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$: BKS (Pty) Ltd TCTA J01599 Final J01599/05 Due diligence ... Due Diligence - Final.pdfReports\10.2 Technical Reports\Portion 1 Due Diligence Final 2011-08-25\05 Due Diligence\J01599-05$
\\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


Reviewed by AM van Niekerk


Approved by F Wimberley


Approved by Dr G H de Villiers


Ready for Issue A Augere


Approval by TCTA

Approved by :


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


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


6.3.1 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


7.1.1 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


7.2.6 Consideration of Integration with Future Long Term AMD Treatment ..................... 67


7.3.1 Shaft Stability ............................................................................................................. 68

7.3.2 Abstraction and collection infrastructure .................................................................. 68


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


8.1.1 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


8.2.7 Consideration of Integration with Future Long-Term AMD Treatment ..................... 93


8.3.1 Shaft Stability ............................................................................................................. 94

8.3.2 Abstraction Infrastructure ......................................................................................... 94


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.



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.



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.



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.



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.



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.



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.



Low probability of stress-induced failure.



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.



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.



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.



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:



Eastern basin:



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




Sodium (Na) mg/ℓ 139 150 325

Sulphate (SO4) mg/ℓ 4,556 5,200 3,275


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




Refer to Basis of Engineering Design (BKS Report No J01599/01), included as Annexure A.



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.



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



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:


Pre-neutralisation with limestone.

Neutralisation and metals removal with lime, produced by the slaking of quicklime.


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.



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.



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.



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.



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:



- 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



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;



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



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.



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



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:



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.


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.



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


WB5 North-East Shaft North-East Shaft areas Battery 7 Open Pit North, Muldersdrift

Loop, or South


WB6 East Champ

d’Or Shaft

East Champ d’Or Shaft

area

Local disposal area

on site

North, Muldersdrift

Loop, or South


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:



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.



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.


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.


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.



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.


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.


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.



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.



In future, reclaimed water for potable use can be pumped to the Krugersdorp or Witpoortjie


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


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


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.


about 3 km from


connected to the

Western Basin.



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.


about 2.5 km from


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 + + + +


Option WB3: Randfontein

Estate + + + +


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:



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+):



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.



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


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:



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.


6.3.1 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


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



(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



(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.



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




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





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


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.



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



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 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





Table 19: Description of Treated Water Pipeline Route (Western Basin)


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.





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





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


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





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


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


Chainage = 2,540-4,150 m

Length = 1,610 m



Table 20: Major Service Crossings - Treated Water Pipeline (Western Basin)

No Service Method of Crossing


5. Main Reef Road (R28) 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



3 Neutralised water discharge

Civil / Structural Work 294,000.00 R1,316,400


4 Sludge Handling and Disposal


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




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.



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



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.



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.



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.


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.



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.


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.


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.



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.


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:



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



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.


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;



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



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.



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.


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


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.



- 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.



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



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.



(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.



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.



Figure 9: Scenario 1 - Pumping 34 Mℓ/day

Figure 10: Scenario 2 - Pumping 57 Mℓ/day



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



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

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Water Level Drawdown at 72 Ml/d and 84 Ml/d

72 Ml/d 84 Ml/d 250m below SWV 400m below SWV



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:



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.



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.


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.



The future scheme considered in the following manner in the short-term due diligence:


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).



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.



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


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




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.




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

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Water Level Fluctuation at 57 Ml/d

Water level ECL




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




for losses)

Duty Pumps (No) 2



Power Absorbed (kW) 2,240



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.



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



Length of Pipe (m) 100


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.



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 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.



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.


A preliminary design of a terrace was done and the plant was laid out on the terrace.


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.



(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.


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.



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


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 Head (m) 20

Duty Pumps (No) 2


(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.



Table 32: Sludge Pipeline (Central Basin)

Parameter Value

Flow (Mℓ/day) 5.3

Flow (m3/s) 0.06





Table 33: Description of Sludge Pipeline Route (Central Basin)


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


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.


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




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


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)


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.



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




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



2 AMD Treatment Plant

Civil / structural work 39,125,000.00 R90,631,838


3 Neutralised Water Discharge

Civil / structural work 150,000.00 R1,172,400



Civil / structural work 1,700,000.00 R6,200,000



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.




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


8.1.1 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



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

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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



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).



