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\\PTAFS\Projects\J01599 - TCTA-AMD\10. Reports\10.2 Technical Reports\Portion 1 Due Diligence Final 2011-08-25\05 Due Diligence\J01599-05 Due Diligence - Final.docx
Project : Witwatersrand Gold Fields: Acid Mine Drainage (Phase 1)
Title : Due Diligence
Project Team : BKS (Pty) Ltd
Client : TCTA
BKS Project No : J01599
Status of Report : Final
BKS Report No : J01599/05
Key Words : Due diligence, Witwatersrand Gold Fields, Acid Mine Drainage, AMD
Date of this Issue : August 2011
For BKS (Pty) Ltd
Compiled by SG Seath
Initials & Surname Signature Date
Compiled by J A van Niekerk
Initials & Surname Signature Date
Reviewed by AM van Niekerk
Initials & Surname Signature Date
Approved by F Wimberley
Initials & Surname Signature Date
Approved by Dr G H de Villiers
Initials & Surname Signature Date
Ready for Issue A Augere
Initials & Surname Signature Date
Approval by TCTA
Approved by :
Initials & Surname Signature Date
TCTA 08-041 Witwatersrand Gold Fields: Acid Mine Drainage (Phase 1) Due Diligence August 2011
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EXECUTIVE SUMMARY
Cabinet appointed an Inter-Ministerial Committee (IMC) in 2010 to address the serious challenges posed by
acid mine drainage (AMD) in the Witwatersrand Goldfields area. The IMC tasked a Technical Committee, co-
chaired by the Director Generals of the Department of Mineral Resources (DMR) and the Department of Water
Affairs (DWA), to investigate the AMD issue. The Technical Committee subsequently appointed a team of
experts, who developed and presented a draft report on AMD to Cabinet on 9 February 2011.
The IMC and Cabinet approved the following recommendations in the team of experts’ Report for emergency
implementation:
Installation of pumps to extract AMD from the mines to on-site treatment plants.
Construction of on-site water treatment plants in each basin, with the option of refurbishing and
upgrading existing treatment facilities owned by the mines.
Installation of infrastructure to convey treated water for discharge into nearby water courses.
The IMC Report indicated that this work is urgently required as the prevention of AMD decanting from the
mining basins is considered to be of national importance. The DWA directed the Trans-Caledon Tunnel
Authority (TCTA) to implement this emergency solution. TCTA has commissioned BKS, in association with Golder
Associates, to design and implement the short-term solutions for the emergency AMD Project.
The scope of work of the project has been divided into the following five tasks:
Task 1: A due diligence review of the Inter-Ministerial Committee Report (as provided by TCTA)
and the recommendation of a solution for each of the mining basins.
Task 2: Development and production of documents supporting the Integrated Regulatory Process
for all basins.
Task 3: Development and production of engineering design and tender documents that will be
used for competitive procurement of a competent contractor(s) combined with detailed
engineering design of the agreed and approved solutions for each of the mining basins, complete
with construction drawings.
Task 4: Monitoring of the Contractor’s activities and commissioning of the works.
Task 5: Monitoring of the works during the defects liability period, taking corrective actions if
required, and the provision of formal operation and maintenance manuals as well as close-out
reports.
Task 6: Operation and maintenance support to the TCTA for all constructed basins.
This report covers the work undertaken, conclusions derived and recommendations made for Task 1 (Due
Diligence Review) of this project.
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The entire Witwatersrand gold mining area is divided into four basins: the Far Western Basin, Western Basin,
Central Basin and Eastern Basin. The Western, Central and Eastern Basins are the focus of the TCTA project.
The Western Basin covers the Krugersdorp, Witpoortjie and Randfontein areas. The mine lease areas in this
basin extend over about 57km². The Central Basin extends from Durban Roodepoort Deep (DRD) in the west to
the East Rand Proprietary Mines (ERPM) in the east. The mine lease areas in this basin extend over about
251km2. The Eastern Basin covers the East Rand area, including the towns of Boksburg, Brakpan, Springs and
Nigel. The mine lease areas in this basin extend over about 768 km2.
Task 1: Due Diligence work was based on the following technical details, which were used to guide the
development of practical technical solutions:
Environmental Critical Level:
- Western Basin: 1,550 m amsl.
- Central Basin: 1,467 m amsl.
- Eastern: 1,280 m amsl.
Water volumes and flow rates:
- Western Basin: sustained base flow = 27 Mℓ/day; peak pumping flow = 35 Mℓ/day
- Central Basin: sustained base flow = 57 Mℓ/day; peak pumping flow = 84 Mℓ/day
- Eastern Basin: sustained base flow = 82 Mℓ/day; peak pumping flow = 110Mℓ/day
AMD water quality: The table below summarises the expected poorest water quality in the basins.
Water quality
Parameter Units
Western Basin
(95th
percentile)
Central Basin
(95th
percentile)
Eastern Basin
(flooded condition)
TDS mg/ℓ 7,174 7,700 5,500
Conductivity mS/m 548 730 450
Calcium (Ca) mg/ℓ 461 580 550
Magnesium (Mg) mg/ℓ 345 380 230
Sodium (Na) mg/ℓ 139 150 325
Sulphate (SO4) mg/ℓ 4,556 5,200 3275
Chloride (Cℓ) mg/ℓ 65 260 260
pH - 3.4-4.0 2.3 (5th
percentile) 5.0
Acidity (CaCO3) mg/ℓ 2,560 2,425 750
Iron (Fe) mg/ℓ 933 1,000 370
Aluminium (Aℓ) mg/ℓ 54 50 1
Manganese (Mn) mg/ℓ 312 60 10
Uranium (U) mg/ℓ 0.2 -- --
The assessment process for the three basins during the Due Diligence task included the following steps:
Collection and review of all available information.
Identification and formulation of options based on aspects such as AMD abstraction points, AMD
treatment sites, sludge waste disposal sites and treated water discharge sites.
Analysis of the identified project options based on a range of criteria.
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Selection of the preferred project option for each basin.
Conceptual design for the preferred option, including process flow diagrams, site layouts, AMD treatment
plant layouts, potential pipeline routes, and conceptual building and infrastructure layouts.
The selection of project options and the conceptual design was developed taking the following overall project
aspects into account:
AMD pumping at the ECL. This is the project base case.
Lowering the water level in the basin to accommodate the needs of the mining companies and other
stakeholders (e.g. Gold Reef City) in the basin. This is particularly applicable in the Central and Eastern
Basins.
The use of infrastructure and equipment supplied by the mining companies, which relates to the possible
use of the existing ERPM treatment plant and mine-supplied dewatering pumps for the Central Basin.
Specialist studies were prepared in support of the Due Diligence work, including:
Assessment of the water level and water balance for the basins.
Technology assessment for the treatment of AMD.
Conceptual AMD treatment process design.
Waste sludge handling, management and disposal.
Assessment of the rock stability in the selected pumping shafts.
The outcomes and recommendations arising from Task 1: Due Diligence are as follows.
AMD Treatment Technology
It is recommended that the following AMD treatment technology and chemical reagent combination be used
for the treatment of the Witwatersrand Gold Fields AMD:
Oxidation by aeration.
Pre-neutralisation and metals removal with limestone.
Final neutralisation and metals removal with lime, produced by the slaking of quicklime.
Gypsum crystallisation to remove excess sulphate from solution.
The proposed AMD treatment plants would be based on the proven and reliable High Density Sludge (HDS)
process with optimisation related to the use of limestone (mainly developed by the CSIR) incorporated into the
final treatment process configurations.
Western Basin: Immediate Mitigation Measures
Immediate AMD mitigation measures can be implemented practically in the Western Basin based on the
following:
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Upgrading and retrofitting of the existing Rand Uranium Treatment Plant as the best opportunity in terms
of treatment capacity and ease of implementation.
Bringing the Rand Uranium Treatment Plant’s additional treatment trains back into operation, after
appropriate mechanical and electrical equipment has been installed.
The potential AMD treatment capacity, including the existing single operational treatment train is
estimated to be 26-32 Mℓ per day.
The formulated immediate AMD mitigation measures use existing mine-owned infrastructure, but the
immediate scheme is not well positioned or of a permanent enough nature to form part of a sustainable short-
or long-term solution.
Key components of short-term AMD management schemes
Western Basin
Abstraction of AMD via installed pumps in Rand Uranium’s No. 8 Shaft at a depth to achieve the ECL.
Construction of a new high density sludge (HDS) treatment plant on the Randfontein Estates site.
Construction of a treated water pipeline to a suitable discharge point on the Tweelopiespruit, flowing to
the Crocodile West River.
Construction of waste sludge disposal pumps / a pipeline to the old opencast pits, including Wes Wits Pit
and the Training Centre Pit.
Central Basin
Abstraction of AMD via installed pumps in the South West Vertical (SWV) Shaft (either to pump to the ECL
or to the Central Rand Gold-proposed mining level of 400m below SWV Shaft level).
Construction of a new HDS plant at SWV Shaft.
Construction of a waste sludge to the DRD Gold (Crown) Knights Gold Plant.
Construction of a treated water pipeline to a suitable discharge point on the Elsburgspruit.
Investigation and planning for a future waste sludge pipeline to the ERGO Brakpan tailings storage facility
(TSF) and, alternatively, to ERPM’s old underground workings
Eastern Basin
Abstraction of AMD via installed pumps in Grootvlei No. 3 shaft at a pump depth to achieve the ECL level or
the level to allow Gold One to continue mining Sub Nigel No. 1 Shaft.
Construction of a new High Density Sludge (HDS) treatment plant adjacent to the Grootvlei No. 3 shaft, on
the agricultural small holding site south of the abstraction point.
Construction of a waste sludge pipeline to the DRD Gold Daggafontein Gold Plan for co-disposal on the
Daggafontein TSF.
Construction of a treated water pipeline to a suitable discharge point on the Blesbokspruit.
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Dewatering mineshaft stability
The Rand Uranium Shaft No. 8 is suitable for use as a pumping shaft.
There are no rock engineering-related fatal flaws with regard to the use of ERPM SWV Shaft, ERPM Ventilation
Shaft, ERPM Cinderella East Shaft and Grootvlei Shaft No. 3 as possible pumping shafts. Sallies Shaft No. 1 is
filled in with rock and cannot be used as a pumping shaft.
Implementation costs
The capital and annual operating cost estimates for the AMD treatment plants for the three basins are shown
in the following tables.
Number Description Western Basin Central Basin Eastern Basin
1 AMD collection infrastructure R40,787,729 R45,127,500 R60,096,771
2 AMD treatment plant R73,255,525 R90,631,838 R108,010,007
3 Neutralised water discharge R1,316,400 R1,172,400 R1,622,400
4 Sludge handling and disposal R1,711,806 R6,200,000 R6,800,000
5 Earthworks and pipe work R31,008,353 R46,196,290 R28,480,441
6 Electrical control and
instrumentation
R25,960,790 R23,735,832 R30,856,582
7 Preliminaries and Generals
(12%)
R20,884,872 R25,567,663 R28,303,944
Total R194,925,475 R238,631,500 R264,170,100
Total (all Basins) R697,727,075
Number Description Western Basin Central Basin Eastern Basin
1 O&M on CAPEX R3,600,100 R4,128,600 R4,571,500
2 Chemical costs R31,177,274 R61,602,829 R60,444,482
3 Electricity costs R13,527,200 R15,146,600 R15,520,700
Total R48,304,574 R80,878,029 R80,536,682
Total (all Basins) R209,719,285
Integrated Regulatory Approval
An optimised regulatory approval process approach has been recommended to help meet the project
milestones for emergency implementation, while ensuring that the necessary regulatory approvals are in place.
The conventional regulatory approach will have to be completed in parallel with the optimised process.
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The essential features of the optimised process are that TCTA will request:
the DWA to provide TCTA with the necessary directives to address AMD without TCTA having to obtain an
upfront Water Use Licence and Environmental Authorisation; and
the DMR to provide exemptions for participating mines so that they do not need to amend their
environmental management programmes immediately.
Risk assessment and risk management
High-level risks of the project were identified using a risk assessment process and relate mainly to:
Management of the AMD treatment plant waste sludge;
Delays in receiving the approvals during the environmental regulatory process;
Delays, opposition and lack of constructive participation by stakeholders (Government, mining companies
and the public);
Project implementation delays during the engineering design phase due to project scope changes arising
from the regulatory approval process; and
Inaccuracies in technical assumptions, such as the inter-connectivity of the mine workings in the respective
basins.
Implementation Plan
The key aspects of the Implementation Plan are as follows:
Commissioning of the AMD treatment plants by August 2011 for the Western and Central Basins, and by
February 2013 for the Eastern Basin.
A flexible and streamlined procurement strategy will be required in order to meet construction targets and
to provide sufficient float into the implementation programme of the project.
Measure and manage the Health and Safety risks of the project through the Hazard Identification and Risk
Assessment (HIRA) process.
Manage the high-level risks identified for the project.
Long-term perspectives
The development and planning of short-term AMD management and mitigation measures were done within
the context of accommodating the long-term mine water reclamation and reuse from the respective mining
basins.
The selection of suitable AMD treatment plant sites, the choice of AMD neutralisation technology, the general
configuration of infrastructure and pipeline routes and corridors were all done to provide seamless integration
with the long-term mine water management.
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TABLE OF CONTENTS
1. INTRODUCTION .................................................................................................................................. 1
1.1 Project Background .............................................................................................................. 1
1.2 Description of the Basins ...................................................................................................... 2
1.3 Project Objectives ................................................................................................................ 3
1.4 Summary of the Scope of Work ............................................................................................ 4
2. PROJECT EXECUTION AND APPROACH ............................................................................................... 4
2.1 Technical Process ................................................................................................................. 4
2.2 Shaft Stability ....................................................................................................................... 7
2.3 Integrated Regulatory Process .............................................................................................. 8
2.4 Risk Management ................................................................................................................. 8
3. ASSUMPTIONS AND LIMITATIONS ..................................................................................................... 9
4. BASIS OF DESIGN ................................................................................................................................ 9
4.1 Summary of Available Information ....................................................................................... 9
4.2 Basis of Engineering Design ................................................................................................ 10
4.3 Mine Water Resources ....................................................................................................... 10
4.3.1 Water Balances for the Basins ................................................................................... 10
4.3.2 Environmental Critical Level (ECL) ............................................................................. 10
4.3.3 Water Volumes and Flow Rates ................................................................................. 11
4.3.4 Water Quality ............................................................................................................ 11
4.4 Treatment Technology ....................................................................................................... 12
4.4.1 Objectives of Mine Water Treatment ........................................................................ 12
4.4.2 Identification and Selection of Treatment Process .................................................... 12
4.4.3 Assessment of Alternative Sources of Alkali .............................................................. 13
4.4.4 Recommendations ..................................................................................................... 14
4.5 Sludge Disposal .................................................................................................................. 14
4.5.1 General ...................................................................................................................... 14
4.5.2 Conceptual Engineering Design ................................................................................. 15
4.6 Technical Aspects ............................................................................................................... 16
4.6.1 Hydraulic Impact of Treated Water Discharge .......................................................... 16
4.6.2 Pumping Philosophy .................................................................................................. 17
4.6.3 Mineshaft Pumping.................................................................................................... 18
5. METHODOLOGY ............................................................................................................................... 19
5.1 Introduction ....................................................................................................................... 19
5.2 Options Selection ............................................................................................................... 19
5.3 Options Analysis ................................................................................................................. 19
5.4 Preferred Option ................................................................................................................ 20
5.5 Conceptual Design .............................................................................................................. 20
6. WESTERN BASIN ............................................................................................................................... 21
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6.1 Status of the Basin .............................................................................................................. 21
6.1.1 Background ................................................................................................................ 21
6.1.2 Mine Water Generation ............................................................................................. 22
6.1.3 Mine Water Flow ....................................................................................................... 22
6.1.4 Water Quality ............................................................................................................ 23
6.1.5 Existing Mine Water Treatment System .................................................................... 23
6.1.6 Immediate Mitigation Measures to Treat AMD ........................................................ 24
6.2 Options for Abstraction and Treatment of AMD ................................................................. 25
6.2.1 Identification of Options ............................................................................................ 25
6.2.2 Assessment of Options .............................................................................................. 31
6.2.3 Continued Mining in the Western Basin .................................................................... 35
6.2.4 Recommendations on Preferred Project Option ....................................................... 35
6.2.5 Emergency Contingency Shafts ................................................................................. 35
6.2.6 Consideration of Integration with Future Long Term AMD Treatment ..................... 35
6.3 Conceptual Design .............................................................................................................. 36
6.3.1 Shaft Stability ............................................................................................................. 36
6.3.2 Abstraction and Collection Infrastructure ................................................................. 36
6.3.3 Plant Infrastructure.................................................................................................... 40
6.3.4 Sludge Handling and Management ............................................................................ 41
6.3.5 Treated Water Discharge ........................................................................................... 42
6.4 Detail Cost Estimates .......................................................................................................... 44
6.4.1 Detail Capital Estimate ............................................................................................... 44
6.4.2 Detailed Operating and Maintenance Cost Estimate ................................................ 44
7. CENTRAL BASIN ................................................................................................................................ 44
7.1 Status of the Basin .............................................................................................................. 45
7.1.1 Background ................................................................................................................ 45
7.1.2 Mine Water Generation ............................................................................................. 45
7.1.3 Mine Water Flow ....................................................................................................... 48
7.1.4 Water Quality ............................................................................................................ 48
7.2 Options for the Collection and Treatment of AMD ............................................................. 48
7.2.1 Identification of Options ............................................................................................ 48
7.2.2 Assessment of Options .............................................................................................. 51
7.2.3 Continued Mining in the Central Basin ...................................................................... 57
7.2.4 Recommendations on Preferred Project Options for the Central Basin .................... 67
7.2.5 Emergency Contingency Shafts ................................................................................. 67
7.2.6 Consideration of Integration with Future Long Term AMD Treatment ..................... 67
7.3 Conceptual Design .............................................................................................................. 68
7.3.1 Shaft Stability ............................................................................................................. 68
7.3.2 Abstraction and collection infrastructure .................................................................. 68
7.3.3 Plant Infrastructure.................................................................................................... 72
7.3.4 Waste Sludge Handling and Management ................................................................ 75
7.3.5 Treated Water Discharge ........................................................................................... 77
7.4 Detailed Cost Estimates ...................................................................................................... 78
7.4.1 Detailed Capital Estimate........................................................................................... 78
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7.4.2 Detailed Operating and Maintenance Cost Estimate ................................................ 79
8. EASTERN BASIN ................................................................................................................................ 79
8.1 Status of the Basin .............................................................................................................. 79
8.1.1 Background ................................................................................................................ 79
8.1.2 ECL, Expected Rate of Rise and Decant ..................................................................... 80
8.1.3 Flows .......................................................................................................................... 82
8.1.4 Water Quality ............................................................................................................ 82
8.2 Options for Collection and Treatment of Water ................................................................. 83
8.2.1 Identification of options ............................................................................................ 83
8.2.2 Assessment of Project Options .................................................................................. 86
8.2.3 Mining Options in the Eastern Basin ......................................................................... 92
8.2.4 Possible Draw-Down Scenarios.................................................................................. 92
8.2.5 Recommendations on preferred options .................................................................. 93
8.2.6 Emergency Contingency Shafts ................................................................................. 93
8.2.7 Consideration of Integration with Future Long-Term AMD Treatment ..................... 93
8.3 Conceptual Design .............................................................................................................. 94
8.3.1 Shaft Stability ............................................................................................................. 94
8.3.2 Abstraction Infrastructure ......................................................................................... 94
8.3.3 Plant Infrastructure.................................................................................................... 98
8.3.4 Waste Sludge Handling and Management .............................................................. 100
8.3.5 Treated water discharge .......................................................................................... 102
8.4 Detailed Cost Estimates .................................................................................................... 103
8.4.1 Detailed Capital Estimate......................................................................................... 103
8.4.2 Detailed Operating and Maintenance Cost Estimate .............................................. 103
9. REGULATORY AND ENVIRONMENTAL ............................................................................................ 104
10. RISK ASSESSMENT .......................................................................................................................... 104
10.1 Risk Assessment Methodology ......................................................................................... 104
10.1.1 Step 1: Risk Identification ........................................................................................ 105
10.1.2 Step 2: Risk Rating ................................................................................................... 105
10.1.3 Step 3: Risk Classification ......................................................................................... 105
10.1.4 Step 4: Risk Mitigation ............................................................................................. 106
10.2 Risk Assessment Results ................................................................................................... 106
11. COST ESTIMATES SUMMARY .......................................................................................................... 110
11.1 Capital Costs ..................................................................................................................... 110
11.2 Operating Costs ................................................................................................................ 110
11.3 Cash flow .......................................................................................................................... 110
12. PROJECT IMPLEMENTATION STRATEGY ......................................................................................... 111
12.1 Introduction ..................................................................................................................... 111
12.2 Project Objectives ............................................................................................................ 111
12.2.1 Western Basin .......................................................................................................... 112
12.2.2 Central Basin ............................................................................................................ 112
12.2.3 Eastern Basin ........................................................................................................... 112
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12.3 Project Tasks and High Level Schedule ............................................................................. 112
12.3.1 Task 1: Due Diligence ............................................................................................... 113
12.3.2 Task 2: Environmental / IRP ..................................................................................... 113
12.3.3 Task 3: Design and Documentation ......................................................................... 113
12.3.4 Task 4: Construction Supervision ............................................................................. 114
12.3.5 Task 5: Assessment and Close Out........................................................................... 114
12.3.6 Task 6: Operation and Maintenance Support .......................................................... 114
12.4 Project Schedule and Key Milestones ............................................................................... 114
12.5 Overarching Project Approach .......................................................................................... 115
12.5.1 Procurement ............................................................................................................ 115
12.5.2 Health and Safety..................................................................................................... 116
12.5.3 Project Risk Assessment .......................................................................................... 117
13. LONG-TERM MINE WATER RECLAMATION AND REUSE .................................................................. 119
13.1 Short-Term Measures ....................................................................................................... 119
13.2 Future Water Reclamation and Reuse .............................................................................. 119
13.3 Technology Aspects of Water Reclamation and Reuse ..................................................... 119
13.4 Water Resources Context of Reclamation and Reuse ....................................................... 120
13.5 Financial Aspects of Water Reclamation ........................................................................... 120
13.6 Institutional Aspects of Water Reclamation and Reuse .................................................... 121
14. RECOMMENDATIONS ..................................................................................................................... 121
14.1 Environmental Critical Level (ECL) .................................................................................... 121
14.1.1 Water volumes and flow rates................................................................................. 122
14.1.2 Water quality ........................................................................................................... 122
14.2 Treatment Technology ..................................................................................................... 123
14.3 Western Basin: Immediate Mitigation Measures .............................................................. 123
14.4 Layout of Short-Term AMD Schemes ................................................................................ 123
14.4.1 Western Basin .......................................................................................................... 123
14.4.2 Central Basin ............................................................................................................ 124
14.4.3 Eastern Basin ........................................................................................................... 124
14.5 Rock Stability .................................................................................................................... 124
14.6 Implementation Costs ...................................................................................................... 124
14.7 Integrated Regulatory Process .......................................................................................... 125
14.8 Risk Assessment and Risk Management ........................................................................... 125
14.9 Implementation Plan ........................................................................................................ 126
15. REFERENCES ................................................................................................................................... 126
LIST OF TABLES
Table 1: Environmental Critical Levels .................................................................................................................. 10
Table 2: Expected Water Quality by Basin ............................................................................................................ 11
Table 3: Target Mine Water Discharge Standards ................................................................................................ 12
Table 4: OPEX – Chemical Cost Comparison of Alkali Options ............................................................................. 13
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Table 5: Hydraulic Impact of Treated Water Discharge ........................................................................................ 17
Table 6: Mine Dewatering and Treatment Flows (Western Basin) ....................................................................... 23
Table 7: Options for Abstraction and Treatment of AMD .................................................................................... 26
Table 8: Fatal Flaw Criteria Assessment ............................................................................................................... 31
Table 9: Summary of the Fatal Flaw Assessment ................................................................................................. 32
Table 10: Decision Matrix (Western Basin) .......................................................................................................... 33
Table 11: Shaft No. 8 Parameters ......................................................................................................................... 36
Table 12: Abstraction Pump Station (Western Basin) .......................................................................................... 38
Table 13: Estimated Electrical Power Load at Shaft No. 8 .................................................................................... 38
Table 14: Abstraction Pipeline (Western Basin) ................................................................................................... 38
Table 15: Description of Abstraction Pipeline Route (Western Basin) ................................................................. 39
Table 16: Major Service Crossings - Abstraction Pipeline (Western Basin) .......................................................... 40
Table 17: Treated Water Pump Station (Western Basin) ..................................................................................... 42
Table 18: Treated Water Pipe Line (Western Basin) ............................................................................................. 42
Table 19: Description of Treated Water Pipeline Route (Western Basin) ............................................................ 42
Table 20: Major Service Crossings - Treated Water Pipeline (Western Basin) ..................................................... 44
Table 21: Detail Capital Estimate for the Western Basin ...................................................................................... 44
Table 22: Detailed Operating and Maintenance Estimate for the Western Basin ............................................... 44
Table 23: Mine Dewatering and Treatment Flows (Central Basin) ....................................................................... 48
Table 24: Central Basin Initial Abstraction Options Screening ............................................................................. 49
Table 25: Decision Matrix (Central Basin) ............................................................................................................. 52
Table 26: Option Assessment (Central Basin) ....................................................................................................... 52
Table 27: Comparison of Costs for Different Operating Levels ............................................................................ 65
Table 28: SWV Shaft Parameters .......................................................................................................................... 68
Table 28: Abstraction Pump Station (Central Basin) ............................................................................................ 71
Table 30: Abstraction Pipeline (Central Basin) ..................................................................................................... 72
Table 31: Sludge Pump Station (Central Basin) .................................................................................................... 75
Table 32: Sludge Pipeline (Central Basin) ............................................................................................................. 76
Table 33: Description of Sludge Pipeline Route (Central Basin) ........................................................................... 76
Table 34: Major Service Crossings – Sludge Pipeline (Central Basin) ................................................................... 77
Table 35: Treated Water Pipeline (Central Basin) ................................................................................................ 78
Table 36: Detailed Capital Cost Estimate for Central Basin .................................................................................. 78
Table 37: Detailed Operating and Maintenance Estimate for Central Basin ........................................................ 79
Table 38: Ingress into Eastern Basin and Pump Rates .......................................................................................... 82
Table 39: Eastern Basin Initial Abstraction Options Screening ............................................................................. 83
Table 40: Decision Matrix (Eastern Basin) ............................................................................................................ 87
Table 41: Option Assessment (Eastern Basin) ...................................................................................................... 88
Table 42: Grootvlei No.3 Shaft Parameters .......................................................................................................... 94
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Table 43: Abstraction Pump Station (Eastern Basin) ............................................................................................ 96
Table 44: Abstraction Pipeline (Eastern Basin) ..................................................................................................... 97
Table 45: Sludge Pump Station (Eastern Basin) .................................................................................................. 100
Table 46: Sludge Pipeline (Eastern Basin) ........................................................................................................... 101
Table 47: Description of Sludge Pipeline Route (Eastern Basin) ......................................................................... 101
Table 48: Major Service Crossings – Sludge Pipeline (Eastern Basin) ................................................................. 102
Table 49: Treated Water Pipeline (Eastern Basin) .............................................................................................. 103
Table 50: Detailed Capital Cost Estimate for the Eastern Basin ......................................................................... 103
Table 51: Detailed Operating and Maintenance Cost Estimate for the Eastern Basin ....................................... 103
Table 52: Summary of Regulatory Processes Required and their Respective Timeframes ................................ 104
Table 53: Likelihood Criteria ............................................................................................................................... 105
Table 54: Risk Matrix .......................................................................................................................................... 106
Table 55: Risk Calculation ................................................................................................................................... 106
Table 56: High Risks ............................................................................................................................................ 107
Table 57: Summary of Capital Costs ................................................................................................................... 110
Table 58: Summary of Operating Costs .............................................................................................................. 110
Table 59: Project Tasks and High Level Schedule ............................................................................................... 112
Table 60: Key Project Milestones ....................................................................................................................... 114
Table 61: Potential Long Lead Items ................................................................................................................... 116
Table 62: High Risks for the Project .................................................................................................................... 117
Table 63: Environmental Critical Levels .............................................................................................................. 122
Table 64: Expected Water Quality by Basin ........................................................................................................ 122
Table 65: Summary of AMD Treatment Plant Capital Costs for All Basins ......................................................... 125
Table 66: Summary of AMD Treatment Plant Annual Operating Costs for All Basins ........................................ 125
LIST OF FIGURES
Figure 1: Western, Central and Eastern Basins in the Witwatersrand Basin .......................................................... 3
Figure 2: Approach to the Technical / Engineering Aspects of the Project ............................................................ 5
Figure 3: Generic Mine Water Neutralisation Process ......................................................................................... 13
Figure 4: Layout of the Western Basin ................................................................................................................. 21
Figure 5: Daily treated, untreated and total discharge volumes in the Western Basin........................................ 23
Figure 6: Locality and extent of the Central Basin ................................................................................................ 45
Figure 7: Predicted rate of water rise in the Central Basin (different rainfall scenarios) ..................................... 46
Figure 8: Ritz Pump Curve (HDM 67 37) .............................................................................................................. 60
Figure 9: Scenario 1 - Pumping 34 Mℓ/day........................................................................................................... 62
Figure 10: Scenario 2 - Pumping 57 Mℓ/day ........................................................................................................ 62
Figure 11: Scenario 3 - Pumping 84Mℓ/day ......................................................................................................... 63
Figure 12: Possible draw-down rates in the Central Basin to accommodate CRG Mining ................................... 64
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Figure 13: Drawdown at average pump rate (Central Basin) ............................................................................. 70
Figure 14: SWV land requirements ....................................................................................................................... 73
Figure 15: Locality and extent of the Eastern Basin ............................................................................................ 79
Figure 16: Predicted rate of water rise in the Eastern Basin ................................................................................ 80
Figure 17: Eastern Basin Options ......................................................................................................................... 85
Figure 18: Cash flow for the Witwatersrand Gold Fields Proposed Solutions ................................................... 111
Annexures
Annexure A – Basis of Engineering Design (BKS Report No J01599/01)
Annexure B – Water Balance and Levels (BKS Report No J01599/06)
Annexure C – Environmental Critical Levels (BKS Report No J01599/03)
Annexure D – Treatment Technology (BKS Report No J01599/07)
Annexure E – Process Design (BKS Report No J01599/09)
Annexure F – Formulation of Western Basin AMD Immediate Mitigation Measures (BKS Report No J01599/02)
Annexure G – Integrated Regulatory Process (IRP) (BKS Report No J01599/04)
Annexure H – Integrated Regulatory Process (IRP) Strategy (BKS Report No J01599/08)
Annexure I – Sludge Disposal Alternatives (BKS Report No J01599/10)
Annexure J – Rock Engineering Assessment (BKS Report No J01599/11)
Annexure K – Options Analysis Matrix
Annexure L – Risk Register
Annexure M – Proposed Project Programme
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LIST OF ABBREVIATIONS AND ACRONYMS
ACR Authorisation Change Request ℓ litre
AMD Acid mine drainage m metre
amsl Above mean sea level m3 Cubic metre
ARLP Acid Rain Leach Potential MAP Mean annual precipitation
ASC Authority steering committee mg Milligram
BBBEE Broad Based Black Economic
Empowerment
Mℓ Megalitre
BID Background Information Document MOU Memorandum of Understanding
BRI Black Reef Incline MPa Mega Pascal
CAPEX Capital Expenditure MPRDA Mineral and Petroleum Resources
Development Act (Act No. 28 of 2002)
CGS Council for Geoscience mS/m milli Siemens per metre
CMS Catchment management strategy MVA Mega Volt Amp
CoE Certificate of Exemption NEA Nuclear Energy Act (Act No. 46 of 1999)
CoR Certificate of Registration NEMA National Environmental Management Act
(Act No. 107 of 1998)
CPS Central Power Station (e.g. CPS Pit) NEM:WA National Environmental Management:
Waste Act (Act No. 59 of 2008)
CRG Central Rand Gold NHRA National Heritage Resources Act (Act No.
25 of 1999)
CSIR Council for Scientific and Industrial
Research
NNR National Nuclear Regulator
d Day NNRA National Nuclear Regulator Act (Act No.
47 of 1999)
DEA Department of Environmental Affairs NORM Naturally occurring radioactive materials
DME Department of Minerals and Energy
(now DMR)
NWA National Water Act (Act No. 36 of 1998)
DMR Department of Mineral Resources NWRS National Water Resource Strategy
DoE Department of Energy O&M Operation and Maintenance
DRD Durban Roodepoort Deep OPEX Operating Expenditure
DWA Department of Water Affairs OTE Oxygen transfer efficiency
DWAF Department of Water Affairs and
Forestry (now DWA)
PP Public participation
EAP Environmental Assessment Practitioner PPE Personal protective equipment
ECL Environmental Critical Level RPM Radiation protection monitors
ECO Environmental Control Officer RPO Radiation protection officer
EIA Environmental Impact Assessment RPS Radiation protection specialist
EMPr Environmental Management Programme RQO Resource quality objectives
ERPM East Rand Proprietary Mines s second
GDARD Gauteng Department of Agriculture and
Rural Development
SAHRA South African Heritage Resource Agency
GPRS General packet radio service Sv Sievert
GSI Geological strength index TCTA Trans Caledon Tunnel Authority
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h Hour TDS Total dissolved solids
HDS High density sludge TSF Tailings storage facility
HIRA Hazard Identification and Risk
Assessment
TTG Technical task group
HT High Tension UCS Uniaxial compressive strength
IAP2 International Association of Public
Participation
VFD/VSD Variable Frequency Drive / Variable
Speed Drive
I&APs Interested and affected parties W Watts
IMC Inter-Ministerial Committee WML Waste Management Licence
INAP International Network for Acid
Prevention
WTP Water Treatment Plant
IRP Integrated Regulatory Process WUC Western Utilities Corporation
IWUL Integrated Water Use Licence
IWWMP Integrated Water and Waste
Management Plan
kg Kilogram
kW Kilowatt
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1. INTRODUCTION
1.1 Project Background
In response to concerns about the Witwatersrand Goldfields Acid Mine Drainage (AMD) impacts on
surface and groundwater resources and land, Cabinet appointed an Inter-Ministerial Committee (IMC)
to address the serious challenges posed by acid mine drainage (AMD). The Inter-Ministerial
Committee tasked a technical committee, co-chaired by the Director Generals of the Department of
Mineral Resources (DMR) and the Department of Water Affairs (DWA), to investigate the AMD issues.
