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October 2017
DE BEERS CONSOLIDATED MINES (PTY) LIMITED - VOORSPOED MINE
Summary of Surface and Groundwater Study for Mine Closure
RE
PO
RT
Report Number: 1663605-316475-5
Distribution:
1 x eCopy Voorspoed Mine.
1 x eCopy [email protected].
Submitted to:
De Beers Consolidated Mines (Pty) Ltd Voorspoed Mine PO Box 1964 KROONSTAD 9500
(91 Gol4er Associates
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Table of Contents
1.0 INTRODUCTION ........................................................................................................................................................ 1
2.0 OBJECTIVES ............................................................................................................................................................ 1
3.0 PROJECT ADMINISTRATION .................................................................................................................................. 1
4.0 HISTORICAL STUDIES ............................................................................................................................................. 2
4.1 Gaps identified during previous modelling work ........................................................................................... 2
4.2 Way forward (from preceding studies) .......................................................................................................... 3
5.0 GEOHYDROLOGICAL INVESTIGATIONS ............................................................................................................... 3
5.1.1 Voorspoed Mine Geological Model ......................................................................................................... 3
5.1.2 Groundwater Quality Assessment (incl. surface ponds) .......................................................................... 4
5.1.3 Groundwater levels and flow directions ................................................................................................. 14
5.2 Appendixes Related to the Hydrogeological Investigation .......................................................................... 17
5.3 Conceptual modelling ................................................................................................................................. 17
5.4 Conclusions and Recommendations (Hydrogeological Investigation) ........................................................ 22
6.0 GEOCHEMICAL ASSESSMENT ............................................................................................................................. 24
6.1 Previous Geochemistry studies .................................................................................................................. 24
6.2 Summary of Water Qualities Observed (near field area) ............................................................................ 24
6.3 Conceptual Model (geochemistry) .............................................................................................................. 25
6.4 Sampling and Laboratory Program ............................................................................................................. 26
6.5 Geochemical Test Results .......................................................................................................................... 27
6.6 Acid Base Accounting ................................................................................................................................. 27
6.7 Drainage Chemistry Analyses..................................................................................................................... 30
6.8 Waste Assessment and Classification ........................................................................................................ 32
6.9 Conclusions (Geochemical Assessment) ................................................................................................... 34
6.10 Appendixes Related to the Geochemical Assessment ............................................................................... 35
7.0 FLOOD LINE ASSESSMENT .................................................................................................................................. 36
8.0 DYNAMIC WATER AND SALT BALANCE ............................................................................................................. 38
8.1 Process Water Reticulation System Description ......................................................................................... 38
8.1.1 Water and waste storage facilities ........................................................................................................ 38
8.1.2 Water demand figures ........................................................................................................................... 41
8.2 Water Balance Modelling Methodology and Results ................................................................................... 41
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8.3 Salt Balance................................................................................................................................................ 42
8.4 Conclusions and Recommendations (Water & Salt Balance) ..................................................................... 42
9.0 NUMERICAL GROUNDWATER FLOW AND CONTAMINANT TRANSPORT MODEL ......................................... 43
9.1 Applicable Conclusions (Numerical Modelling) ........................................................................................... 54
10.0 SYNOPSIS ............................................................................................................................................................... 55
11.0 REFERENCES ......................................................................................................................................................... 57
TABLES
Table 1: Project Team .............................................................................................................................................. 2
Table 2: Water quality guidelines ............................................................................................................................. 8
Table 3: Conceptual source-pathway-receptor characterisation for mine facilities at Voorspoed........................... 26
Table 4: Geochemical Abundance Index for waste rock, coarse residue and fine residue samples. ..................... 27
Table 5: Summary of the Dam Characteristics ....................................................................................................... 38
Table 6: FRDs Summary ........................................................................................................................................ 41
Table 7: Average Water Demands ......................................................................................................................... 41
Table 8: Source terms TDS concentrations............................................................................................................ 42
Table 9: Pit lake water quality range based on static test data............................................................................... 50
FIGURES
Figure 1: 2017 Hydrocensus survey points (with water level data). ......................................................................... 5
Figure 2: Piper Diagram illustration of the 2017 Hydrocensus monitoring sites at Voorspoed Mine. ....................... 6
Figure 3: Schoeller Diagram illustration of the 2017 Hydrocensus monitoring sites at Voorspoed Mine. ................. 7
Figure 4: Groundwater quality time series TDS concentration in borehole MBH02 at Voorspoed Mine. .................. 8
Figure 5: 2007-2016 time series TDS concentration (mg/l) in borehole VDBH01 at Voorspoed Mine, just SW of FRD (Class 1: WRC, 1998). .................................................................................................................... 9
Figure 6: 2007-2016 time series sodium [Na] concentration (mg/l) in borehole VDBH01 at Voorspoed Mine, just SW of .................................................................................................................................................... 10
Figure 7: 2007-2016 time series chloride [Cl] concentration (mg/l) in borehole VDBH01 at Voorspoed Mine, just SW of FRD. ........................................................................................................................................... 10
Figure 8: 2007-2016 time series fluoride [F] concentration (mg/l) in borehole VDBH01 at Voorspoed Mine, just SW of FRD ................................................................................................................................................... 11
Figure 9: Sulphate concentrations of boreholes at the FRD and downstream (MBH02). ....................................... 12
Figure 10: Fluoride (F) concentrations in the Voorspoed mine area, including the pit water (DBV Pit) .................. 13
Figure 11: Water level time series for borehole VBBH04, Voorspoed Mine ........................................................... 15
Figure 12: Water level & CRD Trends - VDBH04 ................................................................................................... 16
Figure 13: Water level & CRD Trends – MBH05 .................................................................................................... 16
Figure 14: Boreholes used for conceptual model design and illustration of secondary geological features (faults/dykes) on the Voorspoed mine site area. ................................................................................... 18
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Figure 15: Voorspoed Mine 3D Conceptual Model (current operational phase) from the South and observed (2017) sulphate concentration levels (mg/l). .......................................................................................... 19
Figure 16: Operational phase conceptual model of the Voorspoed Pit (based on 2017 observations). ................. 20
Figure 17: Voorspoed Mine 3D Conceptual Model (post-closure scenario) from the South showing partially filled pit lake scenario. ................................................................................................................................... 21
Figure 18: Post operational phase conceptual model of the Voorspoed Pit (~50 years after closure). .................. 22
Figure 19: Location of mine waste, seepage and water samples ........................................................................... 29
Figure 20: Plot of NAG pH versus TNPR (Bulk NP/TAP) of coarse and fine residue and waste rock. ................... 30
Figure 21: Piper diagram of waste rock, processed waste rock seepages and pit water samples. ........................ 31
Figure 22: Voorspoed Mine - Perennial and Non-perennial Streams ..................................................................... 37
Figure 23: Voorspoed mine water reticulation system showing monthly water meter figures (viz. minimum, average and maximum). ........................................................................................................................ 40
Figure 24: Inflows to the Voorspoed Mine pit simulated between 2008 and 2017. ................................................. 44
Figure 25: Time series water level data and simulated water level at monitoring site VDH04 (wrongly numbered VBH04) .................................................................................................................................................. 45
Figure 26: Operational hydraulic head distribution (as per 2017 prediction) .......................................................... 46
Figure 27: Simulated drawdown and cone of depression of the Voorspoed Mine site area (as per 2017 hydrocensus processing) ...................................................................................................................... 47
Figure 28: Prediction of the Voorspoed Pit Lake development after closure. ......................................................... 48
Figure 29: Schematic of the Voorspoed Mine post operational pit lake development ............................................ 49
Figure 30: Simulated sulphate (SO4) plume development from post closure phase – after 5, 10, 15 and 30 years. .................................................................................................................................................... 52
Figure 31: Simulated sulphate (SO4) plume development from post closure phase – after 50, 100, 150 and 200 years ..................................................................................................................................................... 53
APPENDICES
APPENDIX A Document Limitations
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1.0 INTRODUCTION
De Beers Consolidated Mines (Pty) Limited’s Voorspoed diamond mine situated in the north-eastern Free
State Province, is approaching its mining operations closure phase (approximately four years ahead). In
preparation for closure permitting, a surface and groundwater study for mine closure requirements covering
the following disciplines were conducted:
i) a geohydrological assessment (groundwater flow and quality), incl. a conceptualization and a
numerical flow and transport model,
ii) a geochemistry study assessment (characterisation of potential contaminant sources to surface and
groundwater resources),
iii) a dynamic water balance model (including user interface which enables the user to update inputs, run
the model and view the results of the simulations; and
iv) a hydrological assessment of potential flood line risks (to confirm the status of perennial/non-perennial
streams in the area).
2.0 OBJECTIVES
In terms of preparing for mine closure status, the following objectives were addressed and investigated as
part of the surface and groundwater study:
A review and assessment of the existing hydrogeological and hydrogeochemical data collated during
previous studies and important observations made in these studies;
Identification of information/data gaps [gap analyses] and address to optimise the surface and
groundwater characteristics of the Voorspoed mine site and surrounding area (~3-5 km
radii);hydrogeological and geochemical aspects;
Undertake a geochemical characterisation (waste assessment and waste classification) of the fine and
coarse tailings deposits and waste rock dump;
Conduct a baseline groundwater situation/status assessment of the mine and surrounding area
(hydrocensus survey and water quality assessment of the mine site and surrounding area); and
Develop a representative conceptualization of the groundwater characteristics on the mine site and
immediate surrounding area based on the available datasets.
Develop a numerical groundwater flow model and contaminated transport model to aid in the post
closure contamination of the aquifers proximal to the mine and post mine lake characteristics;
Develop a long-term dynamic water balance and a salt balance for the mine; and
Undertake a [desktop] flood line assessment on the Voorspoed mine site area.
Based on the CGwM, draft a conceptual source-pathway-receptor model (SPRM) for the mine site.
Prepare a post mining monitoring programme which specifically addresses the mine closure
requirements by Departments of Water and Sanitation and Mineral Resources.
The main objective, therefore, is to update the hydrological and geochemical status and conditions at the
Voorspoed Mine consequently to ensure mine closure requirements are addressed and post mining
hydrological1 status is well monitored and maintained within the closure conditions and limits.
3.0 PROJECT ADMINISTRATION
The agreement between De Beers Consolidated Mines (Pty) Limited and Golder Associates Africa (Pty) Ltd
was signed on the 14th March 2017 and preparations for the hydrocensus work started within a week after
signing the agreement. Induction of the Golder staff member, conducting the hydrocensus were done in
1 Surface water and groundwater components.
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January 2017 already, however, all field activities were stopped due to fact that the agreement was not
legally finalised.
The first “onsite” project initiation meeting were conducted on the 6th of April 2017. A presentation of the
project objectives and approaches was presented by the Golder Team. The Golder Team, at this stage was
selected and is listed in Table 1 below.
Table 1: Project Team
Golder Team Designation Qualification
Senior Hydrogeologist & Project Manager – Technical Reviewer
Eddie van Wyk PhD. (Pr.Sci.Nat. – 400121/10),
Senior Geochemist – Technical Reviewer
David Love PhD, FWISA)
Principal Water Resource Engineer
Trevor Coleman Pr Eng, BSc (Civ Eng), MSc (Eng)
Geochemist Keretia Lupankwa PhD - Env. Geology
Hydrogeologist/Numerical Modeller
Talita Germishuyse (Megan Hill)
MSc (Geohydrology), Pr. Sci. Nat.
Hydrogeologist Lukas Marais (Intern) MSc. Hydrogeology
Water Resource Engineer Dorcas Adjei-Sasu (Amelia Basson)
BSc. Civil Engineering
Two Golder “in-house” team meetings were held during April and May; mainly to discuss the outcome of
our internal data/information Gap analysis process and identification of outstanding data/information.
Several short “one-to-one” discussions are conducted on an ongoing bases where specific aspects of the
project are discussed/planned.
The project team is virtually the same group that has been proposed in the original proposal, except for
Megan Hill (replaced by Ms Talita Germishuyse) and Amelia Basson (replaced by Dorcas Adjei-Sasu).
4.0 HISTORICAL STUDIES
Historical water related investigations undertaken at Voorspoed mine include;
Geocon on behalf of Metago (2004) Geohydrological specialist investigation at the De Beers
Voorspoed Diamond Mine, Report No. G/R/04/10/12;
Hydrologic Consultants, Inc. (HCI), 2004. Predicted ground-water conditions at proposed
Voorspoed Mine based on preliminary ground-water flow modelling. Report prepared by Hydrologic
Consultants, Inc., for KLM Consulting Services (Pty) Ltd., August; and
Itasca Denver, Inc. (2014) Predicted Groundwater Conditions at Voorspoed Mine, Report No. #1809.
Numerical modelling was undertaken concurrently by Geocon and HCI in 2004. The purpose of the two
models were to forecast the groundwater conditions associated with mining activities during the operational
phase of mining.
