EOE (NO.75) PTY LIMITED - Coolamon Shire...2016/12/01 · EOE (NO.75) PTY LIMITED ABN: 95 006 829 787 Ardlethan Tin Mine Prepared by Pitt & Sherry Pty Ltd December 2016 Specialist

EOE (NO.75) PTY LIMITED

ABN: 95 006 829 787

Ardlethan Tin Mine

Prepared by

Pitt & Sherry Pty Ltd

December 2016

Specialist Consultant Studies Compendium Volume 1, Part 1

Groundwater Impact

Assessment

This page has intentionally been left blank

EOE (NO.75) PTY LIMITED

ABN: 95 006 829 787

Prepared for: R.W. Corkery & Co. Pty Limited

62 Hill Street

ORANGE NSW 2800

Tel: (02) 6362 5411

Fax: (02) 6361 3622

Email: [email protected]

On behalf of: EOE (No.75) Pty Limited

ABN: 95 006 829 787

Level 2, 53 Berry Street

NORTH SYDNEY NSW 2060

PO Box 1506

NORTH SYDNEY NSW 2059

Telephone: (02) 9959 5599

Fax: (02) 9959 5577


Prepared by: Pitt & Sherry Pty Ltd

Surrey House

199 Macquarie Street

Hobart TAS 7000

Tel: (03) 6210 1400

Fax: (03) 6223 1299


Job Number No: HB16462

December 2016

Groundwater Impact

Assessment

mailto:[email protected]

EOE (NO.75) PTY LIMITED SPECIALIST CONSULTANT STUDIES Ardlethan Tin Mine Part 1 – Groundwater Impact Assessment Report No. 754/09

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Note: A colour version of this report is available on the digital version of this document

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© EOE (No.75) Pty Limited 2016

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addressed to Pitt & Sherry Pty Ltd.

SPECIALIST CONSULTANT STUDIES EOE (NO.75) PTY LIMITED Part 1 – Groundwater Impact Assessment Ardlethan Tin Mine Report No. 754/09

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Pitt and Sherry Groundwater Assesment Groundwater Impact Assessment

Job Number HB16462

Prepared for RW Corkery & Co Pty Ltd | 15 December 2016

EOE (NO.75) PTY LIMITED SPECIALIST CONSULTANT STUDIES

Ardlethan Tin Mine Part 1 – Groundwater Impact Assessment Report No. 754/09

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Contents

1. Introduction ................................................................................................................... 1-7

1.1 Study Area .......................................................................................................... 1-7

1.2 Objectives ........................................................................................................... 1-7

1.3 Scope of Work .................................................................................................. 1-11

2. PROJECT DESCRIPTION .......................................................................................... 1-11

3. Legislative Context ..................................................................................................... 1-12

3.1 Water Management Act .................................................................................... 1-12

3.2 Water Sharing Plan ........................................................................................... 1-12

3.3 Aquifer Interference Policy ................................................................................ 1-12

4. Existing Environment .................................................................................................. 1-13

4.1 Site Location ..................................................................................................... 1-13

4.2 Geology ............................................................................................................ 1-15 4.2.1 Regional Geological Setting .................................................................. 1-15 4.2.2 Local Geology ....................................................................................... 1-15

5. Existing Groundwater Environment ............................................................................. 1-18

5.1 Background ...................................................................................................... 1-18

5.2 Regional hydrological and groundwater setting ................................................. 1-19

5.3 Regional Water Bore Inventory ......................................................................... 1-20

5.4 Regional and intermediate scale numeric groundwater modelling ..................... 1-21

5.5 Adopted study area for the GIA ......................................................................... 1-23

5.6 Groundwater Quality ......................................................................................... 1-23 5.6.1 1995 Groundwater sampling event ........................................................ 1-23 5.6.2 Groundwater sampling event in 2011 .................................................... 1-24 5.6.3 Groundwater sampling event in 2016 .................................................... 1-27

5.7 Historic Site Observations ................................................................................. 1-28 5.7.1 Anecdotal groundwater observations ..................................................... 1-28 5.7.2 Geotechnical investigations for site rehabilitation in 1995 and 1997 ...... 1-29

5.8 Groundwater Levels .......................................................................................... 1-33 5.8.1 Water table depths at the Mine Site ....................................................... 1-33 5.8.2 Water level in the AWC Open Cut ......................................................... 1-33 5.8.3 Analytical estimates of groundwater inflow to the AWC Open Cut ......... 1-33

5.9 Conceptual Model ............................................................................................. 1-35

6. Classification under AIP .............................................................................................. 1-41

6.1 Groundwater Source ......................................................................................... 1-41

6.2 Level 1 Minimal Impact Considerations ............................................................. 1-41 6.2.1 Water Table ........................................................................................... 1-41 6.2.2 Water pressure ...................................................................................... 1-42 6.2.3 Water Quality ......................................................................................... 1-42

7. Impacts Assessment for SEARs ................................................................................. 1-42

7.1 Preliminary water balance for the AWC Open Cut catchment ........................... 1-42

7.2 Changes in water table in the AWC Open Cut .................................................. 1-42

7.3 Groundwater use-inflows/outflows .................................................................... 1-47

7.4 Changes in groundwater quality in the AWC Open Cut ..................................... 1-47

8. Conclusions ................................................................................................................ 1-49

9. References ................................................................................................................. 1-50


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List of tables

Table 1: Groundwater environmental issues extracted from Table A2-2 of DPE (2016) ......... 1-9

Table 2: Surface and groundwater analyses, November 1995 ............................................. 1-24

Table 3: Recent water table depths and field parameters from three 1995 geotechnical drill holes, and the AWC Open Cut ..................................................................... 1-27

Table 4: Analysis of groundwaters and water from the AWC Open Cut, November 2016 .... 1-28

Table 5: Summary of 1995 geotechnical drilling .................................................................. 1-30

Table 6: Typical permeability ranges for unconsolidated materials. Red type indicates materials like those described in Table 2 for the Mine Site .................................. 1-31

Table 7: Summary of 1997 excavator test pitting (Source: Amaral 1997) ............................. 1-32

Table 8: Estimates of annual groundwater flow from the sides and bottom of the AWC Open Cut ............................................................................................................ 1-35

Table 9: AWC Open Cut estimated freeboard and groundwater flow conditions during tailings reprocessing ........................................................................................... 1-45

Table 10: Trace metal analysis of tailings samples, November 2016 ................................... 1-48

Table 11: Leachate testing of tailings samples, November 2016 ......................................... 1-48

List of Figures

Figure 1: Regional Location ................................................................................................... 1-8

Figure 2: Site Layout ........................................................................................................... 1-14

Figure 3: Regional geology of the Ardlethan district ............................................................. 1-16

Figure 4: Local geology of the Mine Site .............................................................................. 1-17

Figure 5: Aspects of the land-based hydrological cycle........................................................ 1-18

Figure 6: Fundamentals of hydrogeology in a gravity-driven groundwater system, with local, intermediate and regional groundwater systems ........................................ 1-19

Figure 7: Mine Site Location within Murrumbidgee River Basin. .......................................... 1-20

Figure 8: Recorded groundwater bores drilled in the past century in the Ardlethan district .. 1-22

Figure 9: Dissolved constituents in groundwater in the Main Pit and surface water from the northeast and northern evaporation ponds. Locations of samples are otherwise unspecified. ........................................................................................ 1-25

Figure 10: Dissolved constituents in surface water in the Mill Valley Catchment. ................. 1-26

Figure 11: Conceptual half-cross section and simple analytical model through the Ardlethan/Wild Cherry Open Cut ......................................................................... 1-34

Figure 12: Conceptual hydrogeological model of the Mine Site: Section A – B .................... 1-36

Figure 13: Conceptual hydrogeological model of the Mine Site: Section C – D .................... 1-37

Figure 14: Conceptual hydrogeological model of the Mine Site: Section E – F .................... 1-38

Figure 15: Conceptual hydrogeological model of the Mine Site: Section G – H .................... 1-39

Figure 16: Conceptual hydrogeological model of the Mine Site: Section I – J ...................... 1-40

Appendices

Appendix 1 .......................................................................................................................... 1-53

Appendix 2 .......................................................................................................................... 1-59

Appendix 3 .......................................................................................................................... 1-62


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Prepared by: Date: 15 December 2016

William Cromer

Reviewed by: Date: 15 December 2016

Edith O’Shea

Authorised by: Date: 15 December 2016

David Lenel

Revision History

Rev No.

Description Prepared by Reviewed by Authorised by Date

A Draft for comment WC EO DL 12/12/16

B Draft for comment WC EO DL 14/12/16

00 Final WC EO DL 15/12/16


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1. INTRODUCTION

1.1 STUDY AREA

R.W. Corkery & Co. Pty Ltd (RWC) commissioned Pitt & Sherry to compile a Groundwater Impact Assessment (GIA) Report to support an Environmental Impact Statement (EIS) for a proposal to rehabilitate and reprocess tailings at the historic Ardlethan Tin Mine (the “Mine Site”) in south-central New South Wales. The regional location is shown in Figure 1.