The Technical Committee subsequently appointed a team of experts who developed and presented a
draft report on AMD to Cabinet on 9 February 2011.
A number of risks were identified and included:
Flooding risks: Contamination of shallow groundwater, flooding of underground infrastructure,
increased seismic activity.
Decanting of AMD to the environment risks: Ecological impacts, regional impacts on major river
systems and localised flooding in low-lying areas.
There are three main basins in the Witwatersrand Goldfields: the Western, Central and Eastern Basins
and the risks listed above differ from basin to basin. A description of the basins is covered in Section
1.2.
The IMC and Cabinet approved the following recommendations in the Team of Experts’ Report for
emergency implementation:
Installation of pumps to extract water from the mines to on-site treatment plants.
Construction of an on-site water treatment plant in each basin with the option of refurbishing
and upgrading existing ones owned by the mines.
Installation of infrastructure to convey treated water to discharge into nearby watercourses.
Other recommended actions in the IMC report include:
Construction of measures to reduce the water ingress and recharge to the underground
workings.
Comprehensive monitoring.
Investigation into and addressing other sources of AMD.
Investigation and research into finding long-term sustainable solutions.
Investigation into the feasibility of implementing an environmental levy on operating mines.
Ongoing assessment and research.
The IMC Report indicated that this work is urgently required as the prevention of AMD decant in the
basins is considered to be of national importance. The DWA directed the Trans-Caledon Tunnel
Authority (TCTA) to implement this emergency solution. TCTA subsequently commissioned BKS, in
association with Golder Associates, to design and implement the short-term solutions for the
emergency AMD Project.
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The long-term sustainable AMD solution for the three Witwatersrand basins must still be developed,
as recommended by the IMC Report, but the development and implementation of short-term
infrastructure must take the long-term management of AMD into account.
1.2 Description of the Basins
The entire Witwatersrand gold mining area is divided into four basins: the Far Western Basin,
Western Basin, Central Basin and Eastern Basin (see Figure 1). The Western, Central and Eastern
Basins are the focus of the TCTA project.
The Western Basin is located in the Krugersdorp, Witpoortjie and Randfontein areas. The mine
lease areas in the basin cover about 57km². Mintails is active in the basin area with re-mining of
old tailings dams and dumps. Rand Uranium is also re-mining selected sand dumps. Past mining in
the basin has created an underground mine void volume of approximately 43Mm3 at ECL. The
cessation of mining in the basin has resulted in progressive flooding of the void since 1997, until
water started to decant from a number of boreholes and an old shaft in September 2002. The
decants are all located in the north-western section of the Old Randfontein Estates Mine and a
portion of the decanting mine water is intercepted at the decant point referred to as the Black
Reef Incline Shaft (BRI) and pumped to a mine water treatment facility, before being released to
the Tweelopiespruit. The combined treated and untreated AMD flows down the Tweelopiespruit
towards the Crocodile River West.
The Central Basin extends from Durban Roodepoort Deep (DRD) in the west to East Rand
Proprietary Mines (ERPM) in the east. The mine lease areas in the basin extend cover about
251km2. The study area consists of 12 underground mines, with only Central Rand Gold (CRG)
mining the Consolidated Main Reefs property still operational. Mining has created an
underground mine void volume of approximately 280Mm3 at ECL. The underground mines are
interconnected, but due to the elevations of the holings between the mines, the Central Basin
can be divided into four sub-compartments, DRD sub-compartment, Rand Leases sub-
compartment, Central sub-compartment and ERPM sub-compartment.
However, at the current water level and in future at the ECL, the sub-compartments operate as a
single basin. The mine water in the Central Basin is rising with the cessation of pumping in the
basin and is expected to start decanting.
The Eastern Basin covers the East Rand area, including the towns of Boksburg, Brakpan, Springs
and Nigel. The mine lease areas in the basin cover about 768km2. In 2010, the last operational
deep-level gold mine in the Eastern basin, Grootvlei Gold Mine, ceased operation due to
bankruptcy. Therefore, only Gold One operating a training mine close to Nigel is still operating in
the Eastern Basin, although someone may still purchase the Grootvlei Gold Mine. Mining has
created an underground mine void volume of approximately 400Mm3 at ECL. The mining basin
comprises three sub-basins: Sallies, Eastern and Brakpan. However, at the current water level and
in future at the ECL, the sub-compartments operate as a single basin. The mine water in the
Eastern Basin is rising with the recent cessation of pumping in the basin and is expected to start
decanting.
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Figure 1: Western, Central and Eastern Basins in the Witwatersrand Basin
1.3 Project Objectives
The objectives of this project are to:
Define, develop and execute the engineering design and to manage and monitor the construction
of the short-term AMD solution infrastructure. This should be achieved using South African
engineering expertise, supplemented by international expertise (where required) and through
promoting the objectives of Broad Based Black Economic Empowerment (BBBEE) and skills
development.
Develop and implement the project to a level of engineering excellence that will withstand the
test of best international practise.
Deliver the project within the aggressive timeframes stipulated by TCTA in order to address the
growing threats of AMD to the environment and property.
Deliver the project within budget, which implies that the AMD management system must be fully
integrated to ensure that sufficient but not excessive redundancies are provided; existing
infrastructure is used where possible; continued operation by industries and mines during
construction is achieved; and the optimisation of the system has considered all factors, including
varying electricity tariffs (for optimised time of pumping) and a fully optimised treatment
selection has been made for each basin.
To implement the project according to TCTA’s Project Implementation Methodology (PIM), which
was developed to ensure that TCTA’s project implementation processes comply with best
practices and are consistently applied to all TCTA’s projects.
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1.4 Summary of the Scope of Work
The scope of work was divided into the following five tasks:
Task 1: A due diligence review of the Inter-Ministerial Committee Report (as provided by TCTA)
and the recommendation of a solution for each of the mining basins.
Task 2: Development and production of documents supporting the Integrated Regulatory Process
for all basins.
Task 3: Development and production of engineering design and tender documents that will be
used for competitive procurement of a competent contractor(s) combined with detailed
engineering design of the agreed and approved solutions for each of the mining basins, complete
with construction drawings.
Task 4: Monitoring of the Contractor’s activities and commissioning of the works.
Task 5: Monitoring of the works during the defects liability period, taking corrective actions if
required, and the provision of formal operation and maintenance manuals as well as close-out
reports.
Task 6: Operation and maintenance support to the TCTA for all constructed basins.
This report summarises the work undertaken in Task 1: Due Diligence.
2. PROJECT EXECUTION AND APPROACH
2.1 Technical Process
The approach to the technical and engineering aspects of the project is briefly described in terms of
the main components related to:
Retrieval and review of public and private domain reports and information. Supplementary work
was done to refine the available information and to compile a consolidated Basis of Design.
Site visits to assess the physical condition of existing mine water abstraction, treatment and
discharge infrastructure for each mining basin.
Assessment of the mine water collection, treatment and discharge infrastructure available in
each basin and the subsequent formulation of upgrade and retrofit options.
Assessment of different pumping philosophies to manage the water level.
Identification and formulation of alternative AMD management / treatment options, followed by
the selection of a preferred option.
Preparation of preliminary engineering design for the selected AMD management / treatment
option for each basin.
Preparation of CAPEX and OPEX cost estimates.
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Development of a Project Implementation Plan that deals with the different technical and
engineering aspects of the project.
Figure 2 shows a high-level work breakdown structure that reflects the approach adopted in
executing the technical and engineering aspects of the project.
Figure 2: Approach to the Technical / Engineering Aspects of the Project
A review of the public domain information indicated that the Inter-Ministerial Commission’s report on
Acid Mine Drainage remains the best source of current public domain information and thinking
related to the Witwatersrand basin AMD management.
TCTA also acquired the following technical reports, prepared by the Western Utility Corporation
(WUC):
Report on the Water Resource Estimation in the East Rand Basin (Report No. 11590-8757-15).
Resource Estimation. In the West Rand Basin (Report No. 11590-8758-16).
Resource Estimation in the Central Rand Basin (Report No. 11590-8759-17).
Mine water quality assessment of the Witwatersrand mining basins (Report No. 11590-8744-14).
Consideration of Alternatives for Sludge Disposal (Report No. 11590-8911-21).
These documents were the primary source of information for compiling a consolidated Basis of
Engineering Design, reflecting the anticipated mine-water flows, levels and quality.
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The available documents and information were supplemented by additional technical work related to
the definition of the Environmental Critical Level (ECL) for the rising mine water and the response of
the individual mining basins to pumping from the ECL levels.
Contact was made with the remaining active mining companies in the Central and Western Basins and
with Pamodzi (in liquidation) and Aurora Mining Company at Grootvlei Mine in the Eastern Basin. Site
visits were undertaken at the remaining mine dewatering shafts, existing water treatment
infrastructure and plants, treated mine water discharge infrastructure and waste sludge disposal (in
the Western Basin only).
The site visits helped the technical and engineering team familiarise themselves with the local site
conditions and challenges related to the practical implementation of the AMD project.
The available mine-water collection, pumping, treatment, discharge and sludge disposal infrastructure
was evaluated in terms of potential incorporation into the permanent project infrastructure. An
assessment of the following infrastructure components was undertaken:
Shaft heads and dewatering pumping and piping infrastructure.
AMD treatment infrastructure.
Treated AMD discharge infrastructure.
Waste sludge disposal.
Power supply and bulk services available to the respective sites.
The project team formulated a number of the mine-water collection, treatment and discharge system
options, considering the combination of:
Available and accessible shafts from which mine dewatering can take place.
The location of mine water treatment facilities.
Appropriate neutralised mine water discharge points, and
Waste sludge handling and disposal.
The different mine water system options were evaluated, based on selected evaluation criteria, in a
workshop with representation from a spectrum of regulatory authorities and other stakeholders. The
outcome of the workshop was a preferred mine water management system and an identified fallback
option.
Conceptual engineering designs were prepared to address the different components of the selected
AMD management and treatment system for each basin. The conceptual engineering work
incorporated the spectrum of process engineering, civil / structural engineering, mechanical
engineering, electrical engineering and control engineering. Preliminary process flow diagrams, pipe
route selection, plant and infrastructure layouts, main mechanical equipment lists and electrical
power supply requirements were documented.
The conceptual engineering designs served as the basis for preparing the capital investment costs,
operating and maintenance cost estimates.
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The technical and engineering deliverables were used to inform a number of other project
deliverables related to risk assessment and the development of a Project Implementation Plan.
2.2 Shaft Stability
A critical part of the due diligence review of the project is the assessment of the long-term stability of
the pumping shafts proposed for use for the short-term solution. This aspect was assessed through a
rock engineering assessment of the shafts under consideration and is covered in detail in Rock
Engineering Assessment of Shaft Stability (BKS Report No. J01599/11) in Annexure J. The assessment
of the shaft stability included the following approach:
Collection of all available data on and knowledge of the shafts through the Department of
Mineral Resources (DMR) and through interviews with relevant personnel in the basin.
A literature review to assess the regional geology and geotechnical data of the area.
Video camera mapping / logging of the shaft barrels.
Assessments of the shaft barrels, including:
- Structural failure analysis
- Stress-induced failure analysis, and
- Failure due to dynamic loading.
The recommendations from this study are as follows.
Western Basin
Rand Uranium Shaft No. 8 is currently used as a pumping shaft. Based on the information assessed,
this shaft is suitably stable for use as a pumping shaft as part of the short-term work. However, some
concerns have been identified, including obstructions in the different shaft compartments (damage to
the camera was sustained at a depth of 172 m below surface after the camera got stuck). The design
team will need to address these issues.
Central Basin
A number of ERPM shafts (South West Vertical (SWV) Shaft, ventilation shaft at SWV Shaft and
Cinderella East Shaft) were identified as suitable for use as a pump station. The SWV Shaft was
inspected to a depth of 425 m, where the water level was intersected. The investigation highlighted
the following points:
Low probability of structural failure even at 30 degrees strata dip and no major geological
features intersecting the shaft barrel.
Low probability of stress-induced failure due to the size of the shaft pillars.
Low probability of failure due to dynamic loading, including crush-type and shear-type seismic
events, as well as shakedown damage.
Eastern Basin
Grootvlei Shaft No. 3 is suitable for use as a pumping shaft because of:
Low probability of structural failure due to low dip of strata and no major geological features
intersecting the shaft barrel.
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Low probability of stress-induced failure.
Low probability of failure due to dynamic loading, including crush-type and shear-type seismic
events, as well as shakedown damage.
Based on the available data and the analysis, there are no rock engineering-related fatal flaws with
regard to possibly using the following shafts as pump stations:
Rand Uranium Shaft No. 8.
ERPM SWV Shaft
Grootvlei Shaft No. 3
Sallies Shaft No. 1 is filled in with rock and cannot be used as a pumping shaft.
2.3 Integrated Regulatory Process
Based on existing legislation that governs mining, water, waste, environment, heritage and radiation,
the conventional approach for a project of this nature would ordinarily be required. However, the
conventional approach will not allow TCTA to execute the project within the proposed timelines
(construction to begin in January 2012 and commissioning to occur in August 2012). Therefore, the
following approach was adopted for the regulatory process:
An optimised regulatory approach and process for the project was developed to achieve the
required project milestones, while undertaking the conventional approach in parallel.
The optimised approach was presented to the Authority Steering Committee (ASC).
The ASC accepted the optimised approach for regulatory authorisations and requested that an
IRP strategy be developed (this was prepared by the project team).
The IRP assessment is summarised in Section 9. The full details of the IRP are contained in Integrated
Regulatory Process (IRP) (BKS Report No. J01599/04), included in Annexure G and Integrated
Regulatory Process (IRP) Strategy (BKS Report No. J01599/08), included in Annexure H.
2.4 Risk Management
The approach to assessing the risks for the proposed short-term project used the following three-
stage process:
An initial identification of the risks that may be evident in the project was included in the
proposal prepared by the project team. These risks were assessed and preliminary mitigation
measures were identified. The risks were not ranked during this stage.
Option-specific risks were identified for each of the basins during the option definition workshop
on 2 June 2011, but were not assessed in detail during the workshop.
A risk workshop was held on 29 June 2011 to review and revise the risks identified in the
proposal, revise and assess the risks identified in the option definition workshop, and identify and
assess new risks not covered in the previous work.
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The outcome of this work is a risk register that identifies, characterises, rates and identifies mitigation
measures for the risks facing the project. This risk register will be reviewed and updated throughout
the project’s implementation.
3. ASSUMPTIONS AND LIMITATIONS
The following assumptions were included in this phase of the project:
The land that is required for the implementation of the project is readily available, with security
of tenure for TCTA.
The commercial arrangements that will be required for project implementation are achievable
within the project timeframes. This relates to aspects such as the recommended waste disposal
methodology for each of the basins.
There is sufficient connectivity in the mine workings within the basins.
The optimised approach is accepted for environmental approval of the project
The limitations to the project, after the Task 1 work, were identified as follows:
There are still gaps in the background data and information that has been collected for the three
basins. This is particularly evident for the Eastern Basin and the rock engineering assessment.
Recommendations to address the information gaps have been provided.
There has been limited liaison with the mining industry and the mining companies that are
operating in the basins. This is especially the case in the Eastern Basin.
The mine voids, rate of rise of the water and ECLs in the basins are based on the best estimates of
the geo-hydrological information and modelling.
The connectivity of the mine void within the basin may impact on the efficiency of reaching the
ECL throughout the basin.
4. BASIS OF DESIGN
4.1 Summary of Available Information
The primary sources of data for Task 1 of the project include:
The Inter-Ministerial Commission report on Acid Mine Drainage.
The technical reports, prepared by the Western Utility Corporation (WUC), and purchased by
TCTA, that deal with water resource estimation and mine water quality assessment for the
basins.
Information provided by the mining companies that operate in the basins (primarily Rand
Uranium, DRD Gold (including ERPM and Crown) and Central Rand Gold (CRG)).
Information from government departments, primarily the DMR and DWA.
Information from other sources, such as Gold Reef City.
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4.2 Basis of Engineering Design
The project basis of design is comprehensively documented in Basis of Engineering Design (BKS
Report No J01599/01) included in Annexure A. This includes details on the water volumes, flow rates
and the water quality incorporated in preparing conceptual designs for the different basins.
4.3 Mine Water Resources
4.3.1 Water Balances for the Basins
Mine water accumulates in underground workings through the following recharge mechanisms:
Seepage from overlying and adjacent groundwater-bearing aquifers.
Infiltration from old opencast pits and associated workings.
Infiltration from streams and water courses flowing across old mine workings.
Seepage from mine tailings deposition dams and mine waste disposal dumps.
The water balances based on the geo-hydrological assessment of the three basins are covered in
Water Balance and Levels (BKS Report No J01599/06) included in Annexure B.
4.3.2 Environmental Critical Level (ECL)
The Environmental Critical Level (ECL) associated with each of the mining basins was defined as “the
mine water level below which, the risk of negative impacts on the shallow economically exploitable
groundwater resources and the surrounding surface water resources is small.” The ECLs were
established for each of the mining basins, following a consultative process between the BKS-Golder
project team, Council for Geosciences and the Department of Water Affairs. The basis of determining
the ECL for each of the basins is given in the Environmental Critical Levels (BKS Report No J01599/03)
included in Annexure C.
The agreed ECL levels for each of the mining basins are summarised in Table 1.
Table 1: Environmental Critical Levels
Basin
Decant
Level
(m amsl)
Decant
Position
ECL
(m amsl) Rationale
Western 1680 Black Reef
Incline, Winze
No. 17 and 18
1,550 ECL set for protection of the dolomitic
groundwater resources at the Cradle of
Humankind World Heritage Site.
Central 1617 Cinderella East 1,467 ECL set below the decant level for protection
of the weathered and fractured aquifers
within the basin.
Eastern 1549 Nigel No 3
Shaft
1,280 ECL set below the base of the dolomitic
formations in the Eastern Basin for protection
of the dolomitic groundwater resources.
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4.3.3 Water Volumes and Flow Rates
The basis of design also contains the selected mine dewatering rates that are required to deal with
the seasonal variation in water recharge to the old mine workings and to maintain the mine water
level reliably below the selected ECL. The selected mine dewatering rates are given below.
Western basin:
Sustained base flow = 27Mℓ/day
Peak pumping flow = 35Mℓ/day
Central basin:
Sustained base flow = 57Mℓ/day
Peak pumping flow = 84Mℓ/day
Eastern basin:
Sustained base flow = 82Mℓ/day
Peak pumping flow = 110Mℓ/day
Refer to Basis of Engineering Design (BKS Report No J01599/01) included as Annexure A.
4.3.4 Water Quality
The selected design mine water quality was based on the available information, mainly in the IMC and
the Western Utility Corporation reports.
The expected mine water quality to be treated is listed in Table 2 for each mining basin.
Table 2: Expected Water Quality by Basin
Water
Quality Parameter Units
Western Basin
(95th
percentile)
Central Basin
(95th
percentile)
Eastern Basin
(flooded condition)
TDS mg/ℓ 7,174 7,700 5,500
Conductivity mS/m 548 730 450
Calcium (Ca) mg/ℓ 461 580 550
Magnesium (Mg) mg/ℓ 345 380 230
Sodium (Na) mg/ℓ 139 150 325
Sulphate (SO4) mg/ℓ 4,556 5,200 3,275
Chloride (Cℓ) mg/ℓ 65 260 260
pH - 3.4-4.0 2.3 (5th
percentile) 5.0
Acidity (CaCO3)* mg/ℓ 2,560 2,425 750
Iron (Fe) mg/ℓ 933 1,000 370
Aluminium (Aℓ) mg/ℓ 54 50 1
Manganese (Mn) mg/ℓ 312 60 10
Uranium (U) mg/ℓ 0.2 -- --
Refer to Basis of Engineering Design (BKS Report No J01599/01), included as Annexure A.
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Based on the selected treatment technology, the discharge quality in Table 3 is expected to be met.
Table 3: Target Mine Water Discharge Standards
Water Quality Variable Units Concentrations
pH - 6-9
Iron mg/ℓ <1
Manganese mg/ℓ <3
Aluminium mg/ℓ <1
Uranium µg/ℓ <50
Sulphate mg/ℓ <2,400
4.4 Treatment Technology
4.4.1 Objectives of Mine Water Treatment
The main objectives of the proposed mine water treatment are to:
Neutralise the mine water and produce a near-neutral treated mine water with some residual
buffer capacity in the form of alkalinity.
Remove the main metals, specifically iron, aluminium and manganese to acceptable short-term
discharge standards.
Remove radionuclides, specifically uranium to acceptable short-term discharge standards.
Achieve a degree of desalination by removing gypsum (CaSO4) in excess of the saturation levels.
It is also important to select a treatment technology that can be integrated with the long-term mine
water reclamation treatment process, which will involve some desalination.
A separate specialist report on the evaluation of alternative mine water neutralisation technologies
was prepared – refer to Treatment Technology Selection (BKS Report No J10599/07) included as
Annexure D.
4.4.2 Identification and Selection of Treatment Process
Mine water neutralisation technologies are well developed and the global reference technology is
based on the High Density Sludge (HDS) process, which incorporates:
Addition of an alkali, typically lime in the slaked lime or un-slaked lime form.
Aeration to oxidise the iron and manganese.
Neutralisation of the free and metal-related acidity.
Precipitation of the metals in the hydroxide or carbonate form.
Solids separation and production of clear water.
Handling and disposal of waste sludge, which mainly contains metals, hydroxides and gypsum.
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The generic HDS neutralisation treatment plant process configuration is shown in Figure 3.
Figure 3: Generic Mine Water Neutralisation Process
4.4.3 Assessment of Alternative Sources of Alkali
The operating cost of mine water neutralisation is sensitive to the selection of an alkali chemical. The
South African CSIR has developed a number of mine water neutralisation technologies, incorporating
limestone as a relatively cheap source of alkalinity and to augment the use of lime.
An evaluation of alternative mine water neutralisation chemicals was conducted, considering the
following alternatives (for a mine water quality similar to that of the Western Basin):
Option 1 – Quicklime dosing only, including slaking.
Option 2 – Slaked lime dosing only.
Option 3 – Limestone pre-neutralisation and quicklime dosing.
Option 4 – Limestone pre-neutralisation and slaked lime dosing.
The alkali alternatives evaluation indicated that the capital investment cost is similar for the different
treatment options. There are significant operational cost differences, due to the difference in alkali
chemical costs, between the alternatives, as shown in Table 4.
Table 4: OPEX – Chemical Cost Comparison of Alkali Options
Process Option Alkali Source Cost (R/m3)
Option 1 Quicklime 4.54
Option 2 Slaked Lime 5.62
13247-010
AMD
Polymer
Ca(OH)2
Pre-neutralisation
Neutralisation
CaCO3
Acid
SludgeConditioning
GypsumCrystallisation
Sludge recycle
Sludge wasting
Clarifier
Option
NeutralisedAMD
SludgeDisposal
7
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Process Option Alkali Source Cost (R/m3)
Option 3 Limestone 0.67
Quicklime 1.68
Total 2.35
Option 4 Limestone 0.67
Slaked Lime 2.74
Total 3.41
Option 3, the combination of limestone and quicklime, is the most economical of the alkali
alternatives considered.
4.4.4 Recommendations
It is recommended that the following treatment technology and chemical reagent combination be
used for to treat the Witwatersrand Gold Fields AMD:
Oxidation by aeration.
Pre-neutralisation with limestone.
Neutralisation and metals removal with lime, produced by the slaking of quicklime.
Gypsum crystallisation to remove excess sulphate from solution.
A conceptual process design for the three basins is described in Process Design (BKS Report No.
J01599/09) included as Annexure E.
4.5 Sludge Disposal
4.5.1 General
In the process of Acid Mine Drainage treatment (neutralisation and metals removal), sludge is
produced, which needs to be disposed of. The primary sludge stream is a metal hydroxide sludge,
with some gypsum (CaSO4).
The WUC’s Consideration of Alternatives for Sludge Disposal (WUC, Oct 2009) states a metal
hydroxide sludge from a HDS process:
“In order to inform the process of considering the alternatives for the mine water
treatment sludge management options, a hazard rating of the current mine water pre-
treatment sludge generated in each of the various Basins was performed.
The sludge samples were used for predictive leaching tests in accordance with the
Minimum Requirements (DWAF, 1998). The Acid Rain Leach Procedure (ARLP) test was
used to hazard rate the sludge samples since the sludge will not be co-disposed with
organic waste.
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The sludge was classified in terms of the Minimum Requirements (DWAF, 1998). The
sludge has been classified and hazard rated based on the most hazardous constituent of
concern. Furthermore, in order to establish whether the waste can be delisted and
disposed of in a general landfill site, equipped with an engineered leachate management
system or used in a downstream application such as roadways, the allowable maximum
load has been calculated.
The analytical results of the sludge samples indicated the following:
The Central Basin sludge has low concentrations of metals and trace elements in
the acid rain extract (majority below the detection limits), but is non-hazardous
since the concentrations of none of the potential constituents of concern
exceeded the ARLs detailed in the Minimum Requirements. Elevated Ca and SO4
concentrations may cause groundwater pollution should this sludge be disposed
on unlined facilities; and
The Western Basin sludge is non-hazardous since the concentrations of none of
the potential constituents of concern exceeded the ARLs detailed in the Minimum
Requirements. The SO4 concentration of 2,896mg/ℓ in the sludge may cause
groundwater pollution when disposed on an unlined facility.
It was concluded that the mine water pre-treatment sludge is classified as general
waste.”
The following assumptions apply in the consideration of the preferred sludge disposal option for each
basin.
The sludge disposal option will be for a design life of four years (short term) with a
recommendation for a long-term solution beyond four years. This assumption is deemed
acceptable until long-term solutions have been investigated and explored in detail.
The sizing of the pipelines, pump station and sludge disposal facility was based on
information on the Process Flow Diagrams.
To inform the process of considering the disposal alternatives for the treatment sludge, the
expected sludge from all three basins were assumed to be classified as general waste
material with the requirement for an engineered lining system. More analysis and
description of the physical and chemical characteristics of the sludge, including hazard rating,
is required.
4.5.2 Conceptual Engineering Design
The following were identified as the major design drivers for the preferred disposal option.
Driver 1 The water treatment process: The mine water treatment process incorporates a
combination of limestone and lime neutralisation, using the High Density Sludge process. The
expected waste stream from the treatment process is primarily sludge that is mainly
composed of metal hydroxides and some gypsum. The sludge chemical and physical
characteristics are not expected to vary much between the different basins.
Driver 2 Sludge preparation technology: Characterisation of the sludge and whether the
sludge properties can be changed or the volumes reduced.
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Driver 3 Disposal options: Sustainable disposal of the sludge for a minimum period of four
years and consideration of the long-term solution for sludge handling. The following disposal
alternatives were considered:
Impoundment of sludge into an existing Tailings Storage Facility (TSF)
Co-disposal with tailings into an existing TSF
Impoundment of sludge into underground workings or a pit.
Impoundment of sludge into abandoned mining shafts
Impoundment of sludge into a new engineered / lined facility.
Impoundment of thickened sludge into a new engineered / lined facility.
Driver 4 Sludge handling: Consideration of a range of options, depending on the nature of
the sludge (with special reference to the sludge preparation technologies).
Driver 5 – Sludge disposal site alternatives: The site selection process will need to be aligned
with disposal alternatives. The final choice will be linked to:
The preferred water abstraction point.
The locality of the treatment plant and waste disposal site.
Four categories of potential waste sites can be considered:
A green field’s site.
A brown field’s facility.
Underground mine pits or shafts
Co-disposal of the sludge with the existing tailings.
Driver 6 Capital, Operations and Closure Costs Considerations: Capital cost and benefits
analysis.
Driver 7 – Regulatory and Stability Considerations: Sludge classification, geotechnical stability
and reclamation possibility.
4.6 Technical Aspects
4.6.1 Hydraulic Impact of Treated Water Discharge
A high level evaluation of the hydraulic impact of the treated water discharges on the river catchment
was done. This reviewed the predicted runoff of the catchment above the discharge point, during a 1
in 25, 100 and 200 year rainfall event. The results of these calculations are shown in Table 5. It can
be concluded that because the additional discharge is factors smaller than even the 1:25 flood event,
that the impact of the discharge will be negligible on downstream areas.
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Table 5: Hydraulic Impact of Treated Water Discharge
Basin Western Central Eastern
Water Course Tweeloopies-
spruit
Elsburgspruit Blesbokspruit
1 in 25 year flood volume (natural) 28 m3/s 96 – 182 m
3/s 429 – 600 m
3/s
1 in 100 year flood volume (natural) 37 m3/s 125 – 237 m
3/s 543 – 761 m
3/s
1 in 200 year flood volume
(natural)
46 m3/s 154 – 291 m
3/s 655 – 918 m
3/s
Maximum additional discharge 35Ml/d =
0,405m3/s
84Ml/d =
0,972m3/s
110Ml/d =
1.270m3/s
Calculated rise in flood water level 0 - 10mm No change in
water level
0 – 10mm
If necessary, specific areas can be reviewed as part of the IRP process.
4.6.2 Pumping Philosophy
Two distinct pump philosophies can be implemented to control the water level at the ECL:
Operate the pumps at average ingress flow:
- The water level in the basin would be lowered during periods of low inflow and return to the
ECL during periods of higher inflow.
- This requires that the pumps be installed at the lowest possible drawdown level.
- The flow will vary based on the characteristics of the pumps, i.e. at the lowest level the pump
head will be high and the flow low, and vice versa. There will be minimal control over the
system when the ingress flow in a year is above average. When the ingress flow is below
average during a year, the system can be switched off.
- The treatment works can be operated within a narrow band around the average flow, based
on the pump characteristics.
- The additional head to be pumped at the low water level will require additional energy.
Operate the pumps using a Variable Frequency Drive (VFD) to maintain the ECL within a narrow
band:
- The water level in the basin would remain constant, with the benefit that rock containing
pyrite is not periodically exposed to oxygen.
- The pumps can be installed at the ECL.
- The flow will vary based on the VFD setting and will match the ingress flow.
- The treatment works would be operated to match the ingress flow, which will result in peaks
on either side of the average. The treatment works needs to be designed for these peaks, but
the amount of chemicals used is the same for either option, because the volume of water
treated does not change.
- The constant water level will achieve the most cost-effective energy utilisation.
The following scenarios were evaluated in order to compare the two options:
Option 1: Pumping the average ingress flow at the average depth variance in the basin;
Option 2: Pumping at the ECL level, but assuming the flow is at the minimum ingress flow for six
months and the maximum ingress flow for six months.
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This analysis indicates that there is a potential saving of R1.5 million per year for the Central Basin if
option 2 is implemented, i.e. using VFDs to maintain a constant water level in the basin.
It is thus recommended that VFDs be installed in each of the basins to allow for operational flexibility
and the optimum use of electrical energy.
4.6.3 Mineshaft Pumping
The abstraction of water from a mineshaft is analogous to a borehole pumping water from an aquifer.
The hydraulic characteristics of the basin determine the amount of flow into the mineshaft and hence
the level at which the pumps need to be placed. This creates three interrelated issues:
There is a local draw down of the water level in the shaft when pumping starts, until the inflow
into the shaft equals the outflow from the pumps. This can place a constraint on the amount
pumped or require that the pumps be placed at a lower level.
The increase in height of the water level along the length of the central basin to compensate
for the holing friction losses: It is expected that when pumping from a mineshaft, a regional cone
of depression (along the entire length of the basin) will form due to the friction losses through
the interconnected holing. The rate of inflow into the specific mineshaft is related to the friction
losses / amount of holing / transmissivity.
The amount of water that will flow to the pump shaft is not proportional along the entire basin
length: Because of the friction losses along the length of the basin and because “water will
choose the path of least resistance”, the water flow to the pump shaft will be disproportional
along the length of the basin, which could have an impact on seasonal or long-term water quality
(certain areas may have stagnant water, while others have higher flows).
There is minimal information on the level differences across the basins while pumping. To determine
the water level characteristics during pumping would require a pump test and monitoring of the
water level at various positions along the length of the basin while varying the flow rates. However,
there will be no opportunity to undertake these pump tests until the full-scale installation is
operational. Therefore, flexibility needs to be allowed for the installed pump depth.
The proposed pump depth per basin will be based on the following aspects:
The minimum depth for installation of the pumps is the ECL;
The pumps require a minimum depth of water above the pumps (submergence depth) to prevent
vortex formation and the introduction of air into the pipe system;
The pumps should be installed at a depth to take the potential ‘cone of depression’ into account,
i.e. the water level change along the basin;
The pumps should be staggered both horizontally and vertically to prevent water turbulence
interaction between the pumps.
To allow for system flexibility, the following are also proposed:
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- The pumps are operated with VFDs to allow for flow rate and level changes (refer to Section
4.6.2);
- The pumps are installed at the lowest water level that would be achieved if the average flow
was pumped continuously. Although it is not proposed that the system be generally
operated on this basis, this will allow system flexibility, e.g. to conduct pump tests and to
accommodate a higher cone of depression than expected. Should the system not be
operated down to the lower level, there is no electrical cost, as the difference between the
water level and the surface level determines the required pumping head and, therefore,
cost. There is only an additional capital cost for the required pipes.
