Waste Rock Management Plan
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Environmental Department
Environmental Management Plan
Waste Rock
Edition
1
2
Revision
Rev 0
Rev 1
Author
S. Haures
R W Corkery & Co
Pty Limited
Kay Oxley
Document Control
Comment
Initial document
Peer review and
update
Date
22/11/2012
Authorised by
S Haures
DISTRIBUTION: YTC Resources Hera Site records & YTC Resources Orange Office.
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Page Number
CONTENTS
Introduction ......................................................................................................................................... 5
1.
Approved activities ................................................................................................................... 5
2.
Consultation .............................................................................................................................. 8
3.
Environmental management..................................................................................................... 8
4.
3.1
legal and other requirements.......................................................................................... 9
3.2
objectives and outcomes .............................................................................................. 10
3.3
roles and responsibilities ............................................................................................. 10
3.4
competence and awareness training ........................................................................... 11
Implementation of waste rock management measures ......................................................... 11
4.1
introduction ................................................................................................................... 11
4.2
waste rock balance ....................................................................................................... 11
4.3
waste rock management ............................................................................................... 13
4.3.1 waste rock characterisation procedures ............................................................ 13
4.3.2 stockpiling of waste rock .................................................................................... 16
4.3.3 management of acid-formation ........................................................................... 17
4.3.4 placement of potential acid-forming waste rock placement underground ....... 19
4.3.5 non acid-forming waste rock .............................................................................. 20
5.
Monitoring of acid-forming material ....................................................................................... 20
6.
Review and compliance .......................................................................................................... 21
7.
6.1
evaulation of compliance .............................................................................................. 21
6.2
corrective and preventative measures ......................................................................... 21
6.3
incident reporting .......................................................................................................... 22
6.4
review ............................................................................................................................ 22
References .............................................................................................................................. 23
Figures
Figure 1
Locality ............................................................................................................................ 6
Figure 2
Approved Activities......................................................................................................... 7
Figure 3
Underground Material Handling Flowsheet ................................................................. 15
Figure 4
Proposed Design for the Waste Rock Emplacement Area .......................................... 18
Figure 5
Cross Section of Potentially Acid Forming Waste Rock Emplacement Area ............. 19
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Tables
Table 1
Project Approval Conditions .......................................................................................... 9
Table 2
Objectives and Outcomes............................................................................................. 10
Table 3
Roles and Responsibilities ........................................................................................... 10
Table 4
Waste rock balance ...................................................................................................... 12
Table 5
Waste Rock Classification ........................................................................................... 16
Table 6
Parameters and Frequency for Monitoring of Sulfides in Core and Rock-chip
Samples ................................................................................................................................... 20
Table 7
Parameters and Frequency for Monitoring of Water Quality in the Leachate Dam ... 21
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INTRODUCTION
The Hera Mine site (Mine) is located approximately 100km southeast of Cobar and approximately 4km south of the
village of Nymagee (Figure 1). The Mine is an underground mine with an expected operational life of nine years.
This Waste Rock Management Plan (WRMP) has been prepared to comply with Condition 3(43) of Project Approval
10_0191 which was granted on 31 July 2012 by the Director-General of the Department of Planning and
Infrastructure in accordance with the Environmental Planning and Assessment Act 1979. The purpose of this
WRMP is to:
•
Provide employees and contractors with a clear and concise description of their responsibilities in
relation to waste rock management during the operations of the mine.
•
1.
Address the relevant commitments made within the environmental assessment.
APPROVED ACTIVITIES
Hera Resources is to establish an underground mine, processing plant, run-of-mine (ROM) pad, temporary waste
rock emplacement, tailings storage facility, mine camp, site offices and ancillary infrastructure for mining and related
activities.
The operational life of the mine is expected to total nine years, comprising 1.5 years of site establishment activities,
5.5 years of mining and processing operations and 2 years of rehabilitation operations.
The following activities have approval under the Project Approval (Figure 2).
•
Extraction of a maximum of 355 000t per annum of ore using an underground sublevel open stope
mining method.
