for the Dargues Reef Gold Project Modification 1 · Following public exhibition of the Environmental Assessment for the proposed Dargues Reef Gold ... consolidated set of responses

BIG ISLAND MINING PTY LTD ABN 12 112 787 470

Response to Government Agency and Public Submissions

for the

Dargues Reef Gold Project

Modification 1

Project Approval 10_0054

June 2012

Prepared in conjunction with:

R.W. CORKERY & CO. PTY. LIMITED

This page has intentionally been left blank

R. W. CORKERY & CO. PTY. LIMITED

BIG ISLAND MINING PTY LTD ABN 12 112 787 470

Response to Government Agency and Public Submissions

for the

Dargues Reef Gold Project

Modification 1

Project Approval 10_0054

Prepared for:

Big Island Mining Pty Ltd

ABN: 12 112 787 470

Level 5, 72 Kings Park Road

WEST PERTH WA 6005

Telephone: (08) 9485 0577 Facsimile: (08) 9485 0706 Email: [email protected]

Prepared by:

R.W. Corkery & Co. Pty. Limited

Geological & Environmental Consultants

ABN: 31 002 033 712

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


Orange Office: 62 Hill Street ORANGE NSW 2800


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

Telephone: (07) 3205 5400 Email: [email protected]

Ref No. 752/28

June 2012

BIG ISLAND MINING PTY LTD RESPONSE TO GOVERNMENT AGENCY AND PUBLIC SUBMISISONS

Dargues Reef Gold Project Report No. 752/28

ii


This Copyright is included for the protection of this document

COPYRIGHT

© R.W. Corkery & Co. Pty Limited 2012

and

© Big Island Mining Pty Ltd 2012

All intellectual property and copyright reserved.

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

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

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

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

RESPONSE TO GOVERNMENT AGENCY AND PUBLIC SUBMISISONS BIG ISLAND MINING PTY LTD

Report No. 752/28 Dargues Reef Gold Project

CONTENTS Page


iii

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

2. GOVERNMENT AGENCY SUBMISSIONS ..................................................................................... 1

2.1 INTRODUCTION ................................................................................................................... 1

2.2 ENVIRONMENT PROTECTION AUTHORITY ...................................................................... 1

2.3 DEPARTMENT OF PRIMARY INDUSTRIES ...................................................................... 11

2.3.1 NSW Office of Water ................................................................................................. 11

2.4 EUROBODALLA SHIRE COUNCIL ..................................................................................... 13

3. PUBLIC SUBMISSIONS ................................................................................................................ 23

3.1 INTRODUCTION ................................................................................................................. 23

3.2 ISSUE A – DARGUES REEF CONSULTATIVE COMMITTEE ........................................... 24

3.3 ISSUE B – ASSESSMENT OF XANTHATE USE AND RESIDUES ................................... 25

3.4 ISSUE C - GROUNDWATER QUALITY - METALS ............................................................ 26

3.5 ISSUE D – GROUNDWATER QUALITY – ALKALINITY .................................................... 27

3.6 ISSUE E – LONG TERM STABILITY OF PASTE FILL ....................................................... 29

3.7 ISSUE F – ASSESSMENT OF THE APPLICATION ........................................................... 30

3.8 ISSUE G – EUROBODALLA RESIDENTS AS STAKEHOLDERS ..................................... 30

3.9 ISSUE H – CONCLUDING COMMENTS ............................................................................ 31

4. ADDITIONAL COMMITMENTS ..................................................................................................... 35

5. REFERENCES ............................................................................................................................... 36

APPENDICES

Appendix 1 Dargues Reef Paste Fill Testwork and Design .................................................................A1-1

Appendix 2 Backfill Specialists Capability Statement ..........................................................................A2-1

Appendix 3 MSDS – Portland Cement .................................................................................................A3-1

TABLES

Table 1 Indicative Chemical Composition – Low Heat Cement .......................................................... 7

Table 2 Submissions and Issues Raised .......................................................................................... 24

Table 3 Additional Commitment for Inclusion in Statement of Commitments................................... 35



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1

1. I N T RO D U C TI ON

Following public exhibition of the Environmental Assessment for the proposed Dargues Reef

Gold Project Modification 1 to permit the use of Paste Fill (referred to hereafter as RWC,

2012), submissions were received by the Department of Planning and Infrastructure (DP&I)

from:

three government agencies; and

five individuals or non-government agencies.

All submissions received were forwarded by the DP&I to the Proponent, Big Island Mining Pty

Ltd, and R.W. Corkery & Co. Pty Limited (RWC) for the preparation of a response to the issues

raised. This document, presents a consolidated set of responses to each of the submissions

received and has been prepared by the Proponent in conjunction with RWC. This document

also presents in Section 4 additional commitments that the Proponent would be willing to

include in the Statement of Commitments included as Appendix 7 of the revised Project

approval, should it be granted.

2. G OV E R NM EN T AG E N C Y S U BM I SSI O N S

2.1 INTRODUCTION

Submissions were received from the following government agencies.

Environment Protection Authority (dated 7 June 2012).

NSW Department of Primary Industries (dated 12 June 2012).

Eurobodalla Shire Council (dated 30 May 2012).

In addition, the Department of Planning and Infrastructure advised that the following agencies

provided responses supporting the proposed modification or did not provide a submission.

Division of Resources and Energy.

Palerang Shire Council.

The following sub-sections present the submissions received from relevant government

agencies (in italics). A response to each issue raised is presented (in normal text).

2.2 ENVIRONMENT PROTECTION AUTHORITY

This sub-section provides a response to the submission by the Environment Protection

Authority (EPA). The response to each of the issues presented is provided under the same

heading and in the same general order as they appear in the submission.



2


Tailings and Paste Characteristics

Regarding the leaching potential of paste fill, the provided EA appears to include a

number of claims that are based on a level of speculation or a number of assumptions.

The EPA considers cement stablisation to be acceptable in principle, however, submit

that the proponent should be required to conduct suitable trials to optimise the mix

design and provide a trial report for comment before conducting full scale treatment.

Any resulting trial data would provide an evidentiary basis for the EPA, as the

regulatory authority, to amend the EPL as required.

Response:

The Proponent notes that physical testing and confirmation of the paste fill mixture was

completed during the Feasibility Study completed for the Project. The testing methodolgy and

results are contained in a report prepared by Mr Mathew Revell of Revell Resources entitled

Dargues Reef Paste Fill Testwork and Design (P147-R01). That report is, hereafter referred to

as Revell (2010) and is presented in Appendix 1.

In summary, Revell (2010) states that ‘paste fill offers a sound technical solution for backfill at

Dargues Reef’. The testwork completed to confirm the paste fill mixture is described in detail in

Revell (2010) and may be summarised as follows.

Particle size distribution testing was completed to determine the suitability of the

tailings to be used for paste fill (Section 3.2.3, Revell (2010)). Generally to

produce paste fill, the tailings must have nominally 15% to 20% of the particles

smaller than 20µm to prevent segregation of the paste within the paste reticulation

system. Revell (2010) confirms that the tailings have the required particle size

distribution and noted that ‘the Dargues Reef tailings has an almost perfect

[particle size distribution] for paste production’.

Mineralogical analysis was completed on a sample of tailings material with the

primary minerals identified being plagioclase feldspar, quartz and muscovite. It is

noted that feldspars are likely to contribute to moderate paste strength but that

muscovite may adversely impact on the strength characteristics of paste fill. As a

result, strength characteristics would need to be managed during paste filling

operations.

Rheology testing to determine the rate at which the paste would flow or move

once emplaced was undertaken. This involved creation of a conical pile of

uncured paste and measuring how much deformation occurred within a specified

timeframe. Suitable rheology characteristics ensure that the paste, once emplaced

flows into all sections of the stope to be backfilled without being overly fluidised.

Ideal paste composition would result in a slump of 220mm. Revell (2010)

determined that at a solids content of 69.5% and 3% to 6% binder addition this

slump rate could be achieved.




3

Unconfined Compressive Strength (UCS) tests were completed on various paste

mix designs (Section 3.4.1, Revell (2010)). The purpose of this test work is to

generate an understanding of the influence of binder addition, time and solids

content on the strength of the paste fill. The Results of these tests are contained in

Table 5 of Revell (2010) and indicate that with a slump of 220mm and binder

content of 6%, that a UCS of approximately 1000kpa can be achieved (Figure 7,

Revell (2010). Revell (2010) indicates that this is suitable for the proposed paste

filling operations.

Strength testing of the proposed paste fill mixture has been completed over 7, 28,

56, 112 and 260 days and that the strength of the paste fill continues to develop

over that time (Table 5 and Figure 8, Revell (2010)), with a suitable strength for

the majority of the proposed stopes being achieved after 28 days. In addition, the

curing characteristics of the paste fill are considered suitable for the operational

needs of the Project.

Based on the test work completed, the Proponent contends that the paste fill mixture presented

in Table 4 of RWC (2012) would meet the operational requirements of the Project and contends

that it is has been suitably optimised for the Project.

