SECTION 1 Introduction SECTION 2 Description of Approved Cowal Gold Operations SECTION 3 Description of the Modification
COWAL GOLD OPERATIONS MINE LIFE MODIFICATION Environmental Assessment 2016 Cowal Gold Operations Mine Life Modification – Environmental Assessment
TABLE OF CONTENTS
1 INTRODUCTION 1-1 2.11 WORKFORCE 2-11 1.1 EXISTING COWAL 2.12 MANAGEMENT OF CHEMICALS GOLD OPERATIONS OVERVIEW 1-1 AND WASTES 2-11 1.2 MODIFICATION OVERVIEW 1-1 2.13 ENVIRONMENTAL MONITORING AND MANAGEMENT 2-12 1.3 NEED FOR THE PROPOSED MODIFICATION 1-10 3 DESCRIPTION OF THE MODIFICATION 3-1 1.4 CONSULTATION 1-10 3.1 MINING TENEMENT 3-1 1.4.1 State Government 3.2 ORE DEPOSIT AND LIFE OF MINE 3-1 Agencies 1-10 3.3 MINING OPERATIONS 3-1 1.4.2 Local Councils 1-11 3.4 MINE WASTE ROCK MANAGEMENT 3-7 1.4.3 Public Consultation 1-11 3.5 ORE PROCESSING 3-7 1.5 STRUCTURE OF THIS EA 1-12 3.5.1 Cyanide Use and Process 2 DESCRIPTION OF APPROVED COWAL Consumables 3-9 GOLD OPERATIONS 2-1 3.5.2 Cyanide Destruction 3-9 2.1 COWAL GOLD OPERATIONS 3.6 TAILINGS MANAGEMENT 3-9 APPROVAL HISTORY 2-1 3.7 SITE WATER MANAGEMENT 2.2 ORE DEPOSIT DESCRIPTION AND INFRASTRUCTURE 3-15 LIFE OF MINE 2-1 3.8 WATER SUPPLY 3-15 2.3 MINING OPERATIONS 2-4 3.8.1 Site Water Supply 2.3.1 Mining Method Overview 2-4 Requirements 3-15 2.3.2 Open Pit Design 2-4 3.8.2 Revised Site Water Balance 3-15 2.3.3 Mobile Equipment Fleet 2-4 3.8.3 Water Supply Sources 3-15 2.3.4 Blasting 2-4 3.9 INFRASTRUCTURE AND 2.4 MINE WASTE ROCK MANAGEMENT 2-4 SERVICES 3-17 2.4.1 Waste Rock Geochemistry 2-4 3.10 MANAGEMENT OF CHEMICALS 2.4.2 Northern and Southern AND WASTES 3-17 Waste Rock Emplacements 2-5 3.11 ROAD TRANSPORT 3-17 2.4.3 Perimeter Waste Rock 3.12 WORKFORCE AND OPERATING Emplacement 2-5 HOURS 3-17 2.5 ORE PROCESSING 2-5 3.13 CONSTRUCTION ACTIVITIES 3-18 2.5.1 Cyanide Use and Process Consumables 2-5 2.5.2 Cyanide Destruction 2-6 LIST OF TABLES 2.6 TAILINGS MANAGEMENT 2-6 2.7 SITE WATER MANAGEMENT Table 1-1 Summary Comparison of Approved CGO INFRASTRUCTURE 2-7 and the Modification 2.7.1 Lake Isolation System 2-7 Table 2-1 Contained Water Storages 2.7.2 Up-catchment Diversion Table 3-1 Indicative Mining and Ore Processing System 2-7 Schedule 2.7.3 Internal Catchment Table 3-2 Simulated Water Balance of the Life of the Drainage System 2-7 Modification 2.7.4 Integrated Erosion, Sediment and Salinity Control System 2-7 LIST OF FIGURES 2.7.5 Open Pit Sump and Dewatering Borefield 2-9 Figure 1-1 Regional Location 2.8 WATER SUPPLY 2-9 Figure 1-2 Cowal Gold Operations Location 2.8.1 Saline Groundwater Supply 2-10 Figure 1-3a Land Tenure 2.8.2 Eastern Saline Borefield 2-10 Figure 1-3b Landholder Key 2.8.3 Bland Creek Figure 1-4 Modification General Arrangement Palaeochannel Borefield 2-10 Figure 2-1 Current Status of CGO 2.8.4 Lachlan River Water Figure 2-2 Currently Approved CGO Layout Entitlements 2-11 Figure 2-3 Existing Environmental Monitoring 2.9 ELECTRICITY SUPPLY 2-11 Locations 2.10 OTHER SUPPORTING Figure 3-1 Modification Layout INFRASTRUCTURE AND SERVICES 2-11
i Cowal Gold Operations Mine Life Modification – Environmental Assessment
TABLE OF CONTENTS (continued)
Figure 3-2 Conceptual General Arrangement – Year 14 (2018) Figure 3-3 Conceptual General Arrangement – Year 18 (2022) Figure 3-4 Conceptual General Arrangement – Post-Mining Figure 3-5 Indicative Primary Ore Processing Flowsheet Figure 3-6 Conceptual Cross-Section of Central Tailings Storage Facility Area Figure 3-7 Conceptual Embankment Section of Modified Northern Tailings Storage Facility Figure 3-8 Conceptual Embankment Section of Modified Southern Tailings Storage Facility Figure 3-9 Conceptual Embankment Section of Tailings Storage Facility Connector Embankment
LIST OF PLATES
Plate 2-1 Cowal Gold Operations Lake-fill Conditions
LIST OF ATTACHMENTS
Attachment 1 Cowal Gold Operations Development Consent (DA 14/98) Attachment 2 Aquifer Interference Policy Considerations and Water Licensing
LIST OF APPENDICES
Appendix A Hydrogeological Assessment Appendix B Hydrological Assessment Appendix C Geochemistry Assessment Appendix D Noise and Blasting Assessment Appendix E Air Quality and Greenhouse Gas Assessment Appendix F Rehabilitation Proposal
ii Cowal Gold Operations Mine Life Modification – Environmental Assessment
1 INTRODUCTION Mineralised material is also separately stockpiled for potential future processing. This document is an Environmental Assessment (EA) for a modification to the Cowal Gold Gold is extracted from the ore using a conventional Operations (CGO), which is located approximately carbon-in-leach cyanide leaching circuit in the 38 kilometres (km) north-east of West Wyalong in process plant. Tailings are pumped from the New South Wales (NSW) (Figures 1-1 and 1-2). process plant via a pipeline to the TSFs. The gold product is recovered and poured as gold bars or Evolution Mining (Cowal) Pty Limited (Evolution) is doré. the owner and operator of the CGO. A detailed description of existing operations at the This EA has been prepared to support a request to CGO is provided in Section 2. modify the CGO Development Consent (DA 14/98) under section 75W of the NSW Environmental 1.2 MODIFICATION OVERVIEW Planning and Assessment Act, 1979 (EP&A Act) for the CGO Mine Life Modification (the Modification). The Modification involves continued operations at A copy of the CGO Consolidated Development the existing CGO within ML 1535 for an additional Consent (DA 14/98) is provided in Attachment 1. 8 years to allow an additional 1.7 million
ounces (Moz) of gold production (i.e. a total of The Modification involves the continuation of open approximately 5.5 Moz over the life of the modified pit mining and processing operations at the CGO for CGO). an additional operational life of approximately
8 years (i.e. to end 2032). To allow the increase in the total gold produced over
the life of the CGO, an increase to the depth of the 1.1 EXISTING COWAL GOLD existing open pit would be required to access OPERATIONS OVERVIEW additional gold-bearing ore (Figure 1-4).
The location of the CGO is shown on Figures 1-1 Existing CGO infrastructure would continue to be and 1-2. The area of land to which the CGO’s used for the Modification, with some alterations Development Consent (DA 14/98) is relevant where necessary, including modification of the includes that underlying Mining Lease (ML) 1535 existing TSFs to maximise/increase tailings storage and the CGO’s water supply pipeline and Bland capacity (Figure 1-4) and upgrades to the existing Creek Palaeochannel Borefield (Figures 1-1 and leach circuit within the process plant. 1-2). In general, there would be no change to the existing In addition, Evolution holds Development Consent functionality of the CGO due to the Modification, as (DA 2011/64) for the operation of the Eastern Saline the Modification would involve: Borefield (Figure 1-2) which was granted by the • Forbes Shire Council on 20 December 2010. continued mining in the existing open pit for the extraction of gold-bearing ore and waste ML 1535 encompasses approximately rock; 2,650 hectares (ha). It is bordered by Evolution’s • continued use of existing waste rock Exploration Licence (EL) 7750 and is north-west of emplacements for the placement of waste rock Evolution’s EL 1590 (Figure 1-1). extracted from the open pit;
Relevant land ownership within the immediate • continued use of existing ore processing vicinity of the CGO is shown on Figures 1-3a and infrastructure, with some upgrades to the leach 1-3b. circuit; and • continued use of existing TSFs, with some Open pit mining operations at the CGO are alterations to increase the storage capacity of supported by on-site facilities including water the facilities. management infrastructure/storages, a process plant and TSFs. Mined waste rock from the open pit Table 1-1 provides a summary comparison of the is hauled to waste rock emplacements. Ore mined approved CGO and the Modification components. from the open pit is hauled directly to the primary crusher (adjacent to the process plant), run-of-mine (ROM) pads or low grade ore stockpiles prior to processing.
