appendix f water management plan (updated)€¦ · grants lithium project environmental impact...

Grants Lithium ProjectEnvironmental Impact Statement – Supplement

APPENDIX F WATER MANAGEMENT PLAN (UPDATED)

This document was originally submitted as Appendix C to the Draft EIS.

This document replaces all previous versions.

Prepared by EcOz Environmental Consultants for Core ExplorationDoc No. 170579

GRANTS LITHIUM PROJECT

Water Management Plan

Grants Lithium ProjectWater Management Plan

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DOCUMENT CONTROL RECORD

Job EZ18086

Document ID 170579

Author(s) Emma Smith

Reviewer (s) Kylie Welch, EcOz (internal review), Rohan Ash, Environmental Auditor, Out-Task Environmental (independent review)

Approver Kylie Welch

Date original approved 28 Oct 2018

Revision History

Revision Date Details Approver

1 28/10/2018 Submitted for independent review K. Welch

2 15/3/2019 Independent review comments addressed and updated with latest mine design K. Welch

Recipients are responsible for eliminating all superseded documents in their possession.

EcOz Pty Ltd.ABN: 81 143 989 039Winlow House, 3rd Floor75 Woods Street DARWIN NT 0800GPO Box 381, Darwin NT 0800

Telephone: +61 8 8981 1100Facsimile: +61 8 8981 1102Email: [email protected]: www.ecoz.com.au

RELIANCE, USES and LIMITATIONSThis report is copyright and is to be used only for its intended purpose by the intended recipient, and is not to be copied or used in any other way. The report may be relied upon for its intended purpose within the limits of the following disclaimer.

This study, report and analyses have been based on the information available to EcOz Environmental Consultants at the time of preparation. EcOz Environmental Consultants accepts responsibility for the report and its conclusions to the extent that the information was sufficient and accurate at the time of preparation. EcOz Environmental Consultants does not take responsibility for errors and omissions due to incorrect information or information not available to EcOz Environmental Consultants at the time of preparation of the study, report or analyses.

mailto:[email protected]

http://www.ecoz.com.au/


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TABLE OF CONTENTS

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

1.1 Purpose and Scope...........................................................................................................................1

1.1.1 EIS Terms of Reference requirements .............................................................................................11.1.2 WMP Scope......................................................................................................................................41.1.3 Independent peer review ..................................................................................................................6

2 PROJECT DETAILS RELEVANT TO WATER MANAGEMENT...................................................................7

2.1 Project overview................................................................................................................................7

2.2 Project components..........................................................................................................................8

2.3 Mining schedule ................................................................................................................................9

2.4 Water requirements, sources and storages ...................................................................................9

2.4.1 Internal mine site water holding dams ............................................................................................112.4.2 Pit dewatering .................................................................................................................................14

2.5 Erosion and sediment control and flood prevention ...................................................................16

2.5.1 General mine site ESCP measures ................................................................................................162.5.2 Sediment basin design and operation ............................................................................................16

2.6 Ore processing ................................................................................................................................20

2.6.1 Additives .........................................................................................................................................20

2.7 Waste rock dump and tailings storage facility .............................................................................21

2.7.1 Waste rock dump............................................................................................................................212.7.2 Tailings storage facility ...................................................................................................................212.7.3 Waste rock characterisation ...........................................................................................................22

2.8 Non-mineral waste and hazardous materials ...............................................................................24

2.8.1 Predicted waste streams ................................................................................................................242.8.2 Hazardous materials.......................................................................................................................242.8.3 Sewage treatment...........................................................................................................................252.8.4 Product storage and handling.........................................................................................................25

3 CURRENT CONDITIONS.............................................................................................................................26

3.1 Rainfall and evaporation.................................................................................................................26

3.2 Surface water...................................................................................................................................27

3.2.1 Catchments and drainage...............................................................................................................273.2.2 Topography and soils .....................................................................................................................313.2.3 Surface water environmental and social values .............................................................................32

3.3 Groundwater ....................................................................................................................................35

3.3.1 Groundwater aquifers and flows .....................................................................................................353.3.2 Groundwater environmental and social values...............................................................................38

4 HYDROLOGICAL POTENTIAL IMPACTS ..................................................................................................41

4.1 Surface water storage requirements .............................................................................................41

4.2 Potential impacts from surface water extraction .........................................................................41

4.2.1 Darwin Harbour, West Arm catchment ...........................................................................................44


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4.2.2 Bynoe Harbour catchment ..............................................................................................................44

4.3 Mine site flood inundation modelling............................................................................................45

4.4 Potential impacts from increased flows from discharge.............................................................46

5 GROUNDWATER POTENTIAL IMPACTS ..................................................................................................48

5.1 Modelled pit inflows and impacts to existing groundwater aquifers from mining ...................48

5.2 Localised mounding of groundwater ............................................................................................48

5.3 Particle tracking ..............................................................................................................................49

6 BASELINE SURFACE WATER QUALITY...................................................................................................51

6.1 Baseline surface water quality monitoring ...................................................................................51

6.1.1 Monitoring sites...............................................................................................................................516.1.2 Monitoring undertaken ....................................................................................................................54

6.2 Baseline surface water quality results ..........................................................................................54

6.2.1 Field parameters.............................................................................................................................556.2.2 Laboratory parameters ...................................................................................................................56

6.3 Baseline surface water quality summary and potential impacts................................................58

6.3.1 Mine footprint sites..........................................................................................................................586.3.2 Observation Hill Dam and BP33 sites.............................................................................................59

7 BASELINE GROUNDWATER QUALITY.....................................................................................................65

7.1 Baseline groundwater quality monitoring ....................................................................................65

7.1.1 Monitoring bores .............................................................................................................................657.1.2 Monitoring undertaken ....................................................................................................................65

7.2 Baseline groundwater quality results ...........................................................................................65

7.2.1 Field parameters.............................................................................................................................667.2.2 Laboratory parameters ...................................................................................................................66

7.3 Baseline groundwater quality summary and potential impacts .................................................69

7.3.1 BCF aquifer.....................................................................................................................................697.3.2 Laterite surface aquifer ...................................................................................................................70

7.4 Predicted pit water quality and discharge water quality .............................................................79

8 RISK ASSESSMENT....................................................................................................................................82

8.1 Identify hazards and rank risks......................................................................................................82

8.2 Mitigation and management...........................................................................................................84

8.3 Residual risk ....................................................................................................................................84

9 MANAGEMENT MEASURES.......................................................................................................................88

10 WATER QUALITY MONITORING PLAN .................................................................................................96

10.1 Surface water quality monitoring program...................................................................................97

10.1.1 Surface water quality monitoring sites ............................................................................................9710.1.2 Sampling frequency ......................................................................................................................10110.1.3 Parameters measured ..................................................................................................................10110.1.4 Assessment criteria ......................................................................................................................102

10.2 Groundwater quality monitoring program ..................................................................................103


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10.2.1 Groundwater monitoring bores .....................................................................................................10310.2.2 Sampling frequency ......................................................................................................................10410.2.3 Parameters measured ..................................................................................................................10510.2.4 Assessment criteria ......................................................................................................................105

10.3 Recording and reporting ..............................................................................................................105

11 INFORMATION/KNOWLEDGE GAPS ...................................................................................................106

11.1 Identification of information/knowledge gaps............................................................................106

11.2 Filling information/knowledge gaps ............................................................................................107

12 FUTURE WMP UPDATES......................................................................................................................108

13 REFERENCES........................................................................................................................................109

TablesTable 2-1. Project components. ............................................................................................................................8Table 2-2. Mining schedule. ..................................................................................................................................9Table 2-3. Modelled discharges from MWD1 for average rainfall years (50th percentile) over life of mine compared to flow volumes in receiving stream reporting to Catch-5 DS...............................................................................12Table 2-4. Modelled volumes of pit water to be removed (dewatered) per month over life of mine assuming July 2019 start date and average rainfall conditions....................................................................................................15Table 2-5. Sediment basin design criteria. ..........................................................................................................17Table 2-6. Summary of waste rock characteristics...............................................................................................22Table 3-1. Sub-catchment areas and slope. .......................................................................................................28Table 3-2. Groundwater monitoring bore details. ................................................................................................35Table 4-1. Modelled monthly reduction in streamflow from mine site catchment (average rainfall year)............43Table 4-2. Modelled monthly reduction in streamflow from Observation Hill Dam catchment compared to pre-dam conditions (average rainfall year). ................................................................................................................43Table 4-3. Percent increase in streamflows downstream of MWD1 from discharge...........................................47Table 6-1. Baseline surface water quality monitoring undertaken.......................................................................54Table 6-2. Baseline surface water quality monitoring results, field parameters. .................................................61Table 6-3. Baseline surface water quality monitoring results, major anions and cations. ...................................62Table 6-4. Baseline surface water quality monitoring results, dissolved metals. ................................................62Table 6-5. Baseline surface water quality monitoring results, nutrients. .............................................................63Table 7-1. Baseline groundwater quality monitoring undertaken. .......................................................................65Table 7-2. Baseline groundwater quality monitoring results, field parameters....................................................72Table 7-3. Baseline groundwater quality monitoring results, major anions and cations......................................73Table 7-4. Baseline groundwater quality monitoring results, dissolved metals. ..................................................74Table 7-5. Baseline groundwater quality monitoring results, nutrients................................................................75Table 7-6. Comparison of groundwater quality with surface water quality (mine footprint sites). .......................80Table 8-1. Likelihood categories adopted in risk assessment..............................................................................82Table 8-2. Consequence categories adopted in risk assessment........................................................................83Table 8-3. Risk matrix adopted in risk assessment..............................................................................................84Table 8-4. Summary of risk assessment for Hydrological Process and Inland Water Environmental Quality factors.............................................................................................................................................................................85Table 9-1. Water management framework for construction/operations phase.....................................................89Table 10-1. Surface water quality monitoring site details....................................................................................98Table 10-2. Surface water and groundwater quality field and laboratory parameters and field notes. .............101Table 10-3. Water quality objectives / trigger values (assessment criteria) for both surface and groundwater quality. ................................................................................................................................................................103Table 10-4. Groundwater quality monitoring bore details..................................................................................104


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FiguresFigure 1-1. Map of Grants Lithium Project location. ...............................................................................................2Figure 1-2. Map of mine site layout. ......................................................................................................................3Figure 1-3. Map of proposed surface water storages............................................................................................5Figure 2-1. Cross section of ore body within the Burrell Creek Formation (BCF) and open pit shell. ...................7Figure 2-2. Flow diagram of project water inputs, outputs, tasks and storages. .................................................10Figure 2-3. Modelled pit inflows during life of mine. ............................................................................................14Figure 2-4. Map of erosion and sediment controls. .............................................................................................19Figure 3-1. Average monthly rainfall and potential evaporation generated for the project site from the SILO database; records 1900 to 2018...........................................................................................................................26Figure 3-2. Map of project area catchments........................................................................................................29Figure 3-3. Map of mine footprint sub-catchments..............................................................................................30Figure 3-4. Map of surface water, groundwater and aquatic ecology monitoring sites. ......................................34Figure 3-5. Standing water levels (metres below ground level) measured in the six groundwater monitoring bores..............................................................................................................................................................................37Figure 3-6. Hydrograph for shallow laterite aquifer from logger installed in Bore GWB10..................................38Figure 3-7. GDEs mapped for the project area and surrounds (from national-scale dataset available through BoM website The Groundwater Dependent Ecosystems Atlas). ..................................................................................40Figure 5-1. Results of modelling showing the direction and spread of seepage from the WRD. ........................50Figure 6-1. Photos of surface water monitoring sites around mine footprint taken 15 February 2017................52Figure 6-2. Photos of surface water monitoring sites relating to BP 33 historic open cut mining pit taken 15 February 2017. .....................................................................................................................................................53Figure 7-1. Piper plot displaying Grants Lithium project groundwater analyses categorised according to aquifer depth. ...................................................................................................................................................................76Figure 7-2. Dry season (June 2017) stiff plots for Grants Lithium Project groundwater bores............................77Figure 7-3. Wet season (January 2018) stiff plots for Grants Lithium Project groundwater bores......................78Figure 10-1. Map of future surface and groundwater monitoring sites..............................................................100

AppendicesAppendix A Water Balance

Appendix B Independent Reviewer Biographies

Appendix C Independent Peer Review Comments

Appendix D Response to Independent Peer Review Comments

Appendix E TPH/TRH and BTEXN baseline surface water and groundwater quality results


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ABBREVIATIONS AND DEFINITIONS

AEP annual exceedance probabilityAMD acid, saline or metalliferous drainageARI average recurrence intervalAS Australian Standard AS/NZ Australian and New Zealand StandardsASS acid sulfate soils BoM Bureau of Meteorology BTEXN Benzene, Toluene, Ethylbenzene, Xylene, NaphthaleneDMS dense medium separationDO dissolved oxygenDPIR Department of Primary Industry and Resources (Northern Territory)DSO direct shipping oreEC electrical conductivityEMP Environmental Management PlanEIS Environmental Impact StatementESCP Erosion and Sediment Control PlanEY exceedance per yearGDE groundwater dependent ecosystemGL gigalitre (109 litres)ha hectareIECA International Erosion Control AssociationIFD Intensity-Frequency-Duration design rainfallsK Hydraulic conductivitykL kilolitre (103 litres)LOR limit of reporting for laboratory analysismAHD metres above Australian Height DatummBGL metres below ground levelMCA Minerals Council of AustraliaMCP Mine Closure PlanML megalitre (106 litres)ML/a megalitre per yearML Mineral Lease (granted)MMP Mining Management Plan Mt million tonnesNATA National Association of Testing Authorities AustraliaNOI Notice of Intent NT Northern TerritoryNT EPA Northern Territory Environment Protection AuthorityORP oxidation reduction potentialpH power of HydrogenProject/ Proposal Core Exploration Limited’s Grants Lithium Project


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Q design flood peak discharge

RFFE Regional Flood Frequency Estimate: method developed by Engineers Australia to estimate design flood peak discharge (Q)

SILO Scientific Information for Land Owners online climate database

SSTV’sSite Specific Trigger Values: contaminant concentrations derived using the ANZECC 2000a Guidelines methodology above-which water quality impacts may be occurring and investigation of the cause is recommended.

SWL standing water levelTDS total dissolved solids

TPH/TRH Total Petroleum Hydrocarbons NEPM 1999 suite / Total Recoverable Hydrocarbons NEPM 2013 suite

TSS total suspended solids

ToR Terms of Reference for the Preparation of and Environmental Impact Statement, Grants Lithium Project

TSF tailings storage facilityRoM Run of Mine padRWD raw water damWDL Waste Discharge LicenceWMP Water Management PlanWQMP Water Quality Monitoring PlanWRD waste rock dump


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1 INTRODUCTION

Core Exploration Limited (Core) propose to develop the Grants Lithium Project (the project) mining operation located approximately 24 km south of Darwin, and 22 km north-west of Berry Springs (Figure 1-1). The targeted ore body is a near-vertical pegmatite intrusion, rich in the lithium-bearing mineral spodumene. The ore body will be mined via an open-cut pit using drill and blast methods, and processed on site by crushing, screening and water-based dense medium separation (DMS), to produce a concentrate for transport via road to Darwin Port for export. Waste rock from the pit will placed in an onsite waste rock dump (WRD), and waste from processing will be placed in a tailings storage facility (TSF) contained within the WRD. Mine life is expected to be around 35 months followed by rehabilitation and closure. Figure 1-2 shows the general mine site layout.

This Water Management Plan (WMP) covers all water usage, and surface and groundwater interactions of the proposed mining operations. It currently forms part of the Environmental Impact Statement (EIS) submitted to the Northern Territory Environment Protection Authority (NT EPA) for project assessment under the Environmental Assessment Act. Prior to operations commencing, it will be updated to incorporate any water-related recommendations issued by the NT EPA resulting from the EIS process, and become part of the Project’s Mining Management Plan (MMP), as required under the NT Mining Management Act. This WMP will be updated regularly throughout operations to reflect on-ground activities as mining progresses.

1.1 Purpose and Scope

1.1.1 EIS Terms of Reference requirements

Information required in the EIS by the NT EPA is set out in the Terms of Reference for the Preparation of an Environmental Impact Statement (ToR) issued to Core for the Grants Lithium Project in August 2018. As requested in the ToR, and required for the MMP, this WMP is presented in accordance with the NT Department of Primary Industry and Resources Template for the Preparation of a Mining Management Plan, Section 6 Water Management (DPIR 2017), and covers the water-related information requested in ToR sections:

2 Description of the Proposal, Section 2.3.6 Water

4 Preliminary key environmental factors, Section 4.2 Water, which includes the identified key environmental factors: 4.2.1 Inland water environmental quality and 4.2.2 Hydrological processes

The NT EPA’s objectives for the two key environmental factors listed above are respectively:

1. Maintain the quality of groundwater and surface water so that environmental values including ecological health, land uses, and the welfare and amenity of people are protected.

2. Maintain the hydrological regimes of groundwater and surface water so that environmental values are protected.

This WMP aims to assist in achieving these objectives for the project.

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Figure 1-1. Map of Grants Lithium Project location

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Figure 1-2. Map of mine site layout

LegendMineral lease (application)

Mine site footprint

Water supply infrastructure

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1.1.2 WMP Scope

The scope of this WMP includes all:

Water aspects of mining operations within Mineral Lease ML31726 (referred to as mine site/mine area/mine footprint); i.e. that associated with the open pit, WRD, TSF, Run of Mine (RoM) pad, processing plant, access/haul roads, water storages and holding dams, stormwater drains and sediment basins, ablutions and office facilities (Figure 1-2).

Water stores and infrastructure located outside ML31726 within Ancillary Mineral Leases (to be applied for and issued prior to commencement of mining); i.e. Mine Site Dam (MSD), Observation Hill Dam and pipeline linking Observation Hill Dam to the mine site (Figure 1-3).

Surface and groundwater systems influenced by mining operations, including those up-gradient and down-gradient of the mine area, and down-gradient of Observation Hill Dam and MSD.

This WMP does not cover the transport route (i.e. Cox Peninsula Road and Stuart Highway) for product trucked to Darwin’s East Arm Port or Core’s lease area within the Port. The stockpiling and ship loading of product will be managed in accordance with Darwin Port requirements.

In order to cover all relevant ToR and MMP requirements, this WMP includes:

Project details relevant to water management

A description of existing surface water and groundwater systems

Baseline surface and groundwater water quality results

Identified potential impacts of the project on surface and groundwater quality and flows, and on receiving ecosystems and water users

A risk assessment identifying hazards, ranking risks, and outlining management and mitigation measures

Details of surface and groundwater monitoring programs to be undertaken before, during and after operations

Proposed water quality objectives for assessing surface and groundwater quality monitoring results and detecting any impacts

Proposed assessment/performance criteria for detecting any impacts on flows/levels or downstream ecosystems or water users

Management actions/contingency measures to stop/reduce any impacts when detected

Residual impact detailing the extent to which mitigation and management measures will address potential impacts.

A water balance for the proposed mining operations in accordance with the Minerals Council of Australia Water Accounting Framework (MCA 2014); provided in Appendix A.

Identification of knowledge/information gaps and how and when these will be addressed

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Figure 1-3. Map of proposed surface water storages


Mine site footprint




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1.1.3 Independent peer review

As required in the ToR Section 4.2.1.4 Mitigation and monitoring, this WMP has been peer reviewed by an ‘independent, third party, recognised by industry as a senior practitioner and is independent from the Proponent/principal consultant and the proposal’. This review was undertaken by Rohan Ash (Out-Task Environmental Pty Ltd), Environmental Auditor (Industrial Facilities), appointed pursuant to the Environment Protection Act (Victoria); also Bill Howcroft (Principal Hydrogeologist), who reviewed the groundwater-related aspects. Independent reviewer biographies are provided in Appendix B.

The WMP version reviewed was the same as that submitted to the NT EPA along with the EIS that was made available for public comment for a period of six weeks from 3 November to 14 December 2018.

Appendix C provides the independent peer review report from Out-Task Environmental, and Appendix D provides a table of responses to all review comments and how they have been addressed in this updated WMP version.


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2 PROJECT DETAILS RELEVANT TO WATER MANAGEMENT

2.1 Project overview

The project proposes to mine a near-vertical pegmatite ore body (Figure 2-1) that contains the lithium-bearing mineral spodumene. The ore body is approximately 400 m long, by 32 m wide, and will be mined via an open-cut pit (surface footprint approx. 24.3 ha) using drill and blast methods down to approximately 200 m below ground level (-185 mAHD). Around 2.03 million tonnes (Mt) of ore is planned for extraction over the expected 35-month mine life; 29 months of which the pit will be mined.

The pegmatite ore body has intruded into Proterozoic Burrell Creek Formation (BCF) comprising shales, siltstones, and strongly foliated phyllite. The weathering profile extends to depths of 30 to 50 m before reaching fresh, un-weathered BCF. Weathered and fresh BCF comprise the bulk of waste rock requiring excavation to access the ore body. A thin surface layer (less than 5 m thick) of Cenozoic sediments, mainly laterite gravel, sand and clay, lies over most of the proposed mine area.

Figure 2-1. Cross section of ore body within the Burrell Creek Formation (BCF) and open pit shell.


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2.2 Project components

Project components are shown in Figure 1-2 and Figure 1-3, and listed in Table 2-1. Components relating to water management or with implications for hydrological process or water quality are outlined in Sections 2.4 to 2.8. The mine site area (mine footprint) covers approximately 217 ha, encompassed by the wider Mineral Lease ML31726 (total 750 ha). Areas outside the mine footprint but within ML31726 will remain largely undeveloped.

Project components outside ML31726 include the existing Observation Hill Dam, located around 5 km south-east of the mine, and a 6 km-long underground water pipeline linking this dam to the mine (Figure 1-3). A proposed new dam, referred to as Mine Site Dam (MSD) to be constructed, is designed on an ephemeral drainage line immediately west of the mine. The dam wall is within ML31726; however, some of the inundation area would be outside ML31726 (Figure 1-3). Project components outside of ML31726 will be covered by ancillary ML’s.

Table 2-1. Project components.

Components within the mine footprint and ML31726

Open pit and associated heavy vehicle access ramps and haul roadsWaste rock dump (WRD) and integrated tailings storage facility (TSF); two TSF cells within WRDCrushing and screening plant and dense medium separation (DMS) processing plantRun of Mine (RoM) stockpile pad for stockpiling unprocessed ore for feeding the crushing plant, and crushed ore for feeding the DMS plant. Rejects stockpile of low-grade ore from DMS plant for transfer to WRD. Concentrated product stockpile from DMS plant adjacent to the road train load-out loop. Mine operations/administration centre incorporating site offices, equipment laydown, LV car parking and wash-down, emergency facilities, HV workshop and wash-down, and refuelling. Bund (referred to as ‘inundation bund’) around northern and eastern side of mine site to prevent ingress of water from natural drainage lines on either side mine, if these drainage lines were to flood. The inside of this bund also acts to direct run-off within the mine site towards the sediment basins. Bund (referred to as ‘topsoil bund’) around western side of WRD to prevent ingress of run-off from upslope areas into WRD, and to prevent this ‘clean’ water from running on to mine site. Instead, this water is directed around WRD into natural drainage lines. The inside of this bund also acts to direct run-off from the WRD outer walls into drains that lead to the sediment basins. Drains and erosion and sediment controls within mine site to prevent stormwater run-off into open pit and other operational areas, and to direct run-off into drains, through erosion and sediment controls (e.g. rock check dams), and into sediment basins for treatment and testing prior to release off-site. Mine Site Dam (MSD) to be constructed (if required) as additional supply to RWD; dam wall within ML31726, portion of inundation area is outside western boundary of ML31726. Mine Water Dam 1 (MWD1) to hold water from pit dewatering (groundwater inflows and incident rainfall) for use in dust suppression and ore processingMine Water Dam 2 (MWD2) as contingency for holding TSF decant water in excess of that stored in the tank supplying water to ore processing plant, or excess water dewatered from pit to avoid dry season release from MWD1. Raw water dam (RWD) to hold water from Observation Hill Dam and/or Mine Site Dam (see below) for supplying potable/non-potable water to mine operations centre, and additional water for ore processing and dust suppression when pit dewatering and TSF decant is insufficient. Wastewater from ablutions will be treated using either a ‘no release’ or ‘secondary treated’ wastewater management system. The final system design will be subject to Department of Health approvals. If a secondary treated system is adopted, a land capability assessment will be undertaken to select a suitable land disposal site

Components outside ML31726

Observation Hill Dam (existing), located approximately 5 km south-east of mine to supply water to RWD. Underground pipeline (6-km long) to transport water from Observation Hill Dam to mine site.


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2.3 Mining schedule

Table 2-2 below outlines the currently planned mining schedule.

Table 2-2. Mining schedule.

Year/Month Months 1-5 Months 6-29 Month 30-35 Months 36-40 Months 41 onward

Phase Pre-strip & construction

Mining and processing Processing only Rehabilitation &

closure Post-closure

Activities

Removal of oxide waste and oxidised

pegmatite waste. Construction of

site infrastructure and processing

facilities.

Mining of the pegmatite ore

body and adjacent ‘fresh’

waste, and processing/ transport of product to

Darwin Port

Mining in open pit is complete. Continued

processing and transport of product to

Darwin Port

Rehabilitation and mine closure

activities undertaken in

accordance with Mine Closure Plan

On-going monitoring of the

mine site until rehabilitation completion criteria are

achieved and the site is

relinquished.

2.4 Water requirements, sources and storages

The greatest anticipated daily water demand at the peak of mining is 2,018 kL/day. Of this, 1060 kL is for dust suppression (dry season maximum), and 950 kL for ore processing; the remainder (8 kL) is for the mine operations centre (offices, potable, ablutions, vehicle wash-down, workshops etc). Figure 2-2 provides a flow diagram of water inputs, outputs and uses across the mining project.

The project water balance (Appendix A) indicates that pit dewatering (comprising direct rainfall and groundwater inflows) can provide the bulk of ore processing and dust suppression requirements. Combined with reuse of decant water recovered from the TSF (for ore processing only), around 95% of these requirements will be met. Surface water storages will make up the remainder. Potable and non-potable supply to the mine operations centre will also come from surface water storages.

The project plans to utilise the existing Observation Hill Dam as the primary surface water storage. This dam was constructed to supply water for tin and tantalite mining and ore processing that occurred in the 1980’s and 1990’s (Frater 2005). The estimated dam volume when full is around 364 ML (EnviroConsult 2018a). To ensure water security for the project in the event of lower than average rainfall, the project is considering raising the dam wall by approximately 1.5 m to increase storage capacity to around 628 ML (increases inundation area by 9 ha to a total 40 ha).

There are also plans to construct a second surface water storage referred to as the Mine Site Dam (MSD) on an ephemeral drainage line immediately west of the mine (Figure 1-3). This dam may be required to further ensure there is sufficient water for mining operations during a drier than average year and/or unanticipated increases in water requirements.

Current design of the MSD (maximum capacity 387 ML, areal extent 19 ha) is based on topographic and engineering/construction constraints, and the proximity of mine infrastructure such as the WRD, that must remain above the maximum inundation level. It also assumes a worst-case scenario where the Observation Hill Dam wall is not raised, and pumping from the MSD is constant throughout the year without any offsets from reuse of water on-site (pit dewatering, TSF decant), or reduced water demand for dust suppression during the wet season. This was done in order to model the worst-case scenario for potential flow-reduction impacts on downstream natural waterways (see Section 4).


10

Figure 2-2. Flow diagram of project water inputs, outputs, tasks and storages.


11

The current project water balance indicates that water from pit dewatering, TSF decant reuse, and the Observation Hill Dam can most likely meet all water requirements over the mine life. Refinement of the water balance as project components are finalised will inform Core’s final decision whether to proceed with construction of the MSD and if so, its required capacity.

2.4.1 Internal mine site water holding dams

Internal mine site holding dams for the management and use of water include a raw water dam (RWD), and Mine Water Dams 1 and 2 (MWD1 and MWD2); locations shown in Figure 1-2. These dams will ensure water from different sources i.e. pit dewatering, TSF decant, and surface water storages, remains separate (see Figure 2-2), and is used in accordance with its water quality.

The RWD (capacity 60 ML) will hold water pumped from Observation Hill Dam (and/or MSD if required) for use in ore processing, dust suppression and the mine operations centre (offices, potable, ablutions, vehicle wash-down, workshops etc). It’s size aims to contain around 48 hours’ operational supply, topped-up as needed. The project water balance indicates the RWD will be the primary source of water during the first month of mining, supplying around 22 ML for the month. As groundwater inflows into the pit increase with mining depth, the RWD will become a supplementary water supply, and MWD1 (containing water dewatered from the pit) will become the primary supply for dust suppression and ore processing. An average 1.7 ML per month will be required from the RWD after the first month used mainly to supply the mine operations centre (offices, potable, ablutions, vehicle wash-down, workshops etc).

MWD1 (capacity 240 ML) will hold water dewatered from the pit (see Section 2.4.2) for use in ore processing and dust suppression. Its size is based on having no dry season overflow accounting for the rate of pit dewatering inputs, and ore processing and dust suppression outputs. Dry season release is considered undesirable given water wouldn’t naturally flow in the receiving waterways at this time.

It is expected release of water from MWD1 to the environment will be required during the wet season months November to March, when volumes of water removed from the pit will be higher, and dust suppression requirements lower (see water balance Appendix A). Discharge from MWD1 will be managed and monitored in accordance with a Waste Discharge Licence to be applied for and issued under the NT Waste Management and Pollution Control Act. A discussion of the expected MWD1 discharge water quality is provided in the section below.

In regards to discharge volumes, Table 2-3 provides modelled discharge volumes based on an average rainfall year i.e. 50th percentile scenario, and the expected depth of mining (i.e. groundwater inflow volumes) during each wet season. The greatest discharge volumes will occur during the early wet season months of November 2020, December 2020 and November 2021. At this time, streamflow volumes from the mine site catchment i.e. those reporting to ‘Catch-5 DS’ in Figure 3-2 are relatively small, and the discharge is modelled to comprise up to 53% of the streamflow. For January, February and March however, the discharge comprises a very minor proportion (less than 6%), and discharges will be highly diluted.

As will be required by the Waste Discharge Licence, during mining operations, the water quality of discharge will be monitored in accordance with the Water Quality Monitoring Plan and also a real-time automated flow gauge will be installed at the outlet of MWD1 to record the amount of discharge (see Section 10.1).

MWD2 (capacity 60 ML) is designed as a contingency storage for excess TSF decant, or excess pit dewatering volumes. Under normal operations, TSF decant is transferred to a holding tank adjacent to the processing plant for feeding direct into ore processing. If pit dewatering volumes are higher than modelled scenarios, and MWD1 capacity is exceeded, the excess water sent to this dam will avoid the need to discharge during the dry season.


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Table 2-3. Modelled discharges from MWD1 for average rainfall years (50th percentile) over life of mine compared to flow volumes in receiving stream reporting to Catch-5 DS1.

Month Discharge volume (ML/mth)

Modelled streamflow (ML/mth) from mine site reporting to Catch-5 DS

% streamflow comprising MWD1 discharge2

2019 dry season No discharge NA 0November 2019 46.36 501 8December 2019 25.23 121 17January 2020 38.49 2349 2February 2020 40.48 1324 3March 2020 47.12 800 62019 wet season total 194.68 5096 42020 dry season No discharge NA 0November 2020 129.60 501 21December 2020 133.92 121 53January 2021 89.52 2349 4February 2021 51.15 1324 4March 2021 45.58 800 52020 wet season total 449.77 5096 82021 dry season No discharge NA 0November 2021 97.02 501 16December 2021 46.18 121 28January 2022 57.56 2349 2February 2022 51.74 1324 4March 2022 47.76 800 62021 wet season total 300.26 5096 6

1 ‘Catch-5 DS’ as used in EnviroConsult (2019) surface water modelling and shown in Figure 3-2. 2 Note the 50th percentile year that was used for the modelling scenario was 1991. Daily rainfall data is required for the modelling, so the model was run on an example year (in this case 1991). The average annual rainfall for this year (1,652 mm) was closest to the average annual rainfall of 1,687 mm, calculated from the long-term SILO database. As it happened for 1991, the monthly total for December was much less than November, contrary to the average monthly record, see Figure 3-1. The model may be re-run in future using a composite average year if deemed necessary for assessing potential environmental impacts.


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MWD1 discharge water quality overview

MWD1 is expected to contain overall good water quality for most parameters, with the final dam water quality influenced by the relative proportions of groundwater to rainwater flowing into the pit, and amount of direct rainfall into MWD1. Baseline groundwater quality results indicate the groundwater has a neutral pH, low dissolved metal concentrations below the guideline levels for Darwin Harbour (NRETAS 2010), and levels of the nutrient nitrogen, predominantly in the form of nitrate, within the same range as that of surface waters. Aluminium concentrations are elevated but remain below levels in receiving surface waters. Parameters with relatively high concentrations compared to the receiving surface waters include EC (which is actually relatively low for groundwater), arsenic and phosphorus (which are above the guideline level), and iron and lithium (which are elevated compared to surface waters).

Dilution with rainwater into the pit, and into MWD1, will reduce concentrations. Additionally, the proportion of MWD1 discharge in relation to streamflows at the time of discharge is small; less than 6% during January, February and March, as discussed in the Section above.

The naturally occurring process of oxidation and co-precipitation of arsenic and phosphorus with iron whilst the water is held within MWD1 may also assist in reducing levels of dissolved arsenic and phosphorus. Although the extent of this is not yet verified. In the event that arsenic and phosphorus levels remain high, there are a number of commonly-used treatment options available. Removal technologies and treatments have been developed to remove arsenic from groundwater to make it suitable for drinking and removal of phosphorus from wastewater is commonly undertaken to make it suitable for discharge.

Regular testing of MWD1 water quality, as well as that within the mining pit sump itself, is included in the Water Quality Monitoring Plan (Section 10). Measures will be implemented to ensure discharge from MWD1 meets the water quality criteria prescribed in the Water Quality Monitoring Plan prior to release. Detailed discussion of predicted MWD1 water quality is provided in Section 7.4.

Surface water turbidity in the receiving drainage line is always low, even after significant rainfall. The turbidity of groundwater inflows into the pit and rainwater would also be low, however may become elevated on contact with fine sediments within the pit. Measures for minimising turbidity in water dewatered from the pit, such as filtering water as it is pumped from the pit sump and using flocculants in MWD1 will be undertaken to ensure turbidity levels of discharged water are below the water quality criteria prescribed in the Water Quality Monitoring Plan (Section 10).

Prior to any release from MWD1, this discharge point will require approval under the NT Waste Management and Pollution Control Act, and issue of a Waste Discharge Licence (WDL). Core will submit a WDL application to the NT EPA for assessment and approval in the coming months. As mentioned above, water quality monitoring of releases from this point, and also monitoring of the receiving sites downstream, is included in the project’s Water Quality Monitoring Plan (Section 10). This Plan will be updated to align with all conditions in the WDL once issued.


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2.4.2 Pit dewatering

Figure 2-3 and Table 2-4 show the results of modelling undertaken by CloudGMS (2019) of groundwater flows into the pit over the life of mining operations with a nominal start date of July 2019. Note the CloudGMS (2019) nominal start for modelling was June 2018. Given these are monthly outputs for the end of each month, the first output from the groundwater model is for July 2018. This is also equivalent to the July 2019 start date shown in Table 2-4, and which was used as the start date for the project water balance (Appendix A).

The CloudGMS (2019) model predicts that inflow rates will increase as mining progresses, reaching a peak of around 78.52 ML/month (2,617 kL/d) during month thirteen (July 2020).

The total volume of pit dewatering required will be a combination of groundwater inflows and incident rainfall directly into the pit (stormwater drains will prevent any surface water run-off into the pit). Figure 2-3 and Table 2-4 also show the predicted combined volume of groundwater inflows and incident rainfall to be removed from the pit based on an average rainfall scenario (50th percentile). The water balance (Appendix A) also includes predicted pit dewatering volumes for successive above average wet seasons (90th percentile) and successive below average (10th percentile) wet seasons. Only the incident rainfall component changes between the three scenarios. The groundwater inflow component remains constant throughout the period of mining given the groundwater system is affected by periods longer than the 35-month mine life.

Groundwater inflows to the pit are primarily controlled by the hydraulic properties of the host rock, and the head difference between the pit and surrounding groundwater level, which has a very limited range as indicated by the groundwater hydrographs (see Section 3.3). The response time of the groundwater system is much longer than the response time of surface water flows. If the project had a longer timeframe (say 10yrs) it would be worth considering modelling additional scenarios.

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Figure 2-3. Modelled pit inflows during life of mine. Groundwater inflows in blue and direct rainfall input in red.


15

Table 2-4. Modelled volumes of pit water to be removed (dewatered) per month over life of mine assuming July 2019 start date and average rainfall conditions.

Month Mining stageGroundwater

inflow(ML/mth)

Direct rainfall to pit(ML/mth)

Total pit water to be removed

(ML/mth)Jul 2019 Waste 16.83 0.00 16.83Aug 2019 Waste 37.93 0.00 37.93Sep 2019 Waste 44.52 0.22 44.74Oct 2019 Waste 46.29 1.56 47.85Nov 2019 Waste / Ore 48.21 4.18 52.40Dec 2019 Waste / Ore 49.26 6.86 56.12Jan 2020 Waste / Ore 49.80 11.60 61.40Feb 2020 Waste / Ore 54.47 8.84 63.32Mar 2020 Waste / Ore 64.42 8.72 73.14Apr 2020 Waste / Ore 66.25 1.95 68.19May 2020 Waste / Ore 76.37 0.08 76.44Jun 2020 Waste / Ore 73.22 0.00 73.22Jul 2020 Waste / Ore 78.52 0.00 78.52Aug 2020 Waste / Ore 75.61 0.00 75.62Sep 2020 Waste / Ore 76.93 0.22 77.15Oct 2020 Waste / Ore 77.86 1.56 79.42Nov 2020 Waste / Ore 74.36 4.18 78.55Dec 2020 Waste / Ore 71.62 6.86 78.48Jan 2021 Waste / Ore 67.32 11.60 78.92Feb 2021 Waste / Ore 66.26 8.84 75.10Mar 2021 Waste / Ore 64.01 8.72 72.72Apr 2021 Waste / Ore 57.93 1.95 59.88May 2021 Waste / Ore 61.86 0.08 61.94Jun 2021 Waste / Ore 58.85 0.00 58.85Jul 2021 Waste / Ore 59.82 0.00 59.82Aug 2021 Waste / Ore 55.93 0.00 55.93Sept 2021 Waste / Ore 56.79 0.22 57.01Oct 2021 Waste / Ore 55.28 1.56 56.85Nov 2021 Waste / Ore 52.15 4.18 56.34Dec 2021 Nothing 51.61 6.86 58.47Jan 2022 Nothing 50.27 11.60 61.87Feb 2022 Nothing 48.93 8.84 57.77Mar 2022 Nothing 47.59 8.72 56.30Apr 2022 Nothing 46.25 1.95 48.20May 2022 Nothing 44.91 0.08 44.98


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2.5 Erosion and sediment control and flood prevention

The Grants Lithium Project, Erosion and Sediment Control Plan (ESCP) details the controls to be implemented across the site to minimise erosion and sedimentation, and prevent contamination of stormwater by directing it around operational areas. This plan has been developed by a Certified Practitioner in Erosion and Sediment Control, and is consistent with the International Erosion Control Association, Best Practice Erosion and Sediment Control (IECA 2008).

The ESCP will be updated as mining progresses, and ESCP revisions provided along with the annual MMP submission to the NT Department of Primary Industry and Resources. The current ESCP covers the general principals and measures to be implemented. Detailed ESCPs with site-specific dimensioned plans will be developed for each stage of the mining project, and will address the specific seasonal conditions (wet season/dry season) under-which the stage occurs, for example, a specific ESCP will be developed for the vegetation clearance and construction phase of the project, which is currently planned to occur during the dry season (July – October 2019). If however, this stage extends past 1 October 2019, the ESCP will be updated to include the additional controls required for wet season conditions. The following section summarises the general ESCP measures planned for during mining operations. Please refer to the ESCP for more detail.

2.5.1 General mine site ESCP measures

Figure 2-4 shows the internal mine site drainage, erosion and sediment controls, and surrounding bunding. The bund (referred to as ‘topsoil bund’) around western side of WRD is to prevent ingress of run-off from upslope areas into the WRD, and to prevent this ‘clean’ water from running on to the mine site. Instead, this water is directed around the WRD into natural drainage lines. The inside of this bund also acts to direct run-off from the WRD outer walls into drains that lead to the sediment basins 1 and 2 via erosion and sediment controls e.g. rock check dams.

The bund (referred to as ‘inundation bund’) around northern and eastern side of mine site is to prevent ingress of water from natural drainage lines on either side the mine, if these drainage lines were to flood (see flood inundation modelling in Section 4.3). The inside of this bund also acts to direct run-off within the mine site towards the sediment basins.

Internal drains within the mine site act to prevent stormwater run-off flowing into the open pit or other operational areas where it may become contaminated. Instead, this water is directed into drains, via erosion and sediment control measures (e.g. rock check dams), and into the sediment basins for treatment and testing prior to release off-site (see Section 2.5.2).

In order to prevent stormwater contamination, all operational areas such as the DMS plant, workshops, fuel tanks, refuelling areas, heavy and light vehicle wash-down areas etc that store or use potentially contaminating materials such as fuels, chemicals, DMS processing additives etc are designed to the relevant Australian Standards for hazardous materials storage, and are covered and bunded where appropriate (see Section 2.8).

2.5.2 Sediment basin design and operation

The design and operation of the sediment basins is of particular relevance for this WMP. As with all erosion and sediment controls across the site, the design of sediment basins and method of release of water from these basins will be in accordance with IECA (2008).

Sediment basins proposed for the mine site are initially designed as Type D basins, which assume dispersive soils requiring the use of a flocculating agent to settle. This is a conservative approach, representing the worst-case scenario. With the recent finalisation of Appendix B – Sediment Basin Design and Operation (IECA 2008), basin design will be revised prior to implementation of mine development to ensure the most efficient basin configuration is adopted. Table 2-5 provides the minimum design criteria for the sediment basins.


17

The water quality of sediment basins will be monitored and tested as part of the Water Quality Monitoring Plan (see Table 2-5 and Section 10). The results of this testing will guide how this water is treated with flocculants etc, and also identify any issues requiring action such as sources of contamination or improving erosion and sediment control measures.

Table 2-5. Sediment basin design criteria.

Location Capacity Located to maximise collection of sediment-laden runoff

generated within the site Not within a waterway or drainage channel Above the 1 in 5 year ARI Have suitable access for maintenance Placed in close proximity to site perimeter for ease of

dewatering

Large enough to hold a 5-day, 85th percentile rainfall amount for Darwin; 46.2 mm (Table B6, IECA 2008)

Based on project catchment areas and potential soil loss (as provided in Table 4-2 of the ESCP)

Based on project area runoff coefficients for 100 mm rainfall event:o 1 for heavily impacted areas (haul roads, pads, high

traffic, compacted)o 0.75 for vegetated or less compacted (Table B7 IECA

2008) Minimum combined capacity of sediment basins 1 and 2

is calculated as 65,821 m3 based on current site layout; see Table 6-1 in ESCP for calculations

Construction Management and operation

Earth embankments to be certified as structurally sound by geotechnical engineer/specialist

Stable inflow system (eg. rock chute) Minimum 3:1 length to width ratio (may require internal

baffles) Primary outlet (eg. siphon, perforated riser) for controlled

release Emergency spillway (minimum design storm 1 in 50 year

ARI) Marker to identify the sediment storage zone depth

Discharged within 5 days of cessation of rainfall (min 25 mm)

Prior to discharge, water quality to meet project discharge criteria (see below), flocculant or coagulant may be required

Designed to ensure easy and safe access to dose retained water with flocculants as required

Marker peg to be installed to indicate sediment storage capacity

Removal of sediment where sediment storage capacity exceeds 50% and disposal/management of sediment so as not to create an erosion or pollution hazard

Water quality monitoring Discharge criteria Routine water quality monitoring to be undertaken in

accordance with the Water Quality Monitoring Plan (Section 10) involving: o Prior to any controlled release field parameters

(electrical conductivity, temperature, turbidity, pH, dissolved oxygen) are to be measured to confirm water quality meets discharge criteria

o Weekly field parameters during wet season (Nov – Apr) regardless of discharge

o Weekly laboratory parameters (hydrocarbons, heavy metals, nutrients) when discharging

o Monthly laboratory parameters during wet season (Nov – Apr) regardless of discharge

Additional sampling may be required to investigate any water quality issues detected during routine monitoring and validate that management measures have addressed any issues and water quality is suitable for release.

Discharge criteria is as per Table 10-3 in the Water Quality Monitoring Plan (Section 10), this includes for field parameters:o Turbidity 90th percentile NTU not exceeding 100, and

50th percentile NTU not exceeding 60o pH between 5.06 - 8.14o EC less than 200 µS/cmo DO between 50 - 100 %saturation

Assessment criteria for weekly and monthly routine sampling includes the above plus:o Laboratory parameters as per criteria in Table 10-3o Turbidity at downstream water quality monitoring

sites GDS SW1 and GDS SW2 to remain below 20 NTU


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Sediment basin flocculation

Flocculation of basins will be required where the contained water does not meet discharge criteria within five days of cessation of rainfall. The application of a coagulant is to occur within 12 hours of the receipt of runoff producing rainfall. Typically, gypsum (calcium sulfate) is used for this purpose. This requires application across the sediment basin surface (spray or hand cast) at a rate of 32 kg per 100 m3 of water volume.

There are also a range of anionic polymers which may provide a more effective flocculation option. These are also well suited to flow-activated dosing systems, reducing labour associated with flocculation. An option for the site is installation of ‘high efficiency sediment basins’ as outlined in: High efficiency sediment basins, WetlandInfo 2018, Department of Environment and Science, Queensland, viewed 14 March 2019, https://wetlandinfo.des.qld.gov.au/wetlands/management/treatment-systems/for-agriculture/treatment-sys-nav-page/high-efficiency-sediment-basins/.

The final choice of flocculant and dosing methods will be managed adaptively based on monitoring of sediment basin performance over the first wet season of operations.

Receiving waterways and discharge water quality criteria

Discharge from the sediment basins will flow into the very shallow, broad drainage lines present at the project site i.e. the drainage line encircling the western side of the top soil bund (Figure 2-4) from sediment basin 1, and drainage line encircling the eastern side of the inundation bund from sediment basin 2. These drainage lines only flow during the wet season following consistent rainfall periods and have very indistinct channels, which are overgrown with thick grass; see photos in Figure 6-1. As such, given the filtering by grass and vegetation in the drainage lines, relatively low flow volumes and velocities, and lack of exposed soils, turbidity levels of water flowing in these drainages is very low (generally less than 12 NTU; see Section 6).

Turbidity in the sediment basins will be reduced as much as possible, but final discharge from the sediment basins is not always expected to achieve these very low turbidity levels in the receiving drainage lines. As such, the discharge standard recommended for sediment basins in IECA (2008) is adopted:

90th percentile NTU reading not exceeding 100, and 50th percentile NTU reading not exceeding 60

Once discharged, the turbidity of water from the sediment basins is expected to reduce rapidly with dilution in the receiving drainage lines, combined with the filtering effect of the vegetation growing within the drainage lines. The assessment criteria outlined in Table 10-3, applying to all routine surface water monitoring sites downstream of the mine will still apply for turbidity. That is, the turbidity of the sites downstream of the sediment basins (GWS SW1 and GDS SW2) are expected to remain below 20 NTU.

https://wetlandinfo.des.qld.gov.au/wetlands/management/treatment-systems/for-agriculture/treatment-sys-nav-page/high-efficiency-sediment-basins/

https://wetlandinfo.des.qld.gov.au/wetlands/management/treatment-systems/for-agriculture/treatment-sys-nav-page/high-efficiency-sediment-basins/

minepitshelltailings

storagefacility

haul road & pit access

raw water damROM pad

site access culvert

mine water dam 2 Cox Peninsula Rd

mine water dam 1

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sediment basin 1

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0 250 500125

MetresOMAP INFORMATIONProjection: GDA 1994 MGA Zone 52Date Saved: 3/7/2019Client: Core ExplorationAuthor: F Watt (reviewed K Welch)DATA SOURCEProject components: ClientImagery: ESRI basemap (Digital Globe)

Figure 2-4. Map of erosion and sediment controls

LegendSediment basinsTopsoil & inundation bunds (vegetated)dirty water flowclean water flow


- Recommendations of this ESCP are in accordance with the 2008 IECA Best Practice Erosion and Sediment Control Guidelines (IECA 2008). - This ESCP is to be read in conjunction with relevant civil works plans, MMPs and any other written instructions issued in relation to works on-site. - The provided drawings are indicative of appropriate controls and practices to be implemented on-site. - Clean water from areas surrounding the project are to be diverted around project area. - Constructed drains to be protected with non-erosive lining to withstand design discharge velocities, including outlets (refer applicable Engineering Plans). - Flow diversion banks and diversion channels to include rock check dams (RCDs) at min 50m intervals. - Site drainage to be installed during initial stage of construction. - Erosion control to be achieved through stabilisation of bunds, application of soil binder, hardstand surfaces and maintenance of stablisied no-go zones. - Sediment control to be achieved through use of sediment basins and supplementary Type 2/3 controls. - Measures to be monitored regularly (daily during wet season and periods of rainfall). - Measures to be repaired/modified as required to ensure they are performing to their design standard. - Sediment accumulation to be removed from sediment controls where it exceeds 25% capacity

Notes:


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2.6 Ore processing

The 2.03 Mt of fresh pegmatite ore contains approximately 1.5% concentration by weight of lithium oxide (Li2O). Crushing, screening and DMS processing will increase the Li2O concentration in the product to around 5.5%.

Crushing and screening will reduce the ore material to less than 6.3 mm. This material then goes through a wet screen to remove ‘fines’ (material less than 0.5 mm). Fines are sent to the thickener for dewatering, then to the TSF. The remaining material (0.5 to 6.3 mm) is mixed with a water‐based heavy medium (ferrosilicon FeSi) to make a slurry, and then fed to the DMS cyclone. The specific density of the FeSi medium (2.7-2.9) separates the beneficiated product containing concentrated Li2O, which sinks, from the lighter less concentrated material, which floats. The beneficiated product is stockpiled for road train transport to Darwin Port, whereas the ‘floats’ are sent to the rejects stockpile area and then to the TSF. The FeSi medium is recovered and reused.

Water reuse and recovery will minimise the need to source water from surface water storages. Water for processing will be sourced firstly from recovery from the tailings thickener, TSF decant, recovery from dewatering of product and rejects, and from pit dewatering prior to using water from surface water storages (Observation Hill Dam and/or MSD). A statement of operational efficiencies is included in the water balance (Appendix A). This statement indicates a re-use efficiency of 39 % (i.e. 39 % of water requirements comes from water reuse).

2.6.1 Additives

Additives used in ore processing include the ferrosilicate (FeSi) heavy medium to achieve separation of the product, and flocculant in the tailings thickener. Minor residues of these additives will end up in the WRD along with the coarse rejects (FeSi) and TSF with the fines (flocculent), however neither of these present a significant risk to the environment.

Iron (Fe) and silicon (Si) are naturally present in the laterite overlying the site, and dissolved iron is already present in surface and groundwaters (see background surface and groundwater water quality in Sections 6 and 7). The Water Quality Monitoring Plan (Section 10) includes on-going monitoring of dissolved iron levels in surface and groundwater in order to detect any increase above background levels of dissolved metals.

The ferrosilicon product is yet to be chosen, however, as stated in the MSDS’s of various ferrosilicon products available that may be used in the project, the material is an inorganic solid that is inert and insoluble in water, does not absorb onto soil or sediments, and does not bio-accumulate. Following its use in processing, the ferrosilicon will leave the process circuit as a component of the tailings slurry, that will then be thickened and pumped to the TSF. The decant water from the TSF, is not expected to contain any contaminants arising from the use of ferrosilicon, as the material is insoluble in water and is not expected to react with the other tailings components, which will comprise water and fine sediments.

The project will only use ferrosilicon and flocculant products assessed as having low environment risk. Once known, the ingredients of these products will be included in the Water Quality Monitoring Plan; although the current laboratory analysis is likely to already cover all potential ingredients.


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2.7 Waste rock dump and tailings storage facility

2.7.1 Waste rock dump

Over the mine’s life, an estimated total 13,887,008 bank cubic metres3 of waste rock, i.e. weathered, transitional and fresh BCF host rock, will be excavated in order to access the ore body. A WRD will be constructed to accept all waste rock material removed from the pit and coarse rejects from the crushing/screening process. Waste characterisation studies (see Section 2.7.3 below) indicate limited potential for production of acid, saline or metalliferous drainage (AMD) from the waste rock and therefore no requirement for construction of containment cells. The processing rejects are coarse and also do not pose an AMD risk, and therefore will be co-disposed in the WRD. Some waste material has dispersive characteristics and may need to be managed by selective placement and storage towards the centre of the WRD, so as not to affect the stability of the annulus.

2.7.2 Tailings storage facility

The DMS wet screening process will produce fine rejects (tailings). Initial tailings classifications are a silty sand, that should drain successfully. Geochemical characterisation results for the fresh pegmatite ore indicate AMD is not expected to be an issue; see Section 2.7.3 below. No chemical processing is required in the DMS plant. Therefore, tailings solids are expected to be geochemically stable and not contain any contaminants. Further tailings characterisation work will be undertaken as part of processing plant trials, to confirm the tailings characteristics moving into the TSF detailed design phase.

The TSF will be integrated within the WRD. This design concept has the benefit of minimising the mine site footprint and allows for the WRD to entirely encircle the TSF on closure, therefore avoiding ongoing issues associated with water management and revegetation of an exposed tailings dam.

The TSF will be developed in conjunction with the first stage of the WRD construction. The facility will consist of retaining embankments constructed from pit overburden / waste rock. It will comprise two cells (Cell 1 to the north and Cell 2 to the south), with centrally located decant water return structures.

Initial waste classification works indicate the waste from the proposed open cut mine will have a very low risk of AMD. The design has therefore been structured to maximise drainage, without a need for preventative measures for oxidation of the material. The base of the structure will be appropriately treated to provide a low permeability barrier, which, along with the underdrainage system, would allow effective management of any risk of groundwater mounding.

The containment embankments will feature an upstream zone (Zone 1) of low permeability, primarily fine-grained materials sourced from residual soils from pit overburden excavations. This zone will allow the TSF to be a water retaining structure. The majority of the embankment will consist of weathered earth fill / rock fill won from the pit overburden (Zone 3).

Each cell will contain a centrally located decant water return structure, and associated access causeway constructed out of Zone 3 material. Directly around the decant return structure will be a zone of clean, durable filter rock. The decant structures will consist of precast concrete, vertical slotted pipe, with a submersible return pump within the structure.

The embankment batter slopes have been conservatively designed at 2.5 Horizontal: 1 Vertical (2.5H:1V). This will be further refined upon completion of site investigations and testing of the foundations and embankment materials.

The Dam Failure Consequence Category has been assessed as ‘Significant’, in accordance with the Australian National Committee on Large Dams (ANCOLD) “Guidelines on Tailings Dams” (ANCOLD, 2012). The

3 A bank cubic metre is a solid measure of the volume of earth "in situ", i.e. moved from a bank (before excavation or blasting).


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classification was primarily driven by the impact on the business as well as the environment, in the event of a dam failure. The spillway has therefore been sized to accommodate a 0.1 % AEP flood event.

The Environmental Spill Consequence Category has been assessed as ‘Low’, due to the benign nature of tailings and low environmental risk of processing additives. The Design Storage Allowance (DSA) prior to spilling has therefore been set at a nominal 1 % AEP, 72-hour flood event.

Tailings thickening

Tailings are pumped to a thickener where flocculant is added to separate the slurry into an underflow component (tailings approximately 50% solids) and overflow component of process water that is returned back to the processing circuit. The thickened tailings slurry is then pumped to the TSF.

Tailings deposition

Tailings will be pumped approximately 950 m from the plant to the TSF through the main delivery pipeline. At the TSF, the tailings will be sent to either of the two cells, where the slurry will be deposited sub-aerially, through pipelines running around the perimeter of each cell, with spigot offtakes at 50 m centres. This system has been selected in order to minimise the rate of rise and provide an even distribution of tailings deposition, thereby improving consolidation, density and strength properties of the material.

TSF staging

Due to the relatively short mine life, the TSF will be constructed to the full height in a single construction campaign. Cell 1 (to the north) may be constructed first, allowing for tailings deposition to commence during construction of Cell 2.

Water management

The TSF will feature centrally located decant water return structures, along with a system of underdrains, in order to facilitate drainage of the tailings and further promote consolidation of the material. The TSF decant water will be returned directly to the process plant for re-use, or stored in MWD2. wet season run-off will either be stored in the TSF, or pumped to MWD2 for future process / evaporation.

2.7.3 Waste rock characterisation

Table 2-6 summarises the waste rock characteristics for the project determined through testing and analysis reported in EcOz (2018a).

Table 2-6. Summary of waste rock characteristics

Acid Sulphate SoilsNone of the soil samples collected at the site are indicative of ASS. This result concurs with the land unit mapping, which shows the project area has a Nil (class 1) risk of ASS conditions. Acid drainage potentialThe majority of sub-surface material collected (156 samples) at the site have a sulfur concentration less than 0.05 %, which indicates a low risk of PAF material. 17 of 164 samples had an elevated sulfur concentration; only 1 of these within the pit shell is classified as potentially acid forming material. The sulfur concentrations in samples are low; total sulfur concentrations vary between <0.01 %S and 1.88 %S. 148 samples (or 90% of all samples) have total sulfur concentrations <0.05 %S indicating non- PAF material. Approximately 10% of samples have concentrations ≥ 0.05 %S. All of the samples were from depths > 50 m below surface level with the majority coming from deeper than 100 m below surface. All samples with a sulfur concentration > 0.10 %S (7 samples) were from greater than 100 m deep. Subsequent classification of samples based on NAPP and NAGpH (pHOX) results found only two samples classified as PAF. These samples are fresh hard rock phyllite located 125 m deep or deeper from the surface. One sample is from the south east section of the pit shell and the other from the central western half.Overall the waste rocks are considered materials with no AMD potential primarily due to the absence/scarcity of sulfur, which is typical of the sedimentary environment in which it was deposited. Waste rocks that classify as PAF will be limited in volume; they are not confined to a specific area and will be excavated with NAF


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materials and placed in the waste rock dump surrounded and underlain by materials that have sufficient ANC to offset any potential acid generation.Metalliferous drainage potential126 samples were analysed for soluble metal concentrations. Some samples have detectable but very low concentrations of As, Mn, Se and Zn whilst Cd, Cr, Co, Cu, Pb, Ni, V and Hg. All below their limits of reporting.Ten of these samples with Total Sulfur concentrations >0.04 %S was submitted for determination of leachable metals. The leachates contained As (1 sample at 0.2 mg/L), Ba (ten samples at between 0.2 mg/L and 0.3 mg/L), Cu (one sample at 0.1 mg/L), Zn (ten samples at between 0.1 mg/L and 0.4 mg/L) and Mn (ten samples at between 0.2 mg/L and 11.9 mg/L averaging 2.4 mg/L). Be, B, Cd, Cr, Co, Pb, Ni, Se, V and Hg were absent in leachates.Waste rocks may leach metals; however, concentrations will be low. This finding is corroborated by baseline surface and ground water monitoring which indicates:

Groundwater contains elevated concentrations of As (0.009 mg/L and 0.166mg/L) and Fe. Most other metals i.e. Al, Cd, Cr, Cu, Pb, Ni, Se, Zn and Hg are generally absent except for a few minor detections at very low concentrations.

Surface water contains Al (between 0.01 mg/L and 0.08 mg/L) and As (between <0.001 mg/L and 0.007 mg/L) whilst metals such as Cd, Cr, Cu, Pb, Ni, Se, Zn, Sn and Hg are below their limits of reporting.

Saline drainage potentialAll had very low electrical conductivity (0.004 dS/m - 0.280 dS/m) and are considered low saline and highly unlikely to produce saline drainage.Sodic or dispersive potential33% of samples spread across the pit shell and at varying depths, were classified non-sodic but potentially dispersive. These samples have an Emerson Class Number 3 which indicates that remoulding (at moisture content near optimum for compaction) may cause dispersion. A high portion of the samples were from the highly to moderately weathered phyllite, with the highest occurrences in the eastern portion of the pit shell from surface to 5m depth and from 8-54m depth across the whole pit shell. Where this material occurs in the shallow parts of the pit it is a potential source of construction materials and therefore further detailed geotechnical testing and assessment is required to characterise physical characteristics stability. Material from the deeper parts of the pit shell will be placed in the centre of the WRD and therefore dispersive characteristics in these materials is not of management concern.Naturally Occurring Radioactive MaterialBackground and materials to be extracted from the pit shell as waste rocks have low concentrations of NORM which do not warrant further investigation and assessment and/or management measures.


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2.8 Non-mineral waste and hazardous materials

The project involves activities that produce domestic and industrial wastes, and storage/handling of hazardous materials. Sources of waste and methods proposed for storage and disposal are described in the sections below.

2.8.1 Predicted waste streams

The industrial and domestic wastes expected during mining activities are:

General domestic putrescible waste Construction and demolition waste Recyclable wastes (packaging, metals, wood, tyres) Waste oils, lubricants, coolants and filters Wash-down facility wastewater Sewage.

All industrial and domestic waste will be segregated for removal from site by a licenced waste contractor. Domestic waste will be stored in lidded receptacles and removed from site regularly to prevent odour and flies, and access by vermin. Receptacles for recyclable waste will be lidded comingle receptacles. Construction waste, scrap metal and tyres will be placed in open-top skipped bins. Waste oils will be stored in bulk containers and other workshop wastes such as used chemical containers and batteries, will be segregated and stored undercover to prevent ingress of rainfall and subsequent release of contaminated water from storage areas.

General domestic waste, construction wastes and recyclables would be taken either to the nearest Litchfield Shire Waste Transfer Station that accepts commercial waste (i.e. Humpty Doo) or directly to the Shoal Bay Landfill. Hazardous wastes would need to be taken directly to Shoal Bay Landfill as they are not accepted at Humpty Doo. The ultimate approach used for waste segregation, storage, collection and disposal, will be determined by the waste management contractor engaged to manage this aspect of the site operations.

Wastewater produced at the wash-down facility will enter a sump fitted with an oil/water separator for removal of hydrocarbon contaminants. Solid waste (sediments) accumulating in the sump will be removed as required and disposed of to the WRD.

Analysis of hydrocarbons in surface and groundwater is included in the Water Quality Monitoring Plan (Section 10). The objective for these is for concentrations to remain below laboratory detection limits.

2.8.2 Hazardous materials

Diesel fuel will be used to power the on-site generators. Approximately 330,000 litres of diesel will be stored at the mine site in three 110,000 litre above-ground tanks. Additional remote storage will be as follows:

TSF – 1 x 15,000 litre

Observation Hill – 1 x 5,000 litre

Mine Water Dam – 1 x 5,000 litre.

