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SLR Ref. 710.21002.00036 Report No.1

ENVIRONMENTAL IMPACT ASSESSMENT AND ENVIRONMENTAL MANAGEMENT PROGRAMME REPORT

FOR CHANGES TO OPERATIONS AT UMK MINE October 2017

Page V

APPENDIX V: CONCEPTUAL WASTE ROCK DUMP DESIGN REPORT

United Manganese of Kalahari Project

Detailed Design of the UMK Waste Rock Dump No.11

UMK Waste Rock Dump No.11 Site Investigation

SLR Project No.: 710.21002.000047

Report No.: DRAFT

September 2017

DOCUMENT INFORMATION

Title Geotechnical Investigation for the waste rock dump

Project Manager Marline Medallie

Project Manager e-mail [email protected]

Author Carl Fietze

Reviewer Francois van Heerden

Client United Manganese of Kalahari

Date last printed 2017/10/01 03:16:00 PM

Date last saved 2017/09/29 11:03:00 AM

Comments

Keywords Confidential

Project Number 710.21002.00047

Report Number 01

Revision Number Revision No.0

Status Draft

Issue Date September 2017

This report has been prepared by an SLR Group company with all reasonable skill, care and diligence,

taking into account the manpower and resources devoted to it by agreement with the client. Information

reported herein is based on the interpretation of data collected, which has been accepted in good faith as

being accurate and valid.

No warranties or guarantees are expressed or should be inferred by any third parties.

This report may not be relied upon by other parties without written consent from SLR.

SLR disclaims any responsibility to the Client and others in respect of any matters outside the agreed

scope of the work.

SLR South Africa Pty (Ltd)

SLR Ref. 710.21002.00047 Report No.01

Geotechnical Investigation for Waste Rock Dump UMK Mine Site Investigation

September 2017

DETAILED DESIGN OF THE UMK SOUTH WASTE ROCK DUMP

CONTENTS

1 INTRODUCTION ................................................................................................................................... 2

1.1 PROJECT DESCRIPTION ..................................................................................................................... 2

1.1 TERMS OF REFERENCE ..................................................................................................................... 2

2 SCOPE OF WORK ................................................................................................................................ 3

3 AVAILABLE DATA ............................................................................................................................... 3

4 ASSUMPTIONS ..................................................................................................................................... 4

5 BACKGROUND INFORMATION .......................................................................................................... 4

5.1 SITE DESCRIPTION ............................................................................................................................ 4

5.2 TOPOGRAHY ..................................................................................................................................... 4

5.3 CLIMATE ........................................................................................................................................... 5

5.4 HYDROLOGICAL SETTING ................................................................................................................... 6

5.5 HYDROGEOLOGICAL SETTING ............................................................................................................ 8

6 GEOLOGY ............................................................................................................................................. 8

6.1 REGIONAL GEOLOGY ......................................................................................................................... 8

6.2 SITE GEOLOGY ............................................................................................................................... 10

7 GEOTECHNICAL CONDITIONS ........................................................................................................ 12

7.1 GEOTECHNICAL FIELD INVESTIGATION .............................................................................................. 12

7.2 LABORATORY TESTING .................................................................................................................... 13

7.3 WRD SOIL PROFILE ........................................................................................................................ 15

7.4 GROUNDWATER .............................................................................................................................. 15

7.5 PRELIMINARY GEOTECHNICAL MODEL .............................................................................................. 16

7.6 CONCLUSIONS ................................................................................................................................ 16

8 WASTE MATERIAL CHARACTERISATION ...................................................................................... 17

8.1 GEOCHEMICAL CHARACTERISTICS ................................................................................................... 17

8.2 GEOTECHNICAL CHARACTERISTICS .................................................................................................. 18

9 DESIGN OF THE WRD NO.11 ............................................................................................................ 20

9.1 DESIGN CRITERIA ........................................................................................................................... 20

9.2 WASTE DUMP STABILITY ................................................................................................................. 23

9.3 ROCKFALL ANALYSIS ....................................................................................................................... 24

9.4 CONTAINMENT WALLS ..................................................................................................................... 26

9.5 STORMWATER MANAGEMENT .......................................................................................................... 26

9.6 CONTAINMENT BARRIER .................................................................................................................. 26

9.7 WRD DESIGN SUMMARY ................................................................................................................. 29

9.7.1 MATERIAL DEPOSITION ............................................................................................................................... 29

9.7.2 WRD LAYOUT AND DEVELOPMENT .............................................................................................................. 29

9.7.3 WRD CONSTRUCTION METHODOLOGY ......................................................................................................... 29

9.8 CONSTRUCTION COST ESTIMATE ..................................................................................................... 30

10 CLASSIFICATION OF THE WASTE ROCK DUMPS ......................................................................... 30

10.1 SAFETY CLASSIFICATION ................................................................................................................. 30


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September 2017

10.1.1 REQUIREMENTS ARISING FROM SAFETY CLASSIFICATION OF THE WRD........................................................... 32

10.2 WASTE ROCK DUMP STABILITY RATING ........................................................................................... 33

10.2.1 STABILITY RATING ..................................................................................................................................... 33

10.3 SECURITY ....................................................................................................................................... 38

10.4 DECOMMISSIONING AND CLOSURE ................................................................................................... 38

REFERENCES ............................................................................................................................................ 39

LIST OF FIGURES

FIGURE 1: SITE LOCALITY ......................................................................................................................................... 7

FIGURE 2: LOCAL SETTING OF UMK MANGANESE MINE ....................................................................................... 9

FIGURE 3: NORTH-SOUTH CROSS SECTION OF THE LOCAL GEOLOGY AT UMK MINE (UMK, 2013). ............ 11

FIGURE 4: SITE LAYOUT SHOWING TEST PI LOCATIONS .................................................................................... 14

FIGURE 5: FRICTION ANGLE VERSUS NORMAL STRESS FOR VARYING ROCKFILL CONDITIONS (LEPS, 1970) ................................................................................................................................................................... 19

FIGURE 6: WRD NO.11 WASTE PRODUCTION PLAN: VOLUME VERSUS MONTH/YEAR ................................... 22

FIGURE 7: PERCENTAGE MATERIAL TYPE FOR THE WRD NO.11 ...................................................................... 23

FIGURE 8: EXAMPLE OF ROCKFALL ANALYSIS CARRIED OUT ........................................................................... 25

LIST OF TABLES

TABLE 1: REPORTS REVIEWED FOR ASSESSMENT .............................................................................................. 3

TABLE 2: ASSUMPTIONS FOR THE WRD NO.11 DESIGN ....................................................................................... 4

TABLE 3: SUMMARY OF MONTHLY RAINFALL DATA (AECOM, SEPTEMBER 2017) ............................................ 5

TABLE 4: RAINFALL DEPTH FREQUENCY (AECOM, SEPTEMBER 2017) .............................................................. 6

TABLE 5: GENERAL STRATIGRAPHIC COLUMN FOR THE KALAHARI MANGANESE FIELD .............................. 10

TABLE 6: TEST PITS CO-ORDINATES ..................................................................................................................... 12

TABLE 7: LABORATORY TESTING SCHEDULE. ..................................................................................................... 13

TABLE 8: DEPTH AND INFERRED THICKNESS OF SOIL HORIZON. ..................................................................... 15

TABLE 9: PRELIMINARY GEOTECHNICAL MODEL. ................................................................................................ 16

TABLE 10: SUMMARY OF WASTE MATERIALS SHEAR STRENGTH. .................................................................... 21

TABLE 11: SIMPLIFIED WRD NO.11 MINE PRODUCTION PLAN ............................................................................ 22

TABLE 12: WASTE MATERIALS. ............................................................................................................................... 22

TABLE 13: ROCK SIZES USED FOR ASSESSING LINER PENETRATION ............................................................. 25

TABLE 14: LANDFILL DISPOSAL REQUIREMENTS DETAILED IN THE NATIONAL NORMS AND STANDARDS FOR DISPOSAL OF WASTE TO LANDFILL (GN R. 636) .................................................................................. 27

TABLE 15: GENERAL INFORMATION FOR THE SAFETY CLASSIFICATION OF THE WRD ................................. 31

TABLE 16: SAFETY CLASSIFICATION CRITERIA (SANS 10286 (1998)) ................................................................ 31

TABLE 17: SAFETY CLASSIFICATION (SANS 10286) ............................................................................................. 32

TABLE 18: MINIMUM REQUIREMENTS ASSOCIATED WITH A LOW HAZARD WRD ........................................... 32

TABLE 19: STABILITY RATING FOR THE PROPOSED WRD NO.11 ...................................................................... 34

LIST OF APPENDICES

APPENDIX A: SOIL PROFILES .................................................................................................................................... A


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September 2017

ACRONYMS AND ABBREVIATIONS

Below a list of acronyms and abbreviations used in this report.