- As another precaution, it is recommended that the pipes be designed for the possibility that
the pumps need to be lowered by an additional 20% of the ECL level. This may be required if
the transmissivity (holings/connectivity) is lower than expected. Initially, the additional pipes
would not be purchased or installed. The pumps will be sized to allow for the maximum flow
at the additional allowance for head.
5. METHODOLOGY
5.1 Introduction
This section describes the process carried out for the options selection, options analysis, selection of
the preferred option and conceptual design of the preferred option.
The methodology used for the Western, Central and Eastern Basins is similar, but allows basin-specific
issues to be included.
5.2 Options Selection
The various potential options were considered, based on the following aspects or key drivers:
Abstraction point – mineshaft for abstraction from the basin, which requires confidence on the
basin interconnectivity and shaft condition / stability;
Treatment sites – potential area available for short- and long-term treatment requirements;
Sludge disposal sites – identification of options for sludge disposal; and
Water discharge sites – review of the potential for water to circulate back into the basin.
The key drivers were applied to each of the options in the form of a fatal flaw analysis. Options that
had no fatal flaws were analysed further in terms of a more comprehensive set of criteria.
5.3 Options Analysis
The selected options with no fatal flaws were further analysed based on the following criteria:
Shaft collar level
Pumping head to HDS plant
Shaft information availability
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Availability of electricity
Minimize impact to economically sensitive sites
Ease of land acquisition, right-of-way
Negative impact on current activities
Negative impact on future landowners
Minimise impact and disturbance of natural habitats and wildlife
Negative impact of AMD release on safety
Risks to operations / operators from construction activities
Risks to Operations due to operation of the AMD treatment plant
Availability of required area for treatment plant construction
Cost of new treatment plant facilities
Site accessibility
Use of existing infrastructure (shaft, HDS) to support operations
Ease of operations and maintenance
Security of treatment facilities
Constraint on future activities caused by right of way
Risks due to failure during construction
Negative community impacts due to construction
Logistic constraints
A scored matrix (non-weighted) was used to determine whether there was a preferred option. The
assessment was done using a scale of 1-4, where:
Not Applicable = 0
Poor = 1
Acceptable = 2
Good=3
Excellent = 4.
5.4 Preferred Option
The preferred option was chosen based on the highest-scoring option from the analysis matrix.
Where the scoring was inconclusive or where there are other options that would need to be
investigated, the situation was discussed in detail and on this basis, a recommendation was made.
5.5 Conceptual Design
A conceptual design that includes the following information was done for the preferred option:
Process flow diagrams;
Site layout;
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Plant layout;
Potential pipeline routes; and
Conceptual building layouts.
6. WESTERN BASIN
6.1 Status of the Basin
6.1.1 Background
The Witwatersrand Goldfields in the Western Basin comprises the following three gold reefs:
Black Reef
Kimberley Reef
Main Reef
These reefs sub-outcrop on the north-western side of the Gold Fields between Randfontein and
Roodepoort, but the sub-outcrop is isolated from the rest of the Gold Fields by the Witpoortjie and
the Roodepoort Faults.
Open cast mining started along the reef outcrops in the Randfontein / Krugersdorp area and, when
the reefs became too deep for open cast mining underground mining commenced. When most of the
reefs had been removed, underground voids were left that stretch from Randfontein and Krugersdorp
to the Witpoortjie Fault. The Western Basin thus stretches from Randfontein to Roodepoort and is
separated from the Far Western Basin and the Central Basin by the Witpoortjie and Roodepoort
Faults, respectively, as shown in Figure 4.
Figure 4: Layout of the Western Basin
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The Western Basin incorporates the old gold mining operations centred around Randfontein Estates,
West Rand Consolidated, Luipaardsvlei and East Champ d’Or Mines. Mining operations ceased in
around 1998 and the old mine workings progressively filled with water. Water started decanting from
the Black Reef Incline (BRI) shaft in 2002. High rainfall over the past three years has caused decant
from Winze 17 and 18 as well.
The current mining operations on the Western Basin are exclusively associated with the re-mining and
recovering of old sand and tailings deposition dams. The two largest re-mining operations are:
Rand Uranium, which is re-mining the old Dump 20, a source of gold bearing sand. This material is
railed from the Western Basin to the Cooke Gold Plant outside the Western Basin.
Mintails, which is re-mining several gold-bearing tailings dams using its Mogale Gold Plant. The
residual tailings are deposited in the Wes Wits Pit.
Rand Uranium also plans to extend its current gold mining operations, to re-commission the Millsite
Tailings Dam and to use several of the opencast pits associated with the reef sub-outcrops as tailings
deposition sites.
6.1.2 Mine Water Generation
In the case of the Western Basin, a number of distinct surface sources of recharge to the Basin
contribute to the water make:
Old opencast pits, which collect and seep water to the workings.
Old and active tailings and mine residue disposal sites seep water to the workings.
Seepage from groundwater and surface water (for example, the Tweeloopiespruit).
Water started decanting from a number of old mine adits and inclined shafts in 2002. The decanting
mine water flows down the Tweelopiespruit East towards the Crocodile West River. The impacts of
the decanting mine water on the downstream aquatic ecosystem and downstream water users are
well documented.
As the basin is currently decanting, the water level in the basin will have to be lowered to the ECL,
which, for the Western Basin, has been set at 1,550m amsl equivalent to 165 m below the collar
level at Shaft No. 8.
6.1.3 Mine Water Flow
The mine water recharge and corresponding decant flows are seasonal with high recharge occurring
mainly in summer. The result of the mine workings being filled is that no storage or buffer capacity is
left in the old mine workings. As recharge occurs, mine water flows from the decant points. The
seasonal mine water flow pattern is as follows:
The mine water flow peaks in summer.
The flows start decreasing in early winter and reduce progressively as the water level above the
decant level drops.
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By late winter, the flow drops to a lower base flow.
The flow increases again in spring as rainfall and runoff events start occurring.
The recent mine water decant flows from the Western Basin, as monitored and recorded along the
Tweelopiespruit, are shown in Figure 5.
Figure 5: Daily treated, untreated and total discharge volumes in the Western Basin
The estimated flows and, therefore, the estimated pump rates into the Western Basin are listed in
Table 6.
Table 6: Mine Dewatering and Treatment Flows (Western Basin)
Average Maximum
Ingress Flow (Mℓ/d) 27 35
Pump Time (hours) 19 (off peak) 24
Pump Flow (m3/s) 0.39 0.41
Pump and Treatment Flow (Mℓ/d) 34 35
6.1.4 Water Quality
The expected water quality is defined in Basis of Engineering Design (see Annexure A).
6.1.5 Existing Mine Water Treatment System
Mine water currently decants along the Tweelopiespruit (East) valley at the following points:
Winze 17 overflows directly to the spruit, upstream of Portuguese (Porra) Dam.
0.00
10.00
20.00
30.00
40.00
50.00
60.00
70.00
80.00
90.00
Flo
w R
ate
(ML/
d)
Date
BRI to RU Plant Pipeline 1
BRI to RU Plant Pipeline 2
Total Treated
Untreated Discharge
Total Discharge
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Winze 18 overflows to the BRI Dam and to the Porra Dam. Excess flow bypasses the dams and
flows directly to the Tweelopiespruit, downstream of the BRI Dam.
Black Reef Incline Shaft flows directly to the BRI Dam, although the flow has declined in the past
few years, possibly due to scaling.
The AMD collected in the BRI Dam (from Winze 18 and BRI Shaft) is pre-neutralised, using limestone
slurry, before being pumped back up the valley to the Rand Uranium Treatment Plant.
Porra Dam is located on the Tweelopiespruit and mainly contains flow from the upstream Winze 17
AMD decant and from the Winze 18 excess decant flow. Porra Dam water could be fed to BRI Dam for
pre-treatment before being pumped back to the Rand Uranium Treatment Plant.
The Rand Uranium Treatment Plant is a conventional lime neutralisation process (not High Density
Sludge type process) and, in general, consists of:
A premixing basin into which pre-neutralised AMD is pumped.
Lime dosing into a contact tank.
Aeration basins using turbulator -type aerators.
Pump station to lift the pre-treated mine water to the CPS Pit
Limited sludge recycling from the CPS Pit to the treatment plant.
The Rand Uranium Treatment Plant also incorporates:
A limestone storage, make-up and dosing facility.
A lime storage, make-up and dosing facility.
The neutralised mine water (with precipitated metal hydroxides) is discharged to the CPS Pit, where
the solids are precipitated and settled. The clear overflow enters a treated water trench, which
directs the water along the valley and discharges downstream of the Porra Dam into the
Tweelopiespruit. The treated mine water flows close to the undermined areas and may recharge back
into the basin.
The sludge deposits in the CPS Pit are pumped back via the Rand Uranium Treatment Plant. A small
amount of the recycled sludge is used to seed the AMD treatment process and the rest is pumped to
the Millsite Tailings Dam No. 38 for final disposal.
6.1.6 Immediate Mitigation Measures to Treat AMD
A separate comprehensive report containing the formulation of immediate mitigation measures to
deal with the Western Basin AMD was compiled. For details, see Formulation of Western Basin AMD
Immediate Mitigation Measures (BKS Report No J01599/02) in Annexure F.
Consideration was given to the implementation of certain immediate AMD mitigation measures to
relieve the impacts associated with AMD decant from the Western Basin on the downstream aquatic
environment and water users. Three alternative mitigation approaches were investigated:
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Treatment at Rand Uranium Plant (additional treatment modules).
Treatment at Mintails, Mogale Gold Plant’s facility.
Pre-treatment at Rand Uranium Plant and clarification at Mintails Mogale Gold Plant.
The evaluation confirmed that the immediate AMD mitigation measures can be implemented
practically, based on the following:
Replacing the AMD abstraction pumps to provide additional capacity and pump installation depth
at ECL.
Upgrading and retrofitting the existing Rand Uranium Treatment Plant, which offers the best
opportunity in terms of treatment capacity and ease of implementation.
The existing infrastructure of the Rand Uranium Treatment Plant and site was evaluated and it
was found that it would be practical to bring two additional treatment trains into operation after
the installation of appropriate mechanical and electrical equipment.
The potential AMD treatment capacity, including the existing single operational treatment train is
estimated to be 26-30 Mℓ per day.
The current best estimate is that the immediate AMD mitigation measures can be implemented
and placed into operation within 16 weeks, based on certain assumptions related to the supply of
long lead items.
The capital investment cost estimate to implement the proposed immediate measures is
R25 million (excluding VAT), based on the available information and a costing accuracy of -10%,
+20%.
Regulatory approval is essential for the proposed immediate mitigation measures and to reach
contractual closure on using the Rand Uranium plant infrastructure and sludge disposal into Wes
Wits Pit.
The implementation of the proposed immediate AMD mitigation measures will relieve the
pollution load on the downstream environment and water users, and it is proposed that these
measures be used to progressively draw down the mine water level to the ECL in the Western
Basin. This can happen in parallel with the implementation of the short-term AMD neutralisation
plant, which is proposed as part the TCTA AMD management project.
6.2 Options for Abstraction and Treatment of AMD
6.2.1 Identification of Options
Six options were identified for the abstraction and treatment of AMD in the Western Basin. Table 7
summarises the options (refer also to Drawing J01599-01-G-001). The installation of large-diameter
boreholes for the abstraction of AMD closer to the WTP was assessed during this phase, but was not
considered feasible because of the large-diameter for the pumps (related to cost) and the risk of
obtaining poor connectivity to the basin.
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Table 7: Options for Abstraction and Treatment of AMD
Option
No
Abstraction
From Shaft WTP Location Waste Disposal Water Discharge
WB1 Shaft No.8 Between BRI Shaft and
R24 Road
Local disposal area
on site
North, Tweelopiespruit
WB2 Shaft No.8 North of Current Rand
Uranium WTP
Local disposal area
on site
North, Tweelopiespruit
WB3 Shaft No.8 Randfontein Estates west
of Azaadville
Battery 7 Open Pit North, Tweelopiespruit
or South
Wonderfontein Spruit
WB4 Deep Shaft Deep Shaft Battery 7 Open Pit North, Muldersdrift
Loop, or South
Wonderfontein Spruit
WB5 North-East Shaft North-East Shaft areas Battery 7 Open Pit North, Muldersdrift
Loop, or South
Wonderfontein Spruit
WB6 East Champ
d’Or Shaft
East Champ d’Or Shaft
area
Local disposal area
on site
North, Muldersdrift
Loop, or South
Wonderfontein Spruit
Each project option is described in terms of key infrastructure components and aspects of:
Availability of a plant site area.
Convenient and practical mine water abstraction points.
Mine water treatment plant site and bulk infrastructure.
Sludge handling and disposal.
Discharge of treated, neutralised water.
In describing the project options, the location and development of a long-term mine water
reclamation plant was considered. This will be done on the same site as the mine water neutralisation
plant.
Refer to Drawing J01599-01-G-001 for the general layout of the infrastructure required to implement
Project Option WB1 to WB6.
Option WB1: BRI Shaft / R24 Road Site
(a) Area Available
The lowest surface point in the Western Basin is where the Tweelopiespruit crosses the R24 Road,
which is about 800 m north of the BRI Incline Shaft, where AMD first decanted. West of the
Tweelopiespruit, between the R24 Road and the HT electrical power line, is approximately 30 ha that
can be used for a treatment facility.
(b) AMD abstraction
There are various mineshafts in this area, including the following:
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Black Reef Incline (BRI) Shaft.
Winze 17
Winze 18
Shaft No.9
Shaft No.9 East
Shaft No.8
BRI Shaft, Winze 17 and Winze 18 are all inclined shafts and cannot be used to abstract AMD. Shaft
No.9 is inside the Mogale Gold Plant process area and is reported to be partially backfilled with
rubble.
Shaft No.9 East is also inside the Mogale Gold Plant process area and is currently used by Mogale Gold
to augment their water supply. A mine cage is reportedly stuck in the shaft above the ECL so pumps
cannot be lowered below the ECL to draw down the basin.
Shaft No.8 has been used to abstract water for many years. AMD can be abstracted from Shaft No.8
and piped to the treatment plant site at the R24 Road site.
(c) AMD Treatment Plant Site
It is estimated that four hectares will be required for the AMD treatment plant. A platform can be
formed in the north-eastern corner at the proposed site by cut and fill.
Access to the site can be from the R24 Road.
Electrical power supply can be brought in by overhead power line from the Central Power Sub-
station (CPS) at Robertson Pan.
Potable water can be supplied from the nearest Rand Water supply line.
Sewage on site can be disposed of in a septic tank and percolation trench.
(d) Sludge Handling and Disposal
Disposal of sludge onto the Millsite Tailings Storage Facility (TSF) or the Wes Wits Pit would be the
preferred sludge handling and disposal method for this option.
(e) Treated Water Discharge
Treated water can be discharged into the Tweelopiespruit that drains north to the Crocodile West
River.
In future, reclaimed water for potable use can be pumped to the Randfontein, Krugersdorp or
Azaadville municipal reservoirs.
Option WB2: Rand Uranium Plant site
(a) Area Available
The Rand Uranium Water Treatment Plant (WTP) is south-east of the Millsite TSF of Rand Uranium,
and Shaft No.8 lies directly east of the WTP.
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This area is so congested with pipelines and equipment that there is little space for a permanent
treatment facility and a water reclamation plant
The area between the Millsite TSF and the Robinson Lake is a contaminated wetland that is unfit for
the development of a treatment facility.
Directly north of the WTP and south of the railway line is an area that is approximately 25 ha in size
and is large enough to accommodate a treatment facility. It is covered with eucalyptus trees.
(b) AMD abstraction
Water can be abstracted from Shaft No.8 and transferred to the treatment plant site.
(c) AMD Water Treatment Plant Site
After bush clearance, an area of about 4 ha, the south-eastern corner can be used for the treatment
plant. A platform can be formed at the proposed site by cut and fill.
Road access to the site can be from the existing road network.
Electrical power supply will have to be brought in by overhead power line from the Power Plant
or CPS sub-station.
Potable water can be supplied from the nearby Rand Water supply line.
On-site sewage can be disposed of in a septic tank and percolation trench.
(d) Sludge Handling and Disposal
Disposal of sludge onto the Millsite Tailings Storage Facility (TSF) or the Wes Wits Pit would be the
preferred sludge handling and disposal method for this option.
(e) Treated Water Discharge
Treated water can be discharged into the Tweelopiespruit, which drains north to the Crocodile West
River.
Reclaimed water for potable use can be pumped to the Randfontein, Krugersdorp or Azaadville
municipal reservoirs.
Option WB3: Randfontein Estates
(a) Area Available
The area between the SL18 TSF and Uncle Harry’s / Kagiso Road is available for the establishment of a
water treatment plant. A major electrical sub-station is situated in the north eastern corner of the
site.
The site is south of the old access road to the North East Shaft, where a High Tension (HT) electrical
power line follows the road. It is north of the Uncle Harry’s / Kagiso Road and lies on the western side
of the Battery Open Pits. On the eastern side of the site is an HT electrical power line that runs
towards Azaadville.
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The north-eastern part of the area has a fairly even topography and approximately 36 ha are available
for a treatment facility, which can be fitted between the HT electrical power lines.
(b) Mine Water Abstraction
There are various mineshafts in this area, including the following:
North East Shaft
Deep Shaft
North Battery Shaft
SD 32 Shaft
Central Vent Shaft
North Vertical Shaft
Shaft No.8
North East Shaft, Deep Shaft, North Battery Shaft and North Vertical Shaft were backfilled and sealed
off. SD32 Shaft has been demolished and the rubble has been dropped down the shaft.
Central Vent Shaft was used for pumping, but the connecting tunnel has been plugged and the shaft is
no longer connected to the mine workings of the Western Basin.
Shaft No.8 is available and has been used for the abstraction of water for many years. Water can be
abstracted from Shaft No.8 and piped to the treatment plant site.
(c) AMD Treatment Plant Site
After site clearance, approximately 4 ha in the north-eastern corner can be used for the treatment
plant. An earthworks platform can be formed by cut and fill to establish the plant site.
Access to the site can be from the existing road, connecting the site to Main Reef Road (R28).
Electrical power supply will have to be brought in by an overhead power line from the nearby
Power Plant sub-station.
Potable water can be supplied from the nearby Rand Water supply line.
Sewage can be disposed of in a septic tank and percolation trench.
(d) Sludge Handling and Disposal
Sludge can be disposed of in the Training Centre Pit, which can be lined and the sludge can be
pumped from the WTP to the pit. A mine tailings source will need to be secured to produce a stable
fill of the pit for later rehabilitation.
(e) Treated Water Discharge
Neutralised water can be pumped back to the discharge channel that drains to the Tweelopiespruit
and the Crocodile West River or can be discharged to the Wonderfonteinspruit on the Vaal River side
of the catchment.
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In future, reclaimed water for potable use can be pumped to the Randfontein, Krugersdorp or
Azaadville municipal reservoirs.
Option WB4: Deep Shaft
Deep Shaft has been backfilled and sealed off, and is not available for the abstraction of AMD. There
is also no land available for a WTP.
Option WB5: North-East Shaft
North-East Shaft has been backfilled and sealed off, and is not available for the abstraction of AMD.
There is also no land available for a WTP.
Option WB6: East Champ d’Or Shaft
(f) Area Available
The area north of the SL19 TSF around the East Champ d’Or Shaft has sufficient space for a WTP. TSF
SL19 is 350 m south of the Shaft, and the Champ d'Or Industrial Area supply railway line runs 400 m
west of the shaft, and there is an informal settlement on either side of the railway line. Champ d’Or
Road (R558) runs about 600 m east of the shaft. To the north there is rehabilitated mine land.
Approximately 36 ha are available for a treatment facility, which can be fitted into the north of the
East Champ d’Or Shaft.
(g) Mine Water Abstraction
Mine water can be abstracted from the East Champ d’Or Shaft.
(h) Water Treatment Plant Site
After site clearance, approximately 4 ha close to the Shaft can be used for the treatment plant. An
earthworks platform can be formed by cut and fill to establish the plant.
Access to the site can be from Champ d’Or Road.
Electrical power supply will have to be tapped from the overhead power lines.
Potable water can be supplied from the nearby municipal water supply line in Mindalore.
Sewage can be disposed of in a septic tank and percolation trench.
(i) Sludge Handling and Disposal
There are no operational sludge disposal facilities close to this option, so sludge would need to be
pumped to the Wes Wits or Training Pit, or a new-engineered sludge facility would need to be
constructed. There is space on the western side of the site for a new facility.
(j) Treated Water Discharge
Treated water can be discharged across Main Reef Road to the Muldersdriftloop and the Crocodile
West River or into the Klipspruit that drains to the Vaal River.
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In future, reclaimed water for potable use can be pumped to the Krugersdorp or Witpoortjie
municipal reservoirs.
6.2.2 Assessment of Options
A fatal flaw analysis of the six project options used four fatal flaw criteria in assessing the six project
options for a neutralisation plant, and a long-term water reclamation plant:
Land availability for a neutralisation plant, and a long- term water reclamation plant.
Land stability.
Connectivity to the Western Basin.
Sludge disposal.
Table 8 summarises the findings of the fatal flaw analysis for the project options.
Table 8: Fatal Flaw Criteria Assessment
Option No Land
availability Land stability Connectivity Sludge disposal
WB1: BRI
Shaft/R24
Road
Sufficient Outside the
undermined area
but on dolomite.
Special precautions
will be required to
secure
infrastructure.
Water is abstracted
from Shaft No.8, which
is connected to the
Western Basin mine
workings.
Millsite TSF (no
available capacity)
or Wes Wits Pit
WB2: Rand
Uranium
Plant
Sufficient Partially
undermined, but
there is sufficient
land for a complete
WTP.
Water is abstracted
from Shaft No.8, which
is connected to the
Western Basin mine
workings.
Millsite TSF (no
available capacity)
or Wes Wits Pit
WB3:
Randfontein
Estates
Sufficient Outside the
undermined area.
Water is abstracted
from Shaft No.8, which
is connected to the
Western Basin mine
workings.
Training Centre Pit,
about 2 km from
site. The pit is not
connected to the
Western Basin.
WB4: Deep
Shaft
Very limited Undermined Deep Shaft has been
backfilled and sealed
off.
Training Centre Pit,
about 3 km from
site. The pit is not
connected to the
Western Basin.
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Option No Land
availability Land stability Connectivity Sludge disposal
WB5: North-
East Shaft
Very limited Undermined North-East Shaft has
been backfilled and
sealed off.
Training Centre Pit,
about 2.5 km from
site. The pit is not
connected to the
Western Basin.
WB6: East
Champ d’Or
Shaft
Sufficient Undermined Historically, well
connected to the
Western Basin, but
current opinion is that
the connecting tunnel
to the Western Basin
has partially collapsed,
limiting the
connectivity.
New engineered
sludge disposal
facility or sludge
pumped to Wes
Wits or Training
Centre Pit.
Table 9 summarises the outcome of the fatal flaw assessment of the six project options.
Table 9: Summary of the Fatal Flaw Assessment
Option Fatal Flaw Selection Chart TCTA Project: Western Basin
Decision
Solu
tio
n v
aria
nt
FATAL FLAW CRITERIA: Mark solution variants
DEC
ISIO
N
(+) Yes (+) Pursue solution
(-) No (-) Eliminate solution
(?) Lack of Information (?) Collect information
Land availability
Land stability
Connectivity to Basin
Sludge disposal
A
B
C
D
Option WB1: R24
Tweelopiespruit + + + +
Can be considered more +
Option WB2: Shaft No.8 + + + +
Can be considered more +
Option WB3: Randfontein
Estate + + + +
Can be considered more +
Option WB4: Deep Shaft + - - -
Fatal flaw -
Option WB5 North-East
Shaft + - - -
Fatal flaw -
Option WB6: East Champ
d’Or + - - +
Fatal flaw -
The following project options were discarded based on identified fatal flaws:
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Option WB4: Deep Shaft and Option WB5: North East Shaft: The fatal flaw related to using the
shafts for access to pump AMD.
Option WB6: East Champ d’Or Shaft: The shaft may not be adequately connected to the Western
Basin. Although it cannot be confirmed or disproved at this stage, the risk of constructing a
complete WTP with no water to treat is too high.
The remaining project options were evaluated using a more extensive list of criteria (refer to Section
5.3 and the Ranking Matrix in Annexure K). The summary of the ranking scores is shown in Table 10.
Table 10: Decision Matrix (Western Basin)
AMD Abstraction Points AMD Treatment Sites Sludge Disposal Treated Water Disposal
Sites
Option Option Option Option
WB1 WB2 WB3 WB1 WB2 WB3 WB1 WB2 WB3 WB1 WB2 WB3
54 69 71 54 69 71 54 69 71 54 69 71
Table 10 shows that Option WB3: Randfontein Estates has the highest ranking, considering all of the
project infrastructure components.
In summary:
(a) Abstraction Point
Four options were evaluated (Shaft No. 8, Deep Shaft, North-East Shaft and Champ d’Or Shaft). Other
Mintail Shafts (Shaft No. 9 and No. 9E) were not considered because it was discovered early in the
process that they were unsuitable. From the option assessment, the preferred AMD abstraction point
is Shaft No. 8.
(b) Treatment Plant Site
Three site options were evaluated (Tweeloopiespruit Site, the Rand Uranium Treatment Plant Site and
the Randfontein Estates Site). The option assessment showed that the preferred treatment plant site
is the greenfields Randfontein Estates Site. It is a reasonable distance from the abstraction point,
which is not ideal due to the potential problems associated with pumping AMD. However, the
benefits of the site outweigh the technical challenges that need to be overcome in the detailed
design.
(c) Sludge Disposal Site
The disposal of sludge in the Western Basin is described in detail in Sludge Disposal Alternatives (BKS
Report No. J01599/10), which is attached as Annexure I. The conclusion and recommendations in this
report are incorporated here for ease of reference.
The preferred sludge disposal option for the Western Basin is:
Short-term solution (four years):
o Mogale West Wits pit (three to five years); or
o Training Centre pit (one year).
o Total Estimated Cost = R10,615,000.
Long-term solution (30 years+):
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o Agreement with mining companies to co-dispose of sludge, sharing a tailings storage
facility;
o Disposal into the Western Basin mine void; or
o Greenfields engineered disposal facility.
Mogale West Wits Pit is the most feasible sludge disposal option for the AMD sludge in both the
immediate and short-term, based on the following factors:
The site is available for immediate use for sludge disposal and is an operational TSF with
sufficient sludge storage capacity for the next 3-5 years (depending on Mogale Gold’s
operations);
A 5 km sludge delivery pipeline and pump station would be required.
There will only be a marginal increase in the waste load disposed of into the pit;
There is no intention to reclaim or remove sludge from pit;
Sludge geochemical properties in the pit are of little concern;
No management of the additional water that is pumped back to the plant (any water
management could be via the Western Basin);
This option is considered a low capital cost option (R5,840,000) and risk approach, yielding a site
life of four years, which will be sufficient time to confirm the chemical and physical characteristics
of the treatment sludge in order to find a long-term solution.
The risk associated to the long-term legal liability associated with the disposal of sludge on the pit
amounts to a portion of the closure cost. This amount needs to be quantified the various liability
long-term issues must be identified.
There are a number of risks associated with the sludge delivery pipelines, the largest of which is
the settlement of sludge in the pipeline as a result of power a failure. However, the risks do not
constitute a fatal flaw and will be mitigated through the provision of a standby sludge delivery
pipeline.
If required, the Training Centre pit is deemed an attractive solution with respect to low capital costs
of R4,775,000 and the short distance (2 km) from the proposed HDS plant. However, the short site life
of less than one year makes it less viable. This option will only be necessary if additional time is
required to finalise the long-term sludge disposal option.
Co-disposal with tailings on the existing tailings facilities in the immediate and short-term disposal
solution is ruled out because the mines intend to reclaim the existing tailings facilities in the near
future.
The long-term handling of sludge will be necessary, but this will require a detailed options analysis
based on sludge characteristics studies. Additional engagement with the various mining companies to
explore options is required.
The reworking of the tailings facilities will require new tailings facilities. The co-disposal of sludge on
these new tailings facilities is an attractive option that should be investigated in more detail.
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The potential of disposal into the Western Basin (backfilling) should be considered, especially due to
the potential benefits (low cost, alkaline environment, reduced mining void volume).
The use of a new engineered (lined) facility was not considered for the short-term solution, due to the
regulatory requirements, the associated capital cost (R64,300,000) and required 11 ha of land for a
disposal site life of only 2.5 years.
Although an engineered facility can be reviewed as a possible long-term solution, it is expected that
one of the other potential options will be more economical.
6.2.3 Continued Mining in the Western Basin
There is no requirement for the continuation of mining in the Western Basin.
6.2.4 Recommendations on Preferred Project Option
The selection of a project option is based on:
Availability of land on an uncompromised site with favourable geotechnical conditions, off the
dolomitic formations.
Central location from the perspective of future reclaimed water distribution to Rand Water and
municipal reservoirs.
Good access and supply of bulk services, such as electrical power.
Feasible and practical options for long-term waste sludge disposal.
Flexibility in terms of neutralised water discharge.
The recommended project option WB3 is based on the following project infrastructure components:
AMD abstraction from Shaft No.8.
AMD (and future reclamation) treatment plant located on the Randfontein Estates site.
Treated water discharge to the Tweelopiespruit, flowing to the Crocodile West River.
Waste sludge disposal to the old opencast pits, including Wes Wits Pit and the Training Centre Pit.
6.2.5 Emergency Contingency Shafts
Due to the size of the Western Basin, interconnectivity problems are not expected so emergency
contingency shafts have not been identified. After pumping starts at Shaft No. 8, the requirement for
contingency shafts can be reassessed.
6.2.6 Consideration of Integration with Future Long Term AMD Treatment
As part of the due diligence, the future long-term AMD treatment options were considered. Although
there is no certainty on the long-term options, it was accepted that the water will be treated to
drinking-water standards to supply the local municipal areas. Furthermore, waste minimisation and
the recovery of valuable metals from the waste sludge may be part of a future scheme.
The future scheme was allowed for in the following manner during the short-term due diligence:
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An estimate of the space requirement for the future scheme was made and any land procured for
the short-term solution must provide sufficient land for implementation of a long-term scheme.
Sludge handling will be a long-term requirement and the short-term solution has thus reviewed
how sludge can be handled in the long term (30+ years). The long-term requirements need to be
analysed and discussed with the various mines.
Consideration of where the potential connection to the potable water system would be, i.e. by
reviewing potential water demand and water distribution reservoirs. For the Western Basin, this
includes the Randfontein, Krugersdorp, Azaadville or Witpoortjie municipal reservoirs. Detailed
water distribution and master planning needs to be part of the long-term solution.
6.3 Conceptual Design
6.3.1 Shaft Stability
As part of the due diligence, the stability of the mineshaft to allow for long-term pumping
infrastructure was considered. An assessment of the shaft stability for the preferred mineshafts was
done by a rock engineering specialist, whose report is attached as Annexure J. The report concludes
that Rand Uranium Shaft No. 8 is suitable for use in the short-term solution as a pumping shaft.
6.3.2 Abstraction and Collection Infrastructure
(a) Abstraction Point
AMD has been abstracted from Shaft No. 8 for many years and it is proposed that the abstraction of
AMD from Shaft No.8 be continued for the following reasons:
The shaft is well equipped.
The shaft has been used for a long time.
The connectivity of the shaft has proven to be adequate.
The shaft is accessible.
The shaft has two open compartments / conveyances.
Currently, only one of the conveyances is used to pump AMD to the Rand Uranium HDS plant. This
conveyance will remain in use for the Rand Uranium HDS Plant to be upgraded for the immediate
solution.
The remaining conveyance can be used for the abstraction of AMD for the short-term plant. The
shaft’s parameters are listed in Table 11.
Table 11: Shaft No. 8 Parameters
Parameter Value (m amsl) Dimension
Collar Level 1,715.30 m amsl
Shaft Depth 445.00 m
Shaft Bottom Level 1,270.30 m amsl
Environmental Critical Level 1,550.00 m amsl
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(b) Pumps
It is proposed that a submersible pump system be used to abstract AMD for the WTP. These pumps
will be hung in the conveyance suspended from surface.
The headgear is in poor condition and will need to be removed. A new steel gantry and crawl beam
will be installed over this conveyance to facilitate the installation and removal of the pumps.
The pumps shall be chosen to deliver the peak flow (35 Mℓ/d over 24 hours), and with the same
pumps the average flow (27Mℓ/day) can be pumped over 18.5 hours. Pumping during the peak tariff
hours can thus be avoided at times.
(c) Installed Pump Depth
To determine the water level characteristics during pumping of the Western Basin would require a
pump test, monitoring the water level at various positions around the basin while varying the flow
rates. However, there will be no opportunity to undertake these pump tests until the full-scale
installation is operational. Therefore, flexibility needs to be allowed for the installed pump depth.
The expectation for the Western Basin is that the water level variance over the entire basin will be
negligible, due to size of the basin and extensive holing. Therefore, no allowance will be made for
water level variation.
From the water balance model of the Central Basin, it is expected that the water level will fluctuate by
about 7.4m, based on fixed speed pumps at average flow and allowing the basin to be drawn down
during low ingress and filled to ECL during high ingress.
The following basis, therefore, has been used to select the pump depth for the Western Basin:
The ECL level of 1,550 m, with an operational level of at least 2.5 m below ECL (as per the Terms
of Reference for this project);
A submergence depth of 10 m for the pumps;
Pumps staggered by at least one pipe length to reduce possible turbulence interference between
the pumps;
Pumps installed an additional 7.4 m below the [ECL plus submergence depth plus basin variation
plus seasonal variation] level to provide flexibility in operational philosophy (pumping at average
flow, with subsequent variation of the water level).
For more flexibility, it is recommended that the pipes be designed for the possibility that the
pumps are lowered by an additional 20% of the ECL. Initially, these pipes will not be purchased or
installed. The pumps will be sized for the best efficiency at the installation depth, but checked
that they can supply at least average flow at the lowest level.
