BHP Billiton Nickel WestLeinster Operations(L4612/1989/11)Works Approval ApplicationSupplementary InformationTSF Cell FAPPLICATION ATTACHMENTS 1A, 1B, 2, 3A, 6, 7, 8 and 9.

JULY 2019

ii

Table of Contents

1.Purpose of Document 4

2.Premises Details 52.1 Location 5

2.2 Prescribed Premises Category 5

2.3 Other approvals, legislation and guidance 8

3.Description of Proposed Activity 93.1 Scope of works 9

3.1.1 Embankment materials and staging 9

3.1.2 Tailings delivery and distribution 10

3.1.3 Seepage interception system 10

3.1.4 Decant system 10

3.1.5 Return water pond 11

3.2 Supporting infrastructure 11

3.3 Timing and implementation 12

4.Existing Environment 144.1 Climate 14

4.2 Hydrology 15

4.3 Hydrogeology and groundwater 16

4.4 Landforms and soil types 17

4.5 Flora and vegetation 17

4.6 Social environment 18

4.6.1 Aboriginal and European heritage 18

5.Emissions and Discharges 195.1 Dust 19

5.2 Waste management 19

5.3 Water management 19

5.3.1 Stormwater diversion 19

5.3.2 Discharge 21

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5.4 Groundwater 21

6.Risk assessment 236.1 Environmental Management of TSFs 28

7.Fee calculation 29

APPENDIX A:Proof of Occupier Status (Attachment 1A) 31

APPENDIX B:ASIC Company Extract (Attachment 1B) 32

APPENDIX C:TSF Cell F Design Drawings, Figures F001 – F015 33

APPENDIX D:Design Report in Support of Mining Proposal and Works Approval Application (1788205-037-R-Rev2) Golders July 2019 34

APPENDIX E:Flora and Vegetation Mapping 35

List of Tables

Table 1: Schedule of Works Approval Application Attachments .............................................................................. 4Table 2: Prescribed Premises Categories under Current Licence ........................................................................... 5Table 3 Summary of TSF Project Infrastructure .................................................................................................... 11Table 4 TSF Cell F indicative filling schedule ....................................................................................................... 12Table 5 IFD design rainfall depths (mm) for NLN site............................................................................................ 15Table 6: Risk Assessment .................................................................................................................................... 24Table 7: NiW TSF Design and Construction Information ....................................................................................... 28Table 8 TSF Cell F Construction Costs ................................................................................................................ 29Table 9: Fee calculation ....................................................................................................................................... 29

List of Figures

Figure 1: Leinster Nickel Operations TSF Cell F ..................................................................................................... 6Figure 2 Leinster prescribed premises boundary .................................................................................................... 7Figure 3 Mean climate statistics for Leinster air (BoM 2017) ................................................................................. 14Figure 4 IFD curves for rainfall intensity and rainfall depth used in design ............................................................ 15Figure 5 Intermediate rainfall depths for 2% AEP to PMP ..................................................................................... 16Figure 6 Drainage lines at TSF Cell F .................................................................................................................. 19Figure 7 Hydrological overview of TSF Cell F ....................................................................................................... 20

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1. Purpose of Document

BHP Billiton Nickel West Pty Ltd (NiW) is planning to develop a new tailings storage facility (TSF) atthe Leinster Nickel Mine (NLN), located within the Shire of Leonora, 370 km north of Kalgoorlie. Thenew TSF is referred to as ‘Cell F’, and it is required to supplement the existing TSFs at NLN in order toaccommodate expected tailings to be generated until 2040.

This document provides supplementary information to NiW’s Application for Works Approval forL4612/1989/11 and to meet the requirements of the DWER Application form, as shown in Table 1.

Table 1: Schedule of Works Approval Application Attachments

DWERApplicationAttachment #

Description Location within thisSupplementary InformationDocument

1A Proof of occupier status Appendix A1B ASIC Company Extract Appendix B2 Map of Premises Figure 2

3A Description of Activities Section 36A Emissions and Discharges Section 57 Siting and Location Figure 1; and

Appendix C8 Other relevant information Sections 2-49 Fee Calculation Section 7

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2. Premises Details

2.1 Location

The NiW Leinster Operations are located predominately on Mineral Lease 255SA , which is tenuregranted under the State Agreement ratified by the Nickel (Agnew) Agreement Act 1974 (WA) (StateAgreement). The TSF Cell F is located on ML255SA and on G36/49 and G36/50 (to be granted underthe Mining Act 1978 (WA) (Mining Act), pursuant to the State Agreement), as shown in Figure 1.

2.2 Prescribed Premises CategoryNiW Leinster currently holds Environmental Protection Act 1986 Licence L4612/1989/11 and isprescribed under the categories listed in Table 2.

The prescribed premises categories will not change with these works, however the prescribedpremises boundary will require amendment to include the pending general purpose area G36/50.Tailings storage facilities are constructed and operated under Category 5. Refer to Figure 2 for theprescribed premises boundary.

Table 2: Prescribed Premises Categories under Current Licence

Category Number Description Throughput Classification

5 Processing or beneficiationof metallic or non-metallicore

3,600,000 tonnes per year (oreprocessed)

6 Mine dewatering 2,000,000 tonnes per year

57 Used tyre storage 500 tyres or less

64 Class II putrescible landfill 20 tonnes or more per year

85 Sewage facility 44 m3 per day

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Figure 1: Leinster Nickel Operations TSF Cell F

Legend

D d TS F CellF Propose

BHP Tenements LJ Application

CJ Granted

vii

Figure 2 Leinster prescribed premises boundary

270000 272000 274000 276000 278000

Legend

0 L4612/1989/11

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._ ,. , n n "' ,_ -- -

280000 282000

BHP 8HP NIW -Ho1tMm Op.eu11lOII$

Nickel West

Nickel West leinster Nickel Operation

PREMISES BOUNDARY ~~Cll41~-z-:--........,_

s.-ft,N.. '''°.- II"!_,.... SJW ,..,_

o ... , U'OVJOtt I I __ , ___ ,,__,.._,~---

8 0

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viii

2.3 Other approvals, legislation and guidanceActivities on ML255SA are approved by the Minister for State Development, Jobs and Trade, and theState Agreement is administered by the Department of Jobs, Tourism, Science and Innovation(JTSI). NiW operates the Leinster mining operations, including ore processing and tailings storage,under a range of Additional Proposals, approved by the Minister.

Pursuant to Clause 17(2) of the State Agreement NiW has requested JTSI to grant or arrange for thegrant of two general purpose leases (reference G36/49 and G36/50) (GPLs) under the Mining Act,which is required to support the development of the new tailings cell, TSF Cell F and associatedinfrastructure. The two general purpose leases have a combined area of 27.5 hectares.

