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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
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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Recipients are responsible for eliminating all superseded documents in their possession.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: ecoz@ecoz.com.auInternet: 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.
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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)
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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
LegendMineral lease (application)
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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).
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Figure 2-2. Flow diagram of project water inputs, outputs, tasks and storages.
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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.
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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.
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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.
minepitshelltailings
storagefacility
haul road & pit access
raw water damROM pad
site access culvert
mine water dam 2 Cox Peninsula Rd
mine water dam 1
sediment basin 2
sediment basin 1
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Path: Z:\01 EcOz_Documents\04 EcOz Vantage GIS\EZ18086 - Grants Project - EIS\01 Project Files\Water Mgmt Plan\Figure 2-4. Map of erosion and sediment controls.mxd
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
Red box indicates map extent
- 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.
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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.
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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
0.5
2a 3.42b 3.0
0.6
Total 13.6 0.5
mine site dam
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Observation Hill dam
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WestArm
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Figure 3-2 Map of surface water catchments of the project area
LegendMineral lease (application)
Mine site footprint
Water supply infrastructure
Watercourse
Darwin Harbour catchment
Bynoe Harbour catchment
Red box indicates map extent
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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 3-3. Map of mine footprint sub-catchments
LegendMine site footprint
internal drainage
water pipeline
Water supply infrastructure
Sub-catchment boundary
Watercourse
Red box indicates map extent
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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.
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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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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 3-4 Location of baseline surface water, groundwater and aquatic ecology monitoring sites
LegendMineral lease (application)
Mine site footprint
Water supply infrastructure
!( Surface water monitoring site
!( Groundwater monitoring bore
#* Aquatic ecology site
Red box indicates map extent
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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.
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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
2020 dry season No discharge NA NA
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
2020 wet season total 449.77 5096 8
2021 dry season No discharge NA NA
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
2021 wet season total 300.26 5096 8
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.
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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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In regards to potential impacts during mining, the following is highlighted:
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
62
Tabl
e 6-
3. B
asel
ine
surf
ace
wat
er q
ualit
y m
onito
ring
resu
lts, m
ajor
ani
ons
and
catio
ns.
Tota
l ha
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
<0.0
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
.05
<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
.05
<0.0
01<0
.000
1B
P H
ISTO
RIC
PIT
12-1
0-17
<0.0
10.
015
<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
01-0
2-18
0.05
0.00
6<0
.000
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
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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.
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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.
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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
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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.
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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.
TPH/TRH and BTEXN concentrations are always below detection limits.
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Potential impacts
In regards to potential impacts during mining, the following is highlighted:
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.
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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.
TPH/TRH and BTEXN concentrations are always below detection limits.
Potential impacts
In regards to potential impacts during mining, the following is highlighted:
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.
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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.
Grants Lithium Project Water Management Plan
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
Elevated in laterite aquifer but likely reduced below objective with dilution in pit by rainwater
and also BCF water
LeadAlways below detection limit
Always below detection limit
Occasionally above objective
Elevated in laterite aquifer but likely reduced below objective with dilution in pit by rainwater
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
Grants Lithium Project Water Management Plan
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
dilution in pit by rainwater. May also reduce with
absorption/co-precipitation with iron in surface water.
Reactive P Mostly below objective Always above objective Always above objective
High in both aquifers but likely reduced below objective with
dilution in pit by rainwater. May also reduce with
absorption/co-precipitation with iron in surface water.
Grants Lithium Project Water Management Plan
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.
Grants Lithium Project Water Management Plan
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
Grants Lithium Project Water Management Plan
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
Grants Lithium Project Water Management Plan
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
Grants Lithium Project Water Management Plan
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.
Grants Lithium Project Water Management Plan
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
owns
tream
S
urfa
ce W
ater
2Ex
istin
g
Dow
nstre
am o
f GU
S SW
3 an
d G
DS
SW1,
whe
re
ephe
mer
al d
rain
age
lines
on
eith
er s
ide
of m
ine
foot
prin
t joi
n an
d flo
w th
roug
h cu
lver
t und
er C
ox
Peni
nsul
a R
oad.