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).



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.


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



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.



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.


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.



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.




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.



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



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.


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.



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;



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.


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


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.



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:



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.


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.



The costs of a future scheme were estimated the following manner during the short-term due

diligence:


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.



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.



8.3.2 Abstraction Infrastructure


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


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:



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.


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



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.


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




for losses)

Duty Pumps (No) 3




Parameter Value


Power Absorbed (kW) 5,040



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



Parameter Value




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 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



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.


A preliminary design of a terrace was done and, once designed, the plant was laid out on the terrace.


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.



(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.


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



An LV Room, including auxiliary items, control desk and remote control via GPRS or fibre optic

back to the control building.


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


Conceptual layout drawings are provided (drawings J01599-05-004 to 007) for the sludge disposal

infrastructure.

(a) Pumps


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 Head (m) 40

Duty Pumps (No) 2


(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.



Table 46: Sludge Pipeline (Eastern Basin)

Parameter Value Flow (Mℓ/day) 4.7

Flow (m3/s) 0.05




The pipeline route is described in Table 47.

Table 47: Description of Sludge Pipeline Route (Eastern Basin)


1. Proposed HDS

Site

The pipeline will follow the access road as far as possible. The pipeline


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.


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


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


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




Chainage = 3,700-3,750 m

Length = 50 m




8. Southerly

Direction to

N17 Road

The pipeline turns to run in a southerly direction. No services are



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




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)


1. Rural road Half width construction

2. R29 Road 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.



Table 49: Treated Water Pipeline (Eastern Basin)

Parameter Value

Flow (Mℓ/day) 104

Flow (m3/s) 1.2


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



2 AMD Treatment Plant



3 Neutralised Water Discharge







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


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



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



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



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.


\\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 107

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


Delayed/non approval by

Stakeholders (Government)


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

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


Unable to obtain a

favourable RoD (Total

project)

Construction No project 5 2 19 Analyse reasons and update application. Optimised

approach recommended

Environmental


Delayed/non-approval by

Stakeholders (NGO and

general public, )


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

4 3 18 Plan the early procurement of long lead items





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


Rejection of EIA due to lack

of independence -

BKS/Golder doing design,

construction and

engineering as well as

environmental


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





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



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


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


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.



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.



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


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 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



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.



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


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



Task Nr. Key Milestone Description Key Milestone Dates


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.



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.



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


Unable to obtain a favourable

directives for short-term project

implementation

Construction Delay in construction

Environmental


Delayed / non-approval or

opposition by stakeholders

(Government)


Regulatory

approval

Potential delays in NNR

approval.


Waste Waste characterisation.

Impact assessment based on

incomplete information

Design Impact assessment

may be flawed as it

does not have

accurate sludge

characterisation

Environmental


Unable to obtain a favourable

RoD (Total project)

Construction No project

Environmental


Delayed / non-approval by

stakeholders (NGO and general

public, )


Procurement Procurement of long lead items,

deep level pumps, pressure

pipes, treatment mechanical

systems


Design Difficulty in routing pipeline

routes and locating discharge

points

Design Cost



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


Rejection of EIA due to lack of

independence - BKS/Golder

doing engineering design,

construction monitoring as well

as environmental approvals


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.



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:



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.



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.



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:



Central Basin:



Eastern Basin:



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





Water

quality Parameter Units

Western Basin

(95th

percentile)

Central Basin

(95th

percentile)

Eastern Basin

(flooded condition)


Sodium (Na) mg/ℓ 139 150 325

Sulphate (SO4) mg/ℓ 4,556 5,200 3,275


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




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:


Pre-neutralisation with limestone.

Neutralisation and metals removal with lime, produced by the slaking of quicklime.


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.


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.



Construction of a waste sludge disposal pipeline to the old opencast pits, including Wes Wits 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 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.



Table 65: Summary of AMD Treatment Plant Capital Costs for All Basins


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


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.



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)


ANNEXURE A

Basis of Engineering Design

(BKS Report No J01599/01)


ANNEXURE B

Environmental Critical Levels



ANNEXURE C

Water Balance and Levels



ANNEXURE D

Treatment Technology Selection



ANNEXURE E

Process Design Report



ANNEXURE F

Formulation of Western Basin AMD

Immediate Mitigation Measures Report


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