Therefore, the recommended installed highest pump level for flexibility of water level within the
Western Basin will be 1,530.1 m amsl, and the pipes / pumps will be designed so the pumps can be
installed to 1,500.1 m amsl. This relates to the a pump with best efficiency at a flow of 34Mℓ/d
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(27Mℓ/d average, for 19 hour pump time) and a static head of 185.2 m , with the ability to be lowered
to 1,500.1 m amsl (static head = 215.2 m).
A conceptual design for such a pumping system was done, as was a preliminary selection on the
pumps (see Table 12).
Table 12: Abstraction Pump Station (Western Basin)
Parameter Value
Duty Flow (Mℓ/d) 35
Duty Flow (m3/s) 0.405
Duty Head (m) 200 (static plus allowance
for losses)
Duty Pumps (No) 2
Standby Pumps (No) 1 (not installed)
Rotational Speed (RPM) 1,470
Power Absorbed (kW) 985
Power Installed (kW) 1,200
(d) Electrical Power
A 6.6kV power line serves the Rand Uranium Shaft No.8 and two 500kVA miniature sub-stations
supply the power demand at the shaft.
Table 13: Estimated Electrical Power Load at Shaft No. 8
Description Quantity Power Installed (kW) Total Power (kW)
Existing Pumps 2 Duty 220 440
Immediate Measures 3 Duty + 1 Standby 250 750
Short-Term Installation 1 Duty + 1 Standby 1,000 1,000
(e) Pipeline
The pipeline from Shaft No. 8 to the WTP will have the parameters listed in Table 14.
Table 14: Abstraction Pipeline (Western Basin)
Parameter Value
Flow (Mℓ/day) 35
Flow (m3/s) 0.405
Nominal Diameter (m) 0.700
Flow Velocity (m/s) 1.08
Length of Pipe (m) 5,370
The pipeline route can be described as shown in Table 15.
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Table 15: Description of Abstraction Pipeline Route (Western Basin)
No Section Description
1. Pump Station at
Rand Uranium
Shaft No.8
The pumps can be installed in the open conveyance of Shaft No. 8.
Chainage = 0m
2. Shaft No.8 to
Tweelopies Road
From Shaft No.8 the pipeline can follow the access road to the shaft to the
Tweelopies Road. The pipeline can be above the ground on pipe pedestals
to facilitate maintenance.
Chainage = 0-150 m
Length = 150 m
3. Shaft No.8 Access
Road to Treated
Water Channel
Follow Tweelopies Road from the Shaft No.8 access road to the treated
water channel. The pipeline can be above the ground on pipe pedestals to
facilitate maintenance.
Chainage = 150-1,150 m
Length = 1,000 m
4. Crossing the
Treated Water
Channel
The pipeline can cross the treated water channel by conventional open
trench methods. Water in the channel can be led through a pipeline while
crossing is done. The pipeline can be above the ground on pipe pedestals
to facilitate maintenance.
Chainage = 1,150-1,160 m
Length = 10 m
5. Treated Water
Channel to
Western R28
Service Road
From the Treated Water Channel the pipeline follow a route around the
CPS Pit to the Western R28 Service Road. The pipeline can be above the
ground on pipe pedestals to facilitate maintenance.
Chainage = 1,160-2,770 m
Length = 1,610 m
6. Crossing Western
R28 Service Road
The Western R28 Service Road will have to be crossed by conventional
pipe jacking. Existing services can be expected on both sides of the road.
Permission for this crossing will have to be obtained.
Chainage = 2,770-2,790 m
Length = 20 m
7. Western R28
Service Road to
Railway Line
Once across the Western R28 Service Road the pipeline can proceed to
the railway line next to the R28 Road. Existing services can be expected.
The pipeline can be above the ground on pipe pedestals to facilitate
maintenance.
Chainage = 2,790-2,860 m
Length = 70 m
8. Crossing the
railway line
The railway line will have to be crossed by conventional pipe jacking.
Existing services can be expected on both sides of the railway line.
Permission for this crossing will have to be obtained. In this section, the
pipeline will be underground.
Chainage = 2,860-2,890 m
Length = 30 m
9. Crossing the R28
Road
The R28 Road will have to be crossed by conventional pipe jacking.
Existing services can be expected on both sides of the road. Permission for
this crossing will have to be obtained. In this section, the pipeline will be
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No Section Description
underground.
Chainage = 2,890-2,950 m
Length = 60 m
10. R28 Road to
Railway Line
Once across the R28 Road, the pipeline can proceed to the railway line
coming out of the cutting. Existing services can be expected. The pipeline
can be above the ground on pipe pedestals to facilitate maintenance.
Chainage = 2,950-3,380 m
Length = 430 m
11. Crossing the
Railway line
The railway line will have to be crossed by conventional pipe jacking.
Existing services can be expected on both sides of the railway line.
Permission for this crossing will have to be obtained. In this section, the
pipeline will be underground.
Chainage = 3,380-3,410 m
Length = 30 m
12. Railway Line to
Access Road to
WTP
From the railway line, the pipeline can proceed to the WTP access road. In
the process, various overhead high-tension power lines, water pipelines
and gas pipelines will have to be crossed. Permission for crossing these
services will have to be obtained. The pipeline can be above the ground on
pipe pedestals to facilitate maintenance.
Chainage = 3,410-3,690 m
Length = 280 m
13 Following the
Access Road to
WTP
The pipeline can follow the access road to the WTP. Existing services can
be expected along the road. Permission for crossing these services will
have to be obtained. The pipeline can be above the ground on pipe
pedestals to facilitate maintenance.
Chainage = 3,690-5,370 m
Length = 1,680 m
Table 16: Major Service Crossings - Abstraction Pipeline (Western Basin)
No Service Method Of Crossing
4. Treated Water Channel Open Trench
6. Western R28 Service Road Conventional pipe jacking
8. Railway line Conventional pipe jacking
9. Main Reef Road (R28) Conventional pipe jacking
11. Railway line Conventional pipe jacking
6.3.3 Plant Infrastructure
A preliminary site layout was done and the following were addressed:
The site has an even slope of about 1:40 towards the northeast.
The site is vacant and contains no structures.
Numerous existing services cross the site.
The site belongs to Rand uranium.
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See Drawing J01599-01-G-004.
(a) Geotechnical Input
A desktop study of the site geology and geotechnical conditions revealed the following:
Witwatersrand shale and quartz material is likely to be found at the site.
It is unlikely that dolomite will be found on site, but this should be confirmed.
The in-situ material is likely to be suitable for the construction of a terrace by cut and fill.
Fill material may be sourced from some spoil dumps on site.
The site is probably not undermined.
(b) Terrace Design and Plant Layout
A preliminary design of a terrace (200 m long and 150 m wide) was done and the plant was laid out on
it.
(c) Roads and Stormwater
The existing access road to the North-East Shaft and to the electrical sub-station can be upgraded and
used to access the WTP site.
Site roads for the delivery of chemicals and the maintenance of equipment will be designed and the
roads and earthworks will be designed to manage and dispose of stormwater.
(d) Water Supply
A water connection can be installed at the Azaadville reservoir.
(e) Sanitation
If a municipal sewer connection is uneconomical, a septic tank and percolation trench system can be
installed.
(f) Electrical Power Supply and Distribution
The proposed plant is adjacent to an Eskom sub-station and power will be obtained directly from
Eskom. The electrical power supply voltage will be stepped down to 400V to supply electricity to the
various Motor Control Centres.
6.3.4 Sludge Handling and Management
A scheme that is in line with the sludge recommendations in Section 6.2.2 will be implemented to
dispose of the sludge. It will include a pump main from the treatment plant to the Wes Wits pit. The
pipeline route from the treatment plant follows the access road, crosses the R28, then crosses the
railway line and runs northeast and parallel to the railway line. The pipeline direction changes to
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north west, crosses the western R28 service road and discharges into the Wes Wits Pit. The length of
the pipeline is approximately 4 km.
6.3.5 Treated Water Discharge
Treated water will be discharged into the wet sump of the treated water pump station, from where it
will be pumped back to the treated water discharge channel of the Rand Uranium HDS Plant.
(a) Pumps
It is proposed that two duty pumps and a standby pump be installed in a pump station. The design
flows are the same as those of the AMD abstraction pump station, with the same operational
philosophy (pumping average flow over 19 hours.
A conceptual design was done for the treated water pump station. Table 17 shows the parameters.
Table 17: Treated Water Pump Station (Western Basin)
Parameter Value
Duty Flow (Mℓ/d) 35
Duty Flow (m3/s) 0.405
Duty Head (m) 50
Duty Pumps (No) 2
Standby Pumps (No) 1
(b) Pipeline
The treated water pipeline from the WTP to the treated water discharge channel will have the
parameters listed in Table 18.
Table 18: Treated Water Pipe Line (Western Basin)
Parameter Value
Flow (Mℓ/day) 35
Flow (m3/s) 0.405
Nominal Diameter (m) 0.700
Flow Velocity (m/s) 1.08
Length of Pipe (m) 5,310
The pipeline route can be described as shown in Table 19.
Table 19: Description of Treated Water Pipeline Route (Western Basin)
No Section Description
1. Following the
Access Road
from WTP
The pipeline can follow the access road from the WTP. Existing services
can be expected along the road. Permission for crossing these services
will have to be obtained. The pipeline can be above the ground on pipe
pedestals to facilitate maintenance.
Chainage = 0-2,280 m
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No Section Description
Length = 1,620 m
2. From Access
Road to WTP
to Railway Line
From the WTP access road, the pipeline can proceed to the railway line.
In the process, various overhead high-tension power lines, water
pipelines and gas pipelines will have to be crossed. Permission for
crossing these services will have to be obtained. The pipeline can be
above the ground on pipe pedestals to facilitate maintenance.
Chainage = 1,620-1,900 m
Length = 280 m
3. Crossing the
Railway line
The railway line will have to be crossed by conventional pipe jacking.
Existing services can be expected on both sides of the railway line.
Permission for this crossing will have to be obtained. In this section, the
pipeline will be underground.
Chainage = 1,900-1,930 m
Length = 30 m
4. Railway Line to
R28 Road
Once across the railway line, the pipeline can proceed to the R28 Road
running up to the cutting. Existing services can be expected. The pipeline
can be above the ground on pipe pedestals to facilitate maintenance.
Chainage = 1,930-2,360 m
Length = 430 m
5. Crossing the
R28 Road
The R28 Road will have to be crossed by conventional pipe jacking.
Existing services can be expected on both sides of the road. Permission
for this crossing will have to be obtained. In this section, the pipeline will
be underground.
Chainage = 2,360-2,420 m
Length = 60 m
6. Crossing the
Railway Line
The railway line will have to be crossed by conventional pipe jacking.
Existing services can be expected on both sides of the railway line.
Permission for this crossing will have to be obtained. In this section, the
pipeline will be underground.
Chainage = 2,420-2,450 m
Length = 30 m
7. Railway Line to
Western R28
Service Road
Once across the railway line the pipeline can proceed to the Western
R28 Service Road. Existing services can be expected. The pipeline can be
above the ground on pipe pedestals to facilitate maintenance.
Chainage = 2,450-2,520 m
Length = 70 m
8. Crossing
Western R28
Service Road
The Western R28 Service Road will have to be crossed by conventional
pipe jacking. Existing services can be expected on both sides of the road.
Permission for this crossing will have to be obtained.
Chainage = 2,520-2,540 m
Length = 20 m
9. Western R28
Service Road
to Treated
Water Channel
From the Western R28 Service Road the pipeline can follow a route
around the CPS Pit to the treated water channel. The pipeline can be
above the ground on pipe pedestals to facilitate maintenance.
Chainage = 2,540-4,150 m
Length = 1,610 m
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Table 20: Major Service Crossings - Treated Water Pipeline (Western Basin)
No Service Method of Crossing
3. Railway line Conventional pipe jacking
5. Main Reef Road (R28) Conventional pipe jacking
6. Railway line Conventional pipe jacking
8. Western R28 Service Road Conventional pipe jacking
6.4 Detail Cost Estimates
6.4.1 Detail Capital Estimate
A detailed capital cost estimate for the Western Basin option is summarised in Table 21.
Table 21: Detail Capital Estimate for the Western Basin
Number Description Amount (rand) Total*
1 AMD collection infrastructure
Civil / Structural Work 1,856,937.50 R40,787,729
Mechanical 38,930,791.20
2 AMD treatment plant
Civil / Structural Work 48,818,956.06 R73,255,525
Mechanical 24,436,569.00
3 Neutralised water discharge
Civil / Structural Work 294,000.00 R1,316,400
Mechanical 1,022,400.00
4 Sludge Handling and Disposal
Civil / Structural Work 908,806.25 R1,711,806
Mechanical 803,000.00
5 Earthworks and Pipe Work 31,008,353.11 R31,008,353
6 Electrical, Control and Instrumentation 25,960,790.00 R25,960,790
7 Preliminaries and Generals (12%) 20,884,872.00 8 Total R194,925,475
* Totals are rounded to the next full Rand
6.4.2 Detailed Operating and Maintenance Cost Estimate
The detailed operating and maintenance estimate for the Western Basin option is summarised in
Table 22.
Table 22: Detailed Operating and Maintenance Estimate for the Western Basin
Number Description Amount (rand) Total
1 O&M on CAPEX 3,600,100
2 Chemicals Costs 31,177,274
3 Electricity Costs 13,527,200 R48,304,574
7. CENTRAL BASIN
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7.1 Status of the Basin
7.1.1 Background
Mining in the Central Rand portion of the Witwatersrand Goldfields started 125 years ago after the
discovery of gold in 1886. The Central Rand Basin (or Central Basin) stretches approximately 47km
from Roodepoort in the west to Germiston in the east, covering a surface area of approximately
251km2. The locality and extent of the Central Basin is shown in Figure 6.
The Central Rand mines were dewatered to the deepest mining depths until 1974, when most of the
mines in the Central Basin were no longer operational [Scott, 1995]. After 1974, the water level in
some of the mines was allowed to rise, while some mine dewatering continued, but by 1995, the
main dewatering took place on the extreme western and eastern edges of the basin, at Durban
Roodepoort Deep (DRD) and East Rand Proprietary Mines (ERPM) respectively.
In 2008, the last mine dewatering in the Central Basin was stopped at ERPM. The water level in the
basin has been rising since then.
Figure 6: Locality and extent of the Central Basin
7.1.2 Mine Water Generation
As part of this project, the Environmental Critical Level (ECL) was confirmed for the Central Basin as
150 m below the ERPM Cinderella East shaft (a probable decant shaft) collar level (1,617 m), or 1,467
m amsl (186.2 m below South West Vertical (SWV)) – see Section 4.3.2.
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The water level in the Central Basin (measured on 13 May 2011 by DRD Gold) was 1,199 m amsl,
about 454 m below surface measured at SWV Shaft, or about 268 m below the ECL. The water level
measured at Gold Reef City Shaft No.14 on the same day had an identical reading, which indicates
that the water level in at least part of the Central Basin is rising at the same rate over the entire basin.
Figure 7: Predicted rate of water rise in the Central Basin (different rainfall scenarios)
Figure 7 shows the predicted rate of water rise in the Central Basin, based on geo-hydrological
modelling for the basin. The model includes the calculated mine void volume and expected water
ingress into the mining void. Details of the model and methods used to produce Figure 7 can be found
in Water Balance and Levels (BKS Report number J01599/06).
Based on the information in Figure 7, it is expected that the water will reach ECL in August 2012
(average rainfall) while, if allowed to happen, decant would occur around March 2013. These dates
are based on annual average rainfall data. A number of rainfall / recharge scenarios were also
evaluated and the predicted dates for reaching ECL are as follows:
Above average rainfall: June 2012.
Average rainfall: August 2012.
Below average rainfall: December 2012.
The interconnectivity (i.e. locations and levels of cross cuts and holings) of the Central Basin is
reasonably well understood; however, the potential flow rate of water between compartments in the
basin and the water level profile along the length of the basin under various dewatering pump rates is
not fully understood. The DWA is currently developing a water level monitoring system, which can be
used to optimise the required pump level to account for any level changes along the basin.
1200
1250
1300
1350
1400
1450
1500
1550
1600
1650
Ele
vati
on
(m
am
sl)
Date
Predicted Rate of Rise in the Central Basin for Average, Dry and Wet Periods
Water Level (Dry) Water Level (Average) Water Level (Wet) ECL Decant
June 2
012
August 2012
Decem
ber
2012
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Although the interconnectivity of the Central Basin is understood and, until recently (2008), it was
possible to drain the Central Basin from the ERPM South West Vertical shaft, the current condition of
the cross-cuts and holings is unknown. Scott [1995] states that mining on the Witwatersrand created
sheet-like openings that are continuous laterally and with depth, to maximum mined depths of 3,500
m. In cases where the stope is a discontinuous sheet, it is joined by access haulages and drives.
The geological structure is that of a basin, with the rim more steeply dipping than the basin bottom,
which may be horizontal. In the Central Basin, dips of 60-70 degrees can be found and the average dip
is about 45 degrees. Where the mine openings dip steeply, the forces are such that, even when
unsupported, they remain open.
The collapse or closure of cross-cuts and holings is possible and this could impact the possibility of
dewatering the basin from a single point. Filling the cross-cuts and holings with water will provide
support and reduce the risk of collapse. Due to uncertainty on whether or at which point such a
collapse may occur contingency plans were considered as part of the due diligence.
Furthermore, draining the basin to allow mining will remove the water that is providing some of the
support, and it is expected that there may be an initial increase in seismic activity, which could have
an impact on basin connectivity.
The potential decant point has been debated and there is no consensus on the point of decant. As
expected, if the connectivity between the various sub-basins in the Central Basin is good (high
transmissivity), decant will occur at the lowest point connected to the Central Basin void. The lowest
known direct points of connection are the mineshafts on the eastern side of the basin (ERPM shafts),
with Cinderella West and East being the lowest points (collar heights of 1,614 m and 1,617 m amsl,
respectively). There is no direct connectivity of ERPM Hercules South, Far East and South East Vertical
with collar heights of around 1,602 m. There are possibly other points where decant can occur first,
i.e. through reef outcrop, geological faults and old abandoned mine pits or shafts. By the time decant
occurs, level 5 of Gold Reef City Shaft will be flooded.
The Johannesburg CBD has many tall buildings with deep foundations, some of which have piled
foundations. Various reports in the media indicated that these deep foundations might be at risk from
the rising AMD. Johannesburg CBD ground levels are generally above 1,750 m to the North and West,
dropping to about 1,700 m in the South East. Therefore, there is approximately an 80 m buffer at the
expected decant level (1,617 m) and a 230 m buffer at the ECL. The water level is rising at the same
rate across the Central Basin (between ERPM and Crown Mines), so it is expected that decant will
occur without any impact on the buildings in the CBD.
A report for ABSA and Standard Bank by the Mine Water Research Group at the Potchefstroom
Campus of the North West University, headed by Professor Frank Winde, released a press statement
on 28 June 2011 stating that, at the level of expected decant, the water level would be 90 m below
the base of the piles of the ABSA Towers East building (the building with the deepest piles that was
investigated as part of their study). More information on the findings of this report has been
requested.
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7.1.3 Mine Water Flow
The estimated flows into the Central Basin and, therefore, the estimated pump rates are given in
Table 23.
Table 23: Mine Dewatering and Treatment Flows (Central Basin)
Minimum Average Maximum
Ingress Flow (Mℓ/d) 34 57 84
Pump Time (hours) 19 (off peak) 19 (off peak) 24
Pump Flow (m3/s) 0.50 0.83 0.97
Pump and Treatment Flow (Mℓ/d) 43 72 84
The details on the source of information and the motivation for the flows are given in Basis of
Engineering Design (BKS Report No. J01599/01), included as Annexure A.
7.1.4 Water Quality
The expected water quality is defined in Basis of Engineering Design (BKS Report No. J01599/01),
included as Annexure A.
7.2 Options for the Collection and Treatment of AMD
7.2.1 Identification of Options
The Central Basin has a topographical high point south of the Johannesburg CBD (1,750 m amsl), with
the height in the east (ERPM, Germiston) dropping to 1,600 m amsl, and in the west (DRD,
Roodepoort) dropping to 1,640 m amsl.
The east of the basin was selected as the preferred position for abstracting and treating AMD for the
following reasons:
The ERPM mines were the last mines to be mined and dewatered, in particular the ERPM South
West Vertical (SWV) shaft, which was used until 2008 to dewater the basin.
There is interconnectivity with the entire Central Basin.
There is a slight reduction in the required pump head between the east and west, and a
significant reduction when compared to the centre of the Central Basin.
There is infrastructure for the treatment of AMD at the ERPM site, although the it requires
significant refurbishment.
The identification of the Central Basin project options was done by only selecting options that did not
have an immediate fatal flaw, using the methodology discussed in Section 5.
The identified project options included considerations of the following factors:
Abstraction point – mineshaft for abstraction from the basin.
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Treatment sites – potential area available for short- and long-term treatment requirements.
Sludge disposal sites – identification of options for sludge disposal.
Water discharge sites – review of the potential for the water to re-circulate back into the basin.
Future supply of reclaimed water to the Rand Water and/or municipal water supply reservoirs.
(a) Abstraction Point
Based on the selection criteria listed above, the shafts in
Table 24 were evaluated to determine if any fatal flaws precluded their consideration for inclusion in
the project.
Table 24: Central Basin Initial Abstraction Options Screening
Shaft
Description
Collar
Level
(m amsl)
Possibility Reason
Hercules South
Shaft
1,602.10 The shaft is only 286 m deep, which reduces
flexibility for potential deeper-level mining options.
Connectivity with the Central Basin is not confirmed.
South East
Vertical Shaft
1,602.61 Shaft plugged and not connected to the Central
Basin.
Far East Vertical
Shaft
1,604.82 Shaft plugged and not connected to the Central
Basin.
Cinderella West
Shaft
1,613.72 There is insufficient space around the shaft for the
required treatment plant and long-term solution.
Cinderella East
Shaft
1,618.30 Potential shaft, with available land and electrical
supply close by.
Central Shaft 1,625.04 Although initially identified as a potential option,
with the benefit of available surrounding land, DRD
Gold indicates that mine waste was disposed of in
the shaft, so there is a potential risk due to
connectivity issues.
Hercules Shaft 1,626.40 Shaft filled and capped.
Cason Incline
Shaft
1,634.13 Incline shaft.
Comet Vertical
Shaft
1,647.10 Shaft filled.
Angelo Main
incline Shaft
1,652.62 Incline shaft.
South West
Vertical Shaft
1,653.24 This shaft was identified by other studies to serve as
the abstraction point because pumping was done
from this shaft until 2008 and there is a treatment
plant. The electricity supply to the site has been
maintained and is immediately available.
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Shaft
Description
Collar
Level
(m amsl)
Possibility Reason
South West Vent
Shaft
1,653 The vent shaft is on the same site as the treatment
plant, but the vent shaft only has a 6m diameter,
which limits space for pump infrastructure (shaft is
directly adjacent to one of the clarifiers) and the
connectivity to the basin is through a single cross-cut
(high risk).
Angelo Vertical
Shaft
1,653.94 Shaft filled.
Two AMD abstraction options (South West Vertical and Cinderella East shafts) were taken to the
options assessment stage.
(b) Treatment Plant Site
Although the treatment plant site can be located a distance away from the abstraction point, due to
the nature of the AMD, the distance should be as short as possible to reduce the potential for
oxidation, scaling and corrosion. For this reason, one of the selection criteria for the abstraction point
was the availability of land adjacent to the shaft to allow for the construction of a treatment plant.
This was not possible only in one case (Cinderella West), however, the adjacent Cinderella East had
land available and there was no need to consider Cinderella West.
The South West Vertical shaft is adjacent to a High Density Sludge (HDS) treatment plant, which was
commissioned in 1977 and operated until 2008. The HDS plant, however, has been stripped of all
mechanical and electrical equipment and some of the steel components are severely corroded and
need to be replaced.
The South West Vertical site is split into two portions by a railway line. The HDS plant is on the
eastern portion and the shaft is on the western portion. Any future infrastructure, e.g. the long-term
water reclamation process plant and additional sludge handling would need to be situated on the
western portion of the site.
As it was part of the selection criteria, the Cinderella East Shaft has sufficient space for a treatment
plant, both HDS and any future long-term water reclamation plant.
(c) Sludge Disposal Site
Although this project focuses on the short-term solution, sludge disposal will be a long-term
requirement so the potential for the selected solution to cater for the long term was also considered.
Alternatively, where the short-term solution would not accommodate the long-term solution,
possibilities for long-term handling of the sludge were identified.
Based on the general sludge disposal options, the following sites and options were identified:
Engineered facility: There are a number of reclaimed TSFs to the north of Angelo Pan, with space
to construct an engineered waste disposal facility for long-term sludge disposal.
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Five potential shafts were identified for backfilling using the AMD treatment sludge: the Central
shaft, SWV (using Cinderella East as the abstraction point), SWV vent shaft (using Cinderella East
as the abstraction point), Cinderella West (using SWV as the abstraction point) and Cinderella
East (using SWV as the abstraction point).
The ERGO Brakpan TSF, south of Boksburg, was identified as an option for disposal on an existing
TSF, through co-disposal with gold recovery waste sludge. The ERGO Brakpan TSF would require a
25km pipeline, so a sub-option would be to link into the DRD Gold ERGO / Crown disposal
pipeline, either at the ERGO Knights gold processing plant (about 3 km north east of the ERPM
HDS treatment plant) or directly into the sludge disposal line from the Knights processing plant,
which passes close to the shaft abstraction options.
(d) Treated Water Discharge Sites
A key technical consideration was the review of the potential discharge position for the treated water
to minimise recycling of the treated water back into the basin, i.e. creating additional water ingress.
This would possibly be a short-term consideration, as it is expected that in the long term the water
will be reclaimed to potable standards and supplied into the potable water distribution network.
Therefore, the short-term treated water discharge solution will not be required in the long term and
any cost incurred would be wasted expenditure in the long term and should thus be strongly
motivated if required.
The two identified abstraction points would discharge into the Elsburgspruit, which is within the Vaal
River catchment. Downstream of the Elsburg and Cinderella Dams, the streams cross an outcrop of
the Elsburg Reef. Scott [1995] makes the assumption in his ingress model that the losses to the
Elsburg Reef are negligible.
As it is not expected that the ingress volume from the AMD treatment works will be significant, the
following actions are recommended:
Design only for the shortest suitable discharge from the HDS plant to the Elsburgspruit;
Review and monitor the Elsburgspruit for potential ingress points between the discharge point
and where the Elsburg Reef crosses the Elsburgspruit;
If significant ingress points are found, assess the best technical option to reduce ingress (for
example, either a channel for the treated water flow to bypass the ingress point(s) or local
modifications of the natural channel in the Elsburgspruit).
7.2.2 Assessment of Options
The assessment of options used the methodology discussed in Section 5.
(a) Abstraction Point
From the options selection, two options emerged as potential abstraction points and were analysed
based on the assessment criteria, with scoring done in the assessment matrix. The following options
were evaluated:
Abstraction point and treatment plant site:
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CA1 / CT1: South West Vertical
CA2 / CT1: Cinderella East
Waste Disposal:
CS1: Engineered facility on surrounding recovered mine areas
CS2: Backfilling of mine
CS3: Co-disposal on ERGO Brakpan TSF
Treated water disposal is not part of the options analysis because it is recommended that only a single
option be investigated, i.e. disposal at a suitable point as close to the treatment plant as possible.
Table 25: Decision Matrix (Central Basin)
Abstraction Points Treatment Sites Sludge Disposal Sites
Option Option Option
CA1 CA2 CT1 CT2 CS1 CS2 CS3
70 58 70 58 46 62 65
Based on the options assessment (summarised in Table 25), the following are the preferred options:
Abstraction point: South West Vertical shaft.
Treatment site: South West Vertical site.
Sludge disposal option: Co-disposal on the ERGO Brakpan TSF.
Table 26 summarises some of the reasons and motivation for the scoring of each option. Refer to
Annexure K for the complete documentation.
Table 26: Option Assessment (Central Basin)
Assessment
Criteria
Motivation
(SWV = South West Vertical, CE = Cinderella East)
Available
Infrastructure
SWV has an HDS plant with partial capacity for the treatment of AMD.
Significant refurbishment and upgrades will be required before commissioning
the plant. The plant is expected to reduce the time required for construction.
There is no infrastructure at the CE site, other than the collar.
Land Availability SWV is owned by DRD Gold, which has indicated willingness for long-term lease
options or even to transfer the land ownership. The site is divided in two, with a
railway separating the shaft site from the treatment plant. The option of
obtaining the surrounding land portions, e.g. the old hostel and area to the
south of the hostel, should be considered to increase the available space.
CE is owned by Ekurhuleni Local Municipality. The existing land use is open area,
which will require rezoning. As this site is situated in a residential area, it is
expected that there may be resistance from the community to the proposed
development.
Access and
servitudes
SWV has good access to the site and is in an industrial area. There are a number
of existing servitudes over the site and adjacent properties. The site is split by a
railway line.
CE is in a residential area, however, the road access is adequate but heavy
vehicles entering the residential area will not be ideal. The CE shaft is in a
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Assessment
Criteria
Motivation
(SWV = South West Vertical, CE = Cinderella East)
servitude, but there are no servitudes for pipelines and services.
Connection to
Bulk Services
At SWV the ESKOM connection has been maintained and is available. Other
services would need to be connected, but capacity problems are not expected
due to the surrounding industrial land use.
At CE there is a sub-station on the site, but due to the residential area it is
unlikely that sufficient power is available. Furthermore, other bulk services may
be under capacity also due to the residential land use.
Sludge Disposal There is not much to differentiate the sites from each other in terms of sludge
disposal. The preferred option would be to dispose of sludge on an existing TSF,
which would be the Ergo facility. Although the CE shaft is closer to the Ergo TSF,
the pipeline route would probably need to follow the Ergo pipeline servitude,
which reduces the benefit of this option. For the other potential options, the
pipeline lengths would be similar.
Environmental
and social impact
SWV is on an industrial site, with some remaining buildings from the mining
activities. Major environmental and social impacts are not expected.
CE is on a site that would previously have been the site for the mining activities;
however, the site has been rehabilitated and is now open. Although there
would only be a small environmental impact, due to the previous land use on, it
social impacts are expected to be significant.
Security SWV is in an industrial area surrounded by informal areas. The security in the
area is perceived to be worse than the option of CE. However, for both options
the sites need to be securely fenced.
CE is in a middle-income residential area and the security is perceived to be
better than the SWV option.
Discharge/
Delivery
Nothing differentiates the options. The discharge and potential delivery point
distances are equal.
Flexibility for long
term solution
The SWV site is smaller than the CE site, but is big enough to incorporate any
future long-term solution. The site separation (by railway) between the existing
HDS treatment plant and the pump shaft is inconvenient, but access can be
provided under the railway.
The size of the CE site is sufficient to incorporate any future long-term solution.
Selection Based on this options analysis and the motivations, the preferred option is the
South West Vertical shaft. It is recommended that the CE shaft be maintained
as a backup option during the project design stage.
(b) Treatment Plant Site
The selection of a treatment plant site is linked to the selection of the AMD abstraction point. Only
the Cinderella West option did not have sufficient area adjacent to the shaft, but there was no
perceived benefit to transfer the AMD to another site.
The selection of South West Vertical (SWV) Shaft as the preferred abstraction point was not
influenced by the existing HDS plant. Therefore, the following factors would impact the decision to
refurbish or demolish:
The condition of the infrastructure and cost to repair;
The size of the infrastructure relative to the AMD treatment requirements;
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The ability to operate the plant on an adjacent site; and
The integration of the existing HDS plant with any long-term treatment plant.
A cursory visual assessment of the SWV HDS plant helped determine the potential for refurbishing the
infrastructures. The following conclusions were reached:
All electrical and mechanical equipment has been removed from the HDS plant.
The visible pipe work is corroded and possibly blocked due to scaling.
All structural steel, hand railing and grating is severely corroded and will need to be replaced.
Clarifiers: the outside walls seem structurally sound. A few small leaking patches are visible, but
are calcified. Information in ERPM drawings indicate that:
- There are numerous cracks on the clarifier floor panels;
- Some of the concrete floor panels are warped;
- The polysulphide joints are generally in a poor condition and would need to be replaced.
- The condition of the reinforcing is unknown; however, cracks provide access for water, which
can lead to corrosion.
Mixing and Aeration tanks: The concrete structures appear to be in good condition considering
their age and purpose, but some small patches of spalling have occurred. The hoppers of the
aeration tanks have many vertical cracks, with significant calcification.
Based on the available information, it is expected that the plant can be repaired without major
structural repair, i.e. only minor repair and surface treatment. The work will be costly and there is
a risk that unidentified repairs will be discovered during construction. It is still expected that the
cost to repair will be less than replacement. The ongoing maintenance requirement will be higher
than new infrastructure. Coatings applied during the repair will probably only have a life of six to
eight years before they need to be replaced.
One perceived benefit of using the existing infrastructure is the expectation that the plant can be
commissioned earlier than a new treatment plant could. However, the full extent of repair will
only become evident during the construction phase, and any unforeseen work could increase the
repair time.
Other considerations with regard to the re-use of the SWV HDS plant and infrastructure are as
follows:
The HDS plant site boundary almost envelopes the plant. The plant is bounded by Tide Street to
the north, a railway line to the west, a residential area to the east and a small open area to the
south. There is some available space to the south on the site; however this would not be enough
space for the long-term process plant (without obtaining additional open land to the south east
of the site).
ERPM (DRD Gold) located very few drawings of the plant, e.g. only the clarifier floor slab and
underdrains, various pipe work / general drawings and a process flow diagram. No dimensioned
drawings of the mixing and aeration tanks were found. A detailed topographical survey of the site
would be required to obtain information on the process tanks. The time required for the survey
will delay the start of the design work. There is still a potential risk that the additional unit
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processes required for the upgrade will not be compatible with the existing units, e.g. problems
with the hydraulics for the required capacity.
There is a disused ventilation shaft (capped, but directly adjacent to the clarifier on the eastern
side of the site) and ventilation building on the treatment plant site. For safety reasons, it is
proposed that this vent shaft be made more visible by increasing the height of the cap to prevent
construction / maintenance vehicles from driving over the cap.