4.1 Gaps identified during previous modelling work
The following gaps have been identified during the preliminary Voorspoed data/information [gap]
assessment and they are:
As highlighted in Geocon in 2004 and in Itasca in 2014 uncertainty exists over the hydraulic
parameters of the rock/formation units proximal to the Voorspoed pit;
The mass transport plumes associated with the tailings facility were not simulated for the period post
closure and hence no modelling work currently (2017) exists to describe post closure mass transport;
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mitigation requirements, and time series monitoring datasets (specifically, the for area outside the
Voorspoed mine site area); and
The existing models provide no insight of the pit lake conditions likely to develop in the post closure
era (i.e. the rate of filling, the possibility for decant (although unlikely) and the water quality).This type
of information is crucial for guiding the closure process.
During the project period, these gaps were addressed and improved, however, specific ones such as the
actual water quality signature of the [slow re-watering of the] pit lake requires a detailed assessment of the
pit sidewall-rock formation(s) and the anticipated local pit catchment area.
4.2 Way forward (from preceding studies)
Important aspects have been identified during the review of the previous reports and information of the
Voorspoed Mine and tabled for this study, and probably future assessments as well. They are:
In order to develop flow and particle transport models on which mine closure can be achieved it is
necessary that the data gaps previously identified are addressed/closed……..for this current study, all
available data has been collated and incorporated into the 2017 conceptual model of the mine site
area and a number of long-term time series assessments (viz. water levels and water quality trends)
were possible;
While Geocon (2004) previously undertook a hydrocensus in a 6 km radius of the mine, it was
deemed necessary that the hydrocensus be updated. The purpose of the update is to;
Determine if additional potential receptors occur within the study area; and
If water uses have altered over the past decade.
A borehole hydrocensus has been conducted in April 2017 and at least 12 boreholes have been surveyed
outside the Voorspoed Mine Site area of which eight (8) could be recorded (i.e. water level and/or water
quality)
As described above, it was necessary to develop a calibrated numerical model which can be utilised
to simulate mass transport associated with the tailings during the post operational phase. Through
development of such a model, appropriate mitigations strategies can be developed and a suitable
monitoring network established to guide closure.
A model should be developed which can assist in forecasting the actual hydrological and geochemical
characteristics of the pit lake during post mine-closure times(i.e. pit lake water balance, water level
elevation trends, bulk water quality characteristics and impact(s) of long-term evaporation losses) (not
included in this study). Through gaining understanding the hydrological characteristics of a Pit Lake it
can then be determined if the pit will remain a legacy or liability during the post operational phase of
mining and appropriate mitigation strategies can be suggested.
The different components of the mine closure study are summarised as follows (where applicable,
supporting explanations of these components are included, however, references to the main reports are
made subsequently).
5.0 GEOHYDROLOGICAL INVESTIGATIONS
A hydrocensus survey was conducted in April 2017 on the Voorspoed mine site area and in an area ~3-
5 km’s outside the mine site area (mainly private land). The purpose of the hydrocensus survey was to re-
located all available boreholes and other important water resources and update the hydrological
characteristics of time series datasets that are available. The hydrocensus, therefore focussed on the
“impacted” area (source areas) and the non-impacted areas (potential receptors).
5.1.1 Voorspoed Mine Geological Model
The geological model of the Voorspoed mine is described in detail in the Golder Groundwater Model Report
(Rep. No. 1663605-315698-2, sections 2.4 and 2.5). The conceptual groundwater model is based on the
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available borehole drill log sheets and models described in the historical reports of the site. An updated
conceptual model of the Voorspoed Mine (viz. Kimberlite Pipe) is described in section 5.3 below.
5.1.2 Groundwater Quality Assessment (incl. surface ponds)
A total of sixteen water samples were collated during the hydrocensus survey and was submitted to the
Exova Jones Environmental Laboratory in Somerset West (SA) and Deeside (UK). Samples were analysed
and a SANAS accredited analytical report was submitted to Golder on the 3rd of May 2017. The positions of
the boreholes covered during the 2017 Golder hydrocensus survey is shown in Figure 1 below.
Water quality analyses of the sampled groundwater is shown in Figure 2 (Piper Diagram presentation) and
Figure 3 (Schoeller Diagram presentation). These diagrams also include a “Pit Water Sample” (Pit-W) and
seepage samples from the FRD (fine residual deposits), CRD (course residual dump), RWD (raw water
dam) sites.
The Piper Diagram reports natural groundwater quality evolution from the recently recharged waters (left-
hand quadrant of the Piper Diamond) characterised by a Ca/Mg-HCO3 signature to water representative of
dynamic flow, characterised by a Na-HCO3 signature and gradually towards a typical deep Karoo water
quality signature, characterised by Na-Cl (right-hand quadrant of the Piper Diagram). Stagnant
groundwater, or groundwater impacted by industrial/mining activity where elevated levels of chloride (Cl)
and sulphate (SO4) plots towards the top quadrant of the Piper Diamond – or very stagnant deep
groundwater.
The “Pit Water” quality Piper plot portrays a Na-SO4 water quality signature. Similarly, water samples
associated with the Coarse Residue Dumps and Fine Residue Dumps, plot as Na-Cl water types. This
likely indicates a [natural] source of sodium chloride associated with the Kimberlite pipe – associated with
the background hydrochemical signature of Karoo sedimentary formations, i.e. a primary elevated
constituent. Although the Pit Water, FRD, CRD and RWD have high levels of sulphate, the background Na-
Cl signature of the Karoo aquifers still, therefore, dominates the water quality signature in the area.
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Figure 1: 2017 Hydrocensus survey points (with water level data).
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Most of the groundwater quality sampled outside the mine site area, plots in the Ca/Mg-HCO3 quadrant and
represent the upper, shallower part of the aquifer system, which receive frequent rainwater recharge and not
impacted by mining/agricultural activities. Two monitoring sites (GL 1 and GL 2, located towards the western
Far Field Area reports elevated Na-Cl concentrations. The reason(s) for this is not clear, but could be related
to an agricultural related source and is unlikely associated with the mine due to the distance between the
mine and these boreholes.
To conclude, the groundwater quality from the mine site area have slightly elevated salinity levels (TDS ~750
mg/l) compared to the surrounding far field Area (viz. < 500 mg/l TDS).
Figure 2: Piper Diagram illustration of the 2017 Hydrocensus monitoring sites at Voorspoed Mine.
The Schoeller Diagram just reiterates the groundwater quality signatures as noted in the Piper Diagram,
however, the significance of the different water quality criteria (viz. Ca/Mg-HCO3, Na-HCO3 and Na-Cl) is
noted. One should note the strong signatures of HCO3, Na, Cl and SO4 for that matter.
Most of the water sources plots within a Class 0 (Ideal) and Class 1 (Good) with some constituents plots in
the Class 2 (Marginal) categories. To note is the elevated NO3 (as N) concentrations in for the RWD, F&CRD
and the Pit Water (i.e. ~49 mg/l as N).
The poor water quality condition at monitoring site GL2 (── in Figure 3) in the far field area is probably due
to local agricultural activity/pollution. Of all the monitoring points analysed, this site has the highest dissolved
mineral content, and is in fact an anomaly in the area. Due to the distance from the mine site area, the GL2
site has no relation to the mine site area and is regarded as a local [agricultural] impacted case.
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Figure 3: Schoeller Diagram illustration of the 2017 Hydrocensus monitoring sites at Voorspoed Mine.
As mentioned above, groundwater in the far field area is used for domestic supplies and livestock watering.
The water quality guidelines applicable for these uses are summarised in
A medium-term (~5-10 years) water quality (viz, salinity as TDS in mg/l) time series plot of borehole MBH02
(or VD-BH2) is illustrated in Figure 4 and shows a steady increase in the water salinity concentration. This
boreholes lie outside the mine site area and indicate a rising trend in the hydrochemistry signatures. Initial
values in February 2007 were around the 450 mg/l level and dropped to ~350 mg/l during the 2009-2011
wetter rainfall cycles, before starting with a gradual increase towards the ~550 mg/l salinity level. The
hydrochemical constituents causing this rise is sodium and total hardness [as the chloride and sulphate
concentrations are respectively ~50 and ~35 mg/l]. This observation is, however, rather important and should
be seen as a potential risk for the surface water system downstream of the Voorspoed mine site area. The
physical risk should be quantified as part of the 2017 Hydrological Monitoring Program for Voorspoed Mine
[Closure].
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Table 2: Water quality guidelines
Constituent/ Guideline
Chloride (mg/l) Sulphate (mg/l) Sodium (mg/l) Nitrate (mg/l) TDS (mg/l)
Baseline Limit* 48 27 123 43** 902
Drinking water Limits (SANS 241: 2015)
300 (250) 500 200 49 1200
Livestock Limits (Cattle) (DWAF, 2006)
3000 1000 2000 885 2000
*Baseline data taken from Geocon 2004
**Baseline Nitrate is high likely owing to livestock contamination
Figure 4: Groundwater quality time series TDS concentration in borehole MBH02 at Voorspoed Mine.
Other monitoring sites on the Voorspoed mine site area situated close to potential source areas, such as
monitoring site VDBH01 (also referenced as VDBH1), reports a rising trend in TDS values due to rising Na
and Cl concentrations as illustrated in Figure 5, Figure 6 and Figure 7 below.
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Figure 5: 2007-2016 time series TDS concentration (mg/l) in borehole VDBH01 at Voorspoed Mine, just SW of FRD (Class 1: WRC, 1998).
Detailed evaluation of the spatial distribution of chloride (Cl), sodium (Na), sulphate (SO4), and total
dissolved solids (TDS) is covered in section 3.5 of the Golder Report: Hydrogeological Investigation, No.
1663605-315698-2).
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Figure 6: 2007-2016 time series sodium [Na] concentration (mg/l) in borehole VDBH01 at Voorspoed Mine, just SW of
Figure 7: 2007-2016 time series chloride [Cl] concentration (mg/l) in borehole VDBH01 at Voorspoed Mine, just SW of FRD.
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With reference to the fluoride concentrations in the Voorspoed mine site area, the following aspects are
relevant:
The background fluoride concentrations is Karoo groundwater are high. Research work on the fluoride
concentrations indicates value of between 2 and 6 mg/l are common. The 2017 Pit Water analysis
indicates a concentration level of 1.3 mg/l, and all the boreholes on the site area covered during the
2017 hydrocensus survey varies between 0.3 mg/l and 0.9 mg/l;
A Time Series plot of the Fluoride concentrations at Monitoring Site VDBH1, situated just upstream of
the FRD site is illustrated in Figure 8 below. It is obvious that there is virtually no trend in the fluoride
concentration level and the average value (~0.45 mg/l F) is that of a Class 0, Ideal water quality. The
fluoride value during the 2017 hydrocensus survey was 0.4 mg/l;
A map of the fluoride concentrations observed during the 2017 hydrocensus is illustrated in Figure 10
below. The Pit Water concentration is the only one that is above the long-term threshold of 1.0 mg/l.The
fluoride concentration levels in the mine site area (excluding the Pit Water) and the surrounding farm
lands are below 1.00 mg/l as indicated in Figure 10; and
The origin of fluoride in groundwater is generally related to (i) weathering and dissolution of fluoride
containing minerals such as apophyllite in zeolites, and (ii) deep circulating groundwater (viz. along
deep vertical structure such as dolerite dykes and Kimberlite fissures/pipes for example). The
concentrations of the Pit Water sample is in fact too low to indicate a deep water source (normally these
fluoride concentrations are in the order of 6 to 10 g/l and unless significantly diluted by local direct
[rainfall] recharge into the pit area.
Figure 8: 2007-2016 time series fluoride [F] concentration (mg/l) in borehole VDBH01 at Voorspoed Mine, just SW of FRD
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In terms of the sulphate concentration on the Voorspoed mine site area, a detailed discussion thereof of
appear under section 3.5 (viz. Hydrochemistry) of the Hydrogeological Investigation (Golder Report No.
1663605-315698-2). Sulphate was selected as there are no other sources of sulphate proximal to the mine
with the exception of the dumps and hence sulphate is a suitable tracer of mine seepage. A detailed long-
term monitoring has been undertaken at several boreholes both far and near field area, however, the results
conclude that:
That sulphate concentrations at all monitoring sites, except private borehole GL2 (west of the mine site
area) do not exceed the WRC (WRC et al, 1998) drinking water quality limits for sulphate. Thus in terms
of sulphate, the water quality is not deemed to be impacted severely.
Detailed discussion of the long-term monitored sulphate concentrations with time series sulphate
concentrations illustrations at high risk areas, i.e. (i) the waste rock dump (WRD), (ii) course residue dumps
(CRD), and (iii) fine residue dump (CRD) appears on pages 39 to 41 of the above-mentioned groundwater
modelling report (section 3.5). The sulphate concentration [trends] observed in the vicinity of the FRD is
illustrated in Figure 9 below, and although the concentrations are still at Class 0 (viz. Ideal water quality), a
long-term rising trend is present at some boreholes, i.e.
The near field borehole VDBH01 (see Figure 1) was found to gradually be increasing over time. This is
expected as this borehole is on the flow pathway trajectory between the FRD and open pit; and
Similarly a gradual increasing sulphate trend is observed at far field borehole MBH02 (see Figure 1),
which possibly indicates that a plume associated with the FRD is impacting on this borehole via the
small drainage system flowing from the RWD and SWCD (see Figure 10 below).
Figure 9: Sulphate concentrations of boreholes at the FRD and downstream (MBH02).