In light of the above, the Proponent contends that the physical characteristic of the paste have

been adequately tested for, at this stage of the Project. However, the Proponent also notes that

following commissioning of the processing plant and prior to commencement of paste filling

operations, that further testing would be required to determine the physical characteristics of the

paste under operational conditions and confirm the bench-top test results presented in Revell

(2010)

The development of a cement grout is a highly specialised engineering field. It is

recommended that the proponent be required to engage the service of a suitably

qualified expert in the area, with good field experience in underground applications, to

develop any trial and evaluation regime

Response:

The Proponent notes that Mr Mathew Revell, as Principal Backfill Consultant with Revell

Resources has a Bachelor of Engineering (Minerals Processing) and has worked in both

operational and design roles as a metallurgist and project manager since 1997, including

establishing and operating Revell Resources, a specialist paste fill consultancy, in 2005. As a

result, Mr Revell may be considered to be a suitably qualified expert in the field of paste fill. A

Capability Statement is presented as Appendix 2.

It is the Proponent’s intention that Mr Revell would continue to provide consultancy services to

the Project during the commissioning and operational phases of the Project.



4


Depending on the gold extraction process, the chemical residues present in the

tailings/residue can retard or otherwise accelerate the setting of cement. The EPA notes

that the hydrobiology consultant completed leachate testing (TCLP) on a tailings

sample rather than a sample of the paste. In addition, results are only presented for 3

tailings samples and two leachate samples.

Response:

The Environment Protection Agency’s submission raised two issues, namely whether the

chemical residues present in tailings can impact on the physical characteristics of the paste and

why Toxicity Characteristics Leaching Procedure (TCLP) testing was completed on a sample of

the tailings rather than a tailings/paste mixture.

In relation to the first issue, the Proponent notes that the test work described in Revell (2010)

was undertaken using tailing that would have, to the degree possible at the current stage of the

Project, the same chemical and physical characteristics as tailings that would be produced by

the processing plant, once operational. In addition, the Proponent has confirmed that further

test work would be undertaken to confirm the results of Revell (2010), following

commissioning of the processing plant. As a result, the Proponent does not anticipate that

chemical residues, the physical or mineralogical characteristics of the tilings would adversely

impact on paste curing or physical characteristics.

In relation to the use of tailings rather than paste for the characterisation of the leaching

potential of the material, the Proponent notes the following.

The paste, once cured, is a solid mass with permeability of approximately 1x10-

8m/s, which is the same permeability required of the lining for the Tailings

Storage Facility. This would effectively inhibit the ability of the leaching solution

to leach contaminates as only the surface and any cracks of the cured paste fill

would be subject to leaching. By contrast, the use of unbound tailings ensured

that the maximum surface area of the tailings was exposed to the leaching solution

during the test work to create a worst case leachate for assessment of the proposed

modification.

While cured paste could have been crushed and ground for use during the leach

test work, the tailings particles with the potential to leach metals would be

covered with a cement/carbonate matrix, restricting the ability of those particles to

liberate their metals, resulting in a lower concentration in leachate than leaching

of tailings alone.

Finally, while the leach test work could have been undertaken using an uncured

tailings and binder mix, the Proponent contends that this would have resulted in

the curing reaction occurring concurrently with the leaching reactions and would

have produced leach test results that were unrelated to the likely leaching

characteristics of the paste.

As a result, the Proponent contends that the use of unbound tailings to determine the leaching

characteristics of the material is appropriate as it would produce a worst case scenario leachate

for characterisation of the material.




5

The Proponent accepts that there is some ‘speculation’ as to the levels of contaminants that

would be leached from the paste fill material once cured, however, contends that as the tailings

material tested was unbound, that the maximum amount of contaminants were leached from the

tailings. Hence, the speculation is only around the degree to which the binder would prevent

leaching of contaminants into ground water.

The Proponent notes that the contaminants contained in the leachate were all significantly

below the TCLP1 threshold (Tables 5 and 6 of RWC (2012)) and that the paste fill, once cured

has a permeability of 1x10-8

m/s and is expected to further reduce the leaching of contaminants

into groundwater.

In relation to the number of tailings samples tested, the Proponent notes that the issue of the

representativeness of the tailings samples was an issue tested in the Land and Environment

Court case. In particular, the affidavits of Aaron Green and David Morgan, which were

accepted by the Appellants in that case, stated the following.

Alteration and mineralisation within the Dargues Reef deposit is unusually

uniform and homogenous. As a result, the ore material used to produce the

tailings sample tested is representative of the ore body as a whole to the extent

possible considering the relative size of the sample available.

Mr Morgan noted that it is typical to test one sample of tailings per ore type to

determine the physical and geochemical properties of the tailings. As there is

only one ore type within the Dargues Reef ore body, then only one tailings sample

would normally be tested

As a result, the Proponent contends that the number of samples tested adequately represents the

tailings that will be produced during the life of the Project.

No information appears to have been included to provide a comparative analysis of the

differences between the tailings material and the paste material after the reactive

process (binding) has been completed. Although it could be assumed that the paste

would leach at concentrations less than the tailings, it may be appropriate to conduct

bench trials on the paste for confirmation and an appropriate level of due diligence.

Response:

The issue of the use of tailings material in the test work has been addressed previously. In

addition, the Proponent notes that curing of cement is a hydration reaction and does not

anticipate that the reaction would result in the production of contaminants with increased

solubility to groundwater. However, as previously discussed, the cement hydration process

would result in the binding of the tailings material, reducing the permeability and reducing the

leaching potential of the paste fill.



6


In consideration of the total quantity of tailings to be processed, it is likely that the

concentrations of the tailings will vary and may not be a homogeneous material – the

concentrations shown in table 7 as part of the classification process vary to those

presented in Table 3 on the tailings composition. No justification of the number of

samples tested is presented.

Response:

The representativeness of the tailings material has been addressed previously.

The Proponent notes that an explanation regarding the data contained in Tables 3 and 7 of RWC

(2012) is provided in response to Item 5 in Section 2.4.

In addition to the above comments the EPA recommends the proponent be required to

provide the following information to confirm suitability of the paste fill process”

Identification of any chemical species in the tailing material which are capable

of interfering with the setting of cement and means to overcome this problem.

Details of proposed cement/binder type to be used-grade, characteristics,

including any additives to be used.

Details of any proposed surfactant/other chemical additives to be used.

Indication of the likely reaction products of the tailing waste and cement/lime

mixture.

Setting profile or curing strength over the following durations: 24hrs, 7 days, 14

days and 28 days.

Response:

A response to each issue identified by the EPA is provided below.

The Proponent notes that no chemical species have been identified that would

interfere with the curing of the paste fill. Strength testing using tailings material

indicates that the paste fill develops strength consistently over the 260 day test

period (Table 5, Revell (2010)) and that this increase in strength indicates that the

curing process is not being inhibited.

The Proponent has conducted all test work using Low Heat Cement produced by

BGC Cement, which is a blend of Portland Cement and ground granulated blast

furnace slag. An MSDS for BGC Low Heat Cement has been provided as

Appendix 3. The indicative chemical composition of Low Heat Cement is

presented in Table 1.




7

Table 1 Indicative Chemical Composition – Low Heat Cement

Parameter CL Typical

SiO2 29.20%

Al2O3 11.10%

Fe2O3 1.20%

CaO 50.40%

MgO 4.60%

SO3 2.20%

LOI 0.70%

Chloride 0.01%

Na2O 0.40%

Source: Big Island Mining

The Proponent does not intend to use, at this stage, surfactants or other chemicals in

the production of paste fill. As indicated in RWC (2012), the constituents of the

paste fill are tailings, cement binder and water. If constituents other than those

identified are required in response to operational issues, identified during the life of

the Project, then the Proponent would consult with the EPA prior to their use.

The Proponent notes that curing of cement is a hydration reaction and does not

anticipate that the reaction would result in the production of contaminants with

increased solubility to groundwater.

The Proponent notes that strength testing of the paste fill has been completed over 7,

28, 56, 112 and 260 day time frames and that this information is included in Section

3.4, Table 5 and Figure 8 of Revell (2010).

Waste Sampling and Analysis

The provided EA suggests that the paste fill material will be classified as ‘General solid

waste (non-putrescible)’ in accordance with the EPA’s ‘Waste Classification

Guidelines’. In this regard the proponent will need to ensure paste fill continues to meet

that classification throughout the period the waste is to be applied to land.

The EPA recommends frequent testing of the waste for an initial period to establish that

the characteristics of the waste are consistent enough to give the waste generator

confidence to reduce the frequency of testing. It is the responsibility of the waste

generator (in this caste the proponent) to ensure that frequency of testing provides a

representative sample for all contaminants in that waste while the application of waste

continues.



8


It is recommended that any consent include condition to implement an initial testing

regime with capacity for amendment based on an assessment of testing data.

Response:

The Proponent notes that best practice processing operations require regular sampling and

classification of the ore, concentrate and tailings during commissioning and operation of the

process plant and that this would include a period of time prior to the commencement of paste

fill operations. Analysis of these samples would be undertaken using on-site and off-site

laboratories and would be sufficient to comply with the Proponent’s obligations identified by

the Environment Protection Authority.

Noise

The EA does not provide adequate information for the EPA to determine whether the

proposed modification will cause noise impacts at sensitive receiver locations. The EA

does not identify sound power levels for plan and equipment associated with the

proposal (for example the operation of a concrete batching plant or delivery of cement

to the batching plant) and has not considered the cumulative noise impacts generated by

the proposed activities and currently licensed mining activities. In order for the EPA to

be able to determine whether the predicted noise impacts at sensitive receiver locations

are acceptable, it requires the information provided in Attachment A.