Mon
itor i
mpa
cts
imm
edia
tely
dow
nstre
am o
f nor
ther
n si
de o
f min
e fo
otpr
int
incl
udin
g se
dim
ent b
asin
1 d
isch
arge
and
MSD
rele
ases
. Al
so, r
ecei
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
Min
ing
Leas
e.
GU
S SW
3G
rant
s U
pstre
am
Sur
face
Wat
er 3
Exis
ting
Ephe
mer
al d
rain
age
line
upst
ream
of m
ine
foot
prin
t, w
este
rn s
ide
in s
ub-c
atch
men
t 5a.
Th
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
.
Ref
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
.
GU
S SW
4G
rant
s U
pstre
am
Sur
face
Wat
er 4
New
Ephe
mer
al d
rain
age
line
in a
djac
ent s
ub-
catc
hmen
t 2b
not s
ubje
ct to
min
e im
pact
s.
Ref
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
Roa
d an
d w
here
the
wat
erw
ay
mee
ts D
arw
in H
arbo
ur ti
dal w
ater
s.
Mon
itor e
xten
t of i
mpa
cts
(if a
ny) o
n w
ater
way
s fu
rther
dow
nstre
am o
f m
ine.
Mon
thly
dur
ing
wet
se
ason
(Nov
-Apr
)
Sed1
Sed
imen
t bas
in 1
New
Sedi
men
t bas
in 1
, whi
ch re
ceiv
es ru
n-of
f fro
m
WR
D a
nd a
ll op
erat
iona
l are
as in
nor
ther
n ha
lf of
m
ine
site
.
Sed2
Sed
imen
t bas
in 2
New
Sedi
men
t bas
in 2
, whi
ch re
ceiv
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
D1
Min
e W
ater
Dam
1N
ewD
am re
ceiv
es w
ater
dew
ater
ed fr
om th
e pi
t.
Mon
itor w
ater
qua
lity
in s
edim
ent b
asin
s/M
WD
1 to
ens
ure
they
mee
t as
sess
men
t crit
eria
prio
r to
rele
ase.
For
gui
ding
any
wat
er q
ualit
y tre
atm
ent m
easu
res
requ
ired
prio
r to
rele
ase
or m
anag
emen
t act
ions
to
impr
ove
inpu
t wat
er q
ualit
y.
Prio
r to
any
cont
rolle
d re
leas
e fie
ld
para
met
ers
are
to b
e m
easu
red
to c
onfir
m
wat
er q
ualit
y m
eets
di
scha
rge
crite
riaW
eekl
y fie
ld
para
met
ers
durin
g w
et
seas
on (N
ov –
Apr
) re
gard
less
of
disc
harg
eW
eekl
y la
b pa
ram
eter
s w
hen
disc
harg
ing
from
ei
ther
MW
D1
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
D2
Min
e W
ater
Dam
2N
ewTh
is d
am re
ceiv
es e
xces
s TS
F de
cant
wat
er.
Mon
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
urfa
ce w
ater
mon
itorin
g re
sults
.
Wee
kly
field
pa
ram
eter
s w
hen
dam
is
rece
ivin
g w
ater
Mon
thly
lab
para
met
ers
whe
n da
m
is re
ceiv
ing
wat
er
Pit
Min
e P
it S
ump
New
Min
e pi
t sum
p co
llect
s gr
ound
wat
er in
flow
s an
d in
cide
nt ra
infa
ll fo
r pum
ping
to M
WD
1.
Mon
itor q
ualit
y of
gro
undw
ater
inflo
ws
and
prov
ide
early
war
ning
of a
ny
unus
ually
hig
h le
vels
of c
onta
min
atio
n or
AM
D ri
sk.
Wee
kly
field
pa
ram
eter
s ye
ar-ro
und
Mon
thly
lab
para
met
ers
year
-roun
d
OH
DO
bser
vatio
n H
ill D
amEx
istin
gSu
rface
wat
er s
tora
geM
onito
r inc
omin
g qu
ality
of w
ater
bei
ng u
sed
on s
ite.
BPU
S SW
1B
P33
Pit
Ups
tream
S
urfa
ce W
ater
1Ex
istin
gD
owns
tream
of O
HD
but
ups
tream
BP3
3 pi
t
Bynoe Harbour
BPD
S SW
2B
P33
Pit
Dow
nstre
am
Sur
face
Wat
er 2
Exis
ting
Dow
nstre
am o
f OH
D, B
PUS
SW1,
and
BP3
3 pi
t
Mon
itor i
mpa
cts
from
OH
D w
ater
ext
ract
ion
on d
owns
tream
wat
erw
ays.