The remote storage is proposed to be small tanks for security and/or theft mitigation. Smaller tanks will be filled by service trucks as required.

Diesel will be stored in above-ground tanks that comply with Australian Standard AS1940 Storage and handling of flammable and combustible liquids. Diesel fuels will be supplied by a licenced contractor as required and all plant and equipment will be refuelled on site in the refuelling area located within the MOC. Diesel spill response measures are incorporated in the project’s Environmental Management Plan.

Processing additives will be stored in designated undercover storage areas. The additives (in their powdered form) pose limited risk to the environment; however, they are classified as hazardous chemicals under Workplace Health and Safety Regulations and therefore their storage and handling will be regulated by Worksafe NT.


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2.8.3 Sewage treatment

Sewage and wastewater will be managed by connection to an on-site wastewater management system. The system type and design is yet to be finalised, but will either be a ‘no release’ or ‘secondary treated’ wastewater management system that complies with the requirements of the Code of Practice for On-site Wastewater Management (Department of Health 2014). Similarly, if a ‘secondary treated’ waste system is used, the method of wastewater disposal and siting of disposal area will comply with these requirements. This includes the undertaking of a Land Capability Assessment to ensure any proposed disposal area is suitable and won’t result in environmental pollution.

Core is currently liaising with both Department of Health and local suppliers in relation to choosing the best solution for the site. Core will apply for a wastewater design works approval from the Department of Health prior to installation.

2.8.4 Product storage and handling

The concentrate product from the DMS plant will be stockpiled on the product pad. A front-end loader will be used to load the product into quad road trains. Each carriage of the road train will be covered to minimise release of dust during transport. There will be ten trucks loaded per day during operations.

The potential risk of any contaminants leaching from the stockpiled product into surface water or groundwater is very low. The spodumene concentrate produced is composed of Lithium Aluminium Silicate LiAl(SiO3)2, and small amounts of quartz and feldspar. Tailored Safety Data Sheets are yet to be produced, but will be developed as a requirement for shipment of the product. Safety Data Sheets available for similar spodumene concentrates produced from mines in WA provide relevant information about the concentrate product properties, health/safety considerations and ecological/toxicity information.

The product material is a dry, white to beige coloured, granular solid containing a mixture of naturally occurring silicate minerals. The concentrate is not classified as hazardous according to Safe Work Australia criteria and is not classified as a Dangerous Good by the criteria of the Australian Dangerous Goods Code. Leachate test results available for spodumene concentrate exported through Fremantle Port in WA, indicate very low levels of leaching of heavy metals (refer https://www.der.wa.gov.au/images/documents/our-work/licences-and-works-approvals/material-change/L7446mc1.pdf). As the spodumene concentrate that will be produced does not have hazardous properties, the product pad does not require any specific pollution prevention or containment measures. The product pad foundation will be constructed of compacted clay material and drainage from the pad will report to the internal drainage network that reports to sediment basins for testing and treatment prior to off-site discharge.

https://www.der.wa.gov.au/images/documents/our-work/licences-and-works-approvals/material-change/L7446mc1.pdf

https://www.der.wa.gov.au/images/documents/our-work/licences-and-works-approvals/material-change/L7446mc1.pdf


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3 CURRENT CONDITIONS

3.1 Rainfall and evaporation

The project area lies within the wet-dry tropics. The wet season is typically November to March, and the dry season April to October. Figure 3-1 shows average monthly rainfall and evaporation data generated for the project site (coordinates 12°39'S 130°48'E) from the SILO (Scientific Information for Land Owners) database. The SILO database is constructed from observational climate records provided by the Bureau of Meteorology (BoM). The system derives datasets which are spatially and temporally complete; interpolating across data gaps. The data is freely available online: https://legacy.longpaddock.qld.gov.au/silo/.

Almost all rainfall occurs during the wet season, with an average annual rainfall of 1570 mm. The wettest months are typically January and February. Usually no rain falls during the dry season months of June, July and August. As an indication of rainfall variability for the site, the lowest , average and highest annual rainfall scenarios used in the hydrological modelling (EnviroConsult 2019) extracted from SILO comprised respectively 919 mm (occurred in 1979), 1,652 mm (1991) and 2,766 mm (2011).

Average annual potential evaporation is 2,340 mm, which exceeds average annual rainfall by 770 mm. The highest potential evaporation occurs between September and October, and lowest between February and March. Average monthly rainfall exceeds evaporation for only four months (December – March).

For consistency, the groundwater modelling (CloudGMS 2018 and 2019), hydrological modelling (EnviroConsult 2019) and water balance (Appendix A) undertaken for the project all used SILO data derived for the specific project location.

Figure 3-1. Average monthly rainfall and potential evaporation generated for the project site from the SILO database; records 1900 to 2018.

https://legacy.longpaddock.qld.gov.au/silo/


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3.2 Surface water

3.2.1 Catchments and drainage

The Darwin Harbour / Bynoe Harbour catchment boundary cuts across the south-west corner of ML31726 (Figure 3-2). A majority of the lease, and all proposed mining infrastructure lies north of this catchment boundary, where surface water drains north into the West Arm of Darwin Harbour estuary. The small drainage lines starting in the south-west corner of ML31726 flow south-west into a tidal inlet of Bynoe Harbour. These drainage lines flowing to Bynoe Harbour are not subject to any proposed mining impacts and are not discussed further in this WMP.

The existing Observation Hill Dam, proposed to supply a portion of mining water requirements, is located around 5 km south-east of the mine footprint within the Bynoe Harbour catchment (Figure 3-2). It is situated at the headwaters of a drainage line that flows into the lower reaches of the Charlotte River, where it is tidal and becomes part of Bynoe Harbour.

There is no existing stream flow data for the drainage lines or streams relating to the project area. Based on aerial imagery and site visits at various times during the year, it is known there are no permanent watercourses within ML31726 or immediately downstream of Observation Hill Dam. The drainage lines around the mine footprint down to where they flow north under the Cox Peninsula road are very shallow, and lack a well-defined channel or riparian vegetation (see photos of monitoring sites GPUS SW3 and GPDS SW1 in Figure 6-1). They cease to flow early in the dry season and are difficult to locate when not flowing.

These ephemeral watercourses, meet prior to crossing under the Cox Peninsula Road through a culvert. Around 1 km north of the mine, they meet another watercourse (Figure 3-3). Downstream of this confluence, the watercourse maintains pools into the dry season, and a further 1 km downstream, the watercourse flows into a mangrove-lined tidal inlet of Darwin Harbour, West Arm.

Immediately downstream of Observation Hill Dam there is a wet area with poorly defined drainage and some pools near the foot of the dam wall, which appear to remain wet as a result of seepage (see survey undertaken for threatened wetland plant Stylidium ensatum by EcOz 2018). These areas support sedges and herbs in the ground layer during the Wet and early dry season, but mostly dry out later in the dry season.

The ephemeral drainage further downstream has a well-defined channel starting from a point around 1 km downstream of the dam wall (i.e. surface water monitoring site BPUS SW1; see photo in Figure 6-2). A late-dry season (October 2017) site inspection of this watercourse observed pools but no visible flows starting from a point around 2 km downstream of the dam wall. The watercourse at this point has well-developed riparian vegetation (i.e. surface water monitoring site BPDS SW2; see photo in Figure 6-2).

Delineated catchments and sub-catchments

Figure 3-3 shows the sub-catchments for the mine footprint area delineated by EnviroConsult (2018a and 2018b) using available topographic information, aerial imagery, and a 2 m digital elevation model. The catchment referred to as catchment 5 includes the mine footprint, and is divided into sub-catchments 5a and 5b. Catchment 2 lies directly east of the mine, and is divided into sub-catchments 2a and 2b.

Sub-catchments 5a and 5b drain to a culvert under the Cox Peninsula Road located directly north of the mine. Sub-catchment 2b drains to a culvert under the Cox Peninsula Road directly east of the mine. Sub-catchment 2a is on the other (north) side of Cox Peninsula Road and drains into sub-catchment 2b just downstream of the culvert. All four sub-catchments drain to a common outlet, around 1 km north of the project area. As mentioned in the section above, the watercourse at this point maintains pools into the dry season, and a further 1 km downstream, flows into a tidal inlet of Darwin Harbour. Table 3-1 provides sub-catchment areas and slopes.


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Table 3-1. Sub-catchment areas and slope.

Sub-catchment Area (km2) Stream slope %

5a 4.85b 2.4

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KilometresOMAP INFORMATIONProjection: GDA 1994 MGA Zone 52Date Saved: 3/7/2019Client: Core ExplorationAuthor: F Watt (reviewed K Welch)DATA SOURCEProject components: ClientImagery: ESRI basemap (Digital Globe)Catchment data: EnviroConsult Aust

Figure 3-2 Map of surface water catchments of the project area


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Figure 3-3. Map of mine footprint sub-catchments

LegendMine site footprint

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3.2.2 Topography and soils

The topography within ML31726 is relatively flat and stream slope gradients are less than 1% (EnviroConsult 2018a). The highest elevation is 35 mAHD in the south, along the Darwin Harbour / Bynoe Harbour watershed, and the lowest is 10 mAHD, where the drainage lines flow under the Cox Peninsula Road (derived from National Digital Elevation Model 1 Second Shuttle Radar Topography Mission: http://www.ga.gov.au/elvis/).

The mine footprint is on a slight rise within an area mapped as land unit 2a1, comprising rudosol type soil’s, and described as “Low Rises, gradient to 4%; shallow gravelly lithosols: Eucalypt Open Woodland, minor Woodland” (DLRM 2015).

The drainage lines on either side of the mine footprint have seasonally inundated hydrosol soils and are mapped as Land Units 5a and 6b; described as:

Land Unit 5a: “Narrow upland alluvial plains; gradient <1%; hard-setting apedal mottled yellow duplex soils: Grassland with scattered trees”

Land Unit 6b: “Broad lowland plains; gradient <1.5%; shallow to moderately deep siliceous sands: Grevillea/Melaleuca Tall Shrubland to Low Open Woodland, minor Open Woodland”

The drainage line upstream and downstream of Observation Hill Dam is mapped as land unit 5a.

Some areas along the drainage lines either side of the mine footprint, and also downstream of Observation Hill Dam, can retain saturated soils and/or pools into the early dry season. A survey targeting the threatened wetland plant Stylidium ensatum undertaken by EcOz Environmental Consultants in June 2018 (EcOz 2018b) recorded shallow pools remaining in the drainage lines either side of the mine footprint, and also wet areas downstream of Observation Hill Dam; as mentioned in the section above.

The project area, including both ML31726 and Observation Hill Dam, are mapped as having no acid sulfate soil risk; see the Acid Sulfate Risk Categories of the Greater Darwin Area Map (DIPE 2004). There are no areas mapped as “High” risk within 10 km of the project area. The closest risk of acid sulfate soils (“Moderate”) is the Darwin Harbour intertidal area, which is greater than 2 km north of the mine footprint, and the Bynoe Harbour intertidal area, which is greater than 4 km downstream of Observation Hill Dam.

http://www.ga.gov.au/elvis/


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3.2.3 Surface water environmental and social values

Land-use and surface water use

There are no national parks or conservation areas within the catchment upstream or immediately downstream of the proposed mine or Observation Hill Dam. The closest is Channel Island Conservation Reserve, 16 km to the northeast in Darwin Harbour, and Blackmore River Conservation Reserve, which is 20 km to the southeast, and well outside the project area catchment.

There are no residences, farms or industry within the catchment areas upstream or immediately downstream, and no uses for which surface water is currently being extracted. Berry Springs, a small township and rural residential area 22 km southeast of the project, is the closest area of intensive land-use; mainly horticulture and some cattle grazing.

Biodiversity values and Beneficial Uses

The project area including both the mine footprint and Observation Hill Dam catchments as well as surrounding catchment areas are largely undeveloped vacant crown land with only minor disturbances including the sealed Cox Peninsula Road, unsealed access tracks, historic mining pits and dams (see Frater 2005), and mineral exploration activities. Given this, waterways in the project area are largely intact (close to reference condition) and would be considered under the ANZECC 2000a protection level classification as ‘slightly disturbed’.

The NT Government identifies Darwin Harbour as a Site of Conservation Significance with important biodiversity values (see Factsheet NRETAS 2009). The Harbour supports a range of estuarine, freshwater and terrestrial environments including extensive areas of tidal mudflats and mangroves. Fifteen threatened species are reported from within the Site, although none within the catchment upstream or downstream of the project. A survey targeting the threatened wetland plant Stylidium ensatum, undertaken in the project area in June 2018 (EcOz 2018b), found no evidence of this plant. Also, despite the freshwater stream downstream of the mine footprint (between Cox Peninsula Road and Darwin Harbour upper tidal limit) being assessed as in reference or ‘good’ ecological condition (see Baseline aquatic ecology section below), it is not an example of a rare, highly diverse, or significant habitat in the region. Similarly, the ephemeral drainage lines either side of the mine footprint prior to flowing under the Cox Peninsula Road do not maintain flows into the dry season, and do not have a well-defined channel or riparian vegetation (see photos of monitoring sites GPUS SW3 and GPDS SW1 in Figure 6-1).

The watercourse downstream of Observation Hill Dam, starting from a point around 2 km downstream of the dam wall has a well-developed channel and riparian vegetation (i.e. surface water monitoring site BPDS SW2; see photo in Figure 6-2). This section of watercourse may hold some ecological values; although the habitat itself is not rare in the region or the specific habitat of a threatened species.

Darwin Harbour is listed as a wetland of national significance in the Directory of Important Wetlands in Australia (DIWA: NT029 Port Darwin). The drainage lines within the project area and waterways immediately downstream of the mine footprint and Observation Hill Dam do not have any specifically identified important wetlands; only the habitats fringing the Harbour itself e.g. mangroves, saltmarsh, tidal mudflats.

The project area lies within the Darwin Harbour Region declaration of surface water beneficial uses under the NT Water Act (NT Government Gazette No. G27, 7 July 2010). This declaration states that in relation to waterways within the Darwin Harbour Region:

The protection of environment, cultural (aesthetic, recreational and cultural), agriculture and rural stock and domestic to be the beneficial uses of water that apply to all natural waterways in the Darwin Harbour catchment, including all named and unnamed springs, creeks, rivers, lakes, lagoons, swamps or marshes.

The water quality objectives that apply to these waterways under this declaration are the Water Quality Objectives for the Darwin Harbour Region Background Document (NRETAS 2010). For parameters such as metals and other toxicants, where no objective is specified, the Australian and New Zealand Guidelines for Fresh and Marine Water Quality (ANZECC 2000a) apply.


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Each year, the NT Government releases a Darwin Harbour Region Report Card, which summarises the results of water quality monitoring undertaken by the Aquatic Health Unit. The Report Card specific to West Arm, the where the waterways from the project area drain into, has received an “A” grading, indicating excellent water quality, for all years since the report cards started in 2009 (except for 2015 where it received a “B”). The Aquatic Health Unit considers West Arm to be relatively undisturbed with stream inflows limited to wet season run-off from a largely intact undisturbed catchment.

In relation to management and control of surface and groundwater extraction, the project area lies within the Darwin Rural Water Control District declared under the NT Water Act. Pursuant to Section 41 of the Act, a permit is required to construct a dam and pursuant to section 45, a licence is required to take surface water. At the time of writing, mining activities were exempt from this requirement; however, an amendment to the Act to encompass mining is expected in early 2019. Core is anticipating having to apply for these permits in order to construct and extract water from the Mine Site Dam and Observation Hill Dam.

Baseline aquatic ecology

GHD (2017a) completed a baseline aquatic survey for the project in May 2017. This is the only known aquatic ecology survey specific to the project area. The survey sampled for macroinvertebrates and fish species at three sites downstream of the mine footprint; all north of the Cox Peninsula Road (Figure 3-4). Site UC2 is on an ephemeral stream receiving drainage from sub-catchments 5a and 5b, and UC3 is on an ephemeral stream receiving drainage from sub-catchments 2a and 2b. Site UC1 is downstream of the confluence of the streams from these sub-catchments, and is less than 1 km from the mangrove-lined tidal reaches of Darwin Harbour West Arm, where a distinct major increase in electrical conductivity (EC) was measured marking the change to tidal waters.

A forth site, BP, is located outside the catchment area encompassing the mine footprint. This site is in an adjacent catchment, just upstream of the historic BP mine pit. It is intended as a control site for future repeat aquatic ecology surveys (if required) during or post mining.

All sites appeared in a natural undisturbed condition with riparian vegetation, pools and woody debris. The only impact noted was elevated turbidity at UC1 (33 NTU) from an upstream ford constructed where an unsealed vehicle track crosses. Upstream of this ford, at site UC3, turbidity was recorded as very low (2.4 NTU). Sites UC2 and BP also recorded very low turbidity (0.6 and 2.7 NTU respectively).

All sites are freshwater, although the influence of seawater was detected at site UC1, where EC was comparatively higher (162 µS/cm) than the sites upstream UC2 and UC3 (both 19 µS/cm) and BP (24 µS/cm).

The results of macroinvertebrate sampling indicated that sites UC2, UC3 and BP had similar species composition and are un-impacted by pollution and in reference condition. Of the four sites, BP had the highest taxa richness and presence of pollution-sensitive species. Site UC1 differed significantly in its species composition and appeared slightly impacted; although this may be more to do with the species used in the AUSRIVAS Model; where many species recorded at this site are not included in the model used for indicating level of impact. UC1 also recorded an estuarine fish species (out of a total 4 species recorded at this site). Whereas all fish species recorded at the other sites were freshwater (total 7 species; each site having 5 of these). The closer proximity of UC1 to estuarine waters means it has differing aquatic species to the other three sites.

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Figure 3-4 Location of baseline surface water, groundwater and aquatic ecology monitoring sites


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3.3 Groundwater

3.3.1 Groundwater aquifers and flows

CloudGMS (2018) have described and modelled the groundwater aquifers of the project area. Their report is used in the summary below for existing background information relevant to groundwater of the area, and in Section 5 for modelled results of groundwater flows for assessing potential impacts of the proposed mine.

Data is also taken directly and used in the summary below from the groundwater monitoring database established through regular sampling by EcOz of six bores installed on site in May/June 2017 (bore installation by GHD 2017b). Originally, 10 bores were planned, however, only six of these were installed:

GWB01 is a deep bore located close to the centre of the proposed mining pit

GWB08 and GWB10 are a nest of two bores, one deep and one shallow located down-gradient of the pit

GWB03 is a deep bore located at the centre of the proposed WRD site and up-gradient of the pit

GWB06 and GWB07 are a nest of two bores, one shallow and one deep, located up-gradient of the mine footprint

Bore locations are shown in Figure 3-4 and bore details provided in Table 3-2.

Table 3-2. Groundwater monitoring bore details.

Bore ID RN Depth (m)

Screened Interval

(m)Screened Formation Purpose

GWB01 040093 160 88-154 Fresh BCF Deep bore in proposed pit shell, representative of groundwater into the pit.

GWB03 040096 63 50-62 Fresh BCF Deep bore located on site of proposed WRD, up-gradient of proposed pit (W side).

GWB06 040097 18 6-12Clay-highly weathered

shale

Shallow bore in surface aquifer; paired with deep bore GWB07; both cross gradient of mine footprint (SE side). NOTE – this bore is contaminated with cement and cannot be used for water quality; only groundwater levels.

GWB07 040098 63 49-61 Fresh BCFDeep bore in BCF fractured rock aquifer; paired with shallow bore GWB06; both cross gradient of mine footprint (SE side).

GWB08 040095 60 47-59Slightly

weathered to fresh

BCF

Deep bore in BCF; both down-gradient of mine footprint (N side).

GWB10 040094 12 0.5-6 Laterite Shallow bore in surface aquifer; paired with deep bore GWB08; both down-gradient of mine footprint (N side).

Unfortunately, GWB06 was contaminated with cement during drilling and cannot be used for water quality monitoring; only groundwater level measurements.

Additionally, for GWB10, the screened interval starts at 0.5 m depth, which does not comply with the Minimum Construction Requirements for Water Bores in Australia, 2012, 3rd Edition, National Uniform Drillers Licensing Committee (Australia). Screened intervals must start at a minimum of 1.0 m depth from the surface to prevent infiltration of surface water into the bore.

These two bores are the only ones installed in the laterite surface aquifer. Given that water quality samples from GWB06 are contaminated with cement and those from GWB10 may be subject to a component of surface water infiltration, very limited water quality information is currently obtained from this shallow aquifer system. In April 2019, bores GWB06 and GWB10 will be decommissioned and adjacent bores installed which are screened within the shallow aquifer and built in accordance with the Minimum Construction Requirements for Water Bores in Australia, 2012; see Water Quality Monitoring Plan in Section 10.


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Aquifer geology

The substrate and underlying geology of the area around the proposed mine footprint comprises a thin surface layer (less than 5 m thick) of Cenozoic sediments, mainly laterite gravel, sand and clay, underlain by Proterozoic Burrell Creek Formation (BCF) comprising shales, siltstones, and strongly foliated phyllite. The weathering profile goes to depths of 30 to 50 m before reaching fresh, un-weathered BCF (see mine pit profile in Figure 2-1).

The weathered and fractured rock BCF aquifer is a poor groundwater resource with a lack of primary porosity and open fracturing, and bore yields typically less than 0.5 L/s. Localised higher yields can occur where drilling intersects fracture zones or quartz veining; also at the base of the weathered zone. The weathered zone is more permeable than the un-weathered fresh BCF, with the highest permeability’s most likely in the overlying Cenozoic sediments and upper-most weathered (laterised) BCF. The potential of these zones to store and transmit groundwater however is not significant, due to their limited saturated thickness. Minor aquifers may occur in the surface Cenozoic sediments in areas with thicker alluvial cover, such as along drainage lines.

Hydraulic conductivity

Hydraulic conductivity (K) is the ease with which groundwater can move through the geological formation which hosts the aquifer. Where K is high, water will flow through the aquifer easily, and the converse when K is low. Testing to derive Ks for the shallow and deep aquifers under the project area i.e. slug tests and recovery tests (GHD 2017b) found the:

Thin surface laterite aquifer has a moderately high K ranging between 0.068 and 1.7 m/day Weathered zone has a moderate K ranging between 0.022 and 0.16 m/day Fresh BCF has the lowest K ranging between 0.003 and 0.024 m/day.

Groundwater levels

Groundwater levels, measured in metres below ground level (mBGL), i.e. standing water levels (SWLs), have been recorded continuously by loggers installed in each bore since June 2017. SWL’s are also measured manually during water quality sampling rounds. Figure 3-5 shows how SWL’s varied from the peak of the wet season in late January/early February 2018 into the dry season until August 2018.

SWLs in the BCF aquifer ranged from 0.3 to 2.0 mBGL in the wet season, and 4.0 to 6.5 mBGL in the dry season. This equates to a seasonal fluctuation in the BCF aquifer of between 3.3 and 4.5 m, with the largest change in the deep mine pit bore GWB01.

Levels in the shallow laterite aquifer ranged from artesian (flowing at the surface) during the wet season, to around 2.7 mBGL in the dry season. The continuous groundwater levels measured in the shallow laterite bore GWB10 (Figure 3-6) show that levels are highly responsive to rainfall, with spikes following individual rainfall events in the early wet season, sustained levels close to ground level during the wettest months of the wet season, and a steep drop in levels once wet season rains finish. Water quality in this bore also reflects the close connection between surface and groundwater in the shallow laterite aquifer (see Section 7).


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Figure 3-5. Standing water levels (metres below ground level) measured in the six groundwater monitoring bores.


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Figure 3-6. Hydrograph for shallow laterite aquifer from logger installed in Bore GWB10.

Groundwater flows and recharge

Based on the conversion of standing water levels across the site to metres Australian Height Datum (mAHD), groundwater flows were found to be in a north to north-east direction. Levels fluctuate seasonally by up to 4.5 m however, the general flow direction remains the same. Regionally, it is expected the groundwater table is a subdued reflection of the topography, flowing from areas of higher topography to areas of lower topography, and that groundwater from the site flows north towards Darwin Harbour.

Diffuse recharge is expected to be the dominant recharge mechanism, where water is added to the aquifer from percolation of rainfall over a wide area. Evapotranspiration and diffuse discharge are likely the dominant groundwater discharge mechanisms. Discharge to ephemeral drainage lines will also occur but volumes are expected to be small due to the low K of the aquifer. Comparisons of baseline surface water quality with groundwater quality confirm this for the drainage lines upstream and downstream of the mine footprint (see Section 7). Surface water quality downstream of Observation Hill Dam indicates a degree of groundwater inputs.

3.3.2 Groundwater environmental and social values

The BCF fractured and weathered rock aquifer beneath the project area is a poor groundwater resource, with bore yields typically less than 0.5 L/s. Given this, there is limited use of this aquifer for domestic, stock, or agricultural water supply. The closest registered bore currently in use is located on the Cox Peninsula Road, approximately 13 km east of the proposed mining pit (Cloud GMS 2018). This is well outside the modelled groundwater drawdown cone at the end of the two years of mining, which extends approximately 1 km from the pit and will remain within the mining lease boundary. It also does not intersect any of the ephemeral drainage lines around the mine footprint.

The Berry Springs Dolostone aquifer is located around 22 km east of the project area. There are current concerns regarding over-extraction from this aquifer and water allocation is closely managed and subject to the Berry Springs Water Allocation Plan 2016-2026 (DLRM 2016). The BCF fractured rock aquifer beneath the project area has no connection to the Berry Springs Dolostone aquifer. The BCF aquifer has very poor hydraulic conductivity, and would have very poor connectivity over a distance of 22 km. Further, groundwater underneath the project area flows from the higher ground to the south, not the east where the dolostone aquifer is located, similarly, groundwater leaving the mine footprint area flows north towards Darwin Harbour, not east.


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Groundwater dependent ecosystems (GDEs) are “ecosystems which require access to groundwater on a permanent or intermittent basis to meet all or some of their water requirements so as to maintain their communities of plants and animals, ecological processes and ecosystem services” Richardson et al (2011). Types of potential GDEs found in areas around the project area could include vegetation associated with springs or seeps, wetlands that persist throughout the dry season, riparian vegetation or monsoon rainforest patches reliant on groundwater remaining within the root zone for much of the year.

Given the low hydraulic conductivity of the aquifer, groundwater discharge to surface features in the region around the project area is likely minimal. Surface and groundwater quality results for the area around the mine footprint indicate this (see Sections 6 and 7). Therefore, the occurrence of GDE’s dependant on such discharge is unlikely.

CloudGMS (2018) reviewed The Groundwater Dependent Ecosystems Atlas available through the BoM website (http://www.bom.gov.au/water/groundwater/gde/map.shtml). Figure 3-7 reproduced from CloudGMS (2018) shows the low, medium and high potential terrestrial GDEs mapped at a national scale. There are no medium potential terrestrial GDEs located within 2 km of the mine footprint and therefore none within the predicted 1 km drawdown cone from pit dewatering. There is a medium potential GDE located around 2 to 3 km north of the mine, however this is on the northern side of the tidal inlet, which would form a no-flow boundary, preventing connection to groundwater moving north from the project area. Groundwater supply to this GDE would be from the higher ground immediately to the north-east.

In relation to Observation Hill Dam, medium potential GDEs are located up-gradient (west and north-west) and down-gradient along the drainage line that receives overflows from the dam (Figure 3-7). Baseline groundwater quality monitoring undertaken for the project (Section 7) indicates groundwater is contributing to flows in the drainage line downstream of Observation Hill Dam during the wet season. There is however, no evidence of spring-fed surface water flows during the dry season.

Observation Hill Dam is likely a source of recharge to the groundwater aquifer. Prior to construction of the dam, the area now occupied by the dam would also have been a source of recharge; albeit diffuse recharge. The presence of the dam potentially contributes to extended recharge of the aquifer into the dry season. The degree of importance of this recharge and subsequent groundwater supply for maintaining riparian vegetation and ecosystems in the waterway downstream are not known. Late-dry season (October 2017) site inspections of the watercourse found pools but no visible flows at a point starting around 2 km downstream of the dam wall. The well-developed riparian vegetation at this point indicates some level of sub-surface input from groundwater is supporting this vegetation community throughout the dry season.

As discussed in Section 4 below, raising the Observation Hill Dam wall extends the time it takes for the dam to fill and spill once wet season rains start in November/December. Once full, the dam is modelled to remain above its previous capacity of 364 ML until at least the mid-dry season in July/August (see Figure 15 in EnviroConsult 2018b), and therefore, will be supplying the same amount of seepage and groundwater aquifer recharge until this time.

Baseline surveys of riparian vegetation cover and condition downstream of Observation Hill Dam are being undertaken by a highly experienced NT-based EcOz botanist in March 2019, that include ground-based surveys and the recording or aerial imagery using a drone. The results of these surveys will assist in identifying any sensitive vegetation types, such as GDEs, monsoon vine forest etc and allow for future monitoring of any impacts.

http://www.bom.gov.au/water/groundwater/gde/map.shtml


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Figure 3-7. GDEs mapped for the project area and surrounds (from national-scale dataset available through BoM website The Groundwater Dependent Ecosystems Atlas).


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4 HYDROLOGICAL POTENTIAL IMPACTS

Hydrological modelling was undertaken for the project area and proposed water storages (Observation Hill Dam and MSD) by EnviroConsult Australia Pty Ltd (EnviroConsult 2018a, 2018b, 2018c and 2019). Tasks included delineating the catchments and sub-catchments relevant to the project, sourcing required model input data (rainfall, streamflow, landform, run-off, evaporation etc), and building, calibrating and testing the hydrological model (EnviroConsult 2018a). This model was then used to derive a pre- and post-mining water balance for low, average and high rainfall scenarios to investigate potential impacts to downstream flows (EnviroConsult 2018b).

EnviroConsult (2018b) also determined the existing available water storage (Observation Hill Dam) and different scenarios for increasing water storage for the project i.e. raising Observation Hill Dam wall and building a new dam adjacent to the mine (Mine Site Dam).

Modelling was used in EnviroConsult (2018c) to assess how mine infrastructure will change flooding extent for a 1 in 100-year storm event i.e. 1% AEP (Annual Exceedance Probability).

EnviroConsult (2019) addresses comments from the independent review (see Appendices C and D) and updates the modelling to reflect to latest mine site layout and pit dimensions.

4.1 Surface water storage requirements

EnviroConsult (2018a) estimated the current storage capacity of Observation Hill Dam to be 364 ML. This is not considered sufficient to ensure a secure mine water supply in the event of a drier than average year, or if the volume of groundwater inflows to the pit are less than predicted. The use of water from pit dewatering is expected to provide the bulk of water for dust suppression and ore processing (see Section 2.4 above, and Water Balance in Appendix A). The project water balance includes an operational efficiencies statement. This statement indicates a re-use efficiency of 39 % (i.e. 39 % of water requirements comes from water reuse).

EnviroConsult (2018b) modelled the increase in storage capacity for different wall lift scenarios. If a wall lift is undertaken, it is likely the dam wall will be raised by 1.5 m; increasing the storage capacity to 628 ML. This sizing is based on a worst-case scenario where offsets from reuse of water on-site (pit dewatering, TSF decant), or reduced water demand for dust suppression during the wet season are not included.

Additionally, as previously outlined in Section 2.4, in order to ensure sufficient water supply as contingency in the event of a drier than average year, and/or unexpected water needs, an extra dam referred to as the Mine Site Dam (MSD) is being considered for construction on a drainage line immediately north-west of the mine within sub-catchment 5a (Figure 3-3). Based on modelling undertaken by EnviroConsult (2018b), the estimated capacity required for the MSD is around 387 ML. The water surface area for a dam with this capacity (19 ha) is shown in Figure 3-3. This sizing is based on a worst-case scenario where the Observation Hill Dam wall is not raised, and pumping from the MSD is constant throughout the year without any offsets from reuse of water on-site (pit dewatering, TSF decant), or reduced water demand for dust suppression during the wet season.

4.2 Potential impacts from surface water extraction

EnviroConsult (2019) modelled the effect of mine site infrastructure, and the presence and extraction from the MSD, in order to assess the potential effect on downstream flows. The effect on downstream flows from raising the Observation Hill Dam wall by 1.5 m to increase its capacity and extracting water was also modelled. All hydrological modelling results are an overestimation given they are based on the worst-case scenario where surface water storages need to supply all water requirements without inputs from pit dewatering or TSF decant return, and a maximum pumping rate from the dams of 2.02 ML/day throughout the whole year.

Table 4-1 presents the modelled monthly reductions in streamflow volume at three sequential points downstream of the mine site corresponding to the sub-catchment outlets shown in Figure 3-2. Modelling assumes the MSD is empty at the start of each wet season. Changes to surface water drainage caused by mine site infrastructure


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was also taken into account, such as the diversion of drainage around the outer mine site bunds. Capture of direct rainfall within the mine site bunds and within the pit, was treated as being retained on-site and not discharged. As such, discharges from the sediment basins and from MWD1 are not included; which further mean the modelled reductions are an overestimation.

The highest modelled reductions just downstream of the mine site (2&5 DS) for an average wet season occur during the early wet season (November, December) when reductions are up to 29%, and late wet season (April) reductions up to 21%. Flow reductions are between 15 and 18% during the peak wet season months January to March. These reductions are well within the natural climate variability that aquatic ecosystems would be adapted to in these highly ephemeral streams. Table 3 in EnviroConsult (2019) demonstrates this, where the total annual discharge at the 2&5 DS point for natural pre-mining condition is 6,775 ML during a low rainfall year, 16,890 ML for an average year, and 33,631 ML for a high rainfall year. Under natural conditions, flow reduction for a low rainfall year is 60% compared to an average year. Given the short mine life of 35 months, these worst-case reductions of up to 29% are not significant and within the realm of natural variability. Furthermore, even during mining, flow reductions further downstream at DS 4 are always less than 15% for an average rainfall year, and as such not expected to impact on the ecological integrity of the mangrove environment or receiving aquatic habitats.

Despite the low risk, as a precaution, baseline surveys of riparian vegetation cover and condition downstream of the mine site are being undertaken by a highly experienced NT-based EcOz botanist in March 2019, that include ground-based surveys and the recording or aerial imagery using a drone. The results of these surveys will assist in identifying any sensitive vegetation types, such as GDEs, monsoon vine forest etc and allow for future monitoring of any impacts.

Table 4-2 presents the monthly reduction in streamflows downstream of Observation Hill Dam compared to pre-dam natural catchment conditions. Reductions of raising the dam wall combined with the maximum worst-case water extraction of 2.02 ML/day are presented along with the existing catchment (present dam wall height and no pumping). There is no change from current conditions for November and December anywhere downstream of the dam. The largest change at the catchment outlet to Charlotte River is 20%, which occurs during February. There is very little change from the current condition at the Charlotte River outlet to BYnoe Harbour (all less than 3% change.

The NT Water Allocation Planning Framework guideline (DENR 2018) states for ‘Rivers’:

At least 80 per cent of flow at any time in any part of a river is allocated as water for environmental and other public benefit water provision, and extraction for consumptive uses will not exceed the threshold level equivalent to 20 per cent of flow at any time in any part of a river.

This guideline applies to rivers, not ephemeral streams that cease to flow during the dry season. As such, the appropriate point to apply this guideline would be DS 5 downstream of the mine site, and the catchment outlet to the Charlotte River downstream of Observation Hill Dam. This guideline has been used in the discussion below as the basis for assessing the impact from flow reduction in the waterways downstream of the mine footprint (Darwin Harbour, West Arm catchment) and downstream of Observation Hill Dam (Bynoe Harbour catchment).

Despite the low risk, as a precaution, the baseline surveys of riparian vegetation cover and condition mentioned above being undertaken in March 2019, also include the areas downstream of Observation Hill Dam. The results of these surveys will assist in identifying any sensitive vegetation types, such as GDEs, monsoon vine forest etc and allow for future monitoring of any impacts.


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Table 4-1. Modelled monthly reduction in streamflow from mine site catchment (average rainfall year).

Outflow reference Description Nov Dec Jan Feb Mar Apr

2&5 DS Confluence of stream flow from sub-catchments 2 and 5. 29.3% 20.3% 17.5% 15.3% 15.3% 21.4%

DS 5Approx. 2km downstream. Represents stream flow discharge to upper tidal limit of receiving waters.

23.1% 16.9% 14.1% 11.9% 12.0% 16.9%

DS 4Approx. 6 km downstream. Represents stream flow discharge into upper branches of West Arm.

14.5% 12.9% 9.1% 7.8% 7.9% 11.1%

Table 4-2. Modelled monthly reduction in streamflow from Observation Hill Dam catchment compared to pre-dam conditions (average rainfall year).

Site Description Conditions Nov Dec Jan Feb Mar Apr

Current conditions 100% 100% 41.8% 12.2% 25.6% 43.9%

Operational conditions 100% 100% 78.8% 32.4% 44.6% 100%Spillway

Difference 0 0 37 20 19 56

Current conditions 58.3% 52.8% 11.4% 3.1% 6.1% 12.6%

Operational conditions 58.3% 52.8% 27.1% 22.6% 11.0% 28.7%

Approximately 3km downstream. Catchment outlet to Charlotte River.

Difference 0 0 16 20 5 16

Current conditions 12.6% 9.4% 1.6% 0.4% 0.8% 1.7%

Operational conditions 12.6% 9.4% 3.7% 2.9% 1.4% 3.9%

Approximately 4.5 km downstream. Charlotte River outlet to Bynoe Harbour.

Difference 0 0 2 3 1 2


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4.2.1 Darwin Harbour, West Arm catchment

The maximum monthly reduction in flows at the DS 5 point downstream of the mine site occurs in November (Table 4-1). This is the only time when flow reductions are above the 20% guideline limit. This is primarily because the MSD is retaining water as it fills after the dry season. This short period of reduction above the guideline, for one month of the year, and considering the natural variability (see discussion in Section 4.2 above) and short duration of mine life is not considered a significant risk to ecosystems at this point downstream of the mine.

At most, if these modelled reductions in early wet season flows were to occur, there may be a minor alteration in the quality and/or species composition of the riparian zone. In regards to the habitats along the section of waterway between Cox Peninsula Road and Darwin Harbour, these have been assessed using macroinvertebrate assemblages as in reference or ‘good’ ecological condition (see Section 3.2.3). Despite this, the riparian habitat along this waterway is relatively sparse and not an example of a rare, highly diverse, or significant habitat for threatened species in the region. The change in flows is unlikely to result in the loss of riparian vegetation along this section of stream, as it will continue to receive surface water flows through the peak of the wet season, which will fill the temporary waterholes around which riparian species occur.

Risks are of lesser concern for the ephemeral drainage line immediately downstream of the MSD prior to where it flows under the Cox Peninsula Road as this drainage line does not have a well-defined channel or riparian vegetation (see photos of monitoring sites GPUS SW3 and GPDS SW1 in Figure 6 1).

The nearest mangroves are approximately 1.7 km downstream of the mine site, at the upper tidal limit of West Arm. The first freshwater flushes are important for mangrove community health and any alteration to the quality and/or species composition would be greatest on the hinterland margin, which has the greatest diversity of freshwater-dependent species (Kristen Metcalfe, Eco Science NT, pers. comm. Sept 2018). It is possible that the modelled reduction in early wet season flow could alter the quality and/or species composition of the hinterland mangrove zone. Any impact is expected to be very localised as the community will continue to receive some early freshwater inputs from stream flows (60-70% of natural flow) and also from overland flows within the larger part of the catchment that is not affected by the mine site. The reduction in total wet season freshwater input to the upper mangroves has been modelled at 7.5% for an average wet season. Impacts are not expected to be significant because natural flushing of the system will still occur over the wet season, and the system is likely to have some resilience to changes in flow timing due to its reliance on ephemeral flows with a high level of natural variability.

In regards to cumulative impacts on the environment when the project’s extraction is combined with that of existing users and/or potential impacts on other consumptive users of surface water within the catchment of the mine footprint, there are no other commercial or domestic uses for which surface water is currently being extracted. There are no residences, farms or industry within the catchment, and no aquaculture activities downstream in West Arm. There are also no known planned consumptive uses, other than that of the project in the short term.

4.2.2 Bynoe Harbour catchment

Raising the dam wall of Observation Hill Dam wall by 1.5 m, combined with water extraction of 2.02 ML/day, would reduce the total annual spillway outflow volume by 69 % when compared to the existing catchment with the current dam wall height. The reduction in flows compared to an undisturbed catchment prior to dam construction would be even greater.

Comparative flow reductions (compared to the catchment with dam wall at current height) only occur during the mid- to late-wet season months of January February, March and April. There is no change in flow regime for the early to mid-wet season (November, December) because the existing dam wall would have reduced flows during this time anyway. Raising the dam wall extends the time it takes for the dam to fill and spill. Once full, the dam is modelled to remain above its previous capacity of 364 ML until at least the mid-dry season in July/August (see Figure 15 in EnviroConsult 2018b), and therefore, will be supplying the same amount of seepage and groundwater aquifer recharge until this time.


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Immediately downstream of Observation Hill Dam there is a wet area with poorly defined drainage and some deep pools near the foot of the dam wall, which appear to remain wet as a result of seepage (see survey undertaken for threatened wetland plant Stylidium ensatum by EcOz 2018). These areas support sedges and herbs in the ground layer during the Wet and early dry season, but mostly dry out later in the dry season. The area does not support a particularly rare, diverse or important wetland for threatened or migratory species in the region and is also to a degree adapted to annual rainfall variability and periods of dryness. As mentioned above, the rate and timing of seepage from the dam to this area is not expected to change significantly with raising the dam wall and pumping from the dam.

The watercourse further downstream of Observation Hill Dam, starting from a point around 2 km downstream of the dam wall has a well-developed channel and riparian vegetation (i.e. surface water monitoring site BPDS SW2; see photo in Figure 6 2). This section of watercourse may hold some ecological values; although the habitat itself is not rare in the region or the specific habitat of a threatened species. The level of flow reduction to this section of waterway has not been modelled but would be significantly less than 69% given this location receives run-off from an additional 234 ha of catchment. The total catchment area above this section of watercourse is approximately 344 ha, and the catchment above Observation Hill Dam takes up approximately 110 ha of this. Therefore, the amount of catchment area feeding this part of the watercourse has been reduced by about 32%.

Further downstream at the watershed outlet, where the catchment meets the tidal waters of Bynoe Harbour, the total annual reduction in flow is 1.8%. This is well below the guideline of no more than 20% flow reduction. When compared to a natural catchment without any dams, the maximum monthly flows reduction at the watershed outlet is 3.3%, which occurs in early-dry season months November and December (Table 4-2). This is still well below the 20% flow reduction guideline and as such is unlikely to affect mangrove communities in this area.

In regards to the 9 hectares of terrestrial vegetation inundated by raising the Observation Hill Dam wall by 1.5 m, the majority of this is described as Pandanus spiralis, Lophostemon lactifluus, Livistona humilis Low isolated trees (see Chapter 2 in Supplementary EIS). A smaller area of woodland vegetation communities comprising Eucalyptus species will also be inundated. These communities are the most widespread land cover type in the Greater Darwin region (Hempel 2003). For each of the land units that occur within the disturbance footprint, the loss associated with the proposal equates to <1% of the extent mapped within the Greater Darwin region. Loss of these Eucalyptus woodland habitats is expected to have a limited impact to fauna because the area is relatively small and the affected habitat types are well represented in the surrounding areas, with no other industrial development in close proximity that would deter use of these habitats.

4.3 Mine site flood inundation modelling

EnviroConsult (2019) modelled how mine infrastructure may affect flooding in the area resulting from a 1% Annual Exceedance Probability (AEP) rainfall event. AEP is the probability that a given rainfall total accumulated over a given duration will be exceeded in any one year, i.e. a 1% AEP is a 1 in 100-year rainfall event. The modelling found a critical rainfall duration of 6 hours is required to produce such an event at a point located around 2 km downstream of the mine, where the waterway meets the tidal reaches of Darwin Harbour. The probable maximum peak discharge (Q) without mining infrastructure at this point was 118.9 m3/s, and with mining infrastructure 121.0 m3/s (an increase of 2.5%). For total Q, there is a drop of 11% caused by the retention of water within the pit and water holding dams within the mine site.

The modelling indicates that the mine site is protected from flood risk by the inundation bund. Flood water around the mine site drains away through natural stream lines and under the Cox Peninsula Road culverts. Inundation of Cox Peninsula Road is also reduced in time, extent and depth in the post-mining condition compared to the pre-mining condition. This is due to the mine site development envelope effectively removing part of the catchment area and reducing stream discharges.

The modelling for EnviroConsult (2018c) also ran scenarios that included the occurrence of storm surge at the same time as flooding. It was found that storm surge has no effect on inundation levels. The mine site is too far out of the storm surge zone.


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4.4 Potential impacts from increased flows from discharge

Discharge of excess water from the MWD1 is another aspect of the project that could alter surface water flows. Estimates of pit dewatering and subsequent discharge requirements are provided in Sections 2.4.1 and 2.4.2.

Discharge of excess water from MWD1 will be required during the wet season. In the first year of mining, discharges are predicted from January to March, and in the second year, discharges will be required from November to March (Table 4-3). The release of excess water will always be a relatively small percentage of the overall natural streamflow (less than 6%), apart from during the early wet season (November, December), when the percentage increase is between 17 and 53%. Note however, that this does not include potential reduced flows from construction of the MSD, which would reduce these increased flow percentages. Impacts from reduced flows from surface water extraction from the MSD, are assessed in isolation from the assessment of impacts from increased flows from MWD1 discharge due to the differing water quality characteristics i.e. discharge from MWD1 contains groundwater removed from the pit and it is possibly not appropriate to consider this as an ‘environmental flow’.

It is reasonable to say that these increases in streamflow during the early-wet season would remain within the range of natural variability. These increased volumes would easily replicate the occurrence of early-wet season storms. Given this, it is proposed that early-wet season releases of water from MWD1 be undertaken in pulses rather than as a slow continuous realise, which could encourage the growth of algae and eutrophication along the drainage lines, and does not replicate natural storm activity at this time of year.

The Water Quality Monitoring Plan (Section 10) addresses discharge requirements and monitoring, and plans for further baseline monitoring required to increase the certainty around early wet season discharge requirements and appropriate management strategies. Subject to the project gaining approval, discharges from the mine site require separate authorisation by a Waste Discharge Licence under the Water Act, a process which provides an additional layer of regulatory scrutiny and oversight by the NT EPA beyond the EIS process. As a result of these measures it is unlikely that discharge of excess water will significantly alter downstream surface water flows.


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Table 4-3. Percent increase in streamflows downstream of MWD1 from discharge. Streamflow and %increase values are for the Catch-5 DS discharge point in Figure 3-2.

Month Discharge volume (ML/mth)

Modelled streamflow (ML/mth) from mine site reporting to Catch-5 DS

% increase in streamflow from MWD1 discharge4

2019 dry season No discharge NA NA

November 2019 46.36 501 8

December 2019 25.23 121 17

January 2020 38.49 2349 2

February 2020 40.48 1324 3

March 2020 47.12 800 6

2019 wet season total 194.68 5096 4


November 2020 129.60 501 21

December 2020 133.92 121 53

January 2021 89.52 2349 4

February 2021 51.15 1324 4

March 2021 45.58 800 5



November 2021 97.02 501 16

December 2021 46.18 121 28

January 2022 57.56 2349 2

February 2022 51.74 1324 4

March 2022 47.76 800 6


4 Note the 50th percentile year that was used for the modelling scenario was 1991. Daily rainfall data is required for the modelling, so the model was run on an example year (in this case 1991). The average annual rainfall for this year (1,652 mm) was closest to the average annual rainfall of 1,687 mm, calculated from the long-term SILO database. As it happened for 1991, the monthly total for December was much less than November, contrary to the average monthly record, see Figure 3-1. The model may be re-run in future using a composite average year if deemed necessary for assessing potential environmental impacts.


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5 GROUNDWATER POTENTIAL IMPACTS

5.1 Modelled pit inflows and impacts to existing groundwater aquifers from mining

Modelled groundwater inflows into the mining pit and predicted dewatering volumes were outlined in Section 2.4.2. At the end of mining, dewatering from the base of the pit will result in a drawdown cone extending approximately 1 km from the pit (CloudGMS 2018). This is not predicted to affect groundwater levels beneath ephemeral drainage lines or impact groundwater levels outside the mining lease boundary. Furthermore, the (pre-mining) water quality of ephemeral drainage lines around the mine footprint, and downstream of the mine footprint, indicate that groundwater doesn’t presently contribute to baseflows (see Sections 6 and 7).

Numerical modelling undertaken by CloudGMS (2018) predicts that post closure, the mine pit will gradually fill with water over a 50-year period before stabilising at a level around 7 to 8 m below the surrounding land surface. At this time, the water table is expected to be lower than pre-mining levels by 5 m at the pit edge, reducing to 0.5 m at 500 m from the pit edge.

Post-mining, the pit lake will act as a groundwater sink, meaning that groundwater in the immediate vicinity of the pit (within around 500 m) will flow towards the pit. This is because the total annual water loss from the pit from evaporation is greater than total annual groundwater and rainwater inputs. Given this, water quality in the pit lake is not expected to influence water quality in the surrounding aquifer.

Water quality in the final pit lake is expected to be good, with relatively low EC (for groundwater), neutral pH, and low concentrations of dissolved metals and nutrients except for arsenic, phosphorus, iron and lithium in comparison to surface water levels (see Section 7.4). Water quality is good in the nearby inundated BP33 historic mining pit, which has a similar geology to the Grants Project mine pit. EC is lower, and arsenic and phosphorus levels are very low possibly from dilution with rainwater and/or the precipitation and settlement of insoluble arsenic and phosphorus compounds due to oxidation and co-precipitation with dissolved iron.

The closest groundwater bores are more than 13 km from the mine site and will not be impacted. As the drawdown cone will be predominately within Core’s ML31726, and entirely within the areas of Core’s exploration tenements, the proposal is very unlikely to constrain future consumptive land-uses.

5.2 Localised mounding of groundwater

Seepage from the TSF and/or encompassing WRD material, could result in localised recharge of groundwater, and associated mounding of groundwater (where groundwater levels are locally higher than the surrounding aquifer). The majority of water from the TSF will be recovered through the under-drainage system and reused in operations. The TSF will be constructed of low permeable material, limiting infiltration and subsequent groundwater recharge. Seepage is estimated to be 0.1 ML per month. During operations, the flow of groundwater is towards the pit, and the WRD / TSF sit above the groundwater drawdown cone, indicating any seepage will flow towards the pit (with a small proportion possibly flowing towards the north, see Section 5.3 below).

Post-closure, the TSF will be capped with low permeable material, limiting retention of rainwater that could seep into the groundwater. The volume of water seeping from the final closed TSF to the groundwater is expected to be similar, or less than during operations, as the TSF will not be receiving water from pumped tailings. The final pit lake has been modelled as a groundwater sink (see Section 5.1 above), meaning that groundwater in the immediate vicinity, including under the WRD, will predominantly flow towards the pit.

Given the small volume of water, the low hydraulic conductivity of the aquifer, and the location of the WRD within the drawdown cone, it is not expected there will be significant mounding of groundwater during operations or after closure, and regional groundwater flows would be unaffected.


49

The groundwater quality monitoring program (Chapter 10) includes the installation of additional bores up-gradient and down-gradient of the WRD/TSF for monitoring any changes in groundwater levels, and testing water quality parameters designed to detect any contaminants of concern from TSF/WRD seepage.

5.3 Particle tracking

CloudGMS (2018) modelled the predicted direction and spread of seepage from the WRD through the aquifer. The modelling uses forward particle tracks, or streamlines, to simulate the advective transport of solutes. The particles move along the hydraulic gradient (down-gradient) until exiting the model at an outflowing boundary (or ending up in a zone without significant flow velocity). The use of streamlines assumes steady-state flow conditions. Random-Walk Particle-Tracking solutions can be obtained by incorporating dispersive processes to the standard advective particle tracking. These solutions are theoretically consistent with advection - dispersion equation solutions.

The fate of particles seeded beneath the WRD at the end of the mine’s life are presented below in Figure 5-1. The majority of particles terminate at the pit to the east of the WRD as the groundwater gradient is towards the pit. A small proportion of particles beneath the northern portion of the WRD are not captured and terminate to the north of the proposed mine footprint. Reducing the size of the WRD or shifting the location of the WRD further south will result in a greater proportion of leakage being captured by the pit.

Note the analysis assumes that no additional recharge (associated with leakage from the waste rock) is assigned within the footprint of the WRD. Including recharge may result in a mound developing beneath the WRD and a greater proportion of the particles terminating to the north and northeast.

Random walk particle tracking is also used to investigate the fate of seepage from the WRD following mine closure. The particle tracks are similar to those for the end mine life, with the majority of seepage captured by the pit. However, filling of the pit with water has reduced the gradient towards the pit-lake resulting in a greater proportion of seepage from the northern portion of the WRD not being captured by the pit-lake and terminating north toward the drainage line.

As mentioned in the section above, the groundwater quality monitoring program (Section 10) includes the installation of additional bores up-gradient and down-gradient of the WRD/TSF for monitoring any changes in groundwater levels, and testing water quality parameters designed to detect any contaminants of concern from TSF/WRD seepage.


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Figure 5-1. Results of modelling showing the direction and spread of seepage from the WRD.


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6 BASELINE SURFACE WATER QUALITY

6.1 Baseline surface water quality monitoring

6.1.1 Monitoring sites

Baseline surface water quality monitoring has been undertaken for the project since February 2017. Figure 6-1 shows the location of surface water monitoring sites. Sites relating to the proposed mine footprint are:

GDS SW1 (Grants Down Stream Surface Water 1) on an ephemeral drainage line downstream of the proposed mine footprint (eastern side in sub-catchment 5b).

GDS SW2 (Grants Down Stream Surface Water 2) downstream of GUS SW3 and GDS SW1, where the ephemeral drainage lines on either side of the mine footprint join and flow through the culvert under Cox Peninsula Road.

GUS SW3 (Grants Up Stream Surface Water 3) on an ephemeral drainage line upstream of the proposed mine footprint (western side in sub-catchment 5a). During and after mining, this site will remain an upstream reference site not subject to mining impacts.

Surface water monitoring site selection was limited around the project area as drainage lines are very shallow and poorly defined (see photos in Figure 6-1). GDS SW1 and GUS SW3 do not have a distinct channel or riparian vegetation. During the wet season, these sites are identified by where the water flows through the tall grass. Also at GDS SW1, the water flows through a culvert under an unsealed access track. It is difficult to locate these drainage lines when they are dry.

GDS SW2 is on a well-defined channel with riparian vegetation that goes through a culvert under Cox Peninsula Road (see photos in Figure 6-1). Water typically flows at this site throughout the wet season and into the early dry season. Water also flows for much of the wet season and early dry season in the shallow drainages of GDS SW1 and GUS SW3; although cease to flow earlier than GDS SW2.

A further three sites are located in the Bynoe Harbour catchment downstream of Observation Hill Dam (Figure 6-2). The purpose of these sites is to investigate if mining of the BP 33 open cut pit (now filled with water), has resulted in any water quality impacts. This pit was mined between 1997 and 1999 to recover tin and tantalum ore from a pegmatite very similar to that targeted for the Grants Project (Frater 2005). Water quality in the BP33 pit may also indicate groundwater quality flowing into the Grants Project open cut pit. These sites are also downstream of the existing Observation Hill Dam, proposed as a possible water source for mining operations. Furthermore, if Core was to expand mining operations to the BP 33 area in the future, these sites could be used as monitoring sites for these operations. The three sites are:

BP Historic Pit inundated BP 33 open cut mining pit located directly adjacent, 70-80 m west, of the ephemeral drainage line flowing from Observation Hill Dam.

BPUS SW1 (BP 33 Up Stream Surface Water 1) on ephemeral drainage line upstream of BP33 pit and downstream of Observation Hill Dam.

BPDS SW2 (BP 33 Downs Stream Surface Water 2) on ephemeral drainage line downstream of BP33 pit and downstream of BPUS SW1 and Observation Hill Dam.

The ephemeral drainage line of these sites is well-defined by a channel and riparian vegetation, and typically flows throughout the wet season and early dry season (Figure 6-2).

Observation Hill Dam (OHD) was added to the monitoring program in October 2017 following the decision to possibly use this dam as a water source for the project.


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GDS SW1 GDS SW1

GUS SW3 GUS SW3

GDS SW2 GDS SW2

Figure 6-1. Photos of surface water monitoring sites around mine footprint taken 15 February 2017.


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BP Historic Pit BP Historic Pit

BPUS SW1 BPUS SW1

BPDS SW2 BPDS SW2

Figure 6-2. Photos of surface water monitoring sites relating to BP 33 historic open cut mining pit taken 15 February 2017.


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6.1.2 Monitoring undertaken

Sampling was undertaken between February 2017 and August 2018 as outlined in Table 6-1 below.

Table 6-1. Baseline surface water quality monitoring undertaken.

Date Season Sites Sampled

15 Feb 2017 Mid Wet All sites except OHD19 Apr 2017 Late Wet All sites except OHD12 Oct 2017 Late Dry OHD and BP Historic Pit only. All other sites dry.

31 Jan / 1 Feb 2018 Mid Wet All sites except OHD14 Mar 2018 Late Wet All sites except OHD3 May 2018 Early Dry All sites except OHD and GDS SW1 (dry)

8 / 9 Aug 2018 Mid Dry OHD and BP Historic Pit only. All other sites dry.

Rainfall over the 2016/17 and 2017/18 wet seasons was above average. In particular, record high rainfalls were recorded across the Darwin region during January 2018, with total monthly rainfalls greater than 900 mm recorded by the BoM stations closest to the project area (see Section 3.1). This is more than double the average January rainfall for these BoM stations.

Stream flows continued at all sites into the early dry season. Flows began to stop in May (2017 and 2018), starting with GDS SW1, which was not flowing during the 3 May 2018 monitoring round. All sites had stopped flowing by the mid dry season (2017 and 2018) and only sites OHD and BP Historic Pit could be sampled mid to late dry season.

6.2 Baseline surface water quality results

Water quality results are compared to the Water Quality Objectives for the Darwin Harbour Region (NRETAS 2010). These objectives aim to protect the beneficial uses identified for waterways in the Darwin Harbour region as outlined in Section 3.2.3 above. The specific objectives relating to the beneficial use of environment (aquatic ecosystems) are applied given these are the most conservative, and adherence to these would in most cases also protect the other beneficial uses of cultural (aesthetic, recreational and cultural), agriculture and rural stock and domestic water supply.

The NRETAS (2010) water quality objectives developed specifically for ‘freshwater rivers and streams’ are the most appropriate for the types of waterways receiving water from the project area, such as that released from sediment basins, and the MWD1 containing water dewatered from the pit.

Table 6-2 presents the field parameter results, and Table 6-3, Table 6-4 and Table 6-5 present the laboratory results.


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6.2.1 Field parameters

Field parameters for the sites upstream and downstream of the mine footprint (GUS SW3, GDS SW1 and GDS SW2) are discussed separately to the sites relating to Observation Hill Dam and BP33 pit (BPUS SW1, BPDS SW2, BP33 Historic Pit and OHD).

Field parameters measured at the sites upstream and downstream of the mine footprint show the water is:

Fresh, with low EC concentrations generally between 9 and 15 µS/cm, and always well below the water quality objective of 200 µS/cm.

For the three sites, pH varies widely between 5.41 and 8.14 with no apparent seasonal pattern or trends. Within-site variability is also very large with each of the three sites recording both acidic and alkaline pH’s at various times; often above and below the water quality objective range (i.e. is outside the range 50% of the time). The reason for this is that pH in these drainage lines is highly responsive to the effect of photosynthesising/respiring plants and algae within the water causing pH to vary widely over the course of each day. The degree of plant photosynthesis versus respiration removes or adds carbon dioxide to the water depending on the time of day, cloud-cover and shading i.e. removing carbon dioxide when sunlight is available and photosynthesising, and producing carbon dioxide when sunlight is less available and respiring. Carbon dioxide produces carbonic acid when dissolved in water, lowering the pH. Fresh inputs of rainwater (which is naturally acidic in the tropical Darwin region) can also lower pH, whereas stagnating water with an algal bloom can have a high pH during the day. Additionally, these waters have low total alkalinity (all <2 mg/L; see laboratory results below), which means the water has little buffering capacity to neutralise acids and stabilise pH.

Dissolved oxygen (DO) at all three sites is generally between 60 and 100% (median 80%saturation) and remains within the water quality objective range. There was no seasonal pattern or identifiable trends, and within-site variability was large for the same reasons explaining pH variability (i.e. variation from the effect of plant photosynthesis/respiration producing and removing oxygen from the water). Organic matter breakdown also has an influence, removing oxygen from the water. The low DO of 41%saturation measured at GUS SW3 in May 2018 is likely due to low flow conditions as the stream dries up in the absence of rainfall and fresh oxygenated run-off. There is also a high oxygen demand placed on the remaining small volume of water from organic matter breakdown combined with plant respiration (this measurement was taken during the early morning following the night time period where plants are respiring and not photosynthesising).

Turbidity levels are generally always low, even during high rainfall periods; remaining below 12 NTU and well below the water quality objective of 20 NTU. This is because the drainage lines flow through thick groundcover vegetation and their small catchments have minimal exposed soil.

Field parameters measured at the sites relating to Observation Hill Dam and BP33 pit show the water is:

Fresh, with low EC concentrations generally between 14 and 35 µS/cm, and always well below the water quality objective of 200 µS/cm.

Similarly to the mine footprint sites described above, pH varies widely at all four sites between 5.06 and 9.31 with no apparent seasonal pattern or trends. Within-site variability is also very large, with each of the sites recording both acidic and alkaline pH’s at various times; often above and below the guideline range (i.e. is outside the range 50% of the time). The reasons for this pH variability are the same as those explained above for the mine footprint sites.

Dissolved oxygen (DO) is generally between 60 and 100% (median 80%saturation; same as sites around mine footprint) and remains within the guideline range. There was no seasonal pattern or trends, and within-site variability was large for the same reasons explaining pH variability. The low DO of 34, 35 and


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41%saturation measured at the three sites sampled in May 2018 is likely due to organic matter breakdown and the absence of fresh oxygenated rainwater inputs.

Turbidity levels are generally always low, even during high rainfall periods; remaining below 9 NTU and well below the water quality objective of 20 NTU. This is because the catchment areas of these sites are well vegetated with minimal exposed soil.

6.2.2 Laboratory parameters

Anion, cation and total alkalinity concentrations are:

All very low at all seven sites. The concentrations at the three sites upstream and downstream of the mine footprint (GUS SW3, GDS SW1 and GDS SW2) are all below 2 mg/L. Concentrations in the OHD, BP Historic pit and upstream and downstream of BP33 pit are slightly higher (between 2 and 8 mg/L comprising 100% bicarbonate alkalinity). This is because these sites receive some input from groundwater, which is relatively higher in anion and cation concentrations (see Section 7.2.2).

Dissolved metal concentrations are:

All below laboratory detection limits and below the water quality objectives at all seven sites for cadmium, chromium, copper, lead, nickel, selenium, zinc, tin and mercury.