1.2 OBJECTIVES

Issues required to be addressed in the EIS are listed in the Department of Planning and Environment (DPE), Secretary’s Environmental Assessment Requirements (SEARs) issued on 1 September 2016. Those issues paraphrased from the SEARs (Table A2-1) specifically relating to the GIA Report are:

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

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

The environmental issues required to be covered in the EIS are listed in Table A2-2 of the SEARs, with those specifically relating to the current GIA Report summarised in Table 1.


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Figure 1: Regional Location


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Table 1: Groundwater environmental issues extracted from Table A2-2 of DPE (2016)

Govt. Agency

Paraphrased Requirement Relevance to Report

EPA 26/07/16

A detailed and contemporary hydrogeological impact assessment that documents local and regional groundwater features and includes a comprehensive description of the measures that will be implemented in the Ardwest/Wild Cherry open cut pit to protect groundwater.

All

DPI – Office of Water

2/08/16

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

All and see EIS

Section 6

Details of water proposed to be taken (including through inflow and seepage) from each surface water and groundwater source

Section 7.2

Groundwater Assessment

To ensure the sustainable and integrated management of groundwater sources, the EIS needs to include adequate details to assess the impact of the project on all groundwater sources including:

Any proposed groundwater extraction, including purpose, location and construction details of all proposed bores and expected annual extraction volumes.

N/A

Bore construction information is to be supplied to the DPI Water by submitting a “Form A” template. The DPI Water will supply “GW” registration numbers (and licence/approval numbers if required) which must be used as consistent and unique bore identifiers for all future reporting.

N/A

A description of the watertable and groundwater pressure configuration, flow directions and rates and physical and chemical characteristics of the groundwater source (including connectivity with other groundwater and surface water sources).

Section 5

Sufficient baseline monitoring for groundwater quantity and quality for all aquifers and GDEs to establish a baseline incorporating typical temporal and spatial variations.

Section 5.9

The predicted impacts of any final landform on the groundwater regime. Section 6, Section 7

The existing groundwater users within the area (including the environment), any potential impacts on these users and safeguard measures to mitigate impacts.

Section 5.3

An assessment of groundwater quality, its beneficial use classification and prediction of any impacts on groundwater quality.

Section 5.3

An assessment of the potential for groundwater contamination (considering both the impacts of the proposal on groundwater contamination and the impacts of contamination on the proposal).

Section 7

Measures proposed to protect groundwater quality, both in the short and long term. Section 7

Measures for preventing groundwater pollution so that remediation is not required. Section 7

Protective measures for any groundwater dependent ecosystems (GDEs). Section 6

The results of any models or predictive tools used. Section 5.9

Where potential impact/s are identified, the assessment will need to identify limits to the level of impact and contingency measures that would remediate, reduce or manage potential impacts to the existing groundwater resource and any dependent groundwater environment or water users, including information on:

Any proposed monitoring programs, including water levels and quality data. Section 7

Reporting procedures for any monitoring program including mechanism for transfer of information. Section 7

An assessment of any groundwater source/aquifer that may be sterilised from future use as a water supply as a consequence of the proposal.

N/A.

Identification of any nominal thresholds as to the level of impact beyond which remedial measures or contingency plans would be initiated (this may entail water level triggers or a beneficial use category).

N/A.

Groundwater Dependent Ecosystems

The EIS must consider the potential impacts on any Groundwater Dependent Ecosystems (GDEs) at the site and in the vicinity of the site and

Identify any potential impacts on GDEs as a result of the proposal including:

the effect of the proposal on the recharge to groundwater systems; Section 6

the potential to adversely affect the water quality of the underlying groundwater system and adjoining groundwater systems in hydraulic connections; and

Section 6

the effect on the function of GDEs (habitat, groundwater levels, connectivity). N/A.

Detailed modelling of potential groundwater volume, flow and quality impacts of the presence of an inundated final void (where relevant) on identified receptors specifically considering those environmental systems that are likely to be groundwater dependent;

N/A.

The measures that would be established for the long-term protection of local and regional aquifer systems and for the ongoing management of the site following the cessation of the project.

Section 7

EPA 26/07/16

Potential impacts on water quantity and quality A hydrogeological assessment must be undertaken to assess potential groundwater impacts. In particular, the proponent must.

a) Comprehensively determine whether the water contained within the Ardwest/Wild Cherry Open Cut includes any intercepted groundwater;

Section 5.8

b) Identify surrounding groundwater users that may be affected by any adverse impact on groundwater quantity or quality;

Section 5

c) Quantify the impacts that any proposed water extraction may have on the groundwater source; and Section 7

d) Detail any potential groundwater quality impacts from this proposal and identify appropriate measures that will be undertaken to mitigate any potential adverse impact.

Section; EIS

Coolamon Shire

Council 17/08/16

Permeability: The proponent needs to establish the existing water table and soil permeability of the disposal area of the site, in particular the Wild Cherry Pit. Whilst it has regularly been advised that it is impermeable, there has been no documentation or proof to verify this statement.

Section 5



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1.3 SCOPE OF WORK

This GIA Report is based on:

a review and compilation of relevant hydrogeological information from a variety of

sources,

the construction of a subregional numeric groundwater model,

use of a empirical analytical groundwater model to estimate hydrological conditions at

the Ardwest/Wild Cherry Open Cut (AWC Open Cut),

the extent to which current understanding of the hydrogeology of the Mine Site

addresses the requirements of the NSW Aquifer Interference Policy (AIP), and the

DPE’s SEARs dated 1 September 2016 for the Proposal, and

a recent site inspection of the Mine Site by RWC, including water sampling, and

laboratory testing of surface and groundwaters.

This GIA Report also classifies the Mine Site groundwater system(s), and reviews Table 1 of

the NSW AIP in relation to minimal impact considerations.

2. PROJECT DESCRIPTION

The Applicant proposes to seek development consent for the following (Figure 2).

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

Valley Tailings Storage Facilities.

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

Pad.

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

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

Reprocessing of the extracted tailings using a gravity separation reprocessing plant to

produce a tin concentrate suitable for sale to international customers.

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

Rehabilitation of sections of the Mine Site, including:

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

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

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

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

Four reprocessing stages over about 13 – 15 years are proposed:

Stage 1 250,000tpa

Stage 2 500,000tpa

Stage 3 1Mtpa

Stage 4 1.5Mtpa

Water from the AWC Open Cut will be used to slurry the tailings for processing. Except for minor fugitive losses during operations, it is assumed that the process water circuit is closed.

Operations will raise the level of the water in the AWC Open Cut.

The Proposal is a Designated Development, with Coolamon Council the determining authority.


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3. LEGISLATIVE CONTEXT

3.1 WATER MANAGEMENT ACT

The Water Management Act, 2000 (WMA) guides water management activities in NSW. The objectives of the WMA are the sustainable and integrated management of the state's water for the benefit of both present and future generations.

The main tool the WMA provides for managing the state's water resources are Water Sharing Plans (WSP). These are used to set out the rules for the sharing of water from a particular water source between water users and the environment, and include rules for the trading of water in a particular water source.

3.2 WATER SHARING PLAN

The Mine Site is covered by the Water Sharing Plan for the NSW Murray-Darling Basin Fractured Rock Groundwater Sources specifically the Lachlan Fold Belt MDB Groundwater Source. Which commenced in January 2012.

The NSW Murray-Darling Basin (MDB) fractured rock groundwater sources are located within the NSW portion of the MDB. In general, the plan area includes all fractured rock groundwater sources of the MDB that are not included in other water sharing plans. The plan also includes miscellaneous, unmapped alluvial sediments that overly outcropping fractured rock groundwater sources as well as porous rock sediments that occur within groundwater sources that are predominantly fractured rock.

The Lachlan Fold Belt MDB Groundwater Source covers an area of 16,722,000 hectares. It consists of Cambrian to Lower Carboniferous rock successions.

3.3 AQUIFER INTERFERENCE POLICY

The NSW Aquifer Interference Policy, 2012 (AIP) details the water licensing and impact assessment processes for aquifer interference activities under the WMA and other relevant legislation.

There are three key parts to the policy:

All water taken must be properly accounted for.

The activity must address minimal impact considerations for impacts on water table,

water pressure and water quality.

Planning for measures if the actual impacts are greater than predicted, including

making sure that there is sufficient monitoring in place.

This GIA Report classifies the Mine Site groundwater system(s), and reviews Table 1 of the

AIP in relation to minimal impact considerations.

AIP issues include:

Accounting for or preventing the taking of water.

Addressing the minimal impact considerations.

Proposing remedial works if impacts are more than expected.


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Minimal impacts relate to:

Changes in the water table.

Changes in potentiometric (piezometric) levels.

Changes in groundwater quality.

4. EXISTING ENVIRONMENT

4.1 SITE LOCATION

The Mine Site is located about 5.5km WNW of Ardlethan in the shire of Coolamon.

The site has a history of mining dating back to the discovery of tin in 1912. Large scale hard rock mining operations were undertaken from 1964 to 1986 by Ardlethan Tin NL. Further recovery of alluvial tin (in the form of cassiterite) was undertaken by Telminex NL (a subsidiary of Marlborough Resources NL) between 2000 and 2003. All mining at the site ceased in 2003.

