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ENVIRONMENTAL IMPACT STATEMENT EOE (NO.75) PTY LIMITED

Appendix 4 Ardlethan Tin Mine

Report No. 754/08

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Appendix 4

Surface Water Impact Assessment

(Total No. of pages including blank pages = 44)

EOE (NO.75) PTY LIMITED ENVIRONMENTAL IMPACT STATEMENT

Ardlethan Tin Mine Appendix 4

Report No. 754/08

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This page has intentionally been left blank

Prepared by:

December 2016


for the

Ardlethan Tin Mine Rehabilitation and Tailings

Reprocessing Project

R.W. CORKERY & CO. PTY. LIMITED



Report No. 754/08

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for the

Ardlethan Tin Mine Rehabilitation and Tailings

Reprocessing Project

Prepared for:

EOE (No.75) Pty Limited ABN: 95 006 829 787

Level 2, 53 Berry Street NORTH SYDNEY NSW 2060 PO Box 1506 NORTH SYDNEY NSW 2059

Telephone: (02) 9959 5599 Fax: (02) 9959 5577 Email: [email protected]

Prepared by:

R.W. Corkery & Co. Pty. Limited Geological & Environmental Consultants ABN: 31 002 033 712

Brooklyn Office: 1st Floor, 12 Dangar Road PO Box 239 BROOKLYN NSW 2083

Orange Office: 62 Hill Street ORANGE NSW 2800

Brisbane Office: Suite 5, Building 3 Pine Rivers Office Park 205 Leitchs Road BRENDALE QLD 4500

Telephone: (02) 9985 8511 Facsimile: (02) 6361 3622 Email: [email protected]



Ref No. 754/08 December 2016



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This Copyright is included for the protection of this document

COPYRIGHT

© R.W. Corkery & Co. Pty Limited 2016

and

© EOE (No.75) Pty Limited 2016

All intellectual property and copyright reserved.

Apart from any fair dealing for the purpose of private study, research, criticism or review, as permitted under the Copyright

Act, 1968, no part of this report may be reproduced, transmitted, stored in a retrieval system or adapted in any form or by any

means (electronic, mechanical, photocopying, recording or otherwise without written permission. Enquiries should be addressed

to R.W. Corkery & Co. Pty Limited.



Report No. 754/08

CONTENTS Page

A4-vii

LIST OF ACRONYMS ......................................................................................................................... A4-IX

1. INTRODUCTION ........................................................................................................................ A4-1

1.1 SCOPE ..............................................................................................................................A4-1

1.2 PROJECT OVERVIEW .....................................................................................................A4-1

1.3 SECRETARY’S ENVIRONMENTAL IMPACT ASSESSMENT REQUIREMENTS ..........A4-3

1.4 REGULATORY FRAMEWORK ........................................................................................A4-7

2. EXISTING ENVIRONMENT ....................................................................................................... A4-8

2.1 CLIMATE ...........................................................................................................................A4-8

2.2 TOPOGRAPHY ...............................................................................................................A4-10

2.2.1 Regional Topography .........................................................................................A4-10

2.2.2 Local Topography ..............................................................................................A4-10

2.2.3 Mine Site Topography ........................................................................................A4-10

2.3 CATCHMENTS ...............................................................................................................A4-10

2.3.1 Regional Catchment ...........................................................................................A4-10

2.3.2 Local Catchments ..............................................................................................A4-14

2.3.3 Mine Site Catchments ........................................................................................A4-15

3. ASSESSMENT OF POTENTIAL IMPACTS ............................................................................ A4-16

3.1 SITE WATER MANAGEMENT .......................................................................................A4-16

3.1.1 Spring Valley Catchment....................................................................................A4-16

3.1.2 Mill Reclaim Catchment .....................................................................................A4-17

3.1.3 Processing Plant Catchment ..............................................................................A4-19

3.1.4 Ardwest/Wild Cherry Open Cut Catchment .......................................................A4-20

3.1.5 White Crystal Open Cut Catchment ...................................................................A4-21

3.1.6 Stackpool Open Cut Catchment ........................................................................A4-22

3.1.7 Summary ............................................................................................................A4-24

3.2 WATER BALANCE .........................................................................................................A4-25

3.2.1 Inputs..................................................................................................................A4-26

3.2.2 Throughput .........................................................................................................A4-27

3.2.3 Output.................................................................................................................A4-27

3.2.4 Model Set Up .....................................................................................................A4-28

3.2.5 Model Results ....................................................................................................A4-29

3.3 WATER QUALITY ...........................................................................................................A4-31

4. MITIGATION MEASURES ....................................................................................................... A4-31

5. REFERENCES ......................................................................................................................... A4-33



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CONTENTS Page

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FIGURES

Figure 1 Proposed Mine Site Layout .............................................................................................. A4-2

Figure 2 Regional Topography and Drainage .............................................................................. A4-11

Figure 3 Local Topography and Drainage .................................................................................... A4-12

Figure 4 Mine Site Topography and Drainage ............................................................................. A4-13

Figure 5 Site Water Balance Schematic....................................................................................... A4-25

Figure 6 Rainfall Distribution for the Mine Site ............................................................................. A4-26

TABLES

Table 1 Coverage of SEARs ......................................................................................................... A4-3

Table 2 Climate Data..................................................................................................................... A4-9

Table 3 Mine Site Catchment Detail ............................................................................................ A4-15

Table 4 Mill Reclaim Catchment 1% AEP Design Runoff Volumes ............................................ A4-18

Table 5 Mill Reclaim 1% AEP Hourly Discharge Volumes .......................................................... A4-19

Table 6 Assessment of Processing Plant Detention Pond Capacity .......................................... A4-20

Table 7 Assessment of Ardwest/Wild Cherry Open Cut Capacity .............................................. A4-21

Table 8 Assessment of Wild Crystal Open Cut Capacity ............................................................ A4-22

Table 9 Stackpool Open Cut Catchment Design Rainfall Intensities and Calculated Peak Discharges ..................................................................................................................... A4-23

Table 10 Stackpool Open Cut Perimeter Drain Geometry, Peak Discharge Water Levels and Capacity ......................................................................................................................... A4-24

Table 11 Annual Exceedance Probability Rainfall Depths at the Mine Site .................................. A4-27

Table 12 Results of Water Balance Modelling for Ardlethan Tailings Reprocessing and Rehabilitation Project: 30tph Production ........................................................................ A4-29

Table 13 Results of Water Balance Modelling for Ardlethan Tailings Reprocessing and Rehabilitation Project: 60tph Production ........................................................................ A4-30

Table 14 Results of Water Balance Modelling for Ardlethan Tailings Reprocessing and Rehabilitation Project: 120tph Production ...................................................................... A4-30

Table 15 Results of Water Balance Modelling for Ardlethan Tailings Reprocessing and Rehabilitation Project: 180tph Production ...................................................................... A4-30



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LIST OF ACRONYMS

AEP Annual Exceedance Probability

AHD Australian Height Datum

ARI Average Recurrence Interval

BoM Bureau of Meteorology

DPI Department of Primary Industries

DSITI Department of Science, Information Technology and Innovation

DRE Division of Resources and Energy

EC Electrical Conductivity

EIS Environmental Impact Statement

Mt Million tonnes

MI Murrumbidgee Irrigation

RCP Reinforced Concrete Pipe

IFD Intensity Frequency and Duration

SILO Scientific Information for Land Owners

LPIII Log Pearson Type III



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1. I N T RO D U C TI ON

1.1 SCOPE

This Surface Water Impact Assessment has been prepared by R.W. Corkery & Co. Pty. Limited

to support an Environmental Impact Statement (EIS) which was also prepared by R.W. Corkery

& Co. Pty. Limited on behalf of EOE (No.75) Pty Limited (the Applicant). The Surface Water

Impact Assessment and EIS have been prepared in relation to proposed Ardlethan Tin Mine

Rehabilitation and Tailings Reprocessing Project (the Proposal). The purpose of this assessment

is to determine the potential impacts to local and regional surface water resources and users as a

result of the Proposal and identify appropriate management measures to mitigate any identified

impacts.

