300mm/year (Bureau of Meterorology, 2010). Evapotranspiration is implemented in the groundwater model using the Evapotranspiration (EVT) package in Modflow Surfact.

Modflow-Surfact uses a linear depth dependent relationship such that if aquifer water levels are at or above a specified evapotranspiration surface, ET occurs at the maximum specified rate. If the aquifer water level falls below the specified ET surface, the ET rate decreases linearly to zero as the predicted water level reaches an elevation equal to the ET surface minus the extinction depth. The ET rate is also set to zero whenever the aquifer water level is below the elevation equal to the ET surface minus the extinction depth. This is illustrated schematically in Figure 4.7.

An ET rate of 5x10-5m/day was set for all active cells within the model, with the exception of cells where a fixed boundary had been defined (Figure 4.8). An extinction depth of 3m was set

1 Defined as by BoM as: ET that actually takes place, under the condition of existing water supply, from an area so large that the effects of any upwind boundary transitions are negligible and local variations are integrated to an areal average. For example, this represents the evapotranspiration which would occur over a large area of land under existing (mean) rainfall conditions.


GROUNDWATER MODEL


in all cells where the ET package was operative. ET was only applied to the top layer of the model, with the extinction surface assigned consistent with ground surface.

4.3.4 GROUNDWATER ABSTRACTION

Groundwater abstraction from existing production bores tapping the calcrete aquifer was simulated using the Well (WEL) package in Modflow-Surfact. Available monitoring data suggest that abstraction from the calcrete aquifer commenced in April 1987 utilising production bores P18, P22, P61 and P61. Evidently, the Apex Southern Borefield was commissioned in the mid-1986 (Section 1.5.2).

The location of the pumping bores in relation to the model layout is shown in Figure 4.9.

MODFLOW EVAPOTRANSPIRATION PACKAGE SCHEMATIC FIGURE 4.7

WATER TABLEh

ALLUVIUM

EVAPOTRANSPIRATIONRATE

GROUND SURFACE / ET SURFACE

EXTINCTIONDEPTH

ET SURFACE ELEVATION

EXTINCTIONDEPTH

EVAPOTRANSPIRATIONRATE

hc

h - Predcited Water Table

ETmax0

F:\Jobs\1134\C\600_Report\Figures\104a Figures\Fig4.7.srf

EVAPOTRANSPIRATION DISTRIBUTION FIGURE 4.8

No Flow Cells

LEGEND

5e-005

0

3

0

ET Rate (m/d) Extinction Depth (m)

190000 195000 200000 205000 210000 215000 220000 225000 230000 235000

7025000

7030000

7035000

7040000

7045000

7050000

7055000

7060000

7065000

7070000


Easting (m)

Nort

hin

g (

m)



GROUNDWATER MODEL


4.4 MODEL CALIBRATION

4.4.1 PREAMBLE

Model calibration or history matching is a process of demonstrating that a groundwater model can replicate historical monitoring data. The calibration data set includes water levels and groundwater abstraction information over the period October 1986 to September 2009. A total of 37 measured water levels across the modelled area were available for steady state calibration. These water levels were derived from both the DoW and Toro, and were selected on the basis that they reflected pre-development conditions. For the transient calibration, an dataset of water level and abstraction information was available for the West Creek Borefield extending from November 1988 to March 1997. In the case of the Apex Southern Borefield, monthly water level and abstraction records were available for two periods extending from January 1987 to April 1991 and April 2005 to March 2007 (Section 1.5.2).

Monitoring data is not available for all locations over the entire calibration period, however all available/appropriate data was incorporated into the calibration dataset.

During model calibration, aquifer parameters, the proportion of rainfall recharge and the level of the fixed head boundaries were adjusted within realistic limits until a reasonable match between measured and predicted groundwater levels was produced. The calibration process involved numerous iterations and refinements for both the steady state and transient models, with feedback between the two models. These refinements were required to address some of the uncertainties related to hydrogeological conceptualisation of the aquifer systems.

4.4.2 STEADY-STATE CALIBRATION

The steady state (or “long-term average”) calibration provides:

▼ A distribution of water levels across the model domain that reflects the groundwater conditions prior to any development.

▼ Initial groundwater conditions for the transient calibration.

▼ Quantification of the groundwater flow through the model domain, under average conditions prior to any groundwater development.

Groundwater conditions in the study area are dynamic in nature and often respond to extreme cyclonic rainfall events. As a result, groundwater levels may vary significantly over a year, or from year to year. The steady state calibration makes no attempt to model seasonal variations and provides an estimate of the groundwater flow regime under average rainfall conditions prior to any borefield development.

Measured and modelled steady state water levels are presented in Figure 4.10. The Scaled Root Mean Squared Error (SRMS or RMS error divided by the range of measured water levels) is 13.6% which is slightly higher than the accepted 10% error for ‘green fields’ catchments and 5% for developed catchments (MDBC, 2001). Figures 4.10 and 4.11 show that there is a mismatch between the measured and predicted water levels at Diorite Well and Deep Bore. All of the other bores are likely to provide water levels related to the upper alluvium or calcrete aquifer, which it is probable that the water levels in these two bores are associated with bedrock aquifers only. We note that if these two data points are removed from the SRMS calculation, the resulting error is reduced to 8.4%.

Predicted steady state groundwater contours and measured spot heights are presented in Figure 4.11.


GROUNDWATER MODEL


Table 4.3: Adopted Recharge Values

Unit Recharge as % of Rainfall Adopted Steady-State Recharge (m/d)

Fractured Rock 0.01 7.07E-08

Southern Calcrete 1.4 9.90E-06

Eastern Alluvium 0.084 5.94E-07

Western Alluvium 0.084 5.94E-07

Calcrete/Alluvium Transition 1 7.07E-06

Northern Calcrete 1 7.07E-06

Middle Calcrete 1.4 9.90E-06

The percentage of rainfall apportioned to recharge for the alluvium and calcrete are consistent with those values cited in the literature (see Section 2). The distribution of recharge within the model is shown in Figure 4.12.

The calculated steady-state calibration heads and the corresponding observation data are provided in Table B2 of Appendix B. A summary of these data for the West Creek Borefield is presented in Table 4.4.

Table 4.4: Calculated and Adopted Steady-State Calibration Heads for West Creek Borefield

Calibration Bore Calculated Head (m RL)

Adopted Steady-State Calibration Head (m RL)

Error (m)

P18 500.57 499.04 1.5

P22 499.43 497.32 2.1

P26 503.67 502.17 1.5

P31 509.93 511.50 -1.6

P61 499.06 497.08 2.0

P62 498.47 496.76 1.7

P70 502.17 498.87 3.3

Notes: Table 5.5 is an abridged version of data supplied in Table B1, Appendix B. The predicted steady state water balance is presented in Table 4.5.

Table 4.5: Steady State Predicted Water Balance (m3/day)

In Out

Constant Head 25 690

Recharge 1190 0

Evapotranspiration 0 525

Total 1215 1215

Based on the data presented in Table 4.5, recharge accounts for almost all of water inflows into the model domain, with outflows dominated by flow to Lake Way and evapotranspiration.

PUMPING AND MONITORING BORE LOCATIONS FIGURE 4.9

No Flow Cells

Constant Head (CH)

LEGEND

190000 195000 200000 205000 210000 215000 220000 225000 230000 235000

7025000

7030000

7035000

7040000

7045000

7050000

7055000

7060000

7065000

7070000

XP1XP2X

P3XP4X

P5

P18

P22

P26

P61

P62

P70

NO 388

LINDEN BOREDEEP M

ILL WELL

DEEP BORE

COCKARROW WELL

HAYES WELL

NO1 WELL

RAILWAY WELL

NO 408

GOLD TOOTH WELL

TRENNAMANS WELL

FRESHWATER WELL

GARDEN WELL

GARDEN (GOVT NO16) W

ELL

MILLIE MILLIE W

ELL

WARD WELL

P31

P32

LANAGAN BORE

RED HILL WELL

WARD NO1 WELL

DIORITE W

ELL

NO383 CRITCHES BORE LW12

HADJI WELL

BUTCHER WELL

Observation Bores (Existing)

Pumping Bores (Existing)


Nort

hin

g (

m)

Easting (m)


\\aquaterra.com.au\data\at1\Jobs\1134\C\600_Report\Figures\104a Figures\[Fig 4.10 C_S069_WestCreek.xls]Figure 4.10

MEASURED VERSUS MODELLED WATER LEVELS FIGURE 4.10

XP1XP2XP3XP4XP5

NO_388

LINDEN_BORE

DEEP_MILL_WELL

DEEP_BORE

COCKARROW_WELL

HAYES_WELL

NO1_WELL

BUBBLE_WELL

RAILWAY_WELL

NO_408

GOLD_TOOTH_WELL

TRENNAMANS_WELL

FRESHWATER_WELLGARDEN_WELL

GARDEN_(GOVT_NO_16)_WELD

MILLIE_MILLIE_WELL

WARD_WELLP18_CHEVRON

P22_CHEVRON

P26_CHEVRON

P31_CHEVRON

P32_CHEVRON

LANAGAN_BORE

RED_HILL_WELL

WARD_NO_1_WELL

DIORITE_WELL

NO_383_CRITCHES_BOREP61_Chevron

P62_Chevron

P70_Chevron

LW12

470

480

490

500

510

520

530

540

550

560

470 480 490 500 510 520 530 540 550 560Measured Head (m)

