PROJECT: VOORSPOED MINE PIT CLOSURE STUDY · PROJECT: VOORSPOED MINE – PIT CLOSURE STUDY...
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PROJECT: VOORSPOED MINE – PIT CLOSURE STUDY
Date: Technical Memo submitted: 25 November 2015
Final Document submitted: 21 June 2016
To: Hans Kgasago
Company: Voorspoed Mine
Client P/O 41006144750
From: E-TEK Consulting & Redco
Project No: E-TEK :187.3
Report number: E-TEK 10079
7 Solomon Str, Potchefstroom, 2531
PO Box 19144, Noordbrug, 2522
Tel office: +27 18 294 3652
Mobile: +27 83 446 6154
E-mail: [email protected]
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TABLE OF CONTENTS
1. PURPOSE OF DOCUMENT ........................................................................................................................ 6
2. BACKGROUND ........................................................................................................................................... 6
3. SCOPE OF WORK ....................................................................................................................................... 7
4. ALTERNATIVES CONSIDERED ................................................................................................................. 7
5. DISCUSSION AND CLARIFICATION OF ALTERNATIVES ...................................................................... 8
5.1. BASIS OF ESTIMATE FOR THE COSTING OF SCENARIOS ......................................................... 8
5.2. SCENARIO 1: RESOURCE COVER, CONCRETE WALL AND ENVIROBERM .............................. 8
5.2.1. Specifications ......................................................................................................................... 8
5.2.2. Cost: Scenario 1 ................................................................................................................... 11
5.2.3. Feasibility / construction risks ............................................................................................... 12
5.2.4. Water balance ...................................................................................................................... 13
5.3. SCENARIO 2: RESOURCE COVER, RESHAPE TOP BENCH TO 18°, CONCRETE WALL AND ENVIROBERM ........................................................................................................................................... 14
5.3.1. Specifications ....................................................................................................................... 14
5.3.2. Cost: Scenario 2. .................................................................................................................. 17
5.3.3. Feasibility / construction risks ............................................................................................... 17
5.3.4. Water balance ...................................................................................................................... 18
5.4. SCENARIO 3: PARTIAL IN-FILL – ANGLE OF REPOSE, CONCRETE WALL AND ENVIROBERM ........................................................................................................................................... 19
5.4.1. Specifications ....................................................................................................................... 19
5.4.2. Cost: Scenario 3 ................................................................................................................... 21
5.4.1. Feasibility / construction risks ............................................................................................... 21
5.4.2. Water balance ...................................................................................................................... 22
5.5. SCENARIO 4: PARTIAL IN-FILL – RESHAPED TO 18°, CONCRETE WALL AND ENVIROBERM ........................................................................................................................................... 22
5.5.1. Specifications ....................................................................................................................... 22
5.5.2. Cost: Scenario 4 ................................................................................................................... 25
5.5.3. Feasibility / construction risks ............................................................................................... 25
5.5.4. Water balance ...................................................................................................................... 26
5.6. SCENARIO 5: RESOURCE COVER, CONCRETE WALL, ENVIROBERM AND OPTIMISE CATCHMENT ............................................................................................................................................. 26
5.6.1. Specifications ....................................................................................................................... 26
5.6.2. Cost: Scenario 5 ................................................................................................................... 29
5.6.3. Feasibility / construction risks ............................................................................................... 29
5.6.4. Water balance ...................................................................................................................... 30
5.7. SCENARIO 6: COMPLETE IN-FILL WITH ALL AVAILABLE MRD MATERIAL .............................. 31
5.7.1. Specification ......................................................................................................................... 31
5.7.2. Cost: Scenario 6 ................................................................................................................... 33
5.7.3. Feasibility / construction risks ............................................................................................... 33
6. BENEFICIAL LAND USE OF THE FARM INCLUDING THE OPEN PIT ................................................. 34
7. ENHANCED SCENARIO 7: ALTERNATIVE LAND USE OF THE PIT .................................................... 35
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7.1. SCENARIO 7: RESOURCE COVER, ACCESS ROUTE, FENCE, ENVIROBERM AND OPTIMISE CATCHMENT ............................................................................................................................................. 35
7.1.1. Specifications ....................................................................................................................... 35
7.1.2. Cost: Scenario 7 ................................................................................................................... 38
7.1.3. Feasibility / construction risks ............................................................................................... 38
7.1.4. Water balance ...................................................................................................................... 39
8. RISK ASSESSMENT AND COST-BENEIFT ANALYSIS ......................................................................... 39
8.1. METHODOLOGY AND APPROACH ............................................................................................... 39
8.2. OUTPUTS OF RISK ASSESSMENT................................................................................................ 40
9. STANDARD OPERATING PROCEDURE FOR SITE-WIDE CLOSURE .................................................. 47
ANNEXURE A: RISK ASSESSMENT AND COST-BENEFIT ANALYSIS ..................................................... 48
ANNEXURE B: STANDARD OPERATING PROCEDURE FOR CLOSURE ................................................. 49
ANNEXURE C: PRESENTATION OF OPEN PIT CLOSURE SCENARIOS AND COSTS ............................ 50
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FIGURES
Figure 1: Model of the final pit and waste rock dump at life of mine ...........................................................................6
Figure 2: Typical details of the reinforced concrete wall and enviroberm .................................................................10
Figure 3: Scenario 1 – Layout illustrating the concepts (no water) ...........................................................................10
Figure 4: Scenario 1 – Cross section A-A indicates the concepts and estimated pit lake level, NGL and ZOR .......11
Figure 5: Scenario 1 – Cross section B-B indicates the concepts and estimated pit lake level, NGL and ZOR .......11
Figure 6: Modelled rate of rise of the pit lake (108 ha catchment) ............................................................................14
Figure 7: Scenario 2 – Layout illustrating the concepts (no water) ...........................................................................15
Figure 8: Scenario 2 – Layout after filling with water ................................................................................................16
Figure 9: Scenario 2 – Cross section A-A indicates the concepts and estimated pit lake level, NGL and ZOR .......16
Figure 10: Scenario 2 – Cross section B-B indicating the concepts and estimated pit lake level, NGL and ZOR ....17
Figure 11: Scenario 3 – Layout illustrating the concepts (no water) .........................................................................20
Figure 12: Scenario 3 – Layout after filling with water ..............................................................................................20
Figure 13: Scenario 3 – Cross section A-A indicating the concepts and estimated pit lake level, NGL and ZOR ....21
Figure 14: Scenario 3 – Cross section B-B indicating the concepts and estimated pit lake level, NGL and ZOR ....21
Figure 15: Scenario 4 – Layout illustrating the concepts (no water) .........................................................................23
Figure 16: Scenario 4 – Layout after filling with water ..............................................................................................24
Figure 17: Scenario 4 – Cross section A-A indicating the concepts and estimated pit lake level NGL and ZOR .....24
Figure 18: Scenario 4 – Cross section B-B indicating the concepts and estimated pit lake level, NGL and ZOR ....25
Figure 19: Scenario 5 – Layout illustrating the concepts (no water) .........................................................................27
Figure 20: Scenario 5 – Layout after filling with water ..............................................................................................28
Figure 21: Scenario 5 – Cross section A-A indicating the concepts and estimated pit lake level, NGL and ZOR ....28
Figure 22: Scenario 5 – Cross section B-B indicating the concepts and estimated pit lake level, NGL and ZOR ....29
Figure 23: Modelled rate of rise of the pit lake (increased catchment to 180 ha) .....................................................31
Figure 24: Scenario 6 – Layout illustrating the concepts ..........................................................................................32
Figure 25: Scenario 6 – Cross-section A-A indicating the concepts .........................................................................32
Figure 26: Scenario 6 – Cross-section B-B indicating the concepts .........................................................................33
Figure 27: Scenario 7 – Layout illustrating the concepts (no water) .........................................................................36
Figure 28: Scenario 7 – Layout after filling with water ..............................................................................................37
Figure 29: Scenario 7 – Cross section A-A indicating the concepts and estimated pit lake level, NGL and ZOR ....37
Figure 30: Scenario 7 – Cross section B-B indicating the concepts and estimated pit lake level, NGL and ZOR ....37
Figure 31: Risk summary for Accessibility to the Open pit ........................................................................................41
Figure 32: Risk summary for Open pit sidewall stability ...........................................................................................42
Figure 33: Risk summary for impact on Water resources .........................................................................................43
Figure 34: Risk summary for impact on Land capability and End land use ..............................................................44
Figure 35: Risk summary for impact on Natural resources .......................................................................................45
Figure 36: Risk summary for impact associated with Government and stakeholders ..............................................46
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TABLES
Table 1: Scenario 1 – Detail of cost estimate. ..........................................................................................................12
Table 2: Scenario 2 – Detail of implementation cost estimate ..................................................................................17
Table 3: Scenario 3 – Detail of cost estimate. ..........................................................................................................21
Table 4: Scenario 4 – Detail of cost estimate. ..........................................................................................................25
Table 5: Scenario 5 – Detail of cost estimate. ..........................................................................................................29
Table 6: Scenario 6 – Detail of cost estimate. ..........................................................................................................33
Table 7: Enhanced Scenario 7 – Detail of cost estimate. .........................................................................................38
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1. PURPOSE OF DOCUMENT
Basis of design, discussions and estimated cost for the implementation of the Voorspoed Mine (VSM)
pit closure alternatives (technical component), including the associated risks and standard operating
procedures for site-wide closure.
Figure 1: Model of the final pit and waste rock dump at life of mine
2. BACKGROUND
VSM is in the process of planning for mine closure in accordance with the Anglo American Mine
Closure Toolbox (MCT). The current life of mine (LOM) is 2021 and according to the MCT, a mine
needs to aim at developing a Final closure plan within the last five years of operation.
At the time of submission of certain amendments to the Environmental Management Programme
(EMPr), the Department of Mineral Resources (DMR) approved the EMPr subject to certain
suspensive conditions. One condition was that VSP had to backfill all open excavations to natural
ground level (NGL), including the open pit.
High level modelling and cost estimation indicated that backfilling of the pit would result in excessive
costs that were not economically viable. Furthermore, the department was expecting more from the
mining company than what could be considered proportional to the benefits that could be achieved
by mining.
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VSM is preparing to consult with the authorities to propose and negotiate a commitment to implement
a feasible pit closure option that would comfortably fit into the physical and social setting into which
the mine lease area was transformed during mining activities. The chosen option will be aligned with
the agreed final land uses as far as possible and address the identified risks associated with closure.