1.2 PROJECT OVERVIEW

The Applicant currently has approval for a Category 3 exploration activity to extract a 20 000t

bulk sample to be reprocessed within the Mine Site using a modular processing plant (pilot

plant) to assess the feasibility of the reprocessing technology. Following successful completion

of the pilot plant and receipt of development consent, the Applicant would proceed with the

Proposal, which comprises the following:

Extraction and reprocessing of tailings from the Main and Spring Valley Tailings

Storage Facilities;

Placement of the reprocessed tailings into the Ardwest/Wild Cherry Open cut; and

Rehabilitation of sections of the Mine Site, including the footprints of the Main

and Spring Valley Tailings Storage Facilities, former processing plant, workshop

and office area.

The Proposal is fully described in Section 2 of the Environmental Impact Statement. However,

in summary, the Applicant proposes to seek development consent for the following (Figure 1).

Extraction of approximately 10 million tonnes (Mt) of tailings from the Main and

Spring Valley Tailings Storage Facilities.

Transportation of approximately 9.5Mt of pre-flotation tailings to the run-of-mine

(ROM) Pad.

Transportation of approximately 0.5Mt of post-flotation tailings to the White

Crystal Open Cut which has previously been used for placement of post-flotation

tailings.

Reprocessing of the extracted tailings using a gravity separation reprocessing

plant to produce a tin concentrate suitable for sale to international customers.

Transportation of the tin concentrate from the Mine Site to port via road.

Placement of the reprocessed tailings into the Ardwest/Wild Cherry Open Cut.

Rehabilitation of sections of the Mine Site, including:

– the footprints of the Main and Spring Valley Tailings Storage Facilities;

– the former processing plant, workshop and office area; and

– other areas disturbed as a result of the Applicant’s activities.



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Figure 1 Proposed Mine Site Layout

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Figure dated 15/12/16. Inserted 16/12/16



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1.3 SECRETARY’S ENVIRONMENTAL IMPACT ASSESSMENT REQUIREMENTS

Secretary’s Environmental Impact Assessment Requirements (SEARs) were issued for the

Proposal on 1 September 2016. Table 1 presents the surface water related SEARs and where

each is addressed in this document.

Table 1

Coverage of SEARs Page 1 of 5

Government Agency

Paraphrased Requirement Relevant

EIS Section(s)

Department of Planning and Environment

01/09/16

Including

an annual site water balance for representative years over the life of the development and demonstration that sufficient water supplies would be available to meet operational requirements;

Section 3.2

identification of any licensing requirements or other approvals required under the Water Act 1912 and/or Water Management Act 2000;

Section 1.4, Section 4

a description of the measures proposed to ensure the development can operate in accordance with the requirements of any relevant Water Sharing Plan or water source embargo;

an assessment of activities that could cause erosion or sedimentation issues, and the proposed measures to prevent or control these impacts;

Section 3.1

an assessment of the likely impacts of the development on the quality and quantity of surface and groundwater resources, having regard to the requirements of DPI Water, EPA and Council (Attachment 2); and

Section 3.1

a detailed description of the proposed water management system, water monitoring program and other measures to mitigate surface and groundwater impacts.

Section 3.1

DPI – Office of Water 02/08/16

The identification of an adequate and secure water supply for the life of the project. Confirmation that water can be sourced from an appropriately authorised and reliable supply.

Section 4

A detailed and consolidated site water balance. Clear separation and management of clean and dirty water sources and consideration of the sites Maximum Harvestable Rights Dam Capacity.

Section 3.2

Assessment of potential impacts to surface water and groundwater resources, water users, riparian land and groundwater dependent ecosystems, and measures proposed to reduce and mitigate these impacts. Assessment against the NSW Aquifer Interference Policy (2012) using DPI Water’s assessment framework will be required where groundwater is intercepted or potentially impacted. This is especially relevant to the Ardwest/Wild Cherry Open Cut.

Section 3

Details of water proposed to be taken (including through inflow and seepage) from each surface water and groundwater source as defined by the relevant Water Sharing Plan (including ongoing water take following completion of the project).

Section 1.4, Section 3.1, Section 3.2

Details of works and assessment of impacts within waterfront land. Works within waterfront land are to be consistent with the DPI Water’s Guidelines for Controlled Activities on Waterfront Land (2012).

NA

Identification of licensing requirements under the Water Act 1912 and Water Management Act 2000. A Controlled Activity Approval may be required for works within waterfront land.

Section 1.4



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Table 1 (Cont’d)


Government Agency


EIS Section(s)

DPI – Office of Water 02/08/16 (Cont’d)

Water Sharing Plans

The proposal is located within the area covered by the Water Sharing Plan for the NSW Murray Darling Basin Fractured Rock Water Sources 2011 and the Water Sharing Plan for the Murrumbidgee Unregulated and Alluvial Water Sources 2012. The EIS is required to:

Demonstrate how the proposal is consistent with the relevant rules of the Water Sharing Plan including rules for access licences, distance restrictions for water supply works and rules for the management of local impacts in respect of surface water and groundwater sources, ecosystem protection (including groundwater dependent ecosystems), water quality and surface-groundwater connectivity.


Provide a description of any site water use (amount of water to be taken from each water source) and management including all sediment dams, clear water diversion structures with detail on the location, design specifications and storage capacities for all the existing and proposed water management structures.

Section 3

Provide an analysis of the proposed water supply arrangements against the rules for access licences and other applicable requirements of any relevant WSP, including:

Sufficient market depth to acquire the necessary entitlements for each water source.

Ability to carry out a “dealing” to transfer the water to relevant location under the rules of the WSP.

Daily and long-term access rules.

Account management and carryover provisions.

Provide a detailed and consolidated site water balance. Section 3.2

Licensing Considerations

The EIS is required to provide:

Identification of water requirements for the life of the project in terms of both volume and timing (including predictions of potential ongoing groundwater take following the cessation of operations at the site – such as evaporative loss from open voids or inflows).

Section 3.2

Details of the water supply source(s) for the proposal including any proposed surface water and groundwater extraction from each water source as defined in the relevant Water Sharing Plan/s and all water supply works to take water.

Section 3.1, Section 3.2, Section 4

Explanation of how the required water entitlements will be obtained (i.e. through a new or existing licence/s, trading on the water market, controlled allocations etc.).


Information on the purpose, location, construction and expected annual extraction volumes including details on all existing and proposed water supply works which take surface water, (pumps, dams, diversions, etc.).

Section 3.1

Details on all bores and excavations for the purpose of investigation, extraction, dewatering, testing and monitoring. All predicted groundwater take must be accounted for through adequate licensing.

NA



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Table 1 (Cont’d)


Government Agency


EIS Section(s)

DPI – Office of Water 02/08/16 (Cont’d)

Details on existing dams/storages (including the date of construction, location, purpose, size and capacity) and any proposal to change the purpose of existing dams/storages · Details on the location, purpose, size and capacity of any new proposed dams/storages.

Section 3.1

Applicability of any exemptions under the Water Management (General) Regulation 2011 to the project.

Section 1.4

Water allocation account management rules, total daily extraction limits and rules governing environmental protection and access licence dealings also need to be considered.


The Harvestable Right gives landholders the right to capture and use for any purpose 10 % of the average annual runoff from their property. The Harvestable Right has been defined in terms of an equivalent dam capacity called the Maximum Harvestable Right Dam Capacity (MHRDC). The MHRDC is determined by the area of the property (in hectares) and a site-specific run-off factor. The MHRDC includes the capacity of all existing dams on the property that do not have a current water licence. Storages capturing up to the harvestable right capacity are not required to be licensed but any capacity of the total of all storages/dams on the property greater than the MHRDC may require a licence.

NA

Surface Water Assessment

The predictive assessment of the impact of the proposed project on surface water sources should include the following:

Identification of all surface water features including watercourses, wetlands and floodplains transected by or adjacent to the proposed project.