Above the water quality objectives for aluminium most of the time at all three sites upstream and downstream of the mine footprint (GUS SW3, GDS SW1 and GDS SW2). Concentrations up to 0.08 mg/L.

Sometimes above the water quality objective for aluminium at the BPUS SW1 and BPDS SW2 sites.

Always below the water quality objective for aluminium at the OHD and BP Historic Pit sites.

Always below laboratory detection limits and the water quality objective for arsenic at the three sites upstream and downstream of the mine footprint (GUS SW3, GDS SW1 and GDS SW2).

Above laboratory detection limits but remain below the water quality objective for arsenic at OHD and sites upstream and downstream of the BP33 pit. The BP Historic Pit site has the highest arsenic concentrations, however these remain below the water quality objective except for one instance where the concentration was slightly above the objective. The source of arsenic in the BP33 pit, and also OHD and sites upstream and downstream of the BP33 pit is from groundwater inflows (see Section 7.2.2).

All below 0.002 mg/L for lithium at the three sites upstream and downstream of the mine footprint (GUS SW3, GDS SW1 and GDS SW2), and at OHD. Concentrations are slightly higher (up to 0.008 mg/L) in the BP Historic Pit and also the upstream and downstream BP 33 sites. The source of lithium to these sites is from groundwater inflows (see Section 7.2.2).

All below 0.1 mg/L for iron at the three sites upstream and downstream of the mine footprint (GUS SW3, GDS SW1 and GDS SW2), and at OHD and BP Historic Pit. Of note, is that concentrations are generally always higher (up to 0.38 mg/L) at the upstream and downstream BP 33 sites. The source of this is not known but possibly from groundwater inputs from the shallow laterite aquifer (see Section 7.2.2).

Nutrient concentrations are:

Generally always above the water quality objective for nitrate+nitrite (NOx) at all seven sites; typically up to 0.03 mg/L and sometimes up to 0.06 mg/L. Nitrate makes up 100% of the measured NOx concentrations i.e. no nitrite.

Always below the water quality objective for total nitrogen (TN) at the BP Historic Pit site, and upstream and downstream BP33 pit sites.

Generally always below the water quality objective for TN at the sites upstream and downstream of the mine footprint (GUS SW3, GDS SW1 and GDS SW2) and at OHD; except for some isolated spikes.


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Generally always below detection limits for total phosphorus (TP) except for a few isolated spikes in the BP Historic Pit, and the upstream and downstream BP33 pit sites. Note laboratory limit of reporting (LOR) for NOx and reactive phosphorus is greater than water quality objective. As such, unless concentration is above LOR, it is not known if objective is exceeded.

Always below the reactive phosphorus water quality objective except for two isolated instances slightly above the objective at GUS SW3 and BP Historic Pit.

The consistent pre-existing baseline exceedances of the water quality objective for aluminium and NOx, and occasional spikes in TN, TP and reactive phosphorus must be taken into consideration when assessing impacts on water quality during and after mining. The ANZECC (2000a) Guidelines for Fresh and Marine Water Quality recommend under these circumstances to calculate site-specific trigger values based on the 80th percentile of baseline (or reference site) data. It is not however possible at this stage to calculate site-specific trigger values given the ANZECC (2000a) methodology requires at least two years’ worth of monthly data. It is recommended that assessment be based on comparing the baseline range of concentrations with those measured during and after mining, for example NOx ranges between <0.01 and 0.06 mg/L, if concentrations were to become consistently above this range then impacts on water quality can be implicated. Similarly, the occasional spike in TN, TP and reactive phosphorus would be considered background, whereas consistent concentrations above the objective would indicate an impact.

Total Petroleum Hydrocarbons / Total Recoverable Hydrocarbons (TPH/TRH) were analysed for all carbon fractions between C6 and C40, and also Benzene, Toluene, Ethylbenzene, Xylene and Naphthalene (BTEXN) at all sites during all monitoring rounds. Results are provided in Appendix E.

All concentrations were below detection limits except for one isolated instance at site BPUS SW1 in April 2017, where concentrations of TPH C10-C14 and C15-C28 (TRH >C10-C16 and >C16-C34) up to 1450 µg/L were detected. The cause is unknown. The samples were rerun by the laboratory using the silica-gel clean-up method, which removes any naturally occurring organic material such as algae that might give a false reading unrelated to petrochemical hydrocarbons. The silica-gel clean-up results were no different to the original results, therefore the concentrations are from fuel or oil contamination. No evidence of a hydrocarbon spill, or sheen or odours were observed during sampling. The site is remote and there are no known current activities or sources in the catchment. Possibly it came from a small fuel spill by unknown people fishing or hunting in the area. No further hydrocarbon detections occurred at this site during the subsequent three monitoring rounds.


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6.3 Baseline surface water quality summary and potential impacts

6.3.1 Mine footprint sites

When flowing, water quality of the ephemeral drainage lines upstream and downstream of the mine footprint is very fresh, with low EC concentrations generally less than 15 µS/cm, and always well below the water quality objective of 200 µS/cm.

Natural background pH varies widely between 5.41 and 8.14, and is often above or below the objective range. Similarly, DO varies widely, but remains within the objective range of 60 to 100%, with a median DO of 80%saturation. There is no apparent seasonal pattern or trend in the widely varying pH and DO readings. This is because these parameters are highly changeable depending on sunlight levels, the time of day, rainfall, streamflow, and aquatic plant biomass. Variability over the short term is far larger than any seasonal variability. Additionally, in regards to pH, total alkalinity measured at all sites is very low (<2 mg/L), which means the water has little buffering capacity to neutralise acids and stabilise pH.

Low DO levels below 60% can occur during low flow conditions as the stream dries up in the absence of rainfall and fresh oxygenated run-off, and the high oxygen demand placed on the remaining small volume of water from organic matter breakdown combined with plant respiration.

Turbidity levels are generally always low, even during high rainfall periods; remaining below 12 NTU and well below the water quality objective of 20 NTU.

All dissolved metal concentrations are below laboratory detection limits, and as such, below the water quality objectives for arsenic, cadmium, chromium, copper, lead, nickel, selenium, zinc, tin and mercury. Aluminium is above the water quality objective most of the time, with concentrations up to 0.08 mg/L. All lithium concentrations remain below 0.002 mg/L, and iron concentrations below 0.1 mg/L. There are no water quality objectives defined for lithium and iron.

NOx concentrations (made up of 100% nitrate) are generally always above the water quality objective; often up to 0.06 mg/L. Whereas TN, TP and reactive phosphorus are generally always below the water quality objective with the exception of some isolated TN and reactive phosphorus spikes. Note that for the first two monitoring rounds the laboratory limit of reporting (LOR) was higher than the water quality objective for reactive phosphorus, and as such, unless the concentration was above the LOR, it could not be determined whether the objective was exceeded or not. This was rectified in subsequent monitoring rounds, confirming that most of the time reactive phosphorus remains below the objective.

TPH/TRH and BTEXN concentrations are always below detection limits.

Potential impacts

In regards to potential impacts during mining, the following is highlighted:

EC, turbidity and dissolved metals (except aluminium) are very low and well below their respective water quality objectives. Sediment and erosion controls across the site must be highly effective, and the release of stormwater from the sediment basins, and release of water from MWD1, must ensure EC, turbidity and dissolved metals are not increased above the water quality objectives at surface water monitoring sites downstream.

For lithium and iron, which don’t have water quality objectives, downstream levels must remain below the natural background range; i.e. less than 0.002 mg/L and 0.1 mg/L respectively.

pH and DO are naturally highly variable and it will be difficult to distinguish impacts on these parameters from the mine unless pH becomes consistently more acidic (less than 5.4) or highly alkaline (greater than 8.1), or DO becomes consistently above or below the objective range; noting that DO can become naturally low during low flow conditions.


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TPH/TRH and BTEXN concentrations are always below detection limits and must remain so during mining operations.

The consistent pre-existing baseline exceedances of the water quality objectives for aluminium and NOx, and occasional spikes in TN and reactive phosphorus, must be taken into consideration. The ANZECC (2000a) Guidelines recommend under these circumstances to calculate site-specific trigger values based on the 80th percentile of baseline (or reference site) data. It is not however possible at this stage to calculate site-specific trigger values given the ANZECC (2000a) methodology requires at least two years’ worth of monthly data. It is recommended that assessment be based on comparing the baseline range of concentrations with those measured during and after mining, for example NOx ranges between <0.01 and 0.06 mg/L, if concentrations were to become consistently above this range then impacts on water quality can be implicated. Similarly, the occasional spike in TN and reactive phosphorus would be considered background, whereas consistent concentrations above the objective would indicate an impact.

6.3.2 Observation Hill Dam and BP33 sites

Water in the Observation Hill Dam, BP33 pit and in the ephemeral drainage line upstream and downstream of the BP33 (also downstream of Observation Hill Dam) is always fresh, with low EC concentrations generally lower than 35 µS/cm, and always well below the water quality objective of 200 µS/cm.

Similarly, to the mine footprint sites described above, natural background pH varies widely at all four sites ranging between 5.06 and 9.31 and often outside the objective range. DO also varies widely but remains within the objective range with a median DO of 80%saturation. This is because these parameters are highly changeable depending on sunlight levels, the time of day, rainfall, streamflow, and aquatic plant biomass. Variability over the short term is far larger than any seasonal variability. Additionally, in regards to pH, total alkalinity is low (<8 mg/L) which means the water has little buffering capacity to neutralise acids and stabilise pH. Although notably, anion, cation and alkalinity levels are higher at these sites compared to the mine footprint sites. This is because these sites receive some input from groundwater (see Section 7.2.2).

Low DO levels can occur during low flow conditions due to organic matter breakdown and the absence of fresh oxygenated rainwater inputs.

Turbidity levels are generally always low, even during high rainfall periods; remaining below 9 NTU and well below the water quality objective of 20 NTU.

All cadmium, chromium, copper, lead, nickel, selenium, zinc, tin and mercury concentrations are below laboratory detection limits, and as such, below the water quality objectives. Aluminium is sometimes above the water quality objective at the drainage line sites (BPUS SW1 and BPDS SW2), and always below the water quality objective at the impounded water sites (OHD and BP Historic Pit).

Arsenic is higher at these four sites compared to the mine footprint sites. The drainage line sites and OHD site are above laboratory detection limits (up to 0.002 mg/L) but remain below the water quality objective. The BP33 pit has higher concentrations (0.007 to 0.15 mg/L), with the highest being slightly above the objective. Lithium concentrations for all sites is up to 0.008 mg/L; which is also higher than the mine footprint sites. Likewise in regards to higher anion and cation concentrations compared to the mine footprint sites, the source of arsenic and lithium is from groundwater inflows (see Section 7.2.2).

Iron concentrations are always below the detection limit at the impounded water sites (OHD and BP Historic Pit) and relatively high (up to 0.38 mg/L) at the drainage line sites. The source of this is not known, but possibly from groundwater inputs from the shallow laterite aquifer (see Section 7.2.2).

NOx concentrations (made up of 100% nitrate) are generally always above the water quality objective; often up to 0.04 mg/L. Whereas TN, TP and reactive phosphorus are generally always below the water quality objective with the exception of some isolated TN, TP and reactive phosphorus spikes.

TPH/TRH and BTEXN concentrations are generally always below detection limits.

Potential impacts


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Given the only project-related activity in the catchment of these sites will be the extraction of water from Observation Hill Dam, physical (field parameters) and laboratory-measured parameters are not expected to change significantly from baseline levels.

Any water quality impacts resulting from reduced surface water flows and/or reduced groundwater aquifer recharge from extraction of water from Observation Hill Dam, will likely be very subtle and not detectable over the two to three-year mine life.

Continuation of water quality monitoring of these sites will provide further background water quality data for the region for comparison with sites downstream of the mine footprint; also background reference data if Core were to extend mining operations to within this catchment e.g. BP33 pit.


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Table 6-2. Baseline surface water quality monitoring results, field parameters.

pH Temp ORP EC DO Turbidity

pH unit °C mV µS/cm %sat NTU

6.0-7.5 200 50-100 20

GUS SW3 15-02-17 6.59 28.3 248 18.0 61 3.10GUS SW3 19-04-17 6.04 26.2 303 11.4 80 0.60GUS SW3 01-02-18 5.90 28.0 279 11.1 80 2.30GUS SW3 14-03-18 6.54 25.3 178 10.5 72 1.33GUS SW3 03-05-18 8.14 26.8 58 15.3 41 12.10GDS SW1 15-02-17 6.71 28.0 336 14.0 86 4.54GDS SW1 19-04-17 5.66 26.3 300 13.8 76 2.10GDS SW1 31-01-18 7.04 35.6 208 13.1 95 2.80GDS SW1 14-03-18 6.37 29.6 171 11.9 89 5.07GDS SW2 15-02-17 8.07 26.8 178 51.0 81 2.53GDS SW2 19-04-17 5.41 26.3 305 12.1 63 0.80GDS SW2 31-01-18 5.74 30.5 238 10.7 86 1.70GDS SW2 14-03-18 6.20 29.4 152 9.0 92 1.27GDS SW2 03-05-18 5.83 27.6 157 13.1 73 2.80OHD 12-10-17 6.59 31.7 80 19.1 80 3.70OHD 09-08-18 9.31 26.5 -10 34.7 79 8.90BP HISTORIC PIT 15-02-17 6.91 31.2 288 23.9 96 3.35BP HISTORIC PIT 19-04-17 6.65 30.7 272 18.8 98 0.60BP HISTORIC PIT 12-10-17 7.33 32.3 210 22.6 82 3.18BP HISTORIC PIT 01-02-18 8.90 29.9 131 26.2 100 8.40BP HISTORIC PIT 14-03-18 8.27 32.7 159 17.1 69 1.82BP HISTORIC PIT 03-05-18 7.64 30.8 117 20.7 35 1.94BP HISTORIC PIT 08-08-18 8.18 26.5 -15 22.1 94 1.90BPUS SW1 15-02-17 6.46 27.7 324 14.6 84 3.31BPUS SW1 19-04-17 5.45 27.5 308 18.2 72 2.00BPUS SW1 01-02-18 7.78 27.6 270 14.0 85 4.60BPUS SW1 14-03-18 7.24 25.1 173 15.7 73 3.86BPUS SW1 03-05-18 7.42 26.4 118 26.4 34 4.98BPDS SW2 15-02-17 5.06 27.9 437 15.3 82 3.16BPDS SW2 19-04-17 5.49 27.5 306 17.7 70 2.20BPDS SW2 01-02-18 7.84 28.0 243 16.6 85 5.60BPDS SW2 14-03-18 7.26 25.0 169 16.6 54 3.68BPDS SW2 03-05-18 6.67 26.6 145 24.4 41 2.10

Water Quality Objectives Darwin Harbour Region (freshwater rivers & streams)

Site Date Sampled

Field Parameters

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rdne

ss a

s Ca

CO3

Hydr

oxid

e Al

kalin

ity

as C

aCO

3

Carb

onat

e Al

kalin

ity

as C

aCO

3

Bica

rbon

ate

Alka

linity

as

CaCO

3

Tota

l Al

kalin

ity

as C

aCO

3

Sulfa

te

as S

O4

Chlo

ride

Calc

ium

Mag

nesi

umSo

dium

Pota

ssiu

m

mg/

Lm

g/L

mg/

Lm

g/L

mg/

Lm

g/L

mg/

Lm

g/L

mg/

Lm

g/L

mg/

LG

US

SW

315

-02-

17<1

<1<1

<1<1

<11

<1<1

2<1

GU

S S

W3

19-0

4-17

<1<1

<1<1

<1<1

1<1

<1<1

<1G

US

SW

301

-02-

18<1

<1<1

22

<11

<1<1

1<1

GU

S S

W3

14-0

3-18

<1<1

<1<1

<1<1

<1<1

<11

<1G

US

SW

303

-05-

18<1

<1<1

22

<1<1

<1<1

1<1

GD

S S

W1

15-0

2-17

<1<1

<1<1

<1<1

2<1

<12

<1G

DS

SW

119

-04-

17<1

<1<1

11

<12

<1<1

1<1

GD

S S

W1

31-0

1-18

<1<1

<11

1<1

2<1

<12

<1G

DS

SW

114

-03-

18<1

<1<1

<1<1

<1<1

<1<1

1<1

GD

S S

W2

15-0

2-17

<1<1

<12

2<1

1<1

<12

<1G

DS

SW

219

-04-

17<1

<1<1

22

<11

<1<1

1<1

GD

S S

W2

31-0

1-18

<1<1

<11

1<1

2<1

<11

<1G

DS

SW

214

-03-

18<1

<1<1

<1<1

<1<1

<1<1

1<1

GD

S S

W2

03-0

5-18

<1<1

<12

2<1

<1<1

<12

<1O

HD

12-1

0-17

<1<2

<34

4<1

3<1

<12

<1O

HD

09-0

8-18

<1<1

<15

5<1

2<1

<11

<1B

P H

ISTO

RIC

PIT

15-0

2-17

<1<1

<13

3<1

3<1

<12

<1B

P H

ISTO

RIC

PIT

19-0

4-17

<1<1

<14

4<1

2<1

<12

<1B

P H

ISTO

RIC

PIT

12-1

0-17

<1<1

<18

8<1

3<1

<13

<1B

P H

ISTO

RIC

PIT

01-0

2-18

<1<1

<16

6<1

2<1

<12

<1B

P H

ISTO

RIC

PIT

14-0

3-18

<1<1

<15

5<1

<1<1

<12

<1B

P H

ISTO

RIC

PIT

03-0

5-18

<1<1

<16

6<1

1<1

<12

<1B

P H

ISTO

RIC

PIT

08-0

8-18

<1<1

<14

4<1

2<1

<12

<1B

PU

S S

W1

15-0

2-17

<1<1

<12

2<1

1<1

<12

<1B

PU

S S

W1

19-0

4-17

<1<1

<12

2<1

2<1

<12

<1B

PU

S S

W1

01-0

2-18

<1<1

<12

2<1

1<1

<11

<1B

PU

S S

W1

14-0

3-18

<1<1

<14

4<1

<1<1

<11

<1B

PU

S S

W1

03-0

5-18

<1<1

<15

5<1

3<1

<12

<1B

PD

S S

W2

15-0

2-17

<1<1

<12

2<1

1<1

<12

<1B

PD

S S

W2

19-0

4-17

<1<1

<12

2<1

2<1

<12

<1B

PD

S S

W2

01-0

2-18

<1<1

<12

2<1

2<1

<11

<1B

PD

S S

W2

14-0

3-18

<1<1

<14

4<1

<1<1

<12

<1B

PD

S S

W2

03-0

5-18

<1<1

<14

4<1

3<1

<12

<1

Maj

or C

atio

ns

Site

Date

Sa

mpl

ed

Maj

or A

nion

s

Tabl

e 6-

4. B

asel

ine

surf

ace

wat

er q

ualit

y m

onito

ring

resu

lts, d

isso

lved

met

als.

63

Alum

iniu

mAr

seni

cCa

dmiu

mCh

rom

ium

Copp

erLe

adNi

ckel

Sele

nium

Zinc

Lith

ium

Iron

Tin

Mer

cury

mg/

Lm

g/L

mg/

Lm

g/L

mg/

Lm

g/L

mg/

Lm

g/L

mg/

Lm

g/L

mg/

Lm

g/L

mg/

LpH

>6.

5 0.

055

pH

<6.5

0.0

008

0.01

30.

0002

0.00

40.

0014

0.00

340.

011

0.01

10.

008

0.00

06

GU

S S

W3

15-0

2-17

0.07

<0.0

01<0

.000

1<0

.001

<0.0

01<0

.001

<0.0

01<0

.01

<0.0

05-

<0.0

5<0

.001

<0.0

001

GU

S S

W3

19-0

4-17

0.02

<0.0

01<0

.000

1<0

.001

<0.0

01<0

.001

<0.0

01<0

.01

<0.0

05-

<0.0

5<0

.001

<0.0

001

GU

S S

W3

01-0

2-18

0.07

<0.0

01<0

.000

1<0

.001

<0.0

01<0

.001

<0.0

01<0

.01

<0.0

050.

001

0.05

<0.0

01<0

.000

1G

US

SW

314

-03-

180.

02<0

.001

<0.0

001

<0.0

01<0

.001

<0.0

01<0

.001

<0.0

1<0

.005

<0.0

01<0

.05

<0.0

01<0

.000

1G

US

SW

303

-05-

180.

01<0

.001

<0.0

001

<0.0

01<0

.001

<0.0

01<0

.001

<0.0

1<0

.005

0.00

1<0

.05

<0.0

01<0

.000

1G

DS

SW

115

-02-

170.

08<0

.001

<0.0

001

<0.0

01<0

.001

<0.0

01<0

.001

<0.0

1<0

.005

-0.

08<0

.001

<0.0

001

GD

S S

W1

19-0

4-17

0.04

<0.0

01<0

.000

1<0

.001

<0.0

01<0

.001

<0.0

01<0

.01

<0.0

05-

0.05

<0.0

01<0

.000

1G

DS

SW

131

-01-

180.

08<0

.001

<0.0

001

<0.0

01<0

.001

<0.0

01<0

.001

<0.0

1<0

.005

0.00

20.

10<0

.001

<0.0

001

GD

S S

W1

14-0

3-18

0.08

<0.0

01<0

.000

1<0

.001

<0.0

01<0

.001

<0.0

01<0

.01

<0.0

05<0

.001

0.06

<0.0

01<0

.000

1G

DS

SW

215

-02-

170.

05<0

.001

<0.0

001

<0.0

01<0

.001

<0.0

01<0

.001

<0.0

1<0

.005

-0.

05<0

.001

<0.0

001

GD

S S

W2

19-0

4-17

0.02

<0.0

01<0

.000

1<0

.001

0.00

1<0

.001

<0.0

01<0

.01

<0.0

05-

0.06

<0.0

01<0

.000

1G

DS

SW

231

-01-

180.

04<0

.001

<0.0

001

<0.0

01<0

.001

<0.0

01<0

.001

<0.0

1<0

.005

0.00

1<0

.05

<0.0

01<0

.000

1G

DS

SW

214

-03-

180.

02<0

.001

<0.0

001

<0.0

01<0

.001

<0.0

01<0

.001

<0.0

1<0

.005

<0.0

010.

06<0

.001

<0.0

001

GD

S S

W2

03-0

5-18

<0.0

1<0

.001

<0.0

001

<0.0

01<0

.001

<0.0

01<0

.001

<0.0

1<0

.005

<0.0

01<0

.05

<0.0

01<0

.000

1O

HD

12-1

0-17

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10.

002

<0.0

001

<0.0

01<0

.001

<0.0

01<0

.001

<0.0

1<0

.005

<0.0

01<0

.05

<0.0

01<0

.000

1O

HD

09-0

8-18

<0.0

10.

002

<0.0

001

<0.0

01<0

.001

<0.0

01<0

.001

<0.0

1<0

.005

0.00

10.

06<0

.001

<0.0

001

BP

HIS

TOR

IC P

IT15

-02-

170.

020.

008

<0.0

001

<0.0

01<0

.001

<0.0

01<0

.001

<0.0

1<0

.005

-<0

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<0.0

01<0

.000

1B

P H

ISTO

RIC

PIT

19-0

4-17

<0.0

10.

007

<0.0

001

<0.0

01<0

.001

<0.0

01<0

.001

<0.0

1<0

.005

-<0

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<0.0

01<0

.000

1B

P H

ISTO

RIC

PIT

12-1

0-17

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10.

015

<0.0

001

<0.0

01<0

.001

<0.0

01<0

.001

<0.0

1<0

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0.00

6<0

.05

<0.0

01<0

.000

1B

P H

ISTO

RIC

PIT

01-0

2-18

0.05

0.00

6<0

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1<0

.001

<0.0

01<0

.001

<0.0

01<0

.01

<0.0

050.

006

<0.0

5<0

.001

<0.0

001

BP

HIS

TOR

IC P

IT14

-03-

180.

010.

007

<0.0

001

<0.0

01<0

.001

<0.0

01<0

.001

<0.0

1<0

.005

0.00

6<0

.05

<0.0

01<0

.000

1B

P H

ISTO

RIC

PIT

03-0

5-18

<0.0

10.

010

<0.0

001

<0.0

01<0

.001

<0.0

01<0

.001

<0.0

1<0

.005

0.00

8<0

.05

<0.0

01<0

.000

1B

P H

ISTO

RIC

PIT

08-0

8-18

<0.0

10.

008

<0.0

001

<0.0

01<0

.001

<0.0

01<0

.001

<0.0

1<0

.005

0.00

8<0

.05

<0.0

01<0

.000

1B

PU

S S

W1

15-0

2-17

0.04

0.00

2<0

.000

1<0

.001

<0.0

01<0

.001

<0.0

01<0

.01

<0.0

05-

0.17

<0.0

01<0

.000

1B

PU

S S

W1

19-0

4-17

0.01

0.00

1<0

.000

1<0

.001

<0.0

01<0

.001

<0.0

01<0

.01

<0.0

05-

0.09

<0.0

01<0

.000

1B

PU

S S

W1

01-0

2-18

0.04

0.00

1<0

.000

1<0

.001

<0.0

01<0

.001

<0.0

01<0

.01

<0.0

050.

002

0.09

<0.0

01<0

.000

1B

PU

S S

W1

14-0

3 -18

0.02

0.00

1<0

.000

1<0

.001

<0.0

01<0

.001

<0.0

01<0

.01

<0.0

050.

003

0.06

<0.0

01<0

.000

1B

PU

S S

W1

03-0

5-18

0.02

0.00

2<0

.000

1<0

.001

<0.0

01<0

.001

<0.0

01<0

.01

<0.0

050.

007

0.25

<0.0

01<0

.000

1B

PD

S S

W2

15-0

2-17

0.03

0.00

2<0

.000

1<0

.001

<0.0

01<0

.001

<0.0

01<0

.01

<0.0

05-

0.16

<0.0

01<0

.000

1B

PD

S S

W2

19-0

4-17

0.02

<0.0

01<0

.000

1<0

.001

<0.0

01<0

.001

<0.0

01<0

.01

<0.0

05-

0.10

<0.0

01<0

.000

1B

PD

S S

W2

01-0

2-18

0.04

<0.0

01<0

.000

1<0

.001

<0.0

01<0

.001

<0.0

01<0

.01

<0.0

050.

002

0.07

<0.0

01<0

.000

1B

PD

S S

W2

14-0

3-18

0.01

0.00

1<0

.000

1<0

.001

<0.0

01<0

.001

<0.0

01<0

.01

<0.0

050.

003

0.06

<0.0

01<0

.000

1B

PD

S S

W2

03-0

5-18

0.02

0.00

2<0

.000

1<0

.001

<0.0

01<0

.001

<0.0

01<0

.01

<0.0

050.

006

0.38

<0.0

01<0

.000

1

Wat

er Q

ualit

y O

bjec

tives

Dar

win

Har

bour

R

egio

n (fr

eshw

ater

rive

rs &

stre

ams)

Diss

olve

d M

etal

s

Site

Date

Sa

mpl

ed

Tabl

e 6-

5. B

asel

ine

surf

ace

wat

er q

ualit

y m

onito

ring

resu

lts, n

utrie

nts.

Not

e la

bora

tory

lim

it of

repo

rting

(LO

R) f

or N

Ox an

d re

activ

e ph

osph

orus

is s

omet

imes

gre

ater

than

wat

er q

ualit

y ob

ject

ive.

As

such

, unl

ess

conc

entra

tion

is a

bove

LO

R, i

t is

not k

now

n if

obje

ctiv

e is

exc

eede

d.

64

Amm

onia

as

NNi

trite

as

NNi

trate

as

N

Nitri

te +

Ni

trate

as

NTK

N as

NTo

tal

Nitro

gen

as N

Tota

l Ph

osph

orus

as

P

Reac

tive

Phos

phor

us

as P

mg/

Lm

g/L

mg/

Lm

g/L

mg/

Lm

g/L

mg/

Lm

g/L

0.00

80.

230.

010.

005

GU

S S

W3

15-0

2-17

0.11

<0.0

10.

040.

040.

80.

80.

01<0

.01

GU

S S

W3

19-0

4-17

0.04

<0.0

1<0

.01

<0.0

1<0

.1<0

.1<0

.01

<0.0

1G

US

SW

301

-02-

18<0

.01

<0.0

10.

020.

020.

20.

2<0

.01

0.00

6G

US

SW

314

-03-

180.

05<0

.01

<0.0

1<0

.01

<0.1

<0.1

<0.0

1<0

.001

GU

S S

W3

03-0

5-18

0.08

<0.0

10.

030.

030.

40.

4<0

.01

<0.0

01G

DS

SW

115

-02-

170.

06<0

.01

0.06

0.06

0.1

0.2

<0.0

1<0

.01

GD

S S

W1

19-0

4-17

0.04

<0.0

1<0

.01

<0.0

1<0

.1<0

.1<0

.01

<0.0

1G

DS

SW

131

-01-

180.

08<0

.01

0.02

0.02

0.2

0.2

<0.0

10.

003

GD

S S

W1

14-0

3-18

<0.0

1<0

.01

<0.0

1<0

.01

0.2

0.2

<0.0

10.

003

GD

S S

W2

15-0

2-17

0.05

<0.0

10.

030.

03<0

.1<0

.1<0

.01

<0.0

1G

DS

SW

219

-04-

170.

03<0

.01

<0.0

1<0

.01

<0.1

<0.1

<0.0

1<0

.01

GD

S S

W2

31-0

1-18

0.12

<0.0

10.

060.

060.

20.

3<0

.01

0.00

4G

DS

SW

214

-03-

18<0

.01

<0.0

1<0

.01

<0.0

1<0

.1<0

.1<0

.01

<0.0

01G

DS

SW

203

-05-

180.

01<0

.01

<0.0

1<0

.01

0.1

0.1

<0.0

1<0

.001

OH

D12

-10-

170.

03<0

.01

0.03

0.03

0.2

0.2

<0.0

1<0

.01

OH

D09

-08-

180.

01<0

.01

<0.0

1<0

.01

0.3

0.3

<0.0

10.

002

BP

HIS

TOR

IC P

IT15

-02-

170.

08<0

.01

0.02

0.02

<0.1

<0.1

<0.0

1<0

.01

BP

HIS

TOR

IC P

IT19

-04-

170.

03<0

.01

<0.0

1<0

.01

<0.1

<0.1

<0.0

1<0

.01

BP

HIS

TOR

IC P

IT12

-10-

17<0

.01

<0.0

10.

030.

030.

20.

2<0

.01

<0.0

1B

P H

ISTO

RIC

PIT

01-0

2-18

<0.0

1<0

.01

0.03

0.03

0.1

0.1

<0.0

10.

006

BP

HIS

TOR

IC P

IT14

-03-

180.

06<0

.01

<0.0

1<0

.01

0.2

0.2

<0.0

1<0

.001

BP

HIS

TOR

IC P

IT03

-05-

18<0

.01

<0.0

10.

010.

010.

20.

21.

18<0

.001

BP

HIS

TOR

IC P

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65

7 BASELINE GROUNDWATER QUALITY

7.1 Baseline groundwater quality monitoring

7.1.1 Monitoring bores

The context of the six monitoring bores installed on site in and around the proposed mine pit were outlined in Section 3.3.1. Bore locations are shown in Figure 3-4 and bore details provided in Table 3-2. Monitoring of water quality was undertaken in Bore GWB06, however results clearly show this bore is contaminated with cement and not suitable for including in the groundwater quality analysis. This bore can only be used for SWL measurements.

7.1.2 Monitoring undertaken

Sampling was undertaken between June 2017 and August 2018 as outlined in Table 7-1 below. All six bores were sampled each monitoring round. The first round in June 2017 was undertaken by GHD (2017b) around two to three weeks after the bores were installed. All subsequent monitoring rounds were undertaken by EcOz.

Table 7-1. Baseline groundwater quality monitoring undertaken.

Date Season

27 June 2017 Early Dry 31 Jan / 1 Feb 2018 Mid Wet

1 May 2018 Late Wet8/9 August 2018 Mid Dry

Rainfall over the 2017/18 wet season was above average, and groundwater levels in all bores except the deepest bore GWB01 were within 1 m of the ground surface in January and February 2018. At times, after intense rainfall periods, bores GWB03, GWB06, GWB07 and GWB10 were artesian i.e. would have been flowing if not for the bore casing above ground level. Especially after the intense rainfall period that occurred in January 2018, when total monthly rainfall in the project region was over 900 mm, which is more than double the average January monthly total (based on data from nearest BoM stations; listed in Section 3.1 above).

7.2 Baseline groundwater quality results

Water quality results are compared to the Water Quality Objectives for the Darwin Harbour Region (NRETAS 2010). These objectives aim to protect the beneficial uses identified for waterways in the Darwin Harbour region as outlined in Section 3.2.3 above. The specific objectives relating to the beneficial use of environment (aquatic ecosystems) are applied given these are the most conservative, and adherence to these would in most cases also protect the other beneficial uses of cultural (aesthetic, recreational and cultural), agriculture and rural stock and domestic water supply.

The NRETAS (2010) water quality objectives developed specifically for ‘freshwater rivers and streams’ are used. These are the most appropriate given the project includes provision to discharge water dewatered from the pit (comprising groundwater inflows and direct rainfall) during the wet season when this water will be in excess to that required for ore-processing and dust suppression. The water will be discharged from MWD1 into the same a shallow drainage depression adjacent to the mine, as discussed for the sediment basins in Section 2.5.2.

Table 7-2 presents the field parameter results, and Table 7-3, Table 7-4 and Table 7-5 present the laboratory results. Figure 7-1 is a Piper diagram, and Figure 7-2 and Figure 7-3 provide Stiff diagrams; all plotted using the anion and cation analysis results for all monitoring bores. Piper and Stiff diagrams are useful in grouping or discriminating groundwater samples on the basis of their ionic signature.


66

Groundwater quality in the four bores installed in the weathered and un-weathered BCF aquifer (i.e. GWB01, GWB03, GWB07 and GWB08) is distinctly different to that of the bore installed in the shallow laterite surface aquifer (i.e. GWB10). As such, the results for field parameters and laboratory parameters are discussed separately for each of the two different aquifers. Note that interpretations relating to the laterite surface aquifer are based on very limited information; i.e. one bore which is not installed to the relevant standard, see Section .

7.2.1 Field parameters

Field parameters measured in the weathered and un-weathered BCF aquifer show the groundwater:

Is moderately fresh, with relatively low EC concentrations for groundwater ranging between 137 and 281 µS/cm. In relation to the surface water quality objectives however, all concentrations measured in the deep mine pit bore (GWB01) were above the objective (200 µS/cm), and most concentrations in GBW03 were above the objective. Concentrations in GWB07 varied with the first two sampling rounds above the objective in June 2017 and February 2018, and the final two sampling rounds in May and August 2018, below the objective. GWB08 was always below the objective. Notably, GWB08 is screened within the weathered BCF, whereas the others are in the fresh BCF. EC concentrations appear to increase with depth into the aquifer away from the weathered zone.

Has a relatively neutral pH ranging between 6.41 and 7.52, and remaining within the water quality objective range, except for one slightly high pH of 7.52 in GWB01.

As expected for water that has been out of contact with the atmosphere for a period of time, DO was always low and oxidation reduction potential (ORP) always reduced (i.e. negative).

Has a very strong hydrogen sulphide odour, as was observed in bores GWB01, GWB07 and GWB08.

Field parameters measured in the laterite surface aquifer (GWB10) show the groundwater:

Largely reflects the water chemistry expected of rainwater and stream water showing this aquifer is closely connected to surface water.

EC is low (all below 26 µS/cm) and reflective of the surface water and well within the water quality objective.

pH is relatively acidic and below the water quality objective range. This pH is reflective of rainwater, which is naturally acidic in the warm tropical Darwin region, where carbon dioxide in the air readily dissolves in rainwater forming carbonic acid. Notably, pH increases (becomes less acidic) in the absence of rainfall (August 2018 sampling round). The pH of water in the soil can also be lowered through carbon dioxide from respiration by plants and soil organisms, and from the breakdown of organic matter.

DO is higher than that of the deeper BCF aquifer and more oxidised (positive ORP) indicating the water has more recently been in contact with the atmosphere i.e. aquifer is readily recharged with surface water.

Does not have a hydrogen sulphide odour.

7.2.2 Laboratory parameters

Major anion and cations measured in the weathered and un-weathered BCF aquifer show the groundwater:

Has moderate alkalinity (comprising 100% bicarbonate alkalinity) with concentrations increasing with depth into the aquifer i.e. GWB01 has higher concentrations (between 97 and 143 mg/L) than the shallower bores GWB03, GWB07 and GWB08 (between 67 and 107 mg/L).

Hardness is relatively low in all bores; all less than 42 mg/L, which is considered ‘soft’, and low in dissolved ions such as calcium and magnesium.

Piper and Stiff diagrams show a sodium-bicarbonate water signature, and all samples from all bores plot in a tight domain with little variation between sampling events or seasons.


67

Major anion and cations measured in the laterite surface aquifer (GWB10) show the groundwater:

Has negligible alkalinity, hardness and dissolved major cations; similar to those measured in the surface water around the mine footprint (see Section 6.2.2).

Piper and Stiff diagrams for GWB10 plot within a distinct domain, different to that of the deeper BCF aquifer bores and with a greater spread between sampling events.

Piper and Stiff diagrams for GWB6 clearly show the ingress of cement grout into the screen area during construction, and the limited development of this bore (see GHD 2017).

Dissolved metal concentrations measured in the weathered and un-weathered BCF aquifer show the groundwater:

Has very low metal concentrations below laboratory detection limits for all metals except aluminium, arsenic, zinc, lithium and iron (which are discussed below). Nickel levels were mostly very low and below the detection limit, and always well below the objective.

Aluminium concentrations are below the water quality objective except for three instances where it was slightly above the objective; all of which occurred during the first monitoring round (June 2017). All subsequent rounds, the aluminium concentrations were below the objective, and this metal is considered in low concentrations in the BCF aquifer.

Arsenic concentrations are above the water quality objective in all bores, with the highest concentrations in bore GWB07; ranging between 0.131 to 0.290 mg/L. The median concentration for all four bores is 0.060 mg/L, which is more than 4.5 times higher than the water quality objective (0.013 mg/L). Also, if the Australian Drinking Water Quality Guidelines (NHMRC 2011) are considered, these levels are more than 6 times the guideline limit (0.01 mg/L).

Arsenic concentrations in groundwater of the Darwin region were investigated by Karp (2008). The resulting map from this study shows areas of low, medium and high risk of bores producing water with arsenic concentrations above the drinking water guideline. The BCF aquifer as mapped as “high” risk. It is concluded that arsenic present in minerals of the BCF in the project area are being mobilised into the groundwater through natural processes such as oxidation, weathering reactions, and/or biological activity. Significantly, given arsenic levels in surface water sampling undertaken around the mine footprint were all below detection limits (see Section 6.2.2), these drainage lines must receive very little groundwater inflows. Conversely for the drainage lines downstream of OHD, it appears that groundwater inflows do contribute to stream flows, and arsenic is detectable up to concentrations of 0.002 mg/L.

Zinc was slightly elevated above the objective in GWB08 during the January 2018 sampling round (0.010 mg/L). All other monitoring rounds this bore was below the 0.008 mg/L objective. Also, given zinc levels in all other bores during almost all other monitoring rounds was below detection, zinc is not considered elevated in the BCF aquifer. The zinc detection in GWB08 may be from the percolation of water down from the surface laterite aquifer, given zinc is elevated in the shallow laterite aquifer bore GWB10, which is co-located (nested) with GWB08.

Lithium has no water quality objective. As expected, concentrations were highest in the deep mine pit bore (GWB01), where the lithium-bearing mineral spodumene is present. Levels ranged up to 1.730 mg/L. GWB08 had the next highest concentrations, ranging up to 0.279 mg/L, followed by GWB03 (up to 0.189 mg/L). Levels in the BCF aquifer are certainly elevated compared to areas without lithium-bearing mineralisation, and also compared to the surface water in the mine site area, which is below 0.002 mg/L (further evidence the BCF aquifer is not contributing significant groundwater inflows to the drainage lines around the mine site; see arsenic discussion above). Similarly to arsenic, groundwater is contributing to detections of lithium up to 0.007 mg/L in the drainage lines downstream of OHD (see Section 6.2.2).

Iron has no water quality objective. Concentrations were a lot higher in GWB08 (up to 0.77 mg/L) compared to the other three bores (up to 0.33 mg/L). This is higher than the surface water levels, which were up to 0.10 mg/L. GWB08 is screened within the weathered BCF, whereas the other three bores are screened


68

within the fresh BCF. Possibly, these higher dissolved iron concentrations are associated with the weathered zone. Notably, the iron concentrations are similar to those in the highly weathered laterite surface aquifer (GWB10).

Dissolved metal concentrations measured in the laterite surface aquifer (GWB10) show the groundwater:

Has higher concentrations than the BCF aquifer for copper, lead, and zinc (discussed further below), and lower concentrations for arsenic and lithium (largely remaining below the objective for arsenic). Aluminium levels are comparable to the BCF aquifer however, exceed the objective more frequently because of the lower pH. Iron levels are comparable to the weathered zone BCF aquifer and above levels measured in the surface water around the mine footprint.

Similarly, to the BCF aquifer, all other metal concentrations are below detection limits (i.e. cadmium, chromium, selenium, tin and mercury). Nickel levels are mostly very low and always below the objective.

Copper and zinc concentrations are always above the respective water quality objective, and significantly higher than both the BCF aquifer and surface water, which are mostly below detection limits. Lead was above the objective on one occasion. Concentrations of copper, lead and zinc appear to increase in the absence of rainfall, with the dry season concentrations higher than the wet season concentrations.

The higher copper, lead, and zinc levels in GWB10 compared to the bores in the BCF aquifer is possibly related to the weathered laterite host rock. It is not possible however, to determine the reason without more data collected from other bores screened in this same aquifer. Iron and zinc certainly appear to be associated with the weathered rock, given GWB08 also has some elevated concentrations. It is possible the elevated copper and lead concentrations (and a proportion of the zinc concentrations) are associated with poor bore construction.

Nutrient concentrations in the BCF aquifer are:

Above the water quality objective for NOx (made up of 100% nitrate) at least 50% of the time; typically up to 0.03 mg/L. These levels remain well within the baseline surface water range of NOx concentrations (see Section 6.2.2), which are frequently up to 0.03 mg/L, and sometimes up to 0.06 mg/L.

Always below the water quality objective for TN except for one isolated spike in GWB03.

Always above the water quality objective for TP and reactive phosphorus and also well above levels measured in surface waters, which are predominantly below the objectives. Concentrations are particularly high in bores GWB07 and GWB08 (ranging between 0.32 and 0.50 mg/L for TP, and 0.269 and 0.78 mg/L for reactive phosphorus). GWB01 had the lowest concentrations; less than 0.15 mg/L for TP, and less than 0.105 mg/L for reactive phosphorus; but still significantly above the objective. The high phosphorus concentrations appear associated with the mineralogy of the BCF; in particular, that of the more weathered zones; reducing in concentration with depth.

Nutrient concentrations in the laterite surface aquifer (GWB10) are:

Predominantly below the water quality objective for TN, and generally above the water quality objective for NOx (made up of 100% nitrate) with an unexplained spike in concentration (0.21 mg/L) during the August 2018 monitoring round. Disregarding this spike, levels remain within the baseline surface water range of NOx concentrations. More data is required from this bore (and other bores to be installed in this shallow aquifer) to determine the pattern of NOx and TN concentrations.

Generally above the objective for TP and reactive phosphorus, and above the baseline surface water concentrations; although much lower than in the BCF aquifer, presumably from the oxidation and precipitation of phosphorus on reaction with iron and aluminium in the groundwater.

All TPH/TRH and BTEXN concentrations measured in all bores are below detection limits. Results are provided in Appendix E.


69

7.3 Baseline groundwater quality summary and potential impacts

7.3.1 BCF aquifer

The BCF aquifer is moderately fresh, with EC concentrations ranging between 137 and 281 µS/cm. In relation to the water quality objective applying to surface water however (200 µS/cm), this EC range extends above the objective. Groundwater from the deeper fresh BCF has higher EC usually above the objective, whereas groundwater from the shallower weathered BCF zone has lower EC below the objective.

Groundwater pH is generally close to neutral ranging between 6.41 and 7.52 and remaining within the water quality objective range.

As expected for water that has been out of contact with the atmosphere for a period, DO is low and oxidation reduction potential (ORP) always reduced (i.e. negative). DO would increase rapidity to within the objective range when exposed to the atmosphere in the pit and pumped to the holding dam. Likewise, ORP would become positive.

Bicarbonate alkalinity is moderate, with concentrations increasing with depth into the aquifer i.e. deeper groundwater below 88 m is between 97 and 143 mg/L, and shallower groundwater between 67 and 107 mg/L.

Hardness is relatively low throughout the BCF aquifer (less than 42 mg/L), which is considered ‘soft’, and low in dissolved ions such as calcium and magnesium.

The aquifer has a sodium-bicarbonate water signature, with little variation between sampling events or seasons.

The groundwater has a strong hydrogen sulphide odour

Dissolved metal concentrations are below laboratory detection limits for all metals except aluminium, arsenic, zinc, lithium and iron. Nickel levels were mostly very low and below the detection limit, and always well below the objective. Similarly, aluminium and zinc concentrations are predominantly below the water quality objective and not considered elevated in the BCF aquifer.

Lithium has no water quality objective. In relative terms, lithium concentrations are much higher in the BCF aquifer compared to surface water concentrations around the mine footprint. Levels in groundwater are up to 1.730 mg/L, recorded in the mine pit bore, whereas surface waters are below 0.002 mg/L.

Iron has no water quality objective. Concentrations are up to 0.77 mg/L in the weathered BCF compared to up to 0.33 mg/L in the fresh BCF; both of which are significantly higher than surface water levels around the mine footprint (up to 0.10 mg/L).

Arsenic concentrations in the BCF aquifer are significantly elevated above the water quality objective. The median concentration for all four bores is 0.060 mg/L, which is more than 4.5 times higher than the water quality objective (0.013 mg/L). If the Australian Drinking Water Quality Guidelines (NHMRC 2011) are considered, these levels are more than 6 times the guideline limit (0.01 mg/L). The BCF aquifer is a known “high” risk aquifer for arsenic (see Karp 2008). The arsenic is from minerals of the BCF being mobilised into the groundwater through natural processes such as oxidation, weathering reactions, and/or biological activity.

TN concentrations in the BCF aquifer are predominantly below the water quality objective. NOx concentrations (made up of 100% nitrate) are above the water quality objective most of the time however, levels remain well within the baseline surface water range of NOx concentrations. In contrast, TP and reactive phosphorus concentrations are always above the respective water quality objective, and also well above levels measured in surface waters, which are predominantly below the objectives. The high phosphorus concentrations appear associated with the mineralogy of the BCF; in particular, that of the more weathered zones; reducing in concentration with depth.



70

Potential impacts


EC, TP, reactive phosphorus, and arsenic are elevated in the BCF aquifer above the water quality objectives, and above the baseline surface water quality of the mine footprint area. Release of water from MWD1 (which contains a proportion of groundwater dewatered from the mine pit), must ensure the concentration of these parameters is not increased above the water quality objectives at surface water monitoring sites downstream.

Lithium and iron, which don’t have water quality objectives, are also elevated in the BCF aquifer compared to the natural background surface water levels at the mine footprint site. Release of water from MWD1 must ensure the concentration of these parameters in downstream surface water monitoring sites is not increased above the natural background range; i.e. above 0.002 mg/L for lithium and 0.1 mg/L for iron.

All other metals aluminium, cadmium, chromium, copper, lead, nickel, selenium, tin, zinc, mercury are below the water quality objectives and do not pose a hazard to surface waters.

pH in the BCF aquifer is close to neutral and does not pose a hazard to surface waters. Similarly, DO levels are low in the groundwater but will increase rapidly with exposure to the atmosphere and pumping from the pit prior to any release to surface waters.

TPH/TRH and BTEXN concentrations in groundwater are always below detection limits and must remain so during mining operations i.e. no contamination of the groundwater aquifer from hydrocarbon spills or leaks on site.

TN concentrations are mostly below the objective, and NOx concentrations are within the same range as that of that baseline surface water of the mine footprint and do not pose a hazard if released to surface waters.

7.3.2 Laterite surface aquifer

Based on the limited available information for this aquifer (only one bore which is not installed to the relevant standard) water quality of the shallow laterite aquifer largely reflects the water chemistry expected of rainwater / stream water, showing this aquifer is closely connected to surface water. EC is low (below 26 µS/cm), and pH is relatively acidic and reflective of rainwater, which is naturally acidic in the tropical Darwin region.

DO and ORP are higher than in the BCF aquifer; and indicative of an aquifer recently recharged with fresh oxygenated rainwater. Further, the negligible alkalinity, hardness and dissolved major cation concentrations in this aquifer are similar to that measured in the surface water around the mine footprint.

The laterite surface aquifer has higher concentrations of copper, lead and zinc than the BCF aquifer, and lower concentrations of arsenic and lithium (largely remaining below the objective for arsenic). Aluminium levels are comparable to the BCF aquifer however, exceed the objective more frequently because of the lower pH. Iron levels are comparable to the weathered zone BCF aquifer and higher than in the surface water around the mine footprint.

Similarly, to the BCF aquifer, all other metal concentrations are below detection limits (i.e. cadmium, chromium, selenium, tin and mercury). Nickel levels are mostly very low and always below the objective.

Copper and zinc concentrations are always above the respective water quality objective, and significantly higher than in both the BCF aquifer and surface water, which are mostly below detection limits. Lead was above the objective on one occasion.

The higher copper, lead, and zinc levels in GWB10 compared to the bores in the BCF aquifer is possibly related to the weathered laterite host rock. It is not possible to determine the reason without more data collected from other bores screened in this same aquifer. It is possible the elevated copper and lead concentrations (and a proportion of the zinc concentrations) are associated with poor bore construction.


71

TN concentrations are predominantly below the water quality objective, and NOx, concentrations are generally above the water quality objective but within the baseline surface water range of NOx concentrations. More data is required from this bore (and other bores to be installed in this shallow aquifer) to determine the pattern of NOx and TN concentrations.

TP and reactive phosphorus concentrations are generally above the water quality objectives and also above the baseline surface water concentrations; although much lower than in the BCF aquifer, presumably from the oxidation and precipitation of phosphorus on reaction with iron and aluminium in the groundwater.


Potential impacts


Copper, zinc, lead, TP, and reactive phosphorus are elevated in the laterite aquifer above the water quality objectives, and above the baseline surface water quality of the mine footprint area. Release of water from MWD1 (which contains a proportion of groundwater dewatered from the mine pit), must ensure the concentration of these parameters is not increased above the water quality objectives at surface water monitoring sites downstream.

Lithium and iron, which don’t have water quality objectives, are elevated (albeit to a lesser extent than the BCF aquifer) compared to the natural background surface water levels at the mine footprint site. Release of water from MWD1 must ensure the concentration of these parameters in downstream surface water monitoring sites is not increased above the natural background range; i.e. above 0.002 mg/L for lithium and 0.1 mg/L for iron.

All other metals aluminium, cadmium, chromium, nickel, selenium, tin, zinc, mercury are below the water quality objectives or within the range of natural surface water background levels and do not pose a hazard to surface waters.

pH in the laterite aquifer is relatively acidic but no more so than the natural acidity of rainwater in the Darwin region. DO levels are relatively low but will increase rapidly with exposure to the atmosphere and pumping from the pit prior to any release to surface waters.

TPH/TRH and BTEXN concentrations in groundwater are always below detection limits and must remain so during mining operations i.e. no contamination of the groundwater aquifer from hydrocarbon spills or leaks on site.

TN concentrations are mostly below the objective, and NOx concentrations are within the same range as that of that baseline surface water of the mine footprint and do not pose a hazard if released to surface waters.


72

Table 7-2. Baseline groundwater quality monitoring results, field parameters.

SWL pH Temp ORP EC TDS Salinity DO Turbidity

mBGL pH unit °C mV µS/cm mg/L ppt %sat NTU

6.0-7.5 200

GWB01 27-06-17 4.49 6.80 30.0 -64.0 255.0 156.0 - 24 -GWB01 31-01-18 1.97 7.14 31.5 -53.4 247.4 160.4 0.12 2 4.6GWB01 01-05-18 3.26 7.23 31.4 -133.8 280.7 162.5 0.12 2 15.0GWB01 08-08-18 6.50 7.52 31.4 -167.9 236.5 153.7 0.11 4 11.1GWB03 27-06-17 2.16 6.60 28.0 -109.0 238.0 146.0 - 2 -GWB03 01-02-18 0.30 6.77 30.8 -39.1 225.1 146.3 0.10 2 0.9GWB03 01-05-18 -0.54 6.96 31.4 -27.0 250.0 144.0 0.10 23 21.0GWB03 09-08-18 4.06 7.42 30.2 -102.0 185.9 120.9 0.09 27 2.7GWB07 27-06-17 3.64 6.80 28.0 -144.0 213.0 186.0 - 2 -GWB07 01-02-18 -0.81 6.72 30.9 -56.5 204.8 133.4 0.10 2 12.3GWB07 01-05-18 1.88 6.74 31.5 -48.8 168.0 96.9 0.07 12 65.0GWB07 09-08-18 4.79 7.32 30.3 -89.1 137.0 88.9 0.06 13 6.5GWB08 27-06-17 3.00 6.50 29.0 -140.0 187.0 130.0 - 4 -GWB08 31-01-18 0.68 6.41 31.3 -6.5 172.0 111.0 0.08 2 1.2GWB08 01-05-18 1.57 6.57 32.2 -4.3 188.7 107.9 0.08 29 18.0GWB08 08-08-18 3.97 7.23 31.3 -97.7 142.5 92.6 0.07 4 2.8GWB10 27-06-17 1.99 4.60 31.0 1.6 37.0 72.0 - 38 -GWB10 31-01-18 -0.20 4.97 31.0 254.6 21.3 13.8 0.01 57 5.6GWB10 01-05-18 1.02 5.16 33.2 148.1 25.2 14.3 0.01 13 45.0GWB10 08-08-18 2.72 6.39 33.9 62.5 26.2 15.1 0.01 35 195.0

Site Date Sampled

Field Parameters

Water Quality Objectives Darwin Harbour Region (freshwater rivers & streams)

73

Tabl

e 7-

3. B

asel

ine

grou

ndw

ater

qua

lity

mon

itorin

g re

sults

, maj

or a

nion

s an

d ca

tions

.

Tota

l ha

rdne

ss a

s Ca

CO3

Hydr

oxid

e Al

kalin

ity a

s Ca

CO3

Carb

onat

e Al

kalin

ity a

s Ca

CO3

Bica

rbon

ate

Alka

linity

as

CaCO

3

Tota

l Al

kalin

ity a

s Ca

CO3

Sulfa

te a

s SO

4Ch

lorid

eCa

lciu

mM

agne

sium

Sodi

umPo

tass

ium

mg/

Lm

g/L

mg/

Lm

g/L

mg/

Lm

g/L

mg/

Lm

g/L

mg/

Lm

g/L

mg/

LG

WB

0127

-06-

17-

<1<1

9797

23

72

342

GW

B01

31-0

1-18

31<1

<112

612

62

49

236

2G

WB

0101

-05-

1828

<1<1

143

143

<13

82

362

GW

B01

08-0

8-18

37<1

<112

612

6<1

310

334

2G

WB

0327

-06-

17-

<1<1

9191

<16

86

264

GW

B03

01-0

2-18

38<1

<110

510

5<1

57

525

4G

WB

0301

-05-

1842

<1<1

107

107

<15

76

274

GW

B03

09-0

8-18

36<1

<192

92<1

56

525

4G

WB

0727

-06-

17-

<1<1

7070

88

41

333

GW

B07

01-0

2-18

16<1

<188

88<1

73

234

2G

WB

0701

-05-

189

<1<1

6767

<15

21

263

GW

B07

09-0

8-18

9<1

<168

68<1

62

123

2G

WB

0827

-06-

17-

<1<1

7474

<14

74

173

GW

B08

31-0

1-18

34<1

<179

79<1

47

418

3G

WB

0801

-05-

1831

<1<1

8080

<12

64

183

GW

B08

08-0

8-18

31<1

<172

72<1

46

418

3G

WB

1027

-06-

17-

<1<1

66

<13

<1<1

4<1

GW

B10

31-0

1-18

<1<1

<17

7<1

2<1

<12

<1G

WB

1001

-05-

18<1

<1<1

33

<12

<1<1

2<1

GW

B10

08-0

8-18

2<1

<14

4<1

21

<12

<1

Maj

or A

nion

sM

ajor

Cat

ions

Site

Date

Sa

mpl

ed

74

Tabl

e 7-

4. B

asel

ine

grou

ndw

ater

qua

lity

mon

itorin

g re

sults

, dis

solv

ed m

etal

s.

Alum

iniu

mAr

seni

cCa

dmiu

mCh

rom

ium

Copp

erLe

adNi

ckel

Sele

nium

Zinc

Lith

ium

Iron

Tin

Mer

cury

mg/

Lm

g/L

mg/

Lm

g/L

mg/

Lm

g/L

mg/

Lm

g/L

mg/

Lm

g/L

mg/

Lm

g/L

mg/

L

pH >

6.5

0.05

5 p

H <6

.5 0

.000

80.

013

0.00

020.

004

0.00

140.

0034

0.01

10.

011

0.00

80.

0006

GW

B01

27-0

6-17

0.08

0.06

9<0

.000

1<0

.001

<0.0

01<0

.001

0.00

1<0

.01

<0.0

051.

730

<0.0

5<0

.001

<0.0

001

GW

B01

31-0

1-18

0.04

0.06

2<0

.000

1<0

.001

<0.0

01<0

.001

<0.0

01<0

.01

<0.0

051.

640

<0.0

5<0

.001

<0.0

001

GW

B01

01-0

5-18

<0.0

10.

056

<0.0

001

0.00

10.

001

<0.0

01<0

.001

<0.0

1<0

.005

1.54

00.

11<0

.001

<0.0

001

GW

B01

08-0

8-18

<0.0

10.

067

<0.0

001

<0.0

01<0

.001

<0.0

01<0

.001

<0.0

1<0

.005

1.68

00.

19<0

.001

<0.0

001

GW

B03

27-0

6-17

0.08

0.00

6<0

.000

1<0

.001

<0.0

01<0

.001

0.00

2<0

.01

0.00

60.

189

0.33

<0.0

01<0

.000

1G

WB

0301

-02-

18<0

.01

0.01

6<0

.000

1<0

.001

<0.0

01<0

.001

<0.0

01<0

.01

<0.0

050.

153

0.16

<0.0

01<0

.000

1G

WB

0301

-05-

18<0

.01

0.01

5<0

.000

1<0

.001

<0.0

01<0

.001

<0.0

01<0

.01

<0.0

050.

166

0.13

<0.0

01<0

.000

1G

WB

0309

-08-

18<0

.01

0.01

4<0

.000

1<0

.001

<0.0

01<0

.001

<0.0

01<0

.01

<0.0

050.

145

0.09

<0.0

01<0

.000

1G

WB

0727

-06-

170.

060.

131

<0.0

001

<0.0

01<0

.001

<0.0

010.

001

<0.0

1<0

.005

0.09

90.

08<0

.001

<0.0

001

GW

B07

01-0

2-18

0.03

0.29

0<0

.000

1<0

.001

<0.0

01<0

.001

<0.0

01<0

.01

<0.0

050.

076

0.30

<0.0

01<0

.000

1G

WB

0701

-05-

18<0

.01

0.16

7<0

.000

1<0

.001

<0.0

01<0

.001

<0.0

01<0

.01

<0.0

050.

080

0.17

<0.0

01<0

.000

1G

WB

0709

-08-

18<0

.01

0.16

6<0

.000

1<0

.001

<0.0

01<0

.001

<0.0

01<0

.01

<0.0

050.

063

0.11

<0.0

01<0

.000

1G

WB

0827

-06-

170.

010.

065

<0.0

001

<0.0

01<0

.001

<0.0

010.

001

<0.0

1<0

.005

0.27

90.

77<0

.001

<0.0

001

GW

B08

31-0

1-18

<0.0

10.

067

<0.0

001

<0.0

01<0

.001

<0.0

01<0

.001

<0.0

10.

010

0.24

80.

38<0

.001

<0.0

001

GW

B08

01-0

5-18

<0.0

10.

059

<0.0

001

<0.0

01<0

.001

<0.0

01<0

.001

<0.0

1<0

.005

0.22

60.

44<0

.001

<0.0

001

GW

B08

08-0

8-18

<0.0

10.

061

<0.0

001

<0.0

01<0

.001

<0.0

01<0

.001

<0.0

10.

008

0.26

80.

43<0

.001

<0.0

001

GW

B10

27-0

6-17

0.05

0.00

5<0

.000

1<0

.001

<0.0

01<0

.001

0.00

8<0

.01

0.01

20.

018

0.47

<0.0

01<0

.000

1G

WB

1031

-01-

180.

030.

016

<0.0

001

<0.0

010.

002

<0.0

01<0

.001

<0.0

10.

071

0.00

70.

38<0

.001

<0.0

001

GW

B10

01-0

5-18

<0.0

10.

008

<0.0

001

<0.0

010.

002

<0.0

01<0

.001

<0.0

10.

027

0.00

30.

44<0

.001

<0.0

001

GW

B10

08-0

8-18

0.13

0.00

9<0

.000

1<0

.001

0.01

90.

005

0.00

2<0

.01

0.09

90.

044

0.12

<0.0

01<0

.000

1

Diss

olve

d M

etal

s

Site

Date

Sa

mpl

ed

Wat

er Q

ualit

y O

bjec

tives

D

arwi

n H

arbo

ur R

egio

n (fr

eshw

ater

rive

rs &

stre

ams)

75

Tabl

e 7-

5. B

asel

ine

grou

ndw

ater

qua

lity

mon

itorin

g re

sults

, nut

rient

s.N

ote

labo

rato

ry li

mit

of re

porti

ng (L

OR

) for

NO

x is

som

etim

es g

reat

er th

an w

ater

qua

lity

obje

ctiv

e. A

s su

ch, u

nles

s co

ncen

tratio

n is

abo

ve L

OR

, it i

s no

t kno

wn

if ob

ject

ive

is e

xcee

ded.

Amm

onia

as

NNi

trite

as

NNi

trate

as

NNi

trite

+

Nitra

te a

s N

TKN

as N

Tota

l Ni

troge

n as

N

Tota

l Ph

osph

orus

as

P

Reac

tive

Phos

phor

us

as P

mg/

Lm

g/L

mg/

Lm

g/L

mg/

Lm

g/L

mg/

Lm

g/L

0.00

80.

230.

010.

005

GW

B01

27-0

6-17

0.02

--

0.03

<0.1

<0.1

--

GW

B01

31-0

1-18

0.07

<0.0

10.

020.

02<0

.1<0

.10.

150.

105

GW

B01

01-0

5-18

0.06

<0.0

1<0

.01

<0.0

1<0

.1<0

.10.