•
Construction and use of a surface facilities area that would incorporate a range of approved
infrastructure including expanded Hera Resources and contractors’ site offices, ablutions facilities,
vehicle parking, power station, fuel storage, refuelling area, workshop and laydown areas.
•
Construction and use of a processing plant within the surface facilities area comprising crushing
and grinding, gravity, separation, flotation, leach and gold recovery circuits and ancillary
infrastructure.
•
Construction and use of a tailings storage facility.
•
Construction of a mine camp to house up to 80 personnel.
•
Construction and use of a surface water harvesting system, including expansion of an existing dam
(Pete's Tank) to 20ML capacity and construction of a new 90ML capacity dam (Back Tank East).
•
Construction of a water reticulation system that would connect the surface water storage dams and
existing production bores with the raw water dam and the mine camp.
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Locality
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Approved Activities
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Construction and use of the mine site access road and the associated intersection to allow site
access from Burthong Road.
•
Transportation of bulk concentrate from the Mine site to customers using the surrounding public
road network.
•
Construction and use of ancillary infrastructure, including soil stockpiles, core storage yards,
internal roads and tracks, and sediment and erosion management structures not already approved.
In addition, YTC Resources holds approval under Exploration Licence 6162 to construct a range of infrastructure,
including an exploration decline and ancillary infrastructure (the Part 5 Approval). Those works are fully described in
the Review of Environmental Factors (REF) titled “Exploration Decline at the Hera Deposit within Exploration
Licence 6162, via Nymagee” dated December 2006 and approved by the Department of Primary Industries on
2 April 2007.
That document includes a range of approved management plans that are to apply to all work
undertaken under the Part 5 Approval.
Condition 2 (13) of the Project Approval states the following:
“Until they are replaced by an equivalent strategy, plan or program approved under this approval, the
Proponent shall implement the existing strategies, plans or programs for the site that have been approved
under the approved exploration activities described in Review of Environmental Factors (REF) entitled
“Exploration Decline at the Hera Deposit within Exploration Licence 6162”.
This WRMP replaces the existing waste rock management strategies documented in the REF and approved under
the Part 5 Approval.
2.
C O N S U LTAT I O N
Condition 3 (43)(a) of Project Approval requires this WRMP to be prepared in consultation with the Environmental
Protection Authority (EPA) and the NSW Office of Water (NOW) prior to being submitted to the Director-General of
the Department of Planning and Infrastructure (DP&I) for approval.
st
An initial draft of this WRMP was provided to the EPA and NOW for their comment and review on 21 November
2012.
st
In a letter received from the EPA on the 21 December 2012 EPA stated that they reviewed the Waste Rock
Management Plan and had identified the Waste Rock Management Plan met the information requirements.
On the 21st June 2013 NOW responded that they are satisfied that the consultation requirements have been met in
respect of the preparation of the Waste Rock Management Plan.
3.
E N V I R O N M E N TA L M A N A G E M E N T
This section describes the legal requirements, objectives and outcomes, the Hera Resources personnel roles and
responsibilities and the necessary training and awareness required to ensure the management of waste rock.
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LEGAL AND OTHER REQUIREMENTS
The Project Approval stipulates the required criteria that the construction and operational activities of the Mine must
comply with and sets out the core requirements of this WRMP. Relevant conditions associated with this approval
are reproduced in (Table 1).