Response:

The Proponent notes that the proposed modification would result in the installation of a limited

amount of additional equipment, and considers that the proposed modification would have a

negligible additional impact. The Proponent further notes that the anticipated noise-related

impacts of the Project as approved are significantly below the relevant criteria.

In recognition of the Environment Protection Authority’s request for additional information, the

Proponent provides the following.

Identify all noise sources from the development including associated sound power

levels. Detail all potentially noisy activities including ancillary activities such as

transport of goods and raw materials.

Additional noise sources would include the following.

A twin shaft horizontal pug mixer or similar with twin 11kW electric motors

(Photograph 3 of Revell (2010)). Anticipated sound power levels from this

equipment would be approximately 90dB.

A binder screw feeder, an example of which can be seen as the pipe coming from

the base of the silo shown in Photograph 2 of Revell (2010). The Proponent notes

that detailed design of this section of the paste fill plant is unavailable, however,

anticipates that the motor would be less than 10kW and that negligible noise

would be generated by the screw feeder itself.




9

The location of these additional noise sources would be within the footprint of the approved

processing plant and would be both lower and further away from the closest residences than

other more significant noise sources, including operation of the front-end loader on the ROM

pad and the crushing circuit.

Delivery of bulk cement would be undertaken using semi-trailer trucks or similar, the operation

of which has already been considered in RWC (2010a).

There would be no other significant sources of noise associated with the proposed modification.

The Proponent contends that given that noise generated from the additional noise sources,

required as part of this modification, are significantly below that already approved, that no

further assessment of noise impacts is required.

Identify any noise sensitive locations likely to be affected by activities at the site,

such as residential properties, schools, churches, and hospitals.

Noise-sensitive receivers would remain as identified in Section 4.5.1 of RWC (2010a) and

Section 3.2 of RWC (2010b).

Identify the land use zoning of the site and the immediate vicinity and the

potentially affected areas.

The land use zoning remains as identified in Section 1.3.2 of RWC (2010a).

Determine expected noise level and noise character (e.g. tonality, impulsiveness,

vibration, etc) likely to be generated from noise sources during operation.

The anticipated additional noise level is not expected to be tonal or implusive in character, nor

is it likely to result in additional vibration.

Determine the noise levels likely to be received at the most sensitive locations

(these may vary for different activities at each phase of the development).

Noise levels at surrounding residences are not expected to change as a result of the proposed

modification. However, even if a small increase in noise was to result, given that the

anticipated noise impacts associated with the approved Project are significantly below the

relevant criteria, the impacts would still be non-significant.

For developments where a significant level of noise impact is likely to occur,

noise contours for both daytime (7am-10pm) and night time (10pm-7am) periods

should be derived. Particular attention will need to be paid to any potential

impulsive noise characteristics which may occur during some site activities (e.g.

maintenance, heavy vehicle).

Significant noise levels are unlikely to occur.



10


Consider the influence of existing meteorological conditions such as winds and

temperature inversions in the prediction model so as to provide a true

representation of actual noise levels.

Existing meteorological conditions are identified in Sections 4.1.3 and 4.2.4.1 of RWC (2010a)

and have been taken into consideration in the noise assessment prepared for that application.

Assess the effect of noise mitigation measures incorporated into the predictive

modelling.

Noise mitigation measures are identified in Section 4.2.5 of RWC (2010a) and were taken into

consideration in the noise assessment prepared for that application.

Compare the predicted noise levels with the appropriate noise criteria for the

phase of development or activity being considered (determine the appropriate

noise criteria for the surrounding area using the appropriate guideline using the

Industrial Noise Policy).

Predicted noise levels and a comparison with the relevant criteria are presented in Section 4.2.6

of RWC (2010a) and remain valid.

Discuss the findings from the predictive modelling and, where relevant noise

criteria have not been met, recommend additional mitigation measures.

The results of the predicitive modelling is discussed in Section 4.2.6 of RWC (2010a) and that

discussion remains valid

Where relevant noise/vibration criteria cannot be met after application of all

feasible and cost effective mitigation measures the residual level of noise impact

needs to be quantified by identifying:

- locations where the noise level exceeds the criteria and extent of exceedence

- numbers of people (or areas) affected

- times when criteria will be exceeded;

- likely impact on activities (speech, sleep, relaxation, listening, etc)

- change on ambient conditions.

All noise and vibration criteria are expected to be achieved.

Determine the most appropriate noise mitigation measures including both noise

controls and management of impacts for both construction and operational noise.

This will include selecting quiet equipment and construction methods, noise

barriers or acoustic screens, location of stockpiles, temporary offices, compounds

and vehicle routes, scheduling of activities, etc.

The noise mitigation measures identified in Section 4.2.5 of RWC (2010a) and the final

Statement of Commitments remain valid for the modified Project.




11

Variation to Environment Protection Licence

The EPA considers that the proposed medication will be classified as a Scheduled

Activity under the provisions of ‘Schedule 1’ of the ‘Protection of the Environment

Operations Act 1997’ (POEO Act), specifically subsection ’39 Waste Disposal

(application to land)’.

Because the medication will result in the inclusion of an additional scheduled activity,

the proponent will need to make separate application to the EPA for variation to

Environment Protection Licence 20095 prior to undertaking the activity. The required

variation application form can be accessed at the following internet address:

http://www.environment.nsw.gov.au/resources/licensing/20120243varpremises.doc

Response:

The Proponent acknowledges that a variation to Environment Protection Licence 20095 would

be required. The Proponent would submit the variation application to the Environment

Protection Authority as soon as practicable following receipt of project approval, assuming that

it is granted.

2.3 DEPARTMENT OF PRIMARY INDUSTRIES

2.3.1 NSW Office of Water

The Office of Water has identified considerable uncertainty in assessing the impacts of

this proposal. It is recommended this concern be acknowledged and the key issues in

this submission be addressed through amendments to the Water Management Plan

(WMP).

Response:

The Proponent disagrees with the assertion that there is considerable uncertainty in relation to

the impacts of the proposed modification. In particular, the Proponent notes the following.

Paste fill is a widely used technique and the behaviour of paste, both physical and

chemical, is a well understood field. In addition, significant test work has been

undertaken and is documented in Revell (2010)

As indicated in Section 1.6 of RWC (2012), the assessment of the proposed

modification has been prepared with the assistance of Mr Matt Revell, Dr Reinier

Mann and Mr Errol Briese, all recognised experts in the fields of paste fill

engineering, ecotoxicology and groundwater impact assessment respectively.

http://www.environment.nsw.gov.au/resources/licensing/20120243varpremises.doc



12


The assessment of potential impacts from pastefill leachate in the EA is limited to

theories with uncertainty in regards to long term impacts. Whilst the general theories on

paste backfill characteristics and geochemical reactivity appear reasonable, it is

difficult to validate some of the key parameters at the scale of this proposal. This

therefore raises concern over the long term stability of the pastefill and potential

impacts to groundwater quality.

Response:

The Proponent notes that it has undertaken an assessment based on the drill samples that it has

available and that larger scale test work will not be possible until the ore body is exposed and

processing operation commence. However, as noted previously, it was accepted by the

Appellants to the Land and Environment Court action that the Dargues Reef ore body is

unusually homogeneous and uniform and that the tailings samples that exist are likely to closely

reflect the actual tailings characteristics once the Project becomes operational.

It is further noted that project-specific assessments were undertaken in relation to the physical

and leaching characteristics of the material. As a result, the Proponent contends that it has

adequately validated the appropriate key parameters to the extent possible based on the samples

available at this stage.

Finally, given the composition of the paste, namely cement, tailings and water, and the

environment in which it would be emplaced, namely underground in a stable granodiorite rock

mass, there is no reasons to suspect that the paste would degrade or become less stable.

However, in the event that the paste did degrade, the Proponent notes that leach testing was

conducted on unbound samples of the tailings material, which would be representative of a

complete degradation of the paste fill structure. It is also reasonable to assume, that should the

paste fill degrade, that it would occur over a significant period of time and therefore any

leachate from the degrading paste fill would not exceed the contaminant levels presented in

RWC (2012). As a result, the Proponent contends that the leach testing completed adequately

assess the risk from any degradation of the paste fill over time.

The understanding of groundwater quality in the EA is limited to the depth of the

current deepest monitoring bore which is 216 metres. As the proposed mine and

pastefill placement is to a depth of 500 metres, the Office of Water requests

characterisation of groundwater quality to this maximum depth. This characterisation

will need to represent background conditions to the satisfaction of the Office of Water

and will need to be completed prior to commencement of pastefill operations.

Response:

The Proponent notes that the aquifer that hosts the Dargues Reef deposit is a fractured rock

granodiorite aquifer associated with the Braidwood Granodiorite, a massive intrusion with an

aerial extent of approximately 1 000km2 and a depth of at least several kilometres. As a result,

with the exception of a reduction in the transmisivity of water bearing structures with depth, the

Proponent contends that there is no reason to expect that the aquifer properties or groundwater

quality below 216m would be different from above that depth.

In addition, the Proponent further notes that although it is feasible to drill, case and sample a

bore to a depth of 500m below surface, that it would require specialist equipment and

substantial cost to the Proponent with limited benefit.




