Magdalena Discard Dump Conceptual Design rev001€¦ · conceptual design for the Magdalene coal...

Est. 1987

63 Wessel Road Woodmead PO Box 2597 Rivonia 2128

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MAGDALENA COLLEIRY

COAL DISCARD DISPOSAL FACILITY

CONCEPTUAL DESIGN

Compiled for

Zinoju Investments (Pty) Ltd

W Dressel Pr Tech Eng

For GCS (Pty) Ltd

October 2006

Our Ref: SLA.06.190 rev001

Your Ref:

Magdalena Discard Disposal Facility – Conceptual Design i

GCS (Pty) Ltd October 2006 SLA.06.190

MAGDALENA COLLIERY

COAL DISCARD DISPOSAL FACILITY

CONCEPTUAL DESIGN

REPORT NO: SLA.06.190

Client: Zinoju Investments (Pty) Ltd

66 Karellandman Street Dundee 3000

DOCUMENT ISSUE STATUS

Report Issue Final

Reference Number SLA.06.190

Title Name Signature Date

Author Waldo Dressel

Oct 2006

Project Director Waldo Dressel

Oct 2006

Technical Reviewer Lynn Fitschen Oct 2006

This report is not to be used for contractual or engineering purposes unless the report is designated “FINAL”

Magdalena Discard Disposal Facility – Conceptual Design


EXECUTIVE SUMMARY

GCS (Pty) Ltd was appointed by Slater Coal (Zinoju Investments (Pty) Ltd) to carry out a conceptual design for the Magdalene coal discard disposal facility approximately 22 km north- northwest of the town of Dundee in Northern Kwazulu Natal. The purpose of the report is to present the conceptual design for the coal discard facility.

The life of mine is planned for 10 yeas and discard will be generated at 16800 tonnes per month. A site selection process has been followed and a preferred coal discard disposal facility was selected. GCS (Pty) Ltd carried out a preliminary geotechnical investigation at the preferred site.

The discard disposal facility will accommodate the coal discard that will be generated during the life of mine and the facility will have a footprint area of approximately 20 ha and will reach a final height of 28m. The dump will be developed by means of an upstream construction method by tipping dry coal with trucks. The coal discard will be nominally compacted in layers.

The conceptual design includes the following components:

Surface water management infrastructure.

Temporary and final upstream storm water diversion for separation of clean and dirty water.

Under drainage system to minimise seepage to groundwater.

Pollution control measures.

The outer slopes of the discard facility will be constructed at an overall slope of 1:3 (v:h) and will be continuously covered with topsoil and vegetated.



TABLE OF CONTENTS

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

2 PROJECT REQUIREMENTS .......................................................................................... 1

3 SITE LOCATION AND DESCRIPTION ........................................................................... 1

4 AVAILABLE INFORMATION ........................................................................................... 2

5 SURVEY.......................................................................................................................... 2

6 SITE SELECTION ........................................................................................................... 2

6.1 Introduction............................................................................................................... 2

6.2 Identification of Candidate Sites ............................................................................... 2

6.3 Site Locality .............................................................................................................. 3

6.4 Fatal Flaws And Critical Factors............................................................................... 3

6.5 Numerical Assessments ........................................................................................... 3

7 SAFETY CLASSIFICATION ............................................................................................ 4

8 GEOTECHNICAL INVESTIGATION................................................................................ 5

8.1 Site No. 1.................................................................................................................. 5

8.2 Site No. 2.................................................................................................................. 6

9 DEPOSITION MANAGEMENT PLAN ............................................................................. 6

9.1 Coarse Coal Discard ................................................................................................ 6

9.1.1 Capacity Analysis .............................................................................................. 6

9.1.2 Deposition Method ............................................................................................ 7

9.1.3 Access Control .................................................................................................. 7

9.1.4 Dump Construction............................................................................................ 7

9.2 Slurry Disposal ......................................................................................................... 7

9.3 Management............................................................................................................. 8

10 SLOPE STABILITY ANALYSIS.................................................................................... 8

10.1 Methodology ......................................................................................................... 8

10.2 Material Strength Parameters ............................................................................... 9

10.3 Phreatic Conditions............................................................................................... 9

10.4 Earthquake Conditions.......................................................................................... 9

10.5 Slope Stability Results .......................................................................................... 9

11 SURFACE WATER MANAGEMENT PLAN............................................................... 10

11.1 Surface Water Management Principles .............................................................. 10



11.2 Freeboard ........................................................................................................... 10

11.3 Water Discharge Criteria..................................................................................... 10

11.4 Seepage Predictions........................................................................................... 10

11.5 Under Drainage System...................................................................................... 11

11.6 Storm Water Control ........................................................................................... 11

11.7 Water Balance .................................................................................................... 11

11.8 Return Water and Decant Systems .................................................................... 12

12 POLLUTION CONTROL MEASURES ....................................................................... 13

13 EROSION POTENTIAL AND PROTECTION ............................................................ 14

14 CONCEPTUAL REHABILITATION PLAN.................................................................. 15

14.1 Introduction ......................................................................................................... 15

14.2 Objectives ........................................................................................................... 15

14.3 Final Geometry ................................................................................................... 15

14.4 Final Surface Cover ............................................................................................ 15

14.5 Control of Water.................................................................................................. 16

14.6 Vegetation........................................................................................................... 16

15 CONCEPTUAL DRAWINGS...................................................................................... 16

16 CONCLUSIONS AND RECOMMENDATIONS.......................................................... 17

LIST OF TABLES Table 1: Fatal Flaw and Critical Factors ................................................................................. 3

Table 2: Ranking Matrix Results ............................................................................................. 3

Table 3: SABS (0286:1998) Safety Classification................................................................... 4

Table 4: Hazard Rating Results .............................................................................................. 4

Table 5: Summary of Capacity Analyses ................................................................................ 7

Table 6: Dump Construction with Coal Discard ...................................................................... 7

Table 7: Opencast................................................................................................................... 8

Table 8: Material Strength Parameters ................................................................................... 9

Table 9: Slope Stability Results .............................................................................................. 9

Table 10: Climatic Water Balance......................................................................................... 11

Table 11: Summary of Return Water System ....................................................................... 12

Table 12: Pollution Control Measures................................................................................... 13

Table 13: Factors Affecting the Erosion of Cover Systems .................................................. 14

Table 14: Conceptual Drawings............................................................................................ 16



LIST OF APPENDICES

Appendix A Site Selection

Appendix B Geotechnical Investigations

Appendix C Capacity Analysis

Appendix D Slope Stability

Appendix E Conceptual Drawings

Appendix F Safety Classification

Magdalena Discard Disposal Facility – Conceptual Design 1


1 INTRODUCTION

GCS (Pty) Ltd was appointed to carry out the necessary design activities and tasks, in accordance with the specified requirements, to present a conceptual design for the establishment of a coal discard disposal facility for the Magdalena Colliery.

The purpose of this report is to provide a conceptual design for the coal discard facility for a 10 year planned life of mine. The coal slurry will be backfilled into the opencast mine workings. The conceptual design for the coal discard disposal facility addresses the principles of the intended design, but do not include detail specifications. It includes all aspects of the design that will affect the successful operation and subsequent closure of the facility in an environmentally acceptable manner.

2 PROJECT REQUIREMENTS

The requirements of the coal discard disposal facility can be summarised as follows:

Table 1: Design Parameters

Design Life 10 years

Discard (dry tonnes) 16 800 t/month 2 016 000 t (total)

Discard Dry Density (t/m3) 1.4

Discard (m3) 12 000 m3/month 1 440 000 m3 (total)

Slurry tonnes 4 200 t/month 504 000 t (total)

Slurry Dry Density (t/m3) 1.05

3 SITE LOCATION AND DESCRIPTION

Magdalena Colliery is located approximately 22 km north- northwest of the town of Dundee and 63 km southwest of the town of Vryheid in Northern Kwazulu-Natal. Refer to Figure A, Appendix A.

This site consists of abandoned underground workings, current underground workings, rehabilitated opencast workings and un-rehabilitated opencast workings. The position of the current active Magdalena opencast strip is situated across the southwestern half of the site. The opencast mining at the south pit will be backfilled prior to discard disposal and will form a part of the discard disposal area.



4 AVAILABLE INFORMATION

Prior to the investigation the following information was available:

Drawing, General Mine Surface Plan

Drawing, Magdalena Mining Plan, South Pit

Drawing, Mining Plan, Mining / Reserve Plan

5 SURVEY

The Client supplied all the survey information required for the conceptual design of the coal discard disposal facility. The survey was modeled with the Civil Designer and Microstation computer packages to create a three-dimensional model of the proposed site. This model was used for:

Water balance analysis.

Capacity analysis.

Site layout design.

Conceptual closure planning.

6 SITE SELECTION

6.1 Introduction

All possible alternative sites were considered before the preferred sites were identified. Sufficient candidate sites were identified to ensure the due consideration of potential alternatives. In identifying candidate sites, numerous economic, engineering, environmental and public acceptance criteria were considered. These criteria interrelate, as there are always economic implications when candidate sites are sub-optimal in terms of environmental and/or public acceptance characteristics. Also, the public will usually not accept an environmentally unsuitable residue disposal site.

6.2 Identification of Candidate Sites

Early considerations in site selection are to identify the size and general location of the required site. The further phases involved in the approach to site selection are as follows:

Elimination of all areas with associated fatal flaws, and taking note of all critical factors;

Identification of candidate sites based on the site selection criteria;

Ranking of the candidate sites; and

Carrying out a feasibility study on the best option(s).



