mungada east extension waste dump conceptual design

Mungada East Extension Waste Dump Conceptual Design

Report Prepared for

Sinosteel Midwest Corporation Limited

T

Report Prepared by

SRK Consulting (Australasia) Pty Ltd

SMM024

November 2015

SRK Consulting Page i

Mungada East Extension Waste Dump Conceptual Design

Sinosteel Midwest Corporation Limited 7 Rheola Street, WEST PERTH WA 6005

SRK Consulting (Australasia) Pty Ltd Level 1, 10 Richardson Street WEST PERTH WA 6005

e-mail: [email protected] website: srk.com.au

Tel: +61 08 9288 2000 Fax: +61 08 9288 2001

SRK Project Number SMM024

November 2015

Compiled by Peer Reviewed by

Juanita Martin Principal Consultant

Scott McEwing Principal Consultant

Email: [email protected]

Author:

Juanita Martin

MART/MCEW/cass SMM024_Mungada East Extension WRD - Conceptual Design_Rev1 9 November 2015

mailto:[email protected]

SRK Consulting Page ii

Executive Summary Sinosteel Midwest Corporation (SMC) owns and has operated the Mungada pits as part of its Koolanooka and Blue Hills Direct Shipping Iron Ore (DSO) project. To date, the Mungada pit has been mined to completion, and the Mungada East pit was shut down prior to completion. SMC is evaluating the proposed opening and operation of the Mungada East Extension (MEE) pit.

SMC requested SRK to:

• Review the available data and design criteria

• Develop a conceptual design for the MEE waste rock dump (WRD)

• Examine surface water management for the MEE WRD

• Examine backfilling of the Mungada East pit.

SRK was provided with supporting information from work that has been undertaken to date for the MEE pit.

The following observations were made from the work undertaken:

• The waste rock from the proposed MEE pit will be stowed as backfill in the Mungada East pit and a dedicated MEE WRD, and a small balance stowed in the spare capacity in the Mungada East WRD.

• Potentially acid forming (PAF) materials are not anticipated to be encountered during mining of the MEE pit.

• Physical stability of the WRD was analysed on the basis of available information and assumed strength parameters; modelling of the slopes of the WRD indicates that the WRD meets the recommended Factors of Safety (FOS).

• Water management of the site has been incorporated as a key factor, to keep clean water clean and to direct the contact water to the appropriate containment systems.


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Table of Contents

Executive Summary ..................................................................................................................................... ii

Disclaimer ..................................................................................................................................................... v

1 Introduction and Scope of Report ............................................................................... 1

1.1 Setting of the project ........................................................................................................................... 1

1.1.1 Location ................................................................................................................................... 1 1.1.2 Geology ................................................................................................................................... 2

1.1.3 Hydrogeology .......................................................................................................................... 2

1.1.4 Climate .................................................................................................................................... 2

1.1.5 Intensity duration frequency .................................................................................................... 3

1.1.6 Seismic activity ........................................................................................................................ 3

2 Mungada East Extension Operations ......................................................................... 4

2.1.1 Current mining operations ....................................................................................................... 4 2.2 Proposed mining operations ............................................................................................................... 4

2.2.1 Geochemistry .......................................................................................................................... 5

2.2.2 Mungada East Extension WRD design criteria ....................................................................... 6

2.2.3 Waste rock volume estimates ................................................................................................. 7

2.2.4 Mungada East Extension WRD design ................................................................................... 7 2.2.5 Waste management priorities ................................................................................................. 9

2.2.6 Mungada East pit backfilling.................................................................................................... 9

2.3 Mungada East Extension WRD development ................................................................................... 10

3 Stability Assessment ................................................................................................. 11

3.1 WRD cross sections with material zones and properties.................................................................. 11

3.2 Stability analysis results .................................................................................................................... 12

4 Water Management System ....................................................................................... 13

4.1 Catchments ....................................................................................................................................... 14 4.2 Peak flow calculation......................................................................................................................... 14

4.3 Clean water channel ......................................................................................................................... 15

4.4 Contact water channels .................................................................................................................... 15

4.5 Channel design ................................................................................................................................. 16

4.6 Sump ................................................................................................................................................. 16

4.7 Sediment ponds ................................................................................................................................ 16

6 References .................................................................................................................. 18


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List of Tables Table 1-1: Average monthly precipitation and evaporation for Blue Hills ..................................................... 2

Table 1-2: Intensities (mm/h) for various durations and return periods for Blue Hills ................................... 3

Table 2-1: Design criteria used for the MEE WRD design ............................................................................ 6

Table 3-1: Material parameters for stability evaluation ............................................................................... 12

Table 3-2: Results of static stability assessment on the final WRD ............................................................ 12 Table 3-3: Results of static stability assessment with reduced parameters................................................ 12

Table 4-1: Areal extent of catchment areas ................................................................................................ 14

Table 4-2: Peak flow calculation method extracted from ARR .................................................................... 15

Table 4-3: Peak flows .................................................................................................................................. 15

Table 4-4: Channels characteristics ............................................................................................................ 16

Table 4-5: Sediment ponds’ capacities ....................................................................................................... 16