Model

led H

ead (

m) SRMS Error = 13.6%

SRMS Error = 8.4% without Diorite Well & Deep Bore

MEASURED VERSUS MODELLED WATER LEVELS AND PREDICTED STEADY-STATE WATER LEVEL CONTOURSF:\Jobs\1134\C\600_Report\Figures\104a Figures\Fig 4.11.srf

FIGURE 4.11

190000 195000 200000 205000 210000 215000 220000 225000 230000 235000

7025000

7030000

7035000

7040000

7045000

7050000

7055000

7060000

7065000

7070000

495.7495.1

493.9492.9

493

540.5

537.5

513513.3

510.4

503.4

520.4

506.9

503.3

495.4

494.8

501.8

495.9

496.6

495.3

480.7

499

497.3

502.2

511.5

499.4

544.6

508.3

502.2

488.2

513.7

497.1496.8

498.9

490

493.4

492.6

494.5494.3

494493.8

493.6

545.6

549.3

517.6537

509.8

504.2

519.9

507.4

511.6

496.6

498.6

505.1

493.3

493.9

497.9

494.6

500.6

499.4

503.7

510

496.2

534.3

509.7

515.6

522.6

528.1

499.1498.5

502.2

489.6

491.5

493.6

No Flow Cells

Constant Head (CH)

LEGEND

Measured Waterlevel

Modelled Waterlevel469.5

513.6

Predicted Waterlevel Contours550

Calcrete Extent

Easting (m)

Nort

hin

g (

m)


MODELLED RECHARGE DISTRIBUTION FIGURE 4.12F:\Jobs\1134\C\600_Report\Figures\104a Figures\Fig 4.12.srf

Easting (m)

Nort

hin

g (

m)

190000 195000 200000 205000 210000 215000 220000 225000 230000 235000

7025000

7030000

7035000

7040000

7045000

7050000

7055000

7060000

7065000

7070000


Western Alluvium

Calcrete Alluvium Transition

Eastern Alluvium

No Flow Cells

Northern Calcrete

Middle Calcrete

LEGEND

Fractured Bedrock

Southern Calcrete

0.084

1

0.084

1

1.4

0.01

1.4

5.94E-07

7.7E-06

5.94E-07

7.7E-06

9.9E-06

7.7E-08

9.9E-06

Percentage Recharge (m/day)


GROUNDWATER MODEL


4.4.3 TRANSIENT CALIBRATION

Calibration to transient or time varying conditions was completed for the groundwater model for the period October 1986 to November 2009. This period was chosen as it included abstraction from both the West Creek Borefield and the Apex Southern Borefield. The locations of the West Creek and Wiluna South Borefield are shown in Figure 1.1.

The transient calibration was run using a monthly stress period (period over which all stresses remain constant) for the entire calibration period. Other assumptions of the transient calibrations are as follows:

▼ Initial heads from the steady-state calibration.

▼ Rainfall recharge is varied monthly and assigned at the same proportions as the steady state calibration.

▼ Groundwater pumping is varied monthly. Historical abstraction data was sourced from both consultant reports and the DoW database. The available dataset required some interpretation due to the following factors:

− The apparent lumping of several months of abstraction data into a single month.

− Possible typographical errors.

− Missing abstraction information, for example, observed water levels in bore P70 show a decline of ~4m between January 1991 and October 1993 (Figure 1.4), however, no abstraction was recorded.

Calibrated aquifer parameters, including both unconfined and confined storage coefficients are presented in Table 4.6 and shown in Figures 4.2 to 4.4. Aquifer parameters are consistent with available data and as with the steady state calibration, no hydrogeological features that cannot be justified on the basis of current hydrogeological understanding have been included to force or improve model calibration.

Table 4.6: Transient Calibration Model Specific Yield and Storage Coefficient Values

Horizontal Hydraulic Conductivity (m/d)

Vertical Hydraulic Conductivity (m/d)

Storage Coefficient

Specific Yield

Bedrock 0.005 0.0005 1e-005 0.001

Southern Calcrete 25 2.5 0.0001 0.1

Eastern Alluvium 1 0.1 0.0001 0.2

Western Alluvium 1 0.1 0.0001 0.2


2 0.2 0.0001 0.05

Northern Calcrete 2 0.2 0.0001 0.05

Middle Calcrete 12.5 1.25 0.0001 0.1

Clay/Silt 0.5 0.05 1e-005 0.001

The locations of monitoring bores used for transient model calibration are shown in Figure 4.9. Calibration hydrographs for the Apex Southern Borefield are shown in Figure 4.13. Measured groundwater levels in the Apex Southern Borefield (bores XP1 to XP5) are well matched with groundwater elevations are generally within 2m of the observed values. It is noted however that when abstraction rates from the Apex Southern Borefield increase, the match between measured and modelled water levels is not as good. The reliability of pumping data is such that this impact cannot be addressed further with the currently available information.

Calibration hydrographs for the West Creek Borefield bores (P18, P22, P61 and P62) are shown in Figure 4.14. Measured groundwater levels are also generally well matched. Bores P26 and P70 showed little response to pumping which is not predicted by the model. The reason for this


GROUNDWATER MODEL


mismatch is unclear and as with the Apex Southern Borefield the abstraction records available are not sufficient to determine if the mismatch is due to data validity or localised hydrogeological features in the vicinity of bores P26 and P70 that result in no measurable response to pumping from bores P18, P22, P61 and P62.

APEX SOUTHERN BOREFIELD CALIBRATION HYDROGRAPHS FIGURE 4.13

\\aquaterra.com.au\data\at1\Jobs\1134\C\600_Report\Figures\104a Figures\[Fig 4.13 and 4.14_ hydrographs.xls]Fig 4.13

XP1

488

490

492

494

496

498

Oct

-86

Oct

-87

Sep

-88

Sep

-89

Sep

-90

Sep

-91

Sep

-92

Sep

-93

Sep

-94

Sep

-95

Sep

-96

Sep

-97

Sep

-98

Sep

-99

Sep

-00

Sep

-01

Sep

-02

Sep

-03

Sep

-04

Sep

-05

Sep

-06

Sep

-07

Sep

-08

Sep

-09

Wate

r Le

vel (m

AH

D) Observed

Modelled

XP2

488

490

492

494

496

498

Oct

-86

Oct

-87

Sep

-88

Sep

-89

Sep

-90

Sep

-91

Sep

-92

Sep

-93

Sep

-94

Sep

-95

Sep

-96

Sep

-97

Sep

-98

Sep

-99

Sep

-00

Sep

-01

Sep

-02

Sep

-03

Sep

-04

Sep

-05

Sep

-06

Sep

-07

Sep

-08

Wate

r Le

vel (m

AH

D)

XP3

488

490

492

494

496

498

Oct

-86

Oct

-87

Sep

-88

Sep

-89

Sep

-90

Sep

-91

Sep

-92

Sep

-93

Sep

-94

Sep

-95

Sep

-96

Sep

-97

Sep

-98

Sep

-99

Sep

-00

Sep

-01

Sep

-02

Sep

-03

Sep

-04

Sep

-05

Sep

-06

Sep

-07

Sep

-08

Sep

-09

Wate

r Le

vel (m

AH

D)

XP4

488

490

492

494

496

498

Oct

-86

Oct

-87

Sep

-88

Sep

-89

Sep

-90

Sep

-91

Sep

-92

Sep

-93

Sep

-94

Sep

-95

Sep

-96

Sep

-97

Sep

-98

Sep

-99

Sep

-00

Sep

-01

Sep

-02

Sep

-03

Sep

-04

Sep

-05

Sep

-06

Sep

-07

Sep

-08

Sep

-09

Wate

r Le

vel (m

AH

D)

XP5

488

490

492

494

496

498

Oct

-86

Oct

-87

Sep

-88

Sep

-89

Sep

-90

Sep

-91

Sep

-92

Sep

-93

Sep

-94

Sep

-95

Sep

-96

Sep

-97

Sep

-98

Sep

-99

Sep

-00

Sep

-01

Sep

-02

Sep

-03

Sep

-04

Sep

-05

Sep

-06

Sep

-07

Sep

-08

Sep

-09

Wate

r Le

vel (m

AH

D)

WEST CREEK BOREFIELD CALIBRATION HYDROGRAPHS FIGURE 4.14

\\aquaterra.com.au\data\at1\Jobs\1134\C\600_Report\Figures\104a Figures\[Fig 4.13 and 4.14_ hydrographs.xls]Fig 4.14

P22

490492494496498500502504506508

Oct

-86

Oct

-87

Sep-

88

Sep-

89

Sep-

90

Sep-

91

Sep-

92

Sep-

93

Sep-

94

Sep-

95

Sep-

96

Sep-

97

Sep-

98

Sep-

99

Sep-

00

Sep-

01

Sep-

02

Sep-

03

Sep-

04

Sep-

05

Sep-

06

Sep-

07

Sep-

08

Sep-

09

Wat

er L

evel

(mAH

D)

P61

490

492

494

496

498

500

502

504

506

Oct

-86

Oct

-87

Sep-

88

Sep-

89

Sep-

90

Sep-

91

Sep-

92

Sep-

93

Sep-

94

Sep-

95

Sep-

96

Sep-

97

Sep-

98

Sep-

99

Sep-

00

Sep-

01

Sep-

02

Sep-

03

Sep-

04

Sep-

05

Sep-

06

Sep-

07

Sep-

08

Sep-

09

Wat

er L

evel

(mAH

D)