6.3 Site Locality

A total of three candidate sites have been identified (see Figure A, Appendix A).

Site 1: Located approximately 650m due south of the proposed plant area and is located on an area that will be disturbed by opencast mining.

Site 2: Located approximately 1400m south of the proposed plant area.

Site 3: Located approximately 950m due north of proposed plant area.

6.4 Fatal Flaws And Critical Factors

The fatal flaws and critical factors are summarised in Table 2 below:

Table 1: Fatal Flaw and Critical Factors

Site No. Fatal Flaw Critical Factor

1 None None

2 None None

3 None Close proximity to existing settlement

Geological structures traverse the site

6.5 Numerical Assessments

Each of the sites was assessed utilizing a ranking matrix (see Appendix A). The criteria of this matrix were appropriately weighted in order to reflect their relative importance. Scores were assigned for each criterion based on a qualitative assessment, and were added together to provide a total for each site. A maximum score for a particular aspect means that the site is suitable as far as that aspect is concerned.

The results of the ranking matrix are summarized in Table 3 below:

Table 2: Ranking Matrix Results

Site No.

Ranking (%)

1

86

2

77

3

75



The above table indicates that:

All three sites will be suitable for coal discard disposal;

Site 1 is the preferred site for the establishment of a coal discard disposal facility; and

Site 2 ranks second.

7 SAFETY CLASSIFICATION

Great importance is attached to the qualitative safety classification associated with a particular residue disposal facility. This classification defines the potential consequences of a failure of the residue disposal facility.

The Code of Practice for Mine Residue (SABS 0286:1998) calls for a safety classification to differentiate between residue deposits of high, medium and low hazard rating on the basis of their potential to cause harm to life or property within the zone of influence. The classification should be based on the anticipated configuration of the residue disposal facility at the end of its design life, and on satisfying any one of the conditions set out in columns 1 to 4 of Table 4.

Table 3: SABS (0286:1998) Safety Classification

Number of residents in

zone of influence

Number of workers in

zone of influence1)

Value of third party property in zone of

influence2)

Depth to under-ground

mine workings3)

Classification

0 <10 0-R2m <200m Low Hazard

1-10 11-100 R2m – R20m 50 m – 200 m Medium

Hazard

>10 >100 >R20m <50m High Hazard

1) Not including workers employed solely for the purpose of operation of the deposit.

2) The value of third party property should be the replacement value in 1996 terms.

3) The potential for collapse of the residue deposit into the underground workings affectively extends the zone of

influence to below ground level.

The rating, base on the zone of influence, can be summarised as follows (Refer to Figure B, Appendix F):

Table 4: Hazard Rating Results

Item

Condition

Hazard Rating

Overall Rating

1 Number of residents in zone of influence Low

2 Number of workers in zone of influence Low

3 Value of third party property in zone of influence Low

4 Depth to under-ground mine workings Low

LOW



8 GEOTECHNICAL INVESTIGATION

A preliminary geotechnical investigation was carried out by GCS, during September 2006, for the Magdalena coal discard disposal facility to gain an understanding of the sub-surface soil conditions underlying the proposed site.

Two sites were investigated. The first site was indicated on the Proposed Mining Layout Plan and defined within boundary EFGH. The second site was indicated by Mr Frank Talbot during the site visit, and is situated approximately 1km to the southeast of Site 1.

The founding conditions for the proposed discard disposal site is soft sandstone rock that lies directly over soft shale rock. Depth to bedrock is expected to vary between 1m and 5m. It is recommended that all the highly plastic material should be removed from the footprint of the discard disposal facility prior to deposition. Topsoil should also be preserved for progressive rehabilitation and final closure.

The shear parameters of the discard material collected from the existing discard dump respectively reflect internal angles of friction of 45o and cohesions of 7kN/m3. The maximum dry densities of the discard was 1469kg/m3, measured at 95% modified AASHTO.

The results of the geological and geotechnical investigations are presented in Appendix B.

8.1 Site No. 1

• This site is closer to the proposed washing plant than site no. 2.

• The site has an easterly gradient, and is vegetated by short grass and small thorn trees.

• A large portion of the western side of the site is covered by a wide drainage channel in which sandstone rock has been exposed, and has scattered loose dolerite boulders deposited over it.

• Some parts of this drainage channel are covered by soils and completely weathered very soft rock of up to 3.1m in thickness.

• On the southern side of this wide drainage channel, this rock is overlain by soils with a thickness of up to 1.6m.

• The soil profiles are silty clays and display expansive characteristics.

• The soils on the eastern side of the site are much deeper, reaching depths of up to 5.0m.

• A longwall excavation to the south of the site revealed a 1.0m thick completely weathered dolerite (residual soil with occasional boulders) sill at a variable depth (due to the westerly dip).

• The sandstone and shale rock are consistent and are expected to be suitable foundations for a discard dump.

• These rocks are also likely to form a barrier against the percolation of pollutants into the groundwater.



• The clayey nature of the soils are also likely to form a barrier for the lateral movement of pollutants into surrounding areas.

• Excavation of the soils is likely to be soft excavation.

8.2 Site No. 2

• The site has a gentle easterly to north-easterly gradient, and is vegetated by short grass and small thorn trees.

• Large drainage channels draining in a north-easterly direction cross the site, and have eroded down to the bedrock.

• Soils were recorded to depths of between 3.0m and 4.3m.

• The soils are silty clays that display expansive characteristics.

• The soils are underlain by completely weathered soft sandstone rock with a thickness of 0.5m.

• The sandstone is underlain by completely weathered very soft shale.

• The sandstone and shale rock are closely bedded and dip in a westerly direction at approximately 150.

• The sandstone and shale rock are relatively consistent and are expected to be a suitable foundation for a discard dump.

• These rocks are also likely to form a barrier against the percolation of pollutants into the groundwater.

• The clayey nature of the soils are also likely to form a barrier for the lateral movement of pollutants into surrounding areas.

• Excavation of the soils is likely to be soft excavation.

9 DEPOSITION MANAGEMENT PLAN

The purpose of the deposition management plan is to present the principle on which the proposed facility will be operated.

9.1 Coarse Coal Discard

9.1.1 Capacity Analysis

The coal discard disposal facility was three-dimensionally modelled for an accurate determination of the relationship between the height; area and capacity using the computer program Civil Designer and Microstation. The detail was processed with Microsoft Excel to calculate the rates of rise for average production rates and eventually, the life of the facility. The stage capacity curve is attached in Appendix C and can be summarized as follows:



Table 5: Summary of Capacity Analyses

Area (ha)

Deposition rate

(tpm)

Maximum height

(m)

Capacity

(million m3) Basin Final Top Surface

16 800 28 1.82 20 10

9.1.2 Deposition Method

In order to minimize the coal discard exposed to the atmosphere during disposal, the conceptual design allows for the dump to be developed from the lowest elevation via an “upstream” system of tipping by truck.

9.1.3 Access Control

The boundary fence for the disposal facility is indicated on the layout plans. The purpose of the fence, as required by law, is to keep livestock out and discourage people from gaining access.

Access roads to all major components of the discard facility are also shown on the layout plans.

9.1.4 Dump Construction

The Design Engineer will approve the foundation preparation for the starter walls, including the box cuts. The starter walls will be constructed of selected material from the return water dam basin and the coal discard dump basin. The starter wall will be nominally compacted in 200mm thick layers.

Future lifts will be constructed with coal discard. The coal discard material will be nominally compacted in horizontal layers. The proposed outer wall slope geometry can be summarised as follows:

Table 6: Dump Construction with Coal Discard

Slope Angel Benches

Intermediate (v:h)

Overall (v:h)

Width (m)

Vertical Intervals (m)

Max. Vertical Height

(m)

1:2 1:3 13.5 9 28

9.2 Slurry Disposal

Coal slurry will be disposed off in the opencast mining operations. The slurry will be deposited at a density of approximately 1.05 t/m3 and the supernatant water will be returned to the process plant for reuse. A total volume of approximately 500 000 m3 of slurry will be produced over the life of mine.

The following opencast areas will be available for slurry deposition (refer to Figure A, Appendix A):



Table 7: Opencast

Opencast Description Volume Available (m3) Approximate Deposition Period (Years)

Existing void north of under ground

entrance (on farm Magdalena No. 7574) ±130 000 2.6

Proposed opencast extension to the

north (on farm Allen No 1 No. 15592) ±3 000 000 Adequate for life of mine

Existing opencast to the south (on farm

Magdalena No. 7574) To be determined Adequate for life of mine

Prior to closure of the slurry deposition areas the coal slurry will be allowed to settle sufficiently to allow the placement of topsoil and vegetation of the final landform.

9.3 Management

A system of management and monitoring will ensure that the residue disposal facility is operated safely and efficiently, in accordance with good environmental practice and in a manner compatible with the final closure requirements.

10 SLOPE STABILITY ANALYSIS

10.1 Methodology

The following section details the methodology for the slope stability analysis. The overall stability of the outer slopes has been assessed, using potential failure surfaces (Modified Bishop), in the limit equilibrium program WinStabl. This program allows the analysis of numerous potential failure surfaces, and the identification of the critical surface with the lowest factor of safety against failure.