3. SCOPE OF WORK
E-TEK was appointed to assist VSM with the following:
Establishment of open pit closure scenarios or alternatives for VSM (Sections 4 to 7 of this report);
The identification of the associated risks as well as a cost-benefit analysis (Section 8 of this report,
as well Annexure A);
Developing a site wide closure Standard Operating Procedure (SOP) for the implementation of
the closure plan and closure application process for the entire mine. This document was completed
in November 2015 and is referred to as the Voorspoed Mine Closure SOP, which includes the
Mine closure Legal compliance assessment checklist (Section 9 as well as Annexure B); and
Presentation of the various open pit closure scenarios to DMR (Annexure C)
4. ALTERNATIVES CONSIDERED
The following alternatives for closure of the pit have been identified after the screening of alternatives
and consultation with the client. Refer to Section 5 for detailed descriptions of the alternatives:
OPTION DESCRIPTION OF SCENARIO COMMITMENT
Scenario 1 Cover the remaining resource in the pit
Construct a concrete wall around the pit rim, outside the calculated
zone of relaxation (ZOR)
Construct an enviroberm outside of the concrete wall
Scenario 2 Cover the remaining resource in the pit
Construct a concrete wall around the pit rim, outside the calculated
ZOR
Construct an enviroberm outside of the concrete wall
Reshape the top bench to 18 degrees (°)
Scenario 3 Fill pit partially
Slope of infilling at angle of repose – from pit rim to pit floor
Construct a concrete wall and enviroberm as per Scenario 1
Scenario 4 Fill pit partially
Reshape slope infilling to 18° from pit rim to pit floor
Construct a concrete wall and enviroberm as per Scenario 1
Scenario 5 Optimise runoff catchment to increase volume of water stored in the
pit lake
Cover the remaining resource in the pit
Construct a concrete wall around the pit rim, outside the calculated
ZOR
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OPTION DESCRIPTION OF SCENARIO COMMITMENT
Construct an enviroberm outside of the concrete wall
Scenario 6 Complete infill of pit with all mineral resource deposit (MRD) material
available
Enhanced Scenario 7 Optimise runoff catchment to increase volume of water stored in the
pit lake
Cover the remaining resource in the pit
Demolish haul roads below the final pit lake level
Keep only 1 access route from the pit perimeter to the final pit lake
level (Other entrances and switch backs demolished)
Construct a fence all around the pit rim, outside the calculated ZOR
Construct an enviroberm outside of the fence
Excavate a trench around the enviroberm
5. DISCUSSION AND CLARIFICATION OF ALTERNATIVES
5.1. BASIS OF ESTIMATE FOR THE COSTING OF SCENARIOS
Rates used were based on market-related and industry norm rates. The rates are subject to
change upon final design.
It was assumed that the implementation of chosen scenarios will be implemented after mine
closure and not during the operational phase (There can be a significant savings if certain actions
are implemented as an operational cost).
Higher unit rates and preliminary and general costs (P&Gs) for certain items can be expected in
the event of the implementation being done during the operational phase. This is due to regulated
access and expected health and safety requirements.
Quantities and rates were based on conceptual designs and modelling done by the client and
E-TEK and subject to change.
P&Gs and contingencies have been included at indicative values. Detail planning is required,
which will inform the implementation plan, e.g. project duration and whether it will be implemented
as a standalone contract or part of other closure actions.
Allowances where made for P&Gs based on the overall estimated project value.
The costing was done based on current (2015) rates. No inflation factors have been applied.
5.2. SCENARIO 1: RESOURCE COVER, CONCRETE WALL AND ENVIROBERM
Refer to Figure 2, Figure 5 and Table 1.
5.2.1. Specifications
5.2.1.1 Resource cover
Cover the remaining visible resource at the bottom of the pit with a layer of imported waste rock
to a depth of approximately 10 m above the resource. This should discourage illegal miners from
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entering the pit, thereby reducing the risk of illegal mining during the period that the pit lake is
forming.
o Load, haul, dump and spread material sourced from the waste rock dump (WRD). Access the
pit via the existing pit ramps.
Utilise equipment with suitable braking and emergency stop systems.
o Compact to specifications.
5.2.1.2 Concrete wall
Construct a reinforced concrete wall around the entire pit rim approximately 10 m outside the ZOR
of the pit. The ZOR boundary will be delineated by the client.
o The primary function of the reinforced concrete wall is to create a sustainable barrier that will
minimise the risk of access to the pit after closure.
Total length of the reinforced concrete wall will be ±4,070 m.
o Excavate topsoil and incompetent material from the foundation footprint to a minimum
specification of 0.5 x 0.8 m. Rework and compact the in situ material where needed.
o Import suitable waste rock and compact as a base layer up to a depth of 500 mm below NGL
where over excavation has occurred.
o Cast a reinforced concrete strip foundation with construction joints as specified. Install
reinforcement starter bars for the wall to be cast.
o Cast the reinforced concrete wall, in two lifts, on the prepared foundation. The final height of
the concrete wall should be 2.4 m above NGL.
o Backfill and profile the immediate area adjacent to the wall. Slope the terrain away from the
wall to avoid future ponding of runoff water against the foundation of the concrete wall.
5.2.1.3 Enviroberm
Construct an enviroberm approximately 10 m outside the reinforced concrete wall.
o Construct the enviroberm only on the northern and western sides of the pit perimeter and abut
against the WRD on the northern and southern sides. The WRD on the eastern side will fulfil
the same function as the enviroberm.
o The primary function of the enviroberm is to screen the pit perimeter, i.e. for aesthetic reasons
and as a storm water diversion berm where required.
Construction method:
o Excavate the berm’s foundation footprint to a minimum depth of 300 mm and place excavated
material close by to utilise as growth medium after the construction of the enviroberm.
o Load and haul the required material from the WRD, spread in layers, shape and compact to
specifications.
o The specifications of the enviroberm:
Total length: ±1,570 m
Height: minimum of 2 m above NGL
Crest width: ±5 m
Side slopes no steeper than 1:5 to ensure long-term stability
o Spread and profile the excavated material over the enviroberm to serve as a growth medium.
o Ameliorate and vegetate the cover layer.
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Vegetate with indigenous vegetation, i.e. diversity of grass, tree and shrub species on the
crest.
Figure 2: Typical details of the reinforced concrete wall and enviroberm
Figure 3: Scenario 1 – Layout illustrating the concepts (no water)
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Figure 4: Scenario 1 – Cross section A-A indicates the concepts and estimated pit lake level, NGL and ZOR
Figure 5: Scenario 1 – Cross section B-B indicates the concepts and estimated pit lake level, NGL and ZOR
5.2.2. Cost: Scenario 1
The cost estimate to implement Scenario 1 is indicated in Table 1 below.
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Table 1: Scenario 1 – Detail of cost estimate.
5.2.3. Feasibility / construction risks
The following construction activities may pose significant challenges and risks:
o Cover resource:
Non-compliance with regulations and Anglo American plc (AA) health and safety
(H&S) requirements, i.e. the existing policies for safety may not allow the activity to
continue (risk too high);
Compliance with regulations and Anglo American plc (AA) health and safety (H&S)
requirements, i.e. the compliance may introduce excessive measures and costs to
mitigate the safety risk;
Hauling down gradient into the pit may cause brake failures with subsequent fatal
accidents;
Ramp instability and premature failure during construction;
Pit instability – falling rocks and objects, and slope failure may make the pit
inaccessible or cause serious injuries;
Traffic control in the pit will be required to prevent accidents, but this will slow down
production;
Dozer working in confined area while reshaping the cover layer;
Flooding of the pit during construction will temporarily stop backfilling, increase risk
of slope and ramp failures and risk of skidding; and
Inadequately skilled supervision and operators will increase the risk of serious
accidents and reduce production rates.
o Construction of reinforced concrete wall:
Non-compliance and compliance with H&S;
Scenario 1: Description Notes Unit Qty Rate Cost Sub-Total
1 Resource cover at bottom and construct concrete wall and enviroberm around pit
1.1 Construct Enviroberm m 1 570 6 293 650
1.1.1 Prepare foundations Excavate foundation footprint; minimum depth of
300mm; stockpile nearby to utilize as growth medium
after construction of the enviroberm
m3 11 775 42.50R 500 438
1.1.2 Load & haul Load and haul material from WRD; spread and compact in
layers according to specificationsm3 58 875 95.00R 5 593 125
1.1.3 Spread growth
medium
Spread stripped topsoilm3 11 775 8.50R 100 088
1.1.4 Ameliorate and
vegetate
Supply and spread Ameliorate; Supply and spread
indigenous vegetation, i.e. diversity of grass species and
trees and shrubs on crest, thorny / hedge plant
ha 4 25 000.00R 100 000
1.2 Construct Concrete
Wallm 4 070 18 447 682
1.2.1 Excavate foundations Excavate topsoil and incompetent material from
foundation footprint to a minimum depth of 0.5m.
Assume 20% increase due to trench topography.
m3 1 954 85.00R 166 056
1.2.2 Prepare foundations Rework and compact insitu material; Import suitable
waste rock & compact as base layer up to a depth of
500mm where needed (20% of foundatrion length)
m3 326 95.00R 30 932
1.2.3 Cast reinforced - strip
foundation
Including concrete, reinforcement, formwork & labour
m3 977 4 670.00R 4 561 656
1.2.4 Cast reinforced - wall Cast wall in two lifts; Rate including concrete,
reinforcement, formwork & labourm3 2 930 4 670.00R 13 684 968
1.2.5 Backfill Backfill & compact around foundation m3 407 10.00R 4 070
1.3 Resource Cover 8 372 500
1.3.1 Load & haul Haul down ramp; low production; 3km m3 85 000 90.00R 7 650 000
1.3.2 Spread and compact Spread m3 85 000 8.50R 722 500
Sub total 33 113 832
P&G's@ 35% 11 589 841
Contingencies @ 10% 3 311 383
Total ex VAT 48 015 056
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Non-compliance with SABS standards as per scope of work (SOW); and
Inadequately skilled supervision and artisans.
o Construction of enviroberm:
Non-compliance and compliance with H&S;
Non-compliance with SABS standards as per SOW;
Inadequately skilled supervision and operators; and
Inadequately skilled supervision and labour of subcontractors. (Amelioration and
vegetation establishment).
Residual risks after the above mitigation measures have been implemented are provided in the
accompanying risk assessment report.
5.2.4. Water balance
A basic water balance was developed for the pit to assess the likelihood of a pit lake forming and the
extent to which the water level will rise projected over time. The results have been supplied to the
client as an interactive spreadsheet.
Dewatering rates and rainfall records for the corresponding period were obtained from the client
for 2012 to 2015 and used to calibrate the model.
Physical properties of rock formations were obtained from the latest Itasca Groundwater Report
(2014).