Rehabilitation activities have been undertaken in the past, including reinstatement of alluvial mining areas and removal of processing and office infrastructure, although the majority of the site has not been rehabilitated.

The following are located at the site:

A number of filled Tailings Storage Facilities

Three open cut pits (Stackpool, Ardwest/Wild Cherry and White Crystal)

A number of dams and water management features including bunds and pipes

Stockpiles which may include tailings and overburden material

Waste Rock Dumps

Site roads and access tracks, and

Perimeter fencing.

The location of major site features is indicated in Figure 2.


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Figure 2: Site Layout


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4.2 GEOLOGY

4.2.1 Regional Geological Setting

The Mine Site is in the western part of the Lachlan Fold Belt1 within what is called the Wagga Anticlinorial Zone. The oldest rocks are Upper Ordovician clastic sedimentary rocks which have been tightly folded in a north to north-northwest trend, and undergone low-grade regional metamorphism (Paterson, 1990) (Figure 3).

The Upper Ordovician sediments have been intruded by two types of Upper Silurian granitic rocks (Figure 5): the Kikoira Suite (map symbol SG1; dated at about 417 million years) of muscovite-biotite adamellites2 and similar rocks, and a younger group of porphyries and volcanics including the Ardlethan Suite (map symbol SG2; dated at 410 million years).

The sediments and two suites of granites are unconformably overlain by Late Devonian clastic

sediments called the Cocoparra Group, which has been gently folded along north-northwest

trending axes.

4.2.2 Local Geology

In the Mine Site area (Figure 4), the Upper Ordovician sediments were first intruded by the

Mine Granite, a weakly foliated biotite-muscovite adamellite with low tin values, and narrow

metamorphic aureoles, with graded outwards alteration of the intruded country rocks to schists,

then phyllites and slates (Lannen, 1996).

The Mine Granite was then intruded by narrow (up to 5m wide) dykes of olivine basalt (now

altered and brecciated) followed by high level porphyritic intrusives (Kikoira Granite; SG1) and

related extrusions (lavas) of rhyolite, dacite and ignimbrite.

Lastly, the Ardlethan Granite (SG2) was emplaced, trapping at the upper levels of the magma

chamber a volatile-rich porphyry which explosively intruded the Mine Granite, forming

hydrothermal breccias and an alteration pipe with major chloritic alteration, and hosting

cassiterite-wolframite-pyrite-arsenopyrite-bismuthinite mineralisation (tin up to 15,000ppm).

During the Quaternary and Tertiary Periods, erosion produced cassiterite-bearing alluvial

deposits emanating from the subdued uplands around the Mine Site.

1 The Lachlan Fold Belt or Geosyncline is a large geological terrane stretching from Tasmania to Queensland along the eastern

portion of the Australian continent. It is composed of folded and faulted rocks of Middle Palaeozoic age (450 to 340 million years ago). 2Adamellite is a light-coloured, coarse-grained granite with roughly equal proportions of pink orthoclase and white plagioclase

feldspars.


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Figure 3: Regional geology of the Ardlethan district [after Paterson (1990)]


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Figure 4: Local geology of the Mine Site

*Based on Paterson (1990)] but including the mine site boundary, tailings dams, open cuts, surface water catchments, borehole and excavator test pit locations, and cross sections.


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5. EXISTING GROUNDWATER ENVIRONMENT

5.1 BACKGROUND

Critical to an understanding of the hydrogeology of the Mine site and surrounds are the

concepts of hydrological cycle3, groundwater systems4 at local, intermediate and regional

scales, and recharge and discharge conditions (Figure 5 and Figure 6).

It is important to note that discharge conditions create Groundwater Dependent Ecosystems

(GDE), and recharge conditions create Groundwater Independent Ecosystems (GIE).

Figure 5: Aspects of the land-based hydrological cycle

3 The hydrological cycle is the circulation of water in various phases through the atmosphere, over and under the earth’s surface,

to the oceans, and back to the atmosphere. The cycle is solar-powered. Because water is a solvent it dissolves elements, and geochemistry is a fundamental part of the cycle, which is a flux for water, energy, and chemicals. Water enters the land-based cycle as precipitation; it leaves as surface streamflow (runoff), evapotranspiration, or subsurface infiltration. The route which groundwater takes from a recharge point to a discharge point is a flow path.

4 A groundwater system can be defined (Sophocleous, 2004) as “a set of groundwater flow paths with common recharge and

discharge areas. Flow systems are dependent on the hydrogeologic properties of the soil/rock material, and landscape position. Areas of steep or undulating relief tend to have dominant local flow systems (discharging to nearby topographic lows such as ponds and streams). Areas of gently sloping or nearly flat relief tend to have dominant regional flow systems (discharging at much greater distances than local systems in major topographic lows or oceans).” A three-dimensional closed groundwater flow system that contains all the flow paths is called the groundwater basin. In areas of moderate to high relief, the near-surface dominant groundwater flows to depths of the order of a hundred metres or so will be as local systems, with recharge on elevated areas discharging to streams. As depth increases, the dominant groundwater flows become increasingly intermediate and then regional in nature. It is therefore important to recognise the local site in the context of the larger groundwater system.


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Figure 6: Fundamentals of hydrogeology in a gravity-driven groundwater system, with local, intermediate and regional groundwater systems [Adapted from Sophocleous (2004)]

5.2 REGIONAL HYDROLOGICAL AND GROUNDWATER SETTING

The Mine Site is located within the central north sections of the Murrumbidgee River Basin, some 50km southwest of the Basin’s northeast boundary (Figure 7).

Within the catchment area, groundwater flow directions are towards surface drainage lines at all scales: at a local scale, flow is towards minor streams in small catchments; at an intermediate scale, flow is towards longer watercourses in larger catchments; at a regional scale, flow is towards major rivers.

On this basis, it would be expected that intermediate and regional flows in the vicinity of the Mine Site would be in a generally southwest direction, towards and under Mirrool Creek to the Murrumbidgee River.


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Figure 7: Mine Site Location within Murrumbidgee River Basin.

*Adapted from waterinfo.nsw.gov.au/pinneena/interactive/410-mbg-map2.pdf

5.3 REGIONAL WATER BORE INVENTORY

Figure 8 shows the locations of 40 groundwater bores drilled in the past century over an area of some 1,000km2 centred on the Mine Site. Available records of the same bores are tabulated in Appendix 1. Relevant observations are

The average depth drilled was 79m (range: 8m to 218m).

Bedrock types recorded in drillers’ logs included limestone, sandstone, shale,

conglomerate and granite in varying degrees of weathering (from “hard rock” to “pug”).

Unconsolidated sediments included sand, clay and gravel, in some instances to depths

of tens of metres.


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Groundwater was reportedly encountered in 18 (45%) of the 40 bores. The average

reported standing water level in 16 of the 18 bores was 55m below ground (mbg; range

3mbg to 72mbg).

Reported bore yield averaged 0.7L/s (range 0.01L/s to 5L/s). Only one yield exceeded

1.5L/s, and if this outlier is excluded from the data, the average yield reduces to 0.4L/s.

Four out of the 40 bore records include a comment about groundwater quality. In one

bore, quality was recorded as “good”. Another was stated to have TDS in the range

1,000 – 3,000mg/L, and a third had a TDS of >14,000mg/L.

These notes suggest a highly variable groundwater quality with TDS ranging between

1 000mg/L and 14,000mg/L.

No known groundwater users within a radius of at least 5km of the Mine Site were

identified.

The review of from the regional bore inventory indicates/suggested:

Groundwater conditions are unconfined at all scales; there is no artesian water to the

depths drilled, so no potentiometric (piezometric) surface exists.

The unconfined bedrock types are fractured rock aquifers.

The unconsolidated sediments constitute alluvial, unconfined aquifers.

Drilling success rates are low; almost all bores were abandoned.

Bore yields are low (average 0.7L/s, with no yields exceeding 5L/s) reflecting low

permeability aquifers.

Groundwater quality data are sparse, and suggest a fair degree of variability in salinity,

(from low to high); beneficial use of the groundwater would vary similarly.

The paucity of bores over a relatively wide area spanning a century suggests low

groundwater prospectivity. In terms of the AIP groundwater source categories, the

regional aquifers in the area covered in Figure 8 and Appendix 1 are considered “Less

productive groundwater sources”.

5.4 REGIONAL AND INTERMEDIATE SCALE NUMERIC GROUNDWATER MODELLING

Appendix 2 presents the results of numeric groundwater modelling covering about 120km2 centred on Mine Site. The modelling is based on water level data in two bores north and south of the Mine Site, and water level records of five bores drilled within the Mine Site boundary in 1995. Other inputs were estimated in the absence of actual measurements.

The main observations arising from the modelling are:

Groundwater flow directions are from the northeast to the southwest, in agreement with

the direction inferred from basic hydrogeological principles. At a local to intermediate

scale, flow directions vary. Groundwater flow rates also vary, from very slow over most

of the modelled area, to higher rates on lower, flatter ground. The low flow rates are

caused by very low permeability fractured bedrock, and the high flow rates by higher

permeability unconsolidated alluvials.