List of Figures Figure 1-1: Location of Blue Hills Project ....................................................................................................... 1 Figure 2-1: Mungada Project as currently built ............................................................................................... 4

Figure 2-2: Typical conceptual PAF waste rock encapsulation ...................................................................... 5

Figure 2-3: Mungada East Extension Pit and associated infrastructure footprints ........................................ 7

Figure 2-4: Mungada East Extension Project showing with Mungada East Extension pit and associated waste rock dump .......................................................................................................................... 8

Figure 2-5: Mungada East Extension Project showing with Mungada East pit backfilled, the Mungada East waste rock dump filled and the Mungada East Extension pit, associated waste rock dump ....... 9

Figure 3-1: WRD cross section ..................................................................................................................... 11 Figure 3-2: Final WRD configuration modelled in Slide................................................................................ 12

Figure 4-1: WRD water management system .............................................................................................. 13

Figure 4-2: Catchment areas in WRD site .................................................................................................... 14

List of Appendices Appendix A: Drawings


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Disclaimer The opinions expressed in this Report have been based on the information supplied to SRK Consulting (Australasia) Pty Ltd (SRK) by Sinosteel Midwest Corporation Limited (SMC). The opinions in this Report are provided in response to a specific request from SMC to do so. SRK has exercised all due care in reviewing the supplied information. Whilst SRK has compared key supplied data with expected values, the accuracy of the results and conclusions from the review are entirely reliant on the accuracy and completeness of the supplied data. SRK does not accept responsibility for any errors or omissions in the supplied information and does not accept any consequential liability arising from commercial decisions or actions resulting from them. Opinions presented in this Report apply to the site conditions and features as they existed at the time of SRK’s investigations, and those reasonably foreseeable. These opinions do not necessarily apply to conditions and features that may arise after the date of this Report, about which SRK had no prior knowledge nor had the opportunity to evaluate.


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1 Introduction and Scope of Report Sinosteel Midwest Corporation (SMC) owns and has operated the Mungada pits as part of its Koolanooka and Blue Hills Direct Shipping Iron Ore (DSO) project. To date, the Mungada pit has been mined to completion, and the Mungada East pit was shut down prior to completion. SMC is evaluating the proposed Mungada East Extension (MEE) pit.

This report presents the conceptual design for the MEE pit WRD and the surface water system for the WRD and infrastructure catchment area.

1.1 Setting of the project

1.1.1 Location Blue Hills iron ore project is located 250 km south east of Geraldton, and 80 km to the east of Morawa in Western Australia. Figure 1-1 shows its approximate location.

Figure 1-1: Location of Blue Hills Project

The proposed location for the MEE WRD is south east of the proposed extension open pit, and it has been indicated that access will be provided.

Blue Hills



1.1.2 Geology The Blue Hills Project area lies on the Yilgarn Craton, which comprised mainly crystalline Archaean rocks. The Yilgarn Craton in the exploration areas comprises mainly granitoid rocks containing enclaves of older metamorphosed and folded supracrustal sedimentary, mafic and volcanic rocks. The older rocks include banded iron formations (BIFs) which generally form the prominent linear ridges that protrude from the comparatively flat areas that are underlain by granitoid rocks. The surface of the Archaean rocks has been weathered so that fresh rock may be overlain by 100 m or more of weathered material.

1.1.3 Hydrogeology The Blue Hills Project area contains Cainozoic surficial sediments such as alluvial and lacustrine sediments which are recharged by surface drainages and by groundwater flow from the bedrock. The salt lakes within the region are groundwater sinks, where groundwater discharges by evaporation through the halite and gypsum crust.

The groundwater can be high in salinity, sometimes exceeding 20,000 mg/L, but very few bores penetrate these deposits. The near-surface sediments are likely to be low yielding, but high yields of saline or hypersaline groundwater may be obtainable from concealed Tertiary paleochannels in major drainages (Commander, D P and McGowan, R J, 1991).

Granite and gneiss of the Yilgarn block which covers two-thirds of Perenjori have a very low secondary permeability that results from local discontinuous and widely spaced joints, faults and shears (Commander, D P and McGowan, R J, 1991).

A lateritic profile of more permeable weathered rock, and groundwater divides, correspond approximately to the surface water divides. The depth to groundwater is generally less than 10 m, and the surface of the water table closely resembles that of the topography. Groundwater flow in the eastern part of Perenjori is commonly towards the Lake Monger drainage, and in the west, towards the Yarra Yarra Lakes and Lake Eganu. Evaporation is the main controlling factor dominating the position of the water table (Commander, D P and McGowan, R J, 1991).

1.1.4 Climate The climate at Blue Hills is classified as semi-arid with mild wet winters and hot dry summers. Rainfall in the project area is variable, with annual amounts that may be less than 150 mm in one year and greater than 450 mm the following (149 mm in 1922 being the lowest yearly rainfall recorded, and 580 mm in 1958 the highest). A wet season typically occurs from May to September, with over 65% of the annual rainfall occurring during these months.