13

While mining operations will progress to an eventual depth of 500m below surface, they will

not reach this depth until Year 4 of the Project, well after the proposed commencement of paste

filling operations. As a result, the Proponent contends that direct characterisation of the

fracture-hosted granodiorite aquifer between 216m and 500m below surface is not required.

Notwithstanding the above and as noted below, the Proponent would monitor the quality of

groundwater within the underground workings during the life of the Project and following

completion of mining operations until all relevant agencies are satisfied that the proposed paste

fill operations does not pose a threat to groundwater quality.

It is recommended amendments to the WMP demonstrate an ability to monitor and

report on any impacts to groundwater quality associated with the paste backfill to the

full depth of operations, both during operation and following completion of the mine. It

is to also include a trigger response plan and mitigating options.

Response:

The Proponent notes that the dewatering operations would be required to be undertaken from

the deepest section of the underground workings and that this water would be available for

testing as soon as groundwater is intersected in the decline. In addition, potential exists for

infrastructure to remain in place to test groundwater within the deepest sections of the mine

following cessation of dewatering operations at the end of the life of the Project.

The Proponent anticipates that should the approval for modification be granted, that the Water

Management Plan would require updating in consultation with NSW Office of Water to reflect

the revised mining operations.

2.4 EUROBODALLA SHIRE COUNCIL

Eurobodalla Shire Council provided a submission supported by a letter report prepared by Dr

Peter Beck. The text of Dr Beck’s report provided an overview and background to his

comments, with his detailed comments included in a table. The following provides a response

to the tabulated issues identified in Dr Beck’s report.

1. While changes to mining operations are not unusual, it may be useful to obtain an

explanation and discussion that given the benefits highlighted in the BIM 2012

report why the use of paste backfill was not considered in the original proposal, as

more comprehensive and detailed assessment of potential impacts to the

environment could have been undertaken in the context of the overall project. This

modification only touches on some of the relevant issues that will have potential

knock on effects such as changes to the tailing storage facilities and waste rock

dumps.

Response:

The potential use of paste fill at the Project Site was first highlighted in Section 2.7.5 of the

Environmental Assessment prepared to support the original application for development consent

(hereafter referred to as RWC, 2010a). However, as indicated in Section 1.4.5 of RWC (2012),

approval for its use was neither sought nor granted at that time because the relevant studies had

yet to be completed at the time of finalisation of RWC (2010a).



14


The following provides an indicative list of the studies that have been completed into the use of

paste fill since the submission of RWC (2010a).

Mining method trade off study – this assessed the most viable mining method for

the Project and provided for the highest safety, minimisation of environmental

impact and greatest economic return.

Paste fill design and assessment (Revell, 2010) – this study determined the

suitability of the tailings material for use as paste fill and the quantities of water

and cement required.

Rheology and strength testing (Revell, 2010) – this study examined a range of

different mixtures of paste fill to determine their suitability for use in the mine.

Specific Contaminant Concentration testing and Toxicity Characteristics Leaching

Procedure testing of the tailings material – this study assessed the impact on the

environment of emplacement of tailings material underground.

Groundwater studies – these assessments sought to determine the impact of paste

fill on groundwater levels, recharge rates and quality and are included as

Appendices 2 and 3 in RWC (2012).

In relation to the comment that this ‘modification only touches on some of the relevant issues’,

the Proponent notes that it has, in its opinion, addressed all matters relevant to the modification.

In relation to the matters expressly identified by Dr Beck, the Proponent notes the following.

There are no changes to the approved Tailings Storage Facility, with the exception

of the fact that Stage 3 of the facility may not need to be constructed.

The volume of waste rock that would be stored within the temporary waste rock

emplacement/ROM Pad would be increased by approximately 22 290m3, or

approximately 11%, as a result of the proposed modification. This increase would

not significantly change the design or size of the emplacement and that any

increase in size would be into areas already approved for disturbance. In addition,

the expert report of Clayton Rumble prepared for the Land and Environment

Court action and accepted by the Appellants to that action indicated that the waste

rock to be placed within the emplacement would be “naturally slightly alkaline,

non-saline and [non-acid forming].” As a result, there would be no additional

impacts associated with placement of waste rock as a result of the proposed

modification.




15

2. The BIM 2012 report states “Transportation of sulphide concentrate from the

Project Site to the proponent’s customers via public roads surrounding the Project

Site using covered semitrailers”. This appears inconsistent with what my

understanding was. During the meetings it was stated that the sulphate concentrate

would be taken to the ore processing facility in Parks for processing.

Response:

The identified text is a quote directly from RWC (2010a), at which time the Parkes site was not

confirmed as the treatment site. The Proponent notes that the intention at the time of

finalisation of this document is to further process the concentrate at Parkes. However, as other

opportunities may become available in the future the Proponent does not wish to limit the

destination for concentrate from the Project.

3. The BIM 2012 report states “The completed stopes to be backfilled with paste would

be appropriately sealed to prevent leakage of paste during backfilling operations.”

But, no details on how this is to be achieved and verified appear to be provided.

Response:

The Proponent notes that the quote referred to by Dr Beck relates to sealing of the lower

entrances to the stopes (open voids) to prevent paste from flowing out of the stope and down

the decline into the remainder of the workings. The statement is not intended to indicate that

stopes would be fully lined or sealed.

In the interests of clarity, the Proponent notes the following in relation to placement of paste

and the nature of the stopes into which it would be placed..

The tailings would be mixed with cement binder and the precise amount of water

required to cure the mixture and ensure that no or very limited bleed water is

produced.

The paste fill would be a high density product with a consistency similar to

toothpaste.

The paste fill would be emplaced into a granodiorite aquifer where the principal

porosity is fracture-controlled.

The paste fill is expected to be largely cured within hours of emplacement and

fully cured within seven days.

As a result, past is not expected to “leak” from the stopes and not adverse environmental

impacts are anticipated.

4. The BIM 2012 report states that “Approximately, 84% of stopes by volume would be

backfilled with paste, with a further 7% by volume being backfilled with waste rock

as described in Section 2.5.4 of RWC (2010a). The remaining 9% by volume would

not be backfilled.” GHD understood that the original proposal included the

backfilling of all the stopes



16


Considering that backfilling of 84% of the stope volume is now proposed to be

accomplished by paste fill how would this affect the management and placement of

waste rock that was to occupy this volume? Will this increase the size and or

duration of the surface waste storage facilities?

Response:

Dr Beck’s understanding is not consistent with Section 2.4.5 of RWC (2010a) which identified

that, as part of that application, waste rock would be used to stabilise “sections of the proposed

underground mine”, not all stopes created. The Proponent further notes that to completely

backfill all stopes with waste rock would be unachievable using the approved mining method.

As noted previously and in Section 2.4 of RWC (2012), the proposed modification would result

in an increase in waste rock being transported to the surface of approximately 11%. This

increase would not significantly change the design or size of the emplacement and any increase

in size of the emplacement would be into areas already approved for disturbance. The

additional waste rock would be used to backfill the box cut or used in rehabilitation of the

Project Site following the completion of mining operations.

5. Table 3 indicates average crustal abundance for various elements in the crust and

refers to an earlier Bankable feasibility study. Therefore, the source for this data is

unclear.

Response:

The data contained in Table 3 of RWC (2012) is based on data obtained during the Bankable

Feasibility Study prepared for the Project and was also included in RWC (2010a). The source

of the average crustal abundance used in that table was Table 4.15 of Independent

Metallurgical Operations, Dargues Reef Gold Project Bankable Feasibility Study Tailings

Management.

6. The BIM 2012 report states “Waste Classification Guidelines issued by the then

Department of Environment, Climate Change, and Water (now the Office of

Environment and Heritage) in April 2008”. A revised version of these guidelines

was published in December 2009.

The BIM 2012 report should be prepared with reference to the most up to date

version of the guidelines to ensure compliance with up to date requirements.

Otherwise there is a risk that the impact assessment could miss an issue of

relevance.

Response:

The Proponent notes that RWC (2012) incorrectly referred to the April 2008 version of the

Waste Classification Guidelines and that the December 2009 version was in fact used. The

Proponent apologises for this error and notes that no changes to the outcome of the assessment

would have resulted from the use of either version of the guidelines.




17

7. The NSW EPA, Protection Of Environmental Operations (POEO) Act, 1999 defines

waste and waste facilities as follows: “waste includes:

(a) any substance (whether solid, liquid or gaseous) that is discharged, emitted

or deposited in the environment in such volume, constituency or manner as to

cause an alteration in the environment, or

(b) any discarded, rejected, unwanted, surplus or abandoned substance, or

(c) any otherwise discarded, rejected, unwanted, surplus or abandoned

substance intended for sale or for recycling, processing, recovery or purification

by a separate operation from that which produced the substance, or

(d) any processed, recycled, re-used or recovered substance produced wholly or

partly from waste that is applied to land, or used as fuel, but only in the

circumstances prescribed by the regulations, or

(e) any substance prescribed by the regulations to be waste. A substance is not

precluded from being waste for the purposes of this Act merely because it is or

may be processed, recycled, re-used or recovered.

waste facility means:

any premises used for the storage, treatment, processing, sorting or disposal of waste

(except as provided by the regulations).”

Therefore by definition the paste fill is a waste, as noted with respect to (a), (b) and

(e), that must be managed and placed in accordance with relevant guidance and

documents as outlined in the POEO Act and any documents issued under that act.