Acronyms / Abbreviations

Definition

WRD Waste Rock Dump

UMK United Manganese of Kalahari

KMF Kalahari Manganese Field

WRD NO.11 Waste Rock Dump No.11

TDS Total Dissolved Solids

EC Electrical Conductivity

UMO Upper Manganese Ore bodies

MMO Middle Manganese Ore bodies

LMO Lower Manganese Ore bodies

BIF Banded Iron-Formation

mbgl Metres Below Ground Level


SLR Ref. 710.21002.00047 Report No.Doc. no.

Detailed Design for Waste Rock Dump No.11 UMK Site Investigation

September 2017

Page 2

DETAILED DESIGN OF THE UMK SOUTH WASTE ROCK DUMP

1 INTRODUCTION

1.1 PROJECT DESCRIPTION

The United Manganese of Kalahari (Pty) Ltd (“UMK”) mine is an opencast manganese mine located

approximately 80 km north west of Kuruman, 21km north of Hotazel, 42km north of Kathu and 56 km

east of Kuruman in the Northern Cape Province. The study area is located in the Kalahari Manganese

Fields (“KMF”) and UMK mine lies directly adjacent to the west of the R380 provincial road. The UMK

mine consists of open-pit mining sections, crushing and screening operations, run of mine (“ROM”)

stockpiles, Waste Rock Dumps (“WRD”) and product stockpile dumps, and associated support and

administrative infrastructure. The proposed UMK Waste Rock Dump No.11 (“WRD No.11”) is located to

the west of the existing UMK Mine and R380 as shown in Figure 1.

1.1 TERMS OF REFERENCE

In support of environmental studies, SLR Consulting (South Africa) (Pty) Ltd (“SLR”) was appointed by

United Manganese of Kalahari (Pty) Ltd to carry out a detailed design of the Waste Rock Dump (“WRD

NO.11”). As part of obtaining the Mining Right it is necessary to apply for a Waste Management Licence

under the National Environmental Management: Waste Act, 2008 (Act No. 59 of 2008) for the proposed

WRD.

In applying for a Waste Management Licence for the WRD the requirements of the following regulations

need to be satisfied:

• Regulations Regarding the Planning and Management of Residue Stockpiles and Residue Deposits

from a Prospecting, Mining, Exploration or Production Operation, 2015 (GN R.632);

• Waste Classification and Management Regulations, 2013 (GN R.634);

• National Norms and Standards for the Assessment of Waste for Landfill Disposal, 2013 (GN R. 635);

• National Norms and Standards for Disposal of Waste to Landfill, 2013 (GN R.636).

In order to comply with the requirements above the following objectives were established:

• Assessment of the in-situ founding conditions of the footprints area of the Overburden Dump;

• Geotechnical Investigations and assessment of the in-situ founding conditions of the footprints area

of the Waste Rock Dump;

• Geotechnical recommendations and founding designs based on the findings of the geotechnical

investigations;

• Stability analysis of the slopes and founding conditions of the Waste Rock Dump;




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• Detailed geometric design for the operational Waste Rock Dump;

• Preparation of technical specifications.

2 SCOPE OF WORK

The following scope of work was carried out to achieve the terms of reference:

• A review of previous geotechnical work was carried out, including the assessment of foundation

conditions and previous geotechnical recommendations;

• A Geotechnical Investigation was carried out which included an assessment of the in situ founding

conditions;

• A stability analysis of the WRD No.11 slopes and founding conditions was carried out with the

following included in the analysis:

o Foundation consolidation assessment;

o Seismic Assessment including the influence blasting will have on the dump;

o Rock fall analysis for design of rock barriers to protect equipment working (if required).

• Detailed geometric design for Overburden Dump;

• The deliverables of the detailed design are:

o Detail design drawings. The drawings will submitted, in A1 format hardcopy, in a book of

drawings, as well as electronic Adobe pdf and DWG versions;

o Technical specifications (as applicable);

o Schedule of quantities;

o Detailed design report.

3 AVAILABLE DATA

The following reports were provided for design purposes, summarised in Table 1.

TABLE 1: REPORTS REVIEWED FOR ASSESSMENT

Author Date Title Reference

Reports

AGES 2007-03-22 United Manganese of the Kalahari: Specialist Geohydrological Study

AS-R-2007-03-22

SLR 2011-11-04 UMK on site Hydrocensus Report 710-21002-0009

SRK 2013-09-01 Smartt-Rissik Monthly Water Balance update

441612/1 Rev A

UMK Hannes van der Merwe

2013-02-22 Geological Presentation -

SLR 2014-11-11 Groundwater Abstraction Impact Assessment at UMK

710.21002.00022




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Author Date Title Reference

SLR 2016-11-08 Preliminary Mine Closure Plan 710.21002.00035

4 ASSUMPTIONS

The assumptions made for the design of WRD No.11, based on the 2016 waste schedule, is summarised

in Table 2. The waste schedule is currently been updated for 2017 and the results will be used for the

final detailed design.

TABLE 2: ASSUMPTIONS FOR THE WRD NO.11 DESIGN

Item Assumption

WRD configuration dump height Height of Southern WRD approximately 60 m high

WRD volume (m3) 14 250 322

WRD material quality Predominantly weak rocks of low durability/Greater than about 25% fines, overburden

WRD method of construction Thin lifts (< 25m thick), wide platforms

WRD dumping rate Crest advancement rate 0.1m - 1.0m per day

5 BACKGROUND INFORMATION

5.1 SITE DESCRIPTION

The site is located within the municipal boundries of John Taolo Gaetsewe District and Joe Morolong

Local Municipality. The site for WRD N0.11 covers 95.8 ha. The WRD is located adjacent to the west of

the existing UMK Mine and R380 Provincial road (See locality map Figure 1). The predominant

economic activities in the region are cattle grazing and manganese mining, with the Mamatwan Mining

Operations located directly to the south, the Tshipi Borwa Mining Operations located to the south-west of

the site and the Kudumane Mine located to the north.

5.2 TOPOGRAHY

The topography of the Kalahari Manganese Field (“KMF”) is predominately flat-lying at 1100m elevation,

with relatively low relief. The area is characterised by several vegetated northwest and southwest

trending red sand dunes, up to the 10m in height, up to 200m wide and tens of kilometres in length. The

regional drainage pattern is broadly northwards but water-flows in the streams are generally very rare.

The topography of the mining area is also relatively flat and therefore it is expected that the climate of

Kuruman is predominately representative of the surrounding mining area.




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5.3 CLIMATE

The mine falls within the Northern Steppe Climatic Zone, as defined by the South African Weather

Bureau. This is a semi-arid region characterised by seasonal rainfall, hot temperatures in summer, and

colder temperatures in winter (Metago, April 2007). The Mine is characterised by hot summers and cool

winters with rain generally occurring in the form of thunderstorms that last for short periods at a time

during rainy periods. High evaporation rates reduce infiltration, while rainfall events can increase the

erosion potential and the formation of erosion gullies. The presence of vegetation does however reduce

the effects of erosion. The mixing of layers resulting in the formation of temperature inversions, and the

presence of cloud cover limits the dispersion of pollutants in the atmosphere. Wind significantly affects

the amount of material that is suspended from exposed surface to the atmosphere. Although wind

speeds above 5.3m/s can occur, the data shows that on average they are below this value and therefore

not able to carry dust particles. These climatic aspects need to be taken into consideration during

operations, rehabilitation and surface water management planning

Monthly rainfall data and evaporation data for the Milner weather station is summarised in Table 3 below.