As a minor portion of TSF Cell F is on Mining Act tenure, approval of a Mining Proposal for theplanned infrastructure on the GPLs is also required. The existing native vegetation clearing permitCPS 8008/3 will be amended to cover clearing within G36/50 and, if required, a native vegetationclearing permit will be sought to cover clearing within G36/49 (refer Figure 1).

Water abstraction activities, including for dewatering and potable supply, are undertaken inaccordance with Licences to Take Water issued under the Rights in Water and Irrigation Act 1914,GWL58111(5), 63834 (4) and 66248(5).

TSF Cell F is not a significant proposal and does not require referral to the EPA under Part IV of theEnvironmental Protection Act 1986 (EP Act).

Further to the EP Act, this application takes into consideration the requirements of:· Environmental Protection Regulations 1987;· NiW Leinster EP Act Licence (L4612/1989/11);· Native Vegetation Clearing Permit CPS222/4; and· Department of Water and Environmental Regulation Guidance Statement – Risk Assessments

(February 2017).

ix

3. Description of Proposed Activity

BHP NiW (NiW) is planning to develop a new tailings storage facility (TSF) at the Leinster Nickel Mine(NLN), located within the Shire of Leonora, 370 km north of Kalgoorlie. TSF Cell F is required tosupplement the existing TSFs at NLN in order to accommodate expected tailings to be generated until2040.

There are currently four operational TSFs at NLN: TSF2, TSF 3AB, TSF 3CD, and TSF 3E, withtailings deposition being rotated between them. TSF 3AB and TSF 3CD are approaching their finalheights and supplementary tailings capacity is therefore required as part of NiW’s strategic planning tofinancial year (FY) 2040. It is proposed that TSF Cell F and additional future cells provide thiscapacity, refer Appendix C for TSF Cell F design drawings.

3.1 Scope of worksThe proposed TSF Cell F is designed to accommodate up to approximately 29 Mt of tailings over aperiod of 20 years (2021-2040). It has been designed in accordance with recognised tailings-relatedguidelines for the development of TSFs in Western Australia. TSF Cell F is classified as ‘Significant’ interms of ANCOLD and a ‘Significant Hazard, Category 1’ facility in terms of DMIRS guidelines andassociated code of practice. Refer Appendix D for the TSF Cell F Design Report containing TailingsStorage Data Sheet and certification that the TSF Cell F design complies with the required safetyguidelines.

TSF Cell F is planned to be constructed as an above-ground impoundment, which will beprogressively developed in discrete stages. The initial starter embankment (Stage 1A) will be raised ina downstream direction, with two main embankments constructed to the north and east. Stage 1B willinvolve the construction of the southern and western embankments. Stages 1A and 1B embankmentswill be formed from compacted mine waste. Subsequent stages (7 proposed lifts) of TSF Cell Fdevelopment will be constructed in an upstream (inward) direction from compacted tailings sourcedfrom the adjacent tailings beaches, mimicking the procedure that has been adopted for the existingTSF cells. Cell F will provide tailings storage capacity to maintain a rate of rise of on average 1.5m/yr(refer Appendix C, Figure 008).

3.1.1 Embankment materials and staging

A typical cross-section through the TSF Cell F embankment is shown on Appendix C, drawing F005.Stage 1A will be constructed to relative level (RL) 10 516.0 m to accommodate an initial (continuous)~12 months of tailings deposition at an estimated average rate of 4850 t/day of insoluble solids, ataround 35 to 40% solids by mass. It should be noted that deposition rate may vary up to a maximumrate of 8,000 t/day, thereby reducing the time required to fill Stage 1A.

Thereafter, tailings deposition will revert to the other operational TSFs and the Stage 1B embankmentwill be constructed to RL 10 520 m. A temporary bund will be constructed across the basin at Stage1A to divert stormwater runoff from entering the TSF Cell F basin.

Both Stages 1A and 1B embankments will be constructed from imported mine waste, which will becompacted to form a low permeability confining embankment, capable of storing water for a limitedperiod of time. A cut-off key will be formed below Stage 1A down to caprock, limiting the potential forseepage under the embankment.

Following filling of the basin of TSF Cell F to the operational freeboard limit for Stage 1B, sixprogressive upstream raises of approximately 2.5 m in height and one final raise of approximately2.8 m will be constructed, as required through the deposition schedule, refer 3.1.2. The upstreamraises will be constructed from compacted tailings, sourced predominately from the adjacent beaches,mimicking the process that has been successfully implemented at NLN for all existing TSFs since the1970s. The final crest elevation of TSF Cell F is expected to be approximately RL 10 537.8 m.

x

3.1.2 Tailings delivery and distribution

Appendix C, Figure F006 shows the proposed tailings delivery pipeline route and distribution systemaround TSF Cell F. The pipeline will be connected to the existing tailings delivery pipeline at thesouth-western corner of TSF Cell F (north-western corner of TSF 3AB) before bifurcating, with onepipeline feeding the southern and eastern flanks, and one pipeline feeding the western and northernflanks of TSF Cell F.

Spigots will be installed along the pipelines at approximately 40 m centres. The spigots will beopened/closed by means of gate valves. It is expected that five to six adjacent spigots will be openedat any one time to result in uniform beaching, free of significant gullies. To reduce erosion of theupstream (internal) faces of the starter embankments and internal toe drain, 110 mm diameteruPVC12 ‘conductor pipes’ will be placed on the faces, into which the tailings slurry will discharge afterflowing through an open spigot and length of flexible rubber hosing. The conductor pipes will directslurry so that it is discharged at the lowermost opening in the conductor pipes.

3.1.3 Seepage interception system

Appendix C, Figure F007 shows the proposed location and cross-section, as well as outlet locations ofthe internal toe drain that will be provided to collect tailings consolidation water, manage seepage, andcontrol the location of the phreatic surface. The toe drain comprises a filter sand zone, 3 m in width,placed at the upstream (internal) toe of the starter embankment along the northern and eastern flanksof TSF Cell F.

The western flank does not require a drain, as the natural ground topography slopes inwardly alongthat flank. In addition, it is planned to infill between the external slope and waste rock stockpiles alongthe western flank to form an integrated waste landform (refer Appendix C, Figure F004). The southernflank does not require a drain as the natural topography falls away from the northern toe of TSF 3AB,against which TSF Cell F will be formed. The outlet pipes will be extended as required on the outsideof the TSF, so that they discharge into the RWP.

3.1.4 Decant system

Ultimately, a permanent decant structure, comprised of precast concrete rings surrounded by coarserock, will be progressively raised in line with external cell wall lifts, within the centre of TSF Cell F.Decant water will flow into the decant inlet structure which flows into the gravity feed outfall pipeline tothe return water pond, refer Appendix C, Figure F008.