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Figure 10: Fluoride (F) concentrations in the Voorspoed mine area, including the pit water (DBV Pit)
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5.1.3 Groundwater levels and flow directions
A detailed discussion of the groundwater levels (boreholes) appears in section 3.3 of the groundwater
modelling report (Golder Report: Hydrogeological Investigation, No. 1663605-315698-2).
The main aspects of the groundwater levels in far and near field areas of the Voorspoed mine site area, are
as follows:
Water levels on the surrounding farms represented both static and dynamic levels and ranged between
2 mbgl and > 30 mbgl.
Boreholes BH 31 and BH 32 (3.3 km west-south-west of the pit) located on Siding 1568 displayed deep
water levels (> 30 mbgl). However, deep water levels were also measured at the boreholes in 2004
indicating that mine dewatering is unlikely the cause and rather the deep water levels are probably a
consequence of groundwater abstraction for livestock watering and domestic use.
At the time of the census, the pit was at a depth of 1193 mamsl (217 mbgl). The water levels at
boreholes located adjacent to the pit; GDH1602 and GDH 1601 are 53 mbgl and 38 mbgl respectively.
This indicates that the cone of depression associated with the pit is steep and has limited lateral impact.
Water levels in boreholes proximal to the tailings were found to be shallow (< 7 mbgl) which are inferred
to be a result of the effects of seepage from these facilities.
Proximal to the pit groundwater is expected to flow toward the pit due to the effects of evaporation on
the pit area. North of the dumps, groundwater flows north and north easterly from the dump areas.
While south of the mine flow occurs in a south – south westerly flow direction.
A time series water level hydrograph observed at monitoring site VDBH04 (situated on the eastern,
downstream area of the Voorspoed mine site area as shown in Figure 10 above) is illustrated in Figure 11
below, and:
Water level has recovered since it was [probably] used for water supplies prior to 2011;
Water level indicates a slight downward trend (viz. water level recession) since May 2011; and
Moderate aquifer storage response (water table rebounds) following high rainfall events in October-
November 2007, January-February 2010, and October-November 2011.
Water table time series data does not indicate local “dewatering” impacts of the Voorspoed mining
taking place on the mine site area.
VDBH04 is located 400 m from the foot of the coarse waste rock dump. Based on measured water
levels and inferences from topography, groundwater is expected to flow from the waste rock dump
toward this borehole and therefore explains the shallower water table conditions wrt the CRD
simulation. The water level trend at this site closely represent the CRD trend; and
MBH01 - MBH05 are located on adjacent properties north and north east of the mine. With the
exception of MBH01 and MBH 05, the boreholes have sporadically been monitored and consequently
data interpretation is limited. MBH01 and MBH 05 both closely correlate with the CRD trend.
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Figure 11: Water level time series for borehole VBBH04, Voorspoed Mine
The water levels have been compared against the cumulative rainfall departure (CRD) in order to aid in
understanding the water level trends on site, as illustrated in Figure 12 and Figure 13 below.
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Figure 12: Water level & CRD Trends - VDBH04
Figure 13: Water level & CRD Trends – MBH05
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The following observations have been made from the water level dataset:
5.2 Appendixes Related to the Hydrogeological Investigation
Several appendixes containing processed time series water quality and water level datasets are attached to
the separate reports submitted during the project period, they are as follows:
Golder Report: Surface and Groundwater Study for Mine Closure Requirements, No. 1663605-314859-
1: Three appendixes containing the following processed datasets:
Appendix A: Groundwater and open (surface) water LAB certificates and analytical data;
Appendix B: Water Quality and Water Level Graphs; and
Appendix C: Waste chemistry LAB certificates and datasets (same as included in the Geochemical
Assessment Report (Golder Report No. 1663605-316224-4).
Golder Report: Hydrogeological Investigation, No. 1663605-315698-2: Two appendixes containing the
following processed datasets:
Appendix A.1: Fluoride time series graphs; and
Appendix A.2: Elemental chemistry time series graphs.
These are all time series plots of the available water hydrochemistry of the Voorspoed mine site area.
5.3 Conceptual modelling
The geology of the site was described by previous investigators; Geocon (2004), HCI (2004), Shangoni
(2011) and most recently by Itasca (2014) the descriptions presented are used as the basis for describing
the geology of the site below. A plan view of the borehole sites and information [from previous studies] used
in the design of the conceptual model is illustrated in Figure 14 below. The figure also shows the positions
and directions sub-vertical geological features, i.e. faults and dykes which could play a role in the “on-site”
groundwater flow regime.
The basic geological model of the Voorspoed Kimberlite feature and surrounding geology is depicted in
Figure 15 and Figure 17.The Voorspoed mine site area comprises of shales and mudstones of the Volksrust
formation (VRM) which are part of the Ecca Group of the Karoo Supergroup. The Volksrust formation is
underlain by coarser grained; conglomerates, shales and sandstones of the Vryheid formation (VRSSC).
Shale (VRVS) is found to occur at depth. The sedimentary package dips at approximatly150 toward the
north-north-west.
The strata has been intruded by dolerite dykes and sills. Three major sills were identified to intersect the pit,
namely;
Dolerite Sill (#14) (the number assigned in the GEMCOM model) - a sill with a thickness ranging from 1
to 25 m, but more commonly ranging from 3 to 8 m thick in the immediate mine area. The upper contact
zone of the sill is relatively permeable based on packer test data;
Dolerite Sill (#13) - a thicker sill with a thickness ranging from 20 to 180 m, more commonly ranging
from 80 to 120 m in the mine area; and
Dolerite Sill (#12) - a sill in the shale discovered by De Beers in exploration boreholes. The thickness of
this lower sill ranges from 10 to 65 m, most commonly being between 30 and 55 m.
The Kimberlite pipe on the farm Voorspoed 401 is an irregular, approximately oval shaped body. The
dimensions of the pipe are in the order of 490 m x 350 m. An essentially vertical body of Stormberg-age
basalt intruded into the southern part of the kimberlite pipe. The bottom of the basalt body has been
intersected at a depth 430 m below ground surface (Ref. Hydrogeological Investigation, Report No.
1663605-315698-2, section 2.4, Figure 4, page 5).
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Figure 14: Boreholes used for conceptual model design and illustration of secondary geological features (faults/dykes) on the Voorspoed mine site area.
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The following features of the 2017 conceptual model were noted:
The hydraulic parameters of the sedimentary sequence (Karoo Ecca Group) at Voorspoed Mine is low
to insignificant (i.e. based on previous aquifer investigations and test pumping);
Due to the low hydraulic characteristics of the surrounding Karoo Supergroup aquifer systems (viz.
shales and mudstones), the 2017 water table status indicates a limited development of a dewatering
cone due to the mining activity as indicated in Figure 15 below;
The role of [secondary] Karoo dolerite sills probably has a limited impact on the local groundwater flow
regime on the mine site area as this [intrusive] formation also has low to insignificant hydraulic features.
The dolerite-sedimentary contact zone (viz. metamorphosed due to the magma temperature, is
however limited to a small “contact aquifer” system, but obviously not a significant contributor to
groundwater flow in the pit area. These sills have a folder nature in the mine site area, but does not
impact significantly on the local flow regime (not specifically noted in the groundwater piezometric
surface dataset).
Figure 15: Voorspoed Mine 3D Conceptual Model (current operational phase) from the South and observed (2017) sulphate concentration levels (mg/l).
On the other hand, the role of sub-vertical dolerite dykes in the area as illustrated in Figure 14, has
been noted by local geologists and exploratory drilling has shown that high permeable flow paths are
present (i.e. narrow contact fractured water bearing zones) which could play a significant role in the
migration of groundwater [containing, or not-] from the mine site area. To verify this aspect, an upgrade
of the monitoring infrastructure and dedicated monitoring sites on the mine site area are planned for
2017-2018 and monitoring sites will be placed in these areas to monitoring the actual role these sub-
vertical water bearing zones might play during the post-mining period [based a dedicated monitoring
program].
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However, during the 2017 hydrocensus and specific observations in the Voorspoed Pit [where the
above-mentioned features, as well as sub-vertical faults were mapped in the past] no significant water
ingress were noted on the side walls of the pit, a condition confirmed by Voorspoed staff (Pers. Comm.,
2017); and
Limited seepage takes place on the higher elevations in the pit sidewalls, but due to high evaporation in
the area, most of this water evaporates and does not report to the final water make at the pit bottom, as
indicated in Figure 15 above.
A close-up of the Voorspoed Pit hydrological status during operational times is illustrated in Figure 16 and
shows the different pit wall processes and the groundwater elevations in the country rock surrounding the pit
side wall. Based on the local water level observations, a large part of the pit sidewall acts as an unsaturated
zone where any seepages generated by direct rainfall recharge/groundwater seepage, is intercepted by
evaporation and subsequently diminishes long before it all accumulated in the pit sump. It indicates that:
Local seepages (e.g. from rainfall events) occurs near the upper fractured and weathered part of the pit,
and only during exceptional rainfall events, pit sidewall run-off reaches the base of the pit (i.e. as per
Google Image interpretations);
Rock materials in the open pit are likely to generate near neutral drainage with high total dissolved
solids, moderate sulphate and low concentration of trace elements upon exposure to rainfall; and
The drainage from the wall rock is likely to be similar to that of waste rock leachate in the long term, but
the concentrations will rise and fall with inflows and evaporation.
Figure 16: Operational phase conceptual model of the Voorspoed Pit (based on 2017 observations).
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Based on the numerical modelling of the post mine closure phase, water starts too accumulated in the pit
and subsequently forms a pit lake, as illustrated in Figure 17. It is expected that under a partially filled pit
lake condition, the high evaporation uptake in the area will retain the pit lake water table at a negative water
balance, unless additional water ingress will be generated from a larger [engineered] pit lake catchment
area. Depending on the area (viz. hectares) of an engineered pit lake catchment [to enhance the water table
recovery for security reasons] the pit lake water table under normal climate conditions might never reach the
pristine piezometric water table.
Figure 17: Voorspoed Mine 3D Conceptual Model (post-closure scenario) from the South showing partially filled pit lake scenario.
A close-up of the processes that are relevant during a high elevation pit lake scenario, is illustrated in Figure
18 below. The following aspects have relevance [but is discussed in detail in Golder Report: Hydrogeological
Investigation, No. 1663605-315698-2 section 4.3.3.2, Post Closure Hydrochemistry with relation to plumes
associated with the WRD, CRD and FRD]. Basically the pit lake concept indicates that:
During the operational phase, solutes flushed by runoff and seepage from the wall rock are pumped
out;
Pumping of pit water will cease at the end of mining and solutes flushed from the wall rock will
accumulate in the pit;
It is expected that the mass of solutes added will be initially be high due to the large surface area of
exposed wall rock and will decrease with time as pit fills up and surface area of exposed wall rock
decreases; and
Once the water table equilibrates, inflows will be limited to rainfall and so concentrations are likely to
increase due to evaporation effect.
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It is expected that stratification of the pit lake water body will developed over time, leaching in the
unsaturated zone (pit rim area) will continue indefinitely, and chemical reactions in the upper part of the
water body will take place due to the effects of evaporation (higher Salinity) and rainwater ingress (lower
salinity) will take place. As noted above, it is unlikely that the pit lake will reach a state where decanting will
take place under [existing] normal climate conditions – evaporation is just too high in relation with rainfall run-
off events.
Figure 18: Post operational phase conceptual model of the Voorspoed Pit (~50 years after closure).
5.4 Conclusions and Recommendations (Hydrogeological Investigation)
Conclusions:
The following conclusions were drawn from hydrogeological investigation:
The Voorspoed pit at life of mine will reach a final elevation of 1103 mamsl which equates to a pit depth
of 307 m. Throughout life of mine the inflow to the pit has been low owing the low permeability of
mudrocks, sandstones and shale which surrounding the kimberlite pipe.
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Water level responses (i.e. rebounds) shows sharp rise in water level (> 15 m) that were seemingly
associated with significant recharge events. These types of fluctuations are common in low permeability
aquifers.
The cone of depression created through mining is consequently steep and limited in lateral/spatial
extent, 1.2 km to the west and terminates beneath the waste rock dump in the east and north
The water quality of boreholes on farms adjacent to the mine are presently not impacted by seepage
from the facilities nor from drawdown associate with the mining activities, i.e. open cast pit mining.
Corresponding with the seasonal fluctuations observed in the monitored water levels, recharge was
estimated to occur in the high rainfall summer months of the year and little to no recharge occurs in the
winter months.
Groundwater recharge across the study area is expected to be low. Average recharge for most of the
Karoo Supergroup is in the range of 2 to 3 % of MAP with a recurrence rate of 1 in 5 years of a
significant aquifer storage recharge event(s).
The key-potential impacts identified for the post closure phase of the operation is the pit lake rebound rate
and water quality and the migration of contaminant plumes associated with the dumps.
Pit Lake (reference to the numerical modelling part, see section 9.1 below as well)
Due to the low permeability of the country rock proximal to the Kimberlite pipe, the inflows to the pit are
low. Pit abstractions range between 0 l/s to 46.5 l/s (i.e. wetter periods with higher runoff inflow result in
higher abstraction rates).