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Figure 8: Recorded groundwater bores drilled in the past century in the Ardlethan district

*Source:http://allwaterdata.water.nsw.gov.au//water.stm


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Water table elevations across the modelled area range from about 250m Above Sea

Level (ASL) on elevated areas within the mine site boundary, decreasing to below

140mASL on the surrounding plains to the southwest. Steep water table gradients

south of the mine site boundary relate to topography and changes in rock types across

geological boundaries. Modelled water table elevations agree within approximately 10m

of observed elevations in the bores, which is a robust result given the paucity of field

measurements.

The model was developed specifically to explore groundwater conditions at regional and intermediate scales. Its “cell size” is too coarse to shed any useful detail on local-scale groundwater conditions in the vicinity of the AWC Open Cut.

5.5 ADOPTED STUDY AREA FOR THE GIA

The local geological map of the Mine Site and environs (Figure 4) encompasses the relatively

elevated topography of the Mine Site and extends outwards in all directions to include the

surrounding plains. This range of geological and topographic features encompasses all

possible groundwater issues in relation to the proposed rehabilitation and reprocessing

operation, and is therefore the defined study area.

Figure 4 is a compilation from various sources, and includes:

bedrock geology;

superficial Quaternary alluvial deposits;

tailings storage facilities;

topography;

surface water catchments (numbered 1 – 6);

the AWC, White Crystal and Stackpool Open Cuts;

the Mine Site boundary;

approximate locations of bore holes and excavator test pits dating from 1997; and

the locations of five cross sections used to generate five conceptual hydrogeological

models across the study area (refer Figure 4).

5.6 GROUNDWATER QUALITY

5.6.1 1995 Groundwater sampling event

Analyses of seven groundwater and surface/shallow seepage water samples collected during

the 1995 geotechnical drilling program are summarised in Table 2.

A distinct chemical difference existed between the two water types:

the groundwater in the three shallow bores exhibited near-neutral pH and salinity in the

1,000 – 3,000mg/L range (average 1,800mg/L), and is predominantly of the sodium

chloride – calcium/magnesium bicarbonate type with mostly non-detectable trace

metals.


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surface and shallow seepage waters from tailings in Spring Valley and Mill Valley were

noticeably acidic (pH in the 2.6 – 3.1 range), of variable but generally higher salinity

(range 1,500 – 9,000mg/L; average 4,500mg/L), and were of variable major-ion

chemistry with elevated sulphate and trace metals.

Table 2: Surface and groundwater analyses, November 1995

All results in mg/L

pH TDS Na Ca K Mg Cl F NO3 SO4 HCO3 PO4

BH3 7.4 1060 380 13 12 8.5 380 2.4 <0.1 75 330 <0.1

BH5 7.4 3240 760 110 29 120 240 1.8 <0.1 1740 440 0.1

BH9 7.1 1290 420 18 12 26 550 1.7 <0.1 180 120 <0.1

Fresh Water Dam 3.1 8830 2910 500 220 570 970 3.2 <0.1 5290 <1 <0.1

Mill Valley Dam 2.6 4170 150 125 1 190 140 1.5 1.7 2930 <1 1.2

Spring Valley #2 3.1 1470 85 40 <0.1 29 16 3..3 1.3 1055 <1 0.15

Spring Valley #3 2.8 3640 280 175 93 220 240 6.4 <0.1 2323 <1 <0.1

All results in mg/L

NH3-N CN

Phenol Al Cu Pb Zn Cd Cr Fe Mn As Hg

BH3 <0.1 ND ND <0.1 <0.01 <0.01 <0.01 <0.01 <0.01 0.03 0.04 <0.01 <0.00

1

BH5 0.2 ND ND <0.1 <0.01 <0.01 <0.01 <0.01 <0.01 0.01 0.03 <0.01 <0.00

1

BH9 <0.1 ND ND 0.4 0.02 <0.01 <0.01 <0.01 <0.01 0.01 0.21 <0.01 <0.00

1

Fresh Water Dam 21 ND ND 33 1.6 0.04 260 0.37 0.02 27 110 <0.01

<0.001

Mill Valley Dam 1 ND ND 76 34 0.03 270 1.4 0.04 295 31 0.62 <0.00

1

Spring Valley #2 <0.1 ND ND 95 60 0.02 115 0.92 <0.01 7.4 7.8 0.02 <0.00

1

Spring Valley #3 10 ND ND 0.4 2.1 0.03 105 0.12 0.01 125 27 <0.01 <0.00

1

Notes

Compiled from Amaral (1997) and Appendix G of Lavis (2011)

Borehole (BH) numbers correspond to those in Figure 4 and Table 5.

The Fresh Water Dam is located at the lower end of the Spring Valley Catchment

The Mill Valley Dam is located at the lower end of the Mill Valley Catchment

Spring Valley #2 and #3 are located on the tailings surface and at the toe discharge respectively, upgradient from the Fresh Water Dam

5.6.2 Groundwater sampling event in 2011

Lavis (2011) resampled surface and groundwater from the catchments of the Spring Valley

and No. 1 Tailings Dams, and elsewhere on the Mine Site. Figure 9 and Figure 10 are two of

Lavis’ chemical variation diagrams.

Collectively, the water quality results in Table 2 and Figure 9 and Figure 10 are of limited

comparative value since they involve sampling events sixteen years apart.


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Figure 9: Dissolved constituents in groundwater in the Main Pit (AWC Open Cut), and surface water from the northeast and northern evaporation ponds. Locations of samples are otherwise unspecified.

*Reproduced without amendment from Lavis (2011)


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Figure 10: Dissolved constituents in surface water in the Mill Valley Catchment. Dark blue = Reclaim wall; orange = Borehole BH5; aqua = Borehole BH9. *Reproduced without amendment from Lavis (2011)

In summary:

The Northern evaporation ponds appear to have a different chemical signature, which may indicate a lack of connectivity with the AWC Open Cut as inferred by the flow directions of the regional numerical model.

The North Eastern ponds are influenced by runoff from waste rock emplacements upslope.


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Groundwater down gradient of the Mill Valley Catchment appears to be influenced by seepage from Mill Reclaim Dam.

5.6.3 Groundwater sampling event in 2016

RWC conducted limited resampling of the 1995 shallow geotechnical bores that were able to be located, and of the water in the AWC Open Cut, in November 2016. Results5 are summarised in the two tables provided below.

Table 3 summarises field parameter recorded for groundwater in drill holes BH1 and BH9 (BH10 was dry) and the AWC Open Cut. Drill hole BH1 is located downslope from the Spring Valley Tailings Dam, and drill hole BH9 is downstream of the Northern Evaporation Ponds.

The groundwaters are of neutral to slightly acid pH (similar to the 1995 results), and the water

in the AWC Open Cut is acidic (pH = 3.1). BH9 returned a field salinity of about 18,500mg/L,

fifteen times higher than the salinity recorded in 1995 (Table 5). The salinity of approximately

4,000mg/L for the Open Cut is consistent with that recorded by Lavis (2011) in Figure 9.

The laboratory analyses in Table 4 generally confirm the field-measured pH and salinities of the samples. The two groundwaters differ considerably in their character: that from BH1 is sodium sulphate water, whereas that from BH9 is dominantly a sodium chloride water. Both show relatively low trace metals (except for manganese in BH1). The dominant major ions in the AWC Open Cut are sodium, magnesium, sulphate and chloride, with relatively elevated dissolved zinc (130mg/L).

Table 3: Recent water table depths and field parameters from three 1995 geotechnical drill holes, and the AWC

Open Cut

WGS84

Easting Northing Elevation (mASL;

GPS)

Depth (m) to water table

Depth (m) to base bore

Temp (0C)

DO (ppm)

EC

(µS/cm) pH

ORP (mV)

Notes

BH1 485739 6200510 272m 0.12m 6.7 17.4 5.7 3950 7.1 -72 Water approx. 0.10m above ground level. Well purged dry after 20L removed. Allowed to recover over 30 mins and then sampled.

BH9 486926 6202497 250m 4.64 7.9 19.8 3.74 18490 5.9 13 Well purged dry after 10L removed. Allowed to recover over 2 hrs and then sampled.

BH10 486798 6201490 265m Dry 14.5 - - - - - Well dry.

AWC Open Cut

- - 20.6 5.14 3930 3.1 493 Sampled at bottom of ramp. Water level was approx. 1m below top of tongue in centre of pit.