The inlet system comprises a 1.8 m diameter tower, formed from precast concrete rings, 1.2 m inheight. Numerous slots are formed in the concrete rings to allow water to enter the tower. To reducethe turbidity of decant water, coarse rock will be placed around the tower, drawing down the level ofsettled tailings solids.

As the height of tailings within TSF Cell F rise, additional concrete rings will be added to the tower,and additional rock placed surrounding it. For this reason, an access causeway to the decant inlet willbe established to accommodate heavy vehicles for maintenance purposes. Within the concrete tower,there will be vertical riser of perforated pipe, to allow decanted water to flow into the gravity outfallpipe.

In the unlikely event of a threat of the return water pond (RWP) overtopping and spilling to the externalenvironment, decant water can be temporarily held on the surface of the TSF. The decant pipe hasbeen sized to decant water and stormwater from the TSF in a controlled manner and at a ratecommensurate with the capacity RWP pumps returning water to the process plant for re-use.

In Stage 1A (for approximately 12 months), given the topography of the land, it is anticipated decantwater will pond in the north-eastern corner of the TSF. This water will be removed by pumping to theexisting RWP that services TSFs located at the northern flank of TSF 3AB, from where it will bereturned to the process plant for re-use.

xi

A temporary access causeway will be built, varying between 1 m and 1.6 m in height above thecleared ground level to facilitate pumping of water from a sufficiently deep section of TSF.

3.1.5 Return water pond

The proposed return water pond (RWP) will collect decanted supernatant and rainwater from thesurface of the TSF, as well as seepage water discharged from the toe drain. The RWP will beestablished adjacent to the northern wall of Cell F at the commencement of Stage 1b.

The pond has been sized to accommodate discharge of ten hours of water at full capacity from TSFCell F, over and above a normal operating and dead storage volume, without overtopping (approximately 10 000 m3). The RWP will be inspected each shift, and it is thus highly improbable thata malfunctioning/out-of-order pump would be inoperative whilst water inflow persists from the TSF forlonger than this period. Telemetry will be installed to facilitate monitoring of flows from the RWP, andto enable remote checks for leaks in the return water pipeline.

To avoid seepage losses from the pond and to manage the risks of piping erosion of the RWP’sembankments, the RWP will be lined with a 2 mm thick HDPE geomembrane. An emergency spillwaywill be provided, although it is recognised that the likelihood of it being required is very low. Releasefrom the RWP would be considered a non-conformity and require notification to DWER. The RWP willbe surrounded by a cattle-proof security fence.

Upon establishment of TSF Cell F RWP, the existing RWP located at TSF 3AB will bedecommissioned. The gravity outfalls from TSFs 3AB, 3CD and 3E, as well as underdrain flows fromTSF 3, will all be extended through the basin of TSF Cell F and flow into the TSF Cell RWP. ReferAppendix C, Figure F009.

3.2 Supporting infrastructure

A summary of TSF Cell F Project Infrastructure is detailed in Table 3 below.

Table 3 Summary of TSF Project Infrastructure

Infrastructure Description / specification

1 TSF Cell F TSF Cell F constructed in stages 1A and 1B,followed by lifts 1 – 7, (refer Appendix C, F004,F005)

2 Return water pond TSF Cell F return water pond to be constructedpost the completion of stage 1B (referAppendix C, F009)

3 Surface water flow diversion drain Refer Appendix C, F010

4 Groundwater monitoring bores (x 6) Installation of four (4) groundwater monitoringbores to the north to replace existingmonitoring bores north of TSF3 AB.

Installation of two (2) groundwater monitoringbores to the east of TSF Cell F

5 Recovery bore (minimum x 1) Installation of a minimum of one groundwaterrecovery bore (additional recovery bores maybe installed if required) to replace existingrecovery bores to the north of TSF 3AB

6 Drainage outlet pipes from existingTSFs

Decant drainage pipelines from the existingTSFs installed through Cell F andcommissioned following Stage 1B

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3.3 Timing and implementationThe proposed infrastructure works will commence construction immediately upon receipt of thefollowing:

a) Ministerial approval of the Additional Proposal for the works;b) grant of the GPLs for the works;c) approval of the Mining Proposal for the works; andd) approval of the Works Approval for the works.

It is expected that the TSF will become operational between January – June 2020

In order to maximise the storage capacity of TSF Cell F, the scheduling of deposition between TSFCell F, and the TSF 2 and TSF 3 cells has been optimised. Once TSF Cell F is commissioned, it iscurrently proposed to rotate deposition between TSF 2 and TSF 3E. To avoid unacceptable marginalrates of rise on TSF 3E and to provide adequate drying time on TSF Cell F, TSF 2 and TSF 3E will behalf filled. Deposition will then rotate to TSF Cell F to fill a complete 2.5 m raise, it will then revert backto TSF 2 and TSF 3E to complete the second half of the fill.

Table 4 provides an indicative fill schedule for TSF Cell F based on current operations. This schedule isindicative and may vary with future operational requirements and the potential development additionalcells.

Table 4 TSF Cell F indicative filling schedule

Stage Crest RL Commencedeposition

(approximateyears post

commissioningof Stage 1A)

Storagecapacity(Mm3)

Storagelife

(days)

Rate ofrise

(m/year)

Sequence offilling until nextraise on Cell F

Stage1A

10 516.0 m 0 1.14 354 2.86 TSF 2, TSF 3E– both cells willbe filled to halfcapacity to allowrotation back toCell F

Stage1B

10 520.0 m 1.7 2.88 915 1.25 TSF 2 then TSF3E – fill thesecond half ofcapacity

Lift 1 10 522.5 m 4.8 2.76 726 1.01 ½ TSF 2 and ½TSF 3E

Lift 2 10 525.0 m 7.3 2.16 501 1.34 ½ TSF 2 and ½TSF 3E

Lift 3 10 527.5 m 9.3 2.12 465 1.40 ½ TSF 2 and ½TSF 3E

Lift 4 10 530.0 m 11.0 2.10 469 1.37 ½ TSF 2 and ½TSF 3E

Lift 5 10 532.5 m 12.8 2.06 586 1.17 ½ TSF 2 and ½TSF 3E

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Lift 6 10 535.0 m 15.0 1.98 476 1.34 ½ TSF 2 and ½TSF 3E

Lift 7* 10 537.5 m 16.8 2.16 647 1.03 ½ TSF 2 and ½TSF 3E**

Notes: * Last lift on Cell F 2.8 m high, all other lifts are 2.5 m high** Final lifts on TSF 2 and TSF 3E to take them to RL 10 560 m, currently the licenced final height

An alternative to half-filling of TSF 2 and TSF 3E would be to carry out half-height construction ofthose cells, i.e. to construct 1.25 m high embankment raises instead of the standard 2.5 m lifts. BHPwill decide on the most economical alternative during project execution phase. Half-filling or half-raising of the TSF 2 and TSF 3E cells will not have negative impacts on the rates of rise of thosefacilities, and safety and stability will therefore not be compromised. The annualised rates of rise ofboth cells will remain below the target of 1.5 m/year.