100.

079

GW

B01

08-0

8-18

0.21

<0.0

1<0

.01

<0.0

10.

20.

20.

130.

087

GW

B03

27-0

6-17

<0.0

1-

-0.

02<0

.1<0

.1-

-G

WB

0301

-02-

180.

20<0

.01

0.02

0.02

0.4

0.4

0.24

0.27

8G

WB

0301

-05-

180.

19<0

.01

<0.0

1<0

.01

0.2

0.2

0.23

0.21

9G

WB

0309

-08-

180.

10<0

.01

<0.0

1<0

.01

0.2

0.2

0.23

0.27

7G

WB

0727

-06-

170.

01-

-0.

03<0

.1<0

.1-

-G

WB

0701

-02-

180.

03<0

.01

0.03

0.03

<0.1

<0.1

0.50

0.34

3G

WB

0701

-05-

180.

03<0

.01

0.01

0.01

<0.1

<0.1

0.46

0.37

8G

WB

0709

-08-

180.

01<0

.01

<0.0

1<0

.01

<0.1

<0.1

0.34

0.37

5G

WB

0827

-06-

17<0

.01

--

<0.0

1<0

.1<0

.1-

-G

WB

0831

-01-

180.

04<0

.01

0.03

0.03

0.1

0.1

0.37

0.30

1G

WB

0801

-05-

180.

04<0

.01

<0.0

1<0

.01

<0.1

<0.1

0.37

0.30

9G

WB

0808

-08-

180.

03<0

.01

<0.0

1<0

.01

<0.1

<0.1

0.32

0.26

9G

WB

1027

-06-

170.

02-

-0.

030.

10.

1-

-G

WB

1031

-01-

180.

1 7<0

.01

0.06

0.06

0.1

0.2

0.04

0.00

9G

WB

1001

-05-

180.

04<0

.01

<0.0

1<0

.01

<0.1

<0.1

0.03

0.00

5G

WB

1008

-08-

180.

10<0

.01

0.21

0.21

0.1

0.3

0.08

0.04

8

Nutri

ents

Site

Date

Sa

mpl

ed

Wat

er Q

ualit

y O

bjec

tives

D

arwi

n H

arbo

ur R

egio

n (fr

eshw

ater

rive

rs &

stre

ams)

76

Figu

re 7

-1.

Pipe

r plo

t dis

play

ing

Gra

nts

Lith

ium

pro

ject

gro

undw

ater

ana

lyse

s ca

tego

rised

acc

ordi

ng to

aqu

ifer d

epth

.

GW

B10

GW

B6

77

Figu

re 7

-2.

Dry

sea

son

(Jun

e 20

17) s

tiff p

lots

for G

rant

s Li

thiu

m P

roje

ct g

roun

dwat

er b

ores

.

78

Figu

re 7

-3.

Wet

sea

son

(Jan

uary

201

8) s

tiff p

lots

for G

rant

s Li

thiu

m P

roje

ct g

roun

dwat

er b

ores

.

Grants Lithium Project Water Management Plan

79

7.4 Predicted pit water quality and discharge water quality

The project intends to pump water dewatered from the pit (comprising groundwater inflows and direct rainfall) to MWD1, from where it will be reused in dust suppression and ore processing. There will be no discharge from this dam during the dry season when volumes dewatered from the pit are lower and dust suppression requirements higher. Discharge will be required during the wet season months December to March when pit dewatering volumes are highest and dust suppression requirements lowest (Table 2-3). This discharge represents a potential impact to surface water quality depending on the final concentration of parameters in MWD1 compared to existing baseline concentrations in surface water.

Groundwater quality is compared to baseline surface water quality of the drainage lines receiving discharge in Section 7 above, and summarised in Table 7-6. Parameters elevated in the groundwater include EC, arsenic, TP, reactive phosphorus, lithium, and iron. Copper, lead and zinc are elevated in the surface laterite aquifer but not the BCF aquifer.

The final MWD1 water quality will be influenced by the relative proportions of groundwater to rainwater flowing into the pit, and the contribution of direct rainfall into MWD1 (see Table 2-3). Rainwater generally always makes-up more than 50% of the water in MWD1, with the highest dilution occurring during the mid- wet season (up to 69% in January 2020) and lowest during the early-dry season (44% in November 2020). Rainwater makes-up a greater proportion of water in MWD1 during the second year of mining compared to the first, this is because groundwater inflows are greatest during the early phase of mining as the weathered BCF has a higher groundwater specific yield and hydraulic conductivity than the underlying fresh BCF and ore. Once the fresh BCF is intersected, pit inflows decline.

Water quality in the inundated BP33 pit may give an indication of groundwater quality into the Grants Project pit, and also water quality of the final pit lake in the years following the end of mining. Water quality measured in the BP33 pit waters during 2017 and 2018 was generally good. ECs were low (less than 26.2 µS/cm), pH was not acidic (lowest pH was 6.65), dissolved metal concentrations were all below the water quality objectives (except for one isolated instance of arsenic) and nutrient concentrations were not elevated when compared to surface water concentrations. Dilution with rainwater would have contributed to this. Also possibly absorption / co-precipitation and settlement of insoluble arsenic and phosphorus compounds due to oxidation and reaction with iron (see Baken et al. 2015).

Copper, lead and zinc are also not elevated in the BP33 pit, likely because these are only above the water quality objectives in the lateritic surface aquifer, and not the BCF aquifer, which will make up the bulk of groundwater inflows into the pit.

In regards to turbidity, surface water turbidity in the drainage line receiving MWD1 discharge is always low, even after significant rainfall. The turbidity of groundwater inflows into the pit and rainwater would also be low, however may become elevated on contact with fine sediments within the pit. Measures for minimising turbidity in water dewatered from the pit, such as filtering water as it is pumped from the pit sump and using flocculants in MWD1 will be undertaken to ensure turbidity levels of discharged water are below the water quality criteria prescribed in the Water Quality Monitoring Plan (Section 10).

Similarly, if the naturally occurring process of oxidation and co-precipitation of arsenic and phosphorus with iron whilst the water is held within MWD1 is not effective in reducing levels of these metals, there are a number of commonly-used treatment options available. Removal technologies and treatments have been developed to remove arsenic from groundwater to make it suitable for drinking, and removal of phosphorus from wastewater is commonly undertaken to make it suitable for discharge.

Management of discharge from MWD1 will be subject to the provisions in a WDL; yet to be applied for and issued. Presently, water quality testing of MWD1 is planned to be weekly during discharge, and monthly when not discharging (see Water Quality Monitoring Plan Section 10). Discharge water quality will aim to meet the Water Quality Objectives for the Darwin Harbour Region (NRETAS 2010) for most parameters, except for where the background surface water concentrations are already exceeding the objective (i.e. NOx and aluminium) or when there is no objective (i.e. lithium and iron), when the aim will be to remain within the background range.


80

Table 7-6. Comparison of groundwater quality with surface water quality (mine footprint sites).

ParameterBaseline levels

in Surface Water: Mine Footprint

SitesLevels in BCF Aquifer Levels in Laterite

Aquifer Comment

pHHighly variable

above and below objective range

Close to neutral Acidic similar to rainfall No risk

DOHighly variable but

remains within objective range

Low but will increase rapidly on exposure to

atmosphere and pumping to holding dam

Low but will increase rapidly on exposure to

atmosphere and pumping to holding dam

No risk

ECVery low, well below water

quality objective

Relatively low for groundwater but high in comparison to surface water and often above

objective

Very low and below objective

High in BCF aquifer but likely reduced below objective with

dilution in pit by rainwater

CadmiumChromium

NickelSelenium

TinMercury

Always below detection limits

Always below detection limits or objective

Always below detection limits or objective No risk

AluminiumFrequently

elevated above objective

Elevated but generally lower concentrations than

in surface water

Elevated but generally lower concentrations than in surface water

No risk

Lithium Up to 0.002 mg/LElevated above surface

water levels (up to 1.730 mg/L

Elevated but to a lesser extent than BCF aquifer

High in both aquifers but likely reduced below surface water

background levels with dilution in pit by rainwater

Iron Up to 0.1 mg/LElevated above surface

water levels (up to 0.77 mg/L)

Elevated but to a lesser extent than BCF aquifer

High in both aquifers but likely reduced below surface water

background levels with dilution in pit by rainwater

Arsenic Always below detection limit

Elevated with median concentration 0.060 mg/L,

which is more than 4.5 times higher than

objective (0.013 mg/L).

Mostly below objective

High in BCF aquifer but likely reduced below objective with

dilution in pit by rainwater. May also reduce with

absorption/co-precipitation with iron in surface water.

CopperAlways below detection limit

Always below detection limit Mostly above objective

Elevated in laterite aquifer but likely reduced below objective with dilution in pit by rainwater

and also BCF water

ZincAlways below detection limit

Always below detection limit Always above objective


and also BCF water

LeadAlways below detection limit

Always below detection limit

Occasionally above objective


and also BCF water

NOx

Frequently elevated above

objective

Elevated above objective but generally lower than in

surface waters

Elevated above objective but generally lower than

in surface watersNo risk

TN Mostly below objective Mostly below objective Mostly below objective No risk


81

ParameterBaseline levels

in Surface Water: Mine Footprint

SitesLevels in BCF Aquifer Levels in Laterite

Aquifer Comment

TP Always below detection limit Always above objective Always above objective

High in both aquifers but likely reduced below objective with



Reactive P Mostly below objective Always above objective Always above objective

High in both aquifers but likely reduced below objective with




82

8 RISK ASSESSMENT

Risks to hydrological processes and water quality were assessed as part of the whole-of-proposal impact analysis and risk assessment prepared to support the EIS. The principles of qualitative risk management described in AS/NZS 31000:2009 Risk Management – Principles and Guidelines were used to set-up a framework for assessing the risk that the project poses to the NT EPA environmental objectives for ‘Hydrological Processes’ and ‘Inland Water Environmental Quality’, as listed below.

NT EPA objective for ‘Hydrological Processes’:

Maintain the hydrological regimes of groundwater and surface water so that environmental values are protected.

NT EPA objective for ‘Inland Water Environmental Quality’:

Maintain the quality of groundwater and surface water so that environmental values including ecological health, land uses, and the welfare and amenity of people are protected.

8.1 Identify hazards and rank risks

Each project component that could be a source of environmental impact during the construction/operations phase was identified using the project details provided in Section 2 of the EIS. For each project component, events/incidents that could cause impacts to environmental values (receptors) were identified. Potential direct and indirect impacts were then identified by considering cause and effect pathways for impacts.

For each potential environmental impact identified by the project team, the risk assessment considered both the likelihood of the impact occurring and the worst-possible consequence in relation to the NT EPA environmental objectives. The likelihood and consequence categories adopted in the environmental risk assessment are provided in Table 8-1 and Table 8-2. The likelihood and consequence ratings were combined to derive an overall risk rating using the matrix in Table 8-3.

Table 8-1. Likelihood categories adopted in risk assessment

Likelihood category DescriptionAlmost certain The event/impact will occur or is expected to occur. The impact occurs regularly

in association with similar projects and/or in similar environments.Likely The impact will probably occur in most circumstance but there is some

uncertainty about the likelihood. The impact has occurred on more than one occasion in association with similar projects and/or in similar environments.

Possible The impact could occur in some circumstances. The impact has occurred infrequently on similar projects and/or in similar environments.

Unlikely The impact is not expected to occur. The impact occurs very infrequently on similar projects and/or in similar environments.

Rare The impact is very unlikely to occur. The impact has not occurred on similar projects and/or in similar environments.


83

Table 8-2. Consequence categories adopted in risk assessment

Consequence or severity of Impacts

Score Inland Water Environmental

Quality

Hydrological processes (Surface

water)

Hydrological processes

(Groundwater)

Severe

5

Permanent major exceedance of water quality criteria for beneficial uses in the marine receiving waters of West Arm or Bynoe Harbour.

Catchment wide reduction in surface water flow volumes and/or timing of flows/discharges that permanently alters the ecological health, land-uses and/or amenity.

Drawdown of groundwater in a regional scale aquifer that permanently alters ecological health, land-uses and/or amenity.

Major

4

Major exceedance of water quality criteria for beneficial uses at the catchment outlets to West Arm or Charlotte River, that continues for many years post-closure.

Reduction in surface water flow volumes, groundwater levels and/or timing of flows/discharges that compromises ecological health, land-uses and/or amenity for many years post-closure.

Drawdown of groundwater in a regional scale aquifer that compromises ecological health, land-uses and/or amenity for many years post-closure.

Moderate

3

Minor sustained exceedances of water quality criteria for beneficial uses in the ephemeral water courses downstream, that occurs throughout operations but ceases within months’ post-closure.

Localised reduction in surface water flow volumes, and/or timing of flows/discharges with no impact on ecological health, land-uses and/or amenity.

Localised drawdown of groundwater throughout operations that recovers rapidly post-closure.

Minor

2

Minor temporary exceedances of water quality criteria for beneficial uses at the mine site discharge points and immediate sub-catchment area.

Limited reduction in surface water flow volumes, groundwater levels and/or timing of flows/discharges in the immediate sub-catchment area with no impact on ecological health, land-uses and/or amenity.

Limited drawdown of groundwater throughout operations that recovers rapidly once operations cease.

Insignificant

1

No measurable exceedance of pre-development water quality conditions.

No measurable change to hydrological regimes

No measurable change to hydrological regimes


84

Table 8-3. Risk matrix adopted in risk assessment

CONSEQUENCE

1 2 3 4 5

Insignificant Minor Moderate Major Severe

5 Almost Certain 2 Medium 2 Medium 3 High 4 Very High 4 Very High

4 Likely 2 Medium 2 Medium 3 High 4 Very High 4 Very High

3 Possible 1 Low 2 Medium 2 Medium 3 High 4 Very High

2 Unlikely 1 Low 1 Low 2 Medium 2 Medium 3 High

LIK

ELIH

OO

D

1 Rare 1 Low 1 Low 1 Low 2 Medium 3 High

Risks were identified and assessed separately for the construction/operations phase and the rehabilitation/closure phase of the project. The current version of the Water Management Plan addresses only construction/operations phase risks. The requirement for water quality monitoring and management post-closure is specified in the Mine Closure Plan. Future updates of the Water Management Plan will address post-closure requirements.

8.2 Mitigation and management

Measures to avoid, mitigate and manage impacts were identified, focussing on impacts with an inherent risk level of Moderate or above. Suitable controls were generally identified with reference to mining best-practice guidelines and past experience of the mining engineers and other technical experts engaged to work on the proposal. Measures were identified with the goal of reducing all risks to ‘as low as reasonably possible’. For a risk to be ‘as low as reasonably possible’, the cost involved in reducing the risk further would be grossly disproportionate to the benefit gained. Mitigation and management measures for reducing risks to water quality and hydrological processes are provided in Section 9.

8.3 Residual risk

Residual risk ratings were assigned assuming effective implementation of the mitigation and management measures prescribed in this plan. All risks to hydrological processes were reduced to low or moderate. A summary of the risk assessment is provided in Table 8-4.

Impacts assigned a low residual risk rating, with a moderate to high level of certainty, are expected to have limited to no effect on the NT EPA’s environmental objectives. Impacts assigned a residual risk rating of medium or above have some potential for residual impact either because the mitigation and management measures require further work in order to demonstrate they will be effective, or because it is not practicable to avoid some level of impact.

Gra

nts

Lith

ium

Pro

ject

W

ater

Man

agem

ent P

lan

85

Tabl

e 8-

4. S

umm

ary

of ri

sk a

sses

smen

t for

Hyd

rolo

gica

l Pro

cess

and

Inla

nd W

ater

Env

ironm

enta

l Qua

lity

fact

ors

Haza

rd/A

spec

tIn

cide

nt/e

vent

Desc

riptio

n of

Impa

ct

Assu

mpt

ions

Inhe

rent

Ris

kRe

sidu

al R

isk

Inla

nd W

ater

Env

ironm

enta

l Qua

lity

Site

cle

arin

g an

d pr

epar

atio

nEr

osio

n (w

ind/

wat

er)

due

to d

istur

banc

e an

d ex

posu

re o

f gr

ound

surf

ace

Incr

ease

d tu

rbid

ity in

w

ater

cour

ses t

hat f

low

into

W

est A

rm a

ffect

s en

viro

nmen

tal v

alue

s and

/or

othe

r use

rs

• Cl

earin

g w

ill o

ccur

dur

ing

the

dry

seas

on.

• If

site

clea

ring

and

prep

arat

ion

was

to o

ccur

dur

ing

the

wet

seas

on, a

spec

ific

ESCP

in a

ccor

danc

e w

ith IE

CA w

ill

be d

evel

oped

. Al

l ESC

P m

itiga

tion

and

man

agem

ent m

easu

res w

ill b

e in

pla

ce p

rior t

o th

e co

mm

enci

ng o

f any

w

orks

. •

Expo

sed

surf

aces

of t

he in

unda

tion

bund

and

WRD

ann

ulus

will

be

susc

eptib

le to

ero

sion

durin

g fir

st ra

ins.

• M

inor

eph

emer

al d

rain

age

lines

are

the

rece

ivin

g w

ater

s.

• Ba

selin

e w

ater

qua

lity

mon

itorin

g in

dica

tes w

et se

ason

flow

s hav

e lo

w le

vels

of tu

rbid

ity.

3 - H

igh

2 - M

ediu

m

Wat

er su

pply

and

us

eO

verf

low

of R

aw

Wat

er o

r Pro

cess

W

ater

Dam

s

Incr

ease

d tu

rbid

ity in

w

ater

cour

ses t

hat f

low

into

W

est A

rm a

ffect

s en

viro

nmen

tal v

alue

s and

/or

othe

r use

rs

• Ra

w W

ater

Dam

des

igne

d to

be

cont

inuo

usly

pum

ped

to p

roce

ssin

g ci

rcui

t and

dus

t sup

pres

sion.

•

Proc

ess W

ater

Dam

des

igne

d to

rece

ive

pit d

ewat

erin

g an

d TS

F de

cant

and

be

cont

inuo

usly

pum

ped

to

proc

essin

g ci

rcui

t.•

Dam

ove

rflo

ws w

ould

be

cont

aine

d w

ithin

the

min

e sit

e by

dra

inag

e ch

anne

ls an

d th

e di

vers

ion

bund

.

1 - L

ow1

- Low

Wat

er su

pply

and

us

eEr

osio

n of

stre

am

bank

s dow

nstr

eam

of

dam

wal

ls/sp

illw

ays

Incr

ease

d tu

rbid

ity in

re

ceiv

ing

wat

ers d

owns

trea

m

of d

ams a

ffect

s en

viro

nmen

tal v

alue

s and

/or

othe

r use

rs

• Sp

illw

ay m

odel

led

to o

verf

low

dur

ing

Janu

ary

of a

n av

erag

e w

et se

ason

.•

Hydr

ogra

phs s

how

eve

nt b

ased

ove

rflo

ws i

n Ja

n/Fe

b an

d co

ntin

uous

ove

rflo

w in

Feb

/Mar

and

eve

nt b

ased

ag

ain

thro

ugh

late

Mar

into

ear

ly A

pr.

• Da

m w

all a

nd sp

illw

ay d

esig

n ye

t to

be c

ompl

eted

but

will

be

in a

ccor

danc

e w

ith A

NCO

LD g

uide

lines

.•

Wat

erco

urse

s are

eph

emer

al -

no si

gnifi

cant

aqu

atic

or r

ipar

ian

habi

tats

dow

nstr

eam

.

2 - M

ediu

m1

- Low

Wat

er su

pply

and

us

eDi

scha

rge

of e

xces

s w

ater

in w

et se

ason

Poor

wat

er q

ualit

y in

w

ater

cour

ses d

ischa

rgin

g to

W

est A

rm a

ffect

s en

viro

nmen

tal v

alue

s

• Di

scha

rge

wat

er is

gro

undw

ater

dew

ater

ed fr

om p

it an

d th

eref

ore

wat

er q

ualit

y is

expe

cted

to b

e sim

ilar t

o th

e gr

ound

wat

er a

quife

r.•

Arse

nic

and

phos

phor

ous i

s nat

ural

ly e

leva

ted

in th

e gr

ound

wat

er, b

ut n

ot in

surf

ace

wat

er.

• Di

scha

rge

requ

ired

in w

et se

ason

mon

ths o

f Dec

to M

ay i.

e. p

eak

flow

s - m

axim

um d

ilutio

n.•

Wat

er w

ill b

e st

ored

in se

para

te st

orag

e to

pro

cess

wat

er.

• Se

dim

ents

are

key

con

tam

inan

t of c

once

rn.

3 - H

igh

2 - M

ediu

m

Min

ing

and

ore

proc

essin

gCo

ntam

inat

ion

of p

it in

-flow

s due

to

expo

sure

to P

AF

and/

or o

ther

co

ntam

inan

ts in

pit

wal

ls

Poor

wat

er q

ualit

y in

gr

ound

wat

er a

quife

r affe

cts

envi

ronm

enta

l val

ues a

nd/o

r ot

her u

sers

• W

aste

cha

ract

erisa

tion

(EcO

z/Pe

ndra

gon

2018

) doe

s not

iden

tify

any

signi

fican

t PAF

mat

eria

l occ

urre

nces

with

in

the

pit s

hell.

•

Proc

ess w

ater

cou

ld b

e re

dire

cted

to th

e pi

t in

the

even

t of e

xtre

me

flood

eve

nts b

ut w

ill n

ot c

onta

in

cont

amin

ants

of c

once

rn.

• Gr

ound

wat

er fl

ows w

ill b

e to

war

ds th

e pi

t and

ther

efor

e w

ater

qua

lity

in th

e pi

t will

not

influ

ence

gro

undw

ater

in

the

surr

ound

ing

aqui

fer.

1 - L

ow1

- Low

Min

ing

and

ore

proc

essin

gRa

infa

ll on

to m

ine

site

prod

uces

co

ntam

inat

ed ru

noff

that

is re

leas

ed o

ff-sit

e

Poor

wat

er q

ualit

y do

wns

trea

m o

f min

e sit

e af

fect

s env

ironm

enta

l val

ues

and/

or o

ther

use

rs

• O

re a

nd re

ject

s cha

ract

erisa

tion

indi

cate

s mat

eria

l is i

nert

and

gra

vel l

ike

and

ther

efor

e w

ill n

ot le

ach

cont

amin

ants

of c

once

rn. F

ine

sedi

men

ts k

ey c

onta

min

ant o

f con

cern

.•

Stoc

kpile

are

as a

re lo

cate

d w

ithin

the

area

enc

lose

d by

the

inun

datio

n bu

nd a

nd W

RD, s

o no

dire

ct fl

ow p

ath

to

the

envi

ronm

ent.

• Ru

n-of

f dire

cted

to st

orm

wat

er d

rain

s and

sedi

men

t bas

ins,

for t

reat

men

t prio

r to

rele

ase

off-s

ite.

2 - M

ediu

m1

- Low

Was

te ro

ck, r

ejec

ts

and

taili

ngs d

ispos

alSe

epag

e of

wat

er

from

WRD

/TSF

to

grou

ndw

ater

aqu

ifer

Poor

wat

er q

ualit

y in

gr

ound

wat

er a

quife

r affe

cts

envi

ronm

enta

l val

ues a

nd/o

r ot

her u

sers

• W

aste

cha

ract

erisa

tion

(EcO

z/Pe

ndra

gon

2018

) doe

s not

iden

tify

any

AMD

pote

ntia

l. •

Taili

ngs c

hara

cter

isatio

n in

dica

tes t

he m

ater

ial i

s ine

rt w

ith n

o ch

emic

al c

onta

min

ants

. Fi

ne se

dim

ents

is th

e on

ly c

onta

min

ant o

f con

cern

.•

Grou

ndw

ater

flow

dire

ctio

n un

der T

SF is

tow

ards

the

pit.

•

Pit v

oid

is cl

assif

ied

as a

gro

undw

ater

sink

, so

mov

emen

t of c

onta

min

ants

into

gro

undw

ater

not

exp

ecte

d to

oc

cur.

• N

o gr

ound

wat

er u

sers

with

in 1

2 km

of s

ite.

2 - M

ediu

m1

- Low

Gra

nts

Lith

ium

Pro

ject

W

ater

Man

agem

ent P

lan

86

Haza

rd/A

spec

tIn

cide

nt/e

vent

Desc

riptio

n of

Impa

ct

Assu

mpt

ions

Inhe

rent

Ris

kRe

sidu

al R

isk

Was

te ro

ck, r

ejec

ts

and

taili

ngs d

ispos

alRe

leas

e o

f co

ntam

inat

ed

wat

er/t

ailin

gs fr

om

WRD

/TSF

into

surf

ace

wat

er

Poor

wat

er q

ualit

y in

sur

face

w

ater

cour

ses t

hat f

low

into

W

est A

rm a

ffect

s en

viro

nmen

tal v

alue

s

• Ta

iling

s cha

ract

erisa

tion

indi

cate

s the

mat

eria

l is i

nert

with

no

chem

ical

con

tam

inan

ts.

Fine

sedi

men

ts is

the

only

con

tam

inan

t of c

once

rn.

• Ta

iling

s to

be p

lace

d in

TSF

con

stru

cted

in c

entr

e of

the

WRD

and

will

be

surr

ound

ed b

y co

mpe

tent

was

te ro

ck.

• Da

m fa

ilure

and

env

ironm

enta

l spi

ll co

nseq

uenc

e ca

tego

ries a

sses

sed

acco

rdin

g to

AN

COLD

gui

delin

es.

Spill

way

siz

ed to

acc

omm

odat

e 0.

1%AE

P flo

od e

vent

. Des

ign

Stor

age

Allo

wan

ce p

rior t

o sp

illin

g se

t at 1

%AE

P, 7

2hou

rs

flood

eve

nt.

• In

the

even

t of T

SF fa

ilure

/ove

rtop

ping

, the

WRD

ann

ulus

pro

vide

s for

seco

ndar

y co

ntai

nmen

t.•

Run-

off f

rom

land

form

is in

terc

epte

d by

stor

mw

ater

dra

ins a

nd d

irect

ed to

sedi

men

t bas

ins.

2 - M

ediu

m2

- Med

ium

Was

te ro

ck, r

ejec

ts

and

taili

ngs d

ispos

alEr

osio

n of

WRD

an

nulu

s In

crea

sed

turb

idity

in su

rfac

e w

ater

cour

ses t

hat f

low

into

W

est A

rm a

ffect

s en

viro

nmen

tal v

alue

s

• Ru

n-of

f fro

m la

ndfo

rm is

inte

rcep

ted

by st

orm

wat

er d

rain

s and

dire

cted

to se

dim

ent b

asin

s.•

WRD

ann

ulus

will

be

expo

sed

to a

sing

le w

et se

ason

, with

reha

bilit

atio

n pl

anne

d ar

ound

end

of y

ear 1

min

ing

activ

ities

.

3 - H

igh

2 - M

ediu

m

Stor

age

and

hand

ling

of

haza

rdou

s mat

eria

ls

Leak

s and

spill

s fro

m

dies

el fu

el st

orag

e ar

eas e

nter

ing

grou

ndw

ater

Hydr

ocar

bon

cont

amin

atio

n of

aqu

ifer a

ffect

s en

viro

nmen

tal v

alue

s and

/or

othe

r use

rs

• Ab

ove-

grou

nd fu

el st

orag

e ta

nks u

sed

over

shor

t life

of m

ine

- lo

wer

s risk

ass

ocia

ted

with

diff

use

pollu

tion

over

tim

e.•

Fuel

stor

age

and

hand

ling

in d

esig

nate

d ar

eas a

nd a

ccor

danc

e w

ith A

S194

0.

• Gr

ound

wat

er a

quife

r is s

hallo

w b

ut tr

ansm

issiv

ity is

low

.•

Durin

g m

inin

g, g

roun

dwat

er b

enea

th th

e m

ine

site

will

flow

tow

ards

the

pit.

• N

o GD

E's o

r oth

er u

sers

in p

roxi

mity

to si

te.

1 - L

ow1

- Low

Stor

age

and

hand

ling

of

haza

rdou

s mat

eria

ls

Leak

s and

spill

s fro

m

dies

el fu

el st

orag

e ar

eas e

nter

ing

surf

ace

wat

er

Hydr

ocar

bon

cont

amin

atio

n of

dow

nstr

eam

eph

emer

al

wat

erco

urse

s tha

t flo

w in

to

Wes

t Arm

• Ab

ove-

grou

nd fu

el st

orag

e ta

nks u

sed

over

shor

t life

of m

ine

- lo

wer

s risk

ass

ocia

ted

with

diff

use

pollu

tion

over

tim

e.•

Fuel

stor

age

and

hand

ling

in d

esig

nate

d ar

eas a

nd a

ccor

danc

e w

ith A

S194

0.

• Di

vers

ion

bund

aro

und

site

prov

ides

add

ed b

arrie

r to

mov

emen

t of s

pills

off

site

by su

rfac

e w

ater

flow

s.

2 - M

ediu

m1

- Low

Non

-ore

was

te

man

agem

ent

Leak

s fro

m se

ptic

sy

stem

into

gr

ound

wat

er

Bact

eria

l con

tam

inat

ion

of

grou

ndw

ater

ben

eath

the

site

affe

cts e

nviro

nmen

tal

valu

es a

nd/o

r oth

er u

sers

• Ca

paci

ty b

ased

on

max

64

staf

f ons

ite w

ill b

e le

ss th

an 2

,000

l/day

. •

On-

site

was

te w

ater

syst

em w

ill b

e in

stal

led

by a

lice

nsed

plu

mbe

r in

acco

rdan

ce w

ith N

T Co

de o

f Pra

ctic

e fo

r on

site

was

tew

ater

man

agem

ent.

• Gr

ound

wat

er a

quife

r is s

hallo

w b

ut tr

ansm

issiv

ity is

low

. Du

ring

min

ing,

gro

undw

ater

ben

eath

the

min

e sit

e w

ill

flow

tow

ards

the

pit.

1 - L

ow1

- Low

Non

-ore

was

te

man

agem

ent

Leak

s fro

m se

ptic

sy

stem

into

surf

ace

wat

er

Bact

eria

l con

tam

inat

ion

of

surf

ace

wat

er fl

ows a

ffect

s en

viro

nmen

tal v

alue

s

• Ca

paci

ty b

ased

on

max

64

staf

f ons

ite w

ill b

e le

ss th

an 2

,000

l/day

. •

On-

site

was

te w

ater

syst

em w

ill b

e in

stal

led

by a

lice

nsed

plu

mbe

r in

acco

rdan

ce w

ith N

T Co

de o

f Pra

ctic

e fo

r on

site

was

tew

ater

man

agem

ent.

• Di

vers

ion

bund

aro

und

site

prov

ides

add

ed b

arrie

r to

mov

emen

t of s

pills

off

site

by su

rfac

e w

ater

flow

s.

1 - L

ow1

- Low

009

Non

-ore

was

te

man

agem

ent

Haza

rdou

s was

te

stor

age

area

s do

not

have

ade

quat

e co

ntai

nmen

t

Cont

amin

atio

n of

surf

ace

wat

er a

nd/o

r gro

undw

ater

af

fect

s env

ironm

enta

l val

ues

and/

or o

ther

use

rs

•Was

te p

rodu

ced

on si

te w

ill c

ompr

ise w

aste

oils

/lubr

ican

ts, b

atte

ries,

tyre

s.•

Any

rele

ase

of c

onta

min

ants

to g

roun

d w

ould

eith

er se

ep to

gro

undw

ater

, whi

ch fl

ows t

owar

ds th

e pi

t, or

ent

er

the

on-s

ite st

orm

wat

er m

anag

emen

t sys

tem

that

is d

irect

to th

e se

dim

ent b

asin

s.

2 - M

ediu

m1

- Low

Hydr

olog

ical

pro

cess

es

Cons

truc

tion

of

min

e sit

e in

fras

truc

ture

Alte

ratio

n of

surf

ace

wat

er fl

ows a

nd

disc

harg

es

Redu

ced

flow

s affe

cts

envi

ronm

enta

l val

ues

• M

ine

site

infr

astr

uctu

re w

ill c

hang

e st

ream

line

s in

the

uppe

r cat

chm

ent.

• N

o sig

nific

ant o

r sen

sitiv

e w

ater

dep

ende

nt e

nviro

nmen

tal v

alue

s in

ephe

mer

al d

rain

ages

ups

trea

m o

f sal

twat

er

influ

ence

, whe

re m

odel

led

flow

redu

ctio

n is

up to

46%

dur

ing

the

early

wet

seas

on.

• Co

mbi

ned

impa

ct o

f the

min

e sit

e an

d da

m c

ould

redu

ce fl

ows i

nto

the

uppe

r man

grov

es o

f Wes

t Arm

by

16-2

0 %

in th

e ea

rly w

et se

ason

mon

ths N

ov-e

arly

Jan,

dro

ppin

g to

bet

wee

n 1%

and

7%

for t

he re

mai

nder

of t

he w

et

seas

on.

2 - M

ediu

m2

- Med

ium

Gra

nts

Lith

ium

Pro

ject

W

ater

Man

agem

ent P

lan

87

Haza

rd/A

spec

tIn

cide

nt/e

vent

Desc

riptio

n of

Impa

ct

Assu

mpt

ions

Inhe

rent

Ris

kRe

sidu

al R

isk

Wat

er su

pply

and

us

eDa

m w

all f

ailu

re M

ine

Site

Dam

Dow

nstr

eam

floo

ding

in W

est

Arm

cat

chm

ent

• Du

e to

the

prox

imity

of t

he d

am to

the

Cox

Peni

nsul

a Ro

ad, t

he P

opul

atio

n At

Risk

(PAR

) has

bee

n as

sess

ed a

s 1

– 10

. •

Con

sequ

ence

Cat

egor

y as

‘Sig

nific

ant’.

•

Spill

way

has

bee

n de

signe

d to

pas

s a 0

.1%

AEP

floo

d ev

ent.

3 - H

igh

1 - L

ow

Wat

er su

pply

and

us

eDa

m w

all f

ailu

re

Obs

erva

tion

Hill

Dam

Dow

nstr

eam

floo

ding

in

Byno

e ca

tchm

ent

• Po

pula

tion

At R

isk (P

AR) h

as b

een

asse

ssed

as 1

– 1

0.

• C

onse

quen

ce C

ateg

ory

as ‘S

igni

fican

t’.

• Sp

illw

ay h

as b

een

desig

ned

to p

ass a

0.1

% A

EP fl

ood

even

t.

3 - H

igh

1 - L

ow

Wat

er su

pply

and

us

eHa

rves

ting

of su

rfac

e w

ater

flow

s to

fill

OHD

Redu

ced

flow

s dow

nstr

eam

to

Cha

rlott

e Ri

ver a

ffect

s en

viro

nmen

tal v

alue

s

• N

T W

ater

Allo

catio

n Pl

anni

ng F

ram

ewor

k co

ntin

gent

allo

catio

n fo

r env

ironm

enta

l and

pub

lic b

enef

it is

80%

.•

No

publ

ic b

enef

it w

ater

use

s in

catc

hmen

t.•

Ripa

rian

rain

fore

st a

long

dra

inag

es d

owns

trea

m o

f dam

may

be

sens

itive

to re

duce

d flo

ws.

• Th

e m

odel

led

redu

ctio

n in

flow

s at t

he o

utle

t to

Char

lott

e Ri

ver i

s up

to 2

.6%

in F

ebru

ary.

1 - L

ow1

- Low

Wat

er su

pply

and

us

eO

pera

tiona

l ef

ficie

ncie

s not

ac

hiev

ed re

sulti

ng in

in

crea

sed

proj

ect

wat

er re

quire

men

ts

Addi

tiona

l ext

ract

ion

of

wat

er fr

om d

ams d

ecre

ases

do

wns

trea

m fl

ows m

ore

than

pr

edic

ted

• Co

nser

vativ

e ap

proa

ch a

pplie

d to

mod

ellin

g w

ith p

ump

rate

bas

ed o

n en

tire

min

e sit

e su

pply

com

ing

from

a

singl

e so

urce

. •

Site

wat

er b

alan

ce p

repa

red

for f

easib

ility

stag

e de

sign

indi

cate

s pit

dew

ater

ing

expe

cted

to su

pply

mos

t of t

he

site

wat

er re

quire

men

ts. O

bs H

ill D

am c

ould

pro

vide

all

of th

e pr

ojec

ts m

ake-

up w

ater

nee

ds; h

owev

er, m

ine

site

dam

pro

pose

d as

a c

ontin

genc

y su

pply

opt

ion.

•

Any

addi

tiona

l sup

ply

requ

irem

ent i

s not

like

ly to

be

of a

mag

nitu

de th

at w

ould

inc

reas

e th

e m

odel

led

redu

ctio

n of

flow

s.

1 - L

ow1

- Low

Wat

er su

pply

and

us

eDi

scha

rge

of e

xces

s w

ater

in w

et se

ason

Incr

ease

d flo

ws d

owns

trea

m

into

Wes

t Arm

affe

cts

envi

ronm

enta

l val

ues

• Th

e sit

e w

ater

acc

ount

pre

dict

s disc

harg

e re

quire

men

t dur

ing

Dec

to M

ar e

ach

year

.•

Disc

harg

e is

driv

en b

y gr

ound

wat

er in

flow

s to

pit.

• M

odel

par

amet

er e

stim

atio

n w

as u

nder

take

n in

acc

orda

nce

with

bes

t pra

ctic

e gu

idel

ines

(Bar

nett

et a

l, 20

08).

The

mod

el is

dee

med

to m

eet t

he re

quire

men

ts o

f a C

lass

2 m

odel

and

is su

itabl

e fo

r pro

vidi

ng e

stim

ates

of

dew

ater

ing

requ

irem

ents

for m

ines

and

the

asso

ciat

ed im

pact

s.

2 - M

ediu

m1

- Low

Wat

er su

pply

and

us

eHa

rves

ting

of su

rfac

e w

ater

flow

s to

fill

Min

e Si

te D

am

Redu

ced

flow

s dow

nstr

eam

in

to W

est A

rm a

ffect

s en

viro

nmen

tal v

alue

s

• N

T W

ater

Allo

catio

n Pl

anni

ng F

ram

ewor

k co

ntin

gent

allo

catio

n fo

r env

ironm

enta

l and

pub

lic b

enef

it is

80%

.•

No

signi

fican

t or s

ensit

ive

wat

er d

epen

dent

env

ironm

enta

l val

ues i

n ep

hem

eral

dra

inag

es u

pstr

eam

of s

altw

ater

in

fluen

ce, w

here

mod

elle

d flo

w re

duct

ion

is <4

5% d

urin

g th

e ea

rly w

et se

ason

.•

Hint

erla

nd m

angr

oves

1.7

km

dow

nstr

eam

clo

sest

sens

itive

rece

ptor

.•

Com

bine

d im

pact

of t

he m

ine

site

and

dam

cou

ld re

duce

flow

s int

o th

e up

per m

angr

oves

of W

est A

rm b

y 16

-20

% in

the

early

wet

seas

on m

onth

s Nov

-ear

ly Ja

n, d

ropp

ing

to b

etw

een

1% a

nd 7

% fo

r the

rem

aind

er o

f the

wet

se

ason

.

2 - M

ediu

m2

- Med

ium

Min

ing

and

ore

proc

essin

gGr

ound

wat

er in

flow

s to

pit

Draw

dow

n of

gro

undw

ater

le

vels

in a

quife

r affe

cts

envi

ronm

enta

l val

ues a

nd/o

r ot

her u

sers

• G

roun

dwat

er in

flow

s to

pit m

odel

led

over

life

of m

ine.

Mod

el d

eem

ed to

mee

t the

requ

irem

ents

of a

Cla

ss 2

m

odel

(Bar

nett

et a

l 200

8) a

nd is

suita

ble

for p

rovi

ding

est

imat

es o

f min

e de

wat

erin

g re

quire

men

ts.

• En

d of

min

ing

draw

dow

n co

ne m

odel

led

to e

xten

d 1

km fr

om th

e pi

t. •

No

GDE'

s pre

sent

in a

rea.

Dra

wdo

wn

mod

ellin

g in

dica

tes i

mpa

ct w

ill n

ot a

ffect

disc

harg

e to

eph

emer

al

wat

erco

urse

s.•

No

othe

r use

rs w

ithin

12

km o

f site

.

1 - L

ow1

- Low

Was

te ro

ck, r

ejec

ts

and

taili

ngs d

ispos

alAq

uife

r rec

harg

e fr

om

TSF

cells

Loca

lised

mou

ndin

g of

gr

ound

wat

er•

Grou

ndw

ater

flow

dire

ctio

n in

are

a of

TSF

will

be

tow

ards

the

pit v

oid.

• M

odel

led

draw

dow

n co

ne c

over

s are

a be

neat

h W

RD/T

SF la

ndfo

rm.

1 - L

ow1

- Low


88

9 MANAGEMENT MEASURES

This section documents the management measures that will be implemented to reduce construction/operations phase risks to hydrological processes and water quality to ‘as low as reasonably possible’. For each potential impact identified through the environmental risk assessment process, Table 9-1 documents:

Environmental objectives Management actions required to achieve those objectives Monitoring that will be undertaken to measure performance Performance indicators Corrective actions to be applied if performance indicators are not being met Reporting requirements.

Gra

nts

Lith

ium

Pro

ject

W

ater

Man

agem

ent P

lan

89

Tabl

e 9-

1. W

ater

man

agem

ent f

ram

ewor

k fo

r con

stru

ctio

n/op

erat

ions

pha

se

No.

Valu

ePo

tent

ial i

mpa

ctO

bjec

tive

/ ou

tcom

eM

anag

emen

t pro

visi

ons

Targ

ets

/ pe

rfor

man

ce

indi

cato

rs

Mon

itorin

gR

espo

nse

Rep

ortin

g

Hyd

rolo

gica

l pro

cess

es1.

Wes

t Arm

&

Cha

rlotte

Riv

er

catc

hmen

ts

Dow

nstre

am fl

oodi

ng

due

to d

am w

all f

ailu

re

of M

ine

Site

Dam

an

d/or

of O

bser

vatio

n H

ill D

am

No

dam

wal

l fai

lure

of

Min

e Si

te D

am o

r O

bser

vatio

n H

ill D

am

D

esig

n da

m in

ac

cord

ance

with

AN

CO

LD G

uide

lines

Dam

wal

ls m

aint

ain

thei

r stru

ctur

al in

tegr

ityR

egul

ar in

spec

tion

and

test

ing

of d

am

wal

l int

egrit

y

R

epai

r wal

l im

med

iate

ly

Rep

ort

flood

ing

to

DPI

R a

nd N

T EP

A

Inve

stig

ate

caus

e of

fa

ilure

Incl

ude

inci

dent

re

port

in a

nnua

l M

MP

repo

rt

2.W

est A

rm &

C

harlo

tte R

iver

ca

tchm

ents

Alte

red

envi

ronm

enta

l flo

ws

due

to

harv

estin

g of

sur

face

w

ater

to fi

ll M

ine

Site

D

am a

nd O

bser

vatio

n H

ill D

am

Min

imis

e re

duct

ion

of s

urfa

ce w

ater

flo

w v

olum

es

dow

nstre

am o

f the

da

ms

D

esig

n da

ms

base

d on

th

e m

inim

um

requ

irem

ent t

o ac

hiev

e a

sust

aina

ble

wat

er s

uppl

y fo

r the

pro

ject

D

esig

n m

ine

site

to

inco

rpor

ate

addi

tiona

l st

orag

es (M

WD

1 &

2) s

o th

at T

SF d

ecan

t and

pit

dew

ater

ing

can

be u

sed

as th

e pr

imar

y pr

ojec

t w

ater

sup

ply

3.W

est A

rm &

C

harlo

tte R

iver

ca

tchm

ents

Low

er th

an p

redi

cted

en

viro

nmen

tal f

low

s du

e to

incr

ease

d su

rface

wat

er

harv

estin

g be

caus

e of

in

crea

sed

proj

ect

wat

er re

quire

men

ts

No

redu

ctio

n in

su

rface

wat

er fl

ow

volu

mes

bel

ow

thos

e pr

edic

ted

In

clud

e w

ater

effi

cien

cy

and

recy

clin

g in

the

desi

gn o

f pro

cess

ing

faci

lity

Ad

opt a

con

serv

ativ

e ap

proa

ch w

hen

mod

ellin

g po

tent

ial

impa

cts

and

estim

atin

g re

turn

s th

roug

h re

cycl

ing

of w

ater

No

sign

ifica

nt in

crea

se

from

wat

er e

xtra

ctio

n vo

lum

es u

sed

in

mod

ellin

g of

flow

re

duct

ions

Rec

ordi

ng o

f wat

er

extra

ctio

n vo

lum

es

from

Obs

erva

tion

Hill

Dam

and

Min

e Si

te

Dam

As p

er

man

agem

ent

prov

isio

ns

Wat

er u

sage

vo

lum

es a

nd

wat

er b

alan

ce

upda

tes

as

requ

ired

for

annu

al M

MP

repo

rting

4.W

est A

rm

catc

hmen

tAl

tere

d en

viro

nmen

tal

flow

s du

e to

a re

leas

e fro

m M

ine

Site

Dam

of

Min

imis

e in

crea

se o

f su

rface

wat

er fl

ow

volu

mes

D

esig

n m

ine

site

to

inco

rpor

ate

addi

tiona

l st

orag

e (M

WD

2) fo

r de

wat

erin

g of

pit

inflo

ws

N

o no

n-co

nfor

man

ces

of

Was

te D

isch

arge

Li

cenc

e co

nditi

ons

R

ecor

ding

of

disc

harg

e vo

lum

es

from

MW

D1

As p

er

man

agem

ent

prov

isio

ns

W

ater

usa

ge

volu

mes

and

w

ater

bal

ance

up

date

s

Gra

nts

Lith

ium

Pro

ject

W

ater

Man

agem

ent P

lan

90

No.

Valu

ePo

tent

ial i

mpa

ctO

bjec

tive

/ ou

tcom

eM

anag

emen

t pro

visi

ons

Targ

ets

/ pe

rfor

man

ce

indi

cato

rs

Mon

itorin

gR

espo

nse

Rep

ortin

g

wat

er e

xces

s to

re

quire

men

ts

dow

nstre

am o

f the

da

ms

so th

at d

isch

arge

re

quire

d in

wet

sea

son

only

If

early

-wet

sea

son

disc

harg

es a

re re

quire

d,

rele

ase

the

wat

er in

pu

lses

rath

er th

an s

low

co

ntin

uous

rele

ase

to

sim

ulat

e ea

rly w

et

seas

on s

torm

s an

d av

oid

stre

am e

utro

phic

atio

n th

at c

an o

ccur

und

er lo

w-

flow

con

ditio

ns

Adhe

re to

the

disc

harg

e tim

ing

and

volu

mes

that

ar

e au

thor

ised

by

the

proj

ect W

aste

Dis

char

ge

Lice

nce

N

o si

gnifi

cant

im

pact

s on

do

wns

tream

wat

er

qual

ity b

ased

on

asse

ssm

ent u

sing

cr

iteria

in W

ater

Q

ualit

y M

onito

ring

Plan

M

onito

ring

dow

nstre

am im

pact

s in

acc

orda

nce

with

W

ater

Qua

lity

Mon

itorin

g Pl

an a

nd

Was

te D

isch

arge

Li

cenc

e co

nditi

ons

requ

ired

for

annu

al M

MP

repo

rting

An

nual

Was

te

Dis

char

ge

Lice

nce

repo

rting

re

quire

men

ts

and

non-

conf

orm

ance

re

porti

ng

requ

irem

ents

5.Lo

cal a

quife

rsLo

calis

ed m

ound

ing

of

grou

ndw

ater

see

page

fro

m T

SF c

ells

Min

imis

e se

epag

e fro

m th

e TS

F ce

lls

to lo

cal a

quife

r

C

onst

ruct

TSF

fo

unda

tion

from

low

pe

rmea

bilit

y m

ater

ial t

hat

has

been

rolle

d an

d co

mpa

cted

C

ap T

SF a

t clo

sure

and

en

case

with

in W

RD

In

corp

orat

e an

un

derd

rain

age

syst

em in

th

e TS

F de

sign

N

o un

seas

onal

(Dry

-se

ason

) inc

reas

es in

st

andi

ng w

ater

leve

ls

in m

onito

ring

bore

s

No

sign

ifica

nt

incr

ease

s in

co

ntam

inan

t co

ncen

tratio

ns in

gr

ound

wat

er d

ue to

TS

F se

epag

e

Gro

undw

ater

leve

l and

w

ater

qua

lity

mon

itorin

g as

per

W

ater

Qua

lity

Mon

itorin

g Pl

an

As p

er

man

agem

ent

prov

isio

ns

Wat

er q

ualit

y re

sults

as

sess

men

t as

requ

ired

for

annu

al M

MP

repo

rting

Inla

nd w

ater

env

ironm

enta

l qua

lity

6.W

est A

rm

catc

hmen

tTu

rbid

ity d

ue to

ra

infa

ll ru

n-of

f fro

m th

e m

ine

site

No

rele

ase

of tu

rbid

w

ater

dra

inin

g fro

m

the

min

e si

te

U

nder

take

con

stru

ctio

n in

the

dry

seas

on

If si

te c

lear

ing

and

prep

arat

ion

was

to o

ccur

du

ring

the

wet

sea

son,

a

spec

ific

ESC

P in

ac

cord

ance

with

IEC

A w

ill be

dev

elop

ed fo

r thi

s.

All E

SCP

miti

gatio

n an

d

Wat

er re

leas

ed fr

om

sedi

men

t bas

ins

mee

ts

the

75 N

TU c

riter

ia

and

dow

nstre

am

surfa

ce w

ater

m

onito

ring

site

s m

eet

the

20 N

TU c

riter

ia

Wat

er Q

ualit

y M

onito

ring

Plan

–

surfa

ce w

ater

m

onito

ring

Rev

iew

all

on-

site

ero

sion

and

se

dim

ent

cont

rols

and

m

ake

impr

ovem

ents

Wat

er q

ualit

y re

sults

as

sess

men

t as

requ

ired

for

annu

al M

MP

repo

rting

Gra

nts

Lith

ium

Pro

ject

W

ater

Man

agem

ent P

lan

91

No.

Valu

ePo

tent

ial i

mpa

ctO

bjec

tive

/ ou

tcom

eM

anag

emen

t pro

visi

ons

Targ

ets

/ pe

rfor

man

ce

indi

cato

rs

Mon

itorin

gR

espo

nse

Rep

ortin

g

man

agem

ent m

easu

res

will

be in

pla

ce p

rior t

o th

e co

mm

enci

ng o

f any

si

te c

lear

ing

wor

ks

Dur

ing

min

e op

erat

ions

, im

plem

ent t

he E

SCP

to

ensu

re s

tabi

lisat

ion

clea

red

area

s an

d es

tabl

ishm

ent o

f se

dim

ent c

ontro

ls

Des

ign

min

e si

te s

uch

that

all

run-

off i

s in

terc

epte

d by

st

orm

wat

er d

rain

s an

d di

rect

ed to

sed

imen

t ba

sins

Des

ign

and

oper

ate

sedi

men

t bas

ins

in

acco

rdan

ce w

ith th

e ES

CP

Tr

eat t

he w

ater

in

sedi

men

t bas

ins

with

a

flocc

ulen

t and

test

ed

whe

ther

wat

er q

ualit

y cr

iteria

hav

e be

en

achi

eved

prio

r to

rele

ase

7.W

est A

rm &

C

harlo

tte R

iver

ca

tchm

ents

Turb

idity

due

to

eros

ion

of W

RD

an

nulu

s

No

rele

ase

of tu

rbid

w

ater

dra

inin

g fro

m

the

min

e si

te

C

onst

ruct

the

WR

D

annu

lus

from

com

pete

nt

was

te m

ater

ial

Pl

ace

disp

ersi

ve w

aste

in

the

cent

re o

f the

WR

D

Stab

ilise

and

reha

bilit

ate

the

WR

D a

nnul

us a

s pe

r th

e M

ine

Clo

sure

Pla

n

Des

ign

min

e si

te s

uch

that

all

run-

off i

s in

terc

epte

d by

st

orm

wat

er d

rain

s an

d

Gra

nts

Lith

ium

Pro

ject

W

ater

Man

agem

ent P

lan

92

No.

Valu

ePo

tent

ial i

mpa

ctO

bjec

tive

/ ou

tcom

eM

anag

emen

t pro

visi

ons

Targ

ets

/ pe

rfor

man

ce

indi

cato

rs

Mon

itorin

gR

espo

nse

Rep

ortin

g

dire

cted

to s

edim

ent

basi

ns

8.W

est A

rm &

C

harlo

tte R

iver

ca

tchm

ents

Turb

idity

due

to

eros

ion

of

dow

nstre

am s

tream

ba

nks

whe

n da

ms

over

flow

Min

imis

e er

osio

n of

st

ream

ban

ks

dow

nstre

am o

f dam

w

alls

and

spi

llway

s

Im

plem

ent t

he e

rosi

on

and

sedi

men

t con

trols

th

at a

ccom

pany

the

cons

truct

ion

engi

neer

ing

draw

ings

for t

he d

am

wal

ls a

nd s

pillw

ays

D

esig

n da

m w

alls

and

sp

illway

s to

AN

CO

LD

guid

elin

es

Dow

nstre

am tu

rbid

ity

does

not

con

sist

ently

ex

ceed

20

NTU

crit

eria

Wat

er Q

ualit

y M

onito

ring

Plan

–

surfa

ce w

ater

m

onito

ring

In

crea

se

stre

am b

ank

prot

ectio

ns

Slow

dow

n re

leas

e of

w

ater

from

da

ms

Wat

er q

ualit

y re

sults

as

sess

men

t as

requ

ired

for

annu

al M

MP

repo

rting

9.W

est A

rm

catc

hmen

tTu

rbid

ity d

ue to

an

over

flow

of t

he R

aw

Wat

er a

nd/o

r Pro

cess

W

ater

Dam

No

over

flow

of t

he

Raw

Wat

er a

nd/o

r Pr

oces

s W

ater

Dam

D

esig

n da

ms

such

that

, as

a c

ontin

genc

y du

ring

extre

me

wet

wea

ther

ev

ents

, exc

ess

wat

er c

an

be d

irect

ed to

the

pit

and/

or T

SF

Wat

er le

vels

in th

e R

aw W

ater

and

Pr

oces

s W

ater

Dam

s do

not

enc

roac

h w

ithin

0.

8 m

of t

he d

am w

all

tops

.

Mon

itor d

am w

ater

le

vels

dai

lyD

irect

exc

ess

wat

er to

the

pit

and/

or T

SF

Wat

er q

ualit

y re

sults

as

sess

men

t an

d w

ater

ba

lanc

e up

date

s as

re

quire

d fo

r an

nual

MM

P re

porti

ng10

.W

est A

rm

catc

hmen

tTu

rbid

ity a

nd/o

r co

ntam

inat

ion

due

to

a re

leas

e fro

m M

WD

1 of

wat

er e

xces

s to

re

quire

men

ts

Adhe

re to

the

disc

harg

e tim

ing

and

volu

mes

au

thor

ised

by

the

Was

te D

isch

arge

Li

cenc

e

D

isch

arge

exc

ess

wat

er

as p

er th

e tim

ing

and

volu

mes

aut

horis

ed b

y th

e W

aste

Dis

char

ge

Lice

nce

D

owns

tream

turb

idity

do

es n

ot e

xcee

d 20

NTU

obj

ectiv

e

No

sign

ifica

nt

exce

edan

ce o

f wat

er

qual

ity o

bjec

tives

in

rela

tion

to p

oten

tial

cont

amin

ants

D

owns

tream

turb

idity

m

onito

ring

as p

er

Wat

er Q

ualit

y M

onito

ring

Plan

Su

rface

wat

er

mon

itorin

g fo

r co

ntam

inan

ts a

s pe

r W

ater

Qua

lity

Mon

itorin

g Pl

an

M

ake

impr

ovem

ents

to

trea

tmen

t of

wat

er p

umpe

d fro

m th

e pi

t to

min

imis

e tu

rbid

ity

Trea

t wat

er in

M

WD

1 w

ith

flocc

ulan

ts to

re

duce

su

spen

ded

sedi

men

ts a

nd

cont

amin

ants

–

i.e. t

his

may

al

so a

ssis

t in

redu

cing

ar

seni

c an

d P

conc

entra

tions

Al

l Was

te

Dis

char

ge

Lice

nce

non-

conf

orm

ance

s m

ust b

e re

porte

d im

med

iate

ly

follo

wed

by

an

inve

stig

atio

n of

pot

entia

l en

viro

nmen

tal

impa

cts

W

ater

qua

lity

resu

lts

repo

rted

for

annu

al M

MP

repo

rt

Gra

nts

Lith

ium

Pro

ject

W

ater

Man

agem

ent P

lan

93

No.

Valu

ePo

tent

ial i

mpa

ctO

bjec

tive

/ ou

tcom

eM

anag

emen

t pro

visi

ons

Targ

ets

/ pe

rfor

man

ce

indi

cato

rs

Mon

itorin

gR

espo

nse

Rep

ortin

g

W

ater

qua

lity

resu

lts

repo

rted

for

annu

al W

aste

D

isch

arge

Li

cenc

e re

port

11.

Wes

t Arm

ca

tchm

ent

Turb

idity

due

to w

ater

re

leas

ed fr

om th

e W

RD

/TSF

No

rele

ase

of w

ater

fro

m th

e W

RD

/TSF

in

to th

e ca

tchm

ent

C

onst

ruct

the

WR

D

annu

lus

from

com

pete

nt

was

te m

ater

ial

Pl

ace

disp

ersi

ve w

aste

in

the

cent

re o

f the

WR

D

Stab

ilise

and

reha

bilit

ate

the

WR

D a

nnul

us a

s pe

r th

e M

ine

Clo

sure

Pla

n

Des

ign

min

e si

te s

uch

that

all

run-

off i

s in

terc

epte

d by

st

orm

wat

er d

rain

s an

d di

rect

ed to

sed

imen

t ba

sins

Dow

nstre

am tu

rbid

ity

does

not

sig

nific

antly

ex

ceed

20

NTU

cr

iteria

.

Dow

nstre

am tu

rbid

ity

mon

itorin

g as

Wat

er

Qua

lity

Mon

itorin

g Pl

an

Rev

iew

all

on-

site

ero

sion

and

se

dim

ent

cont

rols

and

m

ake

impr

ovem

ents

Wat

er q

ualit

y re

sults

as

sess

men

t as

requ

ired

for

annu

al M

MP

repo

rting

12.

Loca

l aqu

ifers

Con

tam

inat

ion

caus

ed

by s

eepa

ge o

f wat

er

from

the

WR

D/T

SF

No

seep

age

of

cont

amin

ated

wat

er

from

the

WR

D/T

SF

into

gro

undw

ater

C

onst

ruct

TSF

fo

unda

tion

from

low

pe

rmea

bilit

y m

ater

ial t

hat

has

been

rolle

d an

d co

mpa

cted

C

ap T

SF a

t clo

sure

and

en

case

with

in W

RD

In

corp

orat

e an

un

derd

rain

age

syst

em in

th

e TS

F de

sign

No

exce

edan

ce o

f w

ater

qua

lity

obje

ctiv

es in

rela

tion

to

pote

ntia

l con

tam

inan

ts

Gro

undw

ater

m

onito

ring

for

cont

amin

ants

as

per

Wat

er Q

ualit

y M

onito

ring

Plan

As p

er

man

agem

ent

prov

isio

ns

W

ater

qua

lity

resu

lts

asse

ssm

ent

as re

quire

d fo

r ann

ual

MM

P re

porti

ng

Rep

ortin

g of

po

llutio

n in

cide

nt to

NT

EPA

follo

wed

by

in

vest

igat

ion

into

pot

entia

l en

viro

nmen

tal

impa

cts

Gra

nts

Lith

ium

Pro

ject

W

ater

Man

agem

ent P

lan

94

No.

Valu

ePo

tent

ial i

mpa

ctO

bjec

tive

/ ou

tcom

eM

anag

emen

t pro

visi

ons

Targ

ets

/ pe

rfor

man

ce

indi

cato

rs

Mon

itorin

gR

espo

nse

Rep

ortin

g

13.

Wes

t Arm

&

Cha

rlotte

Riv

er

catc

hmen

ts

Loca

l aqu

ifers

Con

tam

inat

ion

caus

ed

by m

isha

ndlin

g an

d/or

in

appr

opria

te s

tora

ge

of fu

els

No

cont

amin

atio

n of

gr

ound

wat

er o

r su

rface

wat

er b

y fu

els

Su

rroun

d st

orag

e ar

eas

for f

uels

and

oils

with

an

impe

rvio

us b

und

that

co

ntai

ns 1

20%

of t

he

larg

est c

onta

iner

sto

red

in th

e bu

nd –

as

per

AS19

40

Ref

uel v

ehic

les

with

in

bund

ed a

reas

M

ake

avai

labl

e sp

ill co

ntai

nmen

t equ

ipm

ent

kits

at t

he w

orks

are

a th

at a

re a

dequ

atel

y-si

zed

to m

anag

e th

e vo

lum

e of

fu

els

that

cou

ld b

e sp

illed

No

dete

ctio

n of

hy

droc

arbo

nsSu

rface

wat

er a

nd

grou

ndw

ater

m

onito

ring

for

hydr

ocar

bons

as

per

Wat

er M

P

Inve

stig

ate

caus

e of

spi

ll an

d up

date

pr

oced

ures

as

nece

ssar

y

14.

Wes

t Arm

&

Cha

rlotte

Riv

er

catc

hmen

ts

Loca

l aqu

ifers

Con

tam

inat

ion

caus

ed

by m

isha

ndlin

g an

d/or

in

appr

opria

te s

tora

ge

of h

azar

dous

was

te

No

cont

amin

atio

n of

gr

ound

wat

er o

r su

rface

wat

er b

y ha

zard

ous

was

te

U

se, h

andl

e, s

tore

and

di

spos

e of

all

haza

rdou

s m

ater

ials

in a

ccor

danc

e w

ith th

e D

ange

rous

G

oods

Act

and

the

Was

te M

anag

emen

t and

P

ollu

tion

Con

trol A

ct

Lo

cate

che

mic

al a

nd

haza

rdou

s go

ods

stor

age

area

s no

less

than

50

m

from

any

are

as o

f co

ncen

trate

d w

ater

flow

, flo

od a

nd p

oorly

-dra

ined

ar

eas

M

ake

avai

labl

e sp

ill co

ntai

nmen

t equ

ipm

ent

kits

at t

he w

orks

are

a th

at a

re a

dequ

atel

y-si

zed

to m

anag

e th

e vo

lum

e of

ha

zard

ous

mat

eria

ls

stor

ed w

ithin

the

wor

ks

area

s

No

exce

edan

ce o

f w

ater

qua

lity

obje

ctiv

es in

rela

tion

to

pote

ntia

l con

tam

inan

ts

(see

Wat

er M

P fo

r de

tail)

Surfa

ce w

ater

and

gr

ound

wat

er

mon

itorin

g fo

r co

ntam

inan

ts a

s pe

r W

ater

Qua

lity

Mon

itorin

g Pl

an

Inve

stig

ate

caus

e of

spi

ll an

d up

date

pr

oced

ures

as

nece

ssar

y

R

epor

ting

of

pollu

tion

inci

dent

to N

T EP

A fo

llow

ed

by

inve

stig

atio

n in

to p

oten

tial

envi

ronm

enta

l im

pact

s

Incl

ude

inci

dent

re

port

in

annu

al M

MP

repo

rt

Gra

nts

Lith

ium

Pro

ject

W

ater

Man

agem

ent P

lan

95

No.