Notes Data provided by RWC, December 2016

DO = Dissolved Oxygen EC = Electrical Conductivity ORP = Oxidation Reduction Potential

5Emailed to Pitt & Sherry December 2016


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Table 4: Analysis of groundwaters and water from the AWC Open Cut, November 2016

Sample Units LOR BH1 BH9 AWC Open Cut

Date sampled 8/Nov/16 8/Nov/16 8/Nov/16

pH pH Units 7.2 6.5 3.1

Electrical Conductivity µS/cm 1 7,100 26,000 4,500

Total Dissolved Solids (grav)

mg/L 5 6,100 21,000 4,200

Calcium - Dissolved mg/L 0.5 250 2.6 150

Potassium - Dissolved mg/L 0.5 72 90 14

Sodium - Dissolved mg/L 0.5 1,500 8,100 500

Magnesium - Dissolved mg/L 0.5 420 890 250

Hydroxide Alkalinity (OH-) as CaCO3 mg/L 5 <5 <5 <5

Bicarbonate Alkalinity as CaCO3 mg/L 5 330 89 <5

Carbonate Alkalinity as CaCO3 mg/L 5 <5 <5 <5

Total Alkalinity as CaCO3 mg/L 5 330 89 <5

Sulphate, SO4 mg/L 1 3,500 2,400 1,800

Chloride, Cl mg/L 1 490 8,200 500

Nitrate as N in water mg/L 0.005 0.37 12 0.5

Aluminium-Dissolved µg/L 10 30 <10 29,000

Arsenic-Dissolved µg/L 1 100 1 6

Barium-Dissolved µg/L 1 14 19 10

Cadmium-Dissolved µg/L 0.1 2.3 0.3 1,600

Chromium-Dissolved µg/L 1 <1 <1 3

Copper-Dissolved µg/L 1 11 2 17,000

Iron-Dissolved µg/L 10 <10 <10 12,000

Mercury-Dissolved µg/L 0.05 <0.05 <0.05 <0.05

Manganese-Dissolved µg/L 5 5,800 43 23,000

Molybdenum-Dissolved µg/L 1 160 1 <1

Nickel-Dissolved µg/L 1 33 9 540

Lead-Dissolved µg/L 1 <1 7 79

Selenium-Dissolved µg/L 1 <1 1 7

Zinc-Dissolved µg/L 1 1,300 82 130,000

Silicon*- Dissolved mg/L 0.2 26 11 22

Notes

LOR = Limit of Reporting

Samples collected by R. W. Corkery Pty Ltd

Participating laboratory: NATA-accredited Envirolab Services, Chatswood, 2067

Laboratory report 157182 dated 21 November 2016

5.7 HISTORIC SITE OBSERVATIONS

5.7.1 Anecdotal groundwater observations

Several reviewed documents [Iliff (1996), Amaral, 1997), Mineral Resources NSW (1998), Perram & Partners (1998), Kolback (1999), EES (2003), Lavis (2011)] include or repeat anecdotal evidence of groundwater conditions at the Mine Site during large-scale open cut mining (1965 – 1986), and subsequently during geotechnical investigations for possible tailings reprocessing in the late 1990s.


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Observations of relevance to the present report are:

During open cut and underground mining, no major aquifers were encountered.

Groundwater was never encountered in production drilling.

Water pumped from underground averaged less than 2L/s, ranging from 50 – 70MLpa.

Areas exposed by mining remained dry for the life of the mine.

Blasting of wall rocks had no observable effect on water inflow into the open cuts.

5.7.2 Geotechnical investigations for site rehabilitation in 1995 and 1997

In November 1995, nine shallow power augured and diamond drilled holes (BH1 – BH9) were

installed across the mine site. Standard Penetration Testing (SPT) was done during drilling,

and soil and water samples submitted for laboratory Atterberg Limits testing and chemical

analyses respectively. The bores were screened, and falling head permeability testing done.

Figure 4 shows the bore locations (including two former mine site bores), and Table 5 summarises bore hole logs and permeability results. The bores, all of them downgradient of water storage or collection dams, are scattered over the study area and provide useful indications of near-surface geology and permeability.

Materials tested included unconsolidated sand/silt/clay/gravel mixtures (presumably near-

surface soils and/or weathered bedrock) and bedrock including granite, siltstone and

sandstone – all within the surface 10m or so.

Permeability in 11 bores ranged from about 5 x 10-10m/s to 4 x 10-9m/s (4 x 10-5 to

3 x 10-4m/day). This is a relatively small range, which increases confidence in applying similar

permeability values across the area.

The geometric mean permeability of the results is 1 x 10-09m/s (1 x 10-4m/day).

Table 6 shows that the measured permeabilities for the ‘Material tested’ column in Table 5 are within the expected range for those materials.


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Table 5: Summary of 1995 geotechnical drilling

Permeability

Bore hole

Depth (m)

Collar RL (m;

approx.)

Depth (m) to water

(m/s) (m/day) Tested interval (m)

Material tested Comment

BH1 8.0 270+/-2 5.1 5 x 10-10

4 x 10-05

5.1 – 8.0 EW HW granite Affected by

Tailings Dam

BH2 9.02 269+/-2 0.3 2 x 10-09

2 x 10-04

1.4 – 5.3 VD silty sand/gravel (N.50)

Affected by Tailings Dam

BH3 8.45 255-256 5.6 1 x 10-09

1 x 10-04

5.5 – 8.4

VSt to H clay/sand/gravel (N26 – 33)

Affected by water supply dam

BH4 6.1 259-260 "Below 5.3m…"

3 x 10-09

2 x 10-04

0 – 6.1

0-3m clay/sand/silt (N18->50); 3-6.1 siltstone, sandstone; subvertical joints

Affected by Reclaim Dam; may not be stabilised

BH5 7.3 258-259 2.9 2 x 10-09

2 x 10-04

4.8 – 7.3

0-7m clay/sand/silt (St-VSt; N13-23); 7-7.3 siltstone, sandstone

Affected by Reclaim Dam; may not be stabilised

BH6 >10 260-262 "Dry" 2 x 10-09

1 x 10-04

0 – 10.0 soil and EW rock

BH7 >10 258-260 "Dry" 2 x 10-09

1 x 10-04


BH8 >10 261.5-263.5 "Dry" 1 x 10-09

1 x 10-04


BH9 8.0 246 5.3 2 x 10-09

1 x 10-04

0 – 8

Hard clay/sand/silt/gravel (N>30)

Affected by evaporation ponds

P585 17.1 248

4 x 10-09

3 x 10-04

"Below RL

255"

Affected by White Crystal Pit

P591 17.4 249

5 x 10-10

4 x 10-05

"Below RL

248"

Affected by White Crystal Pit

Geometric mean 1 x 10-09

1 x 10-04

Notes

From Tables 2, 3 and 4, and borehole logs, of Amaral (1997) Blank cell indicates no data reported Elevations for bores 1 – 9 estimated from contour map P585 and P591 are mine drill holes Permeability tests are described as "Variable head permeability tests" – i.e. falling head tests

Reported permeabilities are rounded to 1 decimal place HW = Highly Weathered; EW = Extremely Weathered D = Dense; H = Hard; VSt = Very Stiff; VD = Very Dense N>50 means more than 50 blows/0.3m from Standard Penetration Test (SPT)


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Table 6: Typical permeability ranges for unconsolidated materials. Red type indicates materials like those described in Table 2 for the Mine Site

Twenty-eight excavator test pits were dug in the program; 17 in 1995 and 11 in 1997. Figure 6 shows the approximate locations of 16 pits between the Spring Valley Tailings and Catch Dams. Table 7 summarises the logs of 11 of the 16 pits, dug in 1997 with a 28t excavator to depths of up to 8m. Details of the 1995 pits have not been located.

Minor seepage was reported from two pits. The rest remained dry 36 hours after digging.

Materials encountered were sandy or clayey silt soil/tailings, weathered granite and

metamorphosed sedimentary rocks.

These results suggest a 1997 water table depth of at least 8m except for local, small-scale

perched conditions, between the two dams.


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Table 7: Summary of 1997 excavator test pitting (Source: Amaral 1997)

Test pit Depth

(m) Collar RL (m;

approx.) Groundwater Summary log

18 5.8 266-267 Pit still dry 36hrs after digging

0-0.5m sandy silt; 0.3-5.8m Granite (EW-HW-MW);

19 7.9 266-267 Minor seepage (perched) at 2m, but

slowing

0-0.6m sandy silt; 0.6-7.9m Granite (EW)

20 7.8 268-269 100L +/- infiltrated overnight

0-0.5m sandy silt; 0.5-7.8m Granite:(EW-HW-EW)

21 7.5 269.5-270.5 Pit still dry 35hrs after digging

0-0.8m sandy silt; 0.8-7.5m Granite (EW)


0-0.8m sandy silt; 0.8-6.8m Granite (EW-HW)


0-1.1m sandy silt; 1.1-2m Granite (HW-MW); refusal


0-0.5m sandy silt; 0.5-7.1m metamorphosed sediments; close-jointed (<0.2m); EW-HW)


0-5m clayey silt with sand, gravel; 5-7.6m metamorphosed sediments?; (EW-HW); granitic texture

26 6.3 268-270 Pit remained dry for 1.5hrs during digging

0-0.8m clayey silt; 0.8-6.3m Granite; (EW-HW-MW)


0-2.5m silty sand with clay, gravel; 2.5-6.4m Metamorphosed sediments (EW)


0-6m clayey silt with sand, gravel; grading to metamorhposed sediments below 4m (EW)

Notes See Figure 6 for approx. test pit locations between the Spring Valley Tailings Dam and Catch

Dam

HW = Highly Weathered; EW = Extremely Weathered

Test pits dug October 1997; Locations shown on site sketch (no grid coordinates)

Equipment was 28t 325B Cat Excavator; 1.2m GP bucket (5 teeth) and 0.9m single tyne ripper


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5.8 GROUNDWATER LEVELS

5.8.1 Water table depths at the Mine Site

Limited data is available on water table depths at the Mine Site, except for the measurements in several 1995 drill holes (Table 5), and readings collected by RWC from three original bores and the AWC Open Cut in November/December 2016 during visits to the site.