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4. Existing Environment

4.1 Climate

The NLN site lies within a semi-arid region, which experiences cool winters and hot summers. TheBureau of Meteorology (BoM) data for Leinster airport records the mean monthly range in dailyminimum temperature as 6° to 23°C and the maximum temperature range as 19°C to 37°C (referFigure 3). Wind strengths are generally moderate, averaging between 16 to 21 km/h throughout theyear, and are typically easterly to north-easterly.

Figure 3 Mean climate statistics for Leinster air (BoM 2017)

High temperatures and low humidity throughout much of the year produce an average yearly panevaporation rate of more than 3200 mm at Leinster. Average evaporation exceeds average rainfall inall months of the year. The long-term average annual rainfall is approximately 260 mm, althoughsubstantial variation occurs.

Mean monthly rainfall peaks during the summer months between January and March (up to 40 mm),and it is at its lowest in spring (refer Figure 3). Although intense rainfall can occur at any time of year,most of the rainfall in the area is associated with two distinct patterns:

I. Summer – Intensive rainfall can occur due to tropical lows, or localised thunderstormsassociated with tropical weather patterns in the north of WA.

II. Winter – Variable intensity rainfall related to westerly frontal systems associated withtemperate rainfall patterns in the south of WA.

Frequency analysis of rainfall data is an important part of hydrological design procedures. Analysis ofrainfall data from single stations is often unreliable and may not provide temporally or spatiallyconsistent data to use for design purposes. Instead, a set of accurate, consistent intensity-frequency-duration (IFD) design rainfall data has been derived for the whole of Australia by the BoM (2017). TheIFD design rainfall depth (mm) for the site per annual exceedance probability (AEP) 4 event ispresented in Table 5.

70 40

60 35

30 50

e 25 ~ g 40 -- e

~ ....... / 20 i ~ / E

i 30 / ..

....... / C

/ 15 ~ / "' " 20 "

/

r,-t-t / 10

10 I I 0 I Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

- Mean rainfall - Mean max. temperature - •Mean min. temperature

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Table 5 IFD design rainfall depths (mm) for NLN site

Duration Design rainfall depth (mm) per AEP event

50% 20% 10% 5% 2% 1%

5 min 4.49 7.19 9.26 11.5 14.9 17.8

10 min 6.91 11.1 14.2 17.6 22.6 26.8

15 min 8.5 13.6 17.5 21.7 27.8 33

30 min 11.4 18.2 23.4 29.1 37.4 44.6

1 hour 14.5 23 29.7 36.9 47.7 57.1

2 hour 18 28.5 36.7 45.6 59 70.6

3 hour 20.4 32.3 41.5 51.5 66.4 79.3

6 hour 25.5 40.2 51.5 63.8 81.6 96.8

12 hour 32.1 50.5 64.6 79.8 101 119

24 hour 39.8 63 80.6 99.7 126 148

48 hour 47.6 75.8 97.5 121 154 182

72 hour 51.3 82.1 106 132 170 202

Acknowledging the arid climatic setting of the TSF, conservative design criteria have been adopted fordesign. This provides for capacity for the TSF to withstand severe weather conditions such as highintensity, short-duration rainfall events that may cause erosion and other control failures, as well ashigh temperatures, low humidity and extended dry periods, which may result in poor vegetationestablishment.

4.2 Hydrology

To support the surface water risk assessment, design rainfall intensity (mm/h) and rainfall depth (mm)have been calculated for the NLN catchments based on the BoM 2013 intensity-frequency-duration(IFD) curves. The IFD curves cover a range of AEP events from 50% to 1% and are shown inFigure 4.

Figure 4 IFD curves for rainfall intensity and rainfall depth used in design

~

~ E !. l:' ... C .. .5 j? C ·;. a:

IFD Design Rainfall Intensity 1000

100

10

1 -1-

0.0 0.1 1.0

Duration (hour)

10.0

- 50%

- 20%

-10%

- 5%

- 2%

- 1%

100.0

1000

E 100 jl !. -s ! I

~ ,. 10 a:

IFD Design Rainfall Depth

- 50%

- 20%

l 4---1 -

0.0 0.1 1.0

Duration {hour)

10.0 100.0

xvi

Probable maximum precipitation (PMP)5 depths have been estimated using the BoM ‘GeneralisedShort Duration Method’, while design rainfall values for AEP events of between 1% AEP (1:100-year)and a PMP event (AEP of 1 × 10-5 %) were derived by using the interpolation procedure (AustralianRainfall and Runoff, Pilgrim et al, 1987). Figure 5 presents the rainfall depths for a number of averagerecurrence intervals (ARI) and storm durations for the NLN site.

Figure 5 Intermediate rainfall depths for 2% AEP to PMP

4.3 Hydrogeology and groundwater

The hydrogeological unit underlying the TSF site is poor to moderate yielding, within deep fracturedbedrock, or the weathered profile described above. This unit does not represent a majorhydrogeological unit due to its interpreted low effective porosity and permeability.

The weathered rocks show a rapid decline in permeability with depth. Groundwater flows within thisunit will only occur within local permeable faults/fracture zones, but these zones are not considered tobe extensive. The inferred regional-scale flow direction for the current groundwater conditions isnorthwards from TSF Cell F. The depth to groundwater varies greatly due to mounding beneath theexisting TSFs, generally ranging between 5 m to 14 m below ground level (bgl), depending on theproximity of monitoring bores to the TSFs.

Current groundwater levels in the vicinity of the TSFs are close to 520 m Australian Height Datum(AHD) due to this localised mounding beneath the TSFs. Prior to mining, the groundwater level was~480 m AHD.

Current groundwater levels around TSF 3 are deeper along the western flank and shallow along theeastern flank, probably due to mine dewatering activity. There is an area of relatively shallowgroundwater to the north of TSF 3 where TSF Cell F is to be located, which is attributed to seepagefrom the existing TSFs which migrates to the north.

Groundwater quality results indicate current nickel concentrations in the groundwater is in the sub-milligram per litre range, except for a few bores along the southern toe of TSF 2, which showedelevated nickel concentrations. Trace elements, other than nickel, show concentrations that are very

RllOO

]00.0

600.0

- 500.0 e s .r.

f 400.0 -0

ii i " "' 300.0

100.0 - ~

0.0 10

--0.SOHour

--1.00 Ho1.1r

--3.CXJ Hoor

100

--0.75 Hour

--2.00 Hour

--4.00 Hour

1,000 10,000

A.RI [years)

100,000 1,000,000 10,000,000

xvii

low, or undetectable, and no trends are evident. Groundwater salinity, measured in terms of electricalconductivity (EC), remains similar to that measured during the 1990s.