Rainfall depth frequency data is summarised in Table 4 below.

The average rainfall at the Milner weather station is 343mm per annum. Given the Milner weather station

is only 3.6km from the mine site, similar rainfall levels can be expected at the mine. The average

evaporation rates recorded at the Milner weather station are 1971mm per annum.

TABLE 3: SUMMARY OF MONTHLY RAINFALL DATA (AECOM, SEPTEMBER 2017)

MONTH RAINFALL (MM) EVAPORATION

Milner – 393083_W WR90

January 58.6 233

February 58.2 185

March 66.1 170

April 33.5 127

May 15.5 100

June 5.9 77

July 2.4 88

August 4.0 124

September 5.6 172

October 17.8 218

November 29.1 233

December 46.4 244

Annual 343.1 1971




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TABLE 4: RAINFALL DEPTH FREQUENCY (AECOM, SEPTEMBER 2017)

RETURN PERIOD (YEARS)

1:2 1:5 1:10 1:20 1:50 1:100 1:200

48 68 82 97 116 131 148

5.4 HYDROLOGICAL SETTING

The water management area under which this site falls is the Lower Vaal, within which the major rivers

are the Harts, Malopa and Vaal. It falls into quaternary catchment D41K. The non-perennial drainage

line Gamagara River is located approximately 5 km to the west of the site, and the non-perennial

drainage line Witleegte Stream is located approximately 2.5 km to the north east of the site. Drainage

from the site is likely to flow in a westerly direction following the local topography. There does not

appear to be any influence on the groundwater level by the presence of the non-perennial stream,

Witleegte, as the groundwater levels do not become shallower with the presence of the stream. This

indicates that the stream is not fed by baseflow from the aquifer (AGES, 2007).




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FIGURE 1: SITE LOCALITY




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5.5 HYDROGEOLOGICAL SETTING

The main regional aquifer is the deep fractured aquifer made of the weathered Dwyka tillite and the

Mooidraai Formation dolomite. The Kalahari sand and the sediment beds that overlie the low

permeability Dwyka tillite is also considered an aquifer. The aquifers are classified as poor to minor.

Borehole yields in the deeper aquifer are low; however structural features such as faults and fractures

can produce high yielding boreholes.

Prior to mining, groundwater flow (baseline) at the site was from south-west to north-east towards the

Gamagara River with the average water level in the area approximately 25 metres below ground level

(“mbgl”) (AGES, 2007). Baseline groundwater quality (AGES, 2007) indicated poor water quality in the

vicinity of the site with high levels of total dissolved solids (“TDS”), nitrate (NO3-N), electrical conductivity

(“EC”), and fluoride (F). The geology of the area and the activity of hydrothermal leaching results in the

possibility of the following constituents being detected in abnormally high concentrations in the

groundwater: carbon dioxide (CO2), manganese oxide (Mn3O4), iron oxide (Fe2O3), calcium oxide (CaO),

magnesium oxide (MgO), lead (Pb) and boron (B) (Du Plooy, 2002).

6 GEOLOGY

6.1 REGIONAL GEOLOGY

The UMK Mine is located on the south western outer rim of the Kalahari Manganese Field (“KMF”). The

stratigraphy of the ore-bearing succession in the area consists of three manganese beds named the

Upper (“UMO”) and Middle (“MMO”) and Lower Manganese (“LMO”) Ore bodies. The LMO has been

sud-divided on the basis of mineralogical composition which is often manifested by visual mineralogical

differences. The mineralised bodies are hosted by altered banded iron-formation (“BI”F) and jaspilites of

the Hotazel Formation, which uncomformably overlies the Ongeluk Lava. The mine is exploiting the

manganese from the lower most bed. The BIF of the Hotazel Formation typically consists of repeated

thin layers of black iron oxides (magnetite or hematite) alternating with bands of iron-poor shales and

cherts. The Hotazel Formation is underlain by basaltic lava of the Ongeluk Formation (Transvaal

Supergroup) and directly overlain by dolomite of the Mooidraai Formation (Transvaal Supergroup).

The Transvaal Supergroup is overlain unconformably by the Olifantshoek Supergroup which consists of

arenaceous sediments, typically interbedded shale, quartzite and lavas overlain by coarser quartzite and

shale. The Olifantshoek Supergroup is overlain by Dwyka Formation which forms the basal part of the

Karoo Supergroup and in turn is covered by typically sands, claystone and calcrete of the Kalahari

Group. The general stratigraphic column for the Kalahari Manganese Field is provided in Table 5.




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FIGURE 2: LOCAL SETTING OF UMK MANGANESE MINE




September 2017

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TABLE 5: GENERAL STRATIGRAPHIC COLUMN FOR THE KALAHARI MANGANESE FIELD Supergroup / Group / Subgroup / Formation Geological Description

Kalahari Group Kalahari sands, calcrete, clays & gravel beds

Kalahari unconformity

Karoo Supergroup Dwyka tillite

Dwyka unconformity

Olifantshoek Supergroup Lucknow Formation White ortho-quartzite

Mapedi Formation Green, maroon and black shales and quartzites

Olifantshoek unconformity

Tra

nsvaal S

uperg

roup

Postm

ansburg

Gro

up

Voelw

ate

r S

ubgro

up

Mooidraai Formation Dolomite, chert

Hotazel Formation

Banded ironstone (upper)

Upper Mn Ore Body

Banded ironstone (middle)

Middle manganese body

Banded ironstone (middle)

Lower manganese body

Banded ironstone (lower)

Ongeluk Formation Andesitic Lava

6.2 SITE GEOLOGY

The local geology of the UMK Mine consists of the Hotazel Formation overlain by the Kalahari Group and

underlain by the Ongeluk lavas. The Kalahari Formation calcrete, clays and gravel beds increase in

thickness to the south and north of the deposit.

The Hotazel Formation BIF is made up of three (3) alternating layers of banded ironstone and

manganese. The mine is currently exploiting the economical horizon which is the lower most bed of the

manganese ore. This lowermost manganese ore bed is predominantly Braunite rock beds and this is the

major ore unit within the Kalahari manganese field. The north-south (Figure 3) cross sections of the

UMK Mine illustrates the upper, middle and lower units of the Hotazel Formation containing the

manganese ore.




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FIGURE 3: NORTH-SOUTH CROSS SECTION OF THE LOCAL GEOLOGY AT UMK MINE (UMK, 2013).




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7 GEOTECHNICAL CONDITIONS

7.1 GEOTECHNICAL FIELD INVESTIGATION

The site investigation of the proposed WRD site was undertaken during the 11th to 14

th September 2017.

A total of ten (10) testpits were excavated with a Tracker Loader Backhoe (“TLB”), CAT 482F2. All

testpits were excavated to refusal depth or to the maximum reach of the machine.

The testpits were geotechnically logged in-situ by a suitably qualified SLR Engineering Geologist and a

visual assessment of geotechnical conditions made. The soil profile was described in terms of standard

descriptors, namely moisture content, colour, consistency, structure, soil type and origin (MCCSSO) as

per the guidelines provide by the Revised Guide to Soil Profiling for Civil Engineering Purposes in

Southern Africa (1990). After profiling and sampling the test pits were backfilled.

Copies of the soil profiles, which graphically represent the soil conditions encountered in the testpits, are

presented in Appendix A. The positions of the test pits were selected based on early conceptual layout

of the facility and positioned to gain maximum coverage of the area. The positions of the test pits were

recorded with a handheld GPS (accuracy of 5 m) with co-ordinates provided on each test pit profile in

WGS84 Datum, South African coordinate system (Lo 29). The test pits co-ordinates are provided in

Table 6. All the test pits excavated from the geotechnical investigations are shown in Figure 4.