1-1 O T TE FOREST 520000 540000 560000 N 580000 600000 MURDA STATE H A M QUEENSLAND FOREST E R G AI D EAST COOKEYS LW I A R Y K GUNNINGBLAND C PLAINS STATE CONDOBOLIN O A SOUTH WEST RAN L FOREST STATE FOREST GE B WOODLAND E 6340000 TO B RIDG 6340000 " ROK LBAR NEW SOUTH WALES EN H NATURE RESERVE UDGE ILL C RAIL WAY ) G TH ad U LA E GIPPS W bolin Ro A do N CH Y arkes Con CowalMONUMEA Gold Operations P N LA ( N I V BEREWOMBENIA N GAP STATE Forbes BATHURST AL G ! ! W L a EY STATE FOREST R FOREST ll I ! W D ! am A un Y G SYDNEY d E G ry West Wyalong o Cre ob k ek an Wallaroi Cree g C ree WARREGAL k EDOLS STATE FOREST E VICTORIA G STATE FOREST ID BANAR R S Island Creek 6320000LAKE BY YARRAGONG 6320000 R B STATE FOREST L DA U E BOGANDILLON R ID G SWAMP E LA E C G H D L I A R N ( H Y W R um IVE R e HE s WEELAH E t R W NR G b D ya Y MANNA I ug STATE FOREST l P R o A n R R g K C STATE FORBES O " C E r o S e C n LACHLAN FOREST d W e o b A k o Y lin SHIRE COUNCIL R o E a d G ) D 6300000 I Bund 6300000 R aburr ah Creek LACHLAN VALLEY G N NATIONAL PARK O L EUGLO SOUTH A NERANG COWAL M STATE FOREST E TOMANBIL NERANG J STATE FOREST COWAL STATE FORBES SHIRE COUNCIL FOREST
AY Oo W ma C MULYANDRY GH ree HI Y k CARAWANDOOL A STATE LL ILW H E RA E EW STATE FOREST S N FOREST N KE R Cowal Gold R Y A P L O AW L T LAKE VIEW Operations GA S IN O LAKE NB N 6280000 STATE FOREST KI W 6280000 OC A COWAL ST Y UNGARIE v STATE FOREST CORRINGLE STATE FOREST
C v L E A E WARRADERRY R k G
R v ee N STATE FOREST I r A D C R G y A E d n CLEAR RIDGE v a OG SOUTH WEST S E MAUDRY STATE FOREST H WOODLAND W STATE PRIDDLE v NATURE RESERVE Y B PULLABOOKA FOREST A lan STATE CALLEEN HW STATE FOREST IG FOREST WA v H d STATE FOREST Y WYRRA STATE N A R Cre W TE 6260000 IL FOREST ES 6260000 SOUTH WEST A P R W e IN R v ID EY E M k RA WOODLAND CH BOXALLS BARBINGAL N R G BOGOLONG STATE U E NATURE RESERVE B STATE STATE FOREST BOGOLONG O v MID WE FOREST T STERN H G IGHWAY N FOREST HILLS LO LITTLE CARAGABAL YA - MI W v AY BACK CREEK STATE FOREST D W T W WEDDIN SHIRE COUNCIL EST S H E G k RN HIG E HI HWAY W L STATE e EL e
r WEST NEW v FOREST " C CARAGABAL GRENFELL SOUTH WEST WYALONG n " a STATE FOREST WOODLAND v WEDDIN WYALONG m BIMBI B d NATURE RESERVE a JINGERANGLE MOUNTAINS e rm STATE
e m NATIONAL PARK d v STATE FOREST THE CHARCOAL TANK m r FOREST WEDDIN MOUNTAIN RANGE a a n R B NATURE RESERVE o a vd 6240000 C 6240000 O O T A WEDDIN
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v 020 v ± FOREST " SOUTH WEST BARMEDMAN Kilometres v THE MARY GILMORE WAY 6220000 WOODLAND GDA 1994 MGA Zone 55 6220000 NATURE RESERVE 520000 540000 560000 580000 600000 HAL-16-41 ML ML Mod_201A HAL-16-41
LEGEND Mining Lease Boundary (ML 1535) Exploration Licence (EL 1590) Exploration Licence (EL 7750) National Park & Nature Reserve State Forest Local Government Area Boundary vvElectricity Transmission Line CGO MINE LIFE MODIFICATION Railway Regional Location
Source: Geoscience Australia (2006); NSW Department of Industry (2016)
Figure 1-1 Figure 1-2 Cowal Gold OperationsLocation Mining Lease Boundary (ML 1535) Mining Lease Boundary of Approved Extent Approximate Development Surface Modification Components State Forest Company-owned Privately-owned Railway Electricity Transmission Line Pipeline Mine Water Supply Borefield Creek Palaeochannel Bland Saline Borefield Eastern Station Pump Eastern " " # ! P ! P LEGEND v CGO MINE LIFE MODIFICATION Source: Evolution (2016); Land and Property Source: (2016); and Property Land InformationEvolution (2016) ! P
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HAL-16-41 ML Mod_001A
Source: Evolution(20 16 ) and Land and Property Information (2016)
CGO MINE LIFE MODIFICATION Landholder Key
Figure 1-3b Figure 1-4 Mining Lease Boundary (ML 1535) Lease Boundary Mining Approved of Extent Approximate Development Surface Components Modification Modification General Arrangement CGO MINE LIFE MODIFICATION LEGEND Source: Evolution - Orthophoto (August 2016)
"
6280000 6275000 540000 Supply Bores
540000 Creek Bland LAKE COWAL (approx 20 km) Saline Groundwater
± Kilometres Palaeochannel Borefield Palaeochannel and EasternBorefield Saline
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Height Increase and Tailings Decant Tailings ST Tailings Storage Facility Tailings E Embankment Buttressing W Soil Stockpiles 6280000 6275000 Soil Stockpiles HAL-16-41 ML ML Mod_203B HAL-16-41 Cowal Gold Operations Mine Life Modification – Environmental Assessment
Table 1-1 Summary Comparison of Approved CGO and the Modification
Development Approved CGO1 Proposed Modification Component Tenement Development approved to occur within the Development No change. Application areas, including ML 1535. Mining Method Open pit mining operations. No change. Life of Mine 20 year operational life of the CGO. 28 year operational life of the CGO, up to 31 December 2032. Gold Producing a total of approximately 3.8 Moz of gold over The modified CGO is expected to produce a total Production the life of the CGO. of approximately 5.5 Moz of gold over the life of the CGO. Open Pit Development of the open pit in stages as it is An increase to the approximate final depth of the Extent progressively deepened and widened within the existing open pit by approximately 70 metres (m). disturbance area. Total open pit area of approximately 131 ha. Ore Approximately 128 million tonnes (Mt) of ore produced Approximately 158 Mt of ore produced over the Production over the life of the CGO. life of the CGO. and Gold extracted from the ore using a conventional No change to processing method. Processing carbon-in-leach cyanide leaching circuit. The Modification would involve upgrades to the existing leach circuit within the process plant to treat flotation tailings and improve gold recovery. Ore processing rate of up to 7.5 million tonnes per No change. annum (Mtpa). Processing of mineralised material, if appropriate Processing of approximately 31 Mt of mineralised market conditions allow. material. Waste Rock Mined waste rock emplaced in the northern, southern No change to footprint of waste rock Management and perimeter waste rock emplacements over the life of emplacements. the CGO. Total waste rock emplacement area of approximately 419 ha. Approximately 296 Mt of waste rock produced over the Approximately 309 Mt of waste rock produced life of the CGO. over the life of the CGO. Stockpiling of mineralised material adjacent to the A temporary increase to the height of the northern waste rock emplacement to a maximum design mineralised material stockpile to approximately height of approximately 273 m Australian Height Datum 288 m AHD before recovery of the material for (AHD). processing. Northern waste rock emplacement to be constructed to No change. a maximum design height of approximately 308 m AHD. Southern waste rock emplacement to be constructed to No change. a maximum design height of approximately 283 m AHD. Perimeter waste rock emplacement to be constructed to No change. a maximum design height of approximately 223 m AHD. Soil Application of soil resources management No change. Management strategies/objectives in accordance with the existing Erosion and Sediment Control Management Plan (ESCMP). Development of new soil stockpiles (including soil No change. stockpile located in the north of ML 1535).
1-7 Cowal Gold Operations Mine Life Modification – Environmental Assessment
Table 1-1 (Continued) Summary Comparison of Approved CGO and the Modification
Development Approved CGO1 Proposed Modification Component Tailings Tailings deposited in two TSFs (northern and southern). Continued tailings deposition in the two existing Storage Each TSF is approved to be subdivided into two cells TSFs. Facilities (i.e. four cells in total available for tailings deposition). Maximising the storage capacity of existing TSFs (TSFs) via additional lifts and converting the area between the existing TSFs into a new storage area. Incorporation of a rock fill buttress cover using waste rock on the outer slopes of the TSF embankments to provide long-term stability. The TSF footprints cover an area of approximately Minor extension of TSF footprints to 350 ha. accommodate the rock buttress within currently approved disturbance areas. Northern and southern tailings storage facilities to be An increase to the maximum design heights of constructed to a maximum design height of the northern and southern tailings storage approximately 248 m AHD and 255 m AHD, facilities, to approximately 264 m AHD (16 m respectively. increase) and 272 m AHD (17 m increase), respectively. Construction work on the TSF embankments within the No change. hours of 7.00 am to 6.00 pm. An increase to the TSF embankment lift fleet. Cyanide Use of cyanide in accordance with the approved No change. Concentration Cyanide Management Plan (CMP). Cyanide Levels concentrations in the aqueous component of the tailings slurry stream at the process plant not to exceed the following: • 20 milligrams per litre (mg/L) weak acid dissociable th cyanide (CNWAD) (90 percentile over 6 months); and
• 30 mg/L CNWAD (maximum permissible limit at any time). Cyanide Cyanide consumption for the primary and oxide circuits Upgrades to the existing leach circuit would Consumption is approximately 0.3 and 0.8 kilograms (kg) of cyanide increase cyanide consumption during primary ore per tonne of ore, respectively. processing to approximately 0.7 kg of cyanide per tonne of primary ore. Cyanide consumption for the oxide circuit would not change as the leach circuit upgrades would not be relevant to oxide ore processing. Water Supply Water used for ore processing is sourced from the No change. Sources and following internal and external sources: Infrastructure • Return water from the TSFs. • Open pit sump and dewatering borefield. • Rainfall runoff from mine waste rock emplacements, and other areas which is collected as part of the Internal Catchment Drainage System (ICDS) in contained water storages. • Saline groundwater supply borefield which is pumped from four2 production bores located in the south-east of ML 1535. • Eastern Saline Borefield3 located approximately 10 km east of Lake Cowal’s eastern shoreline. • Bland Creek Palaeochannel Borefield which comprises four production bores within the Bland Creek Palaeochannel located approximately 20 km to the east-northeast of the CGO. • Licensed water accessed from the Lachlan River which is supplied via a pipeline from the Jemalong Irrigation Channel (i.e. Bore 4 offtake).
1-8 Cowal Gold Operations Mine Life Modification – Environmental Assessment
Table 1-1 (Continued) Summary Comparison of Approved CGO and the Modification
Development Approved CGO1 Proposed Modification Component Water Supply Approval for construction of a new pump station and No change. Sources and associated diesel generator and access track on the Infrastructure eastern side of Lake Cowal adjacent to the existing (continued) mine water supply pipeline to improve capacity/flows. Approval for construction of a new water supply storage (D10) within ML 1535. Bland Creek The maximum extraction of water from the Bland Creek No change. Palaeochannel Palaeochannel will not exceed: Borefield • 15 megalitres per day (ML/day); or Extraction • Limits 3,650 megalitres per annum (ML/annum). Extraction is managed to maintain groundwater levels above the established NSW Office of Water (NOW) trigger levels. Site Water The existing CGO water management infrastructure is No change. Management comprised of the following major components: Infrastructure • Up-catchment Diversion System (UCDS) and the ICDS (including the contained water storages); • lake isolation system (comprising the temporary isolation bund, lake protection bund and perimeter waste rock emplacement); • integrated erosion, sediment and salinity control system; and • open pit sump and dewatering borefield. Biodiversity The Biodiversity Offset Strategy is shown conceptually No change. Offset in Appendix 4 of Development Consent DA 14/98. Strategy Power Supply Electricity to the site via a 132 kilovolt (KV) electricity No change. Activities transmission line (ETL) from Temora, approximately 90 km south of the CGO. Exploration Exploration activities undertaken within ML 1535 in No change. accordance with relevant authorisations. Site Access Site access road following existing roads from West No change. Road Wyalong to the CGO. Light vehicle access from Condobolin and Forbes. Hours of 24 hour operations, seven days a week. No change. Operation Employment The average workforce employed at the CGO is No change, however there would be an additional currently approximately 385 people (including Evolution 8 years of employment opportunity. staff and on-site contractor’s personnel). During peak periods, the CGO employs up to 435 people. 1 Approved CGO approved on 26 February 1999 as modified. 2 Evolution has currently installed two of the four approved production bores. 3 The operation of the Eastern Saline Borefield is approved separately under the EP&A Act.