Annual average evaporation exceeds annual average rainfall. Monthly average precipitation from Morawa station (Bureau of Meteorology station # 8093 and # 8296) and evaporation from the Bureau of Meteorology evaporation maps are shown in Table 1-1.

Table 1-1: Average monthly precipitation and evaporation for Blue Hills

Month Precipitation (mm) Evaporation(mm)

January 17.8 280.0

February 17.9 227.5

March 20.7 196.0

April 18.1 140.0

May 43.0 87.5

June 49.5 56.0



Month Precipitation (mm) Evaporation(mm)

July 49.4 56.0

August 35.4 77.0

September 22.7 122.5

October 12.3 175.0

November 10.0 245.0

December 12.0 280.0

Annual 308.8 1942.5

1.1.5 Intensity duration frequency Intensity-duration-frequency (IDF) rainfall data for an Annual Recurrence Interval (ARI) between 1 and 100 years was retrieved directly from the Australian Bureau of Meteorology (BOM) website and is shown in Table 1-2. Values for 500 and 1000 years were obtained by extrapolation.

Table 1-2: Intensities (mm/h) for various durations and return periods for Blue Hills

Duration Average Storm Recurrence Interval (Years)

Hours Min 1 2 5 10 20 50 100 500* 1000*

0.08 5 46.8 62.2 84.5 99.7 120 150 174 212.5 231.5

0.10 6 43.4 57.7 78.4 92.5 111 139 162 197.4 215.0

0.17 10 34.8 46.2 62.3 73.4 88.1 109 127 154.6 168.4

0.33 20 24.7 32.6 43.5 50.8 60.7 75 86.7 167.7 183.8

0.50 30 19.6 25.8 34.3 40 47.6 58.6 67.6 82.2 89.4

1.00 60 12.7 16.7 22.1 25.6 30.5 37.4 43.1 52.4 56.9

2 120 7.91 10.4 13.8 16 19 23.3 26.9 32.7 35.5

3 180 5.93 7.8 10.4 12.1 14.4 17.7 20.4 24.8 27.0

6 360 3.6 4.76 6.36 7.43 8.89 11 12.7 15.5 16.8

12 720 2.19 2.9 3.9 4.58 5.5 6.82 7.91 9.6 10.5

24 1440 1.33 1.76 2.38 2.81 3.37 4.19 4.88 5.9 6.5

48 2880 0.781 1.04 1.41 1.67 2.01 2.5 2.92 3.6 3.9

72 4320 0.55 0.741 1.01 1.19 1.44 1.8 2.09 2.6 2.8

*Extrapolated values

1.1.6 Seismic activity

Seismic activity in the Blue Hills region is low. According to the Earthquake Hazard Map of Australia 2012 (Burbidge, 2012), Blue Hills lies between the contours corresponding to accelerations of 0.03 - 0.04 m/s2, for a return period of 500 years.

Such low accelerations will not pose a substantial risk to the stability of the landforms, and the static Factor of Safety (FOS>1.5) would be in excess of that required to cover any post-seismic transient loads due to pore pressure increase.



2 Mungada East Extension Operations 2.1.1 Current mining operations

The Mungada mining operation is currently shut down. The Mungada and Mungada East (ME) pits have been mined, with the ME pit shut down shortly before completion. As a consequence, the ME pit was not developed to full design depth and the ME WRD has not been developed to the design capacity.

SRK was provided with the following design information:

• MEE pit design

• ME WRD design

• ME pit design

• MEE infrastructure footprints.

SRK was additionally provided with both a pre-mining topography surface and an as-built surface that shows the project at the time of the closure of the ME pit.

A layout of the current operations based on the as-built surface is given in Figure 2-1.

Figure 2-1: Mungada Project as currently built

2.2 Proposed mining operations SMC is evaluating the MEE project; this consists of an open pit to the east of the ME pit and new infrastructure and WRD facility.

The MEE mine waste is proposed to be used to backfill the abandoned ME pit with the balance to be stowed in the new MEE WRD. SRK has been tasked with developing the conceptual design for the MEE WRD.



2.2.1 Geochemistry No specific MEE pit geochemistry information was available at the time of the MEE WRD assessment. SRK was instructed to base assumptions on the neighbouring ME and Mungada pit. The ME and Mungada information was sourced from a 2014 geochemical review and confirms that the risk of acid mine drainage from WRDs or from wall rock exposed in final mine pit voids at Mungada West and Mungada East is extremely low. No sulphide minerals such as pyrite or chalcopyrite were reported from resource drilling, and no visible leaching of sulphides has been observed in the historical pits.

Statistical analysis had been carried out separately on waste rock from ME and Mungada. Minor differences were observed in total sulphur concentrations in waste rock. At ME, 96% of all samples tested contained less than 0.3% total sulphur. At Mungada, 95% of all samples tested contained less than 0.3% total sulphur.

On this basis, SRK sees no need for specific potentially acid forming (PAF) management. The low concentrations of PAF material encountered will be stowed in the WRD with the balance of non-acid forming (NAF) material.