C
an a
lso
be u
sed
as a
regi
onal
refe
renc
e si
te fo
r mon
itorin
g la
rger
-sca
le
chan
ges
to b
ackg
roun
d w
ater
qua
lity
to e
nabl
e di
stin
ctio
n of
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)
!(!(
!(!(
!(!(
!(!(
!(!(
!(!(
!(
!(
!(
!(
!(
!(
!( !(
!(
!(
!(
!(
!(
GWB06GWB07
GWB10 GWB08
GWB13GWB14
GWB15GWB16
GWB12GWB11
GWB01GWB03
BPUS SW2
BPUS SW1
GDS SW2
OHD
GDS SW5
GUS SW4GUS SW3 GDS SW1
Sed 1
Sed 2MWD 1
Pit
MWD 2
690000 692000 694000 69600085
9400
0
8594
000
8596
000
8596
000
8598
000
8598
000
8600
000
8600
000
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
LegendMineral lease (application)
Mine site footprint
Water supply infrastructure
!( Operations water monitoring site
!( Surface water monitoring site
!( Groundwater monitoring bore
!(Groundwater monitoring bore(to be discontinued)
Red box indicates map extent
Grants Lithium Project Water Management Plan
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
Grants Lithium Project Water Management Plan
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.
Grants Lithium Project Water Management Plan
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.
Grants Lithium Project Water Management Plan
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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.
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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.
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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.
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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.
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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.
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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.
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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.
Grants Lithium Project Water Management Plan
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
6.2.1 Input-Output Statement ..................................................................................................... 15
6.2.2 Accuracy Statement .......................................................................................................... 16
6.2.3 Statement of Operational Efficiencies ............................................................................... 17
6.3 Successive dry years scenario .............................................................................................. 19
6.3.1 Input-Output Statement ..................................................................................................... 19
6.3.2 Accuracy Statement .......................................................................................................... 20
6.3.3 Statement of Operational Efficiencies ............................................................................... 20
6.4 Successive average rainfall years scenario with no dust suppression in January and February ............................................................................................................................................. 22
6.4.1 Input-Output Statement ..................................................................................................... 22
6.4.2 Accuracy Statement .......................................................................................................... 23
6.4.3 Statement of Operational Efficiencies ............................................................................... 24
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.
Grants Lithium Project - Preliminary Mine Site Water Balance Supplementary Report Page 2 of 44
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.
Grants Lithium Project - Preliminary Mine Site Water Balance Supplementary Report Page 3 of 44
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Grants Lithium Project - Preliminary Mine Site Water Balance Supplementary Report Page 5 of 44
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)
50th %ile rainfall (mm)
50th %ile evaporation (mm)
90th %ile rainfall (mm)
10th %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.
Grants Lithium Project - Preliminary Mine Site Water Balance Supplementary Report Page 6 of 44
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.
y = -1340.6x + 91828
0
20000
40000
60000
80000
0 5 10 15 20 25 30 35
Inflo
w (K
L/m
onth
)
Month
Pit Groundwater inflows
1st to 21st month data22nd to 29th month dataEstimated dataLinear (22nd to 29th month data)
Grants Lithium Project - Preliminary Mine Site Water Balance Supplementary Report Page 7 of 44
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:
Grants Lithium Project - Preliminary Mine Site Water Balance Supplementary Report Page 8 of 44
■ 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.
Grants Lithium Project - Preliminary Mine Site Water Balance Supplementary Report Page 9 of 44
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.
Grants Lithium Project - Preliminary Mine Site Water Balance Supplementary Report Page 10 of 44
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.
Grants Lithium Project - Preliminary Mine Site Water Balance Supplementary Report Page 11 of 44
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
80 0 0 2 Estimated/Low
Groundwater
Aquifer interception
0 290 0 3 Estimated/medium
Aquifer interception
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
Total Inputs 105 1073 0
Output Surface Water
Discharge 1114 0 0 Estimated/Low
Evaporation 64 0 0 Estimated/Low
Total Outputs 1178 0 0
Grants Lithium Project - Preliminary Mine Site Water Balance Supplementary Report Page 12 of 44
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%
Grants Lithium Project - Preliminary Mine Site Water Balance Supplementary Report Page 13 of 44
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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Grants Lithium Project - Preliminary Mine Site Water Balance Supplementary Report Page 15 of 44
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.