Valu

ePo

tent

ial i

mpa

ctO

bjec

tive

/ ou

tcom

eM

anag

emen

t pro

visi

ons

Targ

ets

/ pe

rfor

man

ce

indi

cato

rs

Mon

itorin

gR

espo

nse

Rep

ortin

g

15.

Wes

t Arm

&

Cha

rlotte

Riv

er

catc

hmen

ts

Loca

l aqu

ifers

Con

tam

inat

ion

caus

ed

by a

leak

from

the

sept

ic s

yste

m

No

cont

amin

atio

n of

gr

ound

wat

er o

r su

rface

wat

er d

ue to

se

ptic

sys

tem

Lo

cate

and

con

stru

ct th

e se

ptic

sys

tem

bas

ed o

n th

e N

T C

ode

of P

ract

ice

for O

nsite

Was

tew

ater

M

anag

emen

t

No

exce

edan

ce o

f w

ater

qua

lity

obje

ctiv

es in

rela

tion

to

nutri

ents

Surfa

ce a

nd w

ater

gr

ound

wat

er

mon

itorin

g fo

r nu

trien

ts a

s pe

r Wat

er

Qua

lity

Mon

itorin

g Pl

an

Inve

stig

ate

caus

e of

leak

an

d up

date

pr

oced

ures

as

nece

ssar

y


96

10 WATER QUALITY MONITORING PLAN

This Water Quality Monitoring Plan (WQMP) outlines the surface and groundwater quality monitoring to be undertaken during:

The 2018/2019 wet season and 2019 dry season representing a continuation of pre-mining baseline monitoring for informing further development of assessment criteria and identifying potential impacts.

Mining operations (planned to start late 2019 dry season) to provide early warning and trigger management actions for preventing impacts to surface waters and/or groundwater aquifers.

Sections 6 and 7 present the results of baseline (pre-mining) surface and groundwater monitoring undertaken since February 2017 for surface water, and June 2017 for groundwater. This WQMP uses the results of this monitoring to design the surface and groundwater monitoring programs. The selection of monitoring sites, sampling frequency, analytical parameters, and assessment criteria is also designed to assist in monitoring and minimising the potential impacts and risks discussed in the earlier Sections of this WMP.

This WQMP will become part of the project’s Mining Management Plan (MMP), as required under the NT Mining Management Act, and be updated regularly throughout operations to reflect on-ground activities as mining progresses. It will also support the project’s Waste Discharge Licence (WDL) issued under the NT Waste Management and Pollution Control Act to allow discharge from MWD1. Once issued, this WQMP will be updated to reflect all WDL monitoring and reporting requirements.

The monitoring program design, sampling methods, data assessment criteria and reporting are in accordance with:

ANZECC (2000a), Australian and New Zealand Guidelines for Fresh and Marine Water Quality, National Water Quality Management Strategy Paper No 4, Australian and New Zealand Environment and Conservation Council (ANZECC) and Agriculture and Resource Management Council of Australia and New Zealand (ARMCANZ), Canberra.

ANZECC (2000b), Australian Guidelines for Water Quality Monitoring and Reporting, National Water Quality Management Strategy Paper No 7, Australian and New Zealand Environment and Conservation Council (ANZECC) and Agriculture and Resource Management Council of Australia and New Zealand (ARMCANZ), Canberra.

AS/NZ Standards 5667:1998 - Water Quality Sampling Parts 1, 4, 6, 10 and 11.

All surface water and groundwater quality monitoring must be undertaken by a qualified professional in accordance with the standards listed above. All hand-held field parameter meters must be calibrated immediately prior to commencing sampling, and all sample collection for laboratory analysis must be into the appropriate laboratory-supplied bottles and handled in accordance with the standards listed above e.g. samples kept cool in esky until delivered to laboratory, and all samples delivered to laboratory within required holding times. All laboratory samples will be analysed by a NATA accredited laboratory.


97

10.1Surface water quality monitoring program

10.1.1 Surface water quality monitoring sites

Proposed surface water monitoring site locations are shown in Figure 10-1 and detailed in Table 10-1. All existing surface water monitoring sites used in baseline monitoring are retained except for BP Historic Pit, as on-going water quality monitoring of this pit will not provide any further information for detecting or assessing impacts from the mine.

Site GUS SW3 is located within the proposed MSD inundation area. After construction of the MSD, this site will remain as representing water quality in the dam.

An extra reference site (GUS SW4) has been added in order to provide on-going background data for comparing to potentially impacted sites. This site receives water from the sub-catchment 2b, which has a similar size and very similar characteristics to the 5a and 5b catchments subject to mine impacts (see Section 3.2.1 for sub-catchment details). Monitoring of this site will commence immediately.

An extra downstream site (GDS SW5) has been added located further downstream of the mine between Cox Peninsula Road and the upper tidal limit of West Arm, Darwin Harbour. The aim of this site is to monitor any impacts from mining in this stretch of waterway further downstream of where water leaves the mining lease at GDS SW2. Monitoring of this site will commence immediately.

The existing sites GDS SW1 and GDS SW2 will continue to be monitored prior to mine construction to extend the baseline dataset for these sites. Then, following construction of the mine, these sites will be used for monitoring impacts immediately downstream in the drainage lines receiving run-off from the mine footprint, and discharge from the sediment basins and MWD1; as outlined in Table 10-1.

Sites that will be added to the monitoring program following construction of mine site infrastructure include sediment basins 1 and 2, and MWD1. Monitoring of these basins and dams aims to ensure that water quality meets the required assessment criteria prior to release. Weekly sampling of the MWD1 and sediment basins during the wet season (November – April), even when not discharging, will also guide implementation of any treatment measures or management actions needed to improve input water quality or contained water quality. If water is stored in MWD1 for a long period without inputs, pumping out for dust suppression or discharge, it may also become stagnant with low DO, algal bloom and high nutrients. Such conditions would be detected through the water quality monitoring program and management options for treating this prior to release would include oxygenation, removal of organic matter, or using the water for dust suppression rather than in discharging it (during dry season only).

Following the commencement of mining and establishment of the open cut pit, water from the pit sump will be sampled in order to monitor the quality of groundwater entering the pit and being pumped to MWD1 for use in dust suppression and ore processing. This will provide early warning of any unusually high levels of contaminants entering the pit or acid mine drainage (which is not expected refer Section 2.7).

Sampling of MWD2 will be undertaken when this dam is receiving TSF decant water. Obtaining better data on TSF decant water quality will assist in determining the potential contaminants to monitor closely in groundwater and surface water monitoring results for detecting any seepage from the TSF.

Monitoring of Observation Hill Dam and the two sites located downstream will continue. The water quality of Observation Hill Dam is required to establish the incoming water quality of water supplied to the mine. Continued monitoring of BPUS SW1 and BPD SW2 aims to detect any downstream impacts from Observation Hill Dam water extraction and data from these sites can also be used as a regional reference for monitoring larger-scale changes to background water quality, enabling distinction of water quality changes caused from mine impacts as opposed to natural seasonal / climatic changes.

Gra

nts

Lith

ium

Pro

ject

W

ater

Man

agem

ent P

lan

98

Tabl

e 10

-1.

Surf

ace

wat

er q

ualit

y m

onito

ring

site

det

ails

.

Catchment

Site

IDSi

te N

ame

New

/ Ex

istin

g Si

teLo

catio

nPu

rpos

eSa

mpl

ing

Freq

uenc

y

GD

S SW

1G

rant

s D

owns

tream

S

urfa

ce W

ater

1Ex

istin

gEp

hem

eral

dra

inag

e lin

e do

wns

tream

of m

ine

foot

prin

t, ea

ster

n si

de in

sub

-cat

chm

ent 5

bM

onito

r im

pact

s im

med

iate

ly d

owns

tream

of e

aste

rn s

ide

of m

ine

foot

prin

t in

clud

ing

MW

D1

disc

harg

e an

d se

dim

ent b

asin

2 d

isch

arge

.

GD

S SW

2G

rant

s D

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tream

S

urfa

ce W

ater

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g

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nstre

am o

f GU

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3 an

d G

DS

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whe

re

ephe

mer

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rain

age

lines

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eith

er s

ide

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ine

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t joi

n an

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w th

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h cu

lver

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er C

ox

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nsul

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edia

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int

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g se

dim

ent b

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isch

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and

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rele

ases

. Al

so, r

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ves

any

impa

cts

dete

cted

at G

DS

SW1

from

MW

D1

and

sedi

men

t bas

in 2

. R

epre

sent

s w

ater

qua

lity

leav

ing

the

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ing

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e.

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S SW

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rant

s U

pstre

am

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face

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er 3

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ting

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mer

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rain

age

line

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of m

ine

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este

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ide

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atch

men

t 5a.

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is w

ill be

com

e th

e M

SD d

urin

g m

inin

g an

d w

ill co

ntin

ue to

be

sam

pled

.

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eren

ce s

ite u

pstre

am o

f min

e fo

otpr

int p

rior t

o M

SD c

onst

ruct

ion.

The

n w

ill be

mon

itore

d as

the

MSD

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S SW

4G

rant

s U

pstre

am

Sur

face

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er 4

New

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mer

al d

rain

age

line

in a

djac

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ub-

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t 2b

not s

ubje

ct to

min

e im

pact

s.

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eren

ce s

ite in

adj

acen

t cat

chm

ent n

ot s

ubje

ct to

min

e im

pact

s w

ith

sim

ilar s

ize

and

char

acte

ristic

s as

impa

cted

cat

chm

ents

.

Darwin Harbour, West Arm

GD

S SW

5G

rant

s D

owns

tream

S

urfa

ce W

ater

5N

ewW

ater

way

dow

nstre

am o

f all

othe

r site

s be

twee

n C

ox P

enin

sula

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d an

d w

here

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wat

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ts D

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in H

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Mon

thly

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Sed

imen

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men

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ch re

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f fro

m

WR

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ll op

erat

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l are

as in

nor

ther

n ha

lf of

m

ine

site

.

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imen

t bas

in 2

New

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men

t bas

in 2

, whi

ch re

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es ru

n-of

f fro

m

sout

hern

hal

f of W

RD

and

are

as s

outh

of p

it.

Mine Footprint

MW

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Min

e W

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Dam

1N

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am re

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ater

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om th

e pi

t.

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itor w

ater

qua

lity

in s

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asin

s/M

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1 to

ens

ure

they

mee

t as

sess

men

t crit

eria

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r to

rele

ase.

For

gui

ding

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wat

er q

ualit

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atm

ent m

easu

res

requ

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r to

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ase

or m

anag

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t act

ions

to

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ove

inpu

t wat

er q

ualit

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r to

any

cont

rolle

d re

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to b

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g w

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on (N

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) re

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disc

harg

eW

eekl

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ram

eter

s w

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disc

harg

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from

ei

ther

MW

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and/

or

sedi

men

t bas

ins.

M

onth

ly la

b pa

ram

eter

s du

ring

wet

se

ason

(Nov

– A

pr)

rega

rdle

ss o

f di

scha

rge

Gra

nts

Lith

ium

Pro

ject

W

ater

Man

agem

ent P

lan

99

MW

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e W

ater

Dam

2N

ewTh

is d

am re

ceiv

es e

xces

s TS

F de

cant

wat

er.

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itor q

ualit

y of

TSF

dec

ant t

o in

form

det

ectio

n of

any

TSF

see

page

in

grou

ndw

ater

or s

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ce w

ater

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g re

sults

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kly

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ater

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para

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n da

m

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ound

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flow

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r pum

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itor q

ualit

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gro

undw

ater

inflo

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and

prov

ide

early

war

ning

of a

ny

unus

ually

hig

h le

vels

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onta

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atio

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sk.

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pa

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thly

lab

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year

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bser

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n H

ill D

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rface

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er s

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onito

r inc

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g qu

ality

of w

ater

bei

ng u

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on s

ite.

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S SW

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tream

S

urfa

ce W

ater

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istin

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owns

tream

of O

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ups

tream

BP3

3 pi

t

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S SW

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Dow

nstre

am

Sur

face

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er 2

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ting

Dow

nstre

am o

f OH

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SW1,

and

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from

OH

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ater

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to b

ackg

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ater

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to e

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ctio

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wat

er q

ualit

y ch

ange

s ca

used

from

min

e im

pact

s as

opp

osed

to n

atur

al s

easo

nal /

cl

imat

ic c

hang

es.

Mon

thly

dur

ing

wet

se

ason

(Nov

– A

pr)

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GWB10 GWB08

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GWB15GWB16

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GWB01GWB03

BPUS SW2

BPUS SW1

GDS SW2

OHD

GDS SW5

GUS SW4GUS SW3 GDS SW1

Sed 1

Sed 2MWD 1

Pit

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690000 692000 694000 69600085

9400

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Path: Z:\01 EcOz_Documents\04 EcOz Vantage GIS\EZ18086 - Grants Project - EIS\01 Project Files\Water Mgmt Plan\Figure 10-1 Future surface and groundwater monitoring sites.mxd

0 0.5 10.25

KilometresOMAP INFORMATIONProjection: GDA 1994 MGA Zone 52Date Saved: 3/12/2019Client: Core ExplorationAuthor: F Watt (reviewed K Welch)DATA SOURCEProject components: ClientImagery: ESRI basemap (Digital Globe)

Figure 10-1. Map of future surface and groundwater monitoring sites


Mine site footprint


!( Operations water monitoring site

!( Surface water monitoring site

!( Groundwater monitoring bore

!(Groundwater monitoring bore(to be discontinued)



101

10.1.2 Sampling frequency

Sampling frequency will be undertaken as per that outlined in Table 10-1.

10.1.3 Parameters measured

The field and laboratory parameters measured at all sites during all sampling rounds will always be the same (Table 10-2). These are the same parameters measured for baseline surface water monitoring completed so far. The parameters aim to allow the detection of all identified surface water quality-related impacts discussed in the preceding Sections of this WMP, such as causing the elevation of:

Dissolved metals and nutrients in waterways receiving discharge from MWD1, in particular, EC, arsenic, lithium, iron and phosphorus, which are potentially elevated in groundwater dewatered from the pit and transferred to MWD1.

Turbidity in waterways receiving discharge from MWD1, where turbidity may become elevated in water pumped to MWD1 when groundwater and direct rainwater come into contact with fine sediments within the pit.

Turbidity in waterways receiving discharge from sediment basins 1 and 2, where turbidity may become elevated above the allowable discharge criteria in run-off entering the basins indicating more effective flocculent treatment may be required within the basins or improvements to mine site erosion and sediment controls.

Hydrocarbons in waterways receiving run-off from the mine and discharge from sediment basins 1 and 2 and MWD1 due to spills or leaks of fuels, oils, lubricants etc from operational areas of the mine.

Dissolved metals and nutrients in waterways receiving run-off from the WRD or seepage from the TSF.

Whilst at the site, field conditions must also be noted as listed in Table 10-2, and photos taken.

Table 10-2. Surface water and groundwater quality field and laboratory parameters and field notes.

Field Parameters Laboratory Parameters pH (pH units) Electrical Conductivity (µS/cm) Total Dissolved Solids (mg/L) Turbidity (NTU) Temperature (ºC) Oxidation Reduction Potential (mV) Dissolved Oxygen (%) Standing water level (mBGL) for groundwater

Nutrients (ammonia, NOx (nitrate+nitrite), total nitrogen, total phosphorus, reactive phosphorus)

Dissolved and total metals (Al, As, Cd, Cr, Cu, Fe, Li, Hg, Pb, Ni, Zn) Major anions (sulfate, chloride, alkalinity), Major cations (calcium,

magnesium, sodium, potassium)

Hydrocarbons (TPH/TRH, BTEXN) Hydrogen sulphide (groundwater only)

Field Notes Sampler Name/s Date and Time Weather conditions Flow conditions, spillway flowing etc, note pumping rate for groundwater Any visible pollutants, algae, water plants, fish, other biota Water clarity Any odour Take photos


102

10.1.4 Assessment criteria

The water quality objectives that apply to waterways downstream of the mine footprint are those listed in the Water Quality Objectives for the Darwin Harbour Region Background Document (NRETAS 2010). For parameters such as metals and other toxicants, where no objective is specified, the Australian and New Zealand Guidelines for Fresh and Marine Water Quality (ANZECC 2000a) apply.

These objectives aim to protect the beneficial uses identified for waterways in the Darwin Harbour region as outlined in Section 3.2.3. The specific objectives relating to the beneficial use of environment (aquatic ecosystems) are applied here given these are the most conservative, and adherence to these would in most cases also protect the other beneficial uses of cultural (aesthetic, recreational and cultural), agriculture and rural stock and domestic water supply.

The NRETAS (2010) water quality objectives developed specifically for ‘freshwater rivers and streams’ are the most appropriate for the types of waterways receiving water from the project area. These objectives include values for physical parameters (pH, EC, turbidity, and DO) and nutrients (NOx, TN, TP, and reactive phosphorus). For toxicants (dissolved metals and hydrocarbons) the ANZECC (2000a) ‘trigger values for freshwater; 95% species protection’ are the most appropriate.

Baseline surface water quality results found aluminium and NOx consistently exceeded of the water quality objectives, and pH was often above and below the objective range. The ANZECC (2000a) Guidelines recommend under these circumstances to calculate site-specific trigger values based on the 80th percentile of baseline (or reference site) data. It is not however possible at this stage to calculate site-specific trigger values given the ANZECC (2000a) methodology requires at least two years’ worth of monthly data. It is recommended that assessment be based on comparing the baseline range of concentrations with those measured during and after mining. That is, NOx ranges between <0.01 and 0.06 mg/L, aluminium between <0.01 and 0.08 mg/L and pH between 5.06 and 8.14 (not including the alkaline spikes measured in the OHD and BP Historic Pit sites). If concentrations were to become consistently outside these ranges, then impacts on water quality can be implicated.

In regards to the dissolved metals lithium and iron, which don’t have ANZECC (2000a) trigger values, the natural background range is used as the assessment criteria i.e. 0.002 mg/L for lithium and 0.1 mg/L for iron.

As outlined in Section 2.5.2, turbidity in the sediment basins will be reduced as much as possible, but final discharge from the sediment basins is not always expected to achieve the very low turbidity levels in the receiving drainage lines. As such, the discharge standard recommended for sediment basins in IECA (2008) is adopted:

90th percentile NTU reading not exceeding 100, and 50th percentile NTU reading not exceeding 60

Once discharged, the turbidity of water from the sediment basins is expected to reduce rapidly with dilution in the receiving drainage lines, combined with the filtering effect of the vegetation growing within the drainage lines. The assessment criteria outlined in Table 10-3, applying to all routine surface water monitoring sites downstream of the mine will still apply for turbidity. That is, the turbidity of the sites downstream of the sediment basins (GWS SW1 and GDS SW2) are expected to remain below 20 NTU.

For hydrocarbons, which were undetectable in all baseline surface water and groundwater results, the assessment criteria are set at remaining below laboratory detection limits.

The water quality assessment criteria for the project applying to both surface and groundwater is presented in Table 10-3.

It is highlighted in regards to all future monitoring, that laboratory analytical detection limits must be low enough to allow assessment using the objectives/trigger values. This was the case for all parameters during baseline surface and groundwater quality monitoring except for NOx and reactive phosphorus. The analytical limit of reporting (LOR) for both NOx and reactive phosphorus was <0.01 mg/L, whereas the objectives are 0.008 mg/L and 0.005 mg/L respectively.


103

Table 10-3. Water quality objectives / trigger values (assessment criteria) for both surface and groundwater quality.

*Note the turbidity and DO values don’t apply to groundwater. Also, baseline groundwater concentrations of EC, arsenic, iron, lithium and reactive P are often already above these values. Groundwater results will still be compared with these

guidelines for assessment purposes but the background range will also be taken into account for detecting any groundwater contamination. Standing water levels only apply to groundwater monitoring.

Parameter Objective/Triger Value

pH Remain within 5.06 and 8.14EC* 200 µS/cm

Turbidity*20 NTU all sites except Sed1, Sed2, and MWD1,

which are 100 NTU for 90th percentile, and 60 NTU for 50th percentile

DO* Remain within 50-100 %saturationNOx 0.06 mg/LTN 0.23 mg/LTP 0.01 mg/L

Reactive P* 0.005 mg/LAluminium 0.08 mg/LArsenic* 0.013 mg/LCadmium 0.0002 mg/LChromium 0.004 mg/L

Copper 0.0014 mg/LIron* 0.1 mg/LLead 0.0034 mg/L

Lithium* 0.002 mg/LMercury 0.0006 mg/LNickel 0.011 mg/LZinc 0.008 mg/L

Hydrocarbons Remain below detection limitsStanding

Water Levels*Remain within background range as per Section 3.3.1 and do not indicate groundwater mounding.

10.2Groundwater quality monitoring program

10.2.1 Groundwater monitoring bores

Proposed groundwater monitoring site locations are shown in Figure 10-1 and detailed in Table 10-4. All existing monitoring bores used in baseline monitoring are retained except for GWB01, which is located within the mine pit and will be destroyed, and GWB03, which will be decommissioned prior to establishment of WRD over the top. GWB01 and GWB03 will continue to be sampled until infrastructure is in place, in order to extend the existing baseline dataset for these sites.

Seven additional bores are proposed (Table 10-4). GWB17 will be a shallow bore screened in the shallow laterite aquifer to replace GWB06, which is contaminated with cement and cannot be used for water quality monitoring. The existing paired deep bore at this site, GWB07 will continue to be sampled prior to mine construction to extend the baseline dataset. Then, following mine construction, will be used along with GWB17 as a cross gradient site on the south-eastern side of the mine footprint.


104

Existing paired bores GWB08 (screened in BCF aquifer) and GWB10 (screened in surface laterite aquifer) located down-gradient of the mine on the northern side, will continue to be sampled prior to mine construction to extend the baseline dataset for this site. Then, following construction of the mine, this site will be used for monitoring impacts immediately downstream of the mine footprint.

New paired bores GWB11 (screened in BCF aquifer) and GWB12 (screened in surface laterite aquifer) to be installed up-gradient of the WRD/TSF, will used as reference bores for monitoring the un-impacted water quality of groundwater flowing underneath the WRD and then underneath the mine site. Unseasonal increases in standing water levels (SWLs) in these bores during the dry season may indicate groundwater mounding under the WRD. If this was to occur, then these bore would no longer be ‘up-gradient’ as groundwater would start flowing from the WRD/TSF towards these bores.

New paired bores GWB13 (screened in BCF aquifer) and GWB14 (screened in surface laterite aquifer) to be installed down-gradient of the WRD/TSF, will used to detect any impacts on groundwater from TSF seepage, and could also indicate groundwater mounding if SWLs increased during the Dry-season.

New paired bores GWB15 (screened in BCF aquifer) and GWB16 (screened in surface laterite aquifer) to be installed down-gradient of the mine site, will be used to detect any impacts on groundwater from TSF seepage and any other potential contamination sources such as hydrocarbon leakage.

Final bore locations and depths will be decided by a qualified hydrogeologist, who will also manage and supervise the bore drilling program.

Table 10-4. Groundwater quality monitoring bore details.

Bore IDNew/

Existing Site

Screened Aquifer Location and Purpose

GWB01 Existing BCF Baseline data indicating quality of groundwater flowing into mine pit. Note this bore will be destroyed once mining of pit begins.

GWB03 Existing BCF Baseline data beneath WRD. Note this bore will no longer exist following establishment of WRD.

GWB07 Existing BCF

GWB17 Replacement for GWB06 Shallow

Paired bores; cross gradient of mine footprint (SE side).

GWB08 Existing BCF

GWB10 Existing ShallowPaired bores; both down-gradient of mine footprint (N side) for detecting any groundwater contamination from entire mine site operations.

GWB11 New BCF

GWB12 New Shallow

Paired bores; both reference bores up-gradient of WRD/TSF for determining original groundwater quality flowing underneath WRD; may also indicate groundwater mounding if unseasonal rise in SWLs – hence no longer a reference site at that time as would become down-gradient of WRD/TSF.

GWB13 New BCF

GWB14 New ShallowPaired bores; both down-gradient of WRD/TSF for monitoring seepage from TSF and groundwater mounding.

GWB15 New BCF

GWB16 New ShallowPaired bores; both down-gradient of whole mine site for detecting any groundwater contamination from entire mine site operations

10.2.2 Sampling frequency

All bores will be sampled quarterly. This will commence immediately for the existing bores and will commence for the new bores once they are installed. This is expected to occur early 2019. Sampling will be undertaken throughout operations and post-closure until the rehabilitation criteria specified in the Mine Closure Plan are achieved.


105

10.2.3 Parameters measured

Table 10-2 lists the parameters to be measured. Given hydrogen sulphide was detected (through odour) during baseline groundwater sampling, this will be added to the laboratory parameters analysed in all future monitoring.

10.2.4 Assessment criteria

Table 10-3. lists the assessment criteria for comparing with groundwater monitoring results. Note the turbidity and DO values do not apply to groundwater. A high turbidity reading in groundwater would indicate an issue with sampling methods or bore construction/development rather than an impact of mining on water quality. DO is low in groundwater because it has been out of contact with the atmosphere for a period of time and not a result of mining impacts on water quality. DO would be expected to increase rapidly on exposure to the atmosphere and pumping to MWD1.

In regards to EC, arsenic, iron, lithium and reactive phosphorus, these parameters are already often above the assessment criteria (which is based on surface water quality objectives). Groundwater results will still be compared with these values for assessment purposes but the background range will also be taken into account for detecting any groundwater contamination from the TSF or other sources of contamination from mining operations.

10.3 Recording and reporting

All results from surface water and groundwater quality monitoring will be entered into the database (Excel spreadsheet) already established and populated with the baseline monitoring results.

Reporting requirements will align with those required for annual MMP reporting and the reporting required for the WDL.


106

11 INFORMATION/KNOWLEDGE GAPS

11.1Identification of information/knowledge gaps

Identified information and knowledge gaps are:

Discharge volumes from MWD1. Predicted volumes have been modelled based on the best available data (see Water Balance Appendix A). However, there is a level of uncertainly that could mean that discharge is greater or less than the predicted volumes. The amount of discharge will depend on the:

o 1. Rate of groundwater inflows into the pit, which should be relatively constant and predictable, only changing progressively as mining progresses to deeper levels, and

o 2. Amount of direct rainfall into the pit and MWD1, which will change from year to year.

It will not be possible to determine exact volumes until mining commences.

MWD1 water quality. The predicted water quality contained within MWD1 and potentially discharged to the environment has been predicted using baseline groundwater data collected since the instalment of monitoring bores on site in July 2017. Final water quality discharged to the environment will depend on the level of dilution from direct rainfall into the pit and into MWD1. It may also depend on the naturally occurring oxidation reactions and precipitation of chemical constituents in the water on exposure to the surface, pumping to, and retention in MWD1.

Water extraction from surface water storages. Predicted volumes have been modelled based on the best available data (see Water Balance Appendix A). However, there is a level of uncertainly that could mean that extraction is greater or less than the predicted volumes. It will not be possible to determine exact volumes until mining commences.

Turbidity levels in sediment basins. Baseline surface water turbidity levels are very low in the drainage lines receiving discharge from the sediment basins. Levels remain below 12 NTU (well below the water quality objective of 20 NTU) even during heavy rainfall events. The assessment criteria for allowing release of water from the basins is 100 NTU / 60 NTU (90th %ile/50th %ile) with levels decreasing downstream with dilution from catchment run-off to below the water quality objective of 20 NTU. Sediment basins have been designed and sized in accordance with IECA (2008) Best Practice Erosion and Sediment Control, by a Certified Practitioner in Erosion and Sediment Control, however there is still uncertainty in the final levels of turbidity that will be contained within the basins. It will not be possible to know this until the basins are receiving run-off from the site.

AMD risk. The risk of AMD materials in waste rock and tailings has been tested and assessed as low. There is a small risk that during mining AMD materials are encountered and groundwater entering the pit and seepage from the WRD/TSF becomes highly acidic and metalliferous.

Shallow aquifer properties. Unfortunately, only two groundwater bores were installed in the shallow laterite aquifer, and both of these are unsuitable for gaining a proper understanding of the water quality properties of this aquifer. GWB06 was contaminated with cement during drilling and cannot be used for water quality monitoring; only groundwater level measurements. Whereas, the screened interval for GWB10 starts at 0.5 m depth, which does not comply with the Minimum Construction Requirements for Water Bores in Australia, 2012, 3rd Edition, National Uniform Drillers Licensing Committee (Australia). Screened intervals must start at a minimum of 1.0 m depth from the surface to prevent infiltration of surface water into the bore.

A preliminary water quality interpretation of this aquifer is outlined in Section 7 based on the data from GWB10 but additional water quality data collected from bore installed as per the standards is required.


107

11.2Filling information/knowledge gaps

The following will be undertaken to address the above knowledge gaps:

Discharge volumes from MWD1. A flow gauge will be fitted to the outlet of MWD1 to record discharge volumes. Also, from the outset of mining, the volumes of groundwater inflows into the pit will be recorded and the Water Balance updated accordingly. Similarly, a rainfall gauge will be installed onsite for improving water balance calculations.

MWD1 water quality. The water quality of groundwater inflows into the pit will be monitored weekly for field parameters and monthly for laboratory parameters. This monitoring will occur immediately as soon as dewatering of the pit becomes necessary. A rainfall gauge installed onsite will assist in calculating dilution factors. Monitoring of water quality in MWD1 will commence as soon as this dam contains water pumped from the pit. The results of monitoring will inform the level of treatment or management actions required, whether this be to reduce turbidity through better pit sump pumping practices and/or flocculant application, or to reduce contaminant levels through treatment.

If water is stored in MWD1 for a long period without inputs, pumping out for dust suppression or discharge it may also become stagnant with low DO, algal bloom and high nutrients. Such conditions would be detected through the water quality monitoring program and management options for treating this prior to release would include oxygenation, removal of organic matter, or using the water for dust suppression rather than in discharging it (during dry season only).

Water extraction from surface water storages. Water volumes extracted from surface water storages will be recorded and water balance calculations updated accordingly. Similarly, data from the rain gauge installed on site will be used to update the water balance.

Turbidity levels in sediment basins. Turbidity levels in sediment basins, and in surface water sites downstream, will be monitored weekly whilst discharging. If levels are found to be consistently exceeding the assessment criteria, the ESCP will be reviewed and improved accordingly.

AMD risk. On site geologists will be assessing the pit walls daily for any AMD materials, and the pH of water entering the pit will be tested at least weekly. The water quality of TSF decant water will also be tested regularly from MWD2. Quarterly groundwater monitoring will detect any acidic seepage from the TSF.

Shallow aquifer properties. Bores GWB06 and GWB10 will be decommissioned and adjacent bores installed to represent the shallow aquifer in April 2019. Additional bores in this aquifer will also be installed on the south-western, north-western and northern sides of the mine footprint. All, bore installation will be in accordance with the Minimum Construction Requirements for Water Bores in Australia, 2012. Subsequent sampling of these five bores will provide water quality data representative of this aquifer.


108

12 FUTURE WMP UPDATES

The next WMP update is due in May 2019. This update will include:

Details of the newly installed groundwater monitoring bores i.e. those listed in Table 10-4 and shown in Figure 10-1.

Details of the additional surface water quality monitoring sites i.e. those listed in Table 10-1 and shown in Figure 10-1

All baseline groundwater and surface water monitoring results collected since and further baseline sampling to incorporate the new water quality and standing water (logger) results.

A timeline for filling information/knowledge gaps and the implementation of management and mitigation measures.


109

13 REFERENCES

ANZECC (2000a), Australian and New Zealand Guidelines for Fresh and Marine Water Quality, National Water Quality Management Strategy Paper No 4, Australian and New Zealand Environment and Conservation Council (ANZECC) and Agriculture and Resource Management Council of Australia and New Zealand (ARMCANZ), Canberra.

ANZECC (2000b), Australian Guidelines for Water Quality Monitoring and Reporting, National Water Quality Management Strategy Paper No 7, Australian and New Zealand Environment and Conservation Council (ANZECC) and Agriculture and Resource Management Council of Australia and New Zealand (ARMCANZ), Canberra.

Baken, S. Salaets, P. Desmet, N. Seuntjens, P. Vanlierde E. and Smolders, E. (2015), Oxidation of Iron Causes Removal of Phosphorus and Arsenic from Streamwater in Groundwater-Fed Lowland Catchments, Environmental Science and Technology, 49 (5), pp 2886–2894.

CloudGMS (2018). Development of a Groundwater Model for the Grants Lithium Project, Final Version 1.0, Report prepared for Core Exploration Limited by CloudGMS Pty Ltd, September 2018, South Australia.

CloudGMS (2019). Grants Lithium Project, Groundwater Model, Addendum Report, Final Version 1.0, Report prepared for Core Exploration Limited by CloudGMS Pty Ltd, February 2019, South Australia.

DENR (2018), Northern Territory Water Allocation Planning Framework, Department of Environment and Natural Resources (DENR), Northern Territory Government, Darwin. https://denr.nt.gov.au/__data/assets/pdf_file/0011/476669/NT-Water-Allocation-Planning-Framework.pdf

Department of Health (2014), Code of practice for small on-site sewage and sullage treatment systems and the disposal or reuse of sewage effluent, Department of Health, Northern Territory Government, Darwin.

DIPE (2004). Acid Sulfate Risk Categories of the Greater Darwin Area, Edition 1 Map, Conservation and Natural Resources Group, Department of Infrastructure, Planning and Environment (DIPE), October 2004, Northern Territory Government, Palmerston.

DLRM (2015). Landunits of the Greater Darwin Area, May 2015, Map produced by the Department of Land Resource Management (DLRM), Northern Territory Government, Palmerston.

DLRM (2016). Berry Springs Water Allocation Plan 2016-2026, Report: 18/2016D, Department of Land Resource Management (DLRM), Northern Territory Government, Palmerston.

DPIR (2017). Mining Management Plan Structure Guide for Mining Operations, January 2017, Department of Primary Industry and Resources (DPIR), Northern Territory Government, Darwin.

EcOz (2018a). Soil and Waste Characterisation, Grants Lithium Project, Report prepared for Core Exploration Limited by EcOz Environmental Consultants Pty Ltd, October 2018, Darwin.

EcOz (2018b). Stylidium ensatum survey report, Grants Lithium Project, Report prepared for Core Exploration Limited by EcOz Environmental Consultants Pty Ltd, September 2018, Darwin.

EnviroConsult (2018a). Project 1: Existing hydrological condition and hydrology model calibration, Report prepared for Core Exploration Limited by EnviroConsult Pty Ltd, August 2018, Darwin.

EnviroConsult (2018b). Project 2: Mining Lease 31726 and Observation Hill Dam Water Balance, Report prepared for Core Exploration Limited by EnviroConsult Pty Ltd, August 2018, Darwin.

EnviroConsult (2018c). Project 3: Mining Lease 31726 Flood Inundation Study, Report prepared for Core Exploration Limited by EnviroConsult Pty Ltd, August 2018, Darwin.

EnviroConsult (2019). Supplementary Report Appendix H Surface water modelling, Report prepared for Core Exploration Limited by EnviroConsult Pty Ltd, March 2019, Darwin.

https://denr.nt.gov.au/__data/assets/pdf_file/0011/476669/NT-Water-Allocation-Planning-Framework.pdf


110

Frater, K. M. (2005). Tin-tantalum pegmatite mineralisation of the Northern Territory, Northern Territory Geological Survey, Report 16, Northern Territory Government, Darwin.

GHD (2017a). Finniss Lithium Project, Aquatic Ecology Baseline Monitoring, Report prepared for Core Exploration Limited by GHD Pty Ltd, October 2017.

GHD (2017b). Finniss Lithium Project, Groundwater Investigation Report, Report prepared for Core Exploration Limited by GHD Pty Ltd, August 2017.

Hempel, C. 2003. The Application of Landsat imagery to land cover mapping in the greater Darwin region. Technical report number 74. Department of Infrastructure, Planning and Environment, Darwin.

IECA (2008), Best Practice Erosion and Sediment Control, International Erosion Control Association (IECA), Picton, NSW.

Karp, D. (2008). Groundwater Arsenic Concentrations in the Darwin Region, Technical Report No.19/2008D, Land and Water Division, Department of Natural Resources, Environment, the Arts and Sports, Northern Territory Government, Palmerston.

MCA (2014). Water Accounting Framework for the Minerals Industry, User Guide, Version 1.3, January 2014, Minerals Council of Australia.

NRETAS (2010). Water Quality Objectives for the Darwin Harbour Region - Background Document, February 2010, Department of Natural Resources, Environment, The Arts and Sport (NRETAS), Northern Territory Government, Palmerston.

NRETAS (2009). Darwin Harbour, Sites of Conservation Significance, Factsheet, Department of Natural Resources, Environment, The Arts and Sport (NRETAS), Northern Territory Government, Palmerston.

NHMRC (2011). Australian Drinking Water Guidelines Paper 6, National Water Quality Management Strategy. Version 3.5, updated August 2018, National Health and Medical Research Council (NHMRC), National Resource Management Ministerial Council (NRMMC), Commonwealth of Australia, Canberra.

Richardson, E. Irvine, E. Froend, R. Book, P. Barber, S. and Bonneville, B. (2011). Australian groundwater dependent ecosystems toolbox part 1: assessment framework, National Water Commission, Canberra.


APPENDIX A WATER BALANCE

Core Exploration Ltd, Cox Peninsula

Grants Lithium Project Preliminary Mine Site Water Balance Supplementary Report

Report 01000405S

Core Exploration Limited

Grants Lithium Project

Preliminary Mine Site Water Balance Supplementary Report

Report 01000405S

RELIANCE, USES, and LIMITATIONS

This report is copyright and is to be used only for its intended purpose by the intended recipient and is not to be copied or used in any other way. The report may be relied upon for its intended purpose within the limits of the following disclaimer.

This report and analysis are based on the information available to EnviroConsult Australia Pty Ltd at the time of preparation. EnviroConsult Australia Pty Ltd accepts responsibility for the report to the extent that the information was sufficient and accurate at the time of preparation. EnviroConsult Australia Pty does not take responsibility for errors and omissions due to incorrect information or information not available at the time of preparation of the report and any analysis undertaken

Table of Contents

1 Introduction ....................................................................................................................................... 1

2 Objectives and Scope ...................................................................................................................... 1

3 Methodology ..................................................................................................................................... 1

3.1 Water balance model development ......................................................................................... 1

3.2 Deliverables in accordance with the MCA WAF ...................................................................... 2

4 Climatic Data .................................................................................................................................... 5

5 Water Balance Model Setup ............................................................................................................ 6

5.1 Inputs ....................................................................................................................................... 6

5.1.1 Groundwater inflow and pit rainfall ...................................................................................... 6

5.1.2 Off-site Surface Water Storages .......................................................................................... 7

5.1.3 Storage aggregation ............................................................................................................ 7

5.2 Outputs .................................................................................................................................... 8

5.2.1 Entrained water in product and tails .................................................................................... 9

5.2.2 Evaporation .......................................................................................................................... 9

5.2.3 Seepage .............................................................................................................................. 9

5.2.4 Discharge to environment .................................................................................................... 9

5.3 Diversions ................................................................................................................................ 9

5.3.1 Mine site runoff .................................................................................................................... 9

5.4 Operational flows ................................................................................................................... 10

6 MCA WAF Deliverables.................................................................................................................. 11

6.1 Successive average rainfall years scenario .......................................................................... 11

6.1.1 Input-Output Statement ..................................................................................................... 11

6.1.2 Accuracy Statement .......................................................................................................... 12

6.1.3 Statement of Operational Efficiencies ............................................................................... 13

6.2 Successive wet years scenario ............................................................................................. 15




6.3 Successive dry years scenario .............................................................................................. 19




6.4 Successive average rainfall years scenario with no dust suppression in January and February ............................................................................................................................................. 22




6.5 Contextual Statement ............................................................................................................ 26

6.5.1 System boundary description ............................................................................................ 26

6.5.2 Water Resources ............................................................................................................... 26

6.5.3 Water Infrastructure ........................................................................................................... 26

6.5.4 Water Resource Management Instruments ....................................................................... 27

6.5.5 Water Management Bodies ............................................................................................... 27

6.5.6 Climatic Conditions ............................................................................................................ 27

6.5.7 Inputs and Outputs ............................................................................................................ 27

6.5.8 Allocations and Restrictions .............................................................................................. 28

6.5.9 Trading Activity .................................................................................................................. 28

Appendix A. Water balance modelling results for successive average rain fall years scenario ........... 29

Appendix B. Water balance modelling results for successive wet years scenario................................ 33

Appendix C. Water balance modelling results for successive dry years scenario ................................ 37

Appendix D. Water balance modelling results for successive average years scenario with no dust suppression in Jan and Feb .................................................................................................................. 41

List of Figures

Figure 1. Location of Mine Lease Area. .................................................................................................. 3

Figure 2. Site flow chart ........................................................................................................................... 4

Figure 3. linear feature of the pit ground water inflows. .......................................................................... 6

Figure 4. Operational flow chart for successive average rainfall years scenario. ................................. 14

Figure 5. Operational flow chart for successive wet years scenario. .................................................... 18

Figure 6. Operational flow chart for successive dry years scenario. ..................................................... 21

Figure 7. Operational flow chart for successive average years scenario with no dust suppression in January and February ........................................................................................................................... 25

List of Tables

Table 1. SILO climatic data used for different simulation scenarios. ...................................................... 5

Table 2. 1st to 29th month Groundwater inflow data, courtesy of CloudGMS Pty Ltd and estimated 30th to 35th month inflows. ............................................................................................................................... 7

Table 3. Mine site stores and grouped stores. ........................................................................................ 8

Table 4. Dust suppression at each mining stage. ................................................................................... 9

Table 5. Input-Output statement for successive average rainfall years scenario. ................................ 11

Table 6. Volumes (ML) of water in storages for successive average rainfall years scenario. .............. 12

Table 7. Accuracy statement for successive average rainfall years scenario. ...................................... 12

Table 8. Statement of Operational Efficiencies for successive average rainfall years scenario. .......... 13

Table 9. Input-Output statement for successive wet years scenario..................................................... 15

Table 10. Volumes (ML) of water in storages for successive wet years scenario. ............................... 16

Table 11. Accuracy statement for successive wet years scenario. ....................................................... 16

Table 12. Statement of Operational Efficiencies for successive wet years scenario. ........................... 17

Table 13. Input-Output statement for successive dry years scenario ................................................... 19

Table 14. Volumes (ML) of water in storages for successive dry years scenario. ................................ 20

Table 15. Accuracy statement for successive dry years scenario. ....................................................... 20

Table 16. Statement of Operational Efficiencies for successive dry years scenario............................. 20

Table 17. Input-Output statement for successive average years scenario with no dust suppression in January and February. .......................................................................................................................... 22

Table 18. Volumes (ML) of water in storages for successive average years scenario with no dust suppression in January and February. .................................................................................................. 23

Table 19. Accuracy statement for successive average years scenario with no dust suppression in January and February. .......................................................................................................................... 23

Table 20. Statement of Operational Efficiencies for successive average years scenario with no dust suppression in January and February. .................................................................................................. 24

Table 21. Percentage for water resources of total water sourcing activities ......................................... 26

Table 22. inputs and outputs for the operational facility from 1st July 2019 to 31 May 2022 ................ 27

Grants Lithium Project - Preliminary Mine Site Water Balance Supplementary Report Page 1 of 44

1 Introduction

This supplementary water balance report addresses the findings of the independent peer review of the Water Management Plan (completed by Out Task Environmental) and updates the water balance schematics based on revised mine layout design and mining schedule.

The following aspects were updated:

■ The input rainfall and evaporation data are updated using SILO climatic data set.■ The ground water inflow data was updated to meet the updated pit design.■ Two additional climatic conditions (successive dry year and successive wet years) are

assessed.■ The mine site flow chart and input parameters were adjusted to comply with the latest mine

layout design and revised operation schedule.■ The water balance schedule was extended to 35 months to cover the updated life of mine.

As the majority of results presented in the previous water balance report were updated and a considerable number of results added, this supplementary water balance report should be regarded as a replacement of the previous report which is no longer valid.

2 Objectives and Scope

EnviroConsult Australia Pty Ltd was engaged by EcOz Environmental Consulting on behalf of Core Exploration Limited to conduct a preliminary mine site water balance study for the proposed Grants Lithium project. The Mine Lease Area is located near Berry Springs, approximately 25 km southwest of Darwin City, Northern Territory (Figure 1).

The objectives and scope of work are:

■ Development of a preliminary monthly water balance model providing estimates of expectedwater volumes on site and from off-site sources to support site water management;

■ Produce deliverables complying with the Minerals Council of Australia Water AccountingFramework (MCA WAF).

3 Methodology

3.1 Water balance model development

The monthly water balance model was developed using Microsoft Excel for a 35-month operational life of the mine. Ore processing will not be conducted in the first 5 months. The model was simulated for 3 climatic conditions including successive average rainfall years, successive dry years and successive wet years

Prior to developing the water balance model, the schematic of the water balance system was established based on available drawings and design information. The schematic is illustrated by the flow chart in Figure 2.

In the Microsoft Excel spreadsheet, inputs, outputs and flow between components were entered in columns and relationships described by built-in equations. Storages were modelled in separate tables for inputs, outputs and changing inventories.

The detailed water balance modelling results are in the Appendices.


3.2 Deliverables in accordance with the MCA WAF

The Terms of Reference for the Preparation of an Environmental Impact Statement1 for this project indicates that the water balance should be based on the MCA WAF. Therefore, the following deliverables were prepared based on the MCA WAF guidelines and the Microsoft Excel water balance model:

■ Input-Output Statement which lists flows for all input and output categories for the reporting period, along with the change in storage;

■ Accuracy Statement which lists the percentage of flows that were measured, simulated and estimated;

■ Statement of Operational Efficiencies which lists the total flows into the tasks, volume of reused water, reuse efficiency, the volume of recycled water and recycling efficiency.

■ Contextual Statement providing background on the water resources of the facility as well as any conditions that have an impact on the management of those resources

1 NTEPA 2018. Terms of Reference for the Preparation of an Environmental Impact Statement, Grants Lithium Project, Core Exploration Limited.


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4 Climatic Data

Climatic data used in the water balance model were extracted from the SILO data base. SILO products provide national coverage with interpolated infills for missing data. Monthly data for a calendar-year from the SILO record from 1971 to 2018 at 12°39'S 130°48'E were used. This data set is the same as the data used in the updated surface water study2 and the groundwater study3.

The 10th percentile, 50th percentile and 90th percentile monthly rainfall depths from January to December were extracted from the SILO dataset to simulate successive dry years, successive average rainfall years and successive wet years conditions respectively. With respect to evaporation, the 90th percentile, 50th percentile and 10th percentile monthly pan evaporation from the SILO record were used for all successive dry, average and wet years climatic conditions respectively. The climatic data used for different simulation scenarios are in Table 1.

Table 1. SILO climatic data used for different simulation scenarios.

Month

Successive dry years Successive average years Successive wet years

10th %ile rainfall (mm)

90th %ile evaporation (mm)





Jan 221.7 207.5 384.6 173.7 650.3 148.1

Feb 179.2 175.8 293.3 146.8 531.2 127.8

Mar 134.1 192.5 289.1 169.0 484.5 140.7

Apr 14.9 205.9 64.6 183.4 171.9 157.2

May 0.0 214.2 2.5 195.8 33.7 177.6

Jun 0.0 207.1 0.0 189.2 2.1 170.8

Jul 0.0 216.4 0.0 201.4 0.6 184.0

Aug 0.0 240.4 0.1 217.9 2.2 202.9

Sep 0.0 251.4 7.2 227.9 55.8 211.0

Oct 7.9 268.7 51.8 241.3 121.5 215.8

Nov 74.4 234.0 138.8 211.0 199.3 190.1

Dec 112.2 220.9 227.6 195.6 491.7 169.7

2 Enviroconsult 2019. Supplementary Report Appendix H Surface water modelling, Enviroconsult Australia March 2019. 3 CLOUDGMS 2018. Groundwater Model for the Grants Lithium Project Final Version 1.0.


5 Water Balance Model Setup

The water balance model was developed in a Microsoft Excel spreadsheet based on site flow chart in Figure 2. As the modelling results would be used to generate deliverables in accordance with the MCA WAF guidelines, the water balance model was established as the combination of an Inputs-Outputs model which describes the flows between the environment and the boundary of the operational facility (i.e. Inputs, outputs and diversions) and an operational model which describes the flows internal to the operational facility (i.e. the flows between the stores, tasks and treatment plants).

As per the guidelines, a water quality category is assigned to each input, output and diversion. The water quality categories are described in the guidelines as follows:

■ Category 1: Water is of a high quality and may require no or minimal inexpensive treatment (forexample disinfection and pond settlement of solids) to raise the quality to appropriate drinkingwater standards;

■ Category 2: Water is of a medium quality with individual constituents encompassing a widerange of values. It would require a moderate level of treatment such as disinfection,neutralisation, removal of solids and chemicals to meet appropriate drinking water standards;

■ Category 3: Water is of a low quality with individual constituents encompassing high values oftotal dissolved solids, elevated levels of dissolved metals or extreme levels of pH. It wouldrequire significant treatment to remove dissolved solids and metals through neutralisationand/or disinfection to meet appropriate drinking water standards.

5.1 Inputs

Inputs are volumes of water received by the operational facility for use in the water balance system. They are represented by green boxes in Figure 2. Details of data and equations used to calculate inputs are described below.

5.1.1 Groundwater inflow and pit rainfall

Groundwater inflow to the mine pit was estimated via ground water modelling conducted by CloudGMS Pty Ltd. The ground water model simulated the pit ground water inflow during the pit mining stage from the 1st to the 29th month of the life of mine. The ground water inflow in the remaining 6-month life of mine was estimated by linear interpolation based on the simulated ground water inflows from the 22nd to the 35th month, as the variation of the inflow data show a strong linear feature from the 22nd month of the mine life (Figure 3).

Figure 3. linear feature of the pit ground water inflows.

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The monthly groundwater inflows for the 35-month life of mine are shown in Table 2.

Table 2. 1st to 29th month Groundwater inflow data, courtesy of CloudGMS Pty Ltd and estimated

30th to 35th month inflows.

Month Inflow (kL/month) Month Inflow (kL/month)

1 July 16828 19 January 67323

2 August 37925 20 February 66259

3 September 44524 21 March 64007

4 October 46293 22 April 57929

5 November 48212 23 May 61861

6 December 49260 24 June 58854

7 January 49804 25 July 59819

8 February 54473 26 August 55926

9 March 64423 27 September 56789

10 April 66245 28 October 55284

11 May 76366 29 November 52151

12 June 73219 30 December 51610

13 July 78523 31 January 50269

14 August 75612 32 February 48928

15 September 76933 33 March 47588

16 October 77859 34 April 46247

17 November 74363 35 May 44907

18 December 71621

Pit rainfall run-off volume VPit-runoff (ML) is determined as:

VPit-runoff = 0.01 × R × A × 0.15

Where R (mm) is the rainfall depth, A is the pit area (16.34 ha), 0.15 is a common runoff factor for disturbed catchment recommended in MCA WAF.

The pit groundwater inflow and pit rainfall runoff water will be directly pumped into MWD1 (Figure 2).

These flows are assigned to Category 2 water quality.

5.1.2 Off-site Surface Water Storages

Water will be extracted from Observation Hill Dam and the mine site dam to make up the shortfall during mining operations. This volume will be calculated by balancing other inputs and outputs and storage changes of the system. This water is assigned Category 1.

5.1.3 Storage aggregation

To calculate operational efficiency, the MCA WAF guidelines require the storages to be grouped into a Raw Water Store and a Mixed Water Store. As the storages were modelled separately in the Excel water balance model, the modelling results were grouped as follows:


■ The Raw Water Dam (RWD) only receives inflows form off-site water storages (Observation HillDam and Mine Site Dam) and direct rainfall so it is grouped into the Raw Water Store.

■ The Mine Water Dam 1 (MWD1) receives direct rainfall, pit rainfall runoff and ground waterinflow, so it is grouped into the Raw Water Store.

■ The Mine Water Dam 2 (MWD2) receives direct rainfall and decant water from the TSF whichis worked water, so it is a Mixed Water Store.

The TSF acts as both a task and a storage. The TSF stores raw water from direct rainfall and runoff from disturbed areas and worked inflow. The water in the TSF needs to be separated into raw and worked water before calculating the reuse efficiency.

The Sediment Basins are used to receive runoff from disturbed land. Their inputs are rainfall and runoff from the disturbed mine site area which is not involved in mining operations. Therefore, the Sediment Basins are not considered as stores.

The mine site storages and grouped stores are summarised in Table 3.

Table 3. Mine site stores and grouped stores.

Storage name Raw or Mixed Store

Surface Area (m2)

Disturbed Catchment area (m2)

RWD Raw 12000 0

MWD1 Raw 46000 0

Raw water store Total 58000 0

MWD2 Mixed 12000 0

Mixed water store Total 12000 0

TSF N/A 20000 95000

To calculate the volume of rainfall incident on the stores VRainfall (ML):

VRainfall = 10-6 × R × SA

Where R (mm) is the rainfall depth, and SA (m2) is the storage surface areas.

As rainfall is directly incident on the stores, to the contained water is of good quality so it is assigned to Category 1.

The runoff volume to the TSF (VRunoff) is:

VRunoff =10-6 × R × A ×1.0

Where R (mm) is the rainfall depth, A (m2) is the disturbed catchment area and VRunoff is in ML. The runoff factor is taken as 1.0 as the base material of the TSF cell is designed to have a low permeability.

The runoff from the TSF catchment will usually be of a poorer quality therefore it can be assigned to Category 2.

5.2 Outputs

Outputs are volumes of water removed from the operational facility after it has been through a task, treated or stored for use. The outputs are in boxes in Figure 2. Details of data and equations used to calculate outputs are described below.


5.2.1 Entrained water in product and tails

According to the operation schedule, the volume of entrained water in the product was estimated as 28 kL/day. The water entrained in tailings was estimated as 264 kL/day. The water entrained in rejects was estimated as 248 kL/day.

It is assumed that entrained water will be of very poor quality, so it is assigned to Category 3.

5.2.2 Evaporation

Evaporation VEvap from storage surfaces was calculated by:

VEvap = 10-6 × SEvap × PanEvap × f

Where SEvap is the average water surface area (m2) in the storage. PanEvap is the value of measured rates of pan evaporation. f is a correction factor to convert pan evaporation rate into evaporation losses from open storages. An estimate of 0.75 recommended by the MCA WAF guidelines was used.

A constant extra evaporation loss of 40 kL/day was applied to each storage to cover standpipe losses.

There will also be evaporation of the water used for dust suppression and Administration/Ablutions. The dust suppression losses were calculated based on a varying rate for each mining stage (Table 4). The Administration/Ablutions losses were calculated at a rate of 8 kL/day.

Table 4. Dust suppression at each mining stage.

Month of operation Rate (kL/day)

1-5 900

6-29 1020

29-35 420

The quality of evaporated water is assigned to Category 1.

5.2.3 Seepage

Losses due to seepage was not considered in this water balance, as the volume of seepage losses are minor compared to other outputs. The water stores are designed to have a low permeability and the fines are expected to settle to the bottom of the storage to form an impermeable layer.

5.2.4 Discharge to environment

The excess inventory in MWD1 is discharged to the environment during the wet season (November - March). The maximum discharge rate is 50 L/s.

5.3 Diversions

Diversions are flows from an input to an output without being utilised by the operational facility. The flow is not stored with the intention of being used in a task or treated. The diversions are indicated by yellow boxes in Figure 2. Details of data and equations used to calculate diversions are described below.

5.3.1 Mine site runoff

It was assumed that the runoff from the mine site only flows into the Sedimentation Basins. This water will not be involved in mining operations, so it is treated as diverted flow.


The mine site has a hydrological model, but the model was developed in an earlier stage of the project. As the mine site design had been updated during the preparation of this water balance, the site runoff was calculated manually based on the latest mine site design available.

Site run-off volume VRunoff (ML) was calculated as:

VRunoff =0.01 × R × A × β

where R is the rainfall depth (mm), A is the disturbed catchment area (ha) and β is a rainfall/runoff factor.

The total disturbed catchment area bounded by the topsoil and inundation bunds, which does not include the area of storages, pit and TSF, is 163 ha. According to MCA WAF, a common estimate for β is selected as 0.15 for the disturbed area.

As this water is runoff from disturbed area, it is assigned to Category 2.

5.4 Operational flows

Operation flows are internal to the operational facility, such as the flows between the stores and tasks and treatment plants.

Tasks are operational activities that use water. The water received as an input and has not been used in a task is regarded as raw water. The raw water will become worked water after it has been through a task.

The volumes of operational flows are estimated based on the information provided by the design team.

The total crushing and screening water use is estimated as 56 kL/day.

The total DMS makeup water is estimated as 956 kL/day

The process flow from the DMS plant to TSF is estimated to be 736 kL/day

The TSF Decant flow to MWD2 is calculated by balancing the TSF input and output.

As the ore processing will not be conducted in the first 5 months, there will be no operational flows during this course.


6 MCA WAF Deliverables

6.1 Successive average rainfall years scenario

This section shows the input-output statement, accuracy statement and statement of operational efficiencies for successive average rainfall years simulation.

6.1.1 Input-Output Statement

The Input-Output statement is prepared in accordance with the MCA WAF guidelines and the detailed water balance modelling results in Appendix A-D. The reporting period is form 01/07/2019 to 31/05/2022 which is the design life of the mine. The statement is in Table 5.

Table 5. Input-Output statement for successive average rainfall years scenario.

Inputs and Outputs for the reporting period (1st July 2019 to 31st May 2022)

Input/

Output

Source/

Destination

Inputs/

Outputs

Water quality

Note

How were the flows obtained and what is the confidence level of them?

Cat1

(ML)

Cat2

(ML)

Cat3

(ML)

Input

Surface Water

Precipitation and Runoff

394 548 0 1 Estimated/Low

Off-site Storages


Groundwater

Aquifer interception

0 290 0 3 Estimated/medium


0 1739 0 4 Simulated/Medium

Total Inputs 474 2576 0

Output

Surface Water Discharge 948 0 0 5 Estimated/Low

Other Evaporation 1517 0 0 6 Estimated/Medium

Entrainment 0 0 492 7 Estimated/Medium

Total Outputs 2465 0 492

Diversions

Input Surface Water Precipitation

and Runoff 105 1073 0 8 Estimated/Low


Output Surface Water

Discharge 1114 0 0 Estimated/Low

Evaporation 64 0 0 Estimated/Low



Notes for Input-Output statement:

1. The precipitation and runoff were estimated using the equations in section 5.1.1 and 5.1.3 and50th %ile SILO monthly rainfall data from Table 1.

2. The water extracted from off-site storages was estimated by balancing the whole water balancesystem.

3. The pit groundwater inflows (Table 2) are from the result of groundwater modelling conductedby CloudGMS.

4. This part of the groundwater inflows was estimated by linear interpolation. The method isdescribed in section 5.1.1.

5. The water released from MWD1 was estimated by balancing the storage.6. The evaporation from storage was estimated using the equation in Section 5.2.2 and 50th %ile

SILO monthly pan evaporation data from Table 1.7. The entrainment was estimated based on the entrainment rates in Section 5.2.1.8. The site runoff was estimated by the equation in Section 5.3.1. A runoff/rainfall coefficient of

0.15 from the MCA WAF guidelines was adopted for the disturbed area.

The volumes of water in storages at the beginning and end of the reporting period is in Table 6

Table 6. Volumes (ML) of water in storages for successive average rainfall years scenario.

RWD MWD1 MWD2 TSF Total

1st July 2019 0 0 0 0 0

31st May 2022 0 52 41 0 93

Changes in storage 0 52 41 0 93

Total Inputs – Total Outputs = (474+2576) – (2465+492) = 93 ML = Change in storage

The system is in balance

6.1.2 Accuracy Statement

The accuracy statement shows the proportions of flows by volume which are measured, estimated or simulated along with the level of confidence with which that number is known. The proportions of flows are calculated based on the flow volumes in Table 5.

The accuracy statement is in Table 7.

Table 7. Accuracy statement for successive average rainfall years scenario.

Types % of all Flows Confidence (%)

High Medium Low

Measured 0.0% 0.0% 0.0% 0.0%

Estimated 79.2% 0.0% 27.6% 51.6%

Simulated 20.8% 0.0% 20.8% 0.0%

Total 100.0% 0.0% 48.4% 51.6%


6.1.3 Statement of Operational Efficiencies

The stores have been grouped into a Raw Water Store and a Mixed Water Store in Section 5.1.3. An operational flow chart with grouped stores and tasks is then developed based on the modelling results and the water balance schematic in Figure 2. The operational flow chart is in Figure 4. The Statement of Operational Efficiencies is then calculated based on this operational flow chart.

The Statement of Operational Efficiencies for successive average rainfall years condition is in Table 8.

Table 8. Statement of Operational Efficiencies for successive average rainfall years scenario.

Operational efficiencies

Total volume to tasks (ML) 3117

Total volume of reused water (ML) 1477

Reuse efficiency (%) 47

Total volume of recycled water (ML) 0

Recycling efficiency (%) 0

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6.2 Successive wet years scenario

This section shows the input-output statement, accuracy statement and statement of operational efficiencies for the successive wet years scenario.


The input-output statement is shown in the table below:

Table 9. Input-Output statement for successive wet years scenario


Input/

Output

Source/

Destination

Inputs/

Outputs

Water quality

Note


Cat1

(ML)

Cat2

(ML)

Cat3

(ML)

Input

Surface Water



Off-site Storages


Groundwater






Output





Diversions












3. The pit groundwater inflows (Table 2) are from the result of groundwater modelling conductedby CloudGMS.

4. This part of groundwater inflows was estimated by linear interpolation. The method is describedin section 5.1.1.

5. The water released form MWD1 was estimated by balancing the storage.6. The evaporation from storage was estimated using the equation in Section 5.2.2 and 10th %ile



The volumes of water in storages at the beginning and end of the reporting period is in Table 10.

Table 10. Volumes (ML) of water in storages for successive wet years scenario.


1st July 2019 0 0 0 0 0

31st May 2022 11 64 251 16 342


Total Inputs – Total Outputs = 778+3059 - 3003 - 492 = 342 ML = Change in storage.

The system is in balance.

Since no release to the environment from the MWD2 is allowed in the model. The final inventory (251 ML) in MWD2 is much larger than its design storage capacity (60 ML). To deal with the excessive inflowfrom TSF in a successive wet years scenario, either the capacity of MWD2 should be increased orenvironmental release should be allowed


The accuracy statement for the successive wet years scenario is in Table 11.