Table 1 Project Approval Conditions
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Waste Rock Management Plan
3(43)
Section
The Proponent shall prepare and implement a Waste Rock Management Plan to the
satisfaction of the Director–General. The Plan must:
(a) Be developed in consultation with the EPA and NOW;
(b) Submitted for the approval of the Director-General within six months of this
approval;
(c) Include a detail description of the procedures to be implemented to monitor and
manage potential acid forming material;
(d) Reflect the groundwater and surface water monitoring programs to monitor the
potential acid-forming waste rock and any leachate generated, including
appropriately designed detection and response systems for acid generation
(covering monitoring methods, trigger levels and proposed management actions);
(e) Ensure effective isolation of potential acid forming material in rock dumps;
(f) Include procedures for appropriate testing of potentially acid forming waste rock
prior to it being bought to the surface;
(g) Include a procedure for prioritising the relocation of potential acid forming material
to a suitable underground location prior to oxidation;
(h) Include procedures to ensure that material relocated underground does not, to the
extent reasonable and feasible, further oxidise or cause impact to groundwater;
(i) Notwithstanding (e) above, trigger levels for any material that has been oxidised to
the extent that it cannot be placed underground without impacting groundwater
quality and procedures for adequate capping and sealing of such material at the
surface;
(j) Detail proposed neutralising options to be implemented for oxidising material stored
or encapsulated aboveground; and
(k) Where there is unlikely to be an extended time between placement of potential acid
forming material underground, details of proposed methods to prevent oxidation of
the material underground or to otherwise manage acid drainage to prevent impacts
on groundwater.
3
3
6
6, 7
5.3
5.3
5.3.4
5.3.5
5.3.5
5.3.5
5
Management Plan Requirements
5(2)
The Proponent shall ensure that the management plans required under this approval are
prepared in accordance with any relevant guidelines, and include:
(a) detailed baseline data;
(b) a description of:
• the relevant statutory requirements (including any relevant approval, licence or
lease conditions);
• any relevant limits or performance measures/criteria;
• the specific performance indicators that are proposed to be used to judge the
performance of, or guide the implementation of, the project or any management
measures;
(c) a description of the measures that would be implemented to comply with the
relevant statutory requirements, limits, or performance measures/criteria;
(d) a program to monitor and report on the:
• impacts and environmental performance of the project;
• effectiveness of any management measures (see c above);
Management Plan Requirements
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6
5
6, 7
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(e) a contingency plan to manage any unpredicted impacts and their consequences;
(f) a program to investigate and implement ways to improve the environmental
performance of the project over time;
(g) a protocol for managing and reporting any:
• incidents;
• complaints;
• non-compliances with statutory requirements; and
• exceedances of the impact assessment criteria and/or performance criteria; and
(h) a protocol for periodic review of the plan.
7
6
7
8
Note: The Director-General may waive some of these requirements if they are unnecessary or unwarranted for
particular management plans.
3.2
OBJECTIVES AND OUTCOMES
The ooverriding oobjective is to prevent production and escape of acid leachate form the stockpiled waste rock.
Table 2 lists the objectives and outcomes for the WRMP.
Table 2 Objectives and Outcomes
Objective
Outcome
Procedures are developed to ensure that potential acid
forming waste rock is identified during ongoing
underground mining operations and is stockpiled in the
appropriate designed temporary potentially acid
forming waste rock emplacement cell.
Procedures for ongoing classification, storage and
disposal of waste rock implemented to prevent acid
mine drainage.
Competence training has been implemented to ensure
relevant employees and contractors manage potentially
acid forming waste rock material appropriately.
Employees and contractors competently trained in
managing potentially acid forming waste rock material.
To ensure that the temporary waste rock cell is
designed to contain and manage any potential acid
rock drainage.
Impact on surface and groundwater is negligible.
To ensure that potentially acid forming material is
relocated to underground voids as soon as available to
prevent further oxidisation of the material.
Potentially acid forming waste rock material is
relocated underground in the shorter term to prevent
ongoing oxidisation of the material.
3.3
ROLES AND RESPONSIBILITIES
Table 3 lists the roles and responsibilities for the WRMP.
Table 3 Roles and Responsibilities
Position
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General Manager
Must ensure adequate resources are available to enable implementation of
this WRMP.
Accountable for the overall environmental performance of the Mine, including
the outcomes of this Waste Rock Management Plan.
Environmental Officer
Ensure the implementation of this WRMP.
Ensure all site personnel are competent through training and awareness
programs.
Conduct surface and ground water monitoring as specified in this
management plan.
Investigate any exceedances in groundwater and surface water quality and
implement the relevant trigger responses if required.
Project Geologist
Ensure potential acid forming waste rock is identified using appropriate
standards.
Ensure the relevant employees and contractors transport and store
potentially acid forming material to the designated storage areas.