Post operational hydrochemistry
The Piper Diagram shows a natural groundwater quality evolution from the recently recharged waters
characterised by a Ca/Mg-HCO3 signature to water representative of dynamic flow, characterised by a
Na-HCO3 signature and gradually towards a typical deep Karoo water quality signature, characterised
by Na-Cl.
The “Pit Water” quality Piper plot portrays a Na-SO4 water quality signature. Similarly, water samples
associated with the Coarse Residue Dumps and Fine Residue Dumps, plot as Na-SO4 water. This likely
indicates a natural source of sodium and sulphate associated with the Kimberlite pipe.
Most of the groundwater quality in the Far Field Area, plots in the Ca/Mg-HCO3 quadrant and represent
the upper, shallower part of the aquifer systems, which receive frequent rainwater recharge and is not
impacted by mine contamination.
With the exception of the TDS concentrations of the CRD all source concentrations are below the
livestock watering limit for the selected constituents. Sulphate, sodium and nitrate concentrations of the
sources tend to exceed drinking water quality limits and chloride exceeds the baseline water quality
limits.
Plumes associated with the WRD, FRD and CRD
Due to the effects of evaporation, the pit was found to remain as a sink during the post operational
phase of mining and as such a component of seepage from the WRD and FRD continued to be
captured by the pit.
However, due to the low permeability of the aquifer the radius of influence of the pit is limited and
consequently a component of seepage is expected to migrate downgradient toward the identified
receiving boreholes.
Recommendations
Re-design of the surface and groundwater monitoring infrastructure and programme to cover the study
area:
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Specific reference of the surface water monitoring requirement (see discussion immediately above)
is required for the drainage running from the return water dam’s area towards the east.
Dedicated boreholes to monitor the shallow and deep aquifers individually are required especially in the
CRD area;
Establishment of a local weather station on the site; and
Prediction of the long-term evolution of pit lake water chemistry based upon the volume and chemistry
of surface run-off water channelled from the near filed areas to enhancement the pit lake water level
recovery, evaporative mass balance and a long-term mixing model.
6.0 GEOCHEMICAL ASSESSMENT
6.1 Previous Geochemistry studies
Metago Environmental Engineers (Pty) Ltd (2005) carried out an assessment of pollution potential of the
mine residue materials at Voorspoed on a limited number of samples, including one of kimberlite, as part of
the environmental management plan. Six waste rock samples with most carbonaceous bands were
subjected to South African Acid Rain Leach Test (SAAR) and elemental composition determination by X-ray
fluorescence (XRF); and three samples acid base accounting and mineralogical analysis by X-ray Diffraction
(XRD) and optical examination of polished thin sections under the microscope. The samples containing
carbonaceous materials were considered to represent the worst case in terms of potential for acid rock
drainage generation. The findings of the study are detailed under section 3.2 of the geochemistry report
(Golder Report: Geochemical Assessment, No. 1663605-316224-4).
It was concluded that the toxicological pollution potential from the waste rock material was negligible with the
possible exception of manganese. Salinity, from mainly sodium was identified as a major issue requiring
management of drainage from both waste rock and tailings storage facilities at Voorspoed. The potential for
acid rock drainage (ARD) generation was predicted to be low to unlikely due to presence of sufficient
carbonate in the waste rock for neutralising acid generated by oxidation of sulphides.
The potential for acid rock drainage (ARD) generation was predicted to be low to unlikely due to presence of
sufficient carbonate in the waste rock for neutralising acid generated by oxidation of sulphides. It was
concluded that the environmental risk associated with the waste rock material was negligible with the
possible exception of manganese. Salinity was identified as a major issue requiring management of drainage
from both waste rock and tailings storage facilities at Voorspoed.
6.2 Summary of Water Qualities Observed (near field area)
Hydrochemical analyses of the water sources, i.e. mine water, surface water and groundwater
located/monitored on the mine site area, and indicate the following:
Pit water: The water was characterised by alkaline pH (8.2-9.5) and elevated concentrations of TDS
(769-1318 mg/l), sodium (213-375 mg/L), sulphate (173-370 mg/L), nitrate as N (30-120 mg/L) and
fluoride (1.28-1.95 mg/L) that frequently exceeded DWAF (1996) domestic irrigation or livestock
guidelines between June 2013 and June 2015. The concentrations of iron and manganese rarely
exceeded domestic and irrigation water quality guidelines;
Return water Dam water: The water was characterised by near-neutral to alkaline pH (7.3-9.0) and
highly variable concentrations of TDS (196-1779 mg/L), calcium (22-102 mg/L), sodium (16-457 mg/L),
chloride (9.9-544 mg/L), nitrate (<0.057-60 mg/L) and sulphate (21-452 mg/L), which occasionally to
frequently exceeded DWAF water quality guidelines for domestic use, irrigation and livestock watering
between June 2008 and May 2016.
Groundwater: The groundwater from boreholes located close to the waste rock dump (VD BH04 and
MBH 19) was characterised by near-neutral to alkaline pH (6.8-8.7). The concentrations of TDS (236-
666 mg/L), calcium (12-73 mg/L) and sodium (51-237 mg/L) frequently to occasionally (calcium-
marginally) exceeded DWAF water quality guidelines for domestic use, irrigation or livestock watering
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between April 2007 and June 2015 borehole MBH 19. The concentrations of TDS (68-574 mg/L) and
sodium (23-42 mg/L) were relatively low in borehole VD BH04 while calcium (38-82 mg/L) was relatively
high compared to MBH19 and they occasionally (TDS) to consistently (calcium) exceeded the
guidelines. The sulphate concentrations were generally low in groundwater from both VDBH04 (12-46
mg/L) and MBH 19 (19-106 mg/L).
Groundwater from borehole VD BH01, which is located close to the fines residue facilities was characterized
by near-neutral to alkaline pH (7.4-9.5), variable TDS (262-1566 mg/L), calcium (9.0-183 mg/L), sodium (58-
176 mg/L), chloride (21-620 mg/L) and sulphate (14-88 mg/L), which frequently exceeded DWAF water
quality guidelines with the exception of sulphate, which was below the guidelines. Though there were
fluctuations between monitoring events, the concentrations of TDS, sodium and chloride show a general
upward trend over time.
6.3 Conceptual Model (geochemistry)
Detailed discussion of the conceptual models during the Voorspoed operational times appears under section
3.4 of the Golder Report: Geochemical Assessment, No. 1663605-316224-4. In short it comprises of the
following components:
Open pit: where mining is currently taking place using normal drill and blast techniques.
Weathering/oxidation processes, are expected to take place on the wall rock and ore at the bottom of
the pit. The weathering products, including efflorescent salts are likely to be flushed by runoff and
seepage, which collects on the pit floor, from where it is pumped out of the pit (ref. Figure 16 above);
Waste rock dump (WRD): which is located along the pit boundary from the south to north east, and is
heterogeneous in terms of composition and particle size. Contaminants are likely to be transported to
surface water sources by runoff and to groundwater by seepage (ref to Figure 6 in Geochemical
Assessment Report referenced above).
Coarse residue dump (CRD): where wet, course treated kimberlite from the plant is dumped. The
water seeps to the toe drainof the CRD from where it is channelled to the return water dam. Some of
the water evaporates leaving behind white precipitates, which are likely to be dissolved by rainwater
and local surface water flow. Acid rock drainage processes are likely to take place in the dry residue
and contaminants are likely to reach surface water source via runoff and to groundwater through
seepage (ref to Figure 7 in Geochemical Assessment Report referenced above).
Fine residue dump (FRD), where treated kimberlite fines (sit and clay) from the plant are disposed.
The fine residue is deposited as slurry and the process water drains to the return water dam. Though
ARD processes can occur in the dry beach area (see Figure 8 in Geochemical Assessment Report
referenced above).
ROM stockpiles: located adjacent the plant. Ore is expected to be stockpiled for a short period and the
stockpiles are thus not likely to be major sources of contaminants.
In terms of groundwater inflow to the pit, it is understood to be low due to the low permeability of the
surrounding [Karoo Supergroup] Ecca Group strata consisting of mudrocks, sandstones and shale which
surrounding the kimberlite pipe (pers. comm. Voorspoed staff, 2017). The contribution of groundwater in
terms of loads are therefore insignificant in terms of the open pit contribution indicated above.
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Simplified Source-Pathway-Receptor Concept.
A simplified source-pathway-receptor conceptualisation for Voorspoed is presented in Table 3.
Table 3: Conceptual source-pathway-receptor characterisation for mine facilities at Voorspoed.
Source Pathway Proximate Receptor
Ultimate Receptor
Open pit
Run-off on wall rock, ramps and pit floor to sump area.
Seepage through fractures on pit floor.
Non-perennial tributaries of the Heuningspruit and Renosterspruit. Local fractured and weathered aquifer system and contact aquifer system associated with sub-vertical faults/dolerite dykes.
The Vaal River and the regional aquifer
Waste rock dump Runoff on WRD slopes
Seepage through waste rock
ROM stockpiles Run-off
Coarse residue dump
Run-off on CRD slopes
Seepage through the coarse residue
Fine residue dump Run-off on FRD wall slopes
Seepage through fine residue
The major receptors are:
v) Surface water: The mining is taking place on a watershed. Un-named non-perennial tributaries drains
the eastern side into the Heuningspruit, and western side into the Renosterspruit. The Heuningspruit
drains into the Renosterspruit and ultimately the Vaal River. The monitoring database for raw water
dam at Voorspoed indicate that the water quality of Koppies dam, which is located on Renoster, is
alkaline with variable TDS (254-781 mg/L), sodium (42-218 mg/L), chloride (38-303 mg/L) and sulphate
(29-118 mg/L).
vi) Groundwater: Groundwater around Voorspoed occurs in shallow aquifer zone comprising the
weathered and fractured, layered Karoo Ecca Group strata, which is classified as a minor to
insignificant aquifer. Deep water bearing zone may exists, but contribute to a much lesser degree to the
flow regime. Secondary geological structures (viz. sub-vertical faults and dykes) behave as preferential
flow paths for groundwater flow (i.e. contact aquifer units). Close to the pit, groundwater flows towards
the pit and north of the residue dumps, groundwater flows in a northerly and north easterly direction
while south of the mine flow occurs in a south – south westerly flow direction.
Groundwater quality around the mine area monitoring sites are characterised by slightly elevated
salinity levels (TDS ~750 mg/L), with elevated [rising] sulphate, sodium and chloride concentrations.
Although fluoride has been identified as one of the risk constituents in the waste rock classification
study, it is confined to the pit water quality and probably represent a primary deep water source
associated with the remaining Kimberlite orebody.
6.4 Sampling and Laboratory Program
A detailed discussion of this component appears under section 4.0 of the Geochemical Assessment Report
(as referenced above), covering the following aspects:
Sampling Program; and
Laboratory Program.
The actual sampling sites, i.e. mine waste, water and seepages are illustrated in Figure 19 below.
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6.5 Geochemical Test Results
A detailed discussion of this component appears under section 5.0 of the Geochemical Assessment Report
(as referenced above), covering the following aspects:
Environmental Mineralogy:
The mineralogical analysis was aimed at identifying minerals that have a potential of generating acidity
(sulphides and sulphates) and neutralisation potential (including carbonate and silicate minerals).
Neutralisation capacity in the CRD, FRD and WRD materials is expected to be provided by calcite, which is a
fast-reacting (dissolving) buffering mineral. The alumino-silicate minerals are likely to provide additional
buffering capacity in the mine residue materials, albeit at variable rates as these are fast (diopside) to very
slow (microcline) weathering minerals.
Alumino-silicate minerals were rare to major phases in all the samples. Calcite, a carbonate mineral occurred
as a minor phase (2.2-7.4 wt. %) in all samples.
Secondary mineral precipitates were observed mainly on CRD surfaces and around seepage areas. The
precipitates were identified to be sulphate minerals thernardite (Na2(SO4)) and gypsum (Ca(SO4)·2H2O).
These minerals precipitate from sulphate-rich solutions, acting as temporary sinks for dissolved metals,
frequently dissolving again during rainfall events as they are highly soluble (MEND, 2009).
Elemental Composition:
The extent of elemental enrichment in the CRD, FRD and WRD samples was assessed using the
geochemical abundance index (GAI). The elements that were found to be enriched in at least one sample of
the different mine residue materials are provided in Table 4 below.
Table 4: Geochemical Abundance Index for waste rock, coarse residue and fine residue samples.
Source of Sample Material Type Sample count
Elements with GAI > 0 (Elements with GAI > 3 are highlighted in bold)
Coarse Residue Dump Coarse Residue 3 As, Au, Ba, Bi, C, Cr, Hf, La, Pt, S, Se and Te
Waste Rock Dump Waste Rock 3 As, Au, B, Bi, C, Cr, Cs, Hf, Li, Pt, S, Sb, Se, Th and Te
Fine Residue Dump Fine Residue 3 As, Au, Ba, Bi, C, Ce, Cr, Hf, La, Mg, Nd, Ni, Pt, S, Se and Te.
Enrichment of elements in mine residue samples over crustal concentrations was also determined in Figure
12 of the Geochemical Assessment Report (section 5.2, page 18) and can be summarised as follows:
The waste rock, coarse residue and fine residue materials at Voorspoed materials are enriched (in
decreasing order) in tellurium, carbon, bismuth, platinum, gold, selenium, arsenic, antimony, lanthanum,
chromium, boron, barium and sulphur.