P26

490492

494496

498500

502504

506508

Oct

-86

Oct

-87

Sep-

88

Sep-

89

Sep-

90

Sep-

91

Sep-

92

Sep-

93

Sep-

94

Sep-

95

Sep-

96

Sep-

97

Sep-

98

Sep-

99

Sep-

00

Sep-

01

Sep-

02

Sep-

03

Sep-

04

Sep-

05

Sep-

06

Sep-

07

Sep-

08

Sep-

09

Wat

er L

evel

(mAH

D)

P62

490

492

494

496

498

500

502

504

506

Oct

-86

Oct

-87

Sep-

88

Sep-

89

Sep-

90

Sep-

91

Sep-

92

Sep-

93

Sep-

94

Sep-

95

Sep-

96

Sep-

97

Sep-

98

Sep-

99

Sep-

00

Sep-

01

Sep-

02

Sep-

03

Sep-

04

Sep-

05

Sep-

06

Sep-

07

Sep-

08

Sep-

09

Wat

er L

evel

(mAH

D)

P70

490

492

494

496

498

500

502

504

506

508

Oct

-86

Oct

-87

Sep-

88

Sep-

89

Sep-

90

Sep-

91

Sep-

92

Sep-

93

Sep-

94

Sep-

95

Sep-

96

Sep-

97

Sep-

98

Sep-

99

Sep-

00

Sep-

01

Sep-

02

Sep-

03

Sep-

04

Sep-

05

Sep-

06

Sep-

07

Sep-

08

Sep-

09

Wat

er L

evel

(mAH

D)

P18

490

492

494496

498

500

502504

506

508

Oct

-86

Oct

-87

Sep

-88

Sep

-89

Sep

-90

Sep

-91

Sep

-92

Sep

-93

Sep

-94

Sep

-95

Sep

-96

Sep

-97

Sep

-98

Sep

-99

Sep

-00

Sep

-01

Sep

-02

Sep

-03

Sep

-04

Sep

-05

Sep

-06

Sep

-07

Sep

-08

Sep

-09

Wat

er L

evel

(mA

HD

)

Observed

Modelled


GROUNDWATER MODEL


Mass Balance

The cumulative water balance for the Transient Calibration Model (October 1986 to November 2009) is presented in Table 4.7.

Table 4.7: Transient Calibration Model Cumulative Mass Balance (m3)

In Out

Storage 10,028,500 8,564,200

Constant Head 213,600 5,732,200

Recharge 12,084,500 0

Evapotranspiration 0 4,243,000

Wells 0 3,789,500

Total 22,326,600 22,328,900

The following is noted with respect to the Transient Calibration Model:

▼ The total cumulative mass balance error was 2,325m3 or 0.01%.

▼ The mass balance error within individual time steps ranged from -3% and 3%, however, most errors were significantly lower.

▼ The total abstraction from the model was 3,789,455m3, this agrees well with the volume in the input file of 3,789,451m3.

▼ Groundwater elevations in the abstraction bores remained above the base of layer 1 during the entire simulation.

Based on the above and the hydrographs presented in Figure 4.13 and Figure 4.14, the Transient Calibration Model was considered acceptable.

4.5 MODEL PREDICTIONS

4.5.1 SETUP

The calibrated model was used to assess the potential for groundwater abstraction from the calcrete aquifer to supply the project water demand. A number of borefield configurations were simulated including one scenario with pumping from both the West Creek Borefield and the Apex Southern Borefield at the same time. The location of the two borefields is shown in Figure 4.15

Predictive modelling was completed using two different operating constraints. The operating constraints assumed either maintenance of 75% or 60% of the saturated aquifer thickness, to allow set pumping rates to be maintained and to maintain an acceptable habitat for stygofauna. For the 75% case this corresponds to an aquifer drawdown of around 3 metres, with 4 metres for the 60% case. Maximum assigned pumping rates are assigned consistent with historical performance and available bore hydraulic information. These constraints and scenario configurations are presented in Table 4.8.


GROUNDWATER MODEL


Table 4.8: Borefield Prediction Scenarios

Scenario % of Calcrete Saturated Thickness Maintained*

Maximum Total Abstraction (m3/day)@

Existing Production Bore Locations and (Individual Pumping Rates#)

Notional Production Bore Locations (Individual Pumping Rates)

1 75 2090 P18 (311) P22 (519) P61 (286) P62 (977.5)

nil

2 60 2090 P18 (311) P22 (519) P61 (286) P62 (978)

nil

3 75 2090 P18 (303) P26 (286) P62 (917) P70 (303) P21 (286)

nil

4 60 2090 P18 (303) P26 (286) P62 (917) P70 (303) P21 (286)

nil

5 75 2030 P18 (173) P62 (397) P70 (233) P26 (259)

N1 (216) N2 (173) N4(216) N5 (151) N8 (216)

6 60 2030 P18 (173) P62 (397) P70 (233) P26 (259)

N1 (216) N2 (173) N4(216) N5 (151) N8 (216)

7 75 2030 P18 (173) P62 (397) P70 (233) P26 (259)

N1 (216) N2 (173) N4(216) N5 (151) N8 (216)

8 60 2030 P18 (173) P62 (397) P70 (233) P26 (259)

N1 (216) N2 (173) N4(216) N5 (151) N8 (216)

9 60 2030 (excludes Apex Southern Borefield- XP1 to XP5)

P18 (173) P62 (397) P70 (233) P26 (259) XP1 (495)^ XP2 (389)^ XP3 (163)^ XP4 (478)^

XP5 (215)^

N1 (216) N2 (173) N4(216) N5 (151) N8 (216)

Notes: *- Indicates saturation in cells containing simulation wells. ^- Indicates assumes abstraction by another party (not Toro) # -indicates existing bore location only. New boreholes may be required. Pumping rates in m3/day. @- Indicates simulated maximum abstraction rate set in FWL4 fracture well package. Rates will decrease as the FWL4 Pumping Level is reached


GROUNDWATER MODEL


In addition to the constraints outlined in Table 4.8, model predictions assumed:

▼ A total prediction period of 10 years, consistent with the demand period.

▼ The model was run using a monthly stress period.

▼ Initial water levels derived from the end of the transient calibration.

▼ Recharge was assigned consistent with the distribution of the Transient Calibration model assuming average monthly rainfall data (BoM 30 year average 1979-2008) for Wiluna.

▼ Abstraction was simulated using the Fracture Well Package (FWL) of Modflow-Surfact. This package simulates pumping at a maximum specific rate until a minimum groundwater level or operational constraint is reached. The minimum groundwater elevation is set consistent with the operating constraints to maintain either a 60% or 75% saturated thickness of the aquifer as outlined in Table 4.8. The FWL package decreases the assigned pumping rate once water levels approach the assigned water level constraint and allows the pumping rate to increase if water levels increase.

▼ No other groundwater abstraction or development within the model domain.

MODELLED BOREFIELD LOCATIONF:\Jobs\1134\C\600_Report\Figures\104a Figures\Fig 4.15.srf

FIGURE 4.15

215000 220000 225000 230000 2350007045000

7050000

7055000

P18P22

P61P62

P21N1

N2

N4

N5

N8

P70P26

XP1XP2

XP3XP4

XP5

Easting (m)

Nort

hin

g (

m)

No Flow Cells

LEGEND

Simulated Prediction WellProjection: MGA94 Z51

Model Grid


GROUNDWATER MODEL


4.5.2 PREDICTION RESULTS

Predicted pumping rates (m3/day) for Scenarios 1 to 9 over the 10 year prediction period are shown in Table 4.9, Figure 4.16 and Appendix C.

The predictions results suggest that for all Scenarios considered, water demand cannot be met by the modelled borefields. The results of Scenario 6 (which assumes an expanded West Creek Borefield is implemented with a 40% permissible drawdown) predicts the delivery of approximately 1820m3/day (6.6GL/year) after ten years of borefield operation.

Table 4.9: Summary of Results for Modelled Scenarios

Scenario Scenario Description % of Saturated Thickness Maintained*

Maximum Total Borefield Abstraction Rate (m3/day)*

Total Borefield Abstraction Rate after 10 Years (m3/day)

1 Original borefield 75 2093 550

2 Original borefield 60 2093 790

3 Revised original borefield 75 2094 840

4 Revised original borefield 60 2094 1300

5 Expanded borefield 75 2035 1020

6 Expanded borefield 60 2035 1820

7 Expanded borefield No recharge

75 2035 740

8 Expanded borefield No recharge

60 2035 1530

9 Expanded borefield with XP1 to XP5 operating

60 2035 (total excludes pumping from Apex Southern Borefield XP1 to XP5)

1730

Notes: *- Indicates simulated maximum abstraction rate set in FWL4 fracture well package. Rates will decrease as the FWL4 Pumping Constraint Level is reached.

Predicted Watertable and Drawdowns

Predicted watertable contours at an elapsed time of 10 years for Scenarios 6, 8 and 9 are presented in Figures 4.17 to 4.19.

Predicted drawdown contours at an elapsed time of 10 years for Scenarios 6, 8 and 9 are presented in Figures 4.20 to 4.22.