The recent data are presented in Table 4, which shows the water table at the surface in drill hole BH1 below the Spring Valley Tailings Dam and 4.6m below ground in drill hole BH9 downgradient from the Northern Evaporation Ponds (Figure 4). Drill hole BH10 was dry to 14.5m.

5.8.2 Water level in the AWC Open Cut

The water level in the AWC Open Cut was reported to be slowly rising after mining stopped in 1986.

Inspection of Google Earth satellite imagery of the AWC Open Cut for early 2003 and late 2015 indicates that the water level in the excavation has remained essentially constant (within a few metres) over that period.

The current water level reported by RWC during the site inspection in November 2016 is 194mAHD, approximately 80m below the top of the excavation.

The water is groundwater (mixed with incident rain and surface runoff) which enters from the sides and base of the excavation. The rate of groundwater entry has slowly decreased over time as the water level rose and reduced the head difference between it and the surrounding water table.

Due to historic disturbance as a result of mining activity, approximately 20% of rainfall in the AWL contributing catchment reports as runoff to the pit in below average rainfall years (460mm/yr). During above average rainfall, due to saturated catchment conditions, approximately 30% of rainfall reports as runoff with the Stackpool Open Cut and its contributing catchment also becoming hydraulically connected to the AWC and provides recharge to the pit.

In addition, evaporation rates from the Pit lake are influenced by the exposed area of the water surface which is in turn influenced by the volumes in storage (as a consequence of pit geometry). Therefore, groundwater inflows to the pit are in the order of 20ML/yr (refer to Table 8).

The preceding observations indicate that the Open Cut is a groundwater discharge zone on a local scale. Groundwater is flowing towards the AUL Open Cut from all horizontal directions, and from beneath.

5.8.3 Analytical estimates of groundwater inflow to the AWC Open Cut

Figure 11 shows a conceptual half-section through the discharge zone of the unconfined, fractured-rock aquifer at the AWC Open Cut. It illustrates:

rain infiltration to a water table,

groundwater flow to the excavation via a seepage face, and

horizontally and vertically from beneath.


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Steady-state analytical equations (Marinelli and Niccoli, 2000) have been applied to the model

to estimate groundwater flow to the excavation. Of the inputs to the model, annual evaporation

and rainfall is also known, with the proportion of rain infiltrating the water table being estimated

from previous experience in fractured rock regimes. Water depth in the Open Cut is known, as

is the overall depth of the excavation (i.e. ho and hp in Figure 11)

The shallow water table depth, and horizontal and vertical permeabilities (Kh and Kv in Figure 11), are estimated from Table 7.

Reasonable inputs generate a reasonable output (about 20ML/year; Table 8) for the volume of groundwater entering the Open Cut from its sides and bottom – at the higher end of the 25 – in agreement with that estimated in the evaporation/rainfall approach in Section 5.8.2.

Figure 11: Conceptual half-cross section and simple analytical model through the Ardlethan/Wild Cherry Open Cut

*Simplifying assumptions are: isotropic and homogeneous subsurface conditions, steady-state, unconfined, horizontal radial flow; uniformly distributed recharge at the water table, the pit walls approximate a right circular cylinder, the pre-mining water table is horizontal, there is no groundwater flow between Zones 1 and 2, and there is horizontal flow in Zone 1.


35

Table 8: Estimates of annual groundwater flow from the sides and bottom of the AWC Open Cut

Q1 + Q2

ho hp d rp ro ho

(calc) Q1 Q2 Qt Qt

m m m m m m m3/s m3/s m3/s ML/year

144 130 74 100 350 144 0.0004 0.00025 0.00067 21

Evaporation from pit

Annual rainfall

infiltrated

Pit long axis at water level (m) 300 Estimated

Rain (mm/year) 460

Historical data

Pit short axis at water level (m) 210 Estimated

% infiltration 1.5 Estimated

Area of pit at water level (m2) 48 900 Calculated

Infiltrated rain

(mm/year) 6.9 Calculated

Evaporation (m/year) 1.35 Historical data

Infiltrated rain (m/year) 0.0069 Calculated

Evaporation from pit (ML/year) 66 Calculated

Infiltrated rain (m/s) 2 x 2E

-10

Calculated; W

Horizontal and vertical permeabilities

Adopted Kh1 (m/s) 1 x 4E

-08 Est from Table 5 Interim calculations

Adopted Kh2 (m/s) 1 x 4E

-08 Est from Table 5 hp^2 W/Kh1 ro/rp ro^2ln(ro/rp)

(ro^2 - rp^2)/2

Adopted Kv2 (m/s) 1 x 4E

-09 Est from Table 5

m (= (Kh2/Kv2)^0.5) 3.2 Calculated 12100 0.079274 3 197750 40000

*Symbols are as for Figure 11. The estimated total inflow (Qt) is about 0.00000067L/s (about 20ML/year). The radius of influence extends to approximately 350m in all directions.

5.9 CONCEPTUAL MODEL

The following figures present five conceptual hydrogeological cross-sections through the Mine Site. Refer to Figure 4 for the locations of the sections. The interpretations are consistent with groundwater principles and currently known hydrogeological site observations. In the following discussion, refer also to the numeric groundwater model in Appendix 2.


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Figure 12: Conceptual hydrogeological model of the Mine Site: Section A – B

SPECIALIST CONSULTANT STUDIES EOE (NO.75) PTY LIMITED

Part 1 – Groundwater Impact Assessment Ardlethan Tin Mine Report No. 754/09

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Figure 13: Conceptual hydrogeological model of the Mine Site: Section C – D


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Figure 14: Conceptual hydrogeological model of the Mine Site: Section E – F

SPECIALIST CONSULTANT STUDIES EOE (NO.75) PTY LIMITED

Part 1 – Groundwater Impact Assessment Ardlethan Tin Mine Report No. 754/09

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Figure 15: Conceptual hydrogeological model of the Mine Site: Section G – H


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Figure 16: Conceptual hydrogeological model of the Mine Site: Section I – J


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The main features from the hydrogeological cross sections are:

Elevated, undulating and locally disturbed topography (most of the study area and the

Mine Site) some 50 – 100m higher than and surrounded by a gently undulating to flat

plain.

Steeply-dipping, folded and fractured Ordovician sedimentary rocks intruded by Silurian

granites, with local development of unconsolidated Quaternary/Tertiary alluvial leads on

the southeast, east and northeast sides of the topographic high.

A single unconfined, fractured rock aquifer in the Silurian-Ordovician bedrock.

Alluvial aquifers in each of the Quaternary/Tertiary leads.

Regional-scale groundwater flow beneath the topographic high from the northeast to the southwest.

Intermediate-scale groundwater flow radiating in all directions from the topographic high, but at very low rates of movement in bedrock due to very low fracture permeability.

Local-scale groundwater conditions, with variable flow directions, except in the vicinity of the AWC Open Cut where groundwater enters the excavation from all horizontal directions from a distance of probably several hundred metres horizontally;

Recharge conditions (and groundwater independent ecosystems; GIEs) over most of

the study area.

The water surface of the AWC Open Cut is a groundwater discharge area; ordinarily,

this would constitute GDE conditions, except that there are no known ecosystems to

support within the ponded water body. Other discharge areas are very localised.

6. CLASSIFICATION UNDER AIP (DPI – WATER, 2012)

6.1 GROUNDWATER SOURCE

Based on the data available (refer Section 5), groundwater within the Mine Site area is in the

“Less Productive Groundwater Source” and “Fractured Rock” categories.

6.2 LEVEL 1 MINIMAL IMPACT CONSIDERATIONS

6.2.1 Water Table

Whilst placing tailings in the AWC Open Cut will likely raise the water table, this variation will generally be restricted to the radius of influence, which is approximately 350 metres.

The nearest high priority groundwater dependent ecosystem (GDE) listed in the WSP for the Murray-Darling Basin Fractured Rock Groundwater Sources (Lachlan Fold Belt) is located more than 40km from the Mine Site. Other discharge areas are very localised and are not recorded or in on the WSP.


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The WSP also contains the following statement with regards to high priority culturally significant sites:

Culturally significant sites will be identified as a part of the assessment undertaken by the NSW Office of Water during the processing of an application for the granting or amending of a water supply work approval.

As part of the current EIS, the Applicant commissioned a due diligence aboriginal heritage assessment which identified a registered site 49-3-0001 at (AMG 55) 485140E, 6200260N. This site is identified as a water hole/well in the granite hills approximately 1,900m west of the Ardwest/Wild Cherry Open Cut. The area was inspected as part of the due diligence assessment but no site was observed. Refer Appendix 3 for the results of the registered site database search.