6.2.1 Input-Output Statement
The input-output statement is shown in the table below:
Table 9. Input-Output statement for successive wet 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
741 1030 0 1 Estimated/Low
Off-site Storages
37 0 0 2 Estimated/Low
Groundwater
Aquifer interception
0 290 0 3 Estimated/medium
Aquifer interception
0 1739 0 4 Simulated/Medium
Total Inputs 778 3059 0
Output
Surface Water Discharge 1346 0 0 5 Estimated/Low
Other Evaporation 1657 0 0 6 Estimated/Medium
Entrainment 0 0 492 7 Estimated/Medium
Total Outputs 3003 0 492
Diversions
Input Surface Water Precipitation
and Runoff 198 2018 0 8 Estimated/Low
Total Inputs 198 2018 0
Output Surface Water
Discharge 2140 0 0 Estimated/Low
Evaporation 75 0 0 Estimated/Low
Total Outputs 2215 0 0
Notes for Input-Output statement:
1. The precipitation and runoff were estimated using the equations in section 5.1.1 and 5.1.3 and90th %ile SILO monthly rainfall data from Table 1.
2. The water extracted from off-site storages was estimated by balancing the whole water balancesystem.
Grants Lithium Project - Preliminary Mine Site Water Balance Supplementary Report Page 16 of 44
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
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 10.
Table 10. Volumes (ML) of water in storages for successive wet years scenario.
RWD MWD1 MWD2 TSF Total
1st July 2019 0 0 0 0 0
31st May 2022 11 64 251 16 342
Changes in storage 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
6.2.2 Accuracy Statement
The accuracy statement for the successive wet years scenario is in Table 11.
Table 11. Accuracy statement for successive wet years scenario.
Types % of all Flows Confidence (%)
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%
Grants Lithium Project - Preliminary Mine Site Water Balance Supplementary Report Page 17 of 44
6.2.3 Statement of Operational Efficiencies
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.
Operational efficiencies
Total volume to tasks (ML) 3561
Total volume of reused water (ML) 1595
Reuse efficiency (%) 45
Total volume of recycled water (ML) 0
Recycling efficiency (%) 0
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Grants Lithium Project - Preliminary Mine Site Water Balance Supplementary Report Page 19 of 44
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.
6.3.1 Input-Output Statement
The input-output statement is shown in the table below:
Table 13. Input-Output statement for successive dry 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
201 279 0 1 Estimated/Low
Off-site Storages
121 0 0 2 Estimated/Low
Groundwater
Aquifer interception
0 290 0 3 Estimated/medium
Aquifer interception
0 1738 0 4 Simulated/Medium
Total Inputs 322 2307 0
Output
Surface Water Discharge 589 0 0 5 Estimated/Low
Other Evaporation 1529 0 0 6 Estimated/Medium
Entrainment 0 0 492 7 Estimated/Medium
Total Outputs 2117 0 492
Diversions
Input Surface Water Precipitation
and Runoff 54 547 0 8 Estimated/Low
Total Inputs 54 547 0
Output Surface Water
Discharge 551 0 0 Estimated/Low
Evaporation 50 0 0 Estimated/Low
Total Outputs 601 0 0
Notes for Input-Output statement:
1. The precipitation and runoff were estimated using the equations in section 5.1.1 and 5.1.3 and10th %ile SILO monthly rainfall data from Table 1.
2. The water extracted from off-site storages was estimated by balancing the whole water balancesystem.
Grants Lithium Project - Preliminary Mine Site Water Balance Supplementary Report Page 20 of 44
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 90th %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 14.
Table 14. Volumes (ML) of water in storages for successive dry years scenario.
RWD MWD1 MWD2 TSF Total
1st July 2019 0 0 0 0 0
31st May 2022 0 20 0 0 0
Changes in storage 0 20 0 0 0
Total Inputs – Total Outputs = 322+2307 - 2117 - 492 = 20 ML = Change in storage.