\\aquaterra.com.au\data\at1\Jobs\1134\C\600_Report\Figures\104a Figures\[Doc 102b Consolidated FWL output.xls]Figure 4.16

TOTAL ABSTRACTION FOR MODELLED BOREFIELD SCENARIOS FIGURE 4.16

0

500

1000

1500

2000

2500

0 1 2 3 4 5 6 7 8 9 10

Elapsed Time (years)

Pu

mp

ing

Rate

(m

3/

d)

Scenario 1 Scenario 2




Scenario 9

SCENARIO 6 - PREDICTED WATERTABLE AFTER 10 YEARS FIGURE 4.17

No Flow Cells

Constant Head (CH)

LEGEND

190000 195000 200000 205000 210000 215000 220000 225000 230000 235000

7025000

7030000

7035000

7040000

7045000

7050000

7055000

7060000

7065000

7070000

P18P26

P62

P70

N1N2

N4N5

N8

Water Level Contours

Pumping Bores

525


Calcrete Extent

Easting (m)

Nort

hin

g (

m)



No Flow Cells

Constant Head (CH)

LEGEND

190000 195000 200000 205000 210000 215000 220000 225000 230000 235000

7025000

7030000

7035000

7040000

7045000

7050000

7055000

7060000

7065000

7070000

P18P26

P62

P70

N1N2

N4N5

N8


Pumping Bores

525


Nort

hin

g (

m)

Easting (m)

Calcrete Extent



No Flow Cells

Constant Head (CH)

LEGEND

190000 195000 200000 205000 210000 215000 220000 225000 230000 235000

7025000

7030000

7035000

7040000

7045000

7050000

7055000

7060000

7065000

7070000

P18P26

P62

P70

N1N2

N4N5

N8

XP1XP2XP3XP4XP5


Pumping Bores

525


Calcrete Extent

Easting (m)

Nort

hin

g (

m)


SCENARIO 6 - PREDICTED DRAWDOWN AFTER 10 YEARS FIGURE 4.20

No Flow Cells

Constant Head (CH)

LEGEND

190000 195000 200000 205000 210000 215000 220000 225000 230000 235000

7025000

7030000

7035000

7040000

7045000

7050000

7055000

7060000

7065000

7070000

P18P26

P62

P70

N1N2

N4N5

N8

Drawdown Contours

Pumping Bores

525

F:\Jobs\1134\C\600_Report\Figures\104a Figures

Calcrete Extent

Easting (m)

Nort

hin

g (

m)



No Flow Cells

Constant Head (CH)

LEGEND

190000 195000 200000 205000 210000 215000 220000 225000 230000 235000

7025000

7030000

7035000

7040000

7045000

7050000

7055000

7060000

7065000

7070000

P18P26

P62

P70

N1N2

N4N5

N8

Drawdown Contours

Pumping Bores

525


Easting (m)

Nort

hin

g (

m)

Calcrete Extent



No Flow Cells

Constant Head (CH)

LEGEND

190000 195000 200000 205000 210000 215000 220000 225000 230000 235000

7025000

7030000

7035000

7040000

7045000

7050000

7055000

7060000

7065000

7070000

P18P26

P62

P70

N1N2

N4N5

N8

XP1XP2XP3XP4XP5

Drawdown Contours

Pumping Bores

525


Easting (m)

Nort

hin

g (

m)

Calcrete Extent



GROUNDWATER MODEL


4.6 SENSITIVITY ANALYSIS

In any modelling exercise, uncertainties always remain in the adopted parameters. A sensitivity analysis was performed to assess the potential effect of parameter variability, on the predicted groundwater fluxes. The sensitivity analysis can be used to identify critical factors and provide some confidence limits about the predictions. The parameter values for the sensitivity analysis were selected to provide further conservatism in the predictions.

The following sensitivity runs were completed assuming the operational constraints and pumping configuration of Scenario 6 (the case which shows the highest sustainable borefield yield):

▼ Sensitivity Run 1 assumed reduced hydraulic conductivity of the three calcrete units.

▼ Sensitivity Run 2 assumed reduced specific yield of the three calcrete units.

▼ Sensitivity Run 3 assumed reduced specific yield of the two alluvium units.

The aquifer parameters associated with the sensitivity runs are summarised in Table 4.10.

Table 4.10: Sensitivity runs

Aquifer Parameter Model Units Base Case* Sensitivity Run 1

Sensitivity Run 2

Sensitivity Run 3

Hydraulic Conductivity (m/d)


2 1 2 2

Northern Calcrete 2 1 2 2

Middle Calcrete 12.5 6 2 2

Southern Calcrete 25 12.5 2 2

Specific Yield Calcrete/Alluvium Transition

0.05 0.05 0.025 0.05

Northern Calcrete 0.05 0.05 0.025 0.05

Middle Calcrete 0.1 0.1 0.05 0.1

Southern Calcrete 0.1 0.1 0.05 0.1

Specific Yield Eastern and Western Alluvium

0.2 0.2 0.2 0.025

Notes: *- Indicates Scenario 6. Parameters changed for specific sensitivity runs are shown in bold type.

The sensitivity analysis indicates the following:

▼ Sensitivity Run 1- predicts that abstraction from the West Creek Borefield would decrease below 1,920m3/day (0.7GL/year) after 5 to 6 years. After ten years the total abstraction from the borefield would decline to ~1,450m3/day (5.3GL/year).

▼ Sensitivity Run 2- predicts that abstraction from the West Creek Borefield would decrease below 1,920m3/day (0.7GL/year) after 4 to 5 years. After ten years the total abstraction from the borefield would drop to ~1,200m3/day (4.38GL/year).

▼ Sensitivity Run 3- predicts that abstraction from the West Creek Borefield would decrease below 1,920m3/day (0.7GL/year) after 8 to 9 years. After ten years the total abstraction from the borefield would drop to ~1,800m3/day (6.6GL/year).

Figures 4.23 shows the results of the three sensitivity runs, together with those from Scenario 6 for comparison.

PREDICTED ABSTRACTION RATES- SENSITIVITY RUNS FOR SCENARIO 6 FIGURE 4.23

1000

1200

1400

1600

1800

2000

2200

0 1 2 3 4 5 6 7 8 9 10

Years

Ab

stra

ctio

n R

ate

(m

3/

day)

Scenario 6

Sensitivity Run 1 (Calcrete Hydraulic Conductivity Reduced)

Sensitivity Run 2 (Calcrete Specific Yield Reduced)

Sensitivity Run 2 (Alluvium Specific Yield Reduced)


GROUNDWATER MODEL


The results for Sensitivity Run 3 are very similar to those obtained for Scenario 6, indicating that the model is not particularly sensitive to the specific yield of the surrounding alluvial aquifer. Conversely, and as would be expected, the model is sensitive to both hydraulic conductivity and specific yield of the calcrete aquifer. In particular, the model seems to be very sensitive to reductions in specific yield; this would be expected in a situation where much of the water abstracted from the calcrete aquifer is derived from water released from storage.

4.7 GROUNDWATER RECOVERY

Once water supply pumping from the calcrete aquifer ceases, after the projected demand period of ten years, groundwater levels will slowly recover to close to pre-development levels where a balance exists between groundwater inflow (from recharge) and outflow (to Lake Way and via evapotranspiration).

The groundwater flow model was used to predict the time taken for groundwater levels to return to pre-development levels. The prediction assumed:

▼ Initial conditions from the end of Scenario 6 (i.e. after ten years of groundwater abstraction).

▼ Average rainfall recharge conditions.

▼ A recovery prediction period of fifty years.

Predicted water levels for P62, over the ten year supply period and the subsequent fifty year recovery period are shown in Figure 4.24. Predicted water levels suggest that the majority of groundwater recovery closer to 2.5 metres, is completed twenty years after water supply pumping ceases. A further 1.5 metres of recovery is predicted after a further forty years.

FIGURE 4.24F:\Jobs\1134\C\600_Report\Figures\104a Figures\[Fig 4.24 Doc 110a Results for C_P016 and C_C01 (recovery).xls]Figure 4.24

WATER LEVELS FOR MODEL CELL CONTAINING BORE P62- SCENARIO 6 AND RECOVERY RUN

Water Levels for Model Cell Containing Bore P62- Scenario 6 and Recovery Run

490.0

491.0

492.0

493.0

494.0

495.0

496.0

497.0

498.0

499.0

500.0

0 10 20 30 40 50 60

Prediction Elapsed Time (years)

Pre

dic

ted

Wate

r Level (m

RL)

Water Level Recovey

Water Level (AbstractionScenario 6)

Steady-State (Pre-Pumping)Water Level


GROUNDWATER MODEL


4.8 MODEL LIMITATIONS

All of the work carried out has been undertaken at a Pre-Feasibility level of understanding. As a result, there are areas within and surrounding the West Creek area which are not fully understood at this time, in hydrogeological terms. To date these areas have been represented with the available information from the site or from other similar areas. However, to improve model reliability we recommend that the following areas are investigated or addressed and the relevant changes are subsequently made to the conceptual model and the groundwater model.

4.8.1 ABSTRACTION ESTIMATES

To date the groundwater model has been used to predict groundwater abstraction that can be expected based on our current hydrogeological understanding. It is recommended that further hydrogeological testing is completed and the relevant data used to upgrade abstraction predictions to provide greater confidence in aquifer parameters and individual bore yields used for the model predictions.

4.8.2 RECHARGE

To date the model predictions have assumed average long term rainfall recharge. No allowance has been made for extreme wet or dry rainfall conditions (significantly above or below the average conditions adopted) over the wet season months (i.e. January to March). As indicated by Scenario 8, the absence of recharge will adversely affect abstraction from the West Creek Borefield. Conversely, cyclonic recharge events have been known to recharge active borefields to above initial starting water level conditions.