Calculation of the factor of safety for a tailings embankment requires an analysis of the potential failure surfaces of the embankment. There are a number of common failure modes to which embankments may be vulnerable. These include slope failure from rotational slides, overtopping, foundation failure, erosion, piping, and liquefaction. Each failure may result in partial or complete embankment failure.

For the purpose of this stability assessment the rotational sliding and foundation block failure modes were considered. Rotational sliding, so named because the failure surface appears as a segment of a horizontal cylinder, may result in a slope failure ranging from local sloughing of tailings at random areas along the face of an embankment, to a massive circular arc slide extending over the entire structure.



10.2 Material Strength Parameters

A literature survey was carried out to determine the material properties of both the coal tailings and the founding horizon for the discard disposal facility. The parameters used in the analyses are summarised in the table below:

Table 8: Material Strength Parameters

Material Type Moist Density (kN/m3) Cohesion (kPa)

Friction Angle (Degrees) Source of Data

Discard 16 20 40 Geotechnical testing

Soil 18 10 30 Geotechnical testing

Bedrock 22 100 45 Judgmental/estimate

10.3 Phreatic Conditions

A pore pressure co-efficient has been used to account for pore pressures within the voids of the discard.

10.4 Earthquake Conditions

The project area is in a region of low seismicity.

10.5 Slope Stability Results The slope stability results are summarised in the table below and the graphical sections are

attached in Appendix D.

Table 9: Slope Stability Results

ru

Scenario Coarse Coal Discard Foundation

Calculated Factor of Safety Allowable Factor of Safety

Circular Failure

A (fully drained) 0.1 0.0 2.17 1.3

B (partly drained) 0.2 0.1 1.91 1.3

C (near saturation) 0.3 0.2 1.66 1.3

Good international practice is based on an allowable factor of safety of 1.3.



From the above table it can be seen that the overall stability for the discard disposal facility is

satisfactory for all conditions. The discard will be placed in a fairly dry state and compacted

in layers. The near saturation scenario was conducted to illustrate the worst case, however

these conditions are not expected during the operating life of the facility if good management

and monitoring measures are followed.

11 SURFACE WATER MANAGEMENT PLAN

The surface water management plan can be summarised as follows:

11.1 Surface Water Management Principles

The principles on which the surface water management plan is based, and which are implemented in the conceptual design are:

Separation of clean and dirty water.

Clean storm water run-off from the upstream catchments will be diverted around the dump.

Zero discharge of contaminated water to the environment.

Maximisation of seepage to the groundwater.

Minimum storage of water on the dump.

11.2 Freeboard

In South Africa, Government Notice No. 704, Regulation 6 requires that the minimum freeboard for a residue disposal facility and return water dam should be at least 0,8m above full supply level. It also states that a dirty water system must be designed and operated in such a manner that it is at all times capable of handling the 1:50 year flood event on top of its normal operating level without spilling.

11.3 Water Discharge Criteria

The disposal facility has been designed as a closed system, with no discharge of polluted water to the environment. In storm conditions, excess water will be temporarily stored on the benches and top surface from where it will evaporate.

The benches and top surface will accommodate the precipitate from a 1 in 50 year, 24-hour storm event. The return water dam will be utilised for storm events only and therefore not during normal operations.

11.4 Seepage Predictions

The coal discard will be nominally compacted in horizontal layers and it is anticipated that the dump will have a relatively low permeability. Seepage and leachate generation will originate from rainwater only and is expected to be minimal. A series of under drains will be installed to collect seepage water. The discard disposal facility will form part of the regional water monitoring program of the mine and will include groundwater levels and water quality.



The clayey nature of the onsite solis and the bedrock will minimise seepage into the groundwater.

11.5 Under Drainage System

Under drains from selected waste rock or filter stone will be constructed to collect and direct rainwater seepage, that percale through the discard facility, from the base areas to collection/monitoring manholes. The water collection/quality monitoring manholes will be linked with a collector pipe and will have the provision to discharge water from a downstream collector sump and a return water dam.

11.6 Storm Water Control

The surface hydrology design includes surface drainage, storm water diversions and river diversions (where applicable), to meet the requirements of the Water Act. This includes the separation of unpolluted water from polluted water and the containment of polluted water on site in storage facilities.

A storm water diversion trench will be constructed upstream of the dump to prevent the ingress of storm water onto the dump. In the case of large storm events, resulting in flood conditions within the basin of the dump, temporary storm water cut-off berms have been provided to route the surplus water into the natural drainage systems.

The side slopes and benches will be paddocked, covered with a soil layer and vegetated as soon as possible. The top surface of the dump will be soil cladded and graded back towards the hill slopes at a grade of approximately 1: 200 to ensure the save storage of water.

Catchment paddocks will be constructed at the toe of the dump to collect and contain surface run-off and silt from the side slopes.

11.7 Water Balance

A climatic water balance [avg. rainfall (mm) – avg. soil evaporation (mm)] was done for the site to assist with the development of the water management plan.

The mean annual precipitation for the Dundee area is 791.5 mm. Mean wet season precipitation (October – April) is 702,9 mm, and mean dry season precipitation (May – September) is 88.4mm. Mean monthly precipitation is presented in the table below. The data was obtained from the weather Stations at Newcastle and Dundee and can be summarised as follows:

Table 10: Climatic Water Balance

Month Avg. Rainfall Dundee

1896 - 1999 (mm)

Avg. Evaporation Newcastle 1957 - 1987

(mm)

Avg. Soil Evaporation (0.7*A-Pan_mm)

Climatic Water Balance (mm)

Jan 145.6 186.5 130.55 +15.05

Feb 112.1 151.4 105.98 +6.12



Table 10: Climatic Water Balance

Month Avg. Rainfall Dundee

1896 - 1999 (mm)

Avg. Evaporation Newcastle 1957 - 1987

(mm)

Avg. Soil Evaporation (0.7*A-Pan_mm)

Climatic Water Balance (mm)

Mar 76 143.6 100.52 -24.52

Apr 44.1 110.6 77.42 -33.32

May 14.8 89.9 62.93 -48.13

Jun 12.8 66.8 46.76 -33.96

Jul 5.6 80.9 56.63 -51.03

Aug 18.6 125.4 87.78 -69.18

Sept 36.6 159.7 111.79 -75.19

Oct 86.1 179.2 125.44 -39.34

Nov 108.8 177.5 124.25 -15.45

Dec 130.4 199 139.3 -8.9

Total 791.5 1670.5 1169.35 -377.85

The above table indicates that the site can be considered a water deficit area and that significant leachate would not be generated on account of the climate. It is expected that some limited leachate will be generated during the wet months especially during above normal rainfall years when precipitation could exceed evaporation.

11.8 Return Water and Decant Systems

The return water system includes a return water dam, pumps and return water pipeline to the proposed plant. The design can be summarized as follows:

Table 11: Summary of Return Water System

1:50 year, 24h storm event

(mm)

Exposed Coal Discard Surface

(ha)

Run-off factor

Storm Volume

(m3)

Return water dam capacity

(m3)

Return water pipeline length

(m)

125 10 0.8 12 500 14 000 760

The Design Engineer will approve the foundation preparation, including the box cut, for the return water dam. The homogenous embankment will be constructed of selected material from the return water dam basin and the dump basin. The embankment will be compacted in



200mm thick layers to 100% Standard Proctor Density at optimum moisture content to +3% of the optimum moisture content.

The discard disposal facility will always have adequate freeboard to accommodate the 1:50 year, 24-hour storm event. The discard disposal facility is not equipped with a penstock decant system to remove stormwater. It is therefore recommended that a standby portable barge pump and pipeline be available to transfer storm water from the top surface of the discard disposal facility to the return water dam. This will ensure continuously disposal of discard during the wet season. The pump and pipeline should be designed to remove water from a 1:50 year, 24-hour storm event within a reasonable time (generally within 48 to 72 hours).

12 POLLUTION CONTROL MEASURES

A synergistic effect can be achieved by combining different controls together in one dump. Inclusion of the features in the table below is likely to give rise to the lowest pollution potential for the dump, taking not only the capital and operating costs into account, but also the contingent liability associated with potential water contamination.

Table 12: Pollution Control Measures

Control Type Description

Infiltration minimization

Topsoil removed from the footprint area will be stockpiled for future use as soil cover material.

The side slopes and berms of the coal discard dump will be covered with soil during the operational phase.

The soil cover will assist in reducing any contact of rainfall runoff with the coal discard. In addition, the side slopes and berms will be vegetated to minimize erosion. The vegetated soil cover will also deplete oxygen.

The top surface and benches of the dump will be graded back towards the hill slopes. This will reduce the total seepage flux and hence the contaminant load.

After decommissioning, the top surface of the coal discard dump will be shaped to suit drainage requirements and a soil cover provided. The cover will be vegetated to minimize the rate of erosion.

Clean water diversion

The design will include clean water diversion systems for surface water inflow from drainages within the natural catchment basins and precipitation runoff. The clean water systems will be designed so that it is not likely to spill into any dirty water system more than once in 50 years (Regulation 407 of the Water Act refers).

Appropriate erosion protection and energy dissipation measures will be included in the design (if necessary) for long-term closure requirements.

In the case of large storm events, resulting in flood conditions within the basin of the dump, temporary storm water cut-off berms will be provided to route the surplus water into the natural drainage systems.

Under drainage and re-

use of contaminated water

The design will include the implementation of an under drainage system to collect seepage for re-use as process water. This will require the conversion of the temporary storm water diversion systems into seepage collection drains.