Section 2.3

Identification of all surface water sources as described by the relevant water sharing plan.

Section 1.4, Section 3.1

Detailed description of dependent ecosystems and existing surface water users within the area, including basic landholder rights to water and adjacent/downstream licensed water users.

NA

Description of all works and surface infrastructure that will intercept, store, convey, or otherwise interact with surface water resources.

Section 3.1

Assessment of predicted impacts on the following:

flow of surface water, sediment movement, channel stability, and hydraulic regime,

Section 3.1

water quality, Section 3.1

flood regime,

dependent ecosystems,

existing surface water users, and

planned environmental water and water sharing arrangements prescribed in the relevant water sharing plans.



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Table 1 (Cont’d)


Government Agency


EIS Section(s)

Watercourses, Wetlands and Riparian Land

The EIS should address the potential impacts of the project on all watercourses likely to be affected by the project, existing riparian vegetation and the rehabilitation of riparian land. It is recommended the EIS provides details on all watercourses potentially affected by the proposal, including:

NA

Scaled plans showing the location of:

wetlands/swamps, watercourses and top of bank;

riparian corridor widths to be established along the creeks;

existing riparian vegetation surrounding the watercourses (identify any areas to be protected and any riparian vegetation proposed to be removed);

the site boundary, the footprint of the proposal in relation to the watercourses and riparian areas; and

proposed location of any asset protection zones.

Photographs of the watercourses/wetlands and a map showing the point from which the photos were taken.

NA

A detailed description of all potential impacts on the watercourses/riparian land.

NA

A detailed description of all potential impacts on the wetlands, including potential impacts to the wetlands hydrologic regime; groundwater recharge; habitat and any species that depend on the wetlands.

NA

A description of the design features and measures to be incorporated to mitigate potential impacts.

Section 3.1

Geomorphic and hydrological assessment of water courses including details of stream order (Strahler System), river style and energy regimes both in channel and on adjacent floodplains.

NA

EPA 26/07/16

The goals of the project should include the following.

No pollution of waters (including surface and groundwater), except to the extent authorised by the EPA (i.e. in accordance with an Environment Protection Licence);

Section 3.1

Contaminated water (including process waters, wash down waters, polluted stormwater or sewage) captured on the site and collected, treated and beneficially reused, where this is safe and practicable to do so;

Section 3

Anticipate wet weather impacts and develop contingencies into the design of all contaminated water infrastructure and clean water diversions; and

Section 3.2

Insure any proposed discharges are acceptable to the NSW Water Quality and River Flow Objectives and where appropriate propose monitoring and management measures.

Not Applicable

The EIS should document the measures that will achieve the above goals. Section 2.3

Details of the site drainage and any natural or artificial waters within or adjacent to the development must be identified and where applicable measures proposed to mitigate potential impacts of the development on these waters. The EIS should provide details of the proposed design and construction of water management systems for the site to ensure surface and ground waters are protected from contaminants.



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Table 1 (Cont’d)


Government Agency


EIS Section(s)

Coolamon Shire Council 17/08/16

Drainage: Any EIS will need to determine the ongoing treatment of stormwater runoff and drainage to ensure that the new operations do not impact on neighbouring farms and the Mirrool Creek Catchment. Whilst it is acknowledged that as part of the Mine Closure Plan current drainage and runoff is maintained on site, any EIS will need to explain how this will be managed throughout the duration of the mining operations.

Section 3.1

Surface Water Management: Ongoing site management must ensure that there is no future leachate or contaminated drainage leaving the site and entering the Mirrool Creek Catchment or any underground systems. As this proposal will be removing contaminated tailings and then rehabilitating to a final landform, the EIS must provide adequate information on how this will be staged and treated to ensure no immediate or future adverse impacts.

Section 3.1

Issue Management: The EIS should indicate how any issues or concerns the public may have with the operations will be dealt with in an ongoing manner. This should include an open and transparent complaint handling system that records community concerns and details any response or actions taken.

EIS Section 4.11.4

1.4 REGULATORY FRAMEWORK

The Water Management Act 2000 (WM Act) was developed in recognition of the need for

NSW water resources to be managed in a sustainable and integrated manner for the benefit of

both present and future generations. The WM Act is administered by Department of Primary

Industry –Water (DPI-Water) to provide clear arrangements for controlling land-based activities

that affect the quality and quantity of the State’s water resources through water licensing and

approvals.

The WM Act provides for four types of approval, namely:

water use approval – which authorises the use of water at a specified location for a

particular purpose, for up to 10 years;

flood work approval – which authorises the construction and use of specified

flood works at a specified location, for up to 10 years;

water supply work approval – which authorises the construction and use of

specified water supply; and

controlled activity approval – which authorises works carried out within 40m of

waterfront land and aquifer interference activities.

The principles of the WM Act require that operational water sharing plans (WSP) for the

respective river or aquifer system be established to protect the water resource, dependent

ecosystems and surface water users by identifying and establishing available resource

allocations and objectives for the relevant system.



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The relevant WSP for the surface water system in which the Project is situated is the Water

Sharing Plan for the Murrumbidgee Unregulated and Alluvial Water Sources 2012.

The WM Act also establishes that a set of regulations be made to cover any matter required or

permitted by the WM Act. The Water Management (General) Regulation 2011 (WM

Regulations) was therefore developed to complement the WM Act. The WM Regulations

identify access license categories and how each type of access license is managed as well as

identifying where exemption from requiring an access license may occur.

Under the WM Regulation, the management of potentially contaminated runoff generated

within the Mine Site does not require an approval or licence under the WM Act as site water

management infrastructure is considered to be an “Excluded Work” under Schedule 1 of the

WM Regulation. That Regulation relevantly states the following.

“Dams solely for the capture, containment and recirculation of drainage and/or effluent,

consistent with best management practice or required by a public authority to prevent the

contamination of a water source that are located on a minor stream.”

2. E XI ST I NG E N VI RO NM E N T

2.1 CLIMATE

2.1.1.1 Introduction and Data Sources

Meteorological conditions have the potential to influence a range of Proposal-related impacts

on surrounding residences and the environment. This subsection provides a brief overview of

the meteorological conditions surrounding the Mine Site; focusing particularly on those aspects

of the climate that are likely to influence the potential Proposal-related environmental impacts.

Climate data has been sourced from the following Bureau of Meteorology (BoM) weather

stations.

Ardlethan Post Station (BoM ID 074000), situated approximately 5km

southeast of the Mine Site – 1909 to present. Temperature data for this station

is not continuous after 1975.

Yanco Agricultural Institute (BoM ID 074037) – situated approximately

55km southwest of the Mine Site.

Temora Research Station (BoM ID 073038) – situated approximately 65km

southeast of the Mine Site.

Climate data sourced from the above stations is presented in Table 2.

2.1.1.2 Temperature

January is typically the hottest month, with an average maximum temperature of 33.8ºC. July is

the coldest month with a mean maximum temperature of 14.3°C and a mean minimum

temperature of 5.0°C.



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Table 2

Climate Data

Jan Feb Mar April May June July Aug Sept Oct Nov Dec Annual

Temperature (C°) – Yanco Agricultural Institute (BoM ID 074037) (1999 to present)

Mean maximum temperature

33.8 32.4 28.8 24.2 19.0 15.1 14.3 16.3 20.4 24.9 28.9 31.0 24.1

Mean minimum temperature

18.8 18.5 15.3 11.7 7.8 5.9 5.0 5.4 7.7 10.5 14.4 16.3 11.4

Rainfall (mm) – Ardlethan Post Office (BoM ID 074000) (1909 – present)

Mean rainfall 42.7 39.9 37.9 35.5 39.7 42.5 42.3 42.2 38.9 43.9 39.7 37.0 486.8

Highest rainfall

229.0 219.6 195.2 155.4 143.9 177.4 121.3 101.0 148.8 141.2 184.0 172.0 863.9

Lowest rainfall 0 0 0 0 0 0.6 2.0 3.3 1.0 0 0 0 184.9

Highest daily rainfall

99.2 122.9 106.4 50.8 50.8 49.5 46.0 41.4 60.7 49.0 83.6 75.4 122.9

Evaporation (mm) – Temora Research Station (BoM ID 073038) (1978 to 2011)

Mean daily evaporation

8.7 7.8 5.9 3.6 2.0 1.2 1.3 1.8 2.9 4.4 6.5 7.9 4.5

2.1.1.3 Rainfall

Rainfall data has been recorded at the Ardlethan Post Office since 1909. Mean annual rainfall is

486.8mm, with rainfall evenly distributed throughout the year, with between 43.9mm and

35.5mm falling on average each month (Table 2). The driest year on record was 1967 when

184.9mm of rain was recorded. By contrast, the wettest year on record was 1956 when

863.9mm of rain was recorded.