Table 11. Accuracy statement for successive wet years scenario.


High Medium Low

Measured 0.0% 0.0% 0.0% 0.0%

Estimated 85.3% 0.0% 21.1% 64.2%

Simulated 14.7% 0.0% 14.7% 0.0%

Total 100.0% 0.0% 35.8% 64.2%



The operational flow chart for this scenario is in Figure 5. The Statement of Operational Efficiencies is in Table 12.

Table 12. Statement of Operational Efficiencies for successive wet years scenario.







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6.3 Successive dry years scenario

This section shows the input-output statement, accuracy statement and statement of operational efficiencies for the successive dry years scenario.



Table 13. Input-Output statement for successive dry years scenario


Input/

Output

Source/

Destination

Inputs/

Outputs

Water quality

Note


Cat1

(ML)

Cat2

(ML)

Cat3

(ML)

Input

Surface Water



Off-site Storages


Groundwater






Output





Diversions












3. The pit groundwater inflows (Table 2) are from the result of groundwater modelling conductedby CloudgMS.






Table 14. Volumes (ML) of water in storages for successive dry years scenario.


1st July 2019 0 0 0 0 0

31st May 2022 0 20 0 0 0





The accuracy statement for the successive dry years scenario is in Table 15.

Table 15. Accuracy statement for successive dry years scenario.


High Medium Low

Measured 0.0% 0.0% 0.0% 0.0%

Estimated 73.1% 0.0% 36.0% 37.0%

Simulated 26.9% 0.0% 26.9% 0.0%

Total 100.0% 0.0% 63.0% 37.0%


The operational flow chart is in Figure 6 and the Statement of Operational Efficiencies in Table 16.

Table 16. Statement of Operational Efficiencies for successive dry years scenario.







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6.4 Successive average rainfall years scenario with no dust

suppression in January and February

This section shows the input-output statement, accuracy statement and statement of operational efficiencies for the successive average years scenario with no dust suppression in January and February.



Table 17. Input-Output statement for successive average years scenario with no dust

suppression in January and February.


Input/

Output

Source/

Destination

Inputs/

Outputs

Water quality

Note


Cat1

(ML)

Cat2

(ML)

Cat3

(ML)

Input

Surface Water



Off-site Storages


Groundwater






Output





Diversions












3. The pit groundwater inflows (Table 2) are from the result of groundwater modelling conductedby CLOUDGMS.






Table 18. Volumes (ML) of water in storages for successive average years scenario with no dust

suppression in January and February.


1st July 2019 0 0 0 0 0

31st May 2022 0 52 41 0 93





The accuracy statement for the successive average years scenario with no dust suppression in January and February is in Table 19.

Table 19. Accuracy statement for successive average years scenario with no dust suppression

in January and February.


High Medium Low

Measured 0.0% 0.0% 0.0% 0.0%

Estimated 79.2% 0.0% 25.7% 53.5%

Simulated 20.8% 0.0% 20.8% 0.0%

Total 100.0% 0.0% 46.5% 53.5%



The operational flow chart for this scenario is in Figure 7. The Statement of Operational Efficiencies is in Table 20.

Table 20. Statement of Operational Efficiencies for successive average years scenario with no

dust suppression in January and February.







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6.5 Contextual Statement

6.5.1 System boundary description

The operational facility, for which the contextual information is prepared, is the Grant Lithium Project (GLP). The water system comprises of:

■ GLP processing and mining facilities■ Off-site surface water storage■ Ground water supply

6.5.2 Water Resources

water sourcing options of the GLP entity include the harvest of runoff, interception of groundwater and precipitation and extraction from off-site surface water storages.

Interception of groundwater inflows from the mine pit is the principal water resource for the GLP during the reporting period. The surface water sourced from direct precipitation interception and runoff harvesting by mining infrastructures is the second major water resource. Extraction from off-site surface water storages only accounts for a small proportion of water sourcing activities. The percentages for these water resources of total input to the GLP under varies scenarios are in Table 21.

Table 21. Percentage for water resources of total water sourcing activities

Source

Average

years

scenario

Wet

years

scenario

Dry

years

scenario

Average years scenario

without dust suppressing

in Jan & Feb

Interception of ground water 66.5 52.9 77.1 66.5

Direct precipitation interception and runoff harvesting

30.9 46.2 18.3 30.9

Extraction from off-site surface water stores

2.6 0.9 4.6% 2.6

6.5.3 Water Infrastructure

The GLP entity relies on 3 on-on site water stores, Raw Water Dam (RWD), Mine Water Dam 1 (MWD1) and Mine Water Dam 2 (MWD2) to manage operational water use. MWD1 is the largest on-site storage which has a 240 ML capacity, allowing for predicted storage of pit inflows (groundwater and rainfall runoff). MWD2 has a capacity of 60 ML. It has been designed as a contingency storage for pit inflow and TSF wet season runoff. RWD has a capacity of 60 ML. It stores water pumped from the off-site water supply dams.

Observation Hill Dam (OHD) is the major off-site storage located 5 km south-south-east of the GLP mine site. It will be used to accommodate the volume of water required to adequately supply estimated demand as well as mitigate potential risk. It has a maximum holding capacity of 364 ML. Raising the dam wall by 1.5 m to increase the capacity to 628 ML was considered.


A second surface water storage, Mine Site Dam (MSD) is also considered to ensure sufficient water available for mining operations. This dam was designed to have a 280 ML capacity.

6.5.4 Water Resource Management Instruments

Water management for resource activities is regulated through the Water Act (NT). The project location is also within the Darwin Rural Water Control District.

6.5.5 Water Management Bodies

The Department of Natural Resources and Environment (DENR) – Water Division are responsible to administering the Water Act and associated regulations and policy. The department is responsible for setting policy and frameworks for water use in the NT.

6.5.6 Climatic Conditions

The climatic data from 1971 to 2018 at 12°39'S 130°48'E was sourced from SILO database for the water balance model. The 10 %ile, 50%ile and 90%ile monthly statics were selected for the simulation of different scenarios. The detailed monthly data selected are in Table 1.

The total rainfall for the reporting period (1st Jul 2019 to 31st May 2022) are 2233 mm, 4379 mm and 8232 mm for successive dry, average and wet scenarios respectively and the total pan evaporation are 7697 mm, 6870 mm and 6116 mm.

6.5.7 Inputs and Outputs

The major source of inflows into the GLP entity comes from aquifer interception, unregulated surface water harvesting via runoff and rainfall and regulated extraction from off-site surface water stores. The major outflows include evaporation, environmental discharge and entrainment. The predicated volumes of these inputs and outputs for varies scenarios are summarised in Table 22.

Table 22. inputs and outputs for the operational facility from 1st July 2019 to 31 May 2022

Average

years

scenario

Wet years

scenario

Dry years

scenario

Average years

scenario without

dust suppressing

in Jan & Feb

Inputs

Flow from Aquifer interception

2029 ML 66.5%

2029 ML 52.9%

2029 ML 77.1%

2029 ML 66.5%

Unregulated surface water harvesting via runoff and rainfall

942 ML 30.9%

1771 ML 46.2%

480 ML 18.3%

942 ML 30.9%

Regulated extraction from off-site surface water stores 80 ML

2.6% 37 ML 0.9%

121 ML 4.6%

80 ML 2.6%

Outputs

Evaporation 1517 ML 51.3%

1657 ML 47.4%

1529 ML 58.6%

1371 ML 46.4%

Environmental discharge 948 ML 32.1%

1346 ML 38.5%

589 ML 22.6%

1094 ML 37.0%

Entrainment 492 ML 16.6%

492 ML 14.1%

492 ML 18.8%

492 ML 16.6%


6.5.8 Allocations and Restrictions

Water sources for the mine will comprise:

■ Groundwater/rainfall in-flows to the pit, which will be dewatered to MWD 1, and■ Surface water pumped from off-site dams

Under the Water Act (NT), no licence or permit is required for the use of pit inflow water in mining operations. Pit inflows will be used prior to surface water pumped from off-site dams.

Pursuant to the Water Act, the extraction of surface water for use in mining operations requires that proponents obtain a Licence to take or use surface water or groundwater. Core will obtain the required licence prior to extraction of surface water from the off-site dams.

6.5.9 Trading Activity

There is no water trading activities planned to be implemented to source water for Grants Lithium Project.


Appendix A. Water balance modelling results for successive average

rain fall years scenario

Mine Water Dam 1 balance (ML)

Mon

ths

of

oper

atio

n

Gro

und

wat

er

Inflo

w to

pit

Rai

nfal

l to

pit

Dire

ct ra

infa

ll

Eva

pora

tion

+ S

tand

pipe

loss

Dus

t Sup

pres

sion

D

MS

wat

er

mak

eup

Cru

shin

g &

S

cree

ning

E

nviro

Rel

ease

Inv

en

tory

0 0.00

1 16.83 0.00 0.00 8.19 8.64 0.00 0.00 0.00 0.00

2 37.93 0.00 0.00 8.76 27.90 0.00 0.00 0.00 1.28

3 44.52 0.22 0.33 9.06 27.00 0.00 0.00 0.00 10.28

4 46.29 1.56 2.38 9.56 27.90 0.00 0.00 0.00 23.06

5 48.21 4.18 6.38 8.48 27.00 0.00 0.00 46.36 0.00

6 49.26 6.86 10.47 7.99 31.62 0.00 1.75 25.23 0.00

7 49.80 11.60 17.69 7.23 31.62 0.00 1.75 38.49 0.00

8 54.47 8.84 13.49 6.18 28.56 0.00 1.58 40.48 0.00

9 64.42 8.72 13.30 7.03 30.60 0.00 1.69 47.12 0.00

10 66.25 1.95 2.97 7.53 30.60 0.00 1.69 0.00 31.34

11 76.37 0.08 0.12 8.00 31.62 0.00 1.75 0.00 66.54

12 73.22 0.00 0.00 7.73 30.60 0.00 1.69 0.00 99.74

13 78.52 0.00 0.00 8.19 31.62 0.00 1.75 0.00 136.70

14 75.61 0.00 0.00 8.76 31.62 8.96 1.75 0.00 161.24

15 76.93 0.22 0.33 9.06 30.60 17.29 1.69 0.00 180.07

16 77.86 1.56 2.38 9.56 31.62 12.19 1.75 0.00 206.75

17 74.36 4.18 6.38 8.48 30.60 1.47 1.69 129.60 119.84

18 71.62 6.86 10.47 7.99 31.62 0.00 1.75 133.92 33.52

19 67.32 11.60 17.69 7.23 31.62 0.00 1.75 89.52 0.00

20 66.26 8.84 13.49 6.22 29.58 0.00 1.64 51.15 0.00

21 64.01 8.72 13.30 7.07 31.62 0.00 1.75 45.58 0.00

22 57.93 1.95 2.97 7.53 30.60 0.00 1.69 0.00 23.03

23 61.86 0.08 0.12 8.00 31.62 0.00 1.75 0.00 43.72

24 58.85 0.00 0.00 7.73 30.60 0.00 1.69 0.00 62.55

25 59.82 0.00 0.00 8.19 31.62 2.49 1.75 0.00 78.33

26 55.93 0.00 0.00 8.76 31.62 18.39 1.75 0.00 73.74

27 56.79 0.22 0.33 9.06 30.60 17.29 1.69 0.00 72.44

28 55.28 1.56 2.38 9.56 31.62 12.19 1.75 0.00 76.54

29 52.15 4.18 6.38 8.48 30.60 1.47 1.69 97.02 0.00

30 51.61 6.86 10.47 7.99 13.02 0.00 1.75 46.18 0.00

31 50.27 11.60 17.69 7.23 13.02 0.00 1.75 57.56 0.00

32 48.93 8.84 13.49 6.18 11.76 0.00 1.58 51.74 0.00

33 47.59 8.72 13.30 7.07 13.02 0.00 1.75 47.76 0.00

34 46.25 1.95 2.97 7.53 12.60 0.00 1.69 0.00 29.35

35 44.91 0.08 0.12 8.00 13.02 0.00 1.75 0.00 51.68

Total 2028.24 132.02 201.42 279.61 939.48 91.74 51.44 947.73


Mine Water Dam 2 balance (in ML)

Mon

ths

of o

pera

tion

Dire

ct ra

infa

ll

Evap

orat

ion

+ St

andp

ipe

loss

TSF

Dis

char

ge to

M

WD

2

DM

S w

ater

mak

eup

Inv

en

tory

0 0.0

1 0.00 0.00 0.00 0.00 0.00

2 0.00 0.00 0.00 0.00 0.00

3 0.09 0.09 0.00 0.00 0.00

4 0.62 0.62 2.79 0.00 2.79

5 1.67 3.10 13.03 0.00 14.39

6 2.73 3.00 8.59 0.00 22.70

7 4.62 2.80 27.04 0.00 51.56

8 3.52 2.44 6.36 0.00 59.00

9 3.47 2.72 0.00 0.00 59.75

10 0.78 2.85 1.33 0.00 59.00

11 0.03 3.00 0.00 1.67 54.36

12 0.00 2.90 0.00 17.52 33.93

13 0.00 3.05 0.00 18.25 12.63

14 0.00 3.20 0.00 9.43 0.00

15 0.09 0.09 0.00 0.00 0.00

16 0.62 0.62 0.00 0.00 0.00

17 1.67 1.67 0.00 0.00 0.00

18 2.73 2.73 8.59 0.00 8.59

19 4.62 2.80 27.04 0.00 37.44

20 3.52 2.48 17.18 0.00 55.66

21 3.47 2.76 2.63 0.00 59.00

22 0.78 2.85 2.08 0.00 59.00

23 0.03 3.00 0.00 16.78 39.24

24 0.00 2.90 0.00 17.52 18.82

25 0.00 3.05 0.00 15.77 0.00

26 0.00 0.00 0.00 0.00 0.00

27 0.09 0.09 0.00 0.00 0.00

28 0.62 0.62 0.00 0.00 0.00

29 1.67 1.67 0.00 0.00 0.00

30 2.73 2.73 8.59 0.00 8.59

31 4.62 2.80 27.04 0.00 37.44

32 3.52 2.44 17.66 0.00 56.18

33 3.47 2.76 2.11 0.00 59.00

34 0.78 2.85 2.08 0.00 59.00

35 0.03 3.00 0.00 14.64 41.39

Total 52.55 73.71 174.13 111.58


Raw Water Dam balance (in ML)

Mon

ths

of o

pera

tion

Dire

ct ra

infa

ll

Inflo

w fr

om O

HD

&

Min

e Si

te D

am

Evap

orat

ion

+ St

andp

ipe

loss

Adm

inis

tratio

n &

ablu

tion

Dus

t sup

pres

sion

D

MS

wat

er m

akeu

p C

rush

ing

& Sc

reen

ing

Inv

en

tory

0 0.0

1 0.00 22.56 3.05 0.25 19.26 0.00 0.00 0.00

2 0.00 3.45 3.20 0.25 0.00 0.00 0.00 0.00

3 0.09 3.40 3.25 0.24 0.00 0.00 0.00 0.00

4 0.62 3.04 3.41 0.25 0.00 0.00 0.00 0.00

5 1.67 1.67 3.10 0.24 0.00 0.00 0.00 0.00

6 2.73 0.52 3.00 0.25 0.00 0.00 0.00 0.00

7 4.62 0.00 2.80 0.25 0.00 0.00 0.00 1.56

8 3.52 0.00 2.44 0.22 0.00 0.00 0.00 2.42

9 3.47 0.00 2.72 0.24 0.00 0.00 0.00 2.93

10 0.78 0.00 2.85 0.24 0.00 0.00 0.00 0.61

11 0.03 2.61 3.00 0.25 0.00 0.00 0.00 0.00

12 0.00 3.14 2.90 0.24 0.00 0.00 0.00 0.00

13 0.00 3.30 3.05 0.25 0.00 0.00 0.00 0.00

14 0.00 3.45 3.20 0.25 0.00 0.00 0.00 0.00

15 0.09 3.40 3.25 0.24 0.00 0.00 0.00 0.00

16 0.62 3.04 3.41 0.25 0.00 0.00 0.00 0.00

17 1.67 1.67 3.10 0.24 0.00 0.00 0.00 0.00

18 2.73 0.52 3.00 0.25 0.00 0.00 0.00 0.00

19 4.62 0.00 2.80 0.25 0.00 0.00 0.00 1.56

20 3.52 0.00 2.48 0.23 0.00 0.00 0.00 2.37

21 3.47 0.00 2.76 0.25 0.00 0.00 0.00 2.83

22 0.78 0.00 2.85 0.24 0.00 0.00 0.00 0.52

23 0.03 2.71 3.00 0.25 0.00 0.00 0.00 0.00

24 0.00 3.14 2.90 0.24 0.00 0.00 0.00 0.00

25 0.00 3.30 3.05 0.25 0.00 0.00 0.00 0.00

26 0.00 3.45 3.20 0.25 0.00 0.00 0.00 0.00

27 0.09 3.40 3.25 0.24 0.00 0.00 0.00 0.00

28 0.62 3.04 3.41 0.25 0.00 0.00 0.00 0.00

29 1.67 1.67 3.10 0.24 0.00 0.00 0.00 0.00

30 2.73 0.52 3.00 0.25 0.00 0.00 0.00 0.00

31 4.62 0.00 2.80 0.25 0.00 0.00 0.00 1.56

32 3.52 0.00 2.44 0.22 0.00 0.00 0.00 2.42

33 3.47 0.00 2.76 0.25 0.00 0.00 0.00 2.88

34 0.78 0.00 2.85 0.24 0.00 0.00 0.00 0.56

35 0.03 2.66 3.00 0.25 0.00 0.00 0.00 0.00

Total 52.55 79.66 104.43 8.52 19.26 0.00 0.00


TSF balance (in ML)

Mon

ths

of

oper

atio

n

Dire

ct ra

infa

ll

TSF

runo

ff w

ater

Evap

orat

ion

Entra

inm

ent i

n ta

ils

Proc

ess

inflo

w

TSF

deca

nt w

ater

to

mak

e up

DM

S po

sses

sing

Inv

en

tory

Tails

pro

duct

ion

TSF

stor

age

avai

labi

lity

Con

tinge

ncy

wat

er

stor

age

if re

quire

d

0

0.0 515.00 515.00

1 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 515.00 515.00

2 0.00 0.01 0.01 0.00 0.00 0.00 0.00 0.00 515.00 515.00

3 0.14 0.68 0.83 0.00 0.00 0.00 0.00 0.00 515.00 515.00

4 1.04 4.92 3.17 0.00 0.00 0.00 0.00 0.00 515.00 515.00

5 2.78 13.19 2.93 0.00 0.00 0.00 0.00 0.00 515.00 515.00

6 4.55 21.62 2.61 8.17 22.83 29.64 0.00 16.97 498.03 498.03

7 7.69 36.54 2.20 8.17 22.83 29.64 0.00 16.97 481.06 481.06

8 5.87 27.86 2.54 7.38 20.62 26.77 11.30 15.33 465.73 454.43

9 5.78 27.46 2.76 7.91 22.09 28.68 27.28 16.43 449.30 422.02

10 1.29 6.14 3.00 7.91 22.09 28.68 15.89 16.43 432.88 416.99

11 0.05 0.24 2.86 8.17 22.83 27.97 0.00 16.97 415.90 415.90

12 0.00 0.00 3.02 7.91 22.09 11.16 0.00 16.43 399.48 399.48

13 0.00 0.00 3.27 8.17 22.83 11.39 0.00 16.97 382.51 382.51

14 0.00 0.01 3.42 8.17 22.83 11.25 0.00 16.97 365.53 365.53

15 0.14 0.68 3.62 7.91 22.09 11.39 0.00 16.43 349.11 349.11

16 1.04 4.92 3.17 8.17 22.83 17.45 0.00 16.97 332.14 332.14

17 2.78 13.19 2.93 7.91 22.09 27.21 0.00 16.43 315.71 315.71

18 4.55 21.62 2.61 8.17 22.83 29.64 0.00 16.97 298.74 298.74

19 7.69 36.54 2.20 8.17 22.83 29.64 0.00 16.97 281.77 281.77

20 5.87 27.86 2.54 7.64 21.36 27.73 0.00 15.88 265.89 265.89

21 5.78 27.46 2.75 8.17 22.83 29.64 12.88 16.97 248.92 236.04

22 1.29 6.14 2.98 7.91 22.09 28.68 0.75 16.43 232.49 231.74

23 0.05 0.24 2.84 8.17 22.83 12.86 0.00 16.97 215.52 215.52

24 0.00 0.00 3.02 7.91 22.09 11.16 0.00 16.43 199.09 199.09

25 0.00 0.00 3.27 8.17 22.83 11.39 0.00 16.97 182.12 182.12

26 0.00 0.01 3.42 8.17 22.83 11.25 0.00 16.97 165.15 165.15

27 0.14 0.68 3.62 7.91 22.09 11.39 0.00 16.43 148.72 148.72

28 1.04 4.92 3.17 8.17 22.83 17.45 0.00 16.97 131.75 131.75

29 2.78 13.19 2.93 7.91 22.09 27.21 0.00 16.43 115.33 115.33

30 4.55 21.62 2.61 8.17 22.83 29.64 0.00 16.97 98.35 98.35

31 7.69 36.54 2.20 8.17 22.83 29.64 0.00 16.97 81.38 81.38

32 5.87 27.86 2.54 7.38 20.62 26.77 0.00 15.33 66.05 66.05

33 5.78 27.46 2.75 8.17 22.83 29.64 13.40 16.97 49.08 35.68

34 1.29 6.14 4.20 7.91 22.09 28.68 0.06 16.43 32.65 32.59

35 0.05 0.24 0.00 8.17 22.83 15.00 0.00 16.97 15.68 15.68

Total 87.58 415.99 91.96 240.41 671.63 668.69

499.32


Appendix B. Water balance modelling results for successive wet

years scenario


Mon

ths

of

oper

atio

n

Gro

und

wat

er

Inflo

w to

pit

Rai

nfal

l to

pit

Dire

ct ra

infa

ll

Eva

pora

tion

+ S

tand

pipe

loss

Dus

t Sup

pres

sion

D

MS

wat

er

mak

eup

Cru

shin

g &

S

cree

ning

E

nviro

Rel

ease

Inv

en

tory

0 0.00

1 16.83 0.02 0.03 7.59 9.28 0.00 0.00 0.00 0.00

2 37.93 0.07 0.10 8.24 27.90 0.00 0.00 0.00 1.95

3 44.52 1.68 2.56 8.48 27.00 0.00 0.00 0.00 15.25

4 46.29 3.66 5.59 8.69 27.90 0.00 0.00 0.00 34.20

5 48.21 6.01 9.17 7.76 27.00 0.00 0.00 62.84 0.00

6 49.26 14.82 22.62 7.09 31.62 0.00 1.75 46.24 0.00

7 49.80 19.61 29.91 6.35 31.62 0.00 1.75 59.60 0.00

8 54.47 16.02 24.44 5.53 28.56 0.00 1.58 59.26 0.00

9 64.42 14.61 22.29 6.05 30.60 0.00 1.69 62.97 0.00

10 66.25 5.18 7.91 6.62 30.60 0.00 1.69 0.00 40.42

11 76.37 1.02 1.55 7.37 31.62 0.00 1.75 0.00 78.62

12 73.22 0.06 0.10 7.09 30.60 0.00 1.69 0.00 112.62

13 78.52 0.02 0.03 7.59 31.62 0.00 1.75 0.00 150.23

14 75.61 0.07 0.10 8.24 31.62 0.00 1.75 0.00 184.40

15 76.93 1.68 2.56 8.48 30.60 0.00 1.69 0.00 224.81

16 77.86 3.66 5.59 8.69 31.62 0.00 1.75 29.86 240.00

17 74.36 6.01 9.17 7.76 30.60 0.00 1.69 129.60 159.89

18 71.62 14.82 22.62 7.09 31.62 0.00 1.75 133.92 94.57

19 67.32 19.61 29.91 6.35 31.62 0.00 1.75 133.92 37.77

20 66.26 16.02 24.44 5.57 29.58 0.00 1.64 107.70 0.00

21 64.01 14.61 22.29 6.09 31.62 0.00 1.75 61.44 0.00

22 57.93 5.18 7.91 6.62 30.60 0.00 1.69 0.00 32.11

23 61.86 1.02 1.55 7.37 31.62 0.00 1.75 0.00 55.80

24 58.85 0.06 0.10 7.09 30.60 0.00 1.69 0.00 75.43

25 59.82 0.02 0.03 7.59 31.62 0.00 1.75 0.00 94.34

26 55.93 0.07 0.10 8.24 31.62 0.00 1.75 0.00 108.82

27 56.79 1.68 2.56 8.48 30.60 0.00 1.69 0.00 129.09

28 55.28 3.66 5.59 8.69 31.62 0.00 1.75 0.00 151.57

29 52.15 6.01 9.17 7.76 30.60 0.00 1.69 129.60 49.25

30 51.61 14.82 22.62 7.09 13.02 0.00 1.75 116.43 0.00

31 50.27 19.61 29.91 6.35 13.02 0.00 1.75 78.67 0.00

32 48.93 16.02 24.44 5.53 11.76 0.00 1.58 70.51 0.00

33 47.59 14.61 22.29 6.09 13.02 0.00 1.75 63.62 0.00

34 46.25 5.18 7.91 6.62 12.60 0.00 1.69 0.00 38.42

35 44.91 1.02 1.55 7.37 13.02 0.00 1.75 0.00 63.76

Total 2028.24 248.21 378.69 253.61 940.12 0.00 51.44 1346.19



Mon

ths

of o

pera

tion

Dire

ct ra

infa

ll

Evap

orat

ion

+ St

andp

ipe

loss

TSF

Dis

char

ge to

M

WD

2

DM

S w

ater

mak

eup

Inv

en

tory

0

0.0

1 0.01 0.01 0.00 0.00 0.00

2 0.03 0.03 0.00 0.00 0.00

3 0.67 0.67 3.17 0.00 3.17

4 1.46 3.18 11.12 0.00 12.57

5 2.39 2.91 20.38 0.00 32.43

6 5.90 2.77 24.44 0.00 60.00

7 7.80 2.57 0.00 0.00 65.23

8 6.37 2.27 0.00 0.00 69.33

9 5.81 2.47 0.00 0.00 72.68

10 2.06 2.61 0.00 0.00 72.13

11 0.40 2.84 0.00 0.00 69.70

12 0.03 2.74 0.00 0.00 66.99

13 0.01 2.90 0.00 0.00 64.10

14 0.03 3.07 0.00 0.00 61.06

15 0.67 3.10 1.37 0.00 60.00

16 1.46 3.18 1.72 0.00 60.00

17 2.39 2.91 0.52 0.00 60.00

18 5.90 2.77 0.00 0.00 63.13

19 7.80 2.57 0.00 0.00 68.36

20 6.37 2.31 0.00 0.00 72.43

21 5.81 2.51 0.00 0.00 75.74

22 2.06 2.61 0.00 0.00 75.18

23 0.40 2.84 0.00 0.00 72.75

24 0.03 2.74 0.00 0.00 70.04

25 0.01 2.90 0.00 0.00 67.15

26 0.03 3.07 0.00 0.00 64.11

27 0.67 3.10 0.00 0.00 61.68

28 1.46 3.18 0.04 0.00 60.00

29 2.39 2.91 0.52 0.00 60.00

30 5.90 2.77 14.07 0.00 77.20

31 7.80 2.57 63.83 0.00 146.27

32 6.37 2.27 48.64 0.00 199.01

33 5.81 2.51 41.80 0.00 244.12

34 2.06 2.61 3.72 0.00 247.28

35 0.40 2.84 5.87 0.00 250.72

Total 98.79 89.29 241.22 0.00



Mon

ths

of o

pera

tion

Dire

ct ra

infa

ll

Inflo

w fr

om O

HD

&

Min

e Si

te D

am

Evap

orat

ion

+ St

andp

ipe

loss

Adm

inis

tratio

n &

ablu

tion

Dus

t sup

pres

sion

D

MS

wat

er m

akeu

p

Cru

shin

g &

Scre

enin

g Inv

en

tory

0

0.0

1 0.01 21.76 2.90 0.25 18.62 0.00 0.00 0.00

2 0.03 3.29 3.07 0.25 0.00 0.00 0.00 0.00

3 0.67 2.67 3.10 0.24 0.00 0.00 0.00 0.00

4 1.46 1.97 3.18 0.25 0.00 0.00 0.00 0.00

5 2.39 0.76 2.91 0.24 0.00 0.00 0.00 0.00

6 5.90 0.00 2.77 0.25 0.00 0.00 0.00 2.88

7 7.80 0.00 2.57 0.25 0.00 0.00 0.00 7.87

8 6.37 0.00 2.27 0.22 0.00 0.00 0.00 11.75

9 5.81 0.00 2.47 0.24 0.00 0.00 0.00 14.86

10 2.06 0.00 2.61 0.24 0.00 0.00 0.00 14.06

11 0.40 0.00 2.84 0.25 0.00 0.00 0.00 11.38

12 0.03 0.00 2.74 0.24 0.00 0.00 0.00 8.43

13 0.01 0.00 2.90 0.25 0.00 0.00 0.00 5.29

14 0.03 0.00 3.07 0.25 0.00 0.00 0.00 2.01

15 0.67 0.66 3.10 0.24 0.00 0.00 0.00 0.00

16 1.46 1.97 3.18 0.25 0.00 0.00 0.00 0.00

17 2.39 0.76 2.91 0.24 0.00 0.00 0.00 0.00

18 5.90 0.00 2.77 0.25 0.00 0.00 0.00 2.88

19 7.80 0.00 2.57 0.25 0.00 0.00 0.00 7.87

20 6.37 0.00 2.31 0.23 0.00 0.00 0.00 11.70

21 5.81 0.00 2.51 0.25 0.00 0.00 0.00 14.76

22 2.06 0.00 2.61 0.24 0.00 0.00 0.00 13.97

23 0.40 0.00 2.84 0.25 0.00 0.00 0.00 11.29

24 0.03 0.00 2.74 0.24 0.00 0.00 0.00 8.33

25 0.01 0.00 2.90 0.25 0.00 0.00 0.00 5.20

26 0.03 0.00 3.07 0.25 0.00 0.00 0.00 1.91

27 0.67 0.76 3.10 0.24 0.00 0.00 0.00 0.00

28 1.46 1.97 3.18 0.25 0.00 0.00 0.00 0.00

29 2.39 0.76 2.91 0.24 0.00 0.00 0.00 0.00

30 5.90 0.00 2.77 0.25 0.00 0.00 0.00 2.88

31 7.80 0.00 2.57 0.25 0.00 0.00 0.00 7.87

32 6.37 0.00 2.27 0.22 0.00 0.00 0.00 11.75

33 5.81 0.00 2.51 0.25 0.00 0.00 0.00 14.81

34 2.06 0.00 2.61 0.24 0.00 0.00 0.00 14.02

35 0.40 0.00 2.84 0.25 0.00 0.00 0.00 11.33

Total 98.79 37.33 97.65 8.52 18.62 0.00 0.00


TSF balance (in ML)

Mon

ths

of

oper

atio

n

Dire

ct ra

infa

ll

TSF

runo

ff w

ater

Evap

orat

ion

Entra

inm

ent i

n ta

ils

Proc

ess

inflo

w

TSF

deca

nt w

ater

to

mak

e up

DM

S po

sses

sing

Inv

en

tory

Tails

pro

duct

ion

TSF

stor

age

avai

labi

lity

Con

tinge

ncy

wat

er

stor

age

if re

quire

d

0

0.00 515.00 515.00

1 0.01 0.05 0.06 0.00 0.00 0.00 0.00 0.00 515.00 515.00

2 0.04 0.21 0.26 0.00 0.00 0.00 0.00 0.00 515.00 515.00

3 1.12 5.30 3.24 0.00 0.00 0.00 0.00 0.00 515.00 515.00

4 2.43 11.54 2.85 0.00 0.00 0.00 0.00 0.00 515.00 515.00

5 3.99 18.94 2.55 0.00 0.00 0.00 0.00 0.00 515.00 515.00

6 9.83 46.71 2.22 8.17 22.83 29.64 14.90 16.97 498.03 483.13

7 13.01 61.77 1.93 8.17 22.83 29.64 72.77 16.97 481.06 408.29

8 10.62 50.47 2.39 7.38 20.62 26.77 117.94 15.33 465.73 347.79

9 9.69 46.03 3.23 7.91 22.09 28.68 155.93 16.43 449.30 293.37

10 3.44 16.33 4.51 7.91 22.09 28.68 156.70 16.43 432.88 276.18

11 0.67 3.20 4.49 8.17 22.83 29.64 141.10 16.97 415.90 274.80

12 0.04 0.20 4.59 7.91 22.09 28.68 122.26 16.43 399.48 277.22

13 0.01 0.05 4.68 8.17 22.83 29.64 102.65 16.97 382.51 279.85

14 0.04 0.21 4.47 8.17 22.83 29.64 83.45 16.97 365.53 282.08

15 1.12 5.30 4.21 7.91 22.09 28.68 69.78 16.43 349.11 279.32

16 2.43 11.54 3.51 8.17 22.83 29.64 63.54 16.97 332.14 268.59

17 3.99 18.94 3.08 7.91 22.09 28.68 68.36 16.43 315.71 247.35

18 9.83 46.71 2.82 8.17 22.83 29.64 107.10 16.97 298.74 191.64

19 13.01 61.77 3.33 8.17 22.83 29.64 163.56 16.97 281.77 118.20

20 10.62 50.47 6.20 7.64 21.36 27.73 204.44 15.88 265.89 61.45

21 9.69 46.03 10.37 8.17 22.83 29.64 234.81 16.97 248.92 14.11

22 3.44 16.33 16.29 7.91 22.09 28.68 223.78 16.43 232.49 8.71

23 0.67 3.20 16.21 8.17 22.83 29.64 196.47 16.97 215.52 19.05

24 0.04 0.20 15.95 7.91 22.09 28.68 166.26 16.43 199.09 32.83

25 0.01 0.05 15.25 8.17 22.83 29.64 136.10 16.97 182.12 46.02

26 0.04 0.21 13.33 8.17 22.83 29.64 108.04 16.97 165.15 57.11

27 1.12 5.30 11.21 7.91 22.09 28.68 88.75 16.43 148.72 59.97

28 2.43 11.54 8.69 8.17 22.83 29.64 79.00 16.97 131.75 52.75

29 3.99 18.94 7.81 7.91 22.09 28.68 79.10 16.43 115.33 36.23

30 9.83 46.71 8.23 8.17 22.83 29.64 98.35 16.97 98.35 0.00

31 13.01 61.77 12.94 8.17 22.83 29.64 81.38 16.97 81.38 0.00

32 10.62 50.47 14.25 7.38 20.62 26.77 66.05 15.33 66.05 0.00

33 9.69 46.03 15.91 8.17 22.83 29.64 49.08 16.97 49.08 0.00

34 3.44 16.33 17.98 7.91 22.09 28.68 32.65 16.43 32.65 0.00

35 0.67 3.20 0.00 8.17 22.83 29.64 15.68 16.97 15.68 0.00

Total 164.65 782.07 249.02 240.41 671.63 872.02 499.32


Appendix C. Water balance modelling results for successive dry years

scenario


Mon

ths

of

oper

atio

n

Gro

und

wat

er

Inflo

w to

pit

Rai

nfal

l to

pit

Dire

ct ra

infa

ll

Eva

pora

tion

+ S

tand

pipe

loss

Dus

t Sup

pres

sion

D

MS

wat

er

mak

eup

Cru

shin

g &

S

cree

ning

E

nviro

Rel

ease

Inv

en

tory

0

0.00

1 16.83 0.00 0.00 8.71 8.12 0.00 0.00 0.00 0.00

2 37.93 0.00 0.00 9.53 27.90 0.00 0.00 0.00 0.49

3 44.52 0.00 0.00 9.87 27.00 0.00 0.00 0.00 8.14

4 46.29 0.24 0.36 10.51 27.90 0.00 0.00 0.00 16.63

5 48.21 2.24 3.42 9.27 27.00 0.00 0.00 34.23 0.00

6 49.26 3.38 5.16 8.86 31.62 1.84 1.75 13.74 0.00

7 49.80 6.69 10.20 8.40 31.62 0.00 1.75 24.92 0.00

8 54.47 5.40 8.24 7.19 28.56 0.00 1.58 30.79 0.00

9 64.42 4.04 6.17 7.84 30.60 0.00 1.69 34.50 0.00

10 66.25 0.45 0.69 8.30 30.60 10.85 1.69 0.00 15.94

11 76.37 0.00 0.00 8.63 31.62 18.09 1.75 0.00 32.21

12 73.22 0.00 0.00 8.35 30.60 17.75 1.69 0.00 47.05

13 78.52 0.00 0.00 8.71 31.62 18.59 1.75 0.00 64.91

14 75.61 0.00 0.00 9.53 31.62 18.75 1.75 0.00 78.86

15 76.93 0.00 0.00 9.87 30.60 18.53 1.69 0.00 95.10

16 77.86 0.24 0.36 10.51 31.62 17.58 1.75 0.00 112.10

17 74.36 2.24 3.42 9.27 30.60 9.26 1.69 129.60 11.70

18 71.62 3.38 5.16 8.86 31.62 5.19 1.75 44.45 0.00

19 67.32 6.69 10.20 8.40 31.62 0.00 1.75 42.44 0.00

20 66.26 5.40 8.24 7.23 29.58 0.00 1.64 41.46 0.00

21 64.01 4.04 6.17 7.88 31.62 0.00 1.75 32.97 0.00

22 57.93 0.45 0.69 8.30 30.60 11.89 1.69 0.00 6.57

23 61.86 0.00 0.00 8.63 31.62 18.09 1.75 0.00 8.35

24 58.85 0.00 0.00 8.35 30.60 17.75 1.69 0.00 8.82

25 59.82 0.00 0.00 8.71 31.62 18.59 1.75 0.00 7.97

26 55.93 0.00 0.00 9.53 31.62 18.75 1.75 0.00 2.24

27 56.79 0.00 0.00 9.87 28.93 18.53 1.69 0.00 0.00

28 55.28 0.24 0.36 10.51 26.05 17.58 1.75 0.00 0.00

29 52.15 2.24 3.42 9.27 30.60 9.26 1.69 6.99 0.00

30 51.61 3.38 5.16 8.86 13.02 5.19 1.75 31.33 0.00

31 50.27 6.69 10.20 8.40 13.02 0.00 1.75 43.99 0.00

32 48.93 5.40 8.24 7.19 11.76 0.00 1.58 42.05 0.00

33 47.59 4.04 6.17 7.88 13.02 0.00 1.75 35.15 0.00

34 46.25 0.45 0.69 8.30 12.60 11.37 1.69 0.00 13.41

35 44.91 0.00 0.00 8.63 13.02 14.98 1.75 0.00 19.94

Total 2028.24 67.33 102.73 308.15 931.72 298.42 51.44 588.62



Mon

ths

of o

pera

tion

Dire

ct ra

infa

ll

Evap

orat

ion

+ St

andp

ipe

loss

TSF

Dis

char

ge to

M

WD

2

DM

S w

ater

mak

eup

Inv

en

tory

0

0.0

1 0.00 0.00 0.00 0.00 0.00

2 0.00 0.00 0.00 0.00 0.00

3 0.00 0.00 0.00 0.00 0.00

4 0.10 0.10 0.00 0.00 0.00

5 0.89 0.89 5.24 0.00 5.24

6 1.35 3.23 0.00 3.36 0.00

7 2.66 2.66 7.88 0.00 7.88

8 2.15 2.70 4.18 0.00 11.51

9 1.61 2.93 0.00 2.16 8.03

10 0.18 3.05 0.00 5.15 0.00

11 0.00 0.00 0.00 0.00 0.00

12 0.00 0.00 0.00 0.00 0.00

13 0.00 0.00 0.00 0.00 0.00

14 0.00 0.00 0.00 0.00 0.00

15 0.00 0.00 0.00 0.00 0.00

16 0.10 0.10 0.00 0.00 0.00

17 0.89 0.89 0.00 0.00 0.00

18 1.35 1.35 0.00 0.00 0.00

19 2.66 2.66 7.88 0.00 7.88

20 2.15 2.74 3.70 0.00 10.99

21 1.61 2.97 0.00 2.65 6.98

22 0.18 3.05 0.00 4.11 0.00

23 0.00 0.00 0.00 0.00 0.00

24 0.00 0.00 0.00 0.00 0.00

25 0.00 0.00 0.00 0.00 0.00

26 0.00 0.00 0.00 0.00 0.00

27 0.00 0.00 0.00 0.00 0.00

28 0.10 0.10 0.00 0.00 0.00

29 0.89 0.89 0.00 0.00 0.00

30 1.35 1.35 0.00 0.00 0.00

31 2.66 2.66 7.88 0.00 7.88

32 2.15 2.70 4.18 0.00 11.51

33 1.61 2.97 0.00 2.65 7.50

34 0.18 3.05 0.00 4.63 0.00

35 0.00 0.00 0.00 0.00 0.00

Total 26.80 43.05 40.95 24.70



Mon

ths

of o

pera

tion

Dire

ct ra

infa

ll

Inflo

w fr

om O

HD

&

Min

e Si

te D

am

Evap

orat

ion

+ St

andp

ipe

loss

Adm

inis

tratio

n &

ablu

tion

Dus

t sup

pres

sion

D

MS

wat

er m

akeu

p

Cru

shin

g &

Scre

enin

g Inv

en

tory

0 0.0

1 0.00 23.21 3.19 0.25 19.78 0.00 0.00 0.00

2 0.00 3.65 3.40 0.25 0.00 0.00 0.00 0.00

3 0.00 3.70 3.46 0.24 0.00 0.00 0.00 0.00

4 0.10 3.81 3.66 0.25 0.00 0.00 0.00 0.00

5 0.89 2.65 3.31 0.24 0.00 0.00 0.00 0.00

6 1.35 2.13 3.23 0.25 0.00 0.00 0.00 0.00

7 2.66 0.69 3.11 0.25 0.00 0.00 0.00 0.00

8 2.15 0.78 2.70 0.22 0.00 0.00 0.00 0.00

9 1.61 1.56 2.93 0.24 0.00 0.00 0.00 0.00

10 0.18 3.11 3.05 0.24 0.00 0.00 0.00 0.00

11 0.00 3.42 3.17 0.25 0.00 0.00 0.00 0.00

12 0.00 3.30 3.06 0.24 0.00 0.00 0.00 0.00

13 0.00 3.44 3.19 0.25 0.00 0.00 0.00 0.00

14 0.00 3.65 3.40 0.25 0.00 0.00 0.00 0.00

15 0.00 3.70 3.46 0.24 0.00 0.00 0.00 0.00

16 0.10 3.81 3.66 0.25 0.00 0.00 0.00 0.00

17 0.89 2.65 3.31 0.24 0.00 0.00 0.00 0.00

18 1.35 2.13 3.23 0.25 0.00 0.00 0.00 0.00

19 2.66 0.69 3.11 0.25 0.00 0.00 0.00 0.00

20 2.15 0.82 2.74 0.23 0.00 0.00 0.00 0.00

21 1.61 1.61 2.97 0.25 0.00 0.00 0.00 0.00

22 0.18 3.11 3.05 0.24 0.00 0.00 0.00 0.00

23 0.00 3.42 3.17 0.25 0.00 0.00 0.00 0.00

24 0.00 3.30 3.06 0.24 0.00 0.00 0.00 0.00

25 0.00 3.44 3.19 0.25 0.00 0.00 0.00 0.00

26 0.00 3.65 3.40 0.25 0.00 0.00 0.00 0.00

27 0.00 5.37 3.46 0.24 1.67 0.00 0.00 0.00

28 0.10 9.38 3.66 0.25 5.57 0.00 0.00 0.00

29 0.89 2.65 3.31 0.24 0.00 0.00 0.00 0.00

30 1.35 2.13 3.23 0.25 0.00 0.00 0.00 0.00

31 2.66 0.69 3.11 0.25 0.00 0.00 0.00 0.00

32 2.15 0.78 2.70 0.22 0.00 0.00 0.00 0.00

33 1.61 1.61 2.97 0.25 0.00 0.00 0.00 0.00

34 0.18 3.11 3.05 0.24 0.00 0.00 0.00 0.00

35 0.00 3.42 3.17 0.25 0.00 0.00 0.00 0.00

Total 26.80 120.61 111.87 8.52 27.02 0.00 0.00


TSF balance (in ML)

Mon

ths

of

oper

atio

n

Dire

ct ra

infa

ll

TSF

runo

ff w

ater

Evap

orat

ion

Entra

inm

ent i

n ta

ils

Proc

ess

inflo

w

TSF

deca

nt w

ater

to

mak

e up

DM

S po

sses

sing

Inv

en

tory

Tails

pro

duct

ion

TSF

stor

age

avai

labi

lity

Con

tinge

ncy

wat

er

stor

age

if re

quire

d

0 0.00 515.00 515.00

1 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 515.00 515.00

2 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 515.00 515.00

3 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 515.00 515.00

4 0.16 0.75 0.91 0.00 0.00 0.00 0.00 0.00 515.00 515.00

5 1.49 7.07 3.31 0.00 0.00 0.00 0.00 0.00 515.00 515.00

6 2.24 10.66 3.11 8.17 22.83 24.45 0.00 16.97 498.03 498.03

7 4.43 21.07 2.64 8.17 22.83 29.64 0.00 16.97 481.06 481.06

8 3.58 17.02 2.89 7.38 20.62 26.77 0.00 15.33 465.73 465.73

9 2.68 12.74 3.09 7.91 22.09 26.52 0.00 16.43 449.30 449.30

10 0.30 1.42 3.21 7.91 22.09 12.69 0.00 16.43 432.88 432.88

11 0.00 0.00 3.11 8.17 22.83 11.55 0.00 16.97 415.90 415.90

12 0.00 0.00 3.25 7.91 22.09 10.94 0.00 16.43 399.48 399.48

13 0.00 0.00 3.61 8.17 22.83 11.05 0.00 16.97 382.51 382.51

14 0.00 0.00 3.77 8.17 22.83 10.89 0.00 16.97 365.53 365.53

15 0.00 0.00 4.03 7.91 22.09 10.15 0.00 16.43 349.11 349.11

16 0.16 0.75 3.51 8.17 22.83 12.06 0.00 16.97 332.14 332.14

17 1.49 7.07 3.31 7.91 22.09 19.43 0.00 16.43 315.71 315.71

18 2.24 10.66 3.11 8.17 22.83 24.45 0.00 16.97 298.74 298.74

19 4.43 21.07 2.64 8.17 22.83 29.64 0.00 16.97 281.77 281.77

20 3.58 17.02 2.89 7.64 21.36 27.73 0.00 15.88 265.89 265.89

21 2.68 12.74 3.09 8.17 22.83 26.99 0.00 16.97 248.92 248.92

22 0.30 1.42 3.21 7.91 22.09 12.69 0.00 16.43 232.49 232.49

23 0.00 0.00 3.11 8.17 22.83 11.55 0.00 16.97 215.52 215.52

24 0.00 0.00 3.25 7.91 22.09 10.94 0.00 16.43 199.09 199.09

25 0.00 0.00 3.61 8.17 22.83 11.05 0.00 16.97 182.12 182.12

26 0.00 0.00 3.77 8.17 22.83 10.89 0.00 16.97 165.15 165.15

27 0.00 0.00 4.03 7.91 22.09 10.15 0.00 16.43 148.72 148.72

28 0.16 0.75 3.51 8.17 22.83 12.06 0.00 16.97 131.75 131.75

29 1.49 7.07 3.31 7.91 22.09 19.43 0.00 16.43 115.33 115.33

30 2.24 10.66 3.11 8.17 22.83 24.45 0.00 16.97 98.35 98.35

31 4.43 21.07 2.64 8.17 22.83 29.64 0.00 16.97 81.38 81.38

32 3.58 17.02 2.89 7.38 20.62 26.77 0.00 15.33 66.05 66.05

33 2.68 12.74 3.09 8.17 22.83 26.99 0.00 16.97 49.08 49.08

34 0.30 1.42 3.21 7.91 22.09 12.69 0.00 16.43 32.65 32.65

35 0.00 0.00 0.00 8.17 22.83 14.66 0.00 16.97 15.68 15.68

Total 44.67 212.17 98.20 240.41 671.63 548.90 499.32


Appendix D. Water balance modelling results for successive average

years scenario with no dust suppression in Jan and Feb


Mon

ths

of

oper

atio

n

Gro

und

wat

er

Inflo

w to

pit

Rai

nfal

l to

pit

Dire

ct ra

infa

ll

Eva

pora

tion

+ S

tand

pipe

loss

Dus

t Sup

pres

sion

D

MS

wat

er

mak

eup

Cru

shin

g &

S

cree

ning

E

nviro

Rel

ease

Inv

en

tory

0 0.00

1 16.83 0.00 0.00 8.19 8.64 0.00 0.00 0.00 0.00

2 37.93 0.00 0.00 8.76 27.90 0.00 0.00 0.00 1.28

3 44.52 0.22 0.33 9.06 27.00 0.00 0.00 0.00 10.28

4 46.29 1.56 2.38 9.56 27.90 0.00 0.00 0.00 23.06

5 48.21 4.18 6.38 8.48 27.00 0.00 0.00 46.36 0.00

6 49.26 6.86 10.47 7.99 31.62 0.00 1.75 25.23 0.00

7 49.80 11.60 17.69 7.23 0.00 0.00 1.75 70.11 0.00

8 54.47 8.84 13.49 6.18 0.00 0.00 1.58 69.04 0.00

9 64.42 8.72 13.30 7.03 30.60 0.00 1.69 47.12 0.00

10 66.25 1.95 2.97 7.53 30.60 0.00 1.69 0.00 31.34

11 76.37 0.08 0.12 8.00 31.62 0.00 1.75 0.00 66.54

12 73.22 0.00 0.00 7.73 30.60 0.00 1.69 0.00 99.74

13 78.52 0.00 0.00 8.19 31.62 0.00 1.75 0.00 136.70

14 75.61 0.00 0.00 8.76 31.62 8.96 1.75 0.00 161.24

15 76.93 0.22 0.33 9.06 30.60 17.29 1.69 0.00 180.07

16 77.86 1.56 2.38 9.56 31.62 12.19 1.75 0.00 206.75

17 74.36 4.18 6.38 8.48 30.60 1.47 1.69 129.60 119.84

18 71.62 6.86 10.47 7.99 31.62 0.00 1.75 133.92 33.52

19 67.32 11.60 17.69 7.23 0.00 0.00 1.75 121.14 0.00

20 66.26 8.84 13.49 6.22 0.00 0.00 1.64 80.73 0.00

21 64.01 8.72 13.30 7.07 31.62 0.00 1.75 45.58 0.00

22 57.93 1.95 2.97 7.53 30.60 0.00 1.69 0.00 23.03

23 61.86 0.08 0.12 8.00 31.62 0.00 1.75 0.00 43.72

24 58.85 0.00 0.00 7.73 30.60 0.00 1.69 0.00 62.55

25 59.82 0.00 0.00 8.19 31.62 2.49 1.75 0.00 78.33

26 55.93 0.00 0.00 8.76 31.62 18.39 1.75 0.00 73.74

27 56.79 0.22 0.33 9.06 30.60 17.29 1.69 0.00 72.44

28 55.28 1.56 2.38 9.56 31.62 12.19 1.75 0.00 76.54

29 52.15 4.18 6.38 8.48 30.60 1.47 1.69 97.02 0.00

30 51.61 6.86 10.47 7.99 13.02 0.00 1.75 46.18 0.00

31 50.27 11.60 17.69 7.23 0.00 0.00 1.75 70.58 0.00

32 48.93 8.84 13.49 6.18 0.00 0.00 1.58 63.50 0.00

33 47.59 8.72 13.30 7.07 13.02 0.00 1.75 47.76 0.00

34 46.25 1.95 2.97 7.53 12.60 0.00 1.69 0.00 29.35

35 44.91 0.08 0.12 8.00 13.02 0.00 1.75 0.00 51.68

Total 2028.24 132.02 201.42 279.61 793.32 91.74 51.44 1093.89



Mon

ths

of o

pera

tion

Dire

ct ra

infa

ll

Evap

orat

ion

+ St

andp

ipe

loss

TSF

Dis

char

ge to

M

WD

2

DM

S w

ater

mak

eup

Inv

en

tory

0 0.0

1 0.00 0.00 0.00 0.00 0.00

2 0.00 0.00 0.00 0.00 0.00

3 0.09 0.09 0.00 0.00 0.00

4 0.62 0.62 2.79 0.00 2.79

5 1.67 3.10 13.03 0.00 14.39

6 2.73 3.00 8.59 0.00 22.70

7 4.62 2.80 27.04 0.00 51.56

8 3.52 2.44 6.36 0.00 59.00

9 3.47 2.72 0.00 0.00 59.75

10 0.78 2.85 1.33 0.00 59.00

11 0.03 3.00 0.00 1.67 54.36

12 0.00 2.90 0.00 17.52 33.93

13 0.00 3.05 0.00 18.25 12.63

14 0.00 3.20 0.00 9.43 0.00

15 0.09 0.09 0.00 0.00 0.00

16 0.62 0.62 0.00 0.00 0.00

17 1.67 1.67 0.00 0.00 0.00

18 2.73 2.73 8.59 0.00 8.59

19 4.62 2.80 27.04 0.00 37.44

20 3.52 2.48 17.18 0.00 55.66

21 3.47 2.76 2.63 0.00 59.00

22 0.78 2.85 2.08 0.00 59.00

23 0.03 3.00 0.00 16.78 39.24

24 0.00 2.90 0.00 17.52 18.82

25 0.00 3.05 0.00 15.77 0.00

26 0.00 0.00 0.00 0.00 0.00

27 0.09 0.09 0.00 0.00 0.00

28 0.62 0.62 0.00 0.00 0.00

29 1.67 1.67 0.00 0.00 0.00

30 2.73 2.73 8.59 0.00 8.59

31 4.62 2.80 27.04 0.00 37.44

32 3.52 2.44 17.66 0.00 56.18

33 3.47 2.76 2.11 0.00 59.00

34 0.78 2.85 2.08 0.00 59.00

35 0.03 3.00 0.00 14.64 41.39

Total 52.55 73.71 174.13 111.58



Mon

ths

of o

pera

tion

Dire

ct ra

infa

ll

Inflo

w fr

om O

HD

&

Min

e Si

te D

am

Evap

orat

ion

+ St

andp

ipe

loss

Adm

inis

tratio

n &

ablu

tion

Dus

t sup

pres

sion

D

MS

wat

er m

akeu

p

Cru

shin

g &

Scre

enin

g Inv

en

tory

0 0.0

1 0.00 22.56 3.05 0.25 19.26 0.00 0.00 0.00

2 0.00 3.45 3.20 0.25 0.00 0.00 0.00 0.00

3 0.09 3.40 3.25 0.24 0.00 0.00 0.00 0.00

4 0.62 3.04 3.41 0.25 0.00 0.00 0.00 0.00

5 1.67 1.67 3.10 0.24 0.00 0.00 0.00 0.00

6 2.73 0.52 3.00 0.25 0.00 0.00 0.00 0.00

7 4.62 0.00 2.80 0.25 0.00 0.00 0.00 1.56

8 3.52 0.00 2.44 0.22 0.00 0.00 0.00 2.42

9 3.47 0.00 2.72 0.24 0.00 0.00 0.00 2.93

10 0.78 0.00 2.85 0.24 0.00 0.00 0.00 0.61

11 0.03 2.61 3.00 0.25 0.00 0.00 0.00 0.00

12 0.00 3.14 2.90 0.24 0.00 0.00 0.00 0.00

13 0.00 3.30 3.05 0.25 0.00 0.00 0.00 0.00

14 0.00 3.45 3.20 0.25 0.00 0.00 0.00 0.00

15 0.09 3.40 3.25 0.24 0.00 0.00 0.00 0.00

16 0.62 3.04 3.41 0.25 0.00 0.00 0.00 0.00

17 1.67 1.67 3.10 0.24 0.00 0.00 0.00 0.00

18 2.73 0.52 3.00 0.25 0.00 0.00 0.00 0.00

19 4.62 0.00 2.80 0.25 0.00 0.00 0.00 1.56

20 3.52 0.00 2.48 0.23 0.00 0.00 0.00 2.37

21 3.47 0.00 2.76 0.25 0.00 0.00 0.00 2.83

22 0.78 0.00 2.85 0.24 0.00 0.00 0.00 0.52

23 0.03 2.71 3.00 0.25 0.00 0.00 0.00 0.00

24 0.00 3.14 2.90 0.24 0.00 0.00 0.00 0.00

25 0.00 3.30 3.05 0.25 0.00 0.00 0.00 0.00

26 0.00 3.45 3.20 0.25 0.00 0.00 0.00 0.00

27 0.09 3.40 3.25 0.24 0.00 0.00 0.00 0.00

28 0.62 3.04 3.41 0.25 0.00 0.00 0.00 0.00

29 1.67 1.67 3.10 0.24 0.00 0.00 0.00 0.00

30 2.73 0.52 3.00 0.25 0.00 0.00 0.00 0.00

31 4.62 0.00 2.80 0.25 0.00 0.00 0.00 1.56

32 3.52 0.00 2.44 0.22 0.00 0.00 0.00 2.42

33 3.47 0.00 2.76 0.25 0.00 0.00 0.00 2.88

34 0.78 0.00 2.85 0.24 0.00 0.00 0.00 0.56

35 0.03 2.66 3.00 0.25 0.00 0.00 0.00 0.00

Total 52.55 79.66 104.43 8.52 19.26 0.00 0.00


TSF balance (in ML)

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0.00 515.00 515.00

1 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 515.00 515.00

2 0.00 0.01 0.01 0.00 0.00 0.00 0.00 0.00 515.00 515.00

3 0.14 0.68 0.83 0.00 0.00 0.00 0.00 0.00 515.00 515.00

4 1.04 4.92 3.17 0.00 0.00 0.00 0.00 0.00 515.00 515.00

5 2.78 13.19 2.93 0.00 0.00 0.00 0.00 0.00 515.00 515.00

6 4.55 21.62 2.61 8.17 22.83 29.64 0.00 16.97 498.03 498.03

7 7.69 36.54 2.20 8.17 22.83 29.64 0.00 16.97 481.06 481.06

8 5.87 27.86 2.54 7.38 20.62 26.77 11.30 15.33 465.73 454.43

9 5.78 27.46 2.76 7.91 22.09 28.68 27.28 16.43 449.30 422.02

10 1.29 6.14 3.00 7.91 22.09 28.68 15.89 16.43 432.88 416.99

11 0.05 0.24 2.86 8.17 22.83 27.97 0.00 16.97 415.90 415.90

12 0.00 0.00 3.02 7.91 22.09 11.16 0.00 16.43 399.48 399.48

13 0.00 0.00 3.27 8.17 22.83 11.39 0.00 16.97 382.51 382.51

14 0.00 0.01 3.42 8.17 22.83 11.25 0.00 16.97 365.53 365.53

15 0.14 0.68 3.62 7.91 22.09 11.39 0.00 16.43 349.11 349.11

16 1.04 4.92 3.17 8.17 22.83 17.45 0.00 16.97 332.14 332.14

17 2.78 13.19 2.93 7.91 22.09 27.21 0.00 16.43 315.71 315.71

18 4.55 21.62 2.61 8.17 22.83 29.64 0.00 16.97 298.74 298.74

19 7.69 36.54 2.20 8.17 22.83 29.64 0.00 16.97 281.77 281.77

20 5.87 27.86 2.54 7.64 21.36 27.73 0.00 15.88 265.89 265.89

21 5.78 27.46 2.75 8.17 22.83 29.64 12.88 16.97 248.92 236.04

22 1.29 6.14 2.98 7.91 22.09 28.68 0.75 16.43 232.49 231.74

23 0.05 0.24 2.84 8.17 22.83 12.86 0.00 16.97 215.52 215.52

24 0.00 0.00 3.02 7.91 22.09 11.16 0.00 16.43 199.09 199.09

25 0.00 0.00 3.27 8.17 22.83 11.39 0.00 16.97 182.12 182.12

26 0.00 0.01 3.42 8.17 22.83 11.25 0.00 16.97 165.15 165.15

27 0.14 0.68 3.62 7.91 22.09 11.39 0.00 16.43 148.72 148.72

28 1.04 4.92 3.17 8.17 22.83 17.45 0.00 16.97 131.75 131.75

29 2.78 13.19 2.93 7.91 22.09 27.21 0.00 16.43 115.33 115.33

30 4.55 21.62 2.61 8.17 22.83 29.64 0.00 16.97 98.35 98.35

31 7.69 36.54 2.20 8.17 22.83 29.64 0.00 16.97 81.38 81.38

32 5.87 27.86 2.54 7.38 20.62 26.77 0.00 15.33 66.05 66.05

33 5.78 27.46 2.75 8.17 22.83 29.64 13.40 16.97 49.08 35.68

34 1.29 6.14 4.20 7.91 22.09 28.68 0.06 16.43 32.65 32.59

35 0.05 0.24 0.00 8.17 22.83 15.00 0.00 16.97 15.68 15.68

Total 87.58 415.99 91.96 240.41 671.63 668.69 499.32

EnviroConsult Australia Pty Ltd 45 Malak Crescent Malak, NT, 0812 F: +61 (0)4 7519 8875 [email protected]

RELIANCE, USES, and LIMITATIONS

This document is copyright and is to be used only for its intended purpose by the intended recipient and is not to be copied or used in any other way. The document may be relied upon for its intended purpose within the limits of the following disclaimer.

This document and analysis are based on the information available to EnviroConsult Australia Pty Ltd at the time of preparation. EnviroConsult Australia Pty Ltd accepts responsibility for the document to the extent that the information was sufficient and accurate at the time of preparation. EnviroConsult Australia Pty Ltd does not take responsibility for errors and omissions due to incorrect information or information not available at the time of preparation of the proposal and any initial analysis undertaken.

Description Author Checked by Approved for Issue

Name Signature Date

Draft Mike Liu Ken Evans Ken Evans

04/10/2018

Revision 1 Mike Liu Ken Evans

17/10/2018

Final Mike Liu Ken Evans

25/10/2018

Supplementary Mike Liu Ken Evans Ken Evans

07/03/2019


APPENDIX B INDEPENDENT REVIEWER BIOGRAPHIES

Rohan Ash

Principal environmental engineer with 30 years’ experience as an environmental manager, regulator, consultant and expert advisor to industry and government. Rohan is an Environmental Auditor (Industrial Facilities) appointed by EPA Victoria. He is also a ‘Qualified Person’ pursuant to the Waste Management and Pollution Control Act to perform environmental audits in the NT.