1-9 Cowal Gold Operations Mine Life Modification – Environmental Assessment
The Modification involves no change to the The Modification would include implementation of following key components of the existing CGO: mitigation measures, and management measures (including performance monitoring), to minimise • mining tenements; potential impacts on the environment and community (Section 4). • lake isolation system;
• existing/approved surface development extent The Modification would result in additional of the CGO; contributions to regional and NSW output and business turnover and household income for an • water management system and design additional 8 years. objectives; • mining methods; 1.4 CONSULTATION
• ore processing rate; Consultation has been conducted with key State • waste rock emplacement disturbance areas; government agencies, local councils, and the local community during the preparation of this EA. A • cyanide destruction method; summary of this consultation to date is provided • approved cyanide concentration limits in the below. aqueous component of the tailings slurry; Consultation will continue during the public • water supply sources; exhibition of this EA and the assessment of the Modification. • approved daily or annual extraction limits of
the Bland Creek Palaeochannel Borefield; • 1.4.1 State Government Agencies site access road; • power supply; NSW Department of Planning and Environment
• exploration activities; Evolution met with the NSW Department of Planning and Environment (DP&E) in August 2016 to discuss • average or peak annual employment; the scope of environmental assessment for the • hours of operation; or Modification and the assessment and approvals process. • TSF embankment construction hours of 7.00 am to 6.00 pm. Following this, Evolution wrote to DP&E on 1 September 2016 confirming the Modification 1.3 NEED FOR THE PROPOSED environmental assessment scope and proposed MODIFICATION approvals process.
Evolution exploration has identified additional gold The DP&E subsequently responded on resources within the E42 ore deposit at depths 29 September 2016 confirming the approval greater than the currently approved final depth of process for the Modification (i.e. under section 75W the existing open pit. of the EP&A Act), environmental assessment scope and consultation requirements. The Modification provides for the continuation of open pit mining operations at the CGO for a period Regulatory Agencies of approximately 8 years to produce an additional Evolution provided briefing letters in September and 1.7 Moz of gold (i.e. a total of approximately October 2016 presenting an overview description of 5.5 Moz over the life of the CGO). the Modification and proposed scope for the
environmental assessment to the following The Modification would facilitate the continuity of regulatory agencies: employment for the CGO workforce, providing job security for local mine employees and contractors, • NSW Environment Protection Authority (EPA); and would continue to stimulate demand in the local and regional economy. • NSW Department of Primary Industries (Water) (DPI – Water); • NSW Division of Resources and Energy (DRE) (within the Department of Industry, Skills and Regional Development [DISRD]);
1-10 Cowal Gold Operations Mine Life Modification – Environmental Assessment
• NSW Office of Environment and Heritage Following this, Evolution provided a briefing letter (OEH); dated 2 September 2016 to the Bland Shire Council, Forbes Shire Council and Lachlan Shire Council • Dams Safety NSW; and outlining the scope of the Modification, approval • NSW Roads and Maritime Services (RMS). process and environmental assessment.
Evolution also briefed the EPA, DRE and Evolution also met representatives of the Bland DPI-Fisheries during the Annual Review site visit Shire Council, Forbes Shire Council and Lachlan October 2016 on the Modification and potential Shire Council in November 2016 to discuss the environmental impacts. Feedback from these Modification. agencies included: 1.4.3 Public Consultation • EPA – requested that Evolution clearly describe any increase in noise levels resulting Community Environmental Monitoring and from the Modification. Consultative Committee
• DRE – understood that Evolution would revise The CEMCC has been established in accordance the current Mining Operations Plan (MOP) to with Condition 9.1(d) of the CGO Development reflect the Modification (subject to approval of Consent (DA 14/98). The CEMCC currently consists the Modification). of: • DPI – Fisheries – understood that the • Modification would involve no change to the four community representatives (including one existing water management measures member of the Lake Cowal Landholders including the lake isolation system. Association); • one representative of the Lake Cowal Evolution separately briefed the DPI-Water in Foundation (LCF); October 2016 on water management issues associated with the Modification. Long-term • one representative of the Wiradjuri Condobolin seepage drainage, final void water levels and use of Corporation (WCC); Lachlan River water as part of the CGO water • one representative of the Bland Shire Council; supply were discussed. • one representative of the Forbes Shire Dams Safety NSW Council;
On 5 October 2016, the Concept Design for the • one representative of the Lachlan Shire modified TSFs was submitted to Dams Safety NSW Council; for consideration. The Concept Design was • an independent chairperson; and subsequently presented at Dams Safety NSW meetings held on 25 October and • two representatives of Evolution. 2 November 2016. The CEMCC provides a mechanism for ongoing communication between Evolution and the 1.4.2 Local Councils community.
ML 1535 is located within the Bland Local The CEMCC holds quarterly meetings, and Government Area (LGA), while the Bland Creek Palaeochannel and Eastern Saline Borefields are consultation regarding the Modification was located within the Forbes LGA (Figure 1-1). In conducted during the August 2016 meeting. The findings of this EA will be discussed at the addition, one of the preferred access routes to the CEMCC’s December 2016 meeting. This EA will CGO (i.e. from Condobolin) is located within the Lachlan LGA. also be made available to all CEMCC members following submission to the DP&E.
On 30 August 2016, Evolution provided a Affected Landowners presentation on the proposed Modification at a
Community Environmental Monitoring and Evolution consulted with the local community in Consultative Committee (CEMCC) meeting of which October and November 2016. Feedback received representatives from the Bland, Forbes and Lachlan from the local community was that key issues were Shire Councils are members. in relation to potential noise and blasting impacts and that these aspects should be considered in the EA.
1-11 Cowal Gold Operations Mine Life Modification – Environmental Assessment
Potential noise and blasting impacts associated with Attachments 1 and 2, and Appendices A to F the Modification are provided in Appendix D and provide supporting information as follows: Sections 4.3 and 4.5.2. Attachment 1 Cowal Gold Operations Cowal Update Newsletter Development Consent (DA 14/98). Evolution regularly publishes the “Cowal Update” Attachment 2 Aquifer Interference Policy newsletter to provide the wider community with an Considerations and Water update on CGO operations and involvement in Licensing. community activities and sponsorships. The “Cowal Update” newsletter is mailed out to households in Appendix A Hydrogeological Assessment. the Bland, Forbes and Lachlan LGAs on an annual Appendix B Hydrological Assessment. basis, and is also distributed with the local West Wyalong newspaper, the “West Wyalong Advocate”. Appendix C Geochemistry Assessment. Appendix D Noise and Blasting Assessment. The November 2016 edition of the “Cowal Update” contains a description of the Modification, the Appendix E Air Quality and Greenhouse Gas assessment process and potential environmental Assessment. impacts. Appendix F Rehabilitation Proposal.
1.5 STRUCTURE OF THIS EA
This EA is structured as follows:
Section 1 Provides an overview of the approved CGO, describes the nature of the Modification and proposed need for the Modification and includes a summary of the consultation undertaken in relation to the Modification. Section 2 Provides a description of the approved CGO. Section 3 Provides a description of the Modification. Section 4 Provides a review of the existing environment, assesses potential impacts associated with the Modification and describes the existing CGO environmental management systems and proposed measures to manage and monitor any additional potential impacts. Section 5 Describes the rehabilitation and landscape management strategy for the Modification. Section 6 Provides the planning framework and justification for the Modification. Section 7 Lists references referred to in Sections 1 to 6 of this EA. Section 8 Lists abbreviations, acronyms and terms referred to in Sections 1 to 6 of this EA.
1-12 Cowal Gold Operations Mine Life Modification – Environmental Assessment
2 DESCRIPTION OF APPROVED Five modifications (Mods 6, 9, 10, 11 and 12) have COWAL GOLD OPERATIONS been assessed under section 75W of the EP&A Act. Mod 11 is the most recent to involve more
The existing CGO is shown on Figure 2-1, and the substantive changes including increases to open pit approved layout of the CGO is shown on Figure 2-2. depth and area, waste rock emplacements, soil stockpiles, TSFs and water storage. A summary of existing approvals and operations undertaken at the CGO is provided below. Where Development Consent (DA 2011/64) for the relevant, a description of measures incorporated operation of the Eastern Saline Borefield into the existing CGO layout and operation designed (Figure 1-2) was granted by the Forbes Shire to minimise potential environmental impacts is also Council on 20 December 2010. The approved provided. operation of the Eastern Saline Borefield includes the use of two production bores to extract water from the Cowra Formation aquifer and the use of 2.1 COWAL GOLD OPERATIONS existing associated works (including a pipeline) to APPROVAL HISTORY deliver the saline water to the Bland Creek Palaeochannel Borefield pipeline. Mod 10 of A study into the compatibility of the CGO with critical Development Consent (DA 14/98) approved the conservation values of Lake Cowal over the introduction of saline water from the Eastern Saline long-term was completed and reported in the Cowal Borefield to augment the CGO’s external water Gold Project Environmental Impact Statement (EIS) supply. (North Limited, 1998). A Commission of Inquiry was held in November 1998 into the environmental 2.2 ORE DEPOSIT DESCRIPTION AND aspects of the CGO and related infrastructure. LIFE OF MINE
Development Consent (DA 14/98) for the CGO and The CGO currently mines the E42 ore deposit, Bland Creek Palaeochannel Borefield water supply which occurs within a sequence of pipeline (Figure 1-2) was granted by the NSW semi-conformable sedimentary, volcaniclastic and Minister for Urban Affairs and Planning under Part 4 volcanic rock, and is overlain by recent of the EP&A Act on 26 February 1999. sedimentation of the Bland Creek Palaeochannel
and lake-fill events. Separate approvals processes were also undertaken during the same period for the following Two ore types are mined at the CGO: related infrastructure components for the CGO:
• primary ore, which constitutes 80 percent (%) • Upgrade of the mine access road from West of the E42 ore deposit; and Wyalong to the CGO: Approval for the upgrade of the mine access road was granted by the • oxide or weathered ore, which comprises the Bland Shire Council on 21 April 1999 under upper 20% of the orebody. Part 5 of the EP&A Act. The two ore types are selectively handled and • Temora to Cowal 132 kV ETL: Approval for the separated during mining and processing due to the ETL (Figure 1-2) was granted by the NSW different mineral processing requirements for gold Minister for Urban Affairs and Planning on extraction. 3 August 1999 under Part 5 of the EP&A Act.