The ventilation building will need to be demolished if further development is required towards
the south. Indications are that this building is older than 60 years, which means that it will be
subject to heritage regulations.
There is an access under the Transnet railway line, which was used for train access. The details of
this access are unknown, but it is proposed that the infrastructure be installed to allow this
access to be used for vehicular access.
The land ownership in the area of the SWV site is complex, with numerous landowners and small
parcels of land. Consolidation of land parcels may be required in order to obtain a practical
treatment plant.
Access to the existing HDS plant is limited and there is insufficient space for large vehicles to enter the
site and turn around to exit. There are two options for supplying the HDS plants with chemicals:
Provide for a delivery slip lane off Tide Street, where the deliveries can be done by parking the
trucks parallel to the fence line, with a connection / conveyor system outside the fence. Tide
Street (K110) is due to be upgraded and it is expected that the roads authority would not allow
this option. The chemical supply connections outside the fence would also be a security risk.
The preferred option is for the chemical supply, storage and make-up to be done on the SWV
Shaft site, with connection to the HDS plant via the pipeline servitude to provide proper access
along the slurry and lime slurry pipelines.
The process at the HDS Plant was evaluated in terms of the potential to upgrade the plant. The
following conclusions were reached:
The treatment process technology only incorporates neutralisation and aeration and is,
therefore, different to the proposed technology for the purposes of this project (refer to Section
4.4).
The existing neutralisation tanks are approximately the size required for the sludge conditioning
and pre-neutralising tanks. Therefore, by providing additional tanks for the new neutralisation
and gypsum crystallisation tanks, it would be possible to modify the process and provide
sufficient treatment capacity.
The design capacity of the HDS plant is unknown, but it is proposed that the design capacity of
the upgraded plant be equal to the ingress / pump flows, i.e. average of 72Mℓ/d (over 19 hours)
and capable of hydraulic and chemical dosing to treat a peak flow of 84Mℓ/d.
The additional unit processes can be provided in the space available on the site.
The free board on the existing structure will be evaluated. ERPM constructed concrete block walls
to possibly provide additional free board for the aerator spray. A permanent solution will be
found, which will incorporate the hydraulic changes required.
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Due to the severe time constraints on the Central Basin and the identified risks and difficulty of
integrating the abstraction site with the HDS treatment plant, it is recommended that a new
treatment plant be constructed on the site of the SWV shaft.
(c) Sludge Disposal Site
The disposal of sludge in the Central Basin is described in detail in Sludge Disposal Alternatives (BKS
Report No. J01599/10) in Annexure I. The conclusion and recommendations in this report are
incorporated here for ease of reference.
The preferred sludge disposal option for the Central Basin is:
Short-term solution (four years)
o Construction of a pump main to the existing DRD Gold Knights gold processing plant
(five to six years). The sludge will then be co-disposed of on the ERGO Brakpan TSF.
Long term solution (30+ years):
o Pump main to the ERGO Brakpan TSF (DRD Gold has indicated that the life of this
facility is in excess of 30 years);
o Disposal into the Central Basin mine void; or
o Greenfields engineered disposal facility.
Co-disposal of AMD sludge and tailings is regarded as the most feasible and viable option based
on the following:
- It is deemed an acceptable and viable low capital cost, short-term disposal option
(R3,600,000 for a five-year site life)
- The operator of Knights reprocessing plant is willing to co-dispose of tailings and AMD sludge
for final disposal onto the ERGO Brakpan TSF;
- Sludge volumes into Knights tailings plant can be accommodated;
- Servitudes are available between Knights plant and Ergo Brakpan TSF. A 2.8 km sludge
delivery pipeline and pump station from the HDS plant at South West Vertical to the Knights
plant would be required;
- Knights can only accommodate the sludge for five years, so long-term disposal beyond five
years will require the construction of a dedicated 25 km sludge delivery pipeline from South
West Vertical HDS plant to the ERGO Brakpan TSF.
- There are a number of risks associated with the sludge delivery pipelines, such as the
settlement of sludge in the pipeline because of power a failure. However, these risks will be
mitigated by adequate engineering design and the provision of a standby sludge delivery
pipeline and do not, therefore, constitute a fatal flaw;
- The risk associated with the long-term legal liability and responsibility associated with the co-
disposal of sludge on the tailings facility amounts to a portion of the closure cost estimated,
and should be clearly quantified and considered.
- The long-term operations and management of the facilities should be evaluated and
quantified in more detail.
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- The above are all subject to a commercial agreement being in place and confirmation of the
geochemical properties of the AMD sludge.
While co-disposal with tailings at Knights plant is the preferred disposal option in the short term, the
requirement for a long-term solution necessitates the investigation of other alternatives.
The disposal of sludge into one of the ERPM shafts, e.g. Central or Cinderella East / West Shafts has
the following benefits:
There is a potential to reduce the footprint required for sludge disposal.
There is a shaft readily available to be used for sludge disposal;
It is deemed a technically feasible and viable low capital cost option, for long-term disposal.
A sludge delivery pipeline and pump station from the HDS plant at South West Vertical to ERPM
Central or Cinderella (East) Shaft would be required;
There is potential to meet long-term disposal requirements for sludge subject to additional
development studies on the system and how it will function. Environmental acceptability is the
crucial driver of this option;
The volume of the shaft (< 200,000m3) would be too small even for the short-term sludge
disposal, so this option assumes that the sludge will disperse into the lower mine workings
without active backfilling operations at depth. It is expected that this assumption is valid, based
on the low solids concentration. Although the sludge settles well under controlled conditions of a
clarifier, disposal into the water body in the basin will disperse the sludge, which will settle where
the flow is low. In these areas, the sludge, in time, will create an alkaline environment that will
prevent the re-mobilisation of metals.
Central shaft discharges 350 m below the bottom level of South West Vertical shaft (1,400 m), so
although it is connected to the Central Basin, the chance of recycling the metals and sludge is
remote.
Another alternative is to construct a pump main to the ERGO Brakpan TSF. This option will have a high
cost (duty / standby pump mains, 25 km long, with ongoing maintenance due to scaling).
Although land is available, due to the surrounding land use, the cost could be prohibitive.
Furthermore, the capital cost constraint to construct a new engineered / lined facility (R112,300 and
17 hectares in size) for a site life of only 2.5 years, is expected to be the last-resort option.
7.2.3 Continued Mining in the Central Basin
There are currently two operational mines in the Central Basin:
Central Rand Gold (CRG) – The Group has seven prospecting rights to re-mine mining areas from
west to east, namely Western Areas A, B and E, Consolidated Main Reef, Langlaagte, Crown
Mines, Anglo Deeps, Village Main, Robinson Deep, City Deep and Simmer & Jack. CRG initially
intends to mine to a depth of approximately 400 m at the CRG Portal (mining down to a level of
1,278 m amsl), which would be below the ECL for the Central Basin.
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Gold Reef City (Crown Mines Shaft No.14) – This is a tourist destination where the mineshaft is
used as an educational exhibition and museum. No mining occurs, however, tours takes place on
level 5, approximately 226 m below surface (1,480 m amsl – 173.2 m below SWV). This level is
above the ECL (but with only a 13 m level difference). The allowance made in terms of pump
depth installation could, however cater for increasing the gap between the mine level and the
water level).
CRG has indicated that it would initially require the water level to be maintained at 250 m below
surface at the CRG Portal (1,428 m amsl) to continue mining in the short term (18 months to two
years). With reference to Figure 7, it can be expected that the water will reach this level between May
and September 2012.
Thereafter, for CRG to continue mining it would need the water level to be lowered to 400 m below
surface (1,278 m amsl) for mining activities to continue in the medium term (approximately 10 years).
Knowing that the water rise in the Central Basin would impact its mining operation, CRG has acquired
pumps from Ritz Pumps. Part of the due diligence task is to determine whether these pumps are
suitable for the options to pump to ECL and additional options to accommodate mining operations.
In principle, CRG is willing to fund the differential portion of infrastructure and operating costs
required between the ECL and water level it requires for mining, but only if it makes economic sense.
Commercial terms have not been agreed, as CRG requires information from this Due Diligence report
to confirm its financial models.
(a) Description of the CRG Pumps
The two pump / motor units that CRG procured from Ritz Pumps South Africa are Ritz HDM 67 37
pumps combined with 2,400 kW, 4 pole motors. No pipe work, cables or electrical equipment were
included in the order.
The pumps are designed specifically for deep mine dewatering applications. Correspondence between
CRG, Murray and Roberts and Ritz Pumps, locally as well as in Germany, shows that a significant
amount of work went into selecting the pump units, both from a capacity and a materials selection
point of view. After review of the available information, the project team is satisfied that these pumps
are suitable for this particular dewatering application, particularly for the scenario to allow mining
activities at the CRG mine by maintaining the water level 400 m below surface. The use of variable
speed drives makes it possible to achieve a number of alternative duties.
These pumps are suitable for the intended use for the following reasons:
The pumps eliminate any axial thrust, thereby obviating the need for a thrust bearing with a
complicated lubrication system,
The pumps have a high efficiency over a wide range of flow and pump head combinations,
The pumps are manufactured from high quality chrome steels (duplex stainless steel).
Do the pump medium (AMD), the pumps have specials seals, which limit the depth at which the pump
can be placed below the water level to 70 m. This would be particularly important for the mining
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option to draw down the water level in the basin, i.e. the pumps cannot simply be installed at the
required depth, but will need to be lowered over time.
The pumps consist of 15 stages, each containing a radial flow impeller with a diameter of 355 mm.
Impellers are arranged into two opposing trains delivering at the centre of the two trains to balance
axial thrust. Pumps were ordered with an intake shroud to ensure a consistent flow of water over the
motor for cooling purposes.
Operating at 100% speed, the pumps will each deliver a total flow rate of 1,475 m3/h (35.4 Mℓ/d per
pump or 70.8 Mℓ/d from two pumps) against a delivery head of 427 m. The efficiency at this point is
82.1%. The pump can be operated over a wide range of flows varying from 720 m3/h (17.3 Mℓ/d) at a
60% efficiency to 1,897 m3/h (45.5 Mℓ/d) at a 70% efficiency from each pump.
This feature makes the pumps extremely flexible when used in combination with a VSD.
Pump dimensions and mass are as follows:
Total length of pump and motor = 14,621 m.
Diameter, including intake shroud = 1,000 mm.
Mass of pump, motor and intake shroud = approximately 20 tons.
The total mass of the pump / motor unit, including the shroud plus the mass of the pipes and
water column is approximately 130 tonnes for installation at 430 m depth below surface.
The pumps are supplied with a NOREVA stainless steel nozzle check valve. Instrumentation on the
pump units is limited to two temperature transmitters inside the motors.
The pump performance tests took place in July 2011 at the Ritz Pumps factory in Germany. The test
results are almost identical to the theoretical pump curve.
The pipe work required is 400NB stainless steel pipe. At the proposed pumping rates, this diameter
will yield velocities of 2-3.9m/s, which are acceptable for a pump delivery.
A suitable system of vertical riser pipes can be supplied by Ritz Pumps and we recommend that this
system be adopted. The pipes are specifically designed for mine dewatering from a vertical shaft and
are joined with a quick coupling cable that is fed between a spigot and socket joint for quick and easy
installation. The pumps are suspended on the pipes from surface level and it is not necessary for a
person to enter the shaft to fix the pipe work to the shaft.
Instrumentation that will be required at surface level for each of the pumps consists of a pressure
transmitter, a pH transmitter, an ultrasonic flow meter and inline conductivity meter and transmitter.
In addition, a laser level detector will be required to continuously monitor the water level in the shaft
from the surface. Ultrasonic level transmitters are required at the two mixing basins where the pipes
from the two pumps terminate.
All signals from the instrumentation, including the two PT100 temperature transmitters in the motor,
will be fed to the PLC for control and protection purposes.
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(b) Pump Capacity and VSD Control
Figure 8 shows the theoretical full speed pump curve received from Ritz, which indicates that two
pumps can produce the maximum required flow rate of 84 Mℓ/day (2 x 1750 m3/h) against a head of
340 m, as well as the minimum flow rate of 34 Mℓ/d (2 x 708 m3/h against a head of approximately
520 m.
Figure 8: Ritz Pump Curve (HDM 67 37)
Because of the expected varying water levels (seasonal and due to drawdown of the water table) the
use of VSD is recommended.
Rockwell Automation (Pty) Ltd has quoted CRG through Ritz Pumps for the supply of Allen Bradley VSD
equipment for driving the pump motors, however, the VSD equipment was not ordered. The system
that Rockwell Automation has proposed comprises a single VSD for both pumps. The operating
principle is such that the VSD is used to start one pump and to bring the speed up to 100%. The pump
is then switched to a bypass, which maintains the speed at 100% and the VSD is switched to the
second pump. The second pump is started through the VSD and it can be operated to supply the
balance of the demand.
This system is not recommended as there is less flexibility and no backup for the VSD, so if the VSD
fails, no pumps can be operated.
A system consisting of a VSD unit per pump provides redundancy, more flexibility, as well as the
ability to operate the pumps at the most efficient point for any combination of head and flow rate.
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A number of extreme pump operating scenarios were evaluated to confirm the suitability of the Ritz
Pumps:
Figure 9 shows the pumps operating at a low of 34 Mℓ/d,
Figure 10 shows the pumps operating at the average Central Basin yield of 57Mℓ/d, and
Figure 11 shows the pumps operating at the maximum Central Basin yield of 84Mℓ/d.
The figures highlight the following points:
Figure 9 indicates that a flow rate of 34 Mℓ/d over 19 hours per day, when the static head is as
low as 173 m (total pump head 190 m), can be achieved by reducing the pump speed to 960 rpm.
The pump efficiency will still be high (82%).
Figure 9 indicates that if the static head is 400 m (total pump head 427 m), approximately
70.8Mℓ/day can be transferred by the two pumps by operating both pumps at 100% speed
(1,470 rpm) with the pump efficiency at its optimum of 82.1%. The pumps were selected for
operating at this point, i.e. for pumping water from 400 m below surface.
Figure 10 indicates that the average Central Basin flow rate of 57 Mℓ/d can be pumped over 19
hours per day, when the static head is as low as 173 m (total pump head 205 m), by reducing the
pump speed to 1,235 rpm. The pump efficiency will reduce to 72%.
Figure 11 shows that the maximum rate of 84 Mℓ/day can only be achieved when the static head
is above 195 m (total pump head 240 m) by reducing the speed to 1,352 rpm (this is slightly
conservative because, according to the pump curve, it should be possible to reduce the static
head to about 170 m, but it would then be on the edge of the application range and potentially
be unstable). Should the static head be lower than 195 m, the pumping rate will be reduced by
further reducing the pump speed, i.e. the maximum pump rate will not be possible. Artificially
creating additional head loss, e.g. by throttling a valve, will have the same effect. The expected
efficiency of the pump is 69%. The pump should not be operated further to the right on the pump
curve; therefore, if the CRG Ritz pumps are used, it is critical that they be installed and
commissioned before the ECL level is reached, i.e. at 186 m static head.
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Figure 9: Scenario 1 - Pumping 34 Mℓ/day
Figure 10: Scenario 2 - Pumping 57 Mℓ/day
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Figure 11: Scenario 3 - Pumping 84Mℓ/day
A final option would be to modify the pump. The pump is a modular multistage pump, which enables
stages to be removed and replaced by dummy stages (due to the intake on either side of the pump).
By removing stages, even more scenarios will be possible, i.e. by removing a stage of a multistage
pump, the flow will remain the same while the possible pumping head will reduce. Based on this
option, pumping below the estimated 195 m static head would be possible even at the maximum flow
rate of 84Mℓ/d.
Due to the complex nature of the pump, the requirement to modify the pump shaft and the potential
cost of the work, this is not recommended as an option.
(c) Possible Draw-Down Scenarios
To accommodate CRG’s short-term mining requirements, the water level rise will need to be drawn
down to or stopped below 1,428 m amsl (250 m below the CRG Portal), which translates to June 2012
as the target date to start pumping from the Central Basin (predicted date in terms of Figure 7). This is
equivalent to a static pump head of 225 m at South West Vertical. As shown in Figure 11, the
minimum pump head that is achievable at a flow of 84Mℓ/d is approximately 195 m. Therefore,
should the water level be stopped at 1,428 m, the Ritz Pumps would pump at the maximum
treatment plant capacity, even though the efficiency of the pumps will only be 69-70%. For the same
flow rate, the efficiency of the pumping will increase as the level of the water drops progressively.
Figure 12 is an example, using the CRG Ritz pumps, of the impact of increasing the pumping rate on
the expected date to achieve the 250/400 m level, to accommodate CRG’s mining requirements. The
figure shows the rate of abstraction between average (57Mℓ/d over 19 hours) and the maximum
treatment capacity (84Mℓ/d), with a starting point of the ECL (if the rising water is stopped under the
ECL, then the time to 400 m would be reduced). Should the CRG mine implementation plan require
the water level below 400 m around or earlier than October 2014, additional treatment capacity will
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need to be incorporated into the HDS plant (this would be a temporary measure and would,
therefore, be at CRG’s cost).
Figure 12: Possible draw-down rates in the Central Basin to accommodate CRG Mining
Figure 12 is based on average rainfall and ingress into the central basin, so dates can vary depending
on the actual annual rainfall.
Pumping at an increased rate to lower the water level to 400 m below SWV Shaft, increases the short-
term treatment costs until the 400 m level is reached and the annual average dewatering rate can be
implemented, i.e. the volume of treated water between the ECL and the 400 m level. The increased
short-term treatment cost is not in terms of additional infrastructure, but rather increased operating
costs:
For additional chemicals; and
Additional electrical energy to pump at a higher-than-average rate.
This increased temporary operating cost is in addition to the capital and operating costs for pumping
from a deeper level
Capital: Additional pipe work of higher pressure rating; and
Operational: The increase (difference) in electrical energy costs between pumping from ECL and
pumping from 400 m.
1230
1280
1330
1380
1430
1480
1530
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vati
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(m
am
sl)
Date
Water Level Drawdown at 72 Ml/d and 84 Ml/d
72 Ml/d 84 Ml/d 250m below SWV 400m below SWV
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Table 27: Comparison of Costs for Different Operating Levels
ECL (210 m) CRG (275 m) CRG (427 m)
Pipe Column Costs R7,569,900 R8,960,700 * R14,380,000
Pipe Column Difference
R1,390,800 R6,810,100
Energy Cost Total (per month) R581,113 R759,534 R1,176,767
Energy Cost Difference R178,422 R595,654
Basin Dewatering Treatment Cost
R4,670,000 R4,670,00
Basin Dewatering Time (Months)
6 20
* Extrapolated
The treatment costs are based on the difference between the expected average flow (57Mℓ/d) and
the peak flow (84Mℓ/d), i.e. 27Ml/d, multiplied by the expected time to reach the mining level.
The basin model predicts that it will take six months to drop the water level in the basin from ECL to
250 m below surface, and another 20 months to drop the water level in the basin to 400 m below
surface.
The expected operating and maintenance cost for the treatment plant operating at average flow is
R127million per year. If the cost of the power for pumping from ECL is removed, then the O&M cost is
R120 million per year, which equates to a treatment cost of R5.77/m3, making the total cost for
treatment to the two mining level options approximately:
250 m – R28.0 million (R4,670,000 per month)
400 m – R93.4 million (R4,670,000 per month)
(d) Required Infrastructure for the Ritz Pumps
The system for installation of the pumps requires a gantry crane and support structure over the
mineshaft to install and lift the pumps and pipe work. It is expected that routine maintenance of the
pumps will only include lifting the pumps out of the shaft on an annual basis. However, the ability for
the operator to change the level of the pumps requires a dedicated installation.
The Ritz pumps with the special seal for the AMD water must be installed less than 70 m under the
water, so the ability to lift or lower the pumps when necessary is important. This will be particularly
applicable in the Central Basin, where it is expected that the water level will need to be drawn down.
The pump and pipe work is approximately 26 tonne when the water is taken into account; therefore,
the gantry crane would be required to lift this mass plus a factor of safety.
The required infrastructure is described in the next section.
(e) Ritz Pump Recommendation
The pumps are expected to be the longest lead item for this project and purchase of the CRG pumps
could, therefore, be advantageous in terms of the expected programme. The advantage of early
procurement must be compared to the long-term efficiency. The following are thus recommended
with regard to the Ritz pumps procured by CRG:
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Pumping to ECL only: If pumping only to ECL, new pumps should be purchased with more
favourable efficiency for the expected duty. The pumps should match the flexibility that the CRG
Ritz pumps offer in terms of a wide application range for both flow and pump head. If this option
is selected, the CRG Ritz pumps should be considered for installation on the Eastern Basin.
Pumping to 400 m below surface at SWV: If the CRG mining option is implemented, the pumps
need to be operational by June 2012 (anticipated case). The Ritz pumps procured would be ideal
for the application range in terms of flow and pump head. Therefore, if CRG agrees to commercial
terms of the pumping installation, the procurement of the Ritz pumps should be negotiated with
CRG for installation.
The following three commercial / cost aspects must be considered in the negotiations to satisfy their
future mining requirements:
The increased pumping head (and associated power consumption) compared to operating the
Central Basin at ECL.
The potential for lower pumping efficiency (more power consumption) when the proposed Ritz
pumps continued to be used post mining at CRG.
The need to temporarily treat additional AMD volume due to the requirement for lowering of the
Central Basin operating level.
Another factor that needs to be considered is that the current project programme only expects
operation of the system by August 2012. Therefore, to achieve the required CRG programme
(stopping the water level rise 250 m below the CRG portal) would require that the construction
programme be brought forward. The fact that the pumps would be available (they are expected to be
the longest lead items), means that all other items would need to be procured and installed in less
than one year.
The programme to meet the August 2012 deadline is already extremely tight; however, a number of
options can be reviewed to make the project operational, even if only partially, by June 2012:
Install the pump infrastructure and pipeline;
Construct one train of the treatment plant as a priority;
Install the chemical dosing system;
Install the sludge disposal pipeline;
Install the treated water pipeline;
Commission and operate only the first train; and
Continue construction to complete the second train by August 2012.
Initially, a smaller volume of water can be treated to achieve acceptable water quality, while still
slowing the water level rise. It is expected that the construction cost for this option would be higher
than completion of all process trains together by August 2012.
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As the single treatment train will be commissioned in winter, it is expected that the water ingress will
be at a minimum. Therefore, by using only a single train it may be possible to halt the water level rise.
Even if not stopped, the rise rate will be reduced.
7.2.4 Recommendations on Preferred Project Options for the Central Basin
The following scheme for Central Basin AMD management and treatment is recommended:
Pumps are installed at SWV Shaft (either to pump to the ECL or to the CRG-proposed mining level
of 400 m below SWV).
A new HDS plant located at SWV Shaft is constructed;
The construction of the trains to allow for one train to be commissioned as early as possible;
A waste sludge pipeline is constructed to the DRD Gold (Crown) Knights Gold Plant.
A treated water pipeline is constructed to a suitable discharge point on the Elsburgspruit.
Planning is done for a future waste sludge handling option, i.e. either pipeline(s) to the Ergo
Brakpan TSF, an engineered facility or discharge into a nearby mineshaft. This planning would
require the evaluation of the options, together with regulatory approval and permitting.
Aspects that are required to proceed with Task 2: Engineering Design are as follows:
A decision on the pumping depth, i.e. ECL or the CRG proposed 400 m.
Agreement or procurement of required land and servitudes.
A topographical survey of recommended sites and pipeline routes.
A geotechnical investigation of the recommended sites and pipeline routes.
7.2.5 Emergency Contingency Shafts
The following three shafts were identified as potential emergency contingency shafts if the
interconnectivity of the Central Basin is disrupted through a tunnel collapse:
East Deep Vertical shaft (Consolidate Main Reefs 5) on Langlaagte;
Gold Reef City Shaft No.14 on Crown Mines; and
DRD Shaft No.6 on Durban Roodepoort Deep property.
It is proposed that these shafts be secured in terms of agreement or servitude. The access to and
safety of the shafts should be considered part of the current project. After pumping starts at South
West Vertical, additional planning for these shafts can be considered.
7.2.6 Consideration of Integration with Future Long Term AMD Treatment
During the Due Diligence task, the future long-term AMD treatment and sludge handling options were
considered. Although there is no certainty on what will be implemented in the long term, it can be
accepted that the water will be treated to drinking-water standards to supply the local metropolitan
areas. Furthermore, waste minimisation and the recovery of valuable metals from the waste sludge
may be part of a future scheme.
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The future scheme considered in the following manner in the short-term due diligence:
An estimate of the space requirement for the future scheme was made and any land procured for
the short-term solution must provide sufficient land for implementation of a long-term scheme.
Sludge handling will be a long-term requirement and the short-term solution has thus reviewed
how sludge can be handled in the long term.
The location the potential connection to the potable water system would be, i.e. by reviewing
potential water demand and water distribution reservoirs, was considered., including the
surrounding Rand Water reservoirs (Germiston 5 km north and Klipriviersburg 12km west of
SWV).
7.3 Conceptual Design
7.3.1 Shaft Stability
As part of the due diligence phase, the stability of the mineshaft to allow for long-term pumping
infrastructure was considered. A Rock Engineering specialist assessed the shaft stability for the
preferred mineshafts (the report is attached as Annexure J). The report highlights the lack of available
information for a thorough assessment. The general conclusions made for the Central Basin shafts
(SWV and Cinderella East) are:
Low probability of structural failure even at 30 degrees strata dip and no major geological
features intersecting the shaft barrel.
Low probability of stress-induced failure due to the size of the shaft pillars.
Low probability of failure due to dynamic loading, including crush-type and shear-type seismic
events, as well as shakedown damage.
One aspect that is noted for the SWV Shaft is the fall of ground at a deep level (130 m below 24 Level)
in 1997.
7.3.2 Abstraction and collection infrastructure
(a) Abstraction Point
The SWV shaft has been selected as the preferred pump shaft. The shaft has seven compartments
available for the installation of pumps.
Two pumps will be installed in the shaft, so the use of conveyances 2 and 6 is proposed in order to
allow for sufficient space around the pumps. The shaft’s parameters are summarised in Table 28.
Table 28: SWV Shaft Parameters
Parameter Value Dimension
Collar Level 1,753.2 m amsl
Shaft Depth 1400 (Approximate) m
Shaft Bottom Level 350 (Approximate) m amsl
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Parameter Value Dimension
Environmental Critical Level 1,467 m amsl
The surface infrastructure includes:
A platform around the shaft, with openings only for the pumps and safety features in order to
prevent unauthorised access to the shaft openings. The platform will be designed to carry the
weight of the pump, pipe column and water in the column.
A structural steel superstructure and gantry crane to lift / lower the pump / pipe column in and
out of the shaft.
A clamping system to ensure that the pumps are installed safely without the possibility of the
pump / pipe column falling into the shaft.
A final connection piece to the pipeline that conveys the water to the treatment plant.
Pipeline to the treatment plant.
Appropriate instrumentation and control to operate and monitor the pumping installation.
A pipe-stacking yard, truck off-loading area and store. The reach of the gantry crane for the
abstraction pump station shall extend to these areas.
Ancillary infrastructure to support the pump station and associated works, e.g. administration
building, roads, guardhouses and security fencing.
Conceptual layout drawings are provided (see Drawing J01599-03-003) for the SWV shaft
infrastructure.
(b) Pumps
The conceptual design of the abstraction infrastructure is based on the lowest risk option (in terms of
equipment and operational personnel), which does not require underground pumping infrastructure.
Therefore, the only option considered was the suspension of borehole type thrust balanced pumps
into the mineshaft. These pumps require minimal surface infrastructure at the shaft head and do not
require people to enter the mineshaft during pump installation or operation.
The pumps are lowered into the mineshaft and suspended on the pipe column. The required pipes are
designed for the purpose installation in a vertical shaft and are joined with a quick coupling chain that
is fed between a spigot and socket joint for quick and simple installation.
There is no headgear, and a new steel superstructure with gantry crane will be installed over the shaft
to facilitate the installation and removal of the pumps.
The selection of the pumps depends on confirmation from CRG regarding its intention to continue
mining in the Central Basin. The existing CRG Ritz pumps will be used if the basin will be dewatered to
400 m below surface, or new pumps will be purchased to operate at ECL level, depending on which
option is chosen.
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(c) Installed Pump Depth
To determine the water level characteristics for pumping of the Central Basin, a pump test would be
required to monitor the water level at various positions along the length of the basin while varying
the flow rates. However, there will be no opportunity to undertake these pump tests until the full-
scale installation is operational. Therefore, flexibility needs to be allowed for the installed pump
depth.
It is expected that the water level variance along the entire Central Basin will not exceed 10 m due to
extensive holing.
The water balance model of the Central Basin indicates that, based on fixed speed pumps at average
flow and allowing the basin to be drawn down during low ingress and filled to ECL during high ingress,
the water level will fluctuate by about 30 m (refer to Figure 13).
Figure 13: Drawdown at average pump rate (Central Basin)
The following basis was used to select the pump depth for the Central Basin:
The ECL level of 1,467 m;
The submergence depth of 10 m for the pumps;
Pumps installed an additional 10 m below ECL and submergence depth to allow for variations of
water depth along the Central Basin and initial water level drop in the mineshaft.
Pumps staggered by at least 10 m (or one pipe length) to reduce possible turbulence interference
between the pumps;
Pumps installed an additional 30 m below the [ECL plus submergence depth plus basin variation]
level to provide flexibility in operational philosophy and to possibly account for reduced basin
transmissivity.
1430
1435
1440
1445
1450
1455
1460
1465
1470
1475
1480
01
-Au
g-1
2
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-Se
p-1
2
01
-Oct-
12
01
-No
v-1
2
01
-De
c-1
2
01
-Ja
n-1
3
01
-Fe
b-1
3
01
-Ma
r-1
3
01
-Ap
r-1
3
01
-Ma
y-1
3
01
-Ju
n-1
3
01
-Ju
l-1
3
01
-Au
g-1
3
01
-Se
p-1
3
01
-Oct-
13
01
-No
v-1
3
01
-De
c-1
3
01
-Ja
n-1
4
01
-Fe
b-1
4
01
-Ma
r-1
4
01
-Ap
r-1
4
01
-Ma
y-1
4
01
-Ju
n-1
4
01
-Ju
l-1
4
Ele
vati
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(m
am
sl)
Date
Water Level Fluctuation at 57 Ml/d
Water level ECL
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For more flexibility, it is recommended that the pipes be designed for the possibility that the
pumps are lowered by a further 20% of ECL. Initially, these pipes will not be purchased or
installed. They will be sized for the best efficiency at the installation depth, but checked so that
they can supply at least average flow at the lowest level.
The recommended installed pump level for flexibility with regard to the water level in the Central
Basin will be 1414 m amsl, with the pipes / pumps being designed to allow installation to 1384 m
amsl. This relates to the a pump with a maximum flow of 84Mℓ/d, a best efficiency at a flow of
72Mℓ/d (57Mℓ/d average, for only 19 hour pump time) and a normal static head of 209 m, with the
ability to be lowered to increase the static head to 239 m and 269 m.
The same basis will be used to determine the depth of pump installation if the 400 m mining scenario
is implemented, except that the starting level for the pump will be 400 m below SWV, i.e. 1243 m
amsl.
A conceptual design for such a pumping system was done and a preliminary selection was made on
the pumps, using the parameters listed in Table 29.
Table 29: Abstraction Pump Station (Central Basin)
Parameter Value
Duty Flow (Mℓ/d) 72
Duty Flow (m3/s) 0.833
Duty Head (m) 225 (static plus allowance
for losses)
Duty Pumps (No) 2
Standby Pumps (No) 1 (not installed)
Rotational Speed (RPM) 1,470
Power Absorbed (kW) 2,240
Power Installed (kW) 2,400
(d) Electrical Power
Due to the large variation of flow expected, it is recommended that the pumps be started and
controlled with Variable Frequency Drives (VFDs), with a VFD per pump.
At the SWV shaft, DRD Gold has maintained the 3.3 kV / 6.6 kV Eskom power supply with an existing
rating of 10 MVA. The connection is being paid for by DRD gold and arrangements will need to be
made to incorporate it as part of the TCTA Scheme.
The following electrical infrastructure will be required at the shaft:
Single core 6.6 kV lines to the shaft (Eskom supply is 6.6 kV, is close to the shaft and 6.6 kV three
core cable has lower losses and is cheaper than installing 400 V cables).
An electrical control building incorporating a VSD Room, MV Room and LV Room.
Within the LV room, the control PLC and remote control via GPRS or fibre optic to the AMD
treatment plant.
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Water cooling towers next to the VSD Room.
A yard for the transformer / minisub next to the LV Room; and
Transformer / minisub, rated for future use.
The 6.6 kV power lines will tap off at the shaft yard to the MV Switchgear to protect the VSDs. All 6.6
kV power lines between the shaft and the AMD treatment plant will be buried and encased in
concrete for security purposes. The switchgear will supply power to a transformer 6.6 kV / 400 V,
which will be rated big enough for future auxiliary power. The treatment plant will be supplied with a
6.6 kV three-core cable.
CRG has procured two pumps, both of which are operating as duty pumps. Due to the long
procurement time for these pumps, the use of only duty pumps is seen as a potential risk; therefore,
if the CRG pumps are purchased, it is proposed that an additional pump be purchased as a standby.
The standby pump will be stored on site and will not be installed. If the standby pump is required, a
duty pump will be removed and replaced with the standby pump.
(e) Pipeline
The abstraction point and the treatment plant are on the same site. It is not expected that there will
be any major services to cross on the SWV site.
Table 30: Abstraction Pipeline (Central Basin)
Parameter Value
Flow (Mℓ/day) 72
Flow (m3/s) 0.833
Nominal Diameter (m) 0.550
Flow Velocity (m/s) 1.8
Length of Pipe (m) 100
7.3.3 Plant Infrastructure
A new HDS plant will be constructed at the SWV Shaft site. A preliminary site layout addressed the
following:
The site has a slight even slope towards the southeast.