If future work identifies PAF materials warranting encapsulation, there are adequate NAF volume and stowage locations. Conceptual PAF encapsulation management could involve the following:

• The PAF waste rock cell to be constructed progressively to meet the waste rock schedule and to minimise the period that PAF materials are exposed to the climatic conditions.

• The PAF waste rock will be progressively encapsulated within the NAF outer shell as much as possible. This will aim to reduce water and oxygen contact with the PAF material.

• The conceptual design would incorporate a 10 m thick NAF base layer along the lowest point on the WRD site, a 50 m PAF clearance to the WRD external face and a NAF material cover layer of at least 10 m depth over the entire WRD.

• The 10 m thick NAF waste rock base would be placed at the lowest section in the WRD (i.e. the stream location), as this is where any infiltrating water that has passed through the waste rock layers will likely drain towards.

• The NAF base and cover layers should be compacted as far as possible with truck traffic, a measure to reduce permeability and promote lateral rather vertical flow of infiltrating water.

The PAF encapsulation concept is shown in Figure 2-2.

Figure 2-2: Typical conceptual PAF waste rock encapsulation



2.2.2 Mungada East Extension WRD design criteria A summary of the relevant waste dump design criteria for the MEE waste dump is presented in Table 2-1.

SRK notes the following points:

• The footprint of MEE WRD has previously defined by other parties and provided to SRK.

• Maximum elevation of the WRD to be kept under highest point in natural ridge line.

• Drainage systems will minimise risk of contamination of natural water courses/ groundwater.

Table 2-1: Design criteria used for the MEE WRD design

Design Criteria Value Source/Comment

Maximum waste rock storage required 5.5 Mm3 Calculated from SMC pit

shells

Waste rock deposited dry density 2.1 - 1.8 t/m3 Assumed

Ore density 3.1 t/m3 SMC criteria

Lift Height 10 m SMC criteria

Swell factor of waste rock 30% Benchmark assumption

Maximum WRD elevation RL 390 m SRK criteria

Berm width 10 m SMC criteria

WRD slope Batter Slope Global Slope

1:3 (18.3 degrees)

1:3.7 (15 degrees) – with benches SMC criteria

Peak Ground Acceleration (PGA) 500 year event

0.04 m/s2 Seismic Hazard Map

Stability FOS Design Criteria Static (steady state) Post-seismic

1.5 1.1

ANCOLD Guidelines

Design Storms Diversions Sediment ponds

100 year event 24 h 10 y event (68 mm)

BOM

Visual impact Crest of the WRD must be below the highest point of the natural

ridge line (RL 507.5 m) Assumed

SRK was provided with a mine design for the MEE pit along with an estimate of MEE pit contained total ore tonnage. The MEE pit design and associated infrastructure footprints provided by SMC is shown in Figure 2-3.



Figure 2-3: Mungada East Extension Pit and associated infrastructure footprints

2.2.3 Waste rock volume estimates The calculated total MEE pit volume between the provided topography surface and the MEE pit design was 5.56 Mm3. SMC has provided an estimate of 3.7 Mt of ore in the pit which equates to 1.19 Mm3 of ore. This leaves a balance of 4.37 Mm3 of in situ waste to be stowed. When the swell factor is applied to account for broken rock occupying more space than in situ rock, the total waste material volume required to stow the waste is 5.68 Mm3.

SRK calculated the available space in the abandoned ME pit for backfilling by measuring between the provided pre-mining topography surface and a provided post mining topography surface. The estimated volume was 4.17 Mm3.

The balance of volume between the required 5.68 Mm3 of waste rock and the ME pit backfill capacity of 4.17 Mm3 is 1.51 Mm3.

2.2.4 Mungada East Extension WRD design SRK used the provided footprint of the waste rock dump to be a design limit of the dump. A small offset was provided, where possible, between the provided footprint and the toe of the waste dump.

The dump was designed using the criteria in Table 2-1. The design height was keep below 30 m, with the dump crest at 390 m RL. There is a small amount of stowage space left between 390 and 400 m RL that could be used for paddock dumping if additional capacity is sought in the future.



Figure 2-4: Mungada East Extension Project showing with Mungada East Extension pit and associated waste rock dump

The capacity of the MEE WRD is estimated at 1.2 Mm3. This leaves an MEE project shortfall of 292 km3 of waste stowage capacity.

As the prior ME WRD was not developed to full capacity, SRK proposes that the balance of the waste rock will be stowed in the ME WRD.

Figure 2-5 shows the Mungada Project as it would look at completion of the MEE pit. The ME pit is backfilled, the MEE pit is completed, the MEE WRD is completed and the ME WRD is expanded to the completed design.



Figure 2-5: Mungada East Extension Project showing with Mungada East pit backfilled, the Mungada East waste rock dump filled and the Mungada East Extension pit, associated waste rock dump

2.2.5 Waste management priorities Based on the information provided, backfilling the ME pit is noted as the highest priority for the waste management as this addresses permitting requirements.

SRK has observed that the haulage of waste to the ME pit for backfilling is likely to be marginally more expensive initially than hauling to the MEE WRD. The differences in costs will close as the MEE WRD increases in height.