The maximum daily rainfall recorded is 122.9mm which was recorded on 17 February 1928.

Maximum daily rainfall exceeds monthly average rainfall for all months, with the exception of

August, indicating that high intensity storms with significant rainfall over a relatively short

duration may occur, particularly in the summer months.

2.1.1.4 Evaporation

Mean evaporation at the Temora Research Station throughout the year is 4.5mm per day or

1 642mm per year. Mean daily evaporation varies between 1.2mm per day in June and 8.7mm

per day in January (Table 2). Based on the mean daily evaporation, the calculated mean

monthly pan evaporation is greater than mean monthly rainfall in all months with the exception

of June.



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2.2 TOPOGRAPHY

2.2.1 Regional Topography

The Mine Site is located in an area of generally flat topography which slopes gently to the

southeast towards the Murrumbidgee River, with occasional localised hills and ridges

(Figure 2). Maximum elevations include.

360m AHD at the Bygoo Hills, approximately 6km to the northeast of the Mine

Site;

399m AHD at Bolero Mountain, approximately 5km north-northwest of the Mine

Site; and

400m AHD at the Colinroobie Hills, approximately 25km southwest of the Mine

Site.

2.2.2 Local Topography

Locally, the Mine Site occupies an area of elevated topography, with Taylors Hill in the

southern section of the Mine Site rising to an elevation of approximately 355m AHD

(Figure 3). The surrounding land typically has elevations of between 200m AHD and

260m AHD.

2.2.3 Mine Site Topography

Historic mining activity has significantly influenced the topographic features of the Mine Site

(Figure 4). The maximum elevation is approximately 315m AHD on the Main Waste Rock

Emplacement. Three open cuts exist, the Ardwest/Wild Cherry, While Crystal and Stackpool

Open Cuts. The largest of these, the Ardwest/Wild Cherry Open Cut has a minimum elevation

of approximately 124m AHD or approximately 150m below the natural surface. The smaller

White Crystal Open cut has been partially backfilled with tailings and with a minimum

elevation of 255m AHD is only 5m lower than the invert of the open cut at 260m AHD. Two

Tailings Storage Facilities exist within the Mine Site, with the Main Tailings Storage Facility

having a surface elevation between 310 AHD and 270m AHD.

2.3 CATCHMENTS

2.3.1 Regional Catchment

The Mine Site is located within the Murrimbidgee River Catchment (Figure 2). The

Murrimbidgee River Catchment drains an area of approximately 84 000km2 within the Murray-

Darling Basin. The Murrumbidgee River headwaters are situated in the Monaro Plains near

Cooma, NSW and the river travels approximately 1 600km west to its junction with the Murray

River near Balranald, Victoria. A number of hydraulic controls have been constructed within

the Murrumbidgee system with Blowering Dam on the Tumut River (1 628GL capacity) and

Burrinjuck Dam on the Murrumbidgee River (1 026GL capacity) being the two largest.



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Figure 2 Regional Topography and Drainage

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Figure 3 Local Topography and Drainage

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Dated 15/12/16 / Inserted 16/12/16



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Figure 4 Mine Site Topography and Drainage

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2.3.2 Local Catchments

2.3.2.1 Local Watercourses

Local drainage consists of scattered indistinct watercourses converging on Bolaro and Mirrool

Creeks, approximately 4km south of the Mine Site (Figures 2 and 3). Bolaro Creek flows into

Mirrool Creek, approximately 12km southwest of the Mine Site. Mirrool Creek then flows in a

westerly direction before dissipating into flat land approximately 25km to the west of the Mine

Site. The prevailing land use in the region is associated with agricultural and horticultural

activity and this has led to the construction of a number of farm dams in the surrounding region

that opportunistically capture overland flow for farm use.

Mirrool Creek drains a catchment of approximately 11 000km2 and is also used as part of

Murrumbidgee Irrigation Limited’s (MI) distribution network (MI, 2012).

2.3.2.2 Land-use

The prevailing land use surrounding the Mine Site is associated with agricultural and

horticultural activity, primarily cropping and grazing. Other land uses include:

Village residential – the Ardlethan village is located approximately 5km to the

southeast of the Mine Site.

Transport – Road and railway infrastructure exist in the vicinity of the Mine Site,

with the Newell Highway and Burley Griffin Way and the Temora – Hilston

Railway top the south and east of the Mine Site.

Industrial - A bulk grain handling and rail loading facility operated by Graincorp

Operations Limited is located approximately 4km southeast of the Mine Site.

2.3.2.3 Geomorphology

Historic activities to support agriculture, such as land clearing, dam construction and the

establishment of an irrigation network has heavily influenced the geomorphology of surface

watercourses in the vicinity of the Mine Site. In addition, mining of alluvial leads south of the

Mine Site between 2001 and 2003 significantly disturbed that watercourse, requiring extensive

rehabilitation.

Prior to disturbance, the majority of the watercourses present in the region are considered to

have displayed geomorphic behaviour typical of meandering systems that are influenced by low

topographic grade, with relict channels evident in satellite imagery.

2.3.2.4 Water Quality

Water quality information for Bolaro Creek or Mirrool Creek was unavailable for review.

Water quality data collected at DPI-Water monitoring station 4100093 (Old Man Creek) 64km

south of the Mine Site (Figure 2) was reviewed to establish likely water quality in

Murrumbidgee River tributaries similar to Bolaro and Mirrool Creeks. In summary, data from

that station for the period 22 July 1976 to 30 November 2016 indicated that the 75th

percentile

electrical conductivity is 212µS/cm. This is within the desired range of the water quality

objective (35µS/cm to 350µS/cm) for uncontrolled streams in the Murrumbidgee River and

Lake George catchment (DECCW, 2006).



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2.3.3 Mine Site Catchments

Historic disturbance on the Mine Site, such as the development and construction of open cuts,

tailings storage facilities, waste rock emplacements and water storage dams has significantly

altered natural topography and drainage lines within the Mine Site. Historic site water

management infrastructure has created a number of catchments on the Mine Site that drain to

internal water storages, capturing all runoff generated from disturbed catchments. Mine Site

runoff is directed toward water storages via overland flow, open channel or pipe. This

assessment has delineated and identified Mine Site catchments according the receiving storage.

Catchment details are provided in Table 3 and shown on Figure 4.

Table 3

Mine Site Catchment Detail

Page 1 of 2

Catchment Area (ha)

Description Water Management

Infrastructure Disturbed Natural

Spring Valley Catchment

51 51 Situated in southwestern section of the Mine Site. Collects runoff from Spring Valley Tailings Storage Facility and naturally vegetated granite hills via overland flow

Spring Valley Freshwater Dam

Mill Reclaim Dam

36 2 Centrally located within the Mine Site. Collects runoff from Main, Lower and Horseshoe tailings storage facilities as well as the former processing plant area via overland flow and pipes. Captured runoff collected in the Mill Reclaim Dam and is discharged under gravity to Ardwest/Wild Cherry Open Cut via 0.3m diameter concrete pipe.