It was assumed that mining and dewatering will cease in 2021. The results of the analysis indicate
the following:
o A pit lake will form over time mostly due to the inflow from runoff from the pit catchment (108
ha) during rainfall events, i.e. the pit side slopes as well as the area between the pit perimeter
and the reinforced concrete wall.
o There is a 50% probability that the pit level will reach levels between 1,263 and 1,269 mamsl
at the end of 2071.Refer to Figure 6.
o The pit will then store between 8,900,000 m3 and 9,600,000 m3 water.
o Groundwater inflow contributes to about 38% of the annual inflow into the pit at end of LOM
and will decrease to less than 20% after 50 years, i.e. when the water level reaches 1,263
mamsl.
o The pit water levels will fluctuate between 1,260 and 1,265 mamsl if water is abstracted from
the pit lake at a rate of 100,000 to 180,000 m3/annum.
o The current allocation of irrigation water by the department of water and sanitation (DWS) to
farmers is approximately 7,700 m3/ha/annum Using the allocation as a benchmark, it could be
assumed that a farmer could irrigate between 13 and 23 ha of agricultural crops sustainably
from the pit lake.
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Figure 6: Modelled rate of rise of the pit lake (108 ha catchment)
5.3. SCENARIO 2: RESOURCE COVER, RESHAPE TOP BENCH TO 18°,
CONCRETE WALL AND ENVIROBERM
Refer to Figure 2, Figure 7 to Figure 10 and Table 2
5.3.1. Specifications
5.3.1.1 Resource cover
Cover the remaining visible resource at the bottom of the pit with a layer of imported waste rock
to a depth of approximately 10 m. This should discourage illegal miners from entering the pit,
thereby reducing the risk of illegal mining during the period that the pit lake is forming.
Specifications as per Scenario 1 (p. 8).
5.3.1.2 Concrete wall
Construct a reinforced concrete wall around the total pit perimeter approximately 10 m outside the
ZOR of the pit. The ZOR will be delineated by the client.
The primary function of the reinforced concrete wall is to create a sustainable barrier to minimise
the risk of access to the pit after closure.
Specifications as per Scenario 1 (p. 8).
5.3.1.3 Enviroberm
Construct an enviroberm approximately 10 m outside the reinforced concrete wall.
Construct the enviroberm only on the northern and western side of the pit perimeter and abut
against the WRD on the northern and southern sides. The WRD on the eastern side will fulfil the
same function as the enviroberm (Figure 7).
The primary function of the enviroberm is to screen the pit perimeter, i.e. for aesthetic reasons and
to act as a storm water diversion berm where required.
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Specifications as per Scenario 1 (p. 8).
5.3.1.4 Top bench reshape.
Reshape only the top bench around the pit perimeter to 18° by cutting back material and placing
it outside the pit perimeter.
This material could be used for the construction of the enviroberm.
The main function of the reshaped top bench will be to improve the aesthetic quality of the pit rim.
(Unstable material is removed and vegetation will establish).
o Cut back and place the material outside pit ZOR.
o Utilise the excavated material to construct the enviroberm.
o Supply and spread ameliorate and supply and spread indigenous vegetation, i.e. diversity of
grass, tree and shrub species.
Figure 7: Scenario 2 – Layout illustrating the concepts (no water)
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Figure 8: Scenario 2 – Layout after filling with water
Figure 9: Scenario 2 – Cross section A-A indicates the concepts and estimated pit lake level, NGL and ZOR
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Figure 10: Scenario 2 – Cross section B-B indicating the concepts and estimated pit lake level, NGL and ZOR
5.3.2. Cost: Scenario 2.
The cost estimate to implement Scenario 2 is summarised in Table 2.
Table 2: Scenario 2 – Detail of implementation cost estimate
5.3.3. Feasibility / construction risks
The following construction activities provide significant challenges and risks:
o Cover resource:
Non-compliance with regulations and Anglo American plc (AA) health and safety
(H&S) requirements, i.e. the existing policies for safety may not allow the activity to
continue (risk too high);
Scenario 2: Description Notes Unit Qty Rate Cost Sub-Total
2 Resource cover at bottom & Reshape top bench to 18°; construct concrete wall and enviroberm around pit
2.1 Construct Enviroberm m 1 570 5 704 900
2.1.1 Prepare foundations Excavate topsoil from foundation footprint; minimum
depth of 300mm; stockpile nearby to utilize as growth
medium after construction of the berm
m3 11 775 42.50R 500 438
2.1.2 Load & haul Load and haul material from top bench cut back; spread
and compact in layers according to specificationsm3 58 875 85.00R 5 004 375
2.1.3 Spread growth
medium
Spread stripped topsoilm3 11 775 8.50R 100 088
2.1.4 Ameliorate and
vegetate
Supply and spread required ameliorants; Supply and
spread indigenous vegetation seed. i.e. diversity of grass
species, trees and shrubs on crest, thorny / hedge plants. ha 4 25 000.00R 100 000
2.2 Construct Concrete
Wall
See details above - Scenario 1m 4 070 4 532.60R 18 447 682 18 447 682
2.3 Resource Cover See details above - Scenario 1 m3 85 000 98.50R 8 372 500 8 372 500
2.4 Reshape Top Bench Cut back and place outside pit ZOR; utilize cut material to
construct Enviro bermm3 86 000 18.00R 1 548 000 1 548 000
2.5 Ameliorate and
vegetate
Supply and spread required ameliorants; Supply and
spread indigenous vegetation seed. i.e. diversity of grass
species, trees and shrubs on crest, thorny / hedge plants. ha 7 25 000.00R 175 000 175 000
Sub total 34 248 082
P&G's@ 35% 11 986 829
Contingencies @ 10% 3 424 808
Total ex VAT 49 659 719
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Compliance with regulations and Anglo American plc (AA) health and safety (H&S)
requirements, i.e. the compliance may introduce excessive measures and costs to
mitigate the safety risk;
Hauling down gradient into the pit may cause brake failures with subsequent fatal
accidents;
Ramp instability and premature failure during construction;
Pit instability – falling rocks and objects, and slope failure may make the pit
inaccessible or cause serious injuries;
Traffic control in the pit will be required to prevent accidents, but this will slow down
production;
Dozer working in confined area while reshaping the cover layer;
Flooding of the pit during construction will temporarily stop backfilling, increase risk
of slope and ramp failures and risk of skidding; and
Inadequately skilled supervision and operators will increase the risk of serious
accidents and reduce production rates.
o Construction of reinforced concrete wall:
Non-compliance and compliance with H&S;
Non-compliance with SABS standards as per SOW; and
Inadequately skilled supervision and artisans.
o Construction of enviroberm:
Non-compliance and compliance with H&S;
Non-compliance with SABS standards as per SOW;
Inadequately skilled supervision and operators;
Inadequately skilled supervision and labour of subcontractors. (Amelioration and
vegetation establishment.
o Reshape top bench to 18°:
Non-compliance and compliance with H&S (risk too high to allow operation or require
excessive measures and costs to mitigate);
Inadequately skilled supervision and operators will increase the risk of equipment falling
down the bench;
Pit rim instability (top bench) can cause premature failure during operations;
Movement of hauling team (trucks, operators and supervision) in close proximity of
unprotected pit rim can increase the pit rim instability;
Correct sizing of the plant for the operation (breaking force); and
Work on the top bench will have to be delayed while backfilling is in progress, because
risk of injuries due to falling material into the pit is increased if activities run simultaneously
Residual risks after the above mitigation measures have been implemented are provided in the
accompanying risk assessment report.
5.3.4. Water balance
Refer to Scenario 1 water balance (p. 13).
PROJECT: VOORSPOED MINE – PIT CLOSURE STUDY 2015/2016
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5.4. SCENARIO 3: PARTIAL IN-FILL – ANGLE OF REPOSE, CONCRETE WALL AND
ENVIROBERM
Refer to Figure 2, Figure 11 to Figure 14 and Table 3.
5.4.1. Specifications
5.4.1.1 Backfilling
Partially backfill the pit with material from the WRD. Leave the backfilled material at the angle of
repose and fill until the pit side slopes are covered.
End-tipping around the pit perimeter can be done at several positions simultaneously, thereby
increasing production.
Slope the backfilled material from the modified pit rim outwards to reduce any inflow of runoff.
The plan area of the pit will be reduced to approximately 43 ha.
5.4.1.2 Concrete wall.
Construct a reinforced concrete wall around the total pit perimeter approximately 10 m outside the
ZOR of the pit; the ZOR will be delineated by the client.
The primary function of the reinforced concrete wall is to create a sustainable barrier to minimise
the risk of access to the pit after closure.
Specifications as per Scenario 1 (p. 8).
5.4.1.3 Enviroberm.
Construct an enviroberm approximately 10 m outside the reinforced concrete wall.
Construct the enviroberm only on the northern and western side of the pit perimeter and abut
against the WRD on the northern and southern sides. The WRD on the eastern side will fulfil the
same function as the enviroberm (Figure 7).
The primary function of the enviroberm is to screen the pit perimeter, i.e. for aesthetic reasons and
to act as a storm water diversion berm where required.
Specifications as per Scenario 1 (p. 8).
PROJECT: VOORSPOED MINE – PIT CLOSURE STUDY 2015/2016
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Figure 11: Scenario 3 – Layout illustrating the concepts (no water)
Figure 12: Scenario 3 – Layout after filling with water
PROJECT: VOORSPOED MINE – PIT CLOSURE STUDY 2015/2016
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Figure 13: Scenario 3 – Cross section A-A indicating the concepts and estimated pit lake level, NGL and ZOR
Figure 14: Scenario 3 – Cross section B-B indicating the concepts and estimated pit lake level, NGL and ZOR
5.4.2. Cost: Scenario 3
The cost estimate to implement scenario 2 is summarised in Table 3.
Table 3: Scenario 3 – Detail of cost estimate.
5.4.1. Feasibility / construction risks
The following construction activities provide significant challenges and risks:
o Filling pit partially (end tipping from pit perimeter):
Scenario 3: Description Notes Unit Qty Rate Cost Sub-Total
3 Partial Infill at angle of repose construct concrete wall and enviroberm around pit
3.1 Construct Enviroberm See details above in Scenario 1 m 1,570 4,100.00R 6,437,000 6,437,000
3.2 Construct Concrete Wall See details above in Scenario 1m 4,070 4,600.00R 18,722,000 18,722,000
3.3 Partial Infill @ 35deg Fill in from pit perimeter; Load and haul; dump & dozer over
end of fillm3 21,000,000 38.00R 798,000,000 798,000,000
Sub total 823,159,000
P&G's@ 6% 49,389,540
Contingencies @ 10% 82,315,900
Total ex VAT 954,864,440
PROJECT: VOORSPOED MINE – PIT CLOSURE STUDY 2015/2016
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Implementation over long-term period extends decommissioning period and
increases chances for construction risks.