The site has an old storeroom building and an ESKOM substation, as well as a number of
aboveground pipelines. The old chemical dosing silos and some other chemical dosing
infrastructure still exists. There are also remnants of old underground structures.
There are no services crossing the site.
The short-term site belongs to DRD Gold, but some of the surrounding area belongs to other
private companies and sufficient land will need to be procured. It is proposed that parts of
Portion 1 and the servitudes across Portion 209 be secured to meet current and long-term
requirements. The HDS plant site should also be secured as there are a number of existing
servitudes relevant to the disposal of sludge, treated water and supply of water to the mines.
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Figure 14: SWV land requirements
The treatment plant will consist of two independent trains, each comprising a sludge conditioning
tank, a pre-neutralisation tank, a neutralisation tank, a gypsum crystallisation tank and a clarifier /
thickener. Other than these main unit processes, other ancillary treatment infrastructure includes:
Chemical dosing (quick lime, limestone and polyelectrolyte);
Pumps and equipment for the sludge recycle system;
Sludge retention tank (one-day storage to allow for breakdown / maintenance at Knights plant);
Treated water retention tank (one hour storage as pump sump for potential mine use of the
water); and
Buildings for the electrical equipment.
Conceptual layout drawings are provided as Drawings J01599-03-004 and 005 for the treatment plant
infrastructure.
(a) Geotechnical Input
A desktop study of the site geology and geotechnical conditions highlighted the following:
The SWV treatment plant site is underlain by rocks of the Turffontein Sub Group of the Central
Rand Group, Witwatersrand Supergroup.
The Central Rand Group of the Witwatersrand Supergoup is composed of quartzite and gold-
bearing conglomerates along with one significant shale formation, the Booysens Shale Formation.
The Central Rand Group is over 2,800 m thick and, in the Germiston area, the rocks dip to the
south at fairly steep angles. The dip is approximately 45° in the Germiston area although dips of
up to 80° have been recorded.
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The SWV treatment plant is likely to be underlain by quartzite at less than 4 m, with the residual
material being thin and sandy in nature. However, there is a major watercourse to the east of the
site, the Elsburgspruit, and a thickness of alluvium across the site is a possibility.
Fill material may need to be sourced from offsite sources.
The possibility of seismic activity and the presence of undermining need to be considered. All
indications are that the site is not undermined, or undermined at depth (below 1,000 m). The
magnitude of seismic events in the area south of Johannesburg is generally less than 4 on the
Richter scale, and are thus considered minor events that are often felt but rarely cause damage.
Therefore, problems associated with seismicity at the SWV treatment plant and along the
pipelines are considered a very low to low risk.
(b) Terrace Design and Plant Layout
A preliminary design of a terrace was done and the plant was laid out on the terrace.
(c) Roads and Stormwater
A new access road to the south of the SWV site is proposed as it will provide good access for the
regular delivery of lime by larger trucks. The road is through an industrial area and the additional
traffic load should be negligible.
Site roads for the delivery of chemicals and the maintenance of equipment will be designed and the
roads and earthworks will be designed to manage and dispose of stormwater.
(d) Water Supply
A water connection will be installed from the municipal bulk distribution system that supplies the
industrial area.
(e) Sanitation
A municipal sewer connection will be installed.
(f) Electrical Power Supply and Distribution
There is an Eskom sub-station on site and power will be obtained directly from Eskom. The electrical
power supply voltage will be 6.6 kV to the pumps, but will be stepped down to 400 V to supply
electricity to the treatment plant’s various motor control centres.
The following electrical infrastructure will be required at the plant:
Mini-sub, rated for current use and pumps to future treatment works.
An LV Room, including auxiliary items such as a control desk and remote control via fibre optic
back to the control building.
Electrical controls and protection.
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7.3.4 Waste Sludge Handling and Management
For the short-term option, there are two waste streams from the HDS treatment plant, i.e. the
gypsum / metals sludge and the treated AMD water that will be disposed of into the Elsburgspruit.
For the short-term solution, the sludge will be pumped to the DRD Gold (Crown) Knights gold
recovery plant, about 3 km northeast of the SWV site. DRD Gold has indicated that this option can be
used for five to six years, where after it intends stopping gold recovery at the Knights gold recovery
plant and will use its pipeline to pump reclaimed tailings to the ERGO gold recovery plant near
Brakpan. At that stage, it will not be able to accept the sludge with the high metals content and the
sludge will need to be disposed of in a different manner.
A conceptual pipeline route to the Knights gold recovery plant has been designed. This route,
however, needs to be agreed with the landowners.
The infrastructure required for the disposal of the sludge includes:
A sludge pump station, taking the possible future long-distance pumping to the ERGO Brakpan
TSF into account;
A water flushing system; and
A pipeline to the Knights gold recovery plant.
Conceptual layout drawings are provided (refer to Drawings J01599-03-006 and 007) for the treated
AMD water disposal infrastructure.
(a) Pumps
It is proposed that two duty pumps and a standby pump be installed in a pump station. The design
flow and a conceptual design are shown in Table 31.
Table 31: Sludge Pump Station (Central Basin)
Parameter Value
Duty Flow (Mℓ/d) 5.3
Duty Flow (m3/s) 0.06
Duty Head (m) 20
Duty Pumps (No) 2
Standby Pumps (No) 1
(b) Pipeline
The parameters for the sludge pipeline from the WTP to the Knights gold processing plant are listed in
Table 32. Where possible, the pipeline will be placed above ground to allow maintenance. Two
pipelines will be installed to operate as duty standby, due to the expectation of significant scaling. As
another precaution, the pipeline will be designed to allow for regular pigging to remove scale build-
up.
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Table 32: Sludge Pipeline (Central Basin)
Parameter Value
Flow (Mℓ/day) 5.3
Flow (m3/s) 0.06
Nominal Diameter (m) 0.200
Flow Velocity (m/s) 2.0
Length of Pipe (m) 3,100
The pipeline route can be described as shown in Table 33.
Table 33: Description of Sludge Pipeline Route (Central Basin)
No Section Description
1. SWV Site The pipeline will follow the existing servitudes from the SWV shaft site to
the existing HDS plant site. The rail crossing will be used (servitude
conditions may need to be amended). The pipeline can be above ground
on pipe pedestals to facilitate maintenance.
Chainage = 0-600 m
Length = 600 m
2. Crossing Tide
Street
Tide Street will be crossed by conventional pipe jacking. In the process, a
gas pipeline and other municipal services (e.g. bulk sewer) will have to
be crossed and permission for crossing these services will have to be
obtained. The pipeline can be above the ground on pipe pedestals to
facilitate maintenance.
Chainage = 600-650 m
Length = 50 m
3. Parallel to
Knights Road
The pipeline will run parallel to Knights Road, up to the railway line.
Existing services can be expected along Knights Road. Permission for this
crossing will have to be obtained. In this section, the pipeline will be
underground due to the residential properties along Knights Road.
Chainage = 650-1,150 m
Length = 500 m
4. Double
Railway Line
The double railway line will have to be crossed by conventional pipe
jacking. Existing services can be expected on both sides of the railway
line. Permission for this crossing will have to be obtained. In this section,
the pipeline will be underground.
Chainage = 1,150-1,300 m
Length = 150 m
5. Parallel to the
Railway Line
The pipeline will run parallel to the railway line. Existing services can be
expected along the railway line. In this section, the pipeline can be above
the ground on pipe pedestals to facilitate maintenance.
Chainage = 1,300-2,300 m
Length = 1,000 m
6. Northerly
Direction to
The pipeline turns to run in a northerly direction. No services are
expected. The pipeline can be above the ground on pipe pedestals to
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No Section Description
R29 facilitate maintenance
Chainage = 2,300-2,900 m
Length = 600 m
7. Crossing of
R29
The R29 will be crossed by conventional pipe jacking. It is expected that
there will be many municipal services (water, sewer and
telecommunications). Permission for crossing these services will have to
be obtained. The pipeline can be above the ground on pipe pedestals to
facilitate maintenance.
Chainage = 2,900-2,950 m
Length = 50 m
8. Knights Gold
Recovery Plant
The pipeline will be routed through the existing Knights Gold Recovery
Plant to miss any services.
Chainage = 2,520-2,540 m
Length = 150 m
Table 34: Major Service Crossings – Sludge Pipeline (Central Basin)
No Service Method of Crossing
1. Railway line Existing crossing
2. Tide Street Conventional pipe jacking
4. Double railway line crossing Conventional pipe jacking
7. R29 Road Conventional pipe jacking
7.3.5 Treated Water Discharge
DRD Gold has indicated that it would be interested in obtaining a portion of the treated AMD water
for use as a tailings recovery medium. It is thus proposed that the treated AMD water be stored in a
tank on site, with the overflow being piped to the Elsburgspruit. Should DRD Gold obtain a portion of
the water, the storage tank can be used as a pump sump.
The infrastructure required for the disposal of the treated AMD water includes:
A storage sump;
A gravity pipeline to the Elsburgspruit (note that the water is not fit for human consumption and
a pipe is therefore selected instead of a channel, because the pipeline passes a residential area);
and
Suitable energy dissipation and river discharge system.
Conceptual layout drawings are provided (see Drawings J01599-03-004 and 005 for the treated AMD
water disposal infrastructure).
(a) Pipeline
The treated water from the treatment plant will discharge into a sump before excess water is
discharged into the Elsburgspruit. The pumping infrastructure from this sump will be agreed with any
potential water user.
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The parameters for the treated water pipeline from the sump to the Elsburgspruit are listed in Table
35.
Table 35: Treated Water Pipeline (Central Basin)
Parameter Value
Flow (Mℓ/day) 72
Flow (m3/s) 0.833
Nominal Diameter (m) 0.900
Flow Velocity (m/s) 1.5
Length of Pipe (m) 1,500
The pipeline route for the treated water will follow the treated water servitude between the
treatment plant and Elsburgspruit.
There are no major crossings for this route, except the crossing of the railway line, which has a culvert
in which the pipeline can be installed.
7.4 Detailed Cost Estimates
7.4.1 Detailed Capital Estimate
The detailed capital cost estimate for the Central Basin option is summarised in Table 36. The costs
for the pumps are included in the AMD Collection Infrastructure costs.
Table 36: Detailed Capital Cost Estimate for Central Basin
Number Description Amount Total*
1 AMD Collection Infrastructure
Civil / Structural Work 4,850,000.00 R45,127,500
Mechanical 40,277,500.00
2 AMD Treatment Plant
Civil / structural work 39,125,000.00 R90,631,838
Mechanical 51,416,838.00
3 Neutralised Water Discharge
Civil / structural work 150,000.00 R1,172,400
Mechanical 1,022,400.00
4 Sludge Handling and Disposal
Civil / structural work 1,700,000.00 R6,200,000
Mechanical 4,500,000.00
5 Earthworks and Pipe Work 46,196,290.00 R46,196,290
6 Electrical, Control and Instrumentation 23,735,832.38 R23,735,832
7 Preliminaries and Generals (12%) 25,567,663 8 Total R238,631,500
* Totals are rounded to the next full Rand.
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7.4.2 Detailed Operating and Maintenance Cost Estimate
The detailed operating and maintenance estimate for the Central Basin solution is summarised in
Table 37.
Table 37: Detailed Operating and Maintenance Estimate for Central Basin
Number Description Amount Total
1 O&M on CAPEX 4,128,600.00
2 Chemicals Costs 61,602,829.00
3 Electricity Costs 15,146,600.00 R80,878,029
8. EASTERN BASIN
8.1 Status of the Basin
8.1.1 Background
Mining in the Eastern Rand portion of the Witwatersrand Goldfields started in about 1888 at the Nigel
Mines and in about 1892 at Van Ryn Estates, slightly later than the mines on the Central Rand. The
Eastern Rand Basin (or Eastern Basin) encloses a surface area of 768km2
and includes Brakpan, Springs
and Nigel (Scott 1995), as shown in Figure 15.
Figure 15: Locality and extent of the Eastern Basin
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Water ingress into the Eastern Basin has been a problem since the earliest days of mining (Scott
1995). The Eastern Rand mines were dewatered to about 220 m amsl (to accommodate deep level
mining) until the early 1990s, when the basin dewatering taking place from the Sallies No. 1 shaft was
stopped. Dewatering continued at Grootvlei No. 3 shaft, maintaining a level of about 780 m amsl,
until the middle of 2010, when all pumping in the basin stopped. The water level in the basin has
been rising since then.
8.1.2 ECL, Expected Rate of Rise and Decant
The ECL was confirmed for the Eastern Basin as 1,280 m amsl. The reasons for selecting this level as
the ECL are documented in Environmental Critical Levels (BKS report J01599/03).
The water level in the Eastern Basin was not a concern until 2010, when pumping stopped at
Grootvlei No. 3 shaft. The water level, measurement at Grootvlei No. 3 shaft on 21 April 2011 was at
917 m amsl (or 653 m below surface).
Figure 16: Predicted rate of water rise in the Eastern Basin
Figure 16 shows the predicted rate of water rise in the Eastern Basin, based on geo-hydrological
modelling done for the Eastern Basin. The model includes the calculated mine void volume and
expected water ingress into the mining void. Details of the model and methods used to produce
Figure 16 can be found in Water Balance and Levels (BKS Report number J01599/06).
750
850
950
1050
1150
1250
1350
1450
1550
1650
01-M
ay-1
1
01-A
ug
-11
01-N
ov-1
1
01-F
eb
-12
01-M
ay-1
2
01-A
ug
-12
01-N
ov-1
2
01-F
eb
-13
01-M
ay-1
3
01-A
ug
-13
01-N
ov-1
3
01-F
eb
-14
01-M
ay-1
4
01-A
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-14
01-N
ov-1
4
01-F
eb
-15
01-M
ay-1
5
01-A
ug
-15
Ele
vati
on
(m
amsl
)
Date
Predicted Rate of Rise in the Eatern Basin
Water level (Dry) Water level (Average) Water Level (Wet) ECL Decant
Decem
ber
2014
Ap
ril 2
015
May
2015
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Based on the information in Figure 16, it is expected that the ECL water level will be reached in April
2015, while decant (if allowed to happen) would occur in around September 2015. These projected
dates are based on annual average rainfall. If above-average rainfall occurs, the ECL will be reached
earlier, possibly as early as in December 2014 (refer to Figure 16).
The interconnectivity of the Eastern Basin is reasonably well understood, i.e. levels of cross-cuts and
holings; however, the potential flow rate of water between compartments within the basin and the
water level profile across the basin under various pump rates is not fully understood. The Department
of Water Affairs (DWA) is currently developing a water level monitoring system, which can be used to
optimise the required pump level to account for any level changes along the basin.
Although the interconnectivity of the Eastern Basin is understood and until 2010 it was possible to
drain the Eastern Basin from the Grootvlei shaft, the current condition of the cross-cuts and holings is
unknown.
Scott (1995) provides a description of the interconnectivity:
“The mines in the northern part of the area are interconnected and there is no
restriction to water movement between individual mines. In the southern region Sub
Nigel and Nigel Mines are continuously connected. The mines in the central part of the
Eastern Basin are connected only in certain places and water flowing through this region
will have to find and follow preferred pathways. There is no connection between
Marivale Mine, and the Nigel Mine, the connection to the lowest point at Nigel Mine is
via Vogelstruisbult to Sub Nigel at 61 level.
Thus it would appear that the water from Springs Mines, East Daggafontein and
Marivale would first have to flow into Vogelstruisbult where a connection exists (61
level 8 haulage) to Sub Nigel Mine. Water will rise in the Sub Nigel Mine and then into
the Nigel Mine to emanate at surface. Thus the limiting factor is the connection
between Vogelstruisbult and Sub Nigel Mine. If flow is restricted at this level then the
water will rise at Marivale No. 4 or No. 7 shafts instead of in the Sub Nigel and Nigel
Mines.”
Scott [1995] states that the rocks making up the Witwatersrand Supergroup in this area form an
asymmetrical, south-west-plunging syncline. Dips on the northern limb are about 45 degrees, while
those on the southern limb are about 25 degrees. As discussed for the Central Basin, where the mine
openings dip steeply, the forces are such that even when unsupported, they remain open. This could
make the Eastern Basin more sensitive to collapse, especially in the southern limb where the dip is
only around 25 degrees.
Therefore, it can be stated that the risk of collapse or closure of cross-cuts and holings is higher in the
Eastern Basin than in the Central Basin. This could impact the possibility of dewatering the basin from
a single point. Filling of the cross-cuts and holings with water will, however, provide support and
reduce the risk of collapse. Contingency plans have been considered to address the potential risk of
connectivity problems (formation of sub-basins not connected to the Eastern Basin).
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It is expected that decant from the Eastern Basin will occur at Sub-Nigel Shaft 3 (collar level
1,549 m amsl), which is the lowest known connection point to the Eastern Basin void; however,
according to Scott (1995), should the flow between Vogelstruisbult and Sub-Nigel be restricted, the
water will probably decant at the Marivale 4 or 7 shafts instead of in the Sub-Nigel and Nigel Mines.
Furthermore, Gold One, which owns the Sub-Nigel mines, has indicated an interest in possibly
plugging some of the mines to enable the continuation of mining. This could isolate these mines from
the Eastern Basin, but may also have the unexpected consequence of creating a sub-eastern basin in
the Nigel Mines.
The ground levels of the Nigel CBD are approximately at decant level to about 10 m above decant
level. Therefore, at the level of decant, buildings with deep foundations may be impacted if there is
connectivity to the Eastern Basin void (either direct connection or through geological faults).
8.1.3 Flows
The estimated flows into the Eastern Basin and, therefore, the estimated dewatering pump rates are
given in Table 38.
Table 38: Ingress into Eastern Basin and Pump Rates
Minimum Average Maximum
Ingress Flow (Mℓ/d) 38 82 110 (138*)
Pump Time (hours) 19 (off peak) 19 (off peak) 24
Pump Flow (m3/s) 0.56 1.20 1.27
* Although the WUC report (2009) for the Eastern Basin gives the maximum flow as 138Mℓ/d, this is
well above the maximum pump rate ever undertaken and it is thus recommended that the size of
infrastructure rather be based on a lower figure of 110Mℓ/d. Some of the basin’s storage capacity
will be utilised to balance the high peak inflows. Another reason for this proposal is that in the long-
term, it is expected that the ingress into the basin will be reduced, resulting in oversized capacity.
As per Basis of Engineering Design (included in Annexure A), the pump system will be designed to
allow for flexibility in terms of pumping hours, which will enable pumping during off-peak power
demand periods. In the case of the Eastern Basin, the flow variation between 0.56m3/s and 1.27m
3/s
will be allowed for (refer to Table 38).
Balancing within the basin void will be used for any short-term increases in the ingress flows and for
any pump maintenance. The Terms of Reference for this project allowed for pumping to 2.5 m below
the ECL, which would provide a few days of storage and allow enough time to replace a pump. For the
Eastern Basin then, as stated above, pumping to lower than the ECL is proposed in order to allow for
balancing of the possible peak inflows.
8.1.4 Water Quality
The expected water quality is defined in Basis of Engineering Design (BKS Report No J01599/01).
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The Eastern Basin has always had better water quality than the Western and Central Basins, which
seems to be due to the lower concentration of pyrites in the rock below the water level and the
recharge through the alkaline dolomites. This, however, is expected to change as the water rises into
the Kimberley Reef, which typically has higher pyrite content than the Main Reef (Scott 1995). The
Kimberley Reef was mined to a lesser extent than the Main Reef, so it provides a much smaller
contact surface. Also, the rapid filling of the Eastern Basin does not provide contact time between
water, oxygen and pyrite, which should have a positive impact on the AMD water quality.
8.2 Options for Collection and Treatment of Water
8.2.1 Identification of options
The Eastern Basin has a topographical high point around Brakpan at about 1,625 m amsl, and drops to
about 1,550 m amsl in Nigel.
The following three mining shafts were identified and considered for mine dewatering:
Gold One Sub-Nigel No. 1 Shaft: This operational shaft is connected to the Eastern Basin
(although Gold One Sub Nigel No. 1 shaft was selected, this was based on the perception that it
was the best shaft of all the Sub-Nigel and Nigel Shafts because it is operational).
Sallies No. 1 Shaft: The shaft was used to dewater the Eastern Basin until 1991, therefore
connectivity to the Eastern Basin was well established.
Grootvlei No. 3 Shaft: The shaft was operational until 2010. It is connected to the Eastern Basin
and has some infrastructure in place.
The identification of project options was done on the basis of selecting only options that did not have
an immediate fatal flaw. The main considerations in selecting feasible project options centred on the
following criteria:
Mineshaft characteristics (the height of the mineshaft collar, requirements for a vertical and deep
shaft and the long-term stability of the shaft).
Land availability.
Connectivity to the basin.
(a) Abstraction Point
Based on the selection criteria, the mineshafts shown in Table 39 were evaluated for any fatal flaws
that could preclude their selection.
Table 39: Eastern Basin Initial Abstraction Options Screening
Shaft Description
Collar
Level
(m amsl)
Possibility Reason
Gold One - Sub-
Nigel No. 1 shaft
1,593 The mine is situated in an agricultural area, so
land could be available for the required
infrastructure. The benefit of the Sub-Nigel
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Shaft Description
Collar
Level
(m amsl)
Possibility Reason
mine’s lower collar level is, however, not present
on this shaft; it is about 40m higher than Nigel
No. 3 Shaft. The connectivity to the larger Eastern
Basin is confirmed, but Section 8.1.2 discusses
the potential risks.
Sallies No. 1 shaft 1,623 Information was obtained that this shaft has
been filled and capped and would not be suitable
as a pump shaft.
Grootvlei No. 3 shaft 1,570 A pump shaft with an HDS plant. This shaft was
used, until recently, to dewater the Grootvlei
mine workings, which resulted in the dewatering
of the entire Eastern Basin.
Two options (Grootvlei No. 3 and Gold One Sub-Nigel No. 1 Shafts) will be considered in the options
analysis.
(b) AMD Treatment Plant Site
Although it is possible to situate the treatment plant site away from the abstraction point, due to the
nature of the AMD, it is better to keep the distance as short as possible to reduce the potential of
oxidation, scaling and corrosion. For this reason, one of the selection criteria for the AMD abstraction
point was the availability of land adjacent to the shaft to allow for the construction of a treatment
plant.
The starting point for the selection of the Grootvlei No. 3 Shaft is that it is adjacent to an HDS
treatment plant, which was commissioned in 1997 and operated until 2010. The owners of the mine,
Pamodzi Gold Limited, are in liquidation and the mine is not currently operational. Aurora Gold, who
was a preferred bidders for the mine’s assets, operated and had possession of the mine for a time,
but limited mining and dewatering was undertaken during its tenure. A preliminary site visit to the
Grootvlei HDS plant on 15 August 2011 highlighted the impracticality of using the existing site for the
following reasons:
The HDS plant is in poor condition. The tanks are constructed from coated mild steel and show
signs of corrosion.
The mechanical and electrical equipment on the HDS plant is not operational, although most of
the equipment is installed.
Due to the large structures on the existing mining site, space for any upgrade or expansion is
limited, meaning that buildings would have to be demolished. The cost of this will be high, due to
the large concrete foundations. In particular, the hoist winding house and winders would need to
be removed. The age of the buildings may prohibit demolition without the correct heritage
approvals.
The demolition of the buildings would probably require some blasting, which is not
recommended close to the mineshaft.
The Blesbokspruit runs to the north and east of the site, which prohibits expansion in those
directions.
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It is thus proposed that the following options for other available land close to the mineshaft be
considered:
Small holdings south of the Grootvlei Shaft No. 3,
Mine land north west of the Grootvlei site, and
Vacant land east of the Grootvlei site, across the Blesbokspruit.
Although the smallholdings south of the site are closer (requiring a shorter pipeline), it is expected
that the social impact will be high. The mine land to the north west is adjacent to a tailings dam and is
thus not ideal from a future treated-water perspective. There is potentially geotechnical and
undermining issues with the vacant land to the east.
Further work is required to finally select the site for the treatment plant on the Eastern Basin, but for
the purposes of the due diligence, it will be assumed that the Small holdings to the south of the
Grootvlei Shaft will be utilised. The three potential sites will be compared to the demolition costs
that will be required to utilise the Grootvlei Shaft No. 3 area. All sites have sufficient space for a
treatment plant, both HDS and any future long-term water reclamation plant.
Figure 17: Eastern Basin Options
The Gold One – Sub-Nigel No. 1 Shaft has sufficient space for a treatment plant, both HDS and any
future long-term water reclamation plant.
(c) Sludge Disposal Site
Although the project’s current focus is on the short-term solution, sludge disposal will be a long-term
requirement. Therefore, the potential for the selected sludge disposal option to cater for the long-
term was also considered. Alternatively, where the short-term solution would not accommodate the
long-term solution, possibilities for long-term handling of the sludge were considered.
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Based on the general sludge disposal options, the following sites and options were identified:
Disposal on the Grootvlei TSF: This option is only applicable to the Grootvlei mine option;
Co-disposal at the ERGO Daggafontein TSF: This option is only applicable to the Grootvlei mine
option; or
Co-disposal at the ERGO Brakpan TSF in Brakpan: This option is applicable to both abstraction
point options.
(d) Treated Water Discharge Sites
A key technical consideration of the project was to review the potential discharge position for the
treated water to prevent the treated water from recycling back into the basin, i.e. creating additional
water ingress. This could be a short-term option, as it can be expected that in the long term the water
will be treated to potable standards and supplied into the potable water distribution network.
Therefore, the short term water discharge solution will not be required in the long term and should,
due to the wasted expense, be well motivated if it is required.
The Grootvlei and Sub-Nigel abstraction points would discharge into the Blesbokspruit. The difference
is that the Grootvlei option would discharge upstream of the Marievale Ramsar wetland, while the
Sub-Nigel option would discharge downstream of Marievale wetland.
The Blesbokspruit is a known ingress point, so the additional water could recycle back into the Eastern
Basin. However, due to the wetland, it is not expected that the volume of water will increase the
water level significantly, so the driving head will not increase enough to greatly increase the ingress.
Therefore, the water quality will be a far greater consideration. Removing the treated AMD water
from the Blesbokspruit should have a positive environmental impact (removal of the low quality
treated AMD water), and the discharge volume of water volume should not have a significant impact
due to the continuous upstream water supply from Welgedacht Wastewater Treatment Works
(WwTW), which is currently being upgraded (meaning that more water will possibly be discharged to
the Blesbokspruit).
The following can be considered:
Continue discharging the treated AMD water into the Blesbokspruit;
Select the Sub-Nigel option to allow for discharge below the Marievale wetland;
Construct a bypass from Grootvlei to discharge past the Marievale wetland; or
Pump the water from Grootvlei into the adjacent Rietspruit. It is understood that there are DRD
Gold servitudes in place that could be used for this pipeline.
8.2.2 Assessment of Project Options
The assessment of options used the methodology discussed in Section 5.
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(a) Abstraction Point
From the options selection, two options emerged as potential abstraction points and were analysed
based on the assessment criteria, and scoring was done in the assessment matrix. The following
options were evaluated:
Abstraction point and treatment plant site:
EA1: Grootvlei No. 3 Shaft
ET1: Grootvlei No. 3 Shaft or surrounding area
EA2 / ET2: Gold One Sub-Nigel No. 1 Shaft
Waste Disposal:
ES1: Grootvlei TSF
ES2: Co-disposal on ERGO Daggafontein TSF
ES3: Co-disposal on ERGO Brakpan TSF
Treated Water Disposal:
EW1: Grootvlei adjacent site
EW2: Grootvlei bypass
EW3: Rietspruit
Table 40: Decision Matrix (Eastern Basin)
Abstraction Points Treatment Sites Sludge Disposal Sites Treated Water Disposal
Option Option Option Option
EA1 EA2 ET1 ET2 ES1 ES2 ES3 EW1 EW2 EW3
64 53 64 53 53 65 64 54 41 50
The evaluation shows that the Grootvlei option is the preferred project option.
Based on the options assessment (summarised in Table 40), the following are the preferred options:
Abstraction point: Grootvlei No. 3 shaft
Treatment site: Grootvlei No. 3 Shaft or surrounding area
Sludge disposal option: Co-disposal on the ERGO Daggafontein TSF, with the backup option of the
ERGO Brakpan TSF.
Treated water discharge: Grootvlei adjacent to site
Table 41 summarises some of the reasons and motivation for the score assigned to each option.
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Table 41: Option Assessment (Eastern Basin)
Assessment
Criteria
Motivation
(GV = Grootvlei, SN = Sub-Nigel)
Available
Infrastructure
Although GV has an HDS plant with partial capacity for the treatment of AMD, it
was not a major driver due to the poor condition of the plant. The electrical
supply point has also been removed.
There is no infrastructure at the SN site.
Land Availability There is land available close to the mine abstraction shaft, either GV property
(Pamodzi Gold Limited, in liquidation), or vacant / agricultural land. For the Due
Diligence report, the agricultural land south of the Grootvlei site was considered.
The area surrounding the SN property is mainly agricultural land; therefore,
obtaining the required land is not expected to be a problem.
Access and
Servitudes
The access to GV is currently across the Grootvlei mine property, which is not
ideal and it is thus recommended that the access should be selected so that the
portion of land can be independent. This would possibly result in a longer access
road (entrance from the east) or a need for a rail crossing. There are servitudes
available to discharge water to the Rietspruit.
There is ready access to the SN site, although the site is further from potential
future long-term potable water users.
Connection to
Bulk Services
GV has an Eskom connection, but Eskom recently removed the electrical
equipment. The Eskom power lines feeding the GV site pass close to the proposed
vacant land. Other services would need to be provided.
There should be power close to SN because the site is currently maintained on the
mine. The site is, however, only used as a mine training facility (with very low gold
production), so it is not expected to be of sufficient quantity for the short and long
term.
Sludge Disposal There is not much to differentiate between the two options in terms of sludge
disposal. The preferred sludge disposal option would be to dispose of sludge on an
operational TSF, which would imply the ERGO facility (or Daggafontein for the
Grootvlei option). Both GV and SN are equidistant from the ERGO Brakpan TSF (GV
via the ERGO gold processing plant), however, GV can tie into the Daggafontein
processing plant, which is half the distance of the Brakpan TSF. There is a TSF close
to the SN option, but due to the small quantities of mining it is not expected that
sufficient tailings for co-disposal are currently generated.
Environmental
and Social
Impact
The proposed vacant land is an old mining site / agricultural land and major
environmental and social impacts are not expected. The land needs to be
investigated for undermining because there are some subsidence features on the
aerial photographs. The agricultural small holdings will have social impacts.
SN would use some agricultural or open land for the construction of the plant.
Even though the land has been disturbed by farming, this site will have some
environmental and social impacts.
Security Although GV has been in the press for security problems, the site will be isolated
from the Grootvlei mining activity and acts independently.
There is thus no differentiation between the options in terms of security.
Discharge /
Delivery
The discharge from GV has been impacting Marievale wetland for years, but could
be removed. However, these options will require infrastructure and operating
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Assessment
Criteria
Motivation
(GV = Grootvlei, SN = Sub-Nigel)
costs.
The SN option would discharge downstream of the Marievale wetland, but, based
on the position of the site, significant infrastructure would be required to
discharge the water.
Flexibility for
Long-Term
Solution
All options have sufficient space for the future options.
Connection to
the Eastern
Basin
GV has interconnectivity, the shaft has been recently used for dewatering the
Eastern Basin.
SN could have issues with interconnectivity (see Section 8.1.2). Gold One has also
indicated to the Council for Geosciences that it intends plugging the Sub-Nigel
mines to allow for the continuation of mining, which may impact this option.
Selection From the options analysis and the motivations, the preferred option is the
Grootvlei No. 3 Shaft, together with a treatment plant on agricultural to the south
of the shaft. It is, however, recommended that the options for the Gold One Sub-
Nigel No. 1 Shaft be confirmed as a backup option during the project design phase
or for future consideration if a sub-Eastern Basin develops in the Nigel / Sub-Nigel
Mines.
(b) Treatment Plant Site
The selection of an AMD treatment plant site is linked to the selection of the abstraction point. For
the Eastern Basin it was not necessary to review options where the abstraction point was not
adjacent to the treatment plant site.
The preliminary selection of Grootvlei No. 3 Shaft as the abstraction point was only moderately
influenced by the HDS plant. The following factors would impact the decision to refurbish or abandon
the AMD treatment plant:
The condition of the infrastructure and cost of repairs.
The size of the infrastructure relative to the AMD treatment requirements.
The integration of the HDS plant with any long-term (future) reclamation plant.
A visual condition assessment was done on the equipment as the plant is not currently operational,
and the following conclusions emerged:
The plant was not properly decommissioned when operation stopped, so the neutralisation tank
and clarifiers were left filled with sludge;
The neutralisation tank was aerated using floor level air pipes connected to blowers. This system
was probably not operational because there are a number of flexible hoses positioned in the
sludge, which seem to be connected to the blowers. This would be a very inefficient method of
introducing air and would limit mixing.
The neutralisation tank is corroded on the external surface. The internal surface was not visible
due to the layer of sludge.
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Corrosion was visible on the clarifiers, but they seemed to be in a better condition than the
neutralisation tank.
There is no power supply to the plant because Eskom has removed the transformers.
The equipment and electrical cabling is still installed, but it is not expected (even if there was
power) that the plant could be brought into operation without significant cost and work.
The pipe work is visibly corroded and could be filled with sludge.
The chemical dosing equipment was caked with lime, so corrosion should be minimal and it may
be possible to salvage some of the equipment. The 300 tonne silo is in good condition, however
the use of air for bridging control is not recommended, i.e. vibrators would need to be
retrofitted.
The headgear is in poor condition and should be removed, and the openings to the shaft should
be closed, except where the new abstraction pumps are to be fitted.
The HDS plant is 14 years old, which is typically the design life of a mechanical / structural steel
plant of this nature. It can thus be expected that an entire upgrade and replacement of electrical
and mechanical equipment will be required as the equipment has exceeded its normal operating
life.