Mill Reclaim Dam

Discharge Pipe

Processing Plant Area catchment

3.8 1.2 Centrally located within the Mine Site. Collects runoff from the area of the proposed Processing Plant.

Processing Plant Detention Pond

Ardwest/Wild Cherry Open Cut

44 0 Located in the central north section of the Mine Site. Collects runoff from cleared catchment and waste rock emplacement via overland flow. Captured runoff and direct rainfall stored in former open cut pit (Ardwest/Wild Cherry Open Cut)

Ardwest/Wild Cherry Open Cut

White Crystal Open Cut

8 0 Located in the eastern section of the Mine Site. Collects runoff from waste rock emplacement and former open cut via overland flow.

White Crystal Open Cut

Stackpool Open Cut

13 4

Located in the eastern section of the Mine Site. Collects runoff from waste rock emplacement and naturally vegetated areas via overland flow. Runoff directed to the Stackpool Open Cut via open channel and overland flow

Stackpool Open Cut

Stackpool diversion drain

Eastern Evaporation Ponds

6 0 Located in the northeastern section of the Mine Site. Collects runoff from waste rock emplacement and cleared area via overland flow. Runoff directed to evaporation pond for natural attenuation.

Eastern Evaporation Ponds

Perimeter drains and bunds



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Table 3 (Cont’d) Mine Site Catchment Detail

Page 2 of 2

Catchment Area (ha)

Description Water Management

Infrastructure Disturbed Natural

Northern Evaporation Ponds

30 5 Located in the northern section of the Mine Site. Collects runoff from waste rock emplacement and cleared area via overland flow and open channel. Runoff directed to sequential evaporation ponds for natural attenuation.

Northern Evaporation Ponds

Perimeter drains and bunds

Mine Access Road Catchment

2.5 0 Collects runoff from cleared areas adjacent to Mine Access Road. Runoff directed to evaporation ponds for natural attenuation. This catchment is predominantly comprised of the evaporation ponds.

Mine Access Road Evaporation Ponds

3. AS S E S SM E N T O F PO T E N TI AL I M PAC T S

3.1 SITE WATER MANAGEMENT

The nature of the historic disturbance on the Mine Site requires disturbed and sediment laden

runoff to be captured and stored in suitable infrastructure to prevent discharge and subsequent

impacts to downstream (receiving) surface water systems. Historic activity on the Mine Site led

to the construction of water management infrastructure to manage runoff generated on the Mine

Site.

An assessment of the capacity of the water management infrastructure on the Mine Site to

convey and contain site water runoff for the 1% Annual Exceedance Probability (AEP) (100yr

Annual Recurrence Interval) design rainfall event was undertaken using the empirical methods

presented below:

Estimation of Peak Flow: Rational Method.

Open Channel Capacity: Manning’s formula.

Pipe Capacity: Hazen-Williams equation.

The following sections detail the results of the assessment for the key water management

infrastructure in each Mine Site catchment.

3.1.1 Spring Valley Catchment

Runoff generated within this catchment is intercepted at the catchment outlet by the Spring

Valley Freshwater Dam. The Spring Valley Freshwater Dam is an engineered structure

constructed during historic mining operations to capture runoff from the Spring Valley

catchment as well as act as balance storage for externally supplied process water.



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No design information for this structure was available for review, however analysis of supplied

topographic information indicates that, at a minimum, the storage capacity of this structure is

348ML. This volume is sufficient to contain the total modelled annual runoff up to 1% AEP

from this catchment of 146ML/yr.

It is noted that, the large surface area of this storage, coupled with its relatively shallow water

depth necessitates that process make up water for the Project would be preferentially sourced

from the Spring Valley Freshwater Dam to minimise evaporative losses and maximise use of

Mine Site water resources. As a result, the water level in the dam would typically be maintained

at a low level, maximising the available storage capacity

3.1.2 Mill Reclaim Catchment

As noted in Table 4, two key pieces of water management infrastructure are situated in the

catchment to capture and discharge runoff from this catchment.

Mill Reclaim Dam

The Mill Reclaim Dam is an engineered, lined structure situated at the downstream extent of the

Mill Reclaim catchment. This dam intercepts all overland flow from the upstream catchment.

Historically, this structure was hydraulically connected to the Ardwest/Wild Cherry Open Cut

via an open drain and surge dam, however, a 0.3m diameter concrete pipe was installed after

2003. That pipe discharges directly to the Ardwest/Wild Cherry Open Cut. The assessment of

this structure has therefore been undertaken to identify the Mill Reclaim Dam’s ability to act as

retarding/detention basin which ultimately discharges to the Ardwest/Wild Cherry Open Cut.

The volume of available storage for the assessment was calculated as being approximately

13,026m3 using the following data.

Base elevation of 268m AHD, represented by the cover over the discharge pipe.

Maximum elevation of 269m AHD, represented by as the crest of the dam.

Maximum surface area of 1.4ha.

Mill Reclaim Dam Discharge Pipe

This 0.3m diameter pipe was installed to replace the open channel and surge dam that had been

constructed to hydraulically connect the Mill Reclaim Dam to the Ardwest/Wild Cherry Open

Cut. The pipe inlet is protected from fouling by a cover, with the pipe invert approximately

1.5m below this cover. The discharge capacity of the pipe was calculated using the following

information:

pipe type 300mm reinforced concrete pipe.

upstream inlet elevation of 268m AHD.

upstream pipe invert of 266.5m AHD.

downstream pipe invert of 258.5m AHD.

pipe length of approximately 600m.



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3.1.2.1 Capacity Assessment

The capacity assessment utilised Intensity Frequency and Duration (IFD) data generated on 24

October 2016, using the Bureau of Meteorology IFD website using the methodology

established in AR&R (1987). The IFD data for the 1% AEP design rainfall event was used in

conjunction with a saturated catchment runoff coefficient of 0.331 to calculate the volume of

runoff generated from the 38ha Mill Reclaim catchment across a range of intensities and

durations. Table 4 presents the results of the calculations.

Table 4

Mill Reclaim Catchment 1% AEP Design Runoff Volumes

Duration Rainfall

(mm/hr)

Total Rainfall

(mm)

Coefficient of Runoff

Catchment Area (ha)

Total Inflow (m

3)

5 minutes 193 16 0.33 38 2 017

6 minutes 179 18 0.33 38 2 245

10 minutes 144 24 0.33 38 3 010

20 minutes 103 34 0.33 38 4 305

30 minutes 82 41 0.33 38 5 141

1 hour 53 53 0.33 38 6 621

2 hours 32 64 0.33 38 8 026

3 hours 23 70 0.33 38 8 803

6 hours 14 82 0.33 38 10 233

12 hours 8 96 0.33 38 12 038

24 hours 5 115 0.33 38 14 386

48 hours 3 135 0.33 38 16 914

72 hours 2 143 0.33 38 17 877

As shown in Table 4, the storage capacity of the Mill Reclaim Dam (13 026m2) is exceeded

once the event duration becomes greater than approximately 12 hours. However, this does not

consider discharge to the Ardwest/Wild Cherry Open Cut via the 0.3m discharge pipe.

Assuming no blockage or tailwater controls, the capacity of the discharge pipe was assessed

using the Hazen-Williams gravity flow equation (Hazen and Williams, 1905). The general form

of this equation is:

𝑄 = 0.285𝐶𝐷2.63 𝑆0.54

Whereby:

C = friction coefficient = 140 (dimensionless)

D = pipe diameter = 0.3m

S = slope = 0.01m/m

Q = pipe discharge = 0.16m3/s (564 m

3/hr)

1 Refer to Section 3.2 for justification of this coefficient of runoff



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Table 5 presents the results of 1% AEP hourly inflows (5 minute to 72 hour duration) versus

pipe discharge calculations.