4.8.3 AQUIFER CHARACTERISTICS AND CALIBRATION TO TRANSIENT DATA

The sensitivity analysis suggests that the abstraction estimates presented in this report are particularly sensitive to the hydraulic conductivity and storage parameters of the calcrete. Currently there is little hydraulic testing data available for this unit. If however greater confidence could be placed in the West Creek Borefield data used to calibrate the model, the uncertainties associated with hydraulic conductivity and storage values would be reduced. As a result more confidence could be placed in the model predictions. However, if uncertainties with the pumping dataset cannot be resolved it is recommended that conceptual understanding and model setup is supplemented with targeted hydraulic testing for the calcrete aquifer.


DISCUSSION


5 DISCUSSION

5.1 WATER SUPPLY OPTIONS

Based on our current understanding of the West Creek hydrogeology, and the modelling reported above, we provide a discussion of our findings below:

▼ Palaeochannel aquifer- It is considered unlikely that a palaeochannel aquifer in the West Creek area will satisfy the water quality requirements of Wiluna Uranium Project. Additionally, based on the information currently available there is no certainty that such an aquifer exists in the area. Borehole logs for the area suggest that the sediments overlying bedrock are clayey to silty, with no significant coarse horizons.

▼ Maintenance of aquifer saturated thickness- The model results suggest that that a borefield installed in the calcrete where drawdown is limited to maintain 75% of the saturated thickness does not represent a plausible or practical solution to Toro’s water requirement. We also consider that as a minimum, 60% of the initial saturated thickness should be maintained in the calcrete to facilitate efficient bore operation. Environmental factors (stygofauna habitat) may also place limits on the degree of dewatering permitted.

▼ Current West Creek Borefield- The model results suggest that the current West Creek Borefield (installed in the calcrete) comprising bores P18, P22, P61 and P62 will not satisfy the Toro’s water demand of 0.70GL/year for the 10 year project life. These bores may be able to supply the required yield (1,920m3/day) for approximately twelve months (based on Scenario 2), however the modelling suggests that this borefield cannot sustain this yield over the longer term. We note that the borefield has in the past produced ~1,072m3/day for periods of approximately 2 years. However there is no record of sustained abstraction from this borefield to support the premise that an abstraction rate of 0.7GL/year for ten years is feasible. Based on the modelling undertaken for Scenario 2, the yield after 10 years is predicted to be ~790m3/day (0.288GL/year).

▼ Revised West Creek Borefield- The model results suggest that that a reconfiguration of the existing West Creek Borefield (comprising P18, P26, P62, P70 and P21) of could supply the 0.7GL/year water demand of the Wiluna Uranium Project. Based on the modelling undertaken for Scenario 4, the yield after 10 years is predicted to be 1,300m3/day (0.475GL/year).

▼ Expanded West Creek Borefield- The model results suggest that that an expanded West Creek Borefield (installed in the calcrete aquifer) is likely to supply more water than either the existing West Creek or a revised West Creek Borefield. Based on the modelling undertaken for Scenario 6, the yield after 10 years is predicted to be ~ 1,820m3/day (0.664GL/year). Supply is predicted to decline below 1920m3/day (0.70GL/year) after approximately 8 to 9 years of abstraction. The final water quality of the blend of an expanded West Creek Borefield will not be known until further hydrogeological data is collected.

▼ Expanded West Creek Borefield- bore locations- it should be noted that the new production bore locations used in Scenarios 6 to 12 are notional and have been located on the basis of the model geometry, which is in turn based on limited hydrogeological data. A key requirement of this borefield design would be to spread abstraction over as wide as area of the calcrete aquifer as possible, without moving too far south towards Lake Way where groundwater quality deteriorates. Any potential locations of new bores would need to be fully investigated with respect to both yields and quality before Toro committed to those locations.

▼ Well efficiency- Given the limited saturated thickness of the calcrete aquifer, bores installed in this unit will need to be constructed such they provide maximum efficiency (i.e. minimum drawdown per unit of yield). If low efficiency bores are installed the potential of the calcrete aquifer may not be realised. To provide high efficiency ‘over-sized’ large-diameter bores may be required.


DISCUSSION


▼ Apex Southern Borefield- Results from Scenario 9 indicate that if the Apex Southern Borefield (bores XP1 to XP5) is operated simultaneously with the Expanded West Creek Borefield, then yields from the latter will decrease to ~1,790m3/day (0.653GL/year) after 10 years of operation. It should be noted however that under this Scenario the Apex Southern Borefield is operated such that 60% saturation is maintained, and the yields of this borefield are predicted to decrease significantly over time. If an operator of the Apex Southern Borefield attempted to maintain abstraction rates by further lowering the watertable, we would expect to see yields from the Expanded West Creek Borefield decrease faster/further and possibly initiate flow reversal from Lake Way. Such a flow reversal would have serious deleterious effects on groundwater quality.

▼ Other areas for groundwater investigation- to date limited investigations have been undertaken in the north of the calcrete aquifer, or around the northern margins of the study area base of the Finlayson Ranges. It is possible that these areas could supply limited quantities of good quality groundwater due to their proximity to recharge zones associated with outcrops of fractured rock. Such a supply could assist Toro by providing good water for ‘blending’ with that obtained from bores in more marginal areas.

5.2 PREDICTED DRAWDOWNS

Predicted drawdowns for Scenarios 6, 8 and 9 are presented in Figures 4.17 to 4.19. Table 5.1 shows a summary of model predictions for these Scenarios.

Table 5.1: Areas of drawdown- Scenarios 6, 8 and 9

Scenario Scenario Description

Drawdown Contour (m)

Approximate Dimensions of Drawdown Area@

Area (km2)@

Percentage Area of Calcrete@

6 Expanded borefield 0.5 2 4

11 x 6 8 x 3.5 4 x 1.5

42 22 5

42 22 5

8 Expanded borefield (No recharge)

0.5^ 2 4

11.5 x 6 9.5 x 5 4.5 x 3

55 28 8

56 28 8

9 Expanded borefield with XP1 to XP5 operating

0.5 2 4

15 x 6 8 x 4 3 x 2

70 22 3.5

71 22 4

Notes: *- Indicates saturation in cells containing simulation wells. ^ Indicates estimated drawdown due to abstraction only. Whole model area affected by nil recharge applied. @- indicates dimensions are approximate only.

From Table 5.1 it can be seen that although a drawdown of 0.5m is predicted over a wide area of the calcrete aquifer, greater drawdowns are expected to impact significantly smaller areas. For Scenarios 6, 8 and 9 the modelling predicts that, even under conditions of no recharge, less than 10% of the calcrete aquifer will be impacted by waterlevel drawdowns of 4m or more. We consider that the relatively small zone of deeper drawdown predicted is due to the relatively low hydraulic conductivity of the calcrete aquifer.


WEST CREEK BOREFIELD DEVELOPMENT COSTS


6 WEST CREEK BOREFIELD DEVELOPMENT COSTS

6.1 BORE CONSTRUCTION AND TESTING COSTS

Development of the recommended borefield configuration (Scenario 6, Figure 1.3), consisting of 4 existing production bores (P18, P22, P62 and P70) and 6 notional production bores (N1, N2, N4, N5, as well as a standby production bore (SB1), has been costed assuming that:

▼ The existing production bores cannot be rehabilitated and that new production bores need to be constructed using a mud-rotary drilling rig.

▼ Initially, a 5” exploration hole will drilled at each of six proposed new production sites using an Aircore drilling rig. If the results suggest that suitable calcrete horizons are present, a 12” production bore will be constructed alongside the exploration hole using mud-rotary drilling.

▼ All boreholes will be drilled and constructed to a nominal depth of 35m. The 6 exploration holes will be equipped with 50mm Class 18 PVC casing for use as monitoring holes during the test-pumping, as well as for long-term groundwater level monitoring. The 10 production bores will be equipped with 200mm Class 12 PVC casing and gravel-packed screens.

▼ Each production bore will be test pumped to determine aquifer parameters and sustainable bore yields, by conducting a 6hr step-test followed a 48hr constant–discharge test and 12hrs of recovery monitoring.

The borefield development costs are estimated at approximately $1.3M (Table 6.1), which equates to an ‘average’ cost per production bore of ~$123,400.

Table 6.1: West Creek Borefield Development Costs

Description Quantity Costs

Exploration Bore Drilling and Construction* 16 $839,400

Test Pumping 10 $136,000

SUB-TOTAL $975,400

Contingency 10% $97,540

Hydrogeological EPCM 15% $160,941

TOTAL COST (Excl. GST) $1,233,881

Note: * - Includes 10 production bores and 6 monitoring holes.

6.2 PUMP, PIPELINE AND POWER SUPPLY CAPITAL COSTS

A cost estimate has been made for piping water from the West Creek Borefield to the Centipede and Lake Way processing plants, as well as to the proposed mine village on the north-western edge of Lake Way. The conceptual design layout for the proposed water reticulation scheme is shown in Figure 1.3.

The collector pipelines within the borefield were based on the use of PE PN6.3 pipework. It has been assumed that the bore pumps are set in the bore casing at a nominal 20m below ground. Bore pumps are selected to pump their design flow rate when the borefield is also producing its design flow rate (i.e. most of the bore pumps are operating simultaneously) of 1,918m3/day (~22L/s) and that the waterlevel remains with its design operating level.

The proposed transfer pipelines were assumed to also be PE100 pipe PN6.3 (buried), with higher pressure rating pipe as required. Scour valves would be provided along the pipe lines at low points, enabling emptying of the pipe. Air valves would similarly be provided at pipe high points to remove accumulated air, and to allow air inflow for draining the pipeline. Depending on the longitudinal profile of the pipeline, section valving may be desirable to limit the time of scouring and refilling. The cost estimate includes new pipe construction to both the Centipede and Lake Way deposits. There may be some opportunity for cost savings by recovering the




initial transfer pipe line to Centipede after cessation of mining operations, and relaying it to Lake Way, therefore avoiding the cost of purchasing new pipe.