The CGO is approved to produce approximately The CGO Development Consent (DA 14/98) has 128 Mt of ore over the mine life. Based on ore grade been modified on 12 occasions, viz. 11 August 2003 estimates, total gold production for the approved (Mod 1), 22 December 2003 (Mod 2), 4 August CGO is approximately 3.8 Moz. In addition, 2004 (Mod 3), 23 August 2006 (Mod 4), mineralised material is stockpiled separately, and is 12 March 2008 (Mod 5), 11 February 2009 (Mod 7), approved to be processed in the future, subject to 28 August 2009 (Mod 8), 10 March 2010 (Mod 6), market conditions (Section 2.4.2). 17 January 2011 (Mod 9), 6 July 2011 (Mod 10),
22 July 2014 (Mod 11) and 13 May 2016 (Mod 12). Mining operations at the CGO commenced in 2005,
and operations are currently approved to continue The majority of these modifications have involved until 31 December 2024. minor changes to the CGO, and were assessed under section 96 of the EP&A Act.
2-1 Figure 2-1 Current Status of Status CGO Current Mining Lease Boundary (ML 1535) (ML Boundary Mining Lease CGO MINE LIFE MODIFICATION Source: Evolution - Orthophoto (August 2016) LEGEND
"
6280000 6275000 540000 Supply Bores
540000 Creek Bland LAKE COWAL (approx 20 km) Saline Groundwater
± Palaeochannel Borefield Palaeochannel Kilometres and EasternBorefield Saline
GDA 1994 MGA Zone 55 1994 MGA Zone GDA
35 5
01
1
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Cowal Gold Operations Mine Life Modification – Environmental Assessment
2.3 MINING OPERATIONS • haul trucks;
• Mining operations at the CGO are currently dozers; conducted in accordance with Development • loaders; Consent (DA 14/98) and the conditions of ML 1535. • water trucks; The CGO operates 24 hours per day, 7 days per • articulated dump trucks; week. • compactors; 2.3.1 Mining Method Overview • graders; and
• Conventional open pit mining methods are used at drill rigs. the CGO. Waste rock and ore is broken through a routine sequence of in-pit drilling and blasting. 2.3.4 Blasting
Broken waste rock is loaded into large rear dump Ore and waste rock material is broken by drill and trucks using hydraulic excavators and is then hauled blasting techniques. The magnitude of blast sizes is from the open pit to be placed within the dedicated typically approximately 172 kg maximum waste rock emplacements (or for use as instantaneous charge. The blasting frequency construction material). Ore is hauled from the open employed at the CGO is limited to one blast event pit direct to the primary crusher (adjacent to the per day (a single blast event may include a split process plant), ROM pads or to the low grade ore blast with a number of individual blasts fired in quick stockpile (Figure 2-2). succession).
The open pit has been developed in stages as the orebody is progressively mined via widening and 2.4 MINE WASTE ROCK MANAGEMENT deepening of the open pit. Waste rock is placed in a contiguous waste rock emplacement around the open pit consisting of the 2.3.2 Open Pit Design following three areas (Figure 2-2):
The current open pit area is shown on Figure 2-1. • northern waste rock emplacement; The final dimensions of the currently approved open pit are a surface area of approximately 131 ha and a • southern waste rock emplacement; and depth of approximately -263 m AHD (approximately • perimeter waste rock emplacement. 470 m below the natural ground surface).
The open pit has been designed to operate in 2.4.1 Waste Rock Geochemistry consideration of factors of safety appropriate for operating conditions and for the long-term stability Waste rock geochemistry investigations (North of the lake protection bund. Ongoing review of pit Limited, 1998; Environmental Geochemistry wall stability is conducted at the CGO, and berm International Pty Ltd, 2004; Geo-Environmental widths and slopes angles are reviewed and Management Pty Ltd [GEM], 2008; and GEM, 2013) monitored through on-going geotechnical studies. have been conducted for the waste rock mined at the CGO, which have classified waste rock as The Cowal Gold Project Monitoring Programme for non-acid forming (NAF). The results indicate: Detection of any Movement of Lake Protection Bund, Water Storage and Tailings Structures and • oxide waste rock will typically be saline but Pit-Void Walls (LPBMP) describes a monitoring NAF; and programme and management measures in the • event of detection of any movement of the open pit primary waste rock will typically be non-saline walls. and NAF, however sulphate salts will be generated if exposed to surficial weathering processes. 2.3.3 Mobile Equipment Fleet
The existing/approved mobile equipment fleet used for ore extraction, waste rock handling and TSF lift construction includes:
• excavators;
2-4 Cowal Gold Operations Mine Life Modification – Environmental Assessment
As the waste rock is typically NAF, no specific acid The northern waste rock emplacement also contains rock drainage management measures have been segregated mineralised material and temporary required at the CGO. However, due to the potential ROM pad areas. Evolution’s current proposal is to for saline seepage occurring from the waste rock process mineralised material if appropriate market emplacements, the waste rock emplacements have conditions allow. However, if appropriate market been constructed to direct any permeating waters conditions do not prevail, the mineralised material is towards the open pit (Section 2.4.2). proposed to remain as part of the final northern waste rock emplacement landform.
2.4.2 Northern and Southern Waste Rock Emplacements 2.4.3 Perimeter Waste Rock Emplacement
The northern waste rock emplacement has been The perimeter waste rock emplacement has been designed to contain the majority of the waste rock constructed to surround the open pit to the north, generated from the CGO. The northern waste rock east and south (Figure 2-1). emplacement and the southern waste rock emplacement are located to the north-west and The perimeter waste rock emplacement forms part south-west of the open pit, respectively (Figure 2-1). of the series of embankments (i.e. temporary isolation bund and lake protection bund) between The approved maximum height of the northern the open pit and Lake Cowal. The perimeter waste waste rock emplacement is 308 m AHD, and the rock emplacement is located behind the lake approved maximum height of the southern waste protection bund (Figure 2-1) and has been rock emplacement is 283 m AHD (Figure 2-2). constructed from mined oxide waste rock.
The outer batters of the northern and southern The approved maximum height of the perimeter waste rock emplacements are designed to have a waste rock emplacement is 223 m AHD. final profile with an overall 1 vertical (V):5 horizontal (H) slope. Evolution regularly reviews the factors of safety appropriate for the long-term stability of the Design configurations for the northern and southern perimeter waste rock emplacement. These factors waste rock emplacements are detailed in the CGO are incorporated into the design and development of MOP, which is approved by the DRE. the perimeter waste rock emplacement as appropriate. The mine waste rock emplacements have been designed to meet the long-term goal of directing The existing temporary isolation bund and lake potential seepage generated from waste rock protection bund are described further in Section 2.7. emplacement areas during operation and post-closure toward the open pit. 2.5 ORE PROCESSING This has involved construction of a low permeability basal layer for the waste rock emplacements which Ore at the CGO is differentiated into oxide and slopes towards the open pit and would provide primary ore. Gold is extracted from the ore using a drainage control (i.e. the base drainage control conventional carbon-in-leach cyanide leaching zone). Waters permeating through the waste rock circuit in the process plant. emplacements would be intercepted by this low permeability layer and ultimately flow to the open The process plant operates at approximately pit. 890 tonnes per hour (tph) for oxide ore and approximately 925 tph for primary ore on average. In accordance with Environment Protection Licence The annual ore processing rate at the CGO is (EPL) 11912 for the CGO, the waste rock currently approved up to 7.5 Mtpa. emplacement base drainage control zones have been designed with a minimum slope towards the The gold extracted from the ore is recovered and open pit of 1(V):200(H). poured as gold bars or doré. The finely ground rock residue left after the leaching process (i.e. tailings) is passed through a cyanide destruction process before being discharged to the TSFs.
2-5 Cowal Gold Operations Mine Life Modification – Environmental Assessment
2.5.1 Cyanide Use and Process Consumables The most recent independent re-certification audit to the International Cyanide Management Code The use of cyanide at the CGO is managed in occurred in March 2016, and found that the CGO accordance with the CMP. Sodium cyanide is taken maintained full compliance during the previous from the storage facility at the CGO as required and 2 years. mixed in a dedicated mixing tank. The cyanide solution (mixed to 30%) is conveyed to a storage tank then to the leaching circuit in the process plant. 2.6 TAILINGS MANAGEMENT Cyanide consumption for the primary and oxide circuits is approximately 0.3 and 0.8 kg of cyanide Tailings are delivered from the process plant via a per tonne of ore, respectively. pipeline to two TSFs located approximately 3.5 km west of the Lake Cowal shoreline (Figure 2-1). The In addition to cyanide, a number of process approved maximum heights of the northern and consumables (including chemicals and reagents or southern tailings storage facilities are 248 m AHD equivalents) are currently stored and used at the and 255 m AHD, respectively (Figure 2-2). CGO. An initial starter embankment for each TSF was constructed to provide storage for tailings produced 2.5.2 Cyanide Destruction at the commencement of operations at the CGO.
As described above, the tailings slurry is passed As the TSFs are progressively filled, the through a cyanide destruction process before being embankments are raised in a series of upstream lifts discharged to the TSFs. constructed using waste rock stockpiled during mining operations, with the lift section extending The CGO Development Consent (DA 14/98) details from the existing embankment crest and supported the approved cyanide concentrations in the aqueous by the dry tailings beach. component of the tailings slurry stream at the process plant (measured via an automated The batter slope of each lift is approximately sampler), which are: 1(V):3(H), with the overall batter slope of the TSFs approximately 1(V):5(H). th • 20 mg/L CNWAD (90 percentile over 6 months); and The TSFs embankments are constructed using a mix of clay oxide and primary waste rock material • 30 mg/L CNWAD (maximum permissible limit at stockpiled during mining operations. any time). The required free-board is maintained as the CNWAD levels in the aqueous component of the storage fills with tailings via the series of tailings slurry stream are monitoried twice daily. To embankment lifts. date, there has been no exceedance of the approved cyanide concentrations detailed in the Following tailings deposition, supernatant water CGO Development Consent (DA 14/98). drains to the central pond and decant towers. The decant tower is accessible via a causeway. An Cyanide destruction at the CGO is achieved via the underdrainage pipe network has also been installed use of either Caro’s Acid or the INCO (sulfur to facilitate drainage of the tailings mass. The bulk dioxide) process. of the water from each tailings storage drains from the surface of the tailings and collects in the central Caro’s Acid is a mixture of sulphuric acid and decant area/well. hydrogen peroxide. The INCO process involves the introduction of sulphur dioxide as sodium This water, as well as underdrainage water, is metabisulphite (SMBS). Similar to Caro’s Acid, the reclaimed and used within the process plant. The main by-product from the INCO destruction process decant system (including access causeway) is is cyanate which decays through natural processes. progressively raised during development of the TSFs. The quantity of reagents added to the tailings (for either the use of Caro’s Acid or the INCO process) Decant causeways across the full width of each TSF is regulated by an online free cyanide measurement are approved, however not yet constructed. If to monitor the effectiveness of cyanide destruction constructed, this would allow each of the existing in the tailings. storages to be divided into two cells.