The following ‘desktop’ conclusions were also reached:
The dewatering at Grootvlei was done from an underground pump station. The underground
pump station requires that the mine access is maintained, with associated costs (lighting,
ventilation, headgear, maintenance and safety). However, the pump station level has been
flooded, and will be very difficult to reinstate. Furthermore, the level of the pump station was
based on the mining level requirement, which is well below the ECL (500 m below ECL).
The original process design of the Grootvlei HDS plant was based on criteria that will not reliably
meet the project objectives. The AMD water quality is also expected to deteriorate significantly
when the basin floods and it is thus expected that the HDS plant will require retrofitting and
expansion, which may not be justifiable.
The HDS process consists of the following components:
In-line addition of pure oxygen to oxidise dissolved iron;
Addition of 80 t/day of lime to increase the pH of the water and aid in the oxidation and
precipitation of dissolved iron and manganese;
Reaction in an 18 m diameter aeration basin with an effective hydraulic retention time of 10
minutes.
2,300 m3/hr of compressed air is injected to assist with mixing and aeration of the resulting
slurry;
Clarification in two parallel clarifiers, each 30 m in diameter with an effective volume of 6,500 m3.
The design loading rate is 2.2 m/hr.
Polyelectrolyte is dosed to assist the clarification process;
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A portion of sludge from the clarifiers is returned to the aeration basin, while the rest is returned
to the slimes dams for dewatering.
The proposed AMD treatment process for the three basins, i.e. utilising limestone and lime, together
with sludge conditioning and gypsum crystallisation, will be an improvement on the HDS process for
the following reasons:
The operational risks will be lower due to the more conventional design parameters.
The effluent quality is expected to be better and more stable, allowing for larger variations in
incoming water quality and flow.
Using limestone will be more cost effective than only using lime.
Using aeration will be more cost effective than oxygen but the basin retention time would need
to be larger to allow for slower reaction times associated with air.
The process AMD treatment design will allow for some redundancy to allow for regular
maintenance.
Based on the revised process, the only practical aspect of the current HDS process plant to retain is
the clarifiers / thickeners. However, due to the condition of these clarifiers (a long-term maintenance
issue) it is not feasible to retain them.
It is proposed that none of the existing treatment plant be used. There is thus no restriction on the
selection of the site, so it is proposed that a new treatment plant be constructed on the agricultural
land to the south of the Grootvlei Shaft No. 3.
(c) Sludge Disposal Site
The disposal of sludge in the Eastern Basin is described in detail in Sludge Disposal Alternatives (BKS
Report No. J01599/10) attached as Annexure I. The conclusions and recommendations from this
report are incorporated here for ease of reference.
The preferred sludge disposal option for the Eastern Basin is:
Short-term solution (four years)
o Construction of a pump main to the existing DRD Gold Daggafontein gold processing
plant. The sludge will then be co-disposed of on the DRD Gold Dagafontein TSF.
o Total Estimated Cost = R12,308,000.
Long term solution (30+ years):
o Pump main to the ERGO Brakpan TSF (DRD Gold has indicated that the life of this
facility is in excess of 30 years);
o Disposal into the Eastern Basin mine void; or
o Greenfields engineered disposal facility.
The availability of a number of tailings facilities in the area makes co-disposal with tailings an
acceptable and viable option for the short term period for the following reasons:
There is a tailing facility (Daggafontein TSF) approximately 6 km from the proposed HDS
treatment plant.
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The sludge would be pumped as wet slurry to the Daggafontein TSF, blended into the tailings
stream and pumped onto the TSF.
Alternatively, the sludge could be pumped to the ERGO processing plant, 11.8 km to the west,
blended into the tailings stream and pumped a further 6 km to the Brakpan TSF.
There are a number of risks associated with the sludge delivery pipelines, including the
settlement of sludge in the pipeline in the event of a power failure. However, these risks will be
mitigated by the provision of a standby sludge delivery pipeline and do not constitute a fatal flaw;
The above is subject to confirmation of the current operational plans at Daggafontein TSF, failing
which, co-disposal onto the ERGO Brakpan TSF, with a life in excess of 30 years, would be
required.
If no commercial agreement is possible for co-disposal with tailings in the basin, further investigation
of alternative options (disposal into the Eastern Basin) would be required for long-term disposal
options due to the high capital cost for an engineered disposal site.
8.2.3 Mining Options in the Eastern Basin
There are currently two operational underground mines in the Eastern Basin:
Pamodzi Gold Limited (PGL) – The Grootvlei mine may be considered an operational mine due to
the possibility that a willing buyer will be found for the Grootvlei mining assets. PGL was
maintaining the water level at about 780 m amsl, which was required for its mining activities. As
there is no party to discuss the potential of future mining, it has been assumed that mining at
Grootvlei will not continue. Should this change, the mining house will need to replace the
pumping infrastructure installed as part of this project (to allow for deeper-level pumping). The
replaced pumps and pipe work, procured as part of this project, will be stored for when the
mining activities cease and the water level can be allowed to rise to ECL.
Gold One Sub-Nigel No. 1 shaft – This mine is used by Gold One as a training mine for its Modder
East Mine (not connected to the Eastern Basin). It has stated that this mine has already been
closed and that the training facility has moved to Modder East, even though the water level has
not yet reached its mining level. In a press statement on 11 February 2011, the water level was
106 m below its training facility (which makes its mining level roughly 1,040 m amsl). The level of
Gold One’s training facility is below the ECL. Gold One is considering plugging the Sub-Nigel Mines
to separate them from the Eastern Basin and allow mining to continue.
8.2.4 Possible Draw-Down Scenarios
To accommodate Gold One Sub-Nigel No. 1 shaft, the water level rise will need to be stopped below
1,040 m amsl, which translates to the minimum predicted date of April 2013 in terms of Figure 16.
This is equivalent to a total static head of 530 m. Gold One would need to review the economics of
contributing to the pumping costs for the additional 240 m of pumping head and the differential cost
of the pumps, which would equate to approximately R950,000 per month.
The following is recommended with regard to the pump procurement:
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Pumping to ECL only: Purchase new pumps (or consider using CRG’s pumps if they are not used
on the Central Basin), with best efficiency at a flow of 82Mℓ/d (104Mℓ/d at 19 hour pump time)
and a head of 367 m. The pumps should match the flexibility that the Ritz Pumps offer in terms of
a wide application range for both flow and pump head. This option will approximately match the
pumps purchased by CRG for the Central Basin, although an additional pump will be required to
achieve the increased flow rate.
Pumping to 530 m below surface at Grootvlei No. 3 shaft: If the Gold One mining option is
implemented, the pumps need to be operational by April 2013. New pumps would need to be
procured for this option and connectivity at the expected flow rates would need to be confirmed.
8.2.5 Recommendations on preferred options
The following AMD management scheme is recommended in the Eastern Basin:
Pumps are installed at Grootvlei No. 3 shaft at the pump depth to achieve the ECL level or the
level to allow Gold One to continue mining Sub-Nigel No. 1 Shaft.
Construction of a new High Density Sludge (HDS) treatment plant adjacent to the Grootvlei No. 3
shaft, on the agricultural small holding site south of the abstraction point.
A sludge pipeline is constructed to the DRD Gold (Crown) Daggafontein TSF.
A treated water pipeline is constructed to the Blesbokspruit (short-term discharge);
A future sludge pipeline to the ERGO Brakpan TSF is planned (if required).
The aspects that are required to proceed with the design are as follows:
A decision on the pumping depth, i.e. ECL or the Gold One mining requirements, possibly 530 m.
Agreement on or procurement of required land and servitudes.
A topographical survey of recommended sites and pipeline routes.
A geotechnical investigation of recommended sites and pipeline routes.
8.2.6 Emergency Contingency Shafts
It is recommended that Gold One be approached to identify a suitable deep-level shaft that can be
used in case there are connectivity issues between the abstraction point and the Nigel and Sub-Nigel
mines. It is proposed that at least one shaft be secured in terms of agreement or servitude. The access
to this shaft and safety of the shaft should also be considered part of the current project. After
pumping is started at Grootvlei No. 3 shaft, more planning for this shaft can be considered.
8.2.7 Consideration of Integration with Future Long-Term AMD Treatment
During the due diligence, the possible future long-term AMD treatment options were considered.
Although there is no certainty at this stage about what will be implemented in the long term, it can be
accepted that the water will be treated to potable drinking-water standards to supply to Rand Water
and/or municipal reservoirs. Furthermore, waste minimisation and the recovery of valuable metals
from the waste sludge will be part of a future scheme.
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The costs of a future scheme were estimated the following manner during the short-term due
diligence:
An estimate of the space requirement for the future scheme was made and any land procured for
the short-term solution will provide sufficient land for the long-term infrastructure.
Sludge handling will be a long-term requirement and the short-term solution has, therefore,
reviewed how sludge can be handled in the long-term.
Consideration of where the potential connection to the potable water system would be, i.e. by
reviewing potential water demand and water distribution reservoirs.
8.3 Conceptual Design
8.3.1 Shaft Stability
As part of the due diligence, the stability of the mineshaft to allow for long-term pumping
infrastructure was considered. A Rock Engineer specialist assessed the shaft stability for the preferred
mineshafts and the report is attached as Annexure J. It highlights the lack of available information for
a thorough assessment. The conclusions for the Eastern Basin Grootvlei No. 3 Shafts are:
Low probability of structural failure due to low dip of strata and no major geological features
intersecting the shaft barrel.
Low probability of stress-induced failure.
Low probability of failure due to dynamic loading, including crush-type and shear-type seismic
events, as well as shakedown damage.
8.3.2 Abstraction Infrastructure
(a) Abstraction Point
The Grootvlei Shaft No. 3 was selected as the preferred pump shaft. The shaft has six compartments
available for the installation of pumps. The existing pipe work is still installed in conveyances 1 and 2
and there is a ventilation pipe in conveyance 6.
Three pumps will be installed in the shaft, so it is proposed that conveyances 3, 4 and 5 be used to
allow sufficient space around the pumps.
The shaft’s parameters are listed in Table 42.
Table 42: Grootvlei No.3 Shaft Parameters
Parameter Value Dimension
Collar Level 1,570 m amsl
Shaft Depth 800 (Approximate) m
Shaft Bottom Level 770 (Approximate) m amsl
Environmental Critical Level 1,280 m amsl
The surface infrastructure includes:
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A platform around the shaft, with openings only for the pumps and safety features to prevent
unauthorised access to the shaft openings. The platform will be designed to carry the weight of
the pump, pipe column and water in the column;
A structural steel superstructure and gantry crane to lift / lower the pump / pipe column in and
out of the shaft.
A clamping system to ensure that the pumps are safely installed without the possibility of the
pump / pipe column falling into the shaft.
A final connection piece to the pipeline that conveys the water to the treatment plant;
A pipeline to the treatment plant.
Appropriate instrumentation and control to operate and monitor the pumping installation.
A pipe stacking yard, truck off-loading area and store. The reach of the gantry crane for the
abstraction pump station shall extend to the pipe stacking area, truck off-loading area and store.
Ancillary infrastructure to support the pump station and associated works, e.g. administration
building, roads, guardhouses and security fencing.
Conceptual layout drawings are provided (drawing J01599-05-002) for the Grootvlei No. 3 shaft
infrastructure.
(b) Pumps
The conceptual design of the abstraction infrastructure is based on the lowest risk option (in terms of
both equipment and operational personnel), which does not require the placing of pumping
infrastructure underground.
Therefore, the only option considered was suspending borehole type thrust balanced pumps into the
mineshaft. These pumps require minimal surface infrastructure at the shaft head and no access to the
mineshaft is required during installation or operation as the pumps are lowered into the mineshaft
and suspended on the pipe column. The required pipes are designed for the purpose installation in a
vertical shaft and are joined with a quick coupling chain that is fed between a spigot and socket joint
for quick and simple installation.
The headgear is in very poor condition and will need to be removed, and a new steel superstructure
with gantry crane will be installed over the shaft to facilitate the installation and removal of the
pumps.
The selection of the pumps depends on confirmation by Gold One regarding the continuation of
mining in the Basin.
(c) Installed Pump Depth
There is very little information on the level differences across the basin while pumping. However, due
to the current understanding of the basin, this variance will not exceed 10 m, due to extensive holing.
To determine the water level characteristics during pumping of the Eastern Basin, a pump test would
be required in order to monitor the water level at various positions of the basin while varying the flow
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rates. However, there will be no opportunity to do these pump tests until the full-scale installation is
operational, so some flexibility needs to be allowed for the installed pump depth.
Based on the water balance model of the Eastern Basin, it is expected that, based on fixed speed
pumps at average flow and allowing the basin to be drawn down during low ingress and filled to ECL
during high ingress, the water level will fluctuate by 66.7 m.
The following basis has been used to select the pump depth for the Eastern Basin:
The ECL level of 1,280 m;
The submergence depth of 10 m for the pumps;
Pumps installed an additional 10m below ECL and submergence depth to allow for variations of
water depth in the Eastern Basin and initial water level drop in the mineshaft.
Pumps staggered by at least 10 m (or one pipe length) to reduce possible turbulence interference
between the pumps;
Pumps installed an additional 67 m below the (ECL plus submergence depth plus basin variation)
level.
For more flexibility, it is recommended that the pipes be designed for the possibility that the
pumps are lowered by a further 20% of ECL (56 m). Initially, these pipes will not be purchased or
installed. The pumps will be sized for the best efficiency at the installation depth, but checked
that they can supply at least average flow at the lowest level.
Therefore, the recommended installed pump level for flexibility of water level within the Eastern
Basin will be 1,191 m amsl, with the pipes / pumps designed to allow the pumps to be installed to
1134 m amsl. This relates to the a pump with a maximum flow of 110Mℓ/d, a best efficiency at a flow
of 104Mℓ/d (82Mℓ/d average, for only 19 hours pump time) and a normal static head of 313 m, with
the ability to be lowered to increase the static head to 379 m and 435 m.
The same basis will be used to determine the depth of the pump installation if the mining scenario is
implemented, except that the starting level for the pump will be 530 m below Grootvlei No. 3 shaft,
i.e. 1040 m amsl.
A conceptual design for such a pumping system and a preliminary selection was done on the pumps,
the parameters of which are listed in
Table 43.
Table 43: Abstraction Pump Station (Eastern Basin)
Parameter Value
Duty Flow (Mℓ/d) 104
Duty Flow (m3/s) 1.2
Duty Head (m) 350 (static plus allowance
for losses)
Duty Pumps (No) 3
Standby Pumps (No) 1 (not installed)
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Parameter Value
Rotational Speed (RPM) 1,470
Power Absorbed (kW) 5,040
Power Installed (kW) 5,400
(d) Electrical Power
Due to the large variation of flow expected, it is recommended that the pumps be started and
controlled with VFD, with one VFD per pump.
At the Grootvlei No. 3 Shaft, it is expected that a 6.6 kV Eskom supply will be available, but the
connection has been disconnected due to the liquidation of Pamodzi Gold Limited. The electrical
capacity and rating will be determined and an application for supply will be submitted to Eskom on
behalf of TCTA. A new Eskom supply will be installed in a suitable position for the proposed scheme in
the Eastern Basin.
The following electrical infrastructure will be required at the Shaft
Single core 6.6 kV lines to the shaft.
Electrical control building incorporating a VSD Room, MV Room and LV Room.
Within the LV room, a control PLC and remote control via GPRS or fibre optic to the treatment
plant.
Water cooling towers next to the VSD Room.
A yard for transformer next to the LV Room.
The 6.6 kV power lines will tap off at the shaft yard to the MV Switchgear to protect the VSDs. All 6.6
kV power lines between the shaft and the treatment plant will be buried and encased in concrete for
security reasons. The switchgear will supply power to a transformer 6.6 kV / 400 V, which will be
rated big enough for future auxiliary power. The treatment plant will be supplied with a 400 V three
core cable.
Three duty pumps are recommended for the Eastern Basin, with an additional pump as a standby,
which will be stored on site and not installed, meaning that it is not inactive within the corrosive AMD
water and an additional pipe column does not have to be procured.
(e) Pipeline
The abstraction point and the treatment plant are not on the same site and it can thus be expected
that there will be a number of services crossing required. The pipeline needs to cross the
Blesbokspruit and should be suspended on the culvert structure.
Table 44: Abstraction Pipeline (Eastern Basin)
Parameter Value
Flow (Mℓ/day) 104
Flow (m3/s) 1.2
Nominal Diameter (m) 3 x 0.550
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Parameter Value
Flow Velocity (m/s) 1.8
Length of Pipe (m) 1,500
8.3.3 Plant Infrastructure
Although there is an HDS plant adjacent to the Grootvlei Shaft No. 3, for reasons described in this
report, the preferred option does not include the re-use of this infrastructure.
A preliminary site layout revealed the following, which were addressed:
The site has a slight even slope towards the southeast.
There are no services crossing the site.
The short-term site would be on private property and sufficient land will need to be procured.
The treatment plant will comprise three independent trains, each consisting of a sludge conditioning
tank, a pre-neutralisation tank, a neutralisation tank, a gypsum crystallisation tank and a clarifier /
thickener.
Other than these main unit processes, other ancillary treatment infrastructure includes:
Chemical dosing (quick lime, limestone and polyelectrolyte);
Pumps and equipment for a sludge recycle system;
A sludge retention tank (one-day storage to allow for breakdown / maintenance at ERGO plant);
A treated water retention tank (one-hour storage as pump sump for potential use of the water);
and
Buildings for the electrical equipment.
Conceptual layout drawings are provided (refer to drawings J01599-05-003) for the treatment plant
infrastructure.
(a) Geotechnical Input
A desktop study of the site geology and geotechnical conditions revealed the following:
The proposed site for the Eastern Basin treatment plant is underlain by rocks of the Vryheid
Formation of the Ecca Group, Karoo Supergroup.
The Vryheid Formation, Ecca Group, is composed of sandstone and shale along with coal beds
with the Dwyka Tillite Formation being composed of tillite (a mixed assemblage glacial deposit)
and shale. The Malmani Subgroup comprises dolomite and chert, and it is this dolomite that
causes sinkholes and subsidences in this area and to the south of Pretoria.
The treatment plant is likely to be underlain by sandstone and shale and the sandstone is
expected to be encountered at less than 4 m, with the residual material being thin and sandy in
nature. The residual profile developed above any shale would typically comprise clay and silt,
which will be more thickly developed than the residual sandstone. However, there is a major
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watercourse / wetland area to the east of the site and a thickness of alluvium across the site is
possible.
Cognisance needs to be taken of the founding conditions, in this area as well as of the possibility
of seismic activity, the presence of undermining and the presence of dolomite, which is
considered to present a very low to low risk.
It will be necessary to determine whether there is undermining below the treatment plant and
pipelines so that the possibility of subsidence can be assessed and catered for in the design.
The residual soils associated with the dolomite are often very thickly developed and some, such
as wad (a manganese rich material), are highly erodible, highly sensitive and highly compressible.
The presence and nature of the dolomite and dolomitic residuum, if present, will need to be
determined to allow appropriate measures to be taken in the design of the structures.
(b) Terrace Design and Plant Layout
A preliminary design of a terrace was done and, once designed, the plant was laid out on the terrace.
(c) Roads and Stormwater
A new access road to the east of the site is proposed as it will be a good access point for the regular
delivery of lime by larger trucks. The road is through a rural / farming area and the additional traffic
load will have to be considered in terms of the disturbance to local residents and the pavement
design of the access road.
Site roads for the delivery of chemicals and the maintenance of equipment will be designed and the
roads and earthworks will be designed to manage and dispose of stormwater.
(d) Water Supply
A municipal water supply will be preferred; but if this is not available, a borehole will be drilled into
the dolomite to provide potable water to the site. A small package plant for filtration and disinfection
will be provided.
(e) Sanitation
An on-site wastewater treatment system will be installed.
(f) Electrical Power Supply and Distribution
There are Eskom power lines close to the proposed site and power will be obtained directly from
Eskom. The electrical power supply voltage will be 6.6 kV to the pumps, but will be stepped down to
400 V to supply electricity to the treatment plant’s various Motor Control Centres.
The following electrical infrastructure will be required at the plant:
A mini-sub, rated for current use and pumps to future treatment works
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An LV Room, including auxiliary items, control desk and remote control via GPRS or fibre optic
back to the control building.
Electrical controls and protection.
8.3.4 Waste Sludge Handling and Management
For the short-term option, there are two waste streams from the HDS treatment plant, i.e. the lime /
metals sludge and the treated AMD water that will be disposed of into the Rietspruit.
The sludge will, for the short term, be pumped to the DRD (Crown) Daggafontein Gold Recovery Plant,
about 6km south of the proposed treatment plant site. The operation at the Daggafontein TSF may
not have a long remaining life and, therefore, for the life of the treatment plant, planning and
consideration of a pipeline to the ERGO Brakpan TSF will be made.
The infrastructure required for the disposal of the sludge includes:
A sludge pump station, taking the possible future long distance pumping to the ERGO Brakpan
TSF into account;
A water flushing system;
A pipeline to the Daggafontein Gold Plant; and
Electrical controls and protection.
Conceptual layout drawings are provided (drawings J01599-05-004 to 007) for the sludge disposal
infrastructure.
(a) Pumps
It is proposed that two duty pumps and a standby pump be installed in a pump station. The design
flow and a conceptual design are listed in Table 45.
Table 45: Sludge Pump Station (Eastern Basin)
Parameter Value
Duty Flow (Mℓ/d) 4.7
Duty Flow (m3/s) 0.05
Duty Head (m) 40
Duty Pumps (No) 2
Standby Pumps (No) 1
(b) Pipeline
The sludge pipeline from the WTP to the Daggafontein TSF plant will have the parameters shown in
Table 46. Where possible, the pipeline will be above ground to allow for maintenance. Two pipelines
will be installed to operate as duty standby due to the expectation of significant scaling. As another
precaution, the pipeline will be designed to allow for regular pigging to remove scale build-up.
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Table 46: Sludge Pipeline (Eastern Basin)
Parameter Value Flow (Mℓ/day) 4.7
Flow (m3/s) 0.05
Nominal Diameter (m) 0.200
Flow Velocity (m/s) 2.0
Length of Pipe (m) 3,100
The pipeline route is described in Table 47.
Table 47: Description of Sludge Pipeline Route (Eastern Basin)
No Section Description
1. Proposed HDS
Site
The pipeline will follow the access road as far as possible. The pipeline
can be above the ground on pipe pedestals to facilitate maintenance.
Chainage = 0-900 m
Length = 900 m
2. Crossing Farm
Land
The pipeline will cross a section of farmland. The pipeline will be buried
below the farming depth and designed to take vehicle loads.
Chainage = 900-1,900 m
Length = 100 m
3. Crossing Rural
Road
The pipeline will cross a rural road. Conventional half-width construction
will be used. In this section, the pipeline will be underground.
Chainage = 1,900 - 1,950 m
Length = 50 m
4. Parallel to
Rural Road
The pipe runs south parallel to the rural road until the R29 Road. In this
section, the pipeline will be aboveground.
Chainage = 1,950-2,850 m
Length = 900 m
5. Crossing R29 The R29 Road will be crossed by conventional pipe jacking. There may be
services (water, sewer and telecoms). Permission for crossing these
services will have to be obtained. The pipeline can be above the ground
on pipe pedestals to facilitate maintenance.
Chainage = 2,850-2,900 m
Length = 50 m
6. Southerly
Direction to
Railway
The pipeline turns to run in a southerly direction. No services are
expected. The pipeline can be above the ground on pipe pedestals to
facilitate maintenance
Chainage = 2,900-3,700 m
Length = 800 m
7. Crossing of
Railway
The railway will be crossed by conventional pipe jacking. There may be
services (water, sewer and telecoms). Permission for crossing these
services will have to be obtained. The pipeline can be above the ground
on pipe pedestals to facilitate maintenance.
Chainage = 3,700-3,750 m
Length = 50 m
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No Section Description
8. Southerly
Direction to
N17 Road
The pipeline turns to run in a southerly direction. No services are
expected. The pipeline can be above the ground on pipe pedestals to
facilitate maintenance.
Chainage = 3,750-4,250 m
Length = 500 m
9. Crossing N17
Road
The N17 Road will be crossed by conventional pipe jacking. There may be
services (water, sewer and telecoms). Permission for crossing these
services will have to be obtained. The pipeline can be above the ground
on pipe pedestals to facilitate maintenance.
Chainage = 4,250-4,350 m
Length = 100 m
10. To
Daggafontein
TSF
The pipe runs parallel to the N17 Road. In this section, the pipeline will
be aboveground.
Chainage = 4,350-5,850 m
Length = 1,500 m
Table 48: Major Service Crossings – Sludge Pipeline (Eastern Basin)
No Service Method of Crossing
1. Rural road Half width construction
2. R29 Road Conventional pipe jacking
4. Railway line Conventional pipe jacking
7. N17 Road Conventional pipe jacking
8.3.5 Treated water discharge
The treated AMD water will be stored on site in a tank, and the overflow will be piped to the
Blesbokspruit. If there is a demand for the water, the storage tank can be used as a pump sump. In
future, this tank will act as a balancing / storage tank for the long-term solution.
The infrastructure required for the disposal of the treated AMD water includes:
A storage sump;
A channel to the Blesbokspruit; and
A suitable energy dissipation and river discharge system.
Conceptual layout drawings are provided (drawing J01599-05-002) for the treated AMD water
disposal infrastructure.
(a) Channel
The treated water from the treatment plant will discharge into a sump before excess water is
discharged into the Blesbokspruit. If there are potential users of the water, the pumping
infrastructure will be agreed on with the water user.
The parameters for the treated water channel from the sump to the Blesbokspruit are listed in Table
49.
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Table 49: Treated Water Pipeline (Eastern Basin)
Parameter Value
Flow (Mℓ/day) 104
Flow (m3/s) 1.2
Flow Velocity (m/s) 1.5
Length of Channel (m) 1,500
There are no major crossing for this route.
8.4 Detailed Cost Estimates
8.4.1 Detailed Capital Estimate
The detailed capital cost estimate for the Eastern Basin option is summarised in Table 50.
Table 50: Detailed Capital Cost Estimate for the Eastern Basin
Number Description Amount Total*
1 AMD Collection Infrastructure
Civil / Structural Work 4,600,000.00 R60,096,771
Mechanical 55,496,771.00
2 AMD Treatment Plant
Civil / Structural Work 62,460,000.00 R108,010,007
Mechanical 45,550,007.00
3 Neutralised Water Discharge
Civil / Structural Work 600,000.00 R1,622,400
Mechanical 1,022,400.00
4 Sludge Handling and Disposal
Civil / Structural Work 1,850,000.00 R6,800,000
Mechanical 4,950,000.00
5 Earthworks and Pipe Work 28,480,441.00 R28,480,441
6 Electrical, Control and Instrumentation 30,856,582.00 R30,856,582.00
7 Preliminaries and Generals (12%) 28,303,944.00 8 Total R264,170,100
* Totals are rounded to the next Rand
8.4.2 Detailed Operating and Maintenance Cost Estimate
The detailed operating and maintenance cost estimate for the Eastern Basin option is summarised in
Table 51.
Table 51: Detailed Operating and Maintenance Cost Estimate for the Eastern Basin
Number Description Amount Total
1 O&M on CAPEX 4,571,500.00
2 Chemicals Costs 60,444,482.00
3 Electricity Costs 15,520,700.00 R80,536,682
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9. REGULATORY AND ENVIRONMENTAL
Based on legislation that governs mining, water, waste, environment, heritage and radiation, the
conventional approach for a project of this nature would ordinarily be required. However, the
conventional approach will not enable TCTA to execute the project in the proposed timelines, i.e. with
construction to begin in January 2012 and commissioning in August 2012. Accordingly, an optimised
process is required. While the optimised process is being recommended, the conventional approach
will have to be completed in parallel.
The essential feature of the optimised process is that TCTA will that the DWA provide it with the
necessary directives to address AMD without it having to obtain an upfront Water Use Licence and
Environmental Authorisation, The DMR will have to be approached to provide exemptions for
participating mines, so that it does not need to amend its environmental management programmes
immediately.
An Authority Steering Committee (ASC) has been set up with all relevant authorising agents. This
committee has all the relevant decision makers in place to grant authorisations on an accelerated
basis. The optimised approach was presented to the ASC, who accepted this approach in principle,
while not abdicating any responsibility for TCTA to follow the conventional approach in parallel to
obtain the required authorisations.
An IRP strategy document was prepared by the project team. Table 52 summarises the required
process and estimated timeframes required to undertake the IRP strategy.
Regulatory approval for the proposed immediate measures in the Western Basin is required. This will
be focussed on the disposal of sludge into the Wes Wits Pit.
Table 52: Summary of Regulatory Processes Required and their Respective Timeframes
Process Timeframe
Optimised regulatory approach strategy 100 days
Environmental and social screening and fatal flaw assessment 6 weeks
Project communication strategy Throughout
EIA process 18 months to 2 years
Public participation Throughout
EMPr 100 days
Construction monitoring Throughout Construction phase
The full details of the IRP are contained in Integrated Regulatory Process (IRP) (BKS Report No
J01599/04) and Integrated Regulatory Process (IRP) Strategy (BKS Report No J01599/08).
10. RISK ASSESSMENT
10.1 Risk Assessment Methodology
The risk assessment methodology applied for the project consists of the following steps:
Risk identification
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Risk rating
Risk classification
Risk mitigation
10.1.1 Step 1: Risk Identification
Risks related to each of the project components and aspects thereof were identified and defined. The
following project lifecycle phase associated with each risk was identified:
Design
Commissioning
Construction
Operation
Closure
10.1.2 Step 2: Risk Rating
Risks were rated using two criteria: likelihood and consequence. The methodology for assessing these
two criteria is as follows:
Likelihood:
A likelihood rating was chosen for each risk, showing the probability of occurrence, as indicated in
Table 53.
Table 53: Likelihood Criteria
Likelihood Category
99% is occurring E
50% < 99% D
20% < 50% C
1% < 20% B
< 1% A
Consequence:
The expected consequence of each risk was determined. A risk may have multiple consequences. The
following five-point rating of the relative severity of expected outcomes was applied to each
consequence category:
1 - Insignificant
2 - Minor
3 - Moderate
4 - Major
5 - Extreme
10.1.3 Step 3: Risk Classification
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The risk model calculates the risk score and assigns a classification. The overall risk score is
determined by combining the risk score associated with the expected consequence and the likelihood
of occurrence for the risk, as shown in the risk matrix in Table 54.
Table 54: Risk Matrix
Like
liho
od
Rat
ing
E 11 16 20 23 25
D 7 12 17 21 24
C 4 8 13 18 22
B 2 5 9 14 19
A 1 3 6 10 15
1 2 3 4 5
Consequence Rating
Table 55 indicates how the risk magnitude translates into a risk classification.
Table 55: Risk Calculation
Risk Classification Score range
High Risk 17 to 25
Medium Risk 6 to 16
Low Risk 1 to 5
10.1.4 Step 4: Risk Mitigation
Potential mitigation measures were identified and recorded for each risk.
10.2 Risk Assessment Results
The results of the risk assessment are captured in the risk register (refer to Annexure L). Table 56
summarises the 18 risks that facing the project that have been registered as High Risk.
The implementation of the proposed identified mitigation measures for the high risks, as well as the
other ranked risks, should be regularly reviewed during the implementation of the project.
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Table 56: High Risks
Issue Area Issue/Risk Event Lifecycle
Phase Impact Description
Impact
Ranking Likelihood
Risk
Score Mitigation
Waste Availability of sludge
disposal sites. Uncertainty
on waste handling.
Design Short term vs. long
term objectives to
be clarified
5 4 24 Ensure commercial agreement for liability sharing.
Include regulatory approval and institutional
arrangements in short-term and long-term project
planning. Ensure dialogue with stakeholders
(Government, mines, etc.)
Environmental
(natural and social)
Unable to obtain a
favourable directives for
short term projects
Construction Delay in
construction
5 3 22 Ensure the optimised approach is accepted and
implemented
Environmental
(natural and social)
Delayed/non approval by
Stakeholders (Government)
Construction Delay in
construction
4 4 21 Do full investigations and provide detail design /
submission. Early start with process and ongoing
contact with stakeholders through the EIA process.
Regulatory Potential delays in NNR
approval.
Construction Delay in
construction
4 4 21 Early start with process and ongoing contact with
Stakeholders through the EIA process.
Waste Waste characterisation.
Impact assessment may be
wrong as do not have
proper characterisation
Design Impact assessment
may be flawed as
don't have full
characterisation
4 4 21 Include waste classification in design phase
Environmental
(natural and social)
Unable to obtain a
favourable RoD (Total
project)
Construction No project 5 2 19 Analyse reasons and update application. Optimised
approach recommended
Environmental
(natural and social)
Delayed/non-approval by
Stakeholders (NGO and
general public, )
Construction Delay in
construction
4 3 18 Early start with process and ongoing contact with
Stakeholders through the EIA process.
Procurement Procurement of long lead
items, deep pumps,
pressure pipes, treatment
systems
Construction Delay in
construction
4 3 18 Plan the early procurement of long lead items
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Issue Area Issue/Risk Event Lifecycle
Phase Impact Description
Impact
Ranking Likelihood
Risk
Score Mitigation
Design Difficulty in routing pipeline
routes and locating
discharge points
Design Cost 4 3 18 Early identification of pipeline routes and discharge
points. Stakeholder engagement.