Given that no high priority GDE’s or high priority sites of cultural significance exist within 40m of the potential area for groundwater level impact, the Proposal is considered to fall within Level 1 minimal impacts for water levels.

6.2.2 Water pressure

A review of available regional bore data is provided in Section 5.3. Drilling was not generally successful with very low yield and most bores were abandoned. No active production bores were identified within 1,000m of the Mine Site.

Given that the potential area of groundwater impact is restricted and in the absence of any recorded beneficial use, the Proposal is considered to fall within acceptable Level 1 minimal impacts for water pressure.

6.2.3 Water Quality

Based on the available data the AWC Open Cut is a groundwater discharge zone. Groundwater enters the Open Cut from all sides. The Proposal will maintain local-scale discharge conditions. The proposal is therefore considered to fall within acceptable Level 1 impacts for water quality.

7. IMPACTS ASSESSMENT FOR SEARS

7.1 PRELIMINARY WATER BALANCE FOR THE AWC OPEN CUT CATCHMENT

A preliminary annual site water balance for the AWC Open Cut catchment is presented in Appendix 4 of the EIS for the Proposal.

7.2 CHANGES IN WATER TABLE IN THE AWC OPEN CUT

Water used for reprocessing the tailings at the Mine Site will be taken from the AWC Open Cut, tailings will be added, and except for very minor losses of fugitive water, and tin concentrate, the tailings and water will be returned to the excavation.

This is essentially a closed circuit.


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In the AWC Open Cut, the added tailings will raise the water table6 by an amount equal to their volume in the loose state, less their effective porosity (say, 25%)7. The raised water level will result in a decreasing rate of groundwater discharge into the excavation8. Evaporation will continue to be unaffected by operations.

Table 9 presents estimates of annual water levels in the Open Cut for 13 years of reprocessing, assuming reasonable values of tailings volume and porosity, volume of the excavation, and the changing area of the rising lake within it.

If the AWC Open Cut remains a groundwater discharge zone for the life of the reprocessing operations, then operations will have no effect on groundwater flow conditions elsewhere in the study area.

To remain a discharge zone, the level of the unaffected water table outside the AWC Open Cut must remain higher than the water level in it (i.e. a head difference must be maintained). Table 9 presents estimates of this head difference for each year of operation, but uncertainties up to perhaps 10 – 20m or so remain in relation to water levels and head differences.

As indicated previously in Table 8 the radius of influence is likely to be in the order of 350m and any groundwater impacts are therefore also likely to be restricted to this area.

6 Because the groundwater system is unconfined, there is no potentiometric (piezometric) water level.

7For example, 250,000tpa of tailings (a nominal year’s processing in the early stages) at a dry density of 1.8t/m3 is 140,000m3

with a porosity of (say) 25%. This is a solid volume of about 100,000m3. If the surface area of the water in the Open Cut is 50,000m2, its water level is raised by about 2m. The volume of water required to first saturate the tailings for reprocessing is taken from the Open Cut and returned, so does not enter these calculations. 8 Tailings placed in the Open Cut will also tend to physically move into any open fractures in bedrock in the base and walls of the

excavation. This is unlikely to have a significant clogging effect (ie a reduction in groundwater flow into the Cut) since the tailings themselves are likely to be of the same order of permeability as, or more permeable than, the bulk rock permeability of the bedrock. Tailings are typically described as having permeabilities (depending on grain size and distribution, plasticity, etc) in the 10-9 to 10-4m/s (Sarsby, 2000, Table 15.7; SRK Consulting 2010).


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Table 9: AWC Open Cut estimated freeboard and groundwater flow conditions during tailings reprocessing

AWC Open Cut volume calcs (assume cone fulstrum)

Top pit radius (r2; m) 175 Estimated

Bottom pit radius (r1; m) 50 Estimated

Height top to bottom (h; m) 160 Estimated

Volume (m3) 7.0E+06

Dry tailing density (t/m3) 1.700 Assumed

Lake short axis (m) 215 Estimated

Lake long axis (m) 300 Estimated

Surface area of lake in Year 1 (m2) 47405

Top of Open Cut (mASL) 260 Estimated from contours

Lake water level (mASL) at start of Year 1 190 Measured November 2016 as 197mAHD

Annual evaporation from lake surface (m) 1.7

Assume AWC Open Cut approximates a cone fulstrum (above)

Elevation (mASL) of unaffected water table in vicinity of Open Cut 260 Uncertain +/-10m or so. Should be monitored during operations

AWC Open Cut estimated freeboard and groundwater flow conditions during tailings reprocessing

Year 1 Year 2 Year 3 Year 4 Year 5 Year 6 Year 7 Year 8 Year 9 Year 10 Year 11 Year 12 Year 13

Tailings reprocessed (Mt) 0.25 0.25 0.25 0.5 0.5 0.5 1.0 1.0 1.0 1.0 1.5 1.5 1.5

Cumulative tailings reprocessed (Mt) 0.25 0.5 0.75 1.25 1.75 2.25 3.25 4.25 5.25 6.25 7.75 9.25 10.75

Volume of tailings reprocessed (m3) 150,000 147,000 147,000 294,000 294,000 294,000 588,000 588,000 588,000 588,000 882,000 882,000 882,000

Cumulative volume of tailings reprocessed (m3) 150,000 290,000 440,000 740,000 1,030,000 1,320,000 1,910,000 2,500,000 3,090,000 3,680,000 4,560,000 5,440,000 6,320,000

Surface area of lake (m2) 47,405 49,676 50,406 54,973 59,154 61,078 65,631 73,663 76,335 78,917 87,828 97,545 103,210

Water level (mASL) at end of year (less evap) 191 193 194 198 201 204 211 218 224 229 238 245 252

Freeboard (m) remaining in excavation 69 67 66 62 59 56 49 42 36 31 22 15 8

Head difference (m) driving water inflow to Open Cut 69 67 66 62 59 56 49 42 36 31 22 15 8

Groundwater entering Open Cut based on above input assumptions? Yes Yes Yes Yes Yes Yes Yes Very

probably Very

probably Probably Probably Uncertain Uncertain

COMMENT To eliminate potential groundwater effects (of reprocessing) outside the radius of influence of the Open Cut, it is important that the excavation remains a discharge zone for the life of operations. This means that groundwater must flow to it for the life of operations. This means that there must remain a head difference between the unaffected water table elsewhere over the Mine Site, and the water level in the Open Cut (with the latter being at a lower elevation). This can be managed by (a) knowing the current water level in the Open Cut, (b) monitoring the unaffected water table levels, and (c) diverting, if necessary, process water and/or tailings elsewhere.




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7.3 GROUNDWATER USE-INFLOWS/OUTFLOWS

Provided reprocessing operations are managed so as not to reverse water table gradients in the vicinity of the AWL Open Cut, there will be no change to groundwater flow directions, and no groundwater effects at all outside the radius of influence of the cone of depression surrounding the excavation. Accordingly, no measures are necessary to protect groundwater conditions outside the radius of influence before, during and after reprocessing operations.

Provided the extraction of tailings for reprocessing is managed to not alter the current surface water catchments of the existing tailings dams, there will be no changes to local surface flow conditions in the vicinity of the dams.

7.4 CHANGES IN GROUNDWATER QUALITY IN THE AWC OPEN CUT

During the November 2016 site visit, RWC collected two tailings grab samples for trace metal analysis and leachate testing. The latter was intended to simulate possible leaching conditions which might act on reprocessed tailings placed in the AWC Open Cut, and which in turn might affect the chemistry of the water within it. Table 10 shows that arsenic, copper, manganese, lead and zinc are the dominant trace metals in the two tailings samples.

Table 11 summarises the results of two leaching techniques9 (at different pH’s) on the same tailings samples. The TCLP technique used test water collected from the AWC Open Cut. This water had significantly higher concentration of metals than that which was leached from the tailings and this effectively “blinded” the analyses. To provide a clearer picture the ASLP test (using deionised water) was subsequently done. It is likely that the process water will need to be treated to raise its pH so the ASLP results are probably more indicative of post-operations pit water than the current low pH pit water.

Reprocessing mixes tailings with water from the AWC Open Cut. Limited data is available on the AWC Open Cut, and although the tailings samples were collected from a composited pile that is considered to be the most representative of tailings on the Mine Site, uncertainty regarding the leachability of the tailings in the AWC Open Cut remains.

On the basis that operations will retain water in the Open Cut, and that on balance no net water leaves the excavation other than via evaporation, it is unlikely that chemical changes to the contained water will be environmentally significant.