Selenium, arsenic, antimony, chromium, boron and sulphur are environmentally-significant as they are
associated with sulphides, carbonates and mafic silicate minerals, which are fast weathering minerals.
Thus, these elements are potential constituents of concern (PCOCs) from the different residue dumps at
Voorspoed. The other enriched elements, e.g. tungsten, are mainly insoluble and therefore not
environmentally significant.
6.6 Acid Base Accounting
A detailed discussion of this component appears under section 5.3 of the Geochemical Assessment Report
(as referenced above), high-lighting the following observations:
The total sulphur (0.04%-0.11%), sulphide (0.01%-0.03%) and sulphate (0.001%-0.16%) content of all
mine residue materials was very low.
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Bulk neutralization potential (Bulk NP) was generally high in the waste rock (40-48 kg CaCO3 eqv t-1),
coarse residue (47-63 kg CaCO3 eqv t-1) and fine residue samples (56-74 kg CaCO3 eqv t-1). The
carbonate neutralization potential (CaNP) for all mine residue samples (23-52 kg CaCO3 eqv t-1) was
less than Bulk NP indicating that neutralization potential was provided by both carbonate and silicate
minerals;
The alkaline paste pH (9.1-10.9) indicates sufficient reactive NP in all mine residue materials to buffer
acidity generated by the initial oxidation of sulphides during the testing procedure. There is excess
buffering capacity in the coarse residue, fine residue and waste rock materials, with Bulk NP exceeding
acid potential (AP) in all samples.
Classification of acid rock drainage (ARD) potential show that all the coarse residue, fine residue and
waste rock samples are not potentially acid generating (Non-PAG).
Specific references to the applicable guidelines used for the evaluation of the Voorspoed geochemical
analyses (i.e. Bulk NP and ARD) is mentioned in section 5.3 of the Geochemical Assessment Report
[referenced above].
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Figure 19: Location of mine waste, seepage and water samples
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Net acid generation (NAG) pH and TNPR (viz. bulk neutralization potential /total acid producing) of all the
mine residue samples also classify all the materials as Non-PAG and illustrated in Figure 20 below.
Figure 20: Plot of NAG pH versus TNPR (Bulk NP/TAP) of coarse and fine residue and waste rock.
6.7 Drainage Chemistry Analyses
A detailed discussion of this component appears under section 5.4 of the Geochemical Assessment Report
(as referenced above). Australian standard leaching procedure (ASLP) and net acid generation (NAG) leach
tests were carried out on coarse residue, fine residue and waste rock samples, in order to obtain indications
of the potential drainage quality and PCOC from the mine residue dumps at Voorspoed.
These short-term leach tests measure readily soluble components of geological materials but do not predict
long term water quality. Water-rock interactions often develop over periods of time that are much greater
than can be represented in an 18 to 24 hour extraction test.
Leachate generated by net acid generation (NAG) leach tests represents complete and instantaneous
oxidation and leaching of all reactive minerals. These tests were done to assess the maximum (worst case)
quality of drainage from the coarse residue dump, fine residue dump and waste rock dumps. Under field
conditions, sulphide oxidation and release of elements will occur gradually and concentrations in mine
drainage are expected to be lower than NAG leachate chemistry at any given time.
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The results of leach tests, seepage, return water dam and pit water samples are summarized and compared
with DWAF (1996) water quality guidelines in Tables, 6 to 8 and Figures 16 to 18 of the Golder Report:
Geochemical Assessment, No. 1663605-316224-4.
The results were also compared to resource water quality objectives (RWQO) for management units in the
Renoster River catchment. It should however be noted that RWQO are set only for pH, EC, turbidity and
ammonia for catchment C70H, in which the Voorspoed mine is located.
A Piper Diagram plot of the drainage chemistry analyses results for pit water, CRD, FRD and WRD are
illustrated in Figure 21 below and high-lights the strong sodium-chloride (Na-Cl) signature of the Karoo
aquifer system in the Voorspoed area (also with reference to Figure 2 in section 5.1.2 above).
Figure 21: Piper diagram of waste rock, processed waste rock seepages and pit water samples.
With regard to the drainage chemistry analyses of the individual [potential] sources of leachate on the
Voorspoed mine site area, a detailed discussion appears under the following sections of the Geochemical
Assessment Report:
Section 5.4.1: Coarse Residue Dump Drainage –
The coarse residue materials are likely to produce predominantly near-neutral, low-metal drainage
upon exposure to rainfall, and specifically (wrt WRC et al 1996 domestic and irrigation water
quality guidelines):
pH (alkaline), aluminium, iron and manganese, and Sodium absorption ratio (SAR) for irrigation
water.
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The NAG leachate results indicate that the coarse residue materials are likely to generate neutral
mine to acid rock drainage with low metal concentrations and likely to be elevated and to exceed
water guidelines for the following constituents, i.e.:
Manganese, mercury, aluminium, calcium, iron, and total dissolved solids, pH and sodium SAR).
Individual seepage samples from the CRD exceeds pH, electrical conductivity, calcium, sodium and SAR
domestic and irrigation guidelines
Fine Residue Dump Drainage –
The fine residue materials from the three facilities are likely to produce predominantly near-neutral,
low-metal drainage upon exposure to rainfall (wrt WRC et al 1996 domestic, livestock and
irrigation water quality guidelines):
pH (alkaline), aluminium, iron and manganese, and Sodium absorption ratio (SAR) for irrigation
water.
The NAG leachate results indicate that fine residue materials are likely to generate neutral mine to
acid rock drainage with low mental concentrations, i.e.:
pH (alkaline), aluminium, iron, manganese, mercury, total dissolved solids, sodium (SAR), and
calcium.
Water samples from the FRD was neutral mine drainage with low metals, however, the water sample was of
a sodium/chloride signature (see Figure 21) and it exceeded the WRC et al (1996) water quality guidelines
for pH (alkaline), total dissolved solids, nitrate, sulphate, calcium, molybdenum, chloride, sodium, SAR and
selenium.
Waste Rock Dump Drainage –
The waste rock materials are likely to produce predominantly near-neutral, low-metal drainage
upon exposure to rainfall (wrt WRC et al 1996 domestic, livestock and irrigation water quality
guidelines):
Aluminium, pH (alkaline), manganese, iron, SAR.
The NAG leachate results indicate that the waste rock materials are likely to generate neutral mine
to acid rock drainage with low mental concentrations
Manganese, mercury, total dissolved solids, pH (alkaline), sodium (SAR), aluminium, calcium
and iron.
Pit and Return Water Dam –
Sample analyses indicate neutral mine drainage with low metals, with a sodium/chloride signature
(Figure 21) and exceeded the following water quality guidelines selectively for domestic, livestock
and irrigation (WRC et al, 1996):
Total dissolved solids, nitrate, sodium, SAR, sulphate, fluoride and molybdenum.
The elevated nitrate levels could be due to explosives residue. See discussion of the elevated fluoride in
the pit water component in section 5.1.2 above.
6.8 Waste Assessment and Classification
A detailed discussion on the analyses results for the waste assessment appears under section 5.5 of the
Geochemical Assessment Report reference above. Please note that the Waste Classification and
Management Regulations (WCMR) and the Norms and Standards for the Assessment of Waste for Landfill
Disposal (GN R.634 to R636, 23 August 2013) applies herein – see section 2.4 in the Geochemical
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Assessment Report referenced above. In terms of the potential sources of elevated geochemical
constituents, the following observations were made:
Course Residue Dump – (3 samples taken)
Waste Assessment:
Total concentrations of barium, copper, fluoride, manganese, nickel and vanadium exceeded the
total concentration threshold (TCT0) levels; and
The coarse residue material is not Type 4 waste as at least one parameter exceed TCT0 but it
does not meet the definition of Type 3 waste due to low risk from leachable concentrations (LC),
i.e. all parameters LC≤LCT0.
Waste Classification:
Physical hazards: classified as non-hazardous in terms of physical hazards;
Health hazards: The total concentration of aluminium, calcium, iron, magnesium, potassium and
silicon exceeded 1% in the coarse residue samples. However, none of these parameters exceed
1% in leachate and therefore do not constitute a health risk.
Carcinogens (Cd, Ni, As and Cr (VI)): The total and leachable concentrations of carcinogenic
trace metals were <0.1% in the samples from the CRD. Therefore none of these elements
constitute a health risk.
Environmental hazard: The CRD is considered to be non-hazardous to the environment due to
low solubility of elements, i.e. aluminium, calcium, iron, magnesium, potassium and silicon, and
the leachable concentrations of these elements do not exceed the % threshold for environmental
hazard.
Fine Residue Dump – (three samples taken)
Waste Assessment:
Total concentrations of barium, copper, fluoride, manganese, nickel and vanadium exceeded the
TCT0 levels, however, leachable concentrations of all potential constituents of concern were
less than LCT0 in all samples; and
The residue from FRD 1A, FRD 1B and Phase 2 FRD is not Type 4 waste as at least one
parameter exceed TCT0 but it does not meet the definition of Type 3 waste due to low risk from
leachate (all parameters LC≤LCT0).
Waste Classification:
Physical hazards: classified as non-hazardous in terms of physical hazards;
Health hazards: The total concentration of aluminium, calcium, iron, magnesium, potassium and
silicon exceeded 1% in the fine residue samples. However, none of these parameters exceed
1% in leachate and therefore do not constitute a health risk.
Carcinogens (Cd, Ni, As and Cr (VI)): The total and leachable concentrations of carcinogenic
trace metals were <0.1% in the samples from the FRDs. Therefore none of these elements
constitute a health risk.
Environmental hazard: The leachable concentrations of aluminium, calcium, iron, magnesium,
potassium and silicon do not exceed the % threshold for environmental hazard. Therefore the
fine residue material from the FRDs is considered to be non-hazardous to the environment due
to low solubility of elements.
Waste Rock Dump – (three samples taken)
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Waste Assessment:
Total concentrations of arsenic, barium, copper, fluoride, manganese, nickel and vanadium
exceeded the TCT0 levels (at least one of the three samples), however, leachable
concentrations of all analytes were less than LCT0 in all the samples; and
The waste rock material is not Type 4 waste as at least one parameter exceed TCT0 but it does
not meet the definition of Type 3 waste due to low risk from leachate (all parameters LC≤LCT0).
Waste Classification:
Physical hazards: Classified as non-hazardous in terms of physical hazards;
Health hazards: The total concentration of aluminium, calcium, iron, magnesium, potassium and
silicon and sodium exceeded 1% in the waste rock samples. However, none of these
parameters exceed 1% in leachate and therefore do not constitute a health risk.
Carcinogens (Cd, Ni, As and Cr (VI): The total and leachable concentrations of carcinogenic
trace metals were <0.1% in the samples from the WRD. Therefore none of these elements
constitute a health risk.
Environmental hazard: The leachable concentrations of aluminium, calcium, iron, magnesium,
potassium, sodium and silicon do not exceed the % threshold for environmental hazard.
Therefore the waste rock material from the WRD is considered to be non-hazardous to the
environment due to low solubility of elements.
6.9 Conclusions (Geochemical Assessment)
Voorspoed Pit
1) According to monitoring data, the pit water is alkaline and brackish, with sodium, sulphate, nitrate and
fluoride that frequently exceeded DWAF (1996) domestic irrigation or livestock guidelines.
2) The pit water is neutral mine drainage with low metals, but exceedances of multiple parameters in the
domestic, livestock and irrigation water quality guidelines
Waste Rock Dump
3) Previous studies suggested low potential for acid rock drainage from the waste rock and low
environmental risk from seepage, except for elevated manganese.
4) The waste rock is not potentially acid generating (Non-PAG).
5) The waste rock is likely to produce predominantly near-neutral, low-metal drainage upon exposure to
rainfall, with pH likely to exceed RWQO for local catchment management unit C70H; aluminium, iron
and manganese are likely to exceed the domestic and irrigation water quality guideline and Sodium
Absorption Ratio likely to exceed the irrigation water quality guideline.
6) The sampled waste rock from the WRD is classified as non-hazardous waste.
7) Although the waste rock material might be considered as Type 3 for the purpose of cover design (in
terms of GN R. 635 Regulation 7(6)), the environmental risk associated with seepage from the dump is
similar to that of a Type 4 waste.
Coarse Residue Dump
8) The coarse residue is not potentially acid generating (Non-PAG), although secondary sulphate
precipitates were observed on CRD surfaces and around seepage areas.
9) The coarse residue materials are likely to produce predominantly near-neutral, low-metal drainage upon
exposure to rainfall, with pH likely to exceed RWQO for local catchment management unit C70H;
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aluminium, iron and manganese are likely to exceed the domestic and irrigation water quality guidelines
and Sodium Absorption Ratio likely to exceed the irrigation water quality guideline.
10) The material from the CRD is classified as non-hazardous waste.
11) Although the coarse residue material might be considered as Type 3 for the purpose of cover design (in
terms of GN R. 635 Regulation 7(6)), the environmental risk associated with seepage from the dump is
similar to that of a Type 4 waste.
Fine Residue Dump
12) The fine residue is not potentially acid generating (Non-PAG).