The overall water supply system would be controlled via an integrated radio-based telemetry control system requiring logic and interface at the individual control cubicles located at all pumps and tanks. Such a system would avoid excessive staffing costs for manual control at such remote sites. The operation of all bore pumps, transfer pumps and water levels in the tanks (if provided) under normal steady-state operation, would be controlled automatically by the system. Pumps, groundwater-levels and flow rates would be monitored from the telemetry base station at a control centre at the mine site.

A transfer pump station (TPS) and collector tank has not been included within the cost estimates, as the concept system has low pumping heads and it has been assumed that the bores would pump directly to their demand centres (the mining camp, and Centipede or Lake Way Deposit). During design however a TPS may be required for operational control of borefield pumping, or it may be more economical to include a TPS and collector tank at the borefield for other reasons.

Tanks are required for storage at the demand centres and have not been included in the costing provided. The tanks would be liner (reinforced PVC) tanks such as the Highline Water ”Advantage” storage tanks and would include PE nozzles, galvanized steel external and 316 stainless steel internal ladders, and a cyclone rated dome-style roof. Each tank includes the construction of a concrete ring beam and bolting down of the tank walls.

The capital costs for the water reticulation system to the Centipede processing plant and mine village are estimated as $7.8M, including the cost of power supply using individual gensets and contingency, contractor’s preliminaries (including mob / demob) and an allowance for EPCM costs (Table 6.2). The comparative costs for constructing the scheme using a HV power system is $16.2M (Table 6.3). Overhead power line systems reduce the ongoing maintenance requirements compared to a genset power supply option. The overall operating cost for individual gensets would be much higher compared with power line installation, although the net present value of the two options may be similar. If the cheaper system using diesel gensets is initially adopted, then the option always remains of replacing diesel gensets with reticulated power. The capital costs for construction of a similar supply system to the Lake Way processing plant is estimated at $3.0M (Table 6.4)

Table 6.2: Pumping, pipeline and genset power supply capital costs to Centipede

Description Amount

Bore Pumps, Headworks, Pipelines, genset Power Supply etc. $5,714,986

Contingency (10%) $571,499

Engineering Prelims (incl. Mob./Demob.) (15%) $857,248

EPCM (12%) $685,798

TOTAL COSTS (excl. GST) $7,829,531

Table 6.3: Pumping, pipeline and HV power supply capital costs to Centipede

Description Amount

Bore Pumps, Headworks, Pipelines, HV Power Supply etc. $11,814,946

Contingency (10%) $1,181,499

Engineering Prelims (incl. Mob./Demob.) (15%) $1,772,248

EPCM (12%) $1,417,798





Table 6.4: Pumping, pipeline and power supply capital costs to Lake Way

Description Amount

Bore Pumps, Headwork, Pipelines, genset Power Supply etc. $2,210,806

Contingency (10%) $221,081

Engineering Prelims (incl. Mob./Demob.) (15%) $331,621

EPCM (12%) $265,297


The total capital costs for the genset powered, water supply scheme to the Centipede and Lake Way mines, as well as the mine village, is estimated as $12.1M (i.e. total costs from Tables 6.1, 6.2 and 6.4).


CONCLUSIONS


7 CONCLUSIONS

Following the completion of this Study, the following conclusions are presented:

▼ Water quality within the calcrete aquifer in the study area is marginal at best with respect to the Wiluna Uranium Projects water quality constraints.

▼ Water quality within the deeper silty/clayey sediments underlying the calcrete aquifer is unlikely to meet Toro’s water quality constraints.

▼ The model results indicate that borefield operating strategies limiting drawdowns to 25% of the saturated aquifer thickness will not satisfy Toro’s water volume requirements for the Wiluna Uranium Project.

▼ The modelling indicates that the current West Creek Borefield (installed in the calcrete aquifer) comprising bores P18, P22, P61 and P62 is unlikely to satisfy Toro’s water demand of 0.7GL/year for a project life of ten years. As indicated above, these bores may be able to supply the required yields (1,920m3/day) for approximately twelve months, however there is no data to suggest that they can sustain this yield over the longer term.

▼ The modelling indicates that a reconfiguration of the existing West Creek Borefield (comprising P18, P26, P62, P70 and P21) is unlikely supply the required 0.7GL/year for ten years.

▼ The modelling indicates that an expanded West Creek Borefield installed in the calcrete aquifer may meet the Projects water requirements (0.7GL/year) for 8 to 9 years, before declining to ~0.66GL in the tenth year. A key requirement of this borefield design would be to spread abstraction over as wide as area of the calcrete aquifer as possible, without moving too far south towards Lake Way where groundwater quality deteriorates. Following the cessation of pumping, predicted water levels suggest that the majority of groundwater recovery closer to 2.5 metres, is completed twenty years after water supply pumping ceases. A further 1.5 metres of recovery is predicted after a further forty years.

▼ The final water quality of the blend of an expanded West Creek Borefield will not be known until further hydrogeological data is collected.

▼ Operation of the Apex Southern Borefield at significant rates is likely to have a deleterious effect on the operation of the West Creek borefield.

▼ The capital costs of developing a 0.7GL/year capacity water supply scheme to pipe water from the West Creek Borefield to the Centipede and Lake Way mines, as well the mine village, is estimated at $12.1M.

It should be noted that the modelling results presented in this report are based on the current model geometry, which has in turn been developed from the current limited dataset, and it assumes average rainfall conditions. We currently consider that there is insufficient data to develop such a borefield and further hydrogeological investigations are required. The limitations of the modelling work undertaken is presented in Section 4.8.


RECOMMENDATIONS


8 RECOMMENDATIONS

A number of data gaps were identified during this investigation and the following study recommendations are listed to allow final development of a borefield in the West Creek area;

▼ Further hydrogeological investigation of the study area should be undertaken. This should focus in areas of the calcrete that could potentially host an Expanded West Creek Borefield, and areas that could potentially contribute high quality groundwater. The investigation should include:

− Refurbishment/rehabilitation of damaged bores of interest in the study area. We understand that a number of bores have been vandalised.

− Installation of a number of monitoring bores so that groundwater samples can be collected for subsequent analysis, water levels gauged and slug permeability testing undertaken.

− All existing bores in the study area be sampled where practicable.

Assuming the above investigation provides favourable results, we recommend the following further actions:

▼ New test production bores should be installed and test pumped to provide greater information with respect to the hydraulic parameters of the calcrete aquifer. Toro should consider the business case for installing these bores as full production specification items to potentially save costs/time in developing the borefield.

▼ Test pumping of rehabilitated production bores.

▼ Monitoring bores will be required to be installed in the vicinity of the pumping bores.

▼ Monitoring bores should also be installed in the silt/clay underlying the calcrete to monitor for potential upconing effects.

▼ All existing bores in the study area be re-sampled where practicable.

▼ Update the groundwater model for the Study area to include data generated during the above investigations. Water supply predictions should be rerun using the updated model to confirm the current understanding of the West Creek hydrogeology.

▼ If Toro consider that an Expanded West Creek Borefield represents a key component of the Wiluna Uranium Project’s water supply, we recommend that a permanent monitoring network is installed, as soon as possible, with background data collected well in advance of the commissioning of any borefield.

▼ Reassessment of the borefield infrastructure development costs.


REFERENCES


9 REFERENCES

Aquaterra, (2007a): Lake Way / Centipede Deposit Stage 1: Data Review and Scope of Work, report for Nova Energy Limited, August 2007, Report Number 793/B1/018c, Perth, WA, 24p.

Aquaterra (2007b): Costean Programme Dewatering Assessment Centipede Deposit, report to Nova Energy Ltd, October 2007, Report No. 793/B2/045a, Perth, WA.

Aquaterra (2010): Wiluna Uranium Project – Groundwater and Surface Hydrology Studies: Proposal, Document No. 1134B/CA/005b, project proposal submitted to Toro Energy on 6th December 2009.

Australian Groundwater Consulting (1985): Wiluna Gold Project – Water Supply Appraisal (Stage 2), Technical Report 1254 dated November 1985 for Chevron Exploration Corporation, 12p.

Australian Groundwater Consulting (1986): Mt Wilkinson Gold Project – Water Supply Appraisal Stage 3, Draft report prepared for the Chevron Exploration Corporation, May 1986, AGT Report Number 1254, 55p.

Argent Exploration Services, (1987): Report on Hydraulic Test Data Analysis Mt. Wilkinson Gold Project, for Chevron Exploration Corporation, 15th January 1987.

Bureau of Meteorology, 2010. Actual Areal Evapotranspiration Map. http://www.bom.gov.au/jsp/ncc/climate_averages/evapotranspiration/index.jsp.

Department of Water, 2010. Electronic data supplied on 9th March 2010.

Geoscience Australia, 2003. 1:250,000 Sheet SG51-09, Wiluna (2nd Edition).

Geological Survey of Western Australia, 1992. Groundwater Regimes and Their Exploration for mining development in the Eastern Goldfields of Western Australia. Record 1992/3.

Geological Survey of Western Australia, 1999. Geological sheet SG51-09, Wiluna (2nd Edition)..

Geological Survey of Western Australia, 2001. Explanatory notes. Geological sheet SG51-09, Wiluna (2nd Edition).