The return water dam will be sized to accept seepage from the under drainage systems and will be designed so that it is not likely to spill into any clean water system more than once in 50 years (Regulation 407 of the Water Act refers).

The seepage rate from the under drains is expected to become negligible after decommissioning. Only small evaporation facilities will therefore be required, once Plant operations cease.



Table 12: Pollution Control Measures

Control Type Description

Collection and treatment

of seepage

This tertiary control option is the least desirable from a business point of view and will only be planned for implementation as a last resort in the event that the recommended primary and secondary controls fail to meet the required standards.

Should the quality of runoff from the soil cladded side slopes prove unacceptable for discharge, it may be necessary to collect and/or treat the water in the catchment paddocks prior to discharge. The required treatment may comprise one or a combination of the following:

o Evaporation of surface runoff in the catchment paddocks o Settlement of suspended solids

13 EROSION POTENTIAL AND PROTECTION

The consequence of loss of material from the sides of discard disposal facilities is important from a water management perspective.

Firstly the water that comes in contact with the erodable coal discard, pick up solids and may carry it into the environment. Solids may find their way into water bodies where the elevated suspended solids may adversely affect aquatic ecosystems or where the deposition thereof could silt up water bodies and clog waterways.

To meet the requirements for closure, the residue deposit surface generally requires stabilization. Stabilization can range from direct re-vegetation of the surface, if possible, to multiple layered cover systems. Direct re-vegetation is an option where the available nutrients and climate make establishment of sustainable vegetation possible. This will prevent wind erosion but will generally do little to prevent infiltration of precipitation that will eventually seep from the deposit. If there are any contaminants such as heavy metals, the plants may take these up and make them accessible to grazing animals.

The factors listed in the table below are believed to be the most important in terms of erosion of layers of a dry cover system.

Table 13: Factors Affecting the Erosion of Cover Systems

Factor Comment

Slope angle Erosion rate increases with increased slope angle.

Slope length Erosion rate increases with increased slope length.

Material properties Materials with low cohesion, and small particle size (low mass) are more easily detached and entrained into water flow.

Rainfall intensity

Storm intensity defines the amount of runoff flow available for erosion - increased storm size will bring more erosion. It is not a linear relationship; a single large storm event has the ability to produce the majority of erosion experienced at a site over a long period of time.

Vegetation Vegetation increases the strength of the soil and reduces the energy of runoff by creating barriers to flow.

Base flow (antecedent moisture conditions)

Increased erosion occurs at seepage faces due to lower strength of the saturated material as compared to unsaturated material.



14 CONCEPTUAL REHABILITATION PLAN

The conceptual rehabilitation plan can be summarised as follows:

14.1 Introduction

The detailed closure plan will be developed during the life of the mine. The purpose in preparing a conceptual closure plan is to ensure that the design, construction and operating procedures are compatible with the achievement of final closure and rehabilitation to accepted environmental standards and at a reasonable cost. It is anticipated that the conceptual plan will be updated periodically before the preparation of the detailed closure plan.

The rehabilitation programme will be prepared in accordance with the BATNEEC principle (best available technology not exceeding economic cost).

The minimum objectives for the closure and rehabilitation of a residue disposal facility must be to prevent air and water pollution in accordance with the requirements of the relevant regulations and with good international practice. The intended end use should take into consideration the prior land use and the location with respect to current and potential future socio-economic development.

14.2 Objectives

The objectives of the closure and rehabilitation measures will be:

To establish a self-sustaining solution with a minimum of on-going maintenance;

To minimise off-site impacts;

To create safe and stable landforms;

To return the site to beneficial land use; and,

To obtain a closure certificate.

In achieving these objectives, the measures must satisfy the regulations and conform to good international practice.

14.3 Final Geometry

The required final surface geometry will be achieved by the mechanical construction method during the life of the facility, particularly during the final years, and by subsequent limited earthworks. It is intended that the upper surface of the dump should be shaped to retain surface run-off and thus to prevent the erosion of the outer slopes and the discharge of polluted solids to the environment.

The outer slopes of the dump will be shaped and rehabilitated during the operational life of the facility.

14.4 Final Surface Cover

Topsoil removed from the dump base area will be stockpiled and used for capping the coal discard dump.



A direct soil cover is considered the best compromise in terms of cost and performance and is most likely to satisfy closure requirements. This approach involves the placement of topsoil on the side slopes, step-ins and top surface (1,0m thick) at the coal discard dump. This approach allows storm water to run off the deposit quickly and avoid becoming polluted. Vegetation is to be established as soon as the soil cover is in place. Some vegetation will probably establish itself naturally.

14.5 Control of Water

The system of diversion canals to prevent storm water run-off from entering the site will remain in place.

Surface water falling on the top surface of the dump will be held on the dump. The top surface may be divided into separate paddocks, or the water may be allowed to drain in a controlled fashion to a pool. The decision will depend upon information gathered during the operating period. For the pool option, consideration will be given to the need for a buried HDPE liner over the potential pool area, to prevent seepage to the groundwater. An emergency spillway for decanting excess water from the top of the dump will also be considered.

The run-off on the surface of the dump will be further controlled by the creation of low bunds. The establishment of vegetation will reduce erosion but, where necessary, more permanent structures will be constructed with selected material.

14.6 Vegetation

Vegetation on the surface and outer slopes of the dump will reduce erosion and dust generation. It will be necessary to obtain the maximum benefit from the residual moisture in the soil and from the seasonal rainfall. Thus, efforts should be made to commence the establishment of vegetation during the operating life of the facility. It will certainly be possible to begin to establish vegetation on the outer slopes. It is anticipated that the mine will carry out experiments from the time of commissioning of the project. Information available from re-vegetation exercises in similar conditions will be gathered during the planning of the tests.

15 CONCEPTUAL DRAWINGS

The conceptual drawings are listed in the table below and are included in Appendix E.

Table 14: Conceptual Drawings

Drawing No. Date Description

SLA.06.190/1 October 2006 General Arrangement Pre-deposition Civil Works

SLA.06.190/2 October 2006 General Arrangement Final Layout

SLA.06.190/3 October 2006 Typical Sections and Details

SLA.06.190/4 October 2006 Typical Sections and Details

SLA.06.190/5 October 2006 Locality Plan



16 CONCLUSIONS AND RECOMMENDATIONS

The following conclusions can be drawn from the conceptual design phase:

The disposal facility has been designed to minimise the impact of the contaminated water on the surrounding environment. The disposal facility is not expected to give rise to unacceptable levels of contamination of groundwater, surface runoff or air.

The proposed pollution control measures have been selected to minimise the operational and maintenance costs after decommissioning. Management input after decommissioning is expected to be limited to monitoring and maintenance of the cover and storm water control structures. Active control systems such as water treatment systems are not likely to be required after decommissioning.

It is recommended that:

The discard disposal facility should form part of a water quality management strategy and water balance for the entire mine complex.

A detailed design should be prepared for the pre-deposition civil works.

A code of practice and operating manual should be prepared to ensure that the facility is designed, operated and rehabilitated in a responsible manner.



Appendix A

Site Selection



Appendix B

Geotechnical Investigations

Est. 1987

Reg No: 2004/00765/07DIRECTORS: AC Johnstone, W. Dressel, AWC Marais, SE Scawthon, AH Barbour (Non-exec) www.gcs-sa.biz

Johannesburg Durban

Suite 11, Hillcrest Office Park 2 Old Main Road, Hillcrest PO Box 819, Gillitts, 3603

South Africa Tel: +27 (0)31 765 2088 Fax: +27 (0)31 765 8201

[email protected]

Our Ref: SLA.06.190 Your Ref:

PROPOSED MAGDALENA COLLIERY DISCARD FACILITY RESULTS OF GEOTECHNICAL INVESTIGATION

Compiled

by

GCS (Pty) Ltd

L B FITSCHEN Pr.Sci.Nat. Senior Engineering Geologist

for GCS (Pty) Ltd MARCH 2006

Proposed Discard Facility, Magdalena Colliery


TABLE OF CONTENTS 1. TERMS OF REFERENCE .......................................................................................... 1 2. INFORMATION SUPPLIED AND CONSULTED........................................................ 1 3. FIELD INVESTIGATION............................................................................................. 1 4. SITE LOCATION AND DESCRIPTION ...................................................................... 2 4.1 Topography and Drainage........................................................................................ 2 4.2 Geology and Soils..................................................................................................... 3

4.2.1 Residual and Transported Soils................................................................... 3 4.2.2 Rock Types .................................................................................................... 4

5. LABORATORY TESTING .......................................................................................... 5 6. ENGINEERING GEOLOGICAL AND SOIL CONDITIONS AFFECTING

DEVELOPMENT......................................................................................................... 5 6.1 Materials Classification ............................................................................................ 5 6.2 Site Drainage ............................................................................................................. 7

6.2.1 Surface Drainage........................................................................................... 7 6.2.2 Permeability of Soils ..................................................................................... 7

6.3 Erosion Potential....................................................................................................... 7 6.4 Founding Conditions ................................................................................................ 8 6.5 Site Earthworks ......................................................................................................... 8 6.6 Slope Stability ........................................................................................................... 9 7. CONCLUSIONS AND RECOMMEDATIONS............................................................. 9 8. REFERENCES.......................................................................................................... 10

LIST OF TABLES TABLE 1: GPS CO-ORDINATES FOR SOIL PROFILE POSITIONS ................................... 2

TABLE 2: SUMMARY OF LABORATORY TESTING SCHEDULE....................................... 5

TABLE 3: LABORATORY TEST SUMMARY........................................................................ 6

TABLE 4: SUMMARY OF FOUNDATION LEVELS .............................................................. 8

LIST OF APPENDICES Appendix 1 SOIL PROFILE DESCRIPTIONS Appendix 2 LABORATORY TEST RESULTS

LIST OF FIGURES Figure 1 Site Plan

Proposed Discard Facility, Magdalena Colliery page - -


1

1. TERMS OF REFERENCE

Zinoju Investments (Pty) Ltd appointed GCS (Pty) Ltd to conduct a geotechnical

investigation as a part of the EMP, for a coal discard facility at Magdalena Colliery, situated

near to Dundee in KwaZulu-Natal. Mined coal is presently being transported by road to

Dundee, where it is processed. It is the intention of Zinoju Investments to construct a

washing plant at the mine that will require a discard facility. Two possible sites were

investigated, the positions of which are given in Figure 1. The purpose of this report is to

review the results of the geotechnical investigation carried out during September 2006, and

to give conclusions and recommendations with regard to founding and earthworks on the

sites for the proposed discard facility.