The secondary requirement for waste stowage will be the MEE WRD. This location is closer to the MEE pit than the ME WRD and offers the potential of lower costs.

2.2.6 Mungada East pit backfilling Backfilling into the ME pit void can be accomplished in many ways. The cheapest method will involve the mine trucks delivering MEE mine waste to the top of the ME pit haul road. A bulldozer can be used to push the waste into the pit void, progressively filling the pit. This approach will need to be considered from an operational safety viewpoint, as it is possible for the backfill to geotechnically fail and allow the bulldozer to slide into the void. Remote operation of the bulldozer would remove the risk to the operator. A number of mining operations have used this approach for waste disposal.

An alternative approach is to minimise the vertical height of the backfill by filling the ME pit progressively at lower levels. A bulldozer would again push waste material delivered by mine truck into the void. This approach will require additional mine truck haulage as the mine trucks would drive into the ME pit workings. This application is similar to current accepted practices used in stockpile and waste dump development in many mining operations.



2.3 Mungada East Extension WRD development The MEE WRD can be developed either with a cost minimisation philosophy or an approach which allows for PAF encapsulation and progressive rehabilitation.

The haulage cost minimisation approach involves taking the lowest cost haulage route. This leads to the WRD being developed laterally rather than to full height. Over the life of the project, this equates to lower costs in the initial years of operation and high costs in later years.

The alternative construction strategy is to build the WRD to its full height as soon as possible and then progress laterally. This approach allows progressive rehabilitation and surface profiling of the WRD to occur throughout the life of the Mungada East Extension mining as completed areas become available. The alternative strategy would be proposed if future work identify PAF materials, necessitating encapsulation.



3 Stability Assessment A stability assessment of the proposed WRD has been undertaken using a critical representative cross section in the slope stability software, Slide V6.0 (Rocscience 2010). Slide is a 2D slope stability analysis program that combines the CAD-based graphical interface with a wide range of modelling and data interpretation options. Slide calculates the FOS for circular and non-circular slope failure surfaces based on a number of widely used limit equilibrium methods such as Bishop, Janbu and Spencer.

The MEE WRD was assessed, with analysis of the final WRD configuration prior to rehabilitation.

Circular failure surfaces have been considered to be representative of the probable failure mechanism and Spencer’s method has been adopted to obtain the minimum FOS for the analyses as it simultaneously satisfies all conditions of equilibrium.

Only static conditions have been assessed. Blue Hills has a Peak Ground Acceleration of 0.04 m/s2 (Earthquake Hazard Map of Australia 2012), which is considered to be Seismic Hazard Class I (Low) (ICOLD 1989). As a result, static stability FOS would govern the slope design and thus pseudo-static stability analysis is deemed unnecessary.

In the event of having an unforseen large earthquake, soil strength parameters may reduce. To simulate this, a post-seismic run has been conducted and compared to a FOS of 1.1.

3.1 WRD cross sections with material zones and properties It is expected that the waste rock will largely comprise weathered and fresh shale. The cross section selected, shown in Figure 3-1, was chosen because it represents areas of the WRD that comprise the full height. Sections of the WRD are included in SRK Drawing SMM024-002 (Appendix A).

Figure 3-1: WRD cross section

The design parameters used for these analyses are based on professional judgement from experience with similar materials, as no borehole logs or laboratory testing results were available to SRK. A conservative unit weight of 18 kN/m3 has been adopted.

The parameters for each material type used in the analyses are summarised in Table 3-1. From knowledge of the local area, groundwater is not expected to present a stability issue to the WRD due to the arid nature of the landscape and lack of natural springs in the region. The WRD will be developed with suitable surface water drainage to limit seepage into the WRD and erosion of the slopes. As a result of this, the WRD has been modelled as unsaturated with no water table defined. The geometry of the scenario assessed is illustrated in Figure 3-2.



Table 3-1: Material parameters for stability evaluation

Material Unit Weight (kN/m3)

Cohesion c’ (kPa)

Friction Angle φ’ (deg) Strength type

NAF Waste Rock 18 0 38 Mohr-Coulomb

Foundation Soil 20 0 37 Mohr-Coulomb

Figure 3-2: Final WRD configuration modelled in Slide

3.2 Stability analysis results Results of the stability analysis of the MEE WRD are summarised in Table 3-2 and Table 3-3. For all cases, the FOS obtained meets or exceeds the design criteria requirements.

Table 3-2: Results of static stability assessment on the final WRD

Case FOS

Global Failure 2.98

Local Failure 2.39

Table 3-3: Results of static stability assessment with reduced parameters

Case FOS

Global Failure 2.39

Local Failure 1.91



4 Water Management System The primary objective employed for the water management of the MME WRD is to keep clean water clean and direct the contact water to appropriate containment systems. A number of water management strategies have been proposed, mainly utilising diversion and collection structures.

The water management system will be commissioned prior to commencement of the waste rock placement and will be completed by the end of Year 1. As shown in Figure 4-1, a large proportion of the runoff will be away from the WRD, thus minimising contact water.