3.4
COMPETENCE AND AWARENESS TRAINING
Waste rock awareness training shall be a component of the competency based site induction program. All
personnel will be inducted on the significance of acid mine drainage in the Mine area including the following.
•
Procedures for identifying and classifying potential acid forming material.
•
Procedures for temporarily storing potential acid forming material at surface.
•
Awareness of monitoring requirements.
•
Procedures for relocating potential acid forming material underground as soon as a designated void
area is available.
The Environmental Officer shall be responsible for ensuring the appropriate waste rock training is included in the
induction.
4.
I M P L E M E N TAT I O N O F W A S T E R O C K
MANAGEMENT MEASURES
4.1
INTRODUCTION
Condition 3(43) required this WRMP to include procedures for identification of potentially acid forming waste rock,
isolation during storage in a temporary waste rock emplacement and procedures for relocating back underground.
The following sections provide a description of these procedures to ensure potentially acid forming material is
managed effectively.
4.2
WASTE ROCK BALANCE
The waste rock balance during the life of the Hera mine is presented in Table 4. Hera Resources has updated the
mine plan following submission of the Environmental Assessment document. The current estimates indicate that
3
3
some 250 000m of waste rock would be generated during the life of the mine. Approximately 195 000m of waste
rock would be used during stope backfilling operations. The remainder will be used in construction of the ROM pad,
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access roads and the TSF. As a result, there would be no waste rock surplus during the life of the mine and no
waste rock material excess to construction requirements would remain on the surface at the completion of the
mining activities.
Table 4
Waste rock balance
Volume (m 3)
Item
Source
Usage (Approx)
Box cut, portal and decline
20 000
-
Underground waste rock – Trucked to Surface
160 000
-
Underground waste rock – Used Underground
70 000
Site access roads
-
25 000
ROM pad
-
20 000
Tailings storage facility
-
10 000
Stope backfill – Trucked back into the Mine
-
125 000
Stope backfill – Direct from Underground
Total
70 000
250 000
250 000
The mine plan generated for the Hera deposit results in all waste excess to construction requirements being sent
back underground as part of the fill cycle. The detailed Back Fill Model indicates that during the first 30 months of
the operation all underground waste rock will be transported to the surface. From 30 months – 45 months there is a
requirement to fill underground stopes and this will be done using waste generated underground with only
intermittent transport to the surface, preference will be given to using PAF waste rock over NAF waste rock. Post 45
months from the commencement of mining there will be a requirement to progressively truck the waste rock stored
on the surface back underground. In total it is estimated that of the Underground Mine waste rock generated some
3
160,000 m will be truck to the surface the remainder will be placed into back fill stope directly from the source
underground
Rock and samples from drill core in the vicinity of the proposed exploration decline, boxcut, ventilation rise and the
ore body have been analysed and characterised for acid rock drainage (ARD) potential, specifically to determine the
Net Acid Production Potential (NAPP) and Net Acid Generation (NAG) characteristic (Geoterra (2006); Triako
Resources Limited (2006)).
Conclusions reached on the acid rock generation characteristics from the assessments conducted to date are as
follows.
•
Samples tested showed low acid neutralisation potential.
•
Waste rock from the boxcut, ventilation rises and exploration decline, being predominantly
unweathered siltstone, have low NAPP and NAG values and have been characterised as non-acid
forming to uncertain.
•
The ore body samples or samples acquired close to the ore body are potentially acid forming due to
the sulfide contents of these samples.
Using the ARD assessment of all samples previously analysed it was estimated (Triako Resources Limited 2006)
that approximately 30% of the waste rock recovered during various activities would be Potentially Acid Forming
(PAF) and the remaining approximately 70% would be non-acid Forming. For this management plan Hera
Resources have adopted a more conservative view and have planned to be able to manage up to 60% of the waste
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rock trucked to the surface designated as PAF material. Thus there will be sufficient contingency in the plan to
ensure stockpiling capacity available on the surface to appropriately manage PAF waste rock.