4.4 Landforms and soil types

NLN is located within the eastern margin of the Agnew-Wiluna greenstone belt, which is made up of acomplex of Archaean metamorphosed volcanic, intrusive and sedimentary rocks. The stratigraphicsequence of host rocks comprises a lower tholeiitic basalt with minor gabbro. This is overlain by athick sequence of dominantly felsic, volcanic and volcanoclastic rock with minor mafics, chert andother sediments (including a carbonaceous shale). The ultramafic units have been altered and aregenerally serpentinised with varying degrees of talc-and carbonate alteration associated with oremineralisation.

A widespread surficial high iron duricrust has formed below thin soils across the TSF site in variablethicknesses and durability. The duricrust overlies weathered volcanic rocks. The weathered profileoccurs to depths of more than 60 m.

4.5 Flora and vegetation

Western Botanical have assessed the flora and vegetation of this region on several occasions in thepast. The Initial flora and vegetation mapping was conducted in 1996, (Cockerton & Stratford, 1996),noting Calytrix uncinata occurring in this area. At that time, C. uncinata was listed as a Priority 3 taxon.Western Botanical assessed this area again in 2007 during flora and Vegetation surveys for theRocky’s Reward cutback (Western Botanical, 2007), confirming the occurrence of C. uncinata.Subsequently, Calytrix uncinata has been removed from the Priority Flora list (DBCA, Florabase, June2019). In 2017, Western Botanical undertook a Detailed Survey of the Camelot prospect, whichincluded the area covered by the proposed G36/50 lease.

The proposed TSF Cell F lies within the Brooking Land System which is described as ‘Hills and rangeswith Acacia shrublands, prominent ridges of banded iron formation supporting Mulga shrublands,occasional minor halophytic communities in the south east’, Pringle et al, 1994, refer Appendix E. Inthe Leinster – Mt Keith region, the Brooking Land System is associated with the Keith-Kilkenny Faultextending from south of Leinster to north of Mount Keith, some 120 km in extent.

The Study Area is within the Lateritic Mulga Wanderrie Shrublands with grassy understorey (LMWS)community and is located downslope of the adjacent Stony Ironstone Mulga Shrublands (SIMS)community to the west, refer Appendix E.

These are described as:

SIMS: The Stony Ironstone Mulga Shrubland habitat unit occurs on ironstone, quartz andchert ridges and associated slopes. The substrate is a dark red sandy loam with abundantsubangular course fragments ranging in size from large stones on upper slopes to fine gravelon lower slopes. Vegetation is dominated by Acacia aneura sens. lat. Scrub over Eremophilalatrobei subsp. latrobei, Scaevola spinescens Open Low Scrub over Ptilotus schwartzii var.schwartzii, Ptilotus obovatus var. obovatus Open Dwarf Scrub. This community is extensiveand well represented to the west of the TSF Cell F and more broadly between Leinster and MtKeith to the north.

LMWS: LMWS represents the lower foot slope and outwash plains of SIMS hills and supportsAcacia aneura sens. lat. Low Open Woodland with an understorey typically consisting ofPtilotus schwartzii var. schwartzii, Ptilotus obovatus var. obovatus Open Dwarf Scrub andperennial grasses dominated by Monachather paradoxus, Thyridolepis multiculmis, occasionalEragrostis eriopoda.

Both these communities and their component species are widespread and abundant in the local area.

Results of three historical surveys have shown that no species with conservation listing, i.e. no PriorityFlora and no Threatened Flora occur within the footprint of TSF Cell F. Priority Flora known inrelatively close proximity (1 km radius) include Thryptomene sp. Leinster (B.L. Lepschi & L.A. Craven

xviii

4362) P3, Thryptomene nealensis P3, and Calytrix erosipetala P3. However, none of these will bedirectly impacted by the construction of TSF Cell F.

In late 2017, Western Botanical undertook a desktop assessment of significant flora in the Leinsterregion for the studies supporting the Camelot prospect development (Western Botanical 2017). Theresults of this desktop assessment identified a range of conservation significant flora in the region nearLeinster, none of which occur within TSF Cell F.

There are no known Priority Ecological Communities or Threatened Ecological Communities inproximity to TSF Cell F. The closest vegetation related PEC known to the TSF Cell F is the VioletRange (Perseverance Greenstone Belt) vegetation complexes (banded ironstone formation) Priority 1PEC, the south-eastern edge of which is some 17.7 km north-north-west and on the northern side ofLake Miranda.

4.6 Social environment

The land use of the surrounding region is pastoral and mining. Previous pastoral activity has causedland degradation in the region due to clearing and grazing. This has led to extensive vegetation lossand severe erosion in some areas. The TSF Cell F area is located within Albion Downs pastoralstation, which is leased by NiW and its subsidiaries and subleased to a third party.

TSF Cell F is located at the Leinster mine site approximately 14 km north of the Leinster Town site.Given that TSF Cell F is in keeping with the existing landforms at the Leinster operations and has nosensitive adjoining land uses, it is unlikely to have a significant impact to visual amenity.

4.6.1 Aboriginal and European heritage

The Tjiwarl people are the native title holders (determined in April 2017) over approximately 13,000square kilometres of land in the Northern Goldfields region of WA, with NiW operations at Leinster,Cliffs and Mt Keith are in the determination area.

NiW and the Tjiwarl Aboriginal Corporation, on behalf of the Tjiwarl people, have entered into aComprehensive Agreement and an Indigenous Land Use Agreement (ILUA). The ILUA was registeredon the Register of the Indigenous Land Use Agreements on 8 January 2019 (NNTT numberWI2018/014). The Agreement area covers the Proposal area.

The NLN area, including the area required for TSF Cell F, has been archaeologically andethnographically surveyed to identify Aboriginal heritage sites and, where practicable, these sites havebeen avoided through design, planning and engineering solutions. The proposed TSF Cell F does notimpact any identified Aboriginal heritage sites.

xix

5. Emissions and Discharges

5.1 Dust

Dust generated through the construction of the TSF Cell F will be managed through theimplementation of water sprays, maintaining a wet condition for work surfaces and the use of watercart on access roads as required.

5.2 Waste management

The TSF Cell F will capture the tailings waste stream associated with the nickel processing facilities atLeinster. TSF Cell F is an extension of the existing tailings facilities currently in operation.

Any wastes generated as part of the construction process, including packaging etc, will be capturedand disposed of at an appropriate landfill facility. All topsoil will be stockpiled and reused forlandscaping / rehabilitation where practical.

5.3 Water management

5.3.1 Stormwater diversion

Surface water drainage systems around the NLN area and local drainage systems surrounding theproposed TSF development site, including contributing upstream catchments and drainage lines, areshown in Figure 6 and Figure 7.