Representative undisturbed and disturbed soil samples were taken from selected test pits for laboratory

testing. All soil samples were transported to the SANAS-accredited soil testing laboratory GeoTech (Pty)

Ltd, Krugersdorp, Gauteng for testing.

TABLE 6: TEST PITS CO-ORDINATES

Hole ID Latitude Longitude Elevation Depth (m) Comments

UMK01 272116.7 225742.5 1085 3.6 No refusal. Limit of the machine



UMK04 272045.4 225738.7 1083 3.58 Refusal at 3.58m. Hardpan Calcrete





UMK09 272059.4 225737.4 1084 2.98 Refusal at 2.98m. Hardpan Calcrete.


*Test Pit co-ordinates were recorded by hand-held GPS accurate to about 5m




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7.2 LABORATORY TESTING

Disturbed and undisturbed samples were taken from representative test pits at various depths for the

purposes of laboratory testing. Samples taken during test pitting were sent to commercial soil

laboratories for testing. A summary of the testing program is provided in Table 7.

Laboratory tests for foundation engineering purposes will be conducted on selected soil samples taken

from the soil horizons encountered in the test pits and will be provided in the final report. The testing

currently being carried out comprises the following:

• Full Particle Size Distribution Testing;

• Atterberg Limits Testing;

• Permeability Testing;

• Standard Proctor Moisture Density Relationship Testing;

• Consolidated Undrained Triaxial Testing

• Moisture Content

• Bulk Density

• Standard Consolidation Test

TABLE 7: LABORATORY TESTING SCHEDULE.

Hole ID

Depth sampled

Lithology

Geomechanical Testing Requirement

Foundation Indicator

Specific Gravity

Bulk Density

Moisture

Content

Standard Odometer

Permeability Consolidated

Undrained Triaxial

From

To

UMK02 0.88 0.98

Kalahari Aeolian Sand ✔ ✔ ✔ ✔ ✔ ✔ ✔

UMK02 1.58 2.01

Kalahari Aeolian Sand ✔ ✔ ✔ ✔ ✔

UMK10 1.2 1.58

Kalahari Aeolian Sand ✔ ✔ ✔ ✔ ✔ ✔ ✔




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FIGURE 4: SITE LAYOUT SHOWING TEST PI LOCATIONS




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7.3 WRD SOIL PROFILE

The following profile was encountered at the WRD:

• Topsoil: The topsoil was generally intersected from the surface on the across the site. The soils were

found to the low contact depths of between 0.48 m to 0.68 m and generally comprised moist, reddish

brown, sands with local horizons of sand with low silt content. The consistencies of soils derived from

the topsoil are medium dense to dense.

• Transported Aeolian Sands: The transported sand occurs beneath the topsoil and is of Aeolian

origin. The transported Aeolian sand encountered was thick, averaging approximately 2.5 m in

thickness and occur across the site. The transported Aeolian sand was generally moist, reddish to

greyish white, loose to very loose fine sand to silty sand.

• Hardpan Calcrete: The hardpan Calcrete underlies the transported Aeolian sand and was

encountered in test pits UMK09 and UMK10. The consistency of the Calcrete was found to be dense

to very dense. The Calcrete can be described as dry, white to light pinkish, white to light pinkish,

dense to very dense, moderately cemented, non-indurated, silty sand with low gravel content.

For details of the ground conditions at each test location, reference is made to Appendix A. A summary

of depths and inferred thickness of the soil horizon is provided in Table 8.

TABLE 8: DEPTH AND INFERRED THICKNESS OF SOIL HORIZON.

Hole ID

Test Pit Termination Depth (m)

Layer Thickness and Depth to the Base of Horizon (m) Depth to Calcrete

(m)

Depth to Groundwater

(m)

Topsoil Kalahari Aeolian

Sand Calcrete

Depth Thickness Depth Thickness Depth Thickness

UMK01 3.6 0.68 0.68 3.6 2.9 - - - -

UMK02 3.3 0.58 0.58 3.3 2.7 - - - -

UMK03 2.9 0.6 0.60 2.9 2.3 - - - -

UMK04 3.58 0.58 0.58 3.58 3.0 - - - -

UMK05 3.55 0.63 0.63 3.55 3.0 - - - -

UMK06 1.3 0.58 0.58 3.32 2.7 - - - -

UMK07 3.38 0.68 0.68 3.38 2.7 - - - -

UMK08 3.05 0.48 0.48 3.05 2.6 - - - -

UMK09 2.98 0.67 0.67 2.68 2.0 2.84 0.3 2.98 -

UMK10 2.2 0.72 0.72 2.15 1.4 2.2 0.1 2.6 -

7.4 GROUNDWATER

No ground water was encountered in any of the inspection pits and throughout the site.




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7.5 PRELIMINARY GEOTECHNICAL MODEL

The following preliminary geotechnical model has been developed based on the testpit logging and

engineering judgement. This model will be updated as soon as the laboratory test results have been

received. The preliminary geotechnical model is provided in Table 9.

TABLE 9: PRELIMINARY GEOTECHNICAL MODEL. Geotechnical

Domain Depth (m) Unified

Class Density (kg/m3)

Young’s Modules

(MPa)

Poisson’s Ratio

Cohesion (kPa)

Friction Angle

(Degrees)

From (m)

To (m)

Topsoil 0.0 0.60 - - - - - -

Kalahari Sand 0.60 3.0 SW/SM 1700-1800

17-25 0.2 0 33

Calcrete 3.0 5-10 GP/GW 2100 45 0.2 0 38

Clay 5-10 15-20

MH/OH 1500 14 0.35 70 23

7.6 CONCLUSIONS

The following preliminary conclusions have been made following the geotechnical investigation:

• Generally the soil profile below the topsoil material consist of slightly moist, reddish to light greyish

white, loose to dense, non-plastic, silty fine sand of Aeolian origin, which occurs across the site. The

transported aeolian soils are considered to be potentially collapsible; however this will be confirmed

once the geotechnical laboratory testing has been concluded.

• The site comprises approximately 95 ha of open veld with concentrated areas of dense vegetation. A

number of fence lines and gravel roads traverse the site.

• Topographically the site is generally flat. Restricted and minor bulk excavations to create construction

platforms will not be extensive.

• The majority of bulk and restricted excavations should be provisionally classed as ‘soft’ excavation

according to SABS 1200D to an average depth of 2.11 m (but can be deeper than 10 m below

surface in localised areas).

• Groundwater seepage is not anticipated during bulk earthworks.

• The use of materials for construction purposes is generally favourable.




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8 WASTE MATERIAL CHARACTERISATION

8.1 GEOCHEMICAL CHARACTERISTICS

The waste classification and waste type assessment has been undertaken for the Kalahari sand proxy

and WRDsamples. Fourteen samples, representative of the potential waste rock were collected by SLR

and geologists from UMK and submitted to an accredited laboratory for analysis of chemical substances

likely to occur in the waste.

The Kalahari sand and WRD samples were classified as non-hazardous in terms of GN. R. 636. Kalahari

sand and WRD samples were assessed to be Type 3 wastes because barium (Ba), fluoride (F) and

manganese (Mn) exceed total concentration threshold 0 (TCT0) with regards to their total concentration

(TC) and Type 4 wastes based on their leachable concentration (LC) (no exceedances of the leachable

concentration threshold (LCT). These samples thus do not satisfy the complete criteria for a Type 3

waste (LCT0<LC≤LCT1 and TC≤TCT1) or the complete criteria for Type 4 waste (LC≤LCT0 and

TC≤TCT0). The Kalahari sand does not require classification or assessment and thus, the inclusion of

this material in the classification and assessment procedure was purely for comparison purposes.

Annexure 1 to GN R. 634 lists wastes that do not require classification in terms of regulation 4(1) or

assessment in terms of Regulation 8(1)(a). The Kalahari sand is general waste as per Annexure 1

Section 2(a) (viii) (Excavated earth material not containing hazardous waste or hazardous chemicals).