4.3
WASTE ROCK MANAGEMENT
4.3.1
Waste Rock Characterisation Procedures
A mine PAF/NAF model will be developed from existing drilling programs to identify potential high sulphur waste
zones within the designated underground mining area. Additional samples to those collected and analysed by
previous owners Triako Resources have been collected and submitted for NAG Testing (Static Testing).
Net acid generation (NAG) testing determines the balance between the acid producing and acid consuming
components of tailings/waste rock samples. NAG results provide the acid rock drainage characteristics based on
the complete oxidation of the sample’s sulfide content (as well as ferrous iron from siderite dissolution). Acid that is
produced by oxidation is consumed by carbonates and/or other acid consuming components of the material. The pH
of the solution is measured (NAG pH). The acid remaining after the reaction is titrated with standardized NaOH to
determine the net acid generated.
The methodology for characterising the waste rock following the NAG Testing is provided in Table 5.
The dominant sulphide minerals at Hera are as follows:
•
Within Ore Zones are dominantly Galena, Sphalerite with pyyrhotite and minor chalcopyrite
•
Waste zones adjacent the Ore Body (Ore Halo) pyrrhotite, minor galena and sphalerite ± Chalcopyrite
•
Decline Waste Zones are dominantly devoid of sulphides however local fault structures and minor
mineralised zones will be encountered. Locally we may encounter fault zones with minor pyrite.
It should also be noted that sphalerite is non-acid producing, galena is acid consuming. There is a lower relative
acid production potential for arsenopyrite, pyrrhotite and chalcopyrite compared to pyrite. For this reason Hera
Resource will utilise the Static Test results from the additional drillhole samples submitted for analysis combined
with the existing information to enable development of a more definitive Mine PAF/NAF model. This will enable
geological personnel to calibrate the relationship between sulphide species and content of the waste rock and
potential for acid generation on oxidation enabling better visual control on classification of waste rock
Using Kinetic NAG tests on selected samples Hera Resources will quantify the rate at which the different waste
types may begin to oxidise within the stockpile. As the dominant sulphide species at Hera exclude pyrite the rate of
oxidation of the waste rock is expected to be quite slow. The Kinetic Test program will enable Hera Resources to
model waste types based on the rate at which the PAF material is likely to oxidise so as to make more appropriate
stockpile management decisions in respect of how this material is treated to prevent the onset of oxidation.
The process for determining how waste rock mined will be classified and ultimately where the waste rock will be
stored will be the function of the Mine Geological personnel. They will classify material on a mining block basis and
issue instructions to the underground operators was to where this material is to be tipped onto the stockpile
Project Geologists will be trained to identify sulphide zones within the waste material. This process will be validated
by completing Static Tests (NAG) on underground rock chip samples where appropriate. This process of visual
inspection supported by validation through sampling will ensure the Project Geologist will be familiar with the rock
type characterisation techniques for identifying NAF and PAF waste material.
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The decision tree that will be followed by the Mine Geological Personnel is as shown in Figure 3.
Hera Mining Material Handling Flow Sheet
Start
Yes (PAF)
Yes
Is the Rock
Yes Is the
From
Rock
Development
Ore
Yes
No
Stope
Material
Mill Feed
End
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Waste Stockpile
(Cell 2) or
Use Around Site
No (NAF)
Does the Rock
Contain Sulfides
No
Is the
Rock
Possible
Ore
No
Rehandle
Stockpile
PAF Stockpile
Sample
and Assay
Low Grade
Stockpile
Activities Within The PAF
Stockpile Area (Cell 1)
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Underground Material Handling Flowsheet
A Mine Fill Schedule has been developed to determine the timeframe of the availability of underground void areas
for permanent storage of PAF waste rock. It is on the basis of this model that PAF material located in surface
stockpiles will be preferentially used as fill material in underground stopes. Where practicable underground stopes
will be capped with NAF material and compacted with underground mining equipment. PAF material generated
underground that is not ore bearing will be immediately placed into empty stopes where available although it is
anticipated that for at least the first 2 years of mining this material will need to be hauled to the surface. If no space
is available in stopes the PAF material will be placed in temporary stockpiles underground or transported to the
surface and placed in the WREA as per this management plan.