9Leachable metals and other potential contaminants in tailings (and other wastes) may be determined by the Australian Standard

Leaching Procedure (ASLP; AS4439.2 and AS4439.3), or alternatively, the Toxicity Characteristic Leaching Procedure (TCLP; USEPA). See, for example, DER (2015). Both are designed to obtain the likely quality of leachate after percolating water through a soil medium (in this case, tailings)



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Table 10: Trace metal analysis of tailings samples, November 2016

Units LOR Tailings 1 Tailings 2

Date sampled 8/Nov/16 8/Nov/16

Arsenic mg/kg 4 220 320

Barium mg/kg 1 4 6

Beryllium mg/kg 1 <1 <1

Boron mg/kg 3 <3 <3

Cadmium mg/kg 0.4 0.5 0.6

Chromium mg/kg 1 8 8

Cobalt mg/kg 1 1 1

Copper mg/kg 1 220 170

Mercury mg/kg 0.1 <0.1 <0.1

Molybdenum mg/kg 1 <1 <1

Manganese mg/kg 1 180 190

Nickel mg/kg 1 3 3

Lead mg/kg 1 150 240

Antimony mg/kg 7 <7 <7

Selenium mg/kg 2 <2 <2

Tin mg/kg 1 14 17

Zinc mg/kg 1 64 83

Notes





Table 11: Leachate testing of tailings samples, November 2016



Australian Standard Leaching Procedure (ASLP)

Antimony in ASLP µg/L 1 <1

Arsenic in ASLP µg/L 1 2

Boron in ASLP µg/L 5 <5

Barium in ASLP µg/L 1 1

Beryllium in ASLP µg/L 0.5 <0.5

Cadmium in ASLP µg/L 0.1 2.4

Chromium in ASLP µg/L 1 <1

Cobalt in ASLP µg/L 1 2

Copper in ASLP µg/L 1 390

Lead in ASLP µg/L 1 <1

Manganese in ASLP µg/L 5 51

Mercury in ASLP µg/L 0.05 <0.05

Molybdenum in ASLP µg/L 1 <1

Nickel in ASLP µg/L 1 2

Selenium in ASLP µg/L 1 <1

Tin in ASLP µg/L 5 <5

Zinc in ASLP µg/L 1 300

pH of Leaching fluid pH units 0.1 3.1 3.1

pH of final Leachate pH units 0.1 3.2 3.2


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Table 11: Leachate testing of tailings samples, November 2016 (Cont’d)



Toxicity Characteristic Leaching Procedure (TCLP)

Arsenic in TCLP mg/L 0.05 0.05 <0.05

Boron in TCLP mg/L 0.2 0.3 0.3

Barium in TCLP mg/L 0.01 <0.01 <0.01

Beryllium in TCLP mg/L 0.01 0.02 0.02

Cadmium in TCLP mg/L 0.01 1.6 1.6

Chromium in TCLP mg/L 0.01 <0.01 <0.01

Copper in TCLP mg/L 0.01 20 21

Cobalt in TCLP mg/L 0.02 0.7 0.7

Mercury in TCLP mg/L 0.0005 <0.0005 <0.0005

Manganese in TCLP mg/L 0.01 23 23

Molybdenum in TCLP mg/L 0.03 <0.03 <0.03

Nickel in TCLP mg/L 0.02 0.6 0.6

Lead in TCLP mg/L 0.03 <0.03 <0.03

Antimony in TCLP mg/L 0.15 <0.15 <0.15

Selenium in TCLP mg/L 0.12 <0.12 <0.12

Tin in TCLP mg/L 0.05 <0.05 <0.05

Zinc in TCLP mg/L 0.02 140 140

pH of final Leachate pH units 0.1 5

Notes





8. CONCLUSIONS

The main conclusions arising from this GIA are:

Based on the data available, groundwater within the Mine Site area is in the “Less Productive Groundwater Source” and “Fractured Rock” categories for AIP assessment.

Given the low, localised potential for groundwater level and quality impact, the absence of GDEs or culturally significant sites within 40m of the potential impact area, and the absence of beneficial use, impacts from the proposal are considered to be acceptable Level 1 impacts under AIP.

The AWC Open Cut is a groundwater discharge zone. Groundwater enters it from all sides.

Provided reprocessing operations are managed so as not to reverse water table gradients in the vicinity of the Open Cut, there will be no change to groundwater flow directions, and no groundwater effects at all outside the radius of influence of the cone of depression surrounding the excavation.

On the basis that operations will retain water in the Open Cut, and that on balance no net water leaves the excavation other than via evaporation, it is unlikely that chemical changes to the contained water will be environmentally significant.

Accordingly, no measures are necessary to protect groundwater conditions outside the radius of influence before, during and after reprocessing operations.



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As a general recommendation, groundwater water level and quality monitoring in at least three

monitoring bores in the vicinity of the AWC Open Cut should commence before tailings

reprocessing, and should continue through the life of the operation. Existing groundwater

bores should be restored or if this is not possible, additional monitoring bore installed. Bores

should be installed in accordance with the Minimum Construction Requirements for Water

Bores in Australia (National Uniform Drillers Licensing Committee, 2012). It is recommended

that groundwater quality and levels be monitored on a quarterly basis to enable quantification

of water quality and quantity and to assist with meeting regulatory requirements.

Water quality in the AWC Open Cut should also monitored on a similar basis.

9. REFERENCES

Corkery (2016). Ardlethan Tin Mine: Background Paper for Rehabilitation and Tailings Reprocessing Project. Report prepared by R W Corkery & Co Pty Ltd for EOE (No. 75) Pty Limited, July 2016. DER (2015). Background paper on the use of leaching tests for assessing the disposal and re-use of waste-derive materials. Department of Environment Regulation, Government of Western Australia, July 2015. DPE (2016). Secretary’s Environmental Assessment Requirements (SEARS) for the current Ardlethan Proposal. Tables A2-1 and A2-2, Department of Planning and Environment, 1 September 2016. DPI (2012). NSW Aquifer Interference Policy. NSW Department of Primary Industries, September 2012. DPI (2013). Assessing a proposal against the NSW Aquifer Interference Policy – step by step guide. Aquifer Interference Assessment Framework. NSW Department of Primary Industries, August 2013. EES (2003). Mine water characterisation and optimisation study, Ardlethan alluvial tin mine, Ardlethan, New South Wales. Report No 103136 from Environmental & Earth Sciences Pty Ltd to Telminex NL, December 2003. Fitts C. (2016). AnAqSim User Guide: Analytic Aquifer Simulator, 105 p., (available at http://www.fittsgeosolutions.com/AnAqSimUserGuide.pdf) Kolback Environmental Services Pty Ltd (1999). Ardlethan Solid Waste Landfill Project - extract from Commission of Enquiry Report. Iliff, G. D. (1996). Geology and Hydrogeology Of White Chrystal Pit Ardlethan Tin Mine New South Wales. Unpublished report by F. W. Lannen & Associates Pty Ltd for ERM Mitchell McCotter Pty Ltd, January 1996. [Appendix H in Perram & Partners (1998). Ardlethan Mine Rehabilitation Using Solid Waste Landfill: Environmental Impact Statement Volume 2 (Appendices)]. Lavis, R. (2011). The effects on Groundwater from the Ardlethan Tin Mine. Major Project Ground Water EMSC 6025. Unpublished report Marinelli, F. and Niccoli, W. L (2000). Simple Analytical Equations for Estimating Ground Water Inflow to a Mine Pit. GROUND WATER Vol 38, No. 2, March-April 2000, pages 311 – 314

http://www.fittsgeosolutions.com/AnAqSimUserGuide.pdf


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Mineral Resources NSW (1998). Environmental Performance Review Ardlethan Tin Mine. NSW Government Pineena Maps Basin 410 Murrumbidgee River Map 2. http://waterinfo.nsw.gov.au/pinneena/maps.shtml Paterson, R. H. (1990). Ardlethan Tin Deposits in Geology of the Mineral Deposits of Australian and Papua New Guinea (Ed. F. E. Hughes) pp1357 – 1364. (The Australasian Institute of Mining and Metallurgy, Melbourne) Perram & Partners (1998). Ardlethan Mine Rehabilitation Using Solid Waste Landfill: Environmental Impact Statement Volume 1, and Volume 2 (Appendices). Report for Kolbeck Environmental Services. Sarsby, R. (2000). Environmental Geotechnics. Thomas Telford Publishing, London. (Sophocleous (2004). Groundwater recharge, in Groundwater [Eds. Luis Silveria, Stefan Wohnlich and Eduardo J. Usunoff] in Encyclopedia of Life Support Systems (EOLSS), Developed under the Auspices of the UNESCO, Eolss Publishers, Oxford, UK [www.eolss.net] SRK Consulting (2010). Tailings Material Properties. Tailings and HLP Workshop, 28 April to 1 May 2010. www.infomine.com/library/publications/docs/SRKTailings2010e.pdf

http://waterinfo.nsw.gov.au/pinneena/maps.shtml

http://www.infomine.com/library/publications/docs/SRKTailings2010e.pdf



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Appendix

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Appendix 2 Regional – intermediate scale numeric groundwater modelling Compiled by hydrogeologist Mark Hocking



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Appendix 3 Aboriginal Heritage Due Diligence Assessment Locations of Cultural Significant Sites



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Documents

EOE (NO.75) PTY LIMITED - Coolamon Shire...2016/12/01 · EOE (NO.75) PTY LIMITED ABN: 95 006 829 787 Ardlethan Tin Mine Prepared by Pitt & Sherry Pty Ltd December 2016 Specialist