13) The fine residue materials are likely to produce predominantly near-neutral, low-metal drainage upon
exposure to rainfall, with pH likely to exceed RWQO for local catchment management unit C70H;
aluminium, iron and manganese are likely to exceed the domestic and irrigation water quality guidelines
and Sodium Absorption Ratio likely to exceed the irrigation water quality guideline.
14) The sampled materials from all the FRDs are classified as non-hazardous waste.
Although the fine residue material might be considered as Type 3 for the purpose of cover design (in terms
of GN R. 635 Regulation 7(6)), the environmental risk associated with seepage from the three dumps is
similar to that of a Type 4 waste.
A detailed summary of the geochemical assessment appears under section 6.0 of the Geochemical
Assessment Report referenced above.
6.10 Appendixes Related to the Geochemical Assessment
The following appendixes were developed during the project period and are available in the relevant reports:
Golder Report No. 1663605-314859-1 (see References, Item 11.0 below):
Appendix A: Groundwater and open (surface) water LAD certificates and analytical data; and
Appendix C: Waste Chemistry LAB certificates and analytical datasets.
Golder Report No. 1663605-316224-4 (see References, Item 11.0 below):
Appendix B: Method Statement;
Appendix C: QAQC Statement;
Appendix D: Detailed Results; and
Appendix E: Laboratory Certificates (An update of Appendix C above).
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7.0 FLOOD LINE ASSESSMENT
The Voorspoed mine is situated on the farm Voorspoed 401 in the Free State, 30 km from Kroonstad. The
study area is situated within the primary catchment of the Vaal River and within quaternary catchment C70H.
Locally the site is drained by tributaries of the Heuningspruit, which runs in a north-westerly direction where it
joins the Renoster River, approximately 15 km to the north.
The site is located on a high point above the headwaters of four streams that drain the area. The locations of
the perennial and non-perennial streams are shown in Figure 22. There are no identifiable water courses
draining across the site. The distance of the identified water courses from the mine boundary varies between
200m and 800m. Given the distance of the water courses from the mine boundary due to the mine being
located on the catchment divide, no flood lines need to be determined.
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Figure 22: Voorspoed Mine - Perennial and Non-perennial Streams
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8.0 DYNAMIC WATER AND SALT BALANCE
A detailed discussion of the Voorspoed mine site area’s dynamic water and salt balance appears in Golder
Report: Voorspoed Diamond Mine Water and Salt Balance Report 2017, No.1663605-316021-3. A summary
with specific references] is provided herein.
Site locality and description ito the Vaal River Water management Area (WMA) and local drainages
comprising of the Heuningspruit (Quaternary Catchment C70H) and the Renoster River (Quaternary
Catchment C60G), see Figure 22 above.
A description of the Model Data (section 2.0 in the Water and Salt Balance Report) is provided covering the
following aspects of the mine site area:
Climate data, mainly rainfall data from the SAWS Station 0401407 W (Middelweg) showing the
following criteria:
The mean annual precipitation (MAP) at the station is 495 mm/a;
The area is a summer rainfall area with low rainfall from May to September (below 17 mm/month);
The annual precipitation measured at the gauge varies between 265 mm/year and 1 107 mm/year;
24 Hour Storm Rainfall Depths (mm) were conducted (Table 2 under sub-section 2.2, showing that
rain storms generating a downpour of >50 mm (driving a moderate groundwater recharge event)
has a return period of 1 in ~5 years;
Average S-Class pan evaporation is 1551 mm/year measured at C6E001 station (highest average
monthly evaporation occurs in December).
8.1 Process Water Reticulation System Description
The water reticulation diagram for the Voorspoed Mine is shown in Figure 23 below (section 2.3 of the Water
and Salt Balance Report referenced above). There is a single open pit from which ore is mined and sent to
the Plant for processing. Raw water is sourced from the Koppies Dam and transferred to the Renoster
storage. It is then transferred to the Storm Water Control Dam. The Renoster storage also supplies the Raw
Water Dam (RWD) under extreme dry conditions.
There are a few sites on the mine site area where additional flow meters are required, as noted in subsection
2.7 of the Water and Salt Balance Report.
8.1.1 Water and waste storage facilities
A detailed description of the Water Related Infrastructure appears in section 2.4 of the referenced report (viz.
Water Related Infrastructure), and a summary of the Voorspoed Mine Water Storage Facilities is listed in
Table 5 below.
Table 5: Summary of the Dam Characteristics
Dam Catchment area (ha)
Capacity (m3)
Surface area at capacity (m2)
Operating procedure/level maintained
Outflow pump capacities (m3/hr)
Koppies Dam
4,2Mm3 Only release from dam when Renoster storage is below 2.5m wall height through sluice gates
Renoster Storage
200 270,000 100,000
Abstract to maintain 45-55% summer level in SWCD and 55-65% in winter. Abstract to RWD under extreme conditions (RWD below 15%)
220
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Dam Catchment area (ha)
Capacity (m3)
Surface area at capacity (m2)
Operating procedure/level maintained
Outflow pump capacities (m3/hr)
RWD 14 75,000 18,000 Spills to Storm Water Control Dam (SWCD)
250
SWCD None 290,000 86,250
Maintain level:
45-55% summer
and 55-65% in winter
70
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Figure 23: Voorspoed mine water reticulation system showing monthly water meter figures (viz. minimum, average and maximum).
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The Waste Storage Facilities on the Voorspoed Mine are as follows:
Fine Residual Disposal: (listed in Table 1 below)
Table 6: FRDs Summary
FRD Surface area(m2)
FRD (Phase 2) 547,972
FRD 1A 22,816
FRD 1B 24,950
TOTAL 595 738
CRD Dumps: Seepage and runoff collected from CRD reports to the RWD (via trenches). No specific
measurement of this flow is available due to difficulties with flow measurements.
Open pit: An open area of ~75 ha, all runoff and groundwater ingress (insignificant volume) is pumped
to the RWD. An average volume of ~ 14 000 m3/m (~5 l/s) is pumped from the pit sump(s).
8.1.2 Water demand figures
The water demand (m3/month) is listed in Table 7 below.
Table 7: Average Water Demands
Plant Average Water Demand (m3/month)
Voorspoed plant 120,000
LDV refuel bay, stores waste yard, AECL - washwater
1,000
Sandvik workshop - washwater 200
EMV washbay - washwater 1,000
Dust suppression 15 000
TOTAL 137 200
8.2 Water Balance Modelling Methodology and Results
A detailed description of the model characteristics, climate model and model results appears in section 3.0
and 4.0 of the Water and Salt Balance Report [referenced above], includes the following model scenarios:
An average daily water balance model based on actual pumping records and rainfall data:
2015-2016 average water balance model (Figure 8 on page 14).
Forecasts based on rainfall sequences (50 different ones), followed by an statistical summary of the
results:
2017-2018 mean annual water balance model – average year (Figure 9 on page 15);
2017-2018 mean annual water balance model – wet year (> 90th percentile, Figure 10, page 16);
and
2017-2018 mean annual water balance model – dry year (<10th percentile, Figure 11, page 17).
The water management system was simulated for the period January 2014 to October 2018. Total storage
changes (i.e. the balance of Inflows – Outflows) are indicated on each model outcome and indicates a
positive water balance in all cases/scenarios simulated, i.e. between +54 m3/d (dry season), to +65 m3/d (wet
season), with a forecast average water balance of +58 m3/d on average rainfall.
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8.3 Salt Balance
A detailed description of the Voorspoed mine site area’s salt balance is presented in section 5.0 of the Water
and Salt Balance Report 2017. The available Total Dissolved Solids (TDS) concentrations recorded for the
Renoster Storage and the Raw Water Dam were incorporated in the model and used during the calibration
process and includes the following model scenarios:
An average daily water balance model based on actual pumping records and rainfall data:
2015-2016 average water balance model (Figure 12 on page 19).
Forecasts based on rainfall sequences (50 different ones), followed by an statistical summary of the
results:
2017-2018 mean annual water balance model – average year (Figure 13 on page 20);
2017-2018 mean annual water balance model – wet year (> 90th percentile, Figure 14, page 21);
and
2017-2018 mean annual water balance model – dry year (<10th percentile, Figure 15, page 22).
The water management system was simulated for the period January 2014 to October 2018. Total salt load
(i.e. Input load kg/d – Output load kg/d) are indicated on each model outcome and indicates an “in-balance”
salt load varying between 1% and 3% in all cases/scenarios simulated, i.e. -46 kg/d (dry and wet season),
with forecasted -47 kg/d on average rainfall for 2017-2018. Total change in storage, i.e. what is currently
sitting in the storage facilities varies between +740 kg/d (dry season) to +979 kg/d (wet season), with an
average of +831 kg/d forecasted for 2017-2018.
The average TDS concentrations for the various water sources used in the model are presented in Table 8
These values were assumed based on available data for similar sites and/or determined during the
calibration process.
Table 8: Source terms TDS concentrations
Source Average Concentration (mg/l)
Rain 40
Koppies Dam 600
Natural Runoff 400
CRD Runoff and Seepage 1200
Plant Runoff 1000
Ore Moisture 3500
FRD Runoff 2500
Groundwater 400
Wash bay Runoff 2000
Pit Runoff 980
Wash water 200
Potable water 200
A Model User Interface has been designed for the Voorpsoed Mine and special training has been provided
[on the 11th of September 2017 at the Golder, Midrand Offices]. An explanation of the model is provided in
section 6.0 of the Golder Report: Voorspoed Diamond Mine Water and Salt Balance Report 2017,
No.1663605-316021-3).
8.4 Conclusions and Recommendations (Water & Salt Balance)
The following has significance to the water and salt balance study of the Voorspoed Mine:
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Conclusions:
During the 2015/2016 Hydrological Year (which was based on the pumping records):
Approximately 3.5Ml/d, on average, is added to the system, of which almost 1.8Ml/d is sourced from
Koppies Dam;
The largest portion of water is lost from the system via interstitial storage and residual moisture in
the FRD’s and CRD (approximately 2.1Ml/d); and
The change in volume stored on site over the period is insignificant (0.1Ml/d).
Comparing the estimated volumes that need to be brought in from Koppies Dam for an average, wet
and dry year, the 2015/2016 year is comparable to a very dry year.
Due to the current management practices of Renoster Storage and the Storm Water Control Dam,
spillages are likely to occur at both facilities during a wet, average or dry year.
The differences between the water balance (i.e. inflows vs outflows, and what is stored on the mine site
area, are significantly small (~1 m3/d); and
Differences between the salt load inputs and outputs indicate slight in-balances in the order of <5%,
however, improvement of the water monitoring program would eventually minimize these differences.
Due to the nature of the primary salts contained in the rock mass, which is a characteristic of the Karoo
Ecca Group sediments, a positive salt load has been developed on the site, which is currently contained
by the management of seepages from the CRD and FRD sites and a “no discharge” condition I terms of
the water balance the mine site area.
The following observations were made during the flow meter assessments:
There are flow meters with consistent data for most of the lines on the mine.
A flow meter is not installed from the penstock to the RWD. Further to this the abstraction to the plant
from the RWD and the SWCD is not metered separately. This poses a challenge to the assessment of
the actual raw water requirements of the mine.
Water from the EMV wash bay to the plant is not metered. This may be small quantities but helpful in
the understanding of the system.
Recommendations:
Expansion of the water monitoring plan, specifically aimed at gaining confidence in the volumes of water
transferred between facilities on a daily basis and the volume of water stored on site;
Expansion of the water quality monitoring plan, to be able to more accurately model estimate future salt
loads;
Continued data capturing within the input spreadsheets of the water and salt balance model; and
As more data becomes available the calibration of the various unknown elements within the model can
be improved.
9.0 NUMERICAL GROUNDWATER FLOW AND CONTAMINANT TRANSPORT MODEL
As outlined in the objectives of the conceptual model description (see section 5.2 above), the purpose of this
numerical model approach is to;
Aid in charactering the hydrogeological related impacts associated with the Voorspoed mine; and,
To forecast the impacts of the mine post operations.
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Through forecasting the post operational impacts, appropriate mitigation measures can be recommended to
limit the impact of the mine after closure. The preceding sections of this study dealt with the characterisation
the current condition of the site. While the following chapter discusses the set-up and results of a numerical
model used to forecast groundwater conditions.
A detailed discussion of the groundwater flow model and contaminant transport model appears under section
4.0 of the Hydrogeological Investigation Report, Golder Report No. 1663605-315698-2, and highlights the
following aspects of the numerical modelling part of the investigation:
Model Design, with emphasis on:
Boundary conditions, i.e. constant head, specified flux and a combination of the two;
3D Model Layering, i.e. 24 layers with specified hydraulic characteristics down to ~460 m, thus ~
150 m below the base of the pit.
The numerical modelling considered assessing mine development and the post-closure times:
Scenario 1: Steady state model: A steady state model has been developed to describe the aquifer system
under pre-mining conditions (2004 water level information).
Scenario 2: Transient model calibration – Operational period of the mine (2008 -2019). The calibration of the
model is evaluated through pit inflows, water level distributions and water quality data.
Scenario 3A: Transient simulation through the post operational period to quantify pit flooding and mass
transport without the implementation of mitigation measures.