The system is in balance.
6.3.2 Accuracy Statement
The accuracy statement for the successive dry years scenario is in Table 15.
Table 15. Accuracy statement for successive dry years scenario.
Types % of all Flows Confidence (%)
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%
6.3.3 Statement of Operational Efficiencies
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.
Operational efficiencies
Total volume to tasks (ML) 2871
Total volume of reused water (ML) 1287
Reuse efficiency (%) 45
Total volume of recycled water (ML) 0
Recycling efficiency (%) 0
Gra
nts
Lith
ium
Pro
ject
- Pr
elim
inar
y M
ine
Site
Wat
er B
alan
ce S
uppl
emen
tary
Rep
ort
Page
21
of 4
4
Mix
ed W
ater
S
tore
Raw
Wat
er S
tore
Fig
ure
6.
Op
erat
ion
al f
low
ch
art
for
the
succ
essi
ve
dry
yea
rs s
cen
ario
Dir
ect
Rai
nfa
ll
DM
S P
lan
t
Du
st
Su
pp
ress
ion
TS
F C
ells
Eva
po
rati
on
En
trai
nm
ent
in
tail
ing
s
En
trai
nm
ent
in
Pro
du
ct a
nd
R
ejec
t
Pit
Ru
no
ff &
G
rou
nd
wat
er
Infl
ow
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no
ff f
rom
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istu
rbed
Are
as
Cru
shin
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nd
S
cree
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dm
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trat
ion
/ab
luti
on
Dis
char
ge
to
envi
ron
men
t
Div
ersi
on
(Sed
imen
t B
asin
s)
130
27
45
212
240
252
298
25
51 51
98
41
547
551
589
959
959
9
942
0
43
2095
Infl
ow
s fr
om
E
xter
nal
S
tora
ges
121
Figures
arein
MLforthepe
riodfrom
1stJu
ly20
19to
31st
May
2022
.Stores
are
blue
,inpu
tsin
gree
n,ou
tputs
inred,
tasks
ingrey,dive
rsions
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TSFisus
edas
both
astorean
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672
549
5450
Grants Lithium Project - Preliminary Mine Site Water Balance Supplementary Report Page 22 of 44
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.
6.4.1 Input-Output Statement
The input-output statement is shown in the table below:
Table 17. Input-Output statement for successive average years scenario with no dust
suppression in January and February.
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
80 0 0 2 Estimated/Low
Groundwater
Aquifer interception
0 290 0 3 Estimated/medium
Aquifer interception
0 1739 0 4 Simulated/Medium
Total Inputs 474 2576 0
Output
Surface Water Discharge 1094 0 0 5 Estimated/Low
Other Evaporation 1371 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
Total Inputs 105 1073 0
Output Surface Water
Discharge 1121 0 0 Estimated/Low
Evaporation 57 0 0 Estimated/Low
Total Outputs 1178 0 0
Grants Lithium Project - Preliminary Mine Site Water Balance Supplementary Report Page 23 of 44
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 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 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 18.
Table 18. Volumes (ML) of water in storages for successive average years scenario with no dust
suppression in January and February.
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.
6.4.2 Accuracy Statement
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.
Types % of all Flows Confidence (%)
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%
Grants Lithium Project - Preliminary Mine Site Water Balance Supplementary Report Page 24 of 44
6.4.3 Statement of Operational Efficiencies
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.
Operational efficiencies
Total volume to tasks (ML) 2971
Total volume of reused water (ML) 1477
Reuse efficiency (%) 50
Total volume of recycled water (ML) 0
Recycling efficiency (%) 0
Gra
nts
Lith
ium
Pro
ject
- Pr
elim
inar
y M
ine
Site
Wat
er B
alan
ce S
uppl
emen
tary
Rep
ort
Page
25
of 4
4
Mix
ed W
ater
S
tore
Raw
Wat
er S
tore
Fig
ure
7.