Following the outcome of the waste assessment, a source term was developed to estimate the

contaminant mass that could be released from the WRD. The highest predicted concentrations are for

sulphates and chlorides. For the constituents of concern (CoCs) identified in the waste assessment only

F concentrations are predicted to exceed the LCT0 threshold by the modelling. From this data a source

term for the Cl, SO4 and F was developed.

Based on the source term SLR carried out a risk based approach for protection of the quality of water

resources for the UMK WRD. Based on the risk assessment a Class D barrier is recommended for the

following reasons:

• A class C liner is impractical for a WRD due to the possibility of failure;

• The materials were classified as non-hazardous;

• The leachable concentrations of all the constituents are below the LCT0 limit which indicates a low

seepage risk;

• The material will be placed dry and not contain waste water;

• From the geochemical study conducted by SLR it was concluded that the materials are not potentially

acid generating; and




September 2017

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• The area has low rainfall and high evaporation that would limit recharge from the dumps.

• A similar set of circumstances has been encountered at the nearby Kudumane mine. In that instance it

was determined by the relevant authorities (including DWS) that a Class D barrier (including stripping

topsoil and base preparation) will be adequate.

8.2 GEOTECHNICAL CHARACTERISTICS

Generally a Waste Rock Dump will comprise waste rock of varying particle size and shapes of different

geological origin, which makes the predication of the materials, shear strength difficult to predict. Rockfill

research has shown that the relationship between the shear strength and effective normal stress for a

rockfill is non-linear, similar to the relationship of a rock mass.

The percent of material passing 2mm is believed to affect the shear strength of rockfill. Large triaxial

tests for silty gravels were carried out by the USBR (1966). Tests were carried out at 0, 35, 50 and 65%

gravel content. Shear strengths were found to be similar for the 0 and 35% gravel content tests. Shear

strengths increased considerably at 50% and 65% gravel content. Further tests on clayey gravels found

that the shear strength increased considerably between 42 and 50% gravel content. Marsal (1976)

reports two triaxial tests each on rockfill-silt and rockfill-sand mixture and compares these to a test on

rockfill only. The clean rockfill and 10% sand-rockfill mixtures had a friction angle of 34.1° whilst the 30%

sand-rockfill had a friction angle of 39°. Marsal (1976) attributes the difference to the lower initial void

ratio in the 30% sand-rockfill mixture. The 10% silt-rockfill mixture showed a decrease in friction angle to

28.8° whilst the 30% silt rockfill mixture had the strength properties of the silt. In order to estimate the

shear strength of the waste rock the following methods have being applied:

• The shear strength of the waste rock can be represented by a poor quality rock mass using the Hoek

and Brown Failure criteria (H-B criteria);

• The shear strength of the waste rock can be estimated using the method outlined by Leps (1970) for

compacted rockfill. Leps compiled data using a number of large scale triaxial tests on gravels and

rockfill to develop stress dependent shear strength estimates for the following rockfall types:

o High density, well graded rockfill with strong particles;

o Low density, poorly graded rockfill with weak rock particles;

o Average rockfill between a high and low density rockfill.

• The work by Marsal (1973) on the shear strength of rockfill showed that the strength of rockfill may

vary directly with normal effective stress, dry density, particle roughness, particle crushing strength

and inversely with grain size, uniformity of grading, and particle shape. Based on these parameters

the following equation was developed to derive the friction angle of the waste material :




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Φ′ = a + bs ′ c

Where:

a = 36.43 - 0.267Angularity - 0.172Fines + 0.756(c - 2) + 0.0459(UCS - 150)

b = 69.51+10.27Angularity + 0.549Fines - 5.105(c - 2) - 0.408(UCS - 150) - 0.408

c = -0.3974

Angularity is measured on a scale from 2 to 8 with 2 rounded shape, 4 sub-rounded shape, 6 sub-

angular shape and 8 angular shape. Fines are defined as percentage fines passing 0.075 mm (%).

The UCS is the uniaxial compressive strength of the waste rock. Work has been carried out by

Middindi (2013), the results of which are provided in the section below.

FIGURE 5: FRICTION ANGLE VERSUS NORMAL STRESS FOR VARYING ROCKFILL CONDITIONS (LEPS, 1970)

A summary of the waste material shear strength assessment is provided in Table 10. The Kalahari Sand,

Red Clay Bed and the Upper/Basal Gravel geotechnical characteristics can be defined by conventional




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soil mechanics. The Tillite (Dwke), Dolomite and Banded Iron Formation have been assessed using the

techniques described in the introduction.

9 DESIGN OF THE WRD NO.11

9.1 DESIGN CRITERIA

The criteria for the design of the dumps and stockpiles are to minimise the pollution potential associated

with the materials deposited by:

• Ensuring that there is sufficient storage capacity within the available footprint areas to accommodate

the expected volumes of material to be dumped / stockpiled and that the deposition of materials to

those areas takes place in a controlled and structured fashion;

• Ensure the containment and control of surface water runoff and eroded material from the deposits;

• Ensure that, where possible, the geometry of the deposits is such that it facilitates rehabilitation and

closure and minimises the works required at the end of the life of mine to complete the closure

process.

An estimate of the dump/stockpile volumes required is presented in Table 11 and shown in detail in

Figure 2. It has been assumed that the estimated bulking factors have been included in the calculated

volumes. A summary of the waste material which will be deposited is provided in Table 12. The

percentage material type to be deposited on WRD No.11 is shown in Figure 3. WRD No.11 will be

developed over a period of 3 years from 2019 to 2021. The volumes are based on the 2016 LOM plans

which are currently been updated. The updated volumes will be incorporated for the final detailed design

of WRD No.11.

Material is expected to be delivered to the deposits by trucks from the mining fleet and will be spread and

shaped as necessary by earthmoving equipment. Some compaction of the waste is expected to take

place during placement as trucks pass repeatedly over previously placed material on their way to and

from the advancing faces of the deposits. While compaction of wastes is desirable in order to maximise

density and storage capacity, it is not a requirement for structural stability. Compaction will assist in

reducing differential settlements with time, which will assist in ensuring the longer term integrity of the

surface water management measures. Compaction of the topsoil materials should however be kept to a

minimum to facilitate the reuse of the material in the rehabilitation and closure of the mine




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TABLE 10: SUMMARY OF WASTE MATERIALS SHEAR STRENGTH.

Abbreviation Lithology Density (kg/m3)

% Fines passing

0.075 mm

UCS (MPa)

Normal Stress* (MPa)

Soil Fill Rock Fill

Mohr-Coulomb H-B criteria Leps Douglas

Cohesion (kPa)

Friction Angle (degrees)

Cohesion (kPa)


Cohesion (kPa)


Cohesion (kPa)


KS Kalahari Sand 1700 - - - 0 33 - - - - - -

CALC Calcrete Sequence 2100 30 20 0.6 - - 0 27 0 36 0 33

RCB Red Clay Bed 1500 - - - 0 23 - - - - - -

UPB Upper Gravel/pebble Bed 2100 - - - 0 38 - - - - - -

BPB Basal Gravel/pebble Bed

UBIF Hotazel Formation - Upper BIF

2500 10 200 0.93 - - 0 43 0 38 0 43 MBIF Hotazel Formation - Middle BIF

LBIF Hotazel Formation - Lower BIF

Normal Stress calculated for a 30 m slope height




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TABLE 11: SIMPLIFIED WRD NO.11 MINE PRODUCTION PLAN

Year m3

2019 5 397 545

2020 4 864 104

2021 3 988 673

Total Volume 14 250 322

TABLE 12: WASTE MATERIALS.

Abbreviation Lithology

CALC Calcrete Sequence

RCB Red Clay Bed

UPB Upper Gravel/pebble Bed

BPB Basal Gravel/pebble Bed

UBIF Hotazel Formation - Upper BIF

MBIF Hotazel Formation - Middle BIF

FIGURE 6: WRD NO.11 WASTE PRODUCTION PLAN: VOLUME VERSUS MONTH/YEAR




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FIGURE 7: PERCENTAGE MATERIAL TYPE FOR THE WRD NO.11

9.2 WASTE DUMP STABILITY

A series of slope stability analyse has been carried out for the proposed waste dump using limit

equilibrium techniques. These results are preliminary with detailed stability analysis to be carried out

once the geotechnical laboratory test results have been received.