Figure 6 Drainage lines at TSF Cell F

---- -

xx

Figure 7 Hydrological overview of TSF Cell F

An existing stormwater diversion channel runs along the eastern side of the existing TSF 3 cells, southof the proposed TSF Cell F location. The diversion channel currently captures upstream surface waterflows from catchments to the east of the site and conveys water northwards, towards the northerndrainage line in the vicinity of the proposed TSF Cell F development. It is proposed that this channel isextended further northwards. Runoff from the west of TSF Cell F will require short-term diversion untilthe area is in-filled with mine waste material.

Appendix C, Figure F010 shows the details of the stormwater diversion channels. Figure 6 indicatesthe temporary bund that will be constructed across the basin at Stage 1A to divert stormwater runofffrom entering the TSF Cell F basin.

LEGEND

--CATCHMENT DRAINAGE LINES

D CATCHMENT AREAS

D STAGE-1A EXTENT

STAGE-18 & FINAL EXTENT

DRAINAGE INFRASTRUCTURE - Existing Drainage Channel

Proposed Sund

- -- - .. "'.

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5.3.2 Discharge

There will no discharge to surface waters from TSF Cell F. A water balance assessment for TSFCell F has been developed (refer Appendix D, Section 7.8) taking into consideration typical inflowsand outflows during operation of the facility including:

· Inflows – process water and incident rainfall

· Losses – interstitial, seepage and evaporation

· Return – recovered supernatant and rain water

In accordance with ANCOLD and DMIRS guidelines, the TSF has been designed with a minimum totalfreeboard of 500 mm above inflow from the 1:100 AEP 72-hour rainfall event during operation tocontain the design rainfall event, without risk of overtopping.

The seepage interception and decant systems, as detailed in Sections 3.1.3 and 3.1.4 respectively,will ensure that no discharges to surface waters occur.

5.4 Groundwater

The existing TSF 3 Cells (A-E) and the proposed TSF Cell F lie above variably weathered andfractured Archaean granitoid/gneissic rocks and residual clays. Interpretations of the results ofgeophysics surveys and other mapping suggest that preferential flow paths occur withinfractured/faulted hydrogeological units that tend to be of limited length, typically following a north-southalignment and hundreds of metres in length. These units are not generally considered to be ‘aquifers’due to inherent low permeabilities and limited extents of the preferential pathways. The only aquifersof significance in the region are palaeochannel aquifers located approximately 15 km to the north andsouth of TSF 3.

Seepage of tailings porewater from TSF 3 has resulted in variable rates of rise in underlyinggroundwater levels (primarily to the north), with higher rates of rise occurring within thefractured/faulted pathways. While potential pathways exist to the west and east of TSF 3, monitoringdemonstrates that seepage along these pathways is very limited due to hydraulic constraints imposedby the low permeability Perseverance Fault to the west and elevated topography and groundwaterlevels to the east.

Groundwater around the TSFs show little or no correlation with annual rainfall deficits, withgroundwater levels mainly driven by operational factors. Groundwater levels immediately around TSF3 have risen around 20 m since tailings deposition commenced in 1992, on average at a rate ofaround 0.8 m/year. The most recent groundwater level data (June 2018) indicate that groundwaterlevels have risen to within 5.28 m of ground surface at a distance of 400 m north of TSF 3AB, 600 msouth of the northern limit of TSF Cell F. It has been shown previously that groundwater qualitychanges due to seepage are mostly related to potential rises in salinity (total dissolved solidsconcentrations) (Golders 20191). Changes in trace metal concentrations (e.g. nickel) are generally notobserved due to the attenuation processes within the hydrogeological units.

Proposed tailings deposition at TSF Cell F will result in seepage to groundwater in an area that hasalready been affected by seepage. Rates of seepage will be lower than that which occurredhistorically during tailings deposition in the three cells of TSF 3, since the design of TSF Cell Fincorporates an underdrain and so it is expected that seepage will mostly be collected and returned tothe process water circuit. Nonetheless, seepage will affect groundwater conditions to the north of TSFCell F, potentially posing a risk to water receptors to the north.

The nearest water receptor of ‘seepage-affected groundwater’ is ‘McArthurs bore’ locatedapproximately 4 km north of TSF 3AB (Johnson, 1999). The risk of a negative impact to groundwaterquality at this bore is considered low to negligible due to the substantial distance of the bore from TSF

xxii

Cell F and given that fault/fracture (preferential) pathways tend to be limited in length, i.e. hundreds ofmetres rather than kilometres in length1.

It is proposed that four groundwater monitoring wells are established to the north and two to the eastof TSF Cell F to permit ongoing monitoring of groundwater levels and quality, providing early warningof potential seepage impacts. Monitoring and reporting will be conducted in accordance with thelicence L4612/1989/11.

1 Golders 2019, Leinster Nickel Mine Tailings Storage Facility Cell F, Design Report in Support of Mining Proposal and Works Approval ApplicationJune 2019 1788205-307-R-Rev2

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6. Risk assessment

A risk assessment of the proposal covering all works, commissioning and operation was undertaken inaccordance with DWER Guidance on Risk Assessments. Potential environmental risks associatedwith the project are summarised in Table 6.

NiW considers that with the existing and proposed management controls, the residual environmentalrisks associated with the project are deemed to be acceptable.

xxiv

Table 6: Risk Assessment

Risk identification Risk Analysis (Prior to management /control measure) – refer to DWERTables 1 and 2

Risk Management Residual Risk Analysis (Aftermanagement / control measure) – refer toDWER Tables 1 and 2

Detailed RiskAssessmentRequired?

Risk PossibleResult

Environmentalreceptors andexposurepathways

Consequence Likelihood RiskMatrixRating

Management /Control Measures

Consequence Likelihood Risk MatrixRating

Dustemissionsduringconstructionactivities

Airborne dust Soil and vegetation(deposition)

Human health(inhalation)

Slight Likely Medium · Water sprays andwet condition ofwork surfaces;water cart onaccess roads

Slight Possible Low No – typicalconstruction activity /impacts, proposedcontrols consideredsufficient to addresspotential impact.

Hydrocarbonspills fromcontractorplant andequipmentduringconstruction

Hydrocarboncontamination

Soils (directcontact)

Surface Water(runoff)

Groundwater(infiltration)

Minor Possible Medium · Immediate removalof spilled material;contaminatedmaterial disposedof to an approvedlocation.