The surface water management system for the MEE WRD consists of the following elements:

• Clean water diversion channel A to the west of the WRD

• Clean water diversion channel B to the east of the WRD

• Contact water collection channel C north of WRD

• Contact water collection channel D east of WRD

• Contact water collection channel E south of WRD, parallel to the access road

• Sediment pond 1, receiving water from channels C and E

• Sediment pond 2, receiving water from channel D

• Contact water ditch east and south of the infrastructure area

• Sump 1, receiving water from contact water ditch; this water would be pumped into the sediment ponds

• Spillways to discharge contact water from the sediment ponds into the clean water channels and later into the environment.

The configuration of the water management system is shown in Figure 4-1 and in SRK Drawing SMM024-001 (Appendix A)

Figure 4-1: WRD water management system Source: SRK Drawing SMM024-001



4.1 Catchments The total catchment area around the WRD site of 0.84 km2 was divided into four major sub-catchments, as shown in Figure 4-2. The areas of each sub-catchment are outlined in Table 4-1.

Table 4-1: Areal extent of catchment areas

ID Area (km2)

1 0.145

2 0.429

3 0.142

4 0.126

Figure 4-2: Catchment areas in WRD site

4.2 Peak flow calculation Peak flows represent the highest possible flow that a given catchment, channel or other feature can experience for a given storm/ precipitation event.

The peak flows for the channels were calculated using the Australian Rainfall and Runoff (AAR): A Guide to Flood Estimation. The relevant design criteria are shown in Table 4-2.



Table 4-2: Peak flow calculation method extracted from ARR

Parameter Value

Design Average Recurrence Interval (ARI) 1 in 100 years

Region Definition North West

Method Rational Method

Concentration time (tc) estimate 𝑡𝑡𝑐𝑐 = 0.56𝐴𝐴0.38

Runoff Coefficient (C2) estimate 𝐶𝐶2 = 3.07 × 10−1𝐿𝐿−0.20

Peak Flow (QY) 𝑄𝑄𝑌𝑌 = 0.278𝐶𝐶2 �𝐶𝐶𝑌𝑌𝐶𝐶2� 𝐼𝐼𝑡𝑡𝑐𝑐𝐴𝐴

Catchment characteristics are used to estimate concentration times and the runoff coefficient, C2.

The intensity is determined by interpolating the IDF data in Table 1-2 for the storm duration equal to the catchment’s concentration time.

In accordance with recommendations from AAR, peak flows were calculated using the Rational Method. This method is based on a simplified representation of the law of conservation of mass and the hypothesis that the flow rate in a catchment is directly proportional to the size of the contributing area and the rainfall intensity, with the latter a function of the return period.

The peak flows have been calculated for ARIs varying from 1 to 1000 years and are shown in Table 4-3.

Table 4-3: Peak flows

ARI Estimated peak flows (m³/s)

1 2 5 10 20 50 100 500 1000

Cha

nnel

A 0.36 0.57 1.11 1.97 3.84 6.86 9.60 33.83 42.03

B 0.40 0.62 1.22 2.16 4.20 7.50 10.47 40.08 49.86

C 0.44 0.68 1.33 2.35 4.57 8.15 11.37 46.52 57.91

D 0.09 0.15 0.29 0.52 1.01 1.81 2.55 6.80 8.41

E 0.09 0.15 0.29 0.52 1.01 1.81 2.54 6.79 8.40

F 0.09 0.15 0.29 0.52 1.01 1.81 2.55 6.80 8.41

4.3 Clean water channel The clean water diversion system will collect water from the catchment upstream of the WRD facilities and will prevent contact with the WRD. It will run north to south west and north to south east, and then into the natural catchment west and south of the WRD site.

4.4 Contact water channels A channel network was designed to collect the contact water running off the WRD flanks which will finally report to the sediment ponds.

Channel C will run around the toe of the northern flank of the WRD and direct the water into sediment pond 1. Channel D will receive water from the eastern flank of the WRD and direct the water into sediment pond 2. Channel E will run around the southern toe of WRD and parallel to the access road, discharging into sediment pond 1.

Ditches on the east and south of the infrastructure area will direct the contact water to sump 1 where the water will be pumped to sediment pond 2.



4.5 Channel design The channels have been designed for the 100-year peak flow and checked to pass the 500 ARI event without exceeding the freeboard. The runoff amounts have been calculated considering the portion of the catchment that will contribute to each segment of the channels.

A typical channel layout has been calculated using the Manning equation. The channels will be excavated with side slopes of 1V:2H. The characteristics of the channels are shown in Table 4-4.

Clean water channels (A and B) will be protected with a rip rap cover up to the maximum operating water level to minimise erosion while contact water channels will be lined with HDPE. The characteristics of the various channels are shown in Table 4-4.

Table 4-4: Channels characteristics

Channel Base (m) Total height (m) Lining Sidewall slope (z)

Channel A 1.6 1.7 Rip rap 1V:2H

Channel B 1.8 1.8 Rip rap 1V:2H

Channel C (WRD North) 1.0 1.0 HDPE 1V:2H

Channel D (WRD East) 1.0 1.0 HDPE 1V:2H

Channel E (WRD South) 1.0 1.0 HDPE 1V:2H

Channel F (Ditches) 1.0 1.0 HDPE 1V:2H

4.6 Sump The contact water from the ditches around the infrastructure area will report to a sump excavated east of the infrastructure area. A pump will raise the contacted water to sediment pond 2. The location of the sump is shown in SRK Drawing SMM024-001.