KH Morgan and Associates (1997): Annual Groundwater Monitoring Report: April 1996 to March 1997 – Groundwater Licence 32082, Wiluna South Borefield, Project 748, 26th October 1997, report for Wiluna Gold Pty Ltd.

KH Morgan and Associates (2006a): Groundwater development planning for mining Centipede and Lake Way uranium deposits for Nova Energy, 4th April 2006.

KH Morgan and Associates (2006b): Annual groundwater monitoring to March 2006, GWL 57622(3), Eastern Borefield for Agincourt Resources Ltd, 15 August 2006.

Murray Darling Basin Commission (2001), Groundwater flow modelling guideline.

National Health and Medical Research Council (NHMRC) and Natural Resource Management Ministerial Council (NRMMC), 2004. Australian Drinking Water Guidelines.

Resource Investigations, (1989): Review of groundwater production Mt Wilkinson Gold Project, 19th April 1987 to 30th April 1989 for Chevron Exploration Corporation, 1st June 1989.

Resource Investigations, (1991): Report on groundwater Production and Water Level Monitoring – 30/4/89 to 16/1/19, Matilda Gold Project, Wiluna, WA – Groundwater Well Licence Numbers 32065, 32069, 32080 and 32082., for Eon Metal NL, Project No. 049.2, 23rd May 1991.

Rockwater, 1978: Lake Way Uranium Project - Preliminary Groundwater Investigation, October 1978, commissioned by Public Works Department of W.A., on behalf of Wyoming-Delhi-Vam Joint Venture, 34p.

Toro Energy (2010): Wiluna Uranium Project – Environmental Scoping Document, Report No. 100514-PM-WIL-ENV-LC, Toro Energy Ltd, 14 May 2010.

Water and Rivers Commission, (1999): Groundwater Resources of the Northern Goldfields, Western Australia. Report HG2.

APPENDIX A ACTUAL AREAL EVAPOTRANSPIRATION MAP

From http://www.bom.gov.au/jsp/ncc/climate_averages/evapotranspiration/index.jsp.

APPENDIX B STEADY-STATE CALIBRATION GROUNDWATER ELEVATIONS

Table B1- Steady-State Calibration Wells

Easting* Northing* Name Adopted Steady-State Groundwater Elevation

225512 7048063 BUTCHER WELL 492.56

218544 7056170 COCKARROW WELL 510.43

209636 7036416 DEEP BORE 513.28

218974 7036709 DEEP MILL WELL 513.05

210276 7042556 DIORITE WELL 488.23

214014 7047327 FRESHWATER WELL 501.81

224404 7047336 GARDEN (GOVT. NO 16) WELD 496.56

224825 7045137 GARDEN WELL 495.95

220900 7044194 GOLD TOOTH WELL 495.43

227881 7044550 HADJI WELL 493.43

220228 7053626 HAYES WELL 503.43

204292 7044672 LANAGAN BORE 544.59

199936 7035593 LINDEN BORE 537.52

230133 7045444 LW12 490.00

219796 7046549 MILLIE MILLIE WELL 495.34

208178 7043753 NO 383 CRITCHES BORE 513.71

211240 7056756 NO 408 503.28

199204 7040614 NO 388 540.47

219514 7059843 NO1 WELL 520.43

217975 7048831 P18 CHEVRON 499.04

218612 7048277 P22 CHEVRON 497.32

214899 7049344 P26 CHEVRON 502.17

218626 7039677 P31 CHEVRON 511.50

221278 7045574 P32 CHEVRON 499.40

218868 7047746 P61 Chevron 497.08

219129 7047219 P62 Chevron 496.76

216518 7049069 P70 Chevron 498.87

210132 7052433 RAILWAY WELL 506.95

211912 7047241 RED HILL WELL 508.28

221324 7040795 TRENNAMANS WELL 494.81

212525 7043971 WARD NO 1 WELL 502.24

222961 7045442 WARD WELL 480.71

223337 7045560 XP1 495.71

223587 7045860 XP2 495.05

223937 7046160 XP3 493.86

224287 7046460 XP4 492.85

224637 7046760 XP5 493.04

*- Indicates MGA94 Zone 51

Table B2- Steady-State Calibration Wells Calculated vs Adopted Calibration Head

Calibration Bore Calculated Head

Adopted Steady-State Calibration Head

Error (m)