He specialises in:

Environmental impact and risk assessments

EMS, environmental management plans, monitoring programs and performance reporting

Environmental audits of industrial facilities, landfills, wastewater treatment plants, water recycling schemes, mines, quarries and construction sites

Wastewater treatment and water quality management

Water use efficiency, water balances and recycling strategies

Land capability, erosion control, groundwater and catchment management

Statutory approvals, licensing, compliance strategies, regulator/stakeholder liaison

Rohan is regularly sought after to provide these services by a wide range of industries including water, power, landfills, construction, ports, food and other manufacturing businesses, agriculture, industry associations, research bodies and government agencies (federal, state, territory and local). Rohan has conducted a number of audits and independent OEMP and WMP reviews in the NT including for INPEX LNG plant at Bladin Point, Port Melville and AACo abattoir.

Dr Bill Howcroft

Principal hydrogeologist with more than 20 years’ experience conducting hydrogeologic and environmental investigations across Australia including within the Northern Territory and Victoria.

He holds Bachelor's, Master's and PhD degrees in the Geology, Geography and Hydrogeology, respectively and has published scientific articles in internationally recognized, peer-reviewed journals examining groundwater-surface water interaction using aqueous geochemistry and stable and radioactive isotopes.

Dr Howcroft has been involved in numerous mining-related projects, including the development of a new TSF for BHP Billiton on Groote Eylandt, investigation of caustic impacts to groundwater at Rio Tinto's facility in Alcan Gove, geochemical and groundwater transport modelling for Crocodile Gold at its facilities near Pine Creek, and the preparation of a Water Management Plan (WMP) for HNC (Australia) at its Brown's Oxide Mine near Bachelor. Bill was also key part of the OTE’s audit team providing expert hydrogeological review for the AACo’s Livingstone beef abattoir as part of environmental and NTEPA licence compliance audits, and Operational EMP and WMP reviews.

Since 2015, Dr Howcroft has undertaken expert hydrogeological and groundwater audits as part of Rohan’s expert support team for biennial statutory environmental audits of the leached ash landfill within the overburden dump at AGL’s Loy Yang coal fired power station and mine. Rohan and Bill are currently engaged by AGL to conduct this year’s audit.


APPENDIX C INDEPENDENT PEER REVIEW COMMENTS

Email: [email protected] | 0407 349 172| ABN 19 613 982 308 www.ot-environmental.com.au

4 March 2019

Emma Smith EcOz Pty Ltd. Winlow House, 3rd Floor 75 Woods Street Darwin, NT 0800 Dear Emma,

Re: Independent Peer Review of Water Management Plan (WMP) for the Grants Lithium Project, prepared by EcOz Pty Ltd. (EcOz) on behalf of Core Exploration Limited (Core), Northern Territory, Australia, October 2018. Please find below the results of the Out-Task Environmental (OTE) independent peer review of the above referenced WMP for the Grants Lithium Project.

1. Objective

The objective of this WMP review is to respond to the following instruction contained on page 14 of the NTEPA Terms of Reference (ToR) for the preparation of an Environmental Impact Statement (EIS), Grants Lithium Project, CORE Exploration Ltd, dated August 2018:

“The Water Management Plan is to be peer reviewed by an independent, third party. The NT EPA expects the peer reviewer to be recognised by industry as a senior practitioner and be independent from the Proponent/principal consultant and the proposal. The reviewer should demonstrate independence by acting objectively, disclose interests as appropriate and be free from conflicts of interest that may arise in relation to the engagement”.

Out-Task Environmental (OTE) was engaged by EcOz (principal consultant for the Proponent) to conduct an independent peer review of the Grants Lithium Project WMP. This review was undertaken by the following OTE principal experts:

• Rohan Ash, Principal Environmental Engineer (Appointed pursuant to the Environmental Protection Act 1970 (Victoria) and Qualified Person pursuant to the NT Waste Management and Pollution Control Act; and

• Dr Bill Howcroft, Principal Hydrogeologist, and expert support team member approved by EPA Victoria to support Rohan in audit work

Bio-sketches for Rohan and Bill are provided in Attachment A.

It is understood that all reviewer comments and recommendations will be addressed in an updated WMP to be submitted as part of the Supplementary EIS.

I, Rohan Ash, declare that OTE and its staff member do not have any business, financial or other interests in the Grants Lithium Project and is independent of the Proponent and its consultants. There are no conflicts of interest associated with this engagement.

Peer Review of Grants Lithium Project Water Management Plan 2018 Page|2

2. Scope of Work

The Scope of Work conducted by OTE for this WMP review consisted of the following:

(i) Ensuring that the WMP conforms to the WMP content requirements defined in Section 6 of the Mining Management Plan (MMP) Structure Guide for Mining Operations.

(ii) Independent peer review of the WMP document, including ancillary documents that were utilised in preparation of the WMP. For this review, OTE reviewed the following documents: • Water Management Plan (WMP), EcOz (2018a); • Water Balance Report (Appendix J to the WMP), EcOz (2018b); • Erosion and Sediment Control Plan (ESCP), EcOz (2018c); • Development of a Groundwater Model for the Grants Lithium Project, Final Version 1.0,

CloudGMS (2018); • Project 1: Existing Hydrological Condition and Hydrology Model Calibration, EnviroConsult

(2018a); • Project 2: Mining Lease 31726 and Observation Hill Dam Water Balance, Report ECA-HA-

0004-02, EnviroConsult (2018b); • Project 3: Mining Lease 31726 Flood Inundation Study, EnviroConsult (2018c); • Finniss Lithium Project, Groundwater Investigation Report, GHD (2017a); • Finniss Lithium Project, Aquatic Ecology Baseline Monitoring, GHD (2017b), and • Notice of Intent, Grants Lithium Project, Bynoe Harbour, Northern Territory, EcOz (2017).

(iii) Ensuring that the Water Balance is in conformance with the Minerals Council of Australia

Water Accounting Framework (MCA WAF) (iv) Assessment and Reporting

This letter report provides a summary of the findings of the review of the WMP and its ancillary documents, a statement of conformance of the WMP to Section 6 of the MMP, a statement of conformance on the Water Balance Report to MCA WAF, as well as conclusions and recommendations.


3. Summary of Findings

3.1. Conformance of the WMP with Section 6 of the MMP Structure Guide WMP requirements with respect to the MMP Structure Guide The primary purpose of a Mining Management Plan (MMP) is to formalise the actions to be taken and strategies to be implemented that will manage impacts to the environment to acceptable and sustainable limits over both the short- and long-term. A key component of an MMP is the Water Management Plan (WMP), which covers all surface and groundwater on a mine lease, as well as the receiving environment both up- and down-gradient of the lease. In addition, the WMP covers all interactions of those waters with activities related to the mine and its infrastructure, and how those interactions might affect water quality, quantity and/or timing. Towards these purposes, Section 6 of the MMP Structure Guide provides specific requirements for a WMP.

Summary of Findings

A tabulated statement of conformance with Section 6 of the MMP Structure Guide is provided as Attachment B. Overall, OTE’s review indicates that the WMP generally complies with the requirements of the MMP Structure Guide. There are exceptions, however, which comprise the following:

a) Section 6.1 of the MMP Structure Guide specifies that a water balance must be included, and that the water balance “must include consideration of the full range of climatic conditions that the site may experience, i.e. successive drier than average seasons and successive wetter than average wet-seasons and sensitivity to extreme events”. In the Water Balance (EcOz, 2018b; Appendix A to the WMP) report prepared for Grants Lithium WMP, 50th percentile climate (precipitation and evaporation) data from the Darwin Airport weather station were utilised. However, the given Water Balance does not account for successive dry or wet seasons, nor does it account for extreme weather events.

b) As stated in Sections 6.2.2 and 6.3.2 of the MMP Structure Guide, timelines are required for the filling of information/knowledge gaps and actions and strategies to mitigate the identified risks. Timelines associated with these items are not currently outlined in the WMP.

3.2. General Comments on the Water Management Plan (WMP)

OTE has reviewed the WMP in detail and offers the following comments on individual components of the document:

Site Operations a) Section 2.1 of the WMP provides pit dimensions that differ from that outlined in the

groundwater (CloudGMS, 2018) modelling report. Specifically, the WMP states that the pit will extend vertically downward to 180 m whereas, in the groundwater modelling report, the stated pit depth will be 150 m. This discrepancy in pit depths will affect the water balance, pit inflows, and dewatering requirements and should therefore be addressed and corrected, as needed.

b) The inundation modelling report (EnviroConsult, 2018c) recommends extending the bunds and installing a culvert to prevent flood inundation on the eastern side of the mine footprint. Has this been considered? If inundation occurs in this area, how will this water be managed?


c) In Table 8-4, Row 1 of the WMP, site clearing and preparation receives a Moderate residual risk, with most of that risk being avoided provided that these works occur in the Dry season. What if the project is delayed and works then occur during the Wet season?

d) Specify the liner material and permeability for the proposed for the concentrated product pad, and also discuss leachability and risk management for potential contaminants from concentrated product.

e) Specify location of septic tank system and effluent adsorption field, and show on site plans. Also specify buffer from adsorption field to nearest drainage line. Also discuss how seepage and runoff from the adsorption field will be managed (high permeability Cenozoic sediments and laterite gravels, high water tables in wet season).

Groundwater

f) A limited number (6) of monitoring bores have been installed at the proposed mine site. None of these bores are located on the west side of the proposed mine footprint. Consequently, it is considered that the existing monitoring bore network does not provide adequate coverage to fully assess baseline conditions and therefore potential impacts to groundwater associated with the proposed mining operations. It is noted, however, that additional bore installations are proposed within the WMP and these are considered generally acceptable.

g) Hydraulic conductivity values were estimated using slug and recovery tests. The results from these tests differed in some cases by an order of magnitude. In addition, such tests examine only a small area around the screened section of the well being tested. Lastly, the methods by which hydraulic conductivity are estimated apply more to porous media than fractured rock aquifers. Consequently, the derived hydraulic values may not be truly representative of the regional aquifer(s). The results of aquifer these tests should be compared to those performed on the proposed monitoring bores (assuming that aquifer tests will be performed on the new bores).

h) The log for groundwater monitoring bore GWB01 indicates three screened zones with bottom depths of 100, 124 and 154 m, respectively. Also, the gravel pack extends across all three screened zones, i.e. there are no individual seals between the well casings. It is unclear from which well casing the groundwater samples were collected, on which well casing the aquifer tests were conducted, and from which well casing the recorded standing water levels were measured. This should be clarified and the usefulness of water quality, SWL and aquifer test data from this bore for EIS purposes discussed.

i) The groundwater modelling report should be referenced as CloudGMS (2018), not Knapton and Fulton (2018).

j) During the life of mine, it is predicted that a cone of groundwater depression will extend approximately one (1) km from the mine pit. It is also stated that “some” groundwater likely discharges to ephemeral streams to the north (Section 3.3.1, page 1-33 of the WMP) but that this drawdown will not affect groundwater levels beneath the ephemeral streams. However, this drawdown could nonetheless decrease groundwater flux into the streams as a result of reduced hydraulic gradients and a reduced recharge area. This in turn could lead to impacts to riparian vegetation and aquatic species along and within the streams. Groundwater levels within shallow bores located proximal to the streams should be monitoring before commencement of mining operation, during operations and post-closure.

k) Post-mine closure, a pit lake will form in the mining lease. This will result in a groundwater sink and, consequently, alteration, of the local flow regime. It is stated within the groundwater modelling report (and within the WMP) that no change in the water table surface is predicted at the ephemeral water courses. As above, however, this alteration to


the groundwater flow system may decrease groundwater flux into the streams as a result of a reduced hydraulic gradient and recharge areas. As in point “j)” above, groundwater levels within shallow bores located proximal to the ephemeral should be monitoring before commencement of mining operation, during operations and post-closure.

l) Rainfall and evaporation data utilised in the groundwater modelling study differ from that utilised in the Water Balance and the hydrologic studies. Ideally, and to minimise uncertainty, the same (most up to date) climatic data should be utilised in each study.

m) In Table 2-1 of the groundwater modelling report, the more permeable near-surface sediments are not considered to be a hydro-stratigraphic unit. Exclusion of this more permeable unit from the groundwater model may result in an underestimation of groundwater inflows into the mine pit, especially during the early stages of mining operations. Consider inclusion of the shallow surface sediments in the model, or otherwise justify in the text of the WMP and groundwater modelling report its exclusion from the model.

n) Future reporting should include a vertical, two-dimensional equipotential diagram, which documents equipotential gradients, stratigraphic units, bore locations, streams, and bore screen intervals. This will greatly enhance interpretation of hydrogeologic conditions.

o) The groundwater contours (and, therefore, groundwater flow direction) presented in the groundwater modelling report should be considered as approximate and preliminary only. This is due to the fact that the contours were generated from groundwater levels that were measured in a limited number (4) of monitoring bores that are screened at different depth intervals. As a result, groundwater flow direction may be more complex than that indicated.

p) Groundwater flow direction in the shallow aquifer is presently undetermined, as only two bores have been installed within this unit. The flow direction should be subject to review upon completion and monitoring of the new bores as proposed.

q) The rapid response to rainfall exhibited at monitoring bore GWB10 may be due to how the bore was constructed. This bore was installed in a swampy area. In addition, the top of the well screen is just 0.5 m below ground surface (bgs). For these reasons, the observed downward head gradient at this location might be simply due to ingress of surface water into GWB10. For this same reason too, groundwater quality results from this bore may not be truly representative of groundwater quality within the shallow aquifer. Lastly, groundwater monitoring bore GWB10 does not meet the minimum construction standards for water bores in Australia, which specifies a minimum of 1 m of casing between ground surface and the production zone being monitored. This limitation should be discussed in the WMP and associated groundwater modelling/assessment reports. In addition, GWB10 should be decommissioned and replaced with a new monitoring bore.

r) The southern boundary of the groundwater model domain (which is assumed to correspond to that of the surface water catchment divide) differs significantly from that presented in the WMP (Figure 3-2, Section 3.2). It is unclear as to which boundary is correct and how will this difference affect the estimation of groundwater inflows into the pit. Furthermore, if the catchment boundary specified in the groundwater model is correct, this suggests that the ephemeral streams located to the south of the mining lease may, in fact, be affected by mining operations. This should be clarified in the relevant documents.

s) Given a north-northeast inferred groundwater flow direction, groundwater monitoring bores GWB06 and GWB07 are located cross-gradient to the mine footprint, not upgradient, as stated in Section 3.3.1 of the WMP. This should be clarified/amended in relevant documents.

t) The upper Quaternary aquifer is poorly characterised, from both a water quality perspective, as well as from a basic hydrogeologic understanding. Only two bores have been installed within this unit, one of which is poorly constructed and the second which has been


compromised by cement. In addition, groundwater flow gradients within the shallow aquifer are poorly understood. Following installation of the proposed bores within this unit, efforts should be made to more adequately characterise groundwater flow direction and groundwater quality.

Aquatic Ecology and Groundwater Dependent Ecosystems (GDEs)

u) One sampling event was conducted (May 2017) and at an only limited number (4) of locations. Results from this sampling showed that macroinvertebrate and fish species within the streams are typical of watercourses in the NT and are relatively similar across all sites. Justification as to why one or more additional rounds of sampling are unnecessary should be provided in the WMP.

v) No sampling was conducted in the stream course located downstream of the Observation Hill Dam (OHD). Justification as to why this is unnecessary should be provided in the WMP.

w) In Section 3.3.2 of the WMP, medium potential GDEs were noted downstream of the OHD. Raising the OHD wall by 1.5 was shown to significantly reduce discharge to the drainage course downstream of the OHD. If the dam wall is to be raised, and flows decrease, how will the GDEs be affected?

Surface Water

x) In the hydrologic studies, a 2 m DEM was utilised in determining ground surface topography. Yet, within the groundwater modelling study, a different model of topography was utilised. Use of these different data sets may be the reason for the difference in the delineation of the southern catchment boundary (noted in point n above). The WMP should comment as to how this difference could affect flows, including runoff and groundwater inflows into the mine pit.

y) Raising the spillway elevation of the Observation Hill Dam (OHD) will cause inundation of lands previously above dam level. What are the implications of this inundation to aquatic ecology and native habitat around the OHD?

z) Raising the spillway height of the OHD by 1.5 m, as a potential option proposed in the WMP, will reduce flows immediately downstream of the dam by up to 69%. This value exceeds the NT Water Allocation Framework flow reduction guideline of ≤ 20%. The WMP should address possible mitigation strategies to meet this guideline.

aa) Construction of an alternative dam, e.g. the Mine Site Dam, results in a modelled decrease in flow volumes in that stream course of up to 37%. This value exceeds the NT Water Allocation Framework flow reduction guideline of ≤ 20%. The WMP should address possible mitigation strategies to meet this guideline.

bb) There is no hydrogeological data in the area of the proposed Mine Site Dam. Consequently, the impacts of this dam on the groundwater flow system is undetermined. However, it is recognised that two new monitoring bores are proposed in the area of the Mine Site Dam.

cc) Construction of the Mine Site Dam (MSD) is not considered in the CloudGSM (2018) groundwater modelling report, the Water Balance Report (EcOz, 2018b), the Inundation Study (EnviroConsult, 2018c), nor the GHD (2017b) aquatic ecology report. It is unclear what affect, if any, that construction of the MSD will have on the groundwater flow systems, the water balance, inundation and aquatic ecology. The WMP should comment on how construction of the Mine Site Dam may affect the conclusions drawn within these studies.

dd) Likewise, Mine Water Dams 1 and 2, the sedimentation ponds, and the raw water dam are also not considered in the CloudGSM (2018) groundwater modelling report, the Water Balance Report (EcOz, 2018b), the Inundation Study (EnviroConsult, 2018c), nor the GHD


(2017b) aquatic ecology report. What affect, if any, will construction and use of these storages have on the groundwater flow system, the water balance, inundation and aquatic ecology?

ee) In Table 2-1 of the WMP, it is stated that Mine Water Dam 2 acts a contingency for holding excess water dewatered from the pit to avoid “Dry” Season release from MWD1. Should this be “Wet” Season instead of Dry?

ff) In the original ToR, there was to be no discharge of water to the environment. However, within the WMP, water from Mine Water Dam 1 (MWD1) will need to be discharged at a rate not to exceed 50 L/sec. The change from the TOR to the EIS should be made transparent and reasons for the offsite discharge requirement should be explained.

gg) Section 2.4.1 should include discussion on the Sedimentation dams, including volumes and inputs.

hh) It appears that water within the sedimentation ponds may be periodically discharged to the environment. The WMP should state where this water will be discharged.

ii) Table 4-2 of the WMP appears to be missing the reduction to flows if the OHD wall is raised by 1.5 m. Only no dam and existing dam scenarios are included. This table should be revised to include the missing information.

jj) It is clear that, during the wet season, there will be a reduction in stream flow downstream of the MSD in excess of the NT Water Allocation Framework guideline of less than or equal to 20%. It is noted that these reductions “could alter the quality and/or species composition of the riparian zone” but that “the riparian habitat along this waterway is relatively sparse and not an example of a rare, highly diverse, or significant habitat for threatened species in the region”. This argument may not hold much validity and the mine proponent should seek other means by which stream flows could be maintained above the noted threshold. It is probably presumptuous to ascertain that the riparian zone is of limited ecological value.

kk) In Section 4.4 of the WMP, why is increased discharge from the Mine Site Dam (MSD) during the Wet Season decoupled from a similarly predicted reduction in discharge?

Water Quality Monitoring Program

ll) Laboratory parameters for surface water sampling locations should include total metals as well as dissolved metals.

mm) Laboratory parameters for all sampling locations, including surface water and groundwater, should include ionic balance, pH and TDS.

nn) Proposed bores GWB13 and GWB14 appear to be within the footprint of the MSD and may therefore need to be relocated.

oo) Turbidity triggers: the turbidity trigger of 75 NTU taken from the INPEX project, may not be appropriate for the Grants project. INPEX which was a very large footprint project that included wet season construction. The turbidity limit in that project was also subject to a design (major) storm event rather than a blanket trigger, and also subject to adjustment from performance review of monitoring results. Adjust the Grants project turbidity limit and assign a design storm event based the final turbidity trigger adopted by INPEX and approved by NTEPA following review of monitoring data (background and discharge) from that project.


3.3. Conformance of the Water Balance with the MCA WAF

Summary of the MCA WAF

The Terms of Reference (ToR) for the preparation of an Environmental Impact Statement (EIS) for this project dictate that the Water Balance should be prepared in accordance with the MCA WAF. The MCA WAF provides a mechanism by which sites can account for, report upon and compare site water management practices in a rigorous, consistent and unambiguous manner that can be easily understood by non-experts. Companies that utilise the WAF are encouraged, if not required, to seek continual improvement in environmental performance, as well as implement effective, transparent engagement with stakeholders.

Water accounting entails identifying, measuring, recording and importing information on water. Thus, the objectives of the WAF are to provide a: a) consistent approach for quantifying flow into, and out of, a site, based on their sources and destinations, b) consistent approach for reporting of water use, c) consistent approach in quantifying and reporting on water that is reused or recycled, and d) model for a more detailed water balance. The WAF can be applied at two levels, as an Input-Output Model, or as an Operational Model. The Input-Output Model provides a consistent approach for quantifying flows into, and out of, a facility. The Operation Model provides guidance for water processes within a facility. As the Water Balance Report covers inflows, outflows, and water used in processing, the reviewed model is regarded as applying to both purposes.

The WAF contains a certain degree of flexibility. Nonetheless, use of the WAF typically results in the generation four main components (reports): a) an Input-Output Statement, b) a Statement of Operational Efficiencies, c) an Accuracy Statement, and d) a Contextual Information Statement. The Input-Output Statement documents inflows, outflows, changes in storage and diversions, with an emphasis on water quality. The Statement of Operation Efficiencies separates flows into tasks, volume of re-used water, re-use efficiency, volume of recycled water and recycling efficiency. The Accuracy Statement lists the percentage of flows that were measured, simulated or estimated. Finally, the Contextual Information provides information on regional water resources and on the catchment in which a particular site is located. It should be noted that diversions are not included in the Input-Output Statement, as such water is not used in site operations. However, a statement of diversions should be included within the Input-Output Statement.

Three classifications of water quality are defined in the WAF: Category 1) high quality water that requires little, or only minor, treatment, Category 2) medium quality water, which may require moderate levels of treatment, and Category 3) low quality water, which requires significant levels of treatment. In addition, the MCA defines water as either “raw” or “worked”. Raw water is defined as water that is received as input, but which has not been used in a task. In contrast, worked water is water that has been used in a task.

Summary of Findings

A tabulated statement of conformance with the MCA WAF, as well as general comments, are provided in Attachment C and are summarised below:


a) A Contextual Statement is not included in the Water Balance Report. While some contextual information is provided, e.g. climate data in Section 4, the Contextual Statement should provide additional information such as site geology, hydrogeology and topography, catchment details, regional water resources, and water policy and rules applicable to the proposed mining operations. While this information is provided elsewhere in the WMP, and its ancillary documents, a standalone Contextual Statement should be included within the Water Balance report;

b) The Water Balance Model report (Section 3.1) assumes a 25-month operational life of the mine. Yet, in Section 1 of the WMP, the life of the mine is indicated to be 2 to 3 years (Section 1. WMP), a difference ranging from -1 to +11 months. The correct timeline should be made consistent in all updated reports;

c) It is noted that a variety of different climate data are used in the various technical reports, i.e. the groundwater modelling study, the hydrologic studies and, again, in the Water Balance report. Ideally, the same climate data should be used in each study as using variable data introduces unnecessary uncertainty in the results;

d) The Water Balance Model uses 50th percentile climatic data from the Darwin Airport weather station. However, the MMP Structure Guide specifically states that the Water Balance Model should include scenarios of successively drier, or wetter, than average seasons, as well as extreme weather events. This should be addressed in updated reports.

e) Figure 2 should use the colour guidelines specified in Section 3.1 of the MCA WAF. In addition, for consistency with the WMP, the Environmental Dams should be re-labelled as Sedimentation Dams. “Sedimentation” or “Environmental” should include rainfall as an input.

f) The stated pit area (12.6 hectares) in Section 5.1.1 of the Water Balance Report differs from that (14 hectares) stated in the groundwater modelling report. This inconsistency should be corrected and addressed, as pit area will directly affect the amount of rainfall entering the pit and, therefore, the amount of water that requires dewatering.

4. Conclusions and Recommendations

The following conclusions and recommendations are for consideration by the Proponent for and proposed updates to the WMP and ancillary reports as part of the Supplementary EIS:

(i) Inconsistencies in the WMP and associated documents should be corrected if possible and, if not, uncertainties associated with these inconsistencies be commented upon. These inconsistencies include variable climate data and pit dimensions (surface area and depth);

(ii) Incorporate timelines into WMP Sections 9 (Management Measures) and 11.2 (Filling Information/Knowledge Gaps) to fulfil the requirements of the MMP Structure Guide.

(iii) Groundwater monitoring bore GWB10 does not meet the minimum construction standards for water bores in Australia, which specifies a minimum of 1 m of casing between ground surface and the zone being monitored. Consequently, this bore should be decommissioned and a new bore installed with a minimum of 1 m of casing between ground surface and top of the screen.

(iv) The Water Balance Model should be amended so as to include provision for successive drier and wetter climatic conditions, as well as extreme weather events;

(v) A contextual statement should be included in the Water Balance Report;


(vi) Future reporting should include a vertical, two-dimensional equipotential diagram, which documents equipotential gradients, stratigraphic units, bore locations, streams, and bore screen intervals. This will greatly enhance interpretation of hydrogeologic conditions.

(vii) Groundwater flow direction and quality within the shallow aquifer should be added to the Information/Knowledge Gaps section (Section 11) of the WMP.

5. Limitations

Out-Task Environmental (OTE) has prepared this review document in accordance with the usual care and thoroughness of the consulting profession. It has been prepared for use by EcOz Pty Ltd (EcOz), the Proponent, NTEPA and only those parties who have been authorised in writing by OTE.

This document is based on generally accepted practices and standards at the time that it was prepared. No other warranty, expressed or implied, is made as to the professional advice included in this document. It is prepared in accordance with the Scope of Work and for the purpose outlined in this document and the OTE proposal. The methodology adopted and the sources of information used by OTE are outlined in this document.

This report is based on the information reviewed at the time of report preparation. OTE disclaims responsibility for any changes that may have occurred after the date of issue of this report.

This review and its attachments should be read in full. No responsibility is accepted for use of any part of this document in any other context or for any other purpose or by third parties. This document does not purport to give legal advice, which can only be given by qualified legal practitioners.

Should you have any questions or comments regarding the content of this letter report, please do not hesitate to contact Rohan Ash on 0407 349 172.

Dr Bill Howcroft Principal Hydrogeologist Out-Task Environmental [email protected]

4 March 2019

Rohan Ash EPA Appointed Auditor (Industrial Facilities) Appointed pursuant to the Environmental Protection Act 1970 (Victoria) Qualified Person pursuant to the NT Waste Management and Pollution Control Act Out-Task Environmental [email protected]

Attachments Attachment A: OTE Team Bio-sketches

Attachment B: Conformance Statement of WMP, Section 6 of the MMP Structure Guide.

Attachment C: Conformance Statement of the Water Balance relative to the MCA WAF.


Attachment A: OTE Team Bio-sketches Rohan Ash

Principal environmental engineer with 30 years’ experience as an environmental manager, regulator, consultant and expert advisor to industry and government. Rohan is an Environmental Auditor (Industrial Facilities) appointed by EPA Victoria. He is also a Qualified Person pursuant to the Waste Management and Pollution Control Act to perform environmental audits in the NT.

He specialises in:

• environmental impact and risk assessments, • EMS, environmental management plans, monitoring programs and performance reporting • environmental audits of industrial facilities, landfills, wastewater treatment plants, water

recycling schemes, mines, quarries and construction sites • wastewater treatment and water quality management • water use efficiency, water balances and recycling strategies • land capability, erosion control, groundwater and catchment management • statutory approvals, licensing, compliance strategies, regulator/stakeholder liaison

Rohan is regularly sought after to provide these services by a wide range of industries including water, power, landfills, construction, ports, food and other manufacturing businesses, agriculture, industry associations, research bodies and government agencies (federal, state, territory and local). Rohan has conducted a number of audits and independent OEMP and WMP reviews in the NT including for INPEX LNG plant at Bladin Point, Port Melville and AACo abattoir.

Dr Howcroft

Principal hydrogeologist with more than 20 years’ experience conducting hydrogeologic and environmental investigations across Australia including within the Northern Territory and Victoria. He holds Bachelor's, Master's and PhD degrees in the Geology, Geography and Hydrogeology, respectively and has published scientific articles in internationally recognized, peer-reviewed journals examining groundwater-surface water interaction using aqueous geochemistry and stable and radioactive isotopes. Dr Howcroft has been involved in numerous mining-related projects, including the development of a new TSF for BHP Billiton on Groote Eylandt, investigation of caustic impacts to groundwater at Rio Tinto's facility in Alcan Gove, geochemical and groundwater transport modelling for Crocodile Gold at its facilities near Pine Creek, and the preparation of a Water Management Plan (WMP) for HNC (Australia) at its Brown's Oxide Mine near Bachelor. Bill was also key part of the OTE’s audit team providing expert hydrogeological review for the AACo’s Livingstone beef abattoir as part of environmental and NTEPA licence compliance audits, and Operational EMP and WMP reviews. Since 2015, Dr Howcroft has undertaken expert hydrogeological and groundwater audits as part of Rohan’s expert support team for biennial statutory environmental audits of the leached ash landfill within the overburden dump at AGL’s Loy Yang coal fired power station and mine. Rohan and Bill are currently engaged by AGL to conduct this year’s audit.


Attachment B: Conformance Statement of WMP, Section 6 of the MMP Structure Guide.

Atta

chm

ent B

: Con

form

ance

Sta

tem

ent o

f WM

P, S

ectio

n 6

of th

e M

MP

Stru

ctur

e G

uide

.

Item

WAF

Req

uire

men

tM

etN

ot M

etRe

view

er C

omm

ents

Reco

mm

enda

tions

1Cu

rren

t Con

ditio

ns-

--

-1.

1W

ater

Bal

ance

√

The

MM

P St

ruct

ure

Guid

e sp

ecifi

es th

at th

e W

ater

Bal

ance

mus

t in

clud

e co

nsid

erat

ion

of th

e fu

ll ra

nge

of c

limat

ic c

ondi

tions

that

the

min

e sit

e m

ight

exp

erie

nce,

i.e.

succ

essiv

e dr

yer o

r w

ette

r tha

n av

erag

e ra

infa

ll, a

s wel

l as e

xtre

me

wet

her e

vent

s. H

owev

er, t

he W

ater

Bal

ance

Re

port

pre

pare

d fo

r the

WM

P on

ly c

onsid

ers 5

0th p

erce

ntile

clim

atic

con

ditio

ns.

No

prov

ision

s are

mad

e in

the

Wat

er B

alan

ce fo

r dry

er o

r wet

ter c

ondi

tions

, nor

ext

rem

e w

eath

er e

vent

s.

The

Wat

er B

alan

ce sh

ould

be

mod

ified

to in

clud

e dr

yer a

nd w

ette

r tha

n av

erag

e cl

imat

ic

cond

ition

s, a

s wel

l as e

xtre

me

wea

ther

eve

nts.

1.2

Surf

ace

Wat

er√

The

WM

P pr

ovid

es a

full

desc

riptio

n of

surf

ace

wat

er, i

nclu

ding

flow

s, v

olum

es a

nd w

ater

qu

ality

.-

1.3

Grou

ndw

ater

√Th

e W

MP

prov

ides

a c

ompr

ehen

sive

grou

ndw

ater

mod

el fo

r the

pro

pose

d m

ine

site.

-

2In

form

atio

n/Kn

owle

dge

Gap

s-

--

-2.

1Id

entif

icat

ion

of In

form

atio

n/Kn

owle

dge

Gaps

√-

Sect

ion

11.1

of t

he W

MP

iden

tifie

s Inf

orm

atio

n/Kn

owle

dge

gaps

.-

2.2

Filli

ng o

f Inf

orm

atio

n/Kn

owle

dge

Gaps

-√

Sect

ion

11.2

of t

he W

MP

iden

tifie

s act

ions

to b

e ta

ken

to fi

ll th

e id

entif

ied

Info

rmat

ion/

Know

ledg

e ga

ps. H

owev

er, a

com

mitm

ent t

o a

tim

elin

e is

also

requ

ired,

as w

ell

as in

terim

man

agem

ent s

trat

egie

s tha

t will

be

impl

emen

ted

until

such

tim

e th

e in

form

atio

n ga

ther

ing

proc

ess i

s com

plet

ed. A

tim

elin

e an

d in

terim

man

agem

ent s

trat

egie

s are

not

in

clud

ed in

Sec

tion

11.2

.

Iden

tify

the

actio

ns to

be

take

n, a

tim

elin

e by

w

hich

thos

e ac

tions

will

be

take

n, a

nd a

ny in

terim

m

anag

emen

t str

ateg

ies t

hat w

ill b

e im

plem

ente

d.

For e

xam

ple,

if d

ischa

rge

requ

irem

ents

from

M

WD1

exc

eedw

aste

disc

harg

e lic

ense

con

ditio

ns,

wha

t will

be

done

and

whe

n?

2.3

Wat

er A

ccou

nt√

-A

Wat

er A

ccou

nt h

as b

een

prov

ided

in th

e W

ater

Bal

ance

Rep

ort.

-3

Risk

Man

agem

ent

--

-3.

1Id

entif

y Ha

zard

s and

Ran

k Ri

sks

√

-

A ris

k as

sess

men

t is p

rese

nted

in S

ectio

n 8

of th

e W

MP.

How

ever

, it i

s not

ed th

at th

e as

sess

men

t onl

y id

entif

ies r

isks a

ssoc

iate

d w

ith th

e co

nstr

uctio

n an

d op

erat

ion

phas

es o

f the

pr

ojec

t. S

ectio

n 6.

3.1

of th

e M

MP

Stru

ctur

e Gu

ide

indi

cate

s tha

t the

risk

ass

esm

ent m

ust b

e gi

ven

to p

oten

tial s

hort

- and

long

-ter

m im

pact

s, in

clud

ing

min

e cl

osur

e. A

ccor

ding

to th

e W

MP,

pos

t-cl

osur

e re

quire

men

ts w

ill b

e ad

dres

sed

in fu

ture

upd

ates

of t

he W

MP.

Ensu

re th

at ri

sks f

ollo

win

g m

ine-

clos

ure

are

asse

ssed

in fu

ture

upd

ates

of t

he W

MP.

3.2

Actio

ns a

nd S

trat

egie

s in

Resp

onse

to

Iden

tifie

d Ri

sks

-√

Actio

ns a

nd st

rate

gies

to m

itiga

te id

entif

ied

risks

are

out

lined

in S

ectio

n 9

of th

e W

MP.

Ho

wev

er, a

tim

elin

e fo

r im

plem

enta

tion

of th

ese

actio

ns a

nd/o

r str

ateg

ies i

s not

incl

uded

.In

clud

e a

com

mitm

ent t

o an

impl

emen

tatio

n tim

etab

le.

4M

onito

ring

--

--

4.1

Mon

itorin

g Pr

ogra

m

√-

Sect

ion

6 of

the

MM

P St

ruct

ure

Guid

e st

ates

the

oper

ator

shou

ld e

nsur

e th

at a

co

mpr

ehen

sive

data

set h

as b

een

colle

cted

ove

r mul

tiple

seas

ons a

nd y

ears

. It i

s not

ed th

at,

to d

ate,

mon

itorin

g ha

s onl

y be

en c

ondu

cted

dur

ing

the

dry

and

wet

seas

ons o

f 201

7.

How

ever

, the

WM

P st

ates

that

furt

her m

onito

ring

will

be

cond

ucte

d pr

ior t

o co

mm

ence

men

t of

min

ing

oper

atio

ns, s

o th

is sh

ould

be

suffi

cien

t.

-

4.2

Data

Rev

iew

and

Inte

rpre

tatio

n√

--

-5

Man

agem

ent

--

--

5.1

Rem

edia

l or C

orre

ctiv

e M

anag

emen

t Ac

tions

--

Rem

edia

l or c

orre

ctiv

e m

anag

emen

t act

ions

are

out

lined

in S

ectio

n 9

of th

e W

MP.

-

6Ac

tions

Pro

pose

d O

ver t

he R

epor

ting

Perio

d an

d th

eir P

oten

tial t

o Im

pact

Wat

er

Qua

lity

√-

Sect

ion

6.6

of th

e M

MP

Stru

ctur

e Gu

ide

requ

ires t

hat d

etai

ls of

ny

actio

n pl

anne

d or

an

ticip

ated

incl

ude

com

mitm

ents

to p

rovi

de th

e De

part

men

t of P

rimar

y In

dust

ry a

nd

Reso

urce

s to

the

Wat

er M

anag

emen

t Pla

n if

and

whe

n th

ey o

ccur

.

Prov

ide

a co

mm

itmen

t with

in th

e W

MP

as to

ci

rcum

stan

ces a

nd ti

min

g of

whe

n fu

ture

s up

date

s to

the

WM

P m

ay o

ccur

.


Attachment C: Conformance Statement of the Water Balance relative to the MCA WAF.

Atta

chm

ent C

: Con

form

ance

Sta

tem

ent o

f the

Wat

er B

alan

ce re

lativ

e to

the

MCA

WAF

Item

WAF

Req

uire

men

tM

etN

ot M

etRe

view

er C

omm

ents

Reco

mm

enda

tions

1In

put-

Out

put S

tate

men

t√

1.1

Inpu

ts D

efin

ed√

Inpu

ts in

clud

e su

rfac

e flo

ws f

rom

the

OHD

and

Min

e Si

te D

am, d

irect

pre

cipi

tatio

n,

grou

ndw

ater

inflo

ws a

nd ru

noff.

Ent

rain

ed w

ater

with

in th

e or

e is

not i

nclu

ded,

but

is

assu

med

to b

e ne

glig

ible

.-

1.2

Out

puts

Def

ined

√O

utpu

ts in

clud

e w

ater

use

d fo

r dus

t sup

pres

sion,

disc

harg

e to

the

envi

ronm

ent,

evap

orat

ion

and

stan

dpip

e lo

ss, a

dmin

istra

tive

uses

and

abl

utio

n, c

rush

ings

and

scre

enin

g us

age,

task

lo

sses

, ent

rain

men

t in

prod

uct a

nd re

ject

s and

ent

rain

men

t in

taili

ngs.

Out

puts

do

not

incl

ude

seep

age

from

stor

ages

, whi

ch is

ass

umed

to b

e ne

glig

ible

.

-

1.3

Dive

rsio

ns S

peci

fed

√Di

vers

ions

com

prise

runo

ff an

d di

scha

rge

to th

e en

viro

nmen

t fro

m th

e Se

dim

enta

tion

Dam

s.

A St

atem

ent o

f Div

ersio

ns is

app

ende

d to

the

Inpu

t Out

put S

tate

men

t.-

1.4

Wat

er Q

ualit

y Cl

assif

icat

ion

√Th

ree

cate

gorie

s of w

ater

qua

lity

are

incl

uded

in th

e In

put-

Out

put S

tate

men

t.-

1.5

Stor

e Ag

greg

atio

n√

Wat

er is

cla

ssifi

ed a

s "ra

w" o

r "m

ixed

".-

1.6

Chan

ges i

n St

orag

e√

Chan

ges i

n st

orag

e ar

e sp

ecifi

ed in

the

Inpu

t-O

utpu

t Sta

tem

ent.

-2

Accu

racy

Sta

tem

ent

√Th

e Ac

cura

cy S

tate

men

t inc

lude

s flo

ws t

hat a

re m

easu

red,

sim

ulat

ed o

r est

imat

ed.

-3

Stat

emen

t of O

pera

tiona

l Effi

cien

cies

√Re

use

effic

icie

nces

for w

hen

wat

er is

use

d, o

r not

use

d, fo

r dus

t sup

pres

sion

are

estim

ated

at

39%

and

41%

, res

peci

tivel

y.-

4Co

ntex

tual

Sta

tem

ent

√A

Cont

extu

al S

tate

men

t is n

ot in

clud

ed in

the

Wat

er B

alan

ce R

epor

t.Ad

d a

Cont

extu

al S

tate

men

t to

the

Wat

er B

alan

ce

Repo

rt.

5G

ener

al C

omm

ents

5.1

Ope

ratio

nal L

ife o

f Min

e-

-O

pera

tiona

l life

of m

ine

is gi

ven

as 2

5 m

onth

s. H

owev

er, i

n th

e W

MP,

the

oper

atio

nal l

ife o

f m

ine

is gi

ven

as 2

to 3

yea

rs (2

4 to

36

mon

ths)

.

Conf

irm th

at th

e co

rrec

t life

of m

ine

is be

ing

utili

sed

and

re-r

un th

e W

ater

Bal

ance

Mod

el if

ne

cess

ary.

5.2

Clim

ate

Data

--

50th

Per

cent

ile ra

infa

ll an

d ev

apor

atio

n da

ta fr

om th

e Da

rwin

Airp

ort w

eath

er st

atio

n w

ere

utili

sed.

The

se d

ata

diffe

r fro

m th

at u

tilise

d in

the

grou

ndw

ater

and

hyd

rolo

gic

mod

ellin

g re

port

s.-

5.3

Figu

re 2

--

Figu

re 2

nee

ds to

be

mod

ified

so a

s to

inco

rpor

ate

the

colo

ur g

uide

lines

spec

ified

in th

e Se

ctio

n 3.

1 of

the

WAF

. In

addi

tion,

to b

e co

nsist

ent w

ith th

e W

AF, t

he E

nviro

nmen

tal D

ams

shou

ld b

e re

-labe

lled

as S

edim

enta

tion

Dam

s. L

astly

, rai

nfal

l sho

uld

be in

clud

ed a

s an

inpu

t to

the

Envi

ronm

enta

l (Se

dim

enta

tion)

Dam

s.

Use

pro

per c

olou

r gui

delin

es, r

elab

el d

am ti

tles,

an

d sh

ow ra

infa

ll as

an

inpu

t to

the

dam

s.

Out-Task Environmental Pty Ltd

[email protected] | 0407 349 172| ABN 19 613 982 308 www.ot-environmental.com.au


APPENDIX D RESPONSES TO INDEPENDENT PEER REVIEW COMMENTS

Gra

nts

Lith

ium

Pro

ject

Wat

er M

anag

emen

t Pla

n

Res

pons

es to

inde

pend

ent r

evie

w c

omm

ents

rece

ived

from

Roh

an A

sh a

nd B

ill H

owcr

oft (

Out

-Tas

k En

viro

nmen

tal)

Revi

ew su

b-se

ctio

nRe

fRe

late

s to

Revi

ew c

omm

ent

Resp

onse

aW

ater

Ba

lanc

e

Sect

ion

6.1

of th

e M

MP

Stru

ctur

e G

uide

spe

cifie

s th

at a

wat

er

bala

nce

mus

t be

incl

uded

, and

that

the

wat

er b

alan

ce “m

ust

incl

ude

cons

ider

atio

n of

the

full

rang

e of

clim

atic

con

ditio

ns th

at

the

site

may

exp

erie

nce,

i.e.

suc

cess

ive

drie

r tha

n av

erag

e se

ason

s an

d su

cces

sive

wet

ter t

han

aver

age

wet

-sea

sons

and

se

nsiti

vity

to e

xtre

me

even

ts”.

In th

e W

ater

Bal

ance

(EcO

z,

2018

b; A

ppen

dix

A to

the

WM

P) re

port

prep

ared

for G

rant

s Li

thiu

m W

MP,

50t

h pe

rcen

tile

clim

ate

(pre

cipi

tatio

n an

d ev

apor

atio

n) d

ata

from

the

Dar

win

Airp

ort w

eath

er s

tatio

n w

ere

utilis

ed.

How

ever

, the

giv

en W

ater

Bal

ance

doe

s no

t acc

ount

for

succ

essi

ve d

ry o

r wet

sea

sons

, nor

doe

s it

acco

unt f

or e

xtre

me

wea

ther

eve

nts.

The

upda

ted

wat

er b

alan

ce (A

ppen

dix

A) n

ow in

clud

es lo

w,

aver

age

and

high

rain

fall

scen

ario

s an

d al

so u

ses

SILO

dat

a to

be

con

sist

ent w

ith g

roun

dwat

er m

odel

.

3.1

Conf

orm

ance

w

ith S

ec. 6

M

MP

Stru

ctur

e G

uide

bW

MP

As s

tate

d in

Sec

tions

6.2

.2 a

nd 6

.3.2

of t

he M

MP

Stru

ctur

e G

uide

, tim

elin

es a

re re

quire

d fo

r the

fillin

g of

info

rmat

ion/

kn

owle

dge

gaps

and

act

ions

and

stra

tegi

es to

miti

gate

the

iden

tifie

d ris

ks.

Tim

elin

es a

ssoc

iate

d w

ith th

ese

item

s ar

e no

t cu

rrent

ly o

utlin

ed in

the

WM

P.

Tim

elin

es w

ill be

add

ed in

the

next

WM

P up

date

due

in M

ay

2019

.

3.2

Gen

eral

Co

mm

ents

on

WM

Pa

WM

P an

d G

roun

dwat

er

mod

el

Sect

ion

2.1

of th

e W

MP

prov

ides

pit

dim

ensi

ons

that

diff

er fr

om

that

out

lined

in th

e gr

ound

wat

er (C

loud

GM

S 20

18) m

odel

ling

repo

rt. S

peci

fical

ly, t

he W

MP

stat

es th

at th

e pi

t will

exte

nd

verti

cally

dow

nwar

d to

180

m w

here

as, i

n th

e gr

ound

wat

er

mod

ellin

g re

port,

the

stat

ed p

it de

pth

will

be 1

50 m

. Thi

s di

scre

panc

y in

pit

dept

hs w

ill af

fect

the

wat

er b

alan

ce, p

it in

flow

s,

and

dew

ater

ing

requ

irem

ents

and

sho

uld

ther

efor

e be

add

ress

ed

and

corre

cted

, as

need

ed.

All g

roun

dwat

er m

odel

ling

(see

Clo

udG

MS

2019

), hy

drol

ogic

al

mod

ellin

g (s

ee E

nviro

Con

sult

2019

) and

the

wat

er b

alan

ce

(App

endi

x A)

hav

e be

en c

onsi

sten

tly u

pdat

ed u

sing

the

sam

e m

ost-r

ecen

t min

e si

te d

esig

n an

d al

l now

als

o us

e th

e sa

me

SILO

da

ta fo

r clim

ate

inpu

ts.

Gra

nts

Lith

ium

Pro

ject

Wat

er M

anag

emen

t Pla

n

Revi

ew su

b-se

ctio

nRe

fRe

late

s to

Revi

ew c

omm

ent

Resp

onse

bW

MP

The

inun

datio

n m

odel

ling

repo

rt (E

nviro

Cons

ult,

2018

c)

reco

mm

ends

ext

endi

ng th

e bu

nds a

nd in

stal

ling

a cu

lver

t to

prev

ent f

lood

inun

datio

n on

the

east

ern

side

of th

e m

ine

foot

prin

t. Ha

s thi

s bee

n co

nsid

ered

? If

inun

datio

n oc

curs

in th

is ar

ea, h

ow w

ill th

is w

ater

be

man

aged

?

The

upda

ted

inun

datio

n m

odel

ling

(see

Env

iroCo

nsul

t 201

9)

indi

cate

s the

site

is p

rote

cted

by

the

inun

datio

n bu

nd fo

r a 1

%

AEP

even

t and

no

furt

her r

ecom

men

datio

ns w

ere

mad

e.

cW

MP

In T

able

8-4

, Row

1 o

f the

WM

P, si

te c

lear

ing

and

prep

arat

ion

rece

ives

a M

oder

ate

resid

ual r

isk, w

ith m

ost o

f tha

t risk

bei

ng

avoi

ded

prov

ided

that

thes

e w

orks

occ

ur in

the

Dry

seas

on.

Wha

t if t

he p

roje

ct is

del

ayed

and

wor

ks th

en o

ccur

dur

ing

the

Wet

seas

on?

If sit

e cl

earin

g an

d pr

epar

atio

n w

as to

occ

ur d

urin

g th

e w

et

seas

on, a

wet

-sea

son

spec

ific

ESCP

will

be

deve

lope

d in

ac

cord

ance

with

IECA

Gui

delin

es.

This

requ

irem

ent i

s pre

scrib

ed

in th

e Pr

imar

y ES

CP su

bmitt

ed w

ith th

e EI

S. T

his m

anag

emen

t m

easu

re h

as b

een

adde

d to

the

risk

asse

ssm

ent T

able

8.4

and

w

ater

man

agem

ent f

ram

ewor

k Ta

ble

9.1

in th

e W

MP.

dW

MP

Spec

ify th

e lin

er m

ater

ial a

nd p

erm

eabi

lity

for t

he p

ropo

sed

for

the

conc

entr

ated

pro

duct

pad

, and

also

disc

uss l

each

abili

ty a

nd

risk

man

agem

ent f

or p

oten

tial c

onta

min

ants

from

con

cent

rate

d pr

oduc

t.

This

is no

w d

iscus

sed

in S

ectio

n 2.

8.4

of th

e W

MP.

The

st

ockp

iled

prod

uct (

spod

umen

e co

ncen

trat

e) is

not

cla

ssifi

ed a

s ha

zard

ous a

ccor

ding

to S

afe

Wor

k Au

stra

lia c

riter

ia a

nd is

not

cl

assif

ied

as a

Dan

gero

us G

ood

by th

e cr

iteria

of t

he A

ustr

alia

n Da

nger

ous G

oods

Cod

e. L

each

ate

test

resu

lts a

vaila

ble

for

spod

umen

e co

ncen

trat

e ex

port

ed th

roug

h Fr

eman

tle P

ort i

n W

A, in

dica

te v

ery

low

leve

ls of

leac

hing

of h

eavy

met

als.

As t

he

spod

umen

e co

ncen

trat

e th

at w

ill b

e pr

oduc

ed d

oes n

ot h

ave

haza

rdou

s pro

pert

ies,

the

prod

uct p

ad d

oes n

ot re

quire

any

sp

ecifi

c po

llutio

n pr

even

tion

or c

onta

inm

ent m

easu

res.

The

pr

oduc

t pad

foun

datio

n w

ill b

e co

nstr

ucte

d of

com

pact

ed c

lay

mat

eria

l and

dra

inag

e fr

om th

e pa

d w

ill re

port

to th

e in

tern

al

drai

nage

net

wor

k th

at re

port

s to

sedi

men

t bas

ins f

or te

stin

g an

d tr

eatm

ent p

rior t

o of

f-site

disc

harg

e.

eW

MP

Spec

ify lo

catio

n of

sept

ic ta

nk sy

stem

and

effl

uent

ads

orpt

ion

field

, and

show

on

site

plan

s. A

lso sp

ecify

buf

fer f

rom

ad

sorp

tion

field

to n

eare

st d

rain

age

line.

Also

disc

uss h

ow

seep

age

and

runo

ff fr

om th

e ad

sorp

tion

field

will

be

man

aged

(h

igh

perm

eabi

lity

Ceno

zoic

sedi

men

ts a

nd la

terit

e gr

avel

s, h

igh

This

is di

scus

sed

in S

ectio

n 2.

8.3

of th

e W

MP.

A

sept

ic ta

nk

syst

em is

not

suita

ble

for t

he v

olum

es o

f was

tew

ater

that

will

be

prod

uced

by

the

proj

ect.

A se

cond

ary

trea

tmen

t sys

tem

is

prop

osed

with

irrig

atio

n of

trea

ted

was

tew

ater

to a

loca

tion

near

the

min

e ad

min

istra

tion

area

, nor

th-w

est o

f the

pit.

The

Gra

nts

Lith

ium

Pro

ject

Wat

er M

anag

emen

t Pla

n

Revi

ew su

b-se

ctio

nRe

fRe

late

s to

Revi

ew c

omm

ent

Resp

onse

wat

er ta

bles

in w

et se

ason

).sy

stem

des

ign

will

com

ply

with

the

Code

of P

ract

ice

for O

n-sit

e W

aste

wat

er M

anag

emen

t. A

Lan

d Ca

pabi

lity

Asse

ssm

ent w

ill b

e un

dert

aken

to d

eter

min

e a

suita

ble

loca

tion

for t

he ir

rigat

ion

area

and

ass

ocia

ted

man

agem

ent r

equi

rem

ents

for s

eepa

ge a

nd

runo

ff. C

ore

will

app

ly fo

r a w

aste

wat

er d

esig

n w

orks

app

rova

l fr

om D

epar

tmen

t of H

ealth

prio

r to

inst

alla

tion

of th

e sy

stem

.

fW

MP

and

Gro

undw

ater

m

odel

A lim

ited

num

ber (

6) o

f mon

itorin

g bo

res

have

bee

n in

stal

led

at

the

prop

osed

min

e si

te.

Non

e of

thes

e bo

res

are

loca

ted

on th

e w

est s

ide

of th

e pr

opos

ed m

ine

foot

prin

t. C

onse

quen

tly, i

t is

cons

ider

ed th

at th

e ex

istin

g m

onito

ring

bore

net

wor

k do

es n

ot

prov

ide

adeq

uate

cov

erag

e to

fully

ass

ess

base

line

cond

ition

s an

d th

eref

ore

pote

ntia

l im

pact

s to

gro

undw

ater

ass

ocia

ted

with

th

e pr

opos

ed m

inin

g op

erat

ions

. It

is n

oted

, how

ever

, tha

t ad

ditio

nal b

ore

inst

alla

tions

are

pro

pose

d w

ithin

the

WM

P an

d th

ese

are

cons

ider

ed g

ener

ally

acc

epta

ble.

Addi

tiona

l bor

es w

ill be

inst

alle

d as

per

the

loca

tions

indi

cate

d in

Se

ctio

n 10

of t

he W

MP.

The

se w

ill be

inst

alle

d on

ce s

ite

cond

ition

s al

low

i.e.

dry

eno

ugh

follo

win

g th

e en

d of

the

wet

se

ason

(Apr

il 20

19).

Dril

ling

durin

g th

e w

et s

easo

n m

ay g

ive

fals

e gr

ound

wat

er a

quife

r stri

kes

(e.g

tem

pora

ry p

erch

ed a

quife

rs).

R

egul

ar (q

uarte

rly) s

ampl

ing

of e

xist

ing

and

new

bor

es w

ill co

mm

ence

imm

edia

tely

in o

rder

to g

ain

a re

pres

enta

tive

base

line

data

set t

o be

use

d in

futu

re W

MP

upda

tes.

Thi

s w

as a

dded

as

an in

form

atio

n/kn

owle

dge

gap

in S

ectio

n 11

.

gW

MP

and

Gro

undw

ater

m

odel

Hyd

raul

ic c

ondu

ctiv

ity v

alue

s w

ere

estim

ated

usi

ng s

lug

and

reco

very

test

s. T

he re

sults

from

thes

e te

sts

diffe

red

in s

ome

case

s by

an

orde

r of m

agni

tude

. In

add

ition

, suc

h te

sts

exam

ine

only

a s

mal

l are

a ar

ound

the

scre

ened

sec

tion

of th

e w

ell b

eing

te

sted

. La

stly

, the

met

hods

by

whi

ch h

ydra

ulic

con

duct

ivity

are

es

timat

ed a

pply

mor

e to

por

ous

med

ia th

an fr

actu

red

rock

aq

uife

rs.

Con

sequ

ently

, the

der

ived

hyd

raul

ic v

alue

s m

ay n

ot b

e tru

ly re

pres

enta

tive

of th

e re

gion

al a

quife

r(s).

The

resu

lts o

f aq

uife

r the

se te

sts

shou

ld b

e co

mpa

red

to th

ose

perfo

rmed

on

the

prop

osed

mon

itorin

g bo

res

(ass

umin

g th

at a

quife

r tes

ts w

ill be

per

form

ed o

n th

e ne

w b

ores

).

The

slug

and

reco

very

test

met

hods

app

lied

in G

HD

(201

8) a

re

stan

dard

indu

stry

met

hods

for a

quife

rs w

ith lo

w h

ydra

ulic

co

nduc

tivity

(K).

In s

uch

syst

ems

mor

e rig

orou

s aq

uife

r tes

ting

met

hods

(e.g

. mul

ti ob

serv

atio

n bo

re p

umpi

ng te

sts)

are

im

prac

tical

as

bore

yie

lds

are

typi

cally

too

low

to e

licit

a re

spon

se

in o

bser

vatio

n bo

res

with

in s

tand

ard

test

tim

e fra

mes

. Li

mite

d K

estim

ates

are

ava

ilabl

e fo

r the

Bur

rell

Cre

ek fo

rmat

ion

outs

ide

the

field

test

s pe

rform

ed b

y G

HD

(201

8), h

owev

er, t

he

valu

es o

btai

ned

in G

HD

(201

8) a

re c

onsi

sten

t with

the

low

K

aqui

fer d

escr

ibed

in o

ther

regi

onal

gro

undw

ater

stu

dies

targ

etin

g th

e Bu

rrell

Cre

ek F

orm

atio

n.

The

K va

lues

use

d in

the

num

eric

al m

odel

wer

e se

lect

ed u

sing

pa

ram

eter

opt

imis

atio

n an

d w

ere

subj

ect t

o se

nsiti

vity

ana

lysi

s,

both

pro

cess

es th

at g

ive

mor

e co

nfid

ence

that

the

adop

ted

valu

es a

re re

pres

enta

tive

of th

e re

gion

al a

quife

r. To

incr

ease

con

fiden

ce in

the

obse

rved

K ra

nge,

slu

g te

stin

g w

ill

Gra

nts

Lith

ium

Pro

ject

Wat

er M

anag

emen

t Pla

n

Revi

ew su

b-se

ctio

nRe

fRe

late

s to

Revi

ew c

omm

ent

Resp

onse

be u

nder

take

n on

the

new

mon

itorin

g bo

res

prop

osed

in th

e W

MP.

hW

MP

and

Gro

undw

ater

m

odel

The

log

for g

roun

dwat

er m

onito

ring

bore

GW

B01

indi

cate

s th

ree

scre

ened

zon

es w

ith b

otto

m d

epth

s of

100

, 124

and

154

m,

resp

ectiv

ely.

Als

o, th

e gr

avel

pac

k ex

tend

s ac

ross

all

thre

e sc

reen

ed z

ones

, i.e

. the

re a

re n

o in

divi

dual

sea

ls b

etw

een

the

wel

l cas

ings

. It

is u

ncle

ar fr

om w

hich

wel

l cas

ing

the

grou

ndw

ater

sam

ples

wer

e co

llect

ed, o

n w

hich

wel

l cas

ing

the

aqui

fer t

ests

wer

e co

nduc

ted,

and

from

whi

ch w

ell c

asin

g th

e re

cord

ed s

tand

ing

wat

er le

vels

wer

e m

easu

red.

Thi

s sh

ould

be

clar

ified

and

the

usef

ulne

ss o

f wat

er q

ualit

y, S

WL

and

aqui

fer t

est

data

from

this

bor

e fo

r EIS

pur

pose

s di

scus

sed.

Inve

stig

atio

n Bo

re G

WB0

1 is

con

stru

cted

with

a lo

ng s

cree

n in

terv

al fr

om 8

8 - 1

54 m

with

a s

ingl

e ca

sing

stri

ng a

s op

pose

d to

be

ing

a ne

sted

pie

zom

eter

with

thre

e di

scre

te c

asin

g st

rings

, w

hich

is h

ow th

e bo

re is

dep

icte

d in

GH

D (2

018)

. G

roun

dwat

er

pum

ped

from

this

bor

e w

ill re

flect

a c

ompo

site

sam

ple

betw

een

88 -

154

m.

Giv

en th

at th

ere

is n

o ev

iden

ce fr

om th

e gr

ound

wat

er le

vels

or

wat

er q

ualit

y, th

at th

ere

are

mul

tiple

aqu

ifers

with

in th

e Bu

rrell

Cre

ek F

orm

atio

n, w

ater

qua

lity

sam

ples

/hyd

raul

ic te

st re

sults

fro

m G

WB0

1 ar

e co

nsid

ered

repr

esen

tativ

e of

the

aqui

fer.

To d

ate

all s

ampl

ing

of th

is b

ore

has

been

und

erta

ken

with

the

pum

p pl

aced

at 7

0 m

dep

th.

This

is th

e m

axim

um d

epth

pos

sibl

e w

ith th

e eq

uipm

ent u

sed.

Sam

plin

g at

this

dep

th (i

.e. 1

8 m

abo

ve

the

top

of th

e sc

reen

ed in

terv

al) w

ill st

ill ob

tain

a s

ampl

e re

pres

enta

tive

of th

e aq

uife

r as

long

as

the

bore

is p

umpe

d lo

ng

enou

gh to

pur

ge a

min

imum

of t

hree

wel

l vol

umes

and

als

o fo

r en

ough

tim

e th

at fi

eld

para

met

ers

stab

ilise.

Thi

s pr

oced

ure

has

been

use

d in

the

mon

itorin

g pr

ogra

m u

nder

take

n by

EcO

z to

da

te.

iW

MP

The

grou

ndw

ater

mod

ellin

g re

port

shou

ld b

e re

fere

nced

as

Clo

udG

MS

(201

8), n

ot K

napt

on a

nd F

ulto

n (2

018)

.Th

is h

as b

een

chan

ged

in th

e up

date

d W

MP.

jW

MP

and

Gro

undw

ater

m

odel

Dur

ing

the

life

of m

ine,

it is

pre

dict

ed th

at a

con

e of

gro

undw

ater

de

pres

sion

will

exte

nd a

ppro

xim

atel

y on

e (1

) km

from

the

min

e pi

t. It

is a

lso

stat

ed th

at “s

ome”

gro

undw

ater

like

ly d

isch

arge

s to

ep

hem

eral

stre

ams

to th

e no

rth (S

ectio

n 3.

3.1,

pag

e 1-

33 o

f the

W

MP)

but

that

this

dra

wdo

wn

will

not a

ffect

gro

undw

ater

leve

ls

bene

ath

the

ephe

mer

al s

tream

s. H

owev

er, t

his

draw

dow

n co

uld

none

thel

ess

decr

ease

gro

undw

ater

flux

into

the

stre

ams

as a

re

sult

of re

duce

d hy

drau

lic g

radi

ents

and

a re

duce

d re

char

ge

area

. Th

is in

turn

cou

ld le

ad to

impa

cts

to ri

paria

n ve

geta

tion

and

aqua

tic s

peci

es a

long

and

with

in th

e st

ream

s. G

roun

dwat

er le

vels

A ch

ange

in h

ydra

ulic

gra

dien

t will

only

hav

e an

impa

ct o

n gr

ound

wat

er fl

ux b

enea

th th

e ep

hem

eral

cre

eks

if th

e gr

ound

wat

er e

leva

tion

is p

redi

cted

to c

hang

e at

thes

e lo

catio

ns.

No

such

cha

nge

is p

redi

cted

in th

e m

odel

ling

scen

ario

s an

d as

a

resu

lt no

cha

nge

in fl

ux to

the

grou

ndw

ater

sys

tem

ben

eath

the

ephe

mer

al c

reek

s is

ant

icip

ated

.In

ord

er to

pro

vide

real

wor

ld v

erifi

catio

n of

the

mod

el p

redi

ctio

ns

grou

ndw

ater

leve

ls in

bot

h th

e sh

allo

w a

nd d

eepe

r gro

undw

ater

sy

stem

will

be m

onito

red

as o

utlin

ed in

the

WM

P.