2-6 Cowal Gold Operations Mine Life Modification – Environmental Assessment
A number of seepage control measures have been 2.7.2 Up-catchment Diversion System incorporated into the TSFs for the CGO, including: The UCDS conveys upper catchment surface runoff • the pre-stripping of surficial soils beneath each around the western edge of the CGO and into storage footprint; existing drainage lines to the north and south of the • CGO (Figure 2-1). The function of the UCDS on the construction of a moisture-conditioned and northern side of the CGO is shown on Plate 2-1. compacted-low-permeability storage floor, where necessary, to achieve permeability criteria; 2.7.3 Internal Catchment Drainage System
• excavation of a central cut-off trench along the The function of the ICDS is to separate surface length of the starter embankment to a nominal runoff external to the CGO from contained waters 2.5 m below surface level or to the depth of a generated within the CGO disturbance area. low-permeability clay layer, and backfilled with
compacted and moisture-conditioned low The ICDS is a permanent water management permeability clay; feature that involves a low bund running alongside • installation of an underdrainage and decant the UCDS from the western side of TSFs extending network; and around the northern and southern perimeter of the northern and southern waste rock emplacements, • installation of a seepage drainage system including perimeter collector pipes on the TSF respectively. embankments and sumps at the eastern toe of the northern tailings storage facility and Surface water that is collected within the ICDS is southern tailings storage facility and the area managed by a series of contained water storages, between the TSFs. bunds and drains.
Seepage measures are progressively implemented Contained water storages D1 to D5 and D8B and informed by investigations such as geophysical (Figure 2-2) are used to contain surface water runoff testwork, piezometer installation and monitoring and from the mine waste rock emplacements and geotechnical drilling. general site area. Water is pumped to contained water storages D6 or D9 (process water supply 2.7 SITE WATER MANAGEMENT storages) (or D10 once constructed) (Figure 2-2) for use during ore processing. The contained water INFRASTRUCTURE storages have been designed to contain a minimum
The CGO water management infrastructure is 1 in 100 year average recurrence interval (ARI) designed to contain potentially contaminated water rainfall event or greater. However, D5, D6, D9 and (contained water) generated within the mining area, D10 have been designed to contain a 1 in 1,000 and to divert all other water around the perimeter of year ARI rainfall event. the site. The existing CGO water management infrastructure is comprised of the following major Any overflow from contained water storages within components described below. the ICDS would be directed towards the open pit.
Contained water storages are shown on Plate 2-1. 2.7.1 Lake Isolation System A summary of the function and characteristics of the existing/approved contained storages is provided in The lake isolation system has been constructed to Table 2-1. hydrologically isolate the open pit development area from Lake Cowal during mining and post-mining. The lake isolation system is comprised of a series of 2.7.4 Integrated Erosion, Sediment and Salinity isolation embankments designed to prevent the Control System inflow of water from Lake Cowal into the open pit development area. The lake isolation system Sediment control structures, dams and waterways includes the temporary isolation bund, lake around individual infrastructure components have protection bund and perimeter waste rock been constructed at the CGO as part of the ICDS, in emplacement (Figure 2-1). accordance with the erosion and sediment control strategies described in the ESCMP. Plate 2-1 shows Lake Cowal at its maximum capacity during the 2012 and 2016 lake-fill events, as well as the components of the lake isolation system and the separation of the lake and the open pit.
2-7 Up-catchment Diversion System - Southern Waste Rock Emplacement Southern Tailings Storage Facility Stilling Basin and Outfall LAKE ISOLATION SYSTEM Perimeter Waste Rock Emplacement Cowal Gold Operations Lake Protection Open Pit Process Plant Low Grade Ore Bund Stockpile
Temporary D9 Isolation Bund D4 D8B D2 D5 D6
Northern Waste Rock Emplacement
D3
Up-catchment Diversion System LAKE COWAL
D1
Date of Aerial: 6th March 2012
Southern Tailings Storage Facility Up-catchment Diversion System - Southern Waste Rock Emplacement Stilling Basin and Outfall Northern Tailings Storage Facility LAKE ISOLATION SYSTEM Low Grade Ore Perimeter Waste Rock Emplacement Process Plant Stockpile Cowal Gold Operations Lake Protection Open Pit Bund D9 Northern Waste Rock Emplacement D8B D2 Temporary D4 Existing Rehabilitation Isolation Bund D5 D6
Up-catchment Diversion System
D3
CGO MINE LIFE MODIFICATION D1(embankments raised and rock armoured) Cowal Gold Operations LAKE COWAL Lake-fill Conditions
Date of Aerial:21st October 201 6
HAL-16-41 ML Mod_002C Plate 2-1 Cowal Gold Operations Mine Life Modification – Environmental Assessment
Table 2-1 Contained Water Storages
Approximate Storage Number Catchment/Function Storage Capacity (ML) D1 Runoff from northern perimeter of the northern waste rock emplacement. Collected 57 (Existing) water is pumped to D6. D2 Runoff/seepage from ROM and low grade stockpile areas from the northern waste 195 (Existing) rock emplacement area, the batters of the northern tailings storage facility and other areas within the ICDS. Collected water is pumped to D6 or D9. D3 Runoff from perimeter catchment surrounding the open pit and the perimeter waste 39 (Existing) rock emplacement areas. Collected water is pumped to D6. D4 Runoff from the southern perimeter of the southern waste rock emplacement. 69 (Existing) Collected water is pumped to D6 or D9. D5 Process plant area drainage collection. Water is pumped to D6. 92 (Existing and approved to be modified) D6 Process water supply storage. Main source of process plant make-up water 10 (Existing) requirements. D8B Runoff from southern waste rock emplacement, the batters of the southern tailings 43 (Existing) storage facility and other areas within the ICDS. Water is pumped to D9. D9 Process water supply storage. Storage for raw water. Water is pumped to D6. 726 (Existing) Some water used for TSFs lift construction. D10 Process water supply storage. Storage for raw water. Water is pumped to D9. 1,500 (Approved but not yet constructed) Source: After Appendix B.
2.7.5 Open Pit Sump and Dewatering Borefield 2.8 WATER SUPPLY
An open pit dewatering programme is currently in Water requirements for the CGO include ore operation at the CGO to manage surface water and processing, as well as dust suppression and potable groundwater inflows to the open pit. and non-potable uses.
The surface catchment area draining to the open pit The total water supply requirement for the process during operation is restricted to the open pit plant is estimated to be approximately 0.9 kilolitres (i.e. incident rainfall) and the small perimeter area per tonne (kL/t) for primary ore processing and up to enclosed by an external bund. approximately 1.7 kL/t for oxide ore processing.
Water management structures have been installed The majority of water used in processing operations to divert water from other areas outside the external is recycled within the process plant. Water losses bund to contained water storages. from the system include tailings pore water and evaporative loss principally from the TSFs. Water The open pit includes water management structures used for ore processing is sourced from the (face seepage collection drains) and an in-pit sump following internal and external sources: in the floor of the open pit with capacity to contain a 1 in 10 year ARI rainfall event. • Internal water sources (within the ICDS):
- water returned from the TSFs, which is The open pit dewatering bores are located on the stored in contained water storage D6 periphery and within the open pit extent. Individual (process water supply storage); bores have been located to coincide with structures/features (shear zones, fractured dykes - water from the open pit sump and and faults). Saline groundwater generated during dewatering borefield which is stored in open pit dewatering is pumped to the contained contained water storages D6 and/or D9 water storages for use in ore processing. Open pit (process water supply storages); and inflows are licensed by Water Access Licences (WALs) 36615 and 36617 (Attachment 2). A network of piezometers has been installed to monitor groundwater draw-down levels over time.
2-9 Cowal Gold Operations Mine Life Modification – Environmental Assessment
- runoff water from the waste rock 2.8.2 Eastern Saline Borefield emplacements, open pit area and other areas within the ICDS which is collected The location of the existing Eastern Saline Borefield in contained water storages and is shown on Figure 1-2. transferred to the process water supply storages (D6 and/or D9) for re-use in the Operation of the Eastern Saline Borefield is process plant. approved under Development Consent (DA 2011/64) (issued by the Forbes Shire Council) • External water sources (i.e. outside the ICDS): (Section 1.1). The CGO’s Development Consent - water from the saline groundwater supply (DA 14/98) was modified on 6 July 2011 to allow the bores within ML 1535; introduction of saline water from the Eastern Saline Borefield to augment the CGO’s external water - water from the Eastern Saline Borefield supply. located approximately 10 km east of Lake Cowal’s eastern shoreline; Water extraction from the bores within the Eastern Saline Borefield is licensed by WAL 36569 under - water from the Bland Creek the Water Sharing Plan for the Lachlan Unregulated Palaeochannel Borefield, which is and Alluvial Water Sources 2012. The Eastern pumped from four production bores Saline Borefield licences have a zero ML licence located approximately 20 km to the allocation with an allowable temporary transfer of up east-northeast of the CGO in accordance to 750 ML/annum per bore. with approved extraction limits; and
- licensed water accessed from the 2.8.3 Bland Creek Palaeochannel Borefield Lachlan River, which is supplied via a pipeline from the Jemalong Irrigation The location of the existing Bland Creek Channel. Palaeochannel Borefield is shown on Figure 1-2.
Some water from the external water supply sources Water extraction is licensed by WAL 31864 under is treated by a Reverse Osmosis (RO) plant prior to the Water Sharing Plan for the Lachlan Unregulated use in the process plant or to satisfy other and Alluvial Water Sources 2012, which has an operational requirements. Brine from the RO plant is annual extraction limit of 3,650 ML2. The CGO disposed of in the TSFs. Development Consent (DA 14/98) currently limits extraction from the Bland Creek Palaeochannel Further description of external water sources is Borefield to 15 ML/day or 3,650 ML/year. provided below. Groundwater Contingency Strategy 2.8.1 Saline Groundwater Supply In addition to the above, existing extraction from the
Bland Creek Palaeochannel Borefield is managed in The locations of the existing saline groundwater accordance with groundwater trigger levels supply bores within ML 1535 are shown on developed in consultation with DPI-Water and other Figure 2-1. water users within the Bland Creek Palaeochannel,
including stock and domestic users and irrigators, Water extraction from the saline groundwater supply as detailed in the CGO Water Management Plan borefield within ML 1535 is licensed by WAL 36615 (WMP). under the Water Sharing Plan for the Lachlan
Unregulated and Alluvial Water Sources 2012, 1 The trigger levels are as follows: which has an annual extraction limit of 366 ML .
• In practice, water extraction from the saline Bland Creek Palaeochannel Borefield area: groundwater is currently limited to a maximum of Bore GW036553 (trigger levels of approximately 0.7 ML/day (256 ML/annum) due to 137.5 m AHD and 134 m AHD). the capacity of existing pumping infrastructure. • Billabong area: Bore GW036597 (trigger level 145.8 m AHD). The existing saline groundwater supply bores are not currently operational due to the inundation of • Maslin area: Bore GW036611 (trigger level Lake Cowal (i.e. these bores have been 143.7 m AHD). decommissioned and would be recommissioned when lake levels recede).