Slight Unlikely Low No – proposedcontrols consideredsufficient to addresspotential impact

Surfacediversion ordewateringdischarge toenvironment

Sedimentladen waterdischarges tolocal drainage

Surface water(direct discharge)

Minor Unlikely Medium · Surface waterdiversion in place(Golders DesignReport 1788205-037-R-Rev2 (July2019))

· Dewatering ifrequired, withdischarge to TSFReturn water pond

Minor Rare Low No – proposedcontrols consideredsufficient to addresspotential impact

SeepagefromcompletedTSF once inoperation

Groundwatercontaminationfrom tailingsleachateseepage

Groundwater(infiltration)

Moderate Possible Medium · NiW TailingsManagementMaster Plan Parts1-9 (submitted toDWER February2019, as part ofWorks Approvalapplication for raise

Moderate Possible Medium No – commissioningand operation of TSFcells followingcompletion of raise,will be regulatedunder LicenceL4612/1989/11 (to beamended toincorporate Cell F and

xxv

Risk identification Risk Analysis (Prior to management /control measure) – refer to DWERTables 1 and 2

Risk Management Residual Risk Analysis (Aftermanagement / control measure) – refer toDWER Tables 1 and 2

Detailed RiskAssessmentRequired?

Risk PossibleResult

Environmentalreceptors andexposurepathways

Consequence Likelihood RiskMatrixRating

Management /Control Measures

Consequence Likelihood Risk MatrixRating

to Cell E,W6220/2019/1).

· Groundwatermonitoring inaccordance withexisting LicenceL4612/1989/11

associated monitoringbores).

Disturbanceto nativevegetation

Loss of nativevegetationoutsideapprovedclearingfootprint

Vegetation(clearing)

Moderate Unlikely Low · Clearing will beconducted inaccordance withthe requirementsof CPS 8008/2 andCPS 2222/4

Minor Rare Low No – Clearing will beconducted inaccordance with therequirements of CPS8008/2 and CPS2222/4

Disturbanceto AboriginalHeritage

Damage orloss toAboriginalheritage sites

Landforms(damage by miningequipment/vehicles)

Moderate Unlikely Medium · NiW internalEnvironment andHeritage Impactassessmentprocess; (whichrequires checkingof heritage surveyGIS data prior toground disturbanceactivities)

Moderate Rare Medium No – no heritage sitesidentified within theproposed TSF Cell Ffootprint.

Noise fromconstructionactivities

Noiseimpacts tonearbysensitivereceptors

Human health(noise)

Slight Rare Low · No nearbysensitive receptors(located > 5km +from mine site)

Slight Rare Low No – no nearbysensitive receptors.(Occupationalexposure notconsidered in thisassessment).

Failure oftailingsstorage cells

Uncontrolledtailingsdischarge totheenvironment

Land (directdischarge)Surface water(direct discharge)Human health(direct impact)

Severe Unlikely High · Design andconstruct inaccordance withrecognised industryguidelines andinternal standards.

Severe Rare High Detailed riskassessments wereconducted as part ofthe design process,refer:· Appendix D, Section

7 Golders Design

xxvi

Risk identification Risk Analysis (Prior to management /control measure) – refer to DWERTables 1 and 2

Risk Management Residual Risk Analysis (Aftermanagement / control measure) – refer toDWER Tables 1 and 2

Detailed RiskAssessmentRequired?

Risk PossibleResult

Environmentalreceptors andexposurepathways

Consequence Likelihood RiskMatrixRating

Management /Control Measures

Consequence Likelihood Risk MatrixRating

· Construction inaccordance toGolders DesignReport 1788205-037-R-Rev2 (July2019)

· Annual operationaland safety reviewsby independentexperts

· Buttressing ofexternal walls ofLeinster TSFs tomaintain / exceedsafety factors

· NiW TailingsManagementMaster Plan

· TSF Cell F Designthird Party Review(Coffey 2019)

Report 1788205-037-R-Rev2 (July2019)

· TSF Cell F DesignThird Party Review754-PERGE229998(June 2019)

xxvii

Reference: DWER, Guidance Statement: Risk Assessments Part V, Division 3, Environmental Protection Act 1986, Feb 2017

Table 1 - Risk Criteria Table

Consequence

Tho followmg cr1tena wlll b• used to determine the consequences of a nsk event ocwrrlng

Severe

Major

Moderate

Minor

Slight

Environment Public Health* and Amanl ty (such as air • nd water quality, noise, and odour)

on-site impacts: c:atastrophic

off-s ite impacts local scale: high level or abo\le

off-site impacts wider scale: mid level or above

Mid to long tern, orpennanent impact to an area olhigh conservation value°' spedal significance"

Specific Consequence Crkeria (bf e11V1ronment) are significantty exceeded

on-site impacts: high level

off-site impacts local scale: mid level

off-site impacts w ider scale: IOwlevel

Short tern, impact to an area of higt'I conseivation value or spedajsignificanoeA

Spedfic Consequence Cderia (bf envuorvnent) are e,ceed,d

on-site impacts: mid level

off-site impacts local scale: lowlevel

off-site impacts wider scale: minimal

Specific Consequence Cderia (for el'IVlrorwnent) are at risk d not being met

on-site impacts: lowlevel

off-site impacts local scale: minimal

off-site impacts wider scale: notdetectab6e

Specific Consequence Cderia (for environment) likely to be met

on-site impact: ITlll"limal

Specific Consequence Crleria (tor envirorvnent) met

Lossc:Alife

Adversa health effects: high level or ongoi'lgmedical

""atme"' Speck Consequence Critena (for pubic health)are significantly exceeded

Local scale impacts: permanent loss ot a-nerity

Adverse health effects: mid level or ~tmedical treatment

Specl'lc Consequence Crw.eria (tor public health) are exceeded

Local scale impacts: high level impact 1oameoity

AdYerMt health effects: loWlevel orocx:aslOl'lalmedical treatment

Speck Consequence Criteria (for public health) ate at nskof not being met

Local scale impacts: rrvd levet i11pact toamenrty

Specl\c Consequence Criteria (for public health)are ld(ety tobe met

Local scale impacts: low level impact to amenity

Local sea.le: minimal impacts to .wnenrty

Speeh:Consequeooe Criteria (for public health)criteriamet

L1kellhood

The followlng cntena will be used to dltermme the likelihood of the nsk event occurnng

Almost Certain

Likely

PosSible

Unlikely

..,,

The nSk. evenl iS expected to occu- in most e,cunstances

The riSk event wil probably occur In most c:ita.mstances

The risk event wil probably not oc:::cur n mostcirOJmstanc:es.