Non-compliance with regulations and Anglo American plc (AA) health and safety
(H&S) requirements, i.e. the existing policies for safety may not allow the activity to
continue (risk too high);
Compliance with regulations and Anglo American plc (AA) health and safety (H&S)
requirements, i.e. the compliance may introduce excessive measures and costs to
mitigate the safety risk;
Pit rim instability - top bench failure during construction;
Pit instability – failure within ZOR during construction;
Slumping of deposited material into pit during deposition; and
Inadequately skilled supervision and operators.
o Construction of reinforced concrete wall:
Non-compliance and compliance with H&S;
Non-compliance with SABS standards as per SOW; and
Inadequately skilled supervision and artisans.
o Construction of enviroberm:
Non-compliance and compliance with H&S;
Non-compliance with SABS standards as per SOW;
Inadequately skilled supervision and operators; and
Inadequately skilled supervision and labour of subcontractors.(Amelioration and
vegetation establishment.
Residual risks after the above mitigation measures have been implemented are provided in the
accompanying risk assessment report
5.4.2. Water balance
The catchment of the partially backfilled pit is reduced (from 108 ha for Scenario 1 to approximately
43 ha for Scenario 3), due to the backfilled material sloping away from the pit. This will reduce inflow
to the pit. This scenario was not modelled in detail, but the final pit lake volume and levels were
estimated based on the results of the model for Scenario 1. The pit formed by the backfilled material
will have a different stage curve. It was estimated that the water level could rise up to approximately
1,270 mamsl.
5.5. SCENARIO 4: PARTIAL IN-FILL – RESHAPED TO 18°, CONCRETE WALL AND
ENVIROBERM
Refer to Figure 15 to Figure 18 and Table 4.
5.5.1. Specifications
5.5.1.1 Backfilling
Partially backfill the pit with material from the WRD. Leave the backfilled material at the angle of
repose and fill until the pit side slopes are covered.
PROJECT: VOORSPOED MINE – PIT CLOSURE STUDY 2015/2016
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End-tipping around the pit perimeter can be done at several positions simultaneously, thereby
increasing production.
Slope the backfilled material from the modified pit rim outwards to reduce any inflow of runoff.
The plan area of the pit will remain approximately 63 ha.
Ameliorate and vegetate the reshaped pit slopes and surrounding areas.
5.5.1.2 Concrete wall and enviroberm.
The 18° slopes will be stable and safe; therefore, there is no need to construct a concrete wall or
enviroberm to address any possible risk due to slope failure. The pit lake that will form will however
introduce a safety risk due to the possibility of drowning. Construct a reinforced concrete wall to
reduce the possibility of access to the pit.
5.5.1.3 Revegetation
The slopes can be rehabilitated to reduce the visual impact of the bare pit side slopes.
Figure 15: Scenario 4 – Layout illustrating the concepts (no water)
PROJECT: VOORSPOED MINE – PIT CLOSURE STUDY 2015/2016
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Figure 16: Scenario 4 – Layout after filling with water
Figure 17: Scenario 4 – Cross section A-A indicating the concepts and estimated pit lake level NGL and ZOR
PROJECT: VOORSPOED MINE – PIT CLOSURE STUDY 2015/2016
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Figure 18: Scenario 4 – Cross section B-B indicating the concepts and estimated pit lake level, NGL and ZOR
5.5.2. Cost: Scenario 4
The cost estimate to implement scenario 4 is summarised in Table 4.
Table 4: Scenario 4 – Detail of cost estimate.
The same approach for the costing was used as for Scenario 1.
The rate for importing fill material is for the shorter haul distance to the pit perimeter.
Scenario 4 has the additional cost for reshaping the dumped material in the pit to 18° in a balanced
cut and fill action
5.5.3. Feasibility / construction risks
The following construction activities provide significant challenges and risks:
o Filling pit partially:
Implementation over long-term period extends decommissioning period and
increases chances for construction risks.
Non-compliance with regulations and Anglo American plc (AA) health and safety
(H&S) requirements, i.e. the existing policies for safety may not allow the activity to
continue (risk too high);
Compliance with regulations and Anglo American plc (AA) health and safety (H&S)
requirements, i.e. the compliance may introduce excessive measures and costs to
mitigate the safety risk;
Scenario 4: Description Notes Unit Qty Rate Cost Sub-Total
4 Partial Infill at 18°
4.1 Construct Enviroberm See details above in Scenario 1 m 1,570 4,100.00R 6,437,000 6,437,000
4.3 Construct Concrete Wall See details above in Scenario 1m 4,070 4,600.00R 18,722,000 18,722,000
4.4 Partial Infill @ 35deg Fill in from pit perimeter; Load and haul; dump & dozer over
end of fillm3 28,000,000 38.00R 1,064,000,000 1,064,000,000
4.5 Reshape Infill to 18deg Balanced cut & fill to 18deg; estimate 30% of fill material to be
reshapedm
3 8,400,000 18.50R 155,400,000 155,400,000
4.6 Ameliorate and
vegetate
Supply and spread required ameliorants; Supply and spread
indigenous vegetation seed. i.e. diversity of grass species, trees
and shrubs.
ha 66 25,000.00R 1,645,000 1,645,000
Sub total 1,246,204,000
P&G's@ 6% 74,772,240
Contingencies @ 10% 124,620,400
Total ex VAT 1,445,596,640
PROJECT: VOORSPOED MINE – PIT CLOSURE STUDY 2015/2016
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Pit rim instability - top bench failure during construction;
Pit instability – failure within ZOR during construction;
Slumping of deposited material into pit during deposition; and
Inadequately skilled supervision and operators.
o Reshape slope to 18°:
Non-compliance and compliance with H&S;
Inadequately skilled supervision and operators;
Correct sizing of the plant for the operation;
Synchronisation of operations (reshaping while hauling & dumping); and
Inadequately skilled supervision and labour of subcontractors. (Amelioration and
vegetation establishment
Residual risks after the above mitigation measures have been implemented are provided in the
accompanying risk assessment report
5.5.4. Water balance
The catchment of the partially backfilled pit is reduced, from 108 ha for Scenario 1 to approximately
68 ha for Scenario 4, since diversion berms or paddocks will divert or contain storm water and
prevent it from entering the pit.
This will reduce inflow to the pit. This scenario was not modelled in detail, but the final pit lake
volume and levels were estimated based on the results of the model for Scenario 1.
The pit formed by the backfilled material will, however, have a different stage curve. It was
estimated that water levels could rise up to about 1,347 mamsl.
5.6. SCENARIO 5: RESOURCE COVER, CONCRETE WALL, ENVIROBERM AND
OPTIMISE CATCHMENT
Refer to Figure 2, Figure 19 to Figure 22 and Table 5.
5.6.1. Specifications
5.6.1.1 Resource cover
Cover the remaining visible resource at the bottom of the pit with a layer of imported waste rock
to a depth of approximately 10 m. This should discourage illegal miners from entering the pit,
thereby reducing the risk of illegal mining during the period that the pit lake is forming.
Specifications as per Scenario 1 (p. 8).
5.6.1.2 Concrete wall
Construct a reinforced concrete wall around the total pit perimeter approximately 10 m outside the
ZOR of the pit.; the ZOR will be delineated by the client.
The primary function of the reinforced concrete wall is to create a sustainable barrier to minimise
the risk of access to the pit after closure.
Specifications as per Scenario 1 (p. 8).
PROJECT: VOORSPOED MINE – PIT CLOSURE STUDY 2015/2016
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5.6.1.3 Enviroberm
Construct an enviroberm approximately 10 m outside the reinforced concrete wall.
Construct the enviroberm only on the northern and western sides of the pit perimeter and abut
against the WRD on the northern and southern sides. The WRD on the eastern side will fulfil the
same function as the enviroberm (Figure 3).
The primary function of the enviroberm is to screen the pit perimeter, i.e. for aesthetic reasons and
to act as a storm water diversion berm where required.
Specifications as per Scenario 1 (p. 8).
Reshape surrounding areas during final rehabilitation or construct collection drains from
surrounding areas to increase the catchment reporting to the pit lake. There are many different
alternatives to consider but the following rehabilitated areas were added to the catchment:
o Slope of lowest lift of the WRD on the south side of the pit and the area between the toe of the
slope and the concrete wall;
o Slope of lowest lift of the WRD on the east side of the pit and the area between the toe of the
slope and the concrete wall; and
o A portion of the rehabilitated footprint of the plant area.
Figure 19: Scenario 5 – Layout illustrating the concepts (no water)
PROJECT: VOORSPOED MINE – PIT CLOSURE STUDY 2015/2016
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Figure 20: Scenario 5 – Layout after filling with water
Figure 21: Scenario 5 – Cross section A-A indicating the concepts and estimated pit lake level, NGL and ZOR
PROJECT: VOORSPOED MINE – PIT CLOSURE STUDY 2015/2016
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Figure 22: Scenario 5 – Cross section B-B indicating the concepts and estimated pit lake level, NGL and ZOR
5.6.2. Cost: Scenario 5
The cost estimate for the implementation of Scenario 5 is the same as that of Scenario 1, as there
are no additional actions required. This is reflected in Table 5.
Table 5: Scenario 5 – Detail of cost estimate.
5.6.3. Feasibility / construction risks
The following construction activities may pose significant challenges and risks (similar to
Scenario 1):
o Cover resource:
Non-compliance with regulations and Anglo American plc (AA) health and safety
(H&S) requirements, i.e. the existing policies for safety may not allow the activity to
continue (risk too high);
Compliance with regulations and Anglo American plc (AA) health and safety (H&S)
requirements, i.e. the compliance may introduce excessive measures and costs to
mitigate the safety risk;
Hauling down gradient into the pit may cause brake failures with subsequent fatal
accidents;
Ramp instability and premature failure during construction;
Pit instability – falling rocks and objects, and slope failure may make the pit
inaccessible or cause serious injuries;
Traffic control in the pit will be required to prevent accidents, but this will slow down
production;
Scenario 5: Description Notes Unit Qty Rate Cost Sub-Total
5 Resource cover at bottom, optimise catchment and construct concrete wall and enviroberm around pit
5.1 Construct Enviroberm See details above in Scenario 1 m 1 570 4 008.69R 6 293 650 6 293 650
5.2 Construct Concrete
Wall
See details above in Scenario 1m 4 070 4 532.60R 18 447 682 18 447 682
5.3 Resource Cover See details above in Scenario 1 m3 85 000 98.50R 8 372 500 8 372 500
Sub total 33 113 832
P&G's@ 35% 11 589 841
Contingencies @ 10% 3 311 383
Total ex VAT 48 015 056
PROJECT: VOORSPOED MINE – PIT CLOSURE STUDY 2015/2016
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Dozer working in confined area while reshaping the cover layer;
Flooding of the pit during construction will temporarily stop backfilling, increase risk
of slope and ramp failures and risk of skidding; and
Inadequately skilled supervision and operators will increase the risk of serious
accidents and reduce production rates.
o Construction of reinforced concrete wall:
Non-compliance and compliance with H&S;
Non-compliance with SABS standards as per SOW; and
Inadequately skilled supervision and artisans.
o Construction enviroberm:
Non-compliance and compliance with H&S;
Non-compliance with SABS standards as per SOW;
Inadequately skilled supervision and operators; and
Inadequately skilled supervision and labour of subcontractors. (Amelioration and
vegetation establishment
o Changes to storm water management infrastructure:
Access of humans and animals to the open pit through unprotected storm water
structures in the concrete wall; and
Non-compliance with SABS standards as per SOW.