1 Based on 1 ML per unit share. 2 Based on 1 ML per unit share.
2-10 Cowal Gold Operations Mine Life Modification – Environmental Assessment
Groundwater levels associated with the Bland Creek • mineral exploration infrastructure; Palaeochannel Borefield are monitored on a continuous basis by DPI-Water’s groundwater • open pit dewatering bores; monitoring bore GW036553. • waste storage and transfer facility;
Investigation and mitigation contingency measures • administration buildings; have been developed should groundwater levels reach either relative level (RL) 137.5 m AHD (trigger • workshop facilities; for investigation) or RL 134 m AHD (trigger for • TSF fence; and mitigation). • ML 1535 perimeter fence. The effect of the above is that pumping from the Bland Creek Palaeochannel Borefield ceases when required to meet the trigger levels described above, 2.11 WORKFORCE and water requirements at the CGO are met by alternative internal or external water supplies, The existing operations at the CGO have an including Lachlan River Water Entitlements average workforce (including Evolution staff and (Section 2.8.4). on-site contractor’s personnel) of approximately 385 people. During peak periods, the CGO employs up to 435 people. 2.8.4 Lachlan River Water Entitlements
Access to water from the Lachlan River Regulated 2.12 MANAGEMENT OF CHEMICALS AND Water Source is licensed by Evolution’s High WASTES Security WAL 14981 (80 Units), High Security WAL 13749 (zero allocation), and General Security Dangerous Goods and Hazardous and Liquid WAL 13748 (zero allocation). Wastes
High security and general security zero allocation The transport of hazardous and dangerous goods WALs held by Evolution allow water from the required for the existing CGO is conducted in Lachlan River to be accessed, when required, by accordance with the approved Transport of purchasing temporary water available from the Hazardous Materials Study (THMS). The on-site regulated Lachlan River trading market storage and management of hazardous and (Appendix B). dangerous goods and liquid wastes is undertaken in accordance with the CGO’s approved Hazardous During the life of the existing CGO there has been Waste and Chemical Management Plan (HWCMP). reliable supply of temporary water available from the These approved plans have been prepared in Lachlan River trading market, including during years accordance with relevant legislation, Australian of drought. Standards and codes.
Recyclable Domestic Waste 2.9 ELECTRICITY SUPPLY Recyclable domestic waste from office buildings and Electricity to the site is provided via the existing workforce areas is collected regularly and managed 132 kV ETL from Temora. by waste disposal contractors.
2.10 OTHER SUPPORTING Putrescible and Non-Putrescible Waste INFRASTRUCTURE AND SERVICES General solid (putrescible) waste and general solid The CGO has extensive existing infrastructure and (non-putrescible) waste (as defined in the EPA’s services to support its operations, including (in [2014] Waste Classification Guidelines) is either addition to those described in the preceding recycled or disposed in the waste rock sub-sections): emplacements on-site or in an off-site landfill.
Bioremediation Waste • soil stockpiles;
• ROM stockpile areas; Site-generated hydrocarbon-impacted material (general solid [putrescible] waste) is treated in the • minor internal roads and haul roads; on-site designated Bioremediation Facility and is either used as subsoil or disposed within the waste • mine access road; rock emplacements.
2-11 Cowal Gold Operations Mine Life Modification – Environmental Assessment
Trash Screen Oversize Waste • LPBMP;
• Trash screen oversize waste from the milling circuit Noise Management Plan (NMP); (general solid [putrescible] waste) is disposed within • Rehabilitation Management Plan (RMP); the waste rock emplacements. • WMP; Waste Tyres • Soil Stripping Management Plan (SSMP);
Waste tyres are disposed of within designated areas • Surface Water, Groundwater, Meteorological of the waste rock emplacements. and Biological Monitoring Programme (SWGMBMP); and Sewage Treatment and Effluent Disposal • THMS.
Sewage is treated in the on-site sewage treatment Evolution maintains an extensive monitoring plant and is disposed of to the satisfaction of the programme (Figure 2-3) whereby data is collected, Bland Shire Council and the EPA (including the analysed and maintained for reporting, future conditions of EPL 11912). examination and assessment.
2.13 ENVIRONMENTAL MONITORING AND MANAGEMENT
Environmental management at the CGO encompasses a range of management plans and monitoring programmes overseen by statutory planning provisions. Approved and internal management plans/monitoring programmes include:
• Air Quality Management Plan (AQMP); • Biodiversity Offset Management Plan (BOMP); • Blast Management Plan (BLMP); • Bushfire Management Plan; • Compensatory Wetland Management Plan (CWMP); • CMP; • Emergency Response Plan/Pollution Incident Response Management Plan (ERP/PIRMP); • Environmental Management Strategy (EMS); • ESCMP; • Final Hazard Analysis (FHA); • Fire Safety Study; • Flora and Fauna Management Plan (FFMP); • Hazard and Operability Study (HAZOP); • HWCMP; • Heritage Management Plan; • Implementation of the Threatened Species Management Protocol (TSMP) (including Threatened Species Management Strategies); • Indigenous Archaeology and Cultural Heritage Management Plan (IACHMP); • Land Management Plan (LMP);
2-12 Locations Figure 2-3 Mining Lease Boundary (ML 1535) Mining Lease Boundary of Approved Extent Approximate Development Surface Modification Components State Forest Dwelling Company-owned Dwelling Privately-owned Railway Electricity Transmission Line PipelineMine Water Supply Borefield Creek Palaeochannel Bland Saline Borefield Eastern Station Pump Eastern Blast Monitoring Site Monitoring Site Noise Station Meteorological CGO Lake Level Monitoring Site Dust Deposition Gauge SamplerTSPVolume High Site Sample Inflow Groundwater Saline Borefield Eastern Bore Monitoring Groundwater Creek Palaeochannel Bland Monitoring Site Quality and Sediment Water Monitoring Site Bland Creek Bland Transect Control Transect Shore Transect East Channel Transect Irrigation Lachlan Transect Transect Project Existing Environmental Monitoring
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W G ne ML Mod_206A HAL-16-41 Cowal Gold Operations Mine Life Modification – Environmental Assessment
3 DESCRIPTION OF THE 3.2 ORE DEPOSIT AND LIFE OF MINE MODIFICATION The Modification would involve continued The Modification would involve the continued development of the existing open pit to access development of open pit mining and ore processing additional gold-bearing ore within the E42 ore operations at the CGO for an additional 8 years deposit. (i.e. until end 2032). The Modification would extend the life of the CGO to In general, the Modification would not change the approximately 28 years. Mining within the open pit functionality of the currently approved CGO, as it would occur up to Year 20 and ore processing would involve the continued use of the existing open would be undertaken up to Year 28. pit, waste rock emplacements, TSFs and ore processing facilities within ML 1535, with some An indicative mining schedule for the Modification is alterations where necessary to enable the mine life provided in Table 3-1. extension. 3.3 MINING OPERATIONS In comparison to the approved CGO, the Modification would involve the following changes: Mining Method and Schedule
• increasing the final depth of the open pit by The Modification would involve the continuation of 70 m to enable mining of additional ore and an existing CGO open cut mining methods increase in total gold production; (Section 2.3). Mining operations would continue to be conducted 24 hours per day, 7 days per week, • extending the life of the approved CGO by up with tailings lift construction limited to daytime hours to 8 years, to 31 December 2032; only (i.e. 7.00 am to 6.00 pm). • upgrades to the existing leach circuit within the processing plant to improve gold recovery; Open Pit Design
• increasing the total life of mine ore The Modification would not increase the surface production/volume of tailings and mined waste area of the existing/approved open pit. However, the rock; open pit would be deepened by approximately 70 m • maximising tailings storage capacity of the (Figure 3-1) within the deeper primary rock zone. At existing TSFs via additional lifts and converting the end of mining, the open pit would have a the area between the existing TSFs into a new maximum depth of approximately -331 m AHD storage area; (i.e. approximately 540 m below the natural surface level). • incorporation of a rock fill buttress cover on the outer slopes of the TSF embankments to The deepening of the open pit has been designed to provide long-term stability; and maximise ore recovery, while maintaining factors of • an increase to the TSF embankment lift fleet. safety appropriate for operating conditions and the long-term stability of the lake isolation system. Changes to the approved CGO layout as a result of the Modification are shown on Figure 3-1. Consistent with existing operations, the pit slope Conceptual general arrangements of the design criteria of the deepened open pit have been Modification for Years 14 (2018) and 18 (2022) and developed based on findings of geotechnical post-mining are shown on Figures 3-2 to 3-4. investigations. The geotechnical modelling and analysis undertaken to determine suitable pit slope The sub-sections below describe the Modification in design criteria considered historical slope further detail. Where relevant, a description of performance and geotechnical data gained over additional measures designed to minimise potential previous and current studies for the existing open pit environmental impacts is also provided below. for both surficial (soil/highly weathered rock) and hard rock material.
3.1 MINING TENEMENT Batter angles, berm widths and inter-ramp angles in oxide rock would remain unchanged. Mining operations for the CGO are conducted within ML 1535. Primary rock would be mined in multiple benches, with berms up to 13 m in width, batter angles No change to ML 1535 and no additional mining between 60 to 90° and with an inter-ramp angle of tenements would be required for the Modification. 40 to 60° (variable according to open pit sector).
3-1
Cowal Gold Operations Mine Life Modification – Environmental Assessment
Table 3-1 Indicative Mining and Ore Processing Schedule
2 Mineralised 1,2 Ore Mined 2 Ore Processed Waste Material Mined Rock Calendar CGO (Mt) (Mt) Mined2 Year Year (Mt) Oxide Primary Total Oxide Primary Total Oxide Primary Total (Mt)
Existing 2005 to 1 to 12 16.5 82.5 99.0 5.0 12.2 17.2 5.8 69.2 75.0 211.6 CGO 2016
Modified 2017 13 - 9.4 9.4 - 1.1 1.1 - 7.5 7.5 12.6 CGO 2018 14 0.1 9.1 9.2 0.2 1.0 1.1 - 7.4 7.4 22.1
2019 15 - 5.5 5.5 - 1.2 1.2 - 7.3 7.3 23.5
2020 16 - 2.4 2.4 - 1.4 1.4 3.8 3.7 7.5 21.5
2021 17 - 10.5 10.5 - 4.5 4.5 - 7.5 7.5 10.8
2022 18 - 11.9 11.9 - 2.7 2.7 - 7.4 7.4 4.1
2023 19 - 8.4 8.4 - 1.6 1.6 - 7.3 7.3 2.1
2024 20 - 1.9 1.9 - 0.1 0.1 - 7.5 7.5 0.8
2025 21 ------7.5 7.5 -
2026 22 ------7.5 7.5 -
2027 23 ------7.5 7.5 -
2028 24 ------7.5 7.5 -
2029 25 ------7.5 7.5 -
2030 26 ------2.3 5.2 7.5 -
2031 27 ------7.5 - 7.5 -
2032 28 ------2.3 - 2.3 -
Sub-Total 0.1 59.1 59.2 0.2 13.5 13.7 15.9 98.1 114.1 97.4
Total 16.6 141.6 158.1 5.2 25.7 30.9 21.8 167.3 189.1 309.1
1 The maximum annual ore processed would be 7.5 Mtpa. 2 The sequence and quantities of mining and processing primary and oxide ores, mineralised material and waste rock may change over the life of the mine, subject to detailed mine planning requirements. Note: Discrepancies in totals due to rounding.