4.7 Sediment ponds Two sediment ponds with a total capacity of around 17,000 m3 have been designed to provide storage for a 24-hour 10 year runoff event for the combined flow from the WRD and infrastructure area. Capacities for each sedimentation pond are shown in Table 4-5. In order to maintain their settling/ retention capacities, the ponds will need to be maintained and excavated periodically. The location of the sediment ponds is shown in SRK Drawing SMM024-001.

Table 4-5: Sediment ponds’ capacities

Sediment pond Catchment (m2)

Design storm volume (m3)

Available volume (m3)

1 168,000 11,330 13,000

2 49,000 3,928 4,000

Total 17,000

It is assumed, that during flood events greater than the design storm, the volume of the receiving waters will be larger and that retention in the sediment pond will not be a controlling factor.

Spillways designed for closure will be constructed in every sedimentation pond. They will be monitoring points for water quality and quantity.



5 Conclusion The WRD for the MEE project has been conceptually designed to meet particular engineering and environmental objectives, as explained in the relevant sections throughout the report, and specifically in the design criteria adopted for the project.

The waste rock from the proposed MEE pit will be stowed as backfill in the Mungada East pit and a dedicated MEE WRD, and a small balance stowed in the spare capacity in the Mungada East WRD.

No specific MEE pit geochemistry information was available at the time of the MEE WRD assessment. Based on the ME pit geochemistry, potentially acid forming (PAF) materials are not anticipated to be encountered during mining of the MEE pit.

If future work identifies PAF materials warranting encapsulation, it is expected there will be adequate NAF volume and stowage locations.

The MEE WRD design dump crest is 390 m RL, below the highest point of the natural ridge line (RL 507.5 m). There is a small amount of stowage space left between 390 and 400 m RL that could be used for paddock dumping if additional capacity is sought in the future.

Physical stability of the WRD was analysed on the basis of available information and assumed strength parameters, and modelling of the slopes of the WRD indicates that the WRD meets the recommended FOS.

Water management of the site has been incorporated as a key factor, to keep clean water clean and direct the contact water to appropriate containment systems.

Compiled by

Juanita Martin

Principal Consultant

Peer Reviewed by

Scott McEwing

Principal Consultant



6 References Sinosteel Midwest Corporation Limited, 2015. Blue Hills Iron Ore Project Mine Closure Plan Version

4: Tenement Numbers: M59/595, M59/596, M59/649, L59/62.

Australian Rainfall and Runoff: A Guide to Flood Estimation, Volume 1, 1998 (ed: D H Pilgrim) (Institution of Engineers: Barton, ACT).

Ven T Chow, 1959. Open Channel Hydraulics.

Burbidge, D R, 2012. The 2012 Australian Earthquake Hazard Map. Record 2012/071. Geoscience Australia, Canberra


SRK Consulting Appendices

Appendices


SRK Consulting Appendix A

Appendix A: Drawings


3

6

0

m

3

7

5

m

355m

3

6

0

m

365m

3

7

0

m

3

8

0

m

3

8

5

m

3

9

0

m

6776250m N

6776000m N

49

00

00

m E

48

95

00

m E

49

02

50

m E

6776500m N

48

90

00

m E

48

92

50

m E

48

87

50

m E

380m

48

97

50

m E

CLEAN WATER CHANNEL B

INFRASTRUCTURE AREA

CLEAN WATER CHANNEL A

CULVERT

CONTACTED WATER CHANNEL D

CONTACTED WATER CHANNEL C

CONTACTED WATER CHANNEL D

SEDIMENT POND 2

SEDIMENT POND 1

SUMP1

MUNGADA EAST

EXTENSION PIT

1

%

1

%

1

%

1

%

1

%

MUNGADA EAST PIT

49

00

00

m E

48

95

00

m E

49

02

50

m E

48

90

00

m E

48

92

50

m E

48

87

50

m E

48

97

50

m E

6775750m N

6776250m N

6776000m N

6776500m N

6775750m N

WATER DISCHARGED TO

ENVIRONMENT

WATER DISCHARGED TO

ENVIRONMENT

DITCH

SINOSTEEL MIDWEST CORP. LIMITED

MUNGADA EAST EXTENSION WASTE DUMP

CONCEPTUAL STUDY

P:\SMM024 - MUNGADA EAST EXTENSION CONCEPTUAL

STUDY\04_WORKING_FILES_\DRAFTING\00 - DRAWINGS\01 -

SHEETS\SMM024-001

N

PLOTTED:

FOR INFORMATION ONLY

Wednesday, 4 November 2015 12:35:44 PM

CONTOUR INTERVALS U.N.O.