Given below are the results of this review.

2. INFORMATION SUPPLIED AND CONSULTED

For the purpose of the review, the following information was supplied or consulted:

• The Geological Survey of South Africa 1: 250 000 scale geological series map, Sheet

2730 Vryheid 1988 Edition;

• The Topographical Map 2730 CC - Osizweni 1996 Edition at a scale of 1: 50 000;

• A plan entitled ‘Magdalena Colliery, Proposed Mining Layout Plan’ compiled by

GCS (Pty) Ltd at a scale of 1: 2 500, July 2006.

• Electronic copy of a plan entitled ‘Zinoju Investments, Conversion of an Old Order

Mining Right’ at a scale of 1: 10 000 supplied by Mr F W Talbot.

3. FIELD INVESTIGATION

The sites were visited on the 27th September 2006, during which an appraisal was made of

the general geology and geomorphology of the sites. Soil profiles that have been exposed in

eroded gullies and by mining operations were recorded according to the method outlined in

Jennings et al 1, and the profile descriptions are given in Appendix 1. Rock descriptions were

recorded according to the Core Logging Committee 2. The co-ordinate positions of these soil

profiles were recorded using a hand held Garmin GPS 5, and these are listed in Table 1,

below.

Disturbed soil samples were collected from selected soil horizons and submitted to Soilco in

Pietermaritzburg for analysis. The results of the laboratory tests were used to identify and



2

classify the materials underlying the site, and are given in Appendix 2.

TABLE 1: GPS CO-ORDINATES FOR SOIL PROFILE POSITIONS

MAGDALENA DISCARD FACILITY WGS84 / SA Grid

Position Y Co-ordinate X Co-ordinate Soil Profile 1 31 Y0078593 X3096610 Soil Profile 2 31 Y0078539 X3096687 Soil Profile 3 31 Y0078856 X3096970 Soil Profile 4 31 Y0078884 X3096023 Soil Profile 5 31 Y0078878 X3096160 Soil Profile 6 31 Y0078903 X3096260 Soil Profile 7 31 Y0079187 X3096322

4. SITE LOCATIONS AND DESCRIPTION

The sites of the proposed Magdalena discard facility are located approximately 21km to the

north of Dundee. The site can be located by travelling north on the P272 road from Dundee

for approximately 24 km, and then left off this road for approximately 2km.

A large area of site 1 has sandstone rock exposed at the surface in a wide area of erosion

with scattered loose dolerite boulders that have been deposited over it. Some parts of the

exposed sandstone have very soft rock with residual soils overlying it that are vegetated by

grass and small trees. Site 1 is rectangular in shape and covers an area of approximately

34Ha. This site is situated over pre-existing underground workings. The position of the

Magdalena opencast strip is situated across the western half of site 1, of which a large

portion of the southern half is presently being excavated. After mining, this strip will be

backfilled and will form a part of the dump area.

Site 2 covers an area of approximately 44Ha, is triangular in shape and is vegetated by short

grass and small trees. Fairly wide and deep drainage channels that have eroded down to

bedrock traverse the site. A small, low discard dump and associated surface trenches from

previous mining operations lie in the south of the site.

4.1 Topography and Drainage

The surface topography of site 1 is very uneven as a result of erosion of wide drainage

channels and the deposition of large dolerite boulders. The natural ground of this site has

gradients that range between 1: 15 (4o) and 1: 20 (6o), and slopes in an easterly direction.

Surface runoff is therefore expected to flow across the site in an easterly direction, draining



3

into nearby farm dams.

The surface topography of site 2 is relatively flat excepting where northward flowing drainage

channels have formed. The natural ground of this site generally has a gradient of 1: 30 (2o).

Surface runoff is expected to flow across the site in an easterly direction into the drainage

channels and nearby farm dams.

Surface runoff from site 1 will flow into farm dams situated further downstream than the

runoff from site 2. The potential for the spread of pollutants over a larger area is therefore

greater from site 2. Runoff from both sites will flow into the northward flowing

Bloubankspruit.

4.2 Geology and Soils

The soil and rock types at the two sites are similar, and these are discussed as one.

Both sedimentary and intrusive rocks underlie the sites. The sedimentary rocks are of the

Vryheid Formation, which forms a part of the Ecca Group, Karoo Sequence. The Vryheid

Formation consists of coal seams, grits, sandstone, shale, arkoses and mudrocks. These

sedimentary rocks have been intruded by much younger dolerite rock. Most intrusions of

dolerite rock into Karoo Sequence rocks are horizontal, sheet-like and concordant, but they

also occur as gently and evenly inclined discordant sheets to the host sediments. The

dolerite sill observed at the site, extends to under site 1, and is concordant with a near

horizontal orientation. Residual soils overly the bedrock and are in turn overlain by hillwash.

4.2.1 Residual and Transported Soils

The transported soils observed at the site consist of hillwash, and were observed in

Soil Profiles 1 to 7. These soils are slightly moist, dark tan brown, medium dense,

microshattered, silty clay with traces of fine and medium calcareous gravel that is

generally 0.4m in thickness at the surface.

The residual soils at the site consist of residual sandstone and residual dolerite soils.

Residual sandstone soils were recorded in Soil Profiles 1 to 6 and residual dolerite

soils were recorded in Soil Profile 7.

The residual sandstone soils can generally be described as follows:



4

(a) Moist, dark brown, soft, slightly slickensided, silty clay with traces of fine and

medium calcareous gravel, with a thickness of between 0.2m and 1.0m generally

occurring from a depth of 0.4m;

(b) Moist, greyish brown, soft to firm, slightly slickensided, silty clay with traces of

fine and medium calcareous gravel with a thickness of between 0.5m and 1.8m

and generally occurring from a depth of between 0.5m and 1.4m;

(c) Moist, greenish brown mottled orange brown, firm, slickensided, silty clay with

traces of fine and medium calcareous gravel with a thickness of between 0.4m

and 2.3m and generally occurring from a depth of between 1.0m and 2.7m.

The residual dolerite soils were recorded in the opencast mine excavation and are

the remnants of a horizontal concordant dolerite sill. These soils can be described as

follows:

a) Slightly moist, reddish brown, firm, shattered silty clay with traces of coarse and

boulder dolerite gravel at a depth of 2.7m and with a thickness of 1.1m.

4.2.2 Sandstone Rock

The sandstone rock at the site was observed in Soil Profiles 1 to 6. This rock can

generally be described as light grey, completely weathered, thinly bedded, medium to

very coarse-grained soft rock. The thickness of this sandstone was found to be 0.5m

in Soil Profiles 1 to 3, but could not be determined in profiles 4 to 6, as it was not

completely exposed. The depth to the sandstone measured in the soil profiles ranges

between 1.4m and 5.0m. The dip of the sandstone measured at Soil Profile 1 is 15o

west, with a north-south strike. It is expected that a back actor will refuse on this rock

layer.

4.2.3 Shale Rock

The shale rock at the site was observed in Soil Profiles 1,2 and 7. The thickness of

the shale could not be determined due to the depth of exposures. This rock can

generally be described as follows:

a) Light purplish grey banded light orange brown, medium weathered, very thinly

bedded, very fine grained, soft rock and occurs at depths of 3.5m and 4.5m and

is at least 0.9m thick (in Soil Profiles 1 and 2);



5

b) Brownish yellow, completely weathered, very thinly bedded, very fine grained,

soft rock and occurs at a depth of 2.7m and is at least 1.3m thick (in Soil Profile

7).

It is expected that the shale underlying the sandstone in Soil Profiles 1 and 2,

similarly underlies the sandstone described in Soil Profiles 3 to 6. It is likely that a

back actor will refuse on this shale layer.

5. LABORATORY TESTING

Disturbed soil samples were collected from selected soil horizons and submitted to Soilco in

Pietermaritzburg, for analysis. A summary of the samples collected and the testing schedule

are provided in Table 1. The detailed laboratory test results are given in Appendix 2.

TABLE 2: SUMMARY OF LABORATORY TESTING SCHEDULE

Soilco Laboratory Ref. No.

Soil Profile

No.