The berm widths and slope angles would continue Mobile Mine Equipment Fleet to be reviewed and monitored through ongoing geotechnical studies and data collection during mine The existing mobile mine equipment fleet used at development. The design configuration for the the CGO (Section 2.3.3) would be increased for the modified open pit would be detailed in a revised Modification to reflect the deeper open pit. The MOP which would be prepared in consultation with revised fleet list is provided in the Noise and and subject to approval by the DRE. Blasting Assessment (Appendix D). The existing TSF construction fleet would also be increased to The LPBMP would be revised to include a enable the rock buttressing, connection and description of the Modification open pit design and heightening of the TSFs. monitoring (i.e. survey assessment) requirements. Following Year 17 (2021), the mobile mine As there would be no change to the extent of the equipment fleet required would decrease open pit, there would be no change the existing lake proportionally with the decrease in the total waste isolation system that currently separates the open and ore mined (Table 3-1). pit from Lake Cowal (comprising the temporary isolation bund, lake protection bund and perimeter waste rock emplacement).
3-6 Cowal Gold Operations Mine Life Modification – Environmental Assessment
Blasting Waste Rock Emplacements
The typical blast design details and the average A waste rock balance was conducted for the blasting frequency (i.e. maximum of one blast event Modification and it was found that the volume of per day) for the existing operations (Section 2.3.4) additional waste rock produced as a result of the would remain unchanged for the Modification. deepening of the open pit would be approximately similar to the volume of waste rock required for construction of the rock buttresses surrounding the 3.4 MINE WASTE ROCK MANAGEMENT TSFs.
Mine Waste Rock Schedule Therefore, as the additional waste rock mined would
be used for buttressing the TSFs, no additional Approximately 97 Mt of additional waste rock (i.e. a waste rock would be emplaced at the northern, total of approximately 309 Mt of waste rock) would southern or perimeter waste rock emplacements, be mined during the life of the Modification and there would be no change to the extent of the (Table 3-1). northern, southern or perimeter waste rock
emplacements. The maximum quantity of waste rock mined in any one year would be approximately 23.5 Mt (Table 3-1). As such, the Modification would not 3.5 ORE PROCESSING increase the maximum quantity of annual waste rock mined compared to the approved CGO. Ore Processing Rate and Gold Recovery Methods Following Year 15 (2019), annual waste rock quantities would progressively decrease as the The approved maximum ore processing rate of up ore-to-waste ratio improves. to 7.5 Mtpa would not change for the Modification.
Mineralised material would continue to be separately stockpiled adjacent to the northern waste Gold would continue to be extracted from ore using rock emplacement (Figure 3-1). The Modification a conventional carbon-in-leach cyanide leaching would involve temporarily increasing the design circuit. However the Modification would involve height of the existing mineralised material stockpile upgrades to the existing primary ore leach circuit to to approximately 288 m AHD. However, as the allow the recovery of gold from flotation tailings and Modification would involve processing of this to improve gold recovery from the CGO process material, the mineralised material stockpile would be plant (i.e. the existing flotation tails stream would be progressively removed (Table 3-1). leached to improve the overall rate of gold recovery). A conceptual primary ore processing Mine Waste Rock Geochemistry flowsheet including the leach circuit upgrades is provided in Figure 3-5. The additional leach circuit An assessment of the acid-generating potential and components would be located within the existing metal-leaching behaviour of mine waste rock process plant area (Figure 3-1). associated with the development of the Modification has been undertaken (Appendix C). Operation of the upgraded leach circuit would involve an increase in cyanide consumption and The waste rock produced from the Modification some other reagents/process consumables would have similar geochemical characteristics to (Section 3.5.1). However, no new reagents/process waste rock from the approved CGO (Appendix C). consumables would be used, and no change to the On this basis, existing mine waste rock CGO’s existing consumables storage areas, management strategies would continue to be handling or transport methods would be required for implemented for the Modification. the Modification.
Mine waste rock material suitable for use as a cover system for the waste rock emplacements (i.e. for rehabilitation) would also be segregated for use as described in Appendix F.
3-7 CRUSHING GRINDING Process Water SAG MILL
RUN OF MINE ORE
CRUSHED STOCKPILE
STOCKPILE RECLAIM CONVEYOR PRIMARY FEED CRUSHER CONVEYOR
RECYCLE CRUSHER MODIFICATION LEACH CIRCUIT UPGRADE RECYCLE STOCKPILE Leach Cyanide Feed CYCLONES Lime Carbon Carbon Transfer Flotation FLOTATION Reagents FLOTATION TAILS ROUGHERS ABSORPTION TANKS Loaded Carbon BALL MILL CYCLONES CYANIDE DESTRUCTION CYANIDE LEACHING & TAILINGS Cyanide VERTIMILL Lime Carbon M Carbon Transfer Flocculant
ABSORPTION TANKS TAILINGS THICKENER Loaded Carbon Cyanide Donestructi
Reclaim Water GOLD RECOVERY Make-up Borefield Water Water ELUTION ELECTROWINNING COLUMN CELLS BULLION Return to SMELTING Process Stripped Carbon FURNACE
PROCESS WATER POND Regenerated Carbon OVEN TAILINGS STORAGE CARBON FACILITY REGENERATION KILN
HAL-16-41 ML Mod_003A
Source: Evolution (2016)
CGO MINE LIFE MODIFICATION Indicative Primary Ore Process Flowsheet
Figure 3-5 Cowal Gold Operations Mine Life Modification – Environmental Assessment
Ore Processing Schedule The quantity of cyanide destruction reagents added to the tailings (for either Caro’s Acid or INCO Oxide ore would be processed in two separate processes) would continue to be regulated by an campaigns over the life of the Modification on-line free cyanide measurement. (i.e. during Year 16 [2020] and Years 26, 27 and 28 [2030 to 2032]). The majority of oxide ore would be The mitigation and management measures processed during Year 27 of the CGO. The described in the CMP (including the cyanide sequence of processing primary and oxide ore monitoring process) would continue to be however may change over the life, subject to implemented for the Modification. detailed scheduling of mining and processing requirements. 3.6 TAILINGS MANAGEMENT Any changes to the ore processing schedule would be detailed in a revised MOP which would be Geochemical Characteristics of Tailings prepared in consultation with and subject to approval by the DRE. It is expected that the tailings generated from the Modification would have similar geochemical characteristics to those from the approved CGO 3.5.1 Cyanide Use and Process Consumables tailings geochemistry (Appendix C). As such, existing tailings management strategies would The upgrades to the existing leach circuit would continue for the Modification (Appendix C). increase cyanide consumption to approximately 0.7 kg of cyanide per tonne of primary ore. No Tailings Storage Facilities change to cyanide consumption for oxide ore processing (i.e. approximately 0.8 kg of cyanide per The existing northern and southern failings storage tonne of ore) would occur as the leach circuit facilities (Section 2.6) would continue to be used to upgrades would be relevant to primary ore store the additional tailings produced during the life processing only. of the Modification.
The upgraded leach circuit would also involve In approximately Year 16 (2020) construction works increased use of other consumables used and would commence to enable the use of the area in stored at the CGO, including: between the northern tailings storage facility and southern tailings storage facility as additional • hydrochloric acid; tailings storage. Construction works would include:
• lime; • construction of connector embankments • oxygen (for cyanide destruction); between the northern tailings storage facility and southern tailings storage facility; • SMBS; and • construction of a low permeability basement • sodium hydroxide. layer and other seepage control measures; and Additional heavy vehicle deliveries would be associated with the additional use of some • extension of the existing northern tailings consumables. storage facility decant causeway into the new tailings storage area, prior to the point when Section 3.10 describes the management measures tailings deposition in the new area overtops the for the storage, use and transport of chemicals and Stage 6 northern tailings storage facility wastes. embankment.
Following construction of the connector 3.5.2 Cyanide Destruction embankments, tailings would be deposited into the
central section and the northern tailings storage The Modification would not change: facility simultaneously.
• the existing cyanide destruction methods Consistent with approved operations, tailings would currently used at the CGO (i.e. either Caro’s be deposited in the central section via spigots Acid or the INCO process) (Section 2.5.2); or (nominally 60 m apart). These spigots would be
• the approved CNWAD concentration limits of the located on the connector embankments and along aqueous component of the tailings slurry the downstream side of the northern face of the stream (Section 2.5.2). southern tailings storage facility.
3-9 Cowal Gold Operations Mine Life Modification – Environmental Assessment
Tailings would be deposited in the central section The design configuration for the TSFs would until the tailings surface is level with the Stage 6 continue to be detailed in a revised MOP which embankment of the northern tailings storage facility. would be prepared in consultation with and subject Subsequent to this, the northern tailings storage to approval by the DRE. The design, construction, facility and central section would act as one operation and monitoring of the TSFs would continuous area for tailings deposition (Figure 3-6), continue to be conducted in consultation with and to with the existing decant causeway for the northern the satisfaction of Dams Safety NSW (formerly the tailings storage facility extended to the northern face NSW Dams Safety Committee). of the southern tailings storage facility embankment (Figure 3-3). Tailings Storage Facility Water Management
In addition to connecting the TSFs, the approximate Prior to the point when tailings deposition in the new final heights of the northern and southern tailings area overtops the Stage 6 northern tailings storage storage facilities would increase to approximately facility embankment, water would be reclaimed for 264 m AHD and 272 m AHD, respectively, to re-use from the central section via the a new accommodate additional tailings. decant, comprising a series of concrete rings installed from ground level up, surrounded by To maintain suitable geotechnical factors of safety filtration rock. Water would be pumped from the appropriate for operating conditions and long-term centre of the concrete rings back to the contained stability, a rock buttress cover would be constructed water storage (D6) for use in processing. on the outer slopes of the TSFs’ embankments once the final height has been reached. This would Following the integration of the new area with the include a minor expansion of the footprint of the northern tailings storage facility, the northern tailings TSFs within currently approved surface disturbance storage facility decant would service the new tailings areas. area (as well as the northern tailings storage facility itself). Conceptual cross-sections of the modified northern and southern tailings storage facility embankments No changes to the water management for the and the central connector embankment are shown existing TSFs would be required for the Modification on Figures 3-7, 3-8 and 3-9, respectively. (Section 2.6).