5.6.4. Water balance
A basic water balance was developed for the pit to assess the likelihood of a pit lake inform over time
and the extent to which the water level will rise. Scenario 5 was modelled to investigate the increased
yield when the catchment of the pit is increased, i.e. runoff from areas that were outside the “normal”
catchment is routed to the pit lake. The results were also provided to the client as an interactive
spreadsheet.
Dewatering rates and rainfall records for the corresponding period were obtained from the client
for 2012 to 2015 and were used to calibrate the model.
Physical properties of rock formations were obtained from the latest Itasca Groundwater Report
(2014).
It was assumed that mining and dewatering will cease in 2021. The results of the analysis indicate
the following:
o A pit lake will form over time mostly due to the inflow from runoff from the pit catchment (188
ha) during rainfall events, i.e. the pit side slopes as well as the area between the pit perimeter
and the reinforced concrete wall.
o There is a 50% probability that the pit level will reach levels between 1,278 and 1,283 mamsl
at the end of 2071.
o The pit will then store between 10,780,000 m3 and 11,480,000 m3 water.
o Groundwater inflow is about 32% of the annual inflow into the pit at end of LOM and will
decrease to less than 13% after 50 years, i.e. when the water level reaches 1,270 mamsl.
o The pit water levels will fluctuate between 1,260 and 1,265 mamsl if water is abstracted from
the pit lake at a rate between 120,000 and 220,000 m3/annum.
PROJECT: VOORSPOED MINE – PIT CLOSURE STUDY 2015/2016
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o The current allocation of irrigation water by DWS to farmers is approximately 7,700 m3/annum
Using the allocation as a benchmark, it could be assumed that a farmer could irrigate between
15 and 28 ha of agricultural crops sustainably from the pit lake
Figure 23: Modelled rate of rise of the pit lake (increased catchment to 180 ha)
5.7. SCENARIO 6: COMPLETE IN-FILL WITH ALL AVAILABLE MRD MATERIAL
Refer to Figure 24 to Figure 26 and Table 6.
5.7.1. Specification
Fill the entire pit void with all available material from MRDs.
o Place the coarse residue deposit (CRD) material in the bottom of the pit. The conveyor system
can possibly be reversed to increase the work rate. This will give time for the fine residue
deposit (FRD) material to dry out.
o Place the FRD material on top of the CRD material after the material has dried out sufficiently
in order to be handled safely.
o Place the WRD material up to the NGL before commencing with the profiling of a dome over
the backfilled pit.
o Compaction of the backfilled material is not considered, since it will reduce the work rate, but
more so as it is impractical when end-tipping from the pit perimeter.
Fill the pit to approximately 20 m above the NGL to form a dome shape that is free-draining and
that will allow for future settlement of the backfilled material.
Ameliorate and vegetate the backfilled pit dome.
1080
1130
1180
1230
1280
20
21
20
22
20
23
20
24
20
26
20
27
20
28
20
29
20
31
20
32
20
33
20
34
20
36
20
37
20
38
20
39
20
41
20
42
20
43
20
44
20
46
20
47
20
48
20
49
20
51
20
52
20
53
20
54
20
56
20
57
20
58
20
59
20
61
20
62
20
63
20
64
20
66
20
67
20
68
20
69
20
71
Elev
atio
n (
mam
sl)
Min 25% 50% 75% Max
PROJECT: VOORSPOED MINE – PIT CLOSURE STUDY 2015/2016
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Figure 24: Scenario 6 – Layout illustrating the concepts
Figure 25: Scenario 6 – Cross-section A-A indicating the concepts
PROJECT: VOORSPOED MINE – PIT CLOSURE STUDY 2015/2016
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Figure 26: Scenario 6 – Cross-section B-B indicating the concepts
5.7.2. Cost: Scenario 6
The cost estimate to implement Scenario 6 is summarised in Table 6.
Table 6: Scenario 6 – Detail of cost estimate.
The same approach for the costing was used as for Scenario 1, except that the rate for importing
fill material is for the shorter haul distance to the pit perimeter. Scenario 6 has the additional cost
for reshaping the dumped material above the NGL in a dome shape.
5.7.3. Feasibility / construction risks
The following construction activities provide significant challenges and risks:
o Fill pit:
Implementation over long-term period extends decommissioning period and
increases chances for construction risks.
Non-compliance with regulations and Anglo American plc (AA) health and safety
(H&S) requirements, i.e. the existing policies for safety may not allow the activity to
continue (risk too high);
Compliance with regulations and Anglo American plc (AA) health and safety (H&S)
requirements, i.e. the compliance may introduce excessive measures and costs to
mitigate the safety risk;
Pit rim instability - top bench failure during construction;
Pit instability – failure within ZOR during construction;
Slumping of deposited material into pit during deposition; and
Inadequately skilled supervision and operators.
o Reshape dome to specification:
Scenario 6: Description Notes Unit Qty Rate Cost Sub-Total
6 Complete Infill with all MRD material
6.1 Complete Infill Fill in from pit perimeter; Load and haul; dump & dozer over
end of fill; shape final levels above NGLm
3 62,240,000 42.00R 2,614,080,000 2,614,080,000
6.2 Ameliorate and
vegetate
Supply and spread required ameliorants; Supply and spread
indigenous vegetation seed. i.e. diversity of grass species, trees
and shrubs
ha 77 25,000.00R 1,915,000 1,915,000
Sub total 2,615,995,000
P&G's@ 6% 156,959,700
Contingencies @ 10% 261,599,500
Total ex VAT 3,034,554,200
PROJECT: VOORSPOED MINE – PIT CLOSURE STUDY 2015/2016
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Non-compliance and compliance with H&S;
Inadequately skilled supervision and operators;
Correct sizing of the plant for the operation;
Synchronisation of operations (reshaping while hauling & dumping); and
Inadequately skilled supervision and labour of subcontractors. (Amelioration and
vegetation establishment
Residual risks after the above mitigation measures have been implemented are provided in the
accompanying risk assessment report.
6. BENEFICIAL LAND USE OF THE FARM INCLUDING THE OPEN PIT
The scenarios presented above will mitigate the prominent closure risks to varying degrees. All are
associated with a cost which is directly related to the magnitude of intervention investigated.
The cost associated with Scenarios 3, 4 and 6 is exorbitant and cannot be justified when considering:
The NPV of the entire operation.
The benefit to be gained from the money spent after implementing the said scenarios.
Scenarios 1, 2 & 5 provided the more feasible alternatives, but the strict specifications for some
aspects (e.g. concrete wall) inflate the costs resulting in an unrealistically high expense in relation to
the degree that the specific risks can be addressed (e.g. illegal access) and the benefit to be gained.
The client therefore embarked on a further phase of the study to reduce costs while aiming to achieve
an enhanced end land use of which the open pit plays a make or break role in achieving a sustainable
end land use after closure.
This entails the optimization of the pit as reservoir and the utilization of the water source to support
the development of higher value agricultural and industrial business enterprises. The feasibility and
details of the suggested ventures is outside the scope of this study, but the following possibilities,
multiple variations and combinations thereof need to be considered:
Intensive & extensive animal farming;
Intensive & extensive animal feed production;
Cash crops under irrigation;
Green houses with hydroponics,
Aqua culture;
Generation of electricity by using concentrated sunlight to heat water;
Other.
Further reasoning for reducing the strict and expensive access control measures in the previous
scenarios:
Access control can never be accepted to be absolute or guaranteed – practically any passive
barrier can be crossed in some or other way. Rather remove the attraction to illegal entrants.
The site will be managed as an ongoing business after closure and access can be actively
controlled by the operators / owners of the enterprise.
Focus therefore needs to be on discouraging illegal mining per se above all other risks which are
costly to mitigate.
PROJECT: VOORSPOED MINE – PIT CLOSURE STUDY 2015/2016
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7. ENHANCED SCENARIO 7: ALTERNATIVE LAND USE OF THE PIT
7.1. SCENARIO 7: RESOURCE COVER, ACCESS ROUTE, FENCE, ENVIROBERM
AND OPTIMISE CATCHMENT
Enhanced Scenario 7 has been investigated as an extension to Scenario 5.
Refer to:
Figure 27: Scenario 7 – Layout illustrating the concepts (no water)
Figure 28: Scenario 7 – Layout after filling with water
Figure 29: Scenario 7 – Cross section A-A indicating the concepts and estimated pit lake level,
NGL and ZOR
Figure 30: Scenario 7 – Cross section B-B indicating the concepts and estimated pit lake level,
NGL and ZOR
7.1.1. Specifications
7.1.1.1 Resource cover / Access control
Cover the remaining visible resource at the bottom of the pit with a layer of rock blasted from the
nearest bottom benches to a depth of approximately 10 m. Sterilisation of the resource in the pit
will discourage illegal miners from entering the pit, thereby reducing the risk of illegal mining during
the period that the pit lake is forming. The blasting of the bottom benches will be done before
removing the required equipment from the pit bottom at LoM. The cost is therefor considered to
be an operational cost. No allowance for this item is required for scheduled mine closure.
Other specifications as per Scenario 1 and 2 (p. 8) except that the concrete wall is substituted with
a security fence and the design of the trench has been changed. (Refer to § 7.1.1.2 and
§ 7.1.1.3).
Decommission the haul road switchback indicated in Figure 28 above the final estimated resting
water level in the pit. Access along the existing ramps to the bottom of the pit will then be
inaccessible during the period that the pit lake is forming.
The top four benches of the open pit where designed to fail spontaneously and thus need no
further intervention. This will discourage access to the pit floor from the pit perimeter, because this
zone is expected to be difficult to navigate (The haul road should remain stable). The failure
boundary is still within the ZOR which is considered when placing further infrastructure (such as a
fence).
7.1.1.2 Security Fence
Construct a security fence around the entire pit rim approximately 10 m outside the ZOR of the pit.
The ZOR boundary will be delineated by the client.
o The primary function of the fence is to create a visible barrier that will further minimise the risk
of uncontrolled access to the pit after closure.