Table 5

Mill Reclaim 1% AEP Hourly Discharge Volumes

Duration Total Inflow (m3)

Hourly Inflow (m

3)

Hourly Discharge (m

3)

Hours to Discharge Hourly

Inflow

5 minutes 2017 2017 564 4

6 minutes 2245 2245 564 4

10 minutes 3010 3010 564 5

20 minutes 4305 4305 564 8

30 minutes 5141 5141 564 9

1 hour 6621 6621 564 12

2 hours 8026 4013 564 7

3 hours 8803 2934 564 5

6 hours 10233 1705 564 3

12 hours 12038 1003 564 2

24 hours 14386 599 564 1

48 hours 16914 352 564 0.6

72 hours 17877 248 564 0.4

These results shown in Table 5 demonstrate that, when combined, the Mill Reclaim Dam and

the discharge pipe are able to manage runoff for all 1% AEP design rainfall events and prevent

off site discharge.

3.1.3 Processing Plant Catchment

Runoff generated within this catchment drains via overland flow to the Processing Plant

Detention Pond. This storage will be the primary balance storage for process water supply

which will be provided by a pump and pipe system from the Ardwest/Wild Cherry Open Cut.

The volume of the present Processing Plant Detention Pond void is approximately 9,625m3.

The capacity of the Processing Plant Detention Pond to contain rainfall and runoff events for a

range of annual rainfall AEP was calculated using the runoff coefficients presented in

Section 3.2. The storage available to contain the calculated runoff volumes was based on the

current void volume. Table 6 details the results of the calculations for the Processing Plant

Detention Pond.



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Table 6

Assessment of Processing Plant Detention Pond Capacity

AEP (%)

Total Inflow (m

3)

Available Storage (m

3)

Surplus / Deficit Capacity (m

3)

0.2 12 590 9,630 -2 965

0.5 11 970 9,630 -2 345

1 11 440 9,630 -1 815

2 10 850 9,630 -1 225

5 9 970 9,630 -345

10 9 170 9,630 455

20 8 220 9,630 1 405

50 4 190 9,630 5 435

80 3 170 9,630 6 455

90 2 690 9,630 6 935

95 2 330 9,630 7 295

99 1 740 9,630 7 885

As shown in Table 6, insufficient storage is available within the Processing Plant Detention

Pond to manage the 1% AEP runoff. Whilst this storage is proposed to be part of the process

water circuit and would have storage managed by pump and pipe, for the purposes of added

redundancy in the system, an open channel would be cut from the base of the embankment,

below the spillway of this storage, to the Ardwest/Wild Cherry Open Cut to return any spillway

discharge and avoid uncontrolled discharge to downstream systems.

3.1.4 Ardwest/Wild Cherry Open Cut Catchment

Runoff generated within this catchment internally drains via overland flow, however in the

northeastern section of the catchment, a perimeter drain was previously constructed to direct

runoff from an adjacent waste rock emplacement into the excavated mining void. The volume

of the Ardwest/Wild Cherry Open Cut was calculated as being approximately 7 120 000m3

.

The capacity of the Ardwest/Wild Cherry Open Cut to contain rainfall and runoff events for a

range of annual rainfall AEP was calculated using the runoff coefficients and contributing

catchment assumptions presented in Section 3.2. The storage available to contain the calculated

runoff volumes was based on the long-term average pit water level and the level of tailings at

the end of reprocessing operations (i.e. the final landform). Table 7 details the results of the

calculations.



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Table 7

Assessment of Ardwest/Wild Cherry Open Cut Capacity

AEP (%)

Total Inflow (m

3)

Long-term Final Landform


3)


3)


3)


3)

0.2 417,360 5,520,000 5,102,640 530,450 113,090

0.5 396,600 5,520,000 5,123,400 530,450 133,850

1 379,160 5,520,000 5,140,840 530,450 151,290

2 359,720 5,520,000 5,160,280 530,450 170,730

5 330,270 5,520,000 5,189,730 530,450 200,180

10 303,910 5,520,000 5,216,090 530,450 226,540

20 272,350 5,520,000 5,247,650 530,450 258,100

50 117,030 5,520,000 5,402,970 530,450 413,420

80 88,420 5,520,000 5,431,580 530,450 442,030

90 75,080 5,520,000 5,444,920 530,450 455,370

95 65,000 5,520,000 5,455,000 530,450 465,450

99 48,480 5,520,000 5,471,520 530,450 481,970

As shown in Table 7, sufficient storage is available to contain the 1% AEP annual runoff when

the long term average water level in the pit (approximately 190m AHD), representing a volume

of 1,600,000m3 is considered. In addition, sufficient storage remains available to contain the

1% AEP annual runoff when the final landform at the end of reprocessing and tailings

deposition operations is considered. It is noted that this calculation included the Mill Reclaim

catchment contribution for conservatism. It is also noted that, sufficient storage remains

available for annual rainfall and runoff AEP that exceed the assessment criteria (0.2% and 0.5%

AEP).

3.1.5 White Crystal Open Cut Catchment

Runoff generated within this catchment internally drains via overland flow. An earthen bund,

approximately 5m in height has been placed across the old haul route to prevent uncontrolled

inflow/discharge from this catchment. The volume of the present White Crystal Open Cut void

is approximately 237,000m3. The capacity of the White Crystal Open Cut to contain rainfall and

runoff events for a range of annual rainfall AEP was calculated using the runoff coefficients

presented in Section 3.2. The storage available to contain the calculated runoff volumes was

based on the current void volume. Drainage of the final landform would be directed towards the

Ardwest/Wild Cherry Open Cut via the existing Stackpool Open Cut drain with this

arrangement considered in calculations presented in Section 3.1.3. Table 8 details the results of

the calculations for the White Crystal Open Cut prior to the construction of the final landform.



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Table 8

Assessment of Wild Crystal Open Cut Capacity

AEP (%) Total Inflow (m

3)


3)


3)

0.2 23,660 237,000 213,340

0.5 22,490 237,000 214,510

1 21,500 237,000 215,500

2 20,390 237,000 216,610

5 18,720 237,000 218,280

10 17,230 237,000 219,770

20 15,440 237,000 221,560

50 7,360 237,000 229,640

80 5,560 237,000 231,440

90 4,720 237,000 232,280

95 4,090 237,000 232,910

99 3,050 237,000 233,950

As shown in Table 8, sufficient storage is available to contain the 1% AEP annual runoff when

the current void volume of 237,00m3 is considered. It is also noted that, sufficient storage

remains available for annual rainfall and runoff AEP that exceeds the assessment criteria (0.2%

and 0.5% AEP).

3.1.6 Stackpool Open Cut Catchment

Runoff generated within this catchment internally drains to an open channel perimeter drain

that discharges into the Stackpool Open Cut void. The Stackpool Open Cut is hydraulically

connected to the Ardwest/ Wild Cherry Open Cut via two former mining exploration drill holes

located in the walls of the open cut at an elevation of approximately 251m AHD. The capacity

of the channel to convey flow was established via a two-step process whereby:

peak catchment discharge was calculated using the methodology presented in the

“Road Drainage Manual” (TMR, 2013) for calculation of peak flows known as

the “Rational Method”; and

channel capacity was assessed using the Manning Equation (Manning, 1891) for

open channel flow.

Peak Catchment Discharge

As noted in Section 3.1.5, peak catchment discharge was calculated using the empirical

“Rational Method” which uses catchment geometry and IFD coefficients obtained from Bureau

of Meteorology IFD on 24 October 2016. It is noted that, for conservatism, the calculations

included runoff contributions from the White Crystal Open Cut catchment based on the free

draining final landform that is proposed. The general form of this equation is:



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𝑄𝑦 = 𝑘𝐶𝑦𝐼𝑡𝑐,𝑦𝐴

Whereby:

Whereby:

𝑄𝑦 = peak discharge (m3/s) for design rainfall of y ARI = various

𝑘 = area conversion factor (0.278 for km2 and 0.00278 for ha) = 0.00278

𝐶𝑦= coefficient of runoff dimensionless for deign rainfall of y ARI = various

𝐼𝑡𝑐,𝑦 = rainfall intensity (I, mm/hr) for design duration (tc) of y ARI = various

𝐴= catchment area (ha or km2) = 25ha

The design duration is established by calculating the time of concentration for the catchment

using the Bransby-Williams formula (TMR, 2013). The general form of this equation is:

𝑡𝑐 = 𝐹𝐿

𝐴0.1𝑆𝑒0.2

Whereby:

𝐼𝑡𝑐 = time of concentration (minutes) = 30 minutes

𝐹= area conversion factor (58.5 for km2 and 92.7 for ha) = 92.7

𝐿= length (km) of main flow path from headwater to catchment outlet = 0.75km

𝐴= catchment area (ha or km2) = 25ha

𝑆𝑒= equal area slope of catchment (m/km) = 15.7 m/km

Table 9 presents the results of the calculated peak catchment discharge for a range of ARI.