EXISTING TOPOGRAPHY:

DESIGN TOPOGRAPHY:

2m & 10m

2m & 10m

COORDINATE SYSTEM

HORIZONTAL DATUM:

VERTICAL DATUM:

UTM-50S

WGS84

WRD WATER MANEGMENT

LAYOUT

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MART

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04.11.15

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MARTMORE

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ROCH

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ISSUED FOR CLIENTREVIEW

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0

---- ----

SMM024 - 001 0

DRAWING No. DRAWING TITLE REVISION DESCRIPTIONREV. DESIGNED REVIEWED APPROVED DATE

IF THE ABOVE BAR DOES

NOT SCALE 25mm, THE

DRAWING SCALE IS

ALTERED

THIS DRAWING IS

UNCONTROLLED WHEN

PRINTED UNLESS STAMPED

AND SIGNED WITH ORIGINAL

INK AND RECORDED ON A

DISTRIBUTION REGISTER

FILE:

DRAWING NUMBER REVISION

DRAWING TITLE

REFERENCE DRAWING TABLE REVISION HISTORY TABLE

SHEET SIZE

A1

LEAD PROJECT DRAFTER

SRK Perth 10 Richardson Street, West Perth, Western Australia 6005

Tel: +61 8 9288 2000 - Fax: +61 8 9288 2001 - http://www.srk.com.au/

PROJECT MANAGER

DRAWN

LAYOUT PLAN

SCALE 1: 1:2,000

SCALE 1:2,000

2001601208040040

EL

EV

AT

IO

N

EL

EV

AT

IO

N

350m

360m

380m

400m

420m

350m

360m

380m

400m

420m

0m 50m 100m 150m 200m 250m 300m 350m 400m 450m 500m 550m 566m

0m 50m 100m 150m 200m 250m 300m 350m 400m 450m 500m 550m 566m

150m

3.7

1

10m

3

1

3

1

NAF

10m

EL

EV

AT

IO

N

EL

EV

AT

IO

N

350m

360m

380m

400m

420m

350m

360m

380m

400m

420m

0m 50m 100m 150m 200m 250m 300m 350m 400m 420m

0m 50m 100m 150m 200m 250m 300m 350m 400m 420m

3.7

1

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10m

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NAF

100m

3

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0

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3

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m

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m E

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m E

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4

5

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m

920m

48

97

50

m E

INFRASTRUCTURE AREA

CLEAN WATER CHANNEL A

CONTACTED WATER CHANNEL C

SUMP1

1

%

1

%

1

%

1

%

1

%

49

00

00

m E

48

95

00

m E

49

02

50

m E

48

97

50

m E

6776250m N

6776000m N

6776500m N

6775750m N

WATER DISCHARGED TO

ENVIRONMENT

DITCH

1

003

2

003

2

003

1

003

SINOSTEEL MIDWEST CORP. LIMITED

MUNGADA EAST EXTENSION WASTE DUMP

CONCEPTUAL STUDY

P:\SMM024 - MUNGADA EAST EXTENSION CONCEPTUAL

STUDY\04_WORKING_FILES_\DRAFTING\00 - DRAWINGS\01 -

SHEETS\SMM024-002 _B

PLOTTED:

FOR INFORMATION ONLY

Wednesday, 4 November 2015 12:32:40 PM

WASTE ROCK DUMPS

SECTIONS

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MART

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04.11.15

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MARTMORE

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ROCH

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ISSUED FOR CLIENT REVIEW

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0

---- ----

SMM024 - 002 0

DRAWING No. DRAWING TITLE REVISION DESCRIPTIONREV. DESIGNED REVIEWED APPROVED DATE

IF THE ABOVE BAR DOES

NOT SCALE 25mm, THE

DRAWING SCALE IS

ALTERED

THIS DRAWING IS

UNCONTROLLED WHEN

PRINTED UNLESS STAMPED

AND SIGNED WITH ORIGINAL

INK AND RECORDED ON A

DISTRIBUTION REGISTER

FILE:

DRAWING NUMBER REVISION

DRAWING TITLE

REFERENCE DRAWING TABLE REVISION HISTORY TABLE

SHEET SIZE

A1

LEAD PROJECT DRAFTER

SRK Perth 10 Richardson Street, West Perth, Western Australia 6005

Tel: +61 8 9288 2000 - Fax: +61 8 9288 2001 - http://www.srk.com.au/

PROJECT MANAGER

DRAWN

SCALE 1:1,000

100806040

20020

KEY PLAN

SCALE 1: 1:5,000

SECTION

SCALE 1:1000

1

-

SECTION

SCALE 1:1000

2

-

SCALE 1:5,000

5004003002001000100

SRK Consulting Distribution Record

SRK Report Client Distribution Record

Project Number: SMM024 Report Title: Mungada East Extension Waste Rock Dump Date Issued: 9 November 2015

Name/Title Company

Wayne Ennor Sinosteel Midwest Corporation Ltd

Rev No. Date Revised By Revision Details

0 4/11/2015 Juanita Martin Final Report

1 9/11/2015 Juanita Martin Final Report

This Report is protected by copyright vested in SRK Consulting (Australasia) Pty Ltd. It may not be reproduced or transmitted in any form or by any means whatsoever to any person without the written permission of the copyright holder, SRK.


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