Op
erat
ion
al f
low
ch
art
for
the
succ
essi
ve a
vera
ge
rain
fall
ye
ars
scen
ario
wit
h n
o d
ust
su
pp
ress
ion
in
Jan
uar
y an
d F
ebru
ary
Dir
ect
Rai
nfa
ll
DM
S P
lan
t
Du
st
Su
pp
ress
ion
TS
F C
ells
Eva
po
rati
on
En
trai
nm
ent
in
tail
ing
s
En
trai
nm
ent
in
Pro
du
ct a
nd
R
ejec
t
Pit
Ru
no
ff &
G
rou
nd
wat
er
Infl
ow
Ru
no
ff f
rom
D
istu
rbed
Are
as
Cru
shin
g a
nd
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gA
dm
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trat
ion
/ab
luti
on
Dis
char
ge
to
envi
ron
men
t
Div
ersi
on
(Sed
imen
t B
asin
s)
254
53
88
416
240
252
92
112
51 51
92
174
1073
1121
1094
813
813
9
938
4
74
2160
Infl
ow
s fr
om
E
xter
nal
S
tora
ges
80
Figures
arein
MLforthepe
riodfrom
1stJu
ly20
19to
31st
May
2022
.Stores
are
blue
,inpu
tsin
gree
n,ou
tputs
inred,
tasks
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both
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672
669
105
57
Grants Lithium Project - Preliminary Mine Site Water Balance Supplementary Report Page 26 of 44
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.
Grants Lithium Project - Preliminary Mine Site Water Balance Supplementary Report Page 27 of 44
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%
Grants Lithium Project - Preliminary Mine Site Water Balance Supplementary Report Page 28 of 44
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.
Grants Lithium Project - Preliminary Mine Site Water Balance Supplementary Report Page 29 of 44
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
Grants Lithium Project - Preliminary Mine Site Water Balance Supplementary Report Page 30 of 44
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
Grants Lithium Project - Preliminary Mine Site Water Balance Supplementary Report Page 31 of 44
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
Grants Lithium Project - Preliminary Mine Site Water Balance Supplementary Report Page 32 of 44
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
Grants Lithium Project - Preliminary Mine Site Water Balance Supplementary Report Page 33 of 44
Appendix B. Water balance modelling results for successive wet
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 0.02 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
Grants Lithium Project - Preliminary Mine Site Water Balance Supplementary Report Page 34 of 44
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 0.01 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
Grants Lithium Project - Preliminary Mine Site Water Balance Supplementary Report Page 35 of 44
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
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
Grants Lithium Project - Preliminary Mine Site Water Balance Supplementary Report Page 36 of 44
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
Grants Lithium Project - Preliminary Mine Site Water Balance Supplementary Report Page 37 of 44
Appendix C. Water balance modelling results for successive dry 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 8.71 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
Grants Lithium Project - Preliminary Mine Site Water Balance Supplementary Report Page 38 of 44
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 0.00 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
Grants Lithium Project - Preliminary Mine Site Water Balance Supplementary Report Page 39 of 44
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
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
Grants Lithium Project - Preliminary Mine Site Water Balance Supplementary Report Page 40 of 44
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
Grants Lithium Project - Preliminary Mine Site Water Balance Supplementary Report Page 41 of 44
Appendix D. Water balance modelling results for successive average
years scenario with no dust suppression in Jan and Feb
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 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
Grants Lithium Project - Preliminary Mine Site Water Balance Supplementary Report Page 42 of 44
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
Grants Lithium Project - Preliminary Mine Site Water Balance Supplementary Report Page 43 of 44
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
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
Grants Lithium Project - Preliminary Mine Site Water Balance Supplementary Report Page 44 of 44
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 0.01 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 admin@ecaust.com.au
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
Grants Lithium Project Water Management Plan
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.
Grants Lithium Project Water Management Plan
APPENDIX C INDEPENDENT PEER REVIEW COMMENTS
Email: rohanash@ot-environmental.com.au | 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.
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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.
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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?
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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
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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
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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
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(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.
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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:
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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;
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(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 billhowcroft@gmail.com
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 rohanash@ot-environmental.com.au
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.
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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.
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Attachment B: Conformance Statement of WMP, Section 6 of the MMP Structure Guide.
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.-
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
.
Peer Review of Grants Lithium Project Water Management Plan 2018 Page|13
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
rohanash@ot-environmental.com.au | 0407 349 172| ABN 19 613 982 308 www.ot-environmental.com.au
Grants Lithium Project Water Management Plan
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.
Grants Lithium Project Water Management Plan
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
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