Response:

The Proponent acknowledges the above and notes that the material has been classified as

General Solid Waste (non-putrescible) in recognition of this fact. The Proponent further notes

the response to the EPA provide in Section 2.2 in regards to the Environment Protection

Licence.

8. This section [Section 2.2.3.4 - Step 2: Is the waste ‘liquid waste] and information

presented appears contradictory to the basic description provided in the earlier sections

of the BIM 2012 report. The paste fill mixing and emplacement process described

appears to suggest that the material would be in a liquid or sludge type state. The BIM

2012 report does not appear to reference any testing to support the statement made and

as such it is unclear as to whether the assentation that the paste fill is not a liquid waste

can be supported with the information presented in the BIM 2012 report.



18


The key point that needs to be considered is the state of the “waste” when being placed

into the storage facility and as such the material is unlikely to pass this criteria.

Response:

The paste fill may be classified as a non-Newtonian fluid, with a consistency and behaviour

very similar to toothpaste and would not be free flowing. As identified in Table 4 of RWC

(2012), the paste fill has a slump of 220mm and that this slump rate would not classify it as a

liquid. Further information regarding the rheology of the paste fill is provided in Section 3.3 of

Revell (2010).

9. The data in Table 5 of the BIM 2012 report appears to contradict the data presented

in Table 3. Table 3 presents results for Multi Element analysis while Table 5

presents 95% UCL data. So it appears that Table 3 shows average data while 5

shows 95% UCL data. In general it would be expected that that 95% UCL would be

greater than average concentrations, yet the concentrations in Table 3 are routinely

higher than the concentrations in Table 5. Using the data in Table 3 at least nickel

concentrations exceed the General Solid Waste Criteria.

Based on the information included in Appendix 3 the UCL calculation is based on a

triplicate analysis of a single sample. In general a minimum of 5 samples is required

for calculation of UCL (NSW EPA Sampling Design Guidelines 1995, AS4482.1-

2005).

Also the testing of a single sample in triplicate is not considered sufficient to take

into account the potential heterogeneity of the material.

Response:

The Proponent notes that the data presented in Table 3 was reproduced from Table 4.15 of the

Bankable Feasibility Study and was included to ensure consistency with that document.

However, during preparation of RWC (2012), it was recognised that during the preparation of

the sample used to generate the data presented in Table 3 of RWC (2012), that stainless steel

grinding media was used to prepare the sample, contaminating it with small amounts of nickel,

chromium and molybdenum. As correctly identified by Dr Beck, this caused the nickel

concentration of the sample, presented in Table 3 RWC (2012) to exceed the SCC criteria

outlined in the Waste Classification Guidelines dated December 2009. To better replicate actual

paste characteristics, the Proponent prepared further samples of tailings for Specific

Contaminant Concentration testing with mild steel grinding media. The results from these

samples are provided in Table 5 of RWC (2012).

In relation to the number of samples tested, the Proponent notes that as identified in the expert

reports of Aaron Green and David Morgan prepared for the Land and Environment Court and

accepted by the Appellants in that case, the tailings material tested is a composite sample which

was considered to be representative of the Project’s tailings material as a whole and that testing

of multiple samples is not required. This position was accepted by the Appellants in that case.

As a result, the Proponent contends that the samples tested are representative of the tailings

material that would be produced by the Project. Further, the Proponent notes that as the ore

material is largely homogenous, that the variance in the samples tested is small and that as a

result, three samples are adequate to characterise the tailings material and the leachate.




19

10. The BIM 2012 report indicates that TCLP testing was undertaken in accordance

with AS4439.3 using a pH 5 Buffer. Based on the information provided the leach

testing performed would be in accordance with the test designed for a Class 2

Monofilled putrescible landfill where a Acetate buffer st pH 5 is used.

The material tested (tailings) and testing regime (putrescible Class 2 monofilled

landfill scenario) is clearly significantly different from that actually experienced

(tailings and cement mix placed within a groundwater regime). Therefor the testing

conducted is considered to have little value in terms of assessing risks to the

environment due to the proposed pastefill placement.

Given that the addition of cement to the tailings will significantly alter the

geochemistry of the material to potential mobilisation of contaminants needs to be

understood in the context of the environment into which the material is to be placed.

Response:

The Proponent notes that the TCLP was completed in accordance with the Waste Classification

Guidelines dated December 2009 and that based on the SCC testing, the Proponent was not

required to undertake TCLP testing of the tailings material. The Proponent contends that the

TCLP method prescribed in the Waste Classification Guidelines dated December 2009 is

adequate for determining the potential mobility of metals from the tailings material. The

Proponent acknowledges that the paste fill environment will be slightly alkaline, however, that

the acidic buffer (pH 5) that the tailings material has been leached with provides a worst case

leachate for determination of metal mobility.

The Proponent further notes that all testing of the tailings material has been completed on an

unbound, ground up sample, which has maximised the surface area of particles exposed to the

leaching fluid during sampling, thus maximising the concentration of contaminates present in

the leachate. as noted previously, the permeability of the paste fill material, once cured, is

expected to be approximately 1x10-8

m/s. This would severely restrict the ability of the paste to

be leached by groundwater. As a result, the Proponent contends that the leach testing presents

an absolutely worst case leachate scenario, with significantly lower concentrations of

contaminates being available in reality to be leached into groundwater.

11. The testing procedure outlined in this section [Section 2.2.3.5] indicates the use of

distilled water as leaching medium but does not provide an indication of the pH of

the leaching medium. In general this type of test utilises leaching medium of pH

around 7 (ie. Neutral) the report contends that this would be indicative of a worst

case scenario. Clearly as can be seen in the figure shown for Item 10 that if cement

is addend and the pH becomes alkaline then metal solubility increases in

comparison to neutral conditions.

Response:

The issue of metal mobility has been previously addressed in the response to item 10 above.



20


12. Table 7 in the report refers to Hydrobiology 2012 and Hogan 2003 but the

references are not included in the list at the back of the report and no context is

provided for them. In the table reference is made to median groundwater

concentrations based on Hydrobiology 2012. The context of these numbers is not

provided and no methodology on how samples were collected and analysed is

included. The report indicates median Al in groundwater is 2.25mg/L but does not

indicate whether this is total or dissolved Al. Review of the ALS laboratory

certificates suggests that results are total not dissolved which can have a significant

influence on the metal concentrations measured. Also as noted in Item 11, there is a

risk that leach testing was not representative of worst case due to the potentially

higher pH caused by pastefill

Response:

The Proponent acknowledges that these references were not included in the Reference section

of RWC (2012), however that “Hydrobiology (2012)” was identified in Section 4.2.3.1 as being

reproduced in Appendix 3 of that document and Dr Beck has made reference to that document

in his submission.

The Proponent notes that the results referred to in Table 3 of Hydrobiology (2012) are mean

results from Table 2 of that report which indicates that the analyses are of a “1:20 extract

following filtration (45µm)”. As a result, Aluminium results presented in Table 3 of

Hydrobiology (2012) are dissolved.

The issue of metal mobility has been previously addressed in the response to item 10 above.

13. The report discusses aluminium mobility and risk in the context of the leach testing

results and analysis by Hydrobiology. There are a number of issues with the

discussion and consequent conclusions on risk that would warrant further

consideration as the full risk profile may not have been appropriately assessed.

Response:

The discussion of Aluminium mobility in RWC (2012) was based on work prepared by Dr

Rainier Mann of Hydrobiology, an expert in aquatic ecotoxicology whose work was accepted

by the Appellants in the Land and Environment Court action. That discussion was not intended

to be comprehensive and interested readers such as Dr Beck were referred to the report of Dr

Mann which was included as an appendix.

In light of the specific criticisms of Dr Mann’s work, the Proponent notes the following.

Dr Mann is now no longer employed by Hydrobiology and cannot be contacted to

provide a rebuttal of Dr Becks criticisms.

In the unlikely event that minor levels of elevated Aluminium were to be leached

from the paste, that the risk of adverse environmental consequences would be

very small because the elevated Aluminium levels would be reduced through

buffering with the surrounding host rock prior to discharge to surface waters

As a result, the Proponent contends that no further response is warranted.




21

14. The report indicates that the [Mercury] concentrations measured in the leachate

would attenuate as sulphide species in the groundwater and hence not pose a risk to

the groundwater quality. It is unclear in the report what evidence was used to

support this conclusions.

Dr Mann suggests that any soluble Mercury in leachate would form stable, insoluble complexes

with sulphide minerals within the host granodiorite. In light of the specific criticisms of Dr

Mann’s work, the Proponent notes the following.

The worst case leachate concentrations analysed by Dr Mann were very close to

the ANZECC and ARMCANZ trigger values and that real-life concentrations are

likely to be significantly less than those analysed.

That any leachate produced by the paste would be released into a groundwater

environment where it would be:

– buffered by the surrounding granodiorite aquifer

– subject to adsorption of dissolved metal onto clays and other minerals;

– subject to dilution by groundwater from up gradient of the workings; and

– any leachate would not be released into sensitive surface water environments

in the short term, permitting time for the above reactions and dilution to occur.

As a result, the risk of adverse consequences associated with Mercury in leachate is considered

to be negligible and the Proponent contends that that no further response is warranted.