Depth Of

Sample (m)

Shear Box Test

Compaction Test

Grading Analysis

Atterberg Limits

Pinhole Test

P10813 SP 2 1.0 - 2.3 X X P10814 / 6488 SP 2 2.3 - 4.0 X X X

P10815 SP 5 0.5 – 1.0 X X P10816 SP 5 1.0 – 1.4 X X P10817 SP 7 1.6 – 2.7 X X

DISCARD - X X

6. ENGINEERING GEOLOGICAL AND SOIL CONDITIONS AFFECTING DEVELOPMENT

6.1 Materials Classification

A total of 7 disturbed soil samples were submitted for laboratory analysis. Tests conducted

on these samples include full grading and hydrometer and Atterberg Limits, and on one of

the samples a pinhole test to test for dispersivity. One sample consisting of coal discard was

collected from the discard facility at the coal processing plant in Dundee, and was tested for

compaction and shear parameters.

The results of the analysis are given in Appendix 2, and are summarised in Table 2 below:



6

TABLE 3: LABORATORY TEST SUMMARY

Laboratory Number P10813 P10814 6488 P10815 P10816 P10817

Source SP2 SP2 SP5 SP5 SP7 DISCARD

Material Sandy Clay

Sandy Clay

Clayey Sand

Clayey Sand Silty Clay Coal

Discard

Laboratory and Field Data

Depth (m) 1.0 - 2.3 2.3 - 4.0 0.5 - 1.0 1.0 - 1.4 1.6 - 2.7 0 13.2 100 100 100 100 4.75 97 98 98 99 100 2,00 91 96 97 97 99

0,425 85 89 88 89 97 0,075 63 62 56 50 72 0.060 61 61 55 46 70 0,050 60 59 53 43 68 0.026 54 52 44 34 58 0,015 48 45 37 29 50 0.010 46 45 35 27 49 0.074 44 39 33 27 47 0,005 43 37 32 25 43

0.0036 41 36 28 25 41 0.002 39 34 25 21 39

0.0015 37 32 21 20 37 Coarse Sand (%) 7 7 9 8 2 Fine Sand(%) 37 38 43 52 31 Silt(%) 16 20 19 17 25

Soil Mortar

Clay(%) 40 35 29 23 42 Liquid Limit(%) 67 62 43 37 55 Plasticity Index(%) 38 36 25 21 32 Linear Shrinkage(%) 15 18 12 10 15

Atterberg Limits

Equivalent PI(%) 32.3 32.1 22.1 18.7 31.1 Grading Modulus 0.61 0.53 0.60 0.64 0.32 TRH 14 Class A-7-6(16) A-7-6(16) A-7-6(10) A-6(6) A-7-6(18) Potential Expansiveness Very High Very High Low Medium High

Internal Angle of Friction 45o Shear Parameters Cohesion 7

OMC % 8.7 Compaction Parameters MDD kg/m3 1469

Erosion None Pinhole Test Classification ND1

According to the Unified Classification System, the residual sandstone soils are classified as

sandy clays and clayey sands with clay contents varying between 23% and 40%. The

residual dolerite sill soils are classified as silty clays with clay content of 42%.

The samples tested from site 1 are highly plastic, display very high potential expansiveness

and can be classified as A-7-6 (16) in terms of the TRH14 classification. The samples tested

from site 2 are moderately plastic, display medium potential expansiveness and can be

classified as A-7-6 (10) and A-6 (6) in terms of the TRH14 classification. The sample tested

from the residual dolerite sill is highly plastic, displays a high potential expansiveness and

can be classified as A-7-6 (18) in terms of the TRH14 classification.



7

The shear parameters of the sample collected from the existing discard facility, reflects an

internal angle of friction of 45o and cohesion of 7kN/m3. The maximum dry density of the

sample is 1469kg/m3, measured at 95% modified AASHTO.

The sample from Soil Profile 2 tested for dispersivity is non erosive and can be classified as

ND1 (non dispersive).

6.2 Site Drainage

The drainage of the sites is discussed below, with respect to the surface drainage and the

permeability of soils.

6.2.1 Surface Drainage

The surface runoff at the site is expected to flow in an easterly direction along

drainage channels that channel water to the Bloubankspruit. 6.2.2 Permeability of Rock and Soils

Water seepage was not observed at any of the positions where soil profiles were

recorded or in any of the mining excavations at the site, during the site visit.

The permeability of the soils at the site is expected to be low as a result of their high

clay contents. The grading analysis results indicate that when the materials at the

site are compacted they are likely to have moderately low permeability, restricting the

spread of pollutants from the site to surrounding areas.

The unfractured and continuous nature of the sandstone and shale at the site is likely

to form an impermeable barrier for water percolation.

6.3 Erosion Potential

Due to the relatively gentle topography of the sites, sheet erosion as a result of surface

water run-off in this area is not expected to be significantly high. The gradient of site 1 is

steeper, but erosion is expected to be minimal as most of the site consists of sandstone rock

exposed at the surface. Soils that are to be stockpiled for rehabilitation purposes are

susceptible to erosion, and the necessary soil conservation methods need to be adopted in

order to prevent this. The test results indicate that they are non-dispersive.



8

6.4 Founding Conditions

The soft sandstone rock that lies directly over the soft shale rock at both sites is considered

to be a suitable foundation for the discard facility. The dip orientation of the sandstone rock

in relation to the gradient of the sites may result in the discard facility being founded on both

soft sandstone and soft shale rock. The depth to the soft sandstone/shale rock was

measured to be between 1.4m and 5.0m.

The expected foundation depths on the soft sandstone/shale rock are summarised in Table

4 below:

TABLE 4: SUMMARY OF FOUNDATION LEVELS Soil Profile Position Foundation Type

SP1 SP2 SP3 SP4 SP5 SP6 SP7

Soft Sandstone/Shale Rock Depth (m) 3.0 4.0 4.3 3.0 1.4 5.0 2.7

At site 1, where the footprint of the discard facility extends over a large portion of both the

backfilled opencast pit and soft sandstone/shale rock, differential settlement is likely to

occur. Site 1 will also be situated over underground workings from previous mining

operations, which may fail when loaded, affecting the construction of the discard facility as

well as creating the potential for pollutant flow to the groundwater.

The orientation of and the highly plastic and high potentially expansive nature of the dolerite

sill that extends under site 1, makes it unsuitable founding material and should be removed

prior to the deposition of discard. The very soft shale rock below the dolerite sill is likely to be

suitable founding material.

Prior to the preparation of the site for deposition of the discard, it is recommended that the

surface topsoil layer of hillwash be removed and stockpiled in such a way that it is preserved

for future rehabilitation purposes. Similarly, the underlying soils that are excavated should

also be stockpiled and preserved for rehabilitation purposes.

6.5 Site Earthworks

Excavation of the hillwash soils and residual soils at the site is not expected to present any

difficulties, and can generally be classed as soft excavation.

Should excavations be necessary in the soft sandstone rock, blasting may be required.



9

6.6 Slope Stability

The slope of the natural ground surface at the two sites is very gentle, with a gradient of

between 1: 15 (4o) and 1: 20 (60) at site 1 and 1: 30 (20) at site 2, in an easterly direction.

Excavations to create level deposition platforms will expose deeper sidewalls in the west of

the site. The cut slopes should not exceed the angle of internal friction of 30° (1:1.73).

The placement of any discard should be preceded by the removal of all natural vegetation

and hillwash soils. The discard should be deposited in layers, each layer being properly

compacted to a minimum of 95% of Modified AASHTO maximum dry density of 1469kg/m3,

prior to the placement of the subsequent layer. The maximum batter slopes of the discard

dump should be 1: 1,73 (30°).

7. CONCLUSIONS AND RECOMMEDATIONS

A site investigation was carried out for the proposed Magdalena discard facility on the 27th

September 2006, during which exposed soil profiles were recorded. Two sites were

investigated that lie in close proximity to each other. The sites are underlain by hillwash and

residual sandstone soils. Soft sandstone and shale rock underlie these soils. These rocks

have been intruded by a concordant, horizontally orientated dolerite sill.

Disturbed samples of the residual sandstone and dolerite sill were collected and tested. The

soils at site 1 were found to be highly plastic and display a very high potential

expansiveness. The soils at the site 1 are classified as sandy clays. The soils at site 2 were

found to be moderately plastic and display a medium potential expansiveness. The soils at

the site 2 are classified as clayey sands. The dolerite soils were found to be highly plastic

and display a high potential expansiveness. The dolerite soils are classified as silty clays.

A disturbed sample was also collected from the existing discard dump at the washing plant

in Dundee order to determine the shear and compaction parameters.

Water seepage was not observed at any of the positions where soil profiles were recorded or

in any of the mining excavations at the site, during the site visit.

The permeability of the soils at the site is expected to be low as a result of their high clay

contents.

The unfractured and continuous nature of the sandstone and shale at the site is likely to form

an impermeable barrier for water percolation.



10

The soft sandstone rock that lies directly over the soft shale rock at both sites is considered

to be a suitable foundation for the discard facility. The dip orientation of the sandstone rock

in relation to the gradient of the sites may result in the discard facility being founded on both

soft sandstone and soft shale rock.

At site 1, where the footprint of the discard facility extends over a large portion of both the

backfilled opencast pit and soft sandstone/shale rock, differential settlement is likely to

occur. Site 1 will also be situated over underground workings from previous mining

operations, which may fail when loaded, affecting the construction of the discard facility as

well as creating the potential for pollutant flow to the groundwater.