A detailed description of the numerical modelling scenarios appears under section 4.3 of the above-
mentioned report. Scenario 2 (viz. the transient model) simulates the pit inflows over the period January
2008 up to January 2017 (as illustrated in Figure 24 below)
Figure 24: Inflows to the Voorspoed Mine pit simulated between 2008 and 2017.
Qualitatively, the model is deemed to suitably represent inflows to the pit. The resulting cone of depression,
representative of current conditions, extends 1.2 km west of the pit and is limited to the east due to seepage
from the waste rock dump.
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The simulated hydraulic head distribution representing current conditions was evaluated against the
measured data collected during the 2017 hydrocensus and illustrated for [water level] monitoring site VD-
BH4 in Figure 25 below, see position in Figure 1. Monitoring site VD-BH4 is situated directly east of the pit
and waste rock dump.
The 2017 hydraulic head distribution for the Voorspoed Mine’s “catchment area” is illustrated in Figure 26
below and portrays the following characteristics:
Groundwater, regionally reports to the Renoster and Heuningspruit surface water drainages over a
head gradient of ~61 m;
A local “dewatering cone” has developed around the pit area and is illustrated in Figure 27 below.
Figure 25: Time series water level data and simulated water level at monitoring site VDH04 (wrongly numbered VBH04)
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Figure 26: Operational hydraulic head distribution (as per 2017 prediction)
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Figure 27: Simulated drawdown and cone of depression of the Voorspoed Mine site area (as per 2017 hydrocensus processing)
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Post operational impacts (i.e. initiated by the mine closure phase) has been modelled accordingly to the low
permeability of the country rock. Consequently, the key issues envisioned for the post operational period is
the further development of the contaminant plumes associated with CRD, FRD and WRD and secondly the
pit lake re-filling rate and water quality. This aspect is discussed under subsection 4.3.3 of the
Hydrogeological Investigation Report (Scenario 3: Post operational impacts). Of significant importance is the
Pit Lake development.
The pit void was simulated by applying (i) a high hydraulic conductivity to the pit area and correspondingly a
storativity equal to one – water ingress of ~10 l/s, (ii) direct rainfall contribution over the entire pit catchment
footprint – 631238 m2, (iii) and potential evaporation distributed over the year – 1 550 mm. No storm water
inflow was accounted for. The cumulative inflows and corresponding pit water levels are depicted in Figure
28.
The following deductions of this modelling scenario is made (the storage curve of the Voorspoed pit is
described in section 2.5 of the Hydrogeological Investigation Report [referenced above]:
After 10 years from mine closure the Pit Lake water level elevation would be at ~1240 mamsl or 170
meters below surface.
After 200 years the inflows were balanced by evaporation and thus the quasi steady state head is
expected to be at approximately 1367 mamsl (43 m below surface).
In an additional scenario, where the groundwater inflow was assumed to be approximately 4 l/s,
comparable to the operational inflows simulated, the final head elevation within the pit is expected to
be1334 mamsl (76 meters below surface).
Figure 28: Prediction of the Voorspoed Pit Lake development after closure.
The rewatering progression of the Voorspoed Pit Lake is schematically presented in F….. below, and high-
lights the fact that total rewatering will probably never materialises of the inflow to the pit is not enhance by
one or other engineered design, i.e. design of a local Pit Lake catchment system to divert as much of the
local surface runoff to the pit.
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Figure 29: Schematic of the Voorspoed Mine post operational pit lake development
The main focus of Voorspoed post closure phase would be around the impact on the water quality status of
the mine site area and what quality the Pit Lake will have towards the end of the pit rewatering – which
seems to be an extremely long period, unless the runoff component is significantly enhanced which will also
have an effect on the water quality for example if the runoff is generated for example over the waste rock
dump. Water level, or aquifer saturation levels, on the other hand, has only been impacted around the pit,
and will therefore not be a significant factor for a post closure management measure.
The final water quality characteristics of the Pit Lake water body is much more relevant in terms of water
resources impacts. A detailed discussion of the Post Closure Hydrochemistry appears in subsection 4.3.3.2
of the Hydrogeological Investigation Report. The following aspects are relevant:
Plumes associated with the WRD, FRD and CRD:
Due to the effects of evaporation, the pit was found to remain as a sink during the post operational
phase of mining and as such a component of seepage from the WRD and FRD continued to be
captured by the pit;
However, due to the low permeability of the aquifer the radius of influence of the pit is limited and
consequently a component of seepage is expected to migrate downgradient toward receiving
downstream boreholes downstream the mine site area, mainly boreholes BH30 and BH4;
It was found that the sulphate plume which will migrate onto adjacent farms are unlikely to exceed
the SANS 241: 2011 drinking water limits for sulphate (250 mg/l) and similarly the livestock water
quality limit is not exceeded.
Of the receptor boreholes identified through the 2017 hydrocensus, only BH30 and BH4 (viz. both in the
far field area respectively south and east of the mine site area) are expected to be impacted. BH 30 is
expected to be impacted 10 -15 years post operations while BH4 is expected to be impacted 100 years
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following cessation of mining. Thus while the sulphate concentrations in these boreholes will gradually
increase through time it is not expected that the sulphate will exceed drinking water quality.
Surface water resource (receptor):
In addition to the boreholes mentioned above, the unnamed non-perennial tributary (C70H) of the
Heuningspruit) east of the mine is expected to be a sink to the solute plume over time;
As the stream is only perennial it is likely that salt loads will accumulate during the dry periods and
be flushed down stream following rainfall events. Thus while, the groundwater concentrations are
expected to remain below drinking water levels there may be periodic spikes in surface water
quality as a consequence of discharge to the stream.
As sequence of simulated plumes between 5 and 200 years is illustrated in Figure 30 and Figure 31 below.
Pit Lake Chemistry
The chemical composition of pit water as the pit fills up will depend on a number of factors including:
Chemical composition of wall rock and associated geochemical reactions,
Surface area of exposed wall rock;
Quantity and rate of release of solutes through flushing of the wall rock;
Amount of direct rain falling into the pit and evaporation rates;
Groundwater inflow rates; and
Mixing or stratification of the pit water overtime
The static tests on waste rock materials indicated that rock materials in the open pit are likely to generate
near neutral drainage with high total dissolved solids, moderate sulphate and low concentration of trace
elements upon exposure to rainfall.
The drainage from the wall rock is likely to be similar to that of waste rock leachate in the long term, but the
concentrations will rise and fall with inflows and evaporation. Schematic presentations of these conditions
are shown in Figure 16 and Figure 18 above.
A postulation of the minimum and maximum Pit Lake water qualities are illustrated in Table 9.
Table 9: Pit lake water quality range based on static test data
Parameter Units Minimum Maximum
pH s.u 6.1 9.6
Total dissolved solids mg/l 173 1690
Electrical conductivity mS/m 24 221
Sulphate mg/l 30.3 456
Chloride mg/l 1.7 42
Nitrate mg/l 2.6 218
Nitrite mg/l 0.23 0.50
Fluoride mg/l 0.23 1.3
M Alkalinity mg/l 65 293
Aluminium mg/l 3.6 7.9
Arsenic mg/l 0.01 0.06
Barium mg/l 0.03 0.80
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Parameter Units Minimum Maximum
Boron mg/l 0.14 0.28
Cadmium mg/l <0.00036 <0.00036
Calcium mg/l 4.7 181
Chromium mg/l 0.021 0.2
Cobalt mg/l 0.002 0.02
Copper mg/l 0.013 0.09
Iron mg/l 3.1 5.2
Lead mg/l 0.0024 0.0081
Magnesium mg/l 1.2 29.4
Manganese mg/l 0.0030 1.2
Mercury mg/l 0.0001 0.2
Molybdenum mg/l 0.0054 0.2
Nickel mg/l 0.0052 0.2
Potassium mg/l 4.0 57
Selenium mg/l 0.0049 0.047
Silicon mg/l 7.2 217
Sodium mg/l 36 360
Uranium mg/l 0.0011 0.0051
Zinc mg/l 0.023 0.67
In terms of the identified hydrochemical constituents of concern (as picked during the water study), fluoride
and sulphate concentrations becomes elevated. Other constituents such as nitrate (NO3) and a few trace
metals becomes elevated to levels above the drinking water limits for domestic water uses. As indicated
throughout the study, these elevated concentrations will be limited to the Voorspoed mine site area under
normal climate conditions.
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Figure 30: Simulated sulphate (SO4) plume development from post closure phase – after 5, 10, 15 and 30 years.
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Figure 31: Simulated sulphate (SO4) plume development from post closure phase – after 50, 100, 150 and 200 years
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9.1 Applicable Conclusions (Numerical Modelling)
The following conclusions were drawn from the numerical modelling exercise:
Pit Lake development
The pit lake is expected to initially rebound quickly, the simulated water level within the pit after 10
years is expected to be approximately 1238 mamsl or 172 meters below surface.
After 200 years the inflows are expected to be balanced by evaporation and thus the quasi steady state
head is expected to be at approximately 1367 mamsl (43 m below surface).
In an additional scenario, where the groundwater inflow was assumed to be approximately 4 l/s,
comparable to the operational inflows simulated, the final head elevation within the pit is expected to
be1334 mamsl (76 meters below surface).
Thus it is not expected that the pit will decant and rather the pit will continue to act as local sink for
groundwater indefinitely.
Post operational contaminant transport
Sulphate was selected as there are no other sources of sulphate proximal to the mine with the
exception of the dumps and hence sulphate is a suitable tracer of mine seepage.
The contamination from WRD appears to be rainfall driven and hence the behaviour of the plume varies
seasonally.
However, the simulated plume for a period of 200 years indicates that the plume generated from the
waste rock facilities will unlikely exceed the drinking water limits in terms of sulphate on the farms
neighbouring the mine.
The CRD, while having the highest source concentrations, do not appear to impact on nearby
boreholes. It follows that either seepage from this site is not entering the groundwater system or the
boreholes installed do not suitably represent the upper fractured aquifer.
Seepage from the FRD is envisioned in part to migrate toward the pit and off site in a north easterly
direction toward identified receptors.
Similarly, the two receptor boreholes which are likely to be impacted over time, BH30 (15 years post
operations) and BH 4 (100 years post operations) are expected to gradually increase in sulphate
concentration but are not expected to exceed drinking water limits for sulphate.
Plumes associated with the WRD, FRD and CRD
Due to the effects of evaporation, the pit was found to remain as a sink during the post operational
phase of mining and as such a component of seepage from the WRD and FRD continued to be
captured by the pit.
However, due to the low permeability of the aquifer the radius of influence of the pit is limited and
consequently a component of seepage is expected to migrate downgradient toward the identified
receiving boreholes.
It was found that the sulphate plumes which will migrate onto adjacent farms are unlikely to exceed the
SANS 241: 2011 drinking water limits for sulphate (250 mg/l) and similarly the livestock water quality
limit is not exceeded.
Impact on local surface water systems
In addition to the boreholes identified, the unnamed non-perennial tributary north of the mine is
expected to be a sink to the solute plume over time.
As the stream is only perennial it is likely that salt loads will accumulate during the dry periods and be
flushed down stream following rainfall events. Thus while, the groundwater concentrations are expected
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to remain below drinking water levels there may be periodic spikes in surface water quality as a
consequence of discharge to the stream.
10.0 SYNOPSIS
Golder Associates Africa (Pty) Ltd were appointed to undertake a hydrogeological investigation to guide the
closure process of the De Beers Voorspoed mine. The following synopsis was drawn from this study.
During the mining operations since 2008, a diamond pipe has been mined down to a depth of ~307 m. The
host rock formation are sediments of the Ecca Group of the Karoo Supergroup consisting mainly of
mudrocks and interbedded sandstone/siltstone horizons. Secondary geological features, such as faults,
dolerite sills and dykes are present on the mine site area. During mining operations very little groundwater
ingress occurred, and a large portion of the water requirements were obtained from external sources
(surface water supplies – nearby Koppies Dam) supplemented by a few local water supply boreholes on the
mine site area.
The hydraulic characteristics of the host rock formations are indeed low to insignificant, although all
boreholes in the near (mine site) and far (surrounding land) areas have intercepted groundwater at various
depths – highest yields, however, are associated with the sub-vertical dolerite dyke features, i.e. so-called
dolerite contact aquifer systems. The groundwater flow pattern is directed towards the surrounding surface
water drainage systems of which only the Heuningspruit and Renoster River are regarded as perennial
systems. No drainage runs directly through the mine site area, although a small tributary of the
Heuningspruit starts just of the north-eastern boundary of the mine site area.
As a result of the mine workings on the Voorspoed site, four prominent storage facilities have developed
over the time, being (i) the large waste rock dump southeast of pit area (not part of the mine water cycle), the
fine residue dumps consisting of three units and containing the final wash waste from the processing plant,
(iii) the course residue dump, containing the waste portion from the milling/processing plants, (iv) the raw
water dam which includes the captured discharges from the fine and course residue dumps, and (iv) the
storm water control dam.