Programme Delayed feedback from EIA
input into project. May
result in amendments and
delays
Design Delays, cost 4 3 18 Assess environmental impacts in optimised approach
and in developing the EMPr for the project
Underground
mining
Stability of the
underground mining areas
Design Sustainability of the
project
infrastructure
4 3 18 Include geotechnical investigations. Ensure best
practice in the design of the underground mine
infrastructure, including stability analyses and collapse
mitigation assessments
Integration Incompatibility of the
proposed infrastructure to
be used in the short-term
solution
Operation Integration of the
proposed short-term
infrastructure with
the long-term
solution
4 3 18 Include sensitivity assessments in the design phase;
Include integration of long-term planning in the design
Environmental
(natural and social)
Rejection of EIA due to lack
of independence -
BKS/Golder doing design,
construction and
engineering as well as
environmental
Construction Delay in
construction
4 3 18 Outsource EIA or do a significant and robust PPP
process to manage stakeholders, which will drive up
costs
Reputational Poor public and industry
perception of the efficacy
of scheme
Design Reputational 3 4 17 Start public participation process early. Address
comments
Design Assumptions on condition
of existing infrastructure
inaccurate
Design Delays. Impact on
the accuracy of the
outputs of the Due
Diligence
3 4 17 Conduct studies in due diligence. Make
recommendations to address unknowns
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Issue Area Issue/Risk Event Lifecycle
Phase Impact Description
Impact
Ranking Likelihood
Risk
Score Mitigation
Acid mine drainage Assumptions about the
degree of interconnectivity
of the mining voids may
not be accurate
Design Rising water tables
and potential
decant, despite
pumping
3 4 17 Review all available information relating to mine
interconnectivity. Include monitoring and details of
back-up shafts
Geotechnical Increased time
requirements for
geotechnical investigations
and laboratory tests (three
basins).
Design Delay the design
phase and the
construction of the
works
3 4 17 Ensure planning and programming of the geotechnical
works
Eastern Basin Very little information is
available on the Pamodzi /
Aurora mines
Design Additional costs to
address
uncertainties
3 4 17 Identify personnel to engage. Include conservative
approach in design
Operational Treated water quality not
at discharge quality
Operation Environmental
impact; Public
dissatisfaction
3 4 17 Ensure discharge aspects covered in public
consultation. Ensure regulatory approval
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11. COST ESTIMATES SUMMARY
11.1 Capital Costs
A summary of the capital costs for the Western, Central and Eastern Basins is provided in Table 57.
Table 57: Summary of Capital Costs
Number Description Western Basin Central Basin Eastern Basin
1 AMD collection
infrastructure
R40,787,729 R45,127,500 R60,096,771
2 AMD treatment plant R73,255,525 R90,631,838 R108,010,007
3 Neutralised water
discharge
R1,316,400 R1,172,400 R1,622,400
4 Sludge handling and
disposal
R1,711,806 R6,200,000 R6,800,000
5 Earthworks and pipe
work
R31,008,353 R46,196,290 R28,480,441
6 Electrical control and
instrumentation
R25,960,790 R23,735,832 R30,856,582
7 Preliminaries and
Generals (12%)
R20,884,872 R25,567,663 R28,303,944
Total R194,925,475 R238,631,500 R264,170,100
Total all Basins R697,727,075
11.2 Operating Costs
A summary of the operating costs for the Western, Central and Eastern Basins is provided in Table 58.
Table 58: Summary of Operating Costs
Number Description Western Basin Central Basin Eastern Basin
1 O&M on CAPEX R3,600,100.00 R4,128,600.00 R4,571,500.00
2 Chemical Costs R31,177,274.00 R61,602,829.00 R60,444,482.00
3 Electricity Costs R13,527,200.00 R15,146,600.00 R15,520,700.00
Total R48,304,574.00 R80,878,029.00 R80,536,682.00
Total all Basins R209,719,285.00
11.3 Cash flow
Cash flow for the period from July 2011 until end of financial year 2015 is presented in Figure 18.
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Figure 18: Cash flow for the Witwatersrand Gold Fields Proposed Solutions
12. PROJECT IMPLEMENTATION STRATEGY
12.1 Introduction
The current scope of work and proposed further implementation phases of the project are divided
into the following work packages:
Western Basin Immediate Mitigation Measures (Technical and Regulatory Approval Process)
Short-Term Solution (Technical Process)
Short-Term Solution (Integrated Regulatory Process)
This chapter only deals with the implementation of the Technical Process associated with the Short-
Term Solution. For the implementation strategies associated with the other two work packages, refer
to Annexure F (BKS Report J01599/02, Formulation of Western Basin AMD Immediate Mitigation
Measures) and Annexure G (BKS Report J01599/08 Integrated Regulatory Process Strategy Report).
Depending on TCTA’s requirements and approval of the different work packages, these can be
amalgamated into one work package.
12.2 Project Objectives
The objective of the Short-Term Solution (Technical Process) is the implementation of underground
and above-ground infrastructure to mitigate and prevent the potential impacts associated with AMD
decant from the Western, Central and Eastern Basins.
The recommended short-term AMD mitigation schemes for the Western, Central and Eastern Basins
are described hereafter.
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12.2.1 Western Basin
Abstraction of AMD via installed pumps in Shaft No.8 to maintain the water level at or below the
ECL.
Construction of a new HDS treatment plant on the Randfontein Estates site.
Construction of a treated water pipeline to a suitable discharge point on the Tweelopiespruit,
flowing to the Crocodile West River.
Construction of a waste sludge disposal pipeline to the old open-cast pits, including Wes Wits Pit
and the Training Centre Pit.
12.2.2 Central Basin
Abstraction of AMD via installed pumps in SWV Shaft (either to pump to the ECL or to the CRG
proposed mining level of 400 m below SWV Shaft level).
Construction of a new HDS plant located at SWV Shaft.
Construction of a waste sludge to the DRD Gold (Crown) Knights Gold Plant.
Construction of a treated water pipeline to a suitable discharge point on the Elsburgspruit.
Planning for a future waste sludge pipeline to the Ergo Brakpan TSF and the disposal of sludge to
old ERPM underground workings.
12.2.3 Eastern Basin
Abstraction of AMD via installed pumps in Grootvlei No. 3 shaft at the pump depth to achieve the
ECL level, or the level to allow for Gold One to continue mining Sub-Nigel Shaft No. 1.
Construction of a new High Density Sludge (HDS) treatment plant adjacent to the Grootvlei No. 3
shaft, on the agricultural small holding site south of the abstraction point.
Construction of a sludge pipeline to the DRD Gold (Crown) Daggafontein Gold Plant for co-
disposal at the Daggafontein TSF.
Construction of a treated water pipeline to a suitable discharge point on the Blesbokspruit.
12.3 Project Tasks and High Level Schedule
The project tasks are summarised in Table 59.
Table 59: Project Tasks and High Level Schedule
Task
Nr. Task Description
High Level Schedule
Western Basin Central Basin Eastern Basin
1 Due Diligence Complete Complete Complete
2 Environmental / IRP July 11 – Aug 12 July 11 – Aug 12 July 11 – Aug 12
2 Design & Documentation Jul 11 – Jun 12 Jul 11 – Jun 12 Sep 11 – Sep 12
4 Construction Supervision Dec 11 – Aug 12 Dec 11– Aug 12 Mar 12 – Feb 13
5 Assessment and Close-Out Sep 13 – Nov 13 Sep 13 – Nov 13 Feb 14 – May 14
6 Operation and Maintenance Support Nov 13 – End 15 Nov 13 – End 15 May 14 – End 15
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12.3.1 Task 1: Due Diligence
This Task is complete for the Western, Central and Eastern Basins.
12.3.2 Task 2: Environmental / IRP
The key objectives of this task are as follows:
Develop an understanding of the Legislation governing the regulatory processes required to
undertake the project.
Develop a broad strategy to deal with the regulatory process for the project.
Develop a framework plan detailing the applications and documentation required in order to
ensure that the project follows the regulatory process identified.
12.3.3 Task 3: Design and Documentation
The key objectives of this task are as follows:
Augment the knowledge and understanding of the project through data collection and field
investigations in order to optimise the engineering design.
Prepare engineering designs, inclusive of drawings and specifications, for the purposes of inviting
tenders for the supply, construction and installation work.
Develop a Health and Safety specification for each Basin as per legal requirements, client
requirements and international best practice.
Prepare project cost estimates based on the engineering design work.
Develop procurement / contracting strategies for the long lead items and for the supply /
installation / construction work.
Implement a procurement / contracting strategy for the long lead items and for the supply /
installation / construction work, which will culminate in the purchase / delivery of long lead items
and the award of contracts for the supply, installation and construction work.
Develop a strategy to deal with the operations and maintenance of the project after
commissioning and start-up. This work must be done in time to mobilise the selected O&M team
/ company to be part of the project execution.
Complete engineering work to allow the appointed supply, install and construction contractors to
proceed.
Prepare a project operating and maintenance plan.
Implement a procurement / tendering process to select a competent and capable operating and
maintenance contractor.
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12.3.4 Task 4: Construction Supervision
This task will deal with the aspects of:
Construction site administration: engineering to deal with field discovered issues.
Quality Control and Assurance: contracts administration
Health and safety compliance monitoring
Environmental compliance monitoring
This task will also include the management and administration of the pre-commissioning,
commissioning and hand-over of the completed and operational project, including:
Sign-off on completed works
Pre-commissioning tests
Commissioning of works
Performance testing
Mobilisation of appointed O&M contractors(s).
Management and administration of repair and/or rectification of defects
Project hand-over
12.3.5 Task 5: Assessment and Close Out
Ensure conclusion of all contractual obligations.
Record lessons learned.
12.3.6 Task 6: Operation and Maintenance Support
Provide support to the O&M institution.
Review water quality results and action any necessary remedial measures.
12.4 Project Schedule and Key Milestones
Work shall be performed in accordance with the detailed project schedule, as Annexure M attached
to this report. Each task is effectively programmed, taking linkages and overlaps between the tasks
into account.
Key project milestones are summarised in Table 60.
Table 60: Key Project Milestones
Task Nr. Key Milestone Description Key Milestone Dates
Western Basin Central Basin Eastern Basin
2
Commence Task 2: Tender Design and
Documentation 18 Jul 11 18 Jul 11 16 Sep 11
Finalise Procurement / Contracting
Strategy and Plan 29 Jul 11 29 Jul 11 29 Jul 11
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Task Nr. Key Milestone Description Key Milestone Dates
Western Basin Central Basin Eastern Basin
Issue Tender(s) for Supply of Long Lead
Items 19 Sep 11 19 Sep 11 17 Nov 11
Award Contract(s) for Supply of Long
Lead Items 11 Nov 11 11 Nov 11 13 Jan 11
Finalise Tender Designs 27 Sep 11 27 Sep 11 16 Jan 11
Issue Tender(s) for Supply, Installation
and Construction 11 Oct 11 11 Oct 11 31 Jan 11
Award Contract(s) for Supply,
Installation and Construction 28 Nov 11 28 Nov 11 19 Mar 12
3
Commence Task 3: Detailed Design 28 Sep 11 28 Sep 11 17 Jan 12
Issue First Set(s) of Construction
Drawings to Contractor 9 Dec 11 9 Dec 11 30 Mar 12
Finalise Detailed Design 13 Jun 12 13 Jun 12 17 Sep 12
4
Commence Task 4: Site Supervision 9 Dec 11 9 Dec 11 30 Mar 12
Site Handover 9 Dec 11 9 Dec 11 30 Mar 12
Commence Site Establishment 9 Dec 11 9 Dec 11 30 Mar 12
Commence Construction 9 Jan 12 9 Jan 12 27 Apr 12
Commence Commissioning 24 Jul 12 24 Jul 12 14 Jan 13
Sign Off Completed Works. Handover
to O&M Contractor 29 Aug 12 29 Aug 12 27 Feb 13
Commence Operations 30 Aug 12 30 Aug 12 28 Feb 13
5
Commence Task 5: Assessment and
Close-Out 29 Aug 13 29 Aug 13 27 Feb 14
Complete Assessment and Close Out 28 Nov 13 28 Nov 13 29 May 14
12.5 Overarching Project Approach
The overarching approach as defined and contained in the project team’s scope of work will apply for
Tasks 2 through 5.
The following aspects, however, require specific mentioning and attention during project execution.
12.5.1 Procurement
The timeous completion of the project is dictated primarily by: (a) the procurement of long lead items
and (b) the implementation programme for the project. The critical path to completion lies along the
manufacture, supply, installation and commissioning of the large long-lead mechanical and electrical
items.
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A flexible and streamlined procurement strategy will be required in order to meet construction
targets and to provide sufficient float in the implementation programme of the project.
Separate tender and award dates will provide significant flexibility on the project and will allow the
project manager to remove potentially critical tasks and activities from the critical path of the project.
The procurement risks that would impact on the project should be effectively managed between
TCTA and the project team.
Due to the project programme and critical deadlines, certain infrastructure elements are classed as
long lead items that may need to be procured outside of the construction contract to allow sufficient
time for delivery. Potential long lead items are listed in Table 61.
Table 61: Potential Long Lead Items
No. Description Possible Suppliers Expected Procurement Duration
1 Deep Shaft Pipe
Columns
Carl Hamm (Ritz) 6 months
2 Variable Frequency /
Speed Drives
Rockwell Automation,
Siemens
6 to 9 months
3 Abstraction Pumps Ritz 10 months
4 Stainless Steel Pipes Columbus, Macsteel +
Specials
6 to 8 months
5 Aerators * WEC, Eigenbau, Ertec,
Lektatek
5.5 months
6 Gearboxes WEC, Eigenbau, Ertec, Hansen 5.5 months
7 Lime Slaker* Bulkmatic 12 to 14 months. 8 to 10 weeks per
dosing system. 6 dosing systems
are needed.
8 Lime Silo* Bulkmatic 12 to 32 months if we go for a
single supplier. This supplier can
produce 2 silos every 8-10 wks, but
14 are needed. 7 silos for
limestone and 7 for lime. However,
another limestone dosing system
that does not require silos and can
retrofit limestone silos later has
been allowed for.
9 Clarifier Bridges * SAME (SA Mechanical
Erection), Botjeng, Lektratek
6 months
12.5.2 Health and Safety
A Hazard Identification and Risk Assessment (HIRA) was conducted during the Due Diligence task,
based on site visits to the relevant basins. During the process, possible control measures were
identified. The HIRA for the three basins is included in Annexure L.
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The HIRA will is a live document that will be measured, evaluated and updated throughout the
implementation of the project.
12.5.3 Project Risk Assessment
A register of possible risks as developed during the project stage, updated and expanded based on a
formal project risk assessment process. The outcome of this work is a risk register that identifies,
characterise and rates the risks facing the project, as well as indentifies risk mitigation measures. The
risk register is included in Annexure L.
Table 62 summarises the high risks that were identified for the project.
Table 62: High Risks for the Project
Issue Area Issue/Risk Event Lifecycle Phase Impact Description
Waste Availability of sludge disposal
sites. Uncertainty on waste
handling and disposal.
Design Short-term vs. long-
term schemes to be
clarified
Environmental
(natural and social)
Unable to obtain a favourable
directives for short-term project
implementation
Construction Delay in construction
Environmental
(natural and social)
Delayed / non-approval or
opposition by stakeholders
(Government)
Construction Delay in construction
Regulatory
approval
Potential delays in NNR
approval.
Construction Delay in construction
Waste Waste characterisation.
Impact assessment based on
incomplete information
Design Impact assessment
may be flawed as it
does not have
accurate sludge
characterisation
Environmental
(natural and social)
Unable to obtain a favourable
RoD (Total project)
Construction No project
Environmental
(natural and social)
Delayed / non-approval by
stakeholders (NGO and general
public, )
Construction Delay in construction
Procurement Procurement of long lead items,
deep level pumps, pressure
pipes, treatment mechanical
systems
Construction Delay in construction
Design Difficulty in routing pipeline
routes and locating discharge
points
Design Cost
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Issue Area Issue/Risk Event Lifecycle Phase Impact Description
Programme Delayed feedback from
regulatory approval inputs into
project. May result in
amendments and delays
Design Delays, Cost
Underground
mining
Stability of the underground
mining areas
Design Sustainability of the
project infrastructure
Integration Incompatibility of the proposed
infrastructure to be used in the
long-term solution
Operation Integration of the
proposed short-term
infrastructure with
the long-term
solution
Environmental
(natural and social)
Rejection of EIA due to lack of
independence - BKS/Golder
doing engineering design,
construction monitoring as well
as environmental approvals
Construction Delay in construction
Reputational Poor public and industry
perception of the optimisation
of scheme
Design Reputational
Design Assumptions on condition of
existing infrastructure
inaccurate
Design Delays. Impact on the
implementation of
the Due Diligence
recommendations
Acid mine drainage Assumptions about the degree
of interconnectivity of the
mining voids may not be
accurate
Design Rising water tables
and potential decant,
despite mine
dewatering
Geotechnical Increased time requirements for
geotechnical investigations and
laboratory tests (three basins).
Design Delay of the
engineering design
phase and the
construction of the
works
Eastern Basin Very little information is
available on the Pamodzi /
Aurora Mines
Design Additional costs to
address uncertainties
Operational Treated water quality not at
discharge quality
Operation Environmental
impact; Public
dissatisfaction
The Risk Register will be used as part of project implementation toolbox to continuously evaluate the
project risks and potential mitigation measures.
Risk assessment of the project has to be executed continuously during the execution of the project.
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The Risk Register is a living document with new risks identified and added to the register and
anticipated risks either resolved or avoided. These will be indicated as resolved, but will remain on
the risk register for record purposes.
13. LONG-TERM MINE WATER RECLAMATION AND REUSE
13.1 Short-Term Measures
TCTA, related to AMD management, was mandated by the DWA to specifically deal with the following
two aspects and recommendations of the Inter-Ministerial Committee Report:
Stabilise and control the mine water levels in the respective mining basins at or below the ECLs.
Pump the AMD to surface, neutralise it and discharge it.
Planning for the implementation of the short-term AMD management measures was done, keeping
the potential long-term water reclamation and reuse in mind as it relates to:
Quantify the mine water in the respective mining basins, as a reliable long-term water resource.
Location of AMD-related infrastructure, specifically the AMD treatment plants to accommodate
the potential longer-term water reclamation and reuse.
Selecting AMD neutralisation treatment technology, which would be suitable as a pre-treatment
to future desalination and reclamation treatment.
The short-term AMD management measures thus cater for the future reclamation and reuse of mine
water.
13.2 Future Water Reclamation and Reuse
The vision for the future water reclamation and reuse is based on the following:
Treatment of the neutralised AMD to a quality fit for safe drinking water use.
The proposed AMD treatment plants are located close to large urban water use centres:
- The Western Basin AMD treatment plant is located close to Randfontein and Mogale City.
- The Central Basin AMD treatment plant is located close to Germiston and Boksburg.
- The Eastern Basin AMD treatment plant will be located close to Springs and Nigel.
The reclaimed mine water would be supplied to Rand Water or large metropolitan municipal
reservoirs for blending with the Rand Water bulk water supply. The blended water would be
distributed for municipal and industrial use.
A portion of the neutralised AMD would still be supplied to active surface re-mining operations
(and potentially industrial water users).
13.3 Technology Aspects of Water Reclamation and Reuse
A number of mine water desalination technologies can find application to the reclamation of mine
water:
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Sulphate precipitation technology
Membrane desalination
Ion exchange desalination
The sulphate precipitation technology (Barium Sulphate precipitation and the Ettringite process) has
been research and piloted. There are, however, no large industrial-scale treatment plants, using these
precipitation technologies, in operation.
Membrane-based desalination technologies (nano-filtration end reverse osmosis) are well established
and a number of full-scale plants are operational, both globally and in South Africa.
Ion exchange desalination is a well-established technology and can be linked to the recovery of useful
by products. The application of the technology to mine water is demonstrated, but no large-scale
industrial plants are in operation.
The South African water treatment industry is geared and capable of the supply and installation of
mine water reclamation plants, including mine water desalination facilities.
13.4 Water Resources Context of Reclamation and Reuse
The DWA has conducted a number of studies related to the treatment and reuse of mine water. AMD
desalination is considered economically viable compared to future water resource augmentation
projects to the Vaal River system in terms of:
The removal of the salt load associated with the mine water will no longer require the release of
Vaal Dam water to dilute the salinity load for the protection of the middle Vaal River water uses.
The reclaimed mine water is a valuable water resources, strategically located with respect to the
large Gauteng water users.
Mine water as an additional resource can be developed relatively quickly, compared to other
conventional surface water resource development projects, such as the Lesotho Highlands Phase
II.
Reclaimed mine water can help address the predicted medium-term water shortfall in the
Gauteng area, until the Lesotho Highlands Project Phase II is commissioned in 2020.
It thus makes economical sense to develop the Witwatersrand AMD as a strategic source of water to
augment the traditional sources of water to Gauteng in particular and the Vaal River system in
general.
13.5 Financial Aspects of Water Reclamation
The cost of AMD treatment and reclamation is high compared to historical conventional surface water
resources. However, it can be price competitive in the Vaal River system, compared to future water
reclamation schemes, which will bring water over longer distances at escalated costs.
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The AMD treatment and reclamation scheme infrastructure capital investment can be financed by a
combination of:
Capital contributions from gold mines;
Infrastructure and in-kind contributions from gold mines;
Project finance acquired by TCTA;
Infrastructure grants from National Treasury.
The AMD treatment and reclamation scheme operations and management costs can be recovered by:
Sale of neutralised water to mines;
Sale of neutralised water to industry;
Sale of drinking water to Rand Water and metropolitan municipalities.
It is feasible to develop a sustainable financial arrangement around the long-term implementation of
a mine water reclamation and reuse project.
13.6 Institutional Aspects of Water Reclamation and Reuse
National government, through TCTA as the implementing agent has taken the initiative on the
Witwatersrand AMD treatment and potential future mine water reclamation. A viable institutional
model will require involvement and participation from:
Government departments (specifically, the Department of Water Affairs)
TCTA
Mining companies
Bulk water services providers such as Rand Water
Bulk water services authorities, such as the Gauteng metropolitan municipalities
The simplest form of institutional model may be for TCTA to take the lead, as mandated by the DWA,
with Rand Water as the operating company. Alternatively, public-private partnerships involving TCTA,
water companies and mining companies can be considered under the leadership of TCTA. The
initiatives taken by TCTA focused attention on the need to resolve the appropriate institutional
model, both for the short-term AMD management measures as well as the long-term mine water
reclamation and reuse.
14. RECOMMENDATIONS
The recommendations from the Task 1: Due Diligence work are covered in this section.
14.1 Environmental Critical Level (ECL)
The agreed ECL levels for each of the individual mining basins are summarised in Table 63.
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Table 63: Environmental Critical Levels
Basin
Decant
Level
(m amsl)
Decant
Position
ECL
(m amsl) Rationale
Western 1,680 Black Reef
Incline,
Winze No.
17 and 18
1,550 ECL set for protection of the dolomitic
groundwater resources at the Cradle
of Humankind World Heritage Site.
Central 1,617 Cinderella
East
1,467 ECL set below the decant level for
protection of the weathered and
fractured aquifers within the basin.
Eastern 1,549 Nigel Shaft
No 3
1,280 ECL set below the base of the
dolomitic formations on the Eastern
Basin for protection of the dolomitic
groundwater resources.
14.1.1 Water volumes and flow rates
The selected mine dewatering rates are provided below:
Western Basin:
Sustained base flow = 27Mℓ/day
Peak pumping flow = 35Mℓ/day
Central Basin:
Sustained base flow = 57Mℓ/day
Peak pumping flow = 84Mℓ/day
Eastern Basin:
Sustained base flow = 82Mℓ/day
Peak pumping flow = 110Mℓ/day
14.1.2 Water quality
The expected mine water quality to be treated is summarised in Table 64 for the individual mining
basins.
Table 64: Expected Water Quality by Basin
Water
quality Parameter Units
Western Basin
(95th
percentile)
Central Basin
(95th
percentile)
Eastern Basin
(flooded condition)
TDS mg/ℓ 7,174 7,700 5,500
Conductivity mS/m 548 730 450
Calcium (Ca) mg/ℓ 461 580 550
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Water
quality Parameter Units
Western Basin
(95th
percentile)
Central Basin
(95th
percentile)
Eastern Basin
(flooded condition)
Magnesium (Mg) mg/ℓ 345 380 230
Sodium (Na) mg/ℓ 139 150 325
Sulphate (SO4) mg/ℓ 4,556 5,200 3,275
Chloride (Cℓ) mg/ℓ 65 260 260
pH - 3.4-4.0 2.3 (5th
percentile) 5.0
Acidity (CaCO3)* mg/ℓ 2,560 2,425 750
Iron (Fe) mg/ℓ 933 1,000 370
Aluminium (Aℓ) mg/ℓ 54 50 1
Manganese (Mn) mg/ℓ 312 60 10
Uranium (U) mg/ℓ 0.2 -- --
14.2 Treatment Technology
It is recommended that the following treatment technology and chemical reagent combination be
used for the treatment of the Witwatersrand Gold Fields AMD:
Oxidation by aeration.
Pre-neutralisation with limestone.
Neutralisation and metals removal with lime, produced by the slaking of quicklime.
Gypsum crystallisation to remove excess sulphate from solution.
14.3 Western Basin: Immediate Mitigation Measures
The AMD mitigation measures can be implemented practically in the Western Basin based on the
following:
Upgrading and retrofitting the existing Rand Uranium Treatment Plant as the best opportunities
in terms of treatment capacity and ease of implementation.
Bring the Rand Uranium Treatment Plant’s existing infrastructure into operation, after installing
appropriate mechanical and electrical equipment.
The potential AMD treatment capacity, including the existing single operational treatment train is
estimated to be 26Mℓ/d to 32Mℓ/d.
14.4 Layout of Short-Term AMD Schemes
14.4.1 Western Basin
Abstraction of AMD via installed pumps in Shaft No.8 at a depth to achieve the ECL.
Construction of a new HDS treatment plant on the Randfontein Estates site.
Construction of a treated water pipeline to a suitable discharge point on the Tweelopiespruit,
flowing to the Crocodile West River.
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Construction of a waste sludge disposal pipeline to the old opencast pits, including Wes Wits Pit
and the Training Centre Pit.
14.4.2 Central Basin
Abstraction of AMD via installed pumps in SWV Shaft (either to pump to the ECL or to the CRG-
proposed mining level of 400 m below SWV Haft level).
Retrofit and upgrade the HDS plant at SWV Shaft.
Construct a waste sludge pipeline to the DRD Gold (Crown) Knights Gold Plant.
Construct a treated water pipeline to a suitable discharge point on the Elsburgspruit.
Planning for a future waste sludge pipeline to the Ergo Mega Dump.
14.4.3 Eastern Basin
Abstraction of AMD via installed pumps in Grootvlei No. 3 shaft at the pump depth to achieve the
ECL level, or the level to allow for Gold One to continue mining Sub-Nigel Shaft No. 1.
Construction of a new High Density Sludge (HDS) treatment plant adjacent to the Grootvlei No. 3
shaft, on the agricultural small holding site south of the abstraction point.
Construction of a sludge pipeline to the DRD Gold (Crown) Daggafontein Gold Plant.
Construction of a treated water pipeline to a suitable point on the Blesbokspruit.
14.5 Rock Stability
The Rand Uranium Shaft No. 8 may be suitable for use as a pumping shaft, however, very little
information is available for this shaft, even in published form. More information is required to
conduct a meaningful stability analysis on this shaft barrel.
There are no rock engineering-related fatal flaws with regard to the use of ERPM SWV Shaft, ERPM
Ventilation Shaft, ERPM Cinderella East Shaft and Grootvlei Shaft No. 3 as possible pumping shafts.
Sallies Shaft No. 1 is filled in with rock and cannot be used as a pumping shaft.
It is recommended that physical mapping or video camera mapping / logging of the shaft barrels be
done to confirm the conditions of the shaft barrels
14.6 Implementation Costs
The capital and annual operating cost estimates for the AMD treatment plants for the three basins are
shown in the following tables.
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Table 65: Summary of AMD Treatment Plant Capital Costs for All Basins
Number Description Western Basin Central Basin Eastern Basin
1 AMD Collection
Infrastructure
R4,219,500.00 R19,078,800.00 R17,041,300.00
2 AMD Treatment Plant R74,781,400.00 R96,301,000.00 R123,750,000.00
3 Neutralised Water
Discharge
R2,551,700.00 R5,915,500.00 R5,553,000.00
4 Sludge Handling and
Disposal
R742,500.00 R7,095,000.00 R17,000,000.00
5 Earthworks and Pipe Work R82,243,800.00 R53,879,200.00 R44,288,800.00
6 Electrical Control and
Instrumentation
R25,960,800.00 R23,735,800.00 R30,856,600.00
7 Contingencies (15%) R28,574,945.00 R30,900,795.00 R35,773,455.00
Total R219,074,600.00 R236,906,100.00 R274,263,200.00
Total (all Basins) R730,243,900.00
Table 66: Summary of AMD Treatment Plant Annual Operating Costs for All Basins
Number Description Western Basin Central Basin Eastern Basin
1 O&M on CAPEX R3,600,100.00 R4,128,600.00 R4,571,500.00
2 Chemical Costs R83,677,700.00 R108,678,900.00 R80,907,500.00
3 Electricity Costs R13,527,200.00 R15,146,600.00 R15,520,700.00
Total R100,805,000.00 R127,954,100.00 R100,999,700.00
Total (all Basins) R329,758,800.00
14.7 Integrated Regulatory Process
An optimised process approach has been recommended so that the project milestones can be met,
while ensuring that the necessary regulatory approvals are in place. The conventional regulatory
approach will have to be completed in parallel with the optimised process.
The essential feature of the optimised process is that TCTA will request:
The DWA to provide it with the necessary directives to address AMD without it having to obtain
an upfront Water Use Licence and Environmental Authorisation,
The DMR to provide exemptions for participating mines, so that they do not need to amend their
environmental management programmes immediately.
14.8 Risk Assessment and Risk Management
The high-level risks to the project were identified through a risk assessment process. The-high-level
risks relate mainly to:
Management of the AMD treatment plant waste sludge.
Delays in the approvals in the environmental regulatory process.
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Delays and/or non-approval by stakeholders (Government, mining community and the general
public).
Programme delays during the design phase from accommodating project scope changes arising
from the regulatory process.
Inaccuracies in the technical assumptions, such as the inter-connectivity of the mine workings in
the basins.
Potential mitigation measures for the risks were identified.
14.9 Implementation Plan
An implementation plan for the project was prepared, the key aspects of which are as follows:
Commissioning of the AMD treatment plants by August 2011 for the Western and Central Basins,
and by February 2013 for the Eastern Basin.
A flexible and streamlined procurement strategy will be required in order to meet construction
targets and to provide sufficient float into the implementation programme of the project.
Measure and manage the health and safety risks of the project through the Hazard Identification
and Risk Assessment (HIRA) process.
Manage the high-level risks identified for the project.
15. REFERENCES
Scott, R. Flooding of the Central and East Rand Gold Mines: An investigation into controls over the
inflow rate, water quality and predicted impacts of flooded mines, WRC report No. 486/1/95, 1995.
WUC Reports
Report on the Water Resource Estimation in the East Rand Basin (Report No. 11590-8757-15,
WUC by Golder and Associates Africa, July 2009).
Resource Estimation in the West Rand Basin (Report No. 11590-8758-16, WUC by Golder and
Associates Africa, July 2009)
Resource Estimation in the Central Rand Basin (Report No. 11590-8759-17, WUC by Golder and
Associates Africa, July 2009)
Mine water quality assessment of the Witwatersrand mining basins (Report No. 11590-8744-14,
WUC by Golder and Associates Africa, June 2009).
Consideration of Alternatives for Sludge Disposal (Report No. 11590-8911-21, WUC by Golder and
Associates Africa, October 2009)
TCTA 08-041 Witwatersrand Gold Fields: Acid Mine Drainage (Phase 1) Due Diligence August 2011
ANNEXURE A
Basis of Engineering Design
(BKS Report No J01599/01)
TCTA 08-041 Witwatersrand Gold Fields: Acid Mine Drainage (Phase 1) Due Diligence August 2011
ANNEXURE B
Environmental Critical Levels
(BKS Report No J01599/03)
TCTA 08-041 Witwatersrand Gold Fields: Acid Mine Drainage (Phase 1) Due Diligence August 2011
ANNEXURE C
Water Balance and Levels
(BKS Report No J01599/06)
TCTA 08-041 Witwatersrand Gold Fields: Acid Mine Drainage (Phase 1) Due Diligence August 2011
ANNEXURE D
Treatment Technology Selection
(BKS Report No J01599/07)
TCTA 08-041 Witwatersrand Gold Fields: Acid Mine Drainage (Phase 1) Due Diligence August 2011
ANNEXURE E
Process Design Report
(BKS Report No J01599/09)
TCTA 08-041 Witwatersrand Gold Fields: Acid Mine Drainage (Phase 1) Due Diligence August 2011
ANNEXURE F
Formulation of Western Basin AMD
Immediate Mitigation Measures Report
(BKS Report No J01599/02)
TCTA 08-041 Witwatersrand Gold Fields: Acid Mine Drainage (Phase 1) Due Diligence August 2011
ANNEXURE G
Integrated Regulatory Process (IRP) Report
(BKS Report No J01599/04)
TCTA 08-041 Witwatersrand Gold Fields: Acid Mine Drainage (Phase 1) Due Diligence August 2011
ANNEXURE H
Integrated Regulatory Process (IRP)
Strategy Report
(BKS Report No J01599/08)
TCTA 08-041 Witwatersrand Gold Fields: Acid Mine Drainage (Phase 1) Due Diligence August 2011
ANNEXURE I
Sludge Disposal Alternatives Report
(BKS Report No J01599/10)
TCTA 08-041 Witwatersrand Gold Fields: Acid Mine Drainage (Phase 1) Due Diligence August 2011
ANNEXURE J
Rock Engineering Assessment of Shaft
Stability Report
(BKS Report No J01599/11)
TCTA 08-041 Witwatersrand Gold Fields: Acid Mine Drainage (Phase 1) Due Diligence August 2011
ANNEXURE K
Options Analysis Matrix
TCTA 08-041 Witwatersrand Gold Fields: Acid Mine Drainage (Phase 1) Due Diligence August 2011
ANNEXURE L
Risk Register
TCTA 08-041 Witwatersrand Gold Fields: Acid Mine Drainage (Phase 1) Due Diligence August 2011
ANNEXURE M
Proposed Project Programme