The orientation, highly plastic and high potentially expansive nature of the dolerite sill that

extends under site 1, is unsuitable founding material and should be removed prior to the

deposition of discard. The very soft shale rock below the dolerite sill is likely to be suitable

founding material.

Prior to the preparation of the site for deposition of the discard, it is recommended that the

surface topsoil layer of hillwash be removed and stockpiled in such a way that it is preserved

for future rehabilitation purposes. Similarly, the underlying soils that are excavated should

also be stockpiled and preserved for rehabilitation purposes. The residual sandstone soils at

the site are not dispersive, but are susceptible to erosion.

Excavation of the hillwash and residual soils can generally be classed as soft excavation.

Should excavations be necessary in the soft sandstone rock, blasting may be required.

The slope of the natural ground surface at the two sites is very gentle. Cut banks exposed by

excavations to platform level should not exceed a batter of 1: 1.73 (30o).

Discard should be placed in layers, and compacted to a minimum of 95% modified AASHTO

maximum dry density prior to placement of the subsequent layer. The maximum batter

slopes of the discard dump should be 1: 1,73 (30°).

8. REFERENCES

• Jennings, J.E., Brink, A.B.A., and Williams, A.A.B. (1973), Revised Guide to Soil

Profiling for Civil Engineering Purposes in Southern Africa, Trans. South African Inst.

Civil Eng., 15, 3 –12.

• Core Logging Committee of the South African Section of The Association of

Engineering Geologists (1976). A Guide to Core Logging for Rock Engineering.



11

Proceedings of the Symposium on Exploration for Rock Engineering, Johannesburg,

November 1976.

L B FITSCHEN Pr.Sci.Nat.

Senior Engineering Geologist for GCS (Pty) Ltd

SEPTEMBER 2006



APPENDIX 1

SOIL PROFILE DESCRIPTIONS

LEGEND DESCRIPTION

0.4m

0.9m

1.5m

3.0m

3.5m

5.0m

Project No. SLA.06.1901) Soil Profile recorded from eroded drainage channel2) No water table was observed

Light grey, completely weathered, thinly bedded, medium to very coarse grained SOFT ROCK. Vryheid Sandstone Formation

Light purplish grey banded light orangy brown, medium weathered, very thinly bedded, very fine grained, SOFT ROCK. Vryheid Shale Formation

Slightly moist, dark tan brown, medium dense, microshattered, silty CLAY with traces of fine and medium calcareous GRAVEL. Hillwash.

Moist, dark brown, soft, slightly slickensided, silty CLAY with traces of fine and medium calcareous GRAVEL. Residual sandstone

Moist, greyish brown, soft to firm, slightly slickensided, silty CLAY with traces of fine and medium calcareous GRAVEL. Residual sandstone

Moist, greenish brown mottled orangy brown, firm, slickensided, silty CLAY with traces of fine and medium calcareous GRAVEL. Residual sandstone

Magdalena Colliery Proposed Discard Facility

Geotechnical Investigation

1.0

1.5

4.0

3.0

2.0

Project:

DEPTH

SOIL PROFILE No. 1

0.0

0.5

3.5

2.5

4.5

5.0

5.5

LEGEND DESCRIPTION

0.4m

1.0m

2.3m

4.0m

4.5 4.5m

5.4m

Project No. SLA.06.1901) Soil Profile recorded from eroded drainage channel2) No water table was observed3) Disturbed sample taken for analysis from 1.0m to 2.3m and 2.3m to 4.0m

SOIL PROFILE No. 2

3.0

1.0

1.5

2.0

2.5

DEPTH 0.0

0.5

3.5

4.0

Project:

5.0

5.5






Light purplish grey banded light orangy brown, medium weathered, very thinly bedded, very fine grained, SOFT ROCK. Vryheid Shale Formation



LEGEND DESCRIPTION

0.4m

0.9m

2.7m

4.3m

4.5

4.8m


TRIAL HOLE No. 3


0.5

1.0

0.0

1.5

2.0

2.5

3.0

3.5

4.0

Project:


5.0

5.5

DEPTH






LEGEND DESCRIPTION

0.4m

0.8m

1.8m

3.0m

4.5

Project No. SLA.06.1901) Soil Profile recorded from eroded drainage channel

4.0

Investigation

SOIL PROFILE No. 4DEPTH

0.0

0.5

1.5

2.0

2.5

Project:

1.0


3.0

3.5


Geotechnical

5.0

5.5





2) No water table was observed

LEGEND DESCRIPTION

0.5m

1.0m

1.4m

4.5

Project No. SLA.06.190

4.0



0.0

0.5

1.0

3.0

3.5

1.5

2.0






Project:


2.5

1) Soil Profile recorded from eroded drainage channel2) No water table was observed3) Disturbed sample taken for analysis from 0.5m to 1.0m and 1.0m to 1.4m

LEGEND DESCRIPTION

0.4m

1.4m

2.7m

4.5

5.0m

3.0



0.0

2.5

2.0

Project:

5.0

5.5

3.5

4.0

0.5

1.0

1.5








LEGEND DESCRIPTION

0.3m

1.6m

2.7m

4.0m

Slightly moist, reddish brown, firm, shattered silty CLAY with traces of coarse and boulder dolerite gravel. Residual dolerite sill.

Brownish yellow, completely weathered, very fine grained, very thinly bedded, VERYSOFT ROCK shale. Vryheid shale formation.

Abundant, fine to coarse highly weathered shale GRAVEL in a matrix of slightly moist, brownish yellow, silty clay. Overall consistency is medium dense.


DEPTH

3.0

2.0

2.5

0.0


SOIL / ROCK PROFILE No. 7

1.5

3.5

4.0

0.5

1.0

Project:

Magdalena Colliery

4.5

5.0

5.5

Project No. SLA.06.1901) Profile recorded from side of opencast excavation2) No water table was observed

Proposed Discard Facility




APPENDIX 2

LABORATORY TEST RESULTS

SOILCO MATERIALS INVESTIGATIONS (PTY) LTD CIVIL ENGINEERING MATERIALS TESTING LABORATORY Reg. No. : 1965/09585/07

Client : GCS (PTY0 LTD Job Card No. :Project : MAGDALENA COLLIERS Date Received :

Date Tested :Sample Delivered by : 0 Date Reported :

Sample Number : P10815 Field or Pit Number : TP 5

Position in field : 0.60 Depth ( mm ) : 500 - 1000

Sample Description : Light olive brown clayey sand

Equivalent PI : 22.1 Clay fraction of whole sample ( % < 2µ ) : 25

FINE MEDIUM COARSE FINE MEDIUM COARSE FINE MEDIUM COARSE

CLAY FRACTION SILT FRACTION SAND FRACTION GRAVEL FRACTION

The above test results are pertinent only to the samples received and tested at the laboratory. This report shall not be reproduced, except in full, without the prior consent of SOILCO MATERIALS INVESTIGATIONS (PTY) LTD.

11 HALSTED ROAD - 24 DAVLEN PARK - MKONDENI - P.O. BOX 846 - PIETERMARITZBURG - 3200TELEPHONE : ( 033 ) 386 9095 TELEFAX : ( 033 ) 386 1878 email : [email protected]

For Soilco:

POTENTIAL EXPANSIVENESS GRAPH

PARTICLE SIZE DISTRIBUTION CHART

0

2006-09-29

0

2006-10-11

0

5

10

15

20

25

30

35

40

45

50

55

60

65

70

0 5 10 15 20 25 30 35 40 45 50 55 60 65 70

Equi

valen

t PI

Clay fraction of whole sample ( % < 2µ )

Very High

High

Medium

Low

0

10

20

30

40

50

60

70

80

90

100

0.0 0.0 0.0 0.1 1.0 10.0 100.0

% F

iner

Tha

n



FIGURE 1

SITE PLAN

1

SITE 1

SITE 2

DISCARD FACILITY SITES

SP1

SP2

SP3

SP4

SP5

SP6 SP7



Appendix C

Capacity Analysis

1.40 t/m^3Deposition Vertical Elevation Area Area Volume Acc. Acc. Time Acc. Acc. Rate of

rate height volume tonnage time time rise(tpm) (m) (amsl) (m^2) (ha) (m^3) (m^3) (tonnes) (months) (months) (years) (m/y)

16 800 0 1256 6 315 0.0 0 0 0 0.0 0.0 0.00 0.0016 800 4 1260 26 126 2.6 64 883 64 883 90 836 5.4 5.4 0.45 5.5116 800 10 1266 59 961 6.0 258 260 323 143 452 400 21.5 26.9 2.24 2.4016 800 14 1270 70 109 7.0 260 140 583 283 816 596 21.7 48.6 4.05 2.0516 800 19 1275 88 700 8.9 397 024 980 306 1 372 429 33.1 81.7 6.81 1.6216 800 24 1280 92 764 9.3 453 662 1 433 969 2 007 556 37.8 119.5 9.96 1.5516 800 28 1284 100 914 10.1 387 357 1 821 325 2 549 855 32.3 151.8 12.65 1.43

DRY DENSITY:

CAPACITY ANALYSISMagdalena Coal Discard Disposal Facility



Appendix D

Slope Stability

218.75

175.00

131.25

87.50

43.75

00 43.75 87.50 131.25 175.00 218.75 262.50 306.25 350.00

Scenario A - Fully Drained

2.172.192.202.212.232.272.292.292.302.30

Safety Factors

218.75

175.00

131.25

87.50

43.75

00 43.75 87.50 131.25 175.00 218.75 262.50 306.25 350.00

Scenario B - Partly Drained

1.911.931.941.941.962.002.012.022.022.03

Safety Factors

218.75

175.00

131.25

87.50

43.75

00 43.75 87.50 131.25 175.00 218.75 262.50 306.25 350.00

Scenario C - Near Saturation

1.661.671.681.681.691.741.741.741.751.75

Safety Factors



Appendix E

Conceptual Drawings

OWNER: DATEBY

DRAWN

DESIGNEDCHECKED / REVIEW

SCALEDRAWING No. REVISION

DescriptionDate No. Initials

A

GPGP

WD

A0= AS SHOWN

001 GENERAL ARRANGEMENT

ZINOJU INVESTMENT

DISCARD COALFACILITY

(CONCEPTUAL DESIGN)

RETURN WATER DAMSECTIONS & DETAILS

SLA.06.190.004.DWG

A OCT 2006 GP CONCEPTUAL DESIGN ISSUED

Copyright reserved by GCS (Pty) Ltd.