Total length of the fence will be ±4070 at a height of 2.4m.
PROJECT: VOORSPOED MINE – PIT CLOSURE STUDY 2015/2016
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7.1.1.3 Enviroberm and trench
Excavate the trench approximately 15 m outside the security fence. Leave the excavated sides
vertical to allow natural failure of trench sides. Construction the enviroberm using the excavated
material from the trench. The toeline of the enviroberm must be a minimum of 5m from the trench.
Covering the enviroberm with a 1m deep waste rock layer.
Construct the enviroberm only on the northern, western and southern sides of the pit perimeter
and abut against the WRD on the northern and southern sides. The WRD on the northern to
southern sides (clockwise) will fulfil the same function as the enviroberm (Figure 27).
The primary function of the enviroberm is to screen the pit perimeter, i.e. for aesthetic reasons and
to act as a storm water diversion berm where required.
Specifications as per Scenario 1 (p. 8).
Reshape surrounding areas during final rehabilitation and construct collection drains from
surrounding areas to increase the catchment of runoff reporting to the pit. There are many different
alternatives to consider but the following rehabilitated areas were added to the catchment to
increase the runoff volume reporting to the pit:
o Slope of lowest lift of the WRD on the south side of the pit and the area between the toe of the
slope and the fence;
o Slope of lowest lift of the WRD on the east side of the pit and the area between the toe of the
slope and the fence; and
o A portion of the rehabilitated footprint of the plant area.
Figure 27: Scenario 7 – Layout illustrating the concepts (no water)
PROJECT: VOORSPOED MINE – PIT CLOSURE STUDY 2015/2016
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Figure 28: Scenario 7 – Layout after filling with water
Figure 29: Scenario 7 – Cross section A-A indicating the concepts and estimated pit lake level, NGL and ZOR
Figure 30: Scenario 7 – Cross section B-B indicating the concepts and estimated pit lake level, NGL and ZOR
PROJECT: VOORSPOED MINE – PIT CLOSURE STUDY 2015/2016
38
7.1.2. Cost: Scenario 7
Table 7: Enhanced Scenario 7 – Detail of cost estimate.
7.1.3. Feasibility / construction risks
The following construction activities may pose significant challenges and risks (similar to
Scenario 1):
o Cover resource:
Non-compliance with regulations and Anglo American plc (AA) health and safety (H&S)
requirements, i.e. the existing policies for safety may not allow the activity to continue (risk
too high);
Compliance with regulations and Anglo American plc (AA) health and safety (H&S)
requirements, i.e. the compliance may introduce excessive measures and costs to mitigate
the safety risk;
Ramp instability and premature failure during construction;
Pit instability – falling rocks and objects, and slope failure may make the pit inaccessible
or cause serious injuries;
Traffic control in the pit will be required to prevent accidents, but this will slow down
production;
Dozer working in confined area while reshaping the cover layer;
Dozer working on the ramps while reshaping the switch backs and entrances.
Flooding of the pit during construction will temporarily increase risk of slope and ramp
failures and risk of skidding; and
Inadequately skilled supervision and operators will increase the risk of serious accidents
and reduce production rates.
o Construction of fence:
Enhanced Scenario (7):Description Notes Unit Qty Rate Cost Sub-Total
7 Resource cover at bottom and construct fence, enviroberm and trench around pit
7.1 Construct Enviroberm & Trench m 2 220 8 075 400
7.1.1 Prepare foundations Excavate berm foundation footprint; minimum depth of
300mm; stockpile nearby to utilize as growth medium
after construction of the enviroberm (Can be considered
operational cost)
m3 16 650 42.50R 707 625
7.1.2 Load & haul Utilise excavated material from trench; Load and haul
additional material from WRD; spread and compact in
layers according to specifications (Can be considered
operational cost)
m3 83 250 85.00R 7 076 250
7.1.3 Spread growth
medium
Spread stripped topsoil (Can be considered operational
cost) m3 16 650 8.50R 141 525
7.1.4 Ameliorate and
vegetate
Supply and spread Ameliorate; Supply and spread
indigenous vegetation, i.e. diversity of grass species and
trees and shrubs on crest, thorny / hedge plant (Can be
considered operational)
ha 6 25 000.00R 150 000
7.2 Install Security Fence m 4 070 1 648 350
7.2.1 Fence as per Quote Security fence 2.4m high; diamond mesh 50mmx2.5mm
galvanised; flatwrap 500 razorwire; posts 101mm x 2mm
every 30m; standards every 5.5m; with 8m gate; including
erection
m 4 070 405.00R 1 648 350
7.3 Resource Protection 8 422 500
7.3.1 Cover resource Cover resource at bottom of pit @ 10m deep with waste
rock; blast nearest ramps at cessation of miningm3 85 000 98.50R 8 372 500
7.3.2 Decommission
switchbacks
Blast switchbacks above final pit lake water levelsum 1 50 000.00R 50 000
7.3.3 Reshape top benches Reshape top 4 benches to discourage access; no active
works required - benches are desiged to failm3 1 -R 0
Sub total 18 146 250
P&G's@ 35% 6 351 188
Contingencies @ 10% 1 814 625
Total ex VAT 26 312 063
PROJECT: VOORSPOED MINE – PIT CLOSURE STUDY 2015/2016
39
Non-compliance and compliance with H&S;
Non-compliance with SABS standards as per SOW; and
Inadequately skilled supervision and artisans.
o Construction of enviroberm:
Non-compliance and compliance with H&S;
Non-compliance with SABS standards as per SOW;
Inadequately skilled supervision and operators; and
Inadequately skilled supervision and labour of subcontractors. (Amelioration and
vegetation establishment
o Changes to storm water management infrastructure:
Non-compliance with SABS standards as per SOW.
7.1.4. Water balance
A basic water balance was developed for the pit to assess the likelihood of a pit lake forming over
time and the extent to which the water level will rise. Scenario 5 was modelled to investigate the
increased yield when the catchment of the pit is increased, i.e. runoff from areas that were outside
the “normal” catchment is routed to the pit. The results were also provided to the client as an
interactive spreadsheet.
The estimated final level of the pit lake (1280mamsl) will be above the level where remaining traces
of kimberlite is exposed in the pit sidewalls (1198mamsl). There is a 50% chance that the elevation
of 1200 mamsl will be reached between 2032 and 2034. A pit lake level of 1200 mamsl can be
reached quicker by supplementing the natural ingress of water due to rainfall with additional water
with the existing water allocation from the Renoster River Weir. The WUL for this water use is valid
until 2029 on condition it is used for mining related purposes – which it will be. The allocation is
220,000m3/month. The required volume to reach 1198 mamsl is
3,4 million m3 of water. With current allocation from the Renoster River, this can be reached within
1.5 years excluding the rainfall and runoff.
8. RISK ASSESSMENT AND COST-BENEIFT ANALYSIS
8.1. METHODOLOGY AND APPROACH
The focus of the Risk Assessment was to follow a risk-based approach in order to assist the decision-
making process in determining the most feasible open pit closure scenario for closure.
The identified risks were captured in a dedicated spreadsheet that reflects all the respective risks for
each of the open pit closure scenarios. These risks were individually evaluated and ranked for each
of the closure scenarios, before and after implementation of the rehabilitation closure criteria. The
Anglo American 5x5 closure risk matrix was used. Refer to Annexure A of this report for the risk
matrix and different criteria used to determine the risks. The identified risks were rated according to
“probability / likelihood” and “consequence of occurrence”.
To determine the possible consequence, different criteria were used for each of the following
aspects:
Safety
PROJECT: VOORSPOED MINE – PIT CLOSURE STUDY 2015/2016
40
Occupational Health
Environment
Financial
Legal & Regulatory
Social / Community
Reputation
8.2. OUTPUTS OF RISK ASSESSMENT
The Risk assessment was done in the format of an Interactive spreadsheet with the following Index
(refer to Annexure A):
Open pit closure scenarios: Schematic illustration of the different open pit closure scenarios.
Risk matrix: The 5 x 5 risk matrix as per the Anglo American Toolbox.
Risk assessment tool: Detailed list of all risks associated with the different Open Pit Closure
Scenarios, including Low and Medium Risks.
Accessibility to open pit: Summary of risks associated with the risk aspect.
Pit sidewall stability: Summary of risks associated with the risk aspect.
Water resources: Summary of risks associated with the risk aspect.
Land capability and End land use: Summary of risks associated with the risk aspect.
Natural resources: Summary of risks associated with the risk aspect.
Government and stakeholders: Summary of risks associated with the risk aspect.
Cost-benefit analysis: A summary of all residual risks which are associated with the different
closure scenarios as well as the associated costs for the implementation of the different scenarios.
It is important to read all of the abovementioned components of the Risk assessment in correlation
with each other. The following is a summary of the output of the Risk assessment tool.
PROJECT: VOORSPOED MINE – PIT CLOSURE STUDY 2015/2016
41
Figure 31: Risk summary for Accessibility to the Open pit
Voorspoed Open Pit Closure Risk Assessment
SCENARIO 1
SCENARIO 2
SCENARIO 3
SCENARIO 4
SCENARIO 5
SCENARIO 6
SCENARIO 7
SAFETY OCCUPATIONAL HEALTH ENVIRONMENTAL FINANCIAL LEGAL & REGULATORY SOCIAL / COMMUNITY REPUTATION
PRE-MITIGATION NONE 21 (H) 24 (H) 17 (S) 17 (S) 23 (H) 21 (H) 24 (H)
SCENARIO 1 9 (M) 9 (M) 9 (M) 5 (L) 9 (M) 9 (M) 9 (M) UNLIKELY
SCENARIO 2 9 (M) 9 (M) 9 (M) 5 (L) 9 (M) 9 (M) 9 (M) UNLIKELY
SCENARIO 3 9 (M) 9 (M) 9 (M) 5 (L) 9 (M) 9 (M) 9 (M) UNLIKELY
SCENARIO 4 6 (M) 6 (M) 6 (M) 3 (L) 6 (M) 6 (M) 6 (M) RARE
SCENARIO 5 9 (M) 9 (M) 9 (M) 5 (L) 9 (M) 9 (M) 9 (M) UNLIKELY
SCENARIO 6 #N/A #N/A #N/A #N/A #N/A #N/A #N/A NO RISK
SCENARIO 7 9 (M) 9 (M) 9 (M) 5 (L) 9 (M) 9 (M) 9 (M) UNLIKELY
PRE-MITIGATION NONE 23 (H) 23 (H) 25 (H) 20 (S) 23 (H) 25 (H) 25 (H)
SCENARIO 1 9 (M) 9 (M) 9 (M) 9 (M) 9 (M) 9 (M) 9 (M) UNLIKELY
SCENARIO 2 9 (M) 9 (M) 9 (M) 9 (M) 9 (M) 9 (M) 9 (M) UNLIKELY
SCENARIO 3 3 (L) 3 (L) 3 (L) 3 (L) 3 (L) 3 (L) 3 (L) RARE
SCENARIO 4 3 (L) 3 (L) 3 (L) 3 (L) 3 (L) 3 (L) 3 (L) RARE
SCENARIO 5 9 (M) 9 (M) 9 (M) 9 (M) 9 (M) 9 (M) 9 (M) UNLIKELY
SCENARIO 6 #N/A #N/A #N/A #N/A #N/A #N/A #N/A NO RISK
SCENARIO 7 9 (M) 9 (M) 9 (M) 5 (L) 9 (M) 9 (M) 9 (M) UNLIKELY
COVER RESOURCE, 1 ACCESS ROUTE, INCREASE CATCHMENT, FENCE & BERM
RISK RELATED ASPECT: ACCESSIBILITY TO OPEN PIT
MITIGATION MEASURES
RISK CATEGORY
SCENARIO
COVER RESOURCE, WALL & BERM
RESHAPE TOP BENCH 18°, COVER RESOURCE ,WALL & BERM
PARTIAL IN-FILL AT ANGLE OF REPOSE , WALL & BERM
PARTIAL IN- FILL AT 18°, WALL & BERM
COVER RESOURCE, INCREASE CATCHMENT, WALL & BERM
COMPLETE, IN-FILL ALL MRD MATERIAL
RESIDUAL RISK /
IMPACTS AFTER IMPLEMENTATION OF THE
MANAGEMENT MEASURES
Illegal mining due to access to potential resource.