The analyses were carried out deterministically using the two-dimensional limit-equilibrium program Slide

Version 6©, developed by Rocscience. Two methods - Spencer and GLE (General Limit

Equilibrium)/Morgenstern-Price - were applied in the analyses. The GLE/Morgenstern-Price and Spencer

methods are referred to as rigorous limit equilibrium methods because they satisfy complete equilibrium -

both force and moment equilibrium. They are recommended methods for practical slope stability analysis.

The Auto Refine Search option for non-circular surfaces was used in the analyses to search for critical

failure mechanisms. This iterative search method starts with circular surfaces, which then get converted

into non-circular piece-wise linear surfaces. The "Optimization" feature for this search option was turned

on to further facilitate identification of failure surfaces with the lowest factors of safety.

The limit equilibrium modelling was carried out using shear strengths derived in previous sections for the

foundation and for the waste material. A minimum FOS of 1.5 has been adopted for static conditions in

the long term.




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Based on the stability analysis the following is recommended:

• The red bed clays are the weakest of the materials in terms of geotechnical shear parameters. The

following is therefore recommended for the clays:

o The clay should be deposited within the WRD and not form the outer walls of WRD

no.11;

o Lift heights should be restricted to 10 metres;

o The clay should not be deposited at the base of the WRD; it is recommended that a

minimum 10 metre lift of hard rock such as the BIF or hard calcrete form the base of the

WRD before depositing the clay in order to restrict foundation failure.

• Lift heights of 20 metres can be achieved for the Calcrete, Gravel/pebble Beds, and BIF at angles of

repose;

• Minimum overall angles of 1V:2H are achievable; however cognisance needs to be made of overall

angles of 1V:3H for closure requirements. The 1V:3H angles can be achieved by increasing berm

widths.

9.3 ROCKFALL ANALYSIS

Parametric rockfall modelling was carried out to evaluate the impact end tipping of waste rock from a

height of 60 metres would have. This was carried out by evaluating rock bouncing, impact velocity and

moment of rest. Parametric modelling was carried out in ROCFALL© version 5. ROCFALL© is a 2-

dimensional rockfall simulation program which analyses the trajectory of falling blocks based on changes

in velocity as rock blocks roll, slide and bounce on materials that form the slope and endpoint distance.

This is carried out statistically over a number of simulations. For the purposes of this analysis

parameters varied included rock size, initial vertical velocity, normal restitution and tangential restitution.

The height of the slope was modelled at 60 metres. Following the ROCFALL© modelling an assessment

was made of bouncing, impact velocity and final rest position of the falling rock

For the purposes of modelling the following assumptions were made:

• 500 rock boulders were thrown;

• Typical values for the coefficient of normal restitution (Rn) used in rockfall analyses range from 0.3 to

0.5. Typical values used for the coefficient of tangential restitution (Rt) range from 0.4 to 0.95.

Vegetated areas and soft soils occupy the lower end of the ranges, and bedrock and asphalt the

higher end. As the entire slope comprises waste rock material the mean value of coefficient of

normal restitution used was 0.4 and the mean value of coefficient of tangential restitution used was

0.5. These values were also defined by a literature survey after Heidenreich (2004) and the

ROCFALL© database;

• A friction angle of 38 degrees was used;




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• Waste rock block size was varied from ± 0.5 to 1 m3 (summarized in Table 13);

• A unit density of 2700 kg/m3 was used for the rock.

TABLE 13: ROCK SIZES USED FOR ASSESSING LINER PENETRATION

Rock Shape Density (kg/m3) Dimension (m) Mass

block 2700 0.57 x 0.57 x 0.57 500

block 2700 0.718 x 0.718 x 0.718 1000

block 2700 0.822 x 0.822 x 0.822 1500

block 2700 0.905 x 0.905 x 0.905 2000

From the ROCFALL©

modelling and calculation of depth of penetration the following was noted.

Magnitude of impact velocity at moment of rest is depended on the size of the rock. Typically the impact

velocity various between 2.0 and 3.5 m/s for the modelled parameters. Depth of penetration is therefore

depended on rock size, as an example maximum penetration for a 2000 kg rock at an impact velocity of

3.5 m/s would penetrate to a depth of 1.5 m, while for a rock of 500 kg mass at an impact velocity of 3.5

m/s would penetrate to a depth of 0.4 m. Roll length varies between 20 and 40 m depending on block

size. Based on this analysis it is recommended that the a minimum buffer of 50 m is required between

the pit and the toe of the WRD No.11 in order to prevent rolling rock into the pit

FIGURE 8: EXAMPLE OF ROCKFALL ANALYSIS CARRIED OUT




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9.4 CONTAINMENT WALLS

The WRD has been designed with a 1.5m and 2m high inner and outer containment walls respectively.

The inner wall demarcates the waste rock dumping limits before reshaping. The outer wall forms a toe of

the reshaped side slope. Before the reshaping of the side slopes, the area between the two containment

walls will act as catchment paddocks that will temporary store any dirty runoff from non-rehabilitated

slopes.

9.5 STORMWATER MANAGEMENT

It is a legislative requirement that potentially contaminated surface water runoff from the dumps and

stockpiles is prevented from leaving the site and that uncontaminated water from the surrounding areas is

diverted around the deposits.

Stormwater runoff generated in the upper catchments will be diverted around the WRD by a clean

stormwater channel running along the outer containment wall. The stormwater runoff from the non-

rehabilitated slopes is considered dirty water, and will be stored and left to evaporate in the temporary

catchment area between the inner and outer containment walls (see Section 9.4 above). In practise, very

little runoff is likely to be generated by the un-rehabilitated waste rock dump surface due to climatic

conditions. Runoff from rehabilitated areas is expected to be clean and suitable for release to the

environment.

9.6 CONTAINMENT BARRIER

The containment barrier classes required by GN R.634 are given in Table 14. Based on SLR’s risk

based approach for protection of the quality of the water resources for the WRD NO.11 a Class D barrier

is recommended. Class D Barrier will entail the following:

• Removal of topsoil;

• 150 mm of base preparation.




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TABLE 14: LANDFILL DISPOSAL REQUIREMENTS DETAILED IN THE NATIONAL NORMS AND STANDARDS FOR DISPOSAL OF WASTE TO LANDFILL (GN R. 636)

Waste Type Listed Wastes Landfill Disposal requirements Landfill Design specifications

Type 0 None The disposal of Type 0 waste is not allowed to landfill. These wastes must be treated before being reassessed for landfill disposal.

n/a

Type 1 NA Type 1 waste may only be disposed of at a Class A Landfill.

Type 2

Domestic Waste.

Business waste not containing hazardous waste or hazardous chemicals.

Non-infectious animal carcasses.

Garden Waste.

Type 2 waste may only be disposed of at a Class B Landfill.




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Waste Type Listed Wastes Landfill Disposal requirements Landfill Design specifications

Type 3 Post-consumer packaging.

Waste tyres.

Type 3 waste may only be disposed of at a Class C Landfill

Type 4

Building and demolition waste not containing hazardous waste or hazardous chemicals.

Excavated earth material not containing hazardous waste or hazardous chemicals.

Type 4 waste may only be disposed of at a Class D Landfill




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9.7 WRD DESIGN SUMMARY

9.7.1 MATERIAL DEPOSITION

Following the design assessment it is recommended that the Red Bed Clay’s (RCB) are deposited

within the WRD and not form the outer walls of the facility. It is also further recommended that the

clay’s are not deposited at the base of the WRD, a platform of competent rock such as the BIF or hard

calcrete should form the base of the WRD before depositing the clay. This is in order to restrict base

failure of the WRD.