The nSk evert may only oc:::cur., exceptional cn::unstances

,.. Determination of areas of high conservation value or special significance should be informed by the Guidance Statement: EmAronmental Sffing

• In applying public health criteria, DER may have regard to the Department of Health's, Health Rjsk Assessment (Scoping) Guidelines

.. on•s ite" means within the prescribed premises boundary

Table 2 - Risk Rating Matrix

Likelihood Consequence

Slight Minor

Almo.t Certain Medium

Likely Medium Medium

Poulble Low -

Unlikely Low -

Medium Medium

Rare Low Low Medium Medium

xxviii

6.1 Environmental Management of TSFsNiW operates the Leinster Tailings Storage Facilities (TSF) in accordance with the BHP NiW Leinster NickelOperation Tailings Management Master Plan (TMMP) which consists of the following parts:

· Part 1 Description of Existing Facilities· Part 2 TSF Operating Manual· Part 3 TSF Water management plan· Part 4 TSF Monitoring Plan· Part 5 TSF Licensing Plan· Part 6 TSF Risk Management Plan· Part 7 TSF Decommissioning and Closure Plan· Part 8 TSF Emergency Procedures Management Plan· Part 9 TSF Roles and Responsibilities

Copies of these documents have been provided to DWER as part of the assessment of Works ApprovalW6220/2019/1 for the 2019 upstream raise of TSF 3 Cell E, and are held on DWER records.

In addition, the TSF Emergency Response Plan Procedure (NLN HSEC PRO 244) is in place to guide actions inthe event of catastrophic failure of the Leinster TSF from overtopping failure, seismic failure or static failure.

The TMMP documents, whilst reflecting current practice, are currently under review and revision to bringinformation (such as role titles, Government agency title changes etc) up to date. The current TMMP documentsremain in force until these revisions are completed.

The design and maintenance of all new and existing TSF’s are subject to BHP’s internal Water and TailingsStorage Facilities Our Requirements (30 May 2019).

NiW undertakes annual audits of all TSFs using an independent geotechnical specialist, as required by theDepartment of Mines, Industry Regulation and Safety (DMIRS).

Table 7 provides further information regarding controls in place for the safe construction and operation of NiW’stailings storage facilities.

Table 7: NiW TSF Design and Construction Information

Item#

Requirements Specifications (includingprofessional accreditationrequirements)

Rationale NiW Management

1 Independent reviewof the design,construction andoperation of TSF cells

Undertaken by a suitablyqualified engineer orgeotechnical specialist inaccordance with therelevant parts of AustralianNational Committee ofLarge Dams (ANCOLD)(May 2012),Guidelines on tailingsDams – Planning, design,Construction, Operationand Closure; and DMIRS(2017) Tailings storagefacility audit – guide.

The primary controlmechanism to prevent,control and mitigateimpacts to theenvironment from theembankment raise isthe structural integrityof the TSF as a wholestructure, includingfoundations and thecurrent embankmentraise.

TSF Cell F designed inaccordance with Australianand international standards,refer Appendix D

Independent third partyreview of design

NiW undertakes regular damsafety reviews followingconstruction. Further detailsare provided in the TMMPPart 1 - Description ofExisting Facilities

2 Updated TailingsStorageFacility ManagementPlanand/or OperatingStrategy that

In accordance with therelevant parts DMIRS(2017) Tailings storagefacility audit – guide; andDepartment of Mines andPetroleum (August 2015)

Although theconstruction anddesign are critical to thestructural integrity ofthe embankments,other factors may

Seepage management isdescribed in the TMMP Part2 Operating Manual and TSFCell Design Report(Appendix D, Section 7.6)

xxix

Item#

Requirements Specifications (includingprofessional accreditationrequirements)

Rationale NiW Management

includes:- A Seepage

management plan;- Measures for

controllingdeposition andponding within theTSF

Guide to Departmentalrequirements for themanagement and closureof tailings storage facilities(TSFs).

influence stability –such as the size andextent of the saturationzone within the TSF,seepage managementpractices, tailingsdeposition, decantrecovery

The active TSF cells atLeinster are paddock typecells, operated withperimeter deposition, withsupernatant ponds locatedaround the central decantstructures, away fromperimeter embankments tomaintain stability of theseembankments. Decant wateris gravity drained via pondunderdrainage to an HDPElined decant pond, where thewater is returned to theLeinster processing circuit.

3 Updated TailingsStorageFacility ManagementPlanand/or OperatingStrategy Thatincludes:

- A dam break studyfor the new TSF Liftand a waterbalancedemonstratingcapacity to containincidental rainfallfrom a 72 hour1:100-year AnnualRecurrence Intervalrainfall event.

- An EmergencyResponse Plan andTrigger ActionResponse Plan forthe TSF 3E

In accordance with therelevant parts of ANCOLD(May 2012), Guidelines ontailings Dams – Planning,design, Construction,Operation and Closure;and Department of Mines,Industry Regulation andsafety (Tailings storagefacility audit – Guide.2017)

Surface water runoffand flood events thatinundate the base ofthe TSF have the abilityto compromise theembankments. In theevent of anembankment failure or‘dam break’ event,incident impacts arelikely to be significantwith lasting impactsspread over a largegeographical area.

The TSF Cell F DesignReport (Appendix D)- Consideration of Dam

break assessment for CellF (Section 7.5).

Refer to:- TMMP Part 8 TSF

Emergency ProceduresManagement Plan; and

- TSF Emergency ResponseProcedure (in the event ofcatastrophic failure).

7. Fee calculation

The cost of construction of TSF Cell F is outlined in Table 8

Table 8 TSF Cell F Construction Costs

Development Stage Cost ($)Stage 1A and 1BEarthworks and site establishment 3,257,000Decant and drainage systems 751,000Ancillary items 623,000Lifts 1 – 7Earthworks and site establishment 974,000Decant and drainage system upgrades 13,000Ancillary items 348,000Total cost of TSF Cell F Stage 1A, 1B and Lifts 1-7 $5,966,000

Based on the above costing and in accordance with section 12.6 of the Application for Works Approval Form, theapplication fee has been calculated as $12 383, refer Table 9.

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Table 9: Fee calculation

Estimated Costof works $ Fee Units1

Works Approval Fee CalculationFee Unit = $40.602

$ 5,966,000 305 40.60 x 305 = $12,383.00

1 Schedule 3, Environmental Protection Regulations 1987 [as shown below]2 2018-19 Fee schedule, https://www.der.wa.gov.au/our-work/licences-and-works-approvals/489-industry-regulation-faqs

Environmental Protection Regulations 1987 Schedule 3 Works approval fee

Schedule 3 - Works approval fee [r. SBA(!)]

[Heading amended: Gazelle 12 Jun 2018 p. 1889.)

Cost of works

Not more than $IO 000

More than $IO 000 but not more than $50 000

More than $50 000 but not more than $500 000

More than $500 000 but not more than $5 000 000

More than $5 000 000 but not more than $25 000 000

More than $25 000 000 but not more than $ I 00 000 000

More than $ I 00 000 000

Fee units

15

15 plus 5 for every $IO 000 above $ 10 000

35 plus IO for every $50 000 above $50 000

125 plus 20 for every $500 000 above $500 000

305 plus 100 for every $5 000 000 above $5 000 000

705 plus 50 for every $5 000 000 above $25 000 000

1405