Possibility of human and animal injury or death due to
uncontrolled access to the pit (falling down steep slopes or
drowning).
RISK STATEMENT
Risk MatrixPit side wall stability Risk Assessment Tool
Accessibility to open pit
Water resources
Land capability
& ELU
Index
Open Pit Closure Scenarios
Natural resources
Government &
Stakeholders
Cost-Benefit Analysis
PROJECT: VOORSPOED MINE – PIT CLOSURE STUDY 2015/2016
42
Figure 32: Risk summary for Open pit sidewall stability
Voorspoed Open Pit Closure Risk Assessment
SCENARIO 1
SCENARIO 2
SCENARIO 3
SCENARIO 4
SCENARIO 5
SCENARIO 6
SCENARIO 7
SAFETY OCCUPATIONAL HEALTH ENVIRONMENTAL FINANCIAL LEGAL & REGULATORY SOCIAL / COMMUNITY REPUTATION
PRE-MITIGATION NONE 21 (H) 23 (H) 20 (S) 17 (S) 20 (S) 21 (H) 21 (H)
SCENARIO 1 13 (S) 13 (S) 13 (S) 8 (M) 13 (S) 13 (S) 13 (S) POSSIBLE
SCENARIO 2 13 (S) 13 (S) 13 (S) 8 (M) 13 (S) 13 (S) 13 (S) POSSIBLE
SCENARIO 3 8 (M) 8 (M) 8 (M) 8 (M) 8 (M) 8 (M) 8 (M) POSSIBLE
SCENARIO 4 3 (L) 3 (L) 3 (L) 3 (L) 3 (L) 3 (L) 3 (L) RARE
SCENARIO 5 13 (S) 13 (S) 13 (S) 8 (M) 13 (S) 13 (S) 13 (S) POSSIBLE
SCENARIO 6 #N/A #N/A #N/A #N/A #N/A #N/A #N/A NO RISK
SCENARIO 7 5 (L) 5 (L) 5 (L) 5 (L) 9 (M) 9 (M) 9 (M) UNLIKELY
PRE-MITIGATION NONE 23 (H) 23 (H) 23 (H) 17 (S) 23 (H) 21 (H) 21 (H)
SCENARIO 1 13 (S) 13 (S) 13 (S) 8 (M) 13 (S) 13 (S) 13 (S) POSSIBLE
SCENARIO 2 13 (S) 13 (S) 13 (S) 8 (M) 13 (S) 13 (S) 13 (S) POSSIBLE
SCENARIO 3 8 (M) 8 (M) 8 (M) 8 (M) 8 (M) 8 (M) 8 (M) POSSIBLE
SCENARIO 4 3 (L) 3 (L) 3 (L) 3 (L) 3 (L) 3 (L) 3 (L) RARE
SCENARIO 5 13 (S) 13 (S) 13 (S) 8 (M) 13 (S) 13 (S) 13 (S) POSSIBLE
SCENARIO 6 #N/A #N/A #N/A #N/A #N/A #N/A #N/A NO RISK
SCENARIO 7 5 (L) 5 (L) 5 (L) 5 (L) 9 (M) 9 (M) 9 (M) UNLIKELY
RISK RELATED ASPECT: PIT SIDE WALL STABILITY
COVER RESOURCE, WALL & BERM
RESHAPE TOP BENCH 18°, COVER RESOURCE ,WALL & BERM
PARTIAL IN-FILL AT ANGLE OF REPOSE , WALL & BERM
PARTIAL IN- FILL AT 18°, WALL & BERM
COVER RESOURCE, INCREASE CATCHMENT, WALL & BERM
COVER RESOURCE, 1 ACCESS ROUTE, INCREASE CATCHMENT, FENCE & BERM
COMPLETE, IN-FILL ALL MRD MATERIAL
RESIDUAL RISK /
IMPACTS AFTER IMPLEMENTATION OF THE
MANAGEMENT MEASURES
Failure of the open pit side walls, resulting in possible
instability of surrounding areas e.g. remaining infrastructure and
residue deposits (under-estimating the extent of the zone of
relaxation)
Failure of the open pit side walls, resulting in human and animal
injury or death (under-estimating the extent of the zone of
relaxation)
RISK STATEMENT SCENARIO MITIGATION MEASURES
RISK CATEGORY
Risk MatrixPit side wall stability Risk Assessment Tool
Accessibility to open pit
Water resources
Land capability
& ELU
Index
Open Pit Closure Scenarios
Natural resources
Government &
Stakeholders
Cost-Benefit Analysis
PROJECT: VOORSPOED MINE – PIT CLOSURE STUDY 2015/2016
43
Figure 33: Risk summary for impact on Water resources
Voorspoed Open Pit Closure Risk Assessment
SCENARIO 1
SCENARIO 2
SCENARIO 3
SCENARIO 4
SCENARIO 5
SCENARIO 6
SCENARIO 7
SAFETY OCCUPATIONAL HEALTH ENVIRONMENTAL FINANCIAL LEGAL & REGULATORY SOCIAL / COMMUNITY REPUTATION
PRE-MITIGATION NONE #N/A #N/A 18 (S) 5 (L) 8 (M) 5 (L) 5 (L)
SCENARIO 1 #N/A #N/A 18 (S) 5 (L) 8 (M) 5 (L) 5 (L) POSSIBLE
SCENARIO 2 #N/A #N/A 18 (S) 5 (L) 8 (M) 5 (L) 5 (L) POSSIBLE
SCENARIO 3 #N/A #N/A 5 (L) 2 (L) 5 (L) 5 (L) 5 (L) UNLIKELY
SCENARIO 4 #N/A #N/A 5 (L) 2 (L) 5 (L) 5 (L) 5 (L) UNLIKELY
SCENARIO 5 #N/A #N/A 8 (M) 2 (L) 8 (M) 5 (L) 5 (L) POSSIBLE
SCENARIO 6 #N/A #N/A 1 (L) 1 (L) 3 (L) 3 (L) 3 (L) RARE
SCENARIO 7 #N/A #N/A 8 (M) 2 (L) 9 (M) 5 (L) 5 (L) POSSIBLE
PRE-MITIGATION NONE #N/A 9 (M) 9 (M) 2 (L) 8 (M) 5 (L) 5 (L)
SCENARIO 1 #N/A 5 (L) 9 (M) 2 (L) 5 (L) 5 (L) 5 (L) UNLIKELY
SCENARIO 2 #N/A 5 (L) 9 (M) 2 (L) 5 (L) 5 (L) 5 (L) UNLIKELY
SCENARIO 3 #N/A 8 (M) 13 (S) 2 (L) 8 (M) 8 (M) 8 (M) POSSIBLE
SCENARIO 4 #N/A 8 (M) 13 (S) 2 (L) 8 (M) 8 (M) 8 (M) POSSIBLE
SCENARIO 5 #N/A 5 (L) 9 (M) 2 (L) 5 (L) 5 (L) 5 (L) UNLIKELY
SCENARIO 6 #N/A 12 (M) 17 (S) 2 (L) 8 (M) 8 (M) 8 (M) LIKELY
SCENARIO 7 #N/A 5 (L) 9 (M) 2 (L) 5 (L) 5 (L) 5 (L) UNLIKELY
PRE-MITIGATION NONE #N/A #N/A 20 (S) 5 (L) 8 (M) 5 (L) 5 (L)
SCENARIO 1 #N/A #N/A 13 (S) 5 (L) 8 (M) 5 (L) 5 (L) POSSIBLE
SCENARIO 2 #N/A #N/A 13 (S) 5 (L) 8 (M) 5 (L) 5 (L) POSSIBLE
SCENARIO 3 #N/A #N/A 8 (M) 2 (L) 5 (L) 5 (L) 5 (L) POSSIBLE
SCENARIO 4 #N/A #N/A 13 (S) 2 (L) 5 (L) 5 (L) 5 (L) POSSIBLE
SCENARIO 5 #N/A #N/A 13 (S) 5 (L) 8 (M) 5 (L) 5 (L) POSSIBLE
SCENARIO 6 #N/A #N/A 1 (L) 1 (L) 3 (L) 3 (L) 3 (L) RARE
SCENARIO 7 #N/A #N/A 13 (S) 5 (L) 9 (M) 9 (M) 9 (M) POSSIBLE
Surface water:
Ingress of surface water into the open pit having a negative
effect on surrounding water users and wetland systems
(resulting in reduced local surface water yield)
Assume minimum stormwater diversion structures will be
in place
RISK CATEGORYRESIDUAL RISK /
IMPACTS AFTER IMPLEMENTATION OF THE
MANAGEMENT MEASURES
Groundwater:
Impact on local groundwater levels and yield.