9.7.2 WRD LAYOUT AND DEVELOPMENT

The components of the WRD facility are described below:

• The total footprint area is approximately is 95.8 ha;

• A minimum buffer of 50 m is required between the pit and the toe of the WRD No.11 in order to

prevent rolling rock into the pit;

• The total volume of waste material to be accommodated in the WRD facility is 14 250 322 m3;

• Two containment walls have been designed an inner and outer, with the inner demarcating the

dumping limits, the outer wall forms the toe of the reshaped side wall and the two walls will act as

catchment paddocks to store dirty runoff,

• A Type 4 liner will be constructed within the basin of the WRD;

• The WRD No.11 will be constructed using benched slopes with individual lifts between 10 and 20

m in height;

• Benches will be a minimum of 15 m wide;

• Inter-bench slope will be at 1.5H:1V or at angle of repose;

• Benches will be sloped inward at 2% towards the surface drainage system;

• The dump will have a single final slope after reshaping of 3H:1V.

9.7.3 WRD CONSTRUCTION METHODOLOGY

The following section provides guidance on the methodology which will be adopted for the

construction of the waste rock facility:

• Clearance of unsuitable material from the footprint area will be carried out progressively as the

footprint of the WRD increases;

• Base preparation will be carried out progressively as the footprint of the WRD increases;

• A nominal wall of waste material will be constructed prior to the placement of waste material to

define the extent of the dumping area;




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• The deposit will be developed in successive lifts of up to 20m in height with each lift being

completed before commencement of the subsequent lifts. Waste material will be transported from

the open pit to the WRD NO.11 using the main haul roads and waste haul roads to the leading

edge of the facility and tipped. Tipping of waste materials should take place from the leading

edge towards the inside of the facility;

• Following tipping the waste material will be placed within the facility using bulldozers and other

suitable earthmoving equipment;

• Waste material should be placed so that surface water drains back of the facility and the

stormwater channel running along the outer containment wall;

• The deposits will be constructed at angle of repose slopes;

• The control of seepage from the toe of the deposits as well as runoff from the slopes of the first lift

will be achieved by the construction of outer containment walls;

• The outer containment walls will be considered to be the boundary between the clean and

potentially contaminated water systems.

9.8 CONSTRUCTION COST ESTIMATE

The estimate costs for the construction of the WRD will be provided with the final report

10 CLASSIFICATION OF THE WASTE ROCK DUMPS

The classification of WRD No.11 in terms of the requirements of the SANS Code of Practice for Mine

Residue Deposits (SANS 10286, previously SABS 0286:1998) is documented below.

10.1 SAFETY CLASSIFICATION

The preliminary safety classification of proposed WRD No.11 has been carried out in accordance with

the requirements of SANS 10286 (1998). The safety classification system serves to provide a

consistent means of differentiating between high, medium and low hazard deposits on the basis of

their potential to cause harm to life or property. The classification system furthermore provides a

basis for the implementation of safety management practices for specified stages of the life cycle of a

WRD. The code prescribes the aims, principles and minimum requirements that apply to the

classification procedure and the classification in turn gives rise to minimum requirements for

investigation, design, construction, operation and decommissioning. The information used in the

safety classification is presented in Table 15 to Table 16.




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TABLE 15: GENERAL INFORMATION FOR THE SAFETY CLASSIFICATION OF THE WRD

2 Safety Classification (Ref SANS 10286)

2.1 Description of Residue Waste Rock

2.2 Is residue deposited hydraulically? No

2.3 Is deposit still active? Yes

2.4 Time since decommissioning. N/A

2.5 Ultimate maximum height of deposit on closure (Crest elevation and lowest toe elevation)

60m

2.6 Current maximum height of deposit 0m

2.7 When did deposition start? NA

2.8 What is steepest overall outer slope of the deposit? 1 V : 1.35 H

2.9 Steepest ground slope gradient on downstream perimeter of the deposit over a distance of 200m

Approximately 1 V : 22 H

2.10 Is deposit located on undermined ground? No

2.11 What is the shallowest depth to underground excavations?

N/A

2.12 Line diagram of the deposit showing :

• Outline of deposit, and ground contours;

• Zone of potential influence of a failure of the deposit (ref section 3)

• Property / Infrastructure / Services located within the zone of influence

To be supplied with final design report

3 Determination of Zone of Influence

Step 1 Deposition is not hydraulic, go to step 5

Step 2 N/A

Step 3 N/A

Step 4 N/A

3 Determination of Zone of Influence

Step 5 The zone of influence is a distance of twice the maximum design height at the point of consideration, measured from the toe around the full perimeter

To be supplied with final design report

TABLE 16: SAFETY CLASSIFICATION CRITERIA (SANS 10286 (1998))

1 2 3 4 5

No. of Residents in Zone of Influence

No. of Workers in Zone of Influence

1

Value of 3rd

party property in zone

of influence 2

Depth to underground

mine workings 3

Classification

0 < 10 0 – R 2 m > 200 m Low Hazard

1 – 10 11 – 100 R2 m – R 20 m 50 m – 200 m Medium Hazard

> 10 > 100 > R20 m < 50 m High Hazard

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

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

3. The potential for collapse of the residue deposit into the underground workings effectively extends




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the zone of influence to below ground level.

Source : SABS 0286:1998, Table 2 – Safety Classification Criteria

TABLE 17: SAFETY CLASSIFICATION (SANS 10286)

Criteria No.

Criteria Comment Safety

Classification

1 No. of Residents in Zone of Influence

The zone of influence lies completely within the mining operations

Low Hazard

2 No. of Workers in Zone of Influence

The zone of influence covers a scrap yard. It is unlikely that there would be more than 10 workers (other than those involved in

the operation of the WRD) within the zone of influence.

Low Hazard

3 Value of 3

rd party

property in zone of influence

No 3rd

party property is expected to be within the zone of influence.

Low Hazard

4 Depth to underground

mine workings

The depth to the shallowest underground workings is expected to be greater than

200m. Low Hazard

10.1.1 REQUIREMENTS ARISING FROM SAFETY CLASSIFICATION OF THE WRD

The WRD is classified as having a low safety hazard in terms of the requirements of the SANS Code

of Practice for Mine Residue Deposits. A summary of the minimum requirements associated with a

low hazard safety classification is shown in Table 15.

TABLE 18: MINIMUM REQUIREMENTS ASSOCIATED WITH A LOW HAZARD WRD

Planning Stage Design Stage Operation / Commissioning

Stage Decommissioning

Stage

1. Conceptualisation by owner

2. Preliminary site selection by owner

3. Geotechnical investigation by owner (assisted by specialist if necessary)

1. Geotechnical report not mandatory

2. Residue characterisation on basis of past experience

3. Design by suitably qualified person.

4. Risk analysis optional

5. Construction supervision by suitably qualified person

1. Risk analysis optional

2. Suitably qualified person responsible for operation

3. Suitably qualified person to monitor

4. Suitably qualified person to audit every 3 years




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10.2 WASTE ROCK DUMP STABILITY RATING

10.2.1 STABILITY RATING

The northern and southern WRDs were evaluated and assigned a stability rating in accordance with

Mined Rock and Overburden Piles Investigation and Design Manual Interim Guidelines (British

Columbia, 1991). The WRD stability rating system is a semi-quantitative scheme for assessing the

relative potential for dump stability, based on individual point ratings for each of the main factors

affecting dump stability. Each factor is given a point rating based on qualitative and/or quantitative

descriptions accounting for the possible range of conditions. An overall Dump Stability Rating (DSR)

is calculated as the sum of the individual ratings for each of the various factors. The maximum

possible DSR is 1800.

The current northern and southern WRD were assessed, the details the stability rating assessment is

provided in Table 19. The northern WRD has a DSR of 1100 and the southern WRD has a DSR of

1000.

To simplify the rating scheme for possible practical application, four categories or Dump Stability

Classes have been defined, based on Dump Stability Ratings. The Dump Stability Classes are

summarised as follows:

• Class I: Negligible failure hazard with a DSR <300

• Class II: Low failure hazard with a DSR of between 300 and 600

• Class III: Moderate failure hazard with a DSR of between 600 and 1200

• Class IV: High failure hazard with a DSR of greater than 1200

According to the Dumps Stability Classes above, both the northern and southern WRD classify as a

Class II with a low failure hazard.