XP1 494.45 495.71 -1.3

XP2 494.26 495.05 -0.8

XP3 494.03 493.86 0.2

XP4 493.81 492.85 1.0

XP5 493.61 493.04 0.6

NO_388 545.70 540.47 5.2

LINDEN_BORE 549.51 537.52 12.0

DEEP_MILL_WELL 517.55 513.05 4.5

DEEP_BORE 537.02 513.28 23.7

COCKARROW_WELL 509.79 510.43 -0.6

HAYES_WELL 504.22 503.43 0.8

NO1_WELL 519.94 520.43 -0.5

RAILWAY_WELL 507.42 506.95 0.5

NO_408 511.58 503.28 8.3

GOLD_TOOTH_WELL 496.55 495.43 1.1

TRENNAMANS_WELL 498.58 494.81 3.8

FRESHWATER_WELL 505.07 501.81 3.3

GARDEN_WELL 493.29 495.95 -2.7

GARDEN_(GOVT_NO_16)_WELD 493.88 496.56 -2.7

MILLIE_MILLIE_WELL 497.90 495.34 2.6

WARD_WELL 494.62 480.71 13.9

P18_CHEVRON 500.57 499.04 1.5

P22_CHEVRON 499.43 497.32 2.1

P26_CHEVRON 503.67 502.17 1.5

P31_CHEVRON 509.93 511.50 -1.6

P32_CHEVRON 496.21 499.40 -3.2

LANAGAN_BORE 534.33 544.59 -10.3

RED_HILL_WELL 509.67 508.28 1.4

WARD_NO_1_WELL 515.63 502.24 13.4

DIORITE_WELL 522.68 488.23 34.5

NO_383_CRITCHES_BORE 528.18 513.71 14.5

P61_Chevron 499.06 497.08 2.0

P62_Chevron 498.47 496.76 1.7

P70_Chevron 502.17 498.87 3.3

LW12 489.64 490.00 -0.4

HADJI WELL 491.51 493.43 -1.9

BUTCHER WELL 493.57 492.56 1.0

APPENDIX C PREDICTION MODEL ABSTRACTION VOLUMES

Prediction Model Abstraction Volumes

Time Years Scenario 1 Total

Scenario 2 Total

Scenario 3 Total

Scenario 4 Total

Scenario 5 Total

Scenario 6 Total

Scenario 7 Total

Scenario 8 Total

Scenario 9 Total Excludes Apex Southern Borefield

Scenario 9 Apex Southern Borefield Only

Scenario 9 Total Including Apex Southern Borefield Only

31 0.1 2090 2090 2090 2090 2030 2030 2030 2030 2030 1740 3770

61 0.2 2090 2090 2090 2090 2030 2030 2030 2030 2030 1740 3770

92 0.3 2090 2090 2090 2090 2030 2030 2030 2030 2030 1740 3770

123 0.3 2090 2090 2090 2090 2030 2030 2030 2030 2030 1740 3770

151 0.4 1870 2090 2090 2090 2030 2030 2030 2030 2030 1740 3770

182 0.5 1840 2090 2090 2090 2030 2030 2030 2030 2030 1740 3770

212 0.6 1820 2090 2010 2090 2030 2030 2030 2030 2030 1740 3770

243 0.7 1810 2090 2000 2090 2030 2030 2030 2030 2030 1740 3770

273 0.7 1540 2090 1990 2090 2030 2030 2030 2030 2030 1640 3670

304 0.8 1460 2030 1990 2090 2030 2030 2030 2030 2030 1600 3630

335 0.9 1400 1950 1980 2090 2030 2030 2030 2030 2030 1570 3600

365 1.0 1320 1930 1910 2090 2030 2030 2030 2030 2030 1540 3580

396 1.1 1250 1910 1860 2090 2030 2030 2030 2030 2030 1520 3560

426 1.2 1210 1900 1830 2090 2030 2030 2030 2030 2030 1510 3540

457 1.3 1180 1880 1800 2090 2030 2030 2030 2030 2030 1490 3530

488 1.3 1150 1870 1750 2090 2030 2030 2030 2030 2030 1420 3460

517 1.4 1130 1860 1730 2090 2030 2030 2030 2030 2030 1400 3430

548 1.5 1090 1850 1700 2090 2030 2030 2030 2030 2030 1360 3400


Scenario 2 Total

Scenario 3 Total

Scenario 4 Total

Scenario 5 Total

Scenario 6 Total

Scenario 7 Total

Scenario 8 Total




578 1.6 1070 1840 1680 2090 2030 2030 2030 2030 2030 1340 3370

609 1.7 1040 1830 1650 2070 2030 2030 2030 2030 2030 1310 3350

639 1.8 1020 1780 1630 2060 2030 2030 2030 2030 2030 1290 3330

670 1.8 1000 1760 1610 2050 2030 2030 2030 2030 2030 1270 3300

701 1.9 970 1700 1590 2050 2030 2030 2030 2030 2030 1250 3280

731 2.0 950 1610 1570 2050 2030 2030 2030 2030 2030 1200 3230

762 2.1 930 1570 1550 2040 2030 2030 2030 2030 2030 1140 3180

792 2.2 920 1540 1540 2040 2030 2030 2030 2030 2030 1120 3150

823 2.3 910 1510 1530 2040 2030 2030 2030 2030 2030 1100 3140

854 2.3 900 1490 1520 2040 2030 2030 2030 2030 2030 1090 3120

882 2.4 900 1470 1520 2040 2030 2030 2020 2030 2030 1090 3120

913 2.5 880 1440 1490 2030 2030 2030 2010 2030 2030 1050 3090

943 2.6 870 1420 1490 2030 2030 2030 2010 2030 2030 1040 3080

974 2.7 860 1400 1470 2030 2030 2030 1980 2030 2030 1020 3060

1004 2.8 840 1380 1460 2020 2020 2030 1970 2030 2030 1000 3040

1035 2.8 830 1360 1450 2020 2010 2030 1960 2030 2030 980 3020

1066 2.9 820 1340 1430 2020 2010 2030 1960 2030 2030 970 3000

1096 3.0 800 1320 1420 2010 2000 2030 1940 2030 2030 950 2980

1127 3.1 790 1280 1410 2010 1980 2030 1920 2030 2030 940 2970


Scenario 2 Total

Scenario 3 Total

Scenario 4 Total

Scenario 5 Total

Scenario 6 Total

Scenario 7 Total

Scenario 8 Total




1157 3.2 790 1260 1400 2010 1970 2030 1880 2030 2030 930 2960

1188 3.3 780 1250 1380 2000 1970 2030 1870 2030 2030 930 2960

1219 3.3 780 1240 1370 1950 1960 2030 1850 2030 2030 920 2960

1247 3.4 790 1240 1370 1940 1950 2030 1820 2030 2030 930 2970

1278 3.5 770 1210 1350 1920 1920 2030 1800 2030 2030 900 2940

1308 3.6 770 1200 1340 1910 1910 2030 1780 2030 2030 910 2940

1339 3.7 760 1180 1320 1890 1890 2030 1770 2030 2030 890 2920

1369 3.8 750 1170 1310 1880 1870 2030 1750 2030 2030 880 2920

1400 3.8 740 1150 1300 1860 1860 2030 1740 2030 2030 870 2900

1431 3.9 730 1140 1280 1850 1830 2030 1720 2030 2030 850 2890

1461 4.0 720 1120 1270 1830 1810 2030 1710 2030 2030 840 2870

1492 4.1 710 1110 1260 1820 1790 2030 1690 2030 2030 830 2870

1522 4.2 710 1100 1250 1810 1780 2030 1660 2030 2030 830 2860

1553 4.3 710 1100 1250 1810 1780 2030 1630 2030 2030 830 2870

1584 4.3 710 1090 1240 1790 1770 2030 1610 2030 2030 830 2870

1612 4.4 720 1100 1250 1780 1770 2030 1590 2030 2030 840 2880

1643 4.5 700 1080 1230 1760 1750 2030 1570 2030 2030 820 2850

1673 4.6 700 1070 1230 1750 1750 2030 1550 2030 2030 820 2860

1704 4.7 690 1060 1210 1730 1720 2030 1540 2030 2030 810 2840


Scenario 2 Total

Scenario 3 Total

Scenario 4 Total

Scenario 5 Total

Scenario 6 Total

Scenario 7 Total

Scenario 8 Total




1734 4.8 690 1050 1200 1720 1700 2030 1520 2030 2030 800 2840

1765 4.8 680 1040 1190 1710 1680 2030 1510 2030 2030 790 2820

1796 4.9 670 1030 1170 1690 1660 2030 1490 2030 2030 780 2810

1826 5.0 660 1020 1150 1680 1630 2030 1480 2030 2030 770 2800

1857 5.1 660 1010 1140 1670 1610 2030 1460 2030 2030 760 2800

1887 5.2 660 1000 1140 1660 1600 2030 1450 2030 2030 760 2790

1918 5.3 660 1000 1140 1660 1600 2030 1440 2030 2030 770 2800

1949 5.3 660 1000 1130 1650 1590 2030 1420 2030 2030 770 2800

1978 5.4 670 1010 1140 1650 1600 2030 1410 2030 2030 780 2810

2009 5.5 660 990 1120 1630 1570 2030 1400 2030 2020 760 2780

2039 5.6 660 990 1120 1630 1570 2030 1390 2020 2020 760 2780

2070 5.7 650 980 1100 1620 1550 2030 1350 2020 2020 750 2770

2100 5.8 650 970 1090 1610 1540 2030 1320 2010 2010 740 2760

2131 5.8 640 960 1080 1600 1520 2030 1300 2010 2010 730 2740

2162 5.9 630 950 1070 1580 1500 2030 1270 2010 2010 720 2730

2192 6.0 630 940 1060 1570 1490 2030 1250 2000 2000 710 2720

2223 6.1 620 940 1050 1570 1480 2030 1230 2000 2000 710 2710

2253 6.2 620 930 1040 1560 1470 2030 1220 2000 2000 710 2710

2284 6.3 630 940 1040 1560 1470 2030 1200 2000 2000 720 2710


Scenario 2 Total

Scenario 3 Total

Scenario 4 Total

Scenario 5 Total

Scenario 6 Total

Scenario 7 Total

Scenario 8 Total




2315 6.3 630 940 1040 1550 1470 2030 1180 2000 2000 720 2710

2343 6.4 640 940 1050 1560 1480 2030 1160 1990 2000 730 2730

2374 6.5 620 930 1030 1540 1450 2030 1150 1990 1990 710 2700

2404 6.6 630 930 1030 1540 1450 2020 1130 1990 1980 720 2700

2435 6.7 620 920 1020 1530 1440 2020 1120 1990 1970 700 2680

2465 6.8 620 910 1010 1520 1430 2020 1100 1990 1970 700 2670

2496 6.8 610 910 1000 1510 1390 2010 1090 1970 1960 690 2650

2527 6.9 600 900 990 1500 1370 2010 1070 1960 1960 680 2640

2557 7.0 600 890 980 1490 1350 2010 1060 1960 1950 670 2620

2588 7.1 600 890 980 1490 1340 2010 1050 1950 1950 670 2620

2618 7.2 590 890 970 1480 1330 2000 1040 1950 1950 670 2610

2649 7.3 600 890 980 1480 1330 2000 1020 1930 1940 680 2620

2680 7.3 600 890 980 1480 1330 2000 1010 1920 1940 680 2620

2708 7.4 610 900 990 1480 1340 2000 1000 1910 1940 690 2640

2739 7.5 600 880 970 1470 1300 2000 990 1890 1940 670 2610

2769 7.6 600 880 970 1470 1300 2000 980 1860 1940 680 2610

2800 7.7 600 880 960 1460 1280 2000 970 1850 1930 670 2600

2830 7.8 590 870 950 1450 1260 1990 960 1830 1930 660 2590

2861 7.8 590 870 940 1440 1240 1990 950 1820 1920 650 2580


Scenario 2 Total

Scenario 3 Total

Scenario 4 Total

Scenario 5 Total

Scenario 6 Total

Scenario 7 Total

Scenario 8 Total




2892 7.9 580 860 930 1440 1220 1990 940 1810 1920 640 2560

2922 8.0 580 850 920 1430 1200 1990 930 1800 1910 640 2550

2953 8.1 570 850 920 1420 1190 1990 920 1790 1910 630 2540

2983 8.2 570 850 920 1420 1180 1990 910 1780 1910 630 2540

3014 8.3 580 850 920 1420 1190 1990 900 1770 1910 640 2550

3045 8.3 580 850 920 1420 1190 1980 890 1760 1910 640 2550

3073 8.4 590 860 930 1420 1200 1990 880 1750 1910 660 2570

3104 8.5 580 850 920 1410 1170 1980 870 1740 1900 640 2540

3134 8.6 580 850 920 1410 1180 1970 860 1730 1890 650 2540

3165 8.7 580 840 910 1400 1160 1960 850 1720 1880 630 2520

3195 8.8 580 840 900 1400 1150 1960 850 1710 1880 630 2510

3226 8.8 570 830 900 1390 1130 1950 840 1700 1870 620 2490

3257 8.9 560 830 890 1380 1110 1920 830 1690 1850 610 2460

3287 9.0 560 820 880 1380 1100 1910 820 1680 1840 610 2440

3318 9.1 560 820 870 1370 1090 1900 820 1660 1830 600 2430

3348 9.2 560 820 870 1360 1080 1890 810 1650 1820 600 2420

3379 9.3 560 820 880 1360 1090 1890 800 1640 1810 610 2420

3410 9.3 570 820 880 1360 1090 1880 790 1630 1810 610 2420

3439 9.4 580 830 890 1360 1110 1880 790 1610 1810 630 2440


Scenario 2 Total

Scenario 3 Total

Scenario 4 Total

Scenario 5 Total

Scenario 6 Total

Scenario 7 Total

Scenario 8 Total




3470 9.5 560 820 870 1340 1080 1870 780 1600 1790 610 2400

3500 9.6 570 820 880 1340 1090 1870 770 1580 1790 620 2410

3531 9.7 560 810 870 1330 1070 1850 770 1570 1780 610 2380

3561 9.8 560 810 860 1330 1060 1850 760 1560 1770 600 2370

3592 9.8 560 810 860 1320 1050 1840 760 1550 1760 600 2350

3623 9.9 550 800 850 1310 1030 1830 750 1540 1740 590 2330

3653 10.0 550 790 840 1300 1020 1820 740 1530 1730 580 2310

Documents

Water and Environment - Amazon S3€¦ · Water and Environment WEST CREEK WATER SUPPLY GROUNDWATER MODELLING Prepared for Toro Energy Ltd Date of Issue 30 June 2010 Our Reference