In terms of the water balance status of the Voorspoed Mine, external water from the Koppies Dam and a few
boreholes in the mine site area provides the water supply to the Voorspoed operations – which is in balance
with the use as no water is discharged from the mine site area. Management practices at the main storage
facilities on site, i.e. the Renoster Storage and the storm water control dam (SWCR), spillages are likely to
develop during wet, average or dry years. The salt balance, however, indicates a steady increased based on
the primary salt loads of the rock mass on the mine site area. Seepages from the CRD and FRD are
managed and a management protocol of “no discharge to the environment” retains the salt load on the mine
site area. Groundwater quality monitoring in the far field area, i.e. land surrounding the mine site area, does
not indicate any specific increase in the normal slat loads found in the Karoo Ecca Group groundwater
systems. Monitoring of the far field surface water runoff is ominously important – especially downstream of
the storm and return water storage facilities.
The geochemical assessment of the mine site area included all the waste rock dumps (i.e. Karoo Ecca
Group sediments, basalt and dolerite rock), and processed Kimberlite ore (i.e. CRD and FRD dump sites), as
well as the water (i.e. seepages from processed rock dump sites), pit water and storage facilities (i.e. storm
water and return water dams). The geochemical assessment focussed on the (i) acid producing
characteristics, (ii) geochemical constituents of the seepages, and (iii) the leachates of the waste and
processed rock dump sites. The geochemical results indicate (i) not potentially acid generating, (ii) these
sites, upon exposure to rainfall produce a predominantly near-neutral, low-metal drainage with pH likely to
exceed the recommended water quality objectives the C70H quaternary catchment [with regard to pH, EC,
turbidity and ammonia], and (iv) concentrations of aluminium, iron and manganese are likely to exceed the
domestic and irrigation water quality guidelines and (v) Sodium Absorption Ratio likely to exceed the
irrigation water quality guideline. Additionally, the sampled waster rock, and material from the CRD and FRD
are classified as non-hazardous waste. To conclude, although the fine residue material (FRD) might be
considered as Type 3 for the purpose of cover design (in terms of GN R. 635 Regulation 7(6)), the
environmental risk associated with seepage from the three dumps is similar to that of a Type 4 waste,
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however, coarse residue material (CRD), fine residue material (FRD), and waste rock material (WRD) are
considered to be non-hazardous to the environment due to low solubility of elements in crystallised state.
In terms of the groundwater chemical characteristics in the far field area, it is characterised by slightly
elevated salinity levels (TDS ~750 mg/L), sodium, chloride and sulphate concentrations – which abides it’s
salinity (viz. Na-Cl) origin from the ambient Karoo Ecca Group water quality type, and the sulphate probably
from concentrations of primary iron-pyrite in the sandstone layers imbedded in the Ecca Group. Under field
conditions, sulphide oxidation and release of elements will occur gradually and concentrations in mine
drainage are expected to be lower than NAG leachate chemistry at any given time.
In terms of the flood line analyses, the conclusion is that the Voorspoed Mine is situated on the highest
elevation of the C70H quaternary catchment – above the headwaters of this quaternary catchment, as well
as the neighbouring catchments that drains the area. There are no identifiable surface water drainages
across the site.
Finally, the numerical modelling based on a 3D finite element model covers (i) the steady state model (i.e.
describe the aquifer system under pre-mining conditions (2004 conditions), (ii) a transient model calibration
(i.e. operational period 2008-2019), a transient simulation through the post-operational period to quantify pit
flooding and mass transport (excluding mitigation measures). A 3D finite element model, consisting of a 24
layered package (i.e. 460 m), covering the total depth of the Voorspoed pit (~307 m), including three dolerite
sill contact water bearings zones, as well as including the major sub-vertical dolerite dyke and fault line
contact aquifers.
A detailed conceptual model was constructed for the Voorspoed Mine site area based on the regional
geology and the detail geological model of the mine site area. The concept model depicts the dewatering
that took place during the Life of Mine, however, based on the hydrogeological study [and the insignificant
overall hydraulic nature on the surrounding geological formations], impacts such as dewatering and
migration of potential contaminants from the mine site area based on the elevation model, does not progress
significantly into the far field area.
The Steady State numerical model indicates the natural catchment-like groundwater flow regime describes
the status of the aquifer system(s) as depicted in the conceptual model, and recharged water ultimately
reports to the major surface water drainages after a momentous long flow period [due to the low hydraulic
nature of the aquifer systems. Impacts are therefore mainly localised, with a steady recovery supported by
local/direct rainwater recharge and “re-freshing” of the aquifer system.
The Transient Model Calibration (i.e. pit inflows and surrounding water table elevation), indicates (i) the
dewatering cone extends 1.2 km west of the pit and is limited to the east due to seepage from the waste rock
dump, and (ii) impacts (direct infiltration into the upper shallow aquifer system from the coarse residual dump
are deemed valid.
The Post Operational Impacts highlights (i) the Pit Lake development, which indicate that evaporation from
the pit sidewalls and the pit lake will result in a slow recovery rate and after 200 years, the inflows (high
inflow scenario) are balanced by evaporation and thus the quasi steady state head is expected to be at
approximately 1367 mamsl (43 m below surface). It is therefore concluded, that based on the actual inflow
volumes (excluding any engineered, local Pit Lake Catchment design), the final water table elevation will be
between 76 m (4 l/s inflow, + rainfall - evaporation), and 43 m (~10 l/s inflow, + rainfall – evaporation).
Secondly, (ii) the post closure hydrochemistry (Mass Transport Model) based on the calibrated transient
model, was utilised to simulate the post-operational plume migration from the WRD, CRD and
FRD – sulphate was used as the tracer for contamination migration as it was found to be associated with the
waste rock facilities [and not commonly associated with agricultural practices].
The most important results of the mass transport modelling indicate, that (i) the pit will remain as a sink (i.e.
capturing local seepages via the shallow aquifer system) during post operational times due to the effects of
evaporation, (ii) due to the low permeability of the aquifer rock, the current radius of influence of the pit [sink]
is limited and a component of the seepage is expected to migrate downgradient to receiving boreholes
(BH30 and BH04) will be impacted over ~12 and 100 years respectively. In a scenario where the sulphate
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plume migrates to the far field area, the mass transport model predicts that the concentration will unlikely
exceeds the drinking water limits for sulphate (~250 mg/l) and livestock.
Water quality impacts via the surface water flow system has been identified in the drainage path of an
unnamed, non-perennial tributary in the C70H quaternary catchment, just east of the storm water and return
water dam sites due to the accumulation of salt loads during dry periods, and periodic surface flooding will
flush these salt further downstream and may impact on water resources further downstream. This is
conclusion is merely a “desktop observation”, however, and it is recommended that a more detailed
investigation is considered.
The geochemistry evolution of the Pit Lake during rewatering will depend on a number of factors, including (i)
the (geo)chemical composition of the pit-wall rock formations, (ii) the surface area of the exposed rock face,
(iii) the rate at which solutes are released through pit-wall rock flushing, and (iv) the combined effects of
rainwater filling, evaporation rate, groundwater inflow rates/quality, geochemical reactions,
mixing/stratification of the water body in the pit lake – over time.
Static tests on the waste rock materials indicated that rock materials in the open pit are likely to generate
near neutral drainage with (i) high total dissolved solids, (ii) moderate sulphate and (iii) low concentration of
trace elements upon exposure to rainfall. The drainage from the wall rock is likely to be similar to that of
waste rock leachate in the long term, but the concentrations will rise and fall with inflows and evaporation.
Should an engineered, local Pit Lake catchment developed, the final impact could be significantly different.
Further investigations on refined the Pit Lake water quality signatures would require a detailed geochemical
assessment of the pit wall rock face, an aspect not catered in this study.
To conclude, recommendations related to the post-closure phase of the Voorspoed Mine are as follows:
Upgrading of the current water resources monitoring infrastructure (dedicated deep/shallow boreholes
and water meters on pipeline systems), and especially the unnamed non-perennial surface water
drainage east of the SWD and RWD area;
Active practice of the water balance modelling procedure (i.e. GoldSim modelling) and database
maintenance (incl. an updated groundwater component database system, i.e. MS Office – Excel
system);
Establishment of a local weather station on the site; and
Prediction of the long-term evolution of pit lake water chemistry based upon the volume and chemistry
based on the existing water make model of a Pit Lake (natural inflow and side wall leaching and runoff.
In addition, if a larger surface water runoff catchment is engineered in the near filed area to enhance the
pit lake water level recovery, specific aspects such as evaporative mass balance and a long-term
mixing model will have to be addressed.
11.0 REFERENCES
The following Golder reports (viz, study component reports) were consulted in prepare this Summary Report.
Several references to these are made and it is recommended that this Summary Report should be used in
conjunction with the study components reports as detailed references, they are as follows:
1663605-314859-1: Surface and Groundwater Study for Mine Closure Requirements – Enquiry No: VS-
E-085-6, i.e. Progress Report covering the (i) the hydrocensus survey and (ii) water and geochemical
results. Introduction of the water and salt balance program was included;
1663605-315698-2: Hydrogeological Investigation, i.e. addressed the (i) hydrological data assessment,
(ii) preliminary geochemical assessment, and (iii) introduction to the numerical modelling task;
1663605-316021-3: Voorspoed Diamond Mine Water and Salt Balance Report 2017, i.e. addressing the
(i) hydrological aspects of the site area, (ii) complete water and salt balances, and (iii) the GoldSim
modelling process, presented as a training course to Voorspoed staff on the 11th of September 2017;
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1663605 Mem_008: A Technical Memorandum, i.e. Voorspoed Mine Floodline Assessment;
1663605-316224-4: Geochemical Assessment Report, i.e. a comprehensive update of the preliminary
geochemical assessment, including (i) information review, (ii) sampling and laboratory programme, and
(iii) geochemical test results.
Where applicable, references to several Appendixes are made which are included in the above-mentioned
reports. All these reports, and associated datasets were uploaded to the Anglo American Dropbox facility
during September and October 2017. A total of 181 files have been uploaded which includes 14 report files
and dotPPTX presentations.
Talita Germishuyse Eddie van Wyk
Senior Modeller Senior Hydrogeologist
TG/EvW/ck
Reg. No. 2002/007104/07
Directors: RGM Heath, MQ Mokulubete, SC Naidoo, GYW Ngoma
Golder, Golder Associates and the GA globe design are trademarks of Golder Associates Corporation.
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APPENDIX A Document Limitations
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October 2017 Report No. 1663605-316475-5
DOCUMENT LIMITATIONS
This Document has been provided by Golder Associates Africa Pty Ltd (“Golder”) subject to the following
limitations:
vii) This Document has been prepared for the particular purpose outlined in Golder’s proposal and no
responsibility is accepted for the use of this Document, in whole or in part, in other contexts or for any
other purpose.
viii) The scope and the period of Golder’s Services are as described in Golder’s proposal, and are subject to
restrictions and limitations. Golder did not perform a complete assessment of all possible conditions or
circumstances that may exist at the site referenced in the Document. If a service is not expressly
indicated, do not assume it has been provided. If a matter is not addressed, do not assume that any
determination has been made by Golder in regards to it.
ix) Conditions may exist which were undetectable given the limited nature of the enquiry Golder was
retained to undertake with respect to the site. Variations in conditions may occur between investigatory
locations, and there may be special conditions pertaining to the site which have not been revealed by
the investigation and which have not therefore been taken into account in the Document. Accordingly,
additional studies and actions may be required.
x) In addition, it is recognised that the passage of time affects the information and assessment provided in
this Document. Golder’s opinions are based upon information that existed at the time of the production
of the Document. It is understood that the Services provided allowed Golder to form no more than an
opinion of the actual conditions of the site at the time the site was visited and cannot be used to assess
the effect of any subsequent changes in the quality of the site, or its surroundings, or any laws or
regulations.
xi) Any assessments made in this Document are based on the conditions indicated from published sources
and the investigation described. No warranty is included, either express or implied, that the actual
conditions will conform exactly to the assessments contained in this Document.
xii) Where data supplied by the client or other external sources, including previous site investigation data,
have been used, it has been assumed that the information is correct unless otherwise stated. No
responsibility is accepted by Golder for incomplete or inaccurate data supplied by others.
xiii) The Client acknowledges that Golder may have retained sub-consultants affiliated with Golder to
provide Services for the benefit of Golder. Golder will be fully responsible to the Client for the Services
and work done by all of its sub-consultants and subcontractors. The Client agrees that it will only assert
claims against and seek to recover losses, damages or other liabilities from Golder and not Golder’s
affiliated companies. To the maximum extent allowed by law, the Client acknowledges and agrees it will
not have any legal recourse, and waives any expense, loss, claim, demand, or cause of action, against
Golder’s affiliated companies, and their employees, officers and directors.
xiv) This Document is provided for sole use by the Client and is confidential to it and its professional
advisers. No responsibility whatsoever for the contents of this Document will be accepted to any person
other than the Client. Any use which a third party makes of this Document, or any reliance on or
decisions to be made based on it, is the responsibility of such third parties. Golder accepts no
responsibility for damages, if any, suffered by any third party as a result of decisions made or actions
based on this Document.
GOLDER ASSOCIATES AFRICA (PTY) LTD
Golder Associates Africa (Pty) Ltd.
P.O. Box 6001
Halfway House, 1685
Building 1, Maxwell Office Park
Magwa Crescent West
Waterfall City
Midrand, 1685
South Africa
T: [+27] (11) 254 4800
Caption Text