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TABLE 19: STABILITY RATING FOR THE PROPOSED WRD NO.11

Key Factors Affecting Stability

Range of Conditions or Description Point

Rating Site Conditions Rating

DUMP CONFIGURATION DUMP HEIGHT

< 50m 0

Height of Southern WRD approximately 60 m high

50 50m - 100m 50

100m - 200m 100

> 200m 200

DUMP VOLUME Small < 1 million BCM's 0

Medium. Confirmed with the survey 50 Medium 1 - 50 million BCM's 50

Large > 50 million BCM's 100

DUMP SLOPE Flat < 26o 0

The Southern WRD will have a moderate slope 100 Moderate 26o - 35

o 50

Steep > 35o 100

FOUNDATION SLOPE Flat < 10o 0

Foundation slope is flat 0 Moderate 10

o - 25

o 50

Steep 25o - 32

o 100

Extreme > 32o 200

DEGREE OF CONFINEMENT

Confined

- Concave slope in plan or section

0

The WRD is Unconfined 100

- Valley or Cross-Valley fill, toe butressed against opposite valley wall

- Incised gullies which can be used to limit foundation slope during development

Moderately Confined

- Natural benches or terraces on slope

50 - Even slopes, limited natural topographic diversity

- Heaped, Sidehill or broad Valley or Cross-Valley fills

Unconfined - Convex slope in plan or section 100




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- Sidehill or Ridge Crest fill with no toe confinement

- No gullies or benches to assist development

FOUNDATION TYPE

Competent

- Foundation materials as strong or stronger than dump materials

0

Site generally underlain by Kalahari Sands and would be viewed as intermediate. The Sands will

gain strength from consolidation 100

- Not subject to adverse pore pressures

- No adverse geologic structure

Intermediate

- Intermediate between competent and weak

100 - Soils gain strength with consolidation

- Adverse pore pressures dissipate if loading rate controlled

Weak

- Limited bearing capacity, soft soils

200

- Subject to adverse pore pressure generation upon loading

- Adverse groundwater conditions, springs or seeps

- Strength sensitive to shear strain, potentially liquefiable

DUMP MATERIAL QUALITY High

- Strong, durable 0

Large percentage of fines 200

- Less than about 10% fines

Moderate - Moderately strong, variable durability

100 - 10 to 25% fines

Poor - Predominantly weak rocks of low durability

200 - Greater than about 25% fines, overburden

METHOD OF Favourable - Thin lifts (< 25m thick), wide platforms 0 Lifts of between 10 and 20 m will be used to 0




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CONSTRUCTION - Dumping along contours construct the dump with wide platforms

- Ascending construction

- Wrap-arounds or terraces

Mixed - Moderately thick lifts (25m - 50m)

100 - Mixed construction methods

Unfavourable

- Thick lifts (> 50m), narrow platform (sliver fill)

200 - Dumping down the fall line of the slope

- Descending construction

PIEZOMETRIC AND CLIMATIC CONDITIONS

Favourable

- Low piezometric pressures, no seepage in foundation

0

Expected to be favourable due to climatic conditions

0

- Development of phreatic surface within dump unlikely

- Limited precipitation

- Minimal infiltration into dump

- No snow or ice layers in dump or foundation

Intermediate

- Moderate piezometric pressures, some seeps in foundation

100

- Limited development of phreatic surface in dump possible

- Moderate precipitation

- High infiltration into dump

- Discontinuous snow or ice lenses or layers in dump

Unfavourable - High piezometric pressures, springs in foundation 200




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- High precipitation

- Moderate precipitation

- Significant potential for development of phreatic surface or perched water tables in dump

- Continuous layers or lenses of snow or ice in dump or foundation

DUMPING RATE Slow

- < 25 BCM's per lineal metre of crest per day 0

Deposition will be moderate 100

- Crest advancement rate < 0.1m per day

Moderate - 25 - 200 BCM's per lineal metre of crest per day

100 - Crest advancement rate 0.1m - 1.0m per day

High - > 200 BCM's per lineal metre of crest per day

200 - Crest advancement > 1.0m per day

SEISMICITY Low

Seismic Risk Zones 0 and 1 (<10% probability of ground acceleration exceeding 0.08g in 50 years)

0

Seismic Risk Zones 0 and 1 (<10% probability of ground acceleration exceeding 0.08g in 50 years)

0 Moderate Seismic Risk Zones 2 and 3 (<10% probability of ground acceleration exceeding 0.16g in 50 years)

100

High Seismic Risk Zones 4 or higher (>10% probability of ground acceleration exceeding 0.16g in 50 years)

200

DSR 700




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10.3 SECURITY

As the WRD is to be located within the boundary of the mine there will be no need for a specific security

fence or controlled access points. There will be no significant health and safety risks posed by the WRD

that warrant controlled access. The waste rock is not toxic and there are no deep excavations or falling

hazards associated with the WRD.

10.4 DECOMMISSIONING AND CLOSURE

Overburden/waste rock dumps remaining post closure will be shaped to 1V:3H (18°) to create a stable

landform. Thereafter the dumps will be covered with the Kalahari Sand material (i.e. whatever was initially

stripped from the area prior to construction) and revegetated.

Carl Fietze

(Report Author)

Marline Medallie

(Project Manager)

Francois van Heerden

(Project Reviewer)




September 2017

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REFERENCES

AGES, 2007. United Manganese of the Kalahari: Specialist Geohydrological Study, Pretoria: Africa Geo-

Environmental Services. Report Number: AG-R-2007-03-22.

British Columbia, 1991, “Mined Rock and Overburden Piles Investigation and Design Manual, Interim

Guidelines” British Columbia Mine Waste Rock Pile Research Committee, dated May 1991.

Department of Environmental Affairs, 2010. Framework for the Management of Contaminated Land.

Department of Environmental Affairs.

Department of Environmental Affairs, 2013. Government Gazette, Government Notice R634. National

Environmental Management: Waste Act (59/2008): Waste Classification and Management regulations.

The Government Printing Works: Pretoria.


Norms and standards for the assessment of waste for landfill disposal. The Government Printing Works:

Pretoria.


Norms and standards for the disposal of waste for landfill disposal. The Government Printing Works:

Pretoria.

Leps, T.M. (1970) Review of shearing strength of rockfill. A.S.C.E., Journal of the Soil Mechanics and

Foundations Division, 96 (SM4), pp. 1159-1170.

Marsal, R.J. (1976) Mechanical properties of rockfill soil mixtures. Douzieme Congres des Grands

Barrages, Mexico, pp. 179-209.

Revised Guide to Soil Profiling for Civil Engineering Purposes in Southern Africa (1990)

SANS 1200 Standardized Specifications: 1200 D Earthworks.

SANS Code of Practice for Mine Residue Deposits.

USBR (1966) Summary of large triaxial shear tests for silty gravels earth research studies. EM-731,

United States Department of the Interior Bureau of Reclamation - Soils Engineering Branch, Division of

Research.




September 2017

Page A

APPENDIX A: SOIL PROFILES

List contents of appendix




September 2017

RECORD OF REPORT DISTRIBUTION

SLR Reference: 710.21002.00047

Title: Detailed Design of the UNK Waste Rock Dump

Site name: UMK

Report Number: Doc. no. DRAFT

Client: United Manganese of Kalahari

Name Entity No. of copes

Date issued Issuer

COPYRIGHT

Copyright for this report vests with SLR Consulting unless otherwise agreed to in writing. The

report may not be copied or transmitted in any form whatsoever to any person without the

written permission of the Copyright Holder. This does not preclude the authorities’ use of the

report for consultation purposes or the applicant’s use of the report for project-related

purposes.

JOHANNESBURG Fourways Office P O Box 1596, Cramerview, 2060, SOUTH AFRICA Unit 7, Fourways Manor Office Park, 1 Macbeth Ave (On the corner with Roos Street), Fourways, Johannesburg, SOUTH AFRICA T: +27 (0)11 467 0945

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