63 Wessel Road WoodmeadPO Box 2597 Rivonia 2128 South AfricaTel: +27 (0) 11 803 5726Fax: +27 (0) 11 803 5745E-mail:[email protected]

REFERENCES

PROJECT:

DRAWING TITLE:

OCT 2006

REVISIONS

CLIENT:

DescriptionDrawing no.

(P T Y) L T D

W A T E R , E N V I R O N M E N T A L & E A R T H S C I E N C E C O N S U L T A N T S

1.5

1

OCT 2006

OCT 2006

(PTY) LTD.

002 PRI-CIVIL EARTH WORKS

003 COAL DISCARD DUMP SECTIONS & DETAILS

J

5000

1500 15000 1500

1000

1000

1000

1000 1000

900

600

SELECTED HOMOGENOUS MATERIALCOMPACTED TO 100% PROCTOR DENSITYAS APPROVED BY DESIGN ENGINEER

BOX-CUT DEPTH MIN.1m DEEP

NGL

RIP $ COMPACT BASE AREA

C WALL

2

1

200mm RIP & RAP

1251 EL.

NGL

NGL

200mm RIP & RAP

SCALE 1:200

SECTION B-B

1.51

1.51

C

1251 EL.

SPILLWAY

300mm THICK GROUTEDSTONE PITCHING

SCALE 1:50

SECTION J

J

004

004

004

SPILLWAY

PUMP STATION

RETURN WATER DAMOUTLET STRUCTURE

NOT TO SCALE

RETURN WATER DAM (PLAN VIEW)

C INTAKE

300mm MILD STEEL PIPE

M004

M004

FLOW

FLANGE 600/3

25 MPa CONCRETE

25 MPa CONCRETE

20 DIA. M.S. BARS1000mm LONG AT 150mm CENTRES

SCALE 1: 25

RETURN WATER DAM OUTLET STRUCTURE (PLAN VIEW)

C INTAKE

NGL

BEND TO SUIT 300 NB305C/F MILD STEEL PIPE

FLOW

300mm MILD STEEL PIPE

25 MPa CONCRETE

25 MPa CONCRETE

50mm THICK 15 MPaCONCRETE BLINDING

WELDMESH REF 617 STEEL REINFORCEMENT

MS LOST SHUTTER

510330 REDUCERWELDMESH REF 617 STEEL REINFORCEMENT

510 I.D. PRECAST PENSTOCK RING CAST IN FLUSH AND LEVEL

SCALE 1:25

SECTION M004

NOT TO SCALE

N.G.L.

1255

1245

1250

1260

1265

1270

1275

1280

1285

1290

1295

100 150 200 250 300 350 400 4500 50

OWNER: DATEBY

DRAWN




A

GPGP

WD

A0= 1:500/AS SHOWN


ZINOJU INVESTMENT


(CONCEPTUAL DESIGN)

COAL DISCARD DUMPSECTIONS & DETAILS

SLA.06.190.003.DWG




REFERENCES

PROJECT:

DRAWING TITLE:

OCT 2006

REVISIONS

CLIENT:


(P T Y) L T D


SCALE 1:25 (DIMENSIONS IN MM)

SEEPAGE COLLECTION DRAIN

COAL DISCARD MATERIAL

GEOFABRIC

NGL

1000

850

1000DRAIN COLLECTOR PIPE

WASH FILTER STONE

1.51.5

1 1

1000

NGL

1.5

1

1.5

1

1.5

1

1000

MIN. 80

0 (NTS)

NGL


STORM WATER CUT-OFF BERM

1.5

1

2

1

1000CATCHMENT AREA

1000

1:50 GRADIENT

1000

TOP SURFACE TO BE SHAPEDTO A MIN. 0F 1:200 GRADIENT

BERM WALL

CROSS WALL SPACEDAS PER DRAWING REF.OO1

GRASSING TO BE PLACEDCONTINUOUSLY AS SLOPESARE COMPLETED

2

1


DETAIL 1

NGL

ACCESS ROAD

DRAINAGE COLLECTORSUMP

CATCHMENT PADDOCK

TOE DRAIN

STARTER WALL

NGL

NGLTOP SURFACE MIN. 1:200 GRADIENT AS PER DRAWING REF.001

COAL DISCARD DUMP

STORMWATER DIVERSIONBERM

TOE DRAIN

STORMWATER DIVERSIONBERM

TOE DRAIN

PERMANENT STORMWATER DIVESIONBUNDWALL & ACCESS ROAD

TOE DRAIN

OCT 2006

OCT 2006

(PTY) LTD.

002 PRI-CIVIL EARTH WORKS

004 RETURN WATER DAM SECTIONS & DETAILS



(PTY) LTD.

GENERAL ARRANGEMENTPRE - DEPOSITION

CIVIL WORKS


(CONCEPTUAL DESIGN)



REFERENCES

PROJECT:

DRAWING TITLE:

REVISIONS

CLIENT:


EXISTING DIAMOND MESH FENCE

X 309 6000

X 309 6200

X 309 6400

X 309 6600

X 309 6000

X 309 6200

X 309 6400

X 309 6600

Y 79

400

Y 79

200

Y 79

000

Y 78

800

Y 78

600

1240

1300

1295

1290

1285 1280

1275

1270

1265

1260

1255

1250

1245

1240

NEW ACCESS ROAD

15m PADDOCK WALL

DRAIN COLLECTOR PIPE

ACCESS TO EXISTINGHAUL ROAD

CONFINEMENT PADDOCK WALL


STORMWATER CUT-OFF BERMREFER TO DETAIL 1

BARGE PUMP

HDPE OUTFALL LINE

1:20

0

PADDOCK CROSS WALL(TYPICAL)

NEW ACCESS ROADACCESS TO EXISTINGHAUL ROAD


PUMP STATION

RETURN WATER TO PLANT

DRAIN OUTLET PIPE

ZINOJU INVESTMENT

003 DISCARD DUMP SECTIONS & DETAILS


NORT

H

1:20

0

1:20

0

STARTER WALL

MH MH

MH

MH

MH

MH

MHMH

DRAIN OUTLETSUMP

TEMP. STORMWATER CUT-OFF BERMREFER TO DETAIL 1

TEMP. STORMWATER CUT-OFF BERMREFER TO DETAIL 1

OWNER: DATEBY

DRAWN




A

GPGP

WD

A1=1:1500

002 PRE-CIVIL WORKS

(PTY) LTD.

GENERAL ARRANGEMENTFINAL LAYOUT


(CONCEPTUAL DESIGN)

SLA.06.190.001.DWG



REFERENCES

PROJECT:

DRAWING TITLE:

OCT 2006

REVISIONS

CLIENT:


(P T Y) L T D



A003


X 309 6000

X 309 6200

X 309 6400

X 309 6600

X 309 6000

X 309 6200

X 309 6400

X 309 6600

Y 79

400

Y 79

200

Y 79

000

Y 78

800

Y 78

600

Y 79

400

Y 79

200

Y 79

000

Y 78

800

Y 78

600

1300

1295

1290

1285

1280

1275

1270

1265

1260

1255

1250 12

45

1240

1300

1295

1290

1285 1280

1275

1270

1265

1260

1255

1250

1245

1240

NEW ACCESS ROAD

15m PADDOCK WALL

DRAIN COLLECTOR PIPE

ACCESS TO EXISTINGHAUL ROAD

CONFINEMENT PADDOCK WALL


STORMWATER CUT-OFF BERMREFER TO DETAIL 1

BARGE PUMP

HDPE OUTFALL LINE

1:200

1:200

1:200

BERM CROSS WALL(TYPICAL)

BERM WALL(TYPICAL)

PADDOCK CROSS WALL(TYPICAL)

NEW ACCESS ROADACCESS TO EXISTINGHAUL ROAD


PUMP STATION

RETURN WATER TO PLANT

DRAIN OUTLET PIPE

A003

DETAIL 2003

OCT 2006

OCT 2006

ZINOJU INVESTMENT

003 DISCARD DUMP SECTIONS & DETAILS


NORT

H

MH MH

MH

MH

MH

MH

MH

MHMH

COAL DISCARD DUMP

RETURN WATERDAM

B

004

B004



Appendix F

Safety Classification

...\Appendix F - Figure B_Safety Classification(V8) 2D.dgn 2006/10/20 01:38:09 PM

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