In accordance with existing operations, as the TSFs The low permeability basement layer constructed for are filled, the embankments would continue to be the existing TSFs (e.g. targeted vertical permeability raised in a series of upstream lifts. The additional of no greater than 1 x 10-9 metres per second [m/s]) upstream lifts would use the same construction and other existing seepage control measures materials and follow the same lift construction (Section 2.6) would be replicated for the space methodology as the existing CGO (Section 2.6). between the existing TSFs, and would continue to During operations, each upstream lift would also control seepage from the TSFs for the life of the involve placement of an interim rock buttress on the Modification. outer slope of the lift. Once the final embankment is constructed, placement of the final rock buttress In general, the connector embankments would would occur (Figures 3-7 and 3-8). adjoin existing TSF embankments made entirely of homogeneous (clayey) material. Consistent with existing operations, the TSFs would be progressively raised during Years 13 to 28 (i.e. Some of the existing lifts include rockfill shoulder over the life of the Modification) at a rate of not more material. Accordingly, the connector embankments than approximately 5 m per year. would incorporate measures to prevent seepage through the rock fill shoulder material. A low As the heights of the TSFs increase, and the permeability cut-off using slurry/grouting would be effective area for tailings deposition decreases, the constructed in existing embankments for seepage effective rate of rise of the tailings beaches would control where necessary. increase. No changes to seepage flows are expected for the As described in Section 2.6, the existing decant Modification (i.e. the open pit would continue to act causeways are approved to be extended to the as a sink for seepage flows from the TSFs) opposite side of the storages. This would allow (Appendix A). each storage to be divided into two cells.
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Cowal Gold Operations Mine Life Modification – Environmental Assessment
3.7 SITE WATER MANAGEMENT 3.8.2 Revised Site Water Balance INFRASTRUCTURE A revised site water balance has been conducted by There would be no change to the design objectives Hydro Engineering & Consulting Pty Ltd (HEC) for of the existing surface water management system the life of the Modification, and is presented in (Section 2.7). That is: Appendix B. A summary of the simulated water balance for the life of the Modification under various • the UCDS would continue to divert climatic scenarios is provided in Table 3-2. up-catchment runoff around the CGO; It is expected that the majority of total water • the ICDS would continue to control runoff from requirements for the Modification would continue to active mining areas; and be supplied from internal water sources, with the • the lake isolation system would continue to remainder supplied from external water sources separate Lake Cowal from the CGO. (Table 3-2).
There would be no changes to water management 3.8.3 Water Supply Sources infrastructure (Section 2.7) required to maintain the design objectives of the existing water management Consistent with existing operations, site water system as a result of the Modification. supply would continue to be preferentially supplied from internal and external water sources according The Modification would not result in any changes to to the following priority: the existing integrated erosion, sediment and salinity control system (Section 2.7.4). 1. TSF return water.
The Modification would not change the approved 2. Open pit sump dewatering borefield. CGO pit dewatering methods (Section 2.7.5). 3. Contained water storages.
3.8 WATER SUPPLY 4. External water sources (i.e. water supply priority from external water sources subject to The Modification would not change existing annual water market conditions): water supply requirements or sources of internal • Saline groundwater supply bores within and external water supply for the approved CGO ML 1535. (Section 2.8). • Eastern Saline Borefield. Given there would be no increase in the ore • Bland Creek Palaeochannel Borefield. processing rate for the Modification, annual water demand would not materially change in comparison • Lachlan River licensed extraction. to the existing operations. However, as the Modification would involve the continuation of Further detail regarding external water sources is operations at the CGO for an additional 8 years, provided below. total life-of-mine water demand would increase.
Saline Groundwater Supply No additional water supply infrastructure would be required for the Modification. The existing saline groundwater supply bores
within ML 1535 (Section 2.8.1) would continue to be 3.8.1 Site Water Supply Requirements used for the Modification (during suitable lake conditions) in accordance with existing licence Water supply for the Modification would continue to conditions under the Water Sharing Plan for the be required for ore processing in the process plant, Lachlan Unregulated and Alluvial Water as well as dust suppression (e.g. haul roads) and Sources 2012. other potable and non-potable uses. Supply sources are described in Section 3.8.3. The revised site water balance for the Modification has considered the expected availability of the Consistent with existing operations, the total water existing saline groundwater supply bores due to the supply requirement for the process plant is inundation of Lake Cowal (Appendix B). estimated to be approximately 0.9 kL/t for primary ore processing and 1.7 kL/t for oxide ore processing (Section 2.8).
3-15 Cowal Gold Operations Mine Life Modification – Environmental Assessment
Table 3-2 Simulated Water Balance for the Life of the Modification
10th Percentile Rainfall Median Rainfall 90th Percentile Rainfall Expected Water Demand/Supply Sequence (Dry) Sequence Sequence (Wet)
(ML/annum) Outflows 1 Total Expected Water Requirements 8,963 8,950 8,974 Inflows Internal Water Sources Catchment Runoff 837 1,084 1,285 Tailings water return 3,861 3,861 3,861 Open Pit Groundwater 199 199 199 Subtotal – Internal Water Sources 4,897 5,144 5,345 External Water Sources Saline Groundwater Supply Bores 137 94 86 within ML 1535 Eastern Saline Bores 522 516 507 Bland Creek Palaeochannel Borefield 1,998 1,917 1,871 Lachlan River Licensed Extraction2 1,445 1,329 1,268 Subtotal – External Water Sources 4,102 3,856 3,732 Total Expected Water Supply 8,999 9,000 9,077 Source: After Appendix B. 1 Includes water requirements/losses associated with ore process, evaporation, haul road dust suppression and tailings lift construction. 2 Modelled volume of water actually reaching the CGO – excludes irrigation channel losses.
Eastern Saline Borefield The Hydrogeological Assessment for the Modification (Appendix A) predicts that a maximum The operation of the existing Eastern Saline sustainable yield of 5.1 ML/day from the Bland Borefield (Section 2.8.2) would continue for the Creek Palaeochannel Borefield over the life of the Modification in accordance with Development Modification would maintain groundwater levels Consent (DA 2011/64) and existing licence above the relevant trigger levels at groundwater conditions under the Water Sharing Plan for the bores GW036553, GW036597 and GW036611. Lachlan Unregulated and Alluvial Water Sources 2012. As there be would no change to the existing Groundwater Contingency Strategy (i.e. agreed trigger levels) for the ongoing management of Bland Creek Palaeochannel Borefield groundwater levels in the Bland Creek
Palaeochannel or existing daily and annual The operation of the existing Bland Creek extraction limits, no additional impacts to other Palaeochannel Borefield (Section 2.8.3) would groundwater users are predicted due to the continue for the Modification in accordance with continued use of the Bland Creek Palaeochannel existing licence conditions under the Water Sharing Borefield for the Modification (Appendix A). Plan for the Lachlan Unregulated and Alluvial Water
Sources 2012. Lachlan River Water Entitlements
There would be no change to the existing Water from the Lachlan River would continue to be Groundwater Contingency Strategy (i.e. trigger accessed for the Modification, when required, by levels) for the management of groundwater levels in purchasing temporary water available from the the Bland Creek Palaeochannel (Section 2.8.3) due regulated Lachlan River trading market. to the Modification.
3-16 Cowal Gold Operations Mine Life Modification – Environmental Assessment
During the life of the existing CGO there has been Site Security and Communications reliable supply of temporary water available from the Lachlan River trading market, including during Existing site security measures (including the periods of drought. DPI-Water trading records show ML 1535 perimeter fence and perimeter buoys that between approximately 4,000 ML and during periods of lake inundation) would be retained 274,000 ML of temporary water has been traded for the Modification. The existing communications annually since records began in 2004 (Appendix B). systems would also be retained with augmentations By comparison, the predicted average water as required over the life of the Modification (i.e. as requirement from the Lachlan River under a technological advances allow). 10th percentile (dry) rainfall sequence is 1,445 ML/annum over the life of the Modification Potable Water (Table 3-2). The potable water supply for use on-site would
continue to be trucked to the CGO. The existing Given the above, it is expected there would be potable water supply network on-site would continue continued reliable supply of water available from the to service the Modification. Lachlan River trading market for the Modification
(Appendix B). 3.10 MANAGEMENT OF CHEMICALS AND WASTES 3.9 INFRASTRUCTURE AND SERVICES
As discussed in Section 3.5, the Modification would Mineralised Material Stockpile Area result in an increase in the consumption of several
reagents. Notwithstanding, the existing The Modification would involve temporarily management measures as for the approved CGO increasing the design height of the existing (Section 2.12) would continue to apply for the mineralised material stockpile to approximately Modification. 288 m AHD (Section 3.4) and temporarily integrating this stockpile with the adjacent northern waste rock emplacement. As the Modification would 3.11 ROAD TRANSPORT involve processing of mineralised material, the mineralised material stockpile would be The Modification would include upgrades to the progressively removed (Table 3-1). leach circuit which would result in additional deliveries (i.e. an additional 2 to 4 movements per Administration Buildings, Exploration and day or 1 to 2 trucks in, 1 to 2 trucks out) during Workshop Facilities periods of processing primary ore. There would, however be no change during oxide ore processing The existing administration buildings, exploration campaigns. Therefore, there would be no change to and workshop facilities on-site would continue to be the total maximum daily truck movements used during the life of the Modification. (Section 4.5.1).
Mine Access The additional heavy vehicle deliveries would be assessed in an update of the Transport of There would be no change to the preferred access Hazardous Materials Study which would be routes to the CGO for the Modification. prepared in consultation with relevant Councils, the
RMS and the transport provider, and would be Use of the primary access road from West Wyalong subject to approval by the DP&E (Hazards Branch) for light and heavy vehicles would continue for the (Section 4.5.1). Modification. Light vehicle and employee shuttle bus access from Condobolin and Forbes would also There would be no changes to employee vehicle continue for the Modification. movements or other road transport movements
associated with the Modification (Section 4.5.1). Electricity Supply and Distribution
Electricity to the site would continue to be provided via the existing 132 kV ETL from Temora.
Power on-site would continue to be transferred either by overhead cable or underground cable. Standard electrical safety laws and practices (including vehicle clearance considerations) would apply.
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3.12 WORKFORCE AND OPERATING HOURS
Consistent with the existing operating hours at the CGO, operation of the Modification would be 24 hours a day, 7 days a week. Construction of TSFs embankment lifts would continue to be restricted to daytime hours only (i.e. 7.00 am to 6.00 pm).
The Modification would facilitate the continuity of employment for the existing CGO workforce for an additional 8 years.
There would be no change to the average or peak CGO workforce due to the Modification.
3.13 CONSTRUCTION ACTIVITIES
The major components of the Modification (i.e. deepening of the open pit and increased heights of the TSFs) are considered to be part of the continuation of mining operations of the CGO, as opposed to construction activities.
Construction activities associated with the Modification are considered to include construction of the rock buttresses around the TSFs and construction of the upgrades to the leach circuit within the process plant.
Construction of the rock buttresses around the TSFs would occur from approximately Year 13 (2017) and would involve transport of waste rock from the open pit to the embankments of the TSFs for deposition.
Construction of the rock buttresses for the TSFs would be restricted to daytime hours only.
Construction of the leach circuit upgrade is anticipated to commence in Year 13 (2017) and would occur over approximately six months.
Descriptions of the construction activities associated with the leach circuit upgrade and TSF rock buttresses are provided in Sections 3.5 and 3.6, respectively.
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