Gra

nts

Lith

ium

Pro

ject

Wat

er M

anag

emen

t Pla

n

Revi

ew su

b-se

ctio

nRe

fRe

late

s to

Revi

ew c

omm

ent

Resp

onse

with

in s

hallo

w b

ores

loca

ted

prox

imal

to th

e st

ream

s sh

ould

be

mon

itorin

g be

fore

com

men

cem

ent o

f min

ing

oper

atio

n, d

urin

g op

erat

ions

and

pos

t-clo

sure

.

kW

MP

and

Gro

undw

ater

m

odel

Post

-min

e cl

osur

e, a

pit

lake

will

form

in th

e m

inin

g le

ase.

Thi

s w

ill re

sult

in a

gro

undw

ater

sin

k an

d, c

onse

quen

tly, a

ltera

tion,

of

the

loca

l flo

w re

gim

e. I

t is

stat

ed w

ithin

the

grou

ndw

ater

m

odel

ling

repo

rt (a

nd w

ithin

the

WM

P) th

at n

o ch

ange

in th

e w

ater

tabl

e su

rface

is p

redi

cted

at t

he e

phem

eral

wat

er c

ours

es.

As a

bove

, how

ever

, thi

s al

tera

tion

to th

e gr

ound

wat

er fl

ow

syst

em m

ay d

ecre

ase

grou

ndw

ater

flux

into

the

stre

ams

as a

re

sult

of a

redu

ced

hydr

aulic

gra

dien

t and

rech

arge

are

as. A

s in

po

int “

j)” a

bove

, gro

undw

ater

leve

ls w

ithin

sha

llow

bor

es lo

cate

d pr

oxim

al to

the

ephe

mer

al s

houl

d be

mon

itorin

g be

fore

co

mm

ence

men

t of m

inin

g op

erat

ion,

dur

ing

oper

atio

ns a

nd p

ost-

clos

ure.

As a

bove

.

l

Wat

er

Bala

nce

and

Gro

undw

ater

m

odel

Rai

nfal

l and

eva

pora

tion

data

util

ised

in th

e gr

ound

wat

er

mod

ellin

g st

udy

diffe

r fro

m th

at u

tilis

ed in

the

Wat

er B

alan

ce a

nd

the

hydr

olog

ic s

tudi

es.

Idea

lly, a

nd to

min

imis

e un

certa

inty

, the

sa

me

(mos

t up

to d

ate)

clim

atic

dat

a sh

ould

be

utilis

ed in

eac

h st

udy.

All g

roun

dwat

er m

odel

ling

(see

Clo

udG

MS

2019

), hy

drol

ogic

al

mod

ellin

g (s

ee E

nviro

Con

sult

2019

) and

the

wat

er b

alan

ce

(App

endi

x A)

hav

e be

en c

onsi

sten

tly u

pdat

ed u

sing

the

sam

e m

ost-r

ecen

t min

e si

te d

esig

n an

d al

l now

als

o us

e th

e sa

me

SILO

da

ta fo

r clim

ate

inpu

ts.

mG

roun

dwat

er

mod

el

In T

able

2-1

of t

he g

roun

dwat

er m

odel

ling

repo

rt, th

e m

ore

perm

eabl

e ne

ar-s

urfa

ce s

edim

ents

are

not

con

side

red

to b

e a

hydr

o-st

ratig

raph

ic u

nit.

Exc

lusi

on o

f thi

s m

ore

perm

eabl

e un

it fro

m th

e gr

ound

wat

er m

odel

may

resu

lt in

an

unde

rest

imat

ion

of

grou

ndw

ater

inflo

ws

into

the

min

e pi

t, es

peci

ally

dur

ing

the

early

st

ages

of m

inin

g op

erat

ions

. C

onsi

der i

nclu

sion

of t

he s

hallo

w

surfa

ce s

edim

ents

in th

e m

odel

, or o

ther

wis

e ju

stify

in th

e te

xt o

f th

e W

MP

and

grou

ndw

ater

mod

ellin

g re

port

its e

xclu

sion

from

the

mod

el.

The

surfi

cial

silt

y sa

nds

and

grav

els

wer

e in

itial

ly in

clud

ed in

H

SU1

but d

id n

ot im

prov

e m

odel

per

form

ance

. Th

ey w

ere

not

incl

uded

in th

e fin

al m

odel

bec

ause

they

are

spa

tially

di

scon

tinuo

us a

cros

s th

e si

te a

nd a

re ty

pica

lly u

nsat

urat

ed.

nG

roun

dwat

er

mod

el

Futu

re re

porti

ng s

houl

d in

clud

e a

verti

cal,

two-

dim

ensi

onal

eq

uipo

tent

ial d

iagr

am, w

hich

doc

umen

ts e

quip

oten

tial g

radi

ents

, st

ratig

raph

ic u

nits

, bor

e lo

catio

ns, s

tream

s, a

nd b

ore

scre

en

inte

rval

s. T

his

will

grea

tly e

nhan

ce in

terp

reta

tion

of

hydr

ogeo

logi

c co

nditi

ons.

Ther

e is

no

requ

irem

ent t

o in

clud

e th

is s

tyle

of d

iagr

am w

ithin

m

odel

ling

guid

elin

es o

r with

in th

e EI

S te

rms

of re

fere

nce.

If

requ

ired

by re

gula

tors

, suc

h a

diag

ram

can

be

deve

lope

d fo

r fu

ture

repo

rting

. Th

is w

ould

occ

ur a

fter t

he a

dditi

onal

mon

itorin

g bo

res

are

inst

alle

d.

Gra

nts

Lith

ium

Pro

ject

Wat

er M

anag

emen

t Pla

n

Revi

ew su

b-se

ctio

nRe

fRe

late

s to

Revi

ew c

omm

ent

Resp

onse

oG

roun

dwat

er

mod

el

The

grou

ndw

ater

con

tour

s (a

nd, t

here

fore

, gro

undw

ater

flow

di

rect

ion)

pre

sent

ed in

the

grou

ndw

ater

mod

ellin

g re

port

shou

ld

be c

onsi

dere

d as

app

roxi

mat

e an

d pr

elim

inar

y on

ly.

This

is d

ue

to th

e fa

ct th

at th

e co

ntou

rs w

ere

gene

rate

d fro

m g

roun

dwat

er

leve

ls th

at w

ere

mea

sure

d in

a li

mite

d nu

mbe

r (4)

of m

onito

ring

bore

s th

at a

re s

cree

ned

at d

iffer

ent d

epth

inte

rval

s. A

s a

resu

lt,

grou

ndw

ater

flow

dire

ctio

n m

ay b

e m

ore

com

plex

than

that

in

dica

ted.

The

relia

bilit

y of

gro

undw

ater

con

tour

s pr

esen

ted

in th

e m

odel

ling

repo

rt is

lim

ited

by th

e av

aila

bilit

y of

dat

a po

ints

(fou

r), h

owev

er,

thes

e ar

e st

ill co

nsid

ered

use

ful t

o illu

stra

te th

e ge

nera

l gr

ound

wat

er fl

ow d

irect

ion

acro

ss th

e si

te.

They

als

o su

ppor

t the

hy

drog

eolo

gica

l con

cept

ualis

atio

n of

gro

undw

ater

flow

ing

from

hi

gher

ele

vatio

ns in

the

sout

h of

the

site

tow

ard

Dar

win

Har

bour

to

the

north

. Th

e po

tent

iom

etric

sur

face

will

be u

pdat

ed to

bet

ter

refle

ct lo

cal-s

cale

com

plex

ity a

fter a

dditi

onal

bor

es re

com

men

ded

in th

e W

MP

are

inst

alle

d.

pG

roun

dwat

er

mod

el

Gro

undw

ater

flow

dire

ctio

n in

the

shal

low

aqu

ifer i

s pr

esen

tly

unde

term

ined

, as

only

two

bore

s ha

ve b

een

inst

alle

d w

ithin

this

un

it. T

he fl

ow d

irect

ion

shou

ld b

e su

bjec

t to

revi

ew u

pon

com

plet

ion

and

mon

itorin

g of

the

new

bor

es a

s pr

opos

ed.

The

flow

dire

ctio

n in

the

shal

low

aqu

ifer w

ill be

det

erm

ined

bas

ed

on g

roun

dwat

er le

vel m

onito

ring

unde

rtake

n in

sha

llow

bor

es

inst

alle

d as

is p

ropo

sed

in th

e W

MP.

qG

roun

dwat

er

mod

el

The

rapi

d re

spon

se to

rain

fall

exhi

bite

d at

mon

itorin

g bo

re

GW

B10

may

be

due

to h

ow th

e bo

re w

as c

onst

ruct

ed.

This

bor

e w

as in

stal

led

in a

sw

ampy

are

a. In

add

ition

, the

top

of th

e w

ell

scre

en is

just

0.5

m b

elow

gro

und

surfa

ce (b

gs).

For

thes

e re

ason

s, th

e ob

serv

ed d

ownw

ard

head

gra

dien

t at t

his

loca

tion

mig

ht b

e si

mpl

y du

e to

ingr

ess

of s

urfa

ce w

ater

into

GW

B10.

For

th

is s

ame

reas

on to

o, g

roun

dwat

er q

ualit

y re

sults

from

this

bor

e m

ay n

ot b

e tru

ly re

pres

enta

tive

of g

roun

dwat

er q

ualit

y w

ithin

the

shal

low

aqu

ifer.

Las

tly, g

roun

dwat

er m

onito

ring

bore

GW

B10

does

not

mee

t the

min

imum

con

stru

ctio

n st

anda

rds

for w

ater

bo

res

in A

ustra

lia, w

hich

spe

cifie

s a

min

imum

of 1

m o

f cas

ing

betw

een

grou

nd s

urfa

ce a

nd th

e pr

oduc

tion

zone

bei

ng

mon

itore

d. T

his

limita

tion

shou

ld b

e di

scus

sed

in th

e W

MP

and

asso

ciat

ed g

roun

dwat

er m

odel

ling/

asse

ssm

ent r

epor

ts.

In

addi

tion,

GW

B10

shou

ld b

e de

com

mis

sion

ed a

nd re

plac

ed w

ith a

ne

w m

onito

ring

bore

.

This

bor

e w

ill be

dec

omm

issi

oned

and

gro

undw

ater

leve

ls in

the

shal

low

aqu

ifer d

eter

min

ed u

sing

dat

a fro

m a

dditi

onal

sha

llow

bo

res

inst

alle

d as

out

lined

in th

e W

MP.

All

futu

re b

ores

will

be

inst

alle

d co

nfor

min

g to

the

min

imum

con

stru

ctio

n st

anda

rds

for

wat

er b

ores

in A

ustra

lia.

Gra

nts

Lith

ium

Pro

ject

Wat

er M

anag

emen

t Pla

n

Revi

ew su

b-se

ctio

nRe

fRe

late

s to

Revi

ew c

omm

ent

Resp

onse

rW

MP

The

sout

hern

bou

ndar

y of

the

grou

ndw

ater

mod

el d

omai

n (w

hich

is

ass

umed

to c

orre

spon

d to

that

of t

he s

urfa

ce w

ater

cat

chm

ent

divi

de) d

iffer

s si

gnifi

cant

ly fr

om th

at p

rese

nted

in th

e W

MP

(Fig

ure

3-2,

Sec

tion

3.2)

. It

is u

ncle

ar a

s to

whi

ch b

ound

ary

is

corre

ct a

nd h

ow w

ill th

is d

iffer

ence

affe

ct th

e es

timat

ion

of

grou

ndw

ater

inflo

ws

into

the

pit.

Fur

ther

mor

e, if

the

catc

hmen

t bo

unda

ry s

peci

fied

in th

e gr

ound

wat

er m

odel

is c

orre

ct, t

his

sugg

ests

that

the

ephe

mer

al s

tream

s lo

cate

d to

the

sout

h of

the

min

ing

leas

e m

ay, i

n fa

ct, b

e af

fect

ed b

y m

inin

g op

erat

ions

. Th

is

shou

ld b

e cl

arifi

ed in

the

rele

vant

doc

umen

ts.

The

sout

hern

bou

ndar

y of

the

grou

ndw

ater

mod

el is

bas

ed o

n an

ep

hem

eral

dra

inag

e lin

e ra

ther

than

a s

urfa

ce w

ater

cat

chm

ent

divi

de. C

onse

quen

tly, d

iffer

ence

s in

the

exac

t loc

atio

n of

the

sout

hern

cat

chm

ent d

ivid

e in

the

grou

ndw

ater

and

sur

face

wat

er

stud

ies

will

not a

ffect

mod

el e

stim

ates

of p

it in

flow

s fro

m th

e gr

ound

wat

er m

odel

ling.

sW

MP

Giv

en a

nor

th-n

orth

east

infe

rred

grou

ndw

ater

flow

dire

ctio

n,

grou

ndw

ater

mon

itorin

g bo

res

GW

B06

and

GW

B07

are

loca

ted

cros

s-gr

adie

nt to

the

min

e fo

otpr

int,

not u

p-gr

adie

nt, a

s st

ated

in

Sect

ion

3.3.

1 of

the

WM

P. T

his

shou

ld b

e cl

arifi

ed/a

men

ded

in

rele

vant

doc

umen

ts.

This

has

bee

n am

ende

d in

the

WM

P.

tW

MP

The

uppe

r Qua

tern

ary

aqui

fer i

s po

orly

cha

ract

eris

ed, f

rom

bot

h a

wat

er q

ualit

y pe

rspe

ctiv

e, a

s w

ell a

s fro

m a

bas

ic h

ydro

geol

ogic

un

ders

tand

ing.

Onl

y tw

o bo

res

have

bee

n in

stal

led

with

in th

is

unit,

one

of w

hich

is p

oorly

con

stru

cted

and

the

seco

nd w

hich

has

be

en c

ompr

omis

ed b

y ce

men

t. In

add

ition

, gro

undw

ater

flow

gr

adie

nts

with

in th

e sh

allo

w a

quife

r are

poo

rly u

nder

stoo

d.

Follo

win

g in

stal

latio

n of

the

prop

osed

bor

es w

ithin

this

uni

t, ef

forts

sho

uld

be m

ade

to m

ore

adeq

uate

ly c

hara

cter

ise

grou

ndw

ater

flow

dire

ctio

n an

d gr

ound

wat

er q

ualit

y.

Agre

ed, t

he s

hallo

w a

quife

r will

be b

ette

r cha

ract

eris

ed fo

llow

ing

inst

alla

tion

(and

mon

itorin

g) o

f the

new

bor

es a

s ou

tline

d in

the

WM

P. T

his

char

acte

risat

ion

will

be in

clud

ed in

a fu

ture

upd

ate

of

the

WM

P.

Gra

nts

Lith

ium

Pro

ject

Wat

er M

anag

emen

t Pla

n

Revi

ew su

b-se

ctio

nRe

fRe

late

s to

Revi

ew c

omm

ent

Resp

onse

uAq

uatic

Ec

olog

y an

d W

MP

One

sam

plin

g ev

ent w

as c

ondu

cted

(May

201

7) a

nd a

t an

only

lim

ited

num

ber (

4) o

f loc

atio

ns.

Res

ults

from

this

sam

plin

g sh

owed

that

mac

roin

verte

brat

e an

d fis

h sp

ecie

s w

ithin

the

stre

ams

are

typi

cal o

f wat

erco

urse

s in

the

NT

and

are

rela

tivel

y si

mila

r acr

oss

all s

ites.

Jus

tific

atio

n as

to w

hy o

ne o

r mor

e ad

ditio

nal r

ound

s of

sam

plin

g ar

e un

nece

ssar

y sh

ould

be

prov

ided

in th

e W

MP.

Surfa

ce w

ater

and

gro

undw

ater

qua

lity

mon

itorin

g w

ill be

the

prim

ary

met

hod

for d

etec

ting

any

dow

nstre

am im

pact

s fro

m

min

ing.

Wat

er q

ualit

y m

onito

ring

prov

ides

mor

e ra

pid

feed

back

fo

r trig

gerin

g m

anag

emen

t res

pons

es.

Cha

nges

to m

acro

inve

rtebr

ate

asse

mbl

ages

in re

spon

se to

m

inin

g im

pact

s w

ould

be

too

slow

for t

rigge

ring

the

need

to

impl

emen

t man

agem

ent a

ctio

ns; e

spec

ially

giv

en th

e sh

ort 2

-yea

r lif

e of

the

min

e. T

he m

acro

inve

rtebr

ate

stud

y ha

s se

rved

its

purp

ose

in d

eter

min

ing

that

the

dow

nstre

am re

ceiv

ing

wat

erco

urse

s ar

e ty

pica

l of e

phem

eral

stre

ams

and

in u

n-im

pact

ed re

fere

nce

cond

ition

. R

esul

ts o

f the

sur

vey

may

be

used

as

a b

asel

ine

in fu

ture

if p

ost-m

inin

g m

onito

ring

is re

quire

d to

de

term

ine

any

long

-term

impa

cts.

vAq

uatic

Ec

olog

y an

d W

MP

No

sam

plin

g w

as c

ondu

cted

in th

e st

ream

cou

rse

loca

ted

dow

nstre

am o

f the

Obs

erva

tion

Hill

Dam

(OH

D).

Just

ifica

tion

as

to w

hy th

is is

unn

eces

sary

sho

uld

be p

rovi

ded

in th

e W

MP.

A sa

mpl

ing

loca

tion

dow

nstre

am o

f OH

D "S

ite B

P" w

as in

clud

ed

in th

e G

HD

stu

dy a

s a

cont

rol s

ite.

This

cou

ld a

ct a

s a

base

line

site

for m

onito

ring

OH

D im

pact

s in

the

futu

re.

How

ever

, as

expl

aine

d in

the

poin

t 3.2

(u) a

bove

, it i

s no

t exp

ecte

d th

at

aqua

tic e

colo

gy s

tudi

es w

ill be

repe

ated

in fu

ture

as

surfa

ce

wat

er a

nd g

roun

dwat

er q

ualit

y m

onito

ring

will

be th

e pr

imar

y m

etho

ds fo

r det

ectin

g im

pact

s an

d tri

gger

ing

man

agem

ent

actio

ns.

Aqua

tic e

colo

gy s

urve

ys h

ave

limite

d va

lue

for t

his

proj

ect a

nd a

re m

ore

suite

d to

det

ectin

g lo

ng-te

rm im

pact

s.

wW

MP

In S

ectio

n 3.

3.2

of th

e W

MP,

med

ium

pot

entia

l GD

Es w

ere

note

d do

wns

tream

of t

he O

HD

. Rai

sing

the

OH

D w

all b

y 1.

5 w

as s

how

n to

sig

nific

antly

redu

ce d

isch

arge

to th

e dr

aina

ge c

ours

e

Rai

sing

the

Obs

erva

tion

Hill

Dam

wal

l ext

ends

the

time

it ta

kes

for t

he d

am to

fill

and

spill

once

wet

sea

son

rain

s st

art i

n N

ovem

ber/D

ecem

ber.

Onc

e fu

ll, th

e da

m is

mod

elle

d to

rem

ain

Gra

nts

Lith

ium

Pro

ject

Wat

er M

anag

emen

t Pla

n

Revi

ew su

b-se

ctio

nRe

fRe

late

s to

Revi

ew c

omm

ent

Resp

onse

dow

nstre

am o

f the

OH

D. I

f the

dam

wal

l is

to b

e ra

ised

, and

flow

s de

crea

se, h

ow w

ill th

e G

DEs

be

affe

cted

?ab

ove

its p

revi

ous

capa

city

of 3

64 M

L un

til a

t lea

st th

e m

id-d

ry

seas

on in

Jul

y/Au

gust

(see

Fig

ure

15 in

Env

iroC

onsu

lt 20

18b)

, an

d th

eref

ore,

will

be s

uppl

ying

the

sam

e am

ount

of s

eepa

ge a

nd

grou

ndw

ater

aqu

ifer r

echa

rge

until

this

tim

e.

Base

line

surv

eys

of ri

paria

n ve

geta

tion

cove

r and

con

ditio

n do

wns

tream

of O

bser

vatio

n H

ill D

am a

re b

eing

und

erta

ken

in

Mar

ch 2

019,

that

incl

ude

grou

nd-b

ased

sur

veys

and

the

reco

rdin

g of

aer

ial i

mag

ery

usin

g a

dron

e. T

he re

sults

of t

hese

su

rvey

s w

ill m

ap th

e ex

tent

of a

ny s

ensi

tive

vege

tatio

n ty

pes,

su

ch a

s G

DEs

, mon

soon

vin

e fo

rest

etc

. and

est

ablis

h a

base

line

for f

utur

e m

onito

ring

of im

pact

s.

x

Wat

er

Bala

nce

Gro

undw

ater

m

odel

and

W

MP

In th

e hy

drol

ogic

stu

dies

, a 2

m D

EM w

as u

tilis

ed in

det

erm

inin

g gr

ound

sur

face

topo

grap

hy.

Yet,

with

in th

e gr

ound

wat

er

mod

ellin

g st

udy,

a d

iffer

ent m

odel

of t

opog

raph

y w

as u

tilis

ed.

Use

of t

hese

diff

eren

t dat

a se

ts m

ay b

e th

e re

ason

for t

he

diffe

renc

e in

the

delin

eatio

n of

the

sout

hern

cat

chm

ent b

ound

ary

(not

ed in

poi

nt n

abo

ve).

The

WM

P sh

ould

com

men

t as

to h

ow

this

diff

eren

ce c

ould

affe

ct fl

ows,

incl

udin

g ru

noff

and

grou

ndw

ater

inflo

ws

into

the

min

e pi

t.

The

sout

hern

bou

ndar

y of

the

grou

ndw

ater

mod

el is

bas

ed o

n an

ep

hem

eral

dra

inag

e lin

e ra

ther

than

a s

urfa

ce w

ater

cat

chm

ent

divi

de. C

onse

quen

tly, d

iffer

ence

s in

the

exac

t loc

atio

n of

the

sout

hern

cat

chm

ent d

ivid

e in

the

grou

ndw

ater

and

sur

face

wat

er

stud

ies

will

not a

ffect

mod

el e

stim

ates

of p

it in

flow

s fro

m th

e gr

ound

wat

er m

odel

ling.

yW

MP

Rai

sing

the

spillw

ay e

leva

tion

of th

e O

bser

vatio

n H

ill D

am (O

HD

) w

ill ca

use

inun

datio

n of

land

s pr

evio

usly

abo

ve d

am le

vel.

Wha

t ar

e th

e im

plic

atio

ns o

f thi

s in

unda

tion

to a

quat

ic e

colo

gy a

nd

nativ

e ha

bita

t aro

und

the

OH

D?

The

maj

ority

of t

he te

rrest

rial v

eget

atio

n in

unda

ted

by ra

isin

g th

e O

bser

vatio

n H

ill D

am w

all i

s de

scrib

ed a

s P

anda

nus

spira

lis,

Loph

oste

mon

lact

ifluu

s, L

ivis

tona

hum

ilis

Low

isol

ated

tree

s (s

ee

Cha

pter

2 in

Sup

plem

enta

ry E

IS).

A s

mal

ler a

rea

of w

oodl

and

vege

tatio

n co

mm

uniti

es c

ompr

isin

g E

ucal

yptu

s sp

ecie

s w

ill al

so

be in

unda

ted.

No

aqua

tic h

abita

ts w

ill be

inun

date

d. T

he h

abita

t lo

ss a

ssoc

iate

d w

ith th

e pr

opos

al is

exp

ecte

d to

hav

e a

limite

d im

pact

to fa

una

beca

use

the

affe

cted

hab

itat t

ypes

are

wel

l re

pres

ente

d in

the

surro

undi

ng a

reas

, with

no

othe

r ind

ustri

al

deve

lopm

ent i

n cl

ose

prox

imity

that

wou

ld d

eter

use

of t

hese

ha

bita

ts.

zW

MP

Rai

sing

the

spillw

ay h

eigh

t of t

he O

HD

by

1.5

m, a

s a

pote

ntia

l op

tion

prop

osed

in th

e W

MP,

will

redu

ce fl

ows

imm

edia

tely

do

wns

tream

of t

he d

am b

y up

to 6

9%. T

his

valu

e ex

ceed

s th

e N

T W

ater

Allo

catio

n Fr

amew

ork

flow

redu

ctio

n gu

idel

ine

of ≤

20%

. Th

e W

MP

shou

ld a

ddre

ss p

ossi

ble

miti

gatio

n st

rate

gies

to m

eet

The

risk

to d

owns

tream

eco

syst

ems

asso

ciat

ed w

ith th

e m

odel

led

redu

ced

flow

vol

umes

is c

onsi

dere

d lo

w a

s ou

tline

d in

Sec

tion

4.2

of th

e W

MP.

Im

med

iate

ly d

owns

tream

of a

ny d

am, f

low

s w

ill be

re

duce

d by

100

% u

ntil

the

dam

fills

and

ove

rflow

s. In

the

case

of

the

OH

D, t

he c

urre

nt d

am w

all r

educ

es fl

ows

by 1

00%

in

Gra

nts

Lith

ium

Pro

ject

Wat

er M

anag

emen

t Pla

n

Revi

ew su

b-se

ctio

nRe

fRe

late

s to

Revi

ew c

omm

ent

Resp

onse

this

gui

delin

e.N

ovem

ber a

nd D

ecem

ber.

Rai

sing

of t

he d

am w

all w

ill fu

rther

de

crea

se fl

ows

by a

roun

d 30

-80%

in J

anua

ry to

Mar

ch, a

nd

100%

in A

pril,

as

over

flow

of t

he d

am w

ill ce

ase

earli

er th

an it

cu

rrent

ly d

oes.

The

Wat

er A

lloca

tion

Fram

ewor

k gu

idel

ine

is n

ot

dire

ctly

app

licab

le to

the

area

s im

med

iate

ly d

owns

tream

of O

HD

, as

this

gui

delin

e is

inte

nded

to b

e ap

plie

d to

rive

r sys

tem

s. T

he

focu

s of

the

impa

ct a

sses

smen

t and

miti

gatio

n do

cum

ente

d in

the

EIS

is o

n th

e ca

tchm

ent o

utle

t to

Cha

rlotte

Riv

er, a

ppro

xim

atel

y 3k

m d

owns

tream

of t

he O

HD

, whe

re fl

ows

coul

d be

redu

ced

by

betw

een

10-3

0%, o

f whi

ch 1

0-15

% is

attr

ibut

able

to ra

isin

g of

the

dam

wal

l. B

asel

ine

asse

ssm

ent o

f the

ripa

rian

area

s is

bei

ng

unde

rtake

n in

Mar

ch 2

019,

so

that

impa

cts

to th

ese

habi

tats

can

be

ass

esse

d in

futu

re if

requ

ired.

Impa

cts

to s

tream

flow

s do

wns

tream

of t

he O

HD

will

be

min

imis

ed b

y on

ly p

umpi

ng w

ater

from

OH

D a

s re

quire

d fo

r to

ppin

g up

the

site

wat

er s

uppl

y. T

he m

odel

ling

of im

pact

s to

st

ream

flow

s is

bas

ed o

n th

e w

orst

-cas

e sc

enar

io o

f all

wat

er

bein

g so

urce

d fro

m th

e O

HD

, whe

reas

the

wat

er b

alan

ce

indi

cate

s th

at m

ost o

f the

site

s w

ater

requ

irem

ents

will

com

e fro

m

dew

ater

ing

of th

e pi

t and

ext

ract

ion

from

the

Min

e Si

te D

am.

aaW

MP

Con

stru

ctio

n of

an

alte

rnat

ive

dam

, e.g

. the

Min

e Si

te D

am,

resu

lts in

a m

odel

led

decr

ease

in fl

ow v

olum

es in

that

stre

am

cour

se o

f up

to 3

7%. T

his

valu

e ex

ceed

s th

e N

T W

ater

Allo

catio

n Fr

amew

ork

flow

redu

ctio

n gu

idel

ine

of ≤

20%

. The

WM

P sh

ould

ad

dres

s po

ssib

le m

itiga

tion

stra

tegi

es to

mee

t thi

s gu

idel

ine

Upd

ated

mod

ellin

g in

dica

tes

flow

vol

umes

imm

edia

tely

do

wns

tream

of t

he m

ine

site

will

be re

duce

d by

up

to 3

0%; o

r les

s if

disc

harg

e of

cle

an w

ater

from

sed

imen

t dam

s is

take

n in

to

acco

unt.

Agai

n, th

e W

ater

Allo

catio

n Fr

amew

ork

guid

elin

e is

not

di

rect

ly a

pplic

able

to th

e ar

eas

imm

edia

tely

dow

nstre

am o

f the

m

ine

site

, whe

re s

tream

flow

s ar

e ep

hem

eral

. Th

e ep

hem

eral

st

ream

s do

not

sup

port

any

nota

ble

envi

ronm

enta

l val

ues

that

are

lik

ely

to b

e af

fect

ed b

y th

e m

odel

led

decr

ease

in fl

ow.

Furth

er

dow

nstre

am a

t the

poi

nt o

f dis

char

ge to

the

hint

erla

nd m

angr

oves

of

Wes

t Arm

, the

ear

ly s

easo

n de

crea

se in

flow

is a

roun

d 14

-23

%, w

hich

is n

ot o

f a m

agni

tude

exp

ecte

d to

hav

e an

y im

pact

on

the

ecol

ogic

al in

tegr

ity o

f the

man

grov

e en

viro

nmen

t or r

ecei

ving

w

ater

s ha

bita

ts.

Base

line

asse

ssm

ents

of t

he m

angr

oves

are

be

ing

unde

rtake

n in

Mar

ch 2

019,

so

that

impa

cts

to th

ese

habi

tats

can

be

asse

ssed

in fu

ture

if re

quire

d.

Gra

nts

Lith

ium

Pro

ject

Wat

er M

anag

emen

t Pla

n

Revi

ew su

b-se

ctio

nRe

fRe

late

s to

Revi

ew c

omm

ent

Resp

onse

bbG

roun

dwat

er

mod

el

Ther

e is

no

hydr

ogeo

logi

cal d

ata

in th

e ar

ea o

f the

pro

pose

d M

ine

Site

Dam

. Con

sequ

ently

, the

impa

cts

of th

is d

am o

n th

e gr

ound

wat

er fl

ow s

yste

m is

und

eter

min

ed. H

owev

er, i

t is

reco

gnis

ed th

at tw

o ne

w m

onito

ring

bore

s ar

e pr

opos

ed in

the

area

of t

he M

ine

Site

Dam

.

The

MSD

may

cau

se a

load

ing

effe

ct o

n gr

ound

wat

er i.

e.

incr

ease

gro

undw

ater

rech

arge

(mou

ndin

g) u

nder

neat

h th

e da

m.

This

cou

ld c

hang

e th

e pa

rticl

e fa

te m

odel

ling

unde

rtake

n fo

r po

tent

ial c

onta

min

ants

mig

ratin

g in

gro

undw

ater

from

the

TSF.

Si

mon

Ful

ton

to p

rovi

de a

des

crip

tion

for h

ow th

e M

SD m

ay

chan

ge th

e gr

ound

wat

er fl

ow re

gim

e fo

r inc

lusi

on in

the

WM

P.

This

can

be

upda

ted

with

new

dat

a fo

llow

ing

inst

alla

tion

of th

e ne

w b

ores

in A

pril

2019

.

cc

Gro

undw

ater

m

odel

Wat

er

Bala

nce

WM

P

Con

stru

ctio

n of

the

Min

e Si

te D

am (M

SD) i

s no

t con

side

red

in th

e C

loud

GSM

(201

8) g

roun

dwat

er m

odel

ling

repo

rt, th

e W

ater

Ba

lanc

e R

epor

t (Ec

Oz,

201

8b),

the

Inun

datio

n St

udy

(Env

iroC

onsu

lt, 2

018c

), no

r the

GH

D (2

017b

) aqu

atic

eco

logy

re

port.

It is

unc

lear

wha

t affe

ct, i

f any

, tha

t con

stru

ctio

n of

the

MSD

will

have

on

the

grou

ndw

ater

flow

sys

tem

s, th

e w

ater

ba

lanc

e, in

unda

tion

and

aqua

tic e

colo

gy. T

he W

MP

shou

ld

com

men

t on

how

con

stru

ctio

n of

the

Min

e Si

te D

am m

ay a

ffect

th

e co

nclu

sion

s dr

awn

with

in th

ese

stud

ies.

The

Envi

roC

onsu

lt (2

019)

mod

ellin

g an

d w

ater

bal

ance

(A

ppen

dix

A) n

ow in

clud

e th

e M

DS.

ddG

roun

dwat

er

mod

el W

ater

Ba

lanc

e

Like

wis

e, M

ine

Wat

er D

ams

1 an

d 2,

the

sedi

men

tatio

n po

nds,

an

d th

e ra

w w

ater

dam

are

als

o no

t con

side

red

in th

e C

loud

GSM

(2

018)

gro

undw

ater

mod

ellin

g re

port,

the

Wat

er B

alan

ce R

epor

t (E

cOz,

201

8b),

the

Inun

datio

n St

udy

(Env

iroC

onsu

lt, 2

018c

), no

r th

e G

HD

(201

7b) a

quat

ic e

colo

gy re

port.

Wha

t affe

ct, i

f any

, will

cons

truct

ion

and

use

of th

ese

stor

ages

hav

e on

the

grou

ndw

ater

flo

w s

yste

m, t

he w

ater

bal

ance

, inu

ndat

ion

and

aqua

tic e

colo

gy?

As a

bove

.

eeW

MP

In T

able

2-1

of t

he W

MP,

it is

sta

ted

that

Min

e W

ater

Dam

2 a

cts

a co

ntin

genc

y fo

r hol

ding

exc

ess

wat

er d

ewat

ered

from

the

pit t

o av

oid

“Dry

” Sea

son

rele

ase

from

MW

D1.

Sho

uld

this

be

“Wet

” Se

ason

inst

ead

of D

ry?

No,

the

dam

has

bee

n de

sign

ed to

hol

d ex

cess

wat

er o

ver t

he

dry

seas

on to

avo

id d

ry s

easo

n re

leas

es to

a s

yste

m th

at

rece

ives

no

flow

at t

hat t

ime.

ffW

MP

In th

e or

igin

al T

oR, t

here

was

to b

e no

dis

char

ge o

f wat

er to

the

envi

ronm

ent.

How

ever

, with

in th

e W

MP,

wat

er fr

om M

ine

Wat

er

Dam

1 (M

WD

1) w

ill ne

ed to

be

disc

harg

ed a

t a ra

te n

ot to

exc

eed

50 L

/sec

. The

cha

nge

from

the

TOR

to th

e EI

S sh

ould

be

mad

e tra

nspa

rent

and

reas

ons

for t

he o

ffsite

dis

char

ge re

quire

men

t

Thes

e ch

ange

s w

ere

mad

e tra

nspa

rent

in th

e D

raft

EIS.

Sp

ecifi

cally

, Tab

le 1

-1 in

cha

pter

1 s

umm

aris

ed a

ll pr

ojec

t ch

ange

s th

at o

ccur

red

betw

een

the

NO

I and

EIS

. W

ater

di

scha

rges

are

list

ed in

this

tabl

e, a

long

with

the

reas

on w

hy th

e di

scha

rge

requ

irem

ent h

as a

risen

. W

hils

t the

EIS

ToR

did

not

Gra

nts

Lith

ium

Pro

ject

Wat

er M

anag

emen

t Pla

n

Revi

ew su

b-se

ctio

nRe

fRe

late

s to

Revi

ew c

omm

ent

Resp

onse

shou

ld b

e ex

plai

ned.

requ

ire a

ddre

ss o

f dis

char

ges,

as

a re

sult

of th

e pr

ojec

t cha

nges

, th

ese

wer

e de

taile

d in

Cha

pter

2, S

ectio

n 2.

12.3

of t

he D

raft

EIS.

U

pdat

ed d

etai

ls a

re p

rovi

ded

in th

e Su

pple

men

t and

the

Wat

er

Man

agem

ent P

lan.

ggW

MP

Sect

ion

2.4.

1 sh

ould

incl

ude

disc

ussi

on o

n th

e Se

dim

enta

tion

dam

s, in

clud

ing

volu

mes

and

inpu

ts.

This

has

bee

n ad

ded

to th

e W

MP,

see

Sec

tion

2.5.

hhW

MP

It ap

pear

s th

at w

ater

with

in th

e se

dim

enta

tion

pond

s m

ay b

e pe

riodi

cally

dis

char

ged

to th

e en

viro

nmen

t. Th

e W

MP

shou

ld

stat

e w

here

this

wat

er w

ill be

dis

char

ged.

See

Sect

ion

2.5

of u

pdat

ed W

MP.

iiW

MP

Tabl

e 4-

2 of

the

WM

P ap

pear

s to

be

mis

sing

the

redu

ctio

n to

flo

ws

if th

e O

HD

wal

l is

rais

ed b

y 1.

5 m

. Onl

y no

dam

and

ex

istin

g da

m s

cena

rios

are

incl

uded

. Thi

s ta

ble

shou

ld b

e re

vise

d to

incl

ude

the

mis

sing

info

rmat

ion.

Tabl

e 4-

2 ha

s be

en a

men

ded.

jjW

MP

It is

cle

ar th

at, d

urin

g th

e w

et s

easo

n, th

ere

will

be a

redu

ctio

n in

st

ream

flow

dow

nstre

am o

f the

MSD

in e

xces

s of

the

NT

Wat

er

Allo

catio

n Fr

amew

ork

guid

elin

e of

less

than

or e

qual

to 2

0%. I

t is

note

d th

at th

ese

redu

ctio

ns “c

ould

alte

r the

qua

lity

and/

or s

peci

es

com

posi

tion

of th

e rip

aria

n zo

ne” b

ut th

at “t

he ri

paria

n ha

bita

t al

ong

this

wat

erw

ay is

rela

tivel

y sp

arse

and

not

an

exam

ple

of a

ra

re, h

ighl

y di

vers

e, o

r sig

nific

ant h

abita

t for

thre

aten

ed s

peci

es

in th

e re

gion

”. Th

is a

rgum

ent m

ay n

ot h

old

muc

h va

lidity

and

the

min

e pr

opon

ent s

houl

d se

ek o

ther

mea

ns b

y w

hich

stre

am fl

ows

coul

d be

mai

ntai

ned

abov

e th

e no

ted

thre

shol

d. It

is p

roba

bly

pres

umpt

uous

to a

scer

tain

that

the

ripar

ian

zone

is o

f lim

ited

ecol

ogic

al v

alue

.

As in

dica

ted

prev

ious

ly, t

he N

T W

ater

Allo

catio

n Fr

amew

ork

guid

elin

e is

inte

nded

to b

e ap

plie

d to

rive

rs, n

ot m

inor

eph

emer

al

wat

erco

urse

s. T

he ri

paria

n zo

ne o

f the

eph

emer

al c

reek

line

has

be

en a

sses

sed

in e

colo

gica

l sur

veys

, and

it is

evi

dent

that

ther

e is

no

ripar

ian

vege

tatio

n or

inst

ream

hab

itats

that

indi

cate

a h

igh

leve

l of e

colo

gica

l val

ue.

Stre

am fl

ows

are

impo

rtant

to th

e ec

olog

ical

inte

grity

of t

he m

angr

ove

envi

ronm

ents

app

roxi

mat

ely

2 km

dow

nstre

am.

At th

is lo

catio

n, fl

ows

will

be re

duce

d by

12-

23%

, whi

ch is

con

side

red

unlik

ely

to c

ause

a m

easu

rabl

e im

pact

on

the

man

grov

es.

This

is a

dequ

atel

y di

scus

sed

in S

ectio

n 4

of

the

WM

P.

kkW

MP

In S

ectio

n 4.

4 of

the

WM

P, w

hy is

incr

ease

d di

scha

rge

from

the

Min

e Si

te D

am (M

SD) d

urin

g th

e W

et S

easo

n de

coup

led

from

a

sim

ilarly

pre

dict

ed re

duct

ion

in d

isch

arge

?

Impa

cts

from

redu

ced

flow

s fro

m s

urfa

ce w

ater

ext

ract

ion

from

th

e M

SD, a

re a

sses

sed

in is

olat

ion

from

the

asse

ssm

ent o

f im

pact

s fro

m in

crea

sed

flow

s fro

m M

WD

1 di

scha

rge

due

to th

e di

fferin

g w

ater

qua

lity

char

acte

ristic

s i.e

. dis

char

ge fr

om M

WD

1 co

ntai

ns g

roun

dwat

er re

mov

ed fr

om th

e pi

t and

it is

pos

sibl

y no

t ap

prop

riate

to c

onsi

der t

his

as a

n ‘e

nviro

nmen

tal f

low

’.

Gra

nts

Lith

ium

Pro

ject

Wat

er M

anag

emen

t Pla

n

Revi

ew su

b-se

ctio

nRe

fRe

late

s to

Revi

ew c

omm

ent

Resp

onse

llW

MP

Labo

rato

ry p

aram

eter

s fo

r sur

face

wat

er s

ampl

ing

loca

tions

sh

ould

incl

ude

tota

l met

als

as w

ell a

s di

ssol

ved

met

als

This

has

bee

n ad

ded.

mm

WM

PLa

bora

tory

par

amet

ers

for a

ll sa

mpl

ing

loca

tions

, inc

ludi

ng

surfa

ce w

ater

and

gro

undw

ater

, sho

uld

incl

ude

ioni

c ba

lanc

e, p

H

and

TDS.

Ioni

c ba

lanc

e is

not

typi

cally

use

d as

an

indi

cato

r of i

mpa

cts

to

wat

er q

ualit

y as

soci

ated

with

min

ing.

pH

and

TD

S ar

e m

easu

red

in-s

itu in

the

field

, thi

s is

bes

t pra

ctic

e. I

f sam

ples

wer

e se

nt to

a

lab

for p

H th

ey w

ould

be

wel

l out

side

the

6-ho

ur h

oldi

ng ti

me.

nnW

MP

Prop

osed

bor

es G

WB1

3 an

d G

WB1

4 ap

pear

to b

e w

ithin

the

foot

prin

t of t

he M

SD a

nd m

ay th

eref

ore

need

to b

e re

loca

ted.

See

upda

ted

grou

ndw

ater

bor

es to

be

inst

alle

d in

Sec

tion

10 o

f W

MP.

ooW

MP

Turb

idity

trig

gers

: the

turb

idity

trig

ger o

f 75

NTU

take

n fro

m th

e IN

PEX

proj

ect,

may

not

be

appr

opria

te fo

r the

Gra

nts

proj

ect.

INPE

X w

hich

was

a v

ery

larg

e fo

otpr

int p

roje

ct th

at in

clud

ed w

et

seas

on c

onst

ruct

ion.

The

turb

idity

lim

it in

that

pro

ject

was

als

o su

bjec

t to

a de

sign

(maj

or) s

torm

eve

nt ra

ther

than

a b

lank

et

trigg

er, a

nd a

lso

subj

ect t

o ad

just

men

t fro

m p

erfo

rman

ce re

view

of

mon

itorin

g re

sults

. Adj

ust t

he G

rant

s pr

ojec

t tur

bidi

ty li

mit

and

assi

gn a

des

ign

stor

m e

vent

bas

ed th

e fin

al tu

rbid

ity tr

igge

r ad

opte

d by

INPE

X an

d ap

prov

ed b

y N

TEPA

follo

win

g re

view

of

mon

itorin

g da

ta (b

ackg

roun

d an

d di

scha

rge)

from

that

pro

ject

.

As o

utlin

ed in

Sec

tion

2.5.

2, tu

rbid

ity in

the

sedi

men

t bas

ins

will

be re

duce

d as

muc

h as

pos

sibl

e, b

ut fi

nal d

isch

arge

from

the

sedi

men

t bas

ins

is n

ot a

lway

s ex

pect

ed to

ach

ieve

the

very

low

tu

rbid

ity le

vels

in th

e re

ceiv

ing

drai

nage

line

s. A

s su

ch, t

he

disc

harg

e st

anda

rd re

com

men

ded

for s

edim

ent b

asin

s in

IEC

A (2

008)

is a

dopt

ed: 9

0th

perc

entil

e N

TU re

adin

g no

t exc

eedi

ng

100,

and

50t

h pe

rcen

tile

NTU

read

ing

not e

xcee

ding

60.

Onc

e di

scha

rged

, the

turb

idity

of w

ater

from

the

sedi

men

t bas

ins

is e

xpec

ted

to re

duce

rapi

dly

with

dilu

tion

in th

e re

ceiv

ing

drai

nage

line

s, c

ombi

ned

with

the

filte

ring

effe

ct o

f the

veg

etat

ion

grow

ing

with

in th

e dr

aina

ge li

nes.

The

ass

essm

ent c

riter

ia

outli

ned

in T

able

10

3, a

pply

ing

to a

ll ro

utin

e su

rface

wat

er

mon

itorin

g si

tes

dow

nstre

am o

f the

min

e w

ill st

ill ap

ply

for

turb

idity

. Th

at is

, the

turb

idity

of t

he s

ites

dow

nstre

am o

f the

se

dim

ent b

asin

s (G

WS

SW1

and

GD

S SW

2) a

re e

xpec

ted

to

rem

ain

belo

w 2

0 N

TU.

Gra

nts

Lith

ium

Pro

ject

Wat

er M

anag

emen

t Pla

n

Revi

ew su

b-se

ctio

nRe

fRe

late

s to

Revi

ew c

omm

ent

Resp

onse

aW

ater

Ba

lanc

e

A C

onte

xtua

l Sta

tem

ent i

s no

t inc

lude

d in

the

Wat

er B

alan

ce

Rep

ort.

Whi

le s

ome

cont

extu

al in

form

atio

n is

pro

vide

d, e

.g.

clim

ate

data

in S

ectio

n 4,

the

Con

text

ual S

tate

men

t sho

uld

prov

ide

addi

tiona

l inf

orm

atio

n su

ch a

s si

te g

eolo

gy, h

ydro

geol

ogy

and

topo

grap

hy, c

atch

men

t det

ails

, reg

iona

l wat

er re

sour

ces,

and

w

ater

pol

icy

and

rule

s ap

plic

able

to th

e pr

opos

ed m

inin

g op

erat

ions

. Whi

le th

is in

form

atio

n is

pro

vide

d el

sew

here

in th

e W

MP,

and

its

anci

llary

doc

umen

ts, a

sta

ndal

one

Con

text

ual

Stat

emen

t sho

uld

be in

clud

ed w

ithin

the

Wat

er B

alan

ce re

port;

Con

text

ual s

tate

men

t has

bee

n ad

ded.

bW

ater

Ba

lanc

e

The

Wat

er B

alan

ce M

odel

repo

rt (S

ectio

n 3.

1) a

ssum

es a

25-

mon

th o

pera

tiona

l life

of t

he m

ine.

Yet

, in

Sect

ion

1 of

the

WM

P,

the

life

of th

e m

ine

is in

dica

ted

to b

e 2

to 3

yea

rs (S

ectio

n 1.

W

MP)

, a d

iffer

ence

rang

ing

from

-1 to

+11

mon

ths.

The

cor

rect

tim

elin

e sh

ould

be

mad

e co

nsis

tent

in a

ll up

date

d re

ports

;

All g

roun

dwat

er m

odel

ling,

sur

face

wat

er m

odel

ling

and

wat

er

bala

nce

now

use

the

sam

e m

ost u

p to

dat

e m

ine

desi

gn a

nd

timin

g.

c

Wat

er

Bala

nce

Gro

undw

ater

m

odel

and

W

MP

It is

not

ed th

at a

var

iety

of d

iffer

ent c

limat

e da

ta a

re u

sed

in th

e va

rious

tech

nica

l rep

orts

, i.e

. the

gro

undw

ater

mod

ellin

g st

udy,

th

e hy

drol

ogic

stu

dies

and

, aga

in, i

n th

e W

ater

Bal

ance

repo

rt.

Idea

lly, t

he s

ame

clim

ate

data

sho

uld

be u

sed

in e

ach

stud

y as

us

ing

varia

ble

data

intro

duce

s un

nece

ssar

y un

certa

inty

in th

e re

sults

;

All m

odel

ling

now

use

s SI

LO d

ata.

dW

ater

Ba

lanc

e

The

Wat

er B

alan

ce M

odel

use

s 50

th p

erce

ntile

clim

atic

dat

a fro

m

the

Dar

win

Airp

ort w

eath

er s

tatio

n. H

owev

er, t

he M

MP

Stru

ctur

e G

uide

spe

cific

ally

sta

tes

that

the

Wat

er B

alan

ce M

odel

sho

uld

incl

ude

scen

ario

s of

suc

cess

ivel

y dr

ier,

or w

ette

r, th

an a

vera

ge

seas

ons,

as

wel

l as

extre

me

wea

ther

eve

nts.

Thi

s sh

ould

be

addr

esse

d in

upd

ated

repo

rts.

The

wat

er b

alan

ce n

ow in

clud

es th

ese

scen

ario

s.

3.3

Conf

orm

ance

of

Wat

er

Bala

nce

with

M

CA W

AF

eW

ater

Ba

lanc

e

Figu

re 2

sho

uld

use

the

colo

ur g

uide

lines

spe

cifie

d in

Sec

tion

3.1

of th

e M

CA

WAF

. In

addi

tion,

for c

onsi

sten

cy w

ith th

e W

MP,

the

Envi

ronm

enta

l Dam

s sh

ould

be

re-la

belle

d as

Sed

imen

tatio

n D

ams.

Las

tly, t

he “S

edim

enta

tion”

or “

Envi

ronm

enta

l” sh

ould

in

clud

e ra

infa

ll as

an

inpu

t.

Col

our g

uide

s ha

ve b

een

used

. Se

dim

ent b

asin

s no

w in

clud

e ra

infa

ll.

Gra

nts

Lith

ium

Pro

ject

Wat

er M

anag

emen

t Pla

n

Revi

ew su

b-se

ctio

nRe

fRe

late

s to

Revi

ew c

omm

ent

Resp

onse

f

Wat

er

Bala

nce

Gro

undw

ater

m

odel

The

stat

ed p

it ar

ea (1

2.6

hect

ares

) in

Sect

ion

5.1.

1 of

the

Wat

er

Bala

nce

Rep

ort d

iffer

s fro

m th

at (1

4 he

ctar

es) s

tate

d in

the

grou

ndw

ater

mod

ellin

g re

port.

Thi

s in

cons

iste

ncy

shou

ld b

e co

rrect

ed a

nd a

ddre

ssed

, as

pit a

rea

will

dire

ctly

affe

ct th

e am

ount

of r

ainf

all e

nter

ing

the

pit a

nd, t

here

fore

, the

am

ount

of

wat

er th

at re

quire

s de

wat

erin

g.

All g

roun

dwat

er m

odel

ling,

sur

face

wat

er m

odel

ling

and

wat

er

bala

nce

now

use

the

sam

e m

ost u

p to

dat

e m

ine

desi

gn a

nd

timin

g.


APPENDIX E TPH/TRH AND BTEXN BASELINE SURFACE WATER AND GROUNDWATER QUALITY RESULTS

Bas

elin

e su

rfac

e w

ater

hyd

roca

rbon

resu

lts

C6 -

C9

Frac

tion

C10

- C14

Fr

actio

nC1

5 - C

28

Frac

tion

C29

- C36

Fr

actio

n

C10

- C36

Fr

actio

n (s

um)

C6 -

C10

Frac

tion

C6 -

C10

Frac

tion

min

us

BTEX

(F1)

>C10

- C1

6 Fr

actio

n>C

16 -

C34

Frac

tion

>C34

- C4

0 Fr

actio

n

>C10

- C4

0 Fr

actio

n (s

um)

>C10

- C1

6 Fr

actio

n m

inus

Na

phth

alen

e (F

2)Be

nzen

eTo

luen

eEt

hylb

enze

ne

met

a- &

pa

ra-

Xyle

ne

orth

o-Xy

lene

Tota

l Xy

lene

sSu

m o

f BT

EXNa

phth

alen

e

µg/L

µg/L

µg/L

µg/L

µg/L

µg/L

µg/L

µg/L

µg/L

µg/L

µg/L

µg/L

µg/L

µg/L

µg/L

µg/L

µg/L

µg/L

µg/L

µg/L

GU

S S

W3

15-0

2-17

<20

<50

<100

<50

<50

<20

<20

<100

<100

<100

<100

<100

<1<2

<2<2

<2<2

<1<5

GU

S S

W3

19-0

4-17

<20

<50

<100

<50

<50

<20

<20

<100

<100

<100

<100

<100

<1<2

<2<2

<2<2

<1<5

GU

S S

W3

01-0

2-18

<20

<50

<100

<50

<50

<20

<20

<100

<100

<100

<100

<100

<1<2

<2<2

<2<2

<1<5

GU

S S

W3

14-0

3-18

<20

<50

<100

<50

<50

<20

<20

<100

<100

<100

<100

<100

<1<2

<2<2

<2<2

<1<5

GU

S S

W3

03-0

5-18

<20

<50

<100

<50

<50

<20

<20

<100

<100

<100

<100

<100

<1<2

<2<2

<2<2

<1<5

GD

S S

W1

15-0

2-17

<20

<50

<100

<50

<50

<20

<20

<100

<100

<100

<100

<100

<1<2

<2<2

<2<2

<1<5

GD

S S

W1

19-0

4-17

<20

<50

<100

<50

<50

<20

<20

<100

<100

<100

<100

<100

<1<2

<2<2

<2<2

<1<5

GD

S S

W1

31-0

1-18

<20

<50

<100

<50

<50

<20

<20

<100

<100

<100

<100

<100

<1<2

<2<2

<2<2

<1<5

GD

S S

W1

14-0

3-18

<20

<50

<100

<50

<50

<20

<20

<100

<100

<100

<100

<100

<1<2

<2<2

<2<2

<1<5

GD

S S

W2

15-0

2-17

<20

<50

<100

<50

<50

<20

<20

<100

<100

<100

<100

<100

<1<2

<2<2

<2<2

<1<5

GD

S S

W2

19-0

4-17

<20

<50

<100

<50

<50

<20

<20

<100

<100

<100

<100

<100

<1<2

<2<2

<2<2

<1<5

GD

S S

W2

31-0

1-18

<20

<50

<100

<50

<50

<20

<20

<100

<100

<100

<100

<100

<1<2

<2<2

<2<2

<1<5

GD

S S

W2

14-0

3-18

<20

<50

<100

<50

<50

<20

<20

<100

<100

<100

<100

<100

<1<2

<2<2

<2<2

<1<5

GD

S S

W2

03-0

5-18

<20

<50

<100

<50

<50

<20

<20

<100

<100

<100

<100

<100

<1<2

<2<2

<2<2

<1<5

OH

D12

-10-

17<2

0<5

0<1

00<5

0<5

0<2

0<2

0<1

00<1

00<1

00<1

00<1

00<1

<2<2

<2<2

<2<1

<5O

HD

09-0

8-18

<20

<50

<100

<50

<50

<20

<20

<100

<100

<100

<100

<100

<1<2

<2<2

<2<2

<1<5

BP

HIS

TOR

IC P

IT15

-02-

17<2

0<5

0<1

00<5

0<5

0<2

0<2

0<1

00<1

00<1

00<1

00<1

00<1

<2<2

<2<2

<2<1

<5B

P H

ISTO

RIC

PIT

19-0

4-17

<20

<50

<100

<50

<50

<20

<20

<100

<100

<100

<100

<100

<1<2

<2<2

<2<2

<1<5

BP

HIS

TOR

IC P

IT12

-10-

17<2

0<5

0<1

00<5

0<5

0<2

0<2

0<1

00<1

00<1

00<1

00<1

00<1

<2<2

<2<2

<2<1

<5B

P H

ISTO

RIC

PIT

01-0

2-18

<20

<50

<100

<50

<50

<20

<20

<100

<100

<100

<100

<100

<1<2

<2<2

<2<2

<1<5

BP

HIS

TOR

IC P

IT14

-03-

18<2

0<5

0<1

00<5

0<5

0<2

0<2

0<1

00<1

00<1

00<1

00<1

00<1

<2<2

<2<2

<2<1

<5B

P H

ISTO

RIC

PIT

03-0

5-18

<20

<50

<100

<50

<50

<20

<20

<100

<100

<100

<100

<100

<1<2

<2<2

<2<2

<1<5

BP

HIS

TOR

IC P

IT08

-08-

18<2

0<5

0<1

00<5

0<5

0<2

0<2

0<1

00<1

00<1

00<1

00<1

00<1

<2<2

<2<2

<2<1

<5B

PU

S S

W1

15-0

2-17

<20

<50

<100

<50

<50

<20

<20

<100

<100

<100

<100

<100

<1<2

<2<2

<2<2

<1<5

BP

US

SW

119

-04-

17<2

032

014

50<5

017

70<2

0<2

080

084

0<1

0016

4080

0<1

<2<2

<2<2

<2<1

<5B

PU

S S

W1

01-0

2-18

<20

<50

<100

<50

<50

<20

<20

<100

<100

< 100

<100

<100

<1<2

<2<2

<2<2

<1<5

BP

US

SW

114

-03-

18<2

0<5

0<1

00<5

0<5

0<2

0<2

0<1

00<1

00<1

00<1

00<1

00<1

<2<2

<2<2

<2<1

<5B

PU

S S

W1

03-0

5-18

<20

<50

<100

<50

<50

<20

<20

<100

<100

<100

<100

<100

<1<2

<2<2

<2<2

<1<5

BP

DS

SW

215

-02-

17<2

0<5

0<1

00<5

0<5

0<2

0<2

0<1

00<1

00<1

00<1

00<1

00<1

<2<2

<2<2

<2<1

<5B

PD

S S

W2

19-0

4-17

<20

<50

<100

<50

<50

<20

<20

<100

<100

<100

<100

<100

<1<2

<2<2

<2<2

<1<5

BP

DS

SW

201

-02-

18<2

0<5

0<1

00<5

0<5

0<2

0<2

0<1

00<1

00<1

00<1

00<1

00<1

<2<2

<2<2

<2<1

<5B

PD

S S

W2

14-0

3-18

<20

<50

<100

<50

<50

<20

<20

<100

<100

<100

<100

<100

<1<2

<2<2

<2<2

<1<5

BP

DS

SW

203

-05-

18<2

0<5

0<1

00<5

0<5

0<2

0<2

0<1

00<1

00<1

00<1

00<1

00<1

<2<2

<2<2

<2<1

<5

BTEX

N

Site

Date

Sa

mpl

ed

Tota

l Pet

role

um H

ydro

carb

ons

- NEP

M 1

999

Tota

l Rec

over

able

Hyd

roca

rbon

s - N

EPM

201

3

Bas

elin

e gr

ound

wat

er h

ydro

carb

on re

sults

C6 -

C9

Frac

tion

C10

- C14

Fr

actio

nC1

5 - C

28

Frac

tion

C29

- C36

Fr

actio

n

C10

- C36

Fr

actio

n (s

um)

C6 -

C10

Frac

tion

C6 -

C10

Frac

tion

min

us B

TEX

(F1)

>C10

- C1

6 Fr

actio

n>C

16 -

C34

Frac

tion

>C34

- C4

0 Fr

actio

n

>C10

- C4

0 Fr

actio

n (s

um)

>C10

- C1

6 Fr

actio

n m

inus

Na

phth

alen

e (F

2)

Benz

ene

Tolu

ene

Ethy

lben

zene

met

a- &

par

a-Xy

lene

orth

o-Xy

lene

Tota

l Xy

lene

sSu

m o

f BT

EXNa

phth

alen

e

µg/L

µg/L

µg/L

µg/L

µg/L

µg/L

µg/L

µg/L

µg/L

µg/L

µg/L

µg/L

µg/L

µg/L

µg/L

µg/L

µg/L

µg/L

µg/L

µg/L

GW

B01

27-0

6-17

--

--

--

--

--

--

--

--

--

--

GW

B01

31-0

1-18

<20

<50

<100

<50

<50

<20

<20

<100

<100

<100

<100

<100

<1<2

<2<2

<2<2

<1<5

GW

B01

01-0

5-18

<20

<50

<100

<50

<50

<20

<20

<100

<100

<100

<100

<100

<1<2

<2<2

<2<2

<1<5

GW

B01

08-0

8-18

<20

<50

<100

<50

<50

<20

<20

<100

<100

<100

<100

<100

<1<2

<2<2

<2<2

<1<5

GW

B03

27-0

6-17

--

--

--

--

--

--

--

--

--

--

GW

B03

01-0

2-18

<20

<50

<100

<50

<50

<20

<20

<100

<100

<100

<100

<100

<1<2

<2<2

<2<2

<1<5

GW

B03

01-0

5-18

<20

<50

<100

<50

<50

<20

<20

<100

<100

<100

<100

<100

<1<2

<2<2

<2<2

<1<5

GW

B03

09-0

8-18

<20

<50

<100

<50

<50

<20

<20

<100

<100

<100

<100

<100

<1<2

<2<2

<2<2

<1<5

GW

B07

27-0

6-17

--

--

--

--

--

--

--

--

--

--

GW

B07

01-0

2-18

<20

<50

<100

<50

<50

<20

<20

<100

<100

<100

<100

<100

<1<2

<2<2

<2<2

<1<5

GW

B07

01-0

5-18

<20

<50

<100

<50

<50

<20

<20

<100

<100

<100

<100

<100

<1<2

<2<2

<2<2

<1<5

GW

B07

09-0

8-18

<20

<50

<100

<50

<50

<20

<20

<100

<100

<100

<100

<100

<1<2

<2<2

<2<2

<1<5

GW

B08

27-0

6-17

--

--

--

--

--

--

--

--

--

--

GW

B08

31-0

1-18

<20

<50

<100

<50

<50

<20

<20

<100

<100

<100

<100

<100

<1<2

<2<2

<2<2

<1<5

GW

B08

01-0

5-18

<20

<50

<100

<50

<50

<20

<20

<100

<100

<100

<100

<100

<1<2

<2<2

<2<2

<1<5

GW

B08

08-0

8-18

<20

<50

<100

<50

<50

<20

<20

<100

<100

<100

<100

<100

<1<2

<2<2

<2<2

<1<5

GW

B10

27-0

6-17

--

--

--

--

--

--

--

--

--

--

GW

B10

31-0

1-18

<20

<50

<100

<50

<50

<20

<20

<100

<100

<100

<100

<100

<1<2

<2<2

<2<2

<1<5

GW

B10

01-0

5-18

<20

<50

<100

<50

<50

<20

<20

<100

<100

<100

<100

<100

<1<2

<2<2

<2<2

<1<5

GW

B10

08-0

8-18

<20

<50

<100

<50

<50

<20

<20

<100

<100

<100

<100

<100

<1<2

<2<2

<2<2

<1<5

Site

Date

Sa

mpl

ed

BTEX

NTo

tal P

etro

leum

Hyd

roca

rbon

s - N

EPM

199

9To

tal R

ecov

erab

le H

ydro

carb

ons

- NEP

M 2

013