Table 9

Stackpool Open Cut Catchment Design Rainfall Intensities and Calculated Peak Discharges

ARI in years Coefficient of Runoff

1

Time of Concentration

(minutes)

Rainfall Intensity (mm/hr)

Peak Discharge

(m3/second)

1 0.65 30 24 1.1

2 0.65 30 31 1.4

5 0.65 30 43 2.0

10 0.65 30 51 2.3

20 0.73 30 60 3.0

50 0.81 30 73 4.1

100 0.85 30 84 4.9

Note: 1 Estimation of coefficient of runoff for rural catchments (Table 5.9.1(a) TMR, 2013). Adjustment Factors for Runoff Coefficients for Other Average Recurrence Intervals (Table 5.9.1(b) TMR, 2013)



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Capacity Assessment

The capacity for the open channel to contain and convey the design discharge to the Stackpool

Open Cut was undertaken for three channel cross sections (upstream, mid chainage and

downstream) using the Manning equation (Manning, 1891) for open channel flow. The general

form of this equation is:

𝑄 = (1.00

𝑛) 𝐴𝑅0.66√𝑆

Whereby:

𝑄 = flow rate (m3/s) = 4.9m

3/s

𝑛 = Manning’s Roughness Coefficient(for stony channels) = 0.035

𝐴 = cross-sectional flow area (m2) = various

𝑅 = hydraulic radius (m) = various

𝑆 = slope (m/m) = 0.02m/m

The results of the assessment are presented in Table 10.

Table 10

Stackpool Open Cut Perimeter Drain Geometry, Peak Discharge Water Levels and Capacity

Location Channel Invert

(m AHD)

Top of Bank (m AHD)

Design Flow Discharge Water

Level (m AHD)

Peak Discharge Capacity

(m3/second)

Upstream 256.0 256.9 256.2 63

Mid-chainage 255.4 256.9 255.7 83

Downstream 255.3 259.3 255.8 195

The results of the assessment indicate that the open channel draining the Stackpool Open Cut

catchment has sufficient capacity to convey discharge greater than the assessment criterion of

the 1% AEP rainfall event.

3.1.7 Summary

Empirical calculations were used to assess the capacity of site water management infrastructure

to manage runoff volumes and peak flows for the 1% AEP (100yr ARI) design event. The

calculations indicate that the site water management infrastructure meets the performance

criteria and has sufficient capacity to manage runoff from Mine Site catchments internally, thus

preventing discharge of mining disturbed or sediment laden runoff into receiving systems.



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3.2 WATER BALANCE

A water balance model was developed for the Proposal to establish the capacity of Mine Site

water management infrastructure to meet the water demands of the Project across a range of

production scenarios representing reprocessing rates of 30tph, 60tph, 120tph and 180tph. The

key inputs and outputs of the site water balance are presented in Figure 5.

Figure 5 Site Water Balance Schematic


Transfer of water around the Mine Site would be facilitated by a pump and pipe system that

would involve the following. Numbered references relate to those identified in Figure 5.

Transfer of reprocessed tailings to the Ardwest/Wild Cherry Open Cut via pump and pipe;

Return transfer of decant water from the Ardwest/Wild Cherry Open Cut via 1.

pump and pipe to the process water detention pond;

Supply of process water to the processing plant from the process water detention 2.

pond via pump and pipe;

Transfer of water from the Spring Valley Freshwater Dam via pump and pipe to 3.

the Mill Reclaim Dam (for direct discharge to the Ardwest/Wild Cherry Open

Cut); and

Transfer of water from the external sources to meet process water demand should 4.

climatic conditions require.

Transfer of water from the external sources to meet process water demand should 5.

climatic conditions require.



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As shown in Figure 5 the key elements of the site water balance model are as follows.

Inputs rainfall/runoff and external supply.

Throughput recovery of process water.

Output evaporation, dust suppression and process make up water demand.

A description of each key element and how each is represented in the model is discussed below.

3.2.1 Inputs

3.2.1.1 Rainfall

Rainfall data for the Mine Site was sourced from the Scientific Information for Land Owners

(SILO) database, managed by the Queensland Department of Science, Information Technology

and Innovation (DSITI). The program uses historic Bureau of Meteorology datasets and

interpolation techniques to generate continuous daily time step synthetic rainfall and other

climate data for any given location in Australia. The SILO dataset for the period 1 January 1889

to 9 October 2016 was generated for the Mine Site (Latitude -34.35, Longitude 146.85) on 10

October 2016.

The data was then processed using Cunnane’s plotting position formula (Cunnane, 1978) and

Log Pearson Type 3 (LPIII) interpolation (AR&R 1987 and 2016) to establish rainfall events

with a 1 in Y AEP for analysis in the model.

The results of the analysis was assessed for goodness of fit of the rainfall distribution curve

which is presented graphically in Figure 6 below.

Figure 6 Rainfall Distribution for the Mine Site



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Based on the analysis the rainfall depths for the Mine Site across a range of AEP are presented

in Table 11.

Table 11

Annual Exceedance Probability Rainfall Depths at the Mine Site

Annual Exceedance Probability (%) Rainfall (mm/yr)

0.2 896

0.1 852

1 814

2 772

5 709

10 653

20 585

50 460

80 348

90 295

95 256

99 191

Annual rainfall data was then assessed to identify individual years with similar rainfall to the

interpolated AEP values for daily time step water balance modelling.

3.2.1.2 External Supply

Arbitrary base volumes were set for the two primary site water storages (Ardwest/Wild Cherry

Open Cut and Spring Valley Freshwater Dam) in the model. Once the model reached these base

volumes, external supply was triggered in order to identify the volumes of water required to

supplement site water in meeting process water demand.

3.2.2 Throughput

The recovery of process water from the sub aqueous deposition of reprocessed tailings was

estimated to be approximately 60% of the total volume required for reprocessing.

3.2.3 Output

3.2.3.1 Evaporation

Morton’s shallow lake evaporation is a calculated climate variable provided with the SILO

dataset on a daily time step that reflects evaporation rates from shallow water bodies such as

dams and water storages. This variable was extracted from the SILO dataset for the identified

representative rainfall years and used in the daily time step water balance modelling.



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3.2.3.2 Dust Suppression

The volumes of site water used to manage dust generated as a consequence of the Project were

calculated using the equation presented in “Air Pollution Engineering Manual” (A&WMA,

1992), the general form of the equation is:

𝑖 =0.8𝑝𝑑𝑡

100 − 𝐶

Whereby:

𝑖 = application intensity (L/m2) = varies according to production scenario

𝑝 = average daily evaporation rate (mm/hr) = varies (0.7mm/hr summer, 0.4mm/hr rest of year)

𝑑 = average hourly traffic rate = varies according to production scenario

𝑡 = time between application (hr) = 2 hours

𝐶 = control efficiency (%) = 75%

For the purposes of conservatism, the volumes of water required for dust suppression were

included in the model as a fixed daily time step element. The actual volumes required for this

activity will likely vary on a daily basis and be dependent upon climatic factors.

3.2.3.3 Process Water Demand

The volume of water required to meet processing demand was fixed at 4,000L per tonne of

reprocessed tailings (4m3/t) in accordance with guidance from the reprocessing plant

manufacturer. Process water demand in the model therefore varies dependent upon the

production scenario modelled.