Groundwater:
Impact on Groundwater quality
RISK STATEMENT SCENARIO MITIGATION MEASURES
RISK RELATED ASPECT: WATER RESOURCES
COVER RESOURCE, WALL & BERM
RESHAPE TOP BENCH 18°, COVER RESOURCE ,WALL & BERM
PARTIAL IN-FILL AT ANGLE OF REPOSE , WALL & BERM
PARTIAL IN- FILL AT 18°, WALL & BERM
COVER RESOURCE, INCREASE CATCHMENT, WALL & BERM
COVER RESOURCE, 1 ACCESS ROUTE, INCREASE CATCHMENT, FENCE & BERM
COMPLETE, IN-FILL ALL MRD MATERIAL
Risk MatrixPit side wall stability Risk Assessment Tool
Accessibility to open pit
Water resources
Land capability
& ELU
Index
Open Pit Closure Scenarios
Natural resources
Government &
Stakeholders
Cost-Benefit Analysis
PROJECT: VOORSPOED MINE – PIT CLOSURE STUDY 2015/2016
44
Figure 34: Risk summary for impact on Land capability and End land use
Voorspoed Open Pit Closure Risk Assessment
SCENARIO 1
SCENARIO 2
SCENARIO 3
SCENARIO 4
SCENARIO 5
SCENARIO 6
SCENARIO 7
SAFETY OCCUPATIONAL HEALTH ENVIRONMENTAL FINANCIAL LEGAL & REGULATORY SOCIAL / COMMUNITY REPUTATION
PRE-MITIGATION NONE #N/A #N/A 25 (H) 16 (S) 25 (H) 24 (H) 21 (H)
SCENARIO 1 #N/A #N/A 18 (S) 8 (M) 18 (S) 18 (S) 18 (S) POSSIBLE
SCENARIO 2 #N/A #N/A 18 (S) 8 (M) 18 (S) 18 (S) 18 (S) POSSIBLE
SCENARIO 3 #N/A #N/A 24 (H) 12 (M) 24 (H) 24 (H) 21 (H) LIKELY
SCENARIO 4 #N/A #N/A 5 (L) 5 (L) 5 (L) 5 (L) 5 (L) UNLIKELY
SCENARIO 5 #N/A #N/A 13 (S) 8 (M) 13 (S) 13 (S) 13 (S) POSSIBLE
SCENARIO 6 #N/A #N/A 3 (L) 3 (L) 3 (L) 3 (L) 3 (L) RARE
SCENARIO 7 #N/A #N/A 9 (M) 5 (L) 5 (L) 5 (L) 5 (L) UNLIKELY
RISK CATEGORYRESIDUAL RISK /
IMPACTS AFTER IMPLEMENTATION OF THE
MANAGEMENT MEASURES
No beneficial post-closure land use for the open pit
RISK RELATED ASPECT: LAND CAPABILITY & END LAND USE
COVER RESOURCE, WALL & BERM
RESHAPE TOP BENCH 18°, COVER RESOURCE ,WALL & BERM
PARTIAL IN-FILL AT ANGLE OF REPOSE , WALL & BERM
PARTIAL IN- FILL AT 18°, WALL & BERM
COVER RESOURCE, INCREASE CATCHMENT, WALL & BERM
COVER RESOURCE, 1 ACCESS ROUTE, INCREASE CATCHMENT, FENCE & BERM
COMPLETE, IN-FILL ALL MRD MATERIAL
RISK STATEMENT SCENARIO MITIGATION MEASURES
PROJECT: VOORSPOED MINE – PIT CLOSURE STUDY 2015/2016
45
Figure 35: Risk summary for impact on Natural resources
Voorspoed Open Pit Closure Risk Assessment
SCENARIO 1
SCENARIO 2
SCENARIO 3
SCENARIO 4
SCENARIO 5
SCENARIO 6
SCENARIO 7
SAFETY OCCUPATIONAL HEALTH ENVIRONMENTAL FINANCIAL LEGAL & REGULATORY SOCIAL / COMMUNITY REPUTATION
PRE-MITIGATION NONE #N/A #N/A 15 (S) 6 (M) 10 (M) 6 (M) 6 (M)
SCENARIO 1 #N/A #N/A 19 (S) 9 (M) 14 (S) 9 (M) 9 (M) UNLIKELY
SCENARIO 2 #N/A #N/A 19 (S) 9 (M) 14 (S) 9 (M) 9 (M) UNLIKELY
SCENARIO 3 #N/A #N/A 24 (H) 17 (S) 21 (H) 17 (S) 17 (S) LIKELY
SCENARIO 4 #N/A #N/A 24 (H) 17 (S) 21 (H) 17 (S) 17 (S) LIKELY
SCENARIO 5 #N/A #N/A 19 (S) 9 (M) 14 (S) 9 (M) 9 (M) UNLIKELY
SCENARIO 6 #N/A #N/A 25 (H) 20 (S) 23 (H) 20 (S) 20 (S) ALMOST CERTAIN
SCENARIO 7 #N/A #N/A 14 (S) 5 (L) 9 (M) 5 (L) 5 (L) UNLIKELY
RISK CATEGORYRESIDUAL RISK /
IMPACTS AFTER IMPLEMENTATION OF THE
MANAGEMENT MEASURES
Possible resource sterilisation.
RISK RELATED ASPECT: NATURAL RESOURCES
COVER RESOURCE, WALL & BERM
RESHAPE TOP BENCH 18°, COVER RESOURCE ,WALL & BERM
PARTIAL IN-FILL AT ANGLE OF REPOSE , WALL & BERM
PARTIAL IN- FILL AT 18°, WALL & BERM
COVER RESOURCE, INCREASE CATCHMENT, WALL & BERM
COVER RESOURCE, 1 ACCESS ROUTE, INCREASE CATCHMENT, FENCE & BERM
COMPLETE, IN-FILL ALL MRD MATERIAL
RISK STATEMENT SCENARIO MITIGATION MEASURES
Risk MatrixPit side wall stability Risk Assessment Tool
Accessibility to open pit
Water resources
Land capability
& ELU
Index
Open Pit Closure Scenarios
Natural resources
Government &
Stakeholders
Cost-Benefit Analysis
PROJECT: VOORSPOED MINE – PIT CLOSURE STUDY 2015/2016
46
Figure 36: Risk summary for impact associated with Government and stakeholders
Voorspoed Open Pit Closure Risk Assessment
SCENARIO 1
SCENARIO 2
SCENARIO 3
SCENARIO 4
SCENARIO 5
SCENARIO 6
SCENARIO 7
SAFETY OCCUPATIONAL HEALTH ENVIRONMENTAL FINANCIAL LEGAL & REGULATORY SOCIAL / COMMUNITY REPUTATION
PRE-MITIGATION NONE #N/A #N/A #N/A #N/A 23 (H) 21 (H) 14 (S)
SCENARIO 1 #N/A #N/A #N/A #N/A 17 (S) 17 (S) 17 (S) LIKELY
SCENARIO 2 #N/A #N/A #N/A #N/A 17 (S) 17 (S) 17 (S) LIKELY
SCENARIO 3 #N/A #N/A #N/A #N/A 17 (S) 17 (S) 17 (S) LIKELY
SCENARIO 4 #N/A #N/A #N/A #N/A 8 (M) 8 (M) 8 (M) POSSIBLE
SCENARIO 5 #N/A #N/A #N/A #N/A 8 (M) 8 (M) 8 (M) POSSIBLE
SCENARIO 6 #N/A #N/A #N/A #N/A 2 (L) 2 (L) 2 (L) UNLIKELY
SCENARIO 7 #N/A #N/A #N/A #N/A 8 (M) 8 (M) 8 (M) POSSIBLE
RISK CATEGORYRESIDUAL RISK /
IMPACTS AFTER IMPLEMENTATION OF THE
MANAGEMENT MEASURES
Not meeting the expectations of government and stakeholders
with regards to closure and not obtaining the subsequent
certificate of closure.
RISK RELATED ASPECT: GOVERNMENT & STAKEHOLDERS
COVER RESOURCE, WALL & BERM
RESHAPE TOP BENCH 18°, COVER RESOURCE ,WALL & BERM
PARTIAL IN-FILL AT ANGLE OF REPOSE , WALL & BERM
PARTIAL IN- FILL AT 18°, WALL & BERM
COVER RESOURCE, INCREASE CATCHMENT, WALL & BERM
COVER RESOURCE, 1 ACCESS ROUTE, INCREASE CATCHMENT, FENCE & BERM
COMPLETE, IN-FILL ALL MRD MATERIAL
RISK STATEMENT SCENARIO MITIGATION MEASURES
Risk MatrixPit side wall stability Risk Assessment Tool
Accessibility to open pit
Water resources
Land capability
& ELU
Index
Open Pit Closure Scenarios
Natural resources
Government &
Stakeholders
Cost-Benefit Analysis
PROJECT: VOORSPOED MINE – PIT CLOSURE STUDY 2015/2016
47
9. STANDARD OPERATING PROCEDURE FOR SITE-WIDE CLOSURE
The purpose of the procedure for site-wide mine closure is to provide a generic description of the
environmental legal framework which is applicable to the mine closure processes, including
legislation, regulations and guidelines as well as the processes to be followed in terms of the
requirements of the legal framework.
The procedure focuses on the generic environmental requirements and processes for site-wide mine
closure and not only the open pit. The Standard operating procedure (SOP) for site-wide closure is
attached in Annexure B.
The SOP was written in accordance with the legal requirements as contained in the legal
requirements’ checklist. The checklist therefore serves as legal reference to the processes found in
the SOP. The SOP gives effect to these requirements and should ideally ensure that an organisation
meets the legal requirements that culminate in the issuing of a closure certificate.
At the time of the submission of the SOP (beginning of November 2015), the client requested that
only the following be considered and that any regulations that were not yet approved be excluded
from this exercise. The processes include:
Application for a closure certificate in terms of the requirements of the Minerals and Petroleum
Resources Development Act (28 of 2002) (MPRDA) and the MPRDA regulations;
Application for environmental authorisation in terms of the National Environmental Management
Act (107 of 1998) (NEMA) and the Environmental Impact Assessment (EIA) Regulations of
December 2014;
The notification and permit application processes in terms of the National Heritage Resources Act
(25 of 1999); and
The notification process in terms of the National Environmental Management Air Quality Act (39
of 2004).
It should however be noted that Regulations 1147: Regulations pertaining to the Financial provision
for prospecting, exploration, mining or production operations came into effect on 20 November 2015,
just after the submission of the abovementioned, and that this should be incorporated and considered
in the update of the SOP.
PROJECT: VOORSPOED MINE – PIT CLOSURE STUDY 2015/2016
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ANNEXURE A: RISK ASSESSMENT AND COST-BENEFIT ANALYSIS
PROJECT: VOORSPOED MINE – PIT CLOSURE STUDY 2015/2016
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ANNEXURE B: STANDARD OPERATING PROCEDURE FOR CLOSURE
PROJECT: VOORSPOED MINE – PIT CLOSURE STUDY 2015/2016
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ANNEXURE C: PRESENTATION OF OPEN PIT CLOSURE SCENARIOS AND
COSTS