15. The report fails to include sufficient information to allow independent review of the

data used in the assessment. No information on the number of samples utilised for

the data provided in some tables, the calculation of UCL methods or how many

leachate tests were performed was included. The report fails to include the

laboratory analysis certificates or chain of custody information for all analysis work

relied on. Also not included is information on what laboratory performed some of

the testing and whether they were NATA accredited to perform the tests.

Response:

The Proponent contends that this is not standard practice to include this information in an

Environmental Assessment. However, the Proponent is happy to provide any additional

information that the assessment authority requests.

16. This section [Section 4.2.3] of the report needs revision in light of the comments

above.

Response:

The Proponent contends that the issues raised have been appropriately addressed and that no

further revision is required.



22


17. The report suggests no further groundwater monitoring is required with respect to

the proposed change in mining operations. This recommendation is difficult to

support given some of the key data gaps identified, particularly related to the

anticipated changes to the hydrogeochemical environment as a result of the propose

pastefill placement (eg increased pH and temperature in the mine workings

backfilled and surrounding groundwater regime.

Response:

The Proponent notes that an extensive groundwater and surface water monitoring program has

been established for the Project as part of the Water Management Plan and that this plan is

likely to be updated should approval for the proposed modification be received.

The currently approved program has been designed to detect changes in water quality within

and surrounding the Project Site. The Proponent contends that this monitoring program would

detect all relevant changes in water quality as a result of the approved Project and the Project as

modified.

18. As with Item 17. Given the key data gaps identified and considering the comments

and issues raised in relation to the hydrogeochemical analysis the conclusion

reached in this section [Sections 4.3.3 and 4.3.4] may require revision and

modification once the issues raised are addressed.

Response:


further revisions are required.

19. As noted in Item 17 and 18 given the issues raised and data gaps identified this

conclusion needs further consideration once the issues are addressed.

Response: The Proponent contends that the issues raised have been appropriately addressed

and that no further revisions are required.

20. Given that this section [Section 5] is heavily dependent on the outcomes and results

of how the items above are addressed revision and medication of the relevant

sections may be required.

Response:


further revisions are required.

21. Aluminium mobility could significantly increase as a consequence of the increased

pH resulting from the addition of cement.

Response:

The issue of metal mobility has been previously discussed in the response to item 10.




23

22. Potential oxidation of chromium in the tailings to the hexavalent state (CrVI) as a

result of cement addition.

Response:

The issue of metal mobility has been previously discussed in the response to item 10.

23. Most mineral solubility increases with temperature and hence enhanced

mobilisation of metals and other inorganic compounds in the area around the mine

workings could occur as a result of the proposed use of paste fill

As indicated in Section 2.2, low heat cement will be used in the paste fill to reduce the

generation of heat during the curing process. In addition, the relatively small volumes of paste

that would be generated and placed within completed stopes when compared to the massive

volume of granodiorite host rock surrounding the Dargues Reef deposit indicate that any heat

generated by the paste would be insignificant

24. The BIM 2012 report does not include some of the backing information presented

such as laboratory certificates and other information sources.

Response:

The Proponent notes that this item has been previously addressed at item 15.

3. P U B LI C S U BM I SSI ON S

3.1 INTRODUCTION

This section provides a response to the public submissions presented in Table 2. In order to

limit repetition and allow the matters raised to be adequately and efficiently addressed in the

following sub-sections, each submission was reviewed and the matters raised were categorised

as follows.

Issue A – Dargues Reef Consultative Committee

Issue B – Additional Conditions

Issue C – Xanthate Testing

Issue D – Water – Impacts on Groundwater Quality

Issue E – Water – Alkaline Concrete Leaching

Issue F – Long Term Stability of Paste Fill

Issue G – Assessment of the Modification

Issue H – Eurobodalla Residents as Stakeholders

Table 2 identifies the issues raised in each submission.

Finally, in order to provide a ‘flavour’ of the issues raised by the various submissions, selected

sections of each submission are provided in italics in the following subsections.



24


Table 2 Submissions and Issues Raised

Submission No

Respondent Issue

A B C D E F G H

001 Araluen Valley Producers and Protectors of the Ecosystem Coalition (AVPPEC)

X X X X X

002 Peter Cormick X X

X X

003 Coastwatchers X X X

004 Jackie French X X X

005 Brian Sullivan X X

3.2 ISSUE A – DARGUES REEF CONSULTATIVE COMMITTEE

1. The use of a Community Consultation Committee to approve such an amendment

without independent advice

The use of the Community Consultation Committee to “approve’/”support” such an

amendment would appear flawed in terms of capacity to make such a technical decision

without independent advice and/or access to research concerning the environmental

and other issues associated with paste fill operations.

It is apparent that a Consultation Committee can quickly lose both its legitimacy and

value once the broader community gains an understanding that the community people

involved have no independent advice and have only their own (limited we would

suggest) resources to fall back on. This approach is de-valuing of the processes

whereby the community could derive some comfort that the Committee was keeping a

watchful eye upon the operation.

It is respectfully suggested that the Committee be afforded access to independent advice

as matters like this come before it. For example the Water Management Plan currently

released is a dense and technical document and the Committee should have capacity to

source outside advice and information that will assist it consider such technical matters.

To provide only proponent advice to the Committee is to ensure the Committee will

gradually become irrelevant and appears disrespectful to the community participants.

Submission No. 001 – AVPPEC

Response:

The Proponent contends that the role of the DRCCC in this application is not a matter that is

relevant to the determination of the application for modification of PA 10_0054. However, in

acknowledgement of the concerns raised by the submission and as stated in Section 3.2.2 of the

EA, the committee was requested to express support or otherwise for the following statement.

Based on the information presented and relying on Cortona’s assertion as to its accuracy, the DRCCC broadly supports the application to modify Project Approval 10_0054 to permit the use of Pastefill.




25

The committee was not asked to ‘approve’ the application. It was merely asked in its advisory

and non-technical capacity whether, based on the information provided by the Proponent, the

members of the committee broadly supported the proposed modification. The Proponent

contends that this information, and the manner in which information was presented and

feedback sought, is appropriate as significantly more consultation and community engagement

would have been required to be undertaken if the committee was not comfortable with the

proposed modification.

Finally, the Proponent acknowledges that some issues presented to the committee can be

complex and technical in nature. Where issues of this nature are presented, the Proponent has

endeavoured to provide significant support from within the company. However, the Proponent

contends that access to external independent advice is not required or appropriate given the role

of the committee.

3.3 ISSUE B – ASSESSMENT OF XANTHATE USE AND RESIDUES

It is also of note and concern that no test for Xanthate residues has been approved in

NSW and all approvals thus should remain provisional

The waste it makes contains heavy metals. Xanthates bind with heavy metals and pulls

them out of solution. It is difficult to see this material as general waste, because of the

heavy metals. The non-reacted Xanthate is still a reactive chemical. It could react with

heavy metals or wildlife and given the range of unknowns concerning the aquifers and

Araluen Valley it is our contention it absolutely should not be a general waste, it should

be a pollutant. It is a chemical waste and should be treated as such.


Why do the “Tailings Characteristics”, shown in Table 3 at section 2.2.3.2 of the

proposal, not list amyl xanthate? What will its ppm presence be? Also, Table 6 at

section 2.2.3.5 sets out “Toxicity Characteristics Leaching Procedure Test Results” but,

again, amyl xanthate is not included in the list. And yet again, at Table 7, “Paste fill

Leachate Characteristics”, there is no mention of amyl xanthate. Why is that?

Submission No. 002 – Cormick

The Tailings Characteristics table shown at section 2.2.3.2 of the proposal does not list

amyl xanthate, although presumably these tailings, like those destined for the tailings

dam, will be treated. Cortona claim that the Xanthates will bind to the ore sent to the

proposed Parkes Processing plant. They do not, however, supply adequate

substantiation of that, given that expert consensus on the issue is that paste fill is a

relatively new process, and that the many variables mean that both the cement content

and the leachate vary, even on a single site.

Submission No. 004 – French



26


Response:

The Proponent notes that this issue was raised by the DRCCC and that it has been

comprehensively addressed in Appendix 1 of RWC (2012). In summary, however, the

following was agreed by both the Appellant’s and Respondent’s experts during the Land and

Environment Court.

Xanthate binds strongly to sulphide minerals, and to a lesser extent other minerals,

and the vast majority will be removed with the sulphide concentrate.

There is no commonly accepted methodology for directly testing xanthate

concentration in tailings because the xanthate would be destroyed during the

extraction process prior to testing occurring.

The negligible amount of xanthate would be bound to the solidified paste fill and

would not be mobilised in groundwater.

In addition, xanthate is a commonly used chemical, including as a component of commonly

used herbicides and other horticultural and agricultural products, and the Proponent is not aware

of any significant adverse impacts associated with its use as a reagent in mining operations in

Australia.

Further, the Proponent notes that testing for xanthates is not a requirement of the Waste

Classification Guidelines dated December 2009 and that no approved method for the testing of

xanthates exists in NSW.

3.4 ISSUE C - GROUNDWATER QUALITY - METALS

in relation to “Groundwater”, we are told that “Test work results on leachate

chemistry were analysed by Hydrobiology (2012) who confirm that the anticipated

worst-case chemical composition of the leachate that would be leached from the paste

fill would comply with the ANZECC and ARMCANZ (2000) trigger values for the

protection of 95% of aquatic species for all relevant elements except aluminium,

mercury and silver.” What of these levels of Al, Hg and Ag – how far above the trigger

values are they expected to be - and what are there estimated impacts? And, again, what

of the xanthate presence and its impact? To continue: “The levels of those three

elements are sufficiently low that the leachate is unlikely to result in significant adverse

groundwater quality-related impacts.” And, further, we are told that “In light of the

above, the Proponent contends that the proposed modification would not result in

significant adverse impacts to threatened species, Endangered Ecological Communities

or groundwater dependent ecosystems.” (emphases added) In meaningful statistical

terms, what is meant by “significant” and “unlikely”, in the quoted passages?


Response:

Table 15 of the Environmental Assessment provides the relevant concentrations of Aluminium,

Silver and Mercury and the relevant trigger levels.




27

In relation to the use of the terms “unlikely” and “significant adverse impacts”, reference is

made to the ANZEC and ARMCANZ trigger values and the fact that anticipated concentration

of the above elements were determined by Hydrobiology, taking into account the natural

physical and chemical properties of the paste, aquifer and groundwater, to not pose a risk of

environmental harm. The terms are used in a manner that is consistent with Section 5A of the

Environmental Planning and Assessment Act 1979.

Finally, the Proponent acknowledges the expert report of Dr Grant Hose, provided with

Submission No. 001 states.

To the best of my knowledge the leaching tests done on the paste fill sample seem appropriate and the interpretation of those data seem adequate, such that environmental harm from metals in the paste fill is unlikely, as it was for the mine waste rock in the absence of the paste.

3.5 ISSUE D – GROUNDWATER QUALITY – ALKALINITY

There appears to be no study to substantiate the presumption that there will be no risk

of alkaline concrete leaching leading to long term changes in the naturally acidic water

table. Any such change could be devastating to local flora, and persist for decades or

even longer after the facility is decommissioned.

Submission No. 001 - AVPPEC

My concern is that the pH of the leachate (~9) is above the background pH of most of

the groundwater (~7). The significance of this difference is not discussed in the EA or

supplementary report in appendix 3 despite the consultant concluding that the pH of the

groundwater will influence the concentrations of metals. Recent research has suggested

that even limited contact with concrete channels can influence the pH of stream water

(Wright et al 2011) so the dismissal of this issue in the letter from Cortona to the DRCC

seems to me premature. With longer residence times in groundwater compared to

surface streams, it seems likely to me that contact between groundwater and the paste

fill concrete will result in an increase in groundwater pH. As suggested in the

Hydrobiology report, increasing pH will likely reduce the availability of some metals in

the leachate, but it will also have it's own potential affects on biota in the groundwater

and receiving waters. It may be that the buffeting capacity of the groundwater is

sufficient to cope with the change in pH but this should be considered in the report.

Submission No. 001 – AVPPEC (Expert Report – Hose)

Concrete itself is not a stable substance and can present major alkaline leaching. The

EA for the Modification states that the pH of the leachate (~9) is above the background

pH of most of the groundwater (~7). The significance of this difference is not discussed

in the EA or supplementary report in appendix 3 even though the consultant concludes

that the pH of the groundwater will influence the concentrations of metals. The pH of

the groundwater will also have potential effects on biota in the groundwater and

receiving waters. Recent research has suggested that even limited contact with concrete

channels can influence the pH of stream water (Wright et al 2011) and dismissal of this

issue by Cortona is premature. With longer residence times in groundwater compared



28


to surface streams, it is likely that contact between groundwater and paste fill concrete

will result in an increase in groundwater pH. The increased pH of the groundwater will

also have potential affects on biota in the groundwater and receiving waters.

Submission No. 003 – Coastwatchers

There also appears to be no study to substantiate the presumption that there will be no

risk of alkaline concrete leaching leading to long term changes in the naturally acidic

the water table. Any such change could be devastating to local flora, and persist for

decades or even longer after the facility is decommissioned.


My concern is that the pH of the leachate (~9) is above the background pH of most of

the groundwater (~7). The significance of this difference is not discussed in the EA or

supplementary report in appendix 3 despite the consultant concluding that the pH of the

groundwater will influence the concentrations of metals. Recent research has suggested

that even limited contact with concrete channels can influence the pH of stream water

(Wright et al 2011) so the dismissal of this issue in the letter from Cortona to the DRCC

seems to me premature. With longer residence times in groundwater compared to

surface streams, it seems likely to me that contact between groundwater and the paste

fill concrete will result in an increase in groundwater pH. As suggested in the

Hydrobiology report, increasing pH will likely reduce the availability of some metals in

the leachate, but it will also have its own potential affects on biota in the groundwater

and receiving waters. It may be that the buffeting capacity of the groundwater is

sufficient to cope with the change in pH but this should be considered in the report.

Submission No. 005 – Sullivan

Response:

The matter of changes to groundwater pH was addressed in Appendix 1 of RWC (2012) and the

Proponent contends that the information provided in that document adequately addresses the

issues raised by the respondents. However, in recognition of the detailed nature of the

submission by Dr Hose, this sub-section specifically addresses the issues raised.

Firstly, the Proponent notes that Dr Hose is incorrect in stating that the pH of groundwater is

approximately 7. Table 4.19 of RWC (2010a) identifies that the pH of groundwater within the

Project Site varies from 7.0 to 8.2, with a single outlier with a pH of 12.2.

Secondly, the Proponent notes that the permeability of the paste fill, once cured, will be

approximately 1 x 10-8

m/s, the same permeability required for the lining of the Tailings Storage

Facility to minimise leaching of water from that facility. As a result, while Dr Hose is correct

in stating that following recovery of the groundwater levels within the Project Site, once mining

operations are complete, the rate at which water could seep out of the cured mass of paste fill is

extremely low. As a result, any water that did seep from the paste fill would very quickly be

diluted by surrounding groundwater. In addition, as the wider properties of the aquifer would

not be modified, any water that did leach from the paste fill with an elevated pH would be

buffered back to a mildly alkaline pH by the surrounding rock mass.




29

3.6 ISSUE E – LONG TERM STABILITY OF PASTE FILL

Further, there is no mention in the EA regarding the longevity and stability of the

concrete paste fill. How long do the proponents expect that the concrete paste fill will

remain in tact as a solid mass. What is the half life (or similar) of concrete masses such

as they will be creating? I am no concrete engineer but if the concrete deteriorates over

time then the infiltration of groundwater to the paste fill will increase as will the

dissolution of metals and carbonates in the concrete etc. The long term stability of the

paste fill should be considered.

Submission No. 001 – AVPPEC (Expert Report – Hose)

4. What regard has been given to the consequences of the paste fill decomposing over

time?


Of critical importance in determining the likely environmental impacts associated with

the proposed operations is the long term stability of the pastefill. There is no mention of

this in the EA.

How long do the proponents expect that the concrete pastefill will remain intact as a

solid mass? If the concrete deteriorates over time then the infiltration of groundwater to

the pastefill will increase along with the dissolution of metals and carbonates in the

concrete. The Mine Environmental Neutral Damage (MEND) Program Report 10.2

(April 2006) investigates the quality of research on Paste Backfill Geochemistry and the

Environmental Effects of Leaching and Weathering. The report concludes that the

general theories associated with paste backfill characteristics and geochemical

reactivity appear sound, but there is not much field validation on the actual influence of

key parameters. There was little information on the influence of paste backfill on mine

water quality. The report recognised the fact that any backfill has the potential to

generate contaminant plumes in the long term, and potentially influence ground and/or

surface water.


The long term stability and leaching potential of the paste fill should be considered, as

suggested by Dr Hose. As there have been no long term studies of the integrity of

pastefill, this would necessitate monitoring of both pastefill stability and effect on the

pH of the water table beyond the projected lifespan of the project, with a bond in place

to fund on going monitoring and any mitigation measures, if necessary.




pastefill, this would necessitate monitoring beyond the projected lifespan of the project,

with a bond in place to fund on going monitoring and any mitigation measures, if

necessary.




30


Response

The above submissions raise two issues, namely the long-term integrity of the paste fill and the

impact on groundwater quality in the event that the paste degrades.

In relation to the first issue, namely the long-term integrity of the paste fill, the Proponent

contends that there would be no reason why the paste fill would degrade with time as it would

not be subject to weathering, attack by acidic chemicals or natural degradation of the cement

binder. In addition, paste itself is primarily composed of ground granodiorite that is more than

400 million years old and is unlikely degrade. As a result, the stability of the filled voids would

not be adversely impacted even in the highly unlikely event of partial degradation of the cement

binder.

In relation to the second issue, namely the impact on groundwater quality in the unlikely event

that the paste fill does degrade, the Proponent notes that leachate testing of the tailings material

was completed on unbound material. This allowed the leaching solution to access the largest

possible surface area of the tailings material and presents a worst case scenario for leaching of

contaminants. As a result, the Proponent contends that the results presented in RWC (2012)

present the worst-case leachate quality that would result from the complete degradation of the

paste.

3.7 ISSUE F – ASSESSMENT OF THE APPLICATION

Will the Department itself be scrutinizing the claims made in the proposed modification

and involve itself directly in addressing and responding to the questions and concerns

expressed in the submissions it receives or will it be relying on the assessment and

responses of the proponent?

Submission No. 002 - Cormick

Response:

This is a matter for the Department of Planning and Infrastructure. However, the Proponent

anticipates that the Department’s standard assessment procedures will be implemented.

3.8 ISSUE G – EUROBODALLA RESIDENTS AS STAKEHOLDERS

The Moruya Catchment is a major source of Eurobodalla’s water supply, as evidenced

by proceedings initiated in the Land and Environment Court by Eurobodalla Shire

Council against the original DA. The EA for the Project DA acknowledges that the

southern section of the project site occurs within the Moruya catchment. This is why the

Coastwatchers Association recently requested (by email to Sarah Wilson at Planning)

advertisement of this modification for comment in the Eurobodalla newspapers. There

are many Eurobodalla residents who are interested in how this project might affect their

water supply, especially those who live along the Deua and Araluen rivers. As this

request was refused, only a small fraction of stakeholders would have seen the advert in

the Braidwood Times.





31

Response:

This is a matter for the Department of Planning and Infrastructure. However, the Proponent

notes that advertising of the proposed modification was undertaken in a manner that was

consistent with that implemented for the original application. In addition, advertising in

Eurobodalla, located approximately 80km downstream of the Project Site, would, in the

absence of a likely environmental impact, be highly unusual.

3.9 ISSUE H – CONCLUDING COMMENTS

A number of the submissions provided a range of concluding or summary comments. This sub-

section provides brief responses to each of those comments, where relevant.

Approval dependent upon the monitoring and testing arrangement in place for the

tailings material be directly applied to the pastefill material.


Response:

The Proponent anticipates that the Water Management Plan will be required to be revised

should approval for the proposed modification be granted.

Recognition that the pastefill has the potential to generate contaminant plumes in the

long term, and potentially influence ground and/or surface water thus the rehabilitation

and long term monitoring be adjusted to reflect this.


Response:

RWC (2012) examined this issue in detail and concluded that the proposed modification would

be unlikely to result in adverse impacts on groundwater or surface water. However, in

recognition of the modified nature of the Project, the Proponent anticipates that the Water

Management Plan will be required to be revised should approval for the proposed modification

be granted.

and the Proponent contends that the existing monitoring regime would be largely capable of

detecting any adverse impacts should they occur.

3. Any alteration to the pastefill recipe to meet altered stope requirements be subject to

independent testing prior to alteration.


Response:

The Paste fill “recipe” comprises ground rock, cement and water. This is unlikely to change.



32


Inclusion, by the Department of Planning, of Eurobodalla residents as regional

stakeholders. This should be through adverts in the Eurobodalla local newspapers that

inform of the opportunity to comment on proposed changes to the approved Major

Project Application.


Response:

This is a matter for the Department of Planning and Infrastructure, however, the Proponent

contends that the inclusion of Eurobodalla Shire Council on the DRCCC already acknowledges

the residents of the Shire as stakeholders.

Inclusion of data on the expected long term stability of the pastefill in the EA.


Response:

The Proponent contends that there is no reason why the paste fill would degrade with time.

Continuous testing for possible contaminant leaching over time


Response:

The Proponent contends that this is a matter more appropriately dealt with via the relevant

management plans. However, continuous monitoring is unlikely to be required or provide

benefits over periodic monitoring at suitable intervals.

Inclusion of consideration of the buffering capacity of the groundwater to cope with the

predicted change in pH in the EA


Response:

This issue has been discussed in Section 2.4.

Continuous sampling and assessment of the pastefill material as it is produced so that

there is little risk of leaching of toxics into groundwater. Details about how this will

happen need to be specified .


Response:

This is an operational matter, however, continuous monitoring of a homogenous material is

unlikely to provide any benefits over periodic monitoring. The Proponent would, however,

undertake periodic testing of paste produced for its own internal management purposes.




33

Results from testing in points 3 and 5 be made available to the community on the

Company web site within 28 days.


Response:

The Proponent notes that making monitoring data available on the Project website is already a

requirement of PA 10_0054.

That the pastefill contain no more than 1% Xanthate, or its breakdown products.


Response:

This issue has been addressed previously. In addition, imposition of such a requirement

without evidence related to how the figure was determined and the seriousness of any impacts if

it were would not be standard practice.

That the xanthate and breakdown content of the paste fill be tested weekly, and the

results made public on the Cortona web site, as well as the register of concerned public

downstream (which has yet to be put into place by Cortona), within 28 days of such

testing.


Response:

This issue has been addressed previously. In addition, the Proponent contends that this is a

matter more appropriately dealt with via the relevant management plans.

That any spillage of paste fill, or it’s components, must be reported to downstream

residents as soon as possible, and no later than within six hours for residents who use

the water directly downstream for drinking and household use and irrigation.


Response:

As the paste plant would be within the larger processing plant and measures are already

identified to prevent and manage spills of hydrocarbons, reagents or tailings, there is no need

for further measures.

Autopsies of dead fish or amphibians within 10 km downstream of the Project, or where

more than one animal that drinks water from up to 10 km downstream has died from no

apparent cause. These autopsies must be conducted within one week of samples being

provided.




34


Response:

The Proponent has already committed to regular stream health assessments using the

AusRIVAS methodology and contends that further assessment is not required.

A specified testing regime be put into place to determine any increased alkalinity of the

ground or surface water, with remediation to take place within 28 days if a rise in

alkalinity is detected. These results should also be made available on the website and

register. This must be combined with specified remediation measures to be put into

place within 28 days of any rise in the pH.


Response:

The existing Water Management Plan includes a requirement to test the pH of both

groundwater and surface water within and surrounding the Project Site and make those results

available on the Project’s website. In addition, the Proponent anticipates that the Water

Management Plan will be required to be revised should approval for the proposed modification

be granted.



pastefill, this would necessitate monitoring of both pastefill stability and effect on the

pH of the watertable beyond the projected lifespan of the project, with a bond in place

to fund on going monitoring and any mitigation measures, if necessary.


Response:

This issue has been addressed in Section 2.6.

That the pastefill contain no more than 1% Xanthate, or its breakdown products.

That the xanthate and breakdown content of the paste fill be tested weekly, and the

results made public on the Cortona web site, as well as the register of concerned public

downstream (which has yet to be put into place by Cortona), within 28 days of such

testing.

That any spillage of paste fill, or it’s components, must be reported to downstream

residents as soon as possible, and no later than within six hours for residents who use

the water directly downstream for drinking and household use and irrigation.

Autopsies of dead fish or amphibians within 10 km downstream of the Project, or where

more than one animal that drinks water from up to 10 km downstream has died from no

apparent cause. These autopsies must be conducted within one week of samples being

provided. Preferably, an independent body would take such samples and collect the

subject for autopsy, but as in all recent incidents government authorities have no

responded within three weeks in this area to reported spillages, it is unlikely that they

would respond quickly enough for valid samples to be taken.




35

A specified testing regime be put into place to determine any increased alkalinity of the

ground or surface water, with remediation to take place within 28 days if a rise in

alkalinity is detected. These results should also be made available on the website and

register. This must be combined with specified remediation measures to be put into

place within 28 days of any rise in the pH.



pastefill, this would necessitate monitoring beyond the projected lifespan of the project,

with a bond in place to fund on going monitoring and any mitigation measures, if

necessary.


Response:

Each of these issues has been addressed in the response to Submission No. 004 – French.

4. AD D I T I O N AL C OM M I TM EN TS

Table 3 presents an additional commitment that the Proponent would be willing to insert into

the Statement of Commitments presented in Appendix 7 of the revised Project approval, should

it be granted.

Table 3 Additional Commitment for Inclusion in Statement of Commitments

Desired Outcome Commitment Timing

Groundwater

Ensure that the properties of the paste are appropriately understood and managed

6.13 Undertake further testing of the tailings material to confirm the results of test work undertaken prior to the commencement of mining operations and the proposed paste fill operational, management and mitigation measures

Following commencement of processing operations and prior to the commencement of paste fill operations.



36


5. R E F E RE N C ES

Revell (2010). Dargues Reef Paste Fill Testwork and Design (P147-R01), Report prepared for

Big Island Mining Pty Ltd dated October 2010.

R.W. Corkery & Co. Pty Limited (2010a). Environmental Assessment for the Dargues Reef

Gold Project, Major Project Application No. PA10_0054. Report prepared for Big

Island Mining Pty Ltd. September 2010.

R.W. Corkery & Co. Pty Limited (2010b) – Response to Government Agency and Public

Submissions for the Dargues Reef Gold Project, Major Project Application No.

PA10_0054. Report prepared for Big Island Mining Pty Ltd. December 2010.

R.W. Corkery & Co. Pty Limited (2012). Modification Environmental Assessment for the

Dargues Reef Gold Project, Major Project Application No. PA10_0054. Report

prepared for Big Island Mining Pty Ltd.




37

(Total No. of pages including blank pages = 88)

Appendix 1 Dargues Reef Paste Fill Testwork and Design

Appendix 2 Backfill Specialists Capability Statement

Appendix 3 MSDS – Portland Cement



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A1-1

Appendix 1

Dargues Reef Paste Fill Testwork and Design

Dated October 2010 and updated June 2012




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Appendix 3

MSDS – Portland Cement




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Documents

for the Dargues Reef Gold Project Modification 1 · Following public exhibition of the Environmental Assessment for the proposed Dargues Reef Gold ... consolidated set of responses