Table 5 presents the classification of waste rock and the relevant procedures and mitigation measures for location
of temporary storage above ground and the relocation of potentially acid forming material underground when
possible.
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Waste Rock Classification
Waste Rock Classification
Management Procedures
Coded: Green Material
Stored in temporary waste rock emplacement Cell No. 2
for general construction, fill and rehabilitation works.
Non Acid Forming l (NAF)
pH>4 from Static Tests for NAPP.
No sulphide reactivity.
Coded: Yellow Material
Potentially Acid Forming – Low Capacity (PAF LC)
pH<4 but not lower than pH3 from Static Tests for
NAPP.
Low Risk
Stored in temporary waste rock emplacement Cell No. 1
on outer edge area. Relocate underground in area
(when available) that will be saturated by groundwater
1
following completion of mining .
Coded: Red Material
Stored in the centre of temporary waste rock
emplacement Cell No. 1. Relocate underground in area
(when available) that will be saturated by groundwater in
the early years following completion of mining1.
This material may be covered by NAF material while in
the aboveground temporary storage facility to minimise
oxidation rate
Potentially Acid Forming (PAF)
pH<3.
High Risk
1.
Storing of potential and acid forming material below waterline in an anaerobic environment eliminates the
potential for further oxidisation.
Source:
Environment Australia, Managing Sulphidic Mine Wastes and Acid Drainage.
Following the completion of mining activities the groundwater level will be allowed to inundate the mine workings.
This will eliminate the availability of oxygen preventing oxidisation of the potential acid forming material for the long
term.
4.3.2
Stockpiling of Waste Rock
The temporary waste rock emplacement will be designed and constructed to contain the estimated volumes of PAF
and NAF material and enable appropriate sorting as required. The design will aim to minimise acid generation and
prevent the discharge of any low pH leachate formed.
The waste rock emplacement for all material stored from underground will have the following design components:
•
Area of approximately 2.6ha divided into two cell areas, Cell No. 1 (PAF) and Cell No. 2 (NAF),
ROM pad and Low Grade Stockpile
•
Capacity – approximately 200 000m3.
•
Maximum elevation – approximately 10m higher than the existing surface.
•
Outer slope – approximately 45o.
Additionally, the potentially acid-forming Cell No. 1 area will be constructed in a manner that would prevent
potentially acidic leachate from being discharged. In summary, this would include the following design parameters
(see Figure 3, Figure 4 and Figure 5).
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The footprint of the cell will graded and compacted to between 1 to 2% slope towards the WREA
leachate dam to ensure no pooling of water internally and to minimise infiltration into soils within the
waste rock emplacement footprint.
•
The footprint of the Stockpile area will have the topsoils and subsoil removed
•
The footprint of the PAF cell will be made from compacted NAF material to an appropriate depth
•
A bund will be constructed around the perimeter of the PAF cell to capture and divert any potentially
acidic leachate to the WREA leachate dam and to divert any other surface water away from the cell.
•
4.3.2.1
The low-grade and rehandle stockpiles will be located within Cell 1
PAF WREA Leachate Dam and Internal Drains
A WREA Leachate Dam and perimeter drains will be constructed and maintained to ensure any potential acid
leachate is contained within the PAF WREA footprint as follows.
•
To ensure no discharge from the dam during heavy rainfall events, the maximum filling point for the
dam is 870mm below the top of the dam wall, comprising an allowance of 170mm for incident
rainfall1 and 700mm freeboard. The maximum filling point will be marked by a peg and water
levels, in the absence of rainfall input, will not be permitted to rise above this point.
•
The WREA Leachate Dam will be constructed to hold 1.2ML of runoff from the PAF WREA, which
will cater for a 1 in a 100 year rainfall event.
•
The WREA Leachate Dam will be lined with High Density Polyethylene (HDPE)
•
The WREA Leachate Dam will be inspected monthly and after significant rainfall (>12mm). If any
remedial action is required (e.g. pumping, repair) it will be logged and recorded in the Annual
Environmental Management Report.
•
Water from the Leachate Dam will be transferred to the PWD and used for processing.
•
Water levels will be measured and recorded in the Annual Environmental Management Report.
•
Water will be tested on field for pH and Electrical Conductivity (EC) on a monthly basis
•
Water samples will be collected on a monthly basis or prior to being pumped to the PWD, and sent
to the laboratory for analysis (Parameters listed in Table 7).
Figure 5 shows a cross section of the PAF WREA.
4.3.3
Management of acid-formation
As discussed in Section 5.3.1 potentially acid forming material will be graded either as Yellow Material with a NAF
pH less than 4 but not lower than pH 3 or Red Material that has potentially a NAF pH of less than 3. These
materials will be stored within Cell No 1 of the designated WREA. Red material will be stored in the centre of the
cell encompassed by the Yellow material to minimise the surface area that will be exposed to air.
1
The 72-hour 100 year rainfall depth
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The rehandle stockpile and the low-grade stockpile will be located within the PAF Cell. The approximate locations of
these stockpiles are shown in Figure 4.
During the storage phase, prior to backfill underground requirements and the transport of these materials
underground, the following mitigation measures will be implemented.
•
Minimise infiltration of water within the WREA stockpiles by levelling and track rolling the surface of the
stockpiles on a regular basis.
•
If required grading the surface may be undertaken to ensure water runs of the surface and does not pool
on the PAF material
•
Covering with compacted NAF waste rock in completed stockpile areas to reduce infiltration of water and
oxygen.
•
Monitoring of sulphur oxidation will be undertaken prior to underground emplacement to determine rate of
oxidation. The primary method will be via the visual inspection and monitoring of acidity of any runoff or
leachate from the PAF cell
•
Preferential placement underground will be given to Red material, or as a result of monitoring, other
material that has been identified with potential higher sulphur reactivity.
The management of highly oxidised PAF waste rock is discussed in the following section.
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Figure 4
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Proposed Design for the Waste Rock Emplacement Area
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Figure 5
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Cross Section of Potentially Acid Forming Waste Rock Emplacement Area
Placement of Potential acid-forming waste rock placement underground
As previously described in Section 5.3.1 potentially acid forming material will be backfilled into underground void
areas that will be saturated with ground water following the completion of mining. It is anticipated that these areas
will become available within the third year of mining.
Placement underground will be in stopes that are to be filled with loose rock fill and cemented rock fill. The
cemented rockfill stopes will utilise waste rock that has up to 8% cement added as a binder to make the fill stable to
enable extraction of adjacent panels. The addition of the cement to the rock material will act in two ways. Firstly it
will act as a buffer to any acid produced form the material and secondly to act as a coating to the rocks to prevent
further oxidation. The cement has inherent neutralising capacity on PAF material (Department of Industry and
resources, 2007). Hera Resources will conduct leach column tests on PAF material to confirm that the additions of
cement are sufficient to buffer any potential net acid generation from varying waste types.
•
Prior to the placement of material underground, inspection of the waste rock will be made to estimate the
degree of oxidation that may have occurred. Preference for PAF material that is showing signs of oxidation
will to place within the cemented backfill stopes
•
In the event that significant oxidation has occurred then a risk assessment will be completed to ensure
appropriate remediation of the material is made by treating with crushed limestone prior to placement or by
encapsulating in compacted NAF or oxidised fill in the surface stockpile. The risk assessment will consider
the implications of both surface and underground disposal and the implications on groundwater.
•
If required, potential surface PAF wasterock emplacements may include storage within the existing Tailings
Storage Facility following drying of tailings.
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Non acid-forming waste rock
Waste rock material excavated and placed within the temporary waste rock emplacement will initially be ‘paddock
dumped’ in the Cell No. 2 in layers of approximately 3m high. Once the initial waste rock material has been
emplaced, further material will be emplaced using either ‘paddock dumping’ or ‘face tipping’ methods.
Where appropriate, non-acid forming waste rock will be transported directly to other sections of the Hera Mine for
infrastructure establishment including the TSF, site access roads and tracks and, if required, proposed hard stand
areas. The waste rock may be crushed prior to use in construction activities.
Waste rock not required for surface infrastructure or for rehabilitation purposes will be reclaimed and transported
back underground.
5.
M O N I T O R I N G O F A C I D - F O R M I N G M AT E R I A L
Monitoring of surface water and groundwater will be undertaken in order to determine whether mine activities are
causing adverse impacts upon the surrounding environment. Water will be sampled for specific parameters (Refer
to Table 7) and assessed over time and reported in the Annual Environmental Management Report.
In summary, monitoring for the WREA and potential leachate includes the following.
•
Water quality monitoring and visual inspections for the WREA leachate dam will be undertaken
monthly during the life of the emplacement to identify any issue with the proposed management
measures.
•
Visual inspections of underground PAF emplacement cells and water quality monitoring if seepages
are detected.
Water quality in the nearby groundwater bores is monitored monthly for pH and EC and water samples are collected
on a quarterly basis and analysed in a NATA Accredited Laboratory. If water is present in the Leachate Dam a
water sample will be collected prior to the water being pumped to the Process Water Dam (PWD) and sent to a
NATA accredited laboratory.
The initial drilling program into the ore body will identify potential high sulphur waste zones within the designated
underground mining area; this will be confirmed via chip-rock samples collected from the underground wall face.
The core from the drilling program and the chip-rock samples will be analysed using Static Tests for the compounds
in Table 6.
Table 6
Parameters and Frequency for Monitoring of Sulfides in Core and Rock-chip
Samples
Parameter / Test
NAG Static Test,
Kinetic NAG
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As required during the drilling
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Table 7
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As required at the Underground
face wall
Parameters and Frequency for Monitoring of Water Quality in the Leachate Dam
Physical and Chemical Stressors
Frequency
pH
Electrical conductivity
Total Suspended Solids
Metals
aluminium
arsenic
zinc
Monthly or prior to water
being pumped to the PWD
copper
lead
silver
nickel
boron
manganese
cadmium
6.
REVIEW AND COMPLIANCE
6.1
EVAULATION OF COMPLIANCE
Hera Resources will conduct periodic evaluation of compliance with the following reported within the Annual
Environmental Management Report.
•
An overview of waste rock extracted from the underground mine.
•
On overview of the amount of potential acid-forming waste rock extracted and the procedures
implemented to ensure emplacement in designated areas.
•
Results from waste rock and water samples.
•
Actions undertaken, if required, to ensure potential acid-forming waste rock material does not
impact on water quality in the surrounding area.
6.2
CORRECTIVE AND PREVENTATIVE MEASURES
YTC will implement the necessary surface water and groundwater trigger responses in the event that water quality
criteria are exceeded. Full details of the responses are described in the Water Management Plan.
In summary, the following will be implemented.
•
Arrange for further sampling to confirm initial monitoring results.
•
If exceedances are confirmed and in consultation with the relevant government agency, implement
the necessary containment and neutralising measures to ensure impacts are minimised.
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Re-evaluate the containment of potentially acid forming material and determine the measures to be
implemented to further prevent any potential discharges of acid leachate.
6.3
INCIDENT REPORTING
All reports associated with contamination of groundwater will be provided within 7 days to the EPA and other
agencies as required and will be retained for a minimum of four years.
All incidents will be reported in the Annual Environmental Management Report.
6.4
REVIEW
In accordance with Condition 5 (5) of Project Approval, this WRMP will be reviewed and, if required, revised within 3
months of:
•
the submission of an annual review under Condition 5(4);
•
the submission of an incident report under Condition 5(7);
•
the submission of an independent audit report under Condition 5(9); and
•
any modification to the conditions of Project Approval.
This review will include the adequacy of strategies, plans and programs as required under the Project Approval.
Recommendation for appropriate measures or action to improve the environmental performance of the Mine and or
any assessment, plan or program will be incorporated into this WRMP.
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REFERENCES
Department of Industry Tourism and Resources, Leading Practice Sustainable Development program for the Mining
Industry, Managing Acid and Metalliferous Drainage, 2007
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