3.2.4 Model Set Up

The water balance model was established using a spreadsheet that calculated inputs,

throughputs and outputs on a daily time step for representative rainfall years similar to 1% AEP

up to 99% AEP. Surface area available for evaporation was established based on the carryover

volume in storage from the previous time step. The modelling was based on the following

assumptions:

During years of below average rainfall (>50% AEP), no discharge to the

Ardwest/Wild Cherry Open Cut occurs from the Stackpool Open Cut.

During years of below average rainfall (>50% AEP), the coefficient of runoff

from disturbed catchments is 0.2. This coefficient was compared to the coefficient

(0.126) calculated using the regression equations presented in Boughton and

Chiew (2006) for natural catchments in the Murray Darling Basin and is

considered reasonable for highly disturbed catchments essentially devoid of

vegetation.



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The coefficient of runoff for the naturally vegetated areas of the Spring Valley

Catchment of 0.126 was that established using the regression equations presented

in Boughton and Chiew (2006).

During years of above average rainfall (<50% AEP), discharge to the

Ardwest/Wild Cherry Open Cut occurs from the Stackpool Open Cut.

During years of above average rainfall (<50% AEP), the coefficient of runoff

from disturbed catchments is 0.33. This is considered reasonable for a saturated

catchment and was estimated using changes in pit lake levels and rainfall over the

period 5 July 2016 to 10 November 2016.

Two model run series for the full range of AEP and production scenarios were

completed;

– Scenario 1 run series was commenced with initial storage volumes of

1 630 600m3 in Ardwest/Wild Cherry Open Cut, representing the observed pit

water level after three years of below average rainfall and 83,000m3 in Spring

Valley Freshwater Dam, which is representative of the 50% AEP modelled

catchment inflows from rainfall.

– Scenario 2 run series was commenced with initial storage volumes of

199 000m3 in Ardwest/Wild Cherry Open Cut, and 83 000m

3 in Spring Valley

Freshwater Dam, which are representative of the 50% AEP modelled

catchment inflows from rainfall.

3.2.5 Model Results

Tables 12, 13, 14 and 15 present the results of the water balance model for a range of AEP and

production scenarios.

Table 12

Results of Water Balance Modelling for Ardlethan Tailings Reprocessing and Rehabilitation Project: 30tph Production

AEP

(%)

Representative year

Annual Rainfall (mm/yr)

Scenario 1 Scenario 2

Demand

(ML/yr)

Deficit (ML/yr)

Demand

(ML/yr)

Deficit (ML/yr)

1 1894 804 575 0 536 0

2 1974 754 567 0 526 0

5 1992 715 554 0 510 0

10 1955 650 556 0 513 0

20 1988 582 562 0 511 0

50 1964 459 550 0 492 0

80 1991 353 547 0 493 74

90 2004 300 548 0 494 92

99 1967 185 546 0 493 129



Report No. 754/08

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Table 13


AEP (%)

Representative year



Demand (ML/yr)

Deficit (ML/yr)

Demand (ML/yr)

Deficit (ML/yr)

1 1894 804 992 0 922 96

2 1974 754 983 0 918 125

5 1992 715 971 0 911 143

10 1955 650 972 0 910 185

20 1988 582 978 0 915 233

50 1964 459 966 0 909 384

80 1991 353 962 0 913 494

90 2004 300 964 0 914 512

99 1967 185 962 0 913 549

Table 14


AEP (%)

Representative year



Demand (ML/yr)

Deficit (ML/yr)

Demand (ML/yr)

Deficit (ML/yr)

1 1894 804 1824 0 1759 933

2 1974 754 1816 0 1757 964

5 1992 715 1805 0 1753 985

10 1955 650 1806 0 1752 1026

20 1988 582 1811 0 1759 1077

50 1964 459 1798 0 1754 1229

80 1991 353 1793 0 1759 1339

90 2004 300 1794 0 1760 1358

99 1967 185 1792 0 1759 1395

Table 15


AEP

(%)

Representative year



Demand

(ML/yr)

Deficit (ML/yr)

Demand

(ML/yr)

Deficit (ML/yr)

1 1894 804 2637 380 2600 1775

2 1974 754 2630 405 2598 1805

5 1992 715 2624 424 2596 1828

10 1955 650 2624 467 2595 1870

20 1988 582 2630 516 2602 1920

50 1964 459 2622 665 2597 2072

80 1991 353 2627 776 2602 2183

90 2004 300 2628 794 2604 2202

99 1967 185 2626 830 2602 2239



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Based on the results presented above and, provided initial conditions are met, the following

conclusions may be drawn from the water balance modelling:

Due to the variable geometry of the Ardwest/Wild Cherry Open Cut, the volume

of water retained in storage as a result of production demand and/or initial

conditions, significantly influences the surface area available for evaporation and

overall water demand.

Scenario 1, site water demand is met by rainfall up to 99% AEP for production up

to and including 120tph.

Scenario 2, site water demand is met by rainfall up to 80% AEP at a production

rate of 30tph.

Figure 7 displays the range of inputs, outputs and throughputs for all proposed rates of

production and annual rainfall for 1% AEP to 99% AEP.

3.3 WATER QUALITY

The potential impacts to water quality in watercourses downstream of the Mine Site would be

limited as the site water management infrastructure is able to manage runoff generated in the

1% AEP rainfall event and prevent discharge of potentially disturbed or sediment laden runoff

from the Mine Site.

4. M I T I G AT I O N M E AS U R E S

The measures detailed below are proposed as mitigation strategies to manage any potential

impacts to surface water resources as a consequence of the Project.

Obtain supplementary water supply of up to approximately 2.2GL would need to

be obtained from external sources. It is recommended that the Applicant obtain

suitable water licences under the Water Sharing Plan for the Murrumbidgee

Unregulated and Alluvial Water Sources 2012 for transfer to the Mine Site via the

existing Grong Grong Pipeline should production be increased to 180tph, External

water sources have historically been utilised to supplement site water supply via

the Grong Grong pipeline that discharges into the Spring Valley Freshwater Dam.

Develop an integrated Water Management Plan that would be implemented to:

– monitor pH and electrical conductivity of water held in site storages monthly

to detect any change in the composition of Mine Site runoff;

– ensure the satisfactory operation of all water management structures; and

– document water management practices including any required responses in the

Site’s Annual Environmental Monitoring Review.



Report No. 754/08

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Figure 7 Water Balance

Figure dated 16/12/16. Inserted 16/12/16.



Report No. 754/08

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5. R E F E RE N C ES

Pilgrim D.H (Editor In-Chief) (1987) “Australian Rainfall and Runoff: A Guide to Flood

Estimation”, Volume 1 Institution of Engineers, Australia.

Ball J, Babister M, Nathan R, Weeks W, Weinmann E, Retallick M, Testoni I, (Editors)

(2016). “Australian Rainfall and Runoff: A Guide to Flood Estimation”,

Commonwealth of Australia.

Boughton W and Chiew F. (20060. “Estimating Runoff in Ungauged Catchments from

Rainfall, PET and the AWBM Model”, Environmental and Modelling Software,

Volume 22. pp 476-487. Elsevier, Philadelphia.

Cunnane C. (1978). “Unbiased Plotting Positions – A Review”. Journal of Hydrology. Volume

37.pp 205-222. Elsevier, Philadelphia.

Williams G. S and Hazen A. (1905). “Hydraulic Tables: Showing the loss of head due to the

friction of water flowing in pipes, aqueducts, sewers, etc. and the discharge over

weirs” (1st Edition), John Wiley and Sons, New York

Queensland Department of Transport and Main Roads (2013). “Road Drainage Design

Manual”. State of Queensland.

Manning, R. (1891). "On the flow of water in open channels and pipes". Transactions of the

Institution of Civil Engineers of Ireland. Vol 20: 161–207

https://en.wikipedia.org/wiki/Robert_Manning_(